lteSLFrameOffsetPSCCH

PSCCH DM-RS sidelink subframe timing estimate

Syntax

offset = lteSLFrameOffsetPSCCH(ue,waveform)

[offset,corr] = lteSLFrameOffsetPSCCH(ue,waveform)

Description

offset = lteSLFrameOffsetPSCCH(ue,waveform) performs synchronization using PSCCH demodulation reference signal (DM-RS) symbols for the time-domain waveform, waveform, given UE-specific settings, ue.

The returned offset indicates the number of samples from the start of the input waveform to the position in that waveform where the first subframe containing DM-RS begins.

[offset,corr] = lteSLFrameOffsetPSCCH(ue,waveform) also returns a complex matrix, corr, which is used to extract the timing offset.

Examples

Synchronize and Demodulate Transmission Containing PSCCH DM-RS

Synchronize and demodulate a transmission that has been delayed by five samples. The transmission contains PSCCH demodulation reference signal (DM-RS) symbols that are used when estimating the waveform timing offset.

Create a UE configuration specifying 15 resource blocks, a normal cyclic prefix, and a PRBSet of 1.

ue = struct('NSLRB',15,'CyclicPrefixSL','Normal','PRBSet',1);

Create a resource grid and modulate the waveform containing PSCCH DM-RS symbols.

txgrid = lteSLResourceGrid(ue);
txgrid(ltePSCCHDRSIndices(ue)) = ltePSCCHDRS;
txwaveform = lteSLSCFDMAModulate(ue,txgrid);

Add a time delay of five samples.

rxwaveform = [zeros(5,1); txwaveform];

Calculate the timing offset in samples.

offset = lteSLFrameOffsetPSCCH(ue,rxwaveform)

offset = 
5

Correct the timing offset and demodulate the received waveform.

rxGrid = lteSLSCFDMADemodulate(ue,rxwaveform(1+offset:end));

View Correlation Peak in PSCCH DM-RS Transmission

View the correlation peak for a transmission waveform that has been delayed by five samples. The transmission contains PSCCH demodulation reference signal (DM-RS) symbols available for estimating the waveform timing.

Create a UE configuration specifying 15 resource blocks, a normal cyclic prefix, and a PRBSet of 1.

ue = struct('NSLRB',15,'CyclicPrefixSL','Normal','PRBSet',1);

Create a resource grid and modulate the waveform containing PSCCH DM-RS symbols.

txgrid = lteSLResourceGrid(ue);
txgrid(ltePSCCHDRSIndices(ue)) = ltePSCCHDRS;
txwaveform = lteSLSCFDMAModulate(ue,txgrid);

Calculate the timing offset in samples.

[offset corr] = lteSLFrameOffsetPSCCH(ue,txwaveform);

Add a time delay of five samples.

rxwaveform = [zeros(5,1); txwaveform];

Calculate the timing offset in samples.

[offset corrDelayed] = lteSLFrameOffsetPSCCH(ue,rxwaveform);

Plot the correlation data before and after delay is added. Zoom in on the x-axis to view correlation peaks.

plot(corr)
hold on
plot(corrDelayed)
hold off
xlim([0 100])

Correct the timing offset and demodulate the received waveform.

rxGrid = lteSLSCFDMADemodulate(ue,rxwaveform(1+offset:end));

Input Arguments

ue — UE-specific settings

scalar structure

User equipment settings, specified as a parameter structure containing these fields:

SidelinkMode — Sidelink mode

'D2D' (default) | 'V2X' | optional

Sidelink mode, specified as 'D2D' or 'V2X'.

Data Types: char | string

NSLRB — Number of sidelink resource blocks

integer scalar from 6 to 110

Number of sidelink resource blocks, specified as an integer scalar from 6 to 110.

Example: 6, which corresponds to a channel bandwidth of 1.4 MHz.

Data Types: double

CyclicPrefixSL — Cyclic prefix length

'Normal' (default) | 'Extended' | optional

Cyclic prefix length, specified as 'Normal' or 'Extended'.

Data Types: char | string

PRBSet — Zero-based physical resource block index

integer | integer column vector | two-column integer matrix

Zero-based physical resource block (PRB) index, specified as an integer, an integer column vector, or a two-column integer matrix.

For D2D sidelink, the PSCCH is intended to be transmitted in a single PRB in a subframe and therefore, specifying PRBSet as a scalar PRB index is recommended. For V2X sidelink, the PSCCH is intended to be transmitted in a pair of consecutive PRB in a subframe, therefore PRBSet must be a column vector containing two consecutive indices. However, for a more general nonstandard multi-PRB allocation, PRBSet can be a set of indices specified as an integer column vector or as a two-column integer matrix corresponding to slot-wise resource allocations for PSCCH.

Data Types: double

CyclicShift — Cyclic shift for DM-RS

0 (default) | 3 | 6 | 9

Cyclic shift for DM-RS, specified as 0, 3, 6 or 9. The function uses this input only for V2X sidelink.

Data Types: double

Data Types: struct

waveform — Modulated sidelink waveform

numeric matrix

Modulated sidelink waveform, specified as an N_S-by-N_R numeric matrix, where N_S is the number of time-domain samples and N_R is the number of receive antennas. waveform should be at least one subframe long and contain the DM-RS signals.

You can generate this matrix by performing SC-FDMA modulation on a resource matrix. To perform this modulation, use the lteSLSCFDMAModulate function or one of the channel model functions, such as lteFadingChannel or lteMovingChannel.

Data Types: double
Complex Number Support: Yes

Output Arguments

offset — Offset number of samples

scalar integer

Offset number of samples, returned as a scalar integer. This output is the number of samples from the start of the waveform to the position in that waveform where the first subframe containing the DM-RS begins. offset is computed by extracting the timing of the peak of the correlation between waveform and internally generated reference waveforms containing DM-RS signals. The correlation is performed separately for each antenna. The antenna with the strongest correlation is used to compute offset.

Note

offset is the position of mod(max(abs(corr),LSF)), where L_SF is the subframe length.

corr — Signal used to extract the timing offset

numeric matrix

Signal used to extract the timing offset, returned as a complex numeric matrix. corr has the same dimensions as waveform.

Version History

Introduced in R2017a