# Mobility-Enhanced Reliable Geographical Forwarding in Cognitive Radio Sensor Networks
## 1 Introduction  
The wide proliferation of mobile wireless devices and applications is introducing new research challenges in cognitive radio networks. According to the latest worldwide study, for industrial automation alone, the installed base of wireless Internet of Things (IoT) devices reached 10.3 million in 2014 [1]. Furthermore, it is globally recorded that smart devices represented 26 percent of the total mobile devices and connections in 2014; they accounted for 88 percent of the mobile data traffic [2]. Thus, in addition to the spectrum management issues that arise from this trend [3; 4], the fact that the huge emerging network is basically characterized by sensors has brought the area of mobile cognitive radio sensor networks (MCRSN) to the research spot light [5]. Mobility is among the most important factors that affect the effective communication in wireless systems. Although it affects all of the communication layers, however, it poses unique challenges to the routing layer, because it affects numerous network characteristics, such as network capacity [6], connectivity [7] and coverage [8]. It is also an inherent feature to support various types of wireless services in cognitive radio sensor networks (CRSNs). Despite its importance, however, mobility hasnot been adequately addressed in the context of resource-constrained routing in dynamic spectrum access [5]. As at this time, no work has been proposed to tackle the issue of mobile routing in CRSNs. Although, there exist some proposals in the realm of cognitive radio _ad hoc_ networks (CRAHNs), which can seemingly be assumed to be adaptable for CRSNs. However, this is not the case because of the unique resource constraint characteristics of CRSNs, specifically in terms of computation, energy and memory capacity [3]. Nevertheless, the issue of mobile routing in CRAHNs is still an open research issue, as most proposed routing metrics mainly considered metrics that do not directly reflect the effect of node mobility [5]. The main issues that such proposed metrics failed to address with respect to mobility include high route instability and mobile estimation of channel availability. These two metrics are the direct implication of introducing mobility into CR networks. Thus, the effectiveness of any protocol will be seriously impacted if both are not considered as a routing metric. As these metrics are still yet to be incorporatedas active routing metrics [5], the motivation for this work (as further elucidated in Section 2) is mainly to propose a routing scheme that incorporatesboth metrics in routing for CRSNs. It should be recalled that, the CRSN paradigm was introduced to improve overall spectrum utilization. Thus, by dynamically changing its operating parameters, CRSN nodes (the Secondary Users, SUs), senses the spectrum, determines the vacant bands, and makes use of these available bands in an opportunistic manner. With these capabilities, CRSN nodes can operate in both licensed and unlicensed bands. In licensed bands, wireless users with a specific license to communicate over the allocated band (the primary users, PUs), have the priority to access the channel. SUs, are only allowed access to the channel with the condition of not causing interference to the PUs. When a PU starts communication, SUs must detect other potentially vacant bands (spectrum sensing), decide on which channel move to (spectrum decision), and then finally adapt its transceiver so that the active communication is continued over the new channel (spectrum handoff). This sequence of operation which outlines a typical cognitive cycle can also be applied by the SUs over an unlicensed band. This work proposes a mobility-enhanced reliable opportunistic routing (MROR) scheme for routing in CRSN. MROR provides a robust mobility-enhanced framework that is based on a mobility channel availability model, which is still yet to be considered in mobile CRSNs.