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A Review of Geocasting Protocolsfor a Mobile Ad Hoc Network 指導教授：許子衡 教授 報告學生：馬敏修
Outline • Introduction • Geocast routing protocols • 2.1Data-TransmissionOriented • 2.1.1 Location Based Multicast (LBM) • 2.1.2 Voronoi diagram based geocasting • 2.1.3 GeoGRID • 2.2 Routing-CreationOriented • 2.2.1 GeoTORA • 2.2.2 Mesh-basedGeocast Routing Protocol • Conclusions
Introduction • A node inthe geocast region receives ageocast packet, it will flood the geocastpacket to all its neighbors. • Classify the five existing geocast protocols intotwo categories: Data-transmission oriented protocols and routing-creationoriented protocols.
Data-TransmissionOriented(1/9) Location Based Multicast (LBM) GOAL of Protocol: LBM is to decrease deliveryoverhead of geocast packets, by reducing the forwarding space forgeocast packets, while maintaining accuracy of data delivery. Protocol Details: LBM is essentially identical to flooding data packets,with the modification that a node determines whether to forward ageocast packet further via one of two schemes.
Data-TransmissionOriented(2/9) LBM Scheme 1: When a node receives a geocast packet, itwill forwardthe packet to its neighbors if it is within a forwarding zone;otherwise, it will discard the packet.
Data-TransmissionOriented(3/9) LBM Scheme 2:A geocast packetshould be forwarded is based on the position of the sender node atthe transmission of the packet and the position of the geocast region.
Data-TransmissionOriented(4/9) Voronoi diagram based geocasting GOAL of Protocol: The goal of the Voronoi diagram based geocastingprotocol is to increase the success rate and decrease the hopcount and flooding rate of LBM.
Data-TransmissionOriented(6/9) GeoGRID GOAL of Protocol:GeoGRID uses location information, which defines the forwardingzone, and elects a special host (i.e, gateway) in each grid arearesponsible for forwarding the geocast packets. Protocol Details:Instead of every node in a forwardingzonetransmitting data, only gateway nodes take this responsibility.
Data-TransmissionOriented(7/9) • There are two suggestions on how to send geocast packetsby GeoGRID: Flooding-Based GeoGRID and Ticket-Based GeoGRID. • Flooding-Based GeoGRID：Only gateways in every grid withinthe forwarding zone will rebroadcast the received geocast packets. • Ticket-Based GeoGRID：The geocast packets are still forwardedby gateway nodes, but not all the gateways in the forwarding zonewill forward each geocast packet.
Data-TransmissionOriented(9/9) Gateway Election:The mobilehost nearest to the physical center of a grid is elected. Oncethis node is elected, it remains the gateway until it moves out of thegrid. • One problem of this selection process is when another potentialgateway roams closer to the physical center of the grid than the currentlyassigned gateway.
Routing-CreationOriented(1/4) • One advantage of this kind of protocol is thereduced overhead in the transmission of data packets. • One disadvantage of thiskind of protocol is that it requires more latency and control overheadto create routes.
Routing-CreationOriented(2/4) GeoTORA GOAL of Protocol: The goal of GeoTORA is to reduce the overheadof transmitting geocast packets via flooding techniques, whilemaintaining high accuracy. Protocol Details:TORA uses the notion of heights todetermine the direction of each link. Despite dynamic link failures, TORA attempts to maintain adestination-oriented directed acyclicgraph such that each node can reach the destination.
Routing-CreationOriented(3/4) Mesh-basedGeocast Routing Protocol GOAL of Protocol: The protocol that uses a mesh for geocasting in an ad hoc environment in order to provide redundant paths between the source and the group members. • Protocol Details: Instead of flooding geocast packets, the Mesh-based Geocast Routing Protocol tries to create redundant routes via control packets.
Conclusions • Three data-transmission oriented protocols which selectively flood data packets • Two routing-creation oriented protocols which create routes to transmit data packets • Both the Flooding-Based GeoGRID protocol and the Ticket-Based GeoGRID protocol should reduce the overhead of the other two data-transmission oriented protocols presented
Conclusions • Compared to data-transmission oriented protocols the overhead of GeoTORA is reduced. • Mesh-based Geocast Routing Protocol, multiple nodes in the geocast region will receive a geocast packet due to the redundant paths that are created between the source and the geocast region.