GPRS Data Connection Troubleshooting

GPRS Data Connection Troubleshooting

Last updated: March 17, 2009

This section is not applicable to GSM or EGPRS.

Problems Getting the Mobile to Perform a GPRS Attach

If you have problems getting the mobile to perform a GPRS Attach, try working through some or all of the following troubleshooting hints:

Problems Establishing a BLER Data Connection

If you have problems establishing a data connection using the BLER Data Connection Type specifically, you may want to change the setting of the LLC Frame Check Sequence (see CALL:FUNCtion:DATA:BLER:LLC:FCSequence ) or the BLER Block Polling Interval (see CALL:FUNCtion:DATA:BLER:POLLing:INTerval ).

For example, if your mobile is not capable of a high level of GMM_INFORMATION messaging (the type of messaging used to stimulate the mobile to send ACK/NACK responses to the test set), then the data connection will timeout. One possible solution to this is to set the LLC Frame Check Sequence to CORRupt preventing the messaging while still forcing the mobile to send ACK/NACK responses. The BLER Block Polling Interval is the rate at which the RLC/MAC blocks have the MAC header poll bit set, forcing a response (Packet Downlink ACK/NACK) from the mobile.

To change the LLC Frame Check Sequence or BLER Block Polling Interval settings manually, press the More key to access the Control menu ( 2 of 2 ), then press the Protocol Control ( F4 ) key. Block Poll Rate is available under the RLC/MAC ( F1 ) key and BLER FCS is available under the LLC ( F2 ) key. Select a parameter and change its setting.

Problems with BLER Measurements in GPRS/EGPRS

If you have problems in BLER testing, such as dropped call connections, this may be the cause: when you test receiver sensitivity using the BLER measurement by lowering the Cell Power, both the BCH and TCH/PDTCH power levels are lowered the same amount. The test set does not implement a default offset between those two channels. Typically, the test set sends a protocol message setting Network Control Order = 0 (NCO=0), so the mobile decides which cell it will select. Thus, when the BCH signal level decreases, the mobile tries to select a different non-existent neighbor cell. Thus, the call is often dropped before a valid BLER sensitivity test can be completed.

Possible solutions:

Problems with Measurements in ETSI Test Mode A or B

In order to perform measurements in Active Cell operating mode with the Data Connection Type set to ETSI Type A or ETSI Type B test modes, your mobile must fully support these connection types as defined in the standards. ETSI Type B is required if you want to perform BER measurements in active cell mode.

You can specify the first downlink burst to be looped back in the first uplink burst using the command CALL:(PDTCH|PDTChannel):MSLot[:FIRSt]:DOWNlink:LOOPback[:BURSt] .

In ETSI Type B test mode, the BLER measurement is performed using a different method from that used when the test set's data connection type is set to BLER. For more details on the BLER measurement see Block Error Measurement .