John Krumm Eric Horvitz LOCADIO: Inferring Motion and Location from Wi-Fi Signal Strengths. 4-13 2004 conf/mobiquitous/2004 MobiQuitous http://csdl.computer.org/comp/proceedings/mobiquitous/2004/2208/00/22080004abs.htm db/conf/mobiquitous/mobiquitous2004.html#KrummH04