Open Access
Lee, Kyounghwan
Graduate Program:
Electrical Engineering
Doctor of Philosophy
Document Type:
Date of Defense:
October 10, 2007
Committee Members:
  • Aylin Yener, Committee Chair
  • Thomas F Laporta, Committee Member
  • John F Doherty, Committee Member
  • Guohong Cao, Committee Member
  • cognitive
  • relay network
  • hybrid network
Future wireless networks will evolve towards architectures where multiple communication standards or technologies cooperate with each other by sharing the resources and transmitting their information in a cooperative fashion. Such network architectures will be made possible by the use of cognitive radios. This thesis aims to investigate the design and the performance of a new wireless network paradigm termed cognitive hybrid wireless relay network. We first consider a simple three-node hybrid wireless relay network where multiple frequency bands available from the source and the relay are mutually orthogonal. Specifically, we investigate the information-theoretic performance and the corresponding optimum resource allocation for various relaying schemes. Convinced by the merit of the hybrid wireless relay network architecture, we next investigate the design of large hybrid wireless relay networks where source nodes communicate to their destinations via intermediate nodes able to detect spectrum holes. We examine the outage and diversity performance of the resulting two-hop system under fairly general channel conditions. Lastly, we consider more general cognitive wireless networks where a number of cognitive users seek to access unused frequency channels licensed to the primary users. In this setup, we propose cooperative spectrum sensing strategies in which cognitive users collaborate to share their decisions regarding spectrum occupancy of primary users.