A multiple altitude satellite relay system is disclosed in which Medium Earth Orbit satellites are continuously linked with at least one Geosynchronous satellite to provide uninterrupted relaying of messages and data. The Medium Earth Orbit satellites are synchronized with the Geosynchronous satellites...http://www.google.com.hk/patents/US5906337?utm_source=gb-gplus-share專利 US5906337 - Multiple altitude satellite relay system and method
