指導教授：許子衡 教授
報告學生：馬敏修
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1.
2.
Introduction
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
 4.2.1 Performance
 4.2.2 Overhead/Load
 4.2.3 GAMER Analysis
5.
Conclusions
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 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
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 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
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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.
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 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
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 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.
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 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
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 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.
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 In
the creation of the mesh, GAMER floods JOINREQUEST 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.
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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 geomulticasting.
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 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.
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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.
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 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.
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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.
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 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.
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 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.
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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
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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.
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4.1 Simulation Environment
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4.2.1Performance
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4.2.2Overhead/Load
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4.2.3 GAMER Analysis
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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.
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