Survey of Wireless Based Indoor Localization Technologies

The market of localization based service (LBS) is expanding. The acquisition of physical location is the fundamental basis for LBS. GPS, the de facto standard for outdoor localization, does not work well in indoor environment due to the blocking of signals by walls and ceiling. To acquire high accurate localization in indoor environment, many techniques have been developed. The vision based localization involves camera and computer vision technologies which increase the cost. Accelerometer based localization will accumulate the error made by each localization prediction. Wireless based indoor localization can achieve low cost and high accuracy at the same time. In this paper, a systematic analysis of the wireless based indoor localization is conducted. Firstly, we compare the wireless technologies that have been used for localization in recent literatures. The wireless technologies are divided by the distance of coverage. They vary in frequency band and popularity which determine their unique characteristics when used for indoor localization. After that, we explain the mathematical techniqes are used in wireless based localization. Proximity based method can only provide approximate location based on link or connect information. Triangulation can be used to determine angle or distance information retrieve from the received signals from three or more beacon stations to obtain user location. Fingerprint assumes the signal property in each point is different, the location can be found by comparing with pre-built radio-maps. In the end of the paper, we have summarized four trends in the researches in wireless based indoor localization. The use of multiple wireless technologies and cooperation with other technologies can help cover the defect in one technology. Incorporating multiple mathematical methods can reduce the error and increase the accuracy. The advent of mobile phones also provides a ideal device as user device for indoor localization.