Download GSM Overview

Generation Roadmap for
Cellular Telephony
Dated:10.03.07
Prepared by:
MIHIR KUMBHAKAR
AGM(CMTS)
1

Wireless technology is accelerating very
fast.
 It is quickly moving into 1G,2G,2.5G,3G
,4G and NGN
2
st
1
Generation
 The
first generation of mobile cellular
telecommunications systems appeared in the
1980s.
 The first generation used analog transmission
techniques for traffic, which was almost entirely
voice.
 There was no dominant standard but several
competing ones.
3
Such as
Ø
Nordic Mobile Telephone (NMT) – used in
Scandinavia,southern Europe etc
It comes in two variations:
o
NMT-450
o
NMT-900
Ø
Total Access Communications System
(TACS) – used in UK,and middle Eastern
countries.It uses 900MHz band.
Ø
Advanced Mobile Phone Service
(AMPS).- used in US,Australia,New Zealand.It
uses 800MHz band
4
nd
2
Generation

It has been introduced from the year 1992.
 It uses digital radio transmis-sion for traffic.
 The 2G networks have much higher capacity than the
first-generation systems.
 GSM is by far the most successful and widely used 2G
system.
 Data rate supported : 9.6kbps to 14.4 kbps
 It uses Circuit switching
5

There are several standards for 2G systems.such as#Global System for Mobile (GSM) communicationsDesigned and developed by a number of different
organization working together.
# code-division multiple access (CDMA) IS-95Designed and developed by a single company,Qualcomm.
v CDMA uses different codes to separate
transmissions on the same frequency.
v IS-95 is the only 2G CDMA standard so far to be
operated commercially.
v It is used in the United States, South Korea, Hong
Kong, Japan, Singapore etc.
6
Generation 2.5

It has been introduced in the year 2000-2001

“Generation 2.5” is a designation that broadly includes all advanced
upgrades for the 2G networks

2.5G GSM system includes General Packet Radio Services
(GPRS), and Enhanced Data Rates for Global Evolution (EDGE) in
addition to the 2G systems.

Data rate supported: depending on the coding scheme(CS) and the
no. of time slots used( 1 up to 8)

It uses circuit switching and packet switching both

It supports the data rate up to 384 kbps
7
3rd Generation

It has been introduced in the year 2001 as trial
version

It supports the data rate up to 2 mbps

Evolution of GSM and CDMA has taken them as
W-CDMA(UMTS) and CDMA-2000 in third
generation.

It supports both circuit switching and packet
switching
8
4th generation and NGN

This technology is expected to arrive not
before the year 2010 .

It will support the data rate up to 100 mbps.

Multimedia, mobile TV,mobile broadband
wireless access etc will be possible because
of its high band width.

It will support both circuit switching and
packet switching
9
GSM Overview
>GSM stands for “ Global System for Mobile communication”
>GSM Technology is one of the different types of the wireless
communication available in the world.
Frequency range*Uplink Frequency: 890 Mhz –915Mhz
*Downlink Frequency: 935Mhz- 960Mhz.
Modulation Technique- GMSK
10
 Speech is divided into 20 msec sample.Each
20ms sample is encoded using 260 bits.(That
requires 13 kbps.)
 Band width:each radio channel in the GSM system
has a frequency bandwidth of 200khz.
 Number of Channels:124 radio channel.
11
GSM Network
12
Basic GSM Network consist of
MS,BSS&NSS
MS –carried by the subscriber
It consists of
*ME-mobile equipment ,hand portable
or vehicle mounted unit.
*SIM- Subscriber identity module ,it
contains the entire customer related
information (identification,secret key for
authentication etc)
13
BSS
BSS- Controls radio link with mobile station.
It consists of –
BTS (Base transreceiver Station)-It defines a
cell and is responsible to establish the radio
link control protocol with MS.
BSC(Base Station Controller)-Controls multiple
BTSs and manages radio channel set up and
handovers.BSC is the connection between
BTS and the MSCs.

14
NSS
Network & Switching Subsystem(NSS)Mobility management and Switching of calls
between mobile users and between mobile
and fixed network users.
It consists of :
MSC- is the central component of the NSS.

Operates all switching functions for
mobiles within its jurisdiction.Interfaces with
mobile and other (Including fixed) networks.
 Manages the location of mobile

15
Continued…







Switches calls
Manages security features.
Controls hand over between BSCs
Resources management
Interworks with and manages network
database.
Collect call billing data and sends to Billing
center.
Collects traffic statistics for performance
monitoring.
16
Continued..
HLR-Contains all subscriber information for the
purposes of call control and location determination.
VLR- is only a temporary storage while the
particular subscriber is located in the geographical
area controlled by the MSC/VLR.
AUC- Is a protected database that stores the
security information for each subscriber.(A copy of
the secret key is stored in the SIM)
17
Continued…

EIR-It contains three list of IMEI number.
White list.-Valid mobile equipment in the
network
Grey list.- Suspected numbers
Black list-Totally barred.
18
Logical Channels


Five types of logical channels:
1.Traffic Channels
* TCH - Used to carry traffic.
2.Broadcast channels.
*BCCH-used to carry signaling and control info
* FCCH-used to correct the frequency of Mobile
* SCH- used for synchronization of the base station

3.common control channels
*PCH-used to page the mobile
*AGCH-used to access the signaling channel
*RACH-used by MS to request for signaling channel

4.Dedicated Control Channels
*SDCCH-used as signaling channel
*SACCH-used to carry measurement reports
*FACCH-used during handover
5.CellBroad cast channel
*CBCH-used to broadcast short messages in cells
19
MSISDN

The only important number for a user of GSM is the
phone number i.e.MSISDN.

The MSISDN follows the ITU-T standard E.164 for
addresses as it is also used in fixed ISDN networks.

This number consists of the country code(cc) ( 91
for India),the national destination code(NDC) (the
address of the network provider ; e.,g., 9434 for
BSNL WB) and the subscriber number (SN) .
20
IMSI

GSM uses the IMSI for internal unique identification
of a subscriber.

The IMSI follows the ITU-T standard E.212 Number
series.

IMSI consists of mobile country code (MCC)
(e.g.,404 for India),the mobile network code(MNC)
(i.e.,code of the HLR; e.g.,74 of BSNL WB),and finally
the mobile subscriber identification number(MSIN).
21
Location Updating (LU)

When the LU request is received by the new
VLR,authentication is performed.

If authentication is successful,the VLR checks its database to
determine whether it has a record for this MS-subscription.

When VLR finds no record for the MS,it sends a request to
the subscriber’s HLR for a copy of the MS-subscription.

The HLR passes the information to the VLR and updates its
location information for the subs.The HLR instructs the old
VLR to delete the information it has about the MSsubscription.
22
Inbound Roamer registration Location Update-Diagram
WB BSNL
HLR
GMSC
UK
1. UpLoc
2.ISD
NLD
3. ISD_resp
4. UPL_resp
SCCP
CdPA: 44-181-HLRUK
CgPA: 919434099995
(VLR1)
2.ISD
VMSC
/VLR
1. UpLoc
UK
Subscriber
1. UpLoc
2. ISD
3. ISD_resp
GMSC
HLR
4. UPL_resp
SCCP
CdPA: 919434099995(VLR)
CgPA: 44-181-HLRofUK1
MAP
IMSI: 234-15-123456
MSISDN: 44-181-654321
SCCP
CdPA: 44-181-123456
(MGT derived from
IMSIS analysis)
CgPA:919434099995(VLR)
MAP
IMSI: 234-15-123456
MSC/VLR:919434099995
23
Call from an MS(MO Calls)

The MS uses RACH to ask for a signaling channel.

The BSC/TRC allocates a signaling channel,using
AGCH.

The MS sends a call set-up request via SDCCH to the
MSC/VLR.Over SDCCH all signaling preceding a call
takes place (e.g.,authentication, ciphering,sending Bsubscriber’s number,checking of o/g barring
parameter etc.).
24
MO CALL Continued..

The MSC/VLR instructs the BSC/TRC to allocate an
idle TCH.The RBS and MS are told to tune to the
TCH.

The MSC/VLR forwards the B-number to an exchange
in the PSTN,which establishes a connection to the
subscriber.

If the B-subscriber answers,the connection is
established.
25
Call to an MS (MT Calls)

The PSTN subscriber dials in the MS’s telephone number
(MSISDN).The MSISDN is analyzed in the PSTN,which
identifies that this is a call to a mobile network
subscriber.A connection is established to the MS’s home
GMSC.

The GMSC analyzes the MSISDN to find out which HLR
the MS is registered in,and queries the HLR for
information about how to route the call to the serving
MSC/VLR.

The HLR translates MSISDN into IMSI,and determines
which MSC/VLR is currently serving the MS.
26
MT Calls continued..

The HLR requests an MSRN from the serving
MSC/VLR.The MSC/VLR returns an MSRN via HLR to
the GMSC.

The GMSC analyses the MSRN and routes the call to
the MSC/VLR.

The MSC/VLR knows which LA the MS is located in.A
paging message is sent to the BSC’s controlling the
LA.

The BSC’s distribute the paging message to the RBS’s
in the desired LA.
27
MT Calls continued..

The RBS’s transmit the message over the air interface
using PCH with IMSI/TMSI.

When the MS detects the paging message,it sends a
requests on RACH for a SDCCH.

The BSC provides a SDCCH,using AGCH.

SDCCH is used for the call set-up procedures.Over the
SDCCH all signaling preceding takes place.

The MSC/VLR instructs the BSC/TRC to allocate an idle
TCH.The RBS and MS are told to tune to the TCH.The
mobile phone rings.If subscriber answers,the connection
is established.
28
Call to an MS(MT Calls) in RoamingDiagram
UK
WB BSNL
HLR
3.PRN
ACK
2.PRN
GMSC
8.REL
7.ANM
9.REL
ACK
9.REL
ACK
6.ACM
DIALS
7.ANM
8.REL
6.ACM
7.ANM
5.ISUP
IAM
VMSC
/VLR
2.PRN
NLD
MSRN
6.ACM
5.ISUP
IAM
2.PRN
3.PRN
ACK
3.PRN
ACK
IAM
5.ISUP
IAM
GMSC
PSTN
3.PRN
ACK
2.PRN
IMSI
MSRN
1.SRI
9.REL
MSISDN ACK
HLR
4.SRI
ACK
MSRN
6.PAGING
8.Disconnect
UK
Subscriber
44-181-123456
29
MO SMS -Diagram
UK
WB BSNL
MO -FSM
HLR
GMSC
MO -FSM
NLD
GMSC
HLR
MO-FSM-RSP
MO-FSM-RSP
MO -FSM
MO-FSM-RSP
SMSC
SCCP
CdPA: 919434099995(VLR)
CgPA: 44-181-HLRofUK1
VMSC
/VLR
An
UK
Subscriber
SCCP
CdPA: 44-181-123456
(MGT derived from
IMSIS analysis)
CgPA:919434099995(VLR)
MAP
IMSI: 234-15-123456
MS establishes a connection to the network,
as in the normal call set-up.
The MS sends the short message using SDCCH to the
SMSC via MSC/VLR.The SMSC in turn forwards the shor
message to its destination.
30
MT SMS

A user sends a message to a SMSC.

The SMSC sends the message to the SMS-GMSC.

The SMS-GMSC queries the HLR for routing
information.

The HLR returns routing information to the SMSGMSC.

The SMS-GMSC reroutes the message to the
MSC/VLR.

The MS is paged and a connection is set up between
the MS and the network,as in the normal call set-up31
case.
MT SMS Continued…

The MSC/VLR delivers the message to the MS.Short
messages are transmitted on SDCCH.

If the delivery was successful,a report is sent from
the MSC/VLR to the SMSC,if not,the HLR is informed
by the MSC/VLR, and a failure report is sent to SMSC.

The HLR then informs the SMSC when the MS
becomes available.
32
MT SMS -Diagram
UK
WB BSNL-Circle1
SRI-SM ACK
5. MT-FSM_resp
HLR
GMSC
5. MT-FSM_resp
NLD
1.MT- FSM
GMSC
HLR
1. MT-FSM
SRI-SM
1. MT-FSM
5. MT-FSM_resp
1. MT-FSM
SMSC
VMSC
/VLR
SCCP
CdPA: 44-181-SMSCofUK1
CgPA:919434099995(MSC/VLR)
SMS
CdPA:44-181-123456
SCCP
CdPA: 91-9434099995 MSC/VLR
CgPA: 44-181-SMSCofUK1
UK
Subscriber
33
PREPAID SYSTEM

Prepaid system adds few other nodes than the
existing GSM network.

It is the IN system which handles the prepaid
subscriber.
IN system consist of Mainly
1.SCF
2.SDP
3.PPAS
4.IVR


In MSC SSF module handles the prepaid call Scenario
in MSC side.
34
GPRS

GPRS Core network consists of

SGSN:Serving GPRS Support Node; the gateway
between the RNC and the core network in a
GPRS/UMTS network

GGSN:Gateway GPRS Support Node; the gateway
between a cellular network and a IP network.
35
GPRS RELATED LINKS

Gc-The interface between the GGSN and the HLR in a GSM/GPRS network


Gd-The interface between the SGSN and the SMSC in a GSM/GPRS
network
Gf-The interface between the SGSN and the EIR in a GSM/GPRS network

Gi-The interface between the GGSN and the Internet in a GPRS network

Gn-The interface between the GGSN and the SGSN in a GPRS network


Gp-The interfaces between the GGSN/SGSN and the Border Gateway in a
GPRS network
Gr-The interface between the SGSN and the HLR in a GPRS network

Gs-The interface between the SGSN and the MSC in a GSM/GPRS network
36
GPRS ATTACH
8.ISD
ACK
7.ISD
SGSN
6.update location
5.Equipment idemtity
check response
1.GPRS ATTACH
REQUEST
2.Authentication
request
HLR
4.Equipment
identity check
EIR
3.Athentication
res
9.GPRS attach
accepted
37
PDP Context activation
5.Radius
authentication
request
2.DNS
query
(APN)
1.Activate PDP contest
6.Res
3.DNS
Resp(GGSN
DNS
SERVER
Radius
Server
7.DHCP
ADDR.REQ
DHCP
SERVER
IP ADR
10. Activate
PDP Context
Accept
SGSN
4.Create
PDP
Contest
req.
GGSN
8.DHCP
ADDR.RES
9. Create PDP Context
Response
38
CDMA (IS-95) TECHNOLOGY


Code-Division Multiple Access, a digital cellular
technology that uses spread-spectrum techniques
IS-95 CDMA system operates in 800 Mhz

CdmaOne is the brand name of IS-95 technology from
1997.
 CdmaOne is basically an air-interface standard.

IS-95 uses Frequency division duplex.Forward link and
reverse link transmission occur in different frequency
band.
39

Duplex separation used in IS-95 is 45Mhz

Carrier spacing is 1.25 Mhz



Forward link frequency: 824-849Mhz
Reverse Link frequency: 869Mhz-894Mhz
The forward link consists of Base station(BS)
transmitter,radio channel and the MS receiver.
40
CDMA Continues…

CdmaOne system supports four different types of forward
channels
#Pilot channel-is continuously transmitted by each CDMA
carrier and is used by MS to identify the BS and to asses the
suitability of the cell hand over.In this respect it may be
likened to the BCCH carrier in GSM system.
#Synchronous channel-It allows MS to achieve time
synchronization with BS and the network .
#Paging channel-is used to page MSs to alert them to an
incoming call.
#Traffic channel-are assigned to the users as required and41they
may carry speech or user data at bit rates of up to 9.6 kbps.

Each forward channel on a CDMA carrier is assigned a
different 64-bit Walsh code.

The reverse link radio path consists of the Mobile
station(MS) transmitter,the radio channel and the base
station(BS).

CdmaOne system supports two different types of radio
channel on reverse link
#Access channel-as its name would suggest,is used by
MS initially to access the network,e.g. at call initiation or in
response to a paging message.Each Base Station may
support 32 access channels per forward link paging channel
and the MSs within a CeLL are pseudo-randomly
42
distributed between the access channels.
CDMA Continues…
Access channel data are presented in the form of one 96bit frame every 20 ms.Of this 96 bits,88 are used to
carry information and remaing eight are encoder tail
bits.
# Traffic channel-are assigned to the individual user as
required.A reverse link traffic channel may carry
speech and data at bit rates up to 9.6 kbps.
43

The cdmaOne MS does not transmit a pilot signal
as this would significantly decrease reverse link
capacity.

BS receiver uses RAKE receiver to demodulate
the reverse link signal from a particular MS.

MS handover process occur by measuring the
strength of the pilot channels signal from a BS
other than its current BS.

CdmaOne system supports three main types of
handover
44
CDMA Continues…
# Idle mode handover-It occurs when an MS
moves from the coverage area of one BS into the
coverage area of a second BS while an MS is an
idle mode.
# Soft handover- is used between BSs having
CDMA carriers with identical frequency
assignments.
# Hard handover- occur when a mobile is
switched between two BSs using different carriers.
45
Simplified data flow for the access procedure of
a mobile terminated call.
46
Basic cdmaOne diagram
47
CDMA 2000

This is the evaluated 3G version of IS-95/cdmaOne
technology.

CDMA2000 is an ITU-approved standard that was the first 3G
technologies (October,2000).

provides advanced voice communications and high-speed data
connectivity, including access to the Internet, mobile data
applications and multimedia content.

Supports data services at minimum transmission rates of 144
kbps in mobile (outdoor) and 2 Mbps in fixed (indoor)
environments.

The world's first 3G commercial system was launched by SK 48
Telecom (South Korea) in October 2000 using CDMA2000
CDMA2000 represents a family of standards
and includes
>CDMA2000 1X
>CDMA2000 1xEV-DO Technologies
>CDMA2000 1xEV-DO Rev A
>CDMA2000 1xEV-DO Rev B
>Ultra Mobile Broadband - UMB
(CDMA2000 1xEV-DO Rev C)
49
CDMA 2000 continues…

CDMA2000 builds on the inherent advantages of CDMA
technologies,such as
>introduction of Orthogonal Frequency Division
Multiplexing (OFDM and OFDMA)
>advanced control and signaling mechanisms
>improved interference management techniques end-to-end
Quality of Service (QoS)
50
>new antenna techniques such as Multiple
Inputs Multiple Outputs (MIMO) and Space
Division Multiple Access (SDMA) to
increase data throughput rates and quality of
service
>improving network capacity and reducing
delivery cost.
51
CDMA2000 Advantages:
>Superior
Voice quality
>High-Speed Broadband Data connectivity
>Increased Voice and Data Throughput capacity
>Long-Term, Robust and Evolutionary Migration Path with
Forward and Backward Compatibility
>Differentiated Value-Added Services such as VoIP, PTT,
Multicasting, Position Location, etc.
52
>Flexible
Network Architecture with connectivity to ANSI-41,
GSM-MAP and IP-based Networks and flexible Backhaul
Connectivity
>Flexible Spectrum Allocations with Excellent Propagation
Characteristics
>Robust Link Budget for Extended Coverage and Increased Data
Throughputs at the Cell Edge
>Improved Security and Privacy
53
CDMA 2000 NETWORK DIAGRAM
54
UMTS/WCDMA

UMTS (WCDMA)is a 3G evolution of GSM and GPRS

UMTS is one of the Third Generation (3G) mobile systems
being developed within the ITU's IMT-2000 framework

The coverage will be provided by a combination of cell
sizes ranging from 'in building' Pico Cells to Global Cells
provided by satellite, giving service to the remote regions
of the world

created a platform to converge the worlds of speech, data
services and the Internet to create a global market for
mobile multimedia.

UMTS is designed to increase a subscriber’s data rates and
55
system capacity.
Technical Features:

Modulation Techniques used QPSK

Multiple access technology used as CDMA

Frequency reuse pattern : 1*1 (cell*sector)

Maximum data rates supported: 384kbps to 2
mbps

Both packect switch and circuit switch are
supported
56

Radio channels are 5MHz wide

Chip(fundamental unit of transmission in a CDMA
system) rate of 3.84 Mcps

Supports two basic modes of duplex, frequency division
and time division. Current systems use frequency
division, one frequency for uplink and one for downlink.
For time division, UMTS uses 15 slots per radio frame.
57
Technical Features continues .
>Employs coherent detection on uplink and downlink based
on the use of pilot symbols
> Supports inter-cell asynchronous operation
>Variable mission on a 10 ms frame basis
>Adaptive power control
> Multiuser detection and smart antennas can be used to
increase capacity and coverage.
58
>initially poor coverage due to the time it takes to
build a network
>for fully fledged UMTS incorporating Video on
Demand features, one base station needs to be set
up every 1–1.5 km (0.62–0.93 mi). While this is
economically feasible in urban areas, it is
infeasible in less populated suburban and rural
areas.
>Requires huge frequency spectrum
59
UMTS Network Architechture
60
UMTS Network Architechture
Ø UMTS core network architechturally a GSM phase 2+
Core network that is power up so that it can also handle the
higher volume,higher bit rate,UMTS traffic.
Ø RNS(Radio network subsystem) is the additional part for
UMTS network than GSM Phase 2 + network.
Ø RNS consists of RNC (Radio network Controller) and Node
B(part of User Equipment and Base station)
Ø The UMTS terrestrial Radio interface(UTRA) frequency
duplex(FDD) mode is the W-CDMA radio interface of the
UMTS.
Ø Carrier frequency is defined by the UTRA absolute radio
frequency channel number(UARFCN).
61
Physical Channels
there are two basic types of physical channels.
# Dedicated Channels-These are used by UEs for the
duration of the call.There are two Dedicated channels>PCCH-Dedicated physical control channel carries
physical layer control information
>DPDCH-Dedicated physical data channel
transports the user traffic.
#Common channels-these are used to carry information to the
UEs within a cell and are used by the UEs to access the
network. Common channels are of two types: Common
channels are of two types:
1. Down link common channels
62
2. Uplink common channels
Down link common channels

CPICH-Common Pilot Channel provides a common
demodulation reference over all or part of a cell.

P-CCPCH-Primary common control physical channel
caries general network information.

S-CCPCH-Secondary common control physical channel is
used for paging and packet data

SCH-Synchronisation channel is used by UE for its initial
cell search

AICH-Acquisition indication channel controls the use of
common uplink channels.
63
UP Link common physical
channels

PRACH-Physical Random Access Channels used by
UEs initially to access the network

PC-PCH-Physical Common Packet Channel allows
bursts of data to be transferred from UEs to the
network.CPCH is typically used for short,infrequent
burst of data where as dedicated channels are more
suited to long burst.
64
UMTS Frame structure

The duration of a frame is 10ms

One frame contains 15 slots

Each slot duration =0.667 ms

Each slot contains 2560 chips

Chip rate=3.838Mchips/s

One super frame =72 frame= 720ms duration
65
Difference between CDMA2000 and
UMTS technology
>Cdma2000 and UMTS were developed separately
and are 2 separate ITU approved 3G standards
>cdma2000 were developed to be backward
compatible with cdmaOne but UMTS phones are
not meant to be backward compatible with GSM
systems.
>Cdma2000 is easy to implement because operators
do not need new frequencies but implementation
of UMTS is very difficult because of its new
requirement of wide range of frequency and new
66
implementation of the radio access network.
THANKS
67