Broadcast Bit Mapping with Non-Uniform Constellation Tables
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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 significant 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 mapping bits to constellation points, then the mapping and demapping process is simple and easy to implement, but the system performance in terms of bit error rate and frame error rate is far from optimal and leaves a big gap from the Shannon limit
Solution Approach 1:
The patent applies local quality by transitioning from uniform QAM to non-uniform QAM constellations, where different regions of the constellation diagram have different point densities and spacing. This allows optimization for specific SNR ranges and fading channel conditions, improving BER/FER performance in targeted operational scenarios while maintaining practical implementability through standardized NUC designs.
2Reliability
If non-uniform constellations are used to reduce the gap from Shannon limit and improve BER/FER performance, then the system reliability is enhanced, but the constellation design becomes more complex and requires optimization for specific SNR and coding rates
Solution Approach 1:
The patent applies parameter changes by defining specific non-uniform QAM constellations with predetermined parameters (such as 16-NUC, 64-NUC, 256-NUC) optimized for different SNR ranges and coding rates. This allows the system to select appropriate constellation parameters based on channel conditions, achieving improved reliability without requiring complex real-time optimization, thus balancing performance enhancement with implementation feasibility.
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.