Spatially coupled turbo-like codes: a new trade-off between waterfall and error floor

TL;DR

This paper explores how spatial coupling in turbo-like codes improves finite-length performance, balancing near-capacity decoding thresholds with low error floors, thus offering a promising trade-off for practical applications.

Contribution

It provides a detailed analysis of the impact of spatial coupling on the error-floor and minimum distance of turbo-like codes, demonstrating their ability to approach capacity while maintaining low error floors.

Findings

Spatial coupling enhances the error-floor performance of turbo-like codes.

SC-TCs can approach channel capacity with very low error floors.

Conditions are established under which spatial coupling preserves or improves minimum distance.

Abstract

Spatially coupled turbo-like codes (SC-TCs) have been shown to have excellent decoding thresholds due to the threshold saturation effect. Furthermore, even for moderate block lengths, simulation results demonstrate very good bit error rate performance (BER) in the waterfall region. In this paper, we discuss the effect of spatial coupling on the performance of TCs in the finite block-length regime. We investigate the effect of coupling on the error-floor performance of SC-TCs by establishing conditions under which spatial coupling either preserves or improves the minimum distance of TCs. This allows us to investigate the error-floor performance of SC-TCs by performing a weight enumerator function (WEF) analysis of the corresponding uncoupled ensembles. While uncoupled TC ensembles with close-to-capacity performance exhibit a high error floor, our results show that SC-TCs can simultaneously approach capacity and achieve very low error floor.