Efficient MIMO Transmission of PSK Signals With a Single-Radio Reconfigurable Antenna

Crucial developments to the recently introduced signal-space approach for multiplexing multiple data symbols using a single-radio switched antenna are presented. First, we introduce a general framework for expressing the spatial multiplexing relation of the transmit signals only from the antenna scattering parameters and the modulating reactive loading. This not only avoids tedious far-field calculations, but more importantly provides an efficient and practical strategy for spatially multiplexing PSK signals of any modulation order. The proposed approach allows ensuring a constant impedance matching at the input of the driving antenna for all symbol combinations, and as importantly uses only passive reconfigurable loads. This obviates the use of reconfigurable matching networks and active loads, respectively, thereby overcoming stringent limitations of previous single-feed MIMO techniques in terms of complexity, efficiency, and power consumption. The proposed approach is illustrated by the design of a realistic very compact antenna system optimized for multiplexing QPSK signals. The results show that the proposed approach can bring the MIMO benefits to the low-end user terminals at a reduced RF complexity.Comment: 30 pages, 6 figures. IEEE Transactions on Communications, 201

Beamforming via large and dense antenna arrays above a clutter

Abstract — The paper sheds light on the beamforming (BF) performance of large (potentially unconstrained in size) as well as dense (but physically constrained in size) antenna arrays when equipped with arbitrarily many elements. Two operational modes are investigated: Single-layer BF and multi-layer BF. In the first mode, a realistic BF criterion namely the average BF gain is revisited and employed to understand the far-field and the near-field effects on the BF performance of large-scale antennas above a clutter. The diminishing throughput returns in a single-layer BF mode versus the number of antennas necessitate multi-layering. In the multi-layer BF mode, the RF coverage is divided into a number of directive non-overlapping sectorbeams in a deterministic manner within a multi-user multi-input multi-output (MIMO) system. The optimal number of layers that maximizes the user’s sum-rate given a constrained antenna array is found as a compromise between the multiplexing gain (associated with the number of sector-beams) and the inter-beam interference, represented by the side lobe level (SLL)

Implementation of a reconfigurable parasitic antenna for beam-space BPSK transmissions

A successful approach for designing a compact reconfigurable antenna system using a single active and two parasitic reactance-loaded dipoles is proposed. The switched parasitic antenna (SPA) operates at 2.6 GHz using PIN diode technology. It is designed to enable the spatial multiplexing rate of two BPSK signals within previously developed disruptive space-time transmission techniques

Reduced-Complexity Radio Architectures for Enhanced Receive Selection Combining in Multiuser Diversity Systems

Although antenna selection is a simple and efficient technique for enhancing the downlink performance of multiuser diversity systems, the large antenna interelement spacing required for achieving spatial diversity is prohibitive for user terminals due to size restrictions. In order to allay this problem, we propose miniaturized switched beam receiver designs assisted by low-cost passive reflectors. Unlike conventional spatial receive diversity systems, the proposed angular diversity architectures occupy a small volume whereas the antenna system properties are optimized by controlling the strong reactive fields present at small dimensions. The systems are designed for maximum antenna efficiency and low interbeam correlation, thus yielding N practically uncorrelated receive diversity branches. The simulation results show that the proposed enhanced diversity combining systems improve the average throughput of a multiuser network outperforming classical antenna selection especially for small user populations and compact user terminal size