A Topology Aware Routing Algorithm for Mobile Ad-hoc Networks 2017-11-17¢  network topology information

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  • A Topology Aware

    Routing Algorithm for

    Mobile Ad-hoc Networks

    Tyng Wey, Leong

    This report is submitted as partial fulfilment of the requirements for the Honours Programme of the School of Computer Science and Software Engineering,

    The University of Western Australia, 2005

  • Abstract

    A mobile ad-hoc network (MANET) is a collection of wireless mobile hosts form- ing a temporary network without any centralised administration or standard sup- port services. In the MANET, cooperation between nodes is required to route multi-hop messages from the source to destination due to the limited transmission range of each node.

    Traditional routing protocols such as DSDV, AODV, DSR and TORA do not consider sufficient topology information in their routing decision, thus they are slow to react to drastic topology changes. We explore some methods of obtaining network topology information and propose that a topology aware routing protocol will have better performance as it will be able to adapt to the changes caused by node mobility.

    Based on the belief that a more stable route will outlast its more dynamic counterparts, we propose a new metric, the Route Stability Metric (RSM), to be used for route selection in routing protocols. RSM measures the rate at which a route changes based on the relative distances and speeds of node pairs in the route without the use of the Global Positioning System (GPS) or other specialised hardware. We implement the new metric in DSR-RSM and compare its performance with DSR under the cnet simulation environment. Simulation results demonstrate that including topology information into the routing decision improves throughput, reduces overheads and route failures in dynamic mobile networks.

    Keywords: MANET, protocol, topology, metric CR Categories: C.2.1, C.2.2

    ii

  • Acknowledgements

    It has been a long four years since I came to Western Australia from Singapore in July 2001 to pursue a degree in Computer Science at UWA. This last one year has been especially enriching and rewarding for me during my honours research and it would not be possible without the love and support of many people.

    I am fortunate to be supervised in my project by Dr Chris McDonald. His guidance and support kept me on my toes throughout the year and allowed me to complete my project on the cnet network simulator. He also devoted his precious time to read through and correct my many drafts and reports.

    Help also came from Amer Filipovic, an outstanding researcher and cnet ex- pert, who was willing to help me understand much of his DSR code on which my project was based on. He was always eager to share and willing to help in whatever way he could, even on those Sunday afternoons.

    Much care and support during this hectic period came from my girlfriend and soul mate Jocelyn who was always there for me when the stress builds up. She’s always there with a smile to cheer me up. Her love kept me going when the going gets tough.

    Huichoo and Celina made sure that I always have a hot dinner waiting when I come back late on Monday evenings after meeting with Dr Chris. Their friendship provided me with the warmth and energy to work on my project throughout the chilly winter.

    Finally there was Skippy, my adorable chihuahua, who never fails to lift my spirit with her love and affection. All those long nights in front of the computer, she was always there on my lap.

    I am forever grateful and indebted to all of you.

    iii

  • Contents

    Abstract ii

    Acknowledgements iii

    1 Introduction 1

    2 The DSR Routing Protocol 4

    2.1 DSR Route Discovery . . . . . . . . . . . . . . . . . . . . . . . . . 4

    2.2 DSR Route Maintenance . . . . . . . . . . . . . . . . . . . . . . . 6

    3 Basic 802.11 MAC Layer Operations 7

    3.1 Hidden and Exposed Node Problems . . . . . . . . . . . . . . . . 7

    3.2 Medium Access Basics . . . . . . . . . . . . . . . . . . . . . . . . 8

    3.3 Medium Contention in DCF Mode . . . . . . . . . . . . . . . . . 8

    3.3.1 Back Off Mechanism . . . . . . . . . . . . . . . . . . . . . 9

    3.4 Positive Acknowledgement . . . . . . . . . . . . . . . . . . . . . . 10

    4 Range, Position and Orientation in Ad-hoc Networks 11

    4.1 Ranging and Localisation Methods . . . . . . . . . . . . . . . . . 11

    4.1.1 Received Signal Strength Estimation . . . . . . . . . . . . 11

    4.1.2 Time Difference of Arrival(TDOA) . . . . . . . . . . . . . 13

    4.1.3 Triangulation and Trilateration . . . . . . . . . . . . . . . 14

    5 Related Work 17

    5.1 Topology Information in Routing . . . . . . . . . . . . . . . . . . 17

    5.2 Topology Information as A Route Selection Metric . . . . . . . . . 18

    5.3 Topology Information for Faster Route Repairs . . . . . . . . . . 19

    5.4 Our Approach and Hypothesis . . . . . . . . . . . . . . . . . . . . 19

    iv

  • 6 Route Stability Metric 21

    6.1 Free Space Loss (FSL) model . . . . . . . . . . . . . . . . . . . . 21

    6.2 Relative Speed Between Adjacent Nodes . . . . . . . . . . . . . . 22

    6.3 Measuring Link and Route Stability . . . . . . . . . . . . . . . . . 22

    7 Implementation of RSM 25

    7.1 Implementation of RSM in DSR . . . . . . . . . . . . . . . . . . . 25

    7.2 DSR Modifications . . . . . . . . . . . . . . . . . . . . . . . . . . 25

    7.3 802.11 MAC Layer Modifications . . . . . . . . . . . . . . . . . . 27

    8 Methodology 28

    8.1 Simulation Environment . . . . . . . . . . . . . . . . . . . . . . . 28

    8.2 Test Cases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

    8.2.1 Mobility . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

    8.2.2 Traffic Load . . . . . . . . . . . . . . . . . . . . . . . . . . 30

    8.3 Wireless LAN link Characteristics . . . . . . . . . . . . . . . . . . 31

    8.4 Signal Propagation Model . . . . . . . . . . . . . . . . . . . . . . 31

    8.5 MAC layer and Routing Protocol Setup . . . . . . . . . . . . . . . 32

    9 DSR-RSM Performance Analysis 34

    9.1 Protocol Verification . . . . . . . . . . . . . . . . . . . . . . . . . 34

    9.2 Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

    9.3 Routing Overhead . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

    9.4 Route Failure Rate . . . . . . . . . . . . . . . . . . . . . . . . . . 41

    10 Discussion & Conclusions 45

    A Original Honours Proposal 47

    A.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

    A.2 Aim . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

    A.3 Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

    A.4 Software and Hardware Requirements . . . . . . . . . . . . . . . . 50

    v

  • B DSR packet formats 51

    C Basic IEEE 802.11 Frame formats 52

    D Example of a cnet topology file 54

    E Example of a cnet statistics file 55

    vi

  • List of Tables

    8.1 Default characteristics of cnet WLAN links . . . . . . . . . . . . . 32

    8.2 802.11 MAC layer configuration used in the simulations. . . . . . 33

    8.3 DSR-RSM setup used in the simulations. . . . . . . . . . . . . . . 33

    vii

  • List of Figures

    1.1 A simple ad-hoc network diagram. . . . . . . . . . . . . . . . . . . 2

    2.1 DSR route discovery diagram. . . . . . . . . . . . . . . . . . . . . 5

    2.2 DSR route error message diagram. . . . . . . . . . . . . . . . . . . 6

    3.1 802.11 Hidden node diagram. . . . . . . . . . . . . . . . . . . . . 8

    3.2 NAV diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

    3.3 802.11 Exponential backoff. . . . . . . . . . . . . . . . . . . . . . 10

    4.1 RSSI ranging diagram. . . . . . . . . . . . . . . . . . . . . . . . . 12

    4.2 Simple TDOA diagram. . . . . . . . . . . . . . . . . . . . . . . . 13

    4.3 Triangulation diagram. . . . . . . . . . . . . . . . . . . . . . . . . 15

    4.4 Trilateration diagram. . . . . . . . . . . . . . . . . . . . . . . . . 16

    6.1 Distance and speed resolution diagram. . . . . . . . . . . . . . . . 23

    8.1 Cnet simulation screenshot. . . . . . . . . . . . . . . . . . . . . . 29

    9.1 Results from a static network simulation. . . . . . . . . . . . . . . 35

    9.2 Packet Delivered Ratio Comparison. . . . . . . . . . . . . . . . . . 36

    9.3 Combined Packet Delivered Percentage Comparison. . . . . . . . . 37

    9.4 Routing Overhead Comparison. . . . . . . . . . . . . . . . . . . . 39

    9.5 Combined Routing Overhead Comparison. . . . . . . . . . . . . . 40

    9.6 Route Error Comparison. . . . . . . . . . . . . . . . . . . . . . . . 42

    9.7 Combined Route Error Comparison. . . . . . . . . . . . . . . . . . 43

    B.1 DSR packet format. . . . . . . . . . . . . . . . . . . . . . . . . . . 51

    C.1 General 802.11 MAC frame format. . . . . . . . . . . . . . . . . . 52

    C.2 RTS frame format. . . . . . . . . . . . . . . . . . . . . . . . . . . 52

    viii

  • C.3 CTS frame format. . . . . . . . . . . . . . . . . . . . . . . . . . . 52

    C.4 DATA frame format. . . . . . . . . . . . . . . . . . . . . . . . . . 53

    C.5 ACK frame format. . . . . . . . . . . . . . . . . . . . . . . . . . . 53

    D.1 Cnet topology file format. . . . . . . . . . . . . . . . . . . . . . . 54

    E.1 Example Cnet output statistics file. . . . . . . . . . . . . . .