Achieving low latency remains a challenge in today's industrial Internet of Things (IoT) applications, particularly if operated over wireless multi-hop networks. One idea that can distinctly reduce the multi-hop latency is the so-called cut-through forwarding, i.e., a node starts relaying a packet after it has only received a fraction of it by leveraging two radios. This paper proposes the novel concurrent wireless cut-through (CWCT) protocol based on a prototype design which combines two off-the- shelf IoT devices. To improve reliability and eliminate routing overhead, CWCT applies concurrent transmission and Golay error correction coding. Evaluation on a controlled topology and on a medium-size testbed shows the large reduction in latency of CWCT compared to Glossy and the high synchronicity of concurrent transmission. To further improve packet reliability, we need to reduce the out-of-band leakage.

Millimeter-wave (mmWave) communication is a promising technology to cope with the exponential increase in 5G data traffic. Such networks typically require a very dense deployment of base stations. A subset of those, so-called macro base stations, feature high-bandwidth connection to the core network, while relay base stations are connected wirelessly. To reduce cost and increase flexibility, wireless backhauling is needed to connect both macro to relay as well as relay to relay base stations. The characteristics of mmWave communication mandates new paradigms for routing and scheduling. The paper investigates scheduling algorithms under different interference models. To showcase the scheduling methods, we study the maximum throughput fair scheduling problem. Yet the proposed algorithms can be easily extended to other problems. For a full-duplex network under the no interference model, we propose an efficient polynomial-time scheduling method, the schedule-oriented optimization. Further, we prove that the problem is NP-hard if we assume pairwise link interference model or half-duplex radios. Fractional weighted coloring based approximation algorithms are proposed for these NP-hard cases. Moreover, the approximation algorithm parallel data stream scheduling is proposed for the case of half-duplex network under the no interference model. It has better approximation ratio than the fractional weighted coloring based algorithms and even attains the optimal solution for the special case of uniform orthogonal backhaul networks.

Millimeter-wave (mmWave) communication is a promising technology to cope with the expected exponential increase in data traffic in 5G networks. mmWave networks typically require a very dense deployment of mmWave base stations (mmBS). To reduce cost and increase flexibility, wireless backhauling is needed to connect the mmBSs. The characteristics of mmWave communication, and specifically its high directionality, imply new requirements for efficient routing and scheduling paradigms. We propose an efficient scheduling method, so-called schedule-oriented optimization, based on matching theory that optimizes QoS metrics jointly with routing. It is capable of solving any scheduling problem that can be formulated as a linear program whose variables are link times and QoS metrics. As an example of the schedule-oriented optimization, we show the optimal solution of the maximum throughput fair scheduling (MTFS). Practically, the optimal scheduling can be obtained even for networks with over 200 mmBSs. To further increase the runtime performance, we propose an efficient edge-coloring based approximation algorithm with provable performance bound. It achieves over 80% of the optimal max-min throughput and runs 5 to 100 times faster than the optimal algorithm in practice. Finally, we extend the optimal and approximation algorithms for the cases of multi-RF-chain mmBSs and integrated backhaul and access networks.

The recently proposed Glossy protocol demonstrated the high potential of constructive interference (CI) in improving communication performance in wireless sensor networks. This paper presents a network flooding protocol, Ripple, which also exploits CI while improving Glossy in terms of throughput and energy efficiency by a factor of three each. To this end, we propose to pipeline transmissions on multiple channels. Ripple uses a novel packet-based channel assignment to eliminate the time overhead occurring in traditional node-based channel assignment procedures. Moreover, if we apply the Reed-Solomon (RS) erasure code to Ripple, it pushes the reliability close to 100%, surpassing Glossy, being nonetheless computationally practical for TelosB motes. Still, the throughput after error coding doubles, or even triples that of the state-of-the-art reliable data dissemination protocol Splash. By tuning the transmission interval, Ripple balances between high throughput and high reliability, thus suiting an array of network broadcast applications with various QoS requirements.

Wireless sensor networks (WSNs) are increasingly being applied to scenarios that simultaneously demand for high packet reliability and short delay. A promising technique to achieve this goal is concurrent transmission, i.e. multiple nodes transmit identical or different packets in parallel. Practical implementations of concurrent transmission exist, yet its performance is not well understood due to the lack of expressive models that accurately predict the success of packet reception. We experimentally investigate the two phenomena that can occur during concurrent transmission depending on the transmission timing and signal strength, i.e. constructive interference and capture effect. Equipped with the thorough understanding of these two phenomena, we propose an accurate prediction model for the reception of concurrent transmission. The extensive measurements carried out with varying number of transmitters, packet length and signal strength verify the excellent quality of our model, which provides a valuable tool for protocol design and simulation of concurrent transmission in WSNs.

The maintenance of Wireless Sensor Networks (WSNs) can carry high or prohibitive costs, particularly, if the WSN is deployed in unattended areas. Secure monitoring and control of the WSN is vital, however, practical systems are rare and limited with respect to their capabilities. We present a monitoring and control system for WSNs that is secure and additionally equipped with intrusion detection functionality. It allows to reliably assess the actual status of the network, to configure the sensor nodes, and to further use this data to highlight suspicious events.

Interference is one of the key factors impacting the performance and robustness of Wireless Sensor Networks (WSN) operation. For serious WSN applications, it is crucial that interference mitigation acts in a fast and reliable fashion. We describe an adaptive and distributed channel hopping scheme, HOPSCOTCH1. Our scheme is novel in the sense that (1) it is built on a lightweight yet accurate metric to describe the interference, and (2) it is fully distributed in nature and combines a proactive, consent-based as well as a reactive, rendezvous-based hopping technique, which allow for robust operation even in adverse conditions. We show by extensive experimentation that our channel metric models real-world conditions accurately and that HOPSCOTCH provides a very fast response time to adapt the network to interference.

The use of Wireless Sensor Networks (WSN) in application domains such as industrial automation poses strict requirements in terms of communication delay, reliability, etc. Time Division Multiple Access (TDMA) is the preferred access scheme for the above applications, and leading industry standards such as WirelessHART employ it by centrally generating convergecast schedules. Despite the fact that techniques such as multi-channel communication and spatial re-use are currently not harnessed to their full potential, existing scheduling heuristics are often complex while performing far from the optimal solution. We investigate the tree convergecast scheduling with multiple channels (TCMC) problem. In particular, we derive an integer programming-based optimal solution to the min length and buffer size scheduling as well as the min length and channel number scheduling. We further describe TCMC scheduling as a decision problem, which allows us to create a general scheduling framework that is flexible and requires minimal code modification for implementing different TCMC scheduling strategies. Within our framework, we propose and implement four heuristics. Our novel busy-sender-first heuristic is significantly better than the state-of-the-art heuristic in both schedule length (within 0.22% of the optimum) and memory consumption, as well as being conceptually much simpler. Finally, based on the evaluation results of the busy-sender-first heuristic, we derive guidelines on the choice of number of channels and configuration of tree topology, respectively.

Fault tolerant control of dynamic processes is investigated in this paper using an auto-tuning PID controller. A fault tolerant control scheme is proposed composing an auto-tuning PID controller based on an adaptive neural network model. The model is trained online using the extended Kalman filter (EKF) algorithm to learn system post-fault dynamics. Based on this model, the PID controller adjusts its parameters to compensate the effects of the faults, so that the control performance is recovered from degradation. The auto-tuning algorithm for the PID controller is derived with the Lyapunov method and therefore, the model predicted tracking error is guaranteed to converge asymptotically. The method is applied to a simulated two-input two-output continuous stirred tank reactor (CSTR) with various faults, which demonstrate the applicability of the developed scheme to industrial processes.