Te-440 Universal Mobile Telecommunication System (Umts)Marcp

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Universal Mobile

Telecommunication System

1TE 440 Next Generation Wireless Networks

College of Engineering

PAF – Karachi Institute of Economics and Technology



TE 440 Next Generation Wireless Networks 2

UMTS

“UMTS will be a mobile communications system that can offer significant user

benefits including high-quality wireless multimedia services to a convergent

network of fixed, cellular and satellite components.

It will deliver information directly to users and provide them with access to new

and innovative services and applications.

It will offer mobile personalized communications to the mass market regardless of

location, network and terminalused”

.

UMTS Forum 1997




Second Generation Third Generation

GSM - 900

GSM -1800

DECT

TETRA

HIPERLAN

Satellite

UMTS

MBS

WLL




UMTS Main Requirements (3 Ms)

• Multi-media

• Multi-environment

• Multi-operator Virtual operators




Mobile Multimedia Services

VideoConference

(High quality)

VideoConference

(Low quality)

Telephone

Conference

Telephone

VoiceMail

Electronic

Mail FAX

Electronic

Publishing

Electronic

Newspaper

ISDNKaraoke

VideoCatalogshopping

Database AccessRemote medical

service(Medical image) Video on

demand-Sports-News-Movies

Mobile TV

MobileRadio

Image

Data

Voice

Multicast

Multi Point

AsymmetricSymmetric

Point to Point

Broadcast

2M

384K

64K

32K

16K

9.6K

2.4K

1.2K

News

Weatherforecast

Trafficinformation

Sportsinformation

LeisureInformation

Mobile Multimedia

WWW

e-mail

ftp

IP

telephony

etc

Information

Distribution

Services

Internet

Access

pager




Different Environments for UMTS

Global

Suburban

Macro-Cell

Urban

Micro-CellIn- Building

Pico-Cell

Home-Cell



UMTS Bearer Services

The UMTS radio access network and fixed network are expectedto provide four classes of bearer services:

• Class A - Circuit-switched bit pipe

• Class B - Circuit-switched bit pipe for variable bit rate

• Class C - Connection-oriented packet switched bearer

service

• Class D - Connectionless packet-switched bearer service

7TE 440 Next Generation Wireless Networks



On the Air Interface

• Class A – LDD Low Delay Data (real time)

• Class B - LDD-VBR Low Delay Data – Variable Bit

Rate (real time)

• Class C – LCD Long Constrained Delay (50 ms)

• Class D – UDD Unconstrained Delay Data (300ms)





First Phase of UMTS

• Europe has decided to adopt an evolutionary approach for theUMTS core network based on migration from the GSM/GPRSinfrastructure.

• For the actual air interface, a revolutionary approach has beenchosen. That is a new radio air interface for UMTS TerrestrialRadio Access (UTRA).

• There is another parallel activity concerning the UMTS airinterface using an evolutionary approach (an intermediateapproach).




The Two Approaches

NewRadio

Access (UTRAN)

NSS

And

GSN’s

PSTNN-ISDNB-ISDN

IP-basedNetworks

Radio AccessGSM Infrastructure Public Network

Dual-mode

Dual-mode

EvolvedGSM

Radio Access

(GERAN)




Evolutionary approach for the GSM

Air Interface

In this approach the GSM air interface has evolved within GSM phase 2+ to

support higher rate data services. The most important developments in this

approach are:

1. General Packet Radio Services (GPRS )

2. High Speed Circuit Switched Data (HSCSD )

3. Enhanced Data Rates for GSM Evolution (EDGE )

It is referred to GSM/EDGE Radio Access Network (GERAN)




UMTS Terrestrial Radio Access(UTRA)




ETSI SMG2 has selected the wideband CDMA concept for the

paired band (FDD mode) and the TD/CDMA concept for the

unpaired band (TDD mode) for UTRA.

Introduction




Frequency allocation in Europe

1880 1900 1980 2010 2025 2110 2170 2200

DECT UMTSMSS MSS

FDDFDD TDDTDD

UMTSUMTS

1920




Wideband CDMA Specifications

Multiple access DS-CDMA

Transmission mode FDD

Chip rate 3.84 Mchips/s

Carrier spacing 5 MHz

Frame size 10 ms

Spreading technique Variable-spreading factor+multi-code

Channel Coding 1/2-1/3 rate convolutional coding and

Turbo CodingModulation QPSK with roll-off factor a= 0.22



Main Parameters [1]

• WCDMA is a wideband Direct-Sequence Code Division

Multiple Access (DS-CDMA) system

• user information bits are spread over a wide bandwidth by

multiplying the user data with quasi-random bits (called chips)

• to support very high bit rates (up to 2 Mbps), the use of a

variable spreading factor and multi-code connections is

supported

• The chip rate of 3.84 Mcps leads to a carrier bandwidth of

approximately 5 MHz




Allocation of bandwidth in WCDMA in the time-

frequency-code space




Main Parameters [2]

• wide carrier bandwidth

• high user data rates

• multiple 5 MHz carriers to increase capacity

• highly variable user data rates

• data capacity can change from frame to frame• Frequency Division Duplex (FDD)

• Time Division Duplex (TDD)

• asynchronous base stations

•

coherent detection on uplink and downlink using common pilot• Multiuser detection and smart adaptive antennas

• deployed in conjunction with GSM

• handovers between GSM and WCDMA are supported




Spreading and Despreading [1]




Definition of Channels

Logical Channel – Type of information to be transmitted e.g., traffic or controllogical channels.

Transport Channel – How and with what format data is transmitted through

physical links.

Physical Channel – Unit of radio resource of a radio system e.g., frequency

band, time slot, code, etc.

RF Channel – Fixed frequency band of a radio system.

The MAC sublayer is responsible for mapping logical channels onto transport

channels.

The physical layer is responsible for mapping transport channels onto physical

channels.



Transport Channels [1]

Common Channels (CCHs) Dedicated Channel (DCH)(Uplink/Downlink)

Common PacketChannel(CPCH)(Uplink)

Broadcast

Channel (BCH)

(Downlink)

Forward-Access

Channel (FACH)

(Downlink)

Paging

Channel (PCH)

(Downlink)

Random-Access

Channel (RACH)

(Uplink)

Downlink SharedChannel(DSCH)(Downlink)




Dedicated Transport Channel

1. DCH – Dedicated Channel

• Downlink/uplink Transport channel

• A point-to-point channel allocated to a specific user

• Carries information intended for the given user including data and higher

layer control information

• Characterised by features such as

–

fast power control – fast data rate change on a frame-by-frame basis

– possibility of transmission to a certain part of the cell




Common Transport Channels

1. BCH – Broadcast Channel

• It is a downlink channel

• System and cell-specific information over the entire cell

• The terminal cannot register to the cell without the possibility of decoding

the broadcast channel

– transmit with relatively high power

–

low and fixed data rate




2. FACH – Forward Access Channel


• Used to carry control information to a mobile station when the system

knows the location cell of the mobile station

•May also carry short user packets

3. PCH - Paging Channel


• Used to carry control information to a mobile station when the system

does not know the location cell of the mobile station

• It is used to inform the mobile station of incoming calls




4. RACH –

Random Access Channel• It is an uplink channel

• Used to carry control information

• It is used for initiating a call (initial access to the serving BS)

• It may also carry short user packets

• must be heard from the whole desired cell coverage area

5. CPCH – Common Packet Channel

• It is a uplink channel used to carry infrequent medium sized packets

•the main differences to the RACH are: – the use of fast power control

– a physical layer-based collision detection mechanism

– a CPCH status monitoring procedure




6. DSCH – Downlink Shared Channel

• Used to carry infrequent medium and large sized packets

• It can be shared in time between several users

• It is always associated with a downlink DCH



Uplink Physical channels

Common Physical ChannelsDedicated Physical Channels

Dedicated Physical Data Channels(Uplink DPDCH)

Dedicated Physical Control Channel

(Uplink DPCCH)) Physical Random Access Channel(PRACH)

Physical Common Packet Channel(PCPCH)

Physical Channels



Uplink Physical Channels

Dedicated Uplink Physical Channel

1. DPDCH - Dedicated Physical Data Channel

• Used to carry dedicated data i.e. the dedicated transport channel (DCH)

• There may be zero, one, or several uplink DPDCHs

2. DPCCH – Dedicated Physical Control Channel

• Used to carry control information consists of:

– pilot bits to support channel estimation

– transmit power-control (TPC) commands

– feedback information (FBI)

– an optional transport-format combination indicator (TFCI)

• One DPCCH and up to six parallel DPDCHs can be transmittedsimultaneously



Uplink Scrambling Codes

• a complex-valued scrambling code.

• The long scrambling codes are from a set of Gold sequences of 38400

chips. There are 224 long uplink scrambling codes.

• The short scrambling codes are derived from a sequence of the family of

periodically extended S(2) codes. There are 224 short uplink scrambling

codes.

• assigned by higher layers.




Common Uplink Physical Channel

1. PRACH - Physical Random Access Channel

• It is used to carry RACH

• Slotted ALOHA approach with fast acquisition indication

• A UE can start the transmission at a number of well-defined time-slotscalled access slots

• Consist of one or several preambles of length 4096 chips and a message

of length 10 or 20 ms





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

5120 chips

radio frame: 10 ms radio frame: 10 ms

Access slot #0 Random Access Transmission

Access slot #1

Access slot #7

Access slot #14

Random Access Transmission

Random Access Transmission

Random Access TransmissionAccess slot #8

RACH access slot numbers and their spacing



2. PCPCH –

Physical Common Packet Channel

• Carries CPCH

• Its transmission is based on CSMA-CD approach with fast acquisition

indication

•

Access slot and timing structure is same as for RACH• In addition to Access Preamble it also has one Collision Detection

Preamble (CD-P)




Downlink Physical Channels

Dedicated Downlink Physical Channels

1. DPCH - Dedicated Physical Channel

• Time multiplexed

• spreading factor SF:

SF = 512/2k

• In the downlink the spreading factors range from 4 to 512, with some

restrictions on the use of spreading factor 512 in the case of soft handover.

• The downlink DPDCH consists of QPSK symbols. Each symbol consists

of two bits while in the case of uplink the DPDCH consists of BPSK

symbol (one symbol corresponds to one bit).




Common Downlink Physical Channels

1. CPICH - Common Pilot Channel

• Fixed rate carries a pre-defined bit/symbol sequence

• Channel estimation

• Two types of CPICH

– Primary Common Pilot Channel

– Secondary Common Pilot Channel


Pre-defined symbol sequence

Slot #0 Slot #1 Slot #i Slot #14

Tslot = 2560 chips , 20 bits = 10 symbols

1 radio frame: Tf = 10 ms

Frame structure for Common Pilot Channel



1.1 Primary CPICH

• Same channelization code always used

• Scrambled using primary scrambling code

• One per cell

•Broadcast over entire cell

1.2 Secondary CPICH

• Uses either primary or secondary scrambling code

• Zero, one or several per cell

• May be transmitted over a part of cell




3. S-CCPCH - Secondary Common Control Physical Channel

• carry FACH and PCH

• SF = 256/2K

• FACH and PCH can be mapped to same secondary CCPCH

• Primary CCPCH has fixed pre-defined rate while secondary CCPCH has

variable rate

• Primary CCPCH is continuously transmitted over entire cell while

secondary CCPCH is only transmitted only when there is data available

4. SCH – Synchronisation Channel

• Used for cell search

• Consist of two sub channels

– Primary SCH

– Secondary SCH

• Primary SCH consist of a modulated code of length 256 chips

• Secondary SCH consists of repeatedly transmitting a length 15 sequence

of modulated codes of length 256 chipsTE 440 Next Generation Wireless Networks 38



5. PDSCH – Physical Downlink Shared Channel

• Carry DSCH

• Shared by users based on code multiplexing

• As DSCH is always associated with DCH, PDSCH is always associated

with DPCH

• Spreading factor may vary frame-to-frame

•Control information is transmitted on the DPCCH part of the associatedDPCH

• SF = 256 to 4

6. AICH – Acquisition Indicator Channel

• Used to carry Acquisition Indicators (AI)

• Either corresponds to an access preamble or a CD preamble

• Access preamble is an AP-AICH and CD preamble is a CD-AICH




7. PICH – Page Indicator Channel

• Used to carry Page Indicator (PI)

• PICH is always associated with a S-CCPCH to which PCH is mapped





BCH FACH PCH RACH DCH DSCH

P-CCPCH

S-CCPCH

PRACH

Transport

channels CPCH

Physical

channels AICH

PICH

PDSCH

SCH

DPCCH

DPDCH

PCPCHCPICH

Mapping of Transport Channels

onto Physical Channels



Initial Cell Search

The initial Cell Search is carried out in three steps:

Step 1: Slot synchronisation - using the primary synchronisation channel.

Step 2: Frame synchronisation and code-group identification using thesecondary synchronisation channel.

Step 3: Scrambling-code identification-identified through symbol-by-symbol

correlation over the primary CCPCH with all the scrambling codes within the

code group.




Handovers [1]

1. Intra-frequency HO

2. Inter-frequency HO

3. Inter System HO




Handovers [2]

1. Intra-frequency HO

1.1 Softer Handover

• Between two adjacent sectors of a base station

• Communication take place concurrently via two air interface

channels, one for each sector separately.

•The two signals combined at BS

• Only one power control loop per connection





Handovers [3]



Handovers [4]

1.2 Soft Handover

• Between cell coverage area of two different base stations

• The main difference between softer and soft HO is in the uplink direction

• Data at different BS from the MS is combined at RNC

• Frame reliability indicator is used to select the best frame

• Two power control loops per connection are active, one per BS





Handovers [5]




Backward Soft Handover Procedure Example

Target NB RNC MS Serving NB DCCH

Measurement report Measurement reports

Add

Phase

MS monitors the pilots level from neighbouringNBs and compares them to a set of thresholds and

reports them MS acquires the Target

NB and adds it to its active list

1

2

DTCH

DCCH DCCH

DCCH DCCH

Handover "add" request Handover "add" request

Handover "add" completion

Handover "add" request Handover "add" completion

Handover "add" request

DTCH

Handover "add" completion Handover "add" completion

Drop Phase

MS monitors the pilot levels of the serving NBs and compares it with a

Threshold and reports them

1

MS removes one of the

serving NBs, from its active list 2 Handover "drop" completion Handover "drop" completion

DCCH Measurement report Measurement report

Handover "drop" request DCCH

Handover "drop" request Handover "drop" request Handover "drop" request DCCH

Handover "drop" completion Handover "drop" completion

DCCH DCCH

DCCH DCCH

Handover "add" completion

DCCH Measurement report Measurement report

Traffic

Traffic Softhandoverphase



Handovers [7]

2. Inter-frequency HO

• Hard handover

• The handover between two base stations operating at two different

frequencies

•

e.g. HO between two different UMTS operators

3. Inter System HO

• Hard handover

• take place between the WCDMA FDD system and another system

• e.g. such as HO between UMTS to GSM




UMTS Architecture [1]


CN

UTRAN

UE

Uu

Iu

UTRAN UMTS Terrestrial Radio Access Network CN Core Network UE User Equipment





UTRAN Architecture

RNS

RNC

Node B Node B

Iub Iub

Core Network

RNS

RNC

Node B Node B

Iub Iub

Iu Iu

Iur



Network Nodes

1. User Equipment

• Consist of ME and USIM

• The Mobile Equipment (ME) is the radio terminal used for radio

communication over the Uu interface• The UMTS Subscriber Identity Module (USIM) is a smartcard that holds:

– the subscriber identity,

– performs authentication algorithms,

– stores authentication and encryption keys

– subscription information that is needed at the terminal




Core Network [1]

1. Home Location Register –

HLR

• is a database located in the user‟s home system that stores the master copy

of the user‟s service profile

• It is created when a new user subscribes to the system, and remains stored

as long as the subscription is active

2. Mobile Switching Centre/Visitor Location Register – MSC/VLR

• It is the switch (MSC) and database (VLR) that serves the UE in its current

location for Circuit Switched (CS) services

• MSC switches the CS transactions• VLR holds a copy of the visiting user‟s service profile and more precise

information on the UE‟s location within the serving system




Core Network [2]

3. Gateway MSC –

GMSC

• It is the switch at the point where UMTS PLMN is connected to external

CS networks

• All incoming and outgoing CS connections go through GMSC

4. Serving GPRS Support Node – SGSN

• Its functionality is similar to that of MSC/VLR but is typically used for

Packet Switched (PS) services

5. Gateway GSN –

GGSN

• functionality is close to that of GMSC but is in relation to PS services




Interfaces

1. Cu interface

• This is the electrical interface between the USIM smartcard and the ME.

• The interface follows a standard format for smartcards.

2. Uu interface• It is the WCDMA radio interface

• The UE accesses the fixed part of the system through this interface

3. Iu interface

• It connects UTRAN to the CN

• the open Iu interface gives UMTS operators the possibility of acquiring

UTRAN and CN from different manufacturers




4. Iur interface

• The open Iur interface allows soft handover between RNCs

5. Iub interface

•It connects a Node B and an RNC

• UMTS is the first commercial mobile telephony system where the

Controller – Base Station interface is standardised as a fully open interface




Radio Access Network [1]

1. Radio Network Controller

• It is responsible for control of the radio resources in its area

• One RNC can control multiple Node Bs

• Its functionality is equivalent to BSC in GSM/GPRS

•RNCs are more intelligent than BSCs

• RNCs can autonomously handles handovers without involving MSCs and

SGSNs

• RNCs are interconnected using the Iur Interface




Radio Access Network [2]

2. Node B

• It is responsible for air interface L1 processing

• Also performs some RRM function such as inner loop power control

• It is equivalent to BTS in GSM/GPRS

•Node Bs are typically collocated with GSM BTSs

• The enigmatic term „Node B‟ was initially adopted as a temporary term

during the standardization process, but then never changed




General Protocol Model for UTRAN


RadioNetworkLayer

TransportNetworkLayer

Control Plane

ApplicationProtocol

User Plane

DataStream(s)

SignallingBearer(s)

SignallingBearer(s)

Data

Bearer(s)

ALCAP(s)

Transport NetworkUser Plane

Transport NetworkUser Plane

Transport NetworkControl Plane

Physical Layer

Te-440 Universal Mobile Telecommunication System (Umts)Marcp

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