Reduced Overhead Training for Multi Reconfigurable Antennas with Beam-Tilting Capability

This paper proposes low overhead training techniques for a wireless communication system equipped with a Multifunctional Reconfigurable Antenna (MRA) capable of dynamically changing beamwidth and beam directions. A novel microelectromechanical system (MEMS) MRA antenna is presented with radiation patterns (generated using complete electromagnetic full-wave analysis) which are used to quantify the communication link performance gains. In particular, it is shown that using the proposed Exhaustive Training at Reduced Frequency (ETRF) consistently results in a reduction in training overhead. It is also demonstrated that further reduction in training overhead is possible using statistical or MUSIC-based training schemes. Bit Error Rate (BER) and capacity simulations are carried out using an MRA, which can tilt its radiation beam into one of N-dir = 4 or 8 directions with variable beamwidth (approximate to 2 pi/N-dir). The performance of each training scheme is quantified for OFDM systems operating in frequency selective channels with and without Line of Sight (LoS). We observe 6 dB of gain at BER = 10(-4) and 6 dB improvement in capacity (at capacity = 6 bits/sec/subcarrier) are achievable for an MRA with N-dir = 8 as compared to omni directional antennas using ETRF scheme in a LoS environment.