Neighborhood Discovery Approach in WSN for Star Topology Using a Switched Beam Antenna

Wireless Sensor Networks (WSNs) are often used for gathering data collected by sensor nodes spread over large monitored areas. Star topologies, having a sink node at their center, are becoming a clear trend when the size of the monitored area allows it. The range of the radio links used, increases due to the decision to use a sub-GHz frequency and/or a particular signal coding that ensures a significant processing gain in the radio link budget. Even though such long-range radio links are beneficial in specific applications, in spite of the low data rate limit, often remains a weakness for application in many domains. Our overall objective is to consider combining the use of a switched-beam antenna only for the sink node of a star topology and omnidirectional antennas for wireless sensor nodes, in order to achieve a better balance between Range and Data Rate. When switched- beam antennas are used to equip some nodes, usual medium access methods have to be revised as does the discovery of the neighborhood of the sink. In this paper, we propose a scheme that allows the sink node to discover all its neighboring nodes within a limited timeframe, despite the hidden terminal problem effects worsen by antennas directivity. Index Terms-Star topology, wireless Sensor Networks, neigh- borhood discovery, MAC protocols, switched beam antenna