Download Mobile Communication and Mobile Computing

Mobile Communication and Mobile Computing
Mobile Communication and
Mobile Computing
Prof. Dr. Alexander Schill
TU Dresden, Computer Networks Dept.
http://www.rn.inf.tu-dresden.de
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Mobile Communication and Mobile Computing
Contents
1. Motivation
2. Mobile Communication
–
–
–
–
–
–
–
History
Principles
Media Access Methods
Mobile Radio Networks: Overview
GSM
HSCSD, GPRS
UMTS
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Mobile Communication and Mobile Computing
Contents
2. Mobile Communication (Continuation)
– Broadband-Radio Systems
– Wireless Local-area Networks (IEEE 802.11,
Bluetooth etc.)
– Satellite-based Systems
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Mobile Communication and Mobile Computing
Contents
3. Mobile Computing
– Layer 3
• MobileIP v4 & v6
• DHCP
– Layer 4
– Higher Layers and Services
•
•
•
•
•
•
WAP, XML
Mobile RPC
CODA, Databases
Mobile Agents
Middleware for spontaneous networking
Services and system support for Mobile Computing
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Mobile Communication and Mobile Computing
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Literature
Roth, J.: Mobile Computing, dpunkt-Verlag, 2002
Very good overview to mobile communication and mobile computing
Schiller, J., Mobilkommunikation, Techniken für das allgegenwärtige Internet,
Addison-Wesley, 2000
Mobile Communication principles and Mobile Computing
Bernhard, Walke: Mobilfunknetze und ihre Protokolle, 2 Bände. Teubner, 2000
Principles, GSM, UMTS and other cellular Mobile Radio Networks [Vol.1]
Circuit Switched Radio, Cordless Phone Systems, W-ATM, HIPERLAN, Satellite Radio,
UPT [Vol.2]
Schumny, Harald: Signalübertragung, Friedrich Vieweg & Sohn,
Braunschweig/Wiesbaden 1987;
Wave propagation and wireless transmission
A.S. Tanenbaum: Computernetzwerke, 4. Aufl., Prentice Hall, 1998
Protocols, ISO/OSI, standards, fixed networks
Principles
Mobile Communication and Mobile Computing
1. Motivation and Examples
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Mobile Communication and Mobile Computing
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Motivation
Speech- and Data Communication location independent and mobile
New application areas, flexibility, improved workflows
Requirements:
- Mobile end-devices
- Radio transmission
- Localization and signalization/management
- Standards
- Application Concepts for mobile end-devices in distributed systems
- Control of heterogeneous, dynamic infrastructures
Mobile Computing
Mobile Communication and Mobile Computing
Application example: Civil
Engineering, Field Service
Large archives,
Videoconferences
Drafts,
urgent
modification
ATM
ISDN
Building of
enterprise A
(main office)
X.25
ISDN
ATM
Selected drafts,
Videoconferences
GSM
Building of
enterprise B
Building of
enterprise A
(branch office)
Construction
supervisor
Material data,
status data,
dates
Architect
GSM
Building site
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Mobile Communication and Mobile Computing
WAP-Example: Order processing
Order book
• Status of bond transactions.
• Executed and deleted orders are
indicated in the order book for
some days more.
• Partial execution of some order
is presented as one open and
one executed partial order in the
order book.
• Details to an order could be
indicated via dial-up of
correspondent Links.
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Mobile Communication and Mobile Computing
Perspective: Mobile Multimedia
Systems
Local Resources,
Error Protocols
Product Data
Main office
Caching
Maintenance
technician
Client
LAN-Access
Mobile Access
- very different performance and charges: radio networks versus fixed
networks
Software-technical, automatic adaptation to concrete
system environment
Example: Access to picture data/compressed picture
data/graphics/text
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Mobile Communication and Mobile Computing
Application Structure
Ethernet
Distributed
Database
Ethernet
DB
E-Fax-Order
Branch office
Firm
xDSL
Application
GSM
Ethernet
Cache
Resource
Mobile Station
Communication path
Management
DB-Access
Distributed
Database
Client X
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Mobile Communication and Mobile Computing
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Traffic Telematics Systems
Content Provider
Main Office
Content Provider
ATM
Internet
Beam Radio, ISDN
GSM
Radio/Infrared
DAB: Digital Audio Broadcast
Infrastructure
RDS/TMC: Radio Data System/
Traffic Message Channel
Mobile Communication and Mobile Computing
Mobile Communication Networks: Examples
GSM (Global System for Mobile Communications): worldwide
standard for digital, cellular Mobile Radio Networks
UMTS (Universal Mobile Telecommunications System): European
Standard for future digital Mobile Radio Networks
AMPS (Advanced Mobile Phone System): analog Mobile Radio
Networks in USA
DECT (Digital Enhanced Cordless Telecommunications): European
standard for cordless phones
TETRA (Terrestrial Trunked Radio): European standard for circuit
switched radio networks
ERMES (European Radio Message System): European standard for
radio paging systems (Pager)
802.11: International standard for Wireless Local Networks
Bluetooth: wireless networking in close/local area
Inmarsat: geostationary satellite systems
Teledesic: planned satellite system on a non-geostationary orbit
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Mobile Communication and Mobile Computing
Mobile Communication: Development
E (GSM1800)
D (GSM900)
C
Mobile Phone Networks
HSCSD
EDGE
GPRS
Cordless Telephony
CT2
DECT
IMT2000/
UMTS
Packet Networks
Modacom
Mobitex
Circuit Switched Networks
Satellite Networks
Local Networks
Tetra
Iridium/
Globalstar
Inmarsat
Radio-LAN
IEEE 802.11/
Hiperlan
MBS
IR-LAN
1990
1995
2000
2005
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Mobile Communication and Mobile Computing
Used Acronyms
CT2: Cordless Telephone 2. Generation
HSCSD: High Speed Circuit Switched Data
GPRS: General Packet Radio Service
EDGE: Enhanced Data Rates for GSM Evolution
IMT2000: International Mobile Telecommunications by the year 2000
MBS: Mobile Broadband System
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Mobile Communication and Mobile Computing
2. Mobile Communication
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Mobile Communication and Mobile Computing
Principles
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Mobile Communication and Mobile Computing
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Mobile Communication
Tied to electro-magnetic radio transmission
radio transmission
orbital (satellite)
terrestrial
beam radio
broadcast
radio
cellular
equatorial
orbit
non-equatorial
orbit
non-cellular
Principles:
– Propagation and reception of electro-magnetic waves
– Modulation methods and their properties
– Multiplex methods
– Satellite orbits/Sight- and overlap areas
Mobile Communication and Mobile Computing
Cellular Networks: Principles
Channels
801-1600
Interference Zone
R
Channels
1-800
Channels
1-800
Supply- (radius R) and
interference areas (5 R)
2
7
4
5
4
5
3
1
6
3
1
6
2
7
4
4
2
1
2
1
5
5
7
6
7
6
3
3 2 4
2
4
1
5
1
7
5
7
6
6
3
4
3
4
2
2
1
5
7-Cell-Cluster
(repeat sample of the
same radio-channels)
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Mobile Communication and Mobile Computing
Cellular Networks: Principles
Cell structure: Example
Reference cell
Cell in the
interference area of
the reference cell
Further cells, whose
channel distribution
should be known to
the reference cell
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Mobile Communication and Mobile Computing
Kinds of antennas: directional &
sectored
• Energy is radiated in definite directions, for instance xDirection
• So called main propagation directions, for instance
Satellite Antennas
• Often also used in Mobile Radio Systems, such as GSM,
for creation of sectored cells
• Seamless radio supply via partial/overlay of sectors
z
y
x
Directional Antenna
x
Sectored Antenna
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Mobile Communication and Mobile Computing
Media Access Methods
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Mobile Communication and Mobile Computing
Principles
• Multiplex
– Multiple-shift usage of the medium without interference
– 4 multiplex methods:
• Space
• Time
• Frequency
• Code
• Media Access Methods
– controls user access to medium
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Mobile Communication and Mobile Computing
SDMA (Space Division Multiple
Access)
• based on SDM (Space Division Multiplexing, Space Multiplex)
• communication channel obtains definite Space for definite Time on
the definite Frequency with definite Code
• Space Multiplex for instance in the Analog Phone Systems (for each
participant one line) and for Broadcasting Stations
• Problem: secure distance (interferences) between transmitting
stations is required (using one frequency) and by pure Space
Multiplex each communication channel would require an own
transmitting station
• Space Multiplex is only reasonable in combination with other
multiplex methods
• SDMA for instance by base station dedication to an end-device via
Media Access Methods or respectively by segmentation of a Mobile
Radio Network to several areas
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Mobile Communication and Mobile Computing
SDMA: Example
k1
k2
k3
k4
k5
f1
s
SDMA finds selection
s – secure distance
k6
25
Mobile Communication and Mobile Computing
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FDMA (Frequency Division Multiple
Access)
• Based on FDM (Frequency Division Multiplexing, Frequency
Multiplex)
• i.e. to transmission channels several frequencies are permanently
assigned, for instance radio transmitting stations
k1
k2
k3
k4
k5
k6
f
k6
k5
f1
f2
f3
s
FDMA finds
selection
f4
k4
f5
k3
f6
k2
k1
s – secure distance
t
Mobile Communication and Mobile Computing
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TDMA (Time Division Multiple
Access)
• Based on TDM (Time Division Multiplexing, Time Multiplex)
• i.e. to transmission channels is the transmission medium is slot
assigned for certain time, is often used in LANs
• Synchronization (timing, static or dynamic) between transmitting and
receiving stations is required
k1
k2
TDMA finds
selection
k3
k4
k5
f1
k6
f
k1 k2 k3 k4 k5 k6 k1
t
Mobile Communication and Mobile Computing
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Combination: FDMA and TDMA, for instance
GSM
•
•
GSM uses combination of FDMA and TDMA for better use of narrow
resources
the used band width for each carrier is 200 kHz
f in MHz
TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS0
960
TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS0
downlink
25 MHz
935,2
TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS0
915
TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS0
200 kHz
TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS0
890,2
45 MHz
uplink
25 MHz
TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS0
t
Mobile Communication and Mobile Computing
CDMA (Code Division Multiple
Access)
• based on CDM (Code Division Multiplexing, Code multiplex)
• i.e. to transmission channels the definite Code is assigned, this can
be on the same Frequency for the same Time transmitted
• derivates from military area
• via development of cost-efficient VLSI components
• via spread spectrum techniques a good communication security and
tiny fault sensitivity
• but: exact synchronization is required, code of transmitting station
must be known to receiving station, complex receivers for signal
separation are required
• Noise should not be very high
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Mobile Communication and Mobile Computing
CDMA
k1
k2
k3
f1
CDMA
decoded
k4
k5
k6
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Mobile Communication and Mobile Computing
CDMA illustrated by example
The Principle of CDMA can be good illustrated by the example of
some party:
• communication partners stand closely to each other, each
transmission station (Sender) is only so loud, that it does not
interfere to neighbored groups
• transmission stations (Senders) use certain Codes (for
instance, just other languages), they can be just separately
received by other transmission stations
• receiving station (Listener) attunes to this language (Code), all
other Senders are realizing this only as background noise
• if receiving station (Listener) cannot understand this language
(Code), then it can just receive the data, but it cannot do
anything with them
• if two communication partners would like to have some secure
communication line, then they should simply use a secret
language (Code)
• Potential Problems:
– security distance is too tiny: interferences (i.e. Polish und
Czech)
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Mobile Communication and Mobile Computing
CDMA-Example in the theory
Sender A
• Sends Ad =1, Key Ak = 010011 (set: „0“= -1, „1“= +1)
• Transmit signal As =Ad *Ak = (-1, +1, -1, -1, +1, +1)
Sender B
• sends Bd =0, Key Bk = 110101 (set: „0“= -1, „1“= +1)
• Transmit signal Bs =Bd *Bk = (-1, -1, +1, -1, +1, -1)
Both signals superpose additively in air
• Faults are ignored here (noises etc.)
• C = As+ Bs =(-2,0,0,-2,+2,0)
Receiver will listen to Sender A
• uses Key Ak bitwise (internal product)
– Ae = C * Ak =2 +0+0 +2 +2+0 = 6
– Result is greater than 0, so sent bit was „1“
• analog B
– Be = C * Bk =-2 +0 +0 -2 -2 +0 = -6, also „0“
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Mobile Communication and Mobile Computing
Spread Spectrum Techniques
dP
df
dP
df
f
f
• Signal is spread by the Sender before the transmission (overblown)
• dP/df value corresponds with so called Power Density, Energy is
constant (in the Figure: the filled areas)
Objective:
• Increase of robustness against small band-width faults
• listening security: power density of spread-spectrum signals can be
lower than that of background noise
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Mobile Communication and Mobile Computing
Spread Spectrum Techniques
dP
df
dP
df
f
dP
df
f
f
t
• small band-width faults are spread by de-spreading in receiving
station
• band-pass deletes redundant frequency parts
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Mobile Communication and Mobile Computing
Mobile Radio Networks:
Overview
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Mobile Communication and Mobile Computing
Development of Mobile Radio
General technological development
in mobile telephony
Satellite Systems (LEO)
UMTS
GSM Phase II+
Digital cellular
Networks...1800 Mhz
Digital cellular
Networks...900 Mhz
Prognoses
Anal. cellular
Networks...900 Mhz
Anal. cellular
Networks...450 Mhz
Analog
Networks...150Mhz
before 1970
1970
1980
1990
2000
2005
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Mobile Communication and Mobile Computing
Correspondent data rates
10Mbit/s
UMTS
(pico cell)
DAB
1Mbit/s
DECT
EDGE
HSCSD/
GPRS
100kbit/s
10kbit/s
GSM
1995
UMTS
(macro cell)
Satellites
Satelliten (GEO)
2000
2005
2010
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Mobile Communication and Mobile Computing
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Participant quantities in Mobile Radio –
world-wide
November 2002: 1148 Mio. participants world-wide (1119 Mio. digital & 29 Mio
analog)
53069620; 5%
37534680; 3%
165417440; 14%
365190830; 32%
137691590; 12%
369094290; 32%
20059880; 2%
(Source: http://www.emc-database.com)
1... Europe: Western
4... Americas (thereof 15.4 Mio. analog)
2... Asia Pacific
5... USA/Canada (thereof 5.4 Mio. analog)
3... Middle East
6... Africa
7… Europe: Eastern
1
2
3
4
5
6
7
Mobile Communication and Mobile Computing
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Frequency Assignment
Circuit Switched Radio Mobile Phones Cordless Phones Wireless LANs
TETRA
NMT TETRA
380-400 453-457 450-470
CT2
500Mhz
CT1+ GSM900
CT1+
864-868 885-887 890-915 930-932
GSM900
935-960
1GHz
410-430 463-467 (nationally different)
TFTS (Pager, aircraft phones) GSM1800
1670-1675
TFTS
GSM1800
1710-1785 1800-1805 1805-1880
DECT
UMTS
1880-1900
(1885-2025
2110-2200)
WLAN
IEEE 802.11b Bluetooth
IEEE 802.11a: 5,15-5,25; 5,25-5,35; 5,725-5,825
HIPERLAN1 HIPERLAN2
HIPER-Link
MHz
2400-2483 2402-2480
2412-2472
HomeRF...(approx.2400)
TFTS - Terrestrial Flight
Telephone System
5176-5270
Notes:
(ca.5200,5600)
(ca.17000)
- 2,4 GHz license free, nationally different
- () written : Prognoses!
- today speech over license free frequencies up to
61Ghz -> interesting for high data rates
Mobile Communication and Mobile Computing
Broadcast/multicast networks
• several carrier frequencies but participant obtains carrier
for short time only
• often in use by taxi- und logistics enterprises etc., each
own separated frequency reaches
• can use the same frequency packs with FDM- and TDMtechniques, i.e. more efficient handling with narrow
resource frequency spectrum
• improves transition to fixed network, speech- and data
services
• not for public access
• very reliable, cost-efficient
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Mobile Communication and Mobile Computing
TETRA (Terrestrial Trunked
Radio)
• former name: Trans-European Trunked Radio
• frequencies: 380-390, 410-420 MHz Uplink; 390-400, 420-430 MHz
Downlink
• bandwidth of each channel: 25 kHz
• 1991 started by ETSI
• replace of national networks like MODACOM, MOBITEX or
COGNITO
• Services:
– Voice + Data (V+D)- Service: Speech and Data, channel-oriented, uni-,
multi- and broadcast possible
– Packet Data Optimized (PDO)- Service: packet-oriented, improves
connection-oriented or connectionless service, as well as point-to-point
and point-to-multipoint communication
• carrier services with data rate up to 28,8 kbit/s unprotected; 9,6
kbit/s - protected
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Mobile Communication and Mobile Computing
42
TETRA, advantages compared with
GSM, UMTS
• confirmed and/or non-confirmed Group Call (however it’s already
possible with GSM today: up to 16 participants)
• Group call
• listening is possible (so called “open-channel mode”)
• very reliable
• fast dialing: approx. 300 ms (so called “push to talk”), GSM: several
seconds
• certain independence of infrastructure (so called “direct mode”
between end-devices)
• cost-efficient, especially for limited user quantity, because of the
„large“ cells x • 10 km
• also especially suitable for emergency teams (fire department,
ambulance etc.)
Mobile Communication and Mobile Computing
Cordless Telephony - DECT (Digital
Enhanced Cordless Telecommunications)
•
•
•
•
•
•
•
frequency reach: 1880 - 1990 MHz
other than GSM limited to short reaches (1km)
in buildings particularly under 50m
is not designed for use at high rates
mobile phones with GSM and DECT are available in the market
120 full duplex channels
TDD (Time Division Duplex) for directional separation with 10ms
frame length
• frequency reach is divided into 10 carrier frequencies using FDMA
• each station 10mW averaged, max. 250mW of transmitting power,
GSM – radio phones transmit at 1 to 2W, fixed car phones up to 8W
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Mobile Communication and Mobile Computing
DECT – system architecture
D4
D3
D2
HDB
PA
PT
FT
Local
Networks
PA
PT
VDB
D1
FT
Local
Networks
FT..
PT..
PA...
HDB..
VDB..
Fixed Radio Termination
Portable Radio
Termination
Portable Terminations
Home Data Base
Visitor Data Base
Global
Networks
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Mobile Communication and Mobile Computing
DECT - Multiplex
Synchronization
32 bit
Used Data
(Speech)
Signalization
48 bit
Used Data
(Speech)
CRC
160 bit
8 bit
160 bit
CRC
Secure marker
8 bit
64 bit
0,417 ms
DECT-timeslot structure
Transmission reach of fixed part (downlink)
carrier frequency 1:
1 2 3 4 5 6
carrier frequency 2:
1 2 3 4 5 6
carrier frequency 10:
1 2 3 4 5 6
Transmission reach of mobile part (uplink)
....
11
12
1'
2'
3'
4'
5'
6'
....
11'
12'
....
.
.
.
11
12
.
.
.
1'
2'
3'
4'
5'
.
.
.
6'
....
11'
12'
....
11
12
1'
2'
3'
4'
5'
6'
....
11'
12'
1728
kHz
Transmission principle of DECT-system
Channel 1
Channel 2
...
Channel 12 Channel 1’ Channel 2'
...
Channel 12'
fixed part to mobile part
mobile part to fixed part
Time duplex with 10 ms frame length
Structure of DECT-time multiplex frame
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Mobile Communication and Mobile Computing
46
Pager systems: overview
Eurosignal
– to each participant 4 different audio signals using 4 diverse call numbers are
assigned. Meaning must be agreed. Receiving stations are at a size of a
cigarette packet
– 85 senders in the 87 MHz-reach (ultra short waves)
– called person location must be approximately known: 3 area codes: North
0509, Middle 0279, South 0709
Cityruf (city call)
– additionally to 4 audio- or respectively optical signals transmission of short
numerical (15 digitals) or alpha-numerical messages (80 characters) exists
optionally, receiving station is smaller than with Eurosignal
PEP (Pan European Paging)
– preparation for coupling of national services for ERMES
– D: Cityruf, F: Alphapage, GB: Europage, I: SIP
ERMES (European Radio Message System)
– ETSI-Standard for pan-European radio service, similar to PEP but in 169 MHzreach with 60 Mio. addresses
Mobile Communication and Mobile Computing
GSM: Global System for
Mobile Communications
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Mobile Communication and Mobile Computing
GSM: Properties
•
•
•
•
•
•
•
•
•
cellular radio network (2nd Generation)
digital transmission, data communication up to 9600 Bit/s
Roaming (mobility between different net operators, international)
good transmission quality (error detection and -correction)
scalable (large number of participants possible)
Security mechanisms (authentication, authorization, encryption)
good resource use (frequency and time division multiplexing)
integration within ISDN and fixed network
standard (ETSI, European Telecommunications Standards Institute)
48
Mobile Communication and Mobile Computing
Providers in Germany (1)
• D1 T-Mobile
– subscribers: 24,6 Mio (Stand 2003)
• Vodafone D2
– old name: Mannesmann Mobilfunk D2
– subscribers: 22,7 Mio (Stand 2003)
• E-plus
• O2
– old name: VIAG Interkom
49
Mobile Communication and Mobile Computing
Providers in Germany (2)
Providers
Subscribers, millions
2001
2002
2003
World-wide
by 2003
D1 T-Mobile
22,6
23,1
24,6
82
Vodafone D2
21,9
-
22,7
112,5
E-Plus
-
7,5
-
-
O2 VIAG
Interkom
-
3,66
-
-
50
Mobile Communication and Mobile Computing
51
GSM: structure
Fixed network
Switching Subsystems
Radio Subsystems
OMC
Data
networks
VLR
HLR
AuC
EIR
(G)MSC
PSTN/
ISDN
AuC
BSS
BSC
BTS
EIR
HLR
BSC
BTS
BTS
Call Management
Network Management
Authentication Centre
Base Station Subsystem
Base Station Controller
Base Transceiver Station
Equipment Identity Register
Home Location Register
MS
(G)MSC
OMC
PSTN
VLR
ISDN
BSS
Mobile Station
(Gateway) Mobile Switching Centre
Operation and Maintenance Centre
Public Switched Telephone Network
Visitor Location Register
Integrated Services Digital Network
MS
MS
MS
Mobile Communication and Mobile Computing
GSM: Structure
Operation and Maintenance Centre (OMC)
• logical, central structure with HLR, AuC und EIR
Authentication Centre (AuC)
• authentication, storage of symmetrical keys, generation of
encryption keys
Equipment Identity Register (EIR)
• storage of device attributes of allowed, faulty and jammed
devices (white, grey, black list)
Mobile Switching Centre (MSC)
• arrangement centre, partial as gateways to other nets, assigned
to one VLR each
Base Station Subsystem (BSS): technical radio centre
• Base Station Controller (BSC): control centre
• Base Transceiver Station (BTS): radio tower / antenna
52
Mobile Communication and Mobile Computing
53
Radio technical structure
1 TDMA-Frame, 144 Bit in 4,615 ms
8 TDMA-channels, together 271 kBit/s inclusive
error protection information
124 radio frequency channels (carrier), each 200 kHz
890
935
downlink
uplink
915 MHz
960 MHz
2 frequency wavebands, for each 25 MHz, divided into radio
cells
• One or several carrier frequencies per BSC
• Physical channels defined by number and position of time slots
Mobile Communication and Mobile Computing
GSM: protocols, incoming call
BSS
VLR
BSS
(8)
(8)
(9)
BSS
(12)
(4)
(3)
(8)
(9)
(12)
(7)
(11)
(6)
(10)
MSC
HLR
(4)
(5)
(2)
GMSC
(1)
PSTN/
ISDN
(8)
BSS
(1) Call from fixed network was switched via GMSC
(2) GMSC finds out HLR from phone number and transmits need of
conversation
(3) HLR checks whether participant for a corresponding service is
authorized and asks for MSRN at the responsible VLR
(4) MSRN will be returned to GMSC, can now contact responsible MSC
54
Mobile Communication and Mobile Computing
GSM: protocols, incoming call
BSS
VLR
BSS
(8)
(8)
(9)
BSS
(12)
(4)
(3)
(8)
(9)
(7)
(11)
(6)
(10)
MSC
HLR
(4)
(5)
(2)
GMSC
(12)
(8)
BSS
(5) GMSC transmits call to current MSC
(6) ask for the state of the mobile station
(7) Information whether end terminal is active
(8) Call to all cells of the Location Area (LA)
(9) Answer from end terminal
(10 - 12) security check and connection construction
(1)
PSTN/
ISDN
55
Mobile Communication and Mobile Computing
GSM: protocols, outgoing call
BSS
BSS
(4)
(1)
BSS
HLR
VLR
(2)
(3)
MSC
(1) Demand on connection
(2) Transfer by BSS
(3-4) Control for authorization
(5) Switching of the call demand to fixed net
(5)
GMSC
56
Mobile Communication and Mobile Computing
GSM: channel strucure
Traffic Channel
• speech- / data channel (13 kbit/s brutto; differential encoding)
• units of 26 TDMA - Frames
• Half-rate traffic channel: for more efficient speech encoding with
7 kbit/s
Control Channel
• Signal information
• Monitoring of the BSCs for reconnaissance of Handover
Broadcast Control Channel
• BSC to MS (identity, frequency order etc.)
Random Access Channel
• Steering of channel entry with Aloha-procedure
Paging Channel
• signalize incoming calls
57
Mobile Communication and Mobile Computing
Databases
Home Location Register (HLR), stores data of participants, which
are reported in an HLR-area
– Semi-permanent data:
• Call number (Mobile Subscriber International ISDN Number) - MSISDN,
e.g. +49/171/333 4444 (country, net, call number)
• identity (International Mobile Subscriber Identity) - IMSI: MCC = Mobile
Country Code (262 for .de) + MNC = Mobile Network Code (01-D1, 02Vodafone-D2, 03-eplus, 07-O2) + MSIN = Mobile Subscriber
Identification Number
• Personal data (name, address, mode of payment)
• Service profile ( call transfer, Roaming-limits etc.)
– Temporary data:
• MSRN (Mobile Subscriber Roaming Number) (country, net, MSC)
• VLR-address, MSC-address
• Authentication Sets of AuC (RAND (128 Bit), SRES (128 Bit), KC
(64Bit))
• charge data
58
Mobile Communication and Mobile Computing
Databases
Visitor Location Register (VLR)
• local database of each MSC with following data:
–
–
–
–
IMSI, MSISDN
service profile
accounting information
TMSI (Temporary Mobile Subscriber Identity) - pseudonym for data
security
– MSRN
– LAI (Location Area Identity)
– MSC-address, HLR-address
59
Mobile Communication and Mobile Computing
GSM: mobile telephone areas
MSC-area = VLR-area
Handover
Location Area (LA)
radio- with
cell
BTS
LA = smallest
addressable unit
60
Mobile Communication and Mobile Computing
Connection HLR, VLR
HLR
MSC-area
VLR
advantage of the architecture:
Location Update at limited
mobility, as a rule only at VLR,
rarely at (perhaps far remote)
HLR
Location
area
61
Mobile Communication and Mobile Computing
62
Localization at GSM
VLR 10
VLR 9
IMSI LA 2
HLR 26
32311 VLR 9 IMSI
z.B. 0x62F220 01E5
LA 3
+49 0177-26 32311
LA 2
participant call number
in HLR
LA 5
LA 3
Provider
net-entry code
country code number
Mobile Communication and Mobile Computing
63
Data transmission
•
•
•
•
•
each GSM-channel configurable as a data channel; similar structure like
ISDN-B and -D-channels
data rates up to 9600 bit/s now
delay approximately 200 ms
speech channels have as a rule higher priority as data channels
kinds of channels:
– transparent (without error correction; however FEC; fixed data rate; error rate 10-3
up to 10-4)
– non-transparent (repeat of faulty data frames; very low error rate, but also less
throughput)
•
Short-Message-Service (SMS)
– connectionless transmission (up to 160 Byte) on signal channel
•
Cell Broadcast (CB)
– connectionless transmission (up to 80 Byte) on signal channel to all participants,
e.g. one cell
Mobile Communication and Mobile Computing
Data transmission - structure
BSC
MSC IWF
ISDN
UDI
BTS
Modem
TA
PSTN
Internet
IWF - Inter Working Function
UDI - Unspecified Digital
TA - Terminal Adapter
Modem
64
Mobile Communication and Mobile Computing
Security aspects: Subscriber Identity
Module (SIM)
Chip-card (Smart Cart) to personalize a mobile
subscriber (MS):
•
•
•
•
•
IMSI (International Mobile Subscriber Identity)
participant special symmetric key Ki, stored also at AuC
algorithm “A3” for Challenge-Response-Authentication
algorithm “A8” for key generation of Kc for content data
PIN (Personal Identification Number) for entry control
Temporary data:
• TMSI (Temporary Mobile Subscriber Identity)
• LAI (Location Area Identification)
• Encryption key Kc
65
Mobile Communication and Mobile Computing
Security in GSM-networks
SIM
• Entry control and cryptographic algorithms
Single-sided authentication (participant against network)
• Challenge-Response-method (cryptographic algorithm:
A3)
Pseudonyms of participants at the Radio interface
• Temporary Mobile Subscriber Identity (TMSI)
Connection encoding on the Radio interface
• Key generation: A8
• Encryption: A5
66
Mobile Communication and Mobile Computing
MS
Ki
A3
Security aspects:
Authentication
max. 128 Bit
Authentication Request
RAND (128 Bit)
MSC, VLR, AuC
Random number
generator
Ki
A3
SRES
Authentication Response
SRES (32 Bit)
•
•
•
•
Location Registration
Location Update with VLR-change
Call setup (in both directions)
SMS (Short Message Service)
=
67
Mobile Communication and Mobile Computing
Security aspects: Session Key
MS
Netz
Ki
A8
Kc
•
Authentication Request
RAND (128 Bit)
64 Bit
Key generation: Algorithm A8
–
–
–
–
–
–
Stored on SIM and in AuC
with Ki parametric one way function
no (Europe, world wide) standard
can be determined by net operator
Interfaces are standardized
combination A3/A8 known as COMP128
Random number
generator
Ki
A8
Kc
68
Mobile Communication and Mobile Computing
Security aspects: encryption at the
Radio interface
MS
Net
TDMA-framenumber
K
Ciphering Mode Command
c
TDMA-framenumber
Kc
A5
A5
Key block
+
Plain text block
Ciphering Mode Complete
Encrypted Text
114 Bit
•
Data encryption through algorithm A5:
– stored in the Mobile Station
– standardized in Europe and world wide
– weaker algorithm A5* or A5/2 for specific countries
+
Plain text block
69
Mobile Communication and Mobile Computing
GSM-Security: assessment
• cryptographic methods secret, so they are not „well
examined“
• symmetric procedure
– consequence: storage of user special secret keys
with net operators required
• low key length Ki with max. 128 Bit (could be hacked by
using Brute Force Attack in 8-12 hours)
• no mutual authentication intended
– consequence: Attacker can pretend a GSM-Net
• no end-to-end encryption
• no end-to-end authentication
• Key generation and -administration not controlled by the
participants
70
Mobile Communication and Mobile Computing
GSM Phase II+
HSCSD, GPRS
71
Mobile Communication and Mobile Computing
HSCSD: High Speed Circuit
Switched Data
72
Mobile Communication and Mobile Computing
Properties
• higher data rate because of channel
bundling
• parallel usage of several time slots (TCH) of one
frequency on Um
• more efficient channel encoding (14,4 kbit/s per TCH)
• Data rates from 9,6 up to 53,8 kbit/s
• asymmetric transmission (1TCH Uplink /
3TCH Downlink)
73
Mobile Communication and Mobile Computing
HSCSD data rates
non transparent
transparent
up- / downlink 100% coverage
1+1
2+2
1+3
1+4
9,6
19,2
-----
95% coverage 100% coverage
14,4
28,8
-------
9,6
19,2
28,8
38,4
95% coverage
13,2
26,4
39,6
53,8
74
Mobile Communication and Mobile Computing
HSCSD: structure
BSC
MSC IWF
ISDN
UDI
BTS
Modem
TA
n time slots (TCH) of
each
TDMA frame
(theoretically max. 8)
IWF - Inter Working Function
UDI - Unspecified Digital
TA - Terminal Adapter
PSTN
Internet
Modem
75
Mobile Communication and Mobile Computing
HSCSD: changes
n time slots (TCH) of
each TDMA frame
(theoretically max. 8)
BTS
Um
BSC
Abis
MSC
A
multiplex of the
time slots
on each 64 kBit/s
channel
certain changes are necessary at the component
several changes at the software/firmware
minimal changes at the software/firmware
76
Mobile Communication and Mobile Computing
HSCSD radio interface
Required time for setting to
transmission standby
Required time for setting to
receiving standby
MS RECEIVE
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
MS TRANSMIT
5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4
MS MONITOR
Required time for signal strength measure and setting to receiving standby
• parallel usage of several time slots limited to one
frequency
• Cost factor limits number of used TCH‘s to (2+2) or
(1+3, uplink, downlink)
77
Mobile Communication and Mobile Computing
Assessment of HSCSD
+ existing net structure and accounting model maintained
+ in comparison to GPRS only around1/5 of investment
necessary
+ HSCSD is still circuit switched
+ has defined QoS- settings (data rate, delay)
– one logical channel will be switched on all interfaces for the time
of the connection
– Non-efficient for burst-like traffic (Internet) or Flat Rate billing
(Logistics)
– no international acceptance (Roaming!)
• uses also more resources on the radio interface
– problems with handover into a new cell
78
Mobile Communication and Mobile Computing
GPRS: General Packet Radio
Service
79
Mobile Communication and Mobile Computing
Properties
•
•
•
•
•
•
Packet switching service (end- to- end)
Data rates up to 171,2 kbit/s (theoretical)
Effective and flexible administration of the radio interface
adaptive channel encoding
Internetworking with IP- and X.25 nets standardized
dynamic sharing of resources with „classical“ GSM
speech services
• Advantage: Billing and Accounting according to data
volume
• Disadvantage: cost intensive additional net hardware
necessary
80
Mobile Communication and Mobile Computing
Properties
– point-to-point-Packet transfer service
• PTP-CONS (PTP Connection oriented Network Service)
– connection oriented, similar to X.25
• PTP- CLNS (PTP Connectionless Network Service)
– connectionless, similar to IP
– point- to- multipoint
- group communication
81
Mobile Communication and Mobile Computing
82
GPRS: Structure
GSM
BSC
GPRS Nets
other operators
MSC
HLR
BTS
Internet
SGSN
other packet
switching
networks
GGSN
GPRS Backbone
Frame Relay / ATM
Border
Gateway
GGSN
SGSN - Serving GPRS Support Node
GGSN - Gateway GPRS Support Node
signalization data
user data
Mobile Communication and Mobile Computing
83
GPRS: Changes
GMSC
n time slots (TCH) per
TDMA frame
(theoretically max. 8)
per packet!
public
remote fixed nets
Circuit switched traffic
A
BTS
Abis
Um
HLR/AuC
GPRS register
Gs
BSC
PCU
MSC MAP
Gb
Packet arranged
traffic
SGSN
Gn
MAP
Gi
GGSN
other packet
switching
networks
modified network components
new components or extensively modified components
Existing components
PCU - Packet Control Unit
Mobile Communication and Mobile Computing
Tasks: SGSN, GGSN
SGSN:
- mobility management
- session management
MAP
Signalization
(GGSN)
- QoS
- security
BSS
PCU
Client
Client
MAP
Signalization
(SGSN)
Internet
Intranet
SGSN
BSS
PCU
BSS
PCU
External Data Domain
HLR
GGSN
SGSN
SGSN, GGSN:
- Routing
- Signalization
- Resource management
Server
84
Mobile Communication and Mobile Computing
Tasks of the SGSN
• Packet delivery
• mobility management
– apply/ sign off of terminals
– localization
• LLC (Logical Link Control) management
• authentication
• billing
85
Mobile Communication and Mobile Computing
86
Tasks of the GGSN
• mediator between GPRS backbone and
external data networks (Internet, X-25 etc.)
• converts GPRS packets, data Protocol
(PDP) into the corresponding structure
• also converts PDP addresses of incoming
packets into GSM address of the receiver
• saves current data for the SGSN address
of the participant as well as their profile
and data for authentication and invoice
Mobile Communication and Mobile Computing
GPRS: air interface
Radio Link Control (RLC)
• Segmentation of the LLC-Frames in RLC blocks
• Block size dependent on short-term channel
conditions
• Backward error correction and data flow control by
Automatic Repeat Request (ARQ) protocol
– repeating not repairable RLC blocks selectively
Medium Access Control ( MAC)
• Channel reservation contains:
- one/several time slots (Packet Data Channels
PDCH) of one
frequency
– one uplink status flag (USF) per Packet Data Channel
(PDCH), channel partition of up to 8 ms
87
Mobile Communication and Mobile Computing
GPRS: air interface
Medium Access Control ( MAC)
• Reservation in the uplink (MS to BSS):
• MS sends reservation request on a Random Access
Channel (Slotted ALOHA)
– BTS allocates a (split) channel and sends packet assignment
– MS sends data depending on the current priority (USF flag)
• Reservation in the Downlink (BSS to MS):
– BTS displays transmitting request and informs about the reserved
channel
– MS supervises the reserved channel and receives
88
Mobile Communication and Mobile Computing
GPRS: air interface
Physical Link Control
• adaptive forward error correction (FEC) dependent on shortterm channel conditions
• temporal scrambling (Interleaving) of the bursts and Mapping on
reserved PDCH (Packet Data Channel)
• procedure to recognize overbooking situations on the physical
channel
GPRS Channel Encoding
Scheme
Code
Rate
Payload
BCS
Precoded
USF
Tail bits Coded
bits
Punctured
bits
Data
rate
(kbit/s)
CS-1
1/2
181
40
3
4
456
0
9.05
CS-2
~ 2/3
268
16
6
4
588
132
13.4
CS-3
~ 3/4
312
16
6
4
676
220
15.6
CS-4
1
428
16
12
0
456
0
21.4
89
Mobile Communication and Mobile Computing
Quality of Service
• QoS profile agrees service parameters inside the whole network
• Agreed for the duration of one PDP (Packet Data Protocol)
context (session, end terminal is obtainable for the duration of
the context, e.g. obtainable over Internet ) :
– temporary address (IP) for mobile station
– tunneling information, among others GGSN, which is used for
access to corresponding packet arranged network
– type of the connection
– QoS profile
• QoS profile commits:
– precedence class, priority against other services (high, normal, low)
– packet delay class, times are valid for traffic inside the GPRSnetwork
– reliability class
– peak throughput class
– mean throughput class
90
Mobile Communication and Mobile Computing
Quality of Service
Packet delay classes
Size
128 octets
1024 octets
Class
Mean Delay
95% Delay
Mean Delay
95% Delay
1 (predictive)
< 0,5 s
< 1,5 s
<2s
<7s
2 (predictive)
<5s
< 25 s
< 15 s
< 75 s
3 (predictive)
< 50 s
< 250 s
< 75 s
< 375 s
4 (best effort)
Best effort
Security classes
Class
Lost packet
-9
1
10
2
10
3
10
-4
-2
Probability for
Out of
Duplicated
Sequence
packet
packet
-9
10
-5
10
-5
10
-9
10
-5
10
-5
10
Corrupted
packet
-9
10
-6
10
-2
10
91
Mobile Communication and Mobile Computing
Quality of Service
GPRS- using data rates
Coding # of timeslots
Scheme
1
CS-1
9,05
CS-2
13,4
CS-3
15,6
CS-4
21,4
2
18,1
26,8
31,2
42,8
3
27,15
40,2
46,8
64,2
4
36,2
53,6
62,4
85,6
5
45,25
67
78
107
6
54,3
80,4
93,6
128,4
7
63,35
93,8
109,2
149,8
8
72,4
107,2
124,8
171,2
• CS 3 and CS 4 are only reasonable in the second phase of
GPRS introduction
• They will be used adaptively at corresponding good quality of
radio connection
• CS 4 does not comprise error correction, code rate = 1!
92
Mobile Communication and Mobile Computing
Assessment of GPRS
+ An up to 4 times higher data rate in comparison to ordinary GSMdata services
+ better resource management through packet arranged service
+ „always on” data service (email, etc.)
+ GPRS is a more suitable carrier for services like WAP
- IP-derivate, no true guaranties (QoS)
- development of the network infrastructure is relatively expensive,
particularly regarding introduction to UMTS (return of investment)
- GPRS doesn’t give such data rates like advertising has sometimes
promised
93
Mobile Communication and Mobile Computing
26.4 kbit/s
13.2 kbit/s
9.6 kbit/s
CS 1
CS 2
40.2 kbit/s
27.2 kbit/s
26.8 kbit/s
18.1 kbit/s
13.4 kbit/s
9 kbit/s
flow
GPRS
Packet arranged
39.6 kbit/s
HSCSD
Channel packing, NT
Data rate
Development of the GSM-data
services
94
Mobile Communication and Mobile Computing
Enhanced Services - EMS (enhanced
message service)
• Uses widespread existing infrastructure (SMS)
• new Mobile telephones necessary
• allows sending and receiving of messages with formatted texts,
melodies, graphics (32 x 32 Pixel) and animations (16 x 16 Pixel) –
e.g. NOKIA
• new applications like Mobile Ticketing
• tickets will be transferred to mobile phone like a bar code and
checked at the admission
• EMS enables transition to MMS (multimedia messaging service),
which allows transmission of multimedia enriched messages over
UMTS-Network (photos, parts of videos)
• MMS requires new network elements in the Infrastructure of the
operators
95
Mobile Communication and Mobile Computing
MMS - architecture
MMS User
Databases
HLR
LDAP
MMS
Relay
WAP or MExE
(e.g. Java and TCP/IP)
MMS User
Agent
alien MMS
Relay
GSM-MAP or
IS-41-MAP or
TCP/IP
SMTP, HTTP,
POP3,
IMAPv4
SMTP
MMS Server
(e.g. E-Mail)
Based on materials from 3GPP, http://www.3gpp.org
MMS Server
(e.g. Fax)
...
MMS Server
(other service)
96
Mobile Communication and Mobile Computing
UMTS:
Universal Mobile
Telecommunications System, 3G,
3rd generation of mobile radio
97
Mobile Communication and Mobile Computing
98
IMT-2000 - structure
individual carrier
IMT-SC
UWC-136 (EDGE)
multiple carrier
IMT-FT
DECT
IMT-DS
UTRA-FDD
IMT-MC
CDMA2000
• 3 systems
- UMTS
- CDMA2000
- UWC-136
TDMA
• 2 core technologies
- TDMA
- CDMA
IMT-2000
FDD
CDMA
UTRA-TDD
TDD
IMT-TC
TD-SCDMA
satellite- supported network expansion:
- SW-CDMA: Satellite Wideband CMDA
- SW-CDTMA: Satellite Wideband CDMA/TDMA
(Hybride procedure)
- SAT-CDMA: Satellite CDMA
- ICO RTT: ICO Radio Transmission Technology
ICO RTT... Standard by ICO Global Communications
IMT ... International Mobile Telecommunications
UTRA ... Universal Terrestrial Radio Access
UWC ... Universal Wireless Communications
source: www.UMTS-Report.com
IMT-2000 family of radio
interfaces :
–
–
–
In europe
UMTS
–
–
IMT-DS (Direct Spread)
• UTRA-FDD (UMTS)
IMT-MC (Multi Carrier)
• CDMA2000, USA
IMT-TC (Time Code)
• UTRA-TDD (UMTS), TDSCDMA (Synchronous Code
Division Multiple Access,
China)
IMT-SC (Single Carrier)
• UWC-136, USA
IMT-FT (Frequency time)
• DECT
Mobile Communication and Mobile Computing
Worldwide frequency assignment for IMT-200
• developed by ITU
PCS... Personal Communication System
MSS...Mobile Satellite Service
PHS... Personal Handy-Phone System
99
Mobile Communication and Mobile Computing
UMTS - Facts
•
•
•
•
consideration: early 90ies
Universal Mobile Telecommunications System, developed in the EU (ETSI:
European Telecommunication Standards Institute)
UMTS is the European implementation of IMT-2000 (International Mobile
Telecommunications by the year 2000)
Start of network expansion:
– in Europe: 2003 (some trials, e.g. British Telecom on Isle of Man, 2002)
– in the USA: 2005
– in Japan since 2000 : NTT DOCOMO
100
Mobile Communication and Mobile Computing
101
Frequency award in Europe
1700
•
•
•
1750
1800
1850
1900
FDD MSS
Uplink
1950
TDD
GSM1800
Downlink
GSM1800
Uplink
DECT
TDD
230 MHz frequency range for IMT-2000
2000
FDD MSS
Downlink
2050 2100 2150 2200
MSS…Satellite- based
at FDD symmetrical spectrum is necessary, not at TDD (time slots at same
frequency)
gradual new assignment of wavebands
depending on development of the need up to 300-500 MHz frequency range
in 2008
source: www.UMTS-Report.com
Mobile Communication and Mobile Computing
Characteristics
•
system general , worldwide roaming
•
high data rates: 144 kbit/s mobile, up to 2 Mbit/s at local area
•
fusion of different mobile radio communications-, wireless- and pager-systems into
one common system
•
speech-, data-, and multimedia- information services independent of used network
access
•
support of different carrier services:
–
real-time capable/not real-time capable
–
circuit switched/ packet switched
•
Roaming also between UMTS and GSM and satellite networks
•
Asymmetrical data rates in up-/downlink
102
Mobile Communication and Mobile Computing
103
UMTS- Disadvantages
•
•
Technology not yet perfect
rent ability of pico cells („Hotspots“) not yet analyzed
•
•
•
strong contention by WLAN
increased radiation exposure
high data rate only obtainable sometimes (High-Tech-network expansion, stationary
and exclusive usage necessary!)
•
because of high license costs
costs)
high charges necessary (around double GSM-
Mobile Communication and Mobile Computing
UMTS - Performance
Transmission
Real- time (Video)
Not Real-time (SMS etc.)
Bit error rate
10-3 … 10-7
10-5 … 10-8
Permitted delay
20ms … 300ms
> 150 ms
UMTS Photo Report
GPRS
ISDN
Web
Mail
PSTN
GSM
~ 0 sec
Video
Photo
Report Video
Photo
Web
Mail
Web
Mail
10 sec
Report Video
Photo
Web
Photo
1 min
Report
Video
10 min
1h
source: Mobilkom Austria
104
Mobile Communication and Mobile Computing
UMTS - Hardware
•
•
•
big color displays
high resolution
True Color
105
Mobile Communication and Mobile Computing
106
UMTS- cell structure
UMTS-Core
Network
circuit
switched
PSTN/
ISDN
Visitor
Location
Register
Base Station Controller
BTS
Radio
access
network
BTS
BTS
GSM - BSS
Quelle: Mobilkom Austria
Gateway
Mobile
Switching
Centre
Home
Location
Register
Gateway
GPRS
Support
Node
Internet
customer
3G- Serving
GPRS
Intranet
Support
packetNode
3G
Mobile
Switching
Centre
switched
Radio Network Controller
Radio Network Controller
BTS
BTS
BTS
BTS
BTS
BTS
UTRAN- UMTS Terrestrial Radio Access Network
Mobile Communication and Mobile Computing
UMTS: cell structure
Satellite
Zone 4: Global
“World cell”
Zone 3: Suburban
“Macro cell”
Zone 2: Neighborhood
Zone1: In-building
“Micro
cell”
“Pico cell”
PDA terminal
Basic terminal
Audio/visual terminal
Integration with the fixed network
107
Mobile Communication and Mobile Computing
UMTS: hierarchical cell structure
principle:
- all neighbor cells use same frequency channel
- only one waveband is necessary for cellular construction
- further wavebands are necessary for hierarchical structure
Global
Regional
Lokal
Home/
Office
World
Micro
Macro
Max.
velocity
(mph)
Pico
expansion
Data
rate
(kbit/s)
Special features
World Cell
global
-
Macro Cell
Up to 1,24 miles
144
310
complete national UMTS support
Micro Cell
Up to 0,62 miles
384
74
Greater cities, commonly used
Pico Cell
> 60miles
2000
6,2!
„Hotspots“ – e.g. airport, station
no UTRAN, other technology!
108
Mobile Communication and Mobile Computing
Classification
109
Mobile Communication and Mobile Computing
Service concept
• Virtual Home Environment (VHE): offered
services are freely configurable, configuration
still exists in the whole network
• choose of service quality and also arising costs
• behave at bottlenecks (data rates, etc.)
configurable
• dynamic customization to connection
110
Mobile Communication and Mobile Computing
UPT: Universal Personal
Telecommunication Service
• one phone number for several devices (CallManagement)
• subscriber localization e.g. with SIM-card
• call passing
• virtual mobility of fixed networks
111
Mobile Communication and Mobile Computing
Intelligent networks
• Implementation of basic services like subscriber
localization billing etc.
• supply of value added service (Voice-Mailbox, etc.)
– possibility of easy, fast introduction of new services
– flexible service administration
– usage of services also from foreign network possible
– better control of service parameters through
subscriber
112
Mobile Communication and Mobile Computing
UMTS: basic network structure
•
Access Network: base stations, responsible for radio contact to mobile
end devices
•
Core Network (Fixed Network): responsible for structure of connections
•
Intelligent Network (IN): responsible for billing, subscriber localization,
Roaming, Handover
Intelligent Network
Access
Network
User Equipment (UE)
Core Network
113
Mobile Communication and Mobile Computing
General reference architecture
UE
UTRAN
Uu
•
CN
Iu
UTRA: UMTS Terrestrial Radio Access
– UTRAN (UTRA- Network) contains several radio subsystems, so called Radio
Network Subsystems (RNS) and contains functions for mobility management
– RNS controls handover at cell change, capacitates functions for the encoding
and administrates the resources of the radio interface
– Uu connects UTRAN with mobile end devices, so called User Equipment (UE), is
comparable with Um in GSM
– UTRAN is connected over Iu with the Core Network, comparable with the A
interface in GSM between BSC and MSC
– CN contains the interfaces to other networks and mechanisms for connection
handover to other systems
114
Mobile Communication and Mobile Computing
The UMTS-radio interface UTRA
(UMTS Terrestrial Radio Access)
• Two modes defined:
– UTRA/FDD (Frequency Division Duplex)
• mainly in suburban areas for symmetrical transmission of
speech and video
• data rates up to 384 kbit/s, supra-regional roaming
• for circuit- and packet switched services in urban areas
– UTRA/TDD (Time Division Duplex)
• mainly in households and other restricted areas (company's
premises, similar to DECT)
• for broadcast of speech and video, both symmetrical: up to
384 kbit/s
• also asymmetrical:
up to 2 Mbit/s
115
Mobile Communication and Mobile Computing
UTRA/FDD
•
•
•
•
puts wide- band- CDMA (W-CDMA) together with DSSS (Direct
Sequence Spread Spectrum) as spread spectrum technique
channel separation by carrier frequencies, spreading code and phase
position (only uplink)
ca. 250 channels for used data, data rates up to 2 Mbit/s
complex performance control necessary
f in MHz
2169,7
2110,9
carrier 12
.
.
.
carrier 1
downlink
5 MHz
1979,7
1920,9
carrier 12
.
.
.
carrier 1
190 MHz
uplink
t
116
Mobile Communication and Mobile Computing
UTRA/TDD
•
•
•
•
•
•
•
puts wideband- TDMA/CDMA together with DSSS
sends and receives on same carrier (TDD)
ca. 120 channels for used data, data rates up to 2 Mbit/s
channel separation by spread code and time slots
less spreading than at FDD
precise synchronization necessary
lower demand for performance control
f in MHz
uplink
downlink
2020,1
2010,1
carrier 6
1920,1
carrier 4
.
.
.
carrier 1
1900,1
carrier 5
5 MHz
t
117
Mobile Communication and Mobile Computing
118
Frequency award for UMTS
satellite- based
1885 1920
1980
2010
2025
2110
2170
MHz
terrestrial
60 GHz
MBS
Extension Bands (for a future market potential ..from 2005)
Extension Band 1 (worldwide similar) – partly terrestrial, partly satellite- based
Existing Nets
470 862
satellite-based
GSM,
DECT
2290 2300 2520 2670 2700 2900 MHz 880 1885 MHz 1675
1710 MHz
Mobile Communication and Mobile Computing
UMTS-licenses in Germany
•
•
•
•
•
•
E-Plus Hutchison
8.394.492.363 €
RegTP determined:
Group 3G
- till end of 2003 25 % network coverage
8.408.706.278 €
- till end of 2005 50 % network coverage
Vodafone
(Mannesmann Mobilfunk)
8.422.920.192 €
MobilCom Multimedia
8.369.848.095 €
T-Mobil
8.478.344.232 €
O2 (VIAG Interkom)
8.445.008.001 €
17.08.2000: each license got 2 x 5 MHz packets, 60 MHz have been given away
altogether, 150 MHz are available altogether
119
Mobile Communication and Mobile Computing
Summary
• introduced variants are the proposals, which will be
supported by Europe, Japan and partly by the USA
• worldwide accessibility can be realized only with
multimode end devices
• even in Europe combined UTRA-FDD/UTRATDD/GSM- devices are necessary (those are realized
by the identical frame time of 10ms at relatively low
costs)
120
Mobile Communication and Mobile Computing
Wireless Local Networks,
WLAN
121
Mobile Communication and Mobile Computing
Why do we need wireless LANs?
Advantages
• flexibility
• Ad-hoc-network realizable with less expenditure
• No problems with cables
Disadvantages
• high error vulnerability on the transmission link in comparison to
Standard-LANs
• National restrictions, no international standards at used frequency
bands (Industrial Scientific Medical (ISM)- Band)
• security, costs
122
Mobile Communication and Mobile Computing
Application areas
•
•
•
•
•
•
networks in exhibition halls
hospitals
warehouses
airports
structure of networks in historic buildings
extension of existing wired local area networks
in offices, universities etc.
123
Mobile Communication and Mobile Computing
Problems with the use of WLAN‘s
– physical problems
• interference: band spreading
• echo: use of special antennas
• Hidden Terminal problem: use CSMA/CA
– data security
• Wired Equivalent Privacy (WEP) service
further development WiFi (Wireless Fidelity),
WPA (WiFi Protected Access)
124
Mobile Communication and Mobile Computing
Standards
• IEEE 802.11 (a,b,g ; optional e,h,i)
– frequency band 2,4 GHz, also in the 5GHz - band
– data rates: 1 bis 11 Mbit/s (at present, later up to 20 (2,4 GHz) or
54 Mbit/s (5,4 GHz))
– WiFi: Wireless Fidelity, certificate from the WECA (Wireless
Compatibility Allicance), secures the interoperability between the
Radio- LANs and contains improved security mechanisms
• HomeRF
• Bluetooth (IEEE 802.15)
– Frequency band: 2,4 GHz
– Data rate: 1 Mbit/s; in the future also 20 Mbit/s
– connection of peripherals
• HIPERLAN (ETSI) / Wireless ATM
– frequency bands 5,15 / 5,30 GHz and 17,1 / 17,3 GHz
– data rates: 24 Mbit/s or 155 Mbit/s
– however no practical relevance
125
Mobile Communication and Mobile Computing
IEEE 802.11b
• frequency:
– 2,4 GHz frequency band, also called ISM (= Industrial Scientific
Medical Band), not regulated
– 850 - 950 nm at infrared
• transmission power:
– min. 1mW
– max. 100mW in Europe (1W in the USA)
• reach:
– of 10m (IR) to 30km or more with the help of special antennas
(directional antennas)
126
Mobile Communication and Mobile Computing
Basic WLAN- structure
Ad-hoc-network:
3 connected infrastructure networks:
STA4 STA5
AP
AP
AP - Access Point
AP
127
Mobile Communication and Mobile Computing
System architecture IEEE 802.11
802.x LAN
ESS
STA1
802.11 LAN
BSS1
Access
Point
Portal
Distribution System
Access
Point
BSS2
STA2
802.11 LAN
STA3
128
Mobile Communication and Mobile Computing
System architecture IEEE 802.11,
concepts
• Station (STA)
– device with 802.11- concurring interface
• Access Point
– allows the access to the distribution system for registered stations and
secures accessibility of the stations also beyond the BSS
• Coordination Function (CF)
– logical functional unit, which decides when a station can send
• Basic Service Set (BSS)
– consists of several stations, that were controlled by an CF, e.g. BSS2
and STA2, STA3
129
Mobile Communication and Mobile Computing
System architecture IEEE 802.11,
concepts
• Distribution System
– connects several BSS over access points and forms a logically larger
net
• Extended Service Set (ESS)
– Radio networks, which are connected over Distribution System
• Portal
– allows transition into other networks
130
Mobile Communication and Mobile Computing
131
Overview
• 802.11 is the most frequently used solution for wireless connection;
very strong distribution on the market
• interesting future option: „Seamless Handover“ between GSM and
IEEE 802.11; supported by Cisco, Intel etc. (alternative to UMTS?)
• higher data rates already standardized or in use
– 802.11a: physical layer at 5 GHz – Band, data rates up to 54 MBit/s
– 802.11b: extension to physical layer for the 2,4 GHz – band, data rates
up to 11 MBit/s, products available
– 802.11g: at present the industry works on an extension, shall allow the
up to 54Mbit/s in the frequency band around 2.4 GHz
– Study Group 5GSG: examines the harmonization between IEEE 802.11
and ETSI HiperLAN
– Task Group e: MAC functions for QoS-Management and to refine
improved safety functions, introduction of service classes etc.
Mobile Communication and Mobile Computing
132
802.11 – Norms for WLAN
802.11
Since end of 1990; RadioLAN; B=1-2 MBit/s; ISM-Band F=2,4GHz; low Interoperability
and bit rate!
802.11b
11MBit/s, actual Standard, existed NICs and APs; ISM-Band F=2,4GHz; possesses
further sub-standards
802.11a
Since 2000; competition with 802.11b; up to 54 MBit/s; F=5,1 GHz, correspond.
national restrictions: in the buildings
802.11g
Ratification March, 2003; first pre-standard products; ISM-Band 2,4GHz; up to 54
MBit/s;
802.11e
Sub-standard; planed for end 2003; use of QoS-approaches; realization of multimedia
applications/ Voice over IP over WLAN
802.11h
Sub-standard / method for 802.11a; optional functionality – transmission power control
of radio interface by national via RegTP prescribed norms; correspond. especially for
Germany 802.11a or h
802.11i
Sub-standard; security approaches for WLAN (encryption, authentication)
WPA
WiFi Protected Access; Substandard; competition with 802.11i
802.11c
Sub-standard; Method of Wireless-Bridging
802.11d
Sub-standard; country specifics for 802.11b
802.11f
Sub-standard; Routing between radio cells of different vendors by IAPP (Inter-AccessPoint Protocol)
Mobile Communication and Mobile Computing
Parameters
133
Standards 802.11
802.11
802.11b
802.11a / h
802.11g
Frequency
band, GHz
2,4 (ISM-Band)
2,4 (ISM-Band)
5,1
2,4 (ISM-Band)
Bit rate, MBit/s
1-11
11
54
54
Use field
building, territory
building, territory
in the buildings
building, territory
Deployment
End 1990
actually
Since 2000
Since March 2003
Available
Hardware
Marketable NICs
and APs
Marketable NICs
and APs
Experimental
operation
Pre-standard
Products
Data security
WEP
64/128/256 bit
WEP
802.11i - security approaches for
WLAN (encryption, authentication);
WPA - WiFi Protected Access
(competition with 802.11i)
QoS for
multimediatransmission
none
none
802.11e (Ende 2003): use of QoSapproaches; realization of
multimedia applications/ Voice
over IP
Problematic
•
•
low bit rate
low bit rate
low
interoperability
National
restrictions
Pre-standard
Mobile Communication and Mobile Computing
Example: Lucent Wavelan
802.11b WLAN Card
• Wireless connection that acts just like a
conventional Ethernet link
• Technical specifications:
– 11 Mbps wireless connection
– 40-bit WEP or 104-bit RC4 link layer encryption
– Interoperability with other cards of IEEE 802.11b (i.e.
Cisco Aironet or the Apple Airport Card)
– Tiny size - a PCMCIA card less than 1 inch
– Cross-platform support (Linux, Mac, and Win*)
– Very low cost (comparable to a PCMCIA 10/100
Ethernet card)
http://www.lucent.com/
134
Mobile Communication and Mobile Computing
Example: Globalsuntech
802.11b products
• Bit rates: 22/11/5.5/2/1 MBit/s per channel
• WEP 64/128/256 Bit
• Available devices:
–
–
–
–
Card Bus
PCMCIA Card
PCI Card
Mini USB
• DSSS; selectable channels:
– USA, Canada - 11 channels
– Europe - 13 channels
– Japan - 14 channels
• Sensitivity, range:
– 80dBm for 22MBit/s
– 92dBm for 1MBit/s
http://www.globalsuntech.com/
• Cross-platform support (Linux, Win*)
135
Mobile Communication and Mobile Computing
Further Scenarios (1)
Scenario 1: Wireless Access
Wireless Access Point
(Hub Type)
LAN
WLAN
PCs
Wireless PC
136
Mobile Communication and Mobile Computing
Further Scenarios (2)
Scenario 2: Wireless Bridging
Ethernet Hub
Wireless Access
Point (Bridge Type)
Wireless PCs
WLAN LAN
137
Mobile Communication and Mobile Computing
Further Scenarios (3)
Scenario 3: Share Wireless AP
Internet
Cable/DSL-Modem
Wireless Access
Point (Router Type)
WAN
WLAN
Wireless PCs
138
Mobile Communication and Mobile Computing
Further Scenarios (4)
Scenario 4: Wireless/Wired
Routing
Internet
Cable/DSL-Modem
Cable/DSL- Wireless/
Wired Router
WAN
LAN
LAN
WLAN
Wireless PCs
139
Mobile Communication and Mobile Computing
UMTS vs WLAN
140
Mobile Communication and Mobile Computing
141
Mobility and data rates
mobility
UMTS: better mobility, connectivity
WLAN: higher data rates, more cheap, but no telephone
Vehicle
0,4
WLAN
2,0
Walk
3G –
UMTS
UMTS (best support)
5,5
2G
TDSL
65,5
ISDN
in minutes, trailer , 30 MB
Source: Focus, 34/2002
Fixed
WLAN
Bluetooth
0,1
Source: http://www.netant.no
LAN
1
10
100
Data rate [Mbit/s]
Mobile Communication and Mobile Computing
142
WLAN- Spectrum Allocation
HIPERLAN
License exempt.
455 MHz
HIPERLAN
High Speed wireless access
Sharing rules
100 MHz
U-NII
U-NII
Unlicensed
300 MHz
5100
5200
5300
5400
5500
5600
5700
5800
5900
Frequency [MHz]
U-NII ... Unlicensed national information infrastructure
source: www.ist-mind.org, www.3gpp.org
Mobile Communication and Mobile Computing
143
Interworking UMTS/WLAN
- User should be notified of any possible degradation
- subscriber database could be shared, or separated
in HLR/HSS (3GPP) or AAA (IETF) format
Three classes:
- no coupling
- loose coupling
- tight coupling
no coupling
UMTS/WLAN
as completely
independent
Pro:
- Rapid introduction
- no impact on GSN nodes
Contra: - poor handover
- no common database,
billing
AAA ... Authentication, authorization,
accounting
loose coupling
UMTS/WLAN
use same database
in AAA format
- good handling
- no impact on GSN nodes
- poor handover
tight coupling
HIPERLAN/2 is connected
through UTRAN to UMTS,
using special interface
- improved handover
performance
- HIPERLAN/2 have to
support complete UMTS
interface
- feasible if operator have
both networks
Mobile Communication and Mobile Computing
144
Data security in WLAN and UMTS
Data security for WLAN:
• 802.11i
-
•
WPA - WiFi Protected Access
−
−
−
•
new, additionally standards 802.11a/h and
802.11g
complex solution for security
packet encryption
key distribution via RADIUS -Remote Access
Dial-In User Service
packet authentication
partial compatibility with IPsec
relevant against all attacks
preliminary to 802.11i
properties similar to 802.11i
competition to 802.11i
WEP - Wired Equivalent Privacy
-
additionally to standard 802.11b, partially
obsolete!!!
users mobility between several AccessPoints, without re-configuration (roaming)
disadvantages:
-
short key of 64 / 128 bit
different, partially contradictory statements to
offered security
Data security for UMTS:
• IPsec
- Client/Server based, Clients and
IPsec-Servers negotiate dynamic
keys
- tolerant, relevant for key
assignment to IP-subnets and
against all Internet-attacks
- secrecy on the network layer:
• IP-datagrams
• TCP/UDP-segments
• ICMP/SNMP-messages
- Encryption via DES, 3DES and 40bit-DES
- authentication via
- “IP Encapsulating Security
Payload" (RFC 2406, 1998)
- “IP Authentication Header” (RFC
2402, 1998)
Mobile Communication and Mobile Computing
HomeRF (Radio Frequency)
•
•
•
•
competitive standard to IEEE 802.11
Up to 128 network nodes
Frequency jump in separations of 3MHz or 5MHz
Low costs and support of synchronous services: DECT
speech support
• 2,4 GHz (FHSS), transition power max. 100 mW,
• Shared Wireless Access Protocol (SWAP):
– hybrid protocol of DECT (TDMA) and CSMA according to
IEEE802.11 (modified)
• up to 6 wireless fixed network connections
• however sinking market shares in comparison with IEEE
802.11
145
Mobile Communication and Mobile Computing
HomeRF
• data rate 1-2 Mbit/s
• 50 m reach within buildings
• Supplier: e.g. Intel with ANYPOINT (wireless home
network)
• future:
– HomeRF + Bluetooth: DUAL MODE SYSTEM (Symbionics)
+ ad-hoc possibly
+ voice transmission
- today only few manufactures
146
Mobile Communication and Mobile Computing
Wireless City Networking
via 802.16
IEEE Wireless MAN/
ETSI Hiper MAN
147
Mobile Communication and Mobile Computing
Wireless City Networking:
scenarios
• new IEEE 802.16
standards can provide
great regions with
fast Internet services
• Use fields:
–
–
–
–
office materials shops
cafes
at the railway stations
to surf at the parks
148
Mobile Communication and Mobile Computing
USA: Wireless MAN
• Wireless MAN: 802.16-version in USA
• Backgrounds:
– competition to T-Mobile USA - mobile radio
network provider
– great number of 802.11-Internet service
providers (ISP via Wireless LAN)
– wide spread 802.11x – networks in the
country
– via 802.11 provided approx. 2500 regions
149
Mobile Communication and Mobile Computing
Europa: Hiper MAN
• ETSI (European Telecommunications
Standard Institute):
– activities in the range of 802.16 –
development of Hiper MAN
• new marketable products: since July 2004
(according to announcement of Fujitsu
Europe)
150
Mobile Communication and Mobile Computing
802.16 / 802.16a
• Wireless MAN Standard 802.16
–
–
–
–
–
developed end of month January 2003
frequency bandwidth: 10 up to 66 GHz
reach: up to 50 km (30 miles)
data rate: up to 134 MBit/s
new 802.16x standards can provide great regions with fast
Internet service, momentary trial operation in Boston/USA (ISP
via Wireless MAN)
• Start-Standard 802.16a
–
–
–
–
–
–
frequency bandwidth: 2-11 GHz
reach: up to 50 km (30 miles)
data rate: up to 70 MBit/s only
predominantly conceptualized for fast links of hotspots
can be used to establishment of private DSL-links
final operation inset: January 2005
151
Mobile Communication and Mobile Computing
802.16a-Forum
• Members:
– Airspan Networks, Alvarion, Aperto Networks,
Ensemble Communication, Fujitsu of America,
Intel, Nokia, Proxim, Wi-LAN
• Aims:
– to provide compatibility of 802.16a-products
among each other
152
Mobile Communication and Mobile Computing
153
Conclusion: 802.16 vs 802.11
802.11
802.16
+ advantage:
+ advantage:
– in spite of sharp competition to
Mobile Radio (IMT2000/UMTS)
802.11x gained the mass market
– well-elaborated 802.11x (x = a, b,
c, d, e, f, g, h, i, WPA)
− disadvantage:
– existing bandwidth problems (at
most up to 54 Mbit/s)
– reach at most up to 100m without
directional antennas
– covers approx. 50km (30 miles)
– substitution via 802.16 as access
techniques possible
– in future cost-efficient in
comparison to 802.11
− disadvantage:
– averaged investment for leased
circuits amounting to 1000$ per
location necessary
– sharp competition to Mobile Radio
(IMT2000/UMTS): to occupy the
market is for Wireless Networks
more important as for Mobile
Radio!
– final operation inset: planned
January 2005 only
Mobile Communication and Mobile Computing
Better than UMTS: future use
scenarios of 802.16
Scenario: fast Internet
WWWServer/
Internet
(1) via ISDN, Modem,
DSL
WAN
ISP via Wireless MAN
PC/LAN
(2) via Wireless MAN
Access Point
WAN
Wireless MAN 802.16
up to 50 Km (30 miles)
70-134 Mbit/s
Wireless PCs
IntranetFirewall
154
Mobile Communication and Mobile Computing
Bluetooth
155
Mobile Communication and Mobile Computing
Bluetooth - Facts
•
•
•
•
•
•
•
Harald Bluetooth was the King of Denmark in the 10th century
1998 started from Ericsson, Intel, IBM, Nokia, Toshiba
Open Standard: IEEE 802.15.1
Generally for wireless Ad-hoc- piconets (Range < 10m)
Goal: not expensive One-Chip-Decision for radio/ wireless
communication networks
Use fields:
– Connection of peripheral devices
– Support of Ad-Hoc-Nets
– Connection of different networks
Frequency band in IMS-Range of 2,4 GHz
156
Mobile Communication and Mobile Computing
Bluetooth
• Pico nets with up to 8 participants (ad-hoc) (one master,
slaves)
• Scatter nets as an association of different pico nets
• frequency hopping is used for improving of interception
safety and system robustness
157
Mobile Communication and Mobile Computing
158
Bluetooth - properties
•
•
Range:
- 10 cm up to 10 m at 1 mW transmitting power
- up to 100m at 100mW
Data rates:
– 433,9 kBit/s asynchronous-symmetrical
– 723,2 kBit/s / 57,6 kbit/s asynchronousasymmetrical
– 64 kBit/s synchronous, voice service
– In future up to 20 Mbit/s (IEEE 802.15.3)
Basic set-up Bluetooth
2,4-GhzHF
BluetoothBasebandController
HostSystem
Mobile Communication and Mobile Computing
159
Bluetooth-comparison
FUNCTION
Bluetooth v1.1
IrDA Data 1.1
IEEE802.11
(WLAN)
Range w/o PA:
10 meter max.
1 meter max.
50 meter max.
Angle:
omni-directional
ca 30°
omni-directional
RF Frequency
Band:
ISM Band, 2.4 GHz
Infrared Radiation
ISM Band, 2.4 GHz
Mobility:
mobile
stationary
mobile
Data rate:
721kBit/s
4MBit/s
2MBit/s
Security level:
High
Low
High
Source: http://www.okisemi.com
Mobile Communication and Mobile Computing
Bluetooth- functionality
Not connected
Standby
Standby
t =2 s
connectionstatus
Inquiry after
unknown
Address
Page after
unknown
Address
t =0,6 s
active
states
Low-Powerstates
Send data
PARK
MAC-Address
resigned
connected
HOLD
SNIFF
MAC-Address
available
160
Mobile Communication and Mobile Computing
161
Bluetooth – architecture (1)
Applications
Data
Data
TCS,SDP,RFCOMM
L2CAP
HCL
connection between Hardware and upper protocol (only
necessary, if L2CAP not implemented in Hardware!)
LMP
connection between end devices
In hardware
implemented !
Baseband
Radio
Physical connection interface
TCS …Telephony Control Protocol Specification
SDP … Service discovery protocol
RFCOMM … RF communication protocol (cable replacement protocol)
LMP …
Link Manager Protocol
HCL …
Host Controller
L2CAP … Logical Link Control and Adaptation Protocol
Mobile Communication and Mobile Computing
Bluetooth- architecture (2)
Radio Layer
- work area: ISM-Band (2,4 Ghz)
- Spread Spectrum Communication
- Frequency Hopping- Technology
- high error rate acceptability through CVSD-encoding at
heavy micro wave load
Baseband
- controls Radio- Layer
2 Modes:
- Synchronous, connection-oriented transfer (SCO)
voice connections need symmetrical, circuit-switched
point-to-point-connections,
Master reserves two successive time slots (up- and
downstream)
- Asynchronous, connectionless transfer (ACL)
data transfers need symmetrical or
asymmetrical, packet-switched point-to-point/multipointtransfers, master uses polling
CVSD… Continuously Variable Slop Delta (Sprachkodierung)
162
Mobile Communication and Mobile Computing
Bluetooth- architecture
Link Manager Protocol
3 Functions
- Piconet management
- link configuration
- security functions
Logical Link Control and Adaption Protocol
Functions:
- Mutiplexing (different applications can use connection between 2 devices
simultaneously)
- Reduzierung der Paketgröße der Anwendungen auf akzeptable
Baseband- Paket- Größe
- Quality of Service
163
Mobile Communication and Mobile Computing
Possible configurations
Master
Slave
Piconet
Scatter net
164
Mobile Communication and Mobile Computing
possible configurations
Piconet
Scatternet
Slave 3
Slave 1
Master
Slave 4
Master
Slave 5
Scatternet
Slave 2
Piconet 2
Piconet 1
Bluetooth
GSM
a) Peer to Peer (or 1 Master and 1 Slave)
b) Multi-slave (up to 7 "slaves" with 1 Master)
• association of different pico nets
• frequency hopping : jumps in
k steps (k = 0…22 or 79)
with Δf distances in ISM-band
165
Mobile Communication and Mobile Computing
Bluetooth - Frequencies
Country
Frequency range
[MHz]
Spain
2445 – 2475
France
2446,5 – 2483,5
Japan
2471 – 2497
other Europe / USA
2446,5 – 2483,5
RF channels
fk = 2449 + k Δf
fk = 2454 + k Δf
fk = 2473 + k Δf
fk = 2402 + k Δf
Multiplier
k = 0,…,22
k = 0,…,22
k = 0,…,22
k = 0,…,78
Δf… frequency distance between channels
- different frequencies around the world
Goal: Harmonization of wavebands
Source: http://www.mobileinfo.com
166
Mobile Communication and Mobile Computing
167
Bluetooth - Framestructure
Frame
fk
one
Slot
Packet
625 µs
one slot
Single slot frame
source: http://www.intel.com
fk+1
three3slotSlot-packets
Packets
Slave
Master
fk+1
one
Slot
Packet
Slave
Master
fk
Frame
one
Slot
Packet
625 µs
one slot
Multi slot frame
Mobile Communication and Mobile Computing
Bluetooth – security
- 128 Bit Key encryption and authentication
- every device has own 48 Bit- address
- over 281 .1012 devices can keep apart
- low range (manipulation only local!)
PIN
PIN
E2
E2
Authentication
Link Key
Link Key
E3
E3
Encryption
Encryption Key
source: http://www.intel.com
Encyption Key
user input
(Initialization)
(possible)
permanent
storage
temporary
storage
168
Mobile Communication and Mobile Computing
Bluetooth – security
169
Generic access:
Three modes
- non-secure
- service level enforced security
- link level enforced security
For Devices:
two modes
- trusted
- untrusted
Bluetooth device initiates security
procedures before the channel is established
Bluetooth is not secure
enough for critical transmissions
(billing etc.)
for Services:
three modes:
- services that require authorization and authentication
- services that require authentication only
- services that are open to all devices
Sources: http://www.niksula.cs.hut.fi,
Müller T., Bluetooth Security Architecture
Mobile Communication and Mobile Computing
Bluetooth – applications (1)
• replaces perhaps infrared in the area of the coupling of peripherals
completely
• „Intelligent Shop“
– shop informs the buyer about special offers by mobile phone or handles
inquiries for offers in the individual halls
• Bluetooth-capable ticket machine
– Payment over mobile telephone is carried out without contacts
• control of home appliances by mobile telephone
• lower layers are developed further in the context of the IEEE 802.15
working group (WPAN - Wireless Personal Area Networks)
– higher data rates, further frequencies, but possible interferences with
other systems
170
Mobile Communication and Mobile Computing
Bluetooth - applications
wireless connection
Headset Handy
171
Mobile Communication and Mobile Computing
172
HIPERLAN
HIPERLAN/1
wireless LAN (as extension to conventional LANs)
5,15 - 5,25 GHz, ca. 20 Mbps, reach > 50 m,
mobility < 10m/s
decentralized Ad-hoc net, no QoS-guarantee
HIPERLAN/2
wireless ATM-LAN (as extension to ATM and IP nets)
5,15 - 5,25 GHz, ca. 20 Mbps, reach 50 m,
mobility<10m/s
cellular structure with base stations, ATM service classes
point-to-multipoint ATM connections
5,15 - 5,25 GHz, ca. 25 Mbps, reach 5000 m,
stationary/quasi-stationary, point-to-multipoint, ATM service
classes
HIPERACCESS
HIPERLINK
point-to-point ATM connection
17,1 - 17,3 GHz, 155 MBit/s, reach 150 m,
stationary/quasi-stationary, point-to-point, ATM
source: ETSI RES 10, BRAN
Mobile Communication and Mobile Computing
Assessment of HIPERLAN
• despite of some unique characteristics there are
no products available yet, only single prototypes
• is planned as one of the alternatives for BRAN
(Broadband Radio Access Network) in the
Wireless ATM
• planned frequencies are originally not worldwide
available (5,1-53GHz)
173
Mobile Communication and Mobile Computing
174
Wireless ATM
Requirements:
• wireless connection of mobile terminals to ATM-networks
• compatibility to existing standards
• existing networks should be easily upgradeable
• guaranteed service quality properties which other wireless nets don't
offer
• UMTS and WLANs don‘t offer any data rates >50 Mbit/s
Problems:
• ATM is conceived for high data rates
• ATM is optimized on reliable media
• applications should notice nothing of the wireless mode
Mobile Communication and Mobile Computing
Wireless ATM: review
• WATM still is standardization endeavors, no definite standards
approved
• the WATM forum has tried to standardize as much as possible,
the WATM standard is relatively complex
• WATM supports relatively many configurations:
– wireless Ad-hoc networks
– wireless mobile end-devices: access to the network via radio
subsystem, similar to access-points
– mobile end-devices: seamless handover between connected
terminals
– mobile ATM-Switches (for planes, ships, trains etc.)
– fixed ATM-terminals: conventional ATM
– fixed terminals with radio access: comparable with line-of-sight
radio links
• It is not arranged completely for which configuration also
products will exist
175
Mobile Communication and Mobile Computing
Satellite-based systems
176
Mobile Communication and Mobile Computing
Sample system
Inter-Satellite Link (ISL)
Mobile User
Link (MUL)
Gateway
Link (GWL)
User
Gateway
Ground Station
Spot beams
Footprint
PSTN, ISDN, GSM, ...
Internet
177
Mobile Communication and Mobile Computing
Basics (1)
• satellites describe elliptical or circular orbit around the
earth
• distance to the earth remains constant:
FG  m  g R / r 
2
 m  r    FZ (1)
2
FG - Appeal of the Earth
FZ - Centrifugal force
m
R
r
g
ω
f
- Mass of the satellite
- Earth radius, 6.370km
- Distance of the satellite to the Earth’s center
- Grounding acceleration, g = 9,81 m/s2
- Angular frequency:   2    f , T  1 / f  2   / 
- Cycle frequency of the satellite
178
Mobile Communication and Mobile Computing
179
Basics (2)
Formulae transformation:
• F
=m.a
• Fgrav = k . M . m / r2
• mg = k . M . m / R2
• k.M
• FG
(by Newton)
(Gravitation between 2 point masses)
(Appeal on
the Earth surface = Gravitation)
= gR2
= gR2 m/r2 = gm(R/r)2 (transformed)
• δt = 2 . (r-R) / c
Signal propagation delay
Satellite
r-R
Uplink
r-R
Downlink
Mobile Communication and Mobile Computing
Basics (3)
•
(1) resolved to r gives:
•
that means, the distance of a satellite to the earth's surface depends only on its
cycle duration (special case T = 24h - > synchronous distance r=35.786 km)
gR 2
r 3
(2)
2
2  f 
Cycle duration
[h]
velocity [x1000km/h]
20
12
4
Synchronous distance 35.786 km
10
20
30
40 x 106 m
180
Mobile Communication and Mobile Computing
Satellite system classes
GEO (Geostationary Earth Orbit)
ca. 36 000 km
MEO (Medium Earth Orbit)
ca. 6000 - 12 000 km
HEO (Highly Elliptical Orbit)
LEO (Low Earth Orbit)
ca. 500 - 1500 km
Van-Allen-belts
2000 - 6000 km
15 000 - 30 000 km
(no satellite use possible)
181
Mobile Communication and Mobile Computing
Geostationary Satellite systems
Principle:
Satellit
Base for Inmarsat
Uplink
•
•
•
•
Downlink
Constant position to the Earth, 3 satellites cover complete earth (with
the exception of the polar caps), satellites move synchronously to the
Earth
Simple solution, however large distance (36000 km), therefore high
signal propagation delay, long life time of the satellites: ~ 15 years
low data rates, large transmission power required
problems:
– on the other side of the 60th degree of latitude reception problems
(elevation)
– because of a high transmission power unfavorable for mobile telephones
– signal propagation delay too high (0.25 s)
182
Mobile Communication and Mobile Computing
LEO- Systems
• non-stationary satellites (LEO - Low Earth Orbit)
• distance to the earth ~ 500 - 2000 km
• shorter signal runtimes (5-10 ms), lower transmission power of
the mobile stations sufficing
• however more satellites necessary, frequent handover between
satellites, approximately all 10 min.
• examples: Teledesic, Globalstar
• only low transmission power necessary, suitable for mobile
phone networks
• Disadvantages:
– large number is necessary (50 - 200, or more)
– fast handovers within satellites are necessary
– short life time of the satellites because of atmospheric friction (5-8
years)
183
Mobile Communication and Mobile Computing
MEO- Systems
• ~ 10000km, lower number of satellites necessary : ~12
• slow movement: handover between satellites is hardly
necessary
• cycle duration: 6h
• high elevation enables coverage large, highly-populated
areas
• Problems:
– signal propagation delay: 70 to 80 ms
– higher transmission power is necessary
– special antennas for small cells are necessary
184
Mobile Communication and Mobile Computing
Service transitions in Inmarsat-C-service
Inmarsat
Satellite
600 bit/s
185
L-Band 1,5/1,6 GHz
Rx/Tx (GPS)
laptop
600 bit/s
Inmarsat - C – End-Terminal
Graphic table
Terrestrial station
X.25
Buffer memory Interface
Phone-Interface
Mail
Box
X.25 Net
modem
TelefaxInterface
FaxInterface
Email System
PAD
Internet
Fixed network
data +
maps
laptop
text
fax
desktop
data +
maps
desktop
Email
desktop
Mobile Communication and Mobile Computing
186
Examples of satellite-based
systems
Satellites
Height
Data rate
Teledesic (planned)
288 (?)
~ 700 km
64 Mbit/s 
2 / 64 Mbit/s 
Iridium
66 (+6)
~ 780 km
2,4 / 4,8 kbit/s
Globalstar
48 (+4)
~ 1400 km
9,6 kbit/s
ICO
10 (+2)
~ 10 000 km
4,8 kbit/s
Inmarsat
5
geostationary 2,4 kbit/s
Orbcomm
35
LEO-stationary 57,6 kbit/s
Globalstar can transfer bi-directionally up to 144 Kbit/s, through
combination of channels
Orbcomm - first commercial LEO–service worldwide
http://Globalstar.com/
Mobile Communication and Mobile Computing
187
Comparison of satellite-based systems
Satellite-based
system
GEO
MEO
LEO
Distance, km
r = 35.786 km
r-R=6000 –
12000 km
r-R= 500 – 2000 km
Cycle duration, T
24 h
6h
95 – 120 min
Signal propagation
delay, t
0.25 s
70-80 ms
10 ms
Transmission power,
W
10
5
1
Use examples
Numerous systems, approx.
2000:
•Sputnik (1957)
•Intelsat 1-3 (1965, 1967, 1969)
•Marisat (1976)
•Inmarsat-A (1982)
•Inmarsat-C (1988)
ICO 10+2
•Iridium (bankrupt,
2000) 66+6
•Globalstar, 48+4/ 144
kBit/s
•Teledesic (2003),
288/ 2-64 MBit/s
• Orbcomm, 35
Data rate, kBit/s
0.1 – 1
10
1 – 64000
Life time, years
15
10
5-8
Mobile Communication and Mobile Computing
Global Positioning System,
GPS
188
Mobile Communication and Mobile Computing
Overview
• 24 satellites on the 6 orbits (20200 km, time of circulation =
12h)
• 5 earth stations (Hawaii, Ascension Island, Diego Garcia,
Kwajalein, Colorado Springs)
• Accuracy:
– so called P-Code for military applications: on ~6m accurately,
partially 2,8m
– so called Selective Availability Mode, SAM (artificial degradation)
for civil applications: < 100m (1.5.2000 disestablished)
• Functionality principle: Triangulation
• GPS-receiver calculates distance to the satellite on the base of
Time of Arrival of the received signals
• distances to at least three satellites enables the calculation of
position, a fourth satellite can be used for determination of
elevation over zero
• official initiation 1995, testing since 1978
189
Mobile Communication and Mobile Computing
Principle: TOA (Time of Arrival) /
TDOA (Time Difference of Arrival)
Distance d,
Signal Delay T
•
•
•
•
•
Mobile Object
synchronized clocks
measurement of signal delay by speed of light between satellite and
receiver, for instance T = 100 ms
hence calculation of distance:
d = T • c = 1 • 10-1s • 3 • 108 m/s = 3 • 107 m = 30.000 km
calculation of spheres around each satellite
the position is on the intersection point of three spheres
190
Mobile Communication and Mobile Computing
Principles
• satellites send a signal composed of three components 50 times per
second:
– identification component: PRC (Pseudo Random Code), provides
satellite recognition and status information
– position component: exact position of satellite
– time component: time point, when signal is transmitted
• the time offset measured by the receiver is corresponding to the
Time of Arrival, from TOA the distance is calculated
• for measurement of TOA of signals very accurate clocks are
required
• the exact position of the satellites must be known
191
Mobile Communication and Mobile Computing
Sources of errors
Clocks
• highly accurate atom clocks in the satellites
• simple clocks in the receivers are calibrated via measurement of
a fourth satellite
Satellite position
• satellite orbits are relatively stable and forecastable
• deviations are measured by US DoD
• deviations are transmitted as correction factor to the satellites
using the PRC
Miscellaneous error sources
• atmospheric faults
• multi-path propagation
192
Mobile Communication and Mobile Computing
Differential GPS, DGPS
• use of a stationary receiver as reference
• position of this receiver is exactly known
• the stationary receiver carries out position determination
and calculates correction factor from the actually
obtained position on the base of deviations
• correction factor is delivered to the mobile receiver
193
Mobile Communication and Mobile Computing
DGPS accuracy grades
• Accuracy under 10cm:
– professional applications, for instance is interesting in
meterology and respectively for user of wellengineered software decisions (machine control
systems etc.)
• Accuracy under 1m:
– events mapping, control of machines, traffic control
systems, agriculture
• Guaranteed accuracy under 10m:
– agriculture/ forestry, railway (wagon search service),
car navigation (private/commercial)
194
Mobile Communication and Mobile Computing
Galileo
• EU-Project for installation of European satellite
navigation system
• initiation: prospective 2008
• positioning accuracy: 45cm
• 30 satellites
• Approx. costs: 3,2 Billion €
195
Mobile Communication and Mobile Computing
Galileo
196
„ A system that both competes with and complements the American GPS system “
ITS (Intelligent Transport
System)
•based on a constellation of 30 MEO-satellites
•ground stations providing information concerning the positioning of
users
•in many sectors usable:
─transport (vehicle location, route searching, speed control, etc.)
─social services (e.g. aid for the disabled or elderly)
─the justice system ( border controls)
─public works (geographical information systems)
Mobile Communication and Mobile Computing
Galileo architecture
Service
centres
GALILEO
GLOBAL CONTENT
Regional Components
197
Local Components
MEO Constellation
...
BSS
network
Local MS
s-band
.
.
i-band
i-band
BSS
network
GEO
RMS
network
EGNOS
Data link
s-band
.
.
TTC
Local MS
OSS
Network
Data link
OSS
Network
Integrity determination Navigation control & constellation
management
&dissemination
I-Band- NAV
UMTS
UHF- S&R
External complementary
systems
COSPAS-SARSAT
ground segment
User segment
Mobile Communication and Mobile Computing
Broadcast Systems, Distribution
Networks
198
Mobile Communication and Mobile Computing
199
Overview
• special variants of asymmetric communication systems
• HSCSD supports for instance asymmetric connections regarding to
data rate, also ADSL
• WWW is the biggest representative of asymmetric communication:
– data volume of uplink (URLs) is much lower than downlink (complete
HTML-pages)
• Problem of distribution systems: Sender can be optimized for a large
quantity of receivers only, for instance videostreaming
• Examples:
– DVB, Digital Video Broadcast
– DAB, Digital Audio Broadcast
Mobile Communication and Mobile Computing
200
Principle of Distribution Systems
C C C
Time information sequence is
optimized for expected
access behavior of all
consumers
t
C B B
B A A
Individual access sample of
diverse consumers can more or
less deviate from expected access
behavior
Mobile Communication and Mobile Computing
Digital Audio Broadcast, DAB
• Audio-transmission in CD-Quality
• Non-sensible towards interferences of multi-path-propagation
• Use of SFN (Single Frequency Network) – i.e. all senders of
some broadcast-program are working on the same frequency as
a rule
• Frequencies: UHF,VHF, for instance: 174-230 MHz, 1452-1492
MHz
• Modulation methods: DQPSK (Differential Quadrature Phase
Shift Keying)
• Optionally COFDM (Coded Orthogonal Frequency Division
Multiplexing) is used with several carrier frequencies inside
some DAB-channel (its quantity is between 192 and 1536),
1,5MHz bandwidth for each channel
• FEC (Forward Error Correction)-mechanism for fault correction
• Up to 6 stereo-programs by 192 kbit/s in the same frequency
band are transmittable
• alternatively data can be transmitted with up to 1,5 Mbit/s
(responding to the used code rate etc.)
201
Mobile Communication and Mobile Computing
Digital Audio Broadcast, DAB
2 Transport Mechanisms
• Main Service Channel (MSC):
– Data, Audio, Multimedia
– 2 Transport Modes: Stream Mode, Packet Mode
•
Fast Information Channel (FIC):
– Transport of Fast Information Blocks (FIB, 32 Byte) – control data for
interpretation of Data in the MSC, can be also used for services such as Traffic
Dispatches, Paging etc.
•
•
•
•
Audio-converting: PCM 48 kHz & MPEG2-Audiocompression
High transmission rates by high velocities, up to 250 km/h, responding to
distance from sender and error security class, use for instance in highspeed train
MOT (Multimedia Object Transfer) protocol for data transmission
Cyclic repeat and caching of data blocks
202
Mobile Communication and Mobile Computing
Dynamic channel reconfiguration
for DAB
Ensemble-Configuration
Audio 1
192 KBit/s
Audio 2
192 KBit/s
Audio 3
192 KBit/s
Audio 4
160 KBit/s
Audio 5
160 KBit/s
Audio 6
128 KBit/s
PAD
PAD
PAD
PAD
PAD
PAD
Data
D1
Data
D2
Data
D3
Data
D4
Data
D5
Data
D6
Data
D7
Data
D8
Temporarily changed Ensemble-Configuration
Audio 1
192 KBit/s
Audio 2
192 KBit/s
Audio 3
128 KBit/s
Audio 4
160 KBit/s
Audio 5
160 KBit/s
PAD
PAD
Audio 7
96 KBit/s
Audio 8
96 KBit/s
PAD
PAD
PAD
PAD
Data
D1
Data
D10
PAD
Data
D2
Data
D3
Data
D11
Data
D4
Data
D5
Data
D6
Data
D7
Data
D8
203
Mobile Communication and Mobile Computing
DVB - Digital Video
Broadcasting
•
•
•
•
•
•
•
•
1991 ELR (European Launching Group) founded
Goal: joint digital Television System for Europe
Specifications: DVB-S, DVB-T, DVB-C
Frequency reaches: 200, 550, 700 MHz
Cell size: up to 60 km
Used data rate: ~38,5 Mbit/s
Velocity of mobile stations: up to 200 km/h
Central Unit: combined DVB-Receiver-Decoder (set-top-box)
– can receive DVB-Data via satellites, B-ISDN, ADSL…
– some transmission systems offer a feedback channel for Video on
Demand etc.
204
Mobile Communication and Mobile Computing
DVB - Digital Video Broadcasting
• Different Quality Levels defined:
– SDTV (Standard Definition TV)
– EDTV (Enhanced DTV)
– HDTV (High DTV)
• Data transport:
– User Data: MPEG2-Container (Data Transfer Unit) like DAB,
Container doesn’t define the type of data
• Service Information about MPEG2-Container-content:
– NIT (Network Information Table): Information from a provider about
offered services and optional data for the receiver
– SDT (Service Description Table): Description and parameters for
each service in the MPEG2-stream
– EIT (Event Information Table): Data about actual transmission
status
– TDT (Time and Date Table): e.g. updating of DVB-receiver
205
Mobile Communication and Mobile Computing
Possible contents of
DVB/MPEG2-Container
MPEG2/DVB-Container
MPEG2/DVB-Container
HDTV
EDTV
Single channel
(High Definition TV)
MPEG2/DVB-Container
Several channels
(Enhanced DTV)
MPEG2/DVB-Container
SDTV
Several channels
(Standard TV)
Multimedia
(data broadcasting)
206
Mobile Communication and Mobile Computing
DVB used as medium
for asymmetric Internet-access
•
•
•
Client sends data query to Provider, Provider transmits data to the
satellite network, receiver obtains data via DVB-receiver
Feedback channel can be phone network, for on-demand services
Data rates:
– 6 up to 38 Mbit/s downlink, 33 kbit/s up to over 100 kbit/s (ADSL) uplink
•
Advantages:
– data can be transmitted in parallel with TV
– no additional costs for satellite provider
– low priced for low-density populated areas
•
Disadvantages:
– all users need satellite antennas
– only a minor part of the total bandwidth is usable
– not suitable for high-density populated areas
207
Mobile Communication and Mobile Computing
DVB as medium
for the asymmetric Internet-access
Satellite provider
DVB–
Card in
the PC
dedicated line
(user-to-user)
Internet
Content Provider
Service Provider
208
Mobile Communication and Mobile Computing
3. Mobile Computing
209
Mobile Communication and Mobile Computing
Layer 3
Mobile IP v4 & v6
DHCP
210
Mobile Communication and Mobile Computing
Mobile IP (Internet Protocol)
211
Mobile Communication and Mobile Computing
Problem situation
• computer mobility in heterogenic networks
• relocation between different IP-subnets
• Goal: transparent migration and localization,
compatibility to IP, no changes of existing routers
• Idea: introduction of temporary/ actual IP-addresses
(also “care-of-address”, COA);
• mapping of permanent to temporary IP-addresses
using localization technique
212
Mobile Communication and Mobile Computing
213
Requirements to MobileIP
according to IETF
Transparency:
– mobile computer is permanently reachable via its
previous “home-address”
– can change its network access point freely
– can also communicate after coupling/uncoupling
Compatibility:
– supports each layer below IP (also 1 & 2)
– mobile computer can also communicate with each “nonmobileIP”-computer
– no changes to existing computer/routers
Security:
– all registering messages must be authenticated
Mobile Communication and Mobile Computing
IETF Mobile IP Goals/Restrictions
Minimization of overheads:
– mobile connections are possibly wireless and have
limited band width
– mobile connections have possibly higher error rate
Efficiency and scalability:
– support of a large quantities of mobile computers
– support of a theoretically Internet-wide mobility
214
Mobile Communication and Mobile Computing
Architecture model
215
Foreign Agent (FA)
Foreign Subnet
Global
Internet
Mobile Node
Anywhere
Home
Subnet
Home Agent (HA)
Router
Correspondent Node (CN)
Mobile Communication and Mobile Computing
Terms
Mobile Node (MN) with permanent IP-address from Home
Subnet
Home Address permanent address of a mobile computer
Home Agent (HA) with knowledge of actual residence of
all MNs from so called Home Subnet, like GSM-HLR
Care of Address temporary address of a mobile computer
from Foreign Subnet
Foreign Agent (FA) for assignment of temporary IPaddresses (care of address) and packet forwarding to
MNs currently residing in its subnet
216
Mobile Communication and Mobile Computing
Log on via Foreign Agent
Foreign
Subnet
HA
Home
Subnet
FA
MN
•
•
Log on with a FA - Care-of Address (address of FA, is just an intermediate
target for all MN- related packets, tunnel-end) or
Application of a co-located Care-of Address (address from Foreign-Subnet,
MN is tunnel-end itself), but reception of an Agent Advertisement Message
with a set “R”-bit, i.e. the MN is forced to log on with FA itself, although it
can operate autonomously
217
Mobile Communication and Mobile Computing
218
Log on by Home Agent directly
• MN uses co-located Care-of Address
• MN is returned to Home Network and would like to log
on/off itself with the HA
Authentication:
Home
Subnet
MN
•
each mobile entity (MN, HA, FA) must
be able to support a “mobility security
association”, which is indicated via IPaddress and SPI (Security Parameter
Index).
•
Mobile IP provides three different
Authentication Extensions:
•
Mobile - Home Authentication Ext.
•
Mobile - Foreign Authentication Ext.
•
Foreign - Home Authentication Ext.
HA
Mobile Communication and Mobile Computing
Addressing
Problem: For the receivers 2 addresses are necessary
(permanent and temporary IP-address respectively
home address and COA)
Methods of resolution:
• Encapsulation
– IP in IP, standard method in MobileIPv4
– minimal Encapsulation
• IP-Option (not supported by all implementations)
219
Mobile Communication and Mobile Computing
IP in IP Encapsulation
OUTER IP HEADER
IP HEADER
IP HEADER
IP PAYLOAD
IP PAYLOAD
• IP-source/target address of external/outer IP-Header defines the
“end- points” of the tunnel
• IP-source/target address of internal IP-Header represents the actual
packet sender respectively receiver
• Internal IP-Header isn't changed using “Encapsulator” (exception:
TTL)
220
Mobile Communication and Mobile Computing
221
Routing (unicast)
• Mobile Node:
– in Home Network it operates like each other Node
– in Foreign Network it must search a Default Router using the
following rules:
• FA COA:
– ICMP Router Advertisement-Part;
– IP-source address of Agent Advertisements (lower Prior.)
• co-located COA: ICMP Router Advertisement for this address
• Foreign Agent:
– FA must check by reception of tunneled packets whether
internal target address corresponds with one of the IP-addresses
of Visitor List
– FA must route the received packets of registered
MN’s!
Mobile Communication and Mobile Computing
Routing (unicast) II
• Home Agent:
– HA must intercept each packet for absent MN
– in addition IP-target address of each incoming
packets is verified
– if MN has no mobile coupling presently, the packets
sent to it must not be intercepted, MN is situated in
Home Subnet and accepts packets itself or is off-line
222
Mobile Communication and Mobile Computing
223
Routing (necessities)
• ARP (Address Resolution Protocol):
– oriented to resolution of IP-addresses in physical (Hardware, Link
Layer) addresses (Ethernet: MAC-addresses of controllers)
• Proxy ARP:
– Proxy ARP-reply is an ARP-reply, which can be sent instead of a host A
by other host B (with its hardware address)
– Hosts, receiving this reply, associate the hardware-address of node B
with the IP-address of node A and send future packets for A to B
• Gratuitous ARP:
– is an ARP-reply, which is sent from a host, to force other hosts to update
the records in their ARP-Caches
– this ARP-reply contains the IP-address, which should be changed in the
ARP- Caches, as well as the hardware address which should be
updated
Mobile Communication and Mobile Computing
Routing - Scenario
• MN leaves Home Network
• MN decides to register FA Care-of Address
• Before Registration Request: MN re-sets a reaction on
future ARP-requests
• Registration Request
• contains and accepts HA Request, implements
Gratuitous ARP (IP-address MN ===> own hardwareaddress) and uses Proxy ARP to respond to ARPrequests corresponding to MN hardware address
224
Mobile Communication and Mobile Computing
Triangle Routing
FA
CN
CN ===> MN:
Foreign
Network
HA
MN
Home
Network
although CN is in the same
Subnet like MN, packets are
routed respectively tunneled via
FA and primarily HA (possibly
over half of terrestrial globe)!!!
MN ===> CN:
Be routed conventionally via
Default Router
Special case: Routing (MN & CN are in the same Subnet)
Relief (IPv4): Route Optimization
225
Mobile Communication and Mobile Computing
Optimizations: Routing
Terms:
• Binding Cache: table with Mobility Bindings of
MNs (on CN, can tunnel itself now)
• Binding Update: message, contains up-to-date
Mobility Binding of a MN, particularly the Care-of
Address
Procedure:
• Update of Binding Caches
• Control seamless Handoffs between FA‘s
226
Mobile Communication and Mobile Computing
227
Updating of Binding Caches
• Binding Cache of a CN: Care-of Address of one/several
MN‘s, with respective Lifetime
• No Entry: non-optimal Routing, BUT: HA doesn’t only
tunnel a datagram from CN, but also sends a Binding
Update to it
• CN should generate/change Binding Cache-Entry only
then, when trusted Mobility Binding received (Bind. Upd.)
for corresponding MN (ergo: Secure CN <===> HA)
• If FA receives tunneled Packet for a MN that is no longer
in Visitor List, then it must care that corresponding CN
receives a Binding Update (Binding Warning to HA)
Mobile Communication and Mobile Computing
228
Smooth Handoff between FAs
• Problem of Basis-MobileIP: MN is with a new FA, but the packets
tunneled to old FA will be lost
• FA Smooth Handoff: MNs are informed via new FA (packet can be
forwarded)
• also Packets of hosts with non-up-to-date entries in Binding Cache
can be forwarded now from old FA to the new FAs
• Previous Foreign Agent Notification Extension enables to prompt the
new FA to inform the old FA (Binding Update Message)
Mobile Communication and Mobile Computing
MobileIP v4 & v6 in comparison
Mobile IPv4
Routing
Bottle neck
Security
Mobile IPv6
Optimal Routing, only if MN
in the Home Network. (Otherwise
non-efficient „Triangle“-Routing)
Optimal Routing is generally
possible,
if CN knows the Care-of Address
HA is a possible bottleneck,
because all traffic
to the MN is processed over it
HA is load essentially reduced,
because CN‘s can just directly
communicate with mit MN‘s
Authentication is prescribed
only by Registration and then also
between HA and MN only
Authentication and encryption are
possible anywhere, because
they are supported from IPv6
Robustness
Used FA‘s / HA‘s must not be
off-line
Performance
No good performance
due to IPv4-requirements
and non-optimal Routing
Short-time failure/re-configuration of
HA is mastered thanks to
Automatic Home Agent Discovery.
IPv6 is essentially simpler to
upgrade, therewith also Mobile IPv6
Essentially better due to
requirements from IPv6
(uniform Headers, less Overheads) and optimal Routing
229
Mobile Communication and Mobile Computing
Assessment
• Mobile IP enables the unlimited accessibility/roaming of
mobile computers using perpetuation of their addresses
and step-less transfer between subnets
• Particularly necessary for applications without “pull”semantics (for instance, distributed applications with
mobile users, videoconferences, VoIP)
• Keeping of permanent addresses are also important
corresponding to Firewalls etc. in the case of call
semantics
• Successive availability in the form of products
230
Mobile Communication and Mobile Computing
231
Dynamic Host Configuration
Protocol (DHCP)
Properties:
• permits automatic
configuration (IPaddress, subnet-mask,
router, DNS-Server, ...)
and therewith
integration of (mobile)
computers
• Client/Server-Model
• Lease Concept
• Relevant for
management of Careof-Addresses
Server A
Client
Determination
of configuration
Server B
Determination
of configuration
Selection of a configuration
Confirmation
of configuration
Mobile Communication and Mobile Computing
DHCP Assessment
• no secure mechanisms standardized
• no standardized communication (signalization,
for instance information exchange about
managed address areas) between DHCPservers
• good base for allocation of co-located COAs in
MobileIP
232
Mobile Communication and Mobile Computing
IPsec: Network security
233
Mobile Communication and Mobile Computing
IPsec: Security on the network
layer (1)
• IPsec - IP Security Protocol – new developed protocol
from TCP/IP-Stack, related to the IPng - Group
• IPsec uses:
– encryption services -> DES, TripleDES and 40-bit-DES between
hosts at a VPN (virtual private network)
– specification for Internet Key Management Protocol (IKMP),
based on ISAKMP/Oakley (1998, Internet Security Association
and Key Management Protocol - ISAKMP)
• IPSec-tunnels – encapsulation of TCP/IP-data via the
ESP/AH- headers:
– Developed by S.Kent, R. Atkinson „IP Encapsulating Security
Payload" (RFC 2406, 1998) and "IP Authentication Header"
(RFC 2402, 1998)
– relevant for key assignment to IP-subnets
234
Mobile Communication and Mobile Computing
IPsec: Security on the network
layer (2)
•
Secrecy on the network layer: a sending host encrypts/authenticates data
encapsulated in the IP-datagrams
– TCP/UDP-segments
– ICMP/SNMP-messages
•
Authentication on the network layer:
– target host can authenticate source IP-addresses
•
Basic protocols:
– Authentication Header (AH) Protocol
– Encapsulation Security Payload (ESP) Protocol
•
AH and ESP both requires target and source Handshake-Routine:
– establishment of a logical channel via network layer, called Service Agreement
(SA)
– each SA is unidirectional
•
Distinctly determined via:
– security protocol (AH / ESP)
– source IP-address
– Con-ID of 32 Bit
235
Mobile Communication and Mobile Computing
236
Encapsulation Security Payload (ESP)
Protocol
•
•
•
•
offers secrecy, host authentication and data integrity
data, ESP trailers encrypted
next header field is a trailer in the ESP
ESP- authentication field is similar to AH- authentication field;
protocol field = 50
authenticated
encrypted
IP-Header ESP-Header TCP-/UDP-Segment
Protocol = 50
ESP-Trailer
ESP-Auth
Mobile Communication and Mobile Computing
Authentication Header (AH) Protocol
• offers host authentication and data integrity, but no secrecy
• AH headers inserted between IP-Header and IP-data field; protocol
field = 51
• participated routers process datagrams as usually
AH-Header consists of:
• Con-ID
• authentication data: signed message digest calculated via original
IP-Datagram, offers authentication of source hosts and data
integrity
• next header field is specific data type (TCP, UDP, ICMP etc.)
IP-Header
AH-Header
Protocol = 51
TCP-/UDP-Segment
237
Mobile Communication and Mobile Computing
Layer 4
238
Mobile Communication and Mobile Computing
Problems of conventional protocols
Problem:
• Loss of packets on the radio channels with higher biterror rate (BER) results in frequent retransmissions of
packets and therewith in further efficiency loss
• TCP-Protocol uses so called “Slow-Start”-mechanisms:
window size is reduced by significant packet losses; this
is reasonable for fixed networks, to react on overload,
but not for packet losses due to higher BER
• limited suitability of conventional transport protocols for
mobile communication!
239
Mobile Communication and Mobile Computing
Conventional protocols
Congestion Control:
• packet loss as a rule, in fixed networks occurs only by overload of several
components
• reducing of transmission rate
Slow Start:
• sender calculates a traffic window size
• start with window size 1
• exponential growth till to Congestion Threshold
• then linear growth
Fast Retransmit / Fast Recovery:
• If ≥ 3 DUPACK (duplicate ACK) are received
-> sender informs about packet losses and repeats missing packets
240
Mobile Communication and Mobile Computing
Resulting problems in mobile
environment
• packet losses due to transmission errors are
wrongly interpreted as traffic jam (Congestion)!
• > Slow Start is also wrong
• > Ideally the packets lost due to transmission
errors are simply repeated (no effects on
Congestion Control)
• great variances of Round-Trip-Time
241
Mobile Communication and Mobile Computing
Scenario
Access Point 1
Mobile Host
Access Point 2
Fixed Host
242
Mobile Communication and Mobile Computing
Solutions
Sender- transparent:
• to hide the packet losses transparent to the sender
• transmission repeat via Access Point
– on layer 2
– on TCP-layer
Wireless-aware sender:
• sender understands the reason of packet loss
• explicit notification of senders
• sender tries to determine the reason of loss
Where will be the modifications carried out?:
• only by the sender
• only by the receiver
• only on the transient node (Access Point)
• combinations
243
Mobile Communication and Mobile Computing
Solution “Split Connection“
244
– Separation between transport functionality in the fixed network
respectively in the mobile network:
Workstation
TCP
Fixed network
MSR
Mobile TCP
Mobile network
Mobile
node
Mobile Support Router
TCP-Handover
by relocation of mobile
node
MSR
– MobileTCP is specially optimized (up to 100% of efficiency improvement
possible)
– system-internal TCP-Handovers are necessary, however transparent for
fixed computer (Workstation)
Mobile Communication and Mobile Computing
Example of I-TCP (indirect TCP)
•
•
•
•
•
separation of TCP-connection at the Access Point
optimized TCP over the wireless Link (not absolutely necessary)
no changes of TCP for the fixed network
transparent for Fixed Host
loss of End-to-End-semantics
Access Point 1
Mobile Host
„wireless TCP“
„standard TCP“
Fixed Host
245
Mobile Communication and Mobile Computing
Example of I-TCP
• Mobility: status and buffer transfer
Fixed Host
Access Point 1
Mobile Host
Access Point 2
246
Mobile Communication and Mobile Computing
I-TCP Assessment
+
+
+
+
+
─
─
─
─
no changes in the fixed network
the errors in the wireless part aren’t propagated to the fixed network
both parts can be optimized independently
relatively simple: „wireless TCP“ concerns one Hop only
the properties of wireless networks (bit-error rate, delay time) are
known, therefore fast retransmissions are possible
loss of End-to-End-semantics
additional costs (computation time, storage place) concerning the
Access Point
high delay times with handover caused by buffering of data by
Access Point
IT-security mechanisms must be adapted
247
Mobile Communication and Mobile Computing
Example of Snoop
•
•
•
•
transparent extension of Access Point from sender’s viewpoint
Access Point listens to the traffic (snoops) and filters the ACKs
buffering of data, are sent to the mobile computer
after losses of packets in the wireless network a direct
retransmission takes place between Access Point and Mobile Host
• Access Points send NACK after packet losses of MH
Access Point 1
Mobile Host
„local retransmission”
TCP
Buffer
Fixed Host
248
Mobile Communication and Mobile Computing
Snoop Assessment
+
+
+
+
maintenance of End-to-End-semantics
modifications only at the TCP-Stack of Access Points
errors in the wireless part can be corrected locally
Soft State
+ no status transfer at new Access Point is necessary
+ change is possible, also if the new Access Point possesses no Snoop
• no complete transparency of wireless connection
• handling of NACK requires the modifications of MH
• IT-security: encryption can prevent an access to TCP-Header (most
of the up-to-date approaches use End-to-End-encryption!)
249
Mobile Communication and Mobile Computing
Higher Layers and Services
250
Mobile Communication and Mobile Computing
Wireless Application Protocol WAP
Based partially on the materials of WAP-Forum
251
Mobile Communication and Mobile Computing
WAP – Standard Overview
• Goal: Fusion of Internet-Technologies and
mobile radio, creation of new innovative
services
• standardized by WAP-Forum
(http://www.wapforum.org), initiated by
Ericsson, Nokia, Motorola
• specifies application environment and protocols
for mobile end-devices such as radio phones,
PDAs, pagers
252
Mobile Communication and Mobile Computing
Why WAP?
• Mobile radio networks and mobile phones
possess special properties and requirements
– Display: sizes and presented colors, numerical
keyboard, lower processor performance and
storage capacity ...
– Networks: low data rates, high delays and costs
• WAP offers the use of several carriers
– TCP/IP, UDP/IP, USSD, SMS, ...
USSD - unstructured supplementary service data (GSM)
SMS - short message service (GSM)
253
Mobile Communication and Mobile Computing
Why WAP ?
•
•
•
•
WAP-architecture has a modular organization
the modules build together a complete Internet-protocol-stack
WML-contents can be queried by HTTP-request-messages
WAP uses XML (eXtensible Markup Language)-Standard as
well as optimized contents and protocols
• user interface of conventional end-devices is supported by
WML-components
– enhances acceptance by users
• WAP uses conventional HTTP-Servers
– existing development strategies are applicable in the
future (common gateway interface - CGI, active server
pages - ASP, netscape server API - NSAPI...)
254
Mobile Communication and Mobile Computing
255
Why HTTP/HTML doesn’t suffice?
Big pipe - small pipe syndrome
Internet
<HTML>
<HEAD>
<TITLE>NNN Interactive</TITLE>
<META HTTP-EQUIV="Refresh" CONTENT="1800,
URL=/index.html">
</HEAD>
<BODY BGCOLOR="#FFFFFF"
BACKGROUND="/images/9607/bgbar5.gif" LINK="#0A3990"
ALINK="#FF0000" VLINK="#FF0000" TEXT="000000"
ONLOAD="if(parent.frames.length!=0)top.location='htt
p://nnn.com';">
<A NAME="#top"></A>
<TABLE WIDTH=599 BORDER="0">
<TR ALIGN=LEFT>
<TD WIDTH=117 VALIGN=TOP ALIGN=LEFT>
HTTP/HTML
<HTML>
<HEAD>
<TITLE
>NNN
Intera
ctive<
/TITLE
>
<META
HTTPEQUIV=
"Refre
sh"
CONTEN
T="180
0,
URL=/i
ndex.h
tml">
Mobile radio networks
WAP
<WML>
<CARD>
<DO TYPE="ACCEPT">
<GO URL="/submit?Name=$N"/>
</DO>
Enter name:
<INPUT TYPE="TEXT" KEY="N"/>
</CARD>
</WML>
Converting to
binary format
010011
010011
110110
010011
011011
011101
010010
011010
Mobile Communication and Mobile Computing
WAP-overview
WAP-standard defines:
• Environment = Wireless Application Environment
(WAE)
–
–
–
–
–
WML (Wireless Markup Language) micro-browser
WMLScript virtual machine
WMLScript standard library
Wireless Telephony Application (WTA) Interface
Contents = WAP Content Types
–
–
–
–
Wireless Session Protocol (WSP)
Wireless Transaction Protocol (WTP)
Wireless Datagram Protocol (WDP)
Interface definitions for mobile network
• Layer architecture
256
Mobile Communication and Mobile Computing
257
Comparison: Internet/WWW and WAP
Internet
Wireless Application Protocol
HTML
JavaScript
Wireless Application
Environment (WAE)
other services and
applications
Session Layer (WSP)
HTTP
Transaction Layer (WTP)
TLS - SSL
Security Layer (WTLS)
Transport Layer (WDP)
TCP/IP
UDP/IP
Carrier:
SMS
USSD
GPRS
CDMA
CDPD
etc..
SMS - Short Message Service (GSM), GPRS - General Packet Radio Service (GSM II+),
CDMA - Code Division Multiple Access, CDPD - Cellular Digital Packet Data
Mobile Communication and Mobile Computing
Wireless Application Environment
- WAE
• environment for distributed applications with specific
reference to low-performance end-devices with
limited operation comfort and mobile radio networks
• Goals:
–
–
–
–
network-independent application environment
optimized for application in mobile radio systems
Internet, i.e. WWW–programming model
high interoperability level
258
Mobile Communication and Mobile Computing
WAE – abstract network architecture
WSP/HTTP Request {URL}
Client
Gateway
Network
Application
WSP/HTTP Reply {Content}
259
Mobile Communication and Mobile Computing
Constituents
• Architecture
– Programming model
– Browser, Gateway, Content Server
• WML
– as page markup language
• WMLScript
– as scripting language
• WTA
– offers access to phone services
• Content formats
– sets free-defined formats: bitmaps, phonebook records,
dates ...
260
Mobile Communication and Mobile Computing
Options
• User Agent Profiling
– to user, end-device, ... adapted contents
• Push-model
– network initiates delivery of contents
• Options for performance improvement
– Caching, ...
261
Mobile Communication and Mobile Computing
262
Sample: WAP-Gateway
WMLScript
WTAI
etc.
WAP Gateway
WAE User Agent
WML
Web Server
WML Encoder
WSP/WTP
WMLScript
Compiler
Protocol adapter
HTTP
CGI
Scripts
etc.
Contents
WML Decks,
WML-Script
Client
Mobile Communication and Mobile Computing
Sample: WAP - Application Server
Client
WTAI
etc.
WML Encoder
WSP/WTP
WMLScript
Compiler
Protocol adapter
Application
logic
Contents
WML Decks,
WML-Script
WMLScript
WAE User Agent
WML
WAP Application Server
263
Mobile Communication and Mobile Computing
Wireless Markup Language - WML(1)
• HTML-like page markup language
– different font styles are available, tables
and graphics too, but limited
• based on W3C-XML
• uses HTML and HDML-elements
• Deck/Card-metaphor
– interactions-/selection possibilities are
separated in Cards
– navigation (anchor: #) takes place between
Cards
– Deck-stack corresponds to a WML-file
HDML - Handheld Device Markup Language, W3C - World Wide Web
Consortium, XML - eXtensible Markup Language
264
Mobile Communication and Mobile Computing
Wireless Markup Language WML(2)
• explicit navigation model between Decks
– Hyperlinks
– Events from user interface
– History
• variables and status-management
– variable status can tell about validity of a stack
265
Mobile Communication and Mobile Computing
WML– text styles
<wml>
<card id=“Card1” title=“Text Styles”>
<p align="left">
<i>italic</i>,
<b>bold</b>,<br>
<big>big</big>,
<small>small</small>,
<u>underlined</u>
</p>
</card>
</wml>
Card
Deck
266
Mobile Communication and Mobile Computing
WML-example (1)
<wml>
<card id=„Card1" title=„Currency" newcontext="true">
<p>
Amount: <input format="*N" name=„amount" title=„Amount:"/>
From: <select name=“from“ value=" USD“ title=„From:"> Variables
<option value="EUR">Euro</option>
...
<option value="USD">US Dollar</option>
Selected
</select>
input
To: <select name= ...
<br/> = <u>$(conv)</u>
<do type="accept" label=„Calculate">
<go href=“bsp.wmls#convert('conv',
Script call
'$(from)','$(to)',$(amount))"/>
</do>
<do type="help" label="Help">
<go href="#card1_help"/>
Navigation
</do>
</p>
</card>
...
267
Mobile Communication and Mobile Computing
WML-example (1): Processing
268
Mobile Communication and Mobile Computing
269
WML-example (2)
<card id="card1_help" title="Help">
<onevent type="onenterforward">
Events
<go href="bsp.wmls#getInfoDate('date')"/>
processing
</onevent>
<p>
Currency exchange rates stem from Federal
Reserve Bank of New York and are from $(date).
<do type="prev" label=„Back">
<prev/>
</do>
</p>
</card>
</wml>
Mobile Communication and Mobile Computing
WMLScript-overview (1)
• scripting language, similar to JavaScript
– procedures, loops, conditions, ...
– optimized for devices with low storage capacity and
CPU-performance
• integrated with WML, enables:
–
–
–
–
reducing of network workload
validation of inputs
access to vendor-specific APIs
programming of conditional logic
270
Mobile Communication and Mobile Computing
WMLScript-overview (2)
• Bytecode-based Virtual Machine
– stack-oriented design
– ROM-able
– designed with regard to simple, less work-expensive
implementation
• Compiler in network
– better utilization of network capacity and end-device
storage
• Standard library
– basic functionality for processing of strings, URLs, ...
271
Mobile Communication and Mobile Computing
WMLScript-example
extern function getInfoDate(varName)
{
WMLBrowser.setVar(varName,„June,3,2002");
WMLBrowser.refresh();
}
extern function convert(varName,from,to,amount)
{
var multiplier = 0.0;
...
if (from == „EUR")
{
...
if (to == „EUR")
multiplier = 1.0;
else if (to == „RUR")
multiplier = EUR_RUR;
...
} else if ...
WMLBrowser.setVar(varName,returnString);
WMLBrowser.refresh();
}
Procedures
Variables
Statements
272
Mobile Communication and Mobile Computing
Wireless Telephony Application WTA (1)
• offers mechanisms for applications in field of
telephony
• primary focus: operators/providers and
vendors
• security and trust are the emphasis
• WTA Browser
– using improvements of standard WML/WMLScriptbrowsers
– own interface WTAI (... Interface)
273
Mobile Communication and Mobile Computing
Wireless Telephony Application WTA (2)
• WTAI contains:
– call control, messaging, interface to phonebook,
events processing...
• own Client/Server-interaction model
– event signalization...
• security via separation
– browser and port separated
• WTAI in WML and WMLScript available
274
Mobile Communication and Mobile Computing
WAE content formats
• WAE defines uniform formats
– visit cards, so called IMC vCard Standard
– dates, IMC vCalendar Standard
– graphics, WBMP (Wireless BitMaP)
– compiled WML, WMLScript
• Goal: Interoperability
IMC - Internet Mail Consortium
275
Mobile Communication and Mobile Computing
WAP layer architecture
Wireless Session Protocol (WSP)
Wireless Transaction Protocol (WTP)
Wireless Transport Layer Security (WTLS)
Wireless Datagram Protocol (WDP)
Carrier A
Adaptation
Carrier
Service A
Carrier B
Adaptation
Carrier
Service B
Carrier C
Adaptation
Carrier
Service C
Carrier D
Service D
Physical Layer Air Link Technology
276
Mobile Communication and Mobile Computing
Wireless Session Protocol
• supports Client/Server context (shared
state), optimization of content
transmission
• offers semantics and mechanisms,
which are based on HTTP
• and improvements for use in mobile
radio networks with low-performance
end-devices
277
Mobile Communication and Mobile Computing
WSP overview (1)
• HTTP elements:
–
–
–
–
–
extensible request/reply methods
extensible request/reply headers
uniform contents
composed objects
asynchronous requests
• Improvements:
– binary encoding of headers
– session headers (Client & Server)
– confirmed and unconfirmed network-initiated delivery (Push)
278
Mobile Communication and Mobile Computing
WSP overview (2)
• Improvements corresponding to HTTP:
–
–
–
–
negotiations of supported characteristics
session suspend/resume
multiple complete asynchronous transactions
connectionless service
• Why doesn’t HTTP suffice?
– no compact encoding
– insufficient negotiations
– Push doesn't exist
279
Mobile Communication and Mobile Computing
Characteristics
• message size
• protocol options
– Confirmed Push Facility/ Push Facility (unconfirmed)
– Session Resume …
• maximum outstanding (unanswered) requests
• Header Code Pages (known field names in the
protocol headers are separated into pages)
• ...
280
Mobile Communication and Mobile Computing
Suspend/Resume
•
•
•
•
Server knows, when a Client accepts data (Push)
multi-carrier devices
dynamical addressing
enables release of carrier resources
281
Mobile Communication and Mobile Computing
Wireless Transaction Protocol
(WTP)
• Goal:
– efficient request/reply-based transport mechanism for mobile
radio networks and low-performance end-devices
• Properties:
–
–
–
–
–
robust data transmission
no explicit connection set up and connection release
data are transmitted already with the first packet
packet oriented
abortion-function for outstanding (unanswered) requests
282
Mobile Communication and Mobile Computing
Wireless Transaction Protocol
(WTP)
• Properties:
– supports concatenation of messages
– further WTP features:
•
•
•
•
repeated transmission due to packet loss (selective)
fragmentation
port numbers (UDP)
flow control
• Transaction = Interaction between Initiator
and Responder
283
Mobile Communication and Mobile Computing
WTP – transaction classes (1)
• Class 0:
–
–
–
–
non-robust datagram-service
for instance for Push during a session
shouldn’t substitute WDP
the transactions are closed after transmission of
Invoke
• Class 1:
– robust datagram-service
– the transactions are closed after transmission of
Invoke
284
Mobile Communication and Mobile Computing
WTP – transaction classes (2)
• Class 2:
– robust datagram-service with robust Invoke- and
robust Result-messages
– the transactions are closed via the Initiator after
answer confirmation of the Responder
285
Mobile Communication and Mobile Computing
Wireless Datagram Protocol
(WDP)
• provides connectionless, non-robust
datagram-service
• is substituted by UDP, if IP the a carrier
• re-adaptation to the carrier takes place in the
Adaptation Layer
• supports port numbers
286
Mobile Communication and Mobile Computing
Wireless Transport Layer
Security (WTLS)
• enables secure connections, uses protocol
elements of known, secure Internetprotocols (TLS)
• provides mechanisms for encryption, strong
authentication, integrity and key
management
• corresponds to guidelines of national
authorities
• offers end-to-end security
287
Mobile Communication and Mobile Computing
WAP & Security
• WTLS (Wireless Transport Layer Security) offers only
security via encryption of transmitted data (Grade #1)
presently, similar to TLS, only communication trustiness
is protected
• Grade #2 supports Server- and Client-certificates, for
instance via additional chip-cards in mobile phones, so
called WIM - Wireless Identification Module
288
Mobile Communication and Mobile Computing
WAP & Security
UBS (Switzerland)
• data with WTLS class 2, 128 bit 3DES encrypted
• UBS authentication against mobile phone via certificates with a
key size of 1024 bit
• participant authentication against UBS via WAP similarly like via
Internet with agreement number, password and list-number
• automatic connection release (Timeout) embedded
– after ten minutes without interaction participant is demanded to reauthenticate with password und list-number input
Deutsche Bank (Germany)
• WTLS (Wireless Transport Layer Security)
• end-to-end-encryption
• data encryption already at the mobile phone
• decryption at the server
Sources:
UBC.ch,db24.de
289
Mobile Communication and Mobile Computing
WAP-example: access to
enterprise data
Server
WAP-Gateway
WML
HTTP
Web-Server
Server
Java-Servlet-API
LDAP/X.500DirectoryService
Dir-X-wap
Dir-X-Servlet
WMLpages
LDAP-Client
Profiles
LDAP
290
Mobile Communication and Mobile Computing
WAP-example: access to
enterprise data
Example: Siemens Dir-X Meta-Directory Service as a base of a
corporate information pool
• software-package consists of Directory Server (Dir-X-Metahub) and
several Clients, is completely LDAP v3 compatible, based on X.500
• 2 Gateways outwards: Dir-X-Web and Dir-X-wap
• secure access also via WAP available, because all security
properties of Directory-Servers are handed-on to mobile user
• registration via phone number and password, the
authorizations/licenses are deposited within the system in user
profiles
• Java-Servlets built the kernel components of WAP-connection
Dir-X-wap-Server:
• Servlet-components undertake communication with the Web-Server
• LDAP-Client provides data exchange between the Dir-X-wap-Server
and the directory service
291
Mobile Communication and Mobile Computing
WAP-example: access to
enterprise data
Dir-X-Wap-Application:
• consists of a set of WML-pages containing DSL
• Dir-X-Servlet parses DSL-commands
• 2 configuration files for an application necessary:
– Global Profile: contains information for the Servlet
– Application Profile: stores the data that are necessary to
execution of WAP-application
• In principle, each Web-Server is usable with the product,
it must only support the Servlets
DSL: Directory Script Language; Language for processing of directory
requests from Web- or WML-pages and for representation of obtained
results in WML or HTML, contains the language elements for LDAPaccess
292
Mobile Communication and Mobile Computing
WAP-examples
• Bond/Security-Order processing: Consors, Advance Bank, Deutsche
Bank
• Mobile “Yellow Pages” – Orange Telecom
• Mobile Timetable: wap.hafas.de
• Mobile Auctioning: wap.yahoo.de, wap.ebay.de
• Mobile „Last Minute Bargain “:
– 12snap at Vodafone, presently also with WAP
• Mobile marketplaces/stock exchanges (Mobile Brokerage):
– http://www.heizoelboerse.de/
– http://www.amazon.de/
293
Mobile Communication and Mobile Computing
WAP-example: Bond/Security-Order
Bond/Security-Order
•Mobile Banking
•Mobile Brokerage
294
Mobile Communication and Mobile Computing
WAP-example: Bond/Security-Order
Private Banking->
Login page
Other services ...
Lufthansa, Sixt,
etc.
295
Mobile Communication and Mobile Computing
WAP-example: Bond/Security-Order
Main menu
• Brokerage ...
Bond/security info
296
Mobile Communication and Mobile Computing
WAP-example: Bond/Security-Order
Order book
• Status of bond transactions
• Executed and deleted orders are
indicated in the order book for
some days more
• Partial execution of some order
is presented as one open and
one executed partial order in the
order book
• Details to an order could be
indicated via dial-up of
correspondent Links
297
Mobile Communication and Mobile Computing
WAP-example: Bond/Security-Order
Portfolio review
• Bond/security depots
298
Mobile Communication and Mobile Computing
WAP-example: Bond/Security-Order
Brief queries
• exchange rates of
Bonds/Securities with a
delay of approx. 15Min
• search criteria
– Bond/Security-ID and/or
– Bond/Security-name
299
Mobile Communication and Mobile Computing
300
WAP-example: soccer/football score
source:
http://www.wapgoal.com
Mobile Communication and Mobile Computing
Further WAP-examples
soccer/football
scores:
http://wap.goal.com
auctioning:
miscellaneous:
http://wap.12snap.com
http://wap.yahoo.com
301
Mobile Communication and Mobile Computing
WAP-example: timetable service
Input the address
...wait ...
Input
-> English -> Query...
…wait ...
302
Mobile Communication and Mobile Computing
WAP-example: timetable service
Input the start & target
railway stations
...Dresden,
…Hannover
...scroll …
Input
..date, time....
…scroll …
303
Mobile Communication and Mobile Computing
WAP-example: timetable service
After input …
search...
..wait..
Selection of train connections
with departure platform
...earlier/later...
then probably ->
END
304
Mobile Communication and Mobile Computing
305
For comparison: PC-timetable service
PCtimetable
service is
still detailed!
Details
Options
Mobile Communication and Mobile Computing
WAP-result
•
•
•
•
•
•
WML doesn’t bring whole Internet’s diversity to a mobile phone
there are no satisfactory rate models at the moment; the data-rates are
too low even with GPRS
limited input and selection possibilities require a reconsidering of
interaction semantics, WAP isn’t oriented for many applications, for
instance catalogs with a large selection -> PDAs, appliances, voice
input and -recognition
with introduction of data services with higher data-rates WAP could lose
its relevance possibly -> XHTML
however WAP means a first step towards independence from PC by
access to Internet contents -> multi-dimensional distribution channels
for information
WAP means the start for creation of a formidable user population
(potentially all mobile radio participants)!
306
Mobile Communication and Mobile Computing
WAP-Improvements: WAP2.0 (1)
• New version
– Internet-based data services on mobile phones
– approved by WAP Forum mid-2001
– oriented to GPRS and 3G cellular/UMTS
• Useful services at WAP2.0 devices
– color graphics and Pictograms
– location-specific content, navigational functions and user-friendly
menus
– animation representations and streaming media
– Multimedia Messaging Service (MMS)
– large-file downloading (music)
– synchronization of user information with personal information
manager software on a desktop PC in a remote location
Source: http://www.wapforum.org
307
Mobile Communication and Mobile Computing
WAP-Improvements: WAP2.0 (2)
• WAP 2.0 builds upon the latest Internet standards:
– XHTML, TCP/IP, HyperText Transfer Protocol (HTTP/1.1) and
Transport Layer Security (TLS)
– uses mostly TCP as transport
– optimized for small low-performance end-devices
• WAP 2.0 supports additionally:
– Wireless Telephony Application (WTA), Push, and User Agent
Profile (UAPROF) utilize more advanced features in WAP 2.0
than in WAP1.x
308
Mobile Communication and Mobile Computing
WAP-Improvements: WAP2.0 (3)
• Application development
– easier development of WAP applications
– More comfortable user environment
• Migration aspects
– WAP2.0 offers a migration to XHTML (Extensible Hypertext Markup
Language) and TCP (Transmission Control Protocol)
– Supporting XHTML, WAP 2.0 reduces development costs, allowing
developers to write applications for both PC and WAP
• Security
– offers more secure due to “end-to-end encryption” (from the mobile
device to the server)
309
Mobile Communication and Mobile Computing
WAP2.0 and i-mode
• Competition & Fusion
– NTT DoCoMo's I-Mode is a serious
competitor of WAP2.0
– NTT DoCoMo's I-Mode moves in the direction
of support of XHTML and TCP, too
– I-mode and WAP2.0 will probably converge
310
Mobile Communication and Mobile Computing
i-Mode
An overview
Based partially on the materials of NTT-DoCoMo
311
Mobile Communication and Mobile Computing
Structure
312
Mobile Communication and Mobile Computing
Overview
• i-Mode is a product and a trademark of NTTDoCoMo
• The enterprise NTT-DoCoMo started in February
1999 with a proprietary development: i-Mode,
although NTT-DoCoMo is the member of WAPForum itself
• Meantime i-Mode has got a large number of
registered users : over 33 millions
Source: http://www.nttdocomo.com
313
Mobile Communication and Mobile Computing
Properties
• i-Mode is packet oriented
– always online, no time delays to dial-up
– billing regarding data volumes and not regarding to
time
• simple page markup language – compact HTML
(cHTML)
• End of 2002: change into XHTML (WAP 2.0)
• a great success in Japan, because private computers
and private Internet access over fixed networks are
infrequent
• In Germany E-plus has started i-Mode on 16th march
2002
314
Mobile Communication and Mobile Computing
compact HTML
• cHTML or compact HTML is a language subset
of HTML
• very simplified HTML
• Lists, Forms, Selections, Input fields are
possible
• no Frames, no Tables, no CSS
• 166 additional pictograms, for instance
Fine
Heartbreak
Motor sports
WC
315
Mobile Communication and Mobile Computing
compact HTML (2)
•
•
•
•
•
Access key-Attribute for direct link activation respectively for direct
selection of input fields
pictures can be displayed only in GIF-format, max. 5 KB per page. GIFpictures mustn’t larger than 120*128 dots (little display)
also animated GIFs
256 colours (capable of Display)
Compact HTML Sites look like “normal” HTML,
so also “normal” Browsers like Netscape can work with them
i-Mode – on a mobile phone
an i-Mode screenshot
316
Mobile Communication and Mobile Computing
Network Configuration
317
Mobile Communication and Mobile Computing
318
i-Mode network architecture
Connection Network
PDC: Personal Digital Cellular
Telecommunication System
[NSP/Corporate LAN]
PDC-P: PDC Packet System
M-SCP
PGW
M-PGW
i-mode Server
Internet
PPM
PPM
IP
IP
BS: Base Station
IP: Information Provider
BS
BS
BS
BS
M-PGW: Mobile Message-Packet
Gateway Module
MS: Mobile Station
M-SCP: Mobile-Service Control Point
PDC-P
Network
NSP: Network Service Provider
MS
MS
MS
MS
PGW: Packet Gateway Module
PPM: Packet Processing Module
http://www.nttdocomo.co.jp/
Mobile Communication and Mobile Computing
i-Mode network architecture (2)
• i-Mode Server:
- consists of multiple server systems (B-,C-,M-Max ..),
each server system is responsible for special tasks
- represents the contents of „Information Providers“,
operates Internet-Mail and i-Mode-Mail, enables the
connection to Internet
• M-PGW (Mobile Message-Packet Gateway Module):
transforms the protocols: TCP with i-Mode-Server and
TLP (Transport Layer Protocol) with PPM
• PPM (Packet Processing Module):
executes the packet connection with the mobile enddevices/peripherals
319
Mobile Communication and Mobile Computing
i-Mode network architecture (3)
• M-SCP (Mobile-Service Control Point):
authentication of user data (similar to voice
communication)
• PGW (Packet Gateway Module):
transition to other networks, for instance to offer the
enterprises a Virtual Private Network (VPN)
320
Mobile Communication and Mobile Computing
321
i-Mode protocol stack
AL
AL (HTTP)
UITP/NWMP
TLP
CC MM RT
HTTP/
UITP/NWMP SMTP
TLP
RT MM CC PMAP
PMAP PMAP
TCP/IP
TCP/IP
LAPDM
LAPDM
L2
L2
L2
L2
L2
L1
L1
L1
L1
L1
L1
L1
TLP:
CC:
MM:
RT:
LAPDM:
PMAP:
MS
PPM
Transfer Layer Protocol
Call Control
Mobility Management
Radio Frequency Transmission
Management
Link Access Protocol on the
D-Channel, modified
Packet Mobile Application Part
M-PGW
HTTP:
SMTP:
UITP:
NWMP:
TCP/IP:
i-Mode Server
HyperText Transport Protocol
Simple Mail Transport Protocol
User Information Transfer Protocol
Network Management Protocol
Transmission Control Protocol/
Internet Protocol
L1: Layer1 (Physical Layer Protocol)
L2: Layer2 (Data Link Layer Protocol)
Mobile Communication and Mobile Computing
i-Mode protocol stack II
• UITP (User Information Transfer Protocol):
transmits user information such as, for instance, MSN
(Mobile Subscriber Number) to i-Mode-Server
• NWMP (Network Management Protocol):
performs i-Mode Service-functions
• TLP (Transfer Layer Protocol):
has a simplified transmission procedure and can
transmit the signalization and user data together
322
Mobile Communication and Mobile Computing
Java for mobile phones
• base: Java 2 micro edition and Java MIDP
(Mobile Information Device Profile)
• downloading of Java-programs
(ca. 30-50 kByte); color representation;
applications, also games etc.
• billing via micro-payment of operator
(ca. 1-5 € per application)
• products e.g. of Nokia, Ericsson, Siemens;
support through big operators
323
Mobile Communication and Mobile Computing
M-Commerce - applications
•
•
•
•
Mobile Shopping
Mobile Banking
Mobile Brokerage
Mobile Traveling
324
Mobile Communication and Mobile Computing
325
Pervasive Computing
• Operation as parallel as possible of all users
independent of the terminal, it means terminals
with different equipment (PC‘s, mobile phones,
PDAs, Applicances, etc.) should be supported by
most different entrance nets
• It means finding a suitable system architecture
for “multidimensional“ Internet
communication (e.g. regarding end terminals)
over *ML (Markup Languages)
Mobile Communication and Mobile Computing
System architecture, one-dimensional
Thin Clients
databases, etc.
WWW-Browser
Web Server
Firewall
Application Server
Firewall
326
Mobile Communication and Mobile Computing
327
System architecture, one-dimensional
Internet Inter-ORB Protocol
SOAP (Simple Object Access Protocol)
proprietary Transactionmonitors
protocols
BrowserClient
HTTP
HTMLHTMLHTMLDokumente
Dokumente
documents
Inner Firewall
Thin
Client
Outer Firewall
Web-Server
Application- proprietary
protocols
Server
proprietary
protocols
HTMLHTMLCGIDokumente
Dokumente
scripts
business
Software
Mainframeapplications
stateful-connection
Stateless-connection
data bases
Mobile Communication and Mobile Computing
Properties of application servers
main characteristics:
• object-oriented communication systems
• component- framework
• transaction concepts
• security concepts
• connection of legacy applications
• integration of WWW-services
• general support of design, deployment and runtime
328
Mobile Communication and Mobile Computing
329
System architecture, twodimensional
Thin Clients
Data bases, etc.
WWW-Browser
Web Server
Application Server
Firewall
Firewall
WAP Server
WAP-Browser
…e.g.:
BEA WebLogic M-Commerce Solution
Mobile Communication and Mobile Computing
System architecture, twodimensional
WAP-Server
Application Server + WWW Server
Backend
XSLProzessors
convert XML into
HTML, WML
Servlets
call data from the
EJBs and generate
e.g. XML
EJBs
standardize access to
Backend, create
business logic
330
Mobile Communication and Mobile Computing
XML (Extensible Markup
Language)
design principles
use in the Internet
more powerful than HTML
separation of content and style
possibility of definition of user-specific document-types
ability of XML-document processing
331
Mobile Communication and Mobile Computing
XML- document „bibliography“
reference to
Style Sheet File
special
tags
332
Mobile Communication and Mobile Computing
Valid and well-formed documents
XML-Documents can have a DTD (Document Type Definition).
The DTD can be contained in the document or can be referenced by a link.
A DTD specifies, which tags are permitted and how these can be combined.
It has a special meaning for the processing of documents.
The processing programs can check XML- documents for structural errors
with the help of DTD.
If there is no error then a document is valid!
Well-formed documents contain no DTD- reference, but fulfill the XMLsyntax-rules.
333
Mobile Communication and Mobile Computing
334
Accompanying Style Sheet File
RULE for root-element
Insert of lower elements
Cycle
Mobile Communication and Mobile Computing
Presentation in MS IE 5.0
correspondently IE6.0
335
Mobile Communication and Mobile Computing
Other Style Sheet File
336
Mobile Communication and Mobile Computing
Other presentation via XSL
337
Mobile Communication and Mobile Computing
Change of XML- documents
presentation
for processing
XML
XSLProcessor
XSL
•
•
•
EDI/WML
EDI:
Electronic Document Interchange
Conversion of XML- documents into workable formats (with the help of
XSL-Style-Sheets)
e.g. into EDI- formats for commercial data processing
in the mobile field very interesting for conversion into WML!
338
Mobile Communication and Mobile Computing
System architecture, multidimensional
Access-Server
Application Server + WWW Server
Backend
XSLProcessors
convert XML
into *ML
Servlets
call data from EJBs
and generate e.g.
XML
EJBs
Standardize access to
Backend, create
business logic
339
Mobile Communication and Mobile Computing
IBM Websphere Transcoding
Publisher
•
•
•
•
syntax customization of content
easy installation
little administration effort
changeable, expandable architecture of components
340
Mobile Communication and Mobile Computing
IBM Websphere Transcoding
Publisher
&
WAP – capable
mobile phone
Evaluation of used
profiles
1.Request
over port xx
Text Clipper:
transforms HTML into
WML
7.Output of
contents
Fragmentation
Transcoder:
Change into WML-decks
341
Mobile Communication and Mobile Computing
Oracle Application Server Wireless
Edition
•
•
•
syntactic customization of content
renewable, expandable architecture of components
good customization of specific content
Request Manager authentifies user
and calls Master Service
Request
Manager
Client
Request
Master Service
configures und starts an
adapter
Master
Service
Transformer
A transformer
converts
information in
suitable Clientformat
the adapter
fetches the
Information
(via e.g.
HTTP, SQL,
etc.)
Adapter
342
Mobile Communication and Mobile Computing
Oracle Application Server Wireless
Edition
Expiry of a user request
343
Mobile Communication and Mobile Computing
Oracle Application Server Wireless
Edition
Adapter and Transformer
344
Mobile Communication and Mobile Computing
Contents customization with
XML / XSLT
• Separation of content and presentation
• content client- independent in XML
• XSLT: XSL transformations: a XML- data format is changed into a
new data format (not necessarily XML), this new data format can
include platform dependent information about the presentation of
data besides the main information
• presentation client- dependent in some XSLTs
• XML-Support in many data bases
• the server itself needs additional logic
345
Mobile Communication and Mobile Computing
Contents customization with
XML / XSLT
server-sided requests:
• reconnaissance and classification of the client
• choice of the suitable style sheets
• parameter handover to XSLT
• Processing of other documents (e.g. bitmaps)
346
Mobile Communication and Mobile Computing
Example application: Pizza
ordering service
• content and logic in same XML-document
• no presentation-semantic in XML, so all
client- abilities can be used in XSLT
• but stylesheets are not reusable
347
Mobile Communication and Mobile Computing
348
Example application: pizza ordering
service
<?xml version='1.0' encoding="ISO-8859-1" standalone="no" ?>
<?xml-stylesheet type="text/xsl" href="Pizzaservices.xsl"?>
<?xml-stylesheet type="text/xsl" href="Pizzaservices.lynx.xsl" media="lynx"?>
<?xml-stylesheet type="text/xsl" href="Pizzaservices.lynx.xsl" media="palm"?>
<?xml-stylesheet type="text/xsl" href="Pizzaservices.wap.xsl" media="wap"?>
<?cocoon-process type="xsp"?>
<?cocoon-process type="xslt"?>
<xsp:page language="java" xmlns:xsp="http://www.apache.org/1999/XSP/Core">
<xsp:logic>
class Item extends Vector {
private int[] numbers;
public Item () {
super ();
numbers= new int[10];
}
public void setNumber (int nr, int a) {
numbers[nr]=a;
}
public int getNumber (int nr) {
return numbers[nr];
}
}
...
Mobile Communication and Mobile Computing
349
Example application: pizza ordering
service
<services>
<service>
<name>Hi Pizza</name>
<banner>hellopizza.jpg</banner>
<description>Hot Ware on Order</description>
<location zipcode ="01277">
<address>Bodenbacher Strasse 16b, 01277 Dresden</address>
<phone>03512540707</phone>
<fax>03512540708</fax>
</location >
<location zipcode="01127">
<address>Mohnstraße 50, 01127 Dresden</address>
<phone>03518485590</phone>
<fax>03518485558</fax>
</location >
<proposal>
<category name="Pizza">
<food>
<name>Pizza Kentucky</name>
<description>Salami</description>
<price size="Normal">8.00</price>
<price size="Jumbo">15.00</price>
<price size="Pan">10.00</price>
</food>
...
Mobile Communication and Mobile Computing
Pizza ordering service: PC-presentation
350
Mobile Communication and Mobile Computing
Pizza ordering service: presentation on
Palmscape and in WAP
351
Mobile Communication and Mobile Computing
XHTML
352
Mobile Communication and Mobile Computing
XHTML
• XHTML™ 1.0 is Extensible HyperText Markup
Language (Second Edition)
– reformulation of HTML 4 in XML 1.0
– use instead of WML2.0 correspondently cHTML (iMode)
– basis for integration between WAP2.0 and i-Mode
WWW: http://www.w3.org/TR/xhtml1/#xhtml
353
Mobile Communication and Mobile Computing
XHTML
• supporting via as well as WAP-Browsers also Netscape
Navigator and Internet Explorer
• constituents:
– DTD (Document Definition)
– XSL (Extensible Stylesheet Language)
• large quantity of supported tags in comparison with
WML2.0 and cHTML
–
–
–
–
–
CSS
frames
tables
forms/input fields
applet calls
354
Mobile Communication and Mobile Computing
XHTML vs HTML
• XHTML describes data <-> HTML displays data!
• XHTML – combining HTML and XML, and their
strengths
• XHTML is oriented to internet/PC and mobile
internet/ mobile phones and hand helds
• XHTML - compatibility
– everything has to be marked up correctly -> "wellformed" documents
– pages can be read by all XML enabled devices
– upgrading of XML supported browsers
– compatibility to all browsers
– backward browser compatible
355
Mobile Communication and Mobile Computing
Mobile agents
356
Mobile Communication and Mobile Computing
357
The agent- model
• an agent-system consists of the agents themselves
and an execution engine for working with agents. The
execution engine offers basic services to the agents
• Agent is an independent program generally, it consists
of data, code and execution state, it works in interest and
order of a third party (e.g. user, application).
Mobile Communication and Mobile Computing
Agent system
358
Mobile Communication and Mobile Computing
Agent model
Client
Client
create
Agent
simple
Serverinterface
migration
code,
data,
state
result
Agent
code,
data,
state
simple
Serverinterface
• migration: transfer of code, data, state
• local interactions with server
• transfer of the result
359
Mobile Communication and Mobile Computing
360
Properties of mobile agents
Advantages:
+ reduction of network load
+ autonomy and asynchronity
+ dynamic adapting in
environment
+ heterogeneity
+ robustness and error tolerance
+ scalability
+ personalization and
individualization
+ dynamic code-installation
+ encapsulation of protocols
Disadvantages:
– need of special execution
engine (Middleware)
– high security requirements
– transfer of code, data, state
– Decision: migration vs. remote
communication
Mobile Communication and Mobile Computing
Applications
•
•
•
•
•
•
•
•
•
E-commerce
database requests
intelligent e-mails
Office applications/workflow
traffic telematic
Web surfing
load balancing
virtual enterprise
Mobile computing
361
Mobile Communication and Mobile Computing
Existing agent systems
•
•
•
•
•
Voyager (ObjectSpace)
Aglets (IBM)
Concordia (Mitsubishi Electric)
Grasshopper (IKV++)
Odyssey (General Magic)
•
•
•
•
Mole (Stuttgart), Ara (Kaiserslautern)
Agent TCL (Dartmouth University)
MASIF (OMG)
Telescript
362
Mobile Communication and Mobile Computing
Middleware for spontaneous Networking
363
Mobile Communication and Mobile Computing
Vision
• spontaneous networking of electrical devices (but not only
computers)
• very simple connection
JINI
• platform independence
UPnP
364
Mobile Communication and Mobile Computing
JAVA Intelligent Infrastructure, JINI
• „Middleware“ for spontaneous networking; originally
developed from Sun
• JINI Connection Technology enables dynamic control of
networked services and devices
• Partitioning into so called Lookup Groups: different sets
of lookup-services
• basic operations:
– Discovery: offers locating of a directory services (lookup
service)
– Join: enables acquaintance/ registration of the services
implemented from some device
365
Mobile Communication and Mobile Computing
JAVA Intelligent Infrastructure, JINI
• Lookup-Service enables locating of services via
other users/devices per lookup-operations
• Leasing offers time-limited allocation of
resources (using of services)
• Jini integrates distributed events processing and
distributed transactions further on for coordination between services
366
Mobile Communication and Mobile Computing
General procedure: step 1
Lookup service
Discovery & join
protocol
JINI device /
service
Discovery lookup
Client
367
Mobile Communication and Mobile Computing
General procedure: step 2
Lookup Service
Proxy upload
JINI device /
service
Proxy download
Client
368
Mobile Communication and Mobile Computing
General procedure: step 3
Direct Connection
JINI device /
service
Client
• synchronization
• data exchange between Device and Client
over own communication protocol
369
Mobile Communication and Mobile Computing
JINI - Details
• Proxy hides all details of communication and is executed in the form
of Client (dynamic installation of Stubs)
• security over RMI - Security Extension Framework
• new versions of JINI Starter Kits include advanced possibilities, for
instance:
–
–
–
–
Caching of request results by Clients
unicast-discovery
comfortable control of using period (lease)
asynchronous receiving of events among other features
• further development via JINI Community:
– for instance JINI Surrogate Architecture: supports devices that do not
have all required resources for JAVA and JINI
– printer working group
370
Mobile Communication and Mobile Computing
JINI - Assessment
• suitable to support scenarios from the field
of Ubiquitous/Pervasive Computing
• JINI is a part of JAVA 2 Micro Edition
371
Mobile Communication and Mobile Computing
Universal Plug and Play, UPnP
• reply of Microsoft to JINI
• Embedded in UPnP- forum
• with this improvement corresponding to Plug- and- Play
Standards, the PC peripheral devices should be
connected to a home-network problem-less
• via Universal Plug and Play diverse devices can
communicate with each other like with Jini
372
Mobile Communication and Mobile Computing
Universal Plug and Play, UPnP
• essentially based on open standards like TCP/IP and
therefore is compatible to each network
• in Windows ME integrated
• a special toolkit for creation of drivers on the basis of
UPnP developed by INTEL
373
Mobile Communication and Mobile Computing
374
UPnP architecture
Common
Abstractions
Home application
Universal PnP
Common
Interfaces
Discovery
Media
Independence
Description
Usage
Bus attached
Internet Protocol
attached
IrDA
X10
..
IR
PLC
..
(ISA,PCI,USB,
Network media
(Ethernet,HomeRF,
HomePNA,..
IEEE,1394,IR,..)
Mobile Communication and Mobile Computing
Further approaches
HAVi – Home Audio and Video Interop.
• essentially supported by the vendors of consumer-electronics field
• UPnP Forum is interlocked however represented more broadly on
the market (specially also in computer-industry)
HomePlug
• consortium for standardizing of data communication over (low
voltage) power cable
• performance like by IEEE 802.11b
• the members are among others Cisco and Panasonic
375
Mobile Communication and Mobile Computing
Services and system support for
Mobile Computing
376
Mobile Communication and Mobile Computing
Mobile Computing: system support
Essential properties und requirements:
• dynamics, localization
• heterogeneity of networks and enddevices
• security problems
377
Mobile Communication and Mobile Computing
Mobile distributed applications:
example
Local Resources,
Error Protocols
Product Data
Main office
Caching
Maintenance
technician
Client
LAN-Access
Mobile Access
- very different performance and charges: GSM, ISDN, LAN
Software-technical, automatic adaptation to concrete
system environment
Example: Access to picture data/compressed picture
data/graphics/text
378
Mobile Communication and Mobile Computing
Problems and requirements
Problem fields:
• dynamic system and net configuration
• dynamic change of Quality-of-Service-properties
• uncoupling/re-connection
• transparency of resource access
• security aspects
Requirements:
• connection monitoring and selection
• treatment of uncoupling/off-sets and migration; emulation of services
• configuration update
• localization of mobile servers and clients
• advanced security and transaction services
379
Mobile Communication and Mobile Computing
Mobile RPC
Goals:
• Mobile Binding
– Transparent call to an alternative server by non-accessibility
• Datagram RPC
– Queuing of calls in disconnected status
• Queued RPC
– intermediate storage and delivery of results after re-coupling
Realization:
• Attachment on existent RPC- systems (without new implementation
or internal code changes)
380
Mobile Communication and Mobile Computing
Time Behavior Datagram RPC
•Client
•Server
•DCE RPC
•Datagram RPC
T1
T2
Time
T3 T4
Decoupling
Net connection
RPC reaches Server
Return to Client
381
Mobile Communication and Mobile Computing
Message Queuing: MQ Series
example
• Base: Messages, Queues with Queue Manager
• dynamic coupling between applications and local Queues via
logon/logoff
• using of Queues for transmission or receiving; also mixed using is
possible
• coupling of distributed Queue Managers via Message Channels
• Internet Gateway, C++- and Java-Support
• support of essential operating system platforms
382
Mobile Communication and Mobile Computing
Example scenario
Computer A
Computer B
Queue
Manager
AppQueue
lication
Manager
1
MQPUT
Queue
Manager
Message
Channel
Queue
Manager
Application
2
MQGET
• decoupling of application through Queue
Manager:
– Message forwarding is possible even if application
isn’t running
383
Mobile Communication and Mobile Computing
N:M - communication
Access to Server
via multiple Clients
• Load balancing (selective
delivery) or
• Parallel processing
(replicated delivery)
C
A
D
B
Queue, with
optional support of
message priorities
E
384
Mobile Communication and Mobile Computing
385
Message Queuing: Assessment
Advantages
+ simple manageability
+ robust message delivery
+ flexible application fields (for instance load balancing,
parallelization, batch-transmission of branch data etc.)
+ relevant for easy coupling of programs, for instance via Internet, or
for Mobile Computing
Disadvantages
− limited communication semantics
− interaction model is different than with procedures/method
invocations
− limited accessibility of higher services
− only several proprietary decisions up to now, only step-by-step
standardization
Mobile Communication and Mobile Computing
Application Structure
Ethernet
Distributed
Database
Ethernet
DB
E-Fax-Order
Branch office
Firm
xDSL
Application
GSM
Ethernet
Cache
Resource
Mobile Station
Communication path
Management
DB-Access
Distributed
Database
Client X
386
Mobile Communication and Mobile Computing
Domain-concept
387
Mobile Communication and Mobile Computing
Main functionality: Domain and
Station Manager
Domain Manager:
• management of all global objects (users, global
available resources, stations, net topology)
Station Manager:
• management of all local objects of a station (net
access, running applications etc.)
388
Mobile Communication and Mobile Computing
Architecture of Station Manager
Application
Subsystem
(Application Programming Interface)
Subsyste
m
(System Calls)
Location
Service
Registry
Service
Resource
Broker
Application Data
Mobilizer and Manager
Bandwidth and Cost Authentication and Encryption
Service
Management Service
Active
Database
Disconnected Operation Handling Service
(CS, QS, CHS, BMC)
389
Mobile Communication and Mobile Computing
Mobile Multimedia Email: message
transfer
User Agent
email
protocol
Subsystem
email
protocol
Queuing Service
Queuing Service
email
protocol
Email Proxy
Message Store
message transfer
Mobile Enhanced Message Handling
System
390
Mobile Communication and Mobile Computing
Mobile Multimedia Email: selection of
quality parameters
Cent
Cent
391
Mobile Communication and Mobile Computing
Mobile File Manager:
example CODA
• distributed file system, which offers the
unbreakable access to data also in the case of
server shut-down or net failure
• developed at the Carnegie Mellon University
• based on AFS (Andrew File System, distributed
file system in UNIX-environment)
• relatively transparent to the applications
392
Mobile Communication and Mobile Computing
CODA overview
• based on the model of „Disconnected Operations”
• client keeps Read- and Write-access on the data via
inset of a local buffer (Cache) also during temporary
disconnection from net
• with re-connection system forwards changes and
recognizes potential conflicts
• for different operating systems available (for instance
LINUX, Solaris, Windows)
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CODA system model
Replicated Server:
High availability
Net communication
at file open and close
Disconnected Client:
local data access
on Cache
Client
(“Whole-File-Caching”)
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properties of consistence (Coda)
• Callback
– logic reference from server to the active client, used for
immediate information about file changes via other client
• after connection failures the file in client cache remains
valid till to timeout termination (as a rule several minutes)
• thereby reduced consistency
• conflict processing explicitly in interactive form, however
low conflict probability
Mobile Communication and Mobile Computing
Conflict processing (CODA)
• extensive automation as objective purpose, however
isn’t possibly for:
– Update/Update-conflict: independent double update of the same
file
– Delete/Update-conflict: independent erasure respectively update
of the same file
– Name/Name-conflict: generating of two files with the same name
Manual access after user notification
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Mobile Communication and Mobile Computing
Cache management (Coda)
• “Cache-Misses”: searched file isn’t in the ClientCache
– processing failure in the disconnected status
• priority list of important files per user
– the highest priority is always kept in the cache (for instance
by system programs, user profiles, address files etc.)
– other priorities: exchange strategies correspondent to
importance
– dynamic generated files via list of essential operations
referenced (for instance actual test protocol etc.)
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File synchronization under Windows
- Windows: over System Control -> Management -> Services
so called „file replication (server)“ for synchronization of
data between different servers
- under Explorer -> Extras -> Synchronization:
- Synchronization of own Homepage with PC
- Synchronization of Sites in WWW
Mobile Communication and Mobile Computing
E-Hand
- connects existing Enterprise Systems with mobile end-devices
- platform independent
- very simple synchronization and data transfer
- supports XML, ODBC and SyncML
Advantages:
- contains Web-similar user interface for application installation and
for mobile participants
http://www.ehand.com/ehand/
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Mobile Communication and Mobile Computing
E- Hand
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Mobile Communication and Mobile Computing
Mobile databases support
Motivation:
• SFA-Sales-force-automation:
-> actual information about clients, competitors and market trends to
the field (outside-) workers
• emergent business transactions on the site -> efficiency increasing
Example:
Pharmaceutical Industry
• visit of 6 up to 8 distribution medics per day
• to bring dialogue to the point more quickly
– previous information about the medic (contacts, receipt prescription habits)
are recallable from the firm-net
•
•
presently still manually due to dialogue recording and product
documentation
in the future via mobile databases permanently faster access to data
without inconvenient storage, connection establishment etc.
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Mobile databases support
• mobile databases offer principally data synchronization and replication
of enterprise servers and for mobile end-devices like PALM etc.
• due to increasingly mobile business processes there is a necessity of
databases, which must perform these functionalities among other
things:
– quickly
– compatible to as many as possible mobile systems
• 2 mobile database types:
– “asynchronous synchronization”: for instance SQL Remote of Sybase
• data replication between central database and multiple remote databases
• also offline-working is possible due to email-queuing principle (sent, if connected)
– “synchronous synchronization”: for instance Sybase Mobilink
Synchronization Server
• co-operation with databases of other vendors (via Server Middleware)
• permanent connection necessary, for instance via GSM
Mobile Communication and Mobile Computing
IBM DB2 Everyplace
• compatible for instance to Windows CE, PalmOS, EPOC ...
• footprint: ~150 k (storage requirements)
• for data balancing DB Everyplace Sync Server is necessary
– synchronization with other Handhelds without PC!
• includes so called Mobile Devices Administration Center
enables central management of all mobile end-devices of a
enterprise
• supports integration of enterprise data from different databases
and other sources (DB2 replication technology, JDBC, Adapter
API for customized decisions)
• data are encrypted during synchronization (56 or 128 Bit)
• supports automatic conflict processing
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Mobile Communication and Mobile Computing
IBM DB2 Everyplace
Mobile Devices
Source: http.//www.ibm.com
Synchronization
Server
Backend
IBM DB2
Microsoft
Oracle
Informix
Sybase
Other DBMS (JDBC)
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Mobile Communication and Mobile Computing
Oracle Lite
• 3 constituents:
– Oracle Lite DBMS
• database with low footprint (storage requirements)
• Java-enabled
– iConnect
• components for synchronization and creation of messagingapplications (principle of message queues)
– Web-to-go
• components supporting development, deployment and
management of mobile Web-applications
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Mobile Communication and Mobile Computing
Oracle Lite
replication via Internet
File-based replication
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Mobile Communication and Mobile Computing
Sybase SQL Anywhere Studio
•
•
•
•
•
•
•
•
mini-database, can be operated on the PDAs
supports PalmOS, EPOC and WindowsCE
small „footprint“: ~50kByte
developer can adapt the database according to the required SQLproperties, modular design principle
synchronization enables data balancing with the enterprises
database, all well-known database vendors are supported
only the changed data are transmitted
both local (for instance B. Hotsync (Palm)) and remote
synchronization supported
architecture similar to IBM DB2 Mobile Connect
(Source: http://www.sybase.com/products/anywhere/)
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Mobile Communication and Mobile Computing
Further approaches
• Microsoft Mobile Information Server
• Lotus Everyplace
• numerous further products, mostly similar
architecture concepts
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Mobile Communication and Mobile Computing
Further sample applications
• Traffic management
• Mobile Information Services
• M-Commerce
•
•
•
•
•
Service technician
Customer consultant
Field workers in general
Environmental engineering (measurement data logging)
Medic (visits on site)
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Mobile Communication and Mobile Computing
Traffic management
Berlin
“Global” Provider
Paris
Dresden
Service Center
“Local”
Provider
Services:
• Traffic engineering
• Travel information
• Maintenance service
• Mobile Office
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Mobile Communication and Mobile Computing
Traffic management
Internet
Information
Provider
Info
GPS
Info
Info
GSM
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Info
Info
Info
Center B
Center A
Virtual
Private
Network
PSTN/
ISDN
Distributed
Information services
End-user
Distributed Service-Center
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Application scenario: car maintenance
Host
Printer
Notepad
HUB
PC
Terminal
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Online-information services
Client
low band width
Server
for instance WWW
Client (mobile)
low battery resource
• Client/Server-access by individual requests
• additionally: separate broadcast-channel from Server to the mobile
Clients: transmission and caching of frequently requested
information; thereby lower battery consumption (receiving less
expensive as sending for the Client)
Mobile Communication and Mobile Computing
Optimization: basic concept
• information in Publication-Group: regular
Broadcast
• information in On-Demand-Group: Client/Serverqueries
• exchange between both groups on the basis of:
–
–
–
–
access frequency (for instance on WWW-pages)
page modification frequency
channel bandwidths
clients storage volumes (Cache)
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Mobile Communication and Mobile Computing
Mobile e-Mail
• Eudora Internet Suite, consists of:
– Eudora email for the Palm computing platform
– EudoraWeb browser for the Palm Computing platform
– Eudora Mail Conduit
• Properties:
– Eudora and EudoraWeb browser support SSL (Secure Sockets
Layer) and TLS (Transport Layer Security), i.e. end-to-end
security
– synchronization of bookmarks between PC Web-Browser and
EudoraWeb browser via Eudora Web Conduit
– synchronization with PC-Email applications
– several Email-accounts
Quelle: http://www.eudora.com
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Mobile Communication and Mobile Computing
Alternative M-Commerce
applications
• 12snap.de (pronounciation: “one two
snap”)
– Auctioning channel
• www.paybox.de
– Cashless payments
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Sample: 12snap system architecture
Offers via
Cellular
Broadcast
mobile radio
net D2
external
provider
center
Internet
Automatic processing of
the orders which
are incoming via
phone-service;
also coupling of WAP and
telephony
Call
Center
Users are registered by 12snap and enable direct debit,
respectively booking via the credit card;
Orders are sent to a Call-Center via keyboard tone, client
identification takes place via his phone number
(CLIP = Calling Line Identification Presentation)
Mobile Communication and Mobile Computing
Sample: paybox.net
• Client is registered in the Internet by paybox.net and
enables direct debit
• Client obtains as a result so called Paybox-PINs; using
Paybox-PIN client can unblock the transactions
• purchase payments in the Internet are carried out as
follows:
– Client selects „Paybox“ as a payment type
– Merchant sends transaction to Paybox-provider via secure data
connection
– Provider dials up the clients via phone numbers stored in his
master data
– then Client can unblock the transaction with his PIN
– Paybox transfers money via direct debit and forwards it to the
Merchant
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