535 research outputs found
Wireless Broadcast with Network Coding in Mobile Ad-Hoc Networks: DRAGONCAST
Network coding is a recently proposed method for transmitting data, which has
been shown to have potential to improve wireless network performance. We study
network coding for one specific case of multicast, broadcasting, from one
source to all nodes of the network. We use network coding as a loss tolerant,
energy-efficient, method for broadcast. Our emphasis is on mobile networks. Our
contribution is the proposal of DRAGONCAST, a protocol to perform network
coding in such a dynamically evolving environment. It is based on three
building blocks: a method to permit real-time decoding of network coding, a
method to adjust the network coding transmission rates, and a method for
ensuring the termination of the broadcast. The performance and behavior of the
method are explored experimentally by simulations; they illustrate the
excellent performance of the protocol
Opportunistic Networks: Present Scenario- A Mirror Review
Opportunistic Network is form of Delay Tolerant Network (DTN) and regarded as extension to Mobile Ad Hoc Network. OPPNETS are designed to operate especially in those environments which are surrounded by various issues like- High Error Rate, Intermittent Connectivity, High Delay and no defined route between source to destination node. OPPNETS works on the principle of “Store-and-Forward” mechanism as intermediate nodes perform the task of routing from node to node. The intermediate nodes store the messages in their memory until the suitable node is not located in communication range to transfer the message to the destination. OPPNETs suffer from various issues like High Delay, Energy Efficiency of Nodes, Security, High Error Rate and High Latency. The aim of this research paper is to overview various routing protocols available till date for OPPNETs and classify the protocols in terms of their performance. The paper also gives quick review of various Mobility Models and Simulation tools available for OPPNETs simulation
Design and performance study of algorithms for consensus in sparse, mobile ad-hoc networks
PhD ThesisMobile Ad-hoc Networks (MANETs) are self-organizing wireless networks that consist
of mobile wireless devices (nodes). These networks operate without the aid
of any form of supporting infrastructure, and thus need the participating nodes to
co-operate by forwarding each other’s messages. MANETs can be deployed when
urgent temporary communications are required or when installing network infrastructure
is considered too costly or too slow, for example in environments such as
battlefields, crisis management or space exploration.
Consensus is central to several applications including collaborative ones which a
MANET can facilitate for mobile users. This thesis solves the consensus problem in
a sparse MANET in which a node can at times have no other node in its wireless
range and useful end-to-end connectivity between nodes can just be a temporary
feature that emerges at arbitrary intervals of time for any given node pair.
Efficient one-to-many dissemination, essential for consensus, now becomes a challenge:
enough number of destinations cannot deliver a multicast unless nodes retain
the multicast message for exercising opportunistic forwarding. Seeking to keep storage
and bandwidth costs low, we propose two protocols. An eventually relinquishing
(}RC) protocol that does not store messages for long is used for attempting at consensus,
and an eventually quiescent (}QC) one that stops forwarding messages
after a while is used for concluding consensus. Use of }RC protocol poses additional
challenges for consensus, when the fraction, f
n, of nodes that can crash is:
1
4 f
n < 1
2 .
Consensus latency and packet overhead are measured through simulation indicating
that they are not too high to be feasible in MANETs. They both decrease
considerably even for a modest increase in network density.Damascus University
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