8.5.74 PRACH preamble control parameters selection without Concurrent Deployment of 2ms and 10ms TTI (for Enhanced Uplink, FDD only)

25.3313GPPProtocol specificationRadio Resource Control (RRC)Release 17TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

The UE shall select PRACH preamble control parameters (for Enhanced Uplink) according to the following rule. The UE shall:

1> if the TTI signalled in the IE "E-DCH Transmission Time Interval" is equal to 10ms:

2> if the IE "PRACH preamble control parameters extension list Type 1 (for Enhanced Uplink)" is included in System Information Block 22:

3> compile a list of candidate PRACH preamble control parameters from the IE "PRACH preamble control parameters extension list Type 1 (for Enhanced Uplink)" included in System Information Block 22 and the IE "PRACH preamble control parameters (for Enhanced Uplink)" included in "Common E-DCH system info" in System Information Block 5/5bis, in the order of appearance as in System Information Block 22 followed by System Information Block 5/5bis, respectively;

3> select PRACH preamble control parameters randomly from the candidate list as follows:

"Index of selected PRACH preamble control parameters (for Enhanced Uplink)" = rand

where "rand" is a random number taking integer values i, 0  i < K with probability given by the (i+1)^th occurrence of the weight value in the list of candidate PRACH preamble control parameters and K is equal to the number of candidate PRACH preamble control parameters. If any of the K-1 occurences of the IE "Weight" is not present, "rand" is a random number taking integer values i, 0  i < K with equal probability. The candidate PRACH preamble control parameters shall be indexed from 0 to K-1. The random number generator is left to implementation. At start-up of the random number generator in the UE the seed shall be dependent on the IMSI of the UE or time, thereby avoiding that all UEs select the same parameters;

NOTE: The K^th occurrence of the weight value is not explicitly given but calculated by UE, see 10.3.6.134.

3> configure and use the MAC and the physical layer for the PRACH preamble transmission according to the parameters included in the selected IE "PRACH preamble control parameters (for Enhanced Uplink)".

3> for emergency call, the UE is allowed to select any of the PRACH preamble control parameters from the candidate list.

2> else:

3> configure and use the MAC and the physical layer for the PRACH preamble transmission according to the parameters included in the selected "PRACH preamble control parameters (for Enhanced Uplink)" IE according to [15].

1> else:

2> configure and use the MAC and the physical layer for the PRACH preamble transmission according to the parameters included in the selected "PRACH preamble control parameters (for Enhanced Uplink)" IE according to [15].

1> reselect the PRACH preamble control parameters when a new cell is selected. PRACH preamble control parameter reselection may also be performed at the start of each Enhanced Uplink in CELL_FACH state and IDLE mode transmission.