OFDM.zip_actual1vx_ofdm_ofdm处理信号_ofdm系统_staredg5x

%% ************** Preparation part ******************** clear all; clc; % system parameters fs = 20e6; ml = 2; % Modulation level: 2--4QAM; 4--16QAM; 6--64QAM NormFactor = sqrt(2/3*(ml.^2-1)); gi = 1/4; % Guard interval: in the Brazil_E model,the maxmum delay is 2e-6s, equals to 16 points. fftlen = 64; gilen = gi*fftlen; % Length of guard interval (points) blocklen = fftlen + gilen; % total length of the block with CP % index define DataSubcPatt = [1:5 7:19 21:26 27:32 34:46 48:52]'; PilotSubcPatt = [6 20 33 47]; UsedSubcIdx = [7:32 34:59]; % channel coding parameters %trellis = poly2trellis([4 3],[4 5 17;7 4 2]); % 2/3 trellis = poly2trellis(7,[133 171]); % 1/2 % tb is a positive integer scalar that specifies the traceback depth. % If the code rate is 1/2, a typical value for tblen is about five times % the constraint length of the code (here, K = 7). tb = 7*5; ConvCodeRate = 1/2; % 1/2, 2/3 InterleaveBits = 1; % training define % short training for CFO estimation (NumSymbols = 52) ShortTrain = sqrt(13/6)*[0 0 1+j 0 0 0 -1-j 0 0 0 1+j 0 0 0 -1-j 0 0 0 -1-j 0 ... 0 0 1+j 0 0 0 0 0 0 -1-j 0 0 0 -1-j 0 0 0 1+j 0 0 0 1+j 0 0 0 1+j 0 0 0 1+j 0 0].'; NumShortTrainBlks = 10; NumShortComBlks = 16*NumShortTrainBlks/blocklen; % long training for channel estimation and SFO estimation (NumSymbols = 52) LongTrain = [1 1 -1 -1 1 1 -1 1 -1 1 1 1 1 1 1 -1 -1 1 1 -1 1 -1 1 1 1 1 ... 1 -1 -1 1 1 -1 1 -1 1 -1 -1 -1 -1 -1 1 1 -1 -1 1 -1 1 -1 1 1 1 1].'; NumLongTrainBlks = 2; NumTrainBlks = NumShortComBlks + NumLongTrainBlks; % Preamble generation short_train = tx_freqd_to_timed(ShortTrain); %plot(abs(short_train)); short_train_blk = short_train(1:16); short_train_blks = repmat(short_train_blk,NumShortTrainBlks,1); long_train = tx_freqd_to_timed(LongTrain); long_train_syms = [long_train(fftlen-2*gilen+1:fftlen,:); long_train; long_train]; preamble = [short_train_blks; long_train_syms]; % packet information NumBitsPerBlk = 48*ml*ConvCodeRate; NumBlksPerPkt = 50; NumBitsPerPkt = NumBitsPerBlk*NumBlksPerPkt; NumPkts = 500; % channel CFO = 0.1*fs/fftlen h = zeros(gilen,1); h(1) = 1; h(2) = 0.4; h(3)=0.3; h(4)=0.1; h = h/norm(h); channel = fft(h, 64); channel([33:64 1:32]) = channel; channel = channel([7:32 34:59]); % timing parameters ExtraNoiseSamples = 500; %% ************** Loop start*************************** snr = 4:2:10; ber = zeros(1,length(snr)); per = zeros(1,length(snr)); mse = zeros(1,length(snr)); for snr_index = 1:length(snr) num_err = 0; err = zeros(1,NumPkts); err_est = zeros(1,NumPkts); for pkt_index = 1:NumPkts [snr_index pkt_index] %% *********************** Transmitter ****************************** % Generate the information bits inf_bits = randn(1,NumBitsPerPkt)>0; CodedSeq = convenc(inf_bits,trellis); if InterleaveBits rdy_to_mod_bits = tx_interleaver(CodedSeq,48, ml); else rdy_to_mod_bits = CodedSeq; end %Modulate paradata = reshape(rdy_to_mod_bits,length(rdy_to_mod_bits)/ml,ml); ModedSeq = qammod(bi2de(paradata),2^ml)/NormFactor; mod_ofdm_syms = zeros(52, NumBlksPerPkt); mod_ofdm_syms(DataSubcPatt,:) = reshape(ModedSeq, 48, NumBlksPerPkt); mod_ofdm_syms(PilotSubcPatt,:) = 1; tx_blks = tx_freqd_to_timed(mod_ofdm_syms); % Guard interval insertion tx_frames = [tx_blks(fftlen-gilen+1:fftlen,:); tx_blks]; % P/S tx_seq = reshape(tx_frames,NumBlksPerPkt*blocklen,1); tx = [preamble;tx_seq]; %% ****************************** Channel**************************** FadedSignal = filter(h,1,tx); len = length(FadedSignal); noise_var = 1/(10^(snr(snr_index)/10))/2; noise = sqrt(noise_var) * (randn(len,1) + j*randn(len,1)); % add noise rx_signal = FadedSignal + noise; %rx_signal = FadedSignal; % extra noise samples are inserted before the packet to test the packet search algorithm extra_noise = sqrt(noise_var) * (randn(ExtraNoiseSamples,1) + j*randn(ExtraNoiseSamples,1)); % end noise is added to prevent simulation from crashing from incorrect timing in receiver end_noise = sqrt(noise_var) * (randn(170,1) + j*randn(170,1)); rx = [extra_noise; rx_signal; end_noise]; % introduce CFO total_length = length(rx); t = [0:total_length-1]/fs; phase_shift = exp(j*2*pi*CFO*t).'; rx = rx.*phase_shift; %% ************************* Receiver **************************** %packet search rx_signal = rx_find_packet_edge(rx); % CFO coarse estimation and correction rx_signal = rx_frequency_sync(rx_signal,fs); % Fine time synchronization fine_time_est = rx_fine_time_sync(rx_signal, long_train); % Time synchronized signal sync_time_signal = rx_signal(fine_time_est:length(rx_signal)); expected_length = 64*2+80*NumBlksPerPkt; [freq_tr_syms, freq_data_syms, freq_pilot_syms] = rx_timed_to_freqd(sync_time_signal(1:expected_length)); % channel estimation and equalization channel_est = mean(freq_tr_syms,2).*conj(LongTrain); err_est(pkt_index) = mean(abs(channel_est-channel).^2)/mean(abs(channel).^2); % Data symbols channel correction chan_corr_mat = repmat(channel_est(DataSubcPatt), 1, size(freq_data_syms,2)); freq_data_syms = freq_data_syms.*conj(chan_corr_mat); chan_corr_mat = repmat(channel_est(PilotSubcPatt), 1, size(freq_pilot_syms,2)); freq_pilot_syms = freq_pilot_syms.*conj(chan_corr_mat); % Amplitude normalization chan_sq_amplitude = sum(abs(channel_est(DataSubcPatt,:)).^2, 2); chan_sq_amplitude_mtx = repmat(chan_sq_amplitude,1, size(freq_data_syms,2)); data_syms_out = freq_data_syms./chan_sq_amplitude_mtx; chan_sq_amplitude = sum(abs(channel_est(PilotSubcPatt,:)).^2, 2); chan_sq_amplitude_mtx = repmat(chan_sq_amplitude,1, size(freq_pilot_syms,2)); pilot_syms_out = freq_pilot_syms./chan_sq_amplitude_mtx; phase_est = angle(sum(pilot_syms_out)); phase_comp = exp(-j*phase_est); data_syms_out = data_syms_out.*repmat(phase_comp,48,1); Data_seq = reshape(data_syms_out,48*NumBlksPerPkt,1); % To see the effect of CFO-correction %scatterplot(Data_seq);title('After correction'); % demodulate DemodSeq = de2bi(qamdemod(Data_seq*NormFactor,2^ml),ml); SerialBits = reshape(DemodSeq,size(DemodSeq,1)*ml,1).'; if InterleaveBits deint_bits = rx_deinterleave(SerialBits, 48, ml); else deint_bits = SerialBits; end % Viterbi decoding DecodedBits = vitdec(deint_bits(1:length(CodedSeq)),trellis,tb,'trunc','hard'); % Error calculation err(pkt_index) = sum(abs(DecodedBits-inf_bits)); num_err = num_err + err(pkt_index); end ber(snr_index) = num_err/(NumPkts*NumBitsPerPkt); per(snr_index) = length(find(err~=0))/NumPkts; mse(snr_index) = mean(err_est); end %% display SNR-BER semilogy(snr,ber,'-b.');hold on; semilogy(snr,per,'-b.');