Showing papers by "Gam D. Nguyen published in 2017"

Information freshness and popularity in mobile caching

Abstract: We propose a model for mobile caching in which the rate of requests for content is dependent on the popularity and the freshness of the information. We model popularity based on the history of requests and freshness based on the age of the content. We consider a discrete time (slotted) system in which new packets arrive at a limited capacity cache at discrete times. We prove that the optimal policy for choosing the set of packets to reside in a full cache when a packet arrives is to reject the one with the lowest request rate in that particular slot. Thus, there is no advantage to separately knowing the history of requests or the age of the content. Since the optimal policy depends on the profile of the request process, we also study the expected behavior of the request model. We provide a sufficient condition under which the change in the request rate goes to zero and provide some numerical examples that illustrate this behavior. We also consider a slight alteration to the model, in which only the recent history of requests is used for determining the request rate. In this case, we provide a sufficient condition for when the rate is equal to zero, which approximates the duration of requests for content.

Impact of hostile interference on information freshness: A game approach

Abstract: For time critical updates, it is desirable to maintain the freshness of the received information. We address the impact of hostile interference on information freshness by formulating a non-zero-sum two-player game, in which one player is the transmitter aiming to maintain the freshness of the information updates it sends to its receiver, and the other player is the interferer aiming to prevent this. The strategy of a player is the power level transmitted by that player. We then derive the equilibria for both Nash and Stackelberg strategies. We show that both players have the same power cost at Nash equilibrium. In addition, the Stackelberg strategy dominates the Nash strategy, i.e., the Stackelberg utility function exceeds the Nash utility function.

Modeling the age of information in emulated ad hoc networks

Abstract: The age of information is a measure of the freshness of continually updated information, which has been studied theoretically for a variety of queueing models. We conduct an experimental evaluation of the age of information in various emulated network settings to see how well the queue models approximate a network for the purpose of age. We use CORE and EMANE to deploy a one-dimensional multi-hop network, and a two-dimensional grid multi-hop network, and we compare to the theoretical age under the D/M/1 and D/D/1 queue models. We observe that for these regular static networks, the D/D/1 models the average age performance better than the D/M/1 in lightly loaded networks with low loss. When losses increase, the age is greater than predicted by the D/D/1 model.

Packet deadlines in a queue to control the age of information

Abstract: Systems and method are provided for controlling the age of information, or information freshness, for remote status updating through the use of a packet deadline. In an embodiment, a packet deadline determines how long a packet is allowed to wait in a queue at the source before being transmitted, and, if the deadline expires, it is dropped from the system and never transmitted. This mechanism can control the flow of packets into the system, which can be used to control and optimize the age of information, thus providing a fresh status at a monitor.