Inter-Gateway Interference Management in CDMA Satellite Systems
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Solution Overview
Problem
Conventional CDMA satellite systems face challenges in managing interference levels effectively, particularly in multi-gateway scenarios, leading to potential system overload, as direct interference measurement methods are inaccurate and impractical, and existing methods rely on knowing the total number of active channels, which is unknown across gateways.
Innovation Solution
The approach involves indirect inter-gateway interference estimation using received signal-to-interference ratio (SIR) and user terminal (UT) location and power headroom reports, allowing each gateway to autonomously make admission decisions and manage interference without direct measurement, by calculating the interference contribution of each UT and adjusting resource allocation based on residual capacity and priority.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct interference measurement method is used, then interference level can be monitored, but system overload occurs in multi-gateway scenarios due to independent gateway decisions
Solution Approach 1:
The patent introduces an intermediary mechanism where gateways exchange interference measurement data and terminal admission information with each other. This mediator approach allows each gateway to make informed admission decisions considering the overall system state, preventing overload while maintaining accurate interference monitoring through shared information.
Solution Approach 2:
The system implements feedback loops where interference measurements and admission decisions are continuously exchanged between gateways. Each gateway adjusts its admission control based on feedback from other gateways about current system load and interference levels, enabling coordinated interference management across the multi-gateway network.
2Extent of automation
If each gateway makes independent admission decisions based on maximum channels, then gateway autonomy is maintained, but system overload results due to unknown total active channels
Solution Approach 1:
Gateways maintain autonomy by making their own admission decisions, but they do so based on feedback information from other gateways about current system load. Each gateway receives updates about total active channels and interference levels, then independently evaluates whether to admit new terminals based on this feedback, preserving autonomy while ensuring system-wide load control.
Solution Approach 2:
The patent creates a universal information exchange protocol that all gateways use to share admission decisions and interference data. This multi-functional communication mechanism serves multiple purposes: coordinating load distribution, preventing overload, and maintaining autonomous decision-making capability across all gateways simultaneously.
3Device complexity
If conventional interference management is applied, then simple implementation is achieved, but inaccurate interference control occurs in multi-gateway systems
Solution Approach 1:
The patent merges individual gateway interference measurements with system-wide coordination mechanisms. By combining local measurement data with exchanged information from other gateways about their current load and interference levels, the system achieves accurate overall interference control while building upon the relatively simple conventional measurement approach.
Data Source
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AI summary
An approach for inter-gateway interference estimation and admission control is provided. A gateway receives return link signals, each being received via a satellite from a respective user terminal (UT) located within a satellite beam serviced by the gateway. A transmit power factor and an interference factor are determined for each UT based on the respective return link signal. A total interference factor is determined for the UTs based on the transmit power factors and the interference factors. A residual capacity level for the satellite beam is determined based on the total interference factor and a noise power factor. The gateway receives an admission request from a further UT requesting admission for transmission of a return link signal. The gateway determines whether to grant the admission request based on a required capacity level for the return link signal of the further UT relative to the residual capacity level.