lteULFrameOffsetPUCCH3

PUCCH format 3 DM-RS uplink subframe timing estimate

Syntax

offset = lteULFrameOffsetPUCCH3(ue,chs,waveform)

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

Description

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.

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

Examples

Synchronize and Demodulate Using PUCCH Format 3 DM-RS

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)

fOffset = 
7

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

View PUCCH Format 3 DM-RS Transmission Correlation Peaks

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

ue — UE-specific settings

structure

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

Parameter Field	Required or Optional	Values	Description
NULRB	Required	Scalar integer from 6 to 110	Number of uplink resource blocks. ($$N_{\text{RB}}^{\text{UL}}$$)
NCellID	Required	Integer from 0 to 503	Physical layer cell identity
NSubframe	Required	0 (default), nonnegative scalar integer	Subframe number
CyclicPrefixUL	Optional	'Normal' (default), 'Extended'	Cyclic prefix length
NTxAnts	Optional	1 (default), 2, 4	Number of transmission antennas.
Hopping	Optional	'Off' (default), 'Group'	Frequency hopping method.
Shortened	Optional	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.
NPUCCHID	Optional	Integer from 0 to 503	PUCCH virtual cell identity. If this field is not present, NCellID is used as the identity.

Data Types: struct

chs — PUCCH format 3 configuration

scalar structure

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

Parameter Field	Required or Optional	Values	Description
ResourceIdx	Optional	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 ($$n_{PUCCH}^{(3)}$$). Define one index for each transmission antenna.

Data Types: struct

waveform — Time-domain waveform

numeric matrix

Time-domain waveform, specified as a numeric matrix. waveform must be a N_S-by-N_R 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.

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

offset — Number of samples from the start of the waveform to the position in that waveform where the first subframe begins

scalar integer

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 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 numeric matrix. corr has the same dimensions as waveform.

Version History

Introduced in R2014a