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.Comment: Submitted for publication to the IEEE Transactions on Communication