Non-Uniform Constellation Mapping for Lower BER in Broadcast Transmitters
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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 Shannon limit resulting in suboptimal BER/FER performance
Solution Approach 1:
The patent applies local quality by creating different constellation point densities in different regions of the complex plane. The non-uniform constellation has higher density in some regions and lower density in others, optimizing the distribution of signal points to better match the channel conditions and reduce the gap to the Shannon limit, thereby improving BER/FER performance while maintaining practical implementability.
Solution Approach 2:
The patent changes the fundamental parameter of constellation uniformity by transitioning from uniform QAM to non-uniform constellation. This involves modifying the spacing and distribution parameters of constellation points, creating a non-uniform pattern that optimizes capacity for specific SNR ranges and fading channels, thus improving reliability without completely sacrificing implementation simplicity.
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 channel conditions
Solution Approach 1:
The patent applies dynamics by making the constellation design adaptive to specific operating conditions. Different non-uniform constellations are optimized for different SNR ranges and channel types (e.g., AWGN, Rayleigh fading, Rician fading). The system can dynamically select the appropriate constellation based on current channel conditions, achieving near-Shannon-limit performance without requiring a single complex universal design.
Solution Approach 2:
The patent manages complexity by systematically varying constellation parameters (point densities, spacing, distributions) to optimize performance for specific SNR ranges and channel conditions. Rather than creating an overly complex universal solution, the patent establishes a family of optimized constellations with different parameters, each tailored to specific operating conditions, thus balancing performance improvement with design manageability.
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.