Adaptive Hybrid ARQ Systems With BCJR Decoding

• Published in: IEEE transactions on vehicular technology Vol. 57; no. 3; pp. 1606 - 1619
• Main Authors: Mielczarek, B., Krzymien, W.A.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01-05-2008; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Adaptive systems; Algorithms; and Raviv (BCJR) algorithm; Applied sciences; Automatic repeat request; Bahl; Channels; Circuit properties; Cocke; Coding, codes; Convergence; Cyclic redundancy check; Decoding; Educational institutions; Electric, optical and optoelectronic circuits; Electronic circuits; Electronics; Exact sciences and technology; Feedback; Forward error correction; Hybrid Automatic Repeat reQuest (HARQ); incremental redundancy (IR); Information, signal and communications theory; Interference; Jelinek; Links; Lookup tables; Parity; rate-compatible (RC) codes; Signal and communications theory; Signal convertors; Studies; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Throughput; Transmission and modulation (techniques and equipments); incremental redundancy; hybrid ARQ; BCJR algorithm; rate compatible codes; Performance evaluation; Adaptive algorithm; rate-compatible (RC) codes; Adaptive system; Information rate; Feedback regulation; incremental redundancy (IR); Hybrid system; Coding; Cocke; Acknowledgment; Fading channels; Redundancy; Hybrid Automatic Repeat reQuest (HARQ); Rayleigh channels; Decoding circuit; and Raviv (BCJR) algorithm; Decoding; Hybrid mode; Information transmission; Look up table; Algorithm performance; Jelinek; Error correction; Bahl; Automatic repeat request; Transmission error
• ISSN: 0018-9545; 1939-9359
• DOI: 10.1109/TVT.2007.907075

We propose and evaluate a novel method of constructing Hybrid Automatic Repeat reQuest (HARQ) systems using the specific properties of the Bahl, Cocke, Jelinek, and Raviv (BCJR) error-correcting algorithm. Because the convergence to the actual codeword is not always guaranteed with the BCJR approach, we propose a system in which two different types of Negative AcKnowledgement messages (NAKs) are employed. The first type is the conventional 1-bit NAK, and the second type specifies retransmission pattern in such a way that the additional parity bits are concentrated on the parts of the code trellis that did not converge to a valid sequence. This is different from the traditional construction of rate-compatible punctured codes (RCPCs), which attempts to obtain the optimal weight distance properties of the codes without taking the convergence properties of the BCJR decoder into account. We demonstrate the performance of the algorithm using RCPCs, and we show that our system outperforms the best known conventional HARQ scheme in terms of the throughput and the average length of retransmitted blocks on practical Gaussian, Rayleigh, and thresholded Rayleigh channels. Moreover, as opposed to other adaptive HARQ algorithms, our solution requires no precomputed lookup tables, and it is robust to changes in the channel characteristics and only introduces moderate increase in feedback link throughput requirements.