Shared TXOP Scheduling for Coordinated WiFi Station Uplink Access
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Solution Overview
Problem
Current WLAN protocols, such as 802.11, constrain channel utilization efficiency by requiring non-AP STAs to wait for a trigger frame from the AP to initiate UL data transmission, leading to increased latency and low channel utilization efficiency in multi-user transmissions.
Innovation Solution
Non-AP STAs are allowed to perform TXOP scheduling in the time domain, sharing the TXOP with other STAs within the same BSS, either with or without AP coordination, through various message exchanges to inform, gain approval, and schedule channel access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple stations perform simultaneous uplink multi-user MIMO transmissions, then spectral efficiency is improved, but interference between stations occurs and reception quality deteriorates
Solution Approach 1:
The patent implements periodic time-domain scheduling where multiple stations share the channel in alternating time intervals. Specifically, the first station transmits during even time slots while the second station transmits during odd time slots, creating a periodic pattern that eliminates simultaneous transmissions and thus prevents interference while maintaining high spectral efficiency through continuous channel utilization.
2Productivity
If distributed multi-user MIMO is implemented, then system capacity is improved, but coordination complexity between stations increases
Solution Approach 1:
The patent employs feedback mechanisms where the access point transmits reference signals that receiving stations use to estimate channel states. These channel state estimates are fed back to the access point, which then uses this information to coordinate transmissions and allocate time slots optimally, thereby managing coordination complexity through structured feedback loops.
Solution Approach 2:
Before actual data transmissions begin, the patent implements preliminary channel estimation phases where reference signals are exchanged and channel states are measured. This preliminary action allows the system to pre-coordinate transmission parameters and time slot allocations based on current channel conditions, reducing the complexity of real-time coordination during actual transmissions.
3Reliability
If time-division multiplexing is used to avoid interference, then reception quality is improved, but time resource utilization decreases
Solution Approach 1:
The patent merges time-division multiplexing with multi-user MIMO techniques, allowing multiple stations to be served within each time slot through spatial multiplexing. By combining temporal separation with spatial processing, the system achieves both interference-free reception quality and improved time resource utilization, as multiple users can be served concurrently in the spatial domain while maintaining time-division structure for coordination.
Data Source
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AI summary
A wireless local area network (WLAN) protocol allowing a Transmit Opportunity (TXOP) holder to share the TXOP with other stations. An intent to share the TXOP is communicated to the Access Point (AP). Upon gaining channel access, the TXOP holder directly or indirectly communicates that the TXOP can be shared with other STAs, after which scheduling information (time and duration) are shared with the STAs. When the TXOP occurs, the STAs can access the channel at the time and for the duration specified, thus providing increased use of the TXOP to improve efficiency.