11-02-2013, 04:16 PM
Multipath Optimized Link State Routing for Mobile ad hoc Networks
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Abstract
Multipath routing protocols for Mobile Ad hoc NETwork (MANET) address the problem of scalability, security (confidentiality
and integrity), lifetime of networks, instability of wireless transmissions, and their adaptation to applications.
Our protocol, called MP-OLSR (MultiPath OLSR), is a multipath routing protocol based on OLSR [1]. The Multipath Dijkstra
Algorithm is proposed to obtain multiple paths. The algorithm gains great flexibility and extensibility by employing different link
metrics and cost functions. In addition, route recovery and loop detection are implemented in MP-OLSR in order to improve
quality of service regarding OLSR. The backward compatibility with OLSR based on IP source routing is also studied. Simulation
based on Qualnet simulator is performed in different scenarios. A testbed is also set up to validate the protocol in real world. The
results reveal that MP-OLSR is suitable for mobile, large and dense networks with large traffic, and could satisfy critical multimedia
applications with high on time constraints.
Introduction
Staying connected anywhere to a network is really the main
objective of mobile technologies. Mobile Ad hoc NETwork
(MANET) may provide a solution. With MANET, all nodes
are routers and forward packets without any infrastructure.
This kind of network is spontaneous, self-organized and selfmaintained.
In this context, routing the data is the big challenging
task since many issues are covered: scalability, security,
lifetime of network, wireless transmissions, increasing needs
of applications.
Many routing protocols have been developed for ad hoc networks
[2]. They can be classified according to different criteria.
The most important is by the type of route discovery. It enables
to separate the routing protocols into two categories: proactive
and reactive. In reactive protocols, e.g. Dynamic Source Routing
(DSR [3]) and Ad hoc On-demand Distance Vector routing
(AODV [4]), the routing request is sent on-demand: if a
node wants to communicate with another, then it broadcasts
a route request and expects a response from the destination.
Conversely, proactive protocols update their routing information
continuously in order to have a permanent overview of the
network topology (e.g. OLSR [1]).
Multipath OLSR - Functionalities
The MP-OLSR can be regarded as a kind of hybrid multipath
routing protocol which combines the proactive and reactive features.
It sends out HELLO and TC messages periodically to detect
the network topology, just like OLSR. However, MP-OLSR
does not always keep a routing table. It only computes the multiple
routes when data packets need to be sent out.
The core functionality of MP-OLSR has two parts: topology
sensing and route computation. The topology sensing is
to make the nodes aware of the topology information of the
network. This part benefits from MPRs like OLSR. The route
computation uses the Multipath Dijkstra Algorithm [30] [15] to
calculate the multipath based on the information obtained from
the topology sensing. The source route (all the hops from the
source to the destination) is saved in the header of the data packets.
Simulation and Performance Evaluation
The simulations are performed to evaluate MP-OLSR which
includes both the core functionality and the auxiliary functionality
(route recovery and loop detection). The rest of the section
is organized as follows. The simulation environment and
assumption are first introduced in subsection 4.1. Then we compare
the performances between OLSR and MP-OLSR in different
scenarios. The difference between the reactive and proactive
protocols is also analyzed. The performance evaluation will be
done in a real testbed in section 5.