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Indoor positioning is currently a research hot topic for industrial and scientific communities. Wi-Fi signal has been a common positioning signal adapted researchers. Received signal strength indicator is a traditional measurement used for indoor positioning. It can be easily affected by many factors such as the change of environment. Therefore, it is difficult to achieve such an accuracy that can be used in practice and hard to deploy the positioning solution in a large-scale. More and more resear-chers are now focusing on using channel state information as the measurement, which contains an essential description of Wi-Fi signal propagation and provides more details about the communication channel. This information can be transformed to a useful measurement for positioning. In this paper, we introduce the fundamental description of channel state information and classify the positioning approaches into three categories, which are fingerprinting-based, angle of arrival-based and ranging-based, respectively. The current states of these technologies have been reviewed in details, and the pros and cons have been identified and compared. We conclude the paper with a discussion about the directions in this field. [ABSTRACT FROM AUTHOR]