CN107306242B - Carrier phase recovery method and device - Google Patents

Abstract

The present invention provides a carrier phase recovery method and device, wherein the method includes: grouping data to be phase-recovered; for each grouping, obtaining the Euclidean distance F(A ₀ ) corresponding to the angle A ₀ , and the angle The Euclidean distance F(B ₀ ) corresponding to B ₀ , wherein the angle A ₀ and the angle B ₀ are the maximum deviation angle value and the minimum deviation angle value set by the group respectively; obtain the F(A ₀ ) and F(B 0 ) ₀ ), and take the median value of the angle corresponding to the smaller value and the original deviation angle as the new boundary value, repeat the above operation, the number of repetitions is the search depth, and obtain the final deflection angle; obtain the deflection angle and the maximum likelihood phase rotation angle of the data in the group, and use the maximum likelihood phase rotation angle to perform phase recovery on the data in the group, which solves the problem of high complexity of the phase recovery method in the related art and reduces the phase recovery. complexity.

Description

Carrier phase recovery method and device

technical field

The present invention relates to the field of communications, and in particular, to a carrier phase recovery method and device.

Background technique

The high-order modulation format technology in optical communication can effectively improve the spectral efficiency, meet the increasing demand for signal transmission rate, and can be flexibly applied to various communication systems. It has become a key technology in long-distance and large-capacity optical communication systems. For the optical transmission system, the phase rotation affects the reception and demodulation of the signal. The linewidth of the laser and the nonlinear effect of the fiber will also have a certain impact on the phase of the optical signal, especially for the high-order modulation format signals that are sensitive to phase effects. . Therefore, the carrier phase recovery algorithm is an indispensable part of the optical signal processing (Digital Signal Processing, DSP for short) algorithm. In the related art, carrier phase recovery algorithms include Viterbi-Viterbi algorithm, differential demodulation, pilot-based carrier phase recovery algorithm, and blind phase search (Blind Phase Search, BPS for short) and the like. Among them, the combination of the pilot-based carrier phase recovery algorithm and the BPS algorithm can respectively recover the phase roughly and finely, and recover the carrier phase as accurately as possible. The following is the flow of the BPS algorithm (all the following digital symbols are real numbers unless otherwise marked).

下的误差值e_k,m。N为算法分组长度。Step 1: X _k is the input signal, test at different angles

The error value _ek,m under . N is the algorithm packet length.

定义为：

angle

defined as:

The error e _k,m is defined as:

后与距离最近星座点的欧氏距离。N+1为X_k进行一次BPS的数据长度。误差值e_k,m最小的一组对应的判决结果

和初始信息X_k进行第二部最大似然运算。欧式距离定义为：

where d _k,m is defined as the phase rotation of X _k

Then the Euclidean distance from the nearest constellation point. N+1 is the data length for X _k to perform one BPS. A set of corresponding judgment results with the smallest error value _ek,m

Perform the second maximum likelihood operation with the initial information X _k . Euclidean distance is defined as:

Among them, (x ₁ , y ₁ ) and (x ₂ , y ₂ ) are the coordinate values of two points in the two-dimensional plane, respectively.

与X_k进行最大似然运算，得到相位

Step 2:

Perform a maximum likelihood operation with X _k to get the phase

相乘，得到经过BPS相位回复之后的信号

The original signal X _k and

Multiply to get the signal after BPS phase recovery

The above is the BPS phase recovery algorithm. In practical applications, in order to perform phase recovery more accurately, we can do the BPS algorithm twice, that is, the second-order BPS algorithm. The data packet lengths of the second-order BPS algorithm are respectively N1 and N2, and (N1>N2). Performing the second BPS algorithm for shorter data packets can more accurately estimate the phase deviation, making the phase recovery result more accurate.

进行计算求解误差e_k,m，算法的复杂度随着算法的精度的提高而增加，非常不利于实际的硬件实现。The BPS algorithm converts all angles to be compared

When calculating and solving the error _ek,m , the complexity of the algorithm increases with the improvement of the accuracy of the algorithm, which is very unfavorable for actual hardware implementation.

Aiming at the high complexity of the phase recovery method in the related art, there is currently no effective solution.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide a carrier phase recovery method and device, so as to at least solve the problem of high complexity of the phase recovery method in the related art.

According to an embodiment of the present invention, a carrier phase recovery method is provided, comprising: for each group, obtaining the difference between the constellation point corresponding to the group before the phase rotation is performed according to the angle A ₀ and the corresponding constellation point after the phase rotation. The Euclidean distance F(A ₀ ) between the two groups, and the Euclidean distance F(B ₀ ) between the corresponding constellation point before the phase rotation of the grouping according to the angle B ₀ and the corresponding constellation point after the phase rotation, wherein, the The grouping is a data grouping obtained after grouping the data to be phase-recovered, and the angle A ₀ and the angle B ₀ are respectively the maximum deviation angle value and the minimum deviation angle value set by the grouping; obtain the F(A ₀ ) and F(B ₀ ), and take the angle corresponding to the smaller value as the first deflection angle; obtain the maximum likelihood phase rotation angle between the first deflection angle and the data in the grouping , and use the maximum likelihood phase rotation angle to perform phase recovery on the data in the packet.

Optionally, acquiring the smaller value among the F(A ₀ ) and F(B ₀ ) includes: repeating the following steps according to a preset number of times N to obtain the smaller value; redetermining the smaller value according to a preset rule The value of the angle A ₀ and the value of the angle B ₀ respectively obtain the first angle A _i and the second angle B _i ; wherein, A _i =F ^-1 (Min(F(A _i-1 ),F (B _i-1 ))), B _i =(A _i-1 +B _i-1 )/2, i=1,2,3,...,N; when i=N, F(A _N ) and F(B _N ), the smallest value is taken as the smaller value.

Optionally, for each group, obtain the Euclidean distance F(A ₀ ) between the constellation point corresponding to the group before the phase rotation is performed according to the angle A ₀ and the corresponding constellation point after the phase rotation, and the Before grouping the Euclidean distance F(B ₀ ) between the constellation points corresponding to the constellation points before the phase rotation is performed according to the angle B ₀ and the corresponding constellation points after the phase rotation, the method further includes: according to the pilot symbols in the received initial data The position change with the pre-inserted pilot symbols obtains a common phase rotation angle, and the data is phase-recovered according to the common phase rotation angle, wherein the pre-inserted pilot symbols are in the initial data. Pilot symbols pre-inserted by the transmitter.

Optionally, the pre-inserted pilot symbols are pilot symbols inserted at equal intervals at the transmitting end of the initial data.

Optionally, after performing phase recovery on the data in the group by using the maximum likelihood phase rotation angle, the method further includes: reducing the length of the group, and performing the phase recovery on the data in the group after the reduced length. The data is grouped again; for each group, obtain the Euclidean distance F(A ¹ ) between the constellation point corresponding to the group before the phase rotation is performed according to the angle A ¹ and the corresponding constellation point after the phase rotation, and the grouping The Euclidean distance F(B ¹ ) between the corresponding constellation point before the phase rotation is performed according to the angle B ¹ and the corresponding constellation point after the phase rotation, wherein the angle A ¹ and the angle B ¹ are respectively set for the grouping ^The maximum and minimum deviation angle values ^of The second deflection angle is rotated by the maximum likelihood phase rotation angle of the data in the packet, and the phase recovery is performed on the data in the packet using the maximum likelihood phase rotation angle.

According to another embodiment of the present invention, a _carrier phase recovery apparatus is provided, comprising: a first obtaining module, configured to obtain, for each packet, the constellation point and The Euclidean distance F(A _{0 )} between the corresponding constellation points after the phase rotation, and the Euclidean distance F( B ₀ ), wherein the grouping is a data group obtained by grouping the data that needs to be phase-recovered, and the angle A ₀ and the angle B ₀ are respectively the maximum deviation angle value and the minimum deviation angle set by the grouping value; the second acquisition module is used to acquire the smaller value of the F(A ₀ ) and F(B ₀ ), and use the angle corresponding to the smaller value as the first deflection angle; the second phase recovery module , which is used to obtain the maximum likelihood phase rotation angle between the first deflection angle and the data in the group, and use the maximum likelihood phase rotation angle to perform phase recovery on the data in the group.

Optionally, the second obtaining module includes: a repeating execution unit, configured to repeat the following steps according to a preset number of times N, to obtain the smaller value;

A determination unit, re-determining the value of the angle A ₀ and the value of the angle B ₀ according to a preset rule, to obtain the first angle A _i and the second angle B _i respectively; wherein, A _i =F ^-1 ( Min(F(A _i-1 ), F(B _i-1 ))), B _i =(A _i-1 +B _i-1 )/2, i=1,2,3,...,N;

A selection unit for taking the minimum value of F(A _N ) and F(B _N ) as the smaller value when i=N.

Optionally, the device further includes:

The first phase recovery module is used to obtain, for each group, the Euclidean distance F(A ₀ ) between the constellation point corresponding to the group before the phase rotation is performed according to the angle A ₀ and the corresponding constellation point after the phase rotation, And before the Euclidean distance F(B ₀ ) between the corresponding constellation points before phase rotation and the corresponding constellation points after the phase rotation of the grouping according to the angle B ₀ , according to the pilot symbols in the received initial data and the pre-inserted A common phase rotation angle is obtained by the position change between the pilot symbols of Inserted pilot symbols.

Optionally, the pre-inserted pilot symbols are pilot symbols inserted at equal intervals at the transmitting end of the initial data.

Optionally, the apparatus further includes: a grouping module, configured to reduce the length of the grouping after performing phase recovery on the data in the grouping by using the maximum likelihood phase rotation angle, and perform a reduction in the length of the grouped data. The data in the grouping is grouped again ^; the third acquisition module is used for, for each grouping, to acquire the constellation point corresponding to the grouping before the phase rotation is performed according to the angle A1 and the corresponding constellation point after the phase rotation. The Euclidean distance F(A ¹ ), and the Euclidean distance F(B ¹ ) between the constellation point corresponding to the group before the phase rotation is performed according to the angle B ¹ and the corresponding constellation point after the phase rotation, wherein the angle A ¹ and angle B ¹ are respectively the maximum deviation angle value and the minimum deviation angle value set by the group; the fourth obtaining module is used to obtain the smaller value of the F(A ¹ ) and F(B ¹ ), and use the angle corresponding to the smaller value as the second deflection angle; the third phase recovery module is used to obtain the maximum likelihood phase rotation angle between the second deflection angle and the data in the group, and use the maximum The likelihood phase rotation angle performs phase recovery on the data in the packet.

According to the present invention, the data that needs to be phase-recovered are grouped, and the first deflection angle is obtained by using the smaller value of the Euclidean distance corresponding to the maximum offset angle and the minimum offset angle of each group; and the grouping is used. The phase recovery is performed by the maximum likelihood phase rotation angle between the selected optimal deflection angle and the selected optimal deflection angle. It can be seen that the above scheme does not need to calculate all the phase angles of the data to be restored. Therefore, the complexity of the phase recovery is reduced, thereby solving the problem of high complexity of the phase recovery method in the related art.

Description of drawings

The accompanying drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the attached image:

1 is a block diagram of a hardware structure of a mobile terminal of a carrier phase recovery method according to an embodiment of the present invention;

2 is a flowchart of a carrier phase recovery method according to an embodiment of the present invention;

3 is a structural block diagram 1 of a carrier phase recovery apparatus according to an embodiment of the present invention;

4 is a second structural block diagram of a carrier phase recovery apparatus according to an embodiment of the present invention;

5 is a structural block diagram 3 of a carrier phase recovery apparatus according to an embodiment of the present invention;

6 is a structural block diagram 4 of a carrier phase recovery apparatus according to an embodiment of the present invention;

7 is an algorithm flow chart of an improved phase recovery algorithm according to a preferred embodiment of the present invention;

Fig. 8 is the signal processing flow chart of the phase recovery method according to the preferred embodiment of the present invention;

FIG. 9 is a constellation diagram of different phase recovery methods according to a preferred embodiment of the present invention.

Detailed ways

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings and in conjunction with embodiments. It should be noted that the embodiments in the present application and the features of the embodiments may be combined with each other in the case of no conflict.

It should be noted that the terms "first", "second" and the like in the description and claims of the present invention and the above drawings are used to distinguish similar objects, and are not necessarily used to describe a specific sequence or sequence.

Example 1

The method embodiment provided in Embodiment 1 of the present application may be executed in a mobile terminal, a computer terminal, or a similar computing device. Taking running on a mobile terminal as an example, FIG. 1 is a hardware structure block diagram of a mobile terminal of a carrier phase recovery method according to an embodiment of the present invention. As shown in FIG. 1 , the mobile terminal 10 may include one or more (in the figure only Shown is a) processor 102 (processor 102 may include, but is not limited to, processing means such as a microprocessor MCU or programmable logic device FPGA, etc.), memory 104 for storing data, and transmission means 106 for communication functions. Those of ordinary skill in the art can understand that the structure shown in FIG. 1 is only a schematic diagram, which does not limit the structure of the above electronic device. For example, the mobile terminal 10 may also include more or fewer components than those shown in FIG. 1 , or have a different configuration than that shown in FIG. 1 .

The memory 104 can be used to store software programs and modules of the application software, such as program instructions/modules corresponding to the carrier phase recovery method in the embodiment of the present invention. A functional application and data processing are implemented, namely, the above-mentioned method is implemented. Memory 104 may include high-speed random access memory, and may also include non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some instances, the memory 104 may further include memory located remotely from the processor 102, and these remote memories may be connected to the mobile terminal 10 through a network. Examples of such networks include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

Transmission means 106 are used to receive or transmit data via a network. The specific example of the above-mentioned network may include a wireless network provided by the communication provider of the mobile terminal 10 . In one example, the transmission device 106 includes a network adapter (Network Interface Controller, NIC), which can be connected to other network devices through a base station so as to communicate with the Internet. In one example, the transmission device 106 may be a radio frequency (Radio Frequency, RF) module, which is used for wirelessly communicating with the Internet.

A carrier phase recovery method is provided in this embodiment, and FIG. 2 is a flowchart of a carrier phase recovery method according to an embodiment of the present invention. As shown in FIG. 2 , the flowchart includes the following steps:

Step S202, for each grouping, obtain the Euclidean distance F(A ₀ ) between the constellation point corresponding to the group before the phase rotation is performed according to the angle A ₀ and the corresponding constellation point after the phase rotation, and the grouping according to the angle B ₀ is the Euclidean distance F(B ₀ ) between the corresponding constellation point before phase rotation and the corresponding constellation point after phase rotation, wherein the grouping is a data grouping obtained after grouping the data that needs to be phase-recovered, the Angle A ₀ and angle B ₀ are respectively the maximum deviation angle value and the minimum deviation angle value set by the group;

Step S204, obtaining the smaller value among the F(A ₀ ) and F(B ₀ ), and using the angle corresponding to the smaller value as the first deflection angle;

In an optional embodiment of the present application, the smaller value among the F(A ₀ ) and F(B ₀ ) may be obtained in the following manner: repeating the following steps according to a preset number of times N to obtain the smaller value; Re-determine the value of the angle A ₀ and the value of the angle B ₀ according to the preset rules, and obtain the first angle A _i and the second angle B _i respectively; wherein, A _i =F ^-1 (Min(F(A _i-1 ), F(B _i-1 ))), B _i =(A _i-1 +B _i-1 )/2, i=1,2,3,...,N; when i=N , take the minimum value of F(A _N ) and F(B _N ) as the smaller value.

After carrying out the method described in the above-mentioned embodiment, only the Euclidean distance corresponding to the two angle values is compared and the smaller value is selected. In order to obtain the smaller value accurately, the number of times can be set, and the following embodiment method is repeated, Constantly set the new boundary angle value, calculate the Euclidean distance of the new boundary angle value, and then select the smaller value to obtain the first deflection angle.

Step S206: Obtain the maximum likelihood phase rotation angle between the first deflection angle and the data in the group, and use the maximum likelihood phase rotation angle to perform phase recovery on the data in the group.

Optionally, before step S202 is performed, a common phase rotation angle can also be obtained according to the position change between the pilot symbol and the pre-inserted pilot symbol in the received initial data, and the data is processed according to the common phase rotation angle. Phase recovery, wherein the pre-inserted pilot symbols are pilot symbols pre-inserted at the transmitting end of the initial data. The data phase recovery based on the pre-inserted pilot symbols described in this embodiment is a rough phase recovery, similar to the foundation of a project. After the phase recovery described in this embodiment is performed, continuing to execute the method of the present application can Get better phase recovery effect.

In this embodiment, the pre-inserted pilot symbols are pilot symbols inserted at equal intervals at the transmitting end of the initial data, and the pilot symbols are inserted at equal intervals to facilitate the calculation of the common phase rotation angle. In this embodiment, in order to further improve the accuracy of the phase recovery, after the phase recovery is performed on the data in the group by using the maximum likelihood phase rotation angle, the following processing can also be performed on the phase-recovered data in the group:

(1) reduce the length of this grouping, and group the data in this grouping after reducing the length again;

(2) For each group, obtain the Euclidean distance F(A ¹ ) between the constellation point corresponding to the group before the phase rotation is performed according to the angle A ¹ and the corresponding constellation point after the phase rotation, and the grouping according to the angle B ¹ The Euclidean distance F(B ¹ ) between the corresponding constellation point before the phase rotation and the corresponding constellation point after the phase rotation, wherein the angle A ¹ and the angle B ¹ are the maximum deviation angle value and Minimum deviation angle value;

(3) Obtain the smaller value among the F(A ¹ ) and F(B ¹ ), and use the angle corresponding to the smaller value as the first deflection angle;

(4) Obtain the maximum likelihood phase rotation angle between the first deflection angle and the data in the group, and use the maximum likelihood phase rotation angle to perform phase recovery on the data in the group.

What is described in this embodiment is to reduce the length of the data symbol. For example, the previous data group is a group of 128 data. After the phase recovery is performed on the group of 128 data groups, the data is then re-divided into 32 data groups. group, using the solutions shown in steps S202-S208 and the above-mentioned optional solutions to perform phase recovery again.

Optionally, the execution body of the above steps may be a server or a mobile terminal as shown in FIG. 1 , but is not limited thereto.

Through the above steps, the data that needs to be phase-recovered are grouped; and the smaller value in the Euclidean distance corresponding to the maximum offset angle and the minimum offset angle of each grouping is used to obtain the first deflection angle; and the grouping is used The phase recovery is performed by the maximum likelihood phase rotation angle between the data in the middle and the selected optimal deflection angle. It can be seen that the above scheme does not need to calculate all the phase angles of the data to be restored, and calculates two angles each time (that is, the maximum deflection angle Therefore, the complexity of the phase recovery is reduced, thereby solving the problem of high complexity of the phase recovery method in the related art.

Example 2

In this embodiment, a carrier phase recovery apparatus is also provided, and the apparatus is used to implement the above-mentioned embodiments and preferred implementation manners, and what has been described will not be repeated. As used below, the term "module" may be a combination of software and/or hardware that implements a predetermined function. Although the apparatus described in the following embodiments is preferably implemented in software, implementations in hardware, or a combination of software and hardware, are also possible and contemplated.

FIG. 3 is a structural block diagram 1 of a carrier phase recovery apparatus according to an embodiment of the present invention. As shown in FIG. 3 , the apparatus includes:

The first obtaining module 32 is configured to obtain, for each group, the Euclidean distance F(A ₀ ) between the corresponding constellation point before the phase rotation of the group is performed according to the angle A ₀ and the corresponding constellation point after the phase rotation, and the The Euclidean distance F(B ₀ ) between the constellation points corresponding to the grouping before the phase rotation is performed according to the angle B ₀ and the corresponding constellation points after the phase rotation, wherein the grouping is obtained after grouping the data that needs to be phase-recovered The data grouping, the angle A ₀ and the angle B ₀ are respectively the maximum deviation angle value and the minimum deviation angle value set by the group;

The second acquisition module 34, connected with the first acquisition module 32, is used to acquire the smaller value among the F(A ₀ ) and F(B ₀ ), and use the angle corresponding to the smaller value as the first deflection angle;

The second phase recovery module 36, connected to the second acquisition module 34, is used for acquiring the maximum likelihood phase rotation angle between the first deflection angle and the data in the group, and using the maximum likelihood phase rotation angle for the data in the group data for phase recovery.

FIG. 4 is a second structural block diagram of a carrier phase recovery apparatus according to an embodiment of the present invention. As shown in FIG. 4 , the second acquisition module 34 includes:

The repeating execution unit 42 is used for repeating the following steps according to the preset number of times N to obtain the smaller value;

The determination unit 44 is connected with the repeated execution unit 42, and re-determines the value of the angle A ₀ and the value of the angle B ₀ according to preset rules, and obtains the first angle A _i and the second angle B _i respectively; wherein, A _i =F ^-1 (Min(F(A _i-1 ),F(B _i-1 ))), B _i =(A _i-1 +B _i-1 )/2, i=1,2,3 ,...,N;

The selecting unit 46 is connected to the determining unit 44, and is configured to take the minimum value of F(A _N ) and F(B _N ) as the smaller value when i=N.

FIG. 5 is a structural block diagram 3 of a carrier phase recovery apparatus according to an embodiment of the present invention. As shown in FIG. 5 , the apparatus includes:

The first phase recovery module 52 is configured to, for each group, obtain the Euclidean distance F(A ₀ ) between the constellation point corresponding to the group before the phase rotation is performed according to the angle A ₀ and the corresponding constellation point after the phase rotation , and before the Euclidean distance F(B ₀ ) between the corresponding constellation point before the phase rotation of the group and the corresponding constellation point after the phase rotation according to the angle B ₀ , according to the pilot symbol in the received initial data and the preset The position change between the inserted pilot symbols obtains a common phase rotation angle, and phase recovery is performed on the data according to the common phase rotation angle, wherein the pre-inserted pilot symbols are pilot symbols pre-inserted at the transmitting end of the initial data. frequency symbol.

In this embodiment, the pre-inserted pilot symbols are pilot symbols inserted at equal intervals at the transmitting end of the initial data.

FIG. 6 is a fourth structural block diagram of a carrier phase recovery apparatus according to an embodiment of the present invention. As shown in FIG. 6 , the apparatus further includes:

The grouping module 62, connected with the second phase recovery module 36, is used for reducing the length of the grouping after performing phase recovery on the data in the grouping by using the maximum likelihood phase rotation angle, and for reducing the length of the grouping. The data are grouped again;

The third obtaining module 64 is connected to the grouping module 62, and is used for obtaining, for each grouping, the Euclidean distance ^F ( A ¹ ), and the Euclidean distance F(B ¹ ) between the constellation point corresponding to the group before the phase rotation is performed according to the angle B ¹ and the corresponding constellation point after the phase rotation, wherein the angle A ¹ and the angle B ¹ are respectively The maximum deviation angle value and the minimum deviation angle value set for this group;

The fourth acquisition module 66, connected with the third acquisition module 64, is used to acquire the smaller value of the F(A ¹ ) and F(B ¹ ), and use the angle corresponding to the smaller value as the first deflection angle;

The third phase recovery module 68 is connected to the fourth obtaining module 66, and is configured to obtain the maximum likelihood phase rotation angle between the first deflection angle and the data in the group, and use the maximum likelihood phase rotation angle for the data in the group. data for phase recovery.

It should be noted that the above modules can be implemented by software or hardware, and the latter can be implemented in the following ways, but not limited to this: the above modules are all located in the same processor; or, the above modules are located in multiple in the processor.

The following describes in detail with reference to the preferred embodiments of the present invention.

The preferred embodiment of the present invention provides an improved carrier phase recovery algorithm with lower complexity. The improved carrier phase recovery algorithm not only realizes the phase recovery effect of the BPS algorithm, but also reduces the complexity of the algorithm and enhances the feasibility of practical application of the algorithm.

Finding the optimal phase rotation angle in the carrier phase recovery method can be modeled as a mathematical optimization problem, and the objective function is to minimize _ek,m .

使In a noise-free ideal situation, there is

Make

且，

and,

That is, the objective function e(x) has symmetry. At the same time, let

There are the following relationships:

That is, the objective function e(x) has a convex function in the feasible region. That is, the objective function e(x) is a symmetric convex function on the feasible region. Based on the mathematical properties of the symmetric convex function of the function e(x), an improved phase recovery algorithm with lower complexity than the BPS algorithm is proposed.

Fig. 7 is an algorithm flow chart of the improved phase recovery algorithm according to the preferred embodiment of the present invention. As shown in Fig. 7, it shows two parts of the solution described in the preferred embodiment of the present invention. The first part is the coarse phase search. In one part, the pilot frequency is used to correct the phase error, and in the second part, the maximum likelihood phase estimation is used, and the phase recovery is performed according to the maximum likelihood phase rotation angle obtained in the second part. The technical scheme described in the preferred embodiment of the present invention is as follows:

Step 1: Corresponding to the first part of coarse phase recovery in Figure 7, a pilot-based carrier phase recovery algorithm is used to perform phase recovery. The data is grouped at the transmitting end, pilot symbols are inserted at equal intervals in each group of data, and the common phase rotation is calculated at the receiving end using the received pilot symbols and the known inserted pilot symbols, and the receiving end is based on the known insertion The position change of the pilot signal and the received pilot signal obtains a common phase rotation angle, and phase recovery is performed on the group of data.

Step 2: Regroup the signals after the initial phase recovery in the first step, set the search depth N and the search range boundary values A and B, and calculate the error functions corresponding to the angles A and B, namely the Euclidean distances F(A) and F(B ). The search depth in this embodiment means search times, which corresponds to the preset times N in Embodiment 1, and the search range boundary values A and B correspond to the maximum deviation angle value and the minimum deviation angle value in Embodiment 1, respectively.

Step 3: Find the smaller value of F(A) and F(B), and let A=F-1(Min(F(A),F(B))), let B=(A+B) )/2. After finding the smaller value, set new boundary values A and B,

Step 4: Determine whether the search depth is greater than N. If the search depth does not reach the preset value N, return to the second step to repeat the calculation of the smaller value according to the new boundary values A and B obtained in the third step. When the search depth reaches the preset value N, the angle corresponding to the smaller value at the moment is the optimal deflection angle.

Step 5: Using the method of maximum likelihood estimation, estimate the maximum likelihood phase rotation angle between the received data and the optimal deflection angle, and use the obtained maximum likelihood phase rotation angle to perform phase recovery on the set of data.

Step 6: Reduce the length of the grouped data symbols, continue to group the data that has undergone the above phase recovery, and repeat the second to fifth steps to complete the second-order phase recovery algorithm.

In the preferred embodiment of the present invention, the parameters A and B determine the phase range of the algorithm search, that is, the search phase interval of the algorithm is [A, B], and the parameter N determines the accuracy of the algorithm for the search phase. According to the carrier phase of the above method The accuracy of the recovery algorithm is

Fig. 8 is the signal processing flow chart of the phase recovery method according to the preferred embodiment of the present invention, as shown in Fig. 8: first select the maximum value A and the minimum value B of the angle deviation, calculate their Euclidean distances before and after demodulation, and use a predefined The formula obtains new deviation values A and B, and judges whether the preset search depth bisection depth is reached. In the case of reaching the bisection depth, the new deviation value A is recorded as the optimal deflection angle.

The method described in the preferred embodiment of the present invention reduces the complexity of the traditional phase recovery algorithm, and the improved phase recovery algorithm lies in how to find the phase rotation angle corresponding to the minimum decision error. The BPS algorithm is to traverse, calculate and judge all the phase rotation angles that need to be judged, obtain the error sum, and then compare the error sums corresponding to all the phase rotation angles to obtain the error sum and the minimum value. Then the maximum likelihood estimation algorithm is used to obtain the phase rotation angle, and the signal is processed by this angle to restore the phase. The process of the BPS algorithm is cumbersome and complicated. The improved phase recovery algorithm simplifies the process. After analyzing the objective function e(x) as a symmetric convex function in the feasible domain, that is, after verifying the feasibility of the algorithm, it is not necessary to All phase angles are calculated, but two angles are calculated each time for calculation and comparison, and only the angle corresponding to the smaller error is retained, which can reduce the computational complexity at a logarithmic speed. The complexity comparison is as follows:

1. The improved phase recovery algorithm has the advantage of time complexity in serial calculation:

If the serial calculation is considered, in the comparison process, the time complexity of the BPS algorithm is O(n), and the space complexity of the improved phase recovery algorithm is O(time complexity logn). For example: dividing 64 angles, the BPS algorithm compares 64 times, and the improved phase recovery algorithm compares 6 times.

2. The improved phase recovery algorithm has the advantage of space complexity in parallel computing:

If parallel computing is considered, the space complexity of the BPS algorithm is O(n), and the space complexity of the improved phase recovery algorithm is 2. For example: dividing 64 angles, the BPS algorithm needs 64 storage spaces, and the storage space is logarithmically decreased after each comparison. The improved phase recovery algorithm only needs two storage spaces to store the current data and the comparison data each time.

To sum up, compared with the BPS algorithm, the improved phase recovery algorithm has a similar improvement in system performance, and has the advantage of time complexity in serial computing and space complexity in parallel computing. Therefore, the improved phase recovery algorithm has better performance compared with the BPS algorithm. At the same time, the improved phase recovery algorithm can also be extended to a second-order algorithm by setting different packet lengths to enhance the accuracy of the phase recovery algorithm. By doing coarse phase recovery with longer groupings, the influence of noise on the phase recovery algorithm can be effectively reduced. Then, by performing fine phase recovery in smaller groups, the phase can be recovered more accurately by using local phase information.

The carrier phase recovery method and device provided in an optional embodiment of the present invention can be applied to a Nyquist coherent optical communication transmission system, where the symbol rate of the system is 5.8 Gaud, and the modulation format used is 64QAM (Quadrature Amplitude Modulation (Quadrature Amplitude Modulation) , Quadrature Amplitude Modulation, referred to as QAM). The lengths of the fast Fourier transform and the inverse fast Fourier transform are both 128, and 2 pilot signals are used for phase estimation. The number of wavelengths is 8, and the transmission distance is 160km. In the phase recovery algorithm part, the pilot-based carrier phase recovery is used first, and then the second-order phase recovery algorithm is used for further phase recovery.

Step 1: Use pilot-based carrier phase recovery algorithm for phase recovery. At the transmitting end, the data is grouped into groups of 128 symbols, and pilot frequencies PILOT _k,i are inserted into each group of data at equal intervals, where PILOT _k,i is the i-th pilot frequency in the k-th group of data to be transmitted. pilot _k,i is the i-th pilot in the received k-th group of data. Divide the two to obtain the phase rotation amount rotate _k,i , normalize the rotate _k,i and obtain the average phase rotation amount of the kth group of data. The data X _k is divided by the pilot rotation amount to obtain the phase-corrected data.

Step 2: Regroup the recovered signals into groups of 128, and initially set the search depth N=5 and the search range boundary values A=-20°, B=20° and n=0.

Step 3: Calculate the Euclidean distances F (A=-20°) and F (B=20°) corresponding to the angles A=-20° and B=20°. Find the smaller value of F(A=-20°) and F(B=20°), keep the angle corresponding to A=Min(F(A=-20°), F((B=20°)) Let B=(A+B)/2=(-20°+20°)/2=0°, n=n+1.

Step 4: Determine whether the search depth n is equal to N, if not, repeat the steps of the third step and the fourth step according to the new boundary angle value of the third step. If so, record the angle value corresponding to the smaller value as the optimal deflection angle.

Step 5: Using the method of maximum likelihood estimation, the maximum likelihood phase rotation angle between the received data and the optimal deflection angle is estimated. Phase recovery is performed on this set of data using the maximum likelihood phase rotation angle.

The sixth step: reducing the length of the packet data symbols to a group of 32, and repeating the above calculation steps for new packets to complete the second-order improved phase recovery algorithm.

In order to compare the effect of the phase recovery algorithm and the performance of the two algorithms, the bit error rates of the non-phase recovery algorithm, the BPS phase recovery algorithm and the improved phase recovery algorithm are compared. The bit error rates of the three are: 0.0421, 0.0160, 0.0162 respectively. , Fig. 9 is a constellation diagram of different phase recovery methods according to a preferred embodiment of the present invention, as shown in Fig. 9 , the Nyquist coherent optical communication system of 5.8Gaud without adding phase recovery algorithm, BPS algorithm, and improved phase recovery The bit error rate comparison result of the algorithm.

It can be seen from Figure 9 and the three bit error rate results that compared with the BPS phase recovery algorithm, the improved phase recovery algorithm has a similar improvement in system performance, and has the advantage of time complexity in serial computing, and in parallel computing. has the advantage of space complexity. That is, the improved phase recovery algorithm has an advantage in complexity compared with the BPS phase recovery algorithm.

From the description of the above embodiments, those skilled in the art can clearly understand that the method according to the above embodiment can be implemented by means of software plus a necessary general hardware platform, and of course can also be implemented by hardware, but in many cases the former is better implementation. Based on this understanding, the technical solutions of the present invention can be embodied in the form of software products in essence or the parts that make contributions to the prior art, and the computer software products are stored in a storage medium (such as ROM/RAM, magnetic disk, CD-ROM), including several instructions to make a terminal device (which may be a mobile phone, a computer, a server, or a network device, etc.) to execute the methods described in the various embodiments of the present invention.

Example 3

Embodiments of the present invention also provide a storage medium. Optionally, in this embodiment, the above-mentioned storage medium may be configured to store program codes for executing the following steps:

S1, group the data that needs to be phase-recovered;

S2, for each group, obtain the Euclidean distance F(A ₀ ) between the constellation point corresponding to the group before the phase rotation is performed according to the angle A ₀ and the corresponding constellation point after the phase rotation, and the grouping is obtained according to the angle B ₀ . The Euclidean distance F(B ₀ ) between the corresponding constellation point before the phase rotation and the corresponding constellation point after the phase rotation, wherein the angle A ₀ and the angle B ₀ are the maximum deviation angle value and the minimum value set by the group respectively. Deviation angle value;

S3, obtain the smaller value among the F(A ₀ ) and F(B ₀ ), and use the angle corresponding to the smaller value as the first deflection angle;

S4: Obtain the maximum likelihood phase rotation angle between the first deflection angle and the data in the group, and use the maximum likelihood phase rotation angle to perform phase recovery on the data in the group.

Optionally, the storage medium is further configured to store program codes for executing the method steps described in the foregoing embodiments:

Optionally, in this embodiment, the above-mentioned storage medium may include but is not limited to: a U disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a mobile hard disk, a magnetic Various media that can store program codes, such as discs or optical discs.

Optionally, in this embodiment, the processor executes the method steps described in the foregoing embodiments according to program codes stored in the storage medium.

Optionally, for specific examples in this embodiment, reference may be made to the examples described in the foregoing embodiments and optional implementation manners, and details are not described herein again in this embodiment.

Obviously, those skilled in the art should understand that the above-mentioned modules or steps of the present invention can be implemented by a general-purpose computing device, which can be centralized on a single computing device, or distributed in a network composed of multiple computing devices Alternatively, they may be implemented in program code executable by a computing device, such that they may be stored in a storage device and executed by the computing device, and in some cases, in a different order than here The steps shown or described are performed either by fabricating them separately into individual integrated circuit modules, or by fabricating multiple modules or steps of them into a single integrated circuit module. As such, the present invention is not limited to any particular combination of hardware and software.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (8)

1. A carrier phase recovery method, comprising:

for each packet, obtaining the packet at an angle A₀Euclidean distance F (A) between constellation points corresponding to the phase rotation before and after the phase rotation₀) And said grouping is according to an angle B₀Euclidean distance F (B) between constellation points corresponding to the phase rotation before and after the phase rotation₀) Wherein, the grouping is a data grouping obtained by grouping data which needs to be phase recovered, and the angle A is₀And angle B₀A maximum deviation angle value and a minimum deviation angle value set for the grouping, respectively;

obtaining the F (A)₀) And F (B)₀) The smaller value of the first deflection angle is set as the angle corresponding to the smaller value; said obtaining said F (A)₀) And F (B)₀) The smaller of these includes: repeatedly executing the following steps according to a preset number of times N to obtain the smaller value; re-determining the angle A according to a preset rule₀And the angle B₀Respectively obtaining a first angle A_iAnd a second angle B_i(ii) a Wherein A is_i＝F^-1(Min(F(A_i-1),F(B_i-1)))，B_i＝(A_i-1+B_i-1) 2, i ═ 1,2,3, ·, N; when i is N, F (B) will be mixed_N) The minimum value of (3) as the smaller value;

and acquiring the first deflection angle and the maximum likelihood phase rotation angle of the data in the packet, and performing phase recovery on the data in the packet by using the maximum likelihood phase rotation angle.

2. The method of claim 1, wherein for each packet, the packet is obtained at an angle a₀Euclidean distance F (A) between constellation points corresponding to the phase rotation before and after the phase rotation₀) And said grouping is according to an angle B₀Euclidean distance F (B) between constellation points corresponding to the phase rotation before and after the phase rotation₀) Previously, the method further comprises:

and obtaining a common phase rotation angle according to the position change between a pilot symbol in the received initial data and a pilot symbol inserted in advance, and performing phase recovery on the data according to the common phase rotation angle, wherein the pilot symbol inserted in advance is the pilot symbol inserted in advance at the transmitting end of the initial data.

3. The method of claim 2, wherein the pre-inserted pilot symbols are pilot symbols that are inserted at equal intervals at a transmitting end of the initial data.

4. The method of any of claims 1-3, wherein after phase recovering the data in the packet using the maximum likelihood phase rotation angle, the method further comprises:

reducing the length of the packet, and grouping the data in the packet after the length is reduced again;

for each packet, obtaining the packet at an angle A₁Euclidean distance F (A) between constellation points corresponding to the phase rotation before and after the phase rotation₁) And said grouping is according to an angle B₁Euclidean distance F (B) between constellation points corresponding to the phase rotation before and after the phase rotation₁) Wherein the angle A₁And angle B₁A maximum deviation angle value and a minimum deviation angle value set for the grouping, respectively;

obtaining the F (A)₁) And F (B)₁) The smaller value of the first deflection angle and taking the angle corresponding to the smaller value as a second deflection angle;

and acquiring the second deflection angle and the maximum likelihood phase rotation angle of the data in the packet, and performing phase recovery on the data in the packet by using the maximum likelihood phase rotation angle.

5. A carrier phase recovery apparatus, comprising:

a first obtaining module for obtaining, for each packet, the packet at an angle A₀Euclidean distance F (A) between constellation points corresponding to the phase rotation before and after the phase rotation₀) And said grouping is according to an angle B₀Euclidean distance F (B) between constellation points corresponding to the phase rotation before and after the phase rotation₀) Wherein, the grouping is a data grouping obtained by grouping data which needs to be phase recovered, and the angle A is₀And angle B₀Maximum deviation angle value and minimum deviation angle value respectively set for the groupingA value;

a second acquisition module for acquiring the F (A)₀) And F (B)₀) The smaller value of the first deflection angle is set as the angle corresponding to the smaller value; the second obtaining module further comprises: the repeated execution unit is used for repeatedly executing the following steps according to the preset times N to obtain the smaller value; a determining unit for re-determining the angle A according to a preset rule₀And the angle B₀Respectively obtaining a first angle A_iAnd a second angle B_i(ii) a Wherein A is_i＝F^-1(Min(F(A_i-1),F(B_i-1)))，B_i＝(A_i-1+B_i-1) 2, i ═ 1,2,3, ·, N; a selecting unit for selecting F (A) when i is equal to N_N) And F (B)_N) The minimum value of (3) as the smaller value;

and the second phase recovery module is used for acquiring the first deflection angle and the maximum likelihood phase rotation angle of the data in the packet and performing phase recovery on the data in the packet by using the maximum likelihood phase rotation angle.

6. The apparatus of claim 5, further comprising:

a first phase recovery module for obtaining, for each packet, the packet at an angle A₀Euclidean distance F (A) between constellation points corresponding to the phase rotation before and after the phase rotation₀) And said grouping is according to an angle B₀Euclidean distance F (B) between constellation points corresponding to the phase rotation before and after the phase rotation₀) In the prior art, a common phase rotation angle is obtained according to a position change between a pilot symbol in received initial data and a pilot symbol inserted in advance, and phase recovery is performed on the data according to the common phase rotation angle, wherein the pilot symbol inserted in advance is a pilot symbol inserted in advance at a transmitting end of the initial data.

7. The apparatus of claim 6, wherein the pre-inserted pilot symbols are pilot symbols that are inserted at equal intervals at a transmitting end of the initial data.

8. The apparatus of any one of claims 5 to 7, further comprising:

a grouping module for reducing the length of the packet after performing phase recovery on the data in the packet using the maximum likelihood phase rotation angle, and regrouping the data in the packet after the length reduction;

a third obtaining module for obtaining, for each packet, the angle A according to which the packet is₁Euclidean distance F (A) between constellation points corresponding to the phase rotation before and after the phase rotation₁) And said grouping is according to an angle B₁Euclidean distance F (B) between constellation points corresponding to the phase rotation before and after the phase rotation₁) Wherein the angle A₁And angle B₁A maximum deviation angle value and a minimum deviation angle value set for the grouping, respectively;

a fourth obtaining module for obtaining the F (A)₁) And F (B)₁) The smaller value of the first deflection angle and taking the angle corresponding to the smaller value as a second deflection angle;

and the third phase recovery module is used for acquiring the second deflection angle and the maximum likelihood phase rotation angle of the data in the packet and performing phase recovery on the data in the packet by using the maximum likelihood phase rotation angle.

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