ltePSCCH

Physical sidelink control channel

Syntax

sym = ltePSCCH(cw)

Description

sym = ltePSCCH(cw) returns a column vector containing the physical sidelink control channel (PSCCH) complex symbols for the input codeword bits. Channel processing performed by the function includes PSCCH-specific scrambling, QPSK modulation, and SC-FDMA transform precoding, as defined in TS 36.211 [1], Section 9.4.

For more information, see Physical Sidelink Control Channel Processing.

Examples

Generate SCI Message on PSCCH

Create a codeword using an encoded SCI message payload and process the bits on the PSCCH.

Create a UE settings structure and use it to generate SCI message bits. Produce an encoded SCI message codeword.

ue = struct('NSLRB',50,'CyclicPrefixSL','Normal');
[~,scibits] = lteSCI(ue);

cw = lteSCIEncode(ue,scibits);

Generate PSCCH symbols. View the length of the symbol column vector. Plot the constellation to show the effect of the SC-FDMA precoding on the modulation symbols.

symbols = ltePSCCH(cw);
numSymbols = size(symbols)

numSymbols = 1×2

   144     1

plot(symbols,'o')

Input Arguments

cw — PSCCH codeword

vector

PSCCH codeword, specified as an M_bit-by-1 integer vector. M_bit is the number of bits transmitted on the physical sidelink control channel in one subframe and must be a multiple of 12. For more information, see Physical Sidelink Control Channel Processing.

Data Types: double | int8

Output Arguments

sym — Modulated PSCCH symbols

column vector

Modulated PSCCH symbols, returned as an N_RE-by-1 column vector. N_RE is number of PSCCH resource elements in a subframe. For more information, see Physical Sidelink Control Channel Processing.

More About

Physical Sidelink Control Channel Processing

Physical sidelink control channel (PSCCH) processing includes PSCCH-specific scrambling, QPSK modulation, and SC-FDMA transform precoding. PSCCH processing follows the processing steps used for PUSCH, with variations defined in TS 36.211, Section 9.4.

For PSCCH, the input codeword length is M_bits = N_RE × N_bps, where N_RE is the number of PSCCH resource elements in a subframe and N_bps is the number of bits per symbol. Because the PSCCH is QPSK modulated, there are 2 bits per symbol. Nominally, the codeword length for PSCCH is 288 bits for D2D normal cyclic prefix, 240 bits for D2D extended cyclic prefix and 480 for V2X. Nominally, N_RE is 144 for D2D normal cyclic prefix or 120 for D2D extended cyclic prefix. For V2X, it is 240 defined for normal cyclic prefix only. Specifically, N_RE = N_PRB × N_REperPRB × N_SYM and includes symbols associated with the sidelink SC-FDMA guard symbol.

• N_PRB is the number of physical resource blocks (PRB) used for transmission. PSCCH is transmitted on a single PRB.

• N_REperPRB is the number of resource elements in a PRB. Each PRB has 12 resource elements.

• N_SYM is the number of SC-FDMA symbols in a PSCCH subframe, including symbols associated with the sidelink SC-FDMA guard symbol. The number of SC-FDMA symbols is a PSCCH subframe is 12 for D2D normal cyclic prefix or 10 for D2D extended cyclic prefix and V2X.

For D2D sidelink, when an SCI message is sent as a sidelink shared grant, it is transmitted twice on two separate PSCCH instances within the associated PSCCH resource pool. For V2X, only a single instance of PSCCH is transmitted for each scheduling grant.

Physical Sidelink Control Channel Indexing

Use the ltePSCCHIndices indexing function and the corresponding ltePSCCH sequence function to populate the PSCCH subframe resource grid. The PSCCH is transmitted in the available SC-FDMA symbols in a PSCCH subframe, using a single layer representing antenna port 1000. It excludes each symbol per slot assigned to PSCCH DM-RS. For more information on PSCCH DM-RS, see the ltePSCCHDRSIndices function.

The indices are ordered as the PSCCH QPSK modulation symbols should be mapped, applying frequency-first mapping. The resource elements in the last SC-FDMA symbol within a subframe are counted in the mapping process but should not be transmitted. The sidelink-specific SC-FDMA modulation creates this guard symbol.

For more information on mapping symbols to the resource element grid, see Resource Grid Indexing.

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.

Version History

Introduced in R2016b