# Mobility-Enhanced Reliable Geographical Forwarding in Cognitive Radio Sensor Networks
## 7 MROR Comparison  
In this section, MROR has been compared to both CRP [11] and ROR. Why CRP [11] was chosen was because it supports the building of routes across the PU coverage area, which is more in line with the CRSN scenario considered in this work. This contrasts with SEARCH [12] and TIGHT [14], which build routes outside the PU coverage area in all cases. In addition, all available protocols have not considered the unique resource-constrained nature of CRSNs. Thus, for this evaluation, CRP [11] is identified as the most appropriate. ROR [13] was used to show the effect of not considering the speed of mobile nodes in the design of on-demand protocols. In Figure 15, the effect of speed on route stability is presented. All protocols can still maintain route stability until speeds of about 2 m/s. Furthermore, because LMR nodes in ROR were originally designed to be static, the frequent recall of the route maintenance module when mobility was introduced made the whole routing scheme become unstable. In the case of CRP, its proactive nature of  
Figure 14: Goodput _vs._ number of network nodes. Figure 15: Effect of speed on route stability in cognitive radio sensor network (CRSN). discovering a new path in case the current route fails is responsible for it maintaining network stability better than ROR. Furthermore, it was observed that as the speed increased, the active route is already expired before the proactive function finishes implementing the choice of alternative route. However, MROR surpasses both CRP and ROR, first because of its VMH zoning system and its forwarding strategy that does not restrict the forwarding node to a single node, as is the case in CRP. This quality makes MROR more robust at handling the issues mobility poses. As a result, a decrease in the failure rate of about 65% is observed by employing the MROR strategy. The effect of the speed on the throughput is illustrated in Figure 16. The route instability of both CRP and ROR definitely affects the throughput as illustrated. However, an additional factor responsible for the observed performance of MROR as compared to the other two is the spatio-temporal property it considers in the route selection stage that greatly improves the throughput at the sink. As in the case of both CRP and ROR, this metric was not considered for route formation. In general, while MROR tries to maintain the throughput as the speed increases, the values for throughput dwindle at increased speed in the case of CRP, and a more drastic decline is observed for the case of ROR. In Figure 17, the goodput performance of all three cases is illustrated. In general, the speed affects the goodput in all cases, but with varying magnitudes. This effect is most obvious in the case of ROR than CRP, mainly because of the instability of the network at such speeds. However, in the case of MROR, the VMH system greatly enhanced the uninterrupted implementation of the SNR reception metric. In addition, enforcing prioritization for potential receivers also helped the reduction in contention, which subsequently reduced collision during forwarding the packet towards the sink. On the contrary, in the case of CRP, in addition to the instability, the absence of instantaneous channel information often demands the need for multiple re-tries in transmitting the packet. This has also contributed to the observed decline in goodput. Figure 16: Throughput _vs._ speed of the mobile node. The energy consumed per packet is illustrated in Figure 18. MROR outperforms CRP because MROR is designed for CRSNs; Thus, energy was always considered in the creation of routes and in the forwarding of packets. The forwarding scheme also helps in network load distribution, which also affects the energy of the whole network. In contrast, CRP was not designed for CRSNs; therefore, energy was not considered in either the route election or forwarding stages. In addition, the frequent route request that is initiated by the route instability also contributes to the inefficiency (in terms of energy) when compared to MROR.