ESTR - Energy Saving Token Ring Protocol for Wireless Sensor Networks.
Faruk Bagci, Theo Ungerer, Nader Bagherzadeh · 2008
Abstract—Most wireless sensor networks rely on battery energy. In applications with a great number of sensor nodes and a wide area of monitored environment it is not always feasible to replace the battery. In some cases, even the lo-cation of the sensor node is unknown. In order to achieve a long lifetime of the sensor network and the application it is important to save energy. A sensor node consumes the most of its energy in active mode. In sleep mode the energy con-sumption can be a couple of hundred times lesser depending on the hardware. This paper proposes an energy-efficient medium access control (MAC) protocol for wireless sensor networks, called Energy Saving Token Ring Protocol (ESTR). ESTR bases on the well-known token ring protocol. The sensor nodes are connected in rings where only the node that holds the token is active and able to communicate. ESTR establishes sleep times for sensor nodes that don’t need to send or receive messages. Thus, nodes save energy spending less time in active mode. Also ESTR minimizes energy wasted due to idle-listening and overhearing. The sensor network can build multiple rings which are inter-connected. ESTR allows to adjust the maximal permitted ring size offering a flexible mechanism to control through-put and energy consumption. Furthermore the token in-cludes energy information of preceding nodes that allows self-optimization of the ring by dynamically adapting the sleep time of each node. ESTR is tested in the network simulator NS-2 and achieves the best energy results com-pared to other MAC protocols. Index Terms—Wireless sensor network, MAC protocol, energy-saving, energy-efficient, token ring, self-optimization I.