Inter-RAT Handover to GSM for voice call and R99 services

[adewijaya]

Inter-RAT Handover to GSM for voice call and R99 services, the HSDPA service somehow cannot handover to GSM cell, why is happend?

[kilisuci_kdr]

Where is the document or explanation?

[adewijaya]

Where is the document or explanation?

this is a real problem and need solution so why in this thread on Live Optimization :D

[wolverine]

Does the UTRAN support compressed mode for HSDPA connections? Usually this is a separate feature that you have to enable.

[adewijaya]

Does the UTRAN support compressed mode for HSDPA connections? Usually this is a separate feature that you have to enable.

yes supported, but still degraded

[xcatas]

Is there any sign of too late or too early HO triggering?
Perhaps the variation of value for handover triggers (like HO trigger time or EcNo threshold) will make it works..

[adewijaya]

Upon further checking on Measurement control signaling with call tracing, it is found that CN only send the inter frequency measurement control and no Inter-RAT measurement control to UE.Normally CN will send the HO properties of the interactive service in RAB assignment request, ‘service_Handover:handover to GSM should not be performed’. Since CN did not send the HO properties, then the default setting in RNC will be used.

1. HO_TO_GSM_SHOULD_BE_PERFORM: Handover to the 2G network is performed as long as 2G signals are available.
2. HO_TO_GSM_SHOULD_NOT_BE_PERFORM: Handover to the 2G network is performed when 3G signals are weak but 2G signals are strong.
3. HO_TO_GSM_SHALL_NOT_BE_PERFORM: Handover to the 2G network is not performed even if 3G signals are weak but 2G signals are strong.

The Inter-RAT HO failure is caused by wrong setting in RNC (HO_TO_GSM_SHALL_NOT_BE_PERFORM) and therefore, Inter-RAT measurement control is not send to UE. UE did not perform any measurement on Inter-RAT cell, thus the HO is failed.
After the command is executed then UE receive Inter-RAT measurement control and perform measurement on inter-RAT cell after that so Inter-RAT HO is successful.