getPathFilters

Reconstruct the channel impulse response and perform timing offset estimation using path filters of an lte3DChannel System object.

Configure a channel for delay profile CDL-B from TR 38.901 Section 7.7.1, with 1000 ns delay spread, 2 transmit antennas, and 1 receive antenna.

lte3d = lte3DChannel.makeCDL('CDL-B',1000e-9);
lte3d.Seed = 11;
lte3d.TransmitAntennaArray.Size = [1 1 2];
lte3d.ReceiveAntennaArray.Size = [1 1 1];

Create an LTE waveform for reference measurement channel (RMC) R.10 (10MHz, QPSK, R=1/3, 2 CRS ports).

rmc = lteRMCDL('R.10');
rmc.TotSubframes = 1;
data = [1; 0; 0; 1];
[txWaveform,~,txInfo] = lteRMCDLTool(rmc,data);
lte3d.SampleRate = txInfo.SamplingRate;

Pass the waveform through the channel.

[rxWaveform,pathGains] = lte3d(txWaveform);

Perform timing offset estimation using cell-specific reference signals.

corrcfg.CellRS = 'On';
offset = lteDLFrameOffset(rmc,rxWaveform,corrcfg)

offset = 
15

Obtain the path filters used in channel filtering.

pathFilters = getPathFilters(lte3d);

Reconstruct the channel impulse response using the path filters and path gains. Take the average of path gains across all time samples (first dimension). Construct the impulse response, h, for each transmit and receive antenna. Sum the responses for each transmit antenna.

[~,Np,P,R] = size(pathGains);
Nh = size(pathFilters,1);
h = zeros([Nh P R]);
pathGains = permute(mean(pathGains,1),[2 3 4 1]);
for np = 1:Np
    h = h + pathFilters(:,np) .* pathGains(np,:,:);
end
h = permute(sum(h,2),[1 3 2]);
mag = abs(h);

Plot the magnitude of the channel impulse response.

plot(mag,'o:')
title('Magnitude of Channel Impulse Response')
xlabel('Samples')
ylabel('Magnitude')

Estimate the timing offset by finding the peak of the impulse response magnitude.

offset_ref = find(mag==max(mag)) - 1

offset_ref = 
15