Congestion-aware routing with dual cost for satellite-ground integrated networks

The satellite-ground integrated network (SGIN) has emerged as a key sixth-generation (6 G) communication architecture, utilizing inter-satellite links (ISLs) and ground-satellite links (GSLs) to enable end-to-end routing. However, uneven traffic distribution causes traffic to converge on specific ground nodes, creating severe bottlenecks that lead to queue saturation and significant packet drops. Existing centralized approaches mitigate overload but suffer from massive signaling overhead and route-recovery latency under GSL dynamics. Conversely, distributed schemes are responsive but fail to resolve bottlenecks globally. This paper proposes a routing framework that retains the global optimization capability of centralized approaches while addressing their limitations under GSL dynamics. We propose congestion-aware dual cost routing (CADR), which estimates global load from active flows without global state collection to resolve bottlenecks via a dual cost. We also integrate a fast route recovery (FRR) procedure, which suppresses drops by constructing a local detour at the failure node and performing asynchronous synchronization. Simulation results demonstrate that the proposed scheme achieves the best overall performance under heavy uneven traffic load. Notably, it reduces the packet drop rate from 38.44% to 0.30% and improves throughput from 323.58 Gbps to 528.78 Gbps compared to benchmark schemes.