FSK and DPSK over unresolved multipath Rayleigh fading channels

In this paper we present single pulse performance of detection structures for fading multipath channels with common modulation formats such as FSK and DPSK. The multipath components are assumed to be unresolved, with known delays. These delays could have been estimated, for example, by sounding the channel with a pulse of much wider bandwidth than that of the information conveying signal. 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. However the required SNR to achieve such diversity gains is highly dependent on the modulation formats. Properly designed receivers for unresolved multipath channels may reduce the SNR, where the diversity gains are achieved, and lower significantly the error floors. It is shown that a quadratic decorrelation receiver performs well over unresolved multipath channels