USER DESCRIPTION 286/1553-HSC 103 12/15 Uen C

User Description, Adaptive Multi Rate WideBandCopyright

Copyright Ericsson AB 2009-2010. All rights reserved.

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Contents

1 Introduction1.1 General1.2 Main Changes in Ericsson GSM System BSS G10A1.3 Main changes in Ericsson GSM system BSS 09A 2

Capabilities

3

Technical Description

3.1 General3.2 Codec Mode Adaptation for AMR-WB3.3 Setup Procedures3.4 Change of Channel3.5 Packing and Optimization Features3.6 Fallback to Narrowband for TFO3.7 AMR-WB/TFO Impact on TRA R6, R6B and R73.8 AMR-WB Impact on SCTRAP3.9 SQI for AMR-WB3.10 Related Statistics 4

Engineering Guidelines

5

Parameters

5.1 Main Controlling Parameters5.2 Parameters for FER5.3 Parameters for Special Adjustments5.4 Value Ranges and Defaults Values 6

7

Concepts

Glossary Reference List

1 Introduction

1.1 General

Adaptive Multi Rate WideBand (AMR-WB) is a speech and channel codec for full rate GERAN channels and UTRAN defined by 3GPP and ITU-T, with four different codec types. The AMR-WB codec type described in this document is the GERAN GMSK codec type, known as FR_AMR-WB according to the specifications. In the document this codec type will be referred to as AMR-WB.

By adapting the codec rate to the radio conditions the speech quality is enhanced. At low C/I, a large amount of channel coding is applied and less speech coding. When the C/I increases the speech coding is increased and the channel coding is decreased.

AMR-WB requires support in all network nodes, that is MSC/MGw, BSC, BTS and MS. AMR-WB is supported when all TRXs within one channel group are AMR-WB capable.

1.2 Main Changes in Ericsson GSM System BSS G10A

- It is no longer necessary to have support for AMR-WB in the whole cell or subcell. The BSC can now set up AMR-WB as soon as all TRXs within one channel group support AMR-WB.

1.3 Main changes in Ericsson GSM system BSS 09A

Impact from A-Interface over IP introducing TrFO added.

2 CapabilitiesThe feature AMR-WB offers a significant improved speech quality compared to the previously existing codecs.

AMR-WB is supported on TRA R6, TRA R6B and TRA R7 and by all PPC-based transceivers.

3 Technical Description

3.1 General

The AMR-WB speech codec algorithm is standardized in both 3GPP and ITU-T with 9 different encoding bit rates, ranging from 6.6 up to 23.85 kbps. For speech telephony services only five of these nine modes are allowed in 3GPP, for GMSK modulation only the three lowest modes, 6.6, 8.85 and 12.65 kbps are allowed. These 3 codec modes are also known as Configuration set 0 according to Reference [13].

The bandwidth of the analogue input and output signal for AMR-WB will range from 100 Hz to 7000 Hz (for narrowband codecs the bandwidth used range from 300 Hz to 3400 Hz). The extended lower spectrum brings volume and quality while the extended higher spectrum brings clarity and transparency to the speech signal. Together it provides a well-balanced speech signal with substantially higher quality.

Since there is no PCM encoding standard for AMR-WB the speech must be sent compressed throughout the network. This is achieved by means of Tandem Free Operation (TFO) and Transcoder Free Operation (TrFO) for both 2G and 3G networks. As a consequence, all nodes involved in an AMR-WB call from one subscriber to another, must have support for AMR-WB, that is MSs, BTSs, BSCs, MGws and MSC servers. Principles and prerequisites for TFO can be found in Reference [1] and for TrFO in Reference [11].

TFO avoids transcoding the speech but needs the transcoder hardware in the path, while TrFO does not have the transcoder hardware in the path.

A new transcoder pool is added to group all AMR-WB capable transcoder resources for TFO. This new pool will coexist with the previously existing pools.

3.2 Codec Mode Adaptation for AMR-WB

In normal, tandem operation both radio channels are totally independent from each other. This means that codec mode adaptation is done separately in respective radio channel, see Reference [2].

For AMR-WB, that use TFO and TrFO to transport the digitally encoded speech, the optimal codec mode must be suitable to both radio channels, the local uplink and the distant downlink radio channel and vice versa. The channel

with the highest error rate (or smallest capacity) determines the highest possible codec mode. The codec mode used in one direction may however be different from the one used in the other direction.

The principle for codec mode adaptation in TFO and TrFO mode is simple. The radio receivers (for example the local uplink BTS receiver and the distant downlink mobile receiver) estimate the observed radio quality and determine the optimal codec mode. The final codec mode to be used is achieved by taking the minimum of both. The distant mobile sends therefore its codec mode request uplink and this is transferred all the way back to the local BTS. The local BTS takes the minimum of the distant codec mode request and its local codec mode decision and sends the result downlink to the local mobile to be used on the local uplink. The result is also sent to the distant BTS. The selected codec mode will now also be used on the distant downlink radio channel.

This mechanism works symmetrically, but independently in both directions of the speech conversion. This means that the codec mode used in one direction can be different to the codec mode used in the other direction.

3.3 Setup Procedures

3.3.1 Definition of the AMR-WB codec set

The codec set to be used for AMR-WB, together with decision thresholds and hysteresis values, is sent from the BSC to the BTS and MS at setup and handover. In Ericsson BSS only one codec set for AMR-WB is supported, see Table 1 below.

Table 1 AMR-WB Codec Set (= Configuration set 0 according to TS 26.103)

CODEC_MODE_1 6.60 kbpsCODEC_MODE_2 8.85 kbpsCODEC_MODE_3 12.65 kbps

The decision threshold and hysteresis values are settable with the MML command RLADC.

3.3.2 Initial Codec Mode Selection at Call Setup and Handover

The Initial Codec Mode (ICM) to be used at call setup and after handover is sent from the BSC to the BTS and the MS. The initial codec mode is settable with the MML command RLADC.

3.4 Change of Channel

For AMR-WB connections it is possible to decide if, after the first assignment, AMR-WB should be prioritized at change of channel or not, for example at handover. This functionality is also supported for all other speech versions, see Reference [3]. The parameter AMRWBSPVERUSE controls this for AMR-WB connections.

3.5 Packing and Optimization Features

Due to big difference in speech quality between AMR-WB and the half rate codecs it is possible to disable packing and optimization features for calls using AMR-WB. The parameter AMRWBPRIO is used to control the following packing and optimization features for AMR-WB calls only:

DYMA (FR to HR adaptations)

TCH Optimization

Abis Packing

Cell Load Sharing

Subcell Load Distribution

By default the features above will be enabled for AMR-WB connections. This means that an ongoing AMR-WB call can be handed over to a narrowband codec thus impacting speech quality.

If DYMA is used for AMR-WB calls, that is the parameter AMRWBPRIO is set to enable the features above, the parameter AMRWBDYMAPRIO can be used to prioritize AMR-WB calls in favour for AMR FR calls, meaning that AMR FR calls will be moved to half rate before AMR-WB calls.

The list above does not include the Dynamic HR Allocation (DHA) feature nor the DHA part of the Abis Triggered HR Allocation (ATHABIS) feature. It is possible to disable the DHA features for the AMR-WB capable MSs. Thresholds for cell (DTHAMRWB) and Abis load (DHRAABISTHRWB and SDHRAABISTHRWB) are available, see also Reference [12]. Based on these it shall be decided when to prefer a HR channel for the AMR-WB capable MSs. The optional feature Dynamic Half Rate for AMR-WB, is used to be able to decide whether the DHA features

shall be applied to AMR-WB capable MSs or not. Based on the value of the parameter AMRWBDHA, the DHA features shall be applicable to the AMR-WB MSs both at call set up and handover (2), only at call set up (1) or not performed at all (0). Note that even with DHA disabled there will still be times when HR TCHs will be selected for AMR-WB capable MSs.

3.6 Fallback to Narrowband for TFO

For TFO, if AMR-WB can not be established end to end or AMR-WB can not be provided anymore for an ongoing call, for example due to a distant handover that moves the call to a transcoder that does not support AMR-WB, it will be possible to move the call to a narrowband codec, via an intra-cell handover. This functionality is controlled by the parameter AMRWBFB. One reason for the fallback to narrowband is that when AMR-WB is used by only one party in the call, the speech will be sent in narrowband quality. Another reason is to free these TRA resources so that they can be used only when it is possible to establish AMR-WB end to end.

3.7 AMR-WB/TFO Impact on TRA R6, R6B and R7

The support of AMR-WB for TFO will lead to a reduced number of available channels per transcoder board. Table 2 belows shows the capacity for the different transcoder types supporting AMR-WB.

Table 2 AMR-WB/TFO Impact on different transcoder types

TRA R6 TRA R6B TRA R7Tandem Operation (GSM FR, GSM HR, EFR, AMR FR, AMR HR)

192 192 384

TFO for EFR, AMR FR, AMR HR 128 192 384AMR-WB 64 128 256

3.8 AMR-WB Impact on SCTRAP

The capacity identified for the different transcoder types with AMR-WB support, will also have an impact on the SCTRAP feature. The smallest unit that can be reconfigured for use in a different pool is called a MUX group. In Tandem Operation each MUX group always consists of 24 transcoder resources regardless transcoder type. With AMR-WB activated, all TRA resources that belongs to the AMR-WB pool will instead have MUX groups that consists of 8 (TRA R6) or 16 transcoder resources (TRA R6B and TRA R7).

The differentiation is considered during reconfiguration decisions; to calculate number of MUX groups that need to be configured, and after successful reconfiguration, to correctly update the parameter RNOTRA (Required Number Of TRAnscoder resources) used by the MML-command RRTPC. See also Reference [4].

3.9 SQI for AMR-WB

AMR-WB will use a new SQI scale, aligned with the commonly used 5-grade MOS scale, in the range of 1.0 to 5.0 (with 0.1 resolution), instead of -20 to 30 dBQ for the other codecs. This is to adapt to the ITU-T standard P.800, which is commonly used in the speech quality industry.

For AMR-WB there are two thresholds in DL and UL respectively, to classify the SQI values into Good, Acceptable and Bad. These new thresholds will be expressed in the scale 1.0 to 5.0 and thus separate from the dBQ SQI scale.The new threshold values will be 3.0 and 3.5, meaning that speech less than 3.0 will be classified as Bad, speech less than 3.5 will be classified as Acceptable and speech equal to or better than 3.5 will be classified as Good.

The AMR-WB SQI is presented in the Mobile Traffic Recording (MTR) and Cell Traffic Recrording (CTR).

3.10 Related Statistics

3.10.1 Impact on Legacy Counters

AMR-WB will have an impact on legacy counters. All counters that are stepped when a FR channel is used, independent speech version, will also be stepped for an AMR-WB connection.

3.10.2 Statistics for Performance Management

There are a number of STS counters defined for AMR-WB, such as:

New SQI counters that belong to the existing object types CELLSQI and CELLSQIDL.

New SQI counters that belong to the existing object types CHGRP0F and CHGRP0SIQ.

Codec mode utilization counters (uplink and downlink) that belong to the new object type CLTCHFV5C.

FER counters that belong to the existing object type CELLFERF and the new object type CELLAWFER.

Dropped call counters that belong to the new object type CLTCHDRAW.

Traffic level counters that belong to the new object type CLTCHFV5.

One new counter for successful DTM establishment that belong to the existing object type CLDTMEST.

New counters for FR/HR mode adaptation that belong to the existing object type CLRATECHG.

One new counter for transcoder pool resource registrations that belong to the existing object type TRAPCOM.

More information on counters can be found in Reference [5].

4 Engineering GuidelinesThis section is written when the FOA test is performed.

5 Parameters

5.1 Main Controlling Parameters

AMRWBSUPPORT is used to activate AMR-WB support in the BSC.

AMRWBFB controls the fallback solution, see Section 3.6. The parameter is set per BSC.

AMRWBPRIO controls optimization features for AMR-WB, see Section 3.5. The parameter is set per BSC.

AMRWBDYMAPRIO controls the prioritization of AMR-WB when DYMA is active, see Section 3.5. The parameter is set per BSC.

AMRWBSPVERUSE controls prioritization of AMR-WB during change of channel, see Section 3.4. The parameter is set per BSC.

AMRWBDHA controls the use of the DHA features for AMR-WB capable MSs, see Section 3.5. The parameter is set per BSC.

See also Table 3 below.

The parameters are further described in Reference [6].

5.2 Parameters for FER

HIGHFERDLAWB is a threshold value for high FER in downlink. Filtered FER measurements are compared to this threshold to evaluate urgency conditions. The parameter is set per BSC.

HIGHFERULAWB is a threshold value for high FER in uplink. Filtered FER measurements are compared to this threshold to evaluate urgency conditions. The parameter is set per BSC.

See also Table 4 below.

The parameters are further described in Reference [6].

5.3 Parameters for Special Adjustments

BQOFFSETAWB Signal strength corridor for bad quality urgency handover for AMR-WB. This parameter is defined per cell.

QDESDLAWB Desired quality for AMR-WB, downlink. This parameter is defined per subcell.

QDESULAWB Desired quality for AMR-WB, uplink. This parameter is defined per subcell.

QLIMDLAWB Quality limit downlink for handover for AMR-WB. This parameter is defined per subcell.

QLIMULAWB Quality limit uplink for handover for AMR-WB. This parameter is defined per subcell.

QOFFSETDLAWB Offset for quality downlink for AMR-WB. This parameter is defined per subcell.

QOFFSETULAWB Offset for quality uplink for AMR-WB. This parameter is defined per subcell.

RLINKTAWB Radio link time-out on downlink for AMR-WB. This parameter is defined per cell.

RLINKUPAWB Radio link time-out on uplink for AMR-WB. This parameter is defined per cell.

SSDESDLAWB Desired signal strength for AMR-WB, downlink. This parameter is defined per subcell.

SSDESULAWB Desired signal strength for AMR-WB, uplink. This parameter is defined per subcell.

SSOFFSETDLAWB Offset for signal strength downlink for AMR-WB. This parameter is defined per subcell.

SSOFFSETULAWB Offset for signal strength uplink for AMR-WB. This parameter is defined per subcell.

The parameters are further described in Reference [6], Reference [7], Reference [8], Reference [9] and Reference [10].

5.4 Value Ranges and Defaults Values

Table 3 Main Controlling Parameters for AMR-WB

Parameter Name Default Value Recommended Value

Value Range Unit

AMRWBSUPPORT 0 0 0=AMR-WB not activated 1=AMR-WB activated

-

AMRWBFB 1 1 0=Fallback solution not activated

1=Fallback solution activated

-

AMRWBPRIO 0 0 0=Optimization features allowed

1=Optimization features not allowed

-

AMRWBDYMAPRIO 1 1 0=No prioritization of AMR-WB

1=AMR-WB prioritized

-

AMRWBSPVERUSE 1 1 0=AMR-WB not prioritized at change of channel

1=AMR-WB prioritized at change of channel

-

AMRWBDHA 2 2 0=DHA shall not be performed at all

1=only at call set up 2=both at call set up and

handover

-

Table 4 Parameters for FER

Parameter Name Default Value Recommended Value

Value Range Unit

HIGHFERDLAWB 4 4 0-96 FERHIGHFERULAWB 4 4 0-96 FER

6

7 ConceptsAdaptive Multi Rate WideBand (AMR-WB) Speech and channel codec. In Ericsson BSS capable of operating at gross bit rate of 22.8 kbps.

Channel Rate

The available transmission bandwidth on a traffic channel for speech or data, Full Rate (FR) or Half Rate (HR).

Codec Mode A codec rate used within a codec set is called a codec mode.

Codec Set A set of up to 4 different codec modes using the same channel rate.

MGw Media Gateway, node in the core network, hosting the transcoder for 3G.

Speech Version The variant of the speech encoding algorithm within the same channel rate.

TFO Tandem Free Operation, avoids the transcoding function within the transcoders in the networks but needs the transcoder hardware in the path.

TrFO Transcoder Free Operation, avoids the transcoding function within the networks. Does typically not need the transcoder hardware in the path.

Transcoder A transcoder handles encoding/decoding of speech and rate adaptation of data information between the format used on the A-interface and the Abis interface.

Transcoder Resource A transcoder resource is the transcoder support needed for one connection.

GlossaryAMRAdaptive Multi Rate BSCBase Station Controller BSSBase Station System BTSBase Transceiver Station C/ICarrier to Interference ratio dtquDeci transformed GSM quality units EFREnhanced Full Rate FERFrame Erasure Rate FRFull Rate HRHalf Rate ICMInitial Codec Mode MGwMedia Gateway

MUXMultiplexed device MSMobile Station MSCMobile Services Switching Center PCMPulse Code Modulation PPCPower PC SCTRAPSelf Configuring Transcoder Pools SQISpeech Quality Index STSStatistics and Traffic Measurement Subsystem TFOTandem Free Operation TRATranscoder and Rate Adaptor TRXTransceiver TrFOTranscoder Free Operation WBWideBand

Reference List

Ericsson Documents[1] User Description, Tandem Free Operation. [2] User Description, Adaptive Multi Rate. [3] User Description, Channel Administration. [4] User Description, Self Configuring Transcoder Pools. [5] User Description, Radio Network Statistics. [6] User Description, Radio Network Parameters and Cell Design Data for Ericsson's GSM Systems. [7] User Description, Dynamic BTS Power Control. [8] User Description, Dynamic MS Power Control. [9] User Description, Locating. [10] User Description, Intra Cell Handover. [11] User Description, A-interface over IP. [12] User Description, Channel Allocation Optimization. Standards[13] 3GPP TS 26.103, (GSM Specification) [14] 3GPP TS 28.062, (GSM Specification) [15] 3GPP TS 45.009, (GSM Specification)