QPSK&OFDM.zip_16QAM OFDM-rayleigh_AWGN误码率16QAM_QPSK Rayleigh OFD

% 对OFDM系统进行建模，采用16QAM星座映射 clc; clear all; close all; %============= OFDM系统参数设置================ carrier_count=200; symbols_per_carrier=12; bits_per_symbol=4; IFFT_bin_length=512; PrefixRatio=1/4; GI=PrefixRatio*IFFT_bin_length; % 保护前缀长度 beta=1/16; %滚降系数 GIP=beta*(IFFT_bin_length+GI); %加窗扩展时域信号长度 SNR=0:30; for m=1:length(SNR) %=============发送端======================= %=============信号产生===================== baseband_out_length=carrier_count*symbols_per_carrier*bits_per_symbol; %%进行子载波共轭映射，使得OFDM符号经过IFFT之后是实信号 carriers=(1:carrier_count)+(floor(IFFT_bin_length/4)-floor(carrier_count/2)); conjugate_carriers=IFFT_bin_length-carriers+2; % rand('twister',0); baseband_out=round(rand(1,baseband_out_length)); %===============16QAM调制============= complex_carrier_matrix=qam16(baseband_out); complex_carrier_matrix=reshape(complex_carrier_matrix',carrier_count,symbols_per_carrier)'; %================IFFT================== IFFT_modulation=zeros(symbols_per_carrier,IFFT_bin_length); IFFT_modulation(:,carriers)=complex_carrier_matrix; IFFT_modulation(:,conjugate_carriers)=conj(complex_carrier_matrix); %=================未添加保护间隔的OFDM符号=================================== signal_after_IFFT=ifft(IFFT_modulation,IFFT_bin_length,2); time_wave_matrix=signal_after_IFFT; %================添加循环前缀与后缀================== XX=zeros(symbols_per_carrier,IFFT_bin_length+GI+GIP); for k=1:symbols_per_carrier for i=1:IFFT_bin_length XX(k,i+GI)=signal_after_IFFT(k,i); end for i=1:GI XX(k,i)=signal_after_IFFT(k,i+IFFT_bin_length-GI); end for j=1:GIP XX(k,IFFT_bin_length+GI+j)=signal_after_IFFT(k,j); end end time_wave_matrix_cp=XX; %==============OFDM符号加窗================================================= windowed_time_wave_matrix_cp=zeros(1,IFFT_bin_length+GI+GIP); 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 %========================生成发送信号，并串变换==================================== %这样做的目的在于将加窗的OFDM符号经过并串转换之后时，对于循环前缀是每个子信道都需要添加 %但是对于循环后缀不需要每个子信道都添加，因此串并之后只需要对整个串行符号添加就行 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 %================================================================================ Tx_data_withoutwindow =reshape(time_wave_matrix_cp',(symbols_per_carrier)*(IFFT_bin_length+GI+GIP),1)';%未添加窗信号 Tx_data =reshape(windowed_time_wave_matrix_cp',(symbols_per_carrier)*(IFFT_bin_length+GI+GIP),1)';%加窗发送信号 %=============================================================================== temp_time1 = (symbols_per_carrier)*(IFFT_bin_length+GI+GIP); temp_time2 =symbols_per_carrier*(IFFT_bin_length+GI)+GIP; %=================未加窗发送信号频谱=============================================== symbols_per_average = ceil(symbols_per_carrier/5); avg_temp_time = (IFFT_bin_length+GI+GIP)*symbols_per_average; averages = floor(temp_time1/avg_temp_time); 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)); subset_ofdm_f = abs(fft(subset_ofdm)); average_fft = average_fft + (subset_ofdm_f/averages); end average_fft_log = 20*log10(average_fft); %===============加窗的发送信号频谱================================================= % symbols_per_average = ceil(symbols_per_carrier/5); % avg_temp_time = (IFFT_bin_length+GI+GIP)*symbols_per_average; % averages = floor(temp_time1/avg_temp_time); % 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)); % subset_ofdm_f = abs(fft(subset_ofdm)); % average_fft = average_fft + (subset_ofdm_f/averages); % end % average_fft_log = 20*log10(average_fft); %===============添加噪声(AWGN信道)================== Tx_signal_power=var(windowed_Tx_data); linear_SNR=10^(SNR(m)/10); noise_sigma=Tx_signal_power/linear_SNR; noise_scale_factor=sqrt(noise_sigma); noise=randn(1,((symbols_per_carrier)*(IFFT_bin_length+GI)+GIP))*noise_scale_factor; Rx_data=windowed_Tx_data+noise; %==============接收端进行串并转换 去除循环前缀和后缀（对加窗信号进行处理）=========== 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:IFFT_bin_length+GI); %=============================================================================== %====================OFDM解调， 16QAM解星座映射================================== Y1=fft(Rx_data_complex_matrix,IFFT_bin_length,2); Rx_carriers=Y1(:,carriers); Rx_mag=abs(Rx_carriers); Rx_phase=angle(Rx_carriers); %============================================================================ [M, N]=pol2cart(Rx_phase, Rx_mag); Rx_complex_carrier_matrix = complex(M, N); %=============16QAM解调======================================================== Rx_serial_complex_symbols = reshape(Rx_complex_carrier_matrix',size(Rx_complex_carrier_matrix, 1)*size(Rx_complex_carrier_matrix,2),1)' ; Rx_decoded_binary_symbols=demoduqam16(Rx_serial_complex_symbols); %================================================================================ baseband_in = Rx_decoded_binary_symbols; %================误码率计算======================================================= bit_errors=find(baseband_in ~=baseband_out); bit_error_count = size(bit_errors, 2); ber(m)=bit_error_count/baseband_out_length; end figure; semilogy(SNR,ber,'r-^','linewidth',1.5); xlabel('SNR(dB)'); ylabel('BER'); title('the BER performance of the OFDM system(16QAM)'); grid on hold on