How to calculate BCCH TRX's link balance

ZTE Corporation, GSM System Department

There are two methods to calculate the BCCH TRX’s link balance. one is by signalling trace, the other is by performance statistic. we will describe the methods respectively step by step as following.

Method 1 ：By Signalling Trace

1. Open the “Radio Resource Management” Function at OMCR，and modify the POC paramaters,make sure “Allow Uplink Power Control”and “Allow Downlink Power Control” is disable.

2.Open the “Signalling Trace” Function at OMCR,and select the cell that you want to trace,make sure the “Measure report”flag is Enable:

3.Recording the trace file:

4.Stop tracing ,and convert the trace file to MA10 file:

5.Open the converted file by MA10 view tools.

6. Select one call on bcch trx,and trace the call

7.From the “Graph: Measurement results”page ,we can get the value of “Uplink Rx Lever” and “Downlink Rx Lever” ,and the link banalnce value can be calculated.

8.According to the link budget module ,we can see that the best link balance value is 8.5db (BS power – MS power - Combining/Duplexer = 46-33-4.5=8.5db) .With ±7db tolerance(Long-term Fading ±4db, BS power ±1db, MS power ±2db)),the values between 1.5db and 15.5db are both normal.

Method 2: By performance statistic

Step 1. Open the “Radio Resource Management” Function at OMCR，and modify the POC parameters, make sure “Allow Uplink Power Control” and “Allow Downlink Power Control” is enabled. Meanwhile, set the “MS Max. TxPwr.” and” Ms Min. TxPwr.” the same value (5 for GSM900, 0 for DCS1800). Set the “BS Min. TxPwr.” equal to 0.

Step 2. As an option, you can modify the “Performance Survey Report Period (51 MultiFrame)”. The default value is 240. which is about 2 minutes.

Step 3. Open the “Performance Management” Function at OMCR，select the base station that you just have set the POC parameters. Right click mouse button to create a new BTS measurement job. Then the “measurement creation wizard” will guide you to finish the job setting.

Step 4. From the “Measurement type” list box, select the “BTS measurement” item.

Step 5. Give a “Measurement Job name”, for example “BTS”. select the sampling period from “GP” list box, for example “5N” (5 minutes). Then select the objects from the left list that you want to investigate.

Step 6. After you have selected the objects, then the push “Next>” button.

Step 7. Right click the “clock” icon, and select the measurement begin time and measurement stop time.

Step 8. After select the measurement interval, push the “Input” Button, then the “Next”.

Step 9. Select the measurement date and workday, then the “Next”.

Step 10. Finally, the all the setting information will show you. If all the information is OK, then you can finish it. If you find some setting information is not you want, you can back to modify it.

Step 11. If you choose “finish” button on the previous step and create the measurement job successfully, A success dialogue will pop up.

Step 12. After you successfully create the measurement job, and wait for a while. Then you can right click on the measurement job you have created and choose the “History Data Query” menu item to get the performance statistic.

Step 13A. In the “Data Query” dialogue, select the objects you have created measurement job. In the right “Counters” list choose counter 00021 to 00024. make sure the “Export to Excel” is enable and choose the Query time. Finally, push the “Query” button.

Step 13B. In addition, as you like, in step 13, you can also select the counter 0089 to 0092 to get more information.

Step 14. If you have push the “Query” button in previous step, a “History Data Query” dialogue will pop up. In this dialogue, you can view all the performance data. Enable the “Export To Excel” and push the “OK”, It will save all the data to excel file format.

Step 15. Open the excel file you have just saved, you will find the performance data.

Step 16. In order to get the average downlink signal level. You can use the counter 00022 to divide counter 00021. for instance, average downlink signal level from 10:20 to 10:25 is 45455/1434 = 32; In order to get the average uplink signal level. You can use the counter 00024 to divide counter 00023. for instance, average uplink signal level from 10:20 to 10:25 is 54441/1436 = 38; So the link balance value is 38-32 = 6dB. Also, from the counter 00089 to 00092, you can find the Maximum and Minimum signal level during the measurement sampling period (5 minutes).

The end. 2006-4-11