Patent Description:
To meet the demand for wireless data traffic having increased since deployment of <NUM>th generation (<NUM>) communication systems, efforts have been made to develop an improved <NUM>th generation (<NUM>) or pre-<NUM> communication system. Therefore, the <NUM> or pre-<NUM> communication system is also called a "Beyond <NUM> Network" or a "Post long-term evolution (LTE) System".

The <NUM> communication system is considered to be implemented in higher frequency millimeter Wave (mmWave) bands, e.g., <NUM> gigahertz (GHz) bands, so as to accomplish higher data rates.

In the <NUM> system, hybrid frequency-shift keying (FSK) and quadrature amplitude (QAM) modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access(NOMA), and sparse code multiple access (SCMA) as an advanced access technology have also been developed.

For example, technologies, such as a sensor network, machine type communication (MTC), and machine-to-machine (M2M) communication may be implemented by beamforming, MIMO, and array antennas.

Vehicle-to-everything (V2X) is a generic term that refers to all types of communication methods applicable to road vehicles and enables various additional services, as well as safety use cases in the early stage, in combination with the development of wireless communication technology.

Wireless access in vehicular environments (WAVE) standards based on IEEE <NUM>. 11p and IEEE P1609 have been established as a technique for providing V2X services. However, WAVE, which is a kind of dedicated short range communication (DSRC) technology, has a limitation in that a message transmission distance between vehicles is limited.

In order to overcome the above limitation, standardization of cellular-based V2X technology is underway in 3GPP. LTE system-based evolved packet system (EPS) V2X standards have been established in Release <NUM>/Release <NUM>, and the establishment of 5th generation system (5GS) V2X standards based on NR system is in progress in Release <NUM>.

The document <CIT> describes a system, framework and methodologies to compose a user-centric network based on the users spontaneous collaboration requirement. The document <NPL>. The document <NPL>.

Accordingly, an aspect of the disclosure is to provide a method and an apparatus for providing direct communication services in a wireless communication system.

In order to address the above issues, the disclosure provides a method for processing control signals in a wireless communication system, which includes receiving a first control signal transmitted from a base station, processing the received first control signal, and transmitting, to the base station, a second control signal produced based on the processing.

The scope of the present invention may be determined according to the independent claims. Various embodiments of the present invention are outlined in the dependent claims.

Also disclosed herein is a method performed by a first terminal in a wireless communication system. The method includes establishing a unicast link with a second terminal, wherein the unicast link supports one or more service types associated with a first pair of application layer identifiers (IDs) of the first terminal and the second terminal, in case that a data transfer for a service is initiated, determining whether to reuse the established unicast link based on a second pair of application layer IDs associated with the service, and modifying the established unicast link for the service to reuse the established unicast link, in case that the second pair of application layer IDs associated with the service is identical to the first pair of application IDs of the first terminal and the second terminal.

Also disclosed herein is a method performed by a second terminal in a wireless communication system. The method includes establishing a unicast link with a first terminal, wherein the unicast link supports one or more service types associated with a first pair of application layer IDs of the first terminal and the second terminal, and modifying the established unicast link to reuse the established unicast link, in case that a data transfer for a service is initiated, wherein the established unicast link is determined to be reused, in case that the second pair of application layer IDs associated with the service is identical to the first pair of application IDs of the first terminal and the second terminal.

Also disclosed herein is a first terminal in a wireless communication system. The first terminal includes a transceiver configured to transmit and receive signals, and at least one processor coupled with the transceiver and configured to establish a unicast link with a second terminal, wherein the unicast link supports one or more service types associated with a first pair of application layer IDs of the first terminal and the second terminal, in case that a data transfer for a service is initiated, determine whether to reuse the established unicast link based on a second pair of application layer IDs associated with the service, and modify the established unicast link for the service to reuse the established unicast link, in case that the second pair of application layer IDs associated with the service is identical to the first pair of application IDs of the first terminal and the second terminal.

Also disclosed herein is a second terminal in a wireless communication system. The second terminal includes a transceiver configured to transmit and receive signals, and at least one processor coupled with the transceiver and configured to establish a unicast link with a first terminal, wherein the unicast link supports one or more service types associated with a first pair of application layer IDs of the first terminal and the second terminal, and modify the established unicast link to reuse the established unicast link, in case that a data transfer for a service is initiated, wherein the established unicast link is determined to be reused, in case that the second pair of application layer IDs associated with the service is identical to the first pair of application IDs of the first terminal and the second terminal.

According to an embodiment, it is possible to provide an apparatus and a method capable of efficiently providing direct communication services in a wireless communication system.

Hereinafter, the operation principle of the disclosure will be described below in conjunction with the accompanying drawings. In the following description of the disclosure, a detailed description of known functions or configurations incorporated herein will be omitted when it may make the subject matter of the disclosure rather unclear. The terms which will be described below are terms defined based on the functions in the disclosure, and may be different according to users, intentions of the users, or customs. Therefore, the definitions of the terms should be made based on the contents throughout the specification.

The advantages and features of the disclosure and ways to achieve them will be apparent by making reference to embodiments as described below in conjunction with the accompanying drawings.

The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operations to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions that execute on the computer or other programmable apparatus provide operations for implementing the functions specified in the flowchart block or blocks.

As used herein, the "unit" refers to a software element or a hardware element, such as a Field Programmable Gate Array (FPGA) or an Application Specific Integrated Circuit (ASIC), which performs a predetermined function. However, the "unit" does not always have a meaning limited to software or hardware. The "unit" may be constructed either to be stored in an addressable storage medium or to execute one or more processors. Therefore, the "unit" includes, for example, software elements, object-oriented software elements, class elements or task elements, processes, functions, properties, procedures, sub-routines, segments of a program code, drivers, firmware, micro-codes, circuits, data, database, data structures, tables, arrays, and parameters. The elements and functions provided by the "unit" may be either combined into a smaller number of elements, or a "unit", or divided into a larger number of elements, or a "unit". Moreover, the elements and "units" or may be implemented to reproduce one or more CPUs within a device or a security multimedia card. Further, the "unit" in the embodiments may include one or more processors.

In the following description, terms for identifying access nodes, terms referring to network entities, terms referring to messages, terms referring to interfaces between network entities, terms referring to various identification information, and the like are illustratively used for the sake of convenience. Therefore, the disclosure is not limited by the terms as used below, and other terms referring to subjects having equivalent technical meanings may be used.

In the following description, the disclosure uses terms and names defined in the <NUM>, new radio (NR), and long term evolution (LTE) system standards for the convenience of description. However, the disclosure is not limited by these terms and names, and may be applied in the same way to systems that conform other standards.

A detailed description of embodiments of the disclosure will be directed to communication standards defined by the 3GPP. However, based on determinations by those skilled in the art, the main idea of the disclosure may be applied to other communication systems having similar technical backgrounds through some changes and modifications without significantly departing from the scope of the disclosure.

Although embodiments of the disclosure will be described below, based primarily on vehicle communication services, the subject matter of the disclosure may be applied to other services provided in a <NUM> network through some modifications thereof without departing from the scope of the disclosure, which may be readily determined by those skilled in the art.

In a <NUM> system, more various services than an existing <NUM> system are considered to be supported. For example, the most typical services may include enhanced mobile broadband (eMBB), ultra-reliable and low-latency communication (URLLC), massive machine-type communication (mMTC), an evolved multimedia broadcast/multicast service (eMBMS), and the like. In addition, a system that provides URLLC services may be referred to as a "URLLC system", and a system that provides eMBB services may be referred to as an "eMBB system". Further, "service" may be used interchangeably with "system".

Among them, the URLLC services are newly considered in the <NUM> system, unlike the existing <NUM> system, and satisfy conditions of ultra-reliability (for example, a packet error rate of about <NUM>-<NUM>) and low latency (for example, about <NUM> msec), compared to other services. In order to satisfy these strict requirements, the URLLC service may need to apply a transmission time interval (TTI) shorter than that of the eMBB service, and various operation methods utilizing the same are being considered.

Meanwhile, the Internet, which to date has been a human-centered connectivity network in which humans generate and consume information, is now evolving to the Internet of Things (IoT), where distributed entities, or "things", exchange and process information. The Internet of Everything (IoE), which is a combination of IoT technology and big-data processing technology through connection with a cloud server, has emerged. As technology elements, such as sensing technology, wired/wireless communication and network infrastructure, service interface technology, and security technology, have been demanded for IoT implementation, techniques for connecting things, such as a sensor network, machine-to-machine (M2M) communication, machine-type communication (MTC), and the like, have been recently researched.

<FIG> illustrates a configuration of a vehicle communication system according to an embodiment of the disclosure.

Referring to <FIG>, a terminal <NUM> (this may be used interchangeably with a user equipment, a user terminal, or a vehicle UE) may use direct communication <NUM> (e.g., device-to-device (D2D), ProSe, PC5, or sidelink communication) or network communication <NUM> or <NUM> through a mobile communication system <NUM> in order to communicate with another terminal <NUM>. In the case of direct communication, the transmission and reception of messages between the terminal <NUM> and another terminal <NUM> may be performed through a PC5 link. In the case of network communication, a message sent from a transmitting vehicle terminal to a receiving vehicle terminal may be transmitted to a network through a Uu link, and may then be transmitted to the receiving vehicle terminal through a Uu link. The mobile communication system <NUM> may be an EPC system defined in 3GPP, a 5GC system, or a communication system other than 3GPP. The direct communication <NUM> may be provided using a non-3gpp RAT, such as LTE radio access technology (RAT), NR RAT, or wireless fidelity (Wi-Fi).

<FIG> illustrates a control plane protocol stack of a terminal according to an embodiment of the disclosure, and <FIG> illustrates a user plane protocol stack of a terminal according to an embodiment of the disclosure. A terminal <NUM> may be a transmitting terminal, and a terminal <NUM> may be a receiving terminal, which will be referred to as a "terminal <NUM>" and a "terminal <NUM>", respectively, for the convenience of description.

Referring to <FIG>, the control plane protocol stack of the terminal <NUM> or <NUM> may include a PC5 signaling protocol layer <NUM> or <NUM>, a radio resource control (RRC) layer <NUM> or <NUM>, a packet data convergence protocol (PDCP) layer <NUM> or <NUM>, a radio link control (RLC) layer <NUM> or <NUM>, a MAC layer <NUM> or <NUM>, and a physical layer (PHY) layer <NUM> or <NUM>. The RRC layer <NUM> or <NUM>, the PDCP layer <NUM> or <NUM>, the RLC layer <NUM> or <NUM>, and the medium access control (MAC) layer <NUM> or <NUM> may be collectively referred to as an access stratum (AS) layer <NUM> or <NUM>. Hereinafter, in describing the disclosure, the AS layer <NUM> or <NUM> may include at least one of the RRC layer <NUM> or <NUM>, the PDCP layer <NUM> or <NUM>, the RLC layer <NUM> or <NUM>, and the MAC layer <NUM> or <NUM>.

The PC5 signaling protocol layer <NUM> or <NUM> may provide link establishment and link maintenance functions for direct communication <NUM> between the terminal <NUM> and the terminal <NUM> through the procedures shown in <FIG>, <FIG>, and <FIG>.

Referring to <FIG>, a PC5 signaling (PC5-S) message of the terminal <NUM> or <NUM> may be transmitted to the opponent terminal through the PC5 signaling protocol layer <NUM> or <NUM>, the RRC layer <NUM> or <NUM>, the PDCP layer <NUM> or <NUM>, the RLC layer <NUM> or <NUM>, the MAC layer <NUM> or <NUM>, and the PHY layer <NUM> or <NUM>.

Alternatively, referring to <FIG>, a PC5 signaling (PC5-S) message of the terminal <NUM> or <NUM> may be transmitted to the opponent terminal through the PC5 signaling protocol layer <NUM> or <NUM>, the PDCP layer <NUM> or <NUM>, the RLC layer <NUM> or <NUM>, the MAC layer <NUM> or <NUM>, and the PHY layer <NUM> or <NUM>.

Referring to <FIG>, the user plane protocol stack of the terminal <NUM> or <NUM> may include an application layer <NUM> or <NUM>, a service enabling (SE) layer <NUM> or <NUM>, a service data adaptation protocol (SDAP) layer <NUM> or <NUM>, a PDCP layer <NUM> or <NUM>, an RLC layer <NUM> or <NUM>, a MAC layer <NUM> or <NUM>, and a PHY layer <NUM> or <NUM>. The SDAP layer <NUM> or <NUM>, the PDCP layer <NUM> or <NUM>, the RLC layer <NUM> or <NUM>, and the MAC layer <NUM> or <NUM> may be collectively referred to as the AS layer <NUM> or <NUM>. Hereinafter, in describing the disclosure, the AS layer <NUM> or <NUM> may include at least one of the SDAP layer <NUM> or <NUM>, the PDCP layer <NUM> or <NUM>, the RLC layer <NUM> or <NUM>, and the MAC layer <NUM> or <NUM>.

The SE layer <NUM> or <NUM> is an intermediate layer for performing the operation of the application layer <NUM> or <NUM>, and may provide specialized functions to respective applications or services. A single SE layer may support multiple application layers. In addition, a specialized SE layer may be defined for each application layer. For example, application layer <NUM> or <NUM> may be a V2X application layer for providing V2X services. In addition, the SE layer <NUM> or <NUM> may be defined as a V2X layer for the operation of the V2X application layer. Hereinafter, in order to provide V2X services, the application layer <NUM> or <NUM> may be used interchangeably with a V2X application layer, and the SE layer <NUM> or <NUM> may be used interchangeably with a V2X layer.

The SE layer <NUM> or <NUM> may provide a function of transmitting data through a link established between the terminal <NUM> and the terminal <NUM> for direct communication <NUM>. The SE layer <NUM> or <NUM> may include IP protocol, non-IP protocol, and transport protocol (e.g., TCP or UDP) for transmitting messages.

The terminal <NUM> or <NUM> according to an embodiment may acquire and store the following information shown in Table <NUM> in order to use V2X services. The SE layer <NUM> or <NUM> may use stored information.

The SDAP layer <NUM> or <NUM> may be used in transmitting data through direct communication <NUM> between the terminal <NUM> and the terminal <NUM>. For example, when establishing a link for direct communication <NUM> between the terminal <NUM> and the terminal <NUM> and then transmitting data through the established link (for example, PC5 unicast communication or PC5 groupcast), the SDAP layer <NUM> or <NUM> may be used in transmission of messages. In addition, for example, even when transmitting data without establishing a link for direct connection <NUM> between the terminal <NUM> and the terminal <NUM> (for example, PC5 broadcast communication), the SDAP layer <NUM> or <NUM> may be used in transmission of messages.

The PC5 signaling protocol layer <NUM> or <NUM> according to an embodiment may include functions provided by the SE layer <NUM> or <NUM>. Alternatively, the PC5 signaling protocol layer <NUM> or <NUM> may interact with the SE layer <NUM> or <NUM>, the RRC layer <NUM> or <NUM>, the PDCP layer <NUM> or <NUM>, and/or the SDAP layers <NUM> or <NUM> for link establishment and/or link maintenance.

The terminals <NUM> and <NUM> according to an embodiment may store the following information shown in Table <NUM> in order to provide services (e.g., V2X services) using direct communication. The SE layer <NUM> or <NUM> may use the stored information.

Referring to Table <NUM>, QoS parameters may include one or more QoS characteristics. The QoS characteristics may be, for example, a priority level, a packet delay budget, a packet error rate, a maximum data burst volume, an average window, a communication range, and the like. The QoS parameters may include one or more QoS characteristics, and may be referred to as "PQI (5QI for PC5) values".

<FIG> illustrates a configuration of a direct communication link between terminals according to an embodiment of the disclosure.

Referring to <FIG>, the terminal <NUM> and the terminal <NUM> may store and drive the same applications <NUM> and <NUM>. The applications may be identified by application identifications (IDs) (e.g., OSAppIDs or the like). The applications <NUM> and <NUM> may provide one or more services. For example, the applications <NUM> and <NUM> may include service type #<NUM> (<NUM> or <NUM>) and service type #<NUM> (<NUM> or <NUM>). The respective service types may be distinguished by service type IDs (e.g., PSIDs, ITS-AIDs, etc.).

The terminal according to an embodiment may have one or more applications installed therein, and the one or more applications may be simultaneously executed. The application layer user IDs (e.g., terminal IDs, terminal subscriber IDs, user email addresses, etc.) related to the respective applications may be implemented in any of various methods as follows.

For example, one application layer user ID may be used for one application. In this case, the application layer user ID may be assigned as a unique value to each user and application. Referring to <FIG>, in the case where Application #<NUM> (<NUM>), Application #<NUM>, and Application #<NUM> are installed in the terminal <NUM>, respective ones of Application #<NUM> (<NUM>), Application #<NUM>, and Application #<NUM> may be distinguished by application layer user IDs. In this case, the SE layer <NUM> may identify the respective ones of Application #<NUM> (<NUM>), Application #<NUM>, and Application #<NUM> using application layer user IDs.

Alternatively/in addition, one application layer user ID may be used for one or more applications. For example, one or more applications may share one application layer user ID.

Referring to <FIG>, in the case where Application #<NUM> (<NUM>), Application #<NUM>, and Application #<NUM> are installed in the terminal <NUM>, Application #<NUM> (<NUM>) and Application #<NUM> may use one application layer user ID, and Application #<NUM> may use another application layer user ID. In this case, the SE layer <NUM> may identify Application #<NUM> (<NUM>) and Application #<NUM> using the same one application layer user ID, and may identify Application #<NUM> using one application layer user ID.

Alternatively/in addition, one application layer user ID may be used for all applications. For example, all applications may share one application layer user ID.

Referring to <FIG>, in the case where Application #<NUM> (<NUM>), Application #<NUM>, and Application #<NUM> are installed in the terminal <NUM>, all the applications installed in the terminal <NUM> may use one application layer user ID. For example, the applications may not be further identified using application layer user IDs. In this case, the SE layer <NUM> may be aware that one application layer user ID is applied to all applications of the terminal <NUM>, and may use the same.

Hereinafter, in describing the disclosure, the operation of applications <NUM> and <NUM> and/or services types <NUM>, <NUM>, <NUM>, and <NUM> may be understood as the operation of the application layers <NUM> and <NUM> shown in <FIG>. One or more applications and/or service types may be driven by the application layers <NUM> and <NUM>.

The service type may have one or more QoS requirements. The SE layer <NUM> or <NUM> may determine QoS parameters to meet the QoS requirements provided from the applications <NUM> and <NUM> and/or the service types <NUM>, <NUM>, <NUM>, and <NUM>, and may map the same to PQI values shown in Table <NUM>.

The terminal <NUM> and the terminal <NUM> may establish a direct communication link <NUM> using the procedure shown in <FIG>, <FIG>, and <FIG>. The direct communication link <NUM> may be referred to as a "link ID". According to an embodiment of the disclosure, the terminal <NUM> and the terminal <NUM> may establish one direct communication link <NUM> for each of the applications <NUM> and <NUM>, and may provide one or more service types (e.g., PSID, ITS-AID, etc.) using the direct communication link <NUM>. For example, as shown in <FIG>, one application may have one direct communication link.

Alternatively, according to an embodiment of the disclosure, the terminal <NUM> and the terminal <NUM> may establish a direct communication link <NUM> for each service type <NUM>, <NUM>, <NUM>, or <NUM>. One application including a plurality of service types may produce direct communication links <NUM> supporting the respective service types, and each direct communication link may provide each service type (e.g., PSID, ITS-AID, etc.). For example, as shown in <FIG>, one application may have direct communication links equal to the number of supported service types.

The direct communication link <NUM> may include one or more QoS flows. The QoS flows may be mapped to the PQI values shown in Table <NUM>. One QoS flow may be referred to as a "QoS flow identifier (QFI)". For example, as shown in <FIG>, the direct communication link <NUM> may include four QoS flows, and the respective QoS flows may be called "QFI #<NUM>" (<NUM>), "QFI #<NUM>" (<NUM>), and "QFI #<NUM>" (<NUM>), and "QFI #<NUM>" (<NUM>). The respective QoS flows constituting the direct communication link <NUM> may provide different levels of QoSs. A procedure of establishing the direct communication link <NUM> will be described below with reference to <FIG>.

The terminals <NUM> and <NUM> may transmit data using the procedure shown in <FIG>. The terminals <NUM> and <NUM> may transmit data using the QoS flows included in the direct communication link <NUM> for transmission of data. The SE layer <NUM> or <NUM> may select an appropriate QFI according to the QoS required for the data to be transmitted, and may transmit data using the selected QFI. A procedure of transmitting data through the direct communication link <NUM> will be described below with reference to <FIG>.

<FIG> illustrates a procedure of establishing a direct communication link according to an embodiment of the disclosure.

For the description of the disclosure, it is assumed that the transmitting terminal <NUM> may initiate establishment of a direct communication link and that the remaining peripheral terminals <NUM>, <NUM>, and <NUM> are located adjacent to the transmitting terminal <NUM>, and may receive a direct communication request message <NUM> transmitted from the transmitting terminal <NUM>. In addition, it is assumed that at least one of the peripheral terminals <NUM>, <NUM>, and <NUM>, for example, the terminal <NUM>, performs direct communication <NUM> with the transmitting terminal <NUM>.

Referring to <FIG>, the peripheral terminal <NUM>, <NUM>, and <NUM> may determine a destination layer-<NUM> ID for receiving a direct communication request message <NUM>, based on the V2X service policy parameter in Table <NUM> (for example, it corresponds to "The mapping of default destination layer-<NUM> ID(s) for initial signaling to establish unicast connection and the V2X services, e.g., PSID or ITS-AIDs of the V2X application" in Table <NUM>) in operation <NUM>. The destination layer-<NUM> ID for receiving a direct communication request message may be determined to be different values for respective application layers, respective applications supported by the application layer, or respective service types supported by the application layer (e.g., PSID, ITS-AID, etc.). Alternatively, the destination layer-<NUM> ID for receiving a direct communication request message may be determined to be the same default value, regardless of the application layer, the application supported by the application layer, or the service type supported by the application layer.

The application layer <NUM> of the terminal <NUM> to perform the application operation may provide the SE layer <NUM> with at least one of "application data" produced by the application layer <NUM> in operation <NUM> (hereinafter, this will be used interchangeably with "service data" or "data"), a "service type" indicating the type of data, a "communication mode" indicating the communication method of data (e.g., broadcast, groupcast, unicast, or the like), an "application layer user ID" (application layer user identifier) of the transmitting terminal <NUM>, an "application layer user ID" (application layer user identifier) of the receiving terminal <NUM>, and "QoS requirements". In the case of vehicle communication, PSID, ITS-AID, and the like may be used as the service type. The application layer <NUM> may provide the SE layer <NUM> with one or more service types. In addition, the application layer <NUM> may provide the SE layer <NUM> with one or more QoS requirements. Further, the application layer <NUM> may provide the SE layer <NUM> with service types and mapping information between one or more QoS requirements and the service types. An example of information provided by the application layer <NUM> to the SE layer <NUM> in operation <NUM> is as follow.

The SE layer <NUM> of the terminal <NUM> may determine whether or not to perform a link establishment procedure in operation <NUM>, based on information received from the application layer <NUM> in operation <NUM> (e.g., the application data, the communication mode, the service type, and the like). For example, if the communication mode received from the application layer <NUM> is PC5 unicast, the SE layer <NUM> may determine that a link is required to be established. If it is determined whether or not a pre-established direct communication link is recycled, and if it is determined that the pre-established direct communication link is unable to be recycled, the SE layer <NUM> may determine to perform the establishment procedure, thereby performing the following operation. If the pre-established direct communication link is able to be recycled, the SE layer <NUM> may perform the procedure shown in <FIG>.

For example, if there is a link profile that stores application layer user ID of the transmitting terminal <NUM> and/or the application layer user ID of the receiving terminal <NUM> in operation <NUM> from the application layer <NUM>, the SE layer <NUM> may recognize that the terminal <NUM> has a pre-established direct communication link with the terminal <NUM>. Accordingly, the SE layer <NUM> may determine to recycle the pre-established direct communication link, instead of establishing a new direct communication link, and may perform the procedure shown in <FIG>. According to an embodiment of the disclosure, in the case where one application layer user ID is used in each application, the terminal <NUM> may establish one direct communication link with the terminal <NUM> for each application. For example, one direct communication link may be produced for each application, and signaling and data for one application may be transmitted through one direct communication link. Alternatively, in the case where one application layer user ID is used in one or more applications, the terminal <NUM> may establish one direct communication link with the terminal <NUM> for the applications sharing the application layer user ID. For example, applications sharing one application layer user ID may share one direct communication link, and may transmit signaling and data for the applications through one direct communication link. Alternatively, in the case where one application layer user ID is used in all applications, a single direct communication link may be established between the terminal <NUM> and the terminal <NUM>, thereby transmitting signaling and data for all applications supported by the terminal <NUM> and the terminal <NUM> through the single direct communication link.

If there is not a link profile that stores application layer user ID of the transmitting terminal <NUM> and/or the application layer user ID of the receiving terminal <NUM>, the SE layer may perform the following procedure.

The SE layer <NUM> of the terminal <NUM> may assign a link identifier (ID) indicating the direct communication link <NUM> to be established through the processes of operation <NUM> to operation <NUM>. The link ID may be assigned as a unique value in the terminal <NUM>. The SE layer <NUM> may produce a link profile for the direct communication link <NUM> indicated as the link ID assigned by the SE layer <NUM>. The link profile may include application layer user IDs of the transmitting and receiving terminals <NUM> and <NUM> received by the SE layer <NUM> from the application layer <NUM> in operation <NUM>.

In addition, the SE layer <NUM> may convert the QoS requirements received from the application layer <NUM> in operation <NUM> into PQI (PC5 5QI) values that are available for the AS layer <NUM>. One service type may request message a plurality of QoS requirements, and thus, one service type may be mapped to a plurality of PQI values. In addition, the SE layer <NUM> may assign QFIs to respective PQI values. According to an embodiment of the disclosure, if the service types are different with respect to the same PQI value (e.g., PQI #<NUM>), different QFI values (e.g., QFI #<NUM> and QFI #<NUM>) may be assigned thereto. This example is shown in <FIG>.

Alternatively, according to an embodiment of the disclosure, even if the service types are different with respect to the same PQI value (e.g., PQI #<NUM>), the same QFI value (e.g., QFI #<NUM>) may be assigned thereto. This example is shown in <FIG>.

The link profile produced and managed by the SE layer <NUM> may include and store at least one of PQI values associated with a direct communication link, QFI values corresponding to respective PQI values, service types corresponding to respective PQI values, and service types corresponding to respective QFI values.

The SE layer <NUM> may determine its own layer-<NUM> ID of the terminal <NUM> to be used for direct communication, and may assign the same to itself. The SE layer <NUM> may store its own layer-<NUM> ID of the terminal <NUM> in the link profile produced and managed by the SE layer <NUM>. An example of information stored in the link profile produced by the SE layer <NUM> in operation <NUM> is as follows. The link profile may be referred to as a "link ID".

The SE layer <NUM> may produce a direct communication request message for establishing a unicast link. The direct communication request message may include at least one of an "application message", an "application ID", a "service type", an "application layer user ID" (application layer user identifier) of the transmitting terminal <NUM>, an "application layer user ID" (application layer user identifier) of the receiving terminal <NUM>, a "link ID" indicating the direct communication link, "QoS requirements" that must be provided by the direct communication link, a "PQI", a "QFI", and a "layer-<NUM> ID" of the transmitting terminal <NUM>, which are received from the application layer <NUM> in operation <NUM>. An example of information included in the direct communication request message is as follows.

The SE layer <NUM> may determine a source layer-<NUM> ID and a destination layer-<NUM> ID to be included in a MAC header in order to transmit the produced direct communication request message. The SE layer <NUM> may use the layer-<NUM> ID assigned by the terminal <NUM> itself as the source layer-<NUM> ID. The source layer-<NUM> ID may be the same as the layer-<NUM> ID value of the terminal <NUM> stored in the link profile. In addition, the SE layer <NUM> may refer to the V2X service policy parameters in Table <NUM>, which are stored by the terminal, in order to determine the destination layer <NUM>-ID. For example, the destination layer-<NUM> ID may be determined based on "The mapping of default destination layer-<NUM> ID(s) for initial signaling to establish unicast connection and the V2X services, e.g., PSID or ITS-AIDs of the V2X application" in Table <NUM>. The destination layer-<NUM> ID may be the same value as the destination layer-<NUM> ID determined by the peripheral terminals <NUM>, <NUM>, and <NUM> in operation <NUM>.

The SE layer <NUM> may deliver information to the AS layer <NUM> in order to transmit a direct communication request message. The information delivered to the AS layer <NUM> may include at least one of a direct communication request message, a source layer-<NUM> ID of the message, a destination layer-<NUM> ID of the message, a link ID, a PQI value, a QFI value, mapping information between the PQI and the QFI, a communication mode (e.g., PC5 broadcast), and the type of message {e.g., a signal (control) message}. An example of information that the SE layer <NUM> delivers to the AS layer <NUM> is as follows.

The AS layer <NUM> may store information delivered from the SE layer <NUM>, and may manage a sidelink radio bearer (SLRB) for direct communication. According to an embodiment of the disclosure, one QFI value may be assigned to one PQI value, and one QFI value may be mapped to one SLRB (e.g., QFI #<NUM> and SLRB #<NUM>). Alternatively, if the service types are different, different QFI values may be assigned to the same PQI value, and multiple QFI values may be mapped to one SLRB (e.g., QFI #<NUM>, QFI #<NUM>, and SLRB #<NUM>). Alternatively, one QFI value may be assigned to one PQI value, and multiple QFI values may be mapped to one SLRB (e.g., QFI #<NUM>, QFI #<NUM>, and SLRB #<NUM>). This example is shown in <FIG>.

Alternatively, according to an embodiment of the disclosure, one QFI value may be assigned to one PQI value, and one QFI value may be mapped to one SLRB (e.g., QFI #<NUM> and SLRB #<NUM>). Alternatively, even if the service types are different, one QFI value may be assigned to the same PQI value, and one QFI value may be mapped to one SLRB (e.g., QFI #<NUM> and SLRB #<NUM>). Alternatively, one QFI value may be assigned to one PQI value, and multiple QFI values may be mapped to one SLRB (e.g., QFI #<NUM>, QFI #<NUM>, and SLRB #<NUM>). This example is shown in <FIG>.

The AS layer <NUM> may configure a MAC header, based on information delivered from the SE layer <NUM>. An example of configuring a MAC PDU is shown in <FIG>. The MAC PDU may include a MAC header <NUM>. The MAC header may include an SL-SCH sub-header <NUM> and an R/R/E/LCID/F/L sub-header <NUM>. The SL-SCH sub-header <NUM> may be commonly applied to the entire MAC payload <NUM>. The R/R/E/LCID/F/L sub-header <NUM> may sequentially correspond to one MAC SDU <NUM> of the MAC payload.

<FIG> is a diagram illustrating a configuration of a SL-SCH sub-header shown in <FIG> according to an embodiment of the disclosure. The SL-SCH sub-header <NUM> may include a source layer-<NUM> ID <NUM> (corresponding to SRC in Table <NUM>) and a destination layer-<NUM> ID <NUM> (corresponding to DST in Table <NUM>). The source layer-<NUM> ID <NUM> and the destination layer-<NUM> ID <NUM> may have a range of <NUM> octet values or <NUM> octet values, respectively. The AS layer <NUM> may configure the source layer-<NUM> ID delivered from the SE layer <NUM> as the source layer-<NUM> ID <NUM> of the SL-SCH sub-header (corresponding to the SRC in Table <NUM>). In addition, the AS layer <NUM> may configure the destination layer-<NUM> ID delivered from the SE layer <NUM> as the destination layer-<NUM> ID <NUM> of the SL-SCH sub-header (corresponding to the DST in Table <NUM>).

The R/R/E/LCID/F/L sub-header <NUM> may include a logical channel ID (LCID) indicating the type of message of the MAC SDU <NUM> indicated by the sub-header. Table <NUM> shows an example of the LCID. The AS layer <NUM> may determine the LCID, based on the type of message delivered from the SE layer <NUM>. For example, if the type of message indicates a signaling message, the LCID may be set to <NUM>, <NUM>, or <NUM>.

The AS layer <NUM> may configure the MAC header <NUM> as described above, and may include a direct communication request message received from the SE layer <NUM> in the MAC payload <NUM>, thereby transmitting the same to the peripheral terminals <NUM>, <NUM>, and <NUM> through a physical layer <NUM> (operation <NUM>).

The peripheral terminals <NUM>, <NUM>, and <NUM> of the transmitting terminal <NUM> may receive a direct communication request message transmitted from the transmitting terminal <NUM> (operation <NUM>). The peripheral terminals <NUM>, <NUM>, and <NUM> may delivered the received direct communication request message to the SE layer through the PHY layers and the AS layers of the terminals <NUM>, <NUM>, and <NUM>. Upon receiving the direct communication request message, the SE layer may identify a destination address of the message, thereby determining a method of processing the message. If the destination address of the message is the destination layer-<NUM> ID address determined by the terminal in operation <NUM>, the SE layer may determine that the received message is a direct communication request message among the PC5-S signaling messages. The SE layer may select an application layer to which the received message is to be delivered based on at least one of the "destination layer-<NUM> ID address" of the received message, the "service type" included in the received message, the "application layer user ID (application layer user identifier) of the terminal" included in the received message, or the "application ID" included in the received message, and may deliver the received message to the selected application layer.

The application layer <NUM> of the terminal <NUM> receiving the direct communication request message may determine to respond to the received direct communication request message, based on "application data", a "service type", an "application layer user ID" (application layer user identifier) of the transmitting terminal <NUM>, an "application layer user ID" (application layer user identifier) of the receiving terminal <NUM>, and the like included in the received direct communication request message.

The application layer <NUM> of the terminal <NUM> that wishes to accept the received direct communication request may provide the SE layer <NUM> with at least one of the "application data" produced by the application layer <NUM> in operation <NUM> (hereinafter, this will be used interchangeably with "service data" or "data"), a "service type" indicating the type of data, a "communication mode" indicating the communication method of data (e.g., broadcast, groupcast, unicast, or the like), an "application layer user ID" (application layer user identifier) of the transmitting terminal <NUM>, an "application layer user ID" (application layer user identifier) of the receiving terminal <NUM>, and "QoS requirements". In the case of vehicle communication, PSID, ITS-AID, or the like may be used as the service type. The application layer <NUM> may provide the SE layer <NUM> with one or more service types. In addition, the application layer <NUM> may provide the SE layer <NUM> with one or more QoS requirements. Further, the application layer <NUM> may provide the SE layer <NUM> with service types and mapping information between one or more QoS requirements and the service types. An example of information provided by the application layer <NUM> to the SE layer <NUM> in operation <NUM> is as follow.

The SE layer <NUM> of the terminal <NUM> may determine whether or not to perform a link establishment procedure in operation <NUM>, based on the information received from the application layer <NUM> in operation <NUM> (e.g., the application data, the communication mode, the service type, and the like). For example, if the application data received from the application layer <NUM> requires establishment of a direct communication link, the SE layer <NUM> may determine to perform a link establishment procedure. The SE layer <NUM> may perform the following operations, based on the information received from the application layer <NUM> in operation <NUM> and the information received from the transmitting terminal <NUM> in operation <NUM> (operation <NUM>).

The SE layer <NUM> of the terminal <NUM> may assign a link identifier (ID) indicating the direct communication link <NUM> to be established through the processes of operation <NUM> to operation <NUM>. Alternatively, the SE layer <NUM> may use the link ID received from the transmitting terminal <NUM> in operation <NUM>. The link ID may be assigned as a unique value in the terminal <NUM>. The SE layer <NUM> may produce a link profile for the direct communication link <NUM> indicated using the link ID assigned by the SE layer <NUM>. The link profile may include application layer user IDs of the transmitting and receiving terminals received in operation <NUM> or operation <NUM>.

In addition, the SE layer <NUM> may convert the QoS requirements received in operation <NUM> or operation <NUM> into PQI (PC5 5QI) values that are available for the AS layer <NUM> in order to determine the PQIs to be supported in direct communication. Alternatively, the SE layer <NUM> may use the PQI values received in operation <NUM>.

The SE layer <NUM> may determine the QFI mapped to the PQI to be supported in direct communication. Alternatively, the SE layer <NUM> may determine the QFI using mapping information between the PQI value received in operation <NUM> and the QFI.

The method described in operation <NUM> may be applied to the relationship between the service types, the QoS requirements, the PQIs, and the QFIs in a similar manner.

The SE layer <NUM> may determine its own layer-<NUM> ID of the terminal <NUM> to be used for direct communication, and may assign the same to itself. The SE layer <NUM> may store its own layer-<NUM> ID of the terminal <NUM> in a link profile produced and managed by the SE layer <NUM>. An example of information stored in the link profile produced by the SE layer <NUM> in operation <NUM> is as follows. The link profile may be referred to as a "link ID".

The SE layer <NUM> may produce a direct communication response message for establishing a unicast link. The direct communication response message may include at least one of the "application message" received in operation <NUM>, the "application ID" received in operation <NUM> or <NUM>, a "service type", an "application layer user ID" (application layer user identifier) of the transmitting terminal <NUM>, an "application layer user ID" (application layer user identifier) of the receiving terminal <NUM>, a "link ID" indicating the direct communication link, "QoS requirements" that must be provided by the direct communication link, a "PQI", a "QFI", a "layer-<NUM> ID" of the transmitting terminal <NUM>, and a "layer-<NUM> ID" of the transmitting terminal <NUM>. An example of information included in the direct communication request message is as follows.

The SE layer <NUM> may determine a source layer-<NUM> ID and a destination layer-<NUM> ID to be included in a MAC header in order to transmit the produced direct communication response message. The SE layer <NUM> may use the layer-<NUM> ID assigned by the terminal <NUM> itself as the source layer-<NUM> ID. The source layer-<NUM> ID may be the same as the layer-<NUM> ID value of the terminal <NUM> stored in the link profile. In addition, the SE layer <NUM> may use the source layer-<NUM> ID of the direct communication request message received in operation <NUM> as the destination layer-<NUM> ID. The destination layer-<NUM> ID may be the same as the layer-<NUM> ID value of the terminal <NUM> stored in the link profile.

The SE layer <NUM> may deliver information to the AS layer <NUM> in order to transmit a direct communication response message. The information delivered to the AS layer <NUM> may include at least one of a direct communication response message, a source layer-<NUM> ID of the message, a destination layer-<NUM> ID of the message, a link ID, a PQI value, a QFI value, mapping information between the PQI and the QFI, a communication mode (e.g., PC5 broadcast), and the type of message {e.g., a signal (control) message}. An example of information that the SE layer <NUM> delivers to the AS layer <NUM> is as follows.

The AS layer <NUM> may store information received from the SE layer <NUM>, and may manage a sidelink radio bearer (SLRB) for direct communication. The method described in operation <NUM> may be applied to the relationship between the SLRB management, the SLRB, the QFI, and the PQI in a similar manner.

The AS layer <NUM> may configure a MAC header, based on the information received from the SE layer <NUM>. The method described in operation <NUM> may be applied to the method of configuring the MAC header in a similar manner.

The AS layer <NUM> may configure the MAC header as described above, and may include a direct communication response message received from the SE layer <NUM> in the MAC payload, thereby transmitting the same to the terminal <NUM> through a physical layer <NUM> (operation <NUM>).

The SE layer <NUM> of the terminal <NUM> receiving the direct communication response message may determine that the received message is a PC5-S signaling message, based on at least one of a destination layer-<NUM> ID address of the received message, a logical channel ID (LCID), or information received from the AS layer (e.g., an indicator indicating a PC5-S signaling message), and may process the received message as follows. The SE layer <NUM> may identify that the received message is a direct communication response message, and inform the application layer <NUM> that the direct communication link has been established. At this time, the SE layer <NUM> of the terminal <NUM> may further inform the application layer <NUM> of information related to the established direct communication link (e.g., link ID, QFI, etc.). An example of information that the SE layer <NUM> delivers to the application layer <NUM> is as follows.

In addition, the SE layer <NUM> may inform the AS layer <NUM> of information on the established direct communication link (e.g., a link ID, QFI information, and the like). An example of information that the SE layer <NUM> delivers to the AS layer <NUM> is shown below. The AS layer <NUM> may store the received information, and may use the same for direct communication in the future.

The SE layer <NUM> may update the link profile information produced in operation <NUM>, based on the information on the received direct communication response message. For example, the destination layer-<NUM> ID of the direct communication response message received in operation <NUM> may be stored as a "layer-<NUM> ID" of the terminal <NUM>. In addition, if the information included in the direct communication response message received in operation <NUM> {e.g., an "application layer user ID" (application layer user identifier) of the terminal <NUM>, "QoS requirements", "PQIs", "QFIs", and the like} does not match the link profile information produced in operation <NUM>, the link profile information may be updated using the information received in operation <NUM>.

<FIG> illustrates a procedure of transmitting data using a direct communication link according to an embodiment of the disclosure.

Referring to <FIG>, the terminal <NUM> and the terminal <NUM> may complete establishment of a direct communication link through the procedure described with reference to <FIG>. The terminals <NUM> and <NUM> may produce a link profile in the process of establishing the direct communication link, and may store layer-<NUM> ID information on the terminals <NUM> and <NUM> to be used in the direct communication link.

In operation <NUM>, the terminal <NUM> may determine a destination layer-<NUM> ID for receiving data and a signaling message transmitted through the direct communication link produced through the procedure shown in <FIG>. For example, the destination layer-<NUM> ID may be determined as the layer-<NUM> ID of the terminal <NUM> included in the corresponding link profile.

The application layer <NUM> of the terminal <NUM> may deliver, to the SE layer <NUM>, at least one of the "application data" produced by the application layer <NUM> in operation <NUM>, a "link ID" indicating a direct communication link through which data is transmitted, a "service type" indicating the type of data, a "communication mode" indicating the communication method of data (e.g., broadcast, groupcast, unicast, or the like), an "application layer user ID" (application layer user identifier) of the transmitting terminal <NUM>, an "application layer user ID" (application layer user identifier) of the receiving terminal <NUM>, "QoS requirements" required for transmission of data, "PQIs" required for transmission of data, and "QFIs" required for transmission of data.

The SE layer <NUM> may identify link profile information associated with the link ID received in operation <NUM>. The SE layer <NUM> may determine a source layer-<NUM> ID and a destination layer-<NUM> ID for transmitting the "application data" received in operation <NUM>. For example, the source layer-<NUM> ID may be determined using the layer-<NUM> ID of the terminal <NUM> stored in the link profile associated with the link ID. The destination layer-<NUM> ID may be determined using the layer-<NUM> ID of the terminal <NUM> stored in the link profile associated with the link ID (operation <NUM>).

The SE layer <NUM> may determine a QFI for transmitting the application data received in operation <NUM> (operation <NUM>). For example, the SE layer <NUM> may use the QFI received in operation <NUM>. Alternatively, the SE layer <NUM> may determine the QFI corresponding to the PQI received in operation <NUM>. In order to determine the QFI corresponding to the PQI, the SE layer <NUM> may use information preset in the terminal or mapping information between PQIs and QFIs stored in the link profile associated with the link ID. Alternatively, the SE layer <NUM> may determine the QFI corresponding to the QoS requirements received in operation <NUM>. In order to determine the QFI corresponding to the QoS requirements, the SE layer <NUM> may use information preset in the terminal or mapping information between the QoS requirements and QFIs stored in the link profile associated with the link ID.

The SE layer <NUM> may transmit, to the AS layer <NUM>, at least one of the "application data" received in operation <NUM>, the "source layer-<NUM> ID" and the "destination layer-<NUM> ID" determined in operation <NUM>, the "QFI", the "link ID" related to the corresponding direct communication link, the communication mode (e.g., PC5 unicast), and the type of message {e.g., data (user plane) message}. An example of information that the SE layer <NUM> delivers to the AS layer <NUM> is as follows.

The AS layer <NUM> may configure a MAC header, based on the information delivered from the SE layer <NUM>. The method described in operation <NUM> may be applied to the method of configuring the MAC header in a similar way.

The source layer-<NUM> ID of the MAC header may be set to the layer-<NUM> ID of the terminal <NUM> received in operation <NUM>. Alternatively, the source layer-<NUM> ID of the MAC header may be set to the layer-<NUM> ID of the terminal <NUM> mapped to the link ID stored by the AS layer <NUM> in the procedure in <FIG> based on the link ID received in operation <NUM>.

The destination layer-<NUM> ID of the MAC header may be set to the layer-<NUM> ID of the terminal <NUM> received in operation <NUM>. Alternatively, the destination layer-<NUM> ID of the MAC header may be set to the layer-<NUM> ID of the terminal <NUM> mapped to the link ID stored by the AS layer <NUM> in the procedure in <FIG> based on the link ID received in operation <NUM>.

The AS layer <NUM> may determine the QFI for transmitting the application data received in operation <NUM>. The QFI may be determined through a combination of the information received in operation <NUM> (e.g., the QFI) or the information received in operation <NUM> (e.g., the link ID) and the information stored by the AS layer <NUM> in the procedure in <FIG>.

The AS layer <NUM> may determine the LCID, based on the type of message (e.g., data) received in operation <NUM>. The logical channel ID value used in the data message may be different from the logical channel ID value used in the signaling message. In addition, the LCID may be set to the value indicating the QFI through which the message is transmitted.

The SDAP header and/or the MAC header may include at least one of a value indicating the QFI for transmitting the message and a value indicating the link ID.

The AS layer <NUM> may configure the MAC header as described above, and may include the application data received from the SE layer <NUM> in the MAC payload, thereby transmitting the same to the terminal <NUM> through a physical layer <NUM> (operation <NUM>).

The AS layer <NUM> of the terminal <NUM> receiving the "application data" may determine that the received message is a data message, based on the information included in the SDAP header and/or the MAC header of the received message (e.g., a logical channel ID and the like). The AS layer <NUM> may deliver the received message to the SE layer <NUM>. The SE layer <NUM> may determine whether or not the received message is a message for the direct communication link produced according to the above-described procedure, based on the link ID, the destination layer-<NUM> ID, and/or the QFI information of the received message.

In addition, the SE layer <NUM> of the terminal <NUM> may determine that the received message is a data message, based on the information received from the AS layer <NUM> (e.g., an SDAP header, an MAC header, or the like).

In addition, the SE layer <NUM> of the terminal <NUM> may determine the service type or the application ID of the received message, based on the link ID, the destination layer-<NUM> ID, and/or the QFI information of the received message. Based on this, the SE layer <NUM> may deliver the received "application data" to the application <NUM> of the corresponding application layer <NUM> or to the service type included in the application (<NUM> or <NUM>). Alternatively, the SE layer <NUM> may deliver direct communication link information associated with the "application data" (e.g., a link ID, a service type, an application ID, and the like) to the application layer <NUM>.

<FIG> illustrates a procedure of updating a direct communication link according to an embodiment of the disclosure.

In operation <NUM>, the terminal <NUM> may determine a destination layer-<NUM> ID for receiving data and a signaling message transmitted through the direct communication link produced through the procedure shown in <FIG>. For example, the destination layer-<NUM> ID may be set to the layer-<NUM> ID of the terminal <NUM> included in the corresponding link profile.

The application layer <NUM> of the terminal <NUM> may deliver, to the SE layer <NUM>, at least one of the "application data" produced by the application layer <NUM> in operation <NUM>, "a link ID" indicating a direct communication link through which data is transmitted, a "service type" indicating the type of data, a "communication mode" indicating the communication method of data (e.g., broadcast, groupcast, unicast, or the like), an "application layer user ID" (application layer user identifier) of the transmitting terminal <NUM>, an "application layer user ID" (application layer user identifier) of the receiving terminal <NUM>, "QoS requirements" required for transmission of data, "PQIs" required for transmission of data, and "QFIs" required for transmission of data.

If there is a link profile including an application layer user ID of the transmitting terminal <NUM> and/or an application layer user ID of the receiving terminal <NUM> received from the application layer <NUM> in operation <NUM>, the SE layer <NUM> may recognize that the terminal <NUM> has a pre-established direct communication link with the terminal <NUM>. Accordingly, the SE layer <NUM> may determine to recycle the pre-established direct communication link, instead of establishing a new direct communication link, and may determine to perform the link update procedure shown in <FIG> (operation <NUM>). According to an embodiment of the disclosure, in the case where one application layer user ID is used in one application, the terminal <NUM> may establish one direct communication link with the terminal <NUM> for each application. For example, one direct communication link may be produced for each application, and signaling and data for each application may be transmitted through one direct communication link. Alternatively, in the case where one application layer user ID is used in one or more applications, the terminal <NUM> may establish one direct communication link with the terminal <NUM> for the applications sharing the application layer user ID. For example, applications sharing one application layer user ID may share one direct communication link, and may transmit signaling and data for the applications through one direct communication link. Alternatively, in the case where one application layer user ID is used in all applications, one direct communication link may be established between the terminal <NUM> and the terminal <NUM>, thereby transmitting signaling and data for all applications supported by the terminal <NUM> and the terminal <NUM> through the one direct communication link.

If there is no service type received in operation <NUM> in the link profile associated with the link ID, and/or if there is no PQI and/or QFI mapped to the QoS requirements in the link profile associated to the link ID, the SE layer <NUM> may determine to perform a link update procedure (operation <NUM>).

The SE layer <NUM> may determine a new PQI and/or a new QFI that satisfies the QoS requirements received in operation <NUM> in a manner similar to the method described with reference to <FIG>.

The SE layer <NUM> may produce a link update request message. The link update request message may include at least one of the link ID, the new PQI and QFI determined by the SE layer <NUM>, and mapping information between the PQI and the QFI.

In order to transmit the link update request message, the SE layer <NUM> may determine a source layer-<NUM> ID and a destination layer-<NUM> ID similar to the method described with reference to <FIG>.

The SE layer <NUM> may transmit, to the AS layer <NUM>, at least one of a "link update request message", the "source layer-<NUM> ID" and the "destination layer-<NUM> ID" determined in operation <NUM>, a "link ID" related to the corresponding direct communication link, a communication mode (e.g., PC5 unicast), and the type of message (e.g., a PC5-S signaling message). An example of information that the SE layer <NUM> delivers to the AS layer <NUM> is as follows.

The source layer-<NUM> ID of the MAC header may be set to the layer-<NUM> ID of the terminal <NUM> received in operation <NUM>. Alternatively, the source layer-<NUM> ID of the MAC header may be set to the layer-<NUM> ID of the terminal <NUM> mapped to the link ID stored by the AS layer <NUM> in the procedure in <FIG> with reference to the link ID received in operation <NUM>.

The destination layer-<NUM> ID of the MAC header may be set to the layer-<NUM> ID of the terminal <NUM> received in operation <NUM>. Alternatively, the destination layer-<NUM> ID of the MAC header may be set to the layer-<NUM> ID of the terminal <NUM> mapped to the link ID stored by the AS layer <NUM> in the procedure in <FIG> with reference to the link ID received in operation <NUM>.

The AS layer <NUM> may determine the LCID, based on the type of message (e.g., signaling) received in operation <NUM>. The logical channel ID value used in the signaling message may be different from the logical channel ID value used in the data message.

The AS layer <NUM> may configure the MAC header as described above, and may include the link update request message received from the SE layer <NUM> in the MAC payload, thereby transmitting the same to the terminal <NUM> through a physical layer <NUM> (operation <NUM>).

The terminal <NUM> receiving the link update request message may perform the link update corresponding to the link update request message (operation <NUM>).

The AS layer <NUM> of the terminal <NUM> receiving the link update request message may determine that the received message is a signaling message, based on the logical channel ID of the MAC header of the received message. The AS layer <NUM> may deliver the received message to the SE layer <NUM>. The SE layer <NUM> may determine whether or not the received message is a signaling message for the direct communication link produced according to the above-described procedure, based on the link ID, the destination layer-<NUM> ID, and/or the QFI information of the received message.

In addition, the SE layer <NUM> of the terminal <NUM> may determine that the received message is a signaling message, based on the LCID of the message.

The SE layer <NUM> of the terminal <NUM> may store new QoS information (e.g., QoS requirements, PQIs, QFIs, etc.) included in the received message in the link profile associated with the link ID.

The SE layer <NUM> may deliver the changed QoS information to the application layer <NUM>.

In addition, the SE layer <NUM> may deliver, to the AS layer <NUM>, the link ID of the direct communication link and the changed QoS information in relation to the corresponding direct communication link. The AS layer <NUM> may store the received link ID, may update QoS information (e.g., the new PQI and the QFI corresponding thereto), and may use the same for direct communication in the future.

The AS layer (<NUM>) may transmit, to the terminal (<NUM>), a link update respond message including the changed QoS information received from the SE layer (<NUM>) (operation <NUM>). The method described in operation <NUM> may be applied to the operation <NUM> in a similar manner.

<FIG> is a diagram illustrating producing a direct communication link according to an embodiment of the disclosure.

<FIG> is a diagram illustrating QoS flow identifier (QFI) mapping in relation to a direct communication link according to an embodiment of the disclosure.

<FIG> a diagram illustrating QFI mapping in relation to a direct communication link according to an embodiment of the disclosure.

<FIG> is a diagram illustrating sidelink radio bearer (SLRB) mapping in relation to a direct communication link according to an embodiment of the disclosure.

<FIG> is a diagram illustrating a configuration of a medium access control (MAC) protocol data unit (PDU) according to an embodiment of the disclosure.

<FIG> is a diagram illustrating a configuration of a sub-header of a sidelink-shared channel (SL-SCH) according to an embodiment of the disclosure.

<FIG> is a block diagram illustrating a configuration of a network entity according to an embodiment of the disclosure.

A communication system <NUM> may include a network entity according to an embodiment.

Referring to <FIG>, a network entity may include a transceiver <NUM>, a controller <NUM>, and a storage unit <NUM>. The transceiver <NUM>, the controller <NUM>, and the storage unit <NUM> of the network entity may operate according to the above-described communication method of the network entity. However, the configuration of the network entity is not limited to the above-described examples. For example, the network entity may include more or fewer components than the components described above. In addition, the transceiver <NUM>, the controller <NUM>, and the storage unit <NUM> may be implemented into a single chip. Further, the controller <NUM> may include at least one processor.

A receiver <NUM> of the network entity and a transmitter <NUM> of the network entity may be collectively called a "transceiver <NUM>", which may transmit and receive signals. The transmitted and received signals may include control information and data. To this end, the transceiver <NUM> may include an RF transmitter for up-converting and amplifying the frequency of a transmitted signal, and an RF receiver for low-noise-amplifying a received signal and down-converting the frequency thereof. However, this is only an example of the transceiver <NUM>, and the components of the transceiver <NUM> are not limited to the RF transmitter and the RF receiver.

In addition, the transceiver <NUM> may receive a signal through a wireless channel to thus output the signal to the controller <NUM>, and may transmit a signal output from the controller <NUM> through a wireless channel.

The storage unit <NUM> may store programs and data necessary for the operation of the network entity. In addition, the storage unit <NUM> may store control information or data included in the signal obtained from the network entity. The controller <NUM> may include a storage medium, such as a read only memory (ROM), a random access memory (RAM), a hard disk, a compact disc-ROM (CD-ROM), and a digital versatile disc (DVD), or a combination of the storage media.

The controller <NUM> may control a series of processes such that the network entity may operate according to the above-described embodiments. For example, the controller <NUM> may receive a control signal and a data signal through the transceiver <NUM>, and may process the received control signal and data signal. In addition, the controller <NUM> may transmit the processed control signal and data signal through the transceiver <NUM>.

<FIG> is a block diagram illustrating a configuration of a terminal according to an embodiment of the disclosure.

Referring to <FIG>, a block diagram of the internal structure of the terminal <NUM>, <NUM>, <NUM>, or <NUM> is illustrated. The terminal may include a transceiver <NUM>, a controller <NUM>, and a storage unit <NUM>.

The transceiver <NUM>, the controller <NUM>, and the storage unit <NUM> of the terminal may operate according to the above-described communication method of the terminal. However, the configuration of the terminal is not limited to the above-described examples. For example, the terminal may include more or fewer components than the components described above. In addition, the transceiver <NUM>, the controller <NUM>, and the storage unit <NUM> may be implemented into a single chip. Further, the controller <NUM> may include at least one processor.

A receiver <NUM> of the terminal and a transmitter <NUM> of the terminal may be collectively called a "transceiver <NUM>", which may transmit and receive signals to and from a base station. The signals transmitted to and received from the base station may include control information and data. To this end, the transceiver <NUM> may include an RF transmitter for up-converting and amplifying the frequency of a transmitted signal, and an RF receiver for low-noise-amplifying a received signal and down-converting the frequency thereof. However, this is only an example of the transceiver <NUM>, and the components of the transceiver <NUM> are not limited to the RF transmitter and the RF receiver.

The storage unit <NUM> may store programs and data necessary for the operation of the terminal. In addition, the storage unit <NUM> may store control information or data included in the signal obtained from the terminal. The controller <NUM> may include a storage medium, such as a ROM, a RAM, a hard disk, a CD-ROM, and a DVD, or a combination of the storage media.

The controller <NUM> may control a series of processes such that the terminal may operate according to the above-described embodiments. For example, the controller <NUM> may receive a control signal and a data signal through the transceiver <NUM>, and may process the received control signal and data signal. In addition, the controller <NUM> may transmit the processed control signal and data signal through the transceiver <NUM>.

Claim 1:
A method performed by a first terminal (<NUM>) in a wireless communication system, the method comprising:
establishing a unicast link with a second terminal (<NUM>), wherein each of the first terminal (<NUM>) and the second terminal (<NUM>) has a plurality of application layer identifiers, (IDs, and the unicast link supports a plurality of service types associated with a first pair of application layer IDs comprising an application layer ID of the first terminal (<NUM>) and an application layer ID of the second terminal (<NUM>);
identifying whether a second pair of application layer IDs associated with a service type for which a data transfer is to be initiated is identical to the first pair of application layer IDs; and
reusing the established unicast link with the second terminal (<NUM>) to initiate the data transfer, based on the second pair of application layer IDs being identical to the first pair of application layer IDs.