Tutorial II:
Power-line Communication,
Technology and Japanese Activity
Shinji Tsuzuki
Ehime University, Japantsuzuki@ee.ehime-u.ac.jp
http://miyabi.ee.ehime-u.ac.jp/~tsuzuki/PLC/PLC.html

Third International Workshop on Networked Appliances,
IWNA’2001, 01 March - 02 March, 2001
Time: 8:30AM -10:30PM
Date: Friday, 2nd March 2001
Venue: Empress Room, Level 2, Carlton Hotel,
Singapore

Topics? Overview of PLC and home-network? Conventional PLC products? Principle of PLC? High-speed/reliable products? Regulation and standardization activity? Some Japanese activities

Overview of PLC and home-network

Home network (1)Promising candidates? Wire-less network? IEEE802.11, Bluetooth, HomeRF? Wired network? Plastic Optical Fiber? twist-pair wire
? IEEE802.3• cheapest, fastest & (most) reliable• But needs New Wires? IEEE1394 for AV applications? HomePNA• Relatively low-cost, fast, reliable, supports voice &streaming• But limited to existing phone jacks

Overview of PLC and home-network

Home network (2)? Wired network? IEEE802.3, IEEE1394, (HomePNA)○ high speed, reliable
X new wire or re-wiring is needed
Power-Line Communication (PLC),
i.e.,• No costly rewiring• A ‘connection port’ (AC power outlet)
in every room
• ecological method

Overview of PLC and home-network

Home network (2): related standards

PLC
High speed PLC: HomePlug (10Mbps)

Overview of PLC and home-network

Home network (2)Split phase problem

http://www.3com.com/technology/tech_net/white_papers/503081c.html

Overview of PLC and home-network

Home network by PLC (1)Feq. range>1MHz<450kHz

Overview of PLC and home-network

Good point of PLC (1)
PLC can provide both solutions? high-speed data communication(≒10Mbps, developing)? appliance control (low-speed but cheap)…(1)? for DSM (Demand-Side Management)• DSM is to smooth out the daily
peaks and valleys in electricenergy demand to make the mostefficient use of energy resources
and to defer the need to develop
new power plants.

Lowers levels of energy
consumption

Shifts the time of energy use.

http://www.state.hi.us/dbedt/ert/dsm_hi.html#anchor351481

Overview of PLC and home-network

Good point of PLC (2)? appliance control ...(2)? for home automation• can link lighting, entertainment, security,
telecommunications, heating and air conditioning into one
centrally controlled system.
– http://www.homeautomation.org/welcome/welcomeM
AIN_ie.html

Home network by PLC (3)Epoch-making trial of“Internet Over Power-lines”? Nortel (Northern Telecom) and NorWeb Communications:Nov., 1997
? At Seymour Park Primary School in Manchester England? 12 PCs were connected to the Internet by power line.
All 12 computers can operate concurrently from justone connection, from which they obtain permanent
access to the Internet at speeds of up to 1 Mbps.

• Begin to develop higher speed PLCs
• Begin an activity of deregulation
http://www.iihe.ac.be/scimitar/J0398/IntOvPow.html

http://www.3com.com/technology/tech_net/white_papers/503081a.html#figure_3

Home network by PLC (4)Home gateway (a)or power-line

or power-line

Home network by PLC (5)Home gateway using electric power
meter
OpenPLANET server, developed by Shikoku Electric Power
Company.
currently utilizes• Residential network
Echelon's LonWorks• Global network
PHS(Personal
Handy-phone
System)http://www.openplanet.co.jp/html-e/e-kosei.htm

Plastic Optical Fiber (POF) for Gigabit
Communication
http://www.agc.co.jp/english/lucina/? High bandwidth (2.5Gbps over 200-500m)? a graded index (GI) profile? large core fiber → Ease of handling and connection,
Low installation costs• Compatibility withcommercially available
transceivers of Multi Modeglass optical fiber(MMF),
especially 850nm LED,780nm LD, and 850nm
VCSEL transceivers

http://www.arib.or.jp/mmac/download/m0003_3.pdf

An example of POF application to home-network? POF and twist-pair will provide ultra-high speed
But? Please image that, all appliances will need suchhigh speed?, e.g., turning the light on/off.
? ==> PLC will complement them seamlessly.

Conventional PLC products (1)? for the traditional appliance-control, or
home-automation? CEBus, LONtalk, X-10, SMART HOUSE, BatiBUS,

European Home System, European Installation Bus, Japan'sHome Bus System.

? for PC modem? some products around 100kbps

Conventional PLC products (2)http://hometoys.com/htinews/aug97/articles/kwacks/kwacks.htm

Conventional PLC products (3)Standards for home-automation• X-10: registered trademark of X-10 (USA) Inc. • HBS: Home Bus System(Japanese standard for home
• LonTalk: technology of Echelon Corporation
networks. Established in 1988 by the• EIB: European Installation Bus
Electronic Industries Association ofJapan.)• HES: an international standard

Conventional PLC products (4)CEBus (1)? Consumer Electronics Bus (CEBus) : an open standard
EIA-600, developed by the Electronics Industries
Association (EIA)? since 1984
? power-line (SS/chirp modulation), twist-pair, coaxial
cable, IR, RF, optic fiber? Home Plug & Play (HomePnP)? The HomePnP Task Force was formed in late 1995 by
Honeywell, Intel, Microsoft and Thomson Consumer
Electronics? utilizes the Common Application Language (CAL, EIA-721)
for a transport-independent application protocol.

Conventional PLC products (5)CEBus (2)? SCP/CEBus ---- Microsoft? Microsoft has announced its Simple Control
Protocol (SCP), that is a protocol based on CEBus
lowest layer standard definition. SCP and CEBus
devices can coexist on the same network. In the
future, quite likely SCP will replace CEBus.
• SCP: a lightweight, royalty free networking
technology for devices such as smart
appliances and home control products.

Principle of PLC

Electric (& telephone)pole, Japan

6,600V
100V+100V
telephoneTrans.

CATV

Power meterPrinciple of PLC

Merit of PLC? No new wire
? Appliances are already connected to power-line? Available area is wider than radio waves, in indoorcommunication(, in general)? no obstacle such as walls to propagate a signal? At Sakura elementary school in Ehime, we
demonstrated that PLC of 100kbps was possibleat all wall sockets, from 1st floor to 3rd floor, 18classrooms.
? IEEE802.11b LAN was limited to the visiblearea. Beyond a wall, its quality degrades somuch.

Demerit in the conventional PLC using low frequency
band

http://www.echelon.com/products/Transceivers/PLTPresentations/PLTechnology.pdf

High noise from appliances (1)? Noise is additive.
? Dominant noise iscolored, and modeled asa decreasing function of
frequency

The lower frequency
components of transmitting
signals should be suppressedcompared to the higher ones.

High noise from appliances (2)IH cooking heater: periodic noisePower-line
noise at highfrequency band
? Low noiselevel

receives benefitof EMC
regulation

EMC regulation
Limits of CISPR (theInternational Special
Committee on RadioInterference) Pub.11,15,22? Pub.11 (Group2 Class B):
ISM equipment, Microwaves? Pub.15: Fluorescent Lamps,
Luminary? Pub.22: ITE (Information
Technology Equipment;
printer, PC, display, etc.).
? Class B: The equipment
which is used inresidential area.

Required dynamic
range is 80dB

Low impedanceWhat causes attenuation? (2)

PLC channel modelWhat causes attenuation? (3)Appliances’ impedance (1)In low freq.
? 0.? Ω -- ?0Ω
<-- EMC
capacitors
In higher freq.
? Gradually
increases <-inductance (L)? dispersion
decreases

Appliances’ impedance (2)4 types’ resonance (1)Dip typerise typeAppliances’ impedance (3)4 types’ resonance (2)inductance typeflat typeAppliances’ impedance (4)Why
Symbolthe resonanceNameoccurs?
Function
L1

Common mode
choke coil

Suppresses common mode noise.

capacitor(Y-capacitor)differential mode noise.

Noise Suppression Model for Ordinary Switching Power Supplies
Acrossthe supplies,
line
Suppresses
differential
mode noise.
power
noise filters
are installed
as shown? InCLswitchingcapacitor noise being conducted to the AC power supply
below to suppress(X-capacitor)
cable. The capacitor is used as a bypass for noise, and the coilpreventsnoise
conduction to
the cable
by increasing
CB1
Line bypass
Suppresses
commonmode noiseline
and impedance.
CB2

http://www.iijnet.or.jp/murata/products/english/catalog/emc/noise/k_3/acpwr_2.html

Appliances’ impedance (5)Why the resonanceoccurs? (2)? Functions of
Respective Noise
Filters

http://www.iijnet.or.jp/murata/products/english/catalog/emc/noise/k_3/acpwr_8.html

Appliances’ impedance (6)Why the resonance occurs? (3)Example of impedance(Z) -frequency
characteristic of aceramic capacitor? Z (min) < 1Ω
? Freq. of Z (min.)depends on usedcapacitors.
Solution of the low impedance due to the EMC capacitor• Impedance upper made of inductance is connected in series.
---> The size of inductance for 15A is very big and its cost
reductionis difficult!!
http://www.iijnet.or.jp/murata/products/japanese/catalog/c16j4.pdf

What causes attenuation? (3)Appliances’ impedance and its dispersion.
(54 appliances, 89 on/off states)
Gradually decrease

Influence of AC cords

What causes attenuation? (4)Influence of the length of AC-power-supply
cord on the appliance's impedance
Imp. of the cord
Imp. of the charger(distributed constant)(lumped constants)(a) frequency axis in log scale(b) frequency axis in liner scale

Impedance of a battery charger with a cord of length 0m,1m,2m,5m.

Influence of the length of AC-power-supply cord on the appliance's
impedance (2)Equivalent circuit of the battery charger
Z^(t) : is given as a cascade connection ofZ^(1) and Z^(2).

Z^(1) : four terminal
network, composed of a
distributed constantcircuitZ^(2) : two terminal
network, composed of
lumped constants

These values are similar tothe distributed constants of a
VVF cable

Influence of the length of AC-power-supply cord on the appliance's
impedance (3)Equivalent circuit of the battery charger (2)? The distributed constants of Z^(1)? R=0.400[ Ω /m], L=650[nH/m], G=0.600[m MHO /m], C=40.3[pF/m](a) frequency axis in log scale(b) frequency axis in liner scale

What causes attenuation? (4)Power-lines’ impedance and its dispersion.
(24 outlets of Lab.)Transfer function (loss property) between thesame-phase outlets (in Lab., 44 cases)<450kHz & >30MHz: not stable

1M〜20MHz: small loss

Transfer function comparison between thesame-phase and the split-phase
Phase coupling loss:≒10dB at low freq. No phase couplingloss at >1MHz

same-phase outlets

split-phase outlets (in the sameLab., 47 cases)

What causes attenuation? (2)Phase Coupling loss

? Same Phase Communication

6,600V

http://www.intellon.com/docs/appnotes/26001087.pdf

Phase Coupling loss (2)“Split” Phase Communication

Phase Coupling loss (3)Phase to Phase Communication
Through a Coupling Device

Demerit in the conventional PLC using low frequency band

Signal distortion (1)? If the impedance-frequency characteristic
is static, the equalization is possible.
? If not (i.e., the characteristic changes
dynamically), it is not easy!

Signal distortion (2)Switching model of power-line channel (1)? Input AC voltage and current of a switchmode power
supplySwitching model of power-line channel (2)Transfer function model of a power-line towhich a TV is connected? Switching rate: 240 times/sec

Switching model of power-line channel (3)Waveform distortion

Characteristics of power-line as a communication channel

Summary? Why the high frequency band is suitable for high speed
PLC?
Frequency
band
Noise
Attenuation

Low(<450kHz)HighHigh (a)Phase couplingloss
Signal distortion Large
Static(1),switchingHigh(>1MHz)Low
Low

Smaller
Static (2)note
EMC regulation(a)low
impedanceofappliances(1) resonanceofEMC
capacitors(2) multipath

High-speed/reliable products (1)? Modulation technique? multi-carrier, e.g., OFDM, or? spread-spectrum (SS).
? Protocol? Handshake base protocols for the robustness, and? QoS(Quality of Service) support? token passing? CSMA/CA

Nikkan-kougyou shinbun, 2001.1.18 (Japanese)

implemting it on the chip

High-speed/reliable products (2)HomePlug

USA

BPS
10M

10M
10M

NOTE
Based on Intellon’s
technology
partnership with Microsoft(SCP)
Multi home token passing

Itran

Israel

1.5M-2.5M-

3M
3M
1M

Member of HomePlug
business relationship with
ThomsonVery low-cost ($3)
10k-450kHz
Internet Access

Adaptive
USA
Networks
CogencyCanada10M
Inari (Intelogis)
USA 2M, 12M
Nsine
Mitsubishi
Siemens

EnglandJapan
GermanyProto-type is available.

High-speed/reliable products (3)Protocolhttp://miyabi.ee.ehime-u.ac.jp/~tsuzuki/PLC/hiSpeed.html

High-speed/reliable products (2)Direct Sequence/Spread Spectrum(DS/SS) modulation• spreading factor: W/R=15=number of chips

Spread Spectrum (SS)demodulation (1)Spread Spectrum (SS)demodulation (2)? In the demodulation,? the received spread-signal can be demodulated to bea narrow signal.
? On the other hand, the noise is spread so that its
P.S.D. becomes low.
○ Therefore, SS modulation is robust to the noise.
× Since the SS modulation consumes a broadfrequency range, it is not easy to realize highspeed PLCs. CDMA(Code Division Multiple Access)technique is needed additionally.

BPLM-100B(Busicom, Japan)? IC: Adaptive
Networks? 300bps 100kbps? DS/SS
modulation? token-passingIH (Induction Heating / Induction
Heater) cooking-heater

BPLM-100B +IH-heater

BPLM-100B + IH-heater
SS is robust to the noise.

Multi-carrier modulation for the reliablecommunication? 2 carriers’ example: PLT-22 of Echelon Co.
• fixed 2 carriers of 132kHz
and 115kHz• 5kbps• BPSK (Binary Phase Shift
Keyingcf. Echonet (type B)• variable 3 carriersPLT22 (2)Narrow band interference’s case

? When SNR>37dB,? uses only primary carrier(signal=14dBm, noise=-23dBm)? When SNR<17dB,? uses only secondary carrier(signal=14dBm, noise=-2.7dBm)

PLT22 (3)Residential power-line noise’s case
? Both carriers were usedalternatively, but
communication was impossible.
Cf. Echonet Power-Line model? length: 21m? branch:5? inverter fluorescent- lamp: 24? incandescent-lamp: 2

Residential power-line noise’s case (2)SNR in high frequency band (1)? Noise is the decreasing
function? >3MHz: good SNR can be
expectedResidential power-line noise’s case (3)SNR in high frequency band (2)? Spectrum of a handmade BPSKtransmitter of 200kbps? carrier frequency is variable.

? In general, SNR in the highfrequency is better.
? Adaptive selection of carrier
frequency is needed to achieve
the high-speed & reliablecommunication.

http://www.inari.com/2mbps/2mbps_spec.html

High-speed/reliable products (3)Inari (formerly, Intelogis): IPL0201? Number of carrier: 4? Trans. Bandwidth: 3M - 8MHz
? bit rate:? 〜2.01Mbps for QPSK
? 〜1.01Mbps for BPSK
? Evaluation broad: available? Access protocol:? DSMA (Datagram Sensing
Multiple Access)? Centralized Token Passing? QoS control: possible(guaranteed bandwidth:〜460kbps)? Security? 32-byte encryption array? 256-bit Diffie-Hellman public
key exchange? Packet level authentication

Standardization activity (1)Standardization activities(cf.http://www.inari.com/tech/standards.html)? CEA R-7.3 Committee? The R-7 Committee is part of the Consumer Electronics
Association which is part of Electronic Industry Association? with the intention of deciding a standard sometime in 2001.
? (Microsotf, ITRAN)? HomePlug Powerline Alliance (HomePlug), U.S.A? for a high-speed PLC of 10Mbps
http://www.homeplug.org/docs/website_2.20.ppt

Standardization activity (2)? Echonet Consortium, Japan? support home networks that are committed to energy
conservation, boosting security, enhancing homehealth care, etc.
? will use power lines, radio frequency and infra-red toprovide a low-cost implementation of datatransmission without requiring additional wiring.
? The ECHONET Specifications V1.0 was disclosed tothe public on July 26, 2000.
Note: The PLC forum is NOT involved in creating power-line specifications.

Regulation? Standardization activities for a high-speed PLC, e.g.,
HomePlug)? However, the Japanese regulation is too severe to
introduce such standards.
? Deregulation is required in order to activate researchand development more.

American Regulation(FCC CFR47 Part 15. Radio Frequency Devices)
TYPE(conventional) Powerline-carrier system(for high speed PLC)
Carrier current system
Of an
Unintentional-radiators[§15.109(e)]FREQUENCNOTEY RANGE
9k- 490kHz used by an electric[§90.63(g)] power utility entity[§15.113 ]e.g.,radiated emission limits :1.705M–
30μV/m at 30m distance
30.0MHz[§15.209]
conducted limits: none[§15.107]

The frequency band from 9kHz to 30MHz:
Unless the radiated emissions fall in the restricted bands, as
defined in §15.205(a), it is free to use, in principle.

conventional power line carrier system, definedin FCC
defined as: [47CFR15.3(t)]? An unintentional radiator employed as a carrier
current system[47CFR15.3(f)] used by an electric
power utility entity on transmission lines for protective
relaying, telemetry, etc. for general supervision of thepower system.
? The system operates by the transmission of radio frequency
energy by conduction over the electric power transmission
lines of the system. The system does not include thoseelectric lines which connect the distribution substation to thecustomer or house wiring.

Comparison between Japaneseand American(FCC) regulation
Conve
ntional
PLC

OthersFrequency
range
Tx powerlimit

Frequency
range

radiatedemission
limit

FCC
9k-490kHzJapan
10k-450kHz

minimum power
possible [§15.113]

350mW for PSK

Free in principle,
excluding a specificfrequencies[15.205(a)]30μV/m at 30m
distance [§15.209]

Modulation
schemelimit:PSK,ASK,SS
Bit rate limit:
30kbps for PSK

none

Japanese activities? Echonet? OpenPLANET? Internet service

Echonet

http://www.echonet.gr.jp/spec/spec_v10_e.htm

Echonet? Type A (Matsushita, et.al.)? Spread Spectrum (No spreading code is specified.
Differential coding. Sub-band Delay Detection.)? 9600bps? Available PHY-IC: SMK co.Ltd. (2000.10〜)? Type B (Mitsubishi, et.al.)? Multi-carrier (3 variable carriers,
DQPSK/DBPSK/D8PSK)? variable rate (4.06k〜36.5kbps)? IC will be available from 2001.2Q (?)

Japanese PLC network configuration (1)Japanese PLC network configuration (2)Note on Security issue? When the blocking filter exists? no problem? When the blocking filter does not exist, the signal
goes out; Intercept is possible.
? Applications, like Internet access service, is notsecure.
? Presently, the standardized encryption, such as
IEEE802.11’s, does not exist.
? Interoperability is the problem.
? Complementing technology of higher layers,
such as IPsec, VPN, etc., must be used.

Open Platform for Appliances Networking
http://www.openplanet.co.jp/html-e/e-index.htm

Kyushu Electric Power Co.,Inc.,

Internet access service (1)Field test
? 300 houses? until Mar. 2001
? 10kHz - 450kHz? max 3Mbps? 5 slavestations@masterstation on a pole
? collaborates with
Mitsubishi electric Co.

PC

PLC modem

http://pcgaz.nikkeibp.co.jp/pg/pcgaz/minicol/2/col_45.shtml, (2001/02/13)

Internet-access-service experiment

Hokkaido Electric Power Company (HEPCO),
collaborates with Toshiba Co. and Power Net Com, Japan•http://www.hepco.co.jp/press/h12/0126a.html•Asahi newspaper, 2001.1.27•Period: 2001.2〜2002.3•Place: company houses in Sapporo city
•7,000km fiber-optic network, already installed in Hokkaido•Target service speed: 1.5Mbps
100V

internet

Incoming line

Optical fiber

Incoming line
Incoming line

modem

100V

HEPCO

Incoming line

Optical fiber
modem

Incoming
line

ApartmentConclusion? By introducing multi-carrier modulation technique,? about 1Mbps for low (conventional) frequency band(<450kHz)? more than 10Mbps for high frequency band(<30MHz)will be realized in this year.
? The reason why the high frequency band is promising
was explained.
? To use the band, de-regulation is needed in Japan.