To my family Acknowledgements First, I would like to thank my two supervisors, Per Gunningberg and Christian Tschudin, for guiding me during my PhD studies with great patience and support. Their great
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To my family Acknowledgements First, I would like to thank my two supervisors, Per Gunningberg and Christian Tschudin, for guiding me during my PhD studies with great patience and support. Their great knowledge and combination of the big picture view and deep technical skills have provided me with the best possible support. I would like to thank my colleagues in the CoRe research group: Erik Nordström, with whom I have been working together on most papers. Christian Rohner, our Swiss Post-doc, who has always been very helpful and happy to discuss ideas. My fellow PhD students, Richard Gold, Mattias Wiggberg, Oskar Wibling, Olof Rensfelt, Thabotharan Kathiravelu and Laura Feeney. Past PhD students in our research group, Björn Knutsson, Thiemo Voigt and Bob Melander. The senior members of our research group, Arnold Pears, Lars-Åke Larzon and Mats Björkman. There are many MSc. students and project assistants who have been working and contributing to our research projects. Special thanks go to: Henrik Gulbrandsen for his collaboration on my first project as a PhD student. David Lundberg for many efforts with our ad hoc network testbed and wireless LAN. Johan Nielsen and Mattis Fjällström for early work with the ad hoc network testbed. Björn Wiberg for his implementation efforts. Many thanks to all colleagues at the IT-department and at DoCS who provided me with an excellent working and research environment. I would like to thank my former colleagues at Ellemtel Utvecklings AB (EUB) who in many ways inspired me to continue with my studies. Thanks to Jörgen Olsén, who through invitations to many parties in Uppsala made sure that it was Uppsala University that I chose for my continued studies. A number of people deserve special thanks for helping me out the last stressful months of this thesis. Again, my supervisors Per and Christian for helping me out with the thesis and the thesis final paper. Christian Rohner, who helped me with the final paper and reformatted all included papers for this thesis. I would not have met the printing deadline without their help. I would like to thank those who have read and provided constructive feedback on early drafts of this thesis, Mikael Nolin, Jakob Carlström, Laura Feeney, Mats Björkman and Arnold Pears for language proof-reading. Fredrik v Bjurefors, Fredrik Östergren and Kristoffer Kobosko for spending weekends, evenings and sometimes nights performing the Monkey Walk. Finally, I would like thank my family for their love and support. My deepest thanks goes to Chrissie for always supporting and believing in me and making life outside work enjoyable. The work in this thesis was supported and made possible through our generous funders. VINNOVA funded our ARRCANE and SCANET projects. Ericsson partly funded our SCANET project and donated the wireless ORiNOCO PCM- CIA cards to our testbed. PCC++ partly financed courses during my PhD studies. vi List of Included Papers Paper A: Christian Tschudin, Henrik Lundgren and Henrik Gulbrandsen. Active Routing for Ad-hoc Networks. IEEE Communications Magazine, Special issue on Active and Programmable Networks, 38(4), April [TLG00] Paper B: Henrik Lundgren, David Lundberg, Johan Nielsen, Erik Nordström and Christian Tschudin. A Large-scale Testbed for Reproducible Ad hoc Protocol Evaluations. In Proceedings of The Third Annual IEEE Wireless Communications and Networking Conference 2002 (WCNC 2002), March [LLN + 02] Paper C: Henrik Lundgren, Erik Nordström and Christian Tschudin. Coping with Communication Gray Zones in IEEE b based Ad hoc Networks. In Proceedings of The Fifth ACM International Workshop On Wireless Mobile Multimedia 2002 (WoWMoM 2002), September [LNT02] Paper D: Christian Tschudin, Per Gunningberg, Henrik Lundgren, and Erik Nordström. Lessons from Experimental MANET Research. Elsevier Journal on Ad hoc Networks, 3(2), March To appear. [TGLN05] Paper E: Erik Nordström, Per Gunningberg and Henrik Lundgren. A Testbed and Methodology for Experimental Evaluation of Wireless Mobile Ad hoc Networks. In Proceedings of The First International Conference on Testbeds and Research Infrastructures for the Development of Networks and Communities (TRIDENTCOM 2005), February To appear. [NGL05] Paper F: Henrik Lundgren. Experimental Evaluation of Three Ad hoc Routing Protocols. Not yet published [Lun05] Paper A to E have been reprinted with permission from respective publisher. Comments on my Participation Paper A: In the work related to paper A, I participated in implementing two active routing protocols and parts of an audio streaming demo setting. I wrote the sections on the routing protocol description and the implementation and coauthored the rest of the paper. vii Paper B: I am the principal author of paper B. All co-authors have participated in the practical work with different effort and focus. I have participated in all parts, with focus on design and implementation of scenarios, implementation of analysis tools, conducting tests and performing the analysis. Paper C: I am the principal author of paper C and participated in all parts. This work includes an implementation of an ad hoc routing protocol where I initially took part in the implementation phase and later focused on verification and validation. I also supervised a project where this implementation was ported to the ns-2 simulator. Paper D: I participated in discussions, conducted experiments, performed analysis, and co-authored a large part of the paper. Paper E: I participated in all discussions and co-authored the whole paper. Paper F: I am the sole author of this paper. I designed and executed the experiments, and performed the analysis. Other work In addition to the papers A through F, I have also authored, co-authored and in some cases presented the following papers, posters and demos. 1. H. Lundgren, Audio Streaming in a Wireless Active Network, Demo at SAN-day Stockholm Active Networks Day (held in conjunction with ACM SIGCOMM 2000), Aug H. Lundgren, D. Lundberg, J. Nielsen, E. Nordström, C. Tschudin, A Large-scale Testbed for Reproducible Ad hoc Protocol Evaluations, Technical Report , IT Department, Uppsala University, Nov H. Lundgren, E. Nordström, C. Tschudin, Coping with Communication Gray Zones in IEEE b based Ad hoc Networks, Technical Report , IT Department, Uppsala University, Jun H. Lundgren, E. Nordström, C. Tschudin, The Gray Zone Problem in IEEE b based Ad hoc Networks, Mobile Computing and Communication Review (MC2R), Jul H. Lundgren, Implementation and Real-world Evaluation of Routing Protocols for Wireless Ad hoc Networks, Licentiate Thesis, Dec viii 6. C. Tschudin, H. Lundgren, E. Nordström, Embedding MANETs in the Real World, 8th IFIP International Conference on Personal Wireless Communications (PWC 03), Sept H. Lundgren, E. Nordström, R. Gold, M. Wiggberg, DIMA: Distributed Instant Messaging System, Poster at the 1st Swedish National Computer Networking Workshop (SNCNW), Sept C. Rohner, E. Nordström, H. Lundgren, O. Rensfelt, Using Ad Hoc Networking in Orienteering, Demo at The 10th Annual International Conference on Mobile Computing and Networking (MobiCom 2004), Sept ix Contents 1 Introduction Ad hoc Networks Ad hoc Routing Protocols Research Problems Addressed in This Thesis Contributions Research Method Challenges in Ad hoc Networking Evaluation of Ad hoc Routing Protocols Metrics for Protocol Evaluation Evaluation Techniques Simulation Emulation Trace-based Simulation and Emulation Real world Experimentation Testbeds and Experiments Emulators Real world Testbeds Summary Summary of Papers Paper A: Active Routing for Ad-hoc Networks Paper B: A Large-scale Testbed for Reproducible Ad hoc Protocol Evaluations Paper C: Coping with Communication Gray Zones in IEEE b based Ad hoc Networks Paper D: Lessons from Experimental MANET Research Paper E: A Testbed and Methodology for Experimental Evaluation of Wireless Mobile Ad hoc Networks Paper F: Experimental Evaluation of Three Ad hoc Routing Protocols Conclusions Summary in Swedish References xi 1 Introduction During the past decades wireless communication has increased tremendously. Wireless communication for personal use is, and will continue to be, part of our everyday life. The reason for its success is simple: it enables mobility during communication. The most common form of wireless communication today is the use of cellular phones (more commonly called mobile phones ). In recent years, the development of standards for wireless packet networks, such as wireless local area network (Wireless LAN), has resulted in that manufacturers equip everything, from powerful laptops to small embedded devices, with hardware support for different radio technologies. This has increased the popularity of wireless packet networks both in industry and in home networking. Both the mobile telephony network and Wireless LANs are examples of so called infrastructure-based wireless networks. This means that there has to be a pre-existing network infrastructure for these networks to be functioning. Such network infrastructures typically consist of fixed positioned base stations or access points with wire-lines connecting them to a backbone network. The wireless nodes in these networks do not talk directly to each other. Instead, each node is connected to a base station through which it communicates with other nodes. Infrastructure-less wireless networks are usually called multi-hop wireless mobile ad hoc networks. In the rest of this thesis we will use the term ad hoc network. Ad hoc often means improvised, or for the needs of the moment. In computer networking, we think of an ad hoc network as a wireless network without any pre-existing infrastructure. Such networks have no base stations, access points, or wire-line backbone network. Instead, the nodes themselves constitute the network and communicate directly with each other. Most work within ad hoc networking, as well as the work in this thesis, use (or assume) the wireless LAN standards of IEEE [Com97, Com99] as the underlying technology. 1 The wireless LAN radio modems normally operate in infrastructure mode, but can be set to operate in infrastructure-less, or so called ad hoc, mode. 1 Thesis Organization In the remainder of this chapter we will first introduce ad hoc networking and ad hoc routing. Thereafter, we describe the research problems addressed in this thesis and list this thesis contributions. Finally, we discuss the research method applied. The rest of the thesis is organized as follows. Chapter 2 provides a broader view of research challenges for ad hoc networking, identifying and briefly discussing the main issues. Chapter 3 discusses evaluation techniques for ad hoc routing protocols and provides an overview of related work in the area of experimental ad hoc networking testbeds. The included papers are summarized and discussed in Chapter 4, followed by conclusions and outlook in Chapter 5. A brief Swedish summary of this thesis appears in Chapter 6, before the reprints of the papers included in this thesis. 1.1 Ad hoc Networks An ad hoc network consists of a number of nodes with wireless communication capabilities, which potentially move around in an unpredictable way and cause the network topology 2 to change frequently. The ad hoc nodes can be of varying type, ranging from embedded systems like sensors, to powerful computers inside vehicles. The nodes can be scattered so that all nodes are not within radio range of each other. As per definition there is no available infrastructure, the nodes must rely on each other to relay the data packets in a multi-hop situation. This requires that the nodes themselves act as routers (compare with a typical wired LAN where a few dedicated nodes in the wireline backbone act as routers and forward traffic between different network segments). This means that each node need to run software that implements some kind of distributed routing algorithm. The routing algorithm must be capable of establishing and maintaining routes over multiple hops, even in the face of high degree of node mobility and frequent connectivity changes. Figure 1.1 illustrates the two types of networks; (a) with an infrastructure where traffic between two clusters (A,B,C and D,E,F) is forwarded and transported with the help of base stations and pre-installed wires. Figure 1.1 (b) illustrates an infrastructure-less ad hoc network where nodes themselves forward traffic. An ad hoc network often works autonomously and in isolation from other networks. However, it might also very well be connected to other networks, e.g., the Internet, via a gateway. 2 Network topology is how the nodes in the network are arranged with respect to connectivity, i.e., who is connected to whom. 2 A network with wireless infrastructure: transmission range of base station wireless nodes E A C D base station B F base station wireline (a) A wireless ad hoc network: transmission range of ad hoc node E A C D F B (b) Figure 1.1: In figure (a) the mobile nodes communicate via a managed infrastructure. In figure (b) the nodes form an ad hoc network by themselves. Ad hoc Network Usage Scenarios Although the use of ad hoc networks at the time of this writing is conspicuous by its absence, there are many envisaged usage scenarios. The original motivation for ad hoc networks was the military need for a wireless packet network that had battlefield survivability, could operate without pre-placed infrastructure, and could extend their connectivity beyond line-of-sight [FL01]. The emergency/rescue scenario is a commonly referenced usage scenario. This scenario assumes a disaster area where the pre-existing communication infrastructures have been eliminated due to e.g., an earthquake or a terrorist attack. In such disasters emergency personnel need to quickly establish communication between rescue teams as well as to people in distress. Other scenarios include spontaneous meetings, where people meet and want to interact electronically, e.g., at conferences. Another possible scenario is the extension of the radio coverage of a wireless LAN base station by letting one node relay 3 traffic between the base station and nodes outside the coverage. Yet another scenario consists of pre-placed ad hoc nodes forming a multi-hop network. This allows the ad hoc nodes to set up a community network, and to share Internet access among the ad hoc nodes. For example, MIT s roof-top 3 network [Cha02] consists of about 40 stationary ad hoc nodes distributed over the MIT campus area. By using ad hoc network technology there is no need for base station planning and in principle anyone can set up a node and it will establish itself within the network. 1.2 Ad hoc Routing Protocols It is the task of the routing protocol to create and maintain routes to other nodes. These routes should be loop-free and as reliable and durable as possible. A routing protocol uses a distributed algorithm to acquire and maintain route information. Conventional routing protocols used in wired networks were not designed with the specific requirements of ad hoc routing protocols in mind, and unfortunately do not work satisfactorily in ad hoc networks. The key problem with both RIP [Mal98] and OSPF [Moy98] is their slow convergence to a consistent topological view of the network. For example, when the network topology changes, new information has to be propagated through the whole network before it can be considered to be in a correct state. In RIP, each router must recompute its distance vector before it can pass on the new route information. Furthermore, RIP suffers from the count-to-infinity problem [Per00]. Both these issues have a severe negative effect on the convergence time. In OSPF, although link-state information can be disseminated before route recomputation, the propagation of this information slows down convergence. In addition, considering the limited resources of an ad hoc network, both these protocols generate a lot of redundant information that consumes bandwidth in a unnecessary way. In a wireless network bandwidth is more expensive and transmission is minimized since it drains the battery power. Routing Strategies for Ad hoc Networks Ad hoc routing protocols are commonly classified into proactive, reactive and hybrid, based on how they update routing information. The concept of proactive routing means that all nodes (i.e., routers) exchange route information periodically, or whenever the network topology changes, in order to maintain a consistent, complete and up-to-date view of the network at all nodes. Each 3 Each ad hoc node has connected its wireless network interface to an antenna placed on top of the roof. 4 node uses the exchanged route information to calculate the costs (e.g., number of hops) to reach all possible destinations. Optimized Link State Routing (OLSR) [JMC + 01, JC03] and Topology Broadcast Reverse Path Forwarding (TBRPF) [OTL04] are two examples of proactive routing protocols. Reactive routing is generally not dependent on exchanges of periodic route information and route calculations. Instead, whenever a route is needed the source node has to perform a route discovery (disseminate a route request throughout the network and wait for a route reply) before it can send any packets to the destination. The route is thereafter maintained until the destination becomes inaccessible or the route is no longer needed. Examples of reactive protocols are Ad hoc On-demand Distance-Vector (AODV) [PR99, PBRD03] and Dynamic Source Routing (DSR) [JMB00, JMH04]. Hybrid approaches combines the proactive and reactive approaches, for example, the Zone Routing Protocol (ZRP) [PH99] and LUNAR [TGRW04]. Ad hoc routing protocol classifications can be found in e.g., [MM04, AWD04, Fee99, RT99, RS96]. 1.3 Research Problems Addressed in This Thesis The theme of this thesis is experimental evaluation of ad hoc routing protocols. In this thesis we often use the term real world for this experimental approach of protocol evaluation. Our goal is to assess ad hoc routing protocols strength and weaknesses through real world routing protocol evaluations. In contrast to simulations, experimental studies need to handle inherent stochastic factors like the radio environment and node mobility. Simulation is a valuable tool for evaluating ad hoc routing protocols. Simulations are easily repeatable, which makes comparison of different routing protocols straightforward. Furthermore, they facilitate evaluation of routing protocols in different networking contexts by varying parameters like test area size, number of nodes, mobility pattern and data traffic pattern. However, simulation is based on (simplified) models of reality. The problem is that simulations can not capture the effects of the inaccuracies of their own models. Therefore, we believe that it is important to complement simulation studies with experimental studies. Conclusive comparisons and parameter explorations are possible only if repeatability of measurements is addressed. Therefore, the main problem for real world evaluations is: How can we make real world ad hoc routing experiments repeatable? Our approach was to design and build a testbed that can handle and assess repeatability. A related problem concerns test-run execution and how to orchestrate experiments with severeal dozens human participants. Complex testbed handling, such as installation, configuration and execution can 5 negatively affect test-run management and scalability, and easily introduce systematic errors between test-runs. Our next problem addressed is: How can we design and build a test environment such that it supports easy manageable and scalable real world testing of ad hoc routing protocols? Given that we can accurately repeat real world test-runs, it becomes interesting to compare our findings with simulation results. Our final problem addressed is: How can we identify and capture
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