Time frequency training (TFT) OFDM

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Khushboo Singh on 28 Dec 2012

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https://uk.mathworks.com/matlabcentral/answers/57566-time-frequency-training-tft-ofdm

Commented: sneha on 25 Sep 2019

Hello, I m writing a code for LDPC encoded TFT-OFDM technique. I want to plot SNR vs BER graph for this technique for snr = 14:0.5:17. my code is as follow. guys, i m totally stacked in this plzz plzz help me out. ref. D.linglong, Z.Wang and Z.Yang , “Time-Frequency Training OFDM with High Spectral Efficiency and Reliable Performance in High Speed Environments” IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, VOL. 30, NO. 4, MAY 2012 clc; clear all; close all; format long;

SNR = linspace(14, 17, 7); %dB
% GENERATION OF INFORMATION AND LDPC ENCODING
I = randint(1,43200); % INFORMATION BITS
H = dvbs2ldpc(2/3);
l = fec.ldpcenc(H);
codeword = encode(l,I);
% BIT-INTERLEAVING 
Order = (1:64800).';
hIntrlv   = comm.BlockInterleaver(Order);
intrlvrOut = step(hIntrlv,codeword');
iout = intrlvrOut;
% 64-QAM MODULATION AND MAPPING
hmod =comm.RectangularQAMModulator(64,'BitInput',true);
moutp = step(hmod, iout);
mout = (moutp).';
x = 1;
for sym = 1:3  % SYMBOL LOOP
    data = mout(x:x+3599);
    new_sym = zeros(1,3660);
    for i = 1:3600
        new_sym(i+30) = data(i);
    end
    p_sym = zeros(1,3780);
    d = sort(randint(1, 40, [2 3650])); % random index for central pilot
    for i = 1:39
        if (d(i+1) - d(i)) < 5
            d(i+1) = d(i+1) + 1;
        end
    end
    pilt = [-1 1 -1]; %BPSK modulated PILOT
    for k = 1:40
        g = d(k);
        for i = 1:g-2;
            p_sym(i) = new_sym(i);
        end
        for i = g-1:g+1
            p_sym(g-1) = -1;
            p_sym(g) = 1;
            p_sym(g+1) = -1;
        end
        for i = g:3660
            p_sym(i+2) = new_sym(i);
        end
        new_sym = p_sym;
    end
    new_sym = new_sym.';  % SERIAL TO PARALLEL
    signal = ifft(new_sym, 3780);  % 3780- point IFFT
    signal = signal.';  % PARALLEL TO SERIAL
    % Generating PN-Sequence
    load pn_all.mat pn420;
    PN420=transpose(pn420(1,:));
    PN420_MC=sqrt(length(PN420)) * ifft(PN420);
    TS = PN420_MC'; 
    z = cxcorr(TS,TS); % For CIRCULAR CORRELATION THEOREM,
    zz = circcorrcoef(TS,TS); 
    % Appending Training Sequence
    Y =  zeros(1,420);
    for i = 1:420
        Y(1,i) = TS(1,i);
    end
    t_signal = [Y signal]; % SIGNAL TO BE TRANSMITTED
    % AWGN channel
    for snr = 14 %:0.5:17 % SNR loop
        pro = eye(4200)*t_signal';
        r_signal = awgn(pro,snr).';
        %TS-based path delay estimation
        Tao = 1; %possible path
        %Path coefficient estimation
        for i = 1:3780;
            r_block(i) = r_signal(420+i);
        end
        fft_r_block = fft(r_block.',3780);
        for k = 1:40
            for n = 0:3779
                lem(k,n+1)= 1-(exp(-2j*pi*(n/3780))+exp(2j*pi*(n/3780)));
            end
        end
        for n = 0:3779
            thetha(n+1,1) = 1;
            thetha(n+1,2) = n;
        end
        beta = lem*thetha;
        for k = 1:40
            y_p(k) = fft_r_block(d(k));
        end
        A = ((beta')*beta) + eye(2);  %noise variance is assumed = 1
        B = inv(A);
        C = (beta') * (y_p.');
        rho_cap = B * C;
        h_inl = thetha * rho_cap;
        g_i = sum(h_inl)/3780;
        G_i = g_i * eye(3780);
        %channel equalization: which is ONE-TAP-EQUALIZATION for AWGN channel 
        for k = 1:40
            g = d(k);
            for p_indx = 1:3
                fft_r_block(g-1) = [];
            end
        end
        data_block = zeros(3600,1);
        for i = 1:30
            data_block(i) = fft_r_block(i+30);
        end
        x_ik = data_block * ( conj(g_i) / ((abs(g_i)^2) + 1) );
      end
      for o = 1:3600
          x_sym(o,sym) = x_ik(o);
      end
  end
  stream = reshape(x_sym, 1, 10800);
  hdmod =comm.RectangularQAMDemodulator(64,'BitOutput',true);
  dout = step(hdmod, stream.');
  dIntrlv   = comm.BlockDeinterleaver(Order);
  dintrd = step(dIntrlv,dout);
  d = fec.ldpcdec(H);
  final = decode(d,dintrd.');
  be = xor(I,final);