In each case, a spectrum in air was acquired first to judge the quality of the microresonator, then DI water/glycerol mixtures were subsequently
Since the start of the third Millennium, wireless sensor networks (WSNs) generated an increasing interest from industrial and research perspectives [1�C7]. A WSN can be generally described as a network of nodes that cooperatively sense and may control the environment enabling interaction between persons or computers and the surrounding environment [8]. On one hand, WSNs enable new applications and thus new possible markets, on the other hand, the design is affected by several constraints that call for new paradigms.

In fact, the activity of sensing, processing, and communication under limited amount of energy, ignites a cross-layer design approach typically requiring the joint consideration of distributed signal/data processing, medium access control, and communication protocols [9].This paper provides a survey of WSNs technologies, main applications and standards, features in WSNs design with case study, and evolutions. In particular example of performance based on experimental results will be reported. With respect to the literature [1, 2, 10] this paper deals not only with applications and features of WSNs, or only on design of WSNs, but puts together all these aspects, focusing also the attention on technologies and standards.WSNs have several common aspects with wireless ad hoc network [11] and in many cases they are simply considered as a special case of them.

This could be lead to erroneous conclusions, especially when protocols and algorithms designed for ad hoc networks are used in WSN. For this reason in Section 2 an appropriate definition of WSN and discussion is provided.In Section 3, the main application areas for WSNs are categorized according to the type of information measured or carried by the network. Applications, Anacetrapib on top of the stack, set requirements that drive the selection of protocols and transmission techniques; at the other end, the AV-951 wireless channel poses constraints to the communication capabilities and performance. Based on the requirements set by applications and the constraints posed by the wireless channel, the communication protocols and techniques are selected.

The main features in WSNs design are described in Section 4. Specifically, the design of energy efficient communication protocols is a very peculiar issue of WSNs, without significant precedent in wireless network history. Generally, when a node is in transmit mode, the transceiver drains much more current from the battery than the microprocessor in active state or the sensors and the memory chip.