113 research outputs found
HYMAD: Hybrid DTN-MANET Routing for Dense and Highly Dynamic Wireless Networks
In this paper we propose HYMAD, a Hybrid DTN-MANET routing protocol which
uses DTN between disjoint groups of nodes while using MANET routing within
these groups. HYMAD is fully decentralized and only makes use of topological
information exchanges between the nodes. We evaluate the scheme in simulation
by replaying real life traces which exhibit this highly dynamic connectivity.
The results show that HYMAD outperforms the multi-copy Spray-and-Wait DTN
routing protocol it extends, both in terms of delivery ratio and delay, for any
number of message copies. Our conclusion is that such a Hybrid DTN-MANET
approach offers a promising venue for the delivery of elastic data in mobile
ad-hoc networks as it retains the resilience of a pure DTN protocol while
significantly improving performance.Comment: 7 pages, 6 figure
The heterogeneity of inter-contact time distributions: its importance for routing in delay tolerant networks
Prior work on routing in delay tolerant networks (DTNs) has commonly made the
assumption that each pair of nodes shares the same inter-contact time
distribution as every other pair. The main argument in this paper is that
researchers should also be looking at heterogeneous inter-contact time
distributions. We demonstrate the presence of such heterogeneity in the
often-used Dartmouth Wi-Fi data set. We also show that DTN routing can benefit
from knowing these distributions. We first introduce a new stochastic model
focusing on the inter-contact time distributions between all pairs of nodes,
which we validate on real connectivity patterns. We then analytically derive
the mean delivery time for a bundle of information traversing the network for
simple single copy routing schemes. The purpose is to examine the theoretic
impact of heterogeneous inter-contact time distributions. Finally, we show that
we can exploit this user diversity to improve routing performance.Comment: 6 page
Evaluating Mobility Pattern Space Routing for DTNs
Because a delay tolerant network (DTN) can often be partitioned, the problem
of routing is very challenging. However, routing benefits considerably if one
can take advantage of knowledge concerning node mobility. This paper addresses
this problem with a generic algorithm based on the use of a high-dimensional
Euclidean space, that we call MobySpace, constructed upon nodes' mobility
patterns. We provide here an analysis and the large scale evaluation of this
routing scheme in the context of ambient networking by replaying real mobility
traces. The specific MobySpace evaluated is based on the frequency of visit of
nodes for each possible location. We show that the MobySpace can achieve good
performance compared to that of the other algorithms we implemented, especially
when we perform routing on the nodes that have a high connection time. We
determine that the degree of homogeneity of mobility patterns of nodes has a
high impact on routing. And finally, we study the ability of nodes to learn
their own mobility patterns.Comment: IEEE INFOCOM 2006 preprin
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
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