06-10-2012, 04:26 PM
Scalable Multicasting in Mobile Ad Hoc Networks
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INTRODUCTION
The use of mobile and wireless devices are becoming
ubiquitous. Thus the need for efficient intercommunication
among these devices is becoming critical. In addition to
the infrastructure-based cellular wireless network, the study
and developments of infrastructureless wireless networks have
been very popular in recent years. Mobile Ad hoc NETworks
(MANETs) belong to the class of infrastructureless networks,
which do not require the support of wired access points
for intercommunication. It is a dynamically reconfigurable
wireless network where the nodes are mobile resulting in
variable network topology. Due to the limited radio propagation
range, nodes of a MANET communicate either through
single hop or multihop transmissions. The nodes act as both
hosts as well as routers. Applications of MANETs include
battlefield communication, disaster recovery, coordinated task
scheduling (such as earth moving or construction), vehicular
communication for traffic management, data and information
sharing in difficult terrain, and extension of the infrastructurebased
wireless networks.
MULTICASTING IN MANETS: STATE MANAGEMENT AND SCALABILITY
State management of multicast protocols involves timely
updating of the multicast routing tables at the involved nodes
to maintain the correctness of the multicast routing structure,
tree or mesh, according to the current network topology.
Even under moderate node mobility and multicast member
size, state management incurs considerable amount of control
traffic. When the group size grows, and/or number of groups
increase, traditional tree or mesh based methods [22], [23],
[24], [25] become inefficient. To address the scalability issues,
we need to reduce the protocol states and constrain their
distribution, or even use methods that do not need to have
protocol state. A number of research efforts have adopted
this method, which can be classified into the following categories:
overlay multicasting, backbone-based multicasting and
stateless multicasting. We study these different approaches for
constraining protocol states, and their scalability issues.
HIERARCHICAL MULTICASTING
Hierarchical routing[18] approach can be used to significantly
reduce the protocol states in a large scale network. In
this section, we present two hierarchical multicast solutions,
both of which have the goal of achieving lower multicast overhead
and robustness for large-scale multicasting. We refrain
from developing a new multicast routing protocol, but present
a framework for hierarchical multicasting in MANETs. Based
on the framework, a variety of techn
CONCLUSION
In this paper, we apply the hierarchical routing principle to
MANET multicast routing. We categorize the current multicast
routing protocols by the amount and distribution of the
protocol states. We also study the scalability issues of each
category.We propose two different approaches for hierarchical
multicast tree construction: domain-based method and overlaydriven
method. The domain-based method uses the topological
vicinity of nodes to form different levels of hierarchy. At
each level, the same or different multicasting protocol can be
adopted. By keeping the group size small at each of the levels,
efficient small group multicasting protocol could be adopted.
The overlay-driven approach uses two levels of hierarchy; the
higher level is an overlay topology and the lower level is
formed around the nodes of the overlay topology. For the
purpose of evaluation, we have used the DDM multicasting
scheme that has been shown to be very efficient for small
groups.