ESA Wireless Sensor Motes Study

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ESA Wireless Sensor Motes Study

• George Prassinos, SSC, University of Surrey

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EMC/EMI

• Electromagnetic interference can cause
  undesirable behaviour to the electronic devices
  of our spacecraft or even damage them completely.
  
• Motes have no shielding making them even more
  susceptible to EMI.
• Motes need to be contained in order to be
  shielded from radiation.
• The EMI coupling process is initiated from an EMI
  Radiating device which is transmitted even by RF
  or by conduction to our structure.
• For low frequencies the coupling effects are even
  Capacitive or Inductive and for high frequency
  models the effects are Radiative.
• If for conduction the coupling is conductive both
  for low and high frequency modes.

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EMC/EMI

• In space missions there are several sources
  of radiation caused from natural and manmade
  systems
• Sun,
• cosmic,
• radio stars
• the electronic subsystems of the spacecraft

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EMC/EMI

• Wireless communication data links utilize
  free-space propagation and are subject to
  interference and signal disruption from a broad
  spectrum of sources.
• Wireless communication networks utilize several
  different frequencies. (MHz to GHz)
• The effects of noise and interference are
• data link connectivity problem,
• reliability
• data rates of the network.

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Glaramara Board

• SSTL has from previous projects a Glaramara
  Development kit from CompXs.
• The kit provides a way for prototyping and
  application development based on the
  802.15.4/ZigBee protocol.
• PIC18LF452PT microcontroller
• 32 KB of Flash program memory,
• 1536 bytes of RAM data memory
• 256 bytes of EEPROM data memory.
• The microcontroller is interfaced to the Radio
  Module via its built-in SPI interface as well as
  some general I/O pins.

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Glaramara Board
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Scaffell

• The radio module used on the development kit is
  Scafell from CompXs
• Scafell implements a Wireless Personal Area
  Network (WPAN) enabling communication with a wide
  range of devices over relative short distances.
• compliant with IEEE 802.15.4
• provides inherently duplex synchronous-byte
  serial interface between the Network layer and
  the Media Access Control layer (MAC).

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Scafell
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Scafell

• The radio module is using an FCPG processor which
  is very susceptible to EMI.
• The development board is likely to suffer
  performance due to EMI as it has absolutely no
  shielding.
• FLASH and EPROM modules are used to store software

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Alternative Motes

• An alternative solution to the above mentioned
  motes is the Intel Mote 2 Platform.
• based on an Intel PXA270 XScale CPU
• integrates high performance processing including
  DSP capabilities,
• large amounts of RAM and FLASH memory,
• standard and high-speed I/O interfaces as well as
  an advanced security subsystem.
• The platform provides an on-board IEEE 802.15.4
  radio and the option to add other wireless
  standards such as Bluetooth and 802.11b via an
  SDIO Interface.
• based on the 802.15.4 protocol can operate in
  either
• broadcast or
• point-to-point link modes
• The platform features a substantially expanded
  set of I/O interfaces besides the standard ones
  i.e. UART, SPI, USB.
• The processing core is based on the ARM
  architecture enabling to use both TinyOS and
  Linux.
• The mote can run at low frequencies of 13 Mhz up
  to a few hundred MHz.

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Intel Mote 2
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FHSS

• Because there is no way to predict what
  interferers at any given time, frequency and time
  the network must be able to continually sidestep
  these interferences.
• The operating bands of the motes can be sliced
  into several discrete frequency ranges from
• 900-928 MHz,
• 2.400-2.4835 GHz.
• The slices enable an effective frequency hopping
  stream spectrum (FHSS) routine which can
  efficiently sidestep RF interference.

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MICA2

• Another option could be a MICA2 mote from Xbow.
• Designed for embedded sensor networks with more
  than a years lifetime with just a single AA
  battery cell.
• Capability to be used as a router with
  operational frequencies of
• 315 Mhz
• 433 MHz
• or 868/916 MHz.
• Although fixed at these frequencies the radios
  can easily and quickly switch channels to avoid
  interferences caused by EMI.
• It also provides a cost effective solution
  comparing to motes from other manufacturers.

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Preferred Motes
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Preferred Motes

• mostly interested in the
• MPR2400 MICA2 mote operating at 2400-2483.5 MHz
• MPR2600 mote operating at the same frequency
  range.
• high frequencies
• greater robustness against EMI
• faster data rates which are up to 250 kbps for
  the MPR2400.
• Both motes are using the Atmel ATMega 128L
  Processor and are compliant with 802.15.4
  protocol.
• TelosB MOTES
• most recent development in this area and promise
  excellent performance.
• compatible with the IEEE 802.15.4 protocol and
  offer speeds of up to 250 Kbps.
• use the TI MSP430 micro controller which has
  displayed good EMC in previous tests.
• TPR2400 can be easily programmed through a common
  USB port and have very good library support for
  TinyOS.
• It is a platform created for research testing and
  it is recommended to be tested for space system
  suitability.
• Glaramara Development kit with the Scafell Radio
  Module will be used for testing as it has being
  previously used by SSTL to test the capabilities
  of Zigbee.
• Offers
• MAC programming implementing a Wireless Personal
  Area Network (WPAN) enabling communication with
  several devices in relatively short distances.

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Preferred Motes
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Sensor Boards
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Requirements

• We want data rates which at minimum exceed the
  minimum data rate requirements of each subsystem.
  
• SSTL CAN Bus operates with only 32kbps
• MICA2 mote at 433-434.8 MHz
• offer speeds of up to 38.4 Kbps
• FSK Frequency Selectable radio receiver.