Analysis of Peak Age of Information in Blocking and Preemptive Queuing Policies in a HARQ-Based Wireless Link

In this letter, we focus on evaluating Peak Age-of-Information (PAoI) in a typical wireless link in which each packet transmission is successful with some probability. The receiver applies a hybrid ARQ (HARQ) scheme such as chase combining to decode each packet. Thus, several transmissions of the same packet lead to a sequence of strictly increasing successful packet reception probabilities. Moreover, the number of transmissions for each packet is limited. In this link, when the packets are generated randomly, we compare two queueing policies at the transmitter, i.e., blocking and preemptive. The former exploits the capability of HARQ to send the packet to the destination sooner, but the latter tries to send the fresher packets to the destination. We derive analytically the average PAoI at both policies and compare them in different situations.