Slot-Based Channel Access Control in Wireless LAN

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Solution Overview

Problem

In wireless local area networks (WLANs), the increased probability of collisions among multiple stations (STAs) during channel access leads to delays and inefficient use of network resources, especially when some STAs do not listen to beacons or are hidden nodes, resulting in reduced power efficiency and increased power consumption.

Innovation Solution

A slot-based channel access control method where an access point allocates slots to STAs based on priority, using restricted access windows (RAWs) and periodic RAWs, allowing for efficient use of network resources by releasing unused slots and prioritizing STAs that need to save power or transmit urgent data, thereby reducing collisions and power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If slot-based channel access is implemented to reduce collisions, then channel access reliability is improved, but device complexity increases due to slot allocation management

Engineering Contradiction:

Improvechannel access reliabilityVSAvoidslot allocation management complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The channel access time is segmented into discrete slots, with each slot allocated to specific STAs. This segmentation allows the AP to divide the beacon interval into multiple time slots (e.g., first slot, second slot, third slot) and assign them to different STAs or STA groups, thereby reducing collisions while maintaining manageable complexity through structured time division

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Slot allocations are determined in advance before beacons are transmitted. The AP pre-determines slot assignments for STAs based on their needs (e.g., power saving requirements, urgent data transmission) and communicates these allocations through beacon frames, allowing STAs to prepare and access channels without collisions at predetermined times

Inventive Principle:

Principle #10Preliminary action

2Ease of operation

If slots are allocated to all STAs to ensure fair access, then channel access equity is improved, but network resource utilization deteriorates due to unused slots

Engineering Contradiction:

Improvechannel access equityVSAvoidnetwork resource utilization

Core Design Contradiction:

Ease of operationVSProductivity

Solution Approach 1:

The slot allocation system is dynamic rather than static. The AP can adjust slot assignments in different beacon intervals based on current network conditions, STA activity patterns, and resource availability. STAs that do not need slots in certain intervals do not receive them, allowing slots to be reallocated to other STAs, thus maintaining equity while improving overall resource utilization

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

Slots that are not used by allocated STAs are released back to the pool of available resources. The AP identifies unused slots (where allocated STAs have no data to transmit or are in power saving mode) and makes these slots available for reallocation to other STAs in subsequent beacon intervals, thereby recovering wasted network resources

Inventive Principle:

Principle #34Discarding and recovering

3Adaptability or versatility

If STAs perform channel access in DCF mode to handle dynamic traffic, then adaptability is improved, but channel access delay increases due to competition and collisions

Engineering Contradiction:

Improvechannel access adaptabilityVSAvoidchannel access delay

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The system performs preliminary slot allocation through beacon frames before actual data transmission. STAs receive advance notification of their allocated slots and prepare accordingly, eliminating the need for competitive DCF access procedures. This preliminary scheduling ensures that when STAs need to access the channel, they do so at predetermined collision-free times, significantly reducing access delays while maintaining adaptability through dynamic slot reassignment

Inventive Principle:

Principle #10Preliminary action

4Speed

If slot allocation is performed for every beacon interval to improve responsiveness, then channel access responsiveness is improved, but processing overhead increases

Engineering Contradiction:

Improvechannel access responsivenessVSAvoidprocessing overhead

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

Slot allocations are performed periodically at beacon intervals rather than continuously for every transmission opportunity. The AP determines slot assignments at regular beacon intervals and communicates these allocations to STAs, providing responsive channel access scheduling while avoiding the excessive processing overhead of continuous real-time slot allocation for every potential transmission

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS10779318B2Device and method for controlling slot-based channel system, and slot-based channel access terminal in wireless LAN

Publication Date: 2020.09.15 ELECTRONICS & TELECOMM RES INST

AI summary

An apparatus and a method of controlling slot-based channel access by an access point (AP) to manage a network in a wireless local area network (WLAN) environment and a slot-based channel access terminal are disclosed. A slot-based channel access control apparatus of a WLAN system according to an exemplary embodiment determines one of each terminal and a group of terminals as a slot allocation target, allocates a slot defined in a beacon interval to the determined terminal or group to distinguish channel access time, and transmits a beacon including information on the allocated slot.