lteDLPrecode

Downlink precoding of transmission layers

Syntax

out = lteDLPrecode(in,ntxants,txscheme,codebook)

out = lteDLPrecode(enb,chs,in)

Description

out = lteDLPrecode(in,ntxants,txscheme,codebook) performs precoding according to TS 36.211 [1], Section 6.3.4. The out matrix returned is identical to the matrix returned by ltePDSCH for the same set of parameters. The overall operation of the precoder is the transpose of the matrix defined in the specification. The symbols for layers and antennas lie in columns rather than rows.

This function performs precoding of the matrix of layers, in, onto P antennas, using the transmission scheme specified by txscheme. For transmission scheme precoding dependencies, see Algorithms.

out = lteDLPrecode(enb,chs,in) precodes the matrix of layers, in, according to cell-wide settings enb and channel transmission configurations chs.

Examples

Perform Downlink Precoding on Identity Matrix

Perform downlink precoding using an identity matrix as input.

By precoding an identity matrix, you can gain access to the precoding matrices. Obtain the precoding matrix having codebook index 1 for three layers and four antennas.

out = lteDLPrecode(eye(3),4,'SpatialMux',1).'

out = 4×3 complex

   0.2887 + 0.0000i   0.0000 - 0.2887i  -0.2887 + 0.0000i
   0.0000 + 0.2887i   0.2887 + 0.0000i   0.0000 + 0.2887i
  -0.2887 + 0.0000i   0.0000 - 0.2887i   0.2887 + 0.0000i
   0.0000 - 0.2887i   0.2887 + 0.0000i   0.0000 - 0.2887i

Input Arguments

in — Input layers

matrix

Input layers, specified as an N_SYM-by-v matrix, consisting of the N_SYM modulation symbols for transmission on v layers. Generate this matrix using lteLayerMap.

Data Types: double
Complex Number Support: Yes

ntxants — Number of antennas

positive integer

Number of antennas, specified as a positive integer.

Data Types: double

txscheme — Transmission scheme

'Port0' | 'TxDiversity' | 'CDD' | 'SpatialMux' | 'MultiUser' | 'Port5' | 'Port7-8' | 'Port8' | 'Port7-14'

PDSCH transmission scheme, specified as one of the following options.

Transmission scheme	Description
'Port0'	Single antenna port, port 0
'TxDiversity'	Transmit diversity
'CDD'	Large delay cyclic delay diversity scheme
'SpatialMux'	Closed loop spatial multiplexing
'MultiUser'	Multi-user MIMO
'Port5'	Single-antenna port, port 5
'Port7-8'	Single-antenna port, port 7, when NLayers = 1. Dual layer transmission, ports 7 and 8, when NLayers = 2.
'Port8'	Single-antenna port, port 8
'Port7-14'	Up to eight layer transmission, ports 7–14

Data Types: char | string

codebook — Codebook index

integer from 0 to 15

Codebook index to select the precoding matrix, specified as an integer from 0 to 15. This input is ignored for the 'Port0', 'TxDiversity', and 'CDD' transmission schemes. Find the precoding matrix corresponding to a particular codebook index in the TS 36.211 [1], Section 6.3.4. Since codebook is a scalar, the syntax that includes this parameter does not support subband precoding or multiple PMI mode. In the case of 'TxDiversity' and P=1, the function falls back to single port processing.

Data Types: double

enb — eNodeB cell-wide settings

structure

eNodeB cell-wide settings, specified as a structure containing these parameter fields:

Parameter Field	Required or Optional	Values	Description
When chs.TxScheme is set to 'TxDiversity', 'CDD', 'SpatialMux', or 'MultiUser', these parameters are applicable:
CellRefP	Required	1, 2, 4	Number of cell-specific reference signal (CRS) antenna ports
When chs.TxScheme is set to 'SpatialMux', or 'MultiUser' and chs.PMISet is present, these parameters are applicable:.
NCellID	Required	Integer from 0 to 503	Physical layer cell identity
NSubframe	Required	0 (default), nonnegative scalar integer	Subframe number
NDLRB	Required	Scalar integer from 6 to 110	Number of downlink resource blocks ($$N_{\text{RB}}^{\text{DL}}$$)
CFI	Required	1, 2, or 3 Scalar or if the CFI varies per subframe, a vector of length 10 (corresponding to a frame).	Control format indicator (CFI) value. In TDD mode, CFI varies per subframe for the RMCs ('R.0', 'R.5', 'R.6', 'R.6-27RB', 'R.12-9RB')
CyclicPrefix	Optional	'Normal' (default), 'Extended'	Cyclic prefix length
DuplexMode	Optional	'FDD' (default), 'TDD'	Duplexing mode, specified as either: 'FDD' for Frequency Division Duplex 'TDD' for Time Division Duplex
When DuplexMode is set to 'TDD', these parameters are applicable:
TDDConfig	Optional	0, 1 (default), 2, 3, 4, 5, 6	Uplink–downlink configuration
SSC	Optional	0 (default), 1, 2, 3, 4, 5, 6, 7, 8, 9	Special subframe configuration (SSC)

Data Types: struct

chs — Channel-specific transmission configuration

structure | structure array

Channel specific transmission configuration, specified as a structure that can contain the following parameter fields.

Parameter Field	Required or Optional	Values	Description
TxScheme	Optional	'Port0' (default), 'TxDiversity', 'CDD', 'SpatialMux', 'MultiUser', 'Port5', 'Port7-8', 'Port8', 'Port7-14'.	PDSCH transmission scheme, specified as one of the following options. Transmission scheme Description 'Port0' Single antenna port, port 0 'TxDiversity' Transmit diversity 'CDD' Large delay cyclic delay diversity scheme 'SpatialMux' Closed loop spatial multiplexing 'MultiUser' Multi-user MIMO 'Port5' Single-antenna port, port 5 'Port7-8' Single-antenna port, port 7, when NLayers = 1. Dual layer transmission, ports 7 and 8, when NLayers = 2. 'Port8' Single-antenna port, port 8 'Port7-14' Up to eight layer transmission, ports 7–14
When chs.TxScheme is set to 'SpatialMux' or 'MultiUser', these parameters are applicable, include either Codebookidx or both PMISet and PRBSet:
Codebookidx	Optional	Integer from 0 to 15	Codebook index used during precoding
PMISet	Optional	Integer vector with element values from 0 to 15.	Precoder matrix indication (PMI) set. It can contain either a single value, corresponding to single PMI mode, or multiple values, corresponding to multiple or subband PMI mode. The number of values depends on CellRefP, transmission layers and TxScheme. For more information about setting PMI parameters, see ltePMIInfo.
PRBSet	Optional	Integer column vector or two-column matrix	Zero-based physical resource block (PRB) indices corresponding to the slot wise resource allocations for this PDSCH. PRBSet can be assigned as: a column vector, the resource allocation is the same in both slots of the subframe, a two-column matrix, this parameter specifies different PRBs for each slot in a subframe, a cell array of length 10 (corresponding to a frame, if the allocated physical resource blocks vary across subframes). PRBSet varies per subframe for the RMCs 'R.25'(TDD), 'R.26'(TDD), 'R.27'(TDD), 'R.43'(FDD), 'R.44', 'R.45', 'R.48', 'R.50', and 'R.51'.
The fields PMISet and PRBSet determine the frequency-domain position that each precoded symbol in out occupies to apply the correct subband precoder when multiple PMI mode is being used. Alternatively, you can provide CodebookIdx field. CodebookIdx is a scalar specifying the codebook index to use across the entire bandwidth. Therefore, the CodebookIdx field does not support subband precoding. TS 36.213 [2], Section 7.2.4 specifies the relationship between PMI values and codebook indices.

Data Types: struct

Output Arguments

out — Precoded downlink output

matrix

Precoded downlink output, returned as an N_SYM-by-P matrix. N_SYM is the number of symbols per antenna, and P is the number of transmission antennas. The symbols for layers and antennas lie in columns rather than rows.

Data Types: double
Complex Number Support: Yes

Algorithms

For transmission schemes 'CDD', 'SpatialMux', and 'MultiUser', and degenerately 'Port0',

• Precoding involves multiplying a P-by-v precoding matrix, denoted as F, by a v-by-N_SYM matrix, representing N_SYM symbols on each of v transmission layers, to yield a P-by-N_SYM matrix, consisting of N_SYM precoded symbols on each of P antenna ports. Depending on the transmission scheme, the precoding matrix can be composed of multiple matrices multiplied together, but the size of the product, F, is always P-by-v.

For the 'TxDiversity' transmission scheme,

• A P²-by-2v precoding matrix, F, is multiplied by a 2v-by-N_SYM matrix, formed by splitting the real and imaginary components of a v-by-N_SYM matrix of symbols on layers, to yield a P²-by-N_SYM matrix of precoded symbols, which is then reshaped into a P-by-PN_SYM matrix for transmission. As v = P for the 'TxDiversity' transmission scheme, we can consider F be of size P²-by-2P rather than P²-by-2v.

For the other cases, specifically 'CDD', 'SpatialMux', and 'MultiUser' transmission schemes with v ≠ P, and the 'TxDiversity' transmission scheme with P = 4,

• The precoding matrix F is not square; it is rectangular with size P-by-v except for the 'TxDiversity' transmission scheme with P = 4 where it is of size P²-by-(2P= 16)-by-8. The number of rows is always greater than the number of columns that is, the matrix F is size m-by-n with m-by-n.

References

[1] 3GPP TS 36.211. “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation.” 3rd Generation Partnership Project; Technical Specification Group Radio Access Network. URL: https://www.3gpp.org.

[2] 3GPP TS 36.213. “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures.” 3rd Generation Partnership Project; Technical Specification Group Radio Access Network. URL: https://www.3gpp.org.

Version History

Introduced in R2014a