Adaptive Sub-Carrier Assignment for Satellite Interference Avoidance
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Solution Overview
Problem
Very Small Aperture (VSAT) satellite communication systems face significant interference from terrestrial sources like microwave towers, which degrades signal reception at remote terminals and is costly to mitigate using current techniques such as notch filters and robust coding, leading to reduced effective bit rates and bandwidth constraints.
Innovation Solution
An adaptive local interference mitigation system that maintains a local interference map to identify unusable sub-carriers and selects alternative sub-carriers for data transmission, avoiding interference and optimizing sub-carrier assignment based on queue depths and bit rate capacities to ensure continuous utilization and minimal delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If robust coding is applied to reduce signal loss from narrowband interference, then signal reliability is improved, but the effective data rate is reduced
Solution Approach 1:
The system segments the available frequency spectrum into multiple sub-carriers and selectively assigns packets to sub-carriers that are not affected by narrowband interference. This segmentation allows the system to bypass interfered frequency bands while utilizing clean sub-carriers, thereby maintaining high data rates without requiring robust coding that would reduce effective throughput.
Solution Approach 2:
The system dynamically changes the frequency parameter (sub-carrier selection) based on interference conditions. By monitoring which sub-carriers are affected by narrowband interference and adjusting the frequency assignment accordingly, the system can transmit data on clean sub-carriers without needing to apply robust coding, thus preserving both reliability and data rate.
2Object-affected harmful factors
If directional antennas are used to reduce terrestrial interference, then interference rejection is improved, but the cost and complexity increase
Solution Approach 1:
The system replaces the mechanical solution (directional antennas with specific beamwidths) with a signal processing solution (sub-carrier selection and assignment). Instead of physically directing beams to reject interference, the system uses frequency-domain multiplexing to assign packets to sub-carriers that are not interfered with, achieving the same interference rejection effect without complex antenna hardware.
3Device complexity
If a single carrier TDMA system is used, then system simplicity is maintained, but performance degrades under narrowband interference
Solution Approach 1:
The system introduces dynamic sub-carrier assignment within the TDMA framework. While maintaining the overall simplicity of TDMA time-slot structure, the system dynamically selects which sub-carriers to use for each packet transmission based on real-time interference conditions. This dynamic adaptation allows the system to maintain high reception quality without significantly increasing system complexity.
Solution Approach 2:
The system transitions from a single-carrier TDMA approach to a multi-sub-carrier approach, adding a frequency dimension to the time-division multiplexing. By distributing packets across multiple sub-carriers in the frequency domain while maintaining TDMA time slots, the system achieves interference diversity without abandoning the simplicity of structured multiplexing protocols.
Data Source
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AI summary
Systems and method are disclosed and among these is a method for mitigation of interference local to remote terminals, and it can include detecting reception of a packet having one of the remote terminals as a destination terminal and, in response, selecting a sub-carrier among the sub-carriers that are not identified as receiving local interference at the destination terminal, and loading, into a queue for the selected sub-carrier, a coded data from which a content of the packet can be derived, and transmitting the queued coded data on the selected sub-carrier. Among disclosed features is a receiving of an interference report that carries an information indicative of a new local interference and, in response, updating the data identifying sub-carriers having local interference at the destination terminal.