Non-Uniform Constellation Modulator for IEEE 802.11 Capacity
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Solution Overview
Problem
Modern communications systems face challenges in maximizing coding and modulation capacity while reducing bit error rates and signal-to-noise ratio (SNR) requirements, particularly in using uniform constellations which are not optimized for channel conditions.
Innovation Solution
A coding and modulation apparatus that employs non-uniform constellations (NUCs) optimized based on channel conditions, using binary convolutional codes (BCC) or low density parity check codes (LDPC), with a modulator assigning bit combinations to constellation points, and a demodulator decoding these to achieve improved capacity and error reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If uniform constellations are used for modulation, then the system structure is simple, but the coding and modulation capacity is not maximized and bit error rate is higher
Solution Approach 1:
The patent applies asymmetry by transitioning from uniform constellations (symmetric distribution of constellation points) to non-uniform constellations (asymmetric distribution where points are closer to the origin). This asymmetric arrangement optimizes the mapping between coded bits and constellation points, thereby maximizing coding and modulation capacity while improving reliability without significantly increasing system complexity.
2Ease of manufacture
If uniform constellations are used for modulation, then the implementation is straightforward, but the bit error rate is higher and SNR requirements are not reduced
Solution Approach 1:
The patent applies local quality by optimizing the distribution of constellation points based on their local properties (distance from origin, position in I-Q plane). Different regions of the constellation diagram have different point densities, with more points concentrated near the origin. This local optimization reduces bit error rate and lowers SNR requirements while maintaining reasonable implementation complexity through structured non-uniform arrangements.
3Reliability
If non-uniform constellations are used, then coding and modulation capacity is maximized, but the constellation design complexity increases
Solution Approach 1:
The patent applies dynamics by making the constellation configuration adaptable to different coding schemes (BCC, LDPC) and code rates. The non-uniform constellation parameters are dynamically selected based on the specific coding and modulation scheme being used, allowing the system to optimize capacity for each configuration without requiring a completely new design for every case. This dynamic selection approach manages design complexity while maintaining high capacity.
4Reliability
If non-uniform constellations are used, then bit error rate is reduced, but the system complexity increases
Solution Approach 1:
The patent applies parameter changes by systematically varying constellation parameters (point coordinates, scaling factors, offset values) based on the coding scheme and code rate. Specific parameter sets are defined for different configurations (e.g., different M-QAM orders, different code rates), allowing the system to achieve lower bit error rates through optimized parameters without requiring fundamental architectural changes. This parameter-based approach manages system complexity through standardized configurations.
Data Source
AI summary
A coding and modulation apparatus and method are presented, particularly for use in a system according to IEEE 802.11. The apparatus comprises an encoder configured to encode input data into cell words according to a binary convolutional code, BCC, or a low density parity check code, LDPC, and a modulator configured to modulate said cell words into constellation values of a non-uniform constellation and to assign bit combinations to constellation values of the used non-uniform constellation, wherein said modulator is configured to use, based on the code used by the encoder, the total number M of constellation points of the constellation and the code rate.