Sequential opportunistic spectrum access with imperfect channel sensing

Tao Shu, Marwan Krunz

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


In this paper, we exploit channel diversity for opportunistic spectrum access (OSA). Our approach uses instantaneous channel quality as a second criterion (along with the idle/busy status of the channel) in selecting channels to use for opportunistic transmission. The difficulty of the problem comes from the fact that it is practically infeasible for a cognitive radio (CR) to first scan all channels and then pick the best among them, due to the potentially large number of channels open to OSA and the limited power/hardware capability of a CR. As a result, the CR can only sense and probe channels sequentially. To avoid collisions with other CRs, after sensing and probing a channel, the CR needs to make a decision on whether to terminate the scan and use the underlying channel or to skip it and scan the next one. The optimal use-or-skip decision strategy that maximizes the CR's average throughput is one of our primary concerns in this study. This problem is further complicated by practical considerations, such as sensing/probing overhead and sensing errors. An optimal decision strategy that addresses all the above considerations is derived by formulating the sequential sensing/probing process as a rate-of-return problem, which we solve using optimal stopping theory. We further explore the special structure of this strategy to conduct a "second-round" optimization over the operational parameters, such as the sensing and probing times. The aggregate throughput performance when a network of CRs coexist with primary radios is evaluated under homogeneous and heterogeneous spectrum environments, respectively. We show through simulations that significant throughput gains (e.g., about 100%) are achieved using our joint sensing/probing scheme over the conventional one that uses sensing alone.

Original languageEnglish (US)
Pages (from-to)778-797
Number of pages20
JournalAd Hoc Networks
Issue number3
StatePublished - May 2013


  • Channel sensing and probing
  • Opportunistic spectrum access
  • Optimal stopping

ASJC Scopus subject areas

  • Software
  • Hardware and Architecture
  • Computer Networks and Communications


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