Uplink Frequency-Selective Scheduling.pdf

Uplink Frequency-Selective Scheduling

USER DESCRIPTION

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Copyright

Ericsson AB 2011. All rights reserved. No part of this document may bereproduced in any form without the written permission of the copyright owner.

Disclaimer

The contents of this document are subject to revision without notice due tocontinued progress in methodology, design and manufacturing. Ericsson shallhave no liability for any error or damage of any kind resulting from the useof this document.

Trademark List

All trademarks mentioned herein are the property of their respective owners.These are shown in the document Trademark Information.

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Contents

Contents

1 Introduction 1

1.1 Basic Characteristics 1

1.2 Benefits 1

1.3 Additional Information 2

2 Feature Operation 3

2.1 Network Requirements 3

2.2 Feature Operation Sequence Diagram 3

2.3 Feature Operation Details 3

3 Parameters 7

3.1 Introduced Parameters 7

3.2 Affected Parameters 7

4 Network Impact 9

4.1 Capacity 9

4.2 Coverage 9

5 Associated Features and Affected Functions 11

5.1 Prerequisite Features 11

5.2 Affected Features 11

5.3 Related Features 11

5.4 Affected System Functions 11

6 Performance 13

6.1 KPIs 13

6.2 Counters 13

6.3 Events 13

7 O&M Information 15

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Introduction

1 Introduction

This document describes the Uplink Frequency-Selective Scheduling featureand its main benefits and impacts in the LTE RAN.

1.1 Basic Characteristics

This section describes the basic characteristics of the feature.

Feature identity:FAJ 221 1799, Uplink Frequency-Selective Scheduling

Replaces: N/A

Dependencies

This feature requires the following RAN features to be active:

QoS-Aware Scheduler

This feature may affect the following RAN features:

This feature affects no other features.

1.2 Benefits

This section describes the benefits of this feature.

Scheduling is an important functionality in the management of radio resources.The scheduler makes decisions on allocating a certain part of the spectrum to acertain user based on several criteria.

In LTE the radio link quality is not only dependent on variations over time,but also variations within the frequencies of the transmission band. Suchfrequency dependent variations introduce opportunities when performing uplinkscheduling for a UE transmission.

By using frequency-selective gain in uplink scheduling, that is, allocating highchannel quality resources to the UEs, both coverage and capacity will beimproved. Uplink Frequency-Selective Scheduling provides both significant celledge and average cell throughput improvements.

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1.3 Additional Information

More information about this feature and related topics can be found in thefollowing documentation:

Scheduler

Link Adaptation (refer to Power Control)

3GPP TS 36.331, TS 36.211 and TS 36.213

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Feature Operation

2 Feature Operation

This section describes the Uplink Frequency-Selective Scheduling feature inmore detail, including network configuration requirements and operation flows.

2.1 Network Requirements

The following must be fulfilled at feature activation:

The QoS-Aware Scheduler feature must be activated.

The Uplink Frequency-Selective Scheduling feature license must bepresent.

2.2 Feature Operation Sequence Diagram

The high level flow for scheduling, described in Scheduler, also applies whenthe Uplink Frequency-Selective Scheduler is active. The exception is that theUplink Frequency-Selective Scheduler is enabled to allocate resources basedon frequency-selective channel quality information.

2.3 Feature Operation Details

This section gives an overview of the feature functions.

Uplink frequency-selective scheduling means that the spectrum allocation forPUSCH (Physical Uplink Shared Channel) transmissions will be performedbased on frequency-dependent channel knowledge. The frequency awarenessintroduced in Uplink Frequency-Selective Scheduling will allow the schedulerto not only prioritize which users should be scheduled during a certain timeinterval, but to also decide which spectrum resources should be allocated toeach of these users. As such, resource allocation decisions are made by takingboth time and frequency dimensions into account.

By performing uplink frequency-selective scheduling, the uplink schedulerattempts to maximize the spectral efficiency. This is done through allocatingeach UE into a part of the spectrum where the channel quality is good,according to certain measurements, see Figure 1.

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UE1 Allocation

UE1 Channel Quality Profile

UE2 AllocationFrequency

UE2 Channel Quality Profile

L0000550A

Figure 1 UE Allocation Based on Frequency Selective Channel QualityMeasurements

2.3.1 Sounding Reference Signals

The Uplink Frequency-Selective Scheduling feature is dependent on sounding.Sounding is a procedure which utilizes a set of uplink reference signals. Unlikethe uplink Demodulation Reference Signals (DMRS), which are sent withinthe same bandwidth as the uplink signal, Sounding Reference Signals (SRS)can be sent over almost arbitrary channel bandwidths, providing the channelestimation over any part of the spectrum. This gives the possibility of schedulinguplink transmission on resource blocks of instantaneously good quality.

During SRS transmissions, frequency-selective uplink measurements of thesignal power will be made. These power measurements will continuously bereported to the uplink scheduler, which uses these measurements in order toestimate the frequency-selective uplink gain of each UE. The estimated gain,together with the distribution of noise and interference within the serving cell,is used by the uplink scheduler when distributing PRB resources to the UEstargeted for scheduling.

SRS transmissions are performed in the Uplink Part of Time Slot (UpPTS)part of the special subframe.

2.3.2 Allocation of SRS Resources

The Uplink Frequency-Selective Scheduling feature enables the operator toselect if an SRS should be allocated or not per QCI.

The eNodeB will only attempt to allocate an SRS resource to UEs that haveat least one Logical Channel Group (LCG) that triggers request for an SRSresource. An LCG triggers request of an SRS resource when the Quality ofService Class Indicator (QCI) of its highest priority configured logical channelhas been configured with the parameter srsAllocationStrategy set toACTIVATED. Thus, the preference of a UE to request an SRS resource may

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Feature Operation

change both when adding and when removing a radio bearer. Figure 2 showsan example of SRS resource allocation.

L0000527A

eNodeB attempts to allocateSRS resource to UE A

eNodeB will not attempt to allocateSRS resource to UE B

Logical Channel aQCI xPriority: 5SRS: activated

Logical Channel bQCI yPriority: 9SRS: deactivated

Logical Channel cQCI zPriority: 10SRS: activated

Logical Channel bQCI Priority: SRS: deactivated

LCG 1LCG 0

UE A

LCG 3 LCG 2

LCG 1 configured to useSRS resource

LCG 1LCG 0

UE B

LCG 3 LCG 2

No LCG configured to useSRS resource for UE B

y9

Figure 2 Example of SRS Resources Allocation

2.3.3 PUSCH Resource Allocation

The Uplink Frequency-Selective Scheduling feature gives the possibility toselect either Frequency Selective or a Resource Fair resource allocationstrategy per QCI. The Uplink Frequency-Selective Scheduling described inthis document only applies to when the resource allocation strategy is setto Frequency Selective. When using the Resource Fair resource allocationstrategy, the Scheduler does not take into account any frequency-selectivechannel quality information when allocating resources.

The scheduler applies frequency-selective resource allocation for PUSCHdata associated with an LCG whenever the QCI of the highest prioritylogical channel in the LCG is set to use resourceAllocationStrategyFREQUENCY_SELECTIVE. When applying frequency-selective resourceallocation for a UE that has been allocated an SRS resource, the scheduleruses measurements from SRS together with uplink DMRS and interferencemeasurements to allocate the UE to the frequencies with the most favorablesignal quality.

When applying frequency-selective resource allocation for UEs that have notbeen allocated an SRS resource, the scheduler bases the scheduling decisionon frequency averaged measurements from the uplink DMRS, however takingfrequency-selectivity in interference measurements into account .

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Parameters

3 Parameters

This section describes parameters introduced by the Uplink Frequency-SelectiveScheduling feature and parameters affected by activating the feature.

3.1 Introduced Parameters

Table 1 describes the parameters introduced by the feature.

Table 1 Introduced Parameters

Parameter Description

featureStateUlFss Indicates whether the licensed feature Uplink Frequency-SelectiveScheduling is ACTIVATED or DEACTIVATED. The value of theattribute is irrelevant when no valid license key is installed for thefeature.

keyIdUlFss The license key ID for the Uplink Frequency-Selective Schedulingfeature.

serviceStateUlFss Indicates if the Uplink Frequency Selective-Scheduling feature isoperable or inoperable.

UlFssId The value component of the Relative Distinguished Name (RDN).

licenseStateUlFss Indicates whether the licensed state of the feature UplinkFrequency-Selective Scheduling is ENABLED or DISABLED,whether a valid license key is installed for the feature.

resourceAllocationStrategy Defines the resource allocation strategy of the QoS Class Identifier(QCI). Changes to this parameter take effect only if the licensesfor Uplink Frequency-Selective Scheduling and QoS-AwareScheduler are present and the features are active.

srsAllocationStrategy If set to ACTIVATED, an attempt is made to allocate sounding fora UE. If several Data Radio Bearers are setup towards the UE withdifferent QoS configurations, and the QoS configurations havedifferent QCI parameters, an algorithm using the priority parameterin the QoS configuration will resolve which QoS configuration thatwill define sounding.

ulSrsEnable This parameter controls whenever sounding shall be enabled ornot in a cell. When enabled, cell resources are configured forsounding.

3.2 Affected Parameters

The implementation of this feature affects no parameters.

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Network Impact

4 Network Impact

This section describes how the Uplink Frequency-Selective Scheduling featureimpacts the network functions and capabilities.

4.1 Capacity

This section provides information on the impact of the feature on networkcapacity.

Uplink Frequency-Selective Scheduling will improve the capacity because ofmulti-user diversity. However, the improvement is limited by the dependenceon available SRS resources.

4.2 Coverage

This section provides information on the impact of the feature on networkcoverage.

Uplink Frequency-Selective Scheduling provides coverage improvement interms of better allocation, and thus increased SINR, when serving cell edgeusers.

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Associated Features and Affected Functions

5 Associated Features and AffectedFunctions

This section describes how the Uplink Frequency-Selective Scheduling featureaffects other features and functions.

5.1 Prerequisite Features

Table 2 lists prerequisite features to the Uplink Frequency-SelectiveScheduling feature, that is, they must be active prior to introducing UplinkFrequency-Selective Scheduling.

Table 2 Prerequisite Features

Feature Description

QoS-Aware Scheduler Changes to the parameters resourceAllocationStrategy and srsAllocationStrategy take effect only if theservice state for QoS-Aware Scheduler is operable.

5.2 Affected Features

This feature affects no other feature.

5.3 Related Features

This feature is not related to any other feature.

5.4 Affected System Functions

Table 3 lists functions affected by the Uplink Frequency-Selective Schedulingfeature.

Table 3 Affected System Functions

Feature Description

Scheduler The scheduler takes into account frequency-selective channel qualityinformation when allocating resources for data associated with a QCIconfigured to use the Frequency Selective resource allocation strategy.

Power Control The PUSCH Link Adaptation takes into account measurements from SRStransmissions for UEs that are allocated an SRS resource.

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Performance

6 Performance

This section describes performance indicators, counters, and events associatedwith the Uplink Frequency-Selective Scheduling feature.

6.1 KPIs

Table 4 lists the main Key Performance Indicators (KPIs) associated with theUplink Frequency-Selective Scheduling feature.

Table 4 KPIs

KPI Description

Uplink Throughput Uplink Frequency-Selective Scheduling provides both cell edge andaverage cell throughput improvements.

6.2 Counters

Table 5 lists the counters associated with the Uplink Frequency-SelectiveScheduling feature.

Table 5 Counters

Counter Description

pmRadioRecInterferencePwrPrb1


...


The accumulated interference power per PRB.

(In total 100 counters, one per PRB.)

pmRadioThpVolUl The total successfully transferred data volume on MAC level inthe uplink. This counter includes possible padding bits.

pmRadioThpResUl The total amount of physical resources used for transmission inthe uplink. Both successful and unsuccessful transmissions arecounted.

More information about counters can be found in Managed Object Model RBS.

6.3 Events

Table 6 lists the events associated with the Uplink Frequency-SelectiveScheduling feature.

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Table 6 Events

Event Event Parameter Description

INTERNAL_PER_RADIO_CELL_NOISE_INTERFERENCE_PRB

EVENT_PARAM_NOISEINTERF_SUM_PRB1


...


Measurements of the accumulatedinterference power per PRB.

(In total 100 event parameters, oneper PRB.)

More information about events can be found in PM Event List.

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O&M Information

7 O&M Information

This section provides Operation and Maintenance (O&M) information for theUplink Frequency-Selective Scheduling feature.

A license and parameter setting activates the feature. Details of the licenseactivation process can be found in License Management.

Uplink Frequency-Selective Scheduling is enabled or disabled per QCI bysetting the values of the attributes resourceAllocationStrategy andsrsAllocationStrategy in MO class QciProfilePredefined.

By default, the feature is turned off for QCIs, that is, for all instances ofQciProfilePredefined the value of resourceAllocationStrategyis set to RESOURCE_FAIR and the value of srsAllocationStrategy isset to DEACTIVATED. The value of the attribute ulSrsEnable in MO classEUtranCellTDD is by default set to false.

Uplink Frequency-Selective Scheduling is activated for a certain bearer typeby setting resourceAllocationStrategy to FREQUENCY_SELECTIVE.srsAllocationStrategy should be set to ACTIVATED and ulSrsEnableshould be set to true for the eNodeB to make an attempt to allocate a soundingresource.

Setting resourceAllocationStrategy and srsAllocationStrategyto other than the default values only takes effect if the featureF states of theUplink Frequency-Selective Scheduling and QoS-Aware Scheduler featuresare ENABLED. Setting the value of ulSrsEnable to other than its defaultvalue takes effect only if the service state of the Uplink Frequency-SelectiveScheduling feature is ENABLED.

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toc1 Introduction1.1 Basic CharacteristicsDependencies1.2 Benefits1.3 Additional Information2 Feature Operation2.1 Network Requirements2.2 Feature Operation Sequence Diagram2.3 Feature Operation Details2.3.1 Sounding Reference Signals 2.3.2 Allocation of SRS Resources2.3.3 PUSCH Resource Allocation3 Parameters3.1 Introduced Parameters3.2 Affected Parameters4 Network Impact4.1 Capacity4.2 Coverage5 Associated Features and Affected Functions5.1 Prerequisite Features5.2 Affected Features5.3 Related Features5.4 Affected System Functions6 Performance 6.1 KPIs6.2 Counters6.3 Events7 O&M Information

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Uplink Frequency-Selective Scheduling.pdf