Single and Multi-Carrier MIMO Transmission in Beamspace Using Single-RF ESPAR

Beamspace single-carrier and multi-carrier transmission schemes for multiple-input multiple-output (MIMO) systems using single-radio-frequency (RF) electronically steerable parasitic array radiator (ESPAR) antenna are investigated. Single-RF MIMO based on ESPAR antenna has advantages of smaller size, low cost and higher energy efficiency when compared to conventional MIMO antenna. While with mutual coupling and single RF chain, MIMO transmission using ESPAR is conducted in beamspace domain where multiple streams of symbols are mapped onto a set of orthogonal far-field radiation patterns instead of antenna elements. In this work, single-carrier beamspace spatial modulation (SM) as well as generalized SM are studied while for multi-carrier case, SM-orthogonal frequency division multiplexing (OFDM) and OFDM are investigated. By finding the optimal reactive loads of ESPAR, these single and multi-carrier MIMO transmission schemes can be performed by exciting the radiation patterns corresponding to the symbol streams. Simulation example using ESPAR of 5-element uniform circular array for various schemes in frequency-selective channel are provided. It is shown that bit error rate (BER) of the MIMO system using ESPAR with optimized radiation patterns achieves close performance to conventional MIMO systems, demonstrating the effectiveness of the proposed approach and its promise in sixth-generation (6G) wireless communication.