Quadratic decorrelation receiver for unresolved multipath fading channels

We derive suboptimal noncoherent detection structures for multipath fading channels when the multipath delays are assumed to be known but unresolved. The quadratic decorrelation receiver (QDR), a structure that is derived from fundamental principles, consists of an orthogonalization (or decorrelation) stage and then implements a resolved multipath channel decision rule. Single pulse performance over two paths Rayleigh and two paths mixed mode Ricean/Rayleigh fading channels for binary DPSK and binary FSK respectively are considered. This paper shows that it is possible to have diversity-like gains over multipath fading channels with unresolved components even if the channel is not fully tracked. The decorrelation stage of the receiver is crucial for improving performance when the multipath is unresolved.