Unequally Spaced Multi-Ring APSK Constellation for Carrier Synchronization
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Solution Overview
Problem
Existing digital communication systems face limitations in achieving optimal performance and carrier synchronization due to constraints in constellation geometry and bit labeling, particularly in non-linear channels, leading to suboptimal error rates and increased complexity.
Innovation Solution
A multi-ring digital signal constellation is introduced with signal points on at least two concentric rings, where at least one ring has unequally spaced points, forming a subset with uniform angular spacing, optimizing Bit Interleaved Coded Modulation capacity and minimizing signal-to-noise ratio for improved performance and carrier synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If multi-ring constellations with equally spaced signal points are adopted, then the constellation structure is simple and易于制造, but the BICM capacity is suboptimal and error rate performance is degraded
Solution Approach 1:
The patent applies asymmetry by transitioning from equally spaced signal points to unequally spaced signal points on the outer ring. Specifically, the outer ring signal points are positioned at angles that are not uniformly distributed, creating an asymmetric constellation structure that optimizes the BICM capacity and error rate performance while maintaining the multi-ring architecture
Solution Approach 2:
The patent changes the angular position parameters of the signal points on the outer ring from uniform spacing to specific non-uniform angles. The inner rings maintain equal spacing for simplicity, while the outer ring adopts optimized angles that maximize the overall constellation performance in terms of BICM capacity and error rate
2Device complexity
If non-iterative demapping and binary coding/decoding are used, then the system complexity is reduced, but the communication link capacity is reduced compared to Shannon capacity
Solution Approach 1:
The patent optimizes the constellation geometry parameters (signal point positions and distributions) specifically to work with non-iterative demapping schemes. By carefully designing the unequally spaced outer ring and optimizing the bit labeling, the constellation achieves better BICM capacity that approaches Shannon capacity even without iterative processing
Solution Approach 2:
The patent uses bit labeling schemes that create favorable mappings between constellation points and coded bits. The specific bit labeling pattern copies information in a way that maximizes the effectiveness of non-iterative demapping, allowing the system to achieve high capacity without the complexity of iterative schemes
3Reliability
If iterative demapping is used, then the BICM capacity is improved and error rate performance is enhanced, but the computational complexity increases significantly
Solution Approach 1:
The patent designs a constellation that achieves good performance with simpler non-iterative demapping, effectively replacing the need for complex iterative processing. The optimized unequally spaced constellation structure provides sufficient performance with lower complexity operations, making the iterative approach unnecessary in many cases
4Ease of manufacture
If conventional APSK constellations are used, then the implementation is straightforward, but carrier synchronization performance is degraded due to phase errors
Solution Approach 1:
The asymmetric unequally spaced outer ring structure provides distinctive phase reference points that improve carrier synchronization. The non-uniform angular positions create a more robust pattern for phase error detection and correction, enhancing synchronization accuracy while maintaining implementation feasibility
Data Source
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AI summary
The present invention relates to a receiver for a digital communication system comprising a demodulator arranged for demodulating a received signal into a sequence of digital symbols, wherein the digital symbols belong to a multi-ring digital signal constellation (200, 201, 202, 203), which has all signal points placed on at least two concentric rings (200, 201, 202, 203), whereby: a) the total number of signal points is larger than 8, b) at least one ring has unequally spaced points (201), and c) the at least one ring with unequally spaced signal points is constructed to form together with at least one neighbouring ring a subset of neighbouring rings (202), whereby each signal point of the subset has a unique angular coordinate modulo 2π and whereby the angular spacing of the signal points of the subset is uniform.