10 GSM BSS Network KPI (Uplink-Downlink Balance) Optimization Manual[1].Doc

GSM BSS Network KPI (Uplink-Downlink Balance) Optimization Manual Product Name

Confidentiality Level

GSM

INTERNAL

Product Version

Total 32 pages

INTERNAL

V00R02

GSM BSS Network KPI (Uplink-Downlink Balance) Optimization Manual For Internal Use Only

Prepared by

GSM &UMTS Performance Research Department

Yang Jixiang

Date

Reviewed by

Date

Reviewed by

Date

Approved by

Date

2008-1-24

Huawei Technologies Co., Ltd. All rights reserved

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Revision Record Date

Revision version

Change Description

Author

2008-1-24

0.9

Draft completed

Yang Jixiang

2008-2-24

1.0

Revised part of the content and added one case

Yang Jixiang

2012-04-19

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GSM BSS Network KPI (Uplink-Downlink Balance) Optimization ManualKeywords: uplink-downlink balance, uplink-downlink level, uplink level, downlink level, uplink-downlink imbalance Abstract: This document describes the theory, evaluation, and typical cases of the uplinkdownlink balance.

Key words: Reference:

List of abbreviations: Abbreviation

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Contents 1 Precondition and Assumption...........................................................8 2 Principles of Uplink-Downlink Balance............................................10 2.1 Fundamentals of the Uplink-Downlink Balance....................................................................................................10 2.1 Fundamentals of the Uplink-Downlink Balance....................................................................................................10 2.2 Evaluating the Uplink-Downlink Balance..............................................................................................................11 2.2 Evaluating the Uplink-Downlink Balance..............................................................................................................11 2.2.1 Theoretical Calculation of Uplink-Downlink Balance on Huawei Devices.....................................................12 2.2.1 Theoretical Calculation of Uplink-Downlink Balance on Huawei Devices.....................................................12 2.2.2 Evaluating the Uplink-Downlink Balance With the Uplink-downlink Balance Measurement........................13 2.2.2 Evaluating the Uplink-Downlink Balance With the Uplink-downlink Balance Measurement........................13 2.2.3 Evaluating the Uplink-Downlink Balance With the Average Uplink-Downlink Level Difference.................14 2.2.3 Evaluating the Uplink-Downlink Balance With the Average Uplink-Downlink Level Difference.................14 2.2.4 Evaluating the Uplink-Downlink Balance With the Uplink-Downlink Level Distribution.............................15 2.2.4 Evaluating the Uplink-Downlink Balance With the Uplink-Downlink Level Distribution.............................15 2.2.5 Evaluating the Uplink-Downlink Balance With the Uplink-Downlink Cumulative Distribution....................16 2.2.5 Evaluating the Uplink-Downlink Balance With the Uplink-Downlink Cumulative Distribution....................16 2.3 Effects of the Uplink-Downlink Imbalance............................................................................................................17 2.3 Effects of the Uplink-Downlink Imbalance............................................................................................................17

3 Factors Affecting the Uplink-Downlink Balance................................18 3.1 Installation of the Feeder and Antenna...................................................................................................................18 3.1 Installation of the Feeder and Antenna...................................................................................................................18 3.2 TMA Installation.....................................................................................................................................................18 3.2 TMA Installation.....................................................................................................................................................18 3.3 Incorrect Parameter Settings...................................................................................................................................19 3.3 Incorrect Parameter Settings...................................................................................................................................19 3.4 Hardware Fault.......................................................................................................................................................19 3.4 Hardware Fault.......................................................................................................................................................19 3.5 Repeater..................................................................................................................................................................20 3.5 Repeater..................................................................................................................................................................20 3.6 Antenna Matching Problem....................................................................................................................................20 3.6 Antenna Matching Problem....................................................................................................................................20 3.7 Behavior of Mobile Phone Users............................................................................................................................21

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3.7 Behavior of Mobile Phone Users............................................................................................................................21

4 Analysis Procedure for the Uplink-Downlink Balance.......................22 4.1 Abis Signaling Analysis .........................................................................................................................................22 4.1 Abis Signaling Analysis .........................................................................................................................................22 4.2 Analysis Procedure.................................................................................................................................................25 4.2 Analysis Procedure.................................................................................................................................................25 4.3 Description of the Analysis Procedure...................................................................................................................27 4.3 Description of the Analysis Procedure...................................................................................................................27

5 Uplink-Downlink Balance Optimization Cases..................................29 5.1 Case 1: Abnormal DDPU Gain...............................................................................................................................29 5.1 Case 1: Abnormal DDPU Gain...............................................................................................................................29 5.2 Case 2: DTRU Software Problem...........................................................................................................................30 5.2 Case 2: DTRU Software Problem...........................................................................................................................30 5.3 Case 3: Inappropriate Parameter Settings...............................................................................................................31 5.3 Case 3: Inappropriate Parameter Settings...............................................................................................................31

6 Information Required for Uplink-Downlink Balance Problem Feedback .......................................................................................................32

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Figures Uplink-downlink balance level...........................................................14 Distribution of differences between the uplink levels and downlink levels..............................................................................................15 Distribution of the uplink levels and downlink levels..........................16 Cumulative distribution of the uplink level and downlink level............17

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Tables Mapping between the uplink-downlink balance level and the receive level (BSC6000)................................................................................12

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GSM BSS Network KPI (Uplink-Downlink Balance) Optimization Manual

1

Precondition and Assumption

The uplink level (Rx_Lev_UP) and downlink level (Rx_Lev_UP) in this document refer to the uplink level and downlink level after the power decrease in the power control is compensated. That is: Rx_Lev_UP = RxLevUP + Power Decrease in Power Control (MS) Rx_Lev_DL = RxLevDL + Power Decrease in Power Control (BS)

Note: Only the uplink level and downlink level in the MR on the Abis interface and the power control information are considered in the calculation of the uplink level and downlink level in the

preceding formula. The static power level of the BTS does not affect the values of the uplink level and downlink level on the Abis interface, and thus does not affect the uplink-downlink balance measurement. The static power level of the TRX is counted in the calculation of the cabinet-top power. For example:

The MR of the Abis signaling consists of these messages: RxLev-ful-UP, RxLev-sub-UP, RxLev-ful-DL, RxLev-sub-DL, DTX-UP, DTX-DL, BS-Power-level, and MS-Power-level. If the uplink DTX is enabled in the cell, use the value of RxLev-sub-UP in the calculation of the uplink level; otherwise use the value of RxLev-ful-UP. If the downlink DTX is enabled in the cell, use the value of RxLev-sub-DL in the calculation of the downlink level; otherwise use the value of RxLev-ful-DL. In a GSM900 network, the MS-Power-level 5 indicates a transmit power of 33 dBm (the maximum transmit power of the MS). The MS transmit power decreases by 2 dB every time the MS power level increases by one from level 5. In a GSM1800 network, the MS-Power-level 0 indicates a transmit power of 30 dBm (the maximum transmit power of the MS). The MS transmit power decreases by 2 dB every time the MS power level increases by one from level 0. For the transmit power of a BTS, the BS-Power-level 0 indicates the maximum transmit power

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(the static power set for the TRX). The BTS transmit power decreases by 2 dB every time the power level increases by one from level 0. For example, if the maximum power of the TRX power amplifier is 47.8 dBm (60 W), set the static power level to 46 dBm (40 W) if the TRX power amplifier is installed in the cell. After a call is connected, the BTS sends a downlink power control message, in which the value of BS-Power-level is 2, indicating that the transmit power of the BTS is 42 dBm (46 dBm – 2 x 2 dB = 42 dBm).

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Principles of Uplink-Downlink Balance

In GSM, a two-way communication system, both the uplink and downlink have a transmit power and path loss. Balances between the uplink and downlink in each cell are required to achieve optimal system performance and to provide good voice quality during the handover and call connection. Links used for transmissions from the BTS to the MS are referred to as downlinks. Links used for transmissions from the MS to the BTS are referred to as uplinks. The uplink-downlink balance means that the uplink signal and downlink signal cover the cell edge simultaneously. The uplink-downlink imbalance means that the uplink signal and downlink signal cannot cover the cell edge simultaneously. As a result, the uplink restriction or downlink restriction occurs.

2.1 Fundamentals of the Uplink-Downlink Balance When the uplink and downlink are in balance, the maximum uplink path loss (Max_Path_Loss_UL) should be the same as the maximum downlink path loss (Max_Path_Loss_DL). Maximum downlink path loss = Cabinet-top power – BTS feeder loss + BTS antenna gain + MS antenna gain – MS feeder loss – MS receiver sensitivity – Human body loss – Remaining power Maximum uplink path loss = MS power – MS feeder loss + MS antenna gain – Human body loss + BTS antenna gain + Diversity gain + TMA gain – BTS feeder loss – BTS receiver sensitivity – Remaining power

The formula for calculating the cabinet-top power is: Cabinet-top power = TRX transmit power – Combiner loss – Jumper loss. The remaining power (usually 10 dB) is the power required to ensure the voice quality and the connection rate taking into account the interference and loss. The diversity gain consists of the antenna diversity gain and the frequency hopping diversity 2012-04-19

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gain. Due to the reciprocity of the antenna, the antenna has the same effect on the downlink and the uplink. In addition, frequency difference between the uplink and downlink in a GSM network is small; therefore, the radio transmission features are similar. Thus, the human body loss should approximate to the remaining power.

When the tower mounted amplifier (TMA) is not used and the uplink and downlink are in balance: Cabinet-top power – MS receiver sensitivity = MS power + Diversity gain – BTS receiver sensitivity Change the preceding formula in this way: Cabinet-top power – MS power = MS receiver sensitivity + Diversity gain – BTS receiver sensitivity

When the TMA is used and the uplink and downlink are in balance: Cabinet-top power – MS receiver sensitivity = MS power + Diversity gain + TMA gain – BTS receiver sensitivity

Change the preceding formula in this way: Cabinet-top power – MS power = MS receiver sensitivity + Diversity gain + TMA gain – BTS receiver sensitivity

2.2 Evaluating the Uplink-Downlink Balance How can you evaluate whether the uplink and downlink are in balance? One method is to use the uplink level and downlink level in the MR. The detailed evaluation procedure is described as follows:

Downlink receive level = Cabinet-top power – BTS feeder loss + BTS antenna gain – downlink path loss + MS antenna gain – MS feeder loss – Human body loss

Uplink receive level = MS power – MS feeder loss + MS antenna gain – Uplink path loss – Human body loss + BTS antenna gain – BTS feeder loss

Downlink path loss = Uplink path loss, hence, Downlink receive level – Uplink receive level = Cabinet-top power – MS power Formula 1

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Based on the difference calculated in Formula 1, you can evaluate the balance between the uplink and downlink. The radio signal is fluctuating. Hence, statistical analysis on the radio signal should be based on a large amount of data. A fluctuation of 3 dB can be considered in the calculation. The analysis result of adequate test data records can be used to evaluate the balance between the uplink and downlink.

2.2.1 Theoretical Calculation of Uplink-Downlink Balance on Huawei Devices To analyze the uplink-downlink balance on Huawei devices, assume that: The TMA is not considered; The sensitivity of the GSM900 MS is -104 dBm; Huawei BTS receiver sensitivity is -113 dBm; The antenna diversity gain is 2.5 dB. The transmit power of Huawei BTS TRX is 60 W (47.78 dBm); The combiner loss is 4.5 dB. MS receiver sensitivity + Diversity gain – BTS receiver sensitivity = -104 + 2.5 – (-113) = 11.5 dB Considering the complex radio transmission path, a fluctuation of 3 dB is provided. It is concluded that: The average difference between the uplink level and downlink level ranges from 8.5 dB to 14.5 dB. The values 8.5 dB and 14.5 dB correspond to the uplink-downlink balance level 8 and level 9 respectively. Figure 1.1 Mapping between the uplink-downlink balance level and the receive level (BSC6000)

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Uplink-Downlink Balance Level

Downlink Receive Level – Uplink Receive Level -6

1

≤-15 dB

2

-14 dB,-13 dB,-12 dB,-11 dB,-10 dB

3

-9 dB,-8 dB,-7 dB,-6 dB

4

-5 dB,-4 dB,-3 dB

5

-2 dB,-1 dB

6

0 dB

7

1 dB, 2 dB

8

3 dB, 4 dB, 5 dB

9

6 dB, 7 dB, 8 dB, 9 dB

10

10 dB, 11 dB, 12 dB, 13 dB, 14 dB

11

≥15 dB

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On Huawei BTSs, peak levels 8/9/10 in the uplink-downlink balance MR indicate that the uplink level and downlink level comply with the equipment performance specification and the uplink and downlink are in balance.

Take into account the cabinet-top power and MS transmit power: Cabinet-top power – MS transmit power = TRX transmit power – Combiner loss – MS power = 47.78 - 4.5-33 = 10.28 dB < MS receiver sensitivity + Diversity gain – BTS receiver sensitivity

The design power of Huawei BTS TRXs can maintain the uplink-downlink balance, and thus helps you maintain secure network operation.

2.2.2 Evaluating the Uplink-Downlink Balance With the Uplink-downlink Balance Measurement Analyze the uplink-downlink balance according to the Uplink-and-Downlink Balance Measurement per TRX in the MR Measurement. The uplink and downlink are not in balance if either of the two formulas is true:

Rate of Number of MRs (Uplink-and-Downlink Balance Level = 1) + Rate of Number of MRs (Uplink-and-Downlink Balance Level = 2) > 15%. It indicates that the uplink is weaker or the downlink is stronger. Rate of Number of MRs (Uplink-and-Downlink Balance Level = 11) > 30%. It indicates that the downlink is stronger or the uplink is weaker. Cells with serious uplink -downlink imbalance problem can be easily sorted by using the two formulas. For the cells in which the uplink and downlink are slightly imbalanced, tracing of the Abis signaling is required. You can analyze the balance between the uplink and downlink based on the MR in the signaling tracing files.

The following example explains how to evaluate the balance between the uplink and downlink based on the Uplink-and-Downlink Balance Measurement per TRX. Figure 1 shows the distribution of the uplink and downlink balance levels in 24 hours of a day based on the Uplink-and-Downlink Balance Measurement per TRX. The cabinet-top power in the cell is 43.4 dBm. Enable the Abis signaling tracing function to check whether the uplink level and downlink level in the cell comply with the BTS performance specification and whether the uplink and downlink are in balance. The calculation based on the MRs in the signaling shows that the average difference between the uplink level and downlink level is 14 dBm, and Cabinet-top power – MS power = 10.4 dB; that is, Difference between the uplink level and downlink level – (Cabinet-top power – MS power) = 3.6 dB. The result 3.6 dB is within the normal range.

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Hence, the formula Rate of Number of MRs (Uplink-and-Downlink Balance Level = 11) > 30% can be used to judge whether the uplink and downlink are in balance. Figure 1.1 Uplink-downlink balance level

Uplink level– Downlink level 30%

26% 25%

21%

20%

17%

15%

10%

9%

10%

Level 11 (21..26)

Level 10 (16..20)

Level 9 (12..15)

Level 8 (9..11)

Level 7 (7..8)

3% Level 6 (6)

5%

Level 5 (4..5)

5%

Level 4 (1..3)

Level 1 (≤-9)

0%

1% Level 2 (-8..-4)

0%

3% Level 3 (-3..0)

5%

2.2.3 Evaluating the Uplink-Downlink Balance With the Average Uplink-Downlink Level Difference To facilitate the description, select several cells under BSC_test for data analysis. The average cabinet-top power in the cell is 40.63 dBm. Disable the power control function for all cells. Then, trace the RSL signaling on the Abis interface of the selected cells under BSC_test. Analyze the MRs obtained from the Abis signaling tracing results, calculate the average difference between the uplink level and downlink level. The average value should approximate to the difference between the cabinet-top power and MS power. A deviation of ±3 dB is allowed.

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Figure 1.1 Distribution of differences between the uplink levels and downlink levels

DL-DU L UL L-

1000000 800000 600000 400000

23

20

17

14

11

8

5

2

-1

-4

-7

- 10

- 13

- 16

- 19

- 22

0

3 dB, the uplink and downlink are considered to be imbalanced.

2.2.5 Evaluating the Uplink-Downlink Balance With the Uplink-Downlink Cumulative Distribution Analyze the distribution of the uplink level and downlink level with the cumulative distribution function in the ascending order of the level proportion.

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Figure 1.1 Cumulative distribution of the uplink level and downlink level

- 50

- 54

- 58

- 62

- 66

- 70

- 74

- 78

- 82

- 86

- 90

- 94

- 98

- 102

RxLev- UL RxLev- DL

- 106

- 110

100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0%

The value corresponding to the red line in figure xx should approximate to the difference between the cabinet-top power and MS power. The balance between the uplink and downlink can easily be determined with the cumulative distribution. If the value corresponding to the red line in Figure 4 minus the difference between the cabinettop power and MS power is greater than 3 dB, the uplink and downlink are considered to be imbalanced.

2.3 Effects of the Uplink-Downlink Imbalance Uplink restriction: The uplink restriction occurs when the cell edge is covered by the uplink signal but not the downlink signal. That is, the uplink coverage is wider than the downlink coverage. In such a case, the MS inside the uplink coverage area but outside the downlink coverage area will fail to originate a call. Even if the call is successfully connected, the uplink voice is discontinuous (or the called party can be heard but the calling party cannot be heard), and thus causing many call drops. Uplink restriction leads to user complaints and poor user experience. Thus, in the network design, the transmit power of the BTS is decreased to prevent from the uplink restriction. Downlink restriction: The downlink restriction occurs when the cell edge is covered by the downlink signal but not the uplink signal. That is, the uplink coverage is wider than the downlink coverage. In such a case, the coverage of the BTS is relatively small. If the BTS provides seamless coverage and there is no blind coverage area, MS users usually are not aware of the downlink restriction, and thus do not complain about the service quality. Hence, when the downlink is restricted, part of the downlink power is wasted because the BTS can transmit at a higher power. The network with downlink restriction is relatively secure.

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Factors Affecting the UplinkDownlink Balance

Based on the analysis of complaints for various networks and test experiences on site and in the lab, the following factors are determined to be the major factors affecting the uplink-downlink balance: Antenna and feeder installation TMA installation Incorrect parameter settings Hardware fault Repeater Antenna matching problem MS user behavior

3.1 Installation of the Feeder and Antenna The jumper, lightning rod, adapter, grounding solder joint, antenna, and occasionally, power divider are applied between the cabinet top and the antenna. The installation of these devices affects the receiving and transmitting capability of a BTS. For example, the loose connection between the jumper and its connector has different effects on the uplink level and downlink level. Typically, the downlink signal is strong. The signal strength on the feeder is about 30 dBm. The uplink signal, however, is much weaker (generally -80 dBm). Therefore, loose connection results in small uplink level but has no significant impact on the uplink level.

3.2 TMA Installation The TMA is a type of active devices used to amplify the uplink signal only. Nevertheless, the TMA can amplify both the uplink and downlink signals. If a TMA is installed, the Power Attenuation Factor parameter is configured for the RF front end module on the BSC6000. Generally, Power Attenuation Factor is set to a value equal to the actual TMA gain subtracted by 4 dB. The value 4 dB is an estimate for compensating for the feeder loss. Hence, if an uplink TMA is installed, in the calculation of the uplink-and-downlink balance MR, the difference between the downlink level and uplink level is decreased by 4 dB. The uplink level increases by 4 dB. If a two-way TMA is installed, the amplification of the downlink signal should also be taken into account. If gains in two ways are the same and the Power Attenuation Factor is 2012-04-19

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configured, the difference between the downlink level and uplink level increases by a value equal to the actual TMA gain subtracted 4 dB. In summary, when a TMA is installed in the BTS system, the uplink-and-downlink balance measurement per TRX either decreases or increases.

3.3 Incorrect Parameter Settings The uplink level and downlink level parameters involved are, the TMA Power Attenuation Factor and MS_TXPWR_MAX_CCH.

TMA Power Attenuation Factor The installation of a TMA results in an uplink gain, therefore, the TMA Power Attenuation Factor should be configured. If the TMA is not installed but the TMA Power Attenuation Factor is configured, then the uplink level is decreased. The difference between the downlink level and uplink level is increased. In such a case, the gain in the uplink of the BTS is decreased. The decrease can further affect the uplink receive capability of the BTS.

MS_TXPWR_MAX_CCH: MS transmit power levels are interpreted differently in GSM900 and GSM1800. In GSM900, MS power level 5 represents the full power 33 dBm. In GSM1800, however, MS power level 5 represents 20 dBm and the full power 30 dBm is represented by 0.

Be cautious when you configure the TMA Power Attenuation Factor. The factor cannot be too high. If the factor is set to an excessively high value, the uplink gain will be insufficient, which can further lead to uplink receiving problems. The TMA Power Attenuation Factor is usually set to a value equal to the TMA gain subtracted by 4 dB.

3.4 Hardware Fault Faults of either the transceiver receiving module or transceiver transmitting module may result in uplink error, downlink error, and uplink-downlink imbalances. Faults in the receiving module and transmitting module of the RF front end may also affect the receiving capability of the uplink and downlink. One problem may be the uplink-downlink imbalances.

The uplink and downlink MRs are provided based on the TRX. Therefore, the uplink-downlink balance measurement per TRX can be used to analyze whether the uplink and downlink are in balance.

Faults mainly exist in the DDPU and the DTRU. TRX faults are usually caused by a faulty hardware version or the hardware fault of a certain lot. The problems occurring are usually software problems, which consist of the following: 2012-04-19

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DDPU (RF front end module): Uplink gain is greater than the designed gain. Uplink gain is smaller than the designed gain. Inappropriate downlink transmit power is applied.

DTRU (TRX module): Inappropriate downlink transmit power is applied. Uplink gain is greater than the designed gain. Uplink gain is smaller than the designed gain.

A specialized analyzer is required to test the abnormal uplink gain. Therefore, after identifying the uplink gain problem, send the related hardware to Huawei for further analysis with the specialized analysis.

3.5 Repeater A variety of methods can be used to implement the function of a repeater. The application of a repeater will help obtain a certain amount of gain in both the uplink and downlink. Generally, the uplink gain and downlink gain can be adjusted. The adjustment further affects the balance between the uplink and downlink. Suppose a repeater is installed under a BTS, the uplink gain of the repeater is 6 dB, and the downlink gain of the repeater is 10 dB. In such a case, the difference between the uplink level and downlink level is 4 dB greater than the theoretical value. That is, the uplink is 4 dB weaker than the downlink. Such deviation does not affect the KPI; therefore, the adjustment is not required. Abnormal repeater gain in the uplink and downlink can also affect the balance between the uplink and downlink. If uplink-downlink imbalance is caused by the repeater, solve the problem by adjusting the repeater gain in the uplink and downlink. Along with the repeater gain adjustment, the BTS transmit power adjustment can also help rectify the uplink-downlink imbalance.

3.6 Antenna Matching Problem For the antenna with different antenna patterns for the uplink and downlink, the gain in the uplink is different from that in the downlink. When such antenna is installed, the uplink gain is different from the downlink gain. In such a case, the uplink-downlink imbalance can be viewed from the traffic statistics. The test experiences and study on the antenna performance show that the deviation caused by the antenna matching is within 3 dB. The deviation 3 dB is within the allowed fluctuation, and has no significant impact on the uplink-downlink balance measurement. You can solve the uplink-downlink imbalance problem caused by the antenna matching by adjusting the antenna direction or tilt and changing the antenna pattern for the uplink and downlink. You can also rectify the uplink-downlink imbalance by replacing the antenna. 2012-04-19

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3.7 Behavior of Mobile Phone Users Some mobile phone users intend to answer calls without moving the MS on the desk and answer calls through earphones. When a mobile phone is not moving, the propagation characteristics of the uplink are different from those of the downlink. As a result, the distribution of the uplink level will be different from that of the downlink level. That is, the uplink level is higher than the down link level in certain time. The opposite is true in other time. The fixed wireless terminal uses the air interface resources. Being used to provide public services, the fixed wireless terminal can generate a large volume of traffic. If many fixed wireless terminals are installed in a cell, these terminals can result in a great difference between the uplink and the downlink. The consequence is that the uplink receive level or the downlink receive level is weak. To rectify the uplink-downlink imbalance, change the radio transmission characteristics of the area where the mobile phone locates by adjusting the antenna direction and tilt of the main BTS.

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Analysis Procedure for the Uplink-Downlink Balance

4.1 Abis Signaling Analysis Analysis of the signaling tracing result is an effective way for troubleshooting GSM network problems. Generally, the BAM analysis tool is used to analyze the signaling, but few BAM analysis tools provide detailed analysis for the MRs in the signaling tracing result. The BSC6000 LMT provides signaling tracing functions associated with RSL, OML, BSSMAP, and so on. The single MS tracing function is the one of the most frequently used functions in the network optimization process.

You can review the signaling tracing result on the LMT.

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If you save the reviewed signaling tracing results as .txt files, the .txt files can then be processed with Excel.

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The fields of messages in the tracing result should be identified when processing an MR. To identify the field of a message, do as follows: select a Measurement Result message for example; double-click the message; the MsgExplain dialog box is displayed. The field information about all messages is shown in this dialog box. For example, the Rxlev-sub-up corresponds to the six least significant bits of the 42nd bytes, and the corresponding content is 3F. You can also identify the fields of other messages in this way. To analyze problems, you usually need to identify the fields of these messages: rxlev_up(sub) rxlev_dl(sub) rxqual_up(sub) rxqual_dl(sub) rxlev_up(ful) rxlev_dl(ful) rxqual_up(ful) rxqual_dl(ful) BS_power MS_power meas_valid DTX_DL DTX_UL TA

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You may use these functions to process the fields: Hex2dec(): Convert from hexadecimal to decimal. Hex2bin(): Convert from hexadecimal to binary. Hex2dec(): Convert from binary to decimal. Trunc(): Truncates a number to a specified number of decimal places. Right(): Returns the specified number of rightmost characters of a string. Mid(): Returns a specified number of characters from a string. Note that if the Mid() function is applied to a number with zero at the left-most place, an error will occur, because the zero at the right-most place is not counted as a character. To use these functions in Excel, choose Tools > Add-Ins, and then select Analysis ToolPak and Analysis ToolPak – VBA. This method can also be applied to the analysis of handover messages and immediate assignment messages.

4.2 Analysis Procedure The analysis procedure is designed based on the factors affecting the uplink-downlink balance and the on-site optimization conditions. Based on the network optimization conditions, such as devices and the personnel, certain modifications are allowed to efficiently analyze the uplink-downlink balance problem.

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Start

Are the uplink and downlink in balance in the cell?

Yes

No processing is required for the normal cells.

No Check the connection of the antenna and feeder in these cells. Yes Is there any problems with the antenna and feeder connection?

Is the uplink-downlink imbalance rectified?

Yes

No Check the parameter settings in this cell.

Are the parameters set correctly?

The cause of the problem is identified. The flow is complete. Yes

Is the uplink-downlink imbalance rectified?

Yes

No No Test the cabinet-top power.

Is the transmit power normal?

No

Is the uplink-downlink imbalance rectified?

Yes No Trace the signaling on the Abis interface in the faulty cells. The hardware fault is confirmed. Send the faulty TRX to Huawei for further analysis.

Conduct fixed-position tests in the faulty cells and trace the signaling on the Abis interface.

Are the user behaviors normal in the faulty cells?

No

Yes

Is the uplink-downlink imbalance rectified?

Yes

No

Replace the faulty TRX with a normal TRX.

Is there a problem with the hardware?

Yes

Send the faulty hardware to Huawei for further analysis.

No

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4.3 Description of the Analysis Procedure The following section describes the procedure for analyzing the uplink-downlink balance problem. Analyze the Uplink-and-Downlink Balance Measurement per TRX counter in MR Measurement, and then list the cells with the uplink-downlink imbalance. Apply the following formula to the cells to check for the uplink-downlink imbalance. Rate of Number of MRs (Uplink-and-Downlink Balance Level = 1) + Rate of Number of MRs (Uplink-and-Downlink Balance Level = 2) > 15%. If this is true, it indicates that the uplink is weaker or downlink is stronger. Rate of Number of MRs (Uplink-and-Downlink Balance Level = 11) > 30% If this is true, it indicates that the downlink is stronger or the uplink is weaker.

You can also use the average difference between the uplink level and downlink level to check for the uplink-downlink imbalance of the TRX in a cell.

If Average difference between the uplink level and downlink level – (Cabinet-top power – MS power) > 3 dB, the uplink level and downlink level do not comply with the BTS performance specification, and the uplink and downlink are imbalanced.

Divide the cells with the uplink-downlink imbalance into two groups based on the KPI: the group with decreased KPI (high call drop rate) takes precedence over the group with normal KPI (normal call drop rate). The processing flows for the two groups are the same.

Analyze the connections of the hardware in the cell by checking the BTS hardware type, combining mode, TMA type, repeater, antenna specification, and devices connected to the feeder. Then, check whether TMA Power Attenuation Factor and MS_TXPWR_MAX_CCH are set correctly. Check whether the repeater gain in the uplink and downlink is normal. If problems are found during the analysis process, check whether the problems are solved. The analysis flow is completed if the problems are solved. If no problems are found in the preceding analysis, go to the next step. Test the cabinet-top power: Check whether a deviation exists between the actual cabinet-top power and its theoretical value. If a deviation exists, check whether the deviation is the cause for the uplink-downlink imbalance. For example, if the cabinet-top power is 3 dB greater than its theoretical value, and the average difference between the uplink level and downlink level is 3 dB greater than its theoretical value, the uplink-downlink imbalance is caused by excessively high cabinet-top power. If the cabinet power is normal, go to the next step. Trace the RSL signaling on the Abis interface in the cells with the uplink-downlink imbalance by doing the following: retrieve the MR; analyze the uplink level, downlink level and uplinkand-downlink balance distribution in the MR of various users. Signaling of individual users can be extracted by using the Signal Analyze Tool. Without the Signal Analyze Tool, you can save the signaling tracing result as a .txt file through the Review Tracing function and then analyze the file with Excel. Check whether the uplink level, downlink level, and difference between the uplink level and downlink level are normal. If there is a problem with these values, check whether the imbalance problem occurs to part of the users or all users. Go to the next step if the 2012-04-19

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imbalance problem occurs to all users. From the tracing result of the signaling on the Abis interface, you can obtain the following information: the MRs of one user (mtls-ccb), the distance between the user and the BTS (TA), the mobility of the user (fluctuation of the uplink level and downlink level), and the levels when the uplink-downlink imbalance occurs. Trace the signaling of the dialing test conducted at a fixed position: In the main lobe coverage area, dial a fixed-line phone using the test MS in frequency locking mode in a place 500m away from the antenna. The antenna should be in sight at the test position. Enable the single MS tracing function on the LMT to trace the signaling of the test MS. Move the test MS around a circle (diameter: 3m) with the test spot as the center and test for a minimum of 10 minutes. Analyze the MR in the signaling tracing result by making calculation for the uplink level and downlink level in the MR. If the difference between the uplink level and downlink level equals the difference between the cabinet-top power and MS power, you can infer that the uplinkdownlink imbalance is caused by the user behavior rather than the BTS equipment. One possible behavior is that users make calls without moving the MSs. The BTS equipment is the cause for the imbalance if either of the following is true: Difference between the uplink level and downlink level < Cabinet-top power – MS power. It indicates that the uplink gain is greater than its theoretical value. Difference between the uplink level and downlink level > Cabinet-top power – MS power. It indicates that the uplink gain is smaller than its theoretical value. Confirm that the uplink gain is abnormal, and then return the faulty DDPU and DTRU to Huawei for further analysis. The uplink level and downlink level in the test can be used to determine the uplink gain and downlink gain. Typically, at a spot 500m away from the antenna, the cabinet-top power is 44 dBm, the antenna gain is 17 dB, the uplink level is about -73 dBm, and the downlink level is about -61 dBm. The signal strength at a spot within 500m from the antenna varies with reflections; therefore, the uplink level and downlink level are for reference only. The difference between the uplink level and downlink level, however, can be used to analyze whether the uplink and downlink are in balance. If Average difference between the uplink level and downlink level – (Cabinet-top power – MS power) > 3 dB, the uplink and downlink are imbalanced. If the cabinet-top power is determined to be normal in a cell where the uplink and downlink are imbalanced, you can infer that the uplink gain is abnormal. Then, go to the next step.

After you infer that the uplink gain on site is abnormal, replace the DDPU with a normal DDPU to check whether the uplink gain in the DDPU or that in the DTRU is abnormal. If the uplink and downlink are balanced after replacing the DDPU, the uplink gain associated with the DDPU in the problematic cell is abnormal. If the uplink and downlink are still imbalanced after replacing the DDPU, the uplink gain associated with the DTRU in the problematic cell is abnormal. When the hardware problem is confirmed, return the hardware to Huawei in time for further analysis.

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Uplink-Downlink Balance Optimization Cases

5.1 Case 1: Abnormal DDPU Gain Problem Description The uplink-and-downlink measurement results returned by the BTS3012 and BTS3006C are different.

Analysis and Solution The following bar chart shows the uplink-downlink balance measurement distribution from 8:00 to 14:00 on Dec., 25th, 2007 in two cells, cell A and cell B.

Cell A

30%

Cell B 27%

25. 5%

25%

22%

21. 4% 20%

16%

15. 2%

15%

12. 6%

12%

10% 6. 3%

5. 8% 1. 0%

0. 5%

( 16, 17, 18, 19, 20)

( >=21)

( 9, 10, 11)

( 7, 8)

6

5%

3. 1%

( 12, 13, 14, 15)

4. 5% 4%

( 4, 5)

( 1, 2, 3)

1%

6%

2% ( - 3, - 2, - 1, 0)

0% ≤-9

0%

5%

3. 9%

( - 8, - 7, - 6, - 5, - 4)

5%

Trace the signaling messages on the RSL over the Abis interface and analyze the MRsThe uplink-downlink balance measurement results of all users in the two cells differentiate greatly. Calculate the average difference between the uplink level and downlink level in all MRs of the signaling tracing results in the two cells. In cell A, the difference is 3 dB; in cell B, the difference is 11.24 dB.

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Test the transmit power of the two BTSs on site. The test shows that the transmit power of the DTRU is normal. The cabinet-top power complies with the theoretical value. In cell A, the cabinet-top power is 4 dBm; in cell B, the cabinet-top power is 43 dBm.

Calculate the difference between the uplink level and downlink level with formula 3: Uplink receive level - Downlink receive level = Cabinet-top power – MS power Cell A: Cabinet-top power – MS power = 41 – 33 = 8 Cell B: Cabinet-top power – MS power = 43 – 33 = 10 Obviously, the uplink gain in cell A is abnormal (4 dB–5 dB beyond the normal range).

Measure the uplink receive gain of the DDPU with a vector analyzer to ensure that the uplink gain is at least 3 dB greater than the designed value.

The software analysis shows that an error occurs when configuring the LNA gain for this DDPU version. Note: In the old DDPU (48.1.1), the LNA gain is set to an absolute value. No error occurs when configuring the LNA gain. Version 48.1.0 and later versions of the DDPU all work properly. In the new DDPU (48.1.0), the LNA gain in software versions earlier than V100R001C07B229 (V100R001C07B229 not included) is set to an absolute value. An error occurs when configuring the LNA gain. In the new DDPU (48.1.0), the LNA gain in software versions later than V100R001C07B229 (V100R001C07B229 not included) is set to a relative value. No error occurs when configuring the LNA gain.

To solve the problem, upgrade the software version.

5.2 Case 2: DTRU Software Problem Problem Description Various KPIs in a cell are normal, but the uplink-downlink balance measurement on several TRXs shows that the rate of Number of MRs (Uplink-and-Downlink Balance Level = 11) accounts for more than 50%.

Analysis and Solution Trace the RSL signaling on the Abis interface in this cell, and analyze the MRs. The analysis shows that the uplink level is greater than the downlink level for all users served by the problematic TRX. The average difference between the uplink level and downlink level is 17 dB, which is 6 dB greater than the difference between the cabinet-top power and MS power. 2012-04-19

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The cabinet-top transmit power is tested and is found to be normal. Thus, the downlink transmit power is normal.

Analyze the KPIs of this cell. The KPIs are found to be normal. We suspect that the software on the faulty TRX is not running properly; as a result, the reported uplink level on the Abis interface is smaller compared with its actual value.

The faulty TRX is sent to Huawei lab for further analysis. The analysis shows that when reporting the uplink received signal strength indicator (RSSI), the negative symbol or positive symbol in the compensation value reported by the compensation program is reversed. Consequently, the measurement shows the uplink-downlink imbalance.

To solve the problem, upgrade the software version and test in the lab. The solution is incorporated into version V100R001C07B239 and later versions.

5.3 Case 3: Inappropriate Parameter Settings Problem Description In a DCS1800 cell, the MS of the calling party displays maximum signal strength, however, the calling party cannot be heard or only discontinuous voice can be heard after the call is connected.

Analysis and Solution Trace the RSL signaling on the Abis interface in the cell. Then, analyze the MRs in the tracing result. The analysis shows that the uplink level of all users is 20 dB greater than the corresponding downlink level.

The cabinet-top transmit power is tested and is found to be normal.

Analyze the tracing result of the Abis signaling and the uplink level is found to be excessively low.

Check the maximum transmit power of the MS in the MR. The maximum transmit power is incorrectly set to 5.

Modify the parameter settings of this cell: set the maximum transmit power of the MS to 0. The problem is solved.

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Information Required for Uplink-

Downlink Balance Problem Feedback In case the uplink-downlink imbalance occurs, the following information is required when requesting the technical assistance: A list of cells with the uplink-downlink imbalance: A description of the time that the uplinkdownlink imbalance occurs should be included. The configuration file (DAT file) of the BSC with the uplink-downlink imbalance, BSC version, and BTS software version The measured value of the cabinet-top power Information about the antenna and feeder used in the cell with the uplink-downlink problem: antenna specification, TMA specification, and list of other equipment connected to the feeder The traffic statistics data about the BSC (with the uplink-downlink imbalance problem) when the BSC are busy: Uplink-and-Downlink Balance Measurement per TRX in the MR Measurement Data of RSL signaling tracing in the cells: Select several cells with serious uplink-downlink imbalance problem and trace the RSL signaling on the Abis interface in these cells. Signaling tracing data of the MS dialing test: In the main lobe coverage area, dial a fixed-line phone using the test MS in frequency locking mode in a place 500m away from the antenna. The antenna should be in sight at the place. Enable the single MS tracing function on the LMT to trace the signaling of the test MS. Move the test MS around a circle (diameter: 3m) with the test spot as the center and test for a minimum of 10 minutes.

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