OFDM.zip_cp_matlab_ofdm_循环前缀

% clear all; % close all; carrier_count=64;%子载波数 symbols_per_carrier=12;%每子载波含符号数 bits_per_symbol=4;%每符号含比特数,16QAM调制 IFFT_bin_length=512;%FFT点数 PrefixRatio=1/6;%保护间隔与OFDM数据的比例 1/6~1/4 GI=round(PrefixRatio*IFFT_bin_length);%每一个OFDM符号添加的循环前缀长度 即保护间隔长度 beta=1/32;%窗函数滚降系数 for SNR=1:0.1:15 %BER=[]; %SNR=10; %信噪比dB %================================================== %================信号产生=================================== for loop=1:20 baseband_out_length = carrier_count * symbols_per_carrier * bits_per_symbol;%所输入的比特数目 carriers = (1:carrier_count) + (floor(IFFT_bin_length/4) - floor(carrier_count/2));%共轭对称子载波映射 复数数据对应的IFFT点坐标 conjugate_carriers = IFFT_bin_length - carriers + 2;%共轭对称子载波映射 共轭复数对应的IFFT点坐标 baseband_out=round(rand(1,baseband_out_length));%输出待调制的二进制比特流 %==============16QAM调制==================================== complex_carrier_matrix=qam16(baseband_out);%列向量 complex_carrier_matrix=reshape(complex_carrier_matrix',carrier_count,symbols_per_carrier)';%symbols_per_carrier*carrier_count 矩阵 %==============画出16QAM调制后星座图==================================== % figure(1); % plot(complex_carrier_matrix,'*r');%16QAM调制后星座图 % title('16QAM调制后星座图') % axis([-4, 4, -4, 4]); % grid on %=================IFFT=========================== IFFT_modulation=zeros(symbols_per_carrier,IFFT_bin_length);%添0组成IFFT_bin_length IFFT 运算 IFFT_modulation(:,carriers ) = complex_carrier_matrix ;%未添加导频信号 ，子载波映射在此处 IFFT_modulation(:,conjugate_carriers ) = conj(complex_carrier_matrix);%共轭复数映射 %================================================================= signal_after_IFFT=ifft(IFFT_modulation,IFFT_bin_length,2);%OFDM调制 即IFFT变换 time_wave_matrix =signal_after_IFFT;%时域波形矩阵，行为每载波所含符号数，列ITTF点数，N个子载波映射在其内，每一行即为一个OFDM符号 %=========================================================== %=====================添加循环前缀==================================== XX=zeros(symbols_per_carrier,IFFT_bin_length+GI); 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);%添加循环前缀 end end time_wave_matrix_cp=XX;%e添加了循环前缀的时域信号矩阵,此时一个OFDM符号长度为IFFT_bin_lngth+GI=640 %==============OFDM符号加窗========================================== windowed_time_wave_matrix_cp=zeros(1 ,IFFT_bin_length+GI); for i = 1:symbols_per_carrier windowed_time_wave_matrix_cp(i,:) = real(time_wave_matrix_cp(i,:)).*rcoswindow(beta,IFFT_bin_length+GI);%循环后缀的长度20)';%加窗 升余弦窗 end %========================生成发送信号，并串变换================================================== windowed_Tx_data=zeros(1,symbols_per_carrier*(IFFT_bin_length+GI)); windowed_Tx_data(1:IFFT_bin_length+GI)=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))=windowed_time_wave_matrix_cp(i+1,:);%并串转换，循环后缀与循环前缀相叠加 end %======================================================= % Tx_data=reshape(windowed_time_wave_matrix_cp',(symbols_per_carrier)*(IFFT_bin_length+GI),1)'; %Tx_data2=reshape(windowed_time_wave_matrix_cp',(symbols_per_carrier)*(IFFT_bin_length+GI),1)';%加窗后 循环前缀与后缀不叠加 的串行信号 %================================================================= %============================发送信号波形===================================== % temp_time1 = (symbols_per_carrier)*(IFFT_bin_length+GI);%加窗后 循环前缀与后缀不叠加 发送总位数 % figure (2) % subplot(2,1,1); % plot(0:temp_time1-1,Tx_data );%循环前缀与后缀不叠加 发送的信号波形 % grid on % ylabel('Amplitude (volts)') % xlabel('Time (samples)') % title('循环前后缀不叠加的OFDM Time Signal') % temp_time2 =symbols_per_carrier*(IFFT_bin_length+GI); % subplot(2,1,2); % plot(0:temp_time2-1,windowed_Tx_data);%循环后缀与循环前缀相叠加 发送信号波形 % grid on % ylabel('Amplitude (volts)') % xlabel('Time (samples)') % title('循环前后缀叠加的OFDM Time Signal') %===============加窗的发送信号频谱================================= % symbols_per_average = ceil(symbols_per_carrier/5);%符号数的1/5，10行 % avg_temp_time = (IFFT_bin_length+GI+GIP)*symbols_per_average;%点数，10行数据，10个符号 % averages = floor(temp_time1/avg_temp_time); % average_fft(1:avg_temp_time) = 0;%分成5段 % for a = 0:(averages-1) % subset_ofdm = Tx_data(((a*avg_temp_time)+1):((a+1)*avg_temp_time));%利用循环前缀后缀未叠加的串行加窗信号计算频谱 % subset_ofdm_f = abs(fft(subset_ofdm));%分段求频谱 % average_fft = average_fft + (subset_ofdm_f/averages);%总共的数据分为5段，分段进行FFT，平均相加 % end % average_fft_log = 20*log10(average_fft); % figure (3) % subplot(2,1,2) % plot((0:(avg_temp_time-1))/avg_temp_time, average_fft_log)%归一化 0/avg_temp_time : (avg_temp_time-1)/avg_temp_time % hold on % plot(0:1/IFFT_bin_length:1, -35, 'rd') % grid on % axis([0 0.5 -40 max(average_fft_log)]) % ylabel('Magnitude (dB)') % xlabel('Normalized Frequency (0.5 = fs/2)') % title('加窗的发送信号频谱') %====================添加噪声AWGN================================= Tx_signal_power = var(windowed_Tx_data);%发送信号功率 linear_SNR=10^(SNR/10);%线性信噪比 noise_sigma=Tx_signal_power/linear_SNR; noise_scale_factor = sqrt(noise_sigma);%标准差sigma noise=randn(1,((symbols_per_carrier)*(IFFT_bin_length+GI)))*noise_scale_factor;%产生正态分布噪声序列 Rx_data=windowed_Tx_data +noise;%接收到的信号加噪声 %=====================接收信号 串/并变换 去除前缀========================================== Rx_data_matrix=zeros(symbols_per_carrier,IFFT_bin_length+GI); 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));%串并变换 end Rx_data_complex_matrix=Rx_data_matrix(:,GI+1:IFFT_bin_length+GI);%去除循环前缀，得到有用信号矩阵 %============================================================== % OFDM解码 16QAM解码 %=================FFT变换================================= Y1=fft(Rx_data_complex_matrix,IFFT_bin_length,2);%OFDM解码 即FFT变换 Rx_carriers=Y1(:,carriers);%除去IFFT/FFT变换添加的0，选出映射的子载波 %========================接收信号的星座图(极坐标)==================================== Rx_phase =angle(Rx_carriers);%接收信号的相位 Rx_mag = abs(Rx_carriers);%接收信号的幅度 % figure(4); % polar(Rx_phase, Rx_mag,'bd');%极坐标坐标下画出接收信号的星座图 % title('极坐标下的接收信号的星座图') %========================XY坐标接收信号的星座图============================================== [M, N]=pol2cart(Rx_phase, Rx_mag); Rx_complex_carrier_matrix= complex(M, N); % subplot(2,1,1); % plot(Rx_complex_carrier_matrix0,'*r');%XY坐标接收信号的星座图 % title('无GI接收信号的星座图') % axis([-4, 4, -4, 4]); % grid on % subplot(2,1,2); % plot(Rx_complex_carrier_matrix,'*b');%XY坐标接收信号的星座图 % title('有GI接收信号的星座图') % axis([-4, 4, -4, 4]); % grid on %====================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); %======================二进制比特流================================== baseband_in = Rx_decoded_binary_symbols; % figure(6); % subplot(2,1,1); % stem(baseband_out(1:100)); % title('输出待调制的二进制比特流') % subplot(2,1,2); % stem(baseband_in(1:100)); % title('接收解调后的二进制比特流') %================误码率计算========================================== bit_errors=find(baseband_in ~=baseband_out); bit_error_count = size(bit_errors, 2) ; ber(loop)=bit_error_count/baseband_out_length; end Ber=sum(ber)/20; BER6(round(10*SNR-9))