Technical Concerns of Near-Far Effect in GNSS Space Service Volume (SSV)

Abstract

Global Navigation Satellite System (GNSS) is not only widely used in terrestrial positioning, navigation and timing, more attentions have been casted on space utilities, especially in orbit determination of Low Earth Orbit (LEO) spacecraft. However, because of Near-Far Effect and many other technical concerns, GNSS has seldom been used in high precision spacecraft orbit determination at Medium Earth Orbit (MEO) and High Earth Orbit (HEO). In order to analyze and solve the Near-Far Effect that might encounter in GNSS space applications, this work studies the influence factors of Near-Far Effect, such as free space propagation loss, orbital altitude, ionosphere and troposphere Effect, the concept of Strong-to-Weak signal ratio is proposed and analyzed carefully, some results are given as well. Three Near-Far Effect mitigation technical approaches are proposed, namely positive adjustment method, FDMA proposal, and interference cancellation approach. However, more deep research is in need to do comparisons and assess the performance of these methods in future work.