Recent trends in communication networks have focused on Quality of Service (QoS) requirements expressed through timing metrics such as latency or Age of Information (AoI). A possible way to achieve this is coded multipath communication: redundancy is added to a block of information through a robust packet-level code, transmitting across multiple independent channels to reduce the impact of blockages or rate fluctuation. The number of these links can grow significantly over traditional two-path schemes: in these scenarios, the optimization of the timing metrics is non-trivial, and latency and AoI might require different settings. In particular, packet preemption is often the optimal solution to optimize AoI in uncoded communication, but can significantly reduce the reliability of individual blocks. In this work, we model the multipath communication as a fork-join D/M/(K,N)/L queue, where K blocks of information are encoded into N>K redundant blocks. We derive the latency and Peak AoI (PAoI) distributions for different values of the queue size L. Our results show that preemption is not always the optimal choice, as dropping a late packet on one path might affect the reliability of the whole block, and that minimizing the PAoI leads to poor latency performance.

翻译：近年通信网络的研究趋势聚焦于以延时或信息时效（AoI）等时序指标表达的服务质量（QoS）需求。实现该目标的一种可行途径是编码多路径通信：通过鲁棒的包级编码向信息块添加冗余，在多个独立信道上并行传输，以降低阻塞或速率波动的影响。相较于传统双路径方案，此类链路数量可大幅增加：在此场景下，时序指标的优化变得复杂，延时与AoI可能需要不同的配置策略。具体而言，在非编码通信中，包抢占通常是优化AoI的最优解，但会显著降低单个信息块的可靠性。本研究将多路径通信建模为fork-join D/M/(K,N)/L队列，其中K个信息块被编码为N>K个冗余块。我们推导了不同队列长度L下的延时与峰值AoI（PAoI）分布。结果表明：抢占并非始终最优——在单条路径上丢弃延迟数据包可能影响整个信息块的可靠性，且最小化PAoI会导致较差的延时性能。