Configurable Constellation Mapping for Spectral Efficiency Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional communication systems face challenges in controlling spectral efficiency versus signal-to-noise ratio (SNR) with high system complexity and reduced efficiency due to fixed FEC code rates, particularly in low-density parity-check (LDPC) encoder/decoder iterations.
Innovation Solution
The implementation of configurable constellation mapping and LLR de-mapping techniques, referred to as mixed mode, which allows for adjustable modulation schemes to control spectral efficiency over a range of SNR while maintaining a fixed FEC code rate, thereby reducing system complexity and improving LDPC iteration efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple FEC code rates are supported to control spectral efficiency versus SNR, then spectral efficiency control flexibility is improved, but system complexity increases
Solution Approach 1:
The patent changes the modulation order parameter (QAM constellation size) instead of changing FEC code rates to control spectral efficiency. By varying the modulation order (e.g., from QAM-16 to QAM-64 to QAM-256), the system achieves different spectral efficiency levels while maintaining a fixed FEC code rate, thus avoiding the complexity of supporting multiple code rates.
2Adaptability or versatility
If lower FEC code rates are used to control spectral efficiency, then spectral efficiency is reduced, but LDPC encoder/decoder iteration efficiency is reduced
Solution Approach 1:
Instead of varying FEC code rates to control spectral efficiency, the patent varies the modulation order parameter. This allows spectral efficiency adjustment without affecting LDPC iteration efficiency, since the FEC code rate remains fixed at its optimal value and the modulation scheme change does not impact the iterative decoding process.
3Device complexity
If fixed FEC code rate is used, then system complexity is reduced, but spectral efficiency control granularity is reduced
Solution Approach 1:
The patent uses modulation order as a finely granular parameter to control spectral efficiency. By adjusting the modulation order (e.g., 16, 32, 64, 128, 256, 512), the system achieves precise spectral efficiency control with fine granularity while maintaining a fixed FEC code rate, thus avoiding system complexity.
Solution Approach 2:
The patent makes the modulation scheme dynamic and configurable, allowing the system to adaptively select different modulation orders based on channel conditions and spectral efficiency requirements. This dynamic adjustment of modulation order provides fine-grained control without requiring multiple fixed FEC code rates.
Data Source
AI summary
Mixed mode constellation mapping to map a data block to a block of sub-carriers based on a configurable set of one or more constellation mapping schemes, and corresponding mixed mode least likelihood ratio (LLR) de-mapping based on the configurable set of one or more modulation schemes. The set may be configurable to include multiple modulation schemes to provide to a SEvSNR measure that is a non-weighted or weighted average of SEvSNR measures of the multiple modulation schemes. Mixed mode constellation mapping may be useful be configurable to control spectral efficiency versus SNR (SEvSNR) over a range of SNR with relatively fine SNR granularity, and may be configurable to control SEvSNR over a range of SNR at a fixed FEC code rate, which may include a highest available or highest permitted code rate.