1. SRC GRC Annual Review March 8, 2011 Powerline Communications for Enabling Smart Grid Applications Prof. Brian L. Evans Wireless Networking and Communications Group The University of Texas at Austin

2. Task ID 1836.063 2 Task Description: Increase powerline communication (PLC) data rate for better monitoring/control applications for residential and commercial energy uses Anticipated Results: Adaptive methods and real-time prototypes to increase bit-rates in PLC networks Primary Investigator: Prof. Brian L. Evans, The University of Texas at Austin Current StudentsCurrent Status Ms. Jing LinPh. D (expected graduation in May 2014) Mr. Yousof MortazaviPh. D (expected graduation in Dec. 2013) Mr. Marcel NassarPh. D (expected graduation in May 2012) Industrial Liaisons: Dr. Anand Dabak (Texas Instruments), Mr. Leo Dehner (Freescale), Mr. Michael Dow (Freescale) and Mr. Frank Liu (IBM) Starting Date: August 2010

3. Task Deliverables 3  Data and algorithms for receiver synchronization, channel measurements and modeling, and asynchronous impulsive noise mitigation (12/2010)  Single-transmitter single-receiver (1x1) powerline communication system testbed: software package and documentation (5/2011)  Data and algorithms for multichannel transmission for a three- transmitter single-receiver (3x1) powerline communication system (12/2011)  Three-transmitter single-receiver (3x1) powerline communication system testbed: software package and documentation (5/2012)  Data and algorithms for crosstalk cancellation and low-power medium access control scheduling algorithms (12/2012)  Three-transmitter three-receiver (3x3) powerline communication system testbed: software package and documentation (5/2013)

4. Executive Summary  Accomplishments  Investigated PLC standards  Literature survey on powerline channel/noise characterization  Built software and hardware framework for the PLC testbed  Simulated receiver frame synchronization using chirp signal  Current work  Asynchronous impulsive noise mitigation algorithms  Future directions  Smart hand-shaking mechanisms between transmitter and receiver on the best sub-band (with high SNR) for transmission  Algorithms for synchronous impulsive noise mitigation  Noise and channel modeling and analysis 4

5. Background: Smart Grid Big Picture Smart car : charge of electrical vehicles while panels are producing Long distance communication : access to isolated houses Real-Time : Customers profiling enabling good predictions in demand = no need to use an additional power plant Any disturbance due to a storm : action can be taken immediately based on real- time information Smart building : significant cost reduction on energy bill through remote monitoring Demand-side management : boilers are activated during the night when electricity is available Micro- production: better knowledge of energy produced to balance the network Security features Fire is detected : relay can be switched off rapidly Source: ETSI 5

6. Background: Voltage Levels in Grid Medium-Voltage Low-Voltage High-Voltage Source: ERDF 6 “Last mile” PLC communications on low/medium voltage line Concentrator

7. Motivation for “Last Mile” PLC Source: Powerline Intelligent Metering Evolution (PRIME) Alliance Draft v1.3E 7  Concentrator controls medium to subscriber meters  Similar to wireless communications basestation  Applications  Automatic meter reading (right)  Smart energy management  Device-specific billing (plug-in hybrid)  Improving reliability and rate  Mitigate impulsive noise  Transmit over multiple phases  Standards target ~100 kbps  ERDF G3-PLC [Électricité Réseau Dist. France]  PoweRline Intelligent Metering Evolution (PRIME) Alliance 7

8. PRIME Standard: Physical Layer  Orthogonal Frequency Division Modulation (OFDM)  Divides transmission band into many narrow sub-channels Transmission Band42-89 kHz Baseband sampling rate250kHz Subcarrier spacing488.28125Hz Number of subcarriers256 FFT size512 samples Cyclic prefix length48 samples Number of data tones84 (header) / 96 (payload) Number of pilot tones13 (header) / 1 (payload) Subchannel constellationPhase-shift keying (2, 4 or 8 levels) Codingconvolutional coding (rate ½) Max bit rate (uncoded)42.9kbps, 85.7kbps, 128.6kbps 8

9. Challenges  Powerline Channel Impairments  Multipath and frequency-selective time-variant channel attenuation  Background noise, impulsive noise, and narrow-band interference 9 Source: Texas Instruments

10. Challenges (cont.)  Performance degradation due to crosstalk  Induced by energy coupling across the phases or wires  Half-duplex operation eliminates ECHO and NEXT  Without FEXT cancellation, achievable data rate is significantly degraded 10

11. Presentation Roadmap  Framework of PLC Testbed  Receiver frame synchronization using a chirp signal  Modeling of PLC channel noise 11

12. PLC Testbed  Framework of the 1X1 Bidirectional PLC Testbed 12 HardwareSoftware National Instruments (NI) embedded computers process streams of data. National Instruments ADC/DAC generates/receives analog signals. Texas Instruments analog front end enables half-duplex operation. Transceiver algorithms implemented as C++ dynamically linked library, running in real-time embedded processors Desktop PC running LabVIEW provides GUI for configuring and displaying key system parameters

13. Receiver Synchronization Using Chirp PRIME specifies a preamble to begin each burst.  Preamble is a linearly frequency modulated chirp over 42-89 kHz  Chirp has constant envelope (in contrast to an OFDM signal)  Received signal  Correlated with chirp to find start of burst  Used to characterize channel 13

14. Experimental Results for Synchronization  Texas Instrument Development Kit for PLC  Two modems communicate with each other in interleaved manner  Gather samples at 250 kS/s 14 Rx Tx )

15. One Received Signal Burst Preamble  - - - - - - - Payload - - - -  Header 1 Header 2   2.048  - each OFDM symbol is 2.240 ms -   In time domain, a burst has the following structure.

16. Frame Synchronization by Correlation [Bumille & rLampe] Linear scaleLog scale

17. Chirp in Freq. Domain for Channel Est. FFT length is 512

18. Ex. Decoding Second Header Symbol 18 Looking at positive subcarriers only BPSK modulated subcarriers (Information in phase)

19. PLC Channel Noise  The powerline channel suffers from non AWGN noise  Noise as superposition of five noise types [Zimmermann 2000] 19 Source: Broadband Powerline Communications: Network Design

20. PLC Channel Noise  The powerline channel suffers from non AWGN noise  Noise as superposition of five noise types [Zimmermann 2000] 20 Colored Background Noise: PSD decreases with frequency Superposition of numerous noise sources with lower intensity Time varying (order of minutes and hours) Source: Broadband Powerline Communications: Network Design

21. PLC Channel Noise  The powerline channel suffers from non AWGN noise  Noise as superposition of five noise types [Zimmermann 2000] 21 Narrowband Noise: Sinusoidal with modulated amplitudes Affects several subbands Caused by medium and shortwave broadcast channels Source: Broadband Powerline Communications: Network Design

22. PLC Channel Noise  The powerline channel suffers from non AWGN noise  Noise as superposition of five noise types [Zimmermann 2000] 22 Periodic Impulsive Noise Asynchronous to Main: 50-200kHz Caused by switching power supplies Approximated by narrowbands Source: Broadband Powerline Communications: Network Design

23. PLC Channel Noise  The powerline channel suffers from non AWGN noise  Noise as superposition of five noise types [Zimmermann 2000] 23 Periodic Impulsive Noise Synchronous to Main: 50-100Hz, Short duration impulses PSD decreases with frequency Caused by power convertors Source: Broadband Powerline Communications: Network Design

24. PLC Channel Noise  The powerline channel suffers from non AWGN noise  Noise as superposition of five noise types [Zimmermann 2000] 24 Asynchronous Impulsive Noise : Caused by switching transients Arbitrary interarrivals with micro- millisecond durations 50dB above background noise Source: Broadband Powerline Communications: Network Design

25. PLC Channel Noise  The powerline channel suffers from non AWGN noise  Noise as superposition of five noise types [Zimmermann 2000] 25 Source: Broadband Powerline Communications: Network Design Can be lumped together as Generalized Background Noise

26. Generalized Background Noise 26 Source: Broadband Powerline Communications: Network Design Power spectral density of generalized background noise

27. Impulsive Noise  Asynchronous noise dominates this class of noise 27 Source: Broadband Powerline Communications: Network Design  Need to statistically model two aspects:  Impulse amplitude distribution  Inter-arrival time between impulses

28. Asynchronous Impulsive Noise Modeling  Amplitude statistics  Class-A Middleton [Umehara]  Weibull Distribution [Umehara]  Empirical Fits [Zimmermann]  Interarrival statistics  Exponential distribution [Zimmermann]  Empirical Fits [Zimmermann]  Partitioned Markov chains [Zimmermann] 28 Source: Zimmermann

29. Preliminary Noise Measurement 29

30. Preliminary Noise Measurement 30 Colored Background Noise

31. Preliminary Noise Measurement 31 Colored Background Noise Narrowband Noise

32. Preliminary Noise Measurement 32 Colored Background Noise Narrowband Noise Periodic and Asynchronous Noise

33. List of Acronyms/Abbreviations Acronym/AbbreviationMeaning Cyc. Pref.Cyclic Prefix FECForward Error Correction FEXTFar-end crosstalk LV/MVLow-voltage / medium-voltage MACMedium Access Control MIMOMulti-Input Multi-Output NEXTNear-end crosstalk OFDMOrthogonal Frequency Division Multiplexing PAPRPeak to average power ratio PHYPhysical layer PSDPower Spectral Density SFSKSpread Frequency Shift Keying 33

34. References Bumiller and Lampe, “Fast Burst Synchronization for PLC Systems,” Proc. IEEE Int. Sym. Power Line Comm. and its Applications, 2007, pp. 65 - 70 H. Hrasnica, A. Haidine, and R. Lehnert, Broadband Powerline Communications: Network Design, Wiley 2004. A. G. Olson, A. Chopra, Y. Mortazavi, I. C. Wong, and B. L. Evans, “Real-Time MIMO Discrete Multitone Transceiver Testbed”, Proc. Asilomar Conf. on Signals, Systems, and Computers, Nov. 4-7, 2007, Pacific Grove, CA. D. Umehara, S. Hirata, S. Denno, and Y. Morihiro, “Modeling of impulse noise for indoor broadband power line communications”, Proc. IEEE Int. Sym. on Information Theory and Its Applications, Oct. 29-Nov. 1, 2006, pp. 195-200. M. Zimmermann and K. Dostert, "Analysis and modeling of impulsive noise in broad- band powerline communications,” IEEE Trans. on Electromagnetic Compatibility, vol.44, no.1, pp.249-258, Feb 2002. Freescale solutions for smart metering and smart grid enablement, http://www.freescale.com/webapp/sps/site/overview.jsp?nodeId=02430Z6A10 http://www.freescale.com/webapp/sps/site/overview.jsp?nodeId=02430Z6A10 Texas Instruments Powerline Communications solutions http://www.ti.com/ww/en/apps/power_line_communications/index.html?DCMP= plc&HQS=Other+OT+plc http://www.ti.com/ww/en/apps/power_line_communications/index.html?DCMP= plc&HQS=Other+OT+plc 34