ADAPTIVE MODULATION OFDM LTE GENERAL CODE

ADAPTIVE MODULATION OFDM LTE

clc;
clear all;
close all;
%assigning the variables
N = 1536;
bw = 15*10^6;
T = 1/bw;
SNR = 10:1:30;
BER_tar = 10^(-3);
% finding the target snr
M=[2 4 16 64];
for i=1:length(M)
if M(i)==2
SNR_tar(i)=((M(i)-1)*log(.5*10^(-3)))/(-1.5);
else
SNR_tar(i)=((M(i)-1)*log(5*10^(-3)))/(-1.5);
end
end
%Indoor delay
in_delay = [0 50 110 170 290 310];
N_tap = ceil(max(in_delay)*(10^(-9))/T);
c_in = zeros(1,N_tap+1);
c_tap = ceil(in_delay./50)+1;
inPwr_dB = [0 -3 -10 -18 -26 -32];%% power in dB
inPwr = 10.^(inPwr_dB/10);%% converting to linear scale
c_r = abs(((inPwr/2).*randn(1,length(inPwr)))+((inPwr/2).*randn(1,length(inPwr)))*1i);

for k=1:length(c_tap)
c_in(c_tap(k))=c_r(k);
end
hf = fft(c_in,1536);

for s=1:length(SNR)
recSNR = abs(hf.*SNR(s));
for i=1:length(recSNR)
if recSNR(i) < SNR_tar(1)
b(i) = 1;
elseif ((recSNR(i) > SNR_tar(1))&&(recSNR(i) < SNR_tar(2)))
b(i) = 2;
elseif ((recSNR(i) > SNR_tar(2))&&(recSNR(i) < SNR_tar(3)))
b(i) = 4;
else
b(i) = 8;
end
end
spec_indoor(s) = mean(b);
end

% Finding the multipath channel response
out_delay = [0 10 90 135 230 275 310 420 630 635 745 815 830 1430 1790 2075];
N_tap = ceil(max(out_delay)*(10^(-9))/T);
c_out = zeros(1,N_tap+1);
c_tap = ceil(out_delay./50)+1;
outPwr_dB = [-2.6 -8.5 -14.8 -17.5 -19.2 -18.8 -14.9 -14.9 -22.1 -10.3 -22.2 -19.2 -16 -22.9 -20.3 -27.4];
outPwr = 10.^(outPwr_dB/10);
c_r = abs(((outPwr/2).*randn(1,length(outPwr)))+((outPwr/2).*randn(1,length(outPwr)))*1i);

for k=1:length(c_tap)
c_out(c_tap(k))=c_r(k);
end

hf = fft(c_out,1536);

for s=1:length(SNR)
recSNR = abs(hf.*SNR(s));
for i=1:length(recSNR)
if recSNR(i) < SNR_tar(1)
b(i) = 1;
elseif ((recSNR(i) > SNR_tar(1))&&(recSNR(i) < SNR_tar(2)))
b(i) = 2;
elseif ((recSNR(i) > SNR_tar(2))&&(recSNR(i) < SNR_tar(3)))
b(i) = 4;
else
b(i) = 8;
end
end
spec_outdoor(s) = mean(b);
end

plot(SNR, spec_indoor,'r');
hold on;
plot(SNR, spec_outdoor,'b');
grid on;
title('Adaptive Modulation');
xlabel('SNR (db)');
ylabel('Spectral efficiency in bits/Hz');
legend('Indoor','Outdoor');