Abstract—Being able to accurately track a moving object has been one of the main challenges in smart building applications. In this paper, an indoor localization technique for a mobile object using Zigbee-based received signal strength indication (RSSI) is considered. In order to alleviate the multipath effects from surrounding, a method utilizing the smoothness index to select RSSI values with best quality is proposed. The proposed strategy is evaluated via a simple experiment where the object with a receiver antenna is placed on a wheeled mobile robot moving on a predefined trajectory at a constant speed. The result is also compared with other standard filtering approaches, and the performance is analysed in terms of position error at each time instance between the initial and final positions of the object. Experimental results show that the cumulative error can be significantly reduced as compared to the results from other standard approaches.