Space-Time Block Coded GMSK With Low-Complexity Linear Receiver

Existing space-time codes have focused on multiple-antenna systems with linear modulations such as phase-shift keying or quadrature amplitude modulation. Continuous phase modulation (CPM) is an attractive scheme for digital transmission because of its constant envelope which is needed for power-efficient transmitters. Recent research has shown that space-time coded CPM can achieve transmit diversity to improve performance while maintaining the compact spectrum of CPM signals. However, these efforts mainly combine space-time trellis code (STTC) with CPM to achieve spatial diversity at the cost of a high decoding complexity. In this paper, we design space-time block codes (STBC) for Gaussian minimum shift keying (GMSK), a special case of CPM with modulation index 1/2. This scheme has a much lower decoding complexity than STTC CPM and still maintains excellent diversity performances.