subband sinr computation in 5G

Hello,

I have developed the code below to compute the subband sinr in a downlink 5G waveform. The waveform information is shown beside each variable. Basically, I have the waveforms of the signal, interference, and noise, and trying to compute the subband sinr in 13 resource block groups (RBGs), each RBG has 8 RBs. I feel I am missing something though. The sampling rate is 30720000 and Nfft is 2048; That results in a subcarrier spacing of 15 kHz (5G numerology 0). However, for a 20 MHz channel, number of subcarriers = 12 RBGs * 8 RBs * 12 Subcarriers + 1 RBG * 4 RBs * 12 subcarriers = 1200 subcarriers, which is larger than Nfft/2 = 1024! Any idea about this?

Thanks.

function [sinrdB] = sinr_fn(rxWaveform, intrxWaveform, noise, waveformInfo)
        
RMS = @(x) sqrt(mean(abs(x).^2));

%%            
fs = waveformInfo.SamplingRate;     % 30720000
Nfft = waveformInfo.Nfft;           % 2048
RBG = 8*12*15000;                   % Resource block group
% *********************************************************************** %

%% Noise power
wbPnoise = RMS(noise)^2; 

noisefft = fft(noise, Nfft);
psdnoise = (1/(fs*Nfft)) * abs(noisefft).^2;

subPnoise = zeros(13, 1);
for i = 1:length(subPnoise)
    if(i == 13)
        subPnoise(i) = sum(psdnoise( (i-1)*96+1 : (i-1)*96+4*12 ))*RBG;
    else
        subPnoise(i) = sum(psdnoise( (i-1)*96+1 : i*96 ))*RBG;
    end
end
% *********************************************************************** %

%% wideband signal power
wbPsignal = RMS(rxWaveform)^2;

signalfft = fft(rxWaveform, Nfft);
psdSignal = (1/(fs*Nfft)) * abs(signalfft).^2;

subPsignal = zeros(13, 1);
for i = 1:length(subPsignal)
    if(i == 13)
        subPsignal(i) = sum(psdSignal( (i-1)*96+1 : (i-1)*96+4*12 ))*RBG;
    else
        subPsignal(i) = sum(psdSignal( (i-1)*96+1 : i*96 ))*RBG;
    end
end
% *********************************************************************** %

%% Interference power
wbPint = RMS(intrxWaveform)^2; 

intfft = fft(intrxWaveform, Nfft);
psdInt = (1/(fs*Nfft)) * abs(intfft).^2;

subPint = zeros(13, 1);
for i = 1:length(subPint)
    if(i == 13)
        subPint(i) = sum(psdInt( (i-1)*96+1 : (i-1)*96+4*12 ))*RBG;
    else
        subPint(i) = sum(psdInt( (i-1)*96+1 : i*96 ))*RBG;
    end
end
% *********************************************************************** %

%% snr calculations
wbSINR = wbPsignal / (wbPint + wbPnoise);
wbSINR_dB = 10*log10(wbSINR);

subSINR = subPsignal ./ (subPint + subPnoise);
subSINR_dB = 10*log10(subSINR);

sinrdB = [wbSINR_dB; subSINR_dB];
% *********************************************************************** %

end