GSM Performance Analysis Report

7/26/2019 GSM Performance Analysis Report

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s Network Performance Report

Author: ICM N OP MS ND 6 Performance Report Page 1

Network Performance

Report

Network XMonth/ Year





1. INTRODUCTION 3

2. EXECUTIVE SUMMARY 4

3. BSS PERFORMANCE ANALYSIS 5

3.1. Traffic Channel Blocking 5 3.1.1. Traffic Channel Blocking at Network and BSC Level 5 3.1.2. Traffic Channel Blocking at BTS Level 7

3.2. Signalling Channel Blocking 12

3.3. Traffic Analysis 13 3.3.1. Network- and BSC Level Traffic Analysis 13 3.3.2. BTS Level Traffic Analysis 15

3.4. Call Setup Analysis 16 3.4.1. Call Split 17 3.4.2. Call Setup Success Analysis at BTS Level 17

3.5. Call Drop Analysis 21 3.5.1. SDCCH Drops 21 3.5.2. TCH Drops 22

3.6. Interference Analysis: 29

3.7. Handover Analysis 34

3.7.1. Intracell Handover 34 3.7.2. Intercell Intra BSC Handover Success Rate 38 3.7.3. Intercell Inter BSC Handover Success 42

4. SSS PERFORMANCE ANALYSIS 44

4.1. Introduction 44

4.2. GOS – Grade of service 44 4.2.1. Mobile to mobile call 46 4.2.2. Mobile originating call 47 4.2.3. Mobile terminating call 48 4.2.4. Handover 49 4.2.5. Location Update and paging 50 4.2.6. Errors SSS 51 4.2.7. Errors BSS 52

4.3. CCS7 Link Load evaluation 53

4.4. Trunk Group evaluation 54

4.5. Traffic model 55 4.5.1. Traffic model overview 55 4.5.2. BHCA and load 56





1. Introduction

The Siemens Network Analysis Team received traffic measurement data from the GSM 900Network in the city of City Y. The task was to analyse the SSS and BSS Grade of Service, for 1MSC/VLR, 4 BSC´s and 218 Cells (BTS).

Performance Data were taken from SSS and BSS from following Time period.

SSS Performance Data are from: June 26th 2002 until June 28

th 2002

BSS Performance Data are from: June 20th 2002 until June 26

th2002

Below an Overview about the Network Configuration

BSC Name Nr. of BTSMwithin BSC

Nr. of BTSwithin BSC

Nr. of TRX´swithin BSC

BSC01 45 81 236BSC02 12 25 59

BSC03 26 50 182BSC04 28 62 162Sum 111 218 639

Following Grade of Service parameters are evaluated in this report:

•

BSS Performance Analysis:o Traffic Channel Blocking o Signalling Channel Blocking o Call Setup o Call Drop o Handover o Interference

• SSS Performance Analysis:

o GOS- Grade of Service (MMC, MOC, MTC, Handover, Location Update) o CCS7 Link Load Evaluation o Trunk Group Evaluation

o Traffic Model (BHCA, Load, Traffic Model)





2. Executive Summary

In general the Network shows Performance Values within the Siemens Standard Benchmarks,but the current Traffic is not as high as it will be expected during the upcoming holiday Season.During Holiday Seasons it is expected that the number of sites with high Blocking will increaseand therefore the Grade of Service will decrease.

The overall standard of the Network performance is good, especially the Handover Performancehas increased compared to last year.

Nevertheless there are some points, which are highlighted in the report.

• Traffic Channel Blocking at the Air-Interface in some cells of BSC01 and BSC03.

• Uplink Interference problems in some cells within BSC01 and BSC03 were detected.

• Certain cells with high Drop Rate

• The Mobile Originating Performance at the MSC on the 28th

of June is below Siemensstandards, from the SSS Performance data the problem cannot be located. FurtherInvestigations with Interface traces are necessary, if the problem still exists.

• Some external technical Irregularities and Trunk Group Congestion from adjacent SSSNetwork Elements in own PLMN or PSTN were recorded.

The measured CP-Load in the MSC City Y is below the Load A boarder, which leaves enoughspare for future traffic.





3. BSS Performance Analysis

The BSS Performance data are taken from 4 BSC´s in the region of City Y and from June 20 th until June 26

th 2002. Following Grade of Service Parameters is evaluated in detail in this

chapter.

o Traffic Channel Blocking o Signalling Channel Blocking o Traffic Analysis o Call Setup o Call Drop (SDCCH Drops, TCH Drops, Call Failure Reasons) o Interference o Handover

If not explicitly mentioned the data are always related to the busy hour data of the individual

Network element. The Busy hour is defined as the hour of the day in which the measuredNetwork Element shows the highest Traffic.

3.1. Traffic Channel Blocking

3.1.1. Traffic Channel Blocking at Network and BSC Level

The Traffic Channel (TCH-) Blocking is defined as the Rate of blocked Traffic Channel Assignments due to no radio resource available.In the graph below you can see the “Traffic Channel Blocking” from the whole Network (red line)and the Blocking from each BSC (as an average from the connected BTS´s) over themeasurement period of 7 days (20.6 until 26.6.2002). The Network Blocking is the averageTraffic Channel Blocking over all BTS´s in the area of City Y.

Siemens Standard for Network Blocking is 1%, in this case the Traffic Channel Blocking variousbetween 1.24% and 2.75%, which is too high and also not constant. But we can see thatspecially the Traffic Channel Blocking from BSC02 (pink line) various from 0% up to 3.2%.

Traffic Channel Blocking

1.58%

1.24%

2.52%

2.24% 2.18%

2.75%

2.27%

0.00%

0.50%

1.00%

1.50%

2.00%

2.50%

3.00%

3.50%

4.00%

4.50%

20.06.02 21.06.02 22.06.02 23.06.02 24.06.02 25.06.02 26.06.02

Time [dd.mm.yy]

T C H B l o c k i n g [ % ]

Network

BSC01

BSC02

BSC03

BSC04





The Reason for the high Blocking figures will be evaluated in chapter 3.1.2 (Traffic ChannelBlocking at BTS Level). The reason for the big changes in the Blocking can be explainedfollowing.The Blocking of BSC and Network Level is an average of all Call Attempts Failures due to

Blocking from each BTS. If only a few cells (BTS) are showing high Blocking, then the Blockingat BSC Level is mostly depending on the Blocking of this few cells. Below you can see that theBlocking of one individual cell (BTS3) drives the high BSC02 Blocking.

0.00%

2.00%

4.00%

6.00%

8.00%

10.00%

12.00%

14.00%

16.00%

18.00%

0 6 / 2 0

/ 2 0 0 2

0 6 / 2 1

/ 2 0 0 2

0 6 / 2 2

/ 2 0 0 2

0 6 / 2 3

/ 2 0 0 2

0 6 / 2 4

/ 2 0 0 2

0 6 / 2 5

/ 2 0 0 2

0 6 / 2 6

/ 2 0 0 2

BSC02

BTS3

BTS18

BTS19

As it is shown above, that BTS 3 (CI: 37010) has high Traffic Channel Blocking and thereforealso the Blocking at BSC Level is triggered by the Blocking of this cell. The big difference ofBlocking from one day to the other one can be explained by Traffic Channel Connections fromSubscribers.

BusyHour

BSC02,3:TCH_BLOCKING_RATE BSC02,3:TCH Connections

date

06/20/2002 06/21/2002 06/22/2002 06/23/2002 06/24/2002 06/25/2002 06/26/2002

14%

12%

10%

8%

6%

4%

2%

0%

1,500

1,400

1,300

1,200

1,100

1,000

900

800





3.1.2. Traffic Channel Blocking at BTS Level

This chapter is focused on the Traffic Channel Blocking Evaluation at BTS Level. In thefollowing analysis cells are listed, which have higher Blocking then 2% during the busiest hour

of the day. In the report we made two categories:

• Cells with permanent Traffic Channel Blocking higher then 2%

In this list you will find the cells, which have over the measurement period of 7 daysalways a Blocking higher then 2%. Those cells are candidates for expansion or otherTraffic reducing methods should be applied for those cells.

The BTS Feature Directed Retry (is in all cells enabled) will re-route the failed Attemptsto other cells in the neighbourhood of the blocked cell. But if the Blocking Rate is toohigh (e.g. above 5%), this overflow to other cells is a reason for Interference andtherefore also bad speech quality. Furthermore also the Grade of Service parametersare reduced for the whole BSC or Network, if some BTS´s show high Blocking. (As you

can see in previous chapter).

• Cells with sporadic Traffic Channel Blocking higher then 2%.

Those cells show in at least 3 days of the whole measurement period a Traffic ChannelBlocking higher then 2%. These cells should be monitored carefully in the future andalso expansions or other Traffic reducing methods should be applied if necessary.

The Traffic will increase in the upcoming Holiday Season and therefore already currentblocked cells will show higher Blocking and therefore a degradation of Grade of Servicecan be expected.

On the next pages you will find the tables for permanent and sporadic blocked cells:




Author: ICM N O P MS ND 6 Performance Report Page 8

Cells from BSC01 with permanent TCH Blocking Rate Higher then 2%

20.06.02 21.06.02 22.06.02 23.06.02 24.06.02 25.06.02 26.06.02

B T S

N r . :

C I

T C H B

l o c k i n g

T r a f f i c C a r r i e d

T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

16 36071 29.40% 26. 75 30 12.28% 25.77 30 11.54% 25.41 30 7.20% 24.18 30 24.06% 25.76 30 4.37% 24.29 30 11.72% 24.98 30

81 36331 10.22% 10.61 14 14.21% 10.88 14 23.50% 11.82 14 25.88% 11.55 14 28.58% 12.14 1 26.11% 11.64 14 5.78% 9.1 14

29 36102 7.09% 24.29 29 8.91% 23.57 29 21.85% 25.69 29 24.06% 25.79 29 12.67% 24.12 29 22.22% 25.89 29 18.27% 25.71 29

3 36012 5.22% 21.64 29 17.24% 24.26 29 21.28% 25.32 29 16.98% 25.4 29 9.27% 24.6 29 5.41% 22.77 29 6.17% 21.86 29

62 36262 0.59% 14.23 21 7.34% 15 21 3.49% 14.99 21 0.85% 14.31 21 11.53% 16.52 21 6.00% 15.75 21 1.94% 14.11 21

57 36151 0.00% 11.43 22 0.09% 11.84 22 2.93% 13.07 22 2.30% 14.41 22 0.17% 13.39 22 1.27% 13.59 22 2.00% 14.51 22

Cells from BSC01 with sporadic TCH Blocking Rate Higher then 2%

20.06.02 21.06.02 22.06.02 23.06.02 24.06.02 25.06.02 26.06.02

B T S

N r . :

C I

T

C H B

l o c k i n g


T C H A

v a i l a b l e

T

C H B

l o c k i n g


T C H A

v a i l a b l e

T

C H B

l o c k i n g


T C H A

v a i l a b l e

T

C H B

l o c k i n g


T C H A

v a i l a b l e

T

C H B

l o c k i n g


T C H A

v a i l a b l e

T

C H B

l o c k i n g


T C H A

v a i l a b l e

T

C H B

l o c k i n g


T C H A

v a i l a b l e

33 36113 0.00% 1.21 14 0.00% 1.39 14 0.00% 3.65 14 0.00% 3.22 14 0.00% 3.29 14 0.00% 5.29 14 3.16% 8.35 14

49 36192 0.00% 8.78 22 0.00% 8.28 22 0.00% 8.1 22 0.00% 8.78 22 5.19% 15.54 22 2.71% 13.7 22 0.00% 10.22 22

50 36202 0.00% 3.95 14 0.00% 5.08 14 0.00% 5.61 14 0.00% 3.94 14 4.96% 8.55 14 38.02% 12.2 14 0.00% 4.42 14

65 36201 0.89% 7.23 14 0.40% 7.03 14 6.11% 9.1 14 0.00% 7.26 14 1.72% 6.83 14 0.53% 7.27 14 4.92% 8.79 14






20.06.02 21.06.02 22.06.02 23.06.02 24.06.02 25.06.02 26.06.02

B T S

N r . :

C I

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

3 37010 13.18% 23.89 29 4.48% 23.24 29 15.46% 24.1 29 2.48% 20.61 29 4.29% 21.41 29 12.41% 22.86 29 0.00% 18.79 29


20.06.02 21.06.02 22.06.02 23.06.02 24.06.02 25.06.02 26.06.02

B T S

N r . :

C I

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

18 37091 1.13% 2.98 7 0.00% 1.62 7 0.00% 1.89 7 0.00% 1.65 7 1.56% 2.67 7 12.04% 3.33 7 1.54% 2.35 7

19 37092 3.52% 3 7 3.08% 2.34 7 0.00% 2.32 7 0.92% 2.81 7 0.00% 1.89 7 0.00% 2.26 7 0.00% 1.77 7






20.06.02 21.06.02 22.06.02 23.06.02 24.06.02 25.06.02 26.06.02

B T S

N r . :

C I

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

28 38191 3.57% 29.38 37 13.35% 32.22 37 3.64% 29.18 37 1.68% 27.81 37 18.60% 33.2 37 14.01% 32.06 37 18.22% 32.9 37

29 38192 2.02% 21.76 29 4.89% 21.35 29 4.30% 22.28 29 5.78% 23.14 29 3.66% 20.95 29 8.92% 23.07 29 7.59% 22.35 29

64 38302 5.46% 21.74 29 2.22% 21.29 29 11.45% 22.98 29 14.00% 24.59 29 3.49% 20.54 29 6.68% 21.88 29 14.68% 23.74 29

66 38261 12.28% 24.69 29 10.51% 23.55 29 22.48% 25.92 29 22.80% 26.25 29 26.70% 26.29 29 31.04% 26.97 29 25.57% 26.36 29

68 38263 0.94% 14.12 22 7.62% 16.77 22 7.51% 16.2 22 9.84% 16.51 22 5.10% 14.42 22 3.27% 16.01 22 6.98% 16.09 22


20.06.02 21.06.02 22.06.02 23.06.02 24.06.02 25.06.02 26.06.02

B T S

N r . :

C I

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

17 38061 0.00% 12.74 29 0.00% 15.16 29 0.00% 13.99 29 0.00% 13.31 29 0.00% 13.11 29 0.00% 14.69 29 13.53% 23.66 2927 38111 0.00% 14.23 29 0.60% 18.98 29 0.14% 17.51 29 0.00% 17.04 29 0.08% 16.69 29 1.54% 18.78 29 2.78% 20.51 29

28 38191 3.57% 29.38 37 13.35% 32.22 37 3.64% 29.18 37 1.68% 27.81 37 18.60% 33.2 37 14.01% 32.06 37 18.22% 32.9 37

36 38161 0.16% 15.98 29 0.30% 17.08 29 0.26% 17.83 29 0.68% 18.24 29 1.76% 18.5 29 0.00% 17.9 29 4.82% 22.05 29

63 38301 0.92% 16.41 29 0.00% 17.44 29 0.88% 18.9 29 3.35% 20.89 29 0.75% 19.45 29 0.73% 18.91 29 3.35% 20.09 29






20.06.02 21.06.02 22.06.02 23.06.02 24.06.02 25.06.02 26.06.02

B T S

N r . :

C I

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

35 39152 3.29% 9.72 14 17.67% 11.32 14 5.51% 9.77 14 11.18% 10.38 14 21.95% 11.45 14 9.58% 10.04 14 10.29% 10.04 1446 39213 8.14% 24.3 29 0.00% 10.4 29 3.20% 22.15 29 10.16% 24.36 29 6.07% 23.14 29 15.62% 25.41 29 5.44% 23.47 29

49 39223 0.00% 21.15 37 0.00% 19.33 37 8.26% 30.83 37 3.19% 28.55 37 8.68% 29.94 37 2.51% 28.35 37 5.43% 30.38 37


20.06.02 21.06.02 22.06.02 23.06.02 24.06.02 25.06.02 26.06.02

B T S

N r . :

C I

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

T C H B

l o c k i n g


T C H A

v a i l a b l e

16 39071 0.00% 4.53 14 0.00% 4.15 1 2.55% 8.56 14 0.00% 3.53 14 0.00% 3.31 1 0.00% 3.14 14 0.00% 4.8 14

25 39112 3.39% 6.65 14 0.00% 1.39 1 0.00% 5.84 14 0.00% 5.95 14 0.00% 5.42 1 0.00% 6.17 14 0.00% 6.34 14

28 39123 0.36% 6.25 14 0.00% 3.78 1 0.00% 5.68 14 0.37% 5.75 14 0.00% 6.26 1 0.00% 6.49 14 6.55% 8.02 14

40 39171 0.69% 18.54 29 0.00% 7.25 29 2.55% 15.98 29 0.71% 18.83 29 0.06% 17.93 29 1.27% 18.45 29 1.30% 17.12 2953 39231 24.82% 24.95 29 35.22% 25.89 29 0.00% 7.05 29 0.00% 7.63 29 0.00% 9.51 29 0.00% 6.84 29 0.00% 11.06 29





3.2. Signalling Channel Blocking

In this chapter we will describe the Grade of Service for the Signalling Channels at the RadioDomain. Following Channels are evaluated with following results.

• Access Grand Channel (AGCH): No Problems could be identified. The AGCH

Assignment Success Rate is always above 99%, which is in an acceptable rate.

• Random Access Channel (RACH): No Problems could be identified.

• Paging Channel (PCH): No severe problems could be identified, except the Location

Area Code at BSC01 should be monitored in future. There was already a slight PagingChannel Blocking measured at cell 50 and 83 (CI: 36202 and CI: 36250). Furthermore itseems that at BSC04 the BTS 56 (CI: 39241) carries no Traffic at all and has therefore

also no Paging Commands. This site needs to be investigated for Hardware Failures.

• Standalone Dedicated Control Channel (SDCCH):The Signalling Channel (SDCCH) Blocking is defined as the Rate of blocked SignallingChannel SDCCH Assignments due to no radio resource available. Within Siemens wedefine 1% SDCCH Blocking Rate as the Standard Benchmarks, if the SDCCH BlockingRate goes above 1% the Signalling Channels of this cells should be upgraded. In theNetwork of City Y we found only two cells with a SDCCH Blocking higher then 1- %,these cells are listed below.

SDCCH Blocking Rate >= 1%

BSCID Btsn Lac Ci Date BusyHour SDCCH_BLOCKING_RATEBSC01 7 2006 3603106/22/2002 18:00-19:00 1.46%

BSC01 16 2006 3607106/20/2002 22:00-23:00 2.07%

It is important, that the SDCCH Blocking is kept at a Level of 0%, because each Call Setup lostdue to SDCCH Blocking can not be re-routed to other cells, like it is the case for TCH Blocking(Directed Retry does not work for SDCCH!)





3.3. Traffic Analysis

3.3.1. Network- and BSC Level Traffic Analysis

In this chapter we will evaluate the Traffic Situation of the Network in City Y at the NetworkLevel (this means total Traffic of all 4 BSC´s) and the BSC Level (this means Traffic Carried ofeach BSC). The Indicator Traffic Carried provides the Traffic volume in Erlang, which wasprocessed by the individual Network element (e.g. BSC, BTS) or a sum of Network elements(e.g. Network Wide). The Traffic Volume is one Mean Indicator in order to find out the Utilisationof a Network Element with the help of Erlang B formula. (Erlang B applicable for Circuit SwitchTraffic only)

In the graph below it is shown the Traffic Carried of the whole Network in City Y and from eachBSC at the Busy Hour from each day within the measurement period.

Traffic Carried on Network- and BSC Level

1125.85

1185.54 1197.811164.7 1153.12

1180.13 1176.71

0

200

400

600

800

1000

1200

1400

06/20/2002 06/21/2002 06/22/2002 06/23/2002 06/24/2002 06/25/2002 06/26/2002

Date [dd.mm.yy]

T r a f f i c C a r r i e d [ E r l a n g ]

Network

BSC01

BSC02

BSC03

BSC04

As you can see above the Traffic Carried is constant over the whole measurement period at aLevel of 1200 Erlang.





3.3.1.1. Avai lable Traf f ic Ch annel

In order to find out the Utilisation of a Network Element we need to know the number of TrafficChannel available. Below a graph, which shows the Traffic Channel distribution in the Network

and from each BSC.

Traffic Channel Available

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

06/20/2002 06/21/2002 06/22/2002 06/23/2002 06/24/2002 06/25/2002 06/26/2002

Date [dd.mm.yyyy]

N u m

b e r o

f T r a f f u c

C h a n n e

l

Network

BSC01

BSC02

BSC03

BSC04

The Measurement indicates that the number of available TCH is constant over the whole

Measurement Period and that no Half-rate Channels are in use.

3.3.1.2. Mean Traf f ic Channel Holding Time

An other important Indicator is the Mean TCH Holding Time this indicator is defined following.This indicator will give you the mean holding Time in seconds for one single occupied TCH in acell. This Parameter provides the information how long a call stayed on the measured cell.

Mean Traffic Channel Holding Time

41.17

44.0042.63

40.8242.03 42.77

39.87

0.00

10.00

20.00

30.00

40.00

50.00

60.00

06/20/2002 06/21/2002 06/22/2002 06/23/2002 06/24/2002 06/25/2002 06/26/2002

Dtae [dd.mm.yyyy]

M e a n

T C H H o

l d i n g

T i m e

[ S e c o n

d s

]

Network

BSC01

BSC02

BSC03

BSC04





In this case the Mean TCH Holding Time is approximately 40 Seconds, which is in the range ofSiemens Benchmarks. Siemens recommends a Mean TCH Holding Time of 20 to 60 Seconds.Short Holding Times are indications for

• Ping-Pong Handover

• Coverage Holes• Problems in PSTN

But this problems could not be find in the Measurement period.

For further analysis regarding Busy Hour and Traffic please refer to attached document.

Traffic_network_BH_ main.xls

3.3.2. BTS Level Traffic Analysis

In this chapter we will evaluate the Traffic Performance of each individual BTS in the Networkduring the Busy Hour of each BTS over the measurement period.The attached file is showing the Traffic Carried, which was measured by the system and theTraffic Planned @ 2% Blocking. The Traffic Planned is the calculated Traffic with the Erlang Bformula out from the available Traffic Channels and the excepted Blocking (e.g. 2%). In otherwords the Traffic Planned is the Traffic which can be processed by the Network Element at 2%Blocking Rate.

The Utilisation of cell is calculated out from the actual measured traffic against the calculatedplanned Traffic. 100% Utilisation means that the evaluated cell has a Blocking of 2% already.Cells with Utilisation above 100% should be upgraded with Hardware or other Traffic ReducingMeasures should be applied.

Traffic_BSC_BTS_BH.xls





3.4. Call Setup Analysis

The Call Setup Procedure starts from the Assignment Request (by pressing the send key on theMS) send by the Mobile Station until the successful Assignment of a Traffic Channel at the Air-Interface. The Call Setup can mainly fail due to three reasons:

• No SDCCH available (the call will be immediately terminated)

• SDCCH Drop (e.g. in case of Interference or power imbalance the MS is not able toconform the connection setup)

• No Traffic Channel available (due to Blocking, the call can be re-routed to an othercell with the feature directed retry, but for this cell the Call Setup is failed)

The below seen graph shows the Call Setup Success Rate as an average over the wholeNetwork and over each BSC out from measurements taken from the Busy Hour.

Call Setup Success Rate

86.00%

88.00%90.00%

92.00%

94.00%

96.00%

98.00%

100.00%

0 6 / 2 0

/ 2 0 0 2

0 6 / 2 1

/ 2 0 0 2

0 6 / 2 2

/ 2 0 0 2

0 6 / 2 3

/ 2 0 0 2

0 6 / 2 4

/ 2 0 0 2

0 6 / 2 5

/ 2 0 0 2

0 6 / 2 6

/ 2 0 0 2

Date [dd.mm.yyyy]

C a l l S e t u p

S u c c e s s R a t e [ % ]

Network

BSC01

BSC02

BSC03

BSC04

The Call Setup Success Rate for the whole Network is stabile and has a value of 96%. TheSiemens Benchmark of 95% Call Setup Success Rate is reached except the Call SetupSuccess Rate of BSC02 and BSC03. The Call Setup Success Rate of BSC02 and BSC03 isbelow 95%. Detail Analysis for the Causes of this will be shown in next paragraph.

For BSC02 it is the same phenomena as already described in the chapter 3.1.1. (TrafficChannel Blocking at Network and BSC Level). Due to the fact the BSC02 is a small BSC with 25cells and only one cell out from this 25 cells show a high Blocking and therefore the averageBlocking of BSC02 is also high and various from day to day. The same can be seen also withthe Call Setup Success Rate, because Traffic Channel Blocking influences the Setup SuccessRate.





3.4.1. Call Split

Under Call Split we understand the distribution between Mobile Origination Call Attempts andMobile Terminating Call Attempts. In the City Y Network the Mobile Originating Calls are 65% of

all Call Attempts and the Mobile Terminating Calls are 35%.

For further information please refer to attached Document.

Call_Split_Salalah.xls

3.4.2. Call Setup Success Analysis at BTS Level

For the Cell Level Analysis the Benchmark for Call Setup Success Rate is 98%. In the following

graphs we will show how the cells are distributed in Success Rate Margins.

In order to make the analysis more representatives only Measurement data from the busy hourat June 22

nd 2002 (busiest day during the measurement period) are evaluated. Furthermore

only cells are considered with at least 100 Call Attempts during the Busy Hour. This needs to bedone for statistic reasons, because cells with low Call Attempts could distort the evaluation.(E.g. 2 SDCCH Drops from 50 Calls gives a drop rate of 4%)

We defined following Margins:

• >100% Call Setup Success Rate: This margin shows cell, which have a Call Setup

Success Rate higher then 100%. This is actual not possible, but due to directed Retry(which is a kind of Handover) the Target Cell has more successful Traffic Channel

Assignments than Attempts. Cells with a Setup Success Rate higher than 100% areneighbours from cells with high Blocking. So if the Blocking Situation in this area issolved, the number of cells with Success Rate higher than 100% will decrease.

• 98% - 100% Call Setup Success Rate: This is actual the range a cell should be located.

• 90% - 98% Call Setup Success Rate: This range represents cells, which are still

acceptable Success Rate, but should be monitored carefully and further investigationsshould be initiated. (E.g. Reduce SDCCH Blocking, Reduce TCH Blocking.)

• 80% - 90% Call Setup Success Rate: This range represents cells, which needs a more

detailed analysis. Regarding the reason for the low Call Setup Success Rate.

• < 50% Call Setup Success Rate: Cells in this range needs urgent investigations,

because those cells are decreasing the Grade of Service Parameters in the Network.(Reason for this low success rates can be again Blocking or even Interference)





3.4.2.1. Call Setup Success BSC01

Number of Cells in defined Success Rate for

BSC01

03

4

20 20

11

0

5

10

15

20

25

N

u m b e r o f C e l l s

< 50% 50% - 80% 80% - 90% 90% - 98% 98% - 100% > 100%

3 Cells within BSC01 are in the range from 50% to 80% Call Setup Success Rate, those cellsneeds closer investigation regarding Blocking.

For further details regarding this BSC please refer to attached document. Please not, that onlycells with a Number of Call Attempts more than 100 are considered.

Setup_BSC01.xls



BSC02

0 01

13

5

00

2

4

6

8

10

12

14

N u m b e r o f C e l l s

< 50% 50% - 80% 80% - 90% 90% - 98% 98% - 100% > 100%






Setup_BSC02.xls



BSC03

0 0

3

13

22

6

0

5

10

15

20

25

N u m b e r o f C e l l s

< 50% 50% - 80% 80% - 90% 90% - 98% 98% - 100% > 100%


Setup_BSC03.xls







BSC04

0 0 0

12

22

4

0

5

10

15

20

25

N

u m b e r o f C e l l s

< 50% 50% - 80% 80% - 90% 90% - 98% 98% - 100% > 100%


Setup_BSC04.xls





3.5. Call Drop Analysis

In this chapter we will analyse the Grade of Service for Connections, which are alreadyestablished and were disconnected due to Network errors and not by the Subscriber.

3.5.1. SDCCH Drops

The Standalone Dedicated Common Control Channel is used during Call Setup, LocationUpdate, SMS and Subscriber Services Interrogation. In Case of abnormal Release of theSDCCH a Drop is considered. Please find below the analysis for SDCCH Drop.

SDCCH DROPS per BSC (whole day)

BSC01:SDCCH_DROP_RATE BSC02:SDCCH_DROP_RATE BSC03:SDCCH_DROP_RATE

BSC04:SDCCH_DROP_RATE

date

6/20/02 6/21/02 6/22/02 6/23/02 6/24/02 6/25/02 6/26/02

1%

0%

BSCID Date drops BSCID Date drops

BSC01 6/20/02 0.86%BSC03 6/20/02 0.51%

BSC01 6/21/02 0.74%BSC03 6/21/02 0.53%

BSC01 6/22/02 0.66%BSC03 6/22/02 0.43%

BSC01 6/23/02 0.60%BSC03 6/23/02 0.42%

BSC01 6/24/02 0.59%BSC03 6/24/02 0.44%BSC01 6/25/02 0.64%BSC03 6/25/02 0.43%

BSC01 6/26/02 0.66%BSC03 6/26/02 0.42%

BSC02 6/20/02 1.29%BSC04 6/20/02 0.42%

BSC02 6/21/02 1.01%BSC04 6/21/02 0.44%

BSC02 6/22/02 1.00%BSC04 6/22/02 0.37%

BSC02 6/23/02 0.99%BSC04 6/23/02 0.39%

BSC02 6/24/02 1.12%BSC04 6/24/02 0.38%

BSC02 6/25/02 1.11%BSC04 6/25/02 0.36%

BSC02 6/26/02 0.93%BSC04 6/26/02 0.36%

All BSC values are below the threshold of 2%. In the table below you can find all sites with morethen 2% blocking. In the list below, you can find all sites and sites, which have a value over the





threshold in the time range of 20th to 26th of June. There are many sites, which areapproximately 2%, but also with more then 3%.

Table with values of all sites, you can find in the attached document below:

all_sdcch-drops.xls

Table with values over the threshold, you can find in the attached document below:

thresh_sdcch-drops.xls

3.5.2. TCH Drops

The Traffic Channel (TCH) is mainly in use when subscriber conversation takes place, anabnormal Release of an in used Traffic Channel is considered as Call Drop. Below the TrafficChannel Drop Analysis.

In most cases a TCH Call Drop appears under following conditions:

• In dedicated mode, camped on a cell with errors at the Uplink or Downlink Path• During Handover

The graph below shows the Traffic Channel (TCH) Drop Rate. The TCH drop rate is defined asthe ratio between the absolute number of abnormal terminated traffic channel to the totalnumber of successful established connections.

TCH DROP RATE GRAPH:

TCH Drops per BSC (whole day)

BSC01:TCH_DROP_RATE BSC02:TCH_DROP_RATE BSC03:TCH_DROP_RATE BSC04:TCH_DROP_RATE

date

06/20/2002 06/21/2002 06/22/2002 06/23/2002 06/24/2002 06/25/2002 06/26/2002

1%

0%





BSCID Date drops BSCID Date drops

BSC01 6/20/02 0.70%BSC03 6/20/02 0.34%

BSC01 6/21/02 0.60%BSC03 6/21/02 0.37%

BSC01 6/22/02 0.59%BSC03 6/22/02 0.31%

BSC01 6/23/02 0.60%BSC03 6/23/02 0.34%

BSC01 6/24/02 0.58%BSC03 6/24/02 0.33%

BSC01 6/25/02 0.60%BSC03 6/25/02 0.32%

BSC01 6/26/02 0.56%BSC03 6/26/02 0.33%

BSC02 6/20/02 1.33%BSC04 6/20/02 0.48%

BSC02 6/21/02 1.21%BSC04 6/21/02 0.48%

BSC02 6/22/02 1.03%BSC04 6/22/02 0.44%

BSC02 6/23/02 1.07%BSC04 6/23/02 0.44%BSC02 6/24/02 1.19%BSC04 6/24/02 0.42%

BSC02 6/25/02 1.19%BSC04 6/25/02 0.46%

BSC02 6/26/02 1.14%BSC04 6/26/02 0.41%

All BSC values are below the threshold of 2%. In the tables below, you can find all sites andsites, which have a value over the threshold in the time range of 20th to 26th of June. There aremany sites, which are approximately 2%, but also with more then 3%.

• The reason for the higher drop rate in BSC02, can be related to the Location ofBSC2 Area (mostly mountain and country side) --> coverage issue

Table with values of all sites. Only sites which have more then 1000 connections per day. Inother case it should not be counted in the statistic.

"trch-drops_allsites.xls"

Site Table with a high drops rate over the whole week and high drop rate on more then 2 days.

tch-drops_detailed.xls





3.5.2.1. Reasons of TCH Drop in ded icated mo de

The Siemens Radio Equipment is able to store the reasons for an abnormal Call Release, thesereasons can be analysed and with this causes for high Call Drops can be identified. In thefollowing graphs we will show how the distribution of Call Failure in each BSC.

• Reasons of TCH Drop in BSC1

0.00%

5.00%

10.00%

15.00%

20.00%

25.00%

30.00%

35.00%

40.00%

45.00%

50.00%

55.00%

60.00%

65.00%

70.00%

75.00%

80.00%

T 2 0 0 E x pi r e d

Un s ol e c i t e d DMR e p on s e

S e Q u en c eE r r or

T _M S RF P C I E x pi r e d

Di s t an c eL i mi t E x c e e d e d

H an d ov er A c c e s s F ai l ur e

R a d i oL i nk F ai l ur e

R em o t eT r an s c o d er F ai l ur e

A l l O t h er C a u s e s

BSC01 6/20/02

BSC01 6/21/02

BSC01 6/22/02

BSC01 6/23/02

BSC01 6/24/02

BSC01 6/25/02

BSC01 6/26/02






0.00%

5.00%

10.00%

15.00%

20.00%

25.00%

30.00%

35.00%

40.00%

45.00%

50.00%

55.00%

60.00%

65.00%

70.00%

75.00%

80.00%










BSC02 6/20/02

BSC02 6/21/02

BSC02 6/22/02

BSC02 6/23/02

BSC02 6/24/02

BSC02 6/25/02

BSC02 6/26/02


0.00%

5.00%

10.00%

15.00%

20.00%

25.00%

30.00%

35.00%

40.00%

45.00%

50.00%

55.00%

60.00%

65.00%

70.00%

75.00%

80.00%


Un s ol e c i t e d DMR e p

on s e


T _M S RF P C I E x pi r e

d


H an d ov er A c c e s s F a

i l ur e




BSC03 6/20/02

BSC03 6/21/02

BSC03 6/22/02

BSC03 6/23/02

BSC03 6/24/02

BSC03 6/25/02BSC03 6/26/02






0.00%

5.00%

10.00%

15.00%20.00%

25.00%

30.00%

35.00%

40.00%

45.00%

50.00%

55.00%

60.00%

65.00%

70.00%

75.00%

80.00%





Di s t an c eL i mi t E x c e e d

e d



R em o t eT r an s c o d er F

ai l ur e


BSC04 6/20/02

BSC04 6/21/02

BSC04 6/22/02

BSC04 6/23/02

BSC04 6/24/02

BSC04 6/25/02

BSC04 6/26/02

In all BSC the „RadioLinkFailures“ are leading. That means, if the Radio Link Timeout isreached, there will be a message send to the BSC (Connection Failure Indication Message) withcause radio link failure and the call will be released. Basically the reason is that the MS or BTSis unable to decode the SACCH messages on the Uplink/Downlink. The estimation is donethrough a counter, incremented in case of a correctly received block and decrement in the othercase. When the counter reaches a minimum threshold, the link is considered as broken.





3.5.2.2. Reasons for TCH Drop dur ing Handover

Due to the change of the MS from one cell to the other one it can appear that due to quality,level or signalling reasons the call is abnormal released. In this case we speak from a Call Dropduring Handover. This Kind of Drop is already included as well in the TCH DROP RATE

GRAPH. (please refer at top of this chapter)

IntraBSC_Intercell Hadover Drop Rate per BSC (whole day)

BSC01: INTRABSC_INTERCELL_HO_DROP_RATE BSC02:INTRABSC_INTERCELL_HO_DROP_RATE

BSC03: INTRABSC_INTERCELL_HO_DROP_RATE BSC04:INTRABSC_INTERCELL_HO_DROP_RATE

date

06/20/2002 06/21/2002 06/22/2002 06/23/2002 06/24/2002 06/25/2002 06/26/2002

0.46%

0.44%

0.42%

0.4%

0.38%

0.36%

0.34%

0.32%

0.3%

0.28%

0.26%

0.24%

0.22%

0.2%

0.18%

0.16%

0.14%

0.12%

0.1%

0.08%

0.06%

0.04%

0.02%

Here we can see, that again the worst performance in case of drops, is BSC2 –More details related to the Handover performance you will see in the chapter Handover

Analysis, in this report. In the next chart, we can see that the Intracell Ho Performance hasimpact on the Intracell HO Drop Rate.More details, related to the Handover performance you will see in the chapter Handover





Intracell Handover Drop Rate per BSC (whole day)

BSC01:INTRACELL_HO_DROP_RATE BSC02:INTRACELL_HO_DROP_RATE BSC03:INTRACELL_HO_DROP_RATE

BSC04:INTRACELL_HO_DROP_RATE

date06/20/2002 06/21/2002 06/22/2002 06/23/2002 06/24/2002 06/25/2002 06/26/2002

1%

0%





3.6. Interference Analysis:

With the next chart, you can get an idea about the Interference Situation in the Network.The graph is based on the busiest day and the busy hour values on this day. This is the bestway to estimate, when Quality problems are appearing in the Network. Table for the traffic:

BSC Busy day busy hourBSC1 26.6 21BSC2 21.6 22

BSC3 26.6 22

BSC4 21.6 22

This measurements are taken in idle mod e and on ly Uplink m easurements (no analysis

for TCH channel in dedicated mode). For this case Power and Quali ty measurements

have to be taken.

A Classification of Interference Bands was done accordingly:Infband1 -> very goodInfband2 -> goodInfband 3 -> badInfband 4-5 -> very bad





Interferenceband BSC1

0

5

10

15

20

25

30

35

40

0 2 4 6 8 1 0

1

2

1

4

1

6

1

8

2

0

2

2

2

4

2

6

2

8

3

0

3

2

3

4

3

7

3

9

4

1

4

3

4

5

4

7

4

9

5

1

5

3

5

5

5

7

6

1

6

3

6

5

6

7

6

9

7

1

7

3

7

5

7

7

7

9

8

1

8

3

BTS

S h a r e

i n a c e r t a i n

I n t e r f e r e n c e

b a n

d

Infband1 Infband2 Infband3 Infband4 Infband5

As you can see in this chart, many sites have their Infband values in a good range. OnlyE.g. BTS10 has many hits in Interferenceband3 and 5, which is very bad.






0

5

10

15

20

25

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24BTS

S h a r e

i n a c e r t a i n


b a n

d


With this graph, nearly all hits in are in Interferenceband 1 – Only BTS21 nearly all hits inInterferenceband2 – which could be an indicator for a permanent Interference Problem (Uplink)






0

5

10

15

20

25

30

0 1 2 3 4 5 6 7 8

1

1

1

2

1

3

1

4

1

5

1

6

1

7

1

8

1

9

2

2

2

3

2

6

2

7

2

8

2

9

3

0

3

4

3

5

3

6

3

7

3

8

3

9

4

0

4

2

4

3

4

6

4

7

4

8

5

7

5

8

5

9

6

0

6

1

6

2

6

3

6

4

6

5

6

6

6

7

6

8

6

9

BTS

S h a r e

i n a c e r t a i n


b a n

d


In this graph already many BTS e.g. BTS26, BTS12, have many hits in Interferenceband 3 resp.Interferenceband5, which is an indicator of an high Interference level in this areas.






0

5

10

15

20

25

30

01 2 34 56 7 89

1

0

1

1

1

2

1

3

1

4

1

5

1

6

1

7

1

8

1

9

2

0

2

1

2

2

2

3

2

4

2

5

2

6

2

7

2

8

2

9

3

1

3

2

3

3

3

4

3

5

3

6

3

7

3

8

3

9

4

0

4

1

4

2

4

3

4

4

4

5

4

6

4

7

4

8

4

9

5

0

5

2

5

3

5

4

5

5

5

6

5

7

5

8

6

0

6

1

6

2

6

3

6

4

6

5

BTS

S h a r e

i n a c e r t a i n


b a n

d


In this graph, nearly all sites, show a good figure. Only BTS14, BTS15, BTS21 have all their hitsin Interferenceband2, which could be again an indicator of a permanent Interference problem(Uplink).





3.7. Handover Analysis

In this chapter we will analyse the Handover Performance of the City Y GSM Network.

3.7.1. Intracell Handover

Intracell Handover is defined as an Handover from one Traffic Channel to an other TrafficChannel belonging to the same cell.

The Handover Success Rate is defined as ratio between successful finished HandoverOperations and Handover Attempts.

WholeDay

BSC01:INTRACELL_HO_SUCCESS_RATE BSC02:INTRACELL_HO_SUCCESS_RATE

BSC03:INTRACELL_HO_SUCCESS_RATE BSC04:INTRACELL_HO_SUCCESS_RATE

date

06/20/2002 06/21/2002 06/22/2002 06/23/2002 06/24/2002 06/25/2002 06/26/2002

95%

90%

85%80%

75%

70%

65%

60%

55%

50%

45%

40%

35%

30%

25%

20%

15%

10%

5%

0%

BSCID Date IntraCell HO rate

BSC01 6/20/02 97.14%BSC01 6/21/02 97.37%

BSC01 6/22/02 97.12%

BSC01 6/23/02 97.41%

BSC01 6/24/02 97.49%

BSC01 6/25/02 97.58%

BSC01 6/26/02 97.38%

BSC02 6/20/02 96.14%

BSC02 6/21/02 94.68%

BSC02 6/22/02 96.26%

BSC02 6/23/02 95.33%

BSC02 6/24/02 95.33%

BSC02 6/25/02 94.93%





BSC02 6/26/02 97.36%

BSC03 6/20/02 98.11%

BSC03 6/21/02 97.97%

BSC03 6/22/02 97.85%

BSC03 6/23/02 98.12%

BSC03 6/24/02 97.97%

BSC03 6/25/02 98.15%

BSC03 6/26/02 98.11%

BSC04 6/20/02 98.06%

BSC04 6/21/02 97.97%

BSC04 6/22/02 97.73%

BSC04 6/23/02 97.64%

BSC04 6/24/02 98.30%

BSC04 6/25/02 97.94%

BSC04 6/26/02 98.02% The threshold for the Intracell HO is 98%. Many values are closed or at 98%, which is a goodperformance. Only BSC2 shows bad values on 2 days (~94%). The reason for this bad IntracellHandover Success Rate could be an indicator in the Downlink Quality. The assumption can beconfirmed with the next chart (high amount of Intracell HO due to Downlink Quality. In the tablebelow you can find the Intracell Handover Rate for all sites.

Cause of Intracell HO

Intracell HO Cause BSC1

0%

20%

40%

60%

80%

100%

6/20/02 6/21/02 6/22/02 6/23/02 6/24/02 6/25/02 6/26/02

UplinkQuality DownlinkQuality






0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

6/20/02 6/21/02 6/22/02 6/23/02 6/24/02 6/25/02 6/26/02



0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

6/20/02 6/21/02 6/22/02 6/23/02 6/24/02 6/25/02 6/26/02







0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

6/20/02 6/21/02 6/22/02 6/23/02 6/24/02 6/25/02 6/26/02


In this case nearly every day the Handover due to Downlink Quality is approximately 90%. Thismust not mean, that the Handover are not working fine, but the Downlink Quality is much worstthen the Uplink Quality.

Below you find the table with the site specific performance. Only sites with more then 500Intracell Handovers are chosen, because in values under this range are not meaningful in astatistical way.

INtracellHO_succ_site.xls





3.7.2. Intercell Intra BSC Handover Success Rate

The Intercell Intra BSC Handover Success Rate is defined as the ratio between all successfulfinished Handovers and all Handover Attempts from one cell to an other one belonging to thesame BSC.

Intercell IntraBSC Handover Succ Rate (whole day)

BSC01:INTERCELL_INTRABSC_HO_SUCC_RATE BSC02:INTERCELL_INTRABSC_HO_SUCC_RATE

BSC03:INTERCELL_INTRABSC_HO_SUCC_RATE BSC04:INTERCELL_INTRABSC_HO_SUCC_RATE

date6/20/02 6/21/02 6/22/02 6/23/02 6/24/02 6/25/02 6/26/02

95%

90%

85%

80%

75%

70%

65%

60%

55%

50%

45%

40%

35%

30%

25%

20%

15%

10%

5%

0%

BSCID Date Intercell_IntraBSC Ho Succ

BSC01 6/20/02 92.74%

BSC01 6/21/02 93.25%

BSC01 6/22/02 92.40%

BSC01 6/23/02 93.23%

BSC01 6/24/02 93.15%BSC01 6/25/02 92.93%

BSC01 6/26/02 92.99%

BSC02 6/20/02 91.66%

BSC02 6/21/02 92.90%

BSC02 6/22/02 92.70%

BSC02 6/23/02 93.10%

BSC02 6/24/02 92.97%

BSC02 6/25/02 92.41%

BSC02 6/26/02 91.49%

BSC03 6/20/02 97.48%

BSC03 6/21/02 97.33%BSC03 6/22/02 97.46%





BSC03 6/23/02 97.34%

BSC03 6/24/02 97.54%

BSC03 6/25/02 97.60%

BSC03 6/26/02 97.38%

BSC04 6/20/02 95.46%

BSC04 6/21/02 95.40%

BSC04 6/22/02 95.57%

BSC04 6/23/02 96.47%

BSC04 6/24/02 95.55%

BSC04 6/25/02 95.80%

BSC04 6/26/02 95.68%

The values for the Intercell IntraBSC Handover are over the threshold of 90%, which is verygood. BSC3 shows excellent results over the whole week. In the table below you find thestatistic for all sites with more then 1000 Handover Attempts per day. Below 1000 they should

not be considered in this table, due to statistical reason.

IntercellHO_succ_site.xls

3.7.2.1. Intercell IntraBSC Handov er Causes

Intercell IntraBSC Ho Cause - BSC1

0.00%

10.00%

20.00%

30.00%

40.00%

50.00%

60.00%

70.00%

U p l i n k

Q u a l i t y

D o w n l i n k

Q u a l i t y

U p l i n k

S t r e n g t h

D o w n l i n k

S t r e n g t h

D i s t a n c e

B e t t e r C e l l

D i r e c t e d R e t r y

M a i n t e

n a n c e F o r c e d H O

6/20/02 6/21/02 6/22/02 6/23/02 6/24/02 6/25/02 6/26/02

In this graph, the distribution is good. Only the Handover due to Uplink Strength can be lowered.






0.00%

5.00%

10.00%

15.00%

20.00%

25.00%

30.00%

35.00%

40.00%

45.00%

50.00%

U p l i n k

Q u a l i t y

D o w n l i n k

Q u a l i t y

U p l i n k

S t r e n

g t h

D o w n l i n k

S t r e n g t h

D i s t a n c e

B e t t e r C e l l


M a i n t e


6/20/02 6/21/02 6/22/02 6/23/02 6/24/02 6/25/02 6/26/02

In this graph, the Handover due to Uplink Strength is very high. This can be an indicator for acoverage problem or an unbalanced link, but it has to be considered, that the sites of this BSCare in the mountain area. In this case the Uplink Strength range is always a little bit higher.


0.00%

10.00%

20.00%

30.00%

40.00%

50.00%

60.00%

70.00%

80.00%

U p l i n k

Q u a l i t y

D o w n l i n k

Q u a l i t y

U p l i n k

S t r e n g t h

D o w n l i n k

S t r e n g t h

D i s t a n

c e

B e t t e r C e l l

D i r e c t e d

R e t r y

M a i n t e


6/20/02 6/21/02 6/22/02 6/23/02 6/24/02 6/25/02 6/26/02

In this graph the Handover reasons are distributed very well.






0.00%

10.00%

20.00%

30.00%

40.00%

50.00%

60.00%

70.00%

U p l i n k

Q u a l i t y

D o w n l i n k

Q u a l i t y

U p l i n k

S t r e n

g t h

D o w n l i n k

S t r e n g t h

D i s t a n c e

B e t t e r C e l l


M a i n t e


6/20/02 6/21/02 6/22/02 6/23/02 6/24/02 6/25/02 6/26/02

Also in this graph, the Handover reasons are well distributed. Also here, the Downlink Qualityand Uplink Strength Handover rate can be lowered.





3.7.3. Intercell Inter BSC Handover Success

The Intercell Inter BSC Handover Success Rate is defined as the ratio between all successful

finished Handovers and all Handover Attempts from one cell to an other one belonging to thedifferent BSC´s.

Intercell InterBSC Handover Success (whole day)

BSC01:INTERBSC_OUTGOING_SUCC_RATE BSC02:INTERBSC_OUTGOING_SUCC_RATE

BSC03:INTERBSC_OUTGOING_SUCC_RATE BSC04:INTERBSC_OUTGOING_SUCC_RATE

date

6/20/02 6/21/02 6/22/02 6/23/02 6/24/02 6/25/02 6/26/02

95%

90%

85%

80%

75%

70%

65%

60%55%

50%

45%

40%

35%

30%

25%

20%

15%

10%

5%

0%

BSCID Date Intercell InterBSC Handover Succ

BSC01 6/20/02 95.05%

BSC01 6/21/02 95.40%

BSC01 6/22/02 95.53%

BSC01 6/23/02 96.01%

BSC01 6/24/02 95.78%

BSC01 6/25/02 96.09%

BSC01 6/26/02 96.64%

BSC02 6/20/02 89.35%

BSC02 6/21/02 87.83%

BSC02 6/22/02 91.01%

BSC02 6/23/02 88.31%

BSC02 6/24/02 92.75%

BSC02 6/25/02 89.41%

BSC02 6/26/02 87.18%

BSC03 6/20/02 97.54%BSC03 6/21/02 98.07%

BSC03 6/22/02 97.78%





BSC03 6/23/02 97.99%

BSC03 6/24/02 97.91%

BSC03 6/25/02 98.13%

BSC03 6/26/02 98.15%

BSC04 6/20/02 97.72%

BSC04 6/21/02 98.39%

BSC04 6/22/02 97.91%

BSC04 6/23/02 98.04%

BSC04 6/24/02 98.35%

BSC04 6/25/02 97.99%

BSC04 6/26/02 98.38%

All values for the Intercell InterBSC values are over the threshold of 85% for the whole day.BSC3 and BSC4 show excellent values.





4. SSS Performance Analysis

4.1. IntroductionThis study is based on traffic measurements from MSC3.

The objective of this report is to give an outline about the overall performance of the Networkelements.

4.2. GOS – Grade of service

The ‘Grade Of Service’ (GOS) contains the most significant values which indicate theperformance and quality of a MSC/VLR.The GOS is based on the MSC traffic measurements REC MSC, REC VLR andREC CP.

‘Grade of Service’ covers the following main functional aspects:Mobile originating calls to PSTN (e.g. Success rate, Answer rate, B-busy rate...)Mobile to Mobile calls to PLMN (e.g. Success rate, Answer rate, B-busy rate...)Mobile terminating calls (e.g. Success rate, Answer rate, B-busy rate...)Mobile terminating call set-up rateMobile originating call set-up rateHandover part (e.g. total Handover success rate, Intra /Inter HO success rate...)

Location update part (LUP success rate)Paging part (Successful paging rate)MSC / VLR miscellaneous part (e.g. CP load, call attempt distribution, BHCA/Sub...)Problem part (various error counter rates)Call drop rates, call set-up failure rates overallMOC/MTC traffic channel congestion overall

All values are based on the measured PBH (Peak Busy Hour). The PBH is the hour (fourconsecutive quarters of an hour) for which the CP call processing load reaches its maximumvalue.





Fig. 1: Summary Grade of service

The above tables show a brief overview over the evaluated GOS figures.

The following chapters 4.2.1 – 4.2.7 show a graphical display of the individual figures andrelated problems.

Some of the most common problems in a GSM Network are:

Missing traffic channels on the air- and A interface

Missing trunks between exchangesHigh values for internal/external technical irregularitiesPoor radio coverage in parts of the VLR areaDatabase problems

The benchmarks in the diagrams are calculated from values of exchanges (worldwide) with agood performance. I.e. these values may be reachable.Please be aware that looking at one diagram does not pinpoint to exactly one failure reason.One has to look at several results.

H O s u c c e s s

I n t r a M S C S u c c e s s

I n t e r

M S C A S u c c e s s

I n t e r

M S C B S u c c e s s

H O r e

j e c

t e d

H O F a

i l u r e

B S S A P O v e r l o a

d

B S S A P C o n g e s

t i o n

C o n g e s

t i o n o w n

P L M N

C o n g e s

t i o n o

t h e r

P L M N

,

P S T N

D e s

t i n a

t i o n

E r r o r

T e c

h n

i c a

l F a u

l t

R e

l e a s e

b e

f o r e

A C M

L o c a

t i o n

U p

d a

t e s u c c e s

s f u l

P A G I N G s u c c e s s

f u l

T C H c o n g e s

t i o n

M O C

T C H c o n g e s

t i o n

M T C

B S F a

i l u r e s

d u r i n g

c a

l l s e

t u p

B S F a

i l u r e s

c a

l l d r o p s a

f t e r a n s w e r

95% 95% 0% 0% 3% 2% 0.0% 0.0% 0.0% 0.0% 1.0% 0.9% 0.0% 98% 90% 2.9% 2.9% 0.4% 2.7%

95% 95% 0% 0% 2% 3% 0.0% 0.0% 0.0% 0.0% 1.4% 1.2% 0.0% 98% 90% 2.4% 2.4% 0.2% 2.7%

95% 95% 0% 0% 2% 2% 0.0% 0.0% 0.0% 0.0% 1.0% 1.8% 0.0% 98% 91% 2.7% 3.0% 0.2% 2.2%

95% 95% 0% 0% 2% 2% 0% 0% 0% 0% 1% 1% 0% 98% 91% 3% 3% 0% 2%

95% 95% 0% 0% 3% 3% 0% 0% 0% 0% 1% 2% 0% 98% 91% 3% 3% 0% 3%

95% 95% 0% 0% 2% 2% 0% 0% 0% 0% 1% 1% 0% 98% 90% 2% 2% 0% 2%

GOS - Grade of ServiceHandover SSS Trends BSS Trends





4.2.1. Mobile to mobile call

Performance MMC

The MMC Call Performance is slightly below the benchmark value.





4.2.2. Mobile originating call

The MSC MOC Success Rate is on the 26th and the 27

th around the benchmark, on the 28

th it

seems that there is a temporary problem within the Network.

Figure: MSC2, MOC Success Rate, 28th. The problem with this call is all over the day; furtherinvestigations are needed.





4.2.3. Mobile terminating call

Also the MTC Success Rates are above the Benchmark, which is a quite good result.





4.2.4. Handover

The Handover Success is above the Benchmark.





4.2.5. Location Update and paging

The LUP success rates are above the benchmark.

The paging success rates are around 90%, which is an excellent result.





4.2.6. Errors SSS

Recommended values for all of the above shown cases are max. 1%.

One problem from this measurement point of view is a ‘Destination Error’ rate of around 1-% -

1.4%. This could indicate that subscribers dial wrong numbers for which no destination isexisting. Another possible interpretation is that for certain code points there is a wrong setting inthe routing database.

Another problem is “Technical Fault” which is described further in the TGRP Measurement.





4.2.7. Errors BSS

All parameters listed in this chapter have their origin on the BSS side.

In the Network Element the ‘TCH congestion MOC’ rate and the ‘TCH congestion MTC’ isaround 2,5% to 3,0%. This might indicate a systematic shortage of traffic channels on the airinterfaces. We suggest implementing more capacity on the air interfaces in order to avoid aserious congestion situation when subscriber numbers increase further.

We also suggest taking measures to reduce the ‘BSS failures call drops after answer’. This canbe done by taking measures on the radio side such as improving coverage, avoid interferenceand monitor intra and inter MSC Handover success rates.





4.3. CCS7 Link Load evaluation

In a D900 entity all CCS7 signalling links are connected to the CCNC. The CCNC handles themessage exchange between various nodes for controlling and monitoring connections as wellas for operating the signalling Network.In a constantly growing GSM-Network the load on the signalling links is changing permanently.To account for these changes and due to the design specific construction of the CCNC certainconfiguration rules must be considered.

• The CCS7 Link Load analysis calculates the load of each CCS7 link. The resultshows the design specific layout of the CCNC with its allocated HW -units andthe relevant load in Erlang.

According to ITU recommendations Q706 the following load values should be taken intoaccount:CCS7 link load should not exceed the value of 0,2 Erl. Per signalling link, the total load of a

SIPA should not be higher than 1,6 Erl . The threshold for SILTC’s is 0,6-0,8 Erlang. The bestperformance will only be achieved if all four SILT-C’s are connected and carry an evenlybalanced load; the above given recommendations should be applied in the complete D900CCS7 Network. In the following graphs the load is detailed in RX and TX direction. Themaximum load is determined as the maximum of the two values for each SILTC.

The load levels of all parts of the CCNC are well below critical levels. There are no problemswith regard to C7 signalling load existing.

SILTC Load Busy Quarter

0

50

100

150

200

250

300

350

400

S I L T C

- 0

S I L T C

- 1

S I L T C

- 2

S I L T C

- 3

S I L T C

- 4

S I L T C

- 5

S I L T C

- 6

S I L T C

- 7

S I L T C

- 8

S I L T C

- 9

S I L T C

- 1 0

S I L T C

- 1 1

S I L T C - 1

2

S I L T C

- 1 3

S I L T C

- 1 4

S I L T C

- 1 5

S I L T C

- 1 6

S I L T C

- 1 7

S I L T C

- 1 8

S I L T C

- 1 9

S I L T C

- 2 0

S I L T C

- 2 1

S I L T C

- 2 2

S I L T C

- 2 3

S I L T C

- 2 4

S I L T C

- 2 5

S I L T C

- 2 6

S I L T C

- 2 7

S I L T C

- 2 8

S I L T C

- 2 9

S I L T C

- 3 0

S I L T C

- 3 1

m E r l

Rx Load

Tx Load





4.4. Trunk Group evaluation

The Trunk Group evaluation values (subsequent lists) show all relevant data for each TrunkGroup such as busy hour, number of available and required trunks, call attempts, carried trafficand lost calls. The following tables detail the most important TGRP parameters for all MSC’s.

The column ‘CCU_All_Trunks_Busy_Rt’ indicates congestion problem on the respective

TGRP’s. If the value is other than zero, it means that there are calls being rejected due to a lackof trunks. Since this directly affects revenues for the customer, these congestion situationsshould be removed as soon as possible. In the 4 measured Network Elements none of theswitches have problems regarding this.

Regarding lack of trunks, particular interest should be paid to BSSAP TGRP’s. Due to thespecial nature of those TGRP’s, lost calls are not accounted for. In this case, the columns‘available trunks’ and ‘required trunks’ should be compared. To avoid congestion and enhancethe performance of the Network, it is essential to expand these TGRP’s. For those ones whichare not congested but have numbers for ‘required trunks’ approaching numbers for ‘availabletrunks’, actions should be taken to extend numbers of trunks on these TGRP’s.

CCS_Ext_Techn_Irreg_Rt indicates external Irregularities from the next or a subsequentNetwork Element. We have this problem in the “BSALR7”, “BSAL27”, “BMSC67” and in the“BMSC17” Trunk Group.





CCS_Congestion_Rt means, the call was seized successfully in our Switch, but the next or aSubsequent Switch had a congestion problem. This should be checked. (BSALR7, BSAL27,BMSC67)

4.5. Traffic model

4.5.1. Traffic model overviewThis table gives a brief outline over all relevant traffic model parameters of the Network. Thesevalues (current traffic model) need to be compared with the contractual values. If necessary,measures have to be taken to adjust the MSC hardware/software dimensioning to the currentsituation in the Network.




4.5.2. BHCA and load

Documents

GSM Performance Analysis Report