QAM Mapping Tables Using Non-Uniform Constellations for Lower BER
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Solution Overview
Problem
Current broadcasting systems, such as DVB-T2, utilize uniform QAM constellations that leave a significant gap from the theoretical Shannon limit, resulting in suboptimal bit error rate (BER) and frame error rate (FER) performance.
Innovation Solution
The implementation of non-uniform constellations (NUC) that relax the rectangular shape and uniform spacing properties of traditional uniform QAM, optimizing constellation design for specific signal-to-noise ratios (SNR) and fading channels to enhance BER and FER performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If uniform QAM constellation is used, then mapping and demapping is easy, but the gap from Shannon limit is large resulting in suboptimal BER/FER performance
Solution Approach 1:
The patent applies local quality by transitioning from uniform spacing to non-uniform spacing in the QAM constellation, where different regions of the constellation have different spacing characteristics optimized for their specific signal-to-noise ratio conditions, thereby improving overall reliability while maintaining operational feasibility
Solution Approach 2:
The patent changes the spacing parameter of the QAM constellation from uniform to non-uniform, specifically designing different spacing between constellation points based on their position and the associated bit significance, which improves BER and FER performance by better matching the theoretical Shannon limit
2Reliability
If non-uniform constellation is used, then the gap from Shannon limit is reduced improving BER/FER performance, but the complexity of mapping and demapping increases
Solution Approach 1:
The patent manages complexity by applying local quality principles where only specific regions of the constellation require non-uniform spacing treatment, while other regions maintain simpler structures, thereby balancing performance improvement with computational complexity
Solution Approach 2:
The patent reduces complexity through preliminary action by pre-calculating and storing the non-uniform constellation mapping tables, so that during actual transmission the mapping operation becomes a simple table lookup rather than a complex real-time calculation
Data Source
AI summary
A transmitting apparatus is disclosed. The transmitting apparatus includes an encoder to perform channel encoding with respect to bits and generate a codeword, an interleaver to interleave the codeword, and a modulator to map the interleaved codeword onto a non-uniform constellation according to a modulation scheme, and the constellation may include constellation points defined based on various tables according to the modulation scheme.