Directional Channel Access Control for WLAN Scalability

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Solution Overview

Problem

WLAN systems face scalability and coexistence issues when operating in frequency bands shared with other wireless communication systems, particularly in TV white spaces, leading to increased delay times and reduced Quality of Service (QoS) due to the limitations of Distributed Coordination Function (DCF) and Enhanced Distributed Channel Access (EDCA) protocols.

Innovation Solution

A method for controlling channel access in WLAN systems that involves receiving directional channel access control messages from access points, allowing prioritization of data frames and adjusting the number of competing stations, thereby improving scalability and coexistence by using Request To Send (RTS)/Clear To Send (CTS) mechanisms and channel access control messages.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If DCF and EDCA protocols are applied in TV white space environment, then channel access is provided, but scalability is deteriorated due to increased number of users

Engineering Contradiction:

Improvechannel access capabilityVSAvoidscalability

Core Design Contradiction:

ProductivityVSAdaptability or versatility

Solution Approach 1:

The patent segments the coverage area into multiple non-overlapping service areas, each served by a different AP. This segmentation reduces the number of users competing for channel access in each area, thereby improving scalability while maintaining channel access capability through coordinated AP operation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces spatial dimension by using directional antennas to create sectorized service areas. This dimensional approach allows multiple APs to serve different spatial regions simultaneously, resolving the scalability issue without compromising channel access efficiency.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Area of stationary object

If coverage is expanded using TV white space spectrum, then coverage area is remarkably expanded, but number of stations increases causing scalability problems

Engineering Contradiction:

Improvecoverage areaVSAvoidscalability

Core Design Contradiction:

Area of stationary objectVSAdaptability or versatility

Solution Approach 1:

The patent divides the expanded coverage area into multiple smaller service areas, each with a manageable number of stations. This segmentation maintains the overall expanded coverage while ensuring each segment can handle its user load effectively, thus preserving scalability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces AP selection messages and channel access control messages as intermediaries that coordinate between multiple APs and stations. These messages enable efficient user distribution across APs, maintaining scalability in the expanded coverage area.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If multiple unlicensed devices coexist in TV white space, then spectrum utilization is improved, but coexistence problems arise due to interference

Engineering Contradiction:

Improvespectrum utilizationVSAvoidcoexistence

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent segments the service area and assigns different APs to different segments, reducing interference between unlicensed devices. This spatial segmentation maintains spectrum utilization while improving coexistence by isolating potential interference sources.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements feedback mechanisms through channel access control messages that provide information about channel conditions and AP selections. This feedback enables unlicensed devices to adjust their behavior, maintaining coexistence while utilizing the spectrum efficiently.

Inventive Principle:

Principle #23Feedback

4Ease of operation

If conventional channel access control is used, then simple access is provided, but delay time for delay-sensitive data increases

Engineering Contradiction:

Improvechannel access simplicityVSAvoiddata delay time

Core Design Contradiction:

Ease of operationVSLoss of time

Solution Approach 1:

The patent performs preliminary actions by sending AP selection messages and channel access control messages before actual data transmission. This preliminary coordination establishes priority relationships and reduces contention, thereby reducing delay for delay-sensitive data while maintaining operational simplicity.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces channel access control messages as intermediaries that facilitate priority-based access. These messages enable delay-sensitive data to obtain preferential treatment without complicating the basic access mechanism, thus reducing delay while preserving ease of operation.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS9585166B2Method of controlling channel access

Publication Date: 2017.02.28 LG ELECTRONICS INC

AI summary

An embodiment of the present invention provides a method of controlling channel access in a WLAN system, comprising receiving, from an access point, a first channel access control message sent to stations located in some area through a directional antenna of the access point, and attempting to access a channel according to the first channel access control message. The method enables coexistence of several users and improves scalability of a wireless system.