709,893 research outputs found
Data Dissemination Problem in Wireless Networks
In this work, we formulate and study a data dissemination problem, which can
be viewed as a generalization of the index coding problem and of the data
exchange problem to networks with an arbitrary topology. We define -solvable
networks, in which data dissemination can be achieved in communications
rounds. We show that the optimum number of transmissions for any one-round
communications scheme is given by the minimum rank of a certain constrained
family of matrices. For a special case of this problem, called bipartite data
dissemination problem, we present lower and upper graph-theoretic bounds on the
optimum number of transmissions. For general -solvable networks, we derive
an upper bound on the minimum number of transmissions in any scheme with rounds. We experimentally compare the obtained upper bound to a simple lower
bound.Comment: Notation clarificatio
Weather data dissemination to aircraft
Documentation exists that shows weather to be responsible for approximately 40 percent of all general aviation accidents with fatalities. Weather data products available on the ground are becoming more sophisticated and greater in number. Although many of these data are critical to aircraft safety, they currently must be transmitted verbally to the aircraft. This process is labor intensive and provides a low rate of information transfer. Consequently, the pilot is often forced to make life-critical decisions based on incomplete and outdated information. Automated transmission of weather data from the ground to the aircraft can provide the aircrew with accurate data in near-real time. The current National Airspace System Plan calls for such an uplink capability to be provided by the Mode S Beacon System data link. Although this system has a very advanced data link capability, it will not be capable of providing adequate weather data to all airspace users in its planned configuration. This paper delineates some of the important weather data uplink system requirements, and describes a system which is capable of meeting these requirements. The proposed system utilizes a run-length coding technique for image data compression and a hybrid phase and amplitude modulation technique for the transmission of both voice and weather data on existing aeronautical Very High Frequency (VHF) voice communication channels
Data Dissemination in Unified Dynamic Wireless Networks
We give efficient algorithms for the fundamental problems of Broadcast and
Local Broadcast in dynamic wireless networks. We propose a general model of
communication which captures and includes both fading models (like SINR) and
graph-based models (such as quasi unit disc graphs, bounded-independence
graphs, and protocol model). The only requirement is that the nodes can be
embedded in a bounded growth quasi-metric, which is the weakest condition known
to ensure distributed operability. Both the nodes and the links of the network
are dynamic: nodes can come and go, while the signal strength on links can go
up or down.
The results improve some of the known bounds even in the static setting,
including an optimal algorithm for local broadcasting in the SINR model, which
is additionally uniform (independent of network size). An essential component
is a procedure for balancing contention, which has potentially wide
applicability. The results illustrate the importance of carrier sensing, a
stock feature of wireless nodes today, which we encapsulate in primitives to
better explore its uses and usefulness.Comment: 28 pages, 2 figure
Highly intensive data dissemination in complex networks
This paper presents a study on data dissemination in unstructured
Peer-to-Peer (P2P) network overlays. The absence of a structure in unstructured
overlays eases the network management, at the cost of non-optimal mechanisms to
spread messages in the network. Thus, dissemination schemes must be employed
that allow covering a large portion of the network with a high probability
(e.g.~gossip based approaches). We identify principal metrics, provide a
theoretical model and perform the assessment evaluation using a high
performance simulator that is based on a parallel and distributed architecture.
A main point of this study is that our simulation model considers
implementation technical details, such as the use of caching and Time To Live
(TTL) in message dissemination, that are usually neglected in simulations, due
to the additional overhead they cause. Outcomes confirm that these technical
details have an important influence on the performance of dissemination schemes
and that the studied schemes are quite effective to spread information in P2P
overlay networks, whatever their topology. Moreover, the practical usage of
such dissemination mechanisms requires a fine tuning of many parameters, the
choice between different network topologies and the assessment of behaviors
such as free riding. All this can be done only using efficient simulation tools
to support both the network design phase and, in some cases, at runtime
Search and dissemination in data processing
Manual retrieval methods were used to complete 54 searches of interest for the General Aviation Newsletter. Subjects of search ranged from television transmission to machine tooling, Apollo moon landings, electronic equipment, and aerodynamics studies
Data Dissemination Performance in Large-Scale Sensor Networks
As the use of wireless sensor networks increases, the need for
(energy-)efficient and reliable broadcasting algorithms grows. Ideally, a
broadcasting algorithm should have the ability to quickly disseminate data,
while keeping the number of transmissions low. In this paper we develop a model
describing the message count in large-scale wireless sensor networks. We focus
our attention on the popular Trickle algorithm, which has been proposed as a
suitable communication protocol for code maintenance and propagation in
wireless sensor networks. Besides providing a mathematical analysis of the
algorithm, we propose a generalized version of Trickle, with an additional
parameter defining the length of a listen-only period. This generalization
proves to be useful for optimizing the design and usage of the algorithm. For
single-cell networks we show how the message count increases with the size of
the network and how this depends on the Trickle parameters. Furthermore, we
derive distributions of inter-broadcasting times and investigate their
asymptotic behavior. Our results prove conjectures made in the literature
concerning the effect of a listen-only period. Additionally, we develop an
approximation for the expected number of transmissions in multi-cell networks.
All results are validated by simulations
Data Dissemination in Wireless Networks with Network Coding
We investigate the use of network coding for information dissemination over a
wireless network. Using network coding allows for a simple, distributed and
robust algorithm where nodes do not need any information from their neighbors.
In this paper, we analyze the time needed to diffuse information throughout a
network when network coding is implemented at all nodes. We then provide an
upper bound for the dissemination time for ad-hoc networks with general
topology. Moreover, we derive a relation between dissemination time and the
size of the wireless network. It is shown that for a wireless network with N
nodes, the dissemination latency is between O(N) and O(N^2), depending on the
reception probabilities of the nodes. These observations are validated by the
simulation results
Cooperative Coded Data Dissemination for Wireless Sensor Networks
In this poster paper we present a data dissemination transmission abstraction
for over the air programming (OAP) protocol which is fundamentally different
from the previous hop by hop transmission protocols. Instead of imposing the
greedy requirement that at least one node in the ith hop receives all packets
before transmitting packets to the next hop and its neighbours, we take
advantage of the spatial diversity and broadcast nature of wireless
transmission to adopt a cooperative approach in which node broadcast whatever
packets it has received with the expectation that it will recover the lost
packets with high probability by overhearing the broadcast transmissions of its
neighbours. The use of coded transmissions ensures that this does not lead to
the broadcast storm problem. We validate the improved performance our of
proposed transmission scheme with respect to the previous state of the art OAP
protocols on a proof-of-concept two-hops TelosB wireless sensor network
testbed.Comment: This paper appears in: 2016 13th Annual IEEE International Conference
on Sensing, Communication, and Networking (SECON), London, 2016, pp. 1-
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