Abstract: A group radio communication system (20) includes a group controller (24) which communicates through a satellite-based packet switched data communication network (22) to converters (28). The converters (28) are located within radio coverage areas (36) of various radio sub-networks (26). Each radio sub-network (26) includes a base station (32), controller (30) and any number of subscriber radios. The controllers (30) manage point-to-multipoint communications between subscriber radios (34) within their radio sub-networks (26), and the group controller (24) manages point-to-multipoint communications between radio sub-networks (26). The converters (28) translate between protocols (38, 38′) established for communications within specific radio sub-networks (26) and a protocol (56) established for communication over the packet switched data communication network (22). The group controller (24) duplicates and distributes packets (118) originating in one radio sub-network (26) to other radio sub-networks (26).

Abstract: A point-to-multipoint (PTM) communication system (20) includes a cellular radio infrastructure (22) having base stations (32) implemented in satellites (34) placed in low earth orbits (38). PTM subscriber radios (24) share common cellular radio infrastructure (22) multipoint channels (52) to engage in a common PTM communication session while the cellular radio infrastructure (22) also conveys point-to-point communications. A group control computer (28) constructs a channel list (126) which is downloaded to PTM subscriber radios (24). The channel list (126) identifies multipoint channels (52) and indicates when and where the channels (52) are active. Without emitting transmissions to the cellular radio infrastructure (22), PTM subscriber radios (24) autonomously switch to new multipoint channels (52) in response to their current time and location and the channel list (126).

Abstract: A communication system (10) includes a group call controller (GCC) (26) for use in establishing, maintaining, and controlling the provision of group call services within the communication system (10). To initiate a group call session for a particular subscriber group, a group call request is delivered to the GCC (26) that identifies the desired group. Upon receipt of the request, the GCC (26) coordinates the delivery of group call notification to the members of the identified group to notify the members of the initiation of the group call session and to identify to the members a physical communication channel (36) to be used by each member to participate in the group call. Upon receipt of the notification, the group members each tune to a corresponding physical communication channel (36) and are immediately made part of the group call. The group members are not required to make any transmissions on the physical channel (36) to participate in the group call.

Abstract: A point-to-multipoint (PTM) radio communication system (20`) includes a cellular radio infrastructure (22) having base stations (32) implemented in satellites (34) placed in low earth orbits (38). PTM subscriber radios (24) share common cellular radio infrastructure (22) multipoint channels (52) to engage in a common PTM communication session while the cellular radio infrastructure (22) also conveys point-to-point communications. The shared multipoint channels (52) are operated in according with different protocols to deliver system information to PTM subscriber radios (24), to provide access to PTM subscriber radios (24), to provide synchronization, to originate a PTM monolog and to be one of many targets of a PTM monolog.

Abstract: A target detection method collects spatial data relating to a target at an instant in time. This data is converted to an appropriate coordinate system, such as Cartesian coordinates. A centroid of the target is determined. Predictions of the centroid are made at subsequent time intervals. The predicted centroids are averaged with the current determined centroids. When the closest centroid position of the target is determined, an indication is provided for detonating the warhead of a projectile.