998:362

MASTER'S THESIS

Routing Protocols in Wireless Ad-hoc Networks -

A Simulation Study

Tony Larsson, Nicklas Hedman

Civilingenjšrsprogrammet

1998:362 • ISSN: 1402-1617 • ISRN: LTU-EX--98/362--SE

Master’s thesis in Computer Science and Engineering

Routing Protocols in Wireless Ad-hoc Networks -

A Simulation Study

Stockholm, 1998

Tony Larsson and Nicklas Hedman

Luleå University of Technology

Supervisor: Per JohanssonSwitchlabEricsson Telecom AB

Examiner: Mikael DegermarkDepartment of Computer Science and Electrical EngineeringDivision of Computer Communications,Luleå University of Technology

Abstract

Ad-hoc networking is a concept in computer communications, which means that users wanting tocommunicate with each other form a temporary network, without any form of centralized

administration.Each node participating in the network acts both as host and a router and must therefore be willing toforward packets for other nodes. For this purpose, a routing protocol is needed.

An ad-hoc network has certain characteristics, which imposes new demands on the routing protocol.

The most important characteristic is the dynamic topology, which is a consequence of node mobility. Nodes

can change position quite frequently, which means that we need a routing protocol that quickly adapts to

topology changes. The nodes in an ad-hoc network can consist of laptops and personal digital assistants and

are often very limited in resources such as CPU capacity, storage capacity, battery power and bandwidth.

This means that the routing protocol should try to minimize control traffic, such as periodic updatemessages. Instead the routing protocol should be reactive, thus only calculate routes upon receiving aspecific request.

The Internet Engineering Task Force currently has a working group named Mobile Ad-hoc Networksthat is working on routing specifications for ad-hoc networks. This master thesis evaluates some of theprotocols put forth by the working group. This evaluation is done by means of simulation using Networksimulator 2 from Berkeley.

The simulations have shown that there certainly is a need for a special ad-hoc routing protocol when

mobility increases. More conventional routing protocols like DSDV have a dramatic decrease inperformance when mobility is high. Two of the proposed protocols are DSR and AODV. They perform

verywell when mobility is high. However, we have found that a routing protocol that entirely depends onmessages at the IP-level will not perform well. Some sort of support from the lower layer, for instance

linkfailure detection or neighbor discovery is necessary for high performance.

The size of the network and the offered traffic load affects protocols based on source routing, like DSR,

to some extent. A large network with many mobile nodes and high offered load will increase the overhead for

DSR quite drastically. In these situations, a hop-by-hop based routing protocol like AODV is more desirable.