Nov. 29, 2006GLOBECOM /17 A Location-based Directional Route Discovery (LDRD) Protocol in Mobile Ad-hoc Networks Stephen S. Yau, Wei Gao, and Dazhi Huang Dept. of Computer Science and Engineering Arizona State University

Nov. 29, 2006 GLOBECOM /17 Outline Introduction Overview of our approach Three components of our approach  Node Location Service based on Local Coordinates  Directional Route Request  Refinement on Intermediate Nodes Simulation Results Conclusions and Future Work

Nov. 29, 2006 GLOBECOM /17 Introduction Topology-based route discovery protocols (AODV [3], DSR [4]) flood route requests, and hence cause  Large route redundancy  Large overhead of route discovery Challenge: How to reduce route redundancy and overhead of route discovery? Some extra network information must be added to help  Physical Locations of Nodes: Global/Localized

Nov. 29, 2006 GLOBECOM /17 Introduction (cont.) Purpose: to restrict the influencing range of route requests  Greedy packet forwarding (GPSR [7], TBF [8])  Restricted directional flooding (DREAM [9], LAR [10]) A prerequisite of location-based route discovery protocols is a node location service  Use GPS receivers  GPS-free localization: RSSI [12], ToA/TDoA [13]

Nov. 29, 2006 GLOBECOM /17 Location-based Directional Route Discovery (LDRD) LDRD consists of three components:  A Node Location Service based on Local Coordinates (NLS-LC)  An algorithm used by the route requesters to generate directional route requests A directional route request can only be processed and forwarded in allowed geographical areas Its influencing range is only part of the entire network  An algorithm used by intermediate nodes to refine the directional route request to progressively reduce its influencing range

Nov. 29, 2006 GLOBECOM /17 Major Advantages of Our Approach LDRD greatly reduces the route redundancy and overhead of route discovery by using and progressively refining directional route requests LDRD exploits a GPS-free node location service LDRD is insensitive to the accuracy of node locations

Nov. 29, 2006 GLOBECOM /17 Node Location Service based on Local Coordinates (NLS-LC) Each node updates the locations of its neighbors periodically using physical measurements Each node broadcasts updated location information to its neighbors. Each node maintains a location table  All the node coordinates are localized, i.e., are relative to the local coordinate system of table owner  The location record of a node: origintime indicates the generation time of the localized coordinates elapsetime is the elapsed time since origintime

Nov. 29, 2006 GLOBECOM /17 Node Location Service based on Local Coordinates (NLS-LC) (cont.) An example:  We consider the following fragment of network topology A ↔ B ↔ C  B gets location of A by physical measurement at time t 1, and broadcasts this information to C at t 2  C receives the information at time t 3  Records of A in B’s and C’s location tables:

Nov. 29, 2006 GLOBECOM /17 Directional Route Request The direction of forwarding a route request is determined by a destination area DST, and a respondable area RESP.  DST: R = (d max + elapsetime)  V max DST: ( x – x d ) 2 + ( y – y d ) 2 = R 2  RESP:  = 4x d 2 y d 2 – 4(x d 2 – R 2 ) (y d 2 – R 2 )

Nov. 29, 2006 GLOBECOM /17 Directional Route Request (cont.) LDRD is insensitive to the accuracy of node locations   The probability of missing the route destination is

Nov. 29, 2006 GLOBECOM /17 Refinement on Intermediate Nodes The intermediate node refines the route request according to its location information of the route destination The intermediate node nearer to the route destination has more accurate location information of the route destination Every receiver checks whether it is within the defined DST or RESP

Nov. 29, 2006 GLOBECOM /17 Tradeoff on Frequency of Location Updates The frequency of sending location updates needs to be selected carefully:  Too large: LDRD is as bad as flooding-based approaches  Too small: The allowed areas are too narrow to contain a qualified forwarder  Decision making: user’s performance requirements

Nov. 29, 2006 GLOBECOM /17 Simulation Settings 50 nodes are randomly distributed in a 1000m 2 square area with MAC Mobility settings:  V avg : 2m/s – 10m/s Network connectivity settings:  Transmission range: 150m - 400m Network traffic settings:  Number of CBR traffic flows: 1 – 5 Frequency of Location Updates  SIZE/10/V avg

Nov. 29, 2006 GLOBECOM /17 Simulation Results LDRD can greatly reduce the route redundancy and overhead of route discovery

Nov. 29, 2006 GLOBECOM /17 Simulation Results (cont.) LDRD can maintain performance of route discovery without great degradation

Nov. 29, 2006 GLOBECOM /17 Conclusions and Future Work LDRD greatly reduces the route redundancy and overhead of route discovery. LDRD is highly adaptable to the dynamic nature of MANETs  It exploits a GPS-free node location service  It is insensitive to the accuracy of node locations Future work:  Analyze the impact of location errors and the parameters used in NLS-LC  Incorporate service discovery functionality with route discovery to achieve better efficiency

Nov. 29, 2006 GLOBECOM /17 Thanks!