Hierarchical Modulation Constellation Design for Low PAPR Satellite Links
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Solution Overview
Problem
In satellite communications, hierarchical modulation is used to manage high-quality data transmission, but it faces challenges in maintaining a low Peak-to-Average Power Ratio (PAPR) while ensuring unequal protection for different streams, which is crucial for handling varying signal conditions such as rain fading.
Innovation Solution
The method involves identifying clusters of constellation points in an amplitude phase shift keying (APSK) constellation and mapping bits from high-priority (HP) and low-priority (LP) streams to specific constellation points, controlling the distance between constellation points and rings to maintain a low PAPR, and adapting the constellation parameters based on transmission conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hierarchical modulation is used to provide unequal protection for different streams, then transmission reliability under varying signal conditions is improved, but Peak-to-Average Power Ratio increases
Solution Approach 1:
The patent applies parameter changes by carefully adjusting the geometric parameters of the APSK constellation (number of rings, points per ring, radial and angular positions) to achieve a low PAPR while maintaining hierarchical structure. The specific parameter set (2-8-18-26 APSK) is optimized to balance unequal protection requirements with power efficiency, resolving the contradiction between reliability improvement and energy usage.
2Productivity
If constellation points are closely spaced to increase data rate, then transmission capacity is improved, but signal robustness against noise and interference deteriorates
Solution Approach 1:
The patent segments the constellation into multiple rings with different numbers of points (2-8-18-26 distribution), where inner rings carry high-priority data with larger spacing for robustness, and outer rings carry low-priority data with smaller spacing for higher capacity. This segmentation allows simultaneous achievement of data rate improvement and signal robustness through differential spacing strategies.
Solution Approach 2:
The patent applies local quality by assigning different spatial characteristics to different parts of the constellation. Inner rings have larger angular and radial spacing providing better noise immunity for critical data, while outer rings have tighter spacing to maximize capacity for less critical data. This local differentiation resolves the contradiction between overall data rate and local signal robustness.
Data Source
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AI summary
The present invention concerns a method for transmitting data to at least one receiver, data being decomposed in a first and a second streams. The method comprises the steps of: - identifying, from a first number of bits of the first stream, a cluster of constellation points among clusters of constellation points of an amplitude phase shift keying constellation, each cluster of constellation points being comprised in a respective circle sector of a first type, each circle sector of the first type being spaced from another circle sector of the first type by a circle sector of a second type, all circle sectors having the same central point, - identifying, from a second number of bits of the second stream, one constellation point out of the constellation points comprised in the identified cluster, - mapping the bits used for identifying to the identified constellation point of the identified cluster of constellation points, in order to form a symbol to be transmitted, - transmitting the symbol to the at least one receiver.