A unified framework for secondary user accessing/handoff in cognitive heterogeneous network

In future network, various heterogeneous cognitive radio networks (CRNs) are expected to coexist in the same geographical area to suport Quality of Service (QoS) requirements of both primary users (PUs) and secondary users (SUs). In this system, the SUs with multiple interfaces may select the optimal network for accessing or handing off. Although the problem of network selection and user handoff has been considered in previous works, the spectrum handoff issue inside one CRN or between various CRNs is not fully studied. Furthermore, the problem of accessing and handoff strategies are studied individually in previous works, which may result in the limitation of overall system performance due to the competition for system resources between new users and handoff users. In this paper, we propose a unified framework for accessing and handoff strategies in heterogeneous CRNs. Through designing different optimization metrics for accessing and handoff schemes, the joint performance optimization for both new and handoff users can be obtained. Applying a four-dimensional Markov decision process (MDP) model, the proposed accessing and handoff scheme is modeled and detail performance analysis is conducted. The numerical results demonstrate the efficiency of the proposed scheme.