EA002604B1 - Digital broadcast system using satellite direct broadcast and terrestial repeater - Google Patents

Abstract

1. A digital broadcasting system for transmitting a broadcast signal, said broadcast signal being transmitted from an earth station, comprising a satellite for receiving said broadcast signal from said earth station and for transmitting a satellite signal comprising said broadcast signal on a first carrier frequency; and a terrestrial repeater for receiving said satellite signal and for generating and transmitting a terrestrial signal from said satellite signal comprising said broadcast signal on a second carrier frequency that is different from said first carrier frequency, said terrestrial signal being modulated by said terrestrial repeater in accordance with a multipath-tolerant modulation technique. 2. A system as claimed in claim 1, wherein said terrestrial repeater is operable to modulate said terrestrial signal using at least one of adaptive equalized time division multiplexing, coherent frequency hopping adaptively equalized time division multiplexing, multicarrier modulation, and code division multiplexing. 3. A system as claimed in claim 1, wherein said satellite signal is modulated in accordance with at least one of time division multiplexing and code division multiplexing. 4. A system as claimed in claim 1, wherein said terrestrial repeater is operable to modulate said terrestrial signal using multicarrier modulation. 5. A system as claimed in claim 4, wherein said terrestrial repeater is operable to receive said satellite signal and to demodulate said satellite signal into a baseband signal prior to modulating said baseband signal using multicarrier modulation. 6. A system as claimed in claim 1, wherein said satellite signal is assigned a first code division multiple access channel code and said terrestrial signal is assigned a second code division multiple access channel code. 7. A system as claimed in claim 1, further comprising a second satellite, said second satellite being operable to receive said broadcast signal from said earth station and to transmit a second satellite signal comprising said broadcast signal on said first carrier frequency and delayed by a predetermined period of time with respect to the transmission of the first satellite signal. 8. A terrestrial repeater for retransmitting satellite signals to radio receivers, comprising a terrestrial receiver for receiving said satellite signals; and a terrestrial waveform modulator for generating terrestrial signals from said satellite signals, said terrestrial signals being modulated by said terrestrial waveform modulator in accordance with multicarrier modulation; wherein said satellite signals are transmitted from a satellite using a first carrier frequency, and said terrestrial waveform modulator is operable to transmit said terrestrial signals to said radio receivers using a second carrier frequency that is different from said first carrier frequency. 9. A terrestrial repeater as claimed in claim 8, wherein said terrestrial waveform modulator comprises a time division demultiplexer for demultiplexing said satellite signals from a serial time division multiplexed bit stream into a plurality of parallel bit streams; and an inverse fast Fourier transform device for generating a digital analog signal comprising a plurality of discrete Fourier transform coefficients. 10. A method for converting a time division multiplexed bit stream into a plurality of multicarrier modulated signals at a terrestrial repeater, comprising the steps of: receiving said time division multiplexed bit stream from a satellite; dividing said time division multiplexed bit stream into a plurality of parallel bit paths; representing each of a predetermined number of bits in each of said plurality of bit paths as a symbol comprising an imaginary component and a real component; providing said symbols to parallel inputs of an inverse Fourier transform converter as complex number frequency coefficient inputs to generate outputs which comprise modulated, narrow-band, orthogonal carriers; and transmitting said modulated, narrow-band, orthogonal carriers from said terrestrial repeater. 11. A method as claimed in claim 10, further comprising the step of generating a guard interval for said carriers. 12. A method as claimed in claim 11, wherein said generating step comprises the steps of: allocating a fraction of the symbol period corresponding to the duration of each of said symbols to guard time; and reducing the duration of each of said symbols. 13. A method as claimed in claim 12, wherein said reducing step comprises the steps of: storing said outputs of said inverse Fourier transform converter in a memory device every said symbol period; and reading from said memory device after each said fraction of said symbol period has elapsed. 14. A method as claimed in claim 11, wherein said generating step further comprises the step of filling said guard interval with a subset of said outputs of said inverse Fourier transform. 15. A method as claimed in claim 10, further comprising the step of inserting a synchronization symbol every predetermined number of said symbol periods to synchronize a sampling window corresponding to said fraction of said symbol period with respect to said carriers every said symbol period at a receiver for said plurality of multicarrier modulated signals. 16. A method as claimed in claim 10, further comprising the step of puncturing said time division multiplexed bit stream to reduce the total bandwidth associated with said carriers. 17. A method as claimed in claim 16, wherein said puncturing step comprises the step of selectively eliminating bits from said time division multiplexed bit stream prior to providing said symbols to said parallel inputs of said inverse Fourier transform converter. 18. A digital broadcasting system for transmitting a broadcast signal, said broadcast signal being transmitted from an earth station, comprising a first satellite configured to receive said broadcast signal from said earth station and to transmit a time division multiplexed satellite signal comprising said broadcast signal; a terrestrial repeater configured to receive said satellite signal and to generate and transmit a terrestrial signal from said satellite signal comprising said broadcast signal, said terrestrial signal being modulated by said terrestrial repeater in accordance with at least one of adaptive equalized time division multiplexing, coherent frequency hopping adaptive equalized time division multiplexing, code division multiplexing, and multicarrier modulation. 19. A digital broadcasting system as claimed in claim 18, wherein said satellite signal is transmitted using a first carrier frequency, and said terrestrial signal is transmitted using a second carrier frequency that is different from said first carrier frequency. 20. A digital broadcasting system as claimed in claim 18, further comprising at least one radio receiver configured to receive said satellite signal and said terrestrial signal, said radio receiver comprising a diversity combiner for generating an output signal from at least one of said satellite signal and said terrestrial signal. 21. A digital broadcasting system as claimed in claim 18, further comprising a second satellite configured to receive said broadcast signal from said earth station and to transmit a second time division multiplexed satellite signal comprising said broadcast signal, said second satellite signal being delayed with respect to said first satellite signal by a selected time delay. 22. A digital broadcasting system as claimed in claim 21, further comprising at least one radio receiver configured to receive said first satellite signal, said second satellite signal and said terrestrial signal, to delay at least one of said first satellite signal and said terrestrial signal in accordance with said selected time delay, and to generate an output signal from at least one of first satellite signal, said second satellite signal and said terrestrial signal. 23. A digital broadcasting system as claimed in claim 22, wherein said radio receiver comprises a diversity combiner and a switched combiner, said radio receiver using said diversity combiner to perform maximum likelihood decision combining of said first satellite <DP=5signal and said second satellite signal and said switched combiner to select between the output of said diversity combiner and said terrestrial signal depending on which of said output of said diversity combiner and said terrestrial signal has the least number of bit errors. 24. A digital broadcasting system as claimed in claim 22, wherein said radio receiver comprises a diversity combiner to perform maximum likelihood decision combining of said first satellite signal, said second satellite signals and said terrestrial signal. 25. A receiver for receiving a broadcast signal in a combined satellite and terrestrial digital broadcasting system, comprising a first receiver arm for receiving a first satellite signal transmitted from a first satellite on a first carrier frequency, said first satellite signal comprising said broadcast signal and being modulated in accordance with at least one of time division multiplexing and code division multiplexing, said first receiver arm comprising a demodulator for recovering said broadcast signal; a second receiver arm for receiving a terrestrial signal transmitted from a terrestrial station on a second carrier frequency, said terrestrial signal comprising said broadcast signal and being modulated in accordance with at least one of adaptive equalized time division multiplexing, coherent frequency hopping adaptive equalized time division multiplexing, code division multiplexing, and multicarrier modulation, said second receiver arm comprising a demodulator for recovering said broadcast signal; and a combiner for generating an output signal from at least one of said third satellite signal and said terrestrial signal. 26. A receiver as claimed in claim 25, further com

Description

Technical field

A digital broadcasting system is proposed that uses a satellite direct broadcasting system with various options for communication lines to the Earth in combination with a network of terrestrial repeaters using various broadcast options to provide highly affordable reception by mobile, stationary and portable radio communication devices in urban, suburban and rural areas, including open areas and areas characterized by terrain with high elevations.

State of the art

Receivers in existing systems providing digital audio broadcasting (UCR) service are radically affected by multipath effects, leading to a serious deterioration in signal quality, including signal attenuation and intersymbol interference (MI). The effects of attenuation in the broadcast channels to the receivers may depend on the frequency, especially in urban environments or geographical areas with high elevations, where the blocking of signals propagating along the line of sight (LV) from satellites prevails. The locations directly below the satellite (hereinafter referred to as the sub-satellite point) have essentially the highest elevation angles, while the locations distant from the sub-satellite point have essentially decreasing elevation angles and, accordingly, an increase in the angle from the center of the Earth between the sub-satellite point and the location reception. For locations near the sub-satellite point, a virtually unblocked reception by drug is characteristic. Thus, the need for ground-based amplification of potentially blocked signals along the LP is minimal. If the elevation angle of the drug to the satellite becomes less than about 85 °, the blockage by tall buildings or geological elevations (i.e., about 30 m) becomes significant. Terrestrial relay is needed to fill the uncovered spaces to provide satisfactory coverage for mobile, stationary and portable radio communications devices. In areas where the height of buildings or geological objects is relatively small (i.e., less than 10 m), the blockage is negligible until the elevation angle of the drug becomes less than 75 °. Thus, at a location at mid-latitude and high latitudes in the overlapping zones of one or more broadcast satellites, terrestrial relaying is required to achieve acceptable radio reception. There is a need for a fully satisfactory reception of a radio signal that combines satellite transmission to a satellite and terrestrial relay from a satellite downlink.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, there is provided a digital broadcasting system (DAC) that overcomes a number of disadvantages associated with existing broadcasting systems and provides a number of advantages. The DAC according to the present invention comprises a time division multiplexed (DU) satellite carrier delivery system for digital audio transmissions (DACs) and other digital information integrated by a network of terrestrial repeaters for relaying signals from a satellite downlink to radio receivers. Terrestrial repeaters are configured to use modulation methods insensitive to multipath propagation.

In accordance with another aspect of the present invention, the satellite delivery system and the ground repeater operate using different carrier frequencies. The ground repeater uses modulation methods insensitive to multipath propagation.

In accordance with another aspect of the present invention, both the satellite delivery system and the ground repeater utilize multipath-insensitive modulation techniques and may be configured to use the same or different carrier frequencies depending on the type of oscillation used. The satellite delivery system preferably utilizes a slave signal or a code division multiple access (CDMA) signal. The terrestrial repeater preferably uses a signal that is insensitive to multipath propagation, such as a CDMA mode signal, with an adaptively aligned VU (AVVU); with adaptively aligned slave with coherent frequency hopping (HFMCH) or with multi-carrier modulation (MMN).

In accordance with another aspect of the present invention, a single geostationary satellite transmits downlink signals that can be received by radio receivers on a satellite signal LAN, as well as ground-based relays. Each terrestrial repeater is configured to recover a digital group signal from a satellite signal and modulate the signal using multiple carrier modulation (MMN) for relay to radio receivers. The radios are configured to receive both a bit stream from a slave modulated by quadrature phase shift keying (QPSK) and an MMN stream. The radios are programmed to select the broadcast channel demodulated from the bit stream from the slave and from the MMN bit stream, and to select the broadcast channel restored with minimal errors using the diversity combiner.

In accordance with another aspect of the present invention, there is provided a DAC that includes two geostationary satellites in combination with a network of ground-based relays.

Terrestrial repeaters are configured to receive a group satellite signal and modulate this signal through an MMN. The radios are configured to implement diversity logic to select from three diversity signals, including two satellite signals and an MMN signal. Each radio receiver uses the maximum likelihood combining of two satellite signals over the LP with combining by switching between a ground relay or MMN signal and the output signal of the maximum likelihood combiner.

In accordance with another aspect of the present invention, the broadcast channel can be selected from three diversity signals by combining the maximum likelihood of the three signals, i.e. early and late satellite signals on the LP, and the MMN signal from the ground repeater.

Brief Description of the Drawings

These and other features and advantages of the present invention are explained in the following detailed description, illustrated by the drawings, in which the following is presented:

FIG. 1 is a digital broadcasting system for transmitting satellite signals and terrestrial signals in accordance with an embodiment of the present invention;

FIG. 2 is a diagram of a digital broadcasting system comprising a satellite and a terrestrial repeater in accordance with an embodiment of the present invention;

FIG. 3 is a block diagram illustrating a multi-carrier modulation (MMI) signal generation according to an embodiment of the present invention;

FIG. 4 is a block diagram of a radio receiver configured to demodulate MMN signals in accordance with an embodiment of the present invention;

FIG. 5 is a block diagram illustrating demodulation of an MMN signal in accordance with an embodiment of the present invention;

FIG. 6 is a block diagram of a radio receiver configured to demodulate signals with a temporary seal (VU) in accordance with an embodiment of the present invention;

FIG. 7 is a block diagram illustrating the demodulation of a QPSK signal with a slave in accordance with an embodiment of the present invention;

FIG. 8 and 9 are block diagrams of respective embodiments of the present invention for combining diversity signals in a radio receiver;

FIG. 10 is a system for combining three diversity signals using a maximum likelihood decision block in accordance with an embodiment of the present invention;

FIG. 11 is a block diagram illustrating a decompression of a signal from a slave in accordance with an embodiment of the present invention;

FIG. 12 is a system for combining bit streams reconstructed in a radio by means of a maximum likelihood decision block using a first satellite signal and a delayed second satellite signal, and a diversity combiner for a ground repeater signal, and an output signal of a maximum likelihood decision block according to an embodiment of the present invention ;

FIG. 13 is a configuration of a system for home reception of a broadcast signal in accordance with an embodiment of the present invention;

FIG. 14 shows the position of ground repeaters along a channel in accordance with an embodiment of the present invention.

Detailed Description of Preferred Embodiments

In FIG. 1 shows a digital broadcasting system 10 (CVS) comprising at least one geostationary satellite 12 for receiving a satellite signal along a line of sight (LV) with radios indicated at 14. Another geostationary satellite 16 in a different orbital position may be provided for purposes temporal and / or spatial diversity, as discussed below with reference to FIG. 6 and

7. The system 10 also includes at least one terrestrial repeater 18 for relaying satellite signals in geographic areas 20, where the reception by drug is complicated by tall buildings, hills and other obstacles. The radio receiver 14 is preferably configured to operate in two modes for receiving both satellite signals and terrestrial signals, and for selecting one of the signals as the input signal of the receiver.

As noted above, the present invention relates to a DAC 10 providing optimized reception by stationary, portable and mobile radio devices. In accordance with the present invention, the DAC 10 combines the line of sight (LAN) reception of satellite signals that are optimized for satellite delivery with the relay of the signal received via the LAN from satellite or 16 through one or more terrestrial relays 18. Terrestrial relays 18 use other signals which are optimized for ground delivery, where there is a blockage of the signal received through the LAN. Blocking the signal received through the drug is caused by buildings, bridges, trees and other obstacles, usually found in urban centers and suburban areas. Signals that are particularly suitable for satellite transmission over a LAN are time division multiplexing (WL) and code division multiple access (CDMA) signals. Signals that are insensitive to multipath propagation, especially suitable for eliminating the influence of terrestrial multipath fields operating in blocked urban areas, are CDMA signals, signals with adaptive equalization with a VU (AVVU); signals with adaptive equalization with a slave with coherent frequency hopping (AVUKSPCH) and with modulation of many carriers (MMN).

Frequency hopping is described in US Pat. No. 5,283,780, issued to the name 8c1cc1ipap c1 a1., Which is incorporated herein by reference. If the ground repeater 18 uses the ABC signal, the radios 14 use an equalizer (not shown). For AVUV, the bit stream from the slave is received from satellite 12 or 16. This bit stream is converted into a new bit stream from the slave, into which training sequences are entered using the procedure defined as punching. Punching replaces a small fraction of the data bits with the slave training sequences. The number of punched bits is so small that the errors caused by this can be corrected in the receiver by direct error correction. A new bit stream from the WU modulates in the repeater using QPSK a radio frequency (RF) carrier, which is transmitted with high power in a multipath environment, for example, in the central city business district. This transmitted signal is received by a receiver 14 provided with an adaptive equalizer in the time domain. Using training sequences, he can adjust the taps of the inverse multipath processor to constructively summarize the various multipath received components. The signal reconstructed in this way is then processed to recover the bits of the stream from the slave with great accuracy. The direct error correction available at receiver 14 corrects both errors introduced by punching and errors caused by thermal noise and defects in the receiver.

In accordance with another aspect of the present invention, the combination of a satellite-efficient LAN signal and a terrestrial multipath-insensitive signal in a DAC system is an optimal means of realizing reception highly accessible to mobile fixed and mobile radio communication devices in urban, suburban and rural areas . For example, in accordance with the embodiment of the present invention shown in FIG. 2-9, the MMN signal is transmitted from the deployed network of ground repeaters 18 to block the blocked area with a high degree of reception availability. The signal transmission methods described in connection with the present invention are applicable in the frequency range of electromagnetic waves from 200 to 3000 MHz to facilitate combining the signals of satellite transmission over the LAN with the terrestrial relay signal received from satellite 12 or 16.

Optimal satellite signals make it possible to very efficiently convert the solar energy stored by the solar panels of satellites 12 and 16 into transmitted radio frequency power. These oscillations are characterized by a low ratio of maximum power to average (i.e., amplitude coefficient, peak factor), thereby ensuring the operation of high-power amplifiers that feed the satellite’s antennas directed to the Earth at almost maximum output power, and therefore, with the most efficient output power. The signal from the slave is especially suitable for operation with a power of several tenths of a dB from the maximum output power. A CDMA signal using properly selected codes allows operation at a level of about 2 to 4 dB below the maximum output power. Since the MMN signal consists of the sum of hundreds of phase modulated sinusoids, as described below with reference to FIG. 3, the MMN signal essentially has a high ratio of maximum power to average. Therefore, the MMN signal experiences significantly greater amplitude and phase intermodulation distortions in a high-power satellite amplifier. To implement acceptable reception by a satellite receiver over an LP, the MMN signal is supported in a high-power amplifier, taking into account receiver performance defects of at least 6 dB in the downlink as compared to the quadrature phase shift keying (QPSK) signal with a slave. This leads to a four-fold decrease in the signal when converting the satellite power, presenting the signal from the MMN as an unacceptable choice for satellite delivery via LAN to the DAC 10. As for the signals of the AVUU and AVUKCHS, these signals are specifically designed to eliminate the effects of terrestrial multipath ineffective for satellite delivery over the LAN.

With regard to terrestrial amplification by relaying a satellite signal over the LAN from a terrestrial repeater, for example, oscillation from a WU is unsuitable, since its reception is seriously impaired due to multipath propagation. In addition, some proposed systems that use CDMA signals for amplification, repeat the signal of the same program using the code of one channel CDMA for satellite delivery over the LAN and the code of another channel CDMA for delivery by terrestrial relay on carriers that occupy the same range of working frequencies. Reception is implemented using adaptive comb (multi-tap) receivers. These proposed CDMA systems have disadvantages, since there is a ring zone in which reception is not possible, between the region where the amplified signal can be received and the region where the satellite signal can be received via the LAN. The receivers 14 in this ring are unable to receive the terrestrial relay signal because the signal power level is below the receiver threshold for this signal. These receivers 14 are also incapable of receiving a satellite signal via an LP, since there remains a significant relay signal, which interferes with reception from a satellite via an LP. Thus, these receivers 14 in the ring should move far enough from the relay zone to reduce the power of the relay signal below the threshold for creating interference; otherwise, reception from the satellite via the LP will be impossible.

In accordance with a possible embodiment of the present invention, the CDMA signal is adapted to be usable for simultaneous delivery over satellite LAN and via terrestrial relay. CDMA channel codes are assigned for each delivery to different RF carriers. The orthogonality thus created allows two signals (i.e., a satellite signal transmitted over an LP and a signal from a ground repeater) to be separated by RF / IF filtering in a radio receiver.

The identification of effective and ineffective combinations of oscillations for performing terrestrial satellite reception amplification over a satellite in accordance with the present invention is shown in the table. More than one type of modulation or signal formatting method can be used with a satellite signal in the same way as with a ground repeater signal.

Satellite signal Gain signal Recommended by Not recommended RF Carrier Spectra WU WU X Same or different WU ABBU X Same or different

WU MMN X Various WU AVUKCHR X Various WU Mdcr X Various Mdcr Mdcr X Various Mdcr ABBU X Various Mdcr AVUKCHR X Various Mdcr MMN X Various Mdcr any X The same ABBU any X Same or different AVUKCHR any X Same or different MMN any X Same or different

AVUU signals can be satisfactorily implemented and used in multipath environments characterized by propagation delays of signals lasting up to 20 microseconds (μs). It is necessary to ensure that the signals coming from the remote repeaters 18 do not exceed this boundary. Adaptively aligned relayed oscillation can be received by radios 14, designed to use the original unbalanced oscillation with WU, when the first is not manifested significant multipath propagation. This compatibility allows you to continue to use direct-receive radio communication devices over a LAN with an unaligned VU when the AVU relay mode is turned on.

The AVUHFSC signal can be satisfactorily implemented and used in multipath environments characterized by delays of up to 65 μs in duration. It is necessary to ensure that the signals coming from the remote repeaters 18 do not exceed this boundary. The oscillation cannot be received by the radios 14, designed to use the original unbalanced oscillations with WU.

The MMN signal can be satisfactorily implemented and used in multipath environments characterized by delays of up to 65 μs in duration. The maximum delay is affected by the allocation of the guard interval provided for periodically assigning a symbol period to the signal. It is necessary to ensure that the signals coming from the remote repeaters 18 do not exceed this boundary. The signal cannot be received by the radio receivers 14, designed to use the original unbalanced vibration with WU.

The CDMA signal can be satisfactorily implemented and used in multipath environments characterized by delays determined by the time delay interval realized in the channels in the multi-tap receivers 14. It is necessary to ensure that all signals coming from remote transponders 18, multipath reflections and various satellites do not exceed this veri9 tsu. This oscillation cannot be received by radios 14 designed to use the original unbalanced oscillation with WU.

Satellite signals can be transmitted from one or two satellites 12 or 16. The use of two geostationary satellites 12 and 16, significantly remote in orbits, creates a separation in the elevation angles of the drug and azimuths to increase the availability of signal reception. Also, the time diversity provided by relaying a signal from one satellite 12 or 16 or transmitting a signal from two satellites 12 and 16 with a properly selected time difference further increases reception availability.

According to a preferred embodiment of the present invention, a signal comprising a plurality of slave channels with a QPSK, a shift QPSK, a differential QPSK, differentially encoded QPSK, or a minimum phase shift keying (QPSK) modulation is used to transmit signals from a satellite for receiving on an LV radio 14. Terrestrial relay is preferably implemented using an MMN signal designed to transmit a bit stream from a slave with a throughput of up to 3.68 Mbit / s. Preferably, an MMN is used, which creates 400 to 1200 carrier frequencies by an inverse fast Fourier transform, as described below with reference to FIG. 3, which is expressed in the symbol period from 200 to 300 μs. A guard interval of 55 to 65 μs is included in each symbol period. The MMN signal is formed taking into account Doppler shifts in the frequency of the carrier of multipath components that appear simultaneously. Punching is preferably used to remove bits or pairs of bits from the bit stream from the slave to reduce the speed to between 70 and 80% of the 3.68 Mbit / s speed. A special symbol is inserted between each of the selected number of symbol periods generated by the FFT procedure to provide means for restoring symbol period synchronization and carrier frequency synchronization. The receiver 14 preferably implements a Viterbi trellis decoder with a soft solution for recovering bits or pairs of bits deleted during punching in the relay 18, as well as all other transmitted bits by using the erase method. In this method, the decoder simply ignores the bits at the known punching positions in the relay 18.

Satellite carrier delivery with WU in the digital broadcasting system 10 is described in US Patent Application No. 08/971049, filed November 1997, the entire contents of which are hereby incorporated by reference for all purposes. As shown in FIG. 2, the broadcast segment 22 preferably includes encoding a broadcast channel to form a temporally multiplexed (WL) bitstream at 3.68 Megabits per second (Mbps), as shown in block 26. The WL bitstream contains 96 channels with the main transmission speed is 16 kilobits per second (kbit / s) and additional information for synchronization, decompression, control of the broadcast channel and for services. The encoding of the broadcast channel preferably includes encoding an audio signal according to the MPEC standard, forward error correction (FEC), and compression. The resulting bit stream from the WU is modulated using quadrature phase shift keying (QPSK), as shown in block 28, before being transmitted on the uplink 30 to the satellite.

Satellite signal delivery from the WU provides the most efficient on-board payload of the satellite in relation to the conversion of solar energy into electromagnetic wave energy. This is ensured by the fact that when using traveling-wave tubes (TWT) in the single carrier mode from a WU to an active TWT, each TWT operates on a satellite with an output power at the saturation level, which is the most effective operating point. A carrier with a slave in normal use is designed to transmit 96 increments of the basic bit rate, each 16 kbit / s, to small-sized economical radios, overlapped by satellite patterns 12 or 16. From one to eight increments of the main speed are grouped to form a broadcast channel. A broadcast channel can be divided into a number of service channels for transmitting audio, video and multimedia transmission.

The density of the flow of energy delivered to the Earth by carriers from the satellites from satellites 12 and 16 can be made very high and, therefore, provide high-quality reception by the LV 14 radio receivers in cars and trucks when traveling on open highways in rural areas and in suburban areas. However, in urban areas with tall buildings or in forests with tall deciduous trees in high humidity conditions, drug reception is blocked, thereby preventing satisfactory operation of the receiver 14 for drug reception. Attempts to circumvent these conditions by increasing satellite power are associated with high additional costs and are technically impractical. Accordingly, a more practical alternative is to increase the efficiency of direct satellite reception over a LAN by adding a network of terrestrial repeaters 18.

Regarding the blocking of drug reception, the following should be noted. The locations directly below satellites 12 and 16 (i.e., the sub-satellite points) have substantially the highest elevation angles, while locations other than the sub-satellite points are characterized by substantially decreasing elevation angles and an increase in the angle from the center of the earth between the location under satellite and reception location. Receivers 14 at locations close to the sub-satellite point are provided with virtually unblocked reception over the LAN. Thus, the need for ground gain is minimal. However, when the elevation angle of the drug to the satellite becomes less than 85 °, the blockage by tall buildings (i.e. more than 30 m) becomes significant. Accordingly, ground relay is needed to fill gaps in the overlap in order to achieve a satisfactory overlap for mobile radios. In areas where the height of the buildings is small (i.e. less than 10 m), the blockage is negligible until the elevation angle of the drug becomes less than 75 °. In areas at middle latitudes and high latitudes in the overlapping zones with a width of 6 ° of satellites 12 and 16, ground-based relaying of oscillations from the WU is necessary in order to realize acceptable mobile reception. Thus, a fully satisfactory mobile reception requires a system that combines the transmission of an over-the-air from a satellite and the terrestrial relay of satellite oscillation.

The DAC 10 of the present invention relays the satellite signal over the LAN from a plurality of terrestrial repeaters 18 that are purposefully spaced from each other and deployed in the central part of the city, as well as in the outlying areas and suburban areas to achieve maximum coverage. This type of deployment is known for terrestrial digital audio broadcasting (DAC) and cellular telephone systems and can be extended in accordance with the present invention to terrestrial relay of a satellite signal from a WU through a LAN. The deployment uses a combination of relayed power levels ranging from small values from 1 to 10 W for narrow-range repeaters 18 (with a range of up to 1 km), to large values from 100 to 10000 W for repeaters having a wide coverage area (with a radius from 1 to 10 km).

Two preferred embodiments are described below for a DAC system 10 with a satellite LAN / terrestrial relay configuration. The first embodiment includes one satellite 12 or 16 in geostationary orbit (GSO) having a purposefully selected longitude along the GSO arc, which operates in coordination with a network of ground-based relays 18. The second embodiment includes two satellites 12 and 16 having different purposefully selected latitudes of GSO to achieve diversity in space and time.

An embodiment of DAC 10 using one GSO satellite 12 with at least one ground repeater 18 is shown in FIG. 2 for illustration purposes. For each ground-based repeater, the satellite LW signal is received by the antenna 32, working in conjunction with the radio 34, to demodulate and reconstruct the digital baseband signal from the signal broadcast from satellite 12. The delay unit 35 delays the entire digital baseband signal by the amount of diversity time delay (if necessary ) between transmissions from satellites 12 and 16. A digital baseband signal is supplied to a ground-based oscillation modulator 36, which generates a signal that allows digital recovery of the main band signal after transmitting the generated signal from the ground repeater 18 and receiving by the radio 14. The modulated signal is then shifted in frequency by the carrier frequency and amplified, as shown by block 38. The terrestrial relay is specially selected to withstand the dynamic multipath available in the ground the channel between the transmitter antenna 40 and receiver 14. This multipath propagation is caused by reflections and scatterings from and around obstacles such as buildings 44 and the Earth, and from reflections and curvatures of trajectories in the troposphere.

The antenna 32 is configured to receive high gain (greater than 10 άΒί) in the direction of satellite 12 and low gain in other directions, so that the signal on the LAN is received with low noise and, therefore, has a very high quality (i.e., the error rate is less 10 ^-9 ). The demodulator and other receiving elements in the receiver 34 are the same as in the 14 radio receivers used in the DAC 10 and described in the aforementioned US patent application No. 08/971049, filed November 14, 1997. The radios are designed to receive a bit stream from the WU, modulated by the QPSK, at a speed of 3.68 Mbit / s. As stated above, the digital baseband signal is preferably a 3.68 Mb / s modulated QPSK bit stream with slave carrier carrying 16 digital channels having a basic bit rate of 16 kbit / s forming broadcast channels and additional information necessary for synchronization, decompression and management of broadcast channels and for the services they provide. The ground modulator 36 and the signal it generates are aimed at providing reception that is not affected by multipath interference, as shown in position 42 of the terrestrial channel. A possible option for multipath-insensitive signals is adaptive-aligned signals.

WU, adaptive aligned frequency hopping of multiple carriers with adaptive equalization, modulation of multiple carriers of fast Fourier transforms and CDMA mode signals using multi-tap receivers. The relay 18 is configured to receive signals insensitive to multipath propagation, converting the frequency of the signals to the desired RF transmitter of the repeater at a selected power level by means of an RF converter 38 and relaying the signal by antenna 40. Antenna 40 is preferably configured to provide omnidirectional propagation or propagation in the direction of one sector in horizontal plane and straight towards the horizon. The overall antenna gain will range from 10 to 16 άΒί. Antenna 40 may be placed at the top of the building and / or on a tower of the desired height. As mentioned previously, the level of broadcast power can be in the range of 1 to 10,000 W relative to the power of an equivalent isotropic emitter, depending on the application.

A preferred multipath insensitive waveform utilizes multiple carrier modulation (MMN). The signal conditioning method is shown in FIG. 3. A digital stream, such as a stream from a slave at a speed of 3.68 Mbit / s, is divided in time domain into a number of parallel channels (block 102), for example, into 460 parallel channels, each of these parallel channels transmit 8000 bits / s . The bits in each of these channels are grouped in pairs into two-bit characters with one bit denoting the I (imaginary) component and the other denoting the O (real) component of the complex number. This forms a total speed of 4000 characters / s. These bits are fed as 460 parallel input values of the frequency coefficients in complex numbers to a discrete inverse Fourier transform converter implemented using 512 inverse fast Fourier transform coefficients (IFFT) 104. It is well known in the art that the fast Fourier transform algorithm must work with 2 ^P input and output coefficients, where η is any integer. Thus, for η = 9 there will be 2 ⁹ = 512. Since the number of coefficients is 460, the remaining 52 missing input coefficients are set to zero. This is done by assigning 23 equal to zero coefficients to the highest and lowest inputs of the IFFT, thereby leaving 460 central coefficients assigned to non-zero values. The output of the IFFT block 104 is a set of 460 modulated QPSK orthogonal sine coefficients, which are 460 narrowband orthogonal carriers, each of which supports a symbol rate of 4000 symbols / s and, therefore, has a symbol period of 250 μs. At the output of the OBPF block 104, a carrier is not formed for coefficients that were set to zero.

The output signal of the multiple carrier IFFT block 104 is further processed to form a guard interval 105 for a set of 460 complex symbolic narrowband orthogonal carriers (block 106). It is assumed that part Г of the symbol period Te should be placed in the guard interval. For this, the duration of the symbol should be reduced to a value of T8 = (1-G) T8. So, for the example discussed above, T3 = 250 μs. If 25% of symbolic time should fall on the guard interval, then T = 0.25 and T3 = 187.5 μs. For this, the output signal of the symbol period of the IFFT block is stored in the memory every 250 μs and then reproduced for 187.5 μs. To fill the symbol interval of 250 μs, the first samples of the output signal of the IFFT block are again reproduced during the guard interval of 62.5 μs. This procedure causes an increase in the width of the output signal range of the multiple carriers by multiplication by (1ί) -1. Thus, the width of the range required for the output signal of the modulator of multiple carriers is multiplied by 1.33 to obtain a value of 4000x460x1.33 = 2.453 MHz.

Finally, to complete the processing of the multi-carrier modulator, a symbol 106 is periodically introduced containing a synchronization symbol, as shown by block 108. This is done in order to provide means for synchronizing a sampling window of 187.5 μs duration in receiver 14 with the center of a group of multipath components for every 250 μs. A phase reference symbol is also periodically added for differential reference encoding of symbol information. The synchronization symbol and the phase reference symbol are preferably entered every 20-100 symbol periods, depending on the requirements of a particular design.

An additional property of the formation of modulation is the punching of the digital bitstream with the slave, as shown by the dotted block 110, at the input of the modulator 36 to reduce the final width of the range of oscillation of multiple carriers. Punching means the selective, scattered elimination of bits of real data from the data stream fed to the input of the IFFT 104. This can be done for part of the bits of the stream in the expectation that the direct error correction scheme applied in receiver 14 will simply treat the punched bits as errors and correct them. This has the consequence of increasing the signal-to-noise ratio (Ε ^ / Ν _ο ) to obtain the desired bit error rate (FER) of the reception by 1-3 dB depending on the part of the bits deleted by the puncture. The configuration for the punctured signal proportionally reduces the modulation bandwidth of the multiple carriers. For example, if the bit rate in a stream with a slave decreases by 75%, the bandwidth will also be reduced by 75%. For the example given earlier, the bit rate is reduced to 2.76 Mbit / s, and the bandwidth of many carriers to 1.84 Mbit / s. Such bandwidth compression may be necessary in applications where the available frequency spectrum would otherwise be insufficient to provide the desired throughput.

Detailed information regarding preferred multicarrier modulation methods used in the present invention is contained in PCT International Applications No. PCT / EP98 / 02167, PCT / EP98 / 02168, PCT / EP98 / 02169, PCT / EP98 / 02169, PCT / EP98 / 02170 and PCT / EP98 / 02184 April 14, 1998 in the name of RgaiiyoGegSeke Iksyay Hig Rbgbegiid.

It will be appreciated that the ground repeater described with reference to FIG. 2 and 3, is used to reconstruct the signal from the WU from the satellite downlink and to demodulate and reformat the signal from the WU by processing the baseband signal into another signal using, for example, CDMA, AVUU, MMN or AVUKCHR. However, it should be understood that the DAC 10 may comprise ground repeaters 18 with matching channels or with non-matching channels. For example, ground repeaters 18 with matching channels can be used to fill gaps in the overlap that simply amplify and repeat the received satellite signal on the same carrier as the satellite signal. Alternatively, terrestrial repeaters with non-matching channels can be used to fill gaps in the overlap, which amplify and repeat the satellite signal at a different carrier frequency using frequency transfer. In any case, the processing of the satellite signal of the base band is not performed in the repeater. These types of floor space fillers can be used, for example, indoors (Fig. 10) or along roads (Fig. 11).

In the radio receiver 14 shown in FIG. 4, multi-carrier modulated RF oscillation is received by an antenna 201 operating in conjunction with a low noise RF input stage 202. Mixer 203, local oscillator 204, stage 205 first intermediate frequency (IF), second mixer 206, second local oscillator 207, stage 208 second intermediate frequency 208 provides recovery of a multi-carrier modulated carrier. A multicarrier demodulator 209 reconstructs a digital baseband signal from a slave. To demodulate multiple carrier waveforms, the received modulated signal is sampled by a sampler 211, as shown in FIG. 5, with a frequency equal to two from the four-fold modulation band. These samples are taken over a window with a duration of 187.5 μs, which is optimally centered on a group of multipath components distributed over the arrival time during each symbol period once for every 250 μs. The samples are downconverted using the buffer memory 212 to expand them to 460 complex samples in the time domain in the original window with a duration of 250 μs. These samples are then processed by FFT 213 by 512 coefficients to recover the bits of the bit stream from the slave. The receiver 14 then synchronizes the preamble of the slave main frame with block 214, decompresses and aligns the main speed bits with block 215, and then restores the bits of the selected broadcast channel with block 216. These bits then undergo a direct error correction using the serial connection of Viterbi decoder 217 with the soft decision of the inverted interleaver 218, followed by the Reed-Solomon decoder 219 to restore the broadcast channel (VK). This reconstructed VC is supplied as one input to the decision / combining unit 240, as described below with reference to FIG. 6.

For a dual channel receiver 14, as shown in FIG. 6, an MMN signal is received as described above with reference to FIG. 4. The WF satellite RF signal modulated by the QPSK is also received by the antenna 201, which operates in conjunction with a low-noise RF input stage 202, mixer 220, local oscillator 221, first IF stage 222, second mixer 223, second local oscillator 224, and second 225 IF stage, to restore the carrier WU, modulated using QPSK. As shown in FIG. 7, the QPSK demodulator 226 of the carrier WU comprises a demodulator 227 that restores the digital baseband of the WU. The receiver 14 then synchronizes the preamble 228 of the main frame, decompresses the bits 229 of the main speed and then restores the bits of the selected broadcast channel. These bits are then subjected to direct error correction (block 230) using a serial connection of the soft decision Viterbi decoder 231, the inverted interleaver 232 and the Reed-Solomon decoder 232 to restore the broadcast channel. This reconstructed VC is supplied as a second input to decision / combining unit 240.

Block 240, which is a diversity combiner, selects which of the two input

VK should be submitted for further processing. He does this based on the choice of the VK, which is restored with fewer errors. Error estimates are available from soft decision data filed by Viterbi decoders 217 and 231 or Reed-Solomon decoders 219 and 233. The decision is preferably made by hysteresis logic, which requires several difference errors before the decision is reversed. This process is necessary to prevent fluctuations in the choice between two VCs when the solutions are almost the same. The broadcast channel selected by diversity combiner 240 is then supplied to a corresponding source decoder 244 to recover received service (s) data.

The implementation of the DAC 10 using two satellites 12 and 16 at the GSO and with the ground repeater 18 is shown in FIG. 8. In this configuration, two satellites 12 and 16 are separated in longitude by 30-40 ° around the GSO circumference. One satellite relays the signal sent from the ground station, and the other satellite relays the same signal sent from the same ground station, but delays the signal for 5-10 s. The use of two satellites 12 and 16, spaced in space, is expressed in the separation of the elevation angle of the LV channels between the radio receiver 14 on Earth and each satellite 12 and 16. The time delay between the arrival of two satellite signals is expressed in time diversity. Each of these types of diversity, taken separately, can significantly improve the availability of the LP signal for the moving mobile receiver 14, and the improvement in accessibility is further enhanced by diversity in both space and time. Space and time diversity is especially important when the mobile receiver 14 moves in a suburban area or in a rural area where the drug signal is blocked by bridges, trees, and low buildings. However, for central urban areas and outlying areas where tall buildings predominate, the terrestrial signal relay is also used in accordance with the present invention to achieve acceptable coverage of the entire mobile reception area. Thus, the dual satellite configuration works in the same way as the single satellite configuration with respect to the diversity between direct satellite signal reception over the LAN and terrestrial relay reception, but adds the time and space diversity provided by the two satellites. The signal from the leading satellite is a signal relayed by the ground repeater 18. The selection of the leading signal compensates for any delay that occurs when processing the signals in the relay 18 or receiver 14. The ground relay network is otherwise implemented in the same way as described above for a single satellite configuration.

Another difference between a two-satellite system and a single-satellite system is a three-channel radio receiver 14. The receiver 14 introduces corresponding compensating delays by delay units 309 and 310 to provide simultaneous reception for the three received signals and to implement diversity decision logic that selects from three diversity signals. The delay unit 309 provides a time-domain delay for an earlier signal to compensate for the difference in signal propagation between the leading and lagging satellites 12 and 16. The delay unit 310 is preferably a vernier delay to provide accurate compensation for signal equalization. Radio diversity logic is shown in FIG. 8. It includes a maximum likelihood combiner 240 for leading and retarded satellite signals over the LP with a combiner 307 that commutes between the ground relay signal and the output signal of the maximum likelihood combiner 240. When both signals are degraded, combining maximum likelihood can improve reception quality. The improvement can be 3 dB relative to the threshold E _b / s _about when both signals are degraded equally.

The radio receiver 14 is equipped with two receiving channels 301 and 302, which individually receive and recover the WU signals from the leading and lagging satellites, respectively, and selects the desired broadcast channel from each. This is done for each received signal in the same way as described above for receiving the satellite LP signal in FIG. 6. The broadcast channel signal received from the leading satellite is delayed by the delay unit 309 containing the memory device to align its symbol by symbol with the broadcast channel symbols obtained from the delayed satellite signal. This can be done by aligning the two broadcast channels with respect to each other in such a way as to achieve a match of the emissions of the correlation functions of the preamble of the service control header. This match is detected in the correlation comparison unit in the delay unit 309. The next step is to use the likelihood maximum combiner 240 to combine the bits of the two broadcast channels bit by bit, with each bit expressed as a soft decision. The likelihood combining coefficients are determined in bit blocks of 1 ms duration. Next, the output signal of the maximum likelihood combiner 240 is supplied as one of the input signals of the switching combiner 307, the second input of which is the signal from the channel 308 of the ground relay receiver. The choice of one of the input signals for transmission to the output is based on the choice of the VK, which is restored with the least number of errors. According to another embodiment of the present invention, one of the slave signal receiver channels (for example, the receiver channel 302 for the slave signal from the retarded satellite) can be combined to the maximum likelihood with the signal of the relay channel 308 of the terrestrial relay receiver, as shown in FIG. 9. Thus, the switching combiner 307 selects between the output signal of the maximum likelihood combiner 240 and the signal of another channel of the satellite signal receiver (for example, channel 301), as shown in FIG. 9. Delay units 309 and 310 can store the entire recovered bit stream for delay purposes, which requires more buffering but simplifies combining. Alternatively, delay units 309 and 310 may provide storage only for a portion of the recovered bit stream from the WU; however, synchronization requirements for combining become more complex.

As for the switching combiner 307, estimates of the number of errors are available from the soft decision data filed by Viterbi decoders 217 and 231 or Reed-Solomon decoders 219 and 233. The decision is made by hysteresis logic, which requires several difference errors before the decision is reversed. This process prevents fluctuations in the choice between two VCs when the solutions are almost the same. Alternatively, a simple switching logic may be used in which the switching always selects a VC having the least number of errors. Hysteresis is used to prevent these fluctuations. The second implementation eliminates the complexity of combining maximum likelihood. Another alternative would be to combine the maximum likelihood of the three input VCs (for example, receiver channels 301, 302, and 308), as shown in FIG. 10.

The diversity combiner shown in FIG. 10, combines the three signals. Two of them are signals received from two spatially separated satellites 12 and 16, one of which broadcasts an earlier signal, the other broadcasts a later signal. A third signal is received from the ground repeater 18, which relays the earlier satellite signal. These signals are received by receiver channel 301 for leading satellite 12, receiver channel 302 for lagging satellite 16 and receiver circuit 308 for an earlier signal relayed by relay 18. Diversity combiner 312 combines the symbols in the three signals by combining maximum likelihood. Due to this, the symbol samples appearing at the output have the highest probability of representing the original transmitted symbol. To this end, the signals of the leading satellite 12 and the relay 18 are delayed relative to the signal of the delayed satellite by delay units 309 and 310 for aligning the individual symbols of the three signals and combining them in time. A simple a priori adjustment of the delay units 309 and 310 is sufficient for rough alignment of the output of the delay units 309 and 310 in a WU frame with a duration of 138 μs. Thus, the exact alignment of characters in the preamble of the leading frame (PVC) frame VU is not uncertain. To precisely align the symbols of the three PVC signals, for each signal stream it is aligned by fine-tuning the delay units 309 and 310 in a small part of the symbol.

Given the combination of symbols in block 312, the normalized variance a _x ² for the symbols of the signals contained in the background noise and uncorrelated multipath interference are calculated from the observed samples. These variances are calculated for the earlier (E) and later (b) signal symbols, relay 18 or gap filler (C). The corresponding symbol signal samples for earlier signals, later signals, and gap filling signals are then multiplied by their dispersion coefficients (p. ||,) ^-1 . (p. ||.) ^-1 . (p. | _C ) ^-1 . which are defined as follows:

(p. ||,) ^-1 is the weighting coefficient associated with the earlier symbol 8 _E ;

(p. ||.) ^-1 is the weighting coefficient associated with the earlier symbol 8 _b ;

(p. | _C ) ^-1 is a weighting factor associated with an earlier 8 _C character.

These weighting factors are inversely proportional to the estimated variance and normalized so that

(] .. · (] - (] - 1 σ ² · σ · Η db = a _E ² / (aE ² + ab ² + ac ² ) dc = ps ² / (OE ² + a ² + ac ² )

Their sum is symbols combined in accordance with the maximum likelihood ratio. They then pass to the block 250 temporary decompressor / decoder FEC / re-seal VK (Fig. 11), the components of which are described above with reference to Fig. 5, to recover characters combined in accordance with a maximum likelihood ratio by processing in a decision.

The diversity combiner shown in FIG. 12, first combines the signals received from two satellites 12 and 16, one of which broadcasts an earlier signal, the other broadcasts a later signal. The obtained result is then combined by means of a solution determining the minimum bit error with the reception of an early signal, which was relayed by the gap filling relay 18 located on the Earth. The individual signals are received by the receiver channel 301 for the leading satellite, the receiver channel 302 for the delayed satellite and the receiver channel 308 for the earlier signal relayed by the gap filling relay 18. The diversity combiner 412, in accordance with the maximum likelihood ratio, combines the leading and delayed satellite signal symbols, as described above for combiner 312 in FIG. 10 for three signals. Using this method, the ending character appearing at the output of block 412 has the highest probability of representing the original transmitted character.

The result from block 412 is then combined with the result from the ground repeater 18 via block 417 for selecting the minimum bit error rate (FER). At block 417, there are preferably two blocks 250 that make PEC decisions about decoded symbols for the entire broadcast channel frame of the signals fed to their inputs. One block 250 makes its decisions for the output of the maximum likelihood decision block 412, and another 250 for the signal received from the ground relay 18. These decisions also give the number of errors made with each decision over the duration of the broadcast frame. The BER comparison block 414 works in conjunction with the minimum BCH block 417 to select the symbols of this broadcast frame with the least errors, as determined from the input signals from the Viterbi PEC blocks 217 and 231. To implement the necessary delay operations, the earlier signal and the gap filling signal are delayed by delay units 309 and 310 to re-align their individual symbols for time alignment with the symbols received from the delayed satellite. The delay equalization method used in this case is the same as described previously for the implementation of FIG. 10.

In accordance with another aspect of the present invention, an indoor relay system 450 is provided as shown in FIG. 13. Since the reception of a satellite signal through a LV by a radio receiver located inside a building or other structure is usually impossible, if the radio receiver is not in the window on the LV from a satellite 12 or 16, it is necessary to provide amplification of the satellite signals in the room to provide more complete coverage.

As shown in FIG. 13, the antenna 452 may be located outside the building so as to provide reception of satellite signals over the LAN. The tuned input stage RF unit 454 is connected to the antenna 452 and is preferably configured to select a portion of the RF spectrum that essentially includes the contents of the satellite signal and with very low added noise. A connecting cable 456 is provided to provide a signal from the output of the RF unit 454 of the input stage to the amplifier 458. The amplifier 458 is connected to a relay antenna 460 located inside the building.

The amplifier 458 is configured to increase the power of the satellite signal to a level that, when relayed by the antenna 460, is sufficient to provide satisfactory indoor reception for radio receivers. The power level emitted from antenna 460 is high enough to provide satisfactory indoor reception at positions that do not match the satellite LV, but not so high as to cause instability of the signals transmitted in the channel between indoor antenna 460 and one or more receiving antennas 452 Thus, a good isolation (ie, of the order of 70-80 dB) between the indoor antenna 466 and the outdoor antenna 452 is preferable.

There will be reception areas (for example, through windows or other entrances to a building or structure) where the relayed signals in the room are combined with signals from outdoor antennas transmitted directly from the satellite. So that the combination of these signals is not destructive for the content of the signal, the time delay between the signal from the street antenna and the signal from the indoor antenna in the area of the union is preferably less than a portion of the symbol duration of the transmitted signal. For example, for a symbol duration of about 540 ns, a time delay of 50 to 100 ns is acceptable. The time delay is usually due to the time the signal travels through the channel containing the outdoor antenna 452, the cable (where the signals usually travel at 2/3 of the speed of light) and the indoor antenna 460. Another delay occurs when the signal passes from the indoor antenna 460 to the radio 14 in the area covered by the indoor antenna. This time delay is preferably 20% of the symbol duration, i.e. no more than 100 ns for a system in which the symbol duration is 540 ns.

The purpose of a ground-based repeater is to relay a signal received from a satellite to areas where the signal is blocked in some way. A plurality of ground repeaters 18 may be placed along a road or other path at a height of 11 and separated by distances b, as shown in FIG. 14. The heights and dividing distances between ground repeaters should not be the same. The ground repeater 18 contains a receiving antenna 462, which is directed to satellite 12 or 16, a receiver (not shown), which restores the signal and amplifies it with a gain sufficient to excite the transmitting antenna 464 to a power flux density in the channel below it, which is comparable to that is normally expected from the satellite. Transmitting antenna 464 is shielded to prevent the transmission of the transmitted signal to the receiving antenna 462 of the ground repeater with a level leading to instability. Transmitting antenna 464 radiates its power from an aperture of length b sufficient to span a channel of the order of several wavelengths between the transmitter 464 and the receiving antenna of the vehicle at the carrier frequency.

As the vehicle moves along the channel, the radio receiver 14 receives signals coming from more than one ground repeater 18. For example, at location A, the vehicle is the closest to the ground repeater 18b, and the signal from this ground repeater dominates the reception. The signals from the ground repeaters 18a and 18b are low due to the distance and antenna pattern and cause little interference. If the vehicle is at location B, the radio 14 receives signals from both ground repeaters 18c and 18b. Since the distances are approximately equal and assuming that the time difference between the signals transmitted from the ground repeaters 3 and 4 is adjusted to zero, the difference in the arrival time between the signals received in the vehicle is small enough to provide constructive amplification. By properly selecting the distances 11 and b relative to the symbol period of the received digital signal, this condition can be fulfilled.

It is important to ensure diversity in the signals that come to the vehicle from various ground repeaters. If this is not provided, then the signals from two ground-based repeaters, when received at location B, will be combined either in phase or out of phase, or with the phases between these states. If they are in phase, then the signals are amplified, if in antiphase, then the signals are suppressed. When suppressing, the signal completely disappears. In addition, the resulting phase of the carrier signal generated by the addition of terrestrial repeater carriers changes at a rate close to the monochromatic Doppler difference, making it difficult to restore the QPSK modulation. The extension of the arrival time interval caused by diversity transmission caused by the distribution of the transmitted signal over the b aperture or the equivalent time difference b / C, where C is the speed of light, eliminates amplitude compensation and provides the ability to correct the effect of phase changes by using adaptive equalization methods. This applies to all vehicle positions between locations A and B.

An example of the proper selection of distances in relation to the symbol period is shown for a signal having a symbol period of the order of 540-550 ns. The distance b and height 1 are chosen so as to cause a time delay when crossing the slant range (b ² +1 ² ) ^1/2 , to cause a delay of not more than a quarter of the symbol period. In this example, the oblique range is 550 / b = 137.5 feet. One nanosecond equals one foot at the speed of light. Thus, if the height is 20 feet, the distance b is 180 feet. The height 1 is preferably relatively small compared to the distance b for the difference in the distance between the vehicle and each ground repeater 18 to change by an amount sufficient to attenuate the signal level from any of the ground repeaters by 10 dB or more, compared to when ground repeater is located directly above your head. The length b is preferably 5 to 10 feet in order to provide sufficient channel length spacing at the b-band frequencies. If the alignment unit is integrated in the vehicle’s mobile receiver 14, then the arrival time difference can be increased to several characters, thereby increasing the distance between the ground repeaters to more than 100 feet. An equivalent time difference would correspond to signal transmission several times from one source in an interval not exceeding 5-10 ns.

Although various embodiments have been selected to illustrate the invention, one skilled in the art will appreciate that various changes and modifications can be made without altering the scope of the invention defined in the claims.

Claims (41)

CLAIM 1. A digital broadcasting system for transmitting a broadcast signal, said broadcast signal being transmitted from a ground station, comprising a satellite for receiving said broadcast signal from said ground station and for transmitting a satellite signal comprising said broadcast signal at a first carrier frequency and a ground relay for receiving said a satellite signal and for generating and transmitting a terrestrial signal from said satellite signal containing the specified broadcast signal, a second carrier frequency that is different from the first carrier frequency, wherein said terrestrial signal is modulated by said terrestrial repeater in accordance with a modulation method that is not sensitive to multipath propagation. 2. The system according to claim 1, characterized in that said terrestrial repeater provides modulation of said terrestrial signal using at least one of the options including adaptively aligned (temporal multiplexing), adaptively aligned temporal multiplexing with coherent frequency hopping, modulation multiple carriers, code division multiplexing. 3. The system according to claim 1, characterized in that said satellite signal is modulated in accordance with at least one of the options, including time division multiplexing and code division multiplexing. 4. The system according to claim 1, characterized in that said terrestrial repeater provides modulation of said terrestrial signal using multi-carrier modulation. 5. The system according to claim 4, characterized in that said terrestrial repeater provides receiving said satellite signal and demodulating said satellite signal to obtain a baseband signal before modulating said baseband signal by modulating a plurality of carriers. 6. The system according to claim 1, characterized in that the satellite signal is assigned a first code of a multiple access channel with code division, and said ground signal is assigned a second code of a multiple access channel with code division. 7. The system according to claim 1, characterized in that it further comprises a second satellite, said second satellite receiving said broadcast signal from said ground station and transmitting a second satellite signal containing said broadcast signal at said first carrier frequency, delayed by a predetermined a period of time with respect to the transmission of the first satellite signal. 8. A terrestrial repeater for relaying satellite signals to radio receivers, comprising: a terrestrial receiver for receiving said satellite signals and a terrestrial modulator for generating terrestrial signals from said satellite signals, said terrestrial signals being modulated by said terrestrial modulator in accordance with multi-carrier modulation; wherein said satellite signals are transmitted from the satellite using the first carrier frequency, and said terrestrial modulator transmits said terrestrial signals to said radios using a second carrier frequency that is different from said first carrier frequency. 9. The ground repeater of claim 8, wherein said ground modulator comprises a time decompressor for decompressing said satellite signals from a serial bit stream compressed in time into a plurality of parallel bit streams and an inverse fast Fourier transform device for generating a digital analog signal, containing many discrete Fourier transform coefficients. 10. A method of converting a time-compressed bit stream into a plurality of multi-carrier modulated signals, comprising the steps of receiving said time-compressed bit stream from a satellite, dividing said time-compressed bit stream into a plurality of parallel channel bits, presentation of each of a predetermined number of bits in each of the aforementioned set of bit channels as a symbol containing imaginary and real components, supplying said symbols to parallel inputs the inverse Fourier transform generator as input signals of the frequency coefficients of the complex number for generating output signals that contain modulated narrowband orthogonal carriers, and transmitting said modulated narrowband orthogonal carriers from said ground repeater. 11. The method according to claim 10, characterized in that it further comprises the step of forming a guard interval for said carriers. 12. The method according to claim 11, characterized in that said forming step includes the steps of extracting a portion of the symbol period corresponding to the duration of each of said symbols for a guard interval, and reducing the duration of each of said symbols. 13. The method according to p. 12, characterized in that the reduction step includes the steps of storing said output signals of the inverse Fourier transform converter in a storage device in each said symbol period and reading from said storage device after the expiration of each said part of the symbol period. 14. The method according to claim 11, characterized in that the forming step further includes filling said protective interval with a subset of said output signals of the inverse Fourier transform. 15. The method according to claim 10, characterized in that it further includes the step of introducing a synchronization symbol into each predetermined number of symbol periods to synchronize a sampling window corresponding to said part of the symbol period with respect to said carriers in each said symbol period in the receiver for said plurality of signals modulated by multiple carriers. 16. The method according to claim 10, characterized in that it further includes the step of punching said bit stream, time-compressed, to reduce the total width of the range associated with said carriers. 17. The method according to clause 16, wherein the punching step includes the selective removal of bits from said bitstream, time-multiplexed, to provide said symbols at the parallel inputs of the inverse Fourier transform converter. 18. A digital broadcasting system for transmitting a broadcast signal, said broadcast signal being transmitted from a ground station, comprising a first satellite configured to receive said broadcast signal from a ground station and transmitting a time-compressed satellite signal comprising said broadcast signal, a ground repeater, configured to receive said satellite signal and generate and transmit a terrestrial signal from said satellite signal comprising the aforementioned broadcast signal, wherein said ground signal is modulated terrestrial repeater according to at least one embodiment, including adaptive temporary seal aligned adaptively temporary seal aligned with coherent frequency hopping seal code division multiple carrier modulation. 19. The digital broadcasting system of claim 18, wherein said satellite signal is transmitted using a first carrier frequency, and said terrestrial signal is transmitted using a second carrier frequency that is different from said first carrier frequency. 20. The digital broadcasting system of claim 18, further comprising at least a radio receiver adapted to receive said satellite signal and said terrestrial signal, said radio receiver comprising a diversity combiner for generating an output signal of at least from said satellite signal and said terrestrial signal. 21. The digital broadcasting system according to claim 18, further comprising a second satellite configured to receive said broadcast signal from said ground station and transmit a second time-compressed satellite signal comprising said broadcast signal, said second satellite the signal is delayed relative to said first satellite signal by a selected time delay. 22. The digital broadcasting system according to claim 21, characterized in that it further comprises at least a radio receiver configured to receive said first satellite signal, said second satellite signal and said terrestrial signal, for delaying at least one of said first satellite signal and a terrestrial signal in accordance with said selected time delay and for generating an output signal from at least one of said first satellite signal, A satellite signal and a terrestrial signal. 23. The digital broadcasting system of claim 22, wherein said radio receiver comprises a diversity combiner and a switching combiner, said radio receiver using said diversity combiner to perform, in accordance with a maximum likelihood decision, combining said first satellite signal and second satellite signal, and said switching combiner - for choosing between the output signal of said diversity combiner and said ground signal depending and on whether the output signal of said diversity combiner and terrestrial signal has the least number of bit errors. 24. The digital broadcasting system of claim 22, wherein said radio receiver comprises a diversity combiner for performing combining in accordance with a maximum likelihood decision of said first satellite signal, second satellite signal, and ground signal. 25. A receiver for receiving broadcast signals in a combined satellite and terrestrial digital broadcasting system, comprising a first receiver channel for receiving a first satellite signal transmitted from a first satellite at a first carrier frequency, said first satellite signal comprising said broadcast signal and modulated in accordance with at least one of the options, including temporary and code division multiplexing, and said first receiver channel comprises a demodulator for reconstructing said broadcast signal, a second receiver channel for receiving a terrestrial signal transmitted from a ground station at a second carrier frequency, said terrestrial signal comprising said broadcast signal and modulated in accordance with at least one embodiment including an adaptively aligned time division multiplexing, adaptively aligned time division multiplexing with coherent frequency hopping, code division multiplexing, multi-carrier modulation, wherein said second channel the receiver comprises a demodulator for reconstructing said broadcast signal, a combiner for generating an output signal from at least one of said third satellite signal and said terrestrial signal. 26. The receiver according A.25, characterized in that it further comprises a third channel of the receiver for receiving a second satellite signal from a second satellite, which is delayed relative to the first satellite signal in accordance with the selected time delay, said second satellite signal containing said broadcast signal and modulated in accordance with at least one of the options, including temporary and code division multiplexing, and said third receiver channel comprises a demod an amplifier for recovering said broadcast signal, and a delay device for delaying said first satellite signal in accordance with said selected time delay, said combiner working to generate an output signal from at least one of said first satellite signal, second satellite signal, and terrestrial signal. 27. A method for transmitting a broadcast signal to a radio receiver, comprising the steps of modulating said broadcast signal for transmitting to said radio receiver as a first signal in accordance with at least one of the options including time division multiplexing and code division multiplexing, transmitting said first signal to said radio receiver from a first satellite at a first carrier frequency, modulating said broadcast signal at a ground station for transmitting to said radio receiver as a second signal in accordance with at least one of the options, including adaptively aligned temporal multiplexing, adaptively aligned temporal multiplexing with coherent frequency hopping, code division multiplexing, multi-carrier modulation, and transmitting said second signal to said second radio from said ground station at a second carrier frequency that is different from said first frequency. 28. The method according to item 27, wherein the step of modulating said broadcast signal as said second signal includes the steps of receiving said first signal at said ground station and performing processing in the main band of said first signal before modulation in accordance with at least with one of the options, including adaptively aligned time division, adaptively aligned time division with coherent frequency hopping, code division multiplexing, module tion multiple carriers. 29. The method according to p. 28, characterized in that it further includes the step of receiving the aforementioned first signal and the second signal in said radio. 30. The method according to clause 29, wherein the step further includes demodulating each of said received first signal and received second signal to remove said respective modulations and to restore the first restored broadcast signal and the second restored broadcast signal, respectively. 31. The method of claim 30, further comprising the step of generating an output broadcast signal from said first restored broadcast signal and a second restored broadcast signal. 32. The method according to p, characterized in that the forming step includes the step of combining in accordance with the maximum likelihood of said first restored broadcast signal and a second restored broadcast signal. 33. The method according to p. 27, characterized in that it further includes the steps of modulating the broadcast signal for transmission to said radio as a third signal in accordance with at least one of the options, including temporary and code division multiplexing, transmitting said a third signal to said radio receiver from a second satellite, said transmission being delayed with respect to the transmission of said first signal for a predetermined period of time. 34. The method according to claim 33, further comprising the steps of receiving said first signal, second signal and third signal in said radio, demodulating each of said first signal, second signal and third signal to remove respective modulations and to restore the first reconstructed a broadcast signal, a second restored broadcast signal and a third restored broadcast signal, respectively, and generating an output broadcast signal, at least e, of said first restored broadcast signal, a second restored broadcast signal, and a third restored broadcast signal. 35. A room amplification system for receiving satellite signals transmitted by a digital broadcasting system using a radio located in the room, comprising an antenna on the line of sight for receiving satellite signals on the line of sight, a radio frequency input stage unit connected to said antenna on the line of sight for transmitting a frequency spectrum containing the aforementioned satellite signals with low noise, an indoor amplifier, a cable for connecting said input frequency RF unit a cascade to said indoor amplifier, a indoor relay antenna connected to said indoor amplifier, said indoor relay antenna having a power level selected high enough to achieve satisfactory indoor reception of said satellite signals in radio receivers in places where it’s impossible reception over the line of sight of said satellite signals, and low enough to prevent interference due to said satellite signals transmitted between said antenna relay in the room and said antenna line of sight. 36. The indoor amplification system according to claim 35, characterized in that said satellite signals are characterized by a selected symbol period, and the transmission duration of said satellite signals between said antenna on the line of sight and said indoor relay antenna is maintained at a level lower than the selected value mentioned symbolic duration by limiting the length of said cable. 37. The indoor amplification system according to clause 36, wherein said duration of transmission of satellite signals between said antenna on the line of sight and said relay antenna in the room is not more than 20-25% of said selected symbol period. 38. An amplification system for receiving satellite signals transmitted by a digital broadcasting system using an outdoor radio in which said satellite signals are characterized by a selected period, said amplification system comprising at least two terrestrial repeaters, said terrestrial repeaters are characterized by height And they are separated from each other at a distance of ά, the slant range (ά ² + And ² ) ² from one of the above-mentioned ground repeaters to the mentioned radio receiver It is based on the condition that the delay in the reception of the aforementioned satellite signals in the aforementioned radio receiver from one of the aforementioned ground transmitters is limited by 20-25% of the aforementioned symbol period. 39. A digital broadcasting system for transmitting a broadcast signal to a radio receiver, said broadcast signal being transmitted by a ground station comprising a satellite for receiving said broadcast signal from said ground station and for transmitting a satellite signal comprising said broadcast signal to said radio receiver at a first carrier frequency and at least one terrestrial repeater configured to receive said satellite signal and generate and transmit a terrestrial signal of said satellite signal comprising said broadcast signal at said radio receiver at a second carrier frequency that is different from said first carrier frequency, said satellite signal and said terrestrial signal is modulated using the modulation method is not sensitive to multipath propagation. 40. The system of claim 39, wherein said satellite signal is modulated in accordance with code division multiplexing. 41. The system of claim 39, wherein said terrestrial signal is modulated using at least one of the following options, including adaptive aligned temporal multiplexing, adaptive aligned temporal multiplexing with coherent frequency hopping, code division multiplexing, modulation of multiple carriers.