MIMO wireless communications for closely spaced antennas

Future generations of mobile devices will rely on multiple-input multiple-output (MIMO) technology to deliver on the promises of boosted data rates and higher system performance. However, unlike single-antenna terminals, the MIMO handset propagation environment is a function of various factors, related not only to time-frequency, but also to spatial characteristics. Further, in accordance with the emerging cognitive radio technology, the increasing need to combat the spectrum scarcity problem dictates the opportunistic usage of the TV bands (100-800MHz) for which MIMO handsets have not yet been implemented due to physical sizes of antenna structures at lower frequencies. Moreover, with the ongoing trend of integrating many antennas into a small physical device volume, the user coupling effect is even more critical as it results in electromagnetic interaction among the closely-spaced antennas greatly affecting the MIMO handset performance. In fact, the "super-antenna" concept goes beyond the device boundaries to further account for the user head and hand. In all, the performance of MIMO mobile devices is significantly sensitive to the antenna design and a host of other factors that were less significant in single-antenna designs. The purpose of this project is to study and understand the interrelationship among the handset antennas, the device metallic frame (handset chassis), the user and the far-field scattering channel. The project also targets the development of efficient antenna designs and techniques targeted for electrically small terminals supporting different multiple-antenna technologies (such as spatial multiplexing, space-time codes or beamforming) and cognitive radio aspects. Finally, the proposal of proper assessment tools will assist in the accurate performance evaluation of the developed MIMO handsets in various channel conditions.