Interference from PowerLine Comms a'k'a' BPL

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Interference from PowerLine Comms a.k.a. BPL

• Eric E. Johnson
• Klipsch School of Electrical and Computer
  Engineering
• New Mexico State University
• eejohnson _at_ ieee.org

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Threats to HF Spectrum
Demands by Other Users
Our Spectrum Allocations
Noise Floor
BPL Interference
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Access BPL Concept
NTIA BPL Report 04-413 Volume I, Figure 2-2
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Threat from BPL/PLC

• BPL (a.k.a. PLC) operates throughout the HF band
  (1.7 80 MHz)
• Unlike coax or twisted pair, power lines radiate
  profusely
• Field trials in many nations have confirmed the
  interference potential

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German NB30 Radiation Limits

• Frequency dependent limits
• At 1 MHz 40 dB (µV/m) in 9 kHz at 3 m
• Considered too high by radio usersConsidered too
  restrictive by PLC industry

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Field Trials in Arnhem, NL

• PLC installed at 3 transformer stations in 01
  noise measured before/after
• Receivers in affected areas required 25 dB more
  power for same SINAD as before
• Model predicts 34 dB(µV/m) at 1 km radius from
  town with 4 PLC nets per km2
• Terminated in 03 as economically unfeasible

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EC PLC Workshop (Oct 2003)

• Austria proposes 14 dB(µV/m) _at_ 10 mprobably
  40 dB better than industry can meet
• Finland industry proposal of 55 dB(µV/m) is 40
  dB too high
• Switzerland (Fribourg trials results) PLC
  exceeds NB30 limit by up to 24 dB. HF SNRs
  reduced by up to 14 dB.

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US FCC Proposed Rulemaking

• Current Part 15 Rules 1.70530 MHz (freq
  independent) 30 µV/m _at_ 30 m
• (much higher than NB30)
• April 03 FCC requested comments on
  deployment of BPL within this limit

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Objections Raised

• Amateur radio community 53 of survey
  respondents have antennas within 30m of an
  outdoor power line
• NTIA interference to Federal HF users
• FEMA interference to emergency comms
• NAS interference to radio astronomy
• (numerous additional objections)

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FCC Proposed Rulemaking

• Impressed by potential benefits of BPL
• Not impressed by unsupported claims of
  interference
• Proposed rules (04-29, dated 23 Feb 04)
• Existing limits will apply
• National registry of BPL systems
• Adaptive interference mitigation required
• New measurement guidelines

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NTIA Review

• NTIA is US Presidents principal adviser on
  domestic and international telecomms policy
• Manages Federal use of spectrum
• Recently studied potential BPL interference
• Despite study results, supports Part 15 limits

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NTIA Phase I Study

• Evaluated interference range using NEC for BPL
  devices conforming to Part 15 rules

13
NTIA Phase I Study

• Appendix B notes numerous case studies
• Austria massive disruption of Red Cross
  exercise (May 2003) by PLC
• Japan Access PLC found to jam HF comms
• Excessive radiated noise levels reported in
  measurements from Germany, Netherlands, Norway,
  Switzerland

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Air Force Comments

• Do not support NTIA position that current Part 15
  emission levels are sufficient
• Emphasizes HF Comms vital to military
• SCOPE Command
• Allied interoperability
• Slight increase in noise floor may be disastrous

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Air Force Comments

• Notes wide difference from Part 15 to NB30 and
  proposed European standards
• Suggests initial deployment
• No more than 1 year
• Emission limits no higher than Part 15
• Adjust up or down based on experience with these
  limits and the interference mitigation techniques

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Project OPERA

• Open PLC European Research Alliance
• 35 European institutes, universities, agencies
• Working toward new generation PLC
• Simple and standardized
• Higher performance (up to 200 Mbps)
• Addresses radio interference issues

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New Aspect Homeland Security

• Use BPL for remote monitoring (cameras) of
  critical infrastructure
• Carried on high- and medium-voltage lines(noise
  on HV lines may be too severe)
• IP routers for line-fault robustness
• Expands direct BPL interference from residential
  areas to nationwide problem

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Action Required

• Support national authorities in seeking
  acceptable limits on PLC/BPL emanations
• Make high-quality measurements of PLC/BPL effects
  in ongoing trials

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Questions?
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FCC Interference Mitigation

• Dynamic / remote power reduction
• Adjustment of operating frequencies
• Remote shutdown feature(for systems found to be
  interfering)

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FCC Measurement Guidelines

• All Access BPL devices to be measured in situ
• Magnetic loop antenna below 30 MHzElectric field
  antenna above 30 MHz
• Measure at fixed distance along power lineat
  height of 1 meter (for loop antenna)
• Extrapolation allowed (slant range)

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NTIA Phase I Study

• Potential Interference From Broadband Over Power
  Line (BPL) Systems To Federal Government
  Radiocommunications at 1.7 80 MHz, NTIA
  Report 04-413, April 2004
• Available for download www.ntia.doc.gov

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NTIA Phase I Study

• High interference because current methods
  underestimate peak power levels
• NTIA recommends improved compliance measurement
  procedures
• Measure at height of power lines
• At uniform distance of 10 m from device/line
• Use calibrated measuring antenna

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NTIA Phase I Study

• Measurement campaigns
• Horizontally polarized interference peaks near
  BPL device (within 30 m)
• Vertically polarized interference peaks under
  line, at impedance discontinuities far from BPL
  device

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NTIA Phase I Study

• Did not address
• Aggregation of interference from multiple BPL
  devices via ionospheric propagation
• Out of band emissions and IM products
• Interference or damage to BPL devices from
  current spectrum users
• Will be addressed in Phase 2 of study

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NTIA Aggregation Estimates

• Preliminary analysis of aggregated interference
  due to ionospheric propagation
• Harmful interference unlikely from a single
  sizable metropolitan installation
• Aggregate effect from a nationwide deployment
  more significant
• Some questions regarding methodology