QAM Constellation Mapping with Non-Uniform Point Spacing
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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 BER and FER performance is far from optimal
Solution Approach 1:
The patent applies local quality by transitioning from uniform spacing to non-uniform spacing in the QAM constellation. Different regions of the constellation diagram have different point densities and spacing characteristics, allowing optimal placement of constellation points in specific locations to improve error performance while maintaining manageable complexity through structured design methods.
Solution Approach 2:
The patent changes the fundamental parameter of constellation point spacing from uniform to non-uniform. This parameter change allows the system to achieve better BER and FER performance by optimizing the distance between constellation points based on their position in the diagram, rather than maintaining equal spacing throughout.
2Reliability
If non-uniform constellation is used, then gap from Shannon limit is reduced, but constellation design complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the constellation design process into distinct stages: generating candidate constellations, evaluating their performance, and selecting optimal configurations. This structured approach breaks down the complex design task into manageable segments, making the overall process more tractable despite the increased complexity of non-uniform constellations.
Solution Approach 2:
The patent employs preliminary action by pre-generating and evaluating multiple candidate non-uniform constellation designs before actual transmission. This allows the system to prepare optimized constellation configurations in advance, reducing the computational burden during real-time operation while achieving the performance benefits of non-uniform spacing.
3Ease of manufacture
If uniform spacing between constellation points is maintained, then mapping is simple, but BER performance is suboptimal
Solution Approach 1:
The patent applies local quality by implementing different spacing characteristics in different regions of the constellation diagram. Instead of uniform spacing, the system uses non-uniform spacing where constellation points are strategically positioned with varying distances from each other, optimizing local error performance while maintaining overall system functionality.
Solution Approach 2:
The patent introduces asymmetry by abandoning the symmetric uniform spacing pattern in favor of asymmetric non-uniform spacing. This asymmetric arrangement allows constellation points to be positioned optimally for error performance, with different spacing patterns in different directions and regions of the constellation diagram.
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.