WO2017181763A1

WO2017181763A1 - Carrier phase recovery method and apparatus, and storage medium

Info

Publication number: WO2017181763A1
Application number: PCT/CN2017/074016
Authority: WO
Inventors: 费爱梅; 廖屏; 张帆; 吕鑫
Original assignee: 中兴通讯股份有限公司
Priority date: 2016-04-20
Filing date: 2017-02-17
Publication date: 2017-10-26
Also published as: CN107306242B; CN107306242A

Abstract

Provided are a carrier phase recovery method and apparatus, and a storage medium. The method comprises: grouping data needing a phase recovery; with regard to each group, acquiring a Euclidean distance F(A₀) corresponding to an angle A₀, and a Euclidean distance F(B₀) corresponding to an angle B₀, wherein the angle A₀ and the angle B₀ are respectively the maximum deviation angle value and the minimum deviation angle value set by the group; acquiring a smaller value of F(A₀) and F(B₀), and regarding a median value of an angle, corresponding to the smaller value, and an original deviation angle as a new boundary value; repeating the above operations, with the number of times of repetition being a search depth; deriving the final deviation angle; acquiring the maximum likelihood phase rotation angle of the deviation angle and the data in the group; and using the maximum likelihood phase rotation angle to perform a phase recovery on the data in the group.

Description

Carrier phase recovery method, device and storage medium

Technical field

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

Background technique

The high-order modulation format technology in optical communication can effectively improve the spectral efficiency, meet the increasing signal transmission rate requirements, and can be flexibly applied to various communication systems, and has become a key technology in long-distance large-capacity optical communication systems. For optical transmission systems, phase rotation affects the reception and demodulation of the signal. The linewidth of the laser and the nonlinear effect of the fiber also have a certain influence on the phase of the optical signal, especially for high-order modulation format signals that are sensitive to phase effects. . Therefore, the carrier phase recovery algorithm is an indispensable part of the Digital Signal Processing (DSP) algorithm. In the related art, the carrier phase recovery algorithm includes a Viterbi-Viterbi algorithm, a differential demodulation, a pilot-based carrier phase recovery algorithm, and a Blind Phase Search (BPS). Among them, the combination of the pilot-based carrier phase recovery algorithm and the BPS algorithm can roughly restore the phase and fine recovery phase, respectively, and perform carrier phase recovery as accurately as possible.

In practical applications, in order to perform phase recovery more accurately, two BPS algorithms, that is, a second-order BPS algorithm, can be performed. The data packet lengths of the second-order BPS algorithm are respectively N1, N2, and (N-1>N2). A second BPS algorithm for shorter data packets can estimate the phase deviation more accurately, making the phase recovery result more accurate.

BPS algorithm will all angles to be compared

Calculating the solution error e _k,m , the complexity of the algorithm increases with the accuracy of the algorithm, which is very unfavorable for the actual hardware implementation.

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

Summary of the invention

The embodiment of the invention provides a carrier phase recovery method, device and storage medium to solve at least 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, including: for each packet, acquiring a constellation point corresponding to a constellation point and a phase corresponding to a phase rotation before the phase rotation according to the angle A ₀ The Euclidean distance F(A ₀ ) between the two, and the Euclidean distance F(B ₀ ) between the constellation points corresponding to the constellation point and the phase rotation after the phase rotation of the packet according to the angle B ₀ , wherein The grouping is a data group obtained by grouping data that needs to be phase-recovered, and the angle A ₀ and the angle B ₀ are respectively a maximum deviation angle value and a minimum deviation angle value set by the group; and acquiring the F ( a smaller value of A ₀ ) and F(B ₀ ), and taking an angle corresponding to the smaller value as a first deflection angle; acquiring a maximum likelihood phase rotation of the first deflection angle and data in the packet Angle, and phase recovery of data in the packet using the maximum likelihood phase rotation angle.

Optionally, obtaining the smaller value of the F(A ₀ ) and F(B ₀ ) includes: repeating the following steps according to the preset number of times N to obtain the smaller value:

According to a preset rule and re-determining the value of the angle of the angle A ₀ values of B _0, respectively the first angle and the second angle A _i B _i; _{^{where, 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, the minimum value among F(A _N ) and F(B _N ) is taken as the smaller value.

Optionally, for each packet, obtain the Euclidean distance F(A ₀ ) between the constellation points corresponding to the packet before the phase rotation according to the angle A ₀ and the constellation points corresponding to the phase rotation, and the grouping The method further includes: before the Euclidean distance F(B ₀ ) between the corresponding constellation point and the constellation point corresponding to the phase rotation after the phase rotation according to the angle B ₀ , the method further includes:

And obtaining a common phase rotation angle according to the position change between the pilot symbol and the pre-inserted pilot symbol in the received initial data, and performing phase recovery on the data according to the common phase rotation angle, wherein the pre-inserted The pilot symbols are pilot symbols that are pre-inserted at the transmitting end of the initial data.

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

Optionally, after performing phase recovery on the data in the packet by using the maximum likelihood phase rotation angle, the method further includes:

Reducing the length of the packet, and re-grouping the data in the packet after the reduced length; for each packet obtained by the re-grouping, acquiring the packet before the phase rotation according to the angle A ¹ The Euclidean distance F(A ¹ ) between the constellation points and the constellation points corresponding to the phase rotation, and the European constellation between the corresponding constellation points and the constellation points after the phase rotation of the group before the phase rotation according to the angle B ¹ a distance F (B ¹ ), wherein the angle A ¹ and the angle B ¹ are respectively: a maximum deviation angle value and a minimum deviation angle value set by the group obtained by the re-grouping;

Obtaining a smaller value of the F(A ¹ ) and F(B ¹ ), and using an angle corresponding to the smaller value as a second deflection angle;

Obtaining a maximum likelihood phase rotation angle of the second deflection angle and the data in the re-grouped packet, and using the maximum likelihood phase rotation angle to the group obtained by the re-grouping The data is phase restored.

According to another embodiment of the present invention, a carrier phase recovery apparatus is provided, comprising: a first acquisition module configured to acquire, for each packet, a constellation point corresponding to the packet before phase rotation according to the angle A ₀ and The Euclidean distance F(A ₀ ) between the constellation points corresponding to the phase rotation, and the Euclidean distance F between the constellation points corresponding to the constellation points and the phase rotations before the phase rotation of the group before the phase rotation according to the angle B ₀ (B ₀ ), wherein the packet is a data packet obtained by grouping data requiring phase recovery, and the angle A ₀ and the angle B ₀ are respectively a maximum deviation angle value and a minimum deviation set by the packet An angle obtaining value, configured to acquire a smaller value of the F(A ₀ ) and F(B ₀ ), and use an angle corresponding to the smaller value as a first deflection angle; And a module configured to acquire a maximum likelihood phase rotation angle of the first deflection angle and data in the packet, and perform phase recovery on data in the packet using the maximum likelihood phase rotation angle.

Optionally, the second obtaining module includes: a repeating execution unit configured to repeatedly perform the following steps according to the preset number of times N trigger determining unit and the selecting unit to obtain the smaller value;

Determining a unit, re-determining the value of the angle A _{0 and} the value of the angle B ₀ according to a preset rule, respectively obtaining a first angle A _i and a 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;

The unit is selected to be configured to take the minimum value of F(A _N ) and F(B _N ) as the smaller value when i=N.

Optionally, the device further includes: a first phase recovery module;

For each grouping, the first acquisition module acquires the Euclidean distance F(A ₀ ) between the constellation points corresponding to the group before the phase rotation according to the angle A ₀ and the constellation points corresponding to the phase rotation, and Before the grouping point before the phase rotation according to the angle B ₀ and the Euclidean distance F(B ₀ ) between the constellation points corresponding to the phase rotation,

The first phase recovery module is configured to obtain a common phase rotation angle according to a position change between the pilot symbol and the pre-inserted pilot symbol in the received initial data, according to the public The data is phase restored by a common phase rotation angle, wherein the pre-inserted pilot symbols are pilot symbols that are pre-inserted at the transmitting end of the initial data.

Optionally, the apparatus further includes: a grouping module configured to reduce the length of the packet after the second phase recovery module performs phase recovery on the data in the packet using the maximum likelihood phase rotation angle And re-grouping the data in the packet after the reduced length; the third obtaining module is configured to acquire, for each packet obtained by the re-grouping, the phase before the phase rotation according to the angle A ¹ Corresponding to the Euclidean distance F(A ¹ ) between the constellation point and the constellation point corresponding to the phase rotation, and the constellation point corresponding to the constellation point and the corresponding constellation point before the phase rotation of the packet before the phase rotation according to the angle B ¹ The Euclidean distance F(B ¹ ), wherein the angle A ¹ and the angle B ¹ are respectively: a maximum deviation angle value and a minimum deviation angle value set by the group obtained by the re-grouping; and a fourth acquisition module, Configuring to acquire a smaller value of the F(A ¹ ) and F(B ¹ ), and using an angle corresponding to the smaller value as a second deflection angle; and a third phase recovery module configured to acquire the first Two deflection And a maximum likelihood phase rotation angle of the data in the packet obtained by the re-grouping, and phase recovery of the data in the re-packetized packet using the maximum likelihood phase rotation angle.

According to another embodiment of the present invention, there is provided a storage medium storing a computer program, the computer program being executed by a processor to implement the steps:

For each packet, obtain the Euclidean distance F(A ₀ ) between the constellation points corresponding to the segment before the phase rotation according to the angle A ₀ and the constellation points corresponding to the phase rotation, and acquire the packet at the angle B ₀ : Euclidean distance F(B ₀ ) between the constellation points corresponding to the phase rotation and the constellation points corresponding to the phase rotation, wherein the grouping is: a data packet obtained by grouping data requiring phase recovery; The angle A ₀ and the angle B ₀ are respectively: a maximum deviation angle value and a minimum deviation angle value set by the grouping;

Obtaining a smaller value of the F(A ₀ ) and F(B ₀ ), and using an angle corresponding to the smaller value as the first deflection angle;

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

According to the embodiment of the present invention, the data that needs to be phase-recovered is grouped, and the first deflection angle is obtained by using the smaller value of the maximum offset angle and the minimum offset angle corresponding to each packet, and the first deflection angle is used; The data in the group is phase-recovered with the maximum likelihood phase rotation angle of the selected optimal deflection angle. It can be seen that the above solution does not need to calculate all phase angles of the data to be recovered, and only two angles are calculated at a time (ie, The maximum offset angle and the minimum offset angle are sufficient, and therefore, the complexity of phase recovery is reduced, thereby solving the problem of high complexity of the phase recovery method in the related art.

DRAWINGS

The drawings described herein are intended to provide a further understanding of the invention, and are intended to be a part of the invention. In the drawing:

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

2 is a flow chart 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 block diagram 2 of a carrier phase recovery apparatus according to an embodiment of the present invention;

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

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

7 is a flowchart of an algorithm of an improved phase recovery algorithm in accordance with one embodiment of the present invention;

FIG. 8 is a flowchart of signal processing of a phase recovery method according to an embodiment of the present invention; FIG.

9 is a constellation diagram of different phase recovery methods in accordance with one embodiment of the present invention.

detailed description

The invention will be described in detail below with reference to the drawings in conjunction with the embodiments. It should be noted that the embodiments in the present application and the features in the embodiments may be combined with each other without conflict.

It is to be understood that the terms "first", "second" and the like in the specification and claims of the present invention are used to distinguish similar objects, and are not necessarily used to describe a particular order or order.

The following is a brief introduction to the flow of the BPS algorithm (all the following numerical symbols are marked with a real number unless otherwise marked).

The first step: X _k is the input signal, tested at different angles

The error value e _{k,m below} . N is the algorithm packet length.

angle

defined as:

The error e _{k,m is} defined as:

Where d _{k,m is} defined as the X _k phase rotation

After the Euclidean distance from the nearest constellation point. N+1 is the data length of BPS once for _Xk . a set of corresponding decision results with the smallest error value e _k,m

A second maximum likelihood operation is performed with the initial information _Xk . The Euclidean distance is defined as:

Wherein (x ₁ , y ₁ ), (x ₂ , y ₂ ) are coordinate values of two points in a two-dimensional plane, respectively.

The second step:

versus

Perform maximum likelihood operation to get phase

Original signal X _k and

Multiply, get the signal after BPS phase recovery

The above is the BPS phase recovery algorithm.

Example 1

The method embodiment provided by Embodiment 1 of the present application can be executed in a mobile terminal, a computer terminal or the like. 1 is a block diagram of a hardware structure of a mobile terminal according to 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 (only in the figure). A processor 102 is shown (the processor 102 can include, but is not limited to, a processing device such as a microprocessor MCU or a programmable logic device FPGA), a memory 104 configured to store data, and a transmission device 106 configured to communicate functionality. It will be understood by those skilled in the art that the structure shown in FIG. 1 is merely illustrative and 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.

The memory 104 can be configured as a software program and a module for storing application software, such as program instructions/modules corresponding to the carrier phase recovery method in the embodiment of the present invention, and the processor 102 executes by executing a software program and a module stored in the memory 104. Various functional applications and data processing, that is, the above methods are 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 examples, memory 104 may also include memory remotely located relative to processor 102, which may be connected to mobile terminal 10 over a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.

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

A carrier phase recovery method is provided in this embodiment. 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 process includes the following steps:

Step S202, for each group, obtain the Euclidean distance F(A ₀ ) between the constellation points corresponding to the group before the phase rotation according to the angle A ₀ and the constellation points corresponding to the phase rotation, and the group is according to the angle B ₀ , the Euclidean distance F(B ₀ ) between the constellation points corresponding to the phase rotation and the constellation points corresponding to the phase rotation, wherein the packet is a data packet obtained by grouping data requiring phase recovery, 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;

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

In an optional embodiment of the present application, the smaller value of the F(A ₀ ) and the F(B ₀ ) may be obtained by repeatedly performing the following steps according to the preset number of times N to obtain the smaller value; Re-determining the value of the angle A _{0 and} the value of the angle B ₀ according to a preset rule, respectively obtaining a first angle A _i and a 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; in When i=N, the minimum value among F(A _N ) and F(B _N ) is taken as the smaller value.

After the method described in the above embodiment is executed, only the Euclidean distance corresponding to the two angle values is compared, that is, the smaller value is selected. In order to accurately obtain the smaller value, the number of times can be set, and the following 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, acquiring the first deflection angle and the maximum likelihood phase rotation of the data in the group Angle, and phase recovery of the data in the packet using the maximum likelihood phase rotation angle.

Optionally, before the step S202 is performed, the common phase rotation angle may 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 performed according to the common phase rotation angle. Phase recovery, wherein the pre-inserted pilot symbol is a pilot symbol pre-inserted at the transmitting end of the initial data. The data phase recovery performed according to the pre-inserted pilot symbols described in this embodiment is a rough phase recovery. Similar to the engineering foundation, after performing the phase recovery described in this embodiment, the method of the present application can be continued. Get better phase recovery.

In this embodiment, the pre-inserted pilot symbols are pilot symbols inserted at equal intervals on the transmitting end of the initial data, and the pilot symbols are equally inserted to facilitate calculation of a common phase rotation angle. In this embodiment, in order to further improve the accuracy of phase recovery, after phase recovery of the data in the packet using the maximum likelihood phase rotation angle, the following data may be processed for the phase restored data in the packet:

(1) reducing the length of the packet, and re-grouping the data in the packet after the reduced length;

(2) For each packet obtained by the re-grouping, obtain the Euclidean distance F(A ¹ ) between the constellation point corresponding to the packet before the phase rotation according to the angle A ¹ and the constellation point corresponding to the phase rotation, And the Euclidean distance F(B ¹ ) between the constellation points corresponding to the group before the phase rotation according to the angle B ¹ and the constellation points corresponding to the phase rotation, wherein the angle A ¹ and the angle B ¹ are respectively Describe the maximum deviation angle value and the minimum deviation angle value of the group obtained by grouping again;

(3) obtaining a smaller value of the F(A ¹ ) and F(B ¹ ), and using an angle corresponding to the smaller value as the first deflection angle;

(4) acquiring a maximum likelihood phase rotation angle of the first deflection angle and the data in the group obtained by the re-grouping, and using the maximum likelihood phase rotation angle in the group obtained by the re-grouping The data is phase restored.

In this embodiment, the length of the data symbol is reduced. For example, the previous data packet is a group of 128 data. After phase recovery of the group of 128 data sets, the data is then re-divided into 32 data ones. In the group, the phase recovery is performed again by using the schemes shown in steps S202-S208 and the above alternatives.

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

Through the above steps, grouping data that needs to be phase-recovered; and obtaining a first deflection angle by using a smaller value of a maximum offset angle and a minimum offset angle corresponding to each packet; and using the grouping The phase data is recovered from the maximum likelihood phase rotation angle of the selected optimal deflection angle. It can be seen that the above scheme does not need to calculate all phase angles of the data to be recovered, and each time two angles are calculated (ie, the maximum deviation) The angle of shift and the minimum offset angle are sufficient, and therefore, the complexity of phase recovery is reduced, thereby solving the problem of high complexity of the phase recovery method in the related art.

Example 2

A carrier phase recovery device is also provided in this embodiment, and the device is configured to implement the foregoing embodiments and optional implementations, and details are not described herein. As used below, the term "module" may implement a combination of software and/or hardware of a predetermined function. Although the apparatus described in the following embodiments is preferably implemented in software, hardware, or a combination of software and hardware, is 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 acquire, for each packet, an Euclidean distance F(A ₀ ) between the constellation points corresponding to the group before the phase rotation according to the angle A ₀ and the constellation points corresponding to the phase rotation, and the The Euclidean distance F(B ₀ ) between the constellation points corresponding to the constellation points before the phase rotation and the phase rotation after the phase rotation according to the angle B ₀ , wherein the grouping is performed by grouping the data requiring phase recovery Data grouping, the angle A ₀ and the angle B ₀ are respectively a maximum deviation angle value and a minimum deviation angle value set by the group;

The second obtaining module 34 is connected to the first obtaining module 32, configured to acquire a smaller value of the F(A ₀ ) and F(B ₀ ), and use an angle corresponding to the smaller value as the first deflection angle;

The second phase recovery module 36 is coupled to the second acquisition module 34, configured to acquire the maximum deflection phase rotation angle of the first deflection angle and the data in the packet, and use the maximum likelihood phase rotation angle in the group The data is phase restored.

FIG. 4 is a structural block diagram 2 of a carrier phase recovery apparatus according to an embodiment of the present invention. As shown in FIG. 4, the second obtaining module 34 includes:

The repeating execution unit 42 is configured to repeatedly perform the following steps according to the preset number of times N trigger determining unit and the selecting unit to obtain the smaller value;

The determining unit 44 is connected to the repeating execution unit 42 and re-determines the value of the angle A _{0 and} the value of the angle B ₀ according to a preset rule to obtain a first angle A _i and a second angle B _{i respectively} ; _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;

Selecting unit 46, 44 is connected to the determination unit, configured to i = N, the minimum value of F (A _N) and F (B _N) as the smaller value.

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: a first phase recovery module 52,

The first phase recovery module is configured to obtain a common phase rotation angle according to a position change between the pilot symbol and the pre-inserted pilot symbol in the received initial data, according to the public The data is phase restored by a common phase rotation angle, wherein the pre-inserted pilot symbols are pilot symbols pre-inserted at the transmitting end of the initial data.

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

FIG. 6 is a structural block diagram 4 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 is connected to the second phase recovery module 36, and after the second phase recovery module performs phase recovery on the data in the packet using the maximum likelihood phase rotation angle, is configured to reduce the length of the packet, and The data in the group after the length is reduced is grouped again;

The third acquisition module 64, module 62 connected to the packet, is configured to, for each packet obtained via the packet again acquires the packet constellation points corresponding to the phase rotation before and the constellation points according to the phase rotation angle corresponding to A ¹ The Euclidean distance F(A ¹ ) between the Euclidean distances F(A ¹ ) and the Euclidean distance F(B ¹ ) between the corresponding constellation points and the constellation points after the phase rotation of the group before the phase rotation according to the angle B ¹ , wherein the angle A ¹ and angle B ¹ are respectively a maximum deviation angle value and a minimum deviation angle value set by the group obtained by the re-grouping;

The fourth obtaining module 66 is connected to the third obtaining module 64, configured to acquire a smaller value of the F(A ¹ ) and F(B ¹ ), and use an angle corresponding to the smaller value as the second deflecting angle;

The third phase recovery module 68 is connected to the fourth obtaining module 66, configured to acquire the maximum deflection phase rotation angle of the second deflection angle and the data in the regrouped packet, and use the maximum likelihood phase The rotation angle performs phase recovery on the data in the packet obtained by the re-grouping.

It should be noted that each of the above modules may be implemented by software or hardware. For the latter, the foregoing may be implemented by, but not limited to, the foregoing modules are all located in the same processor; or, the modules are located in multiple In the processor.

The following is a detailed description in conjunction with an embodiment of the present invention.

The embodiment of the invention provides an improved carrier phase recovery algorithm with lower complexity. The improved carrier phase recovery algorithm reduces the complexity of the algorithm and enhances the feasibility of the actual application of the algorithm while realizing the phase recovery effect of the BPS algorithm.

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

In the ideal case of no noise, there is

Make

And,

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

Has the following relationship:

That is, the objective function e(x) has a convex function on the feasible domain. That is, the objective function e(x) is a symmetric convex function on the feasible domain. 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.

7 is a flowchart of an algorithm of an improved phase recovery algorithm according to an embodiment of the present invention. As shown in FIG. 7, two parts of the scheme described in the embodiment of the present invention are shown. The first part is a coarse phase search, in the first part. In the first part, the pilot is used to correct the phase error, and the second part is to use the maximum likelihood phase estimation, and the phase recovery is performed according to the maximum likelihood phase rotation angle obtained in the second part. The technical solutions described in the embodiments of the present invention are as follows:

Step 1: Corresponding to the first part of the coarse phase recovery in Figure 7, the pilot-based carrier phase recovery algorithm is used for phase recovery. The data is grouped at the transmitting end, the pilot symbols are inserted at medium intervals in each group of data, and the common phase rotation is calculated at the receiving end by using the received pilot symbols and the known inserted pilot symbols, and the receiving end is inserted according to the known Pilot signal and received guide The positional change of the frequency signal obtains a common phase rotation angle, and phase recovery is performed on the set 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 the present embodiment means the number of lookups, which corresponds to the preset number of 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 of F(A) and F(B) and let A=F-1(Min(F(A),F(B)))), let B=(A+B )/2. After the smaller value is obtained, the new boundary values A and B are set.

Step 4: Determine whether the search depth is greater than N. If the search depth does not reach the preset value N, the new boundary values A and B obtained according to the third step are returned to the second step to repeatedly calculate the smaller value. In the case where the search depth reaches the preset value N, the angle corresponding to the smaller value at this moment is the optimal deflection angle.

Step 5: Using the maximum likelihood estimation method, the maximum likelihood phase rotation angle of the received data and the optimal deflection angle is estimated, and the phase recovery of the group data is performed using the obtained maximum likelihood phase rotation angle.

The sixth step: reducing the length of the packet data symbol, continuing to group the data recovered by the above phase, and repeating the second to fifth steps to complete the second-order phase recovery algorithm.

In an 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 finding the phase, and the carrier phase according to the above method. The accuracy of the recovery algorithm is:

8 is a signal processing flowchart of a phase recovery method according to an embodiment of the present invention. As shown in FIG. 8, first, an angle deviation maximum A and a minimum B are selected, and the Euclidean distances before and after demodulation are respectively calculated, and a predefined The formula obtains new deviation values A and B to determine whether the preset depth of search is reached, and the new deviation is reached when the depth is two The value A is recorded as the optimum deflection angle.

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

1. Improved phase recovery algorithm has time complexity advantages in serial computing:

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

2. The improved phase recovery algorithm has spatial complexity advantages in parallel computing:

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

In summary, the improved phase recovery algorithm is similar to the BPS algorithm in improving the performance of the system, and has the advantage of time complexity in serial computing, and has the advantage of space complexity in parallel computing. Therefore, the improved phase recovery algorithm has better performance than 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 length extensions to enhance the accuracy of the phase recovery algorithm. Make coarse phase recovery through long grouping Complex, can effectively reduce the impact of noise on the phase recovery algorithm. Fine phase recovery is then performed with smaller packets, and local phase information can be utilized to more accurately recover the phase.

The carrier phase recovery method and apparatus provided in an alternative embodiment of the present invention can be applied to a Nyquist Nyquist coherent optical communication transmission system having a symbol rate of 5.8 Gaud and a modulation format of 64QAM (Quadrature Amplitude Modulation) , Quadrature Amplitude Modulation). Both the Fast Fourier Transform and the Fast Fourier Transform are 128 in length, and there are 2 pilot signals for phase estimation. The number of wavelengths is 8, and the transmission distance is 160 km. 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 to further perform phase recovery. Methods include:

The first step: phase recovery using a pilot-based carrier phase recovery algorithm. The data is grouped in groups of 128 symbols at the transmitting end, and the pilot PILOT _{k, i} , PILOT _{k, i} is inserted into the kth group of the transmitted kth group data at equal intervals in each group of data. Pilot _{k, i} is the _i-th pilot in the received _k-th data. The two are divided by the phase rotation amount rotate _{k, i} , normalized to rotate _{k, i} and the average phase rotation amount of the kth group of data is obtained. The data X _{k is} divided by the amount of pilot rotation to obtain phase corrected data.

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

The third step: calculate the Euclidean distance F (A = -20 °) and F (B = 20 °) corresponding to the angle A = -20 ° and B = 20 °. Find the smaller of F (A = -20 °) and F (B = 20 °), leaving the angle corresponding to A = Min (F (A = -20 °), F ((B = 20 °)) Let B = (A + B) / 2 = (-20 ° + 20 °) / 2 = 0 °, n = n + 1.

The fourth step: judging whether the search depth n is equal to N, and if not, repeating the steps of the third step and the fourth step according to the new boundary angle value of the third step. If so, the angle value corresponding to the smaller value is recorded as the optimum deflection angle.

Step 5: Estimate the maximum likelihood phase rotation angle of the received data and the optimal deflection angle by the method of maximum likelihood estimation. Use the maximum likelihood phase rotation angle to enter the set of data Line phase recovery.

Step 6: Reduce the length of the packet data symbols into 32 groups, and repeat the above calculation steps for the new packet 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 rate of the phaseless recovery algorithm, the BPS phase recovery algorithm and the improved phase recovery algorithm are compared. The error rates of the three are: 0.0421, 0.0160, 0.0162. FIG. 9 is a constellation diagram of different phase recovery methods according to an embodiment of the present invention. As shown in FIG. 9, a phase recovery algorithm, a BPS algorithm, and an improved phase recovery algorithm are provided in a 5.8 Gaud Nyquist coherent optical communication system. The BER comparison result graph.

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

Through 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, by hardware, but in many cases, the former is A better implementation. Based on such understanding, the technical solution of the present invention, which is essential or contributes to the related art, may be embodied in the form of a software product stored in a storage medium (such as a read only memory (ROM, Read- Only Memory)/Random Access Memory (RAM), including several instructions for causing a terminal device (which may be a mobile phone, a computer, a server, or a network device, etc.) to perform the present invention. The methods described in the various examples.

Example 3

Embodiments of the present invention also provide a storage medium. Optionally, in the embodiment, the foregoing storage medium may be configured to store program code for performing the following steps:

S1, grouping data that needs phase recovery;

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

S3, obtaining a smaller value of the F(A ₀ ) and F(B ₀ ), and using an angle corresponding to the smaller value as the first deflection angle;

S4: Acquire a maximum likelihood phase rotation angle of the first deflection angle and the data in the group, and perform phase recovery on the data in the group by using the maximum likelihood phase rotation angle.

Optionally, the storage medium is further arranged to store program code for performing the method steps recited in the above embodiments:

Optionally, in this embodiment, the foregoing storage medium may include, but is not limited to, a U disk, a ROM, a RAM, a mobile hard disk, a magnetic disk, or an optical disk, and the like, which can store program codes.

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

For example, the specific examples in this embodiment may refer to the examples described in the foregoing embodiments and the optional embodiments, and details are not described herein again.

It will be apparent to those skilled in the art that the various modules or steps of the present invention described above can be implemented by a general-purpose computing device that can be centralized on a single computing device or distributed across a network of multiple computing devices. Alternatively, they may be implemented by program code executable by the computing device such that they may be stored in the storage device by the computing device and, in some cases, may be different from the order herein. The steps shown or described are performed, or they are separately fabricated into individual integrated circuit modules, or a plurality of modules or steps thereof are fabricated as a single integrated circuit module. Thus, the invention is not limited to any particular The combination of hardware and software.

The above description is only the preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes can be made to the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and scope of the present invention are intended to be included within the scope of the present invention.

Claims

A carrier phase recovery method, the method comprising:

For each packet, obtain the Euclidean distance F(A 0 ) between the constellation points corresponding to the segment before the phase rotation according to the angle A 0 and the constellation points corresponding to the phase rotation, and acquire the packet at the angle B 0 : Euclidean distance F(B 0 ) between the constellation points corresponding to the phase rotation and the constellation points corresponding to the phase rotation, wherein the grouping is: a data packet obtained by grouping data requiring phase recovery; The angle A 0 and the angle B 0 are respectively: a maximum deviation angle value and a minimum deviation angle value set by the group;

Obtaining a smaller value of the F(A 0 ) and F(B 0 ), and using an angle corresponding to the smaller value as the first deflection angle;

Obtaining a maximum likelihood phase rotation angle of the first deflection angle and data in the packet, and performing phase recovery on the data in the packet using the maximum likelihood phase rotation angle.
The method of claim 1 wherein said obtaining a smaller of said F(A 0 ) and F(B 0 ) comprises:

Repeat the following steps according to the preset number of times N to obtain the smaller value:

Re-determining the value of the angle A 0 and the value of the angle B 0 according to a preset rule, respectively obtaining a first angle A i and a 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, the minimum value among F(A N ) and F(B N ) is taken as the smaller value.
The prior method of claim 1, wherein for each packet, obtaining the Euclidean distance F (A 0), and obtaining the Euclidean distances F (B 0), the method further comprising:

Obtaining a common phase rotation angle according to a position change between the pilot symbol and the pre-inserted pilot symbol in the received initial data, and performing the data 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 method of claim 3, wherein the pre-inserted pilot symbols are: pilot symbols inserted at equal intervals at the transmitting end of the initial data.
The method according to any one of claims 1 to 4, wherein after the phase recovery of data in the packet using the maximum likelihood phase rotation angle, the method further comprises:

Reducing the length of the packet, and re-grouping the data in the packet after the reduced length;

For each packet obtained by the re-grouping, acquiring the Euclidean distance F(A 1 ) between the constellation points corresponding to the group before the phase rotation according to the angle A 1 and the constellation points corresponding to the phase rotation, and The Euclidean distance F(B 1 ) between the constellation points corresponding to the constellation points and the constellation points after the phase rotation according to the angle B 1 , wherein the angles A 1 and B 1 are respectively: a maximum deviation angle value and a minimum deviation angle value set by the grouping obtained by the regrouping;

Obtaining a smaller value of the F(A 1 ) and F(B 1 ), and using an angle corresponding to the smaller value as a second deflection angle;

Obtaining a maximum likelihood phase rotation angle of the second deflection angle and the data in the re-grouped packet, and using the maximum likelihood phase rotation angle to the group obtained by the re-grouping The data is phase restored.
A carrier phase recovery device, the device comprising:

a first obtaining module, configured to acquire, for each packet, an Euclidean distance F(A 0 ) between the constellation points corresponding to the group before the phase rotation according to the angle A 0 and the constellation points corresponding to the phase rotation, and acquire The Euclidean distance F(B 0 ) between the constellation points corresponding to the group before the phase rotation according to the angle B 0 and the constellation points corresponding to the phase rotation, wherein the grouping is grouping the data requiring phase recovery After the obtained data group, 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;

a second acquiring module, configured to acquire a smaller value of the F(A 0 ) and F(B 0 ), and use an angle corresponding to the smaller value as a first deflection angle;

a second phase recovery module configured to acquire a maximum likelihood phase rotation angle of the first deflection angle and data in the packet, and perform phase recovery on data in the packet using the maximum likelihood phase rotation angle.
The apparatus of claim 6, wherein the second acquisition module comprises:

Repeating the execution unit, configured to repeatedly perform the following steps according to the preset number of times N trigger determination unit and the selection unit to obtain the smaller value:

Determining a unit, re-determining the value of the angle A 0 and the value of the angle B 0 according to a preset rule, respectively obtaining a first angle A i and a 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;

The unit is selected to be configured to take the minimum value of F(A N ) and F(B N ) as the smaller value when i=N.
The apparatus of claim 6 wherein said apparatus further comprises: a first phase recovery module;

For each grouping, before the first acquisition module acquires the Euclidean distance F(A 0 ) and the Euclidean distance F(B 0 ),

The first phase recovery module is configured to obtain a common phase rotation angle according to a position change between the pilot symbol and the pre-inserted pilot symbol in the received initial data, and perform the data 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 apparatus of claim 8, wherein the pre-inserted pilot symbols are: pilot symbols inserted at equal intervals at a transmitting end of the initial data.
The device according to any one of claims 6 to 9, wherein the device further comprises:

a grouping module configured to reduce a length of the packet and to reduce the length of the packet after the second phase recovery module performs phase recovery on the data in the packet using the maximum likelihood phase rotation angle The data in the group is grouped again;

a third obtaining module, configured to acquire, for each packet obtained by the re-grouping, an Euclidean distance F between the constellation points corresponding to the group before the phase rotation according to the angle A 1 and the constellation points corresponding to the phase rotation (A 1 ), and an Euclidean distance F(B 1 ) between the constellation points corresponding to the group before the phase rotation according to the angle B 1 and the constellation points corresponding to the phase rotation, wherein the angle A 1 and the angle B 1 is respectively: a maximum deviation angle value and a minimum deviation angle value set by the group obtained by the re-grouping;

a fourth acquiring module, configured to acquire a smaller value of the F(A 1 ) and F(B 1 ), and use an angle corresponding to the smaller value as a second deflection angle;

a third phase recovery module configured to acquire a maximum likelihood phase rotation angle of the second deflection angle and the data in the regrouped packet, and use the maximum likelihood phase rotation angle to The data in the packet obtained by the re-grouping is phase-recovered.
A storage medium storing a computer program, the computer program being executed by a processor to implement the steps:

For each packet, obtain the Euclidean distance F(A 0 ) between the constellation points corresponding to the segment before the phase rotation according to the angle A 0 and the constellation points corresponding to the phase rotation, and acquire the packet at the angle B 0 : Euclidean distance F(B 0 ) between the constellation points corresponding to the phase rotation and the constellation points corresponding to the phase rotation, wherein the grouping is: a data packet obtained by grouping data requiring phase recovery; The angle A 0 and the angle B 0 are respectively: a maximum deviation angle value and a minimum deviation angle value set by the group;

Obtaining a smaller value of the F(A 0 ) and F(B 0 ), and using an angle corresponding to the smaller value as the first deflection angle;

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