TDD Beam Nulling Between Airborne and Terrestrial Base Stations
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Solution Overview
Problem
Conventional interference control technologies in mobile communication systems using upper airspace relaying-type and terrestrial base stations reduce communication capacity due to time-division frequency allocation, leading to orthogonal radio signals and underutilization of frequencies.
Innovation Solution
Implementing a mobile communication system with time-synchronized upper-airspace and terrestrial base stations using a TDD method, reversing transmission and reception timings, and employing directional beam null-forming to reduce interference, while sharing the same frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If time-division frequency allocation is used between upper airspace relaying-type base station and terrestrial base station, then interference between the two base stations is reduced, but communication capacity and peak throughput are reduced due to underutilization of frequencies
Solution Approach 1:
The patent changes the frequency allocation parameter from time-division (orthogonal frequency allocation) to simultaneous frequency usage with TDD method. By reversing transmission and reception timings between upper airspace and terrestrial base stations, both can use the same frequency simultaneously without interference, thus improving communication capacity while maintaining interference reduction.
Solution Approach 2:
The patent applies inversion by reversing the transmission and reception timings between upper airspace relaying-type base station and terrestrial base station. Instead of both transmitting or both receiving at the same time, one transmits while the other receives, enabling simultaneous frequency usage without mutual interference.
2Reliability
If time-division use of frequencies is implemented, then orthogonal radio signals are achieved with no mutual interference, but all allocated frequencies cannot be used by either base station
Solution Approach 1:
The patent changes the frequency usage parameter from time-division multiplexing to simultaneous frequency sharing with TDD. By reversing transmission/reception timing between base stations, full frequency utilization is achieved while maintaining signal orthogonality through directional beam null-forming.
Solution Approach 2:
The patent introduces directional beam null-forming as an intermediary mechanism. The terrestrial base station forms nulls in directional beams toward the upper airspace base station, and vice versa, enabling simultaneous frequency usage while maintaining effective signal separation and orthogonality.
3Productivity
If same frequency is shared between upper airspace relaying-type base station and terrestrial base station, then frequency utilization is maximized, but interference control becomes more difficult
Solution Approach 1:
The patent changes the interference control parameter from time-division scheduling to simultaneous frequency usage with TDD and directional beam null-forming. This approach maintains frequency utilization while simplifying interference control through physical layer signal separation rather than scheduling complexity.
Solution Approach 2:
The patent replaces the mechanical scheduling system (time-division frequency allocation) with a signal processing system (TDD with directional beam null-forming). This substitution enables simultaneous frequency usage while controlling interference through beamforming techniques rather than time scheduling.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows full utilization of frequencies, preventing communication capacity loss and enhancing peak throughput by minimizing interference between the base stations.
Implementation Method 1
controls a null of a directional beam of the service link antenna of the terrestrial base station to be directed in the estimated direction to the service link antenna of the upper-airspace relay type base station
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
In a mobile communication system comprising an upper-airspace relay type base station having an antenna mounted on an upper-airspace flying body, etc. (including a UAV, a HAPS, and a communication satellite) and a terrestrial base station, it is intended to improve a frequency utilization efficiency, prevent a decrease in a communication capacity of a terminal, and reduce an interference in an uplink and a downlink of a service link of each base station. Each of the upper-airspace relay type relay base station and the terrestrial base station performs a service-link radio communication with a terminal by a TDD (Time Division Duplex) method using the same frequency. A transmission timing and a reception timing of the radio communication by the TDD method in the service link are reversed between the upper-airspace relay type base station and the terrestrial base station. The terrestrial base station estimates a direction to the service link antenna of the relay communication station, and controls a null of a directional beam of the service link antenna of the terrestrial base station so as to be directed in the estimated direction to the service link antenna of the relay communication station.