BICM Transmitter Mapping with Non-Uniform QAM Constellations
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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 in terms of bit error rate (BER) and frame error rate (FER) due to limitations in capacity, as they do not adapt to signal-to-noise ratio (SNR) or coding rate, leading to suboptimal performance compared to the Shannon limit.
Innovation Solution
The implementation of non-uniform constellations (NUC) that relax the rectangular shape and uniform spacing properties of traditional QAM, optimizing constellation design for specific SNR values 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 and FER performance deteriorates due to capacity gap from Shannon limit
Solution Approach 1:
The patent changes the fundamental parameters of the QAM constellation from uniform spacing and rectangular shape to non-uniform spacing and optimized geometry. This allows the constellation to be tailored for specific SNR values and fading channel conditions, improving BER and FER performance while maintaining practical implementability through predefined NUC patterns.
2Reliability
If non-uniform constellation is used to improve BER and FER performance, then reliability is improved, but device complexity increases due to relaxed square shape and uniform distance properties
Solution Approach 1:
The patent applies local quality by creating constellation regions with different properties optimized for specific signal conditions. Different parts of the non-uniform constellation have different spacing and energy characteristics, allowing local optimization for various SNR levels and channel conditions while maintaining overall system performance.
Solution Approach 2:
The patent introduces dynamic selection of non-uniform constellation patterns based on channel conditions, SNR values, and coding rates. The system can switch between different predefined NUC patterns, making the constellation adaptive to changing conditions rather than static, thereby improving reliability without permanent complexity increase.
3Productivity
If QAM size is increased to increase throughput, then productivity is improved, but BER and FER performance deteriorates due to larger distance between constellation points
Solution Approach 1:
The patent changes the spacing parameters of high-order QAM constellations from uniform to non-uniform, creating optimized patterns for specific SNR values. This allows higher throughput (1K QAM, 2K QAM, etc.) to be achieved while maintaining better error performance through tailored constellation geometry that compensates for the increased density of points.
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.