Post-Detection Combining Diversity Improvement of Four-Phase DPSK System in Mobile Satellite Communications.

In mobile satellite communications with a wide service area, the largest problems in composing the system are the Rician fading, where the direct wave component and the random time-varying scattered wave component interfere with each other, as well as the low received power due to the propagation for a long distance. This paper considers diversity as a means to overcome these problems. The four-phase DPSK system is considered, and a theoretical analysis is made on the error rate improvement by the post-detection combining diversity. The characteristic functions of two orthogonal delayed detection outputs of the branches are used in the derivation of the error rate. Three communication systems of satellite/aircraft, satellite/land mobile and satellite/ship are considered as the models. Theoretical expressions are derived to evaluate the improvements. The error rate is also evaluated for the selective diversity. The result is compared with the case of combining diversity, together with the discussion for the difference between the two schemes. [ABSTRACT FROM AUTHOR]