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IEEE Power Engineering SocietyGeneral MeetingDenver, Colorado

June 7, 2004

Paul S. HenryAT&T Laboratories – Research

Interference and its Mitigation in Access Broadband Power Line Systems:

A Service Provider’s Perspective

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Standards for Access Broadband Power Line

Standards – Ensure compliance with regulations– Enable second source– Promote vendor competition

Special considerations due to interference -- BPL operator is not licensed to use radio spectrum

– Must not interfere with licensed services (e.g. SW, Amateur)– Must accept interference from licensed users– Burden to remediate interference problems falls on operator

Challenge is to develop a large-scale reliable service under these constraints.

– New proposed regulations from the FCC – Role (s) of IEEE

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New Regulatory Directions for Access BPL -- USA

Current law: Part 15 (Code of Federal Regulations Title 47)• Unlicensed systems must satisfy emission limits (~vendor’s responsibility)• Unlicensed users must not interfere with licensed services (~operator’s resp.)• Unlicensed users must accept interference from licensed services (~operator’s resp.)

NPRM (Feb. 04): Solicits input for changes to Part 15 to encourage deployment of Access BPL while ensuring protection of existing licensed services.

1. Define procedures appropriate to BPL for measuring interference– Change existing field-strength limits (up or down)?

2. Dynamic interference management (A new approach to regulation of unlicensed operators)

– Adaptive emission control– Remote shut-down– BPL equipment database– Expedited interference remediation

IEEE: Advise on Item 1; develop standards for Item 2.

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Waves Launched from Coupler and MV Wire

~Guided wave

Radiation

•Traveling-wave (Beverage) antenna•Thoroughly studied

•Guided wave •Carries signal to adjacent coupler and beyond•Fields decay rapidly perpendicular to wire (~1/d**2); slowly along its length

•Radiation•Remote (far-field) effects (~1/d)•‘Source’ is entire length of MV wire

•Coupler field•Localized near coupler (~1/d**3)

•Consistent with April NTIA report•For realistic ground parameters, numerical solution required

Sig Gen

Ground

CouplerMV Wire

Coupler field

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Wire axis

Parallel to wire (m)Perpendicular to wire (m)

dBuV/m

Numerical Modeling at 20 MHz

•Rapid decay perpendicular to wire•Low attenuation parallel to wire

Good signal propagation Persistent interference

•Sharp forward beam (can have >10 dBi effective gain)•Differential excitation can provide >10 dB suppression

>>Comprehensive analysis required to support regulations

Near (Local) Fields Far Fields (Antenna Pattern)

Directly beneath coupler

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Standards for Adaptive Interference Management

• Interface protocols

Notched OFDM

Emergency Services

NetworkManager

BPL EquipmentDatabase

Licensed User

• Are these the major players?• Functional details for BPL network elements

• Network security

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OFDM Notching

Physical• On-off ratio• Speed of response• Maximum number of notches• Signature

Architectural• Distributed vs centralized control • Control protocol (including verification)• Coordination with multiple receivers• Minimization of signal power• Security

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Summary

• BPL– Promising broadband access vehicle– Meager base of field experience for regulations and standards (especially

for MV systems in USA)– Not clear how to balance benefit against cost

• Two roles for IEEE– Advisory: Interference mechanisms and measurement

• Distance dependence includes 1/d**3, 1/d**2, 1/d, and ~constant• Measurement procedures needed to deal with all four

– Standards formulation: Adaptive interference management• Management architecture• Network element functionality• Communication protocols• Security

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Thank you!