Patent ID: 7349707

Claim:
A wireless communications system comprising: (a) at least one mobile terminal; and (b) a receiver that is mobile and includes: (i) reception level acquisition means for acquiring respective reception levels of wireless signals transmitted from the at least one mobile terminal, wherein the reception level acquisition means measures the respective reception levels of the wireless signals; (ii) transmission level acquisition means for acquiring respective transmission levels of the at least one mobile terminal, wherein the transmission level acquisition means retrieves respective transmission levels of the at least one mobile terminal contained in the wireless signals; (iii) difference value calculation means for calculating respective difference values between the transmission levels and the reception levels; and (iv) relative distance estimation means for estimating a relative distance to the mobile terminal in accordance with the respective difference values wherein: the reception level acquisition means retrieve respective reception levels of wireless signals sent from the wireless communications apparatus to the at least one mobile terminals contained in the wireless signals of the at least one mobile terminals; and the transmission level acquisition means measures a transmission level of the wireless communications apparatus to the at least one mobile terminals.