1998:362 MASTER'S THESIS Routing Protocols in Wireless Ad-hoc Networks - A Simulation Study Tony Larsson, Nicklas Hedman Civilingenjörsprogrammet 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 Johansson Switchlab Ericsson Telecom AB Examiner: Mikael Degermark Department of Computer Science and Electrical Engineering Division of Computer Communications, Luleå University of Technology
Abstract Ad-hoc networking is a concept in computer communications, which means that users wanting to communicate 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 to forward 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 update messages. Instead the routing protocol should be reactive, thus only calculate routes upon receiving a specific request. The Internet Engineering Task Force currently has a working group named Mobile Ad-hoc Networks that is working on routing specifications for ad-hoc networks. This master thesis evaluates some of the protocols put forth by the working group. This evaluation is done by means of simulation using Network simulator 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 in performance when mobility is high. Two of the proposed protocols are DSR and AODV. They perform very well when mobility is high. However, we have found that a routing protocol that entirely depends on messages at the IP-level will not perform well. Some sort of support from the lower layer, for instance link failure 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.
Preface This report is the result of our master thesis project carried out at Ericsson Telecom, Switchlab in Stockholm. This master thesis is also the last part of our Master of Science degree at Luleå University of Technology. Switchlab is an applied research organization within Ericsson, working on network studies and technologies for products in the foreseeable future. This master thesis project has been a cooperation between Switchlab in Stockholm and Ericsson Mobile Data Design (ERV) in Gothenburg. Our master thesis consisted of conducting a simulation study of proposed routing protocols in ad-hoc networks. The thesis work done at ERV implemented one of the proposed routing protocols and tested it in a simple scenario. This has made it possible to share thoughts and ideas with each other. We would like to thank the following persons: Per Johansson for being our supervisor at Switchlab, Bartosz Mielczarek for contribution of the realistic scenarios and Mikael Degermark for being our Examiner at Luleå University of Technology. Also thanks to Johan Köpman and Jerry Svedlund in Gothenburg for discussions and comments regarding AODV. Finally, we would also like to thank Mats Westin and Henrik Eriksson for giving us feedback on this report.
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