Patent ID: 12213205

BEST MODE FOR CARRYING OUT THE INVENTION

The terms used in the disclosure are only used to describe specific embodiments, and are not intended to limit the disclosure. A singular expression may include a plural expression unless they are definitely different in a context. Unless defined otherwise, all terms used herein, including technical and scientific terms, have the same meaning as those commonly understood by a person skilled in the art to which the disclosure pertains. Such terms as those defined in a generally used dictionary may be interpreted to have the meanings equal to the contextual meanings in the relevant field of art, and are not to be interpreted to have ideal or excessively formal meanings unless clearly defined in the disclosure. In some cases, even the term defined in the disclosure should not be interpreted to exclude embodiments of the disclosure.

Hereinafter, the disclosure relates to an apparatus and method for effectively supporting vehicle-to-everything (V2X) in a wireless communication system.

In the following description, terms that refer to communication methods, terms that refer to signals, terms that refer to information, terms that refer to network entities, terms that refer to components of devices, etc., are illustrated for convenience of description. Accordingly, the disclosure is not limited to terms to be described later, and other terms having an equivalent technical meaning may be used.

In addition, the disclosure describes various embodiments using terms used in some communication standards {e.g., 3rd generation partnership project (3GPP)}, but these are only examples for description. Various embodiments of the disclosure may be easily modified and applied to other communication systems.

Hereinafter, the operating principle of the disclosure will be described in detail with reference to the accompanying drawings. In the following description of the disclosure, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the disclosure, the detailed description thereof will be omitted. In addition, terms to be described later are terms defined in consideration of functions in the disclosure and may vary according to the intention or practices of users or operators. Therefore, the definition should be made based on the contents throughout this specification. Terms for identifying access nodes, terms referring to network entities, terms referring to messages, terms referring to an interface between network objects, and terms referring to various types of identification information, which are used in the following description, and the like are illustrated for convenience of description. Accordingly, the disclosure is not limited to terms to be described later, and other terms referring to objects having an equivalent technical meaning may be used.

For convenience of description below, this disclosure uses terms and names defined in the 3GPP LTE standard. However, the disclosure is not limited by the terms and names, and may be equally applied to systems according to other standards.

FIG.1illustrates an example of a wireless communication system according to various embodiments of the disclosure. Specifically,FIG.1is a diagram illustrating a structure of an LTE system referred to for description of the disclosure.

Referring toFIG.1, a radio access network of the LTE system includes next-generation base stations (evolved node B, hereinafter, eNB, node B or base station)105,110,115, and120, a mobility management entity (MME)125, and a serving-gateway (S-GW)130. User equipment (UE)135accesses an external network through the eNBs105to120and the S-GW130.

InFIG.1, the eNBs105to120correspond to an existing Node B of a UMTS system. The eNB is connected to the UE135through a radio channel and performs a more complex role than the existing Node B. In the LTE system, all user traffic including real-time services such as Voice over IP (VoIP) through an Internet protocol are serviced through a shared channel, so a device that collects and schedules status information such as buffer status, available transmission power status, and channel status of UEs is required, and the eNBs105to120are responsible for this. One eNB typically controls multiple cells. For example, in order to implement a transmission rate of 100 Mbps, the LTE system uses, for example, orthogonal frequency division multiplexing (hereinafter, referred to as “OFDM”) in a bandwidth of 20 MHz as a radio access technology. In addition, adaptive modulation and coding (hereinafter, referred to as “AMC”) that determines a modulation scheme and a channel coding rate according to the channel state of the UE is applied. The S-GW130is a device that provides a data bearer, and generates or removes the data bearer under the control of the MME125. The MME is a device responsible for various control functions as well as mobility management functions for a UE, and is connected to a number of eNBs.

FIG.2illustrates an example of a radio protocol structure of a wireless communication system according to various embodiments of the disclosure.

FIG.2is a diagram illustrating a radio protocol structure in an LTE system referred to for description of the disclosure.

Referring toFIG.2, the radio protocol of the LTE system is composed of a packet data convergence protocol (PDCP)205or240, a radio link control (RLC)210or235, and a medium access control (MAC)215or230, respectively, at a terminal and a base station. The PDCPs205and240are in charge of operations such as IP header compression/decompression, and the like. The main functions of PDCP are summarized as follows:Header compression and decompression: ROHC onlyTransfer of user dataIn-sequence delivery of upper layer PDUs at PDCP re-establishment procedure for RLC AMFor split bearers in DC (only support for RLC AM): PDCP PDU routing for transmission and PDCP PDU reordering for receptionDuplicate detection of lower layer SDUs at PDCP re-establishment procedure for RLC AMRetransmission of PDCP SDUs at handover and, for split bearers in DC, of PDCP PDUs at PDCP data-recovery procedure, for RLC AMCiphering and decipheringTimer-based SDU discard in uplink.

The radio link controls (RLCs)210and235performs an ARQ operation or the like by reconfiguring a PDCP packet data unit (PDU) to an appropriate size. The main functions of RLC are summarized as follows:Transfer of upper layer PDUsError Correction through ARQ (only for AM data transfer)Concatenation, segmentation and reassembly of RLC SDUs (only for UM and AM data transfer)Re-segmentation of RLC data PDUs (only for AM data transfer)Reordering of RLC data PDUs (only for UM and AM data transfer)Duplicate detection (only for UM and AM data transfer)Protocol error detection (only for AM data transfer)RLC SDU discard (only for UM and AM data transfer)RLC re-establishment

The MACs215and230are connected to several RLC layer devices configured in one terminal, and performs an operation of multiplexing RLC PDUs to an MAC PDU and demultiplexing the RLC PDUs from the MAC PDU. The main functions of MAC are summarized as follows:Mapping between logical channels and transport channelsMultiplexing/demultiplexing of MAC SDUs belonging to one or different logical channels into/from transport blocks (TB) delivered to/from the physical layer on transport channelsScheduling information reportingError correction through HARQPriority handling between logical channels of one UEPriority handling between UEs by means of dynamic schedulingMBMS service identificationTransport format selectionPadding

Physical layers220and225channel-code and modulate upper layer data, make the obtained data into an OFDM symbol, and transmit the OFDM symbol through a radio channel, or demodulate the OFDM symbol received through the radio channel, and channel decode the demodulated OFDM symbol and transmit the obtained data to the upper layer. In addition, the physical layer also uses hybrid ARQ (HARQ) for additional error correction, and the receiving end transmits information indicating whether a packet transmitted by the transmitting end is received, in one bit. This is called HARQ ACK/NACK information. Downlink HARQ ACK/NACK information for uplink transmission may be transmitted through a physical hybrid-ARQ indicator channel (PHICH) physical channel, and uplink HARQ ACK/NACK information for downlink transmission may be transmitted through a physical uplink control channel (PUCCH) or a physical uplink shared channel (PUSCH).

Meanwhile, the PHY layer may be composed of one or a plurality of frequencies/carriers, and a technology for simultaneously configuring and using a plurality of frequencies is referred to as a carrier aggregation (hereinafter, referred to as “CA”) technology. In the CA technology, only one carrier was used for communication between a terminal (or UE) and a base station (E-UTRAN NodeB or eNB), but by additionally using a primary carrier and one or a plurality of subcarriers, the amount of transmission can be dramatically increased by the number of subcarriers. Meanwhile, in LTE, a cell in an eNB that uses a primary carrier is called a primary cell (PCell), and a subcarrier is called a secondary cell (SCell).

Although not shown in this figure, there is a radio resource control (RRC) layer, respectively, above the PDCP layer of the UE and the eNB, and the RRC layer may transmit and receive access and measurement-related configuration control messages for radio resource control.

FIG.3illustrates an example of a structure of a wireless communication system according to various embodiments of the disclosure.

FIG.3is a diagram illustrating a structure of a next-generation mobile communication system to which the disclosure is applied.

Referring toFIG.3, a radio access network of a next-generation mobile communication system is composed of a next-generation base station (new radio node B, hereinafter, referred to as “NR NB”)310, and a new radio core network (NR CN) or a next-generation core network (NG CN)305. User equipment (new radio user equipment, hereinafter, NR UE or terminal)315accesses an external network through the NR NB310and the NR CN305.

InFIG.3, the NR NB310corresponds to an evolved node B (eNB) of an existing LTE system. The NR NB is connected to the NR UE315through a radio channel, and can provide a service superior to that of the existing Node B. In the next-generation mobile communication system, all user traffic is serviced through a shared channel, so a device that collects and schedules status information such as buffer status, available transmission power status, and channel status of UEs, and the NR NB310is responsible for this. One NR NB typically controls multiple cells. In order to implement ultra-high-speed data transmission compared to the existing LTE, it may have an existing maximum bandwidth or more, and OFDM may be used as a radio access technology to additionally incorporate a beamforming technology. In addition, adaptive modulation and coding (hereinafter, referred to as “AMC”) that determines a modulation scheme and a channel coding rate according to the channel status of the UE is applied. The NR CN305performs functions such as mobility support, bearer configuration, and QoS configuration. The NR CN is a device responsible for various control functions as well as a mobility management function for a UE, and is connected to a plurality of eNBs. In addition, the next-generation mobile communication system can be interlocked with the existing LTE system, and the NR CN is connected to an MME325through a network interface. The MME is connected to the eNB330, which is an existing base station.

FIG.4illustrates an example of a radio protocol structure of a wireless communication system according to various embodiments of the disclosure.

FIG.4is a diagram illustrating a radio protocol structure of a next-generation mobile communication system to which the disclosure can be applied.

Referring toFIG.4, the radio protocol of the next-generation mobile communication system is composed of an NR SDAP401or445, an NR PDCP405or440, an NR RLC410or435, and an NR MAC415or430, respectively, at a terminal and an NR base station.

The main functions of the NR SDAPs401and445may include some of the following functions.Transfer of user plane dataMapping between a QoS flow and a DRB for both DL and ULMarking QoS flow ID in both DL and UL packetsMapping reflective QoS flow to DRB for the UL SDAP PDUs.

For the SDAP layer device, a UE may be configured with an RRC message to determine whether to use the header of the SDAP layer device or the function of the SDAP layer device for each PDCP layer device, for each bearer, or for each logical channel. When the SDAP header is configured, the UE can use an NAS QoS reflective configuration 1-bit indicator (NAS reflective QoS) of the SDAP header and an AS QoS reflective configuration 1-bit indicator (AS reflective QoS) to instruct the UE to update or reconfigure mapping information on the QoS flow and data bearer of UL or DL. The SDAP header may include QoS flow ID information indicating QoS. The QoS information may be used as data processing priority, scheduling information, and the like to smoothly support services.

The main functions of the NR PDCPs405and440may include some of the following functions.Header compression and decompression: ROHC onlyTransfer of user dataIn-sequence delivery of upper layer PDUsOut-of-sequence delivery of upper layer PDUsPDCP PDU reordering for receptionDuplicate detection of lower layer SDUsRetransmission of PDCP SDUsCiphering and decipheringTimer-based SDU discard in uplink

In the above, the reordering of the NR PDCP device refers to a function of reordering PDCP PDUs received from a lower layer in order based on a PDCP sequence number (SN), and may include a function of transferring data to an upper layer in the order of reordering or a function of immediately transferring data without considering the order, a function of recording lost PDCP PDUs by recording, a function of reporting the status of the lost PDCP PDUs to a transmitting side, and a function of requesting retransmission of the lost PDCP PDUs.

The main functions of the NR RLCs410and435may include some of the following functions.Transfer of upper layer PDUsIn-sequence delivery of upper layer PDUsOut-of-sequence delivery of upper layer PDUsError Correction through ARQConcatenation, segmentation and reassembly of RLC SDUsRe-segmentation of RLC data PDUsReordering of RLC data PDUsDuplicate detectionProtocol error detectionRLC SDU discardRLC re-establishment

In the above, the in-sequence delivery of the NR RLC device refers to a function of delivering RLC SDUs received from a lower layer to an upper layer in order, and may include a function of, when one RLC SDU is originally divided into multiple RLC SDUs and received, reassembling and delivering the divided RLC SDUs, and a function of rearranging the received RLC PDUs based on RLC sequence number (SN) or PDCP sequence number (SN). In addition, the in-sequence delivery function of the NR RLC device may include a function of recording the lost RLC PDUs by reordering, a function of reporting the status of the lost RLC PDUs to the transmitting side, a function of requesting retransmission of the lost RLC PDUs, a function of sequentially delivering, when there is a lost RLC SDU, only RLC SDUs up to before the lost RLC SDU to the upper layer, a function of sequentially delivering, when a predetermined timer has expired although there is the lost RLC SDU, all RLC SDUs received before the timer starts to the upper layer, and a function of sequentially delivering, when a predetermined timer has expired although there is the lost RLC SDU, all RLC SDUs received so far to the upper layer. In addition, in the above, the RLC PDUs may be processed in the order of reception thereof (regardless of the order of serial number and sequence number, in the order of arrival) and may be delivered to the PDCP device regardless of the order (Out-of sequence delivery). In the case of segment, segments stored in a buffer or to be received in the future may be received, reconfigured into one complete RLC PDU, processed, and then delivered to the PDCP device. The NR RLC layer may not include a concatenation function, and may be performed by the NR MAC layer or may be replaced with a multiplexing function of the NR MAC layer.

In the above, the out-of-sequence delivery of the NR RLC device refers to a function of immediately delivering RLC SDUs received from the lower layer to the upper layer regardless of the order, and may include a function of reassembling and delivering, when one RLC SDU is originally divided into multiple RLC SDUs and received, the received RLC SDUs, and a function of storing the RLC SN or PDCP SN of the received RLC PDUs and recording the lost RLC PDUs by reordering.

The NR MACs415and430may be connected to several NR RLC layer devices configured in one UE, and the main functions of the NR MAC may include some of the following functions.Mapping between logical channels and transport channelsMultiplexing/demultiplexing of MAC SDUsScheduling information reportingError correction through HARQPriority handling between logical channels of one UEPriority handling between UEs by means of dynamic schedulingMBMS service identificationTransport format selectionPadding

The NR PHY layers420and425channel-code and modulate upper layer data, make the obtained data into an OFDM symbol, and transmit the OFDM symbol through a radio channel, or demodulate the OFDM symbol received through the radio channel, and channel decode the demodulated OFDM symbol, and transmit the obtained data to the upper layer.

FIGS.5A to5Cillustrate an example of vehicle-to-everything (V2X) communication in a wireless communication system according to various embodiments of the disclosure. Specifically,FIGS.5A to5Care diagrams illustrating V2X communication within a cellular system referred to in the disclosure.

V2X is a collective term for communication technology through vehicles and all interfaces, and depending on components including the form and communication thereof, there are vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), vehicle-to-pedestrian (V2P), vehicle-to-network (V2N), etc. V2P and V2V basically follow the structure and operation principle of Rel-13 device-to-device (D2D). That is, an actual data packet is transmitted and received through a sidelink (a sidelink, which is based on a PC5 operation and is a transmission channel between terminals, not the uplink and downlink of a base station and a terminal). This basic concept can be applied not only to V2X defined in LTE, but also to V2X that can be newly defined in NR, and upgrades for specific scenarios can be applied.

Referring toFIG.5A, a base station501includes at least one vehicle UE505and510and a pedestrian UE515which are located in a cell502supporting V2X. That is, the vehicle UE505performs cellular communication using the base station501and links (Uu)530and535between the vehicle UE and the base station, and performs communication between devices using sidelinks (PC5)520and525between another vehicle UE510or the pedestrian UE515. In the above, the base station may be a gNB or an upgraded eNB that supports NR. In order for the vehicle UEs505and510and the pedestrian UE515to directly exchange information using the sidelinks520and525, the eNB must allocate a resource pool that can be used for sidelink communication. In the following description, a method for a UE to allocate resources to an eNB in V2X of an LTE system will be described in detail, and a similar approach as in LTE can be applied to V2X introduced in the NR system. However, in NR, a different numerology is used, and the design of a sidelink resource pool may vary to some extent.

According to the method for the eNB to allocate resources to the UE based on the V2X of the LTE system, corresponding resource allocation can be divided into two types: scheduled resource allocation (mode 3) and UE autonomous resource allocation (mode 4). In the case of the above scheduled resource allocation, the eNB allocates resources used for sidelink transmission to RRC-connected UEs in a dedicated scheduling scheme. The above method is effective for interference management and resource pool management (dynamic allocation, semi-persistence transmission) because the eNB can manage the resources of the sidelink. In addition, in the case of the scheduled resource allocation (mode 3) in which the eNB allocates and manages resources for V2X, an RRC-connected UE may transmit, when there is data to be transmitted to other UEs, the data to the eNB using an RRC message or an MAC control element (hereinafter, referred to as “CE”). Here, as the RRC message, a SidelinkUEInformation or UEAssistanceInformation message may be used. Meanwhile, the MAC CE may be, for example, a buffer status report MAC CE of a new format (including an indicator indicating a buffer status report for at least V2X communication and information on the size of data buffered for sidelink communication). Detailed format and contents of the buffer status report used by 3GPP refer to 3GPP standard TS36.321 “E-UTRA MAC Protocol Specification”. On the other hand, in the UE autonomous resource allocation, the eNB provides a sidelink transmission/reception resource pool for V2X as system information, and the UE selects a resource pool according to a predetermined rule. The resource selection method may include zone mapping, sensing-based resource selection, random selection, and the like.

Referring toFIG.5B, in the structure of the resource pool for V2X, resources540,550, and560for scheduling allocation (SA) and resources545,555, and565for data transmission are adjacent to each other to configure one subchannel.

In addition, referring toFIG.5C, the structure of the resource pool for V2X may be used in a manner in which resources for SAs570,575and580and data585,590, and595are not adjacent. Regardless of which of the above two structures is used, the SA is composed of two consecutive PRBs and includes content indicating the location of a resource for data. The number of UEs receiving a V2X service in one cell may be a large number, and the relationship between the eNB501and the UEs505,510, and515described above can be extended and applied.

In addition, in order to transmit and receive sidelink data through the resource pool, V2X of the LTE system basically classifies a V2X service through a Destination Layer2 ID (or destination ID). That is, a Source/Destination Layer2 ID (each 24 bit size) of a UE is included in the header of a V2X data packet transmitted through the sidelink, that is, the header of an MAC PDU, the Source Layer2 ID refers to a unique identifier of the UE, and the Destination Layer2 ID indicates the service type of V2X data traffic transmitted by the UE. If another UE that has received the Destination Layer2 ID sent by a transmitting UE is configured to be subscribed to and receive a service for the corresponding Destination Layer2 ID, the data packet belonging to the corresponding MAC PDU is decoded and transmitted to the upper layer. Mapping information on the Destination Layer2 ID and the V2X data packet is transmitted from a V2X server to a V2X control function, and is provided to the UE.

FIGS.6A to6Gillustrate an example of a resource pool design and characteristics in a frequency domain for a V2X system in a wireless communication system according to various embodiments of the disclosure. Specifically,FIGS.6A to6Gare diagrams illustrating design and characteristics of a resource pool in a frequency domain for a V2X system in a next-generation mobile communication system proposed in the disclosure.

Basically, an NR system has characteristics in a frequency domain different from that of an LTE system. In the LTE system, the system bandwidth in one cell has a fixed value of up to 20M Byte, whereas in the NR system, the system bandwidth in one cell may support 100M Byte or 400M Byte at high frequency. To this end, since there is a hardware difficulty in basically covering a wide frequency band by all UEs, a concept of a bandwidth part (hereinafter, referred to as “BWP”) was introduced, so that a plurality of BWPs configured in various sizes of band widths in one cell are supported and a corresponding system is allowed to operate in a specific BWP. In addition, unlike LTE, the data structure and transmission are supported by various sub-carrier spacings (SCSs), so additional SCSs such as 30, 60, and 120 are supported in addition to a 15 kHz (30 kHz in an extended version also exists, but the basic is 15 kHz) SCS in LTE. The characteristics in the frequency domain in the NR system can be applied as it is to the principle of designing V2X. First, a V2X transmission/reception resource pool configured in an NR V2X system can use uplink transmission resources, so that a specific resource area within an uplink BWP can be allocated and used. That is, the eNB may configure some resources to an NR V2X transmission resource pool transmitted to the SL within the uplink BWP configuration supported by the corresponding cell, and the configured resource pool may be transmitted as system information dedicated to NR V2X. The system information may basically include a bandwidth location, SCS, and cyclic prefix information (normal or extended) including a corresponding transmission resource pool. Alternatively, the identifier of the uplink BWP to which the corresponding transmission resource pool belongs may be transmitted. In relation to the BWP, an additional operation may be required for a specific situation according to the RF capability of the UE. In the case of an idle or inactive UE, a paging message is received from the eNB. At this time, a PDCCH is monitored for a predetermined paging occasion specific to the UE, and a problem may occur when only one RF chain required for the UE to receive the SL exists. When a serving cell in which NR V2X is configured is a time division multiplexing (TDD) configuration, paging is received in a downlink slot, and V2X transmission and reception is performed in an uplink slot configured as a sidelink. However, when a serving cell in which NR V2X is configured is frequency division multiplexing (FDD), since the downlink BWP and the uplink BWP may be configured at different frequencies, a switching operation between the uplink BWP and the downlink BWP is required in order for the corresponding UE to receive paging. In this case, it is suggested to operate in one of the following two methods.

1. An NR V2X UE always monitors an initial DL BWP (initial uplink BWP) for paging and RACH operations, and when the corresponding operation occurs, the paging and RACH operations are prioritized rather than SL transmission, and BWP switching is performed through Uu.

2. A network transmits a paging message through an SL PDU in a specific resource existing in the uplink BWP. Alternatively, a specific slot of the uplink BWP is configured or pre-configured, and reserved as a slot for transmission to the V2X UE. At this time, the transmitted paging may be paging for only NR V2X and may be an indication in the form of a short message (i.e., the paging purpose is included through a few bits.)

605to630ofFIGS.6A to6Findicate design directions in the frequency domain that a resource pool in NR V2X can have. As described above, transmission resource pools640,645,655, and660in the NR V2X use some of the uplink resources, which may be configured in a specific part of the uplink BWP.

Referring toFIG.6G, one or a plurality of the corresponding resource pools640,645,655, and660may exist in the uplink BWPs635and650, and may exist for all of the plurality of uplink BWPs635and650or only in some of the uplink BWPs635and650. In605, an area (physical sidelink control channel, PSCCH) to which a control signal of the NR V2X transmission resource pool is transmitted exists in front of an area (physical sidelink shared channel, PSSCH) to which data is transmitted for the frequency domain of the entire resource pool. In610and615, the area (PSCCH) to which the control signal of the NR V2X transmission resource pool is transmitted exists in front of the area (PSSCH) in which data is transmitted for some frequency domains of the entire resource pool. In620, the area (PSCCH) to which the control signal of the NR V2X transmission resource pool is transmitted is separated by a specific size in the frequency domain from the area (PSSCH) to which data is transmitted, and co-exists in the time domain with respect to the area (PSSCH).625and630are concepts obtained by extending the model in620, and in625and630, a structure in which the PSCCH and the PSSCH continuously share resources in the time domain and are separated in the frequency domain is possible. The difference is that a plurality of sub-channels exist in the corresponding resource pool by applying the concept of sub-channels. Here, the sub-channel is composed of a pair of PSCCH and PSSCH, and depending on the configuration method, one PSCCH-PSSCH pair is repetitively configured as illustrated in625, or the PSCCH is continuously present in the frequency domain and the corresponding PSSCH is subsequently configured in the frequency domain.

FIGS.7A to7Cillustrate an example of design and characteristics of a resource pool in a time domain for a V2X system in a wireless communication system according to various embodiments of the disclosure. Specifically,FIGS.7A to7Care diagrams illustrating design and characteristics of a resource pool in a time domain for a V2X system in a next-generation mobile communication system proposed in the disclosure.

Basically, unlike the LTE system, in an NR system, the minimum unit in the time domain is a slot and symbol unit, not a subframe. Even in an LTE system, a symbol existed as a unit through which physical signals are transmitted, but a subframe is used as a scheduling unit through which data packets are transmitted, which is extended up to the minimum symbol unit in NR. In order to reflect this characteristic of the NR system, a method of configuring an NR V2X transmission resource pool should also be able to configure the NR V2X transmission resource pool in units of slots or symbols, unlike that configured in units of subframes in the sidelink of the existing LTE.

Therefore, in the disclosure, an area that can be used as sidelink transmission resource pools710and720in the time domain is configured as a bitmap, and precisely, a method of configuring the area using a slot-level bitmap and a symbol-level bitmap is proposed. In addition, this configuration can be said to have a greater effect on cells operating in TDD than FDD. An eNB should basically configure a time domain resource of the NR V2X resource pool configured in the uplink BWP so as not to overlap a downlink resource and a resource for sidelink synchronization.

Therefore, referring toFIG.7A, when the NR V2X resource pools710and720are expressed as the bitmap, the above-described resource should be configured to “0”. In addition, when the bitmap size configured according to the entire system frame number (SFN) and the start offset of the transmission pool is applied, a case where the entire slot cannot be covered completely occurs and in order to solve this problem, in LTE, the remaining resource areas in a specific time domain are defined as reserved resources705and715, and are not used for sidelink transmission. Even in the NR V2X transmission resource pools710and720, the above principle may be applied as it is, and the transmission resources705and715that remain according to the bitmap size and the start offset may not be used as sidelink resources, or the transmission slot and symbols705and715that remain in the existing bitmap may be continuously applied. In this case, the configured bitmap can be applied to the remaining slots from the front until there are no remaining slots. In this case, there is an advantage in that resources can be used more efficiently.

The above-described slot-level bitmap and symbol-level bitmap serve to explicitly inform the resource in the time domain that NR V2X can use in the sidelink. Basically, the resource pool in V2X allocates the entire area in which sidelink communication is possible in the frequency-time domain, and a UE may autonomously select the transmission resource within the corresponding resource pool or an eNB may explicitly allocate the transmission resource among the resources within the corresponding resource pool. To this end, it is essential to first configure the transmission resource pool capable of sidelink transmission. In the disclosure, the slot and symbol-level bitmap for configuration in the time domain of the NR V2X transmission resource pool is defined in the following two ways.Option 1: explicitly provide a bitmap indicating which slot and symbol are configured as the resource pool with respect to all slots and symbols present in the SFN,Option 2: explicitly provide a bitmap indicating which slot and symbol are configured as the resource pool with respect to slots and symbols excluding slots allocated as downlink in all SFNs (This is because the UE already knows where the downlink slot is in the corresponding serving cell through a TDD UL-DL pattern provided in SIB1, so it is sufficient to indicate which slot can be allocated to the NR V2X resource pool only for the uplink slot and the flexible slot, through which signaling can be efficiently performed.)

Referring to Option 1 in detail, when NR V2X resource pool configuration information is provided in system information providing NR V2X-related configuration, bitmap information in the time domain of the resource pool is also provided. As for the bitmap information, a slot-level bitmap 1 is mandatory, and a slot-level bitmap 2 may be additionally configured. The slot-level bitmap 1 covers all slots in the time domain and continuously exists in the SFN, and period and bitmap information for bitmap configuration may exist as an example as shown in Table 1 below.

TABLE 1BitmapOfSlot-SL::= CHOICE {Bitmap-slot10BIT STRING (SIZE(10)),Bitmap-slot16BIT STRING (SIZE(16)),Bitmap-slot20BIT STRING (SIZE(20)),Bitmap-slot30BIT STRING (SIZE(30)),Bitmap-slot40BIT STRING (SIZE(40)),Bitmap-slot50BIT STRING (SIZE(50)),Bitmap-slot60BIT STRING (SIZE(60)),Bitmap-slot100BIT STRING (SIZE(100))}

In Table 1, # of Bitmap-slot# means the length of the bitmap, and if # is 16, it means that the bitmap is composed of 16 bits. When “1” is configured in each bitmap, it means a slot that can be configured as the NR V2X resource pool. In addition, BitmapOfSlot-SL IE may be configured for each of various SCSs, provided as BitmapOfSlot15KHZ-SL and BitmapOfSlot30KHZ-SL information to include the bitmap configuration, and may be selected according to the SCS to which the corresponding resource pool is applied. If the corresponding SCS information is separately configured together with the BWP information, it may be omitted.

Referring toFIG.7B, Option 1 of the embodiment illustrates a case in which a slot-level bitmap 1 having a length of 16 bits is configured, and this bitmap indicates whether to use the NR V2X resource pool for all slots continuously present in all SFNs.

725and745are parts allocated as downlink slots, and the eNB should always set the bitmap to “0” for these parts.730and750are switching slots in which downlink and flexible resources (or uplink resources) coexist, and are referred to as special slots in the disclosure. This corresponds to a case in which some symbols in one slot are configured as downlink symbols, and some of the remaining slots are configured as flexible resources and uplink resources. In the case of this special slot, the eNB can always determine whether to configure the special slot to “0” or both “0” and “1”. If the corresponding slot is configured to “1”, the symbol used for downlink in the corresponding slot should always be configured to “0” in the symbol-level bitmap.735and755correspond to flexible slots, and740and760correspond to uplink slots. The eNB can configure the NR V2X resource pool for the slot in which the corresponding resource is configured according to the eNB internal resource management rule, and if necessary, the corresponding slot can be configured as the V2X resource pool by configuring it to “1”.

If period information configured in the slot-level bitmap 1 does not match the actual resource pool design and a user desires to design the period information in a slightly additional pattern, the slot-level bitmap 2 can be added as the option. In this case, the slot-level bitmap 2 is applied subsequent to the slot-level bitmap 1, and a continuous pattern of the two bitmaps is repeated over the entire SFN. A method of configuring the overall bitmap follows the procedure described in slot-level bitmap 1.

In addition, a bitmap indicating whether to use the NR V2X resource pool of all symbols in the corresponding slot applied to bitmaps configured to “1” in the slot-level bitmap is also required. Symbol-level bitmaps765and770are applied as options, and if there is no symbol-level bitmap, all symbols in the slot-level bitmap are configured as the NR V2X resource pool. That is, it is the same as a case where all symbols of the symbol-level bitmap are configured to 1. This may be determined in units of symbols according to resource management of the eNB. The size of the symbol-level bitmap may be determined according to whether an extended cyclic prefix (extended CP) is used in the corresponding serving cell, and is fixed to 14 bits in an unused normal mode. If the extended CP is used, the size of the symbol-level bitmap may be configured to 12 bits.

TABLE 2BitmpOfSymbol-SL::= CHOICE {Bitmap-sym12BIT STRING (SIZE (12)),Bitmap-sym14BIT STRING (SIZE (14)),}

Referring toFIG.7C, in Option 2 of the present embodiment, a difference from the case in which the slot-level bitmap 1 having a length of 16 bits shown in Option 1 is configured will be described, and a case where the length of the entire bitmap can be changed will be described. In Option 2, not all slots for all SFNs are covered with a bitmap, but slots excluding slots allocated as downlink resources among all slots are configured as candidates for bitmap configuration. In this case, since the downlink slot configured in option 1 can be excluded from the bitmap, by using 13 bits for the slot-level bitmap 1 and 11 bits for the slot-level bitmap 2, a bitmap consisting of 16 bits and 14 bits, which is a total of 30 bits in the previous option 1, can be configured with a total of 24 bits, thereby reducing 6 bits of signaling. There is no performance deterioration because the number and area of all slots actually covered are the same. In addition, it is possible to configure whether to apply the special slot, and if the eNB determines not to always use the NR V2X for the corresponding slot, the corresponding slot can also be excluded from the candidate bitmap. However, if it is determined to use a part of the corresponding slot as the NR V2X resource pool or if the special slot is configured to “1” as described in option 1 above, a symbol used as a downlink in a corresponding slot should always be configured to “0” in the symbol-level bitmap.

In addition, a bitmap indicating whether to use the NR V2X resource pool of all symbols in the corresponding slot applied to the bitmaps configured to “1” in the slot-level bitmap is also required. The symbol-level bitmap is applied as an option, and if there is no symbol-level bitmap, all symbols in the slot level bitmap are configured as the NR V2X resource pool. That is, it is the same as the case where all symbols of the symbol level bitmap are configured to “1”. This may be determined in units of symbols according to resource management of the eNB. The size of the symbol-level bitmap may be determined according to whether an extended CP is used in the corresponding serving cell, and is fixed to 14 bits in the unused normal mode. If the extended CP is used, the size of the symbol-level bitmap may be configured to 12 bits.

FIG.8illustrates an example of a data transmission procedure of a new radio (NR) V2X terminal operating in a base station scheduling mode (mode 1) in a wireless communication system according to various embodiments of the disclosure. Specifically,FIG.8is a diagram illustrating a data transmission procedure of an NR V2X UE operating in an eNB scheduling mode (mode 1) in an NR system applied to the disclosure.

Referring toFIG.8, a UE 1801that is camped on in805receives SIB1 in810, which is basic information for accessing a corresponding serving cell from an eNB803, and then receives system information (SIB for NR V2X) for NR V2X in815. The SIB1 includes cell access-related information, scheduling information of other system information, and TDD UL/DL configuration of a corresponding serving cell, and the NR V2X system information includes resource pool information for sidelink data transmission and reception, configuration information for sensing operation, information for configuring synchronization, information for inter-frequency transmission and reception, and the like. The resource pool information includes information for configuring a resource pool in the frequency-time domain proposed in the disclosure. In addition, since even in the RRC connected state and IDLE state, the UE should be able to operate even if the UE receives only system information, the system information related to V2X should be provided in the basically supported eNB and cell without a request from the UE.

When data traffic for V2X is generated in the UE 1801in820, RRC connection with the eNB is performed in825. The RRC connection process may be performed before the data traffic is generated in820. The UE 1801requests a transmission resource capable of V2X communication with another UE802from the eNB830. At this time, the request is made from the eNB by using an RRC message or an MAC CE. Here, as the RRC message, SidelinkUEInformation and UEAssistanceInformation messages may be used. Meanwhile, the MAC CE may be, for example, a buffer status report MAC CE of a new format (including an indicator indicating a buffer status report for at least V2X communication and information on the size of data buffered for sidelink communication). The eNB803allocates a V2X transmission resource to the UE 1801through a dedicated RRC message in835. This message can be included in the RRCConnectionReconfiguration message. The resource allocation may be a V2X resource through Uu or a resource for PC5 according to the type of traffic requested by the UE or whether the corresponding link is congested. For the determination, the UE adds and sends proSe per packet priority (PPPP) and proSe per packet reliability (PPPR) or logical channel identifier (LCID) information of V2X traffic through UEAssistanceInformation or MAC CE. Since the eNB also knows information on resources used by other UEs, the eNB schedules a resource requested by the UE 1 among the remaining resources. In addition, when the RRC message includes SPS configuration information through Uu, the SPS may be activated through DCI transmission through the PDCCH in840. The UE 1801selects a transmission link and a resource according to the resource allocated from the eNB803and a transmission method in845, and transmits data to the UE802in850.

FIG.9illustrates an example of a data transmission procedure of an NR V2X terminal operating in a terminal autonomous resource selection mode (mode 2) in a wireless communication system according to various embodiments of the disclosure. Specifically,FIG.9is a diagram illustrating a data transmission procedure of an NR V2X UE operating in a UE autonomous resource selection mode (mode 2) in an NR system applied to the disclosure.

Unlike an eNB scheduling mode in which an eNB903is directly involved in resource allocation, a UE autonomous resource selection mode (mode 2) operation differs in that a UE 1901autonomously selects a resource and transmits data based on a resource pool previously received through system information. In V2X communication, the eNB903allocates several types of sidelink resource pools (V2V resource pool and V2P resource pool) for the UE 1901. The resource pool is composed of a resource pool in which the UE can autonomously select an available resource pool after sensing resources used by other UEs around the UE, and a resource pool in which the UE randomly selects a resource from a predetermined resource pool.

Referring toFIG.9, the UE 1901that is camped on in905receives SIB1, which is basic information for accessing a corresponding serving cell, from the eNB903, and then receives system information for NR V2X (SIB for NR V2X) in915. The SIB1 includes cell access related information, scheduling information of other system information, TDD UL/DL configuration of a corresponding serving cell, and the like. The NR V2X system information may include resource pool information for sidelink data transmission/reception, configuration information for sensing operation, information for configuring synchronization, information for inter-frequency transmission and reception, and the like. The resource pool information includes information for configuring a resource pool in the frequency-time domain proposed in the disclosure.

In addition, since even in the RRC connected state and IDLE state, the UE should be able to operate even if the UE receives only system information, the system information related to V2X should be provided in the basically supported eNB and cell without a request from the UE.

When data traffic for V2X is generated in the UE 1901in915, the UE 1901selects a resource in925in the time/frequency domain according to a configured transmission operation (e.g., dynamic allocation one-time transmission, dynamic allocation multiple transmission, sensing-based one-time transmission, sensing-based multiple transmission, or random transmission) from the resource pool received from the eNB903through system information, and transmits data to another UE902in930. In general, since a V2X service is implemented for the purpose of periodically transmitting location information of safety-related UEs, in sensing-based multi-transmission in mode 2 operation, the UE senses resources transmitted by other UEs, selects a transmittable resource block from the resource pool in which the corresponding transmission is performed, and then reserves future resources so that they can be transmitted periodically. Next, if the data packet generated by the UE is changed or disappears, a new data packet can be delivered by restarting or canceling the above sensing and resource reservation operation. As described above, the multi-transmission based on the sensing and resource reservation may be basically operated, and if the sensing operation is not well performed, communication may be performed through random resource selection from a corresponding resource pool.

InFIGS.8and9, the configuration of sidelink data transmission and reception and the overall operation in the NR V2X system have been described, and packet design in the user plane for the actually transmitted data packet, radio bearer configuration, and encryption method have been briefly described inFIG.1Eor some of them has been omitted.

FIG.10illustrates an example of a mobility scenario in a wireless communication system according to various embodiments of the disclosure. Specifically,FIG.10is a diagram illustrating a scenario for mobility in an NR V2X system considered in the disclosure.

Basically, V2X supported by an NR system may be designed to follow the frame structure and numerology of the NR system, which will be structurally different from the V2X defined in the LTE system. As an example, the structure of an LTE V2X resource pool will have a structure different from the resource pool to be designed in NR V2X. In an eNB and a UE that support only LTE V2X without supporting NR, it is difficult to support communication with an NR V2X UE and service continuity of NR V2X because there is no configuration information on the NR V2X resource pool. In this disclosure, a method of supporting a V2X service when LTE and NR serving cells exist and a UE moves a corresponding serving cell will be described.

For a scenario in which multiple LTE serving cells1001and NR serving cells1002and1003are mixed, the UE can move in a connected state and move in an idle state, and movement between different radio access types or radio access technologies (RATs) should also be considered. In the disclosure, a scenario is configured to consider mobility in NR and LTE V2X as follows.1. Scenario 1: Movement between NR serving cells1-A. Case 1-1: Movement of NR mode 1 UE in connected state1-B. Case 1-2: Movement of NR mode 2 UE in connected state1-C. Case 1-3: Movement of NR mode 2 UE in IDLE state2. Scenario 2: Movement from LTE serving cell to NR serving cell2-A. Case 2-1: Movement of LTE mode 3 UE in connected state2-B. Case 2-2: Movement of LTE mode 3 UE in connected state2-C. Case 2-3: Movement of LTE mode 4 UE in idle state3. Scenario 3: Movement from NR serving cell to LTE serving cell3-A. Case 3-1: Movement of NR mode 1 UE in connected state3-B. Case 3-2: Movement of NR mode 2 UE in connected state3-C. Case 3-3: Movement of NR mode 2 UE in idle state

In later embodiments of the disclosure, a method of supporting mobility in the scenario and case will be described in detail.

FIG.11illustrates an example of a data transmission procedure of an NR V2X terminal operating in a base station scheduling mode (NR mode 1) in a wireless communication system according to various embodiments of the disclosure. Specifically,FIG.11is a diagram illustrating a data transmission procedure of an NR V2X UE operating in an eNB scheduling mode (NR mode 1) in an NR system applied to the disclosure.

Referring toFIG.11, a UE 11101that is camped on in1105receives SIB1, which is basic information for accessing a corresponding serving cell, from an eNB1103, and then receives system information for NR V2X (SIB for NR V2X) in1115. The SIB1 includes cell access related information, scheduling information of other system information, TDD UL/DL configuration of a corresponding serving cell, and the like. The NR V2X system information may include resource pool information for sidelink data transmission/reception, configuration information for sensing operation, information for configuring synchronization, information for inter-frequency transmission and reception, and the like.

In addition, since even in the RRC connected state and IDLE state, the UE should be able to operate even if the UE receives only system information, the system information related to V2X should be provided in the basically supported eNB and cell without a request from the UE.

When data traffic for V2X is generated in the UE 11101in1120, RRC connection with the eNB is performed in1125. The RRC connection process may be performed before the data traffic is generated in1120. The UE 11101requests a transmission resource capable of V2X communication with another UE1102from the eNB1130. At this time, the request is made from the eNB by using an RRC message or an MAC CE. Here, as the RRC message, SidelinkUEInformation and UEAssistanceInformation messages may be used. Meanwhile, the MAC CE may be, for example, a buffer status report MAC CE of a new format (including an indicator indicating a buffer status report for at least V2X communication and information on the size of data buffered for sidelink communication). The eNB1103allocates a V2X transmission resource to the UE 11101through a dedicated RRC message in1135. This message can be included in the RRCConnectionReconfiguration message. The resource allocation may be a V2X resource through Uu or a resource for PC5 according to the type of traffic requested by the UE or whether the corresponding link is congested. For the determination, the UE adds and sends proSe per packet priority (PPPP) and proSe per packet reliability (PPPR) or logical channel identifier (LCID) information of V2X traffic through UEAssistanceInformation or MAC CE. Since the eNB also knows information on resources used by other UEs, the eNB schedules a resource requested by the UE 1 among the remaining resources. In addition, when the RRC message includes SPS configuration information through Uu, the SPS may be activated through DCI transmission through the PDCCH in1140. The UE 11101selects a transmission link and a resource according to the resource allocated from the eNB1103and a transmission method in1145, and transmits data to the UE1102in1150.

FIG.12illustrates an example of a data transmission procedure of an NR V2X terminal operating in a terminal autonomous resource selection mode (NR mode 2) in a wireless communication system according to various embodiments of the disclosure. Specifically,FIG.12is a diagram illustrating a data transmission procedure of an NR V2X UE operating in a UE autonomous resource selection mode (NR mode 2) in an NR system applied to the disclosure.

Unlike an eNB scheduling mode in which an eNB1203is directly involved in resource allocation, a UE autonomous resource selection mode (mode 2) operation differs in that a UE 11201autonomously selects a resource and transmits data based on a resource pool previously received through system information. In V2X communication, the eNB1203allocates several types of sidelink resource pools (V2V resource pool and V2P resource pool) for the UE 11201. The resource pool is composed of a resource pool in which the UE can autonomously select an available resource pool after sensing resources used by other UEs around the UE, and a resource pool in which the UE randomly selects a resource from a predetermined resource pool.

Referring toFIG.12, the UE 11201that is camped on in1205receives SIB1, which is basic information for accessing a corresponding serving cell, from the eNB1203, and then receives system information for NR V2X (SIB for NR V2X) in1215. The SIB1 includes cell access related information, scheduling information of other system information, TDD UL/DL configuration of a corresponding serving cell, and the like. The NR V2X system information may include resource pool information for sidelink data transmission/reception, configuration information for sensing operation, information for configuring synchronization, information for inter-frequency transmission and reception, and the like. In addition, since even in the RRC connected state and IDLE state, the UE should be able to operate even if the UE receives only system information, the system information related to V2X should be provided in the basically supported eNB and cell without a request from the UE.

When data traffic for V2X is generated in the UE 11201in1215, the UE 11201selects a resource in1225in the time/frequency domain according to a configured transmission operation (e.g., dynamic allocation one-time transmission, dynamic allocation multiple transmission, sensing-based one-time transmission, sensing-based multiple transmission, or random transmission) from the resource pool received from the eNB1203through system information, and transmits data to another UE1202in1230. In general, since a V2X service is implemented for the purpose of periodically transmitting location information of safety-related UEs, in sensing-based multi-transmission in mode 2 operation, the UE senses resources transmitted by other UEs, selects a transmittable resource block from the resource pool in which the corresponding transmission is performed, and then reserves future resources so that they can be transmitted periodically. Next, if the data packet generated by the UE is changed or disappears, a new data packet can be delivered by restarting or canceling the above sensing and resource reservation operation. As described above, the multi-transmission based on the sensing and resource reservation may be basically operated, and if the sensing operation is not well performed, communication may be performed through random resource selection from a corresponding resource pool.

FIG.13illustrates an example of a method for supporting mobility between NR serving cells by a terminal in a connected state in a wireless communication system according to various embodiments of the disclosure. Specifically,FIG.13is a diagram illustrating a method for a UE in a connected state to support mobility between NR serving cells as Embodiment 1 of the disclosure. This embodiment may correspond to Cases 1-1 and 1-2 of scenario 1 described above.

A UE1301in an RRC connected state performs a V2X operation (NR mode 1 or mode 2) in a connected state with a serving cell1302supporting NR V2X, and then reports the measurement result of the neighboring cells due to a channel change caused by mobility to the serving cell. The serving cell1302determines whether to perform handover based on a channel measurement value of the UE1301, and transmits a handover request message to a target cell1303determined in1310, preferentially considering the target cell1303supporting NR V2X as a handover target. In1315, the target cell1303approves the handover of the corresponding UE, transmits a handover request response message, and transmits information necessary for handover to the target cell1303to the serving cell1302. The information includes transmission/reception resource pool information in the target cell1303, synchronization information, exceptional pool information, basic information required for cell access (e.g., random access resources), and the like. In1320, the serving cell1302allows the information received from the target cell to be included in a handover command message and transmits the handover command message to the UE1301.

If the UE1301was operating in the connected NR mode 1, the eNB1302explicitly instructs and uses a specific resource in the resource pool to the UE, so that two configurations are possible in order to ensure that the transmission has continuity even after handover.

1. For seamless transmission, scheduling information for resources available in the target cell1303is provided together so that the UE can apply the scheduling information after handover.

2. If handover is determined, the transmission pool of the target cell1303is applied to operate in NR mode 2 (mode 2) instead of NR mode 1 (mode 1) after handover.

Regardless of whether any one of the above two methods is determined, it is necessary to define what resources to perform transmission/reception through during the handover interruption time. If a method of reducing the handover interruption time is introduced even for sidelink transmission, it may not be necessary. However, assuming that an LTE V2X operation is basically followed, when receiving a handover request from the serving cell, the UE1301activates a T304 timer and at the same time performs NR V2X transmission for the transmission exceptional pool of the target cell1303received in the handover message. Here, the exceptional pool provided for NR V2X in the NR serving cell1302is a separate resource pool different from the exceptional pool provided by the LTE serving cell. Thereafter, when the handover procedure with the target cell1303is finished in1330to1340and scheduling resources received from the target cell1303are available, or NR mode 2 transmission is possible through the resource pool of the target cell1303(for example, if transmittable resources are secured as a result of sensing the transmission resource pool of the target cell1303), the UE1301performs V2X communication through a specific resource of the corresponding resource pool.

FIG.14illustrates an example of a method for supporting mobility between NR serving cells by a terminal in an idle state in a wireless communication system according to various embodiments of the disclosure. Specifically,FIG.14is a diagram illustrating a method for a UE in an idle state of to support mobility between NR serving cells as Embodiment 2 of the disclosure. This embodiment may correspond to Cases 1-3 of scenario 1 described above.

In operation1405, a UE1401in an idle state performs an NR mode 2 (mode 2) operation (a method for a UE to autonomously determine and transmit available resources from the transmission resource pool), and measures a channel from the current serving cell and neighboring cells. If the channel signal strength of the current serving cell1402is weak and the signal strength of the neighboring cell satisfies a condition for performing cell reselection, the UE performs a cell reselection operation to the neighboring cell1403in operation1415. In performing the cell reselection operation, the UE1401may prioritize and search for a frequency and cell supporting NR V2X. Alternatively, cell reselection may be performed by configuring a frequency supporting LTE V2X to have the next priority or the same priority. This is to allow the UE1401performing V2X communication to obtain the maximum service continuity.

In operation1420, after performing cell reselection, the UE1401receives SIB1 from the corresponding cell1403, and when the UE is camped on, the UE1401receives the remaining system information from the camped-on cell1403in operation1425. The SIB1 includes cell access-related information, scheduling information of other system information, and TDD UL/DL configuration of a corresponding serving cell, and the NR V2X system information includes resource pool information for sidelink data transmission and reception, configuration information for sensing operation, information for configuring synchronization, information for inter-frequency transmission and reception, and the like.

The UE1401that has performed cell reselection is required to determine what resource is used during an interruption time before receiving system information from the target cell1403. This means that the UE must be able to quickly receive the system information for NR V2X from the target cell in order to reduce the interruption interval as much as possible in the implementation of the UE, and this interval is regarded as out of coverage (OOC) so that it is also possible to use pre-configured transmission resources. If there is a transmission resource pool applicable after receiving the system information in operation1430, the UE uses an exceptional resource pool provided by the corresponding cell until V2X transmission through the corresponding resource is valid, and then performs sidelink transmission by applying a corresponding normal resource pool after the validity is determined (for example, a case in which the sensing result in the resource pool is valid so that the UE can transmit the sidelink to a specific resource) in operation1435.

FIG.15illustrates an example of a method for supporting mobility from a long term evolution (LTE) serving cell to an NR serving cell by a terminal in a connected state in a wireless communication system according to various embodiments of the disclosure. Specifically,FIG.15is a diagram illustrating a method for a UE in a connected state to support mobility from an LTE serving cell to an NR serving cell as Embodiment 3 of the disclosure. This embodiment may correspond to Cases 2-1 and 2-2 of scenario 2 described above.

A UE1501in an RRC connected state performs a V2X operation (LTE mode 3 or mode 4) in a connected state with a serving cell1502supporting LTE V2X, and then may report the measurement result of neighboring cells due to a channel change caused by mobility to the serving cell in1505. The LTE serving cell1502determines whether to perform handover based on a channel measurement value of the UE, and transmits, if there is a target cell1503supporting NR V2X in the vicinity, a handover request message to the target cell1503determined in1510, considering the corresponding cell as a handover target. A cell providing the LTE V2X may have the highest priority, and may have the same priority if the NR V2X serving cell supports LTE V2X. In operation1515, the target NR cell1503approves the handover of the corresponding UE, transmits a handover request response message, and transmits information necessary for handover to the target cell1503to the LTE serving cell1502. The information includes transmission/reception resource pool information in the target cell1503, synchronization information, exceptional pool information, basic information required for cell access (e.g., random access resources), and the like. In operation1520, the UE allows the information transmitted from the target cell to be included in a handover command message to transmit the handover command message to the UE. In addition, when the NR V2X cell supports the LTE V2X service, LTE V2X resource pool configuration information supported by the corresponding target NR V2X cell is also included in the handover command message1520that transmits the corresponding handover request response message1515and the handover command message1520transmitted from the LTE serving cell to the UE. In the above operation, if the resource pool information provided by the LTE serving cell and the LTE V2X resource pool information provided by the NR serving cell are the same, an indicator indicating that there is no resource pool change will be included in the handover command message provided in operation1520. The indicator may be one bit, and information corresponding to several bits may be provided. Alternatively, the resource pool can be transmitted in a delta signaling perspective. That is, the resource pool may be additionally provided only to parameters that differ from information of the previous serving cell, and information without any change is not signaled. For reference, this embodiment operates on the premise that service continuity of the LTE V2X operation performed in the previous LTE serving cell should be guaranteed even if a handover from an LTE cell to an NR cell occurs.

If the UE was operating in the connected LTE mode 3 (mode 3), the eNB explicitly instructs and uses a specific resource in the resource pool to the UE, so that two configurations are possible in order to ensure that the transmission has continuity even after handover.

1. For seamless transmission, scheduling information for resources available in the target cell is provided together so that the UE can apply the scheduling information after handover.

2. If handover is determined, the transmission pool of the target cell is applied to operate in LTE mode 4 instead of LTE mode 3 after handover.

Regardless of whether any one of the above two methods is determined, it is necessary to define what resources to perform transmission/reception through during the handover interruption time. If a method of reducing the handover interruption time is introduced even for sidelink transmission, it may not be necessary. However, assuming that an LTE V2X operation is basically followed, when receiving a handover request from the serving cell, the UE1301activates a T304 timer and at the same time performs LTE V2X transmission for the transmission exceptional pool of the target cell received in the handover message in1525. However, if the UE does not receive the exceptional pool from the target cell, the UE determines this as OOC and uses a pre-configured exceptional pool. Thereafter, when the handover procedure with the target cell is finished in1530to1540and scheduling resources received from the target cell are available, or LTE mode 4 transmission (mode 4) is possible through the resource pool of the target cell (for example, if transmittable resources are secured as a result of sensing the transmission resource pool of the target cell), the UE performs V2X communication through a specific resource of the corresponding resource pool. However, if the UE does not receive a normal transmission pool from the target cell, the UE determines this as OOC and uses a pre-configured transmission resource pool in1545.

FIG.16illustrates an example of a method for supporting mobility from an LTE serving cell to an NR serving cell by a terminal in an idle state in a wireless communication system according to various embodiments of the disclosure. Specifically,FIG.16is a diagram illustrating a method for a UE in an IDLE state to support mobility from an LTE serving cell to an NR serving cell as Embodiment 4 of the disclosure. This embodiment may correspond to Case 2-3 of scenario 2 described above.

In operation1605, a UE1601in an idle state performs an LTE mode 4 operation (a method for a UE to autonomously determine and transmit available resources from the transmission resource pool), and measures a channel from the current serving cell and neighboring cells. If the channel signal strength of a current serving cell1602is weak and the signal strength of a neighboring cell1603satisfies a condition for performing cell reselection, the UE performs a cell reselection operation to the neighboring cell in operation1615. In performing the cell reselection operation, the UE may configure a frequency and cell supporting NR V2X to have a priority next to those of a frequency and cell supporting LTE V2X, and may perform searching. Alternatively, cell reselection may be performed by configuring the frequency and cell supporting NR V2X to have the same priority as that of the frequency and cell supporting LTE V2X. This is to allow the UE performing V2X communication to obtain the maximum service continuity.

In operation1620, after performing cell reselection, the UE receives SIB1 from the corresponding cell, and when the UE is camped on, the UE receives the remaining system information from the camped-on cell1603in operation1625. The SIB1 includes cell access-related information, scheduling information of other system information, and TDD UL/DL configuration of a corresponding serving cell, and the NR V2X system information includes resource pool information for sidelink data transmission and reception, configuration information for sensing operation, information for configuring synchronization, information for inter-frequency transmission and reception, and the like. In addition, if an NR V2X serving cell supports an LTE V2X service, LTE V2X resource pool configuration information supported by the target NR V2X cell is also included in the corresponding system information or transmitted through system information dedicated to LTE V2X. In the above operation, when the resource pool information provided by the LTE serving cell and the LTE V2X resource pool information provided by the NR serving cell are the same, an indicator indicating that there is no resource pool change may be included in the system information provided in operation1620.

The UE that has performed cell reselection is required to determine what resource is used during an interruption time before receiving system information from the target cell1603. This means that the UE must be able to quickly receive the system information for NR V2X from the target cell in order to reduce the interruption interval as much as possible in the implementation of the UE, and this interval is regarded as out of coverage (OOC) so that it is also possible to use pre-configured transmission resources. If there is a transmission resource pool applicable after receiving the system information in operation1630, the UE uses an exceptional resource pool provided by the corresponding cell until V2X transmission through the corresponding resource is valid, and then performs sidelink transmission by applying a corresponding normal resource pool after the validity is determined (for example, a case in which the sensing result in the resource pool is valid so that the UE can transmit the sidelink to a specific resource) in operation1635.

FIG.17illustrates an example of a method for supporting mobility from an NR serving cell to an LTE serving cell by a terminal in a connected state in a wireless communication system according to various embodiments of the disclosure. Specifically,FIG.17is a diagram illustrating a method for a UE in a connected state to support mobility from an NR serving cell to an LTE serving cell as Embodiment 5 of the disclosure. This embodiment may correspond to Cases 3-1 and 3-2 of scenario 3 described above.

A UE1701in an RRC connected state performs a V2X operation (NR mode 1 or mode 2) in a connected state with a serving cell1702supporting NR V2X, and then may report the measurement result of neighboring cells due to a channel change caused by mobility to the serving cell in operation 2j-05. The NR serving cell1702determines whether to perform handover based on a channel measurement value of the UE, and transmits, if there is a target cell1703supporting LTE V2X in the vicinity, a handover request message to the target cell1703determined in1710, considering the corresponding cell as a handover target. A cell providing the NR V2X may have the highest priority, and may have the same priority or have a priority next to that of the serving cell providing NR V2X. In operation1715, the target LTE cell1703approves the handover of the corresponding UE, transmits a handover request response message, and transmits information necessary for handover to the target cell1703to the LTE serving cell1702. The information includes transmission/reception resource pool information in the target cell, synchronization information, exceptional pool information, basic information required for cell access (e.g., random access resources), and the like. In operation1720, the UE allows the information transmitted from the target cell to be included in a handover command message to transmit the handover command message to the UE. In addition, when the LTE V2X cell supports the NR V2X service, NR V2X resource pool configuration information supported by the corresponding target LTE V2X target cell is also included in a handover request response message1715and a handover command message1720transmitted to the UE by the NR serving cell. In the above operation, if the resource pool information provided by the NR serving cell and the LTE and NR V2X resource pool information provided by the LTE serving cell are the same, an indicator indicating that there is no resource pool change will be included in the handover command message provided in operation1720. The indicator may be one bit, and information corresponding to several bits may be provided. Alternatively, the resource pool can be transmitted in a delta signaling perspective. That is, the resource pool may be additionally provided only to parameters that differ from information of the previous serving cell, and information without any change is not signaled. For reference, this embodiment operates on the premise that service continuity of the LTE V2X operation performed in the previous NR serving cell should be guaranteed even if a handover from the NR cell to the LTE cell occurs. However, if the target LTE cell does not support NR V2X configuration information, the UE can of course use only the LTE V2X configuration information received from the target LTE cell. That is, continuity of the NR V2X service operating in the NR cell cannot be supported. As one method, if handover is performed from the NR serving cell to the LTE serving cell, and if the target LTE cell does not support NR V2X configuration information and wants to use the NR service continuously, the UE determines this as OOC, and may use a pre-configured NR resource pool.

If the UE was operating in NR mode 1 in the connected state, the eNB explicitly instructs and uses a specific resource in the resource pool to the UE, so that the following configurations are possible in order to ensure that the transmission has continuity even after handover.

1. If handover is determined, the transmission pool of the target cell is applied to operate in LTE mode 1 (mode 1) instead of NR mode 1 (mode 1) after handover.

2. If handover is determined, the transmission pool of the target cell is applied to operate in NR mode 2 (mode 2) instead of NR mode 1 (mode 1) after handover.

3. If handover is determined, the transmission pool of the target cell is applied to operate in LTE mode 4 (mode 4) instead of NR mode 1 (mode 1) after handover.

Regardless of whether any one of the above two methods is determined, it is necessary to define what resources to perform transmission/reception through during the handover interruption time. If a method of reducing the handover interruption time is introduced even for sidelink transmission, it may not be necessary. However, assuming that an LTE V2X operation is basically followed, when receiving a handover request from the serving cell, the UE activates a T304 timer and at the same time performs LTE or NR V2X transmission for the transmission exceptional pool of the target cell received in the handover message in1725. However, when failing to receive an exceptional pool from the corresponding target cell, the UE determines this as OOC and uses a pre-configured exceptional pool. Thereafter, when the handover procedure with the target cell is finished in1730to1740and scheduling resources received from the target cell are available, or LTE mode 4 or NR mode 2 transmission is possible through the resource pool of the target cell (for example, if transmittable resources are secured as a result of sensing the transmission resource pool of the target cell), the UE performs V2X communication through a specific resource of the corresponding resource pool. However, if the normal transmission pool cannot be received from the target cell, the UE determines this as OOC and uses a pre-configured transmission resource pool in1745.

FIG.18illustrates an example of a method for supporting mobility from an NR serving cell to an LTE serving cell by a terminal in an IDLE state in a wireless communication system according to various embodiments of the disclosure. Specifically,FIG.18is a diagram illustrating a method for a UE in an idle state to support mobility from an NR serving cell to an LTE serving cell as Embodiment 6 of the disclosure. This embodiment may correspond to Case 3-3 of scenario 3 described above.

In operation1805, a UE1801in an idle state performs an NR mode 2 (mode 2) operation (a method for a UE to autonomously determine and transmit available resources from the transmission resource pool), and measures a channel from the current serving cell and neighboring cells. If the channel signal strength of the current serving cell is weak and the signal strength of the neighboring cell satisfies a condition for performing cell reselection, the UE performs a cell reselection operation to the neighboring cell in operation1815. In performing the cell reselection operation, the UE may configure a frequency and cell supporting NR V2X to have the highest priority, and may perform searching. Alternatively, cell reselection may be performed by configuring the frequency and cell supporting NR V2X to have the same priority as that of the frequency and cell supporting LTE V2X. This is to allow the UE performing V2X communication to obtain the maximum service continuity.

In operation1820, after performing cell reselection, the UE receives SIB1 from the corresponding cell, and when the UE is camped on, the UE receives the remaining system information from the camped-on cell in operation1825. The SIB1 includes cell access-related information, scheduling information of other system information, and TDD UL/DL configuration of a corresponding serving cell, and the V2X system information includes resource pool information for sidelink data transmission and reception, configuration information for sensing operation, information for configuring synchronization, information for inter-frequency transmission and reception, and the like. In addition, if an LTE V2X serving cell supports an NR V2X service, NR V2X resource pool configuration information supported by the target LTE V2X cell is also included in the corresponding system information or transmitted through system information dedicated to NR V2X. In the above operation, when the resource pool information provided by the LTE serving cell and the LTE V2X resource pool information provided by the NR serving cell are the same, an indicator indicating that there is no resource pool change may be included in the system information provided in operation1820.

The UE that has performed cell reselection is required to determine what resource is used during an interruption time before receiving system information from the target cell. This means that the UE must be able to quickly receive the system information for V2X from the target cell in order to reduce the interruption interval as much as possible in the implementation of the UE, and this interval is regarded as OOC so that it is also possible to use pre-configured transmission resources. If there is a transmission resource pool applicable after receiving the system information in operation1830, the UE uses an exceptional resource pool provided by the corresponding cell until V2X transmission through the corresponding resource is valid, and then performs sidelink transmission by applying a corresponding normal resource pool after the validity is determined (for example, a case in which the sensing result in the resource pool is valid so that the UE can transmit the sidelink to a specific resource) in operation1835.

FIG.19illustrates an example of a discrete reception (DRX) operation for an IDLE UE in a wireless communication system according to various embodiments of the disclosure. Specifically,FIG.19is a diagram illustrating a DRX operation for an idle UE in an LTE system.

UEs1910and1915monitor a PDCCH to receive paging from a network1910when the UEs are in an RRC idle state. In LTE, as an efficient method of reducing the power consumption of the UE, a discontinuous reception (hereinafter, referred to as “DRX”) period is configured in units of subframe1920, so that a receiver wakes up only for a predetermined time period and sleeps for the rest of the time. That is, in order to receive paging from the network1910, paging cycles1925and1930, which are predetermined time intervals, are configured. When the UE detects P-RNTI used for paging, the UEs1910and1915process a corresponding downlink paging message. The paging message contains the ID of the UE, and UEs other than the corresponding ID discard the received information and sleep according to the DRX cycle. During the DRX cycle, since the uplink timing is not known, HARQ is not used.

The network configures subframe1920in which the UE should receive paging. For the configuration, the minimum value of a period Tue requested by the UE and a cell-specific period Tc is used. In addition, 32, 64, 128, and 256 frames are configured in the paging cycle. Subframes to be monitored for paging within the above frame can be extracted from an international mobile subscriber identity (IMSI) of the UE. Since each UE has a different IMSI, the UE operates according to a paging instance belonging to each UE at the entire paging occasion1935.

The paging message can be transmitted only in some subframes, and possible configurations are shown in the following Table 3.

TABLE 3Number of paging subframes1/321/16⅛¼½124PagingFDD9999994, 90, 4, 5, 9subframeTDD0000000, 50, 1, 5, 6

FIG.20illustrates an example of a DRX operation for a terminal in an RRC connected state in a wireless communication system according to various embodiments of the disclosure. Specifically,FIG.20is a diagram illustrating a DRX operation for a UE in an RRC connected state in an LTE system.

DRX is also defined in the RRC connected state, and its operation method is different from that of an idle DRX. This DRX is collectively referred to as a connected DRX (connected mode DRX or CDRX). As described above, in order for the UE to acquire scheduling information, continuously monitoring the PDCCH will cause large power consumption. The DRX operation in a basic connection state has a DRX cycle of2000, and the PDCCH is monitored only during an on-duration2005time. In the connected mode, the DRX cycle has two values: long DRX and short DRX. In general, the long DRX cycle is applied, and if necessary, the eNB can trigger the short DRX cycle using a MAC control element (CE). After a certain period of time, the UE changes from the short DRX cycle to the long DRX cycle. Initial scheduling information of a specific UE is provided only in a predetermined PDCCH. Accordingly, the UE can minimize power consumption by periodically monitoring only the PDCCH. If, during the on-duration2005time, scheduling information for a new packet is received by PDCCH, in2010, the UE starts a DRX inactivity timer2015. The UE maintains an active state during the DRX inactivity timer. In other words, PDCCH monitoring is continued. An HARQ RTT timer2020is also started. The HARQ RTT timer is applied to prevent the UE from monitoring the PDCCH unnecessarily during the HARQ round trip time (RTT), and during the timer operation time, the UE does not need to perform PDCCH monitoring. However, while the DRX inactivity timer and HARQ RTT timer operate at the same time, the UE continues to monitor the PDCCH based on the DRX inactivity timer. When the HARQ RTT timer expires, a DRX retransmission timer2025is started. While the DRX retransmission timer is operating, the UE must perform PDCCH monitoring. In general, during the DRX retransmission timer operation time, scheduling information for HARQ retransmission is received in2030. Upon receiving the scheduling information, the UE immediately stops the DRX retransmission timer and starts the HARQ RTT timer again. The above operation continues until the packet is successfully received in2035.

Configuration information related to the DRX operation in the connected mode is delivered to the UE through an RRCConnectionReconfiguration message. The on-duration timer, the DRX inactivity timer, and the DRX retransmission timer are defined as the number of PDCCH subframes. After the timer starts, when the number of subframes defined as PDCCH subframes passes by a predetermined number, the timer expires. In FDD, all downlink subframes belong to PDCCH subframes, and in TDD, downlink subframes and special subframes correspond to this. In TDD, a downlink subframe, an uplink subframe, and a special subframe exist in the same frequency band. Among them, a downlink subframe and a special subframe are considered as a PDCCH subframe.

The eNB can configure two states: longDRX and shortDRX. In general, the eNB may use one of the two states in consideration of power preference indication information and UE mobility record information reported from the UE, and characteristics of the configured DRB. The transition between the two states is achieved by transmitting a specific timer or a specific MAC CE to the UE.

FIG.21illustrates an example of an operation of a packet delay budget report for improving voice over LTE (VoLTE) quality in a wireless communication system according to various embodiments of the disclosure. Specifically,FIG.21is a diagram illustrating a packet delay budget report operation for improving VoLTE quality in a wireless communication system to which the disclosure is applied.

Based on the LTE system, the recommended unidirectional end-to-end (E2E) delay time, which is currently VoLTE's QoS requirement, is within 150 ms and the budget is less than 400 ms. Referring to the drawing, when two UEs2105and2110are performing VoLTE service through connected eNBs2115and2120, respectively, the VoLTE quality of the UE 12105and the UE 22110may be different depending on the channel state in which the UE is connected to the eNB. That is, in the case of UE 1, the VoLTE quality is good, but in the case of UE 2, the VoLTE quality may be poor. In addition, the eNB can adjust the DRX (CDRX) period in the connection state to the UE according to the unidirectional packet delay time of the VoLTE described above, and for an MTC UE, the UE can adjust the period in which the UE can repeatedly transmit. In general, the eNB tries to reduce unnecessary power consumption of the UE by configuring the DRX connection state with the UE when the channel state with the UE is good. Conversely, when the channel state with the terminal is bad, the eNB does not configure the DRX connection state with the UE. In the disclosure, an operation for requesting DRX reconfiguration in a connected state when the VoLTE quality of the UE 12105and UE 22110is poor will be described. It will be described with reference to the following Table 4.

TABLE 4VoLTEChannelDelay budget reportqualityqualitytriggeringConfiguration contenteNB operationPoorpooreNB request delayX ms capable ofPerform eMTCbudget report fromeMTC repetitiverepetitiveUE 2transmission is put intransmissionDBR and transmitted(X ms delay(Type 1)occurs)poorgoodIn order for UE 1 toCDRX cycle value YChange CDRYimprove VoLTEms desired to becycle (by Y ms)quality, preferredchanged (reduced) isCDRS is put input in CDRX cycledelay budget reportvalue Y ms andand transmittedtransmitted (type 2)

As shown in Table 4, when the VoLTE quality of UE 12105and UE 22110is poor, the channel status of UE 12105and an eNB 12115is good, and the channel status of UE 22110and an eNB 22120is poor, it is highly likely that the eNB generally configures the CDRX for the UE 12105and not for the UE 22110. However, the VoLTE communication performance with the UE 22110may be further degraded by the CDRX operation configured in the UE 12105, which is related to a failure to receive a packet transmitted by the UE 2 during the sleep period by the CDRX. If the UE 12105knows the unidirectional E2E delay time with the UE 22110, a budget delay value and CDRX cycle request value for the UE may be calculated in consideration of the corresponding delay time and the CDRX cycle configured by the eNB.
E2Edelay budget=E2Edelay requirement 400 ms−measuredE2Edelay time   Equation 1

That is, if an end-to-end (E2E) delay requirement is 400 ms, and the E2E delay time measured by the UE is 200 ms, an additional delay of 200 ms is allowed to the UE. If the current CDRX cycle is configured to 160 ms to the UE 1, the UE may improve VoLTE performance by adjusting the configured CDRX cycle value or may increase the CDRX cycle to achieve power reduction. The E2E delay time measured above can be regarded as the sum of the configured CDRX cycle value and a packet transmission delay in wireless and wired channels, and the maximum value (E2E delay budget/2) of the CDRX cycle change may be 100 ms. This is a case of considering the operation of another UE when both the channels of the UE 1 and the UE 2 are considered, but the exact value may vary. That is, by reducing the CDRX cycle value, the UE can receive packets more frequently, and thus VoLTE performance can be improved. The CDRX cycle change value that the UE can request may be configured by UE implementation in consideration of the E2E delay value. In addition, since the E2E transmission delay value is a value measured by the UE, the eNB and the network do not know the exact value, so the corresponding operation can be triggered by the UE. That is, in order to report the transmission delay budget, unlike the previously configured CDRX cycle value, the CDRX cycle value Yms to be changed according to the E2E transmission delay value measured by the UE may be requested. The eNB receiving the message may reconfigure the CDRX cycle to a predetermined period.

FIGS.22A to22Billustrate an example of a method for a terminal to measure a packet transmission delay in a wireless communication system according to various embodiments of the disclosure. Specifically,FIGS.22A to22Bare diagrams illustrating a method for a UE to measure a packet transmission delay in a VoLTE system to which the disclosure is applied.

As briefly described inFIG.21, since the eNB and the network cannot measure the unidirectional packet delay time between the UEs, it is impossible to know if the correct packet delay measurement value is not reported. When a VoLTE service is performed, the UE can transmit data using real time protocol (RTP) packets, and can measure the E2E delay time between UEs by transmitting and receiving real time control protocol (RTCP) packets.

Referring toFIG.22A, a sender report format of an RTCP packet is shown. In the format, an E2E packet delay time can be measured by referring to a last sender report (SR) and a delay since last SR (DLSR). That is, as shown inFIG.22B, a unidirectional E2E delay time can be summarized by the following Equation 2.
UnidirectionalE2Edelay time=((timeA−time LSR)−DLSR)/2   Equation 2

This method is only an example, and the packet transmission delay time between UEs can be implemented through other methods. The reason for dividing by 2 in the above equation can be known through round-trip time in order for the transmitting end to measure the unidirectional E2E delay time, and the unidirectional E2E delay time is calculated as half of the round-trip time of the packet.

FIG.23illustrates an example of a method for a terminal to request a change in a connected state DRX cycle and transmit and receive data by applying the request in a wireless communication system according to various embodiments of the disclosure. Specifically,FIG.23is a diagram illustrating a method for a UE to transmit and receive data by requesting a change in a connection state DRX cycle and applying this as an embodiment proposed in the disclosure. Overall operations described in this drawing are applicable to both an LTE system and a next-generation mobile communication system.

A UE 1 and UE 2 in an RRC connected state are connected to an eNB 1 and an eNB 2, respectively, and can transmit and receive voice data through a VoLTE service. In this embodiment, taking VoLTE service as an example, the overall operation in which the UE measures an E2E delay time to request a change in the connection state DRX cycle, and then configures a reconfigured DRX cycle to improve VoLTE call quality is illustrated. However, the above operation is not limited to VoLTE, that is, voice data service, but can be applied equally to other services.

In operation2305, the UE 1 connected to the eNB 1 and the UE 2 connected to the eNB 2 may each perform a voice call through VoLTE. The above VoLTE data transmission and reception may be performed through an RTP packet. In this case, as described inFIG.3H, after a corresponding field value is decoded through the transmission and reception of the RTCP packet, the round-trip time of the packet sent from the transmitting end is determined in2310. In operations2315and2320, the UE 1 and the UE 2 may measure the unidirectional transmission delay time through a signal for E2E measurement received in operation2310. For example, the unidirectional E2E delay time can be obtained as half of the round-trip time of the packet measured in operation2310. For reference, in the present embodiment, both the operations of the UE 1 and the UE 2 are included, but it is known that the operation of each UE is actually performed independently. That is, the UE 1 operation and the UE 2 operation may occur together, but may be performed only on one side. Alternatively, even if they are performed together, they can be performed at different times.

In operations2325and2330, the UE 1 and UE 2 each changes the DRX cycle in a connected state to improve VoLTE quality based on the measured unidirectional transmission delay time and a predetermined E2E delay request time margin, or requests a change in repetitive transmission period for eMTC UEs. In the disclosure, the DRX cycle change is described, and the DRX cycle change request is performed by the UE transmitting a delay budget report to a corresponding eNB. The message may be delivered as UEAssistanceInformation RRC message in2335and2340. The message has the following message format. Here, the DRX cycle change request corresponds to a type1 field value of DelayBudgetReport-14 IE, and when the UE transmits the message, the DRX cycle value requesting the change is configured in the type 1 field and transmitted.

UEAssistanceInformation message-- ASN1STARTUEAssistanceInformation-v1430-IEs ::=SEQUENCE {bw-Preference-r14BW-Preference-r14OPTIONAL,sps-AssistanceInformation-r14SEQUENCE {trafficPatternInfoListSL-r14TrafficPatternInfoList-r14OPTIONAL,trafficPatternInfoListUL-r14TrafficPatternInfoList-r14OPTIONAL,}OPTIONAL,rlm-Report-r14SEQUENCE {rlm-Event-r14ENUMERATED {earlyOutofSync, earlyInSync},excessRsp-MPDCCH-r14ENUMERATED {excessRep1, excessRep2}OPTIONAL}OPTIONAL,delayBudgetReport-r14DelayBudgetReport-r14OPTIONAL,nonCriticalExtensionSEQUENCE { }OPTIONAL}DelayBudgetReport-r14::=CHOICE {Type1ENUMERATED {msMinus1280, msMinus640, msMinus320, msMinus160,msMinus80, msMinus60, msMinus40, msMinus20, ms0, ms20,ms40, ms60, ms80, ms160, ms320, ms640, ms1280},Type2ENUMERATED {msMinus192, msMinus168, msMinus144, msMinus120,msMinus96, msMinus72, msMinus48, msMinus24, ms0,MS24,ms48, ms72, ms96, ms120, ms144, ms168, ms192}}-- ASN1STOP

Various options as follows are possible depending on which DRX cycle value is used in Table 5.1. Option 1: long DRX cycle of MCG (Master Cell Group)Apply long DRX cycle value configured in MCG2. Option 2: short DRX cycle of MCGApply short DRX cycle value configured in MCG3. Option 3: Actual DRX cycle of MCG (long or short which is currently applied)Apply DRX cycle value (applied to both long DRX or short DRX) currently configured in MCG4. Option 4: Short DRX cycle of MCG if short DRX cycle is configured for MCG. Otherwise long DRX cycle of MCGApply short DRX cycle value of MCG if short DRX cycle is configured in MCG5. Option 5: DelayBudgetReport indicates which DRX cycle should be adjustedIndicate which DRX cycle value is applied to DelayBudgetReport

The disclosure further proposes the following method in addition to the above method. The above method basically assumes that the DRX cycle in the MCG is used.1. Proposal 1: uses DRX cycle value of specific cell group1-A. Method 1: uses DRX cycle value of cell group in which logical channel where VoIP (VoLTE) is configured exists1-B. Method 2: uses DRX cycle value of cell group configured from eNB (eNB explicitly instructs to refer to delay budget report of certain cell group)2. Proposal 2: If transmission of UEAssistanceInformation message through SRB3 is possible in MR-DC including EN-DC and NR-NR DC, when indicating DRX cycle value, specify that it is used as DRX cycle value in cell group to which corresponding UEAssistanceInformation is reported

The two proposals may be configured in combination with the long DRX and short DRX selection principles proposed above. That is, the cell group determined in Proposal 1 and 2 is applied instead of a fixed portion by the MCG in the options, and the remaining long DRX and short DRX configuration methods follow the methods in the options. For example, only the long DRX part of Proposal 1 and Option 1 is combined, and the same combination as the long DRX period value of a cell group in which a logical channel in which VoIP (VoLTE) is configured exists is possible.

In operations2345and2350, the eNB 1 and eNB 2 reset the DRX cycle based on a DRX cycle change request signal received from the UEs1and2. In the above-described operation of the eNB, the DRX cycle change request included in the RRC report message of the UE may be performed as it is, but other values may be configured according to determination or implementation of the eNB. In operations2355and2360, the eNB delivers the reconfigured DRX cycle value to the UE through an RRC message. After that, the UE 1 and UE 2 continue to perform services (VoLTE or other data transmission/reception) according to the VoLTE or reconfigured the DRX cycle, and perform an E2E delay time measurement operation as in operation2310, in operation2365. If the currently requested DRX change value calculated based on a unidirectional packet delay time measured by the UE is different from the previously requested DRX cycle, the UE may trigger and repeat the DRX change request operations2325to2360.

FIG.24illustrates an example of an overall operation of a terminal in a wireless communication system according to various embodiments of the disclosure. Specifically,FIG.24is a diagram illustrating the overall operation of a UE to which the disclosure is applied.

In operation2405, a UE in a connected state measures a unidirectional E2E delay. The above operation can be performed through various methods of UE implementation. For example, the above operation may be performed through transmission and reception of an RTP packet, especially an RTCP packet. In this case, as described inFIG.3H, after decoding a specific field value for measuring the E2E delay in the RTCP packet, the round-trip-time of the packet sent from the transmitting end is measured. Then, based on this, the unidirectional E2E delay is measured. In operation2410, the UE may determine the DRX cycle change in the connected state based on the measured unidirectional E2E and predetermined E2E delay requirement (determined in advance according to E2E delay requirement and QoS). That is, if there is a difference from the E2E delay requirement because the currently configured DRX cycle value is too long or too short, it is possible to improve data transmission/reception performance by adjusting the difference. For example, when VoLTE quality is poor for a UE currently executing a VoLTE service and the measured E2E delay value is large compared to the E2E delay requirement, it is possible to achieve the VoLTE quality and E2E delay requirement satisfaction by requesting to reduce the value of the CDRX cycle. For reference, the CDRX cycle value and the E2E delay have a correlation, and reducing the CDRX cycle has an effect of reducing the E2E delay. This is because data transmission/reception does not occur during the CDRX cycle, so the E2E delay must include the CDRX cycle. Conversely, if the VoLTE quality for the UE is good and the measured E2E delay value is small compared to the E2E delay requirement, by requesting an increase in the CDRX cycle value, the power consumption of the UE can be improved.

In operation2415, the UE triggers and generates a delay budget report including the CDRX cycle value for requesting the change determined in the above process. Here, the DRX cycle change request corresponds to the type 1 field value of the DelayBudgetReport-14 IE of the RRC signaling UEAssistanceInformation message, and when the UE transmits the message, the DRX cycle value requesting the change is configured in the type 1 field and transmitted. Alternatively, it may be transmitted including the corresponding information through another type of RRC message or MAC CE.

In operation2420, the UE receives an RRC message (RRC connection reconfiguration) from the eNB and reconfigures the DRX cycle. In operation2425, the UE compares the preferred DRX cycle value in the currently reconfigured state with the previously reported DRX cycle value. If there is no difference, the UE performs a first operation, and if there is a difference, the UE performs a second operation. Operation2430is the first operation, in which the UE maintains the current configuration and transmits and receives data, and in operation2435, the UE triggers a delay budget report as the second operation to re-request a desired CDRX cycle value by RRC signaling. This means repetition of operations2410to2420above.

FIG.25illustrates an example of a block configuration of a terminal in a wireless communication system according to various embodiments of the disclosure. Specifically, as illustrated inFIG.25, a UE according to an embodiment of the disclosure includes a transceiver2505, a controller2510, a multiplexing and demultiplexing unit2515, upper layer processors2520and2525, and a control message processor2530.

The transceiver2505receives data and a predetermined control signal through a forward channel of a serving cell, and transmits data and a predetermined control signal through a reverse channel. When multiple serving cells are configured, the transceiver2505performs data transmission/reception and control signal transmission/reception through the multiple serving cells. The transceiver2505may include at least one transmitter, at least one receiver, or at least one transceiver.

The multiplexing and demultiplexing unit2515multiplexes data generated by the upper layer processors2520and2525or the control message processor2530, or demultiplexes the data received from the transceiver2505to transmits the multiplexed or demultiplexed data to the appropriate upper layer processors2520and2525or the control message processor2530. The control message processor2530transmits and receives a control message from the base station and performs necessary operations. These operations include a function of processing control messages such as RRC messages and MAC CE, reporting of CBR measurement values, and reception of RRC messages for resource pool and UE operation. The upper layer processors2520and2525refer to DRB devices and may be configured for each service. The upper layer processors2520and2525may process data generated from user services such as file transfer protocol (FTP) or Voice over Internet Protocol (VoIP) and transmits the processed data to the multiplexing and demultiplexing unit2515, or may process the data transmitted from the multiplexing and demultiplexing unit2515to transmit the processed data to an upper layer service application.

The controller2510controls the transceiver2505and the multiplexing and demultiplexing unit2515by checking scheduling commands received through the transceiver2505, for example, reverse grants, so that reverse transmission is performed using appropriate transmission resources at an appropriate time. The controller2510may include at least one processor.

Meanwhile, in the above, it has been described that the UE is composed of a plurality of blocks and each block performs a different function, but this is only an exemplary embodiment and is not limited thereto. For example, the controller2510itself may perform a function that the multiplexing and demultiplexing unit2515performs.

FIG.26illustrates an example of a block configuration of a base station in a wireless communication system according to various embodiments of the disclosure. Specifically, an eNB device ofFIG.26includes a transceiver2605, a controller2610, a multiplexing and demultiplexing unit2620, a control message processor2635, upper layer processors2625and2630, and a scheduler2615.

The transceiver2605transmits data and a predetermined control signal through a forward carrier and receives data and a predetermined control signal through a reverse carrier. When multiple carriers are configured, the transceiver2605performs data transmission/reception and control signal transmission/reception through the multiple carriers. The transceiver2505may include at least one transmitter, at least one receiver, or at least one transceiver.

The multiplexing and demultiplexing unit2620multiplexes data generated by the upper layer processors2625and2630or the control message processor2635, or demultiplexes the data received from the transceiver2605to transmit the multiplexed or demultiplexed data to the appropriate upper layer processors2625and2630, the control message processor2635, or the controller2610. The controller2610may include at least one processor.

The control message processor2635receives an instruction from the controller, generates a message to be transmitted to a UE, and transmits the generated message to a lower layer. The upper layer processors2625and2630can be configured for each UE service, and process data generated from user services such as FTP or VoIP, and transmit the processed data to the multiplexing and demultiplexing unit2620or may process the data transmitted from the multiplexing and demultiplexing unit2620to transmit the processed data to an upper layer service application. The scheduler2615allocates transmission resources to the UE at an appropriate time in consideration of the buffer state, the channel state, and the active time of the UE, and may instruct the transceiver to process or transmit signals transmitted by the UE to the UE.

FIG.27illustrates an example of a configuration of a terminal in a wireless communication system according to various embodiments of the disclosure.

Referring toFIG.27, a UE includes a radio frequency (RF) processor2710, a baseband processor2720, a storage unit2730, and a controller2740.

The RF processor2710performs a function for transmitting and receiving a signal through a wireless channel such as band conversion and amplification of a signal. That is, the RF processor2710up-converts a baseband signal provided from the baseband processor2720into an RF band signal and then transmits the up-converted signal through an antenna, and down-converts the RF band signal received through the antenna into a baseband signal. For example, the RF processor2710may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), and the like. In the drawing, only one antenna is shown, but the UE may include a plurality of antennas. In addition, the RF processor2710may include a plurality of RF chains. Furthermore, the RF processor2710may perform beamforming. For the beamforming, the RF processor2710may adjust a phase and a magnitude of each of signals transmitted and received through the plurality of antennas or antenna elements. Further, the RF processor may perform MIMO, and may receive multiple layers when performing the MIMO operation.

The baseband processor2720performs a function of converting between a baseband signal and a bit stream according to the physical layer standard of the system. For example, when transmitting data, the baseband processor2720generates complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the baseband processor2720restores a received bit stream through demodulation and decoding of the baseband signal provided from the RF processor2710. For example, in the case of an orthogonal frequency division multiplexing (OFDM) method, when transmitting data, the baseband processor2720generates complex symbols by encoding and modulating the transmission bit stream, maps the complex symbols to subcarriers, and then configures OFDM symbols through an inverse fast Fourier transform (IFFT) operation and a cyclic prefix (CP) insertion. In addition, when receiving data, the baseband processor2720divides the baseband signal provided from the RF processor2710into OFDM symbol units, restores the signals mapped to subcarriers through a fast Fourier transform (FFT) operation, and then restores the reception bit stream through demodulation and decoding.

The baseband processor2720and the RF processor2710transmit and receive signals as described above. Accordingly, the baseband processor2720and the RF processor2710may be referred to as a transmitter, a receiver, a transceiver, or a communication unit. Furthermore, at least one of the baseband processor2720and the RF processor2710may include a plurality of communication modules to support a plurality of different wireless access technologies. In addition, at least one of the baseband processor2720and the RF processor2710may include different communication modules to process signals of different frequency bands. For example, the different wireless access technologies may include a wireless LAN (e.g., IEEE 802.11, a cellular network (e.g., LTE)), etc. In addition, the different frequency bands may include a super high frequency SHF (e.g., 2.NRHz, NRhz) band and a millimeter wave (e.g., 60 GHz) band.

The storage unit2730stores data such as a basic program, an application program, and configuration information for the operation of the UE. In particular, the storage unit2730may store information related to a second access node that performs wireless communication using a second wireless access technology. Further, the storage unit2730provides stored data according to the request of the controller2740.

The controller2740controls overall operations of the terminal. For example, the controller2740transmits and receives signals through the baseband processor2720and the RF processor2710. Also, the controller2740writes and reads data in the storage unit2740. To this end, the controller2740may include at least one processor. For example, the controller2740may include a communication processor (CP) that controls communication and an application processor (AP) that controls an upper layer such as an application program.

FIG.28illustrates an example of a configuration of a base station in a wireless communication system according to various embodiments of the disclosure.

Referring toFIG.28, an eNB includes an RF processor2810, a baseband processor2820, a backhaul communication unit2830, a storage unit2840, and a controller2850.

The radio frequency (RF) processor2810performs a function for transmitting and receiving a signal through a wireless channel such as band conversion and amplification of a signal. That is, the RF processor2810up-converts the baseband signal provided from the baseband processor2820into an RF band signal and then transmits the up-converted signal through an antenna, and down-converts the RF band signal received through the antenna into a baseband signal. For example, the RF processor2810may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), and the like. In the drawing, only one antenna is shown, but a first access node may include a plurality of antennas. In addition, the RF processor2810may include a plurality of RF chains. Furthermore, the RF processor2810may perform beamforming. For the beamforming, the RF processor2810may adjust a phase and a magnitude of each of signals transmitted and received through the plurality of antennas or antenna elements. The RF processor may perform a downlink multiple-input multiple-output (MIMO) operation by transmitting one or more layers.

The baseband processor2820performs a function of converting between a baseband signal and a bit stream according to the physical layer standard of the first wireless access technology. For example, when transmitting data, the baseband processor2820generates complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the baseband processor2820restores a received bit stream through demodulation and decoding of the baseband signal provided from the RF processor2810. For example, in the case of the OFDM (orthogonal frequency-division multiplexing) scheme, when transmitting data, the baseband processor2820generates complex symbols by encoding and modulating a transmission bit stream, and mapping the complex symbols to subcarriers. Thereafter, OFDM symbols are configured through IFFT operation and CP insertion. In addition, when receiving data, the baseband processor2820divides the baseband signal provided from the RF processor2810into OFDM symbol units, restores signals mapped to subcarriers through FFT operation, and then restores the received bit stream through demodulation and decoding. The baseband processor2820and the RF processor2810transmit and receive signals as described above. Accordingly, the baseband processor2820and the RF processor2810may be referred to as a transmitter, a receiver, a transceiver, a communication unit, or a wireless communication unit.

The backhaul communication unit2830provides an interface for performing communication with other nodes in a network. That is, the backhaul communication unit2830converts a bit stream transmitted from the main station to another node, for example, an auxiliary base station, a core network, etc., into a physical signal, and converts a physical signal received from the other node into a bit stream.

The storage unit2840stores data such as a basic program, an application program, and configuration information for the operation of the main station. In particular, the storage unit2840may store information on a bearer allocated to an accessed terminal and a measurement result reported from the connected UE. In addition, the storage unit2840may store information serving as a criterion for determining whether to provide or stop providing multiple connections to the terminal. In addition, the storage unit2840provides stored data according to the request of the control unit2850.

The controller2850controls overall operations of the main station. For example, the control unit2850transmits and receives signals through the baseband processor2820and the RF processor2810or through the backhaul communication unit2830. Also, the controller2850writes and reads data in the storage unit2840. To this end, the control unit2850may include at least one processor.

Methods disclosed in the claims and/or methods according to various embodiments described in the specification of the disclosure may be implemented by hardware, software, or a combination of hardware and software.

When the methods are implemented by software, a computer-readable storage medium for storing one or more programs (software modules) may be provided. The one or more programs stored in the computer-readable storage medium may be configured for execution by one or more processors within the electronic device. The at least one program may include instructions that cause the electronic device to perform the methods according to various embodiments of the disclosure as defined by the appended claims and/or disclosed herein.

The programs (software modules or software) may be stored in non-volatile memories including a random access memory and a flash memory, a read only memory (ROM), an electrically erasable programmable read only memory (EEPROM), a magnetic disc storage device, a compact disc-ROM (CD-ROM), digital versatile discs (DVDs), or other type optical storage devices, or a magnetic cassette. Alternatively, any combination of some or all of them may form a memory in which the program is stored. Further, a plurality of such memories may be included in the electronic device.

In addition, the programs may be stored in an attachable storage device which may access the electronic device through communication networks such as the Internet, Intranet, Local Area Network (LAN), Wide LAN (WLAN), and Storage Area Network (SAN) or a combination thereof. Such a storage device may access the electronic device via an external port. Further, a separate storage device on the communication network may access a portable electronic device.

In the above-described detailed embodiments of the disclosure, an element included in the disclosure is expressed in the singular or the plural according to presented detailed embodiments. However, the singular form or plural form is selected appropriately to the presented situation for the convenience of description, and the disclosure is not limited by elements expressed in the singular or the plural. Therefore, either an element expressed in the plural may also include a single element or an element expressed in the singular may also include multiple elements.

Although specific embodiments have been described in the detailed description of the disclosure, various modifications and changes may be made thereto without departing from the scope of the disclosure. Therefore, the scope of the disclosure should not be defined as being limited to the embodiments, but should be defined by the appended claims and equivalents thereof.