Method and arrangement for determining terminal position

An arrangement in a positioning unit configured to determine positions of mobile terminals in a cell of a mobile communication network where time alignment (TA) is employed for terminal transmissions in timeslots to a serving base station providing radio coverage in said cell, the arrangement comprising:

• a distance determining unit configured to determine a TA independent distance (D) to the base station for at least one mobile terminal in the cell using a TA independent positioning method;
• an obtaining unit configured to obtain a current TA value used by the at least one mobile terminal for time alignment of uplink signal transmissions in an allocated timeslot;
• a logic unit configured to estimate a relation between the determined TA independent distance and the obtained current TA value for each of the at least one mobile terminals, and to determine a TA bias of the cell based on the estimated relation as a calibration parameter for position determination of any mobile terminals in said cell using a TA based positioning method;
• and
• a position determining unit configured to determine a position of a subsequent mobile terminal using the TA based positioning method and said TA bias by adjusting a current TA value used by the subsequent terminal by the TA bias and determining the position of said subsequent mobile terminal based on the adjusted TA value.