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 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 transmission efficiency.
Innovation Solution
The implementation of non-uniform constellations (NUC) that relax the rectangular shape and uniform spacing constraints of traditional QAM, optimizing constellation design for specific SNR conditions in various fading channels to enhance BER and FER performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If uniform QAM is used for modulation, then mapping and demapping are simple and easy to implement, but the capacity leaves a big gap from the Shannon limit and BER/FER performance is far from optimal
Solution Approach 1:
The patent changes the parameters of the QAM constellation by introducing non-uniform spacing between constellation points. Specifically, the constellation points are arranged with different distances from the origin and non-uniform spacing, allowing the system to achieve better BER/FER performance while approaching the Shannon limit, thus resolving the contradiction between simplicity and performance.
2Productivity
If higher QAM size is used to increase throughput, then transmission capacity increases, but the system becomes less robust to noise and channel conditions
Solution Approach 1:
The patent applies local quality by creating different regions within the constellation diagram with different properties. The constellation points are arranged such that some regions have denser packing for higher throughput while other regions have sparser packing for better noise robustness. This allows the system to achieve both high throughput and reliability by optimizing different parts of the constellation for different purposes.
3Reliability
If non-uniform constellation is used to reduce gap to Shannon limit, then BER and FER performance improve, but constellation design becomes more complex
Solution Approach 1:
The patent employs asymmetry by designing non-uniform constellations where constellation points are not symmetrically distributed. The points have different distances from the origin and non-uniform spacing, creating an asymmetric structure that achieves better performance. This asymmetric design allows the system to approach the Shannon limit while managing complexity through structured asymmetric patterns rather than completely arbitrary arrangements.
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.