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 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 is used for mapping bits to complex constellations, then the mapping and demapping process is simple and easy to implement, but the capacity leaves a big gap from the Shannon limit resulting in suboptimal BER and FER performance
Solution Approach 1:
The patent applies local quality by using different constellation point densities in different regions of the complex plane. Specifically, the non-uniform constellation has higher density in some regions and lower density in others, allowing the system to optimize performance for specific SNR conditions while maintaining manageable complexity through structured design
Solution Approach 2:
The patent changes the fundamental parameter of constellation uniformity by introducing non-uniform QAM constellations with varying point densities. This parameter change allows the system to achieve capacity closer to the Shannon limit by optimizing the distribution of constellation points according to the probability density function of the channel
2Reliability
If non-uniform constellation is used to reduce gap from Shannon limit, then BER and FER performance is improved, but the constellation design becomes more complex requiring optimization for specific SNR and channel conditions
Solution Approach 1:
The patent applies preliminary action by pre-optimizing constellation designs for specific SNR ranges and channel conditions. The system provides a set of pre-designed non-uniform constellations that can be selected based on current channel conditions, avoiding the need for real-time optimization while still achieving near-Shannon-limit performance
Solution Approach 2:
The patent introduces dynamics by making the constellation selection adaptive to changing channel conditions. The system can dynamically switch between different non-uniform constellation designs based on measured SNR and channel characteristics, allowing the receiver to maintain optimal performance across varying conditions
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.