Multiple Bit Differential Detection of SOQPSK with Diversity Reception

Abstract

In this paper, we consider multiple bit differential detection (MBDD) of differentially encoded shapedoffset quadrature phase-shift keying (SOQPSK) over slow fading channels, especially Rayleigh fading channels. SOQPSK is a highly bandwidth efficient and popular form of constant envelope continuous phase modulation (CPM). We present two versions of the MBDD algorithm: the full-size version (FMBDD) which uses a detection window that spans the entire N-bit observation window, and an improved version (I-MBDD) which maintains the original N-bit observation window but detects only N − 2 bits within the window. The complexity of both algorithms is shown to increase linearly with the order of diversity reception, L, and exponentially with the size of the observation window, N; the I-MBDD achieves the best performance for given values of L and N. As expected, the performance in the case of diversity reception shows a marked improvement over the single channel case.