IMPROVEMENT OF NONCOHERENT ORTHOGONAL CODING BY TIME OVERLAPPING

A simple way to increase the performance of noncoherent orthogonal cod ing is suggested. The idea is to overlap the transmitted symbols in ti me using an appropriate set of symbols. The best upper bound of the po ssible performance improvement in terms of E(b)/N(o) when transmitting over the AWGN channel is proven to be M/(M - 1). An example of a set of orthogonal symbols which can be overlapped to achieve this bound is the Walsh functions. The theory is a generalisation of the relation w hich exists between binary FSK and differential PSK for M-ary orthogon al noncoherent modulation.