Non-Uniform Constellation Mapping for Broadcast QAM Signals
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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 simplicity is maintained, but BER/FER performance leaves a significant gap from Shannon limit
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 point densities optimized for specific SNR conditions. This allows the system to achieve better BER/FER performance by concentrating points in regions that maximize information transmission efficiency under given channel conditions, while maintaining manageable complexity through structured design of the non-uniform pattern.
2Reliability
If non-uniform constellation is used, then BER/FER performance improves and gap from Shannon limit reduces, but constellation design complexity increases
Solution Approach 1:
The patent implements dynamics by making the constellation configuration adaptable to different signal-to-noise ratio (SNR) conditions and fading channel characteristics. The system can dynamically select or adjust constellation parameters based on current channel state, allowing optimization of BER/FER performance for varying transmission conditions without requiring completely new constellation designs for each scenario.
Solution Approach 2:
The patent applies parameter changes by modifying key constellation parameters such as point spacing, amplitude levels, and phase angles to create non-uniform patterns. These parameter adjustments are optimized for specific SNR ranges and channel types, enabling the system to achieve better performance by tuning constellation characteristics rather than using a fixed uniform structure.
3Productivity
If higher QAM size is used, then throughput increases, but performance gap from Shannon limit remains significant
Solution Approach 1:
The patent applies local quality by optimizing the density and distribution of constellation points in different regions to maximize throughput while minimizing the gap to Shannon limit. The non-uniform structure allows higher point density in regions that contribute most to information transmission, enabling efficient use of higher QAM sizes (such as 1024-QAM) to increase throughput without sacrificing performance optimality.
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.