8.5.73 PRACH preamble control parameters selection with 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

If the UE supports concurrent deployment and System Information Block type 22 includes the IE "Concurrent deployment of 2ms and 10ms TTI", the UE shall select PRACH preamble control parameters (for Enhanced Uplink) according to the following rule. The UE shall:

1> for common E-DCH TTI value 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 if the TTI signalled in the IE "E-DCH Transmission Time Interval" is equal to 10ms, 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 occurrences 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] if the TTI signalled in the IE "E-DCH Transmission Time Interval" is equal to 10ms.

1> for common E-DCH TTI value equal to 2ms:

2> if the UE supports TTI alignment and Per HARQ process and System Information Block type 22 includes the IE "PRACH preamble control parameters extension list Type 3 (for Enhanced Uplink)", and either of the IE’s "Coffset" or "Scheduled Transmission configuration":

3> compile a list of candidate PRACH preamble control parameters from the IE "PRACH preamble control parameters extension list Type 3 (for Enhanced Uplink)" included in System Information Block 22, in the order of appearance as in System Information Block 22.

2> else if System Information Block type 22 includes the IE "PRACH preamble control parameters extension list Type 2 (for Enhanced Uplink)":

3> compile a list of candidate PRACH preamble control parameters from the IE "PRACH preamble control parameters extension list Type 2 (for Enhanced Uplink)" included in System Information Block 22, in the order of appearance as in System Information Block 22.

2> else:

3> the UE behaviour is not specified.

2> 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 < L with probability given by the (i+1)^th occurrence of the IE "Weight" in the list of candidate PRACH preamble control parameters and L is equal to the number of candidate PRACH preamble control parameters. If any of the first L-1 occurences of the IE "Weight" is not present, "rand" is a random number taking integer values i, 0  i < L with equal probability. The candidate PRACH preamble control parameters shall be indexed from 0 to L-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 L^th occurrence of the weight value is not explicitly given but calculated by UE, see 10.3.6.135.

2> 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)".

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

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.