Reference Phase Offset Regeneration in RTLS
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Solution Overview
Problem
Real-time location systems (RTLS) face challenges in recovering from power cycles, as the process of regenerating reference phase offsets is inconvenient, time-consuming, and often impractical, especially in noisy environments with RF interference, leading to inaccurate location calculations.
Innovation Solution
The system generates a residual reference table based on established reference phase offsets and timing measurements propagated through a chain of receivers, allowing for the re-establishment of valid reference phase offsets without re-obtaining reference tag blink data, thereby avoiding the need for a full regeneration process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reference phase offsets are regenerated after a power cycle by re-obtaining reference tag blink data, then the RTLS system can recover from the power cycle, but the process is time-consuming and inconvenient
Solution Approach 1:
The system performs preliminary actions by maintaining a history of reference phase offsets before power cycles occur. When a power cycle happens, the system can quickly restore reference phase offsets from this pre-established history without needing to re-obtain reference tag blink data, thus resolving the contradiction between reliability and time loss.
Solution Approach 2:
The system creates a copy of the reference phase offset history and stores it in a database. This copy can be quickly restored after power cycles without requiring the original reference tag blink data collection process, thereby reducing recovery time while maintaining reliability.
2Measurement precision
If reference phase offsets are regenerated in noisy environments with RF interference, then the RTLS system can maintain location accuracy, but the process becomes impractical
Solution Approach 1:
The system performs preliminary actions by establishing and storing reference phase offset history before entering noisy environments or before power cycles. This pre-established history remains valid even in challenging RF conditions, eliminating the need to perform difficult regeneration operations in noisy environments while maintaining location accuracy.
Solution Approach 2:
The reference phase offset history database acts as an intermediary that stores pre-established reference information. This intermediary allows the system to bypass the difficult process of regenerating reference phase offsets in noisy RF environments, simply by retrieving stored values, thus maintaining measurement precision while improving ease of operation.
3Reliability
If a full reference regeneration process is performed, then valid reference phase offsets can be re-established, but the process is laborious and time-consuming
Solution Approach 1:
The system segments the reference phase offset information into a history component and a current component. After power cycles, the system can quickly restore the history component from stored data without needing to re-collect all reference tag blink data, thereby maintaining reliability while significantly improving productivity.
Solution Approach 2:
The system discards the need to re-collect reference tag blink data after power cycles and instead recovers reference phase offsets from the stored history database. This approach maintains the validity of reference phase offsets while dramatically reducing the time and effort required for re-establishment.
Data Source
AI summary
Methods and apparatus for reference regeneration in real time location systems are disclosed. An example disclosed method includes obtaining reference phase offsets from a plurality of radio frequency identification (RFID) receivers; transmitting a first synchronization signal via a wireline link to obtain differential wireline coarse sync measurements; determining a residual offset table based at least in part on the differential wireline coarse sync measurements and the reference phase offsets; transmitting a second synchronization signal via the wireline link to obtain revised differential wireline coarse sync measurements; generating revised reference phase offsets by combining the revised differential wireline coarse sync offsets with the residual offset table; and determining a physical location of a RFID tag based at least in part on i) the revised reference phase offsets and ii) RFID receiver clock measurements corresponding to a time-of-arrival of over-the-air data transmitted from the RFID tag.