NGSO Satellite Packet Forwarding with Hierarchical Route Updates

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Solution Overview

Problem

End-to-end data packet forwarding in non-geosynchronous orbit (NGSO) satellite networks is challenging due to dynamic satellite constellations, frequent changes in connectivity, and limited on-board memory, necessitating frequent updates of forwarding tables.

Innovation Solution

Implementing proactive and reactive updates to forwarding tables, using a network controller with SDN capabilities to manage deterministic and ad hoc link connectivity changes, and employing hierarchical two-tuple based forwarding, centralized time-based route computation, and local SDN controllers for efficient packet forwarding.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If forwarding tables are frequently updated to account for dynamic satellite connectivity changes, then packet forwarding reliability is improved, but network bandwidth consumption increases due to continuous table update transmissions

Engineering Contradiction:

Improvepacket forwarding reliabilityVSAvoidnetwork bandwidth consumption

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent applies preliminary action by pre-computing and storing multiple alternative routes between satellite pairs in the forwarding tables before connectivity changes occur. When a link fails or connectivity changes, satellites can immediately switch to pre-computed alternative routes without requiring real-time table updates, thus maintaining packet forwarding reliability while minimizing network bandwidth consumption for control messages.

Inventive Principle:

Principle #10Preliminary action

2Adaptability or versatility

If forwarding tables are made larger to accommodate more route information for dynamic connectivity, then routing flexibility is improved, but satellite on-board memory requirements increase

Engineering Contradiction:

Improverouting flexibilityVSAvoidsatellite on-board memory

Core Design Contradiction:

Adaptability or versatilityVSVolume of stationary object

Solution Approach 1:

The patent applies segmentation by dividing the forwarding table into multiple segments or layers: (1) a compact core routing table stored in satellite memory containing essential next-hop information, and (2) extended route information stored distributedly in ground station memory or computed on-demand. This segmentation allows routing flexibility to be maintained through distributed storage while keeping individual satellite memory requirements manageable.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent extracts frequently changing or less critical route information from satellite on-board memory and stores it in ground-based systems or computes it on-demand. Only essential forwarding information remains in satellite memory, reducing memory requirements while maintaining routing flexibility through external resources.

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If proactive route computation is performed for all possible satellite pairs, then handoff continuity is improved, but computational overhead and processing time increase

Engineering Contradiction:

Improvehandoff continuityVSAvoidcomputational overhead

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies local quality by performing proactive route computation only for satellite pairs that are geographically or topologically relevant to each other, rather than computing all possible routes network-wide. Each satellite computes routes primarily for its local neighborhood and expected handoff targets, reducing computational overhead while maintaining handoff continuity through localized intelligence.

Inventive Principle:

Principle #3Local quality

4Productivity

If centralized control is used to manage forwarding tables across the satellite network, then routing optimization is improved, but network response time to connectivity changes increases

Engineering Contradiction:

Improverouting optimizationVSAvoidnetwork response time

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The patent applies the nested doll principle by implementing a hierarchical control architecture where a centralized controller provides overall routing optimization and policy management, while local satellite controllers handle immediate connectivity changes and forwarding decisions. This nested structure allows centralized optimization benefits to be maintained at higher levels while local rapid response capabilities are preserved at lower levels, eliminating the trade-off between optimization and response time.

Inventive Principle:

Principle #7Nested doll (Nesting)

Data Source

PatentEP3921738B1Data packet forwarding in an NGSO satellite network

Publication Date: 2025.08.27 LOCKHEED MARTIN CORP

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AI summary

A communication system includes a satellite constellation, one or more gateways and a network controller. The satellite constellation includes multiple satellites to facilitate communication between a number of user terminals (UTs). Each gateway communicates with one or more of the satellites. The network controller controls operation of the satellites, the gateways and the UTs. The satellites, the UTs, the gateways and the network controller include hardware that may also be software-defined network (SDN) enabled to ensure a persistent end-to-end data packet forwarding including proactive updates and reactive updates to forwarding tables. The proactive updates handle deterministic and time-synchronized link connectivity changes and the reactive updates handle ad hoc link connectivity changes.