bits transmitted and received are the same even though i added the noise?

hello everyone, i am working on BER in OFDM.as i checked through variable editor in matlab,the bits transmitted and received are the same even though i added the noise.below is part of the code.can anyone help?

 dataType = '16QAM'; % Modulation format.
 totalSubcarriers = 64; % Number of total subcarriers.
 numSymbols = 16; % Data block size.
 Fs = 5e6; % System bandwidth.
 Ts = 1/Fs; % System sampling rate.
 Nos = 4; % Oversampling factor.
 Nsub = totalSubcarriers;
 Fsub = [0:Nsub-1]*Fs/Nsub; % Subcarrier spacing
 numRuns = 1000; % Number of runs.
 M=16;
 s=log2(M);
 EbN0dB = [0:16];
 EsN0dB = EbN0dB + 10*log10(s);
 for ii = 1:length(EbN0dB)
 for n = 1:numRuns,

    % Generate random data.
    if dataType == '16QAM'
       ipBit = randint(1,numSymbols,M);
       ipBit = ipBit.';
       %Data Modulation
       ipMod = (1/sqrt(10))*qammod(ipBit,M); 
    end

    % Time range of the OFDM symbol.
    t = [0:Ts/Nos:Nsub*Ts];

    % OFDM modulation.

    for k = 1:numSymbols,
        y= ipMod(k)*exp(j*2*pi*Fsub(k)*t);

        %adding gaussian noise
        nt = [randn(1,257)+ i*randn(1,257)];
        yt = y + 10^(-EsN0dB(ii)/20)*nt;

        %receiver
        data_rx= yt.*exp(-j*2*pi*Fsub(k)*t); 
        data_rx = data_rx(:,1);
    end

        ipBitHat = qamdemod(data_rx*sqrt(10),M);

 end
 end

Answer 1

[Walter Roberson]

You are overwriting data_rx on each iteration of the "for k" loop.

[f2t1]

u mean i need to take out that data_rx from the k loop?

[Walter Roberson]

Why are you calculating noise per symbol? Is there a separate channel for each symbol? You should be adding noise to each channel once the waveform for the channel has been calculated.