Matlab簡單的OFDM仿真信道估計有BER曲線備課講稿

1、Good is good, but better carries it.精益求精，善益求善。Matlab簡單的OFDM仿真，信道估計，有BER曲線-clearall;closeall;fprintf(nOFDM仿真nn);%-%參數定義%-%IFFT_bin_length=1024;carrier_count=200;bits_per_symbol=2;symbols_per_carrier=50;%子載波數200%位數/符號2%符號數/載波50%訓練符號數10%循環(huán)前綴長度T/4（作者注明）All-zeroCP%調制方式QDPSK%多徑信道數2、3、4（缺?。?信道最大時延7(單位數據符號)

2、%仿真條件收發(fā)之間嚴格同步%SNR=input(SNR=);%輸入信噪比參數SNR=3:14;%定義信噪比范圍BER=zeros(1,length(SNR);baseband_out_length=carrier_count*symbols_per_carrier*bits_per_symbol;%計算發(fā)送的二進制序列長度carriers=(1:carrier_count)+(floor(IFFT_bin_length/4)-floor(carrier_count/2);%坐標：(1to200)+156,157-356conjugate_carriers=IFFT_bin_length-car

3、riers+2;%坐標：1024-(157:356)+2=1026-(157:356)=(869:670)%構造共軛時間載波矩陣，以便應用所謂的RCC，ReducedComputationalComplexity算法，即ifft之后結果為實數%Definetheconjugatetime-carriermatrix%也可以用flipdim函數構造對稱共軛矩陣%-%信號發(fā)射%-%out=rand(1,baseband_out_length);%baseband_out1=round(out);%baseband_out2=floor(out*2);%baseband_out3=ceil(out*

4、2)-1;%baseband_out4=randint(1,baseband_out_length);%四種生成發(fā)送的二進制序列的方法，任取一種產生要發(fā)送的二進制序列%if(baseband_out1=baseband_out2&baseband_out1=baseband_out3)%fprintf(TransmissionSequenceGeneratednn);%baseband_out=baseband_out1;%else%fprintf(CheckCode!nn);%end%驗證四種生成發(fā)送的二進制序列的方法baseband_out=round(rand(1,baseband_ou

5、t_length);convert_matrix=reshape(baseband_out,bits_per_symbol,length(baseband_out)/bits_per_symbol);fork=1length(baseband_out)/bits_per_symbol),modulo_baseband(k)=0;fori=1:bits_per_symbolmodulo_baseband(k)=modulo_baseband(k)+convert_matrix(i,k)*2(bits_per_symbol-i);endend%每2個比特轉化為整數0至3%采用left-msb方式%

6、-%Testbylavabin%Abuilt-infunctionofdirectlychangebinarybitsintodecimalnumbers%-%convert_matrix1=zeros(length(baseband_out)/bits_per_symbol,bits_per_symbol);%convert_matrix1=convert_matrix;%Test_convert_matrix1=bi2de(convert_matrix1,bits_per_symbol,left-msb);%Test_convert_matrix2=bi2de(convert_matrix

7、1,bits_per_symbol,right-msb);%函數說明：%BI2DEConvertbinaryvectorstodecimalnumbers.%D=BI2DE(B)convertsabinaryvectorBtoadecimalvalueD.WhenBis%amatrix,theconversionisperformedrow-wiseandtheoutputDisa%columnvectorofdecimalvalues.Thedefaultorientationofthebinary%inputisRight-MSB;thefirstelementinBrepresentst

8、heleastsignificantbit.%if(modulo_baseband=Test_convert_matrix1)%fprintf(modulo_baseband=Test_convert_matrix1nnn);%elseif(modulo_baseband=Test_convert_matrix2)%fprintf(modulo_baseband=Test_convert_matrix2nnn);%else%fprintf(modulo_baseband=anyTest_convert_matrixnnn);%end%end%wegettheresultmodulo_baseb

9、and=Test_convert_matrix1.%-carrier_matrix=reshape(modulo_baseband,carrier_count,symbols_per_carrier);%生成時間載波矩陣%-%QDPSK調制%-%carrier_matrix=zeros(1,carrier_count);carrier_matrix;%添加一個差分調制的初始相位，為0fori=2symbols_per_carrier+1)carrier_matrix(i,=rem(carrier_matrix(i,+carrier_matrix(i-1,2bits_per_symbol);%差

10、分調制endcarrier_matrix=carrier_matrix*(2*pi)/(2bits_per_symbol);%產生差分相位X,Y=pol2cart(carrier_matrix,ones(size(carrier_matrix,1),size(carrier_matrix,2);%由極坐標向復數坐標轉化第一參數為相位第二參數為幅度%Carrier_plex_carrier_matrix=complex(X,Y);%添加訓練序列training_symbols=1jj1-1-j-j-11jj1-1-j-j-11jj1-1-j-j-11jj1-1-j-j-11jj1-1.-j-j-

11、11jj1-1-j-j-11jj1-1-j-j-11jj1-1-j-j-11jj1-1-j-j-11jj1-1-j-j-1.1jj1-1-j-j-11jj1-1-j-j-11jj1-1-j-j-11jj1-1-j-j-11jj1-1-j-j-11jj1.-1-j-j-11jj1-1-j-j-11jj1-1-j-j-11jj1-1-j-j-11jj1-1-j-j-11jj1-1-j-j.-11jj1-1-j-j-11jj1-1-j-j-11jj1-1-j-j-11jj1-1-j-j-1;%25times1jj1,25times-1-j-j-1,totally200symbolsasarowtra

12、ining_symbols=cat(1,training_symbols,training_symbols);training_symbols=cat(1,training_symbols,training_symbols);%Productionof4rowsoftraining_symbolscomplex_carrier_matrix=cat(1,training_symbols,complex_carrier_matrix);%訓練序列與數據合并%block-typepilotsymbolsIFFT_modulation=zeros(4+symbols_per_carrier+1,IF

13、FT_bin_length);%Herearowvectorofzerosisbetweentrainingsymbolsanddatasymbols!%4trainingsymbolsand1zerosymbol%everyOFDMsymboltakesarowofIFFT_modulationIFFT_modulation(:,carriers)=complex_carrier_matrix;IFFT_modulation(:,conjugate_carriers)=conj(complex_carrier_matrix);%-%Testbylavabin-Findtheindicesof

14、zeros%index_of_zeros=zeros(symbols_per_carrier,IFFT_bin_length-2*carrier_count);%IFFT_modulation1=zeros(4+symbols_per_carrier+1,IFFT_bin_length);%IFFT_modulation2=zeros(4+symbols_per_carrier+1,IFFT_bin_length);%IFFT_modulation1(6:symbols_per_carrier+5,=IFFT_modulation(6:symbols_per_carrier+5,=0;%for

15、i=1:symbols_per_carrier%index_of_zeros(i,=find(IFFT_modulation1(i+5,=1);%end%-time_wave_matrix=ifft(IFFT_modulation);%進行IFFT操作time_wave_matrix=time_wave_matrix;%IfXisamatrix,ifftreturnstheinverseFouriertransformofeachcolumnofthematrix.fori=1:4+symbols_per_carrier+1windowed_time_wave_matrix(i,:)=real

16、(time_wave_matrix(i,:);end%gettherealpartoftheresultofIFFT%這一步可以省略，因為IFFT結果都是實數%由此可以看出，只是取了IFFT之后載波上的點，并未進行CP的復制和添加endofdm_modulation=reshape(windowed_time_wave_matrix,1,IFFT_bin_length*(4+symbols_per_carrier+1);%P2Soperation%-%Testbylavabin%Anotherwayofmatrixtransition%ofdm_modulation_tmp=windowed_

17、time_wave_matrix.;%ofdm_modulation_test=ofdm_modulation_tmp(;%if(ofdm_modulation_test=ofdm_modulation)%fprintf(ofdm_modulation_test=ofdm_modulationnnn);%else%fprintf(ofdm_modulation_test=ofdm_modulationnnn);%end%Wegettheresultofdm_modulation_test=ofdm_modulation.%-Tx_data=ofdm_modulation;%-%信道模擬%-%d

18、1=4;a1=0.2;d2=5;a2=0.3;d3=6;a3=0.4;d4=7;a4=0.5;%信道模擬copy1=zeros(size(Tx_data);fori=1+d1:length(Tx_data)copy1(i)=a1*Tx_data(i-d1);endcopy2=zeros(size(Tx_data);fori=1+d2:length(Tx_data)copy2(i)=a2*Tx_data(i-d2);endcopy3=zeros(size(Tx_data);fori=1+d3:length(Tx_data)copy3(i)=a3*Tx_data(i-d3);endcopy4=ze

19、ros(size(Tx_data);fori=1+d4:length(Tx_data)copy4(i)=a4*Tx_data(i-d4);endTx_data=Tx_data+copy1+copy2+copy3+copy4;%4multi-pathsTx_signal_power=var(Tx_data);foridx=1:length(SNR)%montecarlo仿真模擬linear_SNR=10(SNR(idx)/10);noise_sigma=Tx_signal_power/linear_SNR;noise_scale_factor=sqrt(noise_sigma);noise=ra

20、ndn(1,length(Tx_data)*noise_scale_factor;Rx_Data=Tx_data+noise;%-%信號接收%-%Rx_Data_matrix=reshape(Rx_Data,IFFT_bin_length,4+symbols_per_carrier+1);Rx_spectrum=fft(Rx_Data_matrix);%SupposeprecisesynchronazitionbetweenTxandRxRx_carriers=Rx_spectrum(carriers,:);Rx_training_symbols=Rx_carriers(1:4),:);Rx_

21、carriers=Rx_carriers(5:55),:);%-%信道估計%-%Rx_training_symbols=Rx_training_symbols./training_symbols;Rx_training_symbols_deno=Rx_training_symbols.2;Rx_training_symbols_deno=Rx_training_symbols_deno(1,+Rx_training_symbols_deno(2,+Rx_training_symbols_deno(3,+Rx_training_symbols_deno(4,;Rx_training_symbol

22、s_nume=Rx_training_symbols(1,:)+Rx_training_symbols(2,:)+Rx_training_symbols(3,:)+Rx_training_symbols(4,:);Rx_training_symbols_nume=conj(Rx_training_symbols_nume);%取4個向量的導頻符號是為了進行平均優(yōu)化%都是針對“行向量”即單個的OFDM符號進行操作%原理：尋求1/H，對FFT之后的數據進行頻域補償%1/H=conj(H)/H2becauseH2=H*conj(H)Rx_training_symbols=Rx_training_sy

23、mbols_nume./Rx_training_symbols_deno;Rx_training_symbols=Rx_training_symbols_nume./Rx_training_symbols_deno;Rx_training_symbols_2=cat(1,Rx_training_symbols,Rx_training_symbols);Rx_training_symbols_4=cat(1,Rx_training_symbols_2,Rx_training_symbols_2);Rx_training_symbols_8=cat(1,Rx_training_symbols_4,

24、Rx_training_symbols_4);Rx_training_symbols_16=cat(1,Rx_training_symbols_8,Rx_training_symbols_8);Rx_training_symbols_32=cat(1,Rx_training_symbols_16,Rx_training_symbols_16);Rx_training_symbols_48=cat(1,Rx_training_symbols_32,Rx_training_symbols_16);Rx_training_symbols_50=cat(1,Rx_training_symbols_48

25、,Rx_training_symbols_2);Rx_training_symbols=cat(1,Rx_training_symbols_50,Rx_training_symbols);Rx_carriers=Rx_training_symbols.*Rx_carriers;%進行頻域單抽頭均衡Rx_phase=angle(Rx_carriers)*(180/pi);phase_negative=find(Rx_phase0);%-TestofUsingrem-%Rx_phase1=Rx_phase;%Rx_phase2=Rx_phase;%Rx_phase1(phase_negative)

26、=rem(Rx_phase1(phase_negative)+360,360);%Rx_phase2(phase_negative)=Rx_phase2(phase_negative)+360;%ifRx_phase2(phase_negative)=Rx_phase1(phase_negative)%fprintf(nThereisnoneedusingreminnegativephasetransition.n)%else%fprintf(nWeneedtousereminnegativephasetransition.n)%end%-Rx_phase(phase_negative)=re

27、m(Rx_phase(phase_negative)+360,360);%把負的相位轉化為正的相位Rx_decoded_phase=diff(Rx_phase);%這也是為什么要在前面加上初始相位的原因%“Herearowvectorofzerosisbetweentrainingsymbolsanddatasymbols!”phase_negative=find(Rx_decoded_phase0);Rx_decoded_phase(phase_negative)=rem(Rx_decoded_phase(phase_negative)+360,360);%再次把負的相位轉化為正的相位%-%

28、QDPSK解調%-%base_phase=360/2bits_per_symbol;delta_phase=base_phase/2;Rx_decoded_symbols=zeros(size(Rx_decoded_phase,1),size(Rx_decoded_phase,2);fori=1:(2bits_per_symbol-1)center_phase=base_phase*i;plus_delta=center_phase+delta_phase;%Decisionthreshold1minus_delta=center_phase-delta_phase;%Decisionthreshold2decoded=find(Rx_decoded_phaseminus_d