UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Data communications using coherent minimum frequency shift keying on intrabuilding polyphase power.. 1985

You don't seem to have a PDF reader installed, try download the pdf

Item Metadata

Download

Media
UBC_1986_A7 C48.pdf [ 13.55MB ]
Metadata
JSON: 1.0064794.json
JSON-LD: 1.0064794+ld.json
RDF/XML (Pretty): 1.0064794.xml
RDF/JSON: 1.0064794+rdf.json
Turtle: 1.0064794+rdf-turtle.txt
N-Triples: 1.0064794+rdf-ntriples.txt
Citation
1.0064794.ris

Full Text

DATA COMMUNICATIONS USING COHERENT MINIMUM FREQUENCY SHIFT KEYING ON INTRABUILDING POLYPHASE POWER LINE NETWORKS by Frank Kwok King Chiu B.A.Sc U n i v e r s i t y of B r i t i s h Columbia, 1983 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE i n THE FACULTY OF GRADUATE STUDIES (Department of E l e c t r i c a l Engineering) We accept t h i s t h e s i s as conforming t o the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA December, 1985 (E) Frank Kwok King Chiu, 1985 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of £/ec^c*J? Zmp^eerjy, The University of British Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date ABSTRACT The s u i t a b i l i t y of Coherent Minimum Frequency S h i f t Keying (CMFSK) modulation f o r data communications on polyphase i n t r a b u i l d i n g power d i s t r i b u t i o n c i r c u i t s i s examined. An a c t u a l modem was designed and implemented. Average b i t e r r o r r a t e (BER) versus r e c e i v e d Eb/No measurements were taken f o r an i n d u s t r i a l , commercial, and r e s i d e n t i a l power l i n e environments at 1.2kbps, 4.8kbps, and 19.2kbps data r a t e . The 19.2kbps BER measurements i n d i c a t e t h a t a m a j o r i t y of e r r o r s are caused by impulses o c c u r r i n g i n the power l i n e s , w h i le other e r r o r s a r e caused by momentary r e d u c t i o n s of r e c e i v e d Eb/No. Occurance of e r r o r s c o i n c i d e s mostly with impulses on the power l i n e which are h i g h l y p e r i o d i c with the ac mains v o l t a g e . In a d d i t i o n , the BER measurements r e v e a l t h a t CMFSK modulation a t 1.2kbps and 4.8kbps data r a t e i s l e s s a f f e c t e d by impulse n o i s e than at 19.2kbps. T h i s f i n d i n g i s a t t r i b u t e d t o the i n c r e a s e d r e s i s t a n c e t o impulse n o i s e e f f e c t s as the b i t d u r a t i o n i s i n c r e a s e d . A baseband spectrum s p r e a d i n g technique i s proposed and s u c c e s s f u l l y t e s t e d t o implement low data r a t e t r a n s m i s s i o n s . Spread spectrum s i g n a l l i n g overcomes p o t e n t i a l narrow band impairments by sending a wide 1 band s i g n a l over the power l i n e s . In a d d i t i o n , the reduced power s p e c t r a l d e n s i t y of the spread spectrum t r a n s m i s s i o n reduces narrow band i n t e r f e r e n c e t o other power l i n e communications u s e r s as well as AM r a d i o s and a l l o w s higher output power t o compensate f o r path a t t e n u a t i o n s . — i i i — TABLES OF CONTENTS ABSTRACT i i TABLES OF CONTENTS i i i LIST OF TABLES v LIST OF ILLUSTRATIONS v i i ACKNOWLEDGMENTS x 1. INTRODUCTION 1 1.1 Communications over E l e c t r i c Power L i n e s . . . . 1 1.2 O u t l i n e of T h e s i s 4 2. DISCUSSION OF COMMERCIAL POWER LINE MODEMS 6 2.1 BSR X-10, A Remote C o n t r o l f o r L i g h t s and A p p l i c a n c e s 6 2.2 NON-WIRE Power L i n e Modem 7 2.3 ExpertNets Power L i n e Modem 8 2.4 C o n s u l t a n t ' s Choice Power L i n e Modem 8 2.5 Commercial Power L i n e Modem Technology 8 3. POWER LINE TRANSMISSION CHARACTERISTICS . . . . . . . 11 3.1 I n d u s t r i a l B u i l d i n g Power L i n e Transmission C h a r a c t e r i s t i c s 11 3.2 R e s i d e n t i a l B u i l d i n g Power L i n e Transmission C h a r a c t e r i s t i c s 25 4. POWER LINE NOISE 29 4.1 Power L i n e Noise C h a r a c t e r i s t i c s . 29 4.2 Cross S e c t i o n a l Power L i n e Noise C h a r a c t e r i s t i c s . 33 5. CMFSK POWER LINE MODEM DESIGN CONSIDERATIONS 35 5.1 Power L i n e Modem Design C r i t e r i o n . . . 35 5.2 Design O b j e c t i v e s of a CMFSK Power L i n e Modem . . 37 5.3 Design of a CMFSK Power L i n e Modem 39 5.4 CMFSK Modem T r a n s m i t t e r D e s c r i p t i o n 41 5.5 CMFSK Modem Receive r D e s c r i p t i o n . 41 6. PRELIMINARY CMFSK TESTS TO SELECT SIGNALLING PARAMETERS 47 6.1 CMFSK B i t E r r o r Rates i n AWGn 47 6.2 S p e c t r a l Comparison of an PN Sequence and i t s CMFSK Output 47 6.3 CMFSK C a r r i e r Frequency S e l e c t i o n . . . 51 — i v — 6.4 BER Measurement -for CMFSK i n a 'Remote' Reception 56 7. BER MEASUREMENT RESULTS IN VARIOUS ENVIRONMENTS AND AT VARIOUS DATA RATES 59 7.1 I n t e r f l o o r / I n t e r p h a s e I n d u s t r i a l BER measurements at 1.2kbps, 4.8kbps, and 19.2kbps 59 7.2 I n t e r f l o o r / I n t e r p h a s e Apartment BER measurements at 19.2kbps 60 7.3 I n t e r f l o o r / I n t e r p h a s e R e s i d e n t i a l BER measurements at 19.2kbps 61 7.4 Cross S e c t i o n a l BER Performance at 19.2kbps i n an I n d u s t r i a l B u i l d i n g 61 7.5 C l a s s i f i c a t i o n of Power L i n e Induced E r r o r s . . . 74 7.6. D i s c u s s i o n on Power L i n e Impulse Noise Suppression Techni ques 74 8. SPECTRUM SPREADING 83 8.1 D i s c u s s i o n of Spread Spectrum i n Power L i n e Data Communications . . . . . . 83 8.2 P o t e n t i a l Spread Spectrum A p p l i c a t i o n s i n O f f i c e and R e s i d e n t i a l Power L i n e Communications . . . . 87 8.3 B e n e f i t s of Spread Spectrum i n Low Data Rate Communications 89 8.4 A p p l i c a t i o n of Databand Spread Spectrum i n the CMFSK Power L i n e Modem 91 8.5 Code S y n c h r o n i z a t i o n u s i n g a D i g i t a l Matched F i l t e r 93 8.6 T o l e r a n c e t o Power L i n e Small E r r o r B u r s t s by I n t e r l e a v i n g . . . . . 94 8.7 Experimental R e s u l t s f o r I n t e r l e a v e d Spread Spectrum Data Tran s m i s s i o n s 96 9. CONCLUSIONS 105 9. 1 Summary 105 9.2 Cost Estimate of the CMFSK Modem 107 9.3 Recommendations f o r F u r t h e r Research 107 REFERENCES 110 BIBLIOGRAPHY 115 APPENDIX A. Power L i n e Noise S p e c t r a l D e n s i t y Determination 116 APPENDIX B. Schematics of CMFSK T r a n s m i t t e r and Receiver 123 V LIST OF TABLES Table 4.1 I n d u s t r i a l Power L i n e Noise S p e c t r a l D e n s i t y . . 30 Table 4.2 R e s i d e n t i a l Power L i n e Noise S p e c t r a l D e n s i t y . 30 Table 4.3 I n d u s t r i a l Power L i n e Noise S p e c t r a l D e n s i t y on Four High A c t i v i t y and Four Low A c t i v i t y Days . 34 Table 5.1 Coupled Power i n t o the Power L i n e @ 120kHz . . . 43 Table 6.1 1.2kbps, 4.8kbps, and 19.2kbps BER r e s u l t s i n A d d i t i v e White Gaussian Noise 48 Table 6.2 'Remote' Interphase 19.2kbps BER ver s u s Eb/No a t Tr a n s m i t t e r Output of IV, 2V, 3V, and 4V at Two D i f f e r e n t C a r r i e r F requencies of 60kHz and 120kHz 55 Table 7.1 I n t e r f l o o r / I n t e r p h a s e 19.2kbps BER versus Eb/No at T r a n s m i t t e r Output of IV, 2V, 3V, and 4V i n an I n d u s t r i a l B u i l d i n g 62 Table 7.2 I n t e r f l o o r / I n t e r p h a s e 4.8kbps BER v e r s u s Eb/No at T r a n s m i t t e r Output of .IV, i.2V, .4V, and 2.5V i n an I n d u s t r i a l B u i l d i n g 64 Table 7.3 I n t e r f 1 o o r / I n t e r p h a s e 1.2kbps BER ver s u s Eb/No at T r a n s m i t t e r Output of 150mV and 200mV i n an I n d u s t r i a l B u i l d i n g . . . . . . 66 Table 7.4 I n t e r f l o o r / I n t e r p h a s e 19.2kbps BER versus Eb/No at V a r i o u s T r a n s m i t t e r Output i n an Apartment Complex . . . . . * . . 67 Table 7.5 I n t e r f 1 o o r / I n t e r p h a s e 19.2kbps BER v e r s u s Eb/No at V a r i o u s T r a n s m i t t e r Output i n a R e s i d e n t i a l House with a H a i r Dryer 'ON' and 'OFF' 68 Table 7.6 Cross S e c t i o n a l 19.2kbps BER Measurement . . . 75 Table 7.7 19.2kbps BER Measurement of a 4-Level FSK and the CMFSK Modem 79 Table 8.1 3 1 — B i t I n t e r l e a v e r / D e - i n t e r l e a v e r Connections . 98 Table A . l Parameters of 6th Order Band Pass F i l t e r s . . . 118 Table A.2 Parameters of 4th Order Band Pass F i l t e r s . . . 118 Table A.3 Frequency Response of Power L i n e Coupling Terminated at 100k ohm 118 - v i - Tab l e A.4 Frequency Response of Power L i n e Coupling Terminated at 12 ohm 119 Table A.5 Frequency Response of Power L i n e Coupling Terminated at 3.3 ohm . . . . . . . . . . . . . 120 Table A.6 Measured Noise V o l t a g e i n LOW, MID, and HIBH Frequency Band i n an I n d u s t r i a l B u i l d i n g . . . 121 Tab l e A.7 Measured Noise V o l t a g e i n LOW, MID, and HIBH Frequency Band i n a R e s i d e n t i a l House 122 - v i i — LIST OF ILLUSTRATIONS F i g . 3.1 ' L o c a l ' and 'Remote' Transmission Curves on a Weekday Between 8:30am and 4:30pm i n an I n d u s t r i a l B u i l d i n g 14 F i g . 3.2 ' L o c a l ' and 'Remote' Transmission Curves on a Weekday Between 8:30am and 4:30pm i n an I n d u s t r i a l B u i l d i n g . . . . . 15 F i g . 3.3 ' L o c a l ' and 'Remote' Transmission Curves on a Weekday A f t e r 6:00pm i n an I n d u s t r i a l B u i l d i n g . 16 F i g . 3.4 ' L o c a l ' and 'Remote' Transmission Curves on a Weekend Day 17 F i g . 3.5 P i c t u r e s of Received ' L o c a l ' and 'Remote' S i g n a l s a t V a r i o u s F r e q u e n c i e s 18 F i g . 3.6 0° and 180° Phase Transmission Curves i n a R e s i d e n t i a l House 26 F i g . 3.7 Transmission D i f f e r e n c e between the 0° and 180° Phase With and Without a R e s i s t i v e S i g n a l Bypass 27 F i g . 3.8 Extended 0° and 180° Phase Transmission Curves of the R e s i d e n t i a l House 28 F i g . 4.1 Power L i n e Noise i n Three Frequency Bands . . . 31 F i g . 4.2 Power L i n e Noise S p e c t r a l D e n s i t y 32 F i g . 5.1 Block Diagram of CMFSK T r a n s m i t t e r / R e c e i v e r . . 40 F i g . 5.2 CMFSK Modem Power Output Measurement Method . . 42 F i g . 5.3 Block Diagram of D i g i t a l Integrate/Dump . . . . 44 F i g . 6.1 CMFSK Modem White Noise BER Measurement Method . 48 F i g . 6.2 CMFSK Modem White Noise 19.2kbps BER Performance 49 F i g . 6.3 Spectrum of a 19.2kbps, Length 2047 PN Sequence . 50 F i g . 6.4 Spectrum of a 19.2kbps PN code CMFSK Output . . 50 F i g . 6.5 Interphase 19.2kbps BER versus Eb/No curve a t a C a r r i e r Frequency of 60kHz 52 F i g . 6.6 Interphase 19.2kbps BER versus Eb/No curve at a C a r r i e r Frequency of 120kHz . . . . 53 - v i i i - F i g . 6.7 Spectrum of CMFSK output Superimposed on Power L i n e Noise 54 F i g . 6.8 'Remote' Interphase 19.2kbps BER versus Eb/No at a C a r r i e r Frequency of 120kHz 57 F i g . 7.1 19.2kbps BER versus Eb/No Measurement i n an I n d u s t r i a l B u i l d i n g . . . . . . . . . . . . . . 69 F i g . 7.2 4.8kbps BER versus Eb/No Measurement i n an I n d u s t r i a l B u i l d i n g 70 F i g . 7.3 1.2kbps BER versus Eb/No Measurement i n an I n d u s t r i a l B u i l d i n g 71 F i g . 7.4 19.2kbps BER versus Eb/No Measurement i n an Apartment Complex 72 F i g . 7.5 19.2kbps BER ver s u s Eb/No Measurement i n an R e s i d e n t i a l House 73 F i g . 7.6 Impulse Noise Induced B i t E r r o r s . . . . . . . 76 F i g . 7.7 Comparison of 19.2kbps BER of a 4 - l e v e l FSK and the CMFSK Modem 80 F i g . 7.8 Block Diagram of 4-Level FSK Modulator 81 F i g . 7.9 Block Diagram of 4-Level FSK Demodulator . . . . 82 F i g . 8.1 Proposed High Frequency Bypassing and I s o l a t i o n of a Power L i n e Network 88 F i g . 8.2 Proposed Across-Phase Modem Relay . . . . . . . 88 F i g . 8.3 S p e c t r a l Comparison of BSR X-10 and CMFSK Modem . 90 F i g . 8.4 Block Diagram of Databand Spread Spectrum . . . 92 F i g . 8.5 Block Diagram of D i g i t a l Matched F i l t e r . . . . 95 F i g . 8.6 Block Diagram of Inter1eaver/De-inter1eaver . . . 97 F i g . 8.7 Block Diagram of Simple M a j o r i t y L o g i c D e c i s i o n , I n t e r l e a v e d M a j o r i t y L o g i c D e c i s i o n , and C o r r e l a t i o n D e c i s i o n Methods 100 F i g . 8.8 Comparison of 1.2kbps BER Performance of the I n t e r l e a v e d M a j o r i t y D e c i s i o n , Simple M a j o r i t y D e c i s i o n , C o r r e l a t i o n D e c i s i o n , and Narrow Band Methods 101 — i x - F i g . 8.9 Comparison o-f 4.8kbps BER Performance of the I n t e r l e a v e d M a j o r i t y D e c i s i o n , Simple M a j o r i t y D e c i s i o n , C o r r e l a t i o n D e c i s i o n , and Narrow Band Methods 102 F i g . A . l A Simple Spectrum Analyzer used i n Power L i n e Noise S p e c t r a l D e n s i t y Measurement 117 F i g . B.1 D e t a i l e d T r a n s m i t t e r Block Diagram 124 F i g . B.2 D e t a i l e d Receiver Block Diagram . . . 125 F i g . B.3 Schematics of T r a n s m i t t e r 126 F i g . B.4 Schematics of Receiver - Input C o u p l i n g , 4th Order BPF, and FSK Demodulator 127 F i g . B.5 Schematics of Recei v e r - Hard L i m i t e r , Edge D e t e c t o r , P u l s e S t r e t c h e r , and B i t Clock Recovery 128 F i g . B.6 Schematics of Receiver - D i g i t a l Integrate/Dump, Threshold D e c i s i o n , and Data/Data Clock Output . 129 ACKNOWLEDGEMENTS I would l i k e t o thank Dr. R.W. Donaldson -For h i s s u p e r v i s i o n and Mr. M. Chan -for h i s a s s i s t a n c e i n the modem BER measurements. In a d d i t i o n , I would l i k e t o thank Dr. C.S.K. Leung -for p r o v i d i n g the equipment which made the measurements p o s s i b l e . F i n a n c i a l support d u r i n g t h i s work was pro v i d e d by NSERC Postgraduate S c h o l a r s h i p s . 1 1. INTRODUCTION 1.1 Communications over E l e c t r i c Power L i n e s Over the years power d i s t r i b u t i o n l i n e s have been used by the power i n d u s t r y -for telecommunication purposes f o r remote metering, automatic load management, and other a p p l i c a t i o n s C1D—C53. The aim i s t o achieve automatic c o n t r o l of e l e c t r i c power d i s t r i b u t i o n . S t u d i e s have been performed t o measure the t r a n s m i s s i o n and n o i s e c h a r a c t e r i s t i c s found i n power l i n e s C53-C103. These s t u d i e s demonstrate t h a t an u s a b l e power l i n e bandwidth l i e s between 1kHz and 10kHz. Above 10kHz, the power d i s t r i b u t i o n l i n e c a b l e s , power t r a n s f o r m e r s , a s s o c i a t e d d i s t r i b u t i o n f e e d e r s , power f a c t o r c o r r e c t i o n c a p a c i t o r s , and other equipment e f f e c t i v e l y form a sharp r o l l o f f low pass f i l t e r . The most f r e q u e n t l y encountered n o i s e i s r e l a t e d t o and synchronized with the 60Hz mains v o l t a g e . I t i s c a l l e d harmonic n o i s e and i t s spectrum shows d i s c r e t e l i n e s a t m u l t i p l e s of 60Hz. In order t o s a t i s f y the c o n t r o l and monitoring f u n c t i o n s r e q u i r e d by an u l t i l i t y company, data r a t e s of l e s s than 100bps are s u f f i c i e n t . There are two common modulation schemes employed i n a power l i n e c a r r i e r (PLC) or d i s t r i b u t i o n l i n e c a r r i e r (DLC) communication systems. They are PSK and DPSK modulation methods. In e i t h e r scheme, the c a r r i e r i s locked or synchronized t o a harmonic of ac l i n e frequency. In t h i s way, the spectrum of the t r a n s m i s s i o n (30Hz f o r 15bps, 150Hz f o r 75bps) i s centered between two harmonics. The r e c e i v e r i s a l s o synchronized t o the ac mains v o l t a g e , and t h e r e f o r e , can p r o v i d e e x c e l l e n t harmonic - 2 - n o i s e r e j e c t i o n . The r e s u l t a n t narrow band s i g n a l d e t e c t i o n i s performed i n e s s e n t i a l l y white n o i s e ; and with adequate c a r r i e r r e c o v e r y , both the PSK and DPSK systems are s u p e r i o r t o other modulation te c h n i q u e s i n terms of a c h i e v i n g the lowest average b i t e r r o r r a t e (BER) at the same r e c e i v e d Eb/No. C l i n a r d CI13 and O'Neal C53 d e s c r i b e d the parameters of s e v e r a l experimental and commercial PLC systems. Most of these systems have data r a t e s below 100bps and can e a s i l y s a t i s f y present communication requirements. I t has been suggested t h a t d e d i c a t e d networks, such as f i b r e o p t i c s and s a t e l l i t e l i n k s , would c a r r y an i n c r e a s i n g p a r t of f u t u r e communication needs f o r p o w e r — d i s t r i b u t i o n automation C2D. Recent developments i n l o c a l area networks and p r o l i f e r a t i o n of microprocessor c o n t r o l l e d equipment motivate use of the power l i n e s as a communication medium f o r a c h i e v i n g i n t r a b u i l d i n g l o c a l area networking. There are t h r e e obvious advantages: 1. E l i m i n a t i o n of a custom i n s t a l l e d communication networks, which c o u l d be c o s t l y i f coverage exceeds s e v e r a l rooms and f l o o r s . 2. Ease of a c c e s s i n t o the network through a standard e l e c t r i c a l p lug and o u t l e t r e c e p t a c l e . 3. Inherent network c a p a b i l i t y w i t h i n every b u i l d i n g t h a t has power l i n e s . A power l i n e network would f i n d a p p l i c a t i o n s i n an o f f i c e , a f a c t o r y f l o o r , and a home C123-C143. Uses i n c l u d e home bus c o n t r o l , s e c u r i t y m o n i t o r i n g , and i n t e r a c t i o n s with c e n t r a l i z e d and d i s t r i b u t e d data bases. In these a p p l i c a t i o n s , s h o r t - 3 - messages ensure adequate response time i n heavy t r a f f i c . Long messages, r e s u l t i n g from batch p r o c e s s i n g or f i l e t r a n s f e r , c o u l d prevent other u s e r s from u s i n g the network and would t h e r e f o r e be r e s t r i c t e d from network access u n t i l t r a f f i c has subsided. The p h y s i c a l l a y e r of a power l i n e network r e q u i r e s a power l i n e modem. Modem design i s d i f f i c u l t because of the in h e r e n t i n c o m p a t a b i 1 i t y of the power l i n e s t o c a r r y high f r e q u e n c i e s , and the u n c o n t r o l l e d g e n e r a t i o n of impulse n o i s e by p h a s e - c o n t r o l l e d e l e c t r i c a l equipment. Furthermore, the t r a n s m i t t e r power i s r e g u l a t e d by a p p r o p r i a t e governing bodies [15,16]. L i m i t a t i o n s on t r a n s m i t t e d power prevents a modem from a c h i e v i n g a high t r a n s m i s s i o n r a t e by t r a n s m i t t i n g at high powers; because such t r a n s m i s s i o n s c o u l d cause harmful i n t e r f e r e n c e t o other power l i n e communication systems. Several commercial power l i n e modems are a v a i l a b l e f o r use over e x i s t i n g power l i n e s . They a r e modems from BSR, NONWIRE, ExpertNets, and C o n s u l t a n t ' s Choice, a l l from U.S.A. In a d d i t i o n t o these commercial pr o d u c t s , s e v e r a l r e s e a r c h papers r e p o r t e d s i m i l a r developments. Ochsner [17] d e s c r i b e d a spread spectrum FSK system capable of 1200bps t r a n s m i s s i o n r a t e . Van der Srach t et a l . L181 r e p o r t e d the r e s u l t of a 60bps ac z e r o c r o s s i n g synchronized spread spectrum modem. H i r o s a k i e t a l . [193 d e s c r i b e d a 9600bps spread spectrum modem s u i t a b l e f o r home use. H a r i t o n e t a l . C203 r e p o r t e d a modem IC designed f o r t r a n s m i t t i n g and r e c e i v i n g s i g n a l s over ac power l i n e s u s i n g non-coherent FSK and on—off ASK modulation scheme. Not a l l power l i n e modems can - 4 - operate s a t i s f a c t o r i l y a c r o s s phases and under d i f f e r e n t power l i n e environments. 1.2 O u t l i n e of T h e s i s In t h i s t h e s i s the s u i t a b i l i t y of Coherent Minimum Frequency S h i f t Keying f o r i n t r a b u i l d i n g power l i n e communications i s i n v e s t i g a t e d . An a c t u a l modem i s implemented and t e s t e d , and CMFSK performance measurements f o r r e p r e s e n t a t i v e i n t r a b u i l d i n g l i n e s i s determined. A spectrum spreading technique i s developed t o overcome narrow band impairments i n h e r e n t with low data r a t e s . The modem i t s e l f has s e v e r a l advantages over e x i s t i n g commercial p r o d u c t s , i n c l u d i n g : 1. V a r i a b l e data r a t e s up t o 19.2kbps. 2. Compact s i g n a l spectrum and f a s t s i d e l o b e r o l l o f f u s e f u l i n lowering narrow band i n t e r f e r e n c e . 3. T r a n s m i s s i o n spectrum independent of data r a t e achieved by a databand spread spectrum technique. 4. Operation independent of ac mains v o l t a g e , e l i m i n a t i n g the need t o a d j u s t t o 50/60Hz, 2/3-phase power l i n e s . In Chapter 2, s e v e r a l commercial modems are d i s c u s s e d t o g i v e an understanding of e x i s t i n g power l i n e modem technology. In Chapter 3 and Chapter 4 r e s p e c t i v e l y , power l i n e t r a n s m i s s i o n and power l i n e n o i s e c h a r a c t e r i s t i c s a re presented. In Chapter 5, an a c c e p t a b l e power l i n e modem performance i s p r e s e n t e d , and the design p h i l o s o p h y f o r a CMFSK modem i s o u t l i n e d . - 5 - In Chapter 6, the performance of the CMFSK modem i n AWGN i s r e p o r t e d . The c h o i c e of o p e r a t i n g frequency i s e x p l a i n e d and the compact spectrum of the CMFSK modulaion is-demonstrated. In Chapter 7, BER measurements a t 1.2kbps, 4.8kbps, and 19.2kbps i n i n d u s t r i a l , commercial, and r e s i d e n t i a l power l i n e environments a re g i v e n . Two major e r r o r mechanisms, namely impulse n o i s e and momentary r e c e i v e d Eb/No r e d u c t i o n , a re r e p o r t e d . A m a j o r i t y of s i n g l e - b i t e r r o r s a r e caused by impulse n o i s e , w h i l e m u l t i p l e - b i t e r r o r s a re caused by e i t h e r adjacent impulses or momentary r e c e i v e d Eb/No r e d u c t i o n s . In Chapter 8, the m e r i t s of us i n g spread spectrum i n a power l i n e modem i s d i s c u s s e d . The advantages i n c l u d e minimized c o - s i t e i n t e r f e r e n c e and overcoming of p o t e n t i a l narrow band impairments. In a d d i t i o n , an i n t e r l e a v e d PN code databand spread spectrum technique i s r e p o r t e d , along with i t s a b i l i t y t o r e s i s t small e r r o r b u r s t s . R e s u l t s a re given f o r 1.2kbps and 4.8kbps data r a t e a t a code r a t e of 19.2kbps. A summary of the r e s u l t s t ogether with recommendations f o r f u r t h e r work a r e found i n Chapter 9. - 6 - 2. DISCUSSION OF COMMERCIAL POWER LINE MODEMS Commercial power l i n e modems are manufactured by BSR, NONWIRE, ExpertNet, and C o n s u l t a n t ' s Choice. The i n f o r m a t i o n i s f u r n i s h e d by company l i t e r a t u r e or i n reviews C213-C25D. A b r i e f d e s c r i p t i o n on the modems and t h e i r communication p r o t o c o l s i s a l s o i n c l u d e d . 2.1 BSR X-10. A Remote C o n t r o l f o r L i g h t s and A p p l i a n c e s T h i s system c o n s i s t s of a c e n t r a l command u n i t (master) and a maximum of 255 l i g h t / a p p l i a n c e modules ( s l a v e s ) . A master can o n l y t r a n s m i t and a s l a v e can o n l y r e c e i v e . T h e r e f o r e , the master does not know whether a command sent t o a p a r t i c u l a r s l a v e has been executed or not. T r a n s m i s s i o n s and r e c e p t i o n s are synchronized t o the z e r o c r o s s i n g s of the power l i n e s . T h i s l i m i t s the BSR systems t o s p l i t - s i n g l e - p h a s e supply. A s i n g l e b i t i s sent out between two z e r o c r o s s i n g s , y i e l d i n g a t r a n s m i s s i o n r a t e of 120bps on a 60Hz power l i n e . There i s no forward e r r o r c o r r e c t i o n (FEC) and no automatic request f o r r e t r a n s m i s s i o n (ARQ) b u i l t i n t o the modem. The modulation scheme i s on-off ASK a t a c a r r i e r of 120kHz. Average t r a n s m i t t e r output v a r i e s from 800mV t o 1.2V depending on the impedance of the power l i n e t o which i t i s coupled. There i s no documented BER f o r t h i s system but i s b e l i e v e d t o be small s i n c e r e c e i v e d Eb/No should be very high g i v e n the l e v e l of output power and low data r a t e . T h i s system i s s u i t a b l e f o r use i n an apartment complex or a r e s i d e n t i a l house. - 7 - The c o s t f o r the BSR X-10 system i s about CAN$50 f o r the command c o n s o l e and CAN*25 f o r each remote module. 2.2 NON-WIRE Power L i n e Modem The NON-WIRE c o n s i s t s of a c e n t r a l c o n t r o l u n i t (master) and a maximum of 255 remote u n i t s ( s l a v e s ) . Master and s l a v e can t r a n s m i t t o one another. However, a s l a v e t r a n s m i t s o n l y i n response t o q u e r i e s from the master. An onboard microprocessor c o n t r o l l e d by a firmware program performs e r r o r d e t e c t i o n , and i f p o s s i b l e , e r r o r c o r r e c t i o n on the r e c e i v e d b i t stream. The master w i l l r e t r a n s m i t up t o e i g h t times i f a s l a v e does not acknowledge w i t h i n a s e t time l i m i t ; t h i s s e r v e s as a n e g a t i v e acknowledgement d r i v e n ARQ scheme. The t r a n s m i s s i o n r a t e of t h e system i s 1560bps. A f t e r the e r r o r check b i t s are removed, the throughput i s reduced t o 1.2kbps. The raw BER i s lower than l x l O - = , and the system has at most one undetected e r r o r i n two years of continuous o p e r a t i o n . The modulation technique used i s on-off ASK a t a c a r r i e r frequency of 32kHz. The t r a n s m i t t e d v o l t a g e imposed on the power l i n e i s 8v p-p. T h i s system operates asynchronously with the power l i n e ac v o l t a g e and c o u l d communicate a c r o s s the d i f f e r e n t phases i n e i t h e r a 50/60Hz 2/3—phase power l i n e network. T h i s p r a c t i c e i s not recommended and a separate 3—phase master i s a v a i l a b l e t o communicate a c r o s s the d i f f e r e n t phases. T y p i c a l t r a n s m i s s i o n range exceeds 2000 f e e t i n a power l i n e . The c o s t f o r e i t h e r the master or s l a v e alone i s about CAN $1000. T h i s i n c l u d e s the b a s i c power l i n e modem and an onboard microprocessor which implements the v a r i o u s host inter-face and network communication p r o t o c o l f u n c t i o n s . 2.3 ExpertNets Power L i n e Modem The ExpertNets system i s s i m i l a r t o NONWIRE system at the p r o t o c o l l e v e l . The modem uses a c a r r i e r frequency of 90kHz. The data r a t e i s 700bps at an e r r o r r a t e l e s s than i0~'T. The t r a n s m i s s i o n range i s t y p i c a l l y 600 f e e t between u n i t s i n standard 110v/220v house w i r i n g s . The output power of the modem i s not known. Modem c o s t runs from US$100 t o US$200 per u n i t . 2.4 C o n s u l t a n t ' s Choice Power L i n e Modem T h i s modem boosts of 80,000bps t r a n s m i s s i o n r a t e over ac power l i n e s . The high r a t e i s made p o s s i b l e by a modulation and d e t e c t i o n technology used i n low frequency and high n o i s e environment. The modem uses an I n t e l 8039 microprocessor t o perform e r r o r d e t e c t i o n / c o r r e c t i o n and t o implement the network p r o t o c o l . A h y b r i d on-off ASK and FSK modulation scheme i s used t o combat common ac power l i n e n o i s e s . N e i t h e r the BER nor the modem output v o l t a g e l e v e l i s r e p o r t e d . 2.5 Commercial Power L i n e Modem Technology The above survey shows the dominant modulation technology i s on-off ASK with c a r r i e r f r e q u e n c i e s from 32kHz t o 120kHz. In a d d i t i o n , t he ac z e r o c r o s s i n g s a r e used i n the BSR X-10 system f o r t r a n s m i t t e r / r e c e i v e r s y c h r o n i z a t i o n . - 9 - There are modulation schemes t h a t a re s u p e r i o r t o ASK, i . e . •frequency s h i f t keying (FSK) and phase s h i f t keying (PSK) , i n terms of lower a c h i e v a b l e BER at the same r e c e i v e d Eb/No. Both schemes, however, are more complicated t o implement i n hardware. The s i m p l i c i t y of on-off ASK makes l a r g e s c a l e p r o d u c t i o n f e a s i b l e , which t r a n s l a t e s t o low c o s t power l i n e modems and low c o s t power l i n e l o c a l area networks. The c o s t of a power l i n e l o c a l area network w i l l be one determinant of i t s success i n power l i n e data communication a p p l i c a t i o n s . C o a x i a l c a b l e or f i b r e o p t i c s based communication systems w i l l have a much higher t r a n s m i s s i o n c a p a c i t y (1Mbps t o 100Mbps) and higher r e l i a b i l i t y . At p r e s e n t , the labour c o s t of i n s t a l l i n g a d e d i c a t e d network whose coverage i s as wide and as u n i v e r s a l as the power l i n e s i s o f t e n very expensive. However, t h i s does not apply t o new c o n s t r u c t i o n s where an de d i c a t e d c o a x i a l or f i b r e o p t i c s c a b l e can be l a i d along s i d e the power l i n e s a t a minimum c o s t . I t i s mandatory t h a t the p r i c e of a power l i n e network be kept low enough t h a t i t can be purchased at a small incremental c o s t t o complement a f a s t e r d e d i c a t e d data communication network. The low c o s t requirement makes on-off ASK an a t t r a c t i v e modulation scheme i n commercial power l i n e modems s i n c e i t i s not hardware i n t e n s i v e and i s e s s e n t i a l l y adjustment-free. T h i s i s because an ASK s i g n a l can be generated by a c r y s t a l c o n t r o l l e d o s c i l l a t o r and can be de t e c t e d u s i n g a high Q band pass f i l t e r . T h i s i s u n l i k e other systems such as PSK or FSK which r e q u i r e s - 10 - more hardware. The s e l e c t i o n of c a r r i e r frequency i s determined by t h e n o i s e and t r a n s m i s s i o n c h a r a c t e r i s t i c s of the power l i n e . In g e n e r a l , modems having high t r a n s m i s s i o n r a t e s or which are expected t o operate i n r e s i d e n t i a l houses and apartments use a c a r r i e r frequency from 90kHz t o 120kHz. However, a lower c a r r i e r frequency has t o be used whenever t h e r e i s e x c e s s i v e a t t e n u a t i o n s at the high f r e q u e n c i e s . A low c a r r i e r frequency p l a c e s the s i g n a l spectrum i n high power l i n e n o i s e environments, and the data r a t e i s o f t e n reduced t o ensure an a c c e p t a b l e r e c e i v e d Eb/No. 3. POWER LINE TRANSMISSION CHARACTERISTICS I n t r a b u i l d i n g power l i n e t r a n s m i s s i o n c h a r a c t e r i s t i c s have been r e p o r t e d by Chan C263 and Ochsner C17D. T h e i r r e p o r t s show t h a t a t y p i c a l power l i n e a c t s l i k e a low pass f i l t e r , with a c u t o f f frequency v a r y i n g from 70kHz t o 150kHz depending on the p a r t i c u l a r l o a d p r o f i l e . In a d d i t i o n , s e l e c t i v e frequency fades are a l s o r e p o r t e d . T h e i r presence i s a p o s s i b l e combination of s p e c i a l l i n e l o a d i n g and e x c i t a t i o n of s t a n d i n g waves i n the power l i n e s . 3.1 I n d u s t r i a l B u i l d i n g Power L i n e Transmission C h a r a c t e r i s t i c s A s e t of power l i n e t r a n s m i s s i o n measurements was performed i n an i n d u s t r i a l b u i l d i n g (UBC McLeod b u i l d i n g ) . A t r a n s m i t t e r was f i x e d a t remote phase B (see S e c t i o n 7.1) and the r e c e i v e r was a l t e r n a t e l y plugged i n t o each of the t h r e e phases of a 3—phase bench power supply o u t l e t bar i n Room 442. The s e t of t r a n s m i s s i o n curves are p l o t t e d i n F i g . 3.1. These curves were obtained on a weekday between 8:30am and 4:30pm when the power l i n e was h e a v i l y loaded. T h i s s e t of remote t r a n s m i s s i o n curves i l l u s t r a t e s t h a t : 1. Tr a n s m i s s i o n l o s s from 20dB t o 40dB i s common with the r e c e i v e r and t r a n s m i t t e r on the same phase. 2. No d i s c e r n a b l e d i f f e r e n c e appears i n t r a n s m i s s i o n c h a r a c t e r i s t i c s among the d i f f e r e n t phases i n a remote t r a n s m i s s i o n . 3. No sharp narrow band frequency dropouts >20dB are observed between 30kHz and 150kHz. - 12 - It i s expected t h a t (1) would p r e v a i l i n a power l i n e s i n c e i t i s not intended t o c a r r y high -frequency s i g n a l s . Item <2) seems t o c o n t r a d i c t other -findings C41, i n which t r a n s m i s s i o n d i f f e r e n c e up t o 16dB was r e p o r t e d . T h i s i s not r e a l l y a d i s c r e p a n c y as another s e t of curves taken f o r c l o s e - i n and across-phase t r a n s m i s s i o n s w i l l demonstrate. In t h i s case, a t r a n s m i t t e r was f i x e d i n phase B of the bench supply mentioned above and the r e c e i v e r was a l t e r n a t e l y plugged each of the t h r e e phases. The t r a n s m i s s i o n curves obtained are shown i n F i g . 3.1, which show the 16dB t r a n s m i s s i o n d i f f e r e n c e and some s e l e c t i v e frequency fades around 120kHz. T h i s s e t of curves are de s i g n a t e d as ' l o c a l ' because the r e c e i v e d SNR i s high e r than those i n the 'remote' case. N o t i c e t h a t the ' l o c a l ' t r a n s m i s s i o n curves r e p r e s e n t better power l i n e r e c e p t i o n c o n d i t i o n s , because the r e c e i v e d SNR i s higher than those found i n the 'remote' s e t of curves. The 'remote' t r a n s m i s s i o n curves show t h a t a t y p i c a l power l i n e bandwidth i s q u i t e narrow. In a d d i t i o n , i t shows t h a t the s i g n a l l e v e l s a t remote phases are roughly e q u a l . T h i s c o u l d be a r e s u l t of s i g n a l leak-throughs from the o r i g i n a t i n g phase i n t o adjacent phases v i a e l e c t r i c a l equipment connected t o more than one phase. I t has been observed t h a t an o f f — p h a s e s i g n a l o f t e n became s t r o n g e r than an in-phase s i g n a l , p o s s i b l y because of some p a r t i c u l a r l o a d i n g . In g e n e r a l , s i g n a l leak-throughs tend t o e q u a l i z e the s i g n a l l e v e l s i n adjacent phases of a power l i n e , thereby lowering the energy i n the o r i g i n a t i n g phase and r a i s i n g t h a t i n adjacent phases. I t i s p o s s i b l e t h a t these leak-throughs - 13 - or bypasses reduce the deepness o-f a fade, which e x p l a i n s (3). To observe the e f f e c t s of power l i n e l o a d i n g on t r a n s m i s s i o n c h a r a c t e r i s t i c s , more t r a n s m i s s i o n measurements were performed. Three more s e t of curves a r e obtained and p l o t t e d i n F i g . 3.2 (another weekday between 8:30am and 4:30pm), F i g . 3.3 ( a f t e r 6:00pm on a weekday), and F i g . 3.4 (weekend a f t e r n o o n ) . The l a s t two p l o t s c h a r a c t e r i z e the t r a n s m i s s i o n c o n d i t i o n s of a l i g h t l y loaded power l i n e , and are expected t o show l e s s t r a n s m i s s i o n l o s s . Comparisons between F i g . 3.1 & F i g . 3.2 (loaded) and F i g . 3.3 & F i g . 3.4 ( l i g h t l y loaded) demonstrate t h a t a l i g h t l y loaded power l i n e s u f f e r s from l e s s a t t e n u a t i o n , e s p e c i a l l y i n the high frequency range. In a d d i t i o n , a l i g h t l y loaded power l i n e seems t o support s t a n d i n g waves, p o s s i b l y as a r e s u l t of untapped energy being c o n f i n e d i n the l i n e . Photographs of r e c e i v e d s i g n a l at v a r i o u s f r e q u e n c i e s from ' l o c a l ' and 'remote' t r a n s m i s s i o n s are shown i n F i g . 3.5. In these p i c t u r e s , the e f f e c t s of power l i n e impedance modulation can be c l e a r l y seen from the p e r i o d i c amplitude fades or dropouts i n the r e c e i v e d s i g n a l s C17,203. ' L o c a l ' s i g n a l r e c e p t i o n seems t o be a f f e c t e d the most and e x h i b i t s severe amplitude fades at two f r e q u e n c i e s , 53kHz and 106kHz, one being t w i c e the frequency of the other one. These p i c t u r e s are taken on a weekday between 8:30am and 4:30pm. The bandpass f i l t e r used i n enhancing the 'remote' 100kHz and 120kHz s i g n a l s i n F i g . 3.5 has a c e n t e r frequency of 140kHz with a 50kHz bandwidth. oJB *> I Jo»i **»t fcKflt liMt *>Mt 9*1% wMt IIpW, U*fo IhW* jytfjfe I5*** F i g . 3.1 ' L o c a l ' and 'Remote' Transmission Curves on a Weekday Between 8:30am and 4:30pm i n an I n d u s t r i a l B u i l d i n g -2o# '3* -401 r!- iii! ft it:' 'Si' 1 I: <telki F i g . 3.2 ' L o c a l ' and 'Remote' Transmission Curves Weekday Between 8:30am and 4:30pm i n an I n d u s t r i a l B u i l d i n g -i.it I I I Iii! ihSillif [liiJIî iJ'ltfe ••* -hil iii|pj|jjl|||p yun pin-* 2>f-H 9'*** tot** I I'M* i» H» F i g . 3.3 ' L o c a l ' and 'Remote' Trans m i s s i o n Curves on a Weekday A f t e r 6:00pm i n an I n d u s t r i a l B u i l d i n g >4 I ' * ' 3""" 1 "M* ««JWt /J-»!«t F i g . 3.4 ' L o c a l ' and 'Remote' Trans m i s s i o n Curves on a Weekend Day - 18 - 'Remote' Upper traces 60Hz ac mains v o l t a g e as time r e f e r e n c e Lower t r a c e : Received s i g n a l s with amplitude f a d i n g F i g . 3.5 P i c t u r e s of Received ' L o c a l ' and 'Remote' S i g n a l s a t V a r i o u s F r e q u e n c i e s : 40kHz ' L o c a l ' 'Remote' F i g . 3.5 Cont'd: 60kHz - 20 - - 21 - 'Remote' F i g . 3.5 Cont'd: 100kHz - 22 - * Remote' F i g . 3.5 Cont'd: 120kHz - 23 - F i g . 3.5 Cont'd: BPF 100kHz (upper p i c t u r e ) and BPF 120kHz (lower p i c t u r e ) - 24 106kHz 53 kHz F i g . 3.5 Cont'd: Severe Amplitude Fade at 53kHz and 106kHz - 25 - 3.2 R e s i d e n t i a l B u i l d i n g Power L i n e Transmission C h a r a c t e r i s t i c s S e t s o-f t r a n s m i s s i o n curves are obtained f o r a r e s i d e n t i a l house. They demonstrate t h a t t h e r e i s a wider bandwidth on a r e s i d e n t i a l power l i n e and a l s o t h e r e i s l e s s a t t e n u a t i o n . In a d d i t i o n , the e f f e c t of a s i g n a l bypass i s r e p o r t e d . The two-story house i s f e d by a 110V/2-phase power c i r c u i t . F i g . 3.6 shows the in-phase and across-phase t r a n s m i s s i o n curves. A wide power l i n e bandwidth appears and t h e r e are no s e l e c t i v e frequency f a d e s . F i g 3.7 shows the e f f e c t of a r e s i s t i v e s i g n a l bypass on across-phase t r a n s m i s s i o n s . The f i g u r e demonstrates t h a t t h e r e i s c o n s i s t e n t improvement from 30kHz t o 150kHz. The s i g n a l bypass i s pr o v i d e d by a r e s i s t i v e path connecting a c r o s s the two phases of the power l i n e when a range element i s turned on. The s e t of t r a n s m i s s i o n c u r v e s i s extended beyond 150kHz t o 500kHz i n F i g . 3.8. They show a 20dB frequency fade at 300kHz i n the lBO 4 3 phase. T h i s phase e x h i b i t e d another frequency fade at 600kHz, which was not shown i n these curves. By p r o v i d i n g a r e s i s t i v e s i g n a l bypass, 5dB t o lOdB r e d u c t i o n s i n the depth of these f a d e s were observed. I'M* ••Ml S*H\ MHX hw* *w* "0M*- U* M» ,J*»» F i g . 3 .6 and ISO 0 Phase Transmission Curves i n a R e s i d e n t i a l House I M I loMt 4oKH* 5oW> cV>*H» MH 9 o M l l t 6 M * ""^ l 2 o k U * tof* F i g . 3.7 Transmission D i f f e r e n c e between the 0° and 180° Phase With and Without a R e s i s t i v e S i g n a l Bypass OiB -loiB JoKW* to<Ht *bft)t (oMi 7»jt«, «<H*i 3aW»/«*/* '8»<fc JooWrf* Motfj JHW« F i g . 3.8 Extended 0° and 180° Phase Transmission Curves of the R e s i d e n t i a l House - 29 - 4. POWER LINE NOISE 4.1 Power L i n e Noise C h a r a c t e r i s t i c s The n o i s e -found on a power l i n e i s mainly p e r i o d i c i n nature and shows d i s c r e t e s p e c t r a l l i n e s . T h i s p a r t i c u l a r nature of power l i n e n o i s e has important i m p l i c a t i o n s f o r narrow band t r a n s m i s s i o n s , because these n o i s e s p e c t r a l s p i k e s can be avoided by p l a c i n g the s i g n a l spectrum i n between them, as i s the case i n s e v e r a l PLC communication systems. However, t h i s approach i s l i m i t e d t o low speed t r a n s m i s s i o n s o n l y . Measurements of power l i n e n o i s e s p e c t r a l d e n s i t y are found i n C9,10,27,28,293. A s e t of power l i n e n o i s e data was c o l l e c t e d i n the i n d u s t r i a l b u i l d i n g and r e s i d e n t i a l house. R e s u l t s of the c a l c u l a t e d n o i s e s p e c t r a l d e n s i t y are compiled i n Table 4.1 and Table 4.2. In a d d i t i o n , photographs of the power l i n e n o i s e i n t h r e e frequency bands were taken i n the i n d u s t r i a l b u i l d i n g and are shown i n F i g . 4.1. These p i c t u r e s i n d i c a t e the e x i s t e n c e of high amplitude decaying o s c i l l a t o r y outputs from the BPFs caused by i m p u l s i v e n o i s e s p i k e s a t t h e i n p u t . Furthermore, they a l s o show t h a t the background n o i s e i s a l s o s u s c e p t i b l e t o p e r i o d i c power l i n e impedance modulation e f f e c t s (see S e c t i o n 3.1). One other o b s e r v a t i o n i s the d i f f e r e n t d u r a t i o n p e r i o d s of these impulse e f f e c t s i n the t h r e e frequency bands, about lOOus i n the low frequency band (20kHz-30kHz), 50us i n the mid frequency band (50kHz-70kHz), and 25us t o 30us i n the h i g h frequency band (120kHz-180kHz). The d u r a t i o n of an impulse at the input i s around lOus t o 15us. The d u r a t i o n of an impulse n o i s e s p i k e and - 30 - Table 4.1 I n d u s t r i a l B u i l d i n g Power L i n e Noise S p e c t r a l Oensi t y f a Phase A Phase B Phase C Remote 25kHz 85.0 43.4 43.4 91.2 60kHz 14. 1 22. 1 15.0 16.9 140kHz .373 .290 .381 .211 * Remote B i s an o u t l e t used f o r remote r e c e p t i o n and t r a n s m i s s i o n as d e f i n e d i n S e c t i o n 3.1. note: 1. U n i t i n 10- AV=_ m m/kHz. 2. Coupling t e r m i n a t i n g r e s i s t a n c e , R»r», i s 12 ohm. 3. Refer t o Appendix A f o r n o i s e d e n s i t y d e t e r m i n a t i o n . Table 4.2 R e s i d e n t i a l B u i l d i n g Power L i n e Noise S p e c t r a l D e n s i t y f 0 Phase 0° Phase 180e* 25kHz 1.65 3.28 60kHz 1.22 .802 140kHz .0119 .0305 note: 1. U n i t i n 10-*V 2 1_ m./kHz. 2. Co u p l i n g t e r m i n a t i n g r e s i s t a n c e , R»r», i s 12 ohm. 3. Refer t o Appendix A f o r n o i s e d e n s i t y d e t e r m i n a t i o n . HID BPF C 5b*Wz % 7o/cfe) F i g . 4.1 Power L i n e Noise i n Three Frequency Bands - 32 - HIGH EPF C IZokHz -to fQotHz.) F i g . 4.1 Cont'd 4oKHz 14-6 kHz 1 F i g . 4.2 Power L i n e Noise S p e c t r a l D e n s i t y - 33 - i t s induced e-f-fects on the BPFs may have i m p l i c a t i o n s i n high speed t r a n s m i s s i o n s . As the p e r i o d of a b i t decreases, the p r o b a b i l i t y of i t s i n f o r m a t i o n being destroyed by an impulse i n c r e a s e s . Table 4.1 and Table 4.2 show a downward t r e n d i n power l i n e n o i s e s p e c t r a l d e n s i t y as frequency i n c r e a s e s . T h i s i s i n agreement with r e p o r t e d f i n d i n g s . The data a l s o shows t h a t an i n d u s t r i a l power l i n e i s n o i s i e r than a r e s i d e n t i a l one. A p i c t u r e of the i n d u s t r i a l power l i n e n o i s e s p e c t r a l d e n s i t y i s shown i n F i g . 4.2, i n which s e v e r a l i n t e n s i f i e d n o i s e r e g i o n s appear. In a d d i t i o n , t h e r e e x i s t s an approximate 20dB d i f f e r e n c e i n s p e c t r a l d e n s i t y between the extreme ends of the recorded spectrum. 4.2 Cross S e c t i o n a l Power L i n e Noise C h a r a c t e r i s t i c s Power L i n e n o i s e i s i n f l u e n c e d by p a r t i c u l a r l i n e l o a d i n g . Measurements of n o i s e s p e c t r a l d e n s i t y were performed i n the UBC McLeod B u i l d i n g on f o u r high power l i n e a c t i v i t y and on f o u r low power l i n e a c t i v i t y days. A high a c t i v i t y day i s any non-holiday weekdays between 8:30am and 4:30pm. A low a c t i v i t y day i n c l u d e s any weekend days. Measurement r e s u l t s a r e found i n Table 4.3, which shows a t r e n d of i n c r e a s e d n o i s e on low a c t i v i t y days and decreased n o i s e on high a c t i v i t y days. T h i s t r e n d i s a t t r i b u t e d t o reduced power l i n e a t t e n u a t i o n s on low a c t i v i t y days. But i t has been observed t h a t power l i n e s on a weekend p e r i o d may have n o i s e v a l u e s s i m i l a r t o t h a t of a high a c t i v i t y day, simply because t h e b u i l d i n g ' s power l i n e s a re loaded. - 34 - Tabl e 4.3 I n d u s t r i a l B u i l d i n g Power L i n e Noise S p e c t r a l D e n s i t y on Four High A c t i v i t y and Four Low A c t i v i t y Days Phase A HIGH A c t i v i t y Days Phase B Phase C Remote B* 60kHz .435 1.43 2.72 5. 17 60kHz 6.55 2.02 3. 11 3.31 60kHz 6.26 1.29 3.52 6.26 60kHz 1.57 .513 .870 .828 140kHz .314 .034 . 156 .113 140kHz . 143 .087 .119 . 143 140kHz . 131 .055 .097 .087 140kHz .072 .031 .023 .034 LOW A c t i v i t y Days 60kHz 4.92 3.52 4.43 5.70 60kHz 11.64 5. 17 4.43 6.26 60 kHz 10. 14 3.52 3.96 3.52 60kHz 1.51 1. 19 1.56 1.29 140kHz .298 .026 .087 .934 140kHz .298 . 191 .271 1.38 140kHz .387 .206 .346 .855 140kHz .064 .037 .020 .034 • Remote B i s an o u t l e t used f o r remote r e c e p t i o n and transmi s s i o n de-fined i n S e c t i o n , 3.1. note: 1. U n i t i n 10-* V 2, /kHz. Coup l i n g t e r m i n a t i n g r e s i s t a n c e , R* n, i s 3.3 ohm. 3. Refer t o Appendix A f o r n o i s e d e n s i t y measurement. - 35 - 5. CMFSK POWER LINE MODEM DESIGN CONSIDERATIONS 5.1 Power L i n e Modem Design C r i t e r i o n An a c c e p t a b l e modem design should meet the f o l l o w i n g r e q u i rements: 1. A c c e p t a b l e channel b i t e r r o r r a t e performance a t high t r a n s m i s s i o n r a t e , i . e . 1 0 - 3 or b e t t e r at 19.2kbps. 2. Minimum s p e c t r a l s p i l l o v e r t o reduce harmful i n t e r f e r e n c e t o other power l i n e communication systems and AM r a d i o s . 3. Proven technology g i v i n g high r e l i a b i l i t y , low implementation d i f f i c u l t y , and low c o s t . 4. A b i l i t y t o operate i n 50/60Hz 2/3-phase 110V/220V power l i n e networks with minimum user adjustment. 5. A b i l i t y t o operate c o n t i n u o u s l y i n a power outage. 6. A b i l i t y t o c o — e x i s t with e x i s t i n g power l i n e communication systems i n the same power l i n e network. 7. Meets or exceeds a l l a p p l i c a b l e emission r e g u l a t i o n s . Some r e s e a r c h e r s C17D-C19D have a p p l i e d spread spectrum methods t o power l i n e modems. T h e i r i n t e n t i o n i s t o overcome narrow band frequency fades and t o a c h i e v e Code D i v i s i o n M u l t i p l e Access. In Chapter 8, the advantages and disadvantages of u s i n g spread spectrum s i g n a l l i n g over power l i n e s are d i s c u s s e d i n more d e t a i l . Here a b r i e f summary w i l l s u f f i c e . The primary u s e f u l n e s s of spread spectrum i n our a p p l i c a t i o n l i e s with i t s s p e c t r a l d e n s i t y r e d u c t i o n c a p a b i l i t y . Coupled with the CMFSK modulation with i t s compact spectrum and f a s t s i d e l o b e r o l l o f f , spread spectrum i s a b l e t o t r a n s f o r m remanant s i d e l o b e s p i l l a g e s i n t o 'AWGN'—like n o i s e s . T h e r e f o r e , spread - 36 - spectrum a l l o w s the use of enhanced t r a n s m i t t e r power t o overcome path a t t e n u a t i o n without g e n e r a t i n g unacceptably high l e v e l s of i n t e r f e r e n c e . One should keep i n mind t h a t the u l t i m a t e goal i s t o c o n c e n t r a t e as much energy as p o s s i b l e i n the band of i n t e r e s t , and t o t r a n s f o r m unavoidable s p e c t r a l s p i l l a g e s i n t o white n o i s e . T h i s approach may seem redundant s i n c e the power l i n e i t s e l f w i l l e v e n t u a l l y e l i m i n a t e the high frequency components of a s i g n a l . Although t h i s may be the case i n remote t r a n s m i s s i o n s , much high frequency i n t e r f e r e n c e can reach near—by or c o - s i t e u s e r s . T h i s i s s i m i l a r t o the n e a r / f a r f i e l d problem d i s c u s s e d i n Chapter 8. The use of ac z e r o c r o s s i n g s i n s y n c h r o n i z i n g a t r a n s m i t t e r / r e c e i v e r p a i r i s found i n BSR X-10 and i n C43. The b e n e f i t i s c l e a r i n low t r a n s m i s s i o n r a t e system where small t i m i n g e r r o r s , i n the form of in-phase z e r o c r o s s i n g j i t t e r [ I B ] , can be t o l e r a t e d b e f o r e system performance i s a d v e r s e l y a f f e c t e d . Measured r e s u l t s f o r o f f — p h a s e z e r o c r o s s i n g j i t t e r were not i n c l u d e d i n C183. Our o b s e r v a t i o n s i n d i c a t e t h a t o f f - p h a s e z e r o c r o s s i n g j i t t e r i s much more s e r i o u s than in-phase j i t t e r . T h i s i s t o be expected s i n c e in—phase z e r o c r o s s i n g s are d e r i v e d from the same 60Hz s i g n a l but o f f - p h a s e z e r o c r o s s i n g s are d e r i v e d from t h r e e d i f f e r e n t 60Hz ac v o l t a g e s . In high speed data t r a n s m i s s i o n s , these z e r o c r o s s i n g s may not be a c c u r a t e enough t o p r o v i d e adequate s y n c h r o n i z a t i o n t i m i n g . However, they can s t i l l p r o v i d e c o a r s e t i m i n g r e f e r e n c e . - 37 - Sixty—Hz s y n c h r o n i z a t i o n methods - f a i l d u r i n g a power outage. I t i s argued t h a t t h e r e i s no expected communications needs i n such a s i t u a t i o n , and t h e r e f o r e , outage problems can be ignored. However, t h i s approach i s r a t h e r r e s t r i c t i v e on a power l i n e l o c a l area network c a p a b i l i t y . Power supply networks i n l a r g e b u i l d i n g s may be backed up by g e n e r a t o r s , d i g i t a l systems may be t e m p o r a r i l y backed up by b a t t e r i e s t o perform pre-programmed shutdown o p e r a t i o n s , and power l i n e s e c u r i t y / m o n i t o r networks may be r e q u i r e d t o remain o p e r a t i o n a l d u r i n g power outages. Any modem design f o r use on power d i s t r i b u t i o n networks must c o n s i d e r the problems mentioned i n t h i s and preceding s e c t i o n s . In the f o l l o w i n g s e c t i o n s , the design of a coherent minimum FSK modem i s d e s c r i b e d along with i t s BER measurements at d i f f e r e n t b i t r a t e s and d i f f e r e n t power l i n e environments. 5.2 Design O b j e c t i v e s of a CMFSK Power L i n e Modem From the above d i s c u s s i o n , a compact spectrum modulation scheme with f a s t s i d e l o b e r o l l o f f i s d e s i r a b l e i n c o n t r o l l i n g i n t e r f e r e n c e when output power must be r a i s e d t o compensate f o r t r a n s m i s s i o n l o s s . S everal compact spectrum modulation schemes e x i s t and a r e d i s c u s s e d i n 130,313. A s u i t a b l e modulation scheme has a constant envelope and continuous phase t r a n s i t i o n output waveform. The spectrum f o r ASK, FSK, and PSK modulation schemes has a f i r s t n u l l at 1/T, T being the b i t d u r a t i o n . A more compact spectrum i s r e a l i z e d with coherent minimum FSK (CMFSK). I t has a - 38 - 1st n u l l a t .75/T and a f - " * s p e c t r a l r o l l o f f r a t e , compared t o f - 2 i n e i t h e r PSK or ASK. I t s drawback i s an e x t r a 3dB r e c e i v e d energy i s r e q u i r e d t o achieve the same BER performance of a p e r f e c t l y s y c h r o n i z e d PSK system o p e r a t i n g i n white n o i s e . In p r a c t i c e , the 3dB energy advantage a PSK system enjoys over a coherent FSK system i s sometimes obscured by imperfect c a r r i e r r e c o v e r y C30,32,33,343 and by the presence of im p u l s i v e n o i s e . The impulse n o i s e e f f e c t on a PSK/DPSK and FSK system was re p o r t e d i n 126,35,363. Chan [263 presented the BER s t a t i s t i c s f o r t h i s author's CMFSK modem and f o r a p e r f e c t l y synchronized PSK modem. He s t a t e d t h a t the 3dB advantage of the PSK system d i d not seem t o enhance i t s performance over the CMFSK modem. However, Chan r e p o r t e d more double and t r i p l e b i t e r r o r s from the CMFSK modem and more s i n g l e b i t e r r o r s from the PSK modem a t the same BER, which was a t t r i b u t e d t o the PSK in h e r e n t 3dB advantage. However, t h i s f i n d i n g i s not supported by comparing the Eb/No va l u e s corresponding t o the same BER from e i t h e r modem. A p o s s i b l e i n t e r p r e t a t i o n of Chan's o b s e r v a t i o n i s t h a t the CMFSK modem i s more t o l e r a n t of low l e v e l impulse n o i s e , but makes more e r r o r s when overcome by them. T h i s p o s s i b l e i m p u l s e - t o l e r a n t a b i l i t y of a FSK system may be because s i g n a l d e t e c t i o n o n l y i n v o l v e s t he frequency i n f o r m a t i o n , w h i l e on the other hand, a PSK system r e l i e s on both the c a r r i e r and phase i n f o r m a t i o n of an incoming s i g n a l . T h i s g i v e s PSK the 3dB energy advantage i n AWGN, but not n e c e s s a r i l y so i n impulse or non-Gaussian n o i s e . The BER ver s u s Eb/No curve of the PSK modem, without r e l y i n g on p e r f e c t s y n c h r o n i z a t i o n , should be e s t a b l i s h e d t o i n v e s t i g a t e i f - 39 - th e r e i s any s i g n i f i c a n t energy advantage of PSK over FSK i n impulse n o i s e impaired s i g n a l d e t e c t i o n . The coherent minimum FSK modulation scheme seems t o be a good compromise between a compact spectrum, steep s i d e l o b e s , and e f f i c i e n t use of r e c e i v e d s i g n a l energy. I t s implementation i s f a c i l i t a t e d by proven modulation/demodulation techniques from e x i s t i n g i n t e g r a t e d c i r c u i t c h i p s . The goal of control led i n t e r f e r e n c e can be achieved by a p p l y i n g spread spectrum methods t o the baseband s i g n a l without e x c e s s i v e s p e c t r a l s p i l l o v e r s from the d e s i r e d s i g n a l frequency band. Spread spectrum i s thereby e f f e c t i v e i n re d u c i n g narrow band i n t e r f e r e n c e t o other power l i n e communications users and AM r a d i o s , w h ile a l s o a l l o w i n g a higher t r a n s m i t t e r output t o compensate f o r path a t t e n u a t i o n . 5.3 Design of a CMFSK Power L i n e Modem The h e a r t of the modem l i e s with two EXAR ICs, XR-2206 and XR-2211. The XR-2206 i s a f u n c t i o n generator used i n the t r a n s m i t t e r s e c t i o n f o r g e n e r a t i o n of the two FSK f r e q u e n c i e s . The XR-2211 i s a FSK demodulator used i n the r e c e i v e r . The ICs are chosen f o r t h e i r frequency s t a b i l i t y a g a i n s t power supply and temperature v a r i a t i o n s . The block diagrams of the t r a n s m i t t e r and r e c e i v e r a re found i n F i g . 5.1. More d e t a i l e d schematics a re found i n Appendix B. - 40 - DATA xg-2206 a 5 6 7 8 H H C > 1 5̂ 15̂ 2 F5K Modulator 0') Tr*.v\smftier -0 C £ JJ7V04C -D> 0 — 117WC c l <3 ZnieqirAire /Dump z XR-2211 13 /4 /2 /I HH ^2 FSK Demodulator RPrW DATA c 3 VR1 XK-22/Z. C/ock Kecoi/ery (ii) Receiver F i g . 5.1 Block Diagram o f CMFSK T r a n s m i t t e r / R e c e i v e r - 41 - 5.4 CMFSK Modem T r a n s m i t t e r D e s c r i p t i o n R e f e r r i n g t o the t r a n s m i t t e r block diagram, the two FSK f r e q u e n c i e s a re determined by CI, R l , and R2. The FSK s i g n a l from the XR-2206 i s f e d t o a l i n e a r power a m p l i f i e r . The a m p l i f i e d s i g n a l i s then coupled i n t o the power l i n e v i a p u l s e transformer T l and ac b l o c k i n g c a p a c i t o r C2. The input t o the power a m p l i f i e r i s c o n t r o l l e d by VR1, and t h e r e f o r e , the power d e l i v e r e d t o the power l i n e can be v a r i e d . Measurements were performed t o determine the output power at v a r i o u s t r a n s m i t t e r output v o l t a g e l e v e l s (see F i g . 5.2). The r e s u l t s a re con t a i n e d i n T able 5.1, which shows a maximum output of 0.8W. The power l i n e impedance was a l s o determined t o be 10.5+.5 ohms at 120kHz, which agrees well with other r e p o r t e d v a l u e s 137,383. 5.5 CMFSK Modem Receiver D e s c r i p t i o n The r e c e i v e r c o n s i s t s of an in p u t power l i n e c o u p l i n g network, a bandpass f i l t e r , a FSK demodulator, a b i t c l o c k r e c o v e r y , and a d i g i t a l integrate/dump (see F i g . 5.3). The i n p u t power l i n e c o u p l i n g network i s made up of an ac b l o c k i n g c a p a c i t o r CI, p u l s e transformer T l , and r e s i s t o r R l . The frequency response of t h i s c o u p l i n g network i s f l a t from 30kHz t o beyond 200kHz (+0.0dB, -2.0dB). The bandpass f i l t e r (BPF) i s made up of a hig h pass f i l t e r f o l l o w e d by a low pass f i l t e r . I t s —3dB bandwidth i s about 50kHz and i s cen t e r e d a t 140kHz. The e q u i v a l e n t n o i s e bandwidth i s deduced t o be 60kHz from the BER measurements i n AWGN. - 4 2 - Spra^ue Poise Transferrer 11Z210Q where 2 x V o u * x V„ PF = Power F a c t o r = magnitude I cos |̂  3 P o u t = Power D e l i v e r e d i n t o t he Power L i n e ( V o u ^ X X PF) - l o u t 2 X R m t = ( V o u t x Va x PF) - V j ^ x R i n t R R 2 R m t = I n t e r n a l R e s i s t a n c e o-f the Power L i n e Coupling = measured t o be 3.0+.3 ohms. F i g . 5 . 2 CMFSK Modem Power Output Measurement Method - 43 - Table 5.1 Coupled Power i n t o the Power L i n e @ 120kHz v 4 „ v o u t v „ Pc3«Jlt 1.00+.01V 0.93+.01V 70+2mV 50mW 2.00+.02V 1.86+.02V 138+2mV 200mW 3.00+.02V 2.80+.02V 202+2mV 440mW 4.00+.05V 3.72+.05V 290+2mV 790mW note: 1. P 0 « t = Power d e l i v e r e d i n t o the power l i n e . 2. Power l i n e impedance i s deduced t o be 10.5+.5 ohms @ 120kHz u s i n g t h i s t a b l e and F i g . 5.2. 3. Refer t o F i g . 5.2 f o r power measurement technique. GX DATA CLK A A A A A A /|\ 54rnplithy CLfc -£> J>AT/\ F i g . 5.3 Block Diagram of D i g i t a l Integrate/Dump - 45 - The XR-2211 FSK demodulator i n c o r p o r a t e s a phase locked loop (PLL) t o compare the incoming -frequency with a r e f e r e n c e frequency. The FSK demodulation process generates an analog v o l t a g e at p i n 11, which corresponds t o e i t h e r a sent '1* or '0' p l u s r e c e i v e d n o i s e . The r e f e r e n c e frequency i s c o n t r o l l e d by C2 and VR1 and the bandwidth of PLL response i s s e t by R2 and C3 (see [393 f o r more i n f o r m a t i o n on FSK modulation/demodulation). The recovered analog data p u l s e s a re then low pass f i l t e r e d t o f u r t h e r a t t e n u a t e out-of-band n o i s e . At t h i s p o i n t , the data p u l s e s c o u l d i n s t e a d be analog s i g n a l s , thereby p r o v i d i n g v o i c e communications c a p a b i l i t y v i a the power l i n e s . T h i s method i s used i n most low c o s t r e s i d e n t i a l power l i n e FM intercoms. The analog data p u l s e s , a f t e r h a r d l i m i t i n g , d r i v e a phase locked loop (XR-2212) c o n t r o l l e d b i t c l o c k r e c o v e r y c i r c u i t , which s u p p l i e s t i m i n g s i g n a l s t o the modem's d i g i t a l c i r c u i t r y . The p r i n c i p l e of b i t c l o c k r e c o v e r y i s d i s c u s s e d i n [40,413. In essence, a d i f f e r e n t i a t e d b i t stream has a d i s c r e t e s p e c t r a l l i n e at the b i t r a t e frequency. T h i s l i n e i s then locked onto by a PLL, which p r o v i d e s the a p p r o p r i a t e b i t t i m i n g s i g n a l s . A more d e t a i l e d d e s c r i p t i o n on the o p e r a t i o n of a c l o c k r e c o v e r y c i r c u i t i s found i n [423. The d i g i t a l integrate/dump uses a 1 - b i t A/D co n v e r s i o n t o e x t r a c t 16 samples of e i t h e r '1' or '0' from a raw data p u l s e . At the end of the sampling i n t e r v a l , the 16 samples a r e summed to y i e l d a t h r e s h o l d d e c i s i o n on the data p u l s e . I t s advantage i s t he e l i m i n a t i o n of an ' i n t e g r a t e ' c a p a c i t o r which i s prone t o - 4 6 - a l a r g e v o l t a g e step change caused by an unsuppressed impulse (see F i g 5 . 7 i n C4D). If a d i g i t a l integrate/dump had been used i n t h a t i n s t a n c e , the impulse would l i k e l y have m o d i f i e d one or two samples out of s i x t e e n , r e s u l t i n g i n decreased ' i n t e g r a t o r ' s e n s i t i v i t y t o impulse e f f e c t s . Another b e n e f i t i s the easy a d a p t a t i o n t o other b i t r a t e s by a simple change i n the sampling c l o c k r a t e . F i n a l l y , t h i s d i g i t a l integrate/dump can be e a s i l y i n c o r p o r a t e d i n t o an IC c h i p . Degradation due t o the d i s c r e t e nature of t h i s c i r c u i t does occur because of hard d e c i s i o n s on each sample; however the degradation i n terms of higher BER was not apparent when t h i s d i g i t a l integrate/dump was compared t o an analog integrate/dump. T h i s i s a t t r i b u t e d t o the many samples used i n forming the t h r e s h o l d d e c i s i o n . - 47 - 6. PRELIMINARY CMFSK TESTS TO SELECT SIGNALLING PARAMETERS 6.1 CMFSK B i t E r r o r Rates i n AWGN A white n o i s e t e s t was performed t o v e r i f y modem o p e r a t i o n at 19.2kbps t r a n s m i s s i o n r a t e and o f f s e t frequency of +4.8kHz. The c a r r i e r frequency was chosen t o be 120kHz. The t e s t setup i s as shown i n F i g . 6.1 and the white n o i s e BER ver s u s Eb/No r e s u l t s are p l o t t e d i n F i g . 6.2. A d d i t i o n a l BER t e s t r e s u l t s a t 1.2kbps and 4.8kbps data r a t e were obtained and recorded i n Table 6.1. Using these r e s u l t s , t he e q u i v a l e n t n o i s e bandwidth was estimated t o be 60kHz, which i s l a r g e r than the measured —3dB bandwidth of 52kHz. In white n o i s e the BER of the CMFSK modem i s given by: BER = Q C ( E b / N o ) 1 " 3 3 CO where QZxl = ( 2 7 T ) - 1 ' 2 exp(-y s e/2) dy Eb = average b i t energy = Pb / b i t r a t e = V 2 . i 0 / b i t r a t e No = n o i s e d e n s i t y = V 2 n o , „ / Eqv BW Pb = r e c e i v e d s i g n a l power Eqv BW = E q u i v a l e n t n o i s e bandwidth The s o l i d c urve shown i n F i g . 6.2 r e p r e s e n t s the i d e a l BER performance u s i n g 60kHz as the e q u i v a l e n t n o i s e bandwidth. 6.2 S p e c t r a l Comparison of a PN Sequence and i t s CMFSK Output , The spectrum of a 19.2kbps, le n g t h 2047 PN code i s shown i n F i g . 6.3. The main lobe i s centered at d.c. and i s 40kHz wide. If the spectrum i s centered at 120kHz, i t would r e p r e s e n t the - 48 - Table 6.1 1.2kbps, 4.8kbps, and 19.2kbps BER R e s u l t s i n A d d i t i v e White Gaussian Noise B i t Rate Eb/No BER P r e d i c t e d BER 1.2Kbps 4.95dB 7.2x10"= 3.8xl0~= 1.2kbps 8.47dB 5.7x10-=* 4.0x10-=* 1.2kbps 10.97dB 3.2x10"* 2.1x10-* 1.2kbps 12.55dB 2. 9x10-° 1 . I x l 0 - B 1.2kbps 13.58dB 1.4x10-= 9.0x10-^ 4.8kbps 4.95dB 7.5x10-= 3.8x10-= 4.8kbps 8.47dB 6.8x10-=* 4 . 0 x l 0 - 3 4.8kbps 10.97dB 2.2x10-* 2.1x10-* 4.8kbps 12.18dB 1.5xl0-«» 2.4x10-" 4.8kbps 12.91dB 3.0x10-* 4.9x10~* 4.8kbps 16.99dB < 10-° 7 . 6 x l 0 - 1 3 19.2kbps 4.95dB 6.7x10-* 3.8x10-= 19.2kbps 8.47dB 5.0x10-=* 4.Ox10~ 3 19.2kbps 10.97dB 1.9x10-* 2.1x10-* 19.2kbps 11.99dB Z.4xl0-~ 3.4x10-° 19.2kbps 12.91dB 1.2x10-" 4.9x10-" 19.2kbps 13.74dB 2.6x10— 5.8x10-^ 19.2kbps 14.49dB 2x10-'' 5.7x10-" flojse Generator BER <j- F 5 K henno^nla^ot—I HP /645/A DATA ERROR AM/\LY2ER DATA F i g . 6.1 CMFSK Modem White Noise BER Measurement Method F i g . 6.2 CMFSK Modem White Noise 19.2kbps BER Performance - 5 0 - F i g . G.4 Spectrum of a 19.2kbps PN code CMFSK Output output spectrum of a PSK system with a 120kHz c a r r i e r . The spectrum of the CMFSK output i s shown i n F i g . 6 . 4 . The main lobe i s centered at 120kHz and i s 30kHz wide. A comparison of the two s p e c t r a c o n f i r m s the narrower spectrum and f a s t e r s i d e l o b e r o l l o f f c h a r a c t e r i s t i c s of CMFSK over an e q u i v a l e n t PSK system. 6.3 CMFSK C a r r i e r Frequency S e l e c t i o n The c a r r i e r frequency d i c t a t e s where the s i g n a l spectrum w i l l l i e . I t s s e l e c t i o n i s a compromise between low n o i s e and low a t t e n u a t i o n l o s s . Two f r e q u e n c i e s are chosen, 60kHz (low at t e n u a t i o n ) and 120kHz (low n o i s e ) , t o determine which c a r r i e r frequency i s b e t t e r . The BER was measured at the two d i f f e r e n t f r e q u e n c i e s f o r both a ' l o c a l * and a 'remote' r e c e p t i o n . The ' l o c a l ' r e c e p t i o n r e s u l t s a t 60kHz are p l o t t e d i n F i g . 6.5. The ' l o c a l ' r e c e p t i o n r e s u l t s a t 120kHz are p l o t t e d i n F i g . 6.6. The 'remote' r e c e p t i o n r e s u l t s a re t a b u l a t e d i n Table 6.2. The t e s t s were performed on weekdays between 8:30am and 4:30pm. The BER r e s u l t s were recorded a f t e r about 100 b i t e r r o r s had oc c u r r e d . The e x c e p t i o n s were when the BER measurements surpassed 10 -* BER range and were stopped i r r e g a r d l e s s of the number of e r r o r s . I t i s observed t h a t the 60kHz c a r r i e r frequency s u f f e r s from more power l i n e impairments, i . e . deeper amplitude fades. T h e r e f o r e , the 120kHz c a r r i e r frequency i s chosen f o r i t s o v e r a l l b e t t e r performance. A spectrum a n a l y z e r was used t o r e c o r d the background n o i s e and t o superimpose i t on top of the spectrum of r e c e i v e d s i g n a l p l u s n o i s e . The r e s u l t , shown i n F i g . 6.7, shows the spectrum of F i g . 6.5 Interphase 19.2kbps BER versus Eb/No curve at a C a r r i e r Frequency of 60kHz F i g . 6.6 Interphase 19.2kbps BER versus Eb/No curve at a C a r r i e r Frequency of 120kHz - 5 4 - ^ ' 5 i a l + A/oise F i g . 6 . 7 Spectrum of CMFSK output Superimposed on Power L i n e Noise - 55 - Table 6.2 'Remote' Interphase 19.2kbps BER versus Eb/No at Tr a n s m i t t e r Output o-f IV, 2V, 3V, and 4V at Two D i f f e r e n t C a r r i e r F r e q u e n c i e s of 60kHz and 120kHz Trx Output Trx Fr e q Rcr Locn Rcr Eb/No BER (Rm 442) l.OV 60kHz Bench 'A' 12.2dB 2.0x10"= l.OV 60kHz Bench B' 19.7dB 5.2xl0-» l.OV 60kHz Bench 'C* 14.3dB 7.0x10-= l.OV 120kHz Bench A' ll.OdB 1.0x10-= l.OV 120kHz Bench *B' 17.5dB 3.5x10-* l.OV 120kHz Bench 'C 13.2dB 3.3x10-= 2.0V 60kHz Bench 'A' 18.3dB 4.0xl0~ : s 2.0V 60kHz Bench 'B' 25.5dB 8.0x10-* 2.0V 60kHz Bench 'C 20.0dB 3.2x10-= 2.0V 120kHz Bench *A' 15.6dB 7.5x10-= 2.0V 120kHz Bench B' 24.0dB 4.0x10-° 2.0V 120kHz Bench C* 18.4dB 2.3x10-' 3.0V 60kHz Bench 'A* 22.2dB l . O x l O - 3 3.0V 60kHz Bench *B' 29.8dB 9x10-* 3.0V 60 kHz Bench 'C* 24.3dB 4.0x10-= 3.0V 120kHz Bench 'A' 19.6dB 4.2x10-' 3.0V 120kHz Bench *B* 26.3dB 1.0x10-* 3.0V 120kHz Bench *C* 20.5dB 7.5x10-* 4.0V 60kHz Bench 'A' 24.3dB 2.5x10-* 4.0V 60kHz Bench 'B' 30.7dB 3x10-* 4.0V 60kHz Bench *C 25.3dB 3.7x10-= 4.0V 120kHz Bench 'A' 26.0dB 6.5x10-* 4.0V 120kHz Bench 'B' 32.0dB l.OxlO-* 4.0V 120kHz Bench *C 25.8dB 1.6x10-* note: 1. T r a n s m i t t e r on remote phase B. 2. Bench *C s i g n a l r e c e p t i o n s s u f f e r from severe p e r i o d i c amplitude dropouts a t 60kHz. - 56 - the 120kHz s i g n a l i s concentrated i n a r e l a t i v e l y q u i e t frequency band. T h i s i n d i c a t e s t h a t given the same t r a n s m i t t e r power, a high c a r r i e r frequency w i l l be r e c e i v e d at higher SNR i g n o r i n g the e f f e c t s of path a t t e n u a t i o n . However, b i t e r r o r performance should not be a f f e c t e d by the c h o i c e of c a r r i e r frequency as long as r e c e i v e d Eb/No are the same. The e f f e c t of c a r r i e r frequency on BER can be seen i n the photographs of power l i n e n o i s e i n t h r e e frequency bands shown i n F i g . 4.1, i n which they show an abundance of r i c h impulses i n lower f r e q u e n c i e s . O b s e r v a t i o n s of these impulses on a scope show approximately the same number of impulses i n each frequency band, but the amplitude and d u r a t i o n of the impulses are higher and longer i n the lower f r e q u e n c i e s . T h e r e f o r e , a data s i g n a l on a low frequency c a r r i e r may s u f f e r e x c e s s i v e BER d e t e r i o r a t i o n from a n o i s e impulse. 6.4 BER Measurement f o r CMFSK i n a 'Remote' Reception A s e t of 'remote' r e c e p t i o n BER data was c o l l e c t e d t o check f o r any s i g n i f i c a n t d i f f e r e n c e between a ' l o c a l ' and a 'remote' r e c e p t i o n . The r e s u l t s , p l o t t e d i n F i g . 6.8, show no a p p r e c i a b l e d i f f e r e n c e i n BER performance as long as the same Eb/No i s r e c e i v e d . ' L o c a l * and 'remote' c o n d i t i o n s are d e f i n e d i n S e c t i o n 3.1. T h i s r e s u l t i s u s e f u l because i t was obtained from a c t u a l power l i n e t r a n s m i s s i o n s over an unknown and h o s t i l e s i g n a l path. In a d d i t i o n , the v i a b i l i t y of the CMFSK modem i n power l i n e d ata communications i s c l e a r l y demonstrated. The BER ve r s u s Eb/No curve can be broken down i n t o two r e g i o n s : F i g . 6.8 'Remote' Interphase 19.2kbps BER ve r s u s Eb/No at a C a r r i e r Frequency of 120kHz - 58 - 1. An ex p o n e n t i a l decay i n BER from 10 -* t o 1 0 - 3 , i d e n t i f i e d as the white noise r e g i o n i n the BER versus Eb/No curve. 2. A change from the exp o n e n t i a l t o a gradual l i n e a r d r o p o f f when BER drops below l O - 2 , i d e n t i f i e d as the impulse noise r e g i o n i n the BER versus Eb/No curve. A power l i n e modem s u f f e r s p r i m a r i l y from white n o i s e e f f e c t s at low Eb/No v a l u e s . As the r e c e i v e d Eb/No i n c r e a s e s , impulse n o i s e becomes the dominant cause of b i t e r r o r s , l e a d i n g t o slow BER dro p o f f i n high Eb/No v a l u e s . T h i s t r e n d i s found i n telephone channels and other p r a c t i c a l data l i n k s , where the predominant e r r o r mechanism i s impulse n o i s e . When t h e r e i s very s t r o n g s i g n a l s , o n l y a high amplitude impulse can o c c a s i o n a l l y overwhelm the r e c e i v e r and cause a b i t e r r o r . S i n c e power l i n e impairments are p e r i o d i c , e r r o r s a re a l s o p e r i o d i c (see S e c t i o n 7.5) . - 59 - 7. BER MEASUREMENT RESULTS IN VARIOUS ENVIRONMENTS AND AT VARIOUS DATA RATES Our p r o t o t y p e CMFSK modem was operated under t h r e e d i f f e r e n t power l i n e environments t o o b t a i n BER measurements as well as b i t e r r o r s t a t i s t i c s r e p o r t e d elsewhere C263. The t h r e e environments i n c l u d e an i n d u s t r i a l b u i l d i n g , an apartment complex, and a r e s i d e n t i a l house. A m a j o r i t y of the BER measurements a r e from the 3-phase i n d u s t r i a l b u i l d i n g a t 1.2kbps, 4.8kbps, and 19.2kbps data r a t e . The other b u i l d i n g s were used t o c o l l e c t BER measurements at 19.2kbps data r a t e o n l y . 7.1 I n t e r f l o o r / I n t e r p h a s e I n d u s t r i a l BER Measurements at 1.2kbps. 4.8kbps. and 19.2kbps The i n d u s t r i a l b u i l d i n g used was the McLeod E l e c t r i c a l Eng. b u i l d i n g at UBC. I t i s f o u r s t o r i e s high with a main o f f i c e , a power g e n e r a t i o n l a b o r a t o r y , a high v o l t a g e s t u d i e s l a b o r a t o r y , and many other l a b o r a t o r y f a c i l i t i e s . The power d i s t r i b u t i o n c i r c u i t i s s u p p l i e d by a 110V/3-phase power network. Some heavy machinery such as a b u i l d i n g v e n t i l a t i o n f a n runs c o n t i n u o u s l y . The BER t e s t s were taken a c r o s s al1 the t h r e e phases of the power l i n e network and a c r o s s a l l the f o u r f l o o r s of the b u i l d i n g . The t e s t s were run mostly between 8:30 am t o 4:30 pm, Monday through F r i d a y , when t h e r e was the most v a r i e t y and the h e a v i e s t l o a d i n g of the b u i l d i n g ' s power l i n e s . In t h e t e s t s , the t r a n s m i t t e r was p l a c e d on d i f f e r e n t f l o o r s and the r e c e i v e r was c o n f i n e d t o Room 442 and e x t r a c t e d the s i g n a l from f o u r d i f f e r e n t o u t l e t s . Three of these o u t l e t s - 60 - belong t o a 3—phase power supply o u t l e t bar on one of the benches and the f o u r t h o u t l e t i s underneath a s i n k i n the same room. These o u t l e t s are i d e n t i f i e d as bench supply phase A, bench , supply phase B, bench supply phase C, and remote phase B, r e s p e c t i v e l y . In S e c t i o n 3.1, the 'remote' s e t of t r a n s m i s s i o n curves was obtained by i n j e c t i n g a s i g n a l i n t o remote phase B and r e c o v e r i n g i t i n the t h r e e bench phases. The ' l o c a l ' s e t of t r a n s m i s s i o n curves was obtained by i n j e c t i n g a s i g n a l i n t o phase B and r e c o v e r i n g i t i n the t h r e e phases of the bench supply r a i l . T h e r e f o r e , the ' l o c a l ' phase B p r o v i d e s a r e f e r e n c e a g a i n s t which other t r a n s m i s s i o n curves can be compared with. I t should be noted t h a t the t r a n s m i s s i o n paths between the "under—the—sink- o u t l e t " and bench o u t l e t s are a c t u a l l y worse than those from the basement o u t l e t s t o the 4th f l o o r bench o u t l e t s . The BER measurements are compiled i n T a b l e 7.1 and p l o t t e d i n F i g . 7.1. The same s e t of t e s t s was repeated f o r data r a t e s a t 1.2kbps and 4.8kbps. The BER vs. Eb/No r e s u l t s are compiled i n Table 7.2 and Table 7.3 and p l o t t e d i n F i g . 7.2 and F i g . 7.3. These graphs r e v e a l t h a t the white n o i s e r e g i o n extends t o lower BERs at lower data r a t e s . T h i s i n d i c a t e s the r e c e i v e r has i n c r e a s e d r e s i s t a n c e t o impulse n o i s e at low data r a t e s . 7.2 I n t e r f l o o r / I n t e r p h a s e Apartment BER Measurements at 19.2kbps The t h r e e - s t o r y apartment has about 50 i n d i v i d u a l d w e l l i n g u n i t s . I t p r o v i d e s accomodation t o UBC s t u d e n t s . The b u i l d i n g i s s u p p l i e d by l l O V / s p l i t - s i n g l e - p h a s e power. BER measurements - 61 - were taken f o r across-phase and a c r o s s - f l o o r c o n d i t i o n s at 19.2kbps. Over the d u r a t i o n of the measurement p e r i o d , i t was observed t h a t average background power l i n e n o i s e i s lowest from mid morning t o noon and h i g h e s t from l a t e a fternoon t o midnight. The BER measurements are compiled i n Table 7.4 and p l o t t e d i n F i g . 7.4. The white n o i s e and impulse n o i s e r e g i o n s seem t o be s i m i l a r t o those obtained i n the i n d u s t r i a l b u i l d i n g . The main source of e r r o r s comes from the on/off t r a n s i e n t s of nearby a p p l i a n c e s . A t r a n s i e n t may cause e i t h e r no e r r o r s or upwards of ten or more e r r o r s depending on i t s s t r e n g t h and d u r a t i o n . 7.3 I n t e r f l o o r / I n t e r p h a s e R e s i d e n t i a l BER Measurements at 19.2kbps The two-story house i s s u p p l i e d with 1 l O V / s p l i t - s i n g l e - p h a s e power. A s e t of remote across—phase 19.2kbps BER measurements were taken a c r o s s two f l o o r s . Two s e t s of BER measurements were taken, one with a h a i r d r y e r turned on t o i t s maximum of 1200W and the other with the h a i r d r y e r o f f . When the h a i r dryer was switched on, the average n o i s e l e v e l i n c r e a s e d from llmV t o over 30mV wh i l e the n o i s e peaks jumped from 130mV t o over 850mV. The r e s u l t s a r e p l o t t e d i n F i g . 7.5. The t r a n s m i t t e d output power l e v e l i s high e r i n the h a i r d r y e r "ON" case (see Table 7.5). 7.4 Cross S e c t i o n a l BER Performance at 19.2kbps i n an I n d u s t r i a l B u i l d i n g In a p r a c t i c a l a p p l i c a t i o n , a power l i n e modem operates with a p r e s e t output v o l t a g e l e v e l . T h e r e f o r e , i t i s important t o know how t h e BER performance v a r i e s d u r i n g continuous o p e r a t i o n - 62 - Table 7.1 I n t e r f l o o r / I n t e r p h a s e 19.2kbps BER versus Eb/No at T r a n s m i t t e r Output of IV, 2V, 3V, and 4V i n an I n d u s t r i a l B u i l d i n g Trx Output Trx Locn Rcr Locn (Rm 442) Rcr Eb/No BER l.OV l.OV l.OV l.OV l.OV l.OV l.OV l.OV l.OV l.OV l.OV l.OV l.OV l.OV l.OV l.OV 2.0V 2.0V 2.0V 2.0V 2.0V 2.0V 2.0V 2.0V 2.0V 2.0V 2-OV 2.0V 2.0V 2.0V 2.0V 2.0V Bsmt Bsmt Bsmt Bsmt 2nd f l o o r 2nd f l o o r 2nd f1oor 2nd f l o o r 3rd f l o o r 3rd f l o o r 3rd f1oor 3rd f l o o r 4th f l o o r 4th f l o o r 4th f l o o r 4th f l o o r Bsmt Bsmt Bsmt Bsmt 2nd f l o o r 2nd f l o o r 2nd f l o o r 2nd f l o o r 3rd f l o o r 3rd f l o o r 3rd f l o o r 3rd f l o o r 4th f l o o r 4th f l o o r 4th f l o o r 4th f l o o r Bench Bench Bench Remote Bench Bench Bench Remote Bench Bench Bench Remote Bench Bench Bench Remote Bench Bench Bench Remote Bench Bench Bench Remote Bench Bench Bench Remote Bench Bench Bench Remote A' B' C* B* A' B' C* B' A* B' C B' A' B' C* B' A' B' C* B' A' B' C B' A' B' C* B* A' B' C B' 16.7dB 12.8dB 15.0dB 15.9dB 16.3dB 12.2dB 16.7dB 15.5dB 15.5dB 9.7dB 15.0dB 12.4dB 15.0dB 8.7dB 12.4dB 14.5dB 22.4dB 17.ldB 20.ldB 18.ldB 23.3dB 16.3dB 20.4dB 18.4dB 22.8dB 16.3dB 19.3dB 16.7dB 21.3dB 15.9dB 18.8dB 14.2dB 1.3x10"' 6.0x10"' 2.8x10"' 3.4x10"' 2.2x10"' 8.0x10-=* 4.Ox 10"' 3.5x10"' 7.5x10-' 1.6xlO"= 8.5x10-' 8.5x10-' 2.9x10-' 1.2x10-= 8.0x10-' 7.0x10-' 1.0x10-° 2.3x10-' 1.1x10-* 2.6x10-' 7.0x10-* 1.7x10-' 1.0x10-* 2. 1x10-' 5.0x10-* 2. 1x10-' 2.0x10-* 2.0x10-' 4.5x10-° 3.4x10-' 4.2x10-* 2.5x10-' - 63 - Table 7.1 Cont'd Trx Output Trx Locn Rcr Locn Rcr Eb/No BER (Rm 442) 3.0V Bsmt 3.0V Bsmt 3.0V Bsmt 3.0V Bsmt 3.0V 2nd f l o o r 3.0V 2nd f l o o r 3.0V 2nd f l o o r 3.0V 2nd f l o o r 3.0V 3rd f l o o r 3.0V 3rd f l o o r 3.0V 3rd f l o o r 3.0V 3rd f l o o r 3.0V 4th f l o o r 3.0V 4th f l o o r 3.0V 4th f l o o r 3.0V 4th f l o o r 4.0V Bsmt 4.0V Bsmt 4.0V Bsmt 4.0V Bsmt 4.0V 2nd f l o o r 4.0V 2nd f l o o r 4.0V 2nd f l o o r 4.0V 2nd f l o o r 4.0V 3rd f l o o r 4.0V 3rd f l o o r 4.0V 3rd f l o o r 4.0V 3rd f l o o r 4.0V 4th f l o o r 4.0V 4th f l o o r 4.0V 4th f l o o r 4.0V 4th f l o o r Bench Supply 'A' Bench Supply 'B' Bench Supply 'C* Remote 'B' Bench Supply 'A' Bench Supply 'B' Bench Supply *C Remote *B' Bench Supply 'A* Bench Supply 'B * Bench Supply 'C* Remote 'B' Bench Supply 'A' Bench Supply 'B' Bench Supply *C Remote 'B' Bench Supply 'A* Bench Supply *B' Bench Supply 'C Remote 'B' Bench Supply 'A' Bench Supply 'B' Bench Supply *C* Remote 'B' Bench Supply 'A* Bench Supply 'B* Bench Supply 'C Remote B* Bench Supply 'A' Bench Supply *B' Bench Supply * c Remote 'B' 25.2dB 1.0x10-° 23.7dB 2.0x10-° 24.6dB 3.0x10-° 22.2dB 6.0x10-* 24.8dB 2.0x10-* 22.6dB 3.0x10-* 22.9dB 8.0x10-° 20.4dB 1.2x10"' 23.3dB 5.0x10-° 20.9dB 5.0x10-* 22.4dB 8.0x10-" 19.9dB 1.0x10"' 23.3dB 3.0x10-* 21.1dB 9.0x10-* 22.2dB 4.0x10-° 17.5dB 1.0x10-' 29.5dB < 10-* 22.2dB 3.0x10-* 27.2dB 1.0x10-° 28.5dB 1.0x10-* 26.3dB < 10-* 20.5dB 1.5x10-' 27.6dB 1.5x10-° 33.2dB 1.5x10-° 25.7dB 1.5x10-° 21.8dB 2.2x10-' 24.6dB 1.7x10-* 30.4dB 5.0x10-° 24.3dB 1.0x10-* 20.ldB 3.5x10-' 23.7dB 3.0x10-* 33.5dB < 10-* - 64 - Table 7.2 I n t e r f l o o r / I n t e r p h a s e 4.8kbps BER versus Eb/No at T r a n s m i t t e r Output of .IV, .2, .4V, and 2.5V i n an I n d u s t r i c a l B u i l d i n g Trx Output Trx Locn Rcr Locn Rcr Eb/No BER (Rm 442) lOOmV lOOmV lOOmV lOOmV lOOmV lOOmV lOOmV lOOmV lOOmV lOOmV lOOmV lOOmV lOOmV lOOmV lOOmV lOOmV 200mV 200mV 200mV 200mV 200mV 200mV 200mV 200mV 200mV 200mV 200mV 200mV 200mV 200mV 200mV 200mV Bsmt Bsmt Bsmt Bsmt 2nd f l o o r 2nd f l o o r 2nd f l o o r 2nd f l o o r 3rd f l o o r 3rd f l o o r 3rd f l o o r 3rd f1oor 4th f l o o r 4th f l o o r 4th f l o o r 4th f l o o r Bsmt Bsmt Bsmt Bsmt 2nd f l o o r 2nd f l o o r 2nd f l o o r 2nd f1oor 3rd f l o o r 3rd f l o o r 3rd f l o o r 3rd f l o o r 4th f l o o r 4th f l o o r 4th f l o o r 4th f l o o r Bench Supply Bench Supply Bench Supply Remote Bench Supply Bench Supply Bench Supply Remote Bench Supply Bench Supply Bench Supply Remote Bench Supply Bench Supply Bench Supply Remote Bench Supply Bench Supply Bench Supply Remote Bench Supply Bench Supply Bench Supply Remote Bench Supply Bench Supply Bench Supply Remote Bench Supply Bench Supply Bench Supply Remote A* B' C B' A' B' C* B * A' B* C B' A' B' C* B' A' B* C* B' A* B' C B* A' B' C* B* A' B' C* B' 5.4dB OdB 4.0dB 15.3dB 2.7dB OdB 2.5dB 1.7dB 2.7dB OdB 2.5dB 3.2dB 2.7dB OdB OdB 4.3dB 10.9dB 1.3dB 10.8dB 15.7dB 10.5dB 5.4dB 7.3dB 17.7dB 9. OdB 7. OdB 7.3dB 17.2dB 8.5dB 4.4dB 5.4dB 16.6dB 8.0x10-= 2.5xl0~* 5.0x10-= 1.3x10-' 1.5x10-= 2.5x10-* 7.0x10-= 1.0x10-= 2.0x10-= 2.5x10-* 8.5x10-= 2.5x10-= 3.0x10-= 2.5x10-* 8.5x10-= 1.3x10-= 4.0x10—» 1.3x10-* 1.0x10-= 1.0x10-^ 2.0x10-= 1.1x10-* 4.5x10-= A.OxlO-* 5 2.2x10-= 1.4x10-* 4.5x10-= 1.0xl0~» 3.0x10-= 1.5x10-* 5.5x10-= 2.5xlO- | B - 65 Table 7.2 Cont'd Trx Output Trx Locn Rcr Locn (Rm 442) Rcr Eb/No BER 400mV 400mV 400mV 400mV 400mV 400mV 400mV 400mV 400mV 400mV 400mV 400mV 400mV 400mV 400mV 400mV 2.5V 2.5V 2.5V 2.5V 2.5V 2.5V 2.5V 2.5V 2.5V 2.5V 2.5V 2.5V 2.5V 2.5V 2.5V 2.5V Bsmt Bsmt Bsmt Bsmt 2nd f l o o r 2nd f l o o r 2nd f l o o r 2nd f l o o r 3rd f l o o r 3rd f l o o r 3rd f l o o r 3rd f l o o r 4th f l o o r 4th f l o o r 4th f l o o r 4th f l o o r Bsmt Bsmt Bsmt Bsmt 2nd f1oor 2nd f l o o r 2nd f l o o r 2nd f l o o r 3rd f l o o r 3rd f l o o r 3rd f1oor 3rd f1oor 4th f l o o r 4th f l o o r 4th f l o o r 4th f l o o r Bench Supply Bench Supply Bench Supply Remote Bench Supply Bench Supply Bench Supply Remote Bench Supply Bench Supply Bench Supply Remote Bench Supply Bench Supply Bench Supply Remote Bench Supply Bench Supply Bench Supply Remote Bench Supply Bench Supply Bench Supply Remote Bench Supply Bench Supply Bench Supply Remote Bench Supply Bench Supply Bench Supply Remote A* B' C* B* A' B' C B' A* B' C* B' A' B' C* B* A' B' C B' A' B' C B* A' B' C* B' A' B" C* B' 16.3dB 7.0dB 15.0dB 23.8dB 14.7dB 5.4dB 11.7dB 23.3dB 13.5dB 5.4dB 11-OdB 22.7dB 25.4dB 5.4dB ll.OdB 22.4dB 29.4dB 25.2dB 27.9dB 28.5dB 26.3dB 19.2dB 27.ldB 32.5dB 28.7dB 21.6dB 26.3dB 35.6dB 29.4dB 20.ldB 25.9dB 35.0dB 2x10-* 4.5x10-= 2.5x10-° < i o - * 5x10-* 4.0x10-= 5.5x10-* 2x10-* 4x10-* 3.7x10-= 1.3x10-=* 8 x l 0 ~ * 6x10-* 4.0x10-= 1.7x10-=* 7x10-* 3x10-* 1x10-* < 10-* < i o - * < 10-* 1x10-* < 10-* < 10-* < 10-* 1x10-* < i o - * < i o - * 1x10-* 2x10-* < i o - * < i o - * - 66 - Table 7.3 I n t e r f l o o r / I n t e r p h a s e 1.2kbps BER versus Eb/No at T r a n s m i t t e r Output of 150mV and 200mV i n an I n d u s t r i a l B u i l d i n g Trx Output Trx Locn Rcr Locn Rcr Eb/No BER (Rm 442) 150mV 150mV 150mV 150mV Bsmt Bench Supply A' 16.8dB 5x10-° Bsmt Bench Supply 'B' 9.8dB 3 . 5 x l 0 - ' Bsmt Bench Supply 'C 14.2dB 2 . 0 x l 0 ~ ' Bsmt Remote 'B' 20.6dB 1x10-° 150mV 4th f l o o r Bench Supply 'A' 12.6dB 1x10-° 150mV 4th f l o o r Bench Supply 'B* 10.2dB 1.0x10-' 150mV 4th f l o o r Bench Supply *C* 12.6dB 3.0x10-' 150mV 4th f l o o r Remote 'B' 18.0dB 2 x l 0 ~ " 200mV 200mV 200mV 200mV Bsmt Bench Supply 'A* 15.3dB l x l 0 ~ " Bsmt Bench Supply *B' 6.4dB 6.1x10-= Bsmt Bench Supply 'C 16.3dB 4x10-° Bsmt Remote 'B' 19.3dB < 10~" 200mV 4th f l o o r Bench Supply 'A' 12.4dB 1x10-" 200mV 4th f l o o r Bench Supply *B* 5dB 8.0x10-= 200mV 4th f l o o r Bench Supply * C 8dB 1.0xl0~= 200mV 4th f l o o r Remote 'B' 14.3dB 1x10-" - 67 - Table 7.4 I n t e r f l o o r / I n t e r p h a s e 19.2kbps BER versus Eb/No at V a r i o u s T r a n s m i t t e r Output i n an Apartment Complex Trx Output Trx Locn Rcr Locn Rcr Eb/No BER lOOmV Rm317 Hallway Rm306 16.9dB 1. 3 x l 0 ~ 3 150mV Rm317 Hallway Rm306 18.3dB 3.5xl0~* 300mV Rm317 Hallway Rm306 24.4dB 3.5x10-° 500mV Rm317 Hallway Rm306 29.ldB 1.0xl0~° lOOmV Rm321 S t a i r s 150mV Rm321 S t a i r s 300mV Rm321 S t a i r s 500mV Rm32i S t a i r s Rm306 Rm306 Rm306 Rm306 11.7dB 16.4dB 21.6dB 29.2dB 7.0x10-= 5.0x10— 3. 1x10-* 1.0xl0~ e 50mV Rm217 Hallway Rm306 8.8dB 7.5x10-=* 64mV Rm217 Hallway Rm306 14.2dB 1.4X10-3* lOOmV Rm217 Hallway Rm306 15.6dB 7.0x10-° 200mV Rm217 Hallway Rm306 24.9dB 3.0x10-° 70mV Rm221 S t a i r s lOOmV Rm221 S t a i r s 200mV Rm221 S t a i r s 500mV Rm221 S t a i r s Rm306 Rm306 Rm306 Rm306 10.ldB 14.OdB 19.4dB 28.3dB 7 . 5 x l 0 - 3 1.8x10-=* 1.0x10—• 2.2x10-° lOOmV Rmll7 Hallway Rm306 17.4dB 1.0x10" 150mV Rmll7 Hallway Rm306 21.OdB 3.0x10" 300mV Rmll7 Hallway Rm306 24.2dB 6.5x10" 1.0V Rml17 Hallway Rm306 35.ldB 1.5x10" lOOmV Rml21 S t a i r s 150mV Rml21 S t a i r s 300mV Rml21 S t a i r s 500mV Rml21 S t a i r s Rm306 Rm306 Rm306 Rm306 13.ldB 16.7dB 24.ldB 29.7dB 2.0x10" 1.5x10" 2.0x10" 2.5x10" - 68 - Table 7.5 I n t e r f l o o r / I n t e r p h a s e 19.2kbps BER versus Eb/No at V a r i o u s T r a n s m i t t e r Output i n a R e s i d e n t i a l House with a Ha i r Dryer 'ON' and 'OFF' HAIR DRYER Trx output Rcr Eb/No BER OFF* 35mV lOdB 7.5X10" 3 'OFF' 60mV 16dB 1.2x10-=" OFF* HOmV 20dB 2.0x10-° OFF* 200mV 29dB 3.0x10"-* 'OFF' 500mV 35dB 3x10-" 'ON' 35mV 5dB 7.0x10-= 'ON' HOmV lOdB 3.0x10-= 'ON' 200mV 15dB 2.5x10-=* *0N' 300mV lBdB 5.Ox 10-* 'ON' 500mV 21dB 3.0x10-°  F i g . 7.2 4.8kbps BER versus Eb/No Measurement i n an I n d u s t r i a l B u i l d i n g F i g . 7.3 1.2kbps BER versus Eb/No Measurement i n an I n d u s t r i a l B u i l d i n g F i g . 7.4 19.2kbps BER ve r s u s Eb/No Measurement i n an Apartment Complex F i g . 7.5 19.2kbps BER ve r s u s Eb/No Measurement i n an R e s i d e n t i a l House - 74 - over s e v e r a l days. BER measurements were c a r r i e d out over a 5-day p e r i o d , s t a r t i n g on a Thursday and ending on a Monday. The t r a n s m i t t e r was -fixed at 4V output with the r e m o t e - r e c e i v e r on the same phase as the t r a n s m i t t e r (bench supply 'B' t o remote 'B'). The r e s u l t s are t a b u l a t e d i n Table 7.6. The t r e n d i n c r o s s s e c t i o n a l BER measurement i n d i c a t e s t h a t power l i n e l o a d i n g has an adverse e f f e c t on power l i n e communications, as i n d i c a t e d by the worst case BERs o c c u r r i n g i n the a f t e r n o o n s of two weekdays. During the weekend p e r i o d , the BER drops by a l a r g e amount of t h r e e order i n magnitude or more, i . e . 1 0 — 3 t o 10 _*. T h i s dynamic f l u c t u a t i o n i n BER r e f l e c t s the adverse e f f e c t of power l i n e l o a d i n g . 7.5 C I a s s f i c a t i o n of Power L i n e Induced E r r o r s Power l i n e induced e r r o r s can be c a t e r g o r i z e d as f o l l o w s : 1. Impulse n o i s e induced e r r o r s , e i t h e r p e r i o d i c or a p e r i o d i c . 2. Momentary Eb/No r e d u c t i o n induced e r r o r s , e i t h e r p e r i o d i c or a p e r i o d i c . By f a r the most dominant source of e r r o r s are caused by p e r i o d i c impulse n o i s e . F i g . 7.6 r e c o r d s the p e r i o d i c b i t e r r o r occurance caused by p e r i o d i c impulses i n t h e r e c e i v e d s i g n a l . The g e n e r a t i o n of p e r i o d i c impulses i s l i n k e d t o o p e r a t i o n s of p h a s e - c o n t r o l l e d e l e c t r i c a l equipement C28,29D. A p e r i o d i c impulse n o i s e i s l i k e l y the r e s u l t of high amplitude turn-on and t u r n — o f f t r a n s i e n t s (see F i g 2.8 i n C4D). In a d d i t i o n , i t was observed t h a t power l i n e impulses c o u l d appear 200us t o 300us a p a r t , l e a d i n g t o the impression of small e r r o r b u r s t s 1263. - 75 - Tabl e 7.6 Cross i S e c t i o n a l 19.2kbps BER Measurement Time Thursday F r i day Saturday Sunday Mond. lam n/a 23 0 0 617 2am n/a 7 4 6 315 3am n/a 13 0 0 396 4am n/a 15 0 0 364 5am n/a 7 0 0 410 6am n/a 20 0 0 573 7am n/a 25 0 0 674 8am n/a 23 0 0 622 9am n/a 0 1 0 682 10am n/a 15 5 1 346 1 lam n/a 34 0 1 294 12am n/a 34 0 0 1999 1pm n/a 399 3 2 289 2pm n/a 624 0 0 599 3pm 109 657 O 0 329 4pm 219 1999 0 o n/a 5pm 28 865 0 2 n/a 6pm 188 1286 1 0 n/a 7pm 37 806 3 3 n/a 8pm 27 1426 0 3 n/a 9pm 53 1112 1 0 n/a lOpm 30 588 5 0 n/a 11pm 606 1 0 1005 n/a 12pm 32 0 4 570 n/a note: 1. A l l BERs i n u n i t of 10~*. 2. 1999 i n d i c a t e s e r r o r counter overflow. 3. Continuous BER measurement achieved by l e a v i n g the HP1645A data e r r o r a n a l y z e r on automatic PRINTER mode at EXPONENT of '6'. - 76 - | Impulse. F i g . 7.6 Impulse Noise Induced B i t E r r o r s - 77 - A momentary Eb/No r e d u c t i o n occurs when the s i g n a l undergoes a temporary amplitude dropout or when the n o i s e undergoes a temporary i n c r e a s e . I t i s a l s o p o s s i b l e f o r both the s i g n a l and n o i s e t o e x p e r i e n c e the same amplitude v a r i a t i o n s t o p r e s e r v e the same Eb/No both b e f o r e and a f t e r a momentary amplitude fade. O r i g i n of s i g n a l amplitude v a r i a t i o n s i s l i n k e d t o power l i n e impedance modulation e f f e c t s [17,203. Amplitude f a d i n g a f f e c t s a l l f r e q u e n c i e s but i t s depth i s frequency dependent (see F i g . 3.5). E r r o r s r e s u l t i n g from Eb/No r e d u c t i o n s u s u a l l y occur i n small b u r s t s . E r r o r s caused by e i t h e r p e r i o d i c or a p e r i o d i c momentary Eb/No r e d u c t i o n s are r a r e . T h i s i s because the CMFSK modem i s u s u a l l y o p e r a t i n g i n high Eb/No environments, and an e r r o r o c c u r s mainly as a r e s u l t of a n o i s e impulse. D i s c u s s i o n on p e r i o d i c and a p e r i o d i c s i g n a l amplitude fades a l s o appears i n Chan's t h e s i s [263. 7.6 D i s c u s s i o n on Power L i n e Impulse Noise Suppression Techni ques Most b i t e r r o r s are a r e s u l t of impulse n o i s e . An impulse, upon e n t e r i n g a d e t e c t i o n system, w i l l s h a r p l y reduce Eb/No and cause a p o s s i b l e e r r o r . Some papers have been presented on optimum or near-optimum weak s i g n a l d e t e c t i o n s i n non-Gaussian n o i s e channels [43,443. Impulse n o i s e s u p p r e s s i o n i s e s s e n t i a l l y a n o n - l i n e a r p r o c e s s . One simple approach i s t o c l i p an impulse, thereby l i m i t i n g i t s r e c e i v e d energy. Another approach i s t o use redundancy and d i s c r e t e F o u r i e r t r a n s f o r m a t i o n t o perform impulse - 78 - n o i s e c a n c e l l a t i o n C45]. A t h i r d method i s t o use smearing and de-smearing - f i l t e r s i n data t r a n s m i s s i o n s t o combat the e f f e c t s of impulse n o i s e [463. Here, a scheme i s proposed t o take advantage of the f a c t t h a t a t r a n s m i s s i o n becomes more white n o i s e l i m i t e d as the b i t d u r a t i o n of the t r a n s m i s s i o n i n c r e a s e s . The i d e a i s t o simply i n c r e a s e the o b s e r v a t i o n p e r i o d between d e c i s i o n s . With a longer o b s e r v a t i o n i n t e r v a l , impulse n o i s e e f f e c t s should be reduced. The widening of the o b s e r v a t i o n i n t e r v a l n e c e s s i t a t e s the use of m u l t i l e v e l or M—ary modulation schemes t o maintain the same data r a t e given a reduced t r a n s m i s s i o n r a t e . A p o t e n t i a l drawback i s the requirement of accurate m u l t i l e v e l t h r e s h o l d s . T h i s above concept was t r i e d by d e s i g n i n g and b u i l d i n g a 4 - l e v e l FSK modem and comparing i t s performance with t h a t of t h e b i n a r y CMFSK modem under s i m i l a r power l i n e c o n d i t i o n s . BER measurements are compiled i n Table 7.7 and p l o t t e d i n F i g . 7.7. The graph shows a tr e n d of lower BER performance achieved by the 4 - l e v e l FSK modem. The implementation of the 4 — l e v e l FSK system i s d e s c r i b e d i n F i g . 7.8 and F i g . 7.9. I t appears t o be s t i l l s u f f e r i n g from impulse n o i s e e f f e c t s because i t s t r a n s m i t t e d b i t d u r a t i o n of lOOus i s not wide enough t o overcome an impulse n o i s e whose width i s t y p i c a l l y around 30us. I t i s expected t h a t a 16-1evel FSK system with 200us b i t d u r a t i o n would y i e l d a lower BER at the same r e c e i v e d Eb/No. - 79 - Table 7.7 19.2kbps BER Measurement of a 4-Level FSK and the CMFSK Modem 4-Level FSK Modem Trx V o l t a g e Rcr Eb/No BER 500mV 16. 8dB 5. 7x 1O"5* l.OV 21.8dB 1.3x10-' 1.5V 26.0dB 4.0x10—• 2.0V 27.8dB 7.0xl0-» 3.0V 31.7dB 9.0x10-* CMFSK Modem 500m V 16.8dB S.OxlO" 3 8 l.OV 22.9dB 1.5X10-' 1.5V 27.4dB 4.5xl0—» 2.0V 29.8dB 1.5x10-* 3.0V 33.ldB l . S x l O - " note: T r a n s m i t t e r on Bench 'B'f r e c e i v e r on Remote 'B*. F i g . 7.7 Comparison of 19.2kbps BER of a 4 - l e v e l FSK and the CMFSK Modem - 81 - J±L T 5T 6 3 XR-220& 4-Level FSK 7 FH/R AMp *1 <fo>.</?3 5^ 1 / «—1 loo' ' o l ' CDfoG6 1 <S D f-081 dY-0 Dat«. (X > Q \3.ZMz. 3. &KHz Q d(T2 * ) J tele) Q J15 kHi A = I/KZC = 12. 1 . J KHZ V«f c = 1 ZS KHz F i g . 7.8 Block Diagram of 4-Level FSK Modulator - 82 - u / 9 .2^2. 'Loa6"l— Lea. i ?7 Da-ta. Note: "Load" precedes " Ourr,j3 hi (A n a /c> q -r /I B c 1 1 i 'io' o 2 1 o o I •or o o o 'oo' F i g . 7.9 Block Diagram of 4-Level FSK Demodulator - 83 - 8. SPECTRUM SPREADING 8.1 D i s c u s s i o n of Spectrum Spreading i n Power L i n e Data Commun i c at i on s The use o-f spread spectrum technology i n power l i n e modems has been suggested by s e v e r a l authors 14,17,18,193. C i t e d advantages i n c l u d e the a b i l i t y t o combat narrow band impairments and t o a l l o w simultaneous user access v i a Code D i v i s i o n M u l t i p l e Access ICDMA3. In a d d i t i o n , Ochsner suggested t h a t r e l a t i v e l y high t r a n s m i s s i o n r a t e s may be p o s s i b l e with lower t r a n s m i s s i o n power than -for an e q u i v a l e n t narrow band system i n the h o s t i l e environment o-f a power l i n e channel 1173. These advantages assume t h a t the power l i n e channel has a much wider bandwidth than the baseband s i g n a l spectrum and th a t the channel a t t e n u a t i o n i s assumed t o be re a s o n a b l y f l a t w i t h i n t h i s bandwidth. N e i t h e r assumption i s n e c e s s a r i l y t r u e i n a power l i n e . T r ansmission curves presented i n Chapter 3 and i n other papers 117,263 suggest t h a t an usable power l i n e channel extends -from 30kHz t o 150kHz and t h a t the v a r i a t i o n i n t r a n s m i s s i o n d i f f e r e n c e w i t h i n t h i s 120kHz bandwidth can o f t e n exceed lOdB or even 20dB. Thus, t h i s d e v i a t i o n from a wide and f l a t channel assumption should be i n c o r p o r a t e d i n the a n a l y s i s of any spread spectrum communications systems. The r e s u l t i s an expected d e g r a d a t i o n i n performance i n terms of a lower e q u i v a l e n t p r o c e s s i n g g a i n . Assuming a f l a t power l i n e bandwidth of 120kHz, a d i r e c t sequence CDMA spread spectrum system with 20dB p r o c e s s i n g g a i n can, i n th e o r y , support 100 simultaneous - 84 - 60bps u s e r s . In C183, the authors p r e d i c t e d a maximum number o-f 22 simultaneous 60bps u s e r s as t h e i r system's upper bound performance u s i n g t h e i r experimental s i n g l e - u s e r BER r e s u l t at 60bps. The above h y p o t h e t i c a l CDMA system does not i n c l u d e the e f f e c t s of n e a r / f a r f i e l d and implementation l i m i t a t i o n i n the CDMA a n a l y s i s £47,483. The n e a r / f a r problem u s u a l l y r e s u l t s when a l o c a l r e c e i v e r t r i e s t o p i c k out a remote and much weaker t r a n s m i s s i o n i n the presence of st r o n g c o - s i t e t r a n s m i s s i o n s . T h i s problem i s o f t e n so severe t h a t a co n v e n t i o n a l DS CDMA system can not be used. A remedy i s t o r a i s e t he p r o c e s s i n g g a i n which r e s u l t s i n e i t h e r a r e d u c t i o n i n the number of simultaneous u s e r s or decreased user throughput. U s u a l l y the number of u s e r s i s r e t a i n e d and the throughput i s forgone t o pre s e r v e the s p i r i t of a CDMA system. In a t y p i c a l power l i n e channel with average a t t e n u a t i o n s of 20dB t o 30dB, the n e a r / f a r problem t r a n s l a t e s i n t o a lO O — f o l d t o 1000—fold decrease i n throughput and i n c l u s i o n of implementation l i m i t a t i o n s w i l l f u r t h e r reduce t h i s r a t e . In the h y p o t h e t i c a l DS CDMA system d e s c r i b e d above, the r e s u l t i n g throughput l o s s c o u l d be reduced c o n s i d e r a b l y by us i n g orthogonal codes which have s i m i l a r s p e c t r a l p r o p e r t i e s of long PN sequences 01000 b i t s long) and by u s i n g the power l i n e ac v o l t a g e t o a l i g n and s y n c h r o n i z e a l l user codes. A frequency hopping CDMA system does not s u f f e r as much from the n e a r / f a r problem, but i t s use i s l i m i t e d by a v a i l a b l e power l i n e bandwidth and i n c r e a s e d modem complexity. However, modem complexity can be reduced i f the ac v o l t a g e i s used t o p r o v i d e i n i t i a l hop s y n c h r o n i z a t i o n . - 85 - Ochsner's suggestion t h a t spread spectrum methods may allow a r e l a t i v e l y high t r a n s m i s s i o n r a t e system t o operate with low t r a n s m i s s i o n power i s based on the n o t i o n t h a t a narrow band system would use higher t r a n s m i t t e r power t o combat narrow band -fades. T h i s does not mean t h a t a spread spectrum system with a 300kHz spread bandwidth centered at 150kHz w i l l be more robust than a narrow band system o p e r a t i n g with a bandwidth o-f 1kHz at 40kHz. In -fact, much o-f the wide band t r a n s m i t t e d energy would probably be l o s t t o the channel be-fore r e a c h i n g a remote user. Spread spectrum methods must be c a r e - f u l l y a p p l i e d with regard t o a v a i l a b l e channel bandwidth, high l e v e l o-f low frequency n o i s e , and low t r a n s m i s s i b i 1 i t y of high frequency s i g n a l . A reasonably good s p e c t r a l placement of the spreaded s i g n a l should c o i n c i d e with t h a t range of f r e q u e n c i e s which possess good Eb/No f i g u r e s . In N i e d e r b e r g e r ' s paper C493, he p o i n t e d out t h a t "What i s important f o r a q u a l i t y of a t r a n s m i s s i o n channel i s not the t r a n s m i s s i o n c h a r a c t e r i s t i c or the d i s t u r b a n c e environment on t h e i r own, but the r e l a t i o n s h i p of these q u a n t i t i e s t o each other. The s i g n a l - t o - n o i s e r a t i o i n d i c a t e s those p a r t s of the frequency spectrum where the supply network possesses good or bad t r a n s m i s s i o n q u a l i t y . " (see F i g . II and F i g . I l l i n h i s paper). T h i s range of f r e q u e n c i e s e x i s t s from 50kHz t o 500kHz i n a r e s i d e n t i a l power l i n e . In an i n d u s t r i a l power l i n e , the range i s p r o b a b l y i n the r e g i o n between 50kHz and 100kHz (see T a b l e 6.2). A 30kHz t o 50kHz channel occupancy i s o f t e n s u f f i c i e n t p r o t e c t i o n a g a i n s t narrow band impairments i n e i t h e r an i n d u s t r i a l or a r e s i d e n t i a l power l i n e below 200kHz o p e r a t i o n . - 86 - Wider channel occupancies a r e not recommended s i n c e the r e s u l t a n t s i g n a l spectrum may occupy more of the high n o i s e and low t r a n s m i s s i o n r e g i o n of the power l i n e s , r e s u l t i n g i n reduced SNR and degraded performance. The experimental BER measurements a t 1.2kbps, 4.8kbps, and 19.2kbps i n d i c a t e t h a t the major cause of power l i n e impairments come from impulse n o i s e whose d u r a t i o n approaches t h a t of a data b i t at high data r a t e s . T h e r e f o r e , as the t r a n s m i s s i o n r a t e i s i n c r e a s e d , the system becomes more s u s c e p t i b l e t o impulse n o i s e . T h i s i s analogous t o p u l s e jamming i n DS spread spectrum system. Consequently, more power i s r e q u i r e d t o overcome impulse n o i s e e f f e c t s at high data r a t e s (see BER versus Eb/No curves at 4.8kbps & 19.2kbps), which was not mentioned i n Ochsner's paper. A power l i n e spread spectrum system may be l i m i t e d i n i t s u s e f u l n e s s because of i n s u f f i c i e n t power l i n e bandwidth and high path a t t e n u a t i o n between u s e r s . But i t s other advantage of low s p e c t r a l d e n s i t y i s u s e f u l i n lowering in-band and out-of-band i n t e r f e r e n c e t o c o - s i t e u s e r s . For example, t h i s low power f l u x d e n s i t y f e a t u r e i s important i n s a t e l i t e communication systems design [50,513. In our CMFSK modem, spread spectrum i s a p p l i e d t o low r a t e t r a n s m i s s i o n s t o reduce otherwise narrow band i n t e r f e r e n c e t o low l e v e l 'AWGN'-like n o i s e . Coupled with the compact spectrum and r a p i d s i d e l o b e r o l l o f f of the CMFSK modulation, the modem i s prevented from g e n e r a t i n g narrow band tone i n t e r f e r e n c e , and i t can t h e r e f o r e output more power t o overcome l i n e a t t e n u a t i o n . - 87 - T h i s w i l l be d i s c u s s e d i n more d e t a i l s i n s e c t i o n 8.3. 8.2 P o t e n t i a l Spread Spectrum A p p l i c a t i o n s i n Q-ffice and R e s i d e n t i a l Power L i n e Communications Given s u f f i c i e n t l y wide bandwidth and low a t t e n u a t i o n , a power l i n e spread spectrum system can r e a l i z e many of i t s s t a t e d b e n e f i t s . For example, i f the n e a r / f a r problem i s l i m i t e d t o lOdB and the power l i n e bandwidth becomes 500kHz wide, a DS CDMA system c o u l d support 50 simultaneous u s e r s with pseudorandom PN codes at 500bps/user. In a d d i t i o n , any narrow band fades c o u l d be handled with s l i g h t system de g r a d a t i o n . Such an i d e a l channel c o u l d be found i n a r e s i d e n t i a l house (see F i g . 3.9) with high frequency bypassing between the phases and s i g n a l i s o l a t i o n of the incoming power l i n e s t o c o n f i n e most of the s i g n a l energy w i t h i n the power l i n e s of the house (see F i g . 8.1). Another p o s s i b i l i t y l i e s i n an o f f i c e f l o o r where a s e c t i o n of the power l i n e s i s i s o l a t e d and bypassed t o serve as a l o c a l area network. The s i g n a l bypass and i s o l a t i o n c o u l d be performed at t h e s e r v i c e box t o i s o l a t e t he s e c t i o n of the power l i n e network used i n communications. In a d d i t i o n , a r e l a y modem co u l d be used t o ensure r e l i a b l e communications a c r o s s phases (see F i g . 8.2). The r e l a y c o u l d be i n s t a l l e d i n the s e r v i c e box along with the i s o l a t i o n and bypass hardware. In a custom i n s t a l l a t i o n , the number of simultaneous u s e r s c o u l d be t r a d e d o f f a g a i n s t the r e q u i r e d throughput r a t e . - 88 - r 180° ~r> L Zsolat/'on. Bypass Service Box -O Neutral F i g . 8.1 Proposed High Frequency Bypassing and I s o l a t i o n of a Power L i n e Network X.solext iorx 0° -H> /So0 H > Neutra.1 'Se.n/ice. Box F i g . 8.2 Proposed Across-Phase Modem Relay - 89 - 8.3 Bene-fits o-f Spread Spectrum i n Low Data Rate Commun i c at i ons The a p p l i c a t i o n of spread spectrum t o low speed t r a n s m i s s i o n i s d e s c r i b e d i n t h i s s e c t i o n . The purpose i s t o reduce narrow band i n t e r f e r e n c e generated by low speed t r a n s m i s s i o n s , and t o enable the t r a n s m i t t e r t o output more power t o overcome path a t t e n u a t i o n . The spectrum of a narrow band system, BSR X—10, i s compared with t h a t of the CMFSK modem at the same average output of IV. Both s p e c t r a a r e d i s p l a y e d i n F i g . 8.3. The output of the BSR X-10 system e x h i b i t s a sharp s p e c t r a l peak and a high percentage of energy concentrated i n i t s narrow s i d e l o b e s . On the other hand, the CMFSK output shows a wider main lobe and only a small f r a c t i o n of energy i s con t a i n e d i n the s i d e l o b e s (main lobe c o n t a i n s >99% of the energy). As a r e s u l t , the BSR X-10 system w i l l generate tone i n t e r f e r e n c e and the CMFSK modem w i l l generate 'AWSN'-Iike n o i s e . A l i s t e n i n g t e s t was c a r r i e d out t o c o n f i r m the e f f e c t of narrow and wide band i n t e r f e r e n c e on AM r a d i o s t a t i o n s which occupy the 540-1600kHz frequency band. A *30 AM/FM c l o c k r a d i o was p l a c e d s i d e by s i d e the modem i n an r e s i d e n t i a l o u t l e t . When the BSR u n i t was turned on, s t r o n g tone i n t e r f e r e n c e was heard i n s e v e r a l s t a t i o n s , with i t s e f f e c t s t r o n g e s t i n weak s t a t i o n s . Operating under the same c o n d i t i o n s , except with a l a r g e r t r a n s m i t t e r output v o l t a g e of 4V as compared t o IV i n the BSR X-10 u n i t , the i n t e r f e r e n c e from the CMFSK modem was observed as a l e s s annoying r i s e i n background ' h i s s i n g ' n o i s e . T h i s r e s u l t i n d i c a t e s the b e n e f i t of spread spectrum i n 8.3 S p e c t r a l Comparison of BSR X-10 and CMFSK Modem - 91 - r e d u c i n g narrow band i n t e r f e r e n c e , thereby a l l o w i n g more output power t o be t r a n s m i t t e d without i n f r i n g i n g on FCC r e g u l a t i o n s or other a p p l i c a b l e emission c o n t r o l s . 8.4 A p p l i c a t i o n of Databand Spread Spectrum i n the CMFSK Power L i n e Modem In the CMFSK modem, spectrum spreading was performed at the databand l e v e l . The i d e a i s t o t r a n s m i t a 19.2kbps PN sequence which has been E x c l u s i v e ORed with a lower r a t e data sequence. The r e c e i v e r can recover the data sequence by E x c l u s i v e ORing the r e c e i v e d b i t stream with the same PN sequence and then making m a j o r i t y l o g i c d e c i s i o n s . T h i s baseband spread spectrum method i s shown i n F i g . 8.4. I t i s s i m i l a r i n some r e s p e c t s t o message scrambling/descrambling i n a d i g i t a l communication system. T h e r e f o r e , a t r a n s m i s s i o n can be made secure by u s i n g long PN sequences generated by n o n — l i n e a r s h i f t r e g i s t e r feedback. The drawback of baseband spreading i s the requirement of a minimum SNR t o enable the r e c o v e r y of each code b i t b e f o r e the data i n f o r m a t i o n can be r e t r e i v e d . In a DS or FH spread spectrum system, the data BER r a t h e r than the code BER requirement d i c t a t e s the r e q u i r e d SNR. However, our proposed scheme o f f e r s a f a s t e r a c q u i s i t i o n speed, on the order 50 b i t s t o 100 code b i t s , and i s l e s s complex i n hardware r e a l i z a t i o n than a c o n v e n t i o n a l spread spectrum system. T h i s i s a c l a s s i c a l t r a d e o f f problem between a c q u i s i t i o n speed and r e c e i v e d SNR. B a s i c a l l y , a higher SNR conveys a more r e l i a b l e i n f o r m a t i o n and hence a l l o w s a quicker a c q u i s i t i o n and s i m p l e r implementation. Channel N°iSe. J(k)@ PA/CK) F5K Mc^uhtor Transmitter F5fs Demodulator RAW blTS PN ^aJe OK ftecoven Code Zynckronijdt-t'on OLK *5YNC" J L _ Code. Ge*e rato r- PNCK) O -o F i g . 8.4 Block Diagram of Databand Spread Spect rum - 93 - 8.5 Code S y n c h r o n i z a t i o n u s i n g a D i g i t a l Matched F i l t e r PN code a c q u i s i t i o n i s achieved v i a a d i g i t a l v e r s i o n of the PN code matched f i l t e r d i s c u s s e d i n C523. B a s i c a l l y , a delayed v e r s i o n of the incoming code c h i p s a re b i t - b y - b i t m u l t i p l i e d by a predetermined PN sequence and summed. The summation output w i l l exceed a t h r e s h o l d whenever the r e c e i v e d code sequence i s matched t o the l o c a l sequence. Upon t r i p p i n g the t h r e s h o l d , the r e c e i v e r code i s loc k e d onto the incoming sequence and the r e t r i e v a l of data b i t s begins. If a PN sequence i s generated by a M-stage s h i f t r e g i s t e r , a M—stage DMF i s s u f f i c i e n t f o r a c q u i s i t i o n of the PN sequence. If the incoming b i t stream has e r r o r s , more than M st a g e s a re r e q u i r e d t o g i v e high a c q u i s i t i o n and low f a l s e alarm p r o b a b i l i t y because of the many high ' s i d e l o b e s ' i n the output of the DMF or s l i d i n g c o r r e l a t o r C533. T h i s i s always the case i n an a c q u i s i t i o n system i n which o n l y a small p o r t i o n of a long PN sequence or s h o r t codes are used i n the c o r r e l a t i o n of the a c q u i s i t i o n p r o c e s s . Our CMFSK modem has a 48-stage DMF. The t a p s used i n the DMF multiply—and—sum network were obtained from a p r i n t - o u t of a 11—stage s h i f t r e g i s t e r (code l e n g t h 2047) over 200 b i t s . A 4 8 - b i t sequence c o n t a i n i n g an equal number of ' l ' s and *0"s was chosen as the s y n c h r o n i z a t i o n sequence and corresponding DMF tap v a l u e s . A 11-bit sequence of f i f t y b i t s p r e c e d i n g t h i s s y n c h r o n i z a t i o n sequence was chosen as the i n i t i a l code word s t a t e of the t r a n s m i t t e r PN code generator. T h e r e f o r e , a t r a n s m i s s i o n begins by sending these f i f t y b i t s f o l l o w e d by the 4 8 — b i t 'sync* sequence. In the r e c e i v e r , these - 94 - - f i r s t - f i f t y code c h i p s s e t the b i t c l o c k r e c o v e r y i n motion and a r e a p p r o p r i a t e l y c a l l e d the b i t c l o c k t r a i n i n g sequence. Data t r a n s m i s s i o n begins at the end of the 'sync' sequence. The block diagram of the s l i d i n g c o r r e l a t o r or DMF i s g i v e n i n F i g . 8.5. The 4 8 - b i t s y n c h r o n i z a t i o n sequence and the i n i t i a l 1 1-bit code word s t a t e which i n i t i a t e s a t r a n s m i s s i o n are omitted s i n c e other PN sequences can be used without l o s s of performance pro v i d e d the PN code l e n g t h exceeds 2000 b i t s . Reference C54D c o n t a i n s a c i r c u i t which p r o v i d e s PN code s y n c h r o n i z a t i o n . 8.6 T o l e r a n c e t o Power L i n e Small E r r o r B u r s t s by I n t e r l e a v i n g From Chan's t h e s i s on e r r o r s t a t i s t i c s [263, i t seems t h a t most e r r o r s are h i g h l y c o r r e l a t e d , i . e . small b u r s t s are common. Th e r e f o r e , our proposed t r a n s m i s s i o n scheme w i l l s u f f e r from small b u r s t s of code c h i p e r r o r s . T h i s i s l i k e a DS spread spectrum system being e f f e c t i v e l y jammed by a p u l s e jammer and a FH spread spectrum system being e f f e c t i v e l y jammed by a tone jammer. In both c a s e s , forward e r r o r c o r r e c t i o n reduces the jamming e f f e c t . Observation of e r r o r p a t t e r n s i n d i c a t e s t h a t t h e r e i s a l a r g e e r r o r — f r e e and a small e r r o r — p r o n e r e g i o n . O b v i o u s l y , the e r r o r - p r o n e r e g i o n i s c o n c e n t r a t e d near the s t r o n g impulses i n the r e c e i v e d s i g n a l . Such a r e g i o n may c o n t a i n s i n g l e - b i t or m u l t i p l e - b i t e r r o r s . A small e r r o r b u r s t made up of m u l t i p l e e r r o r s w i l l o f t e n reduce the c a p a b i l i t y of a random e r r o r c o r r e c t i o n code. Although a b u r s t e r r o r code can handle small e r r o r b u r s t s , i t w i l l not operate p r o p e r l y i f a s i n g l e - b i t e r r o r then o c c u r s o u t s i d e the e r r o r c o r r e c t i n g span of the code. '''glial Moitchea. Frl-ter CLK PNCL) & CLK CLK CD4-OS1- R o • • • ?NCi+K)S 7, / / v*\nen in "Sy»c" _/\_ Q 3 Qx n n faralh) k n ^ — J Q s 2V)T,4 coq-oai PS Pi Parallel Load 9 • "5jnc" pul: se +/5v Zo<r a/ PA/ Otnera±of- Ci' = 0 we aw Investor . If Ci = I , Siraiqht Connection. . + i , •- • j Ci+H-8 are the 4-8-brr Sync^on/'jatfort Sequence. F i g . 8.5 Block Diagram of D i g i t a l Matched F i l t e r Threshold De-ttpc-iop <0 - 96 - There-fore, i t i s proposed t o d i s p e r s e the t r a n s m i t t e d b i t s and then re-assemble them i n the r e c e i v e r . The b e n e f i t i s t o a l l o w th e use of random e r r o r c o r r e c t i o n codes on a small e r r o r b u r s t now separated i n t o mostly s i n g l e - b i t e r r o r s , and a l s o on other random e r r o r s as w e l l . The p e n a l t y of performing both b u r s t and random e r r o r c o r r e c t i o n i s a r e d u c t i o n i n throughput. The de- assembly and re-assembly of t r a n s m i s s i o n i s accomplished by b i t i n t e r l e a v i n g and d e - i n t e r l e a v i n g i n the t r a n s m i t t e r and r e c e i v e r r e s p e c t i v e l y . I n t e r l e a v i n g b a s i c l y randomizes e r r o r occurances and a l l o w s the use of random e r r o r c o r r e c t i o n codes i n a b u r s t e r r o r channel. The e r r o r randomization a b i l i t y of b i t i n t e r l e a v i n g i s a l s o u s e f u l i n low data r a t e t r a n s m i s s i o n s . The 19.2kbps r e c e i v e d b i stream i n t h e r e c e i v e r undergoes m a j o r i t y l o g i c d e c i s i o n b e f o r e data b i t i s e x t r a c t e d . A small e r r o r b u r s t c o n c e n t r a t e s a l l the 19.2kbps b i t e r r o r s i n a small time span and d r a s t i c l y i n c r e a s e s the p r o b a b i l i t y of a m a j o r i t y d e c i s i o n e r r o r . T h e r e f o r e , an i n t e r l e a v e r can e f f e c t i v e l y spread out a small e r r o r b u r s t and reduce i t s impact on m a j o r i t y l o g i c d e c i s i o n s . 8.7. Experimental R e s u l t s f o r I n t e r l e a v e d Spread Spectrum Data Transmi s s i ons A 3 1 - b i t i n t e r l e a v e r and d e - i n t e r l e a v e r were b u i l t t o t e s t the above concept ( F i g . 8.6). These were chosen because of hardware s i m p l i c i t y . When i n t e r l e a v i n g i s used with hard d e c i s i o n s , we use the term I n t e r l e a v e d M a j o r i t y D e c i s i o n . With no i n t e r l e a v i n g and hard d e c i s i o n s we use the term Simple D/\rA CLK DATA CLK PATA Q ± CLK M T A Qi QQ CLK CP+ 09 f DATA Q l CLK DATA Q l a 7 Pi Pa 'Q' Pi PS CLK • Loacj CDf-oZj DATA Q<3 I*-ber/easing or De-/iter/ea^ir^ Csee. Tqb/e 8-1 ) m P9 ' ' ' P/6 fara-Uel PL Pe CLK DATA 1 \P2f rar«,llel Ct-K Loud DATA >4 aKf-31 Inter leais-eA on. De-Interleaved b" C L K CJH-SB& Qif. C F P P i DPz DP? t>fr ft I ft I PE MR " 0 < CLK C.DH-52.G) cF DPL V b' o -o' F i g . 8.6 Block Diagram of Inter1eaver/De-inter1eaver - 98 - Table 8.1 31-Bit I n t e r l e a v e r / D e - i n t e r l e a v e r Connections I n t e r l e a v e r D e - i n t e r l e a v i n g Ql -> P8 Ql -> P4 Q2 -> P16 Q2 -> P8 Q3 -> P24 Q3 -> P12 Q4 -> PI Q4 -> P16 Q5 -> P9 Q5 -> P20 06 -> P17 Q6 -> P24 Q7 -> P25 Q7 -> P28 Q8 -> P2 Q8 -> PI Q9 -> P10 Q9 -> P5 Q10 -> P18 Q10 -> P9 Q l l -> P26 Q l l -> P13 Q12 -> P3 Q12 -> P17 Q13 -> P l l Q13 -> P21 Q14 -> P19 Q14 -> P25 Q15 -> P27 Q15 -> P29 Q16 -> P4 Q16 -> P2 Q17 -> P12 Q17 -> P6 Q18 -> P20 Q18 -> P10 Q19 -> P28 Q19 -> P14 Q20 -> P5 Q20 -> P18 Q21 -> P13 Q21 -> P22 Q22 -> P21 Q22 -> P26 Q23 -> P29 Q23 -> P30 Q24 -> P6 Q24 -> P3 Q25 -> P14 Q25 -> P7 Q26 -> P22 Q26 -> P l l Q27 -> P30 Q27 -> P15 Q28 -> P7 Q28 -> P19 Q29 -> P15 Q29 -> P23 Q30 -> P23 Q30 -> P27 Q31 -> P31 Q31 -> P31 - 99 - M a j o r i t y D e c i s i o n . A t h i r d scheme uses so-ft d e c i s i o n s t o r e t r i e v e a data b i t by m u l t i p l y i n g the incoming analog 19.2kbps b i t stream with a l o c a l PN sequence. T h i s p r o c e s s we c a l l C o r r e l a t i o n D e c i s i o n . The t h r e e schemes are o u t l i n e d i n block diagrams i n F i g . 8.7. The performance of these schemes i s compared t o the narrow band r e s u l t s obtained i n the 1.2kbps and 4.8kbps data r a t e t r a n s m i s s i o n s i n Chapter 7. The corresponding BERs, assuming random e r r o r s t a t i s t i c s , a r e given by: 1. I n t e r l e a v e d M a j o r i t y D e c i s i o n , BER = p r"' = 2. Simple M a j o r i t y D e c i s i o n , BER = p 3. C o r r e l a t i o n D e c i s i o n , BER = QC ( n E c / N o ) 1 / 2 3 4. Narrow band, BER = QC (Eb/No) 3 where p = b i t e r r o r r a t e of a code c h i p = QC ( E c / N o ) 1 / 2 3, n = p r o c e s s i n g g a i n ( d i v i s i b l e by 2 ) , Ec = average energy i n a code c h i p , Eb = average energy i n a data b i t = nEc. In AWGN, both the c o r r e l a t i o n and narrow band methods are e q u i v a l e n t and have b e t t e r BER performance over e i t h e r the simple or i n t e r l e a v e d m a j o r i t y l o g i c d e c i s i o n method. Experimental r e s u l t s a t 1.2kbps and 4.8kbps data r a t e at 19.2kbps code r a t e are p l o t t e d i n F i g . 8.8 and F i g . 8.9. From these graphs, i t i s observed t h a t : 1. Narrow band r e s u l t s are best at both data r a t e s . 2. I n t e r l e a v e d m a j o r i t y d e c i s i o n i s next b e s t , with the BER d e c r e a s i n g r a p i d l y at high Eb/No v a l u e s . 3. Both simple m a j o r i t y and c o r r e l a t i o n d e c i s i o n l e a d t o almost i d e n t i c a l BER performance as the two other schemes at 1.2kbps data r a t e . - 100 - Z^teyrn hi/bumf Code clock feco^e ry CLY- cdc Generator Jtt6 MrA C/-K 1 O r*l- •&1~ejrate/ Dump I %\SCLK Code Clock Re Co 31-hii- Pe -inferlea v-er CLK j ] J S r / v c " Code Syr,tkremjaiion & f>A) Cc^e Generator T7 xt6 lArA clk -£>MTA C/'i) Tr\-terleaved Majon'-ty T>ec]sior% Integrate / j>ur»p 7T tl&CLK Fecev-try CLK. Switching Multiplier £ode {fuehrer i^nf/cn tN Code (senera-kor (iii) Corre/a--kien, T> eci's t'otx. R 16-fag* Vtytnf F i g . 8.7 Block Diagram of Simple M a j o r i t y Logic D e c i s i o n , I n t e r l e a v e d M a j o r i t y L o g i c D e c i s i o n , and C o r r e l a t i o n D e c i s i o n Methods -{> DATA F i g . 8.8 Comparison of 1.2kbps BER Performance of the I n t e r l e a v e d M a j o r i t y D e c i s i o n , Simple M a j o r i t y D e c i s i o n , C o r r e l a t i o n D e c i s i o n , and Narrow Band Methods - 102 - F i g . 8.9 Comparison of 4.8kbps BER Performance of the I n t e r l e a v e d M a j o r i t y D e c i s i o n , Simple M a j o r i t y D e c i s i o n , C o r r e l a t i o n D e c i s i o n , and Narrow Band Methods - 103 - 4. Both simple m a j o r i t y and c o r r e l a t i o n d e c i s i o n g i v e s n o t i c e a b l y worsar BER performance when compared t o narrow band r e s u l t s i n i n 4.8kbps data t r a n s m i s s i o n . The i n t e r l e a v e d m a j o r i t y d e c i s i o n , however, i s a b l e t o -follow c l o s e l y the narrow band r e s u l t . The b e n e f i t of a simple 3 1 — b i t i n t e r l e a v e r i s obvious i n (4). The i n t e r l e a v e r s e p a r a t e s every adjacent b i t i n the o r i g i n a l b i t stream by at l e a s t 3 b i t s i n the i n t e r l e a v e d b i t stream. A 6 3 — b i t and 127-bit i n t e r l e a v e r would p r o v i d e 4 — b i t and 5 - b i t minimum s e p a r a t i o n , r e s p e c t i v e l y . Higher degree of i n t e r — l e a v i n g i s not n e c e s s a r i l y b e n e f i c i a l because of the p e r i o d i c i t y i n b i t e r r o r occurance, and a l s o , because of the long d e l a y between r e c e p t i o n and the output of the f i r s t data b i t . The i n t e r l e a v e r used i n t h i s r e p o r t i s a block p e r i o d i c i n t e r l e a v e r and i t s performance may be degraded i n a p e r i o d i c b u r s t e r r o r environment. In t h i s s i t u a t i o n , a puesdorandom i n t e r l e a v e r may prove t o be more robust C553. T h i s PN code i n t e r l e a v e d spread spectrum technique combined with CMFSK modulation has s e v e r a l p o t e n t i a l advantages: 1. Compact t r a n s m i s s i o n spectrum independent of data r a t e . 2. Fast s i d e l o b e r o l l o f f independent of data r a t e . 3. 'AWGN'-like wideband i n t e r f e r e n c e independent of data r a t e . 4. T o l e r a n c e t o small power l i n e induced e r r o r b u r s t s . The main disadvantage with t h i s scheme i s t h a t a minimum SNR must be present at the r e c e i v e r i n order t o operate the code c l o c k r e c o v e r y c i r c u i t . T h i s minimum SNR corresponds t o a code BER of .01 t o .05. When t h i s BER i s exceeded, the recovered b i t - 104 - cl o c k shows high j i t t e r , thus i n c r e a s i n g the p o s s i b i l i t y o-f l o s t t r a c k i n g and missed a c q u i s i t i o n . An improvement o-f t h i s analog c l o c k r e c o v e r y c i r c u i t may be p o s s i b l e by us i n g a d i g i t a l c l o c k r e c o v e r y c i r c u i t . Although a d i g i t a l PLL c o n t r o l l e d b i t c l o c k r e c o v e r y s u f f e r s from higher r e s i d u a l c l o c k j i t t e r because of the d i s c r e t e nature of the c i r c u i t , i t o f f e r s r o b u s t n e s s , ease of implementation, e l i m i n a t i o n of an u l t r a s t a b l e VCO or VCXO (vo l t a g e c o n t r o l l e d o s c i l l a t o r or v o l t a g e c o n t r o l l e d c r y s t a l o s c i l l a t o r ) used i n an analog PLL, high r e l i a b i l i t y , c r y s t a l t i m i n g l e a d i n g t o d r i f t - f r e e and adjustment-free o p e r a t i o n , and easy VLSI a d a p t a b i l i t y . These are important c o n s i d e r a t i o n s i n the design of low c o s t power l i n e modems. Although the narrow band r e s u l t s c o n s i s t e n t l y y i e l d the best BER r e s u l t s , adjustments of the two o f f s e t f r e q u e n c i e s become harder as the data r a t e i s decreased. Such adjustments are necessary because of the l o o s e t o l e r a n c e , low c o s t components used i n the pr o t o t y p e CMFSK modem. Th e r e f o r e , an added bonus i n usi n g spread spectrum i s the a b i l i t y t o use l o o s e t o l e r a n c e p a r t s and components because of the l a r g e frequency d i f f e r e n c e between the two o f f s e t f r e q u e n c i e s . However, i f the o f f s e t f r e q u e n c i e s can be a c c u r a t e l y s e t by a c r y s t a l c o n t r o l l e d FSK modulator i n the t r a n s m i t t e r and i f a d i g i t a l FSK demodulator can be used i n the r e c e i v e r , narrow band methods may prove t o be u s e f u l . - 105 - 9. CONCLUSIONS 9.1 Summary In t h i s t h e s i s , t he c o n c e p t u a l i z a t i o n and design of a Coherent Minimum Frequency S h i f t Keying modulation technique s u i t a b l e f o r communications over an i n t r a b u i l d i n g polyphase power l i n e network i s d e s c r i b e d . The technique i n c l u d e s o p t i o n a l databand spectrum s p r e a d i n g . An a c t u a l modem i s then implemented and t e s t e d . T h i s modem i s subsequently used t o o b t a i n new r e s u l t s d e t a i l i n g the performance of CMFSK s i g n a l l i n g on i n t r a - b u i l d i n g e l e c t r i c power d i s t r i b u t i o n networks. The average B i t E r r o r Rate measurement at 1.2kbps, 4.8kbps, and 19.2kbps t r a n s m i s s i o n speeds i n d i c a t e CMFSK t r a n s m i s s i o n s a re l a r g e l y white n o i s e l i m i t e d at low data r a t e s but become impulse n o i s e l i m i t e d at high data r a t e s . T y p i c a l Eb/No v a l u e s t o achieve I O - 3 BER performance a r e 11.5dB at 1.2kbps, 13dB a t 4.8kbps, and 20dB at 19.2kbps data r a t e , r e s p e c t i v e l y . M u l t i l e v e l and M-ary modulation schemes a r e proposed t o reduce impulse n o i s e e f f e c t s by making a t r a n s m i t t e d b i t longer r e l a t i v e t o an impulse. A 4 - l e v e l FSK system, which was designed and b u i l t t o v e r i f y t h i s concept, showed some BER improvement. F u r t h e r s u p p r e s s i o n of impulse n o i s e e f f e c t s may be p o s s i b l e with more l e v e l s , s i n c e BER degra d a t i o n due t o m u l t i l e v e l t h r e s h o l d s e n s i t i v i t y problems i s not as s e r i o u s as the jamming e f f e c t of impulse n o i s e . The CMFSK modulation technique was found t o emit l e s s - 106 - harmful i n t e r f e r e n c e t o AM s t a t i o n s when compared t o an e x i s t i n g commercial product, BSR X-10. T h i s i n t e r f e r e n c e r e d u c t i o n i s a t t r i b u t e d t o the compact spectrum and r a p i d sideband r o l l o f f of the CMFSK modulation scheme. The a p p l i c a t i o n of CMFSK technology t o low data r a t e t r a n s m i s s i o n s was made more robust by us i n g a databand spread spectrum technique. On power l i n e channels, narrow band t r a n s m i s s i o n s which accompany low data r a t e s are s u b j e c t t o p o t e n t i a l narrow band impairments. A commercial—use power l i n e modem i s r e s t r i c t e d by law from t r a n s m i t t i n g high power t o overcome narrow band impairments. As w e l l , modem c o s t s may be reduced due t o r e l a x e d power output requirements. P r o p e r l y designed spread spectrum s i g n a l l i n g enables a power l i n e modem t o s u r v i v e narrow band impairments at an a c c e p t a b l e t r a n s m i t t e r power l e v e l . The degree of spreading i s l i m i t e d by the power l i n e bandwidth, data bandwidth, n o i s e , and t r a n s m i s s i o n c h a r a c t e r i s t i c s . The e f f e c t of impulse n o i s e jamming i s observed when the b i t e r r o r p a t t e r n s at 19.2kbps t r a n s m i s s i o n c o n t a i n small e r r o r b u r s t s . T h e r e f o r e , a p e r i o d i c 3 1 — b i t block i n t e r l e a v e r was b u i l t t o d i s p e r s e small e r r o r b u r s t s . T h i s i n t e r l e a v e d spread spectrum scheme proved i t s r o b u s t n e s s when BER of an i n t e r l e a v e d and non- i n t e r l e a v e d 4.8kbps data r a t e , 19.2kbps code r a t e spread spectrum system was compared. The i n t e r l e a v e r scheme g i v e s c l o s e t o i d e a l BER performance. In higher speed t r a n s m i s s i o n , the randomization e f f e c t of an i n t e r l e a v e r enables the use of good random e r r o r - 107 - c o r r e c t i o n codes at a s l i g h t r e d u c t i o n i n throughput. B e s i d e s i t s a b i l i t y t o combat narrow band -fades, the spread spectrum CMFSK modulation i s a b l e t o reduce i t s narrow band emi s s i o n s and thereby a l l o w s adequate power t o be t r a n s m i t t e d t o overcome path a t t e n u a t i o n s . T h i s has important i m p l i c a t i o n s because i t i s now p o s s i b l e t o s a t i s f y emission r e g u l a t i o n s even at enhanced output l e v e l s . 9.2 Cost E s t i m a t e of the CMFSK Modem The c o s t of our p r o t o t y p e r e c e i v e r l i e s h e a v i l y with i t s f r o n t end of powr l i n e c o u p l i n g network, BPF, and FSK demodulator ($25). The r e s t of the r e c e i v e r c i r c u i t r y can be implemented from CMOS ICs ($10) and a c r y s t a l c l o c k (#5). The modem power supply i s a l s o r e l a t i v e l y s imple ($10). The r e c e i v e r s e c t i o n of the modem would t y p i c a l l y be under #60 wh i l e the t r a n s m i t t e r s e c t i o n would t y p i c a l l y c o s t an a d d i t i o n a l #10 f o r the FSK modulator and l i n e a r power a m p l i f i e r ICs. 9.3 Recommendations For F u r t h e r Research There a re s e v e r a l items which may be worth i n v e s t i g a t i n g : 1. Means and p r a c t i c a l i t y of high frequency bypassing i n a r e s i d e n t i a l house and an o f f i c e f l o o r v i a the s e r v i c e box, t o improve across—phase t r a n s m i s s i o n c a p a b i l i t y . 2. Use of hig h c a r r i e r frequency, above 250kHz, t o r e a l i z e t r a n s m i s s i o n r a t e s above 50kbps. These high data r a t e s a re d e s i r a b l e i n some o f f i c e automation environments. These high d a t a r a t e s are of course l i m i t e d t o s h o r t d i s t a n c e coverage or power l i n e c o n d i t i o n s d e f i n e d i n S e c t i o n 8.2. 3. FEC by random e r r o r c o r r e c t i o n codes u s i n g e i t h e r the shortened BCH(16,8) of Dunbar et a l . C56] or other codes - 108 - d e s c r i b e d by Batson et a l . C573. A s u i t a b l e code should have double or even t r i p l e e r r o r s c o r r e c t i o n c a p a b i l i t y . 4. FEC by b u r s t e r r o r c o r r e c t i o n codes u s i n g F i r e codes with a 10-bit b u r s t c o r r e c t i n g c a p a b i l i t y . 5. Power l i n e communication p r o t o c o l s which p r o v i d e r e l i a b l e and robust networking with reasonable throughput. A l i k e l y c a n d i d t a t e i s C a r r i e r Sense M u l t i p l e Access with p o s i t i v e acknowledgement. 6. Data p u l s e shaping, modulator output f i l t e r i n g , and c h o i c e of s p e c t r a l e f f i c i e n t modulation methods (see Feher C30,583 and K l o s e e t a l . C593) t o c o n t r o l out-of-band emissions a t enhanced output l e v e l s . 7. Randomization a b i l i t y of a 6 3 - b i t or 127-bit i n t e r l e a v e r on power l i n e induced e r r o r s as compared with t h a t of a puesdorandom i n t e r l e a v e r (see C l a r k et a l . C55D). 8. Impulse n o i s e s u p p r e s s i o n by using smearing and de—smearing f i l t e r s (see Beenker e t a l . C46D). 9. E f f i c i e n t power l i n e spectrum u l t i l i z a t i o n by having one band assigned t o 'ORIGNATE' and another band t o 'REPLY*. 10. M u l t i l e v e l or M-ary schemes t o combate impulse n o i s e e r r o r s . Such a p o s s i b l e scheme i s m u l t i l e v e l FSK, with FSK d e t e c t i o n using FFT t o reduce d e c i s i o n t h r e s h o l d s e n s i t i v i t y problem (see K l o s e et a l . C593 and Feher C583). 11. Use of d i g i t a l b i t s y n c h r o n i z a t i o n methods t o improve the r e l i a b i l i t y and robustness of code c l o c k r e c o v e r y (see Dunbar et a l . C561 and Payz i n C603). 12. Design and implement an i n t e r l e a v e d s o f t d e c i s i o n c o r r e l a t i o n data d e t e c t o r t o check i f i t y i e l d s any improvements over i n t e r l e a v e d hard d e c i s i o n m a j o r i t y l o g i c d e c i s i o n d i s c u s s e d i n S e c t i o n 8.7. Another area worth l o o k i n g i n t o i s the v o i c e communications c a p a b i l i t y of t h i s CMFSK modem. In S e c t i o n 5.5, i t was mentioned t h a t t he raw data output of the XR-2211 FSK demodulator c o u l d be u l t i l i z e d as an analog output. T h i s i s p o s s i b l e because the CMFSK modem i s e s s e n t i a l l y a commercial power l i n e FM intercom converted t o carry d i g i t a l b i t p u l s e s . T h e r e f o r e , analog v o i c e t r a n s m i s s i o n s from t h i s modem i s expected t o be reasonably high - 109 - q u a l i t y and low d i s t o r t i o n . T h i s i s by no means an exh a u s t i v e l i s t of i d e a s f o r f u t u r e work. Some of the above i n v o l v e A/D c o n v e r s i o n at the f r o n t end and d i g i t a l s i g n a l p r o c e s s i n g by the r e c e i v e r . T h i s seems t o be the t r e n d i n f u t u r e communications systems because a d i g i t a l r e c e i v e r i s i n h e r e n t l y more r e l i a b l e and robust than an analog e q u i v a l e n t , and the co s t can be lowered through l a r g e s c a l e p r o d u c t i on. - 110 - REFERENCES 1. D.R. B e u e r l e , A.G. Hudson, and H.J. F i e d l e r , S5B C a r r i e r f o r U t i l i t y C o n t r o l and Communication. IEEE N a t i o n a l Telecommunication Conference, pp. 2.1.1-2.1.7, 1976. 2. Arthur CM. Chen, Automated Power D i s t r i b u t i o n . IEEE Spectrum, pp. 55-60, A p r i l 1982. 3. Glen Lokken, N e i l Jagoda, and Raymond J . D ' A u t e u i l , The Proposed Wisconsin E l e c t r i c Power Company Load Management System Using Power L i n e C a r r i e r Over D i s t r i b u t i o n L i n e s , IEEE N a t i o n a l Telecommunication Conference, pp. 2.2.1-2.2.3, 1976. 4. Peter K. van der Gracht, A Spread Spectrum Modem f o r Use on E l e c t r i c a l Power L i n e s . M.A.Sc T h e s i s , E l e c t r i c a l Eng. Dept., U n i v e r s i t y of B r i t i s h Columbia, Canada, January 1982. 5. J.B. O'Neal, J r . , Overview of Power D i s t r i b u t i o n L i n e Carrier Communication Systems. IEEE Globecom'83, pp. 464-467. 6. J . C a r l o s Dangelo and Sarosh N. Talukdar, A S t o c h a s t i c Model f o r PLC systems. IEEE T r a n s a c t i o n s on Power Apparatus and Systems, v o l . PAS-100, No. 11, pp. 4464-4472, November 1981. 7. M.P. P e r r y and M.R. Stambach, A System A n a l y s i s of Power L i n e C a r r i e r Communications with Gas I n s u l a t e d Conductors and Overhead L i n e s . IEEE 1980 Canadian Communications & Power Conference, pp. 240—243. 8. Ken C. Shuey, D i s t r i b u t i o n Transformers at Power—Line C a r r i e r F r e q u e n c i e s . IEEE Globecom'83, pp. 483-486. 9. W.R. V i n c e n t , J.M. Clemmemsen, and R.L. B o l l e n , The Measurement of Radio Noise A s s o c i a t e d with D i s t r i b u t i o n L i n e s . IEEE Globecom'83, pp. 473-477. 10. K.W. Whang, G.C. Cagle, and J.W. Smart, The power D i s t r i b u t i o n System as a Communication Medium f o r Load Management and D i s t r i b u t i o n Automation. IEEE Globecom'83, pp. 478-482. 11. Kay N. C l i n a r d , U t i l i t y E xperience and D e s i r e s f o r D i s t r i b u t i o n Power L i n e C a r r i e r Communications. IEEE Globecom'83, pp. 487-491. 12. F.W. G u t z w i l l e r , J.E. F r a n c i s , J r . , E.K. Howell, and W.R. K r u e s i , Homenet: A C o n t r o l Network f o r Consumer A p p l i c a t i o n s . IEEE T r a n s a c t i o n s on Consumer E l e c t r o n i c s , v o l . CE-29, No. 3, pp. 297-304, August 1983. - i l l - 13. Masahiro Inoue, Kazuho Uemura, Y o s h i j i Minagawa, Mitsunobu E s a k i , and Yoshiyuki Honda, A Home Automation System. IEEE T r a n s a c t i o n s on Consumer E l e c t r o n i c s , v o l . CE—31, No. 3, pp. 516-527, August 19S5. 14. W i l l i a m R. Kruesi and P h i l l i p R. Rogers, R e s i d e n t i a l C o n t r o l C o n s i d e r a t i o n s . IEEE T r a n s a c t i o n s on Consumer E l e c t r o n i c s , v o l . CE-28, no. 4, pp. 563-570, November 1982. 15. Fe d e r a l Communicatios Commission Rules and R e g u l a t i o n s , Volume 2, Pa r t 15, Subpart A. 16. C a r o l e C. H a r r i s , Impact o-f FCC R e q u l a r t o r y Proceedings Power U t i l i t y Telecommunication Systems. IEEE 1978 Na t i o n a l Telecommunications, pp. 9.2.1—9.2.4. 17. Heinz Ochsner, Data Transmission on Low Vo l t a g e Power D i s t r i b u t i o n L i n e s u s i n g Spread Spectrum Techniques, IEEE 1980 Canadian Communications & Power Conference, pp. 236-239. 18. P.K. van der Gracht and R.W. Donaldson, Communication Using Pseudonoise Modulation on E l e c t r i c Power D i s t r i b u t i o n C i r c u i t s . IEEE Trans, on Communications, v o l . COM-33, No. 9, pp. 964-974, September 1985. 19. Botaro H i r o s a k i , S a t o s h i Hasegawa, and Kaoru Endo, A Power L i n e Home Bus System Using Spread-Spectrum Communication T e c h n o l o g i e s . 1985 I n t e r n a t i o n a l Conference on Consumer E l e c t r o n i c s , conference paper. 20. Dan H a r i t o n and Paul P a t t e r s o n , AC Power L i n e Modem For Consumer and I n d u s t r i a l Environments, 1985 I n t e r n a t i o n a l Conference on Consumer E l e c t r o n i c s , conference paper. 21. BSR X-10 Owners Manual, BSR (Canada) L t d . 22. L i n e upon l i n e . IEEE Spectrum, pp. 25, September 1985. 23. Nonwire M u l t i d r o p Network Users Guide, CYPLEX D i v i s i o n , C o n t r o l o n i c s C o r p o r a t i o n , MA, USA. 24. PowerLAN™, ExpertNets, Acton, MA, USA. 25. Steven E. Sarns, Home C o n t r o l Computer: Part I I . Radio- E l e c t r o n i c s , pp. 64-70, May 1984. 26. Morgan H.L. Chan, Communication Channel C h a r a c t e r i s t i c s and Behaviour of I n t r a b u i l d i n o Power D i s t r i b u t i o n C i r c u i t s M.A.Sc T h e s i s , E l e c t r i c a l Eng. Dept., U n i v e r s i t y of B r i t i s h Columbia, Canada, September 1985. - 112 - 27. A l b e r t A. Smith, J r . , Power L i n e Noise Survey, IEEE T r a n s a c t i o n s on E l e c t r o m a g n e t i c C o m p a t i b i l i t y , v o l . EMC-14, no. 1, pp. 31-32, February 1972. 28. Roger M. V i n e s , H. J o e l T r u s s e l 1 , L o u i s J . Gale, and J . Ben O'Neal, J r . , Noise on R e s i d e n t i a l Power D i s t r i b u t i o n C i r c u i t s . IEEE T r a n s a c t i o n s on E l e c t r o m a g n e t i c C o m p a t i b i l i t y , v o l . EMC-26, No. 4, pp. 161-168, Nov. 1984. 29. R.E. Owen, W.R. V i n c e n t , and W.E. B l a i r , Measurement o-f Impulsive n o i s e on E l e c t r i c D i s t r i b u t i o n Systems. IEEE T r a n s a c t i o n s on Power Apparatus and Systems, v o l . PAS-99, no. 6, pp. 2433-2438, Nov./Dec. 1980. 30. Kamilo Feher, D i g i t a l Communications. S a t e l l i t e / E a r t h S t a t i o n E n g i n e e r i n g . P r e n t i c e H a l l Inc., Englewood Cli - f - f s , N.J., 1983. 31. Subbarayan Pasupathy, Minimum Shi-ft Keying: A S p e c t r a l l y E f f i c i e n t Modulation. IEEE Communications Magazine, v o l . 17, no. 7, pp. 14-22, J u l y 1979. 32. W.C. L i n d s e y , Phase-Shifted-Keyed S i g n a l D e t e c t i o n with Noisy Reference S i g n a l s . IEEE T r a n s a c t i o n s on Aerospace and E l e c t r o n i c Systems, v o l . AES-2, no. 4, pp. 393-401, J u l y 1966. 33. V.K. Prabhu, PSK Performance with Imperfect Carrier Phase Recovery. IEEE T r a n s a c t i o n s on Aerospace and E l e c t r o n i c Systems, v o l . AES-12, no. 2, pp. 275-285, March 1976. 34. V.K. Prabhu, Imperfect C a r r i e r Recovery E f f e c t on F i l t e r e d PSK S i g n a l s . IEEE T r a n s a c t i o n s on Aerospace and E l e c t r o n i c systems, v o l . AES-14, no. 4, pp. 608-615, J u l y 1978. 35. S h i n j i r o O s h i t a and Kamilo Feher, Performance of Coherent PSK and DPSK Systems i n an Impulsive and Gaussian Noise Environment, IEEE 1981 I n t e r n a t i o n a l Communications Conference, pp. 56.4.1—56.4.5. 36. T.A. Schonhoff, L i n e a r Demodulation of CPFSK i n Impulsive Atmospheric Noise. IEEE 1978 Canadian Communications & Power Conference, pp. 46. 37. John A. Malack and John R. Engstrom, RF Impedance of U n i t e d S t a t e s and European Power L i n e s . IEEE T r a n s a c t i o n s on E l e c t r o m a g n e t i c C o m p a t i b i l i t y , v o l . EC—IB, no. 1, pp. 36-38, February 1976. 38. Roger M. V i n e s , H., J o e l T r u s s e l 1 , Kenneth C. Shuey, and J.B. O'Neal, J r . , Impedance of the R e s i d e n t i a l Power— D i s t r i b u t i o n C i r c u i t . IEEE T r a n s a c t i o n s on E l e c t r o m a g n e t i c C o m p a t i b i l i t y , v o l . EMC-27, no. 1, pp. 6-12, February 1985. - 113 - 39. EXAR Integrated Systems, Inc. , S t a b l e FSK Modems F e a t u r i n g the XR-2207. XR-2206. and XR-2211. AN-01. 40. John G. P r o a k i s , D i g i t a l Communications. McGraw-Hill Book Company, 1983, ch. 4, pp. 200-203. 41. R.E. Ziemar and W.H. T r a n t e r , P r i n c i p l e s o-f Communications : Systems. Modulation, an Noise. Houghton M i f f l i n Company, Boston, 1976, ch.7, pp. 340-341. 42. EXAR Inte g r a t e d Systems, Inc. , Clock Recovery System. AN-19. 43. A.D. Spaulding and D. Middleton, Optimum Reception i n an Impulsive I n t e r f e r e n c e Environment — P a r t Is Coherent D e t e c t i o n ; P a r t II — Incoherent D e t e c t i o n . IEEE Trans, on Communications, v o l . COM-25, no. 9, pp. 910-934, Sept. 1977. 44. H.H. Lu and B.A. E i s e n s t e i n , D e t e c t i o n of Weak S i g n a l s i n Non-Gaussian Noise. IEEE Trans, on Information Theory, v o l . IT-27, no. 6, pp. 755-771, November 1981. 45. Jack Kei1 Wolf, Redundancy, the D i s c r e t e F o u r i e r Transform and Impulse Noise C a n c e l l a i o n . IEEE T r a n s a c t i o n s on Communications, v o l . COM-31, no. 3, pp. 458-451, March 1983. 46. G.F.M. Beenker, T.A.C.M. Claasen, and P.J. van Gervwn, Design of Smearing F i l t e r s f o r Data Transmission Systems. IEEE T r a n s a c t i o n s on Communications, v o l . COM-33, no. 9, pp. 955-963, September 1985. 47. Raymond L. P i c k h o l t z , Donald L. S c h i l l i n g , and Laurence B. M i l s t e i n , Theory of Spread—Spectrum Communications — A T u t o r i a l . IEEE T r a n s a c t i o n s on Communications, v o l . COM-30, no. 5, pp. 855-884, May 1982. 48. I r v i n g R. Smith, Tr a d e o f f Between P r o c e s s i n g Gain and I n t e r f e r e n c e Immunity i n C o - S i t e M u l t i c h a n n e l Spread Spectrum Communications. IEEE T r a n s a c t i o n s on Communications, v o l . COM-30, no. 5, pp. 959-966, May 1982. 49. F.P. Nied e r b e r g e r , Return S i g n a l l i n g Systems Used as a Compliment t o Low Frequency-Power L i n e C a r r i e r (LF—PLC). IEEE 1980 Canadian Communications & Power Conference, pp. 181-184. 50. J.W. Seyl and M.H. Kapel1, A p p l i c a t i o n of Spread Spectrum t o the S h u t t l e O r b i t e r Communication System. IEEE N a t i o n a l Telecommunication Conference, pp. 32.1.1-32.1.5, 1976. 51. Edward A. T o r e r r o , A Macromarket f o r m i c r o s t a t i o n s . IEEE Spectrum, pp. 59, November 1985. - 114 - 52. Stephen S. Rapport and Donald M. G r i e c o , Spread-Spectrum S i g n a l A c q u i s i t i o n : Methods and Technology. IEEE Communications Magazine, v o l . 22, no. 6, pp. 6—21, June 19B4. 53. Noman Mahmood, Spread Spectrum Communication System -for C i v i l Use. W i r e l e s s World, pp. 76-80, March 1983. 54. Hewlett-Packard Company, Model 1645A Data E r r o r A n a l y z e r , s e r v i c e manual, 1976. 55. George C. C l a r k , J r . and J . Bibb C a i n , E r r o r - C o r r e c t i o n Coding f o r D i g i t a l Communications. Plenum P r e s s , New York, 1981, ch.B, pp. 345-351. 56. B.J. Dunbar, D.V. Gupta, M.P. Horvath, R.E. Sheehey, and S.P. Verma, Dataport-Channel U n i t s f o r D i g i t a l Data System 56—kbps Rate. The B e l l System T e c h n i c a l J o u r n a l , v o l . 61, no. 9, pp. 2741-2756, November 1982. 57. B.H. Batson and G.K. Hutch, Modulation and Coding f o r Spread Spectrum Communications Systems. IEEE N a t i o n a l Telecommunication Conference, pp. 32.5.1—32.5.5, 1976. 58. Kamilo Feher, D i g i t a l Communications. Microwave A p p l i c a t i o n s . P r e n t i c e H a l l Inc., Englewood C l i f f s , N.J., 1981, ch. 3, ch. 6, & ch. 7. 59. Dirk R. K l o s s and Gwendolyn L. Freeman, Adaptive D i g i t a l D e t e c t i o n of FSK S i g n a l s . IEEE 1978 Canadian Communications & Power Conference, pp. 9—12. 60. A. E r b i l P a y z i n , A n a l y s i s of a D i g i t a l B i t S y n c h r o n i z e r . IEEE T r a n s a c t i o n s on Communications, v o l . COM-31, no. 4, pp. 554-560, A p r i l 1983. - 115 - BIBIOBRAPHY 1. P h i l l i p M. Hopkins, Pseudonoise S y n c h r o n i z a t i o n at Low S i q n a l - t o - N o i s e R a t i o . 1976 Na t i o n a l Telecommunications Conference, pp. 32.2.1-32.2.5. 2. Laurence B. M i l s t e i n and Donald L. S c h i l l i n g , The E f f e c t of F r e q u e n c y - S e l e c t i v e Fading on a Noncoherent FH-FSK System Qperting with P a r t i a l - B a n d Tone I n t e r f e r e n c e . IEEE T r a n s a c t i o n s on Communications, v o l . COM—30, no. 5, pp. 904-912, May 1982. 3. M i t s u h i k o Mizuno, Randomization E f f e c t of E r r o r s by Means of Freguency-Hopping Technigues i n a Fading Channel. IEEE T r a n s a c t i o n s on Communications, v o l . COM—30, no. 5, PP. 1052-1056, May 1982. 4. J.R. Ni c h o l s o n and J.A. Malack, RF Impedance of Power L i n e s and L i n e Impedance S t a b i l i z a t i o n Networks i n Conducted I n t e r f e r e n c e Measurements. IEEE T r a n s a c t i o n s on E l e c t r o m a g n e t i c C o m p a t i b i l i t y , v o l . EC—15, no. 2, pp. 84-86, May 1973. 5. Steve C i a r c i a , B u i l d a Power L i n e C a r r i e r Current Modem. Byte, pp. 36-42, August 1983. 6. R.C. Dixon, Spread Spectrum Systems. 2nd ed., New York: Wiley, 1984. 7. Don L a n c a s t e r , A c t i v e - F i l t e r Cookbook. Howard W. Sams & Co., Inc., 1975. - 116 - APPENDIX A. POWER LINE NOISE SPECTRAL DENSITY DETERMINATION A simple spectrum a n a l y z e r was c o n s t r u c t e d out o-f t h r e e 6th order BPFs ( F i g . A . l ) . The t h e o r e c t i c a l c e n t e r f r e q u e n c i e s and bandwidths of the f i l t e r s a re 30+5kHz, 60+10kHz, and 120+20kHz, with each BPF's Q equal t o 3. A h i g h e r Q i s l i m i t e d by hardware d i f f i c u l t i e s . T h e i r measured parameters are l i s t e d i n Table A . l . T h i s spectrum a n a l y z e r was then used t o c o l l e c t n o i s e v o l t a g e , V n a l . . , and converted t o n o i s e s p e c t r a l d e n s i t y , No: No = Power L i n e Noise S p e c t r a l D e n s i t y = V 2 - — n o t mm ( Gain x A t t e n u a t i o n )= x BPF Bandwidth T h i s No v a l u e i s a c r o s s the power l i n e impedance i n p a r a l l e l with the c o u p l i n g ' s r e s i s t a n c e . C37,383 g i v e s some t y p i c a l power l i n e impedance. C o u p l i n g ' s r e s i s t a n c e i s the sum of the i n t e r n a l r e s i s t a n c e , R i „ t of 3.0+.3 ohm, and the i n p u t r e s i s t a n c e R m of 12 ohm. The v a l u e s of 'Gain' and ' A t t e n u a t i o n ' are those found i n Table A . l t o T a b l e A.5. The n o i s e s p e c t r a l d e n s i t y data shown i n T a b l e 4.1 and Table 4.2 i s d e r i v e d from Tab l e A.6 and T a b l e A.7. A Briie l & Kaejr analog v o l t a g e meter, Model #2426, i s used t o p r o v i d e the v o l t a g e r e a d i n g s . Two 4th order BPFs were i n c o r p o r a t e d i n the r e c e i v e r t o perform t h e c a r r i e r s e l e c t i o n i n S e c t i o n 6.3. Subsequently, both f i l t e r s were used t o c o l l e c t the c r o s s s e c t i o n a l n o i s e d e n s i t y data shown i n Table 4.3. The parameters of these two 4th order BPFs are l i s t e d i n Table A.2. i Spray ue ~fcav6for*t\r * * Z2 - t O Q •O MID O- O HIGH F i g . A . l A Simple Spectrum Analyzer used i n Power L i n e Noise S p e c t r a l Density Measurement - 118 - Table A.1 Parameters of 6th Order Band Pass F i l t e r s fcp Gain BW—f t-iiat->—3CJB- f I O M - S ^ B LOW 24.6kHz 12.05 30.6kHz - 19.6kHz = 11.0kHz MID 58.7kHz 11.05 71.4kHz - 48.2kHz = 23.2kHz HIGH 143.8kHz 11.05 179.5kHz - 119.0kHz = 60.5kHz Tabl e A.2 Parameters of 4th Order Band Pass F i l t e r s fe> Gain BW-f h i 9h-3dB—f I ow-3dB MID 57.3kHz 6.0 71.2kHz - 42.0kHz = 24.2kHz HIGH 137.8kHz 5.5 166.0kHz - 114.0kHz = 52.0kHz Tabl e A.3 Frequency Response of Power L i n e Coupling Terminated at 100k ohm Frequency V±„ V o u t A t t e n u a t i o n 10kHz 4.90 V 4.87V O . l l d B 20kHz 4.95 V 4.92V 0 . l l d B 30kHz 4.97V 4.95V 0.07dB 40kHz 4.99V 4.97 V 0.07dB 60 kHz 5.00 V 4.98V 0.07dB 80kHz 5.00 V 4.99 V 0.03dB 100kHz 5.01V 5.00 V 0.03dB 120kHz 5.05 V 5.02 V 0.03dB 150kHz 5. 03V 5.02V O.OldB 200kHz 5.01V 4.99V 0.07dB 300kHz 4.90 V 4.88 V 0.07dB - 119 - Table A.4 Frequency Response of Power L i n e Coupling Terminated at 12 ohm Frequency V l r i V o u t A t t e n u a t i o n 10kHz 200mV 130mV 3. 74dB 15kHz 200mV 147mV 2. 67dB 20kHz 200mV 150mV 2. 50dB 30kHz 200mV 155mV 2. 21dB 40kHz 200mV 157mV 2. lOdB 50kHz 200mV 158mV 2. 05dB 60 kHz 200mV 158mV 2. 05dB 70kHz 200mV 160mV 1. 94dB 80kHz 200mV 160mV 1. 94dB 90kHz 200mV 160mV 1. 94dB 100kHz 200mV 160mV 1. 94dB 110kHz 200mV 160mV 1. 94dB 120kHz 200mV 160mV 1. 94dB 130kHz 200mV 160mV 1. 94dB 140kHz 200mV 159mV 1. 99dB 150kHz 200mV 159mV 1. 99dB 160kHz 200mV 159mV 1. 99dB 170kHz 200mV 158mV 2. 05dB 180kHz 200mV 158mV 2. 05dB 190kHz 200mV 158mV 2. 05dB 200kHz 200mV 156mV 2. 16dB - 120 - Table A.5 Frequency Response of Power L i n e Coupling Terminated at 3.3 ohm Frequency V 4 r, V o v l t A t t e n u a t i o n 10kHz 200mV 36.5mV 14.7dB 15kHz 200mV 55.0mV 11.2dB 20kHz 200mV 69.OmV 9.24dB 30kHz 200mV 89.5mV 6.98dB 40 kHz 200mV 100.5mV 5.98dB 50kHz 200mV 108.0mV 5.35dB 60kHz 200mV 110.5mV 5.15dB 70kHz 200mV 113.OmV 4.96dB 80 kHz 200mV 113.0mV 4.96dB 90kHz 200mV 113.0mV 4.96dB 100kHz 200mV 113.0mV 4.96dB 110kHz 200mV 111.OmV 5 . l l d B 120kHz 200mV HO.OmV 5.19dB 130kHz 200mV 107.5mV 5.39dB 140kHz 200mV 105.5mV 5.56dB 150kHz 200mV 103.5mV 5.72dB 160kHz 200mV 101.OmV 5.93dB 170kHz 200mV 99.OmV 6. 1ldB 180kHz 200mV 97.5mV 6.24dB 190kHz 200mV 95.OmV 6.47dB 200kHz 200mV 92.5mV 6.70dB - 121 - Table A.6 Measured Noise V o l t a g e i n LOW, MID, and HIGH Frequency Band i n an I n d u s t r i a l B u i l d i n g Phase A Phase B Phase C Remote B~ Input (across 12 ohm, +5%) Rms +2mV Peak LOW BPF output Rms +20mV Peak MID BPF output Rms + 10mV Peak HIGH BPF output Rms +2mV Peak 60mV 1.0V 280mV 3.2V 160mV 2.4V 42mV 0.58 V 58mV 0.7V 200mV 2.0V 200mV 1.6V 37mV 0.60 V 62mV 0.7V 200mV 2.0V 165mV 1.7V 43mV 0.80 V 57mV 0.9V 290mV 3.0V 175mV 2.6V 32mV 1.0V Remote B i s an o u t l e t used t r a n s m i s s i o n as d e f i n e d i n f o r remote r e c e p t i o n and s e c t i o n I l l . i i . - 122 - Table A.7 Measured Noise V o l t a g e i n LOW, MID, and HIGH Frequency Band i n a R e s i d e n t i a l House Phase 0 e Phase 180« Input (across 12 ohm, ±57.) Rms +0.5mV Peak LOW BPF output Rms +2mV Peak MID BPF output Rms +2mV Peak HIGH BPF output 11.5mV 160mV 39mV 0.6V 47mV 0.35 V 13.5mV 220mV 55mV 0.6V 38mV 0.45V Rms +0.5mV Peak 7.5mV 0.9V 12.OmV 0.75 V - 123 - APPENDIX B. SCHEMATICS OF CMFSK TRANSMITTER AND RECEIVER The d e t a i l e d block diagrams o-f the t r a n s m i t t e r and r e c e i v e r showing a l l the sub-systems are shown i n F i g . B . l and F i g . B.2. The schematics o-f the t r a n s m i t t e r i s shown i n F i g . B.3. The schematics o-f the r e c e i v e r i s broken up i n t o t h r e e p a r t s and are shown i n F i g . B.4, F i g . B.5 and F i g . B.6 r e s p e c t i v e l y . F i g . B.4 c o n t a i n s e s s e n t i a l l y the analog c i r c u i t s of the CMFSK r e c e i v e r w h i l e F i g . B.5 and F i g . B.6 c o n t a i n mostly d i g i t a l c i r c u i t s . In F i g . B.6, the i n t e r n a l DATA and CLK s i g n a l s are b u f f e r r e d Cby CD4050] t o p r o v i d e l e v e l — c o m p a t i b l e s i g n a l s f o r the HP1645A data e r r o r r a t e a n a l y z e r i n BER measurements. In both the t r a n s m i t t e r and r e c e i v e r c i r c u i t s the power supply s e c t i o n i s omitted because of i t s simple implementation with a 16V/0.5A power supply t r a n s f o r m e r , f i l t e r c a p a c i t o r s , and a v o l t a g e r e g u l a t o r IC. CLoCK W77A I-24-32 MHz 1 9 . 2 K H z /W Genera-boy* C-D4-Q94- FSK Madu la-tor ^ Pwr Amp 5» Ouiput Cou^lin^ pPC2.oo2 1> I IT VAC o tyd^iie fake Tra.psfor}»er> 11Z2100 F i g - B.1 D e t a i l e d Transmitter Block Diagram A A 117 VAC Input Cou_j>l!ry^ ^ f t U Order BPF FSK Demodulator PLL Sprayue false Hans former 11Z2.LO0 XR-5532. raw data "3 £d$e. Detection. CD 4-olT DATA Threshold D&cfsion O DATA CLK CD4-OI3 CD Sit- Clack Recovery PLL 3O2-7KWZ CD4S2Q Pulse Stteicker CD+538 I9.2KHZ. F i g . B.2 D e t a i l e d Receiver Block Diagram 20 21 22. 23 +I5v ~ M32MHz tHF_ •280 ecu CD409+ DATA Ql Qz <33 (4- 13 9 a io /a •xR-2BOe> 5 I 3 1 r 7 8 50KK2. I OK F i g . B.3 Schematics of T r a n s m i t t e r \AM- 2 . 4 2 2.42K ltzztoo + 7.5v-j- -1>»F IC1 XR-SS3 2. A5K fad ~ p -1/JF BITS w v - -vW 470 fF IC2 XR-5532 X C 3 XR-OQl F i g . B.4 Schematics of Receiver - Input C o u p l i n g , 4th Order BPF, and FSK Demodulator RavJ Bits v W — - V V \ A 4 1 6 13 14- 10 XR-2212 12. s n I C l XR-OQ2. £2nF-~T~ F i g . B.5 Schematics of Receiver - Pulse S t r e t c h e r , and B i t Hard L i m i t e r , Edge Detector, Clock Recovery — < 3 — DATA O- /S.£fc4p* PAX A 2Za E x t O- 19^ KHz CLK 22 o - A / W BER Analyser CD4-094- Qs Ql _t>AT/4_ 56/1:. 56 K 8 C7>^05O 4 2 3 5 Q8 Qi 5 a ; 5 6 * 3 5 f £ ' 3 CD4-0/3 9 IO 1 1 +/Sv OIW NTS — p W v - KE5ET J L - 3 — 38. f KHz. o ^ F i g . B .6 Schematics of Receiver - D i g i t a l Integrate/Dump, Threshold D e c i s i o n , and Data/Data Clock Output

Cite

Citation Scheme:

    

Usage Statistics

Country Views Downloads
United States 12 0
China 6 0
Japan 2 0
Brazil 1 0
City Views Downloads
Unknown 9 5
Beijing 6 0
Mountain View 3 0
Tokyo 2 0
Ashburn 1 0

{[{ mDataHeader[type] }]} {[{ month[type] }]} {[{ tData[type] }]}

Share

Share to:

Comment

Related Items