Problem Solving for Wireless Sensor Networks

Many wireless monitoring and control applications are available for the industrial and home markets. Some hardware platforms are specialized for optimizing only one feature (e.g., high data rate, long transfer range, or lowpower mode). However, the most restrictive parameters for WSNs are both power consumption and distance. This chapter briefly describes different radiofrequency technologies, although many of them are not appropriate or are not yet fully developed for WSNs. Therefore, only appropriate technologies are discussed in depth, and a brief overview of several integrated circuits from different manufacturers is included. 2.1 Bluetooth Technology (IEEE 802.15.1) The Bluetooth wireless communications technology provides a personal area network (PAN) for exchanging data between Bluetooth-capable devices within a certain proximity. Bluetooth technology has a low-powermode and high integrated devices and operates in the unlicensed 2.4-GHz band, but it is limited to short-distance communications. Therefore, this technology is not the most appropriate for developing a WSN. For this reason, Bluetooth is just mentioned and described as an existing technology (Bluetooth SIG). 2.2 Wi-Fi Technology (IEEE 802.11.a/b/h/g) TheWi-Fi technology allows different devices like laptops, personal computers (PCs), cell phones, and personal digital assistants (PDAs) to communicate between one another or to connect to the Internet without needing a cable connection. The Institute of Electrical and Electronics Engineers (IEEE) defined the Wi-Fi network protocols IEEE 802.11a, 802.11b, and 802.11 g operating in the unlicensed radio bands of 2.4 and 5GHz. Therefore, any kind of standard A.-B. Garcı́a-Hernando et al., Problem Solving for Wireless Sensor Networks, DOI: 10.1007/978-1-84800-203-6_2, Springer-Verlag London Limited 2008 3 Wi-Fi–certified device is able to operate all over the world with data rates of 11Mbps for IEEE 802.11b or 54Mbps for IEEE 802.11a. Of course, the greater the distance to the access point, the lower the performance. Wi-Fi technology lacks a low-power mode and is also not very highly integrated. Thus, a low-powered and highly integrated WSN cannot use this technology, which is why we give just an overview of this existing technology (Wi-Fi Home Page). 2.3 UWB Technology (IEEE 802.15.3) The Ultra Wideband (UWB) technology allows information to be transmitted at a large bandwidth in precise pulses that are typically 1 to 2 nanoseconds in length and occupy at least 25% of the center frequency, much more than other systems. The use of this technology is limited to the range of frequencies from 3.1 to 10.6GHz. Another remarkable characteristic of UWB is its better behavior regarding interferences than other technologies due to the use of spread-spectrum modulation techniques. Despite having a greater ratio of transmission velocity over power consumption than other similar technologies like Wi-Fi, UWB is limited to short-range applications. It is therefore appropriate for portable devices, to get long battery life, but not forWSNs requiring larger distances. This is the main reason for not going into further details on UWB technology (Intel UWB). 2.4 Wavenis Technology (EN300–220 and FCC15.247—Coronis Systems) The Wavenis technology, developed by Coronis Systems, provides long-range data connections and services for autonomous devices with extremely limited battery resources and is intended for ultra low-power (ULP) and long-range wireless communications. Wavenis extends the industry standard Bluetooth protocol to provide robust wireless solutions for building ad hoc and fixed networks using autonomous, battery-powered devices. 2.4.1 Wavenis’ Main Characteristics Wavenis is a complete software and hardware solution for wireless communications in low-power devices. The core offer consists of an RF transceiver and a protocol stack, both specifically adapted to provide the optimal combination of secure and reliable connections, long range, and minimal power consumption. Highly resistant to interference and obstacles, Wavenis offers a means for including a wide variety of battery-powered products in PAN, LAN, andWAN 4 2 Radio-Frequency Technologies for WSNs