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CN116073979A - Symbol synchronization method and system of multi-system differential phase shift keying system - Google Patents

Symbol synchronization method and system of multi-system differential phase shift keying system Download PDF

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Publication number
CN116073979A
CN116073979A CN202310123293.1A CN202310123293A CN116073979A CN 116073979 A CN116073979 A CN 116073979A CN 202310123293 A CN202310123293 A CN 202310123293A CN 116073979 A CN116073979 A CN 116073979A
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symbol
sampling point
optimal sampling
phase shift
signal
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Inventor
王倩
赵帮
刘凯捷
李杨梅
曾如意
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Sichuan Jiuzhou ATC Technology Co Ltd
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Sichuan Jiuzhou ATC Technology Co Ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L7/00—Arrangements for synchronising receiver with transmitter
    • H04L7/04—Speed or phase control by synchronisation signals
    • H04L7/041—Speed or phase control by synchronisation signals using special codes as synchronising signal
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J3/00—Time-division multiplex systems
    • H04J3/02—Details
    • H04J3/06—Synchronising arrangements
    • H04J3/0602—Systems characterised by the synchronising information used
    • H04J3/0605—Special codes used as synchronising signal
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

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Abstract

The invention discloses a symbol synchronization method and a system of a multi-system differential phase shift keying system, and relates to the technical field of wireless communication. According to the scheme, the characteristic angle is calculated according to the same-direction output signal and orthogonal output signal according to the characteristic that the deviation between the sending symbol rate and the receiving symbol rate is usually smaller; the result of the frame synchronization process is used as an initial value of symbol synchronization, the optimal sampling point is continuously adjusted, the optimal sampling point of the next symbol is determined according to the offset judgment result, the symbol synchronization is realized, no pilot frequency is required to be additionally introduced, the performance loss of the receiver is reduced, and the structure of the receiver is greatly simplified while the effectiveness is exerted. The invention can realize a fine symbol synchronization process by a simpler design by utilizing the results of frame synchronization and carrier synchronization and the system characteristics.

Description

Symbol synchronization method and system of multi-system differential phase shift keying system
Technical Field
The invention relates to the technical field of wireless communication, in particular to a symbol synchronization method and system of a multi-system differential phase shift keying system.
Background
Symbol synchronization is also called symbol synchronization, bit synchronization, timing synchronization. In digital communication systems, the transmitting end typically uses a baseband filter to pulse the signal so that the spectral width of the transmitted signal is limited. In the receiver, the signal output through down-conversion and filtering is equivalent to the data after sampling the baseband analog signal, and the receiving end needs to select the sampling time, so that the effective signal can be sampled only at the accurate sampling time. The process of selecting the sampling instants is called symbol synchronization. In synchronous digital communications, symbol synchronization is one of the most critical functions in the receiver. In some communication systems, the transmitter and the receiver employ a synchronous clock, which provides an accurate timing signal, and the receiver estimates the delay between transmission and reception, thereby obtaining an accurate clock signal. In addition, the transmitter may add significant clock frequency components to the information signal and then be extracted by the receiver using a narrow band filter. Finally, the clock signal may also be extracted from the received data signal, such a method being referred to as self-synchronization.
In differential phase shift keying systems, the symbol symbols depend on the relative phase between adjacent symbols. One advantage of this modulation method is that the phase of the carrier does not need to be estimated during demodulation, and the demodulation complexity is low. For M-ary differential phase shift keying modulation, the receiver estimates the phase difference of adjacent symbols, calculates the phase difference estimate and
Figure BDA0004080799700000011
distance between them, select nearest theta m As a differential phase estimate.
For the method of synchronizing clocks of the transceiver, the clocks of the transmitter and the receiver are required to be accurately synchronized to the same clock, and the receiver is required to estimate the time delay, so that the implementation difficulty of the method is high, and the method is difficult to realize in many scenes. Another approach is to insert clock frequency information into the information, but this approach can degrade system performance and is generally avoided. When extracting synchronization information from waveforms of unknown information, a more complex receiver design is generally required, and the waveform of the shaped and filtered multi-system differential phase shift keying signal is complex, so that the synchronization difficulty is high.
Disclosure of Invention
The technical problems to be solved by the invention are as follows: the present invention provides a symbol synchronization method and system for a multi-system differential phase shift keying system, which can realize symbol synchronization by using a simple method without additionally introducing pilot signals.
The invention is realized by the following technical scheme:
the scheme provides a symbol synchronization method of a multi-system differential phase shift keying system, which comprises the following steps:
step 1, obtaining a receiving signal of a receiver, and performing analog-to-digital sampling on the receiving signal to obtain an analog-to-digital sampling signal;
step 2, carrying out digital mixing processing on the analog-digital sampling signal to obtain a homodromous output signal and a quadrature output signal;
step 3, calculating a characteristic angle according to the homodromous output signal and the orthogonal output signal;
step 4, under the condition that the frame synchronization is successfully carried out, estimating the estimated optimal sampling point of the next symbol based on the optimal sampling point of the last symbol of the frame start mark; estimating the estimated optimal sampling point of the next symbol based on the optimal sampling point of any one symbol;
step 5, under the condition that the carrier synchronization is successfully performed, performing offset judgment based on the carrier frequency deviation, the characteristic angle and the optimal sampling point of the current symbol: judging whether the estimated optimal sampling point of the next symbol is deviated from the optimal sampling point of the current symbol or not; the carrier frequency difference is the deviation between the carrier frequency of the received signal and the frequency of the local oscillation signal obtained in the carrier synchronization process;
and determining the optimal sampling point of the next symbol according to the offset judgment result, and realizing symbol synchronization.
The working principle of the scheme is as follows: according to the characteristic that the deviation between the sending symbol rate and the receiving symbol rate is usually smaller, the invention uses the result of the frame synchronization process as the initial value of symbol synchronization, continuously adjusts the optimal sampling point under the condition that the frame synchronization and the carrier synchronization are successful, does not need to additionally introduce pilot frequency, and reduces the performance loss of the receiver; the receiver structure is greatly simplified while the effectiveness is exerted.
The invention considers the communication system that the receiving and transmitting sides communicate by taking the frame as a unit, and presumes that the frame synchronization and the carrier synchronization are realized in a certain way. Since differential phase shift keying modulation does not care about the absolute phase information of the symbol, the carrier synchronization referred to in this scheme includes only frequency estimation. On the other hand, the scheme considers that the optimal sampling time of the frame start mark is also determined after the frame synchronization is successful. Based on the above and the characteristics of differential phase shift keying, the invention provides a method for symbol synchronization of signals after frame start marking, and the method can realize a fine symbol synchronization process with a simpler design by utilizing the results of frame synchronization and carrier synchronization and the system characteristics.
The further optimization scheme is that the step 4 comprises the following steps:
with n * The estimated optimal sampling point position of the next symbol is n * +P；
In the case that the frame synchronization has been successfully performed, initializing the position of the first optimal sampling point to the optimal sampling position of the last symbol of the frame start marker;
wherein the method comprises the steps of
Figure BDA0004080799700000021
f l Representing the data rate of the receiver filter output, f s The round function represents rounding the symbol rate agreed for both parties to the communication and then taking the integer value.
In a further optimized scheme, the preprocessing comprises the following steps:
digital mixing processing is carried out on the analog-digital sampling signal:
dividing an analog-digital sampling signal into two paths, wherein one path of the analog-digital sampling signal is input into a same-direction branch (I path) and is subjected to low-pass filtering and extraction to obtain a same-direction output signal; the other path of input quadrature branch (Q path) is subjected to low-pass filtering and extraction to obtain quadrature output signals.
The outputs of the I-path and Q-path multipliers are respectively passed through an integral comb (CIC) filter for low-pass filtering and decimation. The CIC filter can be replaced by a combination of a low pass filter and downsampling. Let the symbol rate agreed by both parties of communication be f s Due to clock skew, the actual symbol rate is equal to f s There may be subtle differences between them. The data rate of the CIC filter output is recorded as
Figure BDA0004080799700000031
Wherein P is a positive integer greater than 1, ">
Figure BDA0004080799700000032
Approach f s The method comprises the steps of carrying out a first treatment on the surface of the The I-path output and the Q-path output of the CIC filter are respectively marked as I n And Q n . Will I n And Q n The corresponding angle value is marked as alpha n When I n And when the characteristic angle is not zero, calculating the characteristic angle according to the following formula:
characteristic angle alpha n ＝arctan(Q n /I n )；
Wherein: q (Q) n Representing quadrature output signals, I n Represents an in-phase output signal, n is a sampling point, arctan is an arctangent function, and the value range is
Figure BDA0004080799700000033
When I n Zero (zero)/(zero)>
Figure BDA0004080799700000034
Further optimizing scheme is that the invention assumes that frame synchronization has been successfully performed and obtains the optimal sampling time of the frame start mark, and marks the optimal sampling point of the last symbol of the frame start mark as n * ：
The characteristic angle includes: characteristic angle of optimal sampling point
Figure BDA00040807997000000315
Characteristic angle +.about.previous sampling point of optimal sampling point>
Figure BDA00040807997000000316
Characteristic angle of next sampling point of optimal sampling point +.>
Figure BDA00040807997000000317
Characteristic angle of P-1 th point after optimal sampling point ∈1>
Figure BDA00040807997000000318
Characteristic angle of P-th point after optimal sampling point +.>
Figure BDA00040807997000000319
And the characteristic angle of the P+1st point after the optimal sampling point +.>
Figure BDA00040807997000000320
The further optimization scheme is that the step 5 comprises the following substeps:
s51, calculating a first intermediate variable delta alpha l A second intermediate variable Deltaalpha and a third intermediate variable Deltaalpha r ：
Figure BDA00040807997000000321
Figure BDA00040807997000000322
Figure BDA00040807997000000323
S52, the first intermediate variable delta alpha l A second intermediate variable Deltaalpha and a third intermediate variable Deltaalpha r Corrected to within the range of [0,2 pi ]
Figure BDA0004080799700000035
And->
Figure BDA0004080799700000036
Figure BDA0004080799700000037
Figure BDA0004080799700000038
Figure BDA0004080799700000039
Wherein mod is modulo arithmetic to
Figure BDA00040807997000000310
For example, a->
Figure BDA00040807997000000311
Wherein k is such that->
Figure BDA00040807997000000312
An integer in the range of [0,2 pi ]; Δf is the carrier frequency offset; Δt is the sampling time interval between the P sampling points;
s53, based on
Figure BDA00040807997000000313
And->
Figure BDA00040807997000000314
And calculating symbol synchronization deviation characteristic values.
Further optimizing scheme is that M-ary differential phase shift keying modulated first deviation characteristic value epsilon l Second deviation feature value epsilon 0 And a third deviation feature value epsilon r Calculated according to the following formula:
Figure BDA0004080799700000041
Figure BDA0004080799700000042
Figure BDA0004080799700000043
where || denotes the absolute value of the expression.
The further optimization scheme is that the fifth step further comprises the following substeps:
s54, comparing the first deviation feature value epsilon l Second deviation feature value epsilon 0 And a third deviation feature value epsilon r To determine a first judgment factor c r And a second judgment factor c l ；
S55, according to the first judgment factor c r And a second judgment factor c l The optimal sampling point is updated.
In a further optimization scheme, step S54 includes the following steps:
determining epsilon l ＜min(ε 0 ，ε r ) Whether or not it is true, if so, let c l ＝c 1 +1，c r ＝0；
Determining epsilon r ＜min(ε 0 ，ε l ) Whether or not it is true, if so, let c r ＝c r +1，c l ＝0；
If epsilon l ＜min(ε 0 ，ε r ) And epsilon r ＜min(ε 0 ，ε 1 ) All are not true, let c r ＝0，c l ＝0；
Wherein c r ，c l The initial values of (2) are all 0; the min (x, y) function represents taking the smaller of x and y.
In a further optimization scheme, step S55 includes the following steps:
judgment c l Whether or not gamma is true, if yes, updating n * Is n * +P-1；
Judgment c r Whether or not gamma is true, if yes, updating n * Is n * +P+1；
If c l Not less than gamma and c r Not holding ≡gamma, updating n * Is n * +P；
Wherein n is * Representing the current optimal sampling point; gamma denotes a preset update threshold.
The present invention also provides a symbol synchronization system of a multi-system differential phase shift keying system, which is configured to implement the symbol synchronization method of a multi-system differential phase shift keying system, and includes:
the sampling module is used for acquiring a received signal of the receiver and performing analog-to-digital sampling on the received signal to obtain an analog-to-digital sampled signal;
the preprocessing module is used for carrying out digital mixing processing on the analog-digital sampling signal to obtain a homodromous output signal and a quadrature output signal;
the first calculation module is used for calculating a characteristic angle according to the homodromous output signal and the orthogonal output signal;
the second calculation module is used for estimating the estimated optimal sampling point of the next symbol based on the optimal sampling point of the last symbol of the frame start mark under the condition that the frame synchronization is successfully carried out; estimating the estimated optimal sampling point of the next symbol based on the optimal sampling point of any one symbol;
the judging module is used for carrying out offset judgment based on the carrier frequency deviation, the characteristic angle and the optimal sampling point of the current symbol under the condition that carrier synchronization is successfully carried out: judging whether the estimated optimal sampling point of the next symbol deviates from the true optimal sampling point or not;
and determining the optimal sampling point of the next symbol according to the offset judgment result, and realizing symbol synchronization.
Compared with the prior art, the invention has the following advantages and beneficial effects:
according to the symbol synchronization method and system of the multi-system differential phase shift keying system, according to the characteristic that the deviation between the sending symbol rate and the receiving symbol rate is usually smaller, the result of the frame synchronization process is used as the initial value of the symbol synchronization, and under the condition that the frame synchronization and the carrier synchronization are successful, the optimal sampling point is continuously adjusted, so that the symbol synchronization is realized. According to the scheme, no pilot frequency is additionally introduced, so that the performance loss of the receiver is reduced; the receiver structure is greatly simplified while the effectiveness is exerted. The invention can realize a fine symbol synchronization process by a simpler design by utilizing the results of frame synchronization and carrier synchronization and the system characteristics.
Drawings
In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the drawings that are needed in the examples will be briefly described below, it being understood that the following drawings only illustrate some examples of the present invention and therefore should not be considered as limiting the scope, and that other related drawings may be obtained from these drawings without inventive effort for a person skilled in the art. In the drawings:
FIG. 1 is a schematic diagram of a symbol synchronization method of the multi-system differential phase shift keying system of the embodiment 1;
fig. 2 is a specific flowchart of a symbol synchronization method of the multi-system differential phase shift keying system of embodiment 2.
Detailed Description
For the purpose of making apparent the objects, technical solutions and advantages of the present invention, the present invention will be further described in detail with reference to the following examples and the accompanying drawings, wherein the exemplary embodiments of the present invention and the descriptions thereof are for illustrating the present invention only and are not to be construed as limiting the present invention.
Example 1
The embodiment provides a symbol synchronization method of a multi-system differential phase shift keying system, which comprises the following steps:
step 1, obtaining a receiving signal of a receiver, and performing analog-to-digital sampling on the receiving signal to obtain an analog-to-digital sampling signal;
step 2, carrying out digital mixing processing on the analog-digital sampling signal to obtain a homodromous output signal and a quadrature output signal;
step 3, calculating a characteristic angle according to the homodromous output signal and the orthogonal output signal;
step 4, under the condition that the frame synchronization is successfully carried out, estimating the estimated optimal sampling point of the next symbol based on the optimal sampling point of the last symbol of the frame start mark; estimating the estimated optimal sampling point of the next symbol based on the optimal sampling point of any one symbol;
step 5, under the condition that the carrier synchronization is successfully performed, performing offset judgment based on the carrier frequency deviation, the characteristic angle and the optimal sampling point of the current symbol: judging whether the estimated optimal sampling point of the next symbol is deviated from the optimal sampling point of the current symbol or not; the carrier frequency difference is the deviation between the carrier frequency of the received signal and the frequency of the local oscillation signal obtained in the carrier synchronization process;
and determining the optimal sampling point of the next symbol according to the offset judgment result, and realizing symbol synchronization.
Example 2
The present embodiment provides a specific symbol synchronization method, as shown in fig. 2:
in step 1, in the receiver, the received signal is converted into an intermediate frequency signal through front-end processing, and analog-to-digital (a/D) sampling is performed on the intermediate frequency signal.
And 2, carrying out digital mixing on the A/D sampling signal, and enabling the A/D sampling to pass through a homodromous branch (I path) multiplier and a quadrature branch (Q path) multiplier.
And 3, respectively passing the output of the I-path multiplier and the output of the Q-path multiplier through an integral comb (CIC) filter to perform extraction and low-pass filtering. Let the symbol rate agreed by both parties of communication be f s Due to clock skew, the actual symbol rate is equal to f s There may be subtle differences between them. The data rate of the CIC filter output is recorded as
Figure BDA0004080799700000061
Wherein P is a positive integer greater than 1, ">
Figure BDA0004080799700000062
Approach f s . The I-path output and the Q-path output of the CIC filter are respectively marked as I n And Q n . Will beI n And Q n The corresponding angle value is marked as alpha n When I n When the time period is not zero,
α n ＝arctan(Q n /I n )，
wherein arctan (x) is an arctangent function, the value range is
Figure BDA0004080799700000063
When I n Zero (zero)/(zero)>
Figure BDA0004080799700000064
The invention assumes that frame synchronization has been successfully performed and obtains the optimal sampling time of the frame start marker, and marks the optimal sampling time of the last symbol of the frame start marker as n * 。
Step 4, calculating
Figure BDA00040807997000000611
Step 5, assuming that the offset between the carrier frequency of the received signal and the local carrier frequency has been obtained by carrier synchronization, denoted Δf. Will I n And I n+P The sampling time interval between the two is recorded as deltat, and the calculation is performed
Figure BDA00040807997000000612
Figure BDA00040807997000000613
Figure BDA00040807997000000614
Step 6, Δα l ，Δα，Δα r Corrected to the range of [0,2 pi ]) to obtain
Figure BDA0004080799700000065
Figure BDA0004080799700000066
Figure BDA0004080799700000067
Wherein mod is a modulo operation; to be used for
Figure BDA0004080799700000068
For example, a->
Figure BDA0004080799700000069
Wherein k is such that->
Figure BDA00040807997000000610
An integer in the range of 0,2 pi).
Step 7, for M-ary differential phase shift keying modulation, calculating the following deviation value
Figure BDA0004080799700000071
Figure BDA0004080799700000072
Figure BDA0004080799700000073
Where round (x) function represents rounding x to an integer value, the |x| function means taking the absolute value of x.
Step 8, when inequality ε l ＜min(ε 0 ，ε r ) When in stand, let c l ＝c l +1，c r =0; when inequality epsilon r ＜min(ε 0 ，ε l ) When in stand, let c r ＝c r +1，c l =0; in other cases, let c r ＝0，c l ＝0。c r ，c l The initial values of (2) are all 0. The min (x, y) function in the inequality represents taking the smaller of x and y.
Step 9, when c l Updating n when gamma is not less than gamma * ＝n * +P-1; when c r Updating n when gamma is not less than gamma * ＝n * +p+1; in other cases, update n * ＝n * +P; gamma is a positive integer and can be selected according to experience; n is n * Representing the optimal sampling position.
Step 10, repeating the steps 4 to 9; as steps 4 to 9 are repeated, the optimal sampling point of each symbol is continuously adjusted, so as to realize symbol synchronization.
Example 3
The present embodiment provides a symbol synchronization system of a multi-system differential phase shift keying system, which is configured to implement the symbol synchronization method of the multi-system differential phase shift keying system described in the previous embodiment, including:
the sampling module is used for acquiring a received signal of the receiver and performing analog-to-digital sampling on the received signal to obtain an analog-to-digital sampled signal;
the preprocessing module is used for preprocessing the analog sampling signal to obtain a homodromous output signal and a quadrature output signal;
the first calculation module is used for calculating a characteristic angle according to the homodromous output signal and the orthogonal output signal;
the second calculation module is used for estimating the estimated optimal sampling point of the next symbol based on the optimal sampling point of the last symbol of the frame start mark under the condition that the frame synchronization is successfully carried out; estimating the estimated optimal sampling point of the next symbol based on the optimal sampling point of any one symbol;
the judging module is used for carrying out offset judgment based on the carrier frequency deviation, the characteristic angle and the optimal sampling point of the current symbol under the condition that carrier synchronization is successfully carried out: judging whether the estimated optimal sampling point of the next symbol deviates from the true optimal sampling point or not;
and determining the optimal sampling point of the next symbol according to the offset judgment result, and realizing symbol synchronization.
The beneficial effects brought by the embodiment are that no pilot frequency is needed to be additionally introduced, and compared with a method based on clock pilot frequency, the method can reduce the performance loss; in addition, the present scheme utilizes the outcome of the frame synchronization process as an initial value of symbol synchronization, followed by continuously adjusting the optimal sampling interval, which is based on the fact that the deviation between the transmitted symbol rate and the received symbol rate is typically small. In summary, the invention meets the practical situation of the system, greatly simplifies the structure of the receiver while exerting efficacy, and avoids performance loss.
The foregoing description of the embodiments has been provided for the purpose of illustrating the general principles of the invention, and is not meant to limit the scope of the invention, but to limit the invention to the particular embodiments, and any modifications, equivalents, improvements, etc. that fall within the spirit and principles of the invention are intended to be included within the scope of the invention.

Claims (10)

1. A symbol synchronization method for a multi-system differential phase shift keying system, comprising:
step 1, obtaining a receiving signal of a receiver, and performing analog-to-digital sampling on the receiving signal to obtain an analog-to-digital sampling signal;
step 2, carrying out digital mixing processing on the analog-digital sampling signal to obtain a homodromous output signal and a quadrature output signal;
step 3, calculating a characteristic angle according to the homodromous output signal and the orthogonal output signal;
step 4, under the condition that the frame synchronization is successfully carried out, estimating the estimated optimal sampling point of the next symbol based on the optimal sampling point of the last symbol of the frame start mark; estimating the estimated optimal sampling point of the next symbol based on the optimal sampling point of any one symbol;
step 5, under the condition that the carrier synchronization is successfully performed, performing offset judgment based on the carrier frequency deviation, the characteristic angle and the optimal sampling point of the current symbol: judging whether the estimated optimal sampling point of the next symbol is deviated from the optimal sampling point of the current symbol or not; the carrier frequency difference is the deviation between the carrier frequency of the received signal and the frequency of the local oscillation signal obtained in the carrier synchronization process;
and determining the optimal sampling point of the next symbol according to the offset judgment result, and realizing symbol synchronization.
2. The symbol synchronization method of a multi-system differential phase shift keying system of claim 1, wherein,
the pretreatment comprises the following steps:
digital mixing processing is carried out on the analog-digital sampling signal:
dividing the analog-digital sampling signal into two paths, wherein one path of analog-digital sampling signal is input into the same-direction branch and the same-direction output signal is obtained through low-pass filtering and extraction; the other input orthogonal branch is subjected to low-pass filtering and extraction to obtain an orthogonal output signal.
3. The symbol synchronization method of a multi-system differential phase shift keying system of claim 2, wherein,
step 4 comprises the following steps:
with n * The estimated optimal sampling point position of the next symbol is n * +P；
In the case that the frame synchronization has been successfully performed, initializing the position of the first optimal sampling point to the optimal sampling position of the last symbol of the frame start marker;
wherein the method comprises the steps of
Figure FDA0004080799690000011
f l Representing the data rate of the receiver filter output, f s The round function represents rounding the symbol rate agreed for both parties to the communication and then taking the integer value.
4. The symbol synchronization method of a multilevel differential phase shift keying system according to claim 1, wherein said characteristic angle comprises: optimum forCharacteristic angle of sampling point
Figure FDA0004080799690000017
Characteristic angle +.about.previous sampling point of optimal sampling point>
Figure FDA0004080799690000012
Characteristic angle of next sampling point of optimal sampling point +.>
Figure FDA0004080799690000013
Characteristic angle of P-1 th point after optimal sampling point ∈1>
Figure FDA0004080799690000014
Characteristic angle of P-th point after optimal sampling point +.>
Figure FDA0004080799690000015
And the characteristic angle of the P+i point after the optimal sampling point +.>
Figure FDA0004080799690000016
The characteristic angle is calculated according to the following formula:
when I n Not zero, characteristic angle alpha n ＝arctan(Q n /I n )；
Wherein: q (Q) n Representing quadrature output signals, I n Represents an in-phase output signal, n is a sampling point, arctan is an arctangent function, and the value range is
Figure FDA0004080799690000021
When I n Zero, characteristic angle
Figure FDA0004080799690000022
5. The symbol synchronization method of a multilevel differential phase shift keying system according to claim 4, wherein the step 5 comprises the sub-steps of:
s51, calculating a first intermediate variable delta alpha l A second intermediate variable Deltaalpha and a third intermediate variable Deltaalpha r ：
Figure FDA0004080799690000023
Figure FDA0004080799690000024
Figure FDA0004080799690000025
S52, the first intermediate variable delta alpha l A second intermediate variable Deltaalpha and a third intermediate variable Deltaalpha r Corrected to the range of [0,2 pi ]) to obtain
Figure FDA0004080799690000026
And->
Figure FDA0004080799690000027
Figure FDA0004080799690000028
Figure FDA0004080799690000029
Figure FDA00040807996900000210
Wherein mod is a modulo operation, Δf is a carrier frequency offset; Δt is the sampling time interval between the P sampling points;
s53, baseIn the following
Figure FDA00040807996900000211
And->
Figure FDA00040807996900000212
And calculating symbol synchronization deviation characteristic values.
6. The symbol synchronization method of a multilevel differential phase shift keying system of claim 5, wherein the first deviation characteristic value epsilon of the M-ary differential phase shift keying modulation l Second deviation feature value epsilon 0 And a third deviation feature value epsilon r Calculated according to the following formula:
Figure FDA00040807996900000213
Figure FDA00040807996900000214
Figure FDA00040807996900000215
where the function represents the absolute value of the expression.
7. The symbol synchronization method of a multilevel differential phase shift keying system according to claim 6, wherein the fifth step further comprises the sub-steps of:
s54, comparing the first deviation feature value epsilon l Second deviation feature value epsilon 0 And a third deviation feature value epsilon r To determine a first judgment factor c r And a second judgment factor c l ；
S55, according to the first judgment factor c r And a second judgment factor c l The optimal sampling point is updated.
8. The symbol synchronization method of a multi-system differential phase shift keying system according to claim 7, wherein the step S54 comprises the steps of:
determining epsilon l ＜min(ε 0 ，ε r ) Whether or not it is true, if so, let c 1 ＝c 1 +1，c r ＝0；
Determining epsilon r ＜min(ε 0 ，ε l ) Whether or not it is true, if so, let c r ＝c r +1，c l ＝0；
If epsilon 1 ＜min(ε 0 ，ε r ) And epsilon r ＜min(ε 0 ，ε 1 ) All are not true, let c r ＝0，c 1 ＝0；
Wherein c r ，c l The initial values of (2) are all 0; the min (x, y) function represents taking the smaller of x and y.
9. The symbol synchronization method of a multi-system differential phase shift keying system according to claim 7, wherein step S55 comprises the steps of:
judgment c l Whether or not gamma is true, if yes, updating n * Is n * +P-1；
Judgment c r Whether or not gamma is true, if yes, updating n * Is n * +P+1；
If c l Not less than gamma and c r Not holding ≡gamma, updating n * Is n * +P；
Wherein n is * Representing the current optimal sampling point; gamma denotes a preset update threshold.
10. A symbol synchronization system for a multilevel differential phase shift keying system, characterized in that it is adapted to implement a symbol synchronization method for a multilevel differential phase shift keying system according to any of claims 1-9, comprising:
the sampling module is used for acquiring a received signal of the receiver and performing analog-to-digital sampling on the received signal to obtain an analog-to-digital sampled signal;
the preprocessing module is used for carrying out digital mixing processing on the analog-digital sampling signal to obtain a homodromous output signal and a quadrature output signal;
the first calculation module is used for calculating a characteristic angle according to the homodromous output signal and the orthogonal output signal;
the second calculation module is used for estimating the estimated optimal sampling point of the next symbol based on the optimal sampling point of the last symbol of the frame start mark under the condition that the frame synchronization is successfully carried out; estimating the estimated optimal sampling point of the next symbol based on the optimal sampling point of any one symbol;
the judging module is used for carrying out offset judgment based on the carrier frequency deviation, the characteristic angle and the optimal sampling point of the current symbol under the condition that carrier synchronization is successfully carried out: judging whether the estimated optimal sampling point of the next symbol deviates from the true optimal sampling point or not;
and determining the optimal sampling point of the next symbol according to the offset judgment result, and realizing symbol synchronization.
CN202310123293.1A 2023-02-16 2023-02-16 Symbol synchronization method and system of multi-system differential phase shift keying system Pending CN116073979A (en)

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