The chapter begins with a discussion of how quantization of message signal in PCM transmission needs to be interpreted as noise and then calculates. This is followed by calculation of quantization noise power. The effect of additive thermal noise on PCM is considered next. SNR at PCM receiver output is calculated that includes both quantization noise and thermal noise. This is used to calculate probability of error for PCM system carrier modulation schemes like PSK, FSK. Next, similar issues like quantization noise, thermal noise and their combined effect in SNR calculation are addressed for DM and corresponding probability of error shown. A comparison of PCM and DM is presented. How noise affects Adaptive DM is discussed through its use in a space shuttle flight.
