Opportunities and Challenges in Wireless Sensor Networks
Due to advances in wireless communications and electronics over the last few years, the development of networks of low-cost, low-power, multifunctional sensors has received increasing attention. These sensors
are small in size and able to sense, process data, and communicate with each other, typically over an RF (radio frequency) channel. A sensor network is designed to detect events or phenomena, collect and
process data, and transmit sensed information to interested users. Basic features of sensor networks are:
• Self-organizing capabilities
• Short-range broadcast communication and multihop routing
• Dense deployment and cooperative effort of sensor nodes
• Frequently changing topology due to fading and node failures
• Limitations in energy, transmit power, memory, and computing power
These characteristics, particularly the last three, make sensor networks different from other wireless ad hoc or mesh networks.
Clearly, the idea of mesh networking is not new; it has been suggested for some time for wireless Internet access or voice communication. Similarly, small computers and sensors are not innovative
per se. However, combining small sensors, low-power computers, and radios makes for a new technological platform that has numerous important uses and applications, as will be discussed in the next section.
Growing Research and Commercial Interest
Research and commercial interest in the area of wireless sensor networks are currently growing exponentially, which is manifested in many ways:
• The number of Web pages (Google: 26,000 hits for sensor networks; 8000 for wireless sensor networks in August 2003)
• The increasing number of
• Dedicated annual workshops, such as IPSN (information processing in sensor networks); SenSys; EWSN (European workshop on wireless sensor networks); SNPA (sensor network protocols and applications); and WSNA (wireless sensor networks and applications)
• Conference sessions on sensor networks in the communications and mobile computing communities (ISIT, ICC, Globecom, INFOCOM, VTC, MobiCom, MobiHoc)
• Research projects funded by NSF (apart from ongoing programs, a new specific effort now focuses on sensors and sensor networks) and DARPA through its SensIT (sensor information Technology), NEST (networked embedded software technology), MSET (multisensor exploitation), UGS (unattended ground sensors), NETEX (networking in extreme environments),
ISP (integrated sensing and processing), and communicator programs
Special issues and sections in renowned journals are common, e.g., in the
IEEE Proceedings
[1] and signal processing, communications, and networking magazines. Commercial interest is reflected in investments by established companies as well as start-ups that offer general and specific hardware and software
Solutions.
Compared to the use of a few expensive (but highly accurate) sensors, the strategy of deploying a large Number of inexpensive sensors has significant advantages, at smaller or comparable total system cost:
Much higher spatial resolution; higher robustness against failures through distributed operation; uniform Coverage; small obtrusiveness; ease of deployment; reduced energy consumption; and, consequently,
Increased system lifetime. The main point is to position sensors close to the source of a potential problem Phenomenon, where the acquired data are likely to have the greatest benefit or impact.
Pure sensing in a fine-grained manner may revolutionize the way in which complex physical systems are understood. The addition of actuators, however, opens a completely new dimension by permitting
management and manipulation of the environment at a scale that offers enormous opportunities for Almost every scientific discipline. Indeed, Business 2.0 (http://www.business2.com/) lists sensor robots
as one of “six technologies that will change the world,” and
Technology Review
at MIT and Global future Identify WSNs as one of the “10 emerging technologies that will change the world” (http://www.globalfuture. com/mit-trends2003.htm). The combination of sensor network technology with MEMS and nanotechnology
Will greatly reduce the size of the nodes and enhance the capabilities of the network. The remainder of this chapter lists and briefly describes a number of applications for wireless sensor
Networks, grouped into different categories. However, because the number of areas of application is Growing rapidly, every attempt at compiling an exhaustive list is bound to fail.