Seems to me that
signalPower(ii) = signalPower(ii) + abs(IQrx(ii-jj))^2;
Should be something more like:
signalPower(ii) = signalPower(ii) + abs(IQrx(ii-jj));
You might want to try something a bit simpler for the signal power like:
pwt=x'*x; % Power in time domain
where x
is your windowed time series value. (inspiration from this link).