Satellite network terminal and gateway time synchronization method, device, system and medium

Abstract

The application relates to the technical field of satellite communication, and particularly provides a satellite network terminal and gateway time synchronization method, device and system and medium, aiming to solve the problem of how to realize time synchronization between a terminal and a gateway without relying on absolute time. For the purpose, the application provides a satellite network terminal and gateway time synchronization method applied to a terminal, which comprises the following steps: receiving time synchronization signaling messages sent by a gateway and adding local time stamps at the time of receiving, wherein the time synchronization signaling messages carry superframe grouping configuration parameters; calculating local delay sending time corresponding to the superframe according to the grouping configuration parameters; obtaining frame boundaries synchronized with the superframe on the gateway side according to the time of the local time stamp and the local delay sending time, so as to realize time synchronization with the gateway.

Description

TECHNICAL FIELD

[0001] The present application relates to satellite communication technology, and specifically provides a satellite network terminal and gateway time synchronization method, device, system and medium. BACKGROUND

[0002] The satellite network system is composed of a ground segment, a space segment and a user segment. As shown in the figure, the gateway GW (Gateway) of the ground segment includes a three-layer IP gateway (IP Gateway), a forward link gateway MCS (MODCOD Servicing System) and a reverse link gateway RCM (Return Channel Manager); the space segment includes a transparent satellite or a low-orbit satellite constellation with regenerative function (the transparent satellite is a satellite that only acts as a transparent repeater, and the regenerative satellite is a satellite that extracts information, performs routing exchange and the like, and then sends to the target user); and the user segment includes a user terminal UT (User Terminal) and a connected terminal network. Figure 2 The RCM divides a frame of a channel into a plurality of subframes and allocates the subframes to different users. The users need to send data according to the allocated subframe positions. Since the terminals are distributed at different positions and the distances from the gateway are different, the transmission delays are different. If the signals sent by two terminals overlap at the gateway, data reception conflicts at the gateway side will be caused. Therefore, the starting points of the frame boundaries of the terminals need to be accurately controlled, and the transmission signal delay time is adjusted to achieve the purpose of synchronization with the frame boundary of the gateway.

[0003] In the prior art, after receiving the absolute time information sent by the network device, the terminal adjusts the clock of the terminal according to the absolute time information and the frame boundary corresponding to the absolute time information, so that the absolute time at the same frame boundary of the terminal and the network device is the same, and the purpose of clock synchronization is achieved. However, this method depends on the absolute time of the gateway. Since the transmission delay is time-varying, and the transmission delay of some terminals and the gateway is large due to the long distance, if the absolute time of the terminal is still determined according to the received absolute time, there will be a large error. At the same time, the terminal needs to constantly adjust the clock of the terminal to meet the "synchronization", which is also easy to cause errors, and the synchronization effect is poor.

[0004] SUMMARY In order to overcome the above defects, the present application is proposed to provide a satellite network terminal and gateway time synchronization method, device, system and medium, which solves or at least partially solves the technical problem of how to achieve time synchronization between the terminal and the gateway without relying on absolute time.

[0005]

[0006] ​In a first aspect, the application provides a satellite network terminal and gateway time synchronization method, applied to a terminal, comprising:

[0007] receiving a time synchronization signaling message sent by the gateway and adding a local timestamp at the time of receiving, the time synchronization signaling message carrying a superframe grouping configuration parameter;

[0008] calculating a local delay sending time corresponding to the superframe according to the grouping configuration parameter;

[0009] obtaining a frame boundary synchronized with the superframe on the gateway side according to the time of the local timestamp and the local delay sending time, to realize time synchronization with the gateway.

[0010] In one technical solution of the above satellite network terminal and gateway time synchronization method,

[0011] The method further comprises:

[0012] synchronizing time and frame number on the physical layer and the link layer of the gateway based on the time synchronization server, to obtain a mapping relationship between time and frame number;

[0013] The physical layer of the gateway organizes and sends the time synchronization signaling based on the mapping relationship.

[0014] In one technical solution of the above satellite network terminal and gateway time synchronization method,

[0015] The grouping configuration parameter comprises: superframe frame number, gateway delay receiving time, sending delay of the time synchronization signaling message, and position information of the gateway and the satellite; wherein the gateway delay receiving time is the time of sending the superframe in advance, and the sending delay of the time synchronization signaling message is obtained based on the grouping prediction of the physical layer of the gateway.

[0016] In one technical solution of the above satellite network terminal and gateway time synchronization method, the calculation of the local delay sending time corresponding to the superframe according to the grouping configuration parameter comprises:

[0017] calculating the transmission time between the gateway and the satellite according to the position information of the gateway and the satellite;

[0018] The gateway delay receiving time minus the sending delay of the time synchronization signaling message and the transmission time between the gateway and the satellite, to obtain the local delay sending time corresponding to the superframe.

[0019] In one technical solution of the above satellite network terminal and gateway time synchronization method, the terminal comprises a physical layer and a link layer;

[0020] The physical layer is configured to add a first local timestamp at the time when the time synchronization signaling packet is received, and send the time synchronization packet to the link layer;

[0021] The link layer is configured to analyze and calculate the time synchronization packet to obtain a local delay sending time corresponding to the superframe;

[0022] The frame boundary synchronized with the superframe on the gateway side is obtained according to the time of the local timestamp and the local delay sending time, including that the physical layer calculates the frame boundary of the superframe corresponding to the gateway side according to the time of the first local timestamp and the local delay sending time;

[0023] The link layer is further configured to add a second local timestamp at the time when the time synchronization signaling packet is received, and record an internal transmission delay time of the time synchronization signaling packet from the physical layer to the link layer;

[0024] The frame boundary synchronized with the superframe on the gateway side is obtained according to the time of the local timestamp and the local delay sending time, and further includes that the link layer calculates the frame boundary of the superframe corresponding to the gateway side according to the second local timestamp, the internal transmission delay time and the local delay sending time.

[0025] In one of the above technical solutions of the satellite network terminal and gateway time synchronization method,

[0026] The method further includes: sending data to the gateway side, obtaining a sending time of the data according to the frame boundary and a time slot offset of a sending subframe in a frame, so that the data reaches the gateway at a subframe receiving time set by the gateway through a transmission delay of the terminal and the gateway.

[0027] In one of the above technical solutions of the satellite network terminal and gateway time synchronization method, the frame number information further includes a superframe interval;

[0028] The method further includes: receiving the time synchronization signaling packet once every superframe interval, and checking whether a new frame boundary needs to be used according to a new time synchronization signaling packet;

[0029] If the absolute value of the difference between the new frame boundary obtained according to the new time synchronization signaling packet and the original frame boundary is less than a first threshold or greater than a second threshold, the original frame boundary is continued to be used; otherwise, the new frame boundary is used; wherein the second threshold is greater than the first threshold.

[0030] In a second aspect, the present application provides a satellite network terminal and gateway time synchronization device, comprising a memory, one or more processors, one or more application programs, wherein the one or more application programs are stored in the memory, and the one or more application programs are configured to be called by the one or more processors, so that the one or more processors execute the method according to any one of the first aspect.

[0031] In a third aspect, the present application provides a satellite network system, comprising the device according to the second aspect.

[0032] In a fourth aspect, a computer readable storage medium is provided, characterized in that it stores a plurality of program codes, which are suitable for being loaded and run by a processor to execute the method according to any one of the first aspect.

[0033] The above one or more technical solutions of the present application have at least one or more of the following beneficial effects:

[0034] In the implementation of the technical solutions of the present application, the terminal receives the time synchronization signaling message sent by the gateway, calculates the frame boundary synchronized with the gateway side super frame by analysis, realizes the alignment of the sending frame boundary and the receiving frame boundary of the gateway, and the frame boundary is based on the time stamp of the terminal local time when receiving the time synchronization signaling message, realizes the time synchronization with the gateway without absolute time, does not need to rely on absolute time, and has good synchronization effect. BRIEF DESCRIPTION OF DRAWINGS

[0035] The disclosure of the present application will become more apparent with reference to the drawings. It is easy for those skilled in the art to understand that these drawings are only for illustrative purposes, and are not intended to limit the scope of protection of the present application. In addition, similar numbers in the figures are used to represent similar components, wherein:

[0036] Figure 1 is a main step flow diagram of a satellite network terminal and gateway time synchronization method according to an embodiment of the present application;

[0037] Figure 2 is a satellite network architecture diagram according to an embodiment of the present application;

[0038] Figure 3 is a reverse link resource allocation diagram according to the present application;

[0039] Figure 4 is a terminal and gateway frame boundary diagram according to the present application;

[0040] Figure 5 is a gateway side time synchronization architecture diagram according to an embodiment of the present application;

[0041] Figure 6 is a schematic diagram of satellite network time synchronization principle according to an embodiment of the present application;

[0042] Figure 7 is a schematic diagram of specific example time synchronization principle according to an embodiment of the present application;

[0043] Figure 8 is a schematic diagram of terminal time synchronization calculation principle according to an embodiment of the present application;

[0044] Figure 9 is a schematic diagram of gateway side time synchronization flow according to an embodiment of the present application;

[0045] Figure 10 is a schematic diagram of terminal side time synchronization architecture according to an embodiment of the present application;

[0046] Figure 11 is a schematic diagram of terminal side time synchronization flow according to an embodiment of the present application. DETAILED DESCRIPTION

[0047] Some embodiments of the present application will be described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present application, and are not intended to limit the protection scope of the present application.

[0048] In the description of the present application, "module" and "processor" can include hardware, software or a combination of both. A module can include hardware circuit, various suitable sensors, communication port, memory, and can also include software part such as program code, and can be a combination of software and hardware. The processor can be a central processor, microprocessor, image processor, digital signal processor or any other suitable processor. The processor has data and / or signal processing function. The processor can be implemented in software, hardware or a combination of both. The non-transitory computer readable storage medium includes any suitable medium that can store program code, such as magnetic disk, hard disk, optical disk, flash memory, read-only memory, random access memory, etc. The term "A and / or B" means all possible combinations of A and B, such as only A, only B or both A and B. The term "at least one of A or B" or "at least one of A and B" has similar meaning as "A and / or B", and can include only A, only B or both A and B. The singular form of the term "one", "this" can also include plural forms.

[0049] As shown in Figure 2 , the satellite network uses time division multiplexing (TDM) technology in the forward direction to transmit a general data stream multiplexed by multiple users. The reverse direction uses multiple frequency time division multiple access (MF-TDMA) technology. As shown in Figure 3As shown, the reverse link resources are organized into multiple reverse available resource groups, and a dynamic contention on-demand allocation mode is used in one group. One group includes multiple channels, but the system configuration parameters are the same, and is managed by one RCM. The resources on each channel are organized into continuous superframes, each superframe includes a fixed number of data frames, each data frame includes a fixed time slot, and multiple continuous time slots constitute a subframe. The number of time slots included in each frame of channels with different symbol rates is different, and different subframes are composed of different numbers of time slots, but one time slot cannot belong to two subframes. The RCM divides one frame of one channel into several subframes and allocates them to different users. The users need to send data according to the allocated subframe positions. Since the terminals are distributed at different positions and the distances from the gateway are different, the transmission delays are different. If the signals sent by two terminals overlap at the gateway, data reception conflicts will occur at the gateway side. Therefore, the starting points of the frame boundaries of each terminal need to be accurately controlled and adjusted according to the transmission signal delay time. For example Figure 4 As shown, subframe 0 of one frame is allocated to user A, subframe 1 is allocated to user B, and subframe 2 is allocated to user C. The starting points of the frame boundaries seen by different users and the gateway are different. The user terminal needs to adjust its own sending frame boundary to achieve the purpose of synchronization with the frame boundary of the receiving gateway. The existing satellite network standard protocol DVB-RCS2 realizes time frame number synchronization through two steps. First, the transmitter periodically broadcasts a network clock reference NCR, and the terminal realizes time synchronization with the gateway by receiving the NCR. The gateway then sends a superframe composition table SCT based on the NCR time, which defines a time-based frame composition schedule. The terminal needs to receive two messages to realize time and frame number synchronization. At the same time, the existing terminal and gateway need to rely on the absolute time of the gateway when realizing synchronization, and the calculation error is large, and the synchronization effect is poor. Accordingly, the present application proposes a terminal and gateway time synchronization method without relying on the absolute time of the gateway.

[0050] Referring to the accompanying Figure 1 , Figure 1 is a main step flow diagram of a satellite network terminal and gateway time synchronization method according to an embodiment of the present application. As shown in Figure 1 A satellite network terminal and gateway time synchronization method according to an embodiment of the present application is applied to a terminal and mainly includes the following steps S101-S103.

[0051] Step S101: Receive the time synchronization signaling message sent by the gateway and add a local timestamp at the receiving time, and the time synchronization signaling message carries the superframe group package configuration parameters;

[0052] In this embodiment, the gateway will periodically generate time synchronization signaling messages and broadcast them to the terminal. The terminal timestamps the message when it receives it. In this invention, all the parameters required for the terminal's calculation, i.e., the packet configuration parameters, are placed in the message through the pre-packetization mode, so that a single message can notify all calculation information.

[0053] In one implementation, the generation of time synchronization signaling messages is based on time synchronization on the gateway side. Gateway-side time synchronization can be achieved by deploying a time synchronization server, specifically, as shown below. Figure 5 As shown, in a satellite network, the gateway provides a unified standard time source, which can be from GPS or BD (BeiDou). The time source provides a pulse-per-second (1PPS) and a time code signal (TOD). A Time Synchronization Server (TSS) is deployed on the gateway side to receive the 1PPS and TOD code. The unified standard time source (TSS can also be configured as a PTP server) serves as the master clock for PTP, and all gateways, including MCS, RCM, and IP gateways, synchronize their time with the time synchronizer. PTP can achieve an accuracy of 100ns. External modems lack a central processing unit (CPU) and cannot directly support PTP. Therefore, the TSS performs time code parsing and broadcasts the time code corresponding to the pulse-per-second, along with additional information such as the relative time sequence number (Sequence) and frame number (FN), to the modem. The modem receives the pulse-per-second signal from the standard time source and can synchronize its frequency with the time source. The modem receives the TOD / Sequence / FN time frame number information from the TSS. In this way, the modem can establish a time boundary corresponding to the pulse-per-second. The RCM synchronizes its local clock with the time source via PTP. Simultaneously, the RCM receives TOD / Sequence / FN time frame number information from the TSS broadcast signaling, establishing a Sequence-and-FN mapping with the modem. This means both the gateway link layer and the physical layer (modem) obtain the time-and-frame-number mapping. The gateway's modem predicts the time synchronization frame transmission delay by packet assembly and broadcasts it within a single time synchronization frame—a time synchronization signaling message. Due to the continuous transmission mode of the forward link, it's impossible to send the time synchronization message at the exact time. However, through packet assembly prediction, the transmission delay of the time synchronization signaling message and the configuration parameters required for terminal calculations can be obtained at the packet assembly time. By pre-assembling the packet, all parameters, including the transmission delay, are broadcast to the terminal via the time synchronization signaling message, enabling a single message to notify all computational information.

[0054] Step S102: Calculate the local delay transmission time corresponding to the superframe based on the packet configuration parameters;

[0055] In the embodiment, the terminal and the gateway time synchronization is realized based on the time synchronization signaling message, and the basic synchronization principle is shown in Figure 6 As shown in the figure, the forward sending module of the gateway side modem starts to organize the time synchronization signaling message at the time T_GO before the frame start time, the delay between the sending time and the organizing time of the signaling message is recorded in the time synchronization signaling message, T_UO is the local delay sending time of the terminal, and the following relationship exists:

[0056] T_UO=T_GO-d-t1-t2-t3-t4

[0057] The frame number FN and T_GO and d are broadcast in the time synchronization signaling message, t1, t2, t3, t4 are calculated based on the ephemeris, the gateway position, the satellite position and the terminal position, and the position information of the gateway and the satellite is configured in the time synchronization signaling message. Therefore, in the application, the packet configuration parameters of the time synchronization signaling message at least include the gateway delay receiving time T_GO, the sending delay d of the time synchronization signaling message and the position information of the gateway and the satellite.

[0058] Step S103: obtaining the frame boundary synchronized with the gateway side superframe according to the time of the local timestamp and the local delay sending time, so as to realize the time synchronization with the gateway.

[0059] In the embodiment, the forward physical layer transmitter and the reverse physical layer receiver use the same frame boundary at the gateway side. At the terminal side, the frame boundary of the terminal physical layer transmitter is adjusted to be aligned with the frame boundary of the reverse receiver. The "alignment" means that the physical layer data frame sent at the frame boundary, such as frame 0, F0 for short, can arrive at the reverse receiver frame boundary F0 after the air interface transmission delay. Since the reverse receiver is a one-to-many receiver, and due to the satellite or user movement, the air interface delay of each user is different and can change over time. When the F0 of each user is aligned with the F0 of the receiver, the data of different users received by the receiver will not collide and can be correctly received. In fact, the F0 of the user and the F0 of the receiver are not the same in absolute time, and they differ by the one-way air interface time of each user. The purpose of time synchronization is to align the F0 of the user with the F0 of the receiver, even if the one-way air interface delay of each user is time-varying.

[0060] As shown in Figure 6As shown, the terminal modem (physical layer) sends the received message, stamped with a timestamp from its local time counter, to the terminal L2 (link layer). The terminal L2 calculates the time boundary corresponding to the frame number indicated by the time synchronization signaling message according to a formula. Simultaneously, the terminal L2 sends a control message to notify the terminal modem of the frame number and the corresponding frame boundary. For example, assuming the timestamp's time counter counts in 1ns, and T_UO is also calculated in 1ns units, the calculation formula is:

[0061] T_UO=T_GO-d-t1-t2-t3-t4

[0062] T_Marker_FN = Timestamp + T_UO

[0063] The timestamp is the value collected by the terminal modem, and T_Marker_FN is the modem frame number and the corresponding frame boundary.

[0064] In one implementation, such as Figure 7 As shown, at the gateway receiver Rx, F0 (or FN, where FN is the start frame number of the superframe). If each superframe has 8 frames, FN (mod 8) = 0. A preset time interval, T_GO, is given before FN. At this time, a system time synchronization signaling message, called SFTR (Super Frame Timing Reference), is periodically sent, carrying the frame number information of the superframe. A superframe equals 8 or more frames, each frame being 40ms, 10ms, or 20ms. If a superframe is 320ms and each frame is 20ms, then each superframe includes 16 frames. The start boundary of the superframe corresponds to the start boundary of the frame number FN. In this invention, the default value for one frame is 40ms, which can be changed through configuration.

[0065] System time synchronization signaling messages cannot be guaranteed to be sent exactly at the edge of T_GO. Depending on the implementation of the gateway physical layer transmitter, they may be sent earlier or later. The gateway physical layer calculates the time interval between the start boundary of the physical encapsulation frame of the system time synchronization signaling message and the T_GO boundary. The physical layer generates a time-series counter with a very small time unit. The time interval is represented by the difference in the counter value. This difference multiplied by the time unit is the time interval, i.e., the transmission delay denoted as d (unit T0, where T0 is the time unit of the physical layer clock counter). After obtaining the time interval d, the physical layer encapsulates both d and T0 into the system time synchronization signaling message. The time interval d is negative if it is earlier than the T_GO boundary and positive if it is later. Generally, the system time synchronization signaling message should be sent in the second physical encapsulation frame after the T_GO boundary or allow sufficient calculation time.

[0066] For example, assume that the time counter unit of the gateway physical layer and the layer 2 (link layer) is T0, which is very small. The time counters of the layer 2 and the physical layer can be synchronized and aligned with the frame number. Assume that the counter corresponding to the physical layer frame number FN (N Mod 8 = 0) is CN, the preset advance time T_GO is converted into a count G, i.e., T_GO = G*T0, then the time synchronization signaling message (FN) of the system should be sent at the time K = CN-G of the physical layer counter. The time synchronization signaling message (FN) of the system can not be sent at the time K of the physical layer counter, or in advance, or lag, assume that the interval of the advance or lag is a count d, the absolute time d*T0, the time synchronization signaling (FN) of the system is actually sent at the time K + / - d.

[0067] The information carried by the time synchronization signaling message of the system includes:

[0068] Frame number of the superframe: FN (updated by the gateway physical layer);

[0069] GW offset time: T_GO (ms), which is a PHY configuration parameter, and the default value is 620;

[0070] Counting unit: T0 (ns), which is a PHY configuration parameter;

[0071] Sending delay of the time synchronization signaling message of the system: d or -d;

[0072] Superframe interval: T_Interval (ms), and the default value is 320

[0073] The corresponding time relationship is as follows:

[0074] T UO = T GO -T G-S-G -2*T U-S -T SFTR-Delay

[0075] That is, the receiving time of the reverse gateway expected to receive "frame N data" and the sending time of the terminal sending "frame N data" satisfy the above time relationship;

[0076] Wherein, T GO is the reverse gateway delay receiving time, i.e., the time difference between the ideal time of sending the superframe and the predetermined receiving time of frame N, and the default value for GEO is 620 ms (270*2+80);

[0077] T SFTR-Delay is the sending delay of the time synchronization signaling message measured by the gateway side;

[0078] T G-ST is the propagation time between the satellite and the terminal;

[0079] T S-U T is the propagation time between the satellite and the terminal;

[0080] T UO T is the terminal delay sending time, i.e. the difference between the ideal receiving time of the terminal receiving the superframe FN and the actual sending time of the terminal sending the frame N data;

[0081] T S-G T is the propagation time between the satellite and the terminal;

[0082] T U-S T is the propagation time between the satellite and the terminal;

[0083] T G-S-G T is the Round Trip time between the satellite and the terminal;

[0084] T G-U T is the delay from the gateway to the user, which is not considered if the gateway is on the satellite.

[0085] Note:

[0086] In the present invention, the subscript S in the present invention represents the satellite (Satellite), G represents the reverse gateway (Gateway), U represents the terminal (User), and O represents the time offset (Offset).

[0087] Regardless of whether the user accesses the gateway on the ground or on the satellite, it is assumed that T G-U = the delay from the gateway to the user, then on the terminal side, the user needs to calculate T UO = T_GO - d*T0 - 2*T G-U to complete the local FN time boundary. d*T0 can be positive or negative through ephemeris and user reference point coordinate calculation.

[0088] In order to realize the time alignment of data sending and receiving between the terminal and the reverse gateway, the terminal needs to rely on the received system time synchronization signaling message to establish a time reference, i.e. the frame boundary. Since the time control is performed at the L1 (modem) of the terminal, better time accuracy can be obtained, therefore the establishment of the time reference of the terminal and the sending time control are mainly responsible for the L1 (modem), and the L2 (software) plays an auxiliary calculation role.

[0089] The terminal establishes a time reference according to the time synchronization signaling message, and the reverse gateway adjusts the time reference every 8 frames (the time interval of one system time synchronization signaling message). Generally, if the new FN and the FN derived from the previous synchronization have a small error, the terminal uses the FN generated from the previous synchronization; otherwise, the terminal uses the time reference established by the latest system time synchronization signaling message to complete the data transmission of the following 8 frames. When a certain system time synchronization signaling message is invalid and the terminal cannot update the current time reference, the last time reference can be repeatedly used to realize the time control of data transmission.

[0090] Three time information needs to be determined for one data transmission of the terminal:

[0091] 1) The time reference information established by the time synchronization signaling message - the relative time origin currently used;

[0092] 2) The delay transmission time information of a specific frame data - the local delay transmission time T UO of the terminal;

[0093] 3) The time information of the slot offset slot_offset of the subframe in a frame data - the time boundary in the frame of the terminal.

[0094] Specifically, as shown in the following table, the terminal L1 (modem) uses the following method to establish a time reference: Figure 8

[0095] 1) The terminal L1 (modem) timestamps each locally received data packet (time synchronization signaling message) (in time counter interval units, the counter value is denoted as m1), and uploads the data packet to the terminal L2 (software);

[0096] 2) The terminal L2 (software) parses the data packet, extracts the frame number of the system time synchronization signaling message, and transmits the frame number information together with the "L1 (modem) marked timestamp" information, denoted as m1, to the terminal L1 (modem). At the same time, L2 records the local system time synchronization signaling timestamp count value m2. Note that m1 and m2 are independent of each other. L2 parses the system time synchronization signaling to obtain d*T0, FN, T_SF, and calculates T UO = T GO -d*T0-2*T G-U , T G-U which is related to the distance from the satellite to the terminal and the gateway, and can be calculated through ephemeris diagram. Assuming that the count interval of the terminal L1 and L2 is t0 (t0 can be equal to T0), and the delay of L1 to L2 is k*t0 (internal transmission delay time). In this way, FN of L2 = m2-k+round(T UO / t0), and L2 also transmits T​UO Transmit to L1.

[0097] 3) The terminal L1 (modem) gets the arrival of the system time synchronization signaling message (FN) to the local time m1 and T UO , establishes the correspondence between the frame number FN of the system time synchronization signaling message and the local time stamp time of L1, uses the "L1 local time stamp time" as the relative time origin, and performs the local delay transmission time calculation. The corresponding local time count value of FN is FN(count)=m1+round(T UO / t0). In order to simplify the calculation amount of the modem, L2 can directly calculate the FN(count) of L1 and send it to the modem together with m1.

[0098] In one embodiment, the access gateway transmits a system time synchronization signaling message every 8 frames, and the user receives a system time synchronization signaling message every 8 frames. For the flexible design of the system, the system time synchronization signaling message is transmitted with a superframe interval. However, because of the variation, the interval of the two system time synchronization signaling messages received by the user can not be 8 frames, and the user needs to check the synchronization every time a system time synchronization signaling message is received. If the difference between the FN generated by the new system time synchronization signaling and the FN generated by the original system time synchronization signaling is less than a first threshold value (delta1) or greater than an unreasonable second threshold value (delta2), the original FN is continued to be used; otherwise, the FN generated by the new system time synchronization signaling is used. The terminal local time not only generates FN, but also generates FN+1, FN+2, …, FN+8, etc. FN+8 can also be generated by the new system time synchronization signaling (FN+8). If the new FN+8 is sufficiently close to the original FN+8, it is not updated; otherwise, the new FN+8 is used. If the new FN+8 is abnormal, it is also not updated.

[0099] The mathematical description is as follows: assuming that the first threshold value delta1 and the second threshold value delta2,

[0100] IF delta1<=|new FN-original calculated FN|<=delta2

[0101] Use the new FN;

[0102] ELSE

[0103] Use the original calculated FN.

[0104] It should be noted that the FN here is the starting frame of the superframe, and the system time synchronization signaling only generates FN, and the terminal itself generates FN+1, FN+2, … thereafter. The system time synchronization signaling is not responsible for the synchronization of non-SF starting frames. However, in practice, if the system feedback needs non-SF starting frame adjustment, it is adjusted according to the need.

[0105] Based on the steps S101-S103, the terminal receives the time synchronization signaling message sent by the gateway, calculates the frame boundary synchronized with the gateway based on the analysis, aligns the sending frame boundary with the receiving frame boundary of the gateway, and takes the time stamp of the terminal at the time of receiving the time synchronization signaling message as the reference, so that the time synchronization with the gateway can be realized without absolute time, and the synchronization effect is good without the dependence on absolute time.

[0106] Specifically, the gateway broadcasts the configuration parameters required by the terminal to the terminal through a time synchronization signaling message, the modem of the terminal starts the time counter and timestamps at the time of receiving the time synchronization signaling message, and the time counter of the modem itself is used as the time stamp, so that the relative time calculation is more simple. The synchronization between the terminal L2 and the gateway is based on the time counter of the terminal L2, and the synchronization between the terminal L1 and the gateway is based on the time counter of the terminal L1. The terminal can realize the time synchronization with the gateway without absolute time.

[0107] It should be noted that, although the steps are described in a specific order in the above embodiment, those skilled in the art can understand that, in order to achieve the effect of the present application, the steps do not have to be executed in such an order, and they can be executed simultaneously (in parallel) or in other orders, and these changes are within the protection scope of the present application.

[0108] Further, the present application also provides a satellite network terminal and gateway time synchronization device, comprising a memory, one or more processors, one or more application programs, wherein the one or more application programs are stored in the memory, and the one or more application programs are configured to be called by the one or more processors, so that the one or more processors execute the method as described in the above steps S101-S103.

[0109] The device in the embodiment of the present application mainly includes a memory and a processor. The memory can be configured to store the program of the satellite network terminal and gateway time synchronization method for executing the above method embodiment. The processor can be configured to execute the program in the memory, which includes but is not limited to the program of the satellite network terminal and gateway time synchronization method for executing the above method embodiment. For the convenience of description, only the parts related to the embodiment of the present application are shown, and the specific technical details are not disclosed, please refer to the method part of the embodiment of the present application.

[0110] In the embodiments of the present application, the satellite network terminal and gateway time synchronization device can be a control device formed by various electronic devices. In some possible implementation manners, the device can include a plurality of storage devices and a plurality of processors. The program for implementing the satellite network terminal and gateway time synchronization method of the above-mentioned method embodiments can be divided into a plurality of sub-programs, each of which can be loaded and run by the processor to perform different steps of the satellite network terminal and gateway time synchronization method of the above-mentioned method embodiments. Specifically, each sub-program can be stored in a different memory, and each processor can be configured to execute the program in one or more memories to jointly implement the satellite network terminal and gateway time synchronization method of the above-mentioned method embodiments, that is, each processor respectively performs different steps of the satellite network terminal and gateway time synchronization method of the above-mentioned method embodiments to jointly implement the satellite network terminal and gateway time synchronization method of the above-mentioned method embodiments.

[0111] The above-mentioned plurality of processors can be processors deployed on the same device, for example, the above-mentioned computer device can be a high-performance device composed of a plurality of processors, and the above-mentioned plurality of processors can be processors configured on the high-performance device. In addition, the above-mentioned plurality of processors can also be processors deployed on different devices, for example, the above-mentioned computer device can be a server cluster, and the above-mentioned plurality of processors can be processors on different servers in the server cluster.

[0112] The above-mentioned satellite network terminal and gateway time synchronization device is used for executing Figure 1 As shown in the satellite network terminal and gateway time synchronization method embodiments, the technical principles, the technical problems solved and the technical effects generated are similar. Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the control device and the related description can refer to the content described in the embodiments of the satellite network terminal and gateway time synchronization method, which will not be described here.

[0113] Further, the present application also provides a satellite network system including the satellite network terminal and gateway time synchronization device of the above-mentioned embodiments. For the convenience of description, only the parts related to the embodiments of the present application are shown, and the specific technical details that are not disclosed are referred to the method part of the embodiments of the present application.

[0114] In one embodiment, the satellite network system further comprises a gateway, i.e. at the gateway side, the standard time source has a standard clock signal, generates a stable second pulse signal and a time code signal. The time synchronization server parses the time code to generate a time frame number mapping broadcast signaling, the RCM receives the broadcast signaling simultaneously with the physical layer modem, and configures the mapping relationship between the frame number and the second pulse counter according to the signaling. The RCM of the gateway system must receive the PTP message at the same time to synchronize the time. A gateway system and a modem under the management of one time synchronization server TSS share a set of frame numbers and time boundaries. The gateway side time synchronization workflow is as shown in Figure 9 The system is designed to divide each frame of time by 1000 ms, and the general value is 10 ms, 20 ms, or 40 ms. Assuming that there are N frames in 1 s, when each frame is 40 ms, N is 25 = 1000 / 40. Let the frame number be FN, and the 1 s counter be Counter_1s, then there is the following relationship between the 1 s counter and the frame number: Counter_1s = FN / N. FN is an unsigned 32-bit integer, and Counter_1s is an unsigned 32-bit integer. When the frame number reaches the maximum value and returns to 0, Counter_1s is forced to also return to 0. That is, Counter_1s will not reach the maximum value. If all TSS servers in the network generate frame numbers using the same rule, such as selecting a fixed time point as the 0 frame start and using the frame number cyclically when it reaches the maximum value, then the frame numbers and the absolute time of the time code in the entire network are unified. All network elements have the same frame number at a certain absolute time.

[0115] The gateway side modem, upon initialization, obtains the system time synchronization signaling advance sending time T_GO (unit: ms) and system time synchronization signaling sending interval time T_Interval (unit: ms) from the NMS (network management system). The NMS can also provide auxiliary information such as gateway deployment location number, satellite number in the air, etc. According to this information, the modem organizes the system time synchronization signaling message at the advance T_GO time of each super frame FN, and calculates the delay Delay between the sending time and the packet assembly time. These information are organized in the system time synchronization signaling message and sent to the terminal. The system time synchronization signaling is a standard control signaling, and the message carries the following table 1:

[0116]

[0117]

[0118] In one embodiment, the satellite network terminal and the gateway time synchronization device, i.e. the terminal, can realize terminal side time synchronization based on the time synchronization signaling message. Specifically, the terminal side time synchronization architecture is as shown in Figure 10The terminal modem is responsible for time stamping the messages with its own time counter. The terminal L2 parses the time synchronization signaling messages, calculates the frame boundary, and sends a frame boundary configuration message to the modem, to achieve the L2 of the terminal, the terminal modem, and the gateway receiver to perform time synchronization based on the superframe. The terminal modem starts the time counter with a counting accuracy requirement of 10 ns, 4 ns, or 1 ns. The time synchronization between the terminal modem and L2 is based on the counter.

[0119] Specifically, the terminal side time synchronization process is as shown in Figure 11 The terminal modem needs to start a time counter with an accuracy of 1 ns, 4 ns, or 10 ns after power-on. The terminal modem needs to time stamp all forward messages received in the forward direction and send them to L2. The time stamp value is the time counter value at the time of reception. L2 parses the time synchronization signaling messages periodically broadcast by the gateway, and calculates the frame boundary through a time synchronization algorithm. The frame boundary is set based on the time counter provided by the modem. L2 sets the mapping relationship between the frame number and the time counter, and the modem adjusts its frame boundary according to the setting. When the terminal sends data, it provides the frame number and the time slot offset value at the time of transmission for each transmitted data message. Since the gateway periodically sends superframe synchronization signaling, the terminal calculates the frame start boundary at any time. When the fluctuation exceeds the preset tolerance value, L2 resets the mapping relationship between the frame number and the time counter, otherwise maintains the original setting value unchanged. The terminal modem needs to be designed to adjust the frame boundary for each superframe. At the same time, the periodic superframe synchronization signaling also means that the terminal clock frequency is synchronized with the gateway.

[0120] The terminal reverse transmission needs to be based on the frame and the time slot offset within the frame to achieve alignment of the frame boundary between L2 and the modem, so that L2 can hand over the data to be sent to the modem at a predictable time. The terminal modem and L2 start their own time counters respectively, and synchronization is achieved based on the respective time counters, without the need for absolute time.

[0121] In the above system, the satellite network of the application provides a standard time source at the gateway side, generates a second pulse and a time code signal, a time synchronization server parses the time code and generates a mapping with a reverse transmission frame number, the time synchronization server broadcasts the mapping of the frame number and the second pulse, synchronizes the modem at the network side with the gateway system, the gateway side periodically generates a time synchronization signaling message, and directly broadcasts the mapping relationship between time and frame to all terminals. The terminal receives the time synchronization signaling message, calculates the transmission delay according to the distance from the satellite, and calculates the synchronized frame boundary. The frame boundary calculated by the terminal L2 is calculated based on the timestamp of the modem at the time when the time synchronization signaling message is received, and the terminal L2 and the physical layer (L1) modem realize time synchronization with the gateway side. The terminal sends data, needs to calculate the accurate sending time according to the frame boundary and the offset of the sending subframe in the frame, and the transmitted signal reaches the gateway at the receiving time set by the receiver modem after the transmission delay, realizes the alignment of the sending frame boundary and the gateway receiving frame boundary, defines the synchronization of the gateway side L2 and L1, the synchronization of the terminal side L2 and L1, and the complete satellite network synchronization scheme of the synchronization of the gateway itself, the synchronization of the terminal itself and the cross-air interface synchronization of the terminal-gateway. After the gateway and the terminal software are implemented, the actual operation effect is good.

[0122] Those skilled in the art can understand that all or part of the processes in the method of the above-mentioned embodiment of the application can also be completed by a computer program instructing related hardware. The computer program can be stored in a computer readable storage medium. When the computer program is executed by a processor, the steps of each method embodiment described above can be implemented. The computer program includes computer program code, which can be in the form of source code, object code, executable files or some intermediate forms. The computer readable storage medium can include any entity or device, medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory, random access memory, electrical carrier signal, telecommunication signal and software distribution medium, etc. that can carry the computer program code. It should be noted that the contents included in the computer readable storage medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer readable storage medium does not include electrical carrier signals and telecommunication signals.

[0123] Further, the present application also provides a computer readable storage medium. In an embodiment of the computer readable storage medium according to the present application, the computer readable storage medium can be configured to store a program of the satellite network terminal and gateway time synchronization method of the above-mentioned method embodiment, which can be loaded and run by the processor to realize the above-mentioned satellite network terminal and gateway time synchronization method. For the convenience of description, only the parts related to the embodiments of the present application are shown, and the specific technical details not disclosed are referred to the method part of the embodiments of the present application. The computer readable storage medium can be a storage device formed by various electronic devices, and optionally, the computer readable storage medium in the embodiments of the present application is a non-transitory computer readable storage medium.

[0124] Further, it should be understood that, since the setting of each module is only for illustrating the functional units of the device of the present application, the corresponding physical device of the module can be the processor itself, or a part of the software, a part of the hardware, or a part of the combination of the software and the hardware in the processor. Therefore, the number of each module in the figure is only illustrative.

[0125] Those skilled in the art can understand that each module in the device can be adaptively split or combined. Such splitting or combining of the specific module does not cause the technical solution to deviate from the principles of the present application, and therefore, the technical solution after splitting or combining will fall within the protection scope of the present application.

[0126] So far, the technical solution of the present application has been described in combination with the preferred embodiments shown in the drawings, but those skilled in the art can easily understand that the protection scope of the present application is obviously not limited to these specific embodiments. Those skilled in the art can make equivalent changes or replacements to the related technical features without deviating from the principles of the present application, and the technical solution after the changes or replacements will fall within the protection scope of the present application.

Claims

1. A method for time synchronization between a satellite network terminal and a gateway, applied to the terminal, characterized in that, The method comprises the following steps: receiving a time synchronization signaling message sent by a gateway and adding a local timestamp at the time of receiving, wherein the time synchronization signaling message carries a superframe grouping configuration parameter, and the superframe grouping configuration parameter comprises a superframe number, a gateway delay receiving time, a sending delay of the time synchronization signaling message, and position information of the gateway and a satellite; calculating a local delay sending time corresponding to the superframe according to the superframe grouping configuration parameter, which comprises the following steps: calculating a transmission time between the gateway and the satellite according to the position information of the gateway and the satellite; subtracting the sending delay of the time synchronization signaling message and the transmission time between the gateway and the satellite from the gateway delay receiving time to obtain the local delay sending time corresponding to the superframe; obtaining a frame boundary synchronized with the superframe on the gateway side according to the time of the local timestamp and the local delay sending time, so as to realize time synchronization with the gateway; the terminal comprises a physical layer and a link layer; the physical layer is configured to add a first local timestamp at the time of receiving the time synchronization signaling message, and send the time synchronization signaling message to the link layer; the link layer is configured to analyze and calculate the time synchronization signaling message to obtain the local delay sending time corresponding to the superframe; the step of obtaining the frame boundary synchronized with the superframe on the gateway side according to the time of the local timestamp and the local delay sending time comprises the following step: the physical layer calculates the frame boundary of the superframe corresponding to the gateway according to the time of the first local timestamp and the local delay sending time; the link layer is further configured to add a second local timestamp at the time of receiving the time synchronization signaling message, and record an internal transmission delay time of the time synchronization signaling message from the physical layer to the link layer; the step of obtaining the frame boundary synchronized with the superframe on the gateway side according to the time of the local timestamp and the local delay sending time further comprises the following step: the link layer calculates the frame boundary of the superframe corresponding to the gateway according to the second local timestamp, the internal transmission delay time and the local delay sending time.

2. The method of claim 1, wherein, The method further comprises the following steps: synchronizing the time and the frame number of the physical layer and the link layer of the gateway based on a time synchronization server to obtain a mapping relationship between the time and the frame number; organizing and sending the time synchronization signaling by the physical layer of the gateway based on the mapping relationship.

3. The method of claim 1, wherein, The gateway delay receiving time is a time of sending the superframe in advance, and the sending delay of the time synchronization signaling message is obtained based on packet grouping prediction of the physical layer of the gateway.

4. The method of claim 1, wherein, The method further comprises the following steps: sending data to the gateway, obtaining a sending time of the data according to the frame boundary and a time slot offset of a sending subframe in a frame, so that the data reaches the gateway at a subframe receiving time set by the gateway after a transmission delay of the terminal and the gateway.

5. The method of claim 1-4, wherein, The superframe grouping configuration parameter further comprises a superframe interval; The method further comprises the following steps: receiving the time synchronization signaling once every superframe interval, and checking whether a new frame boundary needs to be used according to a new time synchronization signaling message. If the absolute value of the difference between the new frame boundary obtained according to the new time synchronization signaling packet and the original frame boundary is less than a first threshold or greater than a second threshold, the original frame boundary is used; otherwise, the new frame boundary is used; wherein the second threshold is greater than the first threshold.

6. A satellite network terminal and gateway time synchronization apparatus, characterized by, A non-transitory computer-readable medium storing code, the code being compatible with one or more processors and one or more applications stored in memory, the one or more applications, when invoked by the one or more processors, cause the one or more processors to perform the method of any of claims 1-5.

7. A satellite network system, characterized by The system comprises the apparatus as claimed in claim 6.

8. A computer-readable storage medium, characterized in that, A non-transitory computer-readable medium storing code, the code being compatible with one or more processors and one or more applications stored in memory, the one or more applications, when invoked by the one or more processors, cause the one or more processors to perform the method of any of claims 1-5.

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