Broadband tech 2005

Presentation to Washington Area CTO Roundtable

Dr. David S. YaneyCurrent Technologies

21 January, 2005

Current Communications Group / Current Technologies 2

Today’s agenda

BPL Overview The Electricity Network CT Overhead System Architecture Power Line Channel OFDM Spectral Citizenship Industry Status and Next Steps Quiz


What is BPL?

“Broadband over Power Line” refers to high speed (multi-megabit) unlicensed digital carrier current radio systems moving data over the medium voltage (MV) and low voltage (LV) segments of a power line network

– “in home” refers to operations akin to the LAN side of conventional networks operating at the customer premise

– “access” refers to operations akin to the WAN side operating on the MV and LV segments of the utility network

– The electric meter is the demarcation point

A very attractive new business opportunity built between a Rock and Hard Place

– The “rock” is FCC Part 15 Regulations– The “hard place” is either noise or attenuation of the existing power networks


Why Is BPL Attractive?

Power lines are our most ubiquitous infrastructure– In appropriate business relationships, their use can be essentially free

Effective Broadband competition– Potential 3rd provider into home– Existing wires – lower cost of deployment

Potential for Enhanced Utility Services– Adds “smart” capabilities to an otherwise “dumb” network


Electricity Distribution Basics

Introduction

Power Plant Step-Up Transformer

High Voltage Lines

(69kV – 765 kV)

Substation Medium Voltage Lines

(4kV – 46 kV)

Low Voltage Lines

(120/240 V)

Generation Transmission

Example CompaniesDistributionDistribution

From the transmission lines, the voltage is stepped down at a substation and distributed to

end-users over the local power grid

From the transmission lines, the voltage is stepped down at a substation and distributed to

end-users over the local power grid

Distribution


Electricity System Layout


Key Architectural Choices For BPL System

Bypass Transformer or Pierce Transformer (MV to LV connectivity )– Bypassing transformer allows lower and more predictable signal loss; piercing

requires no equipment– Safety is paramount and bypass equipment is new for utilities

Signal Repetition– Regenerating data packets at various points allows greater reach at the

expense of lower bandwidth and greater latency

Frequency Plan– Selection of operating frequencies for backbone and service links– FDD vs. TDD– Coexistence with licensed services

Bandwidth and latency– Desired service offerings– Latency sensitive applications – voice and gaming


HomePlug® CPEHomePlug® CPE

4

SolutionsSolutions

InternetVoIP

CT Coupler®CT Coupler®

2

CT Backhaul-Point®

CT Backhaul-Point®

1

CT Bridge®CT Bridge®

3

CT View® Management System

CT View® Management System

5

ComponentsComponents

Medium-voltage lines

5

Low-voltage lines

Backhaul

2

1

2

3

4 4 4

CT Overhead System Architecture


CT Bridge®

CT Coupler®

CT Backhaul-

Point®

CT Overhead Installation


3

2

Detailed CT Overhead Installation


Power Line Is A Hostile Channel for Communications

Power lines are full of channel impairments

– Impedance Mismatch– Unterminated Stubs– Crosstalk– Conducted Noise– Ingress Noise– Attenuation– Frequency Selective

Characteristics– Pesky high

voltage/current– Variation over time– Variation with weather

-90

-80

-70

-60

-50

-40

-30

-20

0 4 8 12 16 20 24 28

Channel Spectral Characteristics Post Ferrite Choke Insertion

Horizontal scale = Frequency (MHz) Vertical Scale = Through Response (dB)


OFDM Offers Superior Performance for BPL Applications

OFDM

Spread Spectrum

Techniques (FH and DS)

Single Carrier

Spectral Efficiency

Good Moderate Moderate

Robustness Against Channel

DistortionsExcellent Poor Good

Robustness Against

Impulsive NoiseFair Fair Good

Ability to adapt to channel changes

Excellent Fair Good

EMC Aspects Good Good-Excellent Poor

Implementation Costs

(Equalizers, etc.)Fair Poor

Poor (Equalizers required)


OFDM Signal Generation

•OFDM carriers are closely spaced

•Note each carrier is placed at the nulls of other carriers

OFDM systems are practical with DSP techniques

Single chip engines available

Image: http://www.ert.rwth-aachen.de/Projekte/Theo/OFDM/node6.html

Image: Communications Systems Design, Dec 2000


OFDM System Example: Homeplug

Homeplug is a standard for power line networking– Used as the LV modem in Current’s solution

84 carriers from 4.5-21 MHz – notches for amateur radio bands

-10

0

10

20

30

40

50

0 4 8 12 16 20 24 28

• Raw Throughout 14 Mbps

• Effective throughput 6-7 Mbps

• DES encryption

• Products Widely Available and Low Cost


Spectral Citizenship

Some parties have expressed concern over potential interference to licensed radio users

– Amateur radio operators most vocal opponents

BPL power limits set by FCC Part 15 limits– Formal FCC BPL R&O issued in October 2004– Limits same as millions of other devices– Verification/Certification must be done in situ– Limits are extremely low– Any resultant interference must be resolved by BPL operator

Current’s Approach to Interference– Avoidance is most effective mitigation technique– Only one device on a link transmits at a time– No overlap with amateur, broadcast, satellite frequencies– Largest BPL deployment in North America– No interference complaints


Status of BPL Industry

3 Commercial US Deployments– Manassas, VA – Municipal utility – Main.Net– Cincinnati, OH – Cinergy & Current Communications JV – Current Technologies– Emmaus, PA – Pennsylvania Power & Light – Main.net and Amperion

30+ trial deployments in US

Commercial deployments in Germany, Spain, Korea, Chile, Brazil,

Image: Network World, 23 Aug 2004


Big Questions for BPL Industry

Technical

– Verify scale - Technology works effectively. It now needs to demonstrate large scale operation

Non-technical

– Business Models - Industry business models need to be verified and shown to work in actual commercial deployment

– Regulatory - BPL industry needs to show that regulatory issues can be handled similar to other industries (cross-subsidization, etc.)


Quiz

Calculate the temperature rise that a hard MV line fault to ground would create if the energy was entirely dumped into 100 pounds of water

Assume:1. MV phase-to-phase voltage is 13.2 KV2. The substation recloser will allow 10,000 amps for 10 cycles

Useful facts:1. 1 joule almost exactly equals 1 watt-second2. 1 joule equals approximately 0.24 calories

Hint: use CGS units


Quiz solution

The total energy Q dissipated as heat:

Q = (phase-ground voltage) * (current) * (time interval) [watt-seconds]

Q = (13.2 KV / 1.732) * (10,000 amps) * (160 msec) * (0.24) [calories]

Q = 2.93E06 calories

If that total energy is dumped into 100 pounds of water:

dT = Q / (mass of water * specific heat)

dT = 2.93E06 / (100 [lbs] * 454 [grams/lb] * 1 [cal/gram/deg C])

dT = 64.5C or 148F

It’s also interesting to note that:

dT/dt = (64.5/0.16) or about 400 degrees C / sec !

Broadband tech 2005

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