# Cooperative Content Caching Framework Using Cuckoo Search Optimization in Vehicular Edge Networks
## 6 Cooperative Content Caching Framework
### Optimisation Using Cuckoo Search
Table 4 details the simulation settings and implementation parameters. ### Non-Cooperative Content Caching (Non-COOP)

In non-cooperative caching, MBS and RSUs make their caching decisions independently. If they want to cache the popular content, then popularity will be calculated on each caching server. There is no cooperation to calculate and download the popular content cooperatively, which leads to computational cost and time consumption; moreover, data duplication will also occur on the same tier. \begin{table}
\begin{tabular}{c c c} \hline
**S. No** & **Parameters** & **Value** \\ \hline
1. & Caching buffer & 100–700 MB \\
2. & Network size & 40, 60, 80, 100, 120 \\
3. & No. of contents & 1000 \\
4. & Content size & 10 MB \\
5. & Vehicle speed & 25–75 km/h \\
6. & Length of cluster (L) & 50 m, 35 m, 20 m \\
7. & Number of iterations & 50 \\
8. & Rate of model learning & 0.002 \\
9. & Validations failures & 8 \\
10. & Hidden layers & 5 \\
11. & Number of polling layers & 3 \\
12. & Training data size & 897,560 \\
13. & Testing data size & 102,440 (11\%) \\
14. & Time taken to train the model & 617 min \\
15. & Testing time & 0.043 ms \\
16 & Exponential decay (\(\lambda\)) & 0.05 \\
17. & No of users & 50–500 \\
18. & RSU transmission range & 100 m \\ \hline \end{tabular}
\end{table} 
Table 4: Simulation settings and modeling parameters. #### 7.1.1 Reactive Caching Model

In the reactive caching technique, when a vehicle sends a request to RSU, it fetches the content from BS or the back-haul server. There is no predicted pre-cached data; RSU will download the data as requests are received [29]. #### 7.1.2 Pro-Active Content Caching Model

Although in proactive caching there is no cooperation between neighboring RSUs and BSs, data are pre-cached on RSU. So, pre-caching is performed here. It takes the same time to download the content from the back-haul link as reactive caching takes. But the delay in delivering the content to the vehicle will be short as compared to reactive caching; due to its pre-caching capability [29]. #### 7.1.3 Cooperative Content Caching (COOP) + K-Means

According to this strategy, we have chosen the list of popular predicted contents and cached them at MBS, then PF content is delivered to the RSUs on demand. Neighboring RSUs share the data cooperatively before requesting to the MBS server. After fetching the data from RSU the vehicle stores the data in its cache for a limited time. At first, when the user sends a request to the RSU, RSU searches the requested data in its clusters and sends the information of caching device to the requesting node; in this way, the devices can get that data from their neighbors with minimum delay. ### Cache Hit Ratio, Caching Cost, Delivery Cost and Delay with Different Cache Sizes

Figure 6 shows that by increasing cache size, the availability of different types of content will increase. In case of content availability, more users can get access to the local cache so the hit ratio will also improve. In the case of maximum cache size COOP (CS), the hit ratio is almost 27% better than COOP (ACO) and around about 43% better than proactive caching. As there is no cooperation in RSUs and in reactive caching, it goes in the same fashion and does not increase, because it will download the content from the upper layer server each time. In our proposed model, the server searches the content in its clusters first and there is no need to search the whole data set, as data are cooperatively cached in the server so the hit ratio will be better. Figure 7 shows that data are required according to the caching capacity, if there is more capacity it will store more data. Caching capacity is bought in BW. There is almost a 10% difference in the result when the caching capacity is higher and in the case of minimum cache size, it is 7% in the COOP (ACO) comparison graph. In COOP (ACO) and NON-COOP (proactive), there is a little bit of difference because it also pre-caches the content but there is a lack of clustering.