An adaptive analog low-density parity-check decoder based on margin propagation

One of the key factors underlying the popularity of low-density parity-check (LDPC) codes is its iterative decoding algorithm which is amenable to efficient analog and digital implementation. However, different applications of LDPC codes (e.g. wireless sensor networks) impose different sets of constraints which include speed, bit error rates (BER) and energy efficiency. Our previous work reported an algorithmic framework for designing margin propagation (MP) based LDPC decoders where the BER performance can be traded off with its energy efficiency. In this paper we present an analog current-mode implementation of an MP-based (32; 8) LDPC decoder. The implementation uses only addition, subtraction and threshold operations and hence is independent of transistor biasing and robust to variations in environmental conditions (e.g. temperature). Measured results from prototypes fabricated in a 0.5m CMOS process verify the functionality of a (32; 8) LDPC decoder and demonstrate superior BER performance compared to the state-of-the-art analog min-sum decoder at SNR greater than 3.5 dB.