Wireless FTM Message Error Fields for Precision Timing
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Solution Overview
Problem
Current satellite positioning systems face challenges in accurately measuring round trip time (RTT) and time of flight (TOF) for precise location-based services, especially in indoor environments, due to limitations in expressing timing errors and range measurements with sufficient precision.
Innovation Solution
The implementation of a method involving fine timing measurement (FTM) messages with a time of departure (TOD) field and an error field capable of expressing maximum TOD error in five bits or less, up to 1.0 msec, and range reports with a field expressing maximum range error in five bits or less, up to 2000 m, to enhance synchronization and accuracy of clock states and range calculations between wireless stations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional timing measurement methods are used, then the measurement process is simple, but the precision of RTT and TOF measurements is insufficient for accurate location-based services
Solution Approach 1:
The patent applies parameter changes by modifying the message structure to include dedicated fields for timing measurements (TOD, TOA) and error expressions. The error fields use exponential notation with 5-bit precision to represent maximum timing errors, enabling precise RTT and TOF measurements while maintaining manageable message complexity through standardized field definitions.
2Measurement precision
If more bits are used to express timing errors, then the measurement precision improves, but the data transmission efficiency decreases
Solution Approach 1:
The patent uses parameter changes by implementing exponential notation for error fields, where 5 bits represent maximum timing errors ranging from 1 picosecond to 1 millisecond. This logarithmic parameter encoding achieves high measurement precision (down to 1 ps) while minimizing data transmission volume compared to linear bit representations.
3Reliability
If synchronization accuracy between wireless stations is improved, then location-based service accuracy improves, but the complexity of error expression and measurement increases
Solution Approach 1:
The patent implements feedback mechanisms where wireless stations exchange FTM messages containing timing measurements and error information. The receiving station uses this feedback to calculate RTT and TOF values, adjusting clock state synchronization based on measured errors. This iterative feedback process improves synchronization accuracy while managing complexity through standardized error expression fields.
4Measurement precision
If range error expression precision is improved, then positioning accuracy improves, but the message field requirements increase
Solution Approach 1:
The patent applies parameter changes by using exponential notation for range error fields, where 5 bits represent maximum range errors from 0.00025 meters to 2000 meters. This logarithmic encoding achieves high positioning accuracy (down to 0.25 mm) while minimizing the number of message fields required, as the same 5-bit structure serves both timing and range error representations.
Data Source
AI summary
Disclosed are systems, devices and methods for transmission of messages between wireless transceiver devices including fields representing values such as, for example, a range between devices, time of transmission of a message or time of receipt of a previous message. In particular embodiments, message may also comprise fields to express a maximum error in values representing range, time of transmission of a message or time of receipt of a previous message.