# Mobility-Enhanced Reliable Geographical Forwarding in Cognitive Radio Sensor Networks
## 6 Performance Evaluation  
From the system model, certain observations were made. From Equation (6), as can be viewed from the Figure 10, in order to ensure both PU protection and the route stability (for routes outside the PU coverage), the density of the keep-out radius has to be increased as the number SU users increases. Since the mobility of nodes increases the chance of an increase in SU density in time, it is proposed that routes that are formed outside PU coverage should be aware of the mobility-induced guard (mguard) distance in addition to the keep-out distance, as formulated in Equation (21). The simulation parameters considered for this case include: \(Z_{o}\) = 250 m, ITL = 0.1 mW, \(\alpha\) = 3.8 and \(\delta_{p}\) = 1/km\({}^{2}\). Figure 9: Flow chart for the MROR node forwarding algorithm. CCC, control channel; SIFS, short inter-frame space; DIFD, data initiative forwarding determination. Secondly, as derived from the Equation (14) it is clear from Figure 11 that at a higher speed, the sensing interval is more dependent on the speed of the mobile nodes than it is on the statistics of the PU traffic. This is a major point that has not been considered in other mobile _ad hoc_ protocols. When considered, this property has the potential of significantly increasing the route throughput and also to save energy, as the number of times the CRSN node has to perform spectrum sensing can be reduced by the nature of the routes formed. This fact is further corroborated in Equation (18), as can be seen in Figure 12, because depending on the number of PU users in the network, the channel availability can be said to become stable only at certain values of \(\ell_{i}\). For the simulation in Equations (14) and (18), the following parameters were set thusly; \(Z_{o}=250\) m, \(v=5\) m/s, \(\delta_{s}=0.1\), \(\delta_{p}=1/\)km\({}^{2}\) and \(P_{on}=0.6\). Figure 11: Effect of speed on spectrum sensing intervals in a cognitive radio sensor network (CRSN). Figure 10: Effect of keep-out radius in routing for cognitive radio sensor networks (CRSNs). The communication complexity in MROR is evaluated and compared to ROR and CRP in the MATLAB-based routing modeling application simulation environment (Rmase) [33; 34] of the probabilistic wireless network simulator (Prowler) [24; 35]. A topology of 40-200 mobile cognitive radio sensor nodes, which are uniformly deployed in a 100 \(\times\) 100 m\({}^{2}\) sensor network, is considered. The sensors are distributed such that they cut across PU coverage. The sink is considered to be static and located with coordinates (120, 120), away from the coverage of the PU network. For each considered case of simulation, an event at coordinates (20, 20) having an event radius of 20 m\({}^{2}\) is reported to the sink node. From the seven channels available, each node makes a selection, as discussed earlier during the RREQ phase. All of the channels are modeled to possess the same bandwidth with overlapping with adjacent channels. This ensures that, during transmission, interference does occur between packets on different channels. In relevant scenarios, results were taken for values of \(P_{on}\) between 0.2 and 0.6. The duration for each simulation was set for 100 s. The final results presented are average values of 10 trials along with 80% confidence intervals. The outlined performance metrics were investigated:  
* Throughput: This metric is used to measure the time performance of the considered application. The throughput is computed as the number of bits-per-second received at the sink. Since certain protocols allow multiple copies to reach the sink, thus unique packets out of the total packets the sink receives are considered in computing the throughput. * Goodput: Goodput is a measure of the reliability of communication in the considered network. It is computed as the ratio of total unique packets the sink receives by the number of packets sent from the source nodes of each stream.