Satellite Constellation Packet Data System Using Orthogonal Codes
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Solution Overview
Problem
Current satellite constellation systems, particularly LEO, MEO, and GEO systems, face challenges in providing reliable packet data services and hand-off management due to dynamically varying beam shapes and the need for orthogonal codes to distinguish users within a given frequency band, especially in systems with rapidly moving satellites and packet data services.
Innovation Solution
A satellite constellation system employing multiple beams with a gateway connected to a PSTN or Internet, using orthogonal codes such as CDMA technology to enable users to initiate or receive packet data messages, and incorporating features like soft handoff and diversity combining to maintain communication quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If satellite constellation systems use dynamically varying beams to cover moving satellites, then system adaptability and coverage are improved, but beam shape stability and user distinction reliability deteriorate
Solution Approach 1:
The patent applies dynamics by implementing soft handoff mechanisms that allow users to be served by multiple satellites simultaneously as satellites move across the sky. The system dynamically adjusts beam assignments and handoff parameters based on satellite position, user location, and signal quality metrics, enabling seamless transitions without fixed beam boundaries
Solution Approach 2:
The system changes parameters including orthogonality constraints on code assignments, handoff thresholds, and beam forming coefficients based on real-time satellite geometry and user distribution. These parameter adjustments maintain user distinction reliability despite varying beam shapes caused by satellite motion
2Measurement precision
If orthogonal codes are used to distinguish users within a frequency band, then user identification capability is improved, but system complexity and code management overhead increase
Solution Approach 1:
The patent segments the code space by assigning different orthogonal code sets to different satellites and time intervals. Each satellite receives a portion of the overall code pool, and codes are systematically allocated to users within each satellite's coverage, reducing the complexity of global code management while maintaining user distinction capability
Solution Approach 2:
The system employs more orthogonal codes than the minimum theoretical requirement by allowing code reuse across different satellites and time slots. This excessive use of codes provides robust user identification even when some codes experience interference or degradation, while the structured allocation prevents excessive overall complexity
3Reliability
If soft handoff and diversity combining are implemented to maintain communication quality, then system reliability is improved, but processing complexity and computational requirements increase
Solution Approach 1:
The patent merges signals from multiple satellites through diversity combining at the user terminal, where received signals are coherently combined after phase alignment. This merging provides reliability through signal diversity while the processing complexity is managed by using efficient combining algorithms and pre-synchronization techniques
Solution Approach 2:
The system implements feedback mechanisms where the network monitors handoff performance, signal quality metrics, and user throughput to dynamically adjust handoff parameters and diversity combining weights. This feedback loop optimizes reliability while adapting processing requirements to actual system conditions, preventing excessive complexity in normal operation
Data Source
AI summary
A satellite communication system is disclosed which provides at least one satellite employing multiple beams to a plurality of user terminals. A gateway is employed to connect to either a PSTN or an Internet communicating with the user terminal over the system so that the users within a given frequency range are distinguished one from the other employing orthogonal codes. The user terminal has the capability of either initiating or receiving packet data messages.