AP-Assisted Wireless Positioning via Scheduled Backoffs
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Solution Overview
Problem
Existing wireless positioning techniques in WLANs impact AP-station link throughput due to high frame exchange requirements, causing measurement latency and bandwidth issues when serving multiple stations.
Innovation Solution
An AP-assisted wireless positioning framework that broadcasts a message with a transmission schedule identifying stations, using distinct backoffs to avoid collisions, and determines range based on received transmission times, reducing latency and bandwidth impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing wireless positioning techniques are used to determine range between AP and station, then positioning information can be obtained, but AP-station link throughput is impacted due to large number of frames exchanged
Solution Approach 1:
The AP schedules positioning transmissions in advance by broadcasting a schedule that identifies when stations should transmit. This preliminary scheduling action eliminates the need for multiple iterative frame exchanges, as the timing is predetermined and coordinated before the actual measurement occurs.
Solution Approach 2:
The patent combines multiple positioning measurements into a single coordinated transmission event. By merging the scheduling information and measurement transmission into a unified approach with distinct backoffs for each station, the system obtains positioning data for multiple stations simultaneously without requiring separate frame exchanges for each measurement.
2Adaptability or versatility
If multiple stations are served for positioning, then positioning coverage is expanded, but measurement latency increases and system throughput is impacted
Solution Approach 1:
The patent segments the positioning process by assigning distinct backoffs to different stations based on their identifiers. This segmentation allows each station to transmit at a predetermined, non-overlapping time slot, enabling the AP to serve multiple stations simultaneously without increasing measurement latency, as each station's measurement is isolated in time.
Solution Approach 2:
The AP performs preliminary scheduling by broadcasting a message that identifies the transmission schedule for all stations before measurements occur. This advance scheduling eliminates coordination delays and ensures that when measurements take place, all stations are ready to transmit at their predetermined times without waiting or collision avoidance delays.
3Measurement precision
If traditional positioning frame exchanges are used, then range can be determined, but bandwidth consumption increases
Solution Approach 1:
The patent merges multiple positioning measurements into a single coordinated transmission window. By scheduling multiple stations to transmit simultaneously with distinct backoffs, the system obtains range information for all stations in one broadband event rather than requiring separate frame exchanges for each station, thereby reducing total bandwidth consumption.
Solution Approach 2:
The AP broadcasts scheduling information in advance that specifies exactly when each station should transmit. This preliminary action ensures that all necessary positioning data can be collected in a single efficient transmission round, eliminating the need for repeated bandwidth-intensive frame exchanges that would be required by traditional iterative measurement approaches.
Data Source
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AI summary
Methods, systems, and devices are described for a wireless positioning framework in which an access point (AP) broadcasts a message within a beacon interval that identifies a transmission schedule for a set of stations. The message may include an information element identifying the stations in the set. The set may be determined based on station clock drifts and/or a ranging accuracy sought by the AP. The AP may also provide a station identifier, and frame spacing and delay parameters, which may be used to determine a distinct backoff for each station. Using distinct backoffs allow the stations to avoid collisions when sending the transmissions. The AP may receive the transmissions according to the identified schedule and may determine a range (e.g., round-trip time) for each station in the set based at least on a time at which the respective transmission is received.