3-WR_003_E1 WCDMA Key Technologies-42

7/30/2019 3-WR_003_E1 WCDMA Key Technologies-42

1/42

ZTE University univ.zte.com.cnThe information contained in the file is solely property of ZTE corporation. Any kind of disclosing without permission is prohibited.

WR_003_E1

WCDMA Basic Theory

Key Technologies of WCDMA

V0507

ZTE University

3G Course Team


2/42


Course Objectives

Master key technologies of WCDMA

Master characteristic of WCDMA system capacity


3/42


Power Control

Handover

Rake receiver

Call Admission Control & traffic control

Capacity of WCDMA system

Agenda


4/42


Why Power Control?

All CDMA users occupy the same frequencyat the same time! Frequency and time are notused as discriminators.

CDMA operates by using CODES todiscriminate between users.

CDMA interference comes mainly fromnearby users

Each user is a small voice in a roaring crowd-- but with a uniquely recoverable code.

Transmit power on all users must be tightly controlled so their signalsreach the base station at the same signal level and at the absolute

minimum power level necessary to ensure acceptable service quality.


5/42


Overpowered by strong signalsBlock the whole cell

Power

f

Near-Far Effect


6/42


Power control

Power

f

Power

f

Nearby terminals have higherprobability of success

Power control tech reduce theinterference among each UEs

and increase system capacity


7/42 ZTE University univ.zte.com.cnThe information contained in the file is solely property of ZTE corporation. Any kind of disclosing without permission is prohibited.

Power Control

Overcome Near-Far effect and fading compensation

Reducing multi-address interference, ensuing network capacity

Prolonging the working time of cell

DL power control

Cell transmitting power

Transmitting power control bit

UE signal

Power control order

UL power control



Three methods of power control

Open loop:

measure received signal level and adjust transmitting power

Inner-loop (closed loop):Frequency:1500HZ

Measured SIR> Target SIR, lower transmitting power

Measured SIR< Target SIR, increase transmitting power

Outer-loop (closed loop):

Measure BLER, adjust target SIR



Power control

UE

RNC

Node B

Open loop power controlno feedback

Closed loop power controlfeedback

UE Node B

RNCOuter-loop

Inner-loop



Open loop power control

If received signal is stronger,then

UE can speak softer

Node

BNode

B

1

2

1

2

problem

Unbalanced for UL/DL signal, not accurate, only used in initial stage

Open loop

If received signal is weaker,then UE

can speak louder


11/42


Closed loop power control

Inner-loop power control is fast

Inner-loop

according to SIR estimation,Node-B control UE transmissionpower.conducted every 0.66ms (1500Hz )

Outer-loop according to BLER measurement estimation RNC control

and adjust SIR target

Node B

...

Power up

Power down

Power down

Power ...SIR estimation

SIR estimationRNCSIR target Power up

TPC:1500HzBER tar SIR tar


12/42


Closed loop power control

Inner Loop Power control UL/DL (fast)

For a fixed SIR target per service (RAB), UE or Node-B will use:

Signaling channel, TCP,

Continuously @ rate 1500 times/s,

To relatively changes (up or down) the power to reach the SIR

target.

Outer loop Power control (Slow)

If the BLER measured (DL@UE, UL@RNC) is below/above the

target,

UE/RNC increase/reduce SIR target.

Use the new target for the Inner loop PC.


13/42


The Effect of Power Control

The purpose of DL power control:

Saving power resource of base station, reducing interference

to other station.

The purpose of UL power control:

Overcoming Near-Far effect, received signal level from all

UEs is the same.


14/42


Power Control

Handover

Rake receiver



Agenda


15/42


Handover

Handover refers to the process in which when a UE

moves from one Node B to another during calling.

Purpose: Keep service continuity.

In the WCDMA system, handover is divided into

soft handover and hard handover.


16/42


Hard Handover

Soft Handover

Hard & Soft Handover

First break,then connect


17/42


Type of handover

Intra-Node B (Softer handover)

Intra-RNC, inter-Node B

Inter-RNC

Softhandover

Same Node B, Inter- sector

Softer handover

Intra-frequency handover Inter-frequency handover

Inter-system (3G&2G)

Inter-mode (FDD&TDD)

Hard handover

WCDMA system support

multi handover technology


18/42


Soft/Softer Hand-over

A

B

C

A

B

C

A

B

C

A

B

C

A

B

C

A

B

C


19/42


Soft/Softer Handover

The soft/softer handover allows to swap from one cell to anotherwithout call interruption or without deleting all old radio links (by

opposition to hard HO).

It also allows the UE to be connected to more than one cell

simultaneously and take benefit from macro-diversity.

Soft Handover Softer Handover

CN CN

Iur

The two Node Bsmay belong to the

same RNC

The two Node Bs may

belong to the Same RNC


SRNCDRNC

CN

Node B

SRNC

CN


Node B

CN


20/42


Hard Handover

The hard handover procedure is used in case of

service quality degradation or for traffic

distribution management.

During the hard handover procedure, all the old

radio links with the UE are abandoned beforenew ones are established.

Hard handover may occur in the following

main cases :

When the UE is handed over another

UTRAN carrier, or technology or mode.

When soft handover is not permitted (if

O&M constraint)

Hard Handover

Node B

SRNC

RNC or

BSC

CN

Node B or

BTS


21/42


Basic concepts

Active Set:

The set of cells connected with UE;

User information is transmitted from these cells.

Monitor Set:

The set of cells not within the active set but being monitored

by a UE according to the adjacent node list allocated by

UTRAN.

Detect Set:

The set of cells in neither the active set nor the monitor set.


22/42


Soft handover process

Measurement The RNC sends a measurement control message to UE.

UE should perform measurement as required and report the measurement

result.

Generally, the measured quantity is the common pilots Ec/No.

Decision

The RNC stores data of different cells according to the measurement results.

The RNC makes preliminary decision according to the event decision method.

e.g.

When the event is reported and the target cell is acceptable, send an active setupdate command to add/delete the cell into/from the active set.

Execution

The RNC sends an active set update command to UE and UE starts handover.


23/42


Example of soft handover

AS_ThAS_Th_Hyst As_Rep_Hyst

As_Th +As_Th_Hyst

Cell 1Connected

Event 1AAddCell 2

Event 1C ReplaceCell 1with Cell 3

Event 1B RemoveCell 3

CPICH 1

CPICH 2

CPICH 3

Time

Measurement

Quantity

T T T


24/42


Power Control

HandoverRake receiver



Agenda


25/42


RAKE Receiving

d1d2

t t t

d3

transmitting ReceivingRake

combinationnoise


26/42


RAKE Receiving

RAKE overcome multi-finger interferenceimprove receive capability

receiver

Single

receiving

Single

receiving

Single

receiving

searcher calculate

combining

tt

s(t) s(t)

signal


27/42


Multi-finger receiver

Traditionally Multi-finger signal is treated as interference

The principle of Multi-finger receiver

Multi-finger signals can be combined through relative process

Multi-finger time delay larger than 0.26us=>78m

Multi-finger Diversity gain through Multi-finger receiver

t1

t2t3

a1

a2a3

+ x

x a3

a2

a1

+

+

xc(t-t1)

c(t-t2)

c(t-t3)

Finger 1

Finger 2

Finger 3


28/42



receivertransmitter

coding decoding

Direct signal

Reflect signal

Dispersive time < 1 chip length

Multi-finger receiver cant supply multi-finger diversity

decodingDirect signal

Reflect signaltransmitter receiver

Dispersive time > 1 chip length

Multi-finger receiver can supply multi-finger diversity,improve signal gain

coding


29/42



Maximal ratio combining (MRC)

at each time delay phase shifting by adding

Finger 1

Finger 2

Finger 3


30/42


Power Control

Handover

Rake receiver



Agenda


31/42


Call Admission Control

When user initiates a call, RRM decides weather

access or deny this call according to the resource

situation.

When accessing, network allocate resource (such as

OVSF, Scramble code)


32/42


Traffic control

When traffic surpass system thresh,

traffic control begin.

To accept as many as possible

services while keep the stability of

the system.


33/42


Example for load control

Breath effect of cell

With the increase of activated

terminals, interference increase

the increase of high speed service,

the increase of interference

The shrink of cell coverage area

Coverage blind spot occurs

Drop of call will happen at the edge of cellCoverage and capacity

are relative


34/42


Power Control

Handover


Rake receiver


Agenda


35/42


Characteristic of system capacity

Characteristic of WCDMA system capacity:


36/42


System capacity and QoS can be interconverted C

Different

combination of

service has

different capacity

Soft Capacity


37/42


Capacity of WCDMA System

=

=

=

Under the circumstance of single services:


38/42


Capacity of WCDMA System

...

Under the circumstance of mixture of services

X Y Z+ +


39/42


Coverage and Capacity

WCDMA performance is determined by such factors as

Number of users

Transmission rate

Mobile rate

Wireless environment

indoors

Outdoors

The sizes of cell depend on such factors as:

Local radio conditions (local interference)

Traffic in neighbouring cells (distanced interference)

Cell Radius decrease according to the decrease of user number


40/42


Coverage/capacity vs Data Rate

>12.2 kbps

>64 kbps

>384 kbps

>144 kbps

Coverage decrease

Subscriber

num

increase

Higher rate needs higher powerHigh data rate transmission is only available nearby the station


41/42


DL transmission diversity (Tx Div)

high power amplifier(TEU 50 W)

UL

tower mounted amplifier (TMA)4RxDiv

MUD

OTSR

DL/UL:

Add carrier

six sectors

smart attenna

Add basestation

last choice

Coverage and Capacity

In order to overcome cell breath caused by increased traffic anddifferent requirement for capacity and coverage in different

environment,such solution supplied:


42/42

Thanks for yourAttention!

Date post:	14-Apr-2018
Category:	Documents
Upload:	leonaveedatscribd
View:	219 times
Download:	0 times

3-WR_003_E1 WCDMA Key Technologies-42

Documents