wr_bt04_e1_1 wcdma key technology 80

8/8/2019 Wr_bt04_e1_1 Wcdma Key Technology 80

1/80

WCDMA Key Technologies

ZTE University


2/80

Objectives

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

Master key technologies of WCDMA

Master characteristic of WCDMA system capacity


3/80

Content


Power Control

Handover Control

Admission Control Load Control

Code Resource Allocation

RAKE Receiver

WCDMA Capacity Features


4/80

Power Control

CDMA is not a new technology

Power control is a key technology of CDMA

system

Power control is the key path for launching thelarge scale CDMA commercial network

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

principle is that any potential surplus transmitted power forprinciple is that any potential surplus transmitted power for

service must be controlled.service must be controlled.


5/80


6/80

Power

f

Overpowered by strong signalsBlock the whole cell

Near-Far Effect


7/80

Each terminal is an interferenceEach terminal is an interferencesource to the others. The Nearsource to the others. The Near--farfar

effect will impact the capacityeffect will impact the capacity

tremendouslytremendously

Power

f

Power control will reduce thePower control will reduce the

cross interference significantlycross interference significantly

and improve the total capacityand improve the total capacity

Power

f

Power control


8/80

Overcome near-far effect and compensate signal fading

Reduce multi-access interference and guarantee cell capacity

Extend battery life

Downlink Power Control

UE transmitted signal

Power control command (TPC)

Uplink Power Control

Cell transmitted power

Power control command (TPC)

Purpose ofPower Control


9/80

Category ofPower control

UE

RNC

Node B

Open loop power controlno feedback

Close loop power controlfeedback

UE Node B

RNCOuter-loop

Inner-loop


10/80

Open LoopMeasure the channel interference condition and adjust the initial transmitted

power

Close LoopInner Loop

Measure the SIR (Signaling to Interference Ratio), compare with the target

SIR value, and then send power control instruction to UE.The frequency of WCDMA inner loop power control is 1500Hz.

If measured SIR>target SIR, decrease the UE transmitted power.

If measured SIR target SIR, decrease the UE transmitted power.

If measured SIR target BLER, decrease the target SIR value.

If measured BLERtarget BLER, decrease the target SIR value.

If measured BLER


11/80

Open Loop Power Control

General principals of open loop power control

Open loop power control is applied to estimate the initial

transmitted power for a new radio link.

P-CPICH signal is used in Downlink Open Loop Power

Control, which is measured by UE to estimate the initialtransmitted power.

The following factors will also be considered, such as

service QoS and data rate, Eb/No requirements of

establishing service, current downlink total TransmittedPower and interference from neighbor cell etc.


12/80

Try to get the equal receivingTry to get the equal receiving

Eb (Energy per bit) of eachEb (Energy per bit) of each

UE at Node BUE at Node B

NodeB UE

TPC instruction

Measure receiving SIR and

compare to target SIR

Inner loop

Set SIRtar

1500Hz1500Hz

Each radio link hasEach radio link has

its own controlits own control

circlecircle

Close Loop Inner Loop Power Control


13/80


General principals of inner loop power control The receiver compares the SIR value of received signal

with target SIR, and then sends back TPC instruction.According to the instruction, the sender will decide toincrease/decrease the transmitted power.

The adjusted rang=TPC_cmdTPC_STEP_SIZE

Inner loop power control is required for thefollowing channels DPCH, PDSCH, PCPCH

Inner loop power control is not required for thefollowing channels P-CPICH(S-CPICH), P-CCPCH(S-CCPCH), PRACH

etc.


14/80

NodeB UE

TP

C instruction

Inner loop

Set SIRtar

Get data flowGet data flowwith stable BLERwith stable BLER

Measure BLERMeasure BLER

of TRCHof TRCH

Outer Loop

RNC

Measure receiving

BLER and compare totarget BLER

Set BLERtar

10-100Hz

Measure receiving SIR

andcompare to target SIR



15/80

Close Loop Outer Loop Power Control

Outer Loop Power Control algorithm Employ the inner loop power control to keep SIR close

to target SIR.

Measure the quality of service, including target BLER,

CRC indicator and SIR Error, then set the value ofSIR_Target.

Tune the target SIR with pre-defined step as the

adjustment parameter for inner loop power control to

keep the service in good quality in time-varying wirelesspropagation environment.

The uplink open loop power control algorithm is

executed in the RNC while the downlink one is

executed in UE.


16/80

The Effect ofPower Control

The purpose of DL power control: Saving power resource of NodeB.

Reducing interference to other NodeB.

The purpose of UL power control: Overcoming Near-Far effect. Extending UE battery life.

WCDMA system capacity depends on the effect of power control


17/80

Content


Power Control

Handover Control



RAKE Receiver



18/80

Whats

When UE is moving from the coverage area of one site to another,or the quality of service is declined by external interference during a

service, the service must be handed over to an idle channel for

sustaining the service.

Handover is used to guarantee the continuity of service

Handover is a key technology for mobile networking


19/80

Category ofHandover

Intra-RNC, inter-Node B

Inter-RNC

Soft handover (SHO)

Same Node B, Inter-sectorSofter handover

Intra-frequency

Inter-frequency

Inter-system (3G&2G)

Inter-mode (FDD&TDD)

Hard handover (HHO)

WCDMA system support

multiple handover technology


20/80

Handover Demonstration

Soft

Handover

Hard Handover


21/80

A

B

C

A

B

C

A

B

C

A

B

C

A

B

C

A

B

C

Soft Handover/SofterHandover

Soft Handover

Soft-Softer Handover

Softer Handover


22/80

Hard Handover

During the hard handoverprocedure, all the old radio links with

the UE are abandoned before new

ones are established, so there must

be service interruption during theHHO.

Hard handover may occur in the

following main cases

When the UE is handed over to another

UTRAN carrier, or another technologymode.

When soft handover is not permitted (if

O&M constraint)

Hard Handover

Node B

SRNC

RNC or

BSC

CN

Node B or

BTS


23/80


24/80

WCDMA General HandoverProcedures

---- Handover Trilogy

Measurement Control UTRAN demands the UE to start measurement through

issuing a measurement control message.

Handover decision

UTRAN makes the decision based on the measurement

reports from UE. The implementation of handover

decision is various for different vendors. It impacts on

the system performance critically.

Handover execution UTRAN and UE execute different handover procedure

according to the handover command .


25/80

General Procedure ofHandover Control (I)

Measuring

The measurement objects are decided by RNC. Usually, eitherEc/N0 or

RSCP (Received Signal Code Power) ofP-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 ofEc/N0

and RSCP is shown as follows:

Ec/N0 RSCP/RSSI

In the above equationRSSIReceived Signal Strength Indicatoris

measured within the bandwidth of associated channels


26/80

General Procedure ofHandover Control (II)

Reporting

Period report triggered handover

Base on the filtered measurement result

Event report triggered handover 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


27/80

General Procedure ofHandover Control (III)

Handover algorithm All the handover algorithms including soft handover,

hard handover and so on are implemented on the event

decision made according to the measurement reports.

Events defined in 3GPP specifications Intra-frequency events1A~1F

Inter-frequency events2A~2F

Inter-RAT events3A~3D

Note: RAT is short for Radio Access Technology, e.g.

WCDMA&GSM


28/80

Concepts Related to Handover

Active Set: A set of cells that have established radio links with a

certain mobile station.

User information is sent from all these cells.

Monitored Set:

A set of cells that are not in the active set but are

monitored according to the list of adjacent cells

assigned by the UTRAN.

Detected Set:

A set of cells that are neither in the active set nor in the

monitor set.


29/80

Soft handover process

Measurement RNC sends a measurement control message to UE.

UE should perform measurement as required and report the measurementresult.

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

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

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.


30/80

Soft handover events

Event Description

1AQuality of target cell improves, entering a

report range of relatively activating set

quality

1B

Quality of target cell decreases, depart from

a 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 than

an absolute threshold

1FQuality of target cell decreases, worse than

an absolute threshold


31/80

An Example of SHOProcedure

Pilot Ec/Io of cell 1

time

PilotEc/Io

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

add cell2replace cell1 with cell 3remove cell3



t t t


32/80

Example of soft handoverU E T a r g e t N o d e

S o u r c e N o d e

N C

C : M e a su r e m e n t

epor t ( E v en t 1 a ) ( F ro m S o u r c e N o d e

to

N C )

N

A

:

a d io L in k S e tup

e qu e s t

N

A

:

a d io L in k S e tup

e spo n s e

E x e cu t in g h a n d o v e r

ju d g e m e n t a n d

a d d in g a ra d io l in k

in T a r g e t N o d e

S ta r t t o r e c e iv e

D is trib u tin g t r a n s m i s s io n r e s o u rc e s o n Iub in t e r

a c e

S ta r t to s e n d

R RC : A c t iv e S e t U pd a te (E 1 a ) ( F ro m S o u r c e N o d e

to U E )

R RC : A c t iv e S e t U pd a t e C o m p l e te ( F r o m S o u r ce & T a r g e t N o d e

to RN C

s im u ta n e ou s ly )

U E c o n n e c ts t o S o u r c e N o d e

a n d T a r g e t N o d e

s im u ta n e o u s ly


33/80

RNS Relocation

RNS relocation can :

Reduce the Iur traffic significantly

Enhance the system adaptability

Core NetworkCore Network

Serving

RNSTarget

RNS

Serviing

RNSTarget

RNS

Iu Iu

Iur

RNS

Radio Network Sub-system


34/80


35/80

Content


Power Control

Handover Control



RAKE Receiver



36/80

Admission Control

The admission control is employed to admit theaccess 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.


37/80

Purpose of Admission Control

When user initiates a call , the admission control shouldimplement admission or rejection for this service

according to the resource situation.

The admission control will sustain the system stability

firstly and try the best to satisfy the new calling servicesQoS request, such as service rate, quality (SIR or BER),

and delay etc. basing on the radio measurement.

Admission control is the only access entry for the

incoming services, its strategy will directly effect the cellcapacity and stability, e.g. call loss rate, call drop rate.


38/80

Admission Control in Uplink

Itotal_old+I >Ithreshold

The current RTWP (Received

Total Wide Power) value of cell,

which is reported by Node B

Access

Threshold

Interference capacity

Service priority

Reserved capacity for

handover

Iown-

cell

0

~N

Iother-

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


39/80

Admission Control in Downlink

Ptotal_old+P>=PthresholdAccess

Threshold

The forecasted TCP value including delta

power 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 CarrierPower*Pmax

Max TCP of cell

Service priority

Reserved capacity for

handover


40/80

Content


Power Control

Handover Control



RAKE Receiver



41/80

Load control

The purpose of load control is to keep the

system load under a pre-planned threshold

through several means of decreasing it, so as to

improve the system stability.

The speed and position

changing of UE may

worsen the wireless

environment.

Increased transmitted

power will increase the

system load.

Purpose of Load Control


42/80

Load Control Flows

Start

DecisionLight loaded Over loaded

Normal loaded

1.Handover in and

access are forbidden

2. TCP increase isforbidden

3. RAB service rate

degrade

4. Handover out

5. Release call (call drop)

1. Handover in and access

are allowed

2. Transmitted code power

(TCP) increase is allowed

3. RAB service rate

upgrade is allowed

1. Handover in

and access are

allowed

2. TCP increase

is allowed


43/80

Load Control in Uplink

Triggers RTWP (Received Total Wide-band Power) value from

measurement report exceeds the uplink overload threshold;

Admission control is triggered when rejecting the access of

services with lower priority due to insufficient load capacity in uplink.

Methods for decreasing load

Decrease the target Eb/No 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.


44/80

Load Control in Downlink

Triggers TCP (Transmitted CarrierPower) value from measurement report

exceeds the downlink overload threshold;

Admission control is triggered when rejecting the access ofservices with lower priority due to insufficient load capacity indownlink.

Methods for decreasing load Decrease the downlink target Eb/No of service in downlink;

Decrease the rate of none real time data service;

Handover to coverage-shared light loaded carrier;

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.


45/80

Cell breathing is

one of the means

for load control

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

spot cell with the light loaded neighbor cells, therefore tospot cell with the light loaded neighbor cells, therefore to

improve the utilization of system capacity.improve the utilization of system capacity.

Cell Breathing Effect


46/80

Example for load control

Cell Breathing EffectCell Breathing Effect

With the increase of activated

terminals and the increase of high

speed services, interference will

increase.

The cell coverage area will shrink.

Coverage blind spot occurs

Drop of call will happen at the edge

of cell

Coverage andcapacity areinterrelated


47/80

Content


Power Control

Handover Control



RAKE Receiver



48/80

WCDMA Code Resource

WCDMA code resource including Channelized Code (OVSF code)

Uplink Channelized Code

Downlink Channelized Code

Scrambling Code (PN code) Uplink Scrambling Code

Downlink Scrambling Code


49/80

Function ofOVSF Code

OC1, OC2

OC3, OC4

OC5, OC6, OC7

OC1 , OC2, OC3

OC1, OC2

OC1, OC2, OC3, OC4

Uplink: distinguish different radio channels from the same UE.

Downlink: distinguish different radio channels from the same NodeB.


50/80

Function ofPN code

Downlink: distinguish different Cells Uplink: distinguish different UEs

PN3 PN4

PN5 PN6

PN1 PN1

Cell Site 1 transmits using PN code 1

PN2 PN2

Cell Site 2 transmits using PN code 2


51/80

Why Code Resource Planning?

The OVSF (Orthogonal Variable Spreading Factor)code tree is a scarce resource and only one codetree can be used in each cell. In order to make fulluse of the capacity, and support as many

connections as possible, it is important to plan andcontrol the usage of channel code resource.

Downlink PN code allocation should be planned toavoid the interference between neighboring cells.

The uplinkP

N codes are sufficient, but RNCshould plan the codes to use for avoidingallocating same code to different users in inter-RNC handover scenario.


52/80

Code Resource Planning

The uplink and downlink scrambling code can beplanned easily by computer.

The uplink channelized code does not need planning, forevery UE can use the whole code tree alone.

Therefore, only the downlink channelized code isplanned with certain algorithm in RNC.

Each cell has one primary scrambling code, whichcorrelates with a channel code tree. All the users underthis cell share this single code tree, so the OVSF code

resource is very limited. The downlink channelized code tree is a typical binary

tree with each layer corresponds to a certain SF rangingfrom SF4 to SF512.


53/80

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 Channelized Code


54/80

OVSF Code Tree


55/80

SF=8

SF=32

SF=16

Channelized 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 offspringnodes, thus the blocked nodes will not be available for allocation

until being unblocked .


56/80

Strategy of Channelized Code Allocation

Full utilization The fewer the blocked codes, the higher 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 codes

for downlink dedicated physical channels.


57/80

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 spots represent the codes that have been allocated

Green spots represent the codes that are blocked by the allocated offspring codes

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

Black spots represent the codes that to be allocated;

Choose one

code from

threecandidates


58/80

Planning of downlink PN code

PN1

PN2

PN3PN7

PN6 PN4

PN5

PN7

PN6 PN4

PN5

PN1

PN2

PN3

PN1

PN2

PN3PN7

PN6 PN4

PN5

PN1

PN2

PN3PN7

PN6 PN4

PN5

PN1

PN2

PN3PN7

PN6 PN4

PN5 PN1

PN2

PN3PN7

PN6 PN4

PN5


59/80

Content


Power Control

Handover Control

Admission Control

Load Control


RAKE Receiver



60/80

RAKE Receiver can effectively overcome the multiRAKE Receiver can effectively overcome the multi--pathpath

interference, consequently improve the receiving performance.interference, consequently improve the receiving performance.

RAKE Receiver

The multi-path signals contain some usefulenergy , therefore the CDMA receiver can

combine these energy of multi-path signals to

improve the received signal to noise ratio.

RAKE receiver adopts several correlationdetectors to receive the multi-path signals, and

then combines the received signal energy.


61/80

RAKE Receiving

d1d2

t t t

d3

transmitting ReceivingRake

combinationnoise


62/80

Multi-finger receiver

Traditional receiver Multi-path signals are treated as interference.

The receiving performance will decline because of the

Multi-address Interference (MAI).

Precondition of Multi-finger receiver Multi-finger receiver utilizes the Multi-path Effect.

Multi-finger signals can be combined through relative

process

Multi-finger time delay is larger than 1 chip interval,which is 0.26us=>78m.


63/80

Multi-finger receiver

receivertransmitter

coding decodingDirect signal

Reflected signal

Dispersive time < 1 chip interval

Multi-finger receiver cant supply multi-finger diversity

decoding

Direct signal

Reflected signaltransmitter receiver

Dispersive time > 1 chip interval

Multi-finger receiver can supply multi-finger diversity, signal gain is improved

coding


64/80

RAKE Receiving

receiverreceiver

Single

receiving

Single

receiving

Single

receiving

searcher calculatecalculate

combining

tt

s(t) s(t)

signal

RAKE Receiving overcomes multi-finger interference, improves

receiving performance


65/80

Combination of Multi-fingers

Maximal ratio combining (MRC)

at each time delay phase shifting by adding

Finger1

Finger 2

Finger 3


66/80

Content


Power Control

Handover Control

Admission Control

Load Control


RAKE Receiver



67/80

Capacity of WCDMA


68/80

Power Rising

Power rising occurs because of the Multiple AccessInterference (MAI) resulting from the non-orthogonal

code channels.

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 hear each other


69/80

Power Rising


70/80

Capacity of WCDMA System

Under the circumstance of single services:

=

=

=


71/80


72/80


WCDMA capacity feature WCDMA capacity is Soft Capacity.

The Concept of Soft Capacity

The system capacity and communication quality are

interconvertible.

Different services have different capacity.

Different proportion of services have different capacity

for mixed services.

The capacity is also restricted to the allocation of coderesource.


73/80

Different combination

of service has

different capacity

Concept of Soft Capacity

System capacity and QoS can be interconverted


74/80

CapacityCapacity

All the key technologies adopted are used to try toAll the key technologies adopted are used to try to

achieve the optimal balance of the three factorsachieve the optimal balance of the three factors

Crucial Factors for WCDMA Network (CQC)


75/80

Coverage and Capacity

WCDMA performance is determined by such factors as Number of users

Transmission rate

Moving speed

Wireless environment

indoors

Outdoors

The radius of cell depends on such factors as:

Local radio conditions (local interference)

Traffic in neighbouring cells (remote interference) Cell Radius decrease according to the Increase of user

number


76/80

Coverage/capacity VS Data Rate

Higher data rate needs higher power High data rate transmission is only available

nearby the station

>12.2 kbps

>64 kbps

>384 kbps

>144 kbps

Coverage decrease

Subscriber

numincrease


77/80

DL/UL:

Add carrier

six sectors

UL

Tower Mounted Amplifier (TMA)

4 Rx Div

OTSR

DL

transmission diversity (Tx Div)

high power amplifier

Add basestation

last choice

Add basestation

last choice

Optimization methods

To overcome Cell Breathing Effect caused byincreased traffic and meet different requirements

for capacity and coverage in different environment,

following solutions can be applied:


78/80

Factors Impact on WCDMA capacity

Power ControlReducing interference, saving power and Increasing

capacity

HandoverControl

Impacting the capacity through applying different proportion

and algorithm of soft handover

AdmissionControl Admitting a connection base on the load and the admissionthreshold of planned capacity

Load ControlMonitoring system load and adjusting the ongoing services

to avoid overload

OVSF CodeThe Allocation of codes impacts the maximum number of

simultaneous connections.

RAKE ReceiverThe advanced receiving and baseband processing

technology is introduced to overcome the fast fading

WirelessEnvironment

Wireless environment such as interferences, UE position

and mobility etc. can influent the cell capacity

Factors affects WCDMA Capacity


79/80

Exercise

what is the near-far effect what is the purpose ofPower Control .

Power control is classify into ( ) ( )and ( )

pls describe WCDMA Handover technologycategory.

Handover procedure includes ( ) ( ) and( )

What is the Cell Breathing Effect. Whats the relation between Capacity, Quality and

Coverage?


80/80

wr_bt04_e1_1 wcdma key technology 80

Documents