Differential space-time modulation with full spatio-spectral diversity and arbitrary number of transmit antennas in ISI channels

We present a differential space-time-frequency (DSTF) modulation scheme for systems with an arbitrary number of transmit antennas over frequency-selective fading channels. The proposed DSTF scheme employs a concatenation of a specially designed spectral encoder and a differential encoder/mapper that yield the maximum spatio-spectral diversity advantage and significant coding gain. To reduce the decoding complexity, the differential encoder is designed with a unitary structure that decouples the maximum likelihood (ML) detection in space and time; meanwhile, the spectral encoder utilizes a new linear constellation decimation (LCD) coding scheme that encodes across minimally required subchannels and, as a result, has the least decoding complexity among all full-diversity codes. Numerical results show that the proposed DSTF scheme compares favorably with several existing differential space-time schemes for frequency-selective channels.