Broadcast Transmitter Constellation Mapping for BER and FER Limits
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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 suboptimal capacity utilization, as they do not adapt to signal-to-noise ratio (SNR) or coding rate variations.
Innovation Solution
The implementation of non-uniform constellations (NUC) that relax the rectangular shape and uniform spacing constraints of traditional uniform QAM, optimizing constellation points for better performance across varying SNR conditions in different fading channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniform QAM is used for modulation, then the mapping and demapping process is simple and easy to implement, but the capacity utilization is suboptimal and BER/FER performance is far from the Shannon limit
Solution Approach 1:
The patent applies local quality by transitioning from uniform QAM with identical spacing between all constellation points to non-uniform QAM where different regions of the constellation have different spacing characteristics. Specifically, the non-uniform constellation optimizes point distribution locally to match the statistical properties of the fading channel, placing more points in regions with lower probability density and fewer points in high-density regions, thereby improving overall capacity utilization and BER/FER performance while maintaining practical implementability
Solution Approach 2:
The patent employs parameter changes by modifying the constellation geometry parameters from uniform to non-uniform distribution. The non-uniform QAM constellation changes the spacing parameter between adjacent points based on the fading channel characteristics, allowing the system to adapt to varying SNR conditions. This parameter transformation enables the system to achieve better theoretical capacity utilization and approach the Shannon limit while remaining computationally feasible for practical implementation
2Ease of operation
If uniform QAM with fixed constellation points is used, then the system is simple to implement without optimization, but it cannot adapt to varying SNR or coding rate conditions
Solution Approach 1:
The patent applies dynamics by making the constellation configuration adaptive to changing channel conditions. The non-uniform QAM constellation is designed with parameters that can be selected based on the observed fading channel characteristics, SNR levels, and coding rates. This dynamic adaptation allows the system to optimize performance for different operating conditions while maintaining a relatively simple implementation structure compared to fully adaptive modulation schemes
Solution Approach 2:
The patent uses parameter changes to enable adaptability by establishing a relationship between constellation parameters and channel conditions. The non-uniform QAM constellation parameters (such as point spacing and distribution) are selected based on the fading channel characteristics, allowing the system to adapt to varying SNR and coding rate conditions. This parameter-based adaptation provides versatility without requiring complex real-time optimization algorithms
3Reliability
If non-uniform constellation is used to improve capacity utilization, then BER/FER performance approaches the Shannon limit, but the constellation design becomes more complex requiring relaxation of uniform spacing constraints
Solution Approach 1:
The patent resolves this contradiction by applying local quality principles to the constellation design, where different regions of the non-uniform constellation have optimized spacing and distribution characteristics tailored to the fading channel statistics. This localized optimization achieves near-Shannon-limit performance without requiring globally complex design, as each local region is optimized independently based on probability density considerations
Solution Approach 2:
The patent manages design complexity through parameter changes by establishing systematic relationships between constellation parameters and channel characteristics. The non-uniform spacing parameters are derived from fading channel statistics and SNR conditions, providing a structured design approach that achieves optimal performance without arbitrary complexity. This parameter-based methodology makes the design process more manageable while maintaining high performance
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.