02-wcdma system radio resource management

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ISSUEISSUE

UMTS Radio Resource Management1.01.0

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Course Contents

Chapter 1 Overview of RRMOverview of RRM

Chapter 2 Channel ConfigurationChannel Configuration

Chapter 3 Power ControlPower Control

Chapter 4 Mobility ManagementMobility Management

Chapter 5 Load Control

Chapter 6 AMR Mode Control



UE Working Modes and statesIdle Mode

The UE has no relation to UTRAN, only to CN. For data transfer,

a signalling connection has to be established.

UE camps on a cell It enables the UE to receive system information from the PLMN

When registered and if the UE wishes to establish an RRC

connection, it can do this by initially accessing the network on the

control channel of the cell on which it is camped

UE can receive "paging" message from control channels of the cell.

It enables the UE to receive cell broadcast services.



UE Working Modes and states

Connected Mode (Cell-DCH, Cell-FACH, Cell-PCH, URA-

PCH) When at least one signalling connection exists, the UE is in

connected mode and there is normally an RRC connection

between UE and UTRAN. The UE position can be known on

different levels: UTRAN Registration Area (URA) level

The UE position is known on URA level. The URA is a set of cells

Cell level

The UE position is known on cell level. Different transport channel

types can be used for data transfer:

Common transport channels (RACH / FACH, DSCH, CPCH)

Dedicated transport CHannels (DCH)



UE Working Modes and states

Cell-DCH In active state

Communicating via its dedicated channels

UTRAN knows which cell UE is in.



Cell-FACH and Cell-PCH State

Cell-FACH In active state

Few data to be transmitted both in uplink and in downlink. There is no

need to allocate dedicated channel for this UE.

Downlink uses FACH and uplink uses RACH.

UE need to monitor the FACH for its relative information.


Cell-PCH No data to be transmitted or received.

Monitor PICH, to receive its paging.

lower the power consumption of UE.


UTRAN have to update cell information of UE when UE roams to

another cell



URA-PCH State

URA-PCH No data to be transmitted or received.

Monitor PICH.

UTRAN only knows which URA (UTRAN Registration Area,

which consists of multiple cells) that UE is in.

UTRAN update UE information only after UE has roamed to

other URA.

A better way to lower the resource occupancy and signaling

transmission



UE states

CELL_DCH CELL_FACH

CELL_PCHURA_PCH

IDLE

DEAD - Scanning networks (PLMN)- ”Camp on” cell

- Monitor paging channel- cell re-selection

- Dedicated Channel- Radio bearers Transmission Services - upper layer Signaling

trigger (CN)

- Reduce action ， DTX ， and save power

RRC connection



Introduction to RRM

RRM: Radio Resource Management

RRM is responsible for supplying optimum coverage, offering the

maximum planned capacity, guaranteeing the required quality of

service (QoS) and ensuring efficient use of physical and transport

resources.

Power is the ultimate radio resource. The best way to utilize the radio

resource is to control the power consumption strictly.

Increasing the transmission power of a certain user can improve its QoS.

However, due to the self-interference, the increasing would result in more

interference on other users and consequently reduce the receiving QoS.



RRM Algorithms in the Call Flow (1)

CN

RNC

Iu

RAB ASSIGNMENT （ QoS)

QoS mapping

Access control

Request of code resource

Configuration of access layer

Channel configuration--fundamental

channel configuration

Load control--access control

Channel configuration--code resource management

Load control--load balance



RRM Algorithms in the Call Flow(2)

Channel setup and call initiated

Power control

Change of service rate

Handover

Call end

Resource release

End

Power control—close loop

Power control—open loop

Channel configuration--DCCC AMRC

Mobility management

Channel configuration--code resource management

Load control--load balance



Classification of RRM

Based on the different objects, RRM is classified as:

Connection oriented RRM, which guarantees QoS of

connection and minimizes the radio resource allocated for the

connection. Channel configuration, power control, handover

A dedicated entity is created to manage the resource

configuration for each connection.

Cell oriented RRM, which maximizes users in cells and thus

increases system capacity while guaranteeing cell stability. Code resource management, load control

A dedicated entity is created for each cell to manage its

resource.



Procedure of RRM

Fundamental procedure of radio resource management

Measurement control

measurement UE, NodeB, RNC

Measurement report

Decision

The implementation of resource control



Course Contents

Chapter 1 Summary of RRM

Chapter 2 Channel Configuration







Channel Configuration

Fundamental channel configuration algorithm

Dynamic channel configuration algorithm

Code resource management algorithm



Fundamental Channel Configuration

Fundamental channel configuration is to map the RAB QoS features

requested by CN into the corresponding parameters and

configuration mode on each AS layer

QoS requested by CN Traffic Classes

Conversational

Streaming

Interactive

Background

Rate demand

Quality demand （ BLER）



QoS Mapping

DPDCH DPCCH

RAB

RB RB

DTCH DTCH DCCH

TrCHTrCH TrCH

CCTrCH

RLC entity

Mac-d Mac-c

Coding& RM&Mux

Radio Bearers

RLC SublayerLogical Channels

MAC SublayerChansport Channels

Physical Layer

DTCH

RB ¡ £¡ £¡ £

Coding& RM&Mux

TrCH



RB and RLC Parameter Configuration

RB parameters RB number

RLC parameters Different RLC transfer modes

transparent mode

Unacknowledged mode

Acknowledged mode

Different logic channel parameters



MAC Parameter Configuration

MAC parameters The mapping/multiplexing relation between logic channel and

transport channel

Different types and parameters of transport channel Dedicated channel

Common channel

Different configurations of MAC entity MAC-d/MAC-c

Priority configuration of MAC sub layer

TFCS configuration



PHY Parameter ConfigurationPHY parameters

Mapping relation from transport channel to physical channel

Coding scheme Convolutional

Turbo

Non

Interleaving length

Rate matching attribute

Spreading factor SF

Power offset

Other physical channel parameters, e.g., diversity mode, etc.



Signaling Used by Fundamental Channel Configuration on Air Interface

RB setup

RB reconfiguration

RB release

Transport channel reconfiguration

Physical channel reconfiguration

The service may already be setup before. Therefore, when these parameters of all layers are configured, any impact on the current service should be avoided and the multiplexing with the current service should be taken into account.



Example of RB Setup

MAC-c

MAC-d

Configuration in L2 before Setup

RLC

TF Select

Common channel (FACH)

Channel Switching

Configuration in L2 after Setup

RNTI MUX

Signallingbearer

DCCH

MUX

MAC-c

MAC-d

RLC

TF Select

Common channel (FACH)

RLC

Channel Switching

MUX

RNTI MUX

Signallingbearer RB1

DCCH DTCH

MUX



Dynamic Channel Configuration

DCCC: Dynamic Channel Configuration Control

Object of DCCC: Best Effort (BE) service

Objective of DCCC Meet bandwidth requirement of users to the best

Make best use of resource on air interface

Meet the fluctuant requirement of users on data transfer

Save downlink channel code (OVSF code) resource

Achieve “bandwidth on demand”



Effect of DCCC

Bandwidth Allocation on Demand

System capacity

Traditional channelconfiguration

Rate of service source

DCCC

Allocation of DCCC



BE Service

Features of BE service rate of service source changes

largely

Less demand on time delay

More demand on bit error rate

RLC uses acknowledged mode,

thus all data should be buffered in

RLC Buffer.

MAC-d

DL Transport Channel Traffic Volume

Threshold

Configuration in L2

RLC

Signalling bearer

DCH1

RLC

TFC Select

DCH2

Channel Switching

DCCH DTCH



Decision of DCCC

Decision of DCCC Measurement report on traffic volume of RLC Buffer

Decide whether to change the bandwidth used by UE dynamically

based on the measurement result.

Consider whether there is limitation on air interface during the

decision of reconfiguration. This is done by measuring the

transmitting power of UE in both downlink and uplink.

The uplink & downlink DCCC decisions are the same, but are made respectively.



Implementation of DCCC

Implementation of DCCC RB reconfiguration/ transport channel reconfiguration

Cell-FACH-->Cell-DCH

Cell-DCH-->Cell-DCH, include reduction/increment of bandwidth

Cell-DCH-->Cell-FACH

DCCC also restricts the selection of TF at MAC layer based on

the request of congestion control.



OVSF

OVSF code tree

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)



OVSF code allocation

Principles of code allocation Increase the usage of code

Reduce the complexity of code allocation scheme

Increase system capacity



Course Contents



Chapter 3 Power Control






frequency

time

codeCDMA

Self-interference System

Many users communicate at the same carrier.Users at the same frequency interfere with each other

A

B

C



Self-interference System

Power control is especially important.

Minimize the interference

How to serve as many users as we can in a

cell?



Received power

f

Far and Near Effect

What is far and near effect? All UEs transmit at their maximum power The farther the UE is from NodeB, the weaker its signal is at

the receiver. Difference for received signals at NodeB varies from 30 to

70dB.



Far and Near Effect

Far and near effect affects network performance hardly

Weak signals can’t be decoded Network capacity decreases Even one UE close to site can block the whole cell

Other UE can’t connect network because of lack of enough power

What can we do?



Far and Near Effect

Power control in uplink can guarantee signal strength balance at the receiver.

Received power for every UE is just enough.

Received power

f

Received power

f



Fast Fading

What is fast fading?

Received signal is composed of multi-path signals Signal varies with peaks and troughs Troughs appear quickly within several centimetres.



Fast Fading

Fast fading makes received signal quality get bad. Bits met with troughs maybe can’t be decoded. BER or BLER will get higher.

Fast power control can conquer this problem. Frequency for fast power control is faster than that of

signal trough.



Power Control Types

Types of power control: Open loop power control Close loop power control

Inner loop power control (ILPC)

Outer loop power control (OLPC)



Power Control Types

Different power control types are applied on different channels.

Physical channel

Open loop Inner loop Outer loop No power control

DPDCH X X

DPCCH X X X

PCCPCH X

SCCPCH X

PRACH X

AICH X

PICH X



Open Loop Power Control

What is open loop power control? Estimate own transmit power through measuring the

received signal

No feedback from the opposite side

Only be used to set the initial power for its Inaccuracy.




For Example Open loop power control on uplink PRACH

Transmission on PRACH after adjustment

Measure downlink signal strength- CPICH RSCP

Estimate uplink transmission power




Speed up SIR convergence With less transmitting power at initial time Less interference

time

power

time

power

Without open loop power control With open loop

power control

SIR target



Inner Loop Power Control

What is inner loop power control? Based on the comparison between received SIR and the target

SIR

The receiver command the transmitter to increase or decrease

the transmitting power

Have a feedback loop between receiver and transmitter

Purpose is to maintain a certain signal-to-interference ratio of

transmission signal




For example Inner loop power control on UL DPCCH

Inner loop

UE

NodeB

Send TPC command

Measure received signal SIR and compare with SIR target

RNC set SIRtar

Frequency:1500Hz/s

Change UL transmission power

1

2

3

4 5




But ? Even if the mean signal-to-interference ratio is above a

certain threshold, the communication quality (BER or FER or

BLER) is not likely fulfilled because of environment changes.

•BLE

R

SIR

BLER

For different environments



Outer Loop Power Control

What is outer loop power control? Based on the comparison between measured BLER and

the target BLER

To set the target SIR for the ILPC.



Outer Loop Power Control

For example Outer loop power control on uplink DCCCH

NodeB

Set SIRtar

Outer loop

RNC

Measures received data BLER and compares it with BLER tar

Set BLERtar

10-100Hz

Received data with BLER stable

data 1

2

3

Modify SIRtar

4



Outer Loop Power Control － Why

The Mapping between BLER and SIR is not fixed.

When propagation environment changed, the

mapping will be changed.

SIR

BLER

The token for service Qos



Outer Loop Power Control － Why

As channel condition changing, the required SIR (target) is

changing slowly.

Outer loop power control is needed.

SIR

BLER SuburbUrban

Dense urban

For example only

X%

Y1 Y2 Y3



Downlink Power Balance

Due to, for example, signalling errors in the air interface it is possible

that each cell interpreting this TPC differently when in SHO. As a

consequence, one cell lowers its transmitting power while the other

cell might increase it, and therefore the downlink power are drifting

apart.

SRNCThe transmission power levels of the connections from the cells in SHO is forwarded to the RNC after they have been averaged. From these measurements the RNC derives a reference power value which is sent to the cells.



Course Contents




Chapter 4 Mobility Management





Handover

Intra-frequency handover Intra-frequency soft handover

Intra-frequency softer handover

Intra-frequency hard handover

Inter-frequency hard handover

Inter-RAT hard handover



Intra-Frequency Soft Handover

UE moveTarget BSSource BS

time

Data UE received/

sentN o “GAP” of communication



Intra-Frequency Softer Handover



Procedure of Soft/Softer Handover

Node B

Node B

Node B

Intra-frequency cells

–Neighbor cells both from same NodeB or other NodeBs

Measurement report

Soft handover decision

Intra-frequency measurement control

Measurement and filtering

Soft handover execution



Soft Handover Measurement

Active set Including all cells currently participating in a SHO connection of a

terminal.

Neighbour Set/Monitored Set This set includes all cells being continuously monitored/measured by

the UE and which are not currently included in the active set.



Example of Soft Handover



Hard Handover

UE moveTarget BSSource BS

time

Data UE received/

sent“GAP” of communication

Features of hard handover: HHO causes a temporary disconnection for RT radio access bearer

and is lossless for NRT bearers.

The UE must either be equipped with a second receiver or support

compressed mode to execute inter-system/inter-RAT measurement.



Application of Hard Handover in 3G

Intra-frequency hard handover When inter-RNC SHO can’t be executed or is not allowed.

Inter-frequency hard handover Needed in certain areas due to network planning

Load balance between frequencies

Inter-RAT handover 2G-3G smooth evolution

The finite coverage range of initial phase of 3G



Selection of Handover Scheme

Handover scheme should be selected based on the traffic QoS Soft handover can provide better service quality.

Soft handover uses more system resource.

Different sizes of active set and soft handover area use different

system resource and provide different QoSs.

Hard handover would bring “gap” during calls.

Hard handover uses less system resource.

Make a tradeoff between occupation of system resource and QoS



Introduction of Compressed Mode

Compressed Mode Intra-frequency neighbours can be measured simultaneously with

nomal transmission by UE using a RAKE reciever.

Inter-frequency or inter-RAT neighbours measurements require the

UE measuring on a different frequency, this has either to be done

with multiple receivers in the UE or in the compressed mode.

CM is to stop the normal transmission and reception for a certain

period of time, enable the UE to measure on the other frequency.



Compressed Mode

Objective of compressed mode: for UE to realize measurement and synchronization to target cell when inter-frequency handover and inter-RAT handover is required.



Classification of Compressed Mode

Downlink compressed mode To create time for UE’s measurement and synchronization.

3 optional schemes -- SF/2, rate matching/puncturing, higher layer

scheduling

Uplink compressed mode To avoid the interference on its own downlink measurement and

synchronization when UE is measuring certain target cells.

Whether compressed mode is needed is determined by UE’s

capacity.

2 optional schemes -- SF/2, higher layer scheduling.



Features of Compressed Mode

Features of compressed mode All parameters of compressed mode are configured by UTRAN.

The usage of compressed mode would reduce the system

performance.



Course Contents









Definition of air interface load

Wideband power-based uplink loading:

Or

Wideband power-based downlink loading:

rxTotal

othownUL P

II

maxtx

txTotalDL P

P

RTWPnoiseBackgroud

UL 1



Definition of air interface load

Throughput-based uplink loading:

Throughput-based downlink loading:

NK

k

kk

UL i

RW1

)1(1

1

N

k

kkkDLDL W

Ri1

1



Interference Margin (IM) vs. Load Factor

An example of downlink interference (noise rise) vs. downlink

loading with balanced links is depicted as:



Classification of Load Control

Technical classification of load control: Call Admission Control

Load balance between cells

Congestion control



Admission Control

AC is used to decide whether a new RAB is admited or a current

RAB can be modified.

Admission control is done in uplink and downlink separately.

The strategy is that a new bearer is admitted only if the total load

after admittance stays below the threshholds defined by RNP.



Load Balance

Load balance between cells Load balance between intra-frequency cells

Cell breathing

Load balance between inter-frequency cells Inter-frequency load balance

Potential user control



Cell Breathing

CRNC

The obj ecti ve of l oad The obj ecti ve of l oad banl ance i s to share banl ance i s to share the l oad of some the l oad of some "hot" cel l s i n "hot" cel l s i n surroundi ng cel l s surroundi ng cel l s wi th l ow l oad, thus wi th l ow l oad, thus to i ncrease the usage to i ncrease the usage of system capaci ty.of system capaci ty.

cel l breathi ng



Potential User Control

Potential user control To avoid the load imbalance effectively when UE enters DCH state

by making UE in idle mode or non-DCH connected mode camp in

cells with low load in advance.

To achieve the objective by changing the cell selection and re-

selection parameters dynamically.

Potential user control is done by using system message.



Congestion Control

The measures to make full use of system resource admission

control, load balance between cells, packet scheduling are not

enough to guarantee the absolute stabilization, hence congestion

control technology must be introduced.

Objective of congestion control To ensure the system load is below the absolutely steady threshold.

Methods of congestion control Temporarily reducing the QoS of traffic with low priority

Temporarily reducing the QoS of CS traffic in some extreme conditions



Course Contents









AMR Coding

WCDMA system uses Adaptive Multi-Rate (AMR) speech code,

which is linear prediction coding.

Rate no.

Sub-flow 1 block size

（bit）


（bit）


（bit）

Combination block size

（bit）

rate（kbps）

0 0 0 0 0 No data 1 39 0 0 39 SID 2 42 53 0 95 4.75 3 49 54 0 103 5.15 4 55 63 0 118 5.9 5 58 76 0 134 6.7 6 61 87 0 148 7.4 7 75 84 0 159 7.95 8 65 99 40 204 10.2 9 81 103 60 244 12.2



MOS--CIR



AMR Speech

Features of AMR speech: At a certain load level (which corresponds with SIR of UE), the Mean

Opinion Score (MOS) the users experience does not increase

linearly with the speech rate which UE uses. That is, at a certain load

level, the most appropriate AMR speech rate used to acquire the

highest MOS does not refer to the highest rate, but an appropriate

middle rate.

The limitation of UE’s maximum transmitting power restricts the

coverage of uplink AMR speech. To increase the uplink coverage of

AMR speech, uplink rate should be reduced without worsening the

UE’s speech quality.



AMR Mode Control

Hence, AMR mode control is to weigh the load level, and: Reduce AMR speech rate on heavy load condition, thus reduce

the system load and improve speech quality relatively.

Increase AMR speech rate on light load condition, thus improve

QoS.

The AMR speech mode control can be done every 20ms!

Reducing of AMR speech rate can widen the uplink

coverage effectively.

02-wcdma system radio resource management

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