Non-Uniform Constellation Mapping for SNR-Adaptive BICM Capacity
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Solution Overview
Problem
Modern communications systems face challenges in maximizing coding and modulation capacity, particularly in non-uniform channels with additive white Gaussian noise and fading, where existing constellations do not optimize constellation points for signal-to-noise ratio and channel characteristics.
Innovation Solution
A coding and modulation apparatus that uses a non-uniform constellation with constellation points defined by specific position vectors, optimizing their locations based on the signal-to-noise ratio and channel characteristics to enhance coding and modulation capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If uniform constellation points are used in conventional BICM systems, then the system achieves reasonable decoding complexity and good performance over non-fading and fading channels, but the coding and modulation capacity is not maximized due to suboptimal constellation point locations for specific channel conditions
Solution Approach 1:
The patent applies local quality by using different constellation point distributions optimized for specific channel conditions (AWGN, fading, etc.). Instead of using a single uniform constellation for all channels, the system selects constellation points with locally optimized positions tailored to the specific channel characteristics, thereby maximizing capacity for each channel type without increasing decoder complexity.
Solution Approach 2:
The patent changes the parameters of the constellation points based on channel conditions. By adjusting the positions and distributions of constellation points according to the specific channel (AWGN, fading, etc.), the system optimizes coding and modulation capacity for each channel type while maintaining the same BICM framework and decoder complexity.
2Reliability
If constellation points are optimized for specific channel conditions, then coding and modulation capacity increases, but the system becomes less adaptable to varying channel characteristics
Solution Approach 1:
The patent implements dynamics by making the constellation selection adaptive to channel conditions. The system dynamically selects the appropriate constellation points based on the detected channel characteristics (AWGN, fading, etc.), allowing it to optimize capacity for each channel type while maintaining overall versatility through the ability to switch between different constellation configurations.
Solution Approach 2:
The patent achieves universality by designing a constellation selection mechanism that works across multiple channel types. The same BICM apparatus can select from different optimized constellations for AWGN channels, fading channels, and other conditions, making the system universally applicable while maintaining optimal performance for each specific channel type.
3Productivity
If non-uniform constellation points are used to maximize capacity, then error-free decoding and throughput improve, but the system complexity increases due to the need for channel condition detection and constellation selection
Solution Approach 1:
The patent applies preliminary action by pre-optimizing constellation points for different channel conditions before transmission. The optimized constellations for various channel types (AWGN, fading, etc.) are prepared in advance, allowing the receiver to simply detect the channel type and select the corresponding pre-optimized constellation, thereby achieving high throughput without requiring complex real-time optimization.
Data Source
AI summary
A coding and modulation apparatus and method are presented. The apparatus comprises an encoder that encodes input data into cell words, and a modulator that modulates said cell words into constellation values of a non-uniform constellation. The modulator is configured to use, based on the total number M of constellation points of the constellation and the signal-to-noise ratio SNR in dB, a non-uniform constellation from a group of constellations comprising one or more of predetermined constellations defined by the constellation position vector w0 . . . b-1, wherein b=M/4.