Distance-Based Alert Packet Prioritization in Multi-Hop Networks

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Solution Overview

Problem

Current wireless multi-hop broadcast networks face challenges in minimizing packet collisions and expanding coverage area efficiently, particularly in vehicular networks, due to the lack of distance-based prioritization and suboptimal back-off time distributions in existing contention control methods.

Innovation Solution

The method assigns priority to nodes based on their distance from the source node, with nodes farther away rebroadcasting first, using GPS or RSSI to determine distances and select optimal back-off times, thereby minimizing collisions and expanding coverage quickly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If random back-off time is chosen from uniform probability distribution, then packet collision probability is minimized, but coverage area expansion is not accelerated

Engineering Contradiction:

Improvepacket collision probabilityVSAvoidcoverage area expansion speed

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent applies local quality by differentiating back-off time selection based on node location relative to the source. Nodes farther from the source (in less-covered areas) are assigned shorter back-off times, while nodes closer to the source use longer back-off times. This location-dependent quality differentiation accelerates coverage expansion without significantly increasing collision probability.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the back-off time parameter dynamically based on inferred distance from the source node. Instead of using a fixed uniform distribution for all nodes, the system adjusts the back-off time parameter according to each node's location, thereby controlling both collision probability and coverage expansion speed through parameter variation.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If maximum back-off time is exponentially biased towards distant nodes, then coverage expansion is accelerated, but collision probability increases in dense areas

Engineering Contradiction:

Improvecoverage expansion speedVSAvoidpacket collision probability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent implements dynamics by making the back-off time adaptive rather than static. The system continuously monitors packet reception and uses this information to dynamically adjust back-off times for different nodes based on their inferred distance from the source. This dynamic adjustment allows the system to optimize both coverage expansion and collision avoidance in real-time.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent employs feedback mechanisms where nodes monitor packet receptions and use this information to infer their distance from the source. This feedback loop allows the system to adjust back-off times based on actual network conditions and node locations, thereby resolving the contradiction between coverage expansion and collision probability.

Inventive Principle:

Principle #23Feedback

3Reliability

If a priori scheduling based on historical trends is used, then access contention is reduced, but adaptability to current network conditions is limited

Engineering Contradiction:

Improveaccess contention probabilityVSAvoidresponse to current network conditions

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent applies preliminary action by having nodes pre-calculate their inferred distance from the source based on packet reception information. This preliminary calculation allows nodes to determine their appropriate back-off time in advance, reducing access contention while maintaining adaptability to current network conditions through the use of real-time packet reception data.

Inventive Principle:

Principle #10Preliminary action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach reduces the probability of collisions and enhances the rapid propagation of alert packets by prioritizing rebroadcasts based on distance, ensuring efficient dissemination of critical safety information in vehicular networks.

Implementation Method 1

The node determines a time of flight for a signal transmitted from the source node to the node

Methodology Applied

Scientific EffectTime of Flight: Time of Flight

Implementation Method 2

Another embodiment uses a received signal strength indication (RSSI). The RSSI is a measurement of power in a received radio signal, which is generally inversely proportional to some power of the distance.

Methodology Applied

Scientific EffectReceived Signal Strength Indication:

Data Source

PatentUS8155044B2Method for broadcasting alert message in mobile multi-hop networks using inferred distance prioritization

Publication Date: 2012.04.10 MITSUBISHI ELECTRIC RESEARCH LABORATORIES INC

AI summary

A method and system broadcasts an alert packet in a wireless multi-hop network of nodes. An event is sensed in a source node of the network, and an alert packet is broadcast in response to sensing the event. The alert packet is received in a set of candidate nodes within a broadcast range of the source node. Each candidate node infers a distance between the candidate node and the source node based on a receive power of the received alert packet, and determines a priority for rebroadcasting the alert packet, wherein the priority is based on the distance to minimizing a probability of collisions while rebroadcasting the alert packet and extend a range of the rebroadcasting.