NeXtworking03 June 2325,2003, Chania, Crete, Greece

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UWB Technology and Sensor Area Networks
(SANs) Magda El Zarki and Vipin Mehta School of
ICS, Dept. of CS UC, Irvine
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SANs for Civil Infrastructures

• Understanding the environment
• Mostly Fixed - no or low mobility
• Dense networks of Heterogeneous sensors
• 1000s of low cost sensors 6 - 10 apart,
• tens of high end sensors 10m - 30m
• Easy to deploy - cost effective, work with
  existing structures
• Low maintenance
• Scalable - progressive deployment over time
• Local processing and filtering of data
• Selective querying

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Design Challenges

• Heterogeneity of sensors - strain, temperature,
  humidity, video
• different data collection capabilities
• different types of data
• Data transmission needs periodic, threshold
  triggered, query based, time sensitive
• No Line of sight embedded in concrete, in
  remote spaces, behind beams
• Power supply, longevity - grid, battery, self
  powered
• Scalability - progressive growth
• Robustness - survive link and node losses
• Self Healing - re-configuration of the system due
  to losses/additions
• Deployment - grid based, arbitrary/random,
  specific angle

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Available Technologies

• Wired solutions - star, mesh, rings, etc.
• Wireless solutions
• Cellular network
• IEEE 802.11a/b/g
• UC Berkeley Mote project
• UCLA environmental sensor project
• Bluetooth
• Current technologies do not provide the desired
  set of features for a SAN

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Ultra Wide Band (UWB)

• Most current UWB systems are based on signals
  using narrow time domain impulses transmitted
  with the aid of time-hopping spread spectrum
  techniques or position modulation (referred to as
  impulse radio (IR) systems).
• In UWB, a signal is transmitted with a bandwidth
  much larger than the data modulation bandwidth
  and thus with a reduced power spectral density.
• IR systems produce a signal that is more covert,
  and has higher immunity to interference effects.

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More on UWB Technology

• IR systems operate in the lowest possible
  frequency band that supports its wide
  transmission bandwidth
• Which means that this radio has the best chance
  of penetrating materials that tend to be more
  opaque at higher frequencies.
• The use of signals with gigahertz bandwidths
  means that multipath is resolvable down to path
  differential delays on the order of a foot or
  less.
• This significantly reduces fading effects
• Allows low transmission power operation

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More

• UWB systems are flexible in terms of trading off
  throughput for range
• E.g., the communication range can be varied
  accordingly to cover an area more optimally. This
  can be used for adaptive configuration of the
  sensor nodes based on their proximity to a
  root/central node. The nodes closer to the root
  will have relatively more aggregated data while
  the ones further away from the root have less of
  it.
• Position Location Capability
• short impulse allows for accurate delay
  estimates, which can be used for accurate
  position location.

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Conclusions

• UWB is a promising technology for sensor network
  applications because of its many desirable
  features
• Need to design a MAC that makes use of the unique
  features that UWB offers us for an efficient SAN
  design and that has hooks for cross layer
  operation