LDPC Bit Mapping for Uniform Constellation Reliability
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Solution Overview
Problem
Existing LDPC encoding and modulation methods result in poor signal quality and low transmission reliability due to sequential mapping of bits to constellation points, leading to high bit error rates.
Innovation Solution
The proposed method involves encoding information bit sequences using a low-density parity-check LDPC matrix and mapping bits in the least reliable code block to non-least reliable bit locations during modulation, ensuring uniform reliability and reducing bit error rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If bits are sequentially mapped to constellation points in bit order, then the modulation process is simple, but signal quality deteriorates and transmission reliability decreases
Solution Approach 1:
The patent applies local quality by differentiating the mapping process for different code blocks. Specifically, bits from least reliable code blocks are mapped to more reliable bit locations (such as less significant bits) in the constellation diagram, while bits from reliable code blocks can be mapped to less reliable locations. This localized adaptation of mapping strategy based on code block reliability resolves the contradiction by maintaining simple overall modulation while optimizing specific mappings for reliability.
Solution Approach 2:
The patent changes the mapping parameter (bit location assignment) based on the reliability characteristics of different code blocks. By dynamically adjusting which bit locations in the constellation diagram receive bits from which code blocks, the system improves transmission reliability without fundamentally changing the modulation process structure, thus resolving the contradiction between simplicity and reliability.
2Ease of manufacture
If sequential bit mapping is used, then implementation is straightforward, but bit error rate increases
Solution Approach 1:
The patent implements local quality by applying different mapping strategies to different portions of the code sequence. Least reliable code blocks are specifically targeted and their bits are mapped to more robust constellation bit locations, while maintaining straightforward implementation for the overall system. This resolves the contradiction by making the implementation only slightly more complex while achieving significant bit error rate reduction.
3Device complexity
If uniform mapping is applied to all code blocks, then the process is simple, but reliability of least reliable code blocks deteriorates
Solution Approach 1:
The patent directly applies local quality by recognizing that different code blocks have different reliability characteristics and assigning them differently to constellation bit locations. Least reliable code blocks are mapped to more reliable positions, creating non-uniform mapping that compensates for the non-uniform reliability of input code blocks, thereby achieving uniform output reliability with minimal added complexity.
Solution Approach 2:
The patent applies inversion by reversing the natural mapping tendency - instead of mapping reliable code blocks to reliable positions and unreliable ones to unreliable positions, it maps unreliable code blocks to reliable positions and vice versa. This inverted approach compensates for the inherent reliability differences and achieves uniform overall reliability.
Data Source
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AI summary
This application relates to the wireless communications field, and discloses an LDPC code encoding and modulation method and a communications apparatus, to resolve a problem of poor transmission performance and low transmission reliability that are caused in an existing modulation method. The method is specifically: obtaining an information bit sequence Sb, and encoding the information bit sequence Sb by using a low-density parity-check LDPC check matrix H, to obtain an encoded code sequence Sc; modulating the code sequence Sc, to obtain a modulated symbol sequence SM, where bits in a least reliable code block in the code sequence Sc are mapped, in a modulation process, to non-least reliable bit locations that are used for constellation modulation; and sending the modulated symbol sequence SM to a receive end. According to technical solutions provided in this application, reliability of all symbols in the modulated symbol sequence SM is relatively high and uniform. In this way, a bit error rate can be effectively reduced, so that encoding performance is improved and more reliable transmission is implemented.