Differential space-frequency modulation for MIMO-OFDM systems via a "smooth" logical channel

In this paper, a differential space-frequency modulation (DSFM) scheme is proposed for MIMO-OFDM systems with assumptions that the channel keeps constant only within each OFDM block, and it may change independently from one OFDM block to another. The transmitted/received signals are differentially en/decoded in the frequency dimension within each OFDM block. The performance of the proposed scheme depends on the channel power delay profile. Moreover, if the statistics of the power delay profile is known at the transmitter, we further propose to permute the channel frequency responses over subcarriers by using the Dijkstra's algorithm to increase the performance of the DSFM scheme. Simulation results show that the DSFM scheme with permutations performs very well for various channel profiles.