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Introduction

Load Control (LC)

Admission Control (AC)

Packet Scheduler (PS)

Power Control (PC) Handover Control (HC)

Resource Manager (RM)


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Radio Resource Management

Target for RRM is to ensure the RAN offers:

The planned coveragefor each targeted service

High capacity i.e. low blocking (new calls, handovers)

The required Quality of Service (QoS)

Optimize the use of available capacity (priorities)

By continuously monitoring/adjusting how the available resources are used in accordancewith user requests

Radio Resource Management (RRM) is responsible for optimalutilisation of the air interface resources

RRM

Link Quality

Cell CoverageCell Capacity



RRM must be able to:

Predict the impact on interference (power) of theadmitting a new user for UL & DL

Perform appropriate actions (e.g. new call admissions,bitrate increase/decrease etc.) in accordance withprevailing load conditions

Provide different quality of service for real time (RT)and non-real time (NRT) users

Take appropriate corrective action when the different

cell load thresholds are exceeded in order to maintaincell stability (i.e. load control)

Overload

Load Target

Overload Margin

Power

Time

Estimated capacity forNRT traffic

Measured load causedby non-controllable load(RT)

RRM Tasks

RT services must have higher quality assurance than NRT



RRM is made up of a number of closely interdependent functions (i.e. algorithms) These functions can be divided into;

Cell Based Load control (LC)

Admission control (AC)

Packet scheduling (PS) High Speed Downlink Packet Access

Resource manager (RM)

Connection Based Handover control (HC)

Power control (PC)

RRM Functional Split

PC

HC

Connection based functions

LC

AC

Cell based functions

PS

RM



RRM Cell Based FunctionsAdmission control (AC) Performs the admission control for new bearers to enter the network.

Predicts interference caused by the bearer and checks whether there is room for it.

Power allocation

Defines transport channel parameters

Packet Scheduler (PS) Scheduling packets on the radio interface (UL/DL)

Ensures fast allocation of resources for NRT users

Load Control (LC) Takes care of radio network stability

Gathers interference information and provides cell load status to AC & PS

Resource manager (RM) Manages the physical resources of RAN

Maintains the code tree and code allocations



RRM Connection Based Functions

Power Control (PC) Continuously monitors the quality of the radio link and adjusts MS, BTS powers

Ensures absolute minimum Tx power is used to maintain required quality

Can be divided into; Closed loop PC

Open loop PC

Outer loop PC

Handover Control (HC) Manages the mobility of the users

Ensures MS is connected to the optimal cell(s) > minimising interference

Can be divided into;

Intra-frequency handovers

Inter-frequency (hard) handovers

Inter-system handovers




Introduction

Load Control (LC)






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Load control States

The load control function within RRM can be divided:

Preventative load control (e.g. congestion)

Overload control (e.g. dropping of calls in worst case)

Preventative actions are performed before the cell is overloaded (threshold y)

Overload actions are performed after cell is overloaded (threshold x)

RNP parameters define the thresholds for the RRM functionalities

The thresholds define a stable functionality within a cell and with surrounding cells

Overloadthreshold x

Load Targetthreshold y

Power

Time

Estimated capacity forNRT traffic.

Measured load caused

by non-controllable load(RT)

Preventative Load Control

Overload Control


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Load Control

LC performs the function of load control in association with AC & PS

Updates load status using measurements & estimations provided by AC and PS

Continuously feeds cell load information to PS and AC;

Interference levels

BTS power levels

Non-controllable load

LC

AC

PS

NRT load

Load change info

Load status


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Introduction

Load Control (LC)






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Admission Control

Responsible for maximising capacity (throughput) whilst providing the requiredquality of service for RT traffic.

Checks that admitting a new user will not sacrifice planned coverage or quality ofexisting connections

Determines whether RABs can be admitted to the RAN Handles RT RABs alone by estimating the increase in non-controllable load

With PS decides whether to admit NRT RABs

In the decision UL interference & DL power measurements by BTS are used

Provides RLC parameters to PS for NRT users, for example Bearer class

Transport Formats

AC sets quality and power parameters for the radio link, for example UL/DL BLER, Eb/No targets, SIR target

Initial DL transmission power


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In uplink the total received wideband interference power measured indicates the trafficload of the radio resources .

For downlink the power change caused by new RT service is obtained from themaximum allowed DL transmission power for the service.

In the admission decision procedure new call (or modified existing call) is admitted ifboth UL and DL admission decisions are passed

Prx_target

Prx_target_BS

UL interference power

Load

Planned load area

Marginal load area

Admission Control

PrxTotal

RNP decisionthresholds


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P k S h d l


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Packet Scheduler

PS allocation times need to be fast to accommodate changing conditions & accurate(up-to-date load info)

Capacity requests sent via traffic volume measurement reports (governed by RNPparameters)

PS comprises two parts: MS specific & Cell specific

power

time

non-controllable load

controllable load

Total Load

Target threshold

Overload threshold

Responsible for scheduling radio resourcesfor both UL and DL NRT RABs

Scheduling period defined by RNP

parameters PS relies on up-to-date information from

AC and LC

Capacity allocated on a needs basis usingbest effort approach


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Introduction

Load Control (LC)

Admission Control (AC) Packet Scheduler (PS)

Power Control (PC)

Handover Control (HC)



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Power Control

Since WCDMA system is interference limited it is beneficial to reduce transmissionpower as far as possible.

Thus, the target of power control (PC) is to achieve the minimum signal-to-interference ratio (SIR) that is required to offer sufficient quality of the connection.

PC works on a per-connection basis.

Power Control

Power ControlLoad Control

RNCBSMS

Power ControlHandover Control

Admission ControlLoad Control

Packet Scheduler


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Power Control (PC) Loops in WCDMA

RNC

Open Loop Power Control (Initial Access)

Fast Closed Loop Power Control

Outer Loop Power Control

MS BTS


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Introduction

Load Control (LC)


Power Control (PC)



H d C t l (HC)


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HC is responsible for;

Managing the mobility aspects of an RRC connection as UE move around network

Maintaining high capacity by ensuring UE is always served by strongest cell

Intra-layerInter-layer

Intra-System

Soft(er) Handover

Hard Handover

Inter-frequency

Intra-frequency

Intra-frequency

Inter-System(Inter-RAT)

Hard HandoverInter-frequency

WCDMA to GSMWCDMA to GPRSGSM to WCDMAGPRS to WCDMA

WCDMA to WCDMA




RequiresCompressed

Mode or DualReceiver UE


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Introduction

Load Control (LC)


Power Control (PC)





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Responsible for managing the logical radio resources of the RNC in co-operation withAC and PS

On request for resources, from either AC(RT) or PS(NRT), RM allocates;

DL spreading code

UL scrambling code

Also looks after code tree management (to maintain orthogonality);

Initial code selection codes concentrated to same branch Code re-fragmentation dynamic reallocation of codes as users enter/leave system

Code Type Uplink Downlink

Scrambling codes

Spreading codes

User separation Cell separation

Data & control channels from same UE Users within one cell

Documents

01 RRM Overview 2006 Partner