The Bus Goes Wireless: Routing-Free Data Collection with QoS Guarantees in Sensor Networks

Abstract—We present the low-power wireless bus (LWB), a new communication paradigm for QoS-aware data collection in lowpower sensor networks. The LWB maps all communication onto network floods by using Glossy, an efficient flooding architecture for wireless sensor networks. Therefore, unlike current solutions, the LWB requires no information of the network topology, and inherently supports networks with mobile nodes and multiple data sinks. A LWB prototype implemented in Contiki guarantees bounded end-to-end communication delay and duplicate-free, inorder packet delivery—key QoS requirements in many control and mission-critical applications. Experiments on two testbeds demonstrate that the LWB prototype outperforms state-of-theart data collection and link layer protocols, in terms of reliability and energy efficiency. For instance, we measure an average radio duty cycle of 1.69 % and an overall data yield of 99.97 % in a typical data collection scenario with 85 sensor nodes on Twist. I

Control-guided Communication: Efficient Resource Arbitration and Allocation in Multi-hop Wireless Control Systems

In future autonomous systems, wireless multi-hop communication is key to enable collaboration among distributed agents at low cost and high flexibility. When many agents need to transmit information over the same wireless network, communication becomes a shared and contested resource. Event-triggered and self-triggered control account for this by transmitting data only when needed, enabling significant energy savings. However, a solution that brings those benefits to multi-hop networks and can reallocate freed up bandwidth to additional agents or data sources is still missing. To fill this gap, we propose control-guided communication, a novel co-design approach for distributed self-triggered control over wireless multi-hop networks. The control system informs the communication system of its transmission demands ahead of time, and the communication system allocates resources accordingly. Experiments on a cyber-physical testbed show that multiple cart-poles can be synchronized over wireless, while serving other traffic when resources are available, or saving energy. These experiments are the first to demonstrate and evaluate distributed self-triggered control over low-power multi-hop wireless networks at update rates of tens of milliseconds.Comment: Accepted final version to appear in: IEEE Control Systems Letter

Adaptive Real-Time Communication for Wireless Cyber-Physical Systems

Low-power wireless technology promises greater flexibility and lower costs in cyber-physical systems. To reap these benefits, communication protocols must deliver packets reliably within real-time deadlines across resource-constrained devices, while adapting to changes in application requirements (e.g., traffic demands) and network state (e.g., link qualities). Existing protocols do not solve all these challenges simultaneously, because their operation is either localized or a function of network state, which changes unpredictably over time. By contrast, this paper claims a global approach that does not use network state information as input can overcome these limitations. The Blink protocol proves this claim by providing hard guarantees on end- to-end deadlines of received packets in multi-hop low-power wireless networks, while seamlessly handling changes in application requirements and network state. We build Blink on the non real-time Low-Power Wireless Bus (LWB), and design new scheduling algorithms based on the earliest deadline first policy. Using a dedicated priority queue data structure, we demonstrate a viable implementation of our algorithms on re- source-constrained devices. Experiments show that Blink: (i) meets all deadlines of received packets; (ii) de- livers 99.97 % of packets on a 94-node testbed; (iii) minimizes communication energy consumption within the limits of the underlying LWB; (iv) supports end-to-end deadlines of 100 ms across 4 hops and 9 sources; and (v) runs up to 4.1× faster than a conventional scheduler implementation on popular microcontrollers

Synchronous Transmissions in Low-Power Wireless: A Survey of Communication Protocols and Network Services

Low-power wireless communication is a central building block of Cyber-physical Systems and the Internet of Things. Conventional low-power wireless protocols make avoiding packet collisions a cornerstone design choice. The concept of synchronous transmissions challenges this view. As collisions are not necessarily destructive, under specific circumstances, commodity low-power wireless radios are often able to receive useful information even in the presence of superimposed signals from different transmitters. We survey the growing number of protocols that exploit synchronous transmissions for higher robustness and efficiency as well as unprecedented functionality and versatility compared to conventional designs. The illustration of protocols based on synchronous transmissions is cast in a conceptional framework we establish, with the goal of highlighting differences and similarities among the proposed solutions. We conclude the paper with a discussion on open research questions in this field.Comment: Submitted to ACM Computing Survey

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