Section: 10.2.3.4 Mapping to resource elements
Content: Each NPDSCH codeword can be mapped to one or more than one subframes, , as given by clause 16.4.1.3 of TS 36.213[ Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures ]  [4], each of which shall be transmitted times. For each of the antenna ports used for transmission of the physical channel, the block of complex-valued symbols shall be mapped to resource elements which meet all of the following criteria in the current subframe: - the subframe is not used for transmission of NPBCH, NPSS, or NSSS, and - except in a special subframe when , they are assumed by the UE not to be used for NRS, and - they are not overlapping with resource elements used for CRS as defined in clause 6 (if any), and - the index in the first slot in a subframe fulfils where is given by clause 16.4.1.4 of TS 36.213[ Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures ]  [4], and - in addition, for frame structure type 2 - in a special subframe, if , they are in DwPTS - in a special subframe, if , they are not NRS locations in subframes which are not special subframes. The mapping of in sequence starting with to resource elements on antenna port meeting the criteria above shall be in increasing order of first the index and then the index, starting with the first slot and ending with the second slot in a subframe. For NPDSCH not carrying BCCH, after mapping to a subframe, the subframe shall be repeated for additional subframes, before continuing the mapping of to the following subframe. The resource elements in a special subframe that are not part of DwPTS are counted but not used in the mapping if . When , the resource elements in a special subframe assumed by the UE for NRSs are counted but not used in the mapping if . For frame structure type 1, - for NPDSCH associated with C-RNTI when interferenceRandomisationConfig is used according to [9], or - for NPDSCH associated with RA-RNTI, TC-RNTI or P-RNTI and transmitted in an NB-IoT carrier configured by SystemInformationBlockType22-NB, or - for NPDSCH associated with C-RNTI in an NB-IoT carrier configured by SystemInformationBlockType22-NB when RadioResourceConfigDedicted-NB is not configured by higher layer, or - for NPDSCH associated with PUR-RNTI/G-RNTI/ SC-RNTI, or for frame structure type 2, - for NPDSCH not carrying the BCCH, define as the block of complex-valued symbols mapped to subframe number and radio frame number . Each complex-valued symbol shall be multiplied with before its transmission, with where the scrambling sequence is given by clause 7.2 and shall be initialized at the start of each subframe with . The mapping of is then repeated until subframes have been transmitted. For frame structure type 2, the resource elements in a special subframe that are not part of DwPTS are counted but not used in the repetition. When , the resource elements in a special subframe assumed by the UE for NRSs are counted but not used in the repetition. For NPDSCH carrying BCCH, the is mapped to subframes in sequence and then repeated until subframes have been transmitted, where - for mapping NPDSCH carrying SystemInformationBlockType1-NB to subframe #3 for frame structure type 1; - otherwise. The NPDSCH transmission can be configured by higher layers with transmission gaps where the NPDSCH transmission is postponed. There are no gaps in the NPDSCH transmission if where is given by the higher layer parameter dl-GapThreshold and is given by [4]. The gap starting frame and subframe is given by where the gap periodicity,, is given by the higher layer parameter dl-GapPeriodicity. The gap duration in number of subframes is given by , where is given by the higher layer parameter dl-GapDurationCoeff. For NPDSCH carrying the BCCH there are no gaps in the transmission. The UE shall not expect NPDSCH in subframe if it is not a NB-IoT downlink subframe, except for transmissions of NPDSCH carrying SystemInformationBlockType1-NB in - subframes 3 and 4 for frame structure type 1; and - subframes 0, 4, and 5 for frame structure type 2. In case of NPDSCH transmissions, in subframes that are not NB-IoT downlink subframes, the NPDSCH transmission is postponed until the next NB-IoT downlink subframe. If higher layer parameter resourceReservationConfigDL is configured, then in case of NPDSCH transmission associated with C-RNTI using UE-specific NPDCCH search space with the Resource reservation field in the DCI set to 1, - In a subframe that is fully reserved as defined in clause 16.4 in [4], the NPDSCH transmission is postponed until the next NB-IoT downlink subframe that is not fully reserved. - In a subframe that is partially reserved, the reserved OFDM symbols shall be counted in the NPDSCH mapping but not used for transmission of the NPDSCH.