MATLAB: Subscript indices must either be real positive integers or logicals

MATLAB

what should i do to not get this error? >> Subscript indices must either be real positive integers or logicals.

Best Answer

Remember,

Q(sqrt(EbN0))

means to take the square root of EbN0, and then try to use that square root as an index into the variable Q (which is a scalar.) There is no implied multiplication in MATLAB: if you want

Q .* sqrt(EbN0)

then you have to write that.

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MATLAB: Please help this semilogy error message

N = 100
ip = rand(1,N)>0.5; % generating 0,1 with equal probability
s = 2*ip-1; % 0 -> -1; 1 -> 0 >> BPSK modulation 
nRx_max = 3; %number of M branches
M_Rx = [1:nRx_max];
%EbN0dB1 = [0:2:12]; EbN0dB2 = [0:2:14]; EbN0dB3 = [0:2:16];
EbN0dB = 0:2:16;
%%%%% EGC %%%%%%%%%%%
for jj = 1:length(M_Rx)
    %%%Common values
    for k = 1:length(EbN0dB)
        n = 1/sqrt(2)*[randn(M_Rx(jj),N) + j*randn(M_Rx(jj),N)]; % White gaussian noise, 0dB variance
        h = 1/sqrt(2)*[randn(M_Rx(jj),N) + j*randn(M_Rx(jj),N)]; % Rayleigh fading channel
        % Channel and noise Noise addition
        sD = kron(ones(M_Rx(jj),1),s);
        %%% In different values of dBN0dB    
        y1 = h.*sD + 10^(-EbN0dB(k)/20)*n; %%%%% EbN0dB1 = [0:2:14] %%%%%%%%%%%                 % equalization with EGC
        y1Hat = y1.*exp(-j*angle(h));     % removing the phase of the channel
        y1Hat = sum(y1Hat,1);             % adding values from all the receive chains  
        % receiver Rx
        ip1Hat = real(y1Hat)>0;
        % numbers the errors
        nErr1(jj,k) = size(find([ip- ip1Hat]),2);    
    end
end
%theoryBer_nRx1 = 0.5.*(1-1*(1+1./EbN0Lin1).^(-0.5)); 
%theoryBer_nRx2 = 0.5*(1 - sqrt(EbN0Lin1.*(EbN0Lin1+2))./(EbN0Lin1+1) );
simBer1 = nErr1/N; % simulated ber
EbN0Lin1 = 10.^(EbN0dB/10); %EbN0 linear
close all
figure(1)
semilogy(EbN0dB(1:end-2),simBer1(1,1:end-2),'mo-','LineWidth',1);hold on;
semilogy(EbN0dB(1:end-1),simBer1(2,1:end-1),'kp-','LineWidth',1);hold on;
semilogy(EbN0dB,simBer1(3,:),'gs-','LineWidth',1);
grid on
legend('M=1', 'M=2', 'M=3');
xlabel('Eb/No, dB');
ylabel('Bit Error Rate');
title('BER for BPSK modulation with Equal Gain Combining in Rayleigh channel');
axis([0 20 10^-6 2])

Since you are creating vectors EbN0dB1 ...3, incrementally, with steps of 2, you can create one vector and access those parts individually,

Try the above

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