Abstract: A satellite direct audio broadcast system includes a plurality of fixed-rate, uniform, frequency division multiple access (“FDMA”) uplinks and a time division multiplexed (“TDM”) downlink. Source audio channels may be divided among and transmitted through a selectable number of fixed-rate uplinks so as to have selectable audio quality at the receiver. Fixed-rate FDMA uplinks include information designating related channels as containing related source information. On-board the satellite baseband processing selects uplink information channels for inclusion into none, one or multiple TDM downlinks. Transmitted audio information may be scrambled, and authorization downloaded to receivers to permit descrambling for paid subscription service.

Abstract: A rate alignment apparatus for a satellite includes an on-board clock, an input switch, an output switch and a ping-pong buffer pair including first and second buffers and connected to the input switch and the output switch. The first and second buffers receive a stream of digital baseband symbols recovered from an uplink signal depending on the operation of the input switch and the output switch. The first buffer of the buffer pair receives the bits in accordance with an uplink clock rate obtained from the uplink signal. The second buffer of the buffer pair substantially simultaneously empties the stored contents thereof to a third buffer in accordance with the on-board clock, the operations of the first and second buffers being reversed upon actuation of the input switch and the output switch. First and second correlators generate a spike when a header denoting when a frame in the stream of baseband symbols is detected.

Abstract: A method of receiving one of a plurality of prime rate channels transmitted via downlink signals from a satellite comprises the step of demodulating downlink signals into a baseband time division multiplex bit stream comprising frames generated by the satellite. Each of the frames comprises a plurality of time slots, each of the time slots having a set of symbols. Each symbol in the set of symbols corresponding to a respective one of the prime rate channels occupies a similer symbol position in each of the time slots. The method further comprises the steps of locating the frames in the bit stream using a master frame preamble inserted therein by the satellite, and retrieving from the set of symbols in each of the time slots of at least one of the frames the symbols that correspond to one of the prime rate channels.

Abstract: A receiver unit for receiving a time division multiplexed downlink data stream from a satellite comprises a phase shift keying demodulator for demodulating the downlink data stream into a stream of symbols. The downlink data stream comprises slots and is provided with a predetermined number of prime rate channels in respective ones of the slots by the satellite. A correlator is connected to the demodulator for locating and synchronzing to a master frame preamble inserted in the stream of symbols by the satellite. A demultiplexer is connected to the correlator for locating a time slot control channel in the stream of symbols. The time slot control channel is inserted into the stream of symbols by the satellite to identify which of the slots comprises the prime rate channels corresponding to each of a plurality of broadcast service providers. An input device is provided to allow an operator to select one the broadcast service providers and to provide an output signal to the demultiplexer.

Abstract: A method for formatting broadcast data for transmission on an uplink carrier to a satellite is provided which combines data streams from a number of service providers into parallel streams on uplink carriers to allow for efficient and economic use of the space segment. Bits in a program are assembled into a first number of prime rate increments having uniform and predetermined rates. A frame having a predetermined duration is generated which comprises each of the prime rate increments and a frame header. The frame is divided into symbols, each of the symbols comprising a predetermined and consecutive number of the program bits. The symbols are demultiplexed into a second number of parallel prime rate channels, with the symbols being provided in ascending order across the prime rate channels so as to separate consecutive symbols. The prime rate channels each comprise a prime rate channel synchronization header for recovering the prime rate channels at said remote receiver units.

Abstract: A satellite direct audio broadcast system includes a plurality of fixed-rate, uniform, frequency division multiple access ("FDMA") uplinks and a time division multiplexed ("TDM") downlink. Source audio channels may be divided among and transmitted through a selectable number of fixed-rate uplinks so as to have selectable audio quality at the receiver. Fixed-rate FDMA uplinks include information designating related channels as containing related source information. On-board the satellite baseband processing selects uplink information channels for inclusion into none, one or multiple TDM downlinks. Transmitted audio information may be scrambled, and authorization downloaded to receivers to permit descrambling for paid subscription service.