QAM Transmitter Mapping With Non-Uniform Constellations
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Solution Overview
Problem
Current broadcasting systems, such as DVB-T2, utilize uniform QAM constellations which 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 implementation of non-uniform constellations (NUC) that relax the rectangular shape and uniform spacing properties of traditional uniform QAM, optimizing constellation design based on signal-to-noise ratio (SNR) and coding rate to improve BER/FER performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If uniform QAM constellation is used, then ease of mapping and demapping is maintained, but the capacity leaves a big gap from the Shannon limit resulting in suboptimal BER/FER performance
Solution Approach 1:
The patent applies local quality by creating different constellation point densities in different regions of the complex plane. The non-uniform constellation has closer spacing in regions with lower noise interference and wider spacing in regions with higher noise interference, optimizing performance locally across different signal-to-noise ratio conditions while maintaining reasonable mapping complexity.
Solution Approach 2:
The patent changes the fundamental parameter of constellation point spacing from uniform to non-uniform. By varying the distance between constellation points based on their position in the complex plane, the system achieves better capacity utilization and BER/FER performance while the mapping process remains computationally feasible through pre-computed lookup tables.
2Reliability
If non-uniform constellation is used, then the gap from Shannon limit is reduced improving BER/FER performance, but the complexity of constellation design and implementation increases
Solution Approach 1:
The patent applies preliminary action by pre-computing and storing the non-uniform constellation points in lookup tables before transmission. The constellation parameters are determined in advance based on channel conditions, and the pre-computed mappings are stored for quick retrieval during transmission, eliminating the need for real-time complex calculations at the transmitter.
Solution Approach 2:
The patent uses copying by storing pre-computed constellation mappings in lookup tables that can be quickly referenced. Instead of performing complex optimization calculations in real-time, the system copies pre-determined optimal constellation configurations from stored tables, significantly reducing implementation complexity while maintaining performance benefits.
3Productivity
If higher QAM size is used, then throughput is increased, but the performance gap from Shannon limit increases resulting in worse BER/FER performance
Solution Approach 1:
The patent changes the constellation parameter from uniform to non-uniform spacing, allowing higher QAM orders to achieve better performance. By optimizing the spacing and distribution of constellation points, the system can utilize higher modulation orders (1024-QAM, 2048-QAM, 4096-QAM) while maintaining or improving BER/FER performance relative to the Shannon limit.
Solution Approach 2:
The patent applies dynamics by making the constellation configuration adaptive to channel conditions. The non-uniform constellation parameters can be adjusted based on signal-to-noise ratio and other channel characteristics, allowing the system to dynamically optimize the trade-off between throughput and reliability for different operating conditions.
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.