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

TL;DR

This paper introduces PSKH, a hypersphere-based modulation for MIMO systems that enhances power efficiency by enabling load-modulated transmitters, and explores methods to generate, shape, and decode these constellations.

Contribution

It proposes new PSKH constellation generation and shaping techniques, including spherical interpolation, to optimize power and bandwidth efficiency in MIMO communications.

Findings

PSKH constellations achieve low PASPR of 1.

Spherical interpolation reduces signal smoothness and PASPR.

Trade-offs between power efficiency, bandwidth, and complexity are analyzed.

Abstract

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 on a multidimensional hypersphere. The use of such constellations with a Peak-To-Average-Sum-Power-Ratio (PASPR) of 1 allows to use load-modulated transmitters which can cope with a small backoff, which in turn results in a high 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 corresponding receiver techniques. 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.