Abstract: A cellular telephone mobile unit position determining method which utilizes a plurality of range transceivers located at known fixed locations adapted to transmit approximately synchronized digital range signals. The method is especially adapted to determine the position of a cellular mobile unit within cellular service areas for determining billing charges and/or access restrictions. According to the invention, the fixed position range transceivers transmit range signals which are received by a mobile unit. The mobile unit determines either the time difference of arrival or absolute time of arrival of the range signals, which in turn is used to determine the mobile unit's position for cellular billing and/or access restriction purposes. The range transceivers are operable to receive an error signal and correspondingly adjust the output of the next transmitted range signal so as to drive the detected synchronization error to approximately zero.