Receiver structures and performance for unresolved Ricean/Rayleigh multipath fading channels

This paper considers receiver structures and performance for unresolved mixed mode Ricean/Rayleigh multipath channels. A fading channel is said to be mixed mode if the first path gain is Ricean distributed and the other path gains are Rayleigh. The optimal receiver for this case consists of a decorrelation stage combined with a quadratic form, as well as a nonlinear term related to the Ricean specular component. Replacing the nonlinear term by a quadratic form, yields a novel family of quadratic sub-optimal receivers, quadratic decorrelation receivers (QDR), that could be more easily implemented. These receivers exploit the decorrelation performed on the signal samples similar to the optimal receiver. Single pulse performance of the QDR and other sub-optimal structures is studied for binary FSK and DPSK. It is shown that SNR gains can be obtained by the use of receivers that exploit the knowledge of the specular component. Furthermore, we demonstrate the importance of the decorrelation operation in eliminating the error floors when the multipath is unresolved