指導教授：許子衡 教授 報告學生：馬敏修 2010/8/20 1

1. Introduction 2. Geocast Routing Protocols  2.1 GAMER Overview 3. GAMER Details  3.1 Building the Mesh  3.2 Adaptation  3.3 Active GAMER vs. Passive GAMER 4. Performance Investigation  4.1 Simulation Environment  4.2 Simulation Results  Performance  Overhead/Load  GAMER Analysis 5. Conclusions 2010/8/20 2

 In an effort to improve the performance of unicast communication, some of the unicast routing protocols use location information in the routing protocol.  A node in the ad hoc network obtains its location from a system such as the Global Positioning System, or GPS 2010/8/20 3

 There has been recent interest in the development of multicast protocols for MNs in an ad hoc network and a variation on multicast communication, i.e., geocast communication.  The goal of a geocast routing protocol is to deliver a packet to a set of nodes within a specified geographical area 2010/8/20 4

Geocast Adaptive Mesh Environment for Routing(GAMER) Overview  GAMER uses the following three concepts: source routing, forwarding zones, and meshes.  Source routing, which is used to route unicast packets in the Dynamic Source Routing (DSR) protocol, is used to route geocast packets in GAMER.  In source routing, each packet carries the full route that the packet should be able to traverse in its header. 2010/8/20 5

 A forwarding zone, which is used to route unicast packets in both LAR and DREAM, is used to route geocast packets in GAMER.  In DREAM, the source node uses its location table to construct a circle centered on the last known location of the destination node.  The source node defines a forwarding zone and then sends its data packets to all one-hop neighbors in the forwarding zone 2010/8/20 6

 LAR is similar to DREAM in that the expected zone for the destination node is a circle formed around the last known location of the destination.  In LAR, two algorithms are proposed to define the forwarding zone  The first algorithm is similar to that of DREAM, except the forwarding zone is defined as a rectangle instead of an angle. 2010/8/20 7

 In the second algorithm, a node decides whether to forward a route request packet by comparing its distance and its neighbor’s distance to the center of the expected zone.  If the node is closer to the destination than its neighbor, it will forward the route request packet; otherwise, it drops the route request packet 2010/8/20 8

 A mesh, which is used to route multicast packets in both On-demand multicast routing protocol(ODMRP) and Core Assisted Mesh Protocol(CAMP), is used to route geocast packets in GAMER.  A mesh is a subset of the network topology that provides multiple paths between multicast senders and receivers. 2010/8/20 9

 In the creation of the mesh, GAMER floods JOIN- REQUEST packets to the MNs within the geocast region via a forwarding zone  We dynamically change the size of the forwarding zone, which ultimately changes the density of the mesh, in real-time.  In other words, GAMER adapts to the current network environment. 2010/8/20 10

3.1Building the Mesh  While a source node in GAMER has geocast packets to transmit, a JOIN-DEMAND (JD) packet is periodically sent to the geocast region.  GAMER uses JOIN-DEMAND packets, instead of conventional JOIN-REQUEST packets, to insist that all MNs in the geocast region join the geocast group.  GAMER provides geo-broadcasting instead of geo- multicasting. 2010/8/20 11

 GAMER dynamically chooses one of three different forwarding approaches (FAs) to forward JD packets to the geocast region.  In one FA, JD packets are flooded throughout the entire ad hoc network.  In the other two FAs, a forwarding zone is defined to reduce the area to flood the JD packets. 2010/8/20 12

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 If an MN receives a non-duplicate JD packet, is within the forwarding zone and is not within the geocast region, then the MN adds its address to the source route contained in the JD packet and forwards the JD packet further  If an MN receives a JD packet and is within the geocast region, then the MN responds to the JD packet by sending a JOIN-TABLE packet to the first address in the reverse source route obtained from the JD packet. 2010/8/20 14

 If an MN receives a non-duplicate JT packet and its ID is within the source route of the JT packet, then the MN sets an internal flag to indicate that it is a part of the mesh, initializes a mesh member timer, and forwards the JT packet to the next address in the reverse source route.  When the JT packet reaches the source, a complete path between the source node and the geocast region is given in the JT packet, which forms one path in the mesh. 2010/8/20 15

3.2Adaptation  A source node in GAMER dynamically chooses the FA applicable to the network environment in real time.  A smaller forwarding zone and a sparser mesh is used to transmit data whenever possible  When the current network environment demands it, a larger forwarding zone and denser mesh is used. 2010/8/20 16

 In order to keep the network load as low as possible, our GAMER protocol begins using the CONE FA and initializes a timer (SWITCH-TIMER).  If the CONE FA fails to create a mesh, then the next JD packet is sent via the CORRIDOR FA.  If the CORRIDOR FA fails to create a mesh, then the next JD packet is sent via the FLOOD FA. 2010/8/20 17

 Once at least one path between the source node and the geocast region is found in GAMER, the source node tries to send the next JD packet via a smaller forwarding zone. 2010/8/20 18

3.3Active GAMER vs. Passive GAMER  Two versions of GAMER are available: the Passive GAMER and the Active GAMER  In the Passive GAMER, there is a fixed frequency to send a JD packet regardless of whether a JT packet is received.  Based on the average round trip time of a JD/JT packet, which is 0.16 seconds in our simulations, SWITCH-TIMER is set to 0.2 seconds 2010/8/20 19

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 In the Active GAMER, there is both a fixed frequency to send JD packets and a mechanism to send JD packets dynamically  If a JD packet succeeds, i.e., a JT packet is received by the source node within SWITCH-TIMER, the Active GAMER schedules the next JD packet for one second after the previous JD packet transmission.  If a JD packet fails, i.e., the SWITCH-TIMER expires, then the Active GAMER transmits a new JD packet immediately. 2010/8/20 21

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4.1 Simulation Environment 2010/8/20 23

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4.2.1Performance 2010/8/20 25

4.2.2Overhead/Load 2010/8/20 26

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4.2.3 GAMER Analysis 2010/8/20 28

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 GAMER dynamically chooses one of three forwarding approaches based on the current network environment.  The Active GAMER is more active in increasing the size of its forwarding zone than the Passive GAMER.  The two versions of GAMER both improve the transmission accuracy significantly without increasing the control overhead significantly when compared to non-adaptive mesh-based geocast routing approaches. 2010/8/20 30