DSSS.rar_DSSS仿真_MATLAB 扩频_扩频解扩_直扩_直扩 解扩

% Basic simulation for DSSS % College of Underwater Acoustic Engineering % Harbin Engineering University % All Rights Reserved. % Programmer:Leigh lilin@hrbeu.edu.cn % Version:1.0 % Last modified:2017-3-14 % Program function: Realize the basic simulation for DSSS clear clc %% Parameter selection load DataForDsss load m_sequence fs = 48000; %Sampling Rate fc = 4000; %carrier frequency bandwidth = 4000; %Bandwidth %% Spread spectrum modulation DataTx = Data(1:200); for i = 1:length(DataTx) if DataTx(i)==0 DataTx(i)=-1; end end m_seq = m_sequence.order9(4,:); DataTxmseq = kron(DataTx,m_seq); %plot(corr_fun(DataTxmseq,m_seq)) %% Upsample NumUpsanple = 2*fs/bandwidth; %N*1/fs = T; B/2 = 1/T (N:NumUpsample B:bandwidth ) DataTxmseqUpsample = rectpulse(DataTxmseq,NumUpsanple); %% Carrier modulation t = 0:1/fs:(length(DataTxmseqUpsample)-1)/fs; carrier = cos(2*pi*fc*t); TxSig = DataTxmseqUpsample.*carrier; %% Generate LFM signal SigSyncLFM = lfmgenerate(0.5,fc+bandwidth/2,fc-bandwidth/2,fs); %% Generate transmate data len = 0.2*fs; %spacing interval SigSpace = zeros(1,len); TxSignalCompleted=[SigSpace SigSyncLFM SigSpace TxSig SigSpace SigSyncLFM SigSpace]; %% Generate .wav file A_signal=25000; %存储为.wav文件 fid=fopen('C:\Users\LEE\Desktop\ExpLongKou\LL05.wav','wb'); fwrite(fid,TxSignalCompleted*A_signal,'int16'); fclose(fid); %% Intend white noise SNR=-18; RxData=awgn(TxSignalCompleted,SNR,'measured'); %% Analog channel h1=[0.4 zeros(1,100) 1 zeros(1,200) 0.6 zeros(1,300) 0.5 zeros(1,200) 0.3]; % h2=[1 zeros(1,500) 0.5 zeros(1,200) 0.3 zeros(1,200) 0.1 zeros(1,100) 0.05]; RxData=conv(RxData,h1); %% Synchronous head detection SyncDection=corr_fun(RxData(1:5*fs),SigSyncLFM ); [MAX, Start]=max(SyncDection); %find the MAX number and it's position in SyncDection % figure(1) % plot(SyncDection) %% Find sync head RxData_Syc = RxData(Start+len:end); %% Carrier demodulation RxInfoDemod = RxData_Syc(1:length(carrier)); RxInfoDemod = RxInfoDemod.*carrier; RxInfo = filterlowpass(RxInfoDemod,bandwidth*8/5,bandwidth*2,0.1,20,fs); %% Downsample RxInfoMseq = resample(RxInfo,fs/NumUpsanple,fs); %% Divide the signal len_m = length(m_seq); RxInfoPara = zeros(length(DataTx),len_m); for i = 1:length(DataTx) RxInfoPara(i,:) = RxInfoMseq((i-1)*len_m+1:i*len_m); end %% Copy related to get the RxInfo RxInfoCom = zeros(1,length(DataTx)); % RxCorrPara = zeros(length(DataTx),len_m*2-1); for i = 1:length(DataTx) CorrPos = corr_fun(RxInfoPara(i,:),m_seq); % RxCorrPara(i,:) = CorrPos; % ConvTRPos = conv(fliplr(CorrPos),CorrPos); CorrNeg = corr_fun(RxInfoPara(i,:),-m_seq); [MAX1,POS1] = max(abs(CorrPos)); [MAX2,POS2] = max(abs(CorrNeg)); if CorrPos(POS1) > CorrNeg(POS2) RxInfoCom(i) = 1; else RxInfoCom(i) = -1; end end %% Bit error rate calculation [Num,Rat] = symerr(RxInfoCom,DataTx);