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 satellite system employing time diversity and a single frequency network of terrestrial re-radiation stations is provided wherein each terrestrial re-radiation station inserts a delay into a terrestrial signal. The delay allows the time of arrival of the early time diversity signal at the center of terrestrial coverage to coincide with the arrival of the corresponding late time diversity signal, thereby improving hand-off between terrestrial and satellite signals at a receiver. The delay also adjusts for distance differences between each terrestrial re-radiation station and the satellite and between each station and the center of the terrestrial coverage region. This adjustment optimizes the TDM-MCM reception by synchronizing at the center of the SFN the phase of the MCM signals re-radiated from the re-radiating stations of the SFN.

Abstract: A digital broadcast system is provided which uses a satellite direct radio broadcast system having different downlink modulation options in combination with a terrestrial repeater network employing different re-broadcasting modulation options to achieve high availability reception by mobile radios (14), static radios and portable radios (14) in urban areas, suburban metropolitan areas, and rural areas, including geographically open areas and geographic areas characterized by high terrain elevations. Two-arm and three-arm receivers are provided which each comprise a combined architecture for receiving both satellite and terrestrial signals, and for maximum likelihood combining of received signals for diversity purposes. A terrestrial repeater is provided for reformatting a TDM satellite signal as a multicarrier modulated terrestrial signal. Configurations for indoor and outdoor terrestrial repeaters are also provided.

Abstract: A satellite payload processing system for processing an uplink signal consisting of a plurality of single-channel-per-carrier, frequency division multiple access carriers comprises a polyphase demultiplexer processor for separating the uplink signal into a time division multiplexed data stream of symbols. The polyphase demultiplexer processor presents the symbols corresponding to each of a plurality of carriers at respective ones of the frequencies in the uplink signal sequentially to an output of the polyphase demultiplexer processor. A phase shift keying demodulator and differential decoder demodulates the stream of symbols into corresponding time division multiplexed stream of digital baseband bits, which are then rate-aligned with respect to an on-board clock.

Abstract: An FDMA/TDM satellite-based digital broadcast system is used to provide digital maps and other types of data to users at remote locations. User selection of the desired data is achieved by monitoring the TDM downlink channels of the broadcast system in accordance with a predetermined schedule or until a specific identification code is detected. The user terminals are equipped with Global Positioning System (GPS) receivers which allow the positions of the users to be determined. Based on the user positions, the user terminals are able to convert general data to location-specific data tailored to the needs of the user. The general data may comprise a digital map covering a wide geographic area, and the location-specific data may comprise a map covering a portion of the geographic region where the user is located.

Abstract: An apparatus for switching symbols in parallel broadcast channels to time division multiplexed data streams comprises first and second ping-pong buffers. The first ping-pong buffer is configured to store a first plurality of the parallel broadcast channels therein. The second ping-pong buffer is operable to store a second plurality of the broadcast channels therein. The second plurality of broadcast channels arrive at the second ping-pong buffer prior to the arrival of the first plurality of broadcast channels at the first ping pong buffer. The apparatus also comprises a routing switch connected to the outputs of the first and second ping-pong buffers, and a first frame assembler connected to the routing switch. The routing switch controls the writing of the contents of the second ping-pong buffer to the first frame assembler.

Abstract: A satellite direct radio broadcast system is provided which assembles bits of broadcast programs into prime rate increments, several of which are assembled into a frame. Frames are divided into symbols which are demultiplexed into alternating ones of a plurality of prime rate channels. The prime rate channels are demultiplexed onto a corresponding number of broadcast frequencies for transmission to a satellite. The satellite payload switches the symbols into time division multiplexed (TDM) data streams. The receivers process the TDM streams using service control headers (SCHs) provided therein by broadcast stations. The SCHs facilitate transmission of different service components within broadcast channel frames, association of a primary broadcast channel with one or more secondary broadcast channels on a frame-to-frame basis, and the transmission of multiframe bit streams, or auxiliary data throughout a broadcast channel that are independent of a service, in contiguous or non-contiguous frames.

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 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 satellite direct radio broadcast system is provided which assembles bits of broadcast programs into prime rate increments, several of which are assembled into a frame. Frames are divided into symbols which are demultiplexed into alternating ones of a plurality of prime rate channels. The prime rate channels are demultiplexed onto a corresponding number of broadcast frequencies for transmission to a satellite. The satellite payload switches the symbols into time division multiplexed (TDM) data streams. The receivers process the TDM streams using service control headers (SCHs) provided therein by broadcast stations. The SCHs facilitate transmission of different service components within broadcast channel frames, association of a primary broadcast channel with one or more secondary broadcast channels on a frame-to-frame basis, and the transmission of multiframe bit streams, or auxiliary data throughout a broadcast channel that are independent of a service, in contiguous or non-contiguous frames.

Abstract: A satellite direct radio broadcast system is provided which assembles bits of broadcast programs into prime rate increments, several of which are assembled into a frame. Frames are divided into symbols which are demultiplexed into alternating ones of a plurality of prime rate channels. The broadcast channel frame is encoded for forward error correction (FEC) using an R-½ Viterbi coder or a R-¾ Viterbi coder, depending on the desired bit rate for a time division multiplexed (TDM) stream comprising the broadcast channel. A broadcast station is configured to format FEC-encoded broadcast channel frames into TDM frames when transmission of the TDM frames by a transparent payload on-board a satellite is used.

Abstract: A system for managing a satellite and a number of broadcast stations, which generate programs for transmission to remote radio receivers on broadcast channels via the satellite, comprises a satellite control system for controlling the attitude and orbit of the satellite and on-board processing of the programs uplinked to the satellite. A broadcast control system is connected to the satellite control center and to the broadcast stations. The broadcast control system assigns selected ones of the broadcast channels to service providers desiring to uplink at least one of the programs to the satellite, to store channel data relating to the assignments of the broadcast channels and provide the channel data to the satellite control system, and to bill the service providers according to the number of the broadcast channels assigned thereto.

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: An FDMA/TDM satellite-based digital broadcast system is used to provide digital maps and other types of data to users at remote locations. User selection of the desired data is achieved by monitoring the TDM downlink channels of the broadcast system in accordance with a predetermined schedule or until a specific identification code is detected. The user terminals are equipped with Global Positioning System (GPS) receivers which allow the positions of the users to be determined. Based on the user positions, the user terminals are able to convert general data to location-specific data tailored to the needs of the user. The general data may comprise a digital map covering a wide geographic area, and the location-specific data may comprise a map covering a portion of the geographic region where the user is located.

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.

Abstract: A satellite clock system in which the frequency of the onboard satellite clock, which is implemented as a relatively high uncertainty voltage-controlled oscillator, is corrected in accordance with a high-stability, low-uncertainty terrestrial clock. Metering bursts are transmitted from the earth station to the satellite where portions of the metering bursts are truncated due to misalignment between the bursts and the synchronization windows timed by the onboard oscillator of the satellite. The patterns of the received bursts which are re-transmitted by the satellite are compared with a stored pattern and a phase shift value determined in accordance with the number of incorrect comparisons. The phase error measurement value is utilized to control a programmable divider connected between the high-stability, low-uncertainty oscillator and the burst transmitter to thus provide a short-term correction.