Tremendous progress in reducing turbo code computational complexity, memory requirements and performance limitations is leading to their wide use in commercial communications systems.ABSTRACT | For decades, the de facto standard for forward error correction was a convolutional code decoded with the Viterbi algorithm, often concatenated with another code (e.g., aReed-Solomon code). But since the introduction of turbo codes in 1993, much more powerful codes referred to collectively as turbo and turbo-like codes have eclipsed classical methods.These powerful error-correcting techniques achieve excellent error-rate performance that can closely approach Shannon's channel capacity limit. The lure of these large coding gains has resulted in their incorporation into a widening array of telecommunications standards and systems. This paper will briefly characterize turbo and turbo-like codes, examine their implications for physical layer system design, and discuss standards and systems where they are being used. The emphasis will be on telecommunications applications, particularly wireless, though others are mentioned. Some thoughts on the use of turbo and turbo-like codes in the future will also be given.
The performance of a concatenated Turbo code with an outer BCH code is examined. The Turbo code was based on simple 4-state constituent codes with a constrained high spread random (HSR) interleaver. Data puncturing, as opposed to puncturing only the parity bits, was used with the Turbo code to improve the convergence performance in the waterfall region. It is shown that this simple approach achieves performance better than the rate 1/2 DVB-S2 concatenated LDPC-BCH code.
The error-rate performance of punctured Turbo codes may be significantly improved by puncturing data symbols as well as parity symbols, yielding partially-systematic Turbo codes (PSTCs). In this paper, it is shown that relatively simple 4-state PSTCs are able to achieve convergence (i.e., waterfall) performance that is 0.26 dB from the binary channel capacity limit at rate 1/2 and 0.18 dB from the limit at rate 8/9. It is also demonstrated that extrinsic information transfer (EXIT) charts do not accurately predict convergence performance for 4-state PSTCs.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.