In industrial environments, publish/subscribe is essential for reliable and efficient machine-to-machine communication. Established protocols like Message Queuing Telemetry Transport (MQTT) and Advanced Message Queuing Protocol (AMQP), which implement this messaging pattern, have architectural limitations that hinder their ability to guarantee hard real-time requirements. To address this limitation, we propose combining MQTT for Sensor Networks (MQTT-SN), a lightweight UDP-based variant of MQTT, with Time-Sensitive Networking (TSN), a set of IEEE standards that enhance Ethernet with real-time capabilities. The resulting protocol, designated as MQTT-TSN, enables time-triggered publish/subscribe using the Time-Aware Shaper (TAS) and guarantees hard real-time compliance for MQTT-SN messages. In this work, we present a conceptual framework for the mapping of real-time MQTT-SN traffic to periodic time-triggered (TT) streams, incorporating configuration and adaptation at runtime. A case study demonstrates the feasibility and limitations of our approach in a simplified scenario.

The increasing demand for flexible, cost-effective sensor and control solutions in Industrial Internet of Things (IIoT) environments has led to a growing interest in using OPC UA on embedded microcontrollers. Although existing studies compare OPC UA to other IoT protocols, they often focus on larger boards or high-level development frameworks, leaving a performance gap for smaller devices with limited resources. In this paper, we benchmark version 1.4 of the open62541 OPC UA Client/Server stack on microcontroller-based systems (ESP32, STM32H747) as well as a more powerful edge platform (RevPi Connect 4). We measure round-trip times under varying client counts and polling rates, assessing near real-time capabilities comparable to traditional PLCs. Our results show that the ESP32 and STM32 can support moderate polling loads and a small number of parallel clients, with average latencies generally under 10 ms. For higher client loads and stricter real-time demands, the RevPi platform sustains sub-ms average latencies for up to 100 parallel clients. These findings inform hardware selection and guide industrial practitioners in deploying embedded OPC UA Client/Server solutions for simple sensor-monitoring tasks or more complex edge applications. We discuss implications and limitations of this approach. Finally, future directions in subscription-based communication and implementing standardized data models on resource-constrained devices are discussed.

The fast positioning of medical service robots in hospitals is a challenging task. Therefore, this paper presents a performance analysis around different LTE Positioning Protocol (LPP) transactions, which are performed over the user plane of a fifth generation (5G) network to transport position-related data. More precisely, the transaction time of the LPP capabilities and location information transactions is investigated depending on the number of additional technologies, such as Wi-Fi and Bluetooth, and the presence of a line of sight (LOS) connection to the serving 5G base station. For this purpose, a Lego Mindstorms EV3 robot, which is used with a Raspberry Pi Zero 2 W, a Quectel RM520N-GL 5G modem, an Archer T2U Nano Wi-Fi adapter and a BMP581 pressure sensor, is moving along three different real-world indoor scenarios: (i) The line of sight is always present, (ii) it is temporarily interrupted (N/LOS), and (iii) the line of sight is permanently broken (NLOS). The statistical results show that the number of used technologies influences the transaction time of LPP location information more than the corresponding LPP capabilities. If the Wi-Fi and Bluetooth technologies and a barometric pressure sensor are used together with 5G, the transaction time of LPP location information transfers increases by 2,521% (capabilities: 31.86%) in the LOS scenario compared to a 5G only case. In contrast, line of sight changes do not appear to have a clear negative impact on the transaction time of LPP capabilities and location information transfers, respectively.

Time-Sensitive Networking (TSN) extends Ethernet to enable deterministic networking making it suitable for latency-sensitive industrial applications. To ensure bounded end-to-end delays and minimal jitter, a network-wide communication schedule with exclusively reserved transmission slots is enforced for time-triggered hard realtime traffic. While numerous scheduling methodologies exist for generating such schedules, their practical applicability remains uncertain. In this paper, we present a testbed for evaluating the real-world suitability of TSN schedules. We describe the hardware and software setup and demonstrate our evaluation methodology.

Fast and accurate positioning of medical service robots is a challenging task. Therefore, this paper presents a performance analysis of various implementation designs around the Location Services User Plane Protocol (LCS-UPP), which is used in fifth generation (5 G) networks to transport positionrelated data. More precisely, the transport time of the LCSUPP is examined depending on the transported LTE Positioning Protocol (LPP) payload size, different Transport Layer Security (TLS) 1.3 implementations and the successive movement of the data path to the underlying Linux operating system. For this purpose, a Raspberry Pi Zero 2 W in combination with the Quectel RM520N-GL modem as a $\mathbf{5 G}$ user equipment (UE) as well as three additional Raspberry Pi 5 and the Ettus USRP B210 Software Defined Radio (SDR), which form the radio access and the core network, are used. The results show that the transport time of the LCS-UPP can be reduced by 42.01%, if the QUICbased MsQuic user space library is used instead of the wolfSSL library that based on the Transmission Control Protocol (TCP). Also the complete movement of the LCS-UPP data path to the Linux operating system decreases the transport time by 5.84% and 16.95% compared to the wolfSSL library and the in-kernel TLS implementation of Linux, respectively.

In Time-Sensitive Networking (TSN), Time-Aware Shaping facilitates the convergence of deterministic and lowpriority traffic in Ethernet networks. The allocation of bandwidth for low-priority traffic is crucial when scheduling timetriggered (TT) streams to prevent starvation and packet loss caused by queue congestion. This issue is particularly pertinent in online scheduling scenarios, where the deletion of streams can lead to schedule fragmentation. To prevent this issue, the time slots of the TT streams must be compressed to provide larger contiguous gaps for low-priority traffic in the schedule. In this paper, we present a novel heuristic approach for compressing schedules, which facilitates the grouping of time slots into units, thereby increasing the bandwidth for low-priority traffic and improving the schedulability of future streams. The proposed heuristic can be tailored to specific use cases through adaptive weighting, allowing a comprehensive evaluation of time slots according to the properties of the associated time slot units, TT streams, and the network.

The proliferation of wireless mobile devices has led to a growing interest in indoor localization applications, such as context-aware services in healthcare. However, the inherent complexities of multipath and non-line-of-sight (NLoS) in indoor environments pose significant challenges to conventional localization methods, often resulting in compromised accuracy. In this paper, we propose a localization approach for wireless systems that uses self-supervised learning and dissimilarity metrics derived from Received Signal Strength Indicator (RSSI) and Angle-of-Arrival (AoA) data to increase the accuracy of indoor localization in NLoS environments. Recent developments showed that self-supervised machine learning with channel state information (CSI) can accurately estimate positions without ground truth data. Accessing the CSI data can be challenging, so we present an approach that uses the more accessible RSSI values and AoA angles. Our evaluation of various neural network architectures and training parameters indicates that employing dissimilarity metrics derived from AoA and RSSI with selfsupervised learning is a promising approach.

WLAN Mesh Networks (WMNs) are a promising network architecture for IoT applications due to their self-healing and robust network formation capabilities. The IEEE 802.11s amendment standard integrates mesh functionality into the WLAN MAC layer, ensuring seamless peering and routing. Initially designed for testing, the Linux implementation of IEEE 802.11s includes basic peer link blocking mechanisms. Based on this, we present a new MAC address filtering approach for reliable topology control in WLAN mesh networks. Our modifications to the Linux kernel enable persistent link blocking and bidirectional link teardown, preventing the sporadic establishment of unwanted connections. Real-world experiments demonstrate the effectiveness of our approach.

Time-Sensitive Networking (TSN) facilitates the implementation of realtime data traffic with deterministic delay and jitter in Ethernet networks. In its time-triggered communication variant, network paths as well as transmission time slots along the paths need to be planned and reserved for all data streams, respectively. Conventionally, such a feasible (i. e., realtime compliant) network schedule is computed and optimized offline, installed upon deployment, and cannot be changed anymore at runtime without stopping the communication. The latter becomes unsuitable for future industrial use cases with a growing demand for flexibility including schedule adjustments. In this paper, we present an online scheduler capable to incrementally integrate new streams at runtime and to adapt the existing schedule, if necessary, while retaining the realtime guarantees given to active streams. For this purpose, the scheduling heuristic identifies streams whose adjustment requires minimal reconfiguration efforts. In a thorough evaluation, we analyze the scheduler's trade-off between resource usage and schedule quality showing its suitability for diverse application scenarios.

In this paper, we present the integration of MQTT for Sensor Networks (MQTT-SN) into OPC Unified Architecture (OPC UA) as a novel publish/subscribe (PubSub) protocol binding in order to enhance the industrial communication stack. By leveraging the lightweight MQTT-SN protocol, which is currently not considered in the architecture, we improve OPC UA's capability for high-frequency, low-latency messaging, which is essential for Industrial Internet of Things (IIoT) applications. We discuss related work and describe the design and implementation in detail. Our hybrid approach combines the rich data modeling and security capabilities of OPC UA with the communication efficiency of MQTT-SN, providing a scalable solution for real- time data management in industrial automation systems.

Real-time capability plays an important role in modern factory communication systems. However, protocols such as MQTT, CoAP, and MQTT-SN, which are increasingly finding their way into industrial environments alongside industrial-grade protocols such as OPC UA and DDS, cannot fulfill the timing requirements without further optimization. In this paper, we present extensions of MQTT-SN to improve the real-time behavior in combination with PREEMPT_RT, which provides different real-time mechanisms for the Linux kernel. We address general, operating system-based, and hardware-specific optimizations. Their benefits are demonstrated by measurements in a practical testbed. The proposed extensions reduce delay and jitter, but do not aim to guarantee an upper bound on end-to-end delay.

In this study, the authors examine the technical challenges associated with wireless localization algorithms in indoor environments. The paper presents an in-depth analysis of various wireless communication technologies, meticulously summarizing their salient features and their implications within the broader scope of research. The outcomes of this study contribute significant technical insights into the capabilities and limitations of Joint Communications and Sensing (JCAS) technology. These insights are pivotal for advancing seamless data exchange and achieving comprehensive connectivity in the realm of 6G wireless communication networks, particularly those that integrate localization functionalities. The detailed findings of this research are poised to inform and influence subsequent technical research and developmental strategies in this specialized field.

The Message Queuing Telemetry Transport (MQTT) protocol is a de-facto standard for machine-to-machine (M2M) communication in the Internet of Things (IoT) domain. However, since it is limited to TCP at transport layer, it is not possible to run MQTT over UDP, which would be desirable for real-time capable publish/subscribe. MQTT for Sensor Networks (MQTT-SN), which is a lightweight version of MQTT, allows the use of UDP, however, is strongly coupled to MQTT by the current specification and cannot be operated independently of it. In this work, we therefore propose a standalone broker implementation of MQTT-SN. In initial measurements, we can show that our approach is much more performant than the approach described in the specification and that our implementation compares very well with the protocols CoAP Pub/Sub and MOTT.

We describe compositional architectures and certifications in the research project certMILS. Compositional architectures enable re-use of certified COTS (commercial off-the-shelf) components with a well-defined delegation of responsibilities between component developers and system integrators during cyber physical system design and certification. We show how we used a Common Criteria certified MILS (Multiple Independent Levels of Safety / Security) platform for compositional designs and IEC 62443-4-1/62443-4-2 security evaluations and certifications for composed systems from the domains of smart grid, railway, and subway, that are safety- and security-critical.

In the age of digitalization, data protection plays an important role. Data is created, modified and shared over the Internet between data owners and data users. A key issue in this context is the respect of data sovereignty. The International Data Spaces (IDS) Reference Architecture has been developed in order to preserve data sovereignty. In this regard, Internet of Things (IoT) devices, such as sensors, play an important role for providing data. However, an IoT device is not capable of being integrated directly into the IDS by default. We propose an approach to enable the IDS for vendor independent IoT devices, using an open interoperability standard for the IoT specified by the Open Geospatial Consortium (OGC). This allows data owners to benefit from providing their own data while retaining control over it.

Today’s operating rooms consist of a multitude of medical devices. Nowadays, the interconnection of these devices is manufacturer-dependent. To overcome this lack of interoperability, the new IEEE 11073 Service-oriented Device Connectivity (SDC) family of standards has been developed. Plenty of use cases take advantages from the interconnection of medical devices among each other, based on SDC. In this paper, we focus on time-critical use-cases, like the activation of a high-frequency surgical device to emit power at the instrument triggered by a networked foot switch. The execution of such remote control operations, are dependent on deterministic data transmission. To fulfill these requirements we propose the usage of the new Time-sensitive Networking (TSN) standards IEEE 802.1. The combination of SDC and TSN enables semantic interoperability and hard real-time communication at the same network, based on standards. We provide a new approach to automatically configure the underlying TSN network by means of the medical devices’ self-description according to the SDC family of standards. Our approach shows that the required information for configuring the TSN network can be extracted from the self-description.

Industrial Internet of Things (IIoT) applications benefit from the knowledge of the device and user positions in a manifold way. Reliable indoor navigation combined with IIoT enables Location-Based-Services (LBS) such as assistance functions of moveable actuators. A crane which follows its operator can significantly increase the efficiency of the process. Safety mechanisms are also enhanced by positioning information. For example, exclusion areas where only automated devices are operating can be implemented. In this paper a novel localization framework is introduced to fuse sensor data from either absolute or relative positioning sources. The core of the framework is an Extended Kalman-Filter (EKF) architecture that is able to handle data from several different sources. Each localization source needs to fulfill requirements regarding data representation and structure defined by the framework, e.g., current state and variance. The approach is verified in a real world scenario with two different sensor types as information sources: Ultra Wide Band localization and Pedestrian Dead Reckoning. We show that the combination of these technologies improves the localization accuracy and evaluate advantages and drawbacks of this approach.

Tracking of goods, containers, and vehicles in harbors is a challenging task because seaports typically are in a secluded area with limited networking capability. Existing solutions use the combination of RFID tagging and Wireless Sensor Networks (WSN). A harbor is considered a harsh industrial environment with metallic components and surfaces. These conditions influence the wireless networking performance. In addition, harbors' areas vary from 500 ha to 7500 ha. Hence, the coverage range of wireless systems and the exposition to interference are considered. LoRa (Long Range) technology becomes a promising solution among other Low Power Wide Area Networks (LPWAN). Therefore, we investigate the LoRa technology to locate and track assets in harbors. Through ns-3 simulations on scalability, interval rate, and coverage range performance metrics, we evaluated the feasibility to use LoRa in seaports. In our experiments, we applied 1000 LoRa nodes within a radius of 2500 m to the gateway. The results exhibit a probability of successful transmission of 85 % in an interval of 300 sec.

This paper investigates research, made on semantic information models for building automation systems. It analyzes what information domains are covered to provide context, the vocabulary provided to describe building automation devices and functions, and how these models are structured. The intention is to find out good practices and try to identify trends, commonalities, differences, and possible next steps.

Vendor-independent interoperability is one of the key-enablers for medical devices in future operating rooms, intensive care units, and medical care in general. Using the paradigm of a Service-Oriented Architecture (SOA) is a promising approach realized by the new IEEE 11073 SDC family of standards. Standard compliant communication stacks will be used to build up systems of networked medical devices. The performance of the stack implementation is crucial for the usability in real-world medical environments. Therefore, we investigate the latency of currently available middleware stacks: SoftICE, openSDC, and OSCLib. The aim is to evaluate the suitability of the underlying concepts, understanding the communication behavior using different hard- and software platforms, and finding problems to support future development. For the latency measurements we build up a use-case independent testbed and instrument the libraries to get more information. On the one hand, our investigations substantiate the suitability of the underlying concept and the available middleware stack implementations. On the other hand, unexpected results occurred, like a strong dependency of communication latency on the combination of hardware platform, Java Virtual Machine (JVM), and JVM configuration and even a strong dependency on the intensity of exchanged data when using Java middleware implementations.

The microservice approach has created a hype in the domain of cloud and enterprise application business. Before, grown, monolithic, software has been pushed to the limits of maintainability and scalability. The microservice architecture approach utilizes the service oriented architecture together with best practices and recent developments in software virtualization to overcome those issues. One monolithic application is split up into a set of distributed services. Those are strongly decoupled to enable high maintainability and scalability. In this case an application is split up in a top down manner. In the internet of things, applications need to be put together from a set of small and independent services. Thus, creating value added services would require to freely combine services of different vendors to fully make use of the IoT's heterogeneity. Even though the direction is different, many of the requirements in microservices are similar to those of the internet of things. This paper investigates patterns and best practices that are used in the microservices approach and how they can be used in the internet of things. Since the companies using microservices have made considerations on how services have to be designed to work together properly, IoT applications might adopt several of these design decisions to improve the ability to create value added applications from a multitude of services.

In the recent past, the development of applications and protocols for the Internet of Things (IoT) made a big leap forward. New approaches have emerged to adopt IoT technologies in the realm of industrial automation. This development is also referred to as Industrial Internet of Things (IIoT) or Industry 4.0. It is predicted for the number of smart interconnected devices participating in automation systems to grow significantly in the future. However, the industrial domain introduces new requirements for IoT technologies regarding the timeliness of interactions. Current IoT protocols, like the Constrained Application Protocol (CoAP), do not yet provide real-time behavior for the inter-device communication. In our previous work, we have already proposed a real-time extension for CoAP that enables deterministic network behavior through a TDMA-based approach. We have shown that the proposed mechanisms for time synchronization, time slot management, and access control can be realized purely software-based. However, a central instance is needed as a time server. This introduces a Single Point of Failure (SPoF) to the system, limiting the robustness and scalability of the approach. In this paper, we introduce a concept for a distributed time server for CoAP. The proposed concept includes a refined time synchronization mechanism as well as strategies to select multiple time servers and share information between them. Furthermore, the described amendments to the real-time extension are integrated into the lightweight platform-independent jCoAP communication stack and evaluated in a multi-device real-world test bed.

Current IoT protocols, like the Constrained Application Protocol (CoAP), do not yet provide real-time behavior for the inter-device communication. In this paper, we propose a real-time extension for the CoAP standard that defines interfaces for the time synchronization among nodes and the time slot management. These interfaces enable a controlled exclusive network access based on a Time Division Multiple Access (TDMA) approach. With this extension, it is possible to realize access control on the application layer without the modification of lower layer protocols. The described interfaces are prototypically implemented within the jCoAP communication stack and evaluated in a multi-device real-world testbed. In our prototype, we used established algorithms for the time synchronization. The results, reveal the weaknesses of the chosen synchronization algorithm. However, the interface definition allows the usage of more accurate algorithms.

The vision of the smart home is increasingly becoming reality. Devices become smart, interconnected and accessible through the Internet. In the classical building automation domain already a lot of devices are interconnected providing interfaces for control or collecting data. Unfortunately for historical reasons they use specialized protocols for their communication hampering the integration into newly introduced smart home technologies. In order to make use of the valuable information gateways are required. BACnet as a protocol of the building automation domain already can make use of IP and defined a way to represent building data as Web services in general, called BACnet/WS. But using full fledged Web services would require too much resources in the scenario of smart home thus we need a more resource friendly solution. In this work a Devices Profile for Web Services (DPWS) adaptation of the BACnet/WS specification is proposed. DPWS enables Web service conform communication with a focus on a small footprint, which in turn enables interdisciplinary communication of constrained devices.

Software-defined networking (SDN) is a principle for the flexible configuration of networks, which recently has aroused an increasing interest of researchers and companies. Today, the operation and configuration of networks as well as their adaptation to changing requirements represent a major challenge if legacy network management protocols are used due to their inability to provide network-wide configuration. Compatibility issues with legacy protocols or even proprietary protocols have further contributed to hardly reconfigurable and inefficient networks and thus prepare the way for the new concept called SDN. SDN implementations are mainly in the data center today. Implementations will find their way into broader networking applications over the next few years. However, even automation networks with highest QoS requirements can benefit from SDN support by achieving significantly more devices that meet these requirements. Therefore, this paper addresses the emulation of SDN-supported automation networks to examine possible design options. Limitations and possibilities when using the popular and widely accepted SDN emulator Mininet are analyzed.

In recent years, cloud computing, which provides users with network resources such as memory and computing power depending on the users' needs, has gained enormously in importance. Providers such as Amazon allow the users to access their cloud storage and computing resources by different interfaces. In this regard, guaranteeing compatibility is a severe issue as many different proprietary interfaces exist for accessing data in different clouds. The solution to this problem is the RESTful Cloud Data Management Interface (CDMI) standard, which has passed the ISO audit as first standard and is therefore evolving into the most common standard for accessing clouds. This paper investigates the combination of CDMI with a P2P-based storage and computing back-end in order to realize a self-organizing cloud for distributed data storage and processing called DuDE-Cloud. The basis is the self-organizing hash table (DHT)-based P2P storage and computing back-end called DuDE, which utilizes the DHT protocol Kad. DuDE is able to bundle existing storage and computing resources of different devices dynamically and has already proven its advantageous performance over centralized solutions. In a test scenario, resources of DuDE-Cloud were successfully accessed through CDMI using a GUI front-end thereby proving the proper functionality. As a result, a resilient high-performance distributed cloud solution is available that is compatible with other clouds.

The term Internet of Things (IoT) describes a scenario where embedded systems are integrated into everyday objects, turning them into smart devices to assist the user in his everyday life. Each of these smart objects only offers a very limited amount of computational power since it is only specialized in a limited set of tasks. In order to achieve complex goals, the devices have to interact with each other. Therefore, they do not only need to be interconnected either by wire or through wireless technology but also need a set of common protocols to enable vendor-independent communication. In the past years, various protocols pursuing this objective have emerged. One of the most promising approaches is the Constrained Application Protocol (CoAP) because it offers high interoperability and very low communication overhead at the same time. Typical IoT applications include the observation and manipulation of their environment through sensors and actuators. Since the physical world is continuous in time and does not wait for calculations to finish, it is essential that the execution times of the applications stay within certain boundaries. These timing constraints are referred to as real-time requirements. However, current protocol implementations do not consider real-time requirements for IoT applications. In this paper, we introduce the jCoAP communication stack as a lightweight Java implementation of CoAP. We give a brief introduction to real-time communication and CoAP and provide insight in the design concept of jCoAP and the offered functionalities. Furthermore, a performance evaluation is done in order to point out the suitability of the jCoAP framework for real-time IoT applications.

The Internet of Things is a great vision but also an important challenge for the current research. Through, the connection of many different devices there are outstanding benefits such as an increasing automation and intelligent energy management. Nevertheless, the integration of legacy devices into the Internet of Things is a significant issue. Legacy meters, e.g., cannot provide metering data automatically and the installation of modern smart meters is cost-intensive and thus often unprofitable. An alternative approach is to extend legacy meters with an automatic meter reading system. Thus, they can be integrated into an intelligent system such as an efficient energy management. In this paper a robust and universal approach for automatic meter reading is proposed. The approach can be applied to water, gas, and electric meters and uses a Web service as standardized and open communication interface. The recognition rate of a prototype implementation is 98 % and the measurement duration is approx. 1.5 seconds. The entire system was implemented on a Raspberry Pi as a cost-efficient hardware platform.

As of today, building automation systems are present in almost any commercial building. They perform climate control, lightning control, access control, surveillance, and quite a few other tasks. As a result of their evolutionary development, building automation systems are divided into separate silos of disciplines that are not well integrated with each other. As of today, a variety of communication protocols, data models and engineering approaches are used by different vendors. Existing standardized building automation protocols as BACnet or KNX allow integration of some disciplines on the communication level but fail to provide means for common description of devices, services and data on the semantic level. This means that building automation applications that span multiple disciplines require a high effort for development, engineering and maintenance. If devices from multiple vendors are integrated in one installation, a set of different engineering tools and vendor-specific knowledge is required. In the ITEA “Building as a Service” (BaaS) project we try to overcome these deficiencies and define a common way to develop, engineer, commission, operate and maintain building automation systems following a service oriented approach. The whole process will be supported by semantic models to reduce costs and time-to-market, which is a quite new approach. In this paper we will present the current state of the work with special regard to domain modeling and model driven processes that are currently being specified for the BaaS platform.

For companies in the automation industry, the development of real-time Ethernet to connect devices is of high economic interest to replace conventional fieldbus systems. Therefore, many approaches for adapting Ethernet to real-time requirements come from industrial applications. This is a challenging task as the original Ethernet standard IEEE 802.3 was not designed for real-time data transmission. Likewise, protocols basing on Ethernet like TCP, UDP, and IP do typically not consider real-time requirements. Hence, adaptations on several OSI layers become necessary to make the industrial system meet hard real-time requirements. For this purpose, a multitude of realtime capable Industrial Ethernet systems has been developed, which solve the problems of standard Ethernet- and TCP/IP- or UDP/IP-based communication in a variety of ways. This paper gives a summary of different Industrial Ethernet protocols for the real-time data transmission via Ethernet in automation environments. Advantages and disadvantages of these protocols are analyzed with regard to their sustainability in terms of their realtime capability, reliability, scalability, self-configuration of the network, and hardware requirements. Against the background of connected devices tremendously growing in number and computational power in the prospective “Industrial Internet”, consequences for future developments are drawn.

Web service technology becomes popular in a growing number of applications. The field of application reaches from smart home over factory automation up to smart cities. One of the main aspects of this technology is a dynamic device and service discovery. For this purpose, the WS-Discovery standard is used. WS-Discovery supports two modes: an infrastructure-based and an ad hoc mode. The infrastructure-based mode requires a service proxy, which represents a single point of failure. The ad hoc mode is based on the multicast and static response time values. Therefore, it shows a low scalability. In this work, we present a novel discovery approach, which bases on distributed hash tables (DHTs). DHTs are often utilized in peer-to-peer networks and represent a well-established technology. The search for devices and services is performed using hash values. The benefit of this approach is a high scalability, deterministic behavior, and flow control. The suggested approach can be applied for networks of any size. Since this approach uses unicast messages, it is not limited to local networks allowing the device and service discovery over multiple subnets or even over the Internet.

Device and service discovery is an essential part of automation networks in order to ensure the interoperability of devices and Plug&Play functionalities. Embedded Web services such as Devices Profile for Web Services are an upcoming technology for building and factory automation. For ad hoc discovery, the WS-Discovery standard is used. This approach avoids single points of failures. However, it shows low scalability due to static response time values. The rising number of devices leads to an increasing network load and especially to an increasing device processing load as a result of the discovery process. In this work, we evaluate the issues of ad hoc service discovery and suggest an optimized algorithm for dynamic data rate reduction in large scale networks. Moreover, the suggested improvements allow reducing peak data rates by more than 50% for constant timing parameters. Using the suggested approach, the ad hoc discovery can be applied in any network size. The desired peak data rates or response times of the system can be significantly reduced and dynamically adjusted according to the desired values. This approach guarantees a scalable ad hoc discovery mechanism and is backward compatible with legacy equipment.

To date, Wireless Sensor Networks (WSN) require their own specific methodologies, tools, and technologies. With the rise of 6LoWPAN protocols (i.e., IPv6 over Low Power Wireless Personal Area Networks), WSNs can use IP to share a common network layer with other networks and the Internet for highly interoperable device communication. But additional efforts are necessary to develop new or adapt existing application layer protocols for IP-enabled WSNs. Hence, this paper investigates W3C SOAP Web Services (WS) in the context of WSNs. In particular, it is shown that the Devices Profile for Web Services (DPWS) can be used as an application layer protocol in WSNs.

There are many applications that use low power wireless sensors to monitor people's vital signs or the environment around people. For mobile applications, smartphones with Internet access have become a commonly used tool to make this data remotely accessible. However, the yet presented architectures are quite complex and lack flexibility. Our aim was to investigate how existing communication architectures for smartphone/WPAN sensor ensembles can be simplified and to provide a transparent solution where the smartphone doesn't require knowledge about sensors for which it serves as an Internet gateway. We therefore present an IP-based communication architecture, that allows applications to easily integrate remote sensor data of mobile users based on existing Internet standards. In particular, our solution provides simple Web service-based APIs and does not require the smartphone to process sensor data. Instead, the smartphone becomes a transparent gateway as it only forwards IP packets.

The actual situation in smart metering is characterized by a coexistence of a large number of proprietary and open standards for wired as well as wireless communication. These standards show low or no interoperability to each other. Therefore, it is very difficult to integrate multi-vendor solutions using one sustainable holistic approach. The proposed approach is to use Web Service technology as an open widespread Internet standard for the creation of a heterogeneous network for smart metering devices. Smart metering is an emerging topic for realizing modern energy policies. Monitoring, analyzing, and controlling of power consumption is the precondition for optimizing energy strategies. This work focuses on the integration of Web Service technology in the area of smart meter communication. Furthermore, mechanisms for reducing Web Service traffic overhead by over 90% is presented.

The increasing level of device connectivity in today's homes and buildings enables numerous opportunities for home owners, building managers, device manufacturers and solution providers. Standardized communication protocols (e.g., ZigBee, Bluetooth) provide physical connectivity and thus serve as a basis for smart home applications. However, beyond physical connectivity, real interoperability to effectively develop such applications requires additional efforts. It requires harmonizing multiple protocol standards, dealing with a heterogeneous device landscape, different data formats, managing resource constraints of devices and providing means to react quickly when devices and applications leave or join the system. We propose to address these application-specific requirements in multiple layers of abstraction. Our research has shown that each layer is used by different types of developers (e.g., device supplier, service provider, home owner) with specific tool support. The paper provides a classification and detailed analysis of requirements that have to be addressed in order to enable application development in smart homes. It further proposes and analyzes WS4D-PipesBox, a multi-layer framework, to illustrate how applications could be developed using multiple layers of abstraction.

A huge momentum towards IP enabled Wireless Sensor Networks (WSN) appeared through the emerging 6LoW-PAN protocols (i.e. IPv6 over Low power Wireless Personal Area Networks). By usage of existing cross domain open standards in contrast of proprietary solutions, deployments of WSNs are not tailored too tight for specific applications. Nevertheless, 6LoWPAN is only the first step for the usage of internet protocols in WSNs. Still efforts on higher layers on top of 6LoWPAN are an urgent need to provide seamless connectivity and interaction of highly resource constrained devices with higher valued services. This paper describes a new approach to bind SOAP to the emerging Constrained Application Protocol (CoAP) protocol. Thereby CoAP provides a lightweight but reliable transport binding for SOAP based protocols. Compared to the widespread TCP based HTTP binding, round trip times can be reduced by 43% in an exemplary scenario. Combined with dedicated XML compressors like the Efficient XML Interchange format (EXI), existing heavy weight SOAP based protocols become also applicable in WSNs.

A huge momentum towards IP enabled Wireless Sensor Networks (WSN) appeared through the emerging 6LoWPAN protocols (i.e. IPv6 over Low power Wireless Personal Area Networks). By using existing cross domain open standards in contrast of proprietary solutions, technologies and deployments are not tailored too tight for specific applications. Nevertheless, 6LoWPAN is only the first step. Still efforts on higher layers on top of 6LoWPAN are an urgent need to provide the seamless connectivity and interaction of highly resource constrained devices with higher valued applications and services. This paper describes a new approach to bind SOAP to the emerging Constrained Application Protocol (CoAP) protocol. Thereby, CoAP provides a lightweight but reliable transport binding for SOAP. Compared to the widespread TCP based HTTP binding, round trip times can be reduced by 43% in an exemplary scenario because of the omitted expensive bidirectional TCP handshake mechanisms. Combined with dedicated XML compressors like EXI, SOAP based protocols become also applicable in WSNs.

Service-oriented architectures and systems designs are powerful concerning reusability of functional blocks and hiding implementation details from functional interfaces. But to compose a complete application, often central entities and engines are required for processing a specific sequence of service. In component-based designs the component itself is capable of describing both not only their offered services and interfaces but also dependencies on other services and interfaces to fulfill a complete task or application logic. This paper investigates on how to transfer and enhance exiting component-based approaches, already known from business applications, into the domain of embedded web services environments. Special focus is on the Devices Profile for Web Services (DPWS) technology which features service orientation also in device centric applications. This paper introduces a new approach to create applications, based on services provided by devices deployed with DPWS, in an abstract and dynamic way.

Wireless Sensor Networks (WSN) have attracted considerable research effort in the community during the past couple of years. One of the most challenging issues so far is the extension of network lifetime with regards to small battery capacity and self-sustained operation. Endeavors to save energy have been made on various frontiers, ranging from hardware improvements over medium access and routing protocols to network clustering and role changing strategies. In addition some authors studied failures in communication regarded as error detection. Yet, only weak attention has been paid to the detection of malicious nodes and its potential for lifetime extension. In this work, we present a short overview of detection and classification of malicious nodes in WSN and describe its potential in terms of network lifetime and reliability.

For Service-oriented Architectures, Web Services are claimed as state of the art to connect business execution layers as well as networking devices. Additionally, the deployment of Wireless Sensor Networks became applicable over the last years. The usage of application layer gateways and proxy concepts allow the integration of these sensor networks into real world scenarios and existing networks that make use of Web Services. This paper presents a new approach to adapt and enhance the Devices Profile for Web Services to be applied in Wireless Sensor Networks directly. Thus, seamless connectivity between business layers, device level networks, and Wireless Sensor Networks are possible.

During the last years, recent technological advances enabled the development of tiny devices equipped with radio, micro controller and sensors, called sensor nodes. Collaborating networks of such devices, known as wireless sensor networks (WSNs), are subject of many researches. A couple of network centric tasks like data transmission and aggregation, self-organisation, localization and energy awareness have been focused in various publications. Researches, e.g. IPv6 over low power WPAN (6LoWPAN), are going to standardize the connection of sensor nodes with common Internet protocols. Nevertheless, until now proprietary techniques are used within most networks, especially for the coupling towards the outside world as well as the data management. Depending on WSN hardware and software, the gateway software as well as storage and presentation of data differs for most sensor networks. In this work we present an infrastructure which bases upon a generic gateway. Standardized dataset will be stored by this device using sensor Web enablement (SWE) and standard protocols. By use of devices profile for Web services (DPWS) plug and play abilities as well as a comfortable query interface for presentation is realized.

Service-oriented architectures (SOA) are nowadays a wide-spread software building approach. The fields of application ranges from embedded devices up to enterprise and business solutions. For distributed services and devices it makes sense to have a mechanism for remote administration to manage their life cycle. Technological standards like OSGi (see section 3) provide such a life cycle management, but device-oriented Web service technologies like the devices profile for Web services (DPWS) do not specifies such a mechanism as a standard. In this paper we present a service-based life cycle manager for an implementation of DPWS to manage the services of a device during runtime through remote reconfiguration. The advantage of the presented solution is the ability to be platform and language independent by using a script-based interaction between the life- cycle-manager and the individual services.

Service-oriented architectures become more and more important in connecting devices with each other. The main advantages of service-oriented architectures are higher abstraction level and interoperability of devices. In this field Web services become the most important standard for communication between devices. But this upcoming technology is only available on powerful devices. Embedded hardware is often excluded from the deployment of Web services because of the lack of resources like computing power and memory. In this area also real-time capabilities for process control are required. This paper presents a new approach to handle Web services communication on deeply embedded hardware with the devices profile for Web services specification.

Currently the developing process for enterprise applications is improved by the Service Oriented Architecture (SOA) paradigms. With SOAs the creation of modular and clearly defined software architectures at a high grade of interoperability and reusability is possible. For resource constraint networked devices the Devices Profile for Web Services (DPWS) specification adapt the SOA paradigms to create a framework for interoperable and standardized communication between embedded devices. This paper explains how special parts of DPWS can be adapted to provide real-time capabilities. So this paper shows how developers of real-time software can use the advantages of Web services and which adaptations are necessary to create Web services with real-time capabilities.

The automatic integration of devices into dynamic, automatically configured networks alone does not take advantage of the entire potential of service oriented architectures (SOA). Using service management, independent services can be directed to perform meta tasks in a SOA network. In this paper we describe and evaluate the service management tool MOBASEC, which consists of two parts: at system runtime, management services are running in order to enforce management policies. The second part of the tool is a graphical model editor which supports the user in setting up the desired management policies easily. This research is part of the European SIRENA (Service Infrastructure for Real-time Embedded Networked Applications). The use of MOBASEC was evaluated by the project in automotive application and the results are summarized here.

Software development for wireless sensor networks requires novel programming paradigms and technologies. This article describes the concept of a new service oriented software architecture for mobile sensor networks. With this architecture, a flexible, scalable programming of applications based on an adaptive middleware is possible. The middleware supports mechanisms for cooperative data mining, self-organization, networking, and energy optimization to build higher-level service structures. The purpose of our research activities is the development of a framework, which radically simplifies the development of software for sensor network applications.

This article describes the current work to extend the Java processor Java Silicon Machine (JSM) for usage in embedded systems. The JSM is a JavaCard processor supporting all JavaCard bytecodes. The JSM is a fully synthesizable 32 bit processor soft core with a very small footprint. The capability of it's integration in small embedded and automation systems is outlined. Special target platform is the SmartDev system which consists of a Java core interfacing to a wide variety of peripherals. SmartDev is intended to be used in mobile embedded systems for administrational, controlling and measurement purposes.

Scheduling time impact on system performance increases especially when using dynamic priority algorithms, because of the enlarged computational effort at runtime. This overhead can be reduced by using dedicated hardware that does the time consuming computations necessary for scheduling. This can be a coprocessor capable of implementing dynamic scheduling algorithms which are, until now, rarely used because of their complex computations at schedule time. One of these algorithms is Least-Laxity-First (LLF). This is an optimal scheduling methodology that allows detection of time constraint violations ahead of reaching a task's deadline, but has the disadvantage of showing poor runtime behavior in some special situations ("thrashing"). In this paper, we present a universal deterministic scheduling coprocessor that implements the newly developed Enhanced Least-Laxity-First-algorithm (ELLF) which eliminates this disadvantage of LLF. Computation time of this device is rather a matter of time resolution than of the number of tasks.