Stacked Alamouti Based Spatial Modulation

Abstract

In this paper, a high-rate and diversity-achieving spatial modulation transmission scheme is proposed, which uses the stacked Alamouti code as the transmitted signal matrix and then is named as stacked Alamouti based spatial modulation (SA-SM) scheme. In this scheme, the spatial constellation (SC) is composed of all the possible activated antennas combinations. According to a specific SC codeword, the corresponding symbols in the stacked Alamouti code are simultaneously activated. Owing to the structure of stacked Alamouti code, the SA-SM scheme can work with arbitrary even number of transmit antennas $n_{T}$ , and any number of activated antennas from 1 to $n_{T}$ . With the same number of activated antennas $n_{A}$ , the SA-SM scheme carries more symbols than the spatially modulated orthogonal space-time block codes (SM-OSTBC) scheme, thus SA-SM can achieve higher spectral efficiency. Without the need of any parameter or matrix optimization, the SA-SM scheme enjoys the non-vanishing determinants property. Moreover, owing to possessing the block-orthogonal structure, SA-SM enables faster metric computations in the QR decomposition-M detection, and then it achieves significant decoding complexity reduction without performance loss. Under various system configurations, the performance advantages of SA-SM over several existing diversity-achieving SM schemes such as GSTSK and SM-OSTBC, are shown by simulation results for various spectral efficiencies.