8.5.76 Actions related to FALLBACK_R99_PRACH_ENABLED variable (FDD only)

25.3313GPPProtocol specificationRadio Resource Control (RRC)Release 17TS

The variable FALLBACK_R99_PRACH_ENABLED shall be set to TRUE only when all the following conditions are met:

1> the variable READY_FOR_FALLBACK_R99_PRACH is set to TRUE;

1> "E-DCH resource index" received is equal to -1;

1> either of the following conditions is met:

2> the IE "CCCH Fallback" is set to TRUE and there is CCCH message(s) for transmission on the uplink;

2> the IE "DCCH Fallback" is set to TRUE and there is DCCH message(s) for transmission on the uplink.

If any of the above conditions is not met and the variable FALLBACK_R99_PRACH_ENABLED is set to TRUE, the UE shall:

1> set the variable FALLBACK_R99_PRACH_ENABLED to FALSE;

If the UE receives "Fallback transmission termination" from MAC with the CMAC-STATUS primitive, the UE shall:

1> set the variable FALLBACK_R99_PRACH_ENABLED to FALSE.

If variable FALLBACK_R99_PRACH_ENABLED is set to TRUE:

1> replace the TFS of the RACH with the one stored in the UE if any;

1> let the physical channel(s) of type PRACH given by the IE(s) "PRACH info" be the default in uplink for the PRACH if UE is in CELL_FACH state;

1> start to receive the physical channel of type AICH using the parameters given by the IE "AICH info" (FDD only) when given allocated PRACH is used;

1> if the IE "Additional Dynamic Transport Format Information for CCCH" is included for the selected PRACH:

2> use this transport format for transmission of the CCCH.

1> else:

2> use the first instance of the list of transport formats as in the IE "RACH TFS" for the used RACH received in the IE "PRACH system information list" when using the CCCH.

1> select PRACH according to subclause 8.5.17;

If the variable FALLBACK_R99_PRACH_ENABLED is set from TRUE to FALSE and the variable READY_FOR_COMMON_EDCH is set to TRUE:

1> use the Enhanced Uplink in CELL_FACH state and Idle mode as specified in section 8.5.45.