Uplink Trigger Frame Mechanism for Simultaneous Multi-User WLAN Transmission
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Solution Overview
Problem
In wireless local area networks (WLANs), existing systems face inefficiencies in radio resource usage due to the lack of simultaneous multi-user uplink transmission capabilities, leading to suboptimal channel access and contention procedures among stations (STAs).
Innovation Solution
A method and apparatus for transmitting frames in WLANs, where a station (STA) receives an uplink transmission trigger frame from an access point (AP), transmits an uplink frame through an allocated resource, and performs a backoff procedure based on channel access parameters determined by the success or failure of the transmission, enabling simultaneous multi-user uplink transmission within overlapping time resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If one STA occupies the entire transmission resource through one channel to transmit/receive a frame to/from an AP, then the transmission reliability of individual STA is improved, but the radio resource usage efficiency deteriorates
Solution Approach 1:
The transmission resource is segmented into multiple channels or frequency resources, allowing multiple STAs to transmit simultaneously on different resources. The AP assigns specific frequency resources to different STAs for uplink transmission, dividing the overall transmission resource into manageable segments that can be allocated to multiple users concurrently.
Solution Approach 2:
The system transitions from single-user transmission in one dimension to multi-user transmission by adding frequency dimension. Multiple STAs transmit uplink frames simultaneously by using different frequency resources, effectively moving from a one-dimensional time-sharing approach to a two-dimensional approach incorporating both time and frequency dimensions.
2Ease of operation
If multiple STAs attempt to access the medium simultaneously using traditional CSMA/CA, then the channel access opportunity is improved, but the contention collision increases
Solution Approach 1:
The AP performs preliminary scheduling by assigning specific frequency resources to different STAs before they transmit. This preliminary allocation prevents contention collisions by ensuring that STAs transmit on designated resources without needing to contend with each other, eliminating the harmful effects of simultaneous random access attempts.
Solution Approach 2:
The AP acts as an intermediary that coordinates uplink transmissions from multiple STAs. Instead of STAs directly contending with each other, the AP mediates the access process by receiving scheduling information from STAs and assigning appropriate frequency resources, thereby preventing collisions that would occur in direct STA-to-STA contention.
3Reliability
If the backoff procedure is performed by each STA independently, then the collision avoidance is improved, but the channel access time increases
Solution Approach 1:
The system implements feedback mechanisms where the AP receives scheduling information from STAs and provides resource allocation decisions. This feedback loop allows the AP to optimize channel access by assigning resources based on current channel conditions and STA priorities, reducing the need for lengthy independent backoff procedures while maintaining collision avoidance.
Data Source
AI summary
Disclosed are a method and apparatus for transmitting a frame. A method for transmitting a frame in a wireless LAN comprises the steps of: an STA receiving an uplink transmission trigger frame from an access point (AP), wherein the uplink transmission trigger frame triggers the transmission of an uplink frame of an STA on an overlapping time resource, and triggers the transmission of one other uplink frame of at least one other STA; the STA transmitting the uplink frame to the access point (AP) through an allocated uplink transmission resource; and the STA performing a backoff process based on channel access parameters, which have been determined according to the success of the uplink frame transmission.