A robust to multi-path ranging technique over IEEE 802.11 networks

In this paper, we present a two-way TOA technique for distance estimation (i.e., ranging) over IEEE 802.11 networks. It is based on repetitively measuring the Round Trip Time (RTT) of IEEE 802.11 MAC frames and carrying out statistical processing in order to identify the multi-path condition of the channel and to improve accuracy. The study demonstrates that a multi-path condition has a negative impact on the ranging accuracy in Non-Dominant Direct Path (NDDP) and Undetectable Direct Path (UDP) situations. In this paper, an approach is presented to detect and overcome this impact. The proposed approach identifies the channel profile (i.e., the multi-path condition) from the statistical features of a set of RTT measurements and uses a ranging algorithm that is sensitive to multi-path. Results demonstrate the feasibility of channel profile identification in real time and a ranging accuracy of around one meter in all possible multi-path situations.