The chapter begins with requirement of a baseband receiver and gently introduces concept of matched filter. The theoretical derivation of an optimal filter and how it is implemented through matched filter and correator are discussed. The logic used applies equally well to both baseband and passband reception of digital data. Probability of error or its upper limit is calculated for different types of transmission mode. Signal space representation of a signal is also used which is particularly useful for M-ary communication. A discussion on relationship between bit error rate and symbol error rate is presented. In all these derivations, it is assumed that symbols are equiprobable and also the cost of making a wrong decision is same for every circumstances. A discussion on maximum likelihood detector and generalized Bayes’ receiver shows how to proceed if it is otherwise. Finally, probability of error of QPR system is presented in full detail followed by comparison of different modulation systems in terms of error probability and bandwidth requirement.
