Broadcast Receiver Modulation Using Non-Uniform QAM Constellations
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Solution Overview
Problem
Current broadcasting systems, such as DVB-T2, utilize uniform QAM constellations that leave a significant gap from the theoretical Shannon limit, resulting in suboptimal bit error rate (BER) and frame error rate (FER) performance.
Innovation Solution
The generation of non-uniform constellations (NUCs) that relax the square shape and uniform distance constraints of traditional QAM, using algorithms to optimize constellation design based on signal-to-noise ratio (SNR) and channel characteristics, thereby increasing capacity and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If uniform QAM constellation is used, then mapping and demapping is easy, but capacity leaves a big gap from Shannon limit and BER/FER performance is suboptimal
Solution Approach 1:
The patent changes the parameters of the QAM constellation by introducing non-uniform spacing between constellation points while maintaining the same number of points. This allows the system to achieve better BER/FER performance and approach the Shannon limit without fundamentally changing the modulation structure, thus resolving the contradiction between ease of operation and reliability
2Reliability
If non-uniform constellation is used, then capacity approaches Shannon limit and BER/FER performance improves, but constellation design becomes more complex
Solution Approach 1:
The patent systematically varies constellation parameters such as point spacing and distribution patterns to achieve optimal performance. By focusing on parameter optimization rather than fundamental redesign, the complexity is managed while achieving near-Shannon-limit performance
Solution Approach 2:
The patent introduces the concept of adaptive constellation selection where the constellation parameters can be dynamically adjusted based on channel conditions and SNR levels. This allows the system to optimize performance for different operating conditions without requiring complex fixed designs for all scenarios
3Productivity
If higher QAM size is used, then throughput increases, but distance between constellation points decreases making it more susceptible to noise
Solution Approach 1:
The patent applies non-uniform spacing patterns where outer constellation points are positioned farther from the origin compared to uniform QAM. This increases the minimum distance between points even at higher QAM orders, reducing noise susceptibility while maintaining high throughput capability
Data Source
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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.