1,057 research outputs found
WiPal: Efficient Offline Merging of IEEE 802.11 Traces
Merging wireless traces is a fundamental step in measurement-based studies
involving multiple packet sniffers. Existing merging tools either require a
wired infrastructure or are limited in their usability. We propose WiPal, an
offline merging tool for IEEE 802.11 traces that has been designed to be
efficient and simple to use. WiPal is flexible in the sense that it does not
require any specific services, neither from monitors (like synchronization,
access to a wired network, or embedding specific software) nor from its
software environment (e.g. an SQL server). We present WiPal's operation and
show how its features - notably, its modular design - improve both ease of use
and efficiency. Experiments on real traces show that WiPal is an order of
magnitude faster than other tools providing the same features. To our
knowledge, WiPal is the only offline trace merger that can be used by the
research community in a straightforward fashion.Comment: 6 page
Plausible Mobility: Inferring Movement from Contacts
We address the difficult question of inferring plausible node mobility based
only on information from wireless contact traces. Working with mobility
information allows richer protocol simulations, particularly in dense networks,
but requires complex set-ups to measure, whereas contact information is easier
to measure but only allows for simplistic simulation models. In a contact trace
a lot of node movement information is irretrievably lost so the original
positions and velocities are in general out of reach. We propose a fast
heuristic algorithm, inspired by dynamic force-based graph drawing, capable of
inferring a plausible movement from any contact trace, and evaluate it on both
synthetic and real-life contact traces. Our results reveal that (i) the quality
of the inferred mobility is directly linked to the precision of the measured
contact trace, and (ii) the simple addition of appropriate anticipation forces
between nodes leads to an accurate inferred mobility.Comment: 8 pages, 8 figures, 1 tabl
Using Neighborhood Beyond One Hop in Disruption-Tolerant Networks
Most disruption-tolerant networking (DTN) protocols available in the
literature have focused on mere contact and intercontact characteristics to
make forwarding decisions. Nevertheless, there is a world behind contacts: just
because one node is not in contact with some potential destination, it does not
mean that this node is alone. There may be interesting end-to-end transmission
opportunities through other nearby nodes. Existing protocols miss such
possibilities by maintaining a simple contact-based view of the network. In
this paper, we investigate how the vicinity of a node evolves through time and
whether such information can be useful when routing data. We observe a clear
tradeoff between routing performance and the cost for monitoring the
neighborhood. Our analyses suggest that limiting a node's neighborhood view to
three or four hops is more than enough to significantly improve forwarding
efficiency without incurring prohibitive overhead.Comment: 5 pages, 5 figures, 1 tabl
Free Small Clauses of Brazilian Portuguese as a TP-Phase
The aim of this paper is to describe the internal structure of an exclamative construction of Brazilian Portuguese (BP), which has scarcely been investigated despite its frequent use by Brazilian speakers. I will call this construction the Free Small Clause (FSC) 1 and define it as the juxtaposition of a predicate and its subject, in that fixed order, without any verb or morphological specification for tens
Architectural Considerations for a Self-Configuring Routing Scheme for Spontaneous Networks
Decoupling the permanent identifier of a node from the node's
topology-dependent address is a promising approach toward completely scalable
self-organizing networks. A group of proposals that have adopted such an
approach use the same structure to: address nodes, perform routing, and
implement location service. In this way, the consistency of the routing
protocol relies on the coherent sharing of the addressing space among all nodes
in the network. Such proposals use a logical tree-like structure where routes
in this space correspond to routes in the physical level. The advantage of
tree-like spaces is that it allows for simple address assignment and
management. Nevertheless, it has low route selection flexibility, which results
in low routing performance and poor resilience to failures. In this paper, we
propose to increase the number of paths using incomplete hypercubes. The design
of more complex structures, like multi-dimensional Cartesian spaces, improves
the resilience and routing performance due to the flexibility in route
selection. We present a framework for using hypercubes to implement indirect
routing. This framework allows to give a solution adapted to the dynamics of
the network, providing a proactive and reactive routing protocols, our major
contributions. We show that, contrary to traditional approaches, our proposal
supports more dynamic networks and is more robust to node failures
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