Proximity estimation for location-based services with round-trip time

A proximity estimation algorithm is proposed to measure distances between a transceiver and a receiver for location-based services in indoor environments. To improve the measurement accuracy, proximity is estimated using the propagation delay caused by the round-trip travel of the signal. Moreover, to reduce power consumption, frequency downconversion with a mixer is adopted to use frequencies below the gigahertz range. Being a low-power design, the proposed architecture is suitable for mobile devices such as wearable and internet-of-things products. In addition, the implementation of this algorithm on Wi-Fi-equipped devices does not need development of special schematics, since it is based on the IEEE 802.11 standard, it could be made with usual Wi-Fi quadrature amplitude modulation (QAM)-modulators. The accuracy enhancement of the proposed estimation was verified in comparison with the conventional algorithms by means of simulation.