Intellectual Merit: Wireless cognitive radio (CR) technology holds great promise to address fruitfully the perceived dilemma of bandwidth under-utilization versus spectrum scarcity, which has rendered fixed-access communication networks inefficient. Accordingly, the need arises for fundamental research in critical cognition infrastructure to sense, learn, and adapt to the environment CR networks operate. This proposal aims to develop this infrastructure for comprehensive situation awareness through the novel notion of RF cartography. Paralleling the success of routing tables, the vision is to jointly utilize interference and channel gains maps to identify opportunistically available bands for re-use, and handoff operation; localize and track user activities; as well control resource allocation and routing decisions. The approach draws from contemporary advances in sparsity-aware regression, compressive sampling, basis expansions, spline interpolation, and kriged Kalman filtering. The project leverages these tools to investigate: (a) distributed, online, and adaptive algorithms for map estimation and tracking; (b) training-based and blind cartography options; (c) spatio-temporal spectrum re-use, and localization in the presence of multipath and shadowing effects; and, (d) cartography-driven network utility maximization for optimal cross-layer design of CR networks.
Broader Impacts: This research is of interest to software radio designs with IEEE 802.11 compliant standards. In a broader sense, advances in sparsity-aware regression, kriging, splines, and spectrum cartography will permeate benefits to a gamut of areas as diverse as machine learning and data mining for social networks, dynamic magnetic resonance imaging, surveillance using wireless sensor networks, as well as navigation and safety systems. Cognition in networking and localization applications will further provide meaningful experiences to undergraduates and integration of the expertise gained to enhance the content of graduate classes. Outreach to the government and industrial sectors will be possible through short courses, tutorials in workshops and conferences, and student-faculty-staff collaboration.
This project developed a cognition infrastructure to sense, learn, and adapt to the radio-frequency (RF) environment that the so-termed cognitive radio (CR) communication networks operate at the physical layer (PHY) layer. It further paved the way to permeate benefits from the PHY to the medium access control (MAC) and CR network layers. Key to achieving these goals is the novel notion of RF cartography, which amounts to constructing two families of maps: (m1) global power spectral density (PSD) maps capturing the distribution of power across space, time, and frequency; and (m2) local channel gain (CG) maps providing the propagation medium per frequency from each node to any point in space and time. Paralleling the success of routing tables, the scientific impact of this novel suite of cognition algorithms is to have CR nodes jointly utilize these maps so as to enable: i) identification of opportunistically available spectrum bands for re-use, and hand-off operation; ii) localization, transmit-power estimation, and tracking of primary user (PU) activities; and iii) interference control and efficient allocation of power and bandwidth resources, thus advancing the state-of-the-art approaches aiming at anywhere-anytime enhanced radio access. Major research findings have included: F1. Cooperative PSD sensing via Kriged Kalman Filtering, and distributed tracking of CG maps; F2. RF cartography-driven network utility maximization and power control for optimal cross-layer design of CR networks under channel uncertainty; and F3. Publication of more than two dozen journal papers, patents, book chapters, and at least as many conference papers in scientific meetings. Broader impact on the educational and outreach fronts has been achieved through: E1. Completion of six (6) PhD Theses; and further training of four (4) postdoctoral researchers; E2. Reading group meetings to educate graduate students on advances related to CR telecommunication and data networks, and the interplay between the latter with the power grid and social networks. E3. More than a dozen keynote addresses and tutorials delivered by the Principal Investigator in major international conferences, and at least as many colloquium speeches at US Industry sites, and Universities worldwide.
