Analysis and design of anytime codes

• Main Author: Yu, Xiaoxi
• Other Authors: Guan Yong Liang
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2024
• Subjects: Engineering; Forward error correction codes
• Online Access: https://hdl.handle.net/10356/180976
• Institution: Nanyang Technological University

Anytime code is a class of forward error-correction (FEC) codes that is crucial for reliable communications of delay-sensitive data over noisy channels. Practical anytime codes have been developed for various channels and applications. This thesis is dedicated to the design and analysis of novel anytime codes that outperform prior-art anytime codes or are tailored for unexplored scenarios and channels. The thesis begins with an in-depth analysis of anytime spatially coupled repeat-accumulate (SC-RA) codes. Specifically, the anytime-reliable properties of the anytime SC-RA codes are rigorously validated over both binary erasure channels (BECs) and additive white Gaussian noise (AWGN) channels. To further improve the error-correcting performance of the codes, novel hybrid automatic repeat request (HARQ) protocols are introduced to address the irreducible error levels encountered by finite block length anytime codes. Subsequently, a family of rate-compatible (RC) anytime code ensembles with a wide range of flexible code rates, constructed based on the anytime SC-RA code ensemble, are designed and analyzed. Furthermore, an expanding-window incremental redundancy HARQ (IR-HARQ) scheme, specifically tailored for anytime-coded HARQ transmission, is proposed. The focus then shifts to enhancing finite-length (i.e., finite block length) anytime codes through the design and construction of protograph-based anytime (P-anytime) codes. By introducing two performance metrics for finite-length anytime codes, a multi-objective optimization algorithm is developed. This algorithm incorporates the objective functions corresponding to the two proposed metrics, facilitating the design of superior P-anytime codes that outperform the prior-art anytime codes. While the preceding studies primarily focused on BECs and AWGN channels, the final section of the thesis extends the investigation to anytime codes over non-ergodic block fading (BF) channels. Novel root-anytime codes are developed, and simulation results demonstrate their improved decoding performance in the non-ergodic BF channel environments.