1,421 research outputs found
Analysis of Link Reversal Routing Algorithms for Mobile Ad Hoc Networks
Link reversal (LR) algorithms provide a simple mechanisme for routing in communication networks whose topology is frequently changing, such as in mobile and ad hoc networks. A LR algorithm routes by imposing a direction on each network link such that the resulting graph is destination oriented (DAG). Whenever a node loses routes to the destination, is reacts by reversing some (or all) of its incident links. This survey presents the worst-case performance analysis of LR algorithms from the excellent work of Costas Busch and Srikanta Tirthapura (SIAM J. on Computing, 35(2):305- 326, 2005). The LR algorithms are studied in terms of work (number of node reversals) and time needed until the algorithm stabilizes to a state in which all the routes are reestablished. The full reversal algorithm and the partial reversal algorithm are considered. • The full reversal algorithm requires O(n2) work and time, where n is the number of nodes that have lost routes to the destination. This bound is tight in the worst case. • The partial reversal algorithm requires O(na*r + n2) work and time, where a*r is a non-negative integral function of the initial state of the network. Further, the partial reversal algorithm requires (na*r + n2) work and time. • There is an inherent lower bound on the worst-case performance of LR algorithms: \Omega(n2). Therefore, surprisingly, the full reversal algorithm is asymptotically optimal in the worst-case, while the partial reversal algorithm is not; since a*r can be arbitrarily larger than n
An Overview of Mobile Ad Hoc Networks for the Existing Protocols and Applications
Mobile Ad Hoc Network (MANET) is a collection of two or more devices or nodes
or terminals with wireless communications and networking capability that
communicate with each other without the aid of any centralized administrator
also the wireless nodes that can dynamically form a network to exchange
information without using any existing fixed network infrastructure. And it's
an autonomous system in which mobile hosts connected by wireless links are free
to be dynamically and some time act as routers at the same time, and we discuss
in this paper the distinct characteristics of traditional wired networks,
including network configuration may change at any time, there is no direction
or limit the movement and so on, and thus needed a new optional path Agreement
(Routing Protocol) to identify nodes for these actions communicate with each
other path, An ideal choice way the agreement should not only be able to find
the right path, and the Ad Hoc Network must be able to adapt to changing
network of this type at any time. and we talk in details in this paper all the
information of Mobile Ad Hoc Network which include the History of ad hoc,
wireless ad hoc, wireless mobile approaches and types of mobile ad Hoc
networks, and then we present more than 13 types of the routing Ad Hoc Networks
protocols have been proposed. In this paper, the more representative of routing
protocols, analysis of individual characteristics and advantages and
disadvantages to collate and compare, and present the all applications or the
Possible Service of Ad Hoc Networks.Comment: 24 Pages, JGraph-Hoc Journa
An enhanced Multipath Strategy in Mobile Ad hoc Routing Protocols
The various routing protocols in Mobile Ad hoc Networks follow different
strategies to send the information from one node to another. The nodes in the
network are non static and they move randomly and are prone to link failure
which makes always to find new routes to the destination. This research mainly
focused on the study of the characteristics of multipath routing protocols in
MANETS. Two of the multipath routing protocols were investigated and a
comparative study along with simulation using NS2 was done between DSR and AODV
to propose an enhanced approach to reach the destination maintaining the QoS. A
possible optimization to the DSR and AODV routing protocols was proposed to
make no node to be overburdened by distributing the load after finding the
alternate multipath routes which were discovered in the Route discovery
process. The simulation shows that the differences in the protocol highlighted
major differences with the protocol performance. These differences have been
analyzed with various network size, mobility, and network load. A new search
table named Search of Next Node Enquiry Table (SONNET) was proposed to find the
best neighbor node. Using SONNET the node selects the neighbor which can be
reached in less number of hops and with less time delay and maintaining the
QoS
Self-stabilizing leader election in dynamic networks
The leader election problem is one of the fundamental problems in distributed computing. It has applications in almost every domain. In dynamic networks, topology is expected to change frequently. An algorithm A is self-stabilizing if, starting from a completely arbitrary configuration, the network will eventually reach a legitimate configuration.
Note that any self-stabilizing algorithm for the leader election problem is also an algorithm for the dynamic leader election problem, since when the topology of the network changes, we can consider that the algorithm is starting over again from an arbitrary state. There are a number of such algorithms in the literature which require large memory in each process, or which take O(n) time to converge, where n is size of the network. Given the need to conserve time, and possibly space, these algorithms may not be practical for the dynamic leader election problem.
In this thesis, three silent self-stabilizing asynchronous distributed algorithms are given for the leader election problem in a dynamic network with unique IDs, using the composite model of computation. If topological changes to the network pause, a leader is elected for each component. A BFS tree is also constructed in each component, rooted at the leader. When another topological change occurs, leaders are then elected for the new components. This election takes O (Diam) rounds, where Diam is the maximum diameter of any component.
The three algorithms differ in their leadership stability. The first algorithm, which is the fastest in the worst case, chooses an arbitrary process as the leader. The second algorithm chooses the process of highest priority in each component, where priority can be defined in a variety of ways. The third algorithm has the strictest leadership stability; if a component contains processes that were leaders before the topological change, one of those must be elected to be the new leader. Formal algorithms and their correctness proofs will be given
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