Average Age of Information in Two-Way Relay Networks with Service Preemptions

In this paper, we aim to derive the average age of information (AAoI) associated with the static link scheduling policies in a buffer-aided two-way relay network, where two sources exchange their updates through an intermediate relay equipped with data buffers. With regard to buffer-aided relaying, we consider the two-mode relaying scheme, where each time slot is dedicated to either broadcast or multiple access mode. Moreover, the link scheduling policy is considered to be static, which randomizes between broadcast and multiple access modes when the relay is backlogged and chooses the multiple access mode, otherwise. We establish AAoI corresponding to the sources in terms of steady-state probabilities of buffers at the relay for different instants of the network. Through numerical results, we show that the joint status of the queues at the relay has a significant effect on determining the optimal static link scheduling policy and further validate our analytical approach via simulations.