Abstract: A dual role antenna assembly operable for use with GEO and LEO/MEO satellites has at least two curled inverted-F substantially omnidirectional antennas mounted on a ground plane. The antennas have asymmetrical gain patterns favoring certain sectors and are oriented such that the favored sectors of the different antenna face different directions. A controller selects the antenna for connection to an RF front-end in accordance with predetermined performance criteria.

Abstract: A wireless communication system includes one or more application servers communicating with remote terminals over connections established via cellular or satellite networks. The application servers are capable of switching between different cellular networks. A satellite gateway communicates with the remote terminals via satellite connections when cellular service is unavailable. The satellite gateway emulates a cellular network so that the application server sees the satellite gateway as another cellular network.

Abstract: A quadrifilar helix antenna system with a finite ground plane has a pair of bifilar helical elements extending upwardly from the finite ground plane. A symmetrical array of monopole elements surrounds the lower portion of the pair of bifilar helical elements in the near field so as to load the lower portion and thereby raise the phase center of the antenna to improve the circularly polarized far-field radiation at low elevation angles.

Abstract: In a satellite-based messaging system messages are exchanged between a ground station and mobile terminals over a wide geographic area covered by multiple satellite beams. Each beam contains one or more carrier frequencies. A message processing center is configured to provision a frame comprising a plurality of subframes to carry data over a forward link to the mobile terminals; hop between beams in the forward link and assign each subframe within a frame to a specific satellite beam; provision a transport medium in the form of virtual carriers each defined by one or more carrier frequency/beam hop combinations, wherein each virtual carrier is assigned a unique virtual carrier identifier; and notify the mobile terminals of carrier frequency/hop combinations for assigned virtual carrier identifiers.