Patent ID: 8457684

Claim:
An asynchronous cellular wireless communication system ( 400 ) comprising: (i) a first macro cell ( 410 A) and a second macro cell ( 420 A); (ii) a femtocell ( 440 A) associated with the first macro cell ( 410 A); (iii) a mobile communication unit ( 450 ) operable to communicate with the femtocell ( 440 A), the first macro cell ( 410 A) and the second macro cell ( 420 A), where the mobile communication unit is at a first distance (D 1 ) from the first macro cell ( 410 A) and at a second distance (D 2 ) from the second macro cell ( 420 A); and signal processing logic ( 412 ) performing the steps of: deriving a first timing difference measurement (dTm 1 ) from a first set of communications (S 1 ), the first set of communications comprising communications between: (i) the mobile communication unit ( 450 ) and the femtocell ( 440 ); and (ii) the mobile communication unit ( 450 ) and the first macro cell ( 410 A); deriving a second timing difference measurement (dTm 2 ), from a second set of communications (S 2 ), the second set of communications comprising communications between: (i) the mobile communication unit ( 450 ) and the femtocell ( 440 ); and (ii) the mobile communication unit ( 450 ) and the second macro cell ( 420 A); combining the first timing difference measurement (dTm 1 ) and the second timing difference measurement (dTm 2 ), to provide a combined timing difference measurement (dTm 12 ); eliminating, from the combined timing difference measurement (dTm 12 ), a value for a timing offset (dTb 12 ) between the first macrocell ( 410 A) and the second macrocell ( 420 A), thereby providing a corrected timing difference measurement (dTm 12 c ); deriving an estimate of a first difference (D 12 ) between the first distance (D 1 ) and the second distance (D 2 ), as an estimate of the difference between the distances of the femtocell ( 440 ) from the first macrocell ( 410 A) and the second macrocell ( 420 A), using the corrected timing difference measurement (dTm 12 c ); and combining the estimate of the first difference (D 12 ) between the first distance (D 1 ) and the second distance (D 2 ) with at least a second distance estimate, thereby determining the geographical location of the femtocell ( 440 ).