nokia viettel report_importante.pdf

Radio Network Planning & Optimization Review Date: 6 May 2004 VIETTEL - VIETNAM

Prepared by Ng Seh Hoong Ha Minh Tu

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Brief Report Radio Network Planning and

Optimization review

Viettel Network Ho Chi Minh city



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TABLE OF CONTENTS

TABLE OF CONTENTS.......................................................................................................................... 2

1. INTRODUCTION............................................................................................................................................................... 3

2. FREQUENCY PLAN REVIEW........................................................................................................................................ 3 2.1 FREQUENCY ALLOCATION AND ASSIGNMENT................................................................................................................ 3

3. NEIGHBOURING PLAN REVIEW................................................................................................................................. 3

4. CONFIGURATION PLAN AND LOCATION AREA PLAN........................................................................................ 4

5. BSS PARAMETER PLANNING....................................................................................................................................... 4

6. COVERAGE PLANNING ................................................................................................................................................. 4

7. INTERFERENCE CALCULATION PLANNING.......................................................................................................... 5

8. QUESTIONS AND ANSWERS FROM VIETTEL ......................................................................................................... 5

9. DRIVE TEST ANALYSIS (WE SHALL REVIEW IN ORDER OF TEST SCHEDULE).......................................... 6 9.1 CLUSTER 8 .................................................................................................................................................................... 6 9.2 CLUSTER 4 .................................................................................................................................................................. 11 9.3 CLUSTER 1 .................................................................................................................................................................. 15 9.4 CLUSTER 2 .................................................................................................................................................................. 21 9.5 CLUSTER 7 .................................................................................................................................................................. 26 9.6 CLUSTER 9 .................................................................................................................................................................. 32

10. NOKIA RECOMMENDED TASKS FOR FUTURE (SHORT TERM).................................................................. 40

11. NOKIA RECOMMENDED TASKS FOR FUTURE (LONG TERM).................................................................... 40 11.1 DAILY MONITORING OF NETWORK STATISTICS .......................................................................................................... 40 11.2 PREPARATION OF WEEKLY AND MONTHLY QUALITY REPORT ................................................................................... 42 11.3 OPTIMIZE BSS PARAMETER TO FURTHER ENHANCE KPI ........................................................................................... 42 11.4 IDENTIFICATION AND OPTIMIZATION OF HOTSPOTS.................................................................................................... 42 11.5 PERIODIC BENCHMARK DRIVE TESTING OF ALL OPERATORS ..................................................................................... 42

12. CONCLUSION ............................................................................................................................................................. 42



3 (42) 1. INTRODUCTION

The purpose of this report is to summarize network planning and optimisation audit and verification exercise conducted by Nokia Networks Vietnam for Viettel Corporation.

During the relatively short period of one week, brief review of the frequency plan, neighbouring cell plan, configuration plan, location area plan, BSS parameter plan, randomly selected site visits and drive test of 6 important clusters, and data analysis were performed. However, without much ‘real’ NMS data available due to mobile network in the pre-launch stage, more time were spent with drive test and analysis of data as it is currently the best way to reflect the performance of the network at this stage.

We would like to state that the network is performing as reasonably can be expected based on the fundamental planning. However, it is not excellent as we found out various problems and inconsistencies with the network planning and optimization method. These problems will rise dramatically when the network is launched commercially.

We will therefore elaborate on this outstanding problems and recommendations in the next few pages.

2. FREQUENCY PLAN REVIEW

2.1 Frequency allocation and assignment

Viettel’s operating GSM Band is 900MHz

Viettel has a total channel of 40 (ARFCN range from 43 -> 83) or (Downlink 943.6Mhz – 951.6Mhz; Uplink 898.6MHz – 906.6MHz)

15 channels were allocated for BCCH band (ARFCN range 43 -> 57)

24 channels were allocated for TCH band (ARFCN range 59-> 82)

Problem: With comparison to other successful Nokia networks in other countries, 15 channels allocated for BCCH is not enough especially currently there are more than sufficient of 24 ARFCN allocated for TCH, which is fully utilized at the moment for the second TRX of 2/2/2 configured cell. With a tight BCCH Channel re-use, the mobile station will have problem decoding channel information from the network due to higher probability of interference. (Please also note that 2/2/2 is currently the maximum configuration for this network.)

Recommendation: We would recommend at least 18 (max 21) be utilized for BCCH, 15 CHs be utilized for the 2nd TCH CHs. Which means there will be 6 CHs spare where you can use it for cells that are experiencing congestion when the network in launched. However, since the network is planned, and launch date is about one month away, we suggest you do not replan the BCCH layer, but do so for the TCH layer. So take the 24 CHs, allocated 3 for additional BCCH layer (incase of inteference where you need to change the frequency immediately). The remaining 21 CHs, use 15 CHs to replan the TCH layer, 6 as spare for immediate expansion or solving interference.

3. NEIGHBOURING PLAN REVIEW

Problem: After reviewing randomly selected cells on the planned/generated neighbour list and drive test data, we found that there are insufficient neighbour cells (average 5-6 cells) in each of the cells. They are generally first tier/layer of the cell surroundings.



4 (42) Recommendation: We suggest Viettel engineers add the second tier/llayer of surrounding cells in

its neighbouring relations.

4. CONFIGURATION PLAN AND LOCATION AREA PLAN

For configuration plan, regarding the PCH, AGCH and SDCCH block etc. capacity to handle the network traffic, after a brief review and discussion with Viettel engineers.

Comment: We believe that the pre-launch dimensioning plan should be sufficient. However, the planned settings should be adjusted once the network is launched commercially where there is ‘real’ traffic. This is done with OMC dump data for network performance monitoring.

For Location area plan, there are currently 2 location area codes, 2901 and 2902, which are separated by BSC border. They currently have 2 BSCs so it is actually one LAC per BSC.

Comment: At this point, we find this plan valid as BSC should not share too many LAC with other BSCs in order to minimize paging load. The border is also not along any major highway so that is valid as well. However, once again, the ‘real’ traffic after network launch will provide a more accurate data where settings could be adjusted then.

5. BSS PARAMETER PLANNING

After reviewing Alcatel’s BSS parameter list for Viettel network, we recommend some parameter settings to be adjusted to make the algorithm more aggressive to ensure a better link quality between the mobile

station and the network.

Alcatel Parameter ListLogical Parameter Name Feature Alcatel Default NokiaA_LEV_HO Handover 8 4A_LEV_PC Power Control 4 2A_PBGT_HO Handover 12 6A_QUAL_HO Handover 8 4A_QUAL_PC Power Control 4 2

Other important parameters are ok whereas most of them are ‘real’ network performance dependant which should be adjusted after performing daily monitoring of the statistics.

6. COVERAGE PLANNING

The purpose of coverage planning is to cover the specified service area with required probability at minimum overall infrastructure cost within the capacity and QOS constraints of the network dimensioning.

Comment: In the urban and dense urban area of HCM city, the area is approximately 245 km2 . We have approvimately 80 sites in this area, which means there will be roughly one site per 3 square km. We found the sites of height range between 20-25m to be acceptable in general for this plan for Phase 1 GSM900 network. It is however not preferred with most antennae equipped with 6deg electrical downtilt. For sites of such height, 0-2 deg downtilt is preferred, and not preset of 6deg. While this is good for the RF interference suppression,



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priority should be given to good coverage. This is proven a problem from drive test data where there is relatively weak outdoor coverage. In the end, more infrastructure cost would incur on the operator to fill the coverage gaps with new cell sites.

7. INTERFERENCE CALCULATION PLANNING

The reference interference ratio is defined in GSM Rec.05.05 as the interference ratio for which the required performance in terms of frame erasure, bit error rate or residual bit error rate is met. The reference interference ratios for BS and all types of MSs are the following:

• co-channel interference: C/Ic <= 9 dB

• first adjacent channel interference: C/Ia <= -9 dB

However, in practice, due to more unpredictable fadings characteristics, C/Ic should be at least 15 dB and C/Ia at least -6 dB to guarantee good quality.

Comment: Should Viettel engineers use the planning tool for network simulations in future, we suggest the above values to guarantee good quality.

8. QUESTIONS AND ANSWERS FROM VIETTEL

Throughout the one week co-operation with Viettel engineers, we found them to be rather disoriented with RF related project handling process and procedures. They are hardworking, motivated, possess the willingness to learn, willingness to listen to advice. In general, they are a wonderful team to work with. However, they would need guidance from experts, consultants and specialists for a period of time. This is especially crucial when the network is commercially launched as more problems will surface as the network load increases.



6 (42) 9. DRIVE TEST ANALYSIS (WE SHALL REVIEW IN ORDER OF TEST SCHEDULE)

We performed the drive test according to the following guidelines:

• Drive all major/important roads/highways (if possible in both directions)

• Special attention made to important areas

• Performing handover verification at cluster borders

• If no major road in between sites, will drive minor roads to test coverage and handover behaviour

9.1 Cluster 8

Problem: Handover failure as Mobile Station attempts to handover from cell HCM0010 sector 3 (CH 43) to HCM0009 sector 2 (CH 44). Both cells are adjacent channel to each other so handover is risky and unpredictable.

Recommendation: Change one of the 2 CHs to avoid adjacent channel interference and handover.



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Problem: A dropped call from cell HCM0014 sector 2 due to co-channel interference (CH 49) from cell HCM0012 sector 1.

Recommendation: Change one of the 2 CHs to avoid co-channel interference immediately.

Problem: Another one is not a dropped call but mobile station experience a lost in link quality as cell HCM0009 sector 2 experience co-channel interference (CH 44) from cell HCM0011 sector 3.

Recommendation: Change one of the 2 CHs to avoid co-channel interference immediately.



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Problem: Cell HCM0001 sector 2 (CH46) , due to poor covereage in the area, is the best server there, however, it experience adjacent channel interference from cell HCM0074 sector 2 (CH47) and cell HCM0029 sector 3 (CH45)

Recommendation: Please check if it is possible to increase the coverage in the area by means of re-direction etc. to have a more dominant server thus increasing the C/I(A) ratio. If not please change the channel of HCM0001 sector 2.



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Problem: Cell HCM0001 sector 1 and 2, has poor covereage in the area.

Recommendation: Please check site HCM0001 sector 1 and 2 for possible antennae installation fault. Also if it is possible to increase the coverage in the area by means of re-direction etc. to have a more dominant server.



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Problem: Cell HCM0011 sector 3 has very strong signal strength in the area, more dominant than cell HCM0010 sector 1 in the circled area. However, it failed to handover to cell HCM0010 sector 3 as it is not on the neighbour list. Causing the dropped call.

Recommendation: Please add cell HCM0010 sector 3 into the neighbour list of cell HCM0011 sector 3 and vice versa.



11 (42) 9.2 Cluster 4

Problem: Cell HCM0068 sector 1 is not on the neighbour list of cell HCM0002 sector 1. Causing mobile station to drag cell coverage and unnecessary handover with multiple cells.

Recommendation: Please add cell HCM0068 sector 1 into the neighbour list of cell HCM0002 sector 1 and vice versa.



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Problem: Mobile station being served by cell HCM0077 sector 3 while travelling north, encounters

poor coverage and suffered degraded quality, and excessive handover to cell HCM0049 S1, HCM0046 S1 and HCM0063 S3

Recommendation: Please check if antennae re-direction possible of some surrounding sites to improve coverage in the area or a new site in the next phase.



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Problem: No main beam of HCM0037 S1 or S3 point along the main road. This caused less than satisfactory coverage along the main road. It does not help when cell HCM0037 S3 is not on cell HCM0053 S2 neighbour list. And they are also adjacent channel to each other.

Recommendation: Please check if antennae re-direction possible for cell HCM0037 S1 to improve coverage or a new site in the next phase. Change the channel of cell HCM0053 S2, and add cell HCM0037 S3 into the neighbour list of HCM0053 S2.



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Problem: RxQual of cell HCM0035 S2 (CH44) is not so good in the circled area even with relatively strong RxLev. We suspect co-channel interference from cell HCM0027 S2 (CH44)

Recommendation: Please perform drive test (pre-launch) with cell HCM0027 S2 locked to confirm interference source. If true, change channel immediately.



15 (42) 9.3 Cluster 1

Problem: Cell HCM0016 S1 is not on the neighbour list on cell HCM0091 S3. No handover causing degraded RxQual.

Recommendation: Please establish neighbouring relation between these 2 cells.



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Problem: Mobile Station while being served by cell HCM0026 S2 experience very poor RxQual even at considerably strong RxLev. We suspect co-channel interference from cell HCM0041 S2 (CH54)

Recommendation: Please verify source of co-channel interference by locking (pre-launch) cell HCM0041 S2. If true, change channel immediately.



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Problem: Mobile Station while being served by cell HCM0040 S3 experience very poor RxQual even with relatively strong RxLev. We suspect co-channel interference from cell HCM0024 S3 (CH57)

Recommendation: Please verify source of co-channel interference by locking (pre-launch) cell HCM0024 S3. If true, change channel immediately.



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Problem: Mobile Station experienced poor coverage in the circled area. There is no dominant server.




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Problem: Mobile Station while being served by cell HCM0016 S1 experienced poor RxQual even with relatively strong RxLev. We suspect co-channel interference from cell HCM0056 S1 (CH57). However, this is not a critical problem.

Recommendation: Please verify source of co-channel interference by locking (pre-launch) cell HCM0056 S1. If true, change the channel.



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Problem: Mobile Station while being served by cell HCM0090 S1 experienced poor RxQual. Best server in the area is cell HCM0034 S3 but as Mobile Station could not decode the BSIC of this neighbour cell soon enough, the RxQual suffered. We believe cell HCM0034 S3 could be interfered by cell HCM0045 S1 (CH47) in that area.

Recommendation: Please verify source of co-channel interference by locking (pre-launch) cell HCM0045 S1. Re-drive the route to test the mobile station handover behavioue. If true, change the channel to enable smooth handover.



21 (42) 9.4 Cluster 2

Problem: Mobile Station while being served by cell HCM0006 S1 experienced poor RxQual even at relatively strong RxLev. We suspect the cell is being interfered by cell HCM0003 S3 (CH48).

Recommendation: Please verify source of co-channel interference by locking (pre-launch) cell HCM0003 S3. Re-drive the route to test the mobile station handover behavioue. If true, change the channel immediately.



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Problem: Mobile Station while being served by cell HCM0019 S1 experienced poor RxQual because cell HCM0068 S3 is the best server in the circled area. However, since cell HCM0068 S3 is not on the neighbour list of cell HCM0019 S1, the mobile station dragged the coverage of the cell, then performed handovers to non-desired cells causing bad RxQual like cell HCM0006 S2. Please note that site HCM0006 has poor coverage in this area.

Recommendation: Please add cell HCM0068 S3 into the neighbour list of cell HCM0019 S1



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Problem: Mobile Station while being served by cell HCM0039 S3 experienced poor RxQual even at relatively strong RxLev. We suspect the cell is being interfered by cell HCM0017 S1 (CH55).

Recommendation: Please verify source of co-channel interference by locking (pre-launch) cell HCM0017 S1. Re-drive the route to test the mobile station handover behavioue. If true, change the channel immediately.



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Problem: Mobile Station while being served by cell HCM0040 S1 experienced poor coverage in the circled area. There is no dominant server there causing RxQual to degrade.




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Problem: Mobile Station while being served by cell HCM0058 S2 experienced poor RxQual even at relatively strong RxLev. We suspect the cell is being interfered by either cell HCM0050 S2 (CH54) or cell HCM0092 S2.

Recommendation: Please verify source of co-channel interference by locking (pre-launch) one at a time, cell HCM0050 S2 and HCM0092 S2. Re-drive the route to test the mobile station handover behavioue. If true, change one of the channels immediately.



26 (42) 9.5 Cluster 7

Problem: Not a serious problem. Mobile Station while being served by cell HCM0065 S3 experienced slight poor RxQual. We suspect the cell is being mildly interfered by surrounding co-channel cells.

Recommendation: Please verify source of co-channel interference by locking (pre-launch) any suspicious sites. Re-drive the route to test the mobile station handover behavioue. If true, change one of the channels immediately.



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Problem: For the circle on the RIGHT, cell HCM0070 S3 (CH43) had adjacent channel interference from cell HCM0081 S2 (CH44) which is also a neighbour which explains the degraded signal. Adjacent channel handover was performed.

Recommendation: Adjacent channel handover should be avoided as much as possible. So please change one of the channel. Whichever is easier.

Problem: For the circle on the LEFT. Because of poor coverage, Mobile Station while being served by cell HCM0060 S2 (CH44) experienced poor RxQual, was possibly interfered by cell HCM0081 S2 (CH44), it then performed a RxQual reason handover to another cell (HCM0070 S3) which is an adjacent channel.

Recommendation: Please check if any surrounding cell’s antennae could be adjusted to have a more dominant server in the area. If not, a new site will solve the problem.



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Problem: Cell HCM0068 S1 has weak coverage in the circled area. Cell HCM0069 S3 is also weak there. Link quality was degraded as a result.

Recommendation: Please verify if installation of antennae and feeders are done correctly. A shorter Averaging Period (as described in point 5 in Page 4) will temporary solve the problem.



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Problem: Cell HCM0022 S3 (CH50) and cell HCM0018 S1 (CH51) face each other and with adjacent channels. This must be avoided as the RxQual is affected.

Recommendation: Please change one of the channels immediately.



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Problem: Cell HCM0072 S1 (CH56) while serving the mobile station, was interfered by adjacent channel cell HCM0074 S1 (CH55) which caused degraded quality.

Recommendation: Please change one of the channels immediately



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Problem: Cell HCM0068 S1 (CH45) while serving the mobile station, was possibly interfered by co- channel cell HCM0028 S2 which caused degraded quality.

Recommendation: Please verify source of co-channel interference by locking (pre-launch) cell HCM0028 S2. Re-drive the route to test the mobile station handover behavioue. If true, change one of the channels immediately



32 (42) 9.6 Cluster 9

Problem: Dropped call. Cell HCM0041 S2 (CH54) while serving the mobile station, experienced strong co-channel interference from cell HCM0026 S2. Causing it to drop the call.

Recommendation: Please verify source of co-channel interference by locking (pre-launch) cell HCM0026 S2. Re-drive the route to test the mobile station handover behavioue. If true, change one of the channels immediately.

6 May 2004Ng Seh HooHa Minh Tu

Radio Network Planning & Optimization Review Date: VIETTEL - VIETNAM

Prepared by ng

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Problem: This diagram shows the same problem where cell HCM0026 S2 interfered by cell HCM0041 S2. Which is vice versa of the previous problem.

Recommendation: Please change channel immediately.



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Problem: When mobile station travelling south, being served by cell HCM0017 S2, could not handover to either cell HCM0013 S1 or S3. After some investigation, we found out that cell HCM0013 S1 and S3 are not on cell HCM0017 S2 neighbour list.

Recommendation: Please establish the neighbour relations immediately.



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Problem: Dropped Call. Cell HCM0013 S1 serves very far. This is also because cell HCM0009 S1 is not the best server there. As a result the mobile station dropped the call. It could not handover to cell HCM0008 S2 and S3 because they are not on cell HCM0013 S1 neighbour list.

Recommendation: Please check the coverage of site HCM0009 and HCM0005, and also establish the neighbour relations between cell HCM0013 S1 and HCM0008 S2 and S3 immediately.

Date:

Radio Network Planning & Optimization Review 6 May 2004 VIETTEL - VIETNAM


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Problem: Mobile station detected a neighbour with broadcast BSIC of 4,5 !! Viettel’s NCC range is only 0-2 ?? Mobile station could not perform handover to this cell with non permitted NCC.

Recommendation: Please check immediately if this is a wrong broadcast from cell HCM0042 S2 or it is a channel possibly used by another operator.



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Problem: Coverage of cell HCM0048 S2 is very weak even mobile station is only 340m away from the site.

Recommendation: Please check if the coverage of this cell is according to design and reduce downtilt if possible.



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Problem: Cell HCM0018 S2 is possible interfered with co-channel by cell HCM0008 S3 (CH57).

Recommendation: Please verify source of co-channel interference by locking (pre-launch) cell HCM0008 S3. Re-drive the route to test the mobile station handover behavioue. If true, change one of the channels immediately.



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Problem: Mobile Station while being served by cell HCM0045 S2 experience very poor RxQual even at considerably strong RxLev. We suspect co-channel interference from cell HCM0048 S1 (CH44)

Recommendation: Please verify source of co-channel interference by locking (pre-launch) cell HCM0048 S1. If true, change channel immediately



40 (42) 10. NOKIA RECOMMENDED TASKS FOR FUTURE (SHORT TERM)

We have mentioned the problems in the previous pages, a few are major problems, and quite a number are not as critical. It is probably too short a time (and also not critical) now to re-plan the network and perform verification all over again prior to launch, so focus should be made on solving the immediate problems. Once again, in prioritised order, are:

• Re-plan TCH layer in the city using fewer channels

• Solve co-channel interference problems

• Establish new neighbour relations for handover problems

• Change channel to avoid adjacent channel handovers

• Solving weak coverage problems (where ever possible)

11. NOKIA RECOMMENDED TASKS FOR FUTURE (LONG TERM)

When the network is launched, where there will be subscriber growth, traffic will increase and thus putting the designed network to the test. So in order to maintain good network performance as the network load increases, various additional tasks/measures should be executed. They are:

11.1 Daily Monitoring of Network Statistics

• Daily sort out of bad performing cells

• Check BTS alarms (example:)



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• Check causes of poor performance (example:)

• Checking Downlink and Uplink Quality (Example:)

• Check interference level (Example:)

• Check handover causes and optimise handover relations (Example:)



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• Check coverage (Example:)

11.2 Preparation of Weekly and Monthly Quality Report

This task is required in order inform all concerned parties of current network performance and also to have a proper record and documentation of periodic network performance.

11.3 Optimize BSS Parameter to Further Enhance KPI

Subscribers in different network of different countries will have different behaviours while using the mobile stations, continuous adjustment of BSS parameters to suit them will ensure a good network performance constantly.

11.4 Identification and Optimization of Hotspots

When there is very high traffic in certain areas of the network, much attention must be paid to continuously maintain good performance and increase revenues for the operator. (For example: solving congestion problem etc.)

11.5 Periodic Benchmark Drive Testing of All Operators

It is important to perform periodic drive testing for all operators to compare network quality and performance to know Viettel’s position in the competitive market.

12. CONCLUSION

The network is performing as reasonably as can be expected. However, after 7 straight days of data analysis of HCM city network, we know much improvement can be made to make it excellent. We would like to thank the Viettel’s RF team for their co-operation. They are indeed a wonderful team to work with.

nokia viettel report_importante.pdf

Documents

location area

drive test

optimization

drive test

coverage planning

configuration

real traffic

tch layer