1+N APSK Return-Link Constellation for Spectral Efficiency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The increasing demand for faster broadband access has congested available radio frequency spectrum allocations, necessitating more efficient utilization of bandwidth resources in satellite communication systems, particularly in the return link, where conventional modulation schemes like 8PSK degrade at higher signal-to-noise ratios and suffer from interference issues.
Innovation Solution
Implementing a novel 1+N-ary constellation with 1+N amplitude and phase-shift keying (APSK) modulation, combined with non-Nyquist partial response filtering and LDPC coding, to arrange constellation points in a unique formation and use NNPR filters, enhancing power and spectral efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional 8PSK modulation is used, then implementation is simple and widely standardized, but spectral efficiency degrades at higher signal-to-noise ratios and adjacent channel interference increases
Solution Approach 1:
The 8-ary constellation is segmented into an inner constellation point at the origin and an outer ring with 7 constellation points. This segmentation creates the 1+7 APSK modulation scheme, which improves spectral efficiency by optimally distributing constellation points to maximize distance from the origin while maintaining implementability through standardized APSK modulation techniques.
Solution Approach 2:
The patent employs asymmetric constellation geometry where one point (inner) is at the origin and the other seven points form an outer ring at a different radius. This asymmetric 1+7 arrangement optimizes the distance distribution of constellation points to improve spectral efficiency and reduce interference, while still using symmetric APSK modulation principles for practical implementation.
2Area of stationary object
If conventional pulse shaping filters are used, then spectral containment is achieved, but adjacent channel interference and signal-to-noise requirements increase
Solution Approach 1:
The patent changes the pulse shaping filter parameters by using a root-raised cosine filter with a specific roll-off factor optimized for the 1+7 APSK modulation. This parameter optimization achieves better spectral containment while minimizing adjacent channel interference and reducing signal-to-noise requirements compared to conventional filter settings used with standard 8PSK modulation.
3Productivity
If higher bits-per-symbol rates are used, then data transmission speed increases, but error rate performance degrades and signal-to-noise requirements increase
Solution Approach 1:
The patent transitions from conventional 2D PSK modulation to 3D APSK modulation by introducing an amplitude dimension with an inner constellation point at the origin and an outer ring. This dimensional change enables 1+7 APSK modulation to achieve higher bits-per-symbol rates with improved error rate performance by optimally distributing constellation points in the complex plane to maximize distance from the origin.
Data Source
AI summary
Systems and methods are described for generating and implementing return-link satellite communications using a novel 1+N-ary constellation. The 1+N-ary constellation arranges M (e.g., 8) constellation points in a novel formation that increases their distances from each other relative to conventional M-ary modulation schemes by locating an inner constellation point centrally with respect to an I-Q plane and distributing the remaining N (i.e., M=N+1) outer constellation points radially around the inner constellation point. 1+N amplitude and phase-shift keying (APSK) modulation can be used to map symbols to the constellation. Embodiments combine the 1+N APSK modulation with additional features, such as non-Nyquist partial response (NNPR) filtering and/or state of the art low-density parity check (LDPC) coding.