Doubling the Accuracy of Indoor Positioning: Frequency Diversity
Determination of indoor position based on fine time measurement (FTM) of the round trip time (RTT) of a signal between an initiator (smartphone) and a responder (Wi-Fi access point) enables a number of applications. However, the accuracy currently attainable—standard deviations of 1–2 m in distance...
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| Format: | Article |
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MDPI AG
2020
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| Online Access: | https://hdl.handle.net/1721.1/125354 |
| _version_ | 1811074908051996672 |
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| author | Horn, Berthold K. P. |
| author2 | Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science |
| author_facet | Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science Horn, Berthold K. P. |
| author_sort | Horn, Berthold K. P. |
| collection | MIT |
| description | Determination of indoor position based on fine time measurement (FTM) of the round trip time (RTT) of a signal between an initiator (smartphone) and a responder (Wi-Fi access point) enables a number of applications. However, the accuracy currently attainable—standard deviations of 1–2 m in distance measurement under favorable circumstances—limits the range of possible applications. An emergency worker, for example, may not be able to unequivocally determine on which floor someone in need of help is in a multi-story building. The error in position depends on several factors, including the bandwidth of the RF signal, delay of the signal due to the high relative permittivity of construction materials, and the geometry-dependent “noise gain” of position determination. Errors in distance measurements have unusal properties that are exposed here. Improvements in accuracy depend on understanding all of these error sources. This paper introduces “frequency diversity,” a method for doubling the accuracy of indoor position determination using weighted averages of measurements with uncorrelated errors obtained in different channels. The properties of this method are verified experimentally with a range of responders. Finally, different ways of using the distance measurements to determine indoor position are discussed and the Bayesian grid update method shown to be more useful than others, given the non-Gaussian nature of the measurement errors. |
| first_indexed | 2024-09-23T09:57:09Z |
| format | Article |
| id | mit-1721.1/125354 |
| institution | Massachusetts Institute of Technology |
| last_indexed | 2024-09-23T09:57:09Z |
| publishDate | 2020 |
| publisher | MDPI AG |
| record_format | dspace |
| spelling | mit-1721.1/1253542022-09-30T17:56:27Z Doubling the Accuracy of Indoor Positioning: Frequency Diversity Horn, Berthold K. P. Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science Determination of indoor position based on fine time measurement (FTM) of the round trip time (RTT) of a signal between an initiator (smartphone) and a responder (Wi-Fi access point) enables a number of applications. However, the accuracy currently attainable—standard deviations of 1–2 m in distance measurement under favorable circumstances—limits the range of possible applications. An emergency worker, for example, may not be able to unequivocally determine on which floor someone in need of help is in a multi-story building. The error in position depends on several factors, including the bandwidth of the RF signal, delay of the signal due to the high relative permittivity of construction materials, and the geometry-dependent “noise gain” of position determination. Errors in distance measurements have unusal properties that are exposed here. Improvements in accuracy depend on understanding all of these error sources. This paper introduces “frequency diversity,” a method for doubling the accuracy of indoor position determination using weighted averages of measurements with uncorrelated errors obtained in different channels. The properties of this method are verified experimentally with a range of responders. Finally, different ways of using the distance measurements to determine indoor position are discussed and the Bayesian grid update method shown to be more useful than others, given the non-Gaussian nature of the measurement errors. 2020-05-20T18:04:36Z 2020-05-20T18:04:36Z 2020-03 2020-02 Article http://purl.org/eprint/type/JournalArticle 1424-8220 https://hdl.handle.net/1721.1/125354 Horn, Berthold K. P. "Doubling the Accuracy of Indoor Positioning: Frequency Diversity." Sensors 20, 5 (March 2020): 1489 © 2020 Author http://dx.doi.org/10.3390/s20051489 Sensors Creative Commons Attribution 4.0 International license https://creativecommons.org/licenses/by/4.0/ application/pdf MDPI AG MDPI |
| spellingShingle | Horn, Berthold K. P. Doubling the Accuracy of Indoor Positioning: Frequency Diversity |
| title | Doubling the Accuracy of Indoor Positioning: Frequency Diversity |
| title_full | Doubling the Accuracy of Indoor Positioning: Frequency Diversity |
| title_fullStr | Doubling the Accuracy of Indoor Positioning: Frequency Diversity |
| title_full_unstemmed | Doubling the Accuracy of Indoor Positioning: Frequency Diversity |
| title_short | Doubling the Accuracy of Indoor Positioning: Frequency Diversity |
| title_sort | doubling the accuracy of indoor positioning frequency diversity |
| url | https://hdl.handle.net/1721.1/125354 |
| work_keys_str_mv | AT hornbertholdkp doublingtheaccuracyofindoorpositioningfrequencydiversity |