Low-Energy Consumption Schemes in Wireless Sensor Networks NIKOLAOS PANTAZIS 1 , DIONISIS KANDRIS 1 , DIMITRIOS D. VERGADOS 2 1 Department of Electronics, School of Technological Applications, Technological Educational Institution (T.E.I.) of Athens GR-12210, Athens, Greece 2 Department of Information and Communication Systems Engineering University of the Aegean GR-83200, Karlovassi, Samos, Greece Abstract: - Sensor networks are dense wireless networks consisting of a large number of small-sized, low-cost sensor nodes that are densely deployed either inside the phenomenon or very close to it. Sensor nodes’ function is to collect, process, and disseminate critical data while their position need not be engineered or predetermined. This means that sensor network protocols and algorithms must possess self-organizing capabilities. Wireless sensor networks are employed in a vast variety of fields – environment, health, home, civil, military. Sensor nodes have various energy and computational constraints because of their inexpensive nature and ad hoc method of deployment. Considerable research has been focused at overcoming these deficiencies through more low-energy consumption schemes. Three basic schemes have been chosen to be studied in this paper. The motivation of the first scheme is twofold, limiting multi-user interference to increase single-hop throughput and reducing power consumption to prolong battery life. The second scheme focuses on energy-aware routing. The third scheme contributes to dynamically increase the lifetime of the sensor network. The survey attempts to provide an overview of these issues as well as the solutions proposed in recent literature. Key-Words: - Wireless Ad Hoc Sensor Networks, Power Control, Low-energy Consumption 1 Introduction Recent advancement in micro-electro-mechanical systems and low-power and highly integrated digital electronics have led to the development of micro- sensors [1-6]. Such sensors are generally equipped with data processing and communication capabili- ties. The sensing circuitry measures ambient condi- tions related to the environment, which surrounds the sensor, and transforms them into an electrical signal. The processing of such a signal reveals some properties about objects located in the neighborhood of the sensor. The sensor sends the collected data, usually via radio transmitter, to a command center (sink) either directly or through a data concentration center (a gateway). The decrease in the size and cost of sensors, resulting from such technological advances, has fueled interest in the possible use of large set of disposable unattended sensors. Such interest has motivated intensive research in the past few years addressing the potential of collaboration among sensors in data gathering and processing and the coordination and management of the sensing activity and data flow to the sink. A natural architecture for such collaborative distributed sensors is a network with wireless links that can be formed among the sensors in an ad hoc manner. Here, we must say that previously, sensor networks consisted of a small number of sensor nodes that were wired to a central processing station. However, nowadays, the interest is focused more on wireless distributed, sensing nodes. But, the question is, why wireless sensing? When the exact location of a particular phenomenon is unknown, distributed sensing allows for closer placement to the phenomenon than a single sensor would permit. Wireless ad-hoc Sensor Networks have been increased enormously the recent years as they are used more and more in the daily life. In order to guarantee the network existence and increase network lifetime in such environments, various schemes have been proposed regarding the resource allocation, routing and Low Energy consumption. Thus, one of the most important issues for the Wireless ad-hoc Sensor Networks’ Survivability is