OFDM.rar_OFDM BPSK 比较_bpsk ofdm_givingaqg_rayleigh_误码率 ofdm

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % All rights reserved by Krishna Pillai, http://www.dsplog.com % The file may not be re-distributed without explicit authorization % from Krishna Pillai. % Checked for proper operation with Octave Version 3.0.0 % Author : Krishna Pillai % Email : [email protected] % Version : 1.0 % Date : 05 June 2008 % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % Script for computing the BER for BPSK in OFDM modulation in the % presence of Rayeligh fading channel clear all nFFT = 64; % fft size nDSC = 52; % number of data subcarriers nBitPerSym = 52; % number of bits per OFDM symbol (same as the number of subcarriers for BPSK) nSym = 10^4; % number of symbols EbN0dB = [0:40]; % bit to noise ratio EsN0dB = EbN0dB + 10*log10(nDSC/nFFT) + 10*log10(64/80); % converting to symbol to noise ratio for ii = 1:length(EbN0dB) % Transmitter ipBit = rand(1,nBitPerSym*nSym) > 0.5; % random 1's and 0's ipMod = 2*ipBit-1; % BPSK modulation 0 --> -1, 1 --> +1 ipMod = reshape(ipMod,nBitPerSym,nSym).'; % grouping into multiple symbolsa % Assigning modulated symbols to subcarriers from [-26 to -1, +1 to +26] xF = [zeros(nSym,6) ipMod(:,[1:nBitPerSym/2]) zeros(nSym,1) ipMod(:,[nBitPerSym/2+1:nBitPerSym]) zeros(nSym,5)] ; % Taking FFT, the term (nFFT/sqrt(nDSC)) is for normalizing the power of transmit symbol to 1 xt = (nFFT/sqrt(nDSC))*ifft(fftshift(xF.')).'; % Appending cylic prefix xt = [xt(:,[49:64]) xt]; % multipath channel %scale=1e-9; %Ts=10*scale; % t_rms=30*scale; %nTap = 10; %pow_e=exp_PDP(t_rms,Ts); %delay_e=(0:length(pow_e)-1)*Ts/scale; %stanDevChan=repmat(sqrt(pow_e(i)),nSym,1); %for i = 1:length(pow_e) % H_e(:,i) = (randn(1,nTap)+1i*randn(1,nTap))/sqrt(2).'*sqrt(pow_e(i); % end % ht= 1/sqrt(nTap)*stanDevChan.*H_e nTap = 30; sampTime=1e-8; delaySprd=-nTap/(log(0.01)); %eps effectively defines how steep profile is (changes min tap value) var0=(1-exp(-1*(sampTime)/delaySprd))/(1-exp(-nTap*sampTime/delaySprd)); %normalises to 1W total k=(1:nTap); vark=var0*exp(-k*sampTime/delaySprd); stanDevChan=repmat(sqrt(vark),nSym,1); %factor root 2 so half power in real and imag. ht = 1/sqrt(nTap)*stanDevChan.*(randn(nSym,nTap)+1i*randn(nSym,nTap)); %nTap = 30; %c_att = 2; %var_ch = exp(-[0:nTap-1]/c_att); %var_ch = var_ch/sum(var_ch); % ht = 1/sqrt(2)*1/sqrt(nTap)*(randn(nSym,nTap) + j*randn(nSym,nTap)); % ht = 1/sqrt(nTap)*(randn(nSym,nTap) + j*randn(nSym,nTap)).* repmat(sqrt(var_ch),nSym,1); % computing and storing the frequency response of the channel, for use at recevier hF = fftshift(fft(ht,64,2)); % convolution of each symbol with the random channel for jj = 1:nSym xht(jj,:) = conv(ht(jj,:),xt(jj,:)); end xt = xht; % Concatenating multiple symbols to form a long vector xt = reshape(xt.',1,nSym*(80+nTap-1)); % Gaussian noise of unit variance, 0 mean nt = 1/sqrt(2)*[randn(1,nSym*(80+nTap-1)) + j*randn(1,nSym*(80+nTap-1))]; % Adding noise, the term sqrt(80/64) is to account for the wasted energy due to cyclic prefix yt = sqrt(80/64)*xt + 10^(-EsN0dB(ii)/20)*nt; % Receiver yt = reshape(yt.',80+nTap-1,nSym).'; % formatting the received vector into symbols yt = yt(:,[17:80]); % removing cyclic prefix % converting to frequency domain yF = (sqrt(nDSC)/nFFT)*fftshift(fft(yt.')).'; % equalization by the known channel frequency response yF = yF./hF; % extracting the required data subcarriers yMod = yF(:,[6+[1:nBitPerSym/2] 7+[nBitPerSym/2+1:nBitPerSym] ]); % BPSK demodulation % +ve value --> 1, -ve value --> -1 ipModHat = 2*floor(real(yMod/2)) + 1; ipModHat(find(ipModHat>1)) = +1; ipModHat(find(ipModHat<-1)) = -1; % converting modulated values into bits ipBitHat = (ipModHat+1)/2; ipBitHat = reshape(ipBitHat.',nBitPerSym*nSym,1).'; % counting the errors nErr(ii) = size(find(ipBitHat - ipBit),2); end simBer = nErr/(nSym*nBitPerSym); EbN0Lin = 10.^(EbN0dB/10); theoryBer = 0.5.*(1-sqrt(EbN0Lin./(EbN0Lin+1))); close all; figure semilogy(EbN0dB,theoryBer,'bs-','LineWidth',2); hold on semilogy(EbN0dB,simBer,'mx-','LineWidth',2); axis([0 40 10^-5 1]) grid on legend('Rayleigh-Theory', 'Rayleigh-Simulation'); xlabel('Eb/No, dB') ylabel('Bit Error Rate') title('BER for BPSK using OFDM in Rayleigh channel with exponential PDP')