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Presented by
samaram
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Introduction
Keywords
Bubble Sensing
Implementation Challenges
Conclusion
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Bubble Sensing System acts as a to support
the persistent sensing of a particular
location, as required by user requests.
We adopt a two tier architecture comprising
the bubble sever on the back end , and
sensor enabled mobile phones as the front
end which perform actions like initiatingbubbles, maintaining bubbles sampling and
reporting sensed data.
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Bubble Creator-device whose user initiates the sensing
request that leads to creation of the sensingbubble.
Bubble Anchor
-keeps the bubble in the region of interestby broadcasting the sensing request.
Sensing Node-perceives the bubble by listening to the
broadcasts , takes samples according torequest and upload the results t the bubbleserver.
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Keywords
Bubble Carrier
-helps to restore a bubble if all
the bubble anchors are lost.
Bubble Server
-binds the results to the bubble,
which can be queried by the bubblecreator at any time.
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Sensing task are created and maintained in the
bubble-sensing system through the interaction
of number of virtual roles.
Sensing Task
Action DurationRegion
location radius
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Bubble Creation
Bubble Maintenance
Location-based
Mobility-based
Bubble Restoration
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Bubble creator is a mobile device at
location of interest with an short range
for local peer interaction.
Creator broadcasts the sensing task.
Bubble Creation
mobile Bubble Server
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If the creator has localization capability, it
populates the region field of the task definition and
the sensing bubble is created with its center at this
location.
Otherwise the region field of the task def. is left
blank until sensing bubble is created with its at
current location of the creator where the area of
bubble is determined by its radio transmission range.
Nodes that receive the task broadcast & meet the h/w
and context requirements for sensing task can then
sense in support of the task and will later upload
sensed data to bubble server in either a delay-tolerant
or real time manner.
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Reason for maintaining the bubble is:
Uncontrolled mobility of the creator.
the creator leaves the bubble location
while the task is still active.
Effect of this, is that no longerappropriate for creator to broadcast the task
since recipients will not be in target bubble
location.
Solution is to anchor the bubble to
location of interest is needed and the node which
takes this role should be relatively stationary at
target location of the task.
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Two variants for bubble anchor selection are: requires localization capability on all nodes
Uses inference from an accelerometer for mobility
detection. All sensing nodes that are able to hear the
broadcast messages are called potential
anchors.
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Location based:
In this location based maintenance , thebubbles are maintained based on the location of
the bubble created.
Each candidate anchor backs off a time
proportional to its mobility in terms of location
fixes.
Mobility based:
In this mobility based maintenance , the
bubbles are maintained based on the radio rangeof the mobile phones.
Each candidate anchor backs off a time
proportional to its mobility in terms of data
collected by its accelerometer
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Due to node mobility, it may happen that no
nodes are available to anchor the bubble to
desired location and bubble may temporarily
disappear.
We can overcome this scenario by using
bubble restoration through the actions of
the bubble carrier nodes.
Mobile phones filling this role require
localization capability and a connection to
backend bubble server.
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Bubble carriers periodically contact thebubble server, update their location, and
request any active sensing bubbles in thecurrent region.
I f a bubble carrier visits location ofone of these bubbles and doesn't hear anytask broadcasts , it attempts to restore thebubble by broadcasting task withoutspecial anchor field set.
As result ,it either be restored with a newanchor node and takes over bubble
maintenance or restoration fails and theprocess continues via bubble carrier untilbubble expires.
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Programming Language The programming language needed is PYS60.
PYS60 not only supports the python languageand it support the symbian platform.
Communication
For communication we can use GPRS,3G,Bluetooth and Wi-Fi.
It uses Ad-Hoc mode when interacting locallywith peers, and infrastructure mode toconnect to the bubble server.
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Increased Bubble Sizes
Bubble DriftAnchor moves
can be reduced timeout to the probabilistic
limit the bubble drift is limited to desired level.
Mobility based maintenance
slow moving anchors in the bubble takes over
the role.
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to support persistent location-specific task
in a wireless sensor network composed of
mobile phones.
Mobile sensor nodes collaborate and sharesensing and communication resources with
each other in a cooperative sensing
environment.
virtual roles nodes can assume in support ofbubble-sensing, including the required local
and backend communication.
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