CN114189415A - Frequency offset compensation method and device, medium and low orbit satellite and ground terminal - Google Patents

Frequency offset compensation method and device, medium and low orbit satellite and ground terminal Download PDF

Info

Publication number
CN114189415A
CN114189415A CN202111458083.5A CN202111458083A CN114189415A CN 114189415 A CN114189415 A CN 114189415A CN 202111458083 A CN202111458083 A CN 202111458083A CN 114189415 A CN114189415 A CN 114189415A
Authority
CN
China
Prior art keywords
satellite
ground terminal
frequency
compensation value
time
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202111458083.5A
Other languages
Chinese (zh)
Inventor
金星
王哓龙
张俊
陈皓
王钊
时东海
张钦波
刘芮
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Beijing Commsat Technology Development Co Ltd
Original Assignee
Beijing Commsat Technology Development Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Beijing Commsat Technology Development Co Ltd filed Critical Beijing Commsat Technology Development Co Ltd
Priority to CN202111458083.5A priority Critical patent/CN114189415A/en
Publication of CN114189415A publication Critical patent/CN114189415A/en
Pending legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0014—Carrier regulation
    • 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
    • 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
    • H04B7/18515—Transmission equipment in satellites or space-based relays
    • 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
    • H04B7/18517—Transmission equipment in earth stations
    • 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
    • H04B7/18519—Operations control, administration or maintenance
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0014—Carrier regulation
    • H04L2027/0024—Carrier regulation at the receiver end
    • H04L2027/0026—Correction of carrier offset

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Astronomy & Astrophysics (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • General Physics & Mathematics (AREA)
  • Radio Relay Systems (AREA)

Abstract

The invention discloses a frequency offset compensation method and device for medium and low orbit satellite communication, a medium and low orbit satellite and a ground terminal, wherein the method comprises the following steps: obtaining a frequency compensation value of Doppler frequency shift of a satellite relative to a ground terminal at least one moment, wherein the frequency compensation value at each moment is related to relative speed or relative position between the satellite and the ground terminal at the corresponding moment; and carrying out frequency offset compensation on the transmission signal at the corresponding moment according to the frequency compensation value at least one moment.

Description

Frequency offset compensation method and device, medium and low orbit satellite and ground terminal
Technical Field
The invention relates to the technical field of satellite communication, in particular to a frequency offset compensation method and device for medium and low orbit satellite communication, a medium and low orbit satellite and a ground terminal.
Background
The satellite communication system uses a satellite as a relay station to transmit microwave signals and communicates among a plurality of ground terminals. Based on the type of satellite orbit, a more sophisticated satellite communication system utilizes geostationary satellites (GEO), which are capable of remaining geostationary and providing wireless access services at heights around 3600 kilometers above the equatorial orbit. However, due to the limitation of the orbit, the system capacity of the communication system is limited, and the service area cannot be covered to a high-dimensional region. The last century has raised the idea of providing global satellite communication coverage by using low-medium orbit (LEO) satellites to construct constellations, and has raised a wave of construction enthusiasm worldwide. However, the first attempt ends up failing due to prohibitive cost and limited digital signal processing techniques. In recent years, with the development of commercial aerospace technology, emission costs have been greatly reduced. And the cost and the computational power of the digital signal processing technology are greatly improved. Therefore, a communication satellite constellation plan based on medium and low orbit satellites is proposed again.
Although building a globally-covered, high-capacity communication system using the LEO constellation can quickly provide wireless access capability to less-developed regions. Establishing wireless links between high-speed moving satellites and terrestrial terminals also faces a number of technical challenges, which are not present in conventional terrestrial cellular networks and are therefore less well studied in the literature. For example, a satellite in a low earth orbit with a height of 1000Km can have a flight speed of 7Km/s, which means a significant Doppler Shift (Doppler Shift) for the communication link. A simple calculation is that in a 1000km orbit constellation and 30GHz carrier frequency communication system, the doppler shift is between-675 KHz and 675KHz, which means that an OFDM system with a carrier frequency of 120KHz will suffer from sub-carrier offsets of more than-6 to 6 integers.
Currently, in communication systems, especially satellite communication systems, methods for estimating and compensating for a large frequency offset (exceeding at least one subcarrier interval) are widely studied, and a ground terminal estimates the frequency offset through a complex search algorithm and then compensates for a received signal before normal data reception can be performed, but this method requires a large amount of computational resources and time delay, since the time for a satellite to sweep over a ground terminal (visible window) is very short, for example, the visible window of a low-orbit satellite at a high latitude and a high latitude is only ten minutes, and if a small included angle of a beam is considered, the time is shorter. This means that the terrestrial terminals need to estimate and compensate frequently for large frequency offsets, which means large overhead, delay and instability, both from a power and time perspective.
Disclosure of Invention
In view of this, embodiments of the present invention provide a frequency offset compensation method and apparatus for medium and low orbit satellite communication, a medium and low orbit satellite, and a ground terminal, so as to solve the problems of large system overhead, high time delay, and low stability brought by the existing frequency offset compensation method.
According to a first aspect, an embodiment of the present invention provides a frequency offset compensation method for medium and low orbit satellite communication, including: obtaining a frequency compensation value of Doppler frequency shift of a satellite relative to a ground terminal at least one moment, wherein the frequency compensation value at each moment is related to relative speed or relative position between the satellite and the ground terminal at the corresponding moment; and carrying out frequency offset compensation on the transmission signal at the corresponding moment according to the frequency compensation value at least one moment.
Optionally, the obtaining a frequency compensation value of the doppler shift of the satellite relative to the ground terminal at least one time includes: acquiring the relative speed or the relative position between the satellite and the ground terminal at least one moment; and calculating the frequency compensation value according to the relative speed or the relative position.
Optionally, the obtaining a frequency compensation value of the doppler shift at least one time includes: and obtaining the frequency compensation value of the satellite relative to the ground terminal at different orbital positions through measurement.
According to a second aspect, an embodiment of the present invention provides a frequency offset compensation method for medium and low orbit satellite communication, applied to a satellite, including: and transmitting the frequency compensation value of the Doppler frequency shift of the satellite relative to the ground terminal at least one moment to the ground terminal, wherein the frequency compensation value at each moment is related to the relative speed or relative position between the satellite and the ground terminal at the corresponding moment, so that the ground terminal performs frequency offset compensation on the transmission signal at the corresponding moment according to the frequency compensation value at least one moment.
Optionally, the satellite transmits a frequency compensation value of the doppler shift of the satellite relative to the ground terminal at least one time to the ground terminal through a broadcast signal; the broadcast signal comprises frequency compensation values corresponding to a plurality of frames, and the frequency compensation values are used for enabling the ground terminal to perform frequency offset compensation on the corresponding frames of the transmission signal according to the frequency compensation values.
Optionally, the broadcast signal further includes beam directions corresponding to a plurality of frames.
Optionally, the frequency offset compensation method further includes: acquiring the direction covering the most ground terminals; such that the beam direction is directed in the direction of the most covered ground terminals.
According to a third aspect, an embodiment of the present invention provides a frequency offset compensation method for medium and low orbit satellite communication, which is applied to a satellite, and includes: transmitting a frequency compensation value for a doppler shift of at least one instant of a following satellite relative to a ground terminal to the following satellite or the ground terminal before the following satellite establishes a service link with the ground terminal; wherein the frequency offset value at each time instant is related to the relative velocity or relative position between the following satellite and the ground terminal at the respective time instant.
Optionally, the frequency offset compensation method further includes: when the service link is established between the following satellite and the ground terminal, the following satellite carries out frequency offset compensation on the sending signal at the corresponding moment according to the frequency compensation value at least one moment; or when the subsequent satellite establishes a service link with the ground terminal, the subsequent satellite sends the frequency compensation value at least one moment to the ground terminal, so that the ground terminal performs frequency offset compensation on the sending signal at the corresponding moment according to the frequency compensation value at least one moment; or when the service link is established between the rear satellite and the ground terminal, the ground terminal performs frequency offset compensation on the transmission signal at the corresponding moment according to the frequency compensation value at least one moment; or when the service link is established between the following satellite and the ground terminal, the ground terminal sends the frequency compensation value at least one moment to the following satellite, so that the following satellite performs frequency offset compensation on the sending signal at the corresponding moment according to the frequency compensation value at least one moment.
According to a fourth aspect, an embodiment of the present invention provides a frequency offset compensation method for medium and low orbit satellite communication, applied to a satellite, including: before the satellite establishes a service link with a ground terminal, receiving a frequency compensation value of the satellite relative to the ground terminal at least one moment transmitted by a previous satellite; or when the satellite establishes a service link with a ground terminal, receiving a frequency compensation value of the satellite relative to the ground terminal at least one moment, which is sent by the ground terminal, wherein the frequency compensation value is sent to the ground terminal by a former satellite; wherein the frequency compensation value at each time instant is related to the relative velocity or relative position between the satellite and the ground terminal at the respective time instant.
According to a fifth aspect, an embodiment of the present invention provides a frequency offset compensation method for medium and low orbit satellite communication, which is applied to a ground terminal, and includes: and transmitting the frequency compensation value of the Doppler frequency shift of the satellite relative to the ground terminal at least one moment to the satellite through an uplink, wherein the frequency compensation value at each moment is related to the relative speed or the relative position between the satellite and the ground terminal at the corresponding moment, and the frequency compensation value at least one moment is used for enabling the satellite to carry out frequency offset compensation on the transmission signal at the corresponding moment according to the frequency compensation value at the at least one moment.
According to a sixth aspect, an embodiment of the present invention provides a frequency offset compensation method for medium and low orbit satellite communication, which is applied to a ground terminal, and includes: receiving a frequency compensation value of Doppler frequency shift of at least one time relative to the ground terminal of a following satellite transmitted by a current satellite during a service link with the current satellite, wherein the frequency compensation value of each time is related to relative speed or relative position between the satellite and the ground terminal at the corresponding time, and the frequency compensation value is used for enabling the satellite to carry out frequency offset compensation on a transmitted signal at the corresponding time according to the frequency compensation value at the at least one time.
Optionally, the frequency offset compensation method further includes: when a service link is established with a following satellite, transmitting a frequency compensation value of Doppler frequency shift of the following satellite relative to the ground terminal at least one time to the following satellite so as to enable the following satellite to perform frequency offset compensation on a transmission signal at a corresponding time according to the frequency compensation value at least one time; or when a service link is established with a following satellite, carrying out frequency offset compensation on the transmission signal at the corresponding moment according to the frequency compensation value at least one moment.
According to a seventh aspect, an embodiment of the present invention provides a frequency offset compensation apparatus for medium and low orbit satellite communication, including: an obtaining unit, configured to obtain a frequency compensation value of a doppler frequency shift of a satellite relative to a ground terminal at least one time, where the frequency compensation value at each time is related to a relative speed or a relative position between the satellite and the ground terminal at the corresponding time; and the compensation unit is used for carrying out frequency offset compensation on the sending signal at the corresponding moment according to the frequency compensation value at least one moment.
According to an eighth aspect, an embodiment of the present invention provides a frequency offset compensation apparatus for medium and low orbit satellite communication, applied to a satellite, including: a sending unit, configured to send, to a ground terminal, a frequency compensation value of a doppler frequency shift of the satellite relative to the ground terminal at least one time, where the frequency compensation value at each time is related to a relative speed or a relative position between the satellite and the ground terminal at the corresponding time, and is used to enable the ground terminal to perform frequency offset compensation on a sending signal at the corresponding time according to the frequency compensation value at the at least one time.
According to a ninth aspect, an embodiment of the present invention provides a frequency offset compensation apparatus for medium and low orbit satellite communication, applied to a satellite, including: a transmitting unit, configured to transmit a frequency compensation value of a doppler shift of at least one time of a succeeding satellite with respect to a ground terminal to the succeeding satellite or the ground terminal before the succeeding satellite establishes a service link with the ground terminal; wherein the frequency offset value at each time instant is related to the relative velocity or relative position between the following satellite and the ground terminal at the respective time instant.
According to a tenth aspect, an embodiment of the present invention provides a frequency offset compensation apparatus for medium and low orbit satellite communication, applied to a satellite, including: a receiving unit, configured to receive, before the satellite establishes a service link with a ground terminal, a frequency compensation value of at least one time of the satellite relative to the ground terminal, which is transmitted by a previous satellite; or for receiving a frequency compensation value of at least one time of the satellite relative to the ground terminal, sent by the ground terminal, when the satellite establishes a service link with the ground terminal, wherein the frequency compensation value is sent to the ground terminal by a previous satellite; wherein the frequency compensation value at each time instant is related to the relative velocity or relative position between the satellite and the ground terminal at the respective time instant.
According to an eleventh aspect, an embodiment of the present invention provides a frequency offset compensation apparatus for medium and low orbit satellite communication, which is applied to a ground terminal, and includes: a sending unit, configured to send, to a satellite through an uplink, a frequency compensation value of a doppler shift of the satellite relative to the ground terminal at least one time, where the frequency compensation value at each time is related to a relative velocity or a relative position between the satellite and the ground terminal at the corresponding time, and configured to enable the satellite to perform frequency offset compensation on a sending signal at the corresponding time according to the frequency compensation value at the at least one time.
According to a twelfth aspect, an embodiment of the present invention provides a frequency offset compensation apparatus for medium and low orbit satellite communication, which is applied to a ground terminal, and includes: a receiving unit, configured to receive, during a service link with a current satellite, a frequency compensation value of a doppler shift of a subsequent satellite at least one time relative to the ground terminal, where the frequency compensation value at each time is related to a relative velocity or a relative position between the satellite and the ground terminal at the corresponding time, and is used for enabling the satellite to perform frequency offset compensation on a transmission signal at the corresponding time according to the frequency compensation value at least one time.
According to a thirteenth aspect, an embodiment of the present invention provides a medium-low orbit satellite, including: the system comprises an antenna, a frequency modulator, a memory and a processor, wherein the memory stores computer instructions, and the processor executes the computer instructions to obtain frequency compensation values of Doppler frequency shift of a satellite relative to a ground terminal at least one moment, wherein the frequency compensation values at each moment are related to relative speed or relative position between the satellite and the ground terminal at the corresponding moment; the frequency modulator is used for carrying out frequency offset compensation on the transmitting signal at the corresponding moment according to the frequency compensation value at least one moment; the antenna is used for transmitting the compensated transmission signal.
According to a fourteenth aspect, an embodiment of the present invention provides a ground terminal, including: the system comprises an antenna, a frequency modulator, a memory and a processor, wherein the memory stores computer instructions, and the processor executes the computer instructions to obtain frequency compensation values of Doppler frequency shift of a satellite relative to a ground terminal at least one moment, wherein the frequency compensation values at each moment are related to relative speed or relative position between the satellite and the ground terminal at the corresponding moment; the frequency modulator is used for carrying out frequency offset compensation on the transmitting signal at the corresponding moment according to the frequency compensation value at least one moment; the antenna is used for transmitting the compensated transmission signal.
According to a fifteenth aspect, an embodiment of the present invention provides a medium-low orbit satellite, including: and the antenna is used for transmitting a frequency compensation value of Doppler frequency shift of the satellite relative to the ground terminal at least one moment to the ground terminal, wherein the frequency compensation value at each moment is related to the relative speed or relative position between the satellite and the ground terminal at the corresponding moment, and the antenna is used for enabling the ground terminal to perform frequency offset compensation on the transmission signal at the corresponding moment according to the frequency compensation value at least one moment.
According to a sixteenth aspect, an embodiment of the present invention provides a medium-low orbit satellite, including: an antenna for transmitting a frequency compensation value of a doppler shift of at least one time instant of a succeeding satellite with respect to a ground terminal to the succeeding satellite or the ground terminal before the succeeding satellite establishes a service link with the ground terminal; wherein the frequency offset value at each time instant is related to the relative velocity or relative position between the following satellite and the ground terminal at the respective time instant.
According to a seventeenth aspect, an embodiment of the present invention provides a medium-low orbit satellite, including: an antenna for receiving a frequency compensation value of at least one time of the satellite relative to the ground terminal transmitted by a previous satellite before the satellite establishes a service link with the ground terminal; or the antenna is used for receiving a frequency compensation value of the satellite relative to the ground terminal at least one moment, which is sent by the ground terminal, when the satellite establishes a service link with the ground terminal, wherein the frequency compensation value is sent to the ground terminal by a previous satellite; wherein the frequency compensation value at each time instant is related to the relative velocity or relative position between the satellite and the ground terminal at the respective time instant.
According to an eighteenth aspect, an embodiment of the present invention provides a ground terminal, including: the antenna is used for transmitting a frequency compensation value of Doppler frequency shift of the satellite relative to the ground terminal at least one moment to the medium and low orbit satellite through an uplink, wherein the frequency compensation value at each moment is related to relative speed or relative position between the satellite and the ground terminal at the corresponding moment, and the frequency compensation value at least one moment is used for enabling the satellite to carry out frequency offset compensation on a transmission signal at the corresponding moment according to the frequency compensation value at the at least one moment.
According to a nineteenth aspect, an embodiment of the present invention provides a ground terminal, including: an antenna for receiving a frequency compensation value of a Doppler shift of a succeeding satellite relative to the ground terminal at least one time during a service link with a current satellite, wherein the frequency compensation value at each time is related to a relative velocity or a relative position between the satellite and the ground terminal at the corresponding time, and the antenna is used for enabling the satellite to perform frequency offset compensation on a transmission signal at the corresponding time according to the frequency compensation value at least one time.
According to the frequency offset compensation method and device for the communication of the medium-low orbit satellite, the medium-low orbit satellite and the ground terminal, when the satellite is at a certain moment or a certain orbit position, the relative speed or the relative position relative to a certain ground terminal is relatively stable and predictable, so that the satellite or the ground terminal can know the frequency compensation value of the Doppler frequency offset of the satellite relative to the ground terminal at each moment in advance, and accordingly, corresponding frequency offset compensation can be performed at corresponding moments quickly. Compared with the scheme that the integer frequency offset is estimated through a complex search algorithm and then the fractional part is estimated in the prior art, the search algorithm and the estimation algorithm do not need to be executed in real time, so that the overhead and the delay of a communication system are reduced, and the stability of the communication system is improved.
Drawings
The features and advantages of the present invention will be more clearly understood by reference to the accompanying drawings, which are illustrative and not to be construed as limiting the invention in any way, and in which:
FIG. 1 shows a schematic diagram of a constellation of medium and low orbit satellites according to an embodiment of the invention;
FIG. 2 is a schematic diagram showing relative velocities and relative positions of a medium to low orbit satellite and a ground terminal according to an embodiment of the invention;
FIG. 3 is a diagram illustrating Doppler shifts produced by satellites relative to ground terminals;
FIG. 4 shows a graph of Doppler shift versus time produced by a satellite relative to a ground terminal;
fig. 5 is a flowchart illustrating a frequency offset compensation method for medium and low orbit satellite communication according to an embodiment of the present invention;
fig. 6 shows a schematic diagram of a subcarrier signal implementing a frequency offset compensation method according to an embodiment of the present invention;
fig. 7 is a flowchart illustrating a frequency offset compensation method for medium and low orbit satellite communication according to another embodiment of the present invention;
fig. 8 illustrates a schematic diagram of frequency offset compensation according to frequency compensation values corresponding to a plurality of frames included in a broadcast signal in a frequency offset compensation method according to an embodiment of the present invention;
fig. 9 is a flowchart illustrating a frequency offset compensation method for medium and low orbit satellite communication according to another embodiment of the present invention;
fig. 10 is a flowchart illustrating a frequency offset compensation method for medium and low orbit satellite communication according to another embodiment of the present invention;
fig. 11 is a flowchart illustrating a frequency offset compensation method for medium and low orbit satellite communication according to another embodiment of the present invention;
fig. 12 is a flowchart illustrating a frequency offset compensation method for medium and low orbit satellite communication according to another embodiment of the present invention;
fig. 13 is a diagram showing a case where frequency compensation is not performed on a transmission signal of a ground terminal;
fig. 14 is a diagram illustrating a case where a transmission signal of a ground terminal is frequency-compensated by a frequency offset compensation method according to an embodiment of the present invention;
fig. 15 is a flowchart illustrating a frequency offset compensation method for medium and low orbit satellite communication according to another embodiment of the present invention;
fig. 16 is a flowchart illustrating a frequency offset compensation method for medium and low orbit satellite communication according to another embodiment of the present invention;
fig. 17 shows a schematic diagram of a medium and low orbit satellite or ground terminal according to an embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Fig. 1 is a schematic diagram of a constellation of medium and low orbit satellites according to an embodiment of the present invention, the constellation being composed of a plurality of orbits, indicated by dashed lines in fig. 1, each orbit having at least one satellite operating thereon, the satellites providing wireless access services to a region of the ground via a communication link. Each medium and low orbit satellite remains mobile with respect to the ground and therefore the area covered by its communication link changes over time. The medium-low orbit satellite moves at any moment along the tangential direction of the orbit at a predetermined speed having a component v in the direction perpendicular to the ground terminaleAs shown in fig. 2, the velocity may also be regarded as an equivalent velocity of the doppler shift, and for the ground terminal, the doppler shift is:
Δf＝ve/c*f0 (1)
wherein f is0Is the carrier frequency, c is the vacuum speed of light, veFor satellites and ground terminals in the vertical directionThe velocity component of (a). The ground terminal may be a semi-static device equipped with a parabolic antenna, i.e. the ground terminal is relatively stationary during most of the time of use, but with the miniaturization of the device, the ground terminal may become a pure mobile handset in the future.
As shown in fig. 3, due to the relative moving speed between the satellite and the ground terminal, the carrier frequency of the service link will be greatly shifted, and when the satellite transmits a signal, the ground received signal is shifted in frequency by, for example, 2 multiple sub-carrier intervals; when the ground terminal transmits a signal, the satellite receives a signal which is also subjected to a frequency offset of 2 multi-subcarrier intervals. In order to enable the receiving end to receive the correct signal, frequency offset compensation needs to be performed on the transmission signal.
When the satellite gradually moves from far to the right above the ground terminal, the velocity component v of the satellite and the ground terminal in the vertical directioneGradually decreases until the velocity component v of the satellite and the ground terminal in the vertical direction when the satellite moves to the position right above the ground terminaleAt 0, the corresponding doppler shift is gradually reduced to 0. And when the satellite gradually moves away from the ground terminal from the right above the ground terminal, the velocity component v of the satellite and the ground terminal in the vertical directioneAnd gradually increases, the corresponding doppler shift frequency gradually increases. Since the frequency offset depends on the relative positions of the satellite and the ground terminal, and different relative positions correspond to different time points, when the satellite gradually moves from a far position to a position right above the ground terminal and then gradually moves away from the ground terminal, the change of the doppler frequency shift with time is from large to small and then from small to large, the maximum value and the minimum value of the doppler frequency shift depend on the maximum elevation angle of the satellite orbit relative to the ground terminal, and the doppler frequency shift as a whole presents an S-shape, as shown in fig. 4, wherein a straight line is a frequency offset time-varying curve when the maximum elevation angle of the satellite relative to the ground terminal is 90 degrees, and a curve is a frequency offset time-varying curve when the maximum elevation angle of the satellite relative to the ground terminal is less than 90 degrees. Therefore, the Doppler frequency shift values of the satellites at different positions or different time points are different and can be measured in advance, and the corresponding frequency offset is obtainedThe shift compensation values are also different.
As described above, the value of the doppler shift is related to the relative velocity between the satellite and the ground terminal, and the relative velocity between the satellite and the ground terminal is determined at different positions when the satellite moves on a predetermined orbit, and thus, the value of the doppler shift can also be determined by the relative positions of the satellite and the ground terminal. For convenience of understanding, the present embodiment is specifically described by taking an example of a satellite keeping a constant circular orbit motion, and theoretically, for a certain ground terminal, the doppler frequency shift is as follows:
Figure BDA0003388572600000101
wherein f is0Is the carrier frequency, c is the vacuum speed of light, rEIs the radius of the earth, r is the satellite orbital height, θmaxThe maximum visible elevation angle of the satellite orbit to the ground terminal,
Figure BDA0003388572600000102
the angular difference between the satellite's current earth surface vertical mapping point and the satellite's earth surface vertical mapping point at the maximum elevation angle is determined. It should be noted that the above is only an example, and in fact, for a satellite moving at a non-uniform speed on an elliptical orbit, the relative speed between the satellite and a ground terminal at different positions is also determined, and those skilled in the art can also obtain the doppler shift of the satellite for a certain ground terminal at different positions. It follows that the doppler shift can be determined from the relative positions of the satellites and the ground terminals.
The satellites moving on the orbit all have satellite ephemeris, the time, the position, the speed and other operation states of the corresponding satellites can be determined according to the satellite ephemeris, and the positions of the ground terminals are also determined, so that the doppler frequency shift between the satellites and each ground terminal can be determined according to the satellite ephemeris, and the doppler frequency shift is substantially compensated and is determined according to the relative speed or the relative position of the satellites and the ground terminals.
Fig. 5 shows a frequency offset compensation method for medium and low orbit satellite communication according to an embodiment of the present invention, where the frequency offset compensation method can be used in a transmitting end, which can be a satellite or a terrestrial terminal, and the method can include the following steps:
s11, obtaining a frequency compensation value of Doppler frequency shift of the satellite relative to the ground terminal at least one moment.
As described above, when a satellite operates in the medium-low orbit, the frequency compensation value of the satellite relative to the ground terminal at each time is related to the relative velocity or relative position between the satellite and the ground terminal at the corresponding time. The satellite and the ground terminal have different relative speeds or relative positions at different times, and at a certain time, the speed or position of the satellite is determined, and the position of the ground terminal within the service window of the satellite is also determined, so that at the certain time, the relative speed or relative position between the satellite and the ground terminal is determined, the doppler shift that will occur to the transmission signal is determined, and the frequency compensation value is also determined, so that the frequency compensation value of the doppler shift of the satellite relative to the ground terminal at each time can be known in advance through step S11, and stored.
If the transmitting end is a satellite, the frequency compensation value may be stored in the satellite, or may be transmitted to the satellite by a ground terminal, so that the satellite can acquire the frequency compensation value. If the transmitting end is a ground terminal, the frequency compensation value may be stored in the ground terminal, or may be sent to the ground terminal by a satellite, so that the ground terminal can obtain the frequency compensation value.
In an alternative embodiment, the satellite or the ground terminal may first acquire the relative velocity or the relative position between the satellite and the ground terminal at least one time, and then calculate the frequency compensation value according to the relative velocity or the relative position. As described above, according to the formula (1), the doppler shift can be calculated by the relative velocity between the satellite and the ground terminal; or the doppler shift can be calculated from the relative position between the satellite and the ground terminal according to equation (2). It should be understood by those skilled in the art that equation (2) is only used to illustrate the embodiment of the present invention by taking the satellite to maintain a constant circular orbit motion as an example, and for the satellite moving at a non-constant speed along other orbits, the doppler frequency shift can be calculated according to the relative position between the satellite and the ground terminal. The frequency compensation value is opposite to the sign of the Doppler frequency shift, and if the Doppler frequency shift is delta f, the frequency compensation value is-delta f.
In another alternative embodiment, the frequency offset of the satellite with respect to the ground terminal at different orbital positions may be obtained by measurement. For example, a test signal can be sent via the satellite to the ground terminal, the test signal including a frequency value of the test signal, e.g. f0The terrestrial terminal, upon receiving the test signal, may measure the frequency value of the received signal, e.g. f1Therefore, the frequency compensation value of the satellite relative to the satellite at different orbit positions can be obtained through a measuring means and recorded, and the recorded frequency compensation value corresponding to the orbit position can be directly utilized when the satellite reaches the orbit position next time. Preferably, in order to obtain a more accurate frequency compensation value through measurement, the ground terminal periodically measures the frequency compensation value every time the satellite passes through a certain orbital position, so that the frequency compensation value relative to the ground terminal when the satellite is at the orbital position is obtained through statistical analysis, for example, by averaging or the like. In the same way, the ground terminal may also send a test signal to the satellite, and the satellite receives the test signal, so that the frequency compensation value of the ground terminal relative to the ground terminal at different orbital positions can also be obtained through measurement.
And S12, carrying out frequency offset compensation on the sending signal at the corresponding moment according to the frequency compensation value at least one moment.
If the transmitting terminal is a satellite, the satellite transmits a signal to the ground terminal through a downlink, and the satellite may perform frequency offset compensation on the transmitted signal at the corresponding time according to the frequency compensation value obtained in step S11. As described above, the frequency compensation value may be obtained by calculation or measurement of the satellite itself, or may be obtained from the ground terminal.
If the transmitting terminal is a ground terminal, the ground terminal transmits a signal to the satellite through the uplink, and the ground terminal may perform frequency offset compensation on the transmitted signal at the corresponding time according to the frequency compensation value obtained in step S11. Also, as described above, the frequency compensation value may be obtained by calculation or measurement by the ground terminal itself, or may be obtained from a satellite.
In the frequency offset compensation method for the medium-low orbit satellite communication according to the embodiment of the present invention, when the satellite is at a certain time or a certain orbit position, the relative speed or the relative position with respect to a certain ground terminal is relatively stable and predictable, so that the satellite or the ground terminal can obtain the frequency compensation value of the doppler frequency shift of the satellite with respect to the ground terminal at each time in advance, and thus, the corresponding frequency offset compensation can be performed at the corresponding time quickly. Compared with the scheme that the integer frequency offset is estimated through a complex search algorithm and then the fractional part is estimated in the prior art, the search algorithm and the estimation algorithm do not need to be executed in real time, so that the overhead and the delay of a communication system are reduced, and the stability of the communication system is improved.
In an alternative implementation manner of the embodiment of the present invention, the step S12 may be implemented in two ways. In the first frequency offset compensation method, the frequency offset to be compensated is input to the subcarrier mapping module in integer number of subcarrier intervals, the transmitter completes the frequency deflection of the whole parallel data block by the mapping method, and the compensation method can realize the compensation of the integer part of the doppler frequency shift. In the second frequency offset compensation method, a sequence whose phase is rotated according to the compensation frequency period is multiplied on the modulated time domain discrete signal to realize the pre-compensation of integral multiple or fractional multiple of the whole data block. It should be noted that the above two compensation methods are not exhaustive, and other frequency offset compensation methods are also possible.
FIG. 6 illustrates a frequency offset compensation method implemented by a satellite or a ground terminal according to an embodiment of the present invention, the satellite or the ground terminal before compensationThe sub-carrier signals of the signal transmitted by the ground terminal occupy the frequency bands 1-4 in the figure, for example, the carrier frequency of a certain sub-carrier signal is fcThe satellite terminal or the ground terminal pre-compensates the carrier frequency of each subcarrier signal in advance, and the carrier frequency of the subcarrier signal of the compensated transmission signal is fcΔ f, where Δ f is a pre-calculated or measured doppler shift value, and the respective subcarrier signals of the compensated transmission signal occupy the frequency bands 1-4 in the figure. Then, the satellite or the ground terminal sends the compensated sending signal to the ground terminal or the satellite, after the compensated sending signal is subjected to Doppler frequency shift, the carrier frequency of the subcarrier signal received by the ground terminal or the satellite is fcThe respective sub-carrier signals of the received signal occupy the frequency bands 1-4 in the figure, so that the terrestrial terminal or satellite can correctly receive the signal.
Fig. 7 illustrates a frequency offset compensation method for medium and low orbit satellite communication according to another embodiment of the present invention, which may be used for a satellite, for example, and which may include the steps of:
and S21, sending the frequency compensation value of the Doppler frequency shift of the satellite relative to the ground terminal at least one moment to the ground terminal.
As the satellite rotates around the earth, when the satellite enters the viewing window of a ground terminal and establishes a service link with the ground terminal, the satellite can transmit to the ground terminal, via the service link, a frequency compensation value for the doppler shift of the satellite relative to the ground terminal at least one time instant, and preferably, the satellite transmits to the ground terminal the frequency compensation value for each time instant during which the satellite is in the viewing window of the ground terminal. The specific manner of obtaining the frequency compensation value can refer to the corresponding description above.
And S22, the ground terminal performs frequency offset compensation on the transmission signal at the corresponding moment according to the frequency compensation value at least one moment.
After receiving the frequency compensation value at each time, the ground terminal may perform frequency offset compensation on the transmission signal at the corresponding time according to the frequency compensation value. Preferably, the terrestrial terminal receives the frequency offset value of the satellite at each time during the viewing window of the terrestrial terminal, so that the terrestrial terminal can frequency compensate the transmitted signal during the entire viewing window of the satellite.
In an alternative embodiment, the satellite may transmit the frequency compensation value of the doppler shift of the satellite relative to the ground terminal at least one time to the ground terminal through a broadcast signal, wherein the broadcast signal includes the frequency compensation values corresponding to a plurality of frames. After receiving the broadcast signal, the ground terminal may perform frequency offset compensation on a frame corresponding to the transmission signal according to a frequency compensation value included in the broadcast signal, as shown in fig. 8, the ground terminal employs a frequency compensation value 1 when transmitting a frame #1, employs a frequency compensation value 2 when transmitting a frame #2, and so on, thereby enabling each frame signal to be compensated, and enabling the satellite to correctly receive the signal.
And S23, the ground terminal sends the compensated sending signal to the satellite.
As shown in fig. 6, after the compensated transmission signal is subjected to doppler frequency shift, the receiving end can correctly receive the signal.
As an optional implementation manner of the embodiment of the present invention, the frequency offset compensation method may further include:
1) and acquiring the direction covering the most ground terminals.
In a medium-low orbit satellite communication system, one satellite can serve multiple ground terminals at the same time, and in order to provide communication services for more ground terminals as much as possible, the satellite needs to acquire the direction covering the ground terminals the most, so as to maximize the system throughput.
2) Such that the beam direction is directed in the direction that covers the ground terminal the most.
Through the steps of the method, the satellite adjusts the self beam direction to enable the self beam direction to point to the direction covering the most ground terminals, thereby providing communication service for more ground terminals
As described above, since the terrestrial terminals at different positions have different relative positions and different relative velocities with respect to the satellites serving the terrestrial terminals, the frequency compensation value compensated by a certain terrestrial terminal by the satellite is not optimal for other terrestrial terminals. For other ground terminals, although the doppler shift cannot be completely compensated, since the initial frequency offset compensation has been performed on the transmission signal, the doppler shift can be still greatly reduced, and other ground terminals can perform secondary frequency offset compensation by using the existing search algorithm, since the frequency offset has been greatly reduced, the search range that other ground terminals need to perform will be greatly reduced, for example, the interval of-6 to 6 subcarriers before the initial frequency offset compensation is never performed is reduced to the interval of-0.5 to 0.5 subcarriers. Therefore, the frequency offset compensation method for medium and low orbit satellite communication in the embodiment can still greatly reduce the search pressure of other ground terminals.
As an optional implementation manner of the embodiment of the present invention, the broadcast signal in the frequency offset compensation method may further include beam directions corresponding to multiple frames, as shown in fig. 8, after receiving the broadcast signal, the ground terminal may adjust an antenna direction of the ground terminal according to the beam direction included in the broadcast signal to track a satellite beam, so that when the antenna of the ground terminal transmits each frame signal, the antenna direction can always track the satellite beam, thereby increasing a transmission rate of the transmitted signal and reducing transmission power consumption.
Fig. 9 illustrates a frequency offset compensation method for medium and low orbit satellite communication according to another embodiment of the present invention, which may be used for a satellite, for example, and which may include the steps of:
and S31, before the service link is established between the following satellite and the ground terminal, sending the frequency compensation value of the Doppler frequency shift of the following satellite relative to at least one moment of the ground terminal to the following satellite. Wherein the frequency compensation value at each time is related to the relative velocity or relative position between the following satellite and the ground terminal at the corresponding time.
In this embodiment, since the medium-low orbit satellites move around the earth, each satellite can only serve a certain ground terminal for a period of time, and then the ground terminal is served by the following satellite. For example, during the time when the current satellite #1 serves a certain ground terminal, the ground terminal obtains that the current satellite #1 directs the beam to itself and performs frequency compensation, and the ground terminal realizes stable reception through precise synchronization. After the current satellite #1 leaves the visible window of the ground terminal, the following satellite #2 enters the visible window of the ground terminal along the same satellite orbit, and the current satellite #1 continues to provide service for the ground terminal, so that the relative velocity and/or relative position of the current satellite #1 and the following satellite #2 relative to the ground terminal are periodically repeated, the current satellite #1 can acquire the frequency compensation value of the doppler shift of the following satellite #2 relative to the ground terminal at each time, and before the following satellite #2 establishes a service link with the ground terminal, the frequency compensation value of the doppler shift of the following satellite #2 relative to the ground terminal at each time is transmitted to the following satellite #2 through an inter-satellite link or through a gateway station forwarding mode.
As an alternative, the current satellite #1 also transmits the beam direction values at the respective time instants to the following satellite # 2.
And S32, when the service link is established between the following satellite and the ground terminal, the following satellite carries out frequency offset compensation on the transmitting signal at the corresponding moment according to the frequency compensation value at least one moment.
When the ground terminal switches the service link from the current satellite #1 to the succeeding satellite #2, the succeeding satellite #2 may perform frequency offset compensation on the transmission signal at the corresponding time according to the frequency compensation value at each time, so that the ground terminal can correctly receive the transmission signal of the succeeding satellite # 2.
And S33, the post satellite sends the compensated sending signal to the ground terminal.
As an alternative embodiment, the following satellite #2 may transmit the frequency compensation value at least one time to the ground terminal for the ground terminal to perform frequency offset compensation on the transmission signal at the corresponding time according to the frequency compensation value at each time, and the ground terminal transmits the compensated transmission signal to the following satellite #2, so that the following satellite #2 can correctly receive the transmission signal of the ground terminal.
In an alternative embodiment, the ground terminal can know the beam direction values of the following satellite #2 at various times in advance, so that the antenna can be adjusted to track the beam of the following satellite # 2.
In this embodiment, since the current satellite informs the following satellite or the ground terminal of the frequency compensation value of the doppler frequency shift at each time of the following satellite relative to the ground terminal, when the ground terminal switches from the current satellite to the service link of the following satellite, the frequency compensation can be performed on the transmission signal of the following satellite or the ground terminal quickly, thereby reducing the overhead and delay of the communication system and improving the stability of the communication system.
Fig. 10 illustrates a frequency offset compensation method for medium and low orbit satellite communication according to another embodiment of the present invention, which may be used for a satellite, for example, and which may include the steps of:
s41, before a service link is established between the following satellite and the ground terminal, the frequency compensation value of the Doppler frequency shift of the following satellite relative to the ground terminal at least one moment is sent to the ground terminal. Wherein the frequency compensation value at each time is related to the relative velocity or relative position between the following satellite and the ground terminal at the corresponding time.
This step is similar to step S31, except that the current satellite transmits the frequency compensation value for the doppler shift at least one time of the following satellite relative to the ground terminal, and the rest can be understood with reference to the description related to step S31.
And S42, when the service link is established between the rear satellite and the ground terminal, the ground terminal performs frequency offset compensation on the transmission signal at the corresponding moment according to the frequency compensation value at least one moment.
This step is similar to step S32 and can be understood with reference to the description relating to step S31.
And S43, the ground terminal sends the compensated sending signal to the following satellite.
Also, as an alternative embodiment, the ground terminal may transmit the frequency compensation value at least one time to the following satellite, so that the following satellite performs frequency offset compensation on the transmission signal at the corresponding time according to the frequency compensation value at each time, and the following satellite transmits the compensated transmission signal to the ground terminal, thereby enabling the ground terminal to correctly receive the transmission signal of the ground terminal.
In an alternative embodiment, the ground terminal can know the beam direction values of the following satellite at various time points in advance, so that the antenna can be adjusted to track the beam of the following satellite.
As shown in fig. 11, an embodiment of the present invention further provides a frequency offset compensation method for medium and low orbit satellite communication, where the frequency offset compensation method may be used for a satellite, for example, and the method may include the following steps:
s51, before the satellite establishes a service link with the ground terminal, receiving a frequency compensation value of at least one moment of the satellite relative to the ground terminal, which is sent by a previous satellite.
S52, when the satellite establishes a service link with the ground terminal, the satellite performs frequency offset compensation on the transmission signal at the corresponding moment according to the frequency compensation value at least one moment.
And S53, the satellite transmits the compensated transmission signal to the ground terminal.
Specific contents of the frequency offset compensation method for medium and low orbit satellite communication in this embodiment can be understood with reference to related contents of the embodiment shown in fig. 9, and are not described herein again.
Likewise, as an optional implementation manner of this embodiment, the satellite may further transmit the frequency compensation value at least one time to the ground terminal, so as to enable the ground terminal to perform frequency offset compensation on the transmission signal at the corresponding time according to the frequency compensation value at each time, and the ground terminal transmits the compensated transmission signal to the satellite, so that the satellite can correctly receive the transmission signal of the ground terminal.
As another alternative, the ground terminal can know the beam direction value of the satellite at each time in advance, so that the antenna can be adjusted to track the beam of the satellite.
As shown in fig. 12, an embodiment of the present invention further provides a frequency offset compensation method for medium and low orbit satellite communication, where the frequency offset compensation method can be used for a satellite, for example, and the method can include the following steps:
s61, when the satellite establishes a service link with the ground terminal, receiving a frequency compensation value of the satellite relative to the ground terminal at least one moment, which is sent by the ground terminal, and sending the frequency compensation value to the ground terminal by the previous satellite.
And S62, the satellite performs frequency offset compensation on the transmission signal at the corresponding moment according to the frequency compensation value at least one moment.
And S63, the satellite transmits the compensated transmission signal to the ground terminal.
Specific contents of the frequency offset compensation method for medium and low orbit satellite communication in this embodiment can be understood with reference to the related contents of the embodiment shown in fig. 10, and are not described herein again.
In the above, the frequency offset compensation method for medium and low orbit satellite communication according to the embodiment of the present invention is described in detail by taking the case of downlink transmission of signals from a satellite to a ground terminal as an example, and in fact, uplink transmission of signals from the ground terminal to the satellite is also possible. Because there is a relative velocity between the satellite and the ground terminal, there is also a doppler shift in the uplink signal transmitted from the ground terminal to the satellite, and the frequency offset compensation method for the medium and low orbit satellite communication according to the embodiment of the present invention can also be used to perform the frequency offset compensation.
As shown in fig. 13, assuming that a certain satellite serves both terrestrial terminal 1 and terrestrial terminal 2, terrestrial terminal 1 causes integer and fractional frequency offset due to the elevation angle, while terrestrial terminal 2 does not cause frequency offset due to the maximum elevation angle, if the transmitted signal is not frequency compensated, there is severe interference in the signal received by the satellite, and in the example of fig. 13, subcarrier 1 interferes with subcarrier 5 and subcarrier 2 interferes with subcarrier 6. It is to be noted that the interference experienced by the received signal is spread out over substantially all carriers due to the fractional frequency offset.
After the frequency offset compensation method for the medium and low orbit satellite communication according to the embodiment of the present invention is adopted, as shown in fig. 14, since the frequency compensation is performed on the transmission signal of the ground terminal 1 in advance, the frequency offset is removed from the signal received by the satellite side, so that the signal between the two ground terminals can be received without interference.
As shown in fig. 15, an embodiment of the present invention further provides a frequency offset compensation method for medium and low orbit satellite communication, where the frequency offset compensation method may be used for a ground terminal, for example, and the method may include the following steps:
s71, sending the frequency compensation value of the Doppler frequency shift of the satellite relative to the ground terminal at least one moment to the satellite through an uplink. The frequency compensation value at each moment is related to the relative speed or relative position between the satellite and the ground terminal at the corresponding moment, and the frequency compensation value at each moment is used for enabling the satellite to perform frequency offset compensation on the transmission signal at the corresponding moment according to the frequency compensation value at least one moment.
And S72, the satellite performs frequency offset compensation on the transmission signal at the corresponding moment according to the frequency compensation value at least one moment.
And S73, the satellite sends the compensated sending signal to the ground terminal.
Specific contents of the frequency offset compensation method for medium and low orbit satellite communication in this embodiment can be understood with reference to related contents of the embodiment shown in fig. 7, and are not described herein again.
Fig. 16 shows a frequency offset compensation method for medium and low orbit satellite communication according to another embodiment of the present invention, which may be used for a ground terminal, for example, and which may include the steps of:
s81, during the service link with the current satellite, receiving the frequency compensation value of the Doppler frequency shift of at least one time of the following satellite relative to the ground terminal, which is transmitted by the current satellite. Wherein the frequency compensation value at each time is related to the relative velocity or relative position between the following satellite and the ground terminal at the corresponding time.
S82, when a service link is established with a subsequent satellite, frequency offset compensation is carried out on the transmission signal at the corresponding moment according to the frequency compensation value at least one moment.
And S83, the ground terminal sends the compensated sending signal to the following satellite.
In an alternative embodiment, the ground terminal transmits a frequency compensation value of the doppler shift of at least one time instant of the following satellite relative to the ground terminal to the following satellite when establishing the service link with the following satellite, so that the following satellite performs frequency offset compensation on the transmission signal of the corresponding time instant according to the frequency compensation value of at least one time instant.
Specific contents of the frequency offset compensation method for medium and low orbit satellite communication in this embodiment can be understood with reference to related contents of the embodiment shown in fig. 9, and are not described herein again.
Accordingly, an embodiment of the present invention provides a frequency offset compensation apparatus for medium and low orbit satellite communication, which may include:
an obtaining unit, configured to obtain a frequency compensation value of a doppler frequency shift of a satellite relative to a ground terminal at least one time, where the frequency compensation value at each time is related to a relative speed or a relative position between the satellite and the ground terminal at the corresponding time. Please refer to the corresponding description of step S11 for details.
And the compensation unit is used for carrying out frequency offset compensation on the sending signal at the corresponding moment according to the frequency compensation value at least one moment. Please refer to the corresponding description of step S12 for details.
In the frequency offset compensation apparatus for medium and low orbit satellite communication according to the embodiment of the present invention, by the above obtaining unit and the compensation unit, since the relative speed or the relative position of the satellite with respect to a certain ground terminal is relatively stable and predictable when the satellite is at a certain time or a certain orbit position, the satellite or the ground terminal can know in advance the frequency compensation value of the doppler frequency shift of the satellite with respect to the ground terminal at each time, and thus can perform corresponding frequency offset compensation at a corresponding time quickly. Compared with the scheme that the integer frequency offset is estimated through a complex search algorithm and then the fractional part is estimated in the prior art, the search algorithm and the estimation algorithm do not need to be executed in real time, so that the overhead and the delay of a communication system are reduced, and the stability of the communication system is improved.
The embodiment of the invention also provides a frequency offset compensation device for medium and low orbit satellite communication, which comprises:
a sending unit, configured to send, to a ground terminal, a frequency compensation value of a doppler frequency shift of the satellite relative to the ground terminal at least one time, where the frequency compensation value at each time is related to a relative speed or a relative position between the satellite and the ground terminal at the corresponding time, and is used to enable the ground terminal to perform frequency offset compensation on a sending signal at the corresponding time according to the frequency compensation value at the at least one time.
The details of the sending unit refer to the corresponding description of step S21.
The embodiment of the invention also provides a frequency offset compensation device for medium and low orbit satellite communication, which is applied to a satellite and comprises the following components:
a transmitting unit, configured to transmit a frequency compensation value of a doppler shift of at least one time of a succeeding satellite with respect to a ground terminal to the succeeding satellite or the ground terminal before the succeeding satellite establishes a service link with the ground terminal; wherein the frequency offset value at each time instant is related to the relative velocity or relative position between the following satellite and the ground terminal at the respective time instant.
The details of the above sending unit refer to the corresponding descriptions of steps S31 and S41.
The embodiment of the invention also provides a frequency offset compensation device for medium and low orbit satellite communication, which is applied to a satellite and comprises the following components:
a receiving unit, configured to receive, before the satellite establishes a service link with a ground terminal, a frequency compensation value of at least one time of the satellite relative to the ground terminal, which is transmitted by a previous satellite; or for receiving a frequency compensation value of at least one time of the satellite relative to the ground terminal, sent by the ground terminal, when the satellite establishes a service link with the ground terminal, wherein the frequency compensation value is sent to the ground terminal by a previous satellite; wherein the frequency compensation value at each time instant is related to the relative velocity or relative position between the satellite and the ground terminal at the respective time instant.
The details of the above receiving unit are described with reference to steps S51 and S61.
The embodiment of the invention also provides a frequency offset compensation device for medium and low orbit satellite communication, which is applied to a ground terminal and comprises the following components:
a sending unit, configured to send, to a satellite through an uplink, a frequency compensation value of a doppler shift of the satellite relative to the ground terminal at least one time, where the frequency compensation value at each time is related to a relative velocity or a relative position between the satellite and the ground terminal at the corresponding time, and configured to enable the satellite to perform frequency offset compensation on a sending signal at the corresponding time according to the frequency compensation value at the at least one time.
The details of the above receiving unit refer to the corresponding description of step S71.
The embodiment of the invention also provides a frequency offset compensation device for medium and low orbit satellite communication, which is applied to a ground terminal and comprises the following components:
a receiving unit, configured to receive, during a service link with a current satellite, a frequency compensation value of a doppler shift of a subsequent satellite at least one time relative to the ground terminal, where the frequency compensation value at each time is related to a relative velocity or a relative position between the satellite and the ground terminal at the corresponding time, and is used for enabling the satellite to perform frequency offset compensation on a transmission signal at the corresponding time according to the frequency compensation value at least one time.
The details of the above receiving unit refer to the corresponding description of step S81.
Specific details of the frequency offset compensation apparatus for medium and low orbit satellite communication according to the embodiment of the present invention can be understood by referring to the corresponding related descriptions and effects in the embodiments shown in fig. 1 to fig. 16, which are not described herein again.
The embodiment of the present invention further provides a medium-low orbit satellite, as shown in fig. 17, the medium-low orbit satellite may include an antenna 91, a processor 92, and a memory 93, and the antenna 91, the processor 92, and the memory 93 may be connected by a bus or other means, for example.
The antenna 91 is used for receiving or transmitting signals and may be, for example, a phased array antenna.
The Processor 92 may be a Central Processing Unit (CPU) or other general purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other Programmable logic device, discrete Gate or transistor logic, discrete hardware components, or any combination thereof.
The memory 93, which is a non-transitory computer-readable storage medium, may be used to store non-transitory software programs, non-transitory computer-executable programs, and modules. The processor 92 executes the non-transitory software programs, instructions and modules stored in the memory 93 to thereby execute various functional applications of the processor and data processing to implement the various method steps in the above-described method embodiments, such as the step of obtaining a frequency compensation value for the doppler shift of the satellite relative to the ground terminal at least one time.
The memory 93 may include a storage program area and a storage data area, wherein the storage program area may store an operating system, an application program required for at least one function; the storage data area may store data created by the processor 92, and the like. Further, the memory 93 may include high speed random access memory, and may also include non-transitory memory, such as at least one magnetic disk storage device, flash memory device, or other non-transitory solid state storage device.
In an optional implementation manner of the embodiment of the present invention, the medium-low orbit satellite may further include a frequency modulator 94, configured to perform frequency offset compensation on the transmission signal at a corresponding time according to a frequency compensation value at least one time; the antenna 91 is used to transmit the compensated transmission signal.
The embodiment of the present invention also provides a ground terminal, as also shown in fig. 17, where the ground terminal may also include an antenna 91, a processor 92, and a memory 93, and optionally, the ground terminal may further include a frequency modulator 94. The antenna 91, the processor 92, the memory 93 and the frequency modulator 94 may be referred to the corresponding descriptions above.
The embodiment of the invention also provides a medium-low orbit satellite, which comprises: and the antenna is used for transmitting a frequency compensation value of Doppler frequency shift of the satellite relative to the ground terminal at least one moment to the ground terminal, wherein the frequency compensation value at each moment is related to the relative speed or relative position between the satellite and the ground terminal at the corresponding moment, and the antenna is used for enabling the ground terminal to perform frequency offset compensation on the transmission signal at the corresponding moment according to the frequency compensation value at least one moment.
The details of the antenna are described with reference to step S21.
The embodiment of the invention also provides a medium-low orbit satellite, which comprises: an antenna for transmitting a frequency compensation value of a doppler shift of at least one time instant of a succeeding satellite with respect to a ground terminal to the succeeding satellite or the ground terminal before the succeeding satellite establishes a service link with the ground terminal; wherein the frequency offset value at each time instant is related to the relative velocity or relative position between the following satellite and the ground terminal at the respective time instant.
Please refer to corresponding descriptions of steps S31 and S41 for details of the antenna.
The embodiment of the invention also provides a medium-low orbit satellite, which comprises: an antenna for receiving a frequency compensation value of at least one time of the satellite relative to the ground terminal transmitted by a previous satellite before the satellite establishes a service link with the ground terminal; or the antenna is used for receiving a frequency compensation value of the satellite relative to the ground terminal at least one moment, which is sent by the ground terminal, when the satellite establishes a service link with the ground terminal, wherein the frequency compensation value is sent to the ground terminal by a previous satellite; wherein the frequency compensation value at each time instant is related to the relative velocity or relative position between the satellite and the ground terminal at the respective time instant.
Please refer to corresponding descriptions of steps S51 and S61 for details of the antenna.
An embodiment of the present invention further provides a ground terminal, including: the antenna is used for transmitting a frequency compensation value of Doppler frequency shift of the satellite relative to the ground terminal at least one moment to the medium and low orbit satellite through an uplink, wherein the frequency compensation value at each moment is related to relative speed or relative position between the satellite and the ground terminal at the corresponding moment, and the frequency compensation value at least one moment is used for enabling the satellite to carry out frequency offset compensation on a transmission signal at the corresponding moment according to the frequency compensation value at the at least one moment.
The details of the antenna are described with reference to step S71.
An embodiment of the present invention further provides a ground terminal, including: an antenna for receiving a frequency compensation value of a Doppler shift of a succeeding satellite relative to the ground terminal at least one time during a service link with a current satellite, wherein the frequency compensation value at each time is related to a relative velocity or a relative position between the satellite and the ground terminal at the corresponding time, and the antenna is used for enabling the satellite to perform frequency offset compensation on a transmission signal at the corresponding time according to the frequency compensation value at least one time.
The details of the antenna are described with reference to step S81.
The details of the medium-low orbit satellite or the ground terminal according to the embodiment of the present invention can be understood by referring to the corresponding related descriptions and effects in the embodiments shown in fig. 1 to fig. 16, which are not described herein again.
It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by a computer program, which can be stored in a computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. The storage medium may be a magnetic Disk, an optical Disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a Flash Memory (Flash Memory), a Hard Disk (Hard Disk Drive, abbreviated as HDD), a Solid State Drive (SSD), or the like; the storage medium may also comprise a combination of memories of the kind described above.
Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations fall within the scope defined by the appended claims.

Claims (26)

1. A method for compensating for frequency offset in medium and low orbit satellite communication, comprising:
obtaining a frequency compensation value of Doppler frequency shift of a satellite relative to a ground terminal at least one moment, wherein the frequency compensation value at each moment is related to relative speed or relative position between the satellite and the ground terminal at the corresponding moment;
and carrying out frequency offset compensation on the transmission signal at the corresponding moment according to the frequency compensation value at least one moment.
2. The method of claim 1, wherein the obtaining a frequency compensation value for the doppler shift of the satellite relative to the ground terminal at least one time comprises:
acquiring the relative speed or the relative position between the satellite and the ground terminal at least one moment;
and calculating the frequency compensation value according to the relative speed or the relative position.
3. The method of claim 1, wherein the obtaining the frequency compensation value for the doppler shift at least one time comprises:
and obtaining the frequency compensation value of the satellite relative to the ground terminal at different orbital positions through measurement.
4. A frequency offset compensation method for medium and low orbit satellite communication is applied to a satellite, and is characterized by comprising the following steps:
transmitting to a ground terminal a frequency compensation value for a Doppler shift of the satellite relative to the ground terminal at least one time instant, wherein
The frequency compensation value at each time is related to the relative speed or relative position between the satellite and the ground terminal at the corresponding time, so that the ground terminal performs frequency offset compensation on the transmission signal at the corresponding time according to the frequency compensation value at least one time.
5. The frequency offset compensation method according to claim 4, wherein the satellite transmits a frequency compensation value of a doppler shift of the satellite with respect to the ground terminal at least one time to the ground terminal through a broadcast signal; wherein
The broadcast signal comprises frequency compensation values corresponding to a plurality of frames, and the frequency compensation values are used for enabling the ground terminal to perform frequency offset compensation on the corresponding frames of the transmission signal according to the frequency compensation values.
6. The method of claim 5, wherein the broadcast signal further comprises a plurality of frame-corresponding beam directions.
7. The frequency offset compensation method of any of claims 4-6, further comprising:
acquiring the direction covering the most ground terminals;
such that the beam direction is directed in the direction of the most covered ground terminals.
8. A frequency offset compensation method for medium and low orbit satellite communication is applied to a satellite, and is characterized by comprising the following steps:
transmitting a frequency compensation value for a doppler shift of at least one instant of a following satellite relative to a ground terminal to the following satellite or the ground terminal before the following satellite establishes a service link with the ground terminal; wherein
The frequency offset value at each time instant is related to the relative velocity or relative position between the following satellite and the ground terminal at the corresponding time instant.
9. The method of frequency offset compensation according to claim 8, further comprising:
when the service link is established between the following satellite and the ground terminal, the following satellite carries out frequency offset compensation on the sending signal at the corresponding moment according to the frequency compensation value at least one moment; or
When the service link is established between the following satellite and the ground terminal, the following satellite sends the frequency compensation value at least one moment to the ground terminal, so that the ground terminal performs frequency offset compensation on the sending signal at the corresponding moment according to the frequency compensation value at least one moment; or
When the service link is established between the rear satellite and the ground terminal, the ground terminal performs frequency offset compensation on the transmission signal at the corresponding moment according to the frequency compensation value at least one moment; or
And when the service link is established between the following satellite and the ground terminal, the ground terminal sends the frequency compensation value at least one moment to the following satellite, so that the following satellite carries out frequency offset compensation on the sending signal at the corresponding moment according to the frequency compensation value at least one moment.
10. A frequency offset compensation method for medium and low orbit satellite communication is applied to a satellite, and is characterized by comprising the following steps:
before the satellite establishes a service link with a ground terminal, receiving a frequency compensation value of the satellite relative to the ground terminal at least one moment transmitted by a previous satellite; or
When the satellite establishes a service link with a ground terminal, receiving a frequency compensation value of the satellite relative to the ground terminal at least one moment, which is sent by the ground terminal, wherein the frequency compensation value is sent to the ground terminal by a former satellite; wherein
The frequency compensation value at each time instant is related to the relative velocity or relative position between the satellite and the ground terminal at the respective time instant.
11. A frequency offset compensation method for medium and low orbit satellite communication is applied to a ground terminal, and is characterized by comprising the following steps:
transmitting a frequency compensation value of a Doppler shift of a satellite relative to the ground terminal for at least one time instant to the satellite through an uplink, wherein
The frequency compensation value at each time is related to the relative speed or relative position between the satellite and the ground terminal at the corresponding time, so that the satellite performs frequency offset compensation on the transmission signal at the corresponding time according to the frequency compensation value at least one time.
12. A frequency offset compensation method for medium and low orbit satellite communication is applied to a ground terminal, and is characterized by comprising the following steps:
receiving a frequency compensation value of Doppler shift of at least one time of a following satellite relative to the ground terminal transmitted by a current satellite during maintenance of a service link with the current satellite, wherein
The frequency compensation value at each time is related to the relative speed or relative position between the satellite and the ground terminal at the corresponding time, so that the satellite performs frequency offset compensation on the transmission signal at the corresponding time according to the frequency compensation value at least one time.
13. The method of frequency offset compensation according to claim 12, further comprising:
when a service link is established with a following satellite, transmitting a frequency compensation value of Doppler frequency shift of the following satellite relative to the ground terminal at least one time to the following satellite so as to enable the following satellite to perform frequency offset compensation on a transmission signal at a corresponding time according to the frequency compensation value at least one time; or
And when a service link is established with a rear satellite, carrying out frequency offset compensation on the transmission signal at the corresponding moment according to the frequency compensation value at least one moment.
14. A frequency offset compensation apparatus for medium and low orbit satellite communication, comprising:
an obtaining unit, configured to obtain a frequency compensation value of a doppler frequency shift of a satellite relative to a ground terminal at least one time, where the frequency compensation value at each time is related to a relative speed or a relative position between the satellite and the ground terminal at the corresponding time;
and the compensation unit is used for carrying out frequency offset compensation on the sending signal at the corresponding moment according to the frequency compensation value at least one moment.
15. A frequency offset compensation device for medium and low orbit satellite communication is applied to a satellite, and is characterized by comprising:
a transmitting unit for transmitting to a ground terminal a frequency compensation value of a Doppler shift of the satellite with respect to the ground terminal at least one time, wherein
The frequency compensation value at each time is related to the relative speed or relative position between the satellite and the ground terminal at the corresponding time, so that the ground terminal performs frequency offset compensation on the transmission signal at the corresponding time according to the frequency compensation value at least one time.
16. A frequency offset compensation device for medium and low orbit satellite communication is applied to a satellite, and is characterized by comprising:
a transmitting unit, configured to transmit a frequency compensation value of a doppler shift of at least one time of a succeeding satellite with respect to a ground terminal to the succeeding satellite or the ground terminal before the succeeding satellite establishes a service link with the ground terminal; wherein
The frequency offset value at each time instant is related to the relative velocity or relative position between the following satellite and the ground terminal at the corresponding time instant.
17. A frequency offset compensation device for medium and low orbit satellite communication is applied to a satellite, and is characterized by comprising:
a receiving unit, configured to receive, before the satellite establishes a service link with a ground terminal, a frequency compensation value of at least one time of the satellite relative to the ground terminal, which is transmitted by a previous satellite; or for receiving a frequency compensation value of at least one time of the satellite relative to the ground terminal, sent by the ground terminal, when the satellite establishes a service link with the ground terminal, wherein the frequency compensation value is sent to the ground terminal by a previous satellite; wherein
The frequency compensation value at each time instant is related to the relative velocity or relative position between the satellite and the ground terminal at the respective time instant.
18. A frequency offset compensation device for medium and low orbit satellite communication is applied to a ground terminal, and is characterized by comprising:
a transmitting unit for transmitting a frequency compensation value of a Doppler shift of a satellite relative to the ground terminal at least one time to the satellite through an uplink, wherein
The frequency compensation value at each time is related to the relative speed or relative position between the satellite and the ground terminal at the corresponding time, so that the satellite performs frequency offset compensation on the transmission signal at the corresponding time according to the frequency compensation value at least one time.
19. A frequency offset compensation device for medium and low orbit satellite communication is applied to a ground terminal, and is characterized by comprising:
a receiving unit for receiving a frequency compensation value of a Doppler shift transmitted from a current satellite at least one time of a succeeding satellite with respect to the ground terminal during maintenance of a service link with the current satellite, wherein
The frequency compensation value at each time is related to the relative speed or relative position between the satellite and the ground terminal at the corresponding time, so that the satellite performs frequency offset compensation on the transmission signal at the corresponding time according to the frequency compensation value at least one time.
20. A medium to low orbit satellite, comprising: an antenna, a frequency modulator, a memory, and a processor, wherein,
the memory stores computer instructions, and the processor executes the computer instructions to obtain frequency compensation values of Doppler frequency shift of a satellite relative to a ground terminal at least one moment, wherein the frequency compensation values at each moment are related to relative speed or relative position between the satellite and the ground terminal at the corresponding moment;
the frequency modulator is used for carrying out frequency offset compensation on the transmitting signal at the corresponding moment according to the frequency compensation value at least one moment;
the antenna is used for transmitting the compensated transmission signal.
21. A ground terminal, comprising: an antenna, a frequency modulator, a memory, and a processor, wherein,
the memory stores computer instructions, and the processor executes the computer instructions to obtain frequency compensation values of Doppler frequency shift of a satellite relative to a ground terminal at least one moment, wherein the frequency compensation values at each moment are related to relative speed or relative position between the satellite and the ground terminal at the corresponding moment;
the frequency modulator is used for carrying out frequency offset compensation on the transmitting signal at the corresponding moment according to the frequency compensation value at least one moment;
the antenna is used for transmitting the compensated transmission signal.
22. A medium to low orbit satellite, comprising:
an antenna for transmitting to a ground terminal a frequency compensation value of a Doppler shift of the satellite with respect to the ground terminal at least one time, wherein
The frequency compensation value at each time is related to the relative speed or relative position between the satellite and the ground terminal at the corresponding time, so that the ground terminal performs frequency offset compensation on the transmission signal at the corresponding time according to the frequency compensation value at least one time.
23. A medium to low orbit satellite, comprising:
an antenna for transmitting a frequency compensation value of a doppler shift of at least one time instant of a succeeding satellite with respect to a ground terminal to the succeeding satellite or the ground terminal before the succeeding satellite establishes a service link with the ground terminal; wherein
The frequency offset value at each time instant is related to the relative velocity or relative position between the following satellite and the ground terminal at the corresponding time instant.
24. A medium to low orbit satellite, comprising:
an antenna for receiving a frequency compensation value of at least one time of the satellite relative to the ground terminal transmitted by a previous satellite before the satellite establishes a service link with the ground terminal; or
The antenna is used for receiving a frequency compensation value of at least one moment of the satellite relative to the ground terminal, which is sent by the ground terminal when the satellite establishes a service link with the ground terminal, wherein the frequency compensation value is sent to the ground terminal by a previous satellite; wherein
The frequency compensation value at each time instant is related to the relative velocity or relative position between the satellite and the ground terminal at the respective time instant.
25. A ground terminal, comprising:
an antenna for transmitting a frequency compensation value of a Doppler shift of the satellite relative to the ground terminal at least one time to a medium-low orbit satellite through an uplink, wherein
The frequency compensation value at each time is related to the relative speed or relative position between the satellite and the ground terminal at the corresponding time, so that the satellite performs frequency offset compensation on the transmission signal at the corresponding time according to the frequency compensation value at least one time.
26. A ground terminal, comprising:
an antenna for receiving a frequency compensation value of a Doppler shift of a succeeding satellite with respect to the ground terminal at least one time transmitted from a current satellite during maintenance of a service link with the current satellite, wherein
The frequency compensation value at each time is related to the relative speed or relative position between the satellite and the ground terminal at the corresponding time, so that the satellite performs frequency offset compensation on the transmission signal at the corresponding time according to the frequency compensation value at least one time.
CN202111458083.5A 2021-12-02 2021-12-02 Frequency offset compensation method and device, medium and low orbit satellite and ground terminal Pending CN114189415A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202111458083.5A CN114189415A (en) 2021-12-02 2021-12-02 Frequency offset compensation method and device, medium and low orbit satellite and ground terminal

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202111458083.5A CN114189415A (en) 2021-12-02 2021-12-02 Frequency offset compensation method and device, medium and low orbit satellite and ground terminal

Publications (1)

Publication Number Publication Date
CN114189415A true CN114189415A (en) 2022-03-15

Family

ID=80541992

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202111458083.5A Pending CN114189415A (en) 2021-12-02 2021-12-02 Frequency offset compensation method and device, medium and low orbit satellite and ground terminal

Country Status (1)

Country Link
CN (1) CN114189415A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117478207A (en) * 2023-12-25 2024-01-30 广东世炬网络科技有限公司 Satellite-to-ground link communication method, device, equipment and storage medium

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104702547A (en) * 2014-09-25 2015-06-10 上海欧科微航天科技有限公司 Pilot frequency information and satellite ephemeris joint Doppler frequency shift estimation and compensation method
CN105871495A (en) * 2015-12-29 2016-08-17 中国科学院国家天文台 Time synchronization method, communication ground station and user terminal
CN207460175U (en) * 2017-11-08 2018-06-05 南京天际易达通信技术有限公司 A kind of satellite communication Doppler shift compensation device and satellite communication system
CN110168962A (en) * 2016-10-28 2019-08-23 瑞典爱立信有限公司 Wireless communication link between the communication equipment based on ground in the air
CN112269198A (en) * 2020-12-14 2021-01-26 中国人民解放军国防科技大学 Satellite determination method and device based on Doppler effect
US20210058148A1 (en) * 2019-05-02 2021-02-25 Dish Wireless L.L.C. Doppler compensation for non-terrestrial network

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104702547A (en) * 2014-09-25 2015-06-10 上海欧科微航天科技有限公司 Pilot frequency information and satellite ephemeris joint Doppler frequency shift estimation and compensation method
CN105871495A (en) * 2015-12-29 2016-08-17 中国科学院国家天文台 Time synchronization method, communication ground station and user terminal
CN110168962A (en) * 2016-10-28 2019-08-23 瑞典爱立信有限公司 Wireless communication link between the communication equipment based on ground in the air
CN207460175U (en) * 2017-11-08 2018-06-05 南京天际易达通信技术有限公司 A kind of satellite communication Doppler shift compensation device and satellite communication system
US20210058148A1 (en) * 2019-05-02 2021-02-25 Dish Wireless L.L.C. Doppler compensation for non-terrestrial network
CN112269198A (en) * 2020-12-14 2021-01-26 中国人民解放军国防科技大学 Satellite determination method and device based on Doppler effect

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117478207A (en) * 2023-12-25 2024-01-30 广东世炬网络科技有限公司 Satellite-to-ground link communication method, device, equipment and storage medium
CN117478207B (en) * 2023-12-25 2024-04-02 广东世炬网络科技有限公司 Satellite-to-ground link communication method, device, equipment and storage medium

Similar Documents

Publication Publication Date Title
US7944993B2 (en) Downstream broad beam diversity
US10673491B2 (en) Multiple access system and method for determining a distance to an endpoint
US6127967A (en) Low-earth orbit satellite acquisition and synchronization system using a beacon signal
EP1433271B1 (en) Calibration of a radio communications system
US6788948B2 (en) Frequency dependent calibration of a wideband radio system using narrowband channels
EP1670094B1 (en) Smart antenna communication system for signal calibration
CN109120561B (en) Medium frequency offset correction method for low-orbit satellite mobile communication system
US7389193B2 (en) Apparatus and method for calibrating transmission paths in a multicarrier communication system using multiple antennas
AU2020397983B2 (en) System and method for uplink compensation gap
KR20010072616A (en) System and method for narrowing the range of frequency uncertainty of a doppler shifted signal
JP2001501313A (en) Distinct position determination method using two low earth orbits and system using this method
CN111416648A (en) Multi-beam adaptive management method and device for low-earth-orbit satellite system
CN113612523B (en) Uplink time precompensation algorithm, terminal synchronization method and system
KR20130113927A (en) High-capacity hybrid terrestrial/satellite cellular radio communication system
US20180019799A1 (en) Systems and methods for signal cancellation in satellite communication
CN114362811B (en) Doppler frequency compensation device and method for space satellite-borne terminal of space satellite
CN114189415A (en) Frequency offset compensation method and device, medium and low orbit satellite and ground terminal
JP7381971B2 (en) Wireless communication system, relay device and wireless communication method
EP2273695A2 (en) Transmit frequency precorrection for satellite terminals
US20230361864A1 (en) System with modulated signal to compensate frequency errors in lte signals
US20220368410A1 (en) Location information in non-terrestrial networks
US11985611B1 (en) Synchronization of multi-user uplink transmissions
JPH06244763A (en) Satellite communication equipment
Im et al. Fine Frequency Offset Synchronization Scheme for Internet of Things Devices in 5G non-terrestrial network
KR20240077977A (en) Apparatus and method for beam selection in wireless communication system

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination