KR20220039573A - Method and apparatus for uplink timing control in non terrestrial network - Google Patents

Abstract

Disclosed are a method and apparatus for controlling uplink timing in a communication system. An operating method of a base station includes the steps of: measuring a first delay value between the base station and a satellite; selecting a position corresponding to a second delay value as an RP; transmitting the second delay value to UE via the satellite; setting a value obtained by subtracting the second delay value from the first delay value as a first TA; and transmitting the first TA to the UE through the satellite. The second delay value means a delay value between the base station and the RP, is smaller than the first delay value, and is greater than or equal to a value obtained by subtracting the maximum compensation distance from the first delay value.

Description

Method and apparatus for controlling uplink timing in a non-terrestrial network

The present invention relates to a method for controlling uplink timing, and more particularly, to a method for controlling uplink timing in a non-terrestrial network.

For processing of rapidly increasing wireless data, a frequency band (eg, a frequency band of 6 GHz or more) higher than a frequency band (eg, a frequency band of 6 GHz or less) of long term evolution (LTE) (or LTE-A) A communication network (eg, a new radio (NR) communication network) using The NR communication network may support a frequency band of 6 GHz or higher as well as a frequency band of 6 GHz or less, and may support various communication services and scenarios compared to an LTE communication network. For example, a usage scenario of the NR communication network may include enhanced Mobile BroadBand (eMBB), Ultra Reliable Low Latency Communication (URLLC), massive Machine Type Communication (mMTC), and the like.

The NR communication network may provide a communication service to terminals located in terrestrial. Recently, as well as on the ground, the demand for communication services for airplanes, drones, satellites, etc. located in non-terrestrial is increasing, and for this purpose, non-terrestrial network (NTN) ) are being discussed. The non-terrestrial network may be implemented based on NR technology. For example, in a non-terrestrial network, communication between a satellite and a communication node located on the ground or a communication node located on the non-ground (eg, an airplane, a drone, etc.) may be performed based on the NR technology. In a non-terrestrial network, a satellite may perform the function of a base station in an NR communication network.

Meanwhile, due to different positions between terminals in a mobile communication network, a propagation delay of a signal between each terminal and a base station may be different. In order to reduce interference due to different propagation delays between terminals, a timing advance (TA) procedure is required. In particular, since the propagation delay value between the terminal and the base station is very large in the non-terrestrial network, a control method for matching uplink timing is required.

An object of the present invention to solve the above problems is to provide a control method and apparatus for matching uplink timing in a non-terrestrial network.

The method of operating a base station according to a first embodiment of the present invention for achieving the above object, the step of measuring a first delay value between the base station and the satellite, selecting a position corresponding to the second delay value as the RP , transmitting the second delay value to the UE through the satellite, setting a value obtained by subtracting the second delay value from the first delay value as a first TA, and setting the first TA through the satellite and transmitting to the UE, wherein the second delay value means a delay value between the base station and the RP, is smaller than the first delay value, and is greater than or equal to a value obtained by subtracting the maximum compensation distance from the first delay value .

According to the present invention, the common TA can maintain a positive value and can maintain the compensation range of the existing TA. Accordingly, even when the propagation delay value is very large due to the very long distance between the satellite and the base station, the uplink timing matching control can be performed without significant change from the existing terrestrial scenario method. Through this, communication quality can be improved by reducing interference between terminals despite a propagation delay due to a very long distance between the satellite and the base station.

1 is a conceptual diagram illustrating a first embodiment of a non-terrestrial network.
2 is a conceptual diagram illustrating a second embodiment of a non-terrestrial network.
3 is a block diagram illustrating a first embodiment of entities constituting a non-terrestrial network.
4 is a conceptual diagram illustrating a first embodiment for obtaining timing advance (TA) in a non-terrestrial network.
5 is a conceptual diagram illustrating a structure of a media access control (MAC) random access response (RAR) including a common TA in a non-terrestrial network.
6 is a conceptual diagram illustrating a second embodiment for obtaining a TA in a non-terrestrial network.
7 is a flowchart illustrating a third embodiment for obtaining a TA in a non-terrestrial network.

Since the present invention can have various changes and can have various embodiments, specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the present invention to specific embodiments, and it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms such as first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component. and/or includes a combination of a plurality of related listed items or any of a plurality of related listed items.

When a component is referred to as being “connected” or “connected” to another component, it may be directly connected or connected to the other component, but it is understood that other components may exist in between. it should be On the other hand, when it is said that a certain element is "directly connected" or "directly connected" to another element, it should be understood that the other element does not exist in the middle.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present application, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning in the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present application. does not

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings. In describing the present invention, in order to facilitate the overall understanding, the same reference numerals are used for the same components in the drawings, and duplicate descriptions of the same components are omitted.

A communication network to which embodiments according to the present invention are applied will be described. The communication system may include a non-terrestrial network (NTN), a 4G communication network (eg, a long-term evolution (LTE) communication network), and/or a 5G communication network (eg, a new radio (NR) communication network). ) communication network). A 4G communication network and a 5G communication network may be classified as a terrestrial network.

The non-terrestrial network may operate based on LTE technology and/or NR technology. The non-terrestrial network may support communication not only in a frequency band of 6 GHz or less, but also in a frequency band of 6 GHz or more. A 4G communication network can support communication in a frequency band of 6 GHz or less. A 5G communication network can support communication in a frequency band of 6 GHz or higher as well as a frequency band of 6 GHz or less. A communication network to which embodiments according to the present invention are applied is not limited to the content described below, and embodiments according to the present invention may be applied to various communication networks (eg, 4G communication network and/or 5G communication network). . Here, a communication network may be used in the same sense as a communication system.

1 is a conceptual diagram illustrating a first embodiment of a non-terrestrial network.

Referring to FIG. 1 , the non-terrestrial network may include a satellite 110 , a communication node 120 , a gateway 130 , a data network 140 , and the like. The non-terrestrial network shown in FIG. 1 may be a transparent payload-based non-terrestrial network. The satellite 110 may be a low earth orbit (LEO) satellite, a medium earth orbit (MEO) satellite, a geostationary earth orbit (GEO) satellite, a high elliptical orbit (HEO) satellite, or an unmanned aircraft system (UAS) platform. The UAS platform may include a high altitude platform station (HAPS).

The communication node 120 may include a communication node located on the ground (eg, user equipment (UE), a terminal) and a communication node located on a non-ground (eg, an airplane, a drone). A service link may be established between the satellite 110 and the communication node 120 , and the service link may be a radio link. Satellite 110 may provide communication services to communication node 120 using one or more beams. The shape of the footprint of the beam of the satellite 110 may be elliptical.

The communication node 120 may perform communication (eg, downlink communication, uplink communication) with the satellite 110 using LTE technology and/or NR technology. Communication between the satellite 110 and the communication node 120 may be performed using an NR-Uu interface. If dual connectivity (DC) is supported, the communication node 120 may be connected to the satellite 110 as well as other base stations (eg, base stations supporting LTE and/or NR functions), and LTE and/or NR DC operation may be performed based on the technology defined in the standard.

The gateway 130 may be located on the ground, and a feeder link may be established between the satellite 110 and the gateway 130 . The feeder link may be a wireless link. The gateway 130 may be referred to as a “non-terrestrial network (NTN) gateway”. Communication between the satellite 110 and the gateway 130 may be performed based on an NR-Uu interface or a satellite radio interface (SRI). The gateway 130 may be connected to the data network 140 . A “core network” may exist between the gateway 130 and the data network 140 . In this case, the gateway 130 may be connected to the core network, and the core network may be connected to the data network 140 . The core network may support NR technology. For example, the core network may include an access and mobility management function (AMF), a user plane function (UPF), a session management function (SMF), and the like. Communication between the gateway 130 and the core network may be performed based on the NG-C/U interface.

Alternatively, a base station and a core network may exist between the gateway 130 and the data network 140 . In this case, the gateway 130 may be connected to the base station, the base station may be connected to the core network, and the core network may be connected to the data network 140 . The base station and the core network may support NR technology. Communication between the gateway 130 and the base station may be performed based on the NR-Uu interface, and communication between the base station and the core network (eg, AMF, UPF, SMF) may be performed based on the NG-C/U interface. can

2 is a conceptual diagram illustrating a second embodiment of a non-terrestrial network.

Referring to FIG. 2 , the non-terrestrial network may include a satellite #1 211 , a satellite #2 212 communication node 220 , a gateway 230 , a data network 1240 , and the like. The non-terrestrial network shown in FIG. 2 may be a non-terrestrial network based on a regenerative payload. For example, each of the satellites #1-2 (211, 212) is attached to a payload received from another entity (eg, communication node 220, gateway 230) constituting a non-terrestrial network. A regeneration operation (eg, a demodulation operation, a decryption operation, a re-encoding operation, a re-modulation operation, and/or a filtering operation) may be performed for the data, and the regenerated payload may be transmitted.

Each of satellites #1-2 (211, 212) may be an LEO satellite, a MEO satellite, a GEO satellite, a HEO satellite, or a UAS platform. The UAS platform may include HAPS. The satellite #1 (211) may be connected to the satellite #2 (212), and an inter-satellite link (ISL) may be established between the satellite #1 (211) and the satellite #2 (212). The ISL may operate at a radio frequency (RF) frequency or an optical band. ISL may be set as optional. The communication node 220 may include a communication node located on the ground (eg, UE, a terminal) and a communication node located on a non-ground (eg, an airplane, a drone). A service link (eg, a radio link) may be established between satellite #1 211 and the communication node 220 . Satellite #1 211 may provide communication services to communication node 220 using one or more beams.

The communication node 220 may perform communication (eg, downlink communication, uplink communication) with the satellite #1 211 using LTE technology and/or NR technology. Communication between satellite #1 211 and the communication node 220 may be performed using an NR-Uu interface. If DC is supported, the communication node 220 may be connected to satellite #1 (211) as well as other base stations (eg, base stations supporting LTE and/or NR functions) and conform to LTE and/or NR standards. DC operation may be performed based on the defined technology.

The gateway 230 may be located on the ground, and a feeder link may be established between the satellite #1 211 and the gateway 230 , and a feeder link may be established between the satellite #2 212 and the gateway 230 . there is. The feeder link may be a wireless link. When the ISL is not established between the satellite #1 (211) and the satellite #2 (212), a feeder link between the satellite #1 (211) and the gateway 230 may be mandatory.

Communication between each of the satellites #1-2 (211, 2122) and the gateway 230 may be performed based on the NR-Uu interface or SRI. The gateway 230 may be connected to the data network 240 . A “core network” may exist between the gateway 230 and the data network 240 . In this case, the gateway 230 may be connected to the core network, and the core network may be connected to the data network 240 . The core network may support NR technology. For example, the core network may include AMF, UPF, SMF, and the like. Communication between the gateway 230 and the core network may be performed based on the NG-C/U interface.

Alternatively, a base station and a core network may exist between the gateway 230 and the data network 240 . In this case, the gateway 230 may be connected to the base station, the base station may be connected to the core network, and the core network may be connected to the data network 240 . The base station and the core network may support NR technology. Communication between the gateway 230 and the base station may be performed based on the NR-Uu interface, and communication between the base station and the core network (eg, AMF, UPF, SMF) may be performed based on the NG-C/U interface. can

Meanwhile, entities (eg, satellites, communication nodes, gateways, etc.) constituting the non-terrestrial network shown in FIGS. 1 and 2 may be configured as follows.

3 is a block diagram illustrating a first embodiment of entities constituting a non-terrestrial network.

Referring to FIG. 3 , the communication node 300 may include at least one processor 310 , a memory 320 , and a transceiver 330 connected to a network to perform communication. In addition, the communication node 300 may further include an input interface device 340 , an output interface device 350 , a storage device 360 , and the like. Each of the components included in the communication node 300 may be connected by a bus 370 to communicate with each other.

However, each of the components included in the communication node 300 may not be connected to the common bus 370 but to the processor 310 through an individual interface or an individual bus. For example, the processor 310 may be connected to at least one of the memory 320 , the transceiver 330 , the input interface device 340 , the output interface device 350 , and the storage device 360 through a dedicated interface. .

The processor 310 may execute a program command stored in at least one of the memory 320 and the storage device 360 . The processor 310 may mean a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which methods according to embodiments of the present invention are performed. Each of the memory 320 and the storage device 360 may be configured of at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 320 may be configured as at least one of a read only memory (ROM) and a random access memory (RAM).

Meanwhile, NTN reference scenarios may be defined as shown in Table 1 below.

When the satellite 110 in the non-terrestrial network shown in FIG. 1 is a GEO satellite (eg, a GEO satellite supporting a transparent function), this may be referred to as “scenario A”. If satellites #1-2 (211, 212) in the non-terrestrial network shown in FIG. 2 are GEO satellites (eg, GEO supporting regenerative function), this will be referred to as “scenario B”. can

When the satellite 110 in the non-terrestrial network shown in FIG. 1 is an LEO satellite with steerable beams, it may be referred to as “scenario C1”. If the satellite 110 in the non-terrestrial network shown in FIG. 1 is an LEO satellite with beams move with satellite, this may be referred to as “scenario C2”. In the non-terrestrial network shown in FIG. 2 , when satellites #1-2 ( 211 , 212 ) are LEO satellites with tunable beams, this may be referred to as “scenario D1”. When satellites #1-2 (211, 212) in the non-terrestrial network shown in FIG. 2 are LEO satellites having beams moving together with the satellite, this may be referred to as “scenario D2”.

Parameters for NTN reference scenarios defined in Table 1 may be defined as shown in Table 2 below.

In addition, in the NTN reference scenarios defined in Table 1, a delay constraint may be defined as shown in Table 3 below.

Next, uplink timing control methods in a communication system will be described. Even when a method (eg, transmission or reception of a signal) performed in a first communication node among communication nodes is described, a corresponding second communication node is a method (eg, a method corresponding to the method performed in the first communication node) For example, reception or transmission of a signal) may be performed. That is, when the operation of the UE is described, the corresponding base station may perform the operation corresponding to the operation of the UE. Conversely, when the operation of the base station is described, the corresponding UE may perform the operation corresponding to the operation of the base station. Also, here, the base station (gNB) may be a concept including a gateway.

Due to different positions between terminals in a communication system, a propagation delay of a signal between each terminal and a base station may be different. Different propagation delays between terminals may cause interference between uplink transmissions or between uplink and downlink transmissions. Accordingly, the base station may perform uplink timing matching control between terminals in order to reduce interference due to different propagation delays between terminals.

In a communication system, uplink allows uplink intra-cell orthogonality, which may mean that uplink transmissions received from other devices in a cell do not interfere with each other. A requirement for maintaining uplink orthogonality may be that the boundaries of uplink slots are aligned in time at the base station. Specifically, the timing alignment error of the received signal may be within a cyclic prefix (CP) range. Accordingly, in order to ensure such receiver-side time alignment, the base station may perform uplink timing coincidence control by adjusting the transmission timing of each user to be slightly earlier or later by TA (timing advance).

According to subcarrier spacing (SCS) according to numerology, the maximum value of TA (timing advance) during initial connection and the maximum value of the distance compensated can be shown in Table 4 below.

In Table 4, the maximum TA value (Max.TA) can be calculated through Equation 1 below.

At this time, the parameter T _A may mean a timing advance command (TAC) value, and if T _A is set to the maximum value and the above equation is calculated, it corresponds to the maximum value of TA in Table 4, and the maximum value when SCS = 15 kHz The distance compensated (Max. distance compensated) can be calculated through Equation 2 below.

[Calculation of TA in NTN]

4 is a conceptual diagram illustrating a first embodiment for obtaining a TA in a non-terrestrial network.

Referring to FIG. 4 , TA in NTN may mean RTD of a feeder link between a base station and a satellite and a service link between a satellite and a UE. In this case, the feeder link delay may be expressed as a common TA, and the service link TA may be expressed as a UE specific TA.

In order to perform an initial access procedure, the UE may transmit an RA preamble to the satellite. The satellite may receive the RA preamble from the UE, and may transmit the received RA preamble to the base station. The base station may receive the RA preamble transmitted by the UE from the satellite, and may measure the common TA through the RA preamble.

The base station may transmit a media access control (MAC) random access response (RAR) message including a common TA to the satellite in response to the RA preamble. The satellite may receive a MAC RAR message including the common TA from the base station, and may transmit the received MAC RAR message to the UE. Thus, the UE may receive a MAC RAR message containing the public TA from the satellite and may obtain the UE specific TA by the global navigation satellite system (GNSS) based on the user's location.

Accordingly, in the non-terrestrial network, the UE may calculate a TA through Equation 3 below.

A public TA may mean a feeder link RTD, and a UE-specific TA may mean a service link RTD. Accordingly, the public TA may have twice the one-way delay time T_0 between the base station and the satellite, and the UE-specific TA may have twice the one-way delay time T_1 between the satellite and the UE.

5 is a conceptual diagram illustrating the structure of a MAC RAR including a public TA in a non-terrestrial network.

Referring to FIG. 5 , the base station may include the calculated common TA in a MAC RAR message and transmit it to the UE. The MAC RAR may include a TAC field, and the TAC field may have a size of 12 bits.

[Calculation of TA through RP setting]

6 is a conceptual diagram illustrating a second embodiment for obtaining a TA in a non-terrestrial network.

Referring to FIG. 6 , by introducing the concept of a reference point (RP) in a non-terrestrial network, the base station can reduce the range of the common TA by first compensating for a common reference TA in the network for each beam. The base station can reduce the burden of data transferred between the base station and the UE by reducing the range of the common TA to be transmitted to the UE.

The base station may select a position having a delay value corresponding to the constant A in the network as the RP, and may inform the UE of the delay value A between the base station and the RP corresponding to the common reference TA for each beam in advance. Therefore, the UE may pre-apply a delay value A between the base station and the RP before receiving the common TA from the base station.

And the UE may transmit the RA preamble to the satellite. The satellite may receive the RA preamble from the UE, and may transmit the received RA preamble to the base station. The base station may receive the RA preamble transmitted by the UE from the satellite, and may measure a delay value B between the base station and the satellite through the received RA preamble.

The base station may calculate a value obtained by subtracting A from B as a common TA, and the common TA may have a value twice the one-way delay time T_0 between the base station and the satellite. Here, T_0 may have a positive value if the RP is on the feeder link, and may have a negative value if the RP is on the service link.

The base station may transmit a MAC RAR message including a common TA to the satellite in response to the RA preamble. The satellite may receive a MAC RAR message including the common TA from the base station, and may transmit the received MAC RAR message to the UE. The UE may receive a MAC RAR message including the public TA from the satellite.

The UE may calculate a UE-specific TA using satellite orbital information and GNSS-based UE location information, and the UE-specific TA may have a value twice the one-way delay time T_1 between the satellite and the UE. The UE may calculate the TA in the same way as in Equation 3 above. In addition, the UE may compensate for the propagation delay by applying the calculated TA during uplink transmission.

[Calculation of TA through RP setting with new conditions added]

7 is a flowchart illustrating a third embodiment for obtaining a TA in a non-terrestrial network.

Referring to FIG. 7 , the TAC field may be defined to accommodate only a delay range and a positive value in a terrestrial scenario. If the TAC field is strengthened to accommodate the extended delay range and negative values in the satellite scenario, data transmitted between the base station and the UE may be burdened. Therefore, it is necessary to obtain a TA by using the existing TAC field as it is.

The UE may transmit the RA preamble to the satellite. The satellite may receive the RA preamble from the UE, and may transmit the received RA preamble to the base station. The base station may receive the RA preamble transmitted by the UE from the satellite, and may measure the delay value B between the base station and the satellite through the RA preamble (S701). Here, the delay value B may mean a first delay value.

The base station can select, as RP, a position having a delay value corresponding to a constant A that satisfies the two conditions of Equations 4 and 5 below in the network, and informs the UE in advance of a delay value between the base station and the RP (ie, constant A) It can be done (S702). Therefore, the UE may pre-apply a delay value A between the base station and the RP before receiving the common TA from the base station. The delay value A between the base station and the RP may mean a second delay value.

이므로 T_0가 양수 값을 가져야 한다는 것을 의미할 수 있다. 따라서, T_0가 양수 값을 갖기 위해서는 RP가 피더 링크에 있어야 함을 의미할 수 있다. 또한, 수학식 5는 B-A에 광속을 곱한 값으로, 상수 A에 해당하는 지연 값을 갖는 위치와 위성 사이의 왕복 거리를 의미할 수 있다. 그리고 해당 거리는 부반송파 간격에 따른 최대 보상 거리 이하의 값을 가져야 한다는 것을 의미할 수 있다.In Equation 4 above,

Therefore, it may mean that T_0 must have a positive value. Therefore, for T_0 to have a positive value, it may mean that the RP must be in the feeder link. In addition, Equation 5 is a value obtained by multiplying BA by the speed of light, and may mean a round trip distance between a position having a delay value corresponding to a constant A and a satellite. In addition, the corresponding distance may mean that it should have a value equal to or less than the maximum compensation distance according to the subcarrier spacing.

That is, when the conditions of Equations 4 and 5 are satisfied, even if the propagation delay value exceeds the range of the propagation delay value in the terrestrial scenario due to the very long distance between the base station and the satellite in the satellite scenario, the non-terrestrial network can utilize the above-mentioned Table 4 as it is.

은 제1 TA를 의미할 수 있다.In addition, the base station may calculate BA, which is the difference between the first delay value and the second delay value, as a common TA, and the common TA may have a double value of the one-way delay time T_0 between the base station and the satellite. Accordingly, T_0 calculated through A satisfying the above two conditions may have a positive value. Here, having a positive value

may mean the first TA.

In response to the RA preamble, the base station may transmit a MAC RAR message including the common TA calculated by the above-described method to the satellite. The satellite may receive the MAC RAR message including the common TA from the base station, and may transmit the received MAC RAR message to the UE (S703).

The UE may receive a MAC RAR message including the public TA from the satellite. That is, the base station may deliver the common TA to the UE through the satellite. In addition, the UE may calculate a UE-specific TA using the satellite orbit information and the GNSS-based UE location information, and the UE-specific TA may have a value twice the one-way delay time T_1 between the satellite and the UE (S704).

Here, the UE-specific TA may mean a second TA. The UE may calculate the TA as the sum of the common TA and the UE-specific TA, as in Equation 3 above, and the TA may mean the sum of the first and second TAs. In addition, the UE may compensate for the propagation delay by applying the calculated TA during uplink transmission (S705).

The methods according to the present invention may be implemented in the form of program instructions that can be executed by various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, etc. alone or in combination. The program instructions recorded on the computer-readable medium may be specially designed and configured for the present invention, or may be known and available to those skilled in the art of computer software.

Examples of computer-readable media include hardware devices specially configured to store and carry out program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include not only machine language codes such as those generated by a compiler, but also high-level language codes that can be executed by a setting computer using an interpreter or the like. The hardware device described above may be configured to operate as at least one software module to perform the operations of the present invention, and vice versa.

Although it has been described with reference to the above embodiments, it will be understood by those skilled in the art that various modifications and changes can be made to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. will be able

Claims (1)

As a method of operating a base station in a communication system,
measuring a first delay value between the base station and the satellite;
selecting a position corresponding to a second delay value as a reference point (RP);
transmitting the second delay value to a user equipment (UE) via the satellite;
setting a value obtained by subtracting the second delay value from the first delay value as a first timing advance (TA); and
transmitting the first TA to the UE via the satellite;
The second delay value means a delay value between the base station and the RP, is smaller than the first delay value, and is greater than or equal to a value obtained by subtracting the maximum compensation distance from the first delay value.

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