Patent ID: 7650155

Claim:
A transmission time difference measurement method in a system having a terminal, two or more base stations that each operate asynchronously, and a control device for controlling the terminal and each of the base stations, said method calculating transmission time differences of signals in each of said base stations and comprising steps wherein: when said terminal is able to simultaneously receive signals from each of said base stations, each of said base stations uses a round trip time measurement function to measure the round trip times of signals to and from said terminal; said terminal uses a turn-around time measurement function to measure, for each of said base stations, the turn-around time from the reception of a signal from the base station until the transmission of a signal to that base station; said terminal uses an arrival time difference measurement function to measure the arrival time difference, which is the difference between the times that signals arrive from each of said base stations; and said control device finds the difference in transmission times of signals in each of said base stations based on: the difference of propagation times between said terminal and each of said base stations that is calculated by subtracting the turn-around time that is measured in said terminal from the round trip time that is measured in each of said base stations, and the arrival time difference that is measured in said terminal; and uses a storage function to store the calculated transmission time differences in association with the calculation times at which the transmission time differences were calculated.