Presented by
Vijaya

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BUBBLE SENSING
A New Paradigm for Binding a Sensing Task to the Physical World using Mobile Phones
Introduction
 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 initiating bubbles, maintaining bubbles sampling and reporting sensed data.
Keywords
 Bubble Creator
-device whose user initiates the sensing request that leads to creation of the sensing bubble.
 Bubble Anchor
-keeps the bubble in the region of interest by broadcasting the sensing request.
 Sensing Node
-perceives the bubble by listening to the broadcasts , takes samples according to request and upload the results t the bubble server.
Bubble Sensing
 Sensing task are created and maintained in the bubble-sensing system through the interaction of number of virtual roles.
Major Operations in Bubble Sensing
 Bubble Creation
 Bubble Maintenance
 Location-based
 Mobility-based
 Bubble Restoration
Bubble Creation
 Bubble creator is a mobile device at location of interest with an short range for local peer interaction.
 Creator broadcasts the sensing task.
Bubble Maintenance
 Reason for maintaining the bubble is:
 Uncontrolled mobility of the creator.
àthe creator leaves the bubble location while the task is still active.
àEffect of this, is that no longer appropriate for creator to broadcast the task since recipients will not be in target bubble location.
àSolution 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.
 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.
 Location based:
 In this location based maintenance , the bubbles 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 range of the mobile phones.
 Each candidate anchor backs off a time proportional to its mobility in terms of data collected by its accelerometer
 Bubble Restoration
 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.
 Bubble carriers periodically contact the bubble server, update their location, and request any active sensing bubbles in the current region.
 I f a bubble carrier visits location of one of these bubbles and doesn't hear any task broadcasts , it attempts to restore the bubble by broadcasting task without special anchor field set.
 As result ,it either be restored with a new anchor node and takes over bubble maintenance or restoration fails and the process continues via bubble carrier until bubble expires.
Implementation
Programming Language
 The programming language needed is “PYS60” .
PYS60 not only supports the python language and it support the symbian platform.
Communication
 For communication we can use GPRS,3G, Bluetooth and Wi-Fi.
 It uses Ad-Hoc mode when interacting locally with peers, and infrastructure mode to connect to the bubble server.
Challenges
 Increased Bubble Sizes
 Bubble Drift
 Anchor moves
àcan be reduced timeout to the probabilistic limit the bubble drift is limited to desired level.
 Mobility based maintenance
àslow moving anchors in the bubble takes over the role.
Conclusion
 to support persistent location-specific task in a wireless sensor network composed of mobile phones.
 Mobile sensor nodes collaborate and share sensing and communication resources with each other in a cooperative sensing environment.
 virtual roles nodes can assume in support of bubble-sensing, including the required local and backend communication.