2 wcdma key technologies 48

7/28/2019 2 WCDMA Key Technologies 48

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Key Technologies of WCDMA

ZTE University

TD&W&PCS BSS Course Team



Course Objectives

At the end of this course, you will be able to:

Master key technologies of WCDMA

Master characteristic of WCDMA systemcapacity



Power Control

Handover

Rake receiver

Call Admission Control & traffic control

Intelligent Antenna and MUD

Capacity of WCDMA system

Content



Overpowered by strong signalsBlock the whole cell

Power

f

Near-Far Effect

Power Control



Power control

Power

f

Power

f

Nearby terminals havehigher probability of success

Power control tech reduce theinterference among each UEs

and increase system capacity

Power Control



Power Control

Overcome Near-Far effect and fading compensation

Reducing multi-address interference, ensuring network capacity

Prolonging the working time of battery

DL power control

Cell transmitting power

Transmitting power control bit

UE signal

Power control order

UL power control

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



Power control

UE

RNC

Node B

Open loop power control（

no feedback （

Closed loop power control （ feedback （

UE Node B

RNCOuter-loop

Inner-loop

Power Control



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

Power Control



Closed loop power control

Inner-loop power control is fast

Inner-loop（

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

Outer-loop （ according to BLER measurement estimation RNC control

and adjust SIR target

Node B

...

”Power down”

Power up command

”Power ...”SIR estimation

SIR estimationRNCSIR target ”Power up”

TPC:1500HzBLER tar SIR tar

Power down command

Power Control



Closed loop power control

Inner Loop Power control UL/DL (fast)

UE or Node-B will use:

Signaling channel, TPC,

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 is below/above the target,

UE/RNC reduce/increase SIR target.

Use the new target for the Inner loop PC.

Power Control



The Effect of Power Control

The purpose of power control:

Saving power resource of NodeB, reducing interference to other

NodeB.

Ensure the call quality

Increase system capacity Over fadings

Overcoming Near-Far effect,

save UE battery power

WC D MA s ys te m ca paci t y

de pe nd o n po we r co n t ro l

Power Control



Power Control

Handover

Rake receiver




Content



Handover

Handover refers to the process in which when a UE

moves from one cell to another during calling.

Purpose:

Keep service continuity.

Balance the traffic

Improve call quality

In the WCDMA system, handover is divided into soft

handover and hard handover.

Handover

H d



Type of handover

Intra-RNC, inter-Node B

Inter-RNC

Soft handover （

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

Handover

H d



Hand-over

Hard Handover

Soft Handover

Handover

H d



Soft/Softer Hand-over

A

B

C

A

B

C

A

B

C

A

B

C

A

B

C

A

B

C

Handover

H d



Soft/Softer Handover

The soft/softer handover allows to swap from one cell to

another without 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


SRNC DRNC

CN

Node B

SRNC

CN


Node B

CN

Handover

H d



Hard Handover

The hard handover procedure is used in case of

service quality degradation or for traffic

distribution management. (intra-fre ,inter-fre,

inter-rat)

During the hard handover procedure, all the old

radio links with the UE are disconnected（ not

release） before new ones are established.

Hard handover may occur in the following

main cases :

When the UE is handed over another UTRAN

carrier, or another technology mode.

When soft handover is not permitted (if O&M

constraint)

Hard Handover

Node B

SRNC

RNC or

BSC

CN

Node B or

BTS

Handover

Handover



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.

Handover

Handover



Soft handover process

Measurement

The RNC sends a measurement control message to UE. (Measured

quantity , report method.)

UE should perform measurement as required and report the measurement

result.

Generally, the measured quantity is the common pilot’s Ec/No for intra/inter

frequency handover. Measured RSSI for inter-RAT handover.

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 set update 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.

Handover

Handover



Soft handover event

Event Description

1AQuality of target cell improves, entering areport range of relatively activating setquality

1B Quality of target cell decreases, depart froma report range of relatively activating setquality

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 thanan absolute threshold

1FQuality of target cell decreases, worse thanan absolute threshold

Handover



Example of soft handover

Handover



Soft handover Case

In especially urban

environment, the

handover regionbetween two cells might

be too small.

If the UE passes such an

area in a very quick

speed, the call might be

dropped.

Handover



Power Control

Handover

Rake receiver




Content

Rake receiver



RAKE Receiving

d1 d2

t t t

d3

transmitting ReceivingRake

combinationnoise

Rake receiver

Rake receiver



Multi-finger receiver

receiver transmitter

coding decoding

Direct signal

Reflect signal

Dispersive time < 1 chip length

Multi-finger receiver can’t 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

Rake receiver

Rake receiver



RAKE Receiving

RAKE overcome multi-finger interference （ improve receive capability

receiverreceiver

Single

receiving

Single

receiving

Single

receiving

searcher calculatecalculate

combining

tt

s(t) s(t)

signal

Rake receiver

Rake receiver



Multi-finger receiver

Maximal ratio combining(MRC)

at each time delay phase shifting by adding

Finger 1

Finger 2

Finger 3

Rake receiver



Power Control

Handover

Rake receiver




Content




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)

&




Call Admission Control

System load threshold Remaining Capacity

Apply access service Increasing volume of load

Increasing volume of load<Remaining

Capacity（

Access

Reject

yes

no




UL Call Admission Control

I total_old +ΔI > I threshold

RTWP

(Received Total Wide Power)

Threshold

service type

I own-cell

0

~ N

I other-cell

Forecast Interference Increasing volume

caused by new service.

service priority




DL Call Admission Control

P total_old + P >= P △ threshold

Threshold

Node B max output power

Forecast increasing output power of Node B

caused by new service （

TCP, Node B report to RNC（ Transmitted Carrier Power*Pmax （

Service priority




Traffic control

When traffic surpass system

threshold, traffic control begin.

To accept as many as possibleservices while keep the stability of

the system.




Traffic control

Start

Judgment

（ 1 （ Allow incoming handover, access

（ 2 （ Allow increase power

（ 3 （ Allow increase data rate

（ 4 （ Others

Low traffic load

High traffic load

Normal traffic load

（ 1 （ Allow incoming handover, access（ 2 （ Allow increase power（ 1 （ Disable

incoming handover

and access（ 2 （ Stop to

increase power

（ 3 （ Reduce data

rate

（ 4 （ Outgoing

handover

（ 5 （ Call drop




Example for load control

Breath effect of cellBreath effect of cellWith 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 cell Coverage andcapacity are

relative



Omni-cell cell with Three sector Cell with smart attenna

Intelligent Antenna




Intelligent Antenna




Multi-user Detection Principle



Power Control

Handover

Rake receiver




Content




System capacity and QoS can be interconverted

Different

combination of

service has

different capacity

Dif f erent

ser vice has

dif f erent

capacit y

Soft Capacity




Capacity of WCDMA System

=

=

=

Under the circumstance of single services ::




Capacity of WCDMA System

…...

Under the circumstance of mixture of services （

X Y Z+ +




Coverage and Capacity

WCDMA performance is determined by such factorsas：

Number of users

Transmission 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 Increase of user

number



DLtransmission diversity (Tx Div)

high power amplifier(TEU 50 W)

DL transmission diversity (Tx Div)

high power amplifier(TEU 50 W)

UL

tower mounted amplifier (TMA)

4RxDiv

OTSR

UL

tower mounted amplifier (TMA)

4RxDiv

OTSR

DL/UL:

Add carrier

six sectors

Smart antenna

DL/UL:

Add carrier

six sectors

Smart antenna

Add basestation

“last choice”

Add basestation

“last choice”

Coverage and Capacity

In order to overcome cell breath caused by increased

traffic and different requirement for capacity and coverage

in different environment ,such solution supplied:

2 wcdma key technologies 48

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