Satellite Beam Management Using TDM and Non-Orthogonal Codes
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Solution Overview
Problem
Current satellite communication systems, particularly LEO and MEO systems, face challenges in hand-off issues due to dynamically varying beam shapes and the need to provide packet data services, which are not adequately addressed by existing technologies that focus on GEO systems or fixed beam coverage.
Innovation Solution
A satellite communication system employing multiple beams with a combination of time division multiplexing (TDM) and non-orthogonal pseudorandom noise (NOPN) codes and time slots to distinguish users within a given frequency band, using a gateway connected to either a PSTN or the Internet, and incorporating diversity combining to improve bit error rate performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If time division multiplexing and non-orthogonal pseudorandom noise codes are used to distinguish users within a frequency band, then user capacity and communication quality are improved, but system complexity and interference management difficulty increase
Solution Approach 1:
The system segments the frequency band into multiple time slots using TDM, allowing different users to transmit in different time intervals. This segmentation enables multiple users to share the same frequency band while maintaining distinguishable signals, directly increasing user capacity without requiring additional frequency resources.
Solution Approach 2:
The system employs non-orthogonal pseudorandom noise codes with varying parameters (code sequences, chip rates, and time offsets) to distinguish users. By changing these parameters dynamically, the system can accommodate more users within the same frequency band while managing interference through parameter optimization and power control mechanisms.
2Adaptability or versatility
If multiple beams are used to cover dynamically varying user locations, then service coverage and adaptability are improved, but hand-off issues and beam management complexity worsen
Solution Approach 1:
The system uses multiple dynamically steerable beams that can adapt their shapes and positions to track mobile users. The beam parameters (direction, width, and position) are continuously adjusted based on user location feedback, enabling the system to maintain reliable coverage as users move between different service areas and reducing hand-off disruptions.
Solution Approach 2:
The system performs preliminary beam alignment and user tracking before complete hand-off is necessary. By anticipating user movement patterns and pre-positioning beams, the system reduces the frequency and impact of hand-off events, thereby improving hand-off reliability and maintaining continuous service coverage.
3Reliability
If diversity combining is implemented to improve bit error rate performance, then communication reliability is improved, but processing complexity and computational requirements increase
Solution Approach 1:
The system merges multiple received signal copies through diversity combining techniques (such as maximal ratio combining or selection combining) to improve bit error rate performance. By combining signals from different diversity branches (spatial, temporal, or frequency diversity), the system achieves better reliability while managing processing complexity through efficient combining algorithms.
Data Source
AI summary
An improved satellite communication system is provided comprising at least one satellite wherein each satellite provides multiple beams, a plurality of UTs, and at least one gateway connected to a PSTN and communicating with said at least one UT or with a constellation, wherein each of the UTs within a given frequency band is distinguished from another of the UTs employing a combination of TDM and NOPN codes and time slots.