# GPU-Accelerated Eclipse-Aware Routing for SpaceWire-Based OBC in Low-Earth-Orbit Satellite Networks
## 4 Experimental Results
### SpaceWire-Based Experiment Results  
In this paper, SpaceWire, a high-speed serial data communication protocol developed by the European Space Agency (ESA), is utilized for satellite and aerospace systems. SpaceWire is widely adopted due to its low latency, high reliability, and real-time data transmission capabilities, making it well-suited for inter-satellite communication. For this study, experiments were conducted using the SpaceWire Brick Mk4 device developed by STAR-Dundee. The SpaceWire Brick Mk4 is a USB-based SpaceWire interface device that facilitates data transmission between a PC and a SpaceWire network, making it a valuable tool for satellite system development and testing. Notably, it supports the Remote Memory Access Protocol (RMAP), enabling direct access to the memory of remote devices, thereby allowing dynamic modification of routing tables. Using this capability, the proposed algorithm was tested by selecting the optimal path and updating the routing tables of remote devices via the SpaceWire network.  
The experimental scenario is described as follows. Figure 11 illustrates the process of the experiment. As shown in Figure 9, the EAR algorithm ultimately selects an optimal path. However, if only the KSP algorithm were applied without EAR, the shortest hop-count path would be chosen as the optimal route. In this case, assuming the receiving router is at node 38, the next node for data transmission would be node 39. However, when applying the EAR algorithm, which considers satellite battery status and eclipse conditions, a more energy-efficient route can be derived compared to the conventional shortest path approach. Consequently, instead of forwarding data to node 39, routing through node 37 becomes a more efficient choice. Based on this observation, the experiment was designed to assume node 38 as the receiving router and modify the routing table to direct data transmission to node 37.  
Due to the limited availability of only two SpaceWire Brick Mk4 devices, replicating a fully operational satellite network was not feasible. Therefore, certain assumptions were made to conduct the experiment, and understanding these constraints is requested.  
Figure 11 provides an overview of the internal structure of the SpaceWire Brick Mk4 device. The integrated SpaceWire router features a total of six ports, with port 0 designated as the configuration port and thus unavailable for use. This leaves five selectable ports for experimentation. In this study, port 4 was assumed to be connected to node 37, and the  
Figure 10: Compare total execution time of OBC with Only CPU vs. OBC with CPU and GPU.  
routing table of the remote device was modified to direct traffic through port 4 according to the EAR algorithm's results.  
Figure 12 presents the SpaceWire GUI output, captured from a laptop connected to the receiving SpaceWire Brick Mk4. The experimental results confirmed that the routing table was successfully updated to direct data through port 4, as per the designed scenario, ensuring that data was correctly delivered to node 37. These findings demonstrate that the proposed accelerated EAR routing method is applicable within SpaceWire networks and is capable of dynamically adjusting remote device routing in real time.