TWI384881B - Frame header recognition method and system - Google Patents

Description

Frame header identification method and system

The present invention relates to a frame header identification method and system, and more particularly to a method and system for distinguishing a transmission mode of a frame header used in a digital television terrestrial broadcast (DTMB) transmission system.

With the rapid advancement of multimedia, users are increasingly demanding multimedia services. Therefore, the People's Republic of China has developed the Digital Terrestrial Multimedia Broadcast (DTMB) transmission system standard as the transmission standard for digital television signals used in China. Due to the DTMB transmission system standard formulated by the People's Republic of China, in order to provide single-carrier and multi-carrier transmission applications, three different length frame headers have been developed, using lengths of 420, 595, and 945, respectively. A pseudo noise sequence (hereinafter referred to as a PN sequence). In the frame header mode using the length 420 and the length 945 symbol, different subframes can choose to use the same or different PN sequences, so the digital television signal transmitted by the transmitting end has multiple PN sequence possible transmission modes. s Choice. The receiving end must be able to correctly recognize the transmission mode of the frame header transmitted by the transmitting end, in order to obtain the correct data interval to decode and generate the required digital television service.

In general, in order to obtain the transmission mode used by the transmitted PN sequence at the receiving end, the corresponding local PN sequence is generated first at the receiving end, and then The window sliding window is used to perform the correlation of the correlation with the received signal, and the transmission mode of the transmitted PN sequence is obtained by finding the corresponding maximum accumulated value. However, this conventional method is greatly affected by the factor of frequency drift. When frequency drift occurs, not only the calculation time and complexity required for judging the transmission mode of the transmitted PN sequence are greatly increased, but also the delay time of the entire system becomes Quite long.

In view of this, the present invention provides a method that can be quickly affected by frequency drift and can quickly obtain a transmission mode of a PN sequence to reduce the delay time of the entire system.

The invention provides a frame header identification method suitable for a digital television terrestrial multimedia broadcasting (DTMB) system. The frame header identification method includes the following steps. First, a packet is received, wherein the packet includes a plurality of frames, each frame has a header and a data interval, and the header corresponds to one of the complex transmission modes, wherein the transmission modes respectively correspond to a specific sequence. Then, the header of one of the frames is correlated with the header of a corresponding specific frame to generate a complex operation result corresponding to the transmission mode. Then, based on the result of the equal operation, the transmission mode of the header is recognized.

The invention further provides a frame header recognition system suitable for a digital television terrestrial multimedia broadcasting (DTMB) system. The frame header recognition system includes a storage unit, a correlation value calculation unit, an operation result generation unit, and a frame header identification unit. The storage unit is configured to receive and store an input signal from a DTMB packet, wherein the packet includes a plurality of frames, each message The box has a header and a data interval, the header corresponds to one of the complex transmission modes and the transmission mode corresponds to a specific sequence, respectively. The correlation value calculation unit performs a correlation operation on the header of one of the frames and the header of a corresponding specific frame to obtain a correlation value. The operation result generation unit receives the correlation value generated by the correlation value calculation unit, and generates a complex operation result corresponding to the transmission mode. The frame header identification unit recognizes the transmission mode used by the header according to the operation result and a predetermined rule.

The invention further provides a frame header identification method suitable for a digital television terrestrial multimedia broadcasting (DTMB) system, which comprises the following steps. First, a packet is received, wherein the packet includes a plurality of frames, each frame has a header and a data interval, and the headers correspond to one of a plurality of transmission modes, wherein the transmission modes respectively correspond to a specific sequence. Then, the header of one of the frames is correlated with the header of a corresponding specific frame, and one of the operations corresponding to one of the transmission modes is generated. Wherein, if the operation result of a transmission mode exceeds a predetermined value, the transmission mode of the determination header is the above transmission mode.

The above and other objects, features and advantages of the present invention will become more <RTIgt;

For example, in the DTMB transmission system standard, a plurality of transmission mode selections are provided on the transmitting end. Therefore, in the embodiment of the present invention, a frame header identification method and a system thereof are provided, and a delay correlation operation is used. Rotated or fixed PN sequence for self-phase Turn off the operation and find the self-related accumulated value. At the same time, the variable PN sequence is used to distinguish between two frame symbol times, and the difference between the PN sequences is not shifted to the left or shifted to the right (ie, a symbol), and the fixed delay is two. The time of the symbol symbol is reduced by one symbol time, or the time of adding a symbol is used to perform self-correlation accumulation of the variable PN sequence, thereby judging the transmission mode of the PN sequence. For example, the selection mode of the transmission mode of the PN sequence can be obtained by any one of the following methods: (a) if the relevant accumulated value exceeds the preset set value; (b) using the relevant accumulated value of the entire segment, The maximum value is obtained; or (c) using the relevant accumulated value of the entire segment to find the maximum standard deviation, the transmission mode of the PN sequence can be obtained, but is not limited thereto.

Figure 1 shows a schematic diagram of a DTMB packet in accordance with an embodiment of the present invention. As shown, the packet 100 includes a plurality of frames 110, each frame having a frame header 112 and a frame body 114, and each frame 110 has the same length. The header 112 has three possible lengths, namely 420, 595, and 945 symbols, and the data interval 114 is a fixed length, which is 3780 symbols. The header 112 contains a specific PN sequence. The PN sequence contained in the header can be a fixed sequence or a rotated sequence of a PN sequence. In the present embodiment, the variable sequence of the PN sequence represents a sequence having the same data as the PN sequence but differing in arrangement (for example, shifting to the left or shifting to the right). Therefore, in this embodiment, the PN sequence of the header has five possible transmission modes, the first transmission mode uses a fixed PN sequence of 420 symbols, and the second transmission mode uses a fixed length of 420 symbols. Variable PN sequence Sequence, the third transmission mode uses a fixed PN sequence of length 595 symbols, the fourth transmission mode uses a fixed PN sequence of length 945 symbols, and the fifth transmission mode uses a fixed PN sequence of length 945 symbols. Variable sequence. For further explanation, please refer to the following instructions.

It is assumed that PN 420, PN 595, and PN 945 represent PN sequences of lengths of 420, 595, and 945 symbols, respectively. The following is an example of the exemplary PN sequence content of the first transmission mode. Taking the fixed PN420 as an example, the length is 420 symbols. Suppose the first 20 symbols of the PN sequence are as follows: -1,1,-1,-1,1,1,1,1,-1,1,-1,1,1,-1,1,-1, -1, -1, -1, 1 The exemplary PN sequence of the second transmission mode (ie, the variable sequence of PN420) can be illustrated by the first 20 symbols of the following frames, where the frame index is 0-5. Represents the first 6 packets received in the packet.

-1,1,-1,-1,1,1,1,1,-1,1,-1,1,1,-1,1,-1,-1,-1,-1,1 The first twenty signals of frame 0

1,-1,-1,1,1,1,1,-1,1,-1,1,1,-1,1,-1,-1,-1,-1,1,-1 The first twenty signals of frame 1

-1,-1,1,-1,-1,1,1,1,1,-1,1,-1,1,1,-1,1,-1,-1,-1,-1 ... this is the first 20 signals of frame index 2

-1,-1,1,1,1,1,-1,1,-1,1,1,-1,1,-1,-1,-1,-1,1,-1,1... ...this is the first twenty signals of frame index 3

-1,-1,-1,1,-1,-1,1,1,1,1,-1,1,-1,1,1,-1,1,-1,-1,-1 This is the first twenty signals of frame index 4.

-1,1,1,1,1,-1,1,-1,1,1,-1,1,-1,-1,-1,-1,1,-1,1,1 ...this is the first twenty signals of frame index 5

It can be seen from the PN sequence PN 420 that the PN sequence of the frame index 2 is shifted to the right by one bit, and the PN sequence of the frame index 4 is shifted to the right by the PN sequence of the frame index 2. One bit is generated, and the PN sequence of the frame index 3 is shifted to the left by one bit to the left, and the PN sequence of the frame index 5 is generated by shifting the PN sequence of the frame index 3 one bit to the left.

Similarly, the exemplary PN sequence of the third transmission mode (i.e., fixed PN 595) has a length of 595 symbols. Assume that the first 20 symbols of the PN sequence are as follows: -1,1,1,1,1,1,1,1,1,1,-1,1,1,-1,1,1,-1,1 , 1, -1, ....

Since the PN sequence PN595 is used for single carrier transmission, in this mode, the transmitted PN sequence is a fixed sequence, that is, the PN sequences of the frame indices 0-5 are the same.

Next, the exemplary PN sequence content of the fourth transmission mode is enumerated, assuming that PN 945 represents a PN sequence of length 945, taking fixed PN945 as an example, and its length is 945 symbols. Assume that the first 20 symbols of the PN sequence are as follows: -1, -1, -1, -1, -1, 1, -1, -1, -1, 1, 1, -1, 1, -1, 1 ,1,1,-1,-1,1 Then, the frame obtained by using the transmission mode of the variable sequence of PN945 (ie, the fifth transmission mode) as its header is as follows: -1, -1, -1, -1, -1, 1, -1, - 1,-1,1,1,-1,1,-1,1,1,1,-1,-1,1... This is the first twenty signals of frame index 0

-1,-1,-1,-1,1,-1,-1,-1,1,1,-1,1,-1,1,1,1,-1,-1,1,- 1 ... this is the first 20 signals of frame index 1

1,-1,-1,-1,-1,-1,1,-1,-1,-1,1,1,-1,1,-1,1,1,1,-1,- 1... This is the first twenty signals of frame index 2

-1,-1,-1,1,-1,-1,-1,1,1,-1,1,-1,1,1,1,-1,-1,1,-1,- 1 This is the first 20 signals of frame index 3

1,1,-1,-1,-1,-1,-1,1,-1,-1,-1,1,1,-1,1,-1,1,1,1,-1 This is the first twenty signals of frame index 4.

-1,-1,1,-1,-1,-1,1,1,-1,1,-1,1,1,1,-1,-1,1,-1,-1,1 This is the first 20 signals of the frame index 5.

Similarly, it can be known from the above PN sequence PN945 that the PN sequence of the frame index 2 is shifted to the right by one bit of the PN sequence of the frame index 0, and the PN sequence of the frame index 4 is the PN sequence of the frame index 2. One bit is generated to the right; the PN sequence of the frame index 3 is shifted to the left by one bit to the left, and the PN sequence of the frame index 5 is shifted to the left by the PN sequence of the frame index 3. Bit generation.

Figure 2 is a diagram showing the PN sequence of various transmission modes in accordance with an embodiment of the present invention. As shown in FIG. 2, in the first transmission mode, since the fixed PN 420 sequence is used, the PN sequences PN0 to PN5 used by the headers of the frame index 0-5 are all the same fixed PN 420 sequence. In the second transmission mode, since the variable sequence of the PN420 sequence is used, the PN sequence PN2 of the frame index 2 is shifted to the right by one bit of the PN sequence PN0 of the frame index 0, and the PN sequence PN4 of the frame index 4 is The PN sequence PN2 of the frame index 2 is shifted to the right by one bit, and the PN sequence PN3 of the frame index 3 is shifted to the left by one bit of the PN sequence PN1 of the frame index 1, and the frame index 5 is The PN sequence PN5 is shifted to the left by one bit from the PN sequence PN3 of the frame index 3. In the third transmission mode, the PN sequences PN0 to PN5 used by the header of the frame index 0-5 are the same fixed PN595 sequence due to the use of the fixed PN595 sequence. In the fourth transmission mode, the PN sequences PN0 to PN5 used by the headers of the frame index 0-5 are the same fixed PN945 sequence due to the use of the fixed PN945 sequence. In the fifth transmission mode, since the variable sequence of the PN945 sequence is used, the PN sequence PN2 of the frame index 2 is shifted to the right by one bit of the PN sequence PN0 of the frame index 0, and the PN sequence PN4 of the frame index 4 is The PN sequence PN2 of the frame index 2 is shifted to the right by one bit, and the PN sequence PN3 of the frame index 3 is shifted to the left by one bit of the PN sequence PN1 of the frame index 1, and the PN sequence PN5 of the frame index 5 is the frame. The PN sequence PN3 of index 3 is shifted one bit to the left. It can be seen from the above that the variable PN sequence is different between the two frame symbol times (for example, frame index 3 and frame index 1 or frame index 4 and frame index 2), and the difference between the PN sequences is not The left shift is a bit to the right, where a frame symbol time represents the total time of a header plus a data portion. For example, if a PN420 sequence is used, one frame symbol time is equal to 420+3780=4200 symbol time; if a PN595 sequence is used, one frame symbol time is equal to 595+3780=4375 symbol time; If the PN945 sequence is used, then one frame symbol time is equal to 945 + 3780 = 4725 symbol time, and so on.

Referring to FIG. 3, a flowchart 300 of a frame header identification method according to an embodiment of the present invention is shown, which is applicable to a DTMB system. First, in step S310, a packet is received (for example, the packet 100 shown in FIG. 1), wherein the packet includes a plurality of frames of the same format, and each frame has a header. And a data interval, and there are multiple sampling points in the header, for example, 420 sampling points in the PN420. Note that each header corresponds to a transmission mode and the transmission mode corresponds to a specific sequence. This particular sequence is a PN sequence or a variable sequence of this PN sequence. Then, in step S320, the header of one of the received packets is correlated with the header of a corresponding specific frame, and an operation result corresponding to the transmission mode is generated. In this step, the correlation value can be obtained by correlating each sampling point of the header of the frame of the packet with a corresponding sampling point of the header of the corresponding specific frame, and then obtaining these The correlation values are accumulated to obtain an operation result. The corresponding specific frame is located before the current receiving frame, in other words, it is a frame that has been received or delayed by a predetermined length. For example, in this embodiment, the corresponding specific frame is separated from the currently received frame by two frame lengths (for example, frame 3 corresponds to frame 1 and frame 2 corresponds to frame 0), wherein The frame length is the length of the frame header and the data portion.

The correlation value corresponding to each transmission mode can be expressed as the following mathematical equation. In the following equation, it is assumed that the variable PN sequence is shifted a little to the right.

Where r() denotes the received input data, d and k denote the time index, r(d) denotes the input signal of the receiver, r(dk) denotes the output signal of the memory, and Λ( d ) denotes self-correlation The accumulated output value. The first to fifth equations respectively represent the calculation results of the correlation values corresponding to the first to fifth transmission modes. For example, Λ _pn420-fixed represents the calculation result corresponding to the first transmission mode using the fixed _{PN 420} sequence as the header, Λ _{pn420-rotated} represents the second transmission mode using the variable _{PN 420} sequence as the header. Corresponding calculation results, and so on.

It can be seen from the first to fifth formulas above that if the transmission mode of the PN sequence at the transmitting end is the first transmission mode, the calculation result of the first equation Λ _pn420-fixed will approach 1 and the second equation The calculation result Λ _{pn420-rotated} will approach 0, and the calculation result of other equations will be smaller than Λ _pn420-fixed , so it can be distinguished that the transmission mode of the PN sequence at the transmitting end is the first transmission mode. Similarly, if the transmission mode of the PN sequence of the transmitting end is the second transmission mode, the calculation result of the first formula Λ _pn420-fixed will approach 0, and the calculation result of the second formula Λ _{pn420-rotated} will approach In 1, the calculation result of the other formula is smaller than Λ _{pn420-rotated} , so the transmission mode of the PN sequence at the transmitting end can be distinguished according to the calculation result as the second transmission mode.

In addition, it can also be assumed that the variable PN sequence is shifted to the left a little, and the first to fifth forms become the following forms:

Where r() denotes the received input data, d and k denote the time index, r(d) denotes the input signal of the receiver, r(dk) denotes the output signal of the memory, and Λ( d ) denotes self-correlation The accumulated output value.

In addition, in order to facilitate calculation and shorten the time required for calculation, the first to fifth formulas can also be rewritten as follows:

0 N <420

Where r() denotes the received input data, d and k denote the time index, r(d) denotes the input signal of the receiver, r(dk) denotes the output signal of the memory, and Λ( d ) denotes self-correlation The accumulated output value.

Then, after the calculation result is obtained, in step S330, according to the operation result, the transmission mode used by the frame header is identified. The decision of the transmission mode of the PN sequence in the frame header can be selected in a variety of ways. In an embodiment, five delay-related values may be sequentially calculated for the received signal according to a predetermined sequence, for example, from the first transmission mode to the fifth transmission mode, until a certain value exceeds a set value, and the PN sequence is obtained. Transmission mode. For example, referring to FIG. 4, a flowchart 400 of a transmission mode decision method in accordance with an embodiment of the present invention is shown. It is assumed that the first transmission mode is selected first (step S410), and the first transmission mode is subjected to an accumulation calculation of the self-correlation value (such as the first equation) (step S420), and if the obtained calculation result exceeds the predetermined value, the first One transmission mode is the transmission mode currently used by the header (step S450). On the other hand, if the obtained calculation result does not exceed the predetermined value (No in step S420), it indicates that the first transmission mode is not the transmission mode used by the current header, and therefore, other transmission modes are selected (ie, the second to the second One of five) (step S440), and performing an accumulated calculation of the self-correlation value (such as the second to fifth formulas) on the selected transmission mode (for example, the second type) until the calculation result of one of them exceeds The established value is the transmission mode used by the current header. In addition, the established value can be based on The parameters or rules of thumb for the transmission environment are set appropriately so that the calculation of the correct transmission mode can exceed this established value. For example, in an embodiment, if the operation result is between a first value V1 and a second value V2, the predetermined value may be set to be approximately equal to half of the sum of the first value and the second value ( V1+V2)/2. Therefore, if the calculation result when calculating a certain transmission mode exceeds the predetermined value (that is, exceeds (V1+V2)/2), it means that the transmission mode is the transmission mode used by the current header. In another embodiment, if the result of the operation does not exceed a maximum value MAX, it may be determined according to the current environment that the predetermined value is set to be approximately equal to half of the maximum value of MAX/2 or MAX of 3/4. Therefore, if the calculation result when calculating a certain transmission mode exceeds the established value (that is, exceeds MAX/2), it means that this transmission mode is the transmission mode used by the current header.

In another embodiment, five delay-related values can be calculated for the received signal in sequence, as shown in Equations 1 to 5, and the five delay-related values are compared to find the maximum value, and the corresponding PN. The sequence is the desired transmission mode. For example, referring to FIG. 5, another flowchart 500 of a transmission mode determining method according to an embodiment of the present invention is shown. In this embodiment, the five transmission modes will be simultaneously calculated to generate five calculation results corresponding to the five transmission modes (step S510), and the comparison results are compared to find the maximum value (step S520). Therefore, the transmission mode corresponding to the calculation result having the maximum value is the requested transmission mode (step S530).

In another embodiment, five delay-related values can be calculated for the received signal and one corresponding standard deviation value can be obtained, and the difference between the five delay-related values and the standard deviation value can be compared to find the standard deviation. One of the largest differences, its corresponding PN The sequence is the desired transmission mode. In this embodiment, the five transmission modes will be simultaneously calculated to generate five calculation results corresponding to the five transmission modes and a standard deviation, and then compare the calculation results with the standard deviation to find the maximum difference from the standard deviation. The result of the calculation of the value. Therefore, the transmission mode corresponding to the calculation result having the largest difference from the standard deviation is the obtained transmission mode.

Figure 6 shows a schematic diagram of a frame header recognition system 600 in accordance with an embodiment of the present invention. The input signal r(d) is transmitted to the storage unit 610 for continuously storing the input signal r(dk) delayed by k sampling points, and then delaying the input signal r(dk) of the k sampling points with the input signal r(d) The conjugate complex number r*(d) is transferred to the correlation value calculation unit 620. The correlation value calculation unit 620 may further include a conjugate complex generation unit (not shown), receiving the input signal r(d) and the input signal r(dk) delayed by k sample points, and generating a desired conjugate. Complex r*(d) or r*(dk). The correlation value calculation unit 620 calculates a signal correlation value by using a sampling window whose sampling window length is a predetermined value N, and the calculation is performed in a mathematical expression as shown in the first to fifth equations of the equation.

The correlation value calculation unit 62 then transmits the obtained correlation result to the operation result generation unit 630. The operation result generating unit 630 may further include an accumulating unit (not shown) for accumulating the correlation results obtained by the correlation value calculating unit 620 to generate a desired operation result, and sending the operation result to the frame. Header identification unit 640. The frame header identification unit 640 determines the transmission mode of the frame header according to the calculated operation result and a predetermined rule, and thereby obtains the data of the data segment. The frame header identification unit 640 may further include a comparator (not shown) for finding a calculation result having a maximum value or a maximum difference from the standard deviation. For example, news The frame header identification unit 640 can determine whether the operation result exceeds a predetermined value or find one of the maximum value or the maximum deviation from the standard deviation according to the flow shown in FIG. 4 or FIG. 5, thereby obtaining the desired result. The transmission mode of the frame header used by the transmitting end.

The above description provides several different embodiments or different methods of applying the invention. The specific devices and methods in the examples are intended to help explain the main spirit and purpose of the invention, and the invention is not limited thereto.

Therefore, the present invention has been described in the above preferred embodiments, and is not intended to limit the invention, and it is possible to make some modifications and refinements without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims.

100‧‧‧Package

110‧‧‧ frame

112‧‧‧ Header

114‧‧‧Information section

PN0-PN5‧‧‧ pseudo noise sequence

S310-S330‧‧‧Execution steps

S410-S450‧‧‧Execution steps

S510-S530‧‧‧Execution steps

600‧‧‧ Frame Header Detection System

610‧‧‧ storage unit

620‧‧‧Related value calculation unit

630‧‧‧Operation result generation unit

640‧‧‧ Frame header identification unit

r()‧‧‧ receiving signal

Λ()‧‧‧ operation result

Figure 1 is a schematic diagram showing a DTMB packet in accordance with an embodiment of the present invention.

Figure 2 is a diagram showing the PN sequence of various transmission modes in accordance with an embodiment of the present invention.

Figure 3 is a flow chart showing a method for identifying a frame header according to an embodiment of the present invention.

Figure 4 is a flow chart showing a method of determining a transmission mode in accordance with an embodiment of the present invention.

Figure 5 is a flow chart showing another method of determining a transmission mode in accordance with an embodiment of the present invention.

Figure 6 is a schematic diagram showing a frame header detection system in accordance with an embodiment of the present invention.

S310-S330‧‧‧Execution steps

Claims (24)

A frame header identification method is applicable to a Digital Terrestrial Multimedia Broadcasting (DTMB) system, comprising the steps of: receiving a packet, wherein the packet includes a plurality of frames, each frame having a header And a data interval, the headers corresponding to one of the plurality of transmission modes and the transmission modes respectively corresponding to a specific sequence; the header of one of the frames is associated with a specific frame The header performs a correlation operation to generate a complex operation result corresponding to the transmission modes, wherein the corresponding specific frame is located before the one of the frames; and the headers are identified according to the operation results The transmission mode used. The method for identifying a frame header according to claim 1, wherein the corresponding frame is separated from the frame by two frames. The frame header identification method of claim 1, wherein each of the headers has a plurality of sampling points, and the step of generating the operation results corresponding to the transmission modes further comprises: Each of the sampling points of the header of the frame is correlated with a sampling point corresponding to one of the headers of the corresponding specific frame to obtain a complex correlation value; and the related values are accumulated , the result of the operation is generated. For example, the frame header identification method described in the first application of the patent scope, The step of identifying the transmission mode used by the headers according to the result of the operations further includes: finding one of the maximum values of the operation results; and determining that the transmission mode of the headers is The transmission mode corresponding to the result of the operation having the largest value found. The method for identifying a frame header according to claim 1, wherein the step of identifying the transmission mode used by the headers according to the operation results further comprises: obtaining one of the operation results corresponding to the operations a standard deviation; finding out that the operation result has one of the greatest differences from the standard deviation; and determining the transmission mode of the headers as the result of finding the maximum difference from the standard deviation The corresponding transmission mode. The method for identifying a frame header according to claim 1, wherein the specific sequence is a pseudo-noise sequence. The method for identifying a frame header according to claim 1, wherein the header corresponds to one of five transmission modes. The method for identifying a frame header according to claim 1, wherein the transmission modes correspond to one of three header lengths, wherein the three header lengths are 420, 595, and 945 symbols, respectively. The method for identifying a frame header according to claim 8, wherein the specific sequence is a fixed sequence or a rotated sequence of the fixed sequence. A frame header recognition system suitable for a digital television floor A media broadcast (DTMB) system includes: a storage unit for receiving and storing an input signal from a DTMB packet, wherein the packet includes a plurality of frames, each frame having a header and a data interval, the labels The header corresponds to one of the complex transmission modes and the transmission modes respectively correspond to a specific sequence; a correlation value calculation unit, the header of one of the frames and the corresponding frame of the specific frame Performing a correlation operation to obtain a correlation value, wherein the corresponding specific frame is located before the one of the frames; and an operation result generating unit receives the correlation value of the correlation value calculation unit to generate a corresponding transmission mode The result of the complex operation; and a frame header identification unit, according to the operation result and a predetermined rule, identify the transmission mode used by the headers. The frame header recognition system of claim 10, wherein the correlation value calculation unit further comprises a conjugate complex generation unit for generating a conjugate complex number corresponding to the received signal to complete the correlation operation. The frame header recognition system of claim 10, wherein the operation result generation unit further comprises an accumulation unit for accumulating the correlation value obtained by the correlation value calculation unit to generate a required value. The result of these operations. The frame header recognition system of claim 10, wherein the frame header identification unit further comprises a comparator for finding that the operation result has a maximum value or has and corresponds to the One of the operation results is a standard deviation of the maximum difference. For example, the frame header identification system described in item 13 of the patent application scope The frame header identification unit determines the transmission mode of the headers according to the operation result of the maximum value found by the comparator. The frame header identification system of claim 13, wherein the frame header identification unit further determines the result of the operation that is found by the comparator to have a maximum difference from the standard deviation. The transmission mode of the header. The frame header recognition system of claim 10, wherein if the operation result of a transmission mode exceeds a predetermined value, the frame header identification unit determines that the transmission mode of the header is the Transfer mode. The frame header recognition system of claim 10, wherein the headers correspond to one of five transmission modes. The frame header recognition system of claim 10, wherein the transmission modes correspond to one of three header lengths, wherein the three header lengths are 420, 595, and 945 symbols, respectively. The frame header recognition system of claim 18, wherein the specific sequence is a fixed sequence or a rotated sequence of the fixed sequence. A frame header identification method is applicable to a Digital Terrestrial Multimedia Broadcasting (DTMB) system, comprising the steps of: receiving a packet, wherein the packet includes a plurality of frames, each frame having a header And a data interval, the headers corresponding to one of a plurality of transmission modes, wherein the transmission modes respectively correspond to a specific sequence; And correlating the header of one of the frames with the header of a corresponding specific frame, and generating an operation result corresponding to one of the transmission modes, wherein the corresponding specific message The frame is located before the one of the frames, wherein if the operation result of a transmission mode exceeds a predetermined value, it is determined that the transmission mode of the header is the transmission mode. The method for identifying a frame header according to claim 20, further comprising: if the operation result of the transmission mode does not exceed the predetermined value, the header of one of the frames corresponds to a corresponding one. The header of the particular frame performs a correlation operation and generates an operation result corresponding to the other of the transmission modes to identify the transmission mode of the headers. The method for identifying a frame header according to claim 20, wherein the operation result is located between a first value and a second value, and the predetermined value is approximately equal to the first value and the second One-half of the sum of the values. The method for identifying a frame header according to claim 20, wherein the operation result does not exceed a maximum value, and the predetermined value is approximately equal to one-half of the maximum value. The method for identifying a frame header according to claim 20, wherein the transmission modes correspond to one of three header lengths, and the three header lengths are 420, 595, and 945 symbol lengths, respectively.