Design Tradeoffs In Joint Powerline and Wireless Transmission For Smart Grid Communications Ghadi Sebaali and Brian L. Evans Department of Electrical and Computer Engineering Wireless Networking and Communications Group The University of Texas at Austin Collaboration with Prof. Naofal Al-Dhahir and Mr. Mostafa Sayed at UT Dallas  Support from National Instruments, and Semiconductor Research Corporation with liaisons Freescale Semiconductor and Texas Instruments

Smart Grid Communications Impairments Channel distortion and time-varying gain Impulsive and thermal noise, and external interference Goal Increase reliability Approach Jointly transmit over PLC and wireless channels Contributions Review channel modeling Review of noise modeling Explore design tradeoffs Explore noise mitigation techniques \ [MaRS Market Insights, 2012] Introduction |PLC/Wireless Links| PLC/Wireless Combining| Wireless Receiver| Summary

D Joint Transmission M Combiner PLC Link Wireless Link Frequency band Transmitter side: send same info over PLC and wireless links Receiver side: combine received signals into one Combiner D M PLC Link Wireless Link Frequency band 3-500kHz (unlicensed) 902-928MHz Introduction |PLC/Wireless Links| PLC/Wireless Combining| Wireless Receiver| Summary

Narrowband PLC Noise Dominant noise Caused by Modeled by Cyclostationary impulsive noise in time and frequency with T = half AC power cycle Caused by Switching mode power supplies Non-linear electronic devices Broadcast stations Modeled by Linear periodically time-varying system hτ(1) hτ(2) hτ(3) AWGN 60% 30% 10% Cyclo- stationary noise N (0,1) 1 2 3 1 1 1 [Nassar et al., 2012] Introduction |PLC/Wireless Links| PLC/Wireless Combining| Wireless Receiver| Summary

Narrowband PLC Channel Multi-path model Parameters: delay, attenuation, total number of paths, etc. Drawback: doesn’t capture topology of channel Transmission-line model Parameters: ABCD parameters Drawback: assumes topology is known Statistical model Extends transmission-line model Accounts for multipath effects due to branches, impedance mismatch [Ferreira, 2010] Introduction |PLC/Wireless Links| PLC/Wireless Combining| Wireless Receiver| Summary

Wireless Link Dominant noise Noise sources Noise model Channel Model Uncoordinated impulsive noise Noise sources Uncoordinated transmissions Non interoperable devices Neighboring devices Noise model Gaussian Mixture Model (GMM) Channel Model Rayleigh Fading [Interference Mitigation Toolbox, UT Austin] Introduction |PLC/Wireless Links| PLC/Wireless Combining| Wireless Receiver| Summary

Combining Reception Combining Schemes Selection Combining Largest SNR Saturated Metric Combining Saturated log likelihood Maximum Ratio Combining Log likelihood ratio [Lai, 2012] Introduction |PLC/Wireless Links| PLC/Wireless Combining| Wireless Receiver| Summary

Combining Reception FFT (N) Cyclic Prefix Length Modulation Combining Schemes for a 5-path channel model Combining Schemes for a 20-path channel model FFT (N) Cyclic Prefix Length Modulation Number of Paths Combining Scheme 128 26 BPSK 5,20 Saturated Metric Selection Maximal Ratio Introduction |PLC/Wireless Links| PLC/Wireless Combining| Wireless Receiver| Summary

Wireless Receiver Design Zero Forcing: detects signal by inverting channel matrix Minimum Mean Square Error: ranks received signals based on their SNR Maximum Likelihood: chooses symbol with least Euclidean Distance for decoding and cancellation [Miridakis, 2013] Introduction |PLC/Wireless Links| PLC/Wireless Combining| Wireless Receiver| Summary

Wireless Receiver Design Parameter Value Channel Multipath Channel Model Rayleigh Channel Taps 6 Noise Model AWGN, GMM GMM Parameters 99% σw= 0.001 and 1% σw= 100 Successive Interference Cancellation Techniques Zero Forcing Min. Mean Squared Error Maximum Likelihood Introduction |PLC/Wireless Links| PLC/Wireless Combining| Wireless Receiver| Summary

Summary Increased reliability via joint PLC/wireless transmission Recommendations Maximal ratio combining for PLC/wireless links Zero-forcing to mitigate wireless interference Future work Coexistence in 900 MHz band between IEEE 802.11ah & 802.15.4g Interferer separation (find critical distance for victim receiver) Link quality indicator for the IEEE 802.15.4g standard Introduction |PLC/Wireless Links| PLC/Wireless Combining| Wireless Receiver| Summary

References [1] M. Sayed and N. Al-Dhahir, “Narrowband-PLC/wireless diversity for smart grid communications,” Proc. IEEE Global Comm. Conf., Dec. 2014. [2] H. Ferreira, Power Line Communications: Theory and Applications for Narrowband and Broadband Communications Over Power Lines, 2010. [3] K. F. Nieman, J. Lin, M. Nassar, K. Waheed, and B. L. Evans, “Cyclic spectral analysis of power line noise in the 3-200 kHz band,” Proc. IEEE Int. Symp. On Power Line Comm. and Its Applications, 2013. [4] M. Nassar, K. Gulati, Y. Mortazavi, and B.L.Evans, “Statistical modeling of asynchronous impulsive noise in powerline communication networks,” Proc. IEEE Global Comm. Conf., Dec. 2011. [5] M. Nassar, B. L. Evans, and P. Schniter, “A factor graph approach to joint OFDM channel estimation and decoding in impulsive noise environments,” IEEE Trans. Signal Proc., vol. 62, no. 6, Mar. 2014. [6] M. Nassar, A. Dabak, I. H. Kim, T. Pande, and B. L. Evans, “Cyclo- stationary noise modeling in narrowband powerline communication for smart grid applications,” Proc. IEEE Int. Conf. Acoustics, Speech, and Signal Proc., Mar. 2012. [7] K. Gulati, M. Nassar, A. Chopra, N. B. Okafor, M. DeYoung, and B. L. Evans. (2011, Apr.) UT Austin Interference Modeling and Mitigation Toolbox. [Online]. Available: http://users.ece.utexas.edu/~bevans/projects/rfi/software/ [8] N. Miridakis and D. Vergados, “A survey on the successive interference cancellation performance for single-antenna and multiple-antenna OFDM systems,” IEEE Comm. Surveys & Tutorials, vol. 15, no. 1, Feb. 2013. [9] S. W. Lai and G. G. Messier, “Using the wireless and PLC channel for diversity,” IEEE Trans. on Comm., Dec. 2012.