Diversity and Coexistence within Smart Grid Communications Prof. Brian L. Evans, Wireless Networking and Communications Group, The University of Texas at Austin Students: Ms. Ghadi Sebaali and Mr. Junmo Sung Current Collaborators: Prof. Naofal Al-Dhahir (UT Dallas) and Mr. Mostafa Sayed (UT Dallas) Past Collaborators: Dr. Jing Lin (Qualcomm), Dr. Marcel Nassar (Samsung), Dr. Aditya Chopra (NI) Sponsors: Semiconductor Research Corporation GRC under Task Id 1836.133 (from Freescale and Texas Instruments) Objective: Improve reliability of smart grid communications (1. Project Overview) (2.1 Wireless/PLC Diversity)  Non-identical channel, noise and interference statistics Maximal Ratio Combining is a maximum likelihood optimal technique for AWGN OFDM transmission with 256 sub-channels and BPSK modulation 0.4 MHz sampling rate Wireless Link noise model: Gaussian Mixture with 2 components PLC Noise Model : cyclostationary noise Legend Wireless Link PLC Link Focus Neighborhood-area smart utility network between a data concentrator and smart meters along two paths  Instantaneous SNR Combining gives 7dB gain over PLC alone (2.2 Coexistence Mechanisms) Powerline (PLC) Link Wireless Link low-voltage power lines in 3-500 kHz band unlicensed wireless 902-928 MHz band 802.11 ah and 802.15.4g standards share the 900 MHz ISM band Path Loss (PL) Model used is outdoor large-zone model Interference Model is used as follows: d(Rxv, Txv) = dD and d(Rxi, Txi) = dU Metric used is desired/undesired signal ratio  Goal Integrating customers in the grid Scale voltage with energy demand Bill customer using real-time rates Analyze customer load profiles Improve system reliability Interferer Victim Victim Required FER (%) Critical distance (m) 802.15.4g 802.11ah 1 5 – 6.5 802.11ah, 801.11g, 801.15.4 5.5 - 13 Project Components Interference Mitigation PLC/wireless Diversity Coexistence Mechanisms PLC/wireless Testbed Limitations Signal attenuation in propagation channel Reflections at impedance discontinuities Noise or interference Frequency selectivity   f selective or wideband: if time difference between the received copies of the transmitted signal (DELAY SPREAD) is significant Nassar Figure 3.11: Part 1: Home area networks (HAN) that connect smart appliances and sensors on indoor power lines with smart meters; Neighborhood area networks (NAN) that connect smart meters to data concentrators that are deployed by local utilities on medium-voltage (MV) lines (in the US) or low-voltage (LV) lines (in Europe); Communication backhaul that carries trac between data concentrators and local utilities. 
 BERavg performance is more sensitive to the accuracy of SNRinst estimates (given same SNRavg for both links) combined average BER that is better than the individual average BER of each link over the whole Eb/No range is the case where the pilot spacing is equal to one, i.e. all the subchannels are pilots. (2.3 Testbed) ( Current Work ) A real-time hardware/software testbed for wired MIMO OFDM communication Algorithms evaluated: bit allocation, time equalization, far-end crosstalk cancellation ( zero-forcing & successive interference)  Add simultaneous wireless communication to the PLC testbed  Evaluate communication performance vs. complexity tradeoffs for wireless diversity methods Project Web Page: http://users.ece.utexas.edu/~bevans/projects/plc/index.html Software Hardware Graphical User Interface (GUI) runs in LabVIEW Real-time operating system running on embedded processors: NI PXI 1045 Embedded Controller NI PXI-5122 for analog-to-digital (A/D) conversion NI PXI-5421 for digital-to-analog (D/A) conversion