Phase Ranging Mitigation for BLE RTLS Interference
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Solution Overview
Problem
Real-Time Location Systems (RTLS) face inaccuracies in ranging values due to environmental conditions, noise, multi-path channel effects, and interference from other RF devices operating on the same frequencies, leading to unreliable location determinations in environments with multiple competing RF systems.
Innovation Solution
The implementation of a BLE communications system that employs phase ranging mitigation techniques, including hop duplication, hop interpolation, and receiver ADC DC offset correction, to improve ranging accuracy by detecting and compensating for interference and using duplicate or interpolated data to replace corrupted hops, thereby enhancing location determination precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase ranging is performed in environments with multiple RF systems, then location determination can be achieved, but ranging accuracy deteriorates due to interference and collision of transmissions
Solution Approach 1:
The system performs preliminary actions by executing multiple hop sequences in advance and storing them in buffers before actual ranging occurs. When interference is detected during ranging, the system can immediately switch to using pre-computed hop data from buffers, avoiding the need for iterative re-measurement and maintaining ranging accuracy despite RF interference.
Solution Approach 2:
The patent implements copying by creating duplicate hop sequences and storing them in separate buffers (first buffer, second buffer, third buffer). When interference corrupts a hop measurement, the system copies alternative hop data from the buffers to replace the corrupted measurement, thereby maintaining measurement accuracy without retransmitting the entire ranging sequence.
2Measurement precision
If iterative measurements and recalculation are performed to correct ranging errors, then location accuracy can be improved, but battery consumption increases
Solution Approach 1:
The system performs preliminary computation of multiple hop sequences and stores them in buffers before actual ranging occurs. When interference is detected during ranging, the system can immediately switch to using pre-computed hop data from buffers, avoiding the need for iterative re-measurement and reducing battery consumption while maintaining location accuracy.
Solution Approach 2:
The patent creates copies of hop data in multiple buffers and uses these copies to replace corrupted measurements when interference occurs. This eliminates the need for iterative re-measurement and recalculation, as the alternative hop data is already prepared and stored, thereby reducing energy consumption while maintaining measurement precision.
Data Source
AI summary
A communications system, including at least one tag and a plurality of beacons. The tags are configured to detect beacon advertisement messages, initiate a connection with at least one of the plurality of and transmit a Constant Tone (CT) to the at least one of the plurality of beacons. The tag is further configured to determine a location thereof based on the sampled CT from both the beacon and the tag and then report the location via the one of the beacons and/or an access point. Phase ranging mitigation techniques which include hop duplication, hop interpolation and ADC DC offset correction are employed so as to provide more accurate ranging values even in the case where there are many other devices in local proximity and which are competing for use of the same RF channels as those used by the tags and beacons.