Experimental Assessment of Orientation Sensing and Constructive Interference in Passive RFID Systems

Publikation: Bog/antologi/afhandling/rapportPh.d.-afhandlingForskning

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Resumé

This thesis focus on passive Radio Frequency IDentication (RFID), a tech-
nology designed for automated identication of tagged objects. The tags
are small passive devices powered by the wireless signal from the reader.
Their simple operation thus solely allows them to reply with their unique ID
when requested by the reader, which is a high power handheld or stationary
transceiver. The RFID technology has matured over the past two decades,
but still there exist ambiguities regarding the reading, or interrogation, of
tags. Due to the passive nature of the tags, they are severely aected by
the environment and the object they are attached to. Hence they may be
rendered unable to reply to the readers request, in spite of being within
the expected read range of the reader. This is referred to as False Negative
Detections (FNDs). Similarly, constructive eects in the environment can en-
able a tag outside the expected read range to reply. This is denoted a False
Positive Detection (FPD). It is desired to reduce the occurrence of these false
positive and negative detections hence in this thesis it is proposed to impose
interference on the communication between reader and tag. Interference has
a well-known blocking eect, and the experimental investigations show how
tag replies outside the expected read range are blocked, as expected. More-
over, tuned and detuned tags alike are aected by the decreased Signal to
Interference and Noise Ratio (SINR) due to the imposed interference, hence
their read ranges are thus eectively equalized. From the investigations it
can therefore be concluded that the imposed interference has a constructive
eect as it enables design of well dened and sharply bounded interrogation
v
zones, where tags are read with high probability regardless of the level of
detuning they might experience.
Moreover, this thesis proposes to use passive RFID tags as orientation
sensors. This is an innovative application for RFID technology in itself,
but orientation sensing can also help existing RFID applications that relies
on the Received Signal Strength (RSS) in the tag reply. Many Ultra High
Frequency (UHF) RFID tags utilize a dipole antenna, and the RSS metric
of the tag reply is thus prone to polarization and gain mismatches between
tag and reader antennas. Being able to estimate the orientation can help
mitigate this eect. It is proposed to let a reader antenna collect information
about the polarization of the received tag reply by decomposing the RSS into
the horizontal and vertical dimensions using a dual linearly polarized reader
antenna. The method is evaluated experimentally, and when the movement
of the tag is limited to two dimensions, i.e. a plane, the results for track-
ing the tag orientation are promising. Tag movements in three dimensions
complicates however the orientation estimate. Multiple reader antenna are
therefore utilized in order to collect samples of the tag reply from multiple
directions, and their data are fused using Kalman ltering. The nal results
show good potential, as even simple data processing enables recognition of
gestures, i.e. predened motions with the tag. However, the estimate of
the three dimensional orientation vector oers relatively low precision, and
does therefore not allow dedicated motion capture of the tag. But it has
been shown through experimental investigations that the orientation infor-
mation is available in the tag reply, and using more advanced methods for
data processing, a reliable orientation estimate can be obtained.
OriginalsprogDansk
Udgivelses stedAalborg Universitet
Antal sider129
ISBN (Trykt)978-87-92328-90-8
StatusUdgivet - 1 sep. 2012

Citer dette

@phdthesis{91665602e5c54c7394b3ff81a2e0980d,
title = "Experimental Assessment of Orientation Sensing and Constructive Interference in Passive RFID Systems",
abstract = "This thesis focus on passive Radio Frequency IDentication (RFID), a tech- nology designed for automated identication of tagged objects. The tags are small passive devices powered by the wireless signal from the reader. Their simple operation thus solely allows them to reply with their unique ID when requested by the reader, which is a high power handheld or stationary transceiver. The RFID technology has matured over the past two decades, but still there exist ambiguities regarding the reading, or interrogation, of tags. Due to the passive nature of the tags, they are severely aected by the environment and the object they are attached to. Hence they may be rendered unable to reply to the readers request, in spite of being within the expected read range of the reader. This is referred to as False Negative Detections (FNDs). Similarly, constructive eects in the environment can en- able a tag outside the expected read range to reply. This is denoted a False Positive Detection (FPD). It is desired to reduce the occurrence of these false positive and negative detections hence in this thesis it is proposed to impose interference on the communication between reader and tag. Interference has a well-known blocking eect, and the experimental investigations show how tag replies outside the expected read range are blocked, as expected. More- over, tuned and detuned tags alike are aected by the decreased Signal to Interference and Noise Ratio (SINR) due to the imposed interference, hence their read ranges are thus eectively equalized. From the investigations it can therefore be concluded that the imposed interference has a constructive eect as it enables design of well dened and sharply bounded interrogation v zones, where tags are read with high probability regardless of the level of detuning they might experience. Moreover, this thesis proposes to use passive RFID tags as orientation sensors. This is an innovative application for RFID technology in itself, but orientation sensing can also help existing RFID applications that relies on the Received Signal Strength (RSS) in the tag reply. Many Ultra High Frequency (UHF) RFID tags utilize a dipole antenna, and the RSS metric of the tag reply is thus prone to polarization and gain mismatches between tag and reader antennas. Being able to estimate the orientation can help mitigate this eect. It is proposed to let a reader antenna collect information about the polarization of the received tag reply by decomposing the RSS into the horizontal and vertical dimensions using a dual linearly polarized reader antenna. The method is evaluated experimentally, and when the movement of the tag is limited to two dimensions, i.e. a plane, the results for track- ing the tag orientation are promising. Tag movements in three dimensions complicates however the orientation estimate. Multiple reader antenna are therefore utilized in order to collect samples of the tag reply from multiple directions, and their data are fused using Kalman ltering. The nal results show good potential, as even simple data processing enables recognition of gestures, i.e. predened motions with the tag. However, the estimate of the three dimensional orientation vector oers relatively low precision, and does therefore not allow dedicated motion capture of the tag. But it has been shown through experimental investigations that the orientation infor- mation is available in the tag reply, and using more advanced methods for data processing, a reliable orientation estimate can be obtained.",
author = "Rasmus Krigslund",
year = "2012",
month = "9",
day = "1",
language = "Dansk",
isbn = "978-87-92328-90-8",

}

Experimental Assessment of Orientation Sensing and Constructive Interference in Passive RFID Systems. / Krigslund, Rasmus.

Aalborg Universitet, 2012. 129 s.

Publikation: Bog/antologi/afhandling/rapportPh.d.-afhandlingForskning

TY - BOOK

T1 - Experimental Assessment of Orientation Sensing and Constructive Interference in Passive RFID Systems

AU - Krigslund, Rasmus

PY - 2012/9/1

Y1 - 2012/9/1

N2 - This thesis focus on passive Radio Frequency IDentication (RFID), a tech- nology designed for automated identication of tagged objects. The tags are small passive devices powered by the wireless signal from the reader. Their simple operation thus solely allows them to reply with their unique ID when requested by the reader, which is a high power handheld or stationary transceiver. The RFID technology has matured over the past two decades, but still there exist ambiguities regarding the reading, or interrogation, of tags. Due to the passive nature of the tags, they are severely aected by the environment and the object they are attached to. Hence they may be rendered unable to reply to the readers request, in spite of being within the expected read range of the reader. This is referred to as False Negative Detections (FNDs). Similarly, constructive eects in the environment can en- able a tag outside the expected read range to reply. This is denoted a False Positive Detection (FPD). It is desired to reduce the occurrence of these false positive and negative detections hence in this thesis it is proposed to impose interference on the communication between reader and tag. Interference has a well-known blocking eect, and the experimental investigations show how tag replies outside the expected read range are blocked, as expected. More- over, tuned and detuned tags alike are aected by the decreased Signal to Interference and Noise Ratio (SINR) due to the imposed interference, hence their read ranges are thus eectively equalized. From the investigations it can therefore be concluded that the imposed interference has a constructive eect as it enables design of well dened and sharply bounded interrogation v zones, where tags are read with high probability regardless of the level of detuning they might experience. Moreover, this thesis proposes to use passive RFID tags as orientation sensors. This is an innovative application for RFID technology in itself, but orientation sensing can also help existing RFID applications that relies on the Received Signal Strength (RSS) in the tag reply. Many Ultra High Frequency (UHF) RFID tags utilize a dipole antenna, and the RSS metric of the tag reply is thus prone to polarization and gain mismatches between tag and reader antennas. Being able to estimate the orientation can help mitigate this eect. It is proposed to let a reader antenna collect information about the polarization of the received tag reply by decomposing the RSS into the horizontal and vertical dimensions using a dual linearly polarized reader antenna. The method is evaluated experimentally, and when the movement of the tag is limited to two dimensions, i.e. a plane, the results for track- ing the tag orientation are promising. Tag movements in three dimensions complicates however the orientation estimate. Multiple reader antenna are therefore utilized in order to collect samples of the tag reply from multiple directions, and their data are fused using Kalman ltering. The nal results show good potential, as even simple data processing enables recognition of gestures, i.e. predened motions with the tag. However, the estimate of the three dimensional orientation vector oers relatively low precision, and does therefore not allow dedicated motion capture of the tag. But it has been shown through experimental investigations that the orientation infor- mation is available in the tag reply, and using more advanced methods for data processing, a reliable orientation estimate can be obtained.

AB - This thesis focus on passive Radio Frequency IDentication (RFID), a tech- nology designed for automated identication of tagged objects. The tags are small passive devices powered by the wireless signal from the reader. Their simple operation thus solely allows them to reply with their unique ID when requested by the reader, which is a high power handheld or stationary transceiver. The RFID technology has matured over the past two decades, but still there exist ambiguities regarding the reading, or interrogation, of tags. Due to the passive nature of the tags, they are severely aected by the environment and the object they are attached to. Hence they may be rendered unable to reply to the readers request, in spite of being within the expected read range of the reader. This is referred to as False Negative Detections (FNDs). Similarly, constructive eects in the environment can en- able a tag outside the expected read range to reply. This is denoted a False Positive Detection (FPD). It is desired to reduce the occurrence of these false positive and negative detections hence in this thesis it is proposed to impose interference on the communication between reader and tag. Interference has a well-known blocking eect, and the experimental investigations show how tag replies outside the expected read range are blocked, as expected. More- over, tuned and detuned tags alike are aected by the decreased Signal to Interference and Noise Ratio (SINR) due to the imposed interference, hence their read ranges are thus eectively equalized. From the investigations it can therefore be concluded that the imposed interference has a constructive eect as it enables design of well dened and sharply bounded interrogation v zones, where tags are read with high probability regardless of the level of detuning they might experience. Moreover, this thesis proposes to use passive RFID tags as orientation sensors. This is an innovative application for RFID technology in itself, but orientation sensing can also help existing RFID applications that relies on the Received Signal Strength (RSS) in the tag reply. Many Ultra High Frequency (UHF) RFID tags utilize a dipole antenna, and the RSS metric of the tag reply is thus prone to polarization and gain mismatches between tag and reader antennas. Being able to estimate the orientation can help mitigate this eect. It is proposed to let a reader antenna collect information about the polarization of the received tag reply by decomposing the RSS into the horizontal and vertical dimensions using a dual linearly polarized reader antenna. The method is evaluated experimentally, and when the movement of the tag is limited to two dimensions, i.e. a plane, the results for track- ing the tag orientation are promising. Tag movements in three dimensions complicates however the orientation estimate. Multiple reader antenna are therefore utilized in order to collect samples of the tag reply from multiple directions, and their data are fused using Kalman ltering. The nal results show good potential, as even simple data processing enables recognition of gestures, i.e. predened motions with the tag. However, the estimate of the three dimensional orientation vector oers relatively low precision, and does therefore not allow dedicated motion capture of the tag. But it has been shown through experimental investigations that the orientation infor- mation is available in the tag reply, and using more advanced methods for data processing, a reliable orientation estimate can be obtained.

M3 - Ph.d.-afhandling

SN - 978-87-92328-90-8

BT - Experimental Assessment of Orientation Sensing and Constructive Interference in Passive RFID Systems

CY - Aalborg Universitet

ER -