10 gsm bss network kpi (uplink downlink balance) optimization manual[1].doc

GSM BSS Network KPI (Uplink-Downlink Balance) Optimization Manual INTERNAL
Product Name Confidentiality Level
GSM INTERNAL
Product Version Total 35 pages
V00R02
GSM BSS Network KPI (Uplink-Downlink
Balance) Optimization Manual
For Internal Use Only
Prepared by GSM &UMTS Performance
Research Department
Yang
Jixiang
Date 2008-1-24
Reviewed by Date
Reviewed by Date
Approved by Date
Huawei Technologies Co., Ltd.
All rights reserved
2014-06-18 HUAWEI Confidential Page 1, Total 35

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

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 uplink-
downlink balance.
Key words:
Reference:
List of abbreviations:
Abbreviation Full Spelling

Contents
1 Precondition and Assumption..................................................................................................11
2 Principles of Uplink-Downlink Balance................................................................................13
2.1 Fundamentals of the Uplink-Downlink Balance....................................................................................................13
2.1 Fundamentals of the Uplink-Downlink Balance....................................................................................................13
2.2 Evaluating the Uplink-Downlink Balance..............................................................................................................14
2.2 Evaluating the Uplink-Downlink Balance..............................................................................................................14
2.2.1 Theoretical Calculation of Uplink-Downlink Balance on Huawei Devices.....................................................15
2.2.1 Theoretical Calculation of Uplink-Downlink Balance on Huawei Devices.....................................................15
2.2.2 Evaluating the Uplink-Downlink Balance With the Uplink-downlink Balance Measurement........................16
2.2.2 Evaluating the Uplink-Downlink Balance With the Uplink-downlink Balance Measurement........................16
2.2.3 Evaluating the Uplink-Downlink Balance With the Average Uplink-Downlink Level Difference.................17
2.2.3 Evaluating the Uplink-Downlink Balance With the Average Uplink-Downlink Level Difference.................17
2.2.4 Evaluating the Uplink-Downlink Balance With the Uplink-Downlink Level Distribution.............................18
2.2.4 Evaluating the Uplink-Downlink Balance With the Uplink-Downlink Level Distribution.............................18
2.2.5 Evaluating the Uplink-Downlink Balance With the Uplink-Downlink Cumulative Distribution....................19
2.2.5 Evaluating the Uplink-Downlink Balance With the Uplink-Downlink Cumulative Distribution....................19
2.3 Effects of the Uplink-Downlink Imbalance............................................................................................................20
2.3 Effects of the Uplink-Downlink Imbalance............................................................................................................20
3 Factors Affecting the Uplink-Downlink Balance..................................................................21
3.1 Installation of the Feeder and Antenna...................................................................................................................21
3.1 Installation of the Feeder and Antenna...................................................................................................................21
3.2 TMA Installation.....................................................................................................................................................21
3.2 TMA Installation.....................................................................................................................................................21
3.3 Incorrect Parameter Settings...................................................................................................................................22
3.3 Incorrect Parameter Settings...................................................................................................................................22
3.4 Hardware Fault.......................................................................................................................................................22
3.4 Hardware Fault.......................................................................................................................................................22
3.5 Repeater..................................................................................................................................................................23
3.5 Repeater..................................................................................................................................................................23
3.6 Antenna Matching Problem....................................................................................................................................23
3.6 Antenna Matching Problem....................................................................................................................................23

3.7 Behavior of Mobile Phone Users............................................................................................................................24
3.7 Behavior of Mobile Phone Users............................................................................................................................24
4 Analysis Procedure for the Uplink-Downlink Balance.......................................................25
4.1 Abis Signaling Analysis .........................................................................................................................................25
4.1 Abis Signaling Analysis .........................................................................................................................................25
4.2 Analysis Procedure.................................................................................................................................................28
4.2 Analysis Procedure.................................................................................................................................................28
4.3 Description of the Analysis Procedure...................................................................................................................30
4.3 Description of the Analysis Procedure...................................................................................................................30
5 Uplink-Downlink Balance Optimization Cases...................................................................32
5.1 Case 1: Abnormal DDPU Gain...............................................................................................................................32
5.1 Case 1: Abnormal DDPU Gain...............................................................................................................................32
5.2 Case 2: DTRU Software Problem..........................................................................................................................33
5.2 Case 2: DTRU Software Problem..........................................................................................................................33
5.3 Case 3: Inappropriate Parameter Settings...............................................................................................................34
5.3 Case 3: Inappropriate Parameter Settings...............................................................................................................34
6 Information Required for Uplink-Downlink Balance Problem Feedback......................35

Figures
Uplink-downlink balance level...................................................................................................17
Distribution of differences between the uplink levels and downlink levels....................18
Distribution of the uplink levels and downlink levels..........................................................19
Cumulative distribution of the uplink level and downlink level........................................20

Tables
Mapping between the uplink-downlink balance level and the receive level (BSC6000) 15

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 (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).

2 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 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
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)
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

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.
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
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.

Figure 1.1 Distribution of differences between the uplink levels and downlink levels
DL- UL
0
200000
400000
600000
800000
1000000
<-24
-22
-19
-16
-13
-10
-7
-4
-1
2
5
8
11
14
17
20
23
DL- UL
According to the calculation of the MR data, the average difference between the uplink level
and downlink level is 4.72 dB. Figure 2 shows that the peak difference is 4 dB. Cabinet-top
power – MS power
= 40.63 - 33
= 7.68 dB
In BSC_test, Difference between the uplink level and downlink level – (cabinet-top power -
MS power) = 3 dB. The value 3 dB is within the normal range. Therefore, the uplink and
downlink in the BSC area are in balance.
Downlink Level Distribution
Analyze all MRs in the tracing result of the Abis signaling under BSC_test, and then analyze
the distribution of the uplink level and downlink level. The analysis result is shown in Figure
3.

Figure 1.1 Distribution of the uplink levels and downlink levels
0
50000
100000
150000
200000
250000
300000
350000
400000
450000
500000
-110
-107
-104
-101
-98
-95
-92
-89
-86
-83
-80
-77
-74
-71
-68
-65
-62
-59
-56
-53
-50
-47
Rxl ev- UL Rxl ev- -DL
Figure 3 shows the peak value of uplink level and that of downlink level.
Peak value of uplink receive level = 81 dBm
Peak value of downlink receive level = 73 dBm
The difference between the uplink level and downlink level is 8 dB.
Cabinet-top power – MS power = 40.63 – 33 = 7.63 dB
In the distribution of the downlink level and uplink level, the difference between the peak
uplink level and the peak downlink level should approximate to the difference between the
cabinet-top power and MS power.
If Difference between the peak uplink level and peak downlink level – (Cabinet-top power –
MS power) > 3 dB, the uplink and downlink are considered to be imbalanced.
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.

Figure 1.1 Cumulative distribution of the uplink level and downlink level
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
-110
-106
-102
-98
-94
-90
-86
-82
-78
-74
-70
-66
-62
-58
-54
-50
RxLev- UL
RxLev- DL
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
cabinet-top 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.

3 Factors Affecting the Uplink-Downlink
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
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:
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.
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.

4 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.

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

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

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.

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 uplink-
and-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 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
uplink-downlink 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.

5 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.
3. 9%
15. 2%
25. 5%
21. 4%
12. 6%
4. 5%
6. 3% 5. 8%
3. 1%
1. 0% 0. 5%0% 1%
2%
5%
6%
4%
12%
22%
27%
16%
5%
0%
5%
10%
15%
20%
25%
30%
≤-9
(-8,-7,-6,-5,-4)
(-3,-2,-1,0)
(1,2,3)
(4,5)
6
(7,8)
(9,10,11)
(12,13,14,15)
(16,17,18,19,20)
(>=21)
Cell A Cell B
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.

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%.
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.
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.
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.

6 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 uplink-
downlink 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.

10 gsm bss network kpi (uplink downlink balance) optimization manual[1].doc

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