KR20220046508A - Method and apparatus for device to device communication in wireless communication system - Google Patents

Abstract

The present invention relates to a communication method performed by a first communication node of a communication system. The method includes the following steps of: receiving first data from a second communication node of the communication system; checking first communication quality information regarding the communication quality between the first and second communication nodes based on the result of the first data reception; generating first connection information based on the first communication quality information; transmitting the first connection information to the second communication node; receiving second data from the second communication node; checking second communication quality information regarding the communication quality between the first and second communication nodes based on the result of the second data reception; generating, based on the first communication quality information and the second communication quality information, second connection information including information on how the communication quality between the first and second communication nodes changes; and transmitting the second connection information to the second communication node.

Description

Communication method and apparatus between terminals in a wireless communication system

The present invention relates to a device-to-device (D2D) technology in a wireless communication system, and more particularly, to a technology for operating a wireless connection between terminals constituting a sidelink-based relay connection in a wireless communication system. it's about

With the development of information and communication technology, various wireless communication technologies are being developed. Representative wireless communication technologies include long term evolution (LTE) and new radio (NR) defined in 3rd generation partnership project (3GPP) standards. LTE may be one of 4G (4th Generation) wireless communication technologies, and NR may be one of 5G (5th Generation) wireless communication technologies.

In order to increase the wireless data transmission rate and support more various application services in a wireless communication system, technologies using a high frequency frequency of a higher frequency band are being studied. However, in high frequency bands, it may be difficult to provide complete network coverage due to high path loss. Accordingly, technologies for improving energy efficiency and extending network coverage by directly exchanging data between terminals or devices located in a physically close distance without passing through a communication network such as a base station or a core network are being studied.

Direct communication between mobile devices or terminals such as smartphones and drones may be referred to as device-to-device (D2D) communication. For example, D2D communication may be performed based on a sidelink technology defined in 3GPP. In an embodiment of the communication system, UE-to-Network (U2N) relay or UE-to-UE (U2U) relay may be performed based on a relay function of a terminal through a sidelink. Through the U2N relay or the U2U relay, the coverage of the communication network may be extended and the communication quality may be improved. In a communication system including a terminal performing U2N relay or U2U relay, a technique for efficiently operating a wireless connection between terminals may be required.

Matters described in this background section are prepared to enhance understanding of the background of the invention, and may include matters that are not already known to those of ordinary skill in the art to which this technology belongs.

An object of the present invention is to provide a wireless communication system in which a terminal (hereinafter, a relay terminal) configuring a relay connection based on a sidelink and a terminal receiving a relay of the relay terminal (hereinafter, a remote terminal) can indicate a change in a channel state in a wireless communication system. An object of the present invention is to provide a communication method and apparatus between terminals for efficiently operating a wireless connection between terminals by transmitting and receiving connection information.

A communication method performed by a first communication node of a communication system according to an embodiment of the present invention for achieving the above object includes the steps of receiving first data from a second communication node of the communication system, the first Checking first communication quality information on communication quality between the first and second communication nodes based on a result of receiving data; generating first connection information based on the first communication quality information; Transmitting the first connection information to the second communication node, receiving second data from the second communication node, based on a result of receiving the second data, the first and second communication nodes Checking second communication quality information for communication quality between the first and second communication quality information, based on the first and second communication quality information, a second connection including information on a change aspect of communication quality between the first and second communication nodes generating information, and transmitting the second connection information to the second communication node.

According to an embodiment of the present invention, in a communication system, a terminal may perform terminal-to-terminal relay (U2U relay) or terminal-to-network relay (U2N relay) based on a sidelink. In a relay structure including a sidelink-based relay terminal, a receiving node receiving data from a transmitting node may monitor a communication quality change aspect based on the received data. The receiving node may generate and transmit connection information including information on the communication quality change aspect to the transmitting node based on the monitoring result of the communication quality change aspect. The transmitting node may check a communication quality change aspect based on the connection information received from the receiving node, and may perform operations for operating a wireless connection in a communication system including a relay structure.

1 is a conceptual diagram illustrating an embodiment of a communication system.
2 is a block diagram illustrating an embodiment of a communication node constituting a communication system.
3A and 3B are conceptual diagrams for explaining an embodiment of a sidelink-based relay method in a communication system.
4 is a conceptual diagram for explaining an embodiment of a communication quality change monitoring method in a communication system.
5 is a flowchart illustrating an embodiment of a method for generating connection information in a communication system.
6A and 6B are conceptual diagrams for explaining a first embodiment of a MAC (Medium Access Control) CE (Control Element) for transmission of connection information.
7 is a conceptual diagram illustrating a second embodiment of a MAC CE for transmission of connection information.
8A to 8C are conceptual diagrams for explaining an embodiment of an operation method of communication nodes constituting a UE-to-UE (U2U) relay structure.
9 is a flowchart illustrating a first embodiment of a method for operating a relay connection in a communication system.
10 is a flowchart illustrating a second embodiment of a method for operating a relay connection in a communication system.
11 is a conceptual diagram illustrating an embodiment of a MAC Protocol Data Unit (PDU) in a communication system.
12A and 12B are conceptual diagrams for explaining an embodiment of a sidelink feedback channel including connection information in a communication system.
13A and 13B are conceptual diagrams for explaining a first embodiment of a method of operating communication nodes constituting a UE-to-Network (U2N) relay structure.
14A and 14B are conceptual diagrams for explaining a second embodiment of a method of operating communication nodes constituting a U2N relay structure.

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.

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, “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”.

When an element is referred to as being “connected” or “connected” to another element, it is understood that it may be directly connected or connected to the other element, but other elements 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 and 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

A communication system to which embodiments according to the present invention are applied will be described. The communication system to which the embodiments according to the present invention are applied is not limited to the content described below, and the embodiments according to the present invention can be applied to various communication systems. Here, a communication system may be used in the same sense as a communication network (network).

Throughout the specification, a network is, for example, a wireless Internet such as WiFi (wireless fidelity), a wireless broadband internet (WiBro) or a mobile Internet such as a world interoperability for microwave access (WiMax), a global system for mobile communication (GSM). ) or 2G mobile communication network such as CDMA (code division multiple access), WCDMA (wideband code division multiple access) or 3G mobile communication network such as CDMA2000, high speed downlink packet access (HSDPA) or high speed uplink packet access (HSUPA) such as It may include a 3.5G mobile communication network, a 4G mobile communication network such as a long term evolution (LTE) network or an LTE-Advanced network, and a 5G mobile communication network.

Throughout the specification, a terminal refers to a mobile station, a mobile terminal, a subscriber station, a portable subscriber station, a user equipment, and an access terminal. and the like, and may include all or some functions of a terminal, a mobile station, a mobile terminal, a subscriber station, a portable subscriber station, a user equipment, an access terminal, and the like.

Here, a desktop computer that can communicate with a terminal, a laptop computer, a tablet PC, a wireless phone, a mobile phone, a smart phone, a smart watch (smart watch), smart glass, e-book reader, PMP (portable multimedia player), portable game console, navigation device, digital camera, DMB (digital multimedia broadcasting) player, digital voice Digital audio recorder, digital audio player, digital picture recorder, digital picture player, digital video recorder, digital video player ) can be used.

Throughout the specification, a base station is an access point, a radio access station, a Node B, an advanced nodeB, a base transceiver station, MMR ( It may refer to mobile multihop relay)-BS, etc., and may include all or some functions of a base station, an access point, a radio access station, a Node B, an eNodeB, a transceiver base station, and an MMR-BS.

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.

1 is a conceptual diagram illustrating an embodiment of a communication system.

1, the communication system 100 is a plurality of communication nodes (110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, 130-6). A plurality of communication nodes 4G communication (eg, long term evolution (LTE), LTE-A (advanced)), 5G communication (eg, NR (new radio)) defined in the 3rd generation partnership project (3GPP) standard ) can be supported. 4G communication may be performed in a frequency band of 6 GHz or less, and 5G communication may be performed in a frequency band of 6 GHz or more as well as a frequency band of 6 GHz or less.

For example, a plurality of communication nodes for 4G communication and 5G communication is a CDMA (code division multiple access) based communication protocol, WCDMA (wideband CDMA) based communication protocol, TDMA (time division multiple access) based communication protocol, FDMA (frequency division multiple access) based communication protocol, OFDM (orthogonal frequency division multiplexing) based communication protocol, Filtered OFDM based communication protocol, CP (cyclic prefix)-OFDM based communication protocol, DFT-s-OFDM (discrete) Fourier transform-spread-OFDM) based communication protocol, OFDMA (orthogonal frequency division multiple access) based communication protocol, SC (single carrier)-FDMA based communication protocol, NOMA (Non-orthogonal multiple access), GFDM (generalized frequency) Division multiplexing)-based communication protocol, FBMC (filter bank multi-carrier)-based communication protocol, UFMC (universal filtered multi-carrier)-based communication protocol, SDMA (Space Division Multiple Access)-based communication protocol, etc. can be supported. .

Also, the communication system 100 may further include a core network. When the communication system 100 supports 4G communication, the core network may include a serving-gateway (S-GW), a packet data network (PDN)-gateway (P-GW), and a mobility management entity (MME). there is. When the communication system 100 supports 5G communication, the core network may include a user plane function (UPF), a session management function (SMF), an access and mobility management function (AMF), and the like.

On the other hand, a plurality of communication nodes (110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130- 4, 130-5, 130-6) may each have the following structure.

2 is a block diagram illustrating an embodiment of a communication node constituting a communication system.

Referring to FIG. 2 , the communication node 200 may include at least one processor 210 , a memory 220 , and a transceiver 230 connected to a network to perform communication. In addition, the communication node 200 may further include an input interface device 240 , an output interface device 250 , a storage device 260 , and the like. Each of the components included in the communication node 200 may be connected by a bus 270 to communicate with each other.

However, each of the components included in the communication node 200 may not be connected to the common bus 270 but to the processor 210 through an individual interface or an individual bus. For example, the processor 210 may be connected to at least one of the memory 220 , the transceiver 230 , the input interface device 240 , the output interface device 250 , and the storage device 260 through a dedicated interface. .

The processor 210 may execute a program command stored in at least one of the memory 220 and the storage device 260 . The processor 210 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 220 and the storage device 260 may be configured as at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 220 may be configured as at least one of a read only memory (ROM) and a random access memory (RAM).

Referring back to FIG. 1 , the communication system 100 includes a plurality of base stations 110 - 1 , 110 - 2 , 110 - 3 , 120 - 1 and 120 - 2 , and a plurality of terminals 130 - 1, 130-2, 130-3, 130-4, 130-5, 130-6). Base stations 110-1, 110-2, 110-3, 120-1, 120-2 and terminals 130-1, 130-2, 130-3, 130-4, 130-5, 130-6 The comprising communication system 100 may be referred to as an “access network”. Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 may form a macro cell. Each of the fourth base station 120-1 and the fifth base station 120-2 may form a small cell. The fourth base station 120-1, the third terminal 130-3, and the fourth terminal 130-4 may belong to the cell coverage of the first base station 110-1. The second terminal 130-2, the fourth terminal 130-4, and the fifth terminal 130-5 may belong to the cell coverage of the second base station 110-2. The fifth base station 120-2, the fourth terminal 130-4, the fifth terminal 130-5, and the sixth terminal 130-6 may belong to the cell coverage of the third base station 110-3. there is. The first terminal 130-1 may belong to the cell coverage of the fourth base station 120-1. The sixth terminal 130-6 may belong to the cell coverage of the fifth base station 120-2.

Here, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, 120-2 is a NodeB (NodeB), an advanced NodeB (evolved NodeB), a BTS (base transceiver station), Radio base station (radio base station), radio transceiver (radio transceiver), access point (access point), access node (node), RSU (road side unit), RRH (radio remote head), TP (transmission point), TRP ( transmission and reception ooint), eNB, gNB, and the like.

Each of the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, 130-6 is a user equipment (UE), a terminal, an access terminal, and a mobile Terminal (mobile terminal), station (station), subscriber station (subscriber station), mobile station (mobile station), portable subscriber station (portable subscriber station), node (node), device (device), IoT (Internet of Thing) It may be referred to as a device, a mounted device (such as a mounted module/device/terminal or on board device/terminal).

Meanwhile, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may operate in different frequency bands or may operate in the same frequency band. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to each other through an ideal backhaul link or a non-ideal backhaul link. , information can be exchanged with each other through an ideal backhaul link or a non-ideal backhaul link. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to the core network through an ideal backhaul link or a non-ideal backhaul link. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 transmits a signal received from the core network to the corresponding terminals 130-1, 130-2, 130-3, 130 -4, 130-5, 130-6), and a signal received from the corresponding terminal (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) is transmitted to the core network can be sent to

In addition, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 transmits MIMO (eg, single user (SU)-MIMO, multi user (MU)- MIMO, massive MIMO, etc.), coordinated multipoint (CoMP) transmission, carrier aggregation (CA) transmission, transmission in an unlicensed band, device to device communication (D2D) (or, ProSe ( proximity services)), and the like. Here, each of the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, 130-6 is the base station 110-1, 110-2, 110-3, and 120-1. , 120-2) and corresponding operations, and operations supported by the base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be performed. For example, the second base station 110-2 may transmit a signal to the fourth terminal 130-4 based on the SU-MIMO method, and the fourth terminal 130-4 may transmit a signal based on the SU-MIMO method. A signal may be received from the second base station 110 - 2 . Alternatively, the second base station 110 - 2 may transmit a signal to the fourth terminal 130 - 4 and the fifth terminal 130 - 5 based on the MU-MIMO scheme, and the fourth terminal 130 - 4 . and each of the fifth terminals 130 - 5 may receive a signal from the second base station 110 - 2 by the MU-MIMO method.

Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 may transmit a signal to the fourth terminal 130-4 based on the CoMP scheme, and the fourth The terminal 130-4 may receive signals from the first base station 110-1, the second base station 110-2, and the third base station 110-3 by the CoMP method. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 is a terminal 130-1, 130-2, 130-3, 130-4 belonging to its own cell coverage. , 130-5, 130-6) and the CA method can transmit and receive signals. Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 controls D2D between the fourth terminal 130-4 and the fifth terminal 130-5. and each of the fourth terminal 130-4 and the fifth terminal 130-5 may perform D2D under the control of the second base station 110-2 and the third base station 110-3, respectively. .

Next, communication methods between terminals in a wireless communication system will be described. Here, even when a method (eg, transmission or reception of a signal) performed in a first communication node among communication nodes is described, a second communication node corresponding thereto is a method corresponding to the method performed in the first communication node (eg, receiving or transmitting a signal). For example, when the operation of the reception node is described, the corresponding transmission node may perform the operation corresponding to the operation of the reception node. Conversely, when the operation of the transmitting node is described, the corresponding receiving node may perform the operation corresponding to the operation of the transmitting node.

3A and 3B are conceptual diagrams for explaining an embodiment of a communication system supporting relay based on a sidelink between terminals.

Referring to FIG. 3A , a communication system 300 may include one or more base stations (BSs) and one or more user equipments (UEs). One or more base stations may form cell coverage in a predetermined communicable area to provide services to terminals within the cell coverage. A terminal located within the cell coverage of one or more base stations among one or more terminals may access a communication network and receive a service by being connected to the base station forming the cell coverage. Alternatively, some of the one or more terminals may not be directly connected to one or more base stations, but may access the communication network by being indirectly connected to one or more base stations through a relay of other terminals. 3A, it can be seen that a communication system including two base stations and a plurality of terminals is illustrated as an example. However, this is only an example for convenience of description, and the embodiment of the present invention is not limited thereto.

In one embodiment, the communication system 300 includes a core network 305 , a first base station 310 , a second base station 320 and a plurality of terminals 330 , 331 , 340 , 341 , 350 , 351, 360, 361). The core network 305 may be the same as or similar to the core network described with reference to FIG. 1 . The first and second base stations 310 and 320 may be the same as or similar to the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 described with reference to FIG. 1 . . The plurality of terminals 330 , 331 , 340 , 341 , 350 , 351 , 360 and 361 are the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130 described with reference to FIG. 1 . -5, 130-6) may be the same or similar to Each of the plurality of terminals is a first terminal 330 , a second terminal 331 , a third terminal 340 , a fourth terminal 341 , a fifth terminal 350 , a sixth terminal 351 , and a seventh terminal It may be referred to as the terminal 360 , the eighth terminal 361 , and the like.

The first and second base stations 310 and 320 may be connected to the core network 305 . The first and second base stations 310 and 320 may form cell coverage 317 and 327 in a predetermined communicable area to provide services to terminals within the cell coverage 317 and 327 . For example, a plurality of terminals 330 , 331 , 340 , 341 , 350 , 351 , 360 , 361 included in the communication system 300 , the first and the first located within the cell coverage 317 of the first base station 310 The second, fifth, and seventh terminals 330 , 331 , 350 , and 360 may be connected to the first base station 310 to access the core network 305 . The third and fourth located within the cell coverage 327 of the second base station 320 among the plurality of terminals 330 , 331 , 340 , 341 , 350 , 351 , 360 , 361 included in the communication system 300 . and the eighth terminals 330 , 331 , and 340 may be connected to the second base station 320 to access the core network 305 .

On the other hand, some of the plurality of terminals (330, 331, 340, 341, 350, 351, 360, 361) are not directly connected to the first base station 310 or the second base station 320, and relay of other terminals It may be indirectly connected to the first base station 310 or the second base station 320 through the. For example, the sixth terminal 451 may not be directly connected to the first base station 310 because it is located outside the cell coverage of the first base station 310 . The sixth terminal 451 may access the core network 305 by being indirectly connected to the first base station 310 through a relay of the fifth terminal 350 connected to the first base station 310 . In other words, the fifth terminal 350 may relay the connection between the sixth terminal 351 and the first base station 310 located within the predetermined communicable area 357 . On the other hand, even in the case of a terminal located within the cell coverage 317, 327 of the first base station 310 or the second base station 320, such as the second terminal 331 and the fourth terminal 341, each A situation in which a channel state with the base stations 310 and 320 is not excellent may occur. For example, although the second terminal 331 is located within the cell coverage 317 of the first base station 310, it is located in a shaded area caused by a building, etc., so that direct communication with the first base station 310 is not easy. can In this case, the second terminal 331 is indirectly connected to the first base station 310 through the relay of the first terminal 330, which facilitates direct communication with the first base station 310, and thereby connects to the core network 305. can connect In other words, the first terminal 330 may relay the connection between the second terminal 331 and the first base station 310 located within the predetermined communication available area 337 . On the other hand, although the fourth terminal 341 is located within the cell coverage 327 of the second base station 320, direct communication with the second base station 320 due to obstacles on the communication path with the second base station 320, etc. This may not be easy. In this case, the fourth terminal 341 is indirectly connected to the second base station 320 through the relay of the third terminal 340 , which facilitates direct communication with the second base station 320 , and thereby connects to the core network 305 . can connect In other words, the third terminal 340 may relay the connection between the fourth terminal 341 and the second base station 320 located within the predetermined communicable area 347 .

On the other hand, the seventh terminal 360 located within the cell coverage 317 of the first base station 310 is located outside the cell coverage 317 of the first base station 310 and the cell coverage of the second base station 320 ( 327), the connection between the eighth terminal 361 and the first base station 310 may be relayed.

Here, first, third, and third relaying the connection between the second, fourth, sixth and eighth terminals 331 , 341 , 351 , 361 and the first and second base stations 310 and 320 . The fifth and seventh terminals 330 , 340 , 350 and 360 may be referred to as 'relay terminals' or 'relay UEs'. On the other hand, the second, fourth, The sixth and eighth terminals 331 , 341 , 351 , and 361 may be referred to as a 'remote terminal' or a 'remote UE'. In an embodiment of the communication system 300 , the connection between the relay terminal and the remote terminal may be established in a sidelink manner. Between the first, third, fifth and seventh terminals 330 , 340 , 350 and 360 as relay terminals and the second, fourth, sixth and eighth terminals 331 , 341 , 351 and 361 as remote terminals Connections may be established with PC5 interfaces 339 , 349 , 359 , 369 . On the other hand, the connection between the first, third, fifth and seventh terminals (330, 340, 350, 360), which are relay terminals, and the first and second base stations (310, 320) is connected to the Uu interface (335, 345, 355, 365) can be set.

In an embodiment of the communication system, for reasons such as a predetermined commercial service or public safety service, each terminal may need to be connected to a base station to transmit and receive data. First, third, fifth and seventh in which direct communication with any one of the base stations 310 and 323 among the plurality of terminals 330, 331, 340, 341, 350, 351, 360, 361 is easy The terminals 330 , 340 , 350 , and 360 may be directly connected to any one of the base stations 310 and 323 to perform data transmission and reception. Meanwhile, the second, fourth, and sixth terminals in which direct communication with any one of the base stations 310 and 323 among the plurality of terminals 330 , 331 , 340 , 341 , 350 , 351 , 360 and 361 is not easy And the eighth terminal (331, 341, 351, 361), the base station (310, 323) through the relay of the first, third, fifth and seventh terminals (330, 340, 350, 360) which are relay terminals. It may be indirectly connected to any one of them to perform data transmission/reception. Here, the connection between the second, fourth, sixth, and eighth terminals 331 , 341 , 351 , 361 as remote terminals and the base stations 310 and 320 may be referred to as an 'indirect connection'. .

The indirect connection between the remote terminals 331 , 341 , 351 , 361 and the base stations 310 and 320 through the relay terminals 330 , 340 , 350 and 360 may be classified into a plurality of types of scenarios. For example, a case in which a relay terminal relays an indirect connection between a remote terminal located outside of coverage (OOC) of a base station and a base station may be referred to as a 'first scenario'. The indirect connection between the sixth terminal 351 and the first base station 310 relayed by the fifth terminal 350 may correspond to the first scenario. On the other hand, a case in which the relay terminal relays an indirect connection between the base station and a remote terminal located within (IC, in coverage) of the base station may be referred to as a second scenario. Indirect connection between the second terminal 331 and the first base station 310 relayed by the first terminal 330 and the fourth terminal 341 and the second base station 320 relayed by the third terminal 340 The indirect connection between them may correspond to the second scenario. Meanwhile, a case in which the relay terminal relays an indirect connection between a predetermined base station and a remote terminal located within the coverage of a base station other than the predetermined base station may be referred to as a third scenario. The indirect connection between the eighth terminal 361 and the first base station 320 relayed by the seventh terminal 360 may correspond to the third scenario.

The relay terminals 330, 340, 350, and 360 that relay the connection between the base stations 310 and 320 and the remote terminals 331, 341, 351, 361 are, between the network and the terminal, U2N (UE-to-) Network) can be seen as performing a relay role. Based on the U2N relay of the relay terminals 330 , 340 , 350 and 360 , the coverage of the base stations 310 and 320 may be extended. Alternatively, based on the U2N relay of the relay terminals 330 , 340 , 350 and 360 , the service provided through the base stations 310 and 320 may be more stably provided.

Terminals performing a relay role based on the sidelink may perform a U2N relay role between base stations and the terminals. Meanwhile, terminals performing a relay role based on a sidelink may perform a U2U relay role between terminals. Hereinafter, another embodiment of a communication system 300 including terminals performing a U2U relay role between terminals based on a sidelink will be described with reference to FIG. 3B .

Referring to FIG. 3B , another embodiment of the communication system 300 may include a plurality of terminals 370 , 380 , and 390 . The plurality of terminals 370, 380, and 390 are the same as the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, 130-6 described with reference to FIG. 1 or may be similar. Each of the plurality of terminals 370 , 380 , and 390 may be referred to as a ninth terminal 370 , a tenth terminal 380 , and an eleventh terminal 390 .

The ninth to eleventh terminals 370 , 380 , and 390 may perform mutual D2D communication. Here, the tenth terminal 380 may perform a relay role between the ninth terminal 370 and the eleventh terminal 390 . The tenth terminal 380 performing the relay role may be referred to as a 'relay terminal' or a 'relay UE'. Meanwhile, the ninth and eleventh terminals 370 and 390 that communicate with each other through the relay of the tenth terminal, which is a relay terminal, may be referred to as a 'remote terminal' or a 'remote UE'.

In one embodiment of the communication system, for reasons such as a predetermined commercial service or public safety service, data transmission/reception through mutual communication between respective terminals may be required. For example, mutual communication between the ninth terminal 370 and the eleventh terminal 390 may be required. The ninth and eleventh terminals 370 and 390 may indirectly communicate with each other through a relay of the tenth terminal 380 when it is not easy to directly communicate with each other. Here, the connection between the ninth and eleventh terminals 370 and 390 that are remote terminals may be referred to as an 'indirect connection'.

In an embodiment of the communication system, the relay by the tenth terminal 380 may be partially related to network coverage extension. Some or all of the ninth to eleventh terminals 370 , 380 , and 390 may be located within a predetermined base station coverage area (IC). Alternatively, some or all of the ninth to eleventh terminals 370 , 380 , and 390 may not be located within any base station coverage. In other words, some or all of the ninth to eleventh terminals 370 , 380 , and 390 may be located outside the base station coverage (OOC). When some of the ninth to eleventh terminals 370 , 380 , and 390 are located within the coverage of the predetermined base station and the rest are located outside the coverage of the predetermined base station, based on the relay of the tenth terminal 380 , the cell of the predetermined base station Coverage or network coverage may be extended.

In an embodiment of the communication system 300 , the connection between the relay terminal and the remote terminal may be established in a sidelink manner. A connection between the tenth terminal 380 as a relay terminal and the ninth and eleventh terminals 370 and 390 as remote terminals may be established through the PC5 interfaces 375 and 385 . One side of the ninth and eleventh terminals 370 and 390 that are remote terminals may be a transmitting remote UE or a transmitting terminal, and the other side may be a receiving remote UE. The transmitting remote terminal may also be referred to as a source UE (source UE). The receiving remote terminal may also be referred to as a destination UE (destination UE). The transmitting remote terminal may transmit the data packet to the receiving remote terminal through the relay terminal. The receiving remote terminal may receive the data packet from the transmitting remote terminal through the relay terminal.

As described with reference to FIGS. 3A and 3B , the relay terminal may relay a connection between a plurality of communication nodes, and the connection between the plurality of communication nodes relayed through the relay terminal is referred to as an 'indirect connection'. can be called When the relay terminal relays the indirect connection between two communication nodes, the indirect connection may be composed of one connection and the other connection based on the relay terminal. Here, when one connection of the relay terminal is a connection with a remote terminal based on a PC5 interface, the other connection may be a connection with a base station based on a Uu interface or a connection with a remote terminal based on a PC5 interface.

Sidelink and relay terminal

In communication between a terminal and a terminal, terminals may be connected to each other through a sidelink to perform communication such as data transmission and reception. The radio signal transmission/reception in the sidelink may be performed in such a way that a corresponding receiving terminal receives a radio signal transmitted by the transmitting terminal.

In an embodiment of the communication system, a plurality of terminals performing sidelink communication may perform sidelink communication using the same or different radio frequencies or the same radio frequency band. A plurality of terminals may perform sidelink communication using the same or different radio resources. The transmitting terminal may provide control information such as radio resource information to the receiving terminal prior to data transmission.

A function of sidelink communication in a wireless communication network may be composed of an interface between a terminal performing sidelink communication and a terminal, and an interface between a sidelink server controlling sidelink communication of the terminal. Here, the sidelink server may exchange or provide information related to sidelink communication by exchanging messages with the terminal. The sidelink server may correspond to a base station or may be connected to a terminal through the base station. For example, the base station may be located on a path between the sidelink server and the terminal, and may mutually transmit packets exchanged between the sidelink server and the terminal. In one embodiment of sidelink communication, the connection between the terminal and the terminal may be established through a PC5 interface, and the connection between the terminal and the sidelink server may be established through a PC3 interface or a Uu interface.

A sidelink may be established between a pair of mutually adjacent terminals. In order to establish sidelink communication, it may be necessary to select or search for mutually adjacent terminals in advance. The terminal may transmit/receive a radio signal for searching for a neighboring terminal in order to perform sidelink communication. In an embodiment of the communication system, the first terminal may transmit a discovery signal for discovering a neighboring terminal in a broadcast manner. Here, the discovery signal may include information related to the first terminal, such as identification information of the first terminal. A second terminal adjacent to the first terminal may receive a discovery signal transmitted from the first terminal. The second terminal may return a response to the discovery signal based on the discovery signal from the first terminal. When the first terminal returns a response to the discovery signal returned from one or more adjacent terminals, such as the second terminal, the search procedure for the adjacent terminal of the first terminal may be completed. The terminal discovering or discovering the adjacent terminal may report information of the discovered or discovered adjacent terminal to the sidelink server. Alternatively, each terminal may report its location-related information to the sidelink server. The sidelink server may check information of mutually adjacent terminals based on a report from each terminal. For example, based on the search result information or location information included in the report from the connected first terminal, the sidelink server determines that the first terminal and the adjacent second terminal information, or that the first terminal and the second terminal are in a mutually adjacent relationship. information can be checked.

In sidelink communication, the transmitting terminal may transmit control information including information on resources allocated for data transmission to the receiving terminal. The transmitting terminal may transmit data to the receiving terminal based on information on resources allocated for data transmission included in the control information. A resource for the transmitting terminal to transmit sidelink data to the receiving terminal may be determined by the transmitting terminal or the base station.

Radio resources used in the sidelink may be operated in units of channels according to their use. For example, the physical channel of the sidelink may include a Physical Sidelink Broadcast CHannel (PSBCH), a Physical Sidelink Control CHannel (PSCCH), a Physical Sidelink Shared Channel (PSSCH), a Physical Sidelink Feedback Channel (PSFCH), and the like. Here, the PSBCH may refer to a channel for transmitting broadcast information through a sidelink. The PSCCH may mean a channel for transmitting sidelink control information. Here, the sidelink control information includes, for example, a Sidelink Primary Synchronization Signal (S-PSS) including a synchronization signal, a Sidelink Secondary Synchronization Signal (S-SSS), and a Channel State Information Reference Signal (CSI-RS) for measuring a sidelink channel. may include PSSCH may mean a channel for transmitting sidelink data. The PSFCH may mean a channel transmitted by the receiving terminal for feedback on the sidelink data transmitted from the transmitting terminal. For example, the receiving terminal receiving the data transmitted from the sidelink may return a feedback signal based on whether the reception is successful to the transmitting terminal. send. The PSFCH may be used independently by one UE or shared by a plurality of UEs.

The relay terminal may relay radio signals such as control signals and data between the communication network and the remote terminal. The relay terminal and the remote terminal are connected through the PC5 interface of the sidelink to perform mutual radio signal transmission and reception. Meanwhile, the relay terminal and the base station may be connected through a Uu interface to perform mutual wireless signal transmission/reception. For example, the relay terminal may transmit a downlink (DL) radio signal transmitted from a base station or a communication network through a Uu interface to a remote terminal through a PC5 interface. Meanwhile, the relay terminal may transmit an uplink (UL) radio signal transmitted from the remote terminal through the PC5 interface to the base station or the communication network through the Uu interface.

Inter-terminal discovery procedure for sidelink configuration

In order to configure the sidelink, terminals may perform a procedure for mutual discovery. In an embodiment of the communication system, the discovery procedure between terminals may follow the following two procedures.

Model A : The first terminal periodically broadcasts a discovery message, and the second terminal receives the discovery message transmitted from the first terminal. Here, the message periodically broadcast transmitted by the first terminal may include the meaning of 'I am here'. Here, the second terminal may be a remote terminal requiring connection with the relay terminal, and the first terminal may be a candidate relay terminal.

Model B : The second terminal broadcasts a request message for connection establishment, and the first terminal transmits a discovery message to the second terminal as a response to the request message received from the second terminal. The message broadcast transmitted by the second terminal may include the meaning of 'are you there'. Here, the second terminal may be a remote terminal requiring connection with the relay terminal, and the first terminal may be a candidate relay terminal.

In both model A and model B cases, the remote terminal may measure the sidelink signal strength of the discovery message sidelink transmitted by the candidate relay terminal. For example, the remote terminal may measure Reference Signal Received Power (RSRP) for the discovery message transmitted by the sidelink by the candidate relay terminal.

In one embodiment of the communication system, the remote terminal may receive a discovery message from one or more candidate relay terminals. The remote terminal may select one relay terminal from among the one or more candidate relay terminals based on the measured sidelink signal strength for each of the one or more discovery messages received from the one or more candidate relay terminals. For example, the remote terminal may compare the sidelink signal strength of the discovery message with a preset threshold. The remote terminal may select all terminals having a sidelink signal strength of the discovery message greater than a preset threshold among terminals transmitting the discovery message in the communication system as candidate relay terminals. The remote terminal may select a candidate relay terminal having the best sidelink signal strength of the discovery message among candidate relay terminals in the communication system as the relay terminal.

4 is a conceptual diagram for explaining an embodiment of a communication quality change monitoring method in a communication system.

Referring to FIG. 4 , a communication system may include a plurality of communication nodes. Each of the communication nodes included in the communication system, the base stations 310 and 320 and the terminals 330, 331, 340, 341, 350, 351, 360, 361, 370, 380, 390) may correspond to any one of the above. For example, the communication system may include two terminals that perform mutual signal transmission/reception through a sidelink. Among the two terminals included in the communication system, one side may transmit data to the other side, and the other side may receive data from the one side. Among the two terminals included in the communication system, a terminal that transmits a radio signal may be referred to as a transmitting user equipment (UE). Among the two terminals included in the communication system, a terminal that receives a radio signal may be referred to as a reception UE. When the receiving UE receives a radio signal from the transmitting UE, it may monitor the communication quality between the receiving UE and the transmitting UE. Hereinafter, in describing an embodiment of a communication quality change monitoring method in a communication system with reference to FIG. 4 , content overlapping with those described with reference to FIGS. 1 to 3B may be omitted.

For example, when the receiving UE receives data from the transmitting UE, it may perform channel state measurement for communication quality monitoring. The channel state measured by the receiving UE may correspond to a sidelink signal strength for the received data. The signal strength for data transmitted through the sidelink may be referred to as 'PSSCH_RSRP'. The receiving UE may perform channel state measurement whenever it receives data from the transmitting UE, and record the measured channel state.

Alternatively, when the receiving UE receives data from the transmitting UE, it may perform hybrid automatic repeat and request (HARQ) error rate measurement for communication quality monitoring. The receiving UE may perform HARQ error rate measurement whenever it receives data from the transmitting UE, and record the measured HARQ error rate.

In an embodiment of the communication system, the receiving UE may perform monitoring for a change aspect of communication quality based on a measurement result of data received from the transmitting UE. The receiving UE may generate connection information indicating the change aspect of communication quality based on the monitoring result for the change aspect of communication quality.

For example, when the receiving UE receives data from the transmitting UE, the receiving UE performs channel state measurement, and information on the channel state for the immediately received data (hereinafter, 'previous channel state') and the information on the channel state for the newly received data. (hereinafter, 'current channel state') may be compared. Here, the 'previous channel state' may be expressed as 'prev_ch'. The 'current channel state' may be expressed as 'curr_ch'. If the current channel state is superior to the previous channel state, it can be considered that the communication quality between the receiving UE and the transmitting UE is improved. On the other hand, if the current channel state is inferior to the previous channel state, it can be seen that the communication quality between the receiving UE and the transmitting UE is bad (worsen).

When the receiving UE compares the previous channel state and the current channel state, the comparison may be performed based on a predetermined offset value. Here, when the difference between the previous channel state and the current channel state is less than or equal to a predetermined offset value, it can be seen that there is no significant change in the communication quality between the receiving UE and the transmitting UE. On the other hand, when the difference between the previous channel state and the current channel state exceeds a predetermined offset value, it can be considered that there is a significant change in the communication quality between the receiving UE and the transmitting UE. The receiving UE may generate channel state change information based on a comparison result between a previous channel state and a current channel state based on a predetermined offset value. Channel state change information may be expressed as 'channel-status'.

Specifically, when the current channel state value is smaller than the previous channel state value and the mutual difference is greater than a predetermined first offset value ( 401 ), the receiving UE may determine that the channel state has deteriorated. In this case, the receiving UE may generate channel state change information indicating that the channel state has deteriorated.

Meanwhile, when the difference between the current channel state value and the previous channel state value is equal to or less than the first offset value ( 402 ), the receiving UE may determine that there is no significant change in the channel state. In this case, the receiving UE may generate channel state change information indicating that there is no change in the channel state.

Specifically, when the current channel state value is greater than the previous channel state value and the mutual difference is greater than a predetermined first offset value ( 403 ), the receiving UE may determine that the channel state has improved. In this case, the receiving UE may generate channel state change information indicating that the channel state has improved.

Meanwhile, in another embodiment of the communication system, the receiving UE may perform monitoring for a change in communication quality based on a measurement result of data received from the transmitting UE. Here, when the receiving UE receives data from the transmitting UE, the HARQ error rate measurement is performed, and information on the HARQ error rate for the immediately received data (hereinafter, 'previous HARQ error rate') and the HARQ error rate for the newly received data information (hereinafter, 'current HARQ error rate') may be compared. The 'previous HARQ error rate' may be expressed as 'prev_HARQ'. The 'current HARQ error rate' may be expressed as 'curr_HARQ'. If the current HARQ error rate is superior to the previous HARQ error rate, it can be considered that the communication quality between the receiving UE and the transmitting UE is improved. On the other hand, if the current HARQ error rate is inferior to the previous HARQ error rate, it can be seen that the communication quality between the receiving UE and the transmitting UE is bad (worsen).

In an embodiment of the communication system, when the receiving UE compares the previous HARQ error rate and the current HARQ error rate, the comparison may be performed based on a predetermined second offset value. The receiving UE may generate HARQ error rate change information based on a comparison result between the previous HARQ error rate and the current HARQ error rate based on the second offset value. HARQ error rate change information may be expressed as 'HARQ-status'.

Specifically, when the current HARQ error rate is greater than the previous HARQ error rate and the difference between them is greater than a predetermined second offset value ( 401 ), the receiving UE may determine that the HARQ error rate has deteriorated. In this case, the receiving UE may generate HARQ error rate change information indicating that the HARQ error rate has deteriorated.

Meanwhile, when the difference between the current HARQ error rate value and the previous HARQ error rate value is equal to or less than the second offset value ( 402 ), the receiving UE may determine that there is no significant change in the HARQ error rate. In this case, the receiving UE may generate HARQ error rate change information indicating that there is no change in the HARQ error rate.

Specifically, when the current HARQ error rate value is greater than the previous HARQ error rate value and the mutual difference is greater than the predetermined second offset value (403), the receiving UE may determine that the HARQ error rate has improved. In this case, the receiving UE may generate HARQ error rate change information indicating that the HARQ error rate has improved.

The receiving UE may generate connection information indicating the change aspect of communication quality based on the monitoring result of the change aspect of communication quality. The connection information may include any one of channel state change information and HARQ error rate change information. Alternatively, the connection information may include both channel state change information and HARQ error rate change information.

The receiving UE may generate a feedback signal including the generated connection information. The receiving UE may transmit a feedback signal including connection information to the transmitting UE. The transmitting UE may receive the feedback signal transmitted from the receiving UE, and may check connection information included in the feedback signal. The transmitting UE may perform operations for operation of a wireless connection based on the connection information included in the feedback signal.

5 is a flowchart illustrating an embodiment of a method for generating connection information in a communication system.

Referring to FIG. 5 , a communication system may include a plurality of communication nodes. The plurality of communication nodes included in the communication system may be the same as or similar to the plurality of communication nodes described with reference to FIG. 4 . For example, the communication system may include a transmitting UE and a receiving UE that perform mutual signal transmission/reception through a sidelink. Hereinafter, in describing an embodiment of a method for generating connection information in a communication system with reference to FIG. 5 , the content overlapping with those described with reference to FIGS. 1 to 4 may be omitted.

The receiving UE may receive a radio signal from the transmitting UE through the sidelink (S510). The radio signal received by the receiving UE may be a data signal. The receiving UE may measure the communication quality between the transmitting UE and the receiving UE by measuring the data received in step S510 ( S520 ). In step S520 , the receiving UE may perform channel state measurement based on the reception result of data transmitted from the transmitting UE in order to measure the communication quality. Here, the measured channel state may correspond to PSSCH_RSRP. Alternatively, the receiving UE may perform HARQ error rate measurement based on a reception result of data transmitted from the transmitting UE in order to measure communication quality. The receiving UE may perform measurements on the channel state and/or HARQ error rate whenever it receives data from the transmitting UE, and may record the measured channel state and/or HARQ error rate.

Each time the receiving UE receives data from the transmitting UE, the receiving UE may check a change aspect of the communication quality measurement result. Whenever the receiving UE receives data from the transmitting UE, it may compare the 'previous communication quality' measured based on the data received immediately before and the 'current communication quality' measured based on the newly received data (S530) . The previous communication quality may include a previous channel state (prev_ch) and/or a previous HARQ error rate (prev_HARQ). The current communication quality may include a current channel state (curr_ch) and/or a current HARQ error rate (curr_HARQ). The receiving UE may generate connection information indicating a change aspect of communication quality based on the comparison result in step S530. The connection information may include channel state change information (channel-status) and/or HARQ error rate change information (harq-status). Here, the channel state change information and the HARQ error rate change information may each have a size of 2 bits. The channel state change information and the HARQ error rate change information having a size of 2 bits can be expressed by dividing the communication quality change into a maximum of four steps. Hereinafter, an embodiment of a method for generating connection information will be described based on an embodiment in which the channel state change information and the HARQ error rate change information each have a size of 2 bits. However, this is only an example for convenience of description, and the embodiment of the present invention is not limited thereto. For example, in another embodiment of the communication system, the channel state change information and the HARQ error rate change information may each have a size of 1 bit or more and 8 bits or less. Channel state change information and HARQ error rate change information having a size of 1 bit or more and 8 bits or less can be expressed by dividing the communication quality change into two or more steps and 256 steps or less.

Specifically, when the current channel state value is greater than the sum of the previous channel state value and the first offset value ( S540 ), the receiving UE may determine that the channel state has improved. In this case, the receiving UE may generate channel state change information indicating that the channel state has improved. Specifically, the initial value of the channel state change information (channel-status) may be [00]. When it is determined that the channel state is improved in step S540, the receiving UE may increase the value of the channel state change information by 1 (S560). When the previous channel state change information was [00], the increased channel state change information may be [01]. When the previous channel state change information was [01], the increased channel state change information may be [10]. When the previous channel state change information was [10], the increased channel state change information may be [11]. If the previous channel state change information was [11], even if it is determined that the channel state has improved in step S540, the channel state change information may not increase in step S560.

Meanwhile, when the current HARQ error rate value is smaller than a value obtained by subtracting the second offset value from the previous HARQ error rate value, the receiving UE may determine that the HARQ error rate has improved. In this case, the receiving UE may generate HARQ error rate change information indicating that the HARQ error rate has improved. Specifically, the initial value of the HARQ error rate change information (harq-status) may be [00]. When the receiving UE determines that the HARQ error rate is improved based on the change in the HARQ error rate, the receiving UE may increase the value of the HARQ error rate change information by 1. If the previous HARQ error rate change information was [00], the increased HARQ error rate change information may be [01]. If the previous HARQ error rate change information was [01], the increased HARQ error rate change information may be [10]. If the previous HARQ error rate change information was [10], the increased HARQ error rate change information may be [11]. If the previous HARQ error rate change information was [11], even if it is determined that the HARQ error rate has improved in step S540, the HARQ error rate change information may not increase.

If the current channel state value is not greater than the sum of the previous channel state value and the first offset value (S540), and the current channel state value is smaller than the value obtained by subtracting the first offset value from the previous channel state value (S550), receive The UE may determine that the channel state has deteriorated (worsen). Alternatively, when the current channel state value has a value smaller than a preset channel state threshold, the receiving UE may determine that the channel state has deteriorated. In this case, the receiving UE may generate channel state change information indicating that the channel state has deteriorated. When the receiving UE determines that the channel state has deteriorated in step S550, it may decrease the value of the channel state change information by 1 (S570). When the previous channel state change information was [11], the reduced channel state change information may be [10]. When the previous channel state change information was [10], the reduced channel state change information may be [01]. When the previous channel state change information was [01], the reduced channel state change information may be [00]. If the previous channel state change information was [00], even if it is determined that the channel state has deteriorated in step S550, the channel state change information may not decrease in step S570.

On the other hand, if the current HARQ error rate value is not smaller than the value obtained by subtracting the second offset value from the previous HARQ error rate value, and the current HARQ error rate is greater than the value obtained by adding the second offset value to the previous HARQ error rate value, the receiving UE indicates that the HARQ error rate has deteriorated. can be judged as Alternatively, the receiving UE may determine that the HARQ error rate has deteriorated when the current HARQ error rate value has a value greater than a preset HARQ error rate threshold value. In this case, the receiving UE may generate HARQ error rate change information indicating that the HARQ error rate has deteriorated. Specifically, when the receiving UE determines that the HARQ error rate has deteriorated based on the change in the HARQ error rate, the receiving UE may decrease the value of the HARQ error rate change information by 1. If the previous HARQ error rate change information was [11], the reduced HARQ error rate change information may be [10]. When the previous HARQ error rate change information was [10], the reduced HARQ error rate change information may be [01]. If the previous HARQ error rate change information was [01], the reduced HARQ error rate change information may be [00]. If the previous HARQ error rate change information was [00], even if it is determined that the HARQ error rate has deteriorated in step S550, the HARQ error rate change information may not decrease.

If the current channel state value is not greater than the sum of the previous channel state value and the first offset value (S540), and the current channel state value is not smaller than the value obtained by subtracting the first offset value from the previous channel state value (S550), The receiving UE may determine that the channel state has not changed significantly. In other words, when the absolute value of the difference between the previous channel state value and the current channel state value is not greater than the first offset, the receiving UE may determine that the channel state has not changed significantly. In this case, the receiving UE may maintain the previous channel state change information value.

On the other hand, if the current HARQ error rate value is not smaller than the value obtained by subtracting the second offset value from the previous HARQ error rate value, and the current HARQ error rate is not greater than the value obtained by adding the second offset value to the previous HARQ error rate value, the receiving UE determines that the HARQ error rate is significant It can be judged that it has not changed significantly. In other words, when the absolute value of the difference between the previous HARQ error rate value and the current HARQ error rate value is not greater than the second offset, the receiving UE may determine that the HARQ error rate does not change significantly. In this case, the receiving UE may maintain the previous HARQ error rate change information value.

The receiving UE may generate connection information including channel state change information and/or HARQ error rate change information determined based on steps S530 to S570 (S580). The receiving UE may transmit a signal including the connection information generated in step S580 to the transmitting UE.

On the other hand, if the receiving UE receives data for the first time, or there is no previous communication quality to be compared according to step S530, or 'previous communication quality change information' to be updated according to steps S560 and S570 (ie, previous channel state change information) and/or when there is no previous HARQ error rate change information, connection information may be generated based on an initial value of communication quality change information (S580). For example, when the receiving UE first receives data, The connection information generated by the receiving UE may be configured to include channel state change information having a value of [00] and HARQ error rate change information having a value of [00].

6A and 6B are conceptual diagrams for explaining a first embodiment of a MAC (Medium Access Control) CE (Control Element) for transmission of connection information.

6A and 6B , a communication system may include a plurality of communication nodes. The plurality of communication nodes included in the communication system may be the same as or similar to the plurality of communication nodes described with reference to FIG. 5 . For example, the communication system may include a transmitting UE and a receiving UE that perform mutual signal transmission/reception through a sidelink. Hereinafter, in the description of the first embodiment of the MAC CE for transmission of connection information with reference to FIGS. 6A and 6B , content overlapping with those described with reference to FIGS. 1 to 5 may be omitted.

The receiving UE may perform monitoring for a change aspect of communication quality based on a reception result of a radio signal transmitted from the transmitting UE. The receiving UE may generate predetermined connection information based on the monitoring result of the change aspect of communication quality. Here, the connection information may include any one of channel state change information indicating a change aspect of the channel state and HARQ error rate change information indicating a change aspect of the HARQ error rate. Alternatively, the connection information may include both channel state change information and HARQ error rate change information. The receiving UE may transmit a signal including the generated connection information to the transmitting UE. Here, the connection information may be transmitted to the transmitting UE through the MAC CE.

It can be seen that FIG. 6A shows a first embodiment of a MAC CE including connection information (hereinafter, connection information MAC CE). In the MAC CE structure of FIG. 6A , the connection information may include 2-bit channel status change information (channel-status) and/or 2-bit HARQ error rate change information (harq-status). However, this is only an example for convenience of description, and the embodiment of the present invention is not limited thereto. For example, the connection information may include channel state change information and/or HARQ error rate change information having a size of 1 bit or more and 4 bits or less. Alternatively, the connection information may include channel state change information or HARQ error rate change information having a size of 5 bits or more and 8 bits or less. Depending on the size of each of the channel state change information and/or the HARQ error rate change information, the level of change that the channel state change information and/or the HARQ error rate change information can separately express may vary. Connection Information Bits other than the bits indicating connection information in MAC CE may correspond to R (Reserved) bits.

It can be seen that FIG. 6B shows an embodiment of a MAC subheader when the MAC CE according to the first embodiment of the MAC CE including the connection information shown in FIG. 6A is transmitted. The MAC subheader may include one or more bits indicating a logical channel identifier (LCID). Bits other than bits indicating the LCID in the MAC subheader may correspond to R (Reserved) bits. Here, as the LCID value, an LCID value for a sidelink shared channel (SL-SCH) may be used. As the LCID value, a reserved value among LCID values for the SL-SCH may be used. As the LCID value, a value of '61' among LCID values for the SL-SCH may be used. The LCID value may be configured as shown in Table 1.

7 is a conceptual diagram illustrating a second embodiment of a MAC CE for transmission of connection information.

Referring to FIG. 7 , a communication system may include a plurality of communication nodes. The plurality of communication nodes included in the communication system may be the same as or similar to the plurality of terminals 370 , 380 , and 390 described with reference to FIG. 3B . The communication system may include a transmitting remote UE, a relay UE, and a receiving remote UE that are interconnected through a sidelink. Here, the transmitting remote UE may transmit a radio signal to the receiving remote UE through the relay UE. The transmitting remote UE may transmit a radio signal to be transmitted to the receiving remote UE to the relay UE. The relay UE may transmit a radio signal received from the transmitting remote UE to the receiving remote UE. In the relationship between the transmitting remote UE and the relay UE, the transmitting remote UE may correspond to the transmitting UE described with reference to FIGS. 6A and 6B, and the relay UE may correspond to the receiving UE described with reference to FIGS. 6A and 6B. In the relationship between the relay UE and the receiving remote UE, the relay UE may correspond to the transmitting UE described with reference to FIGS. 6A and 6B, and the receiving remote UE may correspond to the receiving UE described with reference to FIGS. 6A and 6B. When the MAC CE according to the second embodiment of the MAC CE including the connection information shown in FIG. 7 is transmitted, the MAC subheader may be the same as or similar to that shown in FIG. 6B . Hereinafter, in describing the second embodiment of the MAC CE for transmission of connection information with reference to FIG. 7 , content overlapping with those described with reference to FIGS. 1 to 6B may be omitted.

The receiving remote UE may generate connection information indicating change information of communication quality between the receiving remote UE and the relay UE based on a result of receiving a radio signal from the relay UE. The receiving remote UE may transmit the generated connection information to the relay UE. The relay UE may generate connection information indicating change in communication quality between the relay UE and the transmitting remote UE based on a result of receiving a radio signal from the transmitting remote UE. The relay UE may transmit the generated connection information to the transmitting remote UE. Here, connection information generated by the relay UE and transmitted to the transmitting remote UE may be referred to as first connection information. In addition, connection information generated by the receiving remote UE and transmitted to the relay UE may be referred to as second connection information.

Here, when the relay UE generates the first connection information to be transmitted to the transmitting remote UE, the information included in the second connection information received from the receiving remote UE may be reflected. For example, when the relay UE generates the first connection information, either channel state change information or HARQ error rate change information among information included in the second connection information received from the receiving remote UE is indirect-status information. The first connection information may be configured to be included.

In an embodiment of the communication system, when the relay UE generates the first connection information for transmission to the transmitting remote UE, the first connection including only the indirect information generated based on the second connection information received from the receiving remote UE You can also create information. That is, the relay UE does not include the channel state change information and HARQ error rate change information according to the reception result of receiving the data transmitted from the transmitting remote UE in the first connection information, but the second connection information received from the receiving remote UE The first connection information may be generated by including only the indirect information generated based on the . In this case, upon receiving the first connection information, the transmitting remote UE may monitor information on change in communication quality of the sidelink connection between the relay UE and the receiving remote UE based on the indirect information included in the first connection information.

In the embodiment shown in FIG. 7 , the first connection information may include indirect-status having a size of 2 bits. Here, the indirect information may indicate information related to a change in communication quality between the relay UE and the receiving remote UE. Indirect information may have a size of 2 bits. The indirect information may include either channel state change information or HARQ error rate change information included in the second connection information received from the receiving remote UE. Alternatively, the indirect information may have a size of 4 bits corresponding to two bundles of 2 bits each. The indirect information may include either channel state change information or HARQ error rate change information included in the second connection information received from the receiving remote UE. Alternatively, the indirect information may have a size of 4 bits corresponding to two bundles of 2 bits each. The transmitting remote UE may check a change aspect of communication quality between the transmitting remote UE and the relay UE based on the first connection information received from the relay UE. When the first connection information includes indirect information, the transmitting remote UE may check a change aspect of communication quality between the relay UE and the receiving remote UE based on the indirect information included in the first connection information.

8A to 8C are conceptual diagrams for explaining an embodiment of an operation method of communication nodes constituting a UE-to-UE (U2U) relay structure.

8A to 8C , the communication system 800 may include a plurality of communication nodes 810 , 820 , and 830 . The communication system 800 may include a transmitting remote UE 810 , a relay UE 820 , and a receiving remote UE 830 connected to each other through a sidelink. Here, the transmitting remote UE 810 may be the same as or similar to the transmitting remote UE described with reference to FIG. 7 . The relay UE 820 may be the same as or similar to the relay UE described with reference to FIG. 7 . The receiving remote UE 830 may be the same as or similar to the receiving remote UE described with reference to FIG. 7 . Hereinafter, in describing an embodiment of an operation method of communication nodes constituting the relay structure with reference to FIG. 8 , content overlapping with those described with reference to FIGS. 1 to 7 may be omitted.

The transmitting remote UE 810 may transmit a radio signal to be transmitted to the receiving remote UE 830 to the relay UE 820 . Based on the radio signal reception result in the relay UE 820 , the communication quality for the first connection 815 corresponding to the sidelink connection between the transmitting remote UE 810 and the relay UE 820 , and the change aspect of the communication quality This can be monitored. The relay UE 820 may transmit a radio signal received from the transmitting remote UE 810 to the receiving remote UE 830 . Based on the radio signal reception result in the receiving remote UE 830 , the communication quality and communication quality for the second connection 825 corresponding to the sidelink connection between the relay UE 820 and the receiving remote UE 830 are changed Aspects can be monitored.

As shown in FIG. 8A , when the receiving remote UE 830 moves in a direction away from the relay UE 820, the relay UE 820 moves away from the receiving remote UE 830 until it receives a separate feedback signal. may not be aware of When the receiving remote UE 830 and the relay UE 820 move away from each other, the communication quality of the second connection 825 may deteriorate. The relay UE 820 may transfer the relay data received from the transmitting remote UE 810 to the receiving remote UE 830 without recognizing that the communication quality of the second connection 825 is getting worse.

The receiving remote UE 830 may receive relay data through the relay UE 820 and generate second connection information based on the relay data reception result. The second connection information may include channel state change information and/or HARQ error rate change information indicating that the communication quality of the second connection 825 is getting worse. The receiving remote UE 830 may transmit the generated second connection information to the relay UE 820 .

The relay UE 820 that has received the second connection information from the receiving remote UE 830 may confirm that the communication quality of the second connection 825 is getting worse based on the second connection information. When it is confirmed that the communication quality of the second connection 825 is deteriorated, the relay UE 820 may perform operations for supporting quality of service (QoS) for relay data and reducing data loss. For example, the relay UE 820 may perform the same or similar operations as those shown in FIG. 9 or FIG. 10 .

As shown in FIG. 8B , when the transmitting remote UE 810 moves in a direction away from the relay UE 820 , the communication quality of the first connection 815 may deteriorate. The transmitting remote UE 810 may transmit relay data for transmission to the receiving remote UE 830 to the relay UE 820 without recognizing that the communication quality of the first connection 815 is getting worse.

The relay UE 820 may receive relay data from the transmitting remote UE 810 and generate first connection information based on the relay data reception result. The first connection information may include channel state change information and/or HARQ error rate change information indicating that the communication quality of the first connection 815 is getting worse. The relay UE 820 may transmit the generated first connection information to the transmitting remote UE 810 .

The transmitting remote UE 810 that has received the first connection information from the relay UE 820 may confirm that the communication quality of the first connection 815 is getting worse based on the first connection information. When it is confirmed that the communication quality of the first connection 825 is deteriorated, the transmitting remote UE 810 may perform operations for QoS support for relay data and data loss reduction. For example, the transmitting remote UE 810 may perform the same or similar operations as those shown in FIG. 9 or FIG. 10 .

As shown in FIG. 8c , when the relay UE 820 moves in a direction away from the transmitting remote UE 810 and the receiving remote UE 820 , the communication quality of the first connection 815 and the second connection 825 is can be bad The transmitting remote UE 810 may transmit relay data for transmission to the receiving remote UE 830 to the relay UE 820 without recognizing that the communication quality of the first connection 815 is getting worse. The relay UE 820 may transfer the relay data received from the transmitting remote UE 810 to the receiving remote UE 830 without recognizing that the communication quality of the second connection 825 is getting worse.

The relay UE 820 may generate the first connection information based on the data reception result of the relay data received from the transmitting remote UE 810 . The relay UE 820 may transmit the generated first connection information to the transmitting remote UE 810 . The transmitting remote UE 810 that has received the first connection information from the relay UE 820 may confirm that the communication quality of the first connection 815 is getting worse based on the first connection information.

Meanwhile, the receiving remote UE 830 may generate the second connection information based on the reception result of the relay data received through the relay UE 820 . The receiving remote UE 830 may transmit the generated second connection information to the relay UE 820 . The relay UE 820 that has received the second connection information from the receiving remote UE 830 may confirm that the communication quality of the second connection 825 is getting worse based on the second connection information.

On the other hand, the first connection information transmitted by the relay UE 820 to the transmitting remote UE 810 is indirectly set based on the second connection information received by the relay UE 820 from the receiving remote UE 830 immediately before. It may include indirect information. When the first connection information includes indirect information, the transmitting remote UE 810 that has received the first connection information from the relay UE 820, the communication quality of the first connection 815 and the second connection 825 is It can be confirmed based on the first connection information that everything is getting worse.

As described with reference to FIGS. 8A to 8C , the transmitting remote UE 810 may receive a signal including the first connection information as a response to the relay data after transmitting the relay data to the relay UE 820 . . That is, the transmitting remote UE 810 does not further receive a separate signal, such as a discovery signal, from the relay UE 820 in addition to the signal including the first connection information received as a response to the relay data, the first connection 815 It is possible to monitor changes in the communication quality of If the first connection information includes indirect information, the transmitting remote UE 810 may monitor a change in communication quality of the first connection 815 and the second connection 825 based on the first connection information. there is.

If the communication quality of any one of the first connection 815 and the second connection 825 is bad, the communication quality of the relay path for communication between the transmitting remote UE 810 and the receiving remote UE 830 is bad. can see. The transmitting remote UE 810 may perform operations for reselection of the relay path when it is confirmed one or more times that the communication quality of the relay path is deteriorated based on the first connection information. The transmitting remote UE 810 may perform operations for reselection of the relay path when it is confirmed that the communication quality of the relay path is deteriorated for a predetermined first threshold number of times based on the first connection information. For example, the transmitting remote UE 810 may perform the same or similar operations as those shown in FIG. 9 or FIG. 10 .

Meanwhile, the relay UE 820 may receive a signal including the second connection information as a response to the relay data after transmitting the relay data to the receiving remote UE 830 . That is, the relay UE 820 does not further receive a separate signal, such as a discovery signal, from the receiving remote UE 830 in addition to the signal including the second connection information received as a response to the relay data, the second connection 815 ) of the communication quality can be monitored. When the relay UE 820 confirms that the communication quality of the second connection 825 is getting worse based on the second connection information for a predetermined second threshold number of times, the relay UE 820 may perform operations for reselection of the relay path. there is. For example, the relay UE 810 may perform the same or similar operations as those shown in FIG. 9 or FIG. 10 .

9 is a flowchart illustrating a first embodiment of a method for operating a relay connection in a communication system.

Referring to FIG. 9 , the communication system 900 may include a plurality of communication nodes 901 , 902 , 903 , and 904 . Communication nodes included in the communication system 900 may be referred to as a first communication node 901 , a second communication node 902 , a third communication node 903 , a fourth communication node 904 , and the like. At least some of the first to fourth communication nodes 901 , 902 , 903 , and 904 may be connected to each other through a sidelink to perform D2D communication. The first communication node 901 may be referred to as a relay UE A 901 . The second communication node 902 may be referred to as a transmitting remote UE 902 . The third communication node 903 may be referred to as a relay UE 903 . The fourth communication node 904 may be referred to as a relay UE B 904 . Here, the relay UE A 901 and the relay UE B 904 may be the same as or similar to the candidate relay terminals described with reference to FIGS. 3A and 3B . The transmitting remote UE 902 may be the same as or similar to the transmitting remote UE 810 described with reference to FIGS. 8A to 8C . The relay UE 903 may be the same as or similar to the relay UE 820 described with reference to FIGS. 8A to 8C . The communication system may further include a receiving remote UE (not shown) that receives the relay data transmitted from the transmitting remote UE 902 through the relay UE 903 . Hereinafter, in the description of the first embodiment of the relay connection operation method in the communication system with reference to FIG. 9 , content overlapping with those described with reference to FIGS. 1 to 8C may be omitted.

The transmitting remote UE 902 , the relay UE 903 and the receiving remote UE (not shown) of the communication system 900 may perform relay data transmission/reception. The transmitting remote UE 902 may transmit relay data to the relay UE 903 . The relay UE 903 may transmit relay data to a receiving remote UE (not shown).

The relay UE 903 may receive relay data from the transmitting remote UE 902 (S920). The relay UE 903 may generate connection information based on the relay data received from the transmitting remote UE 902 (S920). The operation of the relay UE 903 generating connection information based on the received relay data may be the same as or similar to the operation according to the connection information generation method described with reference to FIG. 5 .

The relay UE 903 may transmit the connection information generated in step S920 and a feedback signal for the relay data received from the transmitting remote UE 902 to the transmitting remote UE 902 (S930). The transmitting remote UE 902 may receive connection information from the relay UE 903 . When relay data transmission/reception is performed one or more times, connection information transmission/reception may also be performed one or more times. Based on the connection information transmitted from the relay UE 903 to the transmitting remote UE 902 , a relay path reselection procedure S940 may be performed.

Specifically, the transmitting remote UE 902 monitors, based on the connection information received from the relay UE 903, information on the communication quality change aspect for the channel between the transmitting remote UE 902 and the relay UE 903. can be confirmed (S941). The transmitting remote UE 902 may check a change aspect such as channel state change information and/or HARQ error rate change information.

If it is determined in step S941 that the communication quality has not deteriorated, operations for relay path reselection after step S941 may not be performed. On the other hand, as in the embodiment shown in Figure 8b or 8c, when the communication quality of the connection between the transmitting remote UE 902 and the relay UE 903 is getting worse, the transmitting remote UE 902 is the connection received in step S930. Based on the information, it may be determined that the communication quality has deteriorated (S941). That is, the transmitting remote UE 902 may determine that the communication quality of the relay path connected to the receiving remote UE (not shown) through the relay UE 903 has deteriorated. In this case, the transmitting remote UE 902 may perform operations for QoS support and data loss reduction for relay data. For example, when the transmitting remote UE 902 determines that the communication quality of the current relay path is getting worse, the packet stored in the current buffer can be easily transmitted through the current relay path between packets in the MAC. Operations such as processing by adjusting or changing the priority or QoS of data may be performed. The transmitting remote UE 902 determines the amount of data to be transmitted through the relay path, and/or the priority (QoS) of inter-packet data in the MAC based on the determination result according to the monitoring of the communication quality change aspect of the relay path. and can be reflected in scheduling. In addition, when it is confirmed that the communication quality of the current relay path is deteriorating, operations for relay path reselection may be performed.

During the relay path reselection procedure, the transmitting remote UE 902 , the relay UE 903 , and the receiving remote UE (not shown) may perform mutual relay data transmission/reception without releasing the relay path. For example, the transmitting remote UE 902 may schedule relay data to be transmitted to a receiving remote UE (not shown) through the relay UE 903, and may transmit the scheduled relay data to the relay UE 903 ( S942-1, S942-2, S942-3, S942-4). The relay UE 903 may receive relay data from the transmitting remote UE 902 (S942-1, S942-2, S942-3, S942-4), and receive the received relay data from the receiving remote UE (not shown) can be transmitted as

The transmitting remote UE 902 may transmit a discovery request message for connection establishment to other terminals on the communication system 900 (S944-1, S944-2). For example, the transmitting remote UE 902 may broadcast a discovery request message (S944-1, S944-2). Upon receiving the discovery message or the discovery message transmitted as a response to the discovery request message, the transmitting remote UE 902 may select a candidate relay terminal based on the sidelink signal strength for the received discovery message.

The first and fourth communication nodes 901 and 904 on the communication system 900 may receive the discovery request message transmitted from the transmitting remote UE 902 (S944-1, S944-2). The first and fourth communication nodes 901 and 904 may transmit a discovery message or a discovery message to the transmitting remote UE 902 as a response to the received discovery request message (S945-1, S945-2). The transmitting remote UE 902 may recognize the first and fourth communication nodes 901 and 904 as candidate relay UEs based on the result of receiving the discovery message in steps S945-1 and S945-2. Here, the first communication node 901 may be referred to as a relay UE A 901 , and the fourth communication node 904 may be referred to as a relay UE B 904 . The transmitting remote UE 902 may perform relay path reselection by selecting any one of the candidate relay UEs as a new relay UE (S946). For example, the transmitting remote UE 902 may compare the measured sidelink signal strength according to the result of receiving the discovery message in steps S945-1 and S945-2. The transmitting remote UE 902 may determine the relay UE A 901 as a new relay UE for relay communication with the receiving remote UE 904 when the sidelink signal strength transmitted from the relay UE A 901 is better. there is. Through this, relay path reselection may be performed (S946).

The transmitting remote UE 902 may perform an operation of transmitting relay data to a receiving remote UE (not shown) through the relay UE A 901, which is a new relay UE, and a disconnection procedure with the existing relay UE 903. . For example, the transmitting remote UE 902 may schedule relay data to be transmitted to the receiving remote UE (not shown) through the relay UE A 901 , and may transmit the scheduled relay data to the relay UE A 901 . Yes (S960-1, S960-2). The relay UE 903 may receive relay data from the transmitting remote UE 902 (S960-1, S960-2), and may transmit the received relay data to the receiving remote UE (not shown). Meanwhile, the transmitting remote UE 902 may transmit a signal instructing release of the relay connection to the existing relay UE 903 (S970). The existing relay UE 903 may transmit a response to the signal indicating relay connection release received in step S970 to the transmitting remote UE 902 (S980). Through the operations according to steps S920 to S980, operations for relay connection operation such as communication quality monitoring and relay path reselection based on relay data transmission/reception may be performed.

If the communication quality of the relay path between the transmitting remote UE 902 and the receiving remote UE 904 through the existing relay UE 902 is deteriorated or due to reasons such as radio link failure (RLF) occurring When the relay path reselection operation is performed after the sidelink is lost or released, an operation for transmitting and receiving a discovery request message and a discovery message, an operation for selecting a candidate relay UE, and an operation for selecting one relay UE from among the candidate relay UEs are performed In this process, relay data transmission/reception may not be performed. Accordingly, a problem in that relay data transmission and reception is delayed or stopped may occur.

On the other hand, in the relay data transmission/reception process, when it is detected that the communication quality is getting worse according to the monitoring of the communication quality change aspect, the transmission remote data 902 transmits the relay data through the existing relay path without stopping the relay data transmission. A reselection operation may be performed. When relay path reselection is performed, relay data may be transmitted through the same slot as in the existing relay path. Accordingly, a problem of delay or interruption of relay data transmission/reception according to the relay path reselection procedure may not occur.

10 is a flowchart illustrating a second embodiment of a method for operating a relay connection in a communication system.

Referring to FIG. 10 , the communication system 1000 may include a plurality of communication nodes 1001 , 1002 , 1003 , and 1004 . Communication nodes included in the communication system 1000 may be referred to as a first communication node 1001 , a second communication node 1002 , a third communication node 1003 , a fourth communication node 1004 , and the like. At least some of the first to fourth communication nodes 1001 , 1002 , 1003 , and 1004 may be connected to each other through a sidelink to perform D2D communication. The first communication node 1001 may be referred to as a relay UE A 1001 . The second communication node 1002 may be referred to as a transmitting remote UE 1002 . The third communication node 1003 may be referred to as a relay UE 1003 . The fourth communication node 1004 may be referred to as a receiving remote UE 1004 . Here, the relay UE A 1001 may be the same as or similar to the relay UE A 1001 described with reference to FIG. 9 . The transmitting remote UE 1002 may be the same as or similar to the transmitting remote UE 902 described in FIG. 9 . The relay UE 1003 may be the same as or similar to the relay UE 903 described with reference to 9 . The receiving remote UE 1004 may be the same as or similar to the receiving remote UE (not shown) described with reference to FIG. 9 . Hereinafter, in describing the second embodiment of the method for operating a relay connection in a communication system with reference to FIG. 10 , content overlapping with those described with reference to FIGS. 1 to 9 may be omitted.

The transmitting remote UE 1002 , the relay UE 1003 , and the receiving remote UE 1004 of the communication system 1000 may perform relay data transmission/reception. The transmitting remote UE 1002 may transmit relay data to the relay UE 1003 . The relay UE 1003 may transmit relay data to the receiving remote UE 1004 .

The transmitting remote UE 1002 may transmit relay data to the relay UE 1003 . The relay UE 1003 may receive relay data from the transmitting remote UE 1002 . The relay UE 1003 may relay-transmit the relay data received from the transmitting remote UE 1002 to the receiving remote UE 1004 (S1010). The receiving remote UE 1004 may receive the relay data transmitted through the relay UE 1003 (S1011). The receiving remote UE 1004 may generate the first connection information based on the relay data received through the relay UE 1003 (S1011). The first connection information generated in step S1011 may be, for example, the same as or similar to the connection information described with reference to FIG. 6A .

The receiving remote UE 1004 may transmit the first connection information generated in step S1011 and a feedback signal for the relay data received from the relay UE 1003 to the relay UE 1003 (S1012). The relay UE 1003 may receive the first connection information from the receiving remote UE 1004 . When the relay data transmission according to step S1010 is performed one or more times, the first connection information transmission according to step S1012 may also be performed one or more times.

The relay UE 1003 is based on the first connection information received from the receiving remote UE 1004, the relay UE 1003 and the receiving remote UE 1004 to monitor or check the information of the communication quality change aspect for the channel between the There is (S1020). The transmitting remote UE 1002 may check a change aspect such as channel state change information and/or HARQ error rate change information.

If the communication quality of the connection between the relay UE 1003 and the receiving remote UE 1004 is getting worse as in the embodiment shown in Fig. 8a or 8c, the relay UE 1003 is the first connection received in step S1012 Based on the information, it may be determined that the communication quality has deteriorated (S1020). That is, the relay UE 1003 is based on the first connection information received as a response to the relay data relay transmitted to the receiving remote UE 1004, the communication quality of the relay path connected to the receiving remote UE 1004 has deteriorated. can be judged as On the other hand, when the communication quality of the connection between the relay UE 1003 and the receiving remote UE 1004 is not deteriorated, the relay UE 1003 is based on the first connection information received in step S1012, the communication quality is not deteriorated. It can be determined that (ie, improved or there is no change) (S1020). In this case, the relay UE 1003 may perform operations for QoS support and data loss reduction for relay data. For example, when it is confirmed that the communication quality of the current relay path is deteriorating, the relay UE 1003) performs inter-packet communication between packets in the MAC so that the packets stored in the current buffer can be easily transmitted through the current relay path. Operations such as processing by adjusting or changing the priority or QoS of data may be performed. The relay UE 1003 determines the amount of data to be transmitted through the relay path and/or the priority (QoS) of inter-packet data in the MAC based on the determination result according to the monitoring of the communication quality change aspect of the relay path, and It can be reflected in scheduling. In addition, when it is confirmed that the communication quality of the current relay path is getting worse, the relay UE transmits information indicating that the communication quality of the relay path is getting worse (eg, connection information) to the transmitting remote UE 1002. there is.

When the transmitting remote UE 1002 transmits the relay data back to the relay UE 1003 (S1021), the relay UE 1003 transmits the relay data received from the transmitting remote UE 1002 to the receiving remote UE 1004. may perform scheduling and transmit relay data to the receiving remote UE 1004 based on the scheduling result (S1022). The relay UE 1003 may generate the second connection information based on the reception result of the relay data received in step S1021. The relay UE 1003 may transmit the generated second connection information to the transmitting remote UE 1002 .

Here, the relay UE 1003 may generate indirect-status based on information included in the first connection information received from the receiving remote UE 1004 . The relay UE 1003 may generate the second connection information based on the result of the reception of the relay data received in step S1021 and the generated indirect information. The second connection information may be, for example, the same as or similar to the connection information described with reference to FIG. 7 .

The relay UE 1003 may transmit the generated second connection information and a feedback signal for the relay data received in step S1021 to the transmitting remote UE 1002 (S1030). Here, if it is determined in step S1020 that the communication quality has not deteriorated, indirect information may not be included in the second connection information transmitted in step S1030. The transmitting remote UE 1002 may receive the second connection information from the relay UE 1003 (S1030). Based on the second connection information transmitted from the relay UE 1003 to the transmitting remote UE 1002 , a relay path reselection procedure ( S1040 ) may be performed.

Specifically, the transmitting remote UE 1002 is based on the second connection information received from the relay UE 1003, information of the communication quality change aspect for the channel between the transmitting remote UE 1002 and the relay UE 1003 It can be monitored or confirmed (S1041). If the second connection information includes indirect information, the transmitting remote UE 1002 is based on the second connection information received from the relay UE 1003, the channel between the transmitting remote UE 1002 and the relay UE 1003 It is possible to monitor or check the information of the communication quality change aspect for, and the information of the communication quality change aspect for the channel between the relay UE 1003 and the receiving remote UE 1004 (S1041). In other words, if the second connection information includes indirect information, the transmitting remote UE 1002 transmits connected through the relay UE 1003 based on the second connection information received from the relay UE 1003 . It is possible to monitor or confirm information of a communication quality change aspect in a relay path or a communication path between the remote UE 1002 and the receiving remote UE 1004 (S1041).

If it is determined in step S1041 that the communication quality has not deteriorated, operations for relay path reselection after step S1041 may not be performed. On the other hand, as in the embodiment shown in Figs. 8a to 8c, the communication quality of the connection between the transmitting remote UE 1002 and the relay UE 1003, or the connection between the relay UE 1003 and the receiving remote UE 1004 is poor, If there is, the transmitting remote UE 1002 may determine that the communication quality of the relay path is bad based on the second connection information received in step S1030 ( S1041 ). That is, the transmitting remote UE 1002 may determine that the communication quality of the relay path connected to the receiving remote UE 1004 through the relay UE 1003 has deteriorated. In this case, the transmitting remote UE 1002 may perform operations for QoS support and data loss reduction for relay data. For example, when the transmitting remote UE 1002 determines that the communication quality of the current relay path is getting worse, the packet stored in the current buffer can be easily transmitted through the current relay path between packets in the MAC. Operations such as processing by adjusting or changing the priority or QoS of data may be performed. The transmitting remote UE 1002 determines the amount of data to be transmitted through the relay path and/or the priority (QoS) of inter-packet data in the MAC based on the determination result according to the monitoring of the communication quality change aspect of the relay path. and can be reflected in scheduling. In addition, when it is confirmed that the communication quality of the current relay path is deteriorating, operations for relay path reselection may be performed.

During the relay path reselection procedure, the transmitting remote UE 1002 , the relay UE 1003 and the receiving remote UE 1004 may perform mutual relay data transmission/reception without releasing the relay path. For example, the transmitting remote UE 1002 may schedule relay data to be transmitted to the receiving remote UE 1004 through the relay UE 1003, and may transmit the scheduled relay data to the relay UE 1003 (S1042). -1, S1042-2). The relay UE 1003 may receive relay data from the transmitting remote UE 1002 (S1042-1, S1042-2). The relay UE 1003 may schedule the relay data received from the transmitting remote UE 1002, and may transmit the scheduled relay data to the receiving remote UE 1004 (S1043-1, S1043-2). The receiving remote UE 1004 may receive relay data from the relay UE 1003 (S1043-1, S1043-2).

The transmitting remote UE 1002 may monitor a discovery message or a discovery message transmitted from other terminals on the communication system 1000 . When the transmitting remote UE 1002 receives a discovery message or a discovery message from other terminals, it may select a candidate relay terminal based on the sidelink signal strength for the received discovery message.

The first communication node 1001 on the communication system 1000 may broadcast a discovery message or a discovery message at all times or periodically ( S1045 ). The transmitting remote UE 1002 may receive the discovery message transmitted from the first communication node 1001 (S1045). The transmitting remote UE 1002 may recognize the first communication node 1001 as a candidate relay UE based on the result of receiving the discovery message in step S1045 . Here, the first communication node 1001 may be referred to as a relay UE A 1001 . The transmitting remote UE 1002 may perform relay path reselection by selecting any one of the communication nodes recognized as the candidate relay UE, including the first communication node 1001, as the new relay UE (S1046). For example, the transmitting remote UE 1002 may compare the measured sidelink signal strength according to the result of receiving the discovery message from the candidate relay UEs. When the transmitting remote UE 1002 has the best sidelink signal strength for the discovery message transmitted from the relay UE A 1001, the relay UE A 1001 is a new relay for relay communication with the receiving remote UE 1004. It can be decided by the UE. Through this, relay path reselection may be performed (S1046).

The transmitting remote UE 1002 generates relay data to be transmitted to the receiving remote UE 1004 in a state in which the relay path reselection operation and/or the connection operation with the new relay UE according to step S1046 is not completed, the existing relay UE ( 1002), relay transmission can be performed. That is, the transmitting remote UE 1002 may schedule relay data to be transmitted to the receiving remote UE 1004 through the relay UE 1003, and may transmit the scheduled relay data to the relay UE 1003 (S1050). ). The relay UE 1003 may receive relay data from the transmitting remote UE 1002 (S1050). The relay UE 1003 may schedule the relay data received from the transmitting remote UE 1002, and may transmit the scheduled relay data to the receiving remote UE 1004 (S1051). The receiving remote UE 1004 may receive relay data from the relay UE 1003 (S1051).

The transmitting remote UE 1002 may perform an operation of transmitting relay data to the receiving remote UE 1004 through the relay UE A 1001, which is a new relay UE, and a disconnection procedure with the existing relay UE 1003 . For example, the transmitting remote UE 1002 may schedule relay data to be transmitted to the receiving remote UE 1004 through the relay UE A 1001, and may transmit the scheduled relay data to the relay UE A 1001. (S1060). The relay UE 1003 may receive relay data from the transmitting remote UE 1002 (S1060), and may transmit the received relay data to the receiving remote UE 1004 (S1061). Meanwhile, the transmitting remote UE 1002 may transmit a signal instructing release of the relay connection to the existing relay UE 1003 (S1070). The existing relay UE 1003 may transmit a response to the signal instructing relay connection release received in step S1070 to the transmitting remote UE 1002 (S1080). Through the operations according to steps S1020 to S1080, operations for relay connection operation such as communication quality monitoring and relay path reselection based on relay data transmission/reception may be performed.

11 is a conceptual diagram illustrating an embodiment of a MAC Protocol Data Unit (PDU) in a communication system.

Referring to FIG. 11 , a communication system may include a plurality of communication nodes. The plurality of communication nodes included in the communication system may be the same as or similar to the plurality of communication nodes described with reference to FIG. 6A . For example, the communication system may include a transmitting UE and a receiving UE that perform mutual signal transmission/reception through a sidelink. Hereinafter, in describing an embodiment of a MAC PDU in a communication system with reference to FIG. 11 , content overlapping with those described with reference to FIGS. 1 to 10 may be omitted.

The receiving UE may generate a connection signal based on the radio signal received from the transmitting UE. The connection signal generated by the receiving UE may be transmitted to the transmitting UE through the same or similar MAC CE (hereinafter, referred to as connection information MAC CE) as shown in FIG. 6A . The receiving UE may transmit a MAC PDU including connection information MAC CE (MAC CE) to the transmitting UE. Here, only the MAC PDU including the connection information MAC CE may be delivered, or the MAC PDU including the connection information MAC CE and other MAC PDUs may be delivered together. Meanwhile, only the MAC SDU including the connection information MAC CE may be transmitted through the MAC PDU, or the MAC SDU including the connection information MAC CE and other MAC SDUs may be transmitted together.

A MAC PDU transmitted in the sidelink shared channel may be configured to include an SL-SCH subheader and one or more MAC subPDUs. The MAC subPDU may include MAC SDU (MAC subPDU including MAC SDU) or MAC CE (MAC subPDU including MAC CE). The MAC PDU including the connection information MAC CE may include one or more 'MAC subPDU including MAC CE'. MAC CE included in at least some of the one or more 'MAC subPDU including MAC CE' may be connection information MAC CE. Here, the MAC subPDU including the connection information MAC CE may be configured to be disposed at a specific position in the MAC PDU structure. For example, the MAC subPDU including the connection information MAC CE may be configured to be positioned immediately before the MAC subPDU including padding in the MAC PDU structure.

12A and 12B are conceptual diagrams for explaining an embodiment of a sidelink feedback channel including connection information in a communication system.

12A and 12B , a communication system may include a plurality of communication nodes. The plurality of communication nodes included in the communication system may be the same as or similar to the plurality of communication nodes described with reference to FIG. 5 . For example, the communication system may include a transmitting UE and a receiving UE that perform mutual signal transmission/reception through a sidelink. Hereinafter, in describing an embodiment of a MAC PDU in a communication system with reference to FIGS. 12A and 12B , content overlapping with those described with reference to FIGS. 1 to 11 may be omitted.

The sidelink physical channel may include a PSCCH for transmission of a control signal, a PSSCH for transmission of data, and a PSFCH for transmission of a feedback signal. The receiving UE receiving data from the transmitting UE may generate connection information based on the data reception result. In an embodiment of the communication system, the receiving UE may transmit the generated connection information along with a feedback signal such as HARQ feedback through the PSFCH.

It can be seen that FIG. 12A shows an embodiment in which connection information for previous data is transmitted using different slots. That is, connection information for data transmitted through the PSSCH in the Nth sidelink slot may be transmitted through the PSFCH in the N+1th sidelink slot.

Meanwhile, it can be seen that FIG. 12B shows an embodiment in which connection information for data is transmitted within the same slot. That is, connection information for data transmitted through the PSSCH in the Nth sidelink slot may be transmitted through the PSFCH in the Nth sidelink slot, and connection to data transmitted through the PSSCH in the N+1th sidelink slot. Information may be transmitted through the PSFCH in the N+1th sidelink slot.

13A and 13B are conceptual diagrams for explaining a first embodiment of a method of operating communication nodes constituting a UE-to-Network (U2N) relay structure.

13A and 13B , the communication system 1300 may include a plurality of communication nodes 1300 . The communication system 1300 may include a base station 1310 , a relay UE 1320 , and a remote UE 1330 connected to each other through a sidelink. The base station 1310 may be the same as or similar to the first and second base stations 310 and 320 described with reference to FIG. 3A . The relay UE 1320 may be the same as or similar to the first, third, fifth, and seventh terminals 330 , 340 , 350 and 360 described with reference to FIG. 3A . The remote UE 1330 may be the same as or similar to the second, fourth, sixth, and eighth terminals 331 , 341 , 351 and 361 described with reference to FIG. 3A .

The U2N relay structure shown in FIGS. 13A and 13B may correspond to the U2U relay structure shown in FIGS. 8A and 8C . Here, the base station 1310 may correspond to the transmitting remote UE 810 shown in FIGS. 8A and 8C . The relay UE 1320 may correspond to the relay UE 820 illustrated in FIGS. 8A and 8C . The remote UE 1330 may correspond to the receiving remote UE 830 shown in FIGS. 8A and 8C . The first connection 1315 corresponding to the connection between the base station 1310 and the relay UE 1320 may correspond to the first connection 815 illustrated in FIGS. 8A and 8C . The second connection 1325 corresponding to the connection between the relay UE 1320 and the remote UE may correspond to the second connection 825 illustrated in FIGS. 8A and 8C . 13A and 13B , the base station 1310 may transmit relay data to the remote UE 1330 through the relay UE 1320 . In FIG. 13A , it can be seen that the situation in which the remote UE 1330 corresponding to the receiving node moves in a direction away from the relay UE 1320 is shown as in FIG. 8A . In FIG. 13b, as in FIG. 8c, the relay UE 1320 serving as a relay moves in a direction away from the base station 1310 corresponding to the transmitting node and the remote UE 1330 corresponding to the receiving node. there is. In FIGS. 13A and 13B , the operation of the base station 1310 , the relay UE 1320 and the remote UE 1330 , respectively, in FIGS. 8A and 8C , the transmitting remote UE 810 , the relay UE 820 and the receiving remote UE 830 ) It may correspond to each operation. When it is confirmed that the communication quality of the relay path is getting worse, the base station 1310 , the relay UE 1320 and the remote UE 1330 may perform the same or similar operations as those shown in FIGS. 9 and 10 .

14A and 14B are conceptual diagrams for explaining a second embodiment of a method of operating communication nodes constituting a U2N relay structure.

14A and 14B , the communication system 1400 may include a plurality of communication nodes 1400 . The communication system 1400 may include a base station 1410 , a relay UE 1420 , and a remote UE 1430 connected to each other through a sidelink. The base station 1410 may be the same as or similar to the first and second base stations 310 and 320 described with reference to FIG. 3A . The relay UE 1420 may be the same as or similar to the first, third, fifth and seventh terminals 330 , 340 , 350 and 360 described with reference to FIG. 3A . The remote UE 1430 may be the same as or similar to the second, fourth, sixth, and eighth terminals 331 , 341 , 351 and 361 described with reference to FIG. 3A .

The U2N relay structure shown in FIGS. 14A and 14B may correspond to the U2U relay structure shown in FIGS. 8B and 8C . Here, the base station 1410 may correspond to the receiving remote UE 830 shown in FIGS. 8B and 8C . The relay UE 1420 may correspond to the relay UE 820 illustrated in FIGS. 8B and 8C . The remote UE 1430 may correspond to the transmitting remote UE 810 shown in FIGS. 8B and 8C . The first connection 1415 corresponding to the connection between the base station 1410 and the relay UE 1420 may correspond to the second connection 825 illustrated in FIGS. 8B and 8C . The second connection 1425 corresponding to the connection between the relay UE 1420 and the remote UE may correspond to the first connection 815 illustrated in FIGS. 8B and 8C . 14A and 14B , the remote UE 1430 may transmit relay data to the base station 1410 through the relay UE 1420 . In FIG. 14A , as in FIG. 8B , a situation in which the remote UE 1430 corresponding to the transmission node moves in a direction away from the relay UE 1420 can be seen as illustrated. In FIG. 14b, as in FIG. 8c, the relay UE 1420 serving as a relay moves in a direction away from the base station 1410 corresponding to the receiving node and the remote UE 1430 corresponding to the transmitting node. there is. In FIGS. 14A and 14B , the operations of the base station 1410 , the relay UE 1420 and the remote UE 1430 are respectively, the receiving remote UE 830 , the relay UE 820 and the receiving remote UE 810 in FIGS. 8B and 8C . It may correspond to each operation. When it is confirmed that the communication quality of the relay path is getting worse, the base station 1410 , the relay UE 1420 and the remote UE 1430 may perform the same or similar operations as those shown in FIGS. 9 and 10 .

According to an embodiment of the present invention, in a communication system, a terminal may perform terminal-to-terminal relay (U2U relay) or terminal-to-network relay (U2N relay) based on a sidelink. In a relay structure including a sidelink-based relay terminal, a receiving node receiving data from a transmitting node may monitor a communication quality change aspect based on the received data. The receiving node may generate and transmit connection information including information on the communication quality change aspect to the transmitting node based on the monitoring result of the communication quality change aspect. The transmitting node may check a communication quality change aspect based on the connection information received from the receiving node, and may perform operations for operating a wireless connection in a communication system including a relay structure.

In the case of a wireless communication system using NR, it is necessary to search for a higher frequency band, and it may be difficult to provide network coverage at a high frequency frequency. A relay structure or relay topology using sidelinks can help to improve the frequency utilization of valuable frequency resources in a way that is not simply building a high-density network infrastructure from a network point of view. According to an embodiment of the present invention, it is possible to more flexibly operate a sidelink-based relay through a method and an apparatus capable of monitoring an indirect connection in a radio access system supporting inter-terminal communication, and thus, a terminal (UE) From a viewpoint, more services can be provided without additional modules, and delay and performance can be efficiently improved.

However, effects that can be achieved by the method and apparatus for communication between terminals in a wireless communication system according to embodiments of the present invention are not limited to those mentioned above, and other effects not mentioned are described in the specification of the present application. From the configurations described in the present invention will be clearly understood by those of ordinary skill in the art.

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 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)

A communication method performed by a first communication node of a communication system, comprising:
receiving first data from a second communication node of the communication system;
checking first communication quality information on communication quality between the first and second communication nodes based on a result of receiving the first data;
generating first connection information based on the first communication quality information;
transmitting the first connection information to the second communication node;
receiving second data from the second communication node;
checking second communication quality information on communication quality between the first and second communication nodes based on a result of receiving the second data;
generating second connection information including information on a change aspect of communication quality between the first and second communication nodes based on the first and second communication quality information; and
and transmitting the second connection information to the second communication node.

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