US20200351725A1 - Method and apparatus for performing handover procedure in wireless communication system - Google Patents

Method and apparatus for performing handover procedure in wireless communication system Download PDF

Info

Publication number
US20200351725A1
US20200351725A1 US15/929,415 US202015929415A US2020351725A1 US 20200351725 A1 US20200351725 A1 US 20200351725A1 US 202015929415 A US202015929415 A US 202015929415A US 2020351725 A1 US2020351725 A1 US 2020351725A1
Authority
US
United States
Prior art keywords
rlc
data
gnb
pdcp
layer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US15/929,415
Other languages
English (en)
Inventor
Donggun Kim
Soenghun KIM
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Samsung Electronics Co Ltd
Original Assignee
Samsung Electronics Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Samsung Electronics Co Ltd filed Critical Samsung Electronics Co Ltd
Assigned to SAMSUNG ELECTRONICS CO., LTD reassignment SAMSUNG ELECTRONICS CO., LTD ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: KIM, DONGGUN, KIM, SOENGHUN
Publication of US20200351725A1 publication Critical patent/US20200351725A1/en
Priority to US17/661,157 priority Critical patent/US20220256413A1/en
Abandoned legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/08—Reselecting an access point
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H04W36/0055—Transmission or use of information for re-establishing the radio link
    • H04W36/0069—Transmission or use of information for re-establishing the radio link in case of dual connectivity, e.g. decoupled uplink/downlink
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H04W36/0055—Transmission or use of information for re-establishing the radio link
    • H04W36/0064—Transmission or use of information for re-establishing the radio link of control information between different access points
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H04W36/0055—Transmission or use of information for re-establishing the radio link
    • H04W36/0072—Transmission or use of information for re-establishing the radio link of resource information of target access point
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/02—Buffering or recovering information during reselection ; Modification of the traffic flow during hand-off
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/34—Reselection control
    • H04W36/36—Reselection control by user or terminal equipment
    • H04W36/362—Conditional handover
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W76/00—Connection management
    • H04W76/10—Connection setup
    • H04W76/15—Setup of multiple wireless link connections
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W76/00—Connection management
    • H04W76/10—Connection setup
    • H04W76/19—Connection re-establishment
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W76/00—Connection management
    • H04W76/20—Manipulation of established connections
    • H04W76/27—Transitions between radio resource control [RRC] states
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W80/00—Wireless network protocols or protocol adaptations to wireless operation
    • H04W80/02—Data link layer protocols
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/02—Buffering or recovering information during reselection ; Modification of the traffic flow during hand-off
    • H04W36/023—Buffering or recovering information during reselection
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/02—Buffering or recovering information during reselection ; Modification of the traffic flow during hand-off
    • H04W36/023—Buffering or recovering information during reselection
    • H04W36/0235—Buffering or recovering information during reselection by transmitting sequence numbers, e.g. SN status transfer

Definitions

  • the disclosure relates to a method and apparatus for performing a handover procedure in a wireless communication system.
  • the disclosure relates to a method and apparatus for processing communication data in a wireless communication system.
  • a 5G communication system or pre-5G communication system is called a Beyond 4G Network communication system or a Post Long Term Evolution (LTE) system.
  • LTE Post Long Term Evolution
  • mmWave millimeter wave
  • FD-MIMO Full Dimensional MIMO
  • array antenna analog beam-forming, and large-scale antenna
  • Various technologies such as advanced small cell, cloud radio access network (cloud RAN), ultra-dense networks, Device to Device communication (D2D), wireless backhaul, moving networks, cooperative communication, Coordinated Multi-Points (CoMP), and interference cancellation, have been developed for 5G communication systems.
  • technologies such as hybrid frequency shift keying (FSK) and quadrature amplitude modulation (QAM) Modulation (FQAM) and Sliding Window Superposition Coding (SWSC) based on Advanced Coding Modulation (ACM) and Non Orthogonal Multiple Access (NOMA) and Sparse Code Multiple Access (SCMA) based on Filter Bank Multi Carrier (FBMC), have been developed for 5G communication systems.
  • FSK hybrid frequency shift keying
  • QAM quadrature amplitude modulation
  • SWSC Sliding Window Superposition Coding
  • ACM Advanced Coding Modulation
  • NOMA Non Orthogonal Multiple Access
  • SCMA Sparse Code Multiple Access
  • the Internet is evolving from a human-centered network in which humans generate and consume information to an Internet of Things (IoT) network in which distributed components such as objects transmit, receive, and process information.
  • IoT Internet of Things
  • IoE Internet of Everything
  • sensing technology wired/wireless communication
  • network infrastructure network infrastructure
  • service interface technology service interface technology
  • MTC Machine Type Communication
  • an intelligent Internet Technology (IT) service is provided to collect and analyze data generated by connected objects to create new value for human life.
  • the IoT may be applied to various fields, such as smart homes, smart buildings, smart cities, smart cars/connected cars, smart grids, health care, smart appliances, and advanced medical services, through convergence and combination between existing Information Technology (IT) and various industries.
  • technologies such as a sensor network, M2M, and MTC
  • technologies such as beam forming, MIMO, and array antenna, which are 5G communication technologies.
  • Applying a cloud radio access network (CRAN) as big data processing technology is also an example of the convergence of 5G technology and IoT technology.
  • CRAN cloud radio access network
  • the disclosure provides an apparatus and method capable of effectively providing a service in a mobile communication system.
  • a method performed by a terminal in a wireless communication system includes: receiving, from a base station, a radio resource control (RRC) reconfiguration message including configuration information for conditional handover; identifying a cell for conditional handover based on the configuration information for conditional handover; and triggering a packet data convergence protocol (PDCP) status report for a radio bearer, according to an execution of a conditional handover for the identified cell for conditional handover.
  • RRC radio resource control
  • PDCP packet data convergence protocol
  • various functions described below can be implemented or supported by one or more computer programs, each of which is formed from computer readable program code and embodied in a computer readable medium.
  • application and “program” refer to one or more computer programs, software components, sets of instructions, procedures, functions, objects, classes, instances, related data, or a portion thereof adapted for implementation in a suitable computer readable program code.
  • computer readable program code includes any type of computer code, including source code, object code, and executable code.
  • computer readable medium includes any type of medium capable of being accessed by a computer, such as read only memory (ROM), random access memory (RAM), a hard disk drive, a compact disc (CD), a digital video disc (DVD), or any other type of memory.
  • ROM read only memory
  • RAM random access memory
  • CD compact disc
  • DVD digital video disc
  • a “non-transitory” computer readable medium excludes wired, wireless, optical, or other communication links that transport transitory electrical or other signals.
  • a non-transitory computer readable medium includes media where data can be permanently stored and media where data can be stored and later overwritten, such as a rewritable optical disc or an erasable memory device.
  • FIG. 1A shows a structure of a long term evolution (LTE) system to which an embodiment of the disclosure may be applied;
  • LTE long term evolution
  • FIG. 1B shows a radio protocol architecture of an LTE system to which an embodiment of the disclosure may be applied
  • FIG. 1C shows a structure of a next-generation mobile communication system to which an embodiment of the disclosure may be applied
  • FIG. 1D shows a radio protocol architecture of a next-generation mobile communication system to which an embodiment of the disclosure may be applied;
  • FIG. 1E is a view for describing a procedure in which a next generation Node B (gNB) according to an embodiment of the disclosure releases a connection of a user equipment (UE) for the UE to change from a Radio Resource Control (RRC) connected mode to an RRC idle mode and a procedure in which the UE sets up a connection to the gNB to change from the RRC idle mode to the RRC connected mode;
  • gNB next generation Node B
  • RRC Radio Resource Control
  • FIG. 1F shows a handover procedure in a next-generation mobile communication system according to an embodiment of the disclosure
  • FIG. 1G shows a conditional handover procedure according to an embodiment of the disclosure
  • FIG. 1H shows operations of a conditional handover procedure of a UE according to an embodiment of the disclosure
  • FIG. 1I shows a structure of a UE or a wireless node according to an embodiment of the disclosure
  • FIG. 1J shows a block configuration of a Transmission/Reception Point (TRP) or a wireless node in a wireless communication system according to an embodiment of the disclosure
  • FIG. 2A shows a structure of an LTE system to which an embodiment of the disclosure may be applied
  • FIG. 2B shows a radio protocol architecture of an LTE system to which an embodiment of the disclosure may be applied
  • FIG. 2C shows a structure of a next-generation mobile communication system to which an embodiment of the disclosure may be applied
  • FIG. 2D shows a radio protocol architecture of a next-generation mobile communication system to which an embodiment of the disclosure may be applied;
  • FIG. 2E is a view for describing a procedure in which a gNB according to an embodiment of the disclosure releases a connection of a UE for the UE to change from an RRC connected mode to an RRC idle mode and a procedure in which the UE sets up a connection to the gNB to change from the RRC idle mode to the RRC connected mode;
  • FIG. 2F shows a handover procedure in a next-generation mobile communication system according to an embodiment of the disclosure
  • FIG. 2G shows RLC header formats that may be applied in a 1-1 embodiment which are operations of a reception RLC layer in which a RLC UM mode according to an embodiment of the disclosure is set;
  • FIG. 2H shows RLC header formats that may be applied in a 1-2 embodiment which are operations of a reception RLC layer in which an RLC AM mode according to an embodiment of the disclosure is set;
  • FIG. 2IA shows RLC header formats that may be applied in a 2-1 embodiment, and are operations of a reception RLC layer in which an RLC UM mode according to an embodiment of the disclosure is set;
  • FIG. 2IB shows RLC header formats that may be applied in a 2-1 embodiment, and are operations of a reception RLC layer in which an RLC UM mode according to an embodiment of the disclosure is set;
  • FIG. 2J shows RLC header formats that may be applied in a 2-2 embodiment which are operations of a reception RLC layer in which an RLC AM mode according to an embodiment of the disclosure is set;
  • FIG. 2K shows operations of a reception RLC layer of a UE according to an embodiment of the disclosure
  • FIG. 2L shows a structure of a UE or a wireless node according to an embodiment of the disclosure.
  • FIG. 2M shows a block configuration of a TRP or a wireless node in a wireless communication system according to an embodiment of the disclosure.
  • FIGS. 1A through 2M discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged system or device.
  • the expression “at least one of a, b or c” indicates only a, only b, only c, both a and b, both a and c, both b and c, all of a, b, and c, or variations thereof.
  • Examples of a terminal may include a User Equipment (UE), a Mobile Station (MS), a cellular phone, a smartphone, a computer, a multimedia system capable of performing a communication function, or the like.
  • UE User Equipment
  • MS Mobile Station
  • a cellular phone a smartphone
  • smartphone a computer
  • multimedia system capable of performing a communication function, or the like.
  • a controller may also be referred to as a processor.
  • a layer (or a layer) may also be referred to as an entity.
  • the terms used to identify connected nodes the terms indicating network entities, the terms indicating messages, the terms indicating interfaces between network objects, the terms indicating various identification information, etc. are examples for convenience of description. Accordingly, an embodiment of the disclosure is not limited to these terms, and other terms having the equivalent technical meaning may be used.
  • an embodiment of the disclosure uses terms and names defined in a 3 rd Generation Partnership Project Long Term Evolution (3GPP LTE) standard and/or a 3 rd Generation Partnership Project New Radio (3GPP NR) standard.
  • 3GPP LTE 3 rd Generation Partnership Project Long Term Evolution
  • 3GPP NR 3 rd Generation Partnership Project New Radio
  • an embodiment of the disclosure is not limited to the terms and names, and may be applied in the same way to a system based on another standard.
  • evolved Node B (eNB) is mixed with next generation Node B (gNB) for convenience of description. That is, a base station mentioned as an eNB may represent a gNB.
  • the term UE may represent other wireless communication devices, as well as mobile phones, NB-IoT devices, and sensors.
  • a post LTE communication system that is, a 5 th Generation (5G) communication system needs to freely reflect various requirements from users and service providers. Therefore, the 5G communication system needs to support services satisfying various requirements simultaneously. Examples of services considered for the 5G communication system are Enhanced Mobile BroadBand (eMBB), massive Machine Type Communication (mMTC), and Ultra Reliability Low Latency Communication (URLLC).
  • eMBB Enhanced Mobile BroadBand
  • mMTC massive Machine Type Communication
  • URLLC Ultra Reliability Low Latency Communication
  • the eMBB is aimed to provide a data rate that is higher than a data rate supported by existing LTE, LTE-A or LTE-Pro.
  • the eMBB needs to provide a peak data rate of 20 Gbps in a downlink and a peak data rate of 10 Gbps in an uplink with respect to a base station.
  • the 5G communication system needs to provide a high user perceived data rate, while providing a peak data rate.
  • the 5G communication system requires an improvement of various transmission/reception technologies including enhanced Multi Input Multi Output (MIMO) transmission technology.
  • MIMO Multi Input Multi Output
  • existing LTE transmits signals by using a transmission bandwidth of maximally 20 MHz in a 20 GHz band, whereas the 5G communication system uses a wider frequency bandwidth than 20 MHz in a frequency band of 3 to 6 GHz or more, thereby satisfying a required data rate.
  • mMTC is considered to support an application service such as Internet of Thing (IoT) in the 5G communication system.
  • the mMTC may require supporting connections of massive UEs (a large number of UEs) in a cell, UE coverage enhancement, an improved battery lifetime, UE cost reduction, etc. to efficiently provide the IoT.
  • the IoT is connected to various sensors and devices to provide a communication function. Therefore, the IoT needs to support a large number of UEs (for example, 1,000,000 UEs/km 2 ) in a cell.
  • a UE supporting the mMTC has a high probability of being located in a shadow zone such as the basement of a building, which is not covered by a cell, due to its service characteristics, the UE may require wide coverage compared to those required by other services that a 5G communication system provides.
  • the UE supporting the mMTC needs to be a low-cost UE, and requires a long battery lifetime of about 10 years to 15 years because it has difficulties in frequently replacing the batteries.
  • URLLC which is a mission-critical cellular-based wireless communication service may be used in services of remote control for robots or machinery, industrial automation, unmanned aerial vehicle, remote health care, emergency alert, etc. Accordingly, communication provided by the URLLC may need to satisfy ultra-low latency and ultra reliability. For example, a service supporting the URLLC needs to satisfy air interface latency that is shorter than 0.5 milliseconds, and simultaneously, the service may have a requirement of a packet error rate that is equal to or lower than 10 ⁇ 5 .
  • the 5G system needs to provide a smaller Transmit Time Interval (TTI) than other services, and simultaneously, the 5G system requires a design of assigning a wide resource in a frequency band to secure reliability of a communication link.
  • TTI Transmit Time Interval
  • Three services (that is, eMBB, URLLC, and mMTC) which are considered in the above-described 5G communication system may be multiplexed in a system and transmitted.
  • the services may use different transmission/reception methods and different transmission/reception parameters.
  • the above-described mMTC, URLLC, and eMBB are examples of different services types, and service types to which the disclosure is applied are not limited to the above-described examples.
  • embodiments of the disclosure are described based on examples of LTE, LTE-A, LTE Pro, or a 5G (or NR, next-generation mobile communication) system, however, the embodiments of the disclosure may be applied to other communication systems having similar technical backgrounds or channel types. Also, the embodiments of the disclosure may be applied to other communication systems through slight modifications within a range that does not greatly deviate from the scope of the disclosure, under a determination of a person having a skilled technical knowledge.
  • the disclosure proposes a conditional handover method that is efficient in a next-generation mobile communication system.
  • an issue that a source gNB starts late data forwarding to a target gNB and an issue caused when a source gNB fails to recognize a connection release time of a UE may be overcome.
  • the next-generation mobile communication system may support various handover methods for reducing a data interruption time that may be caused when a handover occurs.
  • a source gNB sets a condition for a UE together with a plurality of target gNB candidates, and the UE checks signals from the target gNB candidates based on the condition to select a target gNB candidate from among the plurality of target gNB candidates as a target gNB, thereby starting a handover procedure.
  • the source gNB is not capable of expecting a target gNB to which the UE will perform a handover, the source gNB starts late data forwarding to the target gNB, and also the source gNB may not recognize a time at which the UE releases a connection to the source gNB.
  • FIGS. 1A to 1J a method and apparatus for performing a handover procedure according to an embodiment of the disclosure will be described with reference to FIGS. 1A to 1J .
  • FIG. 1A shows a structure of an LTE system to which an embodiment of the disclosure may be applied.
  • a radio access network of the LTE system may be configured with next-generation Evolved Nodes B (ENBs) (hereinafter, also referred to as Nodes B or base stations) 1 a - 05 , 1 a - 10 , 1 a - 15 , and 1 a - 20 , a Mobility Management Entity (MME) 1 a - 25 , and a Serving-Gateway (S-GW) 1 a - 30 .
  • a UE hereinafter, also referred to as a terminal
  • a UE hereinafter, also referred to as a terminal
  • 1 a - 35 may be connected to an external network through the ENBs 1 a - 05 to 1 a - 20 and the S-GW 1 a - 30 .
  • the ENBs 1 a - 05 to 1 a - 20 may correspond to existing nodes B of a Universal Mobile Telecommunication System (UMTS).
  • the ENBs 1 a - 05 to 1 a - 20 may be connected to the UE 1 a - 35 through a wireless channel, and perform more complicated functions than the existing nodes B.
  • a device for performing scheduling by collecting status information of UEs, such as buffer statuses of UEs, available transmission power states of UEs, channel states of UEs, etc., is needed.
  • the ENBs 1 a - 05 to 1 a - 20 may function as such a device.
  • An ENB may generally control a plurality of cells.
  • the LTE system uses, as radio access technology, Orthogonal Frequency Division Multiplexing (OFDM), for example, in a bandwidth of 20 MHz.
  • OFDM Orthogonal Frequency Division Multiplexing
  • AMC Adaptive Modulation & Coding
  • the S-GW 1 a - 30 which is a device for providing data bearers, may generate or remove data bearers according to a control of the MME 1 a - 25 .
  • the MME 1 a - 25 may be in charge of various control functions, as well as a mobility management function for UEs, and may be connected to a plurality of ENBs.
  • FIG. 1B shows a radio protocol architecture of an LTE system to which an embodiment of the disclosure may be applied.
  • radio protocols of the LTE system may include Packet Data Convergence Protocols (PDCPs) 1 b - 05 and 1 b - 40 , Radio Link Control (RLC) 1 b - 10 and 1 b - 35 , and Medium Access Control (MAC) 1 b - 15 and 1 b - 30 of an UE and an ENB.
  • the PDCPs 1 b - 05 and 1 b - 40 may be in charge of operations of IP header compression/restoration. Main functions of the PDCPs 1 b - 05 and 1 b - 40 may be summarized as follows.
  • the RLC 1 b - 10 and 1 b - 35 may reconstruct a PDCP Packet Data Unit (PDU) to an appropriate size to perform an ARQ operation, etc.
  • PDU Packet Data Unit
  • the MAC 1 b - 15 and 1 b - 30 may be connected to several RLC layers configured in the UE, and perform an operation of multiplexing RLC PDUs into a MAC PDU and demultiplexing RLC PDUs from a MAC PDU.
  • Main functions of the MAC 1 b - 15 and 1 b - 30 may be summarized as follows.
  • Physical layers (PHY) 1 b - 20 and 1 b - 25 may perform an operation of performing channel coding and modulation on upper layer data to generate an OFDM symbol and transmitting the OFDM symbol through a wireless channel, or an operation of demodulating an OFDM symbol received through the wireless channel, performing channel decoding on the OFDM symbol, and transferring the channel-decoded OFDM symbol to an upper layer.
  • FIG. 1C shows a structure of a next-generation mobile communication system to which an embodiment of the disclosure may be applied.
  • a radio access network of a next-generation mobile communication system may be configured with a next-generation New Radio Node B (NR gNB) (also, referred to as a NR base station) 1 c - 10 and a New Radio Core Network (NR CR) 1 c - 05 .
  • NR gNB next-generation New Radio Node B
  • NR CR New Radio Core Network
  • a New Radio User Equipment (NR UE) (also, referred to as a UE) 1 c - 15 may be connected to an external network through the NR gNB 1 c - 10 and the NR CN 1 c - 05 .
  • the NR gNB 1 c - 10 may correspond to an Evolved Node B (eNB) of an existing LTE system.
  • the NR gNB 1 c - 10 may be connected to the NR UE 1 c - 15 through a wireless channel, and provide a more excellent service than an existing node B.
  • a device for performing scheduling by collecting status information of UEs such as buffer statuses of UEs, available transmission power states of UEs, channel states of UEs, etc., is needed.
  • the NR gNB 1 c - 10 may function as such a device.
  • a NR gNB may generally control a plurality of cells.
  • OFDM as radio access technology may be combined with beam-forming technology, while providing an existing maximum bandwidth or more.
  • AMC of determining a modulation scheme and a channel coding rate according to a channel state of a UE may be applied.
  • the NR CN 1 c - 05 may perform functions, such as mobility support, bearer setup, Quality of Service (QoS) setup, etc.
  • the NR CN 1 c - 05 may be in charge of various control functions, as well as a mobility management function for UEs, and may be connected to a plurality of base stations.
  • the next-generation mobile communication system may interwork with an existing LTE system, and the NR CN 1 c - 05 may be connected to the MME 1 c - 25 through a network interface.
  • the MME 1 c - 25 may be connected to an eNB 1 c - 30 which is an existing base station.
  • FIG. 1D shows a radio protocol architecture of a next-generation mobile communication system to which an embodiment of the disclosure may be applied.
  • radio protocols of the next-generation mobile communication system may include NR SDAPs 1 d - 01 and 1 d - 45 , NR PDCPs 1 d - 05 and 1 d - 40 , NR RLC 1 d - 10 and 1 d - 35 , and NR MAC 1 d - 15 and 1 d - 30 of an UE and a NR gNB.
  • Main functions of the NR SDAPs 1 d - 01 and 1 d - 45 may include some of the following functions.
  • the UE may receive, as an RRC message, a setting about whether to use a header of the SDAP layer or whether to use a function of the SDAP layer for each PDCP layer, for each bearer, or for each logical channel.
  • the SDAP header capable of indicating the UE to update or reset mapping information about a QoS flow and a data bearer of a uplink and a downlink with a 1-bit indicator NAS reflective QoS for a NAS reflective QoS setting and a 1-bit indicator AS reflective QoS for an AS reflective QoS setting of the SDAP header may include QoS flow ID information representing QoS.
  • QoS information described above may be used as data processing priority, scheduling information, etc. for supporting a stable service.
  • Main functions of the NR PDCPs 1 d - 05 and 1 d - 40 may include some of the following functions.
  • the reordering function of a NR PDCP device among the above-mentioned functions means a function of reordering PDCP PDUs received from a lower layer in order based on PDCP Sequence Numbers (SNs), and may include a function of transferring data to an upper layer in the reordered order.
  • the reordering function of the NR PDCP device may include a function of directly transferring data regardless of order, a function of reordering and recording lost PDCP PDUs, a function of sending a status report for lost PDCP PDUs to a transmitter, and a function of requesting retransmission of lost PDCP PDUs.
  • Main functions of the NR RLC 1 d - 10 and 1 d - 35 may include some of the following functions.
  • the in-sequence delivery function of a NR RLC device among the above-mentioned functions means a function of transferring RLC SDUs received from a lower layer in order to an upper layer, and may include a function of reassembling, when a RLC SDU is segmented into several RLC SDUs and received, the RLC SDUs and transferring a result of the reassembling, a function of reordering received RLC PDUs based on RLC SNs or PDCP SNs, a function of reordering and recording lost RLC PDUs, a function of sending a status report for lost RLC PDUs to a transmitter, a function of requesting retransmission of lost RLC PDUs, a function of transferring, when there are lost RLC SDUs, RLC SDUs before the lost RLC SDUs in order to the upper layer, a function of transferring, when a preset timer has been expired although there are lost RLC SDUs, all RLC
  • RLC PDUs may be processed in order (in arrival order, regardless of SNs or order of SNs) in which they are received, and transferred to the PDCP device out of sequence delivery, and in the case of segments, segments which have been stored in a buffer or which are to be received later may be received and reconstructed as a compete RLC PDU and then processed and transferred to the PDCP device.
  • a NR RLC layer as described above may include no concatenation function, and the above-described function may be performed in a NR MAC layer or replaced with a multiplexing function of the NR MAC layer.
  • the out-of-sequence delivery function of the NR RLC device as described above means a function of transferring RLC SDUs received from a lower layer to the upper layer regardless of order, and may include a function of reassembling, when a RLC SDU is segmented into several RLC SDUs and received, the RLC SDUs and transferring a result of the reassembling, and a function of storing and ordering RLC SNs or PDCP SNs of the received RLC PDUs and recording lost RLC PDUs.
  • the NR MAC 1 d - 15 and 1 d - 30 may be connected to several NR RLC layers configured in the UE, and main functions of the NR MAC 1 d - 15 and 1 d - 30 may include some of the following functions.
  • NR PHY layers 1 d - 20 and 1 d - 25 may perform an operation of performing channel coding and modulation on upper layer data to generate an OFDM symbol and transferring the OFDM symbol through a wireless channel, or performing demodulation and channel decoding on an OFDM symbol received through the wireless channel and transferring a result of the modulation and channel decoding to an upper layer.
  • FIG. 1E is a view for describing a procedure in which a gNB according to an embodiment of the disclosure releases a connection of an UE for the UE to change from an RRC connected mode to an RRC idle mode and a procedure in which the UE sets up a connection to the gNB to change from the RRC idle mode to the RRC connected mode.
  • the gNB may transmit an RRCConnectionRelease message to the UE to change the UE to the RRC idle mode, in operation 1 e - 01 .
  • the UE (hereinafter, also referred to as an idle mode UE) in which no connection is currently established may perform, when data to be transmitted is generated, an RRC connection establishment process together with the gNB.
  • the UE may establish reverse transmission synchronization with the gNB through a random access process, and transmit an RRCConnectionRequest message to the gNB, in operation 1 e - 05 .
  • the RRCConnectionRequest message may include an identifier of the UE and a cause establishmentCause for connection establishment.
  • the gNB may transmit an RRCConnectionSetup message to the UE to enable the UE to establish an RRC connection, in operation 1 e - 10 .
  • the RRCConnectionSetup message may include RRC connection configuration information, etc.
  • the RRCConnectionSetup message may include at least one information of bearer configuration information of the UE, configuration information of a PHY layer, configuration information of a MAC layer, configuration information of a RLC layer, configuration information of a PDCP layer, or configuration information of a SDAP layer.
  • the configuration information of the PDCP layer may include an indicator indicating whether to trigger a PDCP status report in an RLC UM (unacknowledged mode) mode or an RLC AM (acknowledged mode) mode.
  • the indicator may be an indicator indicating the PDCP layer to generate, configure, and transmit a PDCP status report when a PDCP re-establishment procedure is performed.
  • the UE may trigger, configure, and transmit a PDCP status report for a bearer corresponding to the PDCP layer.
  • the UE may trigger, configure, and transmit a PDCP status report at the PDCP layer in the case that a conditional handover is indicated.
  • the UE may trigger and configure a PDCP status report at the PDCP layer and transmit the PDCP status report to a target gNB in the case that a handover is indicated.
  • the UE may trigger and configure a PDCP status report at the PDCP layer and transmit the PDCP status report to a source gNB in the case that a handover is indicated.
  • An RRC connection is also referred to as a Signaling Radio Bearer (SRB), and may be used to transmit and receive an RRC message which is a control message between a UE and a gNB.
  • the UE which has established an RRC connection may transmit an RRCConnetionSetupComplete message to the gNB, in operation 1 e - 15 .
  • the RRCConnetionSetupComplete message may include a SERVICE REQUEST message as a control message through which the UE requests the MME to set a bearer for a preset service.
  • the gNB may transmit the SERVICE REQUEST message included in the RRCConnetionSetupComplete message to an Access and Mobility Management Function (AMF), in operation 1 e - 20 , and the AMF may determine whether to provide the preset service requested by the UE.
  • AMF Access and Mobility Management Function
  • the AMF may transmit an INITIAL CONTEXT SETUP REQUEST message to the gNB, in operation 1 e - 25 .
  • the INITIAL CONTEXT SETUP REQUEST message may include QoS information to be applied for a Data Radio Bearer (DRB) setting, security-related information (for example, a security key or a security algorithm) to be applied to the DRB, etc.
  • DRB Data Radio Bearer
  • the gNB may exchange a SecurityModeCommand message with a SecurityModeComplete message to set security with the UE, in operations 1 e - 30 and 1 e - 35 .
  • the gNB may transmit an RRCConnectionReconfiguration message to the UE, in operation 1 e - 40 .
  • the RRCConnectionReconfiguration message may include bearer configuration information, configuration information of the PHY layer, configuration information of the MAC layer, configuration information of the RLC layer, configuration information of the PDCP layer, or configuration information of the SDAP layer.
  • the configuration information of the PDCP layer may include an indicator indicating whether to trigger a PDCP status report in the RLC UM mode or the RLC AM mode.
  • the indicator may indicate the PDCP layer to generate, configure, and transmit a PDCP status report when a PDCP re-establishment procedure is performed.
  • the UE may trigger, configure, and transmit a PDCP status report for a bearer corresponding to the PDCP layer.
  • the indicator when the indicator is set, the UE may trigger and configure a PDCP status report at the PDCP layer and transmit the PDCP status report, in the case that a conditional handover is indicated.
  • the UE may trigger and configure a PDCP status report at the PDCP layer and transmit the PDCP status report to a target gNB, in the case that a handover is indicated.
  • the UE may trigger and configure a PDCP status report at the PDCP layer and transmit the PDCP status report to a source gNB, in the case that a conditional handover is indicated.
  • the RRCConnectionReconfiguration message may include configuration information of a DRB by which user data is to be processed, and the UE may apply the configuration information of the DRB to set up the DRB, and transmit an RRCConnectionReconfigurationComplete message to the gNB, in operation 1 e - 45 .
  • the gNB may set up the DRB with the UE and then transmit an initial context setup complete message to the AMF, in operation 1 e - 50 .
  • the AMF may receive the initial context setup complete message, and perform a session management procedure with a User Plane Function (UPF) to establish a PDU session, in operation 1 e - 60 .
  • UPF User Plane Function
  • the UE may transmit/receive data to/from the gNB through the UPF, in operations 1 e - 65 and 1 e - 70 .
  • a general data transmission process may be configured with three operations of RCC connection setup, security setup, and DRB setup. Also, the gNB may transmit an RRCConnectionReconfiguration message to newly set up, add, or change a setting to the UE for a certain reason, in operation 1 e - 75 .
  • the bearer may have a meaning including a SRB and a DRB, wherein the SRB means a Signaling Radio Bearer and the DRB means a Data Radio Bearer.
  • the SRB may be mainly used to transmit and receive RRC messages of the RRC layer, and the DRB may be mainly used to transmit and receive user layer data.
  • UM DRB means a DRB using the RLC layer operating in an Unacknowledged Mode (UM)
  • AM DRB means a DRB using the RLC layer operating in an Acknowledged Mode (AM).
  • FIG. 1F shows a handover procedure in a next-generation mobile communication system according to an embodiment of the disclosure.
  • a UE 1 f - 01 which is in the RRC connected mode may send a cell measurement report to a source gNB 1 f - 02 periodically or when a preset event is satisfied, in operation 1 f - 05 .
  • the source gNB 1 f - 02 may determine whether to perform a handover of the UE 1 f - 01 to an adjacent cell based on the cell measurement information.
  • the handover may be a technique of changing a source gNB providing a service to a UE being in a connected mode to another gNB (or another cell in the same gNB).
  • the source gNB 1 f - 02 may send a handover (HO) request message to a new gNB, that is, a target gNB 1 f - 03 that is to provide a service to the UE 1 f - 01 , thereby requesting a handover, in operation 1 f - 10 .
  • a new gNB that is, a target gNB 1 f - 03 that is to provide a service to the UE 1 f - 01 , thereby requesting a handover, in operation 1 f - 10 .
  • the target gNB 1 f - 03 may transmit a HO request Ack message to the source gNB 1 f - 02 , in operation 1 f - 15 .
  • the source gNB 1 f - 02 may transmit a HO command message to the UE 1 f - 01 , in operation 1 f - 20 .
  • the source gNB 1 f - 02 may transfer the HO command message to the UE 1 f - 01 by using an RRC Connection Reconfiguration message, in operation 1 f - 20 .
  • the UE 1 f - 01 may stop data transmission/reception to/from the source gNB 1 f - 02 , and start a T304 timer, in operation 1 f - 25 .
  • the T304 timer may return the UE 1 f - 01 to its original setting and change the UE 1 f - 01 to an RRC idle state, when the UE 1 f - 01 fails to perform a handover to the target gNB 1 f - 03 within a preset time period.
  • the source gNB 1 f - 02 may transfer a sequence number (SN) status about a transmission/reception status of uplink or downlink data to the target gNB 1 f - 03 , and when there is downlink data, the source gNB 1 f - 02 may transfer the downlink data to the target gNB 1 f - 03 , in operations 1 f - 30 and 1 f - 35 .
  • SN sequence number
  • the UE 1 f - 01 may attempt a random access to a target cell indicated from the source gNB 1 f - 02 , in operation 1 f - 40 .
  • the random access may be aimed to notify the target cell that the UE 1 f - 01 moves through a handover, while synchronizing an uplink.
  • the UE 1 f - 01 may transmit a preamble corresponding to a preamble ID received from the source gNB 1 f - 02 or a randomly selected preamble ID to the target cell.
  • the UE 1 f - 01 may monitor whether a Random Access Response (RAR) message is transmitted from the target cell.
  • RAR Random Access Response
  • a time period in which the UE 1 f - 01 monitors whether the RAR message is transmitted is referred to as a RAR window.
  • the UE 1 f - 01 may transmit a HO complete message as an RRC Reconfiguration Complete message to the target gNB 1 f - 03 , in operation 1 f - 55 .
  • the UE 1 f - 01 may stop the T304 timer, in operation 1 f - 50 .
  • the target gNB 1 f - 03 may request a core network 1 f - 04 to correct paths in operations 1 f - 60 and 1 f - 65 , and notify the source gNB 1 f - 02 of discarding UE context of the UE 1 f - 01 , in operation 1 f - 70 .
  • the UE 1 f - 01 may attempt to receive data with respect to the target gNB 1 f - 03 from when the RAR window starts, and after the RAR message is received, the UE 1 f - 01 may transmit the RRCConnectionReconfigurationComplete message to the target gNB 1 f - 03 and start data transmission/reception to/from the target gNB 1 f - 30 .
  • the source gNB 1 f - 02 may determine that a path of downlink data for the UE 1 f - 01 has changed to the target gNB 1 f - 03 , and perform forwarding of the final data to the target gNB 1 f - 30 .
  • the core network 1 f - 04 may include at least one of a MME, a S-GW, or an ANTE, and further include at least one of a UPF or a SMF.
  • the source gNB 1 f - 02 transmits the HO command message (for example, an RRC Reconfiguration message) to the UE 1 f - 01
  • the HO command message for example, an RRC Reconfiguration message
  • at least one of information about a target gNB to which the UE 1 f - 01 needs to perform a handover, information about a random access transmission resource for a cell, preamble information, bearer configuration information, or cell information may be set in the HO command message.
  • the HO command message may include an indicator defined to indicate what kind of handover the UE 1 f - 01 needs to perform.
  • the source gNB 1 f - 02 may define indicators for a plurality of handover methods, and set one of the defined indicators such that the UE 1 f - 01 perform a handover method corresponding to the set indicator.
  • the plurality of handover methods may include at least one method of a RACH-less handover method, a make before break (MBB) handover method, an enhanced make before break (eMBB) method, or a conditional handover method.
  • MBB make before break
  • eMBB enhanced make before break
  • the HO command message may include an indicator indicating whether or not the UE 1 f - 01 generates a PDCP status report for each bearer (UM DRB or AM DRB) or the PDCP layer and transmits the PDCP status report to the source gNB 1 f - 02 or the target gNB 1 f - 03 .
  • UM DRB or AM DRB UM DRB or AM DRB
  • FIG. 1G shows a conditional handover procedure according to an embodiment of the disclosure.
  • a UE 1 g - 01 which is in the RRC connected mode may send a cell measurement report to a source gNB 1 g - 02 periodically or when a preset event is satisfied, in operation 1 g - 05 .
  • the source gNB 1 g - 02 may determine whether to perform a conditional handover of the UE 1 g - 01 to adjacent cells, based on the cell measurement information.
  • the conditional handover may be a technique of changing a source gNB providing a service to a UE being in a connected mode to another gNB (or another cell in the same gNB).
  • a plurality of target gNB candidates and conditions for determining a target gNB may be set for a UE to enable the UE to select, as a target gNB, a target gNB candidate from among the plurality of target gNB candidates according to the set conditions and perform a handover.
  • various conditions such as a greater frequency signal intensity than a threshold value, a first synchronized signal frequency, a determination according to a UE's implementation without any condition, etc. may be set.
  • the source gNB 1 g - 02 may send HO request messages to a plurality of target gNB candidates including a plurality of new gNBs that are to provide a service to the UE 1 g - 01 , that is, a plurality of target gNBs Target gNB 1 1 g - 03 and Target gNB 2 1 g - 04 , thereby requesting a handover, in operation 1 g - 10 .
  • the plurality of target gNBs 1 g - 03 and 1 g - 04 may transmit HO request Ack messages to the source gNB 1 g - 02 , in operation 1 g - 15 .
  • the source gNB 1 g - 02 may transmit a HO command message to the UE 1 g - 01 , in operation 1 g - 20 .
  • the source gNB 1 g - 02 may transfer the HO command message to the UE 1 g - 01 by using an RRC Connection Reconfiguration message, in operation 1 g - 20 .
  • the source gNB 1 g - 02 transmits the HO command message (for example, an RRC Reconfiguration message) to the UE 1 g - 01
  • the HO command message for example, an RRC Reconfiguration message
  • at least one of information about the plurality of target gNBs 1 g - 03 and 1 g - 04 to which the UE 1 g - 01 needs to perform a handover information about a random access transmission resource for a cell, preamble information, bearer configuration information, or cell information may be set in the HO command message.
  • the HO command message may include an indicator defined to indicate what kind of handover the UE 1 g - 01 needs to perform.
  • the source gNB 1 g - 02 may define indicators for a plurality of handover methods, and set one of the defined indicators such that the UE 1 g - 01 performs a handover method corresponding to the set indicator.
  • the plurality of handover methods may include at least one method of a RACH-less handover method, a MBB handover method, an eMBB method, or a conditional handover method.
  • the HO command message may include an indicator indicating whether or not the UE 1 g - 01 generates a PDCP status report for each bearer (UM DRB or AM DRB) or the PDCP layer and transmits the PDCP status report to the source gNB 1 g - 02 or the target gNB.
  • UM DRB or AM DRB UM DRB or AM DRB
  • the HO command message may include a condition for enabling the UE 1 g - 01 to select a target gNB from among the plurality of target gNBs 1 g - 03 and 1 g - 04 .
  • a condition for enabling the UE 1 g - 01 to select the target gNB various conditions, such as a greater frequency signal intensity than a threshold value, a first synchronized signal frequency, a determination according to implementation of the UE 1 g - 01 without any condition, etc. may be set.
  • the UE 1 g - 01 may start a T304 timer and perform a conditional handover procedure. More specifically, the UE 1 g - 01 may start a cell re-selection procedure or a cell search procedure for the plurality of target gNBs 1 g - 03 and 1 g - 04 or a plurality of frequencies according to the condition included in the HO command message or the implementation of the UE 1 g - 01 , in operation 1 g - 25 .
  • the UE 1 g - 01 may attempt a random access to the determined target gNB 1 g - 03 or the determined cell (also, referred to as a target cell, in operation 1 g - 40 .
  • the random access may be aimed to inform the target cell that the UE 1 g - 01 moves through a handover, while synchronizing an uplink.
  • the UE 1 g - 01 may transmit a preamble corresponding to a preamble ID received from the source gNB 1 g - 02 or a randomly selected preamble ID to the target cell.
  • the UE 1 g - 01 may monitor whether a RAR message is transmitted from the target cell.
  • a time period in which the UE 1 g - 01 monitors whether the RAR message is transmitted is referred to as a RAR window.
  • the UE 1 g - 01 may transmit a HO complete message as an RRCConnectionReconfigurationComplete message to the target gNB 1 g - 03 , in operation 1 g - 55 .
  • the UE 1 g - 01 may stop the T304 timer, in operation 1 g - 50 .
  • the target gNB 1 g - 03 may request route correction, and notify the source gNB 1 g - 02 of discarding UE context of the UE 1 g - 01 . Accordingly, the UE 1 g - 01 may attempt to receive data with respect to the target gNB 1 g - 03 from when the RAR window starts, and after the RAR message is received, the UE 1 g - 01 may transmit the RRCConnectionReconfigurationComplete message to the target gNB 1 g - 03 and start data transmission/reception to/from the target gNB 1 g - 30 .
  • a time at which the UE 1 g - 01 releases a connection to the source gNB 1 g - 02 may be determined by the UE 1 g - 01 based on a first condition described below.
  • the first condition is that when at least one condition among a plurality of conditions described below is satisfied, the UE 1 g - 01 may release a connection to the source gNB 1 g - 02 .
  • conditional handover method according to an embodiment of the disclosure as described above with reference to FIG. 1G may have two issues.
  • a first issue of the issues is that the source gNB 1 g - 02 is not capable of accurately recognizing a time at which the UE 1 g - 01 releases a connection to the source gNB 1 g - 02 , in the conditional handover method.
  • the reason is because, in a conditional handover, the UE 1 g - 01 selects a gNB from among a plurality of target gNBs according to a preset condition and itself releases a connection to the source gNB 1 g - 02 according to the first condition described above.
  • the source gNB 1 g - 02 may transmit downlink data to the UE 1 g - 01 even after the UE 1 g - 01 releases a connection to the source gNB 1 g - 02 . Therefore, massive downlink data loss may occur.
  • a second issue of the issues is that, in a conditional handover, the source gNB 1 g - 02 transmits a handover command message including conditions and configuration information about a plurality of target gNBs to the UE 1 g - 01 so that the source gNB 1 g - 02 is not capable of expecting a target gNB to which the UE 1 g - 01 will perform a handover.
  • the source gNB 1 f - 02 transmits a handover command message including information about the single target gNB 1 f - 03 to the UE 1 f - 01 , the source gNB 1 f - 02 may expect that the UE 1 f - 01 will perform a handover to the target gNB 1 f - 03 . Accordingly, referring to FIG.
  • the source gNB 1 g - 02 may transmit a handover command message to the UE 1 g - 01 , and then immediately start transmitting uplink or downlink data to the target gNB 1 f - 03 together with a transmission/reception status or a SN status of the uplink or downlink data.
  • the source gNB 1 g - 02 may be not capable of recognizing the target gNB 1 g - 03 to which the UE 1 g - 01 performs a handover until the target gNB 1 g - 03 indicates the source gNB 1 g - 02 of a successful handover of the UE 1 g - 01 .
  • the source gNB 1 g - 02 may start late performing a procedure of transmitting uplink or downlink data to the target gNB 1 f - 03 together with a transmission/reception status or a SN status of the uplink or downlink data, resulting in a transmission delay.
  • conditional handover operation for overcoming the first issue that may be occurred in a conditional handover is proposed in detail.
  • a handover procedure when the UE 1 g - 01 receives a handover command message and the handover command message indicates a conditional handover procedure, the following operations may be performed.
  • the PDCP layer may trigger a PDCP re-establishment procedure, discard previously generated data (for example, old PDCP PDU), newly apply header compression, integrity protection, or a ciphering procedure, with a new security key, to data (for example, PDCP SDU) not yet transmitted among uplink data to generate data (for example, PDCP PDU), and transmit the generated data to the target gNB after a handover to the target gNB is completed.
  • a PDCP re-establishment procedure discard previously generated data (for example, old PDCP PDU), newly apply header compression, integrity protection, or a ciphering procedure, with a new security key, to data (for example, PDCP SDU) not yet transmitted among uplink data to generate data (for example, PDCP PDU), and transmit the generated data to the target gNB after a handover to the target gNB is completed.
  • the UE 1 g - 01 may trigger and configure a PDCP status report for the corresponding bearer at the PDCP layer and transmit the PDCP status report.
  • the UE 1 g - 01 may trigger and configure a PDCP status report at the PDCP layer and transmit the PDCP status report, in the case that a conditional handover is indicated.
  • the UE 1 g - 01 may trigger and configure a PDCP status report at the PDCP layer and transmit the PDCP status report to the target gNB, in the case that a handover is indicated.
  • the UE 1 g - 01 may trigger and configure a PDCP status report at the PDCP layer and transmit the PDCP status report to the source gNB 1 g - 02 , in the case that a handover is indicated.
  • a time at which the PDCP layer triggers a PDCP status report when a PDCP status report indicator is set may be one of times included in the first condition described above, when a connection to the source gNB 1 g - 02 is released, or when a handover to the target gNB is successfully performed.
  • the target gNB may discard data (for example, PDCP PDU or PDCP SDU) of which successful transfer has been confirmed from the PDCP status report with respect to the AM bearer, and selectively retransmit data (for example, PDCP PDU or PDCP SDU) of which successful transfer has not been confirmed, thereby reducing data loss.
  • data for example, PDCP PDU or PDCP SDU
  • selectively retransmit data for example, PDCP PDU or PDCP SDU
  • the first issue of the conditional handover method proposed in an embodiment of the disclosure is that the source gNB 1 g - 02 is not capable of accurately recognizing a time at which the UE 1 g - 01 releases a connection to the source gNB 1 g - 02 .
  • the reason is because, in a conditional handover, the UE 1 g - 01 selects a target gNB from among the plurality of target gNBs 1 g - 03 and 1 g - 04 according to a preset condition and itself releases a connection to the source gNB 1 g - 02 according to the first condition described above.
  • the UE 1 g - 01 when the UE 1 g - 01 releases a connection to the source gNB 1 g - 02 according to the first condition described above, the UE 1 g - 01 may indicate the source gNB 1 g - 02 of a connection release.
  • Detailed operations of the second embodiment may be as follows.
  • the following operations may be performed.
  • the UE 1 g - 01 may configure the new MAC CE and transmit the new MAC CE to the source gNB 1 g - 02 to indicate a connection release from the source gNB 1 g - 02 and confirm whether HARQ ACK/NACK of MAC PDU included in the MAC CE is successfully transferred.
  • the UE 1 g - 01 may transmit a RLC control PDU or a PDCP control PDU newly defined for each bearer.
  • the newly defined RRC message, the newly defined indicator of the RRC message, the newly defined MAC CE, the newly defined RLC control PDU, or the newly defined PDCP control PDU may include an indicator indicating a target gNB to which the UE 1 g - 01 performs, attempts, or completes a handover among the plurality of target gNB candidates in the conditional handover method.
  • the indicator indicating the target gNB may be at least one of an identifier of the target gNB, a bitmap of the target gNB, or an indicator indicating a certain target of the plurality of target gNB candidates.
  • the second issue is that, in a conditional handover, the source gNB 1 g - 02 transmits a handover command message including conditions and configuration information about a plurality of target gNBs to the UE 1 g - 01 so that the source gNB 1 g - 02 is not capable of expecting a target gNB to which the UE 1 g - 01 will perform a handover.
  • the source gNB 1 g - 02 may be not capable of recognizing the target gNB to which the UE 1 g - 01 performs a handover until the target gNB indicates the source gNB 1 g - 02 of a successful handover of the UE 1 g - 01 . Accordingly, the source gNB 1 g - 02 may start late a procedure of transferring uplink or downlink data to the target gNB together with a transmission/reception status or a SN status of the uplink or downlink data, resulting in a transmission delay.
  • the third embodiment of the conditional handover operation for overcoming the second issue that may be generated in the conditional handover is as follows.
  • a fourth embodiment of a conditional handover operation for overcoming the second issue that may be generated in the conditional handover according to an embodiment of the disclosure is as follows.
  • the UE 1 g - 01 may perform at least one of the first embodiment, the second embodiment, the third embodiment, or the fourth embodiment of the efficient conditional handover methods proposed in the disclosure, when performing a conditional handover.
  • the UE 1 g - 01 may perform all of the first to fourth embodiments or some of the above-described embodiments together.
  • FIG. 1H shows operations of a conditional handover procedure of a UE according to an embodiment of the disclosure.
  • a UE 1 h - 01 may receive a handover command message from a source gNB, in operation 1 h - 05 .
  • the UE 1 h - 01 may check an indicator indicating a conditional handover from the handover command message, and determine whether a conditional handover is indicated, in operation 1 h - 10 .
  • the UE 1 h - 01 may perform a conditional handover method according to an embodiment of the disclosure, in operation 1 h - 15 .
  • the UE 1 h - 01 may perform at least one of the first embodiment, the second embodiment, the third embodiment, or the fourth embodiment.
  • the UE 1 h - 01 may perform all of the first to fourth embodiments or some of the above-described embodiments together.
  • FIG. 1I shows a structure of a UE or a wireless node according to an embodiment of the disclosure.
  • the UE may include a Radio Frequency (RF) processor 1 i - 10 , a baseband processor 1 i - 20 , a storage device 1 i - 30 , and a controller 1 i - 40 .
  • RF Radio Frequency
  • the RF processor 1 i - 10 may perform a function for transmitting and receiving signals through a wireless channel, such as band conversion, amplification, etc. of signals.
  • the RF processor 1 i - 10 may up-convert a baseband signal provided from the baseband processor 1 i - 20 into a RF band signal, transmit the RF band signal through an antenna, and down-convert an RF band signal received through the antenna into a baseband signal.
  • the RF processor 1 i - 10 may 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), etc.
  • DAC digital-to-analog converter
  • ADC analog-to-digital converter
  • FIG. 1I a single antenna is shown, however, the UE may include a plurality of antennas. Also, the RF processor 1 i - 10 may include a plurality of RF chains.
  • the RF processor 1 i - 10 may perform beamforming. For beamforming, the RF processor 1 i - 10 may adjust phases and magnitudes of signals that are transmitted/received through the plurality of antennas or antenna elements. Also, the RF processor 1 i - 10 may perform MIMO, and when MIMO is performed, the RF processor 1 i - 10 may receive several layers. The RF processor 1 i - 10 may perform sweeping of a received beam by appropriately setting the plurality of antennas or antenna elements according to a control of the controller 1 i - 40 , or may adjust a direction and width of a received beam such that the received beam is coordinated with a beam that is to be transmitted.
  • the baseband processor 1 i - 20 may perform a function of conversion between baseband signals and bit streams according to a physical layer specification of a system. For example, upon data transmission, the baseband processor 1 i - 20 may encipher and modulate a transmission bit stream to generate complex symbols. Also, upon data reception, the baseband processor 1 i - 20 may demodulate and decipher a baseband signal provided from the RF processor 1 i - 10 to restore a reception bit stream.
  • the baseband processor 1 i - 20 may encipher and modulate a transmission bit stream to generate complex symbols, map the complex symbols to subcarriers, and then construct OFDM symbols through inverse fast Fourier transform (IFFT) and cyclic prefix (CP) insertion. Also, upon data reception, the baseband processor 1 i - 20 may segment a baseband signal provided from the RF processor 1 i - 10 in units of OFDM symbols, restore signals mapped to subcarriers through fast Fourier transform (FFT), and then restore a reception bit stream through demodulation and deciphering.
  • IFFT inverse fast Fourier transform
  • CP cyclic prefix
  • the baseband processor 1 i - 20 and the RF processor 1 i - 10 may transmit and receive signals as described above. Accordingly, the baseband processor 1 i - 20 and the RF processor 1 i - 10 are also referred to as a transmitter, a receiver, a transceiver, or a communicator. Furthermore, at least one of the baseband processor 1 i - 20 or the RF processor 1 i - 10 may include a plurality of communication modules to support a plurality of different radio access technologies. Also, at least one of the baseband processor 1 i - 20 or the RF processor 1 i - 10 may include different communication modules to process signals of different frequency bands.
  • the different radio access technologies may include a LET network, a NR network, etc.
  • the different frequency bands may include a super high frequency (SHF) (e.g., 2.1 GHz and 1 GHz) band and a millimeter wave (e.g., 60 GHz) band.
  • SHF super high frequency
  • the UE may transmit/receive a signal to/from a gNB by using the baseband processor 1 i - 20 and the RF processor 1 i - 10 , wherein the signal may include control information and data.
  • the storage device 1 i - 30 may store data, such as basic programs, application programs, and configuration information, for operations of the UE.
  • the storage device 1 i - 30 may provide the stored data according to a request from the controller 1 i - 40 .
  • the storage device 1 i - 30 may be configured with a storage medium, such as read only memory (ROM), random access memory (RAM), a hard disc, compact disc ROM (CD-ROM), digital versatile disc (DVD), and the like, or a combination of such a storage media.
  • the storage device 1 i - 30 may be configured with a plurality of memories.
  • the controller 1 i - 40 may control overall operations of the UE.
  • the controller 1 i - 40 may transmit and receive signals through the baseband processor 1 i - 20 and the RF processor 1 i - 10 .
  • the controller 1 i - 40 may write data in the storage device 1 i - 30 or read data from the storage device 1 i - 30 .
  • the controller 1 i - 40 may include at least one processor.
  • the controller 1 i - 40 may include a communication processor CP for performing control for communication, and an application processor AP for controlling an upper layer of an application program, etc.
  • the controller 1 i - 40 may include multiple connection processor 1 i - 42 for processing multiple connections.
  • the controller 1 i - 40 may control the UE to perform a method for performing the handover procedure described above.
  • at least one component of the UE may be implemented as a single chip.
  • FIG. 1J shows a block configuration of a Transmission/Reception Point (TRP) or a wireless node in a wireless communication system according to an embodiment of the disclosure.
  • TRP Transmission/Reception Point
  • a gNB (also, referred to as a TRP or a wireless node) may include a RF processor 1 j - 10 , a baseband processor 1 j - 20 , a backhaul communicator 1 j - 30 , a storage device 1 j - 40 , and a controller 1 j - 50 .
  • a configuration of the gNB is not limited to the embodiment shown in FIG. 1J , and the gNB may include more or less components than those shown in FIG. 1J .
  • the RF processor 1 j - 10 may perform a function for transmitting and receiving signals through a wireless channel, such as band conversion, amplification, etc. of signals. That is, the RF processor 1 j - 10 may up-convert a baseband signal provided from the baseband processor 1 j - 20 into a RF band signal, transmit the RF band signal through an antenna, and down-convert an RF band signal received through the antenna into a baseband signal.
  • the RF processor 1 j - 10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, etc. In FIG.
  • the gNB may include a plurality of antennas.
  • the RF processor 1 j - 10 may include a plurality of RF chains.
  • the RF processor 1 j - 10 may perform beamforming. For beamforming, the RF processor 1 j - 10 may adjust phases and magnitudes of signals that are transmitted/received through the plurality of antennas or antenna elements.
  • the RF processor 1 j - 10 may perform a downlink MIMO operation by transmitting one or more layers.
  • the baseband processor 1 j - 20 may perform a function of conversion between baseband signals and bit streams according to a physical layer specification of first radio access technology. For example, upon data transmission, the baseband processor 1 j - 20 may encipher and modulate a transmission bit stream to generate complex symbols. Also, upon data reception, the baseband processor 1 j - 20 may demodulate and decipher a baseband signal provided from the RF processor 1 j - 10 to restore a reception bit stream. For example, according to the OFDM method, upon data transmission, the baseband processor 1 j - 20 may encipher and modulate a transmission bit stream to generate complex symbols, map the complex symbols to subcarriers, and then construct OFDM symbols through IFFT and CP insertion.
  • the baseband processor 1 j - 20 may segment a baseband signal provided from the RF processor 1 j - 10 in units of OFDM symbols, restore signals mapped to subcarriers through FFT, and then restore a reception bit stream through demodulation and deciphering.
  • the baseband processor 1 j - 20 and the RF processor 1 j - 10 may transmit and receive signals as described above. Accordingly, the baseband processor 1 j - 20 and the RF processor 1 j - 10 are also referred to as a transmitter, a receiver, a transceiver, a communicator, or a wireless communicator.
  • the gNB may transmit/receive a signal to/from the UE by using the baseband processor 1 j - 20 and the RF processor 1 j - 10 , wherein the signal may include control information and data.
  • the communicator 1 j - 30 may provide an interface for communicating with other nodes in a network.
  • the storage device 1 j - 40 may store data, such as basic programs, application programs, and configuration information, for operations of the gNB. Particularly, the storage device 1 j - 40 may store information about a bearer assigned to a UE connected to the gNB, a measurement result reported from the connected UE, etc. Also, the storage device 1 j - 40 may store information that is used as a determination criterion about whether to provide multiple connections to the UE or whether to release multiple connections to the UE. Also, the storage device 1 j - 40 may provide the stored data according to a request from the controller 1 j - 50 .
  • the storage device 1 j - 40 may be configured with a storage medium, such as ROM, RAM, a hard disc, CD-ROM, DVD, and the like, or a combination of such a storage media. Also, the storage device 1 j - 40 may be configured with a plurality of memories.
  • the controller 1 j - 50 may control overall operations of the gNB.
  • the controller 1 j - 50 may transmit and receive signals through the baseband processor 1 j - 20 and the RF processor 1 j - 10 or through the backhaul communicator 1 j - 30 .
  • the controller 1 j - 50 may write data in the storage device 1 j - 40 or read data from the storage device 1 j - 40 .
  • the controller 1 i - 50 may include at least one processor.
  • the controller 1 j - 50 may include multiple connection processor 1 j - 52 for processing multiple connections.
  • the controller 1 i - 50 may control the gNB such that the UE may perform a method for performing an RRC connection resume procedure as described above.
  • at least one component of the gNB may be implemented as a single chip.
  • an indicator may be proposed to set an in-order delivery function for reception operations of a reception RLC layer of a next-generation mobile communication system with an RRC message, and when the in-order delivery function is set in the RLC layer with the indicator, detailed reception window operations of the RLC layer are proposed for the RLC UM mode or the RLC AM mode.
  • data may be transferred in order to the PDCP layer. Also, data loss that may be generated in the PDCP layer may be prevented, and also, data processing that may be generated upon a handover may be simplified.
  • a reception RLC layer may always perform an out-of-order delivery function.
  • the out-of-order delivery function means a function of reassembling data received by the reception RLC layer in arrival order, without ordering the data in order of RLC SNs, and transferring a result of the reassembling to an upper layer.
  • the out-of-order delivery function may be effective in view of transmission delay, but may cause data loss and increase complexity of handover processing because the PDCP layer drives a timer and moves a window when the timer is expired.
  • FIGS. 2A to 2M a method and apparatus for processing communication data will be described with reference to FIGS. 2A to 2M .
  • FIG. 2A shows a structure of an LTE system to which an embodiment of the disclosure may be applied.
  • a radio access network of an LTE system may be configured with next-generation Evolved Node B (ENBs) (hereinafter, also referred to as Nodes B or base stations), 2 a - 05 , 2 a - 10 , 2 a - 15 , and 2 a - 20 , a MME 2 a - 25 , and a S-GW 2 a - 30 .
  • ENBs next-generation Evolved Node B
  • a UE 2 a - 35 may be connected to an external network through the ENBs 2 a - 05 to 2 a - 20 and the S-GW 2 a - 30 .
  • the ENBs 2 a - 05 to 2 a - 20 may correspond to existing nodes B of a UMTS.
  • the ENBs 2 a - 05 to 2 a - 20 may be connected to the UE 2 a - 35 through a wireless channel, and perform more complicated functions than the existing nodes B.
  • a device for performing scheduling by collecting status information of UEs, such as buffer statuses of UEs, available transmission power states of UEs, channel states of UEs, etc. is needed.
  • the ENBs 2 a - 05 to 2 a - 20 may function as such a device.
  • An ENB may generally control a plurality of cells.
  • the LTE system uses, as radio access technology, OFDM, for example, in a bandwidth of 20 MHz.
  • AMC of determining a modulation scheme and a channel coding rate according to a channel state of a UE may be applied.
  • the S-GW 2 a - 30 which is a device for providing data bearers, may generate or remove data bearers according to a control of the MME 2 a - 25 .
  • the MME 2 a - 25 may be in charge of various control functions, as well as a mobility management function for UEs, and may be connected to a plurality of ENB s.
  • FIG. 2B shows a radio protocol architecture of an LTE system to which an embodiment of the disclosure may be applied.
  • radio protocols of the LTE system may include PDCPs 2 b - 05 and 2 b - 40 , RLC 2 b - 10 and 2 b - 35 , and MAC 2 b - 15 and 2 b - 30 of a UE and an ENB.
  • the PDCPs 2 b - 05 and 2 b - 40 may be in charge of operations of IP header compression/restoration. Main functions of the PDCPs 2 b - 05 and 2 b - 40 may be summarized as follows.
  • the RLC 2 b - 10 and 2 b - 35 may reconstruct a PDCP PDU to an appropriate size to perform an ARQ operation, etc.
  • Main functions of the RLC 2 b - 10 and 2 b - 35 may be summarized as follows.
  • the MAC 2 b - 15 and 2 b - 30 may be connected to several RLC layers configured in the UE, and perform an operation of multiplexing RLC PDUs into a MAC PDU and demultiplexing RLC PDUs from a MAC PDU.
  • Main functions of the MAC 2 b - 15 and 2 b - 30 may be summarized as follows.
  • Physical layers (PHY) 2 b - 20 and 2 b - 25 may perform an operation of performing channel coding and modulation on upper layer data to generate an OFDM symbol and transmitting the OFDM symbol through a wireless channel, or demodulating an OFDM symbol received through the wireless channel, performing channel decoding on the OFDM symbol, and transferring the channel-decoded OFDM symbol to an upper layer.
  • FIG. 2C shows a structure of a next-generation mobile communication system to which an embodiment of the disclosure may be applied.
  • a radio access network of a next-generation mobile communication system may be configured with a next-generation NR gNB (also, referred to as a NR base station) 2 c - 10 and a NR CR 2 c - 05 .
  • a NR UE (also, referred to as a UE) 2 c - 15 may be connected to an external network through the NR gNB 2 c - 10 and the NR CN 2 c - 05 .
  • the NR gNB 2 c - 10 may correspond to an eNB of an existing LTE system.
  • the NR gNB 2 c - 10 may be connected to the NR UE 2 c - 15 through a wireless channel, and provide a more excellent service than an existing node B.
  • a device for performing scheduling by collecting status information of UEs such as buffer statuses of UEs, available transmission power states of UEs, channel states of UEs, etc., is needed.
  • the NR gNB 2 c - 10 may function as such a device.
  • a NR gNB may generally control a plurality of cells.
  • OFDM as radio access technology may be combined with beam-forming technology, while providing an existing maximum bandwidth or more.
  • AMC of determining a modulation scheme and a channel coding rate according to a channel state of a UE may be applied.
  • the NR CN 2 c - 05 may perform functions, such as mobility support, bearer setup, Quality of Service (QoS) setup, etc.
  • the NR CN 2 c - 05 may be in charge of various control functions, as well as a mobility management function for UEs, and may be connected to a plurality of NR gNBs.
  • the next-generation mobile communication system may interwork with an existing LTE system, and the NR CN 2 c - 05 may be connected to the MME 2 c - 25 through a network interface.
  • the MME 1 c - 25 may be connected to an eNB 2 c - 30 which is an existing base station.
  • FIG. 2D shows a radio protocol architecture of a next-generation mobile communication system to which an embodiment of the disclosure may be applied.
  • radio protocols of the next-generation mobile communication system may include NR SDAPs 2 d - 01 and 2 d - 45 , NR PDCPs 2 d - 05 and 2 d - 40 , NR RLC 2 d - 10 and 2 d - 35 , and NR MAC 2 d - 15 and 2 d - 30 of an UE and a NR gNB.
  • Main functions of the NR SDAPs 2 d - 01 and 2 d - 45 may include some of the following functions.
  • the UE may receive, as an RRC message, a setting about whether to use a header of the SDAP layer or whether to use a function of the SDAP layer for each PDCP layer, for each bearer, or for each logical channel.
  • the SDAP header capable of indicating the UE to update or reset mapping information about a QoS flow and a data bearer of a uplink and a downlink with a 1-bit indicator NAS reflective QoS for a NAS reflective QoS setting and a 1-bit indicator AS reflective QoS for an AS reflective QoS setting of the SDAP header may include QoS flow ID information representing QoS.
  • QoS information may be used as data processing priority, scheduling information, etc. for supporting a stable service.
  • Main functions of the NR PDCPs 2 d - 05 and 2 d - 40 may include some of the following functions.
  • the reordering function of a NR PDCP device among the above-mentioned functions means a function of reordering PDCP PDUs received from a lower layer in order based on PDCP SNs, and may include a function of transferring data to an upper layer in the reordered order.
  • the reordering function of the NR PDCP device may include a function of directly transferring data regardless of order, a function of recording lost PDCP PDUs by reordering, a function of sending a status report for lost PDCP PDUs to a transmitter, and a function of requesting retransmission of lost PDCP PDUs.
  • Main functions of the NR RLC 2 d - 10 and 2 d - 35 may include some of the following functions.
  • the in-sequence delivery function of a NR RLC device among the above-mentioned functions means a function of transferring RLC SDUs received from a lower layer in order to an upper layer, and may include a function of reassembling, when a RLC SDU is segmented into several RLC SDUs and received, the RLC SDUs and transferring a result of the reassembling, a function of reordering received RLC PDUs based on RLC SNs or PDCP SNs, a function of reordering and recording lost RLC PDUs, a function of sending a status report for lost RLC PDUs to a transmitter, a function of requesting retransmission of lost RLC PDUs, a function of transferring, when there are lost RLC SDUs, RLC SDUs before the lost RLC SDUs in order to the upper layer, a function of transferring, when a preset timer has been expired although there are lost RLC SDUs, all RLC
  • RLC PDUs may be processed in order (in arrival order, regardless of SNs or order of SNs) in which they are received, and transferred to the PDCP device out of sequence delivery, and in the case of segments, segments which have been stored in a buffer or which are to be received later may be received and reconstructed into a compete RLC PDU and then processed and transferred to the PDCP device.
  • a NR RLC layer as described above may include no concatenation function, and the above-described function may be performed in a NR MAC layer or replaced with a multiplexing function of the NR MAC layer.
  • the out-of-sequence delivery function of the NR RLC device as described above means a function of transferring RLC SDUs received from a lower layer to the upper layer regardless of order, and may include a function of reassembling, when a RLC SDU is segmented into several RLC SDUs and received, the RLC SDUs and transferring a result of the reassembling, and a function of storing and ordering RLC SNs or PDCP SNs of the received RLC PDUs and recording lost RLC PDUs.
  • the NR MAC 2 d - 15 and 2 d - 30 may be connected to several NR RLC layers configured in the UE, and main functions of the NR MAC 2 d - 15 and 2 d - 30 may include some of the following functions.
  • NR PHY layers 2 d - 20 and 2 d - 25 may perform an operation of performing channel coding and modulation on upper layer data to generate an OFDM symbol and transferring the OFDM symbol through a wireless channel, or performing demodulation and channel decoding on an OFDM symbol received through the wireless channel and transferring a result of the modulation and channel decoding to an upper layer.
  • FIG. 2E is a view for describing a procedure in which a gNB according to an embodiment of the disclosure releases a connection of a UE for the UE to change from the RRC connected mode to the RRC idle mode and a procedure in which the UE sets up a connection to the gNB to change from the RRC idle mode to the RRC connected mode.
  • the gNB may transmit an RRCConnectionRelease message to the UE to change the UE to the RRC idle mode, in operation 2 e - 01 .
  • the UE (hereinafter, also referred to as an idle mode UE) in which no connection is currently established may perform, when data to be transmitted is generated, an RRC connection establishment process together with the gNB.
  • the UE may establish reverse transmission synchronization with the gNB through a random access process, and transmit an RRCConnectionRequest message to the gNB, in operation 2 e - 05 .
  • the RRCConnectionRequest message may include an identifier of the UE and a cause establishmentCause for connection establishment.
  • the gNB may transmit an RRCConnectionSetup message to the UE to enable the UE to establish an RRC connection, in operation 2 e - 10 .
  • the RRCConnectionSetup message may include RRC connection configuration information, etc.
  • the RRCConnectionSetup message may include at least one information of bearer configuration information of the UE, configuration information of a PHY layer, configuration information of a MAC layer, configuration information of a RLC layer, configuration information of a PDCP layer, or configuration information of a SDAP layer.
  • the configuration information of the RLC layer may include an indicator defined to indicate whether to set the RLC layer to the RLC TM mode, the RLC UM mode, or the RLC AM mode and whether to set or activate the in-order delivery function for the RLC layer.
  • the gNB may indicate the UE of a setting about an RLC mode and whether or not the in-order delivery function is set for each bearer or for each RLC layer, based on the configuration information of the RLC layer.
  • the UE may set the RLC mode (for example, RLC TM, RLC UM or RLC AM) for the reception RLC layer, and perform an operation of the reception RLC layer to which the in-order delivery function is applied.
  • the UE may perform an operation of the reception RLC layer to which the out-of-order delivery function is basically applied.
  • An RRC connection is also referred to as a Signaling Radio Bearer (SRB), and may be used to transmit and receive an RRC message which is a control message between a UE and a gNB.
  • the UE which has established the RRC connection may transmit an RRCConnetionSetupComplete message to the gNB, in operation 2 e - 15 .
  • the RRCConnetionSetupComplete message may include a SERVICE REQUEST message as a control message through which the UE requests the MME to set a bearer for a preset service.
  • the gNB may transmit the SERVICE REQUEST message included in the RRCConnetionSetupComplete message to an Access and Mobility Management Function (AMF), in operation 2 e - 20 , and the AMF may determine whether to provide the preset service requested by the UE.
  • AMF Access and Mobility Management Function
  • the AMF may transmit an INITIAL CONTEXT SETUP REQUEST message to the gNB, in operation 2 e - 25 .
  • the INITIAL CONTEXT SETUP REQUEST message may include QoS information to be applied for a Data Radio Bearer (DRB) setting, security-related information (for example, a security key or a security algorithm) to be applied to the DRB, etc.
  • DRB Data Radio Bearer
  • the gNB may exchange a SecurityModeCommand message with a SecurityModeComplete message to set security with the UE, in operations 2 e - 30 and 2 e - 35 .
  • the gNB may transmit an RRCConnectionReconfiguration message to the UE, in operation 2 e - 40 .
  • the RRCConnectionReconfiguration message may include bearer configuration information of the UE, configuration information of the PHY layer, configuration information of the MAC layer, configuration information of the RLC layer, configuration information of the PDCP layer, or configuration information of the SDAP layer.
  • the configuration information of the RLC layer may include an indicator defined to indicate whether to set the RLC layer to the RLC TM mode, the RLC UM mode, or the RLC AM mode and whether to set or activate the in-order delivery function for the RLC layer.
  • the gNB may indicate the UE of a setting about the RLC mode and whether or not the in-order delivery function is set for each bearer or for each RLC layer, based on the configuration information of the RLC layer.
  • the UE may set the RLC mode (for example, RLC TM, RLC UM or RLC AM) for the reception RLC layer, and perform an operation of the reception RLC layer to which the in-order delivery function is applied.
  • the UE may perform an operation of the reception RLC layer to which the out-of-order delivery function is basically applied.
  • the RRCConnectionReconfiguration message may include configuration information of a DRB by which user data is to be processed, and the UE may apply the configuration information of the DRB to set up the DRB, and transmit an RRCConnectionReconfigurationComplete message to the gNB, in operation 2 e - 45 .
  • the gNB may transmit an initial context setup complete message to the AMF, in operation 2 e - 50 .
  • the AMF may receive the initial context setup complete message, and perform a session management procedure with a User Plane Function (UPF) to establish a PDU session, in operation 2 e - 60 .
  • UPF User Plane Function
  • the UE may transmit/receive data to/from the gNB through the UPF, in operations 2 e - 65 and 2 e - 70 .
  • a general data transmission process may be configured with three operations of RCC connection setup, security setup, and DRB setup. Also, the gNB may transmit an RRCConnectionReconfiguration message to newly set up, add, or change a setting to the UE for a certain reason, in operation 2 e - 75 .
  • the bearer may have a meaning including a SRB and a DRB, wherein the SRB means a Signaling Radio Bearer and the DRB means a Data Radio Bearer.
  • the SRB may be mainly used to transmit and receive RRC messages of the RRC layer, and the DRB may be mainly used to transmit and receive user layer data.
  • UM DRB means a DRB using the RLC layer operating in an Unacknowledged Mode (UM)
  • AM DRB means a DRB using the RLC layer operating in an Acknowledged Mode (AM).
  • FIG. 2F shows a handover procedure in a next-generation mobile communication system according to an embodiment of the disclosure.
  • a UE 2 f - 01 which is in the RRC connected mode may send a cell measurement report to a source gNB 2 f - 02 periodically or when a preset event is satisfied, in operation 2 f - 05 .
  • the source gNB 2 f - 02 may determine whether to perform a handover of the UE 2 f - 01 to an adjacent cell based on the cell measurement information.
  • the handover may be a technique of changing a source gNB providing a service to a UE being in a connected mode to another gNB (or another cell in the same gNB).
  • the source gNB 2 f - 02 may send a Handover (HO) request message to a new gNB, that is, a target gNB 2 f - 03 that is to provide a service to the UE 2 f - 01 , thereby requesting a handover, in operation 2 f - 10 .
  • a new gNB that is, a target gNB 2 f - 03 that is to provide a service to the UE 2 f - 01 , thereby requesting a handover, in operation 2 f - 10 .
  • the target gNB 2 f - 03 may transmit a HO request Ack message to the source gNB 2 f - 02 , in operation 2 f - 15 .
  • the source gNB 2 f - 02 may transmit a HO command message to the UE 2 f - 01 , in operation 2 f - 20 .
  • the source gNB 2 f - 02 may transfer the HO command message to the UE 2 f - 01 by using an RRC Connection Reconfiguration message, in operation 2 f - 20 .
  • the UE 2 f - 01 may stop data transmission/reception to/from the source gNB 2 f - 02 , and start a T304 timer.
  • the T304 timer may return the UE 2 f - 01 to its original setting and change the UE 2 f - 01 to the RRC idle state, when the UE 2 f - 01 fails to perform a handover to the target gNB 2 f - 03 within a preset time period.
  • the source gNB 2 f - 02 may transfer a SN status about a transmission/reception status of uplink/downlink data to the target gNB 2 f - 03 , and when there is downlink data, the source gNB 2 f - 02 may transfer the downlink data to the target gNB 2 f - 03 , in operations 2 f - 30 and 2 f - 35 .
  • the UE 2 f - 01 may attempt a random access to a target cell indicated from the source gNB 2 f - 02 , in operation 2 f - 40 .
  • the random access may be aimed to notify the target cell that the UE 2 f - 01 moves through a handover, while synchronizing an uplink.
  • the UE 2 f - 01 may transmit a preamble corresponding to a preamble ID received from the source gNB 2 f - 02 or a randomly selected preamble ID to the target cell.
  • the UE 2 f - 01 may monitor whether a Random Access Response (RAR) message is transmitted from the target cell.
  • RAR Random Access Response
  • a time period in which the UE 2 f - 01 monitors whether the RAR message is transmitted is referred to as a RAR window.
  • the UE 2 f - 01 may transmit a HO complete message as an RRC Reconfiguration Complete message to the target gNB 2 f - 03 , in operation 2 f - 55 .
  • the UE 2 f - 01 may stop the T304 timer, in operation 2 f - 50 .
  • the target gNB 2 f - 03 may request a core network 2 f - 04 to correct paths in operations 2 f - 60 and 2 f - 65 , and notify the source gNB 2 f - 02 of discarding UE context of the UE 2 f - 01 , in operation 2 f - 70 .
  • the UE 2 f - 01 may attempt to receive data with respect to the target gNB 2 f - 03 from when the RAR window starts, and after the RAR message is received, the UE 2 f - 01 may transmit the RRCConnectionReconfigurationComplete message to the target gNB 2 f - 03 and start data transmission/reception to/from the target gNB 2 f - 03 .
  • the core network 2 f - 04 may include at least one of an MME, a S-GW, or an AMF, and further include at least one of a UPF or a SMF.
  • the source gNB 2 f - 02 transmits the HO command message (for example, an RRC Reconfiguration message) to the UE 2 f - 01
  • the HO command message for example, an RRC Reconfiguration message
  • at least one of information about a target gNB to which the UE 2 f - 01 needs to perform a handover, information about a random access transmission resource for a cell, preamble information, bearer configuration information, or cell information may be set in the HO command message.
  • the HO command message may include an indicator defined to indicate what kind of handover the UE 2 f - 01 needs to perform.
  • the source gNB 2 f - 01 may define indicators for a plurality of handover methods, and set one of the defined indicators such that the UE 2 f - 01 perform a handover method corresponding to the set indicator.
  • the plurality of handover methods may include at least one method of a RACH-less handover method, an MBB handover method, an eMBB method, or a conditional handover method.
  • the HO command message may indicate whether to set or activate the in-order delivery function for each RLC layer of the UE 2 f - 01 through the indicator.
  • an issue that data loss is generated in the PDCP layer due to the out-of-order delivery of the RLC layer may be generated.
  • the reception PDCP layer may drive a PDCP reordering timer.
  • the PDCP reordering timer may be driven or start when a PDCP SN gap is generated in the reception PDCP layer based on PDCP SNs, and the reception PDCP layer may transfer data to an upper layer in ascending order of the PDCP SNs or COUNT values when data corresponding to the PDCP SN gap does not arrive until the PDCP reordering timer is expired, and move after a PDCP SN transferring a reception window.
  • the arrived data may not be data in the reception window, and therefore, the reception PDCP layer may discard the data, resulting in data loss.
  • a reason why data arrives late may be because several retransmissions of the RLC layer set to the RLC AM mode.
  • a reason why the PDCP reordering timer is triggered may be because the reception RLC layer transfers data quickly to the upper layer through the out-of-order delivery function.
  • a gNB when AM DRB is set for a UE with an RRC message, a gNB may set the in-order delivery function with respect to a reception RLC layer for the UE.
  • the gNB may set or activate the in-order delivery function with respect to the reception RLC layer.
  • each RLC layer may perform out-of-order delivery of data received from different gNBs when a reception PDCP layer of the UE needs to decipher downlink data with different security keys for the different gNBs or needs to perform a compression release procedure for releasing header compression in order.
  • the reception PDCP layer may have high complexity in processing the out-of-order data.
  • the gNB may cause the reception RLC layer of the UE to perform the in-order delivery function, or may indicate the RLC layer to perform the in-order delivery function together with an indicator indicating the preset handover method through the indicator.
  • the indication for setting, activating or deactivating the in-order delivery function may be dynamically set by a transmitter (gNB or UE) by defining a new RLC control PDU instead of an RRC message.
  • the UE may itself fall back to the out-of-order delivery function from the in-order delivery function. For example, after the UE transmits a handover completion message to the target gNB or when the UE drives a preset timer and then the preset timer is expired, the UE may fall back to the out-of-order delivery function from the in-order delivery function.
  • a value of the preset timer may be indicated by the gNB through a handover command message.
  • the UE may change from the in-order delivery function to the out-of-order delivery function.
  • the out-of-order delivery function may be performed as a basic operation.
  • variables used for a window operation of the reception RLC layer in the RLC UM mode may be defined as follows.
  • the reception RLC layer may operate, when receiving a UMD PDU from a lower layer, as follows.
  • the reception RLC layer may operate in regard of the UMD PDU stored in the buffer in the above-described procedure, as follows. That is, when a UMD PDU having an RLC SN of a x value is stored in the buffer, the reception RLC layer may operate as follows.
  • the reception RLC layer may operate as follows.
  • FIG. 2G shows RLC header formats that may be applied in the 1-1 embodiment which are operations of the reception RLC layer in which the RLC UM mode according to an embodiment of the disclosure is set.
  • the transmission RLC layer may apply a RLC header 2 g - 05 including a segmentation info (SI) field (indicating the complete data, a first segment, a final segment, or a middle segment being neither the first segment nor the final segment) without a RLC SN to the data and transmit the data, in the case that a 6-bit RLC SN has been set in the RLC layer.
  • SI segmentation info
  • the transmission RLC layer may apply a RLC header 2 g - 10 including a RLC SN and a SI field to the first segment and transmit the first segment, and apply a RLC header 2 g - 20 including a RLC SN, a SI field, and a segment offset (SO) field (indicating a first byte segmented from the RLC SDU) to the middle or final segment and transmit the middle or final segment.
  • a RLC header 2 g - 10 including a RLC SN and a SI field
  • a RLC header 2 g - 20 including a RLC SN, a SI field, and a segment offset (SO) field (indicating a first byte segmented from the RLC SDU)
  • the transmission RLC layer may apply the RLC header 2 g - 05 including a SI field to the data without a RLC SN and transmit the data, in the case in which a 12-bit RLC SN has been set in the RLC layer.
  • the transmission RLC layer may apply a RLC header 2 g - 15 including a RLC SN and a SI field to the first segment data and transmit the first segment, and apply a RLC header 2 g - 25 including a RLC SN, a SI field, and a SO field (indicating a first byte segmented from the RLC SDU) to the middle or final segment and transmit the middle or final segment.
  • the reception RLC layer when the reception RLC layer according to an embodiment of the disclosure operates in the RLC AM mode may be as follows.
  • the RLC layer may implement an ARQ function, receive an RLC status report (indicating successful data transfer with an RLC SN) from a receiving terminal, and retransmit data not successfully transmitted, thereby preventing data loss.
  • variables that are used for a window operation of the reception RLC layer may be defined as follows.
  • the reception RLC layer When the reception RLC layer receives an AMD PDU including y to z bytes of an RLC SDU having an RLC SN of a x value from a lower layer, the reception RLC layer may operate as follows.
  • the reception RLC layer may operate in regard of the AMD PDU stored in the reception buffer in the procedure, as follows. That is, when the AMD PDU having the RLC SN of the x value is stored in the reception buffer, the RLC layer may operate as follows.
  • the reception RLC layer may operate as follows.
  • FIG. 2H shows RLC header formats that may be applied in a 1-2 embodiment which are operations of the reception RLC layer in which the RLC AM mode according to an embodiment of the disclosure is set.
  • the transmission RLC layer when the transmission RLC layer transmits data (RLC SDU or RLC PDU) as complete data without segmenting the RLC SDU or when the transmission RLC layer transmits a first segment segmented from the RLC SDU, the transmission RLC layer may apply a RLC header 2 h - 05 including a RLC SN and a SI field (indicating the complete data, the first segment, a final segment, or a middle segment being neither the first segment nor the final segment) to the data and transmit the data, in the case that a 12-bit RLC SN has been set in the RLC layer.
  • RLC header 2 h - 05 including a RLC SN and a SI field (indicating the complete data, the first segment, a final segment, or a middle segment being neither the first segment nor the final segment)
  • the transmission RLC layer may apply a RLC header 2 h - 15 including a RLC SN, a SI field, and a SO field (indicating a first byte segmented from the RLC SDU) to the middle or final segment and transmit the middle or final segment.
  • a RLC header 2 h - 15 including a RLC SN, a SI field, and a SO field (indicating a first byte segmented from the RLC SDU) to the middle or final segment and transmit the middle or final segment.
  • the transmission RLC layer when the transmission RLC layer transmits data (RLC SDU or RLC PDU) as complete data without segmenting a RLC SDU or when the transmission RLC layer transmits a first segment segmented from a RLC SDU, the transmission RLC layer may apply, in the case that a 18-bit RLC SN has been set in the RLC layer, a RLC header 2 h - 10 including a RLC SN and a SI field (indicating the complete data, the first segment, a final segment, or a middle segment being neither the first segment nor the final segment) to the data and transmit the data.
  • the transmission RLC layer may apply a RLC header 2 h - 20 including a RLC SN, a SI field, and a SO field (indicating a first byte segmented from the RLC SDU) to the middle or final segment and transmit the middle or final segment.
  • a RLC header 2 h - 20 including a RLC SN, a SI field, and a SO field (indicating a first byte segmented from the RLC SDU) to the middle or final segment and transmit the middle or final segment.
  • the RLC layer may order data based on RLC SNs and transfer the data to an upper layer, when setting or activating of the in-order delivery function is indicated with an RRC message or a RLC control PDU by a gNB, although the RLC layer performs the out-of-order delivery function as a basic operation. Also, according to the above-described second embodiment, when the RLC layer applies the out-of-order delivery function, the RLC layer may immediately discard segments being out of the RLC reassembly window.
  • the RLC layer may attempt to reassemble, instead of immediately discarding the segments being out of the RLC reassembly window, the segments being out of the RLC reassembly window, transfer, when the segments are reassembled into complete RLC SDUs, the RLC SDUs to an upper layer in ascending order of RLC SNs, and discard segments that has failed to be reassembled into the complete RLC SDUs.
  • the RLC layer may order, instead of immediately reassembling a RLC SDU corresponding to a RLC SN when all bytes of the RLC SDU is received and transferring the RLC SDU to the upper layer, RLC SDUs in order of RLC SNs, then reassemble the RLC SDUs, and transfer the RLC SDUs to the upper layer in ascending order of the RLC SNs.
  • the RLC layer may immediately reassemble an RLC SDU corresponding to an RLC SN when all bytes of the RLC SDU are received, and then transfer the RLC SDU to the upper layer.
  • variables that are used in a window operation of the reception RLC layer in the RLC UM mode may be defined as follows.
  • the reception RLC layer may operate, when receiving a UMD PDU from a lower layer, as follows.
  • the reception RLC layer may operate in regard of the UMD PDU stored in the buffer in the above-described procedure, as follows. That is, when a UMD PDU having an RLC SN of an x value is stored in the buffer, the reception RLC layer may operate as follows.
  • the reception RLC layer may operate as follows.
  • FIGS. 2IA and 21B shows RLC header formats that may be applied in the 2-1 embodiment which are the operations of the reception RLC layer in which the RLC UM mode according to an embodiment of the disclosure is set.
  • the transmission RLC layer may apply, when transmitting data (RLC SDU or RLC PDU) as complete data without segmenting the RLC SDU, a RLC header 2 i - 05 to the data and transmit the data in the case that a 6-bit RLC SN has been set in the RLC layer.
  • the RLC header 2 i - 05 includes a SI field (indicating the complete data, a first segment, a final segment, or a middle segment being neither the first segment nor the final segment) without an RLC SN.
  • the transmission RLC layer may apply a RLC header 2 i - 10 including a RLC SN and a SI field to a first segment and transmit the first segment, and apply a RLC header 2 i - 20 including a RLC SN, a SI field, and a SO field (indicating a first byte segmented from the RLC SDU) to a middle or final segment and transmit the middle or final segment.
  • the transmission RLC layer may apply, when transmitting data (RLC SDU or RLC PDU) as complete data without separating the RLC SDU, the RLC header 2 i - 05 including a SI field in the data without a RLC SN to the data and transmit the data, in the case in which a 12-bit RLC SN has been set in the RLC layer.
  • the transmission RLC layer may apply a RLC header 2 i - 15 including a RLC SN and a SI field in the first segment and transmit the first segment, and apply a RLC header 2 i - 25 including a RLC SN, a SI field, and a SO field (indicating a first byte segmented from the RLC SDU) to the middle or final segment and transmit the middle or final segment.
  • the transmission RLC layer may apply, when transmitting data (RLC SDU or RLC PDU) as complete data without segmenting the RLC SDU, a RLC header 2 i - 10 including a RLC SN and a SI field (indicating the complete data, a first segment, a final segment, or a middle segment being neither the first segment nor the final segment) to the data and transmit the data, in the case that a 6-bit RLC SN has been set in the RLC layer, such that the reception RLC layer is capable of ordering the data.
  • data RLC SDU or RLC PDU
  • SI field indicating the complete data, a first segment, a final segment, or a middle segment being neither the first segment nor the final segment
  • the transmission RLC layer may apply the RLC header including a RLC SN and a SI field to the first segment and transmit the first segment, and apply the RLC header 2 i - 20 including a RLC SN, a SI field, and a SO field (indicating a first byte segmented from the RLC SDU) to the middle or final segment and transmit the middle or final segment.
  • the transmission RLC layer may apply, when transmitting data (RLC SDU or RLC PDU) as complete data without segmenting the RLC SDU, a RLC header 2 i - 30 including a RLC SN to the data and transmit the data, in the case that a 6-bit RLC SN has been set in the RLC layer such that the reception RLC layer is capable of ordering the data.
  • the RLC header 2 i - 30 includes a 12-bit RLC SN and a SI field (indicating the complete data, a first segment, a final segment, or a middle segment being neither the first segment nor the final segment), a 1-bit I field, defined by the transmission RLC layer, indicating that the in-order delivery function is capable of being set or applied. That is, the transmission RLC layer may change a length of an RLC SN from 6 bits to 12 bits, and indicate the in-order delivery function with a 1-bit indicator. However, when the transmission RLC layer segments an RLC SDU and transmits segments, the transmission RLC layer may apply the RLC header 2 i - 30 to a first segment and transmit the first segment.
  • the RLC header includes an RLC SN, a SI field and a 1-bit I field, defined by the transmission RLC layer, including an indication representing that the in-order delivery function is capable of being set or applied.
  • the transmission RLC layer may apply an RLC header 2 i - 35 to a middle or final segment and transmit the middle or final segment.
  • the RLC header 2 i - 35 includes a RLC SN, a SI field, a SO field (indicating a first byte segmented from a RLC SDU), and a 1-bit I field, defined by the transmission RLC layer, including an indication representing that the in-order delivery function may be set or applied.
  • the transmission RLC layer may apply, when transmitting data (RLC SDU or RLC PDU) as complete data without segmenting the RLC SDU, the RLC header 2 i - 15 including a RLC SN and a SI field and transmit the data, in the case that a 12-bit RLC SN has been set in the RLC layer.
  • data RLC SDU or RLC PDU
  • RLC header 2 i - 15 including a RLC SN and a SI field
  • the transmission RLC layer may apply the RLC header 2 i - 15 including a RLC SN and a SI field to the first segment and transmit the first segment, and may apply the RLC header 2 i - 25 including a RLC SN, a SI field, and a SO field (indicating a first byte segmented from a RLC SDU) to the middle or final segment and transmit the middle or final segment.
  • the transmission RLC layer may apply, when transmitting data (RLC SDU or RLC PDU) as complete data without segmenting the RLC SDU, the RLC header 2 i - 30 to the data and transmit the data, in the case that a 12-bit RLC SN has been set in the RLC layer.
  • the RLC header 2 i - 30 includes an RLC SN, a SI field, and a 1-bit I field, defined by the transmission RLC layer, including an indication representing that the in-order delivery function is capable of being set or applied.
  • the transmission RLC layer may apply the RLC header 2 i - 30 including a RLC SN, a SI field, and a 1-bit I field, defined by the transmission RLC layer, including an indication representing that the in-order delivery function is capable of being set or applied to the first segment and transmit the first segment, and apply the RLC header 2 i - 35 including a RLC SN, a SI field, a SO field (indicating a first byte segmented from a RLC SDU), and a 1-bit I field, defined by the transmission RLC layer, including an indication representing that the in-order delivery function is capable of being set or applied to the middle or final segment and transmit the middle or final segment.
  • the transmission RLC layer may define a I field in a header format of 2 i - 05 , set the I field to 0 like a header format of 2 i - 40 , and then apply the header format of 2 i - 40 to a RLC SDU not segmented in the case that the in-order delivery function is not set.
  • the transmission RLC layer may configure an RLC header format including the I field according to an embodiment of the disclosure and transmit data including the RLC header format.
  • the reception RLC layer may check the I field to identify an RLC SN, and order the received data.
  • the reception RLC layer may immediately reassemble a RLC PDU of which an I field value is 0 without applying the in-order delivery function to the RLC PDU although the in-order delivery function is set, remove a RLC header, and then transfer the resultant RLC PDU to an upper layer (because the RLC PDU is data transmitted before the in-order delivery function is set).
  • Detailed operations of a 2-2 embodiment when the reception RLC layer according to an embodiment of the disclosure operates in the RLC AM mode may be as follows.
  • the RLC layer may implement an ARQ function, receive an RLC status report (indicating successful data transfer with an RLC SN) from a receiving terminal, and retransmit data not successfully transmitted, thereby preventing data loss.
  • variables that are used for a window operation of the reception RLC layer may be defined as follows.
  • the reception RLC layer When the reception RLC layer receives an AMD PDU including y to z bytes of an RLC SDU having an RLC SN of a x value from a lower layer, the reception RLC layer may operate as follows.
  • the reception RLC layer may operate in regard of the AMD PDU stored in the buffer in the above-described procedure, as follows. That is, when the AMD PDU having the RLC SN of the x value is stored in the buffer, the reception RLC layer may operate as follows.
  • the reception RLC layer may operate as follows.
  • FIG. 2J shows RLC header formats that may be applied in the 2-2 embodiment which are operations of the reception RLC layer in which the RLC AM mode according to an embodiment of the disclosure is set.
  • the transmission RLC layer when the transmission RLC layer transmits data (RLC SDU or RLC PDU) as complete data without segmenting the RLC SDU or when the transmission RLC layer transmits a first segment segmented from the RLC SDU, the transmission RLC layer may apply, in the case that a 12-bit RLC SN has been set in the RLC layer, a RLC header 2 j - 05 including a RLC SN and a SI field (indicating the complete data, the first segment, a final segment, or a middle segment being neither the first segment nor the final segment) to the data and transmit the data.
  • the transmission RLC layer may apply a RLC header 2 j - 15 including a RLC SN, a SI field, and a SO field (indicating a first byte segmented from the RLC SDU) to the middle or final segment and transmit the middle or final segment.
  • a RLC header 2 j - 15 including a RLC SN, a SI field, and a SO field (indicating a first byte segmented from the RLC SDU) to the middle or final segment and transmit the middle or final segment.
  • the transmission RLC layer when the transmission RLC layer transmits data (RLC SDU or RLC PDU) as complete data without segmenting the RLC SDU or when the transmission RLC layer transmits a first segment segmented from the RLC SDU, the transmission RLC layer may apply, in the case that a 18-bit RLC SN has been set in the RLC layer, a RLC header 2 j - 10 including a RLC SN and a SI field (indicating the complete data, the first segment, a final segment, or a middle segment being neither the first segment nor the final segment) to the data and transmit the data.
  • the transmission RLC layer may apply a RLC header 2 j - 20 including a RLC SN, a SI field, and a SO field (indicating a first byte segmented from the RLC SDU) to the middle or final segment and transmit the middle or final segment.
  • a RLC header 2 j - 20 including a RLC SN, a SI field, and a SO field (indicating a first byte segmented from the RLC SDU) to the middle or final segment and transmit the middle or final segment.
  • the same RLC headers shown in FIG. 2J may be applied to both a case that the in-order delivery function is set and a case that the in-order delivery function is not set, according to lengths of RLC SNs, as described above. That is, in the RLC AM mode, the same RLC header format may be applied and used regardless of whether or not the in-order delivery function is set, unlike the RLC UM mode.
  • the transmission RLC layer may define a 1-bit indicator like the RLC UM mode to indicate that the in-order delivery function is set, and define and use an RLC header format.
  • FIG. 2K shows operations of a reception RLC layer of a UE according to an embodiment of the disclosure.
  • the reception RLC layer ( 2 k - 01 ) of the UE may receive data from a lower layer, in operation 2 k - 05 .
  • the UE may determine whether the in-order delivery function is set, based on the received data, in operation 2 k - 10 .
  • the UE may apply the above-described 2-1 embodiment to the RLC UM mode in consideration of a RLC header, and apply the above-described 2-2 embodiment to the RLC AM mode in consideration of a RLC header, in operation 2 k - 20 .
  • the UE may activate the in-order delivery function to order and process the received data and transfer the resultant data to an upper layer.
  • the UE may apply the 1-1 embodiment or the 2-1 embodiment for the reception RLC layer to the RLC UM mode in consideration of a RLC header, and apply the 1-2 embodiment or the 2-2 embodiment for the reception RLC layer to the RLC AM mode in consideration of a RLC header, in operation 2 k - 15 .
  • the UE may process the received data and transfer the processed data to the upper layer according to the out-of-order delivery function.
  • FIG. 2L shows a structure of a UE or a wireless node to which an embodiment of the disclosure may be applied.
  • the UE may include an RF processor 2 l - 10 , a baseband processor 2 l - 20 , a storage device 2 l - 30 , and a controller 2 l - 40 .
  • an internal structure of the UE is not limited to the embodiment shown in FIG. 2L , and the UE may include more or less components than those shown in FIG. 2L .
  • the RF processor 2 l - 10 may perform a function for transmitting and receiving signals through a wireless channel, such as band conversion, amplification, etc. of signals.
  • the RF processor 2 l - 10 may up-convert a baseband signal provided from the baseband processor 2 l - 20 into a RF band signal, transmit the RF band signal through an antenna, and down-convert an RF band signal received through the antenna into a baseband signal.
  • the RF processor 2 l - 10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, etc.
  • FIG. 2I a single antenna is shown, however, the UE may include a plurality of antennas.
  • the RF processor 2 l - 10 may include a plurality of RF chains.
  • the RF processor 2 l - 10 may perform beamforming.
  • the RF processor 2 l - 10 may adjust phases and magnitudes of signals that are transmitted/received through the plurality of antennas or antenna elements. Also, the RF processor 2 l - 10 may perform MIMO, and when MIMO is performed, the RF processor 2 l - 10 may receive several layers. The RF processor 2 l - 10 may perform sweeping of a received beam by appropriately setting the plurality of antennas or antenna elements according to a control of the controller 2 l - 40 , or may adjust a direction and width of a received beam such that the received beam coordinates with a beam that is to be transmitted.
  • the baseband processor 2 l - 20 may perform a function of conversion between baseband signals and bit streams according to a physical layer specification of a system. For example, upon data transmission, the baseband processor 2 l - 20 may encipher and modulate a transmission bit stream to generate complex symbols. Also, upon data reception, the baseband processor 2 l - 20 may demodulate and decipher a baseband signal provided from the RF processor 2 l - 10 to restore a reception bit stream. For example, according to an OFDM method, upon data transmission, the baseband processor 2 l - 20 may encipher and modulate a transmission bit stream to generate complex symbols, map the complex symbols to subcarriers, and then construct OFDM symbols through IFFT and CP insertion.
  • OFDM OFDM
  • the baseband processor 2 l - 20 may segment a baseband signal provided from the RF processor 2 l - 10 in units of OFDM symbols, restore signals mapped to subcarriers through FFT, and then restore a reception bit stream through demodulation and deciphering.
  • the baseband processor 2 l - 20 and the RF processor 2 l - 10 may transmit and receive signals as described above. Accordingly, the baseband processor 2 l - 20 and the RF processor 2 l - 10 are also referred to as a transmitter, a receiver, a transceiver, or a communicator. Furthermore, at least one of the baseband processor 2 l - 20 or the RF processor 2 l - 10 may include a plurality of communication modules to support a plurality of different radio access technologies. Also, at least one of the baseband processor 2 l - 20 or the RF processor 2 l - 10 may include different communication modules to process signals of different frequency bands.
  • the different radio access technologies may include a LET network, a NR network, etc.
  • the different frequency bands may include a SHF (e.g., 2.1 GHz and 1 GHz) band and a mm wave (e.g., 60 GHz) band.
  • the UE may transmit/receive a signal to/from a gNB by using the baseband processor 2 l - 20 and the RF processor 2 l - 10 , wherein the signal may include control information and data.
  • the storage device 2 l - 30 may store data, such as basic programs, application programs, and configuration information, for operations of the UE.
  • the storage device 2 l - 30 may provide the stored data according to a request from the controller 2 l - 40 .
  • the storage device 2 l - 30 may be configured with storage media, such as ROM, RAM, a hard disc, CD-ROM, DVD, and the like, or a combination of such storage media. Also, the storage device 2 l - 30 may be configured with a plurality of memories.
  • the controller 2 l - 40 may control overall operations of the UE.
  • the controller 2 l - 40 may transmit and receive signals through the baseband processor 2 l - 20 and the RF processor 2 l - 10 .
  • the controller 2 l - 40 may write data in the storage device 2 l - 30 or read data from the storage device 2 l - 30 .
  • the controller 2 l - 40 may include at least one processor.
  • the controller 2 l - 40 may include a communication processor CP for performing control for communication, and an application processor AP for controlling an upper layer of an application program, etc.
  • the controller 2 l - 40 may include multiple connection processor 2 l - 42 for processing multiple connections.
  • the controller 2 l - 40 may control the UE to perform a method for processing communication data described above.
  • at least one component of the UE may be implemented as a single chip.
  • FIG. 2M shows a block configuration of a TRP or a wireless node in a wireless communication system according to an embodiment of the disclosure.
  • a gNB (also, referred to as a TRP or a wireless node) may include a RF processor 2 m - 10 , a baseband processor 2 m - 20 , a backhaul communicator 2 m - 30 , a storage device 2 m - 40 , and a controller 2 m - 50 .
  • an internal structure of the gNB is not limited to the embodiment shown in FIG. 2M , and the gNB may include more or less components than those shown in FIG. 2M .
  • the RF processor 2 m - 10 may perform a function for transmitting and receiving signals through a wireless channel, such as band conversion, amplification, etc. of signals. That is, the RF processor 2 m - 10 may up-convert a baseband signal provided from the baseband processor 2 m - 20 into a RF band signal, transmit the RF band signal through an antenna, and down-convert an RF band signal received through the antenna into a baseband signal.
  • the RF processor 2 m - 10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, etc. In FIG.
  • the gNB may include a plurality of antennas.
  • the RF processor 2 m - 10 may include a plurality of RF chains.
  • the RF processor 2 m - 10 may perform beamforming. For beamforming, the RF processor 2 m - 10 may adjust phases and magnitudes of signals that are transmitted/received through the plurality of antennas or antenna elements.
  • the RF processor 2 m - 10 may perform downlink MIMO by transmitting one or more layers.
  • the baseband processor 2 m - 20 may perform a function of conversion between baseband signals and bit streams according to a physical layer specification of first radio access technology. For example, upon data transmission, the baseband processor 2 m - 20 may encipher and modulate a transmission bit stream to generate complex symbols. Also, upon data reception, the baseband processor 2 m - 20 may demodulate and decipher a baseband signal provided from the RF processor 2 m - 10 to restore a reception bit stream. For example, according to the OFDM method, upon data transmission, the baseband processor 2 m - 20 may encipher and modulate a transmission bit stream to generate complex symbols, map the complex symbols to subcarriers, and then construct OFDM symbols through IFFT and CP insertion.
  • the baseband processor 2 m - 20 may segment a baseband signal provided from the RF processor 2 m - 10 in units of OFDM symbols, restore signals mapped to subcarriers through FFT, and then restore a reception bit stream through demodulation and deciphering.
  • the baseband processor 2 m - 20 and the RF processor 2 m - 10 may transmit and receive signals as described above. Accordingly, the baseband processor 2 m - 20 and the RF processor 2 m - 10 are also referred to as a transmitter, a receiver, a transceiver, or a wireless communicator.
  • the gNB may transmit/receive a signal to/from the UE by using the baseband processor 2 m - 20 and the RF processor 2 m - 10 , wherein the signal may include control information and data.
  • the communicator 2 m - 30 may provide an interface for communicating with other nodes in a network.
  • the storage device 2 m - 40 may store data, such as basic programs, application programs, and configuration information, for operations of the gNB. Particularly, the storage device 2 m - 40 may store information about a bearer assigned to a UE connected to the gNB, a measurement result reported from the connected UE, etc. Also, the storage device 2 m - 40 may store information that is used as a determination criterion about whether to provide multiple connections to the UE or whether to release multiple connections to the UE. Also, the storage device 2 m - 40 may provide the stored data according to a request from the controller 2 m - 50 .
  • the storage device 2 m - 40 may be configured with storage media, such as ROM, RAM, a hard disc, CD-ROM, DVD, and the like, or a combination of such storage media. Also, the storage device 2 m - 40 may be configured with a plurality of memories.
  • the controller 2 m - 50 may control overall operations of the gNB.
  • the controller 2 m - 50 may transmit and receive signals through the baseband processor 2 m - 20 and the RF processor 2 m - 10 or through the backhaul communicator 2 m - 30 .
  • the controller 2 m - 50 may write data in the storage device 2 m - 40 or read data from the storage device 2 m - 40 .
  • the controller 2 m - 50 may include at least one processor.
  • the controller 2 m - 50 may include multiple connection processor 2 m - 52 for processing multiple connections.
  • the controller 2 m - 50 may control the gNB such that the UE may perform a method for performing communication data as described above.
  • at least one component in the gNB may be implemented as a single chip.
  • a computer-readable storage medium storing at least one program (software module) may be provided.
  • the at least one program stored in the computer-readable storage medium may be configured for execution by at least one processor within an electronic device.
  • the at least one program may include instructions that cause the electronic device to execute the methods according to the embodiments of the disclosure described in the claims or specification thereof.
  • the program (software module or software) may be stored in RAM, a non-volatile memory including a flash memory, ROM, an electrically erasable programmable ROM (EEPROM), a magnetic disc storage device, CD-ROM, DVDs or other types of optical storage devices, and a magnetic cassette.
  • the program may be stored in a memory that is configured as a combination of some or all of the memories. A plurality of such memories may be included.
  • the program may be stored in an attachable storage device that may be accessed through communication networks such as the Internet, Intranet, a local area network (LAN), a wide LAN (WLAN), and a storage area network (SAN) or a communication network configured in a combination thereof.
  • the storage device may access a device performing the embodiments of the disclosure through an external port. Further, a separate storage device on the communication network may also access the device performing the embodiments of the disclosure.
  • a component included in the disclosure is expressed in a singular or plural form depending on the described embodiments of the disclosure.
  • singular or plural expressions are selected to be suitable for the presented situations for convenience, and the disclosure is not limited to the singular or plural form.
  • a component expressed in a plural form may be configured as a single component, or a component expressed in a singular form may be configured as a plurality of components.
  • the disclosed embodiments provide an apparatus and method capable of effectively providing a service to a mobile communication system.
  • the embodiments of the disclosure disclosed in the present specification and the drawings are specific examples intended to easily describe the technical content of the disclosure and help understanding the disclosure, not intended to limit the scope of the disclosure. That is, it is apparent to those skilled in the art that other modified examples based on the technical spirit of the disclosure may be executed. Also, the embodiments may be combined and used as needed. For example, some parts of the embodiments of the disclosure may be combined to operate the gNB and UE. Also, the embodiments of the disclosure may be applied to other communication systems, and other modified examples based on the technical concept of the embodiments may also be executed.

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)
US15/929,415 2019-05-02 2020-04-30 Method and apparatus for performing handover procedure in wireless communication system Abandoned US20200351725A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US17/661,157 US20220256413A1 (en) 2019-05-02 2022-04-28 Method and apparatus for performing handover procedure in wireless communication system

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
KR10-2019-0051827 2019-05-02
KR1020190051827A KR20200127527A (ko) 2019-05-02 2019-05-02 무선 통신 시스템에서 핸드 오버 절차를 수행하는 방법 및 장치

Related Child Applications (1)

Application Number Title Priority Date Filing Date
US17/661,157 Continuation US20220256413A1 (en) 2019-05-02 2022-04-28 Method and apparatus for performing handover procedure in wireless communication system

Publications (1)

Publication Number Publication Date
US20200351725A1 true US20200351725A1 (en) 2020-11-05

Family

ID=73017485

Family Applications (2)

Application Number Title Priority Date Filing Date
US15/929,415 Abandoned US20200351725A1 (en) 2019-05-02 2020-04-30 Method and apparatus for performing handover procedure in wireless communication system
US17/661,157 Pending US20220256413A1 (en) 2019-05-02 2022-04-28 Method and apparatus for performing handover procedure in wireless communication system

Family Applications After (1)

Application Number Title Priority Date Filing Date
US17/661,157 Pending US20220256413A1 (en) 2019-05-02 2022-04-28 Method and apparatus for performing handover procedure in wireless communication system

Country Status (3)

Country Link
US (2) US20200351725A1 (ko)
KR (1) KR20200127527A (ko)
WO (1) WO2020222527A1 (ko)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20210076111A1 (en) * 2019-09-05 2021-03-11 Ciena Corporation Flexible Ethernet over wireless links
US20210274379A1 (en) * 2020-02-27 2021-09-02 Qualcomm Incorporated Range extension for radio link control status reporting
EP4075903A1 (en) * 2021-04-16 2022-10-19 Deutsche Telekom AG Techniques for steering communication traffic of a user equipment in a wireless communication network
US20230096568A1 (en) * 2021-09-24 2023-03-30 Apple Inc. Truncation of a Packet Data Unit (PDU) for Uplink Transmissions
WO2023054394A1 (ja) * 2021-09-28 2023-04-06 三菱電機株式会社 通信システム

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109478945B (zh) * 2015-05-21 2021-11-26 苹果公司 用于多rat卸载的pdcp状态报告
US10757621B2 (en) * 2017-03-22 2020-08-25 Ofinno, Llc Conditional handover execution

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20210076111A1 (en) * 2019-09-05 2021-03-11 Ciena Corporation Flexible Ethernet over wireless links
US20210274379A1 (en) * 2020-02-27 2021-09-02 Qualcomm Incorporated Range extension for radio link control status reporting
US11856450B2 (en) * 2020-02-27 2023-12-26 Qualcomm Incorporated Range extension for radio link control status reporting
EP4075903A1 (en) * 2021-04-16 2022-10-19 Deutsche Telekom AG Techniques for steering communication traffic of a user equipment in a wireless communication network
WO2022219151A1 (en) * 2021-04-16 2022-10-20 Deutsche Telekom Ag Techniques for steering communication traffic of a user equipment in a wireless communication network
US20230096568A1 (en) * 2021-09-24 2023-03-30 Apple Inc. Truncation of a Packet Data Unit (PDU) for Uplink Transmissions
WO2023054394A1 (ja) * 2021-09-28 2023-04-06 三菱電機株式会社 通信システム

Also Published As

Publication number Publication date
KR20200127527A (ko) 2020-11-11
US20220256413A1 (en) 2022-08-11
WO2020222527A1 (en) 2020-11-05

Similar Documents

Publication Publication Date Title
US11212867B2 (en) Method and apparatus for transmitting and receiving data in wireless communication system
US11330466B2 (en) Method and apparatus for processing a packet in a wireless communication system
US11265759B2 (en) Methods and apparatuses for transmitting and receiving data in wireless communication system
US11438799B2 (en) Method and apparatus for controlling data receiving rate in mobile communication system
US20220256413A1 (en) Method and apparatus for performing handover procedure in wireless communication system
CN113748618A (zh) 用于在无线通信系统中通过使用多个波束发送和接收信号的方法和装置
US11678242B2 (en) Method and apparatus for handover without interruption of transmission and reception of data in next-generation mobile communication system
US11381354B2 (en) Method and apparatus for wireless communication of wireless node in wireless communication system
US11503510B2 (en) Method and apparatus for resource management for conditional handover in wireless communication system
US10863579B2 (en) Method and apparatus for accelerating ciphering and deciphering in wireless communication system
US11943670B2 (en) Method and apparatus for performing handover in wireless communication system
US11382169B2 (en) Methods and apparatuses for transmitting and receiving data in wireless communication system
US20200045766A1 (en) Wireless node communication method and apparatus in wireless communication system
US20210105675A1 (en) Method and apparatus for performing handover in wireless communication system
US11284309B2 (en) Method and apparatus for performing handover in mobile communication system
KR20210076740A (ko) 차세대 이동통신 시스템에서 rrc 메시지의 분할 전송과 관련된 타이머 관리 방법 및 장치
EP4138510A1 (en) Method and apparatus for performing conditional pscell change procedure in next-generation mobile communication system
US11974185B2 (en) Method and device for handover without suspension of data transmission and reception in next generation mobile communication system
CN111955027B (zh) 控制移动通信系统中的数据接收速率的方法和装置
CN113767671A (zh) 下一代移动通信系统中用于无数据发送和接收中断的切换的方法和设备
US20220256412A1 (en) Packet redundancy processing method for supporting enhanced handover in next generation mobile communication system, method for preventing header decompression failure during handover and apparatus therefor
CN111373837A (zh) 用于在无线通信系统中发送和接收数据的方法和装置

Legal Events

Date Code Title Description
AS Assignment

Owner name: SAMSUNG ELECTRONICS CO., LTD, KOREA, REPUBLIC OF

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:KIM, DONGGUN;KIM, SOENGHUN;REEL/FRAME:052543/0049

Effective date: 20200429

STPP Information on status: patent application and granting procedure in general

Free format text: DOCKETED NEW CASE - READY FOR EXAMINATION

STPP Information on status: patent application and granting procedure in general

Free format text: NON FINAL ACTION MAILED

STPP Information on status: patent application and granting procedure in general

Free format text: RESPONSE TO NON-FINAL OFFICE ACTION ENTERED AND FORWARDED TO EXAMINER

STPP Information on status: patent application and granting procedure in general

Free format text: NON FINAL ACTION MAILED

STCB Information on status: application discontinuation

Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION