10.2.3 Narrowband physical downlink shared channel
36.2113GPPEvolved Universal Terrestrial Radio Access (E-UTRA)Physical channels and modulationRelease 17TS
10.2.3.1 Scrambling
Scrambling shall be done according to clause 6.3.1. If the NPDSCH is carrying the BCCH, the scrambling sequence generator shall be initialised with 
. Otherwise, the scrambling sequence generator shall be initialised with 
where
is the first slot of the transmission of the codeword.
In case of NPDSCH repetitions and the NPDSCH carrying the BCCH, the scrambling sequence generator shall be reinitialized according to the expression above for each repetition.
In case of NPDSCH repetitions and the NPDSCH is not carrying the BCCH, the scrambling sequence generator shall be reinitialized according to the expression above after every transmission of the codeword with
and
set to the first slot and the frame, respectively, used for the transmission of the repetition.
10.2.3.2 Modulation
Modulation shall be done according to clause 6.3.2 using one of the modulation schemes in Table 10.2.3-1
Table 10.2.3-1: Modulation schemes
|
Physical channel |
Modulation schemes |
|
NPDSCH |
QPSK, 16QAM |
10.2.3.3 Layer mapping and precoding
Layer mapping and precoding shall be done according to clause 6.6.3 using the same set of antenna ports as the NPBCH.
10.2.3.4 Mapping to resource elements
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 [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 [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.