# Cooperative Caching and Resource Allocation in Integrated Satellite-Terrestrial Networks
## 6 Performance Evaluation
### Performance Comparison for Three Different Scenarios  
Initially, it is assumed that all users are in the coverage of several particular satellites due to the different geographical distribution of users, where the number of access satellites for users is indicated as \(N_{a}\). For the simulation parameters in Table 2, the experiments are conducted to evaluate the performance of content service in three different scenarios of _cooperative caching_, _edge caching_, and _cloud center_, where \(Q=5\), \(N_{a}=4\), and \(M=\{200,210,\cdots,300\}\). In the case of the _cloud center_, the content services of users are just provided by a cloud center, where the contents can be routed by a satellite network from the cloud center to users. For _edge caching_, a satellite network with edge caching can provide edge content services for users. Furthermore, for _cooperative caching_, as proposed in this paper, the content services of users can be provided by an integrated satellite-terrestrial network in a cooperative way. The performance comparison for content service in the three different scenarios, as shown in Figure 4, can be provided for each user service in terms of storage resource usage, network bandwidth consumption, and total deployment costs. The average storage costs of each user service in the three scenarios are shown in Figure 4a. For the _cloud center_, all the content services of users are provided by a cloud center, and the satellite network is just responsible for data routing. Therefore, the onboard storage costs for different users are viewed as 0. For _edge caching_, considering that the content services of users are provided just by a satellite network with edge caching, more content services can be provided for users as the number of contents deployed on satellites increases. Furthermore, for _cooperative caching_, the cooperative content services of users can be provided by an integrated satellite-terrestrial network, where a cloud center on the ground can provide content services by the satellite network for users considering the restricted edge service provisioning. Therefore, the average storage costs of each user service for _Edge Caching_ are more than that of _cooperative caching_. The average storage costs of each user service for _cooperative caching_ can reduce by 30.37% compared with _edge caching_. The average bandwidth costs of each user service in the three scenarios are shown in in Figure 4b, where it can be found that the average bandwidth costs are the largest for the _cloud center_, followed by _cooperative caching_, and then _edge caching_. This is due to the fact that the content services for all users in the _cloud center_ and several users in _cooperative caching_ can be provided by a cloud center. However, the other users in _cooperative caching_ and all users in _edge caching_ will be provided content services by a satellite network with \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & & \multicolumn{4}{c}{Integrated Satellite–Terrestrial Network} \\ \hline
**Name** & Network Hops & Storage Resources & Bandwidth Resources & Sub-network Hops & Serviced Users & Shortest Paths \\
**Value** & 2 & 1000 Mbits & 1000 Mbps & 1 & 30 & 4 \\ \hline \multicolumn{6}{c}{Wireless Communication Channels between Users and Access Satellites and Contents} \\ \hline
**Name** & Bandwidth Resources & Transmission Power & Channel Gain & Noise Power & Data Size & Content Popularity \\
**Value** & [2, 4] MHz & 3 W & \(-\)200 dB & \(-\)174 dbm & [100, 500] Mbits & [1, 10] \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Simulation parameters setting. Figure 4: Performance comparison for content service in three different scenarios. (**a**) Storage costs. (**b**) Bandwidth costs. (**c**) Total costs. edge caching. Note that the cloud-based content service can bring an increase in network bandwidth consumption compared with the edge-based content service.