Immune system-inspired evolutionary opportunistic spectrum access in cognitive radio ad hoc networks

Underutilization of licensed spectrum stimulates the opportunistic spectrum access (OSA) paradigm that aims to enable unlicensed users to detect and access the temporarily unused spectrum bands so as to enhance overall spectrum utilization. However, the realization of these paradigms entails several difficulties such as self-organization of unlicensed users, self-regulation of communication parameters, and self-adaptation to time-varying radio environment. In nature, biological systems intrinsically have these great abilities that can be modeled and adopted to overcome the difficulties posed by opportunistic spectrum access. In this paper, a new Immune system-inspired Evolutionary Opportunistic Spectrum Access (ESA) protocol is introduced. Based on the self-nonself detection and clonal selection principles in immune system, ESA allows unlicensed users to separately detect, share, and access the available spectrum bands without interfering the licensed users. The overall ESA operations do not need for any priori information about the access statistics of licensed users and also do not need for any coordination and message exchanges among the network nodes. In addition, unlike the existing works, ESA does not require any dedicated control channel in the entire network. Furthermore, ESA also exploits the contention among the nodes and their mobility, if exists, towards accelerating the evolution in the system, and hence, yielding higher overall spectrum utilization. Performance evaluation results show that ESA achieves high throughput under various network conditions.