Phase Shift Keying on the Hypersphere: Power-Efficient MIMO Communications

The modulation scheme Phase Shift Keying on the Hypersphere (PSKH), a generalization of conventional Phase Shift Keying (PSK) for Multiple-Input Multiple-Output (MIMO) systems, is introduced. In PSKH, constellation points are distributed over a multidimensional hypersphere. The use of such constellations with Peak-To-Average-Sum-Power-Ratio (PASPR) of 1 allows to use load-modulated transmitters which require much smaller backoff, which in turn results in a higher power efficiency. In this paper we discuss several methods how to generate PSKH constellations and compare their performance. After applying conventional Pulse-Amplitude Modulation (PAM), the PASPR of the continuous time PSKH signal depends on the choice of the pulse shaping method. This choice also influences bandwidth and power efficiency of a PSKH system. In order to reduce the PASPR of the continuous transmission signal, we use spherical interpolation to generate a smooth signal over the hypersphere and present the corresponding receiver. Additionally, complexity reduction techniques are proposed and compared. Finally, we discuss the methods presented in this paper regarding their trade-offs with respect to PASPR, bandwidth, power efficiency and receiver complexity.