HK1024792A - Direct satellite digital broadcast system - Google Patents

Description

Satellite direct broadcast system

no marking

The present invention relates to satellite broadcast systems, the formatting and processing of broadcast data by satellite payloads and remote radio receivers.

More than about 40 billion people now commonly indicate dissatisfaction with the poor sound quality of short wave radio broadcasts, and also with the limited coverage of Amplitude Modulation (AM) and Frequency Modulation (FM) terrestrial radio broadcast systems. These populations are located mainly in africa, central and south america and asia. Therefore, it is necessary to establish a satellite-based direct radio broadcast system for transmitting signals such as voice, data and video to low-consumer receivers.

Many satellite communication networks have been developed for commercial and military use. However, these satellite communication systems have not been proposed to multiple, independent broadcast service providers; a flexible and economical approach to spatial coverage is provided, and no provision is made for consumers to receive high quality radio signals using inexpensive user-owned radio receivers. There is therefore a need for a provider of such services that has direct access to the satellite, selected according to the number of space segments it purchases and uses. In addition, there is a need for a low cost radio receiver that is capable of receiving time division multiplexed, downstream bit streams.

In accordance with one aspect of the present invention, a receiving apparatus for receiving a time division multiplexed, downlink data stream from a satellite includes a phase shift keying demodulator for demodulating the downlink data stream into a symbol stream. The downlink data stream includes slots, and the number of primary rate channels corresponding to the slots is selected to be predetermined by the satellite. A correlator is coupled to the demodulator for locating and synchronizing with a main frame preamble inserted into the symbol stream by the satellite. A demultiplexer is coupled to the correlator for setting a time slot control channel in the symbol stream. The time slot control channel is inserted into the symbol stream by the satellite to determine which time slot contains a prime rate channel corresponding to each and every one of the plurality of broadcast service providers. An input device is provided to enable an operator to select one of the broadcast service providers and to send an output signal to the demultiplexer. The demultiplexer uses the time slot control channel and the output signal to select a number of prime rate channels from the data stream.

In accordance with another aspect of the invention, the correlator may operate in a look-up mode, a synchronous operation mode, and a prediction mode.

According to another aspect of the invention, a method for receiving a multiplexed bit stream from a satellite for transmission of one of a plurality of prime rate channels via a downlink signal includes a step of demodulating the downlink signal into a baseband time division multiplexed bit stream including frames generated by the satellite. Each frame includes a plurality of slots, and each slot has a set of symbols. Each symbol in a set of symbols corresponds to a respective one of a plurality of prime rate channels occupying a similar symbol position in each time slot. The method further comprises the step of locating the frame in the bitstream using a primary frame preamble introduced by the satellite: and retrieving symbols corresponding to one of the prime rate channels from a set of symbols in each slot of the at least one frame.

According to one aspect of the present invention, a method is provided for formatting broadcast data for transmission to a satellite on an upstream carrier, which combines data streams from a number of service providers into parallel streams on the upstream carrier, thereby allowing efficient and economical use of space segments. Bits in the program are assembled into a first number of primary rate increments of a uniform and preset rate. A frame having a predetermined duration is generated that includes a prime rate delta and a header of the frame. The frame is divided into symbols, each symbol comprising a predetermined, consecutive number of program bits. The symbols are demultiplexed into a second number of parallel prime rate channels, the symbols having changeable symbols of the prime rate channels, thereby dividing the successive symbols. Each prime rate channel includes a prime rate channel synchronization header for recovering the prime rate channel at the remote control receiver device. At this point, the prime rate channels are demultiplexed and placed on a corresponding number of uplink carrier frequencies for broadcast transmission.

According to one aspect of the invention, the prime rate increment may be divided into two segments for transmitting two different types of data for special purposes.

According to another aspect of the invention, two tandem coding methods and an interleaved coding method are used to encode frames for forward error preventive correction.

In accordance with one aspect of the invention, the system is used to manage satellites and a plurality of broadcast stations for programming, broadcast from broadcast channels via the satellites to remote radio receivers. The system comprises a satellite control system configured to generate control signals for controlling the attitude and orbit of the satellite; command signals are generated for controlling the processing in the field of programs transmitted upstream to the satellite. At least one of the telemetry, band and control devices is connected to a satellite control center to maintain communication with the satellite to provide control signals and data processing signals thereto. The system also includes a broadcast control system coupled to the satellite control center and the broadcast station. The broadcast control system may operate the following services: selecting channels from the broadcast channels for provision to a service provider desiring at least one program for the uplink, storing channel data relating to the broadcast channel assignments; the satellite control system is provided with channel data and billed to the provider based on the number of broadcast channels assigned to it. The broadcast control system provides a service provider with a wide variety of options including the number of said broadcast channels reserved for uplink transmission; the date and time of the reserved broadcast channel and the number of satellite-related beams used for downlink transmission are used. The broadcast control system informs the satellite control system which beam is to be used and the satellite control system generates corresponding data processing signals to schedule the program routing beam. The broadcast control system may also indicate to the broadcast station on which dates and times of day the use of the assigned broadcast channel is terminated after the broadcast channel is no longer reserved.

According to another aspect of the invention, the broadcast control station may be programmed to perform a segmentation process on the broadcast channel, which may make more efficient use of the segments of space.

According to another aspect of the invention, the transmitted signal is digital, thereby further enhancing the immunity to interference in the presence of noise during transmission. The digital signal provides flexibility to provide full range of services in the future.

According to an aspect of the invention, a switch symbol device for time division multiplexed data streams in parallel broadcast channels comprises first and second ping-pong buffers. The first ping-pong buffer is configured to store a first portion of a plurality of parallel broadcast channels. A second ping-pong buffer may be used to store a second portion of the plurality of broadcast channels. The second portion of the plurality of broadcast channels arrive at the second ping-pong buffer before the first portion of the plurality of broadcast channels arrive at the first ping-pong buffer. The apparatus further includes a selective routing switch coupled to the output of the first and second ping-pong buffers, and a first frame assembler coupled to the selective routing switch. The selective routing switch controls the writing of the buffered contents of the second ping-pong operation into the first frame assembler.

According to another aspect of the invention, the contents of the ping-pong buffer can be switched to two or more frame assembler's corresponding time slots.

In accordance with one aspect of the invention, a satellite payload processing system for processing a single channel per carrier with frequency division multiple access uplink signals includes a polyphase demultiplexer processor for separating the uplink signals into time division multiplexed streams of symbols. The polyphase demultiplexer processor representing symbols corresponding to each of the respective carrier frequencies in the uplink signal; and the uplink signal is sequentially coupled to the output of the polyphase demultiplexer processor. A phase shift keying demodulator is coupled to the output of the polyphase demultiplexer processor for demodulating the symbol stream into a corresponding time division multiplexed digital baseband bit stream.

According to yet another aspect of the invention, a frequency alignment apparatus for a satellite includes an on-board clock, input switches, output switches, a pair of ping-pong buffers including a first buffer and a second buffer coupled to the input switches and the output switches, respectively. The first and second buffers receive the digital baseband symbol streams recovered from the uplink signal in response to operation of the input and output switches. The first buffer in a buffer pair receives bits according to an uplink clock rate derived from the uplink signal. The second buffer of the pair substantially simultaneously drains all of the stored content into the third buffer in response to the on-board clock, and the operation of the first and second buffers in turn enables the input switch and the output switch. First and second correlators are respectively associated with said first and second buffers to generate spikes of pulses in response to detection of a frame in the baseband symbol stream, and the buffer pairs operate to continue writing the baseband symbol stream into one of the buffer pairs until the spikes of pulses occur. The input switch and the output switch are switched to their opposite states and the first and second buffered uplink signals are read to the output terminal according to the satellite-borne clock rate. A sync pulse oscillator is coupled to the first and second correlators to produce a smooth pulse for each symbol read to the output. The counter is connected to the oscillator to count the stationary pulses. The number of bits may be added or subtracted to the header of the data stream depending on the value of the counter.

These and other features and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the accompanying drawings. Which form a part of the original intended disclosure. They include:

fig. 1 is a schematic diagram of a direct satellite broadcast system established according to an embodiment of the present invention.

Fig. 2 is a flow chart depicting a sequence of end-to-end signal processing operations in the system described in accordance with the embodiment of the present invention in fig. 1.

Fig. 3 is a schematic block diagram of a broadcast ground station constructed in accordance with an embodiment of the invention.

Fig. 4 is a schematic diagram illustrating broadcast sector multiplexing according to an embodiment of the present invention.

Fig. 5 is a schematic block diagram of processing a payload on a satellite according to an embodiment of the present invention.

Fig. 6 is a schematic diagram illustrating the demultiplexing and demodulation process at a satellite according to an embodiment of the present invention.

Fig. 7 is a schematic diagram illustrating rate calibration on a satellite according to an embodiment of the present invention.

Fig. 8 is a schematic diagram illustrating conversion and time division multiplexing operations on a satellite according to an embodiment of the present invention.

Fig. 9 is a schematic block diagram of a radio receiver constructed in accordance with an embodiment of the present invention and used in the system depicted in fig. 1.

Fig. 10 is a diagram illustrating receiver synchronization and demultiplexing operations according to an embodiment of the present invention.

FIG. 11 is a diagram illustrating synchronization and multiplexing operations at a receiver to recover a coded broadcast channel, in accordance with an embodiment of the present invention, an

Fig. 12 is a schematic diagram of a system for managing satellites and broadcast stations according to an embodiment of the invention.

SUMMARY

In accordance with the present invention, a satellite-based radio broadcast system 10 broadcasts programming from a number of different broadcast stations 23a and 23b (hereinafter collectively referred to as 23) via a satellite 25, as shown in fig. 1. The subscribers are equipped with radio receivers, generally headed 29, each designed to receive one or more Time Division Multiplexes (TDM) modulated as 1.86 mega symbols per second (Msym/s) L-band carriers 27 downlink from a satellite 25. The subscriber radio receiver 29 is designed to demodulate and demultiplex the TDM carrier to recover the bits constituting the digital information content or to transmit the program from the broadcast channel of the broadcasting station 23. The broadcast station 23 and satellite 25 are configured to format the uplink and downlink signals in accordance with embodiments of the present invention to provide improved reception of broadcast programming using a relatively low cost radio receiver. The radio receiver may be a mobile device 29a mounted on the transport vehicle, such as a handheld device 28b or a processing terminal 29c with a display.

Although only one satellite is shown for illustration in fig. 1. The system 10 preferably includes 3 geostationary satellites 25a, 25b and 25c (fig. 12); the configuration uses a frequency band of 14670 to 1492 mhz. This band has been allocated to Direct Audio Broadcasting (DAB) of a Broadcast Satellite Service (BSS). The broadcast station 23 preferably uses the uplink 21 in the X-band, that is from 7050 to 7075 mhz. Each satellite 25 is preferably configured to operate on three downlink spot beams headed 31a, 31b and 31 c. Each beam covers approximately 1400 kilometres square in the power distribution network, i.e. 4 decibels (dB) from the centre of the beam and 8dB within 2800 kilometres square in the power distribution network. The beam center gain margin can reach 14cB, depending on the receiver gain to temperature ratio of 13 dB/K.

With continued reference to fig. 1, the uplink signal 21 generated from the broadcast station 23 is modulated from a Frequency Division Multiple Access (FDMA) frequency channel of a ground station 23, the ground station 23 preferably being located within the earth's line of sight of a satellite 25. Each broadcast station 23 preferably has the ability to uplink directly from its own device to one of a plurality of satellites and place one or more 16 kilobits per second (kbps) primary rate increments on a single carrier. The use of FDMA channels on the uplink allows for a significant reduction in power consumption by sharing segments of space between multiple independent broadcast stations 23, thereby also reducing the cost of the uplink earth stations 23. A Prime Rate Increment (PRI) of 16 kilobits per second (Kbps) is preferably a building block of most substrates or base units used in the system 10, which is advantageous for channel size and can be combined to achieve higher bit rates. For example, prime rate increments can be combined to create program channels with bit rates up to 128kbps, which is close to compact disc record quality sound or to multimedia broadcast programs containing image data, for example.

Each satellite 25 may be airborne to convert at the baseband level between FDMA channels on the uplink and multi-channel/time division multiplexed (MCPC/IDM) channels on each carrier downlink. As will be described in greater detail below, the prime rate channel transmitted by the broadcast station 23 is demultiplexed at the satellite 25 into individual 16kbps baseband signals. The individual channels are then routed to one or more downstream beams 31a, 31b and 31c, with each downstream beam being a single TDM stream for each carrier signal. Such a baseband processing may provide a high level of channel control with respect to uplink frequency allocation and channel routing between uplink FDMA and downlink TDM signals.

The end-to-end signal processing that occurs in the system 10 will be described with reference to fig. 2. The system components responsible for end-to-end signal processing are described in further detail below with reference to FIGS. 3-11. As shown in fig. 2, the audio signals from the sound sources are preferably encoded using MPEG2, layer 53 (26 program blocks), for example, at the broadcast station 23. The digital information assembled by the broadcast service provider at the broadcast station 23 should preferably be formatted in 16kbps increments or PRIs, where n is the number of PRIs purchased by the service provider (i.e., n x 16 kbps). The digital information is then formatted into a broadcast channel frame having a Service Control Header (SCH) (block 28), as described in further detail below. The periodic frames in system 10 preferably have a periodic interval of 432 milliseconds. Each frame is preferably specified to be n × 224 bits for SCH, so that the bit rate becomes approximately n × 16.519 kbps. Since the pseudo random bit stream is added to the SCH, each frame is then scrambled by adding the pseudo random bit stream to the SCH. A message control for changing the frequency pattern with a key allowing for coding. The bits in the frame are then encoded for early error correction (FEC); preferably, two tandem coding methods are used, such as the Retz-Solomon method, followed by frequency interleaving, and then convolutional coding (e.g., interleaving into trellis convolutional coding described by Holter) (see block 30). The coded bits within each frame correspond to each Primary Rate Increment (PRI). Sequentially, re-distinguished or demultiplexed into n parallel Prime Rate Channels (PRCs) (block 32). To achieve recovery of each PRC, a synchronization header of the PRC should be set. Each of the n PRCs is then differentially encoded and then modulated onto an Intermediate Frequency (IF) carrier frequency using, for example, quadrature phase shift keying (block 34). The n PRC IF carrier frequencies form the broadcast channel of the broadcasting station 23 and are converted to the X band for transmission to the satellite 25 as indicated by arrow 36.

The carriers coming out of the broadcasting station 23 are carriers of single channel/frequency division multiple access (SCPC/FDMA) per carrier. On each satellite 25, the SCPC/FDMA carrier is received, demultiplexed and modulated to recover the prime rate carrier (see block 38). The PRC baseband channel is recovered by the satellite 25 and is subjected to a frequency alignment function to compensate for the difference between the on-satellite clock rate and the clock rate of the carrier of the main rate channel received at the satellite (block 40). The demultiplexed and demodulated digital streams from the PRC are provided to the TDM frame assembly programmer using routing and switching elements. The PRC digital stream is routed from the demultiplexing and demodulation equipment on the satellite 25 to the TDMA frame assembler, which controls the switching sequence device on the satellite via command connections from the ground station (e.g., in fig. 12 the satellite control center 23b controls each operating area). Three TDM carriers may be established corresponding to the 3 satellite beams 31a, 31b and 31c (block 42). After QPSK modulation, the three TDM carriers are upconverted to L-band frequencies, as indicated by arrow 44. The radio receiver 29 is configured to receive any one of the three TDM carriers and to demodulate the received carrier (block 46). The radio receiver 29 is designed to synchronize the TDM bit stream with the main frame preamble provided during processing by the satellite 5 on board. The PRC can also be demultiplexed from the TDM frame using a Time Slotted Control Channel (TSCC). The digital stream is re-multiplexed into the FEC encoded PRC format described above and with reference to block 30 (block 50). The FEC processing preferably includes decoding using a viterbi trellis decoder, e.g., de-interleaving; then, the original broadcast channel including the channel of nx16 kbits/sec and SCH is restored using the reed solomon decoding. The nx16 kbit/s segment of the broadcast channel is provided to an MPEG2.5 layer 3 source decoder for transitioning back to the audio state. According to the present invention, efficient output is achieved by a very low cost broadcast radio receiver 27 because the processing and TDM formatting described above are coupled to the broadcast station 23 and satellite 25 (see block 52). Uplink multiplexing and modulation

Referring now to fig. 3, a signal processing method for converting a data stream from one or more broadcast stations 23 into a parallel data stream for transmission to a satellite 25 will be described. For the sake of explanation, 4 program information sources are employed: 60. 64, 68 and 72. Both sources 60 and 64 or 68 and 72 have been encoded and transmitted together as a single program or service. A description will be given of a program coding method involving the combination of sound sources 60 and 64, the signal processing of a program containing digital information from sources 68 and 72 being the same.

As previously described, the broadcast station 23 aggregates information from one or more information sources 60 and 64 into specific programs, which are sent into broadcast channels, characterized by 16kbps (kilobits per second) increments. These increments are referred to as prime rate increments or PRIs for short, so the bit rate carried in a broadcast channel is n x 16kbps (kilobits per second), where n refers to the number of PRIs used by that particular broadcast service provider. In addition, each 16kbps PRI can be further divided into two 8kbps segments, routed and switched together by the system 10. The mechanism by which the same PRI can carry two different services is segmented, e.g., a data stream with a low bit rate voice signal or two low bit rate language channels for two different languages, etc. The number of PRIs is preferably predetermined, that is, set according to program codes. However, the number n is not a physical limit of the system 10. The value of n is generally set according to the service concerned, such as the cost of a single broadcast channel; whether the service provider is willing to pay a fee. In fig. 3, there are 4 for n of the first broadcast channel 59 of the sources 60 to 64. In the depicted embodiment, 6 are set for the value of n for broadcast channel 67 for sources 68 and 72.

As shown in fig. 3, more than one broadcast service provider may enter a broadcast station 23. For example, a first service provider may generate broadcast channel 59; and a second service provider may generate broadcast channel 67. The signal processing method described herein according to the present invention allows data streams to be transmitted from different broadcast service providers to the satellite in parallel data streams, which reduces broadcast costs for the service providers and makes maximum use of space segments. The broadcasting station can realize components with less power consumption due to the efficiency of maximally utilizing the space section, thereby reducing the expenses. For example, the antenna of the broadcasting station 23 may use a very small aperture output (VSAT) antenna. The payload on the satellite requires less memory, less processing power, and therefore less power to be consumed, thereby reducing the weight of the payload.

As shown in fig. 4, broadcast channel 59 or 67 is characterized by having a 432 millisecond period selected for ease of use with an MPEG source encoder as will be described below, however the frame pairs in system 10 can be set at different predetermined values. If the period duration is 432 milliseconds, a PRI of 16 kbits/sec requires 6912 bits per frame of 16,000 x 0.432 seconds per frame. As shown in fig. 4, the broadcast channel thus contains these 16 kbit/per second PRI values n, which are transmitted as a group in frame 100. As will be explained below, the bits are frequency shifted to enhance demodulation at the radio receiver. This frequency change operation provides a function of changing the service provided to a password transmission according to the opinion of the service provider. Each frame 100 is specified to be no more than n x 224 bits for the Service Control Header (SCH), resulting in a total of n x 7136 bits per frame and a bit rate of n x (16,518 + 14/27) bits per second. The purpose of the SCH is to transmit data to each radio receiver that has been tuned to receive a broadcast channel 59 or 67, in order to control the reception mode of various multimedia services; to display data and images; to send critical information for decryption, to address a particular receiver, and other capabilities.

With continued reference to fig. 3, sources 60 and 64 are encoded with MPEG2.5 layer encoders 62 and 66, respectively. The two sources are then summed together by means of a combiner 76 and then processed by the processor of the broadcast station 23 to provide the encoded signal in frames of 432 milliseconds periods, that is to say n × 7136 bits per frame as already indicated by the processing module 78 in fig. 3. The modules indicated on the broadcast station in fig. 3 correspond to programmed modules executed by the process and associated hardware, such as digital memories and encoder circuits. The bits within the frame 100 are then encoded, protected for FEC using Digital Signal Processing (DSP) software, using special integrated circuits (ASICs) and custom large scale integrated circuit chips for both methods of serial encoding. First, the reed solomon encoder 80a operates to generate bits within the 255 bit frame 100 from the 223 bits input to the encoder for re-encoding in accordance with a known interleaving scheme, as shown by reference numeral 80 b. Interleaving may provide further protection against burst errors encountered in transmission, as this approach may spread the corrupted bits over several channels. With continued reference to the module 80 in process, a known convolutional encoding scheme of constraint length 7 may be employed, using a Viterbi encoder 80 c. The viterbi encoder 83c may generate two output bits for each input bit, producing a net result of 16320 FEC-encoded bits per frame per incremental change of 6912 bits per frame used in the broadcast channel 59. Thus, each FEC-encoded broadcast channel (e.g., channel 59 or 67) contains n × 16320 information bits that have been encoded, rearranged, and re-encoded, such that the original broadcast PRI of 16 kbits/sec is not considered identical. However, the FEC encoded bits are organized according to the original frame structure of 432 milliseconds. The total error-protection coding rate is (255/223) × 2 ═ 2 + 64/223.

With continued reference to fig. 3, the n × 16320 bits of the FEC encoded broadcast channel frame are subdivided or demultiplexed into n parallel prime rate channels using the channel distributor 82, each channel scaled to 8160 sets of two-bit symbols to deliver 16320 bits. This process will be further explained in fig. 4. The broadcast channel 59 is characterized by a 432ms frame 100 with a SCH 102. The remaining portion 104 of the frame includes a PRI of 16 kbits/sec. For each of the n PRIs, it amounts to 6912 bits per frame. Broadcast channel 103 encoded with FEC may have its reed solomon 255/223 concatenated as described below, interleaved and convolutionally encoded with FEC1/2 as previously described, and coupled to module 80. As previously described, the FEC encoded broadcast channel frame 106 contains n × 16320 bits, corresponding to 8160 sets of two bits of code bits. For ease of illustration, each symbol defines a reference numeral 108. The symbols through PRC110 are designated in the manner already described in fig. 4 in accordance with the present invention. The symbols will therefore be spread in terms of time and frequency, which will further reduce the errors of the radio receiver caused during the broadcast. The service provider of broadcast channel 59 has purchased the PRC, while the service provider of broadcast channel 67 has purchased 6 PRCs. Fig. 4 illustrates a first broadcast channel 59 and designated symbols 114 for PRCs 110a, 110b, 110c, and 110d, respectively, across n-4. To perform recovery for each set of two-bit symbols 114 set at the receiver, a PRC synchronization header or preamble 112a, 112b, 112c, and 112d is placed in front of each PRC, respectively. The PRC sync header (hereinafter referred to as a reference numeral 112) contains 48 symbols. The PRC sync header 112 is placed in front of each group of 8160 symbols, thus increasing the number of symbols per 432 millisecond frame to 8208 symbols. Thus, the symbol rate becomes 8208/0.432, which is equal to 19000 kilo symbols per second (Ksym/s) per PRC 110. The 48-symbol PRC preamble 112 is used primarily for synchronization of the PRC clock of the radio receiver to recover symbols from the downlink satellite transmission 27. At the on-board processor 116, the PRC preamble is used to absorb the time difference between the arriving uplink signal symbol rate and the TDM stream on the satellite for switching signals and downlink convergence. Each of the 48 PRC symbols is incremented by a "0", decremented by a "0" or neither during the use of frequency collimation on the satellite. Thus, the PRC preamble carried on the TDM downlink has 47, 48 or 49 symbols as determined by the frequency alignment process. As shown in fig. 4, symbol 114 designates for consecutive PRCs in a round-robin fashion; as such, symbol 1 is designated for PRC110 a; symbol 2 is designated for PRC110 b; symbol 3 is designated for PRC110 c; symbol 4 is designated for PRC110 d; symbol 5 is designated for PRC110e, and so on. This PRC demultiplexing process is performed by the processor of the broadcast station 23 and is shown in fig. 3 as a channel allocation (DEMUX) module 82.

The PRC channel preamble is used to mark the beginning of the PRC frames 110a, 110b, 110c and 110d of the broadcast channel 59 using the preamble module 84 and the adder module 85. The n PRCs are differentially encoded sequentially and then QPSK modulated onto an Intermediate Frequency (IF) carrier frequency using a bank of QPSK modulators 86, as shown in fig. 3. 4 sets of QPSK modulators 86a, 86b, 86c, and 86d are used for PRCs 110a, 110b, 110c, and 110d, respectively, for broadcast channel 59. Thus, a total of 4 PRC IF carrier frequencies make up 3 broadcast channels 59. Each of the 4 carrier frequencies is upconverted in the X-channel to a specified frequency location by an upconverter 88 for transmission to the satellite 25. The upconverted PRC is then transmitted through an amplifier 90 to antennas (e.g., VSAT)91a and 91 b.

According to the invention, the broadcasting station 23 uses a transmission method that combines n single-channel-per-carrier multiplexing and frequency division multiple access (SCPC/FDMA) carriers into the uplink signal 21. The SCPC/FDMA carriers are separated on a grid of center frequencies, preferably 38000 hertz (Hz) from each other, and organized in groups of 48 adjacent center frequencies or carrier channels. The organization of the 48 carrier channels into groups is useful for use on the satellite 25 in preparation for multiplexing and demodulation. The different groups of 48 carrier channels do not have to be connected to each other. The carriers associated with a particular broadcast channel (i.e., channel 59 or 67) need not be contiguous within a group of 48 carrier channels and need not be allocated within the same group of 48 carrier channels. The transmission method illustrated in conjunction with fig. 3 and 4 allows flexibility in selecting frequency locations, optimizes the ability to fill the available spectrum and avoids interference with users sharing the same radio spectrum.

The system 10 is advanced and lays the foundation for the ability of broadcasters or broadcast service providers to multiply, with which it is relatively easy to establish and transmit broadcast channels of different bit rates to the receiver 29. Typical broadcast channel increments or PRIs preferably employ 16, 32, 48, 64, 80, 96, 112 and 128 kbits/sec. The radio receiver can relatively easily determine the different bit rate broadcast channels to tune, see the radio receiver processing described in fig. 4. Accordingly, the size and cost of the broadcasting station can be designed to accommodate the constraints of the power rating and financial resources of the broadcaster. A financially inefficient broadcaster may be equipped with a small VSAT terminal that requires relatively little power to broadcast 16 kbytes/sec of programming to its countries, which is sufficient to transmit languages and music of much better quality than short wave radio. On the other hand, a broadcaster with substantial furniture and high technology needs to broadcast stereo quality with a slightly larger antenna at 64 kbytes of power per second; with further increased power ratings, near Compact Disc (CD) stereo quality can be broadcast at 96 kilobytes/second; the full disc stereo quality is broadcast at 128 kbytes/sec.

To achieve many advantages, the frame size, SCH size, preamble size, and PRC length will be described in conjunction with fig. 4. The processing manner of describing the broadcasting station in conjunction with fig. 3 and 4 is not limited to these numerical values. When using an MPEG source encoder (e.g., encoder 62 or 66), it is convenient for the frame period to reach 432 ms. Each SCH102 uses 224 bits for FEC coding. The 48-symbol PRC preamble 112 is chosen for 8208 symbols per PRC 110; and thereby achieve a simplified implementation of multiplexing and demultiplexing on the satellite 25 to 19,000 Ksym/s per PRC, as will be described in more detail below. For QPSK modulation (i.e. 2)²4), it is convenient to determine that the symbol contains two bits. To further illustrate, if phase shift keying modulation uses 8 phases instead of 4 phases in the broadcast station 23, it would be more convenient to have 3 bits to determine a symbol, since each 3 bits (i.e., 23) can be relative to one of the 8 phases.

If there is more than one broadcast station in the system 10, the software may be provided at the broadcast station 23. Regional broadcast control equipment (RBCF)238 (fig. 12) allocates space segment channel routes by means of a Mission Control Center (MCC)240, a Satellite Control Center (SCC)236 and a Broadcast Control Center (BCC) 244. The software optimizes the use of the uplink spectrum by allocating PRC carrier channels 110 where space in the 48 channel group is available. For example, a broadcast station may wish to provide 64 kilobits per second service on 4 PRC carriers. Due to the current spectrum usage, 4 carriers cannot be used in adjacent areas, but in non-adjacent areas, a group of up to 48 carriers can be used. Further, the RBCF238, using its MCC and SCC, can allocate PRCs to non-adjacent regions across different 48 channel groups. The MCC and SCC software at the RBCF238 or at one of the broadcast stations 23 can reallocate the PRC carriers of a particular broadcast service to other frequencies to avoid interference of an intentional (i.e., jamming) or accident nature at the location of a particular carrier. The present embodiment of the system has 3 RBCF's 238 with one set of equipment for each of the 3 regional satellites. Additional satellites may be controlled by one of the 3 devices.

Events related to satellite processing in fig. 6 are described in further detail below. A polyphase processor, digitally executed on-board the satellite, is used for signal regeneration on the satellite and recovery of the digital baseband of the symbols 114 transmitted in the PRC. Using: groups of 48 carriers spaced apart from each other at the center frequency will facilitate processing by the polyphase processor. The broadcaster 23 or RBCF238 has software that performs the segmentation, i.e., the segmentation process optimizes the PRC uplink carrier channel, i.e., the 48 carrier channel group. The principle of segmenting the uplink carrier frequency is not known to reorganize documents on a computer hard drive, and over time the capacity saved in a zero fragmentation fashion is still insufficient for data access. The BCC functionality on the RBCF allows the RBCF to be directed to remotely supervise and control broadcast stations to ensure their operation is within specified tolerances.

Satellite payload processing

Recovering the baseband on the satellite is important to complete switching, routing, and assembly on the satellite for each TDM downlink carrier with 96 PRCs on the satellite. The TDM carrier is amplified on the satellite 25 using a "one carrier per moving waveguide" method of operation. The satellite 25 preferably includes 8 satellite-based baseband processors, however, only one processor 116 is shown. If the situation requires this, preferably only 6 out of 8 processors are used in a time, providing redundancy in case of a failure and ordering them to abort the transmission as the situation requires. A single processor 116 will be described in conjunction with fig. 6 and 7. It will be appreciated that the same components are preferably provided for each of the other 7 processors. Referring to fig. 5, the encoded PRC uplink carrier 21 is received at the satellite 25 by an X-band receiver 120. The full uplink capacity is preferably between 288 and 384 PRC uplink channels of 16 kbits/sec each (i.e., 6 x 48 carriers if 6 processors are used or 8 x 48 carriers if all 8 processors 116 are used). As will be described further below, 96 PRCs are selected and multiplexed in the first downlink beam 27 for transmission on a carrier having a bandwidth of about 2.5 MHz.

Each uplink PRC channel can be selectively routed to all, some, or none of the downlink beams 27. The order and location of the PRCs in the downlink beam may be addressed by programming from a remote, range and control (TRC) device 24 (fig. 1). Each polyphase demultiplexer and demodulator 122 receives a single FDMA uplink signal in 48 consecutive frequency channel groups and generates a single analog signal on which the data of the 48 FDMA signals are time multiplexed and high speed demodulation of the serial data is accomplished, as will be described in further detail below in conjunction with figure 6. 6 of these polyphase demultiplexers and demodulators 122 will operate in parallel to process 288 FDMA signals. The routing switch and modulator 124 selectively directs each channel of the six serial data stream into all, some, or none of the downlink signals 27 and further modulates and upconverts the 3 downlink TDM signals 27. 3 Traveling Wave Tube Amplifiers (TWTAs) 126 amplify the 3 downlink signals, respectively, which are transmitted to earth using L-band transmit antennas 128.

The satellite 25 also contains three transparent payloads, each including a demultiplexer and downconverter 130 and an amplifier bank 132, all disposed on a common "flex-pipe" channel, which converts the frequency of the incoming signal for retransmission. Thus, each satellite 25 in the system 10 is preferably configured with two communication payloads. The first type of on-board processing payload will be described with reference to fig. 5, 6 and 7. The second type of communication payload is a transparent payload that can convert the TDM carrier on the uplink from a frequency location in the X-band spectrum of the uplink to a frequency location in the L-band downlink spectrum. The transport TDM stream for the transparent payload is assembled at the broadcast station 23 and sent to the satellite 25, received and frequency translated to a downlink frequency location using module 130, augmented with TWTA in module 132 and transmitted to one of the beams. The TDM signals appear the same to the radio receiver 29 whether they come from an on-board processing payload as indicated at 121 or from a transparent payload at 133. The carrier frequency locations of each of the loads 121 and 133 are separated on a grid spaced at 920 khz intervals. The grids are staggered in a bisectional manner such that the carrier positions of the mixed signals from the two payloads 121 and 133 are at 460khz intervals.

The on-board demultiplexer and demodulator 122 will now be described in detail in connection with fig. 6. As shown in fig. 6, each of the SCPC/FDMA carriers is referred to by the reference numeral 136 and is assigned to a group of 48 frequency channels. For illustrative purposes, a set 138 of cases is shown in FIG. 6. The carriers 136 are separated on a grid of center frequencies separated by 38 kilohertz. This spacing determines the design parameters of the polyphase demultiplexer. For each satellite 25, it is most preferable to be able to receive 288 uplink PRC SCPC/FDMA from many broadcast stations 23. Therefore, 6 polyphase demultiplexers and demodulators 122 are preferably used. The on-board processor 116 accepts these PRCSCPC/FDMA uplink carriers 136 and converts them to three downlink TDM carriers, each carrying 96 PRCs in 96 time slots.

288 carriers are received by an uplink beamorb antenna 118, and each group of 48 channels is converted to an Intermediate Frequency (IF) that is then filtered to select the frequency band occupied by that particular group 139. This processing occurs in the receiver 120. The filtered signal is provided to an analog-to-digital (a/D) converter 140 before being provided as an input signal to a polyphase demultiplexer 144. The demultiplexer 144 separates the 48 SCPC/FDMA channels 138 into a time-division multiplexed analog signal stream that includes QPSK modulated symbols enabling the content of the 48 SCPC/FDMA channels to be presented sequentially in the output of the demultiplexer 144. This TDM analog signal stream is routed to a digitally implemented QPSK demodulator and differential decoder 146. The QPSK demodulator and differential decoder 146 sequentially demodulates the QPSK modulated signal into digital baseband bits. The demodulation process requires symbol timing and carrier recovery. With QPSK modulation, the baseband symbols contain two bits, and each baseband symbol is recovered as each carrier symbol. The demultiplexer 144 and demodulator and decoder 146 will hereinafter be referred to as a demultiplexer and demodulator (D/D) 148. D/D is preferably accomplished using high speed digital techniques using known polyphase techniques to demultiplex the uplink carrier 21. QPSK demodulator is an optimal serial sharing, digitally implemented demodulator for recovering baseband two-bit symbols. The recovered symbols 114 from each PRC carrier 110 are sequentially differentially encoded to recover the original PRC symbols 108 applied at the input encoder, that is, at the broadcast station 23, at the channel distributors 82 and 98 of fig. 3. The payload of the satellite 25 preferably comprises 6 digitally implemented 48 carrier D/ds 148. In addition, two spare D/ds are provided in the satellite payload to replace the failed processing device.

Referring next to fig. 6, the processor 116 is programmed according to a software module with a header designation 150 for performing synchronization and rate alignment functions on the time-multiplexed symbol stream generated at the output of the QPSK demodulator differential decoder 146. The software components and hardware components (e.g., digital memory buffer and oscillator) of the rate collimation module 150 in fig. 6 are described in more detail with reference to fig. 7. The frequency collimation module 150 compensates for differences between the satellite-borne clock and the clock of the symbols supported by the single uplink PRC carrier 138 received at the satellite 25. The difference in clock rates is due to different clock rates at different broadcast stations 23 and different doppler frequencies at different locations due to the movement of the satellites 25. The difference in the clock rate of the broadcast station 23 is caused by the clock of the broadcast station 23 itself or at a remote location, the clock rate being transmitted over the ground line between the studio and the broadcast station 23.

The frequency correction module 150 may add or subtract a "0" value sign or otherwise recover the PRC header of the frame 100 every 432 milliseconds without any action. The "0" value symbol is a symbol in which the bit value is 0 in both the I and Q channels containing the QPSK modulated symbol. The PRC header 112 contains 48 symbols under normal conditions, followed by 47 other symbols with an initial symbol having a value of "0". When the symbol time of the uplink clock is recovered by the QPSK demodulator 146 together with the uplink carrier frequency; and the symbol time of the on-board clock 152 is synchronized, the preamble of the PRC need not be changed for that particular PRC 110. When the timing of the arriving uplink signal indicates a symbol later than the on-board clock, a "0" symbol is added to the beginning of the PRC preamble 112 of the PRC of the just-in-time PRC, resulting in a length of 49 symbols. When the timing of the up-link signal is reached indicating a symbol advance from the on-board clock, a "0" symbol is removed from the beginning of the PRC preamble of the PRC currently being processed, resulting in a length of 47 symbols.

As previously described, the input signal to the rate alignment module 150 comprises the recovered baseband two-bit symbol stream for each received uplink PRC at the respective original symbol rate. There are 288 such streams of information that emanate from the D/D148 according to every 1 of the 6 active processors 116. The actions described herein only involve 1D/D148 and one rate alignment module 150, however, it is understood that the remaining 5 on-satellite active processors 116 also perform the same functions.

Three steps must be completed in order to rate align the uplink PRC symbol with the satellite-mounted clock. First, in each of the buffers 149 and 151 of the ping-pong buffer 153, all symbols are grouped according to their original 8208 two-bit symbol PRC frame 110. This requires that the PRC header 112 (which contains 47 symbol unique words) be correlated with a locally stored copy of the unique word in the correlator indicated at 155 in order to locate the symbol in the buffer. Second, the number of ticks of the on-board clock, determined at 152 between correlation peaks, may be used to tune the length of the PRC header 112 to compensate for the difference in rate. Third, the timing of the PRC frame and its revised header is calculated based on the on-board frequency translation to the appropriate location in the switching and routing memory component 156 (FIG. 8).

The PRC symbol enters the ping-pong buffer pair 153 located on the left. This ping-pong action fills one buffer 149 or 151 with the uplink clock rate while simultaneously emptying the other buffer at the on-board clock rate. This action repeatedly shifts from one frame to the next, resulting in a continuous flow between the input and output of buffers 149 and 151. Newly arrived symbols are written into either cache 149 or 151, which may happen to be linked together. The write continues to fill either buffer 149 or 151 until a correlation spike occurs. At this point the writing is stopped and the input and output switches 161 and 163 are turned to the inverted position. The uplink PRC frame is captured such that its 48 header symbols reside in 48 symbol slots, only one slot at the output of the buffer remains unfilled, and 8160 data symbols fill the first 8160 slots. The contents of the subject cache are immediately read into its output at the onboard clock rate. The number of symbols read out is 47, 48 or 49 symbols contained in the PRC header. A "0" value character is removed or added at the beginning of the prime rate channel header to make such a tuning. The length 112 of the header is controlled by a signal from a frame symbol counter 159. the counter 159 counts the frequency symbols of the satellite clock that will be coincident to the PRC frame period to determine the length of the header. This act of forward-to-backward translation changes the role of the cache.

To accomplish this counting, the buffers 149 and 151 are filled as PRC frames, and the frame correlation spikes from the buffer correlator 155 are smoothed by a sync pulse oscillator (SPC). The smoothed sync pulse is used to calculate the symbol epoch for each frame. This number would be 8207, 8208 or 8209, which indicates whether the PRC header should be 47, 48 or 49 symbols in length, respectively. This information enables an appropriate number of symbols to be output from the frame buffer to keep the symbol stream synchronized to the on-board clock regardless of the earth end starting point.

The run time for modifying the preamble is relatively long in anticipation of rate differences in the system 10. For example, 10^-6The clock rate difference can be modified at the PRC preamble on average per 123 frames of PRC frames. The rate tuning achieved enables precise synchronization of the PRC symbol rate with the on-board clock 152. This allows baseband bit symbols to be routed to the appropriate location in the TDM frame. The synchronized PRC is generally indicated at 154 in fig. 6. Referring now to fig. 8, it is illustrated how the PRCs 154 route and switch into TDM frames on the device.

Fig. 6 illustrates how a PRC is handled with one D/D148. The other 5 active D/ds on the satellite also perform a similar processing method, with PRCs emanating from each of the 6D/ds 148, each synchronized and collimated to appear as serial streams each having a symbol rate of 48 x 19000, which is equivalent to 912,000 symbols per second for each D/D148. The serial stream 154 from each D/D148 can be demultiplexed into 48 parallel PRC streams with a symbol rate of 19000 per second, as shown in fig. 7. The sum of the PRC streams from all 6D/D148 on satellite 25 amounts to 288, with each D/D148 containing 19000 symbol/second PRC streams. Thus, the symbol has a signal occurrence time or period of 1/19000 seconds, which is equal to approximately 52.63 microseconds in duration.

As shown in fig. 8, 288 symbols appear at the output of the 6D/D channels 148a, 148b, 148c, 148D, 148e, and 148f for each uplink PRC symbol epoch. Once each PRC symbol occurs, the 288 symbol value is written into the switch and routing memory 156. The contents of the buffer 156 are read into 3 downstream TDM frame assemblies 160, 162, and 164. Using the selection routing and switching elements designated 172, the contents of each of the 288 memory cells are read into each of the 3 TDM frames in the assembled programs 160, 162 and 164 in groups of 96 symbols, totaling 1622 groups; its occurrence time is 136.8 milliseconds and occurs once every TDM frame period of 138 milliseconds. Thus, the scan rate or 136.8/2622 is faster than the duration of one symbol. The selective routing switch and modulator 124 comprises a memory device that operates in a ping-pong fashion, i.e., generally headed 156 devices; caches 156a and 156b are also included, respectively. 288 uplink PRCs headed 154 are used as inputs to permutation switch and modulator 124. The symbols for each PRC are correlated at 19000 symbol rates per second, clocked by the on-board clock. The PRC symbols are written in parallel at a 19000 hz clock rate into 288 locations of the ping-pong memories 156a or 156b as inputs. At the same time, the memory is used as the output of 156b or 156a, respectively, to read the symbols stored in the previous frame into 3 TDM frames at a 3 x 1.84 mhz read-in rate, respectively. This latter rate is sufficient to allow parallel streams of 3 TDM frames to be generated simultaneously, one directed into each of the three beams. The routing of the symbols into their defined beams is controlled by the symbol selection routing switch 172. The switch can arrange the symbols into any 1, 2 or 3 TDM streams. Every 1 TDM stream occurs at a rate of 1.84 million symbols/second. The output memory is clocked at intervals of 136.8 milliseconds and paused for 1.2 milliseconds to allow 96 MFP symbols and 2112 TSCC symbols to be inserted. It should be noted that each symbol is read into more than one TDM stream, with one FDMPRC channel that is not used and can be crossed. The buffers 156a and 156b, which are operated for the ping-pong operation, perform the switching from one frame to another through the switching elements 158a and 158 b.

Referring next to fig. 8, the 96 symbol groups are transmitted into 2622 slots of each TDM frame. The corresponding symbols (i.e., the corresponding symbols for all 96 uplink prime rate channels (i.e., ith symbols) are grouped together in TDM frames as shown by the 166 slots of symbol 1. the content in the 2622 slots in each TDM frame is frequency shifted by adding a pseudo random bit pattern to the entire 136.8 millisecond signal epoch. furthermore, a 1.2 millisecond epoch is appended at the beginning of each TDM frame to insert a 96 symbol Main Frame Preamble (MFP) and 2112 symbol TSCC, shown by 168 and 170 respectively.the total number is 2622 slots, each carrying 96 symbols and the symbols for the MFP and TSCC are 253,920 symbols in each TDM frame, resulting in a downlink symbol rate of 1.84 million symbols/second.

The PRC symbol routing between the 6D/D148A, 148B, 148C, 148D, 148E and 148F outputs and the input to the TDM frame assemblies 160, 162 and 164 is controlled by an on-board switching sequence unit 172 which stores instructions sent up the command lines of the SCC238 (fig. 12) at the surface. Each symbol from the selected uplink PRC symbol stream can be routed into a time slot in the TDM frame for transmission into the desired destination beam 27, the routing method not being dependent on the relationship between the time of occurrence of the different uplink PRC symbols and the time of occurrence of the symbols in the downlink TDM stream. This reduces the complexity of the satellite 25 payload. Furthermore, symbols from the selected PRC of the uplink may be routed to 2 or 3 beams by switch 158. Operation of radio receiver

A radio receiver 29 for use in the present system 10 will now be described with reference to fig. 9. The radio receiver 29 includes a Radio Frequency (RF) section 176 having an antenna 178 for receiving L-band electromagnetic waves and pre-filtering to select the receiver's operating band (e.g., 1452 to 1492 mhz). The rf section 176 may also include a low noise amplifier 180 that receives signals with minimal self-generated noise and may reject interfering signals from other devices sharing the operating band of the receiver 29. The mixer 182 is used to down-convert the received spectrum to an Intermediate Frequency (IF). A high performance intermediate frequency filter 184 selects the desired TDM carrier bandwidth from the outputs of the mixer 182 and local oscillator synthesizer 186, which produces the mixed input frequency required to down-convert the desired signal to the center of the IF filter. The TDM carrier is located at the center frequency with 460KHz separation zones separated on the grid. The bandwidth of the intermediate frequency filter 184 is about 2.5 mhz. The carriers are separated by at least 7 or 8 intervals or about 3.3 mhz. The radio frequency region 176 is designed to select the desired TDM carrier bandwidth with minimal internally generated interference and distortion and to reject interfering carriers that may occur in the operating band from 152 to 192 mhz. In most parts of the world the interfering carrier is rated and, in general, a ratio of interfering signal to useful signal of 30 db to 40 db is sufficiently protected. In some areas, operation in high power transmitters (e.g., near terrestrial microwave transmitters for public telephone networks and or other broadcast audio services) requires a front-end design with better protection. The desired TDM carrier bandwidth is recovered from the downlink signal using the radio frequency section 176 and provided to an analog-to-digital converter 188, and then to a QPSK demodulator 190. QPSK demodulator 190 is designed to recover the TDM bit stream transmitted from satellite 25, which is accomplished by on-board processor payload 121 and on-board transparent payload 133, depending on the selected carrier frequency.

QPSK demodulator 190 performs its best function by first converting the intermediate frequency signal from rf section 176 into digital symbols using analog-to-digital converter 188, and then performing quadrature phase shift keying using known digital processing methods. The demodulation preferably uses symbol timing and carrier frequency recovery and decision circuitry that samples and encodes the symbols of the QPSK demodulated signal into a baseband TDM bit stream.

Preferably, an analog-to-digital converter 188 and a quadrature phase shift keying demodulator 190 are provided on channel recovery integrated circuit chip 187. This is to recover the digital baseband signal of the broadcast channel from the intermediate frequency signal by using the intermediate frequency signal recovered by the rf/if board 176. The channel recovery circuit 187 includes a TDM synchronizer and predictor module 192, a TDM demultiplexer 194, and alignment and multiplexer 196 for a PRC synchronizer, the operation of which will be described in further detail in conjunction with fig. 10. The TDM multiplexed bit stream at the output of the quadrature phase shift keying demodulator 190 is fed to the MFP synchronization correlator 200, which is located within the TDM synchronization correlator and predictor module 192.

The correlator 200 compares the received bit stream with the stored patterns. When no signal is found to be present in the receiver, correlator 200 first enters a search mode in which the desired MFP correlation pattern is found without any time gate or aperture limitations acting on the output. When the correlator finds an event that needs to be corrected, it enters a mode in which the gate is opened at intervals that are advanced to prepare for the next correlation event. The process of time gating repeats if the associated event occurs again within the occurrence of the predetermined signal. For example, if the relevant event occurs 5 consecutive time frames, then the synchronization is determined by the software. However, the synchronization threshold can be varied. If no correlation occurs within a minimum number of consecutive time frames, the correlator will continue to look for correlation patterns in order to reach the synchronization threshold.

Assuming synchronization has occurred, the correlator enters a synchronization mode in which it tunes its parameters to reach the maximum likelihood of continuing synchronization lock. If correlation is lost, the correlator enters a special prediction mode in which the correlator will continue to maintain synchronization by predicting that the next correlation event will come. The correlator can maintain sufficiently accurate synchronization for short signal losses (e.g., up to 10 seconds) so that time recovery can be achieved when the signal comes back. This fast recovery is advantageous because it is important for mobile reception conditions. If the correlation cannot be re-established over a particular period of time, the correlator 200 returns to the inquiry mode. The TSCC can be recovered by the TDM demultiplexer 194 (see block 202 in fig. 10) under the condition that synchronization with the MFP of the TDM frame is maintained. The TSCC contains information that identifies the program providers carried in the time multiplexed frame and can find the channels of each set of program providers for 96 PRCs in the time multiplexed frame. A portion of the TDM frame carrying the initial PRC symbol is preferentially scrambled before any PRC can be demultiplexed from the TDM frame. This can be done because the same scrambling pattern is added to the receiver 29, which has been added to the PRC of the on-board time division multiplexed frame. The scrambling pattern is synchronized by the MFP in a time division multiplex frame.

The symbols of the PRC in a time division multiplexed frame are not grouped together contiguously but extend throughout the frame. 2622 sets of symbols are included in the PRC portion of the time division multiplexed frame. The positions of the symbols in each PRC are counted from 1 to 96, down. Thus, all symbols for the first PRC are in the first position in all 2622 sets. The symbol belonging to PRC2 is then in the second position in all 2622 sets of symbols, and so on, as shown in block 204. According to the present invention, the numbering and positioning of PRCs in time-multiplexed frames can reduce the size of the memory used to perform switching and routing on the satellite and multiplexing at the receiver. As shown in fig. 9, TSCC is recovered from the time-multiplexed demultiplexer 194; and provided to the controller 220 on the receiver 29 to recover the PRC of the particular broadcast channel. The n PRC symbols associated with the broadcast channel are extracted from the time slot positions of the time division multiplexed frame determined at the TSCC. This integration is accomplished by the controller in the radio, which is briefly illustrated at 205 in fig. 10. The controller 220 receives the selection of the broadcast channel determined by the wireless operator and combines this selection with the PRC information contained in the TSCCs, extracts and rearranges the symbols from the time division multiplexed frame to recover the n PRCs.

Referring to block diagrams 196 and 206 in fig. 9 and 10, respectively, each of the n PRC symbols selected by the radio operator (e.g., shown at 207) is associated with a broadcast channel (e.g., shown at 209), and the symbols are re-multiplexed into the format of the Broadcast Channel (BC) encoded by FEC. The n PRCs of a broadcast channel are realigned before the remultiplexing is complete. Realignment is useful because of the repetitive timing of symbol timing problems encountered in multiplexing, demultiplexing, and on-board frequency alignment in the aisle of end-to-end connection lines in the system 10. This problem can result in up to 4 symbol shifts in the relative alignment of the recovered PRC frame. Each of the n PRCs of a broadcast channel has a 48 symbol preamble followed by 8160 encoded PRC symbols. To reassemble these n PRCs into broadcast channels, synchronization is done for the 47, 48 or 49 symbol header in each PRC. The length of the symbol header depends on the timing alignment done on the uplink PRC on the satellite 25. Synchronization is accomplished on the 47 most recently received signals at the header of each of the n PRCs using a preamble correlator. The preamble correlator detects the occurrence of a fault in the correlation and emits a symbol during the peak of the correlation pulse. Respective times at which correlated correlation pulse spikes occur according to the n PRCs associated with the broadcast channel; and the n PRC symbol contents can be accurately aligned and re-multiplexed to recover the FEC encoded broadcast channel according to the operations associated with 4 symbol wide alignment buffers. Re-multiplexing n PRCs in order to reconstruct an FEC encoded broadcast channel requires: the FEC encoded broadcast channels are demultiplexed in reverse order into the PRCs using symbol spreading sequences at the broadcast station 23, as shown by the block diagrams 206 and 208 of fig. 10.

Fig. 11 illustrates by way of example how a broadcast channel including 4 PRCs is recovered at the receiver (block 196 in fig. 9). On the left hand side, the case of 4 demodulated PRCs arriving is shown. Due to the re-timing variation, different time delays occur from the broadcast station through the satellite to the radio reception, and a relative shift of up to 4 symbols can occur between the n PRCs that make up the channel of the broadcast station. The first step in recovery is to realign the symbol content in these PRCs. This is done by a set of first-in-first-out buffers, each buffer having a length equal to the span of the change. Each PRC has its own cache 222. Each PRC is first fed to a correlator 226 which determines the PRC header at the instant of arrival. The instant of arrival of each of the 4 PRCs is represented in the figure by the correlation spike. Each buffer 222 immediately starts writing (W) after the instant the correlation occurs and then continues until the end of the frame. To pass the symbol alignment to the PRC, all cache reads begin at the instant the last correlation event occurs. This results in all of the symbols of the PRC being synchronously read out at the output of the buffer 222 in a parallel fashion (block 206). The next realigned symbols 228 are multiplexed into a single serial stream by multiplexer 230, which is the recovered encoded broadcast channel (block 208). The length of the PRC header may be 47, 48, or 49 symbols long due to the clock 152 rate calibration installed above. This variation can be eliminated at the correlator 226 by using only the last 7 symbols to detect the correlation event.

Referring to block diagrams 198 and 210 in fig. 9, respectively, the FEC encoded broadcast channel is then provided to the FEC processing module 210. Most errors encountered in the transmission between the encoder and decoder locations are correlated by means of the FEC processing module. The FEC processing preferably employs a viterbi trellis decoder followed by deinterleaving and then a reed-solomon decoder. The FEC processing module recovers the original broadcast channel, which contains the n x 16kbps channel increment and its n x 224 bit SCH (block 212).

The n x 16 kbit/s segment of the broadcast channel is provided to a demodulator, such as MPEG2.5 layer 3 source decoder 214, for conversion back to an audio signal. Thus, a receiver processing method using low cost radio for receiving satellites from broadcast channels is feasible. Because the broadcast programming is transmitted digitally via satellite 25, many other services supported by system 10 are also represented in digital format. As previously mentioned, the SCH included in the broadcast channel provides a control channel for a wide range of future service options. Thus, by utilizing the entire time-multiplexed bit stream and its unprocessed demodulation format, the demultiplexed TSCC information bits and the recovered broadcast channel associated errors are recovered for use, a set of bits can be generated to perform the selections of these services, and the radio receiver 29 can also provide unique coding for each radio that is uniformly addressed. The coding may be accessed using bits carried in the SCH channel of the broadcast channel. For mobile operation with the radio receiver 29 according to the present invention, the radio should be configured with means to substantially instantaneously predict and recover the MFP-related pulse position with an accuracy of 1/4 symbols within an interval of tens of seconds. The local oscillator, which has a short-time accuracy better than the billionths symbol timing, is most suitable for installation in a radio receiver, particularly a handheld radio receiver 29 b. Managing satellite and broadcast station systems

As previously described, the system 10 may include one or more satellites 25. For illustrative purposes, 3 satellites are shown in FIG. 12: 25a, 25b, 25 c. A system 10 having several satellites preferably includes several TCR stations 24a, 24b, 24c, 24d, and 24e positioned so that each satellite 25a, 25b, and 25c is in line of sight with two TCR stations. The TCR station, which is typically referred to with reference number 24, is controlled by regional broadcast control equipment (RBCF)238a, 238b or 238 c. Each regional broadcast control device 238a, 238b, and 238c includes a Satellite Control Center (SCC)236a, 236b, and 236c, a Mission Control Center (MCC)240a, 240b, and 240c, and a Broadcast Control Center (BCC)244a, 244b, and 244c, respectively. Each Satellite Control Center (SCC), which is also a place where the space segments manage and control the computers and human resources, controls the satellite data bus and communication payload. The apparatus should be managed 24 hours a day by a number of technicians trained in the management and control of orbiting satellite operations. The satellite control centers 236a, 236b and 236c monitor the satellite-borne components and in particular operate the respective satellites 25a, 25b and 25 c. Each TCR station 24 is preferably directly associated with a corresponding satellite control center 236a, 236b or 236c through a redundant PSTN circuit that is backed up for full day operation.

In each region served by satellites 25a, 25b and 25c, the corresponding RBCF238a, 238b and 238c should leave a broadcast channel for voice, data and image services; the space segment channels are routed through the Mission Control Centers (MCCs) 240a, 240b, 240c and approved for delivery of these services, which are information requiring payment by the broadcast service provider and the service provider.

Each task control center should be configured to achieve the ability to schedule allocation of the spatial sector channels including the uplink PRC frequency and the downlink PRC time division multiplex timeslot allocation. Each task control center performs both dynamic and static control. Dynamic control includes time windows for completing work tasks, that is, space segments are arranged by month, week, and day. The static control includes space segments that do not vary by month, week and day, arranging for the sales department personnel to engage in selling space segment capacity per corresponding RBCF, and providing data indicating the available capacity and instructions for grasping the sold capacity to the mission control center. The mission control center generates a comprehensive plan for occupying the time and frequency space of the system 10. The plan is then converted to instructions for the on-board routing switch 172 and sent to the satellite control center for transmission to the satellites. The schedule can preferably be updated every 12 hours and transmitted to the satellite. The task control centers 240a, 240b and 240c also monitor the time division multiplexed signals received by the respective channel system monitoring devices (CSMEs) 242a, 242b and 242 c. The channel system monitoring apparatus station confirms that the broadcasting station 23 provides the broadcasting channel within the scope of the specification.

Each broadcast control center 244a, 244b, and 244c oversees whether each broadcast ground station 23 within its region is within a selected frequency, power, antenna station tolerance. The broadcast control center can also interface with the corresponding broadcast station to command the offending broadcast station to stop broadcasting. The hub device 246 preferably provides technical support services and backup operations for each satellite control center.

While certain advantageous embodiments have been chosen to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined in the appended claims.

Claims (62)

1. A receiving device for receiving a time division multiplexed downlink data stream from a satellite, comprising:

a phase shift keying demodulator for demodulating said downlink data stream into a symbol stream, said downlink data stream comprising time slots and having an associated predetermined number of prime rate channels in said time slots as designated by said satellite;

a correlator coupled to said demodulator for locating and synchronizing to a main frame preamble inserted into said symbol stream by said satellite, said correlator configured to store a main frame correlation pattern corresponding to said main frame preamble and programmable to operate in one of an inquiry mode and a synchronization mode of operation;

a demultiplexer coupled to said correlator for locating a time slot control channel in said symbol stream, said time slot control channel being inserted into said symbol stream by said satellite to identify which of said time slots contains said prime rate channel corresponding to each of a plurality of broadcast service providers; and

an input device configured to enable an operator to select one of said broadcast service providers and operable to provide an output signal to said demultiplexer, the demultiplexer being operable to extract some of said selected prime rate channels from the prime rate channels using said time slot control channel and the output signal.

2. The receiving apparatus of claim 1, wherein the correlator is configured as follows: the correlator operates in a prediction mode when the correlator detects the primary frame correlation pattern, using one of a time gate and an aperture corresponding to a predicted time interval for the occurrence of a next correlation event at the correlator output, and operates in a query mode without using the time gate and the aperture when the primary frame correlation pattern is not detected.

3. The receiving device of claim 1, wherein said correlator is configured to operate in a synchronous mode when a predetermined minimum number of said primary frame correlation patterns of successive time frames in said downlink data stream are detected; when said primary frame correlation pattern is not detected while operating in said synchronization mode, operating in a prediction mode in which said correlator remains operating with an interval that is a prediction time for determining another of said primary frame correlation modes.

4. The receiving device of claim 3, wherein the correlator is configured to return to operating in the inquiry mode upon failure to detect a predetermined minimum number of the primary frame correlation versions of successive time frames of the downlink data stream during the prediction mode.

5. A receiving apparatus for receiving a time division multiplexed downlink data stream from a satellite, comprising:

a demodulator for demodulating the downlink data stream into a symbol stream, the downlink data stream including time slots having a plurality of slot positions, having a predetermined number of prime rate channels by the satellite; each of said prime rate channels comprising a plurality of symbols, each of said plurality of symbols being respectively assigned to said time slot to extend each of said plurality of symbols to be respectively assigned to said time slot to extend said plurality of symbols corresponding to each of said prime rate channels in said downlink data stream, said plurality of symbols of each of said prime rate channels being assigned to a respective one of said plurality of slot positions in each of said time slots;

a demultiplexer connected to said demodulator for setting a slot control channel inserted into said symbol stream by said satellite for determining which of said plurality of slot positions contains said plurality of symbols corresponding to at least one of said prime rate channels of the selected broadcast service provider;

extracting means for extracting the plurality of symbols from the symbol stream according to the timeslot control channel, the plurality of symbols corresponding to the at least one prime rate channel of the selected broadcast service provider; and

a demultiplexer for demultiplexing said plurality of symbols corresponding to said selected broadcast service provider into a serial broadcast channel data stream.

6. The receiving apparatus of claim 5 wherein said broadcast service provider uses a plurality of said prime rate channels and further comprising a re-collimating device coupled to said extracting means and configured to collimate said plurality of prime rate channels with respect to each other.

7. The receiving apparatus of claim 6 wherein each of said prime rate channels comprises a header and said realignment means comprises:

a buffer for each of said plurality of said prime rate channels, and

a correlator coupled to said buffer and configured to determine an arrival instant of said header of a corresponding one of said prime rate channels and to begin writing said prime rate channels into said buffer, said buffer of each of said plurality of said prime rate channels being capable of being read in upon an arrival instant of said header corresponding to a last one of said prime rate channels, so as to be detectable for generating said serial broadcast channel data stream.

8. A method for recovering at least one prime rate channel from a plurality of prime rate channels transmitted in a time division multiplexed downlink data stream from a satellite, comprising the steps of:

demodulating said downlink data stream into a stream of symbols, a downlink data stream comprising time slots having a plurality of slot positions and having a predetermined number of prime rate channels by said satellites, each of said prime rate channels comprising a plurality of symbols, each of said plurality of symbols being respectively assigned to a time slot to extend said plurality of symbols corresponding to each of said prime rate channels on said downlink data stream, said plurality of symbols of each of said prime rate channels being assigned to a respective one of said plurality of slot positions in each of said time slots;

multiplexing said symbol stream to locate a time slot control channel inserted by said satellite to determine which of said plurality of time slot positions contains symbols corresponding to said plurality of at least one of said prime rate channels of a selected broadcast service provider;

extracting the plurality of symbols corresponding to at least one of the prime rate channels of the selected broadcast service provider from the symbol stream according to the timeslot control channel; and

multiplexing the plurality of symbols corresponding to the selected broadcast service provider into a serial broadcast channel data stream.

9. The method of claim 8, wherein said broadcast service provider uses a plurality of said prime rate channels and further comprising the step of aligning said majority of prime rate channels with one another, said aligning step being performed prior to multiplexing said majority of symbols corresponding to said majority of prime rate channels.

10. The method of claim 9, wherein each of said prime rate channels includes a header and said aligning step comprises the steps of:

writing each of said plurality of prime rate channels into a respective cache at each instant of time at which said header is determined, an

Reading from the cache upon determining the last said arrival instant.

11. A method for receiving one of a plurality of broadcast channels transmitted from a satellite via a downlink signal including a prime rate channel, comprising the steps of:

demodulating said downlink signal into a baseband time division multiplexed bit stream comprising frames generated by said satellite, each of said frames comprising a plurality of time slots, each of said time slots further comprising a set of symbols, each symbol in said set of symbols further corresponding to a respective one of said prime rate frequency channels, said frequency channels occupying similar symbol positions in each of said time slots;

locating the frame in the bitstream by a primary frame preamble inserted in the bitstream by the satellite;

retrieving symbols corresponding to at least one of said prime rate channels from said set of symbols in each of said slots of at least one of said frames;

re-multiplexing said symbols corresponding to said at least one of said prime rate channels for recovery of a corresponding broadcast channel as originally transmitted to said satellite; and

extracting a service control header from the broadcast channel.

12. The method of claim 11, wherein said step of retrieving comprises the steps of:

locating a time slot control channel inserted into said bit stream by said satellite, said control channel indicating which of said time slots contains said symbol corresponding to each of said prime rate channels, and

extracting the symbols corresponding to one of the prime rate channels using the control channel.

13. The method of claim 11, further comprising: a step of determining whether the service control header contains a confirmation code inserted by the broadcasting station in said broadcast channel before being transmitted to said satellite for unique addressing to the radio receiver.

14. The method of claim 11, further comprising the steps of:

determining whether the service control header contains control data; and

operating a radio receiver to perform at least one of a plurality of functions in accordance with said control data, said plurality of functions including operating said radio receiver in a selected reception mode to provide a selected multimedia service, displaying data, displaying an image and decrypting data using a decryption key provided in said service control header.

15. A radio receiver for receiving one of a plurality of prime rate channels transmitted via a downlink signal from a satellite, comprising:

a radio frequency device for receiving said downlink signal;

a channel recovery apparatus for recovering said prime rate channel from said downlink signal, said method comprising: demodulating said downlink signal into a baseband time division multiplexed bit stream, comprising frames generated by said satellite, each of said frames comprising a plurality of time slots, each of said time slots comprising a set of symbols, each symbol in said set of symbols corresponding to a respective one of said prime rate channels occupying a similar symbol position in each of said time slots, positioning said frames in said bit stream using a prime frame preamble inserted into said bit stream by said satellite, retrieving from a set of said symbols in at least one of said time slots of at least one of said frames some symbols corresponding to at least one of said prime rate channels, re-multiplexing said symbols corresponding to at least one of said prime rate channels to recover a corresponding broadcast channel, as in the original method of transmission to the satellite,

extracting a service control header from the broadcast channel; and

a controller operable to accept said service control header from said channel recovery device and to control said radio receiver to perform a plurality of functions including operating the radio receiver in a selected reception mode to provide a selected multimedia service, displaying data, presenting an image, decrypting the data using a decryption key housed in the service control header, and uniquely addressing said radio receiver in response to an identification code presented in said service control header.

16. A method of transmitting a broadcast program from a broadcast service provider to one or more remote receivers, comprising the steps of:

assembling bits corresponding to at least a portion of the program into a first number of prime rate increments having a uniform and predetermined rate;

generating a frame having a predetermined period and including each of said prime rate increments and a frame header;

dividing said frame into symbols, each of said symbols containing a predetermined and consecutive number of said bits;

demultiplexing said symbols of said frame into a 2 nd number of parallel prime rate channels, each of said prime rate channels having the same said predetermined period as said frame, said symbols provided in a predetermined order in a prime rate channel separating successive said symbols, each of said prime rate channels including a prime rate channel synchronization header for recovering said prime rate channel at said remote receiver; and

and modulating the main rate channel to the corresponding number of uplink carrier frequencies for broadcast transmission.

17. The method of claim 16, wherein the frame header contains bits for controlling the receiver device.

18. The method of claim 16, wherein said program is characterized by two sets of services, and further comprising the steps of: dividing at least one primary rate increment into two parts for carrying the bits corresponding to the two respective services.

19. The method of claim 16, wherein said second number of prime rate channels corresponds to said first number of prime rate increments.

20. The method of claim 16, wherein said modulating step comprises the step of modulating each of said prime rate channels with a plurality of quadrature phase shift keying modulators.

21. The method of claim 20, wherein each of said symbols comprises two of said bits.

22. The method of claim 20, wherein said second number of prime rate channels and said plurality of quadrature phase shift keying modulators correspond in number to said first number of prime rate increments.

23. The method of claim 16, wherein the predetermined order is an ascending order.

24. A method of transmitting a broadcast program from a broadcast service provider to one or more remote receiver devices, comprising the steps of:

assembling said program into a first integer having a prime rate increment of uniform and predetermined frequency;

generating a bit frame having a predetermined period and containing each of said prime rate increments and a frame preamble;

encoding the frame to generate an encoded frame comprising bits encoded for forward error correlation protection;

decomposing said encoded frame into symbols, each of said symbols containing a predetermined and consecutive number of said bits;

demultiplexing said signal into a second number of parallel prime rate channels, providing said symbols on said prime rate channels in a predetermined order to separate successive said symbols, each of said prime rate channels including a prime rate channel synchronization header to enable said remote receiver to recover said prime rate channel, and

the prime rate channels are modulated on a corresponding number of uplink carrier frequencies for broadcast transmission.

25. The method of claim 24, wherein said encoding step involves selecting at least one coding scheme from a group consisting of reed solomon coding, interleaved coding, and tesley convolutional coding.

26. The method of claim 24, wherein said encoding step involves the steps of:

encoding the frame according to a first encoding scheme to generate a first encoded frame;

interleaving the first encoded frame to generate an interleaved encoded frame; and

the interlaced coded frame is encoded using a second coding scheme.

27. The method of claim 26, wherein said first coding scheme is a reed-solomon coding scheme.

28. The method of claim 26, wherein said second coding scheme is a trellis convolutional coding scheme.

29. The method of claim 24, wherein the predetermined order is an ascending order.

30. A management system for managing a satellite and a number of broadcast stations for programming, the programming transmitted by the satellite over a broadcast channel to a remote radio receiver, the system comprising:

a satellite control system configured to generate control signals for controlling attitude and orbit of the satellite; generating data processing control signals for processing said programs at the satellite for uplink to said satellite via said broadcast system and for selective routing to downlink time division multiplexed carriers;

at least one remote, range and control system connected to said satellite control system for communicating with said satellite to provide said control signals and said data processing signals from said satellite control system to said satellite; and

a mission control system connected to said satellite control system and said broadcast station, said mission control system for assigning said broadcast channel to a service provider desiring to transmit at least one program via satellite, storing channel data associated with said mission of said broadcast channel and providing said channel data to said satellite control system, and requesting payment from said service provider based on the number of said broadcast channels assigned, said mission control system providing a number of options to said service provider, including: reserving the broadcast channel for uplink transmission, using the date and time of the day of the reserved broadcast channel; the number of time division multiplexed signals for downlink transmission in the number of beams associated with the satellite, the mission control system may be operable to indicate to the satellite control system: those time division multiplexed signals in said beams are used and said satellite control system generates data processing signals relating to said programs for arranging said programs into selected ones of said beams.

31. The system of claim 30, wherein the broadcast channels correspond to frequency locations in a predetermined radio spectrum, and the mission control system is programmable to allocate ones of the broadcast channels that are not contiguous to one of the service providers.

32. A system as claimed in claim 31, wherein the mission control system is operable to perform a combining procedure to reallocate the service providers to different broadcast channels to optimize use of the satellite uplink spectrum.

33. The system of claim 30, further comprising a channel service monitor coupled to said mission control system, said mission control system operable to verify that said transmitted program has sufficient signal strength and sufficiently low bit error rate before requiring payment from said service provider.

34. The system of claim 30, further comprising a broadcast control center for supervising and controlling said broadcast stations to maintain performance of said broadcast stations within predetermined tolerances with respect to carrier frequency allocation, antenna power levels, and antenna orientation.

35. The system of claim 30, further comprising a broadcast control center for supervising and controlling said broadcast stations, operable to instruct said broadcast stations to discontinue use of said broadcast channels.

36. The system of claim 30, further comprising a broadcast control center for supervising and controlling said broadcast stations, operable to generate and transmit a command to at least one of said broadcast stations requesting it to reduce power consumption by said broadcast station.

37. A management system for managing a satellite and a number of broadcast stations for generating programs for transmission via the satellite to a remote radio receiver, the system comprising:

a satellite control system configured to generate control signals for controlling operation of said satellite, said satellite being configured to receive uplink signals comprising frequency division multiple access channels and to generate at least two time division multiplexed downlink signals, each of said signals comprising a plurality of time slots, said broadcast station being operable to modulate said program into prime rate increments for transmission on a selected one of said frequency division multiple access channels, said satellite being further configured to arrange the progression of said prime rate increments so as to arrange said prime rate increments into selected ones of said time slots in accordance with said control signals;

a mission control system associated with said satellite control system and said broadcast station, said mission control system operable to assign a selection of ones of said frequency division multiple access channels to those service providers desiring to transmit said prime rate increments via said satellite; and assigning at least one of said time division multiplexed signals for downlink transmission of said prime rate increments, storing channel data associated with said assignment of said frequency division multiple access channels and time division multiplexed signals and providing said channel data to said satellite control system for use in generating said control signal, an

At least one remote, range and control system is coupled to the satellite control center and configured to communicate with the satellite to provide the control signals from the satellite control system to the satellite.

38. The system of claim 37, wherein the mission control system is programmable to assign discontinuous channels of the frequency division multiple access channel to one of the service providers.

39. The system of claim 37, wherein said system is operable to confirm successful transmission of prime rate increments via at least one time division multiplexed signal prior to providing a ticket to a corresponding said service provider.

40. The system of claim 37 wherein said master control system is operable to provide selected ones of said frequency division multiplexed channels for use by said service provider in a periodic and temporary manner and for selection by said service provider on a monthly, weekly, and daily basis.

41. The system of claim 37, wherein said master control system is operable to provide selected ones of the frequency division multiple access channels to selected ones of said service providers for substantially permanent, exclusive service, thereby effecting static control.

42. The system of claim 37, further comprising a broadcast control system coupled to the broadcast station. The system is operable to monitor the broadcast station to determine whether the broadcast station is operating within a predetermined tolerance of at least one of frequency, power and orientation to an antenna associated with the broadcast station.

43. The system of claim 37, further comprising a broadcast control system coupled to said broadcast station and operable to monitor said broadcast station to determine if said broadcast station is operating within a predetermined tolerance; and may generate and transmit a command to request at least one of the broadcast stations to reduce power consumption of the broadcast station.

44. An apparatus for switching symbols in parallel broadcast channels to a time division multiplexed data stream, comprising:

first and second ping-pong buffers, said first ping-pong buffer configured to store a first plurality of said symbols in said parallel broadcast channel; said second ping-pong buffer is configured to store a second plurality of said symbols in said parallel broadcast channel, said second plurality of said symbols in said parallel broadcast channel arriving at said second ping-pong buffer prior to said first plurality of said symbols arriving at said first ping-pong buffer;

a routing switch coupled to the output of said first and second ping-pong buffers; and

a first frame assembly coupled to said selective routing switch, said selective routing switch operable to control writing of said second buffered content to said first frame assembly.

45. The apparatus of claim 44 further comprising a second frame assembly coupled to said selective routing switch, said routing switch operable to control writing of contents of said second ping pong buffer to at least one of said first frame assembly and said second frame assembly.

46. The apparatus of claim 45, wherein said routing switch is operable to control writing of contents of said second ping pong buffer to both said first frame assembly and said second frame assembly to produce two parallel time division multiplexed data streams.

47. The apparatus of claim 44, wherein said second ping-pong buffer is operable to store in a third plurality of said broadcast channels; the selective routing switch is operable to control writing of contents of the first ping pong buffer to the first frame assembler.

48. The apparatus of claim 44, wherein said first ping-pong buffer is operable to switch as few as one of said first plurality of said symbols in a time.

49. The apparatus of claim 44, wherein said second ping-pong buffer is operable to switch as few as one of said plurality of symbols of said second batch at a time.

50. The apparatus of claim 44 wherein the first frame assembler is operable to insert at least one frame bit in the second ping pong buffer to specify the symbol stored in the second ping pong buffer as a frame.

51. Apparatus as claimed in claim 50, wherein said frame includes a time slot and said first frame assembly is operable to insert at least one bit representing a time slot control channel in a buffer of said second ping pong operation to indicate in which of said time slots said symbol corresponding to one of said parallel broadcast channels is stored.

52. The apparatus of claim 44, wherein said apparatus is located within a satellite and said selective routing switch is controllable by control signals generated by a ground station and transmitted to said satellite.

53. The apparatus of claim 45 wherein said second frame assembly is operable to insert at least one frame bit in said first ping pong buffer to ensure that said symbol has been stored as a frame in said first ping pong buffer.

54. Apparatus as claimed in claim 53, wherein said frame includes a time slot and said second frame assembly is operable to insert at least one bit to indicate a time slot control channel in a buffer of said first ping pong operation to indicate in which of said time slots said symbol corresponding to a respective one of said parallel broadcast channels is stored.

55. A satellite payload processing system for processing uplink signals comprising a plurality of "one-channel-per-carrier" frequency division multiple access carriers, the system comprising:

a polyphase demultiplexer processor for separating said uplink signals into time division multiplexed data streams of symbols and sequentially delivering said symbols corresponding to one of a plurality of carriers at a respective one of said frequencies in said uplink signals to an output of said polyphase demultiplexer processor; and

a phase shift keying demodulator associated with said output of said polyphase demultiplexer for demodulating said symbol streams into corresponding time division multiplexed digital baseband bits.

56. The satellite payload processing system of claim 55 further comprising a differential decoder associated with the phase shift keying demodulator, the differential decoder for recovering the signal stream when the symbol stream is differentially encoded for the uplink carrier signal.

57. The satellite payload processing system of claim 55 wherein the phase-shift keying demodulator is a quadrature phase-shift keying demodulator for demodulating each of the symbols into two corresponding bits.

58. The satellite payload processing system of claim 55, further comprising a switch and routing processor to arrange the digital baseband bit stream into one of a plurality of time division multiplexed downlink carriers.

59. A rate collimation apparatus for a satellite, comprising:

a satellite-borne clock;

an input switch;

an output switch;

a toggle working buffer pair comprising first and second buffers and coupled to said input switch and said output switch. The first and second buffers receive a stream of digital baseband symbols recovered from an uplink signal in accordance with operation of the input switch and the output switch. The first buffer of the buffer pair receives the bits according to an uplink clock rate derived from the uplink signal. The second of the pair of caches empties stored content substantially simultaneously in accordance with the on-board clock. The action of the input switch and the output switch reverses the operation of the first and second caches;

first and second correlators, coupled to the first and second buffers, respectively, are operable to generate a spike when a frame is detected as indicated by the header in the baseband symbol stream. The buffer pair is operable to continue writing the baseband symbol stream into one of the buffer pairs until the spike occurs. The input switch and the output switch thus turn to their opposite states. Said first and said second buffers receive said uplink signal read to their outputs according to said loaded clock rate.

A sync pulse oscillator associated with said first and second correlators and operable to generate a smoothed pulse for each symbol read into said output and a counter associated with said oscillator to count said smoothed pulses, a number of bits being added and subtracted from said header of said bit stream based on the value of said counter.

60. The satellite rate collimation device as recited in claim 59, further comprising a received symbol clock coupled to the first buffer and the second buffer and operable to allow one of the first buffer and the second buffer that is being coupled to the input switch to receive the symbols recovered from the uplink signal.

61. The satellite rate alignment device of claim 59, further comprising an on-board symbol clock coupled to said first buffer and said second buffer and operable to cause an output of said first buffer and said second buffer, now coupled to said output switch, to store said symbols therein.

62. A method for calibrating an uplink symbol rate to a satellite-borne clock, comprising the steps of:

storing a majority of said symbols in a buffer at a rate at which symbols are received;

comparing headers inserted between said symbols with unique frame words to correlate said symbols in said buffer to obtain frames, locating said headers in said symbols already stored in said buffer and generating corrected spikes when headers are located;

calculating clock ticks generated between the related pulse spikes by using a satellite-borne symbol clock; and

the length of the header in the buffer is tuned to compensate for the frequency difference between the received symbol rate and the loaded symbol rate.