Age-Energy Tradeoff of Short Packet Based Transmissions in Multicast Networks with ARQ.

Age of information (AoI) and energy efficiency (EE) are two critical metrics for real-time status update systems. However, these two metrics may not be optimized simultaneously. This paper focuses on the tradeoff between the average AoI and EE of short packets based transmissions in a multicast network with automatic repeat request. The fixed redundancy coding scheme is employed, and the encoded packet is broadcasted to destinations over additive white Gaussian noise channels. The expressions of average AoI and EE are derived and analyzed. In particular, the average AoI-EE ratio is proposed, which is minimized to achieve a tradeoff between average AoI and EE. The numerical results show that there exists an optimal packet length to achieve a compromise between average AoI and EE.