VMS Ph15 Final Report_Rev F.pdf

Acceptance Certificate for RNO Report

Date: ............................

Participants:

For V M S:

Name: Mr. Nguyen Xuan Nghia Position: VMS1 Manager of Technical Department Name: Mr. Nguyen Ngoc Trinh Position: VMS1 Manager of RNO Team For ALCATEL: Name: Mr. Huynh Song Tra Position: Deputy Director of Operation Department of Alcatel Vietnam Name: Mr Nguyen Luu Long Position: Technical Project Manager

This is to certify that ALCATEL implemented Radio Network Optimization work as defined in the

contract:

- Name of Phase : BSS Phase 15 A

- Contract Reference Number : PO-04-90-VMS/CIV – ALCATEL

VMS1 agreed with final optimization report of Alcatel as the below. All results of optimization work are accepted and met fully the contract.

ED DOCUMENT TITLE Released

MND VMS Ph15 – Final Optimization Report REFERENCE Page 1/23

Vietnam Mobile Telecom Service Company VMS Center 1

Technical Department

NGUYEN XUAN NGHIA

ALCATEL – NSV

HUYNH SONG TRA

VVMMSS PPHHAASSEE 1155AA –– FFIINNAALL OOPPTTIIMMIIZZAATTIIOONN RREEPPOORRTT

1 27th May Creation Jean-Maurice Roy Kitichai S. Phan Duc Linh

ED DATE CHANGE NOTE APPRAISAL AUTHORITY ORIGINATOR



TTAABBLLEE OOFF CCOONNTTEENNTTSS

1 Scope ........................................................................................................ 4

2 Optimization information......................................................................... 4

3 QoS statistics............................................................................................. 6

3.1 SDCCH Congestion Rate ..................................................................................6

3.2 SDCCH Drop Rate and SDCCH Establishment Success Rate ........................7

3.3 Daily Full Rate and Half Rate Traffic.................................................................9

3.4 TCH Congestion Rate and TCH Dropped Call Rate .....................................10

3.5 TCH Assignment Success Rate and Call Setup Success Rate.....................12

3.6 Outgoing Handover Success Rate ................................................................13

4 Drive test results ...................................................................................... 14

4.1 RxLevel (Full) ....................................................................................................14

4.2 RxQual (Full).....................................................................................................16

4.3 Speech Quality Index (SQI) ...........................................................................18

4.4 Worst C/I...........................................................................................................18

4.5 Timing Advance ..............................................................................................19

4.6 Drive Test Summary.........................................................................................20

5 Problem solved....................................................................................... 21

5.1 Frequency Plan ...............................................................................................21

5.2 Overlapping coverage...................................................................................22

6 Further recommendations..................................................................... 23

6.1 LAC split............................................................................................................23

6.2 High-rise building problem.............................................................................23

6.3 BTS Power Control............................................................................................23



1 SCOPE This document described the GSM radio network optimization and recommendations as part of VMS Phase 15 project.

The report consists of: optimization information, Quality of Service (QoS) over the optimization area, drive test results, outstanding problems and further recommendations.

2 OPTIMIZATION INFORMATION The optimization activity in Hanoi City is a part of VMS Phase 15 project. The optimization area spans over 7 BSCs i.e. BSC Bo Ho, Gia Lam, Giap Bat 1, Hanoi 4, Hanoi 6, Hyunh Thuc Khang and Thuong Dinh. Total numbers of 468 cells in 144 sites are covered.

According to VMS Phase 15 contract, the targets of the optimization are

1. 1.1% TCH Call Dropped Rate (CDR), and

2. 97.5% Call Setup Success Rate (CSSR).

The optimization activities were performed during 21st Feb – 30th May 2005. The optimization activities can be categorized into 2 main parts:

• Statistical analysis:

Observation for daily statistics and solve problems by:

- Parameters and features tuning and

- Frequency tuning.

• Drive test and drive test analysis:

A number of driving test was performed over Hanoi city. Recommendations were proposed as following:

- Parameters tuning,

- Frequency tuning, and

- Antenna down tilting.

Optimization activities in VMS Phase 15 are shown in the following table:

Table 1: Optimization Activities



Week Activities Week 08 (21 Feb – 27 Feb) • RNO Preparation

Week 09 (28 Feb – 6 Mar) • Drive test sites in Phase 15 • Analysis and CAT report

Week 10 (7 Mar – 13 Mar)

• Kick-off meeting with VMS on 8-Mar • Network assessment • Statistical analysis • Drive test

Week 11 (14 Mar – 20 Mar) • Statistical analysis • Drive test analysis

Week 12 (21 Mar – 27 Mar) • Statistical analysis • Drive test analysis

Week 13 (28 Mar – 3 Apr) • Statistical analysis • Drive test analysis • Network assessment meeting on 31-Mar

Week 14 (4 Apr – 10 Apr) • Statistical analysis • Coverage tuning • Frequency planning

Week 15 (11 Apr – 17 Apr) • Statistical analysis • Coverage tuning • Frequency planning

Week 16 (18 Apr – 24 Apr) • Statistical analysis • Neighboring audit • Implement new frequency on 23 and 24 Apr (Failed)

Week 17 (25 Apr – 1 May) • Statistical analysis • Data check and correction

Week 18 (2 May – 8 May) • Statistical analysis • Neighboring audit

Week 19 (9 May – 15 May)

• Statistical analysis • New frequency plan implementation meeting on 10-Mar • Antenna tilting implementation • Frequency planning for TRX expansion • Data correction at OMC • Implement new frequency on 13-May (Successful)

Week 20 (16 May – 22 May)

• Statistical analysis • Drive test analysis • Drive Test after implementing new frequency plan • Neighboring audit

Week 21 (23 May – 30 May) • Driving Test for the remaining areas • Final report



3 QOS STATISTICS The values of the KPIs after end of optimization are shown in the table below:

Table 2: KPIs of VMS Phase 15 Project

Key Performance Indicators (KPIs) Before optimization Results

(14th May to 20th May) Targets

TCH Call Dropped Rate (CDR)

0.81% 0.78% Less than 1.1%

Call Setup Success Rate (CSSR)

98.2% 98.67% More than 97.5%

The following sections present QoS indicator trends over the optimization area from 21st Feb to 20th May.

3.1 SDCCH Congestion Rate The SDCCH Congestion rate was approximately 0.5% and SDCCH traffic was 4,500 Erlang.

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Figure 1: SDCCH Traffic and SDCCH Congestion Rate

On 24th Apr, the SDCCH Congestion Rate increased to 33% due to failure in implementing new frequency plan. The congestion rate went back to the normal value on 26th Apr.

Because many cells experienced electricity power shortage on 3rd May; the SDCCH Congestion Rate was slightly increased.

Recommendation



Cells that have TCH congestion problem will also have SDCCH congestion e.g. HNI_HBT1_O_DONG_MAC_C, HNI_LBN1_BO_DE_A. TRX expansion will improve this problem. After expansion and TCH congestion problem is solved, number of SDCCH can be adjusted accordingly to solve SDCCH congestion.

3.2 SDCCH Drop Rate and SDCCH Establishment Success Rate The SDCCH Drop Rate was 0.3% and SDCCH Establishment Success Rate was about 96%.

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Figure 2: SDCCH Drop Rate and SDCCH Establishment Success Rate

On 3rd Mar, the counter of RNO tool for SDCCH Establishment Success Rate was abnormal and made this indicator abnormally increased.

SDCCH Drop Rate increased from 13th Mar to 4th Apr. The main reason is higher interference level from unclear frequency allocations caused by a number of congested cells’ TRX expansions. After frequency retune, SDCCH Drop Rate was reduced.

SDCCH Drop Rate was highly increased due to failure in implementing new frequency plan on 24th Apr and it returned to average value on 25th Apr after parameters correction.

After successfully implementing new frequency plan on 13th May, SDCCH Drop Rate was increased in some cells. But after the fine tuning, this indicator reduced to 0.29%.



SDCCH Establishment Success Rate decreased relating to higher SDCCH Congestion Rate [see Figure 3]. From 18th to 20th May, SDCCH Congestion Rate increased in some cells, this rise made SDCCH Establishment Success Rate lower than normal value.

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Figure 3: SDCCH Congestion Rate and SDCCH Establishment Success Rate



3.3 Daily Full Rate and Half Rate Traffic Both daily Full Rate and Half Rate Traffic were 25,000 Elrang and 4,500 Erlang respectively. Traffic volume remained stable from the beginning of the optimization period except that from 29th Apr to 4th May which was a long holiday period.



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Figure 4: Total Full Rate and Half Rate TCH Traffic

3.4 TCH Congestion Rate and TCH Dropped Call Rate TCH Congestion Rate was higher when optimization started; it was 0.7% and reduced to 0.6% on 20th May. TCH Dropped Call Rate was improved from 0.81% on 7th Mar to 0.73% on 20th May.

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Figure 5: TCH Congestion Rate and TCH Dropped Call Rate

After failure in implementing new frequency plan on 24th Apr, TCH Drop Call Rate increased sharply to 0.93%. When the correction for the unexpectedly modified parameters resulting from the failure had finished, TCH Dropped Call Rate went back to 0.74% on 25th Apr.

On 3rd and 4th May, both TCH Congestion Rate and TCH Dropped Call Rate increased because two sites experienced electricity power shortage. These sites were put back in to service on 4th May.

When new frequency plan was successfully implemented on 13th May, TCH Dropped Call Rate was increased. The increase was not due to frequency changes related but transmission problem related. HNI_HBT1_O_DONG_MAC had transmission problem from 14th to 16th May. Number of dropped call for this site was more than 2,000 times daily [see Figure 6].



After finishing the tuning period (20th May), the TCH Dropped Call was 0.73%.

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Figure 6: TCH Dropped Call Rate Distribution

Recommendation For the congested cells, TRX expansion should be performed as soon as possible. Below is the recommended expansion list:



Cell ID Cell Name TCH Congestion Current No. of TRX

No. of TRX required to

expand 10013 HNI_LBN1_GIA_LAM_C 4% 1 1 10911 HNI_LBN1_BO_DE_A 2% 2 1 10083 HNI_TXN2_DINH_CONG_C 3% 1 1 10203 HNI_HBT1_O_DONG_MAC_C 3% 1 1 10352 HNI_DAH1_DONG_ANH_B 4% 1 1 10641 HNI_CGY2_NGHIA_DO_A 4% 1 1 10757 HNI_DDA2_PHUONG_MAI_1800_A 6% 2 1 10791 HNI_CGY2_NGHIA_TAN_A 3% 1 1 10792 HNI_CGY2_NGHIA_TAN_B 4% 1 1 10803 HNI_TXN2_NHAN_CHINH_C 5% 1 1 10954 HNI_TTI2_NGOC_HOI_A 3% 1 1 11151 HNI_HMI1_LINH_DAM_A 3% 1 1 11183 HNI_TXN2_NGUYEN_TRAI_C 4% 1 1 11823 HNI_DDA2_DE_LA_THANH_C 4% 1 1 16122 BNH_TDU1_TIEN_SON_B 5% 1 1

3.5 TCH Assignment Success Rate and Call Setup Success Rate TCH Assignment Success Rate was approximately at 98.7% while Call Setup Success Rate fluctuated in the range of 98.2-98.8%. After the optimization, both indicators were improved.

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Figure 7: TCH Assignment Success Rate and Call Setup Success Rate



3.6 Outgoing Handover Success Rate The Outgoing Handover Success Rate was stable at 97% at the end of tuning period on 20th May.

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Figure 8: Outgoing Handover Success Rate

During the optimization, on 3rd Apr, cell HNI_HMI_GIAP_BAT_B had hardware problem and made incoming handover performance from cells around it degraded. After locking and unlocking TRX of problem cell, the incoming handover problem was solved and hence Outgoing Handover Success Rate was improved to 97%.

On 24th Apr, the Outgoing Handover Success Rate was dropped to 88% due to failure in implementing new frequency plan.

Problem in BSC GIA LAM started on 28th Apr. It lasted until 18th May and made Outgoing Handover Success Rate lower than 97%. Two sites in BSC GIA LAM i.e. NGUYEN VAN CU and GIA LAM were found having low outgoing intra BSC handover success rate. It was also found from drive test that the MS could not attach to the assigned traffic channel during handover. This caused handover failure. BSC-MSC interworking logical definitions, BSC and BTS parameters, and BTS hardware were checked while no error was found. By this mean, a decision to reset GIA LAM BSC was made. After resetting the BSC on 18th May, intra BSC handover become normal and put statistic back to 97%.

Recommendation



Handover between GSM900 and GSM1800 is the problem for some cells. Normally, GSM900 cells will handover to GSM1800 cells by preferred band condition if the measured signal strength of GSM1800 is higher than a threshold (default value is -85 dBm). The handover will not well perform if two cells are too far away and signal strength of GSM1800 is too low. After deleting (outgoing) unnecessary handover relations from GSM900 cells to GSM1800 cells, Outgoing Handover Success Rate improved. Fine tuning (increasing) the threshold for preferred band handover in order to maintain appropriate signal strength level for good handover performance is recommended.

4 DRIVE TEST RESULTS Drive tests were performed twice. The first was performed at the beginning of the optimization. The latter was performed after some antenna tilting and new frequency plan implementation.

Since the Downlink DTX is not used. RxLevel (Full) and RxQual (Full) are presented. Comparison of drive test results between the two tests are shown in the following sections.

4.1 RxLevel (Full) The coverage in Hanoi city from both drive test results are very good, 90% of the samples were greater than -75 dBm for first test and 90.5% of the samples were greater than -75 dBm for second test [see Figure 9].

RxLev Full (dBm) Cummulative Distribution

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Figure 9: RxLev Full (dBm) Cumulative distribution

RxLevel (Full) plots are shown in Figure 10 and Figure 11 respectively.



Figure 10: RxLev (Full) of Hanoi city before implementing new frequency plan



Figure 11: RxLev (Full) of Hanoi city after implementing new frequency plan

4.2 RxQual (Full) RxQual comparison graph is shown in Figure 12. The RxQual was improved. RxQual 0-4 increased from 97.28% to 98.25%.

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Figure 12: RxQaul Full between before and after new frequency plan implementation

RxQual (Full) plots are shown in Figure 13 and Figure 14 respectively.



Figure 13: RxQaul (Full) in Hanoi city before implementing new frequency plan



Figure 14: RxQaul (Full) in Hanoi city after implementing new frequency plan

4.3 Speech Quality Index (SQI) The maximum SQI is 21 which is the maximum value Full Rate speech codec can provide. The percentage samples having SQI 21 improved from 42.08% to 52.39% while lower percentage of poor SQI can be clearly seen.

Speech Quality Cummulative Distribution

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Figure 15: SQI between before and after implementing new frequency plan

4.4 Worst C/I The Worst C/I (carrier-over-interference ratio) value is an indicator which is mostly mapped to GPRS Radio Link throughput. The more the Worst C/I the better the GPRS Radio Link throughput a user can get (up to the limitation according to the supported coding scheme and the number of time slots used).

Generally there is no exact criterion for this figure and is dependable on the drive test routes; nonetheless, in a good coverage area, one would target for a low percentage of Worst C/I samples ≤ 9. From the drive test, this percentage value of Worst C/I ≤ 9 decreased from 2.65% to 1.71%.



Worst C/I Distribution

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Figure 16: Worst C/I between before and after implementing new ferquency plan

4.5 Timing Advance The Timing Advance shows roughly how close to the base stations the calls are (not for the case of reflected signal). This value can be used to as one of the factors to determine the frequency reuse strategy for the area. It can also infer about the overlapping or overshooting coverage if the site-to-site distance is closer. From the graph, more samples of timing advance 0 and 1 values can be seen.



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4.6 Drive Test Summary The summary of all indicators between before and after implementing new frequency plan except timing advance is shown in the following table:

Table 3: Summary of driving test results

Indicators Before implementing new frequency plan

After implementing new frequency plan Results

RxLev (Full) > -75 dBm 90% 90.5% Improved

RxQual (Full) < 5 97.28% 98.25% Improved

SQI 21 42.08% 52.39% Improved

C/I Worst < 9 2.65% 1.71% Improved

TA 0-1 55.58% 61.40% Improved



5 PROBLEM SOLVED The problems solved during the optimization are listed in this section.

5.1 Frequency Plan The frequency assignment in Hanoi city was planned and customized freely without pattern. With this frequency assignment, co-channel interference pairs pointing to each other were commonly found.

Compared to the pattern planning which gives more uniform frequency reuse distance and more uniform interference averaging, this unpatterned assignment gives irregular frequency reuse distances and can result in severe interference if the interfering cell’s coverage is not properly controlled. It also requires much more work for frequency tuning in case of interference or finding new frequency in case of TRX expansions.

To gain the benefit from the already patternized antenna direction in Hanoi City, new frequency plan using a patternized frequency both GSM900 and GSM1800 band was proposed. Frequency patterns for both band used in VMS network are shown in Table 4 and Table 5.

Table 4: Frequency pattern for GSM900 Band

Sector A Sector B Sector C

84 BCCH 98 BCCH 112 BCCH





89 TCH 103 TCH 117 TCH








97 and 111 : Patch frequency

Table 5: Frequency pattern for GSM1800 Band

Sector A Sector B Sector C

579 TCH 590 TCH 601 TCH

580 TCH 591 TCH 602 TCH

581 TCH 592 TCH 603 TCH

582 TCH 593 TCH 604 TCH

583 TCH 594 TCH 605 TCH

584 TCH 595 TCH 606 TCH

585 TCH 596 TCH 607 TCH

586 TCH 597 TCH 608 TCH

587 TCH 598 TCH 609 TCH

588 TCH 599 TCH 610 TCH

589 TCH 600 TCH 611 TCH


614 TCH 624 TCH 634 TCH


616 TCH 626 TCH 636 TCH


618 TCH 628 TCH 638 TCH


620 TCH 630 TCH 640 TCH


612, 622 and 632 : Patch frequency

642, 643 and 644 : In-building frequency



The frequency planning was performed from 4th Apr to 15th Apr. After finishing, the plan was evaluated by VMS’s prediction tool. With good prediction result, VMS decided to implement the

new frequency to Hanoi network on 22nd Apr. Nonetheless, the new frequency plan implementation on that date was failed (see more information in Section 5.2). Another change attempt was performed again on 13th May, this time the change was successful.

5.2 Overlapping coverage From first driving test, overshooting coverage problem were found. This problem made both handover and call quality worse.

BCCH frequency scan was performed mostly on main roads of Hanoi city during 4th and 5th Apr.

29 cells were proposed for antenna down tilting. Nonetheless only 26 cells were tilted (3 cells are at their maximum tilting value already). The List of these cells is shown in Table 6

Table 6: Proposed and implemented antenna tiliting values for overshooting coverage cells

Cell Name Recommended Tilting Value

Existing Value

Implemented Value Antenna Type Remark

HNI_HKM1_TRAN_NHAT_DUAT_B 8 6 7 APX906516-T0

HNI_DDA2_HANG_BOT_C 8 7 7 K739636 Maximum down tilt

HNI_DDA2_THAI_THINH_B 8 6 7 APX906516-T0 HNI_HKM1_HANG_LUOC_C 8 7 8 APX906516-T0 HNI_HBT1_DAM_TRAU_A 7 5 7 APX906516-T0

HTY_HDG2_THANH_XUAN_A 7 4 5 APX906516-T0 HNI_HMI1_LE_TRONG_TAN_C 7 2 4 K739630 HNI_DDA2_PHUONG_MAI_B 7 6 7 K739636 HNI_HBT1_GIAI_PHONG_B 7 8 10 K739636

HNI_TXN2_KHUONG_TRUNG_B 7 5 6 K739630 HNI_TXN2_KHUONG_TRUNG_C 7 5 6 K739630 HTY_HDG2_HOC_VIEN_BCVT_A 7 3 5 K739630 HNI_DDA2_TON_THAT_TUNG_A 8 6 8 K739630 HNI_DDA2_TON_THAT_TUNG_B 8 6 8 K739630 HNI_DDA2_TON_THAT_TUNG_C 8 6 8 K739630 HNI_HMI1_KHUYEN_LUONG_C 8 4 6 K739630

HTY_HDG2_BA_LA_A 6 4 6 AO9009 HTY_HDG2_TRAN_DANG_NINH_A 7 6 7 K739630 HNI_HKM1_PHAN_CHU_TRINH_A 8 7 8 K739630

HNI_BDH2_BACH_THAO_B 8 5 7 K739630 HNI_DDA2_HOANG_CAU_C 7 6 7 K739636

HNI_DDA2_THANH_CONG_A 8 6 8 K739630 HNI_DDA2_LE_DUAN_C 9 8 9 K739630 HNI_HKM1_HOI_VU_A 7 6 7 K739636

HNI_CGY2_VIEN_TIN_C 7 6 7 APX906516-T0 HNI_TXN2_THUONG_DINH_C 8 7 8 APX906516-T0

HNI_DDA2_DANG_TIEN_DONG_C 9 8 8 APX906516-T0 Maximum down tilt

HNI_TXN2_THANH_XUAN_BAC_A 7 6 6 K739636 Maximum down tilt

HNI_DDA2_DUONG_LANG_B 6 5 6 K739630



6 FURTHER RECOMMENDATIONS This section provides recommendations for further performance improvement of network.

6.1 LAC split High paging load (50%) is found in LAC 1. This can normally lead to higher possibility of congestion and difficulty in reaching the call for MS terminating side. By this mean, LAC split is recommended.

It is recommended to split LAC 1 in Hanoi city to two LACs. Taking into account the BTS’s geographical locations and the current BSC service areas, the split would be one LAC consisting of hanoi4, hanoi6 and HUYNH THUC KHANG BSCs and another LAC consisting of BO HO, GIAP BAT 1 and THUONG DINH BSCs.

After the location area split, SDCCH Congestion at the location area borders should also be monitored and solved.

6.2 High-rise building problem There are a lot of customer complaints from subscribers using their MS in high-rise buildings. In-building walk test log files have shown that there is no dominant server in those areas. BCCH carriers of sites located far away are detected with almost equal in strength.

Antenna tilting will help relieving the problem to a certain extent. In no-dominant server case, a dedicated in-building coverage solution is recommended.

6.3 BTS Power Control To further reduce the interference, BTS Power Control activation is recommended. With BTS Power Control feature activated, the BTS (except BCCH) will decrease its transmitted output power to a level just enough to maintain the call at the predefined downlink quality. By this mean, the overall interference level of the network will be decreased.



Documents

VMS Ph15 Final Report_Rev F.pdf