soft_demod.m

B3g_phase2_C语言_Matlab程序及说明

function SoftDetOut = Soft_Demod(s, rou, var, LLR, N)

% sigma2i = rou*(1-var*rou);
% mui = rou;

mui = rou;
SoftDetOut=[];
for kk = 1:N
    sigma2i = var(kk);
	% only for 16QAM
	Xi = real(s(kk));
	Yi = imag(s(kk));
	
	% first bit
	LLR1 = (-abs(Xi - 1/sqrt(10)*mui)^2)/sigma2i - 0.5*LLR(2,kk);
	LLR2 = (-abs(Xi - 3/sqrt(10)*mui)^2)/sigma2i + 0.5*LLR(2,kk);
	LLR3 = (-abs(Xi + 1/sqrt(10)*mui)^2)/sigma2i - 0.5*LLR(2,kk);
	LLR4 = (-abs(Xi + 3/sqrt(10)*mui)^2)/sigma2i + 0.5*LLR(2,kk);
	
	%SoftDetOut = [ SoftDetOut (max(LLR1,LLR2) - max(LLR3,LLR4)) ];
    
    SoftDetOut = [ SoftDetOut (log((exp(LLR1)+exp(LLR2))/(exp(LLR3)+exp(LLR4)))) ];
	
	% second bit
	LLR1 = (-abs(Xi - 3/sqrt(10)*mui)^2)/sigma2i + 0.5*LLR(1,kk);
	LLR2 = (-abs(Xi + 3/sqrt(10)*mui)^2)/sigma2i - 0.5*LLR(1,kk);
	LLR3 = (-abs(Xi - 1/sqrt(10)*mui)^2)/sigma2i + 0.5*LLR(1,kk);
	LLR4 = (-abs(Xi + 1/sqrt(10)*mui)^2)/sigma2i - 0.5*LLR(1,kk);
	
	%SoftDetOut = [ SoftDetOut (max(LLR1,LLR2) - max(LLR3,LLR4)) ];
    
    SoftDetOut = [ SoftDetOut (log((exp(LLR1)+exp(LLR2))/(exp(LLR3)+exp(LLR4)))) ];

	% third bit
	LLR1 = (-abs(Yi - 1/sqrt(10)*mui)^2)/sigma2i - 0.5*LLR(4,kk);
	LLR2 = (-abs(Yi - 3/sqrt(10)*mui)^2)/sigma2i + 0.5*LLR(4,kk);
	LLR3 = (-abs(Yi + 1/sqrt(10)*mui)^2)/sigma2i - 0.5*LLR(4,kk);
	LLR4 = (-abs(Yi + 3/sqrt(10)*mui)^2)/sigma2i + 0.5*LLR(4,kk);
	
	%SoftDetOut = [ SoftDetOut (max(LLR1,LLR2) - max(LLR3,LLR4)) ];

    SoftDetOut = [ SoftDetOut (log((exp(LLR1)+exp(LLR2))/(exp(LLR3)+exp(LLR4)))) ];

	% forth bit
	LLR1 = (-abs(Yi - 3/sqrt(10)*mui)^2)/sigma2i + 0.5*LLR(3,kk);
	LLR2 = (-abs(Yi + 3/sqrt(10)*mui)^2)/sigma2i - 0.5*LLR(3,kk);
	LLR3 = (-abs(Yi - 1/sqrt(10)*mui)^2)/sigma2i + 0.5*LLR(3,kk);
	LLR4 = (-abs(Yi + 1/sqrt(10)*mui)^2)/sigma2i - 0.5*LLR(3,kk);
	
	%SoftDetOut = [ SoftDetOut (max(LLR1,LLR2) - max(LLR3,LLR4)) ];

    SoftDetOut = [ SoftDetOut (log((exp(LLR1)+exp(LLR2))/(exp(LLR3)+exp(LLR4)))) ];

end %for kk = 1:N