The rapid progress of wireless communication and embedded micro-sensing microelectromechanical systems (MEMS) technologies has made wireless sensor networks (WSN) possible. A WSN consists of many inexpensive wireless sensors, which are capable of collecting, storing, processing environmental information, and communicating with neighboring nodes. In the past, sensors are connected by wirelines. With the development of ad hoc networking technologies, tiny sensors can communicate through wireless links in a more convenient manner (Pottie and Kaiser, 2000; Sohrabi et al. 2000). A lot of applications of WSN have been proposed. For example, wildlife-monitoring applications are discussed in (FireBug 2004; GreatDuckIsland 2004) and mobile object tracking issues are addressed in (Lin and Tseng, 2004; Tseng et al., 2003). How to ensure network coverage/ connectivity is discussed in (Huang et al., 2005; Yan et al., 2003). Guiding applications based on wireless sensor networks are presented in (Li et al, 2003; Tseng et al., 2006). Applications of mobile sensors are presented in (Tseng et al., 2005). Many WSN platforms have been developed, such as MICA2, MICAz, TelosB MOTE (Xbow, 2005), and Dust Network (DustNetworks, 2005). To allow different systems to work together, standards are needed. ZigBee/IEEE 802.15.4 protocols are developed for this purpose. ZigBee/IEEE 802.15.4 is a global hardware and software standard designed for WSN requiring high reliability, low cost, low power, scalability, and low data rate. Table 16.1 compares ZigBee/IEEE 802.15.4 against several other wireless technologies. The ZigBee alliance (Zig- Bee, 2004) is to work on the interoperability issues of ZigBee/IEEE 802.15.4 protocol stacks. The IEEE 802.15 WPAN Task Group 4 (IEEE Std 802.15.4, 2003) specifies physical and data link layer protocols for ZigBee/IEEE 802.15.4. The relationship of ZigBee and IEEE 802.15.4 is shown in Fig. 16.1. In the current development, IEEE 802.15 WPAN working group creates two task groups 15.4a and 15.4b. The former is to specify an alternate physical layer, the ultra wide band (UWB) technologies. The latter is to enhance the IEEE 802.15.4 MAC protocol so that it can tightly couple with the network layer functionalities specified by Zig- Bee. ZigBee alliance published the version 1.0 standard in Dec. 2004. Companies such as Chipcon (Chipcon, 2005), Ember (Ember 2005), and Freescale (Freescale 2005) provide system-on-chip solutions of ZigBee/IEEE 802.15.4. For home networking, ZigBee/IEEE 802.15.4 can be used for light control, heating ventilation air conditioning (HVAC), security monitoring, and emergency event detection. For health case, ZigBee/IEEE 802.15.4 can integrate with sphygmomanometers or electronic thermometers to monitor patients statuses. For industrial control, ZigBee/IEEE 802.15.4 devices can be used to improve the current manufacturing control systems, detect unstable situations, control production pipelines, and so on. In the rest of this chapter, we will review IEEE 802.15.4 and ZigBee network layer protocols in Section 2 and Section 3, respectively. Section 4 discusses the beacon scheduling issue in a ZigBee tree network. Section 5 introduces the broadcast procedures in ZigBee. Some application examples of WSN are introduced in Section 6. Finally, we conclude this chapter in Section 7.
|Title of host publication||Sensor Networks and Configuration|
|Subtitle of host publication||Fundamentals, Standards, Platforms, and Applications|
|Publisher||Springer Berlin Heidelberg|
|Number of pages||20|
|ISBN (Print)||3540373640, 9783540373643|
|State||Published - 1 Dec 2007|