bpsk_m.m

bpsk和ofdm结合的基本系统

echo off;clear all;close all;clc;
fprintf( 'OFDM仿真\n') ;
tic
% --------------------------------------------- %
%         Parameter Declaration                 %
% --------------------------------------------- %
% Initialize the parameters
NumLoop = 1000;
NumSubc = 128;
NumCP = 8;
SyncDelay = 0;
%-----------------------------------------------
% 子载波数            128
% 位数/ 符号          2
% 帧个数              1000
% 训练符号数          0
% 循环前缀长度        8   (1/16)*T
% 调制方式            BPSK
% 多径信道数          5 
% IFFT Size          128 
% 信道最大时延        2

% --------------------------------------------- %
%                BPSK Modulation                %
% --------------------------------------------- %
% Generate the random binary stream for transmit test
BitsTx = floor(rand(1,NumLoop*NumSubc)*2);

BPSKTable = [-1 1];
SymBPSK = BPSKTable(BitsTx+1);        % Modulate (Generates BPSK symbols)

% --------------------------------------------- %
%                   IFFT                        %
% --------------------------------------------- %

SymIFFT = zeros(NumSubc,NumLoop);
SymIFFTtmp = reshape(SymBPSK,NumSubc,NumLoop);
SymIFFT = ifft(SymIFFTtmp,NumSubc,1);

% --------------------------------------------- %
%             Add cyclic prefix                 %
% --------------------------------------------- %

NumAddPrefix = NumSubc + NumCP;
SymCP = zeros(NumAddPrefix,NumLoop);
RowPrefix = (NumSubc - NumCP + 1):NumSubc;
SymCP = [SymIFFT(RowPrefix,:);SymIFFT];

% --------------------------------------------- %
%             Go through the channel            %
% --------------------------------------------- %

SymCh = zeros(1,NumAddPrefix*NumLoop);
SymChtmp = SymCP(:).';   % 进行这个转置操作之后就成了一个矢量
                         % 相当于把矩阵的列向量依次排列 改变为一个行向量

Ch = [0.227 0.46 0.688 0.46 0.227];    
SymChtmptmp = filter(Ch,1,SymChtmp);

%--------------------------------------------------------------------------
% 函数说明：
% Firlter data with an infinite impulse response (IIR) or finite impulse response
% (FIR) filter
% y = filter(b,a,X) filters the data in vector X with the filter described by
% numerator coefficient vector b and denominator coefficient vector a. If a(1) is
% not equal to 1, filter normalizes the filter coefficients by a(1). If a(1) equals
% 0, filter returns an error.
%--------------------------------------------------------------------------
% If X is a matrix, filter operates on the columns of X. If X is a multidimensional
% array, filter operates on the first nonsingleton dimension.
%-------------------------------------------------------------------------


BerSnrTable = zeros(30,5);
for snr=0:49;  
    BerSnrTable(snr+1,1) = snr;

    BerSnrTable(snr+1,2) = 10^(BerSnrTable(snr+1,1)/10);      %将信噪比由db变换到一般数据比
    BerSnrTable(snr+1,3) = 1/sqrt(2*BerSnrTable(snr+1,2));    %信道的噪声标准差


SymCh = AWGN(SymChtmptmp,snr,'measured');            % Add the noise


%--------------------------------------------------------------------------
% 函数说明：
%  AWGN Add white Gaussian noise to a signal.
%     Y = AWGN(X,SNR) adds white Gaussian noise to X.  The SNR is in dB.
%     The power of X is assumed to be 0 dBW.  If X is complex, then 
%     AWGN adds complex noise.
%  ------------------------------------------------------------------------
%     Y = AWGN(X,SNR,SIGPOWER) when SIGPOWER is numeric, it represents 
%     the signal power in dBW. When SIGPOWER is 'measured', AWGN measures
%     the signal power before adding noise.
% ------------------------------------------------------------------------- 
%     Y = AWGN(X,SNR,SIGPOWER,STATE) resets the state of RANDN to STATE.
%  
%     Y = AWGN(..., POWERTYPE) specifies the units of SNR and SIGPOWER.
%     POWERTYPE can be 'db' or 'linear'.  If POWERTYPE is 'db', then SNR
%     is measured in dB and SIGPOWER is measured in dBW.  If POWERTYPE is
%     'linear', then SNR is measured as a ratio and SIGPOWER is measured
%     in Watts.
%  
%     Example: To specify the power of X to be 0 dBW and add noise to produce
%              an SNR of 10dB, use:
%              X = sqrt(2)*sin(0:pi/8:6*pi);
%              Y = AWGN(X,10,0);
%  
%     Example: To specify the power of X to be 0 dBW, set RANDN to the 1234th
%              state and add noise to produce an SNR of 10dB, use:
%              X = sqrt(2)*sin(0:pi/8:6*pi);
%              Y = AWGN(X,10,0,1234);
%  
%     Example: To specify the power of X to be 3 Watts and add noise to
%              produce a linear SNR of 4, use:
%              X = sqrt(2)*sin(0:pi/8:6*pi);
%              Y = AWGN(X,4,3,'linear');
%  
%     Example: To cause AWGN to measure the power of X, set RANDN to the 
%              1234th state and add noise to produce a linear SNR of 4, use:
%              X = sqrt(2)*sin(0:pi/8:6*pi);
%              Y = AWGN(X,4,'measured',1234,'linear');

% --------------------------------------------- %
%            Remove Guard Intervals             %
% --------------------------------------------- %

SymDeCP = zeros(NumSubc,NumLoop);
SymDeCPtmp = reshape(SymCh,NumSubc + NumCP,NumLoop);
SymDeCP = SymDeCPtmp((NumCP+1+SyncDelay):NumAddPrefix+SyncDelay,:);

% --------------------------------------------- %
%                     FFT                       %
% --------------------------------------------- %

SymFFTtmp = fft(SymDeCP,NumSubc,1);

% --------------------------------------------- %
%                      Equalize                 %
% --------------------------------------------- %

H = fft(Ch,NumSubc);
for i=1:NumSubc
   W(i) = conj(H(i))/(BerSnrTable(snr+1,3)^2+abs(H(i))^2);
end
E_W=zeros(NumSubc,NumLoop);
for n1=1:NumLoop
   E_W(:,n1)=W;
end 
SymFFT = SymFFTtmp.*E_W;

% --------------------------------------------- %
%        Make Decision(Include DeBPSK)          %
% --------------------------------------------- %

BitsRx = zeros(1,NumSubc*NumLoop);
BitsRxtmp = SymFFT(:).';
for m = 1:NumLoop*NumSubc
    Real =real(BitsRxtmp(1,m));
    if Real>0
        BitsRx(1,m)=1;
    else 
        BitsRx(1,m)=0;
    end
end

% --------------------------------------------- %
%          Compute Error Number/Rate            %
% --------------------------------------------- %

[Num,Ber] = symerr(BitsTx,BitsRx)

BerSnrTable(snr+1,4) = Num ;
BerSnrTable(snr+1,5) = Ber ;
end

figure(1);
subplot(2,1,1);
semilogy(BerSnrTable(:,1),BerSnrTable(:,4),'o-');
subplot(2,1,2);
semilogy(BerSnrTable(:,1),BerSnrTable(:,5),'o-');
% ------------------------------------------------------------------------
time_of_sim = toc
echo on;
% --------------------------------------------- %
%                   The END                     %
% --------------------------------------------- %