OFDM MULTIPATH CODE LTE GENERAL

clc;
clear all;
close all;
% Initializing parameters
Nfft=input('Size of fft N = ');
Nused=input('Number of OFDM symbols to be used m = ');
M=input('Size of constellation M = ');
Type=input('Type of Mapping (1 for PSK) and (2 for QAM) = ');
Phase_Offset=input('phase offset = ');
Ncp=input('cyclic prefix samples Ncp = ');
bw = 15*10^6;%%bandwidth
T = 1/bw;%time period
% Transmitter

if Type == 1
Tx = modem.pskmod('M',M,'PhaseOffset',Phase_Offset,'SymbolOrder','gray');
Rx = modem.pskdemod('M',M,'PhaseOffset',Phase_Offset,'SymbolOrder','gray');
else
Tx = modem.qammod('M',M,'PhaseOffset',Phase_Offset,'SymbolOrder','gray');
Rx = modem.qamdemod('M',M,'PhaseOffset',Phase_Offset,'SymbolOrder','gray');
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
% c_in_s=sum(c_in);

% data generation
Tx_data=randi([0 M-1],Nused,Nfft/2);
% Mapping
mod_data=modulate(Tx,Tx_data);
% Serial to Parallel
s2p=mod_data.';
% insertion of pilots (upsmapling)

upsampled=upsample(s2p,2);

% Amplitude modulation (IDFT using fast version IFFT)

am=ifft(upsampled,Nfft);

% Parallel to serial

p2s=am.';

% Cyclic Prefixing

CP_part=p2s(:,Nfft-Ncp+1:Nfft); % this is the Cyclic Prefix part to be appended.
cp=[CP_part p2s];
% cp_v=reshape(cp,Nused,Nfft+Ncp);

%c_in_v=reshape(c_in,1,8);
conv_data=convn(cp ,c_in);
% Reciever
% Adding Noise using AWGN
SNRstart=3;
SNRincrement=2;
SNRend=11;
c=0;
r=zeros(size(SNRstart:SNRincrement:SNRend));
for snr=SNRstart:SNRincrement:SNRend
c=c+1;

noisy=awgn(conv_data,snr,'measured');
% Remove cyclic prefix part
cpr=noisy(:,Ncp+1:Nfft+Ncp); %remove the Cyclic prefix
% serial to parallel
parallel=cpr.';
% Amplitude demodulation (DFT using fast version FFT)
amdemod=fft(parallel,Nfft);
% Down-Sampling

downsampled=downsample(amdemod,2);
% Parallel to serial
rserial=downsampled.';
% demodulation
Umap=demodulate(Rx,rserial);
% Calculating the Symbol Error Rate
[n, r(c)]=symerr(Tx_data,Umap);

end
figure(1)
snr=SNRstart:SNRincrement:SNRend;
% Plotting SER vs SNR
semilogy(snr,r,'-ok');
grid;
title('OFDM Symbol Error Rate vs SNR');
ylabel('Symbol Error Rate');
xlabel('SNR [dB]');