Abstract— To localize mobile entities within a confined area, a wired infrastructure is neither scalable nor cost-effective. An alternative solution consists in deploying a Wireless Sensor Network (WSN), made of energy-autonomous devices. In an environment where GPS is inoperative, we propose that the position of a mobile is given relatively to a set of tag nodes deployed in the zone of activity and signaling their position. In a symmetrical way, each mobile node is announced periodically thus allowing a mutual detection of radio proximity (tag-mobile or mobile-mobile). During the contact the nodes are able to share and store the information required by the localization application. This information is then largely scattered by using the mobility of nodes to carry data up to the application collection points.
Then arises the question about the choice of the medium access method and its performances for the proximity detection in a cell covered by a tag node. IEEE 802.15.4 unslotted CSMA/CA being largely used in low power WSN, we study its performances according to the density of the mobiles and the load of the cell.

Index Terms— WSN, Contact, Localization, Unslotted CSMA/CA.

Cite:Chakib Baouche, Antonio Freitas and Michel Misson , "Radio Proximity Detection in a WSN to Localize Mobile Entities Within a Confined Area," Journal of Communications, vol. 4, no.4, pp.232-240, 2009.