Satellite Return-Link 1+N APSK Constellation With NNPR Filtering
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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 return links, where conventional modulation schemes like 8PSK degrade at higher signal-to-noise ratios (SNR) and suffer from interference issues.
Innovation Solution
Implementing a novel 1+N-ary constellation, such as 1+7-ary APSK modulation, combined with non-Nyquist partial response (NNPR) filtering and advanced LDPC coding, to arrange constellation points in a unique formation and use Gaussian pulse shaping filters, which reduces adjacent channel interference and lowers SNR requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional M-ary modulation schemes (e.g., 8PSK) are used, then spectral efficiency is achieved, but error rate performance degrades at higher signal-to-noise ratios and adjacent channel interference increases
Solution Approach 1:
The patent applies asymmetry by introducing a central constellation point at the origin (0,0) in addition to the outer ring points, creating an asymmetric 1+N-ary constellation structure. This asymmetric arrangement with one inner point and N outer points optimizes the geometric distribution to minimize Euclidean distances between constellation points, thereby reducing adjacent channel interference and improving error rate performance while maintaining spectral efficiency
Solution Approach 2:
The patent transitions from conventional single-ring M-ary constellations to a two-dimensional constellation structure with an inner ring (central point) and an outer ring. This dimensional change in the constellation geometry allows for optimized point distribution that simultaneously achieves better error rate performance and reduced interference, resolving the contradiction between reliability and harmful factors
2Object-affected harmful factors
If digital baseband Nyquist-based pulse shaping filters are used, then signal containment within spectrum and interference minimization are improved, but bandwidth utilization efficiency decreases
Solution Approach 1:
The patent changes the fundamental parameter of pulse shaping by abandoning traditional Nyquist-based root-raised cosine filters in favor of non-Nyquist pulse shaping filters. This parameter change in the filtering approach, combined with the novel 1+N-ary constellation, achieves both better signal containment and improved bandwidth utilization efficiency, resolving the contradiction between interference minimization and productivity
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.