Ultra Wideband Radio UWB

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Ultra Wideband Radio (UWB)

• Hanbiao Wang
• EE206A
• Spring 2001

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Whats UWB?

• Basically impulses of extremely short duration,
  10s pico-sec to nano-sec
• Definition radio signals with a fractional
  bandwidth ? larger than 25
• where fL and fH are the frequencies measured at
  the 10 dB emission points

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Applications

• Communication
• Tracking
• Radar

Traditional sine waves
UWB coherent pulses
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Advantages in Communication

• Very High Data Rate
• Because extremely narrow pulse width (a few
  nano-seconds) allows very small pulse repetion
  interval (10s nano-sec), UWB could easily reach a
  very high data rate (100s Mbps).

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Advantages cont

• Immunity to Multipath Fading
• With the relatively small ratio of pulse width
  over the pulse repetition interval (0.010.1),
  the direct path has come and gone before the
  reflected path arrives and little cancellation
  occurs.
• Good for indoor or
• in-building use

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Advantages cont

• Very Low Transmision Power
• According to TimeDomain.com, a transmission power
  of only 50 micro-watt is needed for commercial
  communication application, its just 10-4 of a
  cell phone.
• Expected application in communication is
  short-ranged.

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Advantages cont

• Inherent Encryption
• Because very low transmission power and ultra
  wide transmission bandwidth, the resultant
  spectral density is very low. Thus UWB has a very
  low detection probability.
• Time Hopped channel coding makes it random
  noise-like.

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Advantages cont

• Immunity to Hostile Jamming
• Because UWB has inherent encryption, its
  difficult to determine whether UWB transmission
  is on or not. Thus, its difficult for the
  hostile one to decide whether to apply jamming or
  not.
• Because UWB has ultra wide transmission
  bandwidth, jamming wont work even if the hostile
  one know UWB transmission is on.

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Concern in Communication

• ? Interference to Existing Radio Communication or
  Sensing Systems
• Theoretically, UWB will cause little interference
  because of low spectral density and noise-like
  signature.
• NTIA conducted comprehensive tests on the
  potential for interference of UWB to both non-GPS
  and GPS systems.
• http//sss-mag.com/uwb.html

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Interference to Non-GPS

• Feasible between about 3.1 and 5.650 GHz at
  heights of about 2 meters with some operating
  constraints.
• Below 3.1 GHz, "widespread, dense uses will be
  hard to accommodate
• Evaluation limited from 400 MHz to approximately
  6.0 GHz. Potential impact of higher frequency
  unknown.

Announced On 31 January, 2001
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Interference to GPS

• Objective "to define the maximum allowable UWB
  equivalent isotropically radiated power (EIRP)
  levels ... compared to the emission levels
  derived from the limits specified for
  unintentional radiators in C.F.R., Title 47, Part
  15.209 to assess the applicability of the Part 15
  limits to UWB devices.

Announced on 28 February 2001
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Interference to GPS cont

• Given a requisite 6 dB margin for GPS acquisition
  performance, the NTIA demonstrated that a 20 MHz
  (pulse repetition frequency) dithered UWB
  transmission must be at least 33.3 dB down from
  existing Part 15 levels (41.6 dB down for
  non-dithered emissions) in order to not interfere
  with GPS.

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Interference to GPS cont

• Pulse dithering, while making the UWB signal
  appear more "noise like", had a less than 10 dB
  advantage. This advantage was completely "lost
  when a multiple of as few as 3 of these UWB
  signals with equivalent power levels at the GPS
  receiver input are considered in aggregation."

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Interference to GPS cont

• "When multiple noise-like UWB signals with
  equivalent power levels at the GPS receiver input
  are considered, the effective aggregate signal
  level in the receiver IF bandwidth is determined
  by adding the average power of each of the UWB
  signals."
• Aggregate effects are indeed unimportant

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Inplementation Challenges

• UWB transmitters require precise pulse shaping to
  produce the required spectrum and maximize the
  antenna's emission.
• UWB antennas are better described and designed in
  time domain than in frequency domain, in terms of
  convolution of signals with the antennas impulse
  response.

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Advantages in Localization and Tracking

• Advanced time resolution results in very high
  geo-location accuracy, which is good for
  localization
• Very narrow pulse width result in multipath
  fading resistance, which is good for tracking

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FCC Regulatory Process

• Notice of Inquiry issued in August 1998
• Notice of Proposed Rule Making issued on 14 June
  2000
• Requested comment on the first set of NTIA test
  reports for UWB interference to non-GPS systems
  (FCC Public Notice DA 01-171) issued on 24
  January 2001

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Conclusion

• UWB may survive and prosper with high probability
• UWB cant completely replace existing wireless
  systems.