부산대학교 도서관

In data collection area, wireless sensor networks are usually used for their ease of deployment and auto-configuration capabilities. In this paper, we consider a star topology, where the central node is equipped with a switched-beam antenna, while other nodes are using omnidirectional antennas. This configuration enables enhancing the network performance without increasing the cost and complexity of the deployment, and may be suitable for some emerging applications like smart home, smart parking, etc. When directional antennas are used, some common methods like MAC (Medium Access Control) protocols, routing protocols and neighbor discovery protocols need to redesigned. In this work, we propose a neighbor discovery method based on Aloha approach that helps the sink node to discover its neighborhood. Our discovery method uses idle slots reduction mechanism and exploits collaboration between nodes and the sink in order to speed up the discovery process. Collaboration occurs during discovery process when a node shares with the sink its local knowledge of its own neighborhood. We implemented our protocol on contiki OS, and performed several simulations on Cooja. We compared the proposed protocol with a state of the art protocol adapted to work with our network configuration. The results show that our protocol improves the discovery delay by about 25% compared with the PND protocol chosen as reference.