k-channel connected topology control algorithm for cognitive radio networks

Cognitive radio networks (CRNs) enable secondary users (SUs) to access the underutilized spectrum licensed to primary users (PUs) without causing unacceptable interference to the PUs' activities. On appearance of PUs, the available channel of SUs change dynamically over time. A pair of communicating SUs must vacate the channel and has to switch to other available channel, when a PU reclaims the channel in use with SUs. This can sometimes lead to partition of CRNs if there is no alternative channel. Due to temporal variations of channel availability among SUs possess research challenge for ensuring connectivity of CRNs. In CRN, it is crucial to minimize power consumption while maintaining k-channel connectivity. We require topology generated by power setting must be at least k-vertex connected subgraph of the network graph and remains connected when any of (k - 1) channels reclaimed by PUs. This problem is known to be NP-hard. In this paper, we consider k-channel connectivity of a CRN. We combine topology control and channel assignment to achieve conflict free k-channel connected topology in CRN. We present a centralized algorithm, Centralized k-channel Connected Spanning Subgraph (CCSS
_k
), which preserves k-channel connectivity and ensures conflict free channel assignment in CRN. CCSS
_k
preserves minimum energy path between any pair of nodes. Simulation results show that the constructed topology has a small average transmission range and a small average degree than other existing topology control algorithms. Proposed algorithm construct topology which is power-efficient i.e. constant power stretch factor. The simulation results demonstrate that the proposed algorithm can reduce the number of required channels efficiently to achieve k-channel connected topology while preserving conflict free property.