Energy efficient MAC protocols for Wireless Sensor Networks endowed with directive antennas: a cross-layer solution

This paper deals with a novel MAC layer protocol, namely Directive Synchronous Transmission Asynchronous Reception (D-STAR) able to space-time synchronize a Wireless Sensor Network (WSN). To this end, D-STAR integrates directional antennas within the communications framework, while taking into account both sleep/active states, according to a cross-layer design. After characterizing the D-STAR protocol in terms of functional characteristics and antenna model, the related performance is presented, in terms of network lifetime gain, latency and collision probability. It has shown a remarkable gain in terms of energy consumption reduction with respect to the basic approach endowed with omnidirectional antennas, without increasing the signaling overhead nor affecting the set up latency.