Shortest Path Recalculation Using Precomputed Data
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Solution Overview
Problem
Existing methods for calculating the shortest path in networks fail to efficiently recalculate paths when topology changes due to link additions or deletions, as they do not utilize existing shortest path information, leading to increased calculation time.
Innovation Solution
A method that uses previously calculated shortest paths to efficiently recalculate new paths by comparing distances and updating path information, even when links are added or deleted, by employing a control unit to search for candidate paths and update path trees in a network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all shortest paths are recalculated using Dijkstra's algorithm after topological change, then the shortest path information is updated, but the calculation time increases significantly
Solution Approach 1:
The patent stores pre-calculated shortest path information in a shortest path information storage unit before topological changes occur. When a link cost changes, the system retrieves and reuses this pre-calculated information instead of performing a complete recalculation, significantly reducing computation time while maintaining accuracy for unchanged paths.
Solution Approach 2:
The patent identifies and processes only the specific paths affected by the topological change (local update) rather than recalculating all shortest paths in the network. The shortest path calculation unit selectively updates only those paths that pass through the changed link, leaving other paths unchanged based on the stored pre-calculated information.
2Loss of time
If existing shortest path information is reused after topological change, then calculation time is reduced, but the accuracy of shortest path information may be compromised
Solution Approach 1:
The patent implements a feedback mechanism where the shortest path calculation unit continuously monitors and compares path costs. When a topological change occurs, the system uses the stored shortest path information as a baseline, calculates adjustments for affected paths, and updates the shortest path information storage unit with the corrected data, ensuring ongoing accuracy.
Solution Approach 2:
The system performs preliminary validation by comparing the reused shortest path information against the current topology state. The shortest path calculation unit identifies which pre-calculated paths remain valid and which require adjustment, ensuring that only accurate information is retained or updated.
3Device complexity
If the shortest path calculation method only handles link cost changes, then the calculation is simpler, but it cannot handle link additions or deletions
Solution Approach 1:
The patent designs the shortest path calculation unit to handle multiple types of topological changes (link cost changes, link additions, and link deletions) using a unified approach. The same unit retrieves pre-calculated information, identifies affected paths, and performs updates regardless of the specific type of topological change, making the system versatile without proportionally increasing complexity.
Solution Approach 2:
The patent separates the shortest path calculation functionality into distinct modular components: a shortest path information storage unit for pre-calculated data, a shortest path calculation unit for processing changes, and a topological change detection mechanism. This segmentation allows the system to handle different topological change types through standardized processing steps.
Data Source
AI summary
A calculating apparatus calculates a shortest path connecting two nodes of a network. A shortest-path group, which is a set of shortest paths having node Y as their starting points, can be calculated at once by having calculated a shortest path having node Y as its starting point for each of other nodes. When the shortest-path group having node Y as the starting point is calculated and further if a group of shortest paths having node X as their starting points is stored beforehand in a storing unit, then path portions, which belong to the group of shortest paths having node X as the starting points and further which are paths extending from node Y to the nodes located downstream from node Y, are utilized as part of a result of calculation of the shortest path group having node Y as the starting point.