How to combine 340 sub matrices of 117 by 1 into one matrix of 9945 by 1. I'm working on ofdm(subcarriers=128, cp length=32) and got 117 data carriers. That's why ofdm requires input matrix of 117 by 1

kindly tell me how to combine these subsets in one matrix. for example I'm working on following lines.

st=rand(9945,4)
for n=1:85
 Baserow = (n-1) * 117;
for n1 = 1:4
Subset = st(Baserow+(1:117),n1, :)
txSig = ofdmMod(Subset);                      
>> y = awgn(txSig, SNR(k));
>> sigRx = ofdmDemod(y);
end
end

I'm getting 340 sub matrices of "Sigtx" of 117 by 1. How to combine them in a single matrix?

thanku.

[madhan ravi]

ofdmMod?

[Sajid Sarwar]

M = 4;                 % Modulation alphabet
k = log2(M);           % Bits/symbol
numSC = 128;           % Number of OFDM subcarriers
cpLen = 32;            % OFDM cyclic prefix length
ofdmMod = comm.OFDMModulator('FFTLength',numSC,'CyclicPrefixLength',cpLen);
ofdmDemod =        comm.OFDMDemodulator('FFTLength',numSC,'CyclicPrefixLength',cpLen);
channel = comm.AWGNChannel('NoiseMethod','Variance', ...
    'VarianceSource','Input port');
ofdmDims = info(ofdmMod)
numDC = ofdmDims.DataInputSize(1)

[Sajid Sarwar]

madhan ravi sir,

M = 4;                 % Modulation alphabet
k = log2(M);           % Bits/symbol
numSC = 128;           % Number of OFDM subcarriers
cpLen = 32;            % OFDM cyclic prefix length
ofdmMod = comm.OFDMModulator('FFTLength',numSC,'CyclicPrefixLength',cpLen);
ofdmDemod =        comm.OFDMDemodulator('FFTLength',numSC,'CyclicPrefixLength',cpLen);
channel = comm.AWGNChannel('NoiseMethod','Variance', ...
    'VarianceSource','Input port');
ofdmDims = info(ofdmMod)
numDC = ofdmDims.DataInputSize(1)

[Stephen23]

@Sajid Sarwar: please do NOT post the same question multiple times. It does not make it faster or easier for you to get help on this forum.

Answer 1

[Stephen23]

Add these three lines to your code:

C = cell(4,85);
...
for ii = 1:85
    ...
    for jj = 1:4
        sigRx = ...
        C{jj,ii} = sigRx;
    end
end
V = vertcat(C{:})

[Sajid Sarwar]

Stephen Cobeldick sir, getting following error.

C{jj,ii} = sigRx;

↑

Error: The expression to the left of the equals sign is not a valid target for an assignment.

[Sajid Sarwar]

how to fix following error.

C{jj,ii} = sigRx;

↑

Error: The expression to the left of the equals sign is not a valid target for an assignment.

[Stephen23]

Please show the output of this command:

whos sigRx

and upload your complete code by clicking the paperclip button.

[Sajid Sarwar]

correction in above question:

How to combine 340 sub matrices of 117 by 1 into one matrix of 9945 by 4. I'm working on ofdm(subcarriers=128, cp length=32) and got 117 data carriers. That's why ofdm requires input matrix of 117 by 1

[Sajid Sarwar]

CB(:,:,1) = [ 0                  0                  0                  0;...
             -0.1815-1j*0.1318  -0.6351-1j*0.4615   0.6351+1j*0.4615   0.1815+1j*0.1318;...
              0                  0                  0                  0;...
              0.7851            -0.2243             0.2243            -0.7851 ];

CB(:,:,2) = [ 0.7851            -0.2243             0.2243            -0.7851;...
              0                  0                  0                  0;...
             -0.1815-1j*0.1318  -0.6351-1j*0.4615   0.6351+1j*0.4615   0.1815+1j*0.1318;...
              0                  0                  0                  0 ];

CB(:,:,3) = [-0.6351+1j*0.4615   0.1815-1j*0.1318  -0.1815+1j*0.1318   0.6351-1j*0.4615;...
              0.1392-1j*0.1759   0.4873-1j*0.6156  -0.4873+1j*0.6156  -0.1392+1j*0.1759;...
              0                  0                  0                  0;...
              0                  0                  0                  0 ];

CB(:,:,4) = [ 0                  0                  0                  0;...
              0                  0                  0                  0;...
              0.7851            -0.2243             0.2243            -0.7851;...
             -0.0055-1j*0.2242  -0.0193-1j*0.7848   0.0193+1j*0.7848   0.0055+1j*0.2242 ];

CB(:,:,5) = [-0.0055-1j*0.2242  -0.0193-1j*0.7848   0.0193+1j*0.7848   0.0055+1j*0.2242;...
              0                  0                  0                  0;...
              0                  0                  0                  0;...
             -0.6351+1j*0.4615   0.1815-1j*0.1318  -0.1815+1j*0.1318   0.6351-1j*0.4615 ];

CB(:,:,6) = [ 0                  0                  0                  0;...
              0.7851            -0.2243             0.2243            -0.7851;...
              0.1392-1j*0.1759   0.4873-1j*0.6156  -0.4873+1j*0.6156  -0.1392+1j*0.1759;...
              0                  0                  0                  0 ];
M = 4;                 % Modulation alphabet
k = log2(M);           % Bits/symbol
numSC = 128;           % Number of OFDM subcarriers
cpLen = 32;            % OFDM cyclic prefix length
ofdmMod = comm.OFDMModulator('FFTLength',numSC,'CyclicPrefixLength',cpLen);
ofdmDemod =        comm.OFDMDemodulator('FFTLength',numSC,'CyclicPrefixLength',cpLen);
channel = comm.AWGNChannel('NoiseMethod','Variance', ...
    'VarianceSource','Input port');
errorRate = comm.ErrorRate('ResetInputPort',true);
ofdmDims = info(ofdmMod)
numDC = ofdmDims.DataInputSize(1)
K = size(CB, 1); % number of orthogonal resources
M = size(CB, 2); % number of codewords in each codebook
V = size(CB, 3); % number of users (layers)

N = 9945; % SCMA signals in frame

EbN0 = 0:20;
SNR  = EbN0 + 10*log10(log2(M)*V/K)+ 10*log10(numDC/numSC);

errorStats  = zeros(V, length(SNR));
Nbits = zeros(V, length(SNR));
BER   = zeros(V, length(SNR));

maxNumErrs = 100;
maxNumBits = 1e7;
Niter      = 10;
for k = 1:length(SNR)

    N0 = 1/(10^(SNR(k)/10)); % noise power

    while ((min(errorStats (:,k)) < maxNumErrs) && (Nbits(1,k) < maxNumBits))

x = randi([0 M-1], V, N); 
 K=4;
h = 1/sqrt(2)*(randn(K, V, N)+1j*randn(K, V, N));
s = scmaenc(x, CB, h);
>> st=transpose(s);
for n=1:85
 Baserow = (n-1) * 117;
for n1 = 1:4
Subset = st(Baserow+(1:117),n1, :)
txSig = ofdmMod(Subset)                    
>> y = awgn(txSig, SNR(k));
>> sigRx = ofdmDemod(y)
end
end

LLR = scmadec(sigRx, CB, h, N0, Niter);

        % symbol to bit conversion
        r    = de2bi(x, log2(M), 'left-msb');
        data = zeros(log2(M)*N, V);
        for kk = 1:V
            data(:,kk) = reshape(downsample(r, V, kk-1).',[],1);
        end

        % LLR to bit conversion
        datadec = reshape((LLR <= 0), [log2(M) N*V]).';
        datar   = zeros(log2(M)*N, V);
        for kk = 1:V
            datar(:,kk) = reshape(downsample(datadec, V, kk-1).', [], 1);
        end

    
%BER(k,:) = errorStats;
%errorStats = errorRate(x, sigRx,1);
err        = sum(xor(data, datar));
        errorStats (:,k)  = errorStats (:,k) + err.';
        Nbits(:,k) = Nbits(:,k) + log2(M)*N;
end
    BER(:,k) = errorStats (:,k)./Nbits(:,k);
    k
end


figure
semilogy(EbN0,BER)

% this is compelte code whereas there are separe files for scmadec, scmaenc and log_sum_exp

[Sajid Sarwar]

Above i have copied complete code whereas there are separate files for scmadec, scmaenc and log_sum_exp functions are attached below

[Stephen23]

"How to combine 340 sub matrices of 117 by 1 into one matrix of 9945 by 4"

The answer depends on the order that you want, which you did not tell us anything about. Try one of these:

C = {340 submatrices}
reshape([C{:}],9945,4)
reshape([C{:}].',9945,4)
reshape([C{:}],4,9945).'
reshape([C{:}].',4,9945).'

[Sajid Sarwar]

Stephen Cobeldick sir, "combine 340 sub matrices of 117 by 1 into one matrix of 9945 by 4" as follows:

st=rand(9945,4)
for n=1:85
 Baserow = (n-1) * 117;
for n1 = 1:4
Subset = st(Baserow+(1:117),n1, :)
txSig = ofdmMod(Subset);                      
>> y = awgn(txSig, SNR(k));
>> sigRx = ofdmDemod(y);
end
end

then output of sigRx(340 matrices of 117 by 1=9945 by 4

(a_1,1 a_1,2 a_1,3 a_1,4

uptill uptill uptill uptill

a_117,1 a_117,2 a_117,3 a_117,4

uptill uptill uptill uptill

a_9945,1 a_9945,2 a_9945,3 a_9945,4)

i have tried to write a matrix of 9945 by 4, which I required

[Stephen23]

" i have tried to write a matrix of 9945 by 4"

See my last comment, I showed you four ways to do this.

[Sajid Sarwar]

Stephen Cobeldick sir, "combine 340 sub matrices of 117 by 1 into one matrix of 9945 by 4" as follows:

st=rand(9945,4)
for n=1:85
 Baserow = (n-1) * 117;
for n1 = 1:4
Subset = st(Baserow+(1:117),n1, :)
txSig = ofdmMod(Subset);                      
>> y = awgn(txSig, SNR(k));
>> sigRx = ofdmDemod(y);
end
end

then output of sigRx(340 matrices of 117 by 1=9945 by 4

(a_1,1 a_1,2 a_1,3 a_1,4

uptill uptill uptill uptill

a_117,1 a_117,2 a_117,3 a_117,4

uptill uptill uptill uptill

a_9945,1 a_9945,2 a_9945,3 a_9945,4)

i have tried to write a matrix of 9945 by 4, which I required

[Stephen23]

@Sajid Sarwar: why are you just repeating your comments? So far you have totally ignored anything that I have written: your code does not show any attempt to use what I have shown you in my answer or my comments, so I am not quite sure how I can help you, if you just totally ignore what I write.