01_RRM_overview_RU10_v1-

1 © Nokia Siemens Networks Presentation / Author / DateI insert classification level

Course Content

Radio Resource Management OverviewParameter ConfigurationCommon Channels & Power ControlLoad ControlAdmission ControlPacket Scheduling incl. HSPAHandover ControlResource ManagerHSPA RRM and parameters

2 © Nokia Siemens Networks Presentation / Author / Date Soc Classification level

Module Objectives

At the end of the module you will be able to:• Describe the purpose of RRM• List the RRM functional entities• Describe the purpose of each of the RRM functional entities• Identify the location of RRM entities• Identify relationships between RRM entities


Radio Resource Management Overview

• Introduction• Load Control (LC)• Admission Control (AC)• Packet Scheduler (PS) incl. HSPA• Power Control (PC)• Handover Control (HC)• Resource Manager (RM)• RRM of HSPA


Radio Resource Management

Target for RRM is to ensure the RAN offers:• The planned coverage for 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 accordance with user requests

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

RRM

Link Quality

Cell CoverageCell Capacity


RRM Tasks

• RRM must be able to:• Predict the impact on interference (power) of

the admitting a new user for UL & DL• Perform appropriate actions (e.g. new call

admissions, bitrate increase/decrease etc.) in accordance with prevailing 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 maintain cell stability (i.e. load control)

Overload

Load TargetOverload Margin

Powe

r

TimeEstimated capacity for NRT trafficMeasured load causedby non-controllable load (RT)

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

PCHC

Connection based functions

LC

AC

Cell based functions

PSRM





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

Powe

r

Time

Estimated capacity for NRT traffic.Measured load causedby non-controllable load (RT)

Preventative Load ControlOverload Control


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

PSNRT load

Load change info

Load status



• Introduction

• Load Control (LC)

• Admission Control (AC)

• Packet Scheduler (PS) incl. HSPA

• Power Control (PC)

• Handover Control (HC)

• Resource Manager (RM)• RRM of HSPA


Admission Control

• Responsible for maximising capacity (throughput) whilst providing the required quality of service for RT traffic.

• Checks that admitting a new user will not sacrifice planned coverage or quality of existing 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 allocate resources to NRT RABs• In the decision UL interference & DL power measurements by BTS are used• In RAS06 also the UL throughput is considered for AC

• 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


Admission Control, RAS05.1 picture• In uplink the total received wideband interference power measured indicates the traffic

load of the radio resources .

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

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

Prx_target

Prx_target_BS

UL interference power

Load

Planned load area

Marginal load area

PrxTotal

RNP decision thresholds


Admission Control, RAS06 picture, UL

Noise Rise

Own Cell Load Factor (throughput)

i-factor

PrxOffset

Minimum throughput

DCH

PrxLoadMarginDCH

Maximum throughput

DCH

PrxLoadMarginMaxDCH PrxTarget

•Throughput thresholds are calculated from new, configurable Prx thresholds





• 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 RNP parameters)

• PS comprises two parts: UE specific & Cell specific

power

time

non-controllable loadcontrollable load

Total Load

Target threshold

Overload threshold

• Responsible for scheduling radio resources for 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 using ‘best effort’ approach

Packet Scheduler in RNC


Comparing HSUPA to R99 and HSDPA• HSUPA is a marketing name for 3GPP Rel6 “Enhanced-DCH”• main characteristics:

• Fast WBTS packet scheduling• Dedicated channel• L1 HARQ algorithms (CC, IR)• 2ms or 10ms TTI periods• Soft Handover• very small SF (2,4)

FeatureRel99 DCH

Rel5HSDPA

Rel6HSUPA

Var. spreading factor Y N Y

Fast power control Y N Y

Adaptive modulation N Y N

WBTS based scheduling N Y Y

Fast L1 HARQ N Y Y

Soft Handover Y N Y

TTI length [ms]80,40,20,1

0 2 10,2





Power Control

• Since WCDMA system is interference limited it is beneficial to reduce transmission power 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 ControlAdmission ControlLoad ControlPacket

Scheduler





Handover Control (HC)• 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 HandoverInter-frequency

Intra-frequency

Intra-frequency

Inter-System(Inter-RAT)

Hard HandoverInter-frequency

WCDMA to GSMWCDMA to GPRSGSM to WCDMAGPRS to WCDMA

WCDMA to WCDMAIntra-layerInter-layer



Requires Compressed Mode or Dual Receiver UE





Resource Manager (RM)

• Responsible for managing the logical radio resources of the RNC in co-operation with AC 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 de-fragmentation – dynamic reallocation of codes as users enter/leave system

• DL spreading code allocation for HSDPA users can be dynamic in RAS06

Code Type Uplink DownlinkScrambling codes

Spreading codesUser separation Cell separation

Data & control channels from same UEUsers within one cell





HSDPA - general principle

• Fast scheduling is done directly in Node-B based on feedback information from UE and knowledge of current traffic state.

UE2

Channel quality(CQI, Ack/Nack, TPC)

Channel quality(CQI, Ack/Nack, TPC)

Data

Data

Users may be time and/or code multiplexed

New base station functions• HARQ retransmissions • Modulation/coding selection (16QAM)• Packet data scheduling (short TTI)

UE1

0 20 4 0 6 0 80 1 00 1 20 1 40 1 60- 202468

10121416

Time [number of TTIs]

QP SK1/4QP SK2/4QP SK3/4

16QAM 2/416QAM 3/4

Instan

taneo

us Es

No [d

B]


Comparing HSUPA to R99 and HSDPA• HSUPA is a marketing name for 3GPP Rel6 “Enhanced-DCH”• main characteristics:

• Fast WBTS packet scheduling• Dedicated channel• L1 HARQ algorithms (CC, IR)• 2ms or 10ms TTI periods• Soft Handover• very small SF (2,4)

FeatureRel99 DCH

Rel5HSDPA

Rel6HSUPA

Var. spreading factor Y N Y

Fast power control Y N Y

Adaptive modulation N Y N

WBTS based scheduling N Y Y

Fast L1 HARQ N Y Y

Soft Handover Y N Y

TTI length [ms]80,40,20,1

0 2 10,2

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