Unsynchronized Energy-Efficient Medium Access Control and Routing in Wireless Sensor Networks

Various energy saving MAC protocols for all kinds of wireless networks have evolved in the past decades. Reaching from the 802.11 WLAN-standard with its power saving extension, researchers have suggested energy saving MAC protocols for use in wireless ad hoc networks and MANETs, sensor networks and personal area networks. Today’s energy saving wireless MAC protocols periodically switch the radio transceiver hardware between the costly operation modes receive and transmit and an energy-saving sleep mode. The majority of the existing power saving MAC approaches tries to synchronize the state changes of the nodes in the network and introduces mechanisms to let the nodes synchronously wake up at designated points of time in order to exchange pending traffic or control messages. Such synchronization however is not easy to achieve, especially over multiple hops, and the introduction of periodic control messages for global or clusterwise synchronization is energetically costly. With low traffic, the energetic overhead for maintaining synchronization and slot coordination may exceed the energy spent for the actual data traffic. Mechanisms that renounce on synchronization schemes are likely t