# Resource- and Neighbor-Aware Observation Transmission Scheme in Satellite Networks
## 3 Resource- and Neighbor-Aware Observation Transmission Scheme in Satellite Networks  
Figure 2 shows the system model in this paper. There are \(N\) observation satellites. These observation satellites can observe the target when the target is in their coverage. After the observation, each observation satellite needs to deliver the observation to the destination at the ground. For this, the observation satellite can directly transmit the observation to the ground station; however, the observation satellite can transmit the observation to the ground station only when it can have a connection with the ground station, and the opportunities for the connection with the ground station are quite limited [4]. Moreover, even if the observation satellite has a connection with the ground station, the transmission power of the observation satellite is limited. Therefore, a large delay to deliver the observation to the destination can be expected.  
To reduce the delay to deliver the observation to the destination, RNA-OTS periodically decides whether to exploit the resources of relay and observation satellites. Specifically, regarding the usage of the resources of the relay satellite, each observation satellite periodically decides whether to transmit its observation to the relay satellite (or to the ground station) (i.e., whether to use the resources of the relay satellite). When the observation satellite decides to use the resources of the relay satellite, it forwards the observation to the relay satellite at geostationary orbit that always has connection to the ground station.  
\begin{table}
\begin{tabular}{l l l l} \hline \hline
**Ref** & **Objective** & **Decision Element** & **Method** \\ \hline
[13] & Maximize the throughput & Transmission schedule & Algorithm \\ \hline
[14] & Maximize the throughput & Transmission schedule & MDP \\ \hline
[15] & Maximize the number of completed tasks \& & Task schedule & Algorithm \\  & minimize the total power consumption & & \\ \hline
[16] & Maximize the number of completed tasks & Task schedule & Algorithm \\ \hline
[17] & Maximize the task completion rate & Task schedule & Algorithm \\ \hline \hline \end{tabular}
\end{table}
Table 1: Comparison of collaborative approaches.  
Figure 2: System model.  
Then, the relay satellite can relay them to the destination. However, when lots of observation satellites simultaneously forward the observations to the relay satellite (i.e., when excessively using the resource of the relay satellite), the queuing delay at the relay satellite can increase. Therefore, each observation satellite should consider neighbor observation satellites' actions and decide whether to forward its observation to the relay satellite.  
On the other hand, regarding the usage of the resources of the observation satellite, each observation satellite periodically decides whether or not to delay the transmission and to compress the observation before the transmission (i.e., whether to use the storage and computational resources of the observation satellite). However, when excessively using the resources of the observation satellites, the observation satellite cannot conduct its own important tasks (e.g., image processing for environmental monitoring) in a timely manner.  
To sum up, it should be appropriately decided whether to use the resources of two types of satellites by considering their operating environments. Especially for the decision on the usage of the resources of the relay satellite, each observation satellite should consider the transmission policies of neighbor observation satellites to avoid the increased queuing delay at the relay satellite. In addition, for the decision on the usage of its own resources, each observation satellite should consider the average utilization of its resources. For the distributed optimal decision of each observation satellite by considering the transmission policies of neighbor observation satellites and their resource utilization, a constrained stochastic game is developed in the next section.