8.5.77 Actions related to READY_FOR_FALLBACK_R99_PRACH variable (FDD only)

25.3313GPPProtocol specificationRadio Resource Control (RRC)Release 17TS

The variable READY_FOR_FALLBACK_R99_PRACH shall be set to TRUE only when all the following conditions are met:

1> the UE is in CELL_FACH state or in Idle mode;

1> the variable READY_FOR_COMMON_EDCH is set to TRUE;

1> the IE "Fallback R99 PRACH info" is included in system information block type 22;

1> UE supports fallback to R99 PRACH;

1> the IE "E-AI Indication" is set to TRUE;

1> for each configured radio bearer:

2> if the radio bearer is mapped to CCCH and IE "CCCH Fallback" is set to TRUE; or

2> if the radio bearer is mapped to DCCH and IE "DCCH Fallback" is set to TRUE:

3> the RB has a multiplexing option with transport channel type "HS-DSCH" for the DL, and the corresponding MAC-ehs reordering queue is configured, and transport channel type "RACH" for the UL.

3> if the radio bearer is mapped to DCCH and IE "DCCH Fallback" is set to TRUE, then for any logical channel(s) corresponding to that radio bearer:

4> the RLC sizes that apply for the logical channel with transport channel type "RACH" for the UL are the same as the RLC sizes that apply for that logical channel with transport channel type "E-DCH" for the UL, as per subclause 8.5.21.

If any of the above conditions is not met and the variable READY_FOR_FALLBACK_R99_PRACH is set to TRUE, the UE shall:

1> set the variable READY_FOR_FALLBACK_R99_PRACH to FALSE;

If variable READY_FOR_FALLBACK_R99_PRACH is set to TRUE:

1> configure the MAC for CCCH and DCCH fallback according to the IE’s "CCCH Fallback" and "DCCH Fallback" respectively.