WiFiUS: Collaborative Research: Future Small-Cell Networks Using Reconfigurable Antennas

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The future proliferation of wireless systems and services is dependent on the design of flexible radio architectures that can adapt to the rapidly changing wireless environment. Since usable spectrum is limited, and modulation and coding techniques are approaching their Shannon capacity limitation, improving capacity through increased spectrum reuse and interference mitigation has become a high priority in future cellular networks. Industry leaders have focused on a multi-tiered heterogeneous network structure, where small-cell (e.g., pico-cell, femto-cell) base stations are deployed to meet capacity demand. Among the technical challenges making full-scale deployment of small-cell base stations possible, interference management still looms the largest. This project focuses on providing wireless systems with the available hardware and algorithmic tools to make intelligent decisions about antenna configuration for small-cell base stations to mitigate interference and improve network capacity and coexistence in a heterogeneous network environment.This project is composed of three main research thrusts: i.) Algorithm and System Design; ii.) Antenna and Transceiver Design; and iii.) Testbed Implementation. The first focus is on the mathematical modeling and overall system design of small-cell networks making use of reconfigurable antennas. A vital component of this overall system design is the development of efficient and effective analytical tools and algorithms for downlink transmission, focusing on directional network design, algorithms for directionality selection, and base station user association. The second thrust includes the development of practical reconfigurable antennas and transceiver processing techniques for small-cell base stations. The project team is adapting reconfigurable metamaterial and alford loop antenna designs to provide new, compact reconfigurable antenna architectures with both beam steering and variable beam width capabilities. Using these new antenna technologies this research enhances direction of arrival and digital pre-distortion techniques for enhanced small-cell uplink and downlink. The cornerstone of this research is the design of a fully implemented, programmable across-the-stack SDR platform with integrated reconfigurable antennas. This project makes use of open-source technologies and will result in the deployment of a fully functional cellular backbone system, consisting of both macro-cell and small-cell base stations.This project leverages collaboration between Drexel University and WPI, along with a strong international collaboration with the University of Oulu, VTT Technical Research Centre and Tampere University of Technology. This ongoing collaboration with Finnish institutions continues to provide novel international research experiences for undergraduate and graduate students as well as pilot testing for dissemination of the developed testbed.