A paging/messaging system using the L3 transmission channel of a constellation of GPS satellites orbiting the earth, is comprised of an earth-based injection terminal having a source of paging/messaging signals and a radio transmitter for broadcasting paging/messaging on the L3 transmission channel to...http://www.google.com.tw/patents/US5625363?utm_source=gb-gplus-share專利 US5625363 - Paging/messaging system using GPS satellites
