Section: 5.1.4 Random Access Response reception
Content: Once the Random Access Preamble is transmitted and regardless of the possible occurrence of a measurement gap or a Sidelink Discovery Gap for Transmission or a Sidelink Discovery Gap for Reception, and regardless of the prioritization of V2X sidelink communication described in clause 5.14.1.2.2, the MAC entity shall monitor the PDCCH of the SpCell for Random Access Response(s) identified by the RA-RNTI defined below, in the RA Response window which starts at the subframe that contains the end of the preamble transmission,as specified in TS 36.211[ Evolved Universal Terrestrial Radio Access (E-UTRA); Physical channels and modulation ]  [7], plus three subframes and has length ra-ResponseWindowSize. If the UE is a BL UE or a UE in enhanced coverage: - if the random access preamble was transmitted in a non-terrestrial network: - RA Response window starts at the subframe that contains the end of the last preamble repetition plus 3 subframes plus UE-eNB RTT and has length ra-ResponseWindowSize for the corresponding enhanced coverage level; - else: - RA Response window starts at the subframe that contains the end of the last preamble repetition plus three subframes and has length ra-ResponseWindowSize for the corresponding enhanced coverage level. If the UE is an NB-IoT UE: - if the random access preamble was transmitted in a non-terrestrial network: - RA Response window starts at the subframe that contains the end of the last preamble repetition plus X subframes plus UE-eNB RTT and has length ra-ResponseWindowSize for the corresponding enhanced coverage level, where value X is determined from Table 5.1.4-1 based on the used preamble format and the number of NPRACH repetitions; - else: - RA Response window starts at the subframe that contains the end of the last preamble repetition plus X subframes and has length ra-ResponseWindowSize for the corresponding enhanced coverage level, where value X is determined from Table 5.1.4-1 based on the used preamble format and the number of NPRACH repetitions. Table 5.1.4-1: Subframes between preamble transmission and RA Response Window in NB-IoT The RA-RNTI associated with the PRACH in which the Random Access Preamble is transmitted, is computed as: RA-RNTI= 1 + t_id + 10*f_id where t_id is the index of the first subframe of the specified PRACH (0≤ t_id <10), and f_id is the index of the specified PRACH within that subframe, in ascending order of frequency domain (0≤ f_id< 6) except for NB-IoT UEs, BL UEs or UEs in enhanced coverage. If the PRACH resource is on a TDD carrier, the f_id is set to , where is defined in clause 5.7.1 of TS 36.211[ Evolved Universal Terrestrial Radio Access (E-UTRA); Physical channels and modulation ]  [7]. For BL UEs and UEs in enhanced coverage, RA-RNTI associated with the PRACH in which the Random Access Preamble is transmitted, is computed as: RA-RNTI=1+t_id + 10*f_id + 60*(SFN_id mod (Wmax/10)) where t_id is the index of the first subframe of the specified PRACH (0≤ t_id <10), f_id is the index of the specified PRACH within that subframe, in ascending order of frequency domain (0≤ f_id< 6), SFN_id is the index of the first radio frame of the specified PRACH, and Wmax is 400, maximum possible RAR window size in subframes for BL UEs or UEs in enhanced coverage. If the PRACH resource is on a TDD carrier, the f_id is set to , where is defined in clause 5.7.1 of TS 36.211[ Evolved Universal Terrestrial Radio Access (E-UTRA); Physical channels and modulation ]  [7]. For NB-IoT UEs, the RA-RNTI associated with the PRACH in which the Random Access Preamble is transmitted, is computed as: RA-RNTI=1 + floor(SFN_id/4) + 256*carrier_id where SFN_id is the index of the first radio frame of the specified PRACH and carrier_id is the index of the UL carrier associated with the specified PRACH. The carrier_id of the anchor carrier is 0. For NB-IoT UEs operating in TDD mode, the RA-RNTI associated with the PRACH in which the Random Access Preamble is transmitted, is computed as: RA-RNTI = 1 + floor(SFN_id/4) + 256*(H-SFN mod 2) where SFN_id is the index of the first radio frame of the specified PRACH and H-SFN is the index of the first hyper frame of the specified PRACH. The PDCCH transmission and the PRACH resource are on the same carrier. The MAC entity may stop monitoring for Random Access Response(s) after successful reception of a Random Access Response containing Random Access Preamble identifiers that matches the transmitted Random Access Preamble. - If a downlink assignment for this TTI has been received on the PDCCH for the RA-RNTI and the received TB is successfully decoded, the MAC entity shall regardless of the possible occurrence of a measurement gap or a Sidelink Discovery Gap for Transmission or a Sidelink Discovery Gap for Reception, and regardless of the prioritization of V2X sidelink communication described in clause 5.14.1.2.2: - if the Random Access Response contains a Backoff Indicator subheader: - set the backoff parameter value as indicated by the BI field of the Backoff Indicator subheader and Table 7.2-1, except for NB-IoT where the value from Table 7.2-2 is used. - else, set the backoff parameter value to 0 ms. - if the Random Access Response contains a Random Access Preamble identifier corresponding to the transmitted Random Access Preamble (see clause 5.1.3), the MAC entity shall: - consider this Random Access Response reception successful and apply the following actions for the serving cell where the Random Access Preamble was transmitted: - process the received Timing Advance Command (see clause 5.2); - indicate the preambleInitialReceivedTargetPower and the amount of power ramping applied to the latest preamble transmission to lower layers (i.e., (PREAMBLE_TRANSMISSION_COUNTER – 1) * powerRampingStep); - if the SCell is configured with ul-Configuration-r14, ignore the received UL grant otherwise process the received UL grant value and indicate it to the lower layers; - if, except for NB-IoT, ra-PreambleIndex was explicitly signalled and it was not 000000 (i.e., not selected by MAC): - consider the Random Access procedure successfully completed. - else if, the UE is an NB-IoT UE, ra-PreambleIndex was explicitly signalled and it was not 000000 (i.e., not selected by MAC) and ra-CFRA-Config is configured: - consider the Random Access procedure successfully completed. - the UL grant provided in the Random Access Response message is valid only for the configured carrier (i.e. UL carrier used prior to this Random Access procedure). - else: - if the Random Access Preamble was selected by the MAC entity; or - if the UE is an NB-IoT UE, the ra-PreambleIndex was explicitly signalled and it was not 000000 and ra-CFRA-Config is not configured: - set the Temporary C-RNTI to the value received in the Random Access Response message no later than at the time of the first transmission corresponding to the UL grant provided in the Random Access Response message; - if the Random Access Preamble associated with EDT was transmitted and UL grant provided in the Random Access Response message is not for EDT: - indicate to upper layers that EDT is cancelled due to UL grant not being for EDT; - for CP-EDT, flush the Msg3 buffer. - for UP-EDT, update the MAC PDU in the Msg3 buffer in accordance with the uplink grant received in the Random Access Response. - if the Random Access Preamble associated with EDT was transmitted, the UL grant was received in a Random Access Response for EDT, and there is a MAC PDU in the Msg3 buffer: - if the TB size according to edt-SmallTBS-Enabled and as described in clause 8.6.2 and 16.3.3 of TS 36.213[ Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures ]  [2] does not match the size of the MAC PDU in the Msg3 buffer: - the MAC entity shall update the MAC PDU in the Msg3 buffer in accordance with the TB size. - if this is the first successfully received Random Access Response within this Random Access procedure; or - if CP-EDT is cancelled due to the UL grant provided in the Random Access Response message not being for EDT: - if the transmission is not being made for the CCCH logical channel, indicate to the Multiplexing and assembly entity to include a C-RNTI MAC control element in the subsequent uplink transmission; - obtain the MAC PDU to transmit from the "Multiplexing and assembly" entity and store it in the Msg3 buffer. NOTE 1: When an uplink transmission is required, e.g., for contention resolution, the eNB should not provide a grant smaller than 56 bits (or 88 bits for NB-IoT) in the Random Access Response. NOTE 2: If within a Random Access procedure, an uplink grant provided in the Random Access Response for the same group of Random Access Preambles has a different size than the first uplink grant allocated during that Random Access procedure, the UE behavior is not defined except for EDT. If no Random Access Response or, for NB-IoT UEs, BL UEs or UEs in enhanced coverage for mode B operation, no PDCCH scheduling Random Access Response is received within the RA Response window, or if none of all received Random Access Responses contains a Random Access Preamble identifier corresponding to the transmitted Random Access Preamble, the Random Access Response reception is considered not successful and the MAC entity shall: - if the notification of power ramping suspension has not been received from lower layers: - increment PREAMBLE_TRANSMISSION_COUNTER by 1; - if the UE is an NB-IoT UE, a BL UE or a UE in enhanced coverage: - if PREAMBLE_TRANSMISSION_COUNTER = preambleTransMax-CE + 1: - if the Random Access Preamble is transmitted on the SpCell: - indicate a Random Access problem to upper layers; - if NB-IoT: - consider the Random Access procedure unsuccessfully completed; - else: - if PREAMBLE_TRANSMISSION_COUNTER = preambleTransMax + 1: - if the Random Access Preamble is transmitted on the SpCell: - indicate a Random Access problem to upper layers; - if the Random Access Preamble is transmitted on an SCell: - consider the Random Access procedure unsuccessfully completed. - if in this Random Access procedure, the Random Access Preamble was selected by MAC: - based on the backoff parameter, select a random backoff time according to a uniform distribution between 0 and the Backoff Parameter Value; - delay the subsequent Random Access transmission by the backoff time; - else if the SCell where the Random Access Preamble was transmitted is configured with ul-Configuration-r14: - delay the subsequent Random Access transmission until the Random Access Procedure is initiated by a PDCCH order with the same ra-PreambleIndex and ra-PRACH-MaskIndex; - if the UE is an NB-IoT UE, a BL UE or a UE in enhanced coverage: - increment PREAMBLE_TRANSMISSION_COUNTER_CE by 1; - if PREAMBLE_TRANSMISSION_COUNTER_CE = maxNumPreambleAttemptCE for the corresponding enhanced coverage level + 1: - reset PREAMBLE_TRANSMISSION_COUNTER_CE; - consider to be in the next enhanced coverage level, if it is supported by the Serving Cell and the UE, otherwise stay in the current enhanced coverage level; - if the UE is an NB-IoT UE: - if the Random Access Procedure was initiated by a PDCCH order: - select the PRACH resource in the list of UL carriers providing a PRACH resource for the selected enhanced coverage level for which the carrier index is equal to ((Carrier Indication from the PDCCH order) modulo (Number of PRACH resources in the selected enhanced coverage)); - consider the selected PRACH resource as explicitly signalled; - proceed to the selection of a Random Access Resource (see clause 5.1.2).