15. summary
• To perform detection the receiver observes the received
signal for the duration of one symbol and guesses which
particular symbol was sent according to some set of rules.
• In coherent detection the receiver is assumed to be in
possession of exact replicas of the transmitted signals.
• In coherent detection a source of error in decision making
process is additive thermal noise at the receiver
input ,which is modelled as Gaussian noise of zero mean
and constant power spectral density.
16. • When all the signals are transmitted with equal
probability ,the optimum rule turns out to be maximum
likelihood; the criterion for optimality is minimization of
the average probability of symbol error.
• The optimum filters is implemented in the form of a bank of
correlators or matched filters followed but maximum
likelihood detectors.
• In non-coherent detection the receiver has no knowledge of
carrier phase. The presence of phase uncertainty in received
signal is the source of error .
