A hybrid diversity receiver using differential detection and conditional combining

Differential phase shift keying (DPSK) is a modulation, which allows the design of simple receivers since it does not require complex channel estimation as, for example, in the case of coherent PSK. However, when selection or switch diversity is used at the receiver, the use of DPSK modulation is problematic because differential detection requires two consecutive symbols from the same branch to work properly. In this paper we address this issue with a technique called conditional diversity combining. The conditional diversity combining (CDC) receiver uses DPSK and has two receive chains, the same number as the classical SC receiver. While the CDC and the SC receivers have the same number of receive chains, the CDC receiver uses more sophisticated logic, to take advantage of the second chain and improve its performance. We present results which indicate that the performance of the CDC receiver is bounded by the classical SC and the double selection/equal gain combining receivers