arXiv subjects

Hans D. Schotten

Publications and source records attributed to Hans D. Schotten.

At least 73 records · Page 4Linked to original sources

arXiv2025

Benchmarking OpenWiFiSync on ESP32: Towards Cost-Effective Wireless Time Synchronization

Wireless time synchronization of mobile devices is a key enabler for numerous Industry 4.0 applications, such as coordinated and synchronized tasks or the generation of high-precision timestamps for machine learning or artificial intelligence algorithms. Traditional wireline clock synchronization protocols, however, cannot achieve the performance in wireless environments without significant modifications. To address this challenge, we make use of the Reference Broadcast Infrastructure Synchronization protocol, which leverages the broadcast nature of wireless communications and remains both non-invasive and standard-compliant. We implement and validate this protocol on a low-cost testbed using ESP32 modules and a commercial Wi-Fi access point. To support further research and development, we release our implementation as open-source software under the GNU General Public License Version 3 license via the OpenWifiSync project on GitHub. Our results demonstrate that synchronization accuracies within +/-30 microseconds are achievable using energy-efficient and affordable hardware, making this approach suitable for a wide range of use cases.

cs.NI↗

arXiv2025

Cracking the Microsecond: An Efficient and Precise Time Synchronization Scheme for Hybrid 5G-TSN Networks

Achieving precise time synchronization in wireless systems is essential for both industrial applications and 5G, where sub-microsecond accuracy is required. However, since the Industrial Internet of Things (IIoT) market is negligible compared to the consumer electronics market, the so-called IIoT enhancements have not yet been implemented in silicon. Moreover, there is no guarantee that this situation will change soon. Thus, alternative solutions must be explored. This paper addresses this challenge by introducing a scheme that uses a protocol capable of leveraging existing infrastructure to synchronize User Equipments (UEs), with one of the UEs serving as the master. If this master is connected via a wired link to the factory network, it can also function as a boundary clock for the factory network, including any Time-Sensitive Networking (TSN) network. Furthermore, the 5G Core Network (5GC) and 5G Base Station (gNB) can also be synchronized if they are connected either to the factory network or to the master UE. The proposed solution is implemented and evaluated on a hardware testbed using OpenAirInterface (OAI) and Software Defined Radios (SDRs). Time offset and clock skew are analyzed using a moving average filter with various window sizes. Results show that a filter size of 1024 provides the best accuracy for offset prediction between UEs. In a controlled lab environment, the approach consistently achieves synchronization within +/-50 ns, leaving sufficient margin for synchronization errors in real deployments while still maintaining sub-microsecond accuracy. These findings demonstrate the feasibility and high performance of the proposed protocol for stringent industrial use cases.

cs.NI↗

arXiv2025

Network-Centric Anomaly Filtering and Spoofer localization for 5G-NR Localization in LAWNs

This paper investigates security vulnerabilities and countermeasures for the 3rd Generation Partnership Project (3GPP) Fifth Generation New Radio (5G-NR) Time Difference of Arrival (TDoA)-based unmanned aerial vehicle (UAV) localization in low-altitude urban environments. We first optimize node selection strategies under Air to Ground (A2G) channel conditions, proving that optimal selection depends on UAV altitude and deployment density, and propose lightweight User Equipment (UE)-assisted approaches that reduce overhead while enhancing accuracy. Next, we then expose critical security vulnerabilities by introducing merged-peak spoofing attacks where rogue UAVs transmit multiple 5G-NR Positioning Reference Signalss (PRSs) that merge with legitimate signals, bypassing existing detection methods. Through theoretical modeling and sensitivity analysis, we quantify how synchronization quality and geometric factors determine spoofing success probability, thereby revealing fundamental weaknesses in current 3GPP positioning frameworks. To address these vulnerabilities, we design a network-centric anomaly detection framework at the Localization Management Function (LMF) using 3GPP-specified parameters, coupled with recursive gradient descent-based robust localization that filters anomalous data while estimating UAV position. Our unified framework simultaneously provides robust victim localization and spoofer localization, enabling active attacker attribution beyond passive defense. Extensive simulations validate the effectiveness of our optimization and security mechanisms for 3GPP-compliant UAV positioning.

eess.SP↗

arXiv2025

Use Cases, Metrics, and Challenges of Nomadic Non-Public Networks for the 6G Standardization

Wireless communication is evolving with the adoption of dynamic and self-organizing networks. They are expected to play a crucial role in shaping sixth-generation (6G) systems and the ongoing standardization process. The concept of non-public networks (NPNs) introduced in fifth-generation (5G) will be enhanced by nomadic non-public networks (NNPNs), extending mobility and adaptability beyond fixed locations. These networks help overcome the limitations of traditional static infrastructures, making them applicable to areas such as emergency response, transportation, agriculture, and others. This paper examines the transition from NPNs to NNPNs, highlighting key technical aspects such as network architecture, dynamic resource allocation, and wireless backhauling. Several use cases illustrate how NNPNs improve connectivity in environments where traditional networks are limited. Additionally, the study defines Key Performance Indicators (KPIs) to evaluate NNPN applications and establishes a framework for categorizing them based on mobility and operational requirements. Despite their advantages, NNPNs introduce architectural, regulatory, and security challenges such as new approaches for handovers, spectrum policies or cross-border functionality, and trust mechanisms to maintain reliable operations. By identifying use cases, defining evaluation criteria, and addressing technical and regulatory challenges, this paper provides insights into integrating NNPNs into future 6G networks. These findings contribute to ongoing standardization efforts and emphasize the need for adaptable policies and network architectures to maximize the benefits of NNPNs in next-generation communication systems.

cs.NI↗

arXiv2025

Knowledge vs. Experience: Asymptotic Limits of Impatience in Edge Tenants

We study how two information feeds, a closed-form Markov estimator of residual sojourn and an online trained actor-critic, affect reneging and jockeying in a dual M/M/1 system. Analytically, for unequal service rates and total-time patience, we show that total wait grows linearly so abandonment is inevitable and the probability of a successful jockey vanishes as the backlog approaches towards infinity. Furthermore, under a mild sub-linear error condition both information models yield the same asymptotic limits (robustness). We empirically validate these limits and quantify finite backlog differences. Our findings show that learned and analytic feeds produce different delays, reneging rates and transient jockeying behavior at practical sizes, but converge to the same asymptotic outcome implied by our theory. The results characterize when value-of-information matters (finite regimes) and when it does not (asymptotics), informing lightweight telemetry and decision-logic design for low-cost, jockeying-aware systems.

stat.ML↗

arXiv2025

Ultra-Fast Wireless Power Hacking

The rapid growth of electric vehicles (EVs) has driven the development of roadway wireless charging technology, effectively extending EV driving range. However, wireless charging introduces significant cybersecurity challenges. Any receiver within the magnetic field can potentially extract energy, and previous research demonstrated that a hacker could detect the operating frequency and steal substantial power. However, our approach required time to track new frequencies or precise adjustments of inductance and capacitance, which would be less effective against potential rapid transmitter frequency changes or capacitance drift. As a solution, we enhanced the interceptor and enabled it to intrude as well as steal energy within just three cycles of the high-frequency signal. Moreover, it can work without any circuit parameters or look-up tables. The key innovation is synchronizing the receiver current with the phase of the magnetic sensor voltage. Through MATLAB / Simulink simulations, finite-element analysis, and experimental validation, we demonstrated that our improved method can steal over 76% of the power received by a fully resonant receiver under identical conditions. This attack demonstrates that simple frequency-changing power encryption offers limited protection against such threats.

cs.CR↗

arXiv2025

Chronicles of Jockeying in Queuing Systems

Emerging trends in communication systems, such as network softwarization, functional disaggregation, and multi-access edge computing (MEC), are reshaping both the infrastructural landscape and the application ecosystem. These transformations introduce new challenges for packet transmission, task offloading, and resource allocation under stringent service-level requirements. A key factor in this context is queue impatience, where waiting entities alter their behavior in response to delay. While balking and reneging have been widely studied, this survey focuses on the less explored but operationally significant phenomenon of jockeying, i.e. the switching of jobs or users between queues. Although a substantial body of literature models jockeying behavior, the diversity of approaches raises questions about their practical applicability in dynamic, distributed environments such as 5G and Beyond. This chronicle reviews and classifies these studies with respect to their methodologies, modeling assumptions, and use cases, with particular emphasis on communication systems and MEC scenarios. We argue that forthcoming architectural transformations in next-generation networks will render many existing jockeying models inapplicable. By highlighting emerging paradigms such as MEC, network slicing, and network function virtualization, we identify open challenges, including state dissemination, migration cost, and stability, that undermine classical assumptions. We further outline design principles and research directions, emphasizing hybrid architectures and decentralized decision making as foundations for re-conceptualizing impatience in next-generation communication systems.

cs.NI↗

arXiv2025

Adaptive Decentralized Queue Disclosure for Impatient Tenants in Edge and Non-terrestrial Systems

We study how queue-state information disclosures affect impatient tenants in multi-tenant edge systems. We propose an information-bulletin strategy in which each queue periodically broadcasts two Markov models. One is a model of steady-state service-rate behavior and the other a model of the queue length inter-change times. Tenants autonomously decide to renege or jockey based on this information. The queues observe tenant responses and adapt service rates via a learned, rule-based predictive policy designed for decentralized, partially-observed, and time-varying environments. We compare this decentralized, information-driven policy to the classical, centralized Markov Decision Process (MDP) hedging-point policy for M/M/2 systems. Numerical experiments quantify the tradeoffs in average delay, impatience and robustness to stale information. Results show that when full, instantaneous state information and stationarity hold, the hedging-point policy yields less impatience but this diminishes as information becomes partial or stale. The rule-based predictive policy on the other hand is more robust to staleness in dispatched information, making it conducive for conditions typical of edge cloud and non-terrestrial deployments.

eess.SY↗

arXiv2025

Towards Nomadic 6G Communication Networks: Implications on Architecture, Standardization, and Regulatory Aspects

The emergence of nomadic mobile communication networks for sixth-generation (6G) introduces a paradigm shift in how network infrastructure is conceptualized, deployed, and operated. Unlike traditional fixed systems, Nomadic Networks (NNs) consist of mobile and self-organizing nodes that provide radio infrastructure capabilities in motion. This paper explores the architectural implications of such systems, with a particular focus on the design and evolution of network interfaces. We analyze the requirements for inter-node communication, service discovery, and control delegation in dynamic environments. Furthermore, we examine the regulatory and licensing challenges that arise when infrastructure elements traverse jurisdictional boundaries. Based on current 6G visions and relevant research, we identify limitations in existing architectures and propose a set of interface principles tailored to nomadicity. By synthesizing findings from mobile, non-terrestrial, and organic network domains, this work contributes to the architectural foundation for future nomadic 6G communication systems and outlines directions for interface standardization in decentralized, mobile infrastructures.

cs.NI↗

arXiv2025

Fast Energy-Theft Attack on Frequency-Varying Wireless Power without Additional Sensors

With the popularity of wireless charging, energy access protection and cybersecurity are gaining importance, especially in public places. Currently, the most common energy encryption method uses frequency and associated impedance variation. However, we have proven that this method is not reliable, since a hacker can detect the changing frequency and adjust the compensation. However, the previously presented system needed time to follow the updated frequency, while encryption systems may vary the frequency faster to avoid energy theft. Furthermore, the previous system required an additional sensor coil. To solve these problems, we optimized the attack and the associated system, which can intrude and steal energy within 0.2 ms. The key is the elimination of the time-consuming maximum receiver current regulation. Also, we use the main receiving coil rather than any additional sensor antenna to detect the magnetic field. Thus, the new hardware is even simpler. A simulation model and experimental results demonstrate the fast response speed of the attack on encrypted wireless power and steal 65% of the power. Overall, the applicability of the attack is highly improved and leaves less room for hardening the encryption. The results demonstrate that energy access protection needs to be given great attention.

cs.CR↗

arXiv2025

Analysis of an Architecture for Integrated Sensing and Communication in 5G OpenRAN

This paper analyzes the functional requirements and architectural considerations for Integrated Sensing and Communication ( ISAC) in a 5G Open Radio Access Network (OpenRAN) environment, with emphasis on secure and modular deployment. Focusing on a mono-static, half-duplex sensing approach, it evaluates radar setup options, signal types, and processing placement within the Radio Access Network ( RAN), considering performance and security implications. The proposed architecture minimizes hardware modifications by leveraging sniffer Radio Units (RU s) and existing OpenRAN fronthaul interfaces, while protecting sensitive In-phase and Quadrature (I/Q) data and control traffic against potential attacks. Security threats, such as passive sensing, spoofing, and privacy violations, are mapped to mitigation strategies within the OpenRAN framework. The result is a deployment blueprint applicable to both Public Land Mobile Networks ( PLMNs) and Non-Public Networks (NPNs), supporting future 6G ISAC capabilities in a standards-compliant manner.

cs.NI↗

arXiv2025

What is the Most Efficient Technique for Uplink Cell-Free Massive MIMO?

This paper seeks to determine the most efficient uplink technique for cell-free massive MIMO systems. Despite offering great advances, existing works suffer from fragmented methodologies and inconsistent assumptions (e.g., single- vs. multi-antenna access points, ideal vs. spatially correlated channels). To address these limitations, we: (1) establish a unified analytical framework compatible with centralized/distributed processing and diverse combining schemes; (2) develop a universal optimization strategy for max-min power control; and (3) conduct a holistic study among four critical metrics: worst-case user spectral efficiency (fairness), system capacity, fronthaul signaling, and computational complexity. Through analyses and evaluation, this work ultimately identifies the optimal uplink technique for practical cell-free deployments.

cs.IT↗

arXiv2025

Adaptive 6G Networks-in-Network Management for Industrial Applications

This paper presents the application of Dynamic Spectrum Management (DSM) for future 6G industrial networks, establishing an efficient controller for the Networks-in-Network (NiN) concept. The proposed architecture integrates nomadic as well as static sub-networks (SNs with diverse Quality of Service (QoS) requirements within the coverage area of an overlayer network, managed by a centralized spectrum manager (SM). Control plane connectivity between the SNs and the DSM is ensured by the self-organizing KIRA routing protocol. The demonstrated system enables scalable, zero-touch connectivity and supports nomadic SNs through seamless discovery and reconfiguration. SNs are implemented for modular Industrial Internet of Things (IIoT) scenarios, as well as for mission-critical control loops and for logistics or nomadic behavior. The DSM framework dynamically adapts spectrum allocation to meet real-time demands while ensuring reliable operation. The demonstration highlights the potential of DSM and NiNs to support flexible, dense, and heterogeneous wireless deployments in reconfigurable manufacturing environments.

cs.NI↗

arXiv2025

A Comprehensive Tutorial and Survey of O-RAN: Exploring Slicing-aware Architecture, Deployment Options, Use Cases, and Challenges

Open-radio access network (O-RAN) seeks to establish the principles of openness, programmability, automation, intelligence, and hardware-software disaggregation with interoperable and standard-compliant interfaces. It advocates for multi-vendorism and multi-stakeholderism within a cloudified and virtualized wireless infrastructure, aimed at enhancing the deployment, operation, and management of RAN architecture. These enhancements promise increased flexibility, performance optimization, service innovation, energy efficiency, and cost effectiveness across fifth-generation (5G), sixth-generation (6G), and beyond networks. A silent feature of O-RAN architecture is its support for network slicing, which entails interaction with other domains of the cellular network, notably the transport network (TN) and the core network (CN), to realize end-to-end (E2E) network slicing. The study of this feature requires exploring the stances and contributions of diverse standards development organizations (SDOs). In this context, we note that despite the ongoing industrial deployments and standardization efforts, the research and standardization communities have yet to comprehensively address network slicing in O-RAN. To address this gap, this paper provides a comprehensive exploration of network slicing in O-RAN through an in-depth review of specification documents from O-RAN Alliance and research papers from leading industry and academic institutions. The paper commences with an overview of the relevant standardization and open source contributions, subsequently delving into the latest O-RAN architecture with an emphasis on its slicing aspects. Furthermore, the paper explores O-RAN deployment scenarios, examining options for the deployment and orchestration of RAN and TN slice subnets. It also discusses the slicing of the underlying infrastructure and provides an overview of various use cases related...

cs.NI↗

arXiv2025

Wideband Coplanar Waveguide MIMO Antenna for 6G Millimeter-Wave Applications with Defected Ground Structure

This research study introduces a novel small antenna with wideband capacity for the higher frequency range. As a possible contender for 6G wireless networks, the proposed antenna is designed to target the 6G Millimeter-Wave (mmWave) operating bands spanning 25 GHz to 33.5 GHz. With a microstrip patch structure fed by a coplanar waveguide (CPW) with the defected ground structure (DGS), a single antenna is introduced and then a design of 2 x 2 MIMO antenna is presented. The single antenna has 2 elements, while the 2 x 2 MIMO antenna has 8 elements. It achieves remarkably well in terms of return loss of 8.5 GHz wideband, which is anticipated to be used for several applications in 6G mmWave technology.

eess.SP↗

arXiv2025

Reliable Low Latency Wireless Communication Enabling Industrial Mobile Control and Safety Applications

Advanced industrial applications for human-machine interaction such as augmented reality support for maintenance works or mobile control panels for operating production facility set high demands on underlying wireless connectivity solution. Based on 802.11 standard, this paper proposes a concept of a new system, which is capable of those requirements. For increasing reliability, an agile triple-band (2.4 GHz, 5 GHz and 60 GHz) communication system can be used. In order to deal with latency and deterministic channel access, PHY and MAC techniques such as new waveforms or hybrid MAC schemes are investigated. Integration of precise localization introduces new possibilities for safety-critical applications.

eess.SP↗

arXiv2025

MALRIS: Malicious Hardware in RIS-Assisted Wireless Communications

Reconfigurable intelligent surfaces (RIS) enhance wireless communication by dynamically shaping the propagation environment, but their integration introduces hardware-level security risks. This paper presents the concept of Malicious RIS (MALRIS), where compromised components behave adversarially, even under passive operation. The focus of this work is on practical threats such as manufacturing time tampering, malicious firmware, and partial element control. Two representative attacks, power-splitting and element-splitting, are modeled to assess their impact. Simulations in a RIS-assisted system reveal that even a limited hardware compromise can significantly degrade performance metrics such as bit error rate, throughput, and secrecy metrics. By exposing this overlooked threat surface, this work aims to promote awareness and support secure, trustworthy RIS deployment in future wireless networks.

eess.SP↗

arXiv2025

Polygonal Obstacle Avoidance Combining Model Predictive Control and Fuzzy Logic

In practice, navigation of mobile robots in confined environments is often done using a spatially discrete cost-map to represent obstacles. Path following is a typical use case for model predictive control (MPC), but formulating constraints for obstacle avoidance is challenging in this case. Typically the cost and constraints of an MPC problem are defined as closed-form functions and typical solvers work best with continuously differentiable functions. This is contrary to spatially discrete occupancy grid maps, in which a grid's value defines the cost associated with occupancy. This paper presents a way to overcome this compatibility issue by re-formulating occupancy grid maps to continuously differentiable functions to be embedded into the MPC scheme as constraints. Each obstacle is defined as a polygon -- an intersection of half-spaces. Any half-space is a linear inequality representing one edge of a polygon. Using AND and OR operators, the combined set of all obstacles and therefore the obstacle avoidance constraints can be described. The key contribution of this paper is the use of fuzzy logic to re-formulate such constraints that include logical operators as inequality constraints which are compatible with standard MPC formulation. The resulting MPC-based trajectory planner is successfully tested in simulation. This concept is also applicable outside of navigation tasks to implement logical or verbal constraints in MPC.

cs.RO↗