Energy- and Cognitive-Radio-Aware Routing in Cognitive Radio Sensor Networks

Cognitive radio sensor networks (CRSNs) are the next generation wireless sensor networks (WSNs) that mitigate overcrowded unlicensed spectrum bands by opportunistically using temporally unoccupied unlicensed and licensed spectrum bands. In this paper, we propose a new energy- and cognitive-radio-aware routing (ECR) protocol that addresses the unique challenges in CRSNs, including dynamic spectrum access, single transceiver, and energy constraint. In particular, our proposed routing protocol performs joint node-channel assignment by taking energy into consideration, is aware of cognitive radio at the network layer, and can seize spectrum opportunity in other spectrum bands. We present a simple analytical model of the proposed ECR in the viewpoint of network-wide energy and compare it with that of the ad hoc on-demand distance vector (AODV) routing protocol. Furthermore, our simulation results show that, in relatively heavy traffic environment, ECR outperforms AODV in terms of network lifetime and packet delivery ratio. Nevertheless, scalability and communication complexity become the major issues of this protocol. 1. Introduction Wireless sensor networks (WSNs) are a special case of ad hoc networks and have been widely used for monitoring physical phenomena, such as human activities and environment monitoring. Since it is intended to be easily embedded in the physical environment, WSNs are designed with minimum computational facilities and limited power resources. In the future, however, ISM (Industrial, Scientific, and Medical) bands are projected to be congested and overloaded due to numerous wireless networks utilizing the same bands [1]. The explosive implementation of wireless technologies such as 802.11b/g/n (WiFi), 802.15.1 (Bluetooth), and 802.15.4 (WSN) will largely occupy ISM bands and cause unavoidable interference not to mention electrical appliances such as cordless phones, microwaves, and so forth. Meanwhile, cognitive radio ad hoc network (CRAHN) technology offers a good solution to increase spectrum utilization by making use of temporally unused spectrums in an opportunistic manner. By combining cognitive radio (CR) capability to WSNs, the spatially overlapping wireless networks may coexist in ISM bands with minimum interference, and spectrum utilization can be increased. Hence, cognitive radio sensor networks (CRSNs) [2, 3] have become the subject of many studies in the research community. Opportunistic usage of the lower frequency of the licensed bands offers a number of benefits to CRSNs. The main advantage is that lower frequency has