Half Spatially Coupled Turbo-Like Codes

2025-07-02

AI Summary

Existing spatially coupled turbo codes (SC-TCs) suffer from structural complexity and non-deterministic coupling, while binary convolutional codes (BCCs) with windowed decoding incur significant threshold loss. Method: This paper proposes two novel SC-TC families—half-spatially coupled braided convolutional codes (HS-BCCCs) and parallel convolutional codes—employing a deterministic, low-memory (M = 2) full-sequence recoding mechanism over a single time slot to realize spatial coupling. It further integrates windowed decoding with density evolution analysis to eliminate the threshold loss inherent in conventional BCC windowed decoding. Contribution/Results: Theoretical analysis and simulations demonstrate that the proposed codes achieve near-Shannon-limit performance even with minimal coupling memory, significantly outperforming state-of-the-art SC-TCs and BCC-based schemes in both error-correction performance and decoding complexity.

Technology Category

• Cognitive Modeling & Cognitive Systems: Neural Spike Coding
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Search and Optimization: Mixed Discrete/Continuous Search

Application Category

• Search and Retrieval-Augmented AI: Efficiency and scalability of Web search engines
• Security and Privacy: Large-scale security measurements
• Graph Algorithms and Modeling for the Web: Algorithms and analysis for heterogeneous, signed, attributed, multi-relational, temporal, higher-order, and annotated Web-related graphs

Abstract

This paper presents a new class of spatially coupled turbo-like codes (SC-TCs), namely half spatially coupled braided convolutional codes (HSC-BCCs) and half spatially coupled parallel concatenated codes (HSC-PCCs). Different from the conventional SC-TCs, the proposed codes have simpler and deterministic coupling structures. Most notably, the coupling of HSC-BCCs is performed by re-encoding the whole coupling sequence in the component encoder of one time instant, rather than spreading the coupling bits to component encoders of multiple time instants. This simplification not only addresses the window decoding threshold loss issue in existing BCCs, but also allows the proposed codes to attain very close-to-capacity performance with a coupling memory as small as 2. Both theoretical and numerical results are provided to demonstrate the performance advantages of the proposed codes over existing spatially coupled codes.

Problem

• Simplifies coupling structure in spatially coupled turbo-like codes
• Addresses window decoding threshold loss in braided convolutional codes
• Achieves close-to-capacity performance with small coupling memory

Innovation

• Simpler deterministic coupling structures
• Re-encoding whole coupling sequence
• Close-to-capacity performance with small memory