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FPGA Implementation of a Message-Passing OFDM Receiver for Impulsive Noise Channels

LabVIEW DSP Design Module. Local utility. testbench control/data visualization. Prof . Brian L. Evans , Wireless Networking and Communications Group , The University of Texas at Austin Stude nts: Mr. Karl Nieman , Mr. Marcel Nassar and Ms. Jing Lin. LabVIEW.

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FPGA Implementation of a Message-Passing OFDM Receiver for Impulsive Noise Channels

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  1. LabVIEW DSP Design Module Local utility testbench control/data visualization Prof. Brian L. Evans, Wireless Networking and Communications Group, The University of Texas at Austin Students: Mr. Karl Nieman, Mr. Marcel Nassar and Ms. Jing Lin LabVIEW LabVIEW DSP Design Module data symbol generation 43.2 kSps 16-bit DAC zero padding (null tones) 256 IFFT w/ 22 CP insertion NI 5781 sample rate conversion RT controller generatecomplex conjugate pair FlexRIO FPGA Module 1 (G3TX) Host Computer data and reference symbol interleave LabVIEW RT 368.3 kSps 10 MSps 400 kSps 103.6 kSps 51.8 kSps reference symbol LUT 8.6 kSps Objective: Implement real-time OFDM receiver with impulsive noise mitigation for use in power line communications (PLC). differential MCX pair LabVIEW DSP Design Module 8.6 kSps 14-bit ADC BER/SNR calculation w/ and w/o AMP 51.8 kSps NI 5781 256 FFT w/ 22 CP removal, noise injection FlexRIO FPGA Module 2 (G3RX) FlexRIO FPGA Module 3 (AMPEQ) RT controller data and reference symbol de- interleave channel estimation/ZFequalization sample rate conversion Subtract noise estimate from active tones time and frequency offset correction null tone and active tone separation LabVIEW RT 400 kSps 10 MSps 400 kSps 368.3 kSps 43.1 kSps 51.8 kSps AMP noise estimate 256 FFT, tone select 43.1 kSps 184.2 kSps 368.3 kSps 51.8 kSps OFDM Impulsive Noise in PLC MV-LV transformer Outdoor medium-voltage line (St. Louis, MO) Indoor low-voltage line (UT Campus) • OFDM transmits data over multiple independent subcarriers (tones) = 1 MHz Interleave Equalizer and detector Receiver y x + IFFT Filter FFT + + - Vectorof symbolamplitudes(complex) Impulsive noise estimation Gaussian (w) + ImpulsiveNoise (e) Data concentrator Conventional OFDM system Channel FPGA Implementation of a Message-Passing OFDM Receiver for Impulsive Noise Channels Added in our system Smart meters • FFT spreads out impulsive noise across all subcarriers Communication in a Smart Grid Cyclostationary noise becomes impulsive after interleaving AMP PLC Test System Powered by NI Products Approximate Message Passing (AMP) BER Results • Iterative algorithm (4 iterations used) • In-band noise inferred from out-of-band guard tones • LabVIEW DSP Design Module (a high-level graphical synthesis tool) was used to map processing to FPGA • Mapped to fixed-point using MATLAB toolbox TX Chassis RX Chassis 1 × PXIe-1082 1 × PXIe-8133 1 × PXIe-7965R 1 × NI-5781 FAM 1 × PXIe-1082 1 × PXIe-8133 2 × PXIe-7965R 1 × NI-5781 FAM differential MCX pair(quadrature component = 0) LabVIEW Front Panel • BER analyzed over typical PLC operating range • Up to 8 dBSNR recovered using AMP algorithm FPGA Resource Usage with AMP conventional input impulsive noise DSP Design Diagram (step 2 of algorithm) Project supported by NI, Freescale, IBM, and TI Project website: http://users.ece.utexas.edu/~bevans/projects/plc/

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