WO2015078270A1 - 一种前导序列生成方法、定时同步方法和设备 - Google Patents

一种前导序列生成方法、定时同步方法和设备 Download PDF

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Publication number
WO2015078270A1
WO2015078270A1 PCT/CN2014/090319 CN2014090319W WO2015078270A1 WO 2015078270 A1 WO2015078270 A1 WO 2015078270A1 CN 2014090319 W CN2014090319 W CN 2014090319W WO 2015078270 A1 WO2015078270 A1 WO 2015078270A1
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Prior art keywords
pattern
preamble sequence
signal
sequence
correlation value
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PCT/CN2014/090319
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English (en)
French (fr)
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朱伟
曾云宝
康良川
赵慧
赵龙
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华为技术有限公司
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Publication of WO2015078270A1 publication Critical patent/WO2015078270A1/zh
Priority to US15/165,583 priority Critical patent/US10187243B2/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2689—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation
    • H04L27/2692—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation with preamble design, i.e. with negotiation of the synchronisation sequence with transmitter or sequence linked to the algorithm used at the receiver
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/54—Systems for transmission via power distribution lines
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2602—Signal structure
    • H04L27/261—Details of reference signals
    • H04L27/2613—Structure of the reference signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2662—Symbol synchronisation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2668—Details of algorithms
    • H04L27/2681—Details of algorithms characterised by constraints
    • H04L27/2688—Resistance to perturbation, e.g. noise, interference or fading
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/0001—Arrangements for dividing the transmission path
    • H04L5/0003—Two-dimensional division
    • H04L5/0005—Time-frequency
    • H04L5/0007—Time-frequency the frequencies being orthogonal, e.g. OFDM(A), DMT
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/22—Arrangements affording multiple use of the transmission path using time-division multiplexing

Definitions

  • the present invention relates to the field of communications technologies, and in particular, to a preamble sequence generation method, a timing synchronization method, and a device.
  • Synchronization is a practical problem that any communication system needs to solve. Without accurate synchronization, reliable data transmission is impossible, so the synchronization technology is directly related to the performance of the entire communication system.
  • Synchronization is generally divided into timing synchronization and frequency synchronization. Wherein, for timing synchronization, it includes coarse synchronization and fine synchronization, and the purpose is to enable the receiving end of the signal to determine the start and end time of each symbol. In order to enable the receiving end to accurately find the beginning of the data symbol sent by the transmitting end, a common technical method is to add a string of preamble sequences (ie, Preamble, which may be referred to as a preamble symbol) in front of the data symbol to indicate The arrival of the data symbol.
  • Preamble which may be referred to as a preamble symbol
  • the receiving end can use the known preamble sequence to perform correlation calculation between the preamble sequence and the received signal sequence, and obtain the characterization of the preamble sequence and The correlation value of the correlation between the received signal sequences. Specifically, when the receiving end receives the preamble sequence, the correlation value calculated according to the above manner will have a significant peak, so that the receiving end can thereby determine that the preamble sequence is currently received, and then perform timing synchronization.
  • the timing synchronization scheme adopted in the Narrow Band-Power Line Communication (NB-PLC) system is similar to the above scheme, and is also implemented based on the preamble sequence.
  • Narrow Band-Power Line Communication (NB-PLC) is similar to the above scheme, and is also implemented based on the preamble sequence.
  • ITU International Telecommunications Union
  • the preamble sequence as shown in FIG. 1 can be used for timing synchronization of the receiving end signals.
  • the preamble sequence shown in FIG. 1 is mainly composed of a preamble symbol S1 and a preamble symbol S2, wherein S1 is composed of 8 orthogonal frequency division multiplexing (OFDM) symbols carrying the same information, if S is used.
  • S1 is composed of 8 orthogonal frequency division multiplexing (OFDM) symbols carrying the same information, if S is used.
  • the main purpose of repeatedly carrying the same information by using a plurality of consecutive OFDM symbols in FIG. 1 is to resist the bad channel conditions in the NB-PLC system, so as to improve the probability that the receiving end correctly receives the leading symbols, thereby improving the synchronization of the NB-PLC system. rate.
  • the received signal sequence may be first subjected to delayed autocorrelation, that is, the signal sequence of each pair of OFDM symbol lengths received continuously is calculated. Delaying the correlation value until the delay correlation value determined over a period of time is greater than the set number, determining that the preamble symbol arrives, that is, completing the coarse synchronization process; and further, the receiving end uses the locally pre-stored symbol S and after completing the coarse synchronization process
  • the received signal sequence is subjected to sliding correlation. When it is calculated that the locally stored value of the S and the received signal sequence has a negative peak value, it is judged that S2 is detected, so that the timing synchronization point can be determined, that is, the fine synchronization is completed. process.
  • the NB-PLC system mainly works in the frequency range of 3-500 kHz, and its channel mainly consists of slowly varying multipath, colored noise, narrowband interference, pulse interference, periodic noise synchronized to power frequency, and periodicity asynchronous to power frequency. Noise composition.
  • the pulse interference synchronized with the power frequency and the pulse interference asynchronous to the power frequency can be classified into the narrow-band interference in the frequency domain and the burst interference in the time domain.
  • the narrow-band interference in the frequency domain is very serious; at the same time, the non-standardity of the electrical appliances on the power line causes the intensity of the time domain burst interference that is 10-15 dB higher than the noise floor.
  • the channel conditions of the NB-PLC system are made extremely bad.
  • the embodiments of the present invention provide a method and a device for generating a preamble sequence, so as to avoid the problem that the receiving end is difficult to synchronize timing correctly due to interference in the NB-PLC system to destroy the preamble sequence.
  • the embodiment of the invention further provides a timing synchronization method and device.
  • a method for generating a preamble sequence includes: determining a number m of orthogonal frequency division multiplexing OFDM symbols constituting a single pattern in a preamble sequence, where m is not less than 2; generating a preamble sequence according to the m, Each of the m OFDM symbols that are consecutive in the time domain in the generated preamble sequence respectively constitutes a single pattern, and the generated preamble sequence includes at least two patterns, and the patterns are different from each other.
  • the method further includes: according to a correlation value between a preamble symbol stored by the receiving end and each preamble symbol included in the generated preamble sequence, Each of the patterns included in the generated preamble sequence respectively determines a pattern identifier.
  • m is determined in the following manner:
  • m is determined according to the number of OFDM symbols of the preamble sequence generated according to the predetermined composition and the preset mapping relationship between the number and m.
  • the preset mapping relationship includes:
  • L is a predetermined number of OFDM symbols that constitute the generated preamble sequence.
  • a second aspect provides a timing synchronization method, including: receiving, by a receiving end, a signal sequence; the time domain length of the signal sequence is an integer multiple of a time domain length of a single orthogonal frequency division multiplexing OFDM symbol, and is not less than a prescribed number.
  • the receiving end determines a correlation value of each signal subsequence that the signal sequence can include with a stored single OFDM symbol used as a preamble symbol; wherein the signal subsequence contains a signal Point is a plurality of consecutive signal points in the time domain, and The number of signal points included in the signal subsequence is the same as the number N of signal points stored in the stored single OFDM symbol; the receiving end according to the determined correlation value, according to each signal subsequence that the signal sequence can contain Arranging the order in the time domain, and sequentially selecting the determined correlation values to generate the relevant value sets, until the determined correlation values are selected; wherein the number of correlation values included in each correlation value set is equal to N; The receiving end respectively determines the correlation value of the largest modulus value in each correlation value set; when the receiving end determines that the correlation values of the maximum modulus values in the determined correlation value sets have the m correlation values satisfying the specified condition, The m correlation values and the preset pattern
  • the m correlation values satisfying the specified conditions include: sorting the m correlation values according to the receiving order of the signal subsequences. Then, the signal subsequence corresponding to the adjacent two correlation values of the m correlation values respectively can be included in all signal sub-sequences of the signal sequence
  • the arrangement positions in the columns are different by N; the receiving end is represented by the generated pattern identifier when the generated pattern identifier is identical to one of the pattern identifiers determined in advance according to the generation manner for the pattern included in the leader sequence.
  • the position of the pattern in the leader sequence determines the starting position of the leader sequence.
  • the receiving end generates the pattern identifier according to the m correlation values and the preset pattern identifier generation manner, and specifically includes: receiving, according to the m correlation values, the receiving end, And a pre-set decimal number generation method to determine a decimal number as the generated pattern identifier.
  • a third aspect provides a preamble sequence generating apparatus, including: a number determining unit, configured to determine a number m of orthogonal frequency division multiplexing OFDM symbols constituting a single pattern in a preamble sequence, where m is not less than 2; a preamble sequence a generating unit, configured to generate a preamble sequence according to the m determined by the number determining unit, so that each m OFDM symbols consecutive in the time domain in the generated preamble sequence respectively constitute a single pattern, and the generated preamble sequence includes at least two patterns The patterns are different from each other.
  • the device further includes: an identifier determining unit, configured to use, according to the preamble symbol stored by the receiving end, each preamble included in the generated preamble sequence The correlation value between the pilot symbols determines the pattern identifier for each pattern included in the generated leader sequence.
  • the number determining unit determines m by:
  • m is determined according to the number of OFDM symbols of the preamble sequence generated according to the predetermined composition and the preset mapping relationship between the number and m.
  • the preset mapping relationship includes:
  • L is a predetermined number of OFDM symbols that constitute the generated preamble sequence.
  • the fourth aspect provides a receiving end device, including:
  • a signal sequence receiving unit configured to receive a signal sequence;
  • the time domain length of the signal sequence is an integer multiple of a time domain length of a single orthogonal frequency division multiplexing OFDM symbol, and is not less than a time domain length of a specified number of single OFDM symbols ;
  • a first correlation value determining unit configured to determine a correlation value of each signal subsequence that the signal sequence can include, and a stored single OFDM symbol used as a preamble symbol; wherein the signal subsequence includes a signal point a plurality of signal points consecutive in the time domain, and the number of signal points included in the signal subsequence is the same as the number N of signal points included in the stored single OFDM symbol;
  • a correlation value selecting unit configured to generate, according to the determined correlation value, a correlation value set according to an arrangement order of each signal subsequence that can be included in the signal sequence in the time domain, and sequentially select the determined correlation value, Until the determined correlation value is selected; wherein each correlation value set contains a number of correlation values equal to N;
  • a second correlation value determining unit configured to respectively determine a correlation value of a maximum modulus value in each correlation value set
  • a pattern identifier generating unit configured to: when there are m correlation values in the correlation value that is determined to be the largest among the determined correlation value sets, satisfy the specified condition, according to the m correlation values and the pre- The pattern identifier generation manner is generated, and the pattern identifier is generated.
  • the m correlation values satisfying the specified condition specifically include: after the m correlation values are sorted according to the receiving order of the signal subsequence, the m correlation values The arrangement of the signal subsequences corresponding to the two adjacent correlation values in each of the signal subsequences that can be included in the signal sequence are different by N;
  • a start position determining unit configured to: when the generated pattern identifier is the same as one of the pattern identifiers determined in advance for the pattern included in the preamble sequence according to the generation manner, according to the pattern represented by the generated pattern identifier The position in the leader sequence determines the starting position of the leader sequence.
  • the pattern identifier generating unit is specifically configured to:
  • a decimal number as the generated pattern identifier is determined according to the m correlation values and a preset decimal number generation manner.
  • each of the m OFDM symbols in the time domain in the preamble sequence generated in the embodiment of the present invention can form a single pattern, and the preamble sequence includes at least two patterns, each pattern is different from each other, so that the anti-destructive force of the preamble sequence is obtained.
  • a large increase can avoid the problem that the receiving end is difficult to correctly recognize the starting position of the leading sequence due to the interference of the preamble sequence in the NB-PLC system, so that it is difficult to correctly synchronize the timing.
  • the anti-destructive power of the preamble sequence is improved by: each m OFDM symbols can form a pattern together, and each pattern is different from each other, thereby improving the recognizability of the preamble sequence even if a certain preamble symbol is interfered. Being destroyed, it is also ensured that a complete pattern may also exist in the preamble sequence so that the preamble sequence can be correctly identified.
  • Figure 1 is a schematic diagram of a preamble sequence for timing synchronization specified in G.9955;
  • FIG. 2 is a schematic flowchart of implementing a method for generating a preamble sequence according to an embodiment of the present invention
  • FIG. 3 is a schematic diagram of a preamble sequence generated in an embodiment of the present invention.
  • FIG. 4 is a schematic flowchart of implementing a timing synchronization method according to an embodiment of the present invention.
  • FIG. 5 is a schematic diagram of an implementation manner of a solution provided in an NB-PLC system according to an embodiment of the present invention
  • FIG. 6 is a schematic structural diagram of a device for generating a preamble sequence according to an embodiment of the present invention.
  • FIG. 7 is a schematic structural diagram of a receiving end device according to an embodiment of the present disclosure.
  • FIG. 8 is a schematic structural diagram of another apparatus for generating a preamble sequence according to an embodiment of the present invention.
  • FIG. 9 is a schematic structural diagram of another receiving end device according to an embodiment of the present invention.
  • the embodiment of the present invention first provides a preamble sequence generating method.
  • FIG. 2 is a schematic flowchart of a method for generating a preamble sequence according to an embodiment of the present invention, which mainly includes the following steps:
  • Step 21 determining the number m of OFDM symbols constituting a single pattern in the preamble sequence
  • pattern refers to a sequence of symbols consisting of at least two OFDM symbols in a preamble sequence.
  • m may be determined according to the number of OFDM symbols of the preamble sequence generated according to the predetermined composition and the preset mapping relationship between the number and m.
  • the preset mapping relationship may be, but is not limited to, the following formula [1]:
  • L is the number of OFDM symbols of the preamble sequence generated by the predetermined composition.
  • Step 22 Generate a preamble sequence according to m, so that every m OFDM symbols consecutive in the time domain in the generated preamble sequence respectively constitute a single pattern, and the generated preamble sequence includes at least two pictures. As such, the patterns are different from each other.
  • the foregoing method provided by the embodiment of the present invention may further include the steps of: respectively, according to the correlation value between the preamble symbol stored at the receiving end and each preamble symbol included in the generated preamble sequence, respectively, for each pattern included in the generated preamble sequence Determine the pattern ID.
  • the manner of generating the pattern identifier used in the embodiment of the present invention will be described in detail later, and details are not described herein again.
  • the preamble generation method provided by the embodiment of the present invention for example, when the number of OFDM symbols of the preamble sequence generated by the predetermined composition is 8, it can be calculated that m can be equal to 3.
  • a preamble sequence generated by performing step 22 is as shown in FIG. 3
  • the preamble sequence shown in FIG. 3 may include a total of six different patterns, and the pattern identifiers may be numbers in the ellipse in FIG. 3, which are 2-7 respectively.
  • any ellipse in FIG. 3 is satisfied: the pattern of the pattern of the corresponding preamble sequence is identified as the number in the ellipse. For example, if the pattern corresponding to the ellipse containing the number "2" is ⁇ -S, S, -S ⁇ , the pattern of the pattern is identified as 2.
  • the pseudo pattern may be assigned a different pattern from the above.
  • the noise signal appearing before the first OFDM symbol of the preamble sequence may be S or may be -S, in the embodiment of the present invention, it may be the former in the preamble sequence as shown in FIG.
  • the "pseudo pattern" composed of two OFDM symbols is assigned pattern identifications 0 and 1.
  • the pattern identifier assigned to the pseudo pattern ⁇ -S, -S, -S ⁇ may be 0, and the identifier assigned to the pseudo pattern ⁇ S, -S, -S ⁇ may be 1;
  • each of the m consecutive OFDM symbols in the preamble sequence in the embodiment of the present invention constitutes a single pattern, and the preamble sequence includes at least two patterns, the patterns are different from each other, so that the anti-destructive power of the preamble sequence is greatly improved. It can avoid the damage of the preamble sequence due to interference in the NB-PLC system, which makes it difficult for the receiving end to correctly identify the starting position of the preamble sequence, thus making it difficult to synchronize timing correctly. problem.
  • the anti-destructive power of the preamble sequence is improved by: each m OFDM symbols can form a pattern together, and each pattern is different from each other, thereby improving the recognizability of the preamble sequence even if a certain preamble symbol is interfered. Being destroyed, it is also ensured that a complete pattern may also exist in the preamble sequence so that the preamble sequence can be correctly identified.
  • the embodiment of the present invention further provides a method for generating a preamble sequence.
  • the schematic diagram of the specific implementation process of the method is as shown in FIG. 4, and includes the following main steps:
  • Step 41 The receiving end receives the signal sequence
  • the time domain length of the signal sequence is an integer multiple of the time domain length of the single OFDM symbol, and is not less than the time domain length of the specified number of single OFDM symbols.
  • the prescribed number referred to herein is not less than m+1, and m is a predetermined number of orthogonal frequency division multiplexed OFDM symbols constituting a single pattern in the preamble sequence.
  • pattern refers to a sequence of symbols consisting of at least two OFDM symbols in a preamble sequence.
  • the preamble sequence includes at least two patterns, and the preamble sequence includes patterns different from each other.
  • the pseudo pattern may be assigned a different pattern from the above.
  • the pattern identifiers 0 and 1 may be assigned to the "pseudo pattern" formed by the first two OFDM symbols in the preamble sequence as shown in FIG.
  • the pattern identifier assigned to the pseudo pattern ⁇ -S, -S, -S ⁇ may be 0, and the identifier assigned to the pseudo pattern ⁇ S, -S, -S ⁇ may be 1;
  • a certain manner of determining m may be as shown in the formula [1].
  • Step 42 Determine a correlation value between each signal subsequence that the signal sequence can include and a stored single OFDM symbol used as a preamble symbol;
  • the signal subsequence includes a signal point that is a plurality of consecutive signal points in the time domain, and the number of signal points included in the signal subsequence and the number of signal points included in the stored single OFDM symbol used as the preamble symbol. the same.
  • Step 43 According to the determined correlation value, according to the order of the signal subsequences that can be included in the signal sequence in the time domain, sequentially select the determined correlation values to generate a correlation value set until the determined correlation value is determined. Selected
  • the number of correlation values included in each of the above correlation value sets is equal to N.
  • Step 44 respectively determining a correlation value of a maximum modulus value in each correlation value set
  • Step 45 When it is determined that the m correlation values in the determined correlation value set in each of the determined correlation value sets satisfy the specified condition, the generated pattern is generated according to the m correlation values and the preset pattern identification generation manner. Identification
  • the m correlation values satisfying the predetermined condition specifically include: after the m correlation values are sorted according to the receiving sequence of the signal subsequence, the signals corresponding to the adjacent two correlation values of the m correlation values respectively The subsequences differ in the arrangement position of N in all signal subsequences that the signal sequence can contain.
  • Step 46 When the pattern identifier generated by executing step 45 is the same as one of the pattern identifiers determined in advance according to the preset pattern identifier generation manner for the pattern included in the preamble sequence, the pattern represented by the generated pattern identifier is in the preamble The position in the sequence determines the starting position of the leader sequence. Thus timing synchronization is achieved based on the starting position.
  • the pattern identifier generated by executing step 43 is “6”
  • S, S ⁇ corresponds. It can be seen from the position of the pattern ⁇ -S, S, S ⁇ in the preamble sequence as shown in FIG. 3 that the second OFDM symbol continuously received after the m signal subsequences is the preamble sequence. End position.
  • the pattern identifier generated by executing step 43 is “0”, it is the same as the pattern identifier of the pattern included in the preamble sequence, but is identical to the pattern identifier of the “pseudo pattern”, and the received signal sequence is received.
  • the m signal subsequences included do not belong to the preamble sequence, so that the process can be terminated, or the correlation value corresponding to the signal subsequences that can be included in the signal sequence can be continuously determined, and whether there are other m common met values satisfying the above specified conditions. Correlation value; or may continue to receive other signal sequences, and determine whether there are m correlation values that satisfy the above specified conditions among the correlation values corresponding to the signal subsequences that can be included in other signal sequences that continue to be received.
  • step 43 can generate three sets of correlation values, respectively, ⁇ 1 , ⁇ 2 , ⁇ 3 ,..., ⁇ N ⁇ , ⁇ N+1 , ⁇ N+2 , ⁇ N+ 3 ,..., ⁇ 2N ⁇ and ⁇ 2N+1 , ⁇ 2N+2 , ⁇ 2N+3 ,..., ⁇ 3N ⁇ .
  • the set of correlation values ⁇ 1 , ⁇ 2 , ⁇ 3 , . . . , ⁇ N ⁇ , ⁇ N+1 , ⁇ N+2 , ⁇ N+3 , . . . , ⁇ 2N ⁇ may be respectively determined.
  • the maximum correlation values of the modulus values determined from the three sets of correlation values are ⁇ ⁇ 1 , ⁇ ⁇ 2 , and ⁇ ⁇ 3 , respectively .
  • ⁇ 1 has a value range of [1, N]
  • ⁇ 2 has a value range of [N+1, 2N]
  • ⁇ 3 has a value range of [2N+1, 3N].
  • the identifier generation manner is generated, and the pattern identifier is generated; otherwise, the flow may be ended.
  • the timing synchronization method provided by the embodiment of the present invention may further perform similar processing on other signal sequences that continue to be received after receiving the signal sequence.
  • the specific implementation manner of generating the pattern identifier according to the m correlation values and the preset pattern identifier generation manner in the step 45 may include, but is not limited to, determining, according to the m correlation values and the preset decimal number generation manner, A decimal number of the generated pattern ID.
  • the m correlation values can be converted into a decimal number ⁇ as the generated pattern identifier according to the following formula [2]:
  • ⁇ can be calculated.
  • the m correlation values match the pattern in the leader sequence whose pattern is identified as ⁇ .
  • the preamble sequence in the embodiment of the present invention includes at least two patterns, and the patterns included in the preamble sequence are different from each other, even if one of the patterns is interfered, Destruction, the identification of the preamble sequence can also be implemented according to another pattern and the starting position of the preamble sequence can be accurately located.
  • the embodiment of the present invention may determine, when the m correlation values satisfy the specified condition, determine m signal subsequences and preamble sequences corresponding to the m correlation values.
  • the pattern in the matching is matched, and the pattern identifier of the pattern matching the m signal sub-sequences is generated according to the preset pattern identification generation method, so that the pattern represented by the generated pattern identifier is located in the preamble sequence.
  • the position determines the starting position of the preamble sequence, avoiding the problem that the receiving end is difficult to correctly recognize the termination position of the preamble sequence due to the interference of the preamble sequence in the NB-PLC system.
  • the preamble sequence shown in FIG. 3 can be obtained by arranging and combining the OFDM symbols S and -S constituting the preamble sequence.
  • P ⁇ -S, -S, +S, -S, +S, +S, +S, -S ⁇ .
  • S may be an OFDM symbol used as a preamble symbol specified in G.9955.
  • V b [V 1 , V 2 , ..., V 8 ]
  • P(i) represents the ith preamble symbol in the above preamble sequence P.
  • V d represents a sequence of decimal numbers formed by the conversion of every three adjacent binary numbers in V b
  • V d [4,2, according to an algorithm similar to equation [2]. 5,6,7,3].
  • the decimal number in V d is the pattern identifier of each pattern in the preamble sequence as shown in FIG. 3 .
  • FIG. 5 A schematic diagram of the implementation process is shown in FIG. 5, and includes the following steps:
  • Step 51 The receiver obtains four consecutive signal subsequences whose time domain lengths are respectively the same as the time domain length of the OFDM symbol.
  • the number of signal points included in Y is 4N. If y(q) represents a signal point of sequence number q in Y, the range of q is [1, 4N].
  • Step 52 the receiver determines all mutually different signal subsequences that Y can contain
  • the determined arbitrary signal subsequence needs to be satisfied: it includes N consecutive signal points in the time domain.
  • the correlation value ⁇ k of X and Y k can be calculated by the following formula [3]:
  • Step 54 The sequence ⁇ 1 , ⁇ 2 , ⁇ 3 , . . . , ⁇ 3N ⁇ formed by the obtained correlation values is divided into three sets of correlation values, that is, ⁇ 1 , ⁇ 2 , ⁇ 3 , ..., ⁇ N ⁇ , ⁇ N+1 , ⁇ N+2 , ⁇ N+3 ,..., ⁇ 2N ⁇ and ⁇ 2N+1 , ⁇ 2N+2 , ⁇ 2N+3 ,.. ., ⁇ 3N ⁇ , and then determine the correlation value of the largest modulus value among the three correlation value sets.
  • ⁇ 1 denote the sequence number of the correlation value with the largest modulus value in the first correlation value set ⁇ 1 , ⁇ 2 , ⁇ 3 , ..., ⁇ N ⁇ ;
  • ⁇ 2 indicates that the serial number is the above second
  • the correlation value number of the correlation value set ⁇ N+1 , ⁇ N+2 , ⁇ N+3 , ..., ⁇ 2N ⁇ is the largest;
  • the ⁇ 3 indicates that the sequence number is the second correlation value set ⁇ 2N+1 , ⁇ 2N+2 , ⁇ 2N+3 , ..., ⁇ 3N ⁇
  • the sequence number of the correlation value with the largest modulus value then there are the following formulas [4] to [6]:
  • ⁇ 1 argmax
  • ⁇ 2 argmax
  • ⁇ 3 argmax
  • Step 55 determining whether ⁇ 3 - ⁇ 2 and ⁇ 2 - ⁇ 1 are both equal to the number N of signal points included in one OFDM symbol as a preamble symbol; if the determination result is yes, performing step 56; otherwise, the signal may be The first x signal points in sequence Y are deleted, and the x signals originally located after the signal sequence Y are added to Y, that is, a new signal sequence Y including 4N signal points is regenerated, and the new signal sequence Y is Perform step 52 above and subsequent steps.
  • Step 56 will as well as Substituting into the following formula, calculate a decimal number ⁇ :
  • Step 57 it is judged whether the calculated ⁇ belongs to the set ⁇ 2, 3, 4, 5, 6, 7 ⁇ , and if yes, step 58 is performed; otherwise, the first x signal points in the signal sequence Y can be deleted, and Adding x signals originally located after the signal sequence Y to Y, that is, regenerating a new signal sequence Y including 4N signal points, and performing the above step 52 and subsequent corresponding steps on the new signal sequence Y;
  • step 58 according to the position of the calculated pattern represented by ⁇ in the preamble sequence as shown in FIG. 3, timing synchronization can be realized, and the process ends.
  • the receiving end since the receiving end only needs to detect that the OFDM symbol correlation in one pattern is not destroyed, the timing synchronization can be completed, and the capability of resisting channel destruction is greatly improved compared with the design of the traditional preamble sequence;
  • the threshold threshold value of the coarse synchronization is not required, and the timing synchronization can be completed by using the interval detection of the correlation value and the pattern identification matching, so that the synchronization rate of the system can be improved;
  • the receiving end uses the correlation value interval detection and the pattern identification matching method to perform timing synchronization, when the channel quality is good, the timing synchronization can be completed in advance before receiving the first few OFDM symbols, shortening the timing synchronization time and reducing Delay
  • the preamble sequence provided by the embodiment of the present invention has strong scalability, and can be applied not only to a channel environment where there are factors such as pulse interference, but also to other communication environments.
  • the embodiment of the present invention further provides a preamble sequence generating device 60 for the same inventive concept as the preamble sequence generating method provided by the embodiment of the present invention.
  • a schematic diagram of a specific structure of the preamble sequence generating device 60 is shown in FIG. 6, and includes a number determining unit 61 and a preamble sequence generating unit 62. The functions of each unit are as follows:
  • a number determining unit 61 for determining orthogonal frequency division multiplexing constituting a single pattern in the preamble sequence The number m of OFDM symbols, where m is not less than 2;
  • the preamble sequence generating unit 62 is configured to generate a preamble sequence according to the m determined by the number determining unit 61, so that every m OFDM symbols consecutive in the time domain in the generated preamble sequence respectively constitute a single pattern, and the generated preamble sequence includes at least two The patterns are different from each other.
  • the preamble sequence generating device 60 of the embodiment of the present invention may further include: an identifier determining unit, configured to: correlate, according to the preamble symbol stored by the receiving end, each preamble symbol included in the generated preamble sequence The value determines the pattern identifier for each pattern included in the generated leader sequence.
  • the number determining unit 61 may specifically determine m in the following manner:
  • m is determined according to the number of OFDM symbols of the preamble sequence generated according to the predetermined composition and the preset mapping relationship between the number and m.
  • the foregoing preset mapping relationship may include, but is not limited to, including:
  • L is a predetermined number of OFDM symbols that constitute the generated preamble sequence.
  • each of the m consecutive OFDM symbols in the generated preamble sequence may constitute a single pattern, and the preamble sequence includes at least two patterns, and the patterns are different from each other, so that the anti-destructive power of the preamble sequence A large improvement is obtained, which can avoid the problem that the receiving end is difficult to correctly recognize the starting position of the leading sequence due to the interference in the NB-PLC system, thereby making it difficult to correctly synchronize the timing.
  • the anti-destructive power of the preamble sequence is improved by: each m OFDM symbols can form a pattern together, and each pattern is different from each other, thereby improving the recognizability of the preamble sequence even if a certain preamble symbol is interfered. Being destroyed, it is also ensured that a complete pattern may also exist in the preamble sequence so that the preamble sequence can be correctly identified.
  • the embodiment of the present invention further provides a receiving end device 70 for the same inventive concept as the timing synchronization method provided by the embodiment of the present invention.
  • the specific structure of the receiving device 70 is as shown in FIG. 7, and includes the following functional units:
  • a signal sequence receiving unit 71 configured to receive a signal sequence;
  • the time domain length of the signal sequence is a single Orthogonal frequency division multiplexing OFDM symbols, an integer multiple of the time domain length, and not less than a specified number of time domain lengths of a single OFDM symbol;
  • a first correlation value determining unit 72 configured to determine a correlation value of each signal subsequence that the signal sequence can include, and a stored single OFDM symbol used as a preamble symbol; wherein the signal subsequence includes a signal point a plurality of consecutive signal points on the domain, and the number of signal points included in the signal subsequence is the same as the number N of signal points included in the stored single OFDM symbol used as a preamble symbol;
  • the correlation value selection unit 73 is configured to: according to the determined correlation value, sequentially select the determined correlation value to generate the correlation value set according to the order of the respective signal sub-sequences that can be included in the signal sequence in the time domain, until The determined correlation value is selected; wherein each correlation value set contains a number of correlation values equal to N;
  • a second correlation value determining unit 74 configured to respectively determine a correlation value of a maximum modulus value in each correlation value set
  • the pattern identifier generating unit 75 is configured to determine, according to the m correlation values and the preset pattern identifier, when there are m correlation values that satisfy the specified condition in the correlation value that is determined to be the largest among the determined correlation value sets. Generating a pattern, generating a pattern identifier; wherein, the m correlation values satisfying the predetermined condition specifically includes: after sorting the m correlation values according to the receiving order of the signal subsequence, the adjacent two of the m correlation values are related The signal subsequences corresponding to the values respectively differ in the arrangement positions of all the signal subsequences that the signal sequence can contain;
  • a start position determining unit 76 configured to: according to the generated pattern identifier, the one of the pattern identifiers determined in advance according to the preset pattern identifier generation manner for the pattern included in the preamble sequence, according to the generated pattern identifier The position of the pattern in the leader sequence determines the starting position of the leader sequence.
  • the pattern identifier generating unit 75 is specifically configured to: determine a decimal number as the generated pattern identifier according to the m correlation values and a preset decimal number generation manner.
  • each of the m consecutive OFDM symbols in the generated preamble sequence may constitute a single pattern, and the preamble sequence includes at least two patterns, and the patterns are different from each other, so that the anti-destructive power of the preamble sequence A large improvement is obtained, which can avoid the problem that the receiving end is difficult to correctly recognize the starting position of the leading sequence due to the interference in the NB-PLC system, thereby making it difficult to correctly synchronize the timing.
  • the anti-destructive power of the preamble sequence is improved by: each m OFDM symbols can form a pattern together, and each pattern is different from each other, thereby improving the recognizability of the preamble sequence even if a certain preamble symbol is interfered. Being destroyed, it is also ensured that a complete pattern may also exist in the preamble sequence so that the preamble sequence can be correctly identified.
  • the embodiment of the present invention further provides another preamble sequence generating device 80.
  • the specific structure is shown in FIG. 8.
  • the preamble sequence generating device 80 includes: The processor 81, the memory 82 and the bus 83, wherein the processor 81 and the memory 82 are connected by a bus 83 for storing instructions through which the processor 81 calls instructions stored in the memory 82 for Determining the number m of OFDM symbols constituting a single pattern in the preamble sequence, where m is not less than 2; and generating a preamble sequence according to m such that each m OFDM symbols consecutive in the time domain in the generated preamble sequence respectively constitute a single pattern And causing the generated preamble sequence to contain at least two patterns, each pattern being different from each other.
  • the processor 81 is further configured to determine, according to a correlation value between the preamble symbol stored by the receiving end and each preamble symbol included in the generated preamble sequence, respectively, to determine a pattern identifier for each pattern included in the generated preamble sequence. .
  • each of the m consecutive OFDM symbols in the generated preamble sequence may constitute a single pattern, and the preamble sequence includes at least two patterns, and the patterns are different from each other, so that the anti-destructive power of the preamble sequence A large improvement is obtained, which can avoid the problem that the receiving end is difficult to correctly recognize the starting position of the leading sequence due to the interference in the NB-PLC system, thereby making it difficult to correctly synchronize the timing.
  • the anti-destructive power of the preamble sequence is improved by: each m OFDM symbols can form a pattern together, and each pattern is different from each other, thereby improving the preamble sequence. The recognizability, even if a certain preamble symbol is disrupted and destroyed, can ensure that there may be a complete pattern in the preamble sequence so that the preamble sequence can be correctly identified.
  • the embodiment of the present invention further provides another receiving device 90.
  • the specific structure of the device is as shown in FIG. 9, and includes: a receiver 91, and processing. 92 and memory 93.
  • the receiver 91 is configured to receive a signal sequence.
  • the time domain length of the signal sequence is an integer multiple of the time domain length of the single OFDM symbol, and is not less than the time domain length of the specified number of single OFDM symbols.
  • the memory 93 is configured to store instructions; the processor 92, by invoking an instruction stored in the memory 93, is used to determine that each of the signal subsequences that the signal sequence received by the receiver 91 can contain is stored with a single OFDM symbol used as a preamble symbol. Correlation value; according to the determined correlation value, according to the order of the signal subsequences that can be included in the signal sequence in the time domain, the determined correlation values are sequentially selected without generating the correlation value set until the determined correlation value is determined.
  • the pattern identifier is generated according to the m correlation values and the preset pattern identification generation manner; the generated pattern identifier is generated according to the preset pattern identifier in advance
  • the map represented by the generated pattern identifier is In which the position of the leader sequence, the leader sequence determines the starting position.
  • the signal substation includes a signal point that is a plurality of consecutive signal points in the time domain, and the number of signal points included in the signal subsequence is the same as the number N of signal points included in the stored single OFDM symbol used as the preamble symbol;
  • the m correlation values satisfying the specified condition include: after the m correlation values are sorted according to the receiving order of the signal subsequence, the signal subsequence corresponding to the two adjacent correlation values of the m correlation values are respectively The arrangement positions in all signal subsequences that the signal sequence can contain are different by N.
  • the processor 92 generates the pattern identifier according to the m correlation values and the preset pattern identifier generation manner, and specifically includes: the processor determines, according to the m correlation values and the preset decimal number generation manner, the generated pattern. A decimal number of the identifier.
  • each of the m consecutive OFDM symbols in the preamble sequence in the embodiment of the present invention constitutes a single pattern, and the preamble sequence includes at least two patterns, the patterns are different from each other, so that the anti-destructive power of the preamble sequence is greatly improved. It can avoid the problem that the receiving end is difficult to correctly recognize the starting position of the leading sequence due to the interference of the preamble sequence in the NB-PLC system, so that it is difficult to correctly synchronize the timing.
  • the anti-destructive power of the preamble sequence is improved by: each m OFDM symbols can form a pattern together, and each pattern is different from each other, thereby improving the recognizability of the preamble sequence even if a certain preamble symbol is interfered. Being destroyed, it is also ensured that a complete pattern may also exist in the preamble sequence so that the preamble sequence can be correctly identified.
  • each of the m consecutive OFDM symbols in the generated preamble sequence may constitute a single pattern, and the preamble sequence includes at least two patterns, and the patterns are different from each other, so that the anti-destructive power of the preamble sequence A large improvement is obtained, which can avoid the problem that the receiving end is difficult to correctly recognize the starting position of the leading sequence due to the interference in the NB-PLC system, thereby making it difficult to correctly synchronize the timing.
  • the anti-destructive power of the preamble sequence is improved by: each m OFDM symbols can form a pattern together, and each pattern is different from each other, thereby improving the recognizability of the preamble sequence even if a certain preamble symbol is interfered. Being destroyed, it is also ensured that a complete pattern may also exist in the preamble sequence so that the preamble sequence can be correctly identified.
  • the processor may be a central processing unit (“CPU"), and may be other general-purpose processors, digital signal processors (DSPs), and application specific integrated circuits (ASICs). ), off-the-shelf programmable gate arrays (FPGAs) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, and the like.
  • the general purpose processor may be a microprocessor or the processor or any conventional processor or the like.
  • the memory can include read only memory and random access memory, and provides instructions and numbers to the processor according to.
  • a portion of the memory may also include a non-volatile random access memory.
  • the memory can also store information of the device type.
  • embodiments of the present invention can be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or a combination of software and hardware. Moreover, the invention can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) including computer usable program code.
  • computer-usable storage media including but not limited to disk storage, CD-ROM, optical storage, etc.
  • the computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing device to operate in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture comprising the instruction device.
  • the apparatus implements the functions specified in one or more blocks of a flow or a flow and/or block diagram of the flowchart.
  • These computer program instructions can also be loaded onto a computer or other programmable data processing device such that a series of operational steps are performed on a computer or other programmable device to produce computer-implemented processing for execution on a computer or other programmable device.
  • the instructions provide steps for implementing the functions specified in one or more of the flow or in a block or blocks of a flow diagram.

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Abstract

本发明公开了一种前导序列生成方法和设备，用以避免由于NB-PLC系统中的干扰破坏前导序列而导致接收端难以正确定时同步的问题。方法包括：确定构成前导序列中的单个图样的正交频分复用OFDM符号的数目m，其中，m不小于2；根据所述m生成前导序列，使得生成的前导序列中时域上连续的每m个OFDM符号分别构成单个图样，且使得生成的前导序列至少包含两个图样，各图样彼此不同。本发明实施例还提供一种定时同步方法和设备。

Description

一种前导序列生成方法、定时同步方法和设备
本申请要求于2013年11月27日提交中国专利局、申请号为201310616599.7，发明名称为“一种前导序列生成方法、定时同步方法和设备”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本发明涉及通信技术领域，尤其涉及一种前导序列生成方法、定时同步方法和设备。
背景技术
同步是任何一个通信系统都需要解决的实际问题，没有准确的同步，就不可能进行可靠的数据传输，因此同步技术直接关系到整个通信系统的性能。
同步一般分为定时同步和频率同步。其中，针对定时同步而言，其包括粗同步和细同步，目的在于使得信号的接收端能够确定每个符号的起止时刻。为了能使接收端准确地找到发送端所发送的数据符号的开始部分，目前常用的技术手段是在数据符号前面添加一串前导序列(即Preamble，其包含的符号可称为前导符号)来指示该数据符号的到达。由于该前导序列对于接收端来说是已知的，因此接收端就可以利用已知的该前导序列，进行该前导序列和接收到的信号序列的相关性计算，得到用于表征该前导序列和接收到的信号序列之间的相关性大小的相关值。具体而言，接收端接收到前导序列时，其按照上述方式计算出的相关值就会出现明显的峰值，从而接收端就可以由此确定当前接收到的是前导序列，进而进行定时同步。
目前，窄带电力线通信(Narrow Band-Power Line Communication，NB-PLC)系统中采用的定时同步方案与上述方案类似，也是基于前导序列来实现。比如，按照国际电信联盟(International Telecommunications Union，ITU) 在其G.hnem物理层协议G.9955中对于物理帧结构的规定，可以采用如图1所示的前导序列来进行接收端信号的定时同步。
图1所示的该前导序列主要由前导符号S1和前导符号S2组成，其中，S1由8个承载了相同信息的正交频分复用(Orthogonal Frequency Division Multiplexing，OFDM)符号组成，若用S表示S1所包含的单个OFDM符号，则可将S1表示成：S1＝{S,S,S,S,S,S,S,S}；而S2仅包含一个OFDM符号，记为-S，即S2＝{-S}。图1中利用连续的多个OFDM符号来重复承载相同信息的主要目的是为了抵抗NB-PLC系统中恶劣的信道条件，以提高接收端正确接收前导符号的概率，进而提高NB-PLC系统的同步率。
在实际应用中，当接收端欲确定发送端所发送的数据符号的开始部分时，可以首先对接收到的信号序列进行延迟自相关，即计算连续接收到的每对OFDM符号长度的信号序列的延迟相关值，直至在一段时间内确定出的延迟相关值大于设定的个数时，确定有前导符号到达，即完成粗同步过程；进而接收端利用本地预存的符号S与完成粗同步过程后接收的信号序列进行滑动相关，当计算出本地预存的该S与接收到的信号序列的相关值出现一个负的峰值时，则判断检测到S2，从而就可以确定定时同步点，即完成细同步过程。
目前，NB-PLC系统主要工作在3-500kHz的频段，其信道主要由慢变的多径、有色噪声、窄带干扰、脉冲干扰、同步于工频的周期性噪声和异步于工频的周期性噪声组成。其中，同步于工频的脉冲干扰和异步于工频的脉冲干扰可以归为频域的窄带干扰和时域的突发脉冲干扰中。在NB-PLC系统的低频段信道中，频域的窄带干扰非常严重；同时，电力线上电器的不规范性而导致产生的强度比底噪高出10-15dB的时域突发脉冲干扰也会使得NB-PLC系统的信道条件变得异常恶劣。
上述干扰的存在，使得如图1所示的该前导序列容易受到破坏。比如图1中的S2就特别容易被突发脉冲干扰所淹没，进而导致定时同步难以完成。
发明内容
本发明实施例提供一种前导序列生成方法和设备，用以避免由于NB-PLC系统中的干扰破坏前导序列而导致接收端难以正确定时同步的问题。
本发明实施例还提供一种定时同步方法和设备。
本发明实施例采用以下技术方案：
第一方面，提供一种前导序列生成方法，包括：确定构成前导序列中的单个图样的正交频分复用OFDM符号的数目m，其中，m不小于2；根据所述m生成前导序列，使得生成的前导序列中时域上连续的每m个OFDM符号分别构成单个图样，且使得生成的前导序列至少包含两个图样，各图样彼此不同。
结合第一方面，在第一种可能的实现方式中，所述方法还包括：根据接收端所存储的前导符号与所述生成的前导序列所包含的各前导符号之间的相关值，为所述生成的前导序列包含的各图样分别确定图样标识。
结合第一方面或第一方面的第一种可能的实现方式，在第二种可能的实现方式中，采用下述方式确定m：
根据预先规定的组成所述生成的前导序列的OFDM符号的数目，以及所述数目与m的预设映射关系，确定m。
结合第一方面的第二种可能的实现方式，在第三种可能的实现方式中，所述预设映射关系包括：
2m-2≥L-m+1
其中，L为预先规定的组成所述生成的前导序列的OFDM符号的数目。
第二方面，提供一种定时同步方法，包括：接收端接收信号序列；所述信号序列的时域长度为单个正交频分复用OFDM符号的时域长度的整数倍，且不小于规定数目的单个OFDM符号的时域长度；接收端确定所述信号序列能够包含的各信号子序列分别与存储的用作前导符号的单个OFDM符号的相关值；其中，所述信号子序列所包含的信号点为时域上连续的多个信号点，且所 述信号子序列所包含的信号点的数目与存储的所述单个OFDM符号包含的信号点的数目N相同；接收端根据确定出的相关值，按照所述信号序列能够包含的各个信号子序列在时域上的排列顺序，依次不重复地选取确定出的相关值生成相关值集合，直至确定出的相关值被选取完毕；其中，每个相关值集合所包含的相关值的数目均等于N；接收端分别确定各相关值集合中的模值最大的相关值；接收端在判断出确定出的各相关值集合中的模值最大的相关值中存在m个相关值共同满足规定条件时，根据所述m个相关值以及预设的图样标识生成方式，生成图样标识；其中，所述m个相关值共同满足规定条件具体包括：按照信号子序列的接收顺序对所述m个相关值进行排序后，所述m个相关值中的相邻两个相关值分别对应的信号子序列在所述信号序列能够包含的所有信号子序列中的排列位置相差N；接收端在生成的图样标识与预先根据所述生成方式为所述前导序列所包含的图样确定的图样标识之一相同时，根据所述生成的图样标识所表示的图样在所述前导序列中所处的位置，确定所述前导序列的起始位置。
结合第二方面，在第一种可能的实现方式中，接收端根据所述m个相关值以及预设的图样标识生成方式，生成图样标识，具体包括：接收端根据所述m个相关值，以及预先设置的十进制数生成方式，确定作为生成的图样标识的一个十进制数。
第三方面，提供一种前导序列生成设备，包括：数目确定单元，用于确定构成前导序列中的单个图样的正交频分复用OFDM符号的数目m，其中，m不小于2；前导序列生成单元，用于根据数目确定单元确定的所述m生成前导序列，使得生成的前导序列中时域上连续的每m个OFDM符号分别构成单个图样，且使得生成的前导序列至少包含两个图样，各图样彼此不同。
结合第三方面，在第一种可能的实现方式中，所述设备还包括：标识确定单元，用于根据接收端所存储的前导符号与所述生成的前导序列所包含的各前 导符号之间的相关值，为所述生成的前导序列包含的各图样分别确定图样标识。
结合第三方面或第三方面的第一种可能的实现方式，在第二种可能的实现方式中，所述数目确定单元采用下述方式确定m：
根据预先规定的组成所述生成的前导序列的OFDM符号的数目，以及所述数目与m的预设映射关系，确定m。
结合第三方面的第二种可能的实现方式，在第三种可能的实现方式中，所述预设映射关系包括：
2m-2≥L-m+1
其中，L为预先规定的组成所述生成的前导序列的OFDM符号的数目。
第四方面，提供一种接收端设备，包括：
信号序列接收单元，用于接收信号序列；所述信号序列的时域长度为单个正交频分复用OFDM符号的时域长度的整数倍，且不小于规定数目的单个OFDM符号的时域长度；
第一相关值确定单元，用于确定所述信号序列能够包含的各信号子序列分别与存储的用作前导符号的单个OFDM符号的相关值；其中，所述信号子序列所包含的信号点为时域上连续的多个信号点，且所述信号子序列所包含的信号点的数目与存储的所述单个OFDM符号包含的信号点的数目N相同；
相关值选取单元，用于端根据确定出的相关值，按照所述信号序列能够包含的各个信号子序列在时域上的排列顺序，依次不重复地选取确定出的相关值生成相关值集合，直至确定出的相关值被选取完毕；其中，每个相关值集合所包含的相关值的数目均等于N；
第二相关值确定单元，用于分别确定各相关值集合中的模值最大的相关值；
图样标识生成单元，用于在判断出确定出的各相关值集合中的模值最大的相关值中存在m个相关值共同满足规定条件时，根据所述m个相关值以及预 设的图样标识生成方式，生成图样标识；其中，所述m个相关值共同满足规定条件具体包括：按照信号子序列的接收顺序对所述m个相关值进行排序后，所述m个相关值中的相邻两个相关值分别对应的信号子序列在所述信号序列能够包含的所有信号子序列中的排列位置相差N；
起始位置确定单元，用于在生成的图样标识与预先根据所述生成方式为所述前导序列所包含的图样确定的图样标识之一相同时，根据所述生成的图样标识所表示的图样在所述前导序列中所处的位置，确定所述前导序列的起始位置。
结合第四方面，在第一种可能的实现方式中，图样标识生成单元具体用于：
根据所述m个相关值，以及预先设置的十进制数生成方式，确定作为生成的图样标识的一个十进制数。
本发明实施例的有益效果如下：
由于本发明实施例中生成的前导序列中的时域上连续的每m个OFDM符号分别可以构成单个图样，且前导序列至少包含两个图样，各图样彼此不同，从而前导序列的抗破坏力得到较大提升，可以避免由于NB-PLC系统中的干扰破坏前导序列而导致接收端难以正确识别前导序列的起始位置，从而难以正确定时同步的问题。具体而言，前导序列的抗破坏力得到提升表现在：每m个OFDM符号均可以共同构成图样，且各图样彼此不同，从而提高了前导序列的可辨识度，即便某个前导符号受到干扰而被破坏，也可以保证前导序列中还可能存在完整的图样而使得前导序列能够被正确识别。
附图说明
图1为G.9955中规定的用于进行定时同步的前导序列的示意图；
图2为本发明实施例提供的一种前导序列的生成方法的实现流程示意图；
图3为本发明实施例中生成的一种前导序列的示意图；
图4为本发明实施例提供的一种定时同步方法的实现流程示意图；
图5为本发明实施例提供的方案在NB-PLC系统中的实现方式示意图；
图6为本发明实施例提供的一种前导序列的生成设备的结构示意图；
图7为本发明实施例提供的一种接收端设备的结构示意图；
图8为本发明实施例提供的另一种前导序列的生成设备的结构示意图；
图9为本发明实施例提供的另一种接收端设备的结构示意图。
具体实施方式
为了避免由于NB-PLC系统中的干扰破坏前导序列而导致接收端难以正确识别前导序列起始位置的问题，本发明实施例首先提供一种前导序列生成方法。
以下结合说明书附图对本发明的实施例进行说明，应当理解，此处所描述的实施例仅用于说明和解释本发明，并不用于限制本发明。并且在不冲突的情况下，本发明中的实施例及实施例中的特征可以互相结合。
如图2所示，为本发明实施例提供的一种前导序列生成方法的具体流程示意图，其主要包括下述步骤：
步骤21，确定构成前导序列中的单个图样的OFDM符号的数目m；
其中，m不小于2；“图样”是指前导序列中的由至少两个OFDM符号构成的符号序列。
比如，可以根据预先规定的组成生成的前导序列的OFDM符号的数目，以及该数目与m的预设映射关系，确定m。
具体而言，该预设映射关系可以但不限于如下式[1]所示：
2m-2≥L-m+1
其中，L为预先规定的组成生成的前导序列的OFDM符号的数目。
步骤22，根据m生成前导序列，使得生成的前导序列中时域上连续的每m个OFDM符号分别构成单个图样，且使得生成的前导序列至少包含两个图 样，各图样彼此不同。
本发明实施例提供的上述方法还可以进一步包括包括步骤：根据接收端所存储的前导符号与生成的前导序列所包含的各前导符号之间的相关值，为生成的前导序列包含的各图样分别确定图样标识。后文将详细介绍本发明实施例采用的图样标识生成方式，在此不再赘述。
采用本发明实施例提供的该前导序列生成方法，比如当预先规定的组成生成的前导序列的OFDM符号的数目为8时，可以计算出m可以等于3。m＝3时，通过执行步骤22而生成的一种前导序列如图3所示。图3所示的该前导序列一共可以包含互不相同的6个图样，其图样标识可以为如图3中的椭圆中的数字，分别为2～7。其中，图3中的任意椭圆均满足：其所对应的前导序列的图样的图样标识为该椭圆中的数字。比如包含有数字“2”的椭圆对应的图样为{-S,S,-S}，则该图样的图样标识为2。
需要说明的是，由于如图3所示的该前导序列中的前两个OFDM符号与出现在该前导序列之前的一个OFDM符号长度的噪声信号可能共同构成一个与该前导序列包含的图样类似的“伪图样”，且该“伪图样”的存在，可能会导致接收端错误地将其识别为前导序列中的图样，因此，本发明实施例中，可以为该伪图样分配一个不同于上述图样标识2～7的其他标识。考虑到出现在该前导序列的第一个OFDM符号之前的噪声信号有可能是S，也可能是-S，那么，本发明实施例中，可以为如图3所示的该前导序列中的前两个OFDM符号所构成的“伪图样”分配图样标识0和1。比如，为伪图样{-S,-S,-S}分配的图样标识可以为0，为伪图样{S,-S,-S}分配的标识可以为1；反之亦可。
由于本发明实施例中的前导序列中时域上连续的每m个OFDM符号分别构成单个图样，且前导序列至少包含两个图样，各图样彼此不同，从而前导序列的抗破坏力得到较大提升，可以避免由于NB-PLC系统中的干扰破坏前导序列而导致接收端难以正确识别前导序列的起始位置，从而难以正确定时同步的 问题。具体而言，前导序列的抗破坏力得到提升表现在：每m个OFDM符号均可以共同构成图样，且各图样彼此不同，从而提高了前导序列的可辨识度，即便某个前导符号受到干扰而被破坏，也可以保证前导序列中还可能存在完整的图样而使得前导序列能够被正确识别。
出于与该前导序列终止位置的确定方法相同的发明构思，本发明实施例还提供一种前导序列生成方法，该方法的具体实现流程示意图如图4所示，包括如下主要步骤：
步骤41，接收端接收信号序列；
其中，信号序列的时域长度为单个OFDM符号的时域长度的整数倍，且不小于规定数目的单个OFDM符号的时域长度。
这里所说的规定数目不小于m+1，m为预先确定的组成前导序列中的单个图样的正交频分复用OFDM符号的数目。其中，“图样”是指前导序列中的由至少两个OFDM符号构成的符号序列。
本发明实施例中，前导序列至少包含两个图样，且前导序列包含的图样彼此不同。比如图3所示，为本发明实施例中采用的一种前导序列的示意图。图3中假设m＝3，则该前导序列一共可以包含互不相同的6个图样，其图样标识可以为如图3中的椭圆中的数字，分别为2～7。其中，图3中的任意椭圆均满足：其所对应的前导序列的图样的图样标识为该椭圆中的数字。比如包含有数字“2”的椭圆对应的图样为{-S,S,-S}，则该图样的图样标识为2。
需要说明的是，由于如图3所示的该前导序列中的前两个OFDM符号与出现在该前导序列之前的一个OFDM符号长度的噪声信号可能共同构成一个与该前导序列包含的图样类似的“伪图样”，且该“伪图样”的存在，可能会导致接收端错误地将其识别为前导序列中的图样，因此，本发明实施例中，可以为该伪图样分配一个不同于上述图样标识2～7的其他标识。考虑到出现在该前导序列的第一个OFDM符号之前的噪声信号有可能是S，也可能是-S，那么， 本发明实施例中，可以为如图3所示的该前导序列中的前两个OFDM符号所构成的“伪图样”分配图样标识0和1。比如，为伪图样{-S,-S,-S}分配的图样标识可以为0，为伪图样{S,-S,-S}分配的标识可以为1；反之亦可。
本发明实施例中，m的一种确定方式可以如式[1]所示。
以图3为例，若组成该前导序列的OFDM符号的数目L为8，那么根据上式[1]，可计算出m≥3。
步骤42，确定信号序列能够包含的各信号子序列分别与存储的用作前导符号的单个OFDM符号的相关值；
其中，信号子序列所包含的信号点为时域上连续的多个信号点，且信号子序列所包含的信号点的数目与存储的用作前导符号的单个OFDM符号包含的信号点的数目N相同。
步骤43，根据确定出的相关值，按照信号序列能够包含的各个信号子序列在时域上的排列顺序，依次不重复地选取确定出的相关值生成相关值集合，直至确定出的相关值被选取完毕；
其中，每个上述相关值集合所包含的相关值的数目等于N。
步骤44，分别确定各相关值集合中的模值最大的相关值；
步骤45，在判断出确定出的各相关值集合中的模值最大的相关值中存在m个相关值共同满足规定条件时，根据该m个相关值以及预设的图样标识生成方式，生成图样标识；
本发明实施例中，该m个相关值共同满足规定条件具体包括：按照信号子序列的接收顺序对m个相关值进行排序后，m个相关值中的相邻两个相关值分别对应的信号子序列在信号序列能够包含的所有信号子序列中的排列位置相差N。
后文将详细介绍本发明实施例采用的预设的图样标识生成方式，在此不再赘述。
步骤46，当通过执行步骤45而生成的图样标识与预先根据预设的图样标识生成方式为前导序列所包含的图样确定的图样标识之一相同时，根据生成的图样标识所表示的图样在前导序列中所处的位置，确定前导序列的起始位置。从而根据该起始位置实现定时同步。
比如，以图3为例，当通过执行步骤43而生成的图样标识为“6”时，就可以确定该m个相关值对应的m个信号子序列是与前导序列中的图样{-S,S,S}相对应的。由该图样{-S,S,S}在如图3所示的该前导序列中所处的位置可知，在该m个信号子序列之后连续接收到的第二个OFDM符号即为前导序列的终止位置。而当通过执行步骤43而生成的图样标识为“0”时，根据其不同于前导序列所包含图样的图样标识，而是与“伪图样”的图样标识相同可知，接收到的该信号序列中包含的该m个信号子序列不属于前导序列，从而可以结束流程，或可以继续判断该信号序列能够包含的信号子序列对应的相关值中，是否还存在其他的m个共同满足上述规定条件的相关值；或可以继续接收其他信号序列，并判断继续接收到的其他信号序列能够包含的信号子序列对应的相关值中，是否存在m个共同满足上述规定条件的相关值。
以下举例说明如何实现步骤43～步骤45：
假设m＝3，且信号序列的时域长度等于4个OFDM符号的时域长度，那么，若进一步假设确定出的所有相关值记为{ρ1，ρ2，ρ3，...，ρ3N}，则按照步骤43，可以生成三个相关值集合，分别为{ρ1，ρ2，ρ3，...，ρN}、{ρN+1，ρN+2，ρN+3，...，ρ2N}以及{ρ2N+1，ρ2N+2，ρ2N+3，...，ρ3N}。
进一步地，可以分别确定相关值集合{ρ1，ρ2，ρ3，...，ρN}、{ρN+1，ρN+2，ρN+3，...，ρ2N}以及{ρ2N+1，ρ2N+2，ρ2N+3，...，ρ3N}中的模值最大的相关值。比如从这三个相关值集合中确定出的模值最大的相关值分别为ρλ1、ρλ2以及ρλ3。其中，λ1的取值范围为[1,N]，λ2的取值范围为[N+1,2N]，λ3的取值范围均为[2N+1,3N]。
然后，判断λ1、λ2和λ3是否满足：λ3-λ2＝N，λ2-λ1＝N，若判断结果为是， 则就可以根据该m个相关值以及预设的图样标识生成方式，生成图样标识；否则，则可以结束流程，或者，也可以根据本发明实施例提供的该定时同步方法，进一步对在接收到信号序列之后继续接收的其他信号序列进行类似处理。
需要说明的是，步骤45中根据m个相关值以及预先设置图样标识生成方式生成图样标识的具体实现方式可以但不限于包括：根据该m个相关值以及预先设置的十进制数生成方式，确定作为生成的图样标识的一个十进制数。
比如，当m＝3时，可以按照下述公式[2]，将该m个相关值转换成一个作为生成的图样标识的十进制数κ：
Figure PCTCN2014090319-appb-000001
需要说明的是，sgn(number)满足：若number大于0，则sgn(number)＝1；若number等于0，则sgn(number)＝0；若number小于0，则sgn(number)＝-1。
根据
Figure PCTCN2014090319-appb-000002
以及
Figure PCTCN2014090319-appb-000003
按照公式[2]可以计算出κ。该m个相关值与前导序列中的图样标识为κ的图样相匹配。
由本发明实施例提供的上述前导序列终止位置的确定方法可知，由于本发明实施例中的前导序列至少包含两个图样，且前导序列包含的图样互不相同，因此即便其中一个图样受到干扰而被破坏，也可以按照另一个图样来实现对前导序列的识别并准确定位出前导序列的起始位置。
具体而言，基于本发明实施例提供的该前导序列，本发明实施例可以在检测到存在m个相关值共同满足规定条件时，确定该m个相关值对应的m个信号子序列与前导序列中的一个图样相匹配，并按照预设的图样标识生成方法生成与该m个信号子序列相匹配的图样的图样标识，从而可以实现根据生成的图样标识所表示的图样在前导序列中所处的位置确定前导序列的起始位置，避免了由于NB-PLC系统中的干扰破坏前导序列而导致接收端难以正确识别前导序列的终止位置的问题。
以下结合实际，详细说明本发明实施例提供的上述方法在存在脉冲干扰等 严重影响信道环境的NB-PLC系统中的具体实现方式。
首先需要说明的是，在该具体实现方式中，假设前导序列包含8个OFDM符号，从而根据公式[1]，可确定m＝3，即由3个OFDM符号组成一个图样。
根据前导序列包含互不相同图样的准则，通过对组成前导序列的OFDM符号S和-S进行排列组合，可以得到如图3所示的前导序列。将该前导序列记为P，则有P＝{-S,-S,+S,-S,+S,+S,+S,-S}。其中，S可以为G.9955中规定的用作前导符号的OFDM符号。
本发明实施例中，若假设二进制数序列Vb＝[V1,V2,…,V8]，其中
Figure PCTCN2014090319-appb-000004
P(i)表示上述前导序列P中的第i个前导符号。那么，Vb中的每三个相邻二进制数转换形成的十进制数均不相同。若假设以Vd表示Vb中的每三个相邻二进制数转换形成的十进制数构成的十进制数序列，则可以按照与公式[2]类似的算法，计算出Vd＝[4，2，5，6，7，3]。其中，Vd中的十进制数即为如图3所示的前导序列中的各图样的图样标识。
基于如图3所示的该前导序列，以下说明该具体实施方式的实现流程。该实现流程的示意图如图5所示，包括下述步骤：
步骤51，接收机获得连续接收到的4个时域长度分别与OFDM符号的时域长度相同的信号子序列。
由于每个信号子序列所包含的信号点数均与用作前导符号的OFDM符号所包含的信号点数N相同，从而若将上述四个信号子序列构成的信号序列记为Y，那么有Y＝{y(1)，y(2)，y(3)，…，y(4N)}。
其中，Y所包含的信号点的个数为4N，若以y(q)表示Y中的序号为q的信号点，则q的取值范围为[1，4N]。
步骤52，接收机确定Y所能够包含的所有互不相同的信号子序列；
其中，确定出的任意信号子序列需满足：其包含时域上连续的N个信号点。
比如，可以按照滑动选取信号点的方式，依次选取Y中的信号点构成信号子序列，从而可以得到3N个信号子序列。若以Yk表示第k个信号子序列，那么有Yk＝{y(k)，y(k+1)，…，y(k+N)}，k的取值范围为[1，3N]。
步骤53，接收机利用本地预存储的一个作为前导符号的OFDM符号X＝{x(1)，x(2)，…，x(N)}与Yk(k∈[1，3N])进行滑动相关，即分别计算上述3N个信号子序列与X的相关值。
比如，可以采用下式[3]计算X与Yk的相关值ρk：
Figure PCTCN2014090319-appb-000005
步骤54，将得到的相关值构成的序列{ρ1，ρ2，ρ3，...，ρ3N}等分成3个由相关值构成的集合，即{ρ1，ρ2，ρ3，...，ρN}、{ρN+1，ρN+2，ρN+3，...，ρ2N}以及{ρ2N+1，ρ2N+2，ρ2N+3，...，ρ3N}，然后分别确定这三个相关值集合中模值最大的相关值。假设λ1表示序号为上述第一个相关值集合{ρ1，ρ2，ρ3，...，ρN}中模值最大的相关值的序号；假设λ2表示序号为上述第二个相关值集合{ρN+1，ρN+2，ρN+3，...，ρ2N}中的模值最大的相关值序号；λ3表示序号为上述第二个相关值集合{ρ2N+1，ρ2N+2，ρ2N+3，...，ρ3N}中的模值最大的相关值的序号，那么存在下式[4]～[6]：
λ1＝argmax|{ρ1,ρ2,...,ρN}|   [4]
λ2＝argmax|{ρN+1,ρN+2,...,ρ2N}|   [5]
λ3＝argmax|{ρ2N+1,ρ2N+2,...,ρ3N}|   [6]
步骤55，判断λ3-λ2与λ2-λ1是否均等于作为前导符号的一个OFDM符号所包含的信号点的数目N；若判断结果为是，则执行步骤56；否则，可以将信号序列Y中前x个信号点删除，并将原本位于信号序列Y之后的x个信号加入到Y中，即重新生成包含4N个信号点的新的信号序列Y，并对该新的信号序列Y执行上述步骤52以及后续的相应步骤。
其中x代表对信号点进行滑动采样的颗粒度，其越小则对于前导序列进行定位的精确度越高，但相应的耗时则会越久。
步骤56，将
Figure PCTCN2014090319-appb-000006
以及
Figure PCTCN2014090319-appb-000007
代入下式中，计算一个十进制数κ：
Figure PCTCN2014090319-appb-000008
步骤57，判断计算出的κ是否属于集合{2，3，4，5，6，7}，如果是，则执行步骤58，否则，则可以将信号序列Y中前x个信号点删除，并将原本位于信号序列Y之后的x个信号加入到Y中，即重新生成包含4N个信号点的新的信号序列Y，并对该新的信号序列Y执行上述步骤52以及后续的相应步骤；
步骤58，根据计算出的κ所表示的图样在如图3所示的前导序列中的位置，即可实现定时同步，流程结束。
上述具体实施方式被证明可以带来以下有益效果：
首先，由于接收端只需要检测到一个图样中的OFDM符号相关性未被破坏，即可完成定时同步，相对于传统前导序列的设计，大大提高了抵抗信道破坏的能力；
其次，不需要粗同步的门限阈值的设定，只需利用相关值的间隔检测和图样标识匹配的方法即可完成定时同步，故可以提升系统的同步率；
再次，由于接收端利用相关值间隔检测和图样标识匹配的方法进行定时同步，当信道质量较好的情况下，在接收到前几个OFDM符号即提前可完成定时同步，缩短定时同步时间，减少时延；
最后，本发明实施例提供的前导序列设计可扩展性强，不仅可以应用于存在脉冲干扰等因素的信道环境中，针对其它通信环境也可以进行应用。
出于与本发明实施例提供的前导序列生成方法相同的发明构思，本发明实施例还提供一种前导序列生成设备60。该前导序列生成设备60的具体结构示意图如图6所示，包括数目确定单元61和前导序列生成单元62。各单元的功能介绍如下：
数目确定单元61，用于确定构成前导序列中的单个图样的正交频分复用 OFDM符号的数目m，其中，m不小于2；
前导序列生成单元62，用于根据数目确定单元61确定的m生成前导序列，使得生成的前导序列中时域上连续的每m个OFDM符号分别构成单个图样，且使得生成的前导序列至少包含两个图样，各图样彼此不同。
可选的，本发明实施例提供的该前导序列生成设备60还可以进一步包括：标识确定单元，用于根据接收端所存储的前导符号与生成的前导序列所包含的各前导符号之间的相关值，为生成的前导序列包含的各图样分别确定图样标识。
可选的，数目确定单元61具体可以采用下述方式确定m：
根据预先规定的组成所述生成的前导序列的OFDM符号的数目，以及所述数目与m的预设映射关系，确定m。
可选的，上述预设映射关系可以但不限于包括：
2m-2≥L-m+1
其中，L为预先规定的组成所述生成的前导序列的OFDM符号的数目。
在本发明实施例中，生成的前导序列中的时域上连续的每m个OFDM符号分别可以构成单个图样，且前导序列至少包含两个图样，各图样彼此不同，从而前导序列的抗破坏力得到较大提升，可以避免由于NB-PLC系统中的干扰破坏前导序列而导致接收端难以正确识别前导序列的起始位置，从而难以正确定时同步的问题。具体而言，前导序列的抗破坏力得到提升表现在：每m个OFDM符号均可以共同构成图样，且各图样彼此不同，从而提高了前导序列的可辨识度，即便某个前导符号受到干扰而被破坏，也可以保证前导序列中还可能存在完整的图样而使得前导序列能够被正确识别。
出于与本发明实施例提供的定时同步方法相同的发明构思，本发明实施例还提供一种接收端设备70。该接收端设备70的具体结构示意图如图7所示，包括下述功能单元：
信号序列接收单元71，用于接收信号序列；该信号序列的时域长度为单 个正交频分复用OFDM符号的时域长度的整数倍，且不小于规定数目的单个OFDM符号的时域长度；
第一相关值确定单元72，用于确定该信号序列能够包含的各信号子序列分别与存储的用作前导符号的单个OFDM符号的相关值；其中，该信号子序列所包含的信号点为时域上连续的多个信号点，且该信号子序列所包含的信号点的数目与存储的用作前导符号的单个OFDM符号包含的信号点的数目N相同；
相关值选取单元73，用于根据确定出的相关值，按照该信号序列能够包含的各个信号子序列在时域上的排列顺序，依次不重复地选取确定出的相关值生成相关值集合，直至确定出的相关值被选取完毕；其中，每个相关值集合所包含的相关值的数目均等于N；
第二相关值确定单元74，用于分别确定各相关值集合中的模值最大的相关值；
图样标识生成单元75，用于在判断出确定出的各相关值集合中的模值最大的相关值中存在m个相关值共同满足规定条件时，根据该m个相关值以及预设的图样标识生成方式，生成图样标识；其中，该m个相关值共同满足规定条件具体包括：按照信号子序列的接收顺序对该m个相关值进行排序后，该m个相关值中的相邻两个相关值分别对应的信号子序列在该信号序列能够包含的所有信号子序列中的排列位置相差N；
起始位置确定单元76，用于在生成的图样标识与预先根据上述预设的图样标识生成方式为该前导序列所包含的图样确定的图样标识之一相同时，根据生成的图样标识所表示的图样在前导序列中所处的位置，确定前导序列的起始位置。
可选的，图样标识生成单元75具体可以用于：根据该m个相关值，以及预先设置的十进制数生成方式，确定作为生成的图样标识的一个十进制数。
在本发明实施例中，生成的前导序列中的时域上连续的每m个OFDM符号分别可以构成单个图样，且前导序列至少包含两个图样，各图样彼此不同，从而前导序列的抗破坏力得到较大提升，可以避免由于NB-PLC系统中的干扰破坏前导序列而导致接收端难以正确识别前导序列的起始位置，从而难以正确定时同步的问题。具体而言，前导序列的抗破坏力得到提升表现在：每m个OFDM符号均可以共同构成图样，且各图样彼此不同，从而提高了前导序列的可辨识度，即便某个前导符号受到干扰而被破坏，也可以保证前导序列中还可能存在完整的图样而使得前导序列能够被正确识别。
出于与本发明实施例提供的前导序列生成方法相同的发明构思，本发明实施例还提供另一种前导序列生成设备80，其具体结构示意图如图8所示，前导序列生成设备80包括：处理器81、存储器82和总线83，其中，处理器81和存储器82通过总线83相连，该存储器82用于存储指令，该处理器81通过该总线83调用该存储器82中存储的指令，用于：确定构成前导序列中的单个图样的OFDM符号的数目m，其中，m不小于2；以及根据m生成前导序列，使得生成的前导序列中时域上连续的每m个OFDM符号分别构成单个图样，且使得生成的前导序列至少包含两个图样，各图样彼此不同。
可选的，该处理器81还可以用于根据接收端所存储的前导符号与生成的前导序列所包含的各前导符号之间的相关值，为生成的前导序列包含的各图样分别确定图样标识。
在本发明实施例中，生成的前导序列中的时域上连续的每m个OFDM符号分别可以构成单个图样，且前导序列至少包含两个图样，各图样彼此不同，从而前导序列的抗破坏力得到较大提升，可以避免由于NB-PLC系统中的干扰破坏前导序列而导致接收端难以正确识别前导序列的起始位置，从而难以正确定时同步的问题。具体而言，前导序列的抗破坏力得到提升表现在：每m个OFDM符号均可以共同构成图样，且各图样彼此不同，从而提高了前导序列 的可辨识度，即便某个前导符号受到干扰而被破坏，也可以保证前导序列中还可能存在完整的图样而使得前导序列能够被正确识别。
出于与本发明实施例提供的定时同步方法相同的发明构思，本发明实施例还提供另一种接收端设备90，该设备的具体结构示意图如图9所示，包括：接收器91、处理器92和存储器93。接收器91，用于接收信号序列。
其中，信号序列的时域长度为单个OFDM符号的时域长度的整数倍，且不小于规定数目的单个OFDM符号的时域长度。
存储器93用于存储指令；处理器92通过调用存储器93中存储的指令，用于确定接收器91接收的该信号序列能够包含的各信号子序列分别与存储的用作前导符号的单个OFDM符号的相关值；根据确定出的相关值，按照该信号序列能够包含的各个信号子序列在时域上的排列顺序，依次不重复地选取确定出的相关值生成相关值集合，直至确定出的相关值被选取完毕；其中，每个相关值集合所包含的相关值的数目均等于N；分别确定各相关值集合中的模值最大的相关值；在判断出确定出的各相关值集合中的模值最大的相关值中存在m个相关值共同满足规定条件时，根据该m个相关值以及预设的图样标识生成方式，生成图样标识；在生成的图样标识与预先根据预设的图样标识生成方式为前导序列所包含的图样确定的图样标识之一相同时，根据生成的图样标识所表示的图样在前导序列中所处的位置，确定前导序列的起始位置。
其中：
信号子序列所包含的信号点为时域上连续的多个信号点，且信号子序列所包含的信号点的数目与存储的用作前导符号的单个OFDM符号包含的信号点的数目N相同；
m个相关值共同满足规定条件具体包括：按照信号子序列的接收顺序对该m个相关值进行排序后，该m个相关值中的相邻两个相关值分别对应的信号子序列在所述信号序列能够包含的所有信号子序列中的排列位置相差N。
可选的，处理器92根据m个相关值以及预设的图样标识生成方式生成图样标识，具体可以包括：处理器根据m个相关值，以及预先设置的十进制数生成方式，确定作为生成的图样标识的一个十进制数。
由于本发明实施例中的前导序列中时域上连续的每m个OFDM符号分别构成单个图样，且前导序列至少包含两个图样，各图样彼此不同，从而前导序列的抗破坏力得到较大提升，可以避免由于NB-PLC系统中的干扰破坏前导序列而导致接收端难以正确识别前导序列的起始位置，从而难以正确定时同步的问题。具体而言，前导序列的抗破坏力得到提升表现在：每m个OFDM符号均可以共同构成图样，且各图样彼此不同，从而提高了前导序列的可辨识度，即便某个前导符号受到干扰而被破坏，也可以保证前导序列中还可能存在完整的图样而使得前导序列能够被正确识别。
在本发明实施例中，生成的前导序列中的时域上连续的每m个OFDM符号分别可以构成单个图样，且前导序列至少包含两个图样，各图样彼此不同，从而前导序列的抗破坏力得到较大提升，可以避免由于NB-PLC系统中的干扰破坏前导序列而导致接收端难以正确识别前导序列的起始位置，从而难以正确定时同步的问题。具体而言，前导序列的抗破坏力得到提升表现在：每m个OFDM符号均可以共同构成图样，且各图样彼此不同，从而提高了前导序列的可辨识度，即便某个前导符号受到干扰而被破坏，也可以保证前导序列中还可能存在完整的图样而使得前导序列能够被正确识别。
应理解，在本发明实施例中，处理器可以是中央处理单元(Central Processing Unit，简称为“CPU”)，还可以是其他通用处理器、数字信号处理器(DSP)、专用集成电路(ASIC)、现成可编程门阵列(FPGA)或者其他可编程逻辑器件、分立门或者晶体管逻辑器件、分立硬件组件等。通用处理器可以是微处理器或者该处理器也可以是任何常规的处理器等。
存储器可以包括只读存储器和随机存取存储器，并向处理器提供指令和数 据。存储器的一部分还可以包括非易失性随机存取存储器。例如，存储器还可以存储设备类型的信息。
本领域内的技术人员应明白，本发明的实施例可提供为方法、系统、或计算机程序产品。因此，本发明可采用完全硬件实施例、完全软件实施例、或结合软件和硬件方面的实施例的形式。而且，本发明可采用在一个或多个其中包含有计算机可用程序代码的计算机可用存储介质(包括但不限于磁盘存储器、CD-ROM、光学存储器等)上实施的计算机程序产品的形式。
本发明是参照根据本发明实施例的方法、设备(系统)、和计算机程序产品的流程图和/或方框图来描述的。应理解可由计算机程序指令实现流程图和/或方框图中的每一流程和/或方框、以及流程图和/或方框图中的流程和/或方框的结合。可提供这些计算机程序指令到通用计算机、专用计算机、嵌入式处理机或其他可编程数据处理设备的处理器以产生一个机器，使得通过计算机或其他可编程数据处理设备的处理器执行的指令产生用于实现在流程图一个流程或多个流程和/或方框图一个方框或多个方框中指定的功能的装置。
这些计算机程序指令也可存储在能引导计算机或其他可编程数据处理设备以特定方式工作的计算机可读存储器中，使得存储在该计算机可读存储器中的指令产生包括指令装置的制造品，该指令装置实现在流程图一个流程或多个流程和/或方框图一个方框或多个方框中指定的功能。
这些计算机程序指令也可装载到计算机或其他可编程数据处理设备上，使得在计算机或其他可编程设备上执行一系列操作步骤以产生计算机实现的处理，从而在计算机或其他可编程设备上执行的指令提供用于实现在流程图一个流程或多个流程和/或方框图一个方框或多个方框中指定的功能的步骤。
尽管已描述了本发明的优选实施例，但本领域内的技术人员一旦得知了基本创造性概念，则可对这些实施例作出另外的变更和修改。所以，所附权利要求意欲解释为包括优选实施例以及落入本发明范围的所有变更和修改。
显然，本领域的技术人员可以对本发明进行各种改动和变型而不脱离本发明的精髓和范围。这样，倘若本发明的这些修改和变型属于本发明权利要求及其等同技术的范围之内，则本发明也意图包含这些改动和变型在内。

Claims (12)

  1. 一种前导序列生成方法，其特征在于，包括：
    确定构成前导序列中的单个图样的正交频分复用OFDM符号的数目m，其中，m不小于2；
    根据所述m生成前导序列，使得生成的前导序列中时域上连续的每m个OFDM符号分别构成单个图样，且使得生成的前导序列至少包含两个图样，各图样彼此不同。
  2. 如权利要求1所述的方法，其特征在于，所述方法还包括：
    根据接收端所存储的前导符号与所述生成的前导序列所包含的各前导符号之间的相关值，为所述生成的前导序列包含的各图样分别确定图样标识。
  3. 如权利要求1或2所述的方法，其特征在于，采用下述方式确定m：
    根据预先规定的组成所述生成的前导序列的OFDM符号的数目，以及所述数目与m的预设映射关系，确定m。
  4. 如权利要求3所述的方法，其特征在于，所述预设映射关系包括：
    2m-2≥L-m+1
    其中，L为预先规定的组成所述生成的前导序列的OFDM符号的数目。
  5. 一种定时同步方法，其特征在于，包括：
    接收端接收信号序列；所述信号序列的时域长度为单个正交频分复用OFDM符号的时域长度的整数倍，且不小于规定数目的单个OFDM符号的时域长度；
    接收端确定所述信号序列能够包含的各信号子序列分别与存储的用作前导符号的单个OFDM符号的相关值；其中，所述信号子序列所包含的信号点为时域上连续的多个信号点，且所述信号子序列所包含的信号点的数目与存储的所述单个OFDM符号包含的信号点的数目N相同；
    接收端根据确定出的相关值，按照所述信号序列能够包含的各个信号子序 列在时域上的排列顺序，依次不重复地选取确定出的相关值生成相关值集合，直至确定出的相关值被选取完毕；其中，每个相关值集合所包含的相关值的数目均等于N；
    接收端分别确定各相关值集合中的模值最大的相关值；
    接收端在判断出确定出的各相关值集合中的模值最大的相关值中存在m个相关值共同满足规定条件时，根据所述m个相关值以及预设的图样标识生成方式，生成图样标识；其中，所述m个相关值共同满足规定条件具体包括：按照信号子序列的接收顺序对所述m个相关值进行排序后，所述m个相关值中的相邻两个相关值分别对应的信号子序列在所述信号序列能够包含的所有信号子序列中的排列位置相差N；
    接收端在生成的图样标识与预先根据所述生成方式为所述前导序列所包含的图样确定的图样标识之一相同时，根据所述生成的图样标识所表示的图样在所述前导序列中所处的位置，确定所述前导序列的起始位置。
  6. 如权利要求5所述的定时同步方法，其特征在于，接收端根据所述m个相关值以及预设的图样标识生成方式，生成图样标识，具体包括：
    接收端根据所述m个相关值，以及预先设置的十进制数生成方式，确定作为生成的图样标识的一个十进制数。
  7. 一种前导序列生成设备，其特征在于，包括：
    数目确定单元，用于确定构成前导序列中的单个图样的正交频分复用OFDM符号的数目m，其中，m不小于2；
    前导序列生成单元，用于根据数目确定单元确定的所述m生成前导序列，使得生成的前导序列中时域上连续的每m个OFDM符号分别构成单个图样，且使得生成的前导序列至少包含两个图样，各图样彼此不同。
  8. 如权利要求7所述的设备，其特征在于，所述设备还包括：
    标识确定单元，用于根据接收端所存储的前导符号与所述生成的前导序列 所包含的各前导符号之间的相关值，为所述生成的前导序列包含的各图样分别确定图样标识。
  9. 如权利要求7或8任一所述的设备，其特征在于，所述数目确定单元采用下述方式确定m：
    根据预先规定的组成所述生成的前导序列的OFDM符号的数目，以及所述数目与m的预设映射关系，确定m。
  10. 如权利要求9所述的设备，其特征在于，所述预设映射关系包括：
    2m-2≥L-m+1
    其中，L为预先规定的组成所述生成的前导序列的OFDM符号的数目。
  11. 一种接收端设备，其特征在于，包括：
    信号序列接收单元，用于接收信号序列；所述信号序列的时域长度为单个正交频分复用OFDM符号的时域长度的整数倍，且不小于规定数目的单个OFDM符号的时域长度；
    第一相关值确定单元，用于确定所述信号序列能够包含的各信号子序列分别与存储的用作前导符号的单个OFDM符号的相关值；其中，所述信号子序列所包含的信号点为时域上连续的多个信号点，且所述信号子序列所包含的信号点的数目与存储的所述单个OFDM符号包含的信号点的数目N相同；
    相关值选取单元，用于根据确定出的相关值，按照所述信号序列能够包含的各个信号子序列在时域上的排列顺序，依次不重复地选取确定出的相关值生成相关值集合，直至确定出的相关值被选取完毕；其中，每个相关值集合所包含的相关值的数目均等于N；
    第二相关值确定单元，用于分别确定各相关值集合中的模值最大的相关值；
    图样标识生成单元，用于在判断出确定出的各相关值集合中的模值最大的相关值中存在m个相关值共同满足规定条件时，根据所述m个相关值以及预设的图样标识生成方式，生成图样标识；其中，所述m个相关值共同满足规 定条件具体包括：按照信号子序列的接收顺序对所述m个相关值进行排序后，所述m个相关值中的相邻两个相关值分别对应的信号子序列在所述信号序列能够包含的所有信号子序列中的排列位置相差N；
    起始位置确定单元，用于在生成的图样标识与预先根据所述生成方式为所述前导序列所包含的图样确定的图样标识之一相同时，根据所述生成的图样标识所表示的图样在所述前导序列中所处的位置，确定所述前导序列的起始位置。
  12. 如权利要求11所述的接收端设备，其特征在于，图样标识生成单元具体用于：
    根据所述m个相关值，以及预先设置的十进制数生成方式，确定作为生成的图样标识的一个十进制数。
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