How can I simulate the MIMO section only?

Question

Liam 2024-4-18

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2108731-how-can-i-simulate-the-mimo-section-only

回答： Sam Chak 2024-4-21

I am using the example found here: https://uk.mathworks.com/help/phased/ug/improve-snr-and-capacity-of-wireless-communication-using-antenna-arrays.html?searchHighlight=ULA%20MIMO&s_tid=srchtitle_support_results_24_ULA%2520MIMO

How can I just simulate the MIMO section without using the helperMIMOBER function in the example? as the version of MATLAB I am using does not support the function nargin.

I need to simulate this so I can compared existing SISO results which I have obtained previously.

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Sam Chak 2024-4-18

在 MATLAB Online 中打开

Hi @Liam, I couldn't locate the custom helperMIMOBER() function in the provided link. However, @Star Strider shared the function in this comment, and the nargin command is not a new command or function.

function nber = helperMIMOBER(chan, x, snr_param, wt, wr) 
    Nsamp   = size(x,1);
    Nrx     = size(chan,2);
    Ntx     = size(chan,1);
    
    if nargin < 4
        wt = ones(1,Ntx);
    end
    
    if nargin < 5
        wr = ones(Nrx,1);
    end 
    
    xt      = 1/sqrt(Ntx)*(2*x-1)*wt; % map to bpsk
    nber    = zeros(Nrx,numel(snr_param),‘like’,1); % real
    
    for m = 1:numel(snr_param)
        n   = sqrt(db2pow(-snr_param(m))/2)*(randn(Nsamp,Nrx)+1i*randn(Nsamp,Nrx));
        y   = xt*chan*wr+n*wr;
        xe  = real(y)>0;
        nber(:,m) = sum(x~=xe);
    end
end

Liam 2024-4-21

But what I am stuck with is how this: xt = 1/sqrt(Ntx)*(2*x-1)*wt maps to BPSK. and how would i map it to QPSK? would I square it or multiply it all by 2?

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Answer 1

Sam Chak 2024-4-21

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2108731-how-can-i-simulate-the-mimo-section-only#answer_1445206

在 MATLAB Online 中打开

While I'm not an expert in BPSK and QPSK, I haven't encountered any problems when running the script in the link you provided and 'helperMIMOBER()' code on this MATLAB Answers forum.

%% The Script:
c           = 3e8;      % propagation speed
fc          = 60e9;     % carrier frequency
lambda      = c/fc;     % wavelength
txcenter    = [0;0;0];
rxcenter    = [1500;500;0];
[~,txang]   = rangeangle(rxcenter,txcenter);
[~,rxang]   = rangeangle(txcenter,rxcenter);
txsipos     = [0;0;0];
rxsopos     = [0;0;0];
g           = 1;        % gain for the path
sisochan    = scatteringchanmtx(txsipos,rxsopos,txang,rxang,g);
Nsamp       = 1e6;
x           = randi([0 1],Nsamp,1);
ebn0_param  = -10:2:10;
Nsnr        = numel(ebn0_param);
% Now, we call the helperMIMOBER() function:
ber_siso    = helperMIMOBER(sisochan,x,ebn0_param)/Nsamp
ber_siso = 1x11
    0.3274    0.2866    0.2396    0.1861    0.1310    0.0789    0.0374    0.0123    0.0023    0.0002    0.0000
<mw-icon class=""></mw-icon>
<mw-icon class=""></mw-icon>
%% the helperMIMOBER() function
function nber = helperMIMOBER(chan, x, snr_param, wt, wr) 
    Nsamp   = size(x,1);
    Nrx     = size(chan,2);
    Ntx     = size(chan,1);
    
    if nargin < 4
        wt = ones(1,Ntx);
    end
    
    if nargin < 5
        wr = ones(Nrx,1);
    end 
    
    xt      = 1/sqrt(Ntx)*(2*x-1)*wt; % map to bpsk
    nber    = zeros(Nrx,numel(snr_param), 'like', 1); % real
    
    for m = 1:numel(snr_param)
        n   = sqrt(db2pow(-snr_param(m))/2)*(randn(Nsamp,Nrx)+1i*randn(Nsamp,Nrx));
        y   = xt*chan*wr+n*wr;
        xe  = real(y)>0;
        nber(:,m) = sum(x~=xe);
    end
end