Introduction to 3G UMTS

Introduction to UMTS

Ayman Gomaa

Contents

• Part 1 Introduction to UMTS

• Part 2 UMTS Air interface

• Part 3 UMTS Radio Access Network

• Part 4 UMTS Core Network

Contents


• Section 1 History of 3G

• Section 2 UMTS Network Structure

• Section 3 UMTS Network services

Evolution of Mobile communication

AMPS = Advanced Mobile phone service GSM=Global system for Mobile Communications

TACS=Total Access Communications Systems D-AMPS=Digital-AMPS

NMT=Nordic Mobile Telephone PDC=personal digital cellular

1st Generation 1980s (analog)

2nd Generation 1990s (digital)

3rd Generation current (digital)

AMPS

Analog to DigitalTACS

NMT

OTHERS

GSM

CDMA IS95

D-AMPS

PDC

WCDMAFDD

CDMA 2000

WCDMA TDD

Voice to Broadband

History of 3G

• At 1985 : ITU started the process of defining the standard for third generation systems, referred to as International Mobile Telecommunications 2000 (IMT-2000)

• Some of the features that IMT-2000 3G network must include1-Circuit and packet oriented services2-Simultaneous multiple services3-Symmetrical and Asymmetrical services4-Migration path from 2G systems5-Supporting Multimedia services

Car speed environment: 144kbpsWalk speed environment: 384kbpsIndoor environment: 2048kbps

• 1992: 230MHz spectrum was allocated in 2GHz band (WARC92)

History of 3G

• Based on the IMT-200 performance objectives and frequency allocation the ITU-R formally requested a submission of RTT proposals with a closing date at the end of July 1998 .

• By the closing date , there were a total of 10 RTT proposals were submitted from Europe , United states , Japan , Korea and, China. All these proposal where accepted .

• Five RTT for IMT2000• WCDMA FDD• CDMA2000 (1X-EV-DO and 3X modes)• WCDMA-TDD• UWC-136 (based on D-AMPS)• DECT

History of 3G

• Only three 3G network implemented and currently deployed 1-CDMA 2000 (1X-EV-DO)2-WCDMA FDD (UMTS FDD)3-WCDMA TDD (UMTS TDD)

3G standardization organizations

• Standardization organizations such as 3GPP, 3GPP2 were established

3G systemWCDMA

3GPPFDD/TDD mode

CDMA2000

3GPP2

UMTS is a 3rd Generation Mobile System

GSM1993

UMTS2002

EDGE2001

GPRS2000

HSCSD1999

9.6 K57.6 K

115 Kto 171 K

384 K

2 M

UMTS FDD and TDD

• FDD (Frequency Division Duplex)

• TDD (Time Division Duplex)

Base stationMobile Terminal

f 1: for Up Link

f 2: for Down Link

Base stationMobile Terminal

f 1: for Up & Down Link

Up DownTS TS

TS: Time slot

Frequency allocation for IMT2000

• WARC in 1992 230MHz in 2GHZ Band was allocated to IMT2000

USA

1800 2100 2200MHz1900 2000

IMT-2000 IMT-2000

MSS

1980 2010 2025

MSS

21702110

21702110

MSSUMTS

2110

IMT-2000 MSS2170

IMT-2000 MSSPHS

1895 1918 1980 20252010

1850 1930 1990

Unlicensed

MSSUMTSDECT

1880 20101980 2025

1885

PCS

2155

2025

IMT-2000 IMT-2000

IMT-2000

MSS(Reg.2)

MSS(Reg.2)

UMTS

MSSMSS

1900 1920

1910 2110 2150 2165

Reserve MSS

ITU

Japan

Europe/Australia

MSS: Mobile Satellite Service

Frequency spectrum allocation for IMT-2000

• In WARC-92 two frequency bands are allocated to IMT-2000Lower frequency band 1885 – 2025 MHzUpper frequency band 2110 – 2200 MHZ

both bands contain allocation for terrestrial and satellite components• Due to the existing use of parts of these frequency bands in different

regions of the world , there is no common spectrum available world wide for the 3G

• In Europe , the lower band of WARC-92 allocation is shared with the DECT Cordless phone system between 1880 to 1900 MHZ

• In Europe , the IMT-2000/ UMTS will use of the frequencies 1900 – 2025 in the lower band2110 - 2200 in the upper band


• Within Europe • (1920 – 1980) MHz and (2110 to 2170)MHz are paired bands (FDD mode )• (1900 – 1920) MHz and (2010 – 2025) MHz are unpaired bands (TDD mode)• (1980 – 2010) MHZ and (2170 – 2200 ) MHz are satellite allocation

20 1530 3060 60

1900 1950 2025 2140 2200 MHz

GSM

1800

DE

CT

UM

TS-

TD

D

UM

TS-

FDD

UM

TS-

sat

UM

TS-

TD

D

UM

TS-

FDD

UM

TS-

sat

GSM


• WRC2000 Conference has decided to allocate additional bands for IMT-2000, 800MHz, 1.8GHz, and 2.5GHz Band.

IMT-2000

GSM(Current)

PDC(Current)

800 1000 1500 2500 MHz960 1885 2690

2010

2110 2170

19801710806

20252000

880 960 1710 1990

: Additionally assigned for IMT-2000

810 958 1429 1513

UMTS FDD frequency allocations

Operating Band UL Frequencies

UE transmit, Node B receive

DL frequencies

UE receive, Node B transmit

I 1920 – 1980 MHz 2110 –2170 MHz

II 1850 –1910 MHz 1930 –1990 MHz

III 1710-1785 MHz 1805-1880 MHz

IV 1710-1755 MHz 2110-2155 MHz

V 824 – 849 MHz 869-894 MHz

VI 830-840 MHz 875-885 MHz

Operating Band TX-RX frequency separation

I 190 MHz

II 80 MHz.

III 95 MHz.

IV 400 MHz

V 45 MHz

VI 45 MHz

Contents





GSM network architecture

A

A Gb

VLR

MSC

GMSCPSTN

PSTN

EIRF

HLR

AUC

D

C

H

GsSGSN

Abis

BSC

BTSBTS

BSS

Gb

GGSN

Gn

PDNGi

Gf

Gr

Gc

Abis

BSC

BTSBTS

BSS

MS = ME + SIM

Um Um

NSS

UMTS network architecture

Iu-CS

Iu-CS Iu-PS

Iu-PS

Iub

RNC

Node BNode B

RNS

Iur

Iub

RNC

Node BNode B

RNS

VLR

MSC

A

GMSC

Abis

BSC

BTSBTS

BSS

PSTNPSTN

EIRF

HLR

AUC

D

C

H

GsSGSN

Abis

BSC

BTSBTS

BSS

Gb

GGSN

Gn

PDNGi

Gf

Gr

Gc

RAN

UTRAN

UE = ME + USIMMS = ME + SIM

UuUm Uu Um

CS PSCN

UMTS Network Components

• Network Elements• Core Network

• GMSC: Gateway Mobile Services Switching CenterSwitches circuit switched (CS) data to the external network.

• MSC: Mobile Services Switching CenterSwitches circuit switched (CS) data.

• VLR: Visitor Location RegisterStores copy of visiting user’s service profiles.

• HLR: Home Location RegisterStores user’s service profiles.

• GGSN: Gateway GPRS Support NodeHandles packet switched (PS) data to the external network.

• SGSN: Serving GPRS Support NodeHandles packet switched (PS) data.

UMTS Network Components

• Network Elements• UTRAN• RNC: Radio Network Controller

Controls radio resources.• Node-B

Converts Data flow between Iub and Uu interface.• UE

• ME: Mobile EquipmentRadio terminal used for radio communication.

• USIM: UMTS Subscriber Identity ModuleSmart card that stores subscriber identity.

Contents





UMTS Network Services

• Person to person services • Content to person services• Business connectivity services


• Person to person circuit switched services• 1- AMR speech services

• The speech codec in UMTS will employ the Adaptive Multirate(AMR) technique.

• The AMR speech coder has eight source rates: 12.2 ,10.2, 7.95,7.40 , 6.70 , 5.90, 5.15 and 4.75 kbps.

• The bit rate of the AMR speech connection can be controlled by the RAN depending on the air interface loading.

• During high loading, such as during busy hours, it is possible to use lower AMR bit rates to offer higher capacity while providing slightly lower speech quality.

• If the mobile is running out of the cell coverage area and using its maximum transmission power, a lower AMR bit rate can be used to extend the cell coverage area.

• The AMR speech codec is capable of switching its bit rate every 20 ms speech frame upon command.


• The coding scheme for the multirate coding modes is the so-called Algebraic Code Excited Linear Prediction Coder (ACELP).

• Discontinuous transmission (DTX) has some advantages : in the user terminal, battery life will be prolonged or a smaller battery could be used for a given operational duration. From the network point of view, leading to a lower interference level and hence increased capacity.

• Further optimization through AMR Source based rate adaptation


• Person to person circuit switched services• 2-Video telephony

Technical specifications of UMTS recommend ITU-T Rec. H.324M (AMR-H.263) for video telephony.


• Person to person packet switched services• Images and multimedia services

• MMS (multimedia messaging)• Real time video sharing (one way video )


• Push-to-Talk over Cellular (PoC)• voice connection is established by simply pushing a single button and

the receiving user hears the speech without even having to answer the call.

• Voice over IP • Multiplayer Games


• Content to person services• internet browsing • Audio and Video streaming

• Business Connectivity• Remote access to the intranets using UMTS

Contents





Contents


• Section 1 Air interface basic principles

• Section 2 Air interface protocol stack

Multiple Access Techniques

Traffic channels: different users are assigned unique code and transmitted over the same frequency band, for example, WCDMA and CDMA2000

Traffic channels: different frequency bands are allocated to different users,for example, AMPS and TACS

Traffic channels: different time slots are allocated to different users, for example: GSM

FrequencyTime

Power

FrequencyTime

Power

FrequencyTime

Power

FDMA

TDMA

User

User

User User

User User

CDMA


FDMA/TDMA

Frequency is different in each sector.

CDMA

Frequency is same.

Need for

frequency plan (Frequency ReuseFrequency Reuse)

No need for frequency plan

ｆ１ｆ

6

ｆ5

ｆ2ｆ

3ｆ4

ｆ１

ｆ7

ｆ7

ｆ4

ｆ6ｆ

7

ｆ１

ｆ3ｆ4

ｆ6ｆ

7ｆ2

ｆ5ｆ6ｆ2 ｆ

2ｆ5 ｆ

3

ｆ１ｆ7

ｆ6

ｆ5

ｆ2

ｆ4

ｆ１

ｆ1

ｆ7

ｆ1ｆ

7ｆ1ｆ1

ｆ１ｆ

1ｆ1

ｆ1

ｆ1

ｆ1

ｆ1

ｆ1

ｆ1

ｆ1

ｆ1

ｆ1ｆ1

ｆ1ｆ1ｆ1

ｆ1

ｆ1

DS-CDMA

User-A

A

Code 1

User-B

B

Code 2

User-C

C

Code 3

User-A

A

Code 1

User-B

B

Code 2

User-C

C

Code 3

De-spreadingCode

Narrow BandSignal

Wide BandSignal

(Multiple Signal)Spreading DespreadingNarrow BandSignal

CBA

(Receiver A)

(Receiver B)

(Receiver C)

DS-CDMA

• Any two codes x and y are orthogonal if Rxy(0) = ∑ xi yi =0 (correlation or Cross correlation)

i=0• Example of two orthogonal codes are

x= -1-1 1 1 and y= -1 1 1 -1 Rxy(0) = -1 x-1 + -1 x 1 + 1 x 1 + 1 x -1 = 0

• Spreading factor (SF) = chip rate/symbol rate

DS-CDMA

Spreading & de-Spreading

Data xCode

Tx Data

Same code

Code(SF=8)

bitbit Spectrumchip

Multiply(spreading) Tx operation

Bandwidth determinedby chip rate

code of length 8

Multiply

Integrate & Dump

Soft Decisions

In the absence of noise and interference from other non-orthogonal codes the soft decisions would be exactly +8 or -8, however this is never the true in reality

Spreading & de-Spreading with wrong orthogonal code

Data xCode

Tx Data

Different orthogonal

codes

Code(SF=8)

bitbit chip


Multiply

Integrate & Dump

In the absence of noise and interference from other non-orthogonal codes the soft decisions would be exactly 1 in this case, however this is never the true in reality

OVSF code #7

OVSF code #5

Spreading & de-Spreading with incorrect timing

Data xCode

Tx Data

Same code

Code(SF=8)

bitbit chip


Multiply

Integrate & Dump

The soft decisions are garbage => timing / synchronization is very important !!

Code offset by 1 chip

Rake Receiver

A B C

A B C

ABC

Rake

Rake receiver

RXRX

Searcher Searcher

CombinerCombiner

CalculationCalculation

Combined Signal

Electric PowerElectricPower

Delay Profile

Delay Time

Multiple Signal 1Multiple Signal 2

Multiple Signal 3

Delay Time

Finger CircuitFinger Circuit



Output Power

Power control in WCDMA

• Need for uplink power control • Near far problem


• Need for Power control in Downlink • The downlink signals transmitted by one base station are orthogonal.

Signals that are mutually orthogonal do not interfere with each other• It is impossible to achieve full orthogonality in typical usage

environments. Signal reflections cause nonorthogonal interference even if only one base station is considered

• Signals sent from other base stations are, of course, nonorthogonal and thus they increase the interference level


• Two basic types of power control:1- Open loop power control • the transmitting entity measures the channel interference of the received

signal and adjusts its transmission power accordingly. This can be done quickly

• the problem is that, the interference estimation is done on the received signal, and the transmitted signal probably uses a different frequency, which differs from the received frequency by the system’s duplex offset. As uplink and downlink fast fading (on different frequency carriers) do not correlate, this method gives the right power values only on average.

2- Closed loop power control • the quality measurements are done on the other end of the connection

in the base station, and the results are then sent back to the mobile’s transmitter so that it can adjust its transmission power.

• This method gives much better results than the open loop method, but it cannot react to quick changes in channel conditions.


• The UMTS FDD uses a fast closed-loop power control technique both in the uplink and downlink. In this method the received signal-to interference ratio (SIR) is measured over a 667-microsecond period, and based on that value, a decision is made about whether to increase or decrease the transmission power in the other end of the connection.

• The fast closed-loop power control is also called the inner loop power control.

• In the uplink there is also outer loop power control , the RNC adjust the target SIR to the NodeB

• In the Downlink outer loop power control is implemented in the UE• The UMTS FDD uses open loop power control in the uplink random access

channels

WCDMA handover types

• Soft Handover

• UE is connected simultaneously to more than one base station (up to 3 sectors) using the same frequency

• The UE receives the downlink transmissions of two or more base stations. For this purpose it has to employ one of its RAKE receiver fingers for each received signal.

• in the uplink direction , the code channel of the mobile station is received from both base stations, but the received data is then routed to the RNC for combining

• The RNC selects the better frame between the two possible candidates based on frame reliability indicator


• Softer Handover

• UE is connected simultaneously to two sectors of one base station using the same frequency

• The UE receives the downlink transmissions from the two sectors. For this purpose it has to employ one of its RAKE receiver fingers for each received signal.

• in the uplink direction , the code channel of the mobile station is received in each sector, then routed to the same baseband Rake receiver and the maximal ratio combined there in the usual way.


• Hard Handover

• The UE stops transmission on one frequency before it moves to another frequency and starts transmitting again

• During Hard Handover the used radio frequency (RF) of the UE changes


• Inter-system Handover• Handover between two different radio access technologies• Handover between UMTS FDD and GSM• Handover between UMTS FDD and UMTS TDD

Spreading process in WCDMA

• 1st Step: Channelization• Variable Rate Spreading ( According to user data rate)

• 2nd Step: Scrambling Code• Fixed Rate Spreading (3,840 Kchips)

Σ

ChannelizationCode

ScramblingCode

3,840 KcpsCoding &

Interleaving


• Downlink (NodeB to UE )• Scrambling Code: Identifies cell (sector).• Channelization Code: Identifies user channels in cell (Sector).

Scrambling Code A

Scrambling Code B

Scrambling Code C

ChannelizationCode 1

ChannelizationCode 2 Channelization

Code 3

ChannelizationCode 1 Channelization

Code 2




• Up Link (UE to NodeB )• Scrambling Code: Identifies user terminal.• Channelization Code: Identifies channels in user terminal.

Scrambling Code A

Scrambling Code B

Scrambling Code C






• Orthogonal Variable Spreading Factor [OVSF] codes are the channelizationcodes used for signal spreading in the uplink and downlink


• The code used for scrambling of the uplink Channels may be of either long or short type, There are 224 long and 224 short uplink scrambling codes. Uplink scrambling codes are assigned by higher layers.

• For downlink physical channels, a total of 218 -1 = 262,143 scrambling codes can be generated. Only scrambling codes k = 0, 1, …, 8191 are used.

• In the downlink direction 512 of scrambling codes are used to identify the cells in the downlink so downlink code planning is required


Scrambling codes for downlink physical channels

Set 0

Set 1

…

Set 511

Primary scrambling code 0

……

Secondary scrambling code 1

Secondary scrambling code

15

Primary scrambling code

511×16

……

Secondary scrambling code

511×16＋158192

scrambling codes

512 sets

A primary scrambling code and 15 secondary scrambling codes are included in a set.


Group 0

Groupe1

…

Group 63

512 primary scrambling codes

64 primary scrambling code groups

Each group consists of 8 primary scrambling codes

Primary scrambling codes for downlink physical channels


……




8*63

……


63*8＋7

W-CDMA Specification

Contents


• Section 1 Air interface basic principles

• Section 2 Air interface protocol stack

UMTS FDD Air interface protocol stack

UMTS FDD Air interface Channels

Logical channels

Transport channels (DL)

Transport channels (UL)

Physical channels

UMTS channel mapping

Cell search procedure

Cell search procedure#0 #1 #2 #3 #4 #5 #6 #7 #8 #9 #10 #11 #12 #13 #14

1 1 2 8 9 10 15 8 10 16 2 7 15 7 161 1 5 16 7 3 14 16 3 10 5 12 14 12 101 2 1 15 5 5 12 16 6 11 2 16 11 15 121 2 3 1 8 6 5 2 5 8 4 4 6 3 71 2 16 6 6 11 15 5 12 1 15 12 16 11 21 3 4 7 4 1 5 5 3 6 2 8 7 6 81 4 11 3 4 10 9 2 11 2 10 12 12 9 31 5 6 6 14 9 10 2 13 9 2 5 14 1 131 6 10 10 4 11 7 13 16 11 13 6 4 1 161 6 13 2 14 2 6 5 5 13 10 9 1 14 101 7 8 5 7 2 4 3 8 3 2 6 6 4 51 7 10 9 16 7 9 15 1 8 16 8 15 2 21 8 12 9 9 4 13 16 5 1 13 5 12 4 81 8 14 10 14 1 15 15 8 5 11 4 10 5 41 9 2 15 15 16 10 7 8 1 10 8 2 16 91 9 15 6 16 2 13 14 10 11 7 4 5 12 31 10 9 11 15 7 6 4 16 5 2 12 13 3 141 11 14 4 13 2 9 10 12 16 8 5 3 15 61 12 12 13 14 7 2 8 14 2 1 13 11 8 111 12 15 5 4 14 3 16 7 8 6 2 10 11 131 15 4 3 7 6 10 13 12 5 14 16 8 2 111 16 3 12 11 9 13 5 8 2 14 7 4 10 152 2 5 10 16 11 3 10 11 8 5 13 3 13 82 2 12 3 15 5 8 3 5 14 12 9 8 9 142 3 6 16 12 16 3 13 13 6 7 9 2 12 72 3 8 2 9 15 14 3 14 9 5 5 15 8 122 4 7 9 5 4 9 11 2 14 5 14 11 16 162 4 13 12 12 7 15 10 5 2 15 5 13 7 42 5 9 9 3 12 8 14 15 12 14 5 3 2 152 5 11 7 2 11 9 4 16 7 16 9 14 14 42 6 2 13 3 3 12 9 7 16 6 9 16 13 122 6 9 7 7 16 13 3 12 2 13 12 9 16 62 7 12 15 2 12 4 10 13 15 13 4 5 5 102 7 14 16 5 9 2 9 16 11 11 5 7 4 142 8 5 12 5 2 14 14 8 15 3 9 12 15 92 9 13 4 2 13 8 11 6 4 6 8 15 15 112 10 3 2 13 16 8 10 8 13 11 11 16 3 52 11 15 3 11 6 14 10 15 10 6 7 7 14 32 16 4 5 16 14 7 11 4 11 14 9 9 7 53 3 4 6 11 12 13 6 12 14 4 5 13 5 143 3 6 5 16 9 15 5 9 10 6 4 15 4 103 4 5 14 4 6 12 13 5 13 6 11 11 12 143 4 9 16 10 4 16 15 3 5 10 5 15 6 63 4 16 10 5 10 4 9 9 16 15 6 3 5 153 5 12 11 14 5 11 13 3 6 14 6 13 4 43 6 4 10 6 5 9 15 4 15 5 16 16 9 103 7 8 8 16 11 12 4 15 11 4 7 16 3 153 7 16 11 4 15 3 15 11 12 12 4 7 8 163 8 7 15 4 8 15 12 3 16 4 16 12 11 113 8 15 4 16 4 8 7 7 15 12 11 3 16 123 10 10 15 16 5 4 6 16 4 3 15 9 6 93 13 11 5 4 12 4 11 6 6 5 3 14 13 123 14 7 9 14 10 13 8 7 8 10 4 4 13 95 5 8 14 16 13 6 14 13 7 8 15 6 15 75 6 11 7 10 8 5 8 7 12 12 10 6 9 115 6 13 8 13 5 7 7 6 16 14 15 8 16 155 7 9 10 7 11 6 12 9 12 11 8 8 6 105 9 6 8 10 9 8 12 5 11 10 11 12 7 75 10 10 12 8 11 9 7 8 9 5 12 6 7 65 10 12 6 5 12 8 9 7 6 7 8 11 11 95 13 15 15 14 8 6 7 16 8 7 13 14 5 169 10 13 10 11 15 15 9 16 12 14 13 16 14 119 11 12 15 12 9 13 13 11 14 10 16 15 14 169 12 10 15 13 14 9 14 15 11 11 13 12 16 10

1 Frame = 10 ms

0 1 2 3 14..........

1 Time Slot = 2560 Chips

SCH

0 1 2 3 14..........

0 1 2 3 14..........

256 Chips

S S S S S S

78321 1

Cell SearchCell Search

•Slot Timing•Frame Timing - Code Group•NodeB PSC Acquisition

P-SCH

S-SCH

•Same Word in all the Slots•Same Word for all BS

•Same Combination of 15 Words in all the Frames•Each Word of the Combination Can Be One of 16•UMTS Use Only 64 Different Combinations•Neighbours BS Should Use Different Combinations

1 2 3 1 8 6 5 2 5 8 4 4 6 3 71 2 3 1 8 6 5 2 5 8 4 4 6 3 7

t

a

aa

t

1 2 3 1 8 6 5 2 5 8 4 4 6 3 7

Node B 256

Contents





Contents


• Section 1 ATM basic principles

• Section 2 UTRAN protocol stack

Types of switching

• Circuit Switching• Data is sent from the same route, so time delay is fixed • High-speed switching• Fixed rate

• Packet Switching• Support multi-rate switching• Take full advantage of bandwidth• Time delay is not fixed

• Packet switching effects on RT ( voice and Video) traffic transmission • Delay• Jitter ( variable inter-arrival time)

ATM can provides both CBR and VBR services

ATM Network Model

UNI

UNI NNI

NNINNI

NNI NNI

UNI

ATM Switch ATM End terminal

UNI = User to Network InterfaceNNI = Network to Network Interface

VP and VC

• think VP as a bundle of virtual channels. (256 VC on one VP)• the individual virtual channels have unique VCI. The VCI values may be

reused in each virtual path.

ATM Connections

ATM Virtual Connection

UNI cellVPI =1 VCI =1

UNI cellVPI =20 VCI =30

NNI cellVPI =26 VCI =44



1

2

3

1

2

3

1

3 2

2

31

ATM Virtual ConnectionPort VPI VCI

1 26 44

2 2 44

Port VPI VCI

1 2 44

2 6 44

Port VPI VCI

2 6 44

3 20 30

Port VPI VCI

1 1 1

2 26 44A B

In order to exchange cells between A and B, several tables must be set up in network node where the cells passed. After these tables have been set up, all the cells will be transferred along this route. This route is called Virtual Connection.

ATM Protocol stack

ATM traffic classes

ATM applications in UMTS network

• UTRAN

Iub

NodeB

RNC SGSN

RNC

NodeB

NodeB

NodeB

MSC

UE

UE

Uu Iu

Iur

Iu-CS

Iu-PS

ATM applications in UMTS network

Contents


• Section 1 ATM basic principles

• Section 2 UTRAN protocol stack

UTRAN Terrestrial interfaces protocol Stack

• All UTRAN terrestrial interfaces follow a common protocol stack


• Iub interface protocol stack


• Iu-cs interface protocol stack


• Iu-ps interface protocol stack


• Iur interface protocol stack

Contents





3GPP R99 CN structure


• CN elements

• MSC (Mobile services switching center)• Responsible for routing of traffic and signaling information in the

network• MSC has special functionality to handle mobility • MSC handles handover

• GMSC (Gateway Mobile services switching center)• Specialized MSC used to interface with fixed networks as PSTN and

ISDN• Used to interface with other mobile network


• HLR (Home Location Register )• Centralized data base stores all administration and subscription

information related to registered subscriber to the network • HLR also stores the current location of the subscribers and any

supplementary services to which they have access • The permanent data stored for the subscriber includes

• IMSI number and MSISDN number• Authentication information

• VLR (Visitor Location Register)• Data base stores all the information related to subscriber in one MSC

service area• There is one VLR to each MSC


• SGSN (Serving GPRS Support Node)• Handles mobility management and authentication • Protocol conversion between interface to RAN or BSS and interface to

GGSN• GGSN (Gateway GPRS Support Node)

• It is connected to external network like internet or X.25 network• When the GGSN receives data addressed to a specific user, it checks if

the address is active. If it is, the GGSN forwards the data to the SGSN serving the MS, but if the address is inactive, the data are discarded


• The 3GPP R4 introduces separation of the connection, its control, and services for CS domain of CN.

• Media Gateway (MGW): an element for maintaining the connection and performing switching function when required.

• MSC server: an element controlling MGW and responsible for signaling• Packet switched voice

• The CS call is changed to the packet switched call in MGW.

Introduction to 3G UMTS

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