6.3.3 Layer mapping
36.2113GPPEvolved Universal Terrestrial Radio Access (E-UTRA)Physical channels and modulationRelease 17TS
The complex-valued modulation symbols for each of the codewords to be transmitted are mapped onto one or several layers. Complex-valued modulation symbols 
for codeword 
shall be mapped onto the layers 
, 
where 
is the number of layers and 
is the number of modulation symbols per layer, unless 
and "MUST interference presence and power ratio (MUSTIdx)" signalled in the associated DCI is ’00’ for only one codeword in which case 
, where 
for the layer 
for which MUSTIdx is ’00’, and 
for the layer 
for which MUSTIdx is not ’00’. The value of
is determined from Table 6.3.3-1 using MUSTIdx and the modulation order of the codeword for which MUSTIdx is not ’00’.
Table 6.3.3-1: Values for 
|
MUSTIdx |
Modulation order |
||
|
QPSK |
16QAM |
64QAM |
|
|
01 |
8/10 |
32/42 |
128/170 |
|
10 |
50/58 |
144.5/167 |
40.5/51 |
|
11 |
264.5/289 |
128/138 |
288/330 |
6.3.3.1 Layer mapping for transmission on a single antenna port
For transmission on a single antenna port, a single layer is used, 
, and the mapping is defined by
with 
.
6.3.3.2 Layer mapping for spatial multiplexing
For spatial multiplexing, the layer mapping shall be done according to Table 6.3.3.2-1. The number of layers 
is less than or equal to the number of antenna ports 
used for transmission of the physical channel. The case of a single codeword mapped to multiple layers is only applicable when the number of cell-specific reference signals is four or when the number of UE-specific reference signals is two or larger. For subslot/slot-PDSCH, the number of codewords is always one.
Table 6.3.3.2-1: Codeword-to-layer mapping for spatial multiplexing
|
Number of layers |
Number of codewords |
Codeword-to-layer mapping
|
|
|
1 |
1 |
|
|
|
2 |
1 |
|
|
|
2 |
2 |
|
|
|
|
|||
|
3 |
1 |
|
|
|
3 |
2 |
|
|
|
|
|||
|
4 |
1 |
|
|
|
4 |
2 |
|
|
|
|
|||
|
5 |
2 |
|
|
|
|
|||
|
6 |
2 |
|
|
|
|
|||
|
7 |
2 |
|
|
|
|
|||
|
8 |
2 |
|
|
|
|
|||
6.3.3.3 Layer mapping for transmit diversity
For transmit diversity, the layer mapping shall be done according to Table 6.3.3.3-1. There is only one codeword and the number of layers 
is equal to the number of antenna ports 
used for transmission of the physical channel.
Table 6.3.3.3-1: Codeword-to-layer mapping for transmit diversity
|
Number of layers |
Number of codewords |
Codeword-to-layer mapping
|
|
|
2 |
1 |
|
|
|
4 |
1 |
|
If |
two null symbols shall be appended to 