Avoiding to Uplink Interference Effecting in GSM Network

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CBC/PR/N3 Nikko Tan DOCPROPERTY "DocNo" "LangCode" \* MERGEFORMAT

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DOCPROPERTY "ApprovedBy" \* MERGEFORMAT Yazhong Wei2011-07-29PA1 DOCPROPERTY "Reference" \* MERGEFORMAT

Avoiding to uplink interference effecting in GSM network1 IntroduceIn Guangzhou city there are some many serried architectural complexes, and it is difficult to setup normal network to cover it. So, they customer who live there setup the RPT themselves, and our network get more and more uplink interference from it.These RPT impact the network quality and bring so many drop calls and insufferable bad qualities to customer who near these problem regions. Luckily they only affect the GSM900 now. We need to solve these problems by pressure from customer, and for the limitation of network investment and frequency, we need to keep GSM900 base station in site and get enough traffic. Even we need to keep GSM900 to cover special regions because different path loss between GSM900 and GSM1800.It is time to change normal way to use HCS (It is only way to adjust traffic between GSM900 and GSM 1800, even if it cant adjust by uplink measurement).2 Benefits and comments

We start this program on Guangzhou first, and call it: avoiding to uplink interference effecting.

From this method we can improve the KPI special of drop call rate% and uplink quality in MRR. For mobile user near uplink interference area, their abnormal disconnection rate% can be decreased.

Which feature/parameter we need to use for this method is:

HCS

MSRXSUFF

CRO/PT

And this method is designed for algorithm Ericsson1, if you need to use it in algorithm Ericsson3, it is very difficult to find a parameter out to map the MSRXSUFF perfect (there are also some negative effect for others, such as BSTXPWR/OFFSET etc...)3 Introduce to HCS

It is different to Locating algorithm; Locating is based on signal strength, always you can take the strongest signal strength (after calculation). For HCS, we can define priority levels to each cell and each band (up to eight bands and eight Layers); for example, in a network include GSM900 and GSM1800, we can define GSM1800 as Band1, and GSM900 as Band2, then for GSM1800 Cells, they always have high priority than GSM900 Cells, with special parameter definition, we can effect traffic distribution and hold traffic in GSM1800 Cells as our design. The same process and same results will be implemented when you define each Layer to each cell in same Band.

In HCS algorithm process, the input to the HCS algorithm is a basic ranking list of neighboring cell candidates from Locating. The HCS band evaluation rearranges the candidate list in locating according to the priority rules; and for the lowest priority level Cells, they HCS setting will not be take into account. If there only be two Layers in a network, traffic distribution control by high priority level Cells HCS parameter setting (such as Layerthr/Layerhyst etc...).In network of CMCC, we normally set GSM900 Cells as low priority level, then in normally, GSM1800 Cells HCS parameter setting control the traffic distribution.4 Solution In CMCC network, we can use 238 GSM1800 frequencies (512~636; 740~852).

So in Guangzhou network, we design solution basing below situation:

1. Normally signal strength of GSM900 is better than GSM1800s, but after on site test, for signal quality, GSM1800 is better than GSM900s in position even if GSM900s signal strength is better more than 15dB at that time (uplink interference area).2. In uplink interference area, the lowest access level for GSM900 normally is -85dBm~-90dBm. But for GSM1800, it is -100dBm~-105dBm.

3. GSM1800 Cells and GSM900 Cells they normally cover the same place. And it is continuous cover. 4. While GSM900s signal strength (uplink) is lower than a special level (basing on interference level), MS will be dropped by bad quality.

5. In uplink interference area, uplink signal strength and downlink signal strength is approximate (checking by MTR and MRR result).

6. In some faraway area (logically defined by difference of GSM900/GSM1800s pass loss), there only has GSM900s signal.

7. Each Cells interference level can be monitor by FASIt is cover model before (for GSM900/GSM1800 on the same site):

Then we define the target:1. Use GSM1800 instead of GSM900 in special area (where GSM900s uplink signal strength is lower than interference level).2. Keep their traffic level, at lease GSM900s traffic level do not much less than before.3. Improve GSM900s signal quality and don't impact GSM1800s signal quality too much.

4. Improve Customers feeling who near uplink interference area.

And we hope to change the traffic model as below:

KEYPOINT

Use HCS to hold traffic with good quality in GSM900

While GSM900s signal strength is low than LAYERTHR (quality limitation measured by FAS), to keep quality, connection must be transfer to GSM1800 from GSM900

To prevent needless HO happening, mapped parameter of IDLE MODE is necessary

Method:1. Change GSM900 and GSM1800s layer setting, if GSM900s layer setting is layer2 and GSM1800s layer setting is layer1 before, than GSM900s layer change to layer1 and GSM1800s change to layer2.2. Use parameter (MSRXSUFF) to transfer traffic from GSM900 to GSM1800 or GSM900 with good quality in special area. a. MSRXSUFF only be useful in Ericsson1 algorithm (Locating), and will be take into account after HCS ranking. b. Presume normal network background interference is -120dBm, and get data from FAS, which measurement value less than or equal to -110dBm we set their MSRXSUFF to 20. Others we set the MSRXSUFF to (20-(110-abs (VALUE))), limitation is zero(step by 2)3. To map locating parameter and prevent needless HO happening, we need to define IDLE MODE parameter:

a. we presume all cells parameter(ACCMIN) original setting is 110(this value is not constant, basing the factual network setting),

b. with the cells MSRXSUFF setting(after step 2):

i. if MSRXSUFF is equal to 20, then PT=0; ii. if MSRXSUFF is not equal to 20, then PT=31

iii. if MSRXSUFF is equal to 20, then CRO=0

iv. if MSRXSUFF is not equal to 20, then CRO=MSRXSUFF/2

4. Normally in uplink interference area, a GSM connections uplink and downlink measurement strength is approximate, and for special cell, you can get the difference value between uplink and downlink from MRR, and then after calculation we get a logical value of LAYERTHR/LAYERHYST setting for each cell with uplink interference:a. From FAS, we get interference value for each cells each frequencyb. From these value, we get each cells interference mean value : ai. If CELL** have three frequency, and each frequencys interference level is ( 20, 21, 22), then cells interference value is equal to: average(20,21,22)=21c. From MRR, we get CELL**s uplink and downlink signal strength mean value are: -85(uplink) and -83(downlink), then the downlink offset value b is:i. When downlink MRR signal strength is better than uplink MRR signal strength, b is equal to: downlink MRR signal strength mean value uplink MRR signal strength mean value = -83-(-85)=2

ii. When downlink MRR signal strength is lower than uplink MRR signal strength, b is equal to 0(zero)

iii. It is just a empirical value, and the target is prevent GSM900 Cell getting the traffic of bad quality

d. After we get the value b, we set the cells LAYERTHR+LAYERHYST=(110-12-(a+b))i. It is just a empirical value, and the target is prevent GSM900 Cell getting the traffic of bad quality ii. 12 is a protective margin value basing on C/Iiii. To prevent needless HO happening and share the traffic between GSM900 and GSM1800, we normally set a highest limitation value to LAYERTHR+LAYERHYST, in Guangzhou city we set it to 70(68+2), e. After these setting, we need to monitor the KPI and DT result, and adjust the parameter setting to a better setting5 Example: Test in BaiYun area( north to huangshi road)Test area:

Attention: point with color green is test cell

Drop call rate% and HO successful rate% get great improvement. MRR quality always gets improvement5.1 KPI comparison

Key point:

24 hours Comparison between GSM900 and GSM1800

5.1.1 Traffic changevoice traffic21-Mar-1122-Mar-1123-Mar-1124-Mar-1111-Apr-1112-Apr-1113-Apr-11

test cells347389340619368379350447349658352881349307

test cells(GSM900)207730201512207009209893149522204926208987

test cells(GSM1800)224795217256221756220510165450223479230215

test area include test cells and neighbors432918423494470915441463439099442839439638

traffic include voice and data21-Mar-1122-Mar-1123-Mar-1124-Mar-1111-Apr-1112-Apr-1113-Apr-11

test cells890282886141935449861647850830861567858478

test cells(GSM900)533483527796511236478055348134473904483002

test cells(GSM1800)565597558333570454591847441189591646605524


Data traffic of GSM1800 increases

Voice traffic modes do not be changed

5.1.2 Traffic congestion

traffic congestion21-Mar-1122-Mar-1123-Mar-1124-Mar-1111-Apr-1112-Apr-1113-Apr-11

test cells10.43%9.49%7.89%8.70%7.83%7.52%7.29%

test cells(GSM900)12.73%10.84%8.37%10.27%10.39%7.51%9.68%

test cells(GSM1800)7.35%7.49%6.58%5.47%4.73%4.96%7.32%

test area include test cells and neighbors10.43%9.55%7.26%7.74%8.29%7.04%6.81%

From data, the difference is very small.5.1.3 Drop call

Drop call rate%

Drop call%21-Mar-1122-Mar-1123-Mar-1124-Mar-1111-Apr-1112-Apr-1113-Apr-11

test cells0.73%0.78%0.73%0.56%0.69%0.51%0.51%

test cells(GSM900)1.54%1.60%1.42%1.19%1.09%1.07%1.07%

test cells(GSM1800)0.31%0.33%0.33%0.33%0.31%0.31%0.31%


Drop call number:

Drop call numbers21-Mar-1122-Mar-1123-Mar-1124-Mar-1111-Apr-1112-Apr-1113-Apr-11

test cells302515310691292042222841207545207758207279

test cells(GSM900)316681317269276205221207150000200781201589

test cells(GSM1800)64258661826685970068512436695268594


It is a great improvement!And the drop call in GSM1800 is approximate with before. Not too bad.5.1.4 HO

Comparison of Test cells:

daterangeHovercntHoversucHorttochHO success rate%

21-Mar-11test cell131900912668464788496.05%

22-Mar-11test cell134517612824985796695.34%

23-Mar-11test cell119547711655432661397.50%

11-Apr-11test cell8475848321891332498.18%

12-Apr-11test cell113485111141051795998.17%

13-Apr-11test cell124848712271781853598.29%

Comparison of test area includes test cells and neighbors:daterangeHovercntHoversucHorttochHO success rate%

21-Mar-11test area include test cells and neighbors169118016215576366695.88%

22-Mar-11172037616393557458895.29%

23-Mar-11152106614796853672297.28%

11-Apr-11112879911071861858898.09%

12-Apr-11145852814299072457798.04%

13-Apr-11158741215581402532598.16%

A good result!5.1.5 ICM

ICM% = (ICM4+ICM5)/(all ICM)ICM%21-Mar-1122-Mar-1123-Mar-1124-Mar-1111-Apr-1112-Apr-1113-Apr-11

test cells24.22%24.92%27.12%30.03%29.21%29.41%29.48%

test cells(GSM900)55.05%56.16%56.65%58.51%54.81%55.78%56.25%

test cells(GSM1800)0.33%0.42%0.48%0.46%0.33%0.39%0.39%


It is no defference.

5.2 MRR results

5.2.1 Uplink quality%

Uplink quality%= 1-((RXQUALUL6+RXQUALUL7)/ (ALL RXQUALUL))

Total cells special for GSM900 their uplink quality% increases.

GSM1800 decreases but just a little.5.2.2 Downlink quality%

Downlink quality%= 1-((RXQUALDL6+RXQUALDL7)/ (ALL RXQUALDL))

It is no changed any more than before.

5.3 Summary

After implement the scheme, we get: KPI improved special in drop call rate Traffic mode changed to beneficial direction

But we see some negative effect:

Number of HO in road has been increased due to more layer change than before Difficulty of NPI optimization has been improved due to different parameter setting compared to other cells6 Additional commentsThis method would improve your networks KPI effectively, and we also done it in three city (Guangzhou/Fashan/Dongguan). They all had good result in KPI.But we need to know, it just a logical method, it can not solve your interference problem in fact, it just avoids it.

And this method has its limitation:

Because it use Parameter(MSRXSUFF), so it only can be used in Ericsson1, if your network is using Ericsson3, it is very hard to find out any other parameters to map it(No one can get the absolutely same effect) It is only can be used in uplink interference area, or other area where GSM900s uplink quality is bad than GSM1800s

It will affect DT effect

Hope it is useful for you!

Chart2

traffic

voice traffic21-Mar-1122-Mar-1123-Mar-1124-Mar-1111-Apr-1112-Apr-1113-Apr-11

test cells347389340619368379350447349658352881349307

test cells(GSM900)207730201512207009209893149522204926208987

test cells(GSM1800)224795217256221756220510165450223479230215


traffic include voice traffic and data21-Mar-1122-Mar-1123-Mar-1124-Mar-1111-Apr-1112-Apr-1113-Apr-11

test cells890282886141935449861647850830861567858478

test cells(GSM900)533483527796511236478055348134473904483002

test cells(GSM1800)565597558333570454591847441189591646605524


congs

traffic congs21-Mar-1122-Mar-1123-Mar-1124-Mar-1111-Apr-1112-Apr-1113-Apr-11

test cells10.43%9.49%7.89%8.70%7.83%7.52%7.29%

test cells(GSM900)12.73%10.84%8.37%10.27%10.39%7.51%9.68%

test cells(GSM1800)7.35%7.49%6.58%5.47%4.73%4.96%7.32%


drop calls


test cells0.73%0.78%0.73%0.56%0.69%0.51%0.51%

test cells(GSM900)1.54%1.60%1.42%1.19%1.09%1.07%1.07%

test cells(GSM1800)0.31%0.33%0.33%0.33%0.31%0.31%0.31%



test cells3-Apr-2822-Aug-5031-Jul-9911-Feb-1026-Mar-6825-Oct-684-Jul-67

test cells(GSM900)15-Jan-6725-Aug-6821-Mar-5622-Aug-057-Sep-1018-Sep-495-Dec-51

test cells(GSM1800)5-Dec-7512-Mar-8118-Jan-831-Nov-9117-Apr-4021-Apr-8319-Oct-87

test area include test cells and neighbors20-Dec-4715-Aug-6730-Sep-2814-Feb-1911-Jun-4619-Jun-4613-Aug-43

HO


21-Mar-11test cell28-Apr-112-Jul-685-Feb-3196.05%

22-Mar-11test cell18-Dec-8211-May-1113-Sep-5895.34%

23-Mar-11test cell6-Feb-7322-Feb-9110-Nov-7297.50%

11-Apr-11test cell8-Aug-2014-Jun-7823-Jun-3698.18%

12-Apr-11test cell11-Feb-0724-Apr-502-Mar-4998.17%

13-Apr-11test cell28-Mar-1823-Nov-5929-Sep-5098.29%


21-Mar-11test area include test cells and neighbors16-Apr-302-Sep-3922-Apr-7495.88%

22-Mar-1124-Mar-1025-May-8818-Mar-0495.29%

23-Mar-1113-Jul-6428-Mar-5115-Jul-0097.28%

11-Apr-1117-Jul-9015-May-3121-Nov-5098.09%

12-Apr-1123-Apr-9313-Dec-1415-Apr-6798.04%

13-Apr-118-Mar-4614-Jan-662-May-6998.16%

ICM

ICM%21-Mar-1122-Mar-1123-Mar-1124-Mar-1111-Apr-1112-Apr-1113-Apr-11

test cells24.22%24.92%27.12%30.03%29.21%29.41%29.48%

test cells(GSM900)55.05%56.16%56.65%58.51%54.81%55.78%56.25%

test cells(GSM1800)0.33%0.42%0.48%0.46%0.33%0.39%0.39%


Chart3

traffic


test cells347389340619368379350447349658352881349307

test cells(GSM900)207730201512207009209893149522204926208987

test cells(GSM1800)224795217256221756220510165450223479230215



test cells890282886141935449861647850830861567858478

test cells(GSM900)533483527796511236478055348134473904483002

test cells(GSM1800)565597558333570454591847441189591646605524


congs


test cells10.43%9.49%7.89%8.70%7.83%7.52%7.29%

test cells(GSM900)12.73%10.84%8.37%10.27%10.39%7.51%9.68%

test cells(GSM1800)7.35%7.49%6.58%5.47%4.73%4.96%7.32%


drop calls


test cells0.73%0.78%0.73%0.56%0.69%0.51%0.51%

test cells(GSM900)1.54%1.60%1.42%1.19%1.09%1.07%1.07%

test cells(GSM1800)0.31%0.33%0.33%0.33%0.31%0.31%0.31%







HO










22-Mar-1124-Mar-1025-May-8818-Mar-0495.29%

23-Mar-1113-Jul-6428-Mar-5115-Jul-0097.28%

11-Apr-1117-Jul-9015-May-3121-Nov-5098.09%

12-Apr-1123-Apr-9313-Dec-1415-Apr-6798.04%

13-Apr-118-Mar-4614-Jan-662-May-6998.16%

ICM


test cells24.22%24.92%27.12%30.03%29.21%29.41%29.48%

test cells(GSM900)55.05%56.16%56.65%58.51%54.81%55.78%56.25%

test cells(GSM1800)0.33%0.42%0.48%0.46%0.33%0.39%0.39%


Chart3

traffic

voice traffic21-Mar-1122-Mar-1123-Mar-1124-Mar-1111-Apr-1112-Apr-1113-Apr-11voice traffic21-Mar-1122-Mar-1123-Mar-1124-Mar-1111-Apr-1112-Apr-1113-Apr-11

test cells347388.8001957316test area include test cells and neighbors432917.7241996116

total traffic include data and voice21-Mar-1122-Mar-1123-Mar-1124-Mar-1111-Apr-1112-Apr-1113-Apr-11total traffic include data and voice21-Mar-1122-Mar-1123-Mar-1124-Mar-1111-Apr-1112-Apr-1113-Apr-11



test cells(GSM900)


test cells(GSM1800)

congs


test cells10.43%9.49%7.89%8.70%7.83%7.52%7.29%

test cells(GSM900)12.73%10.84%8.37%10.27%10.39%7.51%9.68%

test cells(GSM1800)7.35%7.49%6.58%5.47%4.73%4.96%7.32%


drop calls


test cells0.73%0.78%0.73%0.56%0.69%0.51%0.51%

test cells(GSM900)1.54%1.60%1.42%1.19%1.09%1.07%1.07%

test cells(GSM1800)0.31%0.33%0.33%0.33%0.31%0.31%0.31%



test cells302515310691292042222841207545207758207279

test cells(GSM900)316681317269276205221207150000200781201589

test cells(GSM1800)64258661826685970068512436695268594


HO


21-Mar-11test cell131900912668464788496.05%

22-Mar-11test cell134517612824985796695.34%

23-Mar-11test cell119547711655432661397.50%

11-Apr-11test cell8475848321891332498.18%

12-Apr-11test cell113485111141051795998.17%

13-Apr-11test cell124848712271781853598.29%



22-Mar-11172037616393557458895.29%

23-Mar-11152106614796853672297.28%

11-Apr-11112879911071861858898.09%

12-Apr-11145852814299072457798.04%

13-Apr-11158741215581402532598.16%

ICM


test cells24.22%24.92%27.12%30.03%29.21%29.41%29.48%

test cells(GSM900)55.05%56.16%56.65%58.51%54.81%55.78%56.25%

test cells(GSM1800)0.33%0.42%0.48%0.46%0.33%0.39%0.39%


Chart1

traffic


test cells347389340619368379350447349658352881349307

test cells(GSM900)207730201512207009209893149522204926208987

test cells(GSM1800)224795217256221756220510165450223479230215



test cells890282886141935449861647850830861567858478

test cells(GSM900)533483527796511236478055348134473904483002

test cells(GSM1800)565597558333570454591847441189591646605524


congs


test cells10.43%9.49%7.89%8.70%7.83%7.52%7.29%

test cells(GSM900)12.73%10.84%8.37%10.27%10.39%7.51%9.68%

test cells(GSM1800)7.35%7.49%6.58%5.47%4.73%4.96%7.32%


drop calls


test cells0.73%0.78%0.73%0.56%0.69%0.51%0.51%

test cells(GSM900)1.54%1.60%1.42%1.19%1.09%1.07%1.07%

test cells(GSM1800)0.31%0.33%0.33%0.33%0.31%0.31%0.31%







HO










22-Mar-1124-Mar-1025-May-8818-Mar-0495.29%

23-Mar-1113-Jul-6428-Mar-5115-Jul-0097.28%

11-Apr-1117-Jul-9015-May-3121-Nov-5098.09%

12-Apr-1123-Apr-9313-Dec-1415-Apr-6798.04%

13-Apr-118-Mar-4614-Jan-662-May-6998.16%

ICM


test cells24.22%24.92%27.12%30.03%29.21%29.41%29.48%

test cells(GSM900)55.05%56.16%56.65%58.51%54.81%55.78%56.25%

test cells(GSM1800)0.33%0.42%0.48%0.46%0.33%0.39%0.39%


Chart1

traffic

voice traffic21-Mar-1122-Mar-1123-Mar-1124-Mar-1111-Apr-1112-Apr-1113-Apr-11voice traffic21-Mar-1122-Mar-1123-Mar-1124-Mar-1111-Apr-1112-Apr-1113-Apr-11


total traffic include data and voice21-Mar-1122-Mar-1123-Mar-1124-Mar-1111-Apr-1112-Apr-1113-Apr-11total traffic include data and voice21-Mar-1122-Mar-1123-Mar-1124-Mar-1111-Apr-1112-Apr-1113-Apr-11



test cells(GSM900)


test cells(GSM1800)

congs


test cells10.43%9.49%7.89%8.70%7.83%7.52%7.29%

test cells(GSM900)12.73%10.84%8.37%10.27%10.39%7.51%9.68%

test cells(GSM1800)7.35%7.49%6.58%5.47%4.73%4.96%7.32%


drop calls


test cells0.73%0.78%0.73%0.56%0.69%0.51%0.51%

test cells(GSM900)1.54%1.60%1.42%1.19%1.09%1.07%1.07%

test cells(GSM1800)0.31%0.33%0.33%0.33%0.31%0.31%0.31%



test cells302515310691292042222841207545207758207279

test cells(GSM900)316681317269276205221207150000200781201589

test cells(GSM1800)64258661826685970068512436695268594


HO


21-Mar-11test cell131900912668464788496.05%

22-Mar-11test cell134517612824985796695.34%

23-Mar-11test cell119547711655432661397.50%

11-Apr-11test cell8475848321891332498.18%

12-Apr-11test cell113485111141051795998.17%

13-Apr-11test cell124848712271781853598.29%



22-Mar-11172037616393557458895.29%

23-Mar-11152106614796853672297.28%

11-Apr-11112879911071861858898.09%

12-Apr-11145852814299072457798.04%

13-Apr-11158741215581402532598.16%

ICM


test cells24.22%24.92%27.12%30.03%29.21%29.41%29.48%

test cells(GSM900)55.05%56.16%56.65%58.51%54.81%55.78%56.25%

test cells(GSM1800)0.33%0.42%0.48%0.46%0.33%0.39%0.39%


Documents

Avoiding to Uplink Interference Effecting in GSM Network