Patent ID: 7860014

Claim:
A transmitting terminal constituting part of a ranging system for measuring a distance between terminals operating on a multi-carrier transmission system, said transmitting terminal comprising: a packet transmitting device transmitting a first packet to a receiving terminal communicating with said transmitting terminal; a time information generating device generating at least first packet transmission time information indicating the time at which said first packet was transmitted; a turnaround time estimating device estimating a packet turnaround time between said receiving and said transmitting terminals based on said first packet transmission time information and on second packet reception time information indicating the time at which a second packet was transmitted to said transmitting terminal by said receiving terminal upon receipt of said first packet; a fast discrete Fourier transform processing device subjecting data from said second packet received from said receiving terminal to fast discrete Fourier transform for conversion into first frequency domain data; a frequency domain data processing device acquiring a first impulse response by subjecting said first frequency domain data to a predetermined process and by applying a spectrum estimation algorithm to the processed first frequency domain data; a propagation time correcting device which, upon receipt of a third packet from said receiving terminal in a suitably timed manner, estimates a radio wave turnaround propagation time by subtracting an internal processing delay time placed in said third packet from said packet turnaround time in order to correct, based on said first impulse response and on a second impulse response placed in said third packet, said radio wave turnaround propagation time into a corrected propagation turnaround time; and a distance calculating device acquiring the distance between said transmitting and said receiving terminals in accordance with said corrected propagation turnaround time and with radio wave velocity.