(完整版)OFDMmatlab实现

1、clear all;close all;carrier_cou nt=200;% 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_le ngth=512;%FFT 点数PrefixRatio=1/4;%保护间隔与 OFDM 数据的比例 1/61/4GI=PrefixRatio*IFFT_bin_length ;%每一个 OFDM 符号添加的循环前缀长度为1/4*IFFT bin le ngth即保护间隔长度为 128beta=1/32;%窗函数滚降系数GIP=beta*(IFFT

2、bin le ngth+GI);%循环后缀的长度 20SNR=15; % 信噪比 dB%=%=信号产生=baseba nd_out_le ngth = carrier_co unt * symbols_per_carrier * bits_per_symbol;%所输入的比特数目carriers = (1:carrier_co unt) + (floor(IFFT_b in_len gth/4) - floor(carrier_co un t/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 le ngth - carrier

3、s + 2;%共轭对称子载波映射共轭复数对应的 IFFT 点坐标ran d( state,0);baseba nd_out=rou nd(ra nd(1,baseba nd_out_le ngth);%输出待调制的二进制比特流%=16QAM 调制=complex carrier matrix=qam16(baseba nd out);%歹 U 向量complex carrier matrix=reshape(complex carrier matrix,carrier co un t,symbols per carrier);%symbols per carrier*carrier co un

4、t矩阵figure(1);plot(complex carrier matrix,*r);%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 le ngth 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 modulati on (:,conjugate carriers ) = con

5、j(complex carrier matrix);%共轭复数映射%=figure(2);stem(O:IFFT bin le ngth-1, abs(IFFT modulatio n(2,1:IFFT bin le ngth),b*-)%第一个OFDM 符号的频谱grid onaxis (0 IFFT bin length -0.5 4.5);ylabel(Mag nitude);xlabel(IFFT Bi n);title(OFDM Carrier Frequency Magnitude);figure(3);plot(0:IFFT bin length-1, (180/pi)*angl

6、e(IFFT modulation(2,1:IFFT bin length), go)hold onstem(0:carriers-1, (180/pi)*angle(IFFT_modulation(2,1:carriers),b*-);%第一个 OFDM 符号的相位stem(0:conjugate_carriers-1,(180/pi)*a ngle(IFFT_modulatio n(2,1:conjugate_carriers),b*-);axis (0 IFFT bin le ngth -200 +200)grid onylabel(Phase (degrees)xlabel(IFFT

7、Bi n)title(OFDM CarrierPhase) %=signal_after_IFFT=ifft(IFFT_modulation,IFFT_bin_length,2);%OFDM调制即 IFFT 变换time_wave_matrix =sig nal_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figure(4);subplot(3,1,1);plot(0:IFFT bin le ngth-1,time wave matrix(2,:);%第一个符号的波形axis(0, 700,-0.2, 0.2)

8、;grid on;ylabel(Amplitude);xlabel(Time);title(OFDM Time Signal, One Symbol Period);%= %=添加循环前缀与后缀XX=zeros(symbols_per_carrier,IFFT_bine ngth+GI+GIP);for k=1:symbols per carrier;for i=1:IFFT bin le ngth;XX(k,i+GI)=sig nal after IFFT(k,i);endfor i=1:GI;XX(k,i)=sig nal_after_IFFT(k,i+IFFT_bin_le ngth-G

9、I);%添加循环前缀endfor j=1:GIP;XX(k,IFFT bin le ngth+GI+j)=sig nal after IFFT(k,j);%添加循环后缀endendtime_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=660subplot(3,1,2);plot(0:le ngth(time_wave_matrix_cp)-1,time_wave_matrix_cp(2,:);%第一个符号添加循环前缀后的波形axis(0, 700,-0.2, 0.2);grid on;y

10、label(Amplitude);xlabel(Time);title(OFDM Time Signal with CP, One Symbol Period);%=OFDM 符号加窗wi ndowed time wave matrix cp=zeros(1,IFFT binen gth+GI+GIP);for i = 1:symbols per carrierwi ndowed time wave matrix cp(i,:)=real(time_wave_matrix_cp(i,:).*rcoswi ndow(beta,IFFT_bin_le ngth+GI);%加窗升余弦窗endsubp

11、lot(3,1,3);plot(0:IFFT bin le ngth-1+GI+GIP,wi ndowed time wave matrix cp(2,:);%第一个符号的波形axis(0, 700, -0.2, 0.2);grid on;ylabel(Amplitude);xlabel(Time);title(OFDM Time Signal Apply a Window , One Symbol Period);=生成发送信号，并串变换wi ndowed Tx data=zeros(1,symbols per carrier*(IFFT b inen gth+GI)+GIP);wi ndo

12、wed Tx data(1:IFFT bi n en gth+GI+GIP)=wi ndowed time wave matrix cp(1,:); for i = 1:symbolsper carrier-1 ;wi ndowed_Tx_data(IFFT_bine ngth+GI)*i+1:(IFFT_bine ngth+GI)*(i+1)+GIP)=wi ndowed_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 withoutwi ndow=reshape(time_wave_matrix_cp,(symbols_

13、per_carrier)*(IFFT_bi n_len gth+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(w in dowed_time_wave_matrix_cp,(symbols_per_carrier)*(IFFT_b in_len gth+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figure (5)subplot(2,1,1);plot(0:temp

14、_time1-1,Tx_data );%循环前缀与后缀不叠加发送的信号波形grid onylabel(Amplitude (volts)xlabel(Time (samples)title(OFDM Time Sig nal)temp time2 =symbols per carrier*(IFFT b inen gth+GI)+GIP;subplot(2,1,2);plot(0:temp time2-1,wi ndowed 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)tit

15、le(OFDM Time Sig nal)%= 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_da

16、ta_withoutwi ndow(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endaverage fft log = 20*log10(average fft);figure (6)subplot(2,1,1);plot(0:(avg_temp_time-1)/avg_temp_time, averag

17、e_fft_log)%归一化0/avg_temp_time : (avg_temp_time-1)/avg_temp_timehold onplot(0:1/IFFT bin le ngth:1, -35, rd)grid onaxis(0 0.5 -40 max(average_fft_log)ylabel(Mag ni tude (dB)xlabel(Normalized Freque ncy (0.5 = fs/2)title(OFDM Signal Spectrum without windowing)%=加窗的发送信号频谱= symbols peraverage = ceil(sym

18、bols 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

19、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endaverage 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O/avg temp time:(avg temp time-1)/avg temp timehold onplo

20、t(0:1/IFFT bin le ngth:1, -35, rd)grid onaxis(0 0.5 -40 max(average_fft_log)ylabel(Mag ni tude (dB)xlabel(Normalized Freque ncy (0.5 = fs/2)title(Wi ndowed OFDM Sig nal Spectrum)%=添加噪声Tx sig nal power = var(w in dowed Tx data);%发送信号功率lin ear_SNR=10A(SNR/10);%线性信噪比no ise_sigma=Tx_sig nal_power/li nea

21、r_SNR;noise_scale_factor = sqrt(noise_sigma);%标准差 sigmano ise=ra ndn( 1,(symbols_per_carrier)*(IFFT_b in_len gth+GI)+GIP)* no ise_scale_factor;%产生正态分布噪声序列%noise=wgn(1,length(windowed_Tx_data),noise_sigma,complex);%产生复 GAUSS 白噪声信号Rx_data=wi ndowed_Tx_data +no ise;%接收到的信号加噪声%=接收信号串/并变换去除前缀与后缀Rx_data_m

22、atrix=zeros(symbols_per_carrier,IFFT_b in_len gth+GI+GIP);for i=1:symbols per carrier;Rx_data_matrix(i,:)=Rx_data(1,(i-1)*(IFFT_bin_le ngth+GI)+1:i*(IFFT_bin_le ngth+GI)+GIP);%串并变换endRx_data_complex_matrix=Rx_data_matrix(:,GI+1:IFFT_bin_le ngth+GI);%去除循环前缀与循环后缀，得到有用信号矩阵%=%Rx_carriers=Y1(:,carriers);% 除去 IFFT/FFT 变换添加的 0,选出映射的子载波%=%OFDM 解码 16QAM 解码%=FFT 变换=Y1=fft(Rx_data_comp