The Industrial Internet of Things (IIoT) requires wireless connectivity that meets the strict ind... more The Industrial Internet of Things (IIoT) requires wireless connectivity that meets the strict industrial requirements on metrics such as reliability and latency. Promising approaches include Time Slotted Channel Hopping (TSCH) media access, where nodes operate according to a schedule. Autonomously built schedules typically rely on shared resources, where reliability and latency may suffer depending on traffic scenarios and topologies. We have earlier proposed the Layered scheduler, which belongs to a new category of autonomous schedulers: Flow-based scheduling. Layered allocates resources to traffic flows, and as opposed to typical autonomous schedulers, dedicated resources are guaranteed to be scheduled at every hop from source to destination in a convergecast scenario. In addition, Layered minimizes the number of channels required through the novel employment of autonomous spatial reuse. We extend earlier theoretical analysis and simulations by evaluating Layered using the FIT IoT-LAB testbed and compare it to Orchestra and 6TiSCH Minimal scheduler. The experiments demonstrate the feasibility of spatial reuse and that Layered retains performance independent of network topology and traffic intensity-a desirable feature in industrial scenarios. The performance comes at the expense of energy consumption, which in the worst case is 75 % higher compared to Orchestra and Minimal. We also present lessons learned, such as the impact of TSCH configuration on RPL convergence, the benefits of black-listing on performance, and how co-located TSCH networks could be divided by channel offsets as opposed to physical channels. Lastly, we discuss flow-based scheduling in general, its properties, and future research areas.
The Industrial Internet of Things (IIoT) requires wireless connectivity that meets the strict ind... more The Industrial Internet of Things (IIoT) requires wireless connectivity that meets the strict industrial requirements on metrics such as reliability and latency. Promising approaches include Time Slotted Channel Hopping (TSCH) media access, where nodes operate according to a schedule. Autonomously built schedules typically rely on shared resources, where reliability and latency may suffer depending on traffic scenarios and topologies. We have earlier proposed the Layered scheduler, which belongs to a new category of autonomous schedulers: Flow-based scheduling. Layered allocates resources to traffic flows, and as opposed to typical autonomous schedulers, dedicated resources are guaranteed to be scheduled at every hop from source to destination in a convergecast scenario. In addition, Layered minimizes the number of channels required through the novel employment of autonomous spatial reuse. We extend earlier theoretical analysis and simulations by evaluating Layered using the FIT IoT-LAB testbed and compare it to Orchestra and 6TiSCH Minimal scheduler. The experiments demonstrate the feasibility of spatial reuse and that Layered retains performance independent of network topology and traffic intensity-a desirable feature in industrial scenarios. The performance comes at the expense of energy consumption, which in the worst case is 75 % higher compared to Orchestra and Minimal. We also present lessons learned, such as the impact of TSCH configuration on RPL convergence, the benefits of black-listing on performance, and how co-located TSCH networks could be divided by channel offsets as opposed to physical channels. Lastly, we discuss flow-based scheduling in general, its properties, and future research areas.
International Conference on Sensor Technologies and Applications, Nov 21, 2020
Reducing energy consumption in Wireless Sensor Networks (WSN) is important in order to lengthen t... more Reducing energy consumption in Wireless Sensor Networks (WSN) is important in order to lengthen the network lifetime and reduce maintenance cost. Although its substantial contribution, the energy consumed to overhear is often omitted in energy calculations. However, here it is included to model the tradeoff between the expected number of transmissions, transmission range, number of hops, and overhearing, to discover the optimal distance between the nodes along the routing path. Our calculations show that to reduce energy consumption, the node should choose their successors close enough to prevent the expected number of transmissions from exceeding 1.4. The access protocol is Low Power Listening (LPL), and we also present a solution to reduce the energy consumption of the nodes that are crucial for maintaining an operational network, i.e., the nodes whose successor is the sink.
a series of events dedicated to mobility-at-large, dealing with challenges raised by mobile servi... more a series of events dedicated to mobility-at-large, dealing with challenges raised by mobile services and applications considering user, device and service mobility. Users increasingly rely on devices in different mobile scenarios and situations. "Everything is mobile", and mobility is now ubiquitous. Services are supported in mobile environments, through smart devices and enabling software. While there are well known mobile services, the extension to mobile communities and on-demand mobility requires appropriate mobile radios, middleware and interfacing. Mobility management becomes more complex, but is essential for every business. Mobile wireless communications, including vehicular technologies bring new requirements for ad hoc networking, topology control and interface standardization. We take here the opportunity to warmly thank all the members of the MOBILITY 2015 Technical Program Committee, as well as the numerous reviewers. The creation of such a broad and high qual...
2018 Ubiquitous Positioning, Indoor Navigation and Location-Based Services (UPINLBS), 2018
We study mobility of sensors in our ongoing home care project, where care-purpose sensors togethe... more We study mobility of sensors in our ongoing home care project, where care-purpose sensors together with home automation devices are installed in private houses. The Internet of Things (IoT) solution is implemented in the project, as networks of IP-enabled sensors and devices are built, based on standardized IoT protocols. Since wearable sensors are important for monitoring of health conditions, we investigate the performance of such networks with mobile nodes, by assessing MAC layer protocols and Routing Protocol for Low-Power and Lossy Networks (RPL). We utilize the recently released Contiking operating system and its simulation tool: Cooja. In the first simulation scenario, we place a mobile node in networks with different densities of nodes, comparing MAC layer mechanisms: CSMA/CA and TSCH. In the second scenario, we focus on a given network where sensors are placed as in our modeled apartment. Under the certain network size and topology, we design schedule of TSCH and optimize control message interval of RPL to get better mobility supporting.
Conservation of energy is one of the main challenges in designing a wireless sensor network (WSN)... more Conservation of energy is one of the main challenges in designing a wireless sensor network (WSN). The reason is that these large scaled networks cannot be arranged, configured, or maintained manually. Thus, automated deployment and configuration are required. One important factor determining the total energy consumption is the network topology. This article evaluates the relation between the maximum distance (link lengths) between the nodes in a WSN and the total energy consumed. The optimal topology for the two most commonly used medium access control (MAC) protocols were found. A WSN based on a Time Division Multiple Access (TDMA) protocol is limited by the maximum available or allowed emitted radio power. Thus, the criterion for optimal link lengths is related to the expected number of transmissions over the links. By including the retransmissions over the links we found an optimal internode distance. A Carrier Sense Multiple Access (CSMA) based WSN, on the other hand, is limite...
This paper is devoted to a comparison of two sensor technologies that may be employed in care ser... more This paper is devoted to a comparison of two sensor technologies that may be employed in care services for elderly or disabled persons. The performance of monitoring systems, based on impulse-radar sensors and depth sensors, has been systematically compared in a series of experiments which involved the estimation of several quantities, carrying information important for medical and healthcare services, on the basis of data from those sensors. The results of the experiments have shown that, although in most cases the estimates based on data acquired by means of radar sensors are less accurate than those based on data acquired by means of depth sensors, both types of sensors provide information useful for the medical and healthcare users of the monitoring systems.
Wireless Sensor Networks (WSNs) are applicable in numerous domains, including industrial automati... more Wireless Sensor Networks (WSNs) are applicable in numerous domains, including industrial automation where WSNs may be used for monitoring and control of industrial plants and equipment. However, the requirements in the industrial systems differ from the general WSN requirements. In recent years, standards have been defined by several industrial alliances. These standards are specified as frameworks with modifiable parts that can be defined based on the particular application of WSN. However, limited work has been done on defining industryspecific protocols that could be used as a part of these standards. In this survey, we discuss representative protocols that meet some of the requirements of the industrial applications. Since the industrial applications domain in itself is a vast area, we divide them into classes with similar requirements. We discuss these industrial classes, set of common requirements and various stateof-the-art WSN standards proposed to satisfy these requirements. We then present a broader view towards the WSN solution by discussing important functions like medium access control, routing, and transport in detail to give some insight into specific requirements and the classification of protocols based on certain factors. We list and discuss representative protocols for each of these functions that address requirements defined in the industrial classes. Security function is discussed in brief, mainly in relation to industrial standards. Finally, we identify unsolved challenges that are encountered during design of protocols and standards. In addition some new challenges are introduced and discussed.
Wireless Sensor Networks Running (WSN) functionality depends critically on the network connectivi... more Wireless Sensor Networks Running (WSN) functionality depends critically on the network connectivity. The connectivity is generally determined by the node density and the nodes' transmission range. However, the applied routing protocol decides the routing path topology. A failing node may disrupt the current path topology such that dedicated recovery methods are needed to ensure a loop-free reconnection of the disconnected nodes. In this article, we estimate the probability that disconnected nodes need dedicated recovery methods in networks where the nodes are randomly located and which use RPL as routing protocol. We further calculate the success rate and overhead cost for different RPL fitted recovery protocols to better judge where the different methods should be used.
In a MANET network where nodes move frequently, the probability of connectivity loss between node... more In a MANET network where nodes move frequently, the probability of connectivity loss between nodes might be high, and communication sessions may easily loose connectivity during transmission. The routing protocol is designed to find alternative paths in these situations. This rerouting takes time, and the latency is referred to as the rerouting time. This paper investigates the rerouting time of proactive routing protocols and shows that the rerouting time is considerably affected by queueing. Simulations and analysis are conducted to explore the problem. Finally, we propose a MAC-layer solution that reduces the rerouting time problems due to queueing. Simulations and analysis show that the solution is so effective that it eliminates the entire problem in many situations. 1.
— OSPF is the standard interior routing protocol widely deployed in the fixed Internet. Wireless ... more — OSPF is the standard interior routing protocol widely deployed in the fixed Internet. Wireless OSPF is targeted at extending OSPF in a mobile ad hoc environment in which reducing protocol overhead is of paramount importance. So far two proposals have received most attention and are currently under active investigation within the IETF. In this paper, we present the design and implementation of one of them, referred to as WOSPF-OR in the context, that uses overlapping relays for reliable and efficient flooding. We adopt a plugin module concept in our implementation design and our implementation is developed based on the Quagga routing software platform. I.
Abstract-The task of this interdisciplinary PolishNorwegian project is development of radar techn... more Abstract-The task of this interdisciplinary PolishNorwegian project is development of radar technology for care services. The project has mainly an exploratory design where the capabilities of radar technology are tested out, related to elderly or disabled people living in their own home. A system for preventing and detecting falls, or detecting other potential injurious situations e.g. as nocturnal seizures, is the main goal. Norwegian health care policies suggest strengthening community based services and home based care. Facilitating innovation and appropriation of ambient technology is part of this strategy. The present project relates to telecare as part of ambient assisted living.
Conservation of energy is one of the main challenges in designing a wireless sensor network (WSN)... more Conservation of energy is one of the main challenges in designing a wireless sensor network (WSN). The reason is that these large scaled networks cannot be arranged, configured, or maintained manually. Thus, automated deployment and configuration are required. One important factor determining the total energy consumption is the network topology. This article evaluates the relation between the maximum distance (link lengths) between the nodes in a WSN and the total energy consumed. The optimal topology for the two most commonly used medium access control (MAC) protocols were found. A WSN based on a Time Division Multiple Access (TDMA) protocol is limited by the maximum available or allowed emitted radio power. Thus, the criterion for optimal link lengths is related to the expected number of transmissions over the links. By including the retransmissions over the links we found an optimal internode distance. A Carrier Sense Multiple Access (CSMA) based WSN, on the other hand, is limite...
Automatic discovery of services and resources is a crucial feature to achieve the expected user-f... more Automatic discovery of services and resources is a crucial feature to achieve the expected user-friendliness in Mobile Ad-hoc Networks. Due to limited computing power, scarce bandwidth, high mobility and the lack of a central coordinating entity, service discovery in these networks is a challenging task. In this paper, we develop a service discovery protocol (Mercury) utilizing a combination of different optimization techniques: The performance is increased using cross-layer interaction between the application layer and the routing layer. The service information is described using Bloom filters and distributed using Optimized Link State Routing (OLSR). A caching regime is implemented to obtain further reductions of both overhead and latency. The analysis and simulation results show that our service discovery proposal induces very low overhead to OLSR and is superior to application layer solutions. The proposal is implemented as a plugin to the OLSR implementation olsrd for real-worl...
Concepts such as Industry 4.0 and Cyber-Physical Systems may bring forward a new industrial revol... more Concepts such as Industry 4.0 and Cyber-Physical Systems may bring forward a new industrial revolution. These concepts require extensive connectivity far beyond what is provided by traditional industrial networks. The Industrial Internet of Things (IIoT) bridges this gap by employing wireless connectivity and IP networking. In order for wireless networks to meet the strict requirements of the industrial domain, the Time Slotted Channel Hopping (TSCH) MAC is often employed. The properties of a TSCH network are defined by the schedule, which dictates transmission opportunities for all nodes. We survey the literature for these schedulers, describe and organize them according to their operation: Centralized, Collaborative, Autonomous, Hybrid, and Static. For each category and the field as a whole, we provide a holistic view and describe historical trends, highlight key developments, and identify trends, such as the attention towards autonomous mechanisms. Each of the 76 schedulers is an...
This work illustrates potentials for recognition within ad hoc sensor networks if their nodes pos... more This work illustrates potentials for recognition within ad hoc sensor networks if their nodes possess individual inter-related biologically inspired genetic codes. The work takes ideas from natural immune systems protecting organisms from infection. Nodes in the present proposal have individual gene sets tting into a self organised phylogenetic tree. Members of this population are genetically "relatives". Outsiders cannot easily copy or introduce a new node in the network without going through a process of conception between two nodes in the population. Related nodes can locally decide to check each other for their genetic relation without directly revealing their gene sets. A copy/clone of a gene sequence or a random gene set will appear as alien. Nodes go through a cycle of introduction (conception or "birth") with parents in the network and later exit from it ("death"). Hence the phylogenetic tree is dynamic or possesses a genetic drift. Typical life...
The Industrial Internet of Things (IIoT) requires wireless connectivity that meets the strict ind... more The Industrial Internet of Things (IIoT) requires wireless connectivity that meets the strict industrial requirements on metrics such as reliability and latency. Promising approaches include Time Slotted Channel Hopping (TSCH) media access, where nodes operate according to a schedule. Autonomously built schedules typically rely on shared resources, where reliability and latency may suffer depending on traffic scenarios and topologies. We have earlier proposed the Layered scheduler, which belongs to a new category of autonomous schedulers: Flow-based scheduling. Layered allocates resources to traffic flows, and as opposed to typical autonomous schedulers, dedicated resources are guaranteed to be scheduled at every hop from source to destination in a convergecast scenario. In addition, Layered minimizes the number of channels required through the novel employment of autonomous spatial reuse. We extend earlier theoretical analysis and simulations by evaluating Layered using the FIT IoT-LAB testbed and compare it to Orchestra and 6TiSCH Minimal scheduler. The experiments demonstrate the feasibility of spatial reuse and that Layered retains performance independent of network topology and traffic intensity-a desirable feature in industrial scenarios. The performance comes at the expense of energy consumption, which in the worst case is 75 % higher compared to Orchestra and Minimal. We also present lessons learned, such as the impact of TSCH configuration on RPL convergence, the benefits of black-listing on performance, and how co-located TSCH networks could be divided by channel offsets as opposed to physical channels. Lastly, we discuss flow-based scheduling in general, its properties, and future research areas.
The Industrial Internet of Things (IIoT) requires wireless connectivity that meets the strict ind... more The Industrial Internet of Things (IIoT) requires wireless connectivity that meets the strict industrial requirements on metrics such as reliability and latency. Promising approaches include Time Slotted Channel Hopping (TSCH) media access, where nodes operate according to a schedule. Autonomously built schedules typically rely on shared resources, where reliability and latency may suffer depending on traffic scenarios and topologies. We have earlier proposed the Layered scheduler, which belongs to a new category of autonomous schedulers: Flow-based scheduling. Layered allocates resources to traffic flows, and as opposed to typical autonomous schedulers, dedicated resources are guaranteed to be scheduled at every hop from source to destination in a convergecast scenario. In addition, Layered minimizes the number of channels required through the novel employment of autonomous spatial reuse. We extend earlier theoretical analysis and simulations by evaluating Layered using the FIT IoT-LAB testbed and compare it to Orchestra and 6TiSCH Minimal scheduler. The experiments demonstrate the feasibility of spatial reuse and that Layered retains performance independent of network topology and traffic intensity-a desirable feature in industrial scenarios. The performance comes at the expense of energy consumption, which in the worst case is 75 % higher compared to Orchestra and Minimal. We also present lessons learned, such as the impact of TSCH configuration on RPL convergence, the benefits of black-listing on performance, and how co-located TSCH networks could be divided by channel offsets as opposed to physical channels. Lastly, we discuss flow-based scheduling in general, its properties, and future research areas.
International Conference on Sensor Technologies and Applications, Nov 21, 2020
Reducing energy consumption in Wireless Sensor Networks (WSN) is important in order to lengthen t... more Reducing energy consumption in Wireless Sensor Networks (WSN) is important in order to lengthen the network lifetime and reduce maintenance cost. Although its substantial contribution, the energy consumed to overhear is often omitted in energy calculations. However, here it is included to model the tradeoff between the expected number of transmissions, transmission range, number of hops, and overhearing, to discover the optimal distance between the nodes along the routing path. Our calculations show that to reduce energy consumption, the node should choose their successors close enough to prevent the expected number of transmissions from exceeding 1.4. The access protocol is Low Power Listening (LPL), and we also present a solution to reduce the energy consumption of the nodes that are crucial for maintaining an operational network, i.e., the nodes whose successor is the sink.
a series of events dedicated to mobility-at-large, dealing with challenges raised by mobile servi... more a series of events dedicated to mobility-at-large, dealing with challenges raised by mobile services and applications considering user, device and service mobility. Users increasingly rely on devices in different mobile scenarios and situations. "Everything is mobile", and mobility is now ubiquitous. Services are supported in mobile environments, through smart devices and enabling software. While there are well known mobile services, the extension to mobile communities and on-demand mobility requires appropriate mobile radios, middleware and interfacing. Mobility management becomes more complex, but is essential for every business. Mobile wireless communications, including vehicular technologies bring new requirements for ad hoc networking, topology control and interface standardization. We take here the opportunity to warmly thank all the members of the MOBILITY 2015 Technical Program Committee, as well as the numerous reviewers. The creation of such a broad and high qual...
2018 Ubiquitous Positioning, Indoor Navigation and Location-Based Services (UPINLBS), 2018
We study mobility of sensors in our ongoing home care project, where care-purpose sensors togethe... more We study mobility of sensors in our ongoing home care project, where care-purpose sensors together with home automation devices are installed in private houses. The Internet of Things (IoT) solution is implemented in the project, as networks of IP-enabled sensors and devices are built, based on standardized IoT protocols. Since wearable sensors are important for monitoring of health conditions, we investigate the performance of such networks with mobile nodes, by assessing MAC layer protocols and Routing Protocol for Low-Power and Lossy Networks (RPL). We utilize the recently released Contiking operating system and its simulation tool: Cooja. In the first simulation scenario, we place a mobile node in networks with different densities of nodes, comparing MAC layer mechanisms: CSMA/CA and TSCH. In the second scenario, we focus on a given network where sensors are placed as in our modeled apartment. Under the certain network size and topology, we design schedule of TSCH and optimize control message interval of RPL to get better mobility supporting.
Conservation of energy is one of the main challenges in designing a wireless sensor network (WSN)... more Conservation of energy is one of the main challenges in designing a wireless sensor network (WSN). The reason is that these large scaled networks cannot be arranged, configured, or maintained manually. Thus, automated deployment and configuration are required. One important factor determining the total energy consumption is the network topology. This article evaluates the relation between the maximum distance (link lengths) between the nodes in a WSN and the total energy consumed. The optimal topology for the two most commonly used medium access control (MAC) protocols were found. A WSN based on a Time Division Multiple Access (TDMA) protocol is limited by the maximum available or allowed emitted radio power. Thus, the criterion for optimal link lengths is related to the expected number of transmissions over the links. By including the retransmissions over the links we found an optimal internode distance. A Carrier Sense Multiple Access (CSMA) based WSN, on the other hand, is limite...
This paper is devoted to a comparison of two sensor technologies that may be employed in care ser... more This paper is devoted to a comparison of two sensor technologies that may be employed in care services for elderly or disabled persons. The performance of monitoring systems, based on impulse-radar sensors and depth sensors, has been systematically compared in a series of experiments which involved the estimation of several quantities, carrying information important for medical and healthcare services, on the basis of data from those sensors. The results of the experiments have shown that, although in most cases the estimates based on data acquired by means of radar sensors are less accurate than those based on data acquired by means of depth sensors, both types of sensors provide information useful for the medical and healthcare users of the monitoring systems.
Wireless Sensor Networks (WSNs) are applicable in numerous domains, including industrial automati... more Wireless Sensor Networks (WSNs) are applicable in numerous domains, including industrial automation where WSNs may be used for monitoring and control of industrial plants and equipment. However, the requirements in the industrial systems differ from the general WSN requirements. In recent years, standards have been defined by several industrial alliances. These standards are specified as frameworks with modifiable parts that can be defined based on the particular application of WSN. However, limited work has been done on defining industryspecific protocols that could be used as a part of these standards. In this survey, we discuss representative protocols that meet some of the requirements of the industrial applications. Since the industrial applications domain in itself is a vast area, we divide them into classes with similar requirements. We discuss these industrial classes, set of common requirements and various stateof-the-art WSN standards proposed to satisfy these requirements. We then present a broader view towards the WSN solution by discussing important functions like medium access control, routing, and transport in detail to give some insight into specific requirements and the classification of protocols based on certain factors. We list and discuss representative protocols for each of these functions that address requirements defined in the industrial classes. Security function is discussed in brief, mainly in relation to industrial standards. Finally, we identify unsolved challenges that are encountered during design of protocols and standards. In addition some new challenges are introduced and discussed.
Wireless Sensor Networks Running (WSN) functionality depends critically on the network connectivi... more Wireless Sensor Networks Running (WSN) functionality depends critically on the network connectivity. The connectivity is generally determined by the node density and the nodes' transmission range. However, the applied routing protocol decides the routing path topology. A failing node may disrupt the current path topology such that dedicated recovery methods are needed to ensure a loop-free reconnection of the disconnected nodes. In this article, we estimate the probability that disconnected nodes need dedicated recovery methods in networks where the nodes are randomly located and which use RPL as routing protocol. We further calculate the success rate and overhead cost for different RPL fitted recovery protocols to better judge where the different methods should be used.
In a MANET network where nodes move frequently, the probability of connectivity loss between node... more In a MANET network where nodes move frequently, the probability of connectivity loss between nodes might be high, and communication sessions may easily loose connectivity during transmission. The routing protocol is designed to find alternative paths in these situations. This rerouting takes time, and the latency is referred to as the rerouting time. This paper investigates the rerouting time of proactive routing protocols and shows that the rerouting time is considerably affected by queueing. Simulations and analysis are conducted to explore the problem. Finally, we propose a MAC-layer solution that reduces the rerouting time problems due to queueing. Simulations and analysis show that the solution is so effective that it eliminates the entire problem in many situations. 1.
— OSPF is the standard interior routing protocol widely deployed in the fixed Internet. Wireless ... more — OSPF is the standard interior routing protocol widely deployed in the fixed Internet. Wireless OSPF is targeted at extending OSPF in a mobile ad hoc environment in which reducing protocol overhead is of paramount importance. So far two proposals have received most attention and are currently under active investigation within the IETF. In this paper, we present the design and implementation of one of them, referred to as WOSPF-OR in the context, that uses overlapping relays for reliable and efficient flooding. We adopt a plugin module concept in our implementation design and our implementation is developed based on the Quagga routing software platform. I.
Abstract-The task of this interdisciplinary PolishNorwegian project is development of radar techn... more Abstract-The task of this interdisciplinary PolishNorwegian project is development of radar technology for care services. The project has mainly an exploratory design where the capabilities of radar technology are tested out, related to elderly or disabled people living in their own home. A system for preventing and detecting falls, or detecting other potential injurious situations e.g. as nocturnal seizures, is the main goal. Norwegian health care policies suggest strengthening community based services and home based care. Facilitating innovation and appropriation of ambient technology is part of this strategy. The present project relates to telecare as part of ambient assisted living.
Conservation of energy is one of the main challenges in designing a wireless sensor network (WSN)... more Conservation of energy is one of the main challenges in designing a wireless sensor network (WSN). The reason is that these large scaled networks cannot be arranged, configured, or maintained manually. Thus, automated deployment and configuration are required. One important factor determining the total energy consumption is the network topology. This article evaluates the relation between the maximum distance (link lengths) between the nodes in a WSN and the total energy consumed. The optimal topology for the two most commonly used medium access control (MAC) protocols were found. A WSN based on a Time Division Multiple Access (TDMA) protocol is limited by the maximum available or allowed emitted radio power. Thus, the criterion for optimal link lengths is related to the expected number of transmissions over the links. By including the retransmissions over the links we found an optimal internode distance. A Carrier Sense Multiple Access (CSMA) based WSN, on the other hand, is limite...
Automatic discovery of services and resources is a crucial feature to achieve the expected user-f... more Automatic discovery of services and resources is a crucial feature to achieve the expected user-friendliness in Mobile Ad-hoc Networks. Due to limited computing power, scarce bandwidth, high mobility and the lack of a central coordinating entity, service discovery in these networks is a challenging task. In this paper, we develop a service discovery protocol (Mercury) utilizing a combination of different optimization techniques: The performance is increased using cross-layer interaction between the application layer and the routing layer. The service information is described using Bloom filters and distributed using Optimized Link State Routing (OLSR). A caching regime is implemented to obtain further reductions of both overhead and latency. The analysis and simulation results show that our service discovery proposal induces very low overhead to OLSR and is superior to application layer solutions. The proposal is implemented as a plugin to the OLSR implementation olsrd for real-worl...
Concepts such as Industry 4.0 and Cyber-Physical Systems may bring forward a new industrial revol... more Concepts such as Industry 4.0 and Cyber-Physical Systems may bring forward a new industrial revolution. These concepts require extensive connectivity far beyond what is provided by traditional industrial networks. The Industrial Internet of Things (IIoT) bridges this gap by employing wireless connectivity and IP networking. In order for wireless networks to meet the strict requirements of the industrial domain, the Time Slotted Channel Hopping (TSCH) MAC is often employed. The properties of a TSCH network are defined by the schedule, which dictates transmission opportunities for all nodes. We survey the literature for these schedulers, describe and organize them according to their operation: Centralized, Collaborative, Autonomous, Hybrid, and Static. For each category and the field as a whole, we provide a holistic view and describe historical trends, highlight key developments, and identify trends, such as the attention towards autonomous mechanisms. Each of the 76 schedulers is an...
This work illustrates potentials for recognition within ad hoc sensor networks if their nodes pos... more This work illustrates potentials for recognition within ad hoc sensor networks if their nodes possess individual inter-related biologically inspired genetic codes. The work takes ideas from natural immune systems protecting organisms from infection. Nodes in the present proposal have individual gene sets tting into a self organised phylogenetic tree. Members of this population are genetically "relatives". Outsiders cannot easily copy or introduce a new node in the network without going through a process of conception between two nodes in the population. Related nodes can locally decide to check each other for their genetic relation without directly revealing their gene sets. A copy/clone of a gene sequence or a random gene set will appear as alien. Nodes go through a cycle of introduction (conception or "birth") with parents in the network and later exit from it ("death"). Hence the phylogenetic tree is dynamic or possesses a genetic drift. Typical life...
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Papers by Knut Øvsthus