A 5G satellite communication time synchronization method

Abstract

The present invention discloses a 5G satellite communication time synchronization method, which is applied to a terminal, and includes the following steps: in response to a downlink signal sent by a satellite, each terminal sends an uplink signal to the satellite according to the information carried in the received downlink signal, so that the satellite receives the uplink data sent by each terminal within a preset uplink signal receiving time window; the information carried in the downlink signal includes a carrier frequency and an uplink frame structure for indicating that the terminal sends an uplink signal; the uplink frame structure includes a number of uplink time slots and a unique word inserted between two adjacent uplink time slots, and the unique word is used for time-frequency estimation and correction in the continuous transmission of the uplink time slot. The present invention reduces the complexity of the system by converting the traditional uplink signal strict synchronization mode into a non-strict synchronization mode; by increasing the length of the uplink frame structure, the proportion of the protection interval in the uplink signal receiving time window is reduced, thereby improving the communication efficiency.

Description

Technical Field

[0001] The present invention relates to the field of satellite communication technology, and in particular to a 5G satellite communication time synchronization method. Background Art

[0002] Compared with terrestrial mobile communication networks, satellite communication systems can achieve wide-area or even global coverage, providing non-differentiated communication services to users around the world. At the same time, the terrestrial fifth-generation mobile communication (5G) system already has a complete industrial chain, a huge user base, and a flexible and efficient application service model. Satellite communication and 5G are integrated with each other, complementing each other's strengths and weaknesses, and together form a global seamless coverage of the sea, land, air, and space integrated integrated communication network, which meets the ubiquitous and diverse business needs of users and is an important direction for the future development of communications.

[0003] 5G satellite communication system uses OFDM (Orthogonal Frequency Division Multiplexing) modulation like terrestrial 5G system. OFDM has good anti-noise performance and anti-multipath channel interference ability as well as high frequency utilization, and has great potential in the field of broadband communication. Although OFDM technology has the advantage of natural resistance to multipath fading and is very suitable for high-speed data transmission, it is very sensitive to time deviation, which will cause the timing window deviation between each symbol, resulting in symbol demodulation failure. Therefore, eliminating the impact of time deviation on OFDM system is the key to applying OFDM system in the high-speed mobile environment of satellite communication. In satellite communication system, the distance between satellite and ground terminal is very far, so the one-way signal transmission time is much longer than that of ground communication system, and the distance difference between near-point terminal and far-point terminal and satellite is also very large, so the time deviation is relatively higher; in addition, the moving speed of satellite is much higher than that of ground network scenario, and the time deviation changes much more in unit time. Therefore, countering time deviation is of greater significance for 5G satellite communication system.

[0004] The orbital altitude of Low Earth Orbit (LEO) is about 400-2000 kilometers. Assuming the minimum working inclination of the satellite is 30 degrees, Figure 1 As shown, any position point of the satellite in its orbit corresponds to a near point and a far point, the corresponding maximum distance range is 800-4000 kilometers, and the corresponding one-way transmission time of the wireless signal is 2600us-13300us.

[0005] like Figure 2As shown in the figure, it is a typical uplink frame structure in traditional 5G satellite communication technology. The wireless frame length is 10ms, the subframe length is 1ms, and each subframe is divided into N time slots. The value of N is related to the subcarrier spacing. For example, in the case of 120kHz subcarrier spacing (extended cyclic prefix), N is 8, that is, each subframe is divided into 8 time slots, and the time slot length is 125us. The basic unit of uplink data transmission is 1 time slot, 12 symbols in each time slot, each symbol is 10.4us, and the cyclic prefix length is 2.6us. In order to ensure successful signal demodulation, the time deviation should be less than half of the cyclic prefix length, that is, 1.3us. The 1.3us time deviation is very short compared with the signal transmission time, which makes it very difficult to control the uplink time.

[0006] like Figure 3 As shown in the figure, it is a schematic diagram of the uplink receiving window in the traditional 5G satellite communication technology. The satellite uplink signal receiving time window is equal to the uplink signal time slot length, both of which are 125us. The system will modify the uplink signal sending time of terminals at different locations through the TA process or ephemeris pre-compensation, so that the uplink signals sent by satellite terminals at different locations can reach the satellite at the same time. In addition, the speed of low-orbit satellites relative to the ground is approximately the first cosmic speed of 7.9Km / s. The time deviation difference caused by the distance change per second is about 26us. Considering the 1.3us limit, it is equivalent to the satellite moving 20ms every time, which will cause the time deviation to exceed the demodulation window.

[0007] In order to solve the time deviation problem of 5G satellite communication, the current general method is to use uplink TA (Timing Advance) adjustment and ephemeris pre-compensation, but TA adjustment has an adjustment cycle and occupies the downlink transmission channel, so it is difficult to meet the real-time requirements; ephemeris needs to be stored in the terminal in advance, and it needs to use GNSS information to obtain its own position and accurate time. The flexibility and accuracy are limited, and the terminal may not be able to obtain the latest ephemeris information at any time. Summary of the invention

[0008] In view of the problem in the prior art that it is difficult to achieve strict synchronization of uplink signals of each terminal during 5G satellite communications, an object of the present invention is to provide a 5G satellite communication time synchronization method so as to at least partially solve the above problem.

[0009] To achieve the above object, the technical solution of the present invention is:

[0010] In a first aspect, the present invention provides a 5G satellite communication time synchronization method, the method is applied to a terminal, and the method comprises the following steps:

[0011] In response to the downlink signal sent by the satellite, each terminal sends an uplink signal to the satellite according to the information carried in the received downlink signal, so that the satellite receives the uplink data sent by each terminal within a preset uplink signal reception time window;

[0012] Among them, the information carried in the downlink signal includes the carrier frequency and uplink frame structure used to instruct the terminal to send an uplink signal; the uplink frame structure includes a number of uplink time slots and a unique word inserted between two adjacent uplink time slots, and the unique word is used for time-frequency estimation and correction in continuous transmission of the uplink time slot.

[0013] In a second aspect, the present invention provides a 5G satellite communication time synchronization method, the method is applied to a satellite, and the method comprises the following steps:

[0014] The satellite sends a downlink signal to each terminal, and receives uplink data sent by each terminal within a preset uplink signal receiving time window;

[0015] After receiving the downlink signal, each terminal sends an uplink signal to the satellite according to the information carried in the received downlink signal;

[0016] Among them, the information carried in the downlink signal includes the carrier frequency and uplink frame structure used to instruct the terminal to send an uplink signal; the uplink frame structure includes a number of uplink time slots and a unique word inserted between two adjacent uplink time slots, and the unique word is used for time-frequency estimation and correction in continuous transmission of the uplink time slot.

[0017] Preferably, the window length of the uplink signal receiving time window is equal to the sum of the length of the uplink frame structure and the protection interval, and the protection interval is greater than or equal to the transmission time difference between the uplink signal sent by the far-point terminal and the uplink signal sent by the near-point terminal arriving at the satellite; and the starting point of the uplink signal receiving time window is the moment when the uplink signal sent by the near-point terminal arrives at the satellite.

[0018] Preferably, the starting point of the uplink signal receiving time window is determined by the orbit and inclination of the satellite.

[0019] Preferably, uplink signals having the same uplink frame structure correspond to the same uplink signal receiving time window.

[0020] By adopting the above technical scheme, the beneficial effect of the present invention is that: by changing the uplink frame structure sent by the terminal and the uplink signal receiving time window of the satellite, each terminal only needs to send the uplink signal according to the uplink frame structure after receiving the downlink signal, and the uplink signal can be received and demodulated by the satellite through the uplink signal receiving time window, so that the uplink signals sent by multiple terminals can be received in the same uplink signal receiving time window without complicated calculations, and the traditional uplink signal strict synchronization is converted into non-strict synchronization, thereby greatly reducing the complexity of the system and making it easy to implement. In addition, by configuring the transmission unit of the uplink frame structure as a time slot and setting multiple times, compared with the traditional technology (the transmission unit is a symbol), the length of the uplink frame structure can be effectively increased, thereby reducing the proportion of the protection interval in the uplink signal receiving time window, so that the amount of data that can be received in a single uplink signal receiving time window is greatly increased, thereby improving the communication efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the 5G satellite communication system;

[0022] Figure 2 A schematic diagram of a typical uplink frame sent by a terminal in a 5G satellite communication system in the prior art;

[0023] Figure 3 This is a schematic diagram of the 5G satellite uplink signal receiving time window in the prior art;

[0024] Figure 4 It is a schematic diagram of the principle of the 5G satellite communication time synchronization method in the present invention;

[0025] Figure 5 A schematic diagram of an uplink frame structure sent by a terminal in the present invention;

[0026] Figure 6 Schematic diagram of the composition of the uplink signal receiving time window of the 5G satellite in the present invention;

[0027] Figure 7 This is a working schematic diagram of the uplink signal receiving time window of the 5G satellite in the present invention;

[0028] Figure 8 This is a schematic diagram of the structure of an electronic device in Embodiment 3 of the present invention. DETAILED DESCRIPTION

[0029] The specific embodiments of the present invention are further described below in conjunction with the accompanying drawings. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0030] It should be noted that, in the description of the present invention, the directions or positional relationships indicated by the terms "up", "down", "left", "right", "front", "back", etc. are descriptions of the structure of the present invention based on the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0031] The "first" and "second" in this technical solution are only used to distinguish the names of the same or similar structures, or corresponding structures with similar functions, and are not an arrangement of the importance of these structures, nor do they have a ranking, comparison of size, or other meanings.

[0032] In addition, unless otherwise clearly specified and limited, the terms "installation" and "connection" should be understood in a broad sense. For example, the connection can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be a connection between the two structures. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood based on the overall idea of ​​the present invention and the specific context of the present solution.

[0033] Embodiment 1

[0034] A 5G satellite communication time synchronization method, the method is applied to a terminal, such as Figure 4 As shown, the method comprises the following steps:

[0035] In response to the downlink signal sent by the satellite, each terminal sends an uplink signal to the satellite according to the information carried in the received downlink signal, so that the satellite receives the uplink data sent by each terminal within a preset uplink signal reception time window.

[0036] The information carried in the downlink signal includes the carrier frequency and uplink frame structure used to instruct the terminal to send the uplink signal. Figure 5 As shown in FIG. 1 , the uplink frame structure includes a number of uplink time slots and a unique word inserted between two adjacent uplink time slots. The unique word is used for time-frequency estimation and correction in the continuous transmission of the uplink time slots. In actual operation, the number of time slots and the length of the unique word included in the uplink frame structure can be determined according to demand and configured to each terminal by the satellite base station through downlink signaling.

[0037] like Figure 6As shown, the window length of the uplink signal receiving time window is equal to the sum of the length of the uplink frame structure and the protection interval, and the protection interval is greater than or equal to the transmission time difference between the uplink signal sent by the far-point terminal and the uplink signal sent by the near-point terminal to reach the satellite; and the starting point of the uplink signal receiving time window is the moment when the uplink signal sent by the near-point terminal arrives at the satellite, as shown in FIG. Figure 7 shown.

[0038] In this way, by configuring the transmission unit of the uplink frame structure as a time slot and setting multiple times, compared with the traditional technology (the transmission unit is a symbol), the length of the uplink frame structure can be effectively increased, thereby reducing the proportion of the protection interval in the uplink signal receiving time window, so that the amount of data that can be received in a single uplink signal receiving time window is greatly increased, thereby improving communication efficiency.

[0039] Among them, the starting point of the uplink signal receiving time window is determined by the satellite's orbit and inclination. When the satellite's orbit and inclination are determined, for the periapsis terminal, the time from the downlink signal being sent by the satellite, the periapsis terminal receiving the downlink signal, the periapsis terminal processing the downlink signal, and the periapsis terminal sending the uplink signal are all determined, so the starting point of the uplink signal receiving time window is also determined. Therefore, as long as the satellite's orbit and inclination remain unchanged, the interval between the starting point of the uplink signal receiving time window and the time when the downlink signal is sent is also fixed.

[0040] It can be understood that in order to improve the processing efficiency of the satellite, the uplink signals sent by each terminal are configured so that the uplink signals with the same uplink frame structure correspond to the same uplink signal receiving time window opened by the satellite, so that the uplink signals sent by different terminals and received within the window range of the uplink signal receiving time window can all be successfully demodulated.

[0041] On the contrary, among the uplink signals sent by each terminal, the uplink signals with different uplink frame structures correspond to different uplink signal receiving time windows opened by the satellite. Usually, the satellite can set a variety of uplink frame structures and matching uplink signal receiving time window lengths at different times and carrier frequencies according to specific needs; for the same terminal, the satellite can also allocate different carrier frequency positions, different uplink frame structures and uplink signal receiving time windows to it at different times, thereby achieving more flexible resource allocation.

[0042] Embodiment 2

[0043] A 5G satellite communication time synchronization method, compared with the first embodiment, the only difference is that the method provided in this embodiment is applied to a satellite, and the method includes the following steps:

[0044] The satellite sends a downlink signal to each terminal and receives the uplink data sent by each terminal within a preset uplink signal reception time window;

[0045] After receiving the downlink signal, each terminal sends an uplink signal to the satellite according to the information carried in the received downlink signal;

[0046] Among them, the information carried in the downlink signal includes the carrier frequency and uplink frame structure used to instruct the terminal to send the uplink signal; the uplink frame structure includes several uplink time slots and a unique word inserted between two adjacent uplink time slots. The unique word is used for time and frequency estimation and correction in the continuous transmission of the uplink time slot.

[0047] Embodiment 3

[0048] An electronic device, such as Figure 8 As shown, it includes a memory storing executable program code and a processor coupled to the memory; wherein the processor calls the executable program code stored in the memory to execute the method steps disclosed in the above embodiment.

[0049] Embodiment 4

[0050] A computer storage medium stores a computer program, and when the computer program is executed by a processor, the method steps disclosed in the above embodiment are executed.

[0051] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0052] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0053] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0054] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the scope of protection of the present invention.

Claims

1. A 5G satellite communication time synchronization method, characterized in that: The method is applied to a terminal, and comprises the following steps: In response to the downlink signal sent by the satellite, each terminal sends an uplink signal to the satellite according to the information carried in the received downlink signal, so that the satellite receives the uplink data sent by each terminal within a preset uplink signal reception time window; The information carried in the downlink signal includes a carrier frequency and an uplink frame structure for indicating that the terminal sends an uplink signal; the uplink frame structure includes a number of uplink time slots and a unique word inserted between two adjacent uplink time slots, and the unique word is used for time-frequency estimation and correction in continuous transmission of uplink time slots; Among them, the window length of the uplink signal receiving time window is equal to the sum of the length of the uplink frame structure and the protection interval, the protection interval is greater than or equal to the transmission time difference between the uplink signal sent by the far-point terminal and the uplink signal sent by the near-point terminal to reach the satellite; and the starting point of the uplink signal receiving time window is the moment when the uplink signal sent by the near-point terminal arrives at the satellite; the starting point of the uplink signal receiving time window is determined by the satellite's orbit and inclination.

2. A 5G satellite communication time synchronization method, characterized in that: The method is applied to a satellite and comprises the following steps: The satellite sends a downlink signal to each terminal, and receives uplink data sent by each terminal within a preset uplink signal receiving time window; After receiving the downlink signal, each terminal sends an uplink signal to the satellite according to the information carried in the received downlink signal; The information carried in the downlink signal includes a carrier frequency and an uplink frame structure for indicating that the terminal sends an uplink signal; the uplink frame structure includes a number of uplink time slots and a unique word inserted between two adjacent uplink time slots, and the unique word is used for time-frequency estimation and correction in continuous transmission of uplink time slots; The window length of the uplink signal receiving time window is equal to the sum of the length of the uplink frame structure and the protection interval, and the protection interval is greater than or equal to the transmission time difference between the uplink signal sent by the far-point terminal and the uplink signal sent by the near-point terminal arriving at the satellite; and the starting point of the uplink signal receiving time window is the moment when the uplink signal sent by the near-point terminal arrives at the satellite; the starting point of the uplink signal receiving time window is determined by the satellite's orbit and inclination.

3. The 5G satellite communication time synchronization method according to claim 1 or 2, characterized in that: Uplink signals with the same uplink frame structure correspond to the same uplink signal receiving time window.

4. An electronic device, characterized in that: It comprises a memory storing executable program code and a processor coupled to the memory; wherein the processor calls the executable program code stored in the memory to execute the method according to any one of claims 1 to 3.

5. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 3 is performed.

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