Time-stable geocast for ad hoc
networks and its application with
virtual warning signs
報告學生：馬敏修
2010/4/2
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Outline
Introduction
2. Overview on abiding geocast
3. Design space of abiding geocast
4. Abiding geocast approaches
1.
Server approach
Election approach
Neighbor approach
Simulations
6. Summary
5.
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Introduction(1/2)
Geocast：the transmission of a message to some
or all nodes within a geographical area.
 Virtual warning signs are attached to a certain
geographical position or area.
 Virtual warning sign service need a time-stable
geocast solution.

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Introduction(2/2)
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Overview on abiding geocast
An inherent question of the abiding geocast
semantics is the duration of storage and delivery
availability.
 We provide an best effort service without
guarantees, which means that we cannot provide
guarantees about the duration availability.

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Design space of abiding geocast(1/2)

1)
2)
3)
4)
For a stored geocast solution we identify four
building blocks：
The underlying geocast routing protocol
The storage of geocast messages
The hand over of abiding geocast messages
The delivery of an abiding geocast messages to
new nodes inside the destination region.
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Design space of abiding geocast(2/2)
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Abiding geocast approaches(1/10)
Server approach

The geocast server uses a geocast routing
protocol to deliver the message to the
destination region.
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Abiding geocast approaches(2/10)
Moving node does not know about the defined
destination region of geocast messages stored on
the server.
 Server requires moving nodes to periodically
send their position to the geocast server.

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Abiding geocast approaches(3/10)
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Abiding geocast approaches(4/10)
Election approach

Each node in the destination region is a
candidate for the election process.
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Abiding geocast approaches(5/10)

Geocast message delivery is done as
follows：
The sender of a geocast message uses a
geocast routing protocol to deliver the message.
2) All nodes receive the geocast message and
start the election process.
3) The elected node stores the message and
periodically or on request delivers the message.
1)
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Abiding geocast approaches(6/10)
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Abiding geocast approaches(7/10)

Opposing event geocast is used to address the
whole destination region of the abiding geocast
message that is to be discarded.
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Abiding geocast approaches(8/10)
Neighbor approach
Each node stores all geocast packets destined for
its location and keeps a table of all neighbor
nodes and their location.
 The neighbor approach simply makes use of the
exchanged neighbor information for unicast
routing.

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Abiding geocast approaches(9/10)
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Abiding geocast approaches(10/10)
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Simulations(1/4)
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Simulations(2/4)
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Simulations(3/4)
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Simulations(4/4)
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Summary
Virtual warning signs are attached to a certain
geographical position or area.
 An abiding geocast is a timestable geocast
delivered to all nodes.
 The design space of abiding geocast has the four
dimensions: geocast protocol, geocast storage,
geocast hand over and geocast delivery.
 Three reasonable approaches： Server approach,
Election approach and Neighbor approach.

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