4-DIMENSIONAL SIGNALING FOR BAND-LIMITED-CHANNELS

In this paper we discuss multidimensional signaling for transmission o ver the satellite channel, i.e, a bandlimited radio channel with non-l inearities. We derive a set or basis signals that are orthogonal and w hose bandwidth occupancy is minimal, in the sense that they maximize t he power inside a fixed frequency interval (-B, B). Since we remove th e assumption that the signals be confined in one symbol interval, the concept of orthogonality must be revisited. We design basis signals th at satisfy the following requirements: (a) When passed through their m atched filter, the sample sequence has no intersymbol interference; (b ) when passed through the filter matched to another basis signal, the sample sequence has no interchannel interference, and (c) their bandwi dth occupancy is minimum. The performance of four-dimensional signals designed according to this criterion is evaluated in terms of bandwidt h occupancy and error probability over nonlinear satellite channels. C omparisons with two-dimensional modulation schemes (in particular, QPS K) are also made.