mimo系统 matlab算法
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function
[gn,en_bar,bn_bar,Nstar,b_bar_check,margin]=MAwaterfill(P,SNRmfb,Ex_bar,b_bar,Ntot,gap)
% EE379C 2001-2002 Spring,
% Written by Seong Taek Chung
%
% P is the pulse response
% SNRmfb is the SNRmfb in dB
% b_bar is the normalized bit rate
% Ex_bar is the normalized energy
% Ntot is the total number of real/complex subchannels, Ntot>2
% gap is the gap in dB
%
% gn is channel gain
% en_bar is the energy/dim in the nth subchannel
% bn_bar is the bit/dim in the nth subchannel
% Nstar is the number of subchannel used
% dB into normal scale
Noise_var=Ex_bar*(norm(P)^2)/(10^(SNRmfb/10));
gap=10^(gap/10);
% initialization
en=zeros(1,Ntot);
bn=zeros(1,Ntot);
gn=zeros(1,Ntot);
Hn = zeros(1,Ntot);
% subchannel center frequencies
f=-1/2+1/Ntot:1/Ntot:1/2;
% find Hn vector
for i=1:length(P)
Hn=Hn+P(i)*exp(j*2*pi*f*(i-1));
% This value will be different depending if P represents
% P(1) + P(2)*D^-1 + .... or P(1) + P(2)*D^+1....,
% but we'll get same gn, thus same waterfilling result.
% (Note that both have the same magnitude response!)
end
% find gn vector
gn=abs(Hn).^2/Noise_var;
%plot(gn)
%%%%%%%%%%%%%%%%%%%%%%%
% Now do waterfilling %
%%%%%%%%%%%%%%%%%%%%%%%
%sort
[gn_sorted, Index]=sort(gn); % sort gain, and get Index
gn_sorted = fliplr(gn_sorted);% flip left/right to get the largest
% gain in leftside
Index = fliplr(Index); % also flip index
num_zero_gn = length(find(gn_sorted == 0)); %number of zero gain subchannels
Nstar=Ntot - num_zero_gn;
% Number of used channels,
% start from Ntot - (number of zero gain subchannels)
while(1)
K=(2^(Ntot*b_bar*2)/prod(gn_sorted(1:Nstar)))^(1/Nstar)*gap;
%K=1/Nstar*(Ntot*Ex_bar+gap*sum(1./gn_sorted(1:Nstar)));
En_min=K-gap/gn_sorted(Nstar); % En_min occurs in the worst channel
if (En_min<0)
Nstar=Nstar-1; % If negative En, continue with less channels
else
break; % If all En positive, done.
end
end
En=K-gap./gn_sorted(1:Nstar); % Calculate En
Bn=.5*log2(K*gn_sorted(1:Nstar)/gap); % Calculate bn
bn(Index(1:Nstar))=Bn; % return values in original index
en(Index(1:Nstar))=En; % return values in original index
en_bar=en;
bn_bar=bn;
% calculate b_bar
b_bar_check=1/Ntot*(sum(bn));
%calculate margin
margin=10*log10(Ntot*Ex_bar/sum(en));
%>> [gn,en_bar,bn_bar,Nstar,b_bar_check,margin]=MAwaterfill([1 0.9],10,1,1,8,0) %
%gn =
%
% Columns 1 through 7
%
% 2.9680 10.0000 17.0320 19.9448 17.0320 10.0000 2.9680
%
% Column 8
%
% 0.0552
%
%
%en_bar =
%
% Columns 1 through 7
%
% 0.2000 0.4369 0.4782 0.4868 0.4782 0.4369 0.2000
%
% Column 8
%
% 0
%
%
%bn_bar =
%
% Columns 1 through 7
%
% 0.3361 1.2123 1.5964 1.7103 1.5964 1.2123 0.3361
%
% Column 8
%
% 0
%
% Nstar =
%
% 7
%
%
%b_bar_check =
%
% 1.0000
%
%
%margin = %
% 4.6903
%
