CN114285435B - Method, device, equipment and medium for correcting frequency offset of spread spectrum communication - Google Patents
Method, device, equipment and medium for correcting frequency offset of spread spectrum communication Download PDFInfo
- Publication number
- CN114285435B CN114285435B CN202111663342.8A CN202111663342A CN114285435B CN 114285435 B CN114285435 B CN 114285435B CN 202111663342 A CN202111663342 A CN 202111663342A CN 114285435 B CN114285435 B CN 114285435B
- Authority
- CN
- China
- Prior art keywords
- frequency
- current
- bit sequence
- binary bit
- despread
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 238000001228 spectrum Methods 0.000 title claims abstract description 85
- 238000000034 method Methods 0.000 title claims abstract description 52
- 230000006854 communication Effects 0.000 title claims abstract description 41
- 238000004891 communication Methods 0.000 title claims abstract description 40
- 238000012937 correction Methods 0.000 claims description 42
- 238000012795 verification Methods 0.000 claims description 37
- 238000012804 iterative process Methods 0.000 claims description 7
- 238000004590 computer program Methods 0.000 claims description 3
- 238000010586 diagram Methods 0.000 description 8
- 238000012360 testing method Methods 0.000 description 3
- 230000006978 adaptation Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000010363 phase shift Effects 0.000 description 2
- 230000004044 response Effects 0.000 description 2
- 230000001360 synchronised effect Effects 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 1
- 238000013507 mapping Methods 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
Landscapes
- Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
Abstract
The invention discloses a method, a device, equipment and a medium for correcting frequency offset of spread spectrum communication, which comprise the following steps: receiving a spread spectrum signal; setting a first frequency for iteration according to a tuning value, setting the frequency of the numerical control oscillator as the current first frequency in each iteration, checking the despread binary bit sequence corresponding to the current first frequency and the original binary bit sequence, if the checking fails, obtaining the current second frequency according to the current first frequency, setting the frequency of the numerical control oscillator as the current second frequency, checking the despread binary bit sequence corresponding to the current second frequency and the original binary bit sequence, if the checking fails, setting the frequency of the numerical control oscillator as the first frequency of the next iteration until the checking of the despread binary bit sequence and the original binary bit sequence is successful, and setting the current frequency of the numerical control oscillator as the frequency offset. The invention ensures that the correct frequency offset between the receiving end and the transmitting end is searched in the whole maximum frequency offset range between the receiving end and the transmitting end.
Description
Technical Field
The invention belongs to the technical field of spread spectrum communication, and particularly relates to a method, a device, equipment and a medium for correcting frequency offset of spread spectrum communication.
Background
The spread spectrum communication (spread spectrum communication for short) technology has noise-like concealment, stronger anti-interference performance and good confidentiality, and is widely applied to the fields of military communication and modern civil communication. The spread spectrum communication has the modes of direct sequence spread spectrum, frequency hopping, time hopping spread spectrum, linear frequency modulation and the like, and under the point-to-point communication scene adopting the direct sequence spread spectrum technology, the inconsistency of the reference clocks of the communication equipment can introduce carrier frequency offset (frequency offset for short) between a transmitting end and a receiving end, and if the frequency offset is larger, the demodulation recovery of the signal by the receiving end can be directly affected.
In demodulating and recovering signals, a feedback control loop is generally used to correct frequency offset and phase difference, wherein the feedback control loop comprises a phase detector, a loop filter, a numerical control oscillator and the like, but the frequency offset range which can be directly captured by the feedback control loop is limited by the bit rate R of the signals: taking BPSK (Binary Phase Shift Keying ) modulation as an example, the maximum frequency offset range which can be directly captured by a feedback control loop under ideal signal-to-noise ratio is [ -R/4, +R/4]; taking QPSK (Quadrature Phase Shift Keying ) modulation as an example, the maximum frequency offset range that can be directly captured by the feedback control loop under ideal signal-to-noise ratio is [ -R/8, +r/8]. When the bit rate R and the signal-to-noise ratio of the signal are low, the carrier frequency offset between the receiving end and the transmitting end in the actual communication process can exceed the maximum frequency offset range which can be directly captured by the feedback control loop, and at the moment, the correction of the carrier frequency offset cannot be realized by the feedback control loop.
Disclosure of Invention
The invention aims to: aiming at the problems in the prior art, the invention discloses a method, a device, equipment and a medium for correcting the frequency offset of spread spectrum communication, which solve the problem that the frequency offset beyond the maximum frequency offset range which can be directly captured by a feedback control loop cannot be corrected, and enlarge the frequency offset range which can be corrected.
The technical scheme is as follows: in order to achieve the aim of the invention, the invention adopts the following technical scheme:
a frequency offset correction method for spread spectrum communication comprises the following steps:
receiving a spread spectrum signal, wherein the spread spectrum signal is obtained by operation according to an original binary bit sequence and a spread spectrum sequence sent by a sending end;
taking the minimum frequency offset as a first frequency initial value, and iterating the first frequency within the frequency offset range according to the tuning value;
in each iteration, taking the current first frequency as the current frequency of the numerical control oscillator to obtain a despread binary bit sequence corresponding to the current first frequency, and checking the despread binary bit sequence corresponding to the current first frequency and an original binary bit sequence;
if the verification is successful, the current frequency of the numerical control oscillator is frequency offset;
if the verification fails, obtaining a current second frequency according to the current first frequency, taking the current second frequency as the current frequency of the numerical control oscillator, obtaining a despread binary bit sequence corresponding to the current second frequency, and verifying the despread binary bit sequence corresponding to the current second frequency and an original binary bit sequence, wherein if the verification is successful, the current frequency of the numerical control oscillator is frequency deviation; if the verification fails, taking the first frequency of the next iteration as the current frequency of the numerical control oscillator, wherein the first frequency of the next iteration is calculated according to the current first frequency and the tuning value; repeating the iterative process until the binary bit sequence and the original binary bit sequence are successfully checked and despread, wherein the current frequency of the numerical control oscillator is frequency offset;
and taking the frequency offset as the frequency of a numerical control oscillator, and correcting the frequency offset of a subsequently received spread spectrum signal through the numerical control oscillator.
Further, the tuning value is calculated according to the maximum frequency deviation range, the maximum signal-to-noise ratio and the current signal-to-noise ratio which can be captured by the feedback control loop under the ideal signal-to-noise ratio.
Further, the tuning value f tune The method comprises the following steps:
wherein W is the interval length of the maximum frequency offset range which can be captured by the feedback control loop under the ideal signal-to-noise ratio, SNR max For maximum signal-to-noise ratio, SNR is the current signal-to-noise ratio and α is the empirical value.
Further, the current first frequency is added with the tuning value to obtain the first frequency of the next iteration.
Further, obtaining the current second frequency according to the current first frequency includes:
the spread spectrum signal is sequentially operated with a numerical control oscillator and a spread spectrum sequence to obtain a despread signal;
detecting a correlation peak in each fixed sequence length in the despread signal, wherein the fixed sequence length is the sequence length of a spread spectrum sequence, and the correlation peak is the position with the maximum signal amplitude in each fixed sequence length;
obtaining a rotation angle between coordinate points corresponding to adjacent correlation peaks according to the I-path signal value and the Q-path signal value of each correlation peak position;
obtaining correction frequency according to the rotation angle between coordinate points corresponding to the adjacent correlation peaks;
and obtaining a current second frequency according to the correction frequency and the current first frequency.
Further, the rotation angle between the coordinate points corresponding to the adjacent correlation peaks is:
wherein θ (k) is a rotation angle between a coordinate point corresponding to the (k+1) th correlation peak and a coordinate point corresponding to the (k) th correlation peak, I xcorr (k) And Q xcorr (k) I-path signal value and Q-path signal value of kth correlation peak respectively, I xcorr (k+1) and Q xcorr (k+1) is the I-path signal value and the Q-path signal value of the (k+1) -th correlation peak, and K is the number of the correlation peaks;
the correction frequency f guess_ave The method comprises the following steps:
wherein R is the bit rate;
the current second frequencyThe method comprises the following steps:
wherein,for the current first frequency, l represents the number of iterations.
Further, the I-path signal value and the Q-path signal value of each correlation peak position are represented by signed numbers, binary data corresponding to the despread signals of each fixed sequence length are determined according to the sign bit of the I-path signal value and the sign bit of the Q-path signal value of each correlation peak position, and binary data corresponding to the despread signals of each fixed sequence length are sequentially combined to obtain a despread binary bit sequence.
Further, the original binary bit sequence includes characteristic bit sequence information, the despread binary bit sequence includes characteristic bit sequence information, and if the characteristic bit sequence information of the original binary bit sequence matches with the characteristic bit sequence information of the despread binary bit sequence, the despread binary bit sequence and the original binary bit sequence are successfully checked.
Further, the original binary bit sequence and the despread binary bit sequence are represented by data frames, each data frame includes a plurality of bytes, the bytes defining the fixed position before each data frame are feature bits, and binary data corresponding to the feature bits is feature bit sequence information.
A spread spectrum communication frequency offset correction apparatus comprising:
the signal receiving module is used for receiving a spread spectrum signal, and the spread spectrum signal is obtained by operation according to an original binary bit sequence and a spread spectrum sequence sent by a sending end;
the iteration module is used for taking the minimum frequency offset as a first frequency initial value, and the first frequency is iterated within the frequency offset range according to the tuning value;
in each iteration, taking the current first frequency as the current frequency of the numerical control oscillator to obtain a despread binary bit sequence corresponding to the current first frequency, and checking the despread binary bit sequence corresponding to the current first frequency and an original binary bit sequence; if the verification is successful, the current frequency of the numerical control oscillator is frequency offset; if the verification fails, obtaining a current second frequency according to the current first frequency, taking the current second frequency as the current frequency of the numerical control oscillator, obtaining a despread binary bit sequence corresponding to the current second frequency, and verifying the despread binary bit sequence corresponding to the current second frequency and an original binary bit sequence, wherein if the verification is successful, the current frequency of the numerical control oscillator is frequency deviation; if the verification fails, taking the first frequency of the next iteration as the current frequency of the numerical control oscillator, wherein the first frequency of the next iteration is calculated according to the current first frequency and the tuning value; repeating the iterative process until the binary bit sequence and the original binary bit sequence are successfully checked and despread, wherein the current frequency of the numerical control oscillator is frequency offset;
the frequency offset correction module is used for taking the frequency offset as the frequency of the numerical control oscillator and correcting the frequency offset of the subsequently received spread spectrum signal through the numerical control oscillator.
A spread spectrum communication frequency offset correction apparatus comprising a processor, a memory and a computer program stored on the memory and operable on the processor, the processor implementing any one of the preceding spread spectrum communication frequency offset correction methods when executing the program.
A computer-readable storage medium storing computer-executable instructions for performing the spread spectrum communication frequency offset correction method of any one of the preceding claims.
The beneficial effects are that: compared with the prior art, the invention has the following beneficial effects:
the invention sets the first frequency in the maximum frequency offset range by taking the minimum frequency offset as an initial value and iterating according to the tuning value, checks the despread binary bit sequence obtained according to the first frequency, corrects the first frequency to the second frequency if the check is not passed, checks the despread binary bit sequence obtained according to the second frequency, and checks the despread binary bit sequence obtained according to the first frequency of the next iteration if the check is not passed, and repeats the process, thereby ensuring that the correct frequency offset between the receiving end and the transmitting end is searched in the whole maximum frequency offset range between the receiving end and the transmitting end.
Drawings
Fig. 1 is a flowchart of a frequency offset correction method according to embodiment 1 of the present invention;
fig. 2 is a general block diagram of a frequency offset correction method according to embodiment 2 of the present invention;
fig. 3 is a specific block diagram of a receiving-end frequency offset correction method according to embodiment 2 of the present invention;
fig. 4 is a waveform diagram of an original binary bit sequence at a transmitting end and a signal after spread spectrum modulation according to embodiment 2 of the present invention;
fig. 5 is a diagram of a data frame structure sent by a sending end according to embodiment 2 of the present invention;
fig. 6 is a phase rotation diagram of I/Q data on a constellation diagram at two adjacent correlation peak positions of a receiving end according to embodiment 2 of the present invention;
fig. 7 is a block diagram of a frequency offset correction apparatus according to embodiment 4 of the present invention.
Detailed Description
The invention will be further described with reference to the accompanying drawings.
Example 1:
the embodiment discloses a method for correcting frequency offset of spread spectrum communication, as shown in fig. 1, comprising the following steps:
receiving a spread spectrum signal, wherein the spread spectrum signal is obtained by operation according to an original binary bit sequence and a spread spectrum sequence sent by a sending end;
taking the minimum frequency offset as a first frequency initial value, and iterating the first frequency within the frequency offset range according to the tuning value;
in each iteration, taking the current first frequency as the current frequency of the numerical control oscillator to obtain a despread binary bit sequence corresponding to the current first frequency, and checking the despread binary bit sequence corresponding to the current first frequency and an original binary bit sequence;
if the verification is successful, the current frequency of the numerical control oscillator is frequency offset;
if the verification fails, obtaining a current second frequency according to the current first frequency, taking the current second frequency as the current frequency of the numerical control oscillator, obtaining a despread binary bit sequence corresponding to the current second frequency, and verifying the despread binary bit sequence corresponding to the current second frequency and an original binary bit sequence, wherein if the verification is successful, the current frequency of the numerical control oscillator is frequency deviation; if the verification fails, taking the first frequency of the next iteration as the current frequency of the numerical control oscillator, wherein the first frequency of the next iteration is calculated according to the current first frequency and the tuning value; repeating the iterative process until the binary bit sequence and the original binary bit sequence are successfully checked and despread, wherein the current frequency of the numerical control oscillator is frequency offset;
and taking the frequency offset as the frequency of a numerical control oscillator, and correcting the frequency offset of a subsequently received spread spectrum signal through the numerical control oscillator.
In this embodiment, the first frequency is set in the maximum frequency offset range by iterating with the minimum frequency offset as an initial value according to the tuning value, and the despread binary bit sequence obtained according to the first frequency is checked, if the check is not passed, the first frequency is corrected to the second frequency, and the despread binary bit sequence obtained according to the second frequency is checked, if the check is not passed, the despread binary bit sequence obtained according to the first frequency of the next iteration is checked, and the above process is repeated, so that it is ensured that the correct frequency offset between the receiving end and the transmitting end is searched in the whole maximum frequency offset range between the receiving end and the transmitting end.
In this embodiment, when the feedback control loop is opened, the gradient scanning configuration frequency offset of the numerically controlled oscillator is set, that is, the iterative first frequency is set, so that adjustment of the intermediate frequency point in the analog part of the receiver is avoided, the response time of waiting for the feedback control loop to lock the frequency of the numerically controlled oscillator is avoided, the configuration speed is high, and the method can be rapidly realized.
Further, the tuning value is calculated according to the maximum frequency deviation range, the maximum signal-to-noise ratio and the current signal-to-noise ratio which can be captured by the feedback control loop under the ideal signal-to-noise ratio.
Further, the tuning value f tune The method comprises the following steps:
wherein W is the interval length of the maximum frequency offset range which can be captured by the feedback control loop under the ideal signal-to-noise ratio, SNR max At maximumThe signal-to-noise ratio, SNR is the current signal-to-noise ratio, and α is an empirical value.
In this embodiment, the dynamically set tuning value may be adjusted according to the real-time communication state, which is more accurate than a fixed tuning value.
Further, the current first frequency is added with the tuning value to obtain the first frequency of the next iteration.
Further, obtaining the current second frequency according to the current first frequency includes:
the spread spectrum signal is sequentially operated with a numerical control oscillator and a spread spectrum sequence to obtain a despread signal;
detecting a correlation peak in each fixed sequence length in the despread signal, wherein the fixed sequence length is the sequence length of a spread spectrum sequence, and the correlation peak is the position with the maximum signal amplitude in each fixed sequence length;
obtaining a rotation angle between coordinate points corresponding to adjacent correlation peaks according to the I-path signal value and the Q-path signal value of each correlation peak position;
obtaining correction frequency according to the rotation angle between coordinate points corresponding to the adjacent correlation peaks;
and obtaining a current second frequency according to the correction frequency and the current first frequency.
Further, the rotation angle between the coordinate points corresponding to the adjacent correlation peaks is:
wherein θ (k) is a rotation angle between a coordinate point corresponding to the (k+1) th correlation peak and a coordinate point corresponding to the (k) th correlation peak, I xcorr (k) And Q xcorr (k) I-path signal value and Q-path signal value of kth correlation peak respectively, I xcorr (k+1) and Q xcorr (k+1) is the I-path signal value and the Q-path signal value of the (k+1) -th correlation peak, and K is the number of the correlation peaks;
the correction frequency f guess_ave The method comprises the following steps:
wherein R is the bit rate;
the current second frequencyThe method comprises the following steps:
wherein,for the current first frequency, l represents the number of iterations.
Further, the I-path signal value and the Q-path signal value of each correlation peak position are represented by signed numbers, binary data corresponding to the despread signals of each fixed sequence length are determined according to the sign bit of the I-path signal value and the sign bit of the Q-path signal value of each correlation peak position, and binary data corresponding to the despread signals of each fixed sequence length are sequentially combined to obtain a despread binary bit sequence.
Further, the original binary bit sequence includes characteristic bit sequence information, the despread binary bit sequence includes characteristic bit sequence information, and if the characteristic bit sequence information of the original binary bit sequence matches with the characteristic bit sequence information of the despread binary bit sequence, the despread binary bit sequence and the original binary bit sequence are successfully checked.
In the embodiment, the accuracy of frequency offset estimation is ensured by utilizing the characteristic bit sequence information to carry out verification during frequency offset estimation.
Further, the original binary bit sequence and the despread binary bit sequence are represented by data frames, each data frame includes a plurality of bytes, the bytes defining the fixed position before each data frame are feature bits, and binary data corresponding to the feature bits is feature bit sequence information.
Example 2:
the embodiment discloses a frequency offset correction method for spread spectrum communication, as shown in fig. 2, which comprises four parts, namely a sending end sends a spread spectrum signal, a receiving end receives the spread spectrum signal, frequency offset estimation and frequency correction frequency offset of a locked numerical control oscillator, for realizing frequency synchronization, which is used for expanding the frequency offset correction range of the receiving end and is suitable for BPSK/QPSK spread spectrum communication application scenes with fixed points of low signal to noise ratio.
As shown in fig. 3, the method in this embodiment specifically includes the following steps:
step S1: the transmitting end transmits spread spectrum signal
Before synchronous communication between the receiving end and the transmitting end is established, the transmitting end continuously transmits the original binary bit sequence S T Original binary bit sequence S T Through and spread sequence C PN After operation, spread spectrum signal X is obtained T The method comprises the following steps:
X T ＝S T C PN
the transmitting end spreads the frequency signal X T Transmitted via a transmitter, as shown in fig. 4, the left side is the original binary bit sequence, spread and modulated, and transmitted as a right side waveform.
In this embodiment, the transmitting end transmits the original binary Bit sequence in the form of data frames (frames), each data Frame including several BYTEs (BYTE), each BYTE including 8 bits (Bit). For example, as shown in fig. 5, the bit rate R at which the transmitting end transmits the original binary bit sequence is 8kHz, i.e., 8000 bits per second, and the transmitting end transmits data frames at a rate of 20 frames per second, thus resulting in 50 bytes per data frame.
And setting bytes at specific positions in each data frame of the original binary bit sequence as characteristic bits, wherein bit sequence information corresponding to the characteristic bits is characteristic bit sequence information for verification. In this embodiment, the first 2 BYTEs of each data frame are defined as characteristic bits (BYTE 1 and BYTE 2), and the corresponding binary data is defined as characteristic bit sequence information. The method for verifying the characteristic bit sequence information in the frequency offset estimation ensures the accuracy of the frequency offset estimation.
Step S2: the receiving end receives the spread spectrum signal;
taking the minimum frequency offset as a first frequency initial value, and iterating the first frequency within the frequency offset range according to the tuning value;
in each iteration, taking the current first frequency as the current frequency of the numerical control oscillator to obtain a despread binary bit sequence corresponding to the current first frequency, and checking the despread binary bit sequence corresponding to the current first frequency and an original binary bit sequence;
if the verification is successful, the current frequency of the numerical control oscillator is frequency offset;
if the verification fails, obtaining a current second frequency according to the current first frequency, taking the current second frequency as the current frequency of the numerical control oscillator, obtaining a despread binary bit sequence corresponding to the current second frequency, and verifying the despread binary bit sequence corresponding to the current second frequency and an original binary bit sequence, wherein if the verification is successful, the current frequency of the numerical control oscillator is frequency deviation; if the verification fails, taking the first frequency of the next iteration as the current frequency of the numerical control oscillator, wherein the first frequency of the next iteration is calculated according to the current first frequency and the tuning value; repeating the iterative process until the binary bit sequence and the original binary bit sequence are successfully checked and despread, wherein the current frequency of the numerical control oscillator is frequency offset;
step S21: after receiving a signal sent by a transmitter at a sending end, a receiver at the receiving end carries out ADC (analog-to-digital converter) sampling on the received signal to obtain a spread spectrum signal Y R 。
At this time, since synchronous communication is not established between the receiving end and the transmitting end, that is, the spread spectrum signal Y received by the receiving end R Spread spectrum signal X transmitted with transmitting end T There is a frequency offset between them, which may exceed the maximum frequency offset range that can be directly captured by the feedback control loop, so that it is necessary to set the loop switch of the feedback control loop to be in an open state, and check the signal by the open loop control of the Numerically Controlled Oscillator (NCO)Searching frequency offset, setting the frequency of the numerical control oscillator as the searched frequency offset after searching the correct frequency offset, and setting a loop switch of a feedback control loop as a closed state to realize communication synchronization.
The process of searching the frequency offset by the open loop control of the Numerical Control Oscillator (NCO) and the check information is as follows:
step S22: setting the frequency of the numerical control oscillator to be the initial first frequencyThe initial first frequency is the minimum frequency offset between the receiving end and the sending end obtained by actual test.
Taking BPSK modulation as an example, the frequency f is directly loaded at the transmitting end trs Is known, the frequency and power of the tone beacon signal; the receiving end analyzes the single-tone beacon signal to obtain the frequency f rec Therefore, the frequency offset range (f) between the receiving end and the transmitting end can be obtained through actual test trs -f rec ) Is [ -12kHz, +12kHz]I.e. minimum frequency offset f offset_min = -12kHz with maximum frequency offset f offset_max =12 kHz, thus setting the initial first frequency to-12 kHz. The maximum signal-to-noise ratio SNR can also be obtained by the measurement method of the single-tone beacon signal max 。
Step S23: calculating a despread binary bit sequence corresponding to the current frequency of the numerically controlled oscillator
Spread spectrum signal Y R Obtaining a signal Y to be despread through a numerical control oscillator R ′。
To-be-despread signal Y R Spread spectrum sequence C of' and transmitting end PN Performing despreading correlation operation to obtain despread signal U R The despreading correlation operation is:
wherein N is the sequence length of the spreading sequence, i.e. the number of bits contained in the spreading sequence, m and N are integers between 0 and N-1; j=0, 1,…, J-1, J is the signal Y to be despread R ' ratio of the sequence length of the spreading sequence.
For despread signal U R Segmenting it with a fixed sequence length, i.e. each segmented signal is of a fixed sequence length, which is the spreading sequence C PN Is a sequence length of (2); detecting the correlation peak position of each segment signal, wherein the correlation peak position is the position with the maximum signal amplitude, and storing the complex signal value of the correlation peak position of each segment signal, including the I-path signal value I xcorr And Q-way signal value Q xcorr The signal amplitude at the relevant peak position is
According to the I-path signal value I at the relevant peak position of each segment signal xcorr And Q-way signal value Q xcorr Calculating and judging to obtain a despread binary bit sequence S corresponding to the current frequency of the numerical control oscillator R The calculation and judgment method is as follows: representing I-way signal value I at each segment signal correlation peak position by signed number xcorr And Q-way signal value Q xcorr According to the I-path signal value I xcorr And Q-way signal value Q xcorr The sign bit of (2) results in binary data corresponding to each segment signal. Wherein, I-path signal value I xcorr And Q-way signal value Q xcorr The mapping between sign bits and binary data is determined for the original binary bit sequence.
For example BPSK modulation, the Q-way signal values are all 0, so if the I-way signal value I is expressed xcorr If the sign bit of the signed number is 0, the binary data corresponding to the segment signal is 1, if the I-path signal value I is represented xcorr The sign bit of the signed integer is 1, and the binary data corresponding to the segmented signal is 0; from each segmented signal after despreading signal U R The binary data corresponding to each segment signal is sequentially combined at the position in the sequence, and a despread binary bit sequence S can be obtained R 。
Step S24: checking an original binary bit sequence S T And corresponding digital oscillationDespread binary bit sequence S of current frequency R If the verification is successful, the current frequency of the digital oscillator is the frequency offset between the receiving end and the transmitting end; and if the verification is unsuccessful, correcting the current first frequency to a second frequency.
Original binary bit sequence S T Despread binary bit sequence S R The verification method of (1) comprises the following steps: will despread the binary bit sequence S R By and with the original binary bit sequence S T The same data frame format representation, comparing the original binary bit sequence S T Characteristic bit sequence information and despread binary bit sequence S in each data frame R Characteristic bit sequence information in each data frame, if the characteristic bit sequence information is consistent with the characteristic bit sequence information, verification is successful; if there is no match, the verification is unsuccessful.
Adjusting the frequency of the digital oscillator to: first frequency according to the current first iterationCorrecting the frequency of the digital oscillator to be the second frequency +.>Comprising the following steps:
as shown in fig. 6, the signal value I is based on the I-way signal value I at each segment signal correlation peak position xcorr And Q-way signal value Q xcorr And calculating the rotation angle theta (k) between the coordinate points corresponding to the adjacent correlation peaks at the corresponding coordinate points on the constellation diagram, wherein the rotation angle theta (k) is as follows:
wherein θ (k) is a rotation angle between a coordinate point corresponding to the (k+1) th correlation peak and a coordinate point corresponding to the (k) th correlation peak, I xcorr (k) And Q xcorr (k) Respectively an I-path signal value and a Q-path signal value at the relevant peak position of the kth segment signal, I xcorr (k+1) and Q xcorr (k+1) is the I-path signal value and the Q-path signal value at the relevant peak position of the kth segment signal respectively,k is the number of segmented signals, i.e. the number of correlation peaks.
Calculating correction frequency offset f according to rotation angles between coordinate points corresponding to adjacent correlation peaks guess_ave The method comprises the following steps:
wherein, R is the bit rate of the original binary bit sequence sent by the sender.
By correcting frequency offset f guess_ave Correcting the first frequency of the current first iterationFor the second frequency->
Step S25: setting the frequency of the digital oscillator to the current second frequencyObtaining a despread binary bit sequence S corresponding to the current frequency of the numerically controlled oscillator according to the process of the step S23 R Checking the original binary bit sequence S according to the checking method described in step S24 T Despread binary bit sequence S R If the verification is successful, the current frequency of the digital oscillator is the frequency offset between the receiving end and the transmitting end; and if the verification is unsuccessful, the current first frequency is adjusted to the first frequency of the next iteration.
The current first frequency is adjusted to the first frequency of the next iteration: correcting the current first frequency to the first frequency of the next iteration according to the tuning value, wherein the tuning value f tune The method comprises the following steps:
wherein W is the interval length of the maximum frequency offset range which can be captured by the feedback control loop under the ideal signal-to-noise ratio, SNR max For maximum signal-to-noise ratio, SNR is the current signal-to-noise ratio, α is an empirical value, and both W and α are related to the modulation method.
The first frequency of the next iteration is therefore:
wherein,for the first frequency of the current first iteration, < >>The first frequency for the next iteration, i.e. the first +1 iteration.
For example, the signal bit rate of the transmitting end is 8kHz, so the maximum frequency offset range that can be captured by the feedback control loop in BPSK modulation under ideal signal-to-noise ratio is [ -2kHz, +2kHz ], and in the case of being limited to the signal-to-noise ratio SNR in practice, each tuning value is dynamically set by the signal-to-noise ratio:
step S26: setting the frequency of the digital oscillator to the first frequency of the next iteration, repeating steps S23-S25 until the original binary bit sequence S is verified T Despread binary bit sequence S R The current frequency of the digital oscillator is the frequency offset between the receiving end and the transmitting end.
Step 3: and taking the frequency offset as the frequency of a numerical control oscillator, and correcting the frequency offset of a subsequently received spread spectrum signal through the numerical control oscillator.
After obtaining the frequency offset between the receiving end and the sending end, setting the frequency of the numerical control oscillator as the frequency offset, and setting a loop switch of a feedback control loop to be in a closed state, wherein communication synchronization is realized through the numerical control oscillator.
After the frequency offset problem between the receiving end and the transmitting end is corrected, the phase error between the receiving end and the transmitting end is corrected by closing the feedback control loop phase-locked loop.
In this embodiment, the initial first frequency is set as the minimum frequency offset between the receiving end and the transmitting end obtained by the actual test, the tuning value is dynamically set according to the conditions such as the real-time signal-to-noise ratio, the first frequency of the next iteration is obtained according to the dynamically set tuning value, and the second frequency is searched near the first frequency of each iteration, so that the correct frequency offset can be ensured to be searched in the whole maximum frequency offset range between the receiving end and the transmitting end; meanwhile, the numerical control oscillator is adjusted only through the calculated first frequency and the calculated second frequency, and the adjusting speed is high.
In this embodiment, the dynamically set tuning value may be adjusted according to the real-time communication state, which is more accurate than a fixed tuning value.
In this embodiment, when the feedback control loop is opened, the gradient scan configuration frequency offset of the numerically controlled oscillator is set, that is, the iterative first frequency and the second frequency obtained by the first frequency correction are set, so that the adjustment of the intermediate frequency point in the analog part of the receiver is avoided, the response time of waiting for the feedback control loop to lock the frequency of the numerically controlled oscillator is avoided, the configuration speed is high, and the method can be rapidly realized.
Example 3:
the embodiment discloses a device for correcting frequency offset of spread spectrum communication, as shown in fig. 7, comprising the following steps:
the signal receiving module is used for receiving a spread spectrum signal, and the spread spectrum signal is obtained by operation according to an original binary bit sequence and a spread spectrum sequence sent by a sending end;
the iteration module is used for taking the minimum frequency offset as a first frequency initial value, and the first frequency is iterated within the frequency offset range according to the tuning value;
in each iteration, taking the current first frequency as the current frequency of the numerical control oscillator to obtain a despread binary bit sequence corresponding to the current first frequency, and checking the despread binary bit sequence corresponding to the current first frequency and an original binary bit sequence; if the verification is successful, the current frequency of the numerical control oscillator is frequency offset; if the verification fails, obtaining a current second frequency according to the current first frequency, taking the current second frequency as the current frequency of the numerical control oscillator, obtaining a despread binary bit sequence corresponding to the current second frequency, and verifying the despread binary bit sequence corresponding to the current second frequency and an original binary bit sequence, wherein if the verification is successful, the current frequency of the numerical control oscillator is frequency deviation; if the verification fails, taking the first frequency of the next iteration as the current frequency of the numerical control oscillator, wherein the first frequency of the next iteration is calculated according to the current first frequency and the tuning value; repeating the iterative process until the binary bit sequence and the original binary bit sequence are successfully checked and despread, wherein the current frequency of the numerical control oscillator is frequency offset;
the frequency offset correction module is used for taking the frequency offset as the frequency of the numerical control oscillator and correcting the frequency offset of the subsequently received spread spectrum signal through the numerical control oscillator.
Further, in the iteration module, the tuning value is calculated according to the maximum frequency deviation range, the maximum signal-to-noise ratio and the current signal-to-noise ratio which can be captured by the feedback control loop under the ideal signal-to-noise ratio.
Further, in the iteration module, the tuning value f tune The method comprises the following steps:
wherein W is the interval length of the maximum frequency offset range which can be captured by the feedback control loop under the ideal signal-to-noise ratio, SNR max For maximum signal-to-noise ratio, SNR is the current signal-to-noise ratio and α is the empirical value.
Further, in the iteration module, the current first frequency is added with the tuning value to obtain the first frequency of the next iteration.
Further, in the iteration module, obtaining the current second frequency according to the current first frequency includes:
the spread spectrum signal is sequentially operated with a numerical control oscillator and a spread spectrum sequence to obtain a despread signal;
detecting a correlation peak in each fixed sequence length in the despread signal, wherein the fixed sequence length is the sequence length of a spread spectrum sequence, and the correlation peak is the position with the maximum signal amplitude in each fixed sequence length;
obtaining a rotation angle between coordinate points corresponding to adjacent correlation peaks according to the I-path signal value and the Q-path signal value of each correlation peak position;
obtaining correction frequency according to the rotation angle between coordinate points corresponding to the adjacent correlation peaks;
and obtaining a current second frequency according to the correction frequency and the current first frequency.
Further, in the iteration module, a rotation angle between coordinate points corresponding to the adjacent correlation peaks is:
wherein θ (k) is a rotation angle between a coordinate point corresponding to the (k+1) th correlation peak and a coordinate point corresponding to the (k) th correlation peak, I xcorr (k) And Q xcorr (k) I-path signal value and Q-path signal value of kth correlation peak respectively, I 2corr (k+1) and Q xcorr (k+1) is the I-path signal value and the Q-path signal value of the (k+1) -th correlation peak, and K is the number of the correlation peaks;
the correction frequency f guess_ave The method comprises the following steps:
wherein R is the bit rate;
the current second frequencyThe method comprises the following steps:
wherein,for the current first frequency, l represents the number of iterations.
Further, in the iteration module, the I-path signal value and the Q-path signal value of each correlation peak position are represented by signed numbers, binary data corresponding to the despread signals with each fixed sequence length are determined according to the sign bits of the I-path signal value and the sign bits of the Q-path signal value of each correlation peak position, and the binary data corresponding to the despread signals with each fixed sequence length are sequentially combined to obtain the despread binary bit sequence.
Further, in the iteration module, the original binary bit sequence includes feature bit sequence information, the despread binary bit sequence includes feature bit sequence information, and if the feature bit sequence information of the original binary bit sequence matches with the feature bit sequence information of the despread binary bit sequence, the despread binary bit sequence and the original binary bit sequence are successfully checked.
Further, the original binary bit sequence and the despread binary bit sequence are represented by data frames, each data frame includes a plurality of bytes, the bytes defining the fixed position before each data frame are feature bits, and binary data corresponding to the feature bits is feature bit sequence information.
Example 4:
the embodiment discloses a frequency offset correction device for spread spectrum communication, which comprises a processor, a memory and a computer program stored on the memory and capable of running on the processor, wherein the processor realizes any one of the frequency offset correction methods for spread spectrum communication when executing the program. The memory may be various types of memory, such as random access memory, read only memory, flash memory, etc. The processor may be various types of processors, such as a central processing unit, a microprocessor, a digital signal processor, or an image processor, etc.
The embodiment also discloses a computer readable storage medium, which stores computer executable instructions for executing the spread spectrum communication frequency offset correction method according to any one of the above. The storage medium includes: a usb disk, a removable hard disk, a ROM, a RAM, a magnetic disk, or an optical disk, etc.
The foregoing is only a preferred embodiment of the invention, it being noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the present invention, and such modifications and adaptations are intended to be comprehended within the scope of the invention.
Claims (11)
1. A frequency offset correction method for spread spectrum communication is characterized by comprising the following steps:
receiving a spread spectrum signal, wherein the spread spectrum signal is obtained by operation according to an original binary bit sequence and a spread spectrum sequence sent by a sending end;
taking the minimum frequency offset as a first frequency initial value, and iterating the first frequency within the frequency offset range according to the tuning value;
in each iteration, taking the current first frequency as the current frequency of the numerical control oscillator to obtain a despread binary bit sequence corresponding to the current first frequency, and checking the despread binary bit sequence corresponding to the current first frequency and an original binary bit sequence;
if the verification is successful, the current frequency of the numerical control oscillator is frequency offset;
if the verification fails, obtaining a current second frequency according to the current first frequency, taking the current second frequency as the current frequency of the numerical control oscillator, obtaining a despread binary bit sequence corresponding to the current second frequency, and verifying the despread binary bit sequence corresponding to the current second frequency and an original binary bit sequence, wherein if the verification is successful, the current frequency of the numerical control oscillator is frequency deviation; if the verification fails, taking the first frequency of the next iteration as the current frequency of the numerical control oscillator, wherein the first frequency of the next iteration is calculated according to the current first frequency and the tuning value; repeating the iterative process until the binary bit sequence and the original binary bit sequence are successfully checked and despread, wherein the current frequency of the numerical control oscillator is frequency offset;
taking the frequency offset as the frequency of a numerical control oscillator, and correcting the frequency offset of a subsequently received spread spectrum signal through the numerical control oscillator;
the obtaining the current second frequency according to the current first frequency includes:
the spread spectrum signal is sequentially operated with a numerical control oscillator and a spread spectrum sequence to obtain a despread signal;
detecting a correlation peak in each fixed sequence length in the despread signal, wherein the fixed sequence length is the sequence length of a spread spectrum sequence, and the correlation peak is the position with the maximum signal amplitude in each fixed sequence length;
obtaining a rotation angle between coordinate points corresponding to adjacent correlation peaks according to the I-path signal value and the Q-path signal value of each correlation peak position;
obtaining correction frequency according to the rotation angle between coordinate points corresponding to the adjacent correlation peaks;
obtaining a current second frequency according to the correction frequency and the current first frequency;
the correction frequency is as follows: and summing the products of the rotation angles and the bit rates between the coordinate points corresponding to the adjacent correlation peaks.
2. The method of claim 1, wherein the tuning value is calculated according to a maximum frequency offset range, a maximum signal-to-noise ratio, and a current signal-to-noise ratio that can be captured by the feedback control loop under an ideal signal-to-noise ratio.
3. The method for correcting a spread spectrum communication frequency offset as claimed in claim 2, wherein said tuning value f tune The method comprises the following steps:
wherein W is the interval length of the maximum frequency offset range which can be captured by the feedback control loop under the ideal signal-to-noise ratio, SNR max For maximum signal-to-noise ratio, SNR is the current signal-to-noise ratio and α is the empirical value.
4. The method of claim 1, wherein the current first frequency is added to the tuning value to obtain the first frequency of the next iteration.
5. The method for correcting a spread spectrum communication frequency offset according to claim 1, wherein the rotation angle between coordinate points corresponding to adjacent correlation peaks is:
wherein θ (k) is a rotation angle between a coordinate point corresponding to the (k+1) th correlation peak and a coordinate point corresponding to the (k) th correlation peak, I xcorr (k) And Q xcorr (k) I-path signal value and Q-path signal value of kth correlation peak respectively, I xcorr (k+1) and W xcorr (k+1) is the I-path signal value and the Q-path signal value of the (k+1) -th correlation peak, and K is the number of the correlation peaks;
the correction frequency f guess_ave The method comprises the following steps:
wherein R is the bit rate;
the current second frequencyThe method comprises the following steps:
wherein,for the current first frequency, l represents the number of iterations.
6. The method for correcting frequency offset of spread spectrum communication according to claim 1, wherein the I-path signal value and the Q-path signal value of each correlation peak position are represented by signed numbers, binary data corresponding to the despread signals of each fixed sequence length are determined according to the sign bit of the I-path signal value and the sign bit of the Q-path signal value of each correlation peak position, and the binary data corresponding to the despread signals of each fixed sequence length are sequentially combined to obtain the despread binary bit sequence.
7. The method for correcting frequency offset of spread spectrum communication according to claim 1, wherein the original binary bit sequence includes characteristic bit sequence information, the despread binary bit sequence includes characteristic bit sequence information, and if the characteristic bit sequence information of the original binary bit sequence matches the characteristic bit sequence information of the despread binary bit sequence, the despread binary bit sequence and the original binary bit sequence are successfully checked.
8. The method of claim 7, wherein the original binary bit sequence and the despread binary bit sequence are represented by data frames, each data frame includes a plurality of bytes, the bytes defining a fixed position before each data frame are characteristic bits, and binary data corresponding to the characteristic bits is characteristic bit sequence information.
9. A spread spectrum communication frequency offset correction apparatus, comprising:
the signal receiving module is used for receiving a spread spectrum signal, and the spread spectrum signal is obtained by operation according to an original binary bit sequence and a spread spectrum sequence sent by a sending end;
the iteration module is used for taking the minimum frequency offset as a first frequency initial value, and the first frequency is iterated within the frequency offset range according to the tuning value;
in each iteration, taking the current first frequency as the current frequency of the numerical control oscillator to obtain a despread binary bit sequence corresponding to the current first frequency, and checking the despread binary bit sequence corresponding to the current first frequency and an original binary bit sequence; if the verification is successful, the current frequency of the numerical control oscillator is frequency offset; if the verification fails, obtaining a current second frequency according to the current first frequency, taking the current second frequency as the current frequency of the numerical control oscillator, obtaining a despread binary bit sequence corresponding to the current second frequency, and verifying the despread binary bit sequence corresponding to the current second frequency and an original binary bit sequence, wherein if the verification is successful, the current frequency of the numerical control oscillator is frequency deviation; if the verification fails, taking the first frequency of the next iteration as the current frequency of the numerical control oscillator, wherein the first frequency of the next iteration is calculated according to the current first frequency and the tuning value; repeating the iterative process until the binary bit sequence and the original binary bit sequence are successfully checked and despread, wherein the current frequency of the numerical control oscillator is frequency offset;
the frequency offset correction module is used for taking the frequency offset as the frequency of a numerical control oscillator and correcting the frequency offset of a subsequently received spread spectrum signal through the numerical control oscillator;
the obtaining the current second frequency according to the current first frequency includes:
the spread spectrum signal is sequentially operated with a numerical control oscillator and a spread spectrum sequence to obtain a despread signal;
detecting a correlation peak in each fixed sequence length in the despread signal, wherein the fixed sequence length is the sequence length of a spread spectrum sequence, and the correlation peak is the position with the maximum signal amplitude in each fixed sequence length;
obtaining a rotation angle between coordinate points corresponding to adjacent correlation peaks according to the I-path signal value and the Q-path signal value of each correlation peak position;
obtaining correction frequency according to the rotation angle between coordinate points corresponding to the adjacent correlation peaks;
obtaining a current second frequency according to the correction frequency and the current first frequency;
the correction frequency is as follows: and summing the products of the rotation angles and the bit rates between the coordinate points corresponding to the adjacent correlation peaks.
10. A spread spectrum communication frequency offset correction apparatus comprising a processor, a memory and a computer program stored on the memory and operable on the processor, wherein the processor implements the spread spectrum communication frequency offset correction method as claimed in any one of claims 1 to 8 when the program is executed by the processor.
11. A computer-readable storage medium having stored thereon computer-executable instructions for performing the spread spectrum communication frequency offset correction method of any one of claims 1 to 8.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111663342.8A CN114285435B (en) | 2021-12-31 | 2021-12-31 | Method, device, equipment and medium for correcting frequency offset of spread spectrum communication |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111663342.8A CN114285435B (en) | 2021-12-31 | 2021-12-31 | Method, device, equipment and medium for correcting frequency offset of spread spectrum communication |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN114285435A CN114285435A (en) | 2022-04-05 |
| CN114285435B true CN114285435B (en) | 2024-01-19 |
Family
ID=80879160
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202111663342.8A Active CN114285435B (en) | 2021-12-31 | 2021-12-31 | Method, device, equipment and medium for correcting frequency offset of spread spectrum communication |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN114285435B (en) |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5640431A (en) * | 1995-03-10 | 1997-06-17 | Motorola, Inc. | Method and apparatus for offset frequency estimation for a coherent receiver |
| CN101505290A (en) * | 2009-03-17 | 2009-08-12 | 山东大学 | Improved frequency bias estimation method for wideband MIMO |
| CN110784425A (en) * | 2019-10-18 | 2020-02-11 | 西安烽火电子科技有限责任公司 | Frequency offset blind elimination iteration method |
| CN111245475A (en) * | 2020-01-10 | 2020-06-05 | 上海感悟通信科技有限公司 | Wireless communication data transmitting method, receiving method, wireless communication method and device |
-
2021
- 2021-12-31 CN CN202111663342.8A patent/CN114285435B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5640431A (en) * | 1995-03-10 | 1997-06-17 | Motorola, Inc. | Method and apparatus for offset frequency estimation for a coherent receiver |
| CN101505290A (en) * | 2009-03-17 | 2009-08-12 | 山东大学 | Improved frequency bias estimation method for wideband MIMO |
| CN110784425A (en) * | 2019-10-18 | 2020-02-11 | 西安烽火电子科技有限责任公司 | Frequency offset blind elimination iteration method |
| CN111245475A (en) * | 2020-01-10 | 2020-06-05 | 上海感悟通信科技有限公司 | Wireless communication data transmitting method, receiving method, wireless communication method and device |
Also Published As
| Publication number | Publication date |
|---|---|
| CN114285435A (en) | 2022-04-05 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US7239675B2 (en) | GFSK receiver | |
| WO2018064932A1 (en) | Wake up radio frame with spectrum spreading based single carrier | |
| US20050286661A1 (en) | Symbol timing error detector that uses a channel profile of a digital receiver and a method of detecting a symbol timing error | |
| US9042471B2 (en) | Receiving device, signal processing device, and signal processing method | |
| BG104762A (en) | Orthogonal frequency division multiplex (ofdm) frame synchronization and equalization system | |
| JPH07154436A (en) | Method for msk phase seizure and tracking | |
| WO2006072967A1 (en) | Method and system for synchronization between a transmitter and a receiver in a wireless communication system | |
| US6560298B1 (en) | Method and apparatus for concurrent synchronization and improved automatic frequency control in a communication device | |
| US7042925B2 (en) | Correlation detection improvement by averaging spread spectrum signals | |
| CN114285435B (en) | Method, device, equipment and medium for correcting frequency offset of spread spectrum communication | |
| JP2002536874A (en) | Method of identifying blind frame in communication system | |
| US9692587B2 (en) | Phase tracking | |
| JP4022199B2 (en) | Method and apparatus for pilot signal synchronization verification | |
| US7539167B2 (en) | Spread spectrum receiver and method for carrier frequency offset compensation in such a spread spectrum receiver | |
| CN110224807A (en) | A kind of carrier synchronization method estimated based on AGC frequency deviation and system | |
| CN105471470A (en) | Spread spectrum signal frequency offset estimation method based on decision feedback | |
| KR100921544B1 (en) | Frequency error correction system with initial frequency estimation and feedback tracking | |
| CN112671684B (en) | Self-adaptive demodulation method of short-time burst BPSK signal | |
| US7301969B2 (en) | OFDM transmitting apparatus, receiving apparatus and transmitting system and signal structure of transmission signal for use in the same | |
| JPH09312640A (en) | Burst signal receiving method and device therefor | |
| JP4268498B2 (en) | Phase error correction circuit, receiving apparatus using the same, and phase error correction method | |
| JP2000315991A (en) | Clock frequency control method and receiver used for it | |
| JP4985535B2 (en) | Demodulator circuit | |
| JPH06232939A (en) | Frame synchronization circuit | |
| CN114095317B (en) | Carrier parameter estimation decoupling method and system suitable for high-order APSK modulation |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |