Patent ID: 7298323

Claim:
An apparatus for locating a UE (User Equipment) using a DGPS (Differential Global Positioning System) receiver and a dead-reckoning sensor, comprising: the dead-reckoning (DR) sensor for sensing position angles of the UE at different times with respect to a predetermined reference DR point; and a position detector, comprising: a MODEM for receiving from a Node B serving the UE first information about a first round trip time (RTT) at an initial time and second information about a second RTT at a predetermined time when the UE is in a shadow area of DGPS satellites, the predetermined time following the initial time; and a position estimator for: (a) calculating a first distance between the UE and the Node B, using the first information, the first distance corresponding to the UE at the initial time, (b) determining a first position of the UE at the initial time and a fixed position of the Node B, the first position and the fixed position calculated by the Node B using signals from at least three DGPS satellites, (c) calculating a second distance between the UE and the Node B, using the second information, the second distance corresponding to the UE at the predetermined time, (d) calculating a moved distance that the UE has moved from the initial time to the predetermined time, using the first distance, the second distance and a position angle of the UE at the predetermined time, (e) calculating a moved vector, using the moved distance and the position angle of the UE at the predetermined time, and (f) estimating a second position of the UE at the predetermined time by using the first position and the moved vector.