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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
Current Communications Group / Current Technologies 3
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
Current Communications Group / Current Technologies 4
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
Current Communications Group / Current Technologies 5
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
Current Communications Group / Current Technologies 6
Electricity System Layout
Current Communications Group / Current Technologies 7
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
Current Communications Group / Current Technologies 8
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
Current Communications Group / Current Technologies 9
CT Bridge®
CT Coupler®
CT Backhaul-
Point®
CT Overhead Installation
Current Communications Group / Current Technologies 10
3
2
Detailed CT Overhead Installation
Current Communications Group / Current Technologies 11
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)
Current Communications Group / Current Technologies 12
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)
Current Communications Group / Current Technologies 13
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
Current Communications Group / Current Technologies 14
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
Current Communications Group / Current Technologies 15
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
Current Communications Group / Current Technologies 16
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
Current Communications Group / Current Technologies 17
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.)
Current Communications Group / Current Technologies 18
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
Current Communications Group / Current Technologies 19
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 !