Reconfigurable Orthonormal Basis Patterns Using ESPAR Antennas

Beamspace multiple-input-multiple-output (BS-MIMO) systems with reduced hardware complexity have been recently considered in the literature. So far, BS-MIMO research effort focuses on the development of efficient single-RF MIMO transmission schemes based on parasitic antenna arrays. Single-RF BS-MIMO systems can provide both multiplexing and beamforming capabilities by exploiting the available aerial degrees of freedom of the radiated field while maintaining low space and complexity requirements. Previous studies used electronically steerable passive array radiators (ESPARs) for the multiplexing of multiple data streams utilizing an ESPAR-specific set of orthonormal basis patterns. However, these basis patterns ensure orthogonal transmission of the multiple streams in idealistic rich scattering environments. In this letter, a novel technique is developed for the adaptive selection of the most effective basis patterns in both transmitter and receiver sides based on the actual wireless channel propagation conditions maximizing the system capacity.