指導教授：許子衡 教授報告學生：馬敏修

A Review of Geocasting Protocolsfor a Mobile Ad Hoc Network

2010/5/7

1

Outline

1. Introduction

2. Geocast routing protocols 2.1Data-Transmission Oriented

2.1.1 Location Based Multicast (LBM) 2.1.2 Voronoi diagram based geocasting 2.1.3 GeoGRID

2.2 Routing-Creation Oriented 2.2.1 GeoTORA 2.2.2 Mesh-based Geocast Routing Protocol

3. Conclusions

2010/5/7

2

Introduction

A node in the geocast region receives a geocast packet, it will flood the geocast packet to all its neighbors.

Classify the five existing geocast protocols into two categories: Data-transmission oriented protocols and routing-creation oriented protocols.

2010/5/7

3

Data-Transmission Oriented(1/9)

Location Based Multicast (LBM)GOAL of Protocol: LBM is to decrease delivery overhead

of geocast packets, by reducing the forwarding space for geocast 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 a geocast packet further via one of two schemes.

2010/5/7

4

Data-Transmission Oriented(2/9)

LBM Scheme 1: When a node receives a geocast packet, it will forward the packet to its neighbors if it is within a forwarding zone; otherwise, it will discard the packet.

2010/5/7

5

Data-Transmission Oriented(3/9)

LBM Scheme 2:A geocast packet should be forwarded is based on the position of the sender node at the transmission of the packet and the position of the geocast region.

2010/5/7

6

Data-Transmission Oriented(4/9)

Voronoi diagram based geocastingGOAL of Protocol: The goal of the Voronoi diagram based

geocasting protocol is to increase the success rate and decrease the hop count and flooding rate of LBM.

2010/5/7

7

Data-Transmission Oriented(5/9)

2010/5/7

8

Data-Transmission Oriented(6/9)

GeoGRIDGOAL of Protocol: GeoGRID uses location information,

which defines the forwarding zone, and elects a special host (i.e, gateway) in each grid area responsible for forwarding the geocast packets.

Protocol Details: Instead of every node in a forwarding zone transmitting data, only gateway nodes take this responsibility.

2010/5/7

9

Data-Transmission Oriented(7/9)

There are two suggestions on how to send geocast packets by GeoGRID: Flooding-Based GeoGRID and Ticket-Based GeoGRID.

Flooding-Based GeoGRID ： Only gateways in every grid within the forwarding zone will rebroadcast the received geocast packets.

Ticket-Based GeoGRID ： The geocast packets are still forwarded by gateway nodes, but not all the gateways in the forwarding zone will forward each geocast packet.

2010/5/7

10

Data-Transmission Oriented(8/9)

2010/5/7

11

Data-Transmission Oriented(9/9)

Gateway Election: The mobile host nearest to the physical center of a grid is elected. Once this node is elected, it remains the gateway until it moves out of the grid.

One problem of this selection process is when another potential gateway roams closer to the physical center of the grid than the currently assigned gateway.

2010/5/7

12

Routing-Creation Oriented(1/4)

One advantage of this kind of protocol is the reduced overhead in the transmission of data packets.

One disadvantage of this kind of protocol is that it requires more latency and control overhead to create routes.

2010/5/7

13

Routing-Creation Oriented(2/4)

GeoTORAGOAL of Protocol: The goal of GeoTORA is to reduce the

overhead of transmitting geocast packets via flooding techniques, while maintaining high accuracy.

Protocol Details: TORA uses the notion of heights to determine the direction of each link. Despite dynamic link failures, TORA attempts to maintain a destination-oriented directed acyclic graph such that each node can reach the destination.

2010/5/7

14

Routing-Creation Oriented(3/4)

Mesh-based Geocast 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.

2010/5/7

15

Routing-Creation Oriented(4/4)

2010/5/7

16

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

2010/5/7

17

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.

2010/5/7

18