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lteULFrameOffsetPUCCH3

PUCCH format 3 DM-RS uplink subframe timing estimate

Syntax

offset = lteULFrameOffsetPUCCH3(ue,chs,waveform)
[offset corr] = lteULFrameOffsetPUCCH3(ue,chs,waveform)

Description

example

offset = lteULFrameOffsetPUCCH3(ue,chs,waveform) performs synchronization using PUCCH format 3 demodulation reference signals (DM-RS) for the time-domain waveform, waveform, given UE-specific settings, ue, and PUCCH format 3 configuration, chs.

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

offset provides subframe timing; frame timing can be achieved by using offset with the subframe number, ue.NSubframe. This behavior is consistent with real-world operation because the base station knows when, or in which subframe, to expect uplink transmissions.

example

[offset corr] = lteULFrameOffsetPUCCH3(ue,chs,waveform) also returns a complex-valued matrix corr, which is the signal used to extract the timing offset.

Examples

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Synchronize and demodulate a transmission that has been delayed by seven samples using the PUCCH format 3 demodulation reference signal (DM-RS) symbols.

Initialize configuration structures (ue and pucch3).

ue = struct('NULRB',6,'NCellID',0,'NSubframe',0,'Hopping','Off');
ue.CyclicPrefixUL = 'Normal';
ue.NTxAnts = 1;
ue.Shortened = 0;

pucch3 = struct('ResourceIdx',0);

On the transmit side, populate reGrid, generate waveform, and insert a delay of seven samples.

reGrid = lteULResourceGrid(ue);
reGrid(ltePUCCH3DRSIndices(ue,pucch3)) = ltePUCCH3DRS(ue,pucch3);
waveform = lteSCFDMAModulate(ue,reGrid);
tx = [zeros(7,1); waveform];

On the receive side, perform synchronization using the PUCCH format 3 DM-RS symbols for the time-domain waveform and demodulate adjusting for the frame timing estimate. Show estimated frame timing offset.

fOffset = lteULFrameOffsetPUCCH3(ue,pucch3,tx)
rxGrid = lteSCFDMADemodulate(ue,tx(1+fOffset:end));
fOffset =

     7

View the correlation peak for a transmission waveform that has been delayed. The transmission contains PUCCH format 3 demodulation reference signal (DM-RS) symbols avaliable for estimating the waveform timing.

UE Configuration

Create configuration structures for ue and pucch3.

ue = struct('NULRB',6,'NCellID',0,'NSubframe',0,'Hopping','Off');
ue.CyclicPrefixUL = 'Normal';
ue.NTxAnts = 1;
ue.Shortened = 0;

pucch3 = struct('ResourceIdx',0);

Generate Transmission Waveform

On the transmit side, populate a resource grid and generate a waveform containing PUCCH3 DM-RS.

reGrid = lteULResourceGrid(ue);
reGrid(ltePUCCH3DRSIndices(ue,pucch3)) = ltePUCCH3DRS(ue,pucch3);

tx = lteSCFDMAModulate(ue,reGrid);

Waveform Reception

On the receive side, calculate timing offset using the PUCCH3 DM-RS symbols for the time-domain waveform and return the correlations for the transmit waveform and for a delayed version of the transmit waveform.

[~,corr] = lteULFrameOffsetPUCCH3(ue,pucch3,tx);

txDelayed = [zeros(7,1); tx];
[offset,corrDelayed] = lteULFrameOffsetPUCCH3(ue,pucch3,txDelayed);

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.

rrxGrid = lteSCFDMADemodulate(ue,txDelayed(1+offset:end));

Input Arguments

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UE-specific settings, specified as a structure with the following fields.

Parameter FieldRequired or OptionalValuesDescription
NULRBRequired

Scalar integer from 6 to 110

Number of uplink resource blocks. (NRBUL)

NCellIDRequired

Integer from 0 to 503

Physical layer cell identity

NSubframeRequired

0 (default), nonnegative scalar integer

Subframe number

CyclicPrefixULOptional

'Normal' (default), 'Extended'

Cyclic prefix length

NTxAntsOptional

1 (default), 2, 4

Number of transmission antennas.

HoppingOptional

'Off' (default), 'Group'

Frequency hopping method.

ShortenedOptional

0 (default), 1

Option to shorten the subframe by omitting the last symbol, specified as 0 or 1. If 1, the last symbol of the subframe is not used. For subframes with possible SRS transmission, set Shortened to 1 to maintain a standard compliant configuration.

NPUCCHIDOptional

Integer from 0 to 503

PUCCH virtual cell identity. If this field is not present, NCellID is used as the identity.

Data Types: struct

PUCCH format 3 configuration, specified as a scalar structure with the following fields.

Parameter FieldRequired or OptionalValuesDescription
ResourceIdxOptional

0 (default), integer from 0 to 549, or vector of integers.

PUCCH resource indices which determine the physical resource blocks, cyclic shift, and orthogonal cover used for transmission (nPUCCH(3)). Define one index for each transmission antenna.

Data Types: struct

Time-domain waveform, specified as a numeric matrix. waveform must be a NS-by-NR matrix, where NS is the number of time-domain samples and NR is the number of receive antennas.

Generate waveform by SC-FDMA modulation of a resource matrix using the lteSCFDMAModulate function, or by using one of the channel model functions, lteFadingChannel, lteHSTChannel, or lteMovingChannel.

Data Types: double
Complex Number Support: Yes

Output Arguments

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Number of samples from the start of the waveform to the position in that waveform where the first subframe begins, returned as a scalar integer. 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 and 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 numeric matrix. corr has the same dimensions as waveform.

Introduced in R2014a

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