Digital Communication- Pulse Coded Modulation

Ask

If the number of bits per sample in a Pulse Coded Modulation (PCM) system is increased from 5 bits to 6 bits,the improvement in signal to quantization noise ratio will be

(a) 3 dB          

(b) 6 dB

(c) 2pi dB       

(d) 0 dB

Answer is ( b)

Concept

SNRdb = 6.02n+1.76      ; where n is the number of bits

SNRdb(5) = 6.02 x 5 +1.76 = 31.86 dB 

SNRdb(5) = 6.02 x 6 +1.76 = 37.88 dB      

SNRdb(6) - SNRdb(5) = 37.88 - 31.86 = 6.02 dB

Thus we have 6db as the answer