Transmitter Constellation Mapping for BER Gains Beyond Uniform QAM
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Solution Overview
Problem
Current broadcasting systems, such as DVB-T2, utilize uniform QAM constellations which 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 square shape and uniform distance 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 and capacity utilization deteriorate due to 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 in targeted channel conditions while maintaining manageable complexity through structured design of the non-uniform constellation.
2Reliability
If non-uniform constellation is used, then BER/FER performance and capacity improve by reducing gap from Shannon limit, but mapping and demapping complexity increases
Solution Approach 1:
The patent employs parameter changes by systematically varying the constellation point positions and spacing according to specific design parameters optimized for different SNR ranges and fading conditions. This allows achieving superior BER/FER performance through parameter optimization while managing complexity through the structured approach to parameter selection and the use of lookup tables for efficient mapping.
3Productivity
If higher QAM size is used, then throughput increases, but sensitivity to noise and channel conditions increases, worsening BER performance
Solution Approach 1:
The patent applies dynamics by making the constellation structure adaptive to channel conditions, particularly SNR and fading characteristics. The system can dynamically select from different non-uniform constellation designs optimized for specific conditions, allowing higher throughput in good conditions while maintaining reliability in poor conditions through appropriate constellation selection and the use of pilot symbols for channel estimation.
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.