CN101018085A - A method and system for providing the digital multi-media broadcast signal - Google Patents
A method and system for providing the digital multi-media broadcast signal Download PDFInfo
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Abstract
The disclosed method for digital multimedia broadcast signal comprises: every transmission units receive the HF signal on the first waveband from satellite or ground emitter; then, all transmission devices obtains reference signal from the first HF signal to generate the carrier signal, and converse the signal into second waveband for transmission.
Description
Technical field
The present invention relates to communication technical field, relate in particular to a kind of method and system that digital multimedia broadcasting signal is provided.
Background technology
At the DMB transmission field, single frequency network is a kind of advanced technology of extensive approval in the field of business.So-called single frequency network, promptly some transmitters are launched same signal simultaneously on same frequency range in certain geographic area, to realize the reliable covering to this zone.Because receiver can receive the signal from different transmitters, like this, the single frequency network of multiple spot emission will produce strong multipath effect at the area of coverage.For the simulated television system, this can cause the ghost image problem, therefore the simulated television system can only adopt and extremely consume frequency spectrum resource, and complicated multiple frequency network, MFN networking mode (the Multiple Frequency Network of frequency spectrum planning, MFN) carry out networking, signal is isolated on frequency, avoid the area of coverage overlapping.And for digital television system; owing to used the multi-carrier modulation of OFDM (Orthogonal Frequency DiVision Multiplexing); and the OFDM symbol has protection (Guard Interval) at interval; drop on the multipath signal in the protection at interval; after through processing; not only can not produce the intersymbol interference in front and back, even can strengthen the power of useful signal, so can adopt single frequency network networking mode transmission of digital multimedia broadcast signal in the digital television system.
Single frequency network with its conserve on spectrum resource, advantage that coverage is bigger be widely used in digital audio broadcasting (Digital Audio Broadcasting, DAB), among Digital Television Terrestrial Broadcasting DVB (Digital VideoBroadcasting) and the DMB S-DMB (Digital Multimedia Broadcasting).At present, the network system that is used for mobile digital multi-media broadcast mainly comprises the ground network of supporting DVB-H and DAB, supports the satellite network of S-DMB and the single frequency network of DMB-T/H.
For the ground network of supporting DVB-H and DAB, when setting up single frequency network, the program center need be sent to each cell site to the television multimedia program of preparing broadcasting by paths such as optical fiber, microwave or ADSL, and each website needs unified synchronous refernce clocks to carry out synchronously.
In the DVB-T/H single frequency network, all special equipment---single frequency adapter is realized by adding for frequency and time synchronized at present.This adapter need possess the global position system GPS receiving system.Obtain reference frequency and pps pulse per second signal (1pps) from gps satellite, at the Frequency Synchronization requirement, with all cascade generators in every transmitter of reference frequency driving of GPS; And in the MPEG-2TS code stream, add the MIP bag that comprises time tag by the on-site single frequency adapter of program source; By elementary distributed network (PDN) program stream is sent to each cell site then; The single-frequency network synchronization system of each cell site from the MIP of code stream bag extraction time label, the local pps pulse per second signal of receiving from gps system of contrast to the time-delay adjustment that code stream adds, is sent code stream into modulator afterwards, transmit a common time, to realize time synchronized.
Be different from traditional terrestrial broadcast networks, the S-DMB of Japan and Korea S has adopted the transmission means of satellite broadcasting.Digital broadcasting via satellite and WLAN (wireless local area network) can realize that smoothness receives clearly in moving process.The S-DMB system adopts the satellite transmits mode, can cover bigger scope and area, but the urban area satellite-signal is covered unfavorable place, need realize comprehensive covering by the mode that increases auxiliary transmitter.On the other hand, S-DMB has adopted different coded systems to its two band signal of propagating, and promptly its Ku wave band uses time division multiplexing and S-band use code division multiplexing.Therefore, its benefit point device must carry out complete decoding.
The single frequency network of DMB-T/H has adopted the single frequency network networking mode of similar DVB/DAB.Different is, because system signal frame and Absolute Time Synchronization and employing OFDM modulation system, when realizing single frequency network, the receiving station of DMB-T/H single frequency network can carry out COMPREHENSIVE CALCULATING with the transmission delay of valid data in distribution network, the synchronizing signal that main launch point is sent, the GPS synchronizing signal that the our station point is received, draws the time that this website transmits.In the cell site, center, the DMB-T/H single frequency adapter inserts a controlling packet every a big frame (560ms) in transport stream, this controlling packet comprises label lock in time (from the 1pps of GPS receiver to time difference that big frame begins) and to the maximum delay of next stage cell site.
Carry out when synchronous relying on gps system, the GPS losing lock is a problem that often runs into, and in addition, the GPS service might be by artificial closing, and this single frequency network that will cause making up can't realize synchronously; If use special-purpose clock synchronization network to carry out the synchronous of single frequency network, this will cause project cost too high.
Summary of the invention
The invention provides a kind of method and system that digital multimedia broadcasting signal is provided, exist the simple GPS of dependence to carry out the problem of Time and Frequency Synchronization in the prior art in order to solve.
The invention provides following technical scheme:
A kind of method that digital multimedia broadcasting signal is provided, the method comprising the steps of:
Each retransmission unit receives the high-frequency signal of first wave band that carries digital multimedia broadcasting signal respectively from communication satellite or cell site, ground;
Described each retransmission unit is converted to the high-frequency signal of described first wave band high-frequency signal of second wave band, wherein, each retransmission unit obtains frequency reference signal with the carrier signal in the high-frequency signal that produces described second wave band according to the high-frequency signal of described first wave band;
Described each retransmission unit sends the high-frequency signal of described second wave band.
According to said method:
Described each retransmission unit with the carrier signal of the high-frequency signal of described first wave band as frequency reference signal.
Described each retransmission unit further obtains time synchronization information according to the high-frequency signal of described first wave band, and sends the time of the high-frequency signal of described second wave band according to this time synchronization information control.
After the high-frequency signal down-conversion of described each retransmission unit with described first wave band, from signal frame, obtain described time synchronization information.
The time-delay of the high-frequency signal of second wave band that described each retransmission unit converts to from the high-frequency signal that receives first wave band to transmission is identical, and this delay duration is not less than the duration of each retransmission unit switching signal.
The high-frequency signal of described first wave band is converted in the process of high-frequency signal of second wave band, the signal of described retransmission unit after to down-conversion carries out demodulation and recovers the code word of coding, then to this code word modulate with upconversion process after form the high-frequency signal of described second wave band.
The high-frequency signal of described first wave band is converted in the process of high-frequency signal of second wave band, the signal of described retransmission unit after to down-conversion carries out demodulation and decoding recovers described digital multimedia broadcasting signal, then described digital multimedia broadcasting signal encoded, forms after modulation and the upconversion process high-frequency signal of described second wave band.
The high-frequency signal of described first wave band is converted in the process of high-frequency signal of second wave band, described retransmission unit also further carries out processing and amplifying to signal.
Said method also comprises step:
Receive the high-frequency signal of described second wave band and carry out processing and amplifying, and the high-frequency signal that sends second wave band after amplifying.
Described processing and amplifying comprises step:
Obtain frequency reference signal and with the high-frequency signal down-conversion of second wave band from the high-frequency signal of second wave band that receives;
Amplify the signal after the down-conversion, and the signal after amplifying is carried out the high-frequency signal that upconversion process forms second wave band according to described frequency reference signal.
A kind of retransmission unit comprises:
Receiving element is used for receiving from communication satellite or cell site, ground the high-frequency signal of first wave band that carries digital multimedia broadcasting signal;
Processing unit is used for the high-frequency signal of described first wave band is converted to the high-frequency signal of second wave band, wherein, obtains frequency reference signal with the carrier signal in the high-frequency signal that produces described second wave band according to the high-frequency signal of described first wave band;
Transmitting element is used to send the high-frequency signal of described second wave band.
Described processing unit comprises:
The Frequency Synchronization unit is used for obtaining frequency reference signal according to the high-frequency signal of described first wave band;
The first frequency converting unit is used for the high-frequency signal of described first wave band is carried out down-converted;
Demodulating unit is used for the time-domain signal after the down-conversion is converted to frequency-region signal;
Recovery unit is used for recovering from frequency-region signal the code word of coding;
Modulating unit, the code word that is used for the coding that will recover is converted to time-domain signal;
The second frequency converting unit is used for forming according to described frequency reference signal the high-frequency signal of second wave band that carries described digital multimedia broadcasting signal.
Perhaps, described processing unit comprises:
The Frequency Synchronization unit is used for obtaining frequency reference signal according to the high-frequency signal of described first wave band;
The first frequency converting unit is used for the high-frequency signal of described first wave band is carried out down-converted;
Demodulating unit is used for the time-domain signal after the down-conversion is converted to frequency-region signal;
Decoding unit is used for the frequency-region signal after the demodulation is decoded, and recovers described digital multimedia broadcasting signal;
Coding unit is used for described digital multimedia broadcasting signal is encoded;
Modulating unit is used for the described digital multimedia broadcasting signal behind the coding is converted to time-domain signal;
The second frequency converting unit is used for carrying according to described frequency reference signal shape the high-frequency signal of second wave band of described digital multimedia broadcasting signal.
Described processing unit also comprises:
The time synchronized unit is used for obtaining time synchronization information according to the high-frequency signal of described first wave band, and indicates described transmitting element to send the high-frequency signal of described second wave band according to this time synchronization information.
A kind of single frequency network comprises:
A plurality of retransmission units, wherein, each retransmission unit receives the high-frequency signal of first wave band that carries digital multimedia broadcasting signal respectively from communication satellite or cell site, ground, and the high-frequency signal of described first wave band is converted to the high-frequency signal of second wave band, and the high-frequency signal that sends described second wave band; Wherein, each retransmission unit obtains frequency reference signal with the carrier signal in the high-frequency signal that produces described second wave band according to the high-frequency signal of described first wave band.
Described single frequency network also comprises:
A plurality of benefit point devices are used to receive the high-frequency signal of described second wave band and carry out processing and amplifying, and send the high-frequency signal that amplifies back second wave band.
Described retransmission unit comprises:
Receiving element is used for receiving from communication satellite or cell site, ground the high-frequency signal of first wave band that carries digital multimedia broadcasting signal;
Processing unit is used for the high-frequency signal of described first wave band is converted to the high-frequency signal of second wave band, wherein, obtains frequency reference signal with the carrier signal in the high-frequency signal that produces described second wave band according to the high-frequency signal of described first wave band;
Transmitting element is used to send the high-frequency signal of described second wave band.
Described processing unit comprises:
The Frequency Synchronization unit is used for obtaining frequency reference signal according to the high-frequency signal of described first wave band;
The first frequency converting unit is used for the high-frequency signal down-conversion with described first wave band;
Demodulating unit is used for the time-domain signal after the down-conversion is converted to frequency-region signal;
Recovery unit is used for recovering from frequency-region signal the code word of coding;
Modulating unit, the code word that is used for the coding that will recover is converted to time-domain signal;
The second frequency converting unit is used for forming according to described frequency reference signal the high-frequency signal of second wave band that carries described digital multimedia broadcasting signal.
Perhaps, described processing unit comprises:
The Frequency Synchronization unit is used for obtaining frequency reference signal according to the high-frequency signal of described first wave band;
The first frequency converting unit is used for the high-frequency signal down-conversion with described first wave band;
Demodulating unit is used for the time-domain signal after the down-conversion is converted to frequency-region signal;
Decoding unit is used for the frequency-region signal after the demodulation is decoded, and recovers described digital multimedia broadcasting signal;
Coding unit is used for described digital multimedia broadcasting signal is encoded;
Modulating unit is used for the described digital multimedia broadcasting signal behind the coding is converted to time-domain signal;
The second frequency converting unit is used for carrying according to described frequency reference signal shape the high-frequency signal of second wave band of described digital multimedia broadcasting signal.
Described processing unit also comprises:
The time synchronized unit is used for obtaining time synchronization information according to the high-frequency signal of described first wave band, and indicates described transmitting element to send the high-frequency signal of described second wave band according to this time synchronization information.
Described retransmission unit with the carrier signal of the high-frequency signal of described first wave band as frequency reference signal.
After the high-frequency signal down-conversion of described retransmission unit with described first wave band, from signal frame, obtain described time synchronization information.
Beneficial effect of the present invention is as follows:
1, the present invention is core with the communication satellite, and is aided with some small-power transponder groups and/or mends some device group, constitutes mobile digital multi-media broadcast transmission single frequency network, and described single frequency network is simple in structure, is easy to realize;
2, the present invention directly utilizes the Time and Frequency Synchronization that frequency reference signal that the high-frequency signal that receives from communication satellite gets access to and time synchronization information realize single frequency network, need not to be provided with specially Time and Frequency Synchronization service systems such as GPS again;
3, in the described single frequency network, transponder can adopt half decoding process to reduce interchannel noise, also can adopt the full decoder mode to reduce the interchannel noise and the error rate.
Description of drawings
Fig. 1, Fig. 8 are the structural representation of digital multimedia broadcasting system in the embodiment of the invention;
Fig. 2 is the structural representation of transponder in the embodiment of the invention;
Fig. 3, Fig. 5 are the structural representation of processing unit in the transponder in the embodiment of the invention;
The flow chart that Fig. 4, Fig. 6, Fig. 7 handle the high-frequency signal of first wave band for transponder in the embodiment of the invention;
Fig. 9 is a structural representation of mending the some device in the embodiment of the invention;
Figure 10 is for mending the flow chart that the some device is handled the high-frequency signal of second wave band in the embodiment of the invention;
The flow chart of Figure 11 for by transponder and benefit point device the high-frequency signal of first wave band being handled in the embodiment of the invention.
Embodiment
In the present embodiment, constitute the single frequency network that covers certain zone by retransmission unit.The high-frequency signal of first wave band that carries digital multimedia broadcasting signal that retransmission unit received communication satellite in this single frequency network or cell site, ground transmit, directly from the high-frequency signal of described first wave band, obtain frequency reference signal and carry the high-frequency signal of second wave band of described digital multimedia broadcasting signal, the high-frequency signal of this second ripple is offered signal receiver in described certain zone with formation.Single frequency network in the present embodiment is meant that each retransmission unit that constitutes this single frequency network sends the high-frequency signal in the same wave band, as the high-frequency signal of S-band.First wave band and second ripple can be different-waveband, as, first wave band is the Ku wave band, second wave band is a S-band.Certainly, first wave band also can be identical wave band with second wave band.
A kind of digital multimedia broadcasting system in the present embodiment comprises cell site, ground 100, communication satellite 101, single frequency network 102, terminal equipment 103 as shown in Figure 1.Wherein, cell site, described ground 100 is used to produce digital multimedia broadcasting signal, and carries the high-frequency signal of first wave band (as the Ku wave band) of described digital multimedia broadcasting signal to described communication satellite 101 emissions; Described communication satellite 101 is used to receive the high-frequency signal of first wave band of launching cell site, ground 100 that carries digital multimedia broadcasting signal, and transmits the high-frequency signal of these first wave bands to described single frequency network 102; Here, cell site, described ground 100 also can directly send the high-frequency signal of described first wave band to described single frequency network 102, and do not transmit by described communication satellite 101, this kind of high-frequency signal situation of transmitting described first wave band with cell site, ground 100 by described communication satellite 101 in the present embodiment is that example describes.Described single frequency network 102 is made of a plurality of transponders 1020, wherein, each transponder receives the high-frequency signal of first wave band of described communication satellite 101 forwardings respectively, high-frequency signal to described first wave band carries out processing such as Time and Frequency Synchronization and noise reduction, form send to behind the high-frequency signal of second wave band (as S-band) as described in terminal equipment 103; Wherein, each transponder obtains frequency reference signal with the carrier signal in the high-frequency signal that produces described second wave band according to the high-frequency signal of described first wave band behind the high-frequency signal that receives described first wave band; Described terminal equipment 103 is used to receive the high-frequency signal of described second wave band and plays the digital multimedia content that wherein carries.
Described communication satellite 101 is sent to digital multimedia broadcasting signal the single frequency network 102 on ground by the high-frequency signal of first wave band, this band signal is unique signal source and the reference source of each transponder in the single frequency network 102, has so greatly simplified the structure of single frequency network.The quantity of transponder can be determined according to user's needs and signal cover in the single frequency network 102, covers small network, the local area network (LAN) of (as the sub-district) more among a small circle to form, or covers the large-scale net in (as the city) in a big way.
In the described single frequency network 102, each transponder is the small-power transponder, and the distance between the adjacent transponder is less, therefore the high-frequency signal of first wave band that receives of each transponder is almost completely the same, and, each transponder adopts consistent frequency synchronization method and the same signal processing time-delay, has constituted the time transmission network consistent with frequency.Described single frequency network 102 need not be added special time service equipment such as GPS receiving system, each transponder in the described single frequency network 102 carries out Time and Frequency Synchronization according to the high-frequency signal of first wave band that receives, and, differ to transmit as the S-band signal and penetrate with the service band of receiver.
Concrete, each transponder can be directly obtains its carrier signal with the high-frequency signal of first wave band of satellite transmission by high pass filter when carrying out Frequency Synchronization, and with this carrier signal as frequency reference signal, through phase-locked loop or other frequency synchronization devices, make system reach the synchronous of frequency again.
In addition, because the time-delay of each transponder when carrying out signal processing may exceed the length of the Cyclic Prefix of OFDM symbol, therefore, preferable mode is further to carry out compensation of delay and time synchronizing.In the signal frame of the high-frequency signal of first wave band that described communication satellite 101 sends, carry time synchronizing signal, therefore, each transponder can be by obtaining time synchronization information in the signal frame as timing reference signal, control the time that transponder sends the high-frequency signal of second wave band according to this timing reference signal, so that each transponder keeps synchronous in time in the single frequency network.Wherein, the delay duration of each transponder from the high-frequency signal that receives first wave band to the high-frequency signal that sends out second wave band after the conversion is not less than the duration of its processing signals, and best mode is the duration of described delay duration greater than its processing signals.
The structure of a kind of transponder in the present embodiment is consulted shown in Figure 2, comprising: receiving element 200, processing unit 201, transmitting element 202; Described receiving element 200 is used for receiving from communication satellite the high-frequency signal of first wave band carry digital multimedia broadcasting signal; Described processing unit 201, be used for the high-frequency signal of described first wave band is carried out processing such as Time and Frequency Synchronization and noise reduction, the high-frequency signal that comprises according to described first wave band that deals with obtains frequency reference signal, and forms the high-frequency signal of second wave band that carries described digital multimedia broadcasting signal according to described frequency reference signal; Described transmitting element 202 is used to send the high-frequency signal of described second wave band.Described processing unit 201 also is used for obtaining time synchronization information according to the high-frequency signal of described first wave band, and indicates described transmitting element 202 to send the high-frequency signal of described second wave band according to this time synchronization information.
Further, consult shown in Figure 3ly, described processing unit specifically comprises: Frequency Synchronization unit 300, first frequency converting unit 301, demodulating unit 302, recovery unit 303, modulating unit 304, second frequency converting unit 305; Wherein, described Frequency Synchronization unit 300 is used for obtaining frequency reference signal according to the high-frequency signal of described first wave band; Described first frequency converting unit 301 is used for the high-frequency signal of described first wave band is carried out frequency-selecting and amplification, and with its down-conversion (as downconverting to intermediate frequency or zero-frequency); Described demodulating unit 302, the time-domain signal that is used for after the down-conversion is transformed into frequency domain; Described recovery unit 303 is used for recovering from frequency-region signal the code word of coding, promptly carries out half decoding to improve signal to noise ratio; Described modulating unit 304, the code word that is used for the coding that will recover is converted to time-domain signal; Described second frequency converting unit 305 is used for forming the high-frequency signal of second wave band that carries digital multimedia broadcasting signal and with its amplification according to the frequency reference signal that gets access to.Described processing unit also comprises: time synchronized unit 306 is used for obtaining time synchronization information according to the high-frequency signal of described first wave band, and indicates described transmitting element 202 to send the high-frequency signal of described second wave band according to this time synchronization information.
With repeater structures shown in Figure 3 is example, the flow process that transponder is handled the high-frequency signal of first wave band that receives as shown in Figure 4:
The high-frequency signal down-conversion of step 403, first wave band after will amplifying.
The code word of step 407, the coding that will recover is transformed into time domain.
In the flow process shown in Figure 4, transponder does not need decoding LDPC and encodes, directly through modulation and power amplification, launches with the high-frequency signal of second wave band then.The mode of this half decoding can be controlled at signal processing time in the protection at interval of OFDM symbol.In addition, when up-conversion, the frequency reference signal that is adopted directly extracts from the high-frequency signal of first wave band, launch produce the high-frequency signal of second wave band through phase-locked loop pll after, and, described time synchronization information also obtains from the high-frequency signal of described first wave band, and each transponder does not need special-purpose time and frequency synchronization device.
The another kind of implementation of transponder wherein, replaces with decoding unit 307 and coding unit 308 with the recovery unit in the repeater structures shown in Figure 3 303 as shown in Figure 5 in the present embodiment; Described decoding unit 307 is used for that the frequency-region signal after the demodulation is carried out the LDPC decoding and conciliates outer sign indicating number as RS, to recover described digital multimedia broadcasting signal from frequency-region signal; Described coding unit 308 is used for described digital multimedia broadcasting signal is encoded again.At this moment, described modulating unit 304 is used for described digital multimedia broadcasting signal is converted to time-domain signal.The mode of this full decoder has further reduced the error rate on the basis of half decoding process.
With repeater structures shown in Figure 5 is example, the flow process that transponder is handled the high-frequency signal of first wave band that receives as shown in Figure 6:
Step 600, receive the high-frequency signal of first wave band carry digital multimedia broadcasting signal from communication satellite.
Step 601, the high-frequency signal of described first wave band is carried out high-pass filtering to obtain its carrier signal as frequency reference signal.
Step 602, the high-frequency signal of described first wave band is carried out frequency-selecting and amplification.
Step 603, the high-frequency signal of first wave band after amplifying is carried out down-converted.
Step 604, the signal after the described down-conversion is carried out time domain to the conversion of frequency domain.
Recover described digital multimedia broadcasting signal step 605, the frequency-region signal after demodulation.
Step 606, obtain the time synchronization information that embeds in the signal frame.
Step 607, described digital multimedia broadcasting signal is transformed into time domain.
Step 608, form the high-frequency signal of second wave band that carries digital multimedia broadcasting signal and with its amplification according to the frequency reference signal that gets access to.
Step 609, send the high-frequency signal of second wave band after amplifying according to described time synchronization information.
With digital multimedia broadcasting system structure shown in Figure 1 is example, and the flow process of by transponder the high-frequency signal of first wave band that carries digital multimedia broadcasting signal of communication satellite transmission being handled in the present embodiment is consulted shown in Figure 7:
In the present embodiment, the structure of another kind of digital multimedia broadcasting system is consulted shown in Figure 8, wherein, in single frequency network 102 structures of Fig. 1, a plurality of benefit point devices 1021 have been increased, be used for covering undesirable or coverage hole occurring when (as being blocked by building) at the signal that described transponder 1020 is transmitted, enhancing signal power is to realize comprehensive covering; Wherein, mend the high-frequency signal that the some device receives second wave band that transponder 1020 sends, to and carry out processing and amplifying and the high-frequency signal of transmitting second wave band after amplifying.Terminal equipment receives when signal covers undesirable or coverage hole occurs and mends the signal that the some device sends, terminal equipment 103-1 as shown in FIG.; When signal is strong, receive the signal that transponder sends, terminal equipment 103-2 as shown in FIG.; The fringe region that sends the signal covering at transponder can receive transponder simultaneously and mend the signal that the some device sends, terminal equipment 103-3 as shown in FIG..
Further, a kind of structure of mending a device is consulted shown in Figure 9ly in the present embodiment, comprising: receiving element 900, Frequency Synchronization unit 901, first frequency converting unit 902, amplifying unit 903, second frequency converting unit 904, transmitting element 905; Wherein, described receiving element 900, be used to receive the high-frequency signal of described second wave band; Described Frequency Synchronization unit 901 is used for obtaining frequency reference signal according to the high-frequency signal of described second wave band; Described first frequency converting unit 902 is used for the high-frequency signal of second wave band that receives is carried out frequency-selecting and amplification, and it is carried out down-converted; Described amplifying unit 903 is used for the signal after the down-conversion is carried out processing and amplifying; Described second frequency converting unit 904, the signal after being used for will amplifying according to described frequency reference signal carries out upconversion process to form the high-frequency signal of second wave band; Described transmitting element 905, be used to send the high-frequency signal of second wave band after the amplification.
With benefit point device structure shown in Figure 9 is example, mends flow process that the some device handles the high-frequency signal of second wave band that receives as shown in figure 10:
The high-frequency signal of step 1000, reception second wave band.
The high-frequency signal of second wave band after step 1006, transmission are amplified.
Described each benefit point device is when up-conversion, the reference frequency that is adopted is directly extracted from the high-frequency signal of second wave band that receives, produce the high-frequency signal of second wave band of tranmitting frequency wave band such as S-band through phase-locked loop pll, therefore, each transponder need not special-purpose time and frequency synchronization device.
Because mending the some device, each directly carries out with transmitting frequently, this signal processing time-delay is very little, Cyclic Prefix (Cyclic Prefix far below the OFDM symbol, CP) length, the channel equalizer of receiver can recover the multipath signal within the Cyclic Prefix, can not bring influence to receiver, therefore each is mended the some device and need not to carry out time synchronizing.
With single frequency network structure shown in Figure 8 is example, and the flow process of by transponder and benefit point device the high-frequency signal of first wave band that carries digital multimedia broadcasting signal of communication satellite transmission being handled in the present embodiment is consulted shown in Figure 11:
From the foregoing description as can be known, the present invention is a core with the communication satellite, and is aided with some small-power transponder groups and/or mends some device group, constitutes mobile digital multi-media broadcast transmission single frequency network, and described single frequency network is simple in structure, is easy to realize; The Time and Frequency Synchronization that frequency reference signal that the high-frequency signal that the direct utilization of the present invention receives from communication satellite gets access to and time synchronization information realize single frequency network; Further, in the described single frequency network, transponder can adopt half decoding process to reduce interchannel noise, also can adopt the full decoder mode to reduce the interchannel noise and the error rate.
Obviously, those skilled in the art can carry out various changes and modification to the present invention and not break away from the spirit and scope of the present invention.Like this, if of the present invention these are revised and modification belongs within the scope of claim of the present invention and equivalent technologies thereof, then the present invention also is intended to comprise these changes and modification interior.
Claims (22)
1, a kind of method that digital multimedia broadcasting signal is provided is characterized in that the method comprising the steps of:
Each retransmission unit receives the high-frequency signal of first wave band that carries digital multimedia broadcasting signal respectively from communication satellite or cell site, ground;
Described each retransmission unit is converted to the high-frequency signal of described first wave band high-frequency signal of second wave band, wherein, each retransmission unit obtains frequency reference signal with the carrier signal in the high-frequency signal that produces described second wave band according to the high-frequency signal of described first wave band;
Described each retransmission unit sends the high-frequency signal of described second wave band.
2, the method for claim 1 is characterized in that, described each retransmission unit with the carrier signal of the high-frequency signal of described first wave band as frequency reference signal.
3, the method for claim 1 is characterized in that, described each retransmission unit further obtains time synchronization information according to the high-frequency signal of described first wave band, and sends the time of the high-frequency signal of described second wave band according to this time synchronization information control.
4, method as claimed in claim 3 is characterized in that, after the high-frequency signal down-conversion of described each retransmission unit with described first wave band, obtains described time synchronization information from signal frame.
5, method as claimed in claim 3, it is characterized in that, the time-delay of the high-frequency signal of second wave band that described each retransmission unit converts to from the high-frequency signal that receives first wave band to transmission is identical, and this delay duration is not less than the duration of each retransmission unit switching signal.
6, the method for claim 1, it is characterized in that, the high-frequency signal of described first wave band is converted in the process of high-frequency signal of second wave band, the signal of described retransmission unit after to down-conversion carries out demodulation and recovers the code word of coding, then to this code word modulate with upconversion process after form the high-frequency signal of described second wave band.
7, the method for claim 1, it is characterized in that, the high-frequency signal of described first wave band is converted in the process of high-frequency signal of second wave band, the signal of described retransmission unit after to down-conversion carries out demodulation and decoding recovers described digital multimedia broadcasting signal, then described digital multimedia broadcasting signal encoded, forms after modulation and the upconversion process high-frequency signal of described second wave band.
As each described method of claim 1 to 7, it is characterized in that 8, the high-frequency signal of described first wave band is converted in the process of high-frequency signal of second wave band, described retransmission unit also further carries out processing and amplifying to signal.
9, method as claimed in claim 8 is characterized in that, also comprises step:
Receive the high-frequency signal of described second wave band and carry out processing and amplifying, and the high-frequency signal that sends second wave band after amplifying.
10, method as claimed in claim 9 is characterized in that, described processing and amplifying comprises step:
Obtain frequency reference signal and with the high-frequency signal down-conversion of second wave band from the high-frequency signal of second wave band that receives;
Amplify the signal after the down-conversion, and the signal after amplifying is carried out the high-frequency signal that upconversion process forms second wave band according to described frequency reference signal.
11, a kind of retransmission unit is characterized in that, comprising:
Receiving element is used for receiving from communication satellite or cell site, ground the high-frequency signal of first wave band that carries digital multimedia broadcasting signal;
Processing unit is used for the high-frequency signal of described first wave band is converted to the high-frequency signal of second wave band, wherein, obtains frequency reference signal with the carrier signal in the high-frequency signal that produces described second wave band according to the high-frequency signal of described first wave band;
Transmitting element is used to send the high-frequency signal of described second wave band.
12, device as claimed in claim 11 is characterized in that, described processing unit comprises:
The Frequency Synchronization unit is used for obtaining frequency reference signal according to the high-frequency signal of described first wave band;
The first frequency converting unit is used for the high-frequency signal of described first wave band is carried out down-converted;
Demodulating unit is used for the time-domain signal after the down-conversion is converted to frequency-region signal;
Recovery unit is used for recovering from frequency-region signal the code word of coding;
Modulating unit, the code word that is used for the coding that will recover is converted to time-domain signal;
The second frequency converting unit is used for forming according to described frequency reference signal the high-frequency signal of second wave band that carries described digital multimedia broadcasting signal.
13, device as claimed in claim 11 is characterized in that, described processing unit comprises:
The Frequency Synchronization unit is used for obtaining frequency reference signal according to the high-frequency signal of described first wave band;
The first frequency converting unit is used for the high-frequency signal of described first wave band is carried out down-converted;
Demodulating unit is used for the time-domain signal after the down-conversion is converted to frequency-region signal;
Decoding unit is used for the frequency-region signal after the demodulation is decoded, and recovers described digital multimedia broadcasting signal;
Coding unit is used for described digital multimedia broadcasting signal is encoded;
Modulating unit is used for the described digital multimedia broadcasting signal behind the coding is converted to time-domain signal;
The second frequency converting unit is used for carrying according to described frequency reference signal shape the high-frequency signal of second wave band of described digital multimedia broadcasting signal.
14, as claim 11,12 or 13 described devices, it is characterized in that described processing unit also comprises:
The time synchronized unit is used for obtaining time synchronization information according to the high-frequency signal of described first wave band, and indicates described transmitting element to send the high-frequency signal of described second wave band according to this time synchronization information.
15, a kind of single frequency network is characterized in that, comprising:
A plurality of retransmission units, wherein, each retransmission unit receives the high-frequency signal of first wave band that carries digital multimedia broadcasting signal respectively from communication satellite or cell site, ground, and the high-frequency signal of described first wave band is converted to the high-frequency signal of second wave band, and the high-frequency signal that sends described second wave band; Wherein, each retransmission unit obtains frequency reference signal with the carrier signal in the high-frequency signal that produces described second wave band according to the high-frequency signal of described first wave band.
16, single frequency network as claimed in claim 15 is characterized in that, also comprises:
A plurality of benefit point devices are used to receive the high-frequency signal of described second wave band and carry out processing and amplifying, and send the high-frequency signal that amplifies back second wave band.
17, single frequency network as claimed in claim 15 is characterized in that, described retransmission unit comprises:
Receiving element is used for receiving from communication satellite or cell site, ground the high-frequency signal of first wave band that carries digital multimedia broadcasting signal;
Processing unit is used for the high-frequency signal of described first wave band is converted to the high-frequency signal of second wave band, wherein, obtains frequency reference signal with the carrier signal in the high-frequency signal that produces described second wave band according to the high-frequency signal of described first wave band;
Transmitting element is used to send the high-frequency signal of described second wave band.
18, single frequency network as claimed in claim 17 is characterized in that, described processing unit comprises:
The Frequency Synchronization unit is used for obtaining frequency reference signal according to the high-frequency signal of described first wave band;
The first frequency converting unit is used for the high-frequency signal down-conversion with described first wave band;
Demodulating unit is used for the time-domain signal after the down-conversion is converted to frequency-region signal;
Recovery unit is used for recovering from frequency-region signal the code word of coding;
Modulating unit, the code word that is used for the coding that will recover is converted to time-domain signal;
The second frequency converting unit is used for forming according to described frequency reference signal the high-frequency signal of second wave band that carries described digital multimedia broadcasting signal.
19, single frequency network as claimed in claim 17 is characterized in that, described processing unit comprises:
The Frequency Synchronization unit is used for obtaining frequency reference signal according to the high-frequency signal of described first wave band;
The first frequency converting unit is used for the high-frequency signal down-conversion with described first wave band;
Demodulating unit is used for the time-domain signal after the down-conversion is converted to frequency-region signal;
Decoding unit is used for the frequency-region signal after the demodulation is decoded, and recovers described digital multimedia broadcasting signal;
Coding unit is used for described digital multimedia broadcasting signal is encoded;
Modulating unit is used for the described digital multimedia broadcasting signal behind the coding is converted to time-domain signal;
The second frequency converting unit is used for carrying according to described frequency reference signal shape the high-frequency signal of second wave band of described digital multimedia broadcasting signal.
20, as claim 17,18 or 19 described single frequency network, it is characterized in that described processing unit also comprises:
The time synchronized unit is used for obtaining time synchronization information according to the high-frequency signal of described first wave band, and indicates described transmitting element to send the high-frequency signal of described second wave band according to this time synchronization information.
21, single frequency network as claimed in claim 15 is characterized in that, described retransmission unit with the carrier signal of the high-frequency signal of described first wave band as frequency reference signal.
22, single frequency network as claimed in claim 15 is characterized in that, after the high-frequency signal down-conversion of described retransmission unit with described first wave band, obtains described time synchronization information from signal frame.
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101668191B (en) * | 2008-09-02 | 2011-02-09 | 中广电信有限公司 | Method and system for receiving digital broadcast signal by high-speed running train |
| CN101567719B (en) * | 2008-04-25 | 2012-10-03 | 天津赛乐新创通信技术有限公司 | Method for obtaining frequency hopping synchronization by using baseband decoding |
| CN103944851A (en) * | 2014-04-03 | 2014-07-23 | 西安交通大学 | Method and system for establishing OFDM single frequency network through MMDS device |
| CN105162569A (en) * | 2015-08-21 | 2015-12-16 | 广州丰谱信息技术有限公司 | Asynchronous duplex zero-radio-frequency wireless communication system |
| CN109981514A (en) * | 2019-02-19 | 2019-07-05 | 重庆邮电大学 | A kind of cell DMB single frequency network implementation method based on local area network |
| CN112995659A (en) * | 2021-04-14 | 2021-06-18 | 成都凯腾四方数字广播电视设备有限公司 | Intelligent ground digital television broadcast single frequency network networking coverage monitoring system |
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| CN1312929C (en) * | 2004-04-01 | 2007-04-25 | 清华大学 | Single-frequency network system of ground digital TV broadcast and its realizing method |
| KR20060110420A (en) * | 2005-04-19 | 2006-10-25 | 삼성전자주식회사 | Apparatus and method for offering broadcast service in a dmb system having single frequency network |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101567719B (en) * | 2008-04-25 | 2012-10-03 | 天津赛乐新创通信技术有限公司 | Method for obtaining frequency hopping synchronization by using baseband decoding |
| CN101668191B (en) * | 2008-09-02 | 2011-02-09 | 中广电信有限公司 | Method and system for receiving digital broadcast signal by high-speed running train |
| CN103944851A (en) * | 2014-04-03 | 2014-07-23 | 西安交通大学 | Method and system for establishing OFDM single frequency network through MMDS device |
| CN103944851B (en) * | 2014-04-03 | 2017-10-20 | 西安交通大学 | The method and its system of OFDM SFNs are set up using MMDS equipment |
| CN105162569A (en) * | 2015-08-21 | 2015-12-16 | 广州丰谱信息技术有限公司 | Asynchronous duplex zero-radio-frequency wireless communication system |
| CN105162569B (en) * | 2015-08-21 | 2018-06-22 | 广州丰谱信息技术有限公司 | A kind of zero Radio-Frequency Wireless Communication system of asynchronous duplex |
| CN109981514A (en) * | 2019-02-19 | 2019-07-05 | 重庆邮电大学 | A kind of cell DMB single frequency network implementation method based on local area network |
| CN109981514B (en) * | 2019-02-19 | 2021-11-19 | 重庆邮电大学 | Local area network-based cell DMB single frequency network implementation method |
| CN112995659A (en) * | 2021-04-14 | 2021-06-18 | 成都凯腾四方数字广播电视设备有限公司 | Intelligent ground digital television broadcast single frequency network networking coverage monitoring system |
| CN112995659B (en) * | 2021-04-14 | 2021-08-10 | 成都凯腾四方数字广播电视设备有限公司 | Intelligent ground digital television broadcast single frequency network networking coverage monitoring system |
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