CN116801371A - 5G satellite communication time synchronization method - Google Patents
5G satellite communication time synchronization method Download PDFInfo
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- CN116801371A CN116801371A CN202310822528.6A CN202310822528A CN116801371A CN 116801371 A CN116801371 A CN 116801371A CN 202310822528 A CN202310822528 A CN 202310822528A CN 116801371 A CN116801371 A CN 116801371A
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- 238000004891 communication Methods 0.000 title claims abstract description 35
- 238000000034 method Methods 0.000 title claims abstract description 30
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- 238000012937 correction Methods 0.000 claims abstract description 7
- 238000004590 computer program Methods 0.000 claims description 8
- 238000010586 diagram Methods 0.000 description 15
- 238000005516 engineering process Methods 0.000 description 6
- 230000006870 function Effects 0.000 description 5
- 238000012545 processing Methods 0.000 description 5
- 125000004122 cyclic group Chemical group 0.000 description 3
- 230000008054 signal transmission Effects 0.000 description 3
- 230000008901 benefit Effects 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000010295 mobile communication Methods 0.000 description 2
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Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W56/00—Synchronisation arrangements
- H04W56/0005—Synchronisation arrangements synchronizing of arrival of multiple uplinks
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/185—Space-based or airborne stations; Stations for satellite systems
- H04B7/1851—Systems using a satellite or space-based relay
- H04B7/18513—Transmission in a satellite or space-based system
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W56/00—Synchronisation arrangements
- H04W56/001—Synchronization between nodes
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Abstract
The application discloses a 5G satellite communication time synchronization method, which is applied to a terminal and comprises the following steps: responding to a downlink signal sent by a satellite, and respectively sending uplink signals to the satellite by each terminal according to information carried in the received downlink signal so that the satellite can receive uplink data sent by each terminal in a preset uplink signal receiving time window; the information carried in the downlink signal comprises carrier frequency and an uplink frame structure for indicating the terminal to send the uplink signal; the uplink frame structure comprises a plurality of uplink time slots and unique words inserted between two adjacent uplink time slots, wherein the unique words are used for time-frequency estimation and correction in uplink time slot continuous transmission. The application reduces the complexity of the system by changing the traditional uplink signal strict synchronization mode into the non-strict synchronization mode; by increasing the length of the uplink frame structure, the duty ratio of the guard interval in the uplink signal receiving time window is reduced, thereby improving the communication efficiency.
Description
Technical Field
The application relates to the technical field of satellite communication, in particular to a 5G satellite communication time synchronization method.
Background
Compared with a ground mobile communication network, the satellite communication system can realize wide area and even global coverage and provide indiscriminate communication services for global users. Meanwhile, the ground fifth-generation mobile communication (5G) system has a perfect industrial chain, a huge user group and a flexible and efficient application service mode. The satellite communication and the 5G are mutually integrated, make up for the advantages and make up for the short, together form a global seamless-coverage sea, land, air and sky integrated comprehensive communication network, meet the ubiquitous multiple service demands of users, and are important directions for future communication development.
The 5G satellite communication system adopts an OFDM (orthogonal frequency division multiplexing) modulation mode as the ground 5G system, and the OFDM has good anti-noise performance, multipath channel interference resistance and high-frequency utilization rate, and has great potential in the field of broadband communication. Although OFDM technology has the advantage of natural multipath fading resistance and is well suited for high-speed data transmission, OFDM technology is very sensitive to time-offset, which can deviate the timing window between symbols, resulting in symbol demodulation failure. Therefore, eliminating the influence of time bias on the OFDM system is the key to applying the OFDM system in the satellite communication high-speed mobile environment. In a satellite communication system, the distance between a satellite and a ground terminal is quite far, so that the unidirectional signal transmission time is far longer than that of the ground communication system, the distance difference between a near point terminal and a far point terminal and the satellite is quite large, and the time deviation is relatively higher; in addition, the moving speed of the satellite is far higher than that of a ground network scene, and the time bias change in unit time is also much larger. Thus, countering time bias is of greater importance for 5G satellite communication systems.
The Low Earth Orbit/near Earth Orbit (LEO: low Earth Orbit) is about 400-2000 km in height, and assuming that the minimum working inclination angle of the satellite is 30 degrees, as shown in fig. 1, any position point of the Orbit of the satellite corresponds to a near point and a far point, the maximum distance is 800-4000 km, and the unidirectional transmission time of the corresponding wireless signal is 2600us-13300us.
As shown in fig. 2, for a typical uplink frame structure in the conventional 5G satellite communication technology, the radio frame length is 10ms, the subframe length is 1ms, each subframe is divided into N slots, the value of N is related to the subcarrier interval, for example, in the case of 120kHz subcarrier interval (extended cyclic prefix), the value of N is 8, i.e., each subframe is divided into 8 slots, the slot length is 125us, wherein the basic unit of uplink data transmission is 1 slot, 12 symbols in each slot, and each symbol is 10.4us, wherein the cyclic prefix length is 2.6us, in order to ensure that the signal is successfully demodulated, the time deviation should be less than half the cyclic prefix length, i.e., 1.3us, and the time deviation of 1.3us is very short compared with the signal transmission time, which causes great difficulty in uplink time control.
As shown in fig. 3, which is a schematic diagram of an uplink receiving window in the conventional 5G satellite communication technology, the length of the uplink signal receiving time window of the satellite is equal to that of the uplink signal time slot, and is 125us, the system can modify the uplink signal transmission time of the terminals at different positions by TA flow or ephemeris precompensation, so that the uplink signals transmitted by the satellite terminals at different positions arrive at the satellite at the same time. In addition, the movement speed of the low orbit satellite relative to the ground is approximately 7.9Km/s of the first cosmic speed, the time deviation caused by the distance change per second is about 26us, and considering the limit of 1.3us, the time deviation exceeds the demodulation window when the satellite moves for 20 ms.
In order to solve the time bias problem of 5G satellite communication, the current general method is to adjust and pre-compensate ephemeris by means of uplink TA (Timing Advance), but the TA adjustment has an adjustment period, occupies a downlink transmission channel, and is difficult to meet the requirement in real-time; the ephemeris needs to be stored in the terminal in advance, and the position and accurate time of the ephemeris need to be obtained by means of GNSS information, so that flexibility and accuracy are limited, and the terminal cannot always obtain the latest ephemeris information.
Disclosure of Invention
Aiming at the problem that the uplink signals of all terminals are difficult to realize strict synchronization in the 5G satellite communication process in the prior art, the application aims to provide a 5G satellite communication time synchronization method so as to at least partially solve the problem.
In order to achieve the above purpose, the technical scheme of the application is as follows:
in a first aspect, the present application provides a 5G satellite communication time synchronization method, which is applied to a terminal, the method comprising the steps of:
responding to a downlink signal sent by a satellite, and respectively sending uplink signals to the satellite by each terminal according to information carried in the received downlink signal so that the satellite can receive uplink data sent by each terminal in a preset uplink signal receiving time window;
the information carried in the downlink signal comprises carrier frequency and an uplink frame structure for indicating the terminal to send an uplink signal; the uplink frame structure comprises a plurality of uplink time slots and unique words inserted between two adjacent uplink time slots, wherein the unique words are used for time-frequency estimation and correction in uplink time slot continuous transmission.
In a second aspect, the present application provides a method for time synchronization of 5G satellite communications, the method being applied to a satellite, the method comprising the steps of:
the satellite sends downlink signals to each terminal, and receives uplink data sent by each terminal in a preset uplink signal receiving time window;
after receiving the downlink signal, each terminal sends an uplink signal to the satellite according to information carried in the received downlink signal;
the information carried in the downlink signal comprises carrier frequency and an uplink frame structure for indicating the terminal to send an uplink signal; the uplink frame structure comprises a plurality of uplink time slots and unique words inserted between two adjacent uplink time slots, wherein the unique words are used for time-frequency estimation and correction in uplink time slot continuous transmission.
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 a guard interval, and the guard interval is greater than or equal to the transmission time difference of the uplink signal sent by the far-point terminal and the uplink signal sent by the near-point terminal to the satellite; and the starting point of the uplink signal receiving time window is the time when the uplink signal sent by the near-point terminal reaches the satellite.
Preferably, the start point of the uplink signal receiving time window is determined by the orbit and the inclination angle of the satellite.
Preferably, the uplink signals having the same uplink frame structure correspond to the same uplink signal receiving time window.
By adopting the technical scheme, the application has the beneficial effects that: by changing the uplink frame structure sent by the terminal and the uplink signal receiving time window of the satellite, each terminal can receive and demodulate the uplink signals sent by a plurality of terminals in the same uplink signal receiving time window without complex operation only by sending the uplink signals according to the uplink frame structure after receiving the downlink signals, and the traditional uplink signals are strictly synchronized to be non-strictly synchronized, so that the complexity of the system is greatly reduced and the system is easy to realize. In addition, by configuring the transmission unit of the uplink frame structure as time slots and setting a plurality of transmission units, compared with the traditional technology (the transmission unit is a symbol), the length of the uplink frame structure can be effectively increased, and then the duty ratio of the guard interval in the uplink signal receiving time window is reduced, so that the data quantity which can be received by a single uplink signal receiving time window is greatly improved, and the communication efficiency is improved.
Drawings
FIG. 1 is a schematic diagram of a 5G satellite communication system;
FIG. 2 is a schematic diagram of a typical uplink frame sent by a terminal in a 5G satellite communication system according to the prior art;
FIG. 3 is a diagram of a time window for receiving uplink signals from a 5G satellite according to the prior art;
FIG. 4 is a schematic diagram of a 5G satellite communication time synchronization method according to the present application;
fig. 5 is a schematic diagram of an uplink frame structure sent by a terminal in the present application;
FIG. 6 is a schematic diagram of an uplink signal receiving time window of a 5G satellite according to the present application;
FIG. 7 is a schematic diagram illustrating the operation of the uplink signal reception time window of the 5G satellite according to the present application;
fig. 8 is a schematic structural diagram of an electronic device according to a third embodiment of the present application.
Detailed Description
The following describes the embodiments of the present application further with reference to the drawings. The description of these embodiments is provided to assist understanding of the present application, but is not intended to limit the present application. In addition, the technical features of the embodiments of the present application described below may be combined with each other as long as they do not collide with each other.
It should be noted that, in the description of the present application, the positional or positional relation indicated by the terms such as "upper", "lower", "left", "right", "front", "rear", etc. are merely for convenience of describing the present application based on the description of the structure of the present application shown in the drawings, and are not intended to indicate or imply that the apparatus or element to be referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present application.
The terms "first" and "second" in this technical solution are merely references to the same or similar structures, or corresponding structures that perform similar functions, and are not an arrangement of the importance of these structures, nor are they ordered, or are they of a comparative size, or other meaning.
In addition, unless explicitly stated and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., the connection may be a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communicated with the inside of two structures. It will be apparent to those skilled in the art that the specific meaning of the terms described above in this application may be understood in the light of the general inventive concept in connection with the present application.
Example 1
A 5G satellite communication time synchronization method, which is applied to a terminal, as shown in fig. 4, the method comprising the steps of:
and responding to the downlink signals sent by the satellites, and respectively sending uplink signals to the satellites according to the information carried in the received downlink signals by the terminals so that the satellites can receive uplink data sent by the terminals in 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 the terminal to send the uplink signal. As shown in fig. 5, the uplink frame structure includes a plurality of uplink timeslots and unique words inserted between two adjacent uplink timeslots, and the unique words are used for performing time-frequency estimation and correction in the uplink timeslot continuous transmission. In actual operation, the number of time slots and the unique word length contained in the uplink frame structure can be determined according to the requirement, and the uplink frame structure is configured to each terminal by the satellite base station through downlink signaling.
As shown in fig. 6, 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 guard interval, and the guard 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 start point of the uplink signal receiving time window is the time when the uplink signal transmitted by the near point terminal arrives at the satellite, as shown in fig. 7.
By configuring the transmission units of the uplink frame structure as time slots and setting a plurality of transmission units, compared with the traditional technology (the transmission units are symbols), the length of the uplink frame structure can be effectively increased, the duty ratio of the guard interval in the uplink signal receiving time window is further reduced, the data quantity which can be received by a single uplink signal receiving time window is greatly improved, and therefore the communication efficiency is improved.
The start point of the uplink signal receiving time window is determined by the orbit and the inclination angle of the satellite, and when the orbit and the inclination angle of the satellite are determined, for the near point terminal, the time for the near point terminal to receive the downlink signal from the satellite, the time for the near point terminal to process the downlink signal and the time for the near point terminal to transmit the uplink signal are determined, so that the start point of the uplink signal receiving time window is also determined. Thus, as long as the orbit and tilt angle of the satellite are unchanged, the interval between the start of the uplink signal reception time window and the emission time of the downlink signal is also fixed.
It can be understood that, in order to improve the processing efficiency of the satellite, the uplink signals sent by each terminal are configured to have the same uplink frame structure corresponding to the same uplink signal receiving time window set by the satellite, so that the uplink signals sent by different terminals and received in the window range of the uplink signal receiving time window can be successfully demodulated.
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 set by the satellite respectively. Generally, the satellite can set various uplink frame structures and matched uplink signal receiving time window lengths in different time and carrier frequencies according to specific requirements; for the same terminal, the satellite can also be allocated with different carrier frequency positions, different uplink frame structures and uplink signal receiving time windows at different times, so that more flexible resource allocation is realized.
Example two
Compared with the first embodiment, the method for synchronizing the communication time of the 5G satellite is only different in that the method provided by the embodiment is applied to the satellite, and the method comprises the following steps:
the satellite sends downlink signals to each terminal, and receives uplink data sent by each terminal in a preset uplink signal receiving time window;
after receiving the downlink signal, each terminal sends an uplink signal to the satellite according to information carried in the received downlink signal;
the information carried in the downlink signal comprises carrier frequency and an uplink frame structure for indicating the terminal to send the uplink signal; the uplink frame structure comprises a plurality of uplink time slots and unique words inserted between two adjacent uplink time slots, wherein the unique words are used for time-frequency estimation and correction in uplink time slot continuous transmission.
Example III
An electronic device, as shown in fig. 8, includes a memory storing executable program code and a processor coupled to the memory; wherein the processor invokes executable program code stored in the memory to perform the method steps disclosed in the above embodiments.
Example IV
A computer storage medium having a computer program stored therein, which when executed by a processor performs the method steps disclosed in the above embodiments.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The embodiments of the present application have been described in detail above with reference to the accompanying drawings, but the present application is not limited to the described embodiments. It will be apparent to those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the application, and yet fall within the scope of the application.
Claims (7)
1. A5G satellite communication time synchronization method is characterized in that: the method is applied to the terminal and comprises the following steps:
responding to a downlink signal sent by a satellite, and respectively sending uplink signals to the satellite by each terminal according to information carried in the received downlink signal so that the satellite can receive uplink data sent by each terminal in a preset uplink signal receiving time window;
the information carried in the downlink signal comprises carrier frequency and an uplink frame structure for indicating the terminal to send an uplink signal; the uplink frame structure comprises a plurality of uplink time slots and unique words inserted between two adjacent uplink time slots, wherein the unique words are used for time-frequency estimation and correction in uplink time slot continuous transmission.
2. A5G satellite communication time synchronization method is characterized in that: the method is applied to satellites, and comprises the following steps:
the satellite sends downlink signals to each terminal, and receives uplink data sent by each terminal in a preset uplink signal receiving time window;
after receiving the downlink signal, each terminal sends an uplink signal to the satellite according to information carried in the received downlink signal;
the information carried in the downlink signal comprises carrier frequency and an uplink frame structure for indicating the terminal to send an uplink signal; the uplink frame structure comprises a plurality of uplink time slots and unique words inserted between two adjacent uplink time slots, wherein the unique words are used for time-frequency estimation and correction in uplink time slot continuous transmission.
3. The 5G satellite communication time synchronization method according to claim 1 or 2, wherein: the window length of the uplink signal receiving time window is equal to the sum of the length of the uplink frame structure and a guard interval, and the guard interval is larger than or equal to the transmission time difference of the uplink signal sent by the far-point terminal and the uplink signal sent by the near-point terminal to the satellite; and the starting point of the uplink signal receiving time window is the time when the uplink signal sent by the near-point terminal reaches the satellite.
4. The 5G satellite communication time synchronization method according to claim 1 or 2, wherein: the starting point of the uplink signal receiving time window is determined by the orbit and the inclination angle of the satellite.
5. The 5G satellite communication time synchronization method according to claim 1 or 2, wherein: uplink signals having the same uplink frame structure correspond to the same uplink signal reception time window.
6. An electronic device, characterized in that: comprising a memory storing executable program code and a processor coupled to the memory; wherein the processor invokes executable program code stored in the memory to perform the method of any of claims 1-5.
7. A computer-readable storage medium storing a computer program, characterized in that: the computer program, when executed by a processor, performs the method of any of claims 1-5.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN202310822528.6A CN116801371A (en) | 2023-07-06 | 2023-07-06 | 5G satellite communication time synchronization method |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202310822528.6A CN116801371A (en) | 2023-07-06 | 2023-07-06 | 5G satellite communication time synchronization method |
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| CN116801371A true CN116801371A (en) | 2023-09-22 |
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