sending a first detection signal;

determining a time difference, between a time of receiving the first detection signal by the first device and a time of receiving a second detection signal by the first device, as a first time difference, wherein the second detection signal is sent by a second device in response to the second device receiving the first detection signal;

obtaining a second time difference from the second device, the second time difference being a time difference between a time of receiving the first detection signal by the second device and a time of receiving the second detection signal by the second device; and

determining the distance between the first device and the second device based on the first time difference and the second time difference;

wherein the first detection signal is modulated and sent by the first device using a first carrier frequency; the second detection signal is modulated and sent by the second device using a second carrier frequency; the second time difference is characterized by a data encoding signal, and the data encoding signal is modulated and sent by the second device using a third carrier frequency; and the first carrier frequency, the second carrier frequency, and the third carrier frequency are different from each other; and

wherein the method further comprises:

receiving each of the modulated first detection signal, the modulated second detection signal, and the modulated data encoding signal via a band-pass filter.