multipath.rar_LOS信道_qpsk信号_多径信号幅度_多径信道和AWGN_多径衰减

% File: c14_threeray.m % Software given here is to accompany the textbook: W.H. Tranter, % K.S. Shanmugan, T.S. Rappaport, and K.S. Kosbar, Principles of % Communication Systems Simulation with Wireless Applications, % Prentice Hall PTR, 2004. % % Default parameters % NN = 256; % number of symbols tb = 0.5; % bit time fs = 16; % samples/symbol ebn0db = [1:2:14]; % Eb/N0 vector % % Establish QPSK signals % x = random_binary(NN,fs)+i*random_binary(NN,fs); % QPSK signal % % Input powers and delays % p0 = input('Enter P0 > '); p1 = input('Enter P1 > '); p2 = input('Enter P2 > '); delay = input('Enter tau > '); delay0 = 0; delay1 = 0; delay2 = delay; % % Set up the Complex Gaussian (Rayleigh) gains % gain1 = sqrt(p1)*abs(randn(1,NN) + i*randn(1,NN)); gain2 = sqrt(p2)*abs(randn(1,NN) + i*randn(1,NN)); for k = 1:NN for kk=1:fs index=(k-1)*fs+kk; ggain1(1,index)=gain1(1,k); ggain2(1,index)=gain2(1,k); end end y1 = x; for k=1:delay2 y2(1,k) = y1(1,k)*sqrt(p0); end for k=(delay2+1):(NN*fs) y2(1,k)= y1(1,k)*sqrt(p0) + ... y1(1,k-delay1)*ggain1(1,k)+... y1(1,k-delay2)*ggain2(1,k); end % % Matched filter % b = ones(1,fs); b = b/fs; a = 1; y = filter(b,a,y2); % % End of simulation % % Use the semianalytic BER estimator. The following sets % up the semi analytic estimator. Find the maximum magnitude % of the cross correlation and the corresponding lag. % [cor lags] = vxcorr(x,y); [cmax nmax] = max(abs(cor)); timelag = lags(nmax); theta = angle(cor(nmax)) y = y*exp(-i*theta); % derotate % % Noise BW calibration % hh = impz(b,a); ts = 1/16; nbw = (fs/2)*sum(hh.^2); % % Delay the input, and do BER estimation on the last 128 bits. % Use middle sample. Make sure the index does not exceed number % of input points. Eb should be computed at the receiver input. % index = (10*fs+8:fs:(NN-10)*fs+8); xx = x(index); yy = y(index-timelag+1); [n1 n2] = size(y2); ny2=n1*n2; eb = tb*sum(sum(abs(y2).^2))/ny2; eb = eb/2; [peideal,pesystem] = qpsk_berest(xx,yy,ebn0db,eb,tb,nbw); figure semilogy(ebn0db,peideal,'b*-',ebn0db,pesystem,'r+-') xlabel('E_b/N_0 (dB)'); ylabel('Probability of Error'); grid axis([0 14 10^(-10) 1]) % End of script file.