www.pudn.com > space-timecodingBrankaVuceticJinhongYuan.rar > vblast.m, change:2007-01-15,size:6597b
function [BER_axis]=vblast(Num,alg,modulation,corr,alpha)
%**************************************************************************
% This program implements vblast using perfect channel estimation for a 2x2
% system.
% z=vblast(Num,alg,modulation,corr,alpha) where
% Num-> number of runs
% alg -> algorithm.Choose from 'ZF' (for zero-forcing),'MM'(MMSE
% estimation),'ML'(maximum-likelihood decoding)
% modulation -> 'BPSK,'QPSK','16QAM','64QAM' (Note: for 'ML' algorithm only
% BPSK and QPSK exist and that too only for 2x2 configuration, as otherwise
% run time is too high.
% corr -> 1 for correlation at the receiver, 0 for no correlation
% alpha -> correlation coefficient value from 0 -> 1 and 0 in case corr =0;
% EXAMPLE: vblast(1000,'ZF','QPSK',1,0.5)plots ZF curve for QPSK with 0.5
% correlation coefficient at the receiver using 1000 Monte Carlo runs
%**************************************************************************
% identify bits for each type of modulation
switch modulation
case 'BPSK'
BITS=1;
case 'QPSK'
BITS=2;
case '16QAM'
BITS=4;
case '64QAM'
BITS=6;
end
% define SNR range
EbNo=[0:2:30];
%define plotting axis
SNR_axis=[];
BER_axis=[];
%set initial count
idx=1;
%define numbers of antennas
M=2;%rx antennas
N=2;%tx antennas
%parameters for wait bar
h = waitbar(0,'Please wait...');
wb=6.25;
%clear BER register
BER=[];
%commence SNR loop
for SNR=EbNo
errors=0;
%define standard deviation, sigma, for noise
sigma=0.5/(sqrt(N)*10^(SNR/10));
for iter=1:Num %commence iteration loop
%define a random Rayleigh channel
H=(randn(M,N)+j*randn(M,N))/sqrt(2);
%exercise correlation option, if any
if corr
R=chol([1 alpha;alpha 1]);%cholesky factor of correlation matrix, i.e. 'R' square root of correlation matrix
H=R*H; % R^0.5 *H -> correlation at receiver
end
H_save=H;%assign H to unalterable value
% modulated input data
tx_bits=randn(N,BITS)>0;
temp1=[];
for i=1:N
d1=tx_modulate(tx_bits(i,:),modulation);
temp1=[temp1; d1];
end
d=temp1;
%AWGN noise
AWGN_noise = sqrt(sigma)*(randn(M, N)+j*randn(M, N));
%receiver signal vector added to AWGN noise
r = (H_save*d)/sqrt(N) + sqrt(sigma)*(randn(M, 1)+j*randn(M, 1));
%Zero-forcing algorithm
if alg=='ZF'
%initialization
G=pinv(H);
[gk k0]=min(sum(abs(G).^2,2));
for m=1:N % This FOR loop determines the ordering sequence k1 and determines the 'a' matrix.
%This is just one run,i.e. one for each H matrix.
%The 'a' matrix is automatically sorted as [a1 a2...aM]
k1(m)=k0;
w(m,:)=G(k1(m),:);
y=w(m,:)*r;
a(k1(m),1)=Q(y,modulation);
r = r - a(k1(m)) * H_save(:, k1(m));
H(:,k0)=zeros(M,1);
G=pinv(H);
for t=1:m
G(k1(t),:)=inf;
end
[gk k0]=min(sum(abs(G).^2,2));
end
%MMSE algorithm
elseif alg=='MM'
%initialisation
G=inv(H'*H+N/(10^(0.1*SNR))*eye(N))*H';
[gk k0]=min(sum(abs(G).^2,2));
for m=1:N % This FOR loop determines the ordering sequence k1 and determines the 'a' matrix.
% This is just one run,i.e.one for each H matrix.The 'a' matrix is automatically sorted
% as [a1 a2...aM]
k1(m)=k0;
w(m,:)=G(k1(m),:);
y=w(m,:)*r;
a(k1(m),1)=Q(y,modulation);
r = r - a(k1(m)) * H_save(:, k1(m));
H(:,k0)=zeros(M,1);
G=inv(H'*H+N/(10^(0.1*SNR))*eye(N))*H';
for t=1:m
G(k1(t),:)=inf;
end
[gk k0]=min(sum(abs(G).^2,2));
end
%ML algorithm
elseif alg=='ML'
p=form_ref_matrix(BITS); %create file containing 2x2 sets of constellation symbols as reference
temp2=[];
temp3=H*p/sqrt(N);
if BITS==1
temp4=4; %square(number of symbols in constellation (2 for BPSK)), since this is a 2x2 system
elseif BITS==2
temp4=16;%square(number of symbols in constellation (4 for QPSK)), since this is a 2x2 system
end
for i=1:temp4
temp2(:,i)=abs(r-temp3(:,i)).^2;
end
w=sum(temp2);
[y1 x1]=min(w);
a=[p(1,x1); p(2,x1)];
temp2=[];
w=[];
end
%count errors
if BITS==1 %for BPSK modulation
errors(iter) = sum((sign(real(a))~=sign(real(d))));
else %for QPSK,16QAM and 64QAM modulations
errors(iter) = sum((sign(real(a))~=sign(real(d))) | sign(imag(a))~=sign(imag(d)));
end
end %end of iteration loop Loop
BER(idx)=sum(errors)/(Num) ; % Calculate BER after completion of 'Num' runs
SER(idx)=BER(idx)*BITS; %calculate symbol error rate
idx=idx + 1; %increment count
waitbar(wb/100);
wb=wb+6.25;%increment wait bar
end %end of SNR loop
close(h);%terminate wait bar
SNR_axis=EbNo;
BER_axis=[BER_axis BER];
SER_axis=SER;
%plot BER
%semilogy(SNR_axis,BER_axis,'b-*');
%xlabel('SNR [dB]');
%ylabel('BER/SER');
%title('BER/SER Plots');
%hold;
%plot SER
%semilogy(SNR_axis,SER_axis,'b-o');
%axis([0 30 1e-6 1]);
%grid on;
%legend('BER','SER');
%hold off;
%if alg=='MM'
% alg='MMSE'
%end
%str=['VBLAST System-' '2 x 2 ' alg ' Algorithm with ' modulation ' Modulation'];
%set(gcf,'NumberTitle','off');
%set(gcf,'Name',str);
%grid on