Abstract: A GPS enabled Emergency Messaging System (GEMS) includes: Emergency Response Centers (ERC's) for defining emergency broadcast messages directed to specified geographic areas; a GPS Control Segment (CS) facility that receives messages generated by the ERC's and coordinates uplink and downlink communications with orbiting GPS satellites; a GPS Space Segment (SS) that includes the multiple orbiting GPS satellites and that receives emergency messages from the CS facility and broadcasts transmissions containing both GPS navigational information and an emergency broadcast message; and GEMS-enabled user equipment that is capable of receiving and processing broadcast emergency messages. The system permits emergency messaging data to be superimposed on the existing GPS signal structure and delivered to users with GPS receivers capable of receiving the superimposed messaging data.

Abstract: A satellite network constellation employs a technique for multicasting packets through the network according to the present invention. The network comprises plural satellites in plural orbital planes with each satellite equipped with a plurality of high-speed point-to-point full duplex radio links for inter-satellite communications. A node intending to send a multicast packet to a multicast group or a set of destination satellite nodes initially sends the packet to the orbital planes that include the group members. Once reaching the plane, in-plane routing techniques are used to forward the packet to the intended group members. If there are broken or disabled links, an alternative path is taken to forward the packet without disrupting the functioning links.

Abstract: Network configuration hierarchy information is maintained using flexible mechanisms and methods for establishing routes and transferring information between nodes in ad-hoc data communication networks using on-demand multicast and unicast techniques. Communication nodes use network topology information to build and maintain a dynamically mobile, wireless, ad-hoc network capable of efficiently routing both unicast and multicast traffic. Network nodes that facilitate the collection and distribution of network topology and routing data are dynamically selected, configured, and maintained. Network traffic overhead necessary for maintaining and distributing network routing table information is held to a minimum and efficiently distributed across the network, thereby reducing the potential for network traffic bottlenecks due to network overhead processes.

Abstract: A GPS enabled Emergency Messaging System (GEMS) includes: Emergency Response Centers (ERC's) for defining emergency broadcast messages directed to specified geographic areas; a GPS Control Segment (CS) facility that receives messages generated by the ERC's and coordinates uplink and downlink communications with orbiting GPS satellites; a GPS Space Segment (SS) that includes the multiple orbiting GPS satellites and that receives emergency messages from the CS facility and broadcasts transmissions containing both GPS navigational information and an emergency broadcast message; and GEMS-enabled user equipment that is capable of receiving and processing broadcast emergency messages. The system permits emergency messaging data to be superimposed on the existing GPS signal structure and delivered to users with GPS receivers capable of receiving the superimposed messaging data.