23-07-2012, 10:48 AM
An Efficient Geographic Multicast Protocol for Mobile Ad Hoc Networks
An Efficient Geographic Multicast.pdf (Size: 234.72 KB / Downloads: 63)
Abstract
Group communications is important in supporting
multimedia applications. Multicast is an efficient
method in implementing the group communications. However,
it is challenging to implement efficient and scalable
multicast in Mobile Ad hoc Networks (MANET) due to the
difficulty in group membership management and multicast
packet forwarding over the dynamic topology. We propose
a novel Efficient Geographic Multicast Protocol (EGMP).
EGMP uses a hierarchical structure to implement scalable
and efficient group membership management. And
a network-range zone-based bi-directional tree is constructed
to achieve a more efficient multicast delivery. The
position information is used to guide the hierarchical structure
building, multicast tree construction and multicast
packet forwarding, which efficiently reduces the overhead
for route searching and tree structure maintenance.
INTRODUCTION
Group communications is important in Mobile Ad
Hoc Networks (MANET). Sending action direction to
the soldiers in a battlefield and communications among
the firemen in a disaster area are some examples of
these applications. Group communications are also very
important in supporting multimedia applications such
as gaming and conferencing. With a one-to-many or
many-to-many transmission pattern, multicast is an efficient
method to realize group communications. The
high dynamics of MANET, however, makes the design
of routing protocols much more challenging than that of
wired network.
RELATED WORK
In this section we discuss the conventional multicast
protocols and the geographic multicast algorithms for
MANET.
The conventional topology-based multicast protocols
include tree-based protocols (e.g., [19] [26] [30]) and
mesh-based protocols (e.g., [9] [15] [16]). The conventional
multicast protocols are usually composed of the
following three components and generally they can not
scale to large network size. 1) Group membership management.
The group membership changes frequently as
each node may join or leave a multicast group randomly,
and the management becomes harder for a large group.
2) Creation and maintenance of a tree- or mesh-based
multicast structure. In these protocols, the structures
are based on some non-geographic mechanisms, which
makes the tree-based structure not so robust, while the
mesh-based ones achieve the robustness at the cost of
inefficiently utilizing network resource. Also the nongeographic
routing mechanisms prohibit these protocols
from scaling to a large network size. 3) Multicast packet
forwarding. The multicast packets are forwarded along
the pre-built tree or mesh structure, but the pre-built
paths are vulnerable to be broken over the dynamic
topology, especially in a large network with potentially
longer paths.
EFFICIENT GEOGRAPHIC MULTICAST PROTOCOL
In this section, we will describe the EGMP protocol
in details. We first give an overview of the protocol
in Section III-A, and then introduce the notations and
definitions used in our protocol in Section III-B. In
Section III-C we present the zone structure building process
and the zone-supported geographic routing strategy.
Finally, in Section III-D and Section III-E we introduce
the processes for the multicast tree creation, maintenance
and the multicast packet delivery.
CONCLUSIONS AND FUTURE WORK
We have designed an efficient and robust geographic
multicast protocol for MANET in this paper. This protocol
uses a zone structure to achieve scalability, and
relies on underneath geographic unicast routing for reliable
packet transmissions. We build a zone-based bidirectional
multicast tree at the upper tier to achieve
more efficient multicast membership management and
delivery, and use a zone structure at the lower tier
to realize the local membership management. We also
develop a scheme to handle the empty zone problem
which is challenging for the zone-based protocols.