MXPA99004159A - Direct satellite direct broadcast system - Google Patents

Abstract

A satellite direct radio broadcast system (10) assemblies bits of broadcast programs into prime rate increments assembled into a frame (100). Frames (100) are divided into symbols which are demultiplexed into a plurality of prime rate channels (110). The prime rate channels (110) are demultiplexed into corresponding broadcast frequencies (21) for transmission to a satellite (25). An on board demultiplexer (144) separates uplink signals into time division multiplexed streams of symbols (154). A phase shift keying demodulator (146) demodulates the symbols into digital baseband data. The satellite payload switches the symbols into time division multiplexed data streams using two ping-pong buffers (156) and a routing switch (172). The receivers (29) process TDM streams using frame preambles and control channels provided by the satellite (25) and service control headers provided by broadcast stations (23, 24). A management system is provided to manage the satellite (25) and broadcast stations (23, 24).

Description

Direct broadcast system via direct satellite FIELD OF THE INVENTION The invention relates to satellite broadcasting systems, the formatting of broadcast data and their processing by equipment installed on satellites and remote radio receivers. BACKGROUND OF THE INVENTION There is currently a population of more than four billion people who are generally unsatisfied or poorly served by the poor sound quality of shortwave broadcasts or the coverage limitations of terrestrial broadcasting systems of modulation band. in amplitude (AM) and frequency modulation band (FM). This population is located mainly in Africa, Central and South America and Asia. Therefore, there is a need for a satellite-based direct broadcasting system to transmit signals, for example, audio, data and images to low-cost domestic receivers.

A variety of satellite communications have been developed for commercial and military applications. However, these satellite communications systems have not addressed the need to provide multiple, independent providers of broadcasting services with flexible and economical access to a space segment, nor the consumer's need to receive high-quality radio signals. using low cost domestic radio receiver units. Therefore, there is a need to provide service providers with direct access to a satellite and options regarding the amount of space segment that can be purchased and used. In addition, there is a need for a low cost radio receiver unit capable of receiving a time division multiplexed downlink binary stream. SUMMARY OF THE INVENTION According to one aspect of the present invention, a receiver unit for receiving a downlink (space-to-earth) data stream, time division multiplexed from a satellite, comprises a phase shift modulation demodulator to demodulate the downlink data flow in a symbol stream. The downlink data stream comprises intervals and the satellite provides a predetermined number of fundamental rate channels in the respective ranges. A correlator is connected to the demodulator to locate and synchronize a master block preamble inserted in the symbol flow through the satellite. A demultiplexer is connected to the correlator to locate an interval control channel in the symbol flow. The satellite inserts the interval control channel in the symbol flow to identify which of the intervals comprises the fundamental rate channels corresponding to each of a plurality of broadcasting service providers. An input device is provided so that an operator can select one of the broadcast service providers and provide an output signal to the demultiplexer. The demultiplexer extracts the chosen channels from the fundamental velocity channels of the data stream using the interval control channel and the output signal. According to another aspect of the invention, the correlator can be operated in a search mode, a synchronized operation mode and a predictive mode. According to another aspect of the present invention, a method for receiving one of a plurality of fundamental rate channels, transmitted by means of downlink signals from a satellite, comprises the step of demodulating downlink signals in a binary stream multiplexed by division of baseband time comprising blocks generated by the satellite. Each of the blocks comprises a plurality of intervals, each of the intervals having a set of symbols. Each symbol, in the set of symbols corresponding to a respective channel of the fundamental velocity channels, occupies a similar symbol position in each of the intervals. The method further comprises the steps of locating the blocks in the binary stream using a master block preamble inserted therein by the satellite, and retrieving, from the set of symbols in each of the intervals of at least one of the blocks, the symbols that correspond to one of the fundamental velocity channels. According to one aspect of the present invention, there is provided a method for formatting broadcast data for transmission on an uplink carrier (Earth-space) to a satellite that combines data flows from a plurality of service providers in parallel flows in uplink carriers to allow an efficient and economical use of the space segment. The bits in a program are assembled in a first number of increments of fundamental velocity that have uniform and predetermined speeds. A block having a predetermined duration and comprising each of the fundamental rate increments and a block header is generated. The block is divided into symbols, each of the symbols comprising a predetermined and consecutive number of program bits. The symbols are de-multiplexed in a second number of parallel fundamental velocity channels, the symbols being provided to alternating channels of the fundamental velocity channels to separate consecutive symbols. The fundamental velocity channels each comprise a fundamental rate channel synchronization header for recovering the fundamental rate channels in the said remote receiving units. The fundamental rate channels are then demultiplexed into a corresponding number of uplink carrier frequencies for broadcast transmission. According to one aspect of the invention, the fundamental rate increments can be divided into two segments to transmit two different types of data for a particular service.

According to another aspect of the invention, the blocks are encoded for protection correction of transmission errors using two methods of concatenated interleaving coding. According to one aspect of the present invention, there is provided a system for managing a satellite and a variety of broadcast stations to generate programs for transmission to remote radio receivers in broadcast channels via the satellite. The system comprises a satellite control system configured to generate control signals to control the position and orientation and orbit of the satellite and command signals to control the on-board processing of the programs transmitted uplink to the satellite. At least one telemetry, range and control system is connected to the satellite control center to communicate with the satellite in order to provide control signals and data processing signals thereto. The system also includes a broadcast control system connected to the satellite control center and the broadcast stations. The broadcast control system is operable to assign chosen channels of the broadcast channels to service providers wishing to uplink transmission of at least one of the programs to the satellite; store channel data relating to the assignments of the broadcast channels and provide the channel data of the satellite control system and bill the service providers according to the number of broadcast channels assigned to them. The broadcast control system offers the service providers a plurality of options that include the number of the aforementioned broadcast channels that are reserved for uplink transmission, the dates and times of day to use the reserved broadcast channels and which of a plurality of beams associated with the satellite have to be used for downlink transmission. The broadcast control system notifies the satellite control system which of the beams have to be used and the satellite control system generates corresponding data processing signals to route the program to the chosen beams. The broadcast control system is also operable to give instructions to the broadcast stations regarding when the use of the broadcast channels assigned to them ends during the dates and times of the day when the broadcast channels are not reserved for broadcasting. the same. According to another aspect of the invention, the broadcast control station is programmable to perform a defragmentation process in the allocations of broadcast channels to make a more efficient use of the space segment. According to another aspect of the invention, the transmitted signals are digital and, therefore, are more resistant against transmission impairments. Digital signage also provides flexibility to supply a wide range of future services. According to one aspect of the present invention, an apparatus for switching symbols in parallel broadcast channels to data streams multiplexed by time division comprises a first and a second dynamic alternation memory. The first dynamic memory of alternation is configured to store a first plurality of broadcast channels in parallel therein. The second dynamic alternation memory functions to store a second plurality of broadcast channels therein. The second plurality of broadcast channels arrives at the second dynamic memory of alternation before the arrival of the first plurality of broadcast channels to the first dynamic memory of alternation. The apparatus also comprises a routing switch connected to the outputs of the first and second dynamic alteration memories, and a first block assembler connected to the routing switch. The routing switch controls the writing of the contents of the second dynamic alternation memory to the first block assembler.

According to another aspect of the invention, the content of the dynamic alternation memory can be switched at corresponding intervals in two or more block assemblers. According to one aspect of the present invention, a processing system in the satellite equipment for processing a single channel per carrier, provides a frequency division multiple access uplink signal comprising a polyphase demultiplexer processor for separating the signal from uplink in a data stream of multiplexed symbols by time division. The polyphase demultiplexer processor presents the symbols corresponding to each of a plurality of carriers at the respective frequencies of the frequencies in the uplink signal in sequence to a processor output of the polyphase demultiplexer. A phase shift modulator de-modulator is connected to the processor output of the polyphase demultiplexer to demodulate the flow of symbols in a corresponding time division multiplexed digital baseband bit stream. According to another aspect of the present invention, an apparatus for speed alignment for a satellite comprises an on-board clock, an input switch, an output switch and a pair of dynamic alternating memories that are constituted by a first and a second memory dynamic and connected to the input switch and the output switch. The first and second dynamic memories receive a stream of digital baseband symbols recovered from an uplink signal that depends on the operation of the input switch and the output switch. The first dynamic memory of the memory pair receives the bits according to an uplink base frequency obtained from said uplink signal. The second dynamic memory of the memory pair empties, practically simultaneously, its stored contents to a third dynamic memory in accordance with the on-board clock, the operations of the first and second dynamic memories being inverted when the switch of input and the output switch. The first and second correlators are connected to the first and second dynamic memories, respectively, to generate a switching tip that indicates when a header indicating a block in the baseband symbol stream is detected. The pair of dynamic memories is operable to continue writing the flow of baseband symbols in one of the pair of memories until it produces the switching tip. The input switch and the output switch commute to their reverse states and the uplink signal in the first and second dynamic memories, at their outputs, is read according to the base frequency of the on-board clock. A synchronized pulse oscillator, connected to the first and second correlators, generates a filtered pulse for each of the symbols read at the output. A counter, connected to the oscillator, counts the filtered impulses. A number of bits is added to the headers of the flows, or is deleted from them, according to the value of said counter. BRIEF DESCRIPTION OF THE DRAWINGS These and other features and advantages of the present invention will be more readily understood from the detailed description that follows when read in relation to the accompanying drawings, which form part of this original description and in which: Figure 1 is a schematic diagram of a satellite direct broadcast system constructed according to an embodiment of the present invention. Figure 2 is a flow chart showing the sequence of operations for processing an end-to-end signal in the system depicted in Figure 1 according to an embodiment of the present invention. Figure 3 is a functional diagram of a terrestrial broadcast station constructed according to an embodiment of the present invention.

Figure 4 is a schematic diagram illustrating the multiplexing of diffusion segments according to an embodiment of the present invention. Figure 5 is a functional schematic of an on-board processing equipment for a satellite according to an embodiment of the present invention. Figure 6 is a schematic diagram illustrating demultiplexing and demodulation processing on board the satellite according to an embodiment of the present invention. Figure 7 is a schematic diagram illustrating the speed alignment processing on board the satellite according to an embodiment of the present invention. Figure 8 is a schematic diagram illustrating time division multiplexing and switching operations on board the satellite according to an embodiment of the present invention. Figure 9 is a functional diagram of a radio receiver to be used in the system depicted in Figure 1 and constructed according to an embodiment of the present invention. Figure 10 is a schematic diagram illustrating receiver synchronization and demultiplexing operations according to an embodiment of the present invention. Figure 11 is a schematic diagram illustrating synchronization and multiplexing operations for recovering coded broadcast channels in a receiver according to an embodiment of the present invention; and Figure 12 is a schematic diagram of a system for managing the satellite and broadcast stations according to an embodiment of the present invention. Detailed Description of the Preferred Embodiments General According to the present invention, a satellite broadcasting system 10 is provided for broadcasting satellite programs 25 from a plurality of different broadcast stations 23a and 23b (hereinafter referred to generally as 23) , as illustrated in Figure 1. Users are provided with radio receivers, indicated generally by reference 29, designed to receive one or more L-band carriers, 27, time division multiplexed (TDM) with downlink from satellite 25, which are modulated to 1.65 Mega-symbols per second (Msim / s). The radios 29 of the users are designed to demodulate and demultiplex the TDM carrier to recover bits that constitute the content of digital information or program transmitted in broadcast channels from the broadcast stations 23. According to an embodiment of the invention, the stations of broadcast 23 and satellite 25 are configured to format uplink and downlink signals to allow improved reception of broadcast programs using radio receivers of relatively low cost. A radio receiver can be a mobile unit 29a mounted on a transport vehicle, for example a portable unit 28b or a processing terminal 29c with a screen.

Although only one satellite 25 is presented in Figure 1 for illustrative purposes, the system 10 preferably comprises three geostationary satellites 25a, 25b and 25c (Figure 12) configured to use frequency bands of 1467 to 1492 Megahertz (MHz) which has been assigned for direct audio broadcast (DAB) for broadcast satellites service (BSS). The broadcast stations 23 preferably use feeder uplinks 21 in the X band, ie from 7050 to 7075 MHz. Each satellite 25 is preferably configured to utilize three downlink zonal beams indicated in 31a, 31b and 31c. Each beam covers approximately 14 million square kilometers within power distribution contours that are 4 decibels (dB) below the center of the beam and 28 million square kilometers within contours that are 8 dB below. The central range of the beam can be 12 dB based on a receiver's gain-to-temperature ratio of 12 dB / K.

Continuing to refer to Figure 1, the uplink signals 21, generated from the broadcast stations 23, are modulated in frequency division multiple access (FDMA) channels from the ground stations 23 which are preferably located within the terrestrial visibility of the satellite 25. Each broadcast station 23 preferably has the ability to link directly from its own facilities to one of the satellites and put one or more increments of fundamental speed of 16 kilobits per second (kbps) in a single carrier. The use of FDMA channels for uplink offers considerable flexibility to share the space segment between multiple, independent, broadcast stations 23 and considerably reduces the power and, therefore, the cost of the uplink land stations 23. The fundamental rate increases (PRIs) of 16 kilobits per second (kbps) are preferably the most fundamental building block or rudimentary unit used in system 10 for the size of the channels and can be combined to achieve higher binary traffic speeds. For example, PRIs can be combined to create program channels with binary traffic speeds that reach up to 128 kbps to achieve near CD-quality sound or multimedia broadcast programs comprising image data, for example. Conversion between uplink FDMA channels and multiple channels per bearer / multiplex per time division (MCPC / TDM) downlink is achieved on board each satellite 25 at the baseband level. As will be described in more detail below, the fundamental velocity channels, transmitted by a broadcast station 23, are demultiplexed on the satellite 25 into individual 16 kbps baseband signals. The individual channels are then routed to one or more of the downlink beams 31a, 31b and 31c, each of which is a single TDM stream per carrier signal. This baseband processing provides a high level of channel control in terms of uplink frequency allocation and channel routing between uplink FDMA and downlink TDM signals. End-to-end signal processing, which occurs in system 10, is described with reference to Figure 2. The components of the system, responsible for the processing of end-to-end signals, will be described in more detail below. as reference Figures 3-11. As illustrated in Figure 2, audio signals from the audio source, for example in a broadcast station 23, are preferably encoded using MEGP 2.5 Layer 3 coding (box 26). The digital information assembled by a broadcast service provider in the broadcast station 23 is preferably formatted in increments or PRIs of 16 kpbs, where n is the number of PRIs acquired by the service provider (e.g., n x 16 kpbs). The digital information is then formatted in a broadcast channel block having a service control header (SCH) (box 28), which will be described in more detail below. A periodic block in the system 10 preferably has a period duration of 432 milliseconds (ms). Preferably, each block is allocated n x 224 bits for the SCH, so that the bit rate reaches approximately n x 16,519 kbps. Each block is then mixed by addition of a pseudo-random bit stream to the SCH. The information control of the mixing pattern by means of a key allows encryption. The bits in a block are then encoded for transmission error correction (FEC) protection preferably using two concatenated coding methods, for example the Reed Solomon method, followed by interleaving and then convolution coding (eg, convolution coding). "trellis" described by Viterbi) (box 30). The bits encoded in each block, corresponding to each PRI, are subsequently subdivided or demultiplexed into n parallel fundamental velocity channels (PRCs) (box 32). To perform the recovery of each PRC, a PRC synchronization header is provided. Each of the n PRCs is then differentially encoded and then modulated using, for example, quadrature phase shift modulation at an intermediate frequency (IF) carrier frequency (box 34).

The n IF carrier frequencies of PRC which constitute the diffusion channel of a diffusion station 23 are converted to the X band for transmission to the satellite 25, as indicated by the arrow 36. The carriers coming from the diffusion stations 23 are carriers of Single channel per carrier / multiple access per frequency division (SCPC / FDMA). On board each satellite 25 the SCP / FDMA carriers are received, demultiplexed and demodulated to recover the PRC carriers (box 38). The PRC digital baseband channels, retrieved by satellite 25, are subjected to a speed alignment function to compensate for differences in clock speed between the on-board clock of the satellite and that of the PRC carriers received in the satellite. satellite (block 40) The demultiplexed and demodulated digital flows obtained from the PRCs are provided to TDM block assemblers using routing and switching components The digital PRC flows are routed from demultiplexing and demodulation equipment on board the satellite 25 to the TDMA block assemblers in accordance with a switching sequence unit on board the satellite that is controlled from a ground station via a command link (eg, a satellite control center 236, Figure 12, by each region of operations.) Three TDM carriers are created that correspond to each of the beams of the three satellites 31a, 31b and 31c (box 42) The three TDM carriers are converted to L-band frequencies allowing the modulation of QPSK, as indicated by arrow 44. Radio receivers 29 are configured to receive any of the three TDM carriers and to demodulate the received carrier ( box 46). The radio receivers 29 are designed to synchronize a TDM bit array using a master block preamble provided during processing on board the satellite (box 48). The PRCs are demultiplexed from the TDM block using also an Interval Control Channel (TSCC). The digital flows are multiplexed back into the PRC format encoded by FEC, described above in relation to box 30 (box 50). The FEC processing preferably includes decoding using a Viterbi "trellis" decoder, for example, by deinterleaving, and then decoding by the Reed Solomon system to recover the original broadcast channel comprising the n x 16 kpbs channel and the SCH. The n x 16 kbps segment of the broadcast channel is supplied to an MPEG 2.5 Layer 3 source decoder for audio reconversion. According to the present invention, the audio output is available via each very low cost broadcasting receiver 27 due to the processing and formatting of TDM described above in relation to the broadcast station (stations) 23 and the satellite 25 (box 52). Multiplexing and Upstream Modulation The signal processing to convert data streams from one or more broadcast stations 23 into parallel streams for transmission to a satellite 25 will be described below in relation to Figure 3. For illustrative purposes, they are illustrated four sources 60, 64, 68 and 72 of program information. Two sources 60 and 64, or 68 and 72, are encoded and transmitted together as part of a single program or service. The coding of the program comprising combined audio sources 60 and 64 will be described. Program signal processing, comprising digital information from sources 68 and 72, is identical. As indicated above, the broadcast stations 23 assemble information from one or more sources 60 and 64 for a particular program into broadcast channels characterized by increments of 16 kbps. These increases are known as fundamental speed increases or PRIs. Thus, the binary traffic speed transmitted in a broadcast channel is n x 16 kbps where n is the number of PRIs used by that particular broadcast service provider.

In addition, each 16 kbps PRI can be further divided into two 8 kbps segments that are routed or switched together through system 10. The segments provide a mechanism for executing two different service items in the same PRI, for example a flow data with low-speed voice signals of binary traffic or two low-speed voice channels of binary traffic for two respective languages, and so on. The number of PRIs is preferably predetermined, that is, it is set according to the program code. However, the number n does not constitute a physical limitation of the system 10. The value of n is usually fixed on the basis of commercial issues, such as the cost of a single broadcasting channel and the willingness to pay of the service providers. In Figure 3, the number n corresponding to the first diffusion channel 59, for sources 60 and 64, is equal to 4. The value of n corresponding to the diffusion channel 67, for sources 68 and 72, is set at 6. in the illustrated embodiment. As illustrated in Figure 3, more than one broadcast service provider may have access to a single broadcast station 23. For example, a first service provider generates broadcast channel 59, while a second broadcast service provider may generating the broadcast channel 67. The signal processing, described here and according to the present invention, allows the diffusion of data streams, coming from several diffusion service providers, to a satellite in parallel flows, which reduces the diffusion cost for service providers and maximizes the use of the space segment. By maximizing the utilization efficiency of the space segment, the broadcast stations 23 can be implemented at a lower cost using lower energy consumption components. For example, the antenna in the broadcast station 23 can be a very small aperture terminal antenna (VSAT). The equipment on board the satellite requires less memory, less processing capacity and, therefore, fewer sources of energy, which reduces the weight of the payload. A broadcast channel 59 or 67 is characterized by u? block 100 having a period duration of 432 ms, as indicated in Figure 4. This period length is chosen to facilitate the use of the MPEG source encoder which will be described below; however, the block, paired in system 10, can be set to a different predetermined value. If the period duration is 432 ms, then each 16 kbps PRI requires 16,000 x 0.432 seconds = 6912 bits per block. As illustrated in Figure 4, a broadcast channel therefore consists of an n value of these 16 kbps PRIs that are transmitted as a group in block 100. As will be described below, these bits are mixed ( encrypt) to improve demodulation in radio receivers 29. The mixing or encryption operation also provides a mechanism to encrypt the service at the option of the service provider. To each block 100 nx 224 bits corresponding to a service control header (SCH) are assigned, resulting in a total of nx 7136 bits per block and a binary traffic speed of nx (16,518 + 14 \ 27) bits per second. The purpose of the SCH is to send data to each of the radio receivers 29 tuned to receive the broadcast channel 59 or 67 in order to control reception modes corresponding to various multimedia services, to display on the screen data in images, transmit key information for description, address a specific receiver, among other characteristics. Continuing to refer to Figure 3, sources 60 and 64 are encoded using, for example, encoders 62 and 66 of MPEG 2.5 Layer 3, respectively. The two sources are further summed via a combiner 76 and then processed using a processor in the broadcast station 23 to provide the signals encoded in periodic blocks of 432 ms, that is, nx 7136 bits per block including the SCH, as indicated by means of the processing module 78 in Figure 3. The boxes indicated in the broadcast station in Figure 3 correspond to programmed modules executed by a processor and its Corresponding "hardware" (circuitry), for example digital memory and encoder circuits. The bits in block 100 are further encoded for FEC protection using digital signal processing software (DSP), application-specific integrated circuits (ASICs) and customized large-scale integration (LSI) chips for the two coding methods concatenated. First, a Reed Solomon 80a encoder is provided to produce 255 bits for every 223 bits that arrive at the encoder. The bits in block 100 are then rearranged according to a known interleaving scheme, as indicated by reference number 80b. The interleaving encoding offers greater protection against bursts of error that occur in a transmission, since this method scatters corrupted bits in several channels.

Continuing with the reference to the processing module 80, a known convolution coding scheme of limitation length 7 is applied using a Viterbi 80c encoder. The Viterbi encoder 83c produces two output bits for each input bit producing, as a net result, 16320 bits coded by FEC per block per each increment of 6912 bits per block applied to the broadcast channel 59. Thus, each broadcast channel coded by FEC (eg, channel 59 or 67) comprises nx 16320 bits of information that have been coded, reordered and encoded again, so that the original 16 kbps PRIs are no longer identifiable. However, the FEC encoding bits are organized in terms of the original block structure of 432 ms. The general coding rate for error protection is (255/223) x 2 = 2 + 64/223. Continuing with the reference to Figure 3, the nx 16320 bits of the FEC-encoded broadcast channel block are further subdivided or demultiplexed using a distributor of channels 82 into n parallel fundamental velocity channels (PRCs), each transmitting 16320 bits in terms of sets of 8160 two-bit symbols. This process is further illustrated in Figure 4. The diffusion channel 59 is shown which is characterized by a block 100 of 432 ms having an SCH 102. The remaining portion 104 of the block consists of n PRIs of 16 kbps corresponding to 6912 bits per block for each of the n PRIs. The diffusion channel 106 encoded by FEC is achieved according to Reed Solomon 255/223 concatenation, interleaving and convolution coding FEC 1/2, previously described in relation to the module 80. As indicated above, the diffusion channel block encoded by FEC 106 comprises nx 16320 bits corresponding to 8160 sets of two-bit symbols, each symbol being indicated by a reference number 108 for illustrative purposes. According to the present invention, the symbols are assigned through the PRCs 110 in the manner illustrated in Figure 4. Thus, the symbols will propagate on a time and frequency basis, thereby reducing the errors in the radio receiver caused for interference in transmission. The service provider for the broadcast channel 59 has purchased four PRCs, by way of illustration, while the service provider for the broadcast channel 67 has purchased six PRCs for illustrative purposes. Figure 4 illustrates the first broadcast channel 59 and the symbol assignment 114 through the n = 4 PRCs 110a, 110b, 110c and HOd, respectively. In order to implement the recovery of each two-bit symbol 114 fixed to the receiver, a PRC synchronization header or preamble 112a, 112b, 112c and 112d, respectively, is placed ahead of each PRC. The PRC synchronization header (hereinafter referred to using the reference number 112) contains 48 symbols. The synchronization header PRC 112 is placed ahead of each group of 8160 symbols, thereby increasing the number of symbols per block from 432 ms to 8,208 symbols. Accordingly, the symbol rate reaches 8208 / 0.432 which is equivalent to 19,000 kilo-symbols per second (ksim / s) for each PRC 110. The PRC preamble 112 of 48 symbols is used essentially for synchronization of the PRC clock of the receiver. radio to retrieve the symbols of the downlink transmission of the satellite 27. In the on-board processor 216, the PRC preamble is used to absorb timing differences between the rates or symbol rates of arrival uplink signals and those used on board to switch the signals and assemble the downlink TDM flows. It is done adding, subtracting a "0" or. nothing to each PRC of 48 symbols in the process of speed alignment used on board the satellite. Thus, PRC preambles transmitted on the TDM downlink have 47, 48 or 49 symbols as determined by the speed alignment process. As illustrated in Figure 4, the symbols 114 are assigned to consecutive PRCs of a circular or "round table" shape, so that the symbol 1 is assigned to the PRC 110a, the symbol 2 is assigned to the PRC 110b, the symbol 3 is assigned to PRC 110c, symbol 4 is assigned to PRC HOd, symbol 5 is assigned to PRC 11Oe, and so on. This demultiplexing process of PRC is performed by means of a processor in the broadcast station 23 and is represented in Figure 3 as the channel distribution module (DEMUX) 82. The preambles of PRC channels are assigned to mark the beginning of the PRC blocks 110a, 110b, 110c and HOd for the broadcast channel 59 using the preamble module 84 and the summing module 85. The n PRCs are then differentially encoded and then modulated by QPSK on an IF carrier frequency using a battery of modulators of QPSK 86 as illustrated in Figure 3. Four of the QPSK modulators 86a, 86b, 86c and 86d are used for respective PRCs, 110a, 110b, 110c, HOd, for the diffusion channel 59.

Accordingly, there are four IF carrier frequencies of PRC which constitute the broadcast channel 59. Each of the four carrier frequencies is converted to the position of its assigned frequency in the X-band using a frequency-raising converter 88 for transmission to the satellite 25. The PRCs, converted to higher frequency, are subsequently transmitted through an amplifier 90 to the antenna (eg, a VSAT) 91a and 91b. According to the present invention, the transmission method employed in a broadcast station 23 incorporates a multiplicity of n carriers of Single Channel per Carrier / Multiple Access by Frequency Division (SCPC / FDMA) in the uplink signal 21. These carriers SCPC / FDMA are separated on a lattice of central frequencies separated from each other 38,000 Hertz (Hz) and organized into groups of 48 contiguous central frequencies or carrier channels.

The organization of these groups of 48 bearer channels is useful for the preparation of the demultiplexing and demodulation process carried out on the board of satellite 25. The various groups of 48 bearer channels do not necessarily have to be contiguous with one another. The carriers associated with a particular broadcast channel (e.g., channel 59 or 67) are not necessarily contiguous within a group of 48 bearer channels and do not necessarily have to be allocated in the same group of 48 bearer channels. The transmission method described in relation to Figures 3 and 4 therefore offers flexibility to choose positions or frequency zones and optimizes the possibility of filling the available frequency spectrum and avoiding interference with other users who share the same. radio frequency spectrum. The system 10 is convenient because it provides a common basis for increasing capacity for a multiplicity of broadcast companies or service providers, whereby diffusion channels of various binary traffic speeds can be constructed with relative ease and transmitted to a receiver. The characteristic increases of broadcast channels or PRIs are preferably 16, 32, 46, 64, 80, 96, 112 and 128 kbps. Broadcast channels of various binary traffic speeds are interpreted with relative ease by the radio receiver due to the processing described in relation to Figure 4. The size and cost of a broadcast station can be designed, therefore, for adapt it to the capacity needs and limitations of financial resources of a broadcasting company. A broadcasting company with scarce financial resources can install a small VSAT terminal that requires a relatively small amount of power to broadcast a 16 kbps service to their country, which is sufficient to transmit voice and music with a much better quality than that of the shortwave radio On the other hand, a sophisticated broadcasting company, with considerable financial resources, can transmit FM stereo quality with a slightly larger antenna and more power at 64 kbps and, with additional capacity increases, almost compact disc stereo broadcast quality (CD ) at 96 kpbs and total stereo quality of CD at 128 kbps. The size of the block, the size of SCH, the size of the preamble and the length of PRC, described in relation to Figure 4, are used to achieve a variety of advantages; however, the processing of the diffusion station, described in relation to Figures 3 and 4, is not limited to these values. The block period of 432 ms is convenient when using an MPEG source encoder (e.g., encoder 62 or 66). The 224 bits corresponding to each SCH 102 are chosen to facilitate FEC coding. The PRC preamble of 48 symbols, 112, is chosen to achieve 8208 symbols per PRC 110 to achieve 19,000 ksim / s for each PRC with respect to a simplified multiplexing and demultiplexing embodiment on board the satellite 25, as will be described in more detail later. Defining symbols that comprise two bits is convenient for QPSK modulation (e.g., 2 = 4). For further illustration, if the phase shift modulation in the broadcast station 23 uses eight phases instead of four phases, the defined symbol consisting of three bits would be more convenient since each combination of three bits (eg, 2) may correspond to one of the eight phases. Software may be provided in a broadcast station 23 or, if there is more than one broadcast station in the system 10, a regional broadcast control facility (RBCF) 238 (Figure 12) for assigning channel routing of the space segment via of a mission control center (MCC) 240, a satellite control center (SCC) 236 and a broadcast control center (BCC) 244. The optimal software use of the uplink spectrum allocating carrier channels of PRC 110 whenever space is available in the groups of 48 channels. For example, it may happen that a broadcast station wishes to broadcast a 64 kbps service on four PRC carriers. Due to the current use of the spectrum, the four carriers may not be available in contiguous positions or zones, but only in non-contiguous positions or zones within a group of 48 carriers. In addition, the RBCF 238 that uses its MCC and SCC can assign the PRCs to non-contiguous positions or zones between groups of 48 different channels. The MCC and SCC software in the RBCF 238 or a single broadcast station 23 may reposition PRC carriers of a particular broadcast service to other frequencies to avoid intentional (e.g., intrusion) or accidental interference in specific carrier positions. A current implementation of the system has three RBCFs, one for each of the three regional satellites. Additional satellites can be controlled through one of these three facilities. As will be described in more detail below in relation to the on-board processing of the satellite, Figure 6, a polyphase processor im-plemented on board is used digitally for on-board signal regeneration and digital baseband recovery of the symbols 114 transmitted in the PRCs. The use of groups of 48 carriers, spaced at central frequencies separated by 38,000 Hz, facilitates processing by the polyphase processor. The software available in broadcast station 23 or RBCF 238 can perform "defragmentation", that is, defragmentation processing to optimize assignments of PRC 110 to uplink bearer channels, that is, groups of 48 bearer channels. The essence behind the defragmentation of uplink carrier frequency assignments is no different from the software known to reorganize files on a computer hard drive that, over time, would have been saved in such a fragmentary way that they would be inefficient for data storage. The BCC functions in the RBCF allow the RBCF to remotely monitor and control the broadcast stations to ensure their operation within the assigned tolerances.

On-board Processing of the Satellite The recovery of the baseband on the satellite is important for executing on-board switching and routing and assemblies of downlink TDM carriers, each with 96 PRCs. The TDM carriers are amplified on board satellite 25 using a single-carrier operation by traveling wave tube. The satellite 25 preferably comprises eight on-board baseband processors; however, only one processor 116 is illustrated. Preferably only six of the eight processors are used at the same time, the rest being redundancy in case of failures or anomalies and ordering them to cease transmission if circumstances require. A single processor 116 is described in relation to Figures 6 and 7. It will be understood that identical components are preferably provided for each of the other seven processors 116. With reference to Figure 5, the encoded PRC uplink carriers 21 are receive on satellite 25 by means of an X-band 120 receiver. The overall uplink capability is preferably comprised between 288 and 384 PRC uplink channels of 16 kbps each (e.g., 6 x 48 carriers if six processors 116, or 8 x 48 carriers are used if the eight processors 116 are used). As will be described in more detail below, 96 PRCs are chosen and multiplexed for transmission in each downlink beam 27 in a carrier of approximately 2.5 MHz bandwidth. Each uplink PRC channel can be routed to all, some or none of the downlink beams 27. The order and location of the PRCs in a downlink beam is programmable and selectable from a telemetry, range and control (CRT) 24 (Figure 1). Each polyphase demultiplexer and demodulator 122 receives the individual uplink signals of FDMA in groups of 48 contiguous channels and generates a single analog signal in which the data of the 48 FDMA signals are time-timed and high demodulated. serial data rate, as will be described in more detail below with reference to Figure 6. Six of these polyphase demultiplexers and demodulators 122 operate in parallel for processor 288 FDMA signals. A routing switch and modulator 124 selectively addresses individual channels of the six serial data streams in all, some or none of the downlink signals 27 and further modulates and converts the three downlink TDM signals 27 to higher frequency. Three traveling wave tube amplifiers (T TA) 126 individually amplify the three downlink signals, which are radiated to the ground by means of L 128 band transmission antennas. Satellite 25 also contains three transparent payloads (equipment) each comprising a demultiplexer and converter at lower frequencies 130 and an amplifier group 132 configured in a traditional "tube-like" signal path that converts the frequency of the input signals for transmission.

Thus, each satellite 25 in the system 10 is preferably equipped with two types of communication equipment. The first type of on-board processing equipment is described in relation to Figures 5, 6 and 7.

The second type of communication equipment is the transparent equipment that converts uplink TDM carriers from frequency positions in the uplink X-band spectrum to frequency positions in the L-band downlink spectrum. TDM transmitted for the transparent equipment is assembled in a broadcast station 23, transmitted to satellite 25, the frequency is received and converted to a downlink frequency position using module 130, amplified by a TWTA in module 132 and it is transmitted to one of the beams. To a radio receiver 29, the TDM signals appear identical to it whether they come from an on-board processing equipment indicated at 121, or to the transparent equipment indicated at 133. The positions of the carrier frequencies of each type of equipment 121 and 133 they are separated into separate 920 kHz separation lattices which are interleaved with each other in a bisected manner so that the positions of the carriers of a mixture of signals from both types of equipment 121 and 133 are at 460 kHz spacings. The on-board demultiplexer and demodulator 122 will now be described in more detail with reference to Figure 6. As illustrated in Figure 6, the SCPC / FDMA carriers, each of which is indicated by the reference number 136, They are assigned to groups of 48 channels. A group 138 is presented in Figure 6 for illustrative purposes. The carriers 136 are spaced in a lattice of central frequencies separated by 38 kHz. This spacing determines nominal parameters of the polyphase demultiplexers. For each satellite 25, 288 SCPC / FDMA carriers of uplink PRC can preferably be received from a variety of broadcast stations 23. Therefore, six polyphase demultiplexers and demodulators are preferably used. 122. An on-board processor 116 accepts these uplink carriers of SCPC / FDMA from PRC 136 and converts them into three downlink TMD carriers, each transmitting 96 of the PRCs in 96 slots. The 288 carriers are received by an uplink global beam antenna 118 and the frequency of each group of 48 channels is converted to an intermediate frequency (IF) which is then filtered to select a frequency band occupied by that particular group 138. This process takes place in the receiver 120. The filtered signal is then fed to an analog / digital converter (A / D) before being fed, as input, to a polyphase demultiplexer 144. The demultiplexer 144 separates the 48 channels from SCPC / FDMA 138 in an analog time-division multiplexed signal stream comprising symbols modulated with QPSK having in sequence the content of each of 48 channels of SCPC / FDMA at the output of demultiplexer 144. This flow of analog signals of TDM is routed to a QPSK demodulator and differential decoder 146, implemented digitally. The scrambler and differential decoder of QPSK 146 demodulates in sequence the symbols modulated by QPSK in digital baseband bits. The demodulation process requires symbol timing and carrier recovery. Since the modulation is QPSK, baseband symbols containing two bits each are retrieved for each carrier symbol. The demultiplexer 144 and the demodulator and decoder 146 will hereafter be referred to as a demultiplexer / demodulator (D / D) 148. The D / D is preferably performed using high-speed digital technology using the polyphase (polyphase) technique known to demultiplex the carriers Uplink 21. The QPSK demodulator is preferably a digitally implemented demodulator, shared in series, to retrieve the two-bit symbols of the baseband. The recovered symbols 114 of each PRC carrier 110 are then decoded differentially to retrieve the PRC symbols 108., originals, applied to the input encoders, that is, the channel distributors 82 and 98, FIG. 3, in the broadcast station 23. The payload of the satellite 25 preferably comprises six D / Ds 148, of 48 carriers, implemented digitally In addition, two reserve D / Ds 148 are provided in the payload (equipment) of the satellite to replace any of the units with anomalies. Continuing with the reference to Figure 6, the processor 116 is programmed in accordance with a software module indicated at 150 to perform a speed synchronization and alignment function on the symbol flow multiplexed by time division, generated at the output of the QPSK demodulator and differential decoder 146. The software and hardware components (eg, digital dynamic memories and oscillators) of the speed alignment module 150, Figure 6, will be described in more detail with respect to Figure 7. The alignment module of speeds 150 compensates for differences in the speeds of the clock signals between the on-board clock 142 and the clock signal of the symbols transmitted by the individual uplink PRC carriers 138 received on satellite 25. The speeds or frequencies of base differ due to different base frequencies in the different broadcast stations 23, and different speeds of Doppler from different positions caused by the movement of the satellite 25. The differences in speed or base frequency attributed to the diffusion stations 23 may originate in clocks in the broadcast station itself or in remote clocks, whose base frequencies are transfer by land links between a broadcast study and a broadcast station 23. The speed alignment module 150 adds or deletes a value symbol "0", or does not perform any of these operations, in the header portion of PRC 112 of each block of 432 ms recovered 100. A value symbol "0" is a symbol consisting of a binary value 0 on both channels I and Q of the symbol modulated by QPSK. The header of PRC 112 comprises 48 symbols under normal operating conditions and consists of an initial symbol of value "0", followed by another 47 symbols. When the times of the symbols of the uplink clock signal, retrieved by the QPSK demodulator 146 together with the uplink carrier frequency, and those of the on-board signal 152 are synchronized, no change is made to the preamble. of PRC 112 corresponding to that particular PRC 110. When the incoming uplink symbols have a delay that is delayed behind the on-board clock signal 152 in a symbol, a "0" symbol is added at the beginning of the PRC preamble 112 for the PRC that is being processed, producing a length of 49 symbols. When the incoming uplink symbols have a timing that precedes the on-board clock signal 152 in a symbol, a "0" symbol is suppressed at the beginning of the PRC preamble 112 of the current PRC being processed, producing a length of 47 symbols. As indicated above, the input signal to the velocity alignment module 150 comprises the flow of the two-bit symbols of the baseband recovered by each received uplink PRC at its individual original symbol rates. 288 of the aforementioned flows are issued from the D / D 148 corresponding to each of the six active processors 116. The action comprising exclusively a D / D 148 and a speed alignment module 150 is described, although it will be understood that the five other active processors 116 on the satellite perform similar functions. To align the uplink PRC symbol rate with the on-board clock signal 152, three operations are performed. First, the symbols are grouped in terms of their 8208 PRC blocks of two-bit symbols 110, original, in each dynamic memory 149 and 151 of an alternate memory 153. This operation requires the correlation of the header of PRC 112 (containing a unique word of 47 symbols) with a stored local copy of the unique word in correlators indicated at 155 to place the symbols in a dynamic memory. Second, the number of "beats" of the on-board clock 152 between correlation switching tips is determined and used to adjust the length of the PRC 112 to compensate for the difference in speed. Third, the PRC block, with its modified header, is activated, at the on-board speed in its proper position in a switching and routing memory device 156 (Figure 8). The PRC symbols enter the pair of alternate dynamic memoranda 153 on the left. The alternation action causes a memory 149 or 151 to be filled at the uplink clock rate and the other memory to be emptied simultaneously at the clock speed on board the satellite. The papers are inverted from one block to the next and produce a continuous flow between the input and the output of the dynamic memory 149 and 151. The newly incoming symbols are written to the memory 149 or 151 according to the one they are connected to. Writing continues to fill memory 149 or 151 until the correlation switching tip occurs. The writing is then stopped and the input and output switches 161 and 163 switch to the reverse state. In this way an uplink PRC block is captured so that its 48 header symbols reside in the 48-symbol intervals leaving an unfilled interval at the output end of the memory and the 8160 data symbols fill the first 8160 intervals. The content of the memory in question is read immediately at its output at the speed of the clock signal on board the satellite. The number of symbols read is done so that the PRC header contains 47, 48 or 49 symbols. A value symbol "0" is deleted or added at the beginning of the PRC header to make this adjustment. The header length 112 is controlled by a signal from a block symbol counter 159 that counts the number of on-board clock speed symbols that will be comprised in a PRC block period to determine the length of the header. The alternation action alternates the roles of the memories. To realize the count, the block correlation switching peaks, coming from the correlators of the memories 155, as the PRC blocks fill the memories 149 and 151, are flattened by a synchronization pulse oscillator (SPC) 157. Appropriate timing pulses (filtered) are used to count the number of times of symbols per block. The number will be 8207, 8208 or 8209, indicating that the header of PRC should have a length of 47, 48 or 49 symbols, respectively. This information makes the appropriate number of symbols, which must be received from dynamic block memories, maintain the flow of symbols synchronously with the clock on board the satellite and regardless of the origin of the terrestrial terminal. With respect to the anticipated speed differences in the system 10, the execution times between modifications of the preamble 112 are relatively long. For example, differences in base speeds or frequencies of 10 will cause PRC preamble corrections in a middle term of one block of every 123 blocks of PRC. The resulting velocity settings result in the symbol speeds of the PRCs 110 being accurately synchronized in the on-board clock of satellite 152. This allows the routing of the baseband bit symbols to the appropriate positions in a block of TDM. The synchronized PRCs are indicated generally at 154 in Figure 6. The internal routing and switching of these PRCs 154 in TDM blocks will be described below in relation to Figure 8. Figure 6 illustrates PRC processing by a single D / D 148. The other five active D / Ds, on board the satellite, perform a similar processing.

The PRCs emanating from each of the six D / Ds 148, having been synchronized and aligned, take place in a serial flow having a symbol speed of 48 x 19,000 which is equal to 912,000 symbols per second for each D / D 148. The serial flow of each D / D 148 can be demultiplexed into 48 parallel PRC streams that have speeds of 19,000 symbols per second, as indicated in Figure 7. The aggregate of the preferred PRC flows of the six D / Ds 148, on board the satellite 25, is 288, each D / D transmitting 148 flows of 19,000 sim / s. Therefore, the symbols have epochs or periods of 1 / 19,000 seconds which is equivalent to a duration of approximately 52.63 microseconds. As illustrated in Figure 8, 288 symbols are displayed at the outputs of the six D / Ds 148a, 148b, 148c, 148d, 148e and 148 ~ f for each uplink PRC symbol epoch. Once each PRC symbol epoch, values of 288 symbols are written to a switching and routing memory 156. The contents of the dynamic memory 156 are read in three downlink TDM block assemblies 160, 162 and 164. Using a routing and switching component indicated as 172, the content of each of the 288 memory locations is read in terms of 2622 sets of 96 symbols to each of the three TDM blocks in the assemblers 160, 162 and 164 in one 136.8 ms time that occurs once every TDM block period or 138 ms. The scanning speed of 136.8 / 2622 is therefore faster than the duration of a symbol. The routing switch and modulator 124 comprises an alternate memory configuration indicated generally by reference 156 and comprising dynamic memories 156a and 156b, respectively. The 288 uplink PRCs, indicated at 154, are fed as input to the routing switch and modulator 124. The symbols of each PRC occur at a rate of 19,000 symbols per second corrected to the timing of the on-board clock 152. The PRC symbols are written in parallel to the clock rate or base frequency of 19,000 Hz in 288 positions in the alternate memory 156a or 156b serving as input. At the same time, the memory serving as output, 156b or 156a, respectively, will read the symbols stored in the previous block in the three TDM blocks at a reading speed of 3 x 1.84 MHz. This last speed is sufficient for allow simultaneous generation of the three parallel flows of TDM, one directed to each of the three beams. The routing of the symbols to their allocated beam is controlled by a symbol routing switch 172. This switch can route a symbol to any one, two or three of the TDM flows. Each TDM flow occurs at a rate of 1.84 Msim / s. The output memory is activated for an interval of 136.8 ms with pauses of 1.2 ms to allow the insertion of MFP of 96 symbols and TSCC of 2112 symbols. Note that for each symbol that is read in more than one TDM stream, there is a deflection uplink FDM PRC channel that is not used and skipped. The alternate dynamic memories 156a and 156b exchange the papers block by block via the switching components 158a and 158b. Continuing with the reference to Figure 8, sets of 96 symbols are transferred to 2622 corresponding intervals in each TDM block. The corresponding symbols (eg, the i-th symbols) corresponding to all 96 uplink PRCs are grouped in the same TDM block interval as the one illustrated by the interval 166 in relation to the symbol 1. The content of the 2622 intervals of each TDM block are mixed or encrypted by adding a pseudo-random binary pattern to the full epoch of 136.8 ms. In addition, a time of 1.2 ms is added at the beginning of each TDM block to insert a 96-symbol master block preamble (MFP) and a TSCC of 2112 symbols, as indicated in 168 and 170, respectively. The sum of the 2622 intervals, each carrying 96 symbols, and the symbols corresponding to MFP and TSCC is 253,920 symbols per TDM block, resulting in a downlink symbol rate of 1.84 Msim / s. The routing of the PRC symbols between the outputs of the six D / Ds 148A148B, 148C, 148D, 148E, and 148F and the inputs to the TDM block assemblies 160, 162, and 164 are controlled by a switching sequence unit 172 on board the satellite that stores instructions transmitted thereto via a link. command from SCC 238 (Figure 12) from ground. Each symbol originating in a chosen uplink PRC symbol stream can be routed to a range in a TDM block to be transmitted to a desired destination beam 27. The routing method is independent of the relationships between the time of appearance of the symbols in various uplink PRCs and the appearance of symbols in the downlink TDM flows. This reduces the complexity of the equipment of satellite 25. In addition, a symbol originating in a chosen uplink PRC can be routed to two or three destination beams by means of switch 158. Radio Receiver Operation A radio receiver 29, to be used in the system 10, will be described below in relation to Figure 9. The radio receiver 29 comprises a radio frequency (RF) section 176 having an antenna 178 for receiving L-band electromagnetic waves and pre-filtered to select the operating band of the receiver (eg, 1452 to 1492 MHz). The RF section 176 further comprises a low noise amplifier 180 capable of amplifying the received signal with a minimum of self-introduced noise and capable of withstanding interference signals that may come from another service sharing the operating band of the receiver 29. A mixer 182 it is used for the conversion of the received spectrum to an intermediate frequency (IF). An IF filter 184, of high characteristics, selects the bandwidth of the desired TDM carrier from the output of the mixer 182 and a local oscillator synthesizer 186, which generates the mixed input frequencies necessary to convert the desired signal to a frequency lower than the center of the IF filter. The TDM carriers are located on central frequencies spaced in a grid that has 460 kHz separations. The bandwidth of the IF filter 184 is approximately 2.5 MHz. The separation between carriers is preferably at least seven or eight spaces or approximately 3.3 MHz. The RF section 176 is designed to select the bandwidth of the desired TDM carrier with a minimum of interference and distortion, generated internally. , and to reject unwanted carriers that could occur in the operating band from 152 to 192 MHz. In most areas of the world, the levels of unwanted signals are nominal and, characteristically, the relationships of unwanted signals to desired signals 30 to 40 dB provides sufficient protection. In some areas, operations near high power transmitters (e.g., in the vicinity of terrestrial microwave transmitters for public switched telephone networks or other audio broadcast services) require an input design capable of better protection ratios. The bandwidth of the desired TDM carrier, recovered from the downlink signal, using the RF section 176, is provided to an A / D converter 188 and then to a QPSK 190 demodulator. The QPSK 190 demodulator is designed to recover the binary TDM stream transmitted from the satellite 25, that is, via the on-board processing equipment 121 or the transparent equipment on board 133, on a chosen carrier frequency. The QPSK demodulator 190 is preferably implemented by first converting the IF signal from the RF section 176 into a digital representation using the A / D converter 188 and then implementing QPSK using a known digital processing method. The demodulation preferably utilizes symbol timing and carrier frequency pickup and decision circuits that display and decode the symbols of the QPSK modulated signal in the baseband TDM binary stream. The A / D converter 188 and the QPSK demodulator 190 are preferably provided on a channel recovery chip 187 to recover the digital baseband signal from the diffusion channel of the IF signals recovered by the RF circuit board / IF 176. The channel recovery circuit 187 comprises a TDM synchronizer and predictor module 192, a TDM demultiplexer 194, an alignment synchronizer and PRC multiplexer 196, the operation of which will be described in more detail with respect to FIG. 10. The TDM binary stream at the output of the QPSK demodulator 190 is provided to a correlator of synchronization of MFP 200 in the synchronizer and predictor module of TDM 192. Correlator 200 compares the bits of the received stream with a stored pattern. When there has previously been no signal present in the receiver, the correlator 200 first introduces a search mode in which it searches for the desired MFP correlation pattern without any door limitation or time slot being applied to its output. When the correlator discovers a correlation event, it introduces a mode in which a door is opened at an interval in which a next correlation event is anticipated. If a correlation event occurs again within the time period of the predicted time gate, the process of passage through time gate is repeated. If the correlation takes place with respect to five consecutive time blocks, for example, it is declared that the synchronization has been determined according to the software. However, the synchronization threshold can be changed. If the correlation has not occurred at the minimum number of consecutive intervals to reach the synchronization threshold, the correlator continues to look for the correlation pattern. Assuming that synchronization has occurred, the correlator introduces a synchronization mode in which it adjusts its parameters to maximize the probability of continuous synchronization fixation. If the correlation is lost, the correlator introduces a special predictive mode in which it continues to retain synchronization by predicting the arrival of the next correlation event. With respect to short signal drops (e.g., up to ten seconds), the correlator can maintain sufficiently accurate synchronization to achieve virtually instantaneous recovery when the signal returns. Such rapid recovery is convenient because it is important for mobile reception conditions. If, after a specific period, the correlation is not restored, the correlator 200 returns to the search mode. After synchronization to the MFP of the TDM block, the TSCC can be retrieved by the TDM demultiplexer 194 (box 202 in Figure 10). The TSCC contains information that identifies the program providers transmitted in the TDM block and in which the channel positions of each program provider of 96 can be found.

PRCs. Before any PRCs of the TDM block can be demultiplexed, the portion of the TDM block carrying the PRC symbols is described. The operation is performed by adding the same mixing or encryption pattern in the receiver 29, that which was added to the PRC portion of the TDM block binary stream on board satellite 25. This mixing or encryption pattern is synchronizes by means of the MFP of TDM blocks. The symbols of the PRCs are not grouped in an adjoining fashion in the TDM block, but are propagated through the block. There are 2622 sets of symbols contained in the PRC portion of the TDM block. In each set there is a symbol for each PRC in a position that is numbered in ascending order from 1 to 96. Thus, all symbols belonging to PRC 1 are in the first position of all the 2622 sets. The symbols belonging to PRC 2 are in the second position of all 2622 sets, and so on, as indicated in box 204. This arrangement for numbering and locating the symbols of the PRCs in the TDM block, according to the present invention, minimizes the capacity of the memory to perform the switching and routing on board the satellite and for demultiplexing the receiver. As illustrated in Figure 9, the TSCC is retrieved from the TDM demultiplexer 194 and is provided to the controller 220 at the receiver 29 to retrieve the n PRCs corresponding to a particular broadcast channel. The symbols of the n PRCs, associated with the broadcast channel, are extracted from the positions of the unmixed (encrypt) TDM block slots identified in the TSCC. This association is made by means of a controller contained in the radio apparatus and is indicated generally by reference 205 in Figure 10. The controller 220 accepts a broadcast selection identified by the radio operator, combines this selection with the information of PRC contained in the TSCC and extracts and reorders the symbols of the PRCs of the TDM block to restore the n PRCs. With respect to cells 196 and 206, respectively, Figures 9 and 10, the symbols of each of the n PRCs (eg, as indicated in 207), associated with a broadcast channel (eg, as indicated in 209). ), selected by the radio operator, are remultiplexed in a broadcast channel format (BC) encoded by FEC. Before performing the new multi-plexion, the n PRCs of a broadcast channel are realigned. The realignment is useful because the reactivation of the symbol timing found in the multiplexing, demultiplexing and alignment of speeds on board the satellite in the passage through the end-to-end link in the system 10 can introduce a drift that can reach up to four symbols in the relative alignment of the recovered PRC blocks. Each of the n PRCs of a broadcast channel has a preamble of 48 symbols, followed by 8160 encoded PRC symbols. To recombine these n PRCs in the broadcast channel, the synchronization is carried out in the header of 47, 48 or 49 symbols of each of the PRCs. The length of the header depends on the timing alignment performed in the uplink PRCs on satellite 25. The synchronization is performed using a preamble correlator that acts on the 47 most recent reception symbols of the PRC header for each one of the n PRCs. The preamble correlator detects correlation incidents and issues a single correlation switching tip with duration of a single symbol. Taking as a basis the time relative to the appearance of the correlation switching tips corresponding to the n PRCs associated with the diffusion channel, and which act together with dynamic alignment memories having a width of four symbols, the content of symbols of the n PRCs can be precisely aligned and remultiplexed to retrieve the broadcast channel encoded by FEC. The new multiplexing of the n PRCs, to reform the diffusion channel encoded by FEC, preferably requires that the symbol propagation method, used in the broadcast station 23 to demultiplex the diffusion channel encoded by FEC in the PRCs, be performed in reverse order, as it is indicated in boxes 206 and 208 of Figure 10. Figure 11 illustrates how a broadcast channel, comprising four PRCs, for example, is retrieved in the receiver (box 196 in Figure 9). On the left, the arrival of four demodulated PRCs is indicated. Due to reactivation variations and different delays found in the transmission from the broadcasting station through the satellite to the radio apparatus, up to four relative drift symbols can be produced between the n PRCs that constitute a broadcast channel. The first step in recovery is to realign the symbol content of these PRCs. It is performed by a set of FIFO dynamic memories each of which has a length equal to the range of variation. Each PRC has its own memory 222. Each PRC is first provided to a PRC headend correlator 226 that determines the instant of arrival. The moments of arrival are indicated by a correlation switching tip 224 for each of the four PRCs in the illustration.

The writing (W) is started in each dynamic memory 22 immediately after the instant of the correlation and continues thereafter until the end of the blocking. To align the symbols with the PRCs, the reading (R) of all the memories 222 starts at the instant of the last correlation event. This results in the symbols of all the PRCs being read synchronously in parallel at the outputs of the memory 222 (box 206). The realigned symbols 228 are then multiplexed by means of the multiplexer 230 into a single stream in series which is the recovered coded broadcast channel 232 (box 208). Due to the alignment of clock speeds on board satellite 152, the length of the PRC header may be 47, 48 or 49 symbols. This variation is eliminated in the correlator 226 using only the last 47 symbols to arrive at detecting correlation events. These 47 symbols are selected in a special way to achieve an optimal correlation detection. With respect to blocks 198 and 210 of FIGS. 9 and 10, respectively, the diffusion channel encoded by FEC is further provided to the processing module of FEC 210. Most of the errors found in transmission between the position of the encoders and the decoders are corrected by FEC processing. The FEC processing preferably employs a Trellis Viterbi Decoder, followed by de-interleaving and then a Reed Solomon decoder. With FEC processing, the original broadcast channel comprising n x 16 kbps channel increments and its n x 224 bits SCH (box 212) is recovered. The n x 16 kbps segment of the broadcast channel is provided to a decoder, for example a source decoder 214 MPEG 2.5 Layer 3 for reconversion to audio signals. In this way, the processing of the receiver can be performed using a low-cost radio apparatus for reception of broadcast channels from satellites. As the transmissions of the satellite broadcast programs 25 is digital, the system 10 can provide a variety of other services that are also expressed in digital format. As indicated above, the SCH contained in the broadcast channels provides a control channel for a wide variety of future service options. Thus, chipsets can be produced to implement these service options by making available the entire TDM bit stream and its demodulated raw format, the demultiplexed TSCC information bits and the recovered broadcast channel, corrected for errors. The radio receivers 29 can also be provided with an identification code for the exclusive addressing of each radio apparatus. The code can be accessed by means of bits transmitted on a channel of the SCH of the broadcast channel. For mobile operation employing a radio receiver 29 according to the present invention, the radio apparatus is configured to predict and recover, almost instantaneously, the positions of the MFP correlation switching tips with a precision of 1/4 symbol. for intervals that can reach up to 10 seconds. A local symbol timing oscillator, with a precision of short duration greater than one part per 100,000,000 is preferably installed in the radio receiver, particularly when it is a portable radio apparatus 29b. System for Managing Satellites and Broadcast Stations As indicated above, the system may comprise one or a plurality of satellites 25. Figure 12 depicts three satellites 25a, 25b and 25c for illustrative purposes. A system 10, having several satellites, preferably comprises a plurality of TCR stations 24a, 24b, 24c, 24d and 24e positioned so that each satellite 25a, 25b and 25c is on the pick-up line of two TCR stations . The TCR stations indicated generally by the reference number 24 are controlled by means of a regional broadcast control facility (RBCF) 238a, 238b or 238c. Each RBCH 238a, 238b and 238c comprises 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 SCC controls the satellite bus and communications equipment and is where the computer and human resources of command and control of space segments are located. The installation is preferably assisted 24 hours a day by a variety of technicians trained in the command and control of satellites in the orbit. The SCCs 236a, 236b and 236c monitor the on-board components and essentially use the corresponding satellite 25a, 25b and 25c. Each TCR station 24 is preferably directly connected to a corresponding SCC 236a, 236b or 236c by means of PSTN, double, redundant, full-time circuits. In each of the regions served by satellites 25a, 25b and 25c, the corresponding RBCF 238a, 238b and 238c reserves broadcast channels for audio, data, video image services, allocates routing of segment channels Space through the mission control center (MCC) 240a, 240b, 240c, validates the transmission of the service, which consists of information necessary for billing to a broadcast service provider and invoices the service provider. Each MCC is configured to program the allocation of the channels of the space segment that comprises assignments of uplink PRC frequencies and downlink PRC TDM slots. Each MCC performs dynamic and static control. The dynamic control includes controlling windows of time for assignments, that is, the assignment of use of the space segment on a monthly, weekly and daily basis. Static control includes spatial segment assignments that do not vary on a monthly, weekly and daily basis. A sales office, which has personnel to sell space segment capacity to the corresponding RBCF, provides the MCC with data indicating the available capacity and instructions to enter into possession of the capacity that has been acquired. The MCC generates a general plan to occupy the time and frequency space of the system 10. The plan is then converted into instructions for the on-board routing switch 172 and sent to the SCC for transmission to the satellite. The plan can be updated and transmitted to the satellite preferably once every twelve hours. The MCC 240a, 240b and 240c also monitors the satellite TDM signals received by the corresponding channel system monitor equipment (CSME) 242a, 242b and 242c. The CSME stations verify that the broadcast stations 23 are transmitting broadcast channels within the speci fi cations.

Each BCC 244a, 244b and 244c monitors the terrestrial broadcast stations 23 in their region for proper operation within the chosen frequency, power and addressing tolerances. BCCs can also be connected to corresponding broadcast stations to transmit orders to malfunctioning stations that are not transmitting. A central facility 246 is preferably constituted for technical support services and support operations for each of the SCCs. While certain suitable embodiments have been chosen to illustrate the invention, those skilled in the art will understand that various changes and modifications may be made thereto without departing from its scope as defined in the appended claims.

Claims (62)

1. CLAIMS 1. Receiving unit for receiving a downlink (space-to-earth) data stream, multiplexed by time division, from a satellite, comprising: a phase shift modulation demodulator to demodulate said link data stream descending in a stream of symbols, the downlink data stream comprising intervals and being provided with a predetermined number of fundamental rate channels, at respective intervals, by said satellite; a correlator connected to the demodulator to locate and synchronize with a master block preamble inserted in the symbol stream by the satellite, the correlator being configured to store a master block correlation pattern corresponding to the master block preamble and programmable to operate in a search mode or a synchronized operating mode; a demultiplexer connected to the correlator to locate an interval control channel in the symbol stream, the interval control channel being inserted into the symbol stream by the satellite to identify which of the intervals comprises the fundamental velocity channels corresponding to each one from a plurality of broadcast service providers; and an input device configured for an operator to select one of the broadcast service providers and which can be managed to provide an output signal to the demultiplexer, the demultiplexer being operable to extract selected channels from said fundamental rate channels using the interval control channel and the output signal.
2. 2. Receiving unit according to claim 1, characterized in that the correlator is configured to operate in a predictive mode employing either a time gate or an aperture limitation corresponding to a time interval foreseen for the next correlation event in a output of the correlator, when the correlator detects the master block correlation pattern and to operate in a search mode without employing neither the time gate nor the aperture limitation when the master block correlation pattern is not detected.
3. Receiving unit according to claim 1, characterized in that the correlator is configured to operate in a synchronization mode when the master block correlation pattern is detected during a predetermined minimum number of consecutive intervals of the downlink data stream and to operate in a predictive mode when the master block correlation pattern operating in the synchronization mode is not detected, the correlator maintaining the operation in the referred synchronization mode using a predicted time interval to determine another master block correlation pattern.
4. 4. Receiving unit according to claim 3, characterized in that the correlator is configured to operate again in search mode when the master block correlation pattern is not detected during a predetermined minimum number of consecutive intervals of the downlink data flow during the mode predictive 5.
5. Receiving unit for receiving a time-division multiplexed downlink data stream from a satellite, comprising: a demodulator for demodulating the downlink data stream in a symbol stream, comprising the downlink data stream intervals having a plurality of interval positions and being provided with a predetermined number of fundamental velocity channels by the satellite, each of the fundamental velocity channels comprising a plurality of symbols, each of the plurality of symbols being assigned, respectively, at intervals to propagate the plurality of symbols, corresponding to each of the fundamental velocity channels, by the downlink data stream, the plurality of symbols corresponding to each of the fundamental velocity channels being assigned to the corresponding one of the plurality of positions of intervals in each of said inte rvalos; a demultiplexer connected to the demodulator for locating an interval control channel in the symbol stream through the satellite to identify which of the plurality of interval positions comprises the plurality of symbols of at least one of the fundamental velocity channels corresponding to a chosen broadcast service provider; an extraction device for extracting the plurality of symbols corresponding to the channel or channels of fundamental speed of the broadcast service provider chosen from said symbol flow according to said channel of control of inter-values; and a multiplexer for multiplexing the plurality of symbols corresponding to the chosen broadcast service provider in a data stream of serial broadcast channels.
6. Receiving unit according to claim 5, characterized in that the broadcast service provider uses a plurality of said fundamental speed channels and further comprises a realignment device connected to the extraction device and configured to align the plurality of fundamental speed channels some with respect to others.
7. Receiving circuit according to claim 6, characterized in that each of the fundamental velocity channels comprises a header and the realignment device comprises: a dynamic memory for each of the plurality of fundamental velocity channels; and a correlator connected to the dynamic memory and configured to determine the moment of arrival of the head of a corresponding one of the fundamental velocity channels and to start writing the fundamental velocity channel in the dynamic memory, reading the dynamic memory corresponding to each one of the plurality of fundamental rate channels from immediately after the arrival instant of the header corresponding to the last of the fundamental rate channels that is detected to generate the data stream of serial broadcast channels.
8. A method for recovering at least one fundamental rate channel between several fundamental rate channels transmitted in a time division multiplexed downlink data stream from a satellite, comprising the steps of: demodulating the link data flow descending in a stream of symbols, the downlink data stream comprising slots having a plurality of slot positions and being provided with a predetermined number of fundamental slot channels by the satellite, the slots comprising a plurality of symbols , each of the plurality of symbols being assigned, respectively, to the aforementioned intervals to propagate the plurality of symbols corresponding to each of the fundamental velocity channels by the downlink data flow, the plurality of symbols corresponding to each one being assigned. of the fundamental velocity channels to the correspondent of the plurality of positions of intervals in each of the intervals; demultiplexing the flow of symbols to locate a control channel of intervals inserted therein, by the satellite, to identify which of the plurality of said interval positions comprises the plurality of symbols of at least one of the speed channels fundamental corresponding to a chosen broadcast service provider; extracting the plurality of symbols corresponding to the channel or channels of fundamental velocity of the chosen broadcast service provider of said symbol flow in accordance with the interval control channel; and multiplexing the plurality of symbols corresponding to the chosen service provider in a data stream of serial broadcast channels.
9. The method according to claim 8, characterized in that the diffusion service provider employs a plurality of fundamental velocity channels and because it further comprises the step of aligning the plurality of fundamental velocity channels with respect to each other before multiplexing the plurality of symbols corresponding to the plurality of fundamental velocity channels.
10. 10. Method according to claim 9, characterized in that each of the fundamental velocity channels comprises a header and the alignment stage comprises the steps of: writing each of the plurality of fundamental velocity channels in respective dynamic memories once the determination of the respective instants has been made of arrival of headers; and read the memories once the determination of the last of the arrival instants has been made.
11. 11. Method for receiving one of a plurality of broadcast channels transmitted by downlink signals comprising fundamental rate channels from a satellite, comprising the steps of: demodulating the downlink signals in a binary stream multiplexed by division of baseband time comprising blocks generated by the satellite, each of the blocks comprising a plurality of intervals; each of the intervals comprising a set of symbols; each symbol corresponding in the said set of symbols, with a respective one of the fundamental velocity channels occupying a similar symbol position in each of the intervals; locate the blocks in the binary stream using a master block preamble inserted in the binary stream by the satellite; recovering from the set of symbols in each of the intervals at least one of the symbol blocks corresponding to at least one of the fundamental velocity channels; re-multiplexing the symbols corresponding to the channel or fundamental velocity channels to recover a broadcast channel corresponding to them and as originally transmitted to the satellite; and extracting a service control header from the broadcast channel.
12. Method according to claim 11, characterized in that the recovery step comprises the steps of: locating an interval control channel inserted in the binary stream by the satellite, the control channel indicating which of the intervals contains the symbols corresponding to each one of the fundamental velocity channels; and extract the symbols corresponding to one of the selected fundamental velocity channels using the control channel.
13. The method according to claim 11, characterized in that it further comprises the step of determining whether the service control header comprises an identification code inserted in the broadcast channel by a broadcast station before transmission to the satellite for exclusive addressing of a radio receiver.
14. The method according to claim 11, characterized in that it further comprises the steps of: determining whether the service control header comprises control data; and operating a radio receiver to perform at least one of a plurality of functions depending on the control data, the plurality of functions comprising operating the radio receiver in a reception mode chosen to provide a chosen multimedia service, Present data on screen, present an image on the screen and to describe data using a description key provided in the service control header.
15. 15. A radio receiver for receiving one of a plurality of fundamental rate channels transmitted by downlink signals from a satellite, comprising: a radio frequency device for receiving the downlink signals; a channel recovery device for recovering the fundamental rate channels of the downlink signals by demodulating the downlink signals in a binary time division multiplexed binary stream comprising blocks generated by the satellite, each of which comprises blocks a plurality of intervals, each of the intervals comprising a set of symbols, each symbol corresponding to the set of symbols corresponding to one of the fundamental velocity channels occupying a similar symbol position in each of the intervals; locate the blocks in the binary stream using a master block preamble inserted in the binary stream by the satellite; recovering from the set of symbols, in each of the intervals of at least one of the blocks, the symbols corresponding to at least one of the fundamental velocity channels; re-multiplexing the symbols corresponding to the channel or fundamental velocity channels to recover a broadcast channel corresponding to them and as originally transmitted to the satellite; and extracting a service control header from the broadcast channel; and a controller, which controller can be operated to receive the service control header of the channel recovery device and control the radio receiver to perform a plurality of functions, which comprises operating the radio receiver in a radio mode. reception chosen to provide a chosen multimedia service, present data on the screen, display an image on the screen, describe data using a decryption key provided in the service control header and respond to an identification code provided in the control header of service to address the radio receiver in an exclusive way.
16. 16. Method for transmitting a broadcast program from a broadcast service provider to one or more remote receiving units, which comprises the steps of: assembling bits corresponding to at least a portion of the program in a first number of increments of fundamental velocity having uniform and predetermined speeds; generating a block of predetermined duration and comprising each of the fundamental rate increments and a block header; dividing the block into symbols, each of the symbols comprising a predetermined and consecutive number of said bits; demultiplexing the symbols of the block into a second plurality of parallel fundamental velocity channels, each of the fundamental velocity channels having the same predetermined duration as the said block, the symbols being provided in a predetermined order through the velocity channels fundamental for separating consecutive symbols from said symbols, each of the fundamental velocity channels comprising a fundamental rate channel synchronization header for recovering the fundamental velocity channels in the remote receiving units; and modulating the fundamental velocity channels into a corresponding number of uplink carrier frequencies for broadcast transmission.
17. 17. Method according to claim 16, characterized in that the head of the block comprises bits for controlling the receiving unit.
18. 18. Method according to claim 16, characterized in that the program is characterized by two services and in addition it comprises the step of dividing at least one of the fundamental speed increments into two parts to transmit the corresponding bits to the two services, respectively.
19. The method according to claim 16, characterized in that the second number of fundamental velocity channels corresponds to the first number of fundamental velocity increments.
20. 20. Method according to claim 16, characterized in that the modulation step comprises the step of modulating each of the fundamental velocity channels using a plurality of quadrature phase shift modulation modulators.
21. 21. Method according to claim 20, characterized in that the symbols each comprise two of said bits.
22. 22. A method according to claim 20, characterized in that the second number of fundamental velocity channels and the said plurality of quadrature phase shift modulation modulators correspond in number to the first number of fundamental velocity increments.
23. 23. Method according to claim 16, characterized in that the said predetermined order is a sequential order.
24. 24. Method for transmitting a broadcast program from a broadcast service provider to one or more remote receiving units, comprising the steps of: assembling the program into a first integer number of fundamental rate increments having a predetermined uniform rate; generating a block of bits having a predetermined duration and comprising each of the fundamental rate increments and a block header; encoding the block to generate a coded block comprising coded bits for error correction protection in transmission; dividing the coded block into symbols, each of the symbols comprising a predefined and consecutive number of said bits; demultiplexing the symbols in a second number of parallel fundamental velocity channels, the symbols being provided in a predetermined order through the fundamental velocity channels for separating consecutive symbols from said symbols, each of the fundamental velocity channels comprising a header of synchronization of fundamental velocity channels to recover the fundamental velocity channels in the remote receiving units; and modulating the fundamental velocity channels in a corresponding number of uplink carrier frequencies for broadcast transmission.
25. 25. Method according to claim 24, characterized in that the coding step comprises at least one coding scheme chosen from the group consisting of Reed Solomon coding, intercalation and Trellis convolution coding.
26. 26. The method according to claim 24, characterized in that the coding step comprises the steps: coding the block according to a first coding scheme to generate a first coded block; interleaving the first coded block to generate an interleaved coded block; and encoder the coded block interleaved using a second coding scheme.,
27. 27. Method according to claim 26, characterized in that the first coding scheme is a Reed Solomon coding scheme.
28. 28. Method according to claim 26, characterized in that the second coding scheme is a Trellis convolutional coding scheme.
29. 29. Method according to claim 24, characterized in that said predetermined order is an ascending order.
30. 30. System for managing a satellite and a plurality of broadcast stations to generate programs for transmission to remote radio receivers in broadcast channels via the satellite, the system comprising: a satellite control system configured to generate control signals for control satellite orientation and orbit and data processing control signals to control on-board processing of programs transmitted to satellite uplink (earth-to-space) via broadcast and routing systems to multiplexed carriers by downlink time division; at least one telemetry, range and control system connected to the satellite control system and configured to communicate with the satellite in order to provide control signals and data processing signals from the satellite control system to the satellite; and a mission control system connected to the satellite control system and to the broadcast stations, the mission control system being able to operate to assign selected channels of said broadcast channels to service providers wishing to transmit at least one of the programs via the satellite; store channel data relative to the assignments of the broadcast channels and provide the channel data to the satellite control system, and bill the service providers according to the number of broadcast channels assigned to them, providing the mission control, to the service providers, a plurality of options that include the number of broadcast channels that are reserved for uplink transmission, dates and times of day to use the reserved broadcast channels, and which of a number of Time division multiplexed signals, in a number of beams associated with the satellite, have to be used for downlink transmission, and the mission control system can be operated to indicate to the satellite control system which of the multiplexed signals time division in the beams must be used and generating the satellite control system corresponding data processing signals for routing the program to the selected beams.
31. 31. System according to claim 30, characterized in that the diffusion channels correspond to positions of frequencies in a predetermined radiofrequency spectrum and because the mission control system is programmable to assign non-contiguous channels of said diffusion channels to one. of service providers.
32. 32. The system according to claim 31, characterized in that the mission control system can be operated to carry out a de-fragmentation process in order to reassign the service providers to different diffusion channels in order to optimize the use of satellite uplink spectrum.
33. System according to claim 30, characterized in that it also comprises a channel services monitor connected to the mission control system, the mission control system being able to operate to validate the transmission of programs with sufficient signal intensity and rate. of errors in sufficiently low bits using the channel services monitor before billing service providers.
34. 34. System according to claim 30, characterized by further comprising a broadcast control center for monitoring and controlling the broadcast stations in order to maintain the performance of the broadcast stations within predetermined tolerances in relation to carrier frequency assignments., antenna power levels and antenna orientation.
35. 35. The system of claim 30, characterized by further comprising a broadcast control center for monitoring and controlling the broadcast stations and which can be operated to instruct the broadcast stations to terminate the use of the channels. of diffusion.
36. 36. System according to claim 30, characterized in that it further comprises a broadcast control center for monitoring and controlling the broadcast stations and which can be operated to generate and transmit a command to at least one of the broadcast stations. to disconnect said broadcast station.
37. 37. System for managing a satellite and a plurality of broadcast stations to generate programs for transmission to remote radio receivers via the satellite, the system comprising: a satellite control system configured to generate control signals to control the operation of the satellite, the satellite being configured to receive an uplink comprising multiple access channels by frequency division and to generate at least two time division multiplexed downlink signals, each of the signals comprising a plurality of intervals, the broadcasting stations can be operated to modulate the programs in increments of fundamental speed for transmission in chosen channels of the said multiple frequency division access channels, the satellite also being configured to route the fundamental speed increments to selected intervals of the frequencies. ferides intervals in accordance with the control signals; a mission control system connected to the satellite control system and to the broadcast stations, the mission control system being able to operate to assign chosen channels of the said frequency division multiple access channels to serve providers that wish transmit the aforementioned fundamental speed increases via the satellite; assigning at least one of the time division multiplexed signals for downlink transmission of the fundamental rate increments; storing channel data relative to the aforementioned assignments of the frequency division multiplex access channels and the time division multiplexed signals and providing the channel data to the satellite control system to generate the control signals; and at least one telemetry, range and control system, connected to the satellite control center and configured to communicate with the satellite in order to provide the control signals from the satellite control system to the satellite.
38. 38. System according to claim 37, characterized in that the mission control system is programmable to assign non-contiguous channels of said frequency division multiple access channels to one of the service providers.
39. 39. The system according to claim 37, characterized in that the system can be operated to validate the achieved transmission of fundamental rate increases by way of at least one of the time-division multiplexed signals before generating the respective billing for corresponding service providers.
40. 40. System according to claim 37, characterized in that the master control system can be operated to perform dynamic control by assigning chosen channels of the said multiple frequency division access channels for periodic and temporary use by at least one selected provider of the referred service providers on a monthly, weekly and daily basis.
41. 41. System according to claim 37, characterized in that the master control system can be operated to perform static control by assigning chosen channels of said frequency division multiple access channels to selected providers of said service providers for use. practically constant and exclusive.
42. 42. System according to claim 37, characterized in that a diffusion control system connected to the broadcast stations and that can be operated to monitor the broadcast stations in order to determine if the broadcast stations are operating within predetermined tolerances relating at least to frequency, power or direction of an antenna connected to respective broadcast stations.
43. 43. System according to claim 37, characterized in that it further comprises a diffusion control system connected to the broadcast stations and that can be operated to monitor the broadcast stations and determine if the broadcast stations are operating within predetermined tolerances and to generate and transmitting a command to at least one of the broadcast stations to disconnect said broadcast station.
44. 44. Apparatus for switching symbols in parallel broadcast channels to data streams multiplexed by time division, comprising: a first and a second dynamic alternating memories, the first dynamic alternating memory being configured to store therein a first plurality of the aforementioned symbols contained in the parallel broadcast channels, the second dynamic memory of alternation being operable to store therein a second plurality of the said symbols contained in the parallel broadcast channels, the second plurality of symbols having arrived in the channels of diffusion parallel to the second dynamic memory of alternation before the arrival of the first plurality of symbols in the diffusion channels parallel to the first dynamic memory of alternation; a routing switch connected to the outputs of the first and second dynamic alternating memories; and a first block assembler connected to the routing switch, the routing switch being operable to control writing of the contents of the second dynamic alternate memory in the first block assembler.
45. 45. Apparatus according to claim 44, characterized in that it further comprises a second block assembler connected to the routing switch, the routing switch being operable to control the writing of the content of the second dynamic memory of alternation in at least one of the first block assembler and the second block assembler.
46. 46. Apparatus according to claim 45, characterized in that the routing switch can be operated to control the writing of the content of the second dynamic memory of alternation in the first block assembler and in the second block assembler to generate two data streams. parallels multiplexed by time division.
47. 47. Apparatus according to claim 44, characterized in that the second dynamic alternation memory can be operated to store in a third plurality of broadcast channels, the routing switch being operable to control the writing of the contents of the first dynamic memory of alternation in the first block assembler.
48. 48. Apparatus according to claim 44, characterized in that the first dynamic alternating memory can be operated to switch only one of the first plurality of symbols each time.
49. 49. Apparatus according to claim 44, characterized in that the second dynamic alternating memory can be operated to switch only one of the second plurality of symbols each time.
50. 50. Apparatus according to claim 44, characterized in that the first block assembler can be operated to insert at least one frame bit in the second dynamic alternation memory to identify the symbols stored in the second dynamic memory of alternation as a block. .
51. 51. Apparatus according to claim 50, characterized in that the block comprises intervals and the first block assembler can be operated to insert at least one bit representing an interval control channel in the second dynamic alternation memory to indicate in which of the intervals are stored the symbols corresponding to respective channels of said diffusion channels.
52. 52. Apparatus according to claim 44, characterized in that the apparatus is on board a satellite and the routing switch can be controlled by control signals generated by a ground station and transmitted to the satellite.
53. 53. Apparatus according to claim 45, characterized in that the second block assembler can be operated to insert at least one frame bit in the first dynamic alternation memory to identify the symbols stored in the first dynamic memory of alternation as a block .
54. 54. Apparatus according to claim 53, characterized in that the block comprises intervals and the second block assembler can be operated to insert at least one bit representing an interval control channel in the first dynamic memory of alternation to indicate in which of the intervals are stored the symbols corresponding to respective channels of the said parallel diffusion channels.
55. 55. A satellite equipment processing system for processing an uplink signal consisting of a plurality of single channel frequency division multiple channel access carriers per carrier, comprising: a polyphase demultiplexer processor for separating the signal of uplink in a data symbol stream multiplexed by time division and displaying the corresponding symbols to each of a plurality of carriers at respective frequencies of said frequencies in the uplink signal, in sequence, to a processor output polyphase demultiplexer; and a phase shift modulation demodulator connected to the output of the polyphase demultiplexer processor to demodulate the flow of symbols in a corresponding multiplexed time division digital baseband bit stream.
56. 56. A satellite equipment processing system according to claim 55, further characterized in that it comprises a differential decoder connected to the phase shift modulation demodulator to recover the flow of symbols when the symbol flow is differentially encoded for the signal carrier of the satellite. uplink.
57. 57. A satellite equipment processing system according to claim 55, characterized in that the phase shift modulation demodulator is a quadrature displacement modulation demodulator for demodulating each of the symbols into two corresponding bits.
58. 58. A satellite equipment processing system according to claim 55, further characterized in that it comprises a switching and routing processor for routing the baseband digital bit stream to at least one of a plurality of downlink carriers multiplexed by division of time.
59. 59. Velocity alignment apparatus for a satellite, comprising: an on-board clock; an input switch; an output switch; a pair of dynamic alternating memories constituted by a first and a second dynamic memory and connected to the input switch and the output switch, the first and second dynamic memories receiving a stream of baseband digital symbols retrieved from a link signal ascending that depends on the operation of the input switch and the output switch, the first memory of the dynamic memory pair receiving said bits of compliance with an uplink base frequency obtained from the uplink signal, practically emptying simultaneously the second memory of the pair of dynamic memories its content stored according to the aforesaid base frequency, on board the satellite, inverting the operations of the first and second dynamic memories when the input switch and the output switch act; first and second correlators, connected to the first and second dynamic memories, respectively, and which can be operated to generate a switching tip when a header indicating a block in the baseband symbol stream is detected, the pair of dynamic memories can be operated to continue writing the baseband symbol flow in one of said pair of dynamic memories until the switching tip occurs, switching the input switch and the output switch to their inverse states , the first and second dynamic memories receiving the uplink signal being read out, in accordance with the base frequency on board the satellite; a synchronized pulse oscillator connected to the first and second correlators and which can be operated to generate a flattened pulse (filtering) for each of the symbols read at the output; and a counter connected to the oscillator for counting the flattened pulses, adding a number of bits to the headers of said flows or suppressing them in accordance with the value of the counter.
60. 60. A speed alignment device for a satellite according to claim 59, further characterized in that it comprises a reception symbol clock connected to the first dynamic memory and to the second dynamic memory and that can be operated to activate the first dynamic memory. or the second dynamic memory that is currently connected to the input switch to receive the retrieved symbols of the uplink signal.
61. 61. A speed alignment device for a satellite according to claim 59, characterized in that it further comprises a symbol clock, on board the satellite, connected to the first dynamic memory to the second dynamic memory and which can be operated to activate the first dynamic memory or the second dynamic memory that is currently connected to the output switch to output the symbols stored in it.
62. 62. Method for aligning the speed of uplink symbols to a clock on board a satellite, comprising the steps of: filling a dynamic memory with a plurality of the said symbols at the speed of the received symbols; correlating the memory symbols in blocks by comparing a header, inserted between the symbols, with a unique word of framing to locate the header between the symbols stored in the dynamic memory and generate correlation switching points when the header is located; counting the number of "beats" of the clock generated by a symbol clock on the satellite between said points of correlation switching; and adjust the length of the header in the dynamic memory to compensate for a speed difference between the speed of the symbols received and the speed of the symbols on board the satellite. SUMMARY OF THE INVENTION A direct broadcast satellite system is provided that assembles bits of broadcast programs in increments of fundamental velocity, several of which are assembled in a block. The blocks are divided into symbols that are demultiplexed into a plurality of fundamental velocity channels. The fundamental rate channels are demultiplexed into a corresponding number of broadcast frequencies for transmission to a satellite; an on-board demultiplexer separates uplink signals in symbol flows multiplexed by time division. A phase shift modulation demodulator demodulates the symbols into baseband digital data. The equipment of a satellite switches the symbols in data streams multiplexed by time division (TDM) using two dynamic alternating memories and a routing switch. The receivers process the TDM flows using preambles of blocks and control channels provided by the satellite, and service control headers (SCHs) provided by broadcast stations. A management system is provided to manage and control the satellite and broadcast stations.