Optimizing Information Freshness in Two-Hop Status Update Systems Under a Resource Constraint

In this paper, we investigate the age minimization problem for a two-hop relay system, under resource constraint on average number of forwarding operations at relay. We first design an optimal policy by modelling considered scheduling as constrained Markov decision process (CMDP) problem. Based observed multi-threshold structure policy, then devise low-complexity double threshold relaying (DTR) with only two thresholds, one relay's AoI and other gain between destination derive approximate closed-form expressions destination, DTR tangled evolution chain (MC). Numerical results validate all theoretical analysis, show that can achieve near performance compared CMDP-based policy. Moreover, should always consider its local to maintain low destination. When is relatively tight, it further needs ensure those packets decrease destination's dramatically will be forwarded.