Age of Information in Short Packet Multi-Connectivity Links

In this paper, we investigate multi-connectivity schemes in the context of status update systems with short payloads. As the performance metric, we use the Age of Information (AoI). Due to short payloads, transmission errors must be taken into account. In addition to the well-known schemes of packet duplication, message splitting, and multiplexing, we propose a codeword splitting scheme, where each status update is jointly encoded across multiple channels. We derive closed-form expressions for the average AoI for the different schemes and optimize their corresponding parameters. We show that the AoI of the multiplexing scheme is a convex function in the offset parameters and use this result to prove that for homogeneous channels, the multiplexing scheme outperforms the packet duplication scheme, which is outperformed by the codeword splitting scheme. Analytical comparisons and numerical evaluations show that the codeword splitting scheme achieves the lowest average AoI when joint coding is feasible. In scenarios where joint coding is not feasible, whether message splitting or multiplexing results in a lower average AoI depends on the specific parameters.