Power Line Communication Technology Update By Walter Downey and Phil Sutterlin Echelon Corporation 415 Oakmead Parkway Sunnyvale, CA 9486 1-888-ECHELON (888-324-3566) www.echelon.com 1
Power Line Communications ❿ Power lines are designed for delivering power not data ❿High noise ❿High attenuation ❿Signal distortion ❿ It takes a sophisticated modem to communicate reliably 2
What Causes Attenuation? Panel Transmitting Node 7Vpp 6dB Attenuation 7Vmpp Receiving Node ❿Voltage dividers ❿Wiring inductance ❿Shunt loads Panel loading EMC capacitors ❿Phase coupling loss Attenuation(dB) = 2*LOG 1 (V transmit /V receive ) 3
Power Line Attenuation in Homes 3 1% Number of socket pairs 25 2 15 1 5 96% are =54 db Attenuation 9% 8% 7% 6% 5% 6 121824336424854666727884 Attenuation (db) ❿World wide home attenuation results ❿ 1,889 randomly selected socket pairs ❿ 169 houses, apartments, condominiums ❿ 5 countries ❿ Data taken at 132 khz 4
Noise Sources ❿ Dimmers ❿ Triac controlled lights ❿ Produce large impulses at 1Hz or 12Hz ❿ Switching power supplies ❿ Fundamentals at 2kHz to >1MHz ❿ Rich in harmonics ❿ Power line intercoms ❿ 3V pp to 7V pp from 15kHz to 4kHz ❿ Universal series wound motors ❿ Vacuum cleaners, kitchen appliances, drills ❿ High repetition rate impulses 5
Dimmer Noise Line Neutral Dimmer ❿ Characteristics: ❿ Large 2V to 5 Volt impulses ❿ Repetition rate 1Hz or 12Hz ❿ Ringing tail ~15kHz -6 db Packet Magnification = 25X 5 V/div 2 mv/div.2 ms/div.2 ms/div 6
Switching Power Supply Noise Line Neutral 15k-1MHz Switching Power Supply ❿ Characteristics: ❿ Oscillator 2kHz to >1MHz ❿ Conducts oscillator noise onto power line ❿ Frequency often varies with load ❿ Harmonics can be large Level dbv -1-2 -3-4 -5-6 2mV/div PLT-22 Packet Switching Supply Noise -7-8 -9.1.2.3.4.5.6.7.8.9 1 1.1 Frequency (MHz) 2 ms/div 7
Intercom Noise Amp 15k-5kHz Power Line Intercom or Baby Monitor Line Neutral ❿ Characteristics: ❿ ~ 3kHz bandwidth ❿ Typically 15kHz to 5kHz ❿ Output Level up to 7V pp ❿ Harmonics can be large 2 1-1 Intercom + Harmonics Level dbv -2-3 -4-5 PLT-22 Packet 5 V/div -6-7 -8-9.1.2.3.4.5.6.7.8.9 1 1.1 Frequency (MHz) 2 µs/div 8
Universal Series Wound Motors ❿Characteristics: ❿ Impulse noise ❿ Rep rate of few kilo-hertz ❿ Wide band spectrum -1-2 Level dbv -3-4 -5-6 5 mv/div -7-8 -9.2.4.6.8 1 1.2 Frequency (MHz) 1 ms/div 9
Distortion Amplitude (db) -1-2 -3-4 -5-6 -7-8 -9-1 Phase Amplitude 1 1 1 Frequency (khz) 9 45-45 -9-135 -18-225 -27-315 -36 Phase (degrees) ❿ Non-flat frequency response ❿ Non-linear phase response ❿ Time varying impedance 1
Communication Options ❿Phase Locked Loop - Based Narrow Band ❿ Amplitude Shift Keying ❿ Frequency Shift Keying ❿ Phase Shift Keying ❿Correlator - Based Spread Spectrum ❿ Direct Sequence ❿ Chirp ❿ Frequency Hop ❿ Digital Signal Processing - Based BPSK ❿ Dual Carrier Frequency Operation ❿ Impulse Noise Cancellation ❿ Adaptive Distortion Correction 11
Narrow Band Transmission Data 1 Sine Wave Carrier Amplitude Modulator Amplitude Shift Keying (ASK) 1 Data 1 Sine Wave Carrier Frequency Modulator Frequency Shift Keying (FSK) 1 Data 1 Phase Modulator Phase Shift Keying (PSK) Sine Wave Carrier 1 ❿ In practice the waveforms are shaped to contain their spectra 12
PLL Based Narrow Band Reception ❿ Phase shift keyed receiver example: XI XI LPF I 1 1 Carrier Phase Locked Loop Oscillator 9 Carrier 9 XQ XQ LPF Q 13
What is Spread Spectrum? ❿ A method of transmission where: ❿ The transmitted signal occupies a bandwidth considerably greater than the minimum necessary to send the information and... ❿ Some function other than the information being sent is employed to determine the resulting modulated bandwidth. Data 1 Spreading Signal Modulator Sine wave carrier Phase Modulator Spread Carrier Spread Spectrum Transmission 1 ❿ In practice, a pre-spread carrier waveform may be stored in ROM 14
Spread Spectrum Transmission Data 1 ø Mod Sine wave carrier Phase Modulator Spread Carrier 1 Direct Sequence Data 1 f Mod Sine wave carrier Phase Modulator Spread Carrier 1 Chirp Data 1 f Mod Sine wave carrier Phase Modulator Spread Carrier 1 Frequency Hop ❿ In practice, the waveforms are shaped to control their spectra 15
Spread Spectrum Reception Spread Spectrum Input N samples covering one bit time... 1 25µs/div Sample Clock Pattern Matching Circuit Parallel Correlator 1 Degree of Match Correlation 25µs/div... N sample reference pattern Corresponding to an ideal bit ❿ To contain cost the spread spectrum input is digitized to a single bit in amplitude 16
What Does Spread Spectrum Do? ❿ Aids performance with medium level tones and impulses ❿ The maximum improvement set by the degree of spreading (process gain) ❿ The process gain of a 1kbps, 1kHz-4kHz signal is 15dB (1*log3) ❿ In practice, this gain is only a few db ❿ Increases susceptibility to signal distortion ❿ Requires distortion correction ❿ Not recommended for residential applications TV sets are the most common source of distortion ❿ Degrades tonal noise rejection ❿ Wider receive bandwidth picks up more large amplitude interference 17
Distortion Characteristics ❿ Narrow band signals are subject to much lower levels of distortion than wide band spread spectrum signals Attenuation (db) -1-2 -3-4 -5-6 -7-8 -9-1 1 1 1 1kHz 1kHz 1MHz 9 45-45 -9-135 -18-225 -27-315 -36 Phase (degrees) 9-1 PLT-22 Frequency Range 45-2 -3-45 -4-9 -5-135 -6-18 -7-225 -8-27 -9-315 -1-36 127 129 131 133 135 9-1 Spread Spectrum Frequency Range 45-2 -3-45 -4-9 -5-135 -6-18 -7-225 -8-27 -9-315 -1-36 1 2 3 4 18
Distortion Consequences 1 Linear channel 1 1 Amplitude (db) Narrow -7 Narrow -8 Band Band -9 Receiver Receiver -1-1 -2-3 -4-5 -6 Phase Amplitude 1 1 1 Frequency (khz) 9 45-45 -9-135 -18-225 -27-315 -36 Phase (degrees) Spread Spread Spectrum Spectrum Receiver Receiver Linear channel 1 1 1 Distorted channel distorted channel Decoder Waveforms Correlation Waveforms ❿Spread spectrum requires much more correction 19
Tone Immunity TX Pkt 55dB Atten.. RX Noise Ampl Freq ❿ Level of interfering tone which can be tolerated while receiving a 55dB attenuated packets +1 Interfering Tone Level (dbv) -1-2 -3-4 -5 PLT-22 PLT-22 has 2 to 55 db better tone immunity PLT-21 Spread Spectrum -6 1k Frequency (Hz) 1M 2
Impulse Noise Cancellation TX Pkt Atten Atten Pkt RX Impulse Noise ❿ Digital Signal Processing can overcome impulse noise limitations of narrow band systems Errors Dimmer & 66dB Atten Pkt Conventional PLL based Narrow Band Receiver...11XX1... 5µs/div 1V/div 5µs/div DSP Receiver with: ❿ Dual Carrier Operation ❿ Impulse Noise Canceler ❿ Distortion Correction No Errors...111... 5µs/div 21
Which Technology is Best to Use? Spread Spectrum Dual Frequency Narrow Band Motor and Dimmer noise sources Switching power supplies and Intercoms TVs and other distortion sources Regulatory considerations ❿ Echelon is uniquely qualified to answer this question Echelon is the only company to have fielded both 22
Dimmers and Motors RX TX Pkt Var Atten.. Noise 5 Attenuation Tolerance 5 % Packet error rate 4 3 2 1 DSP-based PLT-22 Spread spectrum % Packet error rate 4 3 2 1 Spread spectrum DSP-based PLT-22 1 2 3 4 5 6 7 8 Attenuation (db) 1 2 3 4 5 6 7 8 Attenuation (db) ❿ Either technology works well in the presence of light dimmers and motor noise ❿ Other impairments must be considered when comparing these two technologies 23
Switch Mode Power Supply RX TX Pkt Var Atten.. Noise % Packet error rate 5 4 3 2 1 Spread spectrum DSP-based PLT-22 1 2 3 4 5 6 7 8 Attenuation (db) ❿ Spread Spectrum has problems with tonal noise ❿ The dual carrier PLT-22 performs far better ❿ Even though a harmonic of this SMPS is directly in the PLT-22 s primary carrier frequency range 24
Switch Mode Power Supplies Attenuation Tolerance (The higher the number the better) TX Pkt Var Atten.. RX SMPS ❿ Compact Fluorescent Lights - 2 randomly selected units Spread spectrum PLT-22 34dB 64dB 43dB 69dB ❿ Electronic Halogen Lights - 2 representative samples Spread spectrum PLT-22 1dB 52dB 17dB 57dB ❿ Electric Toothbrush - A leading brand unit Spread spectrum PLT-22 2dB 56dB ❿ Spread Spectrum has problems with tonal noise ❿ The dual carrier PLT-22 performs far better 25
Power line Intercoms and Baby Monitors RX TX Pkt Var Atten.. Intercom ❿ Tolerable attenuation between transceivers Intercom DSP Based PLT-22 Spread Spectrum Enhanced Spread Spectrum Realistic 43-218B 52dB 8dB 7dB Command WI-3S 58dB 6dB 5dB Radio Shack 43-27C 55dB 6dB 6dB ComTalk GEE-825 53dB 9dB 1dB 26
Performance with TV Sets ❿ 28 randomly selected TV s were tested: W (14 different brands with screen sizes from 13 to 35 ) TX Pkt 15m (5ft) Distorted Pkt RX ❿ Spread spectrum transceivers were unreliable with 1/4 of the TVs I (>25% physical layer packet error rate with 1 of every 4 TVs) ❿ The DSP based PLT-21/22 worked reliably with all 28 of the TVs I H(<1% physical layer packet error rate with each TV) 27
Regulatory Considerations ❿ North American Regulations: PLT-21 Transmit Signal General Use General Use Prohibited Prohibited 1kHz 2kHz 3kHz 4kHz 5kHz 6kHz 7kHz Frequency Band Designations: Band Designations A "A" B "B" "C" C D "D" Electricity Suppliers Electricity Suppliers Electricity and Their Suppliers Licensees and Their Licensees Consumer Use No Protocol Consumer Use Consumer Use with Protocol With Protocol Consumer Use No Protocol Prohibited ❿ CENELEC Regulations (Europe) : PLT-21 Transmit Signal 2kHz 4kHz 6kHz 8kHz 1kHz 12kHz 14kHz 16kHz 28
Performance Summary ❿ Which technology is best? Spread Spectrum Dual Frequency Narrow Band Motor and Dimmer noise sources Switching power supplies and Intercoms TVs and other distortion sources Regulatory considerations ❿ The Dual Frequency PLT-22 has superior performance 29
The PLT-22 Transceiver ❿ World-wide operation ❿ Meets CENELEC, FCC, Industry Canada and Japan MPT regulations ❿ EIA 79.2 compliant ❿ Advanced Technology ❿ Dual carrier frequency operation ❿ Digital signal processing ❿ Backward-compatible with the PLT-21 ❿ Communicates with the PLT-2 and PLT-21 ❿ Pin-compatible PLT-21 replacement 115kHz C-Band 132kHz ❿ European utility support ❿ Dual frequency DSP performance in the A-Band ❿ New A-band channel Does not communicate with PLT-3 A-Band 75kHz 86kHz 3
Dual Carrier Frequency Mode Single carrier PLT-2 and PLT-21 132kHz Dual carrier PLT-22 115kHz 132kHz ❿ Alternate frequency used when 132kHz is blocked ❿More error correction than 132kHz ❿ Improved 132kHz performance ❿ Better distortion correction ❿ Better discrimination between packets and noise Use with 1999 STDXCVR.TYP file to activate dual carrier mode 31
Backward Compatible Operation ❿ Backward compatible with the PLT-2 and PLT-21 Acknowledged service Unacked repeat service 1st and 2nd try 115kHz 132kHz 1st and 3rd packet 3rd and 4th try 115kHz 132kHz Pilot tone 2nd and 4th repeat ❿ Works even when primary frequency is jammed Noise Transmitting node PLT-22 PLT-2 Receiving node Frequency Noisy Device Receiving node PLT-22 Receiving node PLT-21 Packets 32
PLT-22 Pin Compatibility ❿ Pin compatible with the PLT-21 ❿ Same pin functions ❿ Same pin spacing ❿ Smaller outer dimensions than PLT-21 ❿ Supplied as an un-coated SIP Pin 1 marking 39.mm (1.54 ) max 6.mm (.24 ) max 19.3mm (.76 ) max PLT-21 dashed line PLT-22 solid line Be sure the PLT-22 does not contact other conductive components 33
PLT-22 Power Line Technology Superior Performance Backward Compatible Low Price 34