Noise variance calculation for 16APSK Demodulator
This is to take into account the oversampling operation. 

Symbol time = sample time implies no oversampling.

See AWGN model for more details about the conversion among EbN0, EsN0 and SNR.


  For example, if a complex baseband signal is oversampled by a factor of 4, then EsNo exceeds the corresponding SNR by $10\log_{10}(4)$.