Interference and its Mitigation in Access Broadband Power Line Systems: A Service Provider’s Perspective

1. Interference and its Mitigation in Access Broadband Power Line Systems: A Service Provider’s Perspective IEEE Power Engineering Society General Meeting Denver, Colorado June 7, 2004 Paul S. Henry AT&T Laboratories – Research

2. 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

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

4. Waves Launched from Coupler and MV Wire Radiation Sig Gen MV Wire ~ Coupler Coupler field Guided wave Ground • 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

5. Wire axis Numerical Modeling at 20 MHz Far Fields (Antenna Pattern) Near (Local) Fields dBuV/m Directly beneath coupler Parallel to wire (m) Perpendicular to wire (m) • 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

6. Standards for Adaptive Interference Management Notched OFDM • Interface protocols Network Manager Licensed User Emergency Services BPL Equipment Database • Are these the major players? • Functional details for BPL network elements • Network security

7. 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

8. 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

9. Thank you!