Ring Constellation Mapping for Higher-Capacity Digital Receivers
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Solution Overview
Problem
Existing digital communication systems face limitations in achieving maximum capacity due to the use of constellations that do not approach the Gaussian channel capacity, resulting in inefficiencies in bandwidth and power usage, despite attempts to optimize constellations for minimum distance and coding gains.
Innovation Solution
The development of geometrically shaped symbol constellations that optimize capacity by iteratively optimizing the location of constellation points to maximize capacity measures such as parallel decode and joint capacity, allowing for reduced signal-to-noise ratios and increased data transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional constellations are used that maximize minimum distance between points, then reliability is improved through better error performance, but capacity falls significantly below the Gaussian channel capacity limit
Solution Approach 1:
The patent transforms the constellation design from uniform spacing to non-uniform spacing by changing the geometric parameters of constellation points. Specifically, it introduces radial positioning where points are placed at different distances from the origin based on their probability of transmission, with higher-probability points closer to the origin and lower-probability points farther away. This parameter transformation allows the system to approach Gaussian capacity while maintaining reliability through optimized minimum distance properties.
Solution Approach 2:
The patent applies different spatial characteristics to different regions of the constellation diagram. Inner rings contain points with higher transmission probability and are positioned closer to the origin, while outer rings contain points with lower probability positioned farther away. This local differentiation in spatial distribution allows the system to mimic the Gaussian distribution's property of transmitting more frequent symbols with smaller amplitude, thereby increasing capacity without sacrificing error performance.
2Productivity
If coding techniques such as turbo codes and LDPC codes are used to increase capacity, then coding gains are achieved, but the gains are limited by the constellation design
Solution Approach 1:
The patent substitutes the need for complex coding mechanisms by transforming the modulation constellation itself. Instead of relying heavily on turbo codes or LDPC codes to achieve capacity接近Gaussian limits, the system uses non-uniformly spaced constellations with radial positioning that inherently approach Gaussian capacity. This substitution reduces the reliance on complex coding while maintaining or improving capacity, thereby reducing overall system complexity.
3Ease of manufacture
If uniform constellations are used with equal likelihood symbol transmission, then ease of implementation is maintained, but capacity is limited compared to Gaussian capacity
Solution Approach 1:
The patent changes the fundamental parameter of symbol spacing from uniform to non-uniform while maintaining a structured radial arrangement. Points are positioned at specific radial distances from the origin corresponding to different probability levels, creating a geometric progression in spacing. This parameter change increases capacity to approach Gaussian limits while preserving implementation simplicity through the regular radial structure and clear mapping rules.
Solution Approach 2:
The patent introduces a radial dimension to the constellation design, moving beyond traditional two-dimensional grid-based constellations. By positioning points along radial lines at different distances from the origin, the system adds a spatial dimension that encodes probability information, allowing capacity to approach Gaussian limits while maintaining clear mapping and demapping procedures.
Data Source
AI summary
Communication systems are described that use unequally spaced constellations that have increased capacity compared to conventional constellations operating within a similar SNR band. One embodiment is a digital communications system including a transmitter transmitting signals via a communication channel, the transmitter including a coder capable of receiving user bits and outputting encoded bits at a rate, a mapper capable of mapping encoded bits to symbols in a constellation, and a modulator capable of generating a modulated signal for transmission via the communication channel using symbols generated by the mapper, wherein the constellation is unequally spaced and characterizable by assignment of locations and labels of constellation points to maximize parallel decode capacity of the constellation at a given signal-to-noise ratio so that the constellation provides a given capacity at a reduced signal-to-noise ratio compared to a uniform constellation that maximizes the minimum distance between constellation points of the uniform constellation.