Download Mobile Computing Functions

Mobile Computing
Lecture (2)
Evolution of Computing
Mobile Computing Functions
A computing environment is defined as
mobile if it supports one or more of
these characteristics:
 User mobility: User should be able to move

from one physical location to another location
and use same service
Network mobility: User should be able to
move from one network to another network
and use same service
Mobile Computing Functions (Cont.)
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Device mobility: User should be able to move
from one device to another and use same
service
Session mobility: A user session should be
able to move from one user-agent
environment to another.
Service mobility: User should be able to
move from one service to another
Host mobility: The user should can be either
a client or server.
Mobile Computing Functions (Cont.)
Mobile computing functions can be logically divided
into the major segments:
1- User with device: fixed, portable
2- Network: different networks: GSM, CDMA, Ethernet,
Wireless LAN, …etc.
3- Gateway: Interfacing different transport bearers
4- Middleware: handling the presentation and
rendering of the content on a particular device.
5- Content: it is the domain where the origin server
and content is.
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Mobile Computing Functions (Cont.)
Application Server
Device
Adaptation Framework
Origin
Server
Datastore
User
with
device
Networks &
Gateways
Middleware Framework
Content
Networks
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Mobile computing will use different types of
networks: fixed telephone network, GSM, GPRS,
ATM, …etc.
1- Wireline Networks: designed over wire. It is called
fixed network. Copper or fiber optic cables.
2- Wireless Networks: mobile networks
3- Ad-hoc Networks: for this purpose only.
4- Bearers: transport bearers: TCP/IP, http,
protocols for dialup connection.
Middleware and Gateways
Middleware: A software layered between a
user application and operating system.
 Examples: communication middleware,
object oriented middleware, message
oriented middleware, database middleware,
…etc.
In mobile computing we need different types of
middleware components and gateways at
different layers of the architecture. These are:

Types of Middleware
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1- Communication middleware
The application will communicate with different nodes and
services through different communication middleware.
Examples could be NT3270 for IBM mainframe or Javamail
connector
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2- Transaction processing middleware
In many cases a service will offer session oriented dialogue
(SoD). For a session to maintain over the stateless Internet.
This is done through an application server. The user may be
using a device, which demands a short transaction whereas
the service at the backend offers a SoD. In such cases a
separate middleware component will be required to convert a
SoD to a short transaction. Management of the Web
components will be handled by this middleware as well.
Types of Middleware (cont.0

3- Behavior management middleware
For different devices we need different types of rendering. We
can have applications which are developed specially for
different types of rendering. For example, we can have one
application for Web, another for WAP, and a different for SMS.

4- Communication gateways
Between the device and the middleware there will be network of
networks. Gateways are deployed when there are different
transport bearers or network with dissimilar protocols. For
example, we need an IVR gateway to interface voice with a
computer, or a WAP gateway to access internet over a
mobile phone.
Mobile Computing Applications
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Enable the business initiatives by supporting mobility of

Customers

Suppliers and Businesses

Employees
Mobile computing applications
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Wireless messaging (e.g., SMS)
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Mobile ecommerce (M-Commerce) and its variants
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Mobile ebusiness applications (MEBAs), e.g., M-CRM, M-portal
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Specialized applications
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Positional commerce (p-commerce) .
Voice commerce (v-commerce).
Television commerce (T-Commerce)
Location sensitive apps
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Wireless sensor network apps
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Mobile agent apps
Two views:

Mobile applications are fundamentally new applications.

Mobility is another dimension of the existing applications
Mobile Computing Applications
Categorization
B2B
C2B, B2C
B2E, E2B
Business
Consumer
Employees
B2G, G2B
C2G, G2C
Citizens
E2G, G2E
Government
G2G
Employees
Mobile Computing Platforms
Server
(Web Server, eMail server,
Mainframe)
Mobile Device
(Cell Phone, PDA, Pocket PC)
Application
Application
Middleware
Services
Local
Platform
Services
Network
Transport
Services
Mobile
Computing
Platform
Middleware
Services
Local
Platform
Services
Physical Wireless Network
(Antennas, Transceivers, Base Stations,
Cellular Networks, 802.11 LANs,
Satellites)
Network
Transport
Services
Internet as the Network Platform
www.sun.com
arts.um.edu
108.2.11.7
75.10.17.3
IP
WAN3
IP
www.IBM.com
WAN2
Switch
/Gateway
cs.um.edu
108.2.11.5
75.10.17.1
Switch/Gateway
Switch/Gateway
IP
WAN1
Bank1.co..uk
(Typically
ATM,
83.13.17.3
Frame Relay,
Level3.co..uk
X.25)
83.13.17.4
•DNS (Domain Name Services) translates cs.um.edu to 108.2.11.5
•Telnet cs.um.edu = Telnet 108.2.11.5
•FTP cs.um.edu = FTP 108.2.11.5
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The Figure shows a conceptual and partial view of
the Internet. This Internet shows three networks (a
university network with two computers, a
commercial company network, and a network in
UK). Each computer (“host”) on this network has an
IP address and has been assigned a domain name
as well. The Internet is very heterogeneous (i.e.,
different computers, different physical networks).
However, to the users of this network, it provides a
set of uniform TCP/IP services (TCP/IP hides many
details). Once a device (mobile device or a laptop)
has an IP address, then it can send messages to
any other device with another IP address.
Wireless Web
Wireless
Browser
4
Wireless
Network
Wireless
Gateway
http
5
Web
Server
2
1
Web
Browser
http
over
wired Internet
3
Web
Gateway
Content
(XML/HTML)
Back-end
Systems
and
Darabases
1. Access from Web browser to Web Server over wired Internet
2. Access to Web contents from HTML/XML files
3. Access to non-Web content through a Web gateway
4. Access from cellular phone over a wireless network
5. Access from wireless gateway to Web Server over wired Internet
Wireless Middleware and Wireless Gateways
(WAP, i-mode, J2ME, MMIT, BREW)
Wireless middleware, also known as mobile computing middleware,
smoothes over the mobile computing issues, as much as possible, so that
the same applications can run on wired as well as wireless networks. It
performs the following functions:
 Establishes connections between mobile clients and servers over wireless
networks and delivers messages over the connection.
 Transforms data from one format to another (e.g., one type of markup to
another).
 Detects the mobile device characteristics and optimizes the wireless data
output according to device attributes.
 Compresses data to minimize the amount of data being sent over a slow
cellular wireless link.
 Encrypts/decrypts data for security.
 Allows monitoring and troubleshooting of wireless devices and networks.
Naturally not all these features are needed for every mobile computing
application. Some applications need less middleware support than others.
WAP(Wireless Application Protocol)
•Intended for data entry/display on cellular phones
•“An open, global specification that empowers mobile users with wireless devices to
easily access and interact with information and services instantly.” www.wapforum.org
•Complete protocol stack similar to Internet protocols but optimized for wireless
information pull and push transport layer and above; across multiple wireless technologie
WAP and WAE
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WAP is a set of protocols to enable the presentation
and delivery of wireless information and telephony
services on mobile phones and other wireless
devices. The WAP model, shown in Figure, is based
heavily on the existing Web; i.e., a WAP gateway
translates between the Web server and the WAP
clients. WAP provides a Wireless Application
Environment (WAE) for creating WAP applications
and services.
The main elements of WAE are:
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A markup language called Wireless Markup
Language (WML) that is similar to XML but that has
been optimized for wireless links and devices. A
scripting language (WMLScript) is also provided.
Specification of a microbrowser in the wireless
terminal. This is analogous to the standard Web
browser – it interprets WML and WMLScript in the
handset and controls presentation to the user.
A framework, the Wireless Telephony Applications
(WTA) specification, to allow access to telephony
services such as call control, messaging, etc. from
within the WMLScript applets.
WIRELESS NETWORKS
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Different type of wireless networks support
mobile computing applications and platforms
Wireless networks, as the name implies,
interconnect devices without using wires –
instead they use the air as the main
transmission medium. Wireless networks are
enjoying widespread public approval with a
rapidly increasing demand. The unique
features of the wireless networks are:
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The bandwidths, and consequently data rates, of
communication channels are restricted by
government regulations. The government policies
allow only a few frequency ranges for wireless
communications.
The communication channel between
senders/receivers is often impaired by noise,
interference and weather fluctuations.
The senders and receivers of information are not
physically connected to a network. Thus the location
of a sender/receiver is unknown prior to start of
communication and can change during the
conversation.
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The next Figure displays an overall classification of wireless
networks in terms of distance covered, from very short range (10
meters) to very long range (thousands of miles).
Wireless LANs (WLANs) allow workstations in a small area
(typically less than 100 meters) to communicate with each other
without using physical cables. The most popular example of
Wireless LANs are the IEEE 802.11 LANs that deliver between
11Mbps to 54 Mbps data rate. Another example is the Bluetooth
LANs (for the data rates in the 1 Mbps range over 10 meters). Very
short range LANs such as Bluetooth are also known as Wireless
Personal Area Networks (WPANs)
Wireless metropolitan area networks (WMANs) have been used
in traditional packet radio systems often used for law-enforcement or
utility applications. An interesting area of growth for wireless MANs
is the wireless local loop (WLL) that is quite popular with long
distance telephone companies. WLLs are fixed wireless networks
where the devices being connected are stationary.
Wireless WANs (WWANs) provide wireless support over long
distances. Traditional examples of wireless WANs are paging
networks and satellite systems. However, a great deal of wireless
WAN activity at present revolves around the cellular networks that
provide support for cellular phones and other handheld devices such
as PDAs and laptops.
Wireless Networks
Wireless MANs
Wireless LANs
Personal
Area
Networks
Business
LANs
Example1:
Bluetooth
1 Mbps,
10 Meters
Example1:
802.11b
11 Mbps,
100 Meters
Other examples:
wireless sensor
networks, UWB
Other
examples:
802.11g,
HiperLAN2
Wireless
Local Loops
(Fixed Wireless)
Example1:
LMDS
37 Mbps,
2-4 Km
Example2:
FSO
1.25 Gbps
1-2 KM
Wireless WANs
Cellular
Networks
Example1:
GSM, 9.6 Kbps,
wide coverage
Example2:
3G, 2 Mbps,
wide coverage
Satellite
Systems
Example1:
Motorola
Iridium
up to 64 Mbps
globally
Example 2:
Deep space
communication
Paging
Networks
Example1:
FLEX,
1.2 Kbps
Example2:
ReFLEX,
6.4Kbps
Wired
Local Area Networks (LANs)
Metropolitan Area Networks
(MANs)
Wide Area Networks (WANs)
Wired LANs
Wired MANs
Wired WANs
Ethernet (10-100 Mbps, 150 to
500 meters)
FDDI (100 Mbps, 50 Kilometers)
ATM (44 Mbps to 140 Mbps)
Frame Relay (44 Mbps)
Token Ring (4 -16 Mbps, 200 to
500 meters)
Wireless
Wireless LANs
Wireless MANs
Wireless WANs
Bluetooth (1 Mbps, 10 meters)
wireless local loops (10 Mbps,
100 Kilometers)
Current GSM systems at
9.6Kbps, future 3G systems at 2
Mbps
IEEE 802.11 LANs (2-11 Mbps,
100 meters)
Issues unique to wireless
•Frequency allocation
•Multiple Access
•Location
A sample environment that supports
wireless Ethernet LANs

The next Figure shows a sample environment
that supports wireless Ethernet LANs so that
the students can access the school server as
well as the public Internet. In this
configuration, several wireless access points
are connected to a wired LAN that is
connected to the Internet and an internal
server. Each access point supports mobile
computers with wireless Ethernet cards in a
wireless cell that spans around 100 meters.
A Sample Wireless School
Link to
Public Ethernet
C
D
T1
or
LAN Server
DSL
Wireless LAN
Cell
Wireless LAN
Cell
Y
Router
Z
Centrex
Wired Ethernet LAN
•X, Y, Z are
access points
for the wireless
Ethernet LANs
•A, B, C, D are
student laptops
Wireless LAN
Cell
X
A
B
Wireless Personal Area Networks
(WPANs), Bluetooth and UWB
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Wireless Personal Area Networks (WPANs) are short-range (10
meter or less) radio networks for personal, home, and other
special uses. Within the WPAN family, several specifications
such as Bluetooth, wireless sensor networks, and UWB (Ultra
Wideband) have emerged.
Bluetooth is a wireless cable replacement standard that provides
a 1 Mbps data rate over 10 meters or less. It typically consists of
a group of linked devices, such as a computer wirelessly
connecting to a set of peripherals, known as as a “piconet.”
Multiple piconets can be formed to provide wider coverage. Due
to its relatively low data rates and very short distances,
Bluetooth is being used in home appliances, “Bluetooth-enabled”
cars, and other such applications.
Bluetooth
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Founders: Ericsson, IBM, Intel, Nokia, Toshiba; May 98
Currently: Over 850 companies, V1.0 spec issued 7/99
Small form factor, low-cost, short range radio link between
mobile PCs, phones and other portable devices
Relatively fast, short packets
Software for service and device discovery
Typical application: cellular phone to PDA or earphone
The next Figure shows a simple Bluetooth was designed to allow
low-bandwidth wireless connections to become so simple to use
that they seamlessly mesh into your daily life. A simple example
of a Bluetooth application is updating your cellular phone
directory. The main idea is that this could happen automatically
as soon as the phone is within the range (10 meters) of your
desktop computer where your directory resides.
Bluetooth
PSTN
Access
Point
Cellular
Network
Wired
LAN
Bluetooth Piconet
(1 Mbps, 10 meters)
Cellular Communication Networks
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The next Figure shows a high-level view of a cellular
communication network used in wide areas. The cellular network
is comprised of many “cells” that typically cover 1 to 25 miles in
area.
The users communicate within a cell through wireless
communications. A base transceiver station (BTS) is used by the
mobile units in each cell by using wireless communication. One
BTS is assigned to each cell. Regular cable communication
channels are used to connect the BTSs to the mobile telephone
switching office (MTSO). The MTSO determines the destination
of the call received from a BTS and routes it to a proper
destination, either by sending it to another BTS or to a regular
telephone network. Keep in mind that the communications is
wireless within a cell only. The bulk of cell-to-cell communication
is carried through regular telephone lines.
Cell 1
A Cellular Network
Cell 2
Public
Switched
Telephone
Network
(PSTN)
Mobile
Telephone
Switching
Center
(MTSC)
HLR
VLR
Mobile User
Base Transceiver Station (BTS)
Cordless connection
HLR = Home Location Register
Wired connection
VLR = Visitor Location Register
Two issues are of fundamental importance in this conceptual model:
 Cell sizes. The sizes of the cells can be small or large. In some
cases, such as cordless networks, the cell sizes are only a few
feet. But in cellular networks, the cell sizes can be many miles
(10 to 20 miles).
 Location (“Roaming”) support. In some cases, the user is only
covered for his “home cell”; in others, the user can roam between
cells and still be covered adequately. For example, in a cordless
phone, the user is only covered at the home cell, while roaming
is typically supported in a wide coverage area where the user
can travel through several cells.
Cellular networks: What is 3G
Anyway?
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1G: First generation wireless cellular: Early 1980s
 Analog transmission, primarily speech
2G: Second generation wireless cellular: Late 1980s
 Digital transmission
 Primarily speech and low bit-rate data
 High-tier: GSM, IS-95 (CDMA), etc
 Low-tier (PCS): Low-cost, low-power, low-mobility e.g. PACS
2.5G: 2G evolved to medium rate (< 100kbps) data
3G: future: Broadband multimedia
 144 kbps - 384 kbps for high-mobility, high coverage
 2 Mbps for low-mobility and low coverage
Evolution to 3G
Data Rates
2 Mbps
3G
(144Kbps to 2Mbps)
1 Mbps
100 Kbps
2.5G
(10-150Kbps)
10 Kbps
1 Kbps
2G
(9.6Kbps)
1G
(<1Kbps)
1980
1990
2000
Years
2010
Wireless LANs
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First generation of products at about 1-2 Mbps
 Lucent’s WaveLAN, RadioLAN, etc.
 factor of 10 less bandwidth than current Ethernet
Next generation of products at 10-11 Mbps
 factor of 10 less bandwidth than 100 Mbps
Ethernet
IEEE 802.11 standard –
 very successful at present (wi-Fi)
 Can deliver up to 64 mbps
Important niche and enterprise applications (e.g.
hospitals)
Increasing horizontal market interest (e.g. SOHO)
Satellite Communications
Satellite Communications (cont.)
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A satellite system consists of the following components:
Earth Stations – antenna systems on or near the earth
Uplink – transmission from an earth station to a satellite
Downlink – transmission from a satellite to an earth
station (different from uplink, typically faster, can be
broad)
Transponder – electronics in the satellite that
convert/amplify uplink signals to downlink signals. There
are typically 16 to 20 transponders per satellite, each
with 36-50 MHz BW (bandwidth).
The Wireless Business
The next figure shows the main business sectors and
illustrates one view of the complex and multidimensional
aspects of wireless business in terms of the physical
communication network, network transport and
connectivity services, mobile computing platforms, and
mobile computing applications. Some business sectors
concentrate on higher level services such as mobile
applications, while others provide the low-level network
elements. As expected, one large business may be
involved in many business sectors, and vice versa.
Similarly, many small businesses may provide different
elements of one business sector.
Reference
Model
Wireless
Telephone
Wireless Data
Network
Wireless
Management
Wireless
Consulting
Business
Business
Business
Business
7. Application
6. Presentation
5. Session
4. Transport
Wireless
Telephony
Applications
and
Services
PSTN
Routing
Applications
(e.g., SMS,
email,
Wireless Web,
Mobile EC/EB)
Physical Network Elements
1. Physical
Systems
Consulting
IP Data
Network
Routing
3. Network
2. Data Layer
Wireless
Application
and
Platform
Management
(Cellular networks,
Wireless LANs,
Satellites,
Wireless Local Loops)
Wireless
Network
Management
Call
Switching
Wireless
Network
Consulting
and
Engineering
Services
Questions
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1) In your view, what are the top 3 strengths and
weaknesses of wireless systems? Rank them in
order of priority. What can be done to address the
weaknesses?
2) What is a mobile computing platform, what are its
main components and how do these
components support mobile computing applications?
3) What is wireless Internet and what role does
Mobile IP play in wireless Internet?
4) What is wireless middleware and how does it
differ from wireless gateways? Give an example.
5) What are the main elements of wireless
networks? What is the fastest wireless network and
what is the slowest? Which wireless networks go
the farthest and which ones are designed for the
shortest distances