WO2021129633A1

WO2021129633A1 - Uplink data synchronization method and device

Info

Publication number: WO2021129633A1
Application number: PCT/CN2020/138456
Authority: WO
Inventors: 王新玲; 高珂增; 王凯; 李华栋; 杨芸霞; 鲁志兵
Original assignee: 海能达通信股份有限公司
Priority date: 2019-12-26
Filing date: 2020-12-23
Publication date: 2021-07-01
Also published as: CN111193571B; CN111193571A

Abstract

The present application provides an uplink data synchronization method, comprising: after a cell is established, determining a first time sequence unit from a downlink sending time sequence to obtain a downlink sending first time sequence unit; obtaining a benchmark RTT according to RTTs of an earth station and a common reference point, wherein the common reference point is a preset reference point in at least one cell covered by a satellite; and using a moment obtained by delaying the starting moment of the downlink sending first time sequence unit by the reference RTT as a starting moment of an uplink receiving first time sequence unit of the earth station. The present application can ensure that uplink data received by an earth station can be correctly demodulated.

Description

Method and device for synchronizing uplink data

This application claims the priority of the first application part of the Chinese patent application filed with the Chinese Patent Office on January 9, 2020, the application number is 202010023002.8, and the invention title is "A method and device for synchronizing uplink data", and the claim is in 2019 The priority of the Chinese patent application filed with the Chinese Patent Office on December 26, 2010, the application number is 201911368494.8, and the invention title is "A method and device for synchronizing uplink data", the entire content of which is incorporated into this application by reference.

Technical field

This application relates to the field of satellite communications, and in particular to a method and device for synchronizing uplink data.

Background technique

In a satellite communication system, the satellite moves in orbit, and the gateway sends downlink data to the terminal through the satellite. After the terminal receives the downlink data, the terminal sends the uplink data to the gateway through the satellite.

At present, in satellite communication systems, especially low-orbit satellite communication systems, due to the movement of satellites in orbit, the relative positions of the gateways and ground terminals are constantly changing, and the arrival of uplink data will be advanced or delayed. If the gateways communicate on land, In the system, when data is sent and received at the same time sequence, the received data cannot be demodulated correctly, that is, the synchronization of uplink data cannot be realized.

Therefore, a synchronization method for uplink data is needed to improve the performance of the gateway station for demodulating uplink data.

Summary of the invention

This application provides a method and device for synchronizing uplink data, aiming to solve the problem of uplink data synchronization at a gateway.

In order to achieve the above objectives, this application provides the following technical solutions:

This application provides a method for synchronizing uplink data, which is applied to a gateway station, including:

After the cell is established, determine the first time sequence unit from the downlink transmission time sequence to obtain the first time sequence unit for downlink transmission; the first time sequence unit of downlink transmission is any time sequence unit in the downlink transmission time sequence;

Obtaining a reference RTT according to the RTT between the gateway station and a common reference point; the common reference point is a preset reference point in at least one cell covered by a satellite;

The time obtained by delaying the reference RTT on the basis of the start time of the first time sequence unit of the downlink transmission is used as the start time of the first time sequence unit of the uplink reception of the gateway station.

Optionally, the acquiring a reference RTT according to the RTT of the gateway station and the public reference point includes:

The RTT between the gateway station and the public reference point is the real RTT, and the real RTT is the gateway station starting from the downlink sending the first time sequence unit to send the downlink data to the gateway station receiving the public reference point. The delay between the uplink data;

Use the real RTT as the reference RTT.

The RTT of the gateway station and the common reference point is the RTT corresponding to the start time of the first time sequence unit of the downlink transmission of the gateway station; the RTT corresponding to the start time of the first time sequence unit of the downlink transmission is this time The sum of the round-trip delay of the feeder link and the round-trip delay of the user link; the round-trip delay of the feeder link at this moment is the delay corresponding to the round-trip distance between the satellite and the gateway at this moment ; The round-trip delay of the user link at this moment is the delay corresponding to the round-trip distance between the satellite at this moment and the common reference point;

The RTT corresponding to the start time of the first time sequence unit of downlink transmission of the gateway station is used as the reference RTT.

It is determined that the gateway station starts from sending the downlink data in the first time sequence unit of the downlink transmission to the time range formed by the end time when the gateway station receives the uplink data sent at the common reference point. Each time corresponds to the corresponding RTT in the time range. The RTT range formed by the maximum value and the minimum value is the reference RTT range; the RTT corresponding to any time in the time range is the sum of the round-trip delay of the feeder link and the round-trip delay of the user link at that time; The round-trip delay of the feeder link is the time delay corresponding to the round-trip distance between the satellite at that moment and the gateway; the round-trip delay of the user link at this moment is the time between the satellite and the common The delay corresponding to the round-trip distance between reference points;

The reference RTT is any value in the reference RTT range.

This application also provides a method for synchronizing uplink data, which is applied to a terminal, and includes:

In the connected state or idle state, within the range of the time to be maintained in the first time sequence unit for uplink transmission of the terminal, determine the start of the downlink reception first time sequence unit corresponding to the first time sequence unit for uplink transmission of the terminal Start time; the first time sequence unit of the uplink transmission of the terminal is any time sequence unit in the uplink transmission time sequence of the terminal;

Compensate and compensate RTT on the basis of the start time of the first time sequence unit of the downlink reception of the terminal to obtain the start time of the first time sequence unit of the uplink transmission of the terminal; the latest time in the range of the time to be maintained is not Later than the obtained start time of the first time sequence unit for uplink transmission of the terminal;

The compensation RTT is the sum of the first value and the second value, or the second value;

The first value is the difference between the real RTT and the reference RTT; the reference RTT is the gateway station used to obtain the start time of the first time sequence unit for uplink reception, and the value of the start time of the first time sequence unit for downlink transmission. Delay based on the delay; the real RTT is that the gateway station starts from the gateway station sending the downlink data sent by the first time sequence unit, and until the gateway station receives the common reference point, the virtual terminal sends the first uplink data. The time delay between uplink data sent in a time sequence unit; the common reference point is a preset reference point in at least one cell covered by a satellite;

The second value is used to synchronize the time when the uplink data sent by the terminal is transmitted to the satellite at the time obtained by compensating the second value and the time when the uplink data sent by the virtual terminal is transmitted to the satellite.

Optionally, the method for determining the range of the time to be maintained includes:

Obtain a preset difference; the preset difference is the maximum value of the delay difference of all cells in the entire access network; wherein, the delay difference of any cell is the round trip from the user in the cell to the satellite The sum of the maximum value of the difference between the time delay and the round-trip delay between the virtual terminal and the satellite at the common reference point and the maximum value of the difference between the real RTT and the reference RTT in the cell;

In the case that the preset difference value is not less than 0, the difference between the number of the first time sequence unit of the downlink reception of the terminal and the number of the first time sequence unit is calculated to obtain the first number; the number of the first time sequence unit is The absolute value of the ratio between the preset difference and the duration of the time sequence unit is rounded up;

Taking the starting time of the time sequence unit indicated by the first number in the downlink receiving time sequence of the terminal as the latest time in the range of the time to be maintained;

In the case that the preset difference is less than 0, the sum of the number of the first time sequence unit of the downlink reception of the terminal and the number of the second time sequence unit is calculated to obtain the second number; The start time of the time sequence unit indicated by the second number is used as the latest time in the range of the time to be maintained; the number of the second time sequence unit is the absolute value of the ratio between the preset difference and the duration of the time sequence unit Round down to get.

Optionally, the determining the start time of the first time sequence unit for downlink reception corresponding to the first time sequence unit for uplink transmission of the terminal within the range of the time to be maintained for the first time sequence unit for uplink transmission of the terminal includes:

In the case that the preset difference value is not less than 0, determine the downlink reception time sequence unit to which the current execution time belongs, and obtain the second downlink reception time sequence unit;

Estimate the CRS delay change rate at the start time of the downlink reception of the second time sequence unit; according to the CRS time at the start time of the downlink reception of the second time sequence unit and the CRS at the start time of the downlink reception of the second time sequence unit The time delay change rate, and the first quantity, determine the start time of the first time sequence unit of downlink reception of the terminal; the first quantity is the number of the first time sequence unit of downlink reception of the terminal and the first time sequence unit of the downlink reception The difference between the numbers of the two time sequence units; the CRS delay change rate at the start time of the downlink reception of the second time sequence unit refers to: the ratio between the first time offset and the preset time slot standard length; The first time offset is the difference between the first actual difference and the standard duration of the time slot; the first actual difference is the start time of two consecutive time sequences starting from the downlink receiving the second time sequence unit The difference between.

Optionally, it also includes:

In the case that the preset difference is less than 0, acquiring the start time of the first time sequence unit for downlink reception of the terminal;

or,

In a case where the preset difference value is less than 0, determine the downlink receiving time sequence unit to which the current execution time belongs, and obtain the third downlink receiving time sequence unit;

Determine the first time sequence unit for downlink reception of the terminal according to the start time of the third time sequence unit of the downlink reception, the CRS delay change rate at the start time of the third time sequence unit of the downlink reception, and the second quantity The second number is the difference between the number of the third time sequence unit for downlink reception and the number of the first time sequence unit for downlink reception of the terminal; the start of the third time sequence unit for downlink reception The rate of change of the CRS delay at a time refers to: the ratio between the second time offset and the preset standard duration of the time slot; the second time offset is the difference between the second actual difference and the standard duration of the time slot Value; the second actual difference value is the difference between the start time of two consecutive time sequences starting from the downlink receiving the third time sequence unit.

Optionally, the step of compensating and compensating the RTT on the basis of the start time of the first time sequence unit of the terminal for downlink reception to obtain the start time of the first time sequence unit of the terminal for uplink transmission includes:

Determine the compensation RTT; the second value is the difference between the first delay and the second delay; the first delay is the round-trip delay between the satellite and the terminal; the second delay is the satellite and the The round-trip delay between the virtual terminals;

When the compensation RTT is a positive value, the time obtained by advancing the compensation RTT on the basis of the start time of the first time sequence unit of the downlink reception of the terminal is used as the first uplink transmission time sequence of the terminal The starting moment of the unit;

In the case that the compensation RTT is a negative value, the time obtained by delaying the absolute value of the compensation RTT on the basis of the start time of the first time sequence unit of the downlink reception of the terminal will be used as the uplink transmission of the terminal The start time of the first sequential unit.

Optionally, in a case where the value of the reference RTT is the real RTT, the value of the compensation RTT is the second value.

Optionally, in a case where the value of the reference RTT is the RTT at the start time of the gateway station downlink sending the first time sequence unit, the determining the compensation RTT includes:

The sum of the first product and the target difference is used as the compensation RTT; the first product is the product of the real RTT and the downlink CRS delay change rate of the terminal; the target difference is the third delay and the first Four times the delay difference; the third delay is: the ratio of the distance between the satellite and the terminal and the speed of light at the start time of the first time sequence unit when the gateway station downlinks; the fourth The time delay is: the ratio of the distance between the satellite and the virtual terminal and the speed of light at the starting time when the gateway station downlinks the first time sequence unit;

The downlink CRS delay change rate of the terminal is the CRS delay change rate at the start time of the downlink receiving time sequence unit to which the current execution time belongs.

Optionally, the calculation method of the real RTT includes:

Determine the value of the feeder link delay change rate; the feeder link delay change rate is the feeder link delay change rate at the start time of the downlink reception of the terminal in the first time sequence unit;

Determine the value of the feeder link delay corresponding to the value of the feeder link delay change rate;

According to the value of the feeder link time delay, the real RTT is estimated.

Optionally, the determining the value of the feeder link delay change rate includes:

According to the value of the CRS delay change rate at the start time of the downlink reception of the terminal in the first time sequence unit, and the user link delay change rate at the start time of the downlink reception of the terminal in the first time sequence unit Value, and the preset relationship between the delay change rate, and determine the value of the feeder link delay change rate.

Optionally, in the case that the satellite's orbit is passing through the satellite orbit directly above the gateway, the value of the feeder link delay change rate corresponding to the value of the feeder link delay is determined Values include:

According to the preset relationship between the feeder link delay change rate and the target included angle, determine the value of the target included angle corresponding to the value of the feeder link delay change rate; the target included angle is The angle between the speed of the satellite and the direction away from the gateway on the feeder link;

Determine the value of the feeder link distance corresponding to the value of the target included angle according to the preset correspondence between the target included angle and the distance of the feeder link;

The value of the feeder link delay corresponding to the value of the feeder link delay change rate is determined according to the value of the feeder link distance.

Optionally, in the case that the satellite orbit does not pass directly above the gateway, the determination of the value of the feeder link delay change rate corresponding to the value of the feeder link delay includes:

in accordance with

a _d0-F represents the feeder link delay change rate at the start time of the first time sequence unit of the downlink reception of the terminal, a _BC represents the first time sequence unit of the downlink reception of the terminal relative to the virtual gateway station The feeder link delay change rate at the starting time; the position of the virtual gateway is the midpoint of the line segment formed by the first vertical point and the second vertical point; the first vertical point and the second vertical point The two vertical points are the vertical feet obtained by drawing vertical lines from the gateway station to the first orbit plane and the second orbit plane; the first orbit plane and the second orbit plane are the farthest distances in the satellite communication system The plane where the two satellite orbits are located; AC represents the distance of the feeder link; the ratio of the distance of the feeder link to the speed of light is: the delay of the feeder link; BC represents the satellite and the virtual gateway The distance between stations.

This application also provides a device for synchronizing uplink data, which is applied to a gateway station, including:

The first determining module is configured to determine the first time sequence unit from the downlink transmission time sequence after the cell is established to obtain the first time sequence unit of downlink transmission; the first time sequence unit of downlink transmission is any time sequence in the downlink transmission time sequence unit;

An obtaining module, configured to obtain a reference RTT according to the RTT between the gateway station and a common reference point; the common reference point is a preset reference point in at least one cell covered by a satellite;

The delay module is configured to delay the time obtained by delaying the reference RTT on the basis of the start time of the first time sequence unit of the downlink transmission as the start time of the uplink reception of the first time sequence unit of the gateway station.

Optionally, the acquiring module is configured to acquire a reference RTT according to the RTT of the gateway station and the public reference point, including:

The acquiring module is specifically used for the RTT of the gateway station and the common reference point to be the real RTT, and the real RTT is the gateway station starting from the downlink sending the first time sequence unit sending the downlink data to the gateway The time delay between the station receiving the uplink data sent at the common reference point;

Use the real RTT as the reference RTT.

The acquiring module is specifically used for the RTT of the gateway station and the common reference point as the RTT corresponding to the start time of the first time sequence unit of the downlink transmission of the gateway station; the start time of the first time sequence unit of the downlink transmission The RTT corresponding to the start time is the sum of the round-trip delay of the feeder link and the round-trip delay of the user link at that moment; the round-trip delay of the feeder link at this moment is the satellite and the gateway at that moment The delay corresponding to the round-trip distance between the satellites; the round-trip delay of the user link at this moment is the delay corresponding to the round-trip distance between the satellite and the common reference point at this moment;

The acquisition module is specifically configured to determine that the gateway station starts from sending the downlink data by the first time sequence unit in the downlink to the time range constituted by the end time when the gateway station receives the uplink data sent at the common reference point, every time The RTT range formed by the maximum value and the minimum value of the RTTs corresponding to each time is obtained as the reference RTT range; the RTT corresponding to any time in the time range is the round trip delay of the feeder link and the user link at that time The sum of the round-trip delay; the round-trip delay of the feeder link at this moment is the delay corresponding to the round-trip distance between the satellite and the gateway at this moment; the round-trip delay of the user link at this moment is the The time delay corresponding to the round-trip distance between the satellite and the common reference point at the time;

The reference RTT is any value in the reference RTT range.

This application also provides a device for synchronizing uplink data, which is applied to a terminal, and includes:

The second determining module is configured to determine the downlink corresponding to the first time sequence unit of the terminal's uplink transmission within the range of the time to be maintained in the first time sequence unit of the uplink transmission of the terminal when it is in a connected state or an idle state. Receiving the start time of the first time sequence unit; the first time sequence unit of the uplink transmission of the terminal is any time sequence unit in the uplink transmission time sequence of the terminal;

The compensation module is used for compensating and compensating the RTT on the basis of the start time of the first time sequence unit of the downlink reception of the terminal to obtain the start time of the first time sequence unit of the uplink transmission of the terminal; the range of the time to be maintained The latest time, not later than the obtained starting time of the terminal's uplink transmission of the first time sequence unit;

The first value is the difference between the real RTT and the reference RTT; the reference RTT is the starting time for the gateway station to receive the first time sequence unit in the uplink, and to send the first time sequence unit in the downlink. The time delay based on the time; the real RTT is the gateway station from the downlink sending the downlink data sent by the first time sequence unit, until the gateway station receives the virtual terminal at the common reference point in the uplink transmission The time delay between uplink data sent by the first time sequence unit; the common reference point is a preset reference point in at least one cell covered by a satellite;

Optionally, the device may further include a maintenance time range determining module, configured to obtain a preset difference value; the preset difference value is the maximum value of the delay difference values of all cells in the entire access network; wherein, The delay difference of any cell is the maximum value of the difference between the round-trip delay from the user to the satellite in the cell and the round-trip delay from the virtual terminal to the satellite at the common reference point, and the difference between the real RTT in the cell and the reference RTT The sum of the maximum values;

Optionally, the second determining module is configured to determine the first time sequence unit for downlink reception corresponding to the first time sequence unit for uplink transmission of the terminal within the range of the time to be maintained in the first time sequence unit for uplink transmission of the terminal The starting moment of including:

The second determining module is specifically configured to determine the downlink receiving time sequence unit to which the current execution time belongs when the preset difference value is not less than 0, to obtain the downlink receiving second time sequence unit;

Optionally, the second determining module is further specifically configured to obtain the start time of the first time sequence unit for downlink reception of the terminal when the preset difference value is less than 0;

or,

Optionally, the compensation module is configured to compensate and compensate the RTT on the basis of the start time of the first time sequence unit of the downlink reception of the terminal to obtain the start time of the first time sequence unit of the uplink transmission of the terminal, include:

The compensation module is specifically configured to determine the compensation RTT; the second value is the difference between the first delay and the second delay; the first delay is the round-trip delay between the satellite and the terminal; The second delay is the round-trip delay between the satellite and the virtual terminal;

In the case that the compensation RTT is a negative value, the time obtained by delaying the absolute value of the compensation RTT on the basis of the start time of the first time sequence unit of the downlink reception of the terminal is used as the uplink transmission of the terminal The start time of the first sequential unit.

Optionally, in the case where the value of the reference RTT is the RTT at the start time when the gateway station downlinks the first time sequence unit, the compensation module is configured to determine the compensation RTT, including:

The compensation module is specifically configured to use the sum of the first product and the target difference value as the compensation RTT; the first product is the product of the real RTT and the downlink CRS delay change rate of the terminal; the target difference The value is twice the difference between the third time delay and the fourth time delay; the third time delay is: the distance between the satellite and the terminal at the starting time when the gateway station downlinks the first time sequence unit and The ratio of the speed of light; the fourth delay is: the ratio of the distance between the satellite and the virtual terminal at the start time of the first time sequence unit when the gateway station downlinks to the speed of light;

Optionally, the device further includes: a true RTT calculation module, configured to determine the value of the feeder link delay change rate; the feeder link delay change rate is the first time sequence unit of the downlink reception of the terminal The feeder link time delay change rate at the starting time;

Optionally, the real RTT calculation module is used to determine the value of the feeder link delay change rate, including:

The real RTT calculation module is specifically configured to determine the value of the CRS delay change rate at the start time of the first time sequence unit of the downlink reception of the terminal, and the start time of the first time sequence unit of the downlink reception of the terminal The value of the delay change rate of the downlink user link and the preset relationship of the delay change rate determine the value of the feeder link delay change rate.

Optionally, when the satellite's orbit is a satellite orbit directly above the gateway station, the true RTT calculation module is used to determine the value corresponding to the value of the feeder link delay change rate The value of the feeder link delay includes:

The real RTT calculation module is specifically configured to determine the target included angle corresponding to the value of the feeder link delay change rate according to the preset relationship between the feeder link delay change rate and the target included angle The value of; the target included angle is the included angle between the operating speed of the satellite and the direction away from the gateway on the feeder link;

Optionally, when the satellite orbit does not pass directly above the customs station, the real RTT calculation module is used to determine the feeder link time corresponding to the value of the feeder link delay change rate. The value of extension includes:

The real RTT calculation module is specifically used for the basis

In the uplink data synchronization method and device described in this application, the gateway station determines the first time sequence unit from the downlink transmission sequence after the cell is established, and obtains the reference RTT according to the RTT between the gateway station and the common reference point; The time obtained by delaying the reference RTT on the basis of the starting time of the time sequence unit is used as the starting time of the gateway station's uplink reception of the first time sequence unit;

In the connected state or idle state, within the range of the time to be maintained in the first time sequence unit of the terminal’s uplink transmission, determine the start time of the first time sequence unit of the downlink reception corresponding to the first time sequence unit of the terminal’s uplink transmission. On the basis of the start time of the first time sequence unit received in the downlink of the terminal, the compensation RTT is compensated to obtain the start time of the first time sequence unit of the uplink transmission of the terminal.

Since the latest time of the time range to be maintained is no later than the obtained starting time of the first time sequence unit of the terminal’s uplink transmission, it is time to determine the starting time of the first time sequence of the terminal’s uplink reception. The uplink data is sent at the start time of the first sequence of uplink reception.

In this application, on the one hand, both the customs station and the terminal use the virtual terminal at the common reference point as the benchmark. Specifically, the customs station uses the virtual terminal at the public reference point as the benchmark to determine the benchmark RTT. The terminal compensates the second value at the start time when the first time sequence unit is received in the downlink, and is used for the time when the uplink data sent by the terminal at the time when the second value is compensated is transmitted to the satellite, and the virtual terminal sends the first time sequence unit in the uplink. The time when the uplink data sent at the start time is transmitted to the satellite is synchronized.

In addition, the terminal can also compensate the first value based on the start time of the first time sequence unit received in the downlink. The first value is the difference between the real RTT and the reference RTT, that is, the terminal also compensates the real RTT and the gateway station for downlink transmission. The difference between the delayed reference RTTs at the start time of the first timing unit. Therefore, the time when the terminal transmits the uplink data sent to the gateway station at the determined starting time of the first time sequence unit for uplink transmission is the starting time when the gateway station receives the first time sequence unit upward.

On the other hand, the common reference point where the virtual terminal is located is the preset reference point of at least one cell of the satellite, and the gateway station receives uplink data in units of cells. Therefore, the gateway station in this application Both the virtual terminal and the terminal take the virtual terminal as the benchmark and perform corresponding operations to ensure that the uplink data received by the gateway station can be demodulated correctly.

Description of the drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only These are some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work.

FIG. 1 is a schematic diagram of the process from the gateway station sending downlink data to receiving the uplink data sent by the terminal according to an embodiment of the application;

2 is a flowchart of an uplink data synchronization method disclosed in an embodiment of the application;

FIG. 3 is a flowchart of a method for calculating a second value disclosed in an embodiment of the application;

FIG. 4 is a flowchart of another uplink data synchronization method disclosed in an embodiment of the application;

FIG. 5 is a flowchart of another uplink data synchronization method disclosed in an embodiment of the application;

6 is a schematic diagram of assisting in calculating the preset correspondence between the feeder link distance and the target angle when the satellite orbit is the satellite orbit directly above the gateway station disclosed in an embodiment of the application;

FIG. 7 is a schematic diagram of the positional relationship between a satellite orbit and the earth disclosed in an embodiment of the application;

FIG. 8 is a schematic structural diagram of an uplink data synchronization device disclosed in an embodiment of this application;

FIG. 9 is a schematic structural diagram of another uplink data synchronization device disclosed in an embodiment of the application.

Detailed ways

The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of this application.

In the existing terrestrial communication system, the time slot numbered N for the gateway station to send downlink data is the same time slot as the time slot with the same number for the gateway station to receive uplink data. In the system, due to the movement of the satellite in the orbit, the round-trip transmission delay (RTT) between the gateway station and the terminal is increased. Therefore, in the satellite communication system, the gateway station transmits downlink in the same time slot number. When the data is the same as the received uplink data, and the time slot with the same time slot number is the same time slot, the data received by the gateway cannot be demodulated correctly.

Since the gateway station receives uplink data in units of cells, in this embodiment of the application, both the gateway station and the terminal are based on the virtual terminal at the common reference point, where the common reference point is at least one of the satellites. The preset reference point of the cell. The gateway station and the terminal respectively perform the following corresponding operations: the gateway station determines the start time of the uplink reception of the first time sequence unit, the terminal determines the start time of the uplink transmission of the first time sequence unit, and the terminal sends the first time sequence unit in the uplink. The time when the uplink data sent at the starting time of the time sequence unit is transmitted to the gateway station is the starting time when the gateway station receives the first time sequence unit upstream.

Specifically, the gateway station determines the reference RTT based on the virtual terminal at the common reference point, and delays the time obtained by the reference RTT on the basis of the start time of the first time sequence unit of the downlink transmission, as the gateway station’s uplink reception time. The starting time of a sequential unit.

The terminal compensates and compensates the RTT at the start time of the downlink receiving the first time sequence unit as the start time of the terminal's uplink transmission of the first time sequence unit. Wherein, the second value is compensated on the basis of the start time of the first time sequence unit of the terminal's downlink reception, and is used for the time when the uplink data sent by the terminal at the time obtained by compensating the second value is transmitted to the satellite, and the virtual terminal is in the uplink The time when the uplink data sent at the start time of sending the first time sequence unit is transmitted to the satellite is synchronized.

In addition, the terminal can also compensate for the first value based on the start time of the first time sequence unit received in the downlink. The first value is the difference between the real RTT and the reference RTT, that is, the terminal compensates the real RTT and the gateway station for the downlink transmission of the first value. The difference between the delayed reference RTTs at the start time of a time sequence unit. Therefore, the time when the terminal transmits the uplink data sent to the gateway station at the start time of the uplink transmission of the first time sequence unit is the start time when the gateway station receives the first time sequence unit in the uplink, thereby ensuring that the gateway station receives All uplink data sent by terminals in the same cell can be demodulated correctly.

In order to facilitate the introduction of the detailed process for the terminal to determine the start time of the uplink transmission of the first time sequence unit and the detailed process of the gateway station to determine the start time of the uplink reception of the first time sequence unit in the embodiment of the present application, the embodiments of the present application use arbitrary Take a satellite as an example, and take any terminal in any cell covered by the satellite as an example for introduction.

In this embodiment, the terminal equipment and the gateway station send and receive data according to time sequence, and the time sequence is a plurality of time sequence units arranged in sequence, where the time sequence unit may be a slot (time slot) or a subframe. The sequence unit number can be expressed by natural numbers: 1, 2,..., K,...K+1; it can also be numbered according to the traditional 5G cyclic numbering method, including three levels of system frame, subframe, and time slot, and each system frame is 10ms The number range of system frames is 0～1024, a system frame contains 10 subframes, and the number range of subframes is 0-9. How many time slots a subframe contains depends on the subcarrier interval as shown in the table below, assuming that the subcarrier interval is 120KHz, The number of time slots ranges from 0 to 79. The addition and subtraction of time sequence is also in the way of cyclic numbering. For example, the time sequence N is: system frame 1023 time slot 79, then N+1 is: system frame 0 time slot 0, N-1 is system frame 1023 time slot 78, and so on .

子载波间隔Subcarrier spacing	时隙数/系统帧Number of time slots/system frame	时隙数/子帧Number of slots/subframe	时长/时隙Duration/time slot
15KHz15KHz	1010	11	1ms1ms

30KHz30KHz	2020	22	0.5ms0.5ms
60KHz60KHz	4040	44	0.25ms0.25ms
120KHz120KHz	8080	88	0.125ms0.125ms
240KHz240KHz	160160	1616	0.625ms0.625ms

Fig. 1 is a schematic diagram of the process from the gateway station sending downlink data to receiving the uplink data sent by the terminal in a satellite communication system provided by an embodiment of the application, where gNB represents the gateway station.

In the figure, (D-X, t0) indicates that the gateway station sends downlink data at the start time t0 of the X sequence in the downlink transmission sequence.

(D-X, t1) indicates that the satellite sends the downlink data at time t1 after receiving the downlink data.

(D-X, t2) indicates that the virtual terminal at the common reference point receives the downlink data at time t2.

(D-X, t3) indicates that the terminal receives the downlink data at the start time t3 of the X time sequence unit in the downlink receiving sequence.

(U-X, t4) indicates that the terminal transmits uplink data at the starting time t4 of the X time sequence unit in the uplink transmission sequence.

(U-X, t5) indicates that the virtual terminal at the common reference point transmits uplink data at the starting time t5 of the X time sequence unit in its uplink transmission sequence.

(U-X, t6) indicates that the satellite sends the uplink data at time t6.

(U-X, t7) indicates that the gateway station receives the uplink data at the starting time t7 of the X time sequence unit in the uplink receiving sequence.

From this figure, it can be seen that the downlink data sent by the gateway at t0 is transmitted to the gateway at t7 and the uplink data is transmitted to the gateway at t7. Therefore, the downlink data sent by the gateway at t0 is based on the virtual terminal, that is The round-trip transmission delay between the gateway station and the virtual terminal is taken as the round-trip transmission delay (for the convenience of description, it is called the real RTT), and the real RTT is (t7-t5)+(t2-t0).

Therefore, in the embodiment of the present application, in order to ensure accurate synchronization of the uplink data by the gateway, the embodiment of the present application provides an uplink data synchronization method. Specifically, FIG. 2 is a method for synchronizing uplink data provided in an embodiment of the application, and includes the following steps:

S201. After the cell is established, the gateway station determines the first time sequence unit from the downlink transmission time sequence to obtain the first time sequence unit for downlink transmission.

In this embodiment, the gateway station starts to maintain the uplink receiving sequence after the cell is established. Specifically, the gateway station separately maintains the corresponding uplink receiving sequence for each sequence in the downlink transmission sequence, that is, for any sequence in the downlink transmission sequence (for the convenience of description, this arbitrary sequence is referred to as the downlink transmission sequence). A time sequence unit) to determine the start time of the uplink reception of the first time sequence unit.

S202: The gateway station will delay the real RTT from the start time of the first time sequence unit sent in the downlink as the start time of the target time sequence unit.

In this step, for the gateway station in the downlink to send the downlink data sent by the first time sequence unit, it will start from sending the downlink data, and then transmit the downlink data to the virtual terminal at the common reference point, and then transmit the uplink data sent by the virtual terminal. The time delay to the gateway is called the real RTT.

Specifically, the calculation process of the real RTT may include steps M1 to M5:

M1. Acquire the start time of the first time sequence unit of downlink transmission of the gateway.

Taking Figure 1 as an example, assuming that the gateway station sends downlink data in the first time sequence unit for downlink transmission, corresponding to the gateway station in Figure 1 that sends downlink data at time t0, the starting time of the first time sequence unit for downlink transmission obtained in this step is t0.

M2. Calculate the time for the satellite to receive downlink data from the gateway based on the location of the gateway and ephemeris information. In this step, the calculated time corresponds to t1 in Figure 1.

It should be noted that from time t0 to time t1, the satellite is moving, that is, the position of the satellite is changing. That is, this step is to take into account the position change of the satellite, and calculate the time for the satellite to receive the downlink data of the gateway based on the position of the gateway and the ephemeris information. Since the ephemeris information includes the satellite's specific position on the orbit at each time, in this step, taking the position change of the satellite into account, the time for the satellite to receive the downlink data from the gateway can be calculated.

M3. According to the transmission time delay from the common reference point to the satellite, determine the time when the satellite receives the uplink data of the common reference point and sends the uplink data to the gateway.

In this step, the determined time corresponds to time t6 in FIG. 1.

In this embodiment, from time t1 to time t6, the satellite is moving, that is, the position of the satellite changes. However, the transmission delay between the common reference point and the satellite is a known quantity determined by the system, and d0 can be used. Said. Therefore, by adding 2d0 to the time t1, t6 can be obtained.

M4. Determine the time when the gateway station receives the uplink data according to the location of the gateway station and ephemeris information.

In this step, the calculated time corresponds to t7 in Figure 1.

It should be noted that the satellite is moving from t6 to t7, that is, the position of the satellite is changing, that is, this step takes the position change of the satellite into consideration, and calculates the gateway station based on the gateway station position and ephemeris information. The time when the uplink data was received. Since the ephemeris information includes the satellite's specific position on the orbit at each time, in this step, the time when the gateway receives the uplink data can be calculated.

M5. Calculate the real RTT.

In this step, the real RTT is calculated according to the real RTT=(t1-t0)+2d0+(t7-t6).

The starting time of the target time sequence unit obtained in this step is obtained by delaying the real RTT from the starting time of the gateway station's downlink transmission of the first time sequence unit. Among them, the starting time of the first time sequence unit for downlink transmission of the gateway station is known.

S203. Determine the RTT range formed by the maximum value and minimum value of the RTT corresponding to each time in the time range formed by the start time of the first time sequence unit of the gateway station and the end time of the target time sequence unit to obtain Baseline RTT range.

In this step, the RTT at any time in the time range is the sum of the round-trip delay of the feeder link and the round-trip delay of the user link at that time. Wherein, the round-trip delay of the feeder link at this moment is the delay corresponding to the round-trip distance between the satellite and the gateway at this moment. That is, the ratio of 2 times the distance between the satellite and the gateway at this moment to the speed of light. That is, assuming that the satellite is fixed at this time, the ratio of 2 times the distance between the fixed satellite and the gateway station at that time and the speed of light is used.

The round-trip delay of the user link at this time is the time delay corresponding to the round-trip distance between the satellite and the virtual terminal at the time, that is, the ratio of twice the distance between the satellite and the virtual terminal at the time and the speed of light. That is, assuming that the satellite is fixed at this time, the ratio of 2 times the distance between the fixed satellite and the virtual terminal at the time and the speed of light is used.

In this step, when the ephemeris information is known, the distance between the satellite and the gateway at any time in the time range can be calculated. Therefore, the round-trip delay of the feeder link at this time can be calculated. At the same time, the distance between the satellite and the virtual terminal at this moment is known, so the round-trip delay of the user link at this moment can be calculated. Therefore, the gateway can obtain the reference RTT range in this step.

S204. The gateway station delays the time obtained by the reference RTT on the basis of the start time of the first time sequence unit sent in the downlink, as the start time of the first time sequence unit received in the uplink.

In this step, the reference RTT is any value in the reference RTT range. That is, the gateway station randomly selects a value from the reference RTT range as the reference RTT. And delay the reference RTT on the basis of the start time of the first time sequence unit to obtain the delayed time. In this embodiment, the delayed time is used as the start of the first time sequence unit in the uplink receiving time sequence of the gateway. Time, for the convenience of description, the first time sequence unit in the uplink receiving time sequence is referred to as the first uplink receiving time sequence unit.

S205. When the terminal is in a connected state or an idle state, within the range of the time to be maintained in the first time sequence unit of the terminal's uplink transmission, determine the start of the first time sequence unit of the downlink reception corresponding to the first time sequence unit of the terminal's uplink transmission. time.

In this embodiment, the latest time of the time range to be maintained is not later than the start time of the first time sequence unit of the terminal's uplink transmission determined in this step, so that the start time of the first time sequence unit of the terminal's uplink transmission is determined After the start time, there is time to send the uplink data at the start time of the terminal's uplink transmission of the first time sequence unit.

Optionally, in this embodiment, the terminal determining the range of the time to be maintained at the start time of the uplink transmission of the first time sequence unit may include the following steps A1 to A5:

A1. Get the preset difference.

In this step, the preset difference is the maximum value among the delay differences of all cells in the entire access network; wherein, the delay difference of any cell is the sum of the round-trip delay from the user to the satellite in the cell. The sum of the maximum value of the virtual terminal-to-satellite round trip delay difference at the common reference point and the maximum value of the difference between the real RTT and the reference RTT in the cell. The preset difference is configured in the terminal in advance. For the convenience of description, Tmax is used to represent the preset difference.

A2. Determine whether the preset difference is not less than 0, if yes, then execute A3, if not, execute A4.

A3. Calculate the difference between the number of the first time sequence unit of the downlink reception of the terminal and the number of the first time sequence unit to obtain the first number, and use the start time of the time sequence unit indicated by the first number in the downlink reception time sequence of the terminal as the waiting time. The latest time in the maintenance time range.

If the preset difference is not less than 0, perform this step. In this step, the first number of time series units is obtained by rounding up the absolute value of the ratio between the preset difference and the duration of the time series unit. For the convenience of description, the number of the first time sequence unit is represented by M. Specifically, in this step,

Among them, Tslot is the duration of a sequential unit.

In this step, it is assumed that the first time sequence unit of the terminal’s uplink transmission is the terminal’s uplink transmission time sequence X. In this step, the number of the first time sequence unit of the terminal’s downlink reception is X. Therefore, the first time sequence of the terminal’s downlink reception is X. The difference between the number of the unit and the number of the first sequential unit is XM. The starting time of the downlink receiving time sequence X-M of the terminal is taken as the latest time of the time range to be maintained, that is, the terminal estimates the compensation RTT of the uplink time sequence X at least before the downlink receiving time sequence X-M.

A4. Calculate the sum of the number of the first time sequence unit for the downlink reception of the terminal and the number of the second time sequence unit to obtain the second number; use the start time of the time sequence unit indicated by the second number in the downlink reception time sequence of the terminal as the time to be maintained The latest moment of the range.

If the preset difference is less than 0, perform this step. Specifically, in this step, the second sequential unit quantity is obtained by rounding down the absolute value of the ratio between the preset difference and the duration of the sequential unit; for the convenience of description, the second sequential unit quantity is represented by M1, specifically Yes, in this step,

Among them, Tslot is the duration of a sequential unit.

It is also taken as an example that the number of the first time sequence unit of the downlink reception of the terminal is X. In this step, the second number is X+M1. The starting time of the downlink receiving sequence X+M1 of the terminal is taken as the latest time of the time range to be maintained. That is, the terminal needs to estimate the compensation RTT of the uplink timing X at least before the downlink receiving timing X+M1.

Optionally, determining the start time of the first time sequence unit for downlink reception of the terminal may include the following two situations:

Case 1: For the case where the preset difference value is not less than 0: the method of determining the start time of the first sequence of downlink reception of the terminal includes the following steps B1 to B3:

B1. Determine the downlink receiving time sequence unit to which the current execution time belongs, and obtain the second downlink receiving time sequence unit.

In this step, for the convenience of description, the downlink receiving time sequence unit to which the current execution time belongs is referred to as the second downlink receiving time sequence unit.

B2. Estimate the rate of change of the CRS delay at the start time of the downlink reception of the second timing unit.

In this step, the rate of change of the CRS delay at the start time of the downlink reception of the second timing unit refers to the ratio between the first time offset and the preset standard time length of the time slot, where the first time offset is the first time offset. A difference between the actual difference and the standard duration of the time slot, where the first actual difference is the difference between the start time of two consecutive time sequences starting from the downlink receiving the second time sequence unit.

Assume that the second time sequence unit of downlink reception is the downlink reception time sequence X-N of the middle terminal. In this step, the CRS delay change rate at the start time of the terminal's downlink reception timing X-N is estimated.

B3. Determine the start time of the first time sequence unit for downlink reception of the terminal according to the start time of the downlink reception of the second time sequence unit, the CRS delay change rate at the start time of the downlink reception second time sequence unit, and the first quantity .

In this step, the first number is the difference between the number of the first time sequence unit for downlink reception of the terminal and the number of the second time sequence unit for downlink reception of the terminal.

Taking the first time sequence unit of the downlink reception of the terminal as the downlink reception time sequence X of the terminal as an example, in this step, the first number is N. In this step, the starting time of the downlink receiving time sequence X of the terminal=the starting time of the downlink receiving time sequence XN of the terminal+N*Tslot*(1+a _CRS ). Among them, a _CRS represents the CRS time delay change rate at the start time of the terminal's downlink reception time sequence XN. N represents the first number.

Case 2: For the case where the preset difference value is less than 0: the method for determining the start time of the first sequence of downlink reception of the terminal may include two:

Manner 1: The start time of the first time sequence unit of the downlink reception of the terminal is directly obtained.

Method 2: You can go through the following steps C1 to C2:

C1. Determine the downlink receiving time sequence unit to which the current execution time belongs, and obtain the third downlink receiving time sequence unit.

In this step, for the convenience of description, the downlink receiving time sequence unit to which the current execution time belongs is referred to as the third downlink receiving time sequence unit.

C2, according to the start time of the third time sequence unit of downlink reception, the CRS delay change rate at the start time of the third time sequence unit of downlink reception, and the second quantity, determine the start time of the terminal's downlink reception of the first time sequence unit .

In this step, the rate of change of the CRS delay at the start time of the downlink reception of the third timing unit refers to the ratio between the second time offset and the preset standard time slot length, where the second time offset is the first 2. The difference between the actual difference and the standard duration of the time slot, where the second actual difference is the difference between the start time of two consecutive time sequences starting from the downlink receiving the third time sequence unit.

The second number is the difference between the number of the third time sequence unit for downlink reception and the number of the first time sequence unit for downlink reception of the terminal.

Assuming that the third time sequence unit of downlink reception is the downlink reception time sequence X+N of the terminal, and the first downlink reception time sequence of the terminal is the downlink reception time sequence X of the terminal, the second number is N in this step. In this step, the start time of the first time sequence unit of the downlink reception of the terminal=the start time of the downlink reception time sequence X+N-N*Tslot*(1+a _CRS ). Among them, a _CRS represents the CRS delay change rate at the start time of the downlink receiving time sequence X+N, and N represents the second number.

S206. Compensate the compensation RTT based on the start time of the first time sequence unit of the downlink reception of the terminal, where the compensation RTT is the sum of the first value and the second value, or the second value, and the uplink transmission of the terminal is obtained after compensation. The start time of the first sequential unit.

In this step, the first time sequence unit of uplink transmission of the terminal is the same as the number corresponding to the first time sequence unit of downlink transmission of the gateway station in S201, but the corresponding start time is different.

The second value is compensated on the basis of the start time of the first time sequence unit of the terminal's downlink reception. The second value is used for the terminal to send the uplink data to the satellite at the time when the second value is compensated. The time when the uplink data sent at the start time of the time sequence unit is transmitted to the satellite is synchronized.

Taking Fig. 1 as an example, the start time of the first time sequence unit of the downlink reception of the terminal is t3, the start time of the first time sequence unit of the virtual terminal’s downlink reception is t2, and the start time of the first time sequence unit of the virtual terminal’s uplink transmission Time is t5, and t5 is equal to t2.

In this step, the second value is compensated on the basis of time t3 for the time when the uplink data sent by the terminal at the time when the second value is compensated at time t3 is transmitted to the satellite, and the uplink data sent by the virtual terminal at time t5 The time of transmission to the satellite is synchronized, that is, the time when the uplink data is transmitted to the satellite is t6.

The first value is the difference between the real RTT and the reference RTT, that is, the first value is compensated at the start time of the terminal's downlink reception of the first timing unit, which compensates for the real RTT and the gateway station's start of the first timing unit of the downlink transmission. The difference between the reference RTTs delayed at the start time. Therefore, the terminal compensates the RTT based on the start time of the first time sequence unit received in the downlink, and obtains the start time of the first time sequence unit for uplink transmission, so that the terminal sends the uplink data sent at the start time of the first time sequence unit in the uplink. The time of transmission to the gateway is the starting time of the first time sequence unit for uplink reception of the gateway.

Optionally, after determining the start time of the first time sequence unit for downlink reception, the terminal obtains the first time sequence unit for uplink transmission of the terminal by compensating for the RTT based on the start time of the first time sequence unit for downlink reception of the terminal The process at the start time of, may include step D1 to step D2:

D1. The terminal determines the compensation RTT.

In this embodiment, if it is necessary to advance the start time of the first time sequence unit of the downlink reception of the terminal by a period of time, this embodiment may use a positive value of the period to indicate that the period is advanced. On the contrary, if it is necessary to delay a period of time from the start time of the first time sequence unit of the downlink reception of the terminal, the negative value of the period may be used in this embodiment to indicate the delay of the period.

Of course, in practice, a negative value can also be used to indicate advance, and a positive value to indicate delay. This embodiment does not limit the specific manner. In the embodiment of the present application, a positive value is used to indicate advance, and a negative value is used to indicate delay as an example.

Specifically, the compensation RTT is the sum of the first value and the second value, where the first value is the difference between the real RTT and the reference RTT. The specific calculation formula of the compensation RTT is shown in the following formula (1):

Compensation RTT = real RTT-reference RTT + second value (1)

In the formula, the real RTT is the time delay between the gateway station sending the downlink data in the first time sequence unit from the downlink to the gateway station receiving the uplink data sent by the virtual terminal in the uplink sending the first time sequence unit. The reference RTT is a time delay used by the gateway station to determine the start time of the uplink reception of the first time sequence unit, and a delay based on the start time of the downlink transmission of the first time sequence unit.

The second value is the difference between the first delay and the second delay. Among them, the first delay is the round-trip delay between the satellite and the terminal. The second delay is the round-trip delay between the satellite and the virtual terminal. Taking Fig. 1 as an example, suppose that the first time sequence unit of the downstream transmission of the gateway station in this embodiment is: X time sequence in the downlink transmission sequence of the gateway station in Fig. 1, then the first time delay is (t3-t1)+(t6- t4), the second time delay is (t2-t1)+(t6-t5).

Specifically, for the reference RTT in formula (1), the terminal and the customs station have agreed in advance. Therefore, the terminal can obtain the reference RTT through the communication protocol.

The terminal's method for obtaining the real RTT in the above formula (1) may include:

The first type: In the case that the terminal can obtain the position of the customs station, the terminal can calculate the real RTT according to the position of the customs station, the ephemeris information of the satellite and the position of the virtual terminal. The specific calculation process is the existing technology , I won’t repeat it here.

The second type: the gateway station broadcasts the GPS time to the terminal, and the terminal calculates the real RTT according to the GPS time and the time when the virtual terminal receives the downlink data. The specific calculation process is based on the existing technology and will not be repeated here.

The third is that when the gateway station broadcasts the real RTT to the terminal by broadcasting, the terminal directly obtains the real RTT.

The calculation process of the second value in formula (1) is introduced in the embodiment corresponding to FIG. 3 below.

D2. According to the compensation RTT, the terminal determines the start time of the terminal's uplink transmission of the first time sequence unit.

In this embodiment, if the value of the compensation RTT is a negative value, the time obtained by delaying the absolute value of the compensation RTT on the basis of the start time of the terminal's downlink reception of the first time sequence unit will be used as the terminal's uplink transmission time. The starting time of a sequential unit.

If the value of the compensation RTT is a positive value, the time obtained by compensating the RTT in advance on the basis of the start time of the first time sequence unit of the terminal's downlink reception is used as the start time of the first time sequence unit of the terminal's uplink transmission.

It should be noted that when the value of the compensation RTT is a positive value, since the time obtained by compensating for the RTT in advance on the basis of the start time of the first time sequence unit of the terminal's downlink reception, it will be regarded as the first uplink transmission time of the terminal. The start time of the time sequence unit. Therefore, the start time of the first time sequence unit of the terminal's uplink transmission is before the start time of the first time sequence of the terminal's downlink reception. Therefore, in this case, the terminal needs to send the first time sequence in the uplink first. The uplink data is sent in a time sequence, and then the downlink data is received in the downlink receiving the first time sequence unit.

FIG. 3 is a method for calculating a second value provided by an embodiment of the application, including the following steps:

S301: According to the time when the terminal receives the downlink data and the distance between the satellite and the terminal, determine the time when the satellite sends the downlink data to the terminal.

The downlink data in this step is the downlink data sent by the gateway station at the beginning of the downlink sending of the first time sequence unit.

Taking FIG. 1 as an example (the X sequence in FIG. 1 is the first sequence unit of downlink transmission of the gateway station in this embodiment), the time when the terminal receives the downlink data sent by the gateway station is time t3. The ratio of the distance between the satellite and the terminal to the speed of light is the delay required for the downlink data sent by the satellite to be transmitted to the terminal. According to the time t3 and the delay time, the time t1 at which the satellite sends the downlink data to the terminal can be determined.

S302: According to the time when the satellite sends the downlink data, the ephemeris information, and the position of the terminal, determine the distance between the position when the satellite sends the downlink data to the terminal and the terminal to obtain the first distance.

In this step, according to the time when the satellite sends the downlink data and the ephemeris information, the position of the satellite when the downlink data is sent can be obtained. According to the position when the satellite sends the downlink data and the position of the terminal, the distance between the satellite and the terminal when the downlink data is sent can be obtained. For the convenience of description, the obtained distance is called the first distance.

Taking Fig. 1 as an example, according to time t1 and ephemeris information, the position of the satellite at time t1 can be obtained, and further, the distance between the satellite and the terminal at time t1 can be obtained.

S303: According to the time when the satellite sends the downlink data and the distance between the satellite and the virtual terminal, determine the time when the virtual terminal receives the downlink data.

Taking Fig. 1 as an example, the time when the satellite sends the downlink data is time t1. When the satellite is determined, the distance between the satellite and the virtual terminal is a constant. Therefore, the transmission delay from time t1 to time t2 can be determined . According to time t1 and the time delay, time t2 can be obtained.

S304: Determine the time when the satellite receives the uplink data sent by the virtual terminal according to the time when the virtual terminal receives the downlink data and the distance between the satellite and the virtual terminal.

Since the time when the virtual terminal sends the uplink data is equal to the time when the virtual terminal receives the downlink data, in this step, the time when the virtual terminal sends the uplink data can be obtained. In addition, when the satellite is fixed, the distance between the satellite and the virtual terminal is constant. Therefore, the transmission delay of the uplink data sent by the virtual terminal to the satellite is the ratio of this constant to the speed of light. Furthermore, it can be obtained that the satellite receives the virtual terminal. The time when the uplink data was sent.

Taking Fig. 1 as an example, in this step, the time t5 when the virtual terminal sends uplink data to the satellite is equal to t2. Since the distance between the virtual terminal and the satellite is a constant when the satellite is fixed, the delay required for uplink data transmission from the virtual terminal to the satellite can be calculated, and the delay is delayed on the basis of t5. Obtain the time t6 when the satellite receives the uplink data.

S305: Determine the distance between the satellite and the terminal when the uplink data sent by the virtual terminal is received according to the time when the satellite receives the uplink data sent by the virtual terminal, the ephemeris information, and the position of the terminal, to obtain the second distance.

The time when the satellite receives the uplink data sent by the virtual terminal and the ephemeris information can determine the position of the satellite at the time when the uplink data sent by the virtual terminal is received. According to the position of the satellite and the position of the terminal, the distance between the satellite and the terminal can be obtained. For the convenience of description, it is called the second distance.

Taking Figure 1 as an example, the time when the satellite receives the uplink data is t6. Based on the ephemeris information, the position of the satellite at time t6 can be calculated. According to the position of the terminal and the position of the satellite at time t6, the distance between the satellite and the terminal at time t6 can be calculated. For the convenience of description, the distance calculated in this step is called the second distance.

S306. Use the sum of the delays corresponding to the first distance and the second distance as the first delay.

The sum of the ratios of the first distance and the second distance to the speed of light is the first time delay.

S307: Determine the second time delay according to the distance between the satellite and the virtual terminal.

Specifically, the second time delay is the ratio of twice the distance between the satellite and the virtual terminal and the speed of light.

S308. Use the difference between the first delay and the second delay as the second value.

Figure 4 is another method for synchronizing uplink data provided by an embodiment of the application. In this embodiment, the gateway station uses the real RTT as the reference RTT, and the terminal determines the compensation RTT to realize the uplink data based on the reference RTT being the real RTT. The synchronization includes the following steps:

S401: After the cell is established, the gateway station determines the first time sequence unit from the downlink transmission time sequence.

S402. The gateway station uses the real RTT as the reference RTT.

In this step, the meaning of the real RTT and the process by which the gateway station determines the real RTT can refer to the above S202, which will not be repeated here.

S403. The gateway station will delay the reference RTT on the basis of the start time of the first time sequence unit sent in the downlink as the start time of the first time sequence unit received in the uplink.

In this step, the gateway station delays the real RTT based on the start time of the first time sequence unit sent in the downlink, and uses the delayed time as the start time of the first time sequence unit received in the uplink.

S404: When the terminal is in the connected state or idle state, within the range of the time to be maintained in the first time sequence unit of the terminal's uplink transmission, determine the start of the first time sequence unit of the downlink reception corresponding to the first time sequence unit of the terminal's uplink transmission. time.

In this step, the meaning of the time range to be maintained, the determination method, and the determination method of the start time of the downlink receiving first time sequence unit can all refer to S205, which will not be repeated here.

S405. The terminal determines the compensation RTT.

In this step, the terminal can obtain the information that the value of the reference RTT is the real RTT through the protocol. Therefore, in this step, the terminal only needs to determine the value of the second value to obtain the compensated RTT. Specifically, the process for the terminal to determine the second value can refer to S301 to S308, which will not be repeated here.

S406: The terminal determines the start time of the terminal's uplink transmission of the first time sequence unit according to the compensation RTT.

Specifically, in this step, the terminal determines the starting time of the terminal's uplink transmission of the first time sequence unit according to the compensation RTT in this step. For a specific implementation manner, refer to step D2, which will not be repeated here.

Fig. 5 is another method for synchronizing uplink data provided by an embodiment of this application. In this embodiment, the RTT at the start time of the first time sequence unit in the downlink transmission sequence of the gateway is the reference RTT, and the terminal is at the reference RTT. On the basis of determining the compensation RTT to realize the synchronization of uplink data, it specifically includes the following steps:

S501: After the cell is established, the gateway station determines the first time sequence unit from the downlink data transmission time sequence.

S502: The gateway station uses the RTT corresponding to the start time of the downlink transmission of the first time sequence unit as a reference RTT.

Specifically, the RTT corresponding to the start time of the downlink transmission of the first time sequence unit represents the sum of the feeder link round-trip delay and the user link round-trip delay at the start time of the downlink transmission of the first time sequence unit. That is, assuming that the satellite is fixed at the starting time of the first time sequence unit of the downlink transmission of the gateway, the sum of the round-trip delay of the feeder link and the round-trip delay of the user link.

Taking Fig. 1 as an example, assuming that the start time of the first time sequence unit of downlink transmission corresponds to time t0 in Fig. 1, then the RTT corresponding to the start time of the first time sequence unit of downlink transmission is the sum of the first ratio and the second ratio. Among them, the first ratio is the ratio of the round-trip distance between the satellite and the gateway to the speed of light at time t0, and the second ratio is the ratio of the round-trip distance between the satellite and the virtual terminal and the speed of light at time t0.

S503. The gateway station will delay the reference RTT on the basis of the start time of the first time sequence unit sent in the downlink as the start time of the first time sequence unit received in the uplink.

In this step, the gateway station delays the reference RTT based on the start time of the first time sequence unit of the downlink transmission, and the reference RTT is the RTT corresponding to the start time of the first time sequence unit of the downlink transmission, and delays the obtained time , As the starting time of the first time sequence unit for uplink reception.

S504. When the terminal is in the connected state or idle state, within the range of the time to be maintained in the first time sequence unit of the terminal's uplink transmission, determine the start of the downlink reception first time sequence unit corresponding to the first time sequence unit of the terminal's uplink transmission time.

In this step, the meaning and determination method of the time range to be maintained for the first time sequence unit of the terminal for uplink transmission, and the method for determining the start time of the first time sequence for the downlink reception of the terminal, can refer to S205, which will not be repeated here.

S505: The terminal determines the compensation RTT.

In this step, the method for the terminal to determine the compensation RTT includes the following:

The first way:

Refer to the way of calculating the compensation RTT in step D1, which will not be repeated here.

The second way:

Derive according to formula (1) and calculate the compensation RTT, including:

The calculation formula of the compensation RTT is as follows (1):

Compensation RTT = real RTT-base RTT + second value (1)

Taking Fig. 1 as an example, the real RTT in formula (1) is shown in the following formula (2), and the reference RTT is shown in the following formula (3).

Real RTT=d0_F_t1+d0_F_t6+2d0 (2)

Benchmark RTT=2d0_F_t0+2d0 (3)

In the formula, d0-F-t1 represents the ratio of the distance between the satellite and the gateway at t1 to the speed of light, and the delay required for the downlink data sent by the gateway to be transmitted to the satellite, d0-F-t6 represents the time at t6 The ratio of the distance between the satellite and the gateway to the speed of light represents the time delay for the uplink data sent by the satellite at time t6 to be transmitted to the gateway.

2d0_F_t0 represents the round-trip delay between the satellite and the gateway at time t0, and 2d0 represents the round-trip delay between the satellite and the virtual terminal.

The calculation formula of the second value is shown in the following formula (4):

The second value = d1_t1+d1_t6-d0_t1-d0_t6 (4)

In the formula, d1_t1 represents the ratio of the distance between the satellite and the terminal to the speed of light at t1, and the delay of the downlink data sent by the satellite at time t1 to the terminal, and d1_t6 represents the ratio of the distance between the satellite and the terminal at t6 to the speed of light. Indicates the time delay for the uplink data sent by the terminal to be transmitted from the terminal to the satellite. d0_t1 represents the ratio of the distance between the satellite and the virtual terminal at time t1 to the speed of light, and represents the time delay for the downlink data sent by the satellite to arrive at the virtual terminal at time t1. d0_t6 represents the ratio of the distance between the satellite and the virtual terminal to the speed of light at time t6, that is, the delay of uplink data transmission from the virtual terminal to the satellite.

The exact value of the difference between the first time delay and the second time delay given in the above formula (4). In this embodiment, in order to facilitate the calculation of the real RTT, in this step, the second value is transformed into the following formula (5):

The second value = d1_t1+d1_t6-d0_t1-d0_t6-2(d1_t0-d0_t0)+2(d1_t0-d0_t0)(5)

In the formula, 2(d1_t0-d0_t0) represents the difference between the round-trip delay between the satellite and the terminal at time t0 and the round-trip delay between the satellite and the virtual terminal at time t0. For the convenience of description, this implementation For example, 2 (d1_t0-d0_t0) is called the target difference, d1_t0 is called the third time delay, and d0_t0 is called the fourth time delay.

Since d0_t1, d0_t6 and d0_t0 are all d0, the above formula (5) is simplified to the following formula (6):

The second value = d1_t1+d1_t6-2d1_t0+2(d1_t0-d0_t0) (6)

According to the above formulas (1), (2), (3) and (6), the following formula (7) can be obtained:

In the formula, a _d0-F represents the feeder link delay change rate, a _d1 represents the user link delay change rate, and a _CRS represents the terminal's downlink CRS delay change rate, that is, the downlink reception timing unit to which the current execution time belongs The rate of change of the CRS delay at the start time of.

In this embodiment, for the convenience of description, the real RTT*a _{CRS is} called the first product. Since 2 (d1_t0-d0_t0) represents the target difference, the compensation RTT is the sum of the first product and the target difference.

In this embodiment, the terminal obtains a _CRS through measurement. Specifically, the downlink CRS delay change rate of the terminal refers to the ratio between the time offset and the preset standard duration of the time slot (the duration of the preset timing unit), where , The time offset is the difference between the actual difference and the standard duration of the time slot, and the actual difference is the difference between the start time of two consecutive time sequences starting from the downlink receiving time sequence unit to which the current execution time belongs.

It should be noted that when the latest time in the time range to be maintained is before the start time of the terminal's uplink transmission of the first time sequence unit, in this step, the actual difference is calculated at the time when the terminal's uplink transmission is the first time. Before the start time of the time sequence unit, the meaning and determination method of the range of the time to be maintained for the first time sequence unit in the uplink of the terminal can refer to S205.

In formula (7), d0_t0 represents the ratio of the distance between the satellite and the virtual terminal to the speed of light, which is a constant when the satellite is determined.

In this embodiment, if the terminal can obtain the real RTT, based on the measured a _CRS and formula (7), the real RTT*a _CRS can be calculated, and therefore, the compensated RTT can be calculated.

In this embodiment, if the terminal does not obtain the real RTT, the terminal can calculate the real RTT in the following two ways:

The first type: the median value of the two end points of the preset RTT range is taken as the value of the real RTT. Wherein, in this embodiment, the preset RTT range may be a well-known RTT range. Specifically, it can be (20ms-35ms), the endpoints of the preset reference RTT range are 20ms and 35ms, respectively, and the real RTT is 27.5ms. The accuracy of the real RTT result calculated in this way is low.

In order to improve the accuracy of estimating the real RTT, the specific estimation method of the real RTT is the second method: including the following steps F1 to F3:

F1. According to the value of the CRS delay change rate in the first time sequence unit of the terminal's downlink reception, the value of the user link delay change rate at the start time of the terminal's downlink reception in the first time sequence unit, and the preset time The delay change rate relationship determines the value of the feeder link delay change rate at the start time of the terminal's downlink reception of the first time sequence unit.

In this embodiment, the preset delay change rate relationship is the relationship between the feeder link delay change rate, the user link delay change rate, and the downlink CRC delay change rate, that is, a _CRS = a _d0-F +a _d1 .

Among them, a _d1 can be calculated from the position of the terminal and the ephemeris information. The specific calculation formula is shown in the following formula (8):

In the formula, v represents the speed of satellite movement, c represents the speed of light, and β is the angle between v and the user link (the direction away from the terminal in the connection between the satellite and the terminal). In this embodiment, β is the angle between v and the user link (direction away from the terminal) at the start time of the first time sequence unit of the downlink reception of the terminal.

In this step, after determining a _d1 and a _CRS _{, a d0-F} can be calculated.

F2. Determine the value of the feeder link delay corresponding to the value of the feeder link delay change rate according to the value of the feeder link delay change rate.

The first case: in the case that the satellite orbit is the satellite orbit directly above the gateway, the method of determining the value of the feeder link delay change rate corresponding to the value of the feeder link delay includes: Determine the target included angle θ corresponding to the value of the feeder link delay rate of change according to the following formula (9); then determine the feeder based on the preset correspondence between the target included angle θ and the value of the feeder link distance The value of the feeder link distance corresponding to the link delay change rate; then the feeder link delay is determined by the value of the feeder link distance.

In the formula, v represents the speed of satellite movement, c represents the speed of light, and θ is the angle between v and the feeder link (away from the gateway). In this embodiment, θ is the angle between v and the feeder link (direction away from the gateway) at the starting time of the first time sequence unit when the terminal downlinks.

Among them, the preset corresponding relationship between the target included angle θ and the value of the feeder link distance can be calculated with reference to Figure 6 below. In Figure 6, OP represents the distance of the feeder link, QL is the radius of the earth, LP is the height of the satellite from the sea level, β=|90-θ|, in the triangle OQP, according to QP, QO and β, the feed can be obtained The relationship between link distance OP and θ.

According to the relationship between the feeder link distance OP and θ, and the θ calculated by formula (9), the value of the feeder link distance can be calculated. Since the ratio of the distance of the feeder link to the speed of light is the feeder link delay, the feeder link delay in this case can be calculated.

The second case: when the satellite orbit is not passing through the satellite orbit directly above the gateway, the preset correspondence between the feeder link delay change rate and the feeder link distance is as shown in the following formula (10) Show:

In the formula, a _d0-F represents the feeder link delay change rate at the start time of the first time sequence unit of the terminal's downlink reception, that is, the feeder link delay change rate is calculated in step F1. a _BC represents the feeder link delay change rate at the start time of the first time sequence unit of the terminal's downlink reception relative to the virtual gateway.

AC represents the distance of the feeder link, and AC represents the product of the feeder link delay (d0-F) and the speed of light. BC represents the distance between the satellite and the virtual gateway. The position of the virtual gateway station may be the midpoint of the line segment formed by the first vertical point and the second vertical point; among them, the first vertical point and the second vertical point are from the gateway station to the first track plane and the second vertical point. The vertical feet are obtained from the orbit plane as the vertical line; the first orbit plane and the second orbit plane are the planes where the two satellite orbits with the farthest distance in the satellite communication system are located. Of course, in practice, the location of the virtual gateway station can also be other locations. This embodiment only provides a form of the location of the virtual gateway station, and this embodiment does not limit the specific form of the location of the virtual gateway station. .

In the second case, according to the feeder link delay change rate at the start time of the first time sequence unit of the terminal's downlink reception, the specific process of determining the feeder link distance is as follows (take Figure 7 as an example for illustration ):

In Figure 7, the actual orbit of the satellite is satellite orbit 2 in Figure 7. Assume that the position of the virtual gateway is B in Figure 7, the actual gateway is A in Figure 7, and the satellite orbit 1 is the actual signal. The satellite orbit directly above the station, the feeder link is AC.

Specifically, first, triangle ABC is a right-angled triangle. Therefore, AC can be calculated by AB and BC, where AB is the distance between the actual gateway station and the virtual gateway station. When point B is determined, it can be calculated. AB. The calculation method of BC includes: In the triangular AOB, the included angle AOB is the included angle between satellite orbit 1 and satellite orbit 2, OA is the radius of the earth, and the included angle ABO is a right angle. Therefore, BO can be calculated. Since BE=Earth radius+Satellite height-BO, BE can be calculated.

Refer to Figure 6 to determine the preset corresponding relationship between the target included angle θ and the distance of the feeder link. Regarding BO as QL and BE as LP, the feeder chain of the terminal relative to the virtual gateway can be obtained. The relationship between the road distance BC and the target angle θ. Since the included angle ABC is a right angle, the relationship between AC and θ can be obtained.

Since the _{relationship between a BC} and θ is

Therefore, the relationship between _{BC and a BC can be obtained.} Because of

Therefore, the _{relationship between a d0-F} and θ can be obtained, and then the corresponding relationship between _{a d0-F and AC can be obtained.} Therefore, the feeder link distance corresponding to the value of the feeder link delay change rate can be obtained. Wherein, the ratio of the distance of the feeder link to the speed of light is the feeder link delay. Therefore, the value of the feeder link delay corresponding to the value of the rate of change of the feeder link delay can be obtained.

F3. Estimate the real RTT based on the value of the feeder link delay.

Since the real RTT≈2(d0-F+d0), when the satellite is determined, d0-F represents the delay of the feeder link, and d0 represents the ratio of the distance between the satellite and the virtual terminal to the speed of light. Therefore, the satellite is determined In the case of d0, the value of d0 can be calculated. Also, since d0-F has been calculated, the value of the real RTT can be obtained, and the real RTT obtained in this step is an estimated value.

S506: The terminal determines the start time of the terminal's uplink transmission of the first time sequence unit according to the compensation RTT.

For the specific implementation of this step, refer to S407, which will not be repeated here.

From the embodiments corresponding to Figures 2, 4, and 5, the way the gateway station obtains the reference RTT can be obtained. The gateway station obtains the reference RTT according to the RTT between the gateway station and the public reference point, where the public reference point is A preset reference point in at least one cell covered by the satellite.

FIG. 8 is an uplink data synchronization device provided by an embodiment of the application, which is applied to a gateway, and includes: a first determination module 801, an acquisition module 802, and a delay module 803. among them,

The first determining module 801 is configured to determine the first time sequence unit from the downlink transmission time sequence after the cell is established to obtain the first time sequence unit for downlink transmission; the first time sequence unit for downlink transmission is any time sequence unit in the downlink transmission time sequence;

The obtaining module 802 is configured to obtain a reference RTT according to the RTT between the gateway station and a common reference point; the common reference point is a preset reference point in at least one cell covered by the satellite;

The delay module 803 is configured to delay the time obtained by delaying the reference RTT on the basis of the start time of the first time sequence unit of the downlink transmission as the start time of the uplink reception of the first time sequence unit of the gateway station.

Optionally, the obtaining module 802 is configured to obtain the reference RTT according to the RTT of the gateway station and the public reference point, including:

Obtaining module 802, the RTT specifically used for the gateway station and the public reference point is the real RTT, and the real RTT is the gateway station starting from the downlink sending the first time sequence unit to send the downlink data to the gateway station receiving the public reference point. Delay between uplink data; based on real RTT.

The acquiring module 802 is specifically used for the RTT of the gateway station and the common reference point as the RTT corresponding to the starting time of the gateway station’s downlink transmission of the first time sequence unit; the RTT corresponding to the starting time of the downlink transmission first time sequence unit is this The sum of the round-trip delay of the feeder link and the round-trip delay of the user link at the moment; the round-trip delay of the feeder link at this moment is the time corresponding to the round-trip distance between the satellite and the gateway at that moment Delay; the round-trip delay of the user link at this moment is the time delay corresponding to the round-trip distance between the satellite and the common reference point at this moment; corresponds to the starting time of the first timing unit of the downlink transmission of the gateway station RTT is the reference RTT.

The acquiring module 802 is specifically configured to determine that the gateway station starts from sending the downlink data by the first time sequence unit of the downlink to the time range formed by the gateway station receiving the uplink data sent at the common reference point, and each time corresponds to The RTT range formed by the maximum value and the minimum value in the RTT obtains the reference RTT range; the RTT corresponding to any time in the time range is the sum of the round-trip delay of the feeder link and the round-trip delay of the user link at that time; The round-trip delay of the feeder link at the time is the delay corresponding to the round-trip distance between the satellite and the gateway at that time; the round-trip delay of the user link at the time is the time between the satellite and the common reference point at that time The time delay corresponding to the round-trip distance; the reference RTT is any value in the reference RTT range.

FIG. 9 is an uplink data synchronization device provided by this application, which is applied to a terminal and includes: a second determining module 901 and a compensation module 902. among them,

The second determining module 901 is configured to determine the downlink receiving first corresponding to the first time sequence unit of the terminal’s uplink transmission within the range of the time to be maintained in the first time sequence unit of the terminal’s uplink transmission when it is in a connected state or an idle state. The starting time of the time sequence unit; the first time sequence unit of the terminal's uplink transmission is any time sequence unit in the terminal's uplink transmission time sequence.

The compensation module 902 is used for compensating and compensating the RTT on the basis of the start time of the first time sequence unit received by the terminal in the downlink, to obtain the start time of the first time sequence unit of the uplink transmission of the terminal; It is later than the obtained start time of the terminal's uplink transmission of the first time sequence unit.

The first value is the difference between the real RTT and the reference RTT; the reference RTT is the gateway station used to obtain the starting time of the uplink receiving first time sequence unit, which is delayed on the basis of the starting time of the downlink sending first time sequence unit Time delay; the real RTT is the time delay between the gateway station from the downlink sending the downlink data sent in the first time sequence unit to the point where the gateway station receives the common reference point when the virtual terminal sends the uplink data sent in the first time sequence unit in the uplink ; The common reference point is a preset reference point in at least one cell covered by the satellite.

The second value is compensated on the basis of the start time of the first time sequence unit of the terminal's downlink reception, which is used to transmit the uplink data sent by the terminal at the time when the second value is compensated to the satellite, and the uplink data sent by the virtual terminal Synchronize to the time of the satellite.

Optionally, the device may also include a maintenance time range determining module, configured to obtain a preset difference; the preset difference is the maximum value of the delay difference of all cells in the entire access network; wherein, any one The delay difference of a cell is the maximum value of the difference between the user-to-satellite round-trip delay in the cell and the virtual terminal-to-satellite round-trip delay difference at the common reference point, and the maximum value of the difference between the real RTT and the reference RTT in the cell. with;

In the case that the preset difference is not less than 0, calculate the difference between the number of the first time sequence unit received by the terminal and the number of the first time sequence unit to obtain the first number; the number of the first time sequence unit is the preset difference and the time sequence The absolute value of the ratio between the unit durations is rounded up;

Taking the start time of the time sequence unit indicated by the first number in the downlink receiving time sequence of the terminal as the latest time in the time range to be maintained;

In the case that the preset difference is less than 0, the sum of the number of the first time sequence unit of the downlink reception of the terminal and the number of the second time sequence unit is calculated to obtain the second number; the time sequence unit indicated by the second number in the downlink reception time sequence of the terminal is calculated The starting time of is taken as the latest time of the time range to be maintained; the second time sequence unit quantity is the absolute value of the ratio between the preset difference and the time length of the time sequence unit, and is obtained by rounding down.

Optionally, the second determining module 901 is configured to determine the start time of the downlink receiving first time sequence unit corresponding to the first time sequence unit of the terminal's uplink transmission within the range of the time to be maintained for the first time sequence unit of the terminal uplink transmission, include:

The second determining module 901 is specifically configured to determine the downlink receiving time sequence unit to which the current execution time belongs when the preset difference value is not less than 0, to obtain the downlink receiving second time sequence unit;

Estimating the CRS delay change rate at the start time of the downlink reception of the second timing unit; based on the CRS delay change rate at the start time of the downlink reception of the second timing unit and the start time of the downlink reception of the second timing unit, and The first number determines the start time of the first time sequence unit for downlink reception of the terminal; the first number is the difference between the number of the first time sequence unit for downlink reception of the terminal and the number of the second time sequence unit for downlink reception; the second time sequence unit for downlink reception The CRS delay change rate at the start time of the time sequence unit refers to: the ratio between the first time offset and the preset standard duration of the time slot; the first time offset is the difference between the first actual difference and the standard duration of the time slot Difference; the first actual difference is the difference between the start time of two consecutive time sequences starting from the downlink receiving the second time sequence unit.

Optionally, the second determining module 901 is further specifically configured to obtain the start time of the terminal's downlink reception of the first time sequence unit when the preset difference is less than 0; or,

In the case that the preset difference is less than 0, determine the downlink reception time sequence unit to which the current execution time belongs, and obtain the third downlink reception time sequence unit;

Determine the start time of the first time sequence unit for downlink reception of the terminal according to the start time of the third time sequence unit for downlink reception, the CRS delay change rate at the start time point of the third time sequence unit for downlink reception, and the second quantity; The second number is the difference between the number of the third time sequence unit for downlink reception and the number of the first time sequence unit for downlink reception of the terminal; the CRS delay change rate at the start time of the third time sequence unit for downlink reception refers to: the second time offset The ratio between the shift and the preset standard duration of the time slot; the second time offset is the difference between the second actual difference and the standard duration of the time slot; the second actual difference is the continuous start from the downlink receiving the third timing unit The difference between the start moments of the two sequences.

Optionally, the compensation module 902 is configured to compensate and compensate the RTT based on the start time of the first time sequence unit received by the terminal in the downlink to obtain the start time of the first time sequence unit sent by the terminal in the uplink, including:

The compensation module 902 is specifically configured to determine the compensation RTT; the compensation RTT is the sum of the first value and the second value, or the second value; and the second value is the difference between the first time delay and the second time delay ; The first delay is the round-trip delay between the satellite and the terminal; the second delay is the round-trip delay between the satellite and the virtual terminal;

In the case where the compensation RTT is a positive value, the time obtained by compensating the RTT in advance on the basis of the start time of the terminal's downlink reception of the first time sequence unit is used as the start time of the terminal's uplink transmission of the first time sequence unit;

In the case that the compensation RTT is a negative value, the time obtained by delaying the absolute value of the compensation RTT on the basis of the start time of the terminal's downlink reception of the first time sequence unit will be used as the start time of the terminal's uplink transmission of the first time sequence unit. The beginning moment.

Optionally, in the case where the value of the reference RTT is the real RTT, the value of the compensation RTT is the second value.

Optionally, in the case where the reference RTT is the RTT at the starting time of the gateway station's downlink transmission of the first time sequence unit, the compensation module 902 is configured to determine the compensation RTT, including:

The compensation module 902 is specifically configured to use the sum of the first product and the target difference as the compensation RTT; the first product is the product of the real RTT and the downlink CRS delay change rate of the terminal; the target difference is the third delay and the fourth delay. The delay difference is twice the value of the delay; the third delay is: the ratio of the distance between the satellite and the terminal and the speed of light at the beginning of the first time sequence unit of the gateway station downlink transmission; the fourth delay is: the gateway station downlink transmission The ratio of the distance between the satellite and the virtual terminal and the speed of light at the start time of the first time sequence unit;

The downlink CRS delay change rate of the terminal is the CRS delay change rate at the start time of the downlink reception timing unit to which the current execution time belongs.

Optionally, the device further includes: a true RTT calculation module, which is used to determine the value of the feeder link delay change rate; the feeder link delay change rate starts from the first timing unit of the downlink reception of the terminal The feeder link delay change rate at the start time;

According to the value of the feeder link delay, the real RTT is estimated.

The real RTT calculation module is used to determine the value of the CRS delay change rate at the start time of the first time sequence unit of the downlink reception of the terminal, and the user link delay change at the start time of the first time sequence unit of the downlink reception of the terminal The value of the delay rate and the preset relationship of the delay change rate determine the value of the delay change rate of the feeder link.

Optionally, when the satellite's orbit is a satellite orbit directly above the gateway, the true RTT calculation module is used to determine the feeder link corresponding to the value of the feeder link delay change rate The value of the delay includes:

The real RTT calculation module is specifically used to determine the value of the target included angle corresponding to the value of the feeder link delay change rate according to the preset relationship between the feeder link delay change rate and the target included angle; The angle is the angle between the speed of the satellite and the direction away from the gateway on the feeder link;

According to the value of the feeder link distance, the value of the feeder link delay corresponding to the value of the feeder link delay change rate is determined.

Optionally, when the satellite orbit does not pass directly above the customs station, the true RTT calculation module is used to determine the feeder link delay corresponding to the value of the feeder link delay change rate. Values include:

Real RTT calculation module, specifically used as a basis

a _d0-F represents the feeder link delay change rate at the start time of the terminal's downlink reception in the first time sequence unit, a _BC represents the start time of the terminal's downlink reception in the first time sequence unit relative to the virtual gateway station The feeder link delay change rate under the lower; the position of the virtual gateway station is the midpoint of the line segment formed by the first vertical point and the second vertical point; the first vertical point and the second vertical point are the slave gateway stations The vertical feet obtained by drawing perpendicular lines to the first orbital plane and the second orbital plane; the first orbital plane and the second orbital plane are the planes where the two most distant satellite orbits in the satellite communication system are located; AC represents the feeder chain The ratio of the distance of the feeder link to the speed of light is: the delay of the feeder link; BC represents the distance between the satellite and the virtual gateway.

If the functions described in the methods of the embodiments of the present application are implemented in the form of software functional units and sold or used as independent products, they can be stored in a storage medium readable by a computing device. Based on this understanding, the part of the embodiment of the application that contributes to the prior art or the part of the technical solution can be embodied in the form of a software product, the software product is stored in a storage medium, and includes a number of instructions to make a A computing device (which may be a personal computer, a server, a mobile computing device, or a network device, etc.) executes all or part of the steps of the methods described in the various embodiments of the present application. The aforementioned storage media include: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), magnetic disks or optical disks and other media that can store program codes. .

The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the various embodiments can be referred to each other.

The foregoing description of the disclosed embodiments enables those skilled in the art to implement or use this application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, this application will not be limited to the embodiments shown in this document, but should conform to the widest scope consistent with the principles and novel features disclosed in this document.

Claims

A method for synchronizing uplink data, which is characterized in that it is applied to a gateway station and includes:

After the cell is established, determine the first time sequence unit from the downlink transmission time sequence to obtain the first time sequence unit for downlink transmission; the first time sequence unit of downlink transmission is any time sequence unit in the downlink transmission time sequence;

Obtaining a reference RTT according to the RTT between the gateway station and a common reference point; the common reference point is a preset reference point in at least one cell covered by a satellite;

The time obtained by delaying the reference RTT on the basis of the start time of the first time sequence unit of the downlink transmission is used as the start time of the first time sequence unit of the uplink reception of the gateway station.
The method according to claim 1, wherein the acquiring a reference RTT according to the RTT of the gateway station and a common reference point comprises:

The RTT between the gateway station and the public reference point is the real RTT, and the real RTT is the gateway station starting from the downlink sending the first time sequence unit to send the downlink data to the gateway station receiving the public reference point. The delay between the uplink data;

Use the real RTT as the reference RTT.
The method according to claim 1, wherein the acquiring a reference RTT according to the RTT of the gateway station and a common reference point comprises:

The RTT of the gateway station and the common reference point is the RTT corresponding to the start time of the first time sequence unit of the downlink transmission of the gateway station; the RTT corresponding to the start time of the first time sequence unit of the downlink transmission is this time The sum of the round-trip delay of the feeder link and the round-trip delay of the user link; the round-trip delay of the feeder link at this moment is the delay corresponding to the round-trip distance between the satellite and the gateway at this moment ; The round-trip delay of the user link at this moment is the delay corresponding to the round-trip distance between the satellite at this moment and the common reference point;

The RTT corresponding to the start time of the first time sequence unit of downlink transmission of the gateway station is used as the reference RTT.
The method according to claim 1, wherein the acquiring a reference RTT according to the RTT of the gateway station and a common reference point comprises:

It is determined that the gateway station starts from sending the downlink data in the first time sequence unit of the downlink transmission to the time range formed by the end time when the gateway station receives the uplink data sent at the common reference point. Each time corresponds to the corresponding RTT in the time range. The RTT range formed by the maximum value and the minimum value is the reference RTT range; the RTT corresponding to any time in the time range is the sum of the round-trip delay of the feeder link and the round-trip delay of the user link at that time; The round-trip delay of the feeder link at this moment is the time delay corresponding to the round-trip distance between the satellite and the gateway at this moment; the round-trip delay of the user link at this moment is the time between the satellite and the public The delay corresponding to the round-trip distance between reference points;

The reference RTT is any value in the reference RTT range.
A method for synchronizing uplink data, which is characterized in that it is applied to a terminal and includes:

In the connected state or idle state, within the range of the time to be maintained in the first time sequence unit for uplink transmission of the terminal, determine the start of the downlink reception first time sequence unit corresponding to the first time sequence unit for uplink transmission of the terminal Start time; the first time sequence unit of the uplink transmission of the terminal is any time sequence unit in the uplink transmission time sequence of the terminal;

Compensate and compensate RTT on the basis of the start time of the first time sequence unit of the downlink reception of the terminal to obtain the start time of the first time sequence unit of the uplink transmission of the terminal; the latest time in the range of the time to be maintained is not Later than the obtained start time of the first time sequence unit for uplink transmission of the terminal;

The compensation RTT is the sum of the first value and the second value, or the second value;

The first value is the difference between the real RTT and the reference RTT; the reference RTT is the gateway station used to obtain the start time of the first time sequence unit for uplink reception, and the value of the start time of the first time sequence unit for downlink transmission. Delay based on the delay; the real RTT is that the gateway station starts from the gateway station sending the downlink data sent by the first time sequence unit, and until the gateway station receives the common reference point, the virtual terminal sends the first uplink data. The time delay between uplink data sent in a time sequence unit; the common reference point is a preset reference point in at least one cell covered by a satellite;

The second value is used to synchronize the time when the uplink data sent by the terminal is transmitted to the satellite at the time obtained by compensating the second value and the time when the uplink data sent by the virtual terminal is transmitted to the satellite.
The method according to claim 5, wherein the method for determining the range of the time to be maintained includes:

Obtain a preset difference; the preset difference is the maximum value of the delay difference of all cells in the entire access network; wherein, the delay difference of any cell is the round trip from the user in the cell to the satellite The sum of the maximum value of the difference between the time delay and the round-trip delay between the virtual terminal and the satellite at the common reference point and the maximum value of the difference between the real RTT and the reference RTT in the cell;

In the case that the preset difference is not less than 0, calculate the difference between the number of the first time sequence unit received by the terminal and the number of the first time sequence unit to obtain the first number; the number of the first time sequence unit is The absolute value of the ratio between the preset difference and the duration of the time sequence unit is rounded up;

Taking the starting time of the time sequence unit indicated by the first number in the downlink receiving time sequence of the terminal as the latest time in the range of the time to be maintained;

In the case that the preset difference is less than 0, the sum of the number of the first time sequence unit of the downlink reception of the terminal and the number of the second time sequence unit is calculated to obtain the second number; The start time of the time sequence unit indicated by the second number is used as the latest time in the range of the time to be maintained; the number of the second time sequence unit is the absolute value of the ratio between the preset difference and the duration of the time sequence unit Round down to get.
The method according to claim 6, characterized in that, within the range of the time to be maintained in the first time sequence unit of the uplink transmission of the terminal, determining the first downlink reception corresponding to the first time sequence unit of the uplink transmission of the terminal The starting time of the time series unit, including:

In the case that the preset difference value is not less than 0, determine the downlink reception time sequence unit to which the current execution time belongs, and obtain the second downlink reception time sequence unit;

Estimate the CRS delay change rate at the start time of the downlink reception of the second time sequence unit; according to the CRS time at the start time of the downlink reception of the second time sequence unit and the CRS at the start time of the downlink reception of the second time sequence unit The time delay change rate, and the first quantity, determine the start time of the first time sequence unit of downlink reception of the terminal; the first quantity is the number of the first time sequence unit of downlink reception of the terminal and the first time sequence unit of the downlink reception The difference between the numbers of the two time sequence units; the CRS delay change rate at the start time of the downlink reception of the second time sequence unit refers to: the ratio between the first time offset and the preset time slot standard length; The first time offset is the difference between the first actual difference and the standard duration of the time slot; the first actual difference is the start time of two consecutive time sequences starting from the downlink receiving the second time sequence unit The difference between.
The method according to claim 7, further comprising:

In the case that the preset difference is less than 0, acquiring the start time of the first time sequence unit for downlink reception of the terminal;

or,

In a case where the preset difference value is less than 0, determine the downlink receiving time sequence unit to which the current execution time belongs, and obtain the third downlink receiving time sequence unit;

Determine the first time sequence unit for downlink reception of the terminal according to the start time of the third time sequence unit of the downlink reception, the CRS delay change rate at the start time of the third time sequence unit of the downlink reception, and the second quantity The second number is the difference between the number of the third time sequence unit for downlink reception and the number of the first time sequence unit for downlink reception of the terminal; the start of the third time sequence unit for downlink reception The rate of change of the CRS delay at a time refers to: the ratio between the second time offset and the preset standard duration of the time slot; the second time offset is the difference between the second actual difference and the standard duration of the time slot Value; the second actual difference value is the difference between the start time of two consecutive time sequences starting from the downlink receiving the third time sequence unit.
The method according to claim 5, characterized in that, by compensating and compensating RTT on the basis of the start time of the first time sequence unit of the downlink reception of the terminal, the value of the first time sequence unit of the uplink transmission of the terminal is obtained. Starting moment, including:

Determine the compensation RTT; the second value is the difference between the first delay and the second delay; the first delay is the round-trip delay between the satellite and the terminal; the second delay is the satellite and the The round-trip delay between the virtual terminals;

When the compensation RTT is a positive value, the time obtained by advancing the compensation RTT on the basis of the start time of the first time sequence unit of the downlink reception of the terminal is used as the first uplink transmission time sequence of the terminal The starting moment of the unit;

In the case that the compensation RTT is a negative value, the time obtained by delaying the absolute value of the compensation RTT on the basis of the start time of the first time sequence unit of the downlink reception of the terminal is used as the uplink transmission of the terminal The start time of the first sequential unit.
The method according to claim 9, wherein, in a case where the value of the reference RTT is the real RTT, the value of the compensation RTT is the second value.
The method according to claim 9, characterized in that, in the case where the value of the reference RTT is the RTT at the start time of the first time sequence unit downlink sent by the gateway station, the determining the compensation RTT comprises :

The sum of the first product and the target difference is used as the compensation RTT; the first product is the product of the real RTT and the downlink CRS delay change rate of the terminal; the target difference is the third delay and the first Four times the delay difference; the third delay is: the ratio of the distance between the satellite and the terminal and the speed of light at the start time of the first time sequence unit when the gateway station downlinks; the fourth The time delay is: the ratio of the distance between the satellite and the virtual terminal and the speed of light at the starting time when the gateway station downlinks the first time sequence unit;

The downlink CRS delay change rate of the terminal is the CRS delay change rate at the start time of the downlink receiving time sequence unit to which the current execution time belongs.
The method according to claim 11, wherein the calculation method of the real RTT comprises:

Determine the value of the feeder link delay change rate; the feeder link delay change rate is the feeder link delay change rate at the start time of the downlink reception of the terminal in the first time sequence unit;

Determine the value of the feeder link delay corresponding to the value of the feeder link delay change rate;

According to the value of the feeder link time delay, the real RTT is estimated.
The method according to claim 12, wherein the determining the value of the feeder link delay change rate comprises:

According to the value of the CRS delay change rate at the start time of the downlink reception of the terminal in the first time sequence unit, and the user link delay change rate at the start time of the downlink reception of the terminal in the first time sequence unit Value, and the preset relationship between the delay change rate, and determine the value of the feeder link delay change rate.
The method according to claim 13, characterized in that, in the case that the orbit of a satellite is a satellite orbit directly above the gateway station, the value of the delay change rate of the feeder link is determined The value of the corresponding feeder link delay includes:

According to the preset relationship between the feeder link delay change rate and the target included angle, determine the value of the target included angle corresponding to the value of the feeder link delay change rate; the target included angle is The angle between the speed of the satellite and the direction away from the gateway on the feeder link;

Determine the value of the feeder link distance corresponding to the value of the target included angle according to the preset correspondence between the target included angle and the distance of the feeder link;

The value of the feeder link delay corresponding to the value of the feeder link delay change rate is determined according to the value of the feeder link distance.
The method according to claim 13, characterized in that, when the satellite orbit does not pass directly above the customs station, the feeder chain corresponding to the value of the delay change rate of the feeder link is determined The value of road delay includes:

in accordance with
Determine the value of the feeder link delay corresponding to the value of the feeder link delay change rate;

a d0-F represents the feeder link delay change rate at the start time of the first time sequence unit of the downlink reception of the terminal, a BC represents the first time sequence unit of the downlink reception of the terminal relative to the virtual gateway station The feeder link delay change rate at the starting time; the position of the virtual gateway is the midpoint of the line segment formed by the first vertical point and the second vertical point; the first vertical point and the second vertical point The two vertical points are the vertical feet obtained by drawing vertical lines from the gateway station to the first orbit plane and the second orbit plane; the first orbit plane and the second orbit plane are the farthest distances in the satellite communication system The plane where the two satellite orbits are located; AC represents the distance of the feeder link; the ratio of the distance of the feeder link to the speed of light is: the delay of the feeder link; BC represents the satellite and the virtual gateway The distance between stations.
A synchronization device for uplink data, which is characterized in that it is applied to a gateway station and includes:

The first determining module is configured to determine the first time sequence unit from the downlink transmission time sequence after the cell is established to obtain the first time sequence unit of downlink transmission; the first time sequence unit of downlink transmission is any time sequence in the downlink transmission time sequence unit;

An obtaining module, configured to obtain a reference RTT according to the RTT between the gateway station and a common reference point; the common reference point is a preset reference point in at least one cell covered by a satellite;

The delay module is configured to delay the time obtained by delaying the reference RTT on the basis of the start time of the first time sequence unit of the downlink transmission as the start time of the uplink reception of the first time sequence unit of the gateway station.
A device for synchronizing uplink data is characterized in that it is applied to a terminal and includes:

The second determining module is configured to determine the downlink corresponding to the first time sequence unit of the terminal’s uplink transmission within the range of the time to be maintained in the first time sequence unit of the terminal’s uplink transmission when it is in a connected state or an idle state. Receiving the start time of the first time sequence unit; the first time sequence unit of the terminal's uplink transmission is any time sequence unit in the terminal's uplink transmission time sequence;

The compensation module is used for compensating and compensating the RTT on the basis of the start time of the first time sequence unit of the downlink reception of the terminal to obtain the start time of the first time sequence unit of the uplink transmission of the terminal; the range of the time to be maintained The latest time, not later than the obtained starting time of the terminal's uplink transmission of the first time sequence unit;

The compensation RTT is the sum of the first value and the second value, or the second value;

The first value is the difference between the real RTT and the reference RTT; the reference RTT is the starting time for the gateway station to receive the first time sequence unit in the uplink, and to send the first time sequence unit in the downlink. The time delay based on the time; the real RTT is the gateway station from the downlink sending the downlink data sent by the first time sequence unit, until the gateway station receives the virtual terminal at the common reference point in the uplink transmission The time delay between uplink data sent by the first time sequence unit; the common reference point is a preset reference point in at least one cell covered by a satellite;

The second value is used to synchronize the time when the uplink data sent by the terminal is transmitted to the satellite at the time obtained by compensating the second value and the time when the uplink data sent by the virtual terminal is transmitted to the satellite.