Low-Complexity Multi-Domain Resource Optimization-Based AoI Reduction for Relay-Aided Wireless Communications in Short Packet

Abstract

We theoretically investigate average age of information (AoI) derived in a closed form for decode-and-forward (DF) relay-based wireless communications in short packet, with update packets being generated by Poisson process. Also, we propose a low-complexity joint multi-resource optimization (JMO) algorithm from physical layer perspective to reduce average AoI. The proposed JMO algorithm utilizes three-domain transmission resources including channels, transmission power and blocklength, and reduces AoI as much as possible, compared to the previous works considering a single or two transmission resource. The proposed works provide closed-form solutions to power allocation, blocklength optimization and total transmission power determination, respectively, and hence achieve complexity lower than heuristic search. First, a maximum multiplication based channel allocation (MMCA) criterion is proposed by selecting two relatively strong channel gains in two hops, and achieves AoI performance equal to or better than the previous max-min based channel allocation criterion just selecting two equal channel gains in two hops. Second, we propose a closed-form power allocation (CPA) algorithm for AoI reduction, by introducing a power factor to minimize the expectation of the number of the total transmissions in two hops, which is proved to be convex with respect to power factor. Third, we propose a closed-form blocklength optimization (CBO) algorithm to reduce AoI for Poisson-process generation strategy including both service and waiting time. The previous works that consider zero-wait strategy including just service time are not applicable to Poisson-process generation strategy. The proposed CBO algorithm introduces a new auxiliary variable to transform blocklength optimization into a solvable problem. Fourth, we propose a successive linear approximation (SLA) algorithm to determine the near-minimum total transmission power in a closed form, while maintaining AoI performance close to lower bound derived theoretically. Therefore, the proposed works provide a trade-off between AoI, complexity and transmission power.