In cognitive radio networks, to avoid interference with licensed users, unlicensed users must vacate the spectrum accessed by the primary users. Since it takes some time for the unlicensed users to detect and switch to other available spectrum, the ongoing data transmission may have to be interrupted, leading to poor data access performance. Although there is a lot of research on cognitive radio networks, not much work has been done on data access. This project focuses on three intertwined issues to support resilient and efficient data access: (i) Various topology control protocols which carefully assign communication channels considering network robustness and channel interference to achieve better data accessibility, are designed and evaluated; (ii) Delay-constrained caching techniques are introduced to deal with primary user appearance, where data is cached/replicated at appropriate nodes to statistically limit the data access delay; (iii) Spectrum-aware data replication schemes are designed to improve data access performance in intermittently connected cognitive radio networks, by considering both node mobility pattern and primary user appearance. This project will make significant theoretical and technological advances in understanding and supporting resilient and efficient data access in cognitive radio networks. The success of this project is likely to have a broader impact on making cognitive radio networks more affordable and amenable to commercial, civilian, and military applications. The results of the project will be disseminated widely through high quality publications and presentations. The proposed research will also be integrated with the education curricula at the Pennsylvania State University.
