Contributions

Our research in smart grid communication systems has focused on powerline communications.

Approach

Additive impulsive noise is the dominant impairment in low-voltage and medium-voltage power lines in the 3-500 kHz band. However, traditional communication system design approaches have assumed that additive noise is additive spectrally-flat Gaussian noise. When compared with traditional approaches, our research in modeling and mitigating impulsive noise will enable the design of powerline communication systems that achieve 10-100x reduction in bit error rate, or 2x improvement in bit rate for single channel communications, on low-voltage or medium-voltage power lines. We are also investigating multiple transmitters and receivers for powerline communication systems to double bit rates on low-voltage lines (using 2x2 systems) and quadruple bit rates on medium voltage lines (using 4x4 systems).

Goals

The specific goals of this research are to develop
  1. statistical models for aggregate impulsive noise at the receiver
  2. parameter estimation methods for the statistical models
  3. parametric and non-parametric interference cancellation techniques
  4. impulsive noise modeling and mitigation toolbox in MATLAB

Impact

Our research group is having quite a bit of impact on powerline communication system research, design, and standards.

Our channel transfer function models and cyclostationary impulsive noise models have been adopted in the IEEE 1901.2 standard. This work was based on field measurements taken with TI and Aclara using TI modems. We describe the models in the following paper:

M. Nassar, J. Lin, Y. Mortazavi, A. Dabak, I. H. Kim and B. L. Evans, "Local Utility Powerline Communications in the 3-500 kHz Band: Channel Impairments, Noise, and Standards", IEEE Signal Processing Magazine, Special Issue on Signal Processing Techniques for the Smart Grid, vol. 29, no. 5, pp. 116-127, Sep. 2012.

Our more recent work in modeling cyclostationary noise and proposing cyclic bit loading to double bit rates won a Best Paper Award. This work was based on field measurements using Freescale G3 modems and we released the datasets and accompanying Matlab code:

K. F. Nieman, J. Lin, M. Nassar, B. L. Evans, and K. Waheed, "Cyclic Spectral Analysis of Power Line Noise in the 3-200 kHz Band", Proc. IEEE Int. Symp. on Power Line Communications and Its Applications, Mar. 24-27, 2013. Won the Best Paper Award.

For current standards, we have developed generalized approximate message passing receivers to provide 8-10 dB SNR gain for coded transmission in the presence of asynchronous interference. We've mapped the latter receiver to a Xilinx FPGA for real-time implementation.

For future standards, we have developed real-time methods to combat impulsive noise. We have shown that time-domain interleaving can provide a 6 dB SNR gain in cyclostationary noise:

J. Lin and B. L. Evans, "Non-parametric Mitigation of Periodic Impulsive Noise in Narrowband Powerline Communications", Proc. IEEE Int. Global Communications Conf., Dec. 9-12, 2013, Atlanta, GA USA, submitted.

On-Going Research

We propose to develop adaptive digital signal processing methods for peak-to-average power reduction, echo cancellation, crosstalk cancellation, channel equalization, bit loading and multichannel transmission. We also propose to develop low-power medium access control (MAC) scheduling methods to support relaying of data to and from other nodes. Relaying allows a node to communicate with the concentrator through other nodes when there is no direct sustainable connection to the concentrator. Real-time prototypes will allow designers to evaluate adaptive digital signal processing and MAC scheduling algorithms in communication performance vs. implementation complexity tradeoffs.

Power consumption of powerline communication systems is a key limiting factor for widespread deployment in intelligent power meters. For medium-voltage power lines, we propose to use three phases to quadruple the bit rate, or conversely, provide the same bit rate at one-fourth of the transmission power. If the four transceivers were transmitting independently on three phases, then the total bit rate could be lower than the bit rate when using only one wire due to crosstalk [2]. However, using three phases opens up a new dimension (space) to exploit.

To enable our adaptive methods, we will characterize three-phase low-voltage channels. For the MAC layer, we propose to develop low-power scheduling methods to support relaying of data. Finally, we propose to create a real-time 3x1/3x3 OFDM powerline communication testbed by extending our real-time 2x2 OFDM wired testbed [2]. Our 2x2 testbed demonstrates a doubling of bit rate on two wires vs. one wire through crosstalk cancellation, channel equalization and bit loading over in-the-field cables. Crosstalk cancellation accounts for 90% of the gain in bit rate.

References

  1. PoweRline Intelligent Metering Evolution (PRIME) Alliance, http://www.prime-alliance.org.
  2. A. G. Olson, A. Chopra, Y. Mortazavi, I. C. Wong and B. L. Evans, "Real-Time MIMO discrete multitone transceiver testbed", Proc. IEEE Asilomar Conf. on Signals, Systems and Computers, Nov. 2007, Pacific Grove, CA.
  3. Open PLC European Research Alliance, "Theoretical postulation of PLC channel model," Tech. Rep., Apr. 2005. http://www.ist-opera.org/opera1/downloads/D4/D4_Theoretical_Post.pdf
  4. A. Cataliotti, A. Daidone, and G. Tine, "A medium-voltage cable model for power-line communication," IEEE Trans. on Power Delivery, Vol. 24, No. 1, Jan. 2009, pp. 125 - 139.
  5. X. Carccelle, Powerline Communications in Practice, Artech House 2006.
  6. H. Hrasnica, A. Haidine, and R. Lehnert, Broadband Powerline Communication Networks, Wiley, 2004.
  7. K. Gulati, B. L. Evans, J. G. Andrews, and K. R. Tinsley, "Statistics of co-channel interference in a field of Poisson and Poisson-Poisson clustered interferers", IEEE Trans. on Signal Processing, submitted Nov. 29, 2009.
  8. K. Gulati, M. Nassar, A. Chopra, B. Okafor, M. DeYoung, N. Aghasadeghi, A. Sujeeth, and B. L. Evans, "Radio frequency interference modeling and mitigation toolbox in MATLAB," Version 1.4, Feb. 2010. Available: http://users.ece.utexas.edu/~bevans/projects/rfi/software/.
  9. J. Tellado and J. Cioffi, "PAR reduction in multicarrier transmission systems," TIE1.4/97-367, Dec. 8, 1997.
  10. J. Tellado, Multicarrier Modulation with Low Peak to Average Power Applications to XDSL and Broadband Wireless, Ph.D Dissertation, Dept. of Electrical Engineering, Stanford University.
  11. M.-H. Hsieh and C.-H. Wei, "Low-complexity frame synchronization and frequency offset compensation scheme for OFDM systems over fading channels," IEEE Trans. on Vehicular Technology, vol. 48, no. 5, Sept. 1999.
  12. G.-S. Liu and C.-H. Wei, "A new variable fractional sample delay filter with nonlinear interpolation," IEEE Trans. on Circuits and Systems: Analog and Digital Signal Processing, vol. 39, no. 2, Feb. 1992.
  13. R. K. Martin, K. Vanbleu, M. Ding, G. Ysebaert, M. Milosevic, B. L. Evans, M. Moonen, and J. Johnson, "Unification and evaluation of equalization structures and design algorithms for discrete multitone modulation systems," IEEE Trans. on Signal Processing, vol. 53, no. 10, pp. 3880-3894, Oct. 2005.
  14. D. Umehara, H. Yamaguchi, and Y. Morihiro, "Turbo decoding in impulsive noise environment," Proc. IEEE Global Comm. Conf., vol.1, pp. 194-198, 29 Nov.-3 Dec. 2004.
  15. T. Faber, T. Scholand, and P. Jung, "Turbo decoding in impulsive noise environments," IEE Electronics Letters, vol. 39, no. 14, pp. 1069-1071, 10 July 2003.
  16. H. H. Nguyen and T. Q. Bui, "Bit-interleaved coded OFDM with iterative decoding in impulsive noise," IEEE Trans. on Power Delivery, vol. 23, no. 2, pp. 640-649, Apr. 2008.
  17. A. Paulraj, R. Nabar and D. Gore, Introduction to Space-Time Wireless Communications, Cambridge University Press, 2003.

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