Sensor Node Architecture Issues by acm31250


									Sensor Node Architecture Issues

          Stefan Dulman

Current sensor node architecture
  Layered protocol stack (OSI Model)
  Each node is once programmed with a fixed number
  of protocols
  Active Messages (TinyOS – Berkley Motes)
  Sentient Objects (CORTEX project)
  Others … (?)

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                                       Open Questions

Problems to be solved locally:
  Where to fit localization, timing & synchronization…
     They can move in the protocol stack as they pass through
     different phases
     Several blocks might need their data
     Which block is responsible for turning them off
  Managing the existing protocol blocks
     Having several versions of algorithms inside a sensor node
     that get activated while data becomes available
     Updating/replacing/switching the existing modules
  A task scheduler fitted for these operations

                               3                     energy efficient sensor networks
                             (More) Open Questions

The new architecture should enable efficient:
  Error control
     Traditionally performed at all layers
     Each layer is optimized for the worst case
     Higher layers usually support a certain degree of failure of
     the underlying layers
  Energy control
     Traditionally performed at physical layer only – each block
     inside the sensor node is concerned with it
     Switch among different versions of protocols as a function of
     the available energy (or even shut down a few)

                                4                       energy efficient sensor networks
                  (Even More) Open Questions

The nodes are not single & independent!
  Problems addressed:
     Nodes need to exchange data
     Remote procedure calls for expensive operations
New features:
  Heterogeneous network from protocol point of view
  Groups of nodes (clustering!) share groups of
  protocols (memory saving, energy efficiency)
I will route my packets with my neighbor’s
routing protocol using his timing information!

                              5                        energy efficient sensor networks
                                       Existing Architectures

Current EYES architecture
  Does not answer almost ANY of the previous issues
  Far too complicated and impossible to fit inside a
  sensor node
                                           Alternatives for blocks
               Protocol stack layers

                                       6                             energy efficient sensor networks
                                        Existing Architectures (2)
 Active Messages
             Initially designed to answer data centric routing issues

?            Can be extended to cover some more issues
             Relationship with the OS
             Communication inside a sensor node

application                                          sensing application

   routing                    Routing Layer

messaging             Messaging Layer

    packet     Radio Packet     UART Packet

      byte      Radio byte       UART byte                    photo        Temp               SW

       bit     RFM                                clocks       ADC         i2c               HW
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                          Existing Architecture (3)

Sentient Objects (CORTEX)
  Nice ideas involved
  Can be used as a starting point

                             8             energy efficient sensor networks
                        Towards a Solution…

Local data centric architecture
Protocols implemented as entities that
produce/consume data
Each entity (wyber) has:
  Input & outputs

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                          Towards a Solution (2)
Data centric scheduler:
  Unifies the OS scheduling and the entities management
  Can be built on top of the existing Eyes OS

                          10                energy efficient sensor networks
                        Towards a Solution (3)

Data centric schedulers have to connect to each-
other to form a network backbone
Entities publishing/subscribing to data will be able
to use data from entities inside other nodes

                         11               energy efficient sensor networks
                             Issues to be solved

Open issues:
  Choosing entities function of the capabilities
  Compatibility issues among entities
  Minimum number of layers for the backbone
  Service discovery
  Naming schemes
     (Directed Diffusion naming system)

                        12                energy efficient sensor networks
Questions & suggestions (please!!!)

                13            energy efficient sensor networks

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