A METHOD FOR IMPLEMENTING CIPHERED COMMUNICATION FOR SINGLE-HOP TERMINAL-TO-TERMINAL CALLS IN A MOBILE SATELLITE SYSTEM

摘要

A mobile satellite communication system is provided to control the transfer of a terminal for a single-hop call from at least one of a clear mod and a ciphered mode with respect to a gateway station to a ciphered mode with respect to a satellite link connecting the terminal with another terminal for a single-hop, terminal-to-terminal call using a cipher key and an encryption algorithm common to the terminal and the other terminal. Frame number offset data, which indicates a mapping delay between received and transmitted time slots at the satellite, is provided to both terminals in a terminal-to-terminal call for ciphering synchronization.