Dynamic reconfiguration in Wireless Sensor Networks

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Dynamic reconfiguration in Wireless Sensor
Networks Mihai GALOS, Fabien Mieyeville, David
Navarro Lyon Institute of Nanotechnology (INL)
Lyon, France
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Outline

• Introduction to WSN (Wireless Sensor Networks)
• Dynamic Reconfiguration
• Existing solutions
• Motivation
• Our solution
• Supported Architectures
• Results
• Conclusion and Perspecitves

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WSN - Introduction
Wireless sensor networks (WSNs) are composed of
resource-constrained sensor nodes that can
cooperatively monitor physical or environmental
conditions, such as temperature, pressure,
acceleration,

• Applications
• environmental data collection
• security or health monitoring
• Vehicles

• Network standards
• IEEE 802.15.4
• ZigBee

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WSN - Node

• Small size
• Low cost
• Low energy consumption
• Low processing power

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WSN Dynamic Reconfiguration

• Node, typical application
• Sensing of an analog value
• Processing of the read value
• Sending it via RF
• Dynamic Reconfiguration (firmware update) add,
  modify or remove functionalities after deployment
• Reasons for Dynamic Reconfiguration
• Fine-tuning of algorithms (i.e. compensating
  for meteorological conditions)
• Adding / remove algorithms
• Replacing a failing node

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Existing Solutions for Dynamic Reconfiguration

• Operating Systems

• Virtual Machines

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Existing solutions Operating systems

• Fall into two categories
• Monolithic (whole firmware image has to be sent
  over RF to
• reconfigure a node)
• Modular (only the functionality in question is
  transmitted)

Name Type Update Cost Running Costs Heterogeneity support Update Type
TinyOS Monolithic High Low Limited Machine Code
MantisOS Modular Medium Low Limited Machine Code
NanoRK Modular Medium Low Limited Machine Code
SOS Modular Medium Low Limited Machine Code
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Existing solutions Virtual Machines

• Again, two categories
• ASVM (Application-specific virtual machines)
• General-purpose virtual machines

Name Type Update Cost Running Costs Heterogeneity Support Update Type
Maté ASVM Low Medium to High Yes Virtual Machine specific Bytecode
Darjeeling GPVM Low Medium to High Yes Virtual Machine specific Bytecode
VMSTAR GPVM Low Medium to High Yes Virtual Machine specific Bytecode
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Desired solution
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Our approach In situ Compilation

• Goal implement solution to dynamically
  reconfigure a WSN, with the following
  requirements
• Running Cost Low
• Updade Cost Low
• Support for Heterogenity Yes
• Modularity Yes
• Specifications
• Hardware
• 8 or 16 bit CPU architecture running on the node
• Less than 128kB of Flash
• Less than 20Mhz of CPU speed
• Less than 16kB or RAM
• Lack of a Memory Management Unit
• Software
• Size of RAM poses limitations on input file for
  compilation

Execution in Native format
High-level language, small bytecount
compilation
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A new High-level language MinTax
Name Supported?
Identifiers Yes, 2 bytes wide
Data types Yes signed/unsigned 8bit or 16bit
Arithmetic operations Yes, (, -, / , and )
For and While loops Yes
If and Switch-Case clauses Yes
Nesting Yes
Structures Yes
Pointers Experimental
Digital I/O operations Yes
ADC Yes
Preprocessor directives No
Typedefinitions No

• Name Minimal Syntax, inspired from C
• Small syntax means less radio time to transmit
  functionality
• Strongly typed high-level language
• Each clause is delimited from others with the
  delimiter
• Functions do not have explicit return types

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MinTax an example

1. aUk
2. iA2
3. j8
4. ui
5. Wilt99
6. Wjgt0
7. Pi,j
8. ud_at_k
9. j-
11. i
13. u

1. Uint8_t a (uint16_t k)
2. Uint8_t i read_analog_pin(pin2)
3. Uint8_t j 8
4. Uint8_t u i
5. While(ilt99)
6. While(jgt0)
7. Pwm_output(i,j)
8. udelay(k)
9. j - -
11. i
13. return u

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The MinTax Compiler

• Analysis Stage
• Lexical Analysis splitting the input file into
  atoms or tokens Implemented, generated with
  re2c
• Syntactical Analysis validation that the input
  file corresponds to the languages formal grammar
  Not Needed
• Semantical Analysis context evaluation of
  symbols (Symbol Table) Implemented, merged with
  Lexical Analysis to make single-pass compilation

• Synthesis Stage - Implemented
• Variables are allocated to internal registers
• Small functionalities
• Faster execution, less energy used when executing
  generated code
• Position independent Code

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The MinTax Compiler Supported WSN Nodes

• The WSN world usually comprises solutions around
  microcontrollers from Atmel and Texas Instruments

• Mica2

• Z1

• AVRRaven

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Results

• Sending of a Blink application, Mica2 platform
• Compile, and reprogram

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Conclusion and perspectives

• Conclusion
• High-level language (MinTax) coupled with in-situ
  compilation
• Energy-efficient solution for dynamic
  reconfiguration
• Perspectives
• Heterogeneous network validation
• Multi-OS Integration

• ?

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• Thank you !

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