Contents I. Introduction
In the past few years, Wireless Sensor Networks (WSNs) have been gaining increasing attention, both from commercial and technical point of views, because of their potential of enabling of novel and attractive solutions in areas such as industrial automation, asset management, environmental monitoring, transportation business, etc. Many of these applications require the transfer of data collected by the sensors to applications residing on a traditional network infrastructure (e.g Internet, LAN, enterprise network, etc.). Thus the WSNs need to be integrated with these traditional networks. Figure 1 shows the typical structure of such an integrated network, in which gateways are used to connect multiple WSNs to a traditional network. Within the WSNs, a large number of battery-operated Sensor/Actuator (SA) devices, usually equipped with a limited amount of storage and processing capabilities, collect information about their environment and send them to the gateways for further transfer to the applications. Even for networks without actuators, information also flows in the opposite direction, e.g., for sensor management and configuration as well as for software updates.
