Distance estimation in OFDM inter-satellite links

•An RF ranging technique for OFDM inter-satellite links (ISL) was developed.•The ISL was implemented in a real-time testbed using USRP platforms.•The testbed measurement precision is of sub-mm level in the absence of multipath. One of the practical solutions for space deployment of large-scale scientific instruments is satellite formation flying. In this type of space mission, several smaller satellites have the ability to interact and cooperate with each other via inter-satellite links (ISL) for tasks commonly performed by a larger and more complex satellite. Formation flying missions require accurate knowledge of the satellite positioning with regard to orientation and distance. This paper proposes a distance estimation method applicable in an Orthogonal Frequency-Division Multiplexing (OFDM) ISL. In the proposed technique, called enhanced wide-lane (EWL), the distance is estimated using an OFDM training symbol, and the measurement is based on the correlation between the received symbol and a stored replica. More precisely, a coarse estimation is obtained by detecting the correlation maximum, then it is refined by measuring the correlation phase. The theoretical considerations regarding the precision of the estimation and the influence of frequency offset and multipath propagation are validated using MATLAB simulations and an experimental testbed built with Universal Software Radio Peripheral (USRP) platforms. The results show that the precision of EWL is of sub-mm level in the absence of frequency offset and multipath propagation.