ofdm.rar_matlab的ofdm仿真_ofdm_ofdm窗_ofdm窗函数_窗函数

clear all; close all; carrier_count=200;%子载波数 symbols_per_carrier=10;%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=1/4;%保护间隔与OFDM数据的比例 1/6~1/4 GI=PrefixRatio*IFFT_bin_length ;%每一个OFDM符号添加的循环前缀长度为1/4*IFFT_bin_length 即保护间隔长度为128 beta=1/32;%窗函数滚降系数 GIP=beta*(IFFT_bin_length+GI);%循环后缀的长度20 SNR=15; %信噪比dB %================信号产生=================================== 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 rand(1,carrier_count*symbols_per_carrier*4); % rand( 'twister',0); 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 %=================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，每一行即为个OFDM符号 %=====================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);%添加循环前缀 end for j=1:GIP; XX(k,IFFT_bin_length+GI+j)=signal_after_IFFT(k,j);%添加循环后缀 end end time_wave_matrix_cp=XX;%添加了循环前缀与后缀的时域信号矩阵,此时一个OFDM符号长度为IFFT_bin_length+GI+GIP=660 %==============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)';%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)+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,:);%并串转换，循环后缀与循环前缀相叠加 end %======================================================= Tx_data_withoutwindow =reshape(time_wave_matrix_cp',(symbols_per_carrier)*(IFFT_bin_length+GI+GIP),1)';%没有加窗，只添加循环前缀与后缀的串行信号 Tx_data =reshape(windowed_time_wave_matrix_cp',(symbols_per_carrier)*(IFFT_bin_length+GI+GIP),1)';%加窗后 循环前缀与后缀不叠加 的串行信号 %================================================================= temp_time1 = (symbols_per_carrier)*(IFFT_bin_length+GI+GIP);%加窗后 循环前缀与后缀不叠加 发送总位数 %=================未加窗发送信号频谱================================== symbols_per_average = ceil(symbols_per_carrier/5);%符号数的1/5，10行%2 avg_temp_time = (IFFT_bin_length+GI+GIP)*symbols_per_average;%点数，10行数据，10个符号%1320 averages = floor(temp_time1/avg_temp_time);%5 average_fft(1:avg_temp_time) = 0;%分成5段 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));%将发送信号分段求频谱 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 (6) subplot(2,1,1); 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 grid on ylabel('Magnitude (dB)') xlabel('归一化功率') title('OFDM信号功率谱密度') %===============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); 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 grid on ylabel('Magnitude (dB)') xlabel('归一化功率 ') title('升余弦窗函数对功率谱密度的影响')