For a next generation GNSS system, new frequency bands in millimeter wave (MMW) range are expected to emerge as the current low frequency band in L-band is seriously congestive. In case of MMW frequency band, signal attenuation phenomenon through atmosphere is quite different from the L band signal propagation case. In this paper, a basic study and survey is done to consider the MMW band as a candidate frequency band of a future national GNSS signal in space, which basically puts focus on the dominant attenuation factor analysis through the tropospheric propagation.

Keywords: GNSS, millimeter wave, tropospheric, attenuation