Broadcast Modulation Mapping Using Non-Uniform Constellations
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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 manufacture
If uniform QAM constellation is used, then mapping and demapping is simple and easy to implement, but the capacity leaves a big gap from the theoretical Shannon limit 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. This allows the system to achieve better overall performance by having each local region optimized for its operating conditions rather than using a single uniform spacing for all regions.
2Reliability
If non-uniform constellation is used, then the gap from Shannon limit is reduced and BER/FER performance is improved, but the constellation design becomes more complex and requires optimization for specific SNR and fading channels
Solution Approach 1:
The patent applies parameter changes by modifying the spacing parameters of the QAM constellation from uniform to non-uniform values. Specifically, the constellation points are positioned at different distances from the origin based on optimized parameters that account for signal-to-noise ratio and fading channel characteristics. This allows the system to adapt the constellation geometry to match the channel conditions, thereby improving performance while managing complexity through parameter optimization rather than structural redesign.
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.