Recent breakthroughs in wireless technologies have greatly spurred the emergence of industrial wireless sensor networks (IWSNs). To facilitate the adaptation of IWSNs to industrial applications, concerns about networks' full coverage and connectivity must be addressed to fulfill reliability and real-time requirements. Although connected target coverage (CTC) algorithms in general sensor networks have been extensively studied, little attention has been paid to reveal both the applicability and limitations of different coverage strategies from an industrial viewpoint. In this paper, we analyze characteristics of four recent energy-efficient coverage strategies by carefully choosing four representative connected coverage algorithms: 1) communication weighted greedy cover; 2) optimized connected coverage heuristic; 3) overlapped target and connected coverage; and 4) adjustable range set covers. Through a detailed comparison in terms of network lifetime, coverage time, average energy consumption, ratio of dead nodes, etc., characteristics of basic design ideas used to optimize coverage and network connectivity of IWSNs are embodied. Various network parameters are simulated in a noisy environment to obtain the optimal network coverage. The most appropriate industrial field for each algorithm is also described based on coverage properties. Our study aims to provide IWSNs designers with useful insights to choose an appropriate coverage strategy and achieve expected performance indicators in different industrial applications.
RECENTLY, industrial wireless sensor networks (IWSNs), which consist of many sensor nodes, have evolved as a powerful tool for an industrial automation system (IAS). Different from traditional IAS realized through wired communications, sensors of an IWSN can be installed on industrial equipment and monitor critical parameters to ensure normal operations . Also, each sensor has wireless communication capability to provide data delivery service. Due to the absence of cables, the use of inexpensive and tiny sensor nodes contributes to the flexibility and energy efficiency of IAS .
Industrial applications require a high measure of reliability, so any sensing of essential equipment or processes must be prioritized and free of interruption. As a leading application of IAS, supervisory control and data acquisition require a high level of reliability in terms of data integrity and timely reporting . Therefore, an IWSN should guarantee uninterrupted target coverage and connectivity among all sensor nodes and a sink node . This is often referred to as the connected target coverage (CTC) problem, where each discrete target in the network must be within the sensing range of at least one sensor node, and where at least one routing path must be found to connect any source node to the sink node . However, in industrial environments, the coverage area of a sensor node, as well as the link connectivity, may suffer from noise, cochannel interferences, and multipath propagation. In addition, energy is arguably the main constraint of wireless sensor nodes –. Therefore, the energy-efficient CTC problem has become an important issue that urgently needs to be addressed.
V. CONCLUSION AND FUTURE WORK
In this paper, we have analyzed different energy-efficient coverage strategies designed for industrial environments. Through comparing four representative CTC algorithms, properties of each strategy are embodied under different conditions. Since coverage performance is difficult to obtain uniformly, the selection of coverage algorithms should consider which factor (convergence speed, maximum lifetime, etc.) is the focus in a specific practical application. Attention should be paid to improve the performance determined by the main focus. Efforts can then be made to achieve the relative performance of other parameters. Based on our analysis, useful insights are given for IWSN designers to choose an appropriate coverage strategy.
In the future, additional work is required to bridge the gap between ideal simulations and real-world coverage systems. For instance, mobility should be introduced to an IWSN. Static sensor nodes may be disturbed by the vibration of industrial equipment, which could cause a change in network topology. Therefore, simulation results achieved by energy-efficient CTC algorithms should be extended to include possible influences of real industrial applications.