Running time-critical and computationally intensive processes of mobile robots on edge computing infrastructures is a key enabler of flexibility, scalability, and decentralized control. The real-time performance of such off-loaded control tasks strongly depends on the quality and stability of the underlying wireless communication link. In environments with a coexistence of multiple wireless access technologies, this becomes even more challenging. The present paper sets forth an experimental system that combines a nonlinear model predictive control (NMPC) strategy with dynamic switching of wireless connectivity between 5G, WiFi 5 GHz and WiFi 6 GHz. The control logic is executed on an edge server and transmitted to an Automated Guided Vehicle (AGV) over a set of different wireless channels. The proposed architecture is validated through real-time trajectory tracking in a laboratory environment. The findings of this study demonstrate that robust switching mechanisms and network awareness are crucial for stable operation under realistic wireless conditions, underscoring the importance of co-designing communication and control systems for edge-cloud-based robotic applications.

IoT use cases in the domain of critical infrastructure or disaster prevention, such as flood monitoring, have become increasingly popular. These are often implemented via low power wide area networks (LPWAN). LPWAN outages can prevent the delivery of data in such settings, highlighting the importance of transmission resiliency in IoT applications. In this work, we analyze how short-term LPWAN failures can be avoided by adding a payload history to the current message or using multiple LPWAN communication channels. Long-term failures are investigated with a Monte-Carlo-based simulation with a generalized linear model to understand the factors that affect the mean time to failure (MTTF) in such networks. If multiple different LPWAN interfaces are available in an IoT device, a simple parallel use of all networks increases reliability but consumes too much energy for battery-powered devices and can violate duty cycles. For this reason, we propose the MultiPath Low Power Wide Area Network (MP-LPWAN) protocol for IoT devices, which combines multiple LPWANs to deal with such failures. MP-LPWAN improves overall IoT system performance by dynamically adjusting transmission parameters and interface priority to adapt to changing network conditions. We implemented MP-LPWAN on a dual-LPWAN testbed and empirically validated its performance.

Wireless connectivity in vineyards has substantial potential to redefine the wine business using digitalization. To this end, this paper presents a measurement study of 5G performance in the 3.7-3.8 GHz frequency band in several steep vineyards in Germany. The steep terrain causes unique challenges for 5G deployment. The study investigates private nomadic 5G networks that are explicitly provided temporarily. It uses continuous wave and 5G network measurements to examine uplink signal quality, achievable data rates, and coverage area. The results indicate the effects of vineyard topography and settings on 5G efficiency.

Wireless networks have made great strides in recent years in supporting the Industrial Internet of Things (IIoT). However, industrial network security remains a major challenge in the context of wireless access. Notably, many industrial communication services that enable factory floor applications are still based on proprietary and industry-specific protocols that lack essential security features. As a solution to this challenge, in this paper, we propose an application function (AF) based security framework (AERO). This framework enables the 5G security function to meet the security requirements of industrial networks when wireless access is used without implementing redundant mechanisms. The basic idea is that the 5G system implements the user plane cryptographic mechanism over the air, based on industry requirements, without affecting existing industry protocols. We propose ($i$) static configuration and (ii) dynamic configuration mechanisms that facilitate providing the 5G core network security policy used to determine user plane cryptographic requirements. Furthermore, we demonstrate the advantages of our AERO approach by applying it to two specific use cases: Automated Guided Vehicles (AGVs) and Electrified Mono-rail Systems (EMSs). Through our analysis, we establish that our proposal significantly reduces data transmission time when compared to the current 5G mechanism.

Despite decades of evolution, the fundamental trust model of mobile networks remains unchanged. As a result, each mobile device has its own identity chip with network access credentials to be able to use mobile services such as voice telephony or Internet access. The upcoming Internet of Everything (IoE) revolution leads to a massive increase in connected devices and challenges the scalability of this approach. We propose to simplify trust establishment and show how the identity chips storing the credentials can be eliminated for most devices. The key idea is a new trust model in which an authorized subscriber securely delegates trust to other devices such that these other devices can claim legitimacy to connect to the mobile network. Our analysis shows that this proposal significantly reduces costs compared to the 5G trust model.

With 5G technology and its application in industry, the demand for wireless communication is increasing and so is the need for information about the wireless channel. Thus, accurate propagation channel models are required. For this purpose, we analyze our recently measured and published Power Delay Profiles (PDPs) in industrial scenarios using the Saleh Valenzuela (SV) model, compare the results with the results of other scenarios and propose an improved model. Further, we discuss the relation of path loss models, PDPs and the SV-model.

Due to an increasing need for mobility on the factory floor, future industrial applications will often use wireless technologies like 5G. The necessarily high reliability not only needs to be designed into the wireless communication technology, but also has to be experimentally verified. Events that degrade the reliability of highly available systems are rare. Additionally, correlation is inherent to wireless channels and an analysis method that is able to cope with those two challenges is needed. Thus, in this work our aim is to provide such a method. We evaluate the practical usage of the limited relative error (LRE) algorithm and discuss how to obtain confidence intervals based on it. Thereby, the standard normal distribution is approximated, which leads to biased results. We illustrate this by the usage of the Berry-Esseen theorem. To overcome the bias the LRE algorithm is enhanced with moving block bootstrapping (MBB). We call this new method bootstrapping LRE algorithm. We use measurement data from a 5G network for our analysis. Further, the usability of the 5G network for communication purposes based on the black channel paradigm is evaluated with the 5G measurement data and its statistical analysis. Thereby, the performance parameters of cycle time and reliability of the black channel in 5G are determined.

Bandwidth is a scarce resource in industrial wireless networks. At the same time keep-alive-messages are excessively used in these networks to test channel characteristics. This work proposes an approach to reduce bandwidth usage in critical industrial applications, by exploiting channel quality data from 5G. Thereby, the information about the channel is gained from channel state information (CSI) and the radio resource control (RRC) state. This work combines the CSI with the RRC state to determine whether a wireless node is connected. Subsequently, the connection information is exposed towards the application server via the network exposure function (NEF) of the 5G core network and to the mobile application by the UE. Since the CSI and RRC state are always present, this results in a net bandwidth reduction on the air interface of approximately 1.65 Mbps in the examined reference use case in contrast to the standard keep-alive mechanism.

Tomorrow's production facilities will be more flexible and efficient by incorporating new technologies, like massive wireless sensor networks, intelligent logistics solutions, human-machine-cooperation and a tight-knit communication connecting all of these systems. The rise of mobile machines and the required ability for reconfiguration of static production facilities fosters the use of wireless communication technologies. However even communication technologies that provide features specialized for industry, like 5G, will not be able to fulfill all requirements of the industrial environment simultaneously. We show this by analyzing the requirements of industrial use cases and comparing them to the performance of current and future communication technologies. We introduce current fields of research, which focus on technologies and strategies used in the factory context for solving these challenges. To do so the factory of the future will use multiple communication technologies and those need to be orchestrated properly.

Our earlier study shows that ultra-reliable low latency (uRLL) services in 5G are economically difficult if existing architectures and operational models are followed due to the very high infrastructure costs. This is mainly driven by the IT admin cost of distributed and attended datacenters necessary to host such services. Therefore, in this paper we analyze potential uRLL use cases and their traffic profiles in more detail, check alternative architecture solutions, and examine the cost saving potential of different datacenter operational models. The results demonstrate that both the alternative operational models and the new network architecture approaches that avoid the tunneling of user plane packets provide significant cost savings compared to the solution based on evolved packet core with a standard operational model.

5G imposes versatile requirements on radio and mobile core network. Such requirements can be supported by parallel so-called slices, each implementing a service-tailored network architecture. This paper shows how such architectures can be implemented with the evolved packet core (EPC). We furthermore provide a cost analysis of an EPC based, sliced network deployment in Japan for 5G services. It shows that the main cost driver are low latency services, as these require a highly distributed infrastructure. For the expected massive number of IoT devices, a centralized infrastructure keeps costs surprisingly cheap in contrast. Overall, the paper shows that EPC is well suited for the 5G challenges, which is relevant especially for the first 5G deployments in 2020.

Through successive technological innovation, mobile networks have been able to cope with traffic growth and the changing nature of services. However, there is still a gap between the possible transformation in terms of performance and efficiency, and the emerging new service requirements. This paper presents the ongoing mobile network evolution towards 5G, with a focus on the emerging network slicing concept, supposed to cope with the disparate requirements of future services and applications. Network slicing allows for the coexistence of different architectures to address disparate service requirements in a more efficient way. A slice selection function is a key element in the future core network architecture, enabling the UE to be allocated to a proper slice. We proposed a new slice selection mechanism allowing the UE to connect to multiple slices based on service type. The standardization status on this matter and the technical aspects of the proposed selection function are discussed.

Network functions virtualization is one of the most promising networking technology trends for mobile operators. Such functions often are considered as virtualized version of physical devices. They follow the same implementation, deployment, and operation and management model as such physical entities. However, some key characteristics of the underlying cloud technologies, such as the elastic provisioning of resources, the different hardware failure rates and the increasing programmability of the underlying network enable new design paradigms. Thus, virtual network functions should leverage on IT technologies like Software-as-a-Service (SaaS) to reduce operational costs and enable new business models. We introduce a classification of different design paradigms, detail how a SaaS implementation can be performed for mobile network gateways, and provide a comparison of the operation cost implications of employing such paradigms to create network nodes in a mobile network.

The gateways in mobile cellular networks are capable to handle the traffic from millions of subscribers at the same time, while providing high availability guarantee. Such entities are not only expensive, but also inflexible in terms of system deployment and maintenance. In this work, we investigate the feasibilities to virtualize gateway entities used in the Long Term Evolution (LTE) Evolved Packet Core (EPC). We propose a novel PDN Gateway (PGW) architecture, which decouples the control plane from the user plane by using Software Defined Network (SDN) technology. Moreover, we propose to run the user plane forwarding function on low cost IT hardware. The major advantages of our proposal are two-fold. First, our proposal lowers down the expenditure of operating services in LTE networks. Second, fine-grained resource management policies can be implemented in our virtualized gateway, which brings agility and reliability for the mobile cellular network.

Gateways are essential components of cellular networks, they perform accounting, packet inspection, and serve as mobility anchors. In the discussion on a future 5G cellular network architecture, the location of gateway functionality in cellular networks, i.e. their number and placement, is subject to some debate. Both centralized and distributed network architectures are currently considered. In this paper, we take a simulation based approach to compare the cost of such architectures for a typical nation-wide network. The results show that already a low number of well distributed gateways results in costs which are close to the optimum.

To minimize cost, Virtual Network Operators (VNOs) need to consider the required network availability already at the network design stage. One generic approach to reach the availability target is to select only high-quality physical network elements that offer high availability and consequently demand high expenses per element. The other generic approach to achieve high availability is to add protection capacity on the level of the virtual network based on lower cost components. In this paper, we analyze both alternatives with a simulation tool to answer the fundamental question how quality can be traded against capacity. For this purpose, we consider different network topologies and the influence of different parameters and provide a framework to find an optimal strategy between Mean Time Between Failures (MTBF) targets for the physical infrastructure and the usage of additional backup paths on the virtual network level.

Network redundancy and protection have become an even more serious issue after the last tsunami in Japan. Future networks need to be planned and operated keeping such unprecedented failures in mind. In this regard, we consider Virtual Network Embedding (VNE) techniques as an useful tool to realize an optimization between redundancy and resource consumption. However, conventional VNEs mostly concentrate on single network embedding. As VNE is a computationally intractable problem, relaxation methods are often used to offer a workable polynomial time solution. Some of such relaxation methods like flow-splitting do not fit well in real network operation. In this paper, we propose a heuristic VNE algorithm for network site protection without flow splitting. We also provide a solution with joint site and link embedding to achieve better bandwidth consumption. Evaluation results show that our VNE algorithm performs close to theoretical thresholds and consumes less link resources in delivering a VNE solution in polynomial time compared to the conventional algorithm.

Network reliability and survivability are important features for hosting high-demanding services in virtual network environments. Since multiple virtual networks can share the physical resources of the underlying substrate, even a single failure in the substrate can affect a large number of virtual networks and the services they offer. To overcome the physical link failure impact on virtual network operations, backup path mechanisms are investigated in many related works for path protection. However, this one to one path protection cannot handle explicit path availability requirements. In this work, we present a virtual network embedding algorithm which provides path protection with explicit virtual link availability constraints. Evaluation results show that our algorithm performs close to theoretical thresholds and consumes less link resources when delivering a virtual network embedding solution in polynomial time compared to a conventional path backup algorithm.

Fuel-efficient driving is difficult in unknown or complex environments. To aid the driver with this task, we present a novel method of tactical route optimization by calculating a short-term fuel-reduced velocity profile. This profile is based on knowledge of location-dependent velocity profiles that are collected by the vehicles over time and shared with other vehicles. To determine a fuel-efficient velocity profile, we first split the planned route into segments. We cluster the historical velocity profiles within each segment using a Dynamic Time Warping algorithm, obtaining classes of velocity profiles and their probabilities. We construct a transition graph between velocity profile classes from adjacent segments and calculate the most probable path through the next segments ahead. This path represents the most likely future velocity profile under the assumption that the driver behaves like previous drivers on the same segment. Given the constraints defined by this profile, we calculate the fuel-reduced velocity profile with help of a shortest path algorithm in a vehicle-specific fuel-consumption graph. First results in an urban environment indicate possible fuel savings of about 8.3% compared to the most probable profile.

Many applications in vehicular communications require the collection of vehicular position traces. So far this has been done by recording and transmitting unencoded or merely linearly filtered position samples. Depending on the sample frequency and resolution, the resulting data load may be very large, consuming significant storage and transmission resources. In this paper, we propose a method based on two-dimensional cubic spline interpolation that is able to reduce the amount of the measurement data significantly. Our approach allows for a configurable accuracy threshold and performs in O(n3). We evaluate our approach with real vehicular GPS movement traces and show that it is able to reduce the volume of the measurement set by up to 80% for an accuracy threshold of 20 centimeters.

During the analysis of packet log files from network experiments, the question arises which received packet belongs to which of the potentially many binary identical send events. We discuss this send-receive correlation problem for networks with local broadcast media. We can prove that assigning send and receive events is an NP-complete problem. However, there is a solution algorithm that is exponential only in the number of nodes; if the number of network nodes is fixed, its complexity is polynomial.

Access point sharing communities are an attractive solution for low-cost global mobile Internet access. However, existing communities all require a central authority in form of a certificate authority or an authentication server. In this paper, we show how such a community network can be created without a central entity. We introduce a mechanism called remote station approval; a host can use it to offer Internet access without requiring a central instance and without the risk of legal responsibility for the guests' traffic. We discuss how our system preserves the anonymity of its users and present a prototype implementation and some first performance figures.

Repeatability has most often been neglected in experiments with wireless multihop networks. In this paper, we propose to consider repeatability in a coarse-grained fashion on a topological level. For this, a metric for comparing the similarity of topologies in static and mobile setups is presented and used to examine the level of repeatability achievable in such experiments. This metric is able to classify experiments according to the presence or absence of interference and to changes in the behavior of mobile nodes. It can be used to identify experimental runs where application layer performance is influenced by topological effects.

In this paper, we present a methodology and a toolkit to conduct tightly controlled real-world experiments in wireless multihop networks. The main features of our EXC toolkit are a plug-in architecture for easy integration of new functionality, simple scheduling of experiment runs, direct monitoring of experiments, easy management of node mobility, and high portability. EXC does not require specific hardware and can be used for investigating applications and algorithms in real-world environments. We explain the basic features of the toolkit and examine these by means of an experiment with a special focus on repeatability.

In the context of vehicular ad-hoc networks (VANETs), a number of highly promising convenience applications have been proposed. These include collecting and distributing information on the traffic situation, distributed monitoring of road and weather conditions, and finding available parking places in a distributed, cooperative manner. Unfortunately, all of these applications face major problems when a VANET is used as a means to distribute the required information. In particular a large number of vehicles needs to be equipped with dedicated VANET technology before these applications can provide a useful service. Even if customers were willing to purchase a system which is not immediately useful, it would still take quite some time until the required density of equipped cars is reached. In contrast, affordable always-on mobile Internet access is already mainstream. Such Internet connectivity could be used to build the proposed applications in a different fashion: by using peer-to-peer communication, essentially creating a peer-to-peer network of cars sharing traffic information. This allows to overcome the limitations of VANETs, while it preserves their key benefits of decentralization and robustness. In this paper, we describe the technical challenges that arise from such an approach, point out relevant research directions, and outline possible starting points for solutions.