A COMMUNICATION PROTOCOL FOR MOBILE SATELLITE SYSTEMS AFFECTED BY RAIN ATTENUATION

One of the principal challenges to the realization of mobile and personal satellite systems at higher frequencies, such as at K/Ka-band, is the rain attenuation experienced at those frequencies. This paper presents a communication protocol that has been developed as part of a proof of concept K/Ka-band mobile satellite system to be demonstrated with NASA's Advanced Communications Technologies Satellite (ACTS) in 1993. The protocol's objectives are to provide the means for enhancing link availability and continuity by supporting real-time data rate selection and changes during rain events. The protocol is developed with emphasis on being efficient yet robust to the primary channel impairment in such mobile satellite systems, viz., shadowing outages. The system architecture is first briefly presented and the analytical framework from which the protocol originates is pointed out. Link, connection, and packet types are then introduced and the protocol procedures and design rationales discussed. The detailed presentation focuses on link setup with the appropriate data rate(s) and the real-time switching of data rates during a voice conversation to either preserve the link or enhance its quality during rain attenuation events.