TDD Scheduling in Satellite FDD Networks for Half-Duplex UEs
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Solution Overview
Problem
In satellite communications systems, the large propagation delay introduces significant overhead due to the need for large gap periods in time division duplexing (TDD), leading to inefficient use of network resources when using half duplex user equipment (UE).
Innovation Solution
Implementing a full duplex gateway terminal with a scheduler that accounts for propagation delays to allocate downlink (DL) and uplink (UL) time slots efficiently, avoiding overlaps at half duplex UE while allowing overlaps at the gateway, thus optimizing network resource utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If time division duplexing is used in satellite communications systems with half duplex user equipment, then the system can operate with simpler UE hardware, but the large propagation delay requires large gap periods causing significant overhead and inefficient network resource utilization
Solution Approach 1:
The system segments the communication into distinct downlink and uplink time slots with precise timing control. By dividing the communication cycle into separate transmission phases and using timing advance mechanisms, the system eliminates the need for large gap periods while maintaining half-duplex UE simplicity, thereby resolving the contradiction between hardware simplicity and resource utilization efficiency
Solution Approach 2:
The system applies preliminary timing adjustment by advancing uplink transmissions at UE side before the actual communication occurs. This timing advance compensates for propagation delay in advance, allowing the gateway to schedule downlink and uplink slots without requiring large gaps, thus improving network resource utilization while keeping UE hardware simple
2Productivity
If frequency division duplexing is used with full duplex gateway terminal and half duplex UE, then network resource utilization is optimized, but the system complexity increases due to propagation delay compensation requirements
Solution Approach 1:
The system introduces a scheduler as an intermediary component that mediates between the gateway terminal and UE. This scheduler handles the propagation delay compensation and timing coordination, abstracting the complexity from the individual devices. The scheduler calculates appropriate timing advances and slot allocations, enabling efficient resource utilization while managing system complexity through a dedicated coordination layer
Solution Approach 2:
The system implements dynamic timing adjustment where uplink time slots are advanced based on actual propagation delay conditions. Rather than using fixed large gaps, the system dynamically adapts the timing of uplink transmissions to match the downlink schedule, optimizing resource utilization while managing complexity through flexible timing control mechanisms
Data Source
AI summary
Described herein are technologies that utilize full duplex gateway terminals in satellite networks with half duplex user equipment. The disclosed scheduling technologies incorporate the knowledge of the propagation delay between a gateway terminal and each UE in communication with the gateway terminal. Based on this propagation delay, a scheduler can allocate DL and UL time slots in a scheduling frame in a way that avoids allocating overlapping DL and UL time slots at each UE.