Single carrier transmitting system and method thereof
The application be that September 30, application number in 2003 are 03139297.0 the applying date, denomination of invention divides an application for the application for a patent for invention of " single carrier transmitting system and method thereof ".
The present invention relates generally to single carrier transmitting system and method thereof, relate in particular to the single carrier transmitting system and the method thereof of the reliability that can improve the signal that is transmitted.
In communication multimedia, computer and the broadcasting epoch, countries in the world are all always in the broadcasting of digitized simulation type.Particularly, use the digit broadcasting system of satellite to be developed and to have dropped into practicality in developed country such as the U.S., Europe and Japanese.Along with development fast, proposed the different standards that is used for digital broadcasting respectively in various countries.
On December 24th, 1996, the Federal Communications Committee of the U.S. (FCC) passed through the broadcast standard of the digital television standard of Advanced Television Systems Committee as TV of future generation.All terrestrial broadcasting operators must observe and video/audio compression, packet data transmission structure, the modulation ATSC standard relevant with the transmission system standard.Have only the standard of video format not announced (stated), but determine by industrial quarters.
According to the ATSC standard, described video compression scheme adopts the ISO/IEC IS13812-2 standard of motion image expert group 2 (MPEG-2).This standard has been adopted to the standard of all digital broadcasting types of the whole world.Audio compression scheme adopts digital audio compression-3 (AC-3) standard of being proposed by Dolby.The ISO/IEC IS13812 standard of MPEG-2 system has been adopted to a kind of multichannel multiplexing method.This multichannel multiplexing method and video compression scheme are used as in the motion in Europe together.8-vestigial sideband (8-VSB) is adopted to the method for modulation and transmission.Described VSB method is proposed for digital television broadcasting, and the frequency band that uses 6MHz is to obtain the high frequency band efficiency data transfer rate of 19.39Mbps by a simple structure.This also be designed to minimize and the broadcast channel of the existing broadcast system of NTSC (NTSC) between interference.Even for also can stable operation under noise circumstance, this method have been used pilot signal, segment sync signal and field sync signal.Further, for fear of mistake, this method has been used Read-Solomon (RS) sign indicating number and grid (Trellis) coding.
The ATSC digital television standard is to be used to use single carrier VSB method with 6MHz frequency band transmission high-quality video, audio frequency and additional data, and supports terrestrial broadcasting pattern and High Data Rate wired broadcasting pattern simultaneously.The main aspect of this method is the 8-VSB modulator approach, and this method is a kind of modification of existing simulation VSB method, can the modulation of combine digital signal.
Fig. 1 is the schematic block diagram that illustrates according to the digit broadcasting system of ATSC standard.With reference to Fig. 1, described digit broadcasting system comprises scrambler 10, forward error correction (FEC) unit 20, multiplexer (MUX) 30, pilot plug-in unit 40, modulating unit 50 and radio frequency (RF) transducer 60.Described FEC unit 20 comprises Read-Solomon (RS) encoder 21, interleaver 23 and trellis encoder 25.
Scrambler 10 is called as the data random device, and it carries out randomization operation to data signals transmitted, prevent whereby since during synchronous data transmission owing to repeat the problem that synchronizing signal that numeral such as 00000000b or 11111111b cause is lost.The predetermined pattern of scrambler 10 usefulness changes the byte of each data-signal, and this processing be reversed so that accurate value is resumed at receiving terminal.
RS encoder 21 is to add the FEC structure of giving input traffic.FEC is one of technology of revising the bit mistake that takes place during transfer of data.The non-linear of noise in the atmosphere, channelized frequencies, signal attenuation and receiver is the reason of error code.When the data of transmission are that RS encoder 21 afterbodys in 187 bytes add 20 bytes in the MPEG-II transport stream time.20 bytes of this interpolation are called as the Read-Solomon parity bytes.187 bytes that receiver relatively receives and this 20 parity bytes, the accuracy of definite data that receive whereby.Detecting under the wrong situation, receiver finds wrong position, and recovers primary signal by the byte of revising distortion.Each stream can recover many mistakes to 10 bytes by making in this way.Yet, surpass the wrong irrecoverable of 10 bytes, thereby whole stream is dropped.
The order of 23 pairs of data flow of interleaver interweaves, and disperses the data of transmission whereby on time shaft.By doing like this, the data of transmission become and are not afraid of (insensitive) interference.By disperseing the data of transmission, when appearing at certain location, noise kept signal at other frequency band.Receiver reverses above-mentioned processing, reverts to decentralized signal with primary signal just the same whereby.
Different with RS encoder 21, trellis encoder 25 has a dissimilar FEC structure.And different with the RS encoder 21 that constitutes whole M PEG-II stream, trellis encoder 25 considers that the influence of time encodes.This b referred to as convolution code.Trellis encoder 25 is divided into 42 to the byte of 8 bits and compares top grade.Described 2 bit words quilts and previous word compare, and generate the binary code of one 3 bit, and purpose is to describe the change from previous word to current word.This 3 bit code is transferred to the 8 level code elements of described 8-VSB rather than 2 original bit words (3 bits=8 level).Therefore, 2 bit words that are input to trellis encoder 25 are converted and export as 3 bit signals.Because this feature, 8-VSB is called as 2/3 rate coding device sometimes.The advantage of grid coding is that signal can be followed the tracks of with chronomere, thereby has removed error message.
Behind the grid coding of trellis encoder 25, multiplexer 30 inserts the synchronous and frame synchronization of section in transmission signals.Pilot plug-in unit 40 is inserted into the ATSC pilot tone and has been inserted into section synchronously and the transmission signals of frame synchronization.Here, after just finishing modulation, apply a 1.25v that slight DC deviation is arranged to the 8-VSB baseband signal at once.When this takes place, at slight residual carrier of zero frequency point appearance of modulation spectrum.The residual carrier of this generation is called as " ATSC pilot tone ".
Modulating unit 50 is by using the signal modulation of 8-VSB modulation to receiving from pilot plug-in unit 40.The signal of radio frequency converter 60 conversion modulation, and export the signal of conversion by antenna.
The ATSC data segment is made of 187 bytes and 20 bytes of original MPEG-II data flow.Behind grid coding, 207 bytes of section are become the individual 8 level code element stream in 828 (207 * 4).
Segment sync signal is the pulse of 41 bytes, and described pulse is repeatedly added to the beginning of data segment and is used to replace the sync byte of original MPEG-II transport stream.Receiver can be distinguished the segment sync signal of repeat pattern from the data of completely random, even and can also and disturb when being in the level that does not allow the data self-recovery accurately recovered clock at noise.Figure 2 illustrates the section that segment sync signal (that is, section synchronously) is assigned to its transmission signals.As shown, the section of transmission signals comprises the segment sync signal of 4 code elements, the transmission mode that is respectively 3 pseudo noises (PN) sequence of 63 code elements, 24 code elements, 96 reservation code elements and 12 pre-sign indicating number code elements.The PN sequence is the synchronizing information sequence that is used for the synchronous and channel estimating of receiver.The PN sequence is produced by PN sequence generation unit (not shown), and is inserted in the transmission signals by multiplexer 30.
Fig. 3 is the view that the frame structure of ATSC data is shown.With reference to Fig. 3, the field of ATSC data comprises 313 continuous data segments, and ATSC field sync (being field sync) becomes the field data section.The ATSC Frame is made of 2 ATSC data fields.
Repeat the ATSC data field with time interval 24.2ms, the 16.7ms perpendicular separation of this and NTSC is similar.Section has well-known data symbols pattern synchronously, and is used in the receiver to remove ghost image.More particularly, remove ghost image and be by relatively, and use the error vector that draws to adjust ghost image and remove the characteristic of equalizer and realize the signal that comprises mistake and field sync.
Usually, the system information signal of the transmission mode of indication mechanism is by using spread-spectrum and be inserted into PN sequence back or among the field sync unit.Yet owing to the field sync signal and without the FEC unit, many warps that show in transmission process or burst noise can cause the distortion of signal.The distortion of this system information causes the reception problem at the digital broadcast signal receiving terminal subsequently.
Disclose a kind of VSB receiving system in the 09/962nd, No. 263 U.S. Patent application (publication number is US2002041608), this receiving system comprises: tuner, tuning RF signal from the vsb transmitter transmission; The VSB demodulator carries out demodulation to the signal from tuner output; Demultiplexer is decomposed into ATSC data and additional data with the signal multichannel of demodulation; Decoder is to the ATSC data decode; Separate randomizer, the data of decoding are separated randomization.
Summary of the invention
Therefore, the purpose of this invention is to provide a kind of in single carrier type digit broadcasting system by using Walsh the sign indicating number digital broadcasting transmission system and the transmission method thereof of system information signal reliably.
In order to realize top target, provide a kind of single carrier transmitting system.This single carrier transmitting system comprises: the scrambler unit is used for TS (transport stream) scrambler to transmitting; The FEC unit is used for carrying out forward error correction from the TS behind the scrambler of scrambler unit to form the TS of coding; PN sequence generation unit is used to produce the PN sequence; Walsh sign indicating number generation unit is used to produce the Walsh sign indicating number corresponding to identifying information; The logic coupling unit is used for the logic coupling by the Walsh sign indicating number of Walsh sign indicating number generation unit generation and the PN sequence that is produced by PN sequence generation unit; Multiplexer (MUX), be used for inserting by the signal and the section sync symbols of the coupling of logic coupling unit multiplexed to carry out by the TS behind coding: pilot plug-in unit is used for pilot tone is inserted described multiplexed TS; Modulating unit is used for having inserted the TS modulation of pilot tone; And radio frequency converter, be used for carry out the radio frequency conversion from the TS after the modulation of described modulating unit.
According to another aspect of the present invention, provide a kind of single carrier transmission method.Described single carrier transmission method comprises following step: to TS (transport stream) scrambler that will transmit; TS behind the scrambler is carried out forward error correction to form the TS of coding; Produce the PN sequence; Generation is corresponding to the Walsh sign indicating number of an identifying information; To Walsh sign indicating number that produces the step generation at the Walsh sign indicating number and the PN sequence actuating logic coupling that produces the step generation in the PN sequence; Multiplexed by the signal and the section sync symbols that are inserted in the coupling of logic coupling step among the TS behind coding to carry out; Pilot tone is inserted described multiplexed TS; To having inserted the TS modulation of pilot tone; With to carry out the radio frequency conversion from the TS after the modulation of described modulating unit.
Description of drawings
Above-mentioned target of the present invention and feature are by will be more clear to the explanation of embodiments of the invention with reference to accompanying drawing, wherein:
Fig. 1 is the block diagram that schematically shows according to the digit broadcasting system of ATSC standard;
Fig. 2 is the view that is illustrated in the section of the transmission signals in the system of Fig. 1;
Fig. 3 is the view that the frame structure of ATSC data is shown;
Fig. 4 is the view that schematically shows according to digital broadcasting transmission system of the present invention;
Fig. 5 is the flow chart that the digital broadcast transmission method of the system among Fig. 4 is shown:
Fig. 6 is the view that illustrates according to the section of transmission signals of the present invention;
Fig. 7 is the view of frame structure that the transmission signals of the digital broadcasting transmission system shown in Fig. 5 is shown.
Below, be described with reference to the accompanying drawings the preferred embodiments of the present invention.
Fig. 4 is the view that schematically shows according to the digit broadcasting system of an example of the present invention, and Fig. 5 is the flow chart that the digital broadcast transmission method of the system among Fig. 4 is shown.With reference to Fig. 4, digit broadcasting system according to the present invention comprises scrambler 100, forward error correction (FEC) unit 110, pseudo noise (PN) sequence generation unit 120, Walsh sign indicating number generation unit 130, logic coupling unit 140, multiplexer (MUX) 150, pilot plug-in unit 160, modulating unit 170 and radio frequency (RF) transducer 180.Further, FEC unit 110 comprises Read-Solomon (RS) encoder 111, interleaver 113 and trellis encoder 115.
The scrambler 100 that is called as the data random device is in order to prevent during synchronous data transmission because the problem that the synchronizing signal that repetition numeral such as 00000000b or 11111111b cause is lost is carried out randomization operation to data signals transmitted.The predetermined pattern of scrambler 10 usefulness changes the byte of each data-signal, and this processing is reversed to recover accurate original value at receiving terminal.
The error code of relevant input traffic is corrected in FEC unit 110.Because the operation of RS encoder 111, interleaver 113 and trellis encoder 115 is carried out according to the ATSC standard, will omit further instruction here.
PN sequence generation unit 120 produces the PN sequence, that is, it produces and is used for synchronizing information synchronous between transmission ends and receiving terminal, and gives multiplexer 150 the PN sequence transmission that produces subsequently.The PN sequence that is produced by PN sequence generation unit can be realized as the code element of different numbers, such as 255 code elements, 511 code elements, 1023 code elements, 2047 code elements and 8191 code elements.And " transmission ends " in this specification refers to and is equipped with digital broadcasting transmission system to be used for the receiving terminal of broadcasting according to single carrier mode transmission of digital, and " receiving terminal " refers to the receiving terminal that receives the digital broadcasting of transmission according to the single carrier mode.
Walsh sign indicating number generation unit 130 produces the extraneous information of relevant transmission ends, that is, it produces the Walsh sign indicating number.Described " extraneous information " refers to by what transmission ends provided and is used for the receiving terminal identifying information of decoding to received signal fast and easily.Described identifying information can comprise mapping method, code check, at least a about in the frame structure information of the TS of transmission and the data dispersed information.Further, the Walsh sign indicating number is formed by onesize bit stream group, and bit stream is by 2
NForm (N=natural number).
The PN sequence that 140 pairs of logic coupling units are produced by PN sequence generation unit 120 and carry out the logic coupling by the Walsh sign indicating number that Walsh sign indicating number generation unit 130 produces.Logic coupling unit 140 is a NOR gate circuit that is used for XOR coupling PN sequence and Walsh sign indicating number preferably.
Behind the grid coding that trellis encoder 115 is carried out, multiplexer 150 inserts the synchronous and frame synchronization of section in transmission signals.Further, multiplexer 150 inserts PN sequence and the Walsh sign indicating number by 140 couplings of logic coupling unit in transmission signals.Pilot plug-in unit 160 inserts pilot tone synchronously and in the transmission signals of frame synchronization having inserted section.As mentioned above, pilot tone refers to the residual carrier in the zero frequency point generation of modulation spectrum.
170 pairs of signals that receive from pilot plug-in unit 160 of modulating unit are modulated.
Digital modulation is with a processing that converts digital signal in the phase place of carrier wave, amplitude and the frequency.Therein, phase shift keying (PSK) is the processing that changes phase place according to digital value.The most basic PSK is a binary phase shift keying, has 180 ° phase intervals at 1 bit signal ' 0 ' and ' 1 ' intercarrier.Quadrature Phase Shift Keying (QPSK) is the processing that has 90 ° phase intervals corresponding to 1 code element with 42 bits.The value that obtains multiplying each other by cosine wave and bpsk signal and by sinusoidal wave and bpsk signal multiply each other acquisition the value addition and send this value.8-PSK sends the single code element with 8 level signals, and described 8 level signals have the phase intervals of 3 bits and 45 ° respectively.Because the 8-PSK transmission is three times in the information of BPSK under same bandwidth, 8-PSK has much higher frequency efficiency.Yet because at the narrow interval of each phasetophase, it is subjected to The noise easily, therefore very high power is kept same transmitted error rate.
Amplitude-shift keying (ASK) is the processing that changes the amplitude of carrier wave.ASK almost and Modulation and Amplitude Modulation (AM) similar, except modulation signal is not an order, but according to the amplitude level of predetermined number.For example, handle through the ASK to 3 bit informations, the ripple of modulation has 8 level, and by after the ASK processing to 4 bit informations, the ripple of modulation has 16 level.Modulated ripple signal is a double-sideband signal.
Amplitude-phase keying is a mode of all transmitting information at the carrier wave of carrier wave and amplitude.Quadrature amplitude modulation changes the orthogonality relation of carrier wave, merges carrier wave and transmits these carrier waves.For example, described 16-QAM can be in the information of 4 times of same bandwidth for transmission BPSK.Yet, because each yard respectively at narrow interval, therefore needs high power to keep same transmitted error rate.
The frequency spectrum of ASK signal is a double-sideband signal, and therefore, not talkative this channel has been utilized satisfactorily.These signal bands are restricted to vestigial sideband will produce the VSB signal.For example, the digital information of 3 bits is represented with 8 level.Produce the 8-VSB signal by the frequency band limits operation that ASK handles and VSB filters then.Conclusion is: except it can have 8 signals, 8-VSB signal and simulation VSB were very similar.
Signal after 180 pairs of modulation of radio frequency converter is carried out the radio frequency conversion, and by the signal after these modulation of antenna transmission.
Fig. 5 is the flow chart that the digital broadcast transmission method of the system among Fig. 4 is shown.
With reference to Fig. 5, at step S510, the 100 couples of TS that will transmit in scrambler unit (transport stream) scrambler.
At step S520, the 110 couples of TS that encode with formation from the execution of the TS behind the scrambler of scrambler unit 100 forward error correction in FEC unit.
Simultaneously, at step S530, PN sequence generation unit 120 produces the PN sequence, and at step S540, the Walsh sign indicating number that Walsh sign indicating number generation unit 130 produces corresponding to identifying information.
Subsequently at step S550, the PN sequence that 140 pairs of logic coupling units are produced by PN sequence generation unit 120 and carry out the logic coupling by the Walsh sign indicating number that Walsh sign indicating number generation unit 130 produces.When logic coupling unit 140 adopts a NOR gate circuit, Walsh sign indicating number and PN sequence are carried out the XOR coupling operation.
Multiplexer (MUX) 150 is carried out multiplexed by inserting in the TS of coding by the signal and the segment sync signal of the coupling of logic coupling unit at step S560.
Subsequently, at step S570, pilot plug-in unit is inserting a pilot tone from the multiplexed TS of MUX 150 outputs.
Subsequently at step S580, the TS that 170 pairs of modulating units insert pilot tone receives and modulation, and at step S590,180 pairs of radio frequency converters change from the TS after the modulation of modulating unit 170 and by antenna transmission they.
Fig. 6 is the view that illustrates when using the VSB/OQAM modulating mode according to transmission signals section of the present invention, and Fig. 7 is the view that the frame structure of digital broadcast transmission signal shown in Figure 5 is shown.With reference to Fig. 6 and 7, the transmission signals section comprises the system information signal of segment sync signal, two PN sequences (each is respectively 511 code elements and 253 code elements) and 32 code elements of 8 code elements.Further, field of the present invention is made of the suitable data segment of 13 code elements or 26 code elements or 52 code elements.Described field becomes the field data section.
As shown, according to the section of of the present invention section, field and frame structure and ATSC standard, field and frame structure do not have much differences.Further, because the field sync signal of described invention is without the FEC unit, the present invention is very useful.
As mentioned above, synchronizing signal does not need the unit through FEC, can use the Walsh sign indicating number to insert signal according to extraneous information.As a result, the reliability of transmission signals has strengthened.
Though described the preferred embodiments of the present invention, those skilled in the art is to be understood that the present invention is not limited to described preferred embodiment, limits within the spirit and scope of the present invention as claim and can carry out various variations and change.