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Adaptive Multi-Rate (AMR)
Prepared by:Muhammad Imran Naskani
RF Optimization Consultant
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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
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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
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Codec Mode Adaptation: (2/8)
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
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Codec Mode Adaptation: (3/8)
CMA in Uplink:
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Codec Mode Adaptation: (4/8)
CMA in Downlink:
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Codec Mode Adaptation: (5/8)
Threshold Comparison for Codec Adaptation:
These thresholds are configurable at OMC.
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Codec Mode Adaptation: (6/8)
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 5=1: 7,40 kbit/sis part of the subset;
Bit 4=1:6,70 kbit/sis part of the subset;
Bit 3=1: 5,90 kbit/sis part of the subset;
Bit 2=1:5,15 kbit/sis part of the subset;
Bit 1 (least significant)=1:4,75 kbit/sis part of the subset
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Codec Mode Adaptation: (7/8)
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 4=1:6,70 kbit/sis part of the subset;
Bit 3=1: 5,90 kbit/sis part of the subset;
Bit 2=1:5,15 kbit/sis part of the subset;
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)
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Codec Mode Adaptation: (8/8)
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)
Value: 0 30.5 (Step of 0.5)
Value: 0 7.5 (Step of 0.5)
Value: 0 7.5 (Step of 0.5)
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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
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Channel Mode Adaptation: (2/5)
Channel Adaptation Mechanism:
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Channel Mode Adaptation: (3/5)
Cause 26 illustration:
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Channel Mode Adaptation: (4/5)
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
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Channel Mode Adaptation: (5/5)
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
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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
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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
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Questions?
No!....Thanks
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