# Mobility-Enhanced Reliable Geographical Forwarding in Cognitive Radio Sensor Networks
## 8 Conclusions  
This paper presented the MROR routing protocol, which addresses the issues of route stability and the spatio-temporal spectrum availability metric in mobile CRSNs. MROR, which was built upon ROR, also ensures the reliability of communication links in CRSN. It was established that typical routes for CRSNs must not always be built away from the PU coverage area, as a target area of interest might lie within a PU coverage area. Thus, typical CRSN mobile routing should jointly create efficient routes within and outside the PU coverage area as the case may be. For routes built outside the PU coverage area, it was observed that the traditional keep-out radius does not properly account for the protection of the PU when mobility is considered. Therefore, a mobility-induced guard (mguard) distance was introduced into the scheme to both ensure proper PU protection and improve the throughput of the mobile nodes. It was also observed that at higher speeds, the sensing interval was more dependent on the speed of the mobile nodes than it was on the statistics of the PU traffic, which is the strategy used by the reviewed works. Thus, the routing metric in MROR both considers the speed and the PU traffic in creating routes. The main metric that makes the speed important in this respect is the spatio-temporal spectrum availability that is mobility induced. The effect of not considering the speed results in a high level of route instability. As a solution, in addition to creating virtual clusters around potential next hop nodes of the selected routes, MROR also introduces a unique hand-over region that helps to greatly reduce the re-initiation of a new route request and route maintenance operations that is usually caused by mobility. As a result, MROR can record a decrease in the route failure rate of about 65% as against other schemes. Furthermore, simulation studies have shown that MROR can improve both the throughput and goodput at the sink in an energy-efficient manner that is required in CRSNs as against reviewed works. It is important to mention that the presented result for the MROR scheme is limited to the smooth mobility model utilized in the study. In addition, the considered PU and SU scenario for this work is static PUs and mobile SUs. For further improvement, we suggest the modification of the scheme to be adaptable to the random waypoint model, while other scenarios in which both PU and SU are mobile should be considered. It is envisaged that this work will be extended by incorporating a suitable transport layer to ensure advanced congestion control to preserve scarce network resources while considering application-based QoS requirements.  
The authors would like to thank the anonymous reviewers for their valuable comments. This work is financially supported jointly by the Post-Doctoral fellowship scheme for the project \"Development of Reliable Opportunistic Mobile Routing Protocol for Cognitive Radio Sensor Networks\" and the Fundamental Research Grant Scheme (FRGS) Grant : RJ130000.7809.4F397.A.  
**Author Contributions:** [PERSON] designed the study, performed experiments, data analysis and prepared the manuscript. [PERSON] and [PERSON] provided technical oversights at all stages.  
**Conflicts of Interest:** The authors declare no conflict of interest.