Abstract. In this paper, we focus on auto-localization of nodes in a static wireless network, under the assumption of known position of a few initial nodes, denoted as "beacons". Assuming that Ultra Wide Band (UWB) signals are used for inter-node communications, we analyze the impact of the number of beacons on the location accuracy. Three different approaches to localization are considered, namely: the Two-Stage Maximum-Likelihood (TSML) method ; the Plane Intersection (PI) method, and Particle Swarming Optimization (PSO). Simulation results show that PSO allows to obtain accurate postion estimates with a small number of beacons, making it an attractive choice to implement effective localization algorithm.