Directional Antenna at Sink (DAaS) to prolong network lifetime in Wireless Sensor Networks

We investigate the effect of a directional antenna in wireless sensor networks from the perspective of network lifetime extension. Previous studies on wireless sensor networks have assumed only an omni-directional antenna model, since a directional antenna has been considered inappropriate for sensors due to size and cost constraints. In this sense, we propose to mount the directional antenna only on a designated gateway node, so called a sink, which has more energy and computational power to handle a large volume of data. With a directional antenna, the sink's communication range is extended and hence the number of neighbor nodes in the communication range increases. Since these neighbor nodes relay data toward the sink, they tend to deplete their energy more quickly than other nodes. Directional Antenna at Sink (DAaS) prolongs the network lifetime by increasing the number of neighbor nodes of the sink. To realize DAaS, we propose a sink beam pattern scheduling algorithm, which coordinates MAC layer wakeup/sleep schedules of the sink and the neighbor nodes according to the directional antenna's beam pattern schedule. The above scheduling algorithm minimizes the duty-cycle and hence saves more energy of the sink's neighbor nodes. Through extensive simulation experiments, we observe significant improvement of network lifetime with DAaS as the number of beam patterns increases.