25-08-2017, 09:32 PM
Multimedia Ad hoc Networks: Performance Analysis
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Abstract
Wireless ad hoc networks are characterized by
frequent topology changes, unreliable wireless
channel, network congestion and resource contention.
Multimedia applications usually are bandwidth hungry
with stringent delay, jitter and loss requirements.
Designing ad hoc networks which support multimedia
applications, hence, is considered a hard task. In this
paper, we report our work on supporting video
streaming over ad hoc networks and present the
analysis using the OPNET simulation environment. We
briefly survey the main challenges in ad hoc network
research and review the QoS literature for ad hoc
networks. We then evaluate performance of video
streaming application over ad hoc networks by
simulating few scenarios with varying video quality,
different network sizes, and 5 different routing
protocols. The simulations demonstrate that it is
possible to stream fairly good quality video over
medium sized ad hoc networks.
Introduction
Ad hoc wireless networks are increasingly gaining
importance due to their advantages such as low cost
and ease of deployment. An ad hoc network is
characterized by its fully distributed control
mechanisms and self-organized behavior. Such a
network is expected to work in the absence of any
infrastructure by autonomously creating multihop paths
for packet delivery. Ad hoc network applications
include rescue operations, disaster recovery, ad hoc
formation of networks in meetings and conferences,
connecting wirelessly in rural areas where an
infrastructure is not available. For example, the
Swedish Company TerraNet is providing mobile phone
connections based on ad hoc networking for
developing countries in Africa.
Multimedia Ad hoc Networks: A Brief Review of QoS Provisioning Literature
Multimedia traffic is growing rapidly with the
convergence of the Internet and the mobile networks.
Most multimedia services require QoS guarantees. Best
effort network service may work reasonably well on
wired and wireless infrastructure; however, for ad hoc
networks best effort delivery is not good enough.
Different metrics have been used to specify and gauge
QoS level offered by a network. These include packet
dropping probability, end-to-end delay, delay variance,
and throughput. For multimedia applications, all these
metrics are important, however, the network throughput
is the most basic one. The achievements on supporting
multimedia over ad hoc networks are limited due to the
immense difficulty of the task. In the following, we
briefly discuss some of the distinct approaches on this
subject.
Routing Protocols and the OPNET Modeler
Ad hoc network routing protocols have been classified
in the literature based on various characteristics
including route discovery and route maintenance
approaches, network topologies, and on the approaches
which rely on interactions between routing and other
network layers. Major classifications are reactive,
proactive, hybrid, geographical, power-aware, locationaware
and situation-aware routing protocols. Table 1,
taken from the OPNET documentation, gives certain
characteristics of the five routing protocols which we
have used in our simulations; what follows is a brief
description of these protocols. OPNET (Optimized
Network Engineering Tools) Technologies Inc. is a
leading provider of networks R&D software (see
http://www.opnet). OPNET is a discrete-event
network simulator which was first proposed by MIT in
1986. It is the most widely used commercial simulation
software.
Results
In this section, we present results for the simulations
which we have performed using the OPNET Modeler.
We have simulated a total of over 150 scenarios and
have selected few of those for presentation and
discussions in this paper. The application considered in
these selected scenarios is video streaming. In
particular, we simulate various ad hoc networking
scenarios where in a network of size n, one server node
streams video to each of the other n-1 nodes in the
network. We have mentioned earlier that multicasting
is not considered in this paper because we assume that
each client node requires a unique connection. The
transport protocol used in all these simulations is UDP
(User Datagram Protocol).