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clear all
close all
clc
nt_V = [1 2 3 2 4];
nr_V = [1 2 2 3 4];
N0 = 1e-4;
B = 1;
Iteration = 1e2; % must be grater than 1e2
SNR_V_db = [-10:3:20];
SNR_V = 10.^(SNR_V_db/10);
color = ['b';'r';'g';'k';'m'];
notation = ['-o';'->';'<-';'-^';'-s'];
for(k = 1 : 5)
nt = nt_V(k);
nr = nr_V(k);
for(i = 1 : length(SNR_V))
Pt = N0 * SNR_V(i);
for(j = 1 : Iteration)
H = random('rayleigh',1,nr,nt);
[S V D] = svd(H);
landas(:,j) = diag(V);
[Capacity(i,j) PowerAllo] = WaterFilling_alg(Pt,landas(:,j),B,N0);
end
end
f1 = figure(1);
hold on
plot(SNR_V_db,mean(Capacity'),notation(k,:),'color',color(k,:))
clear landas
end
f1 = figure(1)
legend_str = [];
for( i = 1 : length(nt_V))
legend_str =[ legend_str ;...
{['nt = ',num2str(nt_V(i)),' , nr = ',num2str(nr_V(i))]}];
end
legend(legend_str)
grid on
set(f1,'color',[1 1 1])
xlabel('SNR in dB')
ylabel('Capacity bits/s/Hz')
function [Capacity PowerAllo] = WaterFilling_alg(PtotA,ChA,B,N0);
%
% WaterFilling in Optimising the Capacity
%===============
% Initialization
%===============
ChA = ChA + eps;
NA = length(ChA); % the number of subchannels allocated to
H = ChA.^2/(B*N0); % the parameter relate to SNR in subchannels
% assign the power to subchannel
PowerAllo = (PtotA + sum(1./H))/NA - 1./H;
while(length(find(PowerAllo < 0 ))>0)
IndexN = find(PowerAllo <= 0 );
IndexP = find(PowerAllo > 0);
MP = length(IndexP);
PowerAllo(IndexN) = 0;
ChAT = ChA(IndexP);
HT = ChAT.^2/(B*N0);
PowerAlloT = (PtotA + sum(1./HT))/MP - 1./HT;
PowerAllo(IndexP) = PowerAlloT;
end
PowerAllo = PowerAllo.';
Capacity = sum(log2(1+ PowerAllo.' .* H));
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