In CELL_DCH State, after receiving N313 consecutive "out of sync" indications from layer 1 for the established DPCCH or F-DPCH physical channel in FDD, the RRC will start the the UE shall start timer T313. Upon expiry of timer T313, a Radio Link Failure event is triggered.
If N315 successive "in sync" indications are received from layer 1 while the timer was running, the timer is stopped and Radio Link Failure does not occur.
And the L1 reports Out-of-sync to RRC if one of the following criteria is fulfilled:
Once the Radio Link Failure happens, the UE tries to recover from it by sending CELL UPDATE message indicating cause “Radio Link Failure”. If the network responds with a CELL UPDATE CONFIRM while the retries from UE are not exhausted, the Radio Link is restored and the data is resumed. The CELL UPDATE CONFIRM message contains reconfigured parameters for the Physical channel. These make the channel more robust(lowering the Modulation scheme, increasing the redundancy) so that there is more chance of the channel being decoded properly at the UE.
It follows the following states:
If N315 successive "in sync" indications are received from layer 1 while the timer was running, the timer is stopped and Radio Link Failure does not occur.
And the L1 reports Out-of-sync to RRC if one of the following criteria is fulfilled:
- The L1 estimates the DPCCH quality or the quality of the TPC fields of the F-DPCH frame received from the serving HS-DSCH cell over the previous 160 ms period to be worse than a threshold Qout.
- The 20 most recently received transport blocks with a non-zero length CRC attached, as observed on all TrCHs using non-zero length CRC mapped to the DPDCH, have been received with incorrect CRC. In addition, over the previous 160 ms, all transport blocks with a non-zero length CRC attached have been received with incorrect CRC.
Once the Radio Link Failure happens, the UE tries to recover from it by sending CELL UPDATE message indicating cause “Radio Link Failure”. If the network responds with a CELL UPDATE CONFIRM while the retries from UE are not exhausted, the Radio Link is restored and the data is resumed. The CELL UPDATE CONFIRM message contains reconfigured parameters for the Physical channel. These make the channel more robust(lowering the Modulation scheme, increasing the redundancy) so that there is more chance of the channel being decoded properly at the UE.
It follows the following states: