Geometrical Scheduling for Acoustic Positioning Beacons
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Solution Overview
Problem
The Cricket Indoor Location System faces scalability issues due to uncoordinated beacon transmissions, leading to poor performance in large-scale deployments, where listening devices may not receive location updates for multiple seconds, and existing solutions like CSMA/CD and TDMA slow down system performance.
Innovation Solution
A geometrical scheduling algorithm that allows multiple beacons to transmit acoustic pulses simultaneously by timing out beacons based on their acoustic cone overlap, enabling rapid cycling through all beacons and reducing the need for complex data encoding or multiple acoustic frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If beacons transmit acoustic pulses sequentially using CSMA/CD or TDMA to avoid overlap, then transmission coordination is improved, but system scalability and location update speed deteriorate
Solution Approach 1:
The system dynamically adjusts beacon transmission timing based on real-time acoustic environment conditions. Instead of fixed sequential scheduling, beacons can transmit simultaneously when acoustic cone analysis determines no interference will occur, allowing the system to adapt between sequential and parallel transmission modes based on environmental factors
Solution Approach 2:
The patent changes the fundamental parameter from time-division scheduling to spatial-acoustic-division scheduling. By analyzing acoustic cone overlap and adjusting transmission parameters based on spatial relationships and acoustic propagation characteristics, the system enables multiple beacons to transmit concurrently without interference, dramatically improving location update speed while maintaining coordination reliability
2Productivity
If multiple beacons transmit simultaneously, then location update speed improves, but acoustic pulse interference increases
Solution Approach 1:
The system applies local quality analysis by examining the acoustic environment in specific spatial zones. Each beacon's acoustic cone is analyzed individually, and transmission permissions are granted locally based on whether that specific beacon's acoustic propagation path overlaps with others. This allows simultaneous transmission in non-overlapping zones while preventing interference in overlapping zones
Solution Approach 2:
The patent introduces acoustic cone analysis as an intermediary mechanism that mediates between multiple beacons attempting simultaneous transmission. This intermediary evaluates the acoustic environment and determines whether simultaneous transmission will cause interference, acting as a smart gatekeeper that enables concurrency when safe and prevents it when harmful
3Ease of operation
If beacon transmissions are uncoordinated to simplify system operation, then ease of operation improves, but tracking accuracy deteriorates
Solution Approach 1:
The system implements self-service through autonomous acoustic cone analysis at each beacon. Instead of requiring centralized coordination or complex inter-beacon communication, each beacon independently analyzes its own acoustic environment and determines appropriate transmission timing. This self-service approach maintains tracking accuracy while simplifying system operation
Solution Approach 2:
The patent applies preliminary action by pre-calculating and storing acoustic cone characteristics for each beacon before transmission occurs. This preliminary analysis of acoustic propagation paths, boundaries, and overlap potential allows beacons to make immediate transmission decisions without real-time coordination, ensuring both accuracy and operational simplicity
Data Source
AI summary
Described is an improved active-beacon/passive-listener time difference of arrival navigation system that relies on the multiple beacons to transmit uncoded acoustic pulses of a same frequency that propagate in the system at a same time for high-speed device tracking. Listening devices may receive multiple encoded radio frequency pulses (RF) prior to a single acoustic pulse, and then resolve which RF pulse corresponds to the acoustic pulse using triangulation techniques.