Multipath Routing with Load Balancing in Wireless Ad Hoc ... maguire/DEGREE-PROJECT-REPORTS/050315...Multipath Routing with Load Balancing ... thanks to our multipath routing algorithm

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  • Master of Science ThesisStockholm, Sweden 2005

    IMIT/LCN 2005-03

    R O M A I N G R O L E A U

    Multipath Routing with Load Balancingin Wireless Ad Hoc Networks

  • Multipath Routing with Load Balancing in Wireless Ad Hoc Networks

    Master's Thesis Project

    March 2005

    Romain Groleau

    Massachusetts Institute of Technology, MIT Computer Science and Artificial Intelligence Laboratory

    Advisor: Dina Katabi

    Royal Institute of Technology, KTH

    School of Information and Communication Technology

    Advisor: Gerald Q. Maguire Jr.

  • Abstract

    In recent years, routing research concerning wired networks has focused on minimizing the maximum utilization of the links which is equivalent to reducing the number of bottlenecks while supporting the same traffic demands. This can be achieved using multipath routing with load balancing instead of single path routing using of routing optimizers. However, in the domain of ad hoc networks multipath routing has not been investigated in depth. We would like to develop an analogy between wired and wireless networks, but before that we need to identify the major differences between these two in the case of multipath routing. First, in order to increase the network throughput, the multiple paths have to be independent so they don't share the same bottlenecks. Then, due to radio propagation properties the link capacity is not constant. So using the maximum utilization metric for wireless networks is not suitable. Based on the research done in wired networks, which has shown that using multiple paths with load balancing policies between source-destination pairs can minimize the maximum utilization of the links, we investigate if this is applicable to ad hoc networks. This paper proposes a multipath routing algorithm with a load balancing policy. The results obtained from an indoor 802.11g network highlight two major points. The maximum throughput is not achieved with multipath routing, but with single path routing. However, the results on the delivery ratio are encouraging, indeed we observe a real improvement thanks to our multipath routing algorithm.

  • Sammanfattning

    P senare r har routning forskningen angende trdntverken focusen p att minska den maximala anvndingen av lnkar vilket motsvarar n reducering av flaskhalsar medan man stder samma trafikkrav. Det hr kan stadkommas genom att av multivg routning med lasta balansering I stllet fr anvnder enkelvgrouting med routing optimizers. Emellertid har inom ad hoc ntverken multivg routning har inte blivit underskts p djupet. Vi skulle vilja utveckla en analogy emellan trdntverk och trdlsntverken.men frmfre det behver identifiera de store differenserna mellan dessa tv vid multivg routning. Fr det frsta mste de flerfaldiga vgarna vara oberoende fr att ka ntverkens throughput s de inte delar samma flaskhalsar. Sedan r lnkkapaciteten inte constant p grund av radiospridningsegenskaperna. S den maximal anvndningsmetric fr trdls ntverken passar inte.

    Den hr arbetetet freslr en multivg routning algoritm med lasta balanseringen. Resultaten f frn en indoor 802.11g ntverk framhller ger tv store meningen. Den maximala throughput r inte stadkoms med multivg routing, men med enkelvg routning. Emellertid r resultaten p den leveransfrhllande uppmuntrande; vi observera en verklig frbttring tack vare vr multivg routning algoritmen.

  • Acknowledgements

    This masters thesis is my final work for the Master of Science in Computer Science at the Royal Institute of Technology (KTH) in Stockholm. It was performed at the Massachusetts Institute of Technology (MIT) in Cambridge, USA under the supervision of Dina Katabi. I would like to thank her for her help and assistance during the entire work. I also would like to express my appreciation to John Bicket, Sanjit Biswas, and Srikanth Kandula for valuable information and fruitful discussions. Finally, I would like to acknowledge Professor Gerald Q. Maguire for his support and for being my examinator at KTH. I would like to express also my gratitude to the following people for their support, assistance, and cooperation during my masters thesis project.

    My labmates at MIT Sachin Katti and Shan Sinha for their help and the good environment in the office. Michel Gorazko for his availability and technical support.

    My mother Danielle, my father Frederic, and my brother William who have been very supportive throughout my education.

    My two opponents for their valuable remarks and advices: Vincent Hag and Mina Sagha Zadeh.

    All my friends in Sweden, in the USA, and in France for their good mood and their support: Abdennour, Yoann, Paola, Graham, Jason, Tony, Renaud, Thomas, Fabien, Yannick, Frederic, David, Jonathan, David, Timo, Xavier, Boris, Hilary.

    And anybody I missed who deserves to be mentioned.

  • Table of Contents

    1 INTRODUCTION 1

    1.1 PROBLEM 1 1.2 EXPERIMENTAL ENVIRONMENT 4 1.2.1 MIT ROOFNET 4 1.2.2 HARDWARE 5 1.2.3 SOFTWARE 6 1.2.4 ROUTING 6 1.2.5 PERFORMANCE 6 1.2.5.1 Throughput 6 1.2.5.2 Range and Density issues 8 1.2.5.3 Architectural alternatives 8 1.2.5.4 Collisions 9 1.2.5.5 Loss pattern 10 1.2.5.5.1 Spatial distribution 10 1.2.5.5.2 Time variation of loss rate 10

    1.3 SCOPE 10

    2 BACKGROUND 11

    2.1 WIRELESS AD HOC NETWORKS 11 2.1.1 WIRELESS LAYERS MODEL 11 2.1.1.1 Physical Layer 11 2.1.1.2 Data-Link layer 13 2.1.1.2.1 Media Access Control layer (MAC) 13 2.1.1.2.2 Logical Link Control layer (LLC) 14

    2.2 IEEE 802.11B AND IEEE 802.11G 15 2.2 IEEE 802.11B AND IEEE 802.11G 15 2.2.1 STANDARDS 16 2.2.1.1 CCK 17 2.2.1.2 OFDM 17 2.2.2 COMPATIBILITY BETWEEN 802.11B AND 802.11G 19 2.2.3 THROUGHPUT AND COVERAGE AREA ISSUES 20

    2.3 WIRELESS ROUTING 21 2.3.1 THE PATH METRIC 21

  • 2.3.2 WIRELESS UNIPATH ROUTING PROTOCOLS 22 2.3.2.1 DSDV 23 2.3.2.2 AODV 23 2.3.2.3 DSR 24 2.3.2.4 RNR 24 2.3.3 WIRELESS MULTIPATH ROUTING PROTOCOLS 25

    2.4 WIRELESS MULTIPATH ROUTING 26 2.4.1 DISJOINT PATHS 26 2.4.1.1 Interference free paths 26 2.4.1.2 Other approaches 28 2.4.2 ROUTING PROTOCOLS 28 2.4.2.1 First approaches 28 2.4.2.2 Multipath routing with alternate paths 29 2.4.2.2.1 MDSR 29 2.4.2.2.2 AOMDV 29 2.4.2.3 Multipath routing with Load Balancing 29 2.4.2.3.1 SMR 30 2.4.2.3.2 MRP-LB 31 2.4.2.3.3 Single Path vs. Multiple Paths 33 2.4.3 TRANSPORT LAYER ISSUES 34

    3 METHOD 35

    4 ANALYSIS 36

    4.1 THE LINK LEVEL MEASUREMENTS 36 4.1.1 TESTBED 36 4.1.2 RESULTS 38 4.1.2.1 Loss rate 38 4.1.2.2 Capture Effect 41 4.1.2.3 Throughput considerations 41 4.1.2.4 Conclusion 41

    4.2 EVALUATION OF M-RNR 42 4.2.1 THE PROTOCOL M-RNR 42 4.2.1.1 Route Discovery 42 4.2.1.1.1 Path Metric 42 4.2.1.1.2 Gateway Route Discovery 43 4.2.1.1.3 RNR Packet format 43 4.2.1.2 Data Transmission 45 4.2.1.2.1 General Description 45 4.2.1.2.2 GETT 45

  • 4.2.1.2.3 The Gateway Table 46 4.2.1.2.4 The load balancing algorithm 47 4.2.1.2.5 At the gateways 48 4.2.1.3 Route Maintenance 48 4.2.2 M-RNR IN THE INDOOR NETWORK 49 4.2.2.1 The Indoor network 49 4.2.2.2 Experiment description 51 4.2.2.3 Results 54 4.2.2.4 Interpretations 56

    5 CONCLUSIONS 58

    5.1 CONCLUSION 58 5.2 FUTURE WORK 58

  • Table of Figures

    FIGURE 1: WIRELESS ROOFTOP NETWORK NODE SENDING TRAFFIC ......................1 FIGURE 2: ROOFNET CONNECTIVITY MAP.............................................................4 FIGURE 3: AVERAGE TCP THROUGHPUT BETWEEN EACH PAIR IN THE NETWORK. .7 FIGURE 4: AVERAGE TCP THROUGHPUT TO EACH NODE FROM ITS GATEWAY. ......7 FIGURE 5: COMPARISON OF MESH AND ACCESS-POINT ARCHITECTURES................8 FIGURE 6: TCP THROUGHPUTS WITH AND WITHOUT RTS/CTS.............................9 FIGURE 7: 802.11B DATA RATE SPECIFICATIONS .................................................15 FIGURE 8: 802.11G SPECIFICATIONS [47] ............................................................16 FIGURE 9: EFFECT OF MULTIPATH ON CCK [48] ..................................................17 FIGURE 10: EFFECT OF MULTIPATH ON OFDM [48] ............................................18 FIGURE 11: OFDM SYMBOL CONTAINS A GUARD INTERVAL [48]......................18 FIGURE 12: FREQUENCY REPRESENTATION OF THE SUBCARRIERS [48]................19 FIGURE 13A: CONVENTIONAL 802.11B PACKET EXCHANGE ...............................19 FIGURE 13B: 802.11G PACKET EXCHANGE WITH RTS-CTS................................19 FIGURE 13C: 802.11G OFDM PACKET EXCHANGE WITHOUT RTS-CTS.............20 FIGURE 14: LP FORMULATION TO OPTIMIZE THE THROUGHPUT...........................27 FIGURE 15: SPATIAL CONFIGURATION OF THE NODES..........................................37 FIGURE 16: RESULTS FROM THE 802.11 BROADCAST ..........................................38 FIGURE 17: AVERAGE RSSI READINGS FROM THE CARD. ....................................39 FIGURE 18: THROUGHPUT AT A IN THE DUAL SENDER EXPERIMENT. ...................39 FIGURE 19: THROUGHPUT AT A WHEN B IS SENDING. .........................................40 FIGURE 20: THROUGHPUT AT A WHEN C IS SENDING. .........................................40 FIGURE 21: M-RNR HEADER ..............................................................................44 FIGURE 22: TCP/UDP FLOW TABLE ...................................................................46 FIGURE 23: 9TH FLOOR INDOOR NETWORK. ..........................................................49 FIGURE 24: INDOOR NETWORK NODE ..................................................................50 FIGURE 25A: MAP WITH THE NODES USED FOR THE EXPERIMENT. .......................51 FIGURE 25B: MAP WITH THE NODES USED FOR THE EXPERIMENT. .......................52 FIGURE 26: PARAMETERS FOR THE UDP MEASUREMENTS. .................................53 FIGURE 27: RESULTS FROM THE UDP THROUGHPUT EXPERIMENTS ....................