Packet Relay System Link Cost Calculation

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Solution Overview

Problem

Conventional packet relay systems in multihop wireless networks face challenges in accurately calculating link costs, especially when link conditions change, leading to inefficient information communication, traffic congestion, and delayed packet delivery due to temporary link disconnections.

Innovation Solution

A packet relay system with nodes equipped with arrival rate calculation, link cost calculation, and path cost calculation units to determine optimal relay paths, along with packet aggregation and 2-hop adjacent node address storage to manage traffic and re-route packets effectively.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If link cost is calculated using LQI from RREQ packets, then routing information can be obtained, but the link cost calculation becomes inaccurate when link conditions change

Engineering Contradiction:

Improvelink cost calculation accuracyVSAvoidadaptability to link condition changes

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The system uses feedback from packet arrival rate measurements to continuously update link cost calculations. Each node monitors the arrival rate of packets from adjacent nodes and uses this feedback to dynamically adjust link cost values, ensuring accurate routing decisions even when link conditions change due to obstacles or interference.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

Nodes perform self-measurement of packet arrival rates from their adjacent nodes without requiring external intervention. This self-service mechanism allows each node to independently calculate accurate link costs based on its own observations of network traffic patterns, making the system adaptable to local link condition changes.

Inventive Principle:

Principle #25Self-service

2Reliability

If RREQ packets are broadcast at regular intervals to establish upstream paths, then routing paths can be maintained, but the amount of information communicated increases

Engineering Contradiction:

Improverouting path maintenanceVSAvoidnetwork information communication volume

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The system merges multiple routing maintenance functions into existing data packet transmissions. Instead of separate RREQ broadcast packets, nodes embed routing information in the data packets they already need to transmit, eliminating redundant communication and reducing overall network traffic while maintaining reliable routing path establishment.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The system maintains continuous routing information updates by utilizing every data packet transmission as an opportunity to convey routing state. This continuous useful action ensures routing paths remain current without requiring separate maintenance traffic, as each data packet carries forward routing information.

Inventive Principle:

Principle #20Continuity of useful action

3Reliability

If unicast transmission is used to establish downstream paths from sink node, then path establishment is possible, but traffic congestion occurs around the sink node

Engineering Contradiction:

Improvedownstream path establishmentVSAvoidtraffic flow efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The system inverts the traditional downstream path establishment approach by having upstream nodes initiate path confirmation rather than the sink node initiating unicast transmissions to each node. This inversion distributes the path establishment traffic away from the sink node, preventing congestion while maintaining reliable downstream path setup.

Inventive Principle:

Principle #13The other way round (Inversion)

4Reliability

If temporary link disconnection occurs due to obstacles, then link reliability decreases, but packet delivery can be maintained through alternative paths

Engineering Contradiction:

Improvelink connection stabilityVSAvoidpacket delivery speed

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The system implements dynamic path selection where nodes continuously monitor link conditions and automatically switch to alternative paths when temporary disconnections occur. The routing table is dynamically updated with alternative path information, allowing rapid adaptation to changing link conditions without significant packet delivery delays.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system performs preliminary establishment of alternative paths and stores them in routing tables before primary paths fail. When temporary link disconnections occur due to obstacles, nodes can immediately switch to pre-computed alternative paths without waiting for failure detection and recovery procedures, maintaining packet delivery speed despite link instability.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS9450668B2Packet relay system and wireless node

Publication Date: 2016.09.20 OKI ELECTRIC INDUSTRY CO LTD

AI summary

A packet relay system in which each node calculates a link cost of each adjacent node based on an arrival rate of a packet from each adjacent node, acquires an accumulated value of a link cost calculated by each node in a range of nodes from a sink node for each adjacent node, calculates, for each adjacent node, a path cost of the one adjacent node by adding the link cost calculated to the accumulated value, and relays a data packet to one adjacent node selected from among nodes adjacent to the node based on a path cost of each adjacent node. This enables establishment of an upstream path to a sink node without increasing the amount of communication in a network.