ltePSBCH

Physical sidelink broadcast channel

Syntax

sym = ltePSBCH(ue,cw)

Description

sym = ltePSBCH(ue,cw) returns a column vector containing the physical sidelink broadcast channel (PSBCH) symbols for the specified UE settings structure and PSBCH codeword bits. The function performs PSBCH-specific scrambling, QPSK modulation, and SC-FDMA transform precoding, as defined in TS 36.211 [1], Section 9.6. For more information, see Physical Sidelink Broadcast Channel Processing.

Examples

Encode PSBCH Codeword

Create a codeword using the SL-BCH transport channel and encode the bits on the PSBCH.

ue.NSLID = 1;
ue.CyclicPrefixSL = 'Normal';
codeword = lteSLBCH(ue,zeros(40,1));
symbols = ltePSBCH(ue,codeword);

The plot shows the effects of the SC-FDMA precoding on the QPSK modulation symbols.

plot(symbols,'o')

Input Arguments

ue — User equipment settings

structure

User equipment settings, specified as a parameter structure containing this field:

NSLID — Physical layer sidelink synchronization identity

integer from 0 to 355

Physical layer sidelink synchronization identity, specified as an integer from 0 to 355. ($$N_{\text{ID}}^{\text{SL}}$$)

Data Types: double

Data Types: struct

cw — PSBCH codeword

vector

PSBCH codeword, specified as a vector that must be a multiple of 144 bits in length. Since the PSBCH is QPSK modulated, there are 2 bits per symbol. Nominally, the length of cw is 2*N_RE bits, specifically 1152 bits for normal cyclic prefix or 864 for extended cyclic prefix. For V2X sidelink mode, the nominal length will be 1008 bits corresponding to 504 resource elements (it is defined for normal cyclic prefix only).

N_RE is the number of resource elements in a subframe, including the SC-FDMA guard symbol, and is a multiple of 72. Nominally, N_RE is 576 for normal cyclic prefix or 432 for extended cyclic prefix. For V2X sidelink mode, the nominal length will be 504 resource elements (it is defined for normal cyclic prefix only).

Data Types: double

Output Arguments

sym — Modulated PSBCH symbols

column vector

Modulated PSBCH symbols, returned as an N_RE-by-1 column vector.

N_RE is the number of resource elements in a subframe, including the SC-FDMA guard symbol, and is a multiple of 72. Nominally, N_RE is 576 for normal cyclic prefix or 432 for extended cyclic prefix. For V2X sidelink mode, the nominal length will be 504 resource elements (it is defined for normal cyclic prefix only).

Data Types: double
Complex Number Support: Yes

More About

Physical Sidelink Broadcast Channel Processing

The physical sidelink broadcast channel (PSBCH) is transmitted in the central 72 resource elements in the available SC-FDMA symbols of synchronization subframes. For D2D sidelink mode, the available symbols exclude the three symbols per slot assigned to the PSBCH DRS and sidelink synchronization signals. For V2X sidelink, a total of seven symbols will be excluded in a subframe (three symbols for PSBCH DRS and 4 for the PSSS/SSSS). The resource elements in the last SC-FDMA symbol within a subframe are counted in the mapping process. Before transmission, the PSBCH resource elements are removed from the last SC-FDMA symbol by lteSCFDMAModulate during the sidelink-specific SC-FDMA modulation and guard symbol creation.

If a terminal is transmitting a synchronization subframe, then it should be sent every 40 ms for D2D sidelink mode or every 160 ms for V2X, with the exact subframe dependent on the RRC-signaled subframe number offset (syncOffsetIndicator-r12). The subframe also contains values for the ltePSBCHDRSIndices on port 1010 and ltePSSSIndices and lteSSSSIndices on port 1020. No PSCCH or PSSCH transmission will occur in a sidelink subframe configured for synchronization purposes.

Physical Sidelink Broadcast Channel Indexing

Use the ltePSBCHIndices indexing function and the corresponding ltePSBCH sequence function to populate the resource grid for the desired synchronization subframe number. The indices are ordered as the PSBCH QPSK modulation symbols should be mapped, applying frequency-first mapping, and include indices for the last SC-FDMA guard symbol. The PSBCH values returned by ltePSBCH are ordered as they should be mapped into the resource elements of the adjacent symbols using ltePSBCHIndices. 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