I try to run code for precoding in spatial multiplexing in MIMO from the book MIMO OFDM wireless communication system book and the code doesnt work.

% pre_MMSE.m

%MIMO-OFDM Wireless Communications with MATLAB¢ç Yong Soo Cho, Jaekwon Kim, Won Young Yang and Chung G. Kang

%2010 John Wiley & Sons (Asia) Pte Ltd

clear all; clf

%%%%%% Parameter Setting %%%%%%%%%

N_frame=100; N_packet=1000;

b=2; M=2^b; % Number of bits per symbol and Modulation order

mod_obj=modem.qammod('M',M,'SymbolOrder','Gray','InputType','bit');

demod_obj = modem.qamdemod(mod_obj);

NT=4; NR=4; sq2=sqrt(2); I=eye(NR,NR);

N_pbits = N_frame*NT*b;

N_tbits = N_pbits*N_packet;

fprintf('====================================================\n');

fprintf(' Pre-MMSE transmission');

fprintf('\n %d x %d MIMO\n %d QAM', NT,NR,M);

fprintf('\n Simulation bits : %d',N_tbits);

fprintf('\n====================================================\n');

SNRdBs = [0:2:20];

for i_SNR=1:length(SNRdBs)

SNRdB = SNRdBs(i_SNR);

noise_var = NT*0.5*10^(-SNRdB/10);

sigma = sqrt(noise_var);

rand('seed',1); randn('seed',1); N_ebits = 0;

%%%%%%%%%%%%% Transmitter %%%%%%%%%%%%%%%%%%

for i_packet=1:N_packet

msg_bit = randint(N_pbits,1); % bit generation

symbol = modulate(mod_obj,msg_bit).';

Scale = modnorm(symbol,'avpow',1); % normalization

Symbol_nomalized = reshape(Scale*symbol,NT,N_frame);

H = (randn(NR,NT)+j*randn(NR,NT))/sq2;

temp_W = H'*inv(H*H'+noise_var*I);

beta = sqrt(NT/trace(temp_W*temp_W')); % Eq.(12.17)

W = beta*temp_W;

Tx_signal = W*Symbol_nomalized;

%%%%%%%%%%%%% Channel and Noise %%%%%%%%%%%%%

Rx_signal = H*Tx_signal+sigma*(randn(NR,N_frame)+j*randn(NR,N_frame));

%%%%%%%%%%%%%% Receiver %%%%%%%%%%%%%%%%%%%%%

y = Rx_signal/beta; % Eq.(12.18)

Symbol_hat = reshape(y/Scale,NT*N_frame,1);

msg_hat = demodulate(demod_obj,Symbol_hat);

N_ebits = N_ebits + sum(msg_hat~=msg_bit);

end

BER(i_SNR) = N_ebits/N_tbits;

end

semilogy(SNRdBs,BER,'-k^','LineWidth',2); hold on; grid on;

xlabel('SNR[dB]'), ylabel('BER');

legend('Pre-MMSE transmission')

Question:

In the above code, there are lot of functions like modem.qammod , randint that are outdated and are not supported by MATLAB anymore but does have equivalent syntaxes that is supported by the current MATLAB bUT i couldnot find the equivalent of syntax 'modulate' anywhere in the google.Does someone know about this ?

[Harsh]

Hi Samina,

The 'modem.qammod' is not needed anymore, you may remove it. Further, the 'modulate' syntax line can be replaced by the following.

symbol = qammod(msg_bit,M,'gray','InputType','bit')

Answer 1

[wael]

Hello Samina,

If you work with matlab 2016 and later versiones, So mostly the line (msg_bit = randint(N_pbits,1); % bit generation) would not work because the command randint was removed from matlab and you need to work with another command.