Industrial Wireless Applications Research Articles

Formal modeling of industrial wireless applications

Formal modeling of industrial wireless applications

Distributed Multiuser MIMO for LiFi in Industrial Wireless Applications

We present a concept for networked optical wireless communications, also denoted as LiFi, to meet the requirements of industrial wireless applications. These are primarily mobility support with moderate data rates per device, reliable real-time communication, and integrated positioning. We describe a distributed multiuser multiple-input multiple-output architecture, serving mobile devices via an optical wireless infrastructure. The system consists of a central unit, being connected to a number of distributed optical frontends covering a larger area. Our main contribution is a medium access control protocol based on space division multiple access. Evaluation results demonstrate the advantages of joint transmission from adjacent optical frontends and the dynamic switching between spatial diversity and multiplexing. The relevance of spatial multiplexing becomes obvious through channel measurements in an indoor scenario. Moreover, we highlight a low-power physical layer based on on-off-keying for battery-powered mobile devices. Our architecture can easily integrate positioning by simultaneously measuring the time-of-flight between multiple optical frontends and the mobile device. We highlight the use of plastic optical fiber as an analog fronthaul technology and discuss the integration with other networks. The main functions described in this paper will be supported by the upcoming IEEE Std 802.15.13.

Visible Light Communications for Industrial Applications—Challenges and Potentials

Visible Light Communication (VLC) is a short-range optical wireless communication technology that has been gaining attention due to its potential to offload heavy data traffic from the congested radio wireless spectrum. At the same time, wireless communications are becoming crucial to smart manufacturing within the scope of Industry 4.0. Industry 4.0 is a developing trend of high-speed data exchange in automation for manufacturing technologies and is referred to as the fourth industrial revolution. This trend requires fast, reliable, low-latency, and cost-effective data transmissions with fast synchronizations to ensure smooth operations for various processes. VLC is capable of providing reliable, low-latency, and secure connections that do not penetrate walls and is immune to electromagnetic interference. As such, this paper aims to show the potential of VLC for industrial wireless applications by examining the latest research work in VLC systems. This work also highlights and classifies challenges that might arise with the applicability of VLC and visible light positioning (VLP) systems in these settings. Given the previous work performed in these areas, and the major ongoing experimental projects looking into the use of VLC systems for industrial applications, the use of VLC and VLP systems for industrial applications shows promising potential.

Priority Based Centralized Scheduling for Time Slotted Channel Hopping Based Multihop IEEE 802.15.4 Networks

To meet the growing demands of low power and determinism in Industrial Wireless applications, IEEE defined IEEE 802.15.4e amendment that includes many channel access methods. Time Slotted Channel Hopping protocol is one of the most popular MAC protocols under IEEE 802.15.4e. However, scheduling of time slots for time slotted channel hopping, was not part of the protocol and so different scheduling algorithms were proposed by researchers. A new time slotted channel hopping scheduling mechanism that considers priorities to meet the time critical industrial applications is proposed in this work. Latency improvements of about 40 percentage are obtained here, for slot allocations to higher priority devices, when compared with the conventional queuing methods.

Impact of interference free frequency channels on optimum time slot allocation for priority-based TSCH MAC

Time slotted channel hopping (TSCH), the most promising MAC protocol under IEEE 802.15.4 is meeting the growing demands of low power and determinism in time critical industrial wireless applications. An efficient duty cycle is a necessary mandate for time critical applications which can be achieved by an appropriate reduction of active time slots in the slot frame and this saves node power. Even though many attempts were done in realising an optimum scheduling protocol, the impact of the number of channels on the optimum time slot allocation is not yet considered which signifies importance with the present scenario of many channels being induced by interference from neighbouring wireless networks. Optimum time slot is essential for making efficient duty cycle. Hence, a study on the impact of the number of channels on the optimum time slot allocation is necessitated and is accomplished in this paper. It is found that increasing the number of channels beyond a certain value does not have an impact on the optimum slot allocation and there is a direct relationship between the number of channels and the number of links per track and number of root node branches.

Portable Full Channel Sounder for Industrial Wireless Applications With Mobility by Using Sub-Nanosecond Wireless Time Synchronization

Wireless communications have attracted great interest from the industry due to its lower costs and the possibility of enabling new use cases. The new use cases are commonly related to mobile robotics, such as Unmanned Aerial Vehicles or terrestrial robots. The design of wireless systems for these use cases requires deep knowledge of the channel behavior and therefore the use of channel sounders that are able to measure the phase and gain of the channel is mandatory. However, channel sounders require very precise synchronization, which is typically implemented through a wired connection between the nodes. As a result, the mobility of the nodes is constrained to the length of the synchronization wire. In this paper, we present the design and implementation of a portable 802.11-based channel sounder that exploits a sub-nanosecond wireless time synchronization scheme. Thanks to the wireless synchronization, the channel sounder can operate as a channel sounder with wired synchronization, being able to measure synchronized channel impulse response samples. From these samples, relevant channel parameters can be extracted, including the Power Delay Profile, Doppler spectrum, and channel delay. The channel sounder presents several advantages compared to a conventional channel sounder with wire synchronization, such as smaller size and weight, simpler and more flexible operation, and it does not constraint the movement of the environment or nodes. The verification of the channel sounder through a wireless channel emulator and the measurement carried out in an industrial facility confirm its feasibility for industrial wireless and other applications.

Adopting IEEE 802.11 MAC for industrial delay-sensitive wireless control and monitoring applications: A survey

In recent years, wireless communication has been widely adopted in the field of industrial systems. Compared with traditional wired control and monitoring systems, wireless control and monitoring systems are cost-effective and easy to deploy. On the other hand, IEEE 802.11-based wireless technology is widely applied in many areas due to its popularity, flexibility and ease of management, which makes it a good candidate for various industrial wireless control and monitoring applications with different requirements. However, real-time wireless control and monitoring applications usually have varying degrees of timeliness requirements, and the basic IEEE 802.11 MAC mechanism cannot support such requirements due to its inherent drawbacks. Therefore, in this paper we intend to produce a comprehensive survey and classification of the recent deterministic enhancement approaches in IEEE 802.11 networks, which can be applied in wireless control and monitoring systems with different real-time requirements. We explain each mechanism briefly, and give an extensive comparison of the features (especially the timeliness level) of all described MAC mechanisms. Finally, we conclude this paper by identifying some open research issues for future consideration.

Dynamic Spectrum Allocation Algorithms for Industrial Cognitive Radio Networks

Irregular spectrum usage and spectrum scarcity in emergency situations is a common problem in industrial wireless networks. To enhance the dynamic spectrum usage, cognitive radio network (CRN) is introduced in various automotive industrial wireless applications named as industrial cognitive radio network (ICRN). However, establishing the control channel by using channel hopping mechanism in ICRN is a challenging problem. In order to achieve reliable performance in ICRN, efficient channel hopping protocols need to be designed. In this paper, two channel hopping protocols are designed for the ICRN with or without the global clock synchronization to maximize the degree of rendezvous within the shortest time, minimize the inter rendezvous intervals and to reduce the maximum time to rendezvous by two secondary users. Performance evaluation of our protocols outperform in terms of throughput, percentage of rendezvous and average time to rendezvous over existing CRN protocols.

A Method for Dynamically Selecting the Best Frequency Hopping Technique in Industrial Wireless Sensor Network Applications

Industrial wireless applications often share the communication channel with other wireless technologies and communication protocols. This coexistence produces interferences and transmission errors which require appropriate mechanisms to manage retransmissions. Nevertheless, these mechanisms increase the network latency and overhead due to the retransmissions. Thus, the loss of data packets and the measures to handle them produce an undesirable drop in the QoS and hinder the overall robustness and energy efficiency of the network. Interference avoidance mechanisms, such as frequency hopping techniques, reduce the need for retransmissions due to interferences but they are often tailored to specific scenarios and are not easily adapted to other use cases. On the other hand, the total absence of interference avoidance mechanisms introduces a security risk because the communication channel may be intentionally attacked and interfered with to hinder or totally block it. In this paper we propose a method for supporting the design of communication solutions under dynamic channel interference conditions and we implement dynamic management policies for frequency hopping technique and channel selection at runtime. The method considers several standard frequency hopping techniques and quality metrics, and the quality and status of the available frequency channels to propose the best combined solution to minimize the side effects of interferences. A simulation tool has been developed and used in this work to validate the method.

Optical Wireless MIMO Experiments in an Industrial Environment

This paper reports on a field trial in a robotic manufacturing cell. Channel measurements and transmission experiments were conducted, assisting the development of a light-emitting diode-based optical wireless communication (OWC) system tailored for the needs of industrial wireless applications. These are moderate data rates, reliability, and low latency. Since dedicated radio spectrum is hardly available, the usage of light is an interesting alternative. Due to its spatial confinement, OWC links provide enhanced security and are difficult to jam from outside a building—a particularly interesting property for industrial applications. We performed broadband distributed $8\times 6$ multiple-input multiple-output (MIMO) channel measurements in a manufacturing cell. Results confirm that the signal-to-noise ratio is sufficient if a line-of-sight (LOS) is available and bandwidth is limited to a few megahertz. However, small movements and rotations may lead to sudden fades of 10–20 dB, when an LOS is blocked. To improve reliability, antenna diversity concepts are applied. Results show that for reliable communication, MIMO diversity schemes are indispensable as it increases the probability of a free LOS significantly. Based on these insights, we suggest an OWC design tailored to industrial wireless applications.

Det-LB: A Load Balancing Approach in 802.11 Wireless Networks for Industrial Soft Real-Time Applications

Wireless control systems for industrial automation have been gaining popularity in recent years owing to the low cost of their components and their ease of deployment. Wireless local area network (WLAN) is a good candidate for industrial wireless applications, especially for soft real-time control systems. However, unbalanced traffic loads in areas that are covered by several access points (APs) could cause significant performance degradation, and the problem would be more serious in industrial contexts that have high requirements for timeliness and reliability. In this paper, we propose a deterministic load balancing algorithm (Det-LB) for WLAN, which is based on game theory, mainly intended for soft real-time control systems. The procedure of the proposed algorithm is described and analysed in detail. To validate the goodness of the proposed approach, we compare Det-LB with three other load balancing strategies (RLF, MMF, and DLBA) in a simulation. The results show that Det-LB can achieve better load balancing performance and improve network performance significantly. For instance, in a common scenario in which five APs are deployed, the RLF scheme has terrible performance and cannot be applied to industrial applications at all; Det-LB has 35% and 26% performance improvements over MMF in 500- and 250-byte payload size conditions, respectively, and has a 5% deadline miss performance boost and better packet loss performance compared with DLBA when the APs tend to be overloaded.

A cloud-assisted handover optimization strategy for mobile nodes in industrial wireless networks

Connectivity restoration is an important aspect of the survivability strategies of wireless networks. In industrial wireless networks, especially with mobile nodes, connectivity restoration and maintenance directly determines the overall performance of the network. Handover strategies are research hotspots in this field. However, current common handover strategies have many disadvantages, such as frequent handover requests, latency and the lack of consideration of the network performance. These drawbacks are harmful to IoT (Internet of Things) networks. Although studies on wireless networks have proposed many solutions, the proposed schemes are not intended to meet the demands of industrial wireless applications, where real-time and stable performance are required. Therefore, this paper proposes a novel fixed-path mobile node handover strategy (CAFP), which is assisted by cloud services and an ants-colony algorithm. Our approach uses optimization for industrial wireless node handover sequences, execution and handover schemes in different cases. Compared to other traditional handover strategies, our simulation results show that the CAFP has advantages in terms of handover times, latency and the network's average payload. Additionally, this algorithm can decrease the processing capacity of mobile wireless nodes.

Comparison of Fault Diagnosis Approaches in Industrial Wireless Networks: A Review

Wireless sensor networks have received increasing research attention and they can be found in every field of life. The industrial wireless sensor network is one of the boosting and emerging technologies for machine fault diagnosis and monitoring. This study provides a review on vibration fault diagnosis approaches in industrial wireless applications and discusses the causes of machine faults and challenges. Several advanced vibration approaches have been used to quantify machine operating conditions. These approaches provide a fault diagnosis mechanism and expert maintenance solutions through analysis of vibration. The review also shows a broad scope of research for developing a robust fault diagnosis approaches in the field of industrial wireless sensor networks.

Adaptive power control for mutual interference avoidance in industrial internet-of-things

With the vigorous development of the Internet of Things and 5G technology, such as machine-to-machine and device-todevice, all kinds of data transmission including environmental monitoring and equipment control strengthens the key role of wireless sensor networks in the large-scale wireless communication system. However, especially in the complex industrial wireless applications, the low utilization efficiency of the limited wireless radio resource enhances the coexistence problem between heterogeneous networks. In this paper, from the severe mutual interference point of view, a mathematical model regarding cumulative interferences in the industrial wireless sensor networks is described. Then, from the perspective of mutual interference avoidance, an adaptive power control scheme is proposed in order to handle the normal communication needs on both the primary link and the secondary link. At last, nonlinear programming is taken to solve the corresponding optimization problem. Some typical analyses are given to verify the effectiveness of the proposed scheme on optimizing the tradeoff between the system throughput and energy consumption. Especially, the energy-efficiency of the novel scheme for Industrial Internet of Things is also analysed. Results show that the proposed power control is efficient. The throughput could be enhanced and the energy consumption could be reduced with the guarantee of mutual interference avoidance.

Trends in Industrial Wireless Communication and Applications

The importance of automation in the industries has increased dramatically in recent years. Industrial communication is one of the keys to increasing efficiency, reducing total cost of ownership, and improving productivity. The huge potential, especially of wireless communication, opens up new perspectives here – from partial modernization of plants, right up to optimizing complex logistics or production processes.

Random time source protocol in wireless sensor networks and synchronization in industrial environments

ABSTRACTReliability is a crucial aspect of time synchronization for industrial wireless applications in wireless sensor networks. Existing time synchronization algorithms often provide good synchronization in laboratory environments; however, outdoor environments with associated radio interference influence the performance of time synchronization. In this paper, we propose a random time source protocol for industrial wireless applications in wireless sensor network synchronization. Each synchronized node randomly selects its time source for each period in order to prevent reliance on a fixed time source because this may lead to resynchronization once the source fails. We have implemented the algorithm on the SIA2420 platform using TinyOS, and the results show the reliability of our protocol. Copyright © 2011 John Wiley & Sons, Ltd.

Radio-Frequency Electromagnetic Characterization in Factory Infrastructures

In recent years, industrial wireless applications have emerged rapidly. The use of short-range radio communication systems in factories increases the flexibility in industrial processes by reducing the use of cables. However, the technological challenges involved in wireless communication in industrial environments are not trivial; they result in disadvantages with respect to reliability and security because of electromagnetic interference. To gain an understanding of the performance limits of these wireless applications, knowing the characteristics of these environments is essential. In this approach, amplitude probability distribution and rms delay spread measurements have been used to perform electromagnetic site surveys in three factory automation infrastructures.

Exploiting Backbone Routing Redundancy in Industrial Wireless Systems

Industrial wireless applications must interoperate with backbone infrastructure for operation and monitoring by control systems. Most of these systems are designed with multiple backbone routers (BbRs) to enhance reliability. Multiple BbRs have a significant impact on wireless systems as the redundancy of multiple BbRs offers a number of benefits, such as spatial diversity and load balancing. Here, we investigate the advantages of spatial diversity provided by multiple BbRs. BbR-related communication patterns and mesh routing mechanisms optimizing the effects of spatial diversity are shown, and we also clarify the quantitative effectiveness of the redundancy of multiple BbRs with experimental proofs.