Collaborative Research: Full-Duplex Cognitive Radio: Theory and Hardware

Washington State University, Pullman WA

Investigators

Abstract

As the number of wireless devices will increase nearly 2-fold to almost 50 billion, and wireless/mobile data traffic is expected to increase 1000-fold within the next decade, the wireless spectrum has become a scarce commodity. This proposal aims at the development of novel theory and hardware that will significantly improve the ability to reuse the crowded spectrum by leveraging the capabilities of full-duplex mobile users in sensing the spectrum while they are transmitting. The concept of a fully passive full-duplex radio front-end in this proposed research is a fundamental shift from the conventional full-duplex radio designs that shall provide significant power and complexity advantages. The use of the proposed design in cognitive networks to intelligently detect unused radio spectrum is expected to lead to more efficient use of the spectrum and significant capacity enhancement that is not easily achievable using existing technologies. In the long term, the proposed concept has the transformative potential to improve wireless systems in a variety of aspects, ranging from high-capacity distributed multiple-input multiple-output solutions, efficient network protocols to support intelligent interference coordination, and management to reduce latency in multi-hop wireless networks. Besides these societal and technical contributions, this project will also advance discovery and understanding via integrating with both graduate and undergraduate education, and enhance infrastructure for research and education via an interdisciplinary, inter-institutional collaboration. The education and collaboration plans will additionally broaden the participation of underrepresented groups, including those from a predominantly undergraduate institution and female students. Through a collaboration between two experts in different areas (i.e., antenna design and communication theory), the overall objective of the proposed interdisciplinary research project is to develop new architectures and algorithms for full-duplex cognitive radio wireless communications to significantly improve reuse of the crowded spectrum. The specific aims of the project include the following: 1) to design and develop fully passive full-duplex hardware architectures suited for cognitive mobile devices, which significantly cancel the self-interference without the need for adaptive analog cancellation at the 5 Ghz band or below; 2) to investigate the applications of the proposed full-duplex hardware architectures in enhancing white spectrum usage and increasing capacity of cognitive radio links under the context of opportunistic spectrum access; and 3) to investigate the applications of the proposed full-duplex hardware architectures in multiuser cognitive networks for further sensing performance improvement and capacity enhancement. For Aim 1, the merit of the approach is in the use of novel antenna configurations that provide a considerable amount of isolation from self-interference. The design is based on obtaining two identical out-of-phase components of self-interference signals. The design is fully passive and can be used in wideband applications. For Aims 2 and 3, the approach to the information-theoretical characterization of the full-duplex cognitive radio link and network is founded on capacity calculation techniques using novel results in real and complex analysis, probability theory, and optimization theory. The full-duplex capability will be exploited in both simultaneously transmitting/sensing mode and simultaneously transmitting/receiving mode to fundamentally enhance the efficiency of using the vacant spectrum and to significantly improve the capacity of cognitive radio systems.