# Cooperative Content Caching Framework Using Cuckoo Search Optimization in Vehicular Edge Networks
## 5 System Model  
We consider a multi-tier VEN, including vehicles (end-user), RSUs, and MBS. MBS and Backhaul links are connected to the cloud server and database. In VEN, end-users/vehicles  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Algorithm** & **Parameters** & **Complexity** & **Justification** \\ \hline \multirow{4}{*}{CS} & Population (_n_), egg-matching & \multirow{4}{*}{N = 1 always same due to 1 cuckoo,} \\  & probability, number of iterations & Best case: _O (1)_ & Dimension range (0,1), if number of \\  & (_Rmax_), step size/Dimension & _O (n. D. Rmax)_ & iteration increases it will not significantly \\  & size (_D_) & & affect the complexity \\ \hline \multirow{4}{*}{CS} & _1 \(<\) log n\(<\) n \(<\) n \(<\) n \(>\) 2 \(<\) n\({}^{*}\)3\(<\) 2\({}^{*}\)X\(<\) n\({}^{*}\)X \(\rightarrow\)_ Run time from better to worse \\ \hline \hline \end{tabular}
\end{table}
Table 2: _Cont._  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**S. No** & **Abbreviation** & **Full Form** \\ \hline
1. & RSUs & Road site units \\ \hline
2. & MBS & Mobile base station \\ \hline
3. & PCZS & Pre-caching zone selection \\ \hline
4. & PCNS & Pre-caching node selection \\ \hline
5. & P2P & Peer to peer \\ \hline
6. & V2I & Vehicle to infrastructure \\ \hline
7. & OBUs & On-board units \\ \hline
8. & VEN & Vehicular edge network \\ \hline
9. & VANET & Vehicular ad-hoc network \\ \hline
10. & MECs & Mobile edge computing devices \\ \hline
11. & SDVN & Software Define Vehicular Network \\ \hline
12. & PKI & Public key infrastructure \\ \hline
13. & OLSR & Optimized link state routing \\ \hline
14. & ICN & Information centric network \\ \hline
15. & PCMP & Proactive caching with mobility prediction \\ \hline
16. & V2V & Vehicle to vehicle \\ \hline
17. & ACO & Ant colony optimization \\ \hline
18. & PSO & Particle swarm optimization \\ \hline
19. & GA & Genetic algorithm \\ \hline
20. & SA & Simulated annealing \\ \hline
21. & CS & Cuckoo search \\ \hline
22. & LTE-V2I & Long-term evolution vehicle to infrastructure \\ \hline
23. & BS & Base station \\ \hline \hline \end{tabular}
\end{table}
Table 3: Abbreviations and their definitions.  
transmit their data to the connected RSU. RSU covers the circular region of a minimum of 100 m near the roads to facilitate the users in high mobility. The area of RSU is not overlapped; the vehicle that is not in range of RSU will be directly connected to MBS.  
We used cooperative edge caching with K-means for multi-tier caching servers (MBS and RSUs) to cache the single content at multiple servers cooperatively. If the requested content is available in these servers, then it can be fetched by the vehicle through the coverage area. Content delivery from a remote server will increase both delay and cost. First, we focus on the coverage area of MBS, where the number of RSUs is deployed. We consider the number of RSU as D = {D\({}_{1}\), D\({}_{2}\), D\(3\)...... D\({}_{N}\)} coverage areas of RSU and MBS as D\({}_{B}\) and D\({}_{R}\), set of vehicles is V = {V\({}_{1}\), V\({}_{2}\), V\({}_{3}\)...... V\({}_{N}\)}. RSU, MBS, and vehicles are equipped with caching capacities, such as S\({}_{MBS}\), S\({}_{RSU}\), and S\({}_{V}\). MBS acts as a network management controller, collecting data from edge servers and vehicles and making caching decisions. After that, MBS will share the copy of cached data to the connected RSUs to minimize the service delay and cost in terms of bandwidth (BW) utilization. Edge servers share their working state with the controller server, determining whether the server is overloaded or underloaded before transferring the workload. This external layer resource management process can be accomplished by managing the flow of data in access control sources while operation on VMs of edge servers remains undisturbed [40].