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Nokia Customer Confidential

1 2006 Nokia AMR_Presentation_2006_02_09.ppt / TAl

AMR IMPLEMENTATION

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AMR - Adaptive Multi rate Codec

Objectives

This section gives a detailed description of Adaptive Multi Rate (AMR). It

explains the basics of AMR, the HW and SW requirements to run it in the

network, packing and unpacking, parameters, and some optimization

guidelines.

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Before & After AMR

Before AMR the GSM operator had available on the air interface:

2 different Channel Type (Full Rate & Half Rate)

2 different channel Coding (1 @ Full Rate & 1 @ Half Rate)

With the introduction of AMR the GSM operator have the same channel types but with moreimproved coding schemes on the air interface:

2 Different Channel Type (Full Rate / Half Rate)

14 Different Channel Coding (8 @ Full Rate & 6 @ Half Rate)*

The reason of the introduction of 2 different Channel Type is

Exploit where possible the capacity of the TRX

Cope w/ temporary increase of the traffic

The reason of the 14 different Channel Coding is to use in every moment of the conversation thebest trade off between Channel Coding and Speech Coding.

Increased Speech CodingIncreased Voice Reconstruction Accuracy

Increased Channel CodingIncreased RobustnessGood FER in poor C/I environment

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AMR Idea

The AMR idea is based on the fact that in soft limited RF environments (poor C/I)

Speech coding can be decreased in order to improve channel coding

Overall result is an improved voice quality (in terms of FER)

For AMR, the speech and channel coding data rates are dynamically adapted to

best fit the current RF channel conditions.

AMR consists on a family of codec with different Channel Coding operating in GSM Full

Rate (FR) and Half Rate (HR). The aim is to improve channel (FR/HR) quality by adaptingthe most appropriate channel codec based on the current radio conditions.

With AMR, the speech capacity is increased by using the half rate (HR) mode and still

maintaining reasonable voice quality.

The idea behind the AMR codec concept is that it is capable of adapting its operation

optimally according to the prevailing channel conditions.

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AMR Codec

GSM FR/EFR channel gross bit-rate is22.8 kbps in GSM FR/EFR:

13 kbps speech coding

9.8 kbps /channel coding

Note that HR channel gross bit rate 11.4

kbps

For AMR case, different codec use

different bit rate to encode speech

(source coding). The rest of the gross

bit-rate is used for channel protection

0

5

10

15

20

25

FR

12.2

FR

10.2

FR

7.95

FR 7.4 FR 6.7 FR 5.9 FR

5.15

FR

4.75

HR

7.95

HR 7.4 HR 6.7HR 5.9 HR

5.15

HR

4.75

AMR codec mode

Channelbit-rate

(kbit/ Channel coding

Speech codingRobustness

Speech

Qual

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AMR CodecsChannel

mode

Channel

codec

Mode

Source coding

bit-rate, speech

Net bit-

rate, in-

band

channel

Channel

coding

bit-rate,

speech

Channel

coding

bit-rate, in-

band

CH0 -FS 12.20kbit/s (GSMEFR**) 0.10 kbit/s 10.20 kbit/s 0.30 kbit/s

CH1 -FS 10.20 kbit/s 0.10 kb it/s 12.20 kbit/s 0.30 kbit/s

CH2 -FS 7.95 kbit/s 0.10 kbit/s 14.45 kbit/s 0.30 kbit/s

TCH/FR CH3 -FS 7.40 kbit/s (**)- 0.10 kbit/s 15.00 kbit/s 0.30 kbit/s


CH5 -FS 5.90 kbit/s (**) 0.10 kbit/s 16.50 kbit/s 0.30 kbit/s


CH7 -FS 4.75 kbit/s (**) 0.10 kbit/s 17.65 kbit/s 0.30 kbit/s

CH8 -HS 7.95 kbit/s (*) 0.10 kbit/s 3.25 kbit/s 0.10 kbit/s

TCH/HR CH9 -HS 7.40 kbit/s (**)- 0.10 kbit/s 3.80 kbit/ s 0.10 kbit/s

CH10- HS 6.70 kbit/s 0.10 kbit/s 4.50 kbit/s 0.10 kbit/s

CH11 - HS 5.90 kbit/s (**) 0.10 kbit/s 5.30 kbit/s 0.10 kbit/s

CH12- HS 5.15 kbit/s 0.10 kbit/s 6.05 kbit/s 0.10 kbit/s

CH13- HS 4.75 kbit/s (**) 0.10 kbit/s 6.45 kbit/s 0.10 kbit/s

Table: Channel and speech codec modes for AMR

(*) Requires 16 kbit/s TRAU. Therefore it is not seen as a feasible codec mode

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AMR Benefits

Improved BCCH plan AMR-FR allows to tighten the BCCH reuse, going from 4/12 to 3/9 reuse schemes.

This is, however, not applicable when EFR terminals are significant

Benefits in Mixed EFRAMR traffic networks

EFR MSs can benefit from the utilization of more aggressive power control settings

for AMR MSs, as it reduces the overall interference in the network

AMR HR speech quality is significantly better than GSM HR and comparable

with GSM FR in good link conditions

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Algorithms Related to AMR

Codec Mode Adaptation Algorithm = Link Adaptation Algorithm It select the best codec

Channel Mode Adaptation Algorithm

It changes the channel rate between FR and HR codec.

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Codec Mode (Link) Adaptation

Codec Mode Adaptation or Link Adaptation (LA) is the algorithm that selects which codec

has to be used each moment by the MS (in UL) or by the network (in DL direction).

The basic AMR codec mode sets for MS and BTS are provided by BSC via layer 3signalling

Both the MS and the network implement their own independent LA algorithms

There are two link adaptation (LA) modes:

ETSI specified fast LAInband codec mode changes on every other TCH frame = 40msec

Nokia proprietary slow LA Changes only every SACCH frame interval = 480 msec

The suggested LA rate is the fast one.LA algorithms are vendor dependant / proprietary

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Codec mode information is transmitted inband in the speech TCH, using parts of the transmission capacity dedicated to speech data

transmission.

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Channel Mode Adaptation

Channel Mode Adaptation is an HO algorithm that aims at select the correctchannel rate (FR or HR).

The selection of the channel rate depends on 2 main factors: load and quality

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AMR SW and HW requirements in NOKIA

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Software & Hardware Requirements

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Codec supported in the NOKIA BTS

Note that the codec supported from the Nokia BTSs depends from the type ofBTS

These are the codec supported from the different NOKIA BTSs

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AMR parameter setting for Channel & Coded Adaptation

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Channel Adaptation - RTSL parameters to

decide

Following the BSC level AMR feature activation and the addition of circuit pool 23,

AMR FR will be functioning on all sites with default parameters settings.

To configure the RTSL for half rate support, the existing FR only configuration

(TCHF) must be changed to Dual Rate (TCHD) depending upon the traffic need and

blocking on the site.

ZERM:BTS=x,TRX=x, CHx=TCHD;

Configure AMR HR Packing triggers. The value depends upon how aggressive we

want to deploy HR. The setting shall be in accordance with traffic/blocking and

average C/I in the area.

ZEEM:HRU=x,HRL=x;

ZEQY:BTS=x,IHRF=x,IHRH=X;

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Channel Adaptation - Packing & Unpacking mechanism

To trigger the packing of active Full Rate AMR calls to AMR Half Rate, traffic and quality

thresholds must be set.

Spontaneous Packing of AMR FR to AMR HR calls is triggered when:

Free full rate resources reduces below the value of the parameter btsLoadDepTCHRate(HRL)

At least 2 calls in which quality is above the amrHandoverFr(IHRF)

Packing continues until the number of free full rate resources increases above the value of the

parameter btsLoadDepTCHRate (HRU).

Spontaneous unpacking of AMR HR calls to AMR FR calls is triggered when the quality of a

AMR HR call degrades below the amrHandoverHr(IHRH). Cell load does not have an effect.

HRL and HRU are set on BSC level but load evaluation is based on individual BTS.

btsspLoadDepTCHRate (FRL) and (FRU) are BTS specific parameters. They have priority

over btsLoadDepTCHRate (HRL) and (HRU)

The feature is disable when set HRL > HRU or FRL > FRU

Real network behavior shows that if FRL > FRU, but HRL < HRU, the AMR feature is enabled

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Channel Adaptation - Packing & Unpacking mechanism

Example:

HRL = 40%

HRU = 60%

IHRF = 2 IHRH = 4

Packing starts when free FR resources below 40% and calls with RxQual below 2, and stops

when free FR resources above 60%

Unpacking when HR calls RxQual below 4

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Codec Adaptation - Parameters to decide

The parameters "amrConfigurationFr: codecModeSet" (FRC) &

"amrConfigurationHr: codecModeSet" (HRC) determine the set of codecs in

use.

Dynamic code adaptation is based on C/I estimation. Threshold and hysteresis:

FRTx: AMR FR threshold x amrConfigurationFr: thresholdx, with x=1,2,3

FRHx: AMR FR hysteresis x amrConfigurationFr: hysteresisx, with x=1,2,3

HRTx: AMR HR threshold x amrConfigurationHr: thresholdx, with x=1,2,3

HRHx: AMR HR hysteresis x amrConfigurationHr: hysteresisx, with x=1,2,3

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HO and PC in AMR

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HO and PC in AMR environment HOC and POC is done based on RX quality Following actions are taken based on Rx quality

cases of PC & HO algorithms in BSC:

If the quality is below lower thresholds then PC (more power) or HO is triggered depending on the current threshold values. Otherwise if quality is above lower thresholds, nothing is done.

Respectively, if the quality is above upper thresholds then PC (less power) is triggered. Otherwise if

quality is below upper thresholds, nothing is done.

Above cases are valid only in quality HO, not for example in PBGT HO.

New RxQual HO thresholds are specified for FR and HR AMR and they are taken into accountwhen making intra-cell handovers between FR AMR and HR AMR:

Intra HO threshold Rx Qual for AMR FR

Intra HO threshold Rx Qual for AMR HR

Current Nx and Px values of RxQual thresholds are used. Where Px is the number of averages and Nx isthe averages to be taken into account.

All the information (codec usage and quality) goes to BSC statistics part for further

processing.

Intra cell Handover process ( FR to HR packing ) is based upon BTS load , call quality and

current codec being used as shown in the next slide.

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AMR Intracell HO

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ICMI HRI and HRS Parameter Impact on Codec Usage

and Voice Quality

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Voice Quality To ensure better Voice Quality it is important that in HR we start with the 2nd most

robust codec. By default HR starts with the most robust codec

Implicit rule provided in 3GPP 45.009:

If the codec mode set contains 1 mode, it is the Initial Codec mode

If the codec mode set contains 2 or 3 modes, the Initial Codec mode is the most robust mode of the

set with the lowest bit rate.

If the codec mode set contains 4 modes, the Initial Codec mode is the second most robust mode of

the set with the second lowest bit rate.

To manually assign which codec to use in the initial assignment you need to change

the BTS parameter (ICMI) HRI. Then change the HRS parameter.

(ICMI) HRI = AMR HR INITIAL CODEC MODE INDICATOR (ICMI)

0 = Initial codec mode is defined by the implicit rule provided in GSM 05.09 (3GPP 45.009)

1 = Initial codec mode is defined by the Start Mode field (HRS)

HRS = AMR HR START MODE

HRS Range => 00, 10, 10, 11 => Codec Mode 1, 2, 3, & 4

Proposed Values for AMR HR: ICMI HRI = 1 and HRS = 01

Impact => reduced AHS 4.75 codec usage.

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AFS 4.75 Codec Usage

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MAXCAP

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MaxCap Feature MaxCap feature was designed during the MaxCap project in Miami back in 2H2004

It was observed that when inter cell handover and unpacking is triggered, and there is no

suitable target cell, the call remains in HRthe call does not unpack . As a result Voice

Quality of HR call may become worse and customer will experience bad speech quality

The Max Cap feature can be activated/deactivated from CD 3.0 onwards and the default

value is ON (unpacking allowed).

Note that when Max Cap feature is ON unpacking is allowed in the specific condition

described above. Therefore, we expect more number of intra cell HOs (depending upon

quality threshold,nx/px) and this increases the probability of dropping calls

Its very important to reduce the number of packing/unpacking to avoid ping-pong and intra

cell handovers in bad radio conditions that result in drop calls

Deactivating the MAXCAP feature reduces the number of unpacking attempts and under

certain parameter settings can totally disable unpacking.This will prevent unpacking in bad

radio conditions (albeit there is no unpacking with MAXCAP = OFF)

NOTE: In S11.5 there are improvements to AMR that will decrease the probability of dropping

during packing and unpacking.

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MaxCap Behavior (OFF)

If quality HO is triggered without a suitable target cell, the call will stay in HR

and will not unpack.

Case 1:

If HoThresholdsQualUL (quality HO) = amrHandoverHRintraHOthresholdRXQual

(unpacking), then the call will never unpack if there is no suitable neighbor

Case 2:

If HoThresholdsQualUL (quality HO) >

(amrHandoverHRintraHOthresholdRXQual(unpacking),

(e.g. 6 > 5) the call will unpack only if the RXQUALITY does not go higher than the

value set for unpacking. Otherwise the call will not unpack.

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MaxCap OFF Case 1

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MaxCap OFF Case 2a

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MaxCap OFF Case 2b

M C B h i (ON)

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MaxCap Behavior (ON)

If quality HO is triggered and there are no suitable target cells, the call will

unpack.

M C ON C 1

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MaxCap ON Case 1

M C ON C 2

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MaxCap ON Case 2a

M C ON C 2b

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MaxCap ON Case 2b

DCR8C vs Traffic at 100% HR

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DCR8C vs Traffic at 100% HR

UL FER vs Traffic with 100% HR

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UL FER vs Traffic with 100% HR

Recommendation and Future Enhancements

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Recommendation and Future Enhancements

Based on the results of the tests conducted with the MaxCap feature it is

generally recommended to be switched off.

As of today enhancements are being studied and evaluated to improve the

MaxCap feature and bring more significant benefits to the customer.

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AMR Parameter Overview

AMR BSC parameters

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AMR BSC parameters

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Radio Link Timeout (RLT) in AMR

RLT Background

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RLT Background

3GPP 05.08 states that Radio Link Failure (RLF) in the MS is determined by the

success rate of decoding messages on the downlink SACCH

The aim of determining RLF in the MS is to ensure that calls with unacceptable

voice/data quality, which cannot be improved either by RF power control or

handover, are either re-established or released in a defined manner

The Radio Link Timeout (RLT) parameter controls that a forced release (drop) will

not normally occur until the call has degraded to a quality below that at which the

majority of subscribers would have manually released it

The RLF procedure is implemented in the RRM at the BSC and is as follows:

After the assignment of a dedicated channel a counter is initialized to RLT

When a SACCH message is unsuccessfully decoded the counter is decreased by 1

When a SACCH message is successfully decoded the counter is increased by 2 If the counter reaches 0 a RLF is declared Call is released

Reliability of RLT in AMR

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Reliability of RLT in AMR Said that:

RLT is based on SACCH deletion

SACCH dont use a dynamic codec like voice in AMR

The conclusion is that

RLT is not anymore a reliable

Or at least is not reliable using the same EFR value

Using the EFR RLT value an AMR customer can have the call dropped because RLT = 0

when still the FER is good

Note that:

Nokia is implementing only 1 RLT (UL = DL)

Currently, there is only 1 RLT for both EFR and AMR MS. However, we are bringing

separate RLT for EFR and AMR in the future.

Conclusion:

When AMR customers are in the market RLT need to be increased

EFR customers w/ increased RLT due to AMR

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EFR customers wont be negatively effected from increased RLT

The only effect that is visible is a possible decrease in the (Dropped Call Ratio)

DCR due to the fact that, possibly, due to the longer RLT some customer will

close the conversation will the system will release it. Note that these cases

should be pretty rare due to the fact that the cases where the UL link is still

available (RLT > 0) and the DL link is not available (RLT = 0) are rare.

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AMR & Soft Channel Capacity feature (S11.1)

Soft Channel Capacity to help AMR deployment

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p y p p y

In S11, Nokia has introduced the Soft Channel Capacity Feature that allows us

to define all the RTSL in the BSS as Dual Rate.

We can define twice as many TCHs but the actual HW limit remains the same.

There can be 4096 actual installed TCHs but we can define 8192 TCHs and use

only 4096 at the same time.

BSC Capacity Roadmap

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p y p

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AMR Optimization Warnings

AMR Optimization Warnings (1/2)

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It should be noted that the impact to BSC capacity for each dual rate timeslot is

double the impact of a full-rate-only RTSL. This impact is seen in the maximum

number of RTSLs that may be attached to a BCSU (max. 512 = 64 FR TRXs per

BCSU).For this reason, only a limited number of radio timeslots should be

configured as Dual Rate if you do not have the Soft Channel Capacity feature.

In mixed configurations (DR and FR), DR time slots are the last to be allocated FR

traffic. This avoids filling up the valuable DR slots with FR only traffic.

This priority of allocating FR only timeslots overrides the TRP preference defined for

the cell. (i.e. if TRP prefers BCCH but all BCCH timeslots are DR while Hopping

timeslots are FR, FR calls will be assigned to hopping layer first), HR time slots are

allocated based on load thresholds.

Deactivate MaxCap Feature if you are using AMR HR. Until improvements to AMRbecome available with S11.5 it is mandatory that we do not use MaxCap so that

drops due to unpacking do not increase.

AMR Optimization Warnings (2/2)

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Aggressive PC settings shall be used for higher capacity gain where as for

better speech quality conservative PC setting shall be used.

HR shall be used aggressively in well planned dense urban areas where C/I is

good and traffic is very high whereas in rural area FR shall be preferred and

HR shall be used conservatively based on traffic loads

Drive Test Survey: Example of codec

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utilisation

.

DL utilisation:

Codec 12.2 - 57%

Codec 7.48%

Codec 5.918%

Codec 4.7517%

April 2005

MOS Sample Distribution

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April 2005

Nokia AMR Terminals 2004examplesadd new terminals

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All new Nokia volume phones from P3/2004 onwards include

AMR

3200

5140

62206230

6810

7200

6820

9500

Thank you!

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Thank you!

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