Abstract: A communications unit determines that a wireless link between itself and a first communications network has degraded beyond acceptable limits (FIG. 2, 200). The communications unit signals a second, unsynchronized, communications network during a pause in outgoing voice (230) in order to acquire a channel and continue the call using the second network. When the second communications network indicates that sufficient resources are available, the communications unit transmits a Handover Trigger to the second network (FIG. 4, 400). In response to the Handover Trigger, the first and second communications network establish a connection between each other (460, 470). When the connection has been established, the communications unit receives a channel assignment (500) and continues the call using the resources of the second communications network.

Abstract: In a satellite communications system (100), system capacity is improved using a satellite (110 and 120) that includes a main mission antenna (MMA) (310 FIG. 3), antenna subsystem (320), and controller (350). Antenna subsystem (320) comprises a beamformer and associated software to optimize the beam shape and cell position with respect to the satellite's location. In one example, beam optimization is performed using a location based on latitude. Satellite (110 and 120) determines its spatial position and determines its latitudinal location based on this position information. The satellite determines the number of cells, the cell sizes, and the beam steering angles required at this latitudinal location. In other cases, beam optimization is performed using a location based on latitude and longitude, system loading, and satellite health and status.

Abstract: In a satellite communication system, beamforming is performed at baseband frequencies forming only beams which convey information. A received signal is applied to a downconverter (FIG. 1, 30), followed by a channelizer (50), and digital beamformer (60). The order of operations being reversed in order to generate a transmit beam. By performing the beamforming at baseband, the system can be allowed to form only those beams which convey information between a communications node and a subscriber. As a result, the system provides communication services to subscribers in a more cost-effective manner.

Abstract: A communications node (FIG. 1, 5) communicating with an individual subscriber unit (80) determines that a nominal-load condition exists. The communications node (5) then reduces the number of elements of the transmit and receive phased array antennas (10, 60) used to form receive and transmit communication beams. This reduces the amount of power required by the transmit and receive digital beamformers (15,50) which control the transmit antenna (10) and the receive antenna (60). In order to maintain the radio link with the individual subscriber unit (80), the communications node (5) adjusts the modulation characteristics of the radio link between the communications node (5) and the individual subscriber unit (80). This compensates for the loss of the antenna elements and thus reduces the power consumption of the transmit and receive phased array antennas (10, 60) under nominally-loaded conditions.

Abstract: The invention describes a method and system for the calibration of sectionally assembled phased array antennas. When a large, multi-sectioned phased array antenna on board a satellite (10, FIG. 1) is unfolded during deployment, an error in the alignment of a phased array antenna section (25) can cause an error in the pointing angle of the transmit antenna beam (50). A suitable receive antenna (80) receives a signal from the transmit antenna beam (50) which enables a processor unit (95, FIG. 2) to determine the required correction factor. The correction factor is then applied to the beam coefficients which control the beam of the phased array antenna section (25). Subsequent to a first measurment, the correction factor can be updated to minimize the impact of antenna element failures on the resulting antenna pattern.