In this paper, a position recognition system is designed, implemented, and tested using IEEE 802.15.4a PHY (CSS) hardware and Tiny OS environment. The system is designed with extensibility and flexibility. The system consists of five kinds of nodes which have different functions from each other. Three communication channels are used for collision avoidance. In each cell, an arbiter node is used to minimize message collisions. The proposed arbitration protocol is designed to support mobility of arbitrary target nodes. Target nodes calculates their locations with communications to four location reference nodes which are placed on the comers of each cell.