Smart Environments and Cross Layer Design

Abstract

In the last decade we have witnessed a really unpredicted boom in the number and variety of applications based on wireless sensor networks (WSN). From environment monitoring and military applications, to health care and event tracking applications, both the diversity and complexity of the nodes themselves and their networked applications have increased immensely (Yick et al., 2008). A combination of consumer demand for more efficient integrated systems and a steep drop in the price of hardware fuelled by manufacturing process improvements has resulted in a noticeable upward cycle of research in the field of networks that not only sense the data but also provide automated reaction to specific situations known as Wireless Sensor and Actuator Networks (WSAN) (Akyildiz & Kasimoglu, 2004). “Smart environments” are discussed as the next step in these evolutionary developments in intelligent systems automation related to utilities, construction, industry, home and transportation. The “smart environment” is defined as one that is “able to acquire and apply knowledge about the environment and its inhabitants in order to improve their experience in that environment”. The WSN, which are in the heart of the “smart environments” consist of densely deployed microsensor nodes that continuously observe certain physical phenomenon. The existing abundance of WSN applications can be divided into two major groups based on the nature of the supported applications: WSN for monitoring and WSN for event detection/tracking. A major common feature is that both exploit the collective effort of nodes which have computing, transmitting and sensing capabilities. From the user point of view the main objective of WSN is to reliably detect or collect, and estimate event features based on the collective information provided by all sensor nodes. From the engineering design point of view, the main challenge for achieving this objective is posed by the severe energy and processing constraints of the low-end wireless sensor nodes. The collaborative sensing notion of WSN, which is achieved by the networked deployment of sensor nodes, can potentially be used towards overcoming the characteristic challenge of WSN, i.e., resource constraints. To this end, there has been a significant amount of research effort to develop suitable networking protocols in order to achieve communication with maximum energy efficiency. Because of the strict demands of WSN as compared to wired networks and AdHoc networks, the design goals of such system are different from the traditional approaches. The suitability of one of the foundations of networking, the OSI layered protocol architecture, is coming under close scrutiny from the research community. It is repeatedly 3