时变多径信道的matlab仿真（通过输入多普勒频移，时延变量等参数）

%%************************************************************************* %%此程序用来仿真OFDM系统在AWGN信道中的误码特性 %%Function information: %% %%------------------------------------------------------------------------- %% Created by Wei Zhao 2003-04-17 (Version 1.0) %%------------------------------------------------------------------------- %% Recreated by Kunji Wang %%************************************************************************* %%～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～ %% MAIN PROGRAM %%～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～ clear; clc; %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %% System Parameters %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% NumOfSubcarrier = 64; LengthOfGI = 16; % the subcarriers GI(guard interval)contains modulation_mode = 4; %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %% Simulation Parameters %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% NumOfSymbolPerFrame=5; NumOfFrames=100; SNR_in_dB=[0:4:30]; fs=10000; fd=100; Rb=fs; Ts=1/Rb; dt=Ts; n_delay=3; t_delay=[0,100,200]; p_delay=[0.0,-2.0,-6.0]; %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %% Simulation Starting!!! %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% tic; for counter=1:length(SNR_in_dB) P=1; % energy per symbol snr=10^(SNR_in_dB(counter)/10); % signal to noise ratio sgma=sqrt(P/(snr)); % noise variance %Clear the all the counters NumOfErrorBit = 0; SampleIndex=0; for Frame_counter = 1:NumOfFrames %-------------------------------------------------------------------------------------------- % Tx %-------------------------------------------------------------------------------------------- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %% Source Bit Sequence %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Source_Bits=randint(1,2*NumOfSubcarrier*NumOfSymbolPerFrame); %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %% QPSK Modulation %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Modulated_Sequence=modulation(Source_Bits,modulation_mode); R_Modulated_Sequence=reshape(Modulated_Sequence,NumOfSubcarrier,NumOfSymbolPerFrame); %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %% IFFT %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% IFFT_Out_Data(:,:) =sqrt(NumOfSubcarrier)* ifft (R_Modulated_Sequence); %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %% adding guard interval for DATA %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% GI_Added_Frame(1:LengthOfGI,:) = IFFT_Out_Data((NumOfSubcarrier-LengthOfGI+1):NumOfSubcarrier,:); GI_Added_Frame((LengthOfGI+1):(NumOfSubcarrier+LengthOfGI),:) = IFFT_Out_Data(1:NumOfSubcarrier,:); %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %% P -> S %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Serial_Signal = reshape(GI_Added_Frame,1,NumOfSymbolPerFrame*(NumOfSubcarrier+LengthOfGI)); %%%------------------------------------------------------------------------------------------------------------ %% CHANNEL %%%------------------------------------------------------------------------------------------------------------ %-------------------------------------------------------------------------------------------- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %% AWGN channel %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% in=Serial_Signal; [out]=channel(in,fs,fd,n_delay,t_delay,p_delay); Serial_Signal_Ray=Serial_Signal*out; for i=1:NumOfSymbolPerFrame*(NumOfSubcarrier+LengthOfGI) [n_I n_Q]=gngauss(sgma); noise(i)=n_I+j*n_Q; end Noised_Transmited_Signal=Serial_Signal_Ray+noise(i); %-------------------------------------------------------------------------------------------- % Rx %-------------------------------------------------------------------------------------------- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %% Remove the GI %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% for jj=1:NumOfSymbolPerFrame for ii=1:NumOfSubcarrier GI_Removed_Rx_Signal(ii+(jj-1)*NumOfSubcarrier)=Noised_Transmited_Signal(LengthOfGI*jj+ii+(jj-1)*NumOfSubcarrier); end end %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %% S -> P %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Parallel_Rx_Signal = reshape(GI_Removed_Rx_Signal,NumOfSubcarrier,NumOfSymbolPerFrame); %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %% FFT %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Freq_Rx_Signal = fft(Parallel_Rx_Signal)/sqrt(NumOfSubcarrier); Demod_In_Data(1:NumOfSubcarrier,1:NumOfSymbolPerFrame) = Freq_Rx_Signal(1:NumOfSubcarrier,1:NumOfSymbolPerFrame); FFT_Out = conj(Demod_In_Data(:,1:NumOfSymbolPerFrame)'); Serial_Output = reshape(Demod_In_Data,1,NumOfSubcarrier*NumOfSymbolPerFrame); %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %% Demodulation %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Demod_Sequence= demodulation(Serial_Output,modulation_mode); %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %% Calculate the BER %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% for jj = 1:(length(Source_Bits)) if Demod_Sequence(jj) ~= Source_Bits(jj) NumOfErrorBit = NumOfErrorBit + 1; end end end BER(counter) = NumOfErrorBit/(NumOfFrames*NumOfSubcarrier*2*NumOfSymbolPerFrame); end %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % Simulation Completed %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% elapse=toc clock_time = clock; present = fix(clock_time) %---------------------------------------------% %% Draw BER figure %---------------------------------------------% h=figure; semilogy(SNR_in_dB,BER,'r*-'); xlabel('SNR(dB)'); ylabel('BER(bit error rate)'); title( 'BER performance of OFDM in AWGN Channel'); grid on ;