In this work, we introduce a simple and practical location estimation technique which uses AAAs at the central node in WSNs. This localization technique is based on scanning the desired region in azimuth and radial directions by changing parameters of downlink beam. This sweeping process can activate the nodes in the desired region which is specified by antenna beam width and beam direction of the localization beam and also by minimum and maximum thresholds (Rmin and Rmax) for the received signal strength indicator (RSSI). Active nodes in the desired region transmit their IDs and RSSI levels via multi hop communication to the central node. Unlike GPS-based or beacon based localization techniques, the proposed technique does not require any modification in the sensor nodes. The results show that the accuracy of location estimation depends on beam direction, beam width and transmitting power for downlink beams. ©2008 IEEE.