In research and education, a Wireless Sensor Network (WSN) may exist for its own sake and also the specific nodes used in such networks might be considered as study objects. However, in real applications the networks and the nodes are applied to solve real-world issues and, hence, have to be designed for their specific purpose. Since WSNs and according nodes have to cope with significant limitations and challenges, especially regarding energy budgets, it is typically considered as impractical to use a 'one size fits all' network configuration or a 'one size fits all', universal sensor node. Instead, it is necessary for every single component of a node, like processor, memory, radio transceiver, set of sensors, peripherals, and energy source to consider what is necessary and they have to be chosen according to the needs of the envisaged use case. Therefore, designing or at least selecting appropriate nodes is a crucial part for every deployment of WSNs. Based on that also the used networking technologies, the topology, the protocols, etc. have to be developed and chosen. In this chapter, first some general considerations and architectures for sensor nodes are presented. Also, some insights of'how to design' the adequate node for specific use cases are given. The design of sensor nodes for two exemplary missions are discussed in detail. In particular the diverse missions Human Activity Monitoring and Smart Farming are used to reveal the specialty when designing mission-oriented sensor nodes.

During recent years, automation and optimized production processes within a variety of different agriculture sectors allowed farmers to achieve higher harvesting rates and therefore to maximize the outcome of their efforts. Besides harvesting, storing the crop is the next challenging step in improving agricultural practices. Monitoring and adjusting the environmental conditions in storage are important tasks to achieve an optimal and efficient storability. This paper focuses on the communication part of such a monitoring system. Modern warehouses are usually organized as box storage, which means that the crop to be stored is filled into boxes and then piled up in large warehouses. Selective ventilation and air conditioning ensure a maximum storage period. This paper examines which radio frequencies are suitable for transmitting sensor data from stored boxes to a sink. The obtained sensor data could be used, for example, to control the air conditioning of the warehouse more precisely. The investigations are carried out on potatoes as an example, for which first a simulation and then a prototypical sensor node is created.

Energy is the most limiting factor for remote outdoor deployments of Wireless Sensor Networks (WSNs). This paper proposes a novel routing algorithm for dual-platform nodes targeting WSN applications as found in smart farming applications. For scenarios in which high power components of nodes and radio links will be switched on at known points in time, our algorithm tries to make use of scheduled uptimes of nodes with the possibilities to turn other nodes on to send the nodes' data to a sink on time. We compare our method with a traditional flooding-based algorithm as well as with a greedy version which tries to transfer the data immediately. We show that our mechanism works energy-efficient while meeting all deadlines and keeping the amount of control traffic at a necessary minimum.

Time synchronization of several nodes is important for many Wireless Sensor Network (WSN) algorithms, components, and application scenarios. Therefore, it would be very beneficial if a low-cost method for such synchronization was available. The same applies to low-power wakeup of nodes. Ideally, a simplistic and almost no-cost channel should be provided that can be utilized to face such challenges like synchronization and wakeup of nodes. In this demo paper we present the idea for such a method and show first results as well as a proof of concept setup. It is based on an electric pulse generated by, e.g., a regular electric fence which can be detected and utilized by usual ultra low-power micro controller units (MCUs) of a sensor node.

While success stories are likely to be reported, failures are rarely published -- even if a lot can be learned from them. In this paper we present experiences and findings from our testbed and WSN deployments. Our PotatoNet has been deployed on an agricultural area in 2015 to perform several WSN outdoor experiments while measuring the stress of potato crops. It was extended a year later by the PotatoMesh, a solar panel-based mesh network of nodes. Throughout both of these deployments we experienced problems and failures at different stages of the projects. We derive key problems and some important concepts when it comes to outdoor WSN deployments.

In this paper, we present the usage of our two-platform DTN node "Amphisbaena". It is designed for wireless outdoor operation without the need of an external energy supply. A Low Power Platform is running continuously and is able to power up a Linux based SBC on demand. Both parts are using the same communication protocol and appear as a single node to neighbors. In this demonstration we show the system in an example application, which allows to capture an image from a webcam attached to the High Power Platform. The request for the image is sent using a low power link while the answer is transferred using WiFi from the SBC.

The deployment and especially the long-term operation of outdoor Wireless Sensor Network (WSN) testbeds is still a challenging task. If different monitoring tasks with significantly varying demands have to be performed, the handling of scarce resources like energy becomes difficult and might lead to questions about the reliability of the testbed. In this paper, we present "PotatoMesh", a remotely deployed WSN consisting of different classes of nodes. In addition to more regular sensor nodes like INGA [1], we introduce new 'two-platform' nodes which consist out of a higher and a lower processing & communication performance part. Several, different tasks can be assigned to the nodes. Depending on the needs of the tasks, they may be executed on the more energy-efficient low-power part or lead to the boot up of the high-power platform. Experiences made from this deployment are used to create new energy-efficient routing schemes for self-powered wireless network deployments.

In most Wireless Sensor Network deployments, the energy supply is a major challenge. Especially for nodes with high computational power or high bandwidth communication interfaces, the required size of batteries might increase to infeasible levels, even if the option of energy harvesting exists. For many use cases, some nodes are idling most of the time and transmitting only a few bytes from time to time. In this paper, we present a two-platform node consisting of a high-power and a low power platform. Both platforms are using the same Delay Tolerant Networking (DTN) architecture and the same protocols. A novel concept offers the opportunity for both platforms to appear as a single node to communication partners. The high-power part is running a full-featured Linux operating system, the low power platform is built around an energy-efficient 32-bit microcontroller and is able to fulfill tasks, which would have required to wake up the high power node in a conventional setup.Our system can increase the energy efficiency in WSN scenarios where the demand of bandwidth and computational performance is strongly fluctuating.

The Stream Control Transmission Protocol (SCTP) offers several distinct features which can be leveraged for Disruption or Delay Tolerant Networking (DTN). SCTP is able to handle an arbitrary number of independent streams in one connection---termed an association ---and it also supports using multiple networking devices in one association at the same time (multi-homing). With the latter, either switching between network devices, e. g., for fail-over, or even Concurrent Multipath Transfer (CMT) is possible during a transfer. In this paper, we present SCTPCL, a Convergence Layer protocol for the Bundle Protocol, which brings these benefits to DTN implementations. We leverage the multi-streaming capability to handle priorities, such as those of the Bundle Protocol, as well as a separate control stream in parallel. Multi-homing not only enables an increased reliability, but is also especially useful for energy-aware wireless systems where a transfer may be initiated using a low-power device while for larger data it can be switched to a high bandwidth link.

The fault-tolerant character of WSN protocols and applications that do not assume completely reliable systems legitimize undervolting - a highly efficient energy management technique where the supply voltage is set below the minimum specifications. As has been shown in earlier work, by using thereliable IdealVolting undervolting scheme the lifetime of WSN applications can be increased significantly while keeping the node in a safe state even under rough environmental conditions. To show the usability of undervolting in a real world WSN deployment, we performed a long-term study of IdealVolting in a Smart Farming application. All measurements were performed on a generic outdoor testbed for WSNs (PotatoNet) which is also presented within this paper. We collected a long-term dataset of a WSN running for one farming season on a potato fieldto compare the reliability and performance characteristics of IdealVolting against a regular powered WSN.

Automated valet parking services provide great potential to increase the attractiveness of electric vehicles by mitigating their two main current deficiencies: reduced driving ranges and prolonged refueling times. The European research project V-Charge aims at providing this service on designated parking lots using close-to-market sensors only. For this purpose the project developed a prototype capable of performing fully automated navigation in mixed traffic on designated parking lots and GPS-denied parking garages with cameras and ultrasonic sensors only. This paper summarizes the work of the project, comprising advances in network communication and parking space scheduling, multi-camera calibration, semantic mapping concepts, visual localization and motion planning. The project pushed visual localization, environment perception and automated parking to centimetre precision. The developed infrastructure-based camera calibration and semi-supervised semantic mapping concepts greatly reduce maintenance efforts. Results are presented from extensive month-long field tests.

Being able to determine the location of a node is of great advantage in many IoT and WSN applications. For example, in health care scenarios or for autonomous configuration of IoT setups this information can be useful. One of the key challenges in localization is to estimate the distance between nodes. Most present indoor localization systems require additional hardware for this estimation which is costly in terms of money and energy consumption. To overcome this disadvantage, we developed a system which is able to perform distance measurements without adding any extra hardware and costs. It is based on phase measurements performed by the IEEE 802.15.4 transceiver chip that is normally solely used to realize communication. In the evaluation we investigate the performance of our system in different real world environments that are typical for IoT and WSN setups.

The deployment and especially the long-term operation of outdoor Wireless Sensor Network (WSN) testbeds is still a challenging task. If different monitoring tasks with significantly varying demands have to be performed, the handling of scarce resources like energy becomes difficult and might lead to questions about the reliability of the testbed. In this paper, we present "PotatoMesh", a remotely deployed WSN consisting of different classes of nodes. In addition to more regular sensor nodes like INGA [1], we introduce new 'two-platform' nodes which consist out of a higher and a lower processing & communication performance part. Several, different tasks can be assigned to the nodes. Depending on the needs of the tasks, they may be executed on the more energy-efficient low-power part or lead to the boot up of the high-power platform. Experiences made from this deployment are used to create new energy-efficient routing schemes for self-powered wireless network deployments.

We present PotatoNet, an outdoor testbed for Wireless Sensor Networks (WSNs). Its primary focus is robustness, reliability and flexibility. PotatoNet is designed to operate without on-site maintenance for extended periods of time. It can withstand heat, dust and rain and has already been tested running outside for several months.

Localization is an important challenge for all applications with autonomous navigating devices. Systems like GPS solve this challenge for most outdoor applications but such systems are not able to operate indoors. Indoor localization therefore is an active research topic. When it comes to locating nodes that travel from indoors to outdoors most systems are overwhelmed. Thus, we propose a system capable to localize nodes in such applications by using COTS transceiver chips. We utilize the phase measurement unit to perform distance measurements.

ABSTRACTWe present PotatoNet, an outdoor testbed for Wireless Sensor Networks (WSNs). Its primary focus is robustness, reliability and flexibility. PotatoNet is designed to operate without on-site maintenance for extended periods of time. It can withstand heat, dust and rain and has already been tested running outside for several months.