Age of Processed Information Minimization over Fading Multiple Access Channels
S, Jayanth, and Bhat, Rajshekhar V
2022 IEEE International Conference on Communications (ICC): Wireless
Communications Symposium (IEEE ICC’22 - WC Symposium) May 2022
In many real-time applications, timely accessibility to actionable insights, usually obtained by processing raw status updates, is an important requirement. In this paper, we consider users equipped with sensors and actuators. The sensors of a user generate status updates which need to be processed for driving the actuators of the user. The processing task of a user can be carried out locally or it can be offloaded to an edge server, located at a common base station (BS). The users access the BS via a fading multiple access channel using a non-orthogonal multiple access technique. To measure the timeliness of processed information, we adopt a metric called age of processed information (AoPI), defined as the time elapsed since the generation of last successfully processed packet available at the user. In this setting, we formulate a problem for minimizing a long-term average AoPI across the users, when the users are subjected to average power constraints. The BS has to decide when a user should generate a status update and whether it should be processed locally or at the edge server. We cast the problem as a constrained Markov decision process (CMDP) and obtain the optimal policy via Lagrange relaxation. We derive several structural properties of the policy. We also obtain a simpler but suboptimal policy via Lyapunov optimization and bound its performance. Using numerical simulations, we demonstrate the threshold structure of CMDP based solution and study behavior of the average AoPI under different policies when problem parameters are varied.