Non-Uniform Constellation Mapping for Broadcast BER Reduction
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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 ease of mapping and demapping is improved, but the gap from Shannon limit increases and BER/FER performance deteriorates
Solution Approach 1:
The patent applies local quality by creating different constellation point distributions in different regions of the complex plane. The non-uniform constellation assigns different probabilities and spacing to constellation points based on their local position, with inner points having higher probability and closer spacing to improve reliability for weak signals, while outer points have lower probability and larger spacing. This local optimization resolves the contradiction by maintaining simple mapping operations while achieving superior BER/FER performance through position-dependent constellation characteristics.
Solution Approach 2:
The patent employs parameter changes by modifying the constellation parameters (spacing, probability, and position of constellation points) based on the signal-to-noise ratio and channel conditions. The non-uniform constellation uses variable parameters where the distance between constellation points and their occurrence probabilities are adjusted according to local requirements, allowing the system to approach the Shannon limit while maintaining operational simplicity through standardized mapping procedures.
2Reliability
If non-uniform constellation is used, then BER and FER performance is improved, but device complexity increases
Solution Approach 1:
The patent reduces device complexity by applying local quality principles to the constellation design, where each constellation point is optimized independently based on its local position and probability requirements. This modular approach allows the complex non-uniform constellation to be constructed from simple, position-specific parameters rather than requiring complex global optimization, thereby improving BER/FER performance while keeping the implementation complexity manageable through localized design decisions.
3Productivity
If higher QAM size is used, then throughput is increased, but sensitivity to noise and interference increases
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the constellation parameters (spacing, probability, and position) according to the signal-to-noise ratio and channel conditions. For higher QAM sizes, the non-uniform constellation optimizes parameters to increase throughput while simultaneously adjusting the spacing and probability of constellation points to maintain robustness against noise and interference, thereby resolving the contradiction between productivity and sensitivity to harmful factors.
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.