Orthogonal Space-Time Block Coding for Frequency-Domain Equalization of CPM

In this paper, an orthogonal space-time (ST) block coding technique for continuous phase modulation (CPM) is proposed and is combined with frequency-domain equalization (FDE) to obtain high diversity gains over the frequency-selective fading channels. The proposed technique maintains the constant envelope and the phase continuity of the CPM waveforms perfectly by using appropriate tail symbols during the addition of cyclic prefix and interblock transitions and, therefore, has no impact on the spectral efficiency. Depending on the orthogonality of the ST combining, FDE is applied as in the case of single antenna transmissions without any increase in the computational load. As presented by the simulations, the proposed technique improves the performance of the FDE significantly.