rate matching

7/31/2019 Rate Matching

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Aalborg University, RATE/TBS, 2006slide 1

SIPCOM9-2, lecture 10MultiUserComm

Multi-User Communication

Lecture 10

WCDMA Overview



Objective

Introduce WCDMA

from a systems perspective, but with a focuson lower layers (FDD mode)

WCDMA Release 99

giving you, hopefullya technology context to which you can apply

e.g. the theory on multi-user communication

a system context from which you can explorerecent advances on WCDMA (HSxPA) and itsevolution (LTE)


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Outline

WCDMA introduction

UMTS and 3GPP specifications

UTRAN architecture

Basic radio resource management

Physical layer channels and procedures

Short on TDD mode

MUD in WCDMA uplink (gain potential)

References

Acronyms



WCDMA

UE 1Time

(Code) Power

UE 2

UE 3

UE 4

Node BUE

Available resources:Spreading Codes (OVSF)

andTransmission Power

Soft/Softer

Handover

non-orth

ogonal

codes

orthogonalcodes

DATA

Bit rate Chip rate

Channelisationcode

Scrampling

code

Chip rate


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3

5

4

6

7

8

10

9

Cellrange(km)

Maximump

athloss(dB)

100 200 300 400 500 600 700 800 900 1000

145

150

155

160

165

Cell load (kbps)

Downlink 10WDownlink 20W

Uplink(144 kbps / 125 mW terminal)

Typisk maks. tab

3 dB forbedring af dkningsomrde

Downlink 20W

Dkning er

begrnset

af uplink

Kapacitet er

begrnset

af downlink

WCDMA Coverage

and Capacity



3GPP Specifications


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UMTS releases

v3.0.0 v3.1.0 v3.2.0 v3.3.0 v3.4.0

v4.0.0 v4.1.0 v4.2.0

v5.0.0 v5.1.0

etc.

Corrections

New Functions

Release 99

Release 403/01

Release 5

12/99

06/02

Release 606/05 v6.0.0

etc.

etc.

etc.

Standardized by 3rd Generation Partnership Project (3GPP), see http://www.3gpp.org [North America: 3GPP2]

UMTS LongTerm Evolution

UMTS used for designating 3rd generation systems (ITU: IMT-2000)



3GPP specs

Main rule for 3GPP specifications (http://www.3gpp.org): XX.INN

XX: series specification

I: (0) applies to both 3G and GSM (GPRS/EDGE)

(1,2) applies to 3G only

GSM means GERAN 3GPP RAN while 3G means a 3GPP UTRAN RAN

Examples TS25.211 (v. 6.1.0), Physical channels and mapping of transport channels onto physical

channels (FDD), release 6, Technical Specification Group Radio Access Network, July

2004

TS25.213 (v. 6.0.0), Spreading and Modulation (FDD), Technical Specification GroupRadio Access Network, December 2003

TS25.104 (v. 6.8.0), Base Station (BS) radio transmission and reception (FDD),Technical Specification Group Radio Access Network, December 2004

TS25.212 (v. 6.3.0), Multiplexing and channel coding (FDD), Technical SpecificationGroup Radio Access Network, December 2004

TR25.887 (v. 6.0.0), Beamforming enhancements (release 6), Technical SpecificationGroup Radio Access Network, March 2004

TR25.876 (v. 1.7.0), Multiple input multiple output in UTRA, Technical SpecificationGroup Radio Access Network, August 2004

TR25.869 (v. 1.2.1), Tx diversity solutions for multiple antennas, TechnicalSpecification Group Radio Access Network, February 2004


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3GPP Series



UTRAN Architecture

UMTS Terrestrial Radio Access Network


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Radio-specific part

Public Land Mobile Network

UTRAN/GERAN

Uu/Um

CNUE/MS

Iu

From Release 5 GSM and UMTS have the same interface to the radio

specific part of the network

PLMN Architecture



Uu/Um

Node B/BTS

RNC/BSC

Node B/BTS

Node B/BTS

Node B/BTS

RNC/BSC

USIM

ME

Iub/Abis

Iur

MSC/VLR

GMSC

SGSN GGSN

HLR/AuC

UTRAN/GERAN

UE/MS CN External Network

Iu

PLMN, PSTN,

ISDN, etc.

Internet,X25, etc.

PLMN

CS

PS

Radio-specific part

Public Land Mobile Network

PLMN Architecture

The geographical area covered by a PLMN is

partitioned into MSC serving areas; a location

area is a subset of a single MSC serving area.

Typically, there is one (logically speaking)

HLR in an operators PLMN.


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BS C

BT S

BT S

BSS (RAN/ G ERAN)

RN C

Node B

Node B

U T R A N

ME

SIM

USIM

MS

SGSN

PS Domain

GGSN

CS MGW

CS Dom ai nHSS/AuC

RN C

MSC-Serv./VLRAbis

SIM-ME

Iu bisCu

Um

Uu

Iu CsGb

A

Iu PS

C

D

IurGn

Gr Gc

Gs

CS MG WMSC-Serv./VLR

CS MG W

G MSC-Serv.

I MS Dom ai n

(Release 5)

M b/ Gi

Cx

Mc

Nb

Nb

G/E/Nc

Nc

Mc

User E qu ipm ent Dom ain

A ccess Ne t work Dom ain Core Ne t work Dom ain

Inf rast ructure Domain

Circuit-switched core

network

MSC

Packet-switched core

network

SGSN



NRT Packet Switched Data

Protocol stack of a NRT packet switched session in UMTS Release 99

Retransmission, sequence numbering,flow control, multiplexing, etc.


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Basic RRM

Radio Resource Management



I

u

b

I

u

b

Uu Iub

UE Node B RNC

PC

AC

LC

PS

RM

HC PC

PC LC

RRM Overview

AC Admission Control; PS Packet Scheduler; LC Load Control;RM Resource Manager; HC Handover control; PC Power Control

RRM in UMTS Release 99


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Power Control

Fast Closed Loop PowerControl (CLPC)at rate 1500 Hz

RNC adjusts the SIR target in

the Node B for the fast CLPCin response to link quality

UE

Node B RNC

Node B adjusts the power to

keep the SIR at the SIR target

Slow Outer Loop PowerControl (OLPC)at rate 2-100 Hz

In uplink to keep the receivedsignal level the same for all

users (near-far effect)

In downlink to increase thereception quality of stationary

users and users at the cell edge

To increase spectralefficiency

?



Uplink Fast PC

UE1 and UE2 are transmitting atthe same frequency => equalizingreceived powers at Node B iscritical to avoid near-far problems

Closed loop power control: NodeB commands UE to increase or to

decrease its transmission powerat a rate of 1.5 kHz (1 dB steps)

Closed loop power controlfollows also the fast fadingpattern at low and mediumspeeds (< 50 km/h)

Fast PC algorithm in Node B:If Eb/N0 < Eb/N0,target,

send "power-up" command.Else If Eb/N0 > Eb/N0,target,

send "power-down" command.

PCcomm

ands

UE1

UE2

Node B

L1

L2


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500 1000 1500 2000 2500 30004

4.5

5

5.5

6

6.5

7

1 minute period

Estimatedquality better than

required?NoYes

IncreaseEb/N0 target

DecreaseEb/N0 target

Outer Loop PC

General outer loop algorithm

Example adjustments of Eb/N0target for AMR speechservice, BLER target 1%

If error in frame, increaseEb/N0 target by 0.5 dB

If no errors, decrease Eb/N0target with such a rate thatBLER = 1% on average.



Softer Handover

Softer handover

UE is connected totwo sectors of onebase station

Softer handoverprobability 5 - 15 %

UL/DL

Basically sameRake combining asfor multipath andantenna diversity(Node B and UE)

RNC

Sector 1

Sector 2

Uplink combing from two sectorsin Node B Rake receiver (maximalratio combining)


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Soft Handover

Soft handover UE is connected to two base

stations

Soft handover probability is 20 -50 %

Required to avoid near-fareffects

Extra transmission over Iub

More baseband processingneeded (both base stations)

DL Maximal ratio combining in UE

in the same way as with softerhandover or multipath diversity

UL Frame selection combining in

RNC

RNC

Uplink combing fromtwo base stations in RNC(selection combining)



Soft HandoverExecution (1/2)

Active Set (AS) cells have the knowledge of service used by UE

RNC informs the new cell (to be added to AS) about the neededconnection, forwarding the following:

Coding schemes, number of parallel code channels, the differenttransport channel configuration parameters in use by UL and DL

UE ID and uplink scrambling code

The relative timing information of the new cell with respect to theexisting connection (as measured by the UE at its location). Basedon this, the new Node B can determine what should be the timing of

the transmission initiated with respect to the timing of the commonchannels (CPICH) of the new cell

MS is informed about the channelisation codes to be used intransmission and relative timing information through existingconnection


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Soft Handover

Execution (2/2)

PCCCHframe

PDCH/PCCHframe

Measure Toffset

Handovercommandand Toffset

UTRAN

Transmision channeland Toffset

BS Bchannelinformation

BS ABS B

Toffset

The relative timing information, which needs to be madeavailable at the new cell is indicated in the above figure

It makes transmissions capable to be combined in the Rakereceiver from timing point of view



Fast Power Controlin Soft Handover

BS 1

BS 2

Both Node BsDetect downlink PC command from mobile

Adjust downlink transmission power

RNC:Power drifting

control

UE:Check reliability of uplink PC command

Adjust uplink transmission power

Power

drifting

Reliabilitycheck

Independent power control commandsare sent from Node Bs to UE to controluplink transmission power

Base stations detect independently thepower control command from mobile tocontrol downlink transmission power


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DATA

Bit rate Chip rate

Channelisationcode

Scramplingcode

Chip rate

Uplink Downlink

Spreading Separate bearer

services

Separate users/

bearer services

Scrambling Separate users Separate cells

Code Allocation and Code Tree Management

All physical channels are spread with individual spreadingcodes, Cm(n) and subsequently by the scrambling code, CFSCR

Resource Manager generates DL spreading codes.

The code layer, m and the code number, n designates each andevery code in the layered orthogonal code sequences.

Resource Management



Code Types

Downlink OVSF channelisation (or spreading) codes (SF 4 - 512)

Scrambling codes long scrambling code (Gold code with 18 degree polynomial), but

using only one frame (38400 chips) complex valued code is formed by time delayed version of the same

code

limited to 512 possible codes divided into 64 code groups

Uplink OVSF channelisation (or spreading) codes (VSF 4 256)

Scrambling codes short and long codes

long scrambling code (Gold code with 25 degree polynomial), butusing only 38400 chips

complex valued code is formed by time delayed version of the same code

short 256 chips extended S(2) code family complex valued code is formed by combining two codes

millions of scrambling codes


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Resource Manager

Code Allocation Code Allocation Algorithm chooses the proper spreading code depending on

the transport format combination type.

The codes are layered from 0 to 11 according to the code type (~SF)

Only layers 2 to 8 are available for DL and 2 to 7 for UL

C0(0)=(1)

C1(0)=(1,1)

C1(1)=(1,-1)

C2(0)=(1,1,1,1)

C2(1)=(1,1,-1,-1)

C2(2)=(1,-1,1,-1)

C2(3)=(1,-1,-1,1)

C3(0)=()

C3(1)=()

C3(2)=()

C3(3)=()

C3(4)=()

C3(5)=()

C3(6)=()

C3(7)=()

Layer0

Layer1 Layer2 Layer

3



RM Examples

Examples: Ordinary DL speech 30 kbps channel (AMR 12.2-4.75

kbps & control part with 1/3 channel coding - code type7 (128 chips/symbol)

C2(1) code layer = 2; code number = 1 code = 11002

120 kbps channel - code type 5 (32 chips/symbol)

C4(5) code layer = 4; code number = 5 code = 11001100001100112

The Resource Manager maintains code treeorthogonality

If a code Cm(n) is in use, all the codes that are below it inthe same branch and the codes that are above it in thesame branch to the root are made unavailable


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Physical Layer

Channels and Procedures



Transportchannels

Medium Access Control (MAC), Layer 2

Physical Layer, Layer 1

MAC selects appropriate bit rateaccording to the instantaneous

source bit rate.

Physical layer supports variablebit rates up to 2 Mbps

Logical channels

Physical channels

Channel Types


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WCDMA ChannelsBCH

Broadcast

PCCPCHPrimary Common

Control

SCCPCHSecondary

Common Control

PRACH

DPDCH

DPCCHPDSCH

PCPCH

SCHSynchronisation CPICH

CommonPilot

AICHAcquisitionIndication

PICHPaging

Indication

CSICHCPCH Status

Indication

CD/CA-ICHCollision

Detect/Avoidance

FACHForward Access

CPCHCommon Packet

PCHPaging

RACHRandom Access

DCHDedicated

DSCHDownlink SharedTransport Channels

Physical Channels

how and withwhat

characteristics



Transport Channels(1/2)

Random access channel RACH: Data + signaling from one user

Dedicated channel DCH: data + signaling to one user

Broadcast channel BCH: Cell and system info

Forward access channel FACH:Data + signaling for one or more users within one cell

Paging channel PCH: For mobile terminated calls

Downlink shared channel DSCH: Packet data channel.Time multiplexed by several users.

Common packet channel CPCH:Extension of RACH for longer data packets

Mobile

Node B

DSCH optional for network

CPCH optionalfor network


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Transport Channels

(2/2) Due to direct support of variable bit rate and service multiplexing in

UTRA/FDD there is only one dedicated transport channel(DCH). DCHcontains user data and control information from higher layers.

There exist a total of six common transport channelsin UTRA/FDD:

Broadcast channel (BCH): General information of UTRA network or the currentcell (e.g. random access codes, access slots). BCH is sent at low data rate(single TF) and high power to reach all users in intended coverage area.

Forward access channel (FACH): Downlink transmission of control informationto UE's in current cell. Slow power control and low data rates.

Paging channel (PCH): Downlink paging information (e.g. call initiation).

Random access channel (RACH): Uplink control information (e.g. UE requests to

set up connection/initiate call). Single frame only.Optional uplink common packet channel (CPCH): Extended RACH for sending

data over multiple frames.

Optional downlink shared channel (DSCH): Somewhat similar to RACH but canbe shared by multiple users to increase data throughput.



Services in UMTS are classified according to their QoS requirements into

one of 4 service classes

The service classes are characterised by certain bearer attributes provided

by the UMTS Radio Access Bearer

Each Radio Access Bearer (RAB) is transmitted on

a specific Transport Channel (TrCh)

In a multi-service environment (with different QoS requirements)

transmission is done on a combination of TrChs which are transmitted on

the same physical channel(s)

RABs and TrChs


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Transport Format (TF)

group of parameters describing the transmission "mode" on a specific

TrCh during a TTI (TTI size is part of the TF)

TF Set (TFS)

corresponds to a group of TFs applying to one specific TrCh

TF Combination Set (TFCS)

the product of TF Sets of all the TrChs forming the combination

TF Indicator (TFCI)Each TF Combination (TFC) of the TFCS is indexed with the TFC

Index (TFCI) at the physical layer

TrCh Details (1/2)



8

16

32

64

128

256

320

384

8

16

32

64

Examplebit rates for

NRT

64

Peak bit ratein bearer

parametersis requested

from PS

256

Scheduledbit rate

TFS for NRTRB includes

allintermediate

rates

64

32

TFS subsetfor TFCS

construction

0 0 0

32

64

0

16

0

TFCS (SL & NRTRB)

TFCI 0TFCI 3

TFCI 1TFCI 4

TFCI 2TFCI 5

TrCh1

TrCh2

TFI0

TFI1

TFI2

TFI3

TFI4

TFI0

TFI4

TFI3

TFI0

TFI1

TFI0

TFI3

TFI4

TFCI TFITrC

H1

TFITrC

H20 0 0

1 0 3

2 0 4

3 1 0

4 1 3

5 1 4TFCS Construction by cartesian product

Example with radiobearer for user

data and signalling

TrCh Details (2/2)


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Dedicated Channel (DCH/DPCH)

Speech and data services



Target

Characteristics forUL and DL

Dedicated physicalcontrol channel (DPCCH)

Dedicated physicaldata channel (DPDCH)

Keep physical layerconnection running

Carry user data andhigher layer control data

Content

(1) Reference symbol:Channel and SIR estimation(2) Power control signaling(3) TFCI: bit rate information

(1) User data(2) Higher layer signaling

(RRC)

Bit rateConstant bit ratefor reliable detection

Variable bit rate. Bit rateindicated with TFCI on DPCCH.

Dedicated channel (DPCH) consists of two physical channels:

DPCCH keeps physical layer connection running reliably

DPDCH carriers user bits with variable bit rate

Possible to have a power offset between the two channels


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Solution

Target

Multiplexing of

DPCCH and DPDCH

The code consumption is not an issue in uplink since the number ofcodes is very large

The discontinuous transmission is not an issue in downlink sincecommon channels (10-20% of BTS max power) are transmitted all the

time Blind rate detection (no TFCI bits) is easier for the mobile when the

channel bit rate remains constant in time multiplexed solution

Variable rate transmission for data can be implemented bydiscontinuous transmission (DTX) on a slot interval (DL) and frame(UL) basis, symbol repetition where frame is always full, or variablespreading factor (UL).

Uplink Downlink

I/Q code multiplexing Time multiplexing

Continuous transmission reduce audible interference

(1) Only one code needed saves orthogonal codes(2) Support for blind rate detection



Variable Rate inUplink

DPCCH

DPDCH

Service in DTX(e.g. silence in speech)Higher bit rate Low bit rate

Continuous mobile transmission regardless of the bitrate (also during service DTX) Reduced audible interference to other equipment (nothing to do

with normal interference, does not affect the spectral efficiency)

Services can still have DTX, like silence period in speech. Duringthat time no DPDCH transmitted but still continuous DPCCH

Fast power control keeps received power of DPCCHconstant

10 ms frame 10 ms frame 10 ms frame


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DPCH (DPCCH/DPDCH)

SF = (4 - 256)

DPCCH

DPDCH

DPDCH

TTI

TCFI, (DL) TPC, PILOT

Pairedwith

UL

DL

10 ms

SF = 256

Code(Power)

TCFI, (UL) TPC, (PILOT)

SF = 4 - 256

DPCCH

DPDCH

DPDCH

Transmission Time Interval (TTI)

TFCI (DL), TPC, PILOT

TFCI (UL), TPC, (PILOT)

Paired with

Code(Power)

Channel Structure

(DPCH)

Carries the Dedicated(DCH) transport channel

DPCH (DPCCH/DPDCH)

DPDCH Dedicated Physical Data ChannelDPCCH Dedicated Physical Control Channel

TFCI Transport Format Combination IndicatorTPC Transmitter Power Control



UplinkDPDCH/DPCCH

Pilot

Npilot bits

TPC

NTPC bits

Data

Ndata bits

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

Tslot = 2560 chips, 10 bits

1 radio frame: Tf= 10 ms

DPDCH

DPCCHFBI

NFBI bitsTFCI

NTFCI bits

Tslot = 2560 chips, Ndata = 10*2k

bits (k=0..6)

Fixed SF256

Lets the receiverknow what is

coming whichTrChs are activein frame!

Variable SF from 4 to 256 on a frame-by-frame basis aresupported in the uplink


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Uplink Processing

Frame 1 Frame 2 Frame 72

Super frame 720 ms

10 ms


Slot 1 Slot 2Slot 1 Slot 2 Slot 15

(2) Detect PC commandand adjust DL tx power

Slot 0.667 ms = 2/3 ms

Pilot TFCI

Data

DPCCH

DPDCH

TPC

(1) Channel estimate+ SIR estimate for PC for

adjusting UL tx power

(3) Detect TFCI(10 ms frame)

(4) Interleaving (TTI) :Detect data



Uplink TX (I)

CRC encoding: Cyclic redundancy check (CRC)attachment is done to enable error detection atthe receiver. The CRC indicator length can beset to 0/8/12/16/24 bits depending on thedesired error detection accuracy.

Encoder block size adjustment: Transport blockconcatenation is used for smaller amounts of

data in order to reduce the overhead of tail bitsand to increase the block size to improve thechannel encoding performance. On the otherhand, code blocks segmentation is done to avoidexcessively large block sizes.

CRC encoding

Encoderblock sizeadjustment

Raw bits


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Uplink TX (II)

Channel encoding is done in order to improvethe bit or frame error rate (BER/FER)performance of the link. Variable coding issupported (from no coding to high coding). Forthe relatively low data rates (similar to secondgeneration systems), convolutional encoding( and 1/3 rate) is used for simplified detectionand good performance. The highest data ratesuses 1/3-rate Turbo encoding for best codinggain.

Radio frame equalization is done by eitherconcatenating transport blocks together or bysegmenting blocks such that data is dividedinto equal-sized blocks when they do not fit asingle 10 ms frame.

Radio frameequalization

Channelencoding



Uplink TX (III)

Inter-frame interleaving is done whenever thedelay-budget (for the current QoS) allows formore than 10 ms (1 frame) of delay. Theinterleaving length may be 20/40/80 ms.Interleaving reduces correlation betweenadjacent chips and thus improves detection(basic assumption for efficient channeldecoding).

Radio frame segmentation is padding the input bitsequence in order to ensure that the output canbe segmented in an integer number of datasegments of same size (subclause 4.2.6 inTR25.212). The frame segmentation is onlyperformed in the uplink since in the downlink, therate matching output block length is always aninteger multiple of the desired number of datasegments.

Inter-frameinterleaving

Radio framesegmentation


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Rate matching

Transport channel

multiplexing

+

intra-frame

interleaving

+

physical layermapping

DPCCH/DPDCH#

Uplink TX (IV)

Rate matching ensures that the frames arefilled up with data. To do this, either bypuncturing or by repetition. Repetition isusually preferred for the uplink. The ratematching is dynamically updated on aframe-to-frame basis. The rate matchingalgorithm is detailed in TR25.212.

Multiplexing: Finally, all the active transportchannels are multiplexed and a 10 ms intra-frame interleaving is conducted. After the

interleaving, the data is mapped onto thephysical channels.



Uplink TX (V) block diagram

Depending on which data rate is desired, each user can simultaneouslyhave 6 DPDCH channels (data) and one DPCCH channel (controlinformation).

SpreadingDPDCH1

DPDCH3

DPDCH2

DPCCH

Spreading

Spreading

Spreading

Scaling

Scaling

Rotation

Scaling

Scaling

d

d

j

Complex

Scrambling

Re{}

Im{}

cos(t)

sin(t)

RRC

RRC

S(t)

Dual-channel QPSK modulation(BPSK modulation + I/Q code multiplexing)

d

c

Example 3 x DPDCH configuration


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Slot Format #i Channel Bit Rate(kbps)

Channel SymbolRate (ksps)

SF Bits/Frame

Bits/Slot

Ndata

0 15 15 256 150 10 101 30 30 128 300 20 202 60 60 64 600 40 403 120 120 32 1200 80 804 240 240 16 2400 160 1605 480 480 8 4800 320 3206 960 960 4 9600 640 640

Physical Layer Rates

(Uplink)

A single code at SF 4 allows 960 kbps which turns into a user data rate

of 480 kbps with rate coding; 6 parallel DPDCHs at rate codingleads to a maximum user data rate in excess of 2 Mbps.

Beneficial to stick to a single DPDCH for as long as possible to reducePeak to Average Ratio (PAR).



DownlinkDPDCH/DPCCH

One radio frame, Tf= 10 ms

TPC

NTPC bits

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

Tslot = 2560 chips, 10*2k

bits (k=0..7)

Data2

Ndata2 bits

DPDCH

TFCI

NTFCI bits

Pilot

Npilot bits

Data1

Ndata1 bits

DPDCH DPCCH DPCCH

Lets the receiverknow what is

coming whichTrChs are active

in frame!

Constant SFs from 4 to 512 are supported in the downlink (somerestrictions for SF 512).

The SF for the highest transmission data rate determines thechannelisation code reserved from the code tree.


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Downlink Processing


Slot 1 Slot 2 Slot 16

PilotData

Super frame 720 ms

10 ms

Slot 0.667 ms = 2/3 ms

TPC


Slot 1 Slot 2 Slot 15

DPDCH DPDCH

Data

DPCCH DPCCH

TFCI

(2) Detect PC commandand adjust UL tx power

(1) Channel estimate+ SIR estimate for PC for

adjusting DL tx powerCan use CPICH

(3) Detect TFCI(10 ms frame

(4) Interleaving (TTI) :Detect data



Re{}

Im{}

sin(t)

RRC

RRC

S(t)

All channels(except SCH)Odd

bit

Evenbit

Rotation

j

Downlink transmitter

The downlink uses time multiplexing between data and control information.This is possible since there are multiple users and there are always generalcontrol channels being transmitted from the BS (e.g. SCH). On the uplink,multiplexing like this would cause audible interference during discontinuoustransmission.

Spreading

Spreading

ComplexScrambling

Otherchannels(users)

.........

SCH

cos(t)


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Physical Layer Rates

(Downlink)

Spreadingfactor

Channelsymbol

rate(kbps)

Channelbit rate(kbps)

DPDCHchannel bitrate range

(kbps)

Maximum userdata rate with -

rate coding(approx.)

512 7.5 15 36 13 kbps

256 15 30 1224 612 kbps

128 30 60 4251 2024 kbps

64 60 120 90 45 kbps

32 120 240 210 105 kbps

16 240 480 432 215 kbps

8 480 960 912 456 kbps

4 960 1920 1872 936 kbps

4, with 3parallelcodes

2880 5760 5616 2.8 Mbps

Half rate speech

Full rate speech

144 kbps

384 kbps

2 Mbps

Symbol_rate=Chip_rate/SF

Bit_rate=Symbol_rate*2

User_bit_rate=Channel_bit_rate/2

DPCCHoverhead



Signaling 3.4 kbps with 40 ms interleaving

Speech 12.2 kbps Speech 12.2 kbps

40 ms

Radio frame Radio frame Radio frame Radio frame

10 ms

81 class A bits 12 CRC 8 tail 103 class B bits 8 tail 60 class C bits 8 tail+ +AMR 12.2 kbps

136 data bitsRLC+

MAC 12 bits 24 CRCDPCH 3.4 kbps

Downlink Speech + Signalling

Example


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AMR Class A 1/3 rate conv

AMR Class B 1/3 rate conv

AMR Class C 1/2 rate conv

DPCH 1/3 rate conv

Channel coding

SF=256 240 bits

SF=128 510 bits

Downlink L1 bit rates

Spreading factor Bits per frame

960 bits

2040 bits

Bits per 40 ms

Bits per 20 ms Bits per 40 ms

AMR 12.2 kbps 772 bits 1544 bits

DPCH 3.4 kbps - 516 bits

2060 bits

1544 bits

AMR12.2+DPCH

AMR 12.2

Ratematching

1% puncturing

32% repetition

AMR12.2+DPCH

AMR 12.2

SF=128

SF=128

Channelcoding

Transport channelmultiplexing

Most suitable spreadingfactors and required rate

matching

Example



Speech, full rate 128 channels Number of codes withspreading factor of 128

(AMR 12.2 kbps *(128 4)/128 Common channel overhead

and 10.2 kbps) /1.2 Soft handover overhead

= 103 channels

Speech, half rate 2*103 channels Spreading factor of 256

(AMR 7.95 kbps) = 206 channels

Packet data 3.84e6 Chip rate

*(128 4)/128 Common channel overhead/1.2 Soft handover overh ead

*2 QPSK modulation

*0.9 DPCCH overhead

/3 1/3 rate channel coding

/(1 0.3) 30% puncturing

= 2.65 Mbps

4 channels withSF=128 for commonchannels assumed

20% soft handoveroverhead assumed

Result103 speech channels or

2.65 Mbps data withone scrambling code

Note: usually interference limits the capacitybefore the number of orthogonal codes

Downlink Capacity


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29



Basic Procedures

Common channels and

synchronisation



SCH,CP

ICH,AIC

H,PICH

These channels do notcarry transport channels

but are needed fornetwork operation

Synchronizationchannel SCH

Common pilotchannel CPICH

Acquisition indicatorchannel AICH

Paging indicatorchannel PICH

For the mobile to synchronize to the cell.

For the mobile synchronization, channel estimation, andfor the neighbor cell measurements

Response to RACH preamble

For indicating to the mobile that there is paging on PCH

Additional DownlinkPhysical Channels


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30



Common channels (I)

Common pilot channel (CPICH):

Purpose of run-time synchronization betweenthe BS and UE's located in the cell.

CPICH unmodulated, scrambled by cell-specific primary scrambling code (SF=256).

Used for initial synchronization, channelestimation and measurements for handoverand cell selection.

With multiple BS antennas (antenna diversity),CPICH's from each BS antenna are separatedby simple modulation patterns.



CPICH is transmitted continuously and it takes typically 5-15% of thebase station max power (IS-95 typically 20-25%, narrowband =>relatively higher overhead)

CPICH is used for downlink channel estimation in the mobile forcoherent combining of multipath components

CPICH is unmodulatedsignal under the cellspecific scrambling

code

Channelestimation

Other cellmeasurements

CPICH


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31



Common channels (II)

Synchronization channel (SCH):

Purpose of initial synchronization between the BS andUE's located in the cell.

SCH is used for cell search. It consists of primary andsecondary synchronization channels.

The primary channel uses a 256-chip spreadingsequence which is identical for every cell (global).

Secondary channels use sequences individual to eachgroup of cells and which identify one out of 64 possiblescrambling code groups. Once the UE has found the

secondary SCH it has obtained both frame and slotsynchronization.

(determined by the sequence used on the secondary SCHchannel)



SCH

0 1 14...PrimarySCH

0 1 14...SecondarySCH

256-chip sequencemodulated, identifies the code

group of the cell

2560-256=2304 chips256chips

256-chip sequencethe same in every cell


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32



Cell Search

512 scrambling codes in downlink are divided into 64 groups to speedup the cell search, each group contains 8 codes (8 x 64 = 512)

(1) Chip synchronization(2) Symbol synchronization(3) Slot synchronization

Primary SCH

(1) Code group (which of 64)(2) Frame synchronization

Secondary SCH

Exact scrambling code (which of 8)Pilot channel

CPICH

Which part of synchronization is obtainedWhich channel

is used

Step 1

Step 2

Step 3

Note: SCH is not under the cell specific scrambling code because it must bereceived before knowing the scrambling code

As a consequence, SCH is non-orthogonal to other channels

All other downlink channels are under the scrambling code



ML approach: Correlate with the PN sequence at all delays within theuncertainty region, and then determine the delay Thus, the meansynchronization time equals KLT, where Tis the correlation time andKis the number of correlations per chip interval.

Serial search: Correlate with the PN sequence at one delay anddetermine if the output is above the noise+MAI floor. If the output isbelow the the noise+MAI floor, then move the correlator to the nextdelay. Here the mean synchronization time is less than KLT.

Synchronization


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33



Serial Acquisition Scheme



Probability of Detectionand False Alarm


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34



Dual-Dwell Serial

Search



Tracking of PN-Sequences

After coarse synchronization is obtained within +/- one chip, amore accurate synchronization is initiated (tracking).

Tracking of the received PN-sequence is performed separatelyfor each RAKE finger.

Tracking is performed continuously during the transmission

since there is a time-varying drift between the received andlocally generated PN-sequence.

The time-drift is mainly caused by two factors:

Movement of mobile unit. At a speed of 100km/h, the time drift is onthe order of 100nsec/sec.

Oscillator drift between Tx and Rx.


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35



Early-Late Gate

Tracking The early-late gate algorithm aims at maximising the auto-

correlation between the received and the locally generated PN-sequence.

The tracking algorithm is a simple gradient search algorithm

The two power estimates can be obtained from the pilotsignal/symbol.



Tracking Uncertainty

Deterministic uncertainty due to filtering


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36



TDD Mode

In brief!



GeneralCharacteristics

Combined TDMA/CDMA (TDD) multiple access

Allows operation in unpaired band

Requires synchronization between base stationsto avoid uplink/downlink interference

Allows for assymmetric uplink/downlink capacity Discontinuous transmission leads to power

disadvantage cell range reduction

Has the advantage of a reciprocal channel

used for (open loop) uplink power control


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37



WCDMA TDD

UE 1

Time

(Code) Power

UE 2

UE 3

UE 4

Node BUE

non-ort

hogona

lcodes

orthogonalcodes

Available resources:Spreading Codes (OVSF)

and SlotsUp to 16 users codemultiplexed per slot

Single-userdetection

Multi-userdetection

UE 1

UE 2

frame n frame n+1



Generalized TDD Frame

Data symbols

(976 chips)

Data symbols

(976 chips)

Midamble

(512 chips)

Guard

(96 chips)

2560 chips

Data symbols

(976 chips)

Data symbols

(976 chips)

Guard

(96 chips)

TS 0 TS 14

10 ms

Burst Type I

Number of allocated time slots

# allocatedcodes (SF=16)

2.54 Mbps781 kbps195 kbps16

1.26 Mbps390 kbps97 kbps8

158 kbps48.8 kbps12.2 kbps1

1341

Midamble (training sequence) forjoint channel estimation


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38



MultiUser Detection

Interference Cancellation



MUD analysis

If we define the Interference Cancellation receiver efficiency, , as the

ratio between the equivalent intra-cell interference after and before

interference cancellation [Hmlinen], then the required (matched filter)

SINR (Eb/No) of userj (per antenna) can be expressed as

where Wis the chip rate, Rj

the selected data rate for transmission, Pj

the

total receiver power (per antenna), Pown the total received own-cell power

(per antenna), Pother the total received other-cell power (per antenna), and

Pnoise is the background noise power (per antenna).

A practical IC implementation (with acceptable complexity) can achieve

an efficiency of 30%, whereas about optimum for multi-stage IC achieves

70% efficiency

( )( )1j

jj own j other noise

PW

R P P P P

=

+ +


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39



0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

50

100

150

200

250

Cellthrough

putgain[%]

i = 0.0i = 0.2i = 0.4i = 0.6i = 0.8i = 1.0

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

10

20

30

40

50

Cellthroughputgain[%]

i = 0.0i = 0.2

i = 0.4i = 0.6i = 0.8i = 1.0 The gain from IC can be

approximated as:

35

i

iG

UL +

+

1

1

The cell throughput gain from ICdecreases with isince IC is only

effective towards intra-cellinterference.

Also, the impact of the IC efficiencyon the cell throughput gain is scaled

by the uplink fractional load UL.

18%

54

%

=0.7

iis the other-to-own interferenceratio

is the efficiency of the IC receiver

UL is the uplink fractional load

UL

UL

=0.3

27%

100%

IC Gain

from

[ C. Rosa, Enhanced plink Packet Access in WCDMA, Ph.D. dissertation, AAU, December 2004]



Wideband received power based RRM

Throughput based RRM

riseNoise

1-riseNoise1 ==

total

NUL

I

P

( ) ( )

( )

= =

+

+=+=N

j

N

j

jjjb

jUL

RNE

WiLi

1 1

0/1

111

Measure total wideband

received power Itotal

Calculate sum ofthe bit rates in a cell

Noise Rise andfractional load


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40



References and Acronyms



References

H. Holma and A. Toskala, WCDMA for UMTS Radio Access for Third

Generation Mobile Communications, John Wiley & Sons, 3rd edition,

2004 (HSDPA chapter!)

T.E. Kolding et al.,High Speed Downlink Packet Access: WCDMA

Evolution, IEEE Vehicular Technology Society (VTS) News, vol. 50, no.

1, pp. 4-10, February 2003

S. Hmlinen, H. Holma, and A. Toskala, Capacity Evaluation of a

Cellular CDMA Uplink with Multiuser Detection, International

Symposium on Spread Spectrum Techniques and Applications, vol. 1, pp.

339-343, September 1996

C. Rosa, T.B. Srensen, J. Wigard, and P.E. Mogensen, Interference

Cancellation and 4-Branch Antenna Diversity for WCDMA Uplink

Packet Access, Proceedings of VTC Spring 2005, Stockholm, Sweden,

May-June 2005

B. Vejlgaard, Data Receiver for the Universal Mobile

Telecommunications System (UMTS), Ph.D dissertation, AAU, 2000


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Acronyms

3GPP 3rd Generation Partnership Project

AC Admission Control

AuC Authentication Centre

BSS Base Station Subsystem

BTS Base Transceiver Station

CDMA Code Division Multiple Access

CN Core Network

CS Circuit Switched

DL Downlink (broadcast)

EUTRA Evolved UMTS Terrestrial Radio Access

FDD Frequency Division Duplexing

FDMA Frequency Division Multiple Access

GERAN GSM Evolved Radio Access Network

GGSN Gateway GPRS Support Node

GPRS General Packet Radio Service

GSM Global System for Mobile communications

HC Handover Control

HLR Home Location Register

HSS Home Subscriber Services

HSxPA High Speed Downlink/Uplink Packet Access

IMS Internet Multimedia Subsystem IMT International Mobile Telephony (ITU-2000)

ITU International Telecommunications Union

LTE Long Term Evolution

LC Load Control

ME Mobile Equipment

MS Mobile Station



Acronyms (cont.)

MSC Mobile Switching Centre

PLMN Public Land Mobile Network

PS Packet Switched

QoS Quality of Service

PC Power Control

PS Packet Scheduler

RM Resource Manager

RNC Radio Network Controller

RNS Radio Network Subsystem

RRM Radio Resource Management

RTT Round Trip Time

SF Spreading Factor

SGSN Serving GPRS Support Node

SHO Soft Handover

SIP Session Initiation Protocol

SS7 Signalling System 7

TDD Time Division Duplexing

TDMA Time Division Multiple Access

TMSI Temporary Mobile Subscriber Identity

UE User Equipment

UL Uplink (multiple access)

UMTS Universal Mobile Telecommunications System

USIM UE Subscriber Identification Module

UTRAN UMTS Terrestrial Radio Access Network

VLR Visitor Location Register

VSF Variable Spreading Factor

WCDMA Wideband Code Division Multiple Access

rate matching

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