Markov Localization of Wireless Local Area Network Clients

Markov localization has been successfully deployed in robotics using highly precise distance sensors to determine the location and pose of mobile robots. In this setting the scheme has shown to be robust and highly accurate. This paper shows how this approach has been adapted to the problem of locating wireless LAN clients in indoor environments using highly fluctuating radio signal strength measurements. A radio propagation model is used to determine the expected signal strength at a given position in order to avoid tedious offline measurements. Some of the issues that had to be addressed include expressing the calculated signal strengths in terms of probability density functions and detecting movement of the mobile terminal solely on the basis of radio measurements. The conducted experiments show that the proposed technique provides a median error of less than 2m even when there is no line-of-sight to an access point.