adaptive multi-rate (amr)

8/6/2019 Adaptive Multi-Rate (AMR)

1/18

Adaptive Multi-Rate (AMR)

Prepared by:Muhammad Imran Naskani

RF Optimization Consultant


2/18

AMR Feature Overview

Fixed codecs were used for FR (13Kbps), EFR (12.2Kbps) andHR (5.6Kbps) before AMR.

A new Codec mechanism defined by ETSI in GSM Release 98

Able to adapt speech information/speech protection

Mechanism is divided into two parts

Codec Mode Adaptation

Channel Mode Adaptation

Enhanced Voice Quality

B

alanced solution for quality and capacity


3/18

Codec Mode Adaptation: (1/8)

Variable Speech & Channel Coding depending upon C/I

Eight codecs for speech coding in AMR-FR

Five codecs for speech coding in AMR-HR


4/18


List of codecs:

Different number and subset of codecs can be defined

separately for FR and HR calls

Different codec can be used for uplink and downlink within the

same subset during a call

7.95 kbps cannot be used for HR in Alcatel - BSS


5/18


CMA in Uplink:


6/18


CMA in Downlink:


7/18


Threshold Comparison for Codec Adaptation:

These thresholds are configurable at OMC.


8/18


List of Important Parameters for Codec Adaptation:

EN_AMR_FR

EN_AMR_HR

AMR_FR_SUBSET

Bit 8 (most significant)=1: 12,2 kbit/sis part of the subset;

Bit 7=1: 10.2 kbit/sis part of the subset;

Bit 6=1: 7,95 kbit/sis part of the subset;


Bit 4=1:6,70 kbit/sis part of the subset;



Bit 1 (least significant)=1:4,75 kbit/sis part of the subset


9/18


AMR_HR_SUB

SET Bit 8 = Bit 7=0;

Bit 6=1: 7,95 kbit/s is part of the subset; [not supported by Alcatel]

Bit 5=1: 7,40 kbit/sis part of the subset; [not be used as start codec in

HR]




Bit 1 (least significant)=1:4,75 kbit/sis part of the subset

AMR_START_MODE_FR / AMR_START_MODE_HR

0Implicit rule is used for initial codec mode

1Lowest codec mode of the subset2Second lowest codec mode (used only if the subset contains more than

one codec mode)

3Third lowest codec mode (used only if the subset contains more than two

codec modes)

4Highest codec mode (used only if the subset contains four codec modes)


10/18


AMR_FR_THR_1

AMR_FR_THR_2

AMR_FR_THR_3

AMR_FR_HYST

AMR_HR_THR_1

AMR_HR_THR_2

AMR_HR_THR_3

AMR_HR_HYST

The above values are measurement of C/I

Value: 0 30.5 (Step of 0.5)





11/18

Channel Mode Adaptation: (1/5)

Two new handover causes are introduced in AMR: Cause 26 (HR to FR channel adaptation)

Cause 27 (FR to HR channel adaptation)

Works on the measurement of RXQUAL in uplink & downlink

TCH Load is not the prime cause for Cause 26 & Cause 27

If serving cell is not loaded, a call can still be handed over

from AMR-FR to AMR-HR; if RXQUAL is good

If serving cell is loaded, a call can still be handed over from

AMR-HR to AMR-FR; if RXQUAL is bad


12/18


Channel Adaptation Mechanism:


13/18


Cause 26 illustration:


14/18


Cause 27 illustration:

A_QUAL_CA_HR_FR is the averaging window for AMR-HR

to AMR-FR channel reconfiguration

A_QUAL_CA_FR_HR is the averaging window for AMR-FR

to AMR-HR channel reconfiguration


15/18


List of Important Parameters for Channel Adaptation: EN_AMR_CA

THR_RXQUAL_CA_NORMAL

OFFSET_CA_NORMAL

THR_RXQUAL_CA_HIGH

OFFSET_CA_HIGH

EN_INTRA_UL_AMR

EN_INTRA_ DL_AMR

L_RXQUAL_UL_H_AMR

R_RXQUAL_DL_H_AMR

A_QUAL_CA_HR_FR

A_QUAL_CA_FR_HR

RXQual thresholds for Channel

Adaptation when cell is not loaded

RXQual thresholds for Channel

Adaptation when cell is loaded


16/18

TCH Load Evaluation in AMR:

Two new parameters are introduced forLoad Evaluation: THR_FR_LOAD_L_SV3

THR_FR_LOAD_U_SV3

Cell load AV_LOAD() computed from

load samples = NB_BUSY_TS / NB_TS * 100

Calculation ofLOAD_SV3(0):

If previous value ofLOAD_SV3 = false then

IfAV_LOAD > THR_FR_LOAD_U_SV3 then

LOAD_SV3 = true

Else LOAD_SV3 = false

Else (if previous value ofLOAD_SV3 = true then)

IfAV_LOAD


17/18

TCH Allocation in AMR:

New SV3 parameters are used for TCH allocation of AMRsupporting MS on the basis of TCH Load in the cell

Mandatory rule:THR_FR_LOAD_L_SV3


18/18

Questions?

No!....Thanks

adaptive multi-rate (amr)

Documents