Logical Role-Separated RLNC for Low-Latency Satellite Downlinks With Opportunistic Loss Recovery

Reliable low-latency delivery over satellite downlinks remains fundamentally constrained by long propagation delays, burst-correlated packet loss, and the limited effectiveness of retransmission-based recovery. Although Random Linear Network Coding (RLNC) enables feedback-free reliability, existing satellite RLNC designs mainly optimize redundancy volume and throughput, typically transmitting systematic and coded packets sequentially or over uniformly scheduled beams. Consequently, redundancy often becomes available too late to reduce completion latency, leaving RLNC’s latency–reliability potential underexploited. To address this limitation, we propose a logical role-separated RLNC downlink architecture in which systematic packets and coded redundancy are assigned to independently schedulable beams. This design allows redundancy to accumulate in parallel with native delivery without increasing redundancy volume. We further introduce a receiver-centric opportunistic completion policy that continuously tracks decoding rank and initiates recovery as soon as sufficient degrees of freedom become available, thereby avoiding decode-gated delays and unnecessary coded accumulation. The proposed architecture is compatible with cloud-native 5G systems through lightweight containerized RLNC encoder and decoder modules, enabling practical deployment without modifying existing downlink infrastructure. Extensive simulations under burst-correlated loss and decoding-aware modeling show that the proposed architecture consistently achieves better latency–efficiency performance than existing reliable transmission schemes. The results indicate that beam-level logical role separation fundamentally alters the latency–reliability tradeoff of satellite RLNC. They further show that redundancy scheduling, rather than redundancy volume, is the primary determinant of completion latency. These findings position role-separated RLNC as a practical architecture for latency-critical satellite and non-terrestrial network downlinks.