Space-Time Code Division Multiple Access based on Spatial Modulation

This study proposes a novel multiple access method based on a spatial modulation (SM). The aim of this study is to significantly increase the number of multiple-users keeping the performance degradation low but keeping the device simple. The conventional system utilizes SM as a spatial domain modulation and thus can boost transmission rate. In contrast, this study exploits SM technique as the generator of spatial sequence for code division multiple access. It is worth noting that the spatial sequences of individual users include their own channel states which are mutually independent among users. As a result, even if several users utilize identical antenna switching pattern (spatial spreading code), the receiver can detect all users' data by exploiting the difference of channel states. Furthermore, our proposed multiple-access scheme can be combined with the conventional CDMA system. The theoretical analysis and computer simulation reveal that the proposed space-time CDMA can efficiently realize multiple access.