Wireless continuous communication synchronization method and system based on time-frequency joint feedback correction

Abstract

The invention discloses a wireless continuous communication synchronization method and system based on time-frequency joint feedback correction, and the method comprises the steps: a slave computer calculates a carrier frequency offset estimator # imgabs0 # and a timing estimator L of a received signal through a leader sequence; calculating a residual carrier frequency offset estimator # imgabs1 # and a residual timing offset estimator # imgabs2 # through an auxiliary pilot frequency; positioning a data stream starting point by a slave according to the timing estimator L; and the slave feeds back the carrier frequency offset estimator delta F, the residual carrier frequency offset estimator # imgabs3 # and the residual timing offset estimator # imgabs4 # to the global synchronous controller. According to the wireless continuous communication synchronization method and system based on time-frequency joint feedback correction provided by the invention, the data stream is positioned by using the timing estimator L estimated by the time domain leader sequence; and the global synchronization controller carries out correction on the data stream frequency and positioning based on the carrier frequency offset estimator, the residual carrier frequency offset estimator of the frequency domain auxiliary pilot frequency estimation and the residual timing offset estimator.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless communication synchronization, and in particular relates to a wireless continuous communication synchronization method and system based on time-frequency joint feedback correction. Background Art

[0002] Wireless continuous communication synchronization is an important issue in wireless communication systems. Wireless continuous communication refers to the continuous transmission of data streams between two or more communication nodes without frequent establishment and disconnection. Synchronization in wireless continuous communication systems includes timing synchronization and carrier frequency synchronization. Timing synchronization refers to the slave in the wireless communication system correctly determining the sampling time of the received signal so that the sampling point is aligned with the symbol boundary sent by the transmitter. Carrier frequency synchronization refers to the slave adjusting the frequency of its local oscillator to match the carrier frequency of the received signal.

[0003] Existing wireless continuous communication synchronization technologies can be divided into two types, data-assisted and non-data-assisted, depending on whether there is data assistance. Blind synchronization based on non-data assistance has higher bandwidth and power utilization, but the synchronization speed is slow and the accuracy is limited. Data-assisted synchronization can be divided into three types according to the data form: auxiliary pilot, training symbol and signal inherent structure (such as the cyclic prefix of OFDM symbol). The synchronization technology based on auxiliary pilot has large bandwidth and power consumption overhead, complex design and high synchronization accuracy. The synchronization technology based on training symbols is simple, easy to implement and fast, but other mechanisms are required to maintain the synchronization state after synchronization is established. The synchronization technology based on the inherent structure of the signal is simple and easy to implement, but the interference ability is weak and the estimation error is large. Summary of the invention

[0004] The present invention provides a wireless continuous communication synchronization method and system based on time-frequency joint feedback correction to solve the above-mentioned technical problems, and specifically adopts the following technical solutions:

[0005] A wireless continuous communication synchronization method based on time-frequency joint feedback correction, comprising:

[0006] The slave receives the wireless communication frame sent by the master;

[0007] The slave calculates the carrier frequency offset estimate of the received signal through the preamble sequence and timing estimate L, and the residual carrier frequency offset estimate is calculated through the auxiliary pilot and the residual timing offset estimate

[0008] The slave locates the starting point of the data stream based on the timing estimate L;

[0009] The slave device calculates the carrier frequency offset estimate ΔF, the remaining carrier frequency offset estimate and the residual timing offset estimate The information is fed back to the global synchronization controller, and the global synchronization controller corrects the starting position of the data stream and the carrier frequency based on the received information.

[0010] Furthermore, before the slave receives the wireless communication frame sent by the master, the wireless continuous communication synchronization method based on time-frequency joint feedback correction further comprises:

[0011] The slave captures the continuously transmitted wireless communication frames sent by the host all the time without stopping. After capturing the wireless communication frame, it stops capturing the wireless communication frame until the wireless communication frame ends, and then continues to search for the next wireless communication frame.

[0012] Furthermore, the slave captures the wireless communication frame through the leading sequence in the wireless communication frame, and the timing estimation L is calculated by cross-correlation during the capture process.

[0013] Furthermore, the slave calculates the end time of the wireless communication frame through the frame header sequence in the wireless communication frame.

[0014] Furthermore, the residual carrier frequency offset estimate Including integer frequency offset estimates With fractional frequency deviation estimate

[0015] Furthermore, for the fractional frequency deviation estimate Eliminate the sampling clock frequency offset error and obtain the corrected fractional frequency offset estimate

[0016] Furthermore, the residual timing offset estimate Including integer multiples of timing offset and fractional timing offset

[0017] A wireless continuous communication synchronization system based on time-frequency joint feedback correction comprises a host and several slaves;

[0018] The host includes a frame generation module, a frame control module and a DAC module;

[0019] The frame generation module generates a wireless communication frame, including the generation of a leading sequence, a frame header sequence, a data sequence and a check sequence;

[0020] The frame control signal generated by the frame control module is used to control the frame generation module to generate wireless communication frames of different lengths and modulation modes;

[0021] The DAC module converts the wireless communication frame generated by the frame generation module into digital-to-analog format and then sends it through the antenna of the host;

[0022] The slave includes a frame capture module, a frame demodulation module, a global synchronization controller and an ADC module;

[0023] The ADC module performs analog-to-digital conversion on the signal received from the slave;

[0024] The frame capture module captures the converted signal and calculates the carrier frequency offset estimate and a timing estimate L, and locating the starting point of the data stream according to the timing estimate L;

[0025] After locating the starting point of the data stream, the frame demodulation module of the slave recovers the data of each frequency point of the wireless communication frame and demodulates it, and calculates the estimated amount of residual timing offset according to the phase relationship of each frequency point. Calculate the residual carrier frequency offset estimate based on the phase relationship of different symbols at the same frequency point

[0026] The global synchronization controller uses the carrier frequency offset estimate Residual timing offset estimate and the residual carrier frequency offset estimate Correct the starting position of the data stream and the carrier frequency.

[0027] Furthermore, the wireless communication signal used for synchronization adopts an orthogonal frequency division multiplexing signal.

[0028] The benefit of the present invention lies in the wireless continuous communication synchronization method and system based on time-frequency joint feedback correction, which uses the timing estimate L of the time domain preamble sequence estimate to locate the data stream, and the global synchronization controller corrects the data stream frequency and positioning based on the carrier frequency offset estimate, the residual carrier frequency offset estimate of the frequency domain auxiliary pilot estimate, and the residual timing offset estimate. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0030] Figure 1 It is a schematic diagram of wireless communication frame transmission between a host and a slave of the present invention;

[0031] Figure 2 It is a schematic diagram of a wireless continuous communication synchronization method based on time-frequency joint feedback correction of the present invention;

[0032] Figure 3is a schematic diagram of a global synchronization controller based on time-frequency joint feedback correction of the present invention;

[0033] Figure 4 It is a schematic diagram of a wireless continuous communication synchronization system based on time-frequency joint feedback correction of the present invention. DETAILED DESCRIPTION

[0034] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0035] refer to Figure 1 and Figure 2 As shown, the present application provides a wireless continuous communication synchronization method based on time-frequency joint feedback correction, which specifically includes:

[0036] The slave receives the wireless communication frame sent by the master;

[0037] The slave calculates the carrier frequency offset estimate of the received signal through the preamble sequence and timing estimate L, and the residual carrier frequency offset estimate is calculated through the auxiliary pilot and the residual timing offset estimate

[0038] The slave locates the starting point of the data stream based on the timing estimate L;

[0039] The slave sets the carrier frequency offset estimate Residual carrier frequency offset estimate and the residual timing offset estimate The information is fed back to the global synchronization controller, and the global synchronization controller corrects the starting position of the data stream and the carrier frequency based on the received information.

[0040] As a preferred implementation, before the slave receives the wireless communication frame sent by the master, the wireless continuous communication synchronization method based on time-frequency joint feedback correction further includes:

[0041] The slave captures the continuously transmitted wireless communication frames sent by the host all the time without stopping. After capturing the wireless communication frame, it stops capturing the wireless communication frame until the wireless communication frame ends, and then continues to search for the next wireless communication frame.

[0042] Furthermore, the slave calculates the end time of the wireless communication frame through the frame header sequence in the wireless communication frame.

[0043] The wireless continuous communication synchronization method based on time-frequency joint feedback correction provided by the present application uses the timing estimate L estimated by the time domain preamble sequence to locate the data stream, and inputs the carrier frequency offset estimate estimated by the time domain preamble sequence, the residual carrier frequency offset estimate estimated by the frequency domain auxiliary pilot and the residual timing offset estimate into the global synchronization controller, so as to realize the correction of the frequency and positioning of the data stream by the global synchronization controller. The following specifically introduces the process of calculating relevant parameters according to the preamble sequence and the auxiliary pilot of the present application.

[0044] The synchronization method provided in the present application uses a preamble sequence to perform timing estimation and carrier frequency offset estimation. The preamble sequence is a periodic sequence with a period of Np and contains Mp repetition periods and a ZC sequence with good autocorrelation.

[0045] The synchronization method provided in the present application uses the cross-correlation between the received preamble sequence r[n] and the transmitted preamble sequence s[n] to perform time domain timing estimation. In order to avoid erroneous judgments caused by accidental interference and low signal-to-noise ratio, the average power of the data stream is used as the threshold of the cross-correlation. The correlation peak exceeding the threshold is detected Mp times in a row, and the number of correlation peaks exceeding the threshold twice L∈[Np-ε,Np+ε] can be regarded as the timing estimation value, where ε is the correlation peak offset caused by multipath or frequency deviation. If the number of correlation peaks exceeding the threshold twice in a row is not within the above range, the timing estimation process is restarted. Define the normalized value of the timing function M(k):

[0046]

[0047] Where k represents the displacement of the cross-correlation, and ρ is the adjustment coefficient to adjust the estimation threshold in different channel environments. The correlation peak timing point can be determined by:

[0048]

[0049] The synchronization method provided in the present application uses auxiliary pilots to estimate the frequency domain timing and the residual timing offset, and feeds back to the global synchronization controller. Divided into integer multiples of timing offset and fractional timing offset

[0050] The phase shift of the kth subcarrier introduced by the timing offset is proportional to the subcarrier number:

[0051]

[0052] Where T i =NT s Represents the effective symbol period, T s is the sampling period, N is the number of subcarriers, Td , Δt(j) represent integer symbol timing offset and fractional symbol timing offset respectively. Considering the common phase error φ 0 , sampling clock frequency deviation Δf c With the fractional frequency offset Δf, the phase shift of the kth subcarrier of the jth symbol can be obtained as:

[0053]

[0054] Where T=(T u +T g )j,T g is the cyclic prefix period. Let G of each symbol p The subcarrier number of the pilot signal is k=k 1 ,k 2 …k p , then the phase difference of adjacent pilots can be expressed as the pilot subcarrier number difference k i+1 -k i , Normalized symbol timing offset Function:

[0055]

[0056] The timing offset average value obtained by using all pilot phase differences is used to obtain a higher-precision normalized timing offset estimate.

[0057]

[0058] Since φ(j)∈(-π,+π), we can get:

[0059]

[0060] The above formula shows that the symbol timing offset estimation range is limited by the phase deflection angle, is inversely proportional to Δk, and has a maximum value of

[0061] Based on the known normalized timing offset estimate, the entire timing offset estimate can be further divided into integer multiples of the timing offset: and fractional timing offset To facilitate subsequent corrections.

[0062] The synchronization method provided in the present application utilizes the periodicity of the leading sequence to estimate the carrier frequency offset in the time domain, and utilizes the auxiliary pilot to estimate the residual carrier frequency offset in the frequency domain, and the residual carrier frequency offset estimation includes integer frequency offset estimation and fractional frequency offset estimation. The carrier frequency offset estimation in the time domain has the advantage of fast synchronization time, and reduces the carrier interference brought by the carrier frequency offset, so that the residual carrier frequency offset value estimated by the pilot in the frequency domain has a higher estimation accuracy. By feeding back the residual carrier frequency estimation value in the frequency domain to the time domain to correct the data stream, fast and high-precision carrier frequency synchronization can be achieved.

[0063] Define the observation function:

[0064]

[0065] where r n Indicates the nth sample received signal, represents the correlation window length, and d is the symbol timing estimation deviation. Then the time domain frequency offset estimation result, that is, the carrier frequency offset estimation Given by:

[0066]

[0067] Where T represents the total duration of the preamble sequence.

[0068] The synchronization method provided in the present application uses auxiliary pilots to estimate the residual carrier frequency offset in the frequency domain to obtain a residual carrier frequency offset estimate. Residual carrier frequency offset estimate Including integer frequency offset estimates With fractional frequency deviation estimate The fractional frequency offset estimation requires the integer frequency offset estimation as a prerequisite, so the integer frequency offset estimation is performed first, and then the fractional frequency offset estimation is performed.

[0069] The integer frequency offset estimate

[0070]

[0071] W represents the number of continuous pilots, l represents the sliding window length, k represents the subcarrier number, and Y m,k Represents the k subcarrier values ​​of the mth symbol.

[0072] Since the phases of two adjacent symbols at the pilot position have a common factor:

[0073]

[0074] The residual fractional frequency offset estimate can be obtained based on the phase difference between the two

[0075]

[0076] Where P is the number of pilots involved in the estimation. It also includes the error caused by the sampling clock frequency offset. To eliminate the sampling clock frequency offset ΔF sample The impact on Further corrections are made

[0077] First, let the phase difference between two adjacent symbols at the pilot position be Δf pi , where p i is the pilot point position.

[0078]

[0079] When the number of subcarriers is large, the impact of sampling clock frequency offset cannot be ignored. pi Estimate ΔF sample :

[0080]

[0081] Substituting into (10) and averaging, we can obtain the accurate fractional frequency offset estimation result:

[0082]

[0083] like Figure 3 As shown, the global synchronization controller uses the carrier frequency offset estimate Residual carrier frequency offset estimate and the residual timing offset estimate The feedback input corrects the data stream frequency and starting point, where the data stream x after the i-th correction s The relationship between (n) and the data stream x(n) after the i-1th correction is:

[0084]

[0085] Where i is an integer greater than 0, and μ is the adjustment factor. The data stream x after the correction starting point l (n) and the data stream x before the correction starting point s The relationship between (n) is:

[0086]

[0087] like Figure 4As shown, the present application also discloses a wireless continuous communication synchronization system based on time-frequency joint feedback correction, comprising: a host and several slaves. Whether it is a host or a slave, the hardware circuit architecture includes an analog part and a digital part. The analog part includes an analog digital converter (Analog Digital Converter, ADC) / digital analog converter (Digital Analog Converter, DAC), etc. The digital part is mainly a digital logic circuit for digital signal processing and control loop, which can be implemented with a field programmable gate array (Field Programmable Gate Array, FPGA) or an application specific integrated circuit (Application Specific Integrated Circuit, ASIC). The digital logic of the host generates a digital signal with a synchronization sequence and data information for transmission. The digital logic of the slave estimates the offset of the received signal, and uses the estimated offset to calculate the control value of the global synchronization controller.

[0088] Specifically, the host includes a frame generation module, a frame control module and a DAC module. The frame generation module generates wireless communication frames, including the generation of a leading sequence, a frame header sequence, a data sequence and a check sequence. The frame control signal generated by the frame control module is used to control the frame generation module to generate wireless communication frames of different lengths and modulation modes. The DAC module converts the wireless communication frames generated by the frame generation module into digital-to-analog signals and then sends them through the host's antenna.

[0089] The slave includes a frame capture module, a frame demodulation module, a global synchronization controller and an ADC module.

[0090] The ADC module converts the signal received from the slave into digital form. The frame capture module captures the converted signal and calculates the carrier frequency offset estimate. and the timing estimate L, according to the carrier frequency offset estimate The converted signal is subjected to carrier frequency correction, and the starting point of the data stream is located according to the timing estimate L.

[0091] After locating the starting point of the data stream, the frame demodulation module of the slave recovers the data of each frequency point of the wireless communication frame and demodulates it, and calculates the estimated residual timing offset based on the phase relationship of each frequency point. Calculate the residual carrier frequency offset estimate based on the phase relationship of different symbols at the same frequency point

[0092] The global synchronization controller uses the residual timing offset estimate and the residual carrier frequency offset estimate Correct the starting position of the data stream and the carrier frequency.

[0093] In an embodiment of the present application, the wireless communication signal used for synchronization adopts an orthogonal frequency division multiplexing (OFDM) signal. The host sends OFDM, and the slave receives the OFDM signal and provides it to the global synchronization controller through a time-frequency joint feedback correction model.

[0094] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any form, and any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A wireless continuous communication synchronization method based on time-frequency joint feedback correction, characterized in that: Include: The slave receives the wireless communication frame sent by the master; The slave calculates the carrier frequency offset estimate of the received signal through the preamble sequence and timing estimate L, and the residual carrier frequency offset estimate is calculated through the auxiliary pilot and the residual timing offset estimate The slave locates the starting point of the data stream based on the timing estimate L; The slave sets the carrier frequency offset estimate Residual carrier frequency offset estimate and the residual timing offset estimate The information is fed back to the global synchronization controller, and the global synchronization controller corrects the starting position of the data stream and the carrier frequency based on the received information.

2. The wireless continuous communication synchronization method based on time-frequency joint feedback correction according to claim 1 is characterized in that: Before the slave receives the wireless communication frame sent by the master, the wireless continuous communication synchronization method based on time-frequency joint feedback correction further includes: The slave captures the continuously transmitted wireless communication frames sent by the host all the time without stopping. After capturing the wireless communication frame, it stops capturing the wireless communication frame until the wireless communication frame ends, and then continues to search for the next wireless communication frame.

3. The wireless continuous communication synchronization method based on time-frequency joint feedback correction according to claim 1 is characterized in that: The slave captures the wireless communication frame through the leading sequence in the wireless communication frame, and the timing estimation L is calculated by cross-correlation during the capture process.

4. The wireless continuous communication synchronization method based on time-frequency joint feedback correction according to claim 1, characterized in that: The slave calculates the end time of the wireless communication frame through the frame header sequence in the wireless communication frame.

5. The wireless continuous communication synchronization method based on time-frequency joint feedback correction according to claim 1, characterized in that: Residual carrier frequency offset estimate Including integer frequency offset estimates With fractional frequency deviation estimate 6. The wireless continuous communication synchronization method based on time-frequency joint feedback correction according to claim 5, characterized in that: Fractional frequency deviation estimate Eliminate the sampling clock frequency offset error and obtain the corrected fractional frequency offset estimate 7. The wireless continuous communication synchronization method based on time-frequency joint feedback correction according to claim 1 is characterized in that: Residual timing offset estimate Including integer multiples of timing offset and fractional timing offset 8. A wireless continuous communication synchronization system based on time-frequency joint feedback correction, characterized in that: Includes a master and several slaves; The host includes a frame generation module, a frame control module and a DAC module; The frame generation module generates a wireless communication frame, including the generation of a leading sequence, a frame header sequence, a data sequence and a check sequence; The frame control signal generated by the frame control module is used to control the frame generation module to generate wireless communication frames of different lengths and modulation modes; The DAC module converts the wireless communication frame generated by the frame generation module into digital-to-analog format and then sends it through the antenna of the host; The slave includes a frame capture module, a frame demodulation module, a global synchronization controller and an ADC module; The ADC module performs analog-to-digital conversion on the signal received from the slave; The frame capture module captures the converted signal and calculates the carrier frequency offset estimate and a timing estimate L, and locating the starting point of the data stream according to the timing estimate L; After locating the starting point of the data stream, the frame demodulation module of the slave recovers the data of each frequency point of the wireless communication frame and demodulates it, and calculates the estimated amount of residual timing offset according to the phase relationship of each frequency point. Calculate the residual carrier frequency offset estimate based on the phase relationship of different symbols at the same frequency point The global synchronization controller uses the carrier frequency offset estimate Residual timing offset estimate and the residual carrier frequency offset estimate Correct the starting position of the data stream and the carrier frequency.

9. The wireless continuous communication synchronization system based on time-frequency joint feedback correction according to claim 8, characterized in that: The wireless communication signal used for synchronization uses an orthogonal frequency division multiplexing signal.

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