초록 ▼

In a global satellite communication system (10) that provides antenna beams that move with respect to Earth's surface, gateways (22) send ring alerts directed to subscriber units (26) based on a list of antenna beams. The list of antenna beams is determined by a dot product between a subscriber unit

In a global satellite communication system (10) that provides antenna beams that move with respect to Earth's surface, gateways (22) send ring alerts directed to subscriber units (26) based on a list of antenna beams. The list of antenna beams is determined by a dot product between a subscriber unit's basis vector and antenna beam vectors. Ring alerts are transmitted in antenna beams when the dot product exceeds a predetermined threshold. Subscriber units listen for ring alerts in the same antenna beams of the list by calculating the list the same way the gateway calculates the list.

대표청구항 ▼

[ What is claimed is:] [1.] 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 be

[ What is claimed is:] [1.] 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.