KR20040032283A - Single carrier transmission system capable of acclimating dynamic environment and a method therefore - Google Patents

Abstract

PURPOSE: A single carrier transmitting system adaptable to a dynamic environment change and a method thereof are provided to easily keep up with frequent changes of a channel in a dynamic environment. CONSTITUTION: A scrambler(100) randomizes transmitting data signals. An FEC(Forward Error Correction) unit(110) corrects a bit error of an inputted data stream. A domain dividing unit(120) searches the data stream corrected by the FEC unit with counting the number of symbols of the corrected data stream. The domain dividing unit divides the data stream into a plurality of domains based on the counted value. A PN(Pseudo Noise sequence) information generator generates PN information which is synchronous information for synchronization between a transmitting side and a receiving side. A multiplexer(130) inserts the PN information between the divided data streams.

Description

Single carrier transmission system capable of acclimating dynamic environment and a method therefore}

The present invention relates to a single carrier transmission system and a transmission method thereof, and more particularly, to a single carrier transmission system and a transmission method that can adapt to dynamic environment changes.

As communication, computers, and broadcasting converge to become multimedia, countries around the world are digitizing existing analog broadcasting. In particular, advanced countries such as the United States, Europe, and Japan have already performed some digital broadcasting through satellites. In addition, a standard method for digital broadcasting has been prepared, and this standard method is configured slightly differently in Naramama.

The Federal Communications Commission (FCC) of the United States approved the Digital Television Standard of the Advanced Television Systems Committee (ATSC) as the standard for next generation television broadcasting on December 24, 1996. Under this decision, terrestrial broadcasters must comply with the specifications for video and audio compression, packet data transmission structure, modulation, and transmission system specified in the ATSC standard. The decision was made autonomously.

According to the ATSC standard, video compression adopts the Moving Picture Experts Group (MPEG) -2 video (ISO / IEC IS 13818-2) standard. All digital broadcasts around the world have adopted this standard. The audio compression scheme adopts the Digital Audio Compression (AC-3) standard proposed by Dolby. The multiplexing method adopts the MPEG-2 system (ISO / IEC IS 13818-1) standard method. This method is used in Europe as well as video compression. The modulation and transmission method adopts 8-VSB (Vestigial Side Band) method. The VSB method is proposed for digital TV broadcasting, and the data rate of 19.39 Mbps can be obtained by using the 6MHz band, and thus the bandwidth efficiency is high and the structure is simple. In addition, it is designed to minimize interference with the existing National Television Standards Committee (NTSC) broadcasting channel and uses a pilot signal, a segment sync signal, and a field sync signal to operate stably even in a noisy situation. In addition, Reed-Solomon (RS) codes and Trellis codes are used to prevent errors.

ATSC digital TV standard uses single-carrier amplitude modulation residual sideband method (VSB) to transmit high-quality video, audio and auxiliary data with 6MHz bandwidth.Two broadcast modes, simultaneous terrestrial broadcast mode and high data rate cable broadcast mode. It is supposed to support. The main feature of this method is that it uses 8-VSB modulation to modify the digital signal by changing the existing analog VSB method.

1 is a block diagram schematically illustrating a digital broadcasting transmission system using an ATSC standard method. Referring to the drawings, the digital broadcasting system includes a scrambler 10, a forward error correction (FEC) unit 20, a mux 30, a pilot inserter 40, a modulator 50, and an RF converter. 60 is provided. In addition, the FEC unit 20 includes an RS encoder (Reed-Solomon encoder) 21, an interleaver 23, and a trellisencoder 25.

The scrambler 10 is also called a data randomizer, and randomizes the transmitted data signal in order to prevent a problem of losing the synchronization signal by repeating the same number such as 00000000b or 11111111b in the synchronous data transmission. The scrambler 10 changes the value of each byte of the data signal according to a predetermined pattern, and this process is reversed at the receiver to restore the correct value.

The RS encoder 21 is an FEC structure added to the input data stream. FEC refers to a technique for correcting bit errors that occur during transmission. Atmospheric noise, multipath propagation, signal fading, and nonlinearity of the transmitter all contribute to bit error, and the RS encoder 21 adds 20 bytes after 187 bytes in the case of an MPEG-II transport stream. The 20 additional bytes are called Reed Solomon Parity Bytes. The receiver compares the received 187 bytes with 20 parity bytes to determine accuracy. If an error is detected by the accuracy determination, the receiver locates the error and corrects the distorted byte to recover the original signal. In this way up to 10 bytes of error per stream can be recovered. Any further error is not recoverable, and if not recoverable, the entire stream is discarded.

The interleaver 23 disperses the data on the time axis so as to disturb the order of the data streams so that the transmission signal is less sensitive to interference. Even if noise occurs in any part of the signal band due to the dispersion of the transmission signal, signals in other bands are preserved. The receiver reverses this process and restores the distributed transmission back to the correct value.

The trellis encoder 25 forms an FEC structure that is different from the RS encoder 21. Unlike the RS encoder 21 which handles the entire MPEG-II stream, the trellis encoder 25 encodes in consideration of the influence of time, and this process is also called a convolutional code. Trellis encoder 25 divides an 8-bit byte into four 2-bit words. Here, the 2-bit word is compared with the previous word, and a 3-bit binary code is generated for the purpose of describing the change from the previous word to the current word. This 3-bit code replaces the original 2-bit word and is sent as an 8-level symbol of 8-VSB (3 bits = 8 levels). Thus, the 2-bit word input to the trellis encoder 25 is converted into a 3-bit signal and output. For this reason, an 8-VSB system is sometimes called a 2/3 rate coder. The advantage of trellis coding is that error information can be removed by tracking the passage of the signal over time.

After trellis coding by the trellis encoder 25, the mux 30 inserts a segment sync and a frame sync into the transmission signal. The pilot inserter 40 inserts an ATSC pilot (PILOT: Programmed Inquiry Learning Or Teaching) into the transmission signal into which the segment sync and the frame sync are inserted. Here, a slight DC shift (1.25V) is applied to the 8-VSB baseband signal just before modulation, in which case some residual carrier appears at the zero frequency point of the modulated spectrum. This generated residual carrier is called an ATSC pilot.

The modulator 50 modulates the transmission signal received from the pilot inserter 40 using 8-VSB modulation. The RF converter 60 converts the modulated transmission signal into a radio frequency (RF) and transmits the converted transmission signal through an antenna.

The ATSC data segment consists of 187 bytes + 20 bytes of the original MPEG-II data stream. After trellis coding, the segment of 207 bytes is converted into 828 (= 207 x 4), 8-level symbol streams.

The segment sync signal is a repeating four symbol (1 byte) pulse added to the head of the data segment and replaces the sync byte of the original MPEG-II transport stream. The receiver can easily identify repeating segment sync signals from completely random data, and can accurately recover the clock even at noise and interference levels that make data recovery impossible. Segments of the transmission signal to which the segment sync signal is assigned are shown in FIG. 2. That is, the segment of the transmission signal is a segment synchronization signal consisting of four symbols, three pseudo noise sequence (PN) information consisting of 63 symbols, a transmission mode consisting of 24 symbols, 92 reserved symbols, and 12 It consists of three precode symbols. Here, the pseudo noise sequence is a synchronization information sequence for predicting synchronization and channel of a transmission signal in a receiver receiving a signal. The pseudo noise string is generated by the PN information generation unit (not shown) and inserted into the transmission signal by the mux 30.

3 is a diagram illustrating a frame structure of a transmission signal according to the ATSC standard. Referring to the figure, a field of ATSC data consists of 313 consecutive data segments, and ATSC field sync becomes a field data segment. An ATSC data frame consists of two ATSC data fields.

The repetition period of the ATSC data field is 24.2 msec and is similar to the NTSC vertical interval (NTSC period = 16.7 msec). Field sync has a well-known data symbol pattern and is used for ghost cancellation at the receiver. This process is accomplished by comparing the received signal with errors with field synchronization and adjusts the characteristics of the ghost cancellation equalizer using the resulting error vector.

Recently, the Academy of Broadcasting Science (ABS) in China has proposed the Chinese Digital Television Broadcasting-Terrestrial (CDTB-T) standard for independent digital broadcasting in China. The CDTB-T standard, like the ATSC standard in the United States, is a single carrier and uses a QAM modulation method and a QPSK modulation method. That is, the CDTB-T standard uses different modulation schemes for the mobile mode and the fix mode, uses the QPSK modulation method for the mobile mode, and uses the 16QAM modulation method for the fix mode. In addition, 64QAM or 256QAM modulation is used for high capacity data in the fix mode.

4 is a diagram schematically illustrating a frame structure of a transmission signal according to the CDTB-T standard. Referring to the figure, the frame of the transmission signal according to the CDTB-T standard is followed by the frame sync, payload 1, training symbol, payload 2, and tail symbol (tail symbol). Here, the frame sync has a structure in which three pseudo-noise string information consisting of 511 symbols are continuously connected, followed by control bits and remaining bits. Three consecutive pseudonoise sequences are called training symbols. Herein, the control bits refer to bits used for control purposes, such as parity, start and end bits, among all bits transmitted through a communication line for data transmission in data communication.

The spare bit is an area for time axis conversion, bit rate compression, error correction, and the like. The payload is an area for information on the upper layer. The tail symbol region is a region for additional information for transmission and is called a tail symbol region because it is provided in the last node of the frame.

The frame structure of the transmission signal according to the CDTB-T standard is a structure in which three pseudo-noise string information is inserted into the frame sink and a payload 1 is inserted, and a training symbol is inserted twice in one frame. However, such a frame structure has a problem that it is difficult to properly follow the channel change in a dynamic environment that changes faster than the period between the first training symbol and the second training symbol.

The present invention has been made to solve the above problems, and an object thereof is to provide a single carrier transmission system that is easy to adapt to dynamic environmental changes.

1 is a block diagram schematically illustrating a digital broadcasting transmission system using an ATSC standard method;

2 is a diagram illustrating a segment of a transmission signal according to FIG. 1;

3 is a view illustrating a frame structure of a transmission signal according to FIG. 1;

4 is a time series diagram illustrating a frame structure of a transmission signal according to the CDTB-T standard;

5 is a block diagram schematically showing a digital broadcasting transmission system according to the present invention;

6 is a flowchart illustrating a digital broadcast transmission method according to FIG. 5; and

FIG. 7 is a diagram illustrating a frame structure of a transmission signal shown in FIG. 5.

Explanation of symbols on the main parts of the drawings

10, 100: scrambler 20, 110: FEC part

30, 130: mux 120: area classification

121: counter

A single carrier transmission system according to the present invention for achieving the above object is a single carrier transmission system for inserting and transmitting pseudo-noise string information, which is synchronization information for synchronization between a transmitting side and a receiving side, into a transmission signal of a single carrier type. An error correction unit for correcting bit errors with respect to an input data stream, an area division unit for dividing the data stream corrected by the error correction unit into a plurality of areas, and the data separated by the area division unit; And a mux for inserting and multiplexing the pseudo-noise string information between streams. The area separator includes a counter for counting the number of symbols of the corrected data stream, and the area separator separates the data stream when the count value of the counter reaches a predetermined value. The area divider divides the data stream into four areas. The mux inserts a symbol of the pseudo-noise string information corresponding to the number set between the data streams separated by the area separator. In this case, the mux inserts one pseudo-noise sequence information having 255 symbols and one pseudo-noise sequence information having 256 symbols. Alternatively, the mux inserts two pseudo noise string information having 255 symbols. This single carrier transmission system is applied to the CDTB-T standard of Chinese single carrier.

On the other hand, in the single carrier transmission system according to the present invention, in the single carrier transmission method for inserting and transmitting pseudo-noise string information, which is synchronization information for synchronization between a transmitter and a receiver, in a single carrier transmission signal, input data Correcting bit errors for the stream, dividing the data stream corrected by the error correction into a predetermined region, and inserting the pseudo-noise string information between the data streams separated by the region separator. It provides a single carrier transmission method comprising the step of inserting and multiplexing.

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

5 is a block diagram schematically showing a digital broadcasting transmission system according to the present invention. Referring to the drawings, the digital broadcasting transmission system, the scrambler 100, the FEC unit 110, the region division unit 120, the mux 130, the pilot insertion unit 140, the modulator 150, and the RF converter And 160. In addition, the FEC unit 110 includes an RS encoder (Reed-Solomon encoder) 111, an interleaver (113), and a trellis encoder (115). The area separator 120 includes a counter 121.

6 is a flowchart illustrating a digital broadcast transmission method according to FIG. 5. With reference to the drawings will be described in more detail the operation of the single carrier transmission system according to the present invention.

The scrambler 100 randomizes the transmitted data signal in order to prevent a problem in which the same number is repeated, such as 00000000b or 11111111b, in the synchronous data transmission, thereby losing the synchronization signal. The scrambler 100 changes the value of each byte of the data signal according to a predetermined pattern, and this process is reversed at the receiver to restore the correct value.

The FEC unit 110 corrects bit errors for the input data stream (S601). Here, the RS encoder (Reed-Solomon encoder) 111, the interleaver (113), and the trellis encoder (115) provided in the FEC unit 110 is provided in the digital broadcasting transmission system by the ATSC standard method. Since the same operation as the same element is performed, the description thereof is omitted.

The area separator 120 retrieves the data stream corrected by the FEC unit 110. At this time, the counter 121 of the area separator 120 counts the number of symbols of the corrected data stream (S603).

The area divider 120 divides the data stream into a plurality of areas based on the counting value of the counter 121 (S605). Here, the area separator 120 stores preset values for each area of the divided data stream. The area separator 120 compares the counted value by the counter 121 with the stored set value, and when the counted value reaches the set value, distinguishes the data stream at that time. In the case of the CDTB-T standard, the region separator 120 is preferably implemented to divide the data stream into four regions. Too often pseudo-noise sequence information can hinder the flow of transmitted data, so it considers both the dynamic environment change and the data flow due to channel change. Of course, the number of data streams to be distinguished may be set differently.

The PN information generator (not shown) generates pseudo noise string information, which is synchronization information for synchronization between the transmitting side and the receiving side, and transmits the generated pseudo noise string information to the mux 130. Here, the transmitting side refers to a transmitting side having a digital broadcasting transmission system for transmitting digital broadcasting in a single carrier system, and the receiving side refers to a receiving side for receiving digital broadcasting transmitted in a single carrier system.

The pseudo noise information string generated by the PN information generator may be embodied in various numbers of symbols, such as 255, 256, 511, 1023, 2047, 8191, and the like.

FIG. 7 is a diagram illustrating a frame structure of a transmission signal shown in FIG. 5. The figure shows the frame structure corresponding to the frame structure of the CDTB-T. In the CDTB-T standard, the mux 130 may be implemented to insert one pseudo-noise sequence information having 255 symbols and one pseudo-noise sequence information having 256 symbols between the separated data streams. -T The standard considers the insertion of pseudo-noise string information in 511 symbol units. In addition, the MUX 130 may be implemented to insert two pseudo-noise string information having 255 symbols between the divided data streams. In this case, the size of the payload in the frame of the transmission signal is increased by three symbols than the size of the payload of the frame according to the CDTB-T standard.

Here, it is preferable that the area separating unit 120 classifies an area of the data stream such that the pseudo noise string information having 511 symbols is inserted at least three times with respect to one data stream to which the pseudo-noise string information is input.

After trellis coding by the trellis encoder 115, the mux 130 inserts a segment sync at the head of the transmission signal. In addition, the MUX 130 inserts pseudo noise string information generated by the PN information generator between the data streams separated by the area separator 120 (S607). When the MUX 130 inserts a frame sink into the data stream, the pseudo noise string information generated by the PN information generator, the control bits, and the spare bits are combined and inserted at the head of the transmission signal. Here, two terms, a transmission signal and a data stream, are used to distinguish the overall concept of the data stream and the data stream divided into a plurality of regions.

The pilot inserter 140 inserts a pilot into a transmission signal in which segment sync, frame sync, and pseudo noise string information are inserted. Here, the pilot refers to the residual carrier appearing at the zero frequency point of the modulated spectrum.

The modulator 150 modulates the transmission signal received from the pilot inserter 140 using a modulation scheme. The RF converter 160 converts the modulated transmission signal into a radio frequency (RF) and transmits the converted transmission signal through an antenna.

As a result, the single carrier transmission system can be easily adapted to a situation in which the dynamic environment is changed due to the frequent change of the channel.

The single carrier transmission system according to the present invention can be easily adapted to the situation that the channel is changed frequently so that the dynamic environment changes.

Although the preferred embodiments of the present invention have been illustrated and described above, the present invention is not limited to the specific embodiments described above, and the present invention is not limited to the specific embodiments of the present invention without departing from the spirit of the present invention as claimed in the claims. Anyone skilled in the art can make various modifications, as well as such modifications are within the scope of the claims.

Claims (16)

In a single carrier transmission system for inserting and transmitting pseudo-noise string information, which is synchronization information for synchronization between a transmitter and a receiver, into a transmission signal of a single carrier method, Error correction for correcting bit errors for the input data stream; An area division unit for dividing the data stream corrected by the error correction into a plurality of areas; And And a mux for inserting and multiplexing the pseudo-noise string information between the data streams separated by the region separator. The method of claim 1, wherein the area separator, A counter that counts the number of symbols in the corrected data stream, And the area separator divides the data stream when the counting value of the counter reaches a predetermined value. The method of claim 2, The area separator divides the data stream into four areas. The method of claim 3, And the mux inserts the symbols of the pseudo-noise string information corresponding to the set number between the data streams separated by the area separator. The method of claim 3, And the mux inserts one pseudo noise sequence information having 255 symbols and one pseudo noise sequence information having 256 symbols. The method of claim 3, The mux inserts two pseudo-noise sequence information having 255 symbols. The method according to any one of claims 3 to 6, Wherein the error correction unit, the region division unit, and the mux are applicable to the CDTB-T standard of the Chinese single carrier system. The method of claim 7, wherein And the area separator divides an area of the data stream such that the pseudo-noise string information having 511 symbols is inserted at least three times with respect to the input data stream. In a single carrier transmission method for inserting and transmitting pseudo-noise string information, which is synchronization information for synchronization between a transmitter and a receiver, into a transmission signal of a single carrier method, Correcting bit errors for the input data stream; Dividing the data stream corrected by the error correction step into a plurality of areas; And And inserting and multiplexing the pseudo-noise string information between the data streams separated by the region classification step. The method of claim 9, Counting the number of symbols in the corrected data stream, The area classification step is characterized in that the single carrier transmission method for distinguishing the data stream when the counting value by the counting step reaches a predetermined value. The method of claim 10, The region classification step is characterized by dividing the data stream into four regions. The method of claim 11, And the multiplexing step inserts the symbols of the pseudo-noise sequence information corresponding to the number set between the data streams separated by the area classification step. The method of claim 11, And the multiplexing step inserts one pseudo noise sequence information having 255 symbols and one pseudo noise sequence information having 256 symbols. The method of claim 11, The multiplexing step includes inserting two pseudo noise string information having 255 symbols. The method according to any one of claims 11 to 14, Wherein the error correction step, the region division step, and the multiplexing step are applicable to the CDTB-T standard of the Chinese single carrier method. The method of claim 15, And the region classifying step divides the region of the data stream such that the pseudo-noise string information having 511 symbols is inserted at least three times with respect to the input data stream.