Coordinated Beacon Transmission Times in Wi-Fi Hot Spots

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Solution Overview

Problem

In Wi-Fi Hot Spots, existing methods for AP discovery, such as active and passive scanning, lead to broadcast storms and beacon message collisions, resulting in high overhead and long waiting times for mobile devices to associate with access points.

Innovation Solution

A method for coordinating beacon transmission times among multiple access points in a wireless local area network, where each AP generates a neighboring AP list, derives a beacon transmission time, and transmits messages at evenly spaced intervals, allowing for self-coordinated beacon timing without the need for a dedicated control entity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If passive scanning is used for AP discovery, then mobile devices can discover APs by listening to beacon messages, but beacon messages from multiple uncoordinated APs may collide and transmission waiting time increases to nearly 100ms

Engineering Contradiction:

Improvebeacon message delivery reliabilityVSAvoidSTA waiting time for beacon

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

APs perform preliminary discovery of neighboring APs and pre-coordinate their beacon transmission times before actual beacon transmission. Each AP derives a beacon transmission time based on its neighboring AP list, ensuring that beacons are transmitted at evenly spaced intervals without collision.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The beacon transmission time for each AP is dynamically determined based on its specific neighboring AP list rather than using fixed periodic intervals. This allows the system to adapt to different network configurations and eliminate collisions while maintaining regular transmission patterns.

Inventive Principle:

Principle #15Dynamics

2Speed

If active scanning is used for AP discovery, then STAs can quickly discover APs by broadcasting probe requests, but this generates broadcast storms with numerous request and response messages creating high overhead

Engineering Contradiction:

ImproveAP discovery speedVSAvoidmessage transmission overhead

Core Design Contradiction:

SpeedVSLoss of energy

Solution Approach 1:

Instead of continuous or frequent probe request broadcasting, the system uses periodic beacon messages transmitted at coordinated intervals. STAs passively receive these periodic beacons, eliminating the need for repeated active probing and reducing message overhead while maintaining discovery functionality.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The discovery approach is inverted from active scanning (STA-initiated probe requests) to passive scanning (AP-initiated beacon transmissions). By having APs proactively send beacons at coordinated times, the system achieves efficient discovery without the broadcast storm problem caused by multiple STAs simultaneously sending probe requests.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS9888490B2Method for coordinating beacon transmission times in wireless local area network and communications system utilizing the same

Publication Date: 2018.02.06 MEDIATEK SINGAPORE PTE LTD

AI summary

A method for coordinating beacon transmission times for a plurality of access points (APs) in a wireless local area network includes generating a first neighboring AP list listing one or more neighboring AP(s) of a first AP, deriving a first beacon transmission time for the first AP according to the first neighboring AP list, and transmitting a beacon message at the first beacon transmission time by the first AP. The first AP and the one or more neighboring AP(s) are arranged to form a Hot Spot that offers network services over the wireless local area network.