KR20230086625A - Method and apparatus for timing adjustment in communication system - Google Patents

Abstract

A timing adjustment technique in a communication system is disclosed. An operating method performed in a terminal of a communication system, comprising: performing measurement on a serving cell and neighboring cells and transmitting a measurement result to the serving cell; Receiving beam switching setting information including information on a target cell from the serving cell; generating a TA by using information about the target cell; An operating method performed in a terminal may be provided, including performing a random access procedure with the target cell according to the beam switching configuration information to acquire a first TA adjustment value and adjusting the TA.

Description

Timing adjustment method and apparatus in communication system

The present disclosure relates to a timing adjustment technique in a communication system, and more particularly, to a timing adjustment technique in a communication system for timing synchronization between a terminal and a base station according to a change of a base station in the same area in long-distance communication.

Along with the development of information communication technology, various wireless communication technologies may be developed. Representative wireless communication technologies may include long term evolution (LTE), new radio (NR), 6th generation (6G), and the like specified in the 3rd generation partnership project (3GPP) standard. LTE may be one wireless communication technology among 4th generation (4G) wireless communication technologies, and NR may be one wireless communication technology among 5th generation (5G) wireless communication technologies.

For the processing of rapidly increasing wireless data after the commercialization of 4G communication systems (eg, communication systems supporting LTE), the frequency band (eg, frequency bands below 6 GHz) of the 4G communication system as well as the 4G communication system A 5G communication system (eg, a communication system supporting NR) using a frequency band higher than the frequency band of (eg, a frequency band of 6 GHz or higher) may be considered. The 5G communication system may support eMBB (enhanced Mobile BroadBand), URLLC (Ultra-Reliable and Low Latency Communication), and mMTC (massive machine type communication).

In such a communication system, communication interruption may occur in cellular shaded areas such as mountainous areas, desert areas, island areas, and oceans, and ground network collapse areas due to various disasters such as earthquakes, tsunamis, and wars. Accordingly, a non-terrestrial network may be required to prepare for such a communication outage. Since this non-terrestrial network is maintained even when the terrestrial network is collapsed due to a disaster, it is possible to maintain individual survival and safety by preventing communication with the outside from being cut off in the area where a disaster or disaster occurs. In particular, non-terrestrial networks can provide mobile communication services in remote areas where communication is not possible due to the absence of communication infrastructure, thereby enabling a hyper-connected society to be established.

Such a non-terrestrial network may have a relatively long round trip time delay (RTD) and high Doppler shift environment compared to terrestrial communication. In this case, a difference in delay time may occur according to a location of a terminal within a beam serviced by a satellite at the same time. Since this delay time difference affects various procedures of data transmission/reception, a timing synchronization or adjustment method suitable for long-distance communication may be required.

An object of the present disclosure to solve the above problems is to provide a timing adjustment method and apparatus in a communication system for timing synchronization between a terminal and a base station according to a change of base station in the same area in long-distance communication.

A timing adjustment method in a communication system according to a first embodiment of the present disclosure for achieving the above object is an operation method performed in a terminal of the communication system, comprising: performing measurements on a serving cell and neighboring cells; Transmitting measurement results of the serving cell and the neighboring cells to the serving cell; Receiving, from the serving cell, beam switching setting information including information about a target cell among the neighboring cells and a beam switching time based on the measurement result; generating a timing advance (TA) by using the information on the target cell; performing a random access procedure with the target cell according to the beam switching setting information; obtaining a first TA adjustment value from the target cell through the random access procedure; and adjusting the TA using the first TA adjustment value.

Here, receiving service type identification information from the serving cell; and confirming a service type based on the service type classification information, and when the beam switching setting information includes instruction information indicating execution of a random access procedure when the checked service type is a terrestrial fixed service. , The terminal may perform the random access procedure immediately after the end of the service stop time when the confirmed service type is the terrestrial fixed service.

Here, the service type identification information includes a service indicator, and the terminal can recognize the checked service type as the ground fixed type service when the service indicator indicates the ground fixed type service.

Here, the service type identification information includes the service stop time of the corresponding region of the serving cell, and when the service stop time is confirmed, the terminal can recognize the confirmed service type as the terrestrial fixed service.

Here, receiving service type identification information from the serving cell; and checking a service type based on the service type classification information, wherein the beam switching setting information includes information indicating a random access procedure is performed when the checked service type is a terrestrial fixed service, When the confirmed service type is the terrestrial fixed service, the terminal may perform the random access procedure in consideration of the beam switching time.

Here, the method further includes receiving a physical downlink control channel (PDCCH) indication from the serving cell, wherein the beam switching configuration information provides indication information for performing a random access procedure when the PDCCH indication is received from the serving cell. If included, the terminal may perform the random access procedure at the time of receiving the PDCCH indication.

Here, if the beam switching setting information includes information indicating a random access procedure to be performed when uplink data is generated, the terminal may perform the random access procedure based on the generation time of the uplink data.

Here, if the beam switching configuration information includes the second TA correction value for the target cell based on the measurement result, the terminal may generate the TA by referring to the second TA correction value.

Here, setting uplink synchronization using the adjusted TA using the first TA adjustment value; and transmitting an uplink signal to the target cell by applying the set uplink synchronization.

Meanwhile, a timing adjustment method in a communication system according to a second embodiment of the present disclosure for achieving the above object is an operation method performed in a base station including a serving cell and neighboring cells, Receiving a measurement result from a terminal through the serving cell; determining a target cell among the neighboring cells based on the measurement result; generating beam switching setting information including information about the target cell and a beam switching time; Transmitting the beam switching setting information to the terminal through the serving cell; and transmitting a first TA adjustment value to the terminal through a random access procedure performed between the terminal and the target cell according to the beam switching configuration information.

Here, the method further includes transmitting service type identification information indicating the service type of the serving cell to the terminal, and the beam switching setting information instructs performing a random access procedure when the service type is a terrestrial fixed service. Including the indication information to indicate, if the service type identified in the service type information is the terrestrial fixed service, the random access procedure may be performed immediately after the service stop time ends.

Here, the service type identification information includes the service stop time of the corresponding area of the serving cell, and when the service stop time is confirmed, the terminal can recognize the checked service type as the terrestrial fixed service.

Here, when there is data to be transmitted to the terminal, the step of transmitting a PDCCH indication to the terminal through the serving cell is further included, and the beam switching configuration information is random access when the PDCCH indication is received from the serving cell. The random access procedure may be performed at the time when the terminal receives the PDCCH indication, including information indicating the execution of the procedure.

Here, the step of generating a second TA correction value for the target cell based on the measurement result is further included, wherein the beam switching configuration information includes the second TA correction value so that the terminal can perform the second TA correction value. The random access procedure may be performed by referring to the value.

On the other hand, in the communication system according to the third embodiment of the present disclosure for achieving the above object, the timing adjustment device includes a processor as a terminal, and the processor measures the terminal for the serving cell and neighboring cells. perform; Transmitting measurement results for the serving cell and the neighboring cells to the serving cell; Receiving beam switching setting information including information about a target cell among the neighboring cells and a beam switching time based on the measurement result from the serving cell; generating a timing advance (TA) using the information on the target cell; performing a random access procedure with the target cell according to the beam switching configuration information; obtaining a first TA adjustment value from the target cell through the random access procedure; and cause an adjustment of the TA using the first TA adjustment value.

Here, the processor may cause the terminal to receive service type identification information from the serving cell; and operating to further cause confirmation of a service type based on the service type identification information, wherein the beam switching setting information includes instruction information instructing execution of a random access procedure when the checked service type is a terrestrial fixed service. Then, when the confirmed service type is the terrestrial fixed service, the terminal may perform the random access procedure immediately after the service stop time ends.

Here, the service type identification information includes the service stop time of the corresponding region of the serving cell, and when the service stop time is confirmed, the terminal can recognize the confirmed service type as the terrestrial fixed service.

Here, the processor operates to further cause the terminal to receive a PDCCH indication from the serving cell, and the beam switching configuration information indicates to perform a random access procedure when the PDCCH indication is received from the serving cell. information, the terminal may perform the random access procedure at the time of receiving the PDCCH indication.

Here, if the beam switching setting information includes information indicating a random access procedure to be performed when uplink data is generated, the terminal may perform the random access procedure based on the generation time of the uplink data.

Here, if the beam switching configuration information includes the second TA correction value for the target cell based on the measurement result, the terminal may generate the TA by referring to the second TA correction value.

According to the present application, in a ground fixed service scenario, a terminal may change access from a serving aerial mobile vehicle to a target aerial mobile vehicle at the time of service termination. In addition, according to the present application, a terminal can acquire uplink synchronization by rapidly adjusting a TA by accessing a target airborne vehicle and immediately performing a random access procedure at a service end point.

In addition, according to the present application, a terminal can obtain uplink synchronization by accessing a target airborne vehicle at a time when data is generated and performing a random access procedure to adjust a TA. In addition, according to the present application, when a terminal receives a physical downlink control channel (PDCCH) order from a base station, it is possible to quickly obtain uplink synchronization of a TA by performing a random access procedure for a target airborne vehicle.

In addition, according to the present application, the base station may receive a measurement result from the terminal, generate a TA adjustment value for the target airborne vehicle, and transmit it to the terminal. Then, the terminal can set uplink synchronization by reflecting the TA adjustment value received in the process of performing a random access procedure to the base station, and thus quickly acquire uplink synchronization.

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 flowchart illustrating a first embodiment of a method for initial access of a terminal in a communication system.
5 is a conceptual diagram illustrating a first embodiment of a method for supporting handover in a communication system.
6 is a conceptual diagram illustrating a second embodiment of a method for supporting handover in a communication system.
7 is a flowchart illustrating a first embodiment of a timing adjustment method in a communication system.

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

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. These terms are only used for the purpose of distinguishing one component from another. For example, a first element may be termed a second element, and similarly, a second element may be termed a first element, without departing from the scope of the present disclosure. The terms and/or include any combination of a plurality of related recited items or any of a plurality of related recited items.

In embodiments of the present application, “at least one of A and B” may mean “at least one of A or B” or “at least one of combinations of one or more of A and B”. Also, in the embodiments of the present application, “one or more of A and B” may mean “one or more of A or B” or “one or more of combinations of one or more of A and B”.

It is understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, but other elements may exist in the middle. It should be. On the other hand, when an element is referred to as “directly connected” or “directly connected” to another element, it should be understood that no other element exists in the middle.

Terms used in this application are only used to describe specific embodiments, and are not intended to limit the present disclosure. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, the terms "include" or "have" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

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 disclosure belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in this application, they should not be interpreted in an ideal or excessively formal meaning. don't

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

A communication network to which embodiments according to the present disclosure are applied will be described. The communication system includes a non-terrestrial network (NTN), a 4G communication network (eg, a long-term evolution (LTE) communication network), a 5G communication network (eg, a new radio (NR) communication network ), 6G communication network, and the like. 4G communication networks, 5G communication networks and 6G communication networks can be classified as terrestrial networks.

Non-terrestrial networks may operate based on LTE technology and/or NR technology. The non-terrestrial network can support communication in a frequency band of 6 GHz or higher as well as a frequency band of 6 GHz or lower. 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 lower. Communication networks to which embodiments according to the present disclosure are applied are not limited to those described below, and embodiments according to the present disclosure may be applied to various communication networks. Here, the communication network may be used as the same meaning as the communication system.

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

Referring to FIG. 1 , a 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 ground-based communication node (eg, user equipment (UE), terminal) and a non-terrestrial communication node (eg, an airplane or 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 service 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 satellite 110 and communication node 120 may be performed using an NR-Uu interface. When 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 may be connected to LTE and/or NR DC operation can 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 . A feeder link may be a wireless link. 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). Gateway 130 may be connected to data network 140 . A “core network” may exist between gateway 130 and 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 an 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 . Base stations and core networks 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 satellite #1 211 , satellite #2 212 , communication node 220 , gateway 230 , data network 240 , and the like. The non-terrestrial network shown in FIG. 2 may be a regenerative payload-based non-terrestrial network. For example, each of the satellites #1-2 (211, 212) receives a payload from another entity (eg, communication node 220, gateway 230) constituting a non-terrestrial network. A regeneration operation (eg, a demodulation operation, a decoding operation, a re-encoding operation, a re-modulation operation, and/or a filtering operation) may be performed on the regenerated payload, and the regenerated payload may be transmitted.

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

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

The gateway 230 may be located on the ground, a feeder link may be established between satellite #1 211 and the gateway 230, and a feeder link may be established between satellite #2 212 and the gateway 230. there is. A feeder link may be a wireless link. If ISL is not established between satellite #1 211 and satellite #2 212, a feeder link between 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 an NR-Uu interface or SRI. Gateway 230 may be connected to data network 240 . A “core network” may exist between gateway 230 and 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 an 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 . Base stations and core networks 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 constituting the non-terrestrial networks shown in FIGS. 1 and 2 (eg, satellites, communication nodes, gateways, etc.) 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 , an entity 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 entity 300 may further include an input interface device 340 , an output interface device 350 , a storage device 360 , and the like. Each component included in the entity 300 is connected by a bus 370 to communicate with each other.

However, each component included in the entity 300 may be connected through an individual interface or an individual bus centered on the processor 310 instead of the common bus 370 . For example, the processor 310 may be connected to at least one of the memory 320, the transmission/reception device 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 disclosure are performed. Each of the memory 320 and the storage device 360 may include at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 320 may include at least one of a read only memory (ROM) and a random access memory (RAM).

Meanwhile, scenarios in a non-terrestrial network may be defined as shown in Table 1 below.

If 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 may be referred to as “scenario B”. there is.

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

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

In addition, in the scenarios defined in Table 1, delay constraints may be defined as shown in Table 3 below.

Meanwhile, in 5G satellites, GEOs can be geostationary satellites. And, MEO and LEO may be non-geostationary orbit satellites. Here, in a geostationary satellite, a service area may not change with time. In contrast, in non-geostationary satellites, the service area may change with time.

As such, the service area of non-geostationary satellites can be classified into two types. One of the service areas may be an area receiving a service using a ground fixed beam, and another of the service areas may be an area receiving a service using a moving beam. In this case, in the terrestrial fixed beam, cell information may not be changed even if the satellite moves. In contrast, in the mobile beam, cell information may be changed along with a moving satellite.

The non-terrestrial round-trip delay time may vary depending on the location of a satellite, a location of a base station on the ground (hereinafter referred to as a ground station), and a location of a terminal. First, a non-terrestrial round-trip delay time in a terminal at a fixed location may cause delay variation according to satellite mobility. For example, in the case of GEO, the maximum delay change may be 16 ms. In the case of LEO servicing at 1200km, the maximum delay change may be 6.44ms.

A difference in non-terrestrial round-trip delay time may occur according to a location of a terminal within a beam served by a satellite at the same time. The difference in non-terrestrial round-trip delay time may be large in proportion to the beam size. Finally, in a ground station connected to a satellite, the distance between the satellite and the ground station may vary. If a line-of-sight (LOS) environment is not supported, the terminal may be connected to a ground station through a connection with another satellite.

These connections may change depending on satellite deployment. In summary, the non-terrestrial round trip delay time may be defined in consideration of the location between the UE and the satellite in the case of a transparent mode. In contrast, the non-terrestrial round-trip delay time may be defined considering the position between the terminal and the satellite in the case of a re-generative mode, and in addition, considering the position between the satellite and the ground station.

In a non-terrestrial network, a terminal can be classified into a type that knows its location information and a type that does not know its own location information. At this time, the terminal transmits location information through at least one of GPS (global positioning system), A-GNSS (assisted global navigation satellite system), OTDOA (observed time differential of arrival), or E-CID (enhanced cell ID (identifier)) can be obtained

Meanwhile, the round-trip delay time between the terminal and the base station may increase as the cell size increases. In addition, the round-trip delay time between the terminal and the base station may increase as the height of the non-terrestrial node increases. Such an increase in round-trip delay time between the base station and the terminal may affect various parameters related to time. In addition, an increase in round-trip delay time between the base station and the terminal may affect the performance of the entire system. In order to solve this problem, the non-terrestrial network may introduce various offsets for parameters related to round-trip delay time to minimize the effect on existing parameters. In addition, a non-terrestrial network may require a method of compensating timing so that a base station can receive preambles transmitted by all terminals in a cell at similar times during initial access.

4 is a flowchart illustrating a first embodiment of a method for initial access of a terminal in a communication system.

Referring to FIG. 4, the airborne vehicle may transmit a synchronization signal block (SSB) to the terminal. In addition, the airborne vehicle may transmit a system information block (SIB) including location information of the airborne vehicle and a common timing advance (TA) offset to the terminal.

Here, the common TA offset may be a timing advance between the airborne vehicle and the gateway. In addition, the aerial mobile vehicle may be an object located at a high place away from the ground, and may include a satellite and an air vehicle. Here, the air vehicle may be a concept including an airplane, an airship, a drone, and the like. The air vehicle may include TRP.

Meanwhile, the terminal may receive a synchronization signal block (SSB) from the airborne vehicle (S401). And, the terminal may decode system information blocks (SIBs) based on the received SSB (S402). The UE may decode SIBs to detect information about random access channel (RACH) resources. As a result, the terminal can decode airborne vehicle information by decoding the SIBs (S403). Here, the airborne vehicle information may include at least one of various parameters such as location information of the airborne vehicle.

를 획득할 수 있다. 즉, 단말은 단말 자신의 위치와 공중 이동체의 위치에 기반하여 공중 이동체과 단말 사이의 전파 지연 시간을 추정(estimation)할 수 있다. 그리고, 단말은 추정한 전파 지연 시간에 기반하여 단말에 특정한 TA 오프셋을 산출할 수 있다. 여기서, 단말은 일 예로, 단말 자신의 위치를 위치 정보를 GPS, A-GNSS, OTDOA 또는 E-CID 중에서 적어도 하나 이상을 통하여 획득할 수 있다.The UE is a UE-specific TA offset based on the positions (or reference positions) of the UE itself and the airborne vehicle based on the decoded airborne vehicle information, for example.

can be obtained. That is, the terminal can estimate the propagation delay time between the airborne mobile body and the terminal based on the location of the terminal itself and the airborne mobile body. And, the UE may calculate a UE-specific TA offset based on the estimated propagation delay time. Here, as an example, the terminal may acquire location information of its own location through at least one of GPS, A-GNSS, OTDOA, and E-CID.

를 디코딩하여 획득할 수 있다(S404). 이처럼 공통 TA 오프셋은 공중 이동체가 상위 시그널링 또는 물리계층 신호를 이용하여 단말에 설정하거나 지시할 수 있다. 이후에 단말은

와

에 기반하는 단말 특정 TA 보정값을 계산할 수 있고, 계산된 단말 특정 TA 보정값을 적용하여 공중 이동체로 PRACH(physical random access channel)를 송신할 수 있다(S405). On the other hand, the UE decodes the SIBs to obtain a common TA offset, e.g.

It can be obtained by decoding (S404). As such, the common TA offset can be set or instructed by the airborne mobile device to the terminal using upper signaling or a physical layer signal. After that, the terminal

and

A UE-specific TA correction value based on can be calculated, and a physical random access channel (PRACH) can be transmitted to the airborne vehicle by applying the calculated UE-specific TA correction value (S405).

일 수 있다. At this time, the terminal may transmit timing advance (TA) pre-compensation information to the airborne vehicle through the PRACH. The timing advance pre-compensation information may be at least one of delay time information between the terminal and the airborne vehicle, location information of the terminal, and a terminal-specific TA correction value. The air mobile vehicle may receive a PRACH including TA pre-compensation information from the UE. In addition, the airborne vehicle may generate a common TA correction value in consideration of the TA pre-compensation information. As an example, the common TA correction value is

can be

일 수 있다. 여기서,

는 공중 이동체와 단말 사이에서 미리 고정되거나 약속된 TA 오프셋일 수 있다.

는

과 같이 주어질 수 있으며,

일 수 있고,

일 수 있다.Thereafter, the airborne vehicle may transmit a random access response (RAR) including a common TA correction value to the UE. Then, the terminal can receive the RAR including the common TA correction value from the air mobile vehicle (S406). The UE may obtain a UE TA adjustment value by adjusting the TA using Equation 1 based on the received RAR (S407). The terminal TA adjustment value is an example

can be here,

may be a TA offset fixed or promised in advance between the airborne vehicle and the terminal.

Is

can be given as

can be,

can be

The terminal may transmit msg3 to the airborne vehicle by applying the terminal TA adjustment value (S408). Here, msg3 is part of a random access procedure, and includes a cell-radio network temporary identifier (C-RNTI) medium access control (MAC) control element (CE) or common control channel (CCCH) service data unit (SDU). Indicates a message transmitted on an uplink (UL)-shared channel (SCH), and may be the first scheduled transmission of a random access procedure.

Then, the airborne vehicle can receive msg3 from the terminal. In addition, the aerial mobile body may generate a mobile body TA adjustment value based on msg3. The airborne mobile body may transmit the MAC CE including the mobile body TA adjustment value to the terminal. Then, the terminal can receive the MAC CE including the mobile body TA adjustment value from the air mobile vehicle (S409). Thereafter, the UE adjusts the UE TA adjustment value based on the mobile TA adjustment value included in the MAC CE, and transmits a physical uplink shared channel (PUSCH)/physical uplink control channel (PUCCH) over the air based on the adjusted UE TA adjustment value. It can be transmitted to a mobile body (S410). Then, the airborne vehicle can receive the PUSCH/PUCCH from the UE.

Meanwhile, the mobility of a non-geostationary orbit satellite may vary depending on the beam type of the corresponding satellite - a ground fixed beam and a mobile beam. In the case of an earth-fixed beam scenario, even if the satellite moves, the terrestrial cell does not change. On the other hand, in the case of a moving beam scenario, cell information may be changed as the satellite moves. The mobile beam may cause frequent handovers due to movement of satellites even when the terminal does not move, thereby increasing power consumption of the terminal. On the other hand, since the cell of the terrestrial fixed beam does not change even if the satellite moves, it is necessary to minimize the influence on the terminal connected to the existing cell. Here, a service type receiving a service in a ground fixed beam scenario may be referred to as a ground fixed beam service or a ground fixed service. In addition, a service type receiving a service in a moving beam scenario may be referred to as a moving beam service or a mobile service.

5 is a conceptual diagram illustrating a first embodiment of a method for supporting handover in a communication system.

Referring to FIG. 5 , in the case of a ground fixed beam scenario, a cell may be fixed to the ground. Even if the aerial mobile vehicle servicing one cell is changed from the first satellite 510 to the second satellite 520, if the cell information (eg PCID, SSB, etc.) remains the same, the terminal can receive the service without reconfiguration. there is. When only satellite identification information of a satellite currently serving is transmitted through system information, and a satellite servicing a corresponding area is changed due to the mobility of a satellite, a system information update procedure may be performed. This may cause overhead in the system in which active or idle terminals existing in the cell must simultaneously check changed system information.

In order to prevent this, since the base station knows in advance which satellites will serve a specific area, the base station can include satellite identification information of satellites scheduled to provide service to the corresponding cell in system information. The terminal can identify a satellite that is scheduled to provide service to a corresponding area (cell) by using satellite identification information of satellites to provide service and current time/location of the terminal.

The terminal may attempt access by inferring a satellite currently providing a service to itself using satellite identification information received through system information. However, in order to provide accurate information, the base station may provide information (ie, satellite identification information) of a satellite currently providing service to the terminal through connection setting information using a dedicated channel to the terminal.

6 is a conceptual diagram illustrating a second embodiment of a method for supporting handover in a communication system.

Referring to FIG. 6 , in the case of a ground fixed beam scenario, a cell may be fixed to the ground. Even if the aerial mobile vehicle serving one cell is changed from the first aircraft 610 to the second aircraft 620, if the cell information (eg PCID, SSB, etc.) remains the same, the terminal can receive the service without reconfiguration. there is. When only the vehicle identification information of the vehicle currently in service is transmitted through the system information, when the vehicle servicing the area is changed due to the mobility of the vehicle, a system information update procedure may be performed.

This may cause overhead in the system in which active or idle terminals existing in the cell must simultaneously check changed system information. In order to prevent this, since the base station knows in advance the aircraft that will service a specific area, the base station can include vehicle identification information of the vehicle that will provide service to the cell in the system information. The terminal can identify an aircraft scheduled to provide service to a corresponding area (cell) using vehicle identification information and current time/location of the terminal of aircraft to provide service.

The terminal may attempt access by inferring an aircraft currently providing service to itself using the vehicle identification information received through the system information. However, in order to provide accurate information, the base station may provide information (ie, vehicle identification information) of an aircraft currently providing service to the terminal through connection setting information using a dedicated channel to the terminal.

As such, in the terrestrial fixed beam scenario, the cell service area may not be changed by the mobility of non-geostationary satellites or air vehicles, and service may be fixed to a specific area. In such a terrestrial fixed beam scenario, the base station may broadcast time information about when service is to be stopped in a corresponding area through system information to help idle mode users in cell reselection.

When the terminal knows the service interruption time point, it can determine the time point at which the measurement of the neighboring cell to be serviced next should be performed. In addition, the base station may provide a time duration [t1, t2] for handover to the target cell to help the handover of the connected mode terminal.

Depending on the mobility of non-geostationary satellites or aircraft, a scenario in which a base station is changed in a specific service area may be possible when cell IDs are different from each other and cell IDs are the same. When the cell IDs are different, the terminal can select a cell through cell reselection in idle mode and perform TA pre-compensation through initial access. When the UE is in the connected mode, TA pre-compensation may be performed through initial access to the target cell after the handover procedure.

The present disclosure may suggest a method of updating a UE-specific TA in a cell switching environment (hereinafter referred to as a mobile cell switching case) in which a UE in a connected mode does not change a cell ID in a terrestrial fixed beam scenario. Since the location of the satellite/vehicle that stops service and the location of the satellite/vehicle that starts service are different from each other, the difference from the TA value of the terminal currently in service becomes large, and uplink timing adjustment may be required.

7 is a flowchart illustrating a first embodiment of a timing adjustment method in a communication system.

Referring to FIG. 7 , the base station may transmit service type classification information to the terminal through the serving airborne vehicle (S701-1 and S701-2). Here, the service type may be a ground fixed service or a mobile service. And, the service type identification information may be a land fixed type service indicator when the service type is a land fixed type service, and may be a mobile service indicator when the service type is a mobile service.

At this time, the base station may broadcast a SIB including a ground fixed service indicator or a mobile service indicator through the serving airborne vehicle. Then, the terminal can receive the SIB from the serving airborne vehicle and check the service indicator included in the received SIB. And, if the checked service indicator is a ground fixed type service indicator, the terminal can recognize the service type as a ground fixed type service. Unlike this, if the checked service indicator is a mobile service indicator, the terminal can recognize the service type as a mobile service. Here, the base station may be located separately from the airborne vehicle. Alternatively, the base station may be located on an airborne vehicle.

Meanwhile, the service type identification information may include service stop time and/or service start time in the corresponding region. Accordingly, the base station may include location information of the corresponding area, service stop time, and/or service start time in the SIB through the serving airborne vehicle and broadcast. Here, the location information of the corresponding area may be location information and radius information of the center of the cell. Then, the terminal may receive the SIB including the service stop time and/or service start time of the corresponding area from the serving airborne vehicle. In addition, the terminal may check the service stop time and/or service start time of the corresponding region from the received SIB. In this way, if the terminal can check the service stop time and/or service start time of the corresponding area from the received SIB, the service type of the corresponding cell can be recognized as a geo-fixed service.

On the other hand, the serving aerial vehicle may be an air vehicle that detects TRP. In this case, the base station may define a service stop time and/or a service start time for each TRP identifier (ID). And, the base station may broadcast the SIB including the service stop time and/or service start time of the corresponding region for each TRP ID through at least one TRP.

Here, the location information of the corresponding area may be location information and radius information of the center of the cell. Then, the terminal may receive the SIB including the service stop time and/or service start time of the corresponding region through at least one TRP. In addition, the terminal may check the service stop time and/or service start time of the corresponding region from the received SIB. In this way, if the service stop time and/or service start time of the corresponding area can be confirmed from the SIB received by the terminal, the service type of the corresponding cell can be recognized as a terrestrial fixed service.

Meanwhile, the base station may set measurement reporting conditions to the terminal through the serving airborne vehicle. The measurement reporting condition is, for example, when "reference signal received power (RSRP) of adjacent aerial vehicle - RSRP of serving aerial vehicle" or "reference signal received quality (RSRQ) of adjacent aerial vehicle - RSRQ of serving aerial vehicle" is greater than or equal to a threshold value. can be Here, the base station may set a threshold value to the terminal through the serving aerial vehicle in consideration of the altitude and movement time of the serving aerial vehicle prior to the service stop time of the serving aerial vehicle.

The serving aerial mobile unit and neighboring aerial mobile units (neighboring aerial mobile unit 1 to adjacent aerial mobile unit n) may transmit reference signals to the terminal (S702). Then, the terminal may perform a measurement operation on the airborne vehicles (eg, the serving airborne vehicle and/or adjacent airborne vehicles) (S704). That is, the terminal can receive reference signals from airborne vehicles and measure received signal strengths based on the received reference signals. Here, the received signal strength may be RSRP and/or RSRQ. This measurement operation may be performed periodically or non-periodically. At this time, the received signal strength may satisfy the measurement report condition. In this case, the terminal may transmit the measurement report message to the base station through the serving airborne vehicle (S704). The measurement report message may include identifiers and/or received signal strengths (eg, RSRP, RSRQ) of neighboring airborne vehicles 1 to 10, n.

Here, the reference signals include a channel state information reference signal (CSI-RS), a cell reference signal (CRS), a time/frequency tracking reference signal (TRS), and a synchronization signal block. (synchronization signal block, SSB), sounding reference signal (SRS), or demodulation reference signal (DMRS).

Meanwhile, the serving aerial mobile unit and neighboring aerial mobile units (neighboring aerial mobile unit 1 to adjacent aerial mobile unit n) may transmit reference signals to the terminal for each beam. In this case, the measurement report message may include a beam identifier and/or received signal strength (eg, RSRP, RSRQ) for each beam for each beam for multiple beams of the serving aerial mobile unit and adjacent aerial mobile units. In addition, the serving aerial mobile unit and neighboring aerial mobile units (neighboring aerial mobile unit 1 to adjacent aerial mobile unit n) may transmit SSB or CSI-RS to the terminal for each beam. In this case, the measurement report message may include identifiers and/or received signal strengths (eg, RSRP, RSRQ) for each SSB or CSI-RS of neighboring airborne vehicles.

Meanwhile, the terminal may receive a synchronization signal block (SSB) from each of the adjacent airborne vehicles. And, the terminal can decode the system information block (SIB) based on the received SSB. The UE can decode the SIB to detect information about random access channel resources. As a result, the UE can decode information on neighboring airborne vehicles by decoding the SIB. Here, the neighboring airborne vehicle information may include at least one of various parameters such as location information of neighboring airborne vehicles.

The UE may obtain a UE-specific TA offset for each neighboring airborne vehicle based on the positions (or reference positions) of the UE itself and the neighboring airborne vehicles based on the decoded information on the neighboring airborne vehicles. That is, the UE can estimate the propagation delay time between the UE and the adjacent airborne vehicle based on the location of the UE itself and the location of the adjacent airborne vehicle. In addition, the terminal may calculate a terminal-specific TA offset for a corresponding neighboring airborne vehicle based on the estimated propagation delay time.

Meanwhile, the UE may obtain a common TA offset by decoding the SIB. As such, the common TA offset may be set or instructed by a neighboring airborne mobile device to the terminal using higher signaling or a physical layer signal. Thereafter, the UE may calculate a UE-specific TA correction value for each of the adjacent airborne vehicles based on a UE-specific TA offset for each of the adjacent airborne vehicles and a common TA offset for each. The UE may include the calculated UE-specific TA correction value for each neighboring airborne vehicle in a measurement report message and transmit the same to the base station via the serving airborne vehicle. The base station may receive a measurement report message from the terminal.

Similarly, for each of the multi-beams of a neighboring aerial mobile unit, the UE may determine each adjacent aerial mobile unit based on a UE-specific TA offset per beam for each adjacent aerial mobile unit on a beam-by-beam basis and a common TA offset per beam for each adjacent aerial mobile unit. A UE-specific TA correction value for each beam for a moving object may be calculated. The terminal may include the computed terminal-specific TA correction value for each beam for each adjacent aerial vehicle in a measurement report message and transmit the same to the base station via the serving aerial vehicle. The base station may receive a measurement report message from the terminal.

In addition, the terminal is UE-specific for each SSB for each neighboring aerial mobile unit based on a terminal-specific TA offset for each SSB of the neighboring aerial mobile unit and a common TA offset for each SSB for each neighboring aerial mobile unit. TA correction values can be calculated. The terminal may include the calculated terminal-specific TA correction value for each SSB for each neighboring airborne vehicle in a measurement report message and transmit the same to the base station via the serving airborne vehicle. The base station may receive a measurement report message from the terminal.

In addition, the terminal is based on the UE-specific TA offset for each CSI-RS for each neighboring aerial mobile unit and the common TA offset for each CSI-RS for each neighboring aerial mobile unit for each CSI-RS of the neighboring aerial mobile unit. A UE-specific TA correction value for each CSI-RS may be calculated. The UE may include the calculated UE-specific TA correction value for each CSI-RS for each neighboring airborne vehicle in a measurement report message and transmit the same to the base station via the serving airborne vehicle. The base station may receive a measurement report message from the terminal.

Meanwhile, the base station can know identifiers and/or received signal strengths (eg, RSRP, RSRQ) of neighboring airborne vehicles based on information included in the measurement report message. In addition, the base station can know beam-specific identifiers (eg, beam identifiers) and/or received signal strengths (eg, RSRP, RSRQ) of neighboring airborne vehicles based on information included in the measurement report message. In addition, the base station can know SSB-specific identifiers (eg, beam identifiers) and/or received signal strengths (eg, RSRP, RSRQ) of neighboring airborne vehicles based on information included in the measurement report message. In addition, the base station can know identifiers (eg, beam identifiers) for each CSI-RS of neighboring airborne vehicles and/or received signal strengths (eg, RSRP, RSRQ) based on information included in the measurement report message. there is.

In addition to this, the base station can know the UE-specific TA correction value for each neighboring airborne vehicle based on the information included in the measurement report message. In addition, the base station can know the UE-specific TA correction value for each beam for each neighboring airborne vehicle based on the information included in the measurement report message. In addition, the base station can know the UE-specific TA correction value for each SSB for each neighboring air mobile vehicle based on the information included in the measurement report message. In addition, the base station can know the UE-specific TA correction value for each CSI-RS for each neighboring air mobile vehicle based on the information included in the measurement report message.

Accordingly, the base station may select a target airborne vehicle from among neighboring airborne vehicles based on identifiers and received signal strengths of the nearby airborne vehicles. In addition, the base station may select a target aerial mobile unit from among adjacent aerial mobile units based on the received signal strengths and beam identifiers of each beam of the adjacent aerial mobile units, and may select a set beam from among beams of the selected target aerial mobile unit. . Here, the target aerial mobile body may be, for example, the adjacent aerial mobile body 1.

In addition to this, the base station can know the UE-specific TA correction value for each neighboring airborne vehicle based on the information included in the measurement report message. In addition, the base station can know the UE-specific TA correction value for each beam for each neighboring airborne vehicle based on the information included in the measurement report message. In addition, the base station can know the UE-specific TA correction value for each SSB for each neighboring air mobile vehicle based on the information included in the measurement report message. In addition, the base station can know the UE-specific TA correction value for each CSI-RS for each neighboring air mobile vehicle based on the information included in the measurement report message.

Accordingly, the base station may generate a common TA correction value for each of the adjacent airborne vehicles in consideration of the UE-specific TA correction value for each of the adjacent airborne vehicles. In addition, the base station may generate a common TA correction value for each beam of adjacent airborne vehicles in consideration of a UE-specific TA correction value for each beam of adjacent airborne vehicles. In addition, the base station may generate a common TA correction value for each SSB of neighboring airborne vehicles in consideration of a UE-specific TA correction value for each SSB of neighboring airborne vehicles. In addition, the base station may generate a common TA correction value for each CSI-RS of neighboring airborne vehicles in consideration of a UE-specific TA correction value for each CSI-RS of neighboring airborne vehicles.

Thereafter, the base station may generate beam switching configuration information (S704). To this end, the base station may newly define a MAC CE for indicating beam switching for mobile cell switching. Accordingly, the base station can generate beam switching configuration information using the newly defined MAC CE. Here, the beam switching setting information may include beam switching instruction information, an identifier of a target aerial mobile unit, and/or a beam identifier of a beam to be received when accessing the target aerial mobile unit. In addition, the beam switching configuration information may include a common TA correction value for the target airborne vehicle. In addition, the beam switching setting information may include a common TA correction value for the setting beam of the target aerial vehicle.

The base station may transmit the MAC CE including the beam switching configuration information to the terminal through the serving air mobile unit (S705-1, S705-2). Accordingly, the terminal can receive a newly defined MAC CE including beam switching configuration information from the base station. And, the terminal can grasp the beam switching instruction information, the identifier of the target aerial mobile unit, and/or the ID of the beam to be received when the terminal accesses the target aerial mobile unit from the beam switching configuration information. In addition, the terminal can determine a common TA correction value for each beam of adjacent airborne mobile vehicles from the beam switching configuration information. Of course, the base station can adjust the uplink timing by transmitting a TA command to the terminal through a dedicated channel when the uplink timing adjustment is required.

In addition, the base station may define a MAC CE for pre-instructing beam switching for mobile cell switching and a new 1 bit. Accordingly, the base station may inform the terminal that the MAC CE includes the beam switching configuration information by setting the newly defined 1 bit to 1, for example. Accordingly, the base station may transmit beam switching configuration information to the terminal through the corresponding MAC CE through the serving air mobile unit (S705-1, S705-2). Here, the beam switching setting information may be beam switching instruction information, an identifier of a target aerial mobile device, and/or an ID of a beam to be received when the terminal accesses the target aerial mobile device. In addition, the beam switching setting information may include a common TA correction value for each beam of adjacent airborne vehicles. Accordingly, the terminal may receive MAC CE including beam switching configuration information from the base station. And, the terminal can grasp the beam switching instruction information, the identifier of the target aerial mobile unit, and/or the ID of the beam to be received when the terminal accesses the target aerial mobile unit from the beam switching configuration information. In addition, the terminal can determine a common TA correction value for each beam of adjacent airborne mobile vehicles from the beam switching configuration information. Of course, the base station can adjust the uplink timing by transmitting a TA command to the terminal through a dedicated channel when the uplink timing adjustment is required.

In addition, the base station may newly define a beam switching message for instructing beam switching for mobile cell switching in advance. Accordingly, the base station may transmit beam switching configuration information to the terminal through a newly defined beam switching message (S705-1, S705-2). Here, the beam switching setting information may be beam switching instruction information, an identifier of a target aerial mobile device, and/or an ID of a beam to be received when the terminal accesses the target aerial mobile device. In addition, the beam switching setting information may include a common TA correction value for each beam of adjacent airborne vehicles. Accordingly, the terminal may receive a beam switching message including beam switching configuration information from the base station. And, the terminal can grasp the beam switching instruction information, the identifier of the target aerial mobile unit, and/or the ID of the beam to be received when the terminal accesses the target aerial mobile unit from the beam switching setting information. In addition, the terminal can determine a common TA correction value for each beam of adjacent airborne mobile vehicles from the beam switching configuration information. Of course, the base station can adjust the uplink timing by transmitting a TA command to the terminal through a dedicated channel when the uplink timing adjustment is required.

Meanwhile, the base station may not set a switching time in the above beam switching setting information. At this time, the base station may implicitly set the switching time. In this case, the terminal may perform beam switching after the service end point of the serving beam. That is, the terminal may perform transmission and reception on the set beam after the service end time of the serving beam.

As such, the terminal may perform mobile cell switching to change the connection from the serving aerial mobile unit to the target aerial mobile unit according to the beam switching setting information (S706). Here, the target aerial mobile body may be, for example, the adjacent aerial mobile body 1. Such mobile cell switching can be achieved by performing beam switching in which a terminal receives a signal through a beam provided by a target aerial mobile while receiving a signal through a beam provided by a serving aerial mobile. As such, beam switching may be set by the base station before the service end time set for the current serving beam. Accordingly, the point in time at which service is received on the new beam may be after the service end time of the serving beam.

Alternatively, the base station may set a switching time in beam switching configuration information. And, the base station may transmit beam switching configuration information including the switching time to the terminal. Alternatively, the base station may generate switching time information separately from beam switching configuration information. And, the base station may transmit switching time information to the terminal. Accordingly, the terminal can receive switching time information from the base station.

In this case, when the beam ID provided by the MAC CE belongs to an adjacent airborne vehicle (satellite/vehicle), the terminal may transmit/receive on the set beam after a set switching time.

On the other hand, the terminal can synchronize the uplink with the target airborne vehicle. The UE may synchronize uplink with the target airborne vehicle using the UE-specific TA correction value calculated in advance. In addition, the terminal can synchronize uplink with the target airborne vehicle by using the common TA correction value previously received from the base station.

Alternatively, the terminal may obtain a common TA correction value by accessing the target airborne vehicle and performing a random access procedure (S707). As such, the UE may adjust the uplink timing by adjusting the UE-specific TA correction value using the common TA correction value obtained by accessing the target airborne vehicle and performing the random access procedure. At this time, the terminal may proceed with the random access procedure as described in Cases 1 to 3 below.

(Case 1) When the base station adds mobile cell switching to RACH triggering conditions

The base station may add a mobile cell switching case to conditions for triggering a RACH process. Accordingly, the RACH triggering condition added to the terminal by the base station may be a condition that the service type provided by the serving air mobile unit is a ground fixed service. In contrast, the RACH triggering condition added by the base station to the terminal may be a case where the service type provided by the serving aerial vehicle may be a ground fixed type service and the service stop point of the serving aerial vehicle in the corresponding area can be confirmed through the SIB. there is. The base station may transmit such a RACH triggering condition to the terminal. In this case, the base station may include the RACH triggering condition in the beam switching indication information of the beam switching configuration information and transmit the information to the terminal. Accordingly, the terminal may determine that the RACH triggering condition is satisfied when it is known that the service type of the serving airborne vehicle is a ground fixed type service. Alternatively, the UE can determine that the service type of the serving aerial vehicle is a ground fixed type service, and if the service interruption point of the serving aerial vehicle is known through the SIB, it can determine that the RACH triggering condition is satisfied. Accordingly, when the timing alignment timer is driven, the terminal may start a contention free random access (CFRA) or contention based random access (CBRA) random access procedure with the target airborne vehicle regardless of this. At this time, a random access procedure performed by the terminal and the base station may be the same as that of FIG. 4 . Accordingly, the UE can know the UE-specific TA correction value or the common TA correction value for the target airborne vehicle and can perform TA adjustment. However, in this case, after cell switching, the serviced terminals in the cell simultaneously drive the RACH process, which causes waste of RACH resources and congestion/collision, which can degrade system performance.

(Case 2) When the base station or the terminal recognizes the uplink synchronization as unsynchronized

(Case 2-1) The terminal may determine that uplink synchronization is lost when mobile cell switching occurs in connected mode. Accordingly, the terminal may start a random access procedure. In this case, after mobile cell switching, UEs receiving service within the cell may simultaneously drive the CFRA or CBRA RACH procedure. As a result, RACH resource waste and congestion/collision may occur, which may degrade system performance.

(Case 2-2) The base station may recognize uplink synchronization as an unsynchronized state when mobile cell switching is performed in a terminal connected to the serving airborne vehicle. At this time, the base station may transmit a physical downlink control channel (PDCCH) order indicating uplink synchronization recovery to the terminal through the serving airborne vehicle. Here, the order may be an instruction requesting the terminal to perform a certain operation. The PDCCH order may be DCI format 1A, and may additionally include 1 bit indicating that it is due to mobile cell switching. The base station may set the additionally included 1 bit to 1 and transmit it to the terminal. The PDCCH order may include a UE-specific preamble. Accordingly, the terminal can receive the PDCCH order including the terminal-specific preamble from the base station through the serving airborne vehicle.

In this case, the base station may include a condition for instructing to perform a random access procedure when receiving such a PDCCH order in the beam switching instruction information of the beam switching configuration information and transmit it to the terminal. Accordingly, the UE may attempt CFRA with the target airborne vehicle using the UE-specific preamble set in the received PDCCH order. The target airborne vehicle may receive a UE-specific preamble from the UE and may transmit RAR to the UE. And, the base station may allocate resources for MSG3 transmission of the terminal. After receiving the RAR, the UE may transmit MAC CE including pre-compensated TA information (eg, UE TA adjustment value) to the base station through the target airborne vehicle. The base station may receive a MAC CE including pre-compensated TA information from the terminal, and may schedule messages or data thereafter using the received pre-compensated TA information.

(Case 2-3) The base station may transmit a PDCCH order to connected terminals. In this case, the PDCCH order may be of DCI format 1A and may additionally include 1 bit indicating that it is due to a mobile cell switch. The base station may set the additionally included 1 bit to 1 and transmit it to the terminal. The PDCCH order may include a UE-specific preamble. Accordingly, the terminal can receive the PDCCH order including the terminal-specific preamble from the base station through the serving airborne vehicle.

In this case, the base station may include a condition for instructing to perform a random access procedure when a PDCCH order is received in the beam switching indication information of the beam switching configuration information and transmit it to the terminal. Accordingly, the UE may attempt CFRA with the target airborne vehicle using the UE-specific preamble set in the received PDCCH order. The target airborne vehicle may receive a UE-specific preamble from the UE and may transmit RAR to the UE. And, the base station may allocate resources for MSG3 transmission of the terminal. Meanwhile, the UE may perform a logical channel prioritization (LCP) procedure to set the priority of the MAC CE including pre-compensated TA information (eg, UE TA adjustment value) to the highest priority. According to this priority order, after receiving the RAR, the terminal may preferentially transmit the MAC CE including the pre-compensated TA information to the base station through the target airborne vehicle. The base station may receive a MAC CE including pre-compensated TA information from the terminal, and may schedule messages or data thereafter using the received pre-compensated TA information.

(Case 3) In case of performing random access procedure according to data generation

(Case 3-1) When data is generated in the terminal

The base station may include a condition instructing to perform a random access procedure when data is generated in the beam switching instruction information of the beam switching configuration information and transmit the information to the terminal. Accordingly, the terminal may perform a random access procedure when uplink data is generated. The terminal may make an attempt with the target airborne vehicle using the preamble. The target aerial mobile vehicle may receive a preamble from the UE and may transmit RAR to the UE. And, the base station may allocate resources for MSG3 transmission of the terminal. After receiving the RAR, the UE may transmit MAC CE including pre-compensated TA information (eg, UE TA adjustment value) to the base station through the target airborne vehicle. The base station may receive MAC CE including pre-compensated TA information from the terminal, and may schedule messages or data later using the received pre-compensated TA information.

(Case 3-2) When data is generated from the base station

Downlink data may be generated by the base station. In this case, the base station may transmit a PDCCH order to the connected terminals. In this case, the PDCCH order may be of DCI format 1A and may additionally include 1 bit indicating that it is due to a mobile cell switch. The base station may set the additionally included 1 bit to 1 and transmit it to the terminal. The PDCCH order may include a UE-specific preamble. Accordingly, the terminal can receive the PDCCH order including the terminal-specific preamble from the base station through the serving airborne vehicle.

The UE may attempt CFRA with the target airborne vehicle using the UE-specific preamble set in the received PDCCH order. The target airborne vehicle may receive a UE-specific preamble from the UE and may transmit RAR to the UE. And, the base station may allocate resources for MSG3 transmission of the terminal. Meanwhile, the UE may perform a logical channel prioritization (LCP) procedure to set the priority of the MAC CE including pre-compensated TA information to be the highest. According to this priority order, after receiving the RAR, the terminal may preferentially transmit the MAC CE including the pre-compensated TA information to the base station through the target airborne vehicle. The base station may receive a MAC CE including pre-compensated TA information (eg, a UE TA adjustment value) from the terminal, and may schedule messages or data thereafter using the received pre-compensated TA information.

(Case 4) In the case of mobile cell switching, when the beam to be switched is not set in advance

The terminal may perform beam failure recovery (BFR). At this time, the terminal may ignore the conditions for determining the BFR, and select a new beam to drive the random access processor.

Meanwhile, in the case of mobile cell switching, among the uplink timing adjustment methods, a method of reporting a TA for pre-compensating for a new beam to the base station has been described above. If the terminal reports pre-compensation TA information for each beam in advance, transmission and reception may be possible without starting a random access process due to a mobile cell switching case. The base station can activate pre-reporting of pre-compensation TA information for the mobile cell switching case, and the corresponding information can be configured as a broadcast or dedicated message.

The operation of the method according to an embodiment of the present disclosure can be implemented as a computer readable program or code on a computer readable recording medium. A computer-readable recording medium includes all types of recording devices in which information that can be read by a computer system is stored. In addition, computer-readable recording media may be distributed to computer systems connected through a network to store and execute computer-readable programs or codes in a distributed manner.

In addition, the computer-readable recording medium may include hardware devices specially configured to store and execute program instructions, such as ROM, RAM, and flash memory. The program command may include high-level language codes that can be executed by a computer using an interpreter or the like as well as machine code generated by a compiler.

Although some aspects of the present disclosure have been described in the context of an apparatus, it may also represent a description according to a corresponding method, where a block or apparatus corresponds to a method step or feature of a method step. Similarly, aspects described in the context of a method may also be represented by a corresponding block or item or a corresponding feature of a device. Some or all of the method steps may be performed by (or using) a hardware device such as, for example, a microprocessor, programmable computer, or electronic circuitry. In some embodiments, at least one or more of the most important method steps may be performed by such a device.

In embodiments, a programmable logic device (eg, a field programmable gate array) may be used to perform some or all of the functions of the methods described herein. In embodiments, a field-programmable gate array may operate in conjunction with a microprocessor to perform one of the methods described herein. Generally, methods are preferably performed by some hardware device.

Although it has been described with reference to the preferred embodiments of the present disclosure, those skilled in the art can variously modify and change the present disclosure within the scope not departing from the spirit and scope of the present disclosure described in the claims below. You will understand that you can.

Claims (20)

As an operation method performed in a terminal of a communication system,
performing measurements on a serving cell and neighboring cells;
Transmitting measurement results of the serving cell and the neighboring cells to the serving cell;
Receiving, from the serving cell, beam switching setting information including information about a target cell among the neighboring cells and a beam switching time based on the measurement result;
generating a timing advance (TA) by using the information on the target cell;
performing a random access procedure with the target cell according to the beam switching configuration information;
obtaining a first TA adjustment value from the target cell through the random access procedure; and
Adjusting the TA using the first TA adjustment value,
An operation method performed in a terminal. The method of claim 1,
Receiving service type identification information from the serving cell; and
Further comprising the step of confirming a service type based on the service type identification information,
If the beam switching configuration information includes instruction information indicating execution of a random access procedure when the checked service type is the terrestrial fixed service, the terminal terminates the service stop time when the checked service type is the terrestrial fixed service. Performing the random access procedure immediately after
An operation method performed in a terminal. The method of claim 2,
The service type identification information includes a service indicator, and the terminal recognizes the checked service type as the ground fixed service when the service indicator indicates the ground fixed service.
An operation method performed in a terminal. The method of claim 2,
The service type identification information includes the service stop time in the corresponding area of the serving cell, and when the service stop time is confirmed, the terminal recognizes the checked service type as the land fixed service,
An operation method performed in a terminal. The method of claim 1,
Receiving service type identification information from the serving cell; and
Further comprising the step of confirming a service type based on the service type identification information,
The beam switching setting information includes information indicating a random access procedure performed when the checked service type is the terrestrial fixed service, and the terminal considers the beam switching time when the checked service type is the terrestrial fixed service. Performing the random access procedure,
An operation method performed in a terminal. The method of claim 1,
Further comprising receiving a physical downlink control channel (PDCCH) indication from the serving cell,
If the beam switching configuration information includes indication information for performing a random access procedure when the PDCCH indication is received from the serving cell, the terminal performs the random access procedure at the time the PDCCH indication is received,
An operation method performed in a terminal. The method of claim 1,
If the beam switching configuration information includes indication information for performing a random access procedure when uplink data occurs, the terminal performs the random access procedure when the uplink data occurs,
An operation method performed in a terminal. The method of claim 1,
If the beam switching configuration information includes a second TA correction value for the target cell based on the measurement result, the terminal generates the TA by referring to the second TA correction value.
An operation method performed in a terminal. The method of claim 1,
setting uplink synchronization using the adjusted TA using the first TA adjustment value; and
Transmitting an uplink signal to the target cell by applying the set uplink synchronization,
An operation method performed in a terminal. As an operating method performed in a base station including a serving cell and neighboring cells,
Receiving measurement results of the serving cell and the neighboring cells from a terminal through the serving cell;
determining a target cell among the neighboring cells based on the measurement result;
generating beam switching setting information including information about the target cell and a beam switching time;
Transmitting the beam switching setting information to the terminal through the serving cell; and
Transmitting a first TA adjustment value to the terminal through a random access procedure performed between the terminal and the target cell according to the beam switching configuration information,
A method of operation performed at a base station. The method of claim 10,
Further comprising transmitting service type identification information indicating the service type of the serving cell to the terminal,
When the beam switching configuration information includes indication information indicating execution of a random access procedure when the service type is the terrestrial fixed service, and the service type checked by the terminal in the service type information is the terrestrial fixed service, the service To perform the random access procedure immediately after the end of the stop time,
A method of operation performed at a base station. The method of claim 11,
The service type identification information includes the service stop time in the corresponding area of the serving cell, and when the service stop time is confirmed, the terminal recognizes the checked service type as the terrestrial fixed service,
A method of operation performed at a base station. The method of claim 10,
Further comprising transmitting a PDCCH indication to the terminal through the serving cell when there is data to be transmitted to the terminal,
The beam switching configuration information includes indication information for performing a random access procedure when the PDCCH indication is received from the serving cell, so that the terminal performs the random access procedure at the time when the PDCCH indication is received,
A method of operation performed at a base station. The method of claim 10,
Further comprising generating a second TA correction value for the target cell based on the measurement result,
The beam switching configuration information includes the second TA correction value so that the terminal performs the random access procedure by referring to the second TA correction value.
A method of operation performed at a base station. As a terminal,
Including a processor,
The processor is the terminal,
performing measurements on the serving cell and adjacent cells;
Transmitting measurement results for the serving cell and the neighboring cells to the serving cell;
Receiving beam switching setting information including information about a target cell among the neighboring cells and a beam switching time based on the measurement result from the serving cell;
generating a timing advance (TA) using the information on the target cell;
performing a random access procedure with the target cell according to the beam switching setting information;
obtaining a first TA adjustment value from the target cell through the random access procedure; and
Operate to cause an adjustment of the TA using the first TA adjustment value.
Terminal. The method of claim 15
The processor is the terminal,
Receiving service type identification information from the serving cell; and
Operate to further cause identification of a service type based on the service type identification information;
If the beam switching configuration information includes instruction information indicating execution of a random access procedure when the checked service type is the terrestrial fixed service, the terminal terminates the service stop time when the checked service type is the terrestrial fixed service. Performing the random access procedure immediately after
Terminal. The method of claim 16
The service type identification information includes the service stop time in the corresponding area of the serving cell, and when the service stop time is confirmed, the terminal recognizes the checked service type as the land fixed service,
Terminal. The method of claim 15
The processor is the terminal,
Operate to further cause receiving a PDCCH indication from the serving cell;
If the beam switching configuration information includes indication information for performing a random access procedure when the PDCCH indication is received from the serving cell, the terminal performs the random access procedure at the time the PDCCH indication is received,
Terminal. The method of claim 15
If the beam switching setting information includes information indicating a random access procedure to be performed when uplink data is generated, the terminal performs the random access procedure based on the time when the uplink data is generated,
Terminal. The method of claim 15
If the beam switching configuration information includes a second TA correction value for the target cell based on the measurement result, the terminal generates the TA by referring to the second TA correction value.
Terminal.

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