CN106788958B - Signal synchronization method and system - Google Patents
Signal synchronization method and system Download PDFInfo
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- CN106788958B CN106788958B CN201510813375.4A CN201510813375A CN106788958B CN 106788958 B CN106788958 B CN 106788958B CN 201510813375 A CN201510813375 A CN 201510813375A CN 106788958 B CN106788958 B CN 106788958B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L7/00—Arrangements for synchronising receiver with transmitter
- H04L7/04—Speed or phase control by synchronisation signals
- H04L7/041—Speed or phase control by synchronisation signals using special codes as synchronising signal
- H04L7/042—Detectors therefor, e.g. correlators, state machines
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J13/00—Code division multiplex systems
- H04J13/0007—Code type
- H04J13/0055—ZCZ [zero correlation zone]
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J13/00—Code division multiplex systems
- H04J13/10—Code generation
- H04J13/14—Generation of codes with a zero correlation zone
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Abstract
The invention provides a signal synchronization method and a signal synchronization system. According to the method, a transmitter generates a short sequence and a long sequence according to the bandwidth of a preamble signal to be transmitted; and modulating a preamble signal sequentially comprising a plurality of repeated short sequences and at least one long sequence to a communication channel and transmitting the preamble signal. The receiver detects whether the signals of the communication satellite can be acquired or not and receives the preamble signals; if so, searching the end positions of each short sequence by using a search window, and performing coarse synchronization; if not, sliding a preset search window in a preset transmission time length, traversing the baseband signals received in the transmission time length, searching the end positions of the short sequences, and performing coarse synchronization based on the end positions of the short sequences; and then carrying out cross correlation on the received long sequence, and further carrying out signal synchronization based on the obtained cross correlation peak value. The invention solves the problems of inaccurate synchronization and large computation amount in the prior art.
Description
Technical Field
the present invention relates to the field of communications, and in particular, to a signal synchronization method and system.
Background
The synchronization technology is a key technology in a communication system and is a precondition for establishing a communication link. Especially for ad hoc networks, synchronization is the first step to be solved. Common synchronization methods are based on training sequences and blind synchronization schemes.
The Preamble synchronization scheme based on the 802.16e standard adopts three approximately same data components in time domain, which results in insufficient fine synchronization performance and complex relative operation.
And the scheme of blind search by using the cyclic prefix characteristic of the OFDM symbol has long search time in the initial synchronization process. Particularly, in the situation without GPS, the calculation amount is large, and the synchronization is easily affected by interference, resulting in unreliable synchronization.
Accordingly, there is a need for improvements in the art.
disclosure of Invention
In view of the above drawbacks of the prior art, an object of the present invention is to provide a signal synchronization method and system, which are used to solve the problems of inaccurate synchronization and large computation amount in the prior art.
To achieve the above and other related objects, the present invention provides a signal synchronization method for a transmitter, including: generating a short sequence and a long sequence according to the bandwidth of a preamble signal to be transmitted; and modulating a preamble signal sequentially comprising a plurality of repeated short sequences and at least one long sequence to a communication channel and transmitting the preamble signal.
preferably, the rootThe method for generating the short sequence according to the channel bandwidth of the preamble signal to be transmitted includes: inserting N into a preset first ZC sequence in a frequency domainP0-LenshortZC0, and converting the short sequence into a time domain sequence to obtain the short sequence; wherein N isp0For the length of the short sequence, LenshartZCIs a value associated with the bandwidth.
preferably, the generating the long sequence according to the channel bandwidth of the preamble signal to be transmitted includes: inserting N into a preset second ZC sequence in a frequency domainp1-LenshortZC0, converting the sequence into a time domain sequence, and adding identification information corresponding to a receiver in the time domain sequence to obtain the long sequence; wherein N isp1For the length of the long sequence, LenshartZCIs a value associated with the bandwidth.
In view of the above object, the present invention further provides a signal synchronization method for a receiver, including: detecting whether a signal of a communication satellite can be acquired or not, and receiving a baseband signal which is sent by a transmitter and contains a preamble signal; if yes, searching each short sequence ending position which accords with the preset short sequence repetition times and accords with the preset short sequence characteristics in the received baseband signal through a preset search window, and carrying out coarse synchronization with the transmitter based on each short sequence ending position; if not, sliding a preset search window in a preset transmission time length, traversing the baseband signals received in the transmission time length, searching each short sequence ending position which accords with the preset short sequence repetition times and the preset short sequence characteristics, and carrying out coarse synchronization with the transmitter based on each short sequence ending position; determining a long sequence in the preamble signal based on the obtained short sequence end position, and performing cross-correlation on the received long sequence and a preset long sequence; further signal synchronization with the transmitter is performed based on the obtained cross-correlation peak.
Preferably, when it is detected that the signal of the communication satellite is not available, the fine synchronization with the transmitter includes: adjusting a clock signal output by a crystal oscillator based on the determined fine sequence end position.
Preferably, the mode of sliding a preset search window within a preset transmission duration, traversing the baseband signal received within the transmission duration, and searching for each short sequence end position which conforms to the preset short sequence repetition times and conforms to the preset short sequence characteristics includes: sliding a preset search window in a preset transmission duration, and searching a plurality of short sequence end positions which accord with the characteristics of a preset short sequence; and screening the short sequence end positions of the preset short sequence repetition times from the searched short sequence end positions according to preset screening conditions.
preferably, the searching for the end position of each short sequence conforming to the preset short sequence feature and conforming to the preset short sequence repetition number includes: carrying out autocorrelation processing on the two baseband signals sliding in the search window, and obtaining a peak envelope waveform corresponding to the autocorrelation result; and selecting a short sequence end position corresponding to the peak envelope waveform conforming to the short sequence characteristics.
In view of the above, the present invention also provides a signal synchronization method, used in a system formed by a transmitter and a receiver, including: the transmitter transmits a preamble signal according to any one of the methods described above; the receiver receives the preamble signal transmitted by the transmitter and performs signal synchronization according to any one of the methods described above.
based on the above object, the present invention further provides a transmitter, comprising: a generating module, configured to generate a short sequence and a long sequence according to a bandwidth of a preamble signal to be transmitted; and the transmitting module is used for modulating a preamble signal which sequentially comprises a plurality of repeated short sequences and at least one long sequence to a communication channel and sending the preamble signal.
Preferably, the generating module is configured to insert N into a preset first ZC sequence in a frequency domainP0-LenshortZC0, and converting the short sequence into a time domain sequence to obtain the short sequence; wherein N isp0For the length of the short sequence, LenshartZCIs a value associated with the bandwidth.
Preferably, the generating module is configured to insert N into a preset second ZC sequence in a frequency domainp1-LenshortZC0, converting the sequence into a time domain sequence, and adding identification information corresponding to a receiver in the time domain sequence to obtain the long sequence; wherein N isp1For the length of the long sequence, LenshartZCIs a value associated with the bandwidth.
In view of the above object, the present invention also provides a receiver, including: the receiving module is used for detecting whether signals of a communication satellite can be acquired or not and receiving baseband signals which are sent by a transmitter and contain leading signals; if yes, executing a first coarse synchronization module; if not, executing a second coarse synchronization module; the first coarse synchronization module is used for searching each short sequence ending position which accords with the preset short sequence repetition times and accords with the preset short sequence characteristics in the received baseband signal through a preset search window, and performing coarse synchronization with the transmitter based on each short sequence ending position; the second coarse synchronization module is used for sliding a preset search window in a preset transmission time length, traversing the baseband signals received in the transmission time length, searching each short sequence ending position which accords with the preset short sequence repetition times and accords with the preset short sequence characteristics, and performing coarse synchronization with the transmitter based on each short sequence ending position; a fine synchronization module, configured to determine a long sequence in the preamble signal based on the obtained end position of the short sequence, and perform cross-correlation between the received long sequence and a preset long sequence; further signal synchronization with the transmitter is performed based on the obtained cross-correlation peak.
Preferably, when the signal of the communication satellite is detected to be unavailable, the fine synchronization module is further configured to adjust the clock signal output by the crystal oscillator based on the determined end position of the fine sequence.
Preferably, the second coarse synchronization module is further configured to: sliding a preset search window in a preset transmission duration, and searching a plurality of short sequence end positions which accord with the characteristics of a preset short sequence; and screening the short sequence end positions of the preset short sequence repetition times from the searched short sequence end positions according to preset screening conditions.
Preferably, the first coarse synchronization module and the second coarse synchronization module are configured to perform autocorrelation processing on two baseband signals that slide through the search window, and obtain a peak envelope waveform corresponding to the autocorrelation result; and selecting a short sequence end position corresponding to the peak envelope waveform conforming to the short sequence characteristics.
Based on the above object, the present invention further provides a signal synchronization system, comprising: a transmitter as claimed in any one of the above; and a receiver as claimed in any one of the above.
as described above, the signal synchronization method and system of the present invention have the following advantages: the transmitter generates a short sequence only according to the bandwidth, and generates a long sequence based on the bandwidth and the base station number, so that a signal with better autocorrelation can be obtained, and the receiver can conveniently identify the signal; the transmitter sends a plurality of repeated short sequences and a long sequence as a preamble signal to the receiver, the receiver can quickly perform coarse synchronization with the transmitter by using autocorrelation operation according to the repeatedly identified short sequence positions, and further performs signal synchronization with the transmitter by using cross-correlation operation with complex operation on the basis of the coarse synchronization, so that the synchronization speed and the synchronization reliability between the transmitter and the receiver are improved; in addition, the receiver selects different synchronization modes according to whether the satellite signal can be received, so that the calculation amount of synchronization is reduced for the receiver capable of receiving the satellite signal, meanwhile, for the receiver incapable of receiving the satellite signal, the position of a short sequence is accurately searched, the synchronization deviation is reduced, and an accurate synchronization clock is provided for subsequent signal processing; in addition, by adopting the ZC sequence, a more obvious autocorrelation envelope waveform can be provided, and a receiver can conveniently identify the position of a short sequence; particularly for a receiver which can not receive satellite signals, the crystal oscillator is adjusted during coarse synchronization, and the problem that a subsequent adjusting circuit can not be synchronized under the condition of large clock signal deviation can be solved.
Drawings
Fig. 1 is a flow chart of a signal synchronization method according to the present invention.
Fig. 2 is a schematic diagram of a signal synchronization system according to the present invention.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
As shown in fig. 1, the present invention provides a signal synchronization method. The signal synchronization method is mainly executed by a system formed by a transmitter and a receiver. Wherein the transmitter and the receiver are respectively located in different base stations, or respectively located in a base station and a mobile terminal. The base station and the mobile terminal can have the transmitter and the receiver at the same time, wherein the transmitter is used for transmitting the preamble signal to other base stations or mobile terminals, and the receiver is used for receiving the preamble signal of other base stations. The transmitter may be signal synchronized with a plurality of receivers by transmitting corresponding preamble signals.
Wherein, the preamble signal comprises a plurality of continuous repeated short sequences P0 and a long sequence P1 with a cyclic prefix CP. The transmitter transmits the generated preamble signal as follows in steps S11 and S12. Here, the transmitter may transmit the preamble signal at a timing or at a start time previously achieved with the receiver. For example, the transmitter transmits the preamble signal before transmitting paging information. The receiver performs signal synchronization based on the received preamble signal to accurately receive a subsequent signal with data as follows steps S21-S25. Here, the receiver may receive the preamble signal in a timed manner.
in step S11, the transmitter generates a short sequence and a long sequence according to the bandwidth of a preamble signal to be transmitted.
Specifically, the transmitter generates a short sequence P0 and a long sequence P1 according to the frequency band of the channel to be transmitted with the preamble signal and the signal bandwidth that can be transmitted by the channel. Wherein, the short sequence P0 and the long sequence P1 can be self-defined sequences with better autocorrelation property. Preferably, the transmitter generates the short sequence P0 and the long sequence P1 based on a ZC sequence and a bandwidth. The ZC sequences used by the transmitter to generate the short sequence P0 and the long sequence P1 may be the same or different.
Here, the transmitter inserts N into a pre-determined first ZC sequence in the frequency domainP0-LenshortZC0, and converting the short sequence into a time domain sequence to obtain the short sequence; wherein N isp0The length of the short sequence is, for example, 256 bits; lenshartZCIs a value associated with the bandwidth.
For example, the bandwidth and length Len are preset in the transmittershartZCTable 1 of (a):
TABLE 1
The transmitter selects a corresponding signal bandwidth according to a channel frequency band to be transmitted; meanwhile, a frequency domain first ZC sequence is preset in the transmitter, and is defined as:0≤m≤NZC-1
Here, q in the P0 sequence takes 1, and the transmitter transmits xq(m) interpolating 256-Len in the middle of the frequency domainshortZC0, after IFFT, x is obtainedm_p0(m) the sequence P0 is: p0(m) ═ xm_p0(m)0≤m≤255。
Meanwhile, the transmitter also generates a long sequence P1 based on the bandwidth. Here, the transmitter should also include identification information of the receiver (e.g., the number ID of the receiver) in the long sequence P1. Therefore, the transmitter inserts N into the preset second ZC sequence in the frequency domainp1-LenshortZC0, converting the sequence into a time domain sequence, and adding identification information corresponding to a receiver in the time domain sequence to obtain the long sequence; wherein N isp1For the length of the long sequence, LenshartZCIs a value related to the bandwidth。
Here, the generation of said P1 is similar to P0, with q values see Table 2 below, the transmitter interpolates 512-Len among the second ZC sequenceshortZC0, then, the interpolated second ZC sequence is processed by IFFT to obtain xm_p1(n), the sequence of P1 is: p1(n) ═ xm_p1(n)0≤n≤511。
TABLE 2 values of q in the P1 sequence
Take the example that the transmitter can connect 64 receivers simultaneously:
PrmRootTab[64]＝{3,4,5,6,7,9,10,11,14,15,16,20,22,24,25,26,28,32,34,36,37,38,40,41,42,43,44,46,47,48,49,50,
60,61,62,63,64,66,67,68,69,72,75,77,78,80,86,87,88,89,90,93,96,97,99,102,103,106,108,109,113,114,118,120}；
The transmitter combines the generated cyclic prefixes CP of the three P0, P1 and the long sequence P1 into a preamble signal, and performs step S12.
In step S12, the transmitter modulates a preamble signal, which includes a plurality of repeated short sequences and at least one long sequence in this order, into a communication channel and transmits the modulated preamble signal. For example, the preamble signal includes a plurality of repeated short sequences, cyclic prefixes of the long sequences, and the long sequences in this order.
and the transmitter modulates the baseband signal containing the leading signal to a channel frequency band corresponding to the bandwidth and transmits the baseband signal through a transmitting antenna.
In step S21, the receiver detects whether the signal of the communication satellite can be acquired before receiving the preamble signal.
In this case, the receiver uses the clock signal of the receiving communication satellite (e.g., positioning satellite) to adjust its own crystal clock to achieve clock synchronization with the corresponding satellite.
When the receiver can receive the signal of the communication satellite, executing step S22; otherwise, step S23 is executed.
In step S22, the receiver searches each short sequence end position corresponding to a preset short sequence repetition number and corresponding to a preset short sequence characteristic from the received baseband signal through a preset search window, and performs coarse synchronization with the transmitter based on each short sequence end position.
Specifically, the receiver sequentially passes the received baseband signal through the search window, and matches the baseband signal in the search window according to a preset short sequence feature, wherein the receiver can obtain a corresponding short sequence end position each time matching is successful. And when the successful matching times reach the short sequence repetition times, the receiver determines the end position of the last short sequence in the preamble sequence. The receiver verifies whether the end position of the last short sequence is correct or not according to the comparison result of the length between the determined end positions of the adjacent short sequences and the length of the baseband signal corresponding to the short sequence in the preset short sequence characteristics; if the comparison result is within the preset error range, processing such as phase tracking and the like is carried out on the clock signal output by the crystal oscillator of the transmitter according to the end position of the last short sequence so as to achieve the purpose of synchronizing with the transmitter; otherwise, continuing to match. The synchronization at this time is coarse synchronization, and the receiver further performs step S24.
Preferably, the searching for the end position of each short sequence conforming to the preset short sequence feature and conforming to the preset short sequence repetition number comprises the following steps: (none are shown in the drawings)
In step S221, the receiver performs autocorrelation processing on the two baseband signals sliding through the search window, and obtains a peak envelope waveform corresponding to the autocorrelation result.
In step S222, the receiver selects a short sequence end position corresponding to a peak envelope waveform that matches the short sequence feature.
Here, the short sequence features include, but are not limited to: a peak envelope waveform corresponding to the autocorrelation result, an average peak value and an average valley value in the peak envelope waveform, a waveform threshold corresponding to the end position of the short sequence, and the like.
Specifically, the receiver performs autocorrelation operation on two adjacent groups of discrete baseband signals in the sliding search window, and obtains a peak envelope waveform corresponding to the autocorrelation result. And the receiver selects a waveform consistent with the waveform from all the obtained peak envelope waveforms according to the characteristic peak envelope waveforms in the preset short sequence characteristics. Then, the baseband signal at the position corresponding to the waveform threshold in the selected waveform falling edge is determined as the end position of a short sequence. By analogy, the receiver obtains the end positions of the short sequences corresponding to the repetition times of the preset short sequences. After coarse synchronization with the transmitter based on each of the short sequence end positions, the receiver performs step S24.
In step S23, the receiver slides a preset search window within a preset transmission duration, traverses the baseband signals received within the transmission duration, searches for short sequence end positions corresponding to preset short sequence repetition times and corresponding to preset short sequence characteristics, and performs coarse synchronization with the transmitter based on the short sequence end positions.
Here, unlike step S22, the receiver divides the received baseband signal by a preset transmission duration, and slides a preset search window within each transmission duration to traverse the received baseband signal within the transmission duration. The manner in which the receiver slides the search window within each transmission duration to search for the end position of each short sequence corresponding to the preset short sequence feature and corresponding to the preset short sequence repetition number is the same as or similar to step S22, and will not be described in detail herein.
the receiver performs coarse synchronization with the transmitter based on the end position of each short sequence in the same or similar manner as step S22, and is not described in detail herein.
In step S24, the receiver determines a long sequence in the preamble signal based on the obtained short sequence end position, and cross-correlates the received long sequence with a preset long sequence.
Specifically, the receiver uses the next frame of the end position of the last short sequence as the start position of the long sequence, and performs a cross-correlation operation on the received long sequence and a preset long sequence. Preferably, a cyclic prefix CP of the long sequence is also included between the short sequence and the long sequence in the preamble signal, the receiver performs a CP removal operation on the preamble signal according to a preset CP length, uses the baseband signal after the CP removal as an initial position of the long sequence in the preamble signal, performs a cross-correlation operation on the baseband signal and the preset long sequence, and obtains an envelope waveform formed by a cross-correlation peak.
In step S25, the receiver further synchronizes signal with the transmitter based on the obtained cross-correlation peak.
Specifically, the receiver judges whether the envelope waveform of the obtained cross-correlation peak value is larger than a preset envelope waveform characteristic; if yes, determining the baseband signal corresponding to the maximum peak value as the end position of the long sequence, and further adjusting the signal synchronization with the transmitter according to the obtained end position of the long sequence; if not, sliding the baseband signal, taking the slid baseband signal as a start position of the long sequence, and repeatedly executing the step of performing cross-correlation between the received long sequence and the preset long sequence in step S24.
Preferably, when the receiver determines that there are multiple cross-correlation peaks, the fine synchronization module selects a long sequence end position from the multiple cross-correlation peaks according to a preset screening rule, and performs signal synchronization with the transmitter at the selected long sequence end position. For example, the receiver sorts the multiple cross-correlation peaks, and selects the position with the largest cross-correlation peak as the end position of the long sequence. The receiver then performs signal synchronization based on the determined long sequence end position.
If the preamble signal contains a plurality of long sequences, the receiver may further determine an end position of a last long sequence according to a length between end positions of the long sequences corresponding to cross-correlation peaks of the plurality of long sequences, and adjust a phase-locked circuit, a frequency divider, and the like based on the determined end position to achieve signal synchronization with the transmitter.
Here, when the receiver fails to acquire the signal of the satellite, fine synchronization with the transmitter is also performed based on the long sequence end position. Specifically, the receiver adjusts the clock signal output by the crystal oscillator based on the determined long sequence end position. For example, the receiver delays/advances the phase of the clock signal output by the internal crystal oscillator according to the determined end position of the long sequence.
As shown in fig. 2, the present invention provides a signal synchronization system. The signal synchronization system comprises a transmitter 1 and a receiver 2. Wherein the transmitter 1 and the receiver 2 are respectively located in different base stations, or respectively located in a base station and a mobile terminal. The base station and the mobile terminal may have the transmitter 1 and the receiver 2 at the same time, wherein the transmitter 1 is configured to transmit a preamble to another base station or the mobile terminal, and the receiver 2 is configured to receive the preamble of another base station. The transmitter 1 may perform signal synchronization with the plurality of receivers 2 by transmitting corresponding preamble signals.
Wherein, the preamble signal comprises a plurality of continuous repeated short sequences P0 and a long sequence P1 with a cyclic prefix CP. To construct the signal synchronization system of the present invention, the transmitter 1 includes: a generating module 11 and a transmitting module 12. The receiver 2 includes: a receiving module 21, a first coarse synchronization module 22, a second coarse synchronization module 23, and a fine synchronization module 24.
here, the transmitting module 12 may transmit the preamble signal at a timing, or may transmit the preamble signal at a start time previously achieved with the receiver 2. For example, the transmitting module 12 transmits the preamble signal before transmitting paging information. The modules in the receiver 2 perform signal synchronization based on the received preamble signal in order to accurately receive the subsequent data-carrying signal.
The generating module 11 is configured to generate a short sequence and a long sequence according to a bandwidth of a preamble signal to be transmitted.
Specifically, the generating module 11 generates a short sequence P0 and a long sequence P1 according to a channel frequency band of the preamble signal to be transmitted and a signal bandwidth that can be transmitted by the channel. Wherein, the short sequence P0 and the long sequence P1 can be self-defined sequences with better autocorrelation property. Preferably, the generating module 11 generates the short sequence P0 and the long sequence P1 based on the ZC sequence and the bandwidth. Note that the ZC sequences used by the generation module 11 to generate the short sequence P0 and the long sequence P1 may be the same or different.
Here, the generating module 11 inserts N into the preset first ZC sequence in the frequency domainP0-LenshortZC0, and converting the short sequence into a time domain sequence to obtain the short sequence; wherein N isp0The length of the short sequence is, for example, 256 bits; lenshartZCis a value associated with the bandwidth.
For example, the bandwidth and length Len are preset in the generating module 11shartZCTable 3 of (a):
TABLE 3
The generating module 11 selects a corresponding signal bandwidth according to a channel frequency band to be transmitted; meanwhile, the generating module 11 is preset with a frequency domain first ZC sequence, which is defined as:0≤m≤NZC-1
Here, q in the P0 sequence is 1, and the generating module 11 generates xq(m) interpolating 256-Len in the middle of the frequency domainshortZC0, after IFFT, x is obtainedm_p0(m) the sequence P0 is: p0(m) ═ xm_p0(m)0≤m≤255。
meanwhile, the generating module 11 further generates a long sequence P1 based on the bandwidth. Here, the generating module 11 should further include identification information of the receiver 2 (e.g. the number ID of the receiver 2) in the long sequence P1. Therefore, the generating module 11 inserts N into the preset second ZC sequence in the frequency domainp1-LenshortZC0, and converting into a time domain sequence, and adding identification information corresponding to the receiver 2 in the time domain sequence,Obtaining the long sequence; wherein N isp1For the length of the long sequence, LenshartZCis a value associated with the bandwidth.
Here, the generation of said P1 is similar to P0, with q values as seen in Table 4 below, and said generation module 11 interpolates 512-Len between the second ZC sequenceshortZC0, then, the interpolated second ZC sequence is processed by IFFT to obtain xm_p1(n), the sequence of P1 is: p1(n) ═ xm_p1(n)0≤n≤511。
TABLE 4 values of q in the P1 sequence
Taking the example that the generating module 11 can be connected to 64 receivers 2 simultaneously:
PrmRootTab[64]＝{3,4,5,6,7,9,10,11,14,15,16,20,22,24,25,26,28,32,34,36,37,38,40,41,42,43,44,46,47,48,49,50,
60,61,62,63,64,66,67,68,69,72,75,77,78,80,86,87,88,89,90,93,96,97,99,102,103,106,108,109,113,114,118,120}；
The generating module 11 combines the generated cyclic prefixes CP of the three P0, P1 and the long sequence P1 into a preamble signal, and executes the transmitting module 12.
the transmitting module 12 is configured to modulate a preamble signal, which sequentially includes a plurality of repeated short sequences and at least one long sequence, into a communication channel and transmit the modulated preamble signal. For example, the preamble signal includes a plurality of repeated short sequences, cyclic prefixes of the long sequences, and the long sequences in this order.
The transmitting module 12 modulates the baseband signal including the preamble signal to a channel frequency band corresponding to the bandwidth based on a preset starting condition at regular time, and transmits the baseband signal through a transmitting antenna.
Corresponding to the number of the receiver 2 in the long sequence, the receiving module 21 in the corresponding receiver 2 detects whether the signal of the communication satellite can be acquired before receiving the preamble signal.
Here, the receiving module 21 includes a satellite positioning module, an antenna matrix, a signal down-conversion circuit, and the like.
The receiving module 21 adjusts its own crystal oscillator clock by using a clock signal of a receiving communication satellite (e.g., a positioning satellite) to achieve clock synchronization with the corresponding satellite.
When the receiving module 21 can receive the signals of the communication satellite, driving a first coarse synchronization module 22; otherwise, the second coarse synchronization module 23 is driven.
the first coarse synchronization module 22 is configured to search, through a preset search window, each short sequence end position that corresponds to a preset short sequence repetition number and corresponds to a preset short sequence feature in the received baseband signal, and perform coarse synchronization with the transmitter 1 based on each short sequence end position.
Specifically, the first coarse synchronization module 22 sequentially passes the received baseband signal through the search window, and matches the baseband signal in the search window according to a preset short sequence feature, where each time matching is successful, the first coarse synchronization module 22 can obtain a corresponding short sequence end position. When the number of times of successful matching reaches the number of times of short sequence repetition, the first coarse synchronization module 22 determines the end position of the last short sequence in the preamble sequence. The first coarse synchronization module 22 verifies whether the end position of the last short sequence is correct according to the comparison result between the determined length between the end positions of the adjacent short sequences and the length of the baseband signal corresponding to the short sequence in the preset short sequence characteristics; if the comparison result is within the preset error range, processing such as phase tracking and the like is carried out on the clock signal output by the crystal oscillator of the transmitter according to the end position of the last short sequence so as to achieve the purpose of synchronizing with the transmitter 1; otherwise, continuing to match. The synchronization at this time is a coarse synchronization, and the first coarse synchronization module 22 further drives the fine synchronization module 24.
Preferably, the searching for the end position of each short sequence conforming to the preset short sequence feature and conforming to the preset short sequence repetition number comprises the following steps:
The first coarse synchronization module 22 performs autocorrelation processing on the two baseband signals sliding through the search window, and obtains a peak envelope waveform corresponding to the autocorrelation result.
the first coarse synchronization module 22 selects a short sequence end position corresponding to the peak envelope waveform that meets the short sequence characteristics.
Here, the short sequence features include, but are not limited to: a peak envelope waveform corresponding to the autocorrelation result, an average peak value and an average valley value in the peak envelope waveform, a waveform threshold corresponding to the end position of the short sequence, and the like.
Specifically, the first coarse synchronization module 22 performs autocorrelation operation on two adjacent groups of discrete baseband signals in the sliding search window, and obtains a peak envelope waveform corresponding to the autocorrelation result. The first coarse synchronization module 22 selects a waveform with a waveform matching with each other from the obtained peak envelope waveforms according to the characteristic peak envelope waveforms in the preset short sequence characteristics. Then, the baseband signal at the position corresponding to the waveform threshold in the selected waveform falling edge is determined as the end position of a short sequence. By analogy, the first coarse synchronization module 22 obtains the end positions of each short sequence corresponding to the repetition times of the preset short sequence. After performing coarse synchronization with the transmitter 1 based on each of the short sequence end positions, the first coarse synchronization module 22 drives a fine synchronization module 24.
The second coarse synchronization module 23 is configured to slide a preset search window within a preset transmission duration, traverse the baseband signal received within the transmission duration, search each short sequence end position that corresponds to a preset short sequence repetition number and corresponds to a preset short sequence feature, and perform coarse synchronization with the transmitter 1 based on each short sequence end position.
Here, unlike the first coarse synchronization module 22, the second coarse synchronization module 23 divides the received baseband signal according to a preset transmission duration, and slides a preset search window within each transmission duration to traverse the received baseband signal within the transmission duration. The manner of sliding the search window by the second coarse synchronization module 23 within each transmission duration to search for the end positions of short sequences corresponding to the preset short sequence characteristics and corresponding to the preset short sequence repetition times is the same as or similar to that of the first coarse synchronization module 22, and will not be described in detail herein.
The second coarse synchronization module 23 performs coarse synchronization with the transmitter 1 based on the end position of each short sequence in the same or similar manner as the first coarse synchronization module 22, and is not described in detail herein.
The fine synchronization module 24 is configured to determine a long sequence in the preamble signal based on the obtained end position of the short sequence, and perform cross-correlation between the received long sequence and a preset long sequence; and further signal synchronized with the transmitter 1 based on the resulting cross-correlation peak.
Specifically, the fine synchronization module 24 uses the next frame of the end position of the last short sequence as the start position of the long sequence, and performs a cross-correlation operation on the received long sequence and a preset long sequence. Preferably, if a cyclic prefix CP of the long sequence is further included between the short sequence and the long sequence in the preamble signal, the fine synchronization module 24 performs a CP removal operation on the preamble signal according to a preset CP length, uses the baseband signal after the CP removal as a start position of the long sequence in the preamble signal, performs a cross-correlation operation on the baseband signal and the preset long sequence, and obtains an envelope waveform formed by a cross-correlation peak.
Then, the fine synchronization module 24 determines whether the obtained envelope waveform of the cross-correlation peak is larger than a preset envelope waveform characteristic; if yes, determining the baseband signal corresponding to the maximum peak value as the end position of the long sequence, and further adjusting the signal synchronization with the transmitter 1 according to the obtained end position of the long sequence; if not, sliding the baseband signal, taking the slid baseband signal as the initial position of the long sequence, and repeatedly performing cross-correlation on the received long sequence and a preset long sequence.
Preferably, when there are a plurality of cross-correlation peaks determined by the fine synchronization module 24, the fine synchronization module 24 selects a long sequence end position from the cross-correlation peaks according to a preset filtering rule, and performs signal synchronization with the transmitter 1 at the selected long sequence end position. For example, the fine synchronization module 24 sequences a plurality of cross-correlation peaks, and selects a position with the largest cross-correlation peak as an end position of the long sequence. The fine synchronization module 24 then performs signal synchronization based on the determined long sequence end position.
If the preamble signal includes a plurality of long sequences, the fine synchronization module 24 may further determine an end position of a last long sequence according to a length between end positions of the long sequences corresponding to cross-correlation peaks of the plurality of long sequences, and adjust a phase-locked circuit, a frequency divider, and the like based on the determined end position, so as to implement signal synchronization with the transmitter 1.
here, when the receiving module 21 fails to acquire the signal of the satellite, the fine synchronization module 24 performs fine synchronization with the transmitter 1 based on the long sequence end position. Specifically, the fine synchronization module 24 adjusts the clock signal output by the crystal oscillator based on the determined end position of the short sequence. For example, the fine synchronization module 24 delays/advances the phase of the clock signal output by the internal crystal oscillator according to the determined end position of the last long sequence.
In summary, the transmitter in the invention generates the short sequence only according to the bandwidth, and generates the long sequence according to the bandwidth and the base station number, so that a signal with better autocorrelation can be obtained, and the receiver can conveniently identify the signal; the transmitter sends a plurality of repeated short sequences and a long sequence as a preamble signal to the receiver, the receiver can quickly perform coarse synchronization with the transmitter by using autocorrelation operation according to the repeatedly identified short sequence positions, and further performs signal synchronization with the transmitter by using cross-correlation operation with complex operation on the basis of the coarse synchronization, so that the synchronization speed between the transmitter and the receiver is improved; in addition, the receiver selects different synchronization modes according to whether the satellite signal can be received, so that the calculation amount of synchronization is reduced for the receiver capable of receiving the satellite signal, meanwhile, for the receiver incapable of receiving the satellite signal, the position of a short sequence is accurately searched, the synchronization deviation is reduced, and an accurate synchronization clock is provided for subsequent signal processing; in addition, by adopting the ZC sequence, a more obvious autocorrelation envelope waveform can be provided, and a receiver can conveniently identify the position of a short sequence; particularly for a receiver which can not receive satellite signals, the crystal oscillator is adjusted during coarse synchronization, and the problem that a subsequent adjusting circuit can not be synchronized under the condition of large clock signal deviation can be solved. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (16)
1. A signal synchronization method for a transmitter, comprising:
Generating a short sequence according to the bandwidth of a preamble signal to be transmitted, and generating a long sequence according to the bandwidth and the base station number;
And modulating a preamble signal sequentially comprising a plurality of repeated short sequences and at least one long sequence to a communication channel and transmitting the preamble signal.
2. The signal synchronization method of claim 1, wherein the generating the short sequence according to the channel bandwidth of the preamble signal to be transmitted comprises:
Inserting N into a preset first ZC sequence in a frequency domainP0-LenshortZC0, and converting the short sequence into a time domain sequence to obtain the short sequence; wherein N isp0for the length of the short sequence, LenshartZCis a value associated with the bandwidth.
3. the signal synchronization method of claim 1, wherein the generating the long sequence according to the channel bandwidth and the base station number of the preamble signal to be transmitted comprises:
Inserting N into a preset second ZC sequence in a frequency domainp1-LenshortZC0, converting the sequence into a time domain sequence, and adding identification information corresponding to a receiver in the time domain sequence to obtain the long sequence; wherein N isp1For the length of the long sequence, LenshartZCis a value associated with the bandwidth.
4. A signal synchronization method for a receiver, comprising:
detecting whether a signal of a communication satellite can be acquired or not, and receiving a baseband signal which is sent by a transmitter and contains a preamble signal;
If yes, searching each short sequence ending position which accords with the preset short sequence repetition times and accords with the preset short sequence characteristics in the received baseband signal through a preset search window, and carrying out coarse synchronization with the transmitter based on each short sequence ending position;
If not, sliding a preset search window in a preset transmission time length, traversing the baseband signals received in the transmission time length, searching each short sequence ending position which accords with the preset short sequence repetition times and the preset short sequence characteristics, and carrying out coarse synchronization with the transmitter based on each short sequence ending position;
Determining a long sequence in the preamble signal based on the obtained short sequence end position, and performing cross-correlation on the received long sequence and a preset long sequence, wherein the short sequence is generated according to the bandwidth of the preamble signal sent by the transmitter, and the long sequence is generated according to the bandwidth and the base station number;
Further signal synchronization with the transmitter is performed based on the obtained cross-correlation peak.
5. The signal synchronization method of claim 4, wherein when it is detected that a signal of a communication satellite is not available, the fine synchronization with the transmitter comprises:
And adjusting the clock signal output by the crystal oscillator based on the determined long sequence end position.
6. The signal synchronization method according to claim 4, wherein the manner of sliding a preset search window within a preset transmission duration, traversing the baseband signals received within the transmission duration, and searching for the end positions of each short sequence corresponding to the preset short sequence characteristics and corresponding to the preset short sequence repetition times comprises:
Sliding a preset search window in a preset transmission duration, and searching a plurality of short sequence end positions which accord with the characteristics of a preset short sequence;
And screening the short sequence end positions of the preset short sequence repetition times from the searched short sequence end positions according to preset screening conditions.
7. The signal synchronization method according to claim 4 or 6, wherein the searching for the end position of each short sequence according to the preset short sequence feature and corresponding to the preset short sequence repetition number comprises:
Carrying out autocorrelation processing on the two baseband signals sliding in the search window, and obtaining a peak envelope waveform corresponding to the autocorrelation result;
And selecting a short sequence end position corresponding to the peak envelope waveform conforming to the short sequence characteristics.
8. A signal synchronization method for use in a system comprising a transmitter and a receiver, comprising:
The transmitter transmitting a preamble signal according to the method of any one of claims 1-3;
The receiver receives the preamble signal transmitted by the transmitter and performs signal synchronization according to the method of any of claims 4-7.
9. A transmitter, comprising:
A generating module, configured to generate a short sequence according to a bandwidth of a preamble signal to be sent, and generate a long sequence according to the bandwidth and a base station number;
And the transmitting module is used for modulating a preamble signal which sequentially comprises a plurality of repeated short sequences and at least one long sequence to a communication channel and sending the preamble signal.
10. The transmitter of claim 9, wherein the generating module is configured to insert N into the pre-defined first ZC sequence in the frequency domainP0-LenshortZC0, and converting the short sequence into a time domain sequence to obtain the short sequence; wherein N isp0For the length of the short sequence, LenshartZCIs a value associated with the bandwidth.
11. The transmitter of claim 9, wherein the generating module is configured to insert N into the predetermined second ZC sequence in the frequency domainp1-LenshortZC0, converting the sequence into a time domain sequence, and adding identification information corresponding to a receiver in the time domain sequence to obtain the long sequence; wherein N isp1For the length of the long sequence, LenshartZCIs a value associated with the bandwidth.
12. a receiver, comprising:
The receiving module is used for detecting whether signals of a communication satellite can be acquired or not and receiving baseband signals which are sent by a transmitter and contain leading signals; if yes, executing a first coarse synchronization module; if not, executing a second coarse synchronization module;
The first coarse synchronization module is used for searching each short sequence ending position which accords with the preset short sequence repetition times and accords with the preset short sequence characteristics in the received baseband signal through a preset search window, and performing coarse synchronization with the transmitter based on each short sequence ending position;
The second coarse synchronization module is used for sliding a preset search window in a preset transmission time length, traversing the baseband signals received in the transmission time length, searching each short sequence ending position which accords with the preset short sequence repetition times and accords with the preset short sequence characteristics, and performing coarse synchronization with the transmitter based on each short sequence ending position;
A fine synchronization module, configured to determine a long sequence in the preamble signal based on the obtained end position of the short sequence, and perform cross-correlation between the received long sequence and a preset long sequence, where the short sequence is generated according to a bandwidth of the preamble signal sent by the transmitter, and the long sequence is generated according to the bandwidth and a base station number; further signal synchronization with the transmitter is performed based on the obtained cross-correlation peak.
13. The receiver of claim 12, wherein the fine synchronization module is further configured to adjust the clock signal output by the crystal oscillator based on the determined end position of the long sequence when the detection indicates that the signal of the communication satellite is not available.
14. the receiver of claim 12, wherein the second coarse synchronization module is further configured to: sliding a preset search window in a preset transmission duration, and searching a plurality of short sequence end positions which accord with the characteristics of a preset short sequence; and screening the short sequence end positions of the preset short sequence repetition times from the searched short sequence end positions according to preset screening conditions.
15. the receiver according to claim 12 or 14, wherein the first coarse synchronization module and the second coarse synchronization module are configured to perform autocorrelation processing on two baseband signals sliding through the search window, and obtain a peak envelope waveform corresponding to the autocorrelation result; and selecting a short sequence end position corresponding to the peak envelope waveform conforming to the short sequence characteristics.
16. A signal synchronization system, comprising:
The transmitter of any one of claims 9-11;
and a receiver as claimed in any one of claims 12 to 15.
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