33,742 research outputs found
On the Minimum Achievable Age of Information for General Service-Time Distributions
There is a growing interest in analysing the freshness of data in networked
systems. Age of Information (AoI) has emerged as a popular metric to quantify
this freshness at a given destination. There has been a significant research
effort in optimizing this metric in communication and networking systems under
different settings. In contrast to previous works, we are interested in a
fundamental question, what is the minimum achievable AoI in any
single-server-single-source queuing system for a given service-time
distribution? To address this question, we study a problem of optimizing AoI
under service preemptions. Our main result is on the characterization of the
minimum achievable average peak AoI (PAoI). We obtain this result by showing
that a fixed-threshold policy is optimal in the set of all randomized-threshold
causal policies. We use the characterization to provide necessary and
sufficient conditions for the service-time distributions under which
preemptions are beneficial
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
Effects of Rate Adaption on the Throughput of Random Ad Hoc Networks
The capacity of wireless ad hoc networks has been studied in an excellent treatise by Gupta and Kumar [1], assuming a fixed transmission rate. By contrast, in this treatise we investigate the achievable throughput improvement of rate adaptation in the context of random ad hoc networks, which have been studied in conjunction with a fixed transmission rate in [1]. Our analysis shows that rate adaptation has the potential of improving the achievable throughput compared to fixed rate transmission, since rate adaptation mitigates the effects of link quality fluctuations. However, even perfect rate control fails to change the scaling law of the per-node throughput result given in [1], regardless of the absence or presence of shadow fading. This result is confirmed in the context of specific adaptive modulation aided design examples
Cooperative Downlink Multicell Preprocessing Relying on Reduced-Rate Back-Haul Data Exchange
Different-complexity multicell preprocessing (MCP) schemes employing distributed signal-to-interference leakageplus-noise ratio (SILNR) precoding techniques are proposed, which require reduced back-haul data exchange in comparison with the conventional MCP structure. Our results demonstrate that the proposed structures are capable of increasing the throughput achievable in the cell-edge area while offering different geographic rate profile distributions, as well as meeting different delay requirements
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
Unforgeable Noise-Tolerant Quantum Tokens
The realization of devices which harness the laws of quantum mechanics
represents an exciting challenge at the interface of modern technology and
fundamental science. An exemplary paragon of the power of such quantum
primitives is the concept of "quantum money". A dishonest holder of a quantum
bank-note will invariably fail in any forging attempts; indeed, under
assumptions of ideal measurements and decoherence-free memories such security
is guaranteed by the no-cloning theorem. In any practical situation, however,
noise, decoherence and operational imperfections abound. Thus, the development
of secure "quantum money"-type primitives capable of tolerating realistic
infidelities is of both practical and fundamental importance. Here, we propose
a novel class of such protocols and demonstrate their tolerance to noise;
moreover, we prove their rigorous security by determining tight fidelity
thresholds. Our proposed protocols require only the ability to prepare, store
and measure single qubit quantum memories, making their experimental
realization accessible with current technologies.Comment: 18 pages, 5 figure
Privacy Against Statistical Inference
We propose a general statistical inference framework to capture the privacy
threat incurred by a user that releases data to a passive but curious
adversary, given utility constraints. We show that applying this general
framework to the setting where the adversary uses the self-information cost
function naturally leads to a non-asymptotic information-theoretic approach for
characterizing the best achievable privacy subject to utility constraints.
Based on these results we introduce two privacy metrics, namely average
information leakage and maximum information leakage. We prove that under both
metrics the resulting design problem of finding the optimal mapping from the
user's data to a privacy-preserving output can be cast as a modified
rate-distortion problem which, in turn, can be formulated as a convex program.
Finally, we compare our framework with differential privacy.Comment: Allerton 2012, 8 page
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