Project Design Of The Opportunistic Spectrum Access Based On POMDP

With the rapid development of communication, growing demand for wireless services andincreasement of communications bandwidth, the wireless spectrum resource is more and more scare.And the current fixed spectrum allocation policy aggravates the spectrum shortage situation.Opportunistic spectrum access(OSA) technology allows cognitive secondary users to takeadvantage of the authorized user’s idle spectrum in a hierarchical access model. OSA can improvespectrum efficiency under the existing spectrum allocation policy.The dissertation develops an analytical framework for opportunistic spectrum access based onthe theory of partially observable markov decision process(POMDP). Under the framework, aoptimal project for a single user is developed, which solves the sensing channel selection and accessproblems and improve user throughput. To reduce complexity a suboptimal project is proposed. Thesimulation results prove the correctness of the two projects.In a distributed multi-user setting, multiple secondary users will select the same channel whenthey implement the same single user project.It brings about channel contention among secondaryusers and decline in network throughput. So a randomized sensing plan based on the channel beliefvector is proposed to solve the problem. Although the plan can weaken user synchronization, it alsoreduce user throughput. To solve the problem, a randomized sensing project with changeabledomain width is developed. The simulation results show that the project reaches a balance betweenoptimal channel selection and synchronization avoidance.