Section: 5.3.1 DL Assignment reception
Content: Downlink assignments transmitted on the PDCCH indicate if there is a transmission on a DL-SCH for a particular MAC entity and provide the relevant HARQ information. When the MAC entity has a C-RNTI, Semi-Persistent Scheduling C-RNTI, PUR-RNTI or Temporary C-RNTI, the MAC entity shall for each TTI during which it monitors PDCCH and for each Serving Cell: - if a downlink assignment for this TTI and this Serving Cell has been received on the PDCCH for the MAC entity's C-RNTI, PUR-RNTI, or Temporary C-RNTI: - if this is the first downlink assignment for this Temporary C-RNTI; or - if this is the first downlink assignment corresponding to uplink transmission using previous preconfigured uplink grant for this PUR-RNTI: - consider the NDI to have been toggled. - if the downlink assignment is for the MAC entity's C-RNTI and if the previous downlink assignment indicated to the HARQ entity of the same HARQ process was either a downlink assignment received for the MAC entity's Semi-Persistent Scheduling C-RNTI or a configured downlink assignment: - consider the NDI to have been toggled regardless of the value of the NDI. - indicate the presence of a downlink assignment and deliver the associated HARQ information to the HARQ entity for this TTI. - else, if a downlink assignment for this TTI has been received for this Serving Cell on the PDCCH for the MAC entity's Semi-Persistent Scheduling C-RNTI: - if the NDI in the received HARQ information is 1: - consider the NDI not to have been toggled; - indicate the presence of a downlink assignment and deliver the associated HARQ information to the HARQ entity for this TTI. - else, if the NDI in the received HARQ information is 0: - if PDCCH contents indicate SPS release: - clear the configured downlink assignment (if any); - if the timeAlignmentTimer, associated with the TAG containing the serving cell on which the acknowledgement for the downlink SPS release is to be transmitted, is running: - indicate a positive acknowledgement for the downlink SPS release to the physical layer. - else: - store the downlink assignment and the associated HARQ information as configured downlink assignment; - initialise (if not active) or re-initialise (if already active) the configured downlink assignment to start in this TTI, or in TTI according to N=0 in clause 5.10.1 for short TTI, and to recur according to rules in clause 5.10.1; - set the HARQ Process ID to the HARQ Process ID associated with this TTI; - consider the NDI bit to have been toggled; - indicate the presence of a configured downlink assignment and deliver the stored HARQ information to the HARQ entity for this TTI. - else, if a downlink assignment for this TTI has been configured for this Serving Cell and there is no measurement gap in this TTI and there is no Sidelink Discovery Gap for Reception in this TTI; and - if this TTI is not an MBSFN subframe or the MAC entity is configured with transmission mode tm9 or tm10: - instruct the physical layer to receive, in this TTI, transport block on the DL-SCH according to the configured downlink assignment and to deliver it to the HARQ entity; - set the HARQ Process ID to the HARQ Process ID associated with this TTI; - consider the NDI bit to have been toggled; - indicate the presence of a configured downlink assignment and deliver the stored HARQ information to the HARQ entity for this TTI. - if the MAC entity is configured with rach-Skip or rach-SkipSCG and a UE Contention Resolution Identity MAC control element for this TTI has been received on the PDSCH indicated by the PDCCH of the SpCell addressed to the C-RNTI: - indicate to upper layer the successful reception of a PDCCH transmission addressed to the C-RNTI. For configured downlink assignments, the HARQ Process ID associated with this TTI is derived from the following equation: - if the TTI is a subframe TTI: - HARQ Process ID = [floor(CURRENT_TTI/semiPersistSchedIntervalDL)] modulo numberOfConfSPS-Processes, where CURRENT_TTI=[(SFN * 10) + subframe number]. - else: - HARQ Process ID = [floor(CURRENT_TTI/semiPersistSchedIntervalDL-sTTI)] modulo numberOfConfSPS-Processes-sTTI, where CURRENT_TTI = [(SFN * 10 * sTTI_Number_Per_Subframe) + subframe number * sTTI_Number_Per_Subframe + sTTI_number]. Refer to 5.10.1 for sTTI_Number_Per_Subframe and sTTI_number. For BL UEs or UEs in enhanced coverage, CURRENT_TTI refers to the TTI where first transmission of repetition bundle takes place. When the MAC entity needs to read BCCH or BR-BCCH, the MAC entity may, based on the scheduling information from RRC: - if the UE is a BL UE or a UE in enhanced coverage: - the redundancy version of the received downlink assignment for this TTI is determined by RVK = ceiling(3/2*k) modulo 4, where k depends on the type of system information message. - for SystemInformationBlockType1-BR - if number of repetitions for PDSCH carrying SystemInformationBlockType1-BR is 4, k = floor(SFN/2) modulo 4, where SFN is the system frame number. - else if number of repetitions for PDSCH carrying SystemInformationBlockType1-BR is 8, k = SFN modulo 4, where SFN is the system frame number. - else if number of repetitions for PDSCH carrying SystemInformationBlockType1-BR is 16, k = (SFN*10+i) modulo 4, where SFN is the system frame number, and i denotes the subframe within the SFN. NOTE: the set of subframes for SystemInformationBlockType1-BR when number of repetitions for PDSCH is 16 are given by Table 6.4.1-2 in TS 36.211[ Evolved Universal Terrestrial Radio Access (E-UTRA); Physical channels and modulation ]  [7]. - for SystemInformation-BR messages, k=i modulo 4, i =0,1,…, nsw–1, where i denotes the subframe number within the SI window nsw; - indicate a downlink assignment and redundancy version for the dedicated broadcast HARQ process to the HARQ entity for this TTI. - else if a downlink assignment for this TTI has been received on the PDCCH for the SI-RNTI, except for NB-IoT; - if the redundancy version is not defined in the PDCCH format: - the redundancy version of the received downlink assignment for this TTI is determined by RVK = ceiling(3/2*k) modulo 4, where k depends on the type of system information message: for SystemInformationBlockType1 message, k = (SFN/2) modulo 4, where SFN is the system frame number; for SystemInformation messages, k=i modulo 4, i =0,1,…, nsw–1, where i denotes the subframe number within the SI window nsw; - indicate a downlink assignment and redundancy version for the dedicated broadcast HARQ process to the HARQ entity for this TTI. When the MAC entity has SC-RNTI and/or G-RNTI, the MAC entity shall for each TTI during which it monitors PDCCH for SC-RNTI as specified in TS 36.331[ Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification ]  [8] for UEs other than NB-IoT UEs, BL UEs or UEs in enhanced coverage and in clause 5.7a for NB-IoT UEs, BL UEs or UEs in enhanced coverage and for G-RNTI as specified in clause 5.7a and for each Serving Cell and cell that may be additionally configured as a Serving Cell according to the UE capabilities: - if a downlink assignment for this TTI and this Serving Cell has been received on the PDCCH for the MAC entity's SC-RNTI or G-RNTI: - attempt to decode the received data. - if the data which the MAC entity attempted to decode was successfully decoded for this TB: - deliver the decoded MAC PDU to the disassembly and demultiplexing entity.