MUOS Ka-Band Feederlink Availability Model and Performance Analysis

Mobile User Objective System (MUOS) employs a Ka-band feeder uplink and downlink from each satellite to two Radio Access Facilities (RAF). Each feederlink has an availability requirement, where availability is defined as the fraction of time a communications link is able to support communications at the rate and quality specified. In the MUOS system, Ka-band frequencies in the region of 20 GHz to 30 GHz are chosen for the downlink and uplink, respectively. Ka frequencies allow wide-band communication between the satellite and RAF to support end-user capacity. However, signals at these frequencies are known to suffer high propagation losses with rain attenuation being the most significant contributor. Furthermore, the MUOS satellites operate in an inclined orbit. Half of the time during an orbital period, the RAF elevation angle to the satellite, and therefore the propagation loss, will be worse than if the satellites were in a true geosynchronous orbit. In this paper, we present the MUOS Ka-band feederlink availability model. The model is used to analyze link performance, based on design parameters, such as effective isotropic radiated power (EIRP) and gain-on-noise-temperature ratio (G/T). It accounts for propagation effects in accordance with International Telecommunication Union recommendations (ITU-R) and the orbit inclination in order to demonstrate availablity compliance for all satellite-to-RAF feederlinks in the architecture.