Abstract: A receiving device for receiving a satellite broadcast is disclosed which includes a receiver for receiving a sustaining satellite beam and a controller for switching the receiver to receive a high power content beam in response to a determination that the high power content beam can be received by the receiving device. A communication satellite can transmit the high power content beam to different geographical areas at different times. The sustaining beam allows the receiving device to remain synchronized with the communication satellite when the high power content beam is directed elsewhere. The sustaining beam may be a lower power beam. The determination that the high power content beam can be received may be performed based on information in the sustaining beam.

Abstract: A receiving device for receiving a satellite broadcast is disclosed which includes a receiver for receiving a sustaining satellite beam and a controller for switching the receiver to receive a high power content beam in response to a determination that the high power content beam can be received by the receiving device. A communication satellite can transmit the high power content beam to different geographical areas at different times. The sustaining beam allows the receiving device to remain synchronised with the communication satellite when the high power content beam is directed elsewhere. The sustaining beam may be a lower power beam. The determination that the high power content beam can be received may be performed based on information in the sustaining beam.

Abstract: The invention provides a content broadcasting system comprising a communications satellite and a satellite control arrangement for controlling the communications satellite to transmit a satellite broadcast signal. The satellite control arrangement is arranged to control the satellite to transmit the satellite broadcast signal to a first geographical area during a first time interval and to transmit the satellite broadcast signal to a second geographical area during a second time interval. The broadcast signal is not transmitted to the first geographical area during at least the second time interval and the broadcast signal is not transmitted to the second geographical area during at least the first time interval. This enables broadcast content to be provided to a large geographical area, while increasing the radio frequency spectrum efficiency of the system and minimising the continuous power consumption of the satellite required for the broadcast.

Abstract: The invention provides a communication system and method of communication. The communication system includes a satellite transmitter arranged to transmit a first signal to be received within a predefined geographical area by a satellite receiver, and a terrestrial transmitter arranged to transmit a second signal to be received within the predefined geographical area by a terrestrial receiver. The first and second signals share a common radio frequency band and the system is arranged such that the first signal is received at an antenna associated with the satellite receiver at a first angle from the horizontal, the first angle being greater than a second angle from the horizontal at which the second signal is received at the antenna. This enables the satellite receiver to distinguish the first signal from the second signal.

Abstract: A Time-Division Multiple Access (TDMA) synchronization system for a satellite relay system is provided by designating one of the ground stations a "Reference" station and arranging for a sinusoidal signal transmitted from the reference station to be received by other ground stations via the satellite and compared with their own sinusoidal synchronization signals after transmission to and from the satellite. The sinusoidal signal from the "Reference" station uses only a small proportion of the bandwidth of a satellite global beam transponder. Most of the traffic is transmitted to one or more spot beam transponders of the satellite. Each station derives from its symbol-rate clock a pulse indicating the start of each TDMA frame and a local synchronization sinusoidal signal at the frame repetition frequency. The phase of this local sinusoidal signal is such that its positive-going zero crossings coincide with the frame-start pulses.