712 research outputs found
A New Phase Transition for Local Delays in MANETs
We consider Mobile Ad-hoc Network (MANET) with transmitters located according
to a Poisson point in the Euclidean plane, slotted Aloha Medium Access (MAC)
protocol and the so-called outage scenario, where a successful transmission
requires a Signal-to-Interference-and-Noise (SINR) larger than some threshold.
We analyze the local delays in such a network, namely the number of times slots
required for nodes to transmit a packet to their prescribed next-hop receivers.
The analysis depends very much on the receiver scenario and on the variability
of the fading. In most cases, each node has finite-mean geometric random delay
and thus a positive next hop throughput. However, the spatial (or large
population) averaging of these individual finite mean-delays leads to infinite
values in several practical cases, including the Rayleigh fading and positive
thermal noise case. In some cases it exhibits an interesting phase transition
phenomenon where the spatial average is finite when certain model parameters
are below a threshold and infinite above. We call this phenomenon, contention
phase transition. We argue that the spatial average of the mean local delays is
infinite primarily because of the outage logic, where one transmits full
packets at time slots when the receiver is covered at the required SINR and
where one wastes all the other time slots. This results in the "RESTART"
mechanism, which in turn explains why we have infinite spatial average.
Adaptive coding offers a nice way of breaking the outage/RESTART logic. We show
examples where the average delays are finite in the adaptive coding case,
whereas they are infinite in the outage case.Comment: accepted for IEEE Infocom 201
Quantifying Link Stability in Ad Hoc Wireless Networks Subject to Ornstein-Uhlenbeck Mobility
The performance of mobile ad hoc networks in general and that of the routing
algorithm, in particular, can be heavily affected by the intrinsic dynamic
nature of the underlying topology. In this paper, we build a new
analytical/numerical framework that characterizes nodes' mobility and the
evolution of links between them. This formulation is based on a stationary
Markov chain representation of link connectivity. The existence of a link
between two nodes depends on their distance, which is governed by the mobility
model. In our analysis, nodes move randomly according to an Ornstein-Uhlenbeck
process using one tuning parameter to obtain different levels of randomness in
the mobility pattern. Finally, we propose an entropy-rate-based metric that
quantifies link uncertainty and evaluates its stability. Numerical results show
that the proposed approach can accurately reflect the random mobility in the
network and fully captures the link dynamics. It may thus be considered a
valuable performance metric for the evaluation of the link stability and
connectivity in these networks.Comment: 6 pages, 4 figures, Submitted to IEEE International Conference on
Communications 201
Opportunistic Information Dissemination in Mobile Ad-hoc Networks: adaptiveness vs. obliviousness and randomization vs. determinism
In this paper the problem of information dissemination in Mobile Ad-hoc
Networks (MANET) is studied. The problem is to disseminate a piece of
information, initially held by a distinguished source node, to all nodes in a
set defined by some predicate. We use a model of MANETs that is well suited for
dynamic networks and opportunistic communication. In this model nodes are
placed in a plane, in which they can move with bounded speed, and communication
between nodes occurs over a collision-prone single channel. In this setup
informed and uninformed nodes can be disconnected for some time (bounded by a
parameter alpha), but eventually some uninformed node must become neighbor of
an informed node and remain so for some time (bounded by a parameter beta). In
addition, nodes can start at different times, and they can crash and recover.
Under the above framework, we show negative and positive results for different
types of randomized protocols, and we put those results in perspective with
respect to previous deterministic results
Stochastic Analysis of Non-slotted Aloha in Wireless Ad-Hoc Networks
In this paper we propose two analytically tractable stochastic models of
non-slotted Aloha for Mobile Ad-hoc NETworks (MANETs): one model assumes a
static pattern of nodes while the other assumes that the pattern of nodes
varies over time. Both models feature transmitters randomly located in the
Euclidean plane, according to a Poisson point process with the receivers
randomly located at a fixed distance from the emitters. We concentrate on the
so-called outage scenario, where a successful transmission requires a
Signal-to-Interference-and-Noise Ratio (SINR) larger than a given threshold.
With Rayleigh fading and the SINR averaged over the duration of the packet
transmission, both models lead to closed form expressions for the probability
of successful transmission. We show an excellent matching of these results with
simulations. Using our models we compare the performances of non-slotted Aloha
to previously studied slotted Aloha. We observe that when the path loss is not
very strong both models, when appropriately optimized, exhibit similar
performance. For stronger path loss non-slotted Aloha performs worse than
slotted Aloha, however when the path loss exponent is equal to 4 its density of
successfully received packets is still 75% of that in the slotted scheme. This
is still much more than the 50% predicted by the well-known analysis where
simultaneous transmissions are never successful. Moreover, in any path loss
scenario, both schemes exhibit the same energy efficiency.Comment: accepted for IEEE Infocom 201
Stability Oriented Routing in Mobile Ad-Hoc Networks Based on Simple Automatons
International audienceSince wireless ad-hoc networks with mobile nodes have not stable topology, the classical network functions as the routing are difficult to realize. The router nodes and the links between them are not stable and can appear and disappear randomly. So, classic routing algorithms can not be used successfully. New approaches should be used which deals with these dynamic changes. To avoid frequent route requests and volatile routes due to uncertain information, the objective of the routing can correspond to the route stability. The route computation can be based on random variables and becomes probabilistic routing. Our book chapter focuses on modeling the resilience of these information for ad hoc networks where topology information is uncertain. Our model is based on a dynamic graph where the existence of the nodes and the communication capability between them are modeled by simple two state automaton where the transitions are initiated by random events
Airborne Directional Networking: Topology Control Protocol Design
This research identifies and evaluates the impact of several architectural design choices in relation to airborne networking in contested environments related to autonomous topology control. Using simulation, we evaluate topology reconfiguration effectiveness using classical performance metrics for different point-to-point communication architectures. Our attention is focused on the design choices which have the greatest impact on reliability, scalability, and performance. In this work, we discuss the impact of several practical considerations of airborne networking in contested environments related to autonomous topology control modeling. Using simulation, we derive multiple classical performance metrics to evaluate topology reconfiguration effectiveness for different point-to-point communication architecture attributes for the purpose of qualifying protocol design elements
Hybrid Satellite-Terrestrial Communication Networks for the Maritime Internet of Things: Key Technologies, Opportunities, and Challenges
With the rapid development of marine activities, there has been an increasing
number of maritime mobile terminals, as well as a growing demand for high-speed
and ultra-reliable maritime communications to keep them connected.
Traditionally, the maritime Internet of Things (IoT) is enabled by maritime
satellites. However, satellites are seriously restricted by their high latency
and relatively low data rate. As an alternative, shore & island-based base
stations (BSs) can be built to extend the coverage of terrestrial networks
using fourth-generation (4G), fifth-generation (5G), and beyond 5G services.
Unmanned aerial vehicles can also be exploited to serve as aerial maritime BSs.
Despite of all these approaches, there are still open issues for an efficient
maritime communication network (MCN). For example, due to the complicated
electromagnetic propagation environment, the limited geometrically available BS
sites, and rigorous service demands from mission-critical applications,
conventional communication and networking theories and methods should be
tailored for maritime scenarios. Towards this end, we provide a survey on the
demand for maritime communications, the state-of-the-art MCNs, and key
technologies for enhancing transmission efficiency, extending network coverage,
and provisioning maritime-specific services. Future challenges in developing an
environment-aware, service-driven, and integrated satellite-air-ground MCN to
be smart enough to utilize external auxiliary information, e.g., sea state and
atmosphere conditions, are also discussed
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