gprsegprs link quality control(gbss14.0_01)

GPRS/EGPRS Link Quality Control GBSS14.0

Feature Parameter Description

Issue 01

Date 2012-04-28

HUAWEI TECHNOLOGIES CO., LTD.

Copyright © Huawei Technologies Co., Ltd. 2012. All rights reserved.

No part of this document may be reproduced or transmitted in any form or by any means without prior

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GSM BSS

GPRS/EGPRS Link Quality Control Contents

Issue 01 (2012-04-28) Huawei Proprietary and Confidential

Copyright © Huawei Technologies Co., Ltd.

i

Contents

1 Introduction ................................................................................................................................ 1-1

1.1 Scope ............................................................................................................................................ 1-1

1.2 Intended Audience......................................................................................................................... 1-1

1.3 Change History .............................................................................................................................. 1-1

2 Overview...................................................................................................................................... 2-1

3 Technical Description .............................................................................................................. 3-1

3.1 GPRS Coding Scheme Adjustment Algorithm .............................................................................. 3-1

3.2 EGPRS Coding Scheme Adjustment Algorithm ............................................................................ 3-2

3.2.1 Overview ............................................................................................................................... 3-2

3.2.2 Uplink EGPRS Coding Scheme Adjustment Algorithm ........................................................ 3-3

3.2.3 Downlink EGPRS Coding Scheme Adjustment Algorithm .................................................... 3-4

4 Parameters.................................................................................................................................. 4-1

5 Counters ...................................................................................................................................... 5-1

6 Glossary ...................................................................................................................................... 6-1

7 Reference Documents ............................................................................................................. 7-1

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GPRS/EGPRS Link Quality Control 1 Introduction



1-1

1 Introduction

1.1 Scope

This document describes GPRS coding scheme adjustment algorithm, and EGPRS coding scheme adjustment algorithm in the GPRS/EGPRS link quality control feature.

1.2 Intended Audience

It is assumed that users of this document are familiar with GPRS basics and have a working knowledge of GPRS telecommunication.

This document is intended for:

Personnel working on Huawei GPRS products or systems

System operators who need a general understanding of this feature

1.3 Change History

The change history provides information on the changes in different document versions.

There are two types of changes, which are defined as follows:

Feature change

Feature change refers to the change in the GPRS/EGPRS link quality control feature of a specific product version.

Editorial change

Editorial change refers to the change in wording or the addition of the information that was not described in the earlier version.

Document Issues

The document issues are as follows:

01 (2012-04-28)

Draft A (2012-02-15)

01 (2012-04-28)

This is the first release of GBSS14.0.

Compared with issue draft A (2012-02-15) of GBSS14.0, issue 01 (2012-04-28) of GBSS14.0 has no change.

Draft A (2012-02-15)

This is the draft release of GBSS14.0.

Compared with issue 01 (2011-03-31) of GBSS13.0, Draft A (2012-02-15) of GBSS14.0 incorporates the changes described in the following table.

Change Type

Change Description Parameter Change

Feature change

Added the following types of flow control:

Updated picture of 2 Overview.

Added the following parameters:

None

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GPRS/EGPRS Link Quality Control 1 Introduction



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Change Type

Change Description Parameter Change

Editorial change

None None

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GPRS/EGPRS Link Quality Control 2 Overview



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2 Overview

GPRS/EGPRS link quality control is implemented to adjust GPRS/EGPRS coding schemes dynamically according to the radio link quality during packet data transmission. It enables coding schemes to adapt to the variation of the radio environment, maximizes the data throughput, and increases the data rate and system capacity.

At present, the GPRS network is evolved over the GSM network. Therefore, the system capacity is limited. With the demand for radio data services increasing, the limitation of the GPRS bandwidth becomes a critical issue. The maximum data rate per timeslot on the GPRS network is 21.4 kbit/s. The theoretical rate of eight multiplexed timeslots is up to 171.2 kbit/s. The number of GPRS dedicated channels is limited. The CS services have priority to use the channels that can be converted into GPRS dedicated channels. Moreover, most MSs have limited multislot capability and support only a small number of downlink channels. Therefore, the actual throughput of the GPRS system is less than the theoretical rate.

To solve the problem of GPRS bandwidth limitation, the EGPRS technology is introduced. In EGPRS, new modulation schemes, coding schemes, and data acknowledgment mechanisms are used to increase the throughput per timeslot. Thus, the system bandwidth is increased. To achieve a higher bit rate on each timeslot, EGPRS adopts a new modulation scheme, that is, 8 phase shift keying (8PSK). In the 8PSK modulation scheme, symbols are indicated by absolute phases of signals. There are eight possible symbols and each symbol represents three bits of information. In the GMSK modulation scheme, each symbol represents one bit of information. In theory, the modulation rate of 8PSK can be three times that of GMSK. Table 2-1 provides the comparison between GPRS and EGPRS.

Table 2-1 Comparison between GPRS and EGPRS

Parameter GPRS EGPRS

Modulation scheme GMSK 8PSK/GMSK

Chip rate 270 kbit/s 270 kbit/s

Modulation bit rate 270 kbit/s 810 kbit/s

Maximum throughput per timeslot 21.4 kbit/s (CS-4) 59.2 kbit/s (MCS-9)

Maximum throughput every 8 timeslots

171.2 kbit/s 473.6 kbit/s

Four coding schemes, CS-1 to CS-4, are defined for GPRS. Each coding scheme has its specific error correction capability and coding rate. Nine modulation and coding schemes, MCS-1 to MCS-9, are defined for EGPRS. EGPRS provides the same functions as GPRS. In addition, EGPRS has higher coding rates. MCS-1 to MCS-4 are modulated with GMSK, and MCS-5 to MCS-9 are modulated with 8PSK. Figure 2-1 shows the coding schemes and maximum throughputs of GPRS and EGPRS.

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GPRS/EGPRS Link Quality Control 2 Overview



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Figure 2-1 Coding schemes and maximum throughputs of GPRS and EGPRS

In different radio link conditions, each coding scheme has its specific throughput. To achieve the maximum throughput and to adapt to the variation of radio link conditions, coding schemes must be adjusted dynamically according to the radio link quality. The GPRS/EGPRS link quality control algorithm adjusts coding schemes dynamically according to the channel quality to achieve the maximum throughput. This algorithm consists of the GPRS coding scheme adjustment algorithm and the EGPRS coding scheme adjustment algorithm.

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GPRS/EGPRS Link Quality Control 3 Technical Description



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3 Technical Description

3.1 GPRS Coding Scheme Adjustment Algorithm

The GPRS system supports the GMSK modulation scheme and defines four coding schemes: CS-1 to CS-4. The number of parity bits that are added during the coding varies according to the coding scheme. Therefore, the anti-interference capability is coding scheme specific. From CS-1 to CS-4, the number of parity bits decreases sequentially; therefore, the anti-interference capability decreases accordingly. The transmission rate and the requirements for the radio environment, however, increase sequentially. When the C/I is the same, CS-4 has the highest block error ratio (BLER), that is, CS-4 requires a relatively high C/I to ensure the same BLER. In the GPRS system, CS-4 must be used and the C/I must be high to ensure the maximum throughput. Table 3-1 lists the key parameters and theoretical rates of GPRS.

Table 3-1 Key parameters and theoretical rates of GPRS

Coding Scheme

Code Rate Radio Block Excluding USF and BCS

Coded Bits Data Rate (kbit/s)

CS-1 1/2 181 456 9.05

CS-2 ≈ 2/3 268 588 13.4

CS-3 ≈ 3/4 312 676 15.6

CS-4 1 428 456 21.4

The GPRS coding scheme adjustment algorithm is as follows:

1. The BSC determines whether to use a fixed coding scheme based on the setting of UPFIXCS or DNFIXCS. If a fixed coding scheme is required, the current coding scheme is specified by UPFIXCS or DNFIXCS. Otherwise, the initial coding scheme is specified by UPDEFAULTCS or DNDEFAULTCS.

2. In RLC unacknowledged mode, if the current coding scheme is CS-3 or CS-4, the BSC adjusts it to CS-2. Otherwise, the current coding scheme remains unchanged.

3. In RLC acknowledged mode, the BSC selects a coding scheme based on the mean retransmission rate of RLC data blocks, current coding scheme, and coding scheme conversion threshold. The retransmission rate is the percentage of the number of RLC data blocks not received to the total number of RLC data blocks sent in a retransmission rate measurement period. The mean retransmission rate is the filtered retransmission rate. The rules for selecting a coding scheme are as follows:

− If the current coding scheme is CS-1 and the uplink or downlink mean retransmission rate is lower than UPTHDCSUPGRADE1 or DNTHDCSUPGRADE1 respectively, then the BSC selects CS-2.

− If the current coding scheme is CS-2 and the uplink or downlink mean retransmission rate is lower than UPTHDCSUPGRADE2 or DNTHDCSUPGRADE2 respectively, then the BSC selects CS-3; if the current coding scheme is CS-2 and the uplink or downlink mean retransmission rate is higher than UPTHDCSDEGRADE1 or DNTHDCSDEGRADE1 respectively, then the BSC selects CS-1.

− If the current coding scheme is CS-3 and the uplink or downlink mean retransmission rate is lower than UPTHDCSUPGRADE3 or DNTHDCSUPGRADE3 respectively, then the BSC selects CS-4; if the current coding scheme is CS-3 and the uplink or downlink mean retransmission rate is higher than UPTHDCSDEGRADE2 or DNTHDCSDEGRADE2 respectively, then the BSC selects CS-2.

− If the current coding scheme is CS-4 and the uplink or downlink mean retransmission rate is higher than UPTHDCSDEGRADE3 or DNTHDCSDEGRADE3 respectively, then the BSC selects CS-3.

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4. If the TBF is released abnormally when counter N3101 reaches the maximum value, the uplink coding scheme level must be decreased; if the TBF is released abnormally when counter N3105 reaches the maximum value, the downlink coding scheme level must be decreased. Counter N3101 is specified by N3101, and counter N3105 is specified by N3105.

3.2 EGPRS Coding Scheme Adjustment Algorithm

3.2.1 Overview

The EGPRS system defines nine coding and modulation schemes: MCS-1 to MCS-9. MCS-1 to MCS-4 are modulated with GMSK, and MCS-5 to MCS-9 are modulated with 8PSK. In poor radio conditions, the performance of GMSK is better than that of 8PSK. Therefore, EGPRS uses both GMSK and 8PSK modulation schemes. Table 3-2 lists the key parameters and theoretical rates of EGPRS.

Table 3-2 Key parameters and theoretical rates of EGPRS

Coding Scheme

Code Rate

Modulation RLC Blocks per Radio Block (20 ms)

Raw Data Within One Radio Block

Family Data Rate (kbit/s)

MCS-9 1.0 8PSK 2 2 x 592 A 59.2

MCS-8 0.92 2 2 x 544 A 54.4

MCS-7 0.76 2 2 x 448 B 44.8

MCS-6 0.49 1 592

48 + 544

A 29.6

27.2

MCS-5 0.37 1 448 B 22.4

MCS-4 1.0 GMSK 1 352 C 17.6

MCS-3 0.85 1 296

48 + 248

296

A 14.8

13.6

MCS-2 0.66 1 224 B 11.2

MCS-1 0.53 1 176 C 8.8

The EGPRS transmit power in the 8PSK modulation scheme is different from that in the GMSK modulation scheme. From the perspective of network operation, the EGPRS transceiver must have the same spectrum features as an ordinary transceiver. When sending the signals modulated with 8PSK, the EGPRS transceiver uses the transmit power that is 2-5 dB less than the average transmit power of the signals modulated with GMSK. Thus, the requirements for spectrum can be met through the setting of CELL8PSKPOWERLEVEL whose default value is 0. On the BCCH, the transmit power of the signals modulated with 8PSK is up to 4 dB less than the average transmit power of the signals modulated with GMSK. In the timeslot before the timeslot of the BCCH or CCCH, the transmit power of the signals modulated with 8PSK is up to 2 dB less than the average transmit power of the signals modulated with GMSK.

To achieve the possible maximum throughput on radio links, EGPRS uses combined link quality control modes: link adaptation (LA) mode and incremental redundancy (IR) mode. Compared with the pure LA

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mode, the combined mode significantly improves the performance of radio links. The link quality control mode is set to LA or IR through the setting of LQCMODE whose default value is IR.

LA mode

In LA mode, the network side adjusts channel coding schemes dynamically according to the link quality to achieve the maximum throughput. The MS measures the downlink quality; the BTS measures the uplink quality. The network side determines an appropriate coding scheme according to the radio link measurement report sent from the MS. For the cells where the signal quality on the Um interface is good, the link quality control mode is generally set to LA.

IR mode

In IR mode, the transmitter retransmits data blocks in puncturing-scheme-based code diversity mode instead of in time diversity mode to increase redundancy. The receiver does not discard erroneous packets but stores them and combines and decodes them together with the soft information of the same data block. In this way, the gains of channel coding and time diversity can be obtained at the same time. Therefore, in the case that the channel quality is ensured, the BLER decreases and the throughput increases. For the cells where the signal quality on the Um interface is poor, the transmission performance of radio links is comparatively good. In such a case, the link quality control mode is generally set to IR.

3.2.2 Uplink EGPRS Coding Scheme Adjustment Algorithm

Depending on whether the BTS supports sending BEP measurement reports to the BSC, the uplink EGPRS coding scheme adjustment algorithm is carried out in the following ways:

When the BTS supports sending BEP measurement reports to the BSC, the BSC adjusts the uplink EGPRS coding scheme according to the uplink BEP measurement reports sent from the BTS.

When the BTS does not support sending BEP measurement reports to the BSC, the BSC adjusts the uplink EGPRS coding scheme according to the downlink BEP measurement reports sent from the MS.

The uplink frame from the BTS to the BSC carries the information about whether the BTS supports sending BEP measurement reports to the BSC. Based on this information, the BSC determines which coding scheme adjustment algorithm is used.

BSC Adjusting the Uplink EGPRS Coding Scheme According to the Uplink BEP Measurement Report Sent from the BTS

When the BTS supports sending BEP measurement reports to the BSC, it sends the BEP measurement report to the BSC through an uplink data frame. When receiving the uplink data frame from the BTS, the BSC triggers the uplink EGPRS coding scheme adjustment procedure if the BSC finds the change in the current link quality according to the measurement report. When the BTS cannot decode the uplink radio blocks correctly, it sends an uplink information frame to the BSC. The uplink information frame carries the BEP measurement report. After receiving the uplink information frame, the BSC triggers the uplink EGPRS coding scheme adjustment procedure. The uplink EGPRS coding scheme adjustment algorithm is as follows:

1. The BSC determines whether to use the fixed MCS coding scheme in the uplink based on the setting of UPFIXMCS. If the fixed MCS coding scheme is used, the uplink coding scheme is specified by UPFIXMCS. Otherwise, the uplink initial coding scheme is specified by UPDEFAULTMCS. Later, the BSC adjusts the uplink coding scheme according to the uplink BEP measurement report sent from the BTS.

2. Each time the BSC receives an uplink data frame from the BTS or an uplink information frame generated by the BTS when the BTS cannot decode the radio blocks correctly, the BSC filters the BLER and BEP measurement reports. The BEP measurement reports carried by the uplink frames are related to radio blocks. After filtering the measured BEP values of the radio blocks, the BSC obtains the MEAN_BEP and CV_BEP values on each timeslot. Then, the BSC sums up the

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MEAN_BEP and CV_BEP values on the timeslots occupied by the TBF to obtain the MEAN_BEP and CV_BEP values of the TBF. At the same time, the BSC adjusts the MEAN_BEP value of the TBF based on the BLER.

3. Based on the MEAN_BEP and CV_BEP values of the uplink TBF, the BSC chooses the required coding scheme against the uplink BEP to coding scheme mapping table. If the current coding scheme is not the required one, the BSC adjusts the current uplink coding scheme.

4. The modulation scheme may change during the coding scheme adjustment. To enhance the stability of coding scheme adjustment and to prevent ping-pong handovers of modulation schemes, the leaky bucket algorithm is used when the coding scheme in GMSK is changed to the one in 8PSK. The basic principles of the leaky bucket algorithm are as follows: Each time the BSC adjusts the coding scheme in GMSK to the one in 8PSK, the bucket size increases; each time the BSC adjusts the coding schemes within GMSK, the bucket size decreases. The adjustment from GMSK to 8PSK is allowed only when the bucket size reaches a specific value.

BSC Adjusting the Uplink EGPRS Coding Scheme According to the Downlink BEP Measurement Report Sent from the MS

When the BTS does not support sending BEP measurement reports to the BSC, the BSC adjusts the uplink EGPRS coding scheme according to the BEP measurement report in the EGPRS PACKET DOWNLINK ACK/NACK message. The uplink EGPRS coding scheme adjustment algorithm is as follows:

1. The BSC determines whether to use the fixed MCS coding scheme in the uplink based on the setting of UPFIXMCS. If the fixed MCS coding scheme is used, the uplink coding scheme is specified by UPFIXMCS. Otherwise, the uplink initial coding scheme is specified by UPDEFAULTMCS. The BSC adjusts the uplink coding scheme according to the downlink BEP measurement report sent from the MS.

2. After receiving the EGPRS PACKET DOWNLINK ACK/NACK message, the BSC extracts the MEAN_BEP and CV_BEP values of the TBF from the message. Based on the MEAN_BEP and CV_BEP values of the TBF, the BSC chooses the required coding scheme against the uplink BEP to coding scheme mapping table. If the current coding scheme is not the required one, the BSC adjusts the current uplink coding scheme.

3. When counter N3101 reaches the maximum value and the TBF is released abnormally, a lower-rate coding scheme must be used if the requirement for the signal quality on the Um interface after the coding scheme adjustment is higher than that before the adjustment. Counter N3101 is specified by N3101.

3.2.3 Downlink EGPRS Coding Scheme Adjustment Algorithm

The MS measures the downlink quality periodically and filters the measured values to generate a downlink EGPRS channel quality report. The downlink EGPRS channel quality report is carried by the EGPRS PACKET DOWNLINK ACK/NACK message sent from the MS to the BSC. The filtering period of downlink quality measured values is specified by BEPPERIOD. The BSC broadcasts the BEP period in the system information to the MS.

After receiving the EGPRS PACKET DOWNLINK ACK/NACK message, the BSC adjusts the downlink EGPRS coding scheme according to the BEP measurement report in the message. When RLC data blocks are not retransmitted, the downlink EGPRS coding scheme adjustment algorithm is as follows:

1. The BSC determines whether to use the fixed MCS coding scheme in the downlink based on the setting of DNFIXMCS. If the fixed MCS coding scheme is used, the downlink coding scheme is specified by DNFIXMCS. Otherwise, the downlink initial coding scheme is specified by DNDEFAULTMCS. The BSC adjusts the downlink coding scheme according to the downlink BEP measurement report sent from the MS.




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2. After receiving the EGPRS PACKET DOWNLINK ACK/NACK message, the BSC extracts the MEAN_BEP and CV_BEP values of the TBF from the message. The MEAN_BEP and CV_BEP values of the TBF are used for the downlink coding scheme adjustment. Based on the value of the MS OUT OF MEMORY field in the EGPRS PACKET DOWNLINK ACK/NACK message, the downlink coding scheme can be adjusted in the following ways:

− If the value of the MS OUT OF MEMORY field is 0, the MS has sufficient memory to perform the IR function. The BSC adjusts the MEAN_BEP value of the TBF based on the BLER. Then, based on the MEAN_BEP and CV_BEP values of the TBF, the BSC chooses the required coding scheme against the downlink BEP to coding scheme mapping table in IR mode. If the current coding scheme is not the required one, the BSC adjusts the current downlink coding scheme.

− If the value of the MS OUT OF MEMORY field is 1, the MS has no sufficient memory to perform the IR function. Then, based on the MEAN_BEP and CV_BEP values of the TBF, the BSC chooses the required coding scheme against the downlink BEP to coding scheme mapping table in LA mode. If the current coding scheme is not the required one, the BSC adjusts the current downlink coding scheme. To prevent ping-pong handovers of modulation schemes, the leaky bucket algorithm is triggered when the coding scheme is changed from GMSK to 8PSK. For details on the leaky bucket algorithm, see 3.2.2 Uplink EGPRS Coding Scheme Adjustment Algorithm.

3. When counter N3105 reaches the maximum value and the TBF is released abnormally, a lower-rate coding scheme must be used if the requirement for the signal quality on the Um interface after the coding scheme adjustment is higher than that before the adjustment. Counter N3105 is specified by N3105.

For RLC data block retransmission, if the current link quality control mode is IR mode, the RLC data blocks cannot be segmented when the coding scheme needs to be changed during the retransmission. The BSC needs to choose a coding scheme for retransmission from the segmentation-prohibited retransmission coding scheme table. If the current link quality control mode is LA mode, or the value of the MS OUT OF MEMORY field in the EGPRS PACKET DOWNLINK ACK/NACK message is 1, the RLC data blocks can be segmented when the coding scheme needs to be changed during the retransmission. The BSC needs to choose a coding scheme for retransmission from the segmentation-allowed retransmission coding scheme table.


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GPRS/EGPRS Link Quality Control 4 Parameters



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4 Parameters

Table 4-1 Parameter description

Parameter ID NE MML Command Description

BEPPERIOD BSC6900 SET GCELLEGPRSPARA Meaning: Average period for sending the measurement report over the EGPRS channel

GUI Value Range: 0~10

Actual Value Range: 0~10

Default Value: 5

Unit: None

CELL8PSKPOWERLEVEL

BSC6900 SET GCELLBASICPARA Meaning: Timeslot power attenuation level of the EDGE TRX in 8PSK. The attenuation level ranges from 0 to 50, each of which corresponds to an attenuation of 0.2 dB. When the EDGE TRX sends signals in 8PSK, the transmit power must be lower than the mean power in GMSK.



Default Value: 0

Unit: None

DNDEFAULTCS BSC6900 SET GCELLPSCS Meaning: Coding scheme of the default GPRS downlink. Dynamic adjustment coding: the coding scheme used during initial access transmission. If the downlink uses the fixed coding scheme, the TBF uses the fixed coding scheme.

GUI Value Range: CS1(CS1), CS2(CS2), CS3(CS3), CS4(CS4)

Actual Value Range:

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CS1, CS2, CS3, CS4

Default Value: CS2(CS2)

Unit: None

DNDEFAULTMCS BSC6900 SET GCELLEGPRSPARA Meaning: Default coding scheme of the downlink EDGE link. If the downlink adopts the dynamic adjustment coding scheme, this parameter can be used to set the coding scheme for transmission during initial access. If the downlink uses the fixed coding scheme, the TBF uses the fixed coding scheme.

GUI Value Range: MCS1(MCS1), MCS2(MCS2), MCS3(MCS3), MCS4(MCS4), MCS5(MCS5), MCS6(MCS6), MCS7(MCS7), MCS8(MCS8), MCS9(MCS9)

Actual Value Range: MCS1, MCS2, MCS3, MCS4, MCS5, MCS6, MCS7, MCS8, MCS9

Default Value: MCS6(MCS6)

Unit: None

DNFIXCS BSC6900 SET GCELLPSCS Meaning: Adjustment mode of the downlink GPRS link coding scheme. If the fixed coding scheme is used, this parameter is set to a value ranging from CS1 to CS4. If the dynamic coding scheme is used, this parameter is set to UNFIXED.

GUI Value Range: CS1(CS1), CS2(CS2), CS3(CS3), CS4(CS4),

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UNFIXED(UNFIXED)

Actual Value Range: CS1, CS2, CS3, CS4, UNFIXED

Default Value: UNFIXED(UNFIXED)

Unit: None

DNFIXMCS BSC6900 SET GCELLEGPRSPARA Meaning: Coding scheme of the downlink EDGE link. If the downlink uses the fixed coding scheme, this parameter is set to a value ranging from MCS1 to MCS9. If the downlink uses the dynamic adjustment coding scheme, this parameter is set to UNFIXED.

GUI Value Range: MCS1(MCS1), MCS2(MCS2), MCS3(MCS3), MCS4(MCS4), MCS5(MCS5), MCS6(MCS6), MCS7(MCS7), MCS8(MCS8), MCS9(MCS9), UNFIXED(UNFIXED)

Actual Value Range: MCS1, MCS2, MCS3, MCS4, MCS5, MCS6, MCS7, MCS8, MCS9, UNFIXED


Unit: None

DNTHDCSDEGRADE1 BSC6900 SET GCELLPSCS Meaning: Retransmission threshold when the coding mode of the downlink TBF is changed from CS2 to CS1. When the downlink TBF retransmission rate is greater than or equals to this value, the coding mode of the downlink





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TBF is changed from CS2 to CS1.



Default Value: 10

Unit: %

DNTHDCSDEGRADE2 BSC6900 SET GCELLPSCS Meaning: Retransmission threshold when the coding mode of the downlink TBF is changed from CS3 to CS2. When the downlink TBF retransmission rate is greater than or equals to this value, the coding mode of the downlink TBF is changed from CS3 to CS2.



Default Value: 5

Unit: %

DNTHDCSDEGRADE3 BSC6900 SET GCELLPSCS Meaning: Retransmission threshold when the coding mode of the downlink TBF is changed from CS4 to CS3. When the downlink TBF Retransmission rate is greater than or equals to this value, the coding mode of the downlink TBF is changed from CS4 to CS3.



Default Value: 5

Unit: %

DNTHDCSUPGRADE1 BSC6900 SET GCELLPSCS Meaning: Retransmission threshold when the







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coding mode of the downlink TBF is changed from CS1 to CS2. When the downlink TBF retransmission rate is less than or equals to this value, the coding mode of the downlink TBF is changed from CS1 to CS2.



Default Value: 5

Unit: %

DNTHDCSUPGRADE2 BSC6900 SET GCELLPSCS Meaning: Retransmission threshold when the coding mode of the downlink TBF is changed from CS2 to CS3. When the downlink TBF retransmission rate is less than or equals to CS2 to CS1, the coding mode of the downlink TBF is changed from CS2 to CS3.



Default Value: 2

Unit: %

DNTHDCSUPGRADE3 BSC6900 SET GCELLPSCS Meaning: Retransmission threshold when the coding mode of the downlink TBF is changed from CS3 to CS4. When the downlink TBF retransmission rate is less than or equals to this value, the coding mode of the downlink TBF is changed from CS3 to CS4.


Actual Value Range:





GSM BSS




4-6


0~64

Default Value: 2

Unit: %

LQCMODE BSC6900 SET GCELLEGPRSPARA Meaning: It is applicable to the radio transmission environment to improve the link quality. Link adaptation (LA) indicates adjusting the coding mode of the channel dynamically according to the transmission quality of the link. The link transmission quality is measured by the 8PSK MEAN BEP and 8PSK CV BEP in the Packet EGPRS Downlink Ack/Nack message sent by the MS. The network side determines the coding mode for data transmission according to the radio measurement report sent by the MS. The cell with the good transmission quality on the air interface is set to the LA mode. Increment redundancy (IR) mode requires the network side retransmit the data block with different punching codes and the MS store the historical error information. The data block is retransmitted through cooperated error correction function. With the IR mode, the transmission quality on the air interface of the cell can be improved. However, the MS must support this IR mode. The cell with the dissatisfied transmission quality on the air interface is set to the LR

../RNCParaHtml/mbsc/m-para/gcellegprspara_lqcmode.html


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mode.

GUI Value Range: IR(IR), LA(LA)

Actual Value Range: IR, LA

Default Value: IR(IR)

Unit: None

N3101 BSC6900 SET GCELLSTANDARDOPTPARA

Meaning: Maximum value of N3101. In uplink dynamic allocation mode, the BSC enables multiple MSs to share the same uplink channel by identifying the USF values contained in downlink data blocks. The BSC assigns a USF to the uplink TBF (that is, the uplink TBF is successfully established), and starts N3101. The BSC receives the uplink RLC data blocks, and checks whether they are valid.

If the RLC data blocks are valid, N3101 is reset. If the RLC data blocks are invalid, the value of N3101 increases from the original value. When the N3101 overflows, T3169 starts. When T3169 expires, the current uplink TBF is abnormally released.



Default Value: 20

Unit: None

N3105 BSC6900 SET GCELLSTANDARDOPTPARA

Meaning: Maximum value of the N3105 counter. After the downlink TBF is set up successfully, the N3105 is started on the network


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4-8


side. After the downlink RLC data block is added with the RRBP domain on the network side, the valid packet acknowledged message responded by the MS is received in the uplink RLC data block in the RRBP domain. In this case, N3105 is reset. Otherwise, the value of N3105 is increased and the downlink data block of the RRBP is retransmitted. When N3105 is overflowed, T3195 is started. After the timer T3195 expires, the current TBF is released abnormally.



Default Value: 10

Unit: None

UPDEFAULTCS BSC6900 SET GCELLPSCS Meaning: Default coding scheme of the uplink GPRS link. If the uplink adopts the dynamic adjustment coding scheme, this parameter can be used to set the coding scheme for transmission during initial access. If the uplink uses the fixed coding scheme, the TBF uses the fixed coding scheme.

GUI Value Range: CS1(CS1), CS2(CS2), CS3(CS3), CS4(CS4)

Actual Value Range: CS1, CS2, CS3, CS4

Default Value: CS1(CS1)

Unit: None

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UPDEFAULTMCS BSC6900 SET GCELLEGPRSPARA Meaning: Default coding scheme of the uplink EDGE link. If the uplink adopts the dynamic adjustment coding scheme, this parameter can be used to set the coding scheme for transmission during initial access. If the uplink uses the fixed coding scheme, the TBF uses the fixed coding scheme.

GUI Value Range: MCS1(MCS1), MCS2(MCS2), MCS3(MCS3), MCS4(MCS4), MCS5(MCS5), MCS6(MCS6), MCS7(MCS7), MCS8(MCS8), MCS9(MCS9)

Actual Value Range: MCS1, MCS2, MCS3, MCS4, MCS5, MCS6, MCS7, MCS8, MCS9

Default Value: MCS2(MCS2)

Unit: None

UPFIXCS BSC6900 SET GCELLPSCS Meaning: Adjustment mode of the uplink GPRS link coding scheme. If the fixed coding scheme is used, this parameter is a value ranging from CS1 to CS4. If the dynamic coding scheme is used, this parameter is set to UNFIXED.

GUI Value Range: CS1(CS1), CS2(CS2), CS3(CS3), CS4(CS4), UNFIXED(UNFIXED)

Actual Value Range: CS1, CS2, CS3, CS4, UNFIXED

Default Value:





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4-10


UNFIXED(UNFIXED)

Unit: None

UPFIXMCS BSC6900 SET GCELLEGPRSPARA Meaning: Coding scheme of the uplink EDGE link. If the uplink uses the fixed coding scheme, this parameter is set to a value ranging from MCS1 to MCS9. If the uplink uses the dynamic adjustment coding scheme, this parameter is set to UNFIXED.

GUI Value Range: MCS1(MCS1), MCS2(MCS2), MCS3(MCS3), MCS4(MCS4), MCS5(MCS5), MCS6(MCS6), MCS7(MCS7), MCS8(MCS8), MCS9(MCS9), UNFIXED(UNFIXED)

Actual Value Range: MCS1, MCS2, MCS3, MCS4, MCS5, MCS6, MCS7, MCS8, MCS9, UNFIXED


Unit: None

UPTHDCSDEGRADE1 BSC6900 SET GCELLPSCS Meaning: Retransmission threshold when the coding mode of the uplink TBF is changed from CS2 to CS1. When the retransmission rate of the uplink TBF is greater than or equal to this threshold, the coding mode of the uplink TBF is changed from CS2 to CS1.







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4-11


Default Value: 10

Unit: %




Default Value: 5

Unit: %




Default Value: 5

Unit: %

UPTHDCSUPGRADE1 BSC6900 SET GCELLPSCS Meaning: Retransmission threshold when the coding mode of the uplink TBF is changed from CS1 to CS2. When the retransmission rate of the uplink TBF is less than or equal to this threshold, the coding







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4-12


mode of the uplink TBF is changed from CS1 to CS2.



Default Value: 5

Unit: %

UPTHDCSUPGRADE2 BSC6900 SET GCELLPSCS Meaning: Retransmission threshold when the coding mode of the uplink TBF is changed from CS2 to CS3. When the retransmission rate of the uplink TBF is less than or equal to this threshold, the coding mode of the uplink TBF is changed from CS2 to CS3.



Default Value: 2

Unit: %

UPTHDCSUPGRADE3 BSC6900 SET GCELLPSCS Meaning: Retransmission threshold when the coding mode of the uplink TBF is changed from CS3 to CS4. When the retransmission rate of the uplink TBF is less than or equal to this threshold, the coding mode of the uplink TBF is changed from CS3 to CS4.



Default Value: 2

Unit: %





GSM BSS

GPRS/EGPRS Link Quality Control 5 Counters



5-1

5 Counters

There are no specific counters associated with this feature.

GSM BSS

GPRS/EGPRS Link Quality Control 6 Glossary



6-1

6 Glossary

For the acronyms, abbreviations, terms, and definitions, see the Glossary.

Glossary.htm

GSM BSS

GPRS/EGPRS Link Quality Control 7 Reference Documents



7-1

7 Reference Documents

[1] 3GPP TS 45.008: "Radio subsystem link control"

[2] 3GPP TS 44.060: "Radio Link Control/Medium Access Control (RLC/MAC) protocol"

[3] 3GPP TS 43.064: "Overall description of the GPRS radio interface; Stage 2"

[4] 3GPP TS 45.005: "Radio transmission and reception"

[5] BSC6900 Feature List

[6] BSC6900 Optional Feature Description

[7] BSC6900 GSM Parameter Reference

[8] BSC6900 GSM MML Command Reference

[9] BSC6900 Performance Counter Reference

gprsegprs link quality control(gbss14.0_01)

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