| Spatial modulation (SM) is a newly emerging multiple-input-multiple-output technique that activates only a single antenna for transmission at any time instant and uses the index of the active antenna as an additional information-carrying mechanism. However, by its nature, SM decoding is coherent in that channel state information (CSI) is required at the receiver. In fact, coherent SM decoding can be very complex due to the heavily entangled channel estimation and symbol detection. In correspondence, while preserving the single active transmit antenna property, is developed. The proposed scheme can be applied to any constant energy constellation such as phase-shift keying (PSK) and to systems with arbitrary numbers of transmit and receive antennas. And simulation results are presented under various system configurations. With the same spectral efficiency, the proposed scheme is capable of paying no more than 3 dB of signal-to-noise ratio penalty compared with coherent SM and outperforming the single-antenna differential PSK and differential space-time coding schemes. Differential spatial modulation (DSM) is a newly-emerging differential scheme tailored to the spatial modulation technique, which selects only one among a group of antennas for transmission at any time instant. DSM, however, gives rise to pro-hibitive search complexity when the number of transmit antennas is large. A low-complexity suboptimal detector is proposed for DSM. It is designed based on the maximum-likelihood criterion but takes more candidates for the antenna activation orders into account. The detection is performed in two steps:the first step is to confine the number of candidates for the modulated symbols to a small portion by exploiting the symmetry of the signal constellation; the second step is to select the most likely modulated symbols from the output of the first step Analyses and simulations show that the proposed detector achieves near-optimal performance yet largely reduces the search complexity. |
