www.gusucode.com > MIMO与SISO仿真程序 > MIMO-OFDM/all code/SISO_v3_5_with64qam.m
% OFDM 2 transmitter/receiver transmission % Name: Benjamin Pham % Student ID: 25957066 % % Task: to simulate a transmission of data using OFDM technique % blocks to so simulate, modulation block, IFFT, P/S, % FFT, demodulate, recover signal. then add (2) Noise,(3) Multipath Channel clc;clear all;close all; warning off %% Set Parameters % amount of data to be transmitted % 64kb is 2^16 % ^20 is a megabit n = 16; bits = 2^n; p = log2(bits); %pilot length n_p = 0.1*bits; % Modulation type (4QAM or 16QAM) 4QAM = 1; 16QAM = 2; mod_type = '4QAM'; mod_types = {'4QAM','16QAM'}; mod_value = find (ismember (mod_types, mod_type)); % Eb/No assume 4G network, SNR = Eb/No * Rb/B % rb is bit rate = 100Mbps , B = 20MHz % Rb = 100*10^6; % B = 20*10^6; % fft/ifft size n_fft = 64; % cyclic prefix size n_cp = 16; % snr snr = [0:1:30]; % attenuationx attenuation = rand()+j*rand(); attenuation = attenuation/abs(attenuation); % eb_no = snr.*(B/Rb); t_data = round(rand(bits,1)); for mod_value = [1:3] % bits per symbol if mod_value == 1 symbols = 2; elseif mod_value == 2 symbols = 4; else symbols = 6; while floor(length(t_data)/symbols) ~= length(t_data)/symbols t_data = [t_data; zeros(1,1)]; %padding for symbol mapping end while floor(length(t_data)/symbols/n_fft) ~= length(t_data)/symbols/n_fft t_data = [t_data; zeros(6,1)]; %padding for subcarriers mapping end end %% TRANSMITTER %% symbol mapping % 4QAM, 16QAM % must be a char vector mod_method = 2^symbols; mod_data = qammod(t_data,mod_method,'unitaveragepower',true,'inputtype','bit'); %figure() %scatterplot(mod_data) %% IFFT % Moves the data from the time domain to the frequency domain X = mod_data; X_blocks = reshape(X,n_fft,length(X)/n_fft); % reshape into 64 block subcarriers x = ifft(X_blocks); % Inverse fast fourier transform %% add CP x_cp = [x(:,(end - n_cp + 1) :end),x]; % add CP to end of data %% Parallel data to Serial stream x_s = x_cp(:); %% CHANNEL %% Multipath Channel % delays and attentuation that affects channel = 1; %attenuation; H_x = conv(x_s,channel,'same'); %H_x = x_s; %% AWGN Noise for i = 1:length(snr) H_noise = awgn(H_x,snr(i),'measured'); %% RECEIVER %% Serial to Parallel y_p = reshape(H_noise, n_fft, length(H_noise + n_cp - 1)/n_fft); % remove cp x_p_cp = y_p(:,(n_cp + 1):end); %% FFT % converts signal from time domain to frequency domain Y_blocks = fft(x_p_cp,n_fft); Y = reshape(Y_blocks, length(X),1); %% Channel Estimation % because we send pilot symbols, we can estimate the channel. symbols that % are known beforehand. So its the received signal divided by the pilot % symbol. H_hat = Y(1:n_p)./X(1:n_p); % estimating channel using pilot symbols %Y_hat = H_hat .* X(1:n_p); % % mean squared error % for m = 1:length(H_hat) % se(m) = (abs(Y(m) - Y_hat(m)))^2; % mse(m) = sum(se)/length(se); % end % mmse(mod_value,i) = min(mse); %% equalisation H_hate = mean(H_hat); % found a mistake where taking the abs of it caused a very weird results in the equalisation Y_blocks2 = Y_blocks./H_hate; % cancelling out the channel effects %% Demodulate y = qamdemod(Y_blocks,mod_method,'unitaveragepower',true,'outputtype','bit'); received_sym = y; received_sig = reshape(received_sym, length(t_data), 1); errors(mod_value,i) = 0; for k = [1:length(received_sig)] if received_sig(k) ~= t_data(k) errors(mod_value,i) = errors(mod_value,i) + 1; end end ber(mod_value,i) = errors(mod_value,i)/length(t_data); %% Demodulate equalistation part y2 = qamdemod(Y_blocks2,mod_method,'unitaveragepower',true,'outputtype','bit'); received_sym2 = y2; received_sig2 = reshape(received_sym2, length(t_data), 1); errors2(mod_value,i) = 0; for m = [1:length(received_sig2)] if received_sig2(m) ~= t_data(m) errors2(mod_value,i) = errors2(mod_value,i) + 1; end end ber2(mod_value,i) = errors2(mod_value,i)/length(t_data); end %figure() %semilogy(snr,ber(mod_value,:),'x-',snr,ber2(mod_value,:),'o-'); semilogy(snr,ber2(mod_value,:),'o-'); title('Single Transmitter and Receiver System'); legend('4QAM','16QAM','64QAM'); xlabel('SNR'); ylabel('BER'); grid on; hold on end