T H E Effect 01 a N Kandomlv Time-varving Channel on Mutual Information. \ Limk+=

Abstract : W e examine the e f f ec t of a the rate of change of the channel. r a n d o m l y t ime-va ry ing channe l on m u t u a l Suppose. as a special case. that we can describe the information between receiver a n d sender when channel by a Gauss-Markov model. We assume that. at my the channel is m t h o rde r hlarkov. time. the taps of the channel are mutually independent and that the expected energy of the tap corresponding to a we investigate the effect of a randomly time-var)ring given delay does not (:hange In time. Let Tc be the channel upon the mutual information between sender and coherence time O f the channel. roughly the inverse of the receiver. Such channels often occur i n mobile Dopplerspread. Let T , be the time spread of the channel, communications and can affect the achievable rate. If the proportional to A " The channel may be modelled as channel is perfectly known, then the mutual i n f o ~ " m becoming decorrelated in time exponentially with rate between a receiver and an arbitrary number of senders ma?' inversely proportional to T,. We may write that: be found, even if the channel is time-varying [l] . In this paper we consider the case of a single receiver and sender pair to set the framework for the more interesting multiple access case. We consider a discrete-tlme matnx model for O u r