Power Characterization of a Gbit/s FPGA Convolutional LDPC Decoder

Abstract

In this thesis, we present an FPGA implementation of parallel-node low-density-parity-check convolutional-code (PN-LDPC-CC) encoder and decoder. A 2.4 Gbit/s rate-1/2 (3, 6) PN-LDPC-CC encoder and decoder were implemented on an Altera development and education board (DE4). Detailed power measurements of the FPGA board for various configurations of the design have been conducted to characterize the power consumption of the decoder module. For an Eb/N0 of 5 dB, the decoder with 9 processor cores (pipelined decoder iteration stages) has a bit-error-rate performance of 10E-10 and achieves an energy-per-coded-bit of 1.683 nJ based on raw power measurement results. The increase in Eb/N0 can effectively reduce the decoder power and energy-per-coded-bit for configurations with 5 or more processor cores for Eb/N0 < 5 dB. The incremental decoder power cost and incremental energy-per-coded-bit also hold a linearly decreasing trend for each additional processor core. Additional experiments are performed to account for the effect of the efficiency of the DC/DC converter circuitry on the raw power measurement data. Further experiments have also been conducted to quantify the effect of clipping thresholds, bit width for each processor core on bit-error-rate (BER) performance, power consumption, and logic utilization of the decoder. A “6Core" decoder with growing bit-width log-likelihood ratios (LLRs) has been found to have a BER performance near that of a “6Core" 6-bit decoder while consuming similar power, and logic utilization to that of a 5-bit “6Core" decoder.