Distance Estimation Based on Molecular Absorption at THz Frequencies.

One of the main approaches for distance estimation is the received signal strength (RSS) based techniques. Their drawbacks include the requirement of accurate knowledge of the transmit power and antenna gains. Also, the traditional RSS-based techniques do not take into account the molecular absorption that occurs at terahertz frequencies. In this paper, we propose a distance estimation method for the line-of-sight case that actually takes advantage of the molecular absorption. The proposed method measures the RSS at two frequencies and does not require known transmit powers and antenna gains, which are assumed to be almost the same at the two frequencies. Therefore, the two frequencies have to be relatively close to each other. The proposed distance estimation method calculates the difference of the received powers (in the dB domain) at the two frequencies and finds the link distance based on it and the humidity level.