8.5.50 Common E-RNTI selection (1.28 Mcps TDD only)

25.3313GPPProtocol specificationRadio Resource Control (RRC)Release 17TS

When the IE "Common E-RNTI Information" is included in System Information Block type 5, and if the UE is in CELL_FACH state or Idle mode, and if the variable E_RNTI is not set, UE shall use a common E-RNTI for CCCH transmission (i.e. the common E-RNTI identifies the initial access, including RRC connection request and cell update after cell re-selection):

1> configure the MAC layer with the information in the IE(s) "Common E-RNTI information";

1> when a CCCH message is to be sent, and if the variable E_RNTI is not set, the MAC layer operates as follows:

2> select an E-RUCCH;

2> select the instance of the IE(s) "Common E-RNTI information" which is related to the selected E-RUCCH;

2> select a common E-RNTI which is related to the selected E-RUCCH according to the following procedure:

3> compile a list of candidate common E-RNTI group from the selected instance of the IE(s) "Common E-RNTI information" in the order of appearance in System Information Block type 5, and select a common E-RNTI group from the list of candidate Common E-RNTI groups based on the E-RUCCH transmission occasion:

"Index of selected Common E-RNTI group" = SFNE-RUCCH mod K, for TTI of E-RUCCH = 10ms;

or "Index of selected Common E-RNTI group" = SFN’E-RUCCH mod K, for TTI of E-RUCCH = 5ms;

Where K is the number of E-RNTI groups related to the E-RUCCH; SFN_E-RUCCH or SFN’_E-RUCCH is the frame or sub-frame on which the E-RUCCH shall be sent [33].

3> select a common E-RNTI randomly amongst the candidate the candicate E-RNTIs in the selected group.

2> use the value of the selected common E-RNTI as UE identity in current E-RUCCH transmission, and in the E-AGCH reception within the common E-RNTI scheduling window which is of K frames or K sub-frames length.