Non-Uniform Constellation Mapping for BICM Broadcast Transmission
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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 conditions 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 asymmetry by transitioning from uniform QAM with equal spacing between constellation points to non-uniform QAM where the spacing between constellation points is deliberately made non-uniform. This asymmetric distribution optimizes the constellation for specific SNR ranges and fading conditions, improving BER and FER performance while maintaining practical implementability through predefined constellation designs.
2Productivity
If higher QAM size is used to increase throughput, then the data transmission capacity increases, but the system becomes more sensitive to noise and channel conditions
Solution Approach 1:
The patent applies parameter changes by optimizing constellation parameters (spacing, distribution, and geometry) for different SNR ranges and fading conditions. Non-uniform QAM constellations are designed with specific parameter configurations that adapt to channel conditions, allowing higher order modulation (16QAM, 64QAM, 256QAM) to achieve better throughput while maintaining robustness through optimized point distribution that accounts for noise sensitivity.
3Reliability
If non-uniform constellation is used to reduce gap from Shannon limit, then bit error rate and frame error rate performance improves, but the mapping and demapping complexity increases compared to uniform QAM
Solution Approach 1:
The patent applies preliminary action by pre-defining and pre-optimizing non-uniform QAM constellation configurations for specific SNR ranges and fading conditions. These predetermined constellation designs allow the system to switch between optimized configurations based on channel conditions without requiring complex real-time optimization calculations, thus improving performance while controlling implementation complexity through lookup tables and predefined parameters.
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.