OFDM.zip_ofdm_ofdm仿真_简单OFDM_链路仿真

clear all; close all; clc %% 参数设置 %% carrier_count = 200; symbols_per_carrier = 20; bits_per_symbol = 4; %16QAM = 4bit IFFT_bin_length = 512; %子载波个数 = FFT长度 PrefixRatio = 1/4; %循环前缀比值 GI = PrefixRatio*IFFT_bin_length; %保护间隔 beta = 1/32; %滚降系数 GIP = beta*(IFFT_bin_length+GI); %循环后缀长度 SNR = 30; %% OFDM信号产生 %% baseband_out_length = carrier_count*symbols_per_carrier*bits_per_symbol; %数据总bit数 carriers = (1:carrier_count)+(floor(IFFT_bin_length/4)-floor(carrier_count/2)); %OFDM符号子载波的序号 conjugate_carriers = flip(IFFT_bin_length-carriers-2,2); baseband_out = round(rand(1,baseband_out_length)); baseband_M = bi2M(baseband_out,2^bits_per_symbol); complex_carrier_matrix = qammod(baseband_M,2^bits_per_symbol); % scatterplot(complex_carrier_matrix) %星座图 complex_carrier_matrix = reshape(complex_carrier_matrix',carrier_count,symbols_per_carrier)'; %分解成20×200的矩阵形式 IFFT_modulation = zeros(symbols_per_carrier,IFFT_bin_length); IFFT_modulation(:,carriers) = complex_carrier_matrix; %将第一个200数据存入512子载波中 IFFT_modulation(:,conjugate_carriers) = conj(complex_carrier_matrix); %将第二个200数据存入512子载波中 signal_after_IFFT = ifft(IFFT_modulation,IFFT_bin_length,2); %对每一行进行IFFT变换 time_wave_matrix = signal_after_IFFT; %% 添加循环前、后缀 %% XX = zeros(symbols_per_carrier,IFFT_bin_length+GI+GIP); for k=1:symbols_per_carrier for i=1:GI XX(k,i) = signal_after_IFFT(k,i+IFFT_bin_length-GI); end %第一段数据：循环前缀128 for i=1:IFFT_bin_length XX(k,i+GI) = signal_after_IFFT(k,i); end %第二段数据：OFDM信号512 for j=1:GIP XX(k,IFFT_bin_length+GI+j) = signal_after_IFFT(k,j); end %第三段数据：循环后缀20 end time_wave_matrix_cp = XX; %% 加窗 %% windowed_time_wave_matrix_cp = zeros(symbols_per_carrier,IFFT_bin_length+GI+GIP); rolloff = 0.25; % Rolloff factor span = 6; % Filter span in symbols sps = 4; for i = 1:symbols_per_carrier windowed_time_wave_matrix_cp(i,:) = real(time_wave_matrix_cp(i,:)).*rcoswindow(beta,IFFT_bin_length+GI)'; end %% 形成串行发射信号 %% windowed_Tx_data = zeros(1,symbols_per_carrier*(IFFT_bin_length+GI)+GIP); windowed_Tx_data(1:IFFT_bin_length+GI+GIP)=windowed_time_wave_matrix_cp(1,:); for i=1:symbols_per_carrier-1 windowed_Tx_data((IFFT_bin_length+GI)*i+1:(IFFT_bin_length+GI)*(i+1)+GIP)=windowed_time_wave_matrix_cp(i+1,:); end %加窗+重叠,但后端信号的前缀覆盖了前端信号的后缀 Tx_data_withoutwindow = reshape(time_wave_matrix_cp',(symbols_per_carrier)*(IFFT_bin_length+GI+GIP),1)'; %未加窗+不重叠 Tx_data = reshape(windowed_time_wave_matrix_cp',(symbols_per_carrier)*(IFFT_bin_length+GI+GIP),1)'; %加窗+不重叠 temp_time1 = (symbols_per_carrier)*(IFFT_bin_length+GI+GIP); %% 未加窗+不重叠 信号频谱 %% symbols_per_average = ceil(symbols_per_carrier/5); %单个子载波时每段处理的符号数 avg_temp_time = (IFFT_bin_length+GI+GIP)*symbols_per_average; %N个子载波时每段处理的符号数 averages = floor(temp_time1/avg_temp_time); %段数 average_fft(1:avg_temp_time) = 0; for a = 0:(averages-1) subset_ofdm = Tx_data_withoutwindow(((a*avg_temp_time)+1):((a+1)*avg_temp_time)); %第a段 subset_ofdm_f = abs(fft(subset_ofdm)); %对第a段做fft average_fft = average_fft+(subset_ofdm_f/averages); %叠加取平均 end average_fft_log = 20*log10(average_fft); %功率谱dB %%%%%%%%%%%%%%%%%%%%%% 画图 %%%%%%%%%%%%%%%%%%%%% figure plot((0:(avg_temp_time-1))/avg_temp_time,average_fft_log) hold on grid on axis([0 0.5 -20 max(average_fft_log)]) xlabel('Normalized Frequency(0.5=fs/2)') ylabel('Mag(dB)') title('Without Window OFDM Signal Spectrum') %%%%%%%%%%%%%%%%%%%%%% 画图 %%%%%%%%%%%%%%%%%%%%% %% 加窗+不重叠 信号频谱 %% symbols_per_average = ceil(symbols_per_carrier/5); %单个子载波时每段处理的符号数 avg_temp_time = (IFFT_bin_length+GI+GIP)*symbols_per_average; %N个子载波时每段处理的符号数 averages = floor(temp_time1/avg_temp_time); %段数 average_fft(1:avg_temp_time) = 0; for a = 0:(averages-1) subset_ofdm = Tx_data(((a*avg_temp_time)+1):((a+1)*avg_temp_time)); %第a段 subset_ofdm_f = abs(fft(subset_ofdm)); %对第a段做fft average_fft = average_fft+(subset_ofdm_f/averages); %叠加取平均 end average_fft_log = 20*log10(average_fft); %功率谱dB %%%%%%%%%%%%%%%%%%%%%% 画图 %%%%%%%%%%%%%%%%%%%%% figure plot((0:(avg_temp_time-1))/avg_temp_time,average_fft_log) hold on grid on axis([0 0.5 -20 max(average_fft_log)]) xlabel('Normalized Frequency(0.5=fs/2)') ylabel('Mag(dB)') title('Window OFDM Signal Spectrum') %%%%%%%%%%%%%%%%%%%%%% 画图 %%%%%%%%%%%%%%%%%%%%% %% 加窗+重叠信号 AWGN %% Rx_data = awgn(windowed_Tx_data,SNR,'measured'); %% OFDM解调 %% Rx_data_matrix = zeros(symbols_per_carrier,IFFT_bin_length+GI+GIP); for i=1:symbols_per_carrier Rx_data_matrix(i,:) = Rx_data(1,(i-1)*(IFFT_bin_length+GI)+1:i*(IFFT_bin_length+GI)+GIP); end Rx_data_complex_matrix = Rx_data_matrix(:,GI+1:GI+IFFT_bin_length); %去掉前、后缀 Y1 = fft(Rx_data_complex_matrix,IFFT_bin_length,2); %FFT完成OFDM解调 Rx_carriers = Y1(:,carriers); % Rx_phase = angle(Rx_carriers); % Rx_mag = abs(Rx_carriers); % [M,N] = pol2cart(Rx_phase,Rx_mag); % Rx_complex_carrier_matrix = complex(M,N); figure plot(Rx_carriers,'*r'); axis([-4,4,-4,4]); grid on