UE Trace Analysis

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Example: Call Setup in CELL_FACH Failed


Initial condition: UE was configured to URA_PCH after having sent SCRI with cause UERequestedPSDataSessionEnd​.

 

  1. UE could not stay in URA_PCH and performs Cell Update in transient FACH with cause “re-entered Service Area”.

  2. SRNC configures UE in CELL_FACH.

  3. UE reports Physical Channel Failure (Cause “Cell Update Occurred”). Then a Mobile Terminated Call (pagingType2) is received in CELL_FACH.

  4. Only SIB 7 (uplink interference level) are shown in downlink and at the same time the UE TX power is switched off.

  5. After about 40 sec later, the UE performs Cell Update with cause “RLC unrecoverable error”.

  6. SRNC releases the UE abnormally by sending RRC Connection Release cause “unspecified".

 

What went wrong in UE when changing to URA_PCH?

What causes UE/UTRAN to fail in setting up the MTC?

 

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Example: Throughput Down to Zero 

 

  1. FTP Download of 100 Mbyte using HS-DSCH started in CELL_DCH.

  2. Throughput followed CQI Reporting from UE and was always > 1 Mbps.

  3. After having received around 2..10 Mbyte, the throughput dropped to zero.

  4. SRNC reconfigured the UE to CELL_PCH after a few seconds of zero kbps throughput.

  5. Problem is reproducible.

 

Why? What is the root cause?

 

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>>Recorded and displayed by TEMS™ Investigation: www.ascom.com. © 2014 by Ascom Group. All rights reserved. <<

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>>Recorded and displayed by TEMS™ Investigation: www.ascom.com. © 2014 by Ascom Group. All rights reserved. <<

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Example: Fatal Radio Link Addition

 

  1. UE sends Measurement Report Event 1A for PSC:42.

  2. SRNC sends ActiveSetUpdate Command and orders RL-Addition with “tm” and “off” reported by UE before.

  3. UE sends ActiveSetUpdateComplete but SRNC seems not receiving it as further MR’s with Event1A for new strong PSC:41 are ignored by SRNC.

  4. Radio Conditions deteriorate for the voice call and even the Event 2D Measurement Reports are ignored by SRNC.

  5. It seems SRNC has a problem but that is not completely true – SRNC never received ActiveSetUpdateComplete for PSC:42.

  6. Intermediate conclusion: the last MR for PSC:42 caused UTRAN to fail!

 

Why did the SRNC not respond?

 

>>Recorded and displayed by TEMS™ Investigation: www.ascom.com. © 2014 by Ascom Group. All rights reserved. <<

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