international conference on embedded wireless systems and networks, Feb 20, 2017
LoRa technology is an increasingly popular option for applications that can exploit its low power... more LoRa technology is an increasingly popular option for applications that can exploit its low power and long range capabilities. While most efforts to date have studied its characteristics for smart city environments, we take LoRa outside the city limits, exploring how the environment affects its core communication properties. Specifically, we offer two novel parameter explorations to understand first how vegetation affects communication range and second how antennas change radio behavior. Our results provide insight into LoRa in non-urban environments, specifically showing that vegetation dramatically reduces the communication range and that the antenna selection can have a profound effect.
Policy makers have implemented multiple non-pharmaceutical strategies to mitigate the COVID-19 wo... more Policy makers have implemented multiple non-pharmaceutical strategies to mitigate the COVID-19 worldwide crisis. Interventions had the aim of reducing close proximity interactions, which drive the spread of the disease. A deeper knowledge of human physical interactions has revealed necessary, especially in all settings involving children, whose education and gathering activities should be preserved. Despite their relevance, almost no data are available on close proximity contacts among children in schools or other educational settings during the pandemic.Contact data are usually gathered via Bluetooth, which nonetheless offers a low temporal and spatial resolution. Recently, ultra-wideband (UWB) radios emerged as a more accurate alternative that nonetheless exhibits a significantly higher energy consumption, limiting in-field studies. In this paper, we leverage a novel approach, embodied by the Janus system that combines these radios by exploiting their complementary benefits. The v...
Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies, 2021
Proximity detection is at the core of several mobile and ubiquitous computing applications. These... more Proximity detection is at the core of several mobile and ubiquitous computing applications. These include reactive use cases, e.g., alerting individuals of hazards or interaction opportunities, and others concerned only with logging proximity data, e.g., for offline analysis and modeling. Common approaches rely on Bluetooth Low Energy (BLE) or ultra-wideband (UWB) radios. Nevertheless, these strike opposite tradeoffs between the accuracy of distance estimates quantifying proximity and the energy efficiency affecting system lifetime, effectively forcing a choice between the two and ultimately constraining applicability. Janus reconciles these dimensions in a dual-radio protocol enabling accurate and energy-efficient proximity detection, where the energy-savvy BLE is exploited to discover devices and coordinate their distance measurements, acquired via the energy-hungry UWB. A model supports domain experts in configuring Janus for their use cases with predictable performance. The late...
2013 IEEE Eighth International Conference on Intelligent Sensors, Sensor Networks and Information Processing, 2013
In recent years, indoor localization has become a hot research topic with some sophisticated solu... more In recent years, indoor localization has become a hot research topic with some sophisticated solutions reaching accuracy on the order of ten centimeters. While certain classes of applications can justify the corresponding costs that come with these solutions, a wealth of applications have requirements that can be met at much lower cost by accepting lower accuracy. This paper explores one specific application for monitoring patients in a nursing home, showing that sufficient accuracy can be achieved with a carefully designed deployment of low-cost wireless sensor network nodes in combination with a simple RSSI-based localization technique. Notably our solution uses a single radio sample per period, a number that is much lower than similar approaches. This greatly eases the power burden of the nodes, resulting in a significant lifetime increase. This paper evaluates a concrete deployment from summer 2012 composed of fixed anchor motes throughout one floor of a nursing home and mobile units carried by patients. We show how two localization algorithms perform and demonstrate a clear improvement by following a set of simple guidelines to tune the anchor node placement. We show both quantitatively and qualitatively that the results meet the functional and non-functional system requirements.
2017 International Smart Cities Conference (ISC2), 2017
Many smart city applications involve groups of individuals that wish to remain together as they m... more Many smart city applications involve groups of individuals that wish to remain together as they move throughout the city. For example, a group of tourists may be monitored by a tour operator to keep the group together and on schedule. Alternatively, a group of elementary school children in transit to school should be closely supervised by an adult to ensure the children stay safe. This paper presents LASSO, a smartphone- based service that exploits wireless devices carried by each group member to provide infrastructure-free group formation and monitoring. We show how smartphones equipped with Bluetooth Low Energy (BLE) can be used as personal beacons in a device- to-device group monitoring protocol to allow each user to join a group and see a distributed view of group membership in real time. While LASSO is general purpose in nature, we demonstrate it and evaluate its performance through a prototype application used by a tourist guide to monitor tour participants.
To address the challenges of the EWSN dependability competition we extended our synchronous trans... more To address the challenges of the EWSN dependability competition we extended our synchronous transmission protocol, CRYSTAL, with techniques to mitigate interference -- channel hopping and noise detection -- and with the capability to deliver aperiodic events to multiple actuators.
Event-triggered control ( ETC ) holds the potential to significantly improve the efficiency of wi... more Event-triggered control ( ETC ) holds the potential to significantly improve the efficiency of wireless networked control systems. Unfortunately, its real-world impact has hitherto been hampered by the lack of a network stack able to transfer its benefits from theory to practice specifically by supporting the latency and reliability requirements of the aperiodic communication ETC induces. This is precisely the contribution of this article. Our Wireless Control Bus ( WCB ) exploits carefully orchestrated network-wide floods of concurrent transmissions to minimize overhead during quiescent, steady-state periods, and ensures timely and reliable collection of sensor readings and dissemination of actuation commands when an ETC triggering condition is violated. Using a cyber-physical testbed emulating a water distribution system controlled over a real-world multi-hop wireless network, we show that ETC over WCB achieves the same quality of periodic control at a fraction of the energy costs...
2018 IEEE 12th International Conference on Self-Adaptive and Self-Organizing Systems (SASO), 2018
Today's "smart" domains are driven by lightweight battery operated devices carried by people and ... more Today's "smart" domains are driven by lightweight battery operated devices carried by people and embedded in environments. Many applications rely on continuous neighbor discovery, i.e., the ability to detect other nearby devices. Application uses for neighbor discovery are widely varying, but they all rely on a protocol in which devices exchange periodic beacons containing device identifiers. Many applications also ultimately involve assessing and adapting to context information sensed about the physical world and the device's situation in that world (e.g., its location or speed, the ambient temperature or sound, etc.). In this paper, we define Proactive Implicit Neighborhood Context Heuristics (PINCH), which leverages unused payload in periodic neighbor discovery beacons to opportunistically distribute context information in a local area. PINCH's selforganizing algorithms use limited local views of the state of a one-hop network neighborhood to determine the most useful type of context information for a device to sense and share. In this paper, we develop the algorithms, integrate an implementation of PINCH with a smart city simulator, and benchmark the tradeoffs of self-organized local context sharing with 2.4GHz neighbor discovery beacons.
Proceedings of the 16th ACM/IEEE International Conference on Information Processing in Sensor Networks, 2017
Identifying "who is around" is key in a plethora of smart scenarios. While many solutions exist, ... more Identifying "who is around" is key in a plethora of smart scenarios. While many solutions exist, they often take a theoretical approach, reasoning about protocol behavior with an abstract model that makes simplifying assumptions about the environment. This approach creates a gap between protocol implementations and the models used during design and analysis. In this paper, we take a system approach to continuous neighbor discovery: starting with the concrete technology of Bluetooth Low Energy (BLE) we build a protocol, called BLEnd, tailored to its constraints. Moreover, we also consider the very real effects of packet collisions, to our knowledge a first in this domain. Our ultimate goal is to directly empower developers with the ability to determine the optimal protocol configuration for their applications; in this respect, the slotless operation of BLEnd offers richer alternatives than state-of-the-art protocols. Developers specify the minimum discovery probability, the target discovery latency, and the maximum expected node density; these are used by an optimizer tool to parameterize the BLEnd implementation towards maximum lifetime. This paper shows that BLEnd not only achieves the user-specified goals, but does so more efficiently than analogous configurations of competing protocols. CCS CONCEPTS •Networks →Network protocol design; •Human-centered computing →Ubiquitous and mobile computing systems and tools;
Proceedings of the 2019 CHI Conference on Human Factors in Computing Systems, 2019
Technology increasingly offers parents opportunities to monitor children, reshaping the way contr... more Technology increasingly offers parents opportunities to monitor children, reshaping the way control and autonomy are negotiated within families. This paper investigates the views of parents and primary school children on mobile technology designed to support child independent mobility in the context of the local walking school buses. Based on a schoolyear long field study, we report findings on children's and parents' experience with proximity detection devices. The results provide insights into how the parents and children accepted and socially appropriated the technology into the walking school bus activity, shedding light on the way they understand and conceptualize a technology that collects data on children's proximity to the volunteers' smartphone. We discuss parents' needs and concerns around monitoring technologies and the related challenges in terms of trust-control balance. These insights are elaborated to inform the future design of technology for child independent mobility.
In wireless environments, transmission and 1 reception costs dominate system power consumption, m... more In wireless environments, transmission and 1 reception costs dominate system power consumption, motivating 2 research effort on new technologies capable of reducing the 3 footprint of the radio, paving the way for the Internet of 4 Things. The most important challenge is to reduce power 5 consumption when receivers are idle, the so called idle-listening 6 cost. One approach proposes switching off the main receiver, 7 then introduces new wake-up circuitry capable of detecting 8 an incoming transmission, optionally discriminating the packet 9 destination using addressing, then switching on the main radio 10 only when required. This wake-up receiver technology represents 11 the ultimate frontier in low power radio communication. In 12 this paper, we present a comprehensive literature review of 13 the research progress in wake-up radio (WuR) hardware and 14 relevant networking software. First, we present an overview of 15 the WuR system architecture, including challenges to hardware 16 design and a comparison of solutions presented throughout the 17 last decade. Next, we present various medium access control and 18 routing protocols as well as diverse ways to exploit WuRs, both 19 as an extension of pre-existing systems and as a new concept to 20 manage low-power networking.
Proceedings of the 14th ACM Conference on Embedded Network Sensor Systems CD-ROM, 2016
Data prediction in wireless sensor networks replaces the commonly used (periodic) data reporting ... more Data prediction in wireless sensor networks replaces the commonly used (periodic) data reporting with a model, updated (infrequently) at the sink to accurately reproduce real data trends. This technique abates up to 99% of application messages; yet, recent work has shown it achieves "only" up to a 7x lifetime improvement when executed atop a mainstream network stack (e.g., CTP + BoX-MAC), as the idle listening and topology maintenance in the latter are ill-suited to the sparse traffic induced by data prediction. This paper presents a novel network stack designed for data prediction, Crystal, that exploits synchronous transmissions to quickly and reliably transmit model updates when these occur (infrequently but often concurrently), and minimizes overhead during the (frequent) periods with no updates. Based on 90node experiments in the Indriya testbed and with 7 public datasets, we show that Crystal unleashes the full potential of data prediction, achieving per-mille duty cycle with perfect reliability and very small latency.
This paper describes the application of a wireless sensor network to a 31 meter-tall medieval tow... more This paper describes the application of a wireless sensor network to a 31 meter-tall medieval tower located in the city of Trento, Italy. The effort is motivated by preservation of the integrity of a set of frescoes decorating the room on the second floor, representing one of most important International Gothic artworks in Europe. The specific application demanded development of customized hardware and software. The wireless module selected as the core platform allows reliable wireless communication at low cost with a long service life. Sensors include accelerometers, deformation gauges, and thermometers. A multi-hop data collection protocol was applied in the software to improve the system's flexibility and scalability. The system has been operating since September 2008, and in recent months the data loss ratio was estimated as less than 0.01%. The data acquired so far are in agreement with the prediction resulting a priori from the 3-dimensional FEM. Based on these data a Bayesian updating procedure is employed to real-time estimate the probability of abnormal condition states. This first period of operation demonstrated the stability and reliability of the system, and its ability to recognize any possible occurrence of abnormal conditions that could jeopardize the integrity of the frescos.
Wireless sensor networks (WSNs) are evolving to support sense-andreact applications, where actuat... more Wireless sensor networks (WSNs) are evolving to support sense-andreact applications, where actuators are physically interspersed with the sensors that trigger them. This solution maximizes localized interactions, improving resource utilization and reducing latency w.r.t. solutions with a centralized sink. Nevertheless, application development becomes more complex: the control logic must be embedded in the network, and coordination among multiple tasks is needed to achieve the application goals. This paper presents TeenyLIME, a WSN middleware designed to address the above challenges. TeenyLIME provides programmers with the high-level abstraction of a tuple space, enabling data sharing among neighboring devices. These and other WSN-specific constructs simplify the development of a wide range of applications, including sense-and-react ones. TeenyLIME yields simpler, cleaner, and more reusable implementations, at the cost of only a very limited decrease in performance. We support these claims through a source-level, quantitative comparison between implementations based on TeenyLIME and on mainstream approaches, and by analyzing measures of processing overhead and power consumption obtained through cycle-accurate emulation.
Content-based publish-subscribe is emerging as a communication paradigm able to cope with the nee... more Content-based publish-subscribe is emerging as a communication paradigm able to cope with the needs of scalability, flexibility, and reconfigurability typical of highly dynamic distributed applications. However, very few efforts address dynamic changes in the topology of the publish-subscribe distributed dispatching infrastructure-a fundamental challenge in mobile computing scenarios. In this chapter we illustrate the problems posed by mobility in the context of publish-subscribe, discuss protocols and integrated solutions proposed by our research group, and survey the state of the art in this research area.
A new class of models, formalisms and mechanisms has recently evolved for describing concurrent a... more A new class of models, formalisms and mechanisms has recently evolved for describing concurrent and distributed computations based on the concept of "coordination". The purpose of a coordination model and associated language is to provide a means of integrating a number of possibly heterogeneous components together, by interfacing with each component in such a way that the collective set forms a single application that can execute on and take advantage of parallel and distributed systems. In this chapter we initially define and present in sufficient detail the fundamental concepts of what constitutes a coordination model or language. We then go on to classify these models and languages as either "data-driven" or "control-driven" (also called "process-" or "task-oriented"). Next, the main existing coordination models and languages are described in sufficient detail to let the reader appreciate their features and put them into perspective with respect to each other. The chapter ends with a discussion comparing the various models and some conclusions.
Wireless sensor networks (WSNs) often rely on dutycycling, alternating periods of low-power stand... more Wireless sensor networks (WSNs) often rely on dutycycling, alternating periods of low-power stand-by with others where sensing, computation, and communication are performed. Duty-cycling brings substantial energy savings, but may complicate the WSN design. The effectiveness of a node in performing its task (e.g., sensing events occurring in an area) is affected by its wake-up schedule. Random schedules lead to deployments that are either ineffective (e.g., insufficient sensing coverage) or inefficient (e.g., areas covered by multiple nodes simultaneously awake). In this paper, we focus on the problem of scattering the nodes' wake-up times optimally, to achieve maximal coverage of a given area. In previous work [5], we presented a decentralized protocol that improves significantly over random wake-up schedules. Instead, here we provide a centralized optimal solution that complements the work in [5] by identifying the theoretical upper bound to distributed protocols. Moreover, the modeling framework we present, based on integer programming techniques, is general enough to encompass alternative formulations of the problem. These include the inverse problem of determining the optimal schedule given a desired coverage, as well as other problems based on constraints other than coverage (e.g., latency of data dissemination).
2018 17th ACM/IEEE International Conference on Information Processing in Sensor Networks (IPSN), 2018
Aperiodic data collection received little attention in wireless sensor networks, compared to its ... more Aperiodic data collection received little attention in wireless sensor networks, compared to its periodic counterpart. The recent Crystal system uses synchronous transmissions to support aperiodic traffic with near-perfect reliability, low latency, and ultra-low power consumption. However, its performance is known under mild interference-a concern, as Crystal relies heavily on the (noise-sensitive) capture effect and targets aperiodic traffic where "every packet counts". We exploit a 49-node indoor testbed where, in contrast to existing evaluations using only naturally present interference to evaluate synchronous systems, we rely on JamLab to generate noise patterns that are not only more disruptive and extensive, but also reproducible. We show that a properly configured, unmodified Crystal yields perfect reliability (unlike Glossy) in several noise scenarios, but cannot sustain extreme ones (e.g., an emulated microwave oven near the sink) that instead are handled by routing-based approaches. We extend Crystal with techniques known to mitigate interference-channel hopping and noise detection-and demonstrate that these allow Crystal to achieve performance akin to the original even under multiple sources of strong interference.
2018 IEEE 12th International Conference on Self-Adaptive and Self-Organizing Systems (SASO), 2018
Pervasive sensing and actuation applications are increasingly being built using distributed devic... more Pervasive sensing and actuation applications are increasingly being built using distributed devices connected with low-power wireless links. Most of these applications exploit anarchic protocols in which devices independently attempt to seize communication resources, supporting only besteffort applications as the communication they rely on cannot be guaranteed. For strict quality of service requirements, a few, non-anarchic, disciplined approaches exist in which nodes coordinate and resources are guaranteed to individual devices. Unfortunately, these solutions come at a considerable cost to form and conform to rigid communication schedules while considering the inherent volatility of the wireless environment. This work proposes REINS-MAC, a fully distributed solution that adapts to changes in the wireless environment and forms a flexible communication schedule able to support quality of service requirements. Inspired by pulse-coupled oscillators, the mathematical formulation of firefly flash synchronization, our approach forms and reserves communication slots of variable size in an online and adaptive manner. REINS-MAC tailors communication resources to network conditions that vary in time and space as well as to the explicit communication needs of devices by enabling distributed, dynamic changes to established schedules. Ultimately, REINS-MAC allows higher level abstractions to rein in the protocol anarchy, laying the foundation for reliable wireless applications.
2 On Global Virtual Data Structures Gian Pietro Picco Amy L. Murphy Gruia-Catalin Roman Abstract ... more 2 On Global Virtual Data Structures Gian Pietro Picco Amy L. Murphy Gruia-Catalin Roman Abstract In distributed computing, global information is rarely available and most actions are carried out locally. However, when proving system properties we frequently turn to defining ...
international conference on embedded wireless systems and networks, Feb 20, 2017
LoRa technology is an increasingly popular option for applications that can exploit its low power... more LoRa technology is an increasingly popular option for applications that can exploit its low power and long range capabilities. While most efforts to date have studied its characteristics for smart city environments, we take LoRa outside the city limits, exploring how the environment affects its core communication properties. Specifically, we offer two novel parameter explorations to understand first how vegetation affects communication range and second how antennas change radio behavior. Our results provide insight into LoRa in non-urban environments, specifically showing that vegetation dramatically reduces the communication range and that the antenna selection can have a profound effect.
Policy makers have implemented multiple non-pharmaceutical strategies to mitigate the COVID-19 wo... more Policy makers have implemented multiple non-pharmaceutical strategies to mitigate the COVID-19 worldwide crisis. Interventions had the aim of reducing close proximity interactions, which drive the spread of the disease. A deeper knowledge of human physical interactions has revealed necessary, especially in all settings involving children, whose education and gathering activities should be preserved. Despite their relevance, almost no data are available on close proximity contacts among children in schools or other educational settings during the pandemic.Contact data are usually gathered via Bluetooth, which nonetheless offers a low temporal and spatial resolution. Recently, ultra-wideband (UWB) radios emerged as a more accurate alternative that nonetheless exhibits a significantly higher energy consumption, limiting in-field studies. In this paper, we leverage a novel approach, embodied by the Janus system that combines these radios by exploiting their complementary benefits. The v...
Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies, 2021
Proximity detection is at the core of several mobile and ubiquitous computing applications. These... more Proximity detection is at the core of several mobile and ubiquitous computing applications. These include reactive use cases, e.g., alerting individuals of hazards or interaction opportunities, and others concerned only with logging proximity data, e.g., for offline analysis and modeling. Common approaches rely on Bluetooth Low Energy (BLE) or ultra-wideband (UWB) radios. Nevertheless, these strike opposite tradeoffs between the accuracy of distance estimates quantifying proximity and the energy efficiency affecting system lifetime, effectively forcing a choice between the two and ultimately constraining applicability. Janus reconciles these dimensions in a dual-radio protocol enabling accurate and energy-efficient proximity detection, where the energy-savvy BLE is exploited to discover devices and coordinate their distance measurements, acquired via the energy-hungry UWB. A model supports domain experts in configuring Janus for their use cases with predictable performance. The late...
2013 IEEE Eighth International Conference on Intelligent Sensors, Sensor Networks and Information Processing, 2013
In recent years, indoor localization has become a hot research topic with some sophisticated solu... more In recent years, indoor localization has become a hot research topic with some sophisticated solutions reaching accuracy on the order of ten centimeters. While certain classes of applications can justify the corresponding costs that come with these solutions, a wealth of applications have requirements that can be met at much lower cost by accepting lower accuracy. This paper explores one specific application for monitoring patients in a nursing home, showing that sufficient accuracy can be achieved with a carefully designed deployment of low-cost wireless sensor network nodes in combination with a simple RSSI-based localization technique. Notably our solution uses a single radio sample per period, a number that is much lower than similar approaches. This greatly eases the power burden of the nodes, resulting in a significant lifetime increase. This paper evaluates a concrete deployment from summer 2012 composed of fixed anchor motes throughout one floor of a nursing home and mobile units carried by patients. We show how two localization algorithms perform and demonstrate a clear improvement by following a set of simple guidelines to tune the anchor node placement. We show both quantitatively and qualitatively that the results meet the functional and non-functional system requirements.
2017 International Smart Cities Conference (ISC2), 2017
Many smart city applications involve groups of individuals that wish to remain together as they m... more Many smart city applications involve groups of individuals that wish to remain together as they move throughout the city. For example, a group of tourists may be monitored by a tour operator to keep the group together and on schedule. Alternatively, a group of elementary school children in transit to school should be closely supervised by an adult to ensure the children stay safe. This paper presents LASSO, a smartphone- based service that exploits wireless devices carried by each group member to provide infrastructure-free group formation and monitoring. We show how smartphones equipped with Bluetooth Low Energy (BLE) can be used as personal beacons in a device- to-device group monitoring protocol to allow each user to join a group and see a distributed view of group membership in real time. While LASSO is general purpose in nature, we demonstrate it and evaluate its performance through a prototype application used by a tourist guide to monitor tour participants.
To address the challenges of the EWSN dependability competition we extended our synchronous trans... more To address the challenges of the EWSN dependability competition we extended our synchronous transmission protocol, CRYSTAL, with techniques to mitigate interference -- channel hopping and noise detection -- and with the capability to deliver aperiodic events to multiple actuators.
Event-triggered control ( ETC ) holds the potential to significantly improve the efficiency of wi... more Event-triggered control ( ETC ) holds the potential to significantly improve the efficiency of wireless networked control systems. Unfortunately, its real-world impact has hitherto been hampered by the lack of a network stack able to transfer its benefits from theory to practice specifically by supporting the latency and reliability requirements of the aperiodic communication ETC induces. This is precisely the contribution of this article. Our Wireless Control Bus ( WCB ) exploits carefully orchestrated network-wide floods of concurrent transmissions to minimize overhead during quiescent, steady-state periods, and ensures timely and reliable collection of sensor readings and dissemination of actuation commands when an ETC triggering condition is violated. Using a cyber-physical testbed emulating a water distribution system controlled over a real-world multi-hop wireless network, we show that ETC over WCB achieves the same quality of periodic control at a fraction of the energy costs...
2018 IEEE 12th International Conference on Self-Adaptive and Self-Organizing Systems (SASO), 2018
Today's "smart" domains are driven by lightweight battery operated devices carried by people and ... more Today's "smart" domains are driven by lightweight battery operated devices carried by people and embedded in environments. Many applications rely on continuous neighbor discovery, i.e., the ability to detect other nearby devices. Application uses for neighbor discovery are widely varying, but they all rely on a protocol in which devices exchange periodic beacons containing device identifiers. Many applications also ultimately involve assessing and adapting to context information sensed about the physical world and the device's situation in that world (e.g., its location or speed, the ambient temperature or sound, etc.). In this paper, we define Proactive Implicit Neighborhood Context Heuristics (PINCH), which leverages unused payload in periodic neighbor discovery beacons to opportunistically distribute context information in a local area. PINCH's selforganizing algorithms use limited local views of the state of a one-hop network neighborhood to determine the most useful type of context information for a device to sense and share. In this paper, we develop the algorithms, integrate an implementation of PINCH with a smart city simulator, and benchmark the tradeoffs of self-organized local context sharing with 2.4GHz neighbor discovery beacons.
Proceedings of the 16th ACM/IEEE International Conference on Information Processing in Sensor Networks, 2017
Identifying "who is around" is key in a plethora of smart scenarios. While many solutions exist, ... more Identifying "who is around" is key in a plethora of smart scenarios. While many solutions exist, they often take a theoretical approach, reasoning about protocol behavior with an abstract model that makes simplifying assumptions about the environment. This approach creates a gap between protocol implementations and the models used during design and analysis. In this paper, we take a system approach to continuous neighbor discovery: starting with the concrete technology of Bluetooth Low Energy (BLE) we build a protocol, called BLEnd, tailored to its constraints. Moreover, we also consider the very real effects of packet collisions, to our knowledge a first in this domain. Our ultimate goal is to directly empower developers with the ability to determine the optimal protocol configuration for their applications; in this respect, the slotless operation of BLEnd offers richer alternatives than state-of-the-art protocols. Developers specify the minimum discovery probability, the target discovery latency, and the maximum expected node density; these are used by an optimizer tool to parameterize the BLEnd implementation towards maximum lifetime. This paper shows that BLEnd not only achieves the user-specified goals, but does so more efficiently than analogous configurations of competing protocols. CCS CONCEPTS •Networks →Network protocol design; •Human-centered computing →Ubiquitous and mobile computing systems and tools;
Proceedings of the 2019 CHI Conference on Human Factors in Computing Systems, 2019
Technology increasingly offers parents opportunities to monitor children, reshaping the way contr... more Technology increasingly offers parents opportunities to monitor children, reshaping the way control and autonomy are negotiated within families. This paper investigates the views of parents and primary school children on mobile technology designed to support child independent mobility in the context of the local walking school buses. Based on a schoolyear long field study, we report findings on children's and parents' experience with proximity detection devices. The results provide insights into how the parents and children accepted and socially appropriated the technology into the walking school bus activity, shedding light on the way they understand and conceptualize a technology that collects data on children's proximity to the volunteers' smartphone. We discuss parents' needs and concerns around monitoring technologies and the related challenges in terms of trust-control balance. These insights are elaborated to inform the future design of technology for child independent mobility.
In wireless environments, transmission and 1 reception costs dominate system power consumption, m... more In wireless environments, transmission and 1 reception costs dominate system power consumption, motivating 2 research effort on new technologies capable of reducing the 3 footprint of the radio, paving the way for the Internet of 4 Things. The most important challenge is to reduce power 5 consumption when receivers are idle, the so called idle-listening 6 cost. One approach proposes switching off the main receiver, 7 then introduces new wake-up circuitry capable of detecting 8 an incoming transmission, optionally discriminating the packet 9 destination using addressing, then switching on the main radio 10 only when required. This wake-up receiver technology represents 11 the ultimate frontier in low power radio communication. In 12 this paper, we present a comprehensive literature review of 13 the research progress in wake-up radio (WuR) hardware and 14 relevant networking software. First, we present an overview of 15 the WuR system architecture, including challenges to hardware 16 design and a comparison of solutions presented throughout the 17 last decade. Next, we present various medium access control and 18 routing protocols as well as diverse ways to exploit WuRs, both 19 as an extension of pre-existing systems and as a new concept to 20 manage low-power networking.
Proceedings of the 14th ACM Conference on Embedded Network Sensor Systems CD-ROM, 2016
Data prediction in wireless sensor networks replaces the commonly used (periodic) data reporting ... more Data prediction in wireless sensor networks replaces the commonly used (periodic) data reporting with a model, updated (infrequently) at the sink to accurately reproduce real data trends. This technique abates up to 99% of application messages; yet, recent work has shown it achieves "only" up to a 7x lifetime improvement when executed atop a mainstream network stack (e.g., CTP + BoX-MAC), as the idle listening and topology maintenance in the latter are ill-suited to the sparse traffic induced by data prediction. This paper presents a novel network stack designed for data prediction, Crystal, that exploits synchronous transmissions to quickly and reliably transmit model updates when these occur (infrequently but often concurrently), and minimizes overhead during the (frequent) periods with no updates. Based on 90node experiments in the Indriya testbed and with 7 public datasets, we show that Crystal unleashes the full potential of data prediction, achieving per-mille duty cycle with perfect reliability and very small latency.
This paper describes the application of a wireless sensor network to a 31 meter-tall medieval tow... more This paper describes the application of a wireless sensor network to a 31 meter-tall medieval tower located in the city of Trento, Italy. The effort is motivated by preservation of the integrity of a set of frescoes decorating the room on the second floor, representing one of most important International Gothic artworks in Europe. The specific application demanded development of customized hardware and software. The wireless module selected as the core platform allows reliable wireless communication at low cost with a long service life. Sensors include accelerometers, deformation gauges, and thermometers. A multi-hop data collection protocol was applied in the software to improve the system's flexibility and scalability. The system has been operating since September 2008, and in recent months the data loss ratio was estimated as less than 0.01%. The data acquired so far are in agreement with the prediction resulting a priori from the 3-dimensional FEM. Based on these data a Bayesian updating procedure is employed to real-time estimate the probability of abnormal condition states. This first period of operation demonstrated the stability and reliability of the system, and its ability to recognize any possible occurrence of abnormal conditions that could jeopardize the integrity of the frescos.
Wireless sensor networks (WSNs) are evolving to support sense-andreact applications, where actuat... more Wireless sensor networks (WSNs) are evolving to support sense-andreact applications, where actuators are physically interspersed with the sensors that trigger them. This solution maximizes localized interactions, improving resource utilization and reducing latency w.r.t. solutions with a centralized sink. Nevertheless, application development becomes more complex: the control logic must be embedded in the network, and coordination among multiple tasks is needed to achieve the application goals. This paper presents TeenyLIME, a WSN middleware designed to address the above challenges. TeenyLIME provides programmers with the high-level abstraction of a tuple space, enabling data sharing among neighboring devices. These and other WSN-specific constructs simplify the development of a wide range of applications, including sense-and-react ones. TeenyLIME yields simpler, cleaner, and more reusable implementations, at the cost of only a very limited decrease in performance. We support these claims through a source-level, quantitative comparison between implementations based on TeenyLIME and on mainstream approaches, and by analyzing measures of processing overhead and power consumption obtained through cycle-accurate emulation.
Content-based publish-subscribe is emerging as a communication paradigm able to cope with the nee... more Content-based publish-subscribe is emerging as a communication paradigm able to cope with the needs of scalability, flexibility, and reconfigurability typical of highly dynamic distributed applications. However, very few efforts address dynamic changes in the topology of the publish-subscribe distributed dispatching infrastructure-a fundamental challenge in mobile computing scenarios. In this chapter we illustrate the problems posed by mobility in the context of publish-subscribe, discuss protocols and integrated solutions proposed by our research group, and survey the state of the art in this research area.
A new class of models, formalisms and mechanisms has recently evolved for describing concurrent a... more A new class of models, formalisms and mechanisms has recently evolved for describing concurrent and distributed computations based on the concept of "coordination". The purpose of a coordination model and associated language is to provide a means of integrating a number of possibly heterogeneous components together, by interfacing with each component in such a way that the collective set forms a single application that can execute on and take advantage of parallel and distributed systems. In this chapter we initially define and present in sufficient detail the fundamental concepts of what constitutes a coordination model or language. We then go on to classify these models and languages as either "data-driven" or "control-driven" (also called "process-" or "task-oriented"). Next, the main existing coordination models and languages are described in sufficient detail to let the reader appreciate their features and put them into perspective with respect to each other. The chapter ends with a discussion comparing the various models and some conclusions.
Wireless sensor networks (WSNs) often rely on dutycycling, alternating periods of low-power stand... more Wireless sensor networks (WSNs) often rely on dutycycling, alternating periods of low-power stand-by with others where sensing, computation, and communication are performed. Duty-cycling brings substantial energy savings, but may complicate the WSN design. The effectiveness of a node in performing its task (e.g., sensing events occurring in an area) is affected by its wake-up schedule. Random schedules lead to deployments that are either ineffective (e.g., insufficient sensing coverage) or inefficient (e.g., areas covered by multiple nodes simultaneously awake). In this paper, we focus on the problem of scattering the nodes' wake-up times optimally, to achieve maximal coverage of a given area. In previous work [5], we presented a decentralized protocol that improves significantly over random wake-up schedules. Instead, here we provide a centralized optimal solution that complements the work in [5] by identifying the theoretical upper bound to distributed protocols. Moreover, the modeling framework we present, based on integer programming techniques, is general enough to encompass alternative formulations of the problem. These include the inverse problem of determining the optimal schedule given a desired coverage, as well as other problems based on constraints other than coverage (e.g., latency of data dissemination).
2018 17th ACM/IEEE International Conference on Information Processing in Sensor Networks (IPSN), 2018
Aperiodic data collection received little attention in wireless sensor networks, compared to its ... more Aperiodic data collection received little attention in wireless sensor networks, compared to its periodic counterpart. The recent Crystal system uses synchronous transmissions to support aperiodic traffic with near-perfect reliability, low latency, and ultra-low power consumption. However, its performance is known under mild interference-a concern, as Crystal relies heavily on the (noise-sensitive) capture effect and targets aperiodic traffic where "every packet counts". We exploit a 49-node indoor testbed where, in contrast to existing evaluations using only naturally present interference to evaluate synchronous systems, we rely on JamLab to generate noise patterns that are not only more disruptive and extensive, but also reproducible. We show that a properly configured, unmodified Crystal yields perfect reliability (unlike Glossy) in several noise scenarios, but cannot sustain extreme ones (e.g., an emulated microwave oven near the sink) that instead are handled by routing-based approaches. We extend Crystal with techniques known to mitigate interference-channel hopping and noise detection-and demonstrate that these allow Crystal to achieve performance akin to the original even under multiple sources of strong interference.
2018 IEEE 12th International Conference on Self-Adaptive and Self-Organizing Systems (SASO), 2018
Pervasive sensing and actuation applications are increasingly being built using distributed devic... more Pervasive sensing and actuation applications are increasingly being built using distributed devices connected with low-power wireless links. Most of these applications exploit anarchic protocols in which devices independently attempt to seize communication resources, supporting only besteffort applications as the communication they rely on cannot be guaranteed. For strict quality of service requirements, a few, non-anarchic, disciplined approaches exist in which nodes coordinate and resources are guaranteed to individual devices. Unfortunately, these solutions come at a considerable cost to form and conform to rigid communication schedules while considering the inherent volatility of the wireless environment. This work proposes REINS-MAC, a fully distributed solution that adapts to changes in the wireless environment and forms a flexible communication schedule able to support quality of service requirements. Inspired by pulse-coupled oscillators, the mathematical formulation of firefly flash synchronization, our approach forms and reserves communication slots of variable size in an online and adaptive manner. REINS-MAC tailors communication resources to network conditions that vary in time and space as well as to the explicit communication needs of devices by enabling distributed, dynamic changes to established schedules. Ultimately, REINS-MAC allows higher level abstractions to rein in the protocol anarchy, laying the foundation for reliable wireless applications.
2 On Global Virtual Data Structures Gian Pietro Picco Amy L. Murphy Gruia-Catalin Roman Abstract ... more 2 On Global Virtual Data Structures Gian Pietro Picco Amy L. Murphy Gruia-Catalin Roman Abstract In distributed computing, global information is rarely available and most actions are carried out locally. However, when proving system properties we frequently turn to defining ...
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