This work presents a low power outdoor localization system that implements a power management technique in order to control the wakeup and sleep of the different modules in the system. Through this technique, the system achieves 6.7 µA in sleep mode. A new weighted least mean squares solution algorithm that is based on received signal strength indicator (RSSI) measurements is introduced. Both simulation and measurement results are presented. It is shown that over 50% improvement in position estimation is achieved using the proposed weighted least mean squares algorithm.