LDPC Constellation Mapping for Lower Bit Error Rates
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Solution Overview
Problem
Existing LDPC encoding and modulation methods result in poor signal quality and low transmission reliability due to bits in the least reliable code block being mapped to least reliable bit locations, leading to high bit error rates.
Innovation Solution
The proposed method involves mapping bits in the least reliable code block to non-least reliable bit locations during constellation modulation, ensuring uniform reliability and improving encoding performance by preventing them from being mapped to the least reliable positions, thereby reducing the bit error rate.
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 the signal quality is poor and transmission reliability is low
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 most reliable bit locations in the constellation diagram, while bits from most reliable code blocks are mapped to least reliable bit locations. This localized differentiation in mapping strategy improves overall transmission reliability without significantly complicating the modulation process.
Solution Approach 2:
The patent employs inversion by reversing the conventional mapping approach. Instead of mapping reliable bits to reliable locations and unreliable bits to unreliable locations, it inverts the strategy by mapping unreliable bits (from least reliable code blocks) to reliable locations (most reliable bit locations in constellation). This inverted mapping approach directly addresses the reliability issue while maintaining operational simplicity.
2Device complexity
If bits in the least reliable code block are mapped to least reliable bit locations, then the mapping process is straightforward, but the bit error rate is high
Solution Approach 1:
The patent applies local quality by implementing different mapping strategies for different code blocks based on their reliability characteristics. Least reliable code blocks have their bits mapped to most reliable bit locations, while most reliable code blocks have their bits mapped to least reliable bit locations. This localized quality enhancement reduces bit error rates without significantly increasing mapping process complexity.
Solution Approach 2:
The patent changes the mapping parameter assignment by dynamically assigning bit locations based on code block reliability. Instead of using a fixed sequential mapping, the system adjusts which bit locations receive bits from which code blocks, changing the mapping parameters adaptively to reduce bit error rates while maintaining acceptable processing complexity.
3Reliability
If uniform bit reliability is achieved through remapping, then transmission reliability improves, but the modulation process becomes more complex
Solution Approach 1:
The patent achieves uniform bit reliability through local quality enhancement by applying specific mapping rules to different code blocks. Least reliable code blocks are remapped to most reliable bit locations, creating uniform reliability across all transmitted bits. The complexity increase is localized to the mapping stage rather than affecting the entire modulation process, thereby balancing reliability improvement with acceptable process complexity.
Data Source
AI summary
An LDPC code encoding and modulation method and a communications apparatus are provided to resolve a problem of poor transmission performance and low transmission reliability that are caused in an existing modulation method. Under the method, an information bit sequence Sb can be obtained. The Sb can be encoded by using a LDPC matrix H to generate an encoded code sequence Sc. The Sc can be modulated to obtain a modulated symbol sequence SM. This modulation may include mapping bits in a least reliable code block in the Sc to non-least reliable bit locations for constellation modulation. SM can be sent to a receive end. In this way, reliability of all symbols in the SM is relatively high and uniform. A bit error rate can be effectively reduced, so that encoding performance is improved and more reliable transmission is implemented.