Abstract
Wireless sensor networks (WSNs) are becoming increasingly popular, which is changing the way people perceive the world largely, as well as the living styles of human beings. To give readers a basic, wide view of WSNs and make them understood more deeply, this chapter introduces their various aspects briefly, including basic concepts, architectures and protocols, etc. Moreover, it discusses their recent developments, challenges and new trends, based on analysis of many meaningful references. Some classic applications are also shown to approve the popularity of Wireless Sensor Networks.
TopWhat Are Wireless Sensor Networks?
The concept of WSNs was proposed by the U.S. military as early as 1970’s. From then on, many research projects, applications and theories about WSNs have come forth. Recalling the history of the development of sensor networks, we can roughly divide it into several stages as follows (Chong, & Kumar, 2003).
In the 1970s, the emergence of some prototypes of sensor networks with traditional point-to-point transmission could be referred to as the first generation of sensor networks. In 1979, the Defense Advanced Research Projects Agency (DARPA) of USA launched the Distributed Sensor Networks Program (DSN). It was one of the representatives.
From 1980s to 1990s, processing and communications capabilities of sensor nodes were improved obviously, which made these nodes can work together by networking with each other. However, during this period, research work still mainly focused on the military field such as, SensIT plan (Sensor Information Technology), WINS (Wireless integrated network sensors) launched by DARPA. It is regarded as the second generation sensor networks.
With the continuous development of related technologies such as microelectronics, wireless communications, network transmission, from the end of the 20th century, WSNs have attracted wide attentions from academia, military and industry, which really set off a high wave of the development of WSNs technologies. Many projects have been launched and many applications have been deployed in various fields, which include military, environment monitoring, health care, intelligent home, urban transportation, space exploration, public safety monitoring, etc. Some representative projects are C4KISR Plan of DARPA, ALERT of U.S National Weather Service, SSIM program of Wayne State University, etc.
Although WSNs have affected various aspects of our work and life, different people still have different understandings about WSNs.
Key Terms in this Chapter
Time Synchronization: It aims at synchronizing the time of all sensor nodes in a wireless sensor network, or making different events take place in some specified order.
Data-centric: Refers to approaches, methods that focus on the data instead of processing nodes.
Wireless Sensor Network: A network consisting of some wireless sensor nodes that are distributed spatially for cooperatively monitoring physical or environmental conditions.
Middleware: A flexible software component that exists between the above application layer and the below network, link layers, which can simplify the development of software and improve its reusability, reliability and scalability.
Localization: It aims at locating the places where various events take places exactly.
Resource-Aware: Refers to methods that pay main attention to resources such as power, bandwidth, memory, etc.
Generality: The generality can be regarded as the integration of the compatibility, interchangeability, and simplicity, etc., which make the system more extendable and standardized.