UNESCO/CISM SECOND ADVANCED SCHOOL OF INFORMATICS

UNESCO PROJECT

Advanced Course on Networking

Introduction to Cellular Wireless Networks

On the Road to UMTS

Mobile Communications system Evolution

Outline

GSM GPRS UMTS CDMA WCDMA Summery

What is GSM??(Global System for Mobile Communications)

GSM Architecture

Three broad parts Mobile Station (MS): carried by the subscriber Base Station Subsystem: control radio link with

MS Network Subsystem: its main part is MSC

Interfaces: Um Interface : known as air interface or radio link. Abis Interface: between BTS and BSC A Interface: between BSC and MSC

Mobile Station

ME(mobile equipment) the terminal

SIM (Subscriber identity Module) provides personal mobility. Can insert the SIM card into

another GSM terminal and use

Base Station Subsystem

BTS (Base Transceiver Station) handle the radio link protocols

with the Mobile Station many BTSs in a large urban area

BSC (Base Station Controller) manages the radio resources for

one or more BTSs handles such as: channel setup ,

frequence hopping and handovers.

connection between MS and MSC

Network Subsystem

MSC (Mobile Services Switching Center) acts like a normal switching node of

the PSTN or ISDN provides the connection to the fixed

networks (such as the PSTN or ISDN).

HLR (Home Location Register ) contains information of each

subscriber registered in the corresponding GSM network, along with the current location of the mobile.

logically one HLR per GSM network

Network Subsystem cont.

VLR (Visitor Location Register) contains selected information from the HLR,

necessary for call control and provision of the subscribed services,

each mobile currently located in the geographical area controlled by the VLR.

EIR (The Equipment Identity Register) a database that contains a list of all

valid mobile equipment on the network,

AuC (The Authentication Center) is a protected database:secret key of

SIM

GSM Features

Multiple access: use TDMA/FDMA to share the limited radio spectrum The FDMA part involves the division by

frequency of the (maximum) 25 MHz bandwidth into 124 carrier frequencies spaced 200 kHz apart.

Each of these carrier frequencies is then divided in time, using a TDMA scheme.

GSM is a digital network Based on Circuit-switch

GSM Features cont.

SMS: Short Message Service is a bi-directional service for short (up to

160 bytes) messages. Messages are transported in a store-and-forward fashion.

an acknowledgement of receipt is provided to the sender.

can also be used in a cell-broadcast mode, for sending messages such as traffic updates or news updates. Messages can also be stored in the SIM card for later retrieval

GPRS System(General Packet Radio Service)

GPRS Architecture

Introduce two new nodes into GSM network SGSN (the Serving GPRS Support Node):

– Keep track of the location of the mobile within its service area and send/receive packets from the mobile , passing them on, or receiving them from the GGSN

GGSN (Gateway GPRS Support Node): – convert the GSM packets into other packet protocols

(e.g.IP or X.25) and send them out into another network.

GPRS Features

Log on to GPRS A GPRS-capable terminal communicates

with GSM base Stations, but unlike circuit-switched data calls which connects to MSC, GPRS packets are sent from the base station to SGSN, SGSN communicates with GGSN.

Establishes a Packet Data Protocol (PDP) which is logical connection between the mobile and GGSN

now visible to the outside fixed networks

GPRS Features Cont.

SGSN and GGSN use GPRS tunnel protocol (GTP) which operates over the top of TCP/IP to encapsulate the packets

Tunnels: information may be encrypted and additional data is added to each packet to prevent tampering

Packed based No dial-up, just as with a LAN connection. No delay for sending data

GPRS Features Cont.

pay for the amount of data they actually communicate, and not the idle time

users need to confirm their agreement to pay for the delivery of content from the service. This is performed by using WAP (Wireless Application Protocol)

unsolicited packets may not be charged voice and Data Communication at the same

time can be viewed as a sub-network of the Internet

GPRS Features Cont.

Spectrum Efficiency users can share the resource (Radio link),it

is used only when users are actually sending or receiving data

Speed: Based on GMSK a modulation technique known as Gaussian

Minimum-shift keying. Theoretical Max speeds up to 171.2kbps.

(GSM:9.6Kbps)

GPRS Features Cont.

a channel that is 200kHz wide, is divided into 8 separate data streams, each carrying maximum 20kbps(14.4kbps typical), GSM only use one channel, GPRS combine up to 8 of these channels.

complement rather than replace the current data services available through today’s GSM doesn't require new radio spectrum supports TDMA: also use for IS-136

Scenario for Migration from 2G to 3G

What are 3G Technologies? UMTS (Universal Mobile Telecommunications Service)

EDGE can co-exist with UMTS– e.g. Edge provide high speed services for wide-area

coverage while UMTS is deployed in urban hot spots.

Cdma 2000 based on the cdma One standard, two air

modes: – one based on the parallel use of 3 contiguous

cdmaOne carriers (multi-carrier approach),

– the other one on the use of the corresponding 3 carriers width spreading (direct spread approach)

What does UMTS provide?

Circuit- and Packet-Oriented Services Seamless Global Roaming Capacity and Capability to serve

more than 50% population A Wide Range of Services

Voice, low-rate data and high-rate data 144kb/s, 384kb/s , 2Mb/s

UMTS coverage vs. bit rate

Outdoors

Vehicle

Walk

Fixed

Indoors

155Mb/s2.00.5

GSM

UMTS

Broadband Radio

UTRAN-UMTS Terrestrial Radio Access Network

Core Network

RNC

Node BNode B

RNC

Node BNode B

RNC

Node BNode B

MH

lu lu lulur lur

Uu

lub

Frequency Allocation

1920-1980 MHz paired with 2110-2170 MHz

Total 35 MHz unpaired band

1920 1980 2010 2025

C C A MSS B A’

2110 2170 2200

MSS

FDD vs. TDD

•Both FDD and TDD are available in UMTS•TDD has been designed for use in high density areas•The highest bearer rate:

•TDD-2.048Mb/s•FDD-384kb/s

CDMA(Coded Division Multiple Access)

In CDMA, every user assigned a uniqueCode

WCDMA

Radio Parameters Performance Improvement Channels Channel Generation Power Control Handoff

WCDMA Radio Parameters

Group 200KHz bands into 4.2-5.0 MHz carriers

Chip Rate is 4.096 Mchips/sec System Capacity of 128 channels

per cell provided by 5 MHz bandwidth

WCDMA Performance Improvement

Capacity Improvement No Frequency Planning Multiple Services per Connection Frequency Handoff

HCS Hot Spot

HCS & Hot-Spot

HCS-Scenario

f1 f1f2

Macro MacroMicro

Handoff between layers is alwayse needed

f1 f1f1

f2

Hot-Spot Scenario

Hot-Spot

Handoff at Hot-Spot is sometimes needed

WCDMA Channels Transport channels are the services which the

physical layer provides to higher layers. The number of transport channels is much

higher than for GSM as more services are needed.

Transport channels are grouped into two classes: Common channels (where information is

transmitted to all mobile terminals without distinction)

Dedicated channels (where communication takes place towards a single terminal by associating it with a physical channel, i.e. a code and a frequency or, in the case of TDD, also a time slot).

WCDMA Channels.. Cont.

The following common channels are provided: BCH (Broadcast Channel): used on the downlink to transmit system

information in the entire cell. FACH (Forward Access Channel): used on the downlink to transmit

control information to mobile terminal. It also can be used to transport short data packets (as with GSM Short Message Service). FACH is used when the system knows the cell in which the terminal is registered.

PCH (Paging Channel): used on the downlink to transmit control information to mobile terminal whose location is not known. Transmission here is associated with paging indicator which informs the mobile terminal that the information is present on the paging channel, thus permitting lower battery consumption.

SCH (Synchronization Channel): used on the downlink to permit synchronization between the mobile terminal and base station.

RACH (Random Access Channel): used on the uplink to transport control information transmitted by the mobile terminal.

CPCH (Common Packet Channel): used on the uplink to transport data packets especially burst traffic.

DSCH (Downlink Shared Channel): used in the downlink to transport data packets. Access is shared by various users and is regulated by the base station.

WCDMA Channels.. Cont.

There are certain physical channels which are not associated with a transport channel. They are used to transport physical layer information that does not need to be sent to higher layers.

These channels are as follows:

CPICH (Common Pilot Channel): a downlink channel on which a known un-modulated sequence is transmitted.

DPCCH (Dedicated Physical Control Channel): physical channel present on both links and used to transport physical layer signalling.

AICH (Acquisition Indication Channel): present on the downlink and used to inform the mobile terminal that there is a message on the FACH channel in response to an access attempt.

PICH (Paging indication Channel): present on the downlink and used to inform the mobile terminal that there is a message on the PCH channel.

WCDMA Channels.. Cont. Physical Channels: are typically based on

the following structure: Radio frame: has a length of 10 ms and

consists of 15 time slots. Time slot: has a length of 10/15 ms. Each

slot consists of a number of symbols which varies according to the bit rate of the service to be transmitted.

Symbol: this is the information element after the channel encoding operations (i.e. after error correction codes are inserted)

Power Control In WCDMA

Near-Far Problem in CDMA Different Performance for Subscriber

Links A Few Subscribers closest to the BTS

may contribute too much multiple Access Interference.

Power Control In WCDMA

How to do power control Force all users to transmit the

minimum amount of power Reduce the power transmitted by

users closest to the BTS; increase the power transmitted by users farst to the BTS

Power Control In WCDMA

Open Loop vs. Close Loop Open Loop Power Control

Subscriber measures the DL power and adjusts its transmission power

Close Loop Power ControlBS measures the UL power. MS measures the DL power and reports to the BS. BS instructs the user to raise or lower it transmission power

WCDMA Soft Handoff

Active set = BS1

BS1

BS2

Active set = BS1 & BS2BS2 SS > add threshold

BS1

BS2

Active set = BS2BS1 SS < drop threshold

BS1

BS2

Active Research Topics

Cellular system architecture UMTS air interface Power control in CDMA Handoff Satellite-UMTS traffic Integrated All-IP 3G-WLAN

Reference

http://www.europe.alcatel.fr/telecom/rcd/keytech/ http://www.comms.eee.strath.ac.uk/~gozalvez/gsm/ http://www.gsmworld.com/ http://www.ibctelecoms.com/ http://www.span.net.au/ http://www.cdg.org/tech/a_ross/ http://www.nokia.com/networks/mobile/ http://www.gsmdata.com/ http://www.sds.lcs.mit.edu/~turletti/gmsk/ http://www.wirelessweek.com/issues/3G/

Reference http://www.umts-forum.org/reports.html http://www.itu.int/imt/ http://www.etsi.org/ Flavio Muratore: UMTS, Mobile Communications for future,

John Wiley & Sons, 2001. S. Dutnall, N. Lobley, A. Clapton, UMTS: The mobile part of

broadband communications for the next century IEEE Atm Workshop, Proceedings. p242-252,1998

S. Breyer, G. Dega, V. Kumar, L. Szabo, Global view of the UMTS concept Alcatel Telecommunications Review. n 3 1999. p 219-227

M. Lee, CDMA Network Security , Prentice-Hall, 1998 U. Black, Mobile & Wireless Networks, Prentice-Hall, 1999 M. Gallagher, W. Webb, UMTS: The next generation of mobile

radio, IEE Review. v 45 n 2 1999. p 59-63

Reference A. Samukic, UMTS Universal Mobile Telecommunications

System:Development of standards for the third generation, IEEE Global Telecommunications Conference & Exhibition. v 4 1998. p 1976-1983

N. Prasad, GSM evolution towards third generation UMTS/IMT2000, IEEE International Conference on Personal Wireless Communications 1999, p 50-54

A. Samukic, UMTS universal mobile telecommunications system: Development of standards for the third generation, IEEE Transactions on Vehicular Technology. v 47 n 4 Nov

1998. p 1099-1104

Thank you !!!Thank you !!!

UNESCO PROJECT

Advanced Course on Networking Professor Khalid Al-Begain

UNESCO/CISM SECOND ADVANCED SCHOOL OF INFORMATICS

University of Damascus, Syria, 06 - 15 April 2004