Differential full diversity spatial modulation (DFD-SM) is a differential spatial modulation scheme that makes use of a cyclic unitary M-ary phase shift keying (M-PSK) constellation to achieve diversity gains at both the transmitter and receiver. In this paper, we extend the power allocation concept of generalized differential modulation (GDM) to DFD-SM to improve its block-error rate (BLER). A novel power allocation scheme is formulated, and its optimum power allocation is derived. An asymptotic upper bound is presented for the new scheme and results are verified through Monte Carlo simulations. It can be seen that for a large enough frame length, the proposed scheme can almost achieve coherent performance. We also propose a low complexity detection scheme for DFD-SM. We evaluate the computational complexity of the maximum-likelihood (ML) detector and compare it to that of the proposed algorithm. It is shown that our scheme is independent of the constellation size. Numerical simulations of the BLER are presented, and it can be seen that the proposed scheme provides near ML performance throughout the entire signal-to-noise ratio (SNR) range with a complexity reduction of about 55% and 52% for one and two receive antennas respectively, in the high SNR region.
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