Asynchronous Multi-AP Scheduling via Frequency Segmentation
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Solution Overview
Problem
Existing multi-access point (AP) wireless communication systems require strict physical layer protocol data unit (PPDU) alignment to avoid adjacent channel interference, which constrains transmission and increases overhead, especially when sufficient frequency/spatial separation exists between coordinated APs' basic service sets (BSSs).
Innovation Solution
A lightweight Orthogonal Frequency-Division Multiple Access (OFDMA) mechanism that allows coordinated APs to operate without PPDU alignment by a coordinating AP allocating time-frequency resources within a transmission opportunity (TXOP), enabling transmission power control and reducing overhead, while allowing asynchronous transmissions on different frequency segments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If strict PPDU alignment is required to avoid adjacent channel interference, then interference is prevented, but transmission flexibility is constrained and overhead increases
Solution Approach 1:
The patent divides the frequency spectrum into multiple non-contiguous frequency segments (e.g., 20 MHz segments separated by guard bands) that are allocated to different coordinated APs. This segmentation allows each AP to transmit independently on its assigned frequency segment without requiring time synchronization, thereby eliminating the need for strict PPDU alignment while preventing adjacent channel interference through frequency separation.
Solution Approach 2:
The patent transitions from time-domain synchronization (PPDU alignment) to frequency-domain resource allocation. Instead of coordinating transmissions in the time dimension by aligning PPDUs, the system allocates specific frequency segments to each AP, moving the coordination mechanism to the frequency dimension. This dimensional shift eliminates the need for temporal alignment while maintaining interference prevention.
2Reliability
If PPDU alignment is enforced for multi-AP coordination, then adjacent channel interference is avoided, but spectrum efficiency deteriorates due to reduced transmission opportunities
Solution Approach 1:
The coordinating AP segments the available spectrum into multiple frequency segments and allocates them to different coordinated APs independently. Each AP can transmit on its allocated frequency segment at any time within the TXOP without waiting for alignment opportunities, significantly increasing transmission opportunities and spectrum efficiency while maintaining interference avoidance through frequency separation.
Solution Approach 2:
By allowing asynchronous transmissions on different frequency segments, the system enables continuous useful transmission actions from multiple APs simultaneously. Unlike PPDU alignment which creates periodic transmission opportunities, this approach allows each AP to transmit continuously whenever data is available, maximizing spectrum utilization and eliminating idle time caused by synchronization requirements.
3Device complexity
If coordinated APs transmit asynchronously on different frequency segments, then overhead is reduced and flexibility increases, but interference control becomes more challenging
Solution Approach 1:
The patent introduces a coordinating AP as an intermediary that performs frequency segment allocation and transmission power control. The coordinating AP receives allocation requests from coordinated APs, assigns appropriate frequency segments, and communicates the allocation decisions back to the coordinated APs. This intermediary mechanism simplifies interference control by centralizing the coordination function while allowing asynchronous transmissions.
Solution Approach 2:
The system dynamically adjusts transmission parameters including frequency segment allocation, transmission power levels, and guard band configurations based on channel conditions and interference requirements. By changing these parameters adaptively, the system maintains effective interference control despite asynchronous transmissions, with the coordinating AP managing parameter adjustments based on feedback from coordinated APs and channel measurements.
Data Source
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AI summary
This disclosure describes systems, methods, and devices related to scheduling asynchronous transmissions by other access point (AP) devices in a multi-AP environment. A method may include a coordinating AP identifying a first time for a first coordinated AP device to send a first physical layer (PHY) protocol data unit (PPDU) using a first frequency segment; identifying a second time different than the first time for a second coordinated device to send a second PPDU using a second frequency segment; generating one or more frames comprising indications that the first AP device is to send the first PPDU using the first frequency segment and that the second AP device is to send the second PPUD using the second frequency segment; and causing to send the one or more frames to the first coordinated AP device and the second coordinated AP device.