Dual antenna downlink performance package.pdf

Dual-Antenna Downlink PerformancePackage

USER DESCRIPTION

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Copyright

Ericsson AB 20092012. 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 Dependencies and Associated Features 1

2 Feature Overview 3

2.1 Benefits 4

2.2 Impacts 4

2.3 Further Information 4

3 Feature Operation Details 5

3.1 Network Configuration Requirements 6

3.2 High Level Flow Chart 6

3.3 Process Steps 7

4 Parameters 11

4.1 Introduced Parameters 11

4.2 Affected Parameters 11

5 Network Impact 13

5.1 Capacity 13

5.2 Coverage 13

6 Associated Features 15

6.1 Prerequisite Features 15

6.2 Affected Features 15

6.3 Affected System Functions 15

6.4 Related Features 15

7 Performance 17

7.1 KPIs 17

7.2 Counters and Events 17

8 O&M Information 19

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Dual-Antenna Downlink Performance Package

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Introduction

1 Introduction

This document describes the Dual-Antenna Downlink Performance Packagefeature.

The information in this document reflects the feature at the time of its release.

The main characteristics of the feature are presented below.

1.1 Basic Characteristics

Feature identity:FAJ 221 0962, Dual-Antenna DL Performance Package

This feature has replaced:N/A

Connected to: N/A

1.2 Dependencies and Associated Features

This section lists related features. For more detailed information, see Section 6on page 15.

This feature requires the following RAN features to be active:

No prerequisite features required

This feature may affect the following RAN features:

Scheduling (part of LTE Basic)

Power Control (part of LTE Basic)

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Feature Overview

2 Feature OverviewThe Dual-Antenna Downlink Performance Package uses the followingtransmission modes:

Transmission mode 2 with the transmit diversity transmission scheme fixedfor the entire session

Transmission mode 3 where the transmission scheme can be dynamicallychanged between transmit diversity and Large delay Cyclic Delay Diversity(CDD) during a session to adapt to the channel quality fed back from theUser Equipment (UE)

Transmission mode 2 is commonly referred to as Transmit Diversity (TXD)and Transmission mode 3 is commonly referred to as Open Loop SpatialMultiplexing (OLSM).

The multi-antenna transmission modes and related transmission schemesare described in the following table:

Table 1 Transmission Modes and Transmission Schemes

Transmission Mode Transmit Diversity Large Delay CyclicDelay Diversity

TXD (mode 2)

OLSM (mode 3)

Transmit diversity provides better coverage and throughput to lowSignal-to-Interference-and-Noise-Ratio (SINR) users, such as those at celledge.

Large delay CDD benefits high SINR users with higher average and peakthroughputs.

Both the TXD and OLSM modes are valid for two transmit antennas. Duringinitial Random Access (RA), transmission mode 2 is used toward the UE. Afterthe RRC Connection Setup message is received by the UE, transmissionmode 3 is used.

The scheduler is involved in selecting the Physical Resource Blocks (PRBs).With large delay CDD, the UE can use one or two transport blocks. Theinformation sent on a stream is either a new transmission or retransmission.

Link adaptation is involved by selecting the appropriate transport format andModulation and Coding Scheme (MCS). For rank 2 transmissions, the sameformat is used for both code words. This is because the Channel QualityIndicator (CQI) is reported only for code word 0 in transmission mode 3, andtreated the same for both code words.

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This feature is controlled by the parameter featureStateDualAntDlPerfPkg. The license depends on the Managed Object Model (MOM) configuration ofnoOfTxAntennas. For more detailed information, see Section 3.1 on page 6.

2.1 Benefits

Activating this feature with two transmit antennas in the downlink can resultin major improvements in coverage and capacity. When only one transmitantenna exists, the UE is configured with a single antenna port.

With the TXD transmission scheme, low SINR users experience coverage andcell-edge throughput gains. This can, for example, be beneficial in large cells.

With large delay CDD used in the OLSM transmission scheme, high SINRusers experience higher peak throughputs. This can be beneficial, for example,in small cells with optimal tilts.

The TXD and OLSM transmission schemes serve to increase the cell capacityand throughput.

2.2 Impacts

Parameters must be configured to ensure the full benefits of this feature. Formore detailed information in license and configuration setup, see Section 3.1on page 6.

2.3 Further Information

For further information about this feature and related topics, refer to thefollowing documentation:

Scheduler

Power Control

Managed Object Model RBS

Parameter and Counter Limitations

3GPP TS 36.300, TS 36.211, TS 36.212, TS 36.213, TS 36.321, TS 36.322

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Feature Operation Details

3 Feature Operation Details

The Dual-Antenna Downlink Performance Package introduces two different3GPP multi-antenna transmission modes to the LTE RAN downlink; TXD andOpen Loop Spatial Multiplexing (OLSM).

The TXD mode uses an Alamouti (space-frequency block code) scheme in thefrequency domain to transmit one code word on two antennas. The TXD modeis always rank 1 and does not in itself enhance the data rates. Instead, the gainin using TXD is that it provides a better SINR at the UE side.

OLSM mode supports both rank 1 and rank 2 transmissions. The rank 1 formof OLSM is equivalent to TXD, as described above. The rank 2 form usesa large delay CDD transmission scheme to transmit two code words on twoantennas by using spatial multiplexing. When the conditions are fulfilled, spatialmultiplexing enhances the data rates of the transmission.

To optimize radio resource use, the LTE OLSM mode enables the adaptiveselection of the multi-antenna scheme with the most suitable properties.

For lower SINR, transmit diversity is the best suited multi-antenna scheme, andfor higher SINR, the UE benefits from using spatial multiplexing, as shownin the following figure:

L0000170A

Optimal switching pointSINR [dB]

Spe

ctra

l effi

cien

cy [b

its/s

/Hz]

Transmit diversity (rank 1)Spatial multiplexing (rank 2)Adaptive scheme

Figure 1 Adaptive Spatial Multiplexing

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To adaptively switch the rank of the transmission, as in OLSM transmissionmode, Channel State Information (CSI) is necessary on the transmitter side.In LTE, the UE estimates the signal quality and determines the most suitablerank for transmission.

Information about signal quality and preferred rank is returned to the RBS inCQI reports and Rank Indicators (RIs). If TXD mode is used, RIs are nottransmitted since the rank is statically set to 1. Precoding matrix information isunnecessary for OLSM since large delay CDD is used.

3.1 Network Configuration Requirements

The Dual-Antenna Downlink Performance Package requires the cellto be configured with two transmit antennas. The Dual-AntennaDownlink Performance Package is controlled by the license parameterfeatureStateDualAntDlPerfPkg.

The license depends on the configuration of the parameter noOfTxAntennas.When noOfTxAntennas is set to more than one without theappropriate license, an attempt to unlock the cell fails and the alarmResourceAllocationFailure is raised.

When only one transmit antenna exists, or more than one transmit antennawithout a valid license, the UE is configured with a single antenna port.

If the Dual-Antenna Downlink Performance Package license is removed froman RBS, the operating cells are released. The cells must be reconfigured (setnoOfTxAntennas supported by the corresponding license) or a license mustbe installed. When a license is installed, a manual lock or unlock must beperformed for the affected cells, or the node must be restarted.

3.2 High Level Flow Chart

An overview of the processes for downlink scheduling and Layer 1 processingfor one UE in one subframe is shown in the following figure:

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L0000169A

DCI format selection

DCI* format

Preferred number of bits

Downlink assignment- MCS- PRB resource

RI

CQI

Resource allocation

-RBS resource-Number of codewords

1

2

Spatial multiplexing

Link adaptationUE

Downlink Scheduling

Layer 1 processing

TX diversity

Antenna port 0 Antenna port 1

Number oftransport blocks

*DCI = Downlink Control Information

Figure 2 Downlink Scheduling and Layer 1 Processing

If multiple UE is scheduled during one subframe, the steps of the schedulingprocess are repeated, after multiple downlink assignments are provided asinput to Layer 1 processing.

3.3 Process Steps

The Dual-Antenna Downlink Performance Package introduces a number ofenhancements in the processes for:

Configuring channel state information

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Downlink scheduling

Link adaptation

Layer 1 processing.

The process steps differ depending on whether the transmission mode is set toTXD (transmission mode 2) or OLSM (transmission mode 3).

3.3.1 Configuration of UE Channel State Information

The UE is requested to provide periodic CSI with different contents andfrequency, depending on the transmission mode. If the transmission modeis set to TXD, the UE must provide CQI reports. If the transmission mode isset to OLSM, the UE also reports RIs, in addition to CQI. The transmissionmode and contents of the CSI reporting is set via Radio Resource Control(RRC) signalling.

3.3.2 Downlink Scheduling and Link Adaptation

When a UE is selected for scheduling, the first step is to select a DownlinkControl Information (DCI) format. Supported DCI formats for the differenttransmission modes are described in the following table:

Table 2 DCI Format Types

TransmissionMode

DCI Format Format Characteristics

OLSM DCI format 2A DCI format 2A supports transmissionon one or two code words. Supportsresource allocations of type 0, bit mapallocations.

TXD DCI format 1 DCI format 1 supports transmissionon only one code word. Supportsresource allocations of type 0, bit mapallocations.

Based on the resource allocation types for the DCI format, the UE is thenassigned a candidate set of PRBs. This set of PRB resources, together with thepreferred number of code words and number of bits for transmission, serve asinput to the link adaptation function.

Link adaptation keeps track of the UE-provided RI feedback. If the schedulerindicates that it is possible to transmit on two code words, and the latestindicated RI feedback is two, then two transport blocks are allocated. Thetransport format for the transmission, and the required set of PRB resourcesout of the candidate set, are determined based on the channel measurementsprovided by the UE in CQI reports and the available number of bits.

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After reception, the UE feedback separates the Hybrid Automatic RepeatRequest (HARQ) acknowledgements for each transmitted code word tooptimize the use of the radio resource.

3.3.3 Layer 1 Processing

When the scheduler process is completed, the result is a set of downlinkassignments that are provided as input to the Layer 1 processing unit. Theassignments are described in chapters 6.3.3.2, 6.3.3.3, 6.3.4.2.2, and 6.3.4.3of 3GPP TS 36.211.

The process for each downlink assignment differs depending on the numberof code words used:

With one code word, Layer 1 processing uses the transmit diversitytransmission scheme that involves layer mapping and precoding fortransmit diversity.

With two code words, Layer 1 processing uses large delay CDD spatialmultiplexing transmission scheme that involves layer mapping for spatialmultiplexing and precoding for large delay CDD

For both transmission modes, the output after mapping code words to layersand precoding is two sequences of complex valued symbols that are mapped toresource elements for transmission on antenna ports 0 and 1.

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Parameters

4 Parameters

This section describes the parameters introduced by the Dual-AntennaDownlink Performance Package and parameters affected by activating thefeature.

4.1 Introduced Parameters

The table below describes the parameters introduced by the Dual-AntennaDownlink Performance Package:

Table 3 Parameters Introduced by Dual-Antenna Downlink PerformancePackage

Parameter Description

featureStateDualAntDlPerfPkg A parameter of the MO DualAntDlPerfPkg. Activatesor deactivates the licensed feature Dual-Antenna DownlinkPerformance Package. The value of the attribute is irrelevantwhen no valid license key is installed for the Dual-AntennaDownlink Performance Package.

noOfTxAntennas The number of antennas that can be used for downlinktransmission. A parameter of the MO EUtranCellTDD.

See limitations of this parameter in Parameter and CounterLimitations.

4.2 Affected Parameters

No parameters are significantly affected by the implementation of this feature.

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Network Impact

5 Network Impact

This section describes how Dual-Antenna Downlink Performance Packageimpacts the network functions and capabilities.

5.1 Capacity

Cell Capacity is increased by implementing this feature. This is evident throughthe higher user rates at cell edge using the TXD scheme and at high SINRusing the large delay CDD scheme.

5.2 Coverage

Cell coverage is increased by the use of TXD scheme available in bothtransmission modes. This enables an increase of SINR, which allows users tomaintain sessions at higher path loss from the RBS.

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Associated Features

6 Associated Features

This section describes how the Dual-Antenna Downlink Performance Packagefeature affects other features and functions.

6.1 Prerequisite Features

There are no prerequisite features required for this feature to work properly.

6.2 Affected Features

No features are affected by this feature.

6.3 Affected System Functions

No system functions are affected by this feature.

6.4 Related Features

No other features are related to this feature.

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Performance

7 Performance

This section describes performance indicators, counters, and events associatedwith the Dual-Antenna Downlink Performance Package feature.

7.1 KPIs

No Key Performance Indicators (KPIs) are associated with the Dual-AntennaDownlink Performance Package feature.

7.2 Counters and Events

The important counters and events associated with this feature are listedin the following table:

Table 4 Dual-Antenna Downlink Performance Package Counters

Counter Description

pmRadioTxRankDistr The transmission mode / rank distributions gives moredetailed information on how much each transmission modeand rank is used.

pmRadioUeRepRankDistr The reported rank distribution indicates the rank of UE thatare in open and closed loop spatial multiplexing mode,where rank is reported.

pmRadioUeRepCqiDistr The reported CQI value from UE in a distribution.

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O&M Information

8 O&M Information

The Dual-Antenna Downlink Performance Package feature is activated witha license. For full details of the license activation process, refer to LicenseManagement.

Note: If this feature is deactivated, the change will only take effect afterthe affected cells have been manually locked and unlocked usingAdminState. Alternatively, the eNodeB can be restarted.

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toc1 Introduction1.1 Basic Characteristics1.2 Dependencies and Associated Features2 Feature Overview2.1 Benefits2.2 Impacts2.3 Further Information3 Feature Operation Details3.1 Network Configuration Requirements3.2 High Level Flow Chart3.3 Process Steps3.3.1 Configuration of UE Channel State Information3.3.2 Downlink Scheduling and Link Adaptation3.3.3 Layer 1 Processing4 Parameters4.1 Introduced Parameters4.2 Affected Parameters5 Network Impact5.1 Capacity5.2 Coverage6 Associated Features6.1 Prerequisite Features6.2 Affected Features6.3 Affected System Functions6.4 Related Features7 Performance 7.1 KPIs7.2 Counters and Events8 O&M Information

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Dual antenna downlink performance package.pdf