Patent ID: 8242958

Claim:
A system for positioning using signal transmit power and signal receive packet error rate (PER), comprising: a ranging signal collecting unit, configured to collect ranging signals from a ranging signal transmitting unit, the ranging signal transmitting unit being configured to repeatedly transmit a predetermined number of ranging signal packets within a predetermined time period, wherein the ranging signal transmitting unit is one of an active radio frequency identification (RFID) tag working in intermittent mode in an active RFID tag system and an active RFID reader, and the ranging signal collecting unit is the other of the active RFID tag and the active RFID reader; a packet loss rate (PLR) calculating unit, configured to calculate the PLR of the ranging signals according to the number of received ranging signal packets received by the ranging signal collecting unit and the predicted number of data packets transmitted by the ranging signal transmitting unit; and a position determining unit, configured to determine, based on a predetermined policy, the distance between the ranging signal transmitting unit and the ranging signal collecting unit according to the PLR and transmit power of the ranging signals; wherein the predetermined policy is: ln x =[ln q−G ( Er ) −b ( N )]/ n , where x is the distance between the ranging signal transmitting unit and the ranging signal collecting unit; q is the transmit power of the ranging signals; Er is the PLR; n is an environment attenuation index determined in advance or based on experience; b(N)=ln (N/A), where N is the ambient noise strength, and A is signal transmission efficiency parameter of the ranging signal transmitting unit; and G(Er)=ln g(Er), where g(Er) is signal to noise ratio (SNR) of the strength of ranging signals received by the ranging signal collecting unit to the ambient noise strength, which is determined according to the mapping between Er and g(Er).