TOF is called time of flight in English. TOF ranging technology is a method of TDOA ranging. Traditional ranging technology is divided into two-way ranging technology and one-way ranging technology. TOF ranging method belongs to two-way ranging technology, which mainly uses the time of flight between two transceivers to measure the distance between nodes.
Figure 1 TOF ranging principle
Main advantages of TOF ranging
The method of TOF ranging is bidirectional ranging, which can reduce the ranging error compared with unidirectional ranging;
TOF ranging depends on the flight time, the time measurement accuracy does not change significantly with the increase of the test distance, the performance is more stable, and the distance can be measured more accurately;
Error analysis of TOF ranging
1. The interval of wireless transmission is very short. In the TOF ranging scheme, the distance measurement depends on the time measurement, but the speed of light is as high as 300000 km / s, small time error will lead to large distance error, so in order to obtain the accurate distance, the timing system of the transmitter and receiver becomes very high.
2. Time delay. Time delay includes transmit delay, receive delay and antenna delay. When the ranging signal is transmitted by digital and analog signal processing and modulation, there will be a certain delay error when it is transmitted and received by radio. There will be a certain delay in the transmit / receive signal of the antenna, and the delay may not be uniform, because the delay in one radiation direction may be different from that in the other radiation direction, and the delay time of different antennas will be different due to the difference of antenna quality.
3. Multipath refers to the phenomenon that the transmitted signal passes through multiple reflections and diffraction from the transmitter to the receiver. When there is an obstacle between the transmitter and the receiver, the impact will become serious.