NR Symbol Demodulation of Complex Data Symbols

This example shows how to use the NR Symbol Demodulator block to demodulate complex NR data symbols to data bits or LLR values.

Set Input Data Parameters

Map modulation names to values. Set the NR Symbol Demodulator block with numerical values and configure the nrSymbolDemodulate (5G Toolbox) function with strings.

rng(0);
framesize = 10;

% 0 - BPSK
% 1 - QPSK
% 2 - 16-QAM
% 3 - 64-QAM
% 4 - 256-QAM
% 5 - pi/2-BPSK
% others - QPSK
modSelVal = [0;1;2;3;4;5];
modSelStr = {'BPSK','QPSK','16QAM','64QAM','256QAM','pi/2-BPSK'};

decType = 'Soft';

numframes = length(modSelVal);
dataSymbols  = cell(1,numframes);
modSelTmp = cell(1,numframes);
nrFcnOutput = cell(1,numframes);

Generate Input Data

Generate frames of random input samples. Convert the framed input data to a stream of samples and input the stream to the NR Symbol Demodulator Simulink® block.

for ii = 1:numframes
    dataSymbols{ii} = complex(randn(framesize,1),randn(framesize,1));
    modSelTmp{ii} = fi(modSelVal(ii)*ones(framesize,1),0,3,0);
end

idlecyclesbetweensamples = 0;
idlecyclesbetweenframes  = 0;
[sampleIn, ctrl] = whdlFramesToSamples(dataSymbols,idlecyclesbetweensamples,...
    idlecyclesbetweenframes);
[modSel, ~] = whdlFramesToSamples(modSelTmp,idlecyclesbetweensamples,...
    idlecyclesbetweenframes);
validIn = logical(ctrl(:,3)');

sampletime = 1;
samplesizeIn = 1;
simTime = size(ctrl,1)*8;

Run Model

Running the Simulink model exports the stream of demodulated samples from Simulink to the MATLAB® workspace.

modelname = 'nrhdlSymbolDemodulatorModel';
open_system(modelname);
set_param([modelname '/NRDemod/NR Symbol Demodulator'],'DecisionType',decType)
sim(modelname);

nrHDLOutput = sampleOut(validOut).';

Generate Reference Data

Demodulate data symbols with nrSymbolDemodulate function and use its output as a reference data.

for ii = 1:numframes
 nrFcnOutput{ii} = nrSymbolDemodulate(dataSymbols{ii},modSelStr{ii},'DecisionType',decType,1).';
end

Compare Model Output with Function Output

Compare the output of the Simulink model against the output of nrSymbolDemodulate function.

nrFcnOutput = double(cell2mat(nrFcnOutput));

figure(1)
stem(nrHDLOutput,'b')
hold on
stem(nrFcnOutput,'--r')
grid on
legend('Reference','Simulink')
xlabel('Sample Index')
ylabel('Magnitude')
title('Comparison of Simulink block and MATLAB function')