Microsoft Power Point - 9 OMF000407 Multiple Rate Algorithm ISSUE2

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Multiple Rate Algorithm

Page2Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.

Objectives

� Upon completion of this course, you will be able to:

� Understand the multiple rate algorithm function and types.

� Master the parameters of multiple rate algorithm.

� Be able to configure the data of multiple rate algorithm.


Full Rate

� Traffic Channel (TCH) carries coded voice data. The full-

rate TCH is initially adopted to carry information at the

gross rate 22.8Kbit/s. The information contains the source

coding rate of 13Kbit/s.

� As technologies develop, the enhanced full rate, half rate,

multiple rate and other coding are introduced.


Circuit Pool Function

� “Circuit pool number” actually represents the circuit type,

indicating the support capability of the voice codec.

� Different circuit pool numbers can support different voice rates.



FR speech version 2；FR data (12, 6, 3.6 Kbps)

HR speech version 1；HR data (6, 3.6 Kbps) 6

FR speech version 1；FR speech version 2

FR data (12, 6, 3.6 Kbps) 5

FR speech version 2；FR data (12, 6, 3.6 Kbps) 4

FR speech version 1；FR data (12, 6, 3.6 Kbps)；

HR speech version 1；HR data (6, 3.6 Kbps)3

HR speech version 1；HR data (6, 3.6 Kbps) 2

FR speech version 1；FR data (12, 6, 3.6 Kbps) 1

Supported RateCircuit Pool Number





HR speech version 1；HR speech version 3

HR data (6, 3.6 Kbps)

27



HR speech version 3

25


HR speech version 3 24

FR speech version 3；HR speech version 323


FR data (12, 6, 3.6 Kbps)；HR speech version 1

HR data (6, 3.6 Kbps)

7

Supported RateCircuit Pool Number


Contents

1. EFR

2. HR

3. AMR


The Function of EFR

� The Enhanced Full Rate (EFR) is a speech coding scheme with

an enhanced full rate. Using this coding scheme, you can provide

services with better speech quality.

� In the wireless communications system, the EFR applies to only

speech services and is irrelevant to data services or signaling

services.

� The EFR function adopts the CELP( Code Excited Linear

Predictive Coding) coding scheme, thus improves the quality of

the speech signal.

� When EFR is adopted, the transmission rate of the speech

signal of an MS on the air interface is 12.2 kbit/s.


EFR Call Set-up Flow

Determine whether the circuit

pool where a call ocuupies the

CIC supports EFR

Common call (FR)

EFR call

Speech version in the

assignment request is EFR

Start

Finish

Yes

No


EFR Call Signaling Processing

BSC

ASS REQ(1)

Channel ACT(2)

Channel ACT ACK(3)

ASS CMD(4)

SABM(5)

UA(6)

EST IND(7)

ASS CMP(8)

ASS CMP(9)

MS MSCBTS


EFR Data Configuration

� In BSC, to support EFR function, it is necessary to configure

the number of the circuit pool in A interface.

� If the half rate and AMR functions are not adopted, the

number of the circuit pool for the EFR function is

recommended to set to 5.

� You can dynamically modify the number of the circuit pool

that the circuits reside on the FTC board. choose BSC �

Dynamic Configuration without Command �Trunk Circuit.

The dialog box is displayed as shown in following slides.





� Click Trunk Circuit.

� The select FTC dialog box is displayed as shown in the following.




Contents

1. EFR

2. HR

3. AMR


The Function of HR

� The half rate voice coding uses a new voice coding

algorithm to reduce the voice coding rate to half that of full

rate voice service. Thus, one physical channel that can

only support one call under the full rate can support two

calls under half rate.

� If the half rate service is used, the voice capacity expands

twice without adding TRXs. By adopting half rate service,

the operator can fully use the current network to expand

the system capacity. This saves the cost and eases the

spectrum use.


The Function of HR

T T T T T T T T T T T S T T T T T T T T T T T T IT

T T T T T T S T T T T T T

T T T T T T T T T T T T S


The Function of HR

� Single：When a timeslot is used as two TCH/H channels, one

TCH/H channel is busy and another is idle. The idle

TCH/H channel is called single channel or channel

fragment or fragment.

Idle Busy


The Function of HR

� Couple：When a timeslot is used as two TCH/H

channels, and these two channels are both free. This

timeslot is called a couple.

Idle Idle

Busy Busy


The Function of HR

I: Idle B：：：：Busy

I B B B B B B BBIB BB B BB

I I B B B B B BBBB BB B BB


Channel Assignment Strategies

� If the half rate function is used, when BSC receives the

“assignment request” from the MSC, it will decides to use the

channel allocation algorithm according to channel assignment

strategy specified in the data configuration.

� MSC channel assignment strategy

� Assign the channel according to the MSC request. If the request from MSC

is "TCHF preferred", assign the full rate channel preferentially. If it is

"TCHH preferred", assign the half rate channel preferentially.

� BSC channel assignment strategy

� When the assignment request sent from MSC is "Full rate TCH preferred"

or" Half rate TCH preferred", BSC assigns the proper channel according to

the availability of idle full rate channel in the cell and the allowance of MSC.


Channel Assignment Strategies

� The BSC channel allocation strategy is the default strategy.

That is, when the network is idle, the full rate is used,

otherwise, the half rate is used.

� For the call that uses the half rate preferentially, the single

channel is assigned preferentially to reduce the fragment.

� If a cell has multiple TRXs, the channels on the TRXs that do

not allow the rate adjustment are assigned preferentially.


Rate Adjustment Flow

� If the channel assignment request is to choose the full rate channel only:

� When there is idle full rate channel, assign the channel directly.

� When there is no idle full rate channel in the cell, but there is idle couple

channel, convert the couple channel to full rate channel and then assign the

converted full rate channel.

� When there is no idle full rate channel and idle couple channel in the cell, but

there is idle single channel, check whether the number of single channel in

the cell is more than one. If yes, initiate intracell handover to form a couple

channel and then convert the couple channel to full rate to assign.

� Otherwise, reject the assignment request.



Yes

Yes

Yes

No

No

No

Assignment request

for TCHF only

Full rate available?

Couple channel

available?

More than one half

rate channel?

Request reject

Assign full rate channel

Convert couple channel to full

rate channel and then assign

the converted channel

Initiate intra-cell handover to

form couple channel, and then

convert the couple channel to

full rate channel to assign

Start

End



� If the channel assignment request is to half rate only :

� When there is idle single channel in the cell, assign the idle half rate channel

on the single channel directly.

� When there is no idle single channel in the cell, but there is idle couple channel

in the cell, assign the idle half rate channel on the couple channel.

� When there is no idle single channel and idle couple channel in the cell, but

there is idle full rate channel in the cell, convert the full rate channel into couple

channel and then assign the idle half rate channel on the couple channel.

� Otherwise, reject the request.



Yes

Yes

Yes

No

No

No

Half rate assignment request

Single channel available?

Couple channel available?

Full rate channel available?

Assignment fails

Assign half rate channel

Assign the half rate channel

on the couple channel

Convert the full rate channel

into couple channel and

then assign the half rate

channel on it

Start

End



� If the channel assignment request is to choose the full rate channel

preferentially:

� When there is idle full rate channel in the cell, assign it directly.

� When there is no idle single channel in the cell, but there is idle couple channel

in the cell, convert the couple channel into full rate channel and then assign it.

� When there is no idle full rate channel and couple channel in the cell, check

whether the number of adjustable half rate channel in the cell is more than one.

If yes, initiate intracell handover to form a couple channel and then convert the

couple channel to full rate to assign

� Otherwise, assign the idle half rate channel on the single channel.



Yes

Yes

No

No

No

Yes

Assign request for full rae preferentially

Full rate available?

Couple channel available?

More than one half rate

channel?

Assign full rate channel

Convert the couple channel

into full rate channel to

assign

Form couple channel by

intracell handover and then

convert couplechannel into

full rate to assign

Start

End

Assign request for full rae preferentially


HR Data Configuration

� First configure the BIE as half rate networking.



� Configure the system information


HR Data Configuration � Configure the parameters for TRX



� Configure whether channel rate is adjustable





� TCH Traffic Thrsh(%)

� Content：During the allocation of BSC channel, if the

occupation rate of the current channel reaches or exceeds this

threshold, the dual rate user is allocated with half-rate channel

preferentially. Otherwise, allocate the full-rate channel

preferentially.

� Value range:0-100

� Recommendation:50



� Enhanced Chan. Convert Enable

� Content：Determines whether to allow handing over the call on

the SINGLE and then trigger the adjustment when converting

half-rate channel into full-rate channel.

� Recommendation: selected





� Chan. Conversion Timer(100ms)

� Content：This timer measures the waiting time for the channel

conversion during call establishment. If the channel conversion

does not complete within the time, the call is cleared and the

timer counts the timeout times.

� Value Range:20-255

� Recommendation:30


Contents

1. EFR

2. HR

3. AMR


The Function of AMR

� The Adaptive Multi Rate (AMR) is a set of multiple voice

Codec algorithms. The BTS and MS can automatically

choose a proper Codec algorithm according to the actual

radio environment to adjust the rate. Thus the voice quality

can be improved. Different Codec algorithm generates

different rate voice code stream.

� The AMR is only used in voice service. It is not used in the

data service or signaling service. Thus, the AMR is not

considered when process the signaling of data service or

signaling service.


The Function of AMR� The core thought is that compromise and balance shall be realized between

the channel coding and source coding in sharing the bandwidth of wireless air

interface (the full rate channel 456/20 = 22.8Kbit/s, and the half arte channel

is at 11.4Kbit/s).

� When interference increase is detected at the network side and it exceeds a

certain threshold, the voice coding rate will be reduced automatically. In other

words, some useful voice information is removed. The redundancy of voice

coding is added on condition of the unchanged transmission bandwidth. As a

result, distortion of the voice recovered at the receiver side may rise. The

error rate falls because elements for error check and correction increase. It

prevents the voice quality from deteriorating sharply.

� The AMR coder selects one from multiple rates in real time according to the

channel type (full rate or half rate). By so doing, the optimal combination of

the voice coding and channel coding to satisfy the transient wireless channel

condition and local capacity requirement.


AMR

� The core functions of the AMR are to provide multiple voice Codec

algorithms and automatically choose of voice coding rate according to

radio communication quality.

� Full Rate AMR

It supports full rate channel AMR voice coding and decoding and includes

8 voice rates: 12.2k (GSM EFR), 10.2k, 7.95k, 7.40k (IS-641), 6.70k,

5.90k, 5.15k, 4.75k;The full rate AMR can adjust the coding rate according

to the radio quality indication (RQI). The coding rate is adjusted in the

active coding set (ACS).

� Half Rate AMR

It supports half rate channel AMR voice coding and decoding and includes

5 voice rates: 7.40k (IS-641), 6.70k, 5.90k, 5.15k, 4.75k;The half rate

AMR can adjust the coding rate according to the radio quality indication

(RQI). The coding rate is adjusted in the ACS.


E xpe r im e nt 1 a - Te s t R e s ults

1.0

2.0

3.0

4.0

5.0

C o n d i t i o n s

M O S

EFR

12.210 .2

7.95

7.46.7

5.95.15

4.75

EFR 4.01 4 .01 3 .65 3 .05 1.53

12 .2 4.01 4 .06 4 .13 3 .93 3 .44 1.46

10 .2 4.06 3 .96 4 .05 3 .80 2.04

7.95 3.91 4 .01 4 .08 3 .96 3.26 1 .43

7.4 3.83 3 .94 3 .98 3 .84 3.11 1 .39

6.7 3.77 3 .80 3 .86 3.29 1 .87

5.9 3.72 3 .69 3.59 2 .20

5.15 3.50 3 .58 3.44 2 .43

4.75 3.50 3 .52 3.43 2 .66

No Er rors C/I=16 dB C/I=13 dB C/I=10 dB C/I= 7 dB C/I= 4 dB C/I= 1 dB

MOS (Mean Opinion Score)

AMR


AMR Call Set Up Process

Y

Deciding whether to assign

channel that supports AMR

function

Finishes AMR call set up

Deciding whether to

support AMR functionNormal Call

N

BSC receives the assigning

request sent by MSC

Y

NNormal Call


AMR Channel Allocation and Rate Adjust

� When the call is just set up, the rate configured in “starting

mode” will be adopted.

� MS/BTS automatically adjust the current voice codec rate

based on a certain algorithm and the RQI.

� In AMR, the number and range of adjustable rates depend

on the activated code set. In accordance with the protocol, 4

activated code sets at most can be supported.



� The AMR coding rate adjustment means the coding rate is

judged and adjusted based on the MS reported RQI (call

carrier-to-interference ratio).

� When RQI is high, it will be adjusted to a high rate. When

RQI is low, it will be adjusted to a low rate.



CODEC_MODE_4

CODEC_MODE_3

CODEC_MODE_2

CODEC_MODE_1

C/I

THR_1 + HYST_1 = THR_MX_Up(1)

THR_1 = THR_MX_Dn(2)







� When MS responds to uplink AMR rate adjustment, it should be the

next voice frame if possible, and not more than three voice frames.

� If rate adjustment crosses the code set, for example, adjustment

from coding rate 1 to coding rate 4, MS continuously adjusts rates. It

adjusts the rate to coding rate 2, then to coding rate 3, and finally to

coding rate 4. There are two voice frames in each process.

� When BS responds to downlink AMR rate adjustment, the rate must

be adjusted in the earliest voice frame, unless BS is under network

control, and MS request need be ignored.



� Normally, AMR rate is adjusted step be step. However, it is

adjusted by leaping over steps in the following cases:

� Handover: After handover is completed, MS uses the initial

coding rate, regardless of the coding rate it used previously.

� The AMR configuration request message changes AMR

configuration.



� When the uplink code is checked on the BS side, the coding mode

change command is initiated if it is found to reach the above configured

threshold. After converting the coding mode, MS returns the coding mode

indication.

BTS found RQI threshold is met

coding mode change command

coding mode indication



� The downlink code is checked on the MS side. When it is found to reach

the threshold with the same algorithm, MS initiates the coding mode

request. As required, BS ignores this request or immediately responds to

this request. It then sends the coding mode indication to MS.

BTS found RQI threshold is met

coding mode request

coding mode indication


AMR Feature

� Activated voice code set: Supporting setting of different ACS,

coding rate adjustment threshold and hysteresis , and initial

coding rate according to cell

� Adding the statistic index of AMR call at the cell level to cell

performance measurement

� Providing the RQI performance statistic function distributed by TA

at the carrier level

� TC support capability can be queried at the BSC maintenance

console: If various voice code algorithms are supported


AMR Feature

� Supporting dynamic configuration of the Activated Code Set (ACS)

and threshold used for the cell, enabling or disabling it (dynamic

configuration does not affect the established AMR call)

� Supporting real time query about the coding mode currently used

for the specified channel: the system can output the used coding

mode and C/I information (indicating RQI) in the queried period

� Providing the user’s cell capacity and quality equalization control

policy by realizing the HR-FR handover in cell based on RQI

� Adopting different power control parameters for AMR call and non

AMR call, keeping the algorithm consistent


Configuration

� To enable the AMR function, it is a must to set “Allow full rate

voice coding and decoding algorithm 3” and “Allow half rate voice

coding and decoding algorithm 3” at MSC configuration. In

addition, it is necessary to configure the phase flag of A interface

protocol to PhaseII+.

� Configure the following data at BSC: the A interface circuit to

support the AMR function. As described in the protocol, the circuit

pool number indicates the support capability of the voice codec.

To support the AMR function, it is recommended to configure the

circuit pool to 27. The configuration interface is shown below.


Configuration


Configuration

� The circuit support capability configured for the circuit pool

cannot exceed the actual support capability of TC board.

� Check the support capability of TC board from the

maintenance console: Select the TC board through the

maintenance console, and then right click to select “Query

board” from the floating menu. The board querying interface

is shown below.


Configuration


Configuration


Configuration

� If ACS contains four coding rates, “Initial coding mode” can

be configured to 0, 1, 2 or 3. Both of the coding rate

adjustment thresholds and hysteresis is significant and must

be configured correctly.

�The configuration of the coding rate adjustment threshold and

the hysteresis must observe the following rules:

� 0 < th[i] < th[i+1] < 63; i = 1, 2

� 0 < th[i] + hyst[i] < th[i+1] + hyst[i+1] < 63; i = 1, 2


Configuration


Configuration


Summary

� In this course，we learn about：

� Master the function of EFR, HR, AMR

� Configuration of EFR, HR, AMR

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Microsoft Power Point - 9 OMF000407 Multiple Rate Algorithm ISSUE2