Method and device for using a preamble

Abstract

The purpose of the embodiment of the present application is to provide a method and device for using a preamble code. The method implemented in the present application includes: inserting a first preamble code and / or a second preamble code into the time domain sequence of the signal to be sent to the ONU device, wherein the first preamble code is used for frame synchronization and rough estimation of the intermediate frequency, and the second preamble code is used for fine correction of the frequency and recovery of the carrier phase; sending a signal containing the first preamble code and / or the second preamble code to the ONU device. The embodiment of the present application has the following advantages: by inserting two preamble codes into the time domain sequence of the signal to be sent to the ONU device to assist the ONU device in frequency and phase estimation, the method of inserting the preamble code into the time domain sequence will not reduce the optical power of the effective signal; the method according to this embodiment is easy to implement and has low computational complexity.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a method and device for using a preamble. Background Art

[0002] With the development of technologies such as 5G mobile backhaul / fronthaul, high-definition video applications, virtual / augmented reality, and cloud computing, their demand for bandwidth has also increased exponentially. High-speed passive optical networks (PONs) are considered the most important component for providing last-mile signal transmission to end users. In April 2021, the International Telecommunication Union (ITU-T) defined the next-generation 50G PON standard. It uses traditional intensity modulation / direct detection (IM / DD) technology and non-return-to-zero (NRZ) on-off-keying (OOK) modulation patterns, and utilizes digital signal processing (DSP) to improve receiver performance.

[0003] For high-speed data transmission such as 100Gb / s and above, it will be difficult for the IM / DD scheme to achieve the required power budget due to the low receiving sensitivity and the rapidly increasing dispersion effect. On the other hand, the coherent detection scheme can well restore linear distortion and effectively improve the receiving sensitivity through the power amplification of the local oscillator (LO). However, due to the need for highly complex optical devices with polarization and phase diversity, its cost is relatively high. Therefore, low-cost coherent detection schemes have also received widespread attention from academia and industry in recent years. Many research groups have proposed various simplified coherent receivers, the simplest of which is the heterodyne coherent receiver based on Alamouti encoding / decoding.

[0004] In a coherent receiver, mixing between the received signal and the local oscillator introduces frequency and phase offsets, resulting in a rotating circular constellation. In traditional transmission networks, many existing techniques for estimating frequency offset and carrier phase exist to correct the frequency and phase errors of the received signal. However, these existing techniques are not suitable for simple coherent receivers because such receivers lack sufficient information, whereas traditional coherent receivers can obtain all the information, including in-phase and quadrature signals for both X and Y polarizations. In other words, existing techniques make it difficult to extract frequency and phase information in a simplified coherent receiver. Summary of the Invention

[0005] The purpose of the embodiments of the present application is to provide a method and device for using a preamble.

[0006] An embodiment of the present application provides a method for providing a preamble in an OLT device, wherein the method includes:

[0007] Inserting a first preamble and / or a second preamble into a time domain sequence of a signal to be sent to an ONU device, wherein the first preamble is used for frame synchronization and rough intermediate frequency estimation, and the second preamble is used for fine frequency correction and carrier phase recovery;

[0008] A signal including the first preamble and / or the second preamble is sent to the ONU device.

[0009] An embodiment of the present application provides a method for using a preamble in an ONU device, wherein the method includes:

[0010] Receiving a signal including a first preamble and / or a second preamble sent by an OLT device, wherein the first preamble is used for frame synchronization and rough intermediate frequency estimation, and the second preamble is used for fine frequency correction and carrier phase recovery;

[0011] performing frame synchronization and intermediate frequency coarse estimation based on the received first preamble code;

[0012] Based on the received second preamble, fine correction of frequency and recovery of carrier phase are performed.

[0013] An embodiment of the present application provides an OLT device, wherein the OLT device includes:

[0014] A device for inserting a first preamble and / or a second preamble into a time domain sequence of a signal to be sent to an ONU device, wherein the first preamble is used for frame synchronization and rough intermediate frequency estimation, and the second preamble is used for fine frequency correction and carrier phase recovery;

[0015] The invention also provides a device for sending a signal including a first preamble code and / or a second preamble code to the ONU device.

[0016] An embodiment of the present application provides an ONU device, wherein the ONU device includes:

[0017] An apparatus for receiving a signal including a first preamble and / or a second preamble sent by an OLT device, wherein the first preamble is used for frame synchronization and rough intermediate frequency estimation, and the second preamble is used for fine frequency correction and carrier phase recovery;

[0018] means for performing frame synchronization and coarse intermediate frequency estimation based on the received first preamble;

[0019] Means for performing fine correction of frequency and recovery of carrier phase based on the received second preamble.

[0020] An embodiment of the present application provides an OLT device, the OLT device including a processor and a memory, the memory storing a computer program, and when the computer program is executed by the processor, the following steps are implemented:

[0021] Inserting a first preamble and / or a second preamble into a time domain sequence of a signal to be sent to an ONU device, wherein the first preamble is used for frame synchronization and rough intermediate frequency estimation, and the second preamble is used for fine frequency correction and carrier phase recovery;

[0022] Send a signal including the first preamble and / or the second preamble to the ONU device

[0023] An embodiment of the present application provides an ONU device, the ONU device including a processor and a memory, the memory storing a computer program, and when the computer program is executed by the processor, the following steps are implemented:

[0024] Receiving a signal including a first preamble and / or a second preamble sent by an OLT device, wherein the first preamble is used for frame synchronization and rough intermediate frequency estimation, and the second preamble is used for fine frequency correction and carrier phase recovery;

[0025] performing frame synchronization and intermediate frequency coarse estimation based on the received first preamble code;

[0026] Based on the received second preamble, fine correction of frequency and recovery of carrier phase are performed.

[0027] An embodiment of the present application provides a computer-readable storage medium, wherein a computer program is stored in the computer-readable storage medium. When the computer program is executed by an OLT device, the following steps are implemented:

[0028] Inserting a first preamble and / or a second preamble into a time domain sequence of a signal to be sent to an ONU device, wherein the first preamble is used for frame synchronization and rough intermediate frequency estimation, and the second preamble is used for fine frequency correction and carrier phase recovery;

[0029] A signal including the first preamble and / or the second preamble is sent to the ONU device.

[0030] An embodiment of the present application provides a computer-readable storage medium, wherein a computer program is stored in the computer-readable storage medium. When the computer program is executed by an ONU device, the following steps are implemented:

[0031] Receiving a signal including a first preamble and / or a second preamble sent by an OLT device, wherein the first preamble is used for frame synchronization and rough intermediate frequency estimation, and the second preamble is used for fine frequency correction and carrier phase recovery;

[0032] performing frame synchronization and intermediate frequency coarse estimation based on the received first preamble code;

[0033] Based on the received second preamble, fine correction of frequency and recovery of carrier phase are performed.

[0034] Compared with the prior art, the embodiments of the present application have the following advantages: by inserting two preamble codes into the time domain sequence of the signal to be sent to the ONU device to assist the ONU device in frequency and phase estimation, the method of inserting the preamble code into the time domain sequence will not reduce the optical power of the effective signal; the method according to this embodiment is easy to implement and has low computational complexity; by inserting several zero symbols before and after the reference data carrying symbol in the second preamble code, inter-symbol interference is avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments made with reference to the following drawings:

[0036] Figure 1 A flow chart of a method for using a preamble according to an embodiment of the present application is shown;

[0037] Figure 2 A schematic diagram showing the structure of an exemplary preamble according to an embodiment of the present application is shown;

[0038] FIG3( a ) shows a schematic diagram of the internal structure of an exemplary first preamble according to an embodiment of the present application;

[0039] FIG3( b ) shows a schematic diagram of the internal structure of an exemplary second preamble according to an embodiment of the present application;

[0040] Figure 4 shows an exemplary system experiment schematic diagram according to an embodiment of the present application;

[0041] FIG5( a ) shows a schematic diagram of the structure of a second preamble in an exemplary system experiment according to an embodiment of the present application;

[0042] FIG5( b ) shows a 16QAM constellation diagram in an exemplary system experiment according to an embodiment of the present application;

[0043] FIG6( a ) shows a schematic diagram of the result of frame synchronization using the first preamble according to an embodiment of the present application;

[0044] FIG6( b ) is a schematic diagram showing the result of roughly estimating the intermediate frequency using the first preamble according to an embodiment of the present application;

[0045] FIG7( a ) shows a constellation diagram of a received signal before and after phase recovery using the second preamble according to an embodiment of the present application;

[0046] FIG7( b ) shows a schematic diagram of phase variation over time before and after fine frequency correction according to an embodiment of the present application;

[0047] Figure 8 A schematic structural diagram of an OLT device and an ONU device according to an embodiment of the present application is shown.

[0048] The same or similar reference numerals in the drawings represent the same or similar components. DETAILED DESCRIPTION

[0049] Before discussing the exemplary embodiments in more detail, it should be mentioned that some exemplary embodiments are described as processes or methods depicted as flow charts. Although the flow charts describe the various operations as sequential processes, many of the operations therein can be implemented in parallel, concurrently, or simultaneously. In addition, the order of the various operations can be rearranged. The process can be terminated when its operation is completed, but can also have additional steps not included in the accompanying drawings. The process can correspond to a method, function, procedure, subroutine, subprogram, etc.

[0050] The methods discussed below (some of which are illustrated by flow charts) can be implemented by hardware, software, firmware, middleware, microcode, hardware description language, or any combination thereof. When implemented by software, firmware, middleware, or microcode, the program code or code segments for performing the necessary tasks can be stored in a machine or computer readable medium (such as a storage medium). (One or more) processors can perform the necessary tasks.

[0051] The specific structural and functional details disclosed herein are merely representative and are for the purpose of describing exemplary embodiments of the present invention. However, the present invention may be embodied in many alternative forms and should not be construed as being limited to only the embodiments set forth herein.

[0052] It should be understood that although the terms "first," "second," and the like may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used solely to distinguish one element from another. For example, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element, without departing from the scope of the exemplary embodiments. The term "and / or" as used herein includes any and all combinations of one or more of the listed associated items.

[0053] It should be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element, or intervening elements may be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements. Other words used to describe the relationship between elements should be interpreted in a similar manner (e.g., "between" versus "directly between," "adjacent to" versus "directly adjacent to," etc.).

[0054] The terms used herein are intended only to describe specific embodiments and are not intended to limit exemplary embodiments. Unless the context clearly indicates otherwise, the singular forms "a", "an", "an item" used herein are also intended to include the plural. It should also be understood that the terms "comprise" and / or "include" used herein specify the presence of stated features, integers, steps, operations, units and / or components, and do not preclude the presence or addition of one or more other features, integers, steps, operations, units, components and / or combinations thereof.

[0055] It should also be noted that, in some alternative implementations, the functions / actions mentioned may occur in a different order than that indicated in the accompanying drawings. For example, two figures shown in succession may actually be performed substantially simultaneously or may sometimes be performed in the reverse order, depending on the functions / actions involved.

[0056] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by those skilled in the art to which the exemplary embodiments belong. It should also be understood that, unless expressly defined herein, terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and should not be interpreted in an idealized or overly formal sense.

[0057] The present invention is further described in detail below with reference to the accompanying drawings.

[0058] Figure 1A flow chart of a method for using a preamble according to an embodiment of the present application is shown. The method includes steps S101 and S102 performed by an OLT device, and steps S201, S202, and S203 performed by an ONU device.

[0059] Among them, the OLT device and ONU device according to the embodiment of the present application are included in a coherent optical access network (CoherentPON).

[0060] In step S101 , a first preamble and / or a second preamble is inserted into a time domain sequence of a signal to be sent to an ONU device.

[0061] The first preamble code is used for frame synchronization and rough intermediate frequency estimation.

[0062] The second preamble code is used for fine frequency correction and carrier phase recovery.

[0063] According to one embodiment, the setting rules of the first preamble code include: the first preamble code includes several symbol blocks, each symbol block includes several symbols, and the symbols in the first half and the second half of the symbol block are the same, and all symbol blocks are simultaneously modulated and output in the polarization directions of the X-axis and the Y-axis.

[0064] According to one embodiment, the setting rules of the second preamble include: inserting several zero symbols before and after the reference data bearing symbols in the second preamble; the data symbols of the second preamble adopt a low-order modulation code type; and the second preamble is sent periodically.

[0065] In step S102, the OLT device sends a signal including the first preamble and / or the second preamble to the ONU device.

[0066] In step S201, an ONU device receives a signal including a first preamble and / or a second preamble sent by an OLT device.

[0067] In step S202 , based on the received first preamble code, the ONU device performs frame synchronization and rough intermediate frequency estimation.

[0068] According to one embodiment, step S202 includes step S2021 and step S2022.

[0069] In step S2021, for the received first preamble code, frame synchronization is performed by calculating the Euclidean distance of the signal vector in the sliding window.

[0070] In step S2022, a fast Fourier transform algorithm is executed using the first preamble, and a rough intermediate frequency estimation is performed using a frequency domain peak search method.

[0071] In step S203 , based on the received second preamble, the ONU device performs fine frequency correction and carrier phase recovery.

[0072] According to one embodiment, step S203 includes step S2031 and step S2032.

[0073] In step S2031, for the received periodic second preamble, phase-related information is extracted from the periodic second preamble.

[0074] In step S2032, based on the phase-related information, the average phase in the second preamble is calculated to restore the carrier phase, and the phase change between adjacent second preambles is calculated to perform fine correction of the frequency offset.

[0075] According to one embodiment, the method includes step S100 performed by an OLT device.

[0076] In step S100 , a transmission rule of the first preamble and the second preamble is configured, so that a signal including the first preamble and / or the second preamble is transmitted to the ONU device based on the transmission rule.

[0077] The sending rules include various rules indicating how to send the first preamble and the second preamble to the ONU device. For example, the sending rules may specify the sending conditions, sending frequencies, etc. of the first preamble and the second preamble.

[0078] According to one embodiment, the method includes step S204 performed by the ONU device, and step S102 includes step S1021 and step S1022.

[0079] In step S204, when a frequency tracking anomaly occurs, the ONU device sends a retransmission request to the OLT device to request the OLT device to resend the first preamble.

[0080] In step S1021 , for a first preamble, in response to a registration request or a retransmission request from an ONU device, a signal including the first preamble is sent to the ONU device.

[0081] In step S1022, for the second preamble, a signal including the second preamble is periodically sent to the ONU device.

[0082] According to the method of an embodiment of the present application, two preamble codes are inserted into the time domain sequence of the signal to be sent to the ONU device to assist the ONU device in performing frequency and phase estimation. The way of inserting the preamble code in the time domain sequence will not reduce the optical power of the effective signal; the method according to this embodiment is easy to implement and has low computational complexity; and several zero symbols are inserted before and after the reference data carrying symbol in the second preamble code to avoid inter-symbol interference.

[0083] The following combination Figure 2 3 and 3 illustrate the leading code of the embodiment of the present application.

[0084] Figure 2 A schematic diagram of the structure of an exemplary preamble according to an embodiment of the present application is shown.

[0085] FIG3( a ) and FIG3 ( b ) respectively show schematic diagrams of the internal structures of an exemplary first preamble and a second preamble according to an embodiment of the present application.

[0086] The first preamble and the second preamble according to this example are represented as Preamble_1 and Preamble_2 respectively. The structure of the transmission signal time domain sequence including Preamble_1, Preamble_2 and payload is as follows: Figure 2 shown.

[0087] The sending rules of Preamble_1 and Preamble_2 configured on the OLT device are as follows:

[0088] In response to a registration request or a retransmission request from an ONU, the OLT device sends a signal including Preamble_1 to the ONU device. Furthermore, the OLT device periodically sends a signal including a second preamble to the ONU device.

[0089] According to the above rules, when an ONU accesses the network, the OLT sends preamble_1 and preamble_2 to the ONU. After the ONU uses preamble_1 to roughly estimate the intermediate frequency, the OLT only periodically sends preamble_2. Furthermore, if the frequency offset is too large and the ONU cannot lock to the frequency, the ONU sends a retransmission request to the OLT, requesting the retransmission of preamble_1.

[0090] Also, set the following for Preamble_1 and Preamble_2:

[0091] Preamble_1: Referring to Figure 3(a), Preamble_1 contains m symbol blocks, each containing k symbols. The symbols in the first and second halves of the symbol blocks are identical. All symbol blocks are modulated and output simultaneously in the x-axis and y-axis polarization directions.

[0092] Based on the received Preamble_1, the ONU device performs frame synchronization by calculating the Euclidean distance of the signal vector in the sliding window. The calculation formula is as follows:

[0093]

[0094] Among them, t represents the number of the symbol block, r t (n+1:n+k) and r t (n+k+1:n+2k) represents the vector consisting of the received signals in the first and second halves of the symbol block in the sliding window, and ρ represents the Euclidean distance between the two vectors. Furthermore, the ONU uses Preamble_1 to perform a fast Fourier transform (FFT) algorithm and a frequency-domain peak search to roughly estimate the intermediate frequency.

[0095] Preamble_2: Referring to Figure 3(b), several zero symbols are inserted before and after the reference data-bearing symbols in Preamble_2 to avoid inter-symbol interference (ISI). The data symbols in Preamble_2 use a low-order modulation pattern, such as 0 (continuous wave) or 1 (binary phase-shift keying). This makes the combined signal from the two polarizations very simple, and phase information can be easily extracted from it. In the example shown in Figure 3(b), the "A" symbol is modulated in the X polarization, and the "B" and "C" symbols are modulated in the Y polarization.

[0096] The ONU device extracts phase-related information from the received Preamble_2 and calculates the average phase in Preamble_2 to recover the carrier phase. In addition, the ONU device calculates the phase change between adjacent Preamble_2s and performs fine correction of the frequency offset based on the following formula:

[0097]

[0098] in, Indicates the phase change between adjacent Preamble_2, Baud_Rate indicates the baud rate of the signal, and n_sym indicates the number of symbols between adjacent Preamble_2.

[0099] The following is an illustrative experiment to illustrate the embodiments of the present application.

[0100] Figure 4 A schematic diagram of an exemplary system experiment according to an embodiment of the present application is shown.

[0101] In this example, the system experiment uses Alamouti coding and a simple heterodyne coherent receiver to implement a 100Gb / s / λ coherent PON. Figure 4 As shown, the experimental system includes:

[0102] The transmitter in this experiment is a coherent transmitter, which includes a digital signal processor (represented as Tx DSP in the figure), an arbitrary waveform generator (AWG), an external cavity laser (ECL), two electrical amplifiers (EA), a polarization beam splitter (PBC), a polarization beam combiner (PBC), and two dual parallel Mach-Zehnder modulators (DP-MZM).

[0103] The receiving end of this experiment is a low-complexity coherent receiver, which includes a digital signal processor (represented as Rx DSP in the figure), an external cavity laser (ECL), a 2x2 optical coupler and a balanced photodetector BPD, an oscilloscope (OSC), and a trans-impedance amplifier (TIA).

[0104] In addition, the experimental parameters are set as shown in Table 1 below:

[0105] Table 1

[0106]

[0107]

[0108] The coherent transmitter hardware setup in this experiment is the same as the coherent transmission setup in a general optical core network. However, to achieve polarization-insensitive reception in the receiver, Alamouti encoding is implemented in the Tx DSP. This encoding groups individual symbols and performs orthogonal encoding on two polarization states, as shown below:

[0109]

[0110] Among them, s1, s2, s3, s4 represent the symbols of transmission, * represents the complex conjugate, Ex and E y represent the electric field polarized in the X-axis and Y-axis directions respectively.

[0111] Note that to ensure low coherent receiver complexity, the transmitted signal should be Alamouti-encoded. Furthermore, heterodyne reception should be maintained to recover in-phase and quadrature information from the received signal. After the signal is sampled by an oscilloscope, the receiver DSP performs resampling, frame synchronization, frequency and phase recovery, and equalization.

[0112] With the above reference Figure 2 Similar to the embodiment of FIG3 , the first preamble and the second preamble in this experiment are represented as Preamble_1 and Preamble_2, respectively. Furthermore, the following settings are performed for Preamble_1 and Preamble_2, respectively:

[0113] Preamble_1: Preamble_1 contains 100 symbol blocks, for a total of 1e4 (1x10^4) symbols. The internal structure of Preamble_1 is shown in Figure 3(a). The symbols in the first and second halves of the symbol blocks are identical, and the data is randomly selected points from the 16QAM constellation diagram shown in Figure 5(b). All symbol blocks are modulated and output simultaneously in the X-axis and Y-axis polarization directions. The receiving end Rx DSP calculates the Euclidean distance of the signal vector in the sliding window based on the received Preamble_1 using the above formula (1) to perform frame synchronization.

[0114] Preamble_2: The structure of Preamble_2 in X-axis polarization and Y-axis polarization is shown in Figure 5(a). It contains 100 symbol blocks. Among them, the first 20 symbols and the last 20 symbols are "0" to protect the middle symbols from the influence of inter-symbol interference (ISI). The middle symbol in the X-axis polarization carries the symbol "S1", and the middle symbol in the Y-axis polarization carries the symbols "S4" and "S 13 ”.

[0115] Figures 6(a) and 6(b) show the results of the above experiment using Preamble_1 for frame synchronization and rough estimation of the intermediate frequency, respectively. Figure 6(a) shows the result of calculating the Euclidean distance of the signal vector in the sliding window using the above formula (1). By searching for the minimum value, the starting point of the frame can be simply detected. Figure 6(b) shows the signal spectrum after executing the Fast Fourier Transform (FFT) algorithm and performing a rough estimation of the intermediate frequency by using the frequency domain peak search method. The intermediate frequency is located at the position indicated by "IF" in the figure.

[0116] FIG7( a ) and FIG7 ( b ) respectively show the results of the above experiment using Preamble_2 to perform carrier phase recovery and frequency fine correction.

[0117] 7(a) is a constellation diagram of the received signal before and after phase recovery using Preamble_2, and FIG7(b) is a phase change over time before and after fine frequency correction.

[0118] By measuring the average phase of each of the 11 Preamble_2s and compensating for the phase difference using these average phase values, the carrier phase can be recovered as shown in Figure 7(a). Furthermore, the frequency offset can be accurately corrected through the phase change shown in Figure 7(b).

[0119] It can be seen from the above-mentioned 100 Gb / s / λ coherent PON system experimental results that the solution of the embodiment of the present application can accurately estimate the frequency and phase of the signal in the high-speed coherent PON.

[0120] Figure 8 A schematic structural diagram of an OLT device and an ONU device according to an embodiment of the present application is shown.

[0121] The OLT device includes: a device for inserting a first preamble and / or a second preamble into a time domain sequence of a signal to be sent to an ONU device (hereinafter referred to as "insertion device 101"), and a device for sending a signal containing the first preamble and / or the second preamble to the ONU device (hereinafter referred to as "sending device 102").

[0122] The ONU device includes: a device for receiving a signal containing a first preamble code and / or a second preamble code sent by an OLT device (hereinafter referred to as "receiving device 201"), a device for performing frame synchronization and rough intermediate frequency estimation based on the received first preamble code (hereinafter referred to as "first execution device 202"), and a device for performing fine frequency correction and carrier phase recovery based on the received second preamble code (hereinafter referred to as "second execution device 203").

[0123] Among them, the OLT device and ONU device according to the embodiment of the present application are included in a coherent optical access network (CoherentPON).

[0124] The inserting device 101 inserts the first preamble and / or the second preamble into the time domain sequence of the signal to be sent to the ONU device.

[0125] The first preamble code is used for frame synchronization and rough intermediate frequency estimation.

[0126] The second preamble code is used for fine frequency correction and carrier phase recovery.

[0127] According to one embodiment, the setting rules of the first preamble code include: the first preamble code includes several symbol blocks, each symbol block includes several symbols, and the symbols in the first half and the second half of the symbol block are the same, and all symbol blocks are simultaneously modulated and output in the polarization directions of the X-axis and the Y-axis.

[0128] According to one embodiment, the setting rules of the second preamble include: inserting several zero symbols before and after the reference data bearing symbols in the second preamble; the data symbols of the second preamble adopt a low-order modulation code type; and the second preamble is sent periodically.

[0129] The sending device 102 sends a signal including the first preamble code and / or the second preamble code to the ONU device.

[0130] The receiving device 201 receives a signal including a first preamble and / or a second preamble sent by the OLT device.

[0131] Based on the received first preamble code, the first execution module 202 performs frame synchronization and rough intermediate frequency estimation.

[0132] According to one embodiment, the first execution device 202 performs frame synchronization on the received first preamble by calculating the Euclidean distance of the signal vector in the sliding window. Furthermore, the first execution device 202 uses the first preamble to perform a fast Fourier transform algorithm and perform a rough intermediate frequency estimation using a frequency domain peak search method.

[0133] Based on the received second preamble, the second execution module 203 performs fine frequency correction and carrier phase recovery.

[0134] According to one embodiment, the second execution module 203 extracts phase-related information from the received periodic second preamble. Furthermore, based on the phase-related information, the second execution module 203 calculates an average phase in the second preamble to recover the carrier phase, and calculates a phase change between adjacent second preambles to perform fine frequency offset correction.

[0135] According to one embodiment, the OLT device includes a device for configuring a sending rule of the first preamble code and the second preamble code, thereby sending a signal containing the first preamble code and / or the second preamble code to the ONU device based on the sending rule (hereinafter referred to as "rule configuration device").

[0136] The rule configuration device configures a transmission rule of the first preamble and the second preamble, thereby transmitting a signal including the first preamble and / or the second preamble to the ONU device based on the transmission rule.

[0137] The sending rules include various rules indicating how to send the first preamble and the second preamble to the ONU device. For example, the sending rules may specify the sending conditions, sending frequencies, etc. of the first preamble and the second preamble.

[0138] According to one embodiment, the ONU device includes a device (hereinafter referred to as "retransmission request device") for sending a retransmission request to the OLT device when a frequency tracking abnormality occurs, so as to request the OLT device to retransmit the first preamble code.

[0139] When a frequency tracking anomaly occurs, the retransmission request device sends a retransmission request to the OLT device to request the OLT device to resend the first preamble code.

[0140] For the first preamble, the sending device 102 sends a signal including the first preamble to the ONU device in response to a registration request or a retransmission request from the ONU device.

[0141] For the second preamble, the sending device 102 periodically sends a signal including the second preamble to the ONU device.

[0142] According to the solution of an embodiment of the present application, two preamble codes are inserted into the time domain sequence of the signal to be sent to the ONU device to assist the ONU device in performing frequency and phase estimation. The way of inserting the preamble code in the time domain sequence does not reduce the optical power of the effective signal; the method according to this embodiment is easy to implement and has low computational complexity; and several zero symbols are inserted before and after the reference data carrying symbol in the second preamble code to avoid inter-symbol interference.

[0143] The software program of the present invention can be executed by a processor to implement the steps or functions described above. Similarly, the software program of the present invention (including related data structures) can be stored in a computer-readable recording medium, such as a RAM memory, a magnetic or optical drive, a floppy disk, or the like. In addition, some steps or functions of the present invention can be implemented using hardware, for example, as a circuit that cooperates with a processor to perform the various functions or steps.

[0144] In addition, a portion of the present invention may be applied as a computer program product, such as computer program instructions, which, when executed by a computer, can call or provide the method and / or technical solution according to the present invention through the operation of the computer. The program instructions for calling the method of the present invention may be stored in a fixed or removable recording medium, and / or transmitted through a data stream in a broadcast or other signal-carrying medium, and / or stored in a working memory of a computer device that operates according to the program instructions. Here, according to one embodiment of the present invention, a device is included, which includes a memory for storing computer program instructions and a processor for executing the program instructions, wherein, when the computer program instructions are executed by the processor, the device is triggered to operate based on the aforementioned methods and / or technical solutions according to multiple embodiments of the present invention.

[0145] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the invention is defined by the appended claims rather than the above description, and it is intended that all changes that fall within the meaning and scope of the equivalent elements of the claims be included in the present invention. Any figure marks in the claims should not be regarded as limiting the claims involved. In addition, it is obvious that the word "comprising" does not exclude other units or steps, and the singular does not exclude the plural. Multiple units or devices stated in the system claim may also be implemented by one unit or device through software or hardware. Words such as first, second, etc. are used to indicate names and do not indicate any particular order.

Claims

1. A method for providing a preamble in an OLT device, wherein: The method comprises: Inserting a first preamble and a second preamble into a time domain sequence of a signal to be sent to an ONU device, wherein the first preamble is used for frame synchronization and rough intermediate frequency estimation, and the second preamble is used for fine frequency correction and carrier phase recovery; Sending a signal comprising a first preamble and a second preamble to the ONU device; The setting rules of the structure of the second preamble include: inserting a number of zero symbols before and after the reference data bearing symbols in the second preamble; The data symbol of the second preamble adopts a low-order modulation pattern; The second preamble is sent periodically.

2. The method according to claim 1, wherein The method comprises: A sending rule of the first preamble and the second preamble is configured, so that a signal including the first preamble and the second preamble is sent to the ONU device based on the sending rule.

3. The method according to claim 1 or 2, wherein: The method comprises: For the first preamble, in response to a registration request or a retransmission request from the ONU device, sending a signal including the first preamble to the ONU device; For the second preamble, a signal containing the second preamble is periodically sent to the ONU device.

4. The method according to claim 1 or 2, wherein: The setting rules of the structure of the first preamble include: The first preamble code includes several symbol blocks, each symbol block includes several symbols, and the symbols in the first half and the second half of the symbol block are the same. All symbol blocks are simultaneously modulated and output in the polarization directions of the X-axis and the Y-axis.

5. A method for using a preamble in an ONU device, wherein: The method comprises: receiving a signal including a first preamble and a second preamble sent by an OLT device, wherein the first preamble is used for frame synchronization and rough intermediate frequency estimation, and the second preamble is used for fine frequency correction and carrier phase recovery; performing frame synchronization and intermediate frequency coarse estimation based on the received first preamble code; Based on the received second preamble, performing fine frequency correction and carrier phase recovery; The setting rules of the structure of the second preamble include: inserting a number of zero symbols before and after the reference data bearing symbols in the second preamble; The data symbol of the second preamble adopts a low-order modulation pattern; The second preamble is sent periodically.

6. The method according to claim 5, wherein: The step of performing frame synchronization and rough intermediate frequency estimation based on the received first preamble code includes: For the first received preamble, frame synchronization is performed by calculating the Euclidean distance of the signal vector in the sliding window; A fast Fourier transform algorithm is executed using the first preamble, and a frequency domain peak search method is used to perform a rough estimation of the intermediate frequency.

7. The method according to claim 5, wherein: The step of performing fine frequency correction and carrier phase recovery based on the received second preamble code includes: For the received periodic second preamble, extract phase-related information from the periodic second preamble; Based on the phase-related information, the average phase in the second preamble is calculated to restore the carrier phase, and the phase change between adjacent second preambles is calculated to perform fine correction of the frequency offset.

8. The method according to any one of claims 5 to 7, wherein The method comprises: When a frequency tracking abnormality occurs, a retransmission request is sent to the OLT device to request the OLT device to resend the first preamble code.

9. An OLT device, wherein: The OLT device includes: A device for inserting a first preamble and a second preamble into a time domain sequence of a signal to be sent to an ONU device, wherein the first preamble is used for frame synchronization and rough intermediate frequency estimation, and the second preamble is used for fine frequency correction and carrier phase recovery; Means for sending a signal comprising a first preamble and a second preamble to the ONU device; The setting rules of the structure of the second preamble include: inserting a number of zero symbols before and after the reference data bearing symbols in the second preamble; The data symbol of the second preamble adopts a low-order modulation pattern; The second preamble is sent periodically.

10. An ONU device, wherein: The ONU device includes: An apparatus for receiving a signal including a first preamble and a second preamble sent by an OLT device, wherein the first preamble is used for frame synchronization and rough intermediate frequency estimation, and the second preamble is used for fine frequency correction and carrier phase recovery; means for performing frame synchronization and coarse intermediate frequency estimation based on the received first preamble; Means for performing fine frequency correction and carrier phase recovery based on the received second preamble; The setting rules of the structure of the second preamble include: inserting a number of zero symbols before and after the reference data bearing symbols in the second preamble; The data symbol of the second preamble adopts a low-order modulation pattern; The second preamble is sent periodically.

11. An OLT device, comprising a processor and a memory, wherein the memory stores a computer program, and when the computer program is executed by the processor, the following steps are implemented: Inserting a first preamble and a second preamble into a time domain sequence of a signal to be sent to an ONU device, wherein: The first preamble is used for frame synchronization and rough intermediate frequency estimation, and the second preamble is used for fine frequency correction and carrier phase recovery; A signal including a first preamble and a second preamble is sent to the ONU device.

12. An ONU device, comprising a processor and a memory, wherein the memory stores a computer program, and when the computer program is executed by the processor, the following steps are implemented: A signal including a first preamble and a second preamble is received from an OLT device, wherein: The first preamble is used for frame synchronization and rough intermediate frequency estimation, and the second preamble is used for fine frequency correction and carrier phase recovery; performing frame synchronization and intermediate frequency coarse estimation based on the received first preamble code; Based on the received second preamble, performing fine frequency correction and carrier phase recovery; The setting rules of the structure of the second preamble include: inserting a number of zero symbols before and after the reference data bearing symbols in the second preamble; The data symbol of the second preamble adopts a low-order modulation pattern; The second preamble is sent periodically.

13. A computer-readable storage medium storing a computer program, wherein when the computer program is executed by an OLT device, the following steps are implemented: Inserting a first preamble and a second preamble into a time domain sequence of a signal to be sent to an ONU device, wherein: The first preamble is used for frame synchronization and rough intermediate frequency estimation, and the second preamble is used for fine frequency correction and carrier phase recovery; Sending a signal comprising a first preamble and a second preamble to the ONU device; The setting rules of the structure of the second preamble include: inserting a number of zero symbols before and after the reference data bearing symbols in the second preamble; The data symbol of the second preamble adopts a low-order modulation pattern; The second preamble is sent periodically.

14. A computer-readable storage medium storing a computer program, wherein when the computer program is executed by an ONU device, the following steps are implemented: A signal including a first preamble and a second preamble is received from an OLT device, wherein: The first preamble is used for frame synchronization and rough intermediate frequency estimation, and the second preamble is used for fine frequency correction and carrier phase recovery; performing frame synchronization and intermediate frequency coarse estimation based on the received first preamble code; Based on the received second preamble, performing fine frequency correction and carrier phase recovery; The setting rules of the structure of the second preamble include: inserting a number of zero symbols before and after the reference data bearing symbols in the second preamble; The data symbol of the second preamble adopts a low-order modulation pattern; The second preamble is sent periodically.

Images