CN101442369A - Ground forwarding synchronization system and method for mobile multimedia broadcast satellite distribution system - Google Patents
Ground forwarding synchronization system and method for mobile multimedia broadcast satellite distribution system Download PDFInfo
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Abstract
The invention discloses a ground forwarding synchronization system for a mobile multimedia broadcast satellite distribution system, which utilizes asynchronous distribution data for synchronous recovery. The ground forwarding synchronization system comprises a sampling synchronization device, a carrier synchronization device, and a time synchronization device, wherein a sampling clock is recovered from a signal modulated by QPSK, the sampling synchronization device utilizes the real-time depth detection to FIFO of a stored TS stream to obtain the sampling rate error and further to modify the frequency of the clock through a first phase-locked loop, thereby recovering the sampling clock; the carrier synchronization device utilizes the sampling clock recovered by the sampling synchronization device as a reference clock, and recovers a synchronous S-waveband carrier signal through a second phase-locked loop; the time synchronization device demodulates the QPSK signal, performs the OFDM modulation after the delay, and then forwards an OFDM modulation signal to a user receiver to ensure that the user receiver can receive the OFDM modulation signal which belongs to the same time at the same time further to ensure that the total time delay of the QPSK signal in a ground forwarding system is equal to the preset time delay. The invention also discloses a corresponding synchronization method.
Description
Technical field
The present invention relates to the ground forwarding technology of mobile multimedia broadcast satellite dissemination system, more particularly, relate to synchro system and method for synchronous that the ground based repeater of mobile multimedia broadcast satellite dissemination system utilizes the asynchronous distribution data to recover synchronously.
Background technology
Mobile multimedia broadcast system covers, supports high-quality to fix or the multimedia digital that move to receive is looked, audio frequency and data service broadcast service in 30MHz～3000MHz frequency range for the user provides on a large scale.Wherein, programme information can divide two paths of signals to transmit: after 1) source of program signals was carried out the OFDM modulation by the mobile multimedia modulator, directly the S-band broadcast channel provided large tracts of land broadcasting to cover to the user via satellite.2) source of program signals is carried out program distribution by data distribution network to each land-based repeaters simultaneously, and after carrying out OFDM modulation again by land-based repeaters, under specific synchronous condition, on S-band, broadcast, the direct broadcast singal of satellite S-band is replenished covering.
Because the transmission delay that China is vast in territory, satellite-signal arrives various places differs greatly (for example satellite-signal arrives Beijing and Shanghai will have the transmission delay that differs Millisecond), this delay will have a strong impact on the performance of whole mobile multimedia broadcast system, therefore, how to overcome transmission delay, accomplish that transmitting synchronous is a problem that extremely receives publicity.
Summary of the invention
The present invention aims to provide synchro system and the method for synchronous that the ground based repeater of mobile multimedia broadcast satellite dissemination system utilizes the asynchronous distribution data to recover synchronously, the channel synchronization ground of multimedia broadcast satellite dissemination system emission can be transmitted.
The present invention's the ground forwarding synchro system that a kind of mobile multimedia broadcast satellite dissemination system is provided on the one hand, utilize the asynchronous distribution data to recover synchronously, the transmitting terminal of this mobile multimedia broadcast satellite dissemination system is handled the data of synchronization back to satellites transmits with following dual mode: carry out the QPSK modulation after being modulated into the TDM frame again, be transmitted to satellite afterwards; And carry out OFDM modulation, be transmitted to satellite after adding a predetermined delay T1; Signal after wherein QPSK modulation and OFDM modulate has different character rates; Satellite is transmitted to receiver user in such a way with the signal of receiving: the signal for after the OFDM modulation of receiving directly is transmitted to receiver user via satellite; Signal for after the QPSK modulation of receiving is transmitted to receiver user by the ground forwarding synchro system; Wherein, signal after this ground forwarding synchro system is modulated QPSK carries out sample-synchronous, carrier synchronization and time synchronizing, again carry out being transmitted to described receiver user after the OFDM modulation, make described receiver user to receive the data that should belong to synchronization at synchronization, wherein, comprise the satellite distribution channels transmit in the signal after the described QPSK modulation constantly and the broadcasting-satellite channel x time, this satellite distribution channels transmit represents that constantly symbol after current 0 time slot packet distribution, first bit is modulated through QPSK is in the natural time value of the x time of distribution channels; This broadcasting-satellite channel x time represents that symbol after current 0 time slot packet distribution, first bit is through the OFDM modulation is in the natural time value of the x time of broadcast channel;
This ground synchronous repeater system comprises: the sample-synchronous device, from the signal after the QPSK modulation, recover sampling clock, the utilization of wherein said sample-synchronous device obtains the sample rate error for the real-time deep detection of the FIFO of storage TS stream, and then by the first phase-locked loop correction clock frequency, thereby recover sampling clock; The carrier synchronization device utilizes the sampling clock that is recovered by the sample-synchronous device as reference clock, recovers synchronous S-band carrier signal by second phase-locked loop; Time synchronism apparatus, with the demodulation of QPSK signal, carry out the OFDM modulation after the delay, afterwards ofdm modulation signal is transmitted to receiver user, making receiver user to receive at synchronization transmits from satellite, and should belong to the ofdm modulation signal of synchronization by ground forwarding, promptly make the total time-delay of QPSK signal in the ground forwarding system equal T1.
The present invention on the other hand, a kind of ground forwarding method for synchronous of mobile multimedia broadcast satellite dissemination system is provided, utilize the asynchronous distribution data to recover synchronously, the transmitting terminal of this mobile multimedia broadcast satellite dissemination system is handled the data of synchronization back to satellites transmits with following dual mode: carry out the QPSK modulation after being modulated into the TDM frame again, be transmitted to satellite afterwards; And carry out OFDM modulation, be transmitted to satellite after adding a predetermined delay T1; Signal after wherein QPSK modulation and OFDM modulate has different character rates; Satellite is transmitted to receiver user in such a way with the signal of receiving: the signal for after the OFDM modulation of receiving directly is transmitted to receiver user via satellite; Signal for after the QPSK modulation of receiving is transmitted to receiver user by the ground forwarding synchro system; Wherein, signal after this ground forwarding synchro system is modulated QPSK carries out sample-synchronous, carrier synchronization and time synchronizing, again carry out being transmitted to described receiver user after the OFDM modulation, make described receiver user to receive the data that should belong to synchronization at synchronization, wherein, comprise the satellite distribution channels transmit in the signal after the described QPSK modulation constantly and the broadcasting-satellite channel x time, this satellite distribution channels transmit represents that constantly symbol after current 0 time slot packet distribution, first bit is modulated through QPSK is in the natural time value of the x time of distribution channels; This broadcasting-satellite channel x time represents that symbol after current 0 time slot packet distribution, first bit is through the OFDM modulation is in the natural time value of the x time of broadcast channel;
This ground synchronous retransmission method comprises: the sample-synchronous step, from the signal after the QPSK modulation, recover sampling clock, the utilization of wherein said sample-synchronous step obtains the sample rate error for the real-time deep detection of the FIFO of storage TS stream, and then by the first phase-locked loop correction clock frequency, thereby recover sampling clock; The carrier synchronization step utilizes the sampling clock that is provided by the sample-synchronous step as reference clock, recovers synchronous S-band carrier signal by second phase-locked loop; The time synchronized step, with the demodulation of QPSK signal, carry out the OFDM modulation after the delay, afterwards ofdm modulation signal is transmitted to receiver user, making receiver user to receive at synchronization transmits from satellite, and should belong to the ofdm modulation signal of synchronization by ground forwarding, promptly make the total time-delay of QPSK signal in the ground forwarding system equal T1.
Adopt technical scheme of the present invention, can be constantly and the broadcasting-satellite channel x time according to the satellite distribution channels transmit in the signal of the transmitting terminal of mobile multimedia broadcast satellite dissemination system emission, effectively, accurately recover synchronised clock, sync carrier and lock in time, realize the synchronous of sample-synchronous, carrier synchronization and launch time, guarantee that receiver user can receive the data that belong to synchronization at synchronization.
Description of drawings
In the present invention, identical Reference numeral is represented identical feature all the time, wherein,
Fig. 1 is the structure chart that is used to realize the mobile multimedia broadcast satellite dissemination system of the ground forwarding synchro system of mobile multimedia broadcast satellite dissemination system of the present invention and method for synchronous;
Fig. 2 is the structure chart of distributing data frame in the mobile multimedia broadcast satellite dissemination system of the present invention;
Fig. 3 is the structure chart according to the ground forwarding synchro system of the mobile multimedia broadcast satellite dissemination system of one embodiment of the invention;
Fig. 4 is the structure chart according to the sample-synchronous device of one embodiment of the invention;
Fig. 5 a is the circuit structure diagram of sample rate error-detecting module in the sample-synchronous device shown in Figure 4;
Fig. 5 b is the circuit structure diagram of first phase-locked loop in the sample-synchronous device shown in Figure 4;
Fig. 6 is the structure chart according to the time synchronism apparatus of one embodiment of the invention;
Fig. 7 is the flow chart according to the ground forwarding method for synchronous of the mobile multimedia broadcast satellite dissemination system of one embodiment of the invention.
Embodiment
The mobile multi-media broadcasting data dissemination system
When data distribution network adopts the satellite transmits mode, mobile multi-media broadcasting data dissemination system structure as shown in Figure 1, multimedia broadcast data dissemination system 100 shown in Figure 1 can be realized mobile multimedia broadcast satellite distribution data of the present invention encapsulation and method for synchronous.
Continuation is with reference to figure 1, data sync behind the channel coding is sent to TDM exciter 126, after data encapsulation format conversion and QPSK modulation (GS/T 17700 standards are followed in strictness) and inserting time synchronization information, be converted to the Ku wave band by the 2nd Ku wave band frequency conversion amplifier 128 and send to synchronous satellite 104.Satellite 104 directly sends to land-based repeaters 106 with the Ku wave band with this TDM modulation signal.Land-based repeaters 106 is carried out demodulation with the TDM modulation signal that receives, and carries out the OFDM modulation again, under specific synchronous condition, broadcasts on S-band, and the direct S-band broadcast singal of satellite is replenished covering.Terrestrial user receiver 108 receives signal the replenishing as the S-band signal that sends for satellite 104 of being transmitted by land-based repeaters 106.
In the OFDM exciter 122 of the mobile multimedia modulator 102 of Fig. 1, added a Postponement module 122b.After the adding of this module will guarantee that the professional information source information in the identical moment is modulated into ofdm signal and QPSK signal respectively, satisfy a regular time delay T1 on the delivery time of space, this postpones T1 will be by land-based repeaters in order to the signal Synchronization between satellite S-band broadcast singal and the transponder S-band broadcast singal.
Mobile multimedia broadcast satellite distribution data encapsulation and synchronically controlling information insert
Mobile multimedia broadcast satellite distribution data carries out data encapsulation according to characteristics such as structure of time slot, signal bandwidth and modulating modes, the distributing data frame that has constituted distribution transmission package with 19 188 bytes and be unit is (referring to GY/T 220.1-2006, Mobile Multimedia Broadcasting, part 1: broadcast channel frame structure, chnnel coding and modulation).Its frame structure as shown in Figure 2, each distributing data frame has the distributing data frame head of one 21 byte, be positioned at the distribution transmission package 0, carried various control informations such as time-gap number, frequency point information, modulating mode in this distributing data frame head.Wherein there are two control informations to be respectively: the satellite distribution channels transmit moment and broadcasting-satellite channel x time.The satellite distribution channels transmit is represented symbol after current 0 time slot packet distribution, first bit is through the OFDM modulation constantly in the natural time value of the x time of broadcast channel, and the identified time precision is 100ns, and the identified time scope is 1 second; The broadcasting-satellite channel x time is represented symbol after current 0 time slot packet distribution, first bit is through the OFDM modulation in the natural time value of the x time of broadcast channel, and the identified time precision is 100ns, and the identified time scope is 1 second.For each the distribution transmission package in the distribution transmission package 0-distribution transmission package 18, the packet header that all has one 5 byte.For distribution transmission package 0, because distributing data frame head with 21 bytes, so the quantity of its symbol data is 162 bytes, remaining distribution transmission package 1-17, and the quantity of its symbol data is 183 bytes.
Distributing data in the mobile multimedia broadcast satellite dissemination system need carry out rate adapted through after the data encapsulation, can be suitable with the channel transmission rate of satellite QPSK modulation.Rate adaption method is: when distribution channels need send packet and the distribution transmission package of broadcast channel when also not in place, distribution channels is inserted adaptive bag automatically and is sent.Adaptive bag is the same with distribution transmission package size, all is 188 bytes.Insert the process of adaptive bag because rate adapted is one at random according to transmission state, thus through adaptive data through the QPSK modulation, formed symbol has constituted a kind of asynchronous relation with distributing data frame structure before adaptive.
Land-based repeaters in the mobile multimedia broadcast satellite dissemination system needs according to the satellite qpsk modulation signal that receives, based on the data structure of distributing data frame carry out sample frequency synchronously, carrier frequency synchronization and time synchronized.Because qpsk modulation signal with being asynchronous relationship between the distributing data frame, therefore is this difficulty that caused synchronously.The present invention aim to provide a kind of land-based repeaters utilize satellite asynchronous distribution symbol carry out sample frequency synchronously, the solution of carrier frequency synchronization and time synchronized.
The ground forwarding synchro system of mobile multimedia broadcast satellite dissemination system
The ground forwarding synchro system of mobile multimedia broadcast satellite dissemination system provided by the invention, utilize the asynchronous distribution data to recover synchronously, the transmitting terminal of this mobile multimedia broadcast satellite dissemination system is handled the data of synchronization back to satellites transmits with following dual mode:
Carry out the QPSK modulation again after being modulated into the TDM frame, be transmitted to satellite afterwards; And
Carry out OFDM modulation, be transmitted to satellite after adding a predetermined delay T1;
Signal after wherein QPSK modulation and OFDM modulate has different character rates;
Satellite is transmitted to receiver user in such a way with the signal of receiving:
Signal for after the OFDM modulation of receiving directly is transmitted to receiver user via satellite;
Signal for after the QPSK modulation of receiving is transmitted to receiver user by the ground forwarding synchro system;
Wherein, signal after this ground forwarding synchro system is modulated QPSK carries out sample-synchronous, carrier synchronization and time synchronizing, again carry out being transmitted to described receiver user after the OFDM modulation, make described receiver user to receive the data that should belong to synchronization at synchronization, wherein, comprise the satellite distribution channels transmit in the signal after the described QPSK modulation constantly and the broadcasting-satellite channel x time, this satellite distribution channels transmit represents that constantly symbol after current 0 time slot packet distribution, first bit is modulated through QPSK is in the natural time value of the x time of distribution channels; This broadcasting-satellite channel x time represents that symbol after current 0 time slot packet distribution, first bit is through the OFDM modulation is in the natural time value of the x time of broadcast channel;
With reference to shown in Figure 3, this ground synchronous repeater system 300 comprises:
Sample-synchronous device 302, from the signal after the QPSK modulation, recover sampling clock, wherein sample-synchronous device 302 utilizes the real-time deep of the FIFO that flows for storage TS to detect and obtains the sample rate error, and then by the first phase-locked loop correction clock frequency, thereby recover sampling clock;
Time synchronism apparatus 306, with the demodulation of QPSK signal, carry out the OFDM modulation after the delay, afterwards ofdm modulation signal is transmitted to receiver user, making receiver user to receive at synchronization transmits from satellite, and should belong to the ofdm modulation signal of synchronization by ground forwarding, promptly make the total time-delay of QPSK signal in the ground forwarding system equal T1.
The sample-synchronous device
In mobile multimedia broadcast system, the character rate of satellite QPSK modulation is 20M (integral multiple of 2.5M), and the character rate of OFDM modulation is 10M.Therefore, the ground forwarding transponder need recover 20M sampling clock accurately.
Fig. 4 formula has gone out the structure chart of an embodiment of sample-synchronous device among above-mentioned Fig. 3, and this sample-synchronous device 302 comprises:
Antenna 402 receives the QPSK signal that satellite is transmitted, and this QPSK signal meets GS/T 17700 standards;
DVB-S receiver 404 carries out demodulation to the QPSK signal that is received, and based on the sampling clock of self-recovery the TS stream that demodulation obtains is written among the FIFO;
FIFO 406, storage TS stream;
Variable bit rate timepiece drive module 408 provides local clock, and a predetermined initial local clock is provided during these variable bit rate timepiece drive module 408 beginnings;
Local distributing data frame rate recovery device 410, the clock that provides according to the variable bit rate timepiece drive module generates through the local distributing data frame structure after the rate adapted, and reads the 2nd TS stream according to the speed of this this locality distributing data frame structure from FIF O406;
FIFO depth detection apparatus 412 detects the FIFO depth information in real time;
Sample rate error-detecting module 414 is according to the FIFO depth information detection sample rate error of FIFO depth detection apparatus output;
First phase-locked loop 416 carries out the frequency correction according to the sample rate error generation sample rate correction value of sample rate error-detecting module 414 outputs and to the local clock that variable bit rate timepiece drive module 408 provides; The sampling clock that this revised local clock recovers as sample-synchronous device 302 and exporting.
With reference to figure 5a, above-mentioned sample rate error-detecting module 414 comprises following functional block further:
Segmental averaging device 502 receives the FIFO depth information that the FIFO depth detection apparatus is exported, and wherein, this segmental averaging device 502 carries out segmental averaging with a plurality of FIFO depth informations that are consecutively detected in a period of time, and the length of segmentation is adjustable parameter;
Deferred mount 504 receives the output from segmental averaging device 502, will postpone through the FIFO depth information after the segmental averaging, to carry out the front and back Difference Calculation;
First adder 506 receives the output from segmental averaging device 502 and deferred mount 504, will carry out the front and back Difference Calculation through the FIFO depth information after the segmental averaging, and the difference that obtains is exported as the sample rate error.
Similarly, with reference to figure 5b, show the structure of the first above-mentioned phase-locked loop 416.Wherein C is an adjustable parameter.The output of first phase-locked loop 416 drives local clock driver module 408, according to phase-locked principle, can recover accurate system sampling clock.
The carrier synchronization device
In mobile multimedia broadcast system, land-based repeaters is at first carried out correct demodulation to the QPSK signal of Ku band satellite distribution.Then the multimedia broadcasting information source information that receives is carried out again OFDM modulation, and upconvert to S-band and replenish the broadcasting covering.Therefore, land-based repeaters need recover strict S-band carrier signal.
The clock of 20M accurately that utilizes the sample-synchronous device to obtain is used for sampling clock.As reference clock, can obtain accurate S-band carrier signal with the 20M clock by phase-locked loop.
Time synchronism apparatus
With reference to shown in Figure 6, time synchronism apparatus 306 of the present invention comprises:
Reception antenna 602 receives the QPSK signal that satellite is transmitted, and this QPSK signal meets the GS/T17700 standard;
DVB-S receiver 604 carries out demodulation to the QPSK signal that is received, and based on the sampling clock of self-recovery the TS stream that demodulation obtains is written among the FIFO 606;
OFDM modulation module 608, adorn 302 according to sample-synchronous and put the sampling clock of recovery, generate through the local distributing data frame structure after the rate adapted, and from FIFO 606, read the 2nd TS stream, the 2nd TS stream is carried out the OFDM modulation according to the speed of this this locality distributing data frame structure;
X time information extraction modules 610 detects the TS stream through the QPSK demodulation, and first bit that detects 0 time slot of current packet distribution is modulated first moment T of back in ground satellite station Ku band emission through QPSK
QPSK, and first bit of same 0 time slot is through second moment T of OFDM modulation back in the emission of ground satellite station S-band
OFDM, wherein, this first moment T
QPSKRelevant constantly with described satellite distribution channels transmit, this second moment T
OFDMRelevant with described broadcasting-satellite channel x time; This x time information extracting device calculates described predetermined delay T1=T
OFDM-T
QPSK
Emission postpones control module 612, calculates the time of delay of frame before emission after 608 modulation of OFDM modulation module, and be calculated as this time of delay: time of delay T2=T1-(T
D1+ T
D2), wherein, T
D1Be the intrinsic receive delay of DVB-S receiver and FIFO, T
D2Delay for the OFDM modulation module.
Transmitting antenna 614 is used to launch through modulation and the data after postponing.
In mobile multimedia broadcast system, the S-band ofdm signal that land-based repeaters is transmitted should arrive receiver user simultaneously with the S-band ofdm signal of direct satellite broadcasting.For the land-based repeaters design, need guarantee that ofdm signal that forwards and the satellite OFDM retention time that receives are synchronous.
Concerning single land-based repeaters, the Ku wave band TDM signal that satellite is transmitted has identical transmission path with the S-band ofdm signal, therefore has identical transmission delay T
DAt ground satellite station (mobile multimedia modulator), the OFDM modulating part has added a Postponement module (be T1 time of delay), and therefore identical information source information sends to satellite from OFDM modulation link the moment is than the TDM modulation link late T1 time: first bit of each 0 time slot is T through QPSK modulation back in ground satellite station Ku band emission constantly
QPSKFirst bit of same 0 time slot is T through OFDM modulation back at ground satellite station S-band x time
OFDMSo: T1=T
OFDM-T
QPSKT
OFDMAnd T
QPSKBe placed in the distributing data frame head.
In land-based repeaters, be T1 as long as guarantee the processing total time of TDM demodulation-OFDM modulation-forwarding, just can satisfy the time synchronized requirement of system.This section provides a kind of x time information of utilizing, and carries out the synchronous method of land-based repeaters automatic time.
The x time information extraction modules detects the TS stream of QPSK demodulation output, first bit that detects pairing 0 time slot of current packet distribution from the distributing data frame head is respectively through after QPSK modulation and the OFDM modulation, at the x time of ground satellite station.By these two moment T
OFDMAnd T
QPSK, just can calculate the x time difference T1 of current 0 time slot in ground satellite station Ku wave band and S-band.The intrinsic receive delay of design DVB-S receiver and FIFO is fixed value T
D1If, the delay T of OFDM modulation module
D2Also be known, T2 time of delay of Postponement module is so:
T2＝T1-(T
d1+T
d2)；
Therefore, adaptive through the delay of Postponement module, can guarantee that the total delay that transponder is transmitted is:
T
d1+T
d2+T2＝T1。
The ground forwarding method for synchronous of mobile multimedia broadcast satellite dissemination system
The present invention also provides a kind of ground forwarding method for synchronous of mobile multimedia broadcast satellite dissemination system, utilize the asynchronous distribution data to recover synchronously, the transmitting terminal of this mobile multimedia broadcast satellite dissemination system is handled the data of synchronization back to satellites transmits with following dual mode:
Carry out the QPSK modulation again after being modulated into the TDM frame, be transmitted to satellite afterwards; And
Carry out OFDM modulation, be transmitted to satellite after adding a predetermined delay T1;
Signal after wherein QPSK modulation and OFDM modulate has different character rates;
Satellite is transmitted to receiver user in such a way with the signal of receiving:
Signal for after the OFDM modulation of receiving directly is transmitted to receiver user via satellite;
Signal for after the QPSK modulation of receiving is transmitted to receiver user by the ground forwarding synchro system;
Wherein, signal after this ground forwarding synchro system is modulated QPSK carries out sample-synchronous, carrier synchronization and time synchronizing, again carry out being transmitted to described receiver user after the OFDM modulation, make described receiver user to receive the data that should belong to synchronization at synchronization, wherein, comprise the satellite distribution channels transmit in the signal after the described QPSK modulation constantly and the broadcasting-satellite channel x time, this satellite distribution channels transmit represents that constantly symbol after current 0 time slot packet distribution, first bit is modulated through QPSK is in the natural time value of the x time of distribution channels; This broadcasting-satellite channel x time represents that symbol after current 0 time slot packet distribution, first bit is through the OFDM modulation is in the natural time value of the x time of broadcast channel;
With reference to shown in Figure 7, this ground synchronous retransmission method 700 comprises:
702. sample-synchronous step, from the signal after the QPSK modulation, recover sampling clock, the utilization of wherein said sample-synchronous step obtains the sample rate error for the real-time deep detection of the FIFO of storage TS stream, and then by the first phase-locked loop correction clock frequency, thereby recover sampling clock.According to an embodiment, this sample-synchronous step 702 is carried out as follows: receive the QPSK signal that satellite is transmitted, wherein this QPSK signal meets GS/T 17700 standards; The QPSK signal that is received is carried out demodulation, and the TS stream that demodulation obtains is written among the FIFO based on the sampling clock of self-recovery; Storage TS stream; One predetermined initial local clock is provided; Generate through the local distributing data frame structure after the rate adapted according to the clock that is provided, and from FIFO, read the 2nd TS stream according to the speed of this this locality distributing data frame structure; Detect the FIFO depth information in real time; FIFO depth information according to the output of FIFO depth detection apparatus detects the sample rate error; According to the sample rate error of sample rate error-detecting module output, generate the sample rate correction value and local clock is carried out the frequency correction by first phase-locked loop; The sampling clock that this revised local clock recovers as the sample-synchronous step and exporting.The process of above-mentioned detection sample rate error can further comprise: receive the FIFO depth information of FIFO depth detection apparatus output and a plurality of FIFO depth informations that are consecutively detected in a period of time are carried out segmental averaging, the length of segmentation is adjustable parameter; To postpone through the FIFO depth information after the segmental averaging, to carry out the front and back Difference Calculation; To carry out the front and back Difference Calculation through the FIFO depth information after the segmental averaging, the difference that obtains is exported as the sample rate error.
704. the carrier synchronization step utilizes the sampling clock that is provided by the sample-synchronous step as reference clock, recovers synchronous S-band carrier signal by second phase-locked loop;
706. time synchronized step, with the demodulation of QPSK signal, carry out the OFDM modulation after the delay, afterwards ofdm modulation signal is transmitted to receiver user, making receiver user to receive at synchronization transmits from satellite, and should belong to the ofdm modulation signal of synchronization by ground forwarding, promptly make the total time-delay of QPSK signal in the ground forwarding system equal T1.According to one embodiment of the invention, the time synchronized step can be achieved as follows: receive the QPSK signal that satellite is transmitted, this QPSK signal meets GS/T 17700 standards; The QPSK signal that is received is carried out demodulation, and the TS stream that demodulation obtains is written among the FIFO based on the sampling clock of self-recovery; Storage TS stream; Sampling clock according to the sample-synchronous step is recovered generates through the local distributing data frame structure after the rate adapted, and reads the 2nd TS stream according to the speed of this this locality distributing data frame structure from FIFO, and the 2nd TS stream is carried out the OFDM modulation; TS stream through the QPSK demodulation is detected, and first bit that detects 0 time slot of current packet distribution is modulated first moment T of back in ground satellite station Ku band emission through QPSK
QPSK, and first bit of same 0 time slot is through second moment T of OFDM modulation back in the emission of ground satellite station S-band
OFDM, wherein, this first moment T
QPSKRelevant constantly with the satellite distribution channels transmit, this second moment T
OFDMRelevant with described broadcasting-satellite channel x time; Calculate predetermined delay T1=T
OFDM-T
QPSKFrame the time of delay before emission of calculating after OFDM modulation module modulation, be calculated as this time of delay: time of delay T2=T1-(T
D1+ T
D2), wherein, T
D1Be the intrinsic receive delay of DVB-S receiver and FIFO, T
D2Delay for the OFDM modulation module.Launch through modulation subsequently and the data after postponing.
Need to prove that the ground forwarding method for synchronous of mobile multimedia broadcast satellite dissemination system of the present invention is suitable for top in conjunction with described all details of the ground forwarding synchro system of mobile multimedia broadcast satellite dissemination system equally.
Adopt technical scheme of the present invention, can be constantly and the broadcasting-satellite channel x time according to the satellite distribution channels transmit in the signal of the transmitting terminal of mobile multimedia broadcast satellite dissemination system emission, effectively, accurately recover synchronised clock, sync carrier and lock in time, realize the synchronous of sample-synchronous, carrier synchronization and launch time, guarantee that receiver user can receive the data that belong to synchronization at synchronization.
Claims (10)
1. the ground forwarding synchro system of a mobile multimedia broadcast satellite dissemination system, it is characterized in that, utilize the asynchronous distribution data to recover synchronously, the transmitting terminal of this mobile multimedia broadcast satellite dissemination system is handled the data of synchronization back to satellites transmits with following dual mode:
Carry out the QPSK modulation again after being modulated into the TDM frame, be transmitted to satellite afterwards; And
Carry out OFDM modulation, be transmitted to satellite after adding a predetermined delay T1;
Signal after wherein QPSK modulation and OFDM modulate has different character rates;
Satellite is transmitted to receiver user in such a way with the signal of receiving:
Signal for after the OFDM modulation of receiving directly is transmitted to receiver user via satellite;
Signal for after the QPSK modulation of receiving is transmitted to receiver user by the ground forwarding synchro system;
Wherein, signal after this ground forwarding synchro system is modulated QPSK carries out sample-synchronous, carrier synchronization and time synchronizing, again carry out being transmitted to described receiver user after the OFDM modulation, make described receiver user to receive the data that should belong to synchronization at synchronization, wherein, comprise the satellite distribution channels transmit in the signal after the described QPSK modulation constantly and the broadcasting-satellite channel x time, this satellite distribution channels transmit represents that constantly symbol after current 0 time slot packet distribution, first bit is modulated through QPSK is in the natural time value of the x time of distribution channels; This broadcasting-satellite channel x time represents that symbol after current 0 time slot packet distribution, first bit is through the OFDM modulation is in the natural time value of the x time of broadcast channel;
This ground synchronous repeater system comprises:
The sample-synchronous device, from the signal after the QPSK modulation, recover sampling clock, the utilization of wherein said sample-synchronous device obtains the sample rate error for the real-time deep detection of the FIFO of storage TS stream, and then by the first phase-locked loop correction clock frequency, thereby recover sampling clock;
The carrier synchronization device utilizes the sampling clock that is recovered by the sample-synchronous device as reference clock, recovers synchronous S-band carrier signal by second phase-locked loop;
Time synchronism apparatus, with the demodulation of QPSK signal, carry out the OFDM modulation after the delay, afterwards ofdm modulation signal is transmitted to receiver user, making receiver user to receive at synchronization transmits from satellite, and should belong to the ofdm modulation signal of synchronization by ground forwarding, promptly make the total time-delay of QPSK signal in the ground forwarding system equal T1.
2. ground forwarding synchro system as claimed in claim 1 is characterized in that, described sample-synchronous device comprises:
Antenna receives the QPSK signal that satellite is transmitted, and this QPSK signal meets GS/T 17700 standards;
The DVB-S receiver carries out demodulation to the QPSK signal that is received, and based on the sampling clock of self-recovery the TS stream that demodulation obtains is written among the FIFO;
FIFO, storage TS stream;
The variable bit rate timepiece drive module provides local clock, and this variable bit rate timepiece drive module provides a predetermined initial local clock when beginning;
Local distributing data frame rate recovery device, the clock that provides according to the variable bit rate timepiece drive module generates through the local distributing data frame structure after the rate adapted, and reads the 2nd TS stream according to the speed of this this locality distributing data frame structure from described FIFO;
The FIFO depth detection apparatus detects described FIFO depth information in real time;
Sample rate error-detecting module is according to the FIFO depth information detection sample rate error of described FIFO depth detection apparatus output;
First phase-locked loop carries out the frequency correction according to the sample rate error generation sample rate correction value of sample rate error-detecting module output and to the local clock that the variable bit rate timepiece drive module provides; The sampling clock that this revised local clock recovers as the sample-synchronous device and exporting.
3. ground forwarding synchro system as claimed in claim 2 is characterized in that, described sample rate error-detecting module comprises:
The segmental averaging device receives the FIFO depth information that the FIFO depth detection apparatus is exported, and wherein, this segmental averaging device carries out segmental averaging with a plurality of FIFO depth informations that are consecutively detected in a period of time, and the length of segmentation is adjustable parameter;
Deferred mount receives the output from the segmental averaging device, will postpone through the FIFO depth information after the segmental averaging, to carry out the front and back Difference Calculation;
First adder receives the output from segmental averaging device and deferred mount, will carry out the front and back Difference Calculation through the FIFO depth information after the segmental averaging, and the difference that obtains is exported as the sample rate error.
4. ground forwarding synchro system as claimed in claim 1 is characterized in that described time synchronism apparatus obtains sampling clock from the sample-synchronous device, and this time synchronism apparatus comprises:
Reception antenna receives the QPSK signal that satellite is transmitted, and this QPSK signal meets GS/T 17700 standards;
The DVB-S receiver carries out demodulation to the QPSK signal that is received, and based on the sampling clock of self-recovery the TS stream that demodulation obtains is written among the FIFO;
FIFO, storage TS stream;
The OFDM modulation module, sampling clock according to described sample-synchronous device recovery, generate through the local distributing data frame structure after the rate adapted, and from described FIFO, read the 2nd TS stream, the 2nd TS stream is carried out the OFDM modulation according to the speed of this this locality distributing data frame structure;
The x time information extraction modules detects the TS stream through the QPSK demodulation, and first bit that detects 0 time slot of current packet distribution is modulated first moment T of back in ground satellite station Ku band emission through QPSK
QPSK, and first bit of same 0 time slot is through second moment T of OFDM modulation back in the emission of ground satellite station S-band
OFDM, wherein, this first moment T
QPSKRelevant constantly with described satellite distribution channels transmit, this second moment T
OFDMRelevant with described broadcasting-satellite channel x time; This x time information extracting device calculates described predetermined delay T1=T
OFDM-T
QPSK
Emission postpones control module, calculates the time of delay of frame before emission after the modulation of OFDM modulation module, and be calculated as this time of delay: time of delay T2=T1-(T
D1+ T
D2), wherein, T
D1Be the intrinsic receive delay of DVB-S receiver and FIFO, T
D2Delay for the OFDM modulation module;
Transmitting antenna, emission is through the data of modulation and time-delay.
5. ground forwarding synchro system as claimed in claim 1 is characterized in that, the described satellite distribution channels transmit moment and broadcasting-satellite channel x time identified time precision are 100ns, and the identified time scope is 1 second.
6. ground forwarding synchro system as claimed in claim 5 is characterized in that, the character rate of described OFDM modulation is 10M, and the character rate of QPSK modulation is 20M.
7. the ground forwarding method for synchronous of a mobile multimedia broadcast satellite dissemination system, it is characterized in that, utilize the asynchronous distribution data to recover synchronously, the transmitting terminal of this mobile multimedia broadcast satellite dissemination system is handled the data of synchronization back to satellites transmits with following dual mode:
Carry out the QPSK modulation again after being modulated into the TDM frame, be transmitted to satellite afterwards; And
Carry out OFDM modulation, be transmitted to satellite after adding a predetermined delay T1;
Signal after wherein QPSK modulation and OFDM modulate has different character rates;
Satellite is transmitted to receiver user in such a way with the signal of receiving:
Signal for after the OFDM modulation of receiving directly is transmitted to receiver user via satellite;
Signal for after the QPSK modulation of receiving is transmitted to receiver user by the ground forwarding synchro system;
Wherein, signal after this ground forwarding synchro system is modulated QPSK carries out sample-synchronous, carrier synchronization and time synchronizing, again carry out being transmitted to described receiver user after the OFDM modulation, make described receiver user to receive the data that should belong to synchronization at synchronization, wherein, comprise the satellite distribution channels transmit in the signal after the described QPSK modulation constantly and the broadcasting-satellite channel x time, this satellite distribution channels transmit represents that constantly symbol after current 0 time slot packet distribution, first bit is modulated through QPSK is in the natural time value of the x time of distribution channels; This broadcasting-satellite channel x time represents that symbol after current 0 time slot packet distribution, first bit is through the OFDM modulation is in the natural time value of the x time of broadcast channel;
This ground synchronous retransmission method comprises:
The sample-synchronous step, from the signal after the QPSK modulation, recover sampling clock, the utilization of wherein said sample-synchronous step obtains the sample rate error for the real-time deep detection of the FIFO of storage TS stream, and then by the first phase-locked loop correction clock frequency, thereby recover sampling clock;
The carrier synchronization step utilizes the sampling clock that is provided by the sample-synchronous step as reference clock, recovers synchronous S-band carrier signal by second phase-locked loop;
The time synchronized step, with the demodulation of QPSK signal, carry out the OFDM modulation after the delay, afterwards ofdm modulation signal is transmitted to receiver user, making receiver user to receive at synchronization transmits from satellite, and should belong to the ofdm modulation signal of synchronization by ground forwarding, promptly make the total time-delay of QPSK signal in the ground forwarding system equal T1.
8. ground forwarding method for synchronous as claimed in claim 7 is characterized in that, described sample-synchronous step further comprises:
Receive the QPSK signal that satellite is transmitted, wherein this QPSK signal meets GS/T 17700 standards;
The QPSK signal that is received is carried out demodulation, and the TS stream that demodulation obtains is written among the FIFO based on the sampling clock of self-recovery;
Storage TS stream;
One predetermined initial local clock is provided;
Generate through the local distributing data frame structure after the rate adapted according to the clock that is provided, and from FIFO, read the 2nd TS stream according to the speed of this this locality distributing data frame structure;
Detect described FIFO depth information in real time;
FIFO depth information according to described FIFO depth detection apparatus output detects the sample rate error;
According to the sample rate error of sample rate error-detecting module output, generate the sample rate correction value and local clock is carried out the frequency correction by first phase-locked loop; The sampling clock that this revised local clock recovers as the sample-synchronous step and exporting.
9. ground forwarding method for synchronous as claimed in claim 8 is characterized in that, the step of described detection sample rate error comprises:
Receive the FIFO depth information of FIFO depth detection apparatus output and a plurality of FIFO depth informations that are consecutively detected in a period of time are carried out segmental averaging, the length of segmentation is adjustable parameter;
To postpone through the FIFO depth information after the segmental averaging, to carry out the front and back Difference Calculation;
To carry out the front and back Difference Calculation through the FIFO depth information after the segmental averaging, the difference that obtains is exported as the sample rate error.
10. ground forwarding method for synchronous as claimed in claim 7 is characterized in that, described time synchronized step is obtained sampling clock with the sample-synchronous step, and this time synchronized step comprises:
Receive the QPSK signal that satellite is transmitted, this QPSK signal meets GS/T 17700 standards;
The QPSK signal that is received is carried out demodulation, and the TS stream that demodulation obtains is written among the FIFO based on the sampling clock of self-recovery;
Storage TS stream;
Sampling clock according to described sample-synchronous step is recovered generates through the local distributing data frame structure after the rate adapted, and reads the 2nd TS stream according to the speed of this this locality distributing data frame structure from FIFO, and the 2nd TS stream is carried out the OFDM modulation;
TS stream through the QPSK demodulation is detected, and first bit that detects 0 time slot of current packet distribution is modulated first moment T of back in ground satellite station Ku band emission through QPSK
QPSK, and first bit of same 0 time slot is through second moment T of OFDM modulation back in the emission of ground satellite station S-band
OFDM, wherein, this first moment T
QPSKRelevant constantly with described satellite distribution channels transmit, this second moment T
OFDMRelevant with described broadcasting-satellite channel x time; Calculate described predetermined delay T1=T
OFDM-T
QPSK
Frame the time of delay before emission of calculating after OFDM modulation module modulation, be calculated as this time of delay: time of delay T2=T1-(T
D1+ T
D2), wherein, T
D1Be the intrinsic receive delay of DVB-S receiver and FIFO, T
D2Delay for the OFDM modulation module;
Emission is through the data of modulation and time-delay.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104038306A (en) * | 2013-03-05 | 2014-09-10 | 上海航天测控通信研究所 | Method and asynchronous FIFO for low-latency real-time transmission of multi-rate bit stream data |
| CN111727377A (en) * | 2018-02-16 | 2020-09-29 | 皇家飞利浦有限公司 | Improved carrier phase tracking using multiple carriers |
| CN115296722A (en) * | 2022-08-11 | 2022-11-04 | 中国电子科技集团公司第三十四研究所 | Variable-rate data transmission device and method for satellite modem |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP3840435B2 (en) * | 2002-07-05 | 2006-11-01 | 松下電器産業株式会社 | Radio communication base station apparatus, radio communication mobile station apparatus, and radio communication method |
| WO2006028337A1 (en) * | 2004-09-06 | 2006-03-16 | Samsung Electronics Co., Ltd. | Apparatus and method for receiving digital multimedia broadcasting signals |
| KR100709585B1 (en) * | 2004-09-16 | 2007-04-20 | 삼성전자주식회사 | The apparatus and method for satellite DMB receive |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104038306A (en) * | 2013-03-05 | 2014-09-10 | 上海航天测控通信研究所 | Method and asynchronous FIFO for low-latency real-time transmission of multi-rate bit stream data |
| CN104038306B (en) * | 2013-03-05 | 2017-09-29 | 上海航天测控通信研究所 | The method and its asynchronous FIFO of low delay real-time Transmission multi code Rate of Chinese character bit stream data |
| CN111727377A (en) * | 2018-02-16 | 2020-09-29 | 皇家飞利浦有限公司 | Improved carrier phase tracking using multiple carriers |
| CN111727377B (en) * | 2018-02-16 | 2023-10-31 | 皇家飞利浦有限公司 | Improved carrier phase tracking using multiple carriers |
| CN115296722A (en) * | 2022-08-11 | 2022-11-04 | 中国电子科技集团公司第三十四研究所 | Variable-rate data transmission device and method for satellite modem |
| CN115296722B (en) * | 2022-08-11 | 2023-05-02 | 中国电子科技集团公司第三十四研究所 | Variable rate data transmission device and method for satellite modem |
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