Multi-AP CoA Frame Coordination for Hidden Node Protection
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Solution Overview
Problem
Existing multi-AP operations in wireless local area networks (WLANs) face challenges in coordinating AP operations to address hidden nodes and ensuring compatibility with legacy STAs, leading to disrupted transmissions and inefficient resource allocation.
Innovation Solution
The proposed solution involves a coordinated announcement (CoA) frame that includes resource allocations for coordinated APs, allowing them to transmit duplicated legacy frames and CTS frames to inhibit associated station transmissions, and supports legacy STA operations through signaling mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multi-AP operations are implemented to improve throughput and latency, then network performance is improved, but coordination complexity between APs increases
Solution Approach 1:
A coordinator AP is designated as an intermediary to manage resource allocation and coordination among multiple APs. The coordinator AP receives resource allocation information and transmits it to other coordinated APs, centralizing the coordination function to reduce overall system complexity while enabling multi-AP operations for improved throughput and latency
Solution Approach 2:
The multi-AP system is segmented into distinct functional roles: a coordinator AP that manages resource allocation and coordinated APs that execute transmissions. This segmentation allows complex coordination tasks to be divided into manageable functions, with the coordinator handling decision-making and individual APs handling execution, thereby reducing coordination overhead
2Reliability
If coordinated APs transmit duplicated legacy frames to protect against hidden nodes, then medium protection is improved, but airtime consumption increases
Solution Approach 1:
Coordinated APs transmit duplicated legacy frames (such as CTS frames) in advance before actual data transmissions to reserve the medium and protect against hidden node interference. This preliminary action ensures that stations associated with coordinated APs are already inhibited from transmitting during the protected period, preventing conflicts without requiring additional protection mechanisms during data transmission
Solution Approach 2:
Instead of creating entirely new protection mechanisms, the system uses copies of existing legacy wireless frames (such as CTS frames) that stations already recognize and respond to. By transmitting these duplicated legacy frames, the system leverages existing protocol knowledge at stations to achieve medium protection while maintaining compatibility with traditional frame structures
3Productivity
If resource allocation is centralized in one AP, then coordination efficiency is improved, but single point of failure risk increases
Solution Approach 1:
The coordinator AP serves as an intermediary that receives resource allocation information and distributes it to coordinated APs. This intermediary role enables centralized coordination efficiency while the system maintains reliability through the distributed nature of actual data transmissions across multiple APs, so failure of one coordinator can be mitigated by the distributed architecture
Data Source
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AI summary
An extremely high throughput (EHT) access point (AP) may be configured to operate as a coordinated AP (API) in a multi-AP group that includes a coordinator AP (APO) and one or more other coordinated APs of a set of coordinated APs. The set of coordinated APs may include at least the AP1 and a second coordinated AP (AP2). The AP1 may decode a coordinated announcement (CoA) frame received from the AP0 during a transmission opportunity (TXOP) acquired by the AP0. The CoA frame may indicate a resource allocation for the AP1 and a resource allocation for the AP2. The resource allocations may be for use during a remainder of the TXOP for data (MU DL or UL) communication/exchange with their associated stations. The CoA frame may comprise instructions to instruct the AP1 and the AP2 to transmit duplicated legacy frames to inhibit transmissions of associated stations during the resource allocations.