Ring Constellation Mapping for Lower-SNR Digital Transmission
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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 efforts to optimize constellations based on minimum distance criteria.
Innovation Solution
The development of geometrically shaped symbol constellations that optimize capacity measures such as parallel decode and joint capacity, allowing for reduced signal-to-noise ratios and increased data transmission rates with reduced power consumption, without requiring specialized coding mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional constellations maximizing minimum distance are used, then error rate performance is improved, but capacity approaches Gaussian channel capacity limit
Solution Approach 1:
The patent applies local quality by creating unequally spaced constellation points where different regions of the constellation have different spacing properties. Specifically, points are positioned to provide larger minimum distance in certain directions while maintaining overall capacity efficiency, allowing the system to achieve both good error rate performance and high capacity by optimizing local spacing characteristics rather than using uniform spacing throughout.
Solution Approach 2:
The patent changes the spacing parameter of constellation points from uniform to non-uniform distribution. By optimizing the positions of constellation points to create variable spacing, the system achieves a balance between minimum distance requirements for reliability and overall constellation density for capacity, directly addressing the contradiction between error rate performance and channel capacity.
2Productivity
If coded modulation schemes are used to approach Gaussian capacity, then channel capacity is improved, but system complexity increases
Solution Approach 1:
The patent extracts the capacity-approaching functionality from complex coded modulation schemes and implements it directly through optimized constellation geometry. By designing constellations with unequally spaced points that inherently achieve capacity efficiency, the system eliminates the need for separate coding mechanisms, thereby reducing system complexity while maintaining high channel capacity.
Solution Approach 2:
The constellation design itself provides the capacity-approaching performance without requiring external coding mechanisms. The optimized geometric arrangement of unequally spaced points makes the modulation scheme self-sufficient in achieving Gaussian capacity limits, eliminating the need for additional coding layers and simplifying the overall system architecture.
3Ease of manufacture
If uniform constellations are used, then implementation simplicity is maintained, but capacity efficiency is reduced
Solution Approach 1:
The patent changes the spacing parameter from uniform to non-uniform distribution to improve capacity efficiency. By optimizing the positions of constellation points with variable spacing, the system achieves better capacity performance while maintaining a relatively simple implementation structure that does not require complex adaptive mechanisms.
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.