Adaptive channel tracking using peak fade depth estimation over a slot

Abstract

Peak fade depth is measured () over a period of time, and a bandwidth of a channel filter () is then determined () according to the measured peak fade depth (). In preferred embodiments the average peak fade depth over two or more time slots is used. In a specific embodiment, an α filter () is used to determine the bandwidth of the matched filter (), in which α is determined based upon the measured peak fade depth (). In various embodiments, peak fade depth is correlated to the Doppler shifting of the channel, which in turn is used to determine the bandwidth of the matched filter by way of the α parameter. Hence, a non-linear equation can be used to determine the value of α which yields a minimum bit error rate for the matched filter (). More specifically, a matched filter () is matched to a received signal r(t) having k states according to a plurality of matched filters Mand outputs a signal given by |r(t)−C(t)*M(t)|, in which C(t) is a channel estimate provide by a channel tracker () for a state k at time period t that is given by C(t)=α*c(t)+(1−α)*C(t−1), c(t)=M*r(t)/(M*conj(M)), and conj(M) is the complex conjugate of M. For each time slot, α is computed from the running average of the peak fade depth () according to a predetermined equation ().