Collaborative Service Set AP Coordination for Interference Alignment
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Solution Overview
Problem
In densely populated wireless local area networks (WLANs), existing technologies lack effective methods for coordinating transmissions between access points (APs) to enhance throughput and reduce interference, leading to suboptimal performance due to lack of coordination and synchronization among APs.
Innovation Solution
A collaborative service set (CSS) system and method that includes a controller AP coordinating transmissions with member APs and stations, using null data packet announcements (NDPAs) and null data packets (NDPs) for channel sounding and interference alignment, enabling simultaneous multi-AP transmissions and oscillator frequency offset compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple APs are densely populated to increase wireless throughput, then network capacity and coverage are improved, but interference between APs increases and coordination becomes more difficult
Solution Approach 1:
The system segments the wireless network into a hierarchical structure with one controller AP and multiple member APs. The controller AP manages and coordinates transmissions from multiple member APs, allowing dense deployment while maintaining control over interference through centralized scheduling and coordination mechanisms.
Solution Approach 2:
The controller AP acts as an intermediary between member APs and stations. It receives channel feedback from stations, processes it, and coordinates transmissions among member APs. This intermediary role enables the controller to align interfering signals and manage the dense AP deployment effectively.
2Productivity
If APs transmit simultaneously to increase throughput, then network capacity is improved, but signal interference and synchronization requirements increase
Solution Approach 1:
The system performs preliminary channel sounding before simultaneous transmissions. The controller AP coordinates channel sounding procedures where stations measure channels from multiple member APs and provide feedback. This preliminary action enables the controller to pre-code signals and align interference before actual data transmissions occur.
Solution Approach 2:
The system changes signal parameters through pre-coding at the member APs based on channel feedback. The controller AP processes channel state information and determines precoding matrices that transform the transmitted signals, allowing simultaneous transmissions while managing interference through parameter transformation.
3Measurement precision
If channel sounding is performed with multiple APs to improve channel estimation accuracy, then transmission coordination is improved, but feedback overhead and processing complexity increase
Solution Approach 1:
The channel feedback mechanism is designed to serve multiple functions simultaneously. Stations provide channel feedback that is used not only for channel estimation but also for precoding calculation, interference alignment, and coordination of simultaneous transmissions. This multi-functionality reduces the need for separate signaling channels and procedures.
Solution Approach 2:
Stations perform self-measurement of channels from multiple APs and generate their own feedback reports. The feedback includes channel state information that stations autonomously calculate and report to the controller AP, reducing the need for complex centralized measurement and coordination infrastructure.
Data Source
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AI summary
In one embodiment, a collaborative service set (CSS) includes a controller access point (AP) configured to be associated with a first plurality of stations and a first member AP, where the first member AP is associated with a second plurality of stations, where the controller AP is configured to coordinate transmissions between the first member AP and the second plurality of stations with transmissions between the controller AP and the first plurality of stations, where the controller AP and the first member AP are configured to transmit messages simultaneously.