4,469 research outputs found
Practical Run-time Checking via Unobtrusive Property Caching
The use of annotations, referred to as assertions or contracts, to describe
program properties for which run-time tests are to be generated, has become
frequent in dynamic programing languages. However, the frameworks proposed to
support such run-time testing generally incur high time and/or space overheads
over standard program execution. We present an approach for reducing this
overhead that is based on the use of memoization to cache intermediate results
of check evaluation, avoiding repeated checking of previously verified
properties. Compared to approaches that reduce checking frequency, our proposal
has the advantage of being exhaustive (i.e., all tests are checked at all
points) while still being much more efficient than standard run-time checking.
Compared to the limited previous work on memoization, it performs the task
without requiring modifications to data structure representation or checking
code. While the approach is general and system-independent, we present it for
concreteness in the context of the Ciao run-time checking framework, which
allows us to provide an operational semantics with checks and caching. We also
report on a prototype implementation and provide some experimental results that
support that using a relatively small cache leads to significant decreases in
run-time checking overhead.Comment: 30 pages, 1 table, 170 figures; added appendix with plots; To appear
in Theory and Practice of Logic Programming (TPLP), Proceedings of ICLP 201
Optimal Geographic Caching In Cellular Networks
In this work we consider the problem of an optimal geographic placement of
content in wireless cellular networks modelled by Poisson point processes.
Specifically, for the typical user requesting some particular content and whose
popularity follows a given law (e.g. Zipf), we calculate the probability of
finding the content cached in one of the base stations. Wireless coverage
follows the usual signal-to-interference-and noise ratio (SINR) model, or some
variants of it. We formulate and solve the problem of an optimal randomized
content placement policy, to maximize the user's hit probability. The result
dictates that it is not always optimal to follow the standard policy "cache the
most popular content, everywhere". In fact, our numerical results regarding
three different coverage scenarios, show that the optimal policy significantly
increases the chances of hit under high-coverage regime, i.e., when the
probabilities of coverage by more than just one station are high enough.Comment: 6 pages, 6 figures, conferenc
A software-defined architecture for next-generation cellular networks
In the recent years, mobile cellular networks are undergoing fundamental changes and many established concepts are being revisited. New emerging paradigms, such as Software-Defined Networking (SDN), Mobile Cloud Computing (MCC), Network Function Virtualization (NFV), Internet of Things (IoT),and Mobile Social Networking (MSN), bring challenges in the design of cellular networks architectures. Current Long-Term Evolution (LTE) networks are not able to accommodate these new trends in a scalable and efficient way. In this paper, first we discuss the limitations of the current LTE architecture. Second, driven by the new communication needs and by the advances in aforementioned areas, we propose a new architecture for next generation cellular networks. Some of its characteristics include support for distributed content routing, Heterogeneous Networks(HetNets) and multiple Radio Access Technologies (RATs). Finally, we present simulation results which show that significant backhaul traffic savings can be achieved by implementing caching and routing functions at the network edge
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