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Anthony Ephremides
University of Maryland, College Park
Wireless networkDistributed computingCommunication channelComputer networkComputer science
492Publications
51H-index
17kCitations
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Publications 472
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We consider the problem of minimizing the time average cost of sampling and transmitting status updates by users over a wireless channel subject to average Age of Information constraints (AoI). Errors in the transmission may occur and the scheduling algorithm has to decide if the users sample a new packet or attempt for retransmission of the packet sampled previously. The cost consists of both sampling and transmission costs. The sampling of a new packet after a failure imposes an additional cos...
#1Qing HeH-Index: 5
#1Qing He (KTH: Royal Institute of Technology)
Last. Anthony EphremidesH-Index: 51
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Link scheduling, i.e., which links should transmit together and for how long, has been and remains a cornerstone optimization problem in wireless networking. In minimum-time scheduling, the task is to minimize the amount of time before emptying the data demand residing at the source nodes. We derive a complete structural characterization of the solution that unifies and significantly extends the known results. First, we approach link scheduling with a general system model without restrictions on...
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#1Meng WangH-Index: 4
#2Chen WeiH-Index: 26
Last. Anthony EphremidesH-Index: 51
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For the emerging Internet of Things (IoT), one of the most critical problems is the real-time reconstruction of signals from a set of aged measurements. During the reconstruction, distortion occurs between the observed signal and the reconstructed signal due to sampling and queueing delay. We focus on minimizing the average distortion defined as the 1-norm of the difference of the two signals under the scenario that a Poisson counting process is reconstructed in real-time on a remote monitor. We...
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In this paper, we investigate a network where Nlinks contend for the channel using the well-known carrier sense multiple access scheme. By leveraging the notion of stochastic hybrid systems, we find: 1) a closed-form expression of the average age when links generate packets at will 2) an upperbound of the average age when packets arrive stochastically to each link. This upperbound is shown to be generally tight, and to be equal to the average age in certain scenarios. Armed with these express...
3 CitationsSource
This paper considers a status update communication system consisting of a source-destination link with timeliness requirements. First, we study the properties of a sample path of the age of information (AoI) process at the destination. Under the assumption of ergodicity, we obtain a general formula of the stationary distribution of the AoI. We relate this result to a discrete time queueing system and provide a general expression of the generating function of AoI in relation with the system time ...
#1Ali MaatoukH-Index: 4
#2Yin SunH-Index: 21
Last. Mohamad AssaadH-Index: 16
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In this paper, we consider a transmission scheduling problem, in which several streams of status update packets with diverse priority levels are sent through a shared channel to their destinations. We introduce a notion of Lexicographic age optimality, or simply lex-age-optimality, to evaluate the performance of multi-class status update policies. In particular, a lex-age-optimal scheduling policy first minimizes the Age of Information (AoI) metrics for high-priority streams, and then, within th...
#1Ali MaatoukH-Index: 4
#2Saad KriouileH-Index: 1
Last. Anthony EphremidesH-Index: 51
view all 4 authors...
In this paper, we consider the average age minimization problem where a central entity schedules M users among the N available users for transmission over unreliable channels. It is well-known that obtaining the optimal policy, in this case, is out of reach. Accordingly, the Whittle's index policy has been suggested in earlier works as a heuristic for this problem. However, the analysis of its performance remained elusive. In the sequel, we overcome these difficulties and provide rigorous result...
7 Citations
#1Song Huang (SCUT: South China University of Technology)H-Index: 2
#2Di Yuan (Linköping University)H-Index: 27
Last. Anthony Ephremides (UMD: University of Maryland, College Park)H-Index: 51
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Conventional cognitive communications rely heavily on the smartness of secondary (unlicensed) users (SUs) to achieve high spectrum utilization, which involves the optimization of the SUs' policies and behaviors for dynamic spectrum access, power allocation among multiple channels, etc. Due to the inherent randomness of the primary users' (PUs') transmission, those efforts inevitably increase the implementation complexity and sensing overheads of the SUs, and in turn lower the spectrum utilizatio...
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#1Ali MaatoukH-Index: 4
#2Saad KriouileH-Index: 1
Last. Anthony EphremidesH-Index: 51
view all 4 authors...
In this paper, we introduce a new performance metric in the framework of status updates that we will refer to as the Age of Incorrect Information (AoII). This new metric deals with the shortcomings of both the Age of Information (AoI) and the conventional error penalty functions as it neatly extends the notion of fresh updates to that of fresh "informative" updates. The word informative in this context refers to updates that bring new and correct information to the monitor side. After properly m...
Jul 1, 2019 in ISIT (International Symposium on Information Theory)
#1Antzela KostaH-Index: 3
#2Nikolaos PappasH-Index: 17
Last. Vangelis AngelakisH-Index: 15
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We consider a system consisting of a source-destination communication link. At the transmitter of the source there is a buffer that stores packets containing status information. These randomly generated packets should keep the destination timely updated and they can be discarded to avoid wasting network resources for the transmission of stale information. In this setup, we provide an analysis of the age of information (AoI) and peak age of information (PAoI) performance of the system, with and w...
3 CitationsSource
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