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Publication Metadata only Age of Information Scaling in Large Networks with Hierarchical Cooperation(IEEE, 2019) Buyukates, Baturalp; Soysal, Alkan; Ulukus, Sennur; University System of Maryland; University of Maryland College Park; Bahcesehir UniversityGiven n randomly located source-destination (S-D) pairs on a fixed area network that want to communicate with each other, we study the age of information with a particular focus on its scaling as the network size n grows. We propose a three-phase transmission scheme that utilizes hierarchical cooperation between users along with mega update packets and show that an average age scaling of O(n(alpha(h)) log n) per-user is achievable where h denotes the number of hierarchy levels and alpha(h) = 1/3.2(h)+1 which tends to 0 as h increases such that asymptotically average age scaling of the proposed scheme is O(log n). To the best of our knowledge, this is the best average age scaling result in a status update system with multiple S-D pairs.Publication Metadata only Age of Information Scaling in Large Networks(IEEE, 2019) Buyukates, Baturalp; Soysal, Alkan; Ulukus, Sennur; University System of Maryland; University of Maryland College Park; Bahcesehir UniversityWe study age of information in a multiple source-multiple destination setting with a focus on its scaling in large wireless networks. There are n nodes that are randomly paired with each other on a fixed area to form n source-destination (SD) pairs. We propose a three-phase transmission scheme which utilizes local cooperation between the nodes by forming what we call mega update packets to serve multiple S-D pairs at once. We show that under the proposed scheme average age of an S-D pair scales as O(n(1/4) log n) as the number of users, n, in the network grows. To the best of our knowledge, this is the best age scaling result for a multiple source-multiple destination setting.Publication Metadata only Age of Information in Multicast Networks with Multiple Update Streams(IEEE, 2019) Buyukates, Baturalp; Soysal, Alkan; Ulukus, Sennur; Matthews, MB; University System of Maryland; University of Maryland College Park; Bahcesehir UniversityWe consider the age of information in a multicast network where there is a single source node that sends time-sensitive updates to n receiver nodes. Each status update is one of two kinds: type I or type II. To study the age of information experienced by the receiver nodes for both types of updates, we consider two cases: update streams are generated by the source node at-will and update streams arrive exogenously to the source node. We show that using an earliest k(1) and k(2) transmission scheme for type I and type II updates, respectively, the age of information of both update streams at the receiver nodes can be made a constant independent of n. In particular, the source node transmits each type I update packet to the earliest k(1) and each type II update packet to the earliest k(2) of n receiver nodes. We determine the optimum k(1) and k(2) stopping thresholds for arbitrary shifted exponential link delays to individually and jointly minimize the average age of both update streams and characterize the pareto optimal curve for the two ages.Publication Metadata only Age of Information in Two-Hop Multicast Networks(IEEE, 2018) Buyukates, Baturalp; Soysal, Alkan; Ulukus, Sennur; Matthews, MB; University System of Maryland; University of Maryland College Park; Bahcesehir UniversityWe consider the age of information in a two-hop multicast network where there is a single source node sending lime-sensitive updates to n(2) end nodes through 11, middle nodes. In the first hop, the source node sends updates to n middle nodes, and in the second hop each middle node relays the update packets that it receives to n end users that are connected to it. We study the age of information experienced by the end nodes, and in particular, its scaling as a function of n. We show that, using an earliest Is transmission scheme, the age of information at the end nodes can be made a constant independent of n. In particular, the source node transmits each update packet to the earliest k(1) of the n middle nodes, and each middle node that receives the update relays it to the earliest k(2) out of 'n end nodes that are connected to it. We determine the optimum k(1) and k(2) stopping values for arbitrary shifted exponential link delays.Publication Metadata only Age of Information in G/G/1/1 Systems(IEEE, 2019) Soysal, Alkan; Ulukus, Sennur; Matthews, MB; Bahcesehir University; University System of Maryland; University of Maryland College ParkWe consider a single server communication setting where the interarrival times of data updates at the source node and the service times to the destination node are arbitrarily distributed. We consider two service discipline models. In the first model, if a new update arrives when the service is busy, it is blocked, in the second model, a new update preempts the current update in service. For both models, we derive exact expressions for the age of information metric with no restriction on the distributions of interarrival and service times. In addition, we derive upper bounds that are easier to calculate than the exact expressions. In the case with blocking, we also derive a second upper bound by utilizing stochastic ordering if the interarrival and service times have log-concave distribution.