Non-Uniform Constellation Mapping for BER-Limited Transmitters
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Solution Overview
Problem
Current broadcasting systems using Bit Interleaved and Coded Modulation (BICM) with uniform Quadrature Amplitude Modulation (QAM) fall short of optimal performance due to a gap from the 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 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 is used for simplicity and ease of mapping, then device complexity is reduced, but BER/FER performance deteriorates due to gap from Shannon limit
Solution Approach 1:
The patent applies parameter changes by transitioning from uniform QAM with fixed constellation parameters to non-uniform QAM where constellation parameters (spacing, amplitude levels) are dynamically adjusted based on SNR conditions and channel characteristics. This allows the system to optimize mapping parameters for specific operating conditions, improving BER/FER performance while maintaining reasonable complexity through parameter adaptation rather than structural redesign.
2Reliability
If non-uniform constellation is used to approach Shannon limit, then BER/FER performance is improved, but device complexity increases due to optimized mapping requirements
Solution Approach 1:
The patent implements dynamics by making the constellation mapping adaptive rather than static. The non-uniform QAM mapper dynamically adjusts constellation parameters based on feedback about SNR conditions and channel state. This dynamic adaptation allows the system to achieve near-Shannon-limit performance across varying conditions without requiring completely different mapping structures for each scenario, thereby managing complexity through intelligent adaptation.
Solution Approach 2:
The system changes mapping parameters (constellation spacing, amplitude levels, phase angles) based on operating conditions. By pre-defining multiple non-uniform constellation configurations optimized for different SNR ranges and channel types, the system can switch between configurations rather than implementing complex real-time optimization, reducing computational complexity while maintaining performance benefits.
3Ease of operation
If uniform spacing between constellation points is maintained, then ease of demapping is improved, but throughput deteriorates due to suboptimal capacity utilization
Solution Approach 1:
The patent applies local quality by using different spacing characteristics in different regions of the constellation diagram. Instead of uniform spacing throughout, the non-uniform constellation provides tighter spacing in regions where higher data rates are desired and larger spacing in regions requiring higher reliability. This local optimization allows the system to achieve better overall throughput while maintaining demapping feasibility through the structured non-uniform pattern.
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.