Collection of GSM RNP technical problems and replies(No.1)-20040528-A-1.0.pdf

Collection of GSM RNP technical problems and replies(Issue 1)

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Collection of GSM RNP technical problems and replies(No. 1) (For internal use only)

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Huawei Technologies Co., Ltd. All rights reserved

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Confidential Information of Huawei. No Spreading without Permission

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Contents 1 How to realize diversity for different CDU configurations .................................3 2 Meaning of an interface band statistics................................................................3 3 Function Control problem ....................................................................................4 4. IUO problem1 .....................................................................................................4 5. IUO problem2 .....................................................................................................5 6. IUO problem3 .....................................................................................................5 7. IUO prbolem4 .....................................................................................................6 8. IUO traffic statistics............................................................................................6 9. RACH min. access level ......................................................................................6 10. The effect of Tower Mounted Amplifier on Diversity Receiving ....................7 11. The measurement result of “TCH call drop connected” deviates a lot from that of “TCH call drop connected”. ...............................................................................7 12. No measurement result outputs for traffic statistic.........................................8 13. It is hard to make a call in the case of signal with the receiving level of -80dBm. .................................................................................................................................8 14. Over-sea coverage.............................................................................................8 15 Signaling procedure ...........................................................................................9 16 BTS configuration after Capacity expansion.....................................................9 17 Rural network...................................................................................................10 18 Direct retry in combined networking.............................................................10 19 Please explain the T3105 and Max resent times of physical information .......11 20 Why No response for paging ...........................................................................11

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1. How to realize diversity for different CDU configurations Problem

How to realize diversity for different CDU configurations

Detail

For a 3/4-TRX sector, EDU+CDU mode (requiring three sets of antennas, generally not

Description

adopted ) is used. The three channels of TRXs of a 3-TRX sector have a loss of 1.0dB. Two channels of TRXs of a 4-TRX sector have a loss of 1.0dB, and the other two have a loss of 4.5dB. IUO mode can adopted as a coverage solution. For a 4-TRX sector, how can we realize diversity in EDU+CDU mode?

Reply

CDU

EDU

2-in-1 Duplexer 1-to-4 1-to-2

TRX0－1

Main receiving

TRX2－3

Diversity receiving

The 4-TRX EDU+CDU mode

As shown in the figure above, the EDU+CDU mode supports at most four TRXs in case of three antennas & feeders. In case each sector is with four TRXs, two TRXs reach the antenna feeder via CDU’s 2-in-1 combining unit and duplex with the loss of 4.5dB (in case each sector is with three TRXs, one TRX reaches the antenna feeder directly via the duplexer with the loss of 1.0dB); two other TRXs reach the antenna feeder via EDU’s 2-channel duplexer with the loss of 1.0dB.

Via the 1-to-4 distribution unit, receiving of

CDU serves as the main receiving of three or four TRXs; via two 1-to-2 distribution units, 2-channel receiving of EDU serves as the diversity receiving of three or four TRXs.

2. Meaning of an interface band statistics Problem

Meaning of an interface band statistics

Detail

What does the parameter “Average amount of idle TCHs in interference band 4 during

Description

the statistics period” means?

Reply

The BTS measures idle TCHs in the interference band 4 with the SACCH frame of every 26 frames over the inactive TCH channels (the SACCH frame over the active TCH channels are for the statistic of measurement reports). Every multi-frame reports the number of the idle TCHs. The BSC averages all of the measurement results in a measurement period. Even if the measurement results of the interference band 0-2 are small, it does not mean that there is not any interference since the measurement is a statistic of idle TCHs. On

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peak hours, TCH are almost all occupied, so the measurement results of various interference bands may be small.

3. Function Control problem Problem

Function control problem

Detail

For BTS3X 00.0529 and later, BSC 00.07.0520B and later, they all support HW_2

Description

function control down. In this case, it is necessary to enable the BTS measurement report pre-processing to set HW_2 function control data. Questions: Whether the HW-2 function control is related to the BTS measurement report pre-processing? Which function control the data configuration is delivered to, HW-1 or HW-2? Will the function control be affected if we disable the function control down?

Reply

The setting of the BTS measurement report pre-processing parameter decides where the measurement report is pre-processed. Function control proceeds at the BTS side when the parameter is set as “Y”, and at the BSC side when it is set as “N”. Before, setting this parameter, users must consider whether the BTS supports the corresponding function control algorithm. ”Function control down” indicates the function control proceeds at the BTS side. The BTS measurement report pre-processing parameter must be set as “Y" to enable “function control down”. ”If the BTS or the BSC supports the function control, the “function control down” function is irrelative to the generations (HW_1 or HW_2) of the function control. If the BTS measurement report pre-processing is disabled, the functiron control proceeds at the BSC side. It is HW-2 function control that takes effect since the Field function control table is configured with HW-2 function control. The function control down can improve the system performance. It lessens Abis interface signaling flows and BSC load, shortens the response time and optimizes the network performance.

4. IUO problem1 Problem

IUO problem1

Detail

The setting of Assign-Optimum-Level Thrsh. takes effect when the user selects the option

description

of system optimization. Suppose the Assign-Optimum-Level Thrsh. is 18, will the MS prefer the overlaid subcell when the MS receiving level is higher than -92dBm, and the underlaid subcell if otherwise?

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For any value configured for Assign-Optimum-Level Thrsh., the underlaid subcell is always congested, why? Reply

If the Assign-Optimum-Level Thrsh. is set as 18, the overlaid subcell is preferred if the uplink level in SDCCH measurement report is greater than -92dBm, and the underlaid subcell is preferred if otherwise. If an MS keeps on selecting the underlaid subcell, the uplink signals may be too weak. In this case, view the result of the measurement task “uplink and downlink balance performance measurement” ，and check whether there are any hardware faults. Inconsistency between the receiving level threshold and the assignment preferable range may lead to frequent handovers between the overlaid subcell and the underlaid subcell, thus causing congestion in the underlaid subcell.

5. IUO problem2 Problem Detail description

IUO problem2 1. For the configuration of preferring underlaid subcell, does it mean an MS will select the underlaid subcell first no matter how higher the receiving level is, and it selects the overlaid subcell only when the underlaid subcell is busy? 2. For the configuration of preferring overlaid subcell, does it mean an MS will select the overlaid subcell first no matter how higher the receiving level is, and it selects the underlaid subcell only when the overlaid subcell is busy? 3. For the configuration of no preferment, does it mean an MS prefers the overlaid subcell within coverage of the overlaid subcell, and selects the underlaid subcell only when the overlaid subcell is congested,

Reply

。

1. Yes. It is true. 2. Yes. It is true. 3. In this case, channels are allocated based on channel allocation algorithm.I or II.

6. IUO problem3 Problem

IUO Problem3

Detail

What is the signal intensity difference between the overlaid subcell and the underlaid

description

subcell? What will happen if this parameter is not configured correctly?

Reply

Since the differences in transmission power and path loss between the overlaid subcell and the underlaid subcell may lead to differences in receiving signal intensity accordingly. The value set for this parameter indicates a power compensation for the overlaid subcell. The configuration of this parameter must be accurate since it is the level of the overlaid subcell after power compensation functions in the handover decision procedure. If otherwise, such handovers as PBGT handover and edge handover will be either delayed

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or advanced.

7. IUO prbolem4 Problem

IUO problem4

Detail

Can the Assign-Optimum-Level Thrsh. be lower than the edge handover threshold?

description Reply

The Assign-Optimum-Level Thrsh. has two options: 1. In the case of up-downlink unbalance, the Assign-Optimum-Level Thrsh. equals to the sum of the receiving level threshold and the up-down link balance margin. 2. In the case of up-downlink balance, the Assign-Optimum-Level Thrsh. equals to the receiving level threshold. Therefore, Assign-Optimum-Level Thrsh. cannot be lower than the sum of the edge handover threshold and signal intensity difference between the underlaid subcell and the overlaid subcell.

8. IUO traffic statistics Problem

IUO traffic statistics

Detail

Most of the O3 sites are configured as IUO cell. According to the traffic statistics of IUO

description

performance measurement, the congestion and all-busy event occurs to the underlaid subcells frequently, and sometimes for hundreds of times. While according to TCH performance measurement, the all-busy event seldom occurs to the cocentric cells, and so does the TCH assignment failure. Therefore, the customers double that the all-busy event and assignment failure frequently occur to the TCH occupation in the underlaid subcells. In my view, however, the traffic statistic result of the IUO performance measurement indicates only the times of all-busy events in underlaid subcell assignment, but not assignment failures since the overlaid subell

assignment takes place instead. What is

your opinion? Reply

Yes, you are right. The traffic statistics of IUO performance measurement measures the all-busy events occurring only to the underlaid/overlaid subcell, and that of the TCH performance measurement measures the all-busy events occurring to both the underlaid subcell and the overlaid subcell.

9. RACH min. access level Problem 2004-05-288

RACH min. access level Confidential Information of Huawei. No Spreading without Permission

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Detail

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Does the parameter “ RACH min. access level ” have any impact upon handover access?

description Reply

For the BTS20, there is only one parameter (RACH busy threshold) set for handover access, and this parameter takes effect also for RACH BURST handover access. For BTS30, the parameter RACH min. access level is additional. Neither the RACH min. access level nor the RACH busy threshold functions in handover access.

10. The effect of Tower Mounted Amplifier on Diversity Receiving Problem

The effect of Tower Mounted Amplifier on Diversity Receiving

Detail

1. Please explain in a cell with two branches of feeders, the different effect of Tower

description

Mounted Amplifier on Diversity Receiving between the TMA used on a branch and used on two branches. 2, The TMA gain is about 12Db, can the TMA used on one branches bring alarm message?

Reply

1. the arithmetic of HUAWEI diversity receiving is to set a weighing value on main diversity according to S/N and signal strength, the bigger is the weighing value, the more is the contribution. If the TMA is used on only one branch, the S/N and signal strength of this branch will be much stronger than the other’s. When the TMA used, the CDU should be configured Power attenuation factor. So the signal on the branch without TMA will be attenuated a lot, and even be none when the uplink signal is very weak. Thereby, there will be no combined gain of 3.5dB. 2. There will be no alarm message.

11. The measurement result of “TCH call drop connected” deviates a lot from that of “TCH call drop connected”. Problem

The measurement result of “TCH call drop connected” deviates a lot from that of “TCH call drop connected”.

Detail

The measurement result of “TCH call drop connected” deviates a lot from that of “TCH

description

call drop”.

Reply

“TCH call drop connected” measures the call-drops after the “connect" message, while “TCH call drop” measures the call-drops after the “assignment complete” message. Therefore, it is normal that the measurement result of “TCH call drop connected” deviates a lot from that of “TCH call drop”.

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No measurement result outputs for traffic statistic

Problem

No measurement result outputs for traffic statistic.

Detail

No measurement result outputs for traffic statistic in the module1 between 3 o’clock and

description

4 o’clock.

Reply

The traffic statistic task will re-register at the next 3:15 in the morning after addition or deletion of sites/cells/TRXs, modification to cell installation state or dynamic data configuration of cell CGI. Therefore, if the operations are completed before 3:15 in the morning of the day, the traffic statistic task will re-register at 3:15 in the morning of the day. If otherwise, the traffic statistic task will re-register at 3:15 in the morning of the next day. As a result, there will be no traffic statistic results for some periods.

13. It is hard to make a call in the case of signal with the receiving level of -80dBm. Problem

It is hard to make a call in the case of signal with the receiving level of -80dBm.

Detail

The customer said that it is hard to make a call when the signal intensity is -80dBm.

description Reply

According to data configuration specification, BTS adjusts the CDU gain based on “Tower-mounted amplifier flag ” and “ Power attenuation factor ”. Suppose TMA gain is G dB, then CDU power attenuation factor should be configured as G - 4. The “ Power attenuation factor ” in the network is also set as 10 when there is no TMA, the attenuation of uplink signals will be great, thus leading to access failure even if the downlink signals are intensive.

14. Over-sea coverage Problem

Network planning for over-sea coverage

Detail

What should be taken into consideration in network planning and site selection for

description

over-sea coverage, especially for coverage along course line and over fishing waters?

Reply

1. Antenna height has great impact upon the coverage effect. Generally, sites of high position are chosen as locations for BTSs to realize broad over-sea coverage.

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2. The sites of BTSs should be as near as possible to the sea. There must be not any barriers between the BTSs and the destination covered. 3.

The single-polarized antenna of high gain (such as 18DBI) is preferred in antenna selection. If the area nearby the BTS to be covered is broad, the antenna of wide (such as 90 ) horizontal half-power angle is recommended. °

4. The inter-cell angle is subject to the width of the horizontal beam of the antenna. For 65 antenna, the inter-cell angle must be greater than 70 , and for 90 antenna, it °

°

°

must be greater than 90 . °

15. Signaling procedure Problem

Signaling procedure

Detail

1. In different assignment modes (early assignment or late assignment), when does the

Description

calling party hears the alerting and at the same time which the signaling is the called party at)? 2. When is the calling number (MSISDN) sent to the called party?

Reply

1. Upon receiving an ACM message (from PSTN subscriber) or ALERTING message (from mobile subscriber), the MSC sends an ALERTING message to the calling party, who converts it to a alerting tone. In this case, the signaling of the corresponding called MS is ALERTING. The MS has already occupied the TCH, and the signaling is sent on the SACCH channel. 2. The calling number is sent to the called party with the SETUP signaling, generally on SDCCH channel. In early assignment mode, it is s ent on the SACCH channel.

16. BTS configuration after Capacity expansion Problem

BTS configuration after Capacity expansion

Detail

A BTS is configurated as S1/1/1, and the customer plans to configure it as S4/4/4 in a

Descrip

capacity expansion.

tion

Since the output power over the cabinet top of the previous BTS is 46dBm, we recommended to configuration the BTS as S3/3/3 in the capacity expansion. The customer agreed and asked whether it is necessary to replace the CDU if configuring the BTS as S4/4/4 in the future capacity expansion, whether there are any better solutions. Which is better for the configuration, BTS3.0 or BTS312?

Reply

1. BTS312 is recommended for the configuration. 2. The cabinet top output power of the previous BTS is 46dBm. At present, we select the TRX board of large power (60W) or adopts the (40W+PBU)+EDU mode to solve the problem. Therefore, each cell requires two dual polarization antennas, four feeders and an additional cabinet. Consideration must be taken for the cabinet top output

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power, antenna gain and feeder type to ensure the coverage in capacity expansion. 3. To configure the BTS as S4/4/4 in CDU mode, it is necessary to replace the combiner and the antenna.

17. Rural network Problem

Rural network

Detail

Which points should we concern in rural network planning?

Descrip tion Reply

1. The interference of cells around covered by other manufacturers must be taken into consideration in frequency planning. If the previous frequency planning has not been done separately for BCCH and TCH, it is also necessary to consider the interface of TCH in frequency planning. 2. Emphasis must be put on the configuration of neighbor cell relationship, especially for the location of the opposite cell and the correctness of the parameter configuration. 3. For rural network in some areas, inter-BSC handover frequently fails, generally caused by data configuration error. Therefore, make sure to confirm the configuration of such parameters as BCCH, BSIC, CGI and so on to make them consistent in devices from different manufactories.

18. Direct retry in combined networking Problem

Direct retry in combined networking

Detail

Around an Huawei iSite with S1/1 configuration, the adjacent BTSs are all provided by

Descrip

other manufacturers. Now we consider to use direct retry to share the traffic load, will it

tion

be any troubles to carry out this plan, and how about the data configuration?

Reply

The BSC checks whether the “direct retry allowed” is enabled when finding that there are not idle TCHs available in the cell to which the MS accessed. If the “direct retry allowed” is enabled, the BSC initiates a handover request with the reason value of “DIRECTED RETRY”, and then implements the handover as normal. This course is referred to as direct retry. The unique difference compared with the normal handover is that the target BSC may either send a ASS IGNMENT COMPLETE message or a HANDOVER COMPLETE message to the MSC upon receipt of a HANDOVER COMPLETE message from the MS. When the handover completes, the direct retry procedure ends, and the subsequent signaling is processed at the target BSC. Therefore, the subsequent procedure after direct retry can be treated as a normal handover procedure.

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Data configuration should be done according to Data Configuration Requirements.

19. Please explain the T3105 and Max resent times of physical information Problem

Please explain the T3105 and Max resent times of physical information.

Detail

Please explain the T3105 and Max resent times of physical information

Descrip tion Reply

During the asynchronous handover, MS constantly sends the handover access Burst to BTS. When BTS detects the Burst, BTS send physical information to the MS on the main DCCH/FACCH, and starts timer T3105. At the same time, it sends the MSG_ABIS_HO_DETECT message to BSC. The physical information contains related information of different physical layers so as to guarantee the correct access of MS. If the timer T3105 times out before receiving the SAMB frame from MS, BTS re-sends physical information to MS. This parameter specifies the maximum times Ny1 for re-sending physical information. If the number of resending times exceeds Ny1 and BTS still has not received any correct SAMB frame from MS, BTS will send BSC the connection failure message and handover failure message. After BSC receives the messages, it will release the assigned dedicated channel and stop timer T3105. See Protocol 0858 and 0408. The value of this parameter can be increased correspondingly when the handover becomes slow and handover success rate is low which is caused by clock or bad transmission condition. When Ny1 * T3105 > the duration between EST IND and HO DETECT, MS handover will succeed. Otherwise, MS handover will fail.

20. Why No response for paging Problem

Why No response for paging

Detail

The MS is out of the serving cell due to frequent inter-LA cell reselection. The reason is

Descrip tion

that the MS has already reselected a new cell during the paging, but not initiate or completed location update.

then,

the MS gives the information indicating out of the

serving cell.Can you explain the phenomenon in details? Reply

1. After the MS finishes a cell reselection but before complete the location update, the paging to MS is still delivered to the previous LA. The MS cannot make a response for the paging in the course of LA updating. 2. in addition, the first three paging actions by the MSC are delivered to the LA of the MS fetched at the time. If the MSC receives no response after the first three paging actions, it delivers the fourth and the fifth paging actions to all LAs of the MS in the local MSC. If the new LA of the MS after LA updates belongs to anther MSC, then the original MSC certainly cannot receive a response for the paging actions.

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Collection of GSM RNP technical problems and replies(No.1)-20040528-A-1.0.pdf

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