Accurate positioning and distributed time synchronization for short-range personal area networks ... more Accurate positioning and distributed time synchronization for short-range personal area networks (PAN) are expected to boost the impact of mobile wireless systems in a variety of applications. At the moment, wireless ranging and time synchronization are often addressed independently. The two main underlying reasons are: 1) the different accuracy requirements for time-of-arrival measurements and local clock correction and 2) the intrinsic difficulty to timestamp the received radio frames with uncertainty lower than some nanoseconds due to the joint effect of clock resolution, wideband noise, clock frequency offsets, and multipath propagation. Of course, if the influence of such phenomena were minimized, time synchronization could benefit from accurate one-way ranging and vice versa. One of the most recent and promising communication schemes to reach this goal is chirp spread spectrum (CSS) modulation. Indeed, this is also one of the alternative physical (PHY) layers for PANs recommended in the amendment IEEE 802.15.4a-2007, recently included in the standard IEEE 802.15.4-2011. In this paper, the features of IEEE 802.15.4a CSS signals for low-level timestamping are analyzed both theoretically and through simulations under the effect of various uncertainty contributions. Accordingly, an effective solution for frame timestamping at the symbol level is proposed. Some experimental results based on a software defined radio implementation of the IEEE 802.15.4a PHY layer confirm that CSS can be successfully adopted both for time synchronization and ranging.
The increasing diffusion of mobile and portable devices provided with wireless connectivity makes... more The increasing diffusion of mobile and portable devices provided with wireless connectivity makes the problem of distance measurement based on radio-frequency technologies increasingly important for the development of next-generation nomadic applications. In this paper, the performance limitations of two classic wireless ranging techniques based on received signal strength (RSS) and two-way time-of-flight (ToF) measurements, respectively, are analyzed and compared in detail. On the basis of this study, a data fusion algorithm is proposed to combine both techniques in order to improve ranging accuracy. The algorithm has been implemented and tested on the field using a dedicated embedded prototype made with commercial off-the-shelf components. Several experimental results prove that the combination of both techniques can significantly reduce measurement uncertainty. The results obtained with the developed prototype are not accurate enough for fine-grained position tracking in Ambient Assisted Living applications. However, the platform can be successfully used for reliable indoor zoning, e.g., for omnidirectional and adjustable hazard proximity detection. Most importantly, the proposed solution is absolutely general, and it is quite simple and light from the computational point of view. Accuracy could be further improved by using a more isotropic antenna and by integrating the ToF measurement technique at the lowest possible level on the same radio chip used for communication. Usually, this feature is not available in typical low-cost short-range wireless modules, e.g., for wireless sensor networks. Thus, the results of this research suggest that combining RSS with ToF measurements could be a viable solution for chip manufacturers interested in adding ranging capabilities to their radio modules.
Proc. IEEE International Instrumentation and Measurement Technology Conference (I2MTC 2012)
An increasing number of distributed measurement and control applications requires that network no... more An increasing number of distributed measurement and control applications requires that network nodes are able to estimate the position and the time measured by other devices on a common spatio-temporal reference frame. Accurate packet timestamping is a necessary condition to achieve this goal. However, in the case of wireless networks, timestamping accuracy is generally quite poor due to the combination of multiple uncertainty sources (e.g., variable signal attenuation and interferences) affecting wireless message propagation. Various communication schemes have been proposed to improve performance. One of the most recent and promising is the Chirp Spread Spectrum (CSS) modulation. In this paper, the timestamping accuracy of CSS signals similar to those defined in the standard IEEE 802.15.4a is analyzed experimentally using two different platforms based on a Software Defined Radio (SDR). Some results confirm that CSS can be successfully employed for accurate time synchronization and ranging.
Proc. 7th IEEE International Symposium on Industrial Embedded Systems (SIES), 2012 , Jun 2012
Wireless distance measurement techniques based on portable embedded platforms are expected to pla... more Wireless distance measurement techniques based on portable embedded platforms are expected to play a key role in several industrial and domestic applications. In this paper the ranging accuracy of a commercial Chirp Spread Spectrum (CSS) kit is evaluated experimentally in a real-world context. The proposed analysis provides more precise and exhaustive information than what it is usually reported in the technical literature. In fact, this paper is specifically focused on performance evaluation and it deals with the case of short-range indoor scenarios in both Line-of-Sight (LOS) and Non-Line-of-Sight (NLOS) repeatable conditions. The resulting analysis represents the first step towards the design of a custom indoor embedded navigation system for a smart rollator assisting impaired people to move safely in an indoor public environment.
In this paper, we analyze the accuracy of indoor localization measurement based on a wireless sen... more In this paper, we analyze the accuracy of indoor localization measurement based on a wireless sensor network. The position estimation procedure is based on the received-signal-strength measurements collected in a real indoor environment. Two different classes of low-computational-effort algorithms based on the centroid concept are considered, i.e., the weighted centroid localization method and the relative-span exponential weighted localization method. In particular, different sources of measurement uncertainty are analyzed by means of theoretical simulations and experimental results.
Proc. IEEE International Workshop on Measurements and Networking (M&N 2011)
Proximity sensors are increasingly used in distributed monitoring applications, e.g. for surveill... more Proximity sensors are increasingly used in distributed monitoring applications, e.g. for surveillance purposes. However, most of existing solutions have two different, usually contrasting requirements, i.e. either they have strong directional features, or they just cover very short distances. In order to tackle such issues, in this paper a new, almost omnidirectional proximity detection technique is described. The proposed approach is explicitly conceived for wearable wireless sensor networks (WSN) nodes and it relies on the fusion of time-of-flight (ToF) and received signal strength (RSS) values. Even though it is not accurate enough for fine-grained indoor localization, the proposed solution is robust in detecting when a given threshold is crossed by a moving object. Also, it is flexible, light from the computational point of view and easy to implement using commercial off-the-shelf (COTS) components.
Proc. IEEE International Workshop on Measurements and Networking (M&N 2011)
Wireless sensor networks (WSNs) are commonly considered as a key enabling technology for ambient ... more Wireless sensor networks (WSNs) are commonly considered as a key enabling technology for ambient assisted living (AAL) and smart home services. Essential requirements for this kind of applications are: small node size, long lifetime, little invasiveness and reliable communication over a range of few tens of meters even in presence of obstacles. For this reason, in this paper a low-cost WSN node architecture for body fall detection is presented. Our node is partially inspired to the well-known TelosB/Tmote Sky so as to maintain full software compatibility with TinyOS, but it is highly optimized in size, it is equipped with a chip antenna with better performance than the typical inverted-F printed one and it is powered by a compact high-capacity lithium-ion polymer rechargeable battery. Several experimental results confirm that the node lifetime may exceed one week of operation in the expected working conditions.
Proc. IEEE International Instrumentation and Measurement Technology Conference (I2MTC 2010)
In this paper we show the results of an experimental assessment of an indoor localization system ... more In this paper we show the results of an experimental assessment of an indoor localization system based on a Wireless Sensor Network. The estimated position of a target node embedded in the monitored environment is obtained by running of the Relative Span Exponentially Weighted Localization (REWL) algorithm, a novel localization procedure recently proposed in the literature. The inputs of the algorithm are the Received Signal Strength (RSS) measurements collected in a real indoor scenario. A description of the developed system and a metrological characterization of the proposed technique is presented in this paper.
Proc. IEEE Workshop on Environmental, Energy, and Structural Monitoring Systems (EESMS 2009)
Flexible, distributed monitoring systems are essential to support decisions in a variety of conte... more Flexible, distributed monitoring systems are essential to support decisions in a variety of contexts such as, for instance, vehicular traffic control, emergency evacuation plans, energy optimization services, pollutant detection or intelligent agriculture applications. In this paper, we present WSNAP, a platform for wireless sensor network (WSN) deployment. WSNAP relies on standard technologies, which enable users to interact easily with different types of sensors. Its main advantage is the ability to be easily adapted to the requirements of different applications, regardless of network topology and sensor board architecture. WSNAP was tested on a small WSN deployed at the ldquoDipartimento di Ingegneria e Scienza dell'Informazionerdquo (DISI) of the University of Trento, Trento, Italy. In the following, after describing the structure and the main features of the platform, the results of some experiments are reported.
Accurate positioning and distributed time synchronization for short-range personal area networks ... more Accurate positioning and distributed time synchronization for short-range personal area networks (PAN) are expected to boost the impact of mobile wireless systems in a variety of applications. At the moment, wireless ranging and time synchronization are often addressed independently. The two main underlying reasons are: 1) the different accuracy requirements for time-of-arrival measurements and local clock correction and 2) the intrinsic difficulty to timestamp the received radio frames with uncertainty lower than some nanoseconds due to the joint effect of clock resolution, wideband noise, clock frequency offsets, and multipath propagation. Of course, if the influence of such phenomena were minimized, time synchronization could benefit from accurate one-way ranging and vice versa. One of the most recent and promising communication schemes to reach this goal is chirp spread spectrum (CSS) modulation. Indeed, this is also one of the alternative physical (PHY) layers for PANs recommended in the amendment IEEE 802.15.4a-2007, recently included in the standard IEEE 802.15.4-2011. In this paper, the features of IEEE 802.15.4a CSS signals for low-level timestamping are analyzed both theoretically and through simulations under the effect of various uncertainty contributions. Accordingly, an effective solution for frame timestamping at the symbol level is proposed. Some experimental results based on a software defined radio implementation of the IEEE 802.15.4a PHY layer confirm that CSS can be successfully adopted both for time synchronization and ranging.
The increasing diffusion of mobile and portable devices provided with wireless connectivity makes... more The increasing diffusion of mobile and portable devices provided with wireless connectivity makes the problem of distance measurement based on radio-frequency technologies increasingly important for the development of next-generation nomadic applications. In this paper, the performance limitations of two classic wireless ranging techniques based on received signal strength (RSS) and two-way time-of-flight (ToF) measurements, respectively, are analyzed and compared in detail. On the basis of this study, a data fusion algorithm is proposed to combine both techniques in order to improve ranging accuracy. The algorithm has been implemented and tested on the field using a dedicated embedded prototype made with commercial off-the-shelf components. Several experimental results prove that the combination of both techniques can significantly reduce measurement uncertainty. The results obtained with the developed prototype are not accurate enough for fine-grained position tracking in Ambient Assisted Living applications. However, the platform can be successfully used for reliable indoor zoning, e.g., for omnidirectional and adjustable hazard proximity detection. Most importantly, the proposed solution is absolutely general, and it is quite simple and light from the computational point of view. Accuracy could be further improved by using a more isotropic antenna and by integrating the ToF measurement technique at the lowest possible level on the same radio chip used for communication. Usually, this feature is not available in typical low-cost short-range wireless modules, e.g., for wireless sensor networks. Thus, the results of this research suggest that combining RSS with ToF measurements could be a viable solution for chip manufacturers interested in adding ranging capabilities to their radio modules.
Proc. IEEE International Instrumentation and Measurement Technology Conference (I2MTC 2012)
An increasing number of distributed measurement and control applications requires that network no... more An increasing number of distributed measurement and control applications requires that network nodes are able to estimate the position and the time measured by other devices on a common spatio-temporal reference frame. Accurate packet timestamping is a necessary condition to achieve this goal. However, in the case of wireless networks, timestamping accuracy is generally quite poor due to the combination of multiple uncertainty sources (e.g., variable signal attenuation and interferences) affecting wireless message propagation. Various communication schemes have been proposed to improve performance. One of the most recent and promising is the Chirp Spread Spectrum (CSS) modulation. In this paper, the timestamping accuracy of CSS signals similar to those defined in the standard IEEE 802.15.4a is analyzed experimentally using two different platforms based on a Software Defined Radio (SDR). Some results confirm that CSS can be successfully employed for accurate time synchronization and ranging.
Proc. 7th IEEE International Symposium on Industrial Embedded Systems (SIES), 2012 , Jun 2012
Wireless distance measurement techniques based on portable embedded platforms are expected to pla... more Wireless distance measurement techniques based on portable embedded platforms are expected to play a key role in several industrial and domestic applications. In this paper the ranging accuracy of a commercial Chirp Spread Spectrum (CSS) kit is evaluated experimentally in a real-world context. The proposed analysis provides more precise and exhaustive information than what it is usually reported in the technical literature. In fact, this paper is specifically focused on performance evaluation and it deals with the case of short-range indoor scenarios in both Line-of-Sight (LOS) and Non-Line-of-Sight (NLOS) repeatable conditions. The resulting analysis represents the first step towards the design of a custom indoor embedded navigation system for a smart rollator assisting impaired people to move safely in an indoor public environment.
In this paper, we analyze the accuracy of indoor localization measurement based on a wireless sen... more In this paper, we analyze the accuracy of indoor localization measurement based on a wireless sensor network. The position estimation procedure is based on the received-signal-strength measurements collected in a real indoor environment. Two different classes of low-computational-effort algorithms based on the centroid concept are considered, i.e., the weighted centroid localization method and the relative-span exponential weighted localization method. In particular, different sources of measurement uncertainty are analyzed by means of theoretical simulations and experimental results.
Proc. IEEE International Workshop on Measurements and Networking (M&N 2011)
Proximity sensors are increasingly used in distributed monitoring applications, e.g. for surveill... more Proximity sensors are increasingly used in distributed monitoring applications, e.g. for surveillance purposes. However, most of existing solutions have two different, usually contrasting requirements, i.e. either they have strong directional features, or they just cover very short distances. In order to tackle such issues, in this paper a new, almost omnidirectional proximity detection technique is described. The proposed approach is explicitly conceived for wearable wireless sensor networks (WSN) nodes and it relies on the fusion of time-of-flight (ToF) and received signal strength (RSS) values. Even though it is not accurate enough for fine-grained indoor localization, the proposed solution is robust in detecting when a given threshold is crossed by a moving object. Also, it is flexible, light from the computational point of view and easy to implement using commercial off-the-shelf (COTS) components.
Proc. IEEE International Workshop on Measurements and Networking (M&N 2011)
Wireless sensor networks (WSNs) are commonly considered as a key enabling technology for ambient ... more Wireless sensor networks (WSNs) are commonly considered as a key enabling technology for ambient assisted living (AAL) and smart home services. Essential requirements for this kind of applications are: small node size, long lifetime, little invasiveness and reliable communication over a range of few tens of meters even in presence of obstacles. For this reason, in this paper a low-cost WSN node architecture for body fall detection is presented. Our node is partially inspired to the well-known TelosB/Tmote Sky so as to maintain full software compatibility with TinyOS, but it is highly optimized in size, it is equipped with a chip antenna with better performance than the typical inverted-F printed one and it is powered by a compact high-capacity lithium-ion polymer rechargeable battery. Several experimental results confirm that the node lifetime may exceed one week of operation in the expected working conditions.
Proc. IEEE International Instrumentation and Measurement Technology Conference (I2MTC 2010)
In this paper we show the results of an experimental assessment of an indoor localization system ... more In this paper we show the results of an experimental assessment of an indoor localization system based on a Wireless Sensor Network. The estimated position of a target node embedded in the monitored environment is obtained by running of the Relative Span Exponentially Weighted Localization (REWL) algorithm, a novel localization procedure recently proposed in the literature. The inputs of the algorithm are the Received Signal Strength (RSS) measurements collected in a real indoor scenario. A description of the developed system and a metrological characterization of the proposed technique is presented in this paper.
Proc. IEEE Workshop on Environmental, Energy, and Structural Monitoring Systems (EESMS 2009)
Flexible, distributed monitoring systems are essential to support decisions in a variety of conte... more Flexible, distributed monitoring systems are essential to support decisions in a variety of contexts such as, for instance, vehicular traffic control, emergency evacuation plans, energy optimization services, pollutant detection or intelligent agriculture applications. In this paper, we present WSNAP, a platform for wireless sensor network (WSN) deployment. WSNAP relies on standard technologies, which enable users to interact easily with different types of sensors. Its main advantage is the ability to be easily adapted to the requirements of different applications, regardless of network topology and sensor board architecture. WSNAP was tested on a small WSN deployed at the ldquoDipartimento di Ingegneria e Scienza dell'Informazionerdquo (DISI) of the University of Trento, Trento, Italy. In the following, after describing the structure and the main features of the platform, the results of some experiments are reported.
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Papers by Paolo Pivato