# Anti-Jamming Low-Latency Channel Hopping Protocol for Cognitive Radio Networks
## 5 Simulation
The ALL protocol performs better than OLAA_T and OLAA_R in both synchronous and asynchronous networks because each SU running ALL can adjust the positions of \(T\) frames according to the fixed \(R\) frames of its intended receivers to increase the number of guaranteed rendezvous. Specifically, when compared to the OLAA_T and OLAA_R protocols, the ALL protocol achieves an average of 25% and 20% improvement in terms of throughput and TTR, respectively. The simulation results also reveal that the ALL protocol has similar performance in synchronous and asynchronous networks. When SUs are synchronous, the sender and its receiver have a rendezvous only in the columns where their corresponding ID digits are different. That is, two nodes have many rendezvous when their IDs are very different. When SUs, say sender \(a\) and receiver \(b\), are asynchronous but the first column of \(M_{a}\) overlays with that of \(M_{b}\), the rendezvous condition is similar to that of a synchronous network. When the first column of \(M_{a}\) does not overlay with that of \(M_{b}\), there is a guaranteed rendezvous between the first column of \(M_{a}\) and a column other than the first one in \(M_{b}\). SUs \(a\) and \(b\) will have many rendezvous when their IDs corresponding to other columns are very different. Because the node IDs are uniformly distributed in the simulations, similar numbers of rendezvous can be found for synchronous and asynchronous networks. The ALL protocol also achieves similar performance in different topologies. Note that the ALL protocol outperforms the OLAA_T and OLAA_R protocols in all three different topologies. The central node of the star topology and the bottleneck node in the bottleneck topology suffer from transmission collisions, and thus, the produced ATTR values are higher than that of the mesh topology. For example, when 20 channels are used in a synchronous network, the throughput for the mesh, bottleneck, and star topologies is 64.1, 63.8, and 63.9 MB, respectively. The ATTR in the same environment for the three topologies is 78.5, 79.1, and 79.0 slots, respectively. When 20 channels are used in an asynchronous network, the throughput for the mesh, bottleneck, and star topologies is 64.1, 63.7, and 63.9 MB, respectively, while the ATTR for three topologies is 78.5, 79.1, and 79.0 slots, respectively. Since the performance in different topologies is similar and whether SUs are synchronous has little impact on performance, to avoid redundancy, we present the results of the mesh topology with synchronized SU nodes in the following simulations. Figure 4: This figure illustrates the three network topologies employed in the simulations: (**a**) mesh, (**b**) star, and (**c**) bottleneck. Figure 5: This figure displays the impact of the number of channels on the mesh topology’s performance in a synchronous network, as measured by two metrics: (**a**) throughput and (**b**) ATTR. Figure 6: _Cont._  
Figure 6: This figure displays the impact of the number of channels on the bottleneck topology’s performance in a synchronous network, as measured by two metrics: (**a**) throughput and (**b**) ATTR. Figure 7: This figure displays the impact of the number of channels on the star topology’s performance in a synchronous network, as measured by two metrics: (**a**) throughput and (**b**) ATTR. Figure 8: This figure displays the impact of the number of channels on the mesh topology’s performance in an asynchronous network, as measured by two metrics: (**a**) throughput and (**b**) ATTR. Figure 9: _Cont._  
Figure 10: This figure displays the impact of the number of channels on the star topology’s performance in an asynchronous network, as measured by two metrics: (**a**) throughput and (**b**) ATTR. Figure 9: This figure displays the impact of the number of channels on the bottleneck topology’s performance in an asynchronous network, as measured by two metrics: (**a**) throughput and (**b**) ATTR.