Network nodes can have actual or logical communication with all devices such a communication defines a topology according to the application. A WSN aims to gather environmental data and the node devices placement may be known or unknown a priori. Wireless sensor networks (WSN) are composed of a finite set of sensor devices geographically distributed in a given indoor or outdoor environment (usually predefined).
Section 6 depicts the advantages and disadvantages of the reviewed works finally, Section 7 presents the concluding remarks with a series of opened questions which drive further research in the area. Section 5 shows the commonly used standards and protocols for WSN. Section 3 focuses on the centralized networks classification Section 4 describes the distributed networks classification. This paper is organized as follows: Section 2 presents the WSN generalities and the way the reviewed works are classified according to several features. The survey is dedicated to recent works and presents a discussion of their advantages and drawbacks. The analysis is focused on whether a single or multiple sinks are employed, nodes are static or mobile, the formation is event detection based or not, and network backbone is formed or not. In the former, nodes are autonomous and the communication is only between neighboring nodes while, for the latter, the network formation is controlled by a single device. In this paper, the reviewed research works are classified into distributed and centralized techniques. This survey presents most recent formation techniques and mechanisms for the WSNs. The design complexity of a WSN depends on the specific application requirements such as the number of nodes, the power consumption, the life span of the sensors, information to be sensed and its timing, geography of where the sensors are placed, the environment, and the context. This information is then forwarded to a leader node or to a base station known as sink. The sensor information is usually collected through the available gateways in a given topology. In fact, the topology is mostly defined based on the application environment and context. A key factor in this is the way the network is formed. In all cases for the design of any application, one of the main objectives is to keep the WSN alive and functional as long as possible. Some application fields include tracking, monitoring, surveillance, building automation, military applications, and agriculture, among others. IntroductionÄespite the open research areas in wireless sensor networks (WSNs), there are already a high number of current problems in which these networks can be applied. Finally, the paper overviews a series of open issues which drive further research in the area. We focus on recent works and present a discussion of their advantages and drawbacks. In this paper, the reviewed works are classified into distributed and centralized techniques.
Despite the open problems in WSNs, there are already a high number of applications available. Nowadays, wireless sensor networks (WSNs) emerge as an active research area in which challenging topics involve energy consumption, routing algorithms, selection of sensors location according to a given premise, robustness, efficiency, and so forth.