01-0-WCDMA Wireless Principle and Key Technology-102

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WCDMA Wireless Principle and Key

Technology



Content

WCDMA System Overview

WCDMA Wireless Principle

WCDMA Key Technology



Evolution of Cellular Mobile Communication

SystemFirst

Generat ion(80s’)

Analog

Third

Generation

(2000)

Wideband

Multimedia

Second

Generat ion(90s’)

Digital

AMPS

TACS

NMT

Others

A n a l o g

T e c h n o l o g y

GSM

CDMAIS95

TDMA

IS-136

PDC

Market

Driven

UMTS

WCDMA

CDMA

2000

Market

Driven

TD-

SCDMA

D i g i t a l T e c h n o l o g y

V o i c e S e r v i c e

B r o a d b a n d S e r v i c e



Background of 3G

Essential impetus: awider range and higher

data rate of services,

higher spectrum

efficiency

Improve the compatibility

between different

networks

The international

standard—IMT-2000

comes forth as the

requirement



3G Technology Evolution

3G

Standard

WCDMA

TD-SCDMA CDMA2000

CDMA is the Mainstream Technology of 3G

CN：based on MAP

CN：based on ANSI-41 CN：based on MAP



3G Standard and Beyond 3G Evolution

TD-SCDMAEnhancedTD-SCDMA

2005

• R4 • R5/6LTE

FDD/TDD

• HSDPA

Phase1

• HSUPA

Phase1

• HSDPA

Phase2

•HSUPA

Phase2

• MBMS•WCDMA

•R4

2004 2005 2006 2007 2008 After 2009

• R5

• R6

•CDMA

•1X

• EV-DO 0 • EV-DO A

• BCMCSAIE

Phase 2

AIE

Phase1

N×DO

3GPP 4G

3GPP2 4G

WiMAX

802.16d

WiMAX

802.16e



WCDMA Standard Evolution

Introduce Iu

Interface

MAX. Speed: 2Mbps

Commercial Release

2001.6+ following

CR

R99

R4

R5

R6

2000.3 2001.3 2002.6 Time for function frozen

Control andBearer

Separation

Introduce IMS

Domain

Introduce HSDPA for

Radio Interface

Study on Interoperability

of IMS and

PLMN/PSTN/ISDN

Circuit Switch Network

MBMS

Study on Frame

Structure



Characteristics of WCDMA

Bidirectional fast closed-loop power control

(High capability to overcome interference, fading, and ensure the service quality and system capacity)

Bidirectional coherent demodulation by pilots bit

（3dB Gains）

Transmitter and receiver diversity

High chip rate(3.84Mcps）

Channel coding tech with high gain

（ Add the redundant bit to protect user data）

Unnecessary for GPS synchronization among base stations

Multiple handover technology（intra-frequency soft handover/ Hard handover, Inter frequency hard handover, Inter-RAT

handover ）

Multiple transport rate

Advanced radio resource management algorithm



WCDMA Entire IP Network EvolutionR99

BillingServer

OMC

SCP

HLR

MMSC

GMLC

MSCGMSC

GGSNSGSN

PSCS

R99 CN smoothly evolves from

GSM/GPRS network

R4 CN separate the Control Plane

from Bearer Plane in CS Domain

R5 CN Introduces IMS，

RAN Adopts IP

RNS

BSS

MGWGMGW GGSNSGSN

PSCS

R4 R5

Billing

Server

OMC

SCP

HLR

MMS

C

GMLC

CS

MSCserver

GMSCserver

Billing

ServerOMC

SCP

HLR

MMS

C

GMLC

BSS

RNSRNSBSS

MGWGMGW GGSNSGSN

PSCS

WCDMA Entire IP Network Evolution coincide with the development

tendency of the next generation network



WCDMA CDMA2000

Carrier spacing 5M 1.25/5/10/15/20 MHz

Chip rate 3.84M N*1.2288Mcps N=1,3,6,9,12

Spreading way DS-CDMA DS-CDMA & MC-CDMA

Duplex mode FDD/TDD FDD

Frame size 10ms 20ms（general data and control channel）

5ms（basic and designated control channel)

Channel coding Convolutional codes Turbo

codes

Convolutional codes Turbo codes

Scrambling Walsh+Gold sequence Walsh+M sequence

Modulation

mode

QPSK/BPSK QPSK/BPSK

Power control Open-loop and fast closed-

loop 1.5KHz）

Open-loop and fast closed-loop（800Hz）

Base station

synchronization

Synchronization/Asynchrono

us

synchronization

Comparison of the Three 3G Technologies (I)



Content






Characteristic of Radio Propagation

Electromagnetic propagation: direct radiation、reflection、diffraction and scattering

Signal attenuation:

Path loss： Loss of electromagnetic waves in large

scope of the spread reflects the trend of the received

signal in the spreading。

Slow fading：Loss because of being blocked by the

building and hill in the propagation path

Fast fading：Electromagnetic signals rapidly decline

in a few dozens wavelength ranges

Description of Fast fading distribution

Rayleigh distribution：non line-of –sight transmission

Rician distribution：line-of –sight transmission



Multi-Path Effects

receiving signal

time

strength

0

sending signal



Power

Power

Power

FDMA

TDMA

CDMA

Frequency division multiple access

technology Channels in different frequency are

allocated to different users, e.g. TACS

AMPS

Time division multiple accesstechnology channels in different time are allocated to

different users, e.g. GSM DAMPS

ode division multiple accesstechnology

Users distinguished by scramble code, e.g.

CDMA

Multiple Access



f

S（f）

f0

Before spreading

signal

S（f）

ff0

After spreading

signal

S（f）

ff0

After despreading

signal

White noise

f

S（f）

f0

Before despreading

signal

White noise

signal interference White noise

Sketch Map of Spreading



Spreading Mode

Direct sequence spread（DS－SS）

Base band data is spreaded by multiplication of pseudo-noise sequence and base-band pulse, the pseudo-noisesequence generated by the pseudo-noise generator

BER subject to Multiple Access Interference and near-fareffect

Power control can overcome the near-far effect, but it islimited by power detection accuracy

WCDMA uses DS-SS

Frequency hopping spread（FH-SS）

Data is transmitted in the random channel by the carrierfrequency hopping

Before FH again, data is transmitted using traditionalnarrowband modulation

No near-far effect



Characteristics of Spreading Communication

High anti-multi-path- interference capability (Rakereceiver, Power control etc)

Anti-sudden-pulse

High security(OVSF and scrambling code)

Lower transmitting power Easy to implement large-capacity Multiple Access

Communication

Occupy band wide

Complex realization



Purpose of Channel Coding

purpose: By adding redundant information in the original data

stream, receivers can detect and correct the error

signal, and improve data transmission rates.

No correct coding: BER<10-1 ~ 10-2Can not satisfy

the communication

Convolutional coding：BER<10-3Can satisfy the

speech communication

Turbo coding： BER<10-6 Can satisfy the

data communication



Principle of Channel Coding

Convolution coding Error-correcting ability obtains by adding redundancy

in the original data

Convolutional coding and Turbo coding （1/2，1/3）

are widely applied.

Increase redundancy and transmission time

Suitable to correct few non-continuous errors）



Principle of Interleave Technology

advantage Interleave is to change the sequence of data to

random the unexpected errors

Advance the correcting validity

disadvantage：

Increase the processing delay

Especially, Several independent random errors may

intertwined for the unexpected error .

x1 x6 x11 x16 x21

x2 x7 … x22

x3 x8 … x23

x4 x9 … x24

x5 x10 … x25

Data input A = (x1 x2 x3 x4 x5 … x25)

Data output A’= (x1 x6 x11 x16… x25)

e.g.



Concept of Diversity Technology

Double meanings：

scattered transmission,concentrative process.

Achieved by using and finding the independent

multi-access signals in the wireless communication

environment .

If the signals in one path decay seriously, but in

other independent path are still strong.

advantage：

Easy to achieve relatively stable signal

Achieve the diversity gain

Improve SNR



Diversity Categories

Space diversity

Also called antenna diversity, if the distance between theantennae is greater than 10 times of the wavelength, thesignals from different antenna are not related.

Time diversity

The signal repeats over Channel Coherent time interval, sothat the environment is independent.

Frequency diversity

The signal repeats in the different frequencies.

Polarization Diversity Signal reflects in the different direction, since the reflection

coefficients of different polarization directions are not thesame, the signals in different polarization direction is notrelated



Symbol rate × SF = 3.84Mcps

WCDMA，SF of uplink channeliezd code：4~256

SF of downlink channelized code:4~512

OVSF: Orthogonal Variable Spreading Factor

OVSF Code Scramble Code

Data bit

Chip

after

Spreading

Spreading of WCDMA



∑

∑

Real part

and

Imaginary part

separate

Pulse

shaping

Pulse

shaping

serial

parallel

transfer

serialparallel

transfer

……

……

DL physical channel 1Cch,SF,m

j

I+jQ Sdl,n

G1

Cch,SF,m

j

I+jQ

Sdl,n

G2

DL physical channel 2Gp

Gp

P-SCH

S-SCH

cos(wt)

-sin(wt)

T

T

Re(T)

Im(T)

Spreading, Scrambling and modulation of WCDMA

Downlink physical channel spreading and modulation：



Real part

and

Imaginary part

separate

Pulse

shaping

Pulse

shaping

cos(wt)

-sin(wt)

Sdpch,n

S

Re(S)

Im(S)

∑

Cd,1 βd

I

cc

Q

j

I+jQ

∑

∑

DPDCH1

Cd,3 βdDPDCH3

Cd,5 βdDPDCH5

Cd,2 βdDPDCH2

Cd,4 βdDPDCH4

Cd,6 βdDPDCH6

ccCc βcDPCCH

Q

Spreading, Scrambling and modulation of WCDMA

Uplink physical channel spreading and modulation：



Despreading of WCDMA

Method of despreading

Input signal

Local PN code

When T=Ts, judge

Output after despreading

integral

0

Ts

(*)dt



Symbol

Spreading

Despreading

1

-1

1

-1

1

-1

1-1

1

-1

Data =

010010

Spreading code

Spread signal= Data × code

Spreading code =

1 -1 -1 1 -1 1 1 -1

( SF = 8 )

Data =Spread signal× code

Chip

Sketch map of Spreading and Despreading of

WCDMA



Processing Gain

Spreading definition and processing gain

Processing gain: PG=Wc/R

Wc: chip rate

R: signal rate

PG=10lg(Wc/R), dB units

Despreading by receiver will be able to resume the

original signal

More spreading of multiples, higher the processinggain, stronger anti-jamming



Convolutional Code

Mainly used in the voice channel and control signalchannel

Coding rate is 1/2和1/3。

Output 0

G 0 = 557 (octal)

InputD D D D D D D D

Output 1

G 1 = 663 (octal)

Output 2G 2 = 711 (octal)

Rate 1/3 convolutional coder



Characteristics of Convolutional code

Easy decode Short delay

Generally use the Viterbi Algorithm

Channel bit error rate is 10－3 magnitude

Suitable to realtime service e.g. speech and video service.



Turbo Code

Used in Data service channel

Code Rate is 1/3 Can be implemented in the transmission for large block and

long delay services

Turbo coding structure is based on two or more weak error

control code combinations. The information bits are interleaved

in the two Encoder, and generate two information flow. At last,this information can be multiplexed and punctured

Decoding needs cycle iterative calculation

Interleaver

Encoder 1

Encoder 2

M u l t i p l e x

input output



Interleave Technology of WCDMA

Intra-frame interleave Bits transform in the internal frame

Inter-frame interleave

Data transform among the frames

Intra-Turbo codes interleave

Complex nesting of intra-frame and inter-frame

interleave



Content






Capacity of WCDMA



Power Rise

Power rising occurs because of the Multiple Access

Interference (MAI) resulting from the non-orthogonal codechannels.

WCDMA network Meeting Room

Code channel transmit talk with dialects Channel power voice tone

Promised channel quality listen clearly

Channel power rise voice tone rise

Power climb voice climb

Collapse over the range can not listen for each other

Interference outside the cell Noise outside the room



Power Rise

Quantity of Subscriber

Quantity of Subscriber-- The Total Bandwidth Received by Node B

T h e T o t a l B

a n d w i d t h P o w e r R e c e i v e d b y N o d e B ( d B m

)



WCDMA Capacity Feature

WCDMA capacity feature

WCDMA capacity is Soft Capacity

The Concept of Soft Capacity

Inter-convertibility between system capacity andcommunication quality

Different service has different capacity

Different proportion of services has different capacity

for mixed services



Capacity

All the WCDMA technologies adopted is try to achieve

the most optimal balance of the three factors

Crucial Factors for WCDMA Capacity



Factors Impact on WCDMA capacity Category

Power Control Reducing interference, saving power and Increasingcapacity

Radio ResourceManagement（RRM）

Handover ControlImpacting the capacity through applying different

proportion and algorithm of soft handover

Admission Control Admitting a connection base on the load and theadmission threshold of planned capacity

Load Control Monitoring system load and adjusting the ongoing

services to avoid overloadOVSF Code The Allocation of codes impacts the maximum number of

simultaneous connections.

RAKE Receiver The advanced receiving and baseband processingtechnology is introduced to overcome the fast fading

Key Technology

Smart Antenna Reducing interference, saving power and expandingcoverage through tracking the user with beam forming

antenna array.

MUD Reducing the Multi-Access Interference (MAI).

Service Class andCombination

The class and combination of services impact thecapacity directly

Service Attribute

WirelessEnvironment

Wireless environment such as interferences, UE positionand mobility etc. can influent the cell capacity

WirelessPropagationEnvironment

Factors Affecting WCDMA Capacity



Power Control

CDMA is not a new technology

Power control is a key technology of CDMA system

Power control is the key method for launching the

large scale CDMA commercial network

CDMA is a typical self-interference system, thus the chief

principle is that any potential surplus transmitted power forservice must be controlled.



Each terminal is an

inter ference sou rce to the

oth ers. The Near-far effect

wi l l imp act the capaci ty

t remendously

Power

f

Power con tro l wi l l reduc e

the cros s inter ference

signi f icant ly and improve

the total capacity

Near-Far Effect

Power

f



Purpose of Power Control

• Overcome near-far effect and compensate signal fading

• Reduce multi-access interference and guarantee cell capacity

• Extend battery life

Downlink Power Control

Cell transmitted power

Report power control bit (TPC)

UE transmitted signal

Power control command (TPC)

Uplink Power Control



Open Loop Power Control

General principals of open loop power control

Open loop power control is applied to estimate the

initial transmitted code power (TCP) for a new radio

link.

The downlink Open Loop Power Control is using P-

CPICH signal which is measured by UE to estimatethe initial TCP and the following factors will also be

considered, such as service QoS and data rate,

Eb/No requirements of establishing service, current

downlink total Transmitted Power and interference

from neighbor cell etc..

P-CPICH,SCH, PCCPCH,AICH,FACH,DPDCH,DPCCH,PRACH



Try to get the equal receiving

Eb (Energy per bit) of each

UE at Node B

NodeB UE

TPC instruction

Measure receiving SIR and

compare to target SIR

Inner loop

Set SIRtar

1500Hz

Each radio l ink has

i ts own con t ro l

circle

Close Loop– Inner Loop Power Control



NodeB UE

TPC instruction

Inner loop

Set SIRtar

Get data flow

with stable BLER

Measure BLER

of TRCH

Outer Loop

RNC

Measure receiving

BLER and compare to

target BLER

Set BLERtar

10-100Hz

Close Loop– Outer Loop Power Control

Measure receiving SIR

and

compare to target SIR



Close Loop– Open Loop Power Control

General principals of open loop power control

The algorithm is implemented as following: Employ theinner loop power control to keep SIR close to target SIR;Measure the quality of service, e.g. through CRCI report,and tune the target SIR with pre-defined step; Thereforekeep the call in good quality event in changing wireless

propagation environment.

Input parameters include target BLER, CRC indicator andSIR Error, output parameter is SIR Target.

Open loop power control algorithm is implemented in two

ways: FER period report triggered; FER event reporttriggered.

The uplink open loop power control algorithm is executed inthe RNC while the downlink one is executed in the UE.



Purpose of Handover Control

Purpose:

Keep service continuity.

Balance the traffic

Improve call quality



Handover Demonstration

Hard

Handover

Soft

Handover



A

B

C

A

B

C

A

B

C

A

B

C

A

B

C

A

B

C

Soft Handover/Softer Handover



WCDMA General Handover Procedures

Measurement Control

Measured object（Neighbor cell list）

Measured quantity（RSCP/Ec/Io etc）

Measurement report method

Event report

Periodical report Handover decision

UTRAN makes the decision based on themeasurement reports from UE. The implementation ofhandover decision is various for different vendors. It

impacts on the system performance critically.

Handover execution

UTRAN and UE execute different handover procedureaccording to the handover command .



(A) RNC sends

measurement control

message to UE (Measurement

Control)

(B) UE starts measurement

task with the parameters

included in the message,

and reports measurement

results（MeasurementReport）

(C) RNC stores the

measurement results

according to frequencies and

cells

(D) RNC Estimates the

quality of each carrier

(including intra-frequency

and inter-frequency)

(E) QualityDecision

(G) Allocate

resource in target

cell of the virtual

active set, prepare

to execute handover

(F) maintain

the active set

and monitored

set

(H) Allocate

resource in target

cell, prepare to

execute handover

Currentcarrier has

good quality

Othersystem

has good

qualityOther carrier has

good quality

（I）If handover is required, RNC sends

handover command with target cell to UE

Handover Flows



General Procedure of Handover Control (I)

Measuring

The measurement quantity are decided by RNC.

Usually, either Ec/N0 or RSCP (Received Signal

Code Power) of P-CPICH channel is used for

handover decision.

ZTE RNC adopts Ec/N0 measurement, because

Ec/N0 embodies both the received signal strength

and the interference. The relation of Ec/N0 and

RSCP is shown as follows:

Ec/N0＝RSCP/RSSI

In the above equation，RSSI（Received Signal

Strength Indicator ）is measured within the

bandwidth of associated channels



General Procedure of Handover Control (II)

Filtering

The measurement results should be filtered before being

reported. Measurement filtering can be regarded as a low pass

filtering procedure.

The following equation is applied for filtering

Fn=(1-a)Fn-1＋a*Mn

Variants definition：

Fn：filtered measurement result；

Fn-1：last filtered measurement result；

Mn：latest Ec/I0 or RSCP measurement result received from physicallayer;

a = 1/2(k/2), k means the ―Filter coefficient‖, which is included in the

Measurement Control message. It is decided by the UTRAN.

F0 is initialized by the first measurement result M1.



General Procedure of Handover Control (III)

Reporting

Period report triggered handover

Event report triggered handover

Base on the filtered measurement result

Base on the event

Soft

Handover

Hard

Handover

Period

Event

Measurement result filtered in UE

Event decided in RNC

Handover decided in RNC

Measurement result filtered in UE

Event decided in UE

Handover decided in RNC



General Procedure of Handover Control (IV)

Handover algorithm

All the handover algorithms including soft handover,

hard handover and so on are implemented on the

event decision made from measurement report.

Events defined in 3GPP specifications

Intra-frequency events：1A~1F

Inter-frequency events：2A~2F

Inter-RAT events：3A~3D

H d



Handover event

Event Description

1AQuality of target cell improves, entering a report range of

relatively activating set quality

1BQuality of target cell decreases, depart from a report range of

relatively activating set quality

1CThe quality of a non-activated set cell is better than that of a

certain activated set cell

1D Best cell generates change

1EQuality of target cell improves, better than an absolute

threshold

1FQuality of target cell decreases, worse than an absolute

threshold



C t R l t d t H d



Concepts Related to Handover

Active Set: A set of cells that have established radio

links with a certain mobile station. User informationis sent from all these cells.

Monitored Set: Have configured neighbor cell

relation with the cell in active set ;Signal is

not strong enough to enter AS or AS already full Detected Set: A set of cells that are neither in the

active set nor in the monitor set

Signal is weak; Monitor set is full; Cell has not

configured neighbor cell relation with the cell inactive set.

A E l f H d P d



An Example of Handover Procedure

Pilot Ec/Io of cell 1

time

Pilot

Ec/Io

Connect to cell1 Event 1A Event 1C Event 1B

（add cell2）（replace cell1 with cell 3）（remove cell3）



⊿t ⊿t ⊿t

RNS R l ti



RNS Relocation

Core NetworkCore Network

Service

RNSTarget

RNS

Service

RNSTarget

RNS

Iu Iu

Iur

RNS

Radio Network Sub-system

RNS relocation can : Reduce the Iur traff ic signif icant ly

Enhance the sys tem adaptabi l i ty

H d H d



Hard Handover

Hard handover measurement is much more complex

for UE than soft handover measurement.

Inter-frequency hard handover requires UE to

measure the signal of other frequency.

WCDMA employs compressed mode technology to

support inter-frequency measurement.



C d M d



Compressed Mode

Comp ressed Mode Transmiss ion Diagram

Transmit gaps（Maximum 7 slots = 4.7ms） 1 frame（10ms）

10ms

Generation of Compressed Mode Frame



Generation of Compressed Mode Frame

Puncturing

Lower the symbol rate of physical channel whenprocessing the rate matching procedure

SF halving

Employ half SF, e.g. employ SF64 to replace SF128

High layer scheduling

Decrease the bit rate from up layer

Disadvantage: Power control will be not accurate

Channel anti-interference capability will be degrade

Admission Control



Admission Control

The admission control is employed to admit the

access of incoming call. Its general principal is

based on the availability and utilization of the

system resources.

If the system has enough resources such as load

margin, code, and channel element etc. the

admission control will accept the call and allocate

resources to it.

Purpose of Admission Control



Purpose of Admission Control

The admission control should implement admission

or rejection for the new users, new RAB and new RL

(for example handover) according to the current

resource situation. The admission control will

sustain the system stability firstly and try the best to

satisfy the new calling service QoS request, such asservice rate, quality (SIR or BER), and delay etc.,

basing on the radio measurement.

Admission Control in Uplink




I total_old +ΔI >I threshold

The current RTWP (Received

Total Wide Power) value of cell,

which is reported by Node B

Access

Threshold

Interference capacityService priority

Reserved capacity for

handover

I own-

cell

0

~ N

I other- cell

The forecasted interference including the deltainterference brought by the incoming service is

calculated by the admission algorithm, and its

result depends on the QoS and transmission

propagation environment





Different ultimate user numbers

Different interference threshold under different

ultimate user number conditions

Different ultimate throughputs


Quantity of Subscriber-- The Total Bandwidth Received by Node B

T h e T o t a l B a n d w i d t

h P o w e r R e c e i v e d b y N o d e B ( d B m

)

Throughput

Throughput -- The Total Bandwidth Received by Node B

T h e T o t a l B a n d w i d t h

P o w e r R e c e i v e d b y N o d e B ( d B m

)

Ultimate Situation for different service rate

Admission Control in Downlink




P total_old + △P>=P threshold

Access

Threshold

The forecasted TCP value including deltapower required for the incoming service is

calculated by the admission algorithm, and its

result depends on the QoS and transmission

propagation environment.

The current TCP value of cell, which

is reported by Node B

（Transmitted Carrier Power*Pmax）

Max TCP of cell

Service priority

Reserved capacity for

handover






T h e T o t a l T r a n

s m i s s i o n P o w e r ( d B m )

Red：low speed serviceBlue：high speed service

The above figure illustrates the relation between ultimate user

number corresponds to different service rate and distance

under equidistant distribution condition



Purpose of Load Control



Load controlThe purpose of load control is to keep the system

load under a pre-planned threshold through

decreasing the load in several ways, therefore to

improve the system stability.

The speed and

position changing of

UE may worsen the

wireless environment.

Increasing of

transmitted power

will increase the

system load

Purpose of Load Control

Load Control Flows



Start

Decision Light load Over load

Normal load

1. Handover in and access

are forbidden

2. TCP increasing isforbidden

3. RAB service rate degrade

4. Handover out

5. Release call

Load Control Flows

1. Handover in and

access are allowed

2. Transmitted codepower (TCP) increasing

is allowed

3. RAB service rate

upgrade is allowed

1. Handover in

and access are

allowed

2. TCP

increasing is

allowed

Load Control in Uplink



Load Control in Uplink

Triggers

RTWP (Received Total Wind-band Power) value frommeasurement report exceeds the uplink overload threshold;

Admission control triggers when rejecting the high priorityservice’s access due to insufficient load capacity in uplink.

Methods for decreasing load Decrease the target Eb/N0 of service in uplink;

Decrease the rate of none real time data service;

Handover to GSM system;

Decrease the rate of real time service, e.g. voice call;

Release calls.

Methods for increasing load

Increase the service rate.

Load Control in Downlink



Load Control in Downlink

Triggers

TCP (Transmitted Carrier Power) value from measurementreport exceeds the downlink overload threshold;

Admission control triggers when denying the high priorityservice’s access due to insufficient load capacity indownlink.

Methods for decreasing load Decrease the downlink target Eb/N0 of service in downlink;

Decrease the rate of none real time data service;

Handover out to coverage-shared light loaded carrier;

Handover out to GSM system;

Decrease the rage of real time service, e.g. voice call; Release calls.

Methods for increasing load

Increase the service rate.

Cell Breathing



Cell breathing isone of the means

for load control

The purpose of cell breathing is to share the load of hot-

spot cell with the light loaded neighbor cells, therefore to

improve the utilization of system capacity.

Cell Breathing

Purpose of Code Resource Planning



Purpose of Code Resource Planning

WCDMA system adopts primary scrambling code to

distinguish the cells and channel code to distinguishphysical channels in downlink, and adoptsscrambling code to distinguish users in uplink. TheOVSF (Orthogonal Variable Spreading Factor) codetree is a sparse resource and only one tree can be

used in each cell. In order to make full use of thecapacity, and support as many connections aspossible, it is important to plan and control theusage of channel code resource.

Although the uplink scrambling codes are sufficient,the RNC should plan to use the codes for avoidingallocating same code to different users in inter-RNChandover scenario.

Code Resource Planning



Code Resource Planning

Code types in WCDMA system

Uplink Scrambling Code

Uplink Channelization Code

Downlink Scrambling Code

Downlink Channelization Code

The uplink scrambling code and downlink scrambling code can

be planned easily, and uplink channel code does not need

planning, therefore, only the downlink channel code is planned

with certain algorithm in RNC.

Each cell has one primary scrambling code, which correlates

with a channel code tree. The downlink channel code tree is a

typical binary tree with each layer corresponds to a certain SF

ranging from SF4 to SF512.

Generation of Channel Code



SF = 1 SF = 2 SF = 4

Cch,1,0 = (1)

Cch,2,0 = (1,1)

Cch,2,1 = (1,-1)

Cch,4,0 =(1,1,1,1)

Cch,4,1 = (1,1,-1,-1)

Cch,4,2 = (1,-1,1,-1)

Cch,4,3 = (1,-1,-1,1)

Generation of Channel Code

OVSF Code Tree



OVSF Code Tree

Channel Code Characters



SF=8

SF=32

SF=16

Channel Code Characters

Code allocation restriction：

The code to be allocated must fulfill the condition that

its ancestor nodes including from father node to root

node and offspring nodes in the sub tree are not

allocated;

Code allocation side effect： The allocated node will block its ancestor nodes and

offspring nodes, thus the blocked nodes will not be

available for allocation until being unblocked .

Strategy of Channel Code Allocation



Strategy of Channel Code Allocation

Full utilization

The fewer the blocked codes, the higher the code tree

utilization rate.

Low Complexity

Short code first.

Allocate codes for common channels and physical

shared channels prior to dedicated channels.

Guarantee the code allocation for common physical

channels.

Apply certain optimized strategy to allocate codesfor downlink dedicated physical channels.

An Example of Code Allocation



An Example of Code Allocation

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

SF = 4

SF = 8

SF = 16

SF = 32

SF = 4

SF = 8

SF = 16

SF = 32

Red circles represent the codes that have been allocated；

Green circles represent the codes that are blocked by the allocated offspring codes；

Blue circles represent the codes that are blocked by the allocated ancestor codes;

Black circles represent the codes that are to be allocated;

Choose one

code from

three

candidates

RAKE Receiver



d d2

d3

RAKE Receiver can effectively overcome the multi-path

interference, consequently improve the receiving performance.

RAKE Receiver

The multi-path signals contain some useful energy , therefore

the CDMA receiver can combine these energy of multi-pathsignals to improve the received signal to noise ratio.

RAKE receiver adopts several correlation detectors to receive

the multi-path signals, and then combines the received signal

energy.

RAKE Receiver



RAKE Receiver

Single path

receiving circuit

Single path

receiving circuit

Single pathreceiving circuit

Multi-path search

engine

Calculate signal

strength and

delay

Combiner Combined

Signal

tt

s(t) s(t)

Receiver

Multi-User Detection



Multi User Detection

WCDMA telecommunication system can provide

communication environment for simultaneous multi-user access. The research result indicates that

multi-access interference and channel noise have

different statistical characters.

Multi-access interference has the estimable andreproducible features.

The purpose of MUD is to reduce the multi-access

interference till 0 through collecting the useful

information of all users and adopting certain signalprocessing method.

Multi-User Detection Technology



Multi User Detection Technology

The CDMA receiver is based on the principal of RAKE receiving, and

the interference from other users is treated as noise.

The capacity of RAKE receiving based CDMA system is interferencelimited.

The true optimal receiver adopts join-detection technology to detect all

the received signals, and removes the interference from other users.

Multi-User Detection (MUD), also named as Join-detection orInterference-elimination，can reduce the multi-access interference,thereby improve the capacity.

MUD can eliminate the near-far effect.

The near optimal MUD receiver and interference eliminated receiverare actually applied instead of the true optimal MUD receiver becauseof the implementation complexity.

True Optimal Multi-User Detection



p

The true optimal detection consists of K matched

filters and one Viterbi algorithm implementation.

The complexity has an exponents relation to the

user number.

Matched Filter 1

Synchronize

Z1（i）

Matched Filter 2Z2（i）

Matched Filter kZk （i）

Viterbi

Algorithm

Implementation

b1（i）

b2（i）

bk （i）

r(t)

Synchronize

Synchronize

Linear De-correlation Detection



De-correlation detection transforms the multi-access

interference, which is generated in multi-userenvironment, into an equivalent transmission

response matrix，i.e. the channel codes correlation

matrix R。

The complexity has an exponents relation to theuser number.

Matched Filter 1

Matched Filter 2

Matched Filter k

Linear

Transformation

R －1

b1

b2

bk

r(t)

Bit Decision

Bit Decision

Bit Decision

Summary



y

WCDMA Wireless Technology

Spreading Channel Coding (Convolutional Coding, Turbo coding)

Interleaving

Diversity

WCDMA Radio Resource Management（RRM)

Power Control

Handover Control

Admission Control

Load Control

Code Allocation


RAKE Receiver

MUD

01-0-WCDMA Wireless Principle and Key Technology-102

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Transcript of 01-0-WCDMA Wireless Principle and Key Technology-102