Stanford CS 334A - Study Notes (8 pages)

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Study Notes



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Study Notes

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Stanford University
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Cs 334a - Convex Optimization I
Convex Optimization I Documents
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Tenet An Architecture for Tiered Embedded Networks Ramesh Govindan Eddie Kohler Deborah Estrin Krishna Chintalapudi Om Gnawali Ramakrishna Gummadi Thanos Stathopoulos Fang Bian Sumit Rangwala Abstract ity arguments state where functionality should reside in a network Our arguments are modeled after the end toFuture large scale sensor network deployments will be end principle 15 which states how functionality should tiered with the motes providing dense sensing and a be placed in data communication networks We call our higher tier of 32 bit master nodes with more powerful principle radios providing increased overall network capacity In The Tenet Multi node data fusion functionthis paper we describe a functional architecture for wireality and complex application logic should be less sensor networks that leverages this structure to simimplemented only in a tier of relatively highplify the overall system Our Tenet architecture has the powered Stargate class nodes which we call nice property that the mote layer software is generic and masters The cost and complexity of implereusable and all application functionality resides in masmenting this functionality in motes outweighs ters the performance benefits of doing so 1 Introduction The tiered embedded networks built on this principle which we also call Tenets contain both small form factor motes and Stargate class masters Tiered organizations have been discussed before 20 our contribution is to simplify the architecture by explicitly limiting mote functionality Motes contain sensing and actuation functionality and enable infrastructure less instrumentation of physical spaces and artifacts while masters are free of energy constraints and provide increased network and computational capacity enabling large scale deployments All mote sensor data is routed to computational elements running on masters or users and databases attached to masters Motes are tasked by applications running on masters and can implement simple logical elements such as thresholds and compression but any further computation takes place only on masters Excluding multi sensor fusion and complex application logic from motes will have two advantages first the application runs in a less resource constrained environment reducing development cycles and and improving overall system robustness and second the principle makes it possible to conceive of a generic mote layer that need be implemented once and reused for a variety of applications The disadvantage a potential loss of efficiency is a small price to pay for increased robustness and manageability We emphasize that the development of Tenet does not supplant research on mote class devices Motes are essential for low cost dense sensing and ongoing research on software architectures for the motes 1 and on various Over the last five years sensor network research has seen significant advances in the development of hardware devices and platforms and in the design of services and infrastructural elements such as routing localization and time synchronization Deployed systems however have lagged behind Existing deployments are smallto medium scale continuous data acquisition systems in which all sensor data is collected at a central location This is far from the vision enunciated in early sensor networks work in which sensor networks incorporate significant in network processing for energy efficiency Yet attempts to move these deployments closer to the vision have foundered Our experience with sensor deployments has convinced us that the problem is with the vision The constraints on programming low power mote class systems sensing uncertainty wireless communication vagaries and limited energy processing and memory are difficult enough to handle on their own yet the Application Specific principle 6 on which much sensor research is based suggests that each application must tackle these problems combined with application specific data fusion constraints This is leading us to develop systems that are exceedingly complex unmanageable and not re usable A new architecture is needed This paper discusses the architectural foundations of sensor networking Our focus is on the functional architecture the principles that based on cost and complex1 mote subsystems such as medium access time synchronization and localization will remain highly relevant for Tenets Tenet opens up several novel research directions One important area is the development of a generic master tomote interface that can be used by several applications Another is the design of robust subsystems necessary for an operational Tenet a robust routing system reliable delivery of data between masters and motes effective congestion control for high data rate applications lowoverhead network monitoring and automated networking management and tuning The design of these subsystems can leverage masters and the perspective they have of the mote network for simplicity and efficiency The Tenet architecture can greatly accelerate the development of applications and hence the adoption of this highly promising technology This paper discusses the Tenet architectural framework and briefly discusses how it can simplify the design and development of sensor network applications location Such systems typically employ a clustered architecture in which a master node is the head of a cluster of motes and master nodes are connected to each other via a high speed wireless backbone Sensor data from each mote is transmitted multi hop to the nearest master and thence to a back end database for storage Why this disconnect between research and deployment An in depth examination is beyond the scope of this paper but we believe the answer is in the architecture Most sensor network research has accepted and worked within an architectural principle the community articulated early on In 1999 we expressed this principle as follows Application Specific Traditional networks are designed to accommodate a wide variety of applications We believe it is reasonable to assume that sensor networks can be tailored to the sensing task at hand In particular this means that intermediate nodes can perform applicationspecific data aggregation and caching or informed forwarding of requests for data This is in contrast to routers that facilitate node to node packet switching in traditional networks 6 Section 2 2 The Tenet Architecture In this section we first briefly review the progress of sensor networks research so far then


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