Last updated: December 3, 2008
During remote operation of the bit error measurement you should configure the trigger arm to single, see SETup:BERRor:CONTinuous .
If the trigger arm is not set to single, the measurement may not return a result. When trigger arm is continuous the measurement rearms itself and starts another measurement cycle, during remote operation the fetch query may not be synchronized to the measurement cycle, see
Measurement States
.
If you have a BER measurement active and your mobile drops the call it may be that you have the SETup:BERRor:SLControl[:STATe] command set to OFF. This is likely to occur with mobiles that do not respond to downlink signalling when loopback is closed. To solve this problem set the command to ON.
If a GSM voice call is active and the Measurement Type is set to Data or Residual Data, no results are returned by the measurement because it can not sync to the signal being looped back from the mobile station. Change the Measurement Type to an appropriate value.
If a GSM circuit switched data (CSD) call is active and the Measurement Type is not set to Data or Residual Data, no results are returned by the measurement because it can not sync to the signal being looped back from the mobile station. Change the Measurement Type to an appropriate value.
The error correction which is a feature of channel coding scheme CS-1 will mask low to medium bit error rates if used during GBER measurements. This will result in measurement results which are not ideal. Therefore, CS-4 is the recommended coding scheme for GBER measurements. You use the command CALL:(PDTCH|PDTChannel):CSCHeme:UPLink to set the channel coding scheme.
During remote operation of the GPRS bit error measurement you should configure the trigger arm to single, see SETup:GBERror:CONTinuous .
The GBER measurement only provides results when the test set's operating mode is:
GBER measurements cannot be run concurrently with SRB Loopback BER or BLER measurements. The test set closes the GBER measurement if you start either the SRB Loopback BER or BLER measurement while it is running.
During remote operation of the bit error measurement you should configure the trigger arm to single, see SETup:SBERror:CONTinuous .
If the trigger arm is not set to single, the measurement may not return a result. When trigger arm is continuous the measurement rearms itself and starts another measurement cycle, during remote operation the fetch query may not be synchronized to the measurement cycle, see
Measurement States
.
SBER measurements cannot be run concurrently with GBER or BLER measurements. The test set closes the SBER measurement if you start either the GBER or BLER measurement while it is running.
When the operating mode is EGPRS BCH+ PDTCH and the each burst in the downlink is assigned an MCS/PS, the GBER and the SBER measurements may not give accurate results. This is because they are not able to synchronize and calculate a BER if the downlink and the uplink slot being compared do not have the same length of data bytes. For example, if the downlink has MCS5/P1 on burst 1 and MCS3/P2 on burst 2, and the uplink has MCS5 on burst 1 and MCS4 on burst 2, then only burst 1 can be used to calculate the BER. An attempt to calculate the BER on burst 2 makes the measurement either not synchronize or have a large BER.
The EGPRS SRB Bit Error rate measurement does not currently support Asymmetric SRB Loopback. If you have the uplink configured to use a different modulation format than the downlink, you may see very large BER results that you did not expect. When the number of bits in the received data blocks is different from the number transmitted on the downlink, the test set treats each bit that was originally transmitted on the downlink as an error.
To correct this problem, configure the Downlink Modulation Coding Scheme parameter in the test set to use the same modulation format as either the Uplink Modulation Coding Scheme parameter in the test set or, if you are using EGPRS BCH+PDTCH test mode, the modulation format you have configured your mobile station to use for the uplink.
MCS-1 through MCS-4 use GMSK modulation. MCS-5 through MCS-9 use 8PSK modulation.
See Test Set Configuration for instructions on manually configuring the test set's parameters.
For information on programmatically changing the modulation coding scheme parameters, see CALL:(PDTCH|PDTChannel):MCSCheme or, if you are using EGPRS BCH+PDTCH test mode, see CALL:(PDTCH|PDTChannel):MCSCheme:EBPTest:BURSt<2|3|4|5> .