NGSO Satellite Routing via Fixed Ground Cells

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Solution Overview

Problem

Non-geostationary orbit (NGSO) wireless data communications systems, such as low earth orbit (LEO) satellite systems, face challenges in maintaining long-term data communications circuits between geographically diverse endpoints due to high routing complexity and significant delay caused by multiple satellite-gateway hops.

Innovation Solution

A method is implemented to determine and manage radio resource routes for committed bit rate data communications circuits by selecting uplink and downlink satellites for each time interval, ensuring valid inter-satellite links and minimizing handovers, allowing for fixed cell patterns on the ground that reduce handover frequency and maintain continuous connectivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If multiple satellite-gateway hops are used to provide data communications between geographically diverse terminals, then geographic coverage is improved, but routing complexity and transmission delay increase significantly

Engineering Contradiction:

Improvegeographic coverageVSAvoidrouting complexity

Core Design Contradiction:

Area of stationary objectVSDevice complexity

Solution Approach 1:

The patent segments the data transmission path into dedicated circuit segments assigned to specific satellites and time intervals. Each circuit is broken down into discrete hops with assigned satellites, allowing independent optimization of each segment rather than managing complex dynamic routing across the entire network.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent performs preliminary routing determination by pre-calculating and assigning satellite circuits for future time intervals based on predicted satellite positions. This advance planning eliminates real-time routing complexity by establishing fixed paths before transmission begins.

Inventive Principle:

Principle #10Preliminary action

2Area of stationary object

If multiple satellite-gateway hops are used to traverse wide geographic distances, then geographic coverage is improved, but transmission delay increases significantly

Engineering Contradiction:

Improvegeographic coverageVSAvoidtransmission delay

Core Design Contradiction:

Area of stationary objectVSLoss of time

Solution Approach 1:

The patent performs preliminary circuit establishment by pre-assigning satellite hops and preparing transmission paths in advance based on predicted satellite positions. This eliminates real-time routing delays and allows packets to follow pre-determined optimal paths.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent maintains continuous circuit assignments across multiple time intervals, ensuring that data packets traverse predetermined satellite paths without interruption or re-routing. This continuity eliminates delays associated with dynamic path selection and handover procedures.

Inventive Principle:

Principle #20Continuity of useful action

3Area of stationary object

If fixed beams sweep across the ground as the satellite moves, then coverage area is improved, but handover frequency increases causing synchronization overhead

Engineering Contradiction:

Improvecoverage areaVSAvoidsynchronization overhead

Core Design Contradiction:

Area of stationary objectVSDevice complexity

Solution Approach 1:

The patent segments the coverage area into fixed ground cells and assigns specific satellites to service specific cells during specific time intervals. This segmentation reduces handover frequency by ensuring that a terminal remains served by the same satellite throughout its assigned circuit duration.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of having satellites sweep fixed beams across the ground, the patent inverts the approach by having satellites serve fixed ground cells from predetermined positions. This reversal eliminates the need for frequent beam sweeping and handovers, as terminals remain in the coverage area of their assigned satellite throughout the circuit duration.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentEP3513596B1Radio resource management and routing for fixed data circuits in an NGSO satellite data communications system

Publication Date: 2021.07.21 HUGHES NETWORK SYST

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Figure 2A~2B

AI summary

A method for determining routes for a data circuit between source and destination terminals, where the circuit is formed via satellites traveling in respective non-geostationary orbits, and a total time during which the circuit is active is divided into time intervals. The determination of each route comprises, for each time interval, (i) selecting an uplink satellite to service the source terminal as an ingress node for the circuit, and (ii) determining a series of inter-satellite links connecting the uplink satellite to a downlink satellite servicing the destination terminal during the respective time interval, wherein the series of links is determined to be valid during the respective time interval. Each of the plurality of time intervals is of a duration based on a validity time, based on the satellites traveling in their respective orbits, for the inter-satellite link of all of the routes that is of the shortest duration.