cards by multiplying the time of flight with the speed of light a wifi access point computes the distance between each of its antennas and the client hence localizing it an implementation on commodity wifi cards demonstrates that the system 39 s accuracy is comparable to state of the art localization systems which use four or five access points application_number US 201615072592 A description the following notation is generally used in the description below in the case of inconsistency between this list and the text of the description text should be followed u03c4 is the true propagation time time of flight between two nodes in the case of multiple paths u03c4 0 denotes the time on a direct path and u03c4 p denotes the delay on the p th indirect path d is the true range between the nodes d c u03c4 where c is the propagation speed f 0 is the frequency of local oscillator which determines the carrier frequency of a transmission in hertz tx rx in general superscript tx denotes a quantity at the node initiating a range measurement i e the transmitter of an initial packet and superscript rx denotes the quantity at the node to which the range is being determined in general an optional initial subscript i denotes a quantity for an i th measurement 1 u2266 i u2266 n for example f i 0 rx denotes the local oscillator frequency at a receiver on the i th measurement e g at the i th frequency band u03c6 0 is the phase of the corresponding.