4.1.1 Performing Interface Board Port Timeslot Loopback
You can perform interface board port timeslot loopback on any one of the following boards: GE(O)IUA, GE(O)IUB, GE(O)IUT, and GE(O)IUP. There are two loopback modes: remote loopback and local loopback.
Remote loopback: The signal received in the timeslot is not processed but directly sent out in the TX direction of the timeslot. During the loopback, the interface board still continues to receive the signal sent in the timeslot.
Local loopback: The signal that needs to be sent in the timeslot is not sent out but directly taken back in the RX direction of the timeslot. During the loopback, the interface board still continues to receive the signal sent in the timeslot.
Abis interface board timeslot loopback is frequently used in voice troubleshooting. A interface timeslot loopback can be replaced by external voice loopback.
The procedure for performing interface board port timeslot loopback is as follows:
(1) Click Device Maintenance, choose BSC Maintenance > Interface Board Port Timeslot
Loopback, and specify Subrack No. and Slot No.
Note:
During the Abis /Ater interface board timeslot loopback, you must set the loopback timeslot correctly. You can calculate the E1 timeslot by using the timeslot queried in section 3.24 "Single User Resource Check".
4.1.2 Performing BTS Voice Loopback
You can perform the BTS voice loopback test on a traffic channel to verify whether the voice channel of the TRX from the air interface to the internal DBUS of the BTS is connected normally. During the test, the TMU board loops back the DBUS timeslot corresponding to the tested voice channel and the connection can be checked according to whether the users occupying the channel can hear their own voices. If the users can hear their own voices, the connection is normal; otherwise, the connection is abnormal.
After a voice problem such as noise occurs, a BTS voice loopback test can be performed. If the users can hear noise, the voice problem may be located in the downlink direction of the Abis interface; otherwise, the voice problem is located in the uplink direction of the Abis interface.
The procedure for performing BTS voice loopback is as follows:
(1) Click Device Maintenance, choose BTS Maintenance > Maintain TRX > Test Channel
Loopback, specify Site, Cell, TRX No., and Channel, and set Test Project to BTS Voice Loop Test.
(2) Read the three precautions in Description, specify Duration, and click Start to perform the test.
Note:
You can set TRX No. and Channel to the TRX number and channel number queried in section 3.24 "Single User Resource Check".
4.1.3 Performing TRX Voice Loopback
You can perform the TRX voice loopback test on a traffic channel to verify whether the voice channel of the TRX from the air interface to the codec of the baseband DSP is connected normally. During the test, the baseband DSP directly encodes the decoded data of the traffic channel and
After a voice problem, such as noise, occurs, a TRX voice loopback test can be performed. If the users can hear noise, the voice problem may be located in the downlink direction of the DBUS (and TRX); otherwise, the voice problem is located in the uplink direction of the TRX.
The procedure for performing TRX voice loopback is similar to the procedure for performing BTS voice loopback. The procedure for performing TRX voice loopback is as follows:
(1) Click Device Maintenance, choose BTS Maintenance > Maintain TRX > Test Channel
Loopback, specify Site, Cell, TRX No., and Channel, and set Test Project to TRX Voice Loop Test.
(2) Read the three precautions in Description, specify Duration, and click Start to perform the test.
4.1.4 Performing BIU Loopback
You can perform the BIU loopback test on only idle channels. On the LMT, choose BTS
Maintenance > Maintain TRX > Test Channel Loopback and specify Site, Cell, TRX No., and Channel. Set Test Project to BIU Loop Test. Click Start to perform the test. After the test is
complete, the test results are returned.
Note:
You must perform BIU loopback on all channels of the target TRX, four times per channel. The loopback test results are returned in a table. An example of the loopback test results is listed as follows:
Loopback Mode/Test MS MS A at a Problem Site MS B at a Normal Site Local Abis Interface
Loopback
Cannot hear A and B Can hear A and B
Remote Abis Interface Loopback
Can hear A but cannot hear B
Can hear A but cannot hear B
perform each loopback for at least four times.
4.2 Modifying the BTS Soft Parameters
Run the SET GCELLBTSSOFT command to modify the BTS software parameters. For example,
SET GCELLBTSSOFT: IDTYPE=BYID, CELLID=112, ITEMINDEX=39, ITEMVALUE=254;
4.3 Reducing the Interference Band Software Parameters
No help or auxiliary information about modifying the software parameters of the cell can be obtained from the Web LMT because the BSC hides the command for modifying the software parameters of the cell. The procedure for modifying the interference band software parameters is as follows:
1> Open the MML window.
2> Use 200K filter bandwidth to calculate the interference band of the MRFU V2. Run the
following command in the MML window or batch processing window:
SET GCELLBTSSOFT: IDTYPE=BYID, CELLID=Cell index value, ITEMINDEX=56, ITEMVALUE=127;
Note:
Bit 7 of software parameter 56 indicates that the 200K filter switch is used to calculate the interference band of the MRFU V2. If bit 7 is set to 0, the switch is enabled. If bit 7 is set to
1, the switch is disabled. When the software parameter is used, you need to query the value of
the software parameter before setting the software parameter because each bit has its own
meaning. In this way, other function switches will not be affected when this function is enabled.
LST GCELLBTSSOFT: IDTYPE=BYID, CELLID=Cell index value;
After the bit occupation of the software parameter is determined, set bit 7 to 0 to recalculate the value of the software parameter.
If the queried value of software parameter 56 is 223, namely 0xDF (corresponding to the binary code 11011111), bit 5 has been set to 0. In this case, the 200K filter bandwidth switch BIT7 must be enabled, namely, bit 7 must be set to 0. Therefore, the recalculated value of software parameter 56 is 0x5F, namely 95.
SET GCELLBTSSOFT: IDTYPE=BYID, CELLID=Cell index value, ITEMINDEX=56, ITEMVALUE=95;
3> Select an interference band reporting combination algorithm (applicable to all modules
except MRRU V2):
SET GCELLBTSSOFT: IDTYPE=BYID, CELLID=Cell index value, ITEMINDEX=59, ITEMVALUE=239;
Note:
Bit 5 and bit 4 of software parameter 59 indicate the interference band reporting combination algorithm. When the two bits are set to 10, it means selecting the average value. When the two bits are set to 01, it means selecting the minimum value. When the two bits are set to 00 or 01, it means selecting the maximum value. The default value is 11. The following table shows the details.
BIT5 BIT4 Algorithm
1 1 The maximum value of each antenna is used in interference band reporting by default.
interference band reporting.
When the software parameter is used, you need to query the value of the software parameter before setting the software parameter because each bit has its own meaning. In this way, other function switches will not be affected when this function is enabled.
LST GCELLBTSSOFT: IDTYPE=BYID, CELLID=Cell index value;
After the bit occupation of the software parameter is determined, set bit 5 and bit 4 to the corresponding value to recalculate the value of the software parameter.
[Example] The value of software parameter 59 queried above is 254, namely, 0xDF, and bit 5 is already 0. In this case, the average value must be used in interference band reporting, namely, bit 5 and bit 4 must be set to 10. Therefore, the recalculated value of software parameter 59 is 0xEE, namely, 238.
SET GCELLBTSSOFT: IDTYPE=BYID, CELLID=Cell index value, ITEMINDEX=59, ITEMVALUE=238;
4> Set the interference band reduction factor (applicable to all modules except MRRU V2): SET GCELLBTSSOFT: IDTYPE=BYID, CELLID=Cell index value, ITEMINDEX=19, ITEMVALUE=255;
Bit 5 to bit 2 of software parameter 19 indicate a reduction factor. The value 1111 is the default value and the factor is not used.
1010–1110 are invalid values and can be normalized to 1001, namely, reducing 9 dB. The
following table lists the possible parameter values:
BIT5 BIT4 BIT3 BIT2
Meaning
0
0
0
0
Reducing 0
dB
0
0
0
1
Reducing 1
dB
0
0
1
0
Reducing 2
dB
0
0
1
1
Reducing 3
dB
0
1
0
0
Reducing 4
dB
0
1
0
1
Reducing 5
dB
0
1
1
0
Reducing 6
dB
0
1
1
1
Reducing 7
dB
1
0
0
0
Reducing 8
dB
1
0
0
1
Reducing 9
dB
1
0
1
0
Invalid
1
0
1
1
Invalid
1
1
0
0
Invalid
1
1
0
1
Invalid
1
1
1
0
Invalid
1
1
1
1
Invalid
（（1（ To reduce the interference band by 3 dB when bit 5 to bit 2 of software parameter 19 are set to 0011, run the following command:
SET GCELLBTSSOFT: IDTYPE=BYID, CELLID=Cell index value, ITEMINDEX=19, ITEMVALUE=204;
Note:
The following command for modifying the IF filter bandwidth affects the performance of the service and is not recommended when being used to reduce the interference band.
5> Run the following command to modify level-1 filter bandwidth for the MRFU V1/MRRU
V1:
SET GCELLBTSSOFT: IDTYPE=BYID, CELLID=Cell index value, ITEMINDEX=91, ITEMVALUE=251;
coefficient of the IF filter.
The following table lists the meanings of bit 2 and bit 1.
BIT2-BIT1 00 01 10 11
Filter bandwidth
260K 200K Reserved 260K
6> Run the following command to modify level-1 filter bandwidth for the DRRU/DRFU: SET GCELLBTSSOFT: IDTYPE=BYID, CELLID=Cell index value, ITEMINDEX=91, ITEMVALUE=239;
Bit 4 and bit 3 of software parameter 91 are used to configure the coefficient of the IF filter. The following table lists the meanings of bit 4 and bit 3.
BIT4-BIT3
00
01
10
11
Filter
bandwidth
260K
200K
Reserved
200K
Note:
1. When the IF filter coefficients of D series and M series are configured, use different bits of the same software parameter.
The default values (10 and 11) in the IF filter coefficient configuration of D series and M series are different. The default value of D series is 200K bandwidth, and the default value of M series is 260K bandwidth. The reserved value 10 cannot be configured.