Wireless LAN Transmission Opportunity Granting for Multi-User MIMO
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Solution Overview
Problem
The existing CSMA/CA-based channel access method in wireless LAN systems is inefficient, particularly in VHT systems, leading to low throughput and challenges in supporting multiple user MIMO, where simultaneous channel access by multiple stations is needed.
Innovation Solution
A contention-free transmission opportunity is granted using a combined channel with multiple subchannels, where a transmission opportunity granting frame, such as an A-MPDU or MP frame, is transmitted to acknowledge and schedule multiple stations, allowing them to access the channel simultaneously through spatial multiplexing and different subchannels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If CSMA/CA-based channel access method is used, then wireless LAN system operates with basic access mechanism, but throughput is low and multiple user MIMO support is challenging
Solution Approach 1:
The channel is divided into multiple subchannels, and the transmission opportunity is segmented and allocated to multiple stations simultaneously. Each station receives a CF-poll frame indicating specific subchannels it can use, enabling parallel data transmission across different subchannels and achieving throughput of 1 Gbps or greater
Solution Approach 2:
The patent transitions from single-channel sequential access to multi-subchannel simultaneous access by introducing a new dimension of channel utilization. Multiple stations access the channel at the same time through different subchannels, moving from one-dimensional (single channel, sequential) to two-dimensional (multiple subchannels, parallel) channel access
2Productivity
If single channel is used, then channel access is simple, but radio resource usage efficiency is low
Solution Approach 1:
The combined channel is segmented into multiple subchannels (first subchannel, second subchannel, etc.), allowing the access point to allocate different subchannels to different stations. This segmentation enables more efficient utilization of radio resources by allowing simultaneous transmissions on multiple subchannels
Solution Approach 2:
The combined channel structure serves multiple functions: it provides both a first subchannel and a second subchannel for simultaneous data transmission to different stations. The channel structure is designed to be universally applicable for supporting multiple user MIMO and achieving high throughput
3Productivity
If multiple stations access channel simultaneously, then throughput increases, but channel access coordination becomes complex
Solution Approach 1:
The access point performs preliminary action by transmitting CF-poll frames to multiple stations before they transmit data. These frames indicate which subchannels each station should use, pre-coordinating the simultaneous access and avoiding conflicts during actual data transmission
Solution Approach 2:
The CF-poll frames serve as feedback from the access point to stations, providing information about which subchannels are allocated to each station. This feedback mechanism enables coordinated simultaneous access by informing stations of their assigned resources before transmission begins
Data Source
AI summary
According to one embodiment, a method for granting a transmission opportunity in a wireless local area network includes: transmitting a transmission opportunity (TXOP) granting frame to grant a TXOP to a plurality of target stations; and receiving a frame from each of the plurality of target stations that has acquired the TXOP upon receiving the TXOP granting frame.