TXOP Protection via Trigger Frame CTS Exchange
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Solution Overview
Problem
The existing RTS/CTS frame exchange protocol in WLAN systems is not suitable for uplink Multi-User (MU) environments, failing to effectively protect Transmission Opportunity (TXOP) in downlink and uplink MU transmissions.
Innovation Solution
A method is introduced where a trigger frame containing information on the first duration for exchanging multiple Clear-to-Send (CTS) frames is received by a reception STA, allowing it to transmit CTS frames within a specified duration, thereby protecting the TXOP for downlink data transmission and enabling TXOP protection in uplink MU environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If simple RTS/CTS frame exchange is used, then device complexity is reduced, but TXOP protection reliability deteriorates in MU environments
Solution Approach 1:
The patent segments the traditional single RTS/CTS exchange into multiple CTS frame exchanges. The access point transmits a trigger frame that initiates multiple STAs to send CTS frames sequentially, dividing the protection mechanism into discrete manageable units that can be individually controlled and tracked
Solution Approach 2:
The patent introduces dynamic elements by allowing the access point to flexibly configure the number of CTS frames to be exchanged based on the number of STAs and transmission requirements. The trigger frame dynamically specifies parameters such as the number of CTS frames, resource allocation, and timing, adapting the protection mechanism to varying MU transmission scenarios
2Ease of operation
If traditional RTS/CTS protocol is applied, then ease of operation is maintained, but adaptability to MU environments deteriorates
Solution Approach 1:
The patent creates a universal protection mechanism that functions across both traditional and MU environments. The trigger frame-based multiple CTS exchange protocol can handle single-STA and multi-STA scenarios, resource allocation for multiple users, and different transmission types (uplink, downlink, mixed), making it adaptable to various MU transmission configurations while maintaining operational simplicity through standardized frame structures
Solution Approach 2:
The trigger frame serves as an intermediary that coordinates the interaction between the access point and multiple STAs. It carries configuration information for the upcoming CTS exchange sequence, resource allocation details, and timing parameters, mediating the complex MU transmission coordination while presenting a simplified interface to participating STAs
3Reliability
If multiple CTS frames are exchanged, then TXOP protection effectiveness is improved, but loss of time increases due to additional frame exchanges
Solution Approach 1:
The patent structures the multiple CTS frame exchanges as periodic, sequential actions with predetermined timing intervals. Each STA transmits its CTS frame at a specific time slot following the trigger frame, creating a regular pattern that allows other STAs to predict and avoid transmissions during the protected period, thereby reducing actual collision time while maintaining protection effectiveness
Solution Approach 2:
The trigger frame performs preliminary action by announcing the upcoming multiple CTS exchange sequence, specifying the number of CTS frames, resource allocation, and timing parameters in advance. This allows receiving STAs to prepare and configure their NAV (network allocation vector) beforehand, knowing when the channel will be occupied, thus minimizing unnecessary waiting time and reducing overall time loss
Data Source
AI summary
Provided is a method and apparatus for protecting a TXOP in a wireless communication system. The method for protecting a TXOP may comprise the steps of: receiving a trigger frame containing information on a first interval for an exchange of multiple clear-to-send (CTS) frames from a transmission station (STA) by a reception STA; and transmitting CTS frames to the transmission STA in the first interval by the reception STA.