EXIT Trajectories of Irregular LDPC Codes

Abstract

In this paper, we propose the concept of extrinsic information transfer (EXIT) trajectories, and show how to use it to analyze convergence performance of belief propagation (BP) decoding for irregular low-density parity-check (LDPC) codes. The proposed analysis method utilizes the EXIT characteristics in an improved way, and allows us to calculate the convergence threshold quickly and accurately. On the binary phase-shift keying (BPSK) modulated additive white Gaussian noise (AWGN) channel, the achieved threshold values for the enumerated irregular LDPC codes have error to those computed by density evolution only about 0.03 dB.