6 – Technologies for WSANs

No standard enabling technologies devoted to WSANs exists. ZigBee wireless technology is a short-range communication system. ZigBee wireless technology has two options, PHY layer (IEEE 802.15.4 and UWB IEEE 802.15.4a), and Bluetooth (IEEE 802.15.1). The key features of ZigBee wireless technology are low complexity, low cost, low power consumption, and low data rate transmissions, supported by cheap fixed or moving devices. The main field of application of this technology is the implementation of WSNs. The IEEE 802.15.4 Working Group 1 focuses on the standardization of the bottom two layers of the ISO/OSI protocol stack. Industrial consortia such as the ZigBee Alliance normally specify the other layers. The ZigBee core system consists of an RF transceiver and the protocol stack. The system offers low-rate services that enable the connection of possibly mobile low-complexity devices based on the carrier sensing multiple accesses with collision avoidance (CSMA/CA) channel access technique. The ZigBee physical layer operates in three different unlicensed bands with different modalities according to the geographical area where the system is deployed. However, direct sequence spread spectrum (DS-SS) is used wherever mandatory to reduce the interference level in shared unlicensed bands.