Patent ID: 6072986
Filing Date: 2000-06-06
Classification: H04B

Abstract:
In a global satellite communication system comprised of communication satellites each providing a plurality of antenna beams moving with respect to earth's surface wherein each antenna beam having a beam vector associated therewith identifying a location of the antenna beam on earth's surface, a method of sending a ring alert to a subscriber unit comprising the steps of:receiving an incoming call at a gateway;said gateway retrieving a basis vector for said subscriber unit, said basis vector having information about said subscriber unit including location information;the gateway determining a first dot product between said basis vector and each of said beam vectors;adding ones of said antenna beams to a first list of antenna beams when said dot product exceeds a threshold value; andtransmitting a ring-alert for said incoming call to said subscriber unit, said ring-alert being transmitted within antenna beams on said first list in response to the receiving step, andwherein the method further comprises the steps of:the subscriber unit retrieving the basis vector from a memory of the subscriber unit;the subscriber unit determining a second dot product between said basis vector and each of said beam vectors;the subscriber unit adding antenna beams of said plurality to a second list of antenna beams when said second dot product exceeds said threshold value; andthe subscriber unit monitoring broadcast channels of an antenna beam on said second list for transmission of said ring-alert.