# A Hybrid Genetic Algorithm for Ground Station Scheduling Problems
## 5 Experiment Results and Analysis
Compared to the greedy-based FCFSA and the PA, the ITGA achieves an improvement of approximately 3 to 19 tasks in the ANCT metric, an increase of about 6.61% to 19.8% in the ATER metric, and an enhancement of roughly 10.59% to 21.62% in the ANOTER metric. Since the FCFSA and the PA do not involve an iterative process, no comparison is made for the ART metric. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Type** & **Number** & **Parameter** \\ \hline
7.5 m Antenna & 3 & Operating mode: dual circular polarization frequency reuse; operating frequency bands: L, X. \\ \hline L SDC & 2 & Primarily utilized for signal frequency conversion in the L-band. \\ \hline X SDC & 2 & Primarily utilized for signal frequency conversion in the X-band. \\ \hline X Demodulator & 2 & Primarily utilized for demodulation tasks in X-band \\ \hline  & & Primarily utilized for demodulation tasks in X-band links; decoding methods include RS code, CRC \\  & & decoding, differential decoding, convolutional code, and forward error correction; differential decoding: NRZ\_L, \\  & & NRZ\_M, etc.; demodulation schemes: BPSK, QPSK, etc.; demodulation code rate: 10–800 Mbps. \\ \hline L Demodulator & 2 & Primarily utilized for demodulation in L-band links; demodulation code rate ranging from 10 to 640 Mbps; other parameters are identical to those of the X Demodulator. \\ \hline RD & 4 & Input method: TCP/IP protocol format; maximum single-channel code rate of 600 Mbps with a combined code rate for five channels not exceeding 1200 Mbps. \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Ground station resources. When compared to the TGA, the ITGA employs a heuristic rule-based conflict resolution approach. This leads to an improvement of one task execution in the ANCT metric and a 1.57% increase in the ATER metric specifically in experimental scenario 2, which has a higher number of data transmission conflicts. However, in scenarios 1, 3, and 4, where conflicts are fewer or cannot be resolved by trimming transmission durations, both algorithms perform similarly. This underscores the effectiveness of the conflict resolution method in scenarios with more conflicts. Regarding the ART metric, ITGA achieves a speedup of 0.5 s to 1.69 s due to the introduction of the task set partitioning method. This reduction in the traversal of conflict-free tasks, combined with the parallelism of the GA and asynchronous multitasking execution techniques, allows for simultaneous solution finding for sub-task sets, ultimately enhancing algorithm efficiency. In comparison to the DFSGA, the ITGA demonstrates improvements in the ANCT, ATER, and ANOTER metrics by one task, 1.57%, and 11.18% in scenarios 2 and 4, respectively. In scenarios 1 and 3, both algorithms perform similarly due to fewer conflicts in the data transmission task set. As for the ART metric, ITGA achieves an improvement of 7.36 s to 28.46 s.  
In addition, due to the existence of numerous conflicting time periods within the satellite-to-ground visibility windows in experimental case 2, the scheduling outcomes achieved in this particular scenario are better suited to demonstrate the effectiveness of the ITGA. Therefore, this study carries out a detailed analysis of four key metrics in experimental case 2: ground resource allocation results, distribution of ground station resource usage time, algorithm convergence speed, and algorithm stability. The task scheduling outcomes achieved by the ITGA in experimental case 2 are illustrated in Figure 9.  
The figure illustrates the task schedule for satellites over a 24 h period, with the \(x\)-axis representing time of day in seconds and the \(y\)-axis denoting satellite names. The small squares in the graph represent the individual tasks assigned to each satellite throughout the day. Red squares indicate tasks that were not executed due to an unsuccessful allocation of ground station hardware resources, while green squares represent tasks that were successfully allocated resources and executed.