Time-Sensitive Networking (TSN) extends Ethernet with deterministic communication and is therefore well suited to latency-sensitive industrial applications. For time-triggered traffic with hard real-time requirements, transmissions must be scheduled along defined paths at precise times to achieve low end-to-end latency and bounded jitter. Although many scheduling methods have been proposed, their practical applicability, particularly in dynamic scenarios, requires experimental validation. This paper presents a testbed with commercial off-the-shelf hardware for evaluating static and dynamic TSN schedules in real systems. The testbed supports automated experiments and runtime reconfiguration, enabling the investigation of dynamic TSN scheduling methods. We present the testbed architecture, the time-synchronization configuration, the controller software, and initial measurements of real-time performance in a static scenario under load.

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.

Time-Sensitive Networking (TSN) is a key technology for converged industrial communication systems enabling the integration of traffic with diverse Quality of Service (QoS) requirements such as timeliness, throughput, and reliability. To ensure that all data streams meet their requirements, the Network Calculus (NC) allows to analytically derive worst-case performance estimations. In this paper, we model rate-constrained streams alongside time-triggered hard real-time traffic in a line topology. Additionally, we compare the analytical results with a simulation conducted in the OMNeT++ network simulator. Our comparison shows that the worst-case delay predicted by the NC is 3 to 4 times higher than the delay observed in a simulation. Similarly, the estimated backlog (i.e., the amount of data queued in TSN switches) is 2 to 3 times larger than the simulation results.

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.

In the modern world, accurate crowd counting is integral to a multitude of applications, including urban planning, transportation management, and crowd control. The advent of opportunistic communication networks, which enable devices to sporadically exchange data in a decentralized fashion, has introduced a new set of challenges in crowd estimation. This paper delves into two opportunistic people counting protocols: UrbanCount and HeartBeatCount. UrbanCount, while a robust protocol in its own right, comes with certain limitations that hinder its real-world applicability. In response to these limitations, this paper introduces refinements to UrbanCount, making it more practical and effective. Additionally, a novel protocol called HeartBeatCount is presented, which significantly enhances crowd size estimation accuracy, particularly in sparse scenarios. Through an evaluation, we compare the performance of these protocols and conclude that HeartBeatCount offers a more resilient solution for opportunistic people counting in various real-world scenarios.

This paper addresses the growing need for efficient autonomous underwater vehicle (AUV) path planning, used in environmental monitoring, underwater surveillance, and search and rescue operations. The aim was to develop robust path planning strategies that ensure safe and efficient AUV navigation in complex and unpredictable underwater environments. Our approach combines path planning algorithms with the OMNeT++ network simulator. The procedures for the implementation of these algorithms and AUV motion simulation have been outlined. The algorithms were applied not only to single AUV missions but also to scenarios involving multiple AUVs, allowing exploration of cooperative and coordinated mission planning in diverse underwater settings. The results of the study demonstrate the potential of our approach to address real-world challenges encountered by AUVs. AUV behavior was observed in different simulated mission scenarios and environmental conditions. Our findings shed light on the adaptability of AUVs in the face of unexpected obstacles and dynamic ocean currents. In conclusion, this study contributes to the field of AUV applications, offering a path planning and simulation strategy adaptable to diverse AUV mission requirements. By utilizing simulation models, we illustrate AUVs' ability to autonomously adapt their mission plan and avoid obstacles during missions, improving operational efficiency and safety.

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.

Time-Sensitive Networking (TSN) becomes increasingly important for a wide variety of business sectors as it offers advanced means to implement data communication with hard real-time constraints using standardized Ethernet. To counter faulty transmissions and lost data, TSN comes with Frame Replication and Elimination for Reliability (FRER) that provides mechanisms to redundantly send data frames on multiple network paths from a source to a destination. Although clearly increasing fault-tolerance, the FRER sub-standard misses formulas to derive the resulting communication reliability, i. e., the probability that at least one of the replicated frames finally reaches the destination. Determining this reliability, however, is essential for designing fault-tolerant and resilient network infrastructures. This paper shows two methods for calculating the communication reliability that are evaluated on network topologies with increasing redundancy. The advanced algorithm intelligently decomposes the network topology in order to compute accurate results in acceptable time.

Time-Sensitive Networking (TSN) disrupts realtime communication technology by making IEEE Ethernet realtime-capable. For time-triggered, hard realtime traffic, TSN provides standardized mechanisms to reserve communication paths as well as individual transmission time slots for data frames. By leveraging these means in a precomputed network schedule, TSN allows for bounded end-to-end delays and minimal jitter. Not being part of the IEEE standard, corresponding scheduling algorithms are an active field of research. Unfortunately, due to differing model assumptions, evaluation setups, and key metrics, a fair comparison of schedulers is impossible so far. In this paper, we present a systematic and reproducible approach to benchmark TSN schedulers. First, we provide a scheduler taxonomy that enables to cluster schedulers by their characteristics. Second, we analyze interactions of input parameters and scheduler results to derive a benchmarking parcour for quantitative comparisons. Finally, we use the approach to benchmark existing schedulers and show subtle interaction effects. This way, our approach enables-for the first time-comparability between schedulers, fueled by the public availability of our benchmarking scenarios.

With content-based publish/subscribe, publishers issue notifications that are matched against subscriptions issued by subscribers to which only the matching notifications are delivered in turn. Due to the expressiveness of content-based filtering, each notification requires an individual delivery tree. This fact and because subscriptions potentially change over time make it hard to preinstall delivery trees into the switch infrastructure. In this paper, we present novel notification distribution strategies implemented in P4 that install virtual trees (VTs) in the switch infrastructure. For deriving VTs, we use topological information as well as pub/sub-specific information such as the distribution of publishers and subscribers and their interests. A greedy algorithm constructs a notification-specific delivery tree at runtime by combining VTs and encoding additional routing information into the notification headers to extent, connect, and prune VTs. We present a detailed evaluation investigating the performance of the strategies in real-world topologies and under changing subscriptions. The results confirm that our strategies construct efficient distribution trees requiring only little additional routing information in the notification headers. They also show that the size of this routing information grows when subscriptions change and that the increase depends on to what extend the respective strategy tailors the delivery trees to the active subscriptions.

—Recently, cooperative Autonomous Underwater Ve- hicles (AUVs) have been deployed in application areas such as surveillance and protection of marine infrastructures for inspec- tion and monitoring purposes. These cooperative methodologies require wireless transmission of data between the different AUVs operating in the underwater environment. Communication over ranges exceeding 100 meters exclusively relies on underwa- ter acoustic communication. However, the propagating acoustic waves suffer from several challenges due to the presence of path loss, multi-path propagation, the slow and variant propagation speed, background noise, and Doppler distortion. Due to the difficulties of real experiments, the modeling and simulation of underwater acoustic communication play an essential role in studying and developing these systems. We provide a modular simulation model for acoustic underwater communication of AUVs implemented in the network simulator OMNeT++ using the INET framework. More specifically, we extend several INET modules in such a way as to reflect the characteristics of underwater communication. We study and analyze the dependence of the message quality on different properties such as those mentioned above. The model focuses on the transmission medium and physical layer of the communication channel.

Recently, cooperative autonomous underwater vehicles (AUVs) have been deployed in application areas such as surveillance and protection of maritime infrastructures for inspection and monitoring purposes. These cooperative methodologies require wireless transmission of data between the different AUVs operating in the underwater environment. Communication over ranges exceeding 100 m exclusively relies on underwater acoustic communication. However, the propagating acoustic waves suffer from several challenges due to the presence of path loss, multi-path propagation, the slow and variant propagation speed, background noise, and Doppler distortion. Since the power supply of the AUVs is limited, communication must be very energy efficient and energy constraints have to be known to be able to plan the mission of AUVs. Due to the difficulties of real experiments, the modeling and simulation of the energy consumption and underwater acoustic communication play an essential role in studying and developing these systems. We provide a modular simulation model for the energy consumption and acoustic underwater communication of AUVs implemented in the network simulator OMNeT++ using the INET framework. More specifically, we extend several INET modules in such a way as to reflect the characteristics of AUVs and underwater communication. We study and analyze the AUVs’ energy consumption and dependence of the message quality on different properties such as those mentioned above.

In modern applications such as in the prospective smart factory, timely and faultfree communication is one of the main concerns. Communication failures may lead to huge economic losses. Moreover, they can even endanger human life. Therefore, the TimeSensitive Networking (TSN) task group has introduced new standards for real-time capable Ethernet, which also include a fault tolerance mechanism called Frame Replication and Elimination for Reliability (FRER) as IEEE standard 802.1CB. This standard introduces procedures and protocols for bridges and end stations in time-sensitive networks. It also provides mechanisms for the identification and duplication of frames to enable redundant transmissions. In this paper, a simulation model is developed that implements the IEEE 802.1CB standard in OMNeT++. In addition, as supplement to the standard we propose a reliability mechanism for establishing redundant paths and an error model to model transient and permanent errors. As proof of concept, we evaluate the model with different topologies under various conditions.

—In this paper, we survey work that relates to our fully distributed protocol called UrbanCount for counting large numbers of people using opportunistic device-to-device communication. We provide an overview of existing approaches that address mobile opportunistic networks for parallel data dissemination and processing. First, works are presented that are concerned exclusively with the dissemination of information in opportunistic networks. We continue to present approaches that are dedicated to both opportunistic data dissemination and processing in mobile networks. In this context, we outline gossiping algorithms and fog computing-based techniques. Sub-sequently, we present methods that use mobile crowd sensing for data dissemination and processing. We contrast them with procedures that leverage opportunistic data processing and finally we conclude open research questions. In this regard, our research objectives are to investigate how the modeling can be carried out for a scenario such as UrbanCount and for which other use cases opportunistic networks for data dissemination and processing are suitable.

The ability to locate assets and humans will lead to many services such as location based services especially in the material handling domain. The development of Industrial Internet of Things (IIoT) necessitates precise positioning, especially for moving objects in industrial environment. This way, automation processes with less human errors, and more safe environments are feasible. In order to achieve a wide reaching penetration of new control and tracking schemes in the Material Handling Domain (MHD), localization of assets needs to be realized in a cost efficient way with sufficient quality of positioning. The cost and quality of localization need to be weighted against each other and depend on the use case. We investigate variations of a indoor localization system, this is done through acquiring raw measurements from an Ultra Wide-Band (UWB) ranging system and comparing various processing approaches to achieve accurate positioning. We then compare the computational cost and quality of positioning of these approaches. Three multilateration algorithms are compared: gradient descent, least square, and recursive least square. Additionally, we investigate the impact of anchor node placement and additional filtering through a Kalman filter. We show that the maximum positioning error is mitigated by up to 30 % and the mean error by up to 4 % when using additional Kalman filtering of multilateration position estimates at comparably low additional computation cost. Our results suggest there are significant differences of localization quality and computational cost between the examined multilateration methods with no clear correlation of computational cost and positioning quality. We also show that the positioning quality and filtering improvement strongly depends on the UWB anchor height.

Time (or clock) synchronization is a large and vital field of research, as synchronization is a precondition for many applications. A few example applications are distributed data acquisition, distributed databases, and real-time communication. First, this survey paper introduces the research area of time synchronization and emphasizes its relation to other research areas. Second, we give an overview of the state-of-the-art of time synchronization. Herein, we discuss both established protocol and research approaches. We analyze all techniques according to three criteria: used estimation algorithm, achievable synchronization accuracy, and the experimental conditions. In our opinion, this analysis highlights potential improvements. The most important question in this survey is as follows: which estimation method can be used to achieve which accuracies under which conditions? The intention behind this is to identify estimation methods that are particularly worth considering, as these already achieve good results in the wireless area but have not yet been examined in the wired area (and vice versa). This survey paper differs from other surveys in particular through the consideration of wireless and wired synchronization and the focus on estimation algorithms and their achievable accuracy.