Abstract
Introduction
Wireless sensor networks (WSNs) have been a growing interest in the scientific and industrial community thanks to innovations that have occurred during the last decades in the domains of microelectronics, MEMS (micro-electro-mechanical system) design, energy harvesting, and wireless technologies. 1 Wireless communication systems and especially distributed sensor networks have received growing attention in recent years from various perspectives. The thriving numbers behind wireless communication systems adoption and contribution have contributed to a new kind of entrepreneurship and innovation. The inclusion of WSNs is envisioned to be useful for advancing in many research and academic fields, as well as many industries by introducing new dimensions and artifact improvements.
This special collection is composed of eight contributions and oriented toward analyzing many and different aspects of mobile and WSNs. Particularly, different domains of human activity such as e-health, cyber-physical systems, traffic systems, games, GPS, urban computing applications, smart cities infrastructures, cultural heritage management, among others that were considered as novel contributions for this collection. Thus, these technical contributions describe applications and timely services that involve in the activities of daily life.
New wireless technologies become more and more advanced so does their expanse of applications. Other new and innovative wireless communication networks such as WSNs have emerged as highly flexible and dynamic facets that are being deployed in almost every type of environment whether it is rural, suburban, or urban in nature. 2 Thus, WSNs play an important role to face many challenges related to smart city applications, miniaturization of electronic devices, high energy consumption, and better algorithm to improve the performance for sharing and transferring data. However, WSNs have few limitations such as low battery power, limited computation capabilities and small memory of the sensor nodes that are being tacked by different proposals with different initiatives, perspectives, and research models.
This editorial paper is organized as follows: section “General discussion” presents a brief discussion regarding some trends and hot topic related to WSNs. Section “Overview of the selected papers” presents a summary of the research papers that compose this collection. Section “Open issues for services and applications of WSNs” offers a description of the open issues for services and applications of WSNs. Conclusions are presented in section “Conclusion.”
General discussion
Many works have been developed in the last years, especially with the increasing interest in smart applications based on wireless communications systems. Particularly, distributed sensor networks is a hot topic of discussion among the research community. In this section, we briefly surveyed variants and potential advancements in this development. WSNs require a cost-effective and reliable communication network that relays the monitored information in a timely way so that effective monitoring of the power system can take place. Energy efficiency remains a key issue in WSNs, duty-cycled mechanisms acquired much interest due to their ability to reduce energy consumption. So, a context-aware paradigm allows sensors to adapt their functional behavior, according to the context in order to enhance the network performance. 3 Lim et al. 4 presents an effective monitoring system for electrical distribution based on WSN to control the power system’s voltage, current, and frequency variations. In addition, Magno et al. 5 proposed a low-cost wireless sensor system to optimize the illumination in green buildings with a smart led lighting system to automatically adjust the intensity to save energy.
New approaches in innovative applications to sense the state of the environment especially in agricultural systems based on WSNs are facing new strategies and breaking barriers to improve the quality of the products. Karimi et al. 6 developed a WSN system for remote real-time monitoring and collection of micro-meteorological parameter data in three distant vineyards. At the same time, Ojha et al. 7 presented a survey related directly to agricultural applications in the context of the WSNs, describing a review of possible challenges, cases studies, and future directions. In the context of smart cities applications, there is an increasing and motivating development of systems based on WSNs. For instance, surveillance is a highly appreciated service and most governments are already promoting using different types of devices to provide high levels of security. An algorithm to position multiple mobile sinks in wireless visual sensor networks deployed along roads and streets was proposed in Peixoto and Costa. 8 In Moridi et al., 9 a monitoring and communication system based on WSN for underground mine environments using the ZigBee network was developed.
There has been a host of research works on WSNs for medical applications. Negra et al. 10 proposed a wireless body area network to a continuous health monitoring of a patient without constraint on his normal daily life activities. Due to the lack of data management, Lounis et al. 11 presented an innovative architecture for collecting and accessing a large amount of data generated by medical sensor networks. Hadjidj et al. 12 proposed a WSN focused on rehabilitation supervision. Recently, there are new and timely sets of WSN applications, which are taken into consideration as hot topics and subjects by the research and academic community, such as environmental monitoring, focused on forest fire scenarios, 13 habitat monitoring, 14 and landslides detection, 15 smart grid, 16 industrial systems, 17 and urban environments such as. 18
Overview of the selected papers
In Algabri et al., a visual servoing system to detect and track a moving object by using an unmanned aerial vehicle is proposed. The proposed prototype was evaluated on a real flight, by using an “AR.Drone 2.0 Quadcopter.” According to the outcomes, the performance of the proposed method is fully suitable for object-following tasks in surveillance applications. This is a timely contribution because during the last few decades, the use of unmanned aerial vehicles has grown in the military and has seen new civil applications decreasing the cost and hovering capabilities.
Chen et al. proposed a novel efficient group-based discovery method based on relative distance, which makes a delicate trade-off between discovery delay and energy consumption. The effectiveness of the design was demonstrated with extensive simulations in which the results indicated that the efficient group-based discovery statistically achieves a good trade-off between energy cost and discovery latency. Thus, the efficient group-based discovery also shows one order of magnitude reduction in discovery delay with a maximum of 6.5% increasing in energy consumption compared with typical discovery methods. This contribution considers one of the most challenging problems in WSNs that is the combination of constrained power, low duty cycle, and high mobility.
Lee and Yang proposed a smart power management framework system to comprise the following parts: (1) a smart plug, (2) a smart gateway, and (3) a management platform. The first part consists of controlling the switching power supply, and different sensors can be mounted for different application environments. The second part acts as a mediation module for communication and implements the concept of fog computing. The third part was designed to data visualization and a remote control for a user interface medium for scheduling. In recent years, this issue is very important, so the present contribution is addressed to the growth in power demand and energy management.
Peizhe et al. proposed a prioritization mechanism that considers the heterogeneous characteristics of smart grid traffic. Moreover, an innovative channel allocation and traffic scheduling scheme named the preemptive tidal flow queuing model was presented. This scheme achieves differentiated services for diverse communication data when the wireless multimedia sensor network accesses to the core network and ensures the performance of high-priority data at the performance expense for low-priority data. This contribution is very timely because nowadays the smart grid incorporates a two-way communication system between customers and the utility for advanced monitoring and intelligent control of supply and demand.
Sher et al. proposed three energy-efficient routing protocols for underwater WSNs. The first one is the sparsity-aware energy-efficient clustering, the second is the circular sparsity-aware energy-efficient clustering, and third is the circular depth–based sparsity-aware energy-efficient clustering. They are used to minimize the energy consumption of sparse regions, whereas sparsity search algorithm finds sparse regions and the density search algorithm locates dense regions inside the network. Simulation results showed that these schemes perform better than their counter-part schemes, particularly in terms of energy efficiency.
Kim proposed the development of novel routing algorithms to tackle acoustic transmission problems in underwater sensor networks. The scheme is based on reinforcement learning and game theory and is designed as a routing game model to provide an effective packet-forwarding mechanism. It is important to emphasize that underwater sensor networks have recently emerged as a promising networking technique for various underwater applications. However, acoustic routing of underwater sensor networks in the aquatic environment presents challenges in terms of dynamic structure, high rates of energy consumption, long propagation delay, and narrow bandwidth.
Zhao et al. proposed an algorithm to construct an energy-efficient barrier to detect intruders moving along restricted crossing paths in the target area. Simulations showed that the energy-efficient barrier repair algorithm improved the barrier coverage and prolonged the network life-time by minimizing the maximum sensor moving distance. In comparison with the state of the art, the energy-efficient barrier algorithm increased by 18% of network lifetime on average. This work is addressed to the energy-efficient coverage for directional sensor networks with mobile devices.
Aseeri et al. presented a detection approach of attacks by unknown trespassers on border surveillance sensor networks. It uses the Dempster–Shafer theory and the time difference of arrival method to identify and locate an attacked node. In this context, the effective border security can be achieved introducing autonomous and heterogeneous sensor devices, which are embedded with cameras and other sensors that provide a continuous monitoring.
Open issues for services and applications of WSNs
There are many potential applications of WSNs as well as required services that improve special domains and particular features. In addition, there exist factors for improvement in WSNs, which require further attention in the future:
Cost. A low-cost solution is always desirable for increasing the scope and spreading out the applications.
Autonomous functionality. The future solutions should include the provision for autonomous operations in order to survive for a long time.
Smart capacity. An implicit intelligence will enable future solutions to react dynamically to multiple challenges, from keeping energy to real-time response.
Portability. Recent advances in the embedded systems would help to solve this fact.
Low maintenance. Essential to design a system that requires minimum maintenance effort in order to minimize certainly the average cost of the production.
Energy-efficiency. To ensure extended life time with the autonomous operation, it is necessary to implement intelligent algorithms for energy efficiency.
Robust architecture. A robust and fault-tolerant architecture for the emerging applications is required to ensure sustainable tasks.
Readable operation. Users of these applications are non-technical persons. Thus, these applications need to be simple and easy to use.
Interoperability. The interaction between different components and communication technologies would enhance the overall functionality of the systems.
Figure 1 shows the open issues for services and applications of WSNs and the future applications in the domain of urban environments. Thus, technical concepts that are not yet totally incorporated in the WSNs such as Fog Computing, Cloud Computing, Big Data Analytics, and the Internet of Things will be envisioned:
Sensor-fog computing consists of applying an architecture that uses one or more collaborative end-user clients or near-user edge devices to carry out a substantial amount of storage, communication, control, configuration, measurement, and management. It can be perceived both in large cloud systems and big data structures, making reference to the growing difficulties in accessing information objectively.
Sensor-cloud computing refers to integrate many data sources in a particular space. The goal is to improve data management and access control.
Big Data Analytics would be applied to find meaningful insight from a large volume of data with various data types. It could be able to apply many intelligent approaches to datasets from various sensor networks.
Internet of Things focused on extending the development of ubiquitous systems with heterogeneous devices that can be integrated with interoperable communication technologies.
Open issues for services and applications of WSNs.
Conclusion
The inclusion of WSNs is envisioned to be useful for advancing in many application domains and innovative services. This survey presents a brief comprehensive review of the state of the art focused on innovative applications of WSNs. We introduced important challenges that have to be faced such as services and applications of WSNs. This special collection, in fact, is oriented toward defining a starting point of an ongoing debate for the required convergence of innovative services and applications with WSNs. We will meet again in the future with an updated discussion on the subject matter of this special collection.