A communication system includes a spacecraft which produces a plurality of overlapping spot beams. The spacecraft moves periodically in the N-S direction. Terrestrial user terminals may lie in one spot beam when the spacecraft is in one position, and in another spot beam at a later time. The system also...http://www.google.com.hk/patents/US6118998?utm_source=gb-gplus-share專利 US6118998 - Spacecraft cellular communication system with spot beam pairing for reduced updates
