Non-Uniform Constellation Mapping for Lower BER in QAM Transmission
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Solution Overview
Problem
Current broadcasting systems using uniform QAM in DVB-T2 fail to optimize performance in terms of bit error rate (BER) and frame error rate (FER) due to suboptimal capacity, leaving a significant gap from the theoretical Shannon limit.
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 is used for modulation, then the mapping and demapping process is simple and easy to implement, but the capacity leaves a big gap from the Shannon limit and BER/FER performance is far from optimal
Solution Approach 1:
The patent applies local quality by making different parts of the constellation have different properties. Specifically, it uses non-uniform spacing between constellation points and non-square rectangular shapes, where different regions of the constellation diagram have optimized characteristics for their specific signal-to-noise ratio conditions, thereby improving overall BER/FER performance while maintaining practical implementability
Solution Approach 2:
The patent changes the parameters of the QAM constellation from uniform to non-uniform. It modifies the spacing between constellation points and the shape of the constellation rectangle, using optimized parameters that are specifically tailored for different signal-to-noise ratio conditions and fading channel characteristics, thus closing the gap from the Shannon limit
2Productivity
If higher QAM size is used to increase throughput, then the data rate increases, but the complexity of the modulation and demodulation process increases
Solution Approach 1:
The patent applies preliminary action by pre-optimizing the constellation parameters for different signal-to-noise ratio conditions and channel types before transmission. The non-uniform constellation parameters are predetermined and stored, allowing the receiver to efficiently select and use the appropriate constellation without real-time optimization, thus managing complexity while maintaining high throughput
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.