27,035 research outputs found
Age of Information in Downlink Systems: Broadcast or Unicast Transmission?
We analytically decide whether the broadcast transmission scheme or the
unicast transmission scheme achieves the optimal age of information (AoI)
performance of a multiuser system where a base station (BS) generates and
transmits status updates to multiple user equipments (UEs). In the broadcast
transmission scheme, the status update for all UEs is jointly encoded into a
packet for transmission, while in the unicast transmission scheme, the status
update for each UE is encoded individually and transmitted by following the
round robin policy. For both transmission schemes, we examine three packet
management strategies, namely the non-preemption strategy, the preemption in
buffer strategy, and the preemption in serving strategy. We first derive new
closed-form expressions for the average AoI achieved by two transmission
schemes with three packet management strategies. Based on them, we compare the
AoI performance of two transmission schemes in two systems, namely, the remote
control system and the dynamic system. Aided by simulation results, we verify
our analysis and investigate the impact of system parameters on the average
AoI. For example, the unicast transmission scheme is more appropriate for the
system with a large number UEs. Otherwise, the broadcast transmission scheme is
more appropriate
Optimizing Age-of-Information in a Multi-class Queueing System
We consider the age-of-information in a multi-class queueing system,
where each class generates packets containing status information. Age of
information is a relatively new metric that measures the amount of time that
elapsed between status updates, thus accounting for both the queueing delay and
the delay between packet generation. This gives rise to a tradeoff between
frequency of status updates, and queueing delay. In this paper, we study this
tradeoff in a system with heterogenous users modeled as a multi-class
queue. To this end, we derive the exact peak age-of-Information (PAoI) profile
of the system, which measures the "freshness" of the status information. We
then seek to optimize the age of information, by formulating the problem using
quasiconvex optimization, and obtain structural properties of the optimal
solution
Age-Optimal Updates of Multiple Information Flows
In this paper, we study an age of information minimization problem, where
multiple flows of update packets are sent over multiple servers to their
destinations. Two online scheduling policies are proposed. When the packet
generation and arrival times are synchronized across the flows, the proposed
policies are shown to be (near) optimal for minimizing any time-dependent,
symmetric, and non-decreasing penalty function of the ages of the flows over
time in a stochastic ordering sense
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