Hierarchical Trellis Coding for Higher Gain With Lower Complexity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing trellis coded modulation (TCM) techniques face limitations in achieving high coding gains without excessive decoding complexity, particularly in Asymmetric Digital Subscriber Lines (ADSL) systems, where proposed turbo coded schemes are complex and not standardized due to high complexity, preventing their adoption as alternatives to traditional TCM.
Innovation Solution
The implementation of Hierarchical Trellis Coded Modulation (HTCM) which uses a hierarchy of component trellis codes with different error correcting capabilities, combining a high protection turbo code and a low protection trellis coded modulation code to achieve a balance between coding gain and complexity, specifically using a turbo code as the high protection component and a 16-state 4D Wei code for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multidimensional TCM codes are used to improve coding gain, then coding gain increases, but decoding complexity increases excessively
Solution Approach 1:
The patent segments the information bits into multiple groups, with different groups having different protection levels. Some bits are encoded with high protection codes (turbo codes) while others use low protection codes (TCM), creating a hierarchical structure that balances performance and complexity
Solution Approach 2:
Different portions of the information are assigned different coding schemes based on their importance. Critical information bits receive high protection through turbo codes, while less critical bits use simpler TCM, optimizing the overall system performance without uniform complexity increase
2Reliability
If turbo coded schemes with multiple concatenated codes are used, then coding gain improves, but device complexity increases
Solution Approach 1:
The patent divides the coding structure into hierarchical levels where different codes operate on different bit groups. This segmentation allows the system to achieve diversity in error correction capability without requiring all bits to go through complex concatenated decoding
Solution Approach 2:
Instead of applying full turbo code concatenation to all information bits, the patent applies high protection codes only to critical portions of the data, while other portions receive standard TCM protection, achieving sufficient error correction with reduced complexity
Data Source
AI summary
A system and method for encoding information is disclosed. In one embodiment, information is encoded using a high protection code for the least significant bit and a low protection code for the next three most significant bits. The remaining bits are uncoded. The high protection code may be a turbo code and the low protection code may be a trellis coded modulation code. In this embodiment, the collection of bits is then mapped according to a diagonally shifted QAM constellation technique.