On the Benefits of Waiting in Status Update Systems

This paper explores the potential of waiting before packet transmission in improving the Age of Information (AoI) in status update systems. We consider a non-preemptive queue with Poisson arrivals and independent general service distribution, which we term
$M/GI/1/2\ast$
. There is a single unit buffer that captures the latest arriving status update packet and discards the previous one. As a means to improve AoI performance, we allow “server waiting” in this queuing model. Depending on idle or busy system state, the server waits for a deterministic time before starting service of the packet so as to capture a potential newer arrival. Different from most existing works, we analyze AoI evolution by indexing the incoming packets, which is enabled by an alternative method of partitioning the area under the evolution of instantaneous AoI to calculate its time average. We obtain average AoI expressions for the
$M/GI/1/2\ast$
discipline with waiting for two distributions. Our numerical results demonstrate that waiting before service can bring significant improvement in average age – more than 75% in some cases – particularly, for heavy-tailed service distributions.