Recent developments in location-based services have heightened the needs for decent accuracy localization system for different applications. The Global Positioning System (GPS) provides adequate accuracy in the outdoor environment but suffers from poor localization accuracy in the complex and dynamic indoor environment. Therefore, the number of indoor localization researches to apply in different applications with different technologies have increased in recent years. The purpose of this paper is to summarize recent advancements in Radio Frequency (RF) based indoor localization techniques and provide insights in the indoor localization field especially in the range based localization. The range based localization is then categorized into few common algorithms such as AOA, TOA, TDOA and RSS. The discussion between algorithms in term of their advantages, disadvantages and improvement strategies to improve their accuracy are also present in this paper.
