lteSLFrameOffsetPSCCH

PSCCH DM-RS sidelink subframe timing estimate

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Syntax

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

Description

example

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.

example

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

Examples

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Open Live Script

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));
Open Live Script

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

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

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

Data Types: char | string

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

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

Data Types: char | string

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

Cyclic shift for DM-RS, specified as 0, 3, 6 or 9. It only applies for V2X sidelink.

Data Types: double

Data Types: struct

Modulated sidelink waveform, specified as an NS-by-NR numeric matrix, where NS is the number of time-domain samples and NR 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

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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 LSF is the subframe length.

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

See Also

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Introduced in R2017a

LTE Toolbox Documentation

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