design tradeoffs in joint powerline and wireless transmission for smart grid communications 1 ghadi...
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Design Tradeoffs In Joint Powerline and Wireless Transmission For
Smart Grid Communications
1
Ghadi Sebaali and Brian L. Evans
Department of Electrical and Computer EngineeringWireless 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
ImpairmentsChannel distortion and time-varying gainImpulsive and thermal noise, and external interference
GoalIncrease reliability
ApproachJointly transmit over PLC and wireless channels
Contributions Review channel modeling Review of noise modelingExplore design tradeoffsExplore noise mitigation techniques
Smart Grid Communications
2Introduction |PLC/Wireless Links| PLC/Wireless Combining| Wireless Receiver| Summary
[MaRS Market Insights, 2012]
PLC Link Wireless LinkFrequency band
3-500kHz (unlicensed)
902-928MHz(unlicensed)
3
Joint Transmission
Transmitter side: send same info over PLC and wireless links
Receiver side:combine received signals into one
Introduction |PLC/Wireless Links| PLC/Wireless Combining| Wireless Receiver| Summary
Com
bine
r
DM
Dominant noiseCyclostationary impulsive noisein time and frequency with T = half AC power cycle
hτ
(1)
hτ
(2)
hτ
(3)
AWGN
60%
30%
10%
Cyclo-stationary
noiseN (0,1)
Caused bySwitching mode power suppliesNon-linear electronic devices Broadcast stations
Modeled by Linear periodically time-varying system
[Nassar et al., 2012]
4
Narrowband PLC Noise
Introduction |PLC/Wireless Links| PLC/Wireless Combining| Wireless Receiver| Summary
11 12 13
Narrowband PLC Channel
Multi-path model
Transmission-line modelParameters: ABCD parametersDrawback: assumes topology is known
Extends transmission-line modelAccounts for multipath effects due to branches, impedance mismatch
Parameters: delay, attenuation, total number of paths, etc.Drawback: doesn’t capture topology of channel
5Introduction |PLC/Wireless Links| PLC/Wireless Combining| Wireless Receiver| Summary
Statistical model
[Ferreira, 2010]
Dominant noiseUncoordinated impulsive noise
Noise sourcesUncoordinated transmissionsNon interoperable devicesNeighboring devices
Noise modelGaussian Mixture Model (GMM)
Channel Model Rayleigh Fading
6
Wireless Link
[Interference Mitigation Toolbox, UT Austin]
Introduction |PLC/Wireless Links| PLC/Wireless Combining| Wireless Receiver| Summary
7
Combining Reception
Combining Schemes
SelectionCombining
Largest SNR
Saturated Metric Combining
Saturated log likelihood
Maximum Ratio Combining
Log likelihood ratio
Introduction |PLC/Wireless Links| PLC/Wireless Combining| Wireless Receiver| Summary
[Lai, 2012]
8
Combining Reception
FFT (N)
Cyclic Prefix Length Modulation Number of Paths Combining Scheme
128 26 BPSK 5,20 Saturated MetricSelection Maximal Ratio
Combining Schemes for a 5-path channel model Combining Schemes for a 20-path channel model
Introduction |PLC/Wireless Links| PLC/Wireless Combining| Wireless Receiver| Summary
9
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
10
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 ForcingMin. Mean Squared ErrorMaximum Likelihood
Introduction |PLC/Wireless Links| PLC/Wireless Combining| Wireless Receiver| Summary
11
Increased reliability via joint PLC/wireless transmissionRecommendations
Maximal ratio combining for PLC/wireless linksZero-forcing to mitigate wireless interference
Future workCoexistence in 900 MHz band between IEEE 802.11ah & 802.15.4gInterferer separation (find critical distance for victim receiver)Link quality indicator for the IEEE 802.15.4g standard
Summary
Introduction |PLC/Wireless Links| PLC/Wireless Combining| Wireless Receiver| Summary
[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.
References