The Time-Triggered Wireless Architecture

Wirelessly interconnected sensors, actuators, and controllers promise greater flexibility, lower installation and maintenance costs, and higher robustness in harsh conditions than wired solutions. However, to facilitate the adoption of wireless communication in cyber-physical systems (CPS), the functional and non-functional properties must be similar to those known from wired architectures. We thus present Time-Triggered Wireless (TTW), a wireless architecture for multi-mode CPS that offers reliable communication with guarantees on end-to-end delays among distributed applications executing on low-cost, low-power embedded devices. We achieve this by exploiting the high reliability and deterministic behavior of a synchronous transmission based communication stack we design, and by coupling the timings of distributed task executions and message exchanges across the wireless network by solving a novel co-scheduling problem. While some of the concepts in TTW have existed for some time and TTW has already been successfully applied for feedback control and coordination of multiple mechanical systems with closed-loop stability guarantees, this paper presents the key algorithmic, scheduling, and networking mechanisms behind TTW, along with their experimental evaluation, which have not been known so far. TTW is open source and ready to use: https://ttw.ethz.ch

The Time-Triggered Wireless Architecture (Artifact)

This artifact contains a stable version of all the data and source code required to reproduce or replicate the results presented in The Time-Triggered Wireless Architecture. One GitHub repository serves as main hub for all information related to the artifact. The README file contains detailed instructions for - Running the TTnet model - Compiling and running TTnet - Running the TTW scheduler - Reproducing the data processing - Reproducing the plot

Wireless model-based predictive networked control system over cooperative wireless network

Owing to their distributed architecture, networked control systems (NCSs) are proven to be feasible in scenarios where a spatially distributed feedback control system is required. Traditionally, such NCSs operate over real-time wired networks. Recently, in order to achieve the utmost flexibility, scalability, ease of deployment, and maintainability, wireless networks such as IEEE 802.11 wireless local area networks (LANs) are being preferred over dedicated wired networks. However, conventional NCSs with event-triggered controllers and actuators cannot operate over such general purpose wireless networks since the stability of the system is compromised due to unbounded delays and unpredictable packet losses that are typical in the wireless medium. Approaching the wireless networked control problem from two perspectives, this work introduces a practical wireless NCS and an implementation of a cooperative medium access control protocol that work jointly to achieve decent control under severe impairments, such as unbounded delay, bursts of packet loss and ambient wireless traffic. The proposed system is evaluated on a dedicated test platform under numerous scenarios and significant performance gains are observed, making cooperative communications a strong candidate for improving the reliability of industrial wireless networks

A novel multipath-transmission supported software defined wireless network architecture

The inflexible management and operation of today\u27s wireless access networks cannot meet the increasingly growing specific requirements, such as high mobility and throughput, service differentiation, and high-level programmability. In this paper, we put forward a novel multipath-transmission supported software-defined wireless network architecture (MP-SDWN), with the aim of achieving seamless handover, throughput enhancement, and flow-level wireless transmission control as well as programmable interfaces. In particular, this research addresses the following issues: 1) for high mobility and throughput, multi-connection virtual access point is proposed to enable multiple transmission paths simultaneously over a set of access points for users and 2) wireless flow transmission rules and programmable interfaces are implemented into mac80211 subsystem to enable service differentiation and flow-level wireless transmission control. Moreover, the efficiency and flexibility of MP-SDWN are demonstrated in the performance evaluations conducted on a 802.11 based-testbed, and the experimental results show that compared to regular WiFi, our proposed MP-SDWN architecture achieves seamless handover and multifold throughput improvement, and supports flow-level wireless transmission control for different applications

Overcoming Bandwidth Limitations in Wireless Sensor Networks by Exploitation of Cyclic Signal Patterns: An Event-triggered Learning Approach

Wireless sensor networks are used in a wide range of applications, many of which require real-time transmission of the measurements. Bandwidth limitations result in limitations on the sampling frequency and number of sensors. This problem can be addressed by reducing the communication load via data compression and event-based communication approaches. The present paper focuses on the class of applications in which the signals exhibit unknown and potentially time-varying cyclic patterns. We review recently proposed event-triggered learning (ETL) methods that identify and exploit these cyclic patterns, we show how these methods can be applied to the nonlinear multivariable dynamics of three-dimensional orientation data, and we propose a novel approach that uses Gaussian process models. In contrast to other approaches, all three ETL methods work in real time and assure a small upper bound on the reconstruction error. The proposed methods are compared to several conventional approaches in experimental data from human subjects walking with a wearable inertial sensor network. They are found to reduce the communication load by 60–70%, which implies that two to three times more sensor nodes could be used at the same bandwidth

Scalable QoS-aware Mobility for Future Mobile Operators

Telecom operators and Internet service providers are heading for a new shift in communications paradigms. The forthcoming convergence of cellular and wireless data networks is often manifested in an “all IP approach” in which all communications are based on an end-to-end IP protocol framework. The approach to network design becomes user and service-centered, so that continuous reachability of mobile users and sustained communication capabilities are default requirements for a prospective architecture. In this article, we describe a network architecture which is able to provide seamless communication mobility, triggered either by the user or by the network, across multiple technologies. The architecture allows for media independent handovers and supports optimized mobility and resource management functions. The main focus of the article is on major technical highlights of mobility and quality-of-service (QoS) management subsystems for converged networks.Publicad