A Simple Multiphase Coding Technique for Transmit Diversity in Continuous Fading Channels

We propose a simple constellation-precoding technique for coherent phase-shift keying (PSK) modulation. The constellation of coded symbols is designed for a multiple-input-multiple-output (MIMO) system in frequency-nonselective Nakagami-m fading channels. Such a signaling mechanism, which is composed of the precoding technique and orthogonal pulse shaping, is shown to provide error performance and bandwidth efficiency comparable with those of the conventional space-time block codes (STBCs). We present a low-complexity coherent receiver, error bounds, and a code-search criterion for the considered system, which can alternatively operate with or without full channel-state information (CSI). Numerical and simulation results are provided to verify the significant performance improvement obtained by the proposed diversity scheme over Nakagami-m fading. The proposed approach is shown to be more robust against the decrease of adjacent fading sample correlation than the conventional STBCs while continuous fading is considered. For certain wireless environment limitations such as full CSI absence and fast fading, the scheme provides an alternative solution to mitigate the fading effects at the cost of low implementation complexities.