NSF Career Award Winner

Zhu Han
Dr. Zhu Han, Fellow IEEE, Fellow AAAS
John and Rebecca Moores Professor
Office Location: W302 Engineering Building 2
Phone: 713-743-4437 | Fax: 713-743-4444
Email: zhan2 [at] uh.edu


Mutual Benefit in Cognitive Radio Networks: A Coalitional Game Framework

Cognitive radio (CR) is a revolutionary wireless communication paradigm in which cognitive users are able to observe, learn, optimize, and intelligently adapt in order to improve utilization of spectrum without interfering with traditionally licensed users. Yet major technical challenges remain in order to make this vision a reality. First, to avoid interfering with primary users, the cognitive users must explore and sense the spectrum opportunities to determine whether there are ongoing activities before data transmission. Second, a critical issue is dynamic and opportunistic resource allocation over time-varying heterogeneous interfering environments. Third, due to hardware limitation, each cognitive user should distributively choose the candidate channels to either sense or access (i.e., exploration and exploitation).

Due to the distributed nature, the future network and protocol architectures for cognitive radio networks should be self-organized, distributed, and collaborative to overcome the above challenges. Game theory is a powerful and flexible mathematical tool to study how the autonomous users interact and cooperate with each other. Motivated by these facts, this proposed research constructs a framework to investigate the cooperative and competitive relations among individual distributed cognitive users, based on a variety of approaches to cope with the time-varying channel/traffic conditions, heterogenous user profiles, different QoS requirements, and security

Intellectual Merit: The proposed five-year activities are primarily targeted at uncovering the fundamental design challenges/tradeoffs, proposing distributed solutions based on the game theory, and constructing hardware/software platforms with easy online access to other researchers.

  • Identify Major Problems in CR Networks. The PI investigates Spectrum Sensing aspects such as collaborative sensing and its inherent tradeoff between false-alarm and detection probabilities; Dynamic Spectrum Access aiming at maximizing utilization of the limited radio bandwidth while accommodating the increasing amount of services and applications in wireless networks; and Exploration & Exploitation for balancing between spectrum sensing and spectrum accessing with consideration of channel variation, the licensed users’ presence, and other cognitive users’ activities.
  • Propose Coalitional Game Theory Approaches. The PI proposes to employ the novel cooperative game theory that emphasizes mutual benefit management with simple distributed solutions. In the literature, only a small number of work has investigated the applications of the strong analytical tools of cooperative games in cognitive radio networks. The PI proposes solutions based on three categories of cooperative games: Canonical Coalitional Game, Coalitional Formation Game, and Coalitional Graph Game.
  • Hardware Implementation and Software Protocol Development. The proposed schemes and frameworks will be implemented using the hardware/software platform in the newly established Wireless Networking, Signal Processing, and Security Lab at the University of Houston. The research outcomes will be shared and publicly available for other researchers worldwide.

Broader Impact: The proposed program is interdisciplinary and combines concepts from signal processing, economics, decision theory, optimization, information theory, communications, networking, and control theory. The results and design philosophy are transformative and can potentially be applied to other research areas. The results will be publicly available through publications and over the Internet for hardware/software platforms. Ultimately, the proposed framework will provide a blueprint for building new perspectives on future cognitive radio design. The research results will be integrated into the existing combined education and research effort at the University of Houston. Furthermore, the education component will equip both graduate and undergraduate students with the skills needed to contribute to the field of wireless networks partially based on the PI’s three textbooks. Outreach activities will be directed to middle school and high school students and teachers, and will emphasize increasing the participation of women and minorities in science and engineering. As such, the broader impact resulting from the proposed activities is also reflected through the integration of research and education for the training of the future engineering workforce.