Space-Time Frequency-Shift Keying Based on Hadamard Matrix Modulation

Focusing on the problem that existing Space-Time Frequency-Shift Keying (ST-FSK) incurs a spectral efficiency loss, this paper proposes a novel ST-FSK based on Hadamard matrix modulation coined as HST-FSK. HST-FSK uses the Hadamard matrix to expand a newly defined FSK waveform in both spatial and temporal dimensions according to the Kronecker product, and it achieves a higher spectral efficiency than ST-FSK owing to the more parameters are introduced into the new FSK waveform. As a special unitary space-time code, HST-FSK is appropriate for arbitrary number of transmit antennas and can be non-coherently detected with the absent of Channel State Information (CSI) at the receiver. Moreover, HST-FSK is easier to design and enjoys full antenna diversity, which are the advantages of HST-FSK over other Unitary Space-Time Modulation (USTM) designs. Theoretical analysis and simulation results show that compared with the existing typical USTM schemes, HST-FSK achieves a performance comparable to ST-FSK for the same spectral efficiency, and a better performance than the systematic designed USTM for high spectral efficiency.