Access Point Beacon Frames for Wireless Location Accuracy
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Solution Overview
Problem
In multi-channel wireless networks, the limited frequency of probe requests from client devices, especially due to power-saving measures, hinders accurate location tracking by access points, as they rely on these requests to determine device location.
Innovation Solution
The solution involves configuring access points to transmit beacon frames with false data indications on specific channels, allowing them to collect more signal samples from client devices, even when they are in power-save mode, and coordinating multiple access points to switch channels and collect signal strength data across different channels for triangulation-based location estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If access points rely on periodic probe requests from client devices to determine location, then location tracking can be implemented, but location accuracy deteriorates because probe requests are transmitted infrequently
Solution Approach 1:
Instead of waiting for client devices to send probe requests, the access point initiates communication by sending beacon frames to client devices. This inversion of the communication direction allows the access point to actively solicit responses and collect signal strength measurements, thereby increasing the quantity of location data without relying on client-initiated probe requests.
Solution Approach 2:
The patent introduces an intermediary mechanism where the access point sends beacon frames that trigger client responses. These beacon frames act as intermediaries that facilitate communication between the access point and client devices, enabling the collection of location information without requiring direct client-initiated probe requests.
2Measurement precision
If client devices transmit probe requests frequently to improve location accuracy, then location accuracy improves, but device battery life deteriorates
Solution Approach 1:
The communication initiative is inverted from client-to-access point to access point-to-client. The access point sends beacon frames that client devices respond to, shifting the energy burden from frequent client transmissions to less frequent access point transmissions. This reduces client device battery consumption while maintaining location tracking accuracy.
Solution Approach 2:
The access point performs the work of initiating location tracking communications by sending beacon frames, rather than requiring client devices to actively send probe requests. This self-service approach by the access point reduces the energy requirements for client devices while maintaining the ability to track location accurately.
3Productivity
If multiple access points operate on different channels simultaneously, then network capacity increases, but location tracking deteriorates because access points cannot coordinate to collect sufficient signal samples
Solution Approach 1:
The access points employ periodic action by scheduling their beacon frame transmissions and channel switching in coordinated time intervals. This periodic coordination ensures that multiple access points operating on different channels can systematically collect signal samples from client devices without interfering with each other, maintaining both network capacity and location tracking accuracy.
Solution Approach 2:
The access points dynamically switch channels in a coordinated manner, adjusting their operating channels based on scheduled time periods. This dynamic channel switching allows multiple access points to share the wireless medium efficiently while ensuring that each access point can collect sufficient signal samples for accurate location tracking at appropriate times.
Data Source
AI summary
The present disclosure discloses a method and network device for improving location accuracy in multi-channel wireless networks. Specifically, to coordinate with other Access Points (APs) and improve location accuracy of client devices, each access point can (a) obtain a schedule of another neighboring AP; (b) switch to the operating channel of the neighboring AP at a scheduled time for communication exchanges between the neighboring AP and the client device, (c) listen to the communication exchanges between the neighboring AP and the client device; (d) collecting signal samples, e.g., signal strength associated with messages originated from the client device; and (e) send the report to the location engine to allow the location engine collect more signal samples associated with the client device, thereby more accurately determine the location of the client device; etc.