Abstract – Wireless Sensor Networks (WSNs) represent a very promising solution in the field of wireless technologies for industrial applications. However, for a credible deployment of WSNs in an industrial environment, four main properties need to be fulfilled, i.e., energy efficiency, scalability, reliability, and timeliness. In this paper we focus on IEEE 802.15.4 WSNs and show that they can suffer from a serious unreliability problem. This problem arises whenever the power management mechanism is enabled for energy efficiency, and results in a very low packet delivery ratio, also when the number of sensor nodes in the network is very low (e.g., 5). We carried out an extensive analysis – based on both simulation and experiments on a real WSN – to investigate the fundamental reasons of this problem, and we found that it is caused by the contention-based MAC (Medium Access Control) protocol used for channel access and its default parameter values. We also found that, with a more appropriate MAC parameters setting, it is possible to mitigate the problem and achieve a delivery ratio up to 100%, at least in the scenarios considered in this paper. However, this improvement in communication reliability is achieved at the cost of an increased latency, which may not be acceptable for industrial applications with stringent timing requirements. In addition, in some cases this is possible only by choosing MAC parameter values formally not allowed by the standard.

In recent years, the use of wireless sensor networks for industrial applications has rapidly increased. However, energy consumption still remains one of the main limitations of this technology. As communication typically accounts for the major power consumption, the activity of the transceiver should be minimized, in order to prolong the network lifetime. To this end, this paper proposes an Adaptive Staggered sLEEp Protocol (ASLEEP) for efficient power management in wireless sensor networks targeted to periodic data acquisition. This protocol dynamically adjusts the sleep schedules of nodes to match the network demands, even in time-varying operating conditions. In addition, it does not require any a-priori knowledge of the network topology or traffic pattern. ASLEEP has been extensively studied with simulation. The results obtained show that, under stationary conditions, the protocol effectively reduces the energy consumption of sensor nodes (by dynamically adjusting their duty-cycle to current needs) thus increasing significantly the network lifetime. With respect to similar non-adaptive solutions, it also reduces the average message latency and may increase the delivery ratio. Under timevarying conditions the protocol is able to adapt the duty-cycle of single nodes to the new operating conditions while keeping a consistent sleep schedule among sensor nodes. The results presented here are also confirmed by an experimental evaluation in a real testbed.

Abstract — Industrial wireless mesh networks are deployed in harsh and noisy environments for process measurement and control applications. Compared with wireless community networks, they have more stringent requirements on communication reliability and real-time performance. Missing or delaying of the process data by the network may severely degrade the overall control performance. In this paper, we abstract the primary reliability requirements in typical wireless industrial process control applications and define three types of reliable routing graphs for different communication purposes. We present efficient algorithms to construct them and describe the recovery mechanisms. Data link layer communication schedules between devices are further generated based on these graphs to achieve end-to-end real-time performance. We have built a complete WirelessHART communication system and integrated our solutions into its Network Manager. We demonstrate through extensive experiment results that our algorithms can achieve highly reliable routing, improved communication latency and stable realtime communication in large-scale networks at the cost of modest overheads in device configuration. I.

Abstract—Control applications over wireless sensor networks (WSNs) require timely, reliable, and energy efficient communications. Cross-layer interaction is an essential design paradigm to exploit the complex interaction among the layers of the protocol stack and reach a maximum efficiency. Such a design approach is challenging because reliability and latency of delivered packets and energy are at odds, and resource constrained nodes support only simple algorithms. In this paper, the TREnD protocol is introduced for control applications over WSNs in industrial environments. It is a cross-layer protocol that embraces efficiently routing algorithm, MAC, data aggregation, duty cycling, and radio power control. The protocol parameters are adapted by an optimization problem, whose objective function is the network energy consumption, and the constraints are the reliability and latency of the packets. TREnD uses a simple algorithm that allows the network to meet the reliability and latency required by the control application while minimizing for energy consumption. TREnD is implemented on a test-bed and compared to some existing protocols. Experimental results show good performance in terms of reliability, latency, low duty cycle, and load balancing for both static and time-varying scenarios. I.

Abstract: Taking a network QoS designer’s point of view, this paper firstly reviews some of the recent advances on the NCS (Networked Control Systems) design then analyzes its requirements in terms of network QoS guarantees and its capacity to tolerate network performance variation. Current deterministic QoS design approach (including traffic schedulability analysis) may lead to network resource overprovisioning problem since worst-case scenario is often dictated to network QoS designers by the control application. We show that integrated control and network QoS co-design consists in a better solution to this problem. Taking into account the current available results, we see that more research efforts remain to do on control and network QoS co-design and on the development of on-line adaptive QoS mechanisms. Keywords: Networked control system, Network, Quality of Service, Co-design. 1.

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� Network planning and signal measurement with SINEMA E

The use of wireless technology is continuously gaining interest in industrial automation. With the standardization of the IEEE 802.15.4 protocol, low-power sensor network protocols have been introduced in this field. Recently, we investigated the real-time communication capabilities of this protocol. This study is now extended by incorporating the security mechanisms as provided by the protocol standard. In contrast to other papers, which studied the effectiveness of these security techniques, we are interested in whether the real-time capabilities are affected by encryption and message authentication and to which extend. Based on extensive simulations, we investigated the interdependency of protocol parameters and available security options. The results can be used for optimally selecting such parameters according to the quality of service requirements of the application scenario. 1.

Abstract—Sensor networks have been investigated in many scenarios and a good number of protocols have been developed. With the standardization of the IEEE 802.15.4 protocol, sensor networks became also an interesting topic in industrial automation. Here, the main focus is on real-time capabilities and reliability. We analyzed the IEEE 802.15.4 standard both in a simulation environment and analytically to figure out to which degree the standard fulfills these specific requirements. Our results can be used for planning and deploying IEEE 802.15.4 based sensor networks with specific performance demands. Furthermore, we clearly identified specific protocol limitations that prevent its applicability for delay bounded realtime applications. We therefore propose some protocol modifications that enable real-time operation based on standard IEEE 802.15.4 compliant sensor hardware. I.

Retransmission strategies for cyclic polling over wireless channels