Mobile telephone location process making use of handoff data

Claim 1

In a wireless communication system in which a service area is divided into cells, and in which a road is located within the service area, a position determining apparatus comprising: a mobile station, for providing communication to a remote subscriber of the wireless communication system; a serving base station, for serving the mobile station located in one of the cells, and for accepting information representing a signal strength for a communication channel between the mobile station and the base station, as well as for accepting information representing signal strengths for communication channels between the mobile station and other, non-serving base stations, and for forming a mobile data vector from the signal strengths information for the serving and non-serving base stations; and position determining means, for accepting the mobile data vector from the base station and determining the location of the mobile unit as indicated by a position data set, the position determining means further comprising mapping means that associates a set of mobile data vectors with the road, with a single mobile data vector associated with a constant segment of the road along which the mobile data values remain constant, and wherein the mapping means associates identical mobile data vectors with two or more constant segments along the road, and wherein an index data value is also provided by the mapping means with each position data set, the index value thus identifying a constant segment along the road; and whereby the position determining means additionally maintains information concerning a last known position for the mobile unit along the road, and compares the last known position to the position data set including the constant segment index to uniquely identify the position of the mobile unit to one of the constant segments along the road.

Claim 3

A method for determining the location of a remote unit within a service area covered by a wireless communication system, the method comprising the steps of: (a) collecting a data vector having two or more data elements that vary according to the position of the remote unit, the values of the data elements being identical for at least two location sub-portions, or constant segments, of the service area; (b) using the data vector to determine an initial position estimate in the form of an initial position (xi,yi); (c) using the initial (xi,yi) position to determine a segment index, i, that denotes a possible constant segment associated with a particular feature of the service area; (d) using the segment index i to determine an associated point vector (i, Rx, Ry, Pi) with Rx, Ry representing a first point in the service area associated with the constant region, and with Pi representing the sequential index of another constant segment associated with the same particular feature of the service area, and with the sequential index Pi being set to zero if there are no other such other constant segments; (e) if Pi as determined in step (d) is zero, then indicating that the position of the remote unit as (xi,yi); (f) if Pi as determined in step (d) is not zero, then creating a list of position point vectors by the steps of: (i) selecting the point vector (i, Rx, Ry, Pi) as a first element of the list; (ii) setting a last sequential index to Pi; (iii) determining an index, j, of a next point vector from the last sequential index; (iv) using the index j to determine a next point vector (j,Rx,Ry,Pj) (v) setting the last sequential index to Pj; and (vi) repeating steps (iii) through (vi) until a point vector, k, is reached for which Pk=0; and (g) indicating the position of the remote unit by selecting one of the (Rx, Ry) points selected from among the k point vectors by traversing the list of position point vectors.

Claim 4

A method for determining the location of a remote unit within a service area covered by a wireless communication system, the method comprising the steps of: (a) collecting a data vector having two or more data elements that vary according to the position of the remote unit, the values of the data elements being identical for at least two location sub-portions, or constant segments, of the service area; (b) using the data vector to determine an initial position estimate in the form of an initial position (xi,yi); (c) using the initial (xi,yi) position to determine a segment index, i, that denotes a possible constant segment associated with a particular feature of the service area; (d) using the segment index i to determine an associated point vector (i, Rx, Ry, Pi) with Rx, Ry representing a first point in the service area associated with the constant region, and with Pi representing the sequential index of another constant segment associated with the same particular feature of the service area, and with the sequential index Pi being set to zero if there are no other such other constant segments; (e) if Pi as determined in step (d) is zero, then indicating that the position of the remote unit as (xi,yi); (f) if Pi as determined in step (d) is not zero, then creating a list of position point vectors by the steps of: (i) selecting the point vector (i, Rx, Ry, Pi) as a first element of the list; (ii) setting a last sequential index to Pi; (iii) determining an index, j, of a next point vector from the last sequential index; (iv) using the index j to determine a next point vector (j,Rx,Ry,Pj) (v) setting the last sequential index to Pj; and (vi) repeating steps (iii) through (vi) until a point vector, k, is reached for which Pk=0; and (g) indicating the position of the remote unit by selecting one of the (Rx, Ry) points selected from among the k point vectors by traversing the list of position point vectors.