12 research outputs found
Age Optimal Information Gathering and Dissemination on Graphs
We consider the problem of timely exchange of updates between a central
station and a set of ground terminals , via a mobile agent that traverses
across the ground terminals along a mobility graph . We design the
trajectory of the mobile agent to minimize peak and average age of information
(AoI), two newly proposed metrics for measuring timeliness of information. We
consider randomized trajectories, in which the mobile agent travels from
terminal to terminal with probability . For the information
gathering problem, we show that a randomized trajectory is peak age optimal and
factor- average age optimal, where is the mixing
time of the randomized trajectory on the mobility graph . We also show that
the average age minimization problem is NP-hard. For the information
dissemination problem, we prove that the same randomized trajectory is
factor- peak and average age optimal. Moreover, we propose an
age-based trajectory, which utilizes information about current age at
terminals, and show that it is factor- average age optimal in a symmetric
setting
Optimizing Age of Information with Correlated Sources
We develop a simple model for the timely monitoring of correlated sources
over a wireless network. Using this model, we study how to optimize
weighted-sum average Age of Information (AoI) in the presence of correlation.
First, we discuss how to find optimal stationary randomized policies and show
that they are at-most a factor of two away from optimal policies in general.
Then, we develop a Lyapunov drift-based max-weight policy that performs better
than randomized policies in practice and show that it is also at-most a factor
of two away from optimal. Next, we derive scaling results that show how AoI
improves in large networks in the presence of correlation. We also show that
for stationary randomized policies, the expression for average AoI is robust to
the way in which the correlation structure is modeled. Finally, for the setting
where correlation parameters are unknown and time-varying, we develop a
heuristic policy that adapts its scheduling decisions by learning the
correlation parameters in an online manner. We also provide numerical
simulations to support our theoretical results.Comment: To be presented at ACM MobiHoc 202
A Whittle Index Approach to Minimizing Functions of Age of Information
We consider a setting where multiple active sources send real-time updates
over a single-hop wireless broadcast network to a monitoring station. Our goal
is to design a scheduling policy that minimizes the time-average of general
non-decreasing cost functions of Age of Information.
We use a Whittle index based approach to find low complexity scheduling
policies that have good performance, for reliable as well as unreliable
channels. We prove that for a system with two sources, having possibly
different cost functions and reliable channels, the Whittle index policy is
exactly optimal. For reliable channels, we also derive structural properties of
an optimal policy, that suggest that the performance of the Whittle index
policy may be close to optimal in general. These results might also be of
independent interest in the study of restless multi-armed bandit problems with
similar underlying structure. Finally, we provide simulations comparing the
Whittle index policy with optimal scheduling policies found using dynamic
programming, which support our results.Comment: Accepted for Allerton'1
Age of information and mobility
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2019Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 99-105).Age of information is a recently proposed metric that measures the freshness of information at a destination receiving data from an information source. It has become popular in the networking and queuing community, especially for studying delivery of real time status updates. In this thesis, we explore applications of AoI to mobile and adhoc networks. More specifically, we look at two problems - 1) Age optimal information collection and dissemination from locations arranged on a graph, using a mobile agent that travels between them, and 2) Age-based transmission schemes for a group of mobile agents which need to continuously exchange information while moving around in a cell partitioned network. We also derive expressions for age metrics for discrete time queuing systems under various service disciplines, and service and arrival time distributions.by Vishrant Tripathi.S.M.S.M. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Scienc
A Whittle Index Approach to Minimizing Functions of Age of Information
© 2019 IEEE. We consider a setting where multiple active sources send real-time updates over a single-hop wireless broadcast network to a monitoring station. Our goal is to design a scheduling policy that minimizes the time-average of general non-decreasing cost functions of Age of Information. We use a Whittle index based approach to find low complexity scheduling policies that have good performance, for reliable as well as unreliable channels. We prove that for a system with two sources, having possibly different cost functions and reliable channels, the Whittle index policy is exactly optimal. For reliable channels, we also derive structural properties of an optimal policy, that suggest that the performance of the Whittle index policy may be close to optimal in general. These results might also be of independent interest in the study of restless multi-armed bandit problems with similar underlying structure. Finally, we provide simulations comparing the Whittle index policy with optimal scheduling policies found using dynamic programming, which support our results
Age Debt: A General Framework for Minimizing Age of Information
We consider the problem of minimizing age of information in general
single-hop and multihop wireless networks. First, we formulate a way to convert
AoI optimization problems into equivalent network stability problems. Then, we
propose a heuristic low complexity approach for achieving stability that can
handle general network topologies; unicast, multicast and broadcast flows;
interference constraints; link reliabilities; and AoI cost functions. We
provide numerical results to show that our proposed algorithms behave as well
as the best known scheduling and routing schemes available in the literature
for a wide variety of network settings.Comment: To be presented at the 4th AoI Workshop, IEEE INFOCOM 202