Adaptive Symbol Mapping for QAM Bit Reliability in Retransmission
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Solution Overview
Problem
The existing symbol mapping methods, such as gray mapping in 16-QAM, result in varying bit reliability, which affects the reception performance, specifically the block error rate, due to differences in how codewords are mapped to symbols, and do not adequately consider reliability in retransmissions in wireless communication systems.
Innovation Solution
A symbol mapping apparatus and method that dynamically adjusts bit-to-symbol mapping schemes (BSM schemes) to improve reception performance by complementing bit reliability in initial and retransmission mappings, utilizing a combination of constellation shifts and bit rearrangements across different transmission blocks and antennas to achieve optimal diversity gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If gray mapping is used for symbol mapping in 16-QAM, then the modulation process is simple and standardized, but the bit reliability varies significantly across different bit positions, degrading reception performance
Solution Approach 1:
The patent applies local quality by differentiating the mapping strategy for different bit positions. Within each QAM symbol, bits are assigned to constellation points based on their reliability requirements - some bit positions map to more reliable constellation transitions while others map to less reliable ones. This localized optimization of mapping quality resolves the contradiction by maintaining simple overall structure while achieving differentiated reliability across bit positions.
Solution Approach 2:
The patent changes the mapping parameters dynamically based on channel conditions and transmission requirements. By adjusting which bits map to which constellation point transitions, the system can optimize bit reliability without changing the fundamental QAM modulation structure. This parameter adjustment resolves the contradiction between fixed simple mapping and variable reliability requirements.
2Ease of operation
If fixed bit-to-symbol mapping is used for initial transmission, then the mapping process is straightforward, but the block error rate remains high due to insufficient consideration of bit reliability
Solution Approach 1:
The patent introduces dynamic adaptation to the mapping process. The bit-to-symbol mapping is not fixed but is adjusted based on channel conditions, transmission block type (initial or retransmission), and reliability requirements. This dynamic approach allows the system to optimize block error rate while maintaining operational simplicity through standardized adaptation rules.
Solution Approach 2:
The patent employs different mapping schemes periodically for initial transmission versus retransmission. By alternating between complementary mapping patterns, the system achieves diversity gain and reduces block error rate. This periodic variation in mapping strategy resolves the contradiction between fixed simple mapping and the need for optimized reliability.
3Stability of the object's composition
If the same bit-to-symbol mapping scheme is used for retransmission, then the implementation is consistent and simple, but diversity gain is insufficient and block error rate remains high
Solution Approach 1:
The patent inverts the mapping approach for retransmissions by using complementary bit-to-symbol mapping schemes. Instead of repeating the same mapping, the system deliberately uses different mapping patterns that complement the initial transmission mapping. This inversion strategy maximizes diversity gain by ensuring that retransmitted bits experience different reliability characteristics, thereby resolving the contradiction between consistency and diversity requirements.
4Reliability
If adaptive bit-to-symbol mapping is implemented to optimize bit reliability, then reception performance improves, but the complexity of the mapping apparatus increases
Solution Approach 1:
The patent achieves adaptive optimization through parameter changes rather than structural complexity. The mapping apparatus adjusts mapping parameters (which bits map to which constellation transitions) based on controllable inputs like transmission block type and channel conditions, without requiring complex hardware modifications. This parameter-based adaptation resolves the contradiction by achieving high reception performance through software-controlled parameter adjustment rather than hardware complexity.
Solution Approach 2:
The patent uses periodic alternation between different mapping schemes for initial and retransmission blocks. This periodic pattern allows the system to achieve diversity gain and optimized reception performance through predictable, repeating mapping patterns that can be implemented with simple state machines and lookup tables, thereby minimizing apparatus complexity while maximizing reliability.
Data Source
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AI summary
In a symbol mapping apparatus, a channel coder outputs a codeword including a plurality of information bits and a plurality of redundancy bits by encoding transmission data. A symbol mapper maps the codeword to the symbol while changing a mapping scheme in the unit of the codeword.