On Interference Level in Satellite Uplink for Satellite/ Terrestrial Integrated Mobile Communication System

Abstract

This paper describes a fundamental analysis on the interference level in Satellite/Terrestrial Integrated Mobile Communication System (STICS). STICS is a research and development project in Japan which provides both satellite and terrestrial communications systems to dual-mode terminals. When the Mobile Satellite Service (MSS) frequency band is shared by the terrestrial and the satellite system, inter-system interference occurs. In this study, we focus on the interference level in satellite uplink (satellite reception link) in which the interference level depends on the number of terrestrial service users and thus the permissible interference level in this link determines the user capacity of the terrestrial system. Interference estimation in the satellite uplink has been carried out for two categories; the interference caused by terrestrial system uplinks and satellite system uplinks. A newly developed interference estimation simulator based on signal power calculation is utilized for the estimation. The MSS frequency band is reused by seven frequency bands. Japanese main island with part of Exclusive Economic Zone (EEZ) is covered by twentythree satellite spot-beams. Terminals and base stations using terrestrial link are located in the main island under uniform distribution. Spatial guard-band concept is introduced to reduce the interference level in satellite uplink. The effect of the spatial guard-band is verified by evaluating the relationship among spatial guard-band level, carrier to interference level, and terrestrial user capacity. A coverage rate of the terrestrial system as a function of spatial guard-band is also evaluated. Finally, a co-channel interference level caused by the uplinks from satellite link users in other satellite cells is evaluated.