CN110739993A

CN110739993A - Method and apparatus for transmitting and receiving data using multiple carriers

Info

Publication number: CN110739993A
Application number: CN201911225502.3A
Authority: CN
Inventors: 金成勋; G.J.范利舒特; 张宰赫
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2014-01-29
Filing date: 2015-01-29
Publication date: 2020-01-31
Also published as: KR102216510B1; KR20150090815A; KR20150090808A; EP3100376A1; KR20150090806A; KR20150090804A; EP3100376A4; CN106134099A; CN106134099B

Abstract

bearer reconfiguration method performed by a User Equipment (UE) in a wireless communication system supporting multiple bearers includes reordering Packet Data Convergence Protocol (PDCP) Protocol Data Units (PDUs) received through the multiple bearers using a timer after the bearer reconfiguration is completed if the UE performs bearer reconfiguration from a single bearer to the multiple bearers, and processing the reordered PDCP PDUs into at least PDCP Service Data Units (SDUs). the method may further include reordering PDCP PDUs received through the multiple bearers using the timer until a predetermined condition is satisfied and processing the reordered PDCP PDUs into at least PDCP SDUs if the UE performs bearer reconfiguration from the multiple bearers to the single bearer.

Description

Method and apparatus for transmitting and receiving data using multiple carriers

The present application is a divisional application of an invention patent application having an application date of 29/1/2015, an application number of 201580016867.9, entitled "method and apparatus for transmitting and receiving data using multiple carriers in a mobile communication system".

Technical Field

The present disclosure relates to a method and apparatus for transmitting and receiving data using a plurality of carriers in a mobile communication system.

Background

Mobile communication systems have been developed to provide communication services while ensuring mobility of users. Recently, mobile communication systems have reached a stage capable of providing not only a voice communication service but also a high-speed data communication service.

In recent years, a Long Term Evolution (LTE) system proposed by the third generation partnership project (3GPP) is providing its services in many countries as of the th-generation mobile communication systems.

Recently, commercialization of an LTE-Advanced (LTE-a) communication system, the transmission rate of which has been improved by combining various new technologies for the LTE communication system, is underway the most typical technology among the technologies to be re-introduced may include Carrier Aggregation (CA), unlike a technology in which a UE according to the related art transmits and receives data using forward carriers and reverse carriers, the term "carrier aggregation" as used herein may refer to a technology in which terminals or User Equipments (UEs) use multiple forward carriers and multiple reverse carriers in transmitting and receiving data.

However, currently, evolved node b (enb) -only CA. is defined in LTE-a, which may lead to a reduced applicability of CA functionality, leading to a possible problem of being unable to aggregate macro and pico cells, especially in scenarios where multiple pico cells and macro cells are operated in an overlapping manner.

To the extent that any of above is referred to as being prior art, no determination has been made, and no assertion was made, as to whether or not the present disclosure might apply.

Disclosure of Invention

Technical problem

Accordingly, aspects of the present disclosure are to provide a method and apparatus for efficiently transmitting and receiving data using multiple carriers in a mobile communication system.

Another aspect of the present disclosure is to provide methods and apparatus for inter evolved node b (enb) Carrier Aggregation (CA).

Another aspect of the present disclosure is to provide a method and apparatus for Packet Data Convergence Protocol (PDCP) operation handover in a mobile communication system supporting multi-bearers.

Another aspect of the present disclosure is to provide a method and apparatus for PDCP reordering in a mobile communication system supporting multiple bearers.

Solution to the problem

According to aspects of the present disclosure, there is provided a bearer reconfiguration method performed by a User Equipment (UE) in a wireless communication system supporting multiple bearers, the bearer reconfiguration method including reordering PDCP Protocol Data Units (PDUs) received through the multiple bearers using a timer after completion of the bearer reconfiguration if the UE performs bearer reconfiguration from a single bearer to the multiple bearers, and processing the reordered PDCP PDUs into at least PDCP Service Data Units (SDUs).

According to another aspect of the present disclosure, a bearer reconfiguration method performed by a UE in a wireless communication system supporting multiple bearers, the bearer reconfiguration method includes, if the UE performs bearer reconfiguration from the multiple bearers to a single bearer, reordering PDCP PDUs received through the multiple bearers using a timer until a predetermined condition is satisfied, processing the reordered PDCP PDUs into at least PDCP SDUs.

According to another aspect of the present disclosure, there is provided UE. a UE in a wireless communication system supporting multiple bearers, including a receiver configured to receive data, and a controller configured to reorder PDCP PDUs received through the multiple bearers using a timer after completing bearer reconfiguration if the UE performs bearer reconfiguration from a single bearer to the multiple bearers, and process the reordered PDCP PDUs into at least PDCP SDUs.

According to another aspect of the present disclosure, there is provided UE. a UE in a wireless communication system supporting multiple bearers, including a receiver configured to receive data, and a controller configured to, if the UE performs bearer reconfiguration from the multiple bearers to a single bearer, reorder PDCP PDUs received through the multiple bearers using a timer until a predetermined condition is satisfied, and process the reordered PDCP PDUs into at least PDCP SDUs.

According to another aspect of the present disclosure, there is provided a method of a User Equipment (UE) in wireless communication systems, the method including receiving packet data convergence protocol data units (PDCP PDUs) from a lower layer, determining a count value of the received PDCP PDUs, deciphering the received PDCP PDUs using the count value of the received PDCP PDUs, storing at least PDCP Service Data Units (SDUs) corresponding to the deciphered PDCP PDUs in a buffer, and delivering at least PDCP PDUs after header decompression to an upper layer based on the count value of the received PDCP PDUs after performing the header decompression to the stored at least PDCP SDUs.

According to another aspect of the present disclosure, there is provided a user equipment, UE, in a wireless communication system, the UE including a transceiver, and a controller configured to control the transceiver to receive a packet data convergence protocol data unit, PDCP PDU, from a lower layer, determine a count value of the received PDCP PDU, decrypt the received PDCP PDU using the count value of the received PDCP PDU, store at least PDCP service data units, SDUs, corresponding to the decrypted PDCP PDU in a buffer, and deliver at least PDCP SDUs after header decompression to an upper layer based on the count value of the received PDCP PDU after performing header decompression on the stored at least PDCP SDUs.

According to another aspect of the present disclosure, there is provided a method of a base station BS in wireless communication systems, the method including receiving a packet data convergence protocol data unit, PDCP PDU, from a lower layer, determining a count value of the received PDCP PDU, decrypting the received PDCP PDU using the count value of the received PDCP PDU, storing at least PDCP service data units, SDUs, corresponding to the decrypted PDCP PDU, in a buffer, and delivering at least PDCP SDUs after header decompression to an upper layer based on the count value of the received PDCP PDU after performing header decompression on the stored at least PDCP SDUs.

According to another aspect of the present disclosure, there is provided a base station BS in wireless communication systems, the BS including a transceiver, and a controller configured to control the transceiver to receive a packet data convergence protocol data unit (PDCP PDU) from a lower layer, determine a count value of the received PDCP PDU, decrypt the received PDCP PDU using the count value of the received PDCP PDU, store at least PDCP service data units SDUs corresponding to the decrypted PDCP PDU in a buffer, and deliver at least PDCP SDUs after header decompression to an upper layer based on the count value of the received PDCP PDU after performing header decompression on the stored at least PDCP SDUs.

Other aspects, advantages, and salient features of the disclosure will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses various embodiments of the disclosure.

Drawings

The above and other aspects, features and advantages of particular embodiments of the present disclosure will become more apparent from the following description when taken in conjunction with the accompanying drawings, in which:

fig. 1 illustrates a structure of a Long Term Evolution (LTE) system according to an embodiment of the present disclosure;

fig. 2 illustrates a radio protocol structure in an LTE system according to an embodiment of the present disclosure;

fig. 3 illustrates evolved node b (enb) intra-Carrier Aggregation (CA) in an LTE system according to an embodiment of the present disclosure;

fig. 4 illustrates inter-ENB CA in an LTE system according to an embodiment of the present disclosure;

fig. 5 illustrates a connection structure of a Packet Data Convergence Protocol (PDCP) device in an LTE system according to an embodiment of the present disclosure;

fig. 6 illustrates a PDCP operation handover process in an LTE system according to an embodiment of the present disclosure;

fig. 7 illustrates reconfiguration of a Radio Link Control (RLC) device during a PDCP operation handover process in an LTE system according to an embodiment of the present disclosure;

fig. 8 illustrates an operation of a User Equipment (UE) during bearer reconfiguration in an LTE system according to an embodiment of the present disclosure;

fig. 9 illustrates upper layer delivery conditions of PDCP operation in an LTE system according to an embodiment of the present disclosure;

fig. 10 illustrates an operation of a PDCP receiving apparatus in an LTE system according to an embodiment of the present disclosure;

fig. 11 illustrates operations performed in the PDCP receiving apparatus as illustrated in fig. 10 when the timer 1 expires according to an embodiment of the present disclosure;

fig. 12 illustrates operations of a UE setting a Prioritized Bit Rate (PBR) for multiple bearers according to an embodiment of the disclosure;

fig. 13 illustrates a format of a status PDU according to an embodiment of the present disclosure;

fig. 14 illustrates an operation of an RLC receiving apparatus generating a status Protocol Data Unit (PDU) according to an embodiment of the present disclosure;

fig. 15 illustrates an operation of an RLC transmission apparatus receiving a status PDU according to an embodiment of the present disclosure;

fig. 16 is a block diagram illustrating a configuration of a UE in an LTE system according to an embodiment of the present disclosure;

fig. 17 is a block diagram illustrating a configuration of an ENB in an LTE system according to an embodiment of the present disclosure;

fig. 18 illustrates an operation in which an ENB performs downlink data transmission/reception with a UE that has reported three categories according to an embodiment of the present disclosure;

fig. 19 illustrates UE operation according to an embodiment of the present disclosure;

fig. 20, 24, 28 and 29 illustrate various examples of UE operation during bearer reconfiguration according to various embodiments of the present disclosure;

fig. 21 illustrates an operation of a PDCP receiving apparatus operating per multi-bearer according to an embodiment of the present disclosure;

fig. 22 illustrates an operation of a PDCP receiving apparatus switching to PDCP operation 5 when a bearer is reconfigured from a multi bearer to a Master Cell Group (MCG) bearer according to an embodiment of the present disclosure;

fig. 23 illustrates an operation of the PDCP receiving apparatus performed when the timer 3 expires according to an embodiment of the present disclosure;

fig. 25 illustrates a PDCP operation 7 of a PDCP receiving apparatus operating per multi-bearer according to an embodiment of the present disclosure;

fig. 26 illustrates an operation of the PDCP receiving apparatus performed when the timer 3 expires according to an embodiment of the present disclosure; and

fig. 27 illustrates an operation of determining whether a UE has repeatedly received PDCP PDUs according to an embodiment of the present disclosure.

Throughout the drawings, the same reference numerals will be understood to refer to the same parts, components and structures.

Detailed Description

The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the disclosure as defined by the claims and their equivalents. It includes various specific details to assist in this understanding, but these are to be considered merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. Moreover, descriptions of well-known functions and constructions may be omitted for clarity and conciseness.

It should be apparent, therefore, to those skilled in the art that the following description of the various embodiments of the present disclosure is provided for the purpose of illustration only and not for the purpose of limiting the disclosure as defined by the appended claims and their equivalents.

Thus, for example, reference to "component surface" includes reference to or more of these surfaces.

By the term "substantially" it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but may be subject to variation or variation in amounts that do not preclude the effect that the characteristic is intended to provide, including for example, tolerances, measurement error, measurement accuracy limitations, and other factors known to those of skill in the art.

The present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the present disclosure are shown.

Fig. 1 illustrates a structure of an LTE system according to an embodiment of the present disclosure.

Referring to fig. 1, a Radio Access Network (RAN) of an LTE system may include evolved node bs (enbs) (or node bs or base stations) 105, 110, 115, and 120, a Mobility Management Entity (MME)125, and a serving gateway (S-GW) 130. A User Equipment (UE) (or terminal) 135 may access an external network (not shown) through

ENBs

105, 110, 115, and 120 and S-GW 130.

The

ENBs

105, 110, 115, and 120 may correspond to legacy node Bs in a Universal Mobile Telecommunications System (UMTS) system the

ENBs

105, 110, 115, and 120 may be connected with the UE 135 through a wireless channel and may perform a more complex role than the legacy node Bs, in the LTE system, since all user traffic including real-time services such as voice over Internet protocol (VoIP) is served through a shared channel, a device that performs scheduling by collecting status information such as buffer status, available transmission power status, and channel status of the UE is required, and scheduling is managed by the

ENBs

105, 110, 115, and 120, of the

ENBs

105, 110, 115, and 120 may generally control a plurality of cells.

Fig. 2 illustrates a radio protocol structure in an LTE system according to an embodiment of the present disclosure.

Referring to fig. 2, in a radio protocol structure of an LTE system, a UE and an ENB may include Packet Data Convergence Protocols (PDCP)205 and 240, Radio Link Controls (RLC)210 and 235, and Medium Access Controls (MAC)215 and 230, respectively.

The

PDCPs

205 and 240 are responsible for operations such as Internet Protocol (IP) header compression/decompression, and the RLC's 210 and 235 can reconstruct PDCP Protocol Data Units (PDUs) in an appropriate size to perform automatic repeat reQuest (ARQ) operations, the MAC's 215 and 230 connected to a plurality of RLC layer devices configured in UEs can perform operations of multiplexing RLC PDUs in and demultiplexing RLC PDUs from the MAC PDUs, the physical layers (PHYs) 220 and 225 can channel-encode and modulate upper layer data to make OFDM symbols and transmit them through radio channels, and the

physical layers

220 and 225 can demodulate and channel-decode OFDM symbols received through the radio channels and deliver them to their upper layers.

Fig. 3 illustrates intra-ENB (intra-ENB) CA in an LTE system according to an embodiment of the present disclosure.

Referring to fig. 3, ENBs may generally transmit and receive multiple carriers over multiple frequency bands, for example, when transmitting a carrier 315 having a forward center frequency f1 and a carrier 310 having a forward center frequency f3 from an ENB305, UEs may transmit and receive data using any of two carriers f1 and f3 according to the related art, however, a CA-capable UE 330 may simultaneously transmit and receive data over multiple carriers, the ENB305 may allocate more carriers to the CA-capable UE 330 according to circumstances, thereby increasing a transmission rate of the UE 330, this method of aggregating forward (or downlink) and reverse (or uplink) carriers transmitted and received by the ENB may be referred to as intra-ENB CA., however, in cases, downlink and uplink carriers transmitted and received from/at different ENBs may need to be aggregated, unlike in the example shown in fig. 3.

Fig. 4 illustrates inter-ENB (inter-ENB) CA in an LTE system according to an embodiment of the present disclosure.

Referring to fig. 4, when ENB 1405 transmits and receives data through a carrier having a center frequency f1 and ENB2415 transmits and receives data through a carrier having a center frequency f2, UE 430 may aggregate (or combine) a carrier having a downlink center frequency f1 and a carrier having a downlink center frequency f2, resulting in a result of UEs aggregating carriers from two or more ENBs.

Terms used herein will be described below.

In a conventional sense, when downlink carriers transmitted by ENBs and uplink carriers received by the ENBs constitute cells, "carrier aggregation" may be interpreted as an operation in which a UE simultaneously transmits and receives data through a plurality of cells.

Herein, an expression that a UE receives data through any downlink carrier or transmits data through any uplink carrier has the same meaning as the following expression: that is, the UE transmits and receives the representation of data using the control channel and the data channel provided by the cell corresponding to the center frequency and the frequency band characterizing the carrier. In this document, CA will be expressed as "multiple serving cells are set up" and terms such as PCell and SCell or enabled serving cells will be used. These terms may have the same meaning as those used in the LTE mobile communication system. In the present disclosure, terms such as carrier, component carrier, and serving cell will be used interchangeably.

Herein, the set of serving cells controlled by the same ENB will be defined as a cell group or Carrier Group (CG). the cell group may be subdivided into a Master Cell Group (MCG) and a Secondary Cell Group (SCG). MCG refers to the set of serving cells controlled by the ENB controlling the PCell (e.g., master ENB (menb)), and SCG refers to information about whether the serving cell belongs to an MCG or SCG, which the ENB provides to UE. in setting the serving cells may set MCGs and or more SCGs for UEs, although it is assumed herein that SCGs are set even though 5 or more SCGs are set, it may be interpreted as applying the disclosed details that the serving cell is set for UEs and or more SCGs. although the PCell may be set in cooperation with SCell 3, the PCell may be defined herein based on the PCell and SCell status, although the PCell status may be interpreted as being a primary cell group or secondary cell group (SCell). the SCell) and the SCell may be set as a PCell.

In addition , the pico cell, which is a cell controlled by the SeNB, may provide service in a significantly narrower area than a typical macro cell.

Referring to fig. 4, if the ENB 1405 is an MeNB and the ENB2415 is an SeNB, the serving cell 410 having the center frequency f1 may be a serving cell belonging to an MCG, and the serving cell 420 having the center frequency f2 may be a serving cell belonging to an SCG.

In the following description, other terms instead of MCG and SCG may be used for better understanding. For example, terms such as primary and secondary sets or groups of primary and secondary carriers may be used. In this case, however, it should be noted that although the terms are different, their meanings are the same. The main purpose of these terms is to determine whether a certain cell is controlled by an ENB of a PCell controlling a specific UE, and the operation mode of the UE and the cell may vary according to whether the cell is controlled by an ENB of a PCell controlling a specific UE.

Although or more SCGs can be set for a UE, it will be assumed herein for convenience only that a maximum of SCGs are set-the SCGs may include multiple scells, any of which may have special attributes.

In a typical intra-ENB CA, a UE may transmit not only Hybrid Arq (HARQ) feedback and Channel State Information (CSI) of a PCell but also HARQ feedback and CSI of an SCell through a Physical Uplink Control Channel (PUCCH) of the PCell. This will apply CA even for UEs that cannot transmit uplink simultaneously.

In the case of inter-ENB CA, it may not be practical to transmit HARQ feedback and csi for a CSG SCell through an uplink control channel PUCCH as a PCell-HARQ feedback should be delivered within a HARQ Round Trip Time (RTT) (typically 8ms) because the transmission delay between MeNB and SeNB may be longer than the HARQ RTT.

Generally, user services may be served by Evolved Packet System (EPS) bearers, and EPS bearers may be connected with radio bearers the radio bearers may be configured with PDCP and RLC, and in inter-ENB CA, data transmission/reception efficiency can be improved by arranging PDCP and RLC devices of radio bearers on different ENBs.

Fig. 5 illustrates a connection structure of a PDCP device in an LTE system according to an embodiment of the present disclosure.

Referring to fig. 5, in case of, for example, a high capacity data service, a user service may transmit and receive data to and from both MeNB and SeNB by forming two RLC devices as shown by reference numeral 510, if the user service is a service having strict quality of service (QoS) requirements like voice over LTE (VoLTE) , the user service may transmit and receive data by arranging the RLC devices on only the MeNB as shown by reference numeral 505, hereinafter, a bearer 505 will be referred to as a single bearer and a bearer 510 will be referred to as a multi bearer for convenience of description, a PDCP device of a single bearer may be connected with RLC devices and a PDCP device of a multi bearer may be connected with two RLC devices, an RLC device to transmit and receive data from or on by an MCG (which is connected with a MAC device of a service cell associated with an MCG) will be referred to g 515, and an RLC device to transmit and receive data from or on an MCG will be referred to as MCG between an RLC device and a MAC device of a logical MAC channel associated with an MCG-MAC channel is referred to as SCG 515, and RLC device to transmit and MAC channel is referred to as an MCG-MAC channel is referred to as SCG-MAC channel transmit and MAC device is connected between an MCG logical MAC channel.

In the following, for convenience of description, a macro cell region refers to a region where no small cell signal is received and only a macro cell signal is received, and a small cell region refers to a region where a macro cell signal is received and -start, when a UE having a large demand for downlink data has moved from the macro cell region to the small cell region, a small cell may be additionally set for the UE, and among bearers of the UE, a bearer having a large amount of downlink data like a File Transfer Protocol (FTP) may be reconfigured from a single bearer to a multi bearer, in other words, when the UE moves from the macro cell region to the small cell region and back to the macro cell region, a specific bearer may be reconfigured from a single bearer to a multi bearer, and reconfigured back to a single bearer, because a PDCP device of a single bearer is connected with RLC and delivers sequential (or ordered) packets to the PDCP device, a PDCP device may process sequentially packets delivered by another aspect, and a PDCP device may be connected with two RLC devices and may not, thus, a PDCP device may not be configured to handle sequentially sequential single bearers, or may be operated after a PDCP bearer is changed from a PDCP device.

In an embodiment of the present disclosure, the operation of the UE may be divided into PDCP operation 1, PDCP operation 2, and PDCP operation 3.

The details of the above operation follow section 5.1.2 of 3GPP standard TS36.323 PDCP operation 2 is another operation applied to the PDCP of a single bearer, and PDCP operation 1 is applied in the case of .

PDCP operation 2 may be applied in exceptional cases where the lower layer device is not able to perform reordering (e.g., during a handover situation or Radio Resource Control (RRC) connection re-establishment procedure) PDCP operation 2 details of the above operations also follow section 5.1.2 of 3GPP standard TS36.323 when operating in PDCP operation 1, PDCP may perform necessary processing on the assumption that the order of received packets is correct, and then deliver the received packets and packets with sequence numbers lower than those of the received packets to the upper layer aspect, where the lower layer device does not perform reordering, PDCP may store the packets in PDCP operation 2, for example, without delivering them to the upper layer, since the order of the received packets may not be correct in PDCP operation 2, PDCP may store the packets in PDCP buffer, and thereafter, when reordering is again provided by the lower layer device (e.g., if handover is complete or RRC connection re-establishment procedure is complete), PDCP may switch to operation 1, and a short time handover control may occur between PDCP Service Data Units (SDUs) stored and PDCP just after the PDCP operation has been received.

In another aspect , in PDCP operation 3, the PDCP may first determine whether the received PDCP PDUs are reordered, then process only the ordered PDCP PDUs into PDCP SDUs and deliver them to an upper layer, even in PDCP operation 3, the PDCP PDUs may be processed into PDCP SDUs, and then reorder the PDCP PDUs, the reordering is performed, the details of PDCP operation 1, PDCP operation 2, and PDCP operation 3 will be described below, although PDCP operation 2 may be temporarily applied in a handover situation, while PDCP bearer operation 3 may be continuously applied in parallel with PDCP operation in PDCP multi-bearer operation, PDCP operation 3 may be applied in PDCP single bearer operation, or PDCP bearer operation may be performed if a handover from PDCP bearer to multi-bearer operation occurs, when PDCP PDU is being applied to PDCP bearer operation 3, or PDCP PDU loss occurs in early stage, when PDCP bearer operation 3 is not necessary.

Fig. 6 illustrates a PDCP operation handover process in an LTE system according to an embodiment of the present disclosure.

With reference to FIG. 6, the operation of the UE and the ENB in association with bearer reconfiguration including a process in which the UE performs PDCP operation handover at an appropriate time will be described in more detail.

Referring to fig. 6, in a mobile communication system including a UE605, an MeNB610 and a SeNB 615, the MeNB610 may determine to add a serving cell of the SeNB 615 to the UE605 at any time and perform a procedure of the serving cell addition with the SeNB 615 in operation 620 if the MeNB610 first sets an SCell of the SeNB 615 for the UE605 (e.g., if the MeNB610 sets SCG SCell), the MeNB610 and the SeNB 615 may determine which bearers the MeNB610 will serve and which bearers the SeNB 615 will serve.

In operation 625, the MeNB610 may transmit a predetermined RRC control message to the UE 605. The RRC control message may contain SCell configuration information and multi-bearer information. The SCell configuration information is for a newly added SCell, and may further include information indicating whether the SCell is an MCG SCell or an SCG SCell. The multi-bearer configuration information is information on a radio bearer reconfigured from a single bearer to a multi-bearer, and may include an identifier of the radio bearer and SCG RLC configuration information.

In operation 630, upon receiving the control message, the UE605 may generate an SCG RLC device for the bearer indicated by the bearer identifier to connect it with the PDCP device, and may connect the SCG RLC device to the MAC device for SCG. The UE605 may switch from PDCP operation 1 to PDCP operation 3 when the configuration of the multi-bearer is completed or when the random access described below is completed. An existing RLC device (e.g., MCG RLC) of the bearer may perform normal data transmission/reception operations (e.g., an operation of delivering in-order PDCP PDUs to the PDCP device and storing out-of-order (or out-of-order) PDCP PDUs in an RLC buffer in an attempt to recover the missing PDUs through an ARQ process) even during the reconfiguration process. As will be described below, the MCG RLC apparatus can also stop the RLC reception operation and then perform the RLC reconfiguration process in the reconfiguration process from the multi-bearer to the single bearer, unlike in the reconfiguration process from the single bearer to the multi-bearer.

In operation 635, the UE605 may perform random access in the newly added SCG SCell. Through the random access procedure, the UE605 may establish uplink synchronization with the newly added SCG SCell and set uplink transmission power. If the random access procedure is completed, the UE605 may switch the operation of the PDCP device reconfigured to the multi-bearer from the PDCP operation 1 to the PDCP operation 3 in operation 640. The time when the random access procedure is completed may include a time when the UE receives a valid random access response message if the dedicated preamble is used, and a time when the UE receives an uplink grant or a downlink assignment addressed to a cell-radio network temporary identifier (C-RNTI) and indicating a new transmission if the random preamble is used. Other details regarding random access follow the LTE standard TS 36.321.

In operation 645, the UE605 may transmit a predetermined RRC control message to the MeNB610 to report completion of the SCell configuration and multi-bearer reconfiguration. In operation 650, upon receiving the reported information, MeNB610 may forward multi-bearer downlink data to SeNB 615, and SeNB 615 may initiate transmission of the downlink data to UE605 over the multi-bearer SCG RLC.

In operation 655, the UE605 may transmit an RRC control message, then receive downlink data of the multi-bearer from the MCG RLC device and the SCG RLC device, and apply PDCP operation 3 to the received PDCP PDUs.

Thereafter, in operation 670, MeNB610 or SeNB 615 may determine to release the SCG SCell at any time. After performing the procedure for releasing the SCG SCell, MeNB610 or SeNB 615 may send an RRC control message to UE605 in operation 675 to indicate the release of the SCG SCell.

In operation 680, upon receiving the control message, the UE605 may release the SCG SCell in response to the instruction. If the control message indicates the release of the last SCG SCell (e.g., if the UE605 releases the SCG SCell in response to the command of the control message), the UE605 may perform the necessary procedures for reconfiguration from multi-bearer to single bearer even if there are no more SCG scells or no separate command. The UE605 may similarly perform operations for reconfiguration from multi-bearer to single bearer even if the control message explicitly indicates the reconfiguration from multi-bearer to single bearer.

Reconfiguration operation from multi-bearer to single bearer:

1) releasing the SCG RLC of the indication of the multi-bearer;

2) reconfiguring an MCG RLC receiving means of the indication of the multiple bearers;

3) discarding downlink HARQ buffer data of the MCG-MAC; and

4) triggering a PDCP status report.

In the procedure of releasing the SCG RLC, the UE605 may reconfigure downlink RLC PDUs stored in the SCG RLC into RLC SDUs and then deliver them to the PDCP, and may discard uplink RLC PDUs and downlink RLC SDUs stored in the SCG RLC. RLC SDU/PDCP PDUs delivered from the SCG RLC are out-of-sequence RLC SDU/PDCP PDUs (i.e., even if they are sent earlier than RLC SDU, there are RLC SDUs that have not yet been received).

The expression that the UE reconfigures the MCG RLC reception apparatus may refer to the following expression: the UE initializes a reception window, initializes a reception sequence number, delivers downlink RLC PDUs capable of being reconfigured into RLC PDUs among the downlink RLC PDUs stored in its reception buffer to the PDCP, and discards the remaining downlink RLC PDUs. The UE may not discard the uplink RLC PDUs and RLC SDUs stored in its transmit buffer.

The PDCP status report may be triggered for each radio bearer, and the UE605 may examine the sequence numbers of PDCP packets stored in its buffer of the PDCP of a bearer reconfigured from the multi-bearer to a single bearer to generate a PDCP status report including information associated with the sequence number of the missing PDCP packet. The PDCP buffer may store therein PDCP PDUs delivered from the SCGRLC and PDCP PDUs delivered from the MCG RLC.

The PDCP status report is control information used to prevent loss of PDCP packets during handover or RRC connection re-establishment. The handover or RRC connection re-establishment procedure may be accompanied by re-establishment of all RLC devices configured in the UE605 (e.g., re-establishment of lower layers from the perspective of the PDCP device). If a handover or RRC connection re-establishment procedure is initiated, the UE605 may trigger PDCP status report for all Data Radio Bearers (DRBs) that satisfy the following PDCP status report generation condition 1. If the last SCG SCell is released, the UE605 may trigger PDCP status report for all DRBs that satisfy the following PDCP status report generation condition 2. If the bearer is reconfigured from multi-bearer to single bearer, the UE605 may check whether the bearer satisfies the following PDCP status report generation condition 3 to determine whether to generate a PDCP status report.

PDCP status report generation condition 1:

among the DRBs in which the RLC Acknowledged Mode (AM) is set, a DRB in which statesreportrequired is set.

PDCP status report generation condition 2:

multi-bearer among DRBs of RLC AM and statesreportrequired is set.

PDCP status report generation condition 3:

at least of the multiple bearers of SCG RLC and MCG RLC operate in RLC AM.

StatusReportrequired follows the description in the standards TS36.331 and TS 36.323.

If the UE605 reconfigures the multi-bearer to a single bearer, the UE605 may switch operation of PDCP of the reconfigured bearer from PDCP operation 3 to PDCP operation 2 in operation 685. The PDCP may store therein out-of-sequence PDCP SDUs delivered from the MCG RLC and out-of-sequence PDCP SDUs delivered from the SCG RLC. The PDCP may store PDCP SDUs delivered in the reconfiguration process of the MCG RLC and PDCP SDUs delivered in the release process of the SCG RLC in its PDCP buffer in order of COUNT (COUNT), generate a PDCP status report in which both the reception status of the PDCP SDUs delivered from the MCG RLC and the reception status of the PDCP SDUs delivered from the SCG RLC are reflected, and transmit the PDCP status report to the MeNB 610.

In operation 690, the UE605 may transmit a predetermined RRC control message to the MeNB610 to report successful completion of the above procedure, and the UE605 and the MeNB610 may exchange uplink data and downlink data with each other through the MCG SCell.

Particularly in the reconfiguration process from a multi-bearer to a single bearer, the UE may not only release the SCG RLC apparatus but also reconfigure the MCG RLC apparatus. In principle, the MCG RLC apparatus is not affected in the reconfiguration process from a multi-bearer to a single bearer, so it is not necessary to reconfigure the MCG RLC apparatus.

However, in embodiments of the present disclosure, the MCG RLC apparatus may be manually reconfigured in order to make efficient handover of PDCP operation as shown in the example of fig. 7.

Fig. 7 illustrates reconfiguration of an RLC apparatus during a PDCP operation handover process in an LTE system according to an embodiment of the present disclosure.

Referring to fig. 7, out-of-order PDCP PDUs [10] and PDCP PDUs [11] may be stored in the MCG RLC 710 (i.e., PDCP PDU [9] is missing) when a reconfiguration from, for example, a multi-bearer to a single bearer is indicated, and out-of-order PDCP PDUs [7], PDCP PDU [8], PDCP PDU [12], PDCP PDU [13] and PDCP PDU [14] may be stored in the SCG RLC715 for reference, it will be assumed that the front number of the rectangle represents the RLC sequence number, for example, the RLC sequence number of the PDCP PDU [10] is 5, and the RLC sequence number of the PDCP PDU [11] is 6.

In other words, the UE may release the SCG RLC apparatus and reconfigure the MCG RLC apparatus, and then switch PDCP operation from PDCP operation 3 to PDCP operation 2 if th PDCP PDU is received after the bearer is reconfigured to be a single bearer, the PDCP may switch from PDCP operation 2 to PDCP operation 1.

Fig. 8 illustrates an operation of a UE during bearer reconfiguration in an LTE system according to an embodiment of the present disclosure. In the example of fig. 8, the operation of the UE to reconfigure an arbitrary bearer x from a normal bearer to a multi-bearer and back to the normal bearer will be described.

Referring to fig. 8, in operation 805, the UE may apply PDCP operation 1 for bearer x, which is a single bearer. In operation 810, the UE may receive a control message for reconfiguring bearer x into a multi-bearer. In operation 815, the UE may generate/configure an SCG RLC device to be connected with the multi-bearer according to the configuration information indicated by the control message, and then connect the SCGRLC device with the PDCP. In operation 820, the UE may switch PDCP operation from PDCP operation 1 to PDCP operation 3. In other words, the UE may check whether to reorder the PDCP PDUs starting from the PDCP PDUs received first after the bearer is reconfigured into a multi-bearer, and then apply PDCP operation 3 in order to determine whether to deliver the PDCP PDUs to an upper layer. Thereafter, by applying PDCP operation 3 to the PDCP PDUs of the reconfigured bearer, the UE can perform an operation of converting the PDCP PDUs into PDCP SDUs and delivering the sequenced PDCP SDUs to an upper layer.

Upon receiving the control message indicating the reconfiguration of the multi-bearer to the single bearer in operation 825, the UE may release the SCG RLC and re-establish the MCG RLC in operation 830. In this case, the UE may release both the transmitting apparatus and the receiving apparatus for the SCG RLC and re-establish only the receiving apparatus for the MCG RLC. In other words, the UE may normally process RLC SDUs and RLC PDUs stored in the MCG RLC transmission apparatus without discarding them, and may assemble all RLC PDUs capable of being assembled in the RLC SDUs among the RLC PDUs stored in the RLC reception apparatus into RLC PDUs, then deliver them to PDCP and discard the remaining RLC PDUs.

In operation 835, the UE may first switch PDCP operation to PDCP operation 2 without immediately switching PDCP operation from PDCP operation 3 to PDCP operation 1 in other words, the UE may convert PDCP PDUs delivered from the MCG RLC and SCG RLC into PDCP SDUs by processing the PDCP PDUs according to the count, and then store all SDUs immediately following the -th missing SDU in a buffer.

In operation 840, the UE may apply PDCP operation 1 for PDCP PDUs starting from the PDCP PDU that is first received after the bearer is reconstructed into a single bearer, in other words, after the UE converts th PDCP PDU into SDUs, even if there are missing SDUs having a lower count than the received SDU among the SDUs, the UE may deliver SDUs whose count is consecutive around the count of the received SDUs to an upper layer, thereby determining that the SDUs are sequential.

Operations 830, 835 and 840 may be modified as follows the UE may release the SCG RLC and maintain MCGRLC in operation 830 and may switch PDCP operation from PDCP operation 3 to PDCP operation 2 in operation 835 in other words the UE may process PDCP PDUs delivered from the SCG RLC and store out-of-order PDCP SDUs in the PDCP buffer without delivering them to the upper layer in operation 840, if handover to a single bearer is complete or if the th PDU is received after handover to a single bearer, the UE may start a predetermined timer 2. the UE may maintain PDCP operation 2 while timer 2 is in operation and may switch from PDCP operation 2 to PDCP operation 1 if timer 2 expires in other words while timer 2 is in operation, the UE may wait until out-of-order PDCP PDUs that have occurred due to release of SCG are sequential.

As for PDCP operation 1, PDCP operation 2, and PDCP operation 3, it can be understood that a plurality of specific operations which should be applied to PDCP PDUs delivered from the RLC device are listed in the order of series.

TABLE 1

[ Table 1]

How to determine the Hyper Frame Number (HFN)/COUNT (COUNT) of received PDCP PDUs given in table 1, the COUNT being a 32 bit integer and increasing from zero (0) may be allowed COUNTs per PDCP packet and COUNTs may be used for security related operations such as ciphering/deciphering of PDCP packets, the COUNT may increase monotonically in the order in which PDCP packets are delivered to the lower layers and, in principle, may be assigned in the order in which PDCP SDUs are delivered from the upper layers, the COUNT may be configured with (or may include) an HFN and a PDCP Sequence Number (SN), although a PDCP SN may be sent by being included in the header of a PDCP packet, but may not explicitly deliver an HFN, thus, the receiving apparatus should determine on its own the HFN of a received packet if the transmitting apparatus is in compliance with predetermined conditions (e.g. the condition that a packet is transmitted such that the loss of the PDCP SN may be less than the half sequence number of a PDCP SN that can be indicated by the PDCP SN when transmitting the packet, the receiving apparatus is able to process a current packet with a higher sequence number if the highest sequence number received packet is received by the PDCP SN, the decompression standard 5.1.2.12. the header 36. the header of a PDCP SN, the receiving apparatus may be able to discard the highest sequence number if the packet is received PDCP SN, the decompression standard 36, e.g. the sequence number received packet is received by a decompression standard 36, the decompression standard 36 is not repeated.

Processing the PDCP PDU whose HFN and count are determined into a PDCP SDU may refer to decoding the PDCP PDU and decompressing a header of an IP packet included in the PDCP PDU, and the details thereof may follow the description in the standard 36.323.

Hereinafter, for convenience of description, a COUNT (COUNT) corresponding to Last _ subject _ PDCP _ RX _ SN will be referred to as Last _ subject _ PDCP _ RX _ COUNT, a COUNT corresponding to the received PDCP SN will be referred to as a received PDCP COUNT, and a COUNT corresponding to Next _ PDCP _ RX _ SN will be referred to as Next _ PDCP _ RX _ COUNT.

Upper layer delivery condition 1 of PDCP operation 1 is as follows.

Upper layer delivery condition 1 for PDCP operation 1

If processing for any PDCP SDU [ X ] is completed in PDCP operation 1, the UE may determine that "SDU with count lower than X" and "SDU with count lower than the lowest missing count among the missing counts greater than X" among PDCP SDUs stored in the buffer have satisfied upper layer delivery condition 1 and then deliver these SDUs to the upper layer, for example, if PDCP SDU [90] -PDCP SDU [99], PDCP SDU [101] -PDCP SDU [110], and PDCP [112] -PDCP [115] are stored in the PDCP buffer when PDCP SDU [100] is received, PDCP SDU [100], PDCP SDU [90] -PDCP SDU [100] (is PDCP SDU with count lower than the count of PDCP SDU [100 ]) and PDCP PSDU [101] -PDCP SDU [110] (which is PDCP SDU [111 ]) SDU, PDCP [111] is a PDCP SDU among PDCP SDU with count higher than PDCP SDU [100 ]) SDU ) and may be delivered on PDCP SDU [112, and may be delivered to the PDCP layer upon receiving PDCP SDU [100] and may be further delivered to the PDCP SDU, the PDCP SDU [112, the PDCP layer may be delivered by the PDCP layer, and the PDCP PDU may be delivered, if the PDCP SDU [1, the PDCP SDU is not delivered, the PDCP SDU is received, the.

Upper layer delivery condition 2 of PDCP operation 2 is as follows.

Upper layer delivery condition 2 for PDCP operation 2

In the PDCP operation 2 triggered by receiving any PDCP SDU, if the received PDCP SDU is the missing PDCP SDU having the lowest COUNT (e.g., if the received PDCP COUNT is the same as a value obtained by adding 1 to Last _ transmitted _ PDCP _ RX _ COUNT), the next missing PDCP SDU including the received PDCP SDU can be delivered to the upper layer. If the received PDCP SDU is not the missing PDCP SDU with the lowest count, the PDCP SDU can be stored in a PDCP buffer. In PDCP operation 3 triggered by receiving any PDCP PDU, it is checked whether there is an SDU satisfying the upper layer delivery condition 3 among PDCP SDUs (including processed PDCP SDUs) stored in the PDCP buffer, and only SDUs satisfying the upper layer delivery condition 3 can be delivered to the upper layer.

The upper layer delivery condition 3 of the PDCP operation 3 will be described below.

Upper layer delivery condition 3 for PDCP operation 3

Fig. 9 illustrates upper layer delivery conditions of PDCP operation in an LTE system according to an embodiment of the present disclosure.

Referring to fig. 9, in a single bearer 905 in which logical channels are established, a PDCP transmitting apparatus 910 may deliver packets [1], packet [2], packet [3], and packet [4] to an RLC receiving apparatus 915 in the order of the packets, the packets may be received at the RLC transmitting apparatus 920 through a MAC apparatus and a radio channel, in which case, if an error occurs in the radio channel, retransmission/error recovery may be performed using HARQ and ARQ, so the order of the packets received by the RLC transmitting apparatus 920 in this process may be different from the order of the packets already transmitted by the PDCP transmitting apparatus 910, the RLC transmitting apparatus 920 may reorder the out-of-order packets and then deliver the packets to a PDCP receiving apparatus 925, for example, the RLC transmitting apparatus 920 may deliver the packets to the PDCP receiving apparatus 925 in the order of the packet [1], the packet [2], the packet [3], and the packet [4 ].

In the case of the multi-bearer 930 with two logical channels established, the PDCP sending means 935 may deliver the packet to the two RLC sending means 940 and 945 for example, the PDCP sending means 935 may deliver the packet [1] and the packet [3] to the -th RLC sending means 940 and deliver the packet [2] and the packet [4] to the second RLC sending means 945.

The th RLC transmitting device 940 may deliver packets to the th RLC receiving device 950 and the second RLC transmitting device 945 may deliver packets to the second RLC receiving device 955 the th RLC receiving device 950 may reorder the received packets in the order in which the th RLC transmitting device 940 has received packets from the PDCP transmitting device 935. in other words, the th RLC receiving device 950 may deliver the packets to the PDCP receiving device 960 in the order of the packet [1] and the packet [3], similarly, the second RLC receiving device 955 may reorder the received packets in the order in which the second RLC transmitting device 945 has received packets from the PDCP transmitting device 935.in other words, the second RLC transmitting device 945 may deliver the packets to the PDCP receiving device 960 in the order of the packet [2] and the packet [4 ].

However, the packets delivered by the st RLC receiving device 950 and the second RLC receiving device 955 may not be in order, for example, the packets delivered by the st RLC receiving device 950 and the second RLC receiving device 955 may be delivered in the order of packet [1], packet [2], packet [4], and packet [3] or in the order of packet [2], packet [4], packet [1], and packet [3], thus, the PDCP receiving device 960 may need to reorder the packets delivered by the two or more

RLC receiving devices

950 and 955.

In an embodiment of the present disclosure, whether any missing PDCP SDU [ x ] is reordered may be determined according to whether the reordering condition 3 is satisfied. The reordering condition 3 can be summarized as follows.

Arbitrary PDCPSDU [ x ]]Reordering condition 3 of

PDCP SDUs having higher counts than X have been received from both the MCG RLC and SCG RLC, and the associated timer 1 has expired.

If a PDCP SDU with a higher count than x is received from the RLC SCG, timer 1 is started and timer 1 will cope with out-of-order reception phenomena between MeNB and SeNB.

In the following description, the expression that any missing PDCP SDU [ x ] is reordered may mean that a subsequent operation is performed in consideration of the fact that SDU [ x ] is received, because there is no longer a possibility of receiving the missing SDU [ x ], if the missing SDU [ x ] is reordered, SDUs whose COUNT is between [ x +1] and y among received SDUs having a COUNT higher than x may be delivered to an upper layer, and then Last _ Submitted _ PDCP _ RX _ COUNT may be updated to y, which is a value obtained by subtracting 1 from the COUNT of th missing PDCP SDU higher than x.

TABLE 2

[ Table 2]

For example, if SDU [11] is received from the MCG RLC at an arbitrary time t1, the SDU can be delivered to an upper layer and the relevant variable can be updated to 11 because the SDU is a sequential SDU.

If SDU [13] is received from the MCG RLC at any time t2, a case may occur where RLC SDU [12] is missing and the UE may store SDU [13] in the PDCP buffer.

Thereafter, the UE may receive SDU [15] from the SCG RLC at any time t 3. The UE may start a T1 timer because the count of SDUs received from the SCG RLC is higher than the missing count. If missing PDUs are not received before the expiration of the T1 timer, it means that missing PDUs are not received from at least the SCG RLC.

Thereafter, the UE may receive SDU [14] from SCG RLC at any time T4, and thereafter, a T1 timer related to SDU [15] (or to SDU [12 ]) may expire at any time T5. because higher COUNTs than the missing COUNT have been received from both MCG RLC and SCG RLC, and the related T1 timer has expired, the UE may deliver PDCP SDUs [13], [14] and [15] (which are SDUs whose COUNTs are between 1 higher COUNT to 12 and lower COUNT to 16 higher COUNT than the missing SDU) to the upper layer, and update Last _ Submitted _ PDCP _ RX _ COUNT to 15.

When it is determined that any PDCP SDU is not received as described above, the timer 1 may be related to "the lowest count received from the SCG RLC among the counts higher than the missing count", "the count first received from the SCGRLC among the counts higher than the missing count", or "the missing count". In the above example, timer 1 may be timer 1 related to 12 or 15 because the sequence number of the missing SDU is 12 and the count received first from the SCG RLC among the counts higher than 12 is 15. The size of timer 1 may be determined to be large enough to cope with out-of-order reception that may occur between MeNB and SeNB. In other words, the size of the timer 1 may be determined to correspond to a possible maximum value of the reception time difference between two packets that have undergone an out-of-order reception phenomenon, which is defined as a phenomenon in which a packet transmitted by the MeNB to the SeNB at any time arrives at the SeNB earlier than a packet transmitted before the packet.

Fig. 10 illustrates an operation of a PDCP receiving apparatus in an LTE system according to an embodiment of the present disclosure. This is an operation performed when the multi-bearer PDCP receiving apparatus receives PDCP PDUs from the RLC receiving apparatus.

Referring to fig. 10, in operation 1005, a PDCP receiving apparatus may receive a PDCP PDU [ x ] from the RLC receiving apparatus in operation 1010, a UE may decode the PDCP PDU [ x ] and decompress a header of an IP packet included in the PDCP PDU [ x ] to reconfigure (i.e., convert or restore) the PDCP PDU [ x ] to a PDCP SDU [ x ]. if the PDCP SDU [ x ] is repeatedly received, the UE may discard the PDCP SDU [ x ] and wait until the next PDUs are received.

In operation 1020, the UE may determine whether PDCP SDU [ x ] has been received from the SCG RLC. If so, the UE may proceed to operation 1025, and if not, the UE may proceed to operation 10445. In operation 1025, the UE may determine whether there is an missing SDU having a lower sequence number than that of SDU [ x ] and SDU [ x ] is the first received SDU from the SCG RLC apparatus after the missing SDU occurs (e.g., whether there is no timer 1 in operation associated with the missing SDU). If the condition is satisfied, the UE may proceed to operation 1030, and if the condition is not satisfied, the UE may proceed to operation 1045. In operation 1030, the UE may start timer 1 and associate timer 1 with a count (e.g., a reception count, an absence count, or a value obtained by adding 1 to the reception count) related to the absent SDU.

In operation 1035, the PDCP receiving apparatus may determine whether there is a sequential SDU among the SDUs stored in the PDCP buffer. For example, if SDU [ x ] is a missing SDU, the above condition may be satisfied, and the PDCP receiving apparatus may deliver the sequenced SDU to an upper layer in operation 1040. An ordered SDU may refer to an SDU between the "highest count delivered to upper layers" or "highest count of order" and the "lowest count among missing counts" before SDU [ x ] is received. The PDCP receiving apparatus may deliver the sequenced SDUs to an upper layer in order in operation 1040. If the above condition is not satisfied, the UE may proceed to operation 1045.

First, the UE may determine whether there is a missing SDU having a count lower than the highest count received from the SCG RLC and the highest count received from the MCG RLC among the missing SDUs, for example, in the case where the count of the missing SDU is 10, the highest count received from the MCG RLC is a, and the highest count received from the SCG RLC is B, the condition may be satisfied if both a and B are higher than 10, and the condition may not be satisfied if of them are lower than 10.

In operation 1050, the UE may determine whether a timer 1 associated with the missing SDU or associated with Y has expired, if so, the UE may proceed to operation 1055, and if not, the UE may proceed to operation 1060. in operation 1055, the UE may deliver a predetermined SDU to an upper layer and then to operation 1060. the predetermined SDU may be an SDU between "[ Y +1 ]" and "the lowest count among the missing counts higher than Y". for example, if Y is 10 and the missing counts higher than 10 are 15, 20, and 25, the UE may deliver SDU [11], SDU [12], SDU [13], and SDU [14] to the upper layer and store the remaining SDUs in a PDCP buffer.

Fig. 11 illustrates operations performed in the PDCP receiving apparatus as illustrated in fig. 10 when the timer 1 expires according to an embodiment of the present disclosure.

Referring to fig. 11, in operation 1105, a timer 1 associated with any missing PDCP SDU [ z ] expires in this case, the UE may consider that there is no possibility that PDCP SDU [ z ] is missing due to an out-of-order reception phenomenon between the MeNB and the SeNB.

In operation 1110, the UE may determine whether the highest count received from the SCG RLC and the highest count received from the MCG RLC are higher than z, because timer 1 associated with the missing SDU [ z ] is started when receiving PDCP SDUs having a count higher than z from the SCG RLC, the UE may simply determine whether the highest count received from the MCG RLC is higher than z in operation 1110, if the condition is satisfied in operation 1110, the UE may deliver SDUs before the lower missing SDUs having a count higher than z to the upper layer among SDUs having a count higher than z in operation 1115, thereby determining that there is no possibility of re-receiving the missing SDU [ z ] and may consider that SDUs having the highest count up among SDUs delivered to the upper layer are sequential in operation 1120, the UE may wait until the reception of the lower PDUs or the expiration of timer 1 associated with another missing SDUs in operation 1110, if the condition is not satisfied in operation 1110, the UE may wait until the reception of the lower PDUs.

In the present disclosure, the expression that PDCP receives PDCP PDUs from MCG RLC may have the same meaning as follows: that is, the PDCP PDUs reconfigured according to the received data are received from the MCG serving cell or the MCG-MAC. The PDCP receiving the expression of the PDCP PDU from the SCG RLC may have the same meaning as follows: that is, the PDCP PDUs reconfigured according to the received data are received from the SCG serving cell or the SCG-MAC.

As another operation of reordering PDCP PDUs according to an embodiment of the present disclosure, methods may be proposed, which include performing timer-based reordering in case a bearer is reconfigured from a single bearer to a multi-bearer, determining a time when the reordering operation will be stopped, using a timer in case a bearer is reconfigured from a multi-bearer to a single bearer, and performing reordering and determining a stop time using the same timer as the two timers.

Fig. 20 illustrates UE operation during bearer reconfiguration according to an embodiment of the present disclosure. First, the UE may receive a control message for bearer reconfiguration from the ENB and then perform bearer reconfiguration based on the control message.

Referring to fig. 20, in operation 2005, the UE may apply PDCP operation 1 for bearer x, which is a single bearer. In operation 2010, the UE may receive a control message for reconfiguring bearer x into a multi-bearer. In operation 2015, the UE may create/configure an SCG RLC device to be connected with the multi-bearer according to the configuration information indicated by the control message, and then connect the SCGRLC device with the PDCP device. In operation 2020, the UE may switch operation of the PDCP device from PDCP operation 1 to PDCP operation 4. In other words, the UE may determine whether the PDCP PDUs are reordered starting from the PDCP PDUs received first after bearer x is reconfigured into multiple bearers, and then apply PDCP operation 4 in order to determine whether to deliver the PDUs to the upper layers. Thereafter, by applying PDCP operation 4 to the PDCP PDUs of the reconfigured bearer, the UE can perform an operation of converting the PDCP PDUs into PDCP SDUs and delivering the sequenced PDCP SDUs to an upper layer. The UE may use a timer 3 in determining whether the PDCP PDUs are reordered.

Upon receiving the control message indicating the reconfiguration of the multi-bearer to the single bearer in operation 2025, the UE may release the SCG RLC, switch from PDCP operation 4 to PDCP operation 5, and start timer 3 in operation 2030. The UE may perform PDCP operation 5 while the timer 3 is in operation, and if the timer 3 expires, the UE may stop the PDCP operation 5 and switch to PDCP operation 1 in operation 2035.

As for PDCP operation 1, PDCP operation 4, and PDCP operation 5, it can be understood that a plurality of specific operations that should be applied to PDCP PDUs delivered from the RLC device are listed in the order of series.

TABLE 3

[ Table 3]

Upper layer delivery condition 5 for PDCP operation 5

In the PDCP operation 5 applied while the timer 3 is operating, if the sequence number of the received PDCP SDU is the sequence number of the missing PDCP SDU having the lowest sequence number/count (e.g., if the received PDCP SN is the same as a value obtained by adding 1 to Last _ SUMITTED _ PDCP _ RX _ SN), the UE may deliver SDUs having consecutive sequence numbers/counts up to the next missing PDCP SDUs (including the received PDCP SDU) to the upper layer.

Hereinafter, for convenience of description, the sequence number will be used interchangeably with the count.

Upper layer delivery condition 4 for PDCP operation 4

If the sequence number of the received PDCP SDU is the same as the sequence number of the missing PDCP SDU with the lowest sequence number (e.g., if the received PDCP SN is the same as the value obtained by adding 1 to Last _ terminated _ PDCP _ RX _ SN), the UE may deliver sequentially received SDUs up to the lower missing PDCP SDUs (including the received PDCP SDU) to the upper layer if the received PDCP SDU is not the missing PDCP SDU with the lowest sequence number, the PDCP SDU may be stored in a PDCP buffer if the timer 3 is in operation, the UE may wait until the lower PDCP SDUs are received, and if the timer 3 is not in operation, the UE may start a timer 3 and store the Reordering _ RX _ COUNT, which is 1 higher than the highest COUNT among the COUNTs of the PDCP SDUs received at that time, if the timer 3 expires, the UE may store a COUNT with a lower PDCP _ RX _ COUNT than the Reordering _ RX _ COUNT and a higher COUNT than the highest COUNT of the PDCP SDU among the PDCP SDUs received at that time, and store the Last PDCP SDU COUNT of the PDCP SDU in a higher PDCP _ backing _ rlc _ RX _ N + counting buffer, and if the Last PDCP SDU is not delivered to the PDCP SDU, the UE may store a higher counting than the Last PDCP SDU buffer, and the lower PDCP _ receiving PDCP SDU, and the lower PDCP SDU.

Fig. 21 illustrates an operation of a PDCP receiving apparatus operating per multi-bearer according to an embodiment of the present disclosure. This shows the operation of the PDCP receiving operation in which a packet has been received from the RLC receiving apparatus.

Referring to fig. 21, in operation 2105, the PDCP receiving apparatus may receive PDCP PDU [ x ] from the RLC receiving apparatus, in operation 2110, the PDCP receiving apparatus may determine HFN of the received packet using a sequence number (received PDCP SN), Next _ PDCP _ RX _ SN, Reordering _ Window, and Last _ transmitted _ PDCP _ RX _ SN of the received packet, the PDCP receiving apparatus may calculate a count associated with the PDCP packet by concatenating (concatenating) the determined HFN and the received PDCP.

If the following condition is satisfied, meaning that the received packet is a missing packet with the lowest count, the UE may proceed to operation 2130, and if the following condition is not satisfied, the UE may wait until the next PDCP PDUs are received in operation 2125.

Condition for determining whether a received packet is a missing packet with a lowest count

Receiving PDCP SN ═ Last _ transmitted _ PDCP _ RX _ SN + 1; or

Receiving PDCP SN ═ Last _ transmitted _ PDCP _ RX _ SN-Maximum _ PDCP _ SN

In operation 2130, the PDCP receiving apparatus may deliver PDCP SDUs associated with consecutive counts among the PDCP SDUs stored in the PDCP buffer to an upper layer in order of counting from the counting of the received PDCP SDUs, and set Last _ transmitted _ PDCP _ RX _ SN to a sequence number of the Last delivered PDCP SDU. For example, if PDCP SDUs having the counts of [ M ], [ M +1], [ M +2], [ M +4], and [ M +5] are stored in a PDCP buffer and PDCP SDUs having the counts of [ M-1] are received, the PDCP receiving apparatus may deliver PDCP SDUs having the counts of [ M-1], [ M +1], and [ M +2] to an upper layer.

In operation 2135, after the PDCP receiving apparatus performs the above operations, the PDCP receiving apparatus may determine whether at least PDCP SDUs are still stored in the PDCP buffer out of order, if so, the PDCP receiving apparatus may proceed to operation 2140, and if not, the PDCP receiving apparatus may proceed to operation 2125.

In operation 2140, the PDCP receiving apparatus may determine whether the timer 3 is in operation. If so, the PDCP receiving device may proceed to operation 2125, and if the timer 3 is not operating, the PDCP receiving device may proceed to operation 2145.

In operation 2145, the PDCP receiving apparatus may start the timer 3 and set Reordering _ PDCP _ RX _ COUNT to a value obtained by concatenating RX _ HFN and Next _ PDCP _ RX _ SN. In other words, the PDCP receiving apparatus may store a value higher than the highest COUNT that has been received so far by 1 in Reordering _ PDCP _ RX _ COUNT. Thereafter, the PDCP receiving apparatus may proceed to operation 2125.

Fig. 22 illustrates an operation of a PDCP receiving apparatus which switches to PDCP operation 5 when a bearer is reconfigured from a multi bearer to an MCG bearer according to an embodiment of the present disclosure.

The MCG bearer may be a bearer that transmits and receives data only through the MCG among single bearers. If the PDCP receiving apparatus releases the SeNB and the SCB due to the UE leaving the region of the SeNB while performing DC, the multi-bearer can be reconfigured as an MCG bearer.

Referring to fig. 22, in operation 2205, a PDCP receiving apparatus may receive a control message for instructing reconfiguration of a multi-bearer to an MCG bearer. The control message may be, for example, an instruction to explicitly reconfigure a multi-bearer to an MCG bearer, and the control message may be a control message to release the last SCG cell, but the control message is not an explicit reconfiguration instruction.

In operation 2210, the PDCP receiving apparatus may release the multi-bearer SCG-RLC, assemble all PDCP SDUs that can be assembled in the PDCP PDU among RLC packets stored in the RLC in the PDCP PDU, and then deliver the assembled PDCP PDUs to an upper layer.

In operation 2215, the PDCP receiving apparatus may determine whether the timer 3 is currently in operation, for example, operation 2215 may be performed upon completion of the analysis of the control message indicating handover to the MCG bearer, or operation 2215 may be performed upon receipt of PDCP PDUs from the released SCG-RLC.

If the timer 3 is not in operation, the PDCP receiving device may proceed to operation 2225, and if the timer 3 is in operation, the PDCP receiving device may proceed to operation 2220. in operation 2220, several operations are possible.

1) The PDCP receiving apparatus may stop the timer 3 currently in operation, restart the timer 3, and then proceed to operation 2230.

2) The PDCP receiving apparatus may restart the timer 3 after waiting for the expiration of the timer 3 currently in operation, and then proceed to operation 2230.

3) Upon receiving the PDCP PDU from the released SCG-RLC, the PDCP receiving apparatus may stop the timer 3 currently in operation, restart the timer 3, and then proceed to operation 2230. If the PDCP PDU is not received from the released SCG-RLC, the PDCP receiving apparatus may maintain the timer 3 currently in operation and switch to the PDCP operation 1 when the timer 3 currently in operation expires without proceeding to operation 2230.

In operation 2225, several operations are possible. The PDCP receiving apparatus may perform the following operations

a) And of b).

a) The PDCP receiving apparatus may start the timer 3 and proceed to operation 2230.

b) Upon receiving the PDCP PDU from the released SCG-RLC, the PDCP receiving apparatus may start a timer 3 and proceed to operation 2230. If the PDCP PDU is not received from the released SCG-RLC, the PDCP receiving apparatus can immediately switch to PDCP operation 1 without proceeding to operation 2230.

In operation 2230, the PDCP receiving apparatus may wait until the timer 3 expires, and if the timer 3 expires, the PDCP receiving apparatus may deliver all PDCP SDUs currently stored in the PDCP buffer to an upper layer in order of counting, and set Last _ transmitted _ PDCP _ RX _ SN to the sequence number of the Last delivered SDU. Thereafter, the PDCP receiving apparatus may switch to PDCP operation 1.

Fig. 23 illustrates an operation of the PDCP receiving apparatus performed when the timer 3 expires according to an embodiment of the present disclosure.

Referring to fig. 23, in operation 2305, a timer 3 of a PDCP receiving apparatus of an arbitrary bearer may expire.

In operation 2310, the PDCP receiving apparatus may determine whether the bearer is a multi-bearer or an MCG bearer. If the bearer is a multi-bearer, the PDCP receiving apparatus may proceed to operation 2315, and if the bearer is an MCG bearer, the PDCP receiving apparatus may proceed to operation 2320. Proceeding to operation 2320 means that the bearer is reconfigured from the multi-bearer to the MCG bearer, and since the timer 3 has expired, the PDCP receiving apparatus may stop the PDCP operation 5 and deliver all PDCP SDUs currently stored in the PDCP buffer to the upper layer to switch to the PDCP operation 1.

Proceeding to operation 2315 means that the PDCP receiving apparatus operates in PDCP operation 4, and the PDCP receiving apparatus can deliver all PDCP SDUs having a lower COUNT than Reordering _ PDCP _ RX _ COUNT and all PDCP SDUs associated with consecutive COUNTs among the PDCP SDUs stored in the PDCP buffer to an upper layer starting from the Reordering _ PDCP _ RX _ COUNT based on the Reordering _ PDCP _ RX _ COUNT. In other words, the PDCP receiving apparatus can deliver PDCP SDUs corresponding to the conditions in the following table 4 to an upper layer.

TABLE 4

[ Table 4]

The PDCP receiving apparatus may update Last _ terminated _ PDCP _ RX _ SN in operation 2325, and determine whether at least of the PDCP SDUs are left in the PDCP buffer in operation 2330 if at least PDCP SDUs are left in the PDCP buffer, the PDCP receiving apparatus may proceed to operation 2335, and if no PDCP SDUs are left in the PDCP buffer, the PDCP receiving apparatus may proceed to operation 2340.

In operation 2335, the PDCP receiving device may start the timer 3 and set Reordering _ PDCP _ RX _ COUNT to a value obtained by concatenating RX _ HFN and Next _ PDCP _ RX _ SN.

In operation 2340, the PDCP receiving device may wait until the arrival of the lower PDCP PDUs.

As shown in the above example, the PDCP receiving apparatus may use a variable managed by the sequence number of the PDCP SDU when determining whether the received PDCP SDU is a missing SDU, and may use a variable managed by the count when determining the PDCP SDU to be delivered to the upper layer as the timer 3 expires.

As another operation of reordering PDCP PDUs according to an embodiment of the present disclosure, methods may be proposed, which include performing timer-based reordering in case a bearer is reconfigured from a single bearer to a multi bearer, determining a time when the reordering operation is to be stopped, using a timer in case a bearer is reconfigured from a multi bearer to a single bearer, and determining an amount of data stored in a reordering buffer and whether a lower layer is re-established in order to determine the stop time.

Fig. 24 illustrates UE operation during bearer reconfiguration according to an embodiment of the present disclosure.

Referring to fig. 24, in operation 2405, the UE may apply PDCP operation 6 for bearer x, which is a single bearer. In operation 2410, the UE may receive a control message for reconfiguring bearer x into multiple bearers. In operation 2415, the UE may generate/configure an SCG RLC device to be connected with the multi-bearer according to the configuration information indicated by the control message and then connect the SCG RLC device with the PDCP device. In operation 2420, the UE may switch the operation of the PDCP device from PDCP operation 6 to PDCP operation 7. The PDCP operation 6 will be described later. In other words, the UE may apply PDCP operation 7 for PDCP PDUs in order from the PDCP PDU received first after the bearer is reconfigured into a multi-bearer, and the PDCP operation 7 will be described later. Thereafter, by applying PDCP operation 7 to the PDCP PDUs of the bearer reconfigured into the multi-bearer, the UE can determine whether the received PDCP PDUs are reordered, convert the sequential PDCP PDUs into PDCP SDUs, and deliver the PDCP SDUs to an upper layer. The UE may use a timer 3 in determining whether the PDCP PDUs are sequential.

Upon receiving a control message indicating reconfiguration of multiple bearers into a single bearer in operation 2425, the UE may release the SCG RLC in operation 2430, the out-of-order PDCP PDUs may be delivered to the PDCP device because of release of the SCG RLC, and the PDCP device may continue to apply PDCP operations 7 for the PDCP PDUs, the PDCP operations 7 may be applied until a reordering stop condition is satisfied, and if the reordering stop condition is satisfied, the UE may determine whether the reordering stop condition is satisfied because of "re-establishment of lower layer" or "absence of out-of-order packets" in operation 2435, if the reordering stop condition is satisfied because of "absence of out-of-order packets", the UE may switch to PDCP operations 6 in operation 2440 and then end processing, in aspect , if the reordering stop condition is satisfied because of "re-establishment of lower layer", the UE may proceed to operation 2445.

As for the PDCP operation 6 and the PDCP operation 7, it can be understood that a plurality of specific operations that should be applied to the PDCP pdu delivered from the RLC apparatus are listed in the series order, the specific operations constituting the operations and the order thereof are listed in the following table 5.

TABLE 5

[ Table 5]

Although the UE determines whether the duplicate reception occurs in the PDCP operation 6, the UE may not determine whether the duplicate reception occurs in the PDCP operation 7. This is because in the case where the PDCP operation 6 is applied, the packet that has been received is likely to be repeatedly received after the handover, but there is no such possibility in the PDCP operation 7. The repeatedly received PDUs may be processed into SDUs before being discarded in order to update the header decompression context. In case that the PDCP operation 7 is applied, the UE does not have to perform an operation of determining a repeatedly received packet, processing the repeatedly received packet into an SDU, and then discarding the repeatedly received packet.

In PDCP operation 6, the UE may first process received PDUs into SDUs, then store the out-of-sequence SDUs in a buffer and deliver the in-sequence SDUs to an upper layer in another aspect, in PDCP operation 7, the UE may first determine whether received PDUs are in-sequence, and for only in-sequence PDUs, the UE may process these PDUs into SDUs and deliver them to an upper layer.

In case that the PDCP operation 6 is applied, if a packet [ X ] is received, the UE may not determine whether the received packet [ X ] is reordered because a packet having a sequence number lower than that of the packet [ X ] is no longer received, so there is no problem in a header decompression operation even if the UE processes the received packet into an SDU. However, in case that the PDCP operation 7 is applied, since out-of-order packets can be always received, the UE should process the received packets into SDUs after reordering the received packets first in order to prevent errors in the header decompression operation.

The upper layer delivery condition 7 of the PDCP operation 7 may be for PDCP PDUs instead of PDCP SDUs, and the upper layer delivery condition 7 may be the same as the upper layer delivery condition 4 except that the packet satisfying the condition is not delivered to the upper layer but to the PDCP PDU processing means.

Upper layer delivery condition 7 for PDCP operation 7

If the sequence number of the received PDCP PDU is the sequence number of the missing PDCP PDU with the lowest sequence number (e.g., if the received PDCP SN is the same as the value obtained by adding 1 to Last _ committed _ PDCP _ RX _ SN), the UE may deliver sequentially received PDUs up to the next missing PDCP PDUs (including the received PDCP PDU) to a processing means (e.g., a header decompression means or a decoding means) — the decoding means may refer to means for decoding the received PDCP PDUs, the PDUs may be delivered to an upper layer after being processed into SDUs in the processing means, if the received PDCP PDUs are not the missing PDCP PDUs with the lowest sequence number, the PDCP PDUs may be stored in a PDCP buffer, if timer 3 is in operation, the UE may wait until the next PDCP PDUs are received, and if timer 3 is not in operation, the UE may start timer 3 and store a higher COUNT than the highest COUNT of the counted PDCP PDUs among the PDCP PDUs received PDCP PDUs in operation, the Last PDCP PDU may be associated with the Last PDCP PDU delivering the PDCP _ commit _ COUNT to the UE.

If the multi-bearer is reconfigured to a single bearer, the UE should switch PDCP operation from PDCP operation 7 to PDCP operation 6. In an embodiment of the present disclosure, the PDCP device may continue to apply PDCP operation 7 until a reordering stop condition is satisfied after the multi-bearer is reconfigured into a single bearer, and may switch to PDCP operation 6 if the reordering stop condition is satisfied. The reordering stop condition may be satisfied if the lower layer is reconstructed (reconstruction of the lower layer) or there is no more PDU to reorder (absence of out-of-order packets).

Lower layer reestablishment may occur if a handover command is received by a UE that is operating, for example, on a single bearer. In this case, the out-of-order PDCP PDUs stored in the MCG-RLC apparatus are all delivered to the PDCP receiving apparatus, and the UE may switch to PDCP operation 6 in which the out-of-order PDCP PDUs currently stored in the PDCP buffer and the PDCP PDUs delivered from the lower layer are sequentially processed into PDCP PDUs in order of counting, the sequenced SDUs are delivered to the upper layer, the out-of-order SDUs are stored in the buffer, and then the SDUs to be delivered to the upper layer are determined based on the sequence numbers of the PDUs received from the re-established lower layer.

The expression that there are no more PDUs to be reordered may refer to a case where, as a result of a reordering operation using timer 3, there are no more missing PDUs after the UE processes the PDUs (which are considered out-of-order by the missing PDUs as the timer 3 associated with the missing PDUs expires) into SDUs and then delivers the SDUs to an upper layer. For example, if the value obtained by adding 1 to Last _ transmitted _ PDCP _ RX _ SN is the same as Next _ PDCP _ RX _ SN, this may mean that there are no missing PDUs anymore or there are no out-of-sequence PDUs anymore. Since the expression that the condition is satisfied means that no PDUs are stored in the PDCP buffer, the PDCP receiving apparatus can immediately switch to the PDCP operation 6.

The PDCP operation 7 is the same as the PDCP operation 4 shown in fig. 25 except the following, so a detailed description thereof will be omitted.

Fig. 25 illustrates a PDCP operation 7 of the PDCP receiving apparatus operating per multi-bearer according to an embodiment of the present disclosure. The example of fig. 25 shows the operation of the PDCP receiving apparatus having received a packet from the RLC receiving apparatus.

Referring to fig. 25, a PDCP receiving apparatus may receive a PDCP PDU [ x ] from an RLC receiving apparatus in operation 2505. In operation 2510, the PDCP receiving apparatus may determine the HFN of the received packet using the sequence number (received PDCP SN), Next _ PDCP _ RX _ SN, Reordering _ Window, and Last _ transmitted _ PDCP _ RX _ SN of the received packet. The PDCP receiving means may calculate a count associated with the PDCP packet by concatenating the determined HFN and the received PDCP SN. By applying the count, the PDCP receiving device can determine whether the received packet is a missing packet with the lowest count.

If the following condition is satisfied in operation 2520, meaning that the received packet is a missing packet having the lowest count, the PDCP receiving apparatus may proceed to operation 2530, and if the following condition is not satisfied, the PDCP receiving apparatus may wait until the next PDCP PDUs are received in operation 2525.

Receiving PDCP SN ═ Last _ transmitted _ PDCP _ RX _ SN + 1; or

Receiving PDCP SN ═ Last _ transmitted _ PDCP _ RX _ SN-Maximum _ PDCP _ SN

In operation 2530, the PDCP receiving apparatus may process PDCP PDUs associated with consecutive counts among the PDCP PDUs stored in the PDCP buffer into PDCP SDUs in order of the counts, starting from the counts of the received PDCP PDUs, and then deliver the PDCP SDUs to an upper layer, and may set Last _ terminated _ PDCP _ RX _ SN as a sequence number of the Last delivered PDCP SDU, for example, if PDCP PDUs having the counts of [ M ], [ M +1], [ M +2], [ M +4], and [ M +5] are stored in the PDCP buffer and the PDCP PDU having the count of [ M-1] is received, the PDCP receiving apparatus may deliver the PDCP PDUs having the counts of [ M-1], [ M +1], and [ M +2] to a lower processing apparatus to convert them into PDCP SDUs, and then deliver the PDCP SDUs to the upper layer, after the PDCP receiving apparatus performs the above operations, the PDCP receiving apparatus may determine whether the PDCP PDUs are , and if the PDCP PDUs are not, the PDCP receiving apparatus may perform the operation 2535.

In operation 2540, the PDCP receiving apparatus may determine whether the timer 3 is in operation. If so, the PDCP receiving apparatus may proceed to operation 2525, and if not, the PDCP receiving apparatus may proceed to operation 2545. In operation 2545, the PDCP receiving apparatus may start the timer 3 and set Reordering _ PDCP _ RX _ COUNT to a value obtained by concatenating RX _ HFN and Next _ PDCP _ RX _ SN. In other words, the PDCP receiving apparatus may store a value higher than the highest COUNT that has been received so far by 1 in Reordering _ PDCP _ RX _ COUNT. Thereafter, the PDCP receiving apparatus may proceed to operation 2525.

Fig. 26 illustrates an operation of the PDCP receiving apparatus performed when the timer 3 expires according to an embodiment of the present disclosure.

Referring to fig. 26, in operation 2605, a timer 3 of a PDCP receiving apparatus of any bearer expires. In operation 2516, the PDCP receiving apparatus may process all PDCP PDUs having lower COUNTs than Reordering _ PDCP _ RX _ COUNT and PDCP PDUs associated with consecutive COUNTs among the PDCP PDUs stored in the PDCP buffer into PDCP SDUs in order of COUNTs from the Reordering _ PDCP _ RX _ COUNT based on the Reordering _ PDCP _ RX _ COUNT, and then deliver the PDCP SDUs to an upper layer. In other words, the PDCP receiving apparatus can process PDCP PDUs corresponding to the conditions in the following table 6 into PDCP SDUs and then deliver the PDCP SDUs to an upper layer.

TABLE 6

[ Table 6]

The PDCP receiving apparatus may update Last _ terminated _ PDCP _ RX _ SN in operation 2625 and determine whether at least PDCP PDUs are left in the PDCP buffer in operation 2630. if at least PDCP PDUs are left in the PDCP buffer, the PDCP receiving apparatus may proceed to operation 2635, and if at least PDCP PDUs are not left in the PDCP buffer, the PDCP receiving apparatus may proceed to operation 2640. in operation 2635, the PDCP receiving apparatus may start a timer 3 and set Reordering _ PDCP _ RX _ COUNT to a value obtained by concatenating RX _ HFN and Next _ PDCP _ RX _ SN. in operation 2640, the PDCP receiving apparatus may wait until the Next PDCP PDUs arrive.

As another operation of reordering PDCP PDUs according to an embodiment of the present disclosure, methods may be proposed in which a bearer may be reconfigured from a single bearer to a multi-bearer and a PDCP receiving apparatus may operate per multi-bearer, in this embodiment, if a bearer is reconfigured from a single bearer to a multi-bearer, a UE may process sequential PDUs among received PDCP PDUs into PDCP SDUs and then deliver the PDCP SDUs to an upper layer, and may process out-of-order PDCP PDUs into incomplete (half) PDCP SDUs and then store the incomplete PDCP SDUs in a buffer until they become sequential.

The reason for decoding packets received on multiple bearers and then storing the decoded packets in a reordering buffer is that if the SCG of the UE is changed, the decoding key may be changed, and in this case, if PDCP PDUs which have not yet been decoded are stored in the PDCP device to be reordered, the UE should apply different security keys to the first PDCP PDUs and the newly received PDCP PDUs, resulting in an increase in complexity.

Fig. 28 illustrates UE operation during bearer reconfiguration according to an embodiment of the present disclosure.

Referring to fig. 28, in operation 2805, the UE may apply PDCP operation 6 for bearer x, which is a single bearer. In operation 2810, the UE may receive a control message for reconfiguring bearer x into a multi-bearer. In operation 2815, the UE may generate/configure an SCG RLC device to be connected with the multi-bearer according to the configuration information indicated by the control message and then connect the SCG RLC device with the PDCP device. In operation 2820, the UE may switch operation of the PDCP device from PDCP operation 6 to PDCP operation 8. In other words, the UE may apply PDCP operations 8 for PDCP PDUs in sequence starting from the PDCP PDU received first after the bearer is reconfigured into a multi-bearer.

Specifically, by applying the PDCP operation 8 to the PDCP PDUs of the bearer reconfigured into the multi-bearer, the UE can process the sequenced PDCP PDUs among the received PDCP PDUs into PDCP SDUs and deliver the PDCP SDUs to the upper layer, and can process the out-of-sequence PDCP PDUs into incomplete PDCP SDUs, store the incomplete PDCP SDUs in the PDCP reordering buffer, and then start the timer 3 as necessary.

After that, upon receiving a control message indicating that multiple bearers are reconfigured into a single bearer in operation 2825, the UE may release the SCG RLC in operation 2830. the out-of-order PDCP PDU may be delivered to the PDCP device because of the release of the SCG RLC, and the PDCP device may continue to apply PDCP operations 8 to the PDCP PDU, the PDCP operations 8 may be applied until a reordering stop condition is satisfied, and if the reordering stop condition is satisfied, the UE may determine in operation 2835 whether the reordering stop condition is satisfied due to "re-establishment of lower layer" or "absence of out-of-order packet", the UE may switch to PDCP operation 6 in operation 2840, then end processing, in another aspect , if it is determined in operation 2835 that the reordering stop condition is satisfied due to "absence of out-of-order packet" in operation 2840, the UE may switch to PDCP operation 6, then to complete re-establishment of SDU, the UE may proceed to operation 2845, the lower layer may be a PDCP-storing means, a PDCP PDU may store the PDU in the PDCP buffer, and the PDCP PDU may store the PDU in the PDCP buffer, the PDCP buffer 3645, and the PDCP PDU may store the PDU in the PDCP buffer , the PDCP PDU may store the complete the PDCP PDU, and the PDU, if it is not store the PDCP PDU, the PDCP PDU may store the PDU, the PDU may store the PDU, or the PDU may store the PDU, and if it may store the PDU, the PDU may store the PDU, if it may store the PDU, in the PDCP PDU, the PDU, if it may store the PDU, in operation, the PDCP PDU, in operation, the PDCP buffer, the PDCP PDU, the complete, the PDCP PDU, if the PDCP PDU.

The fact that there is the sequenced PDCP PDU or the incomplete PDCP SDU determined in operation 2845 may refer to the fact that there is a PDCP PDU or incomplete PDCP SDU having a sequence number higher than 1 than Last _ transmitted _ PDCP _ RX _ SN among the PDCP PDUs or the incomplete PDCP SDUs.

As for the PDCP operation 6 and the PDCP operation 8, it can be understood that a plurality of specific operations that should be applied to the PDCP pdu delivered from the RLC apparatus are listed in the order of series, the specific operations constituting the

PDCP operations

6 and 8 and the order thereof are listed in the following table 7, and the specific operations can be performed in the order from top to bottom in the table 7.

TABLE 7

[ Table 7]

In addition, the UE may process only the sequenced incomplete PDCP SDUs into PDCP SDUs by applying remaining PDCP processing operations (e.g., header decompression) to the sequenced incomplete PDCP SDUs and then deliver the PDCP SDUs to an upper layer, and may store the out-of-sequence incomplete PDCP SDUs in the buffer without converting them into PDCP SDUs.

The following upper layer delivery condition 8 of the PDCP operation 8 may be used for an incomplete PDCP SDU instead of a PDCP SDU, and the upper layer delivery condition 8 may be the same as the upper layer delivery condition 7 except that a packet satisfying the condition is not delivered to the th PDCP processing means (e.g., decoding means) but to the second PDCP processing means (e.g., header decompression means). in cases, not only the out-of-order incomplete PDCP SDU but also the out-of-order PDCP SDU may be stored in the PDCP receiving means.

Upper layer delivery condition 8 for PDCP operation 8

If the sequence number of the received PDCP PDU is the same as the sequence number of the missing PDCP with the lowest sequence number (e.g., if the received PDCP SN is the same as the value obtained by adding 1 to Last _ terminated _ PDCP _ RX _ SN), the UE may deliver consecutive incomplete PDCP SDUs (or multiple incomplete PDCP SDUs corresponding thereto) up to the next missing PDCP PDUs to the next PDCP processing means (e.g., header decompression means) including the received PDCP PDU (or the incomplete PDCP SDU corresponding thereto). the multiple incomplete PDCP SDUs may be processed into multiple PDCP SDUs in the next PDCP processing means and then delivered to the upper layer.

If the multi-bearer is reconfigured to a single bearer, the UE should switch PDCP operation from PDCP operation 8 to PDCP operation 6. In an embodiment of the present disclosure, the PDCP processing device may continue to apply PDCP operations 8 until a reordering stop operation is satisfied after the multi-bearer is reconfigured into a single bearer, and may switch to PDCP operations 6 if the reordering stop operation is satisfied. The reordering stop condition may be satisfied if the lower layer is reconstructed (reconstruction of the lower layer) or there is no more PDU to reorder (absence of out-of-order packets).

If a UE operating, for example, on a single bearer receives a handover command, a lower layer re-establishment may occur. In this case, the out-of-order PDCP PDUs stored in the MCG-RLC apparatus are all delivered to the PDCP receiving apparatus, and the UE may switch to PDCP operation 6, in which out-of-order incomplete PDCP SDUs currently stored in the PDCP buffer and PDCP PDUs delivered from the lower layer are sequentially processed into PDCP SDUs in order of counting, the sequential SDUs are delivered to the upper layer, the out-of-order SDUs are stored in the buffer, and then SDUs to be delivered to the upper layer are determined based on the sequence numbers of PDUs received from the newly established lower layer in the PDCP operation 6.

The expression that there are no more PDUs to be reordered may refer to the following: as a result of the reordering operation using the timer 3, there is no longer a missing PDU after the UE processes incomplete PDCP SDUs, which are considered out of order by the missing PDU as the timer 3 associated with the missing PDU expires, into SDUs and then delivers the SDUs to an upper layer. Otherwise, the absence of an expression of the PDUs to be reordered may refer to a case where the PDCP PDUs delivered from the lower layer are missing PDCP PDUs with the lowest sequence numbers. For example, after a bearer is reconfigured from a multi-bearer to a single bearer, if the sequence number of the received PDCP PDU is the same as the value obtained by adding 1 to Last _ subject _ PDCP _ RX _ SN and Last _ subject _ PDCP _ RX _ SN is the same as Next _ PDCP _ RX _ SN, this may mean that there is no missing PDU anymore or no out-of-order incomplete PDCP SDU anymore. Since the expression that the condition is satisfied means that there are no more incomplete PDCP SDUs stored in the PDCP buffer, the PDCP receiving apparatus can immediately switch to the PDCP operation 6.

In the embodiments of the present disclosure, operations performed by the PDCP receiving apparatus when a bearer is reconfigured will be described.

The reconfiguration of the bearers may refer to, for example, a case where the MCG bearer is reconfigured into a multi-bearer, the multi-bearer is reconfigured into the MCG bearer, or the multi-bearer is reconfigured into the multi-bearer.

During bearer reconfiguration, the UE may apply PDCP operation 9 and PDCP operation 10 alternately or sequentially.

Examples of the PDCP operation 9 and the PDCP operation 10 will be described with reference to the following table 8.

TABLE 8

[ Table 8]

TABLE 9

[ Table 9]

Watch 10

[ Table 10]

Since the expression that the condition in table 9 is satisfied means that the received PDCP PDU is the missing PDCP PDU with the lowest sequence number (e.g., the received PDCP SN ═ Last _ transmitted _ PDCP _ RX _ SN +1), sequential PDCP PDUs may occur as the PDU is received.

The PDCP PDUs satisfying the conditions in table 10 may refer to all missing PDUs having sequence numbers lower than those of the received PDCP PDU and the plurality of PDCP PDUs sequentially received, including the missing PDCP PDU.

In table 8, the th PDU may be a PDCP PDU received due to re-establishment or release of a lower layer and may occur during handover, in other words, if handover is indicated, out-of-order PDCP PDUs stored in the RLC layer may be delivered to the PDCP device, and these PDCP PDUs will be referred to as " th PDU".

In table 8, the second PDU may be a PDCP PDU received neither due to lower layer re-establishment nor due to lower layer release, and the second PDU may be a PDCP PDU received from the target cell after handover is completed.

Upon handover, the th PDU can be interpreted as an out-of-order PDCP PDU received from the source cell and the second PDU can be interpreted as a PDCP PDU received from the target cell.

In embodiments of the present disclosure, the MeNB may use an RRC connection reconfiguration control message to reconfigure a particular bearer or indicate a handover. In this case, the UE may perform an optimized operation according to the type of reconfiguration indicated in the RRC connection reconfiguration message.

Fig. 29 illustrates UE operation during bearer reconfiguration according to an embodiment of the present disclosure.

Referring to fig. 29, in operation 2905, the UE may receive a bearer reconfiguration message related to a multi-bearer. In this embodiment, the phrase "related to multiple bearers" means that the multiple bearers are changed to, for example, MCG bearers or multiple bearers, or MCG bearers are changed to multiple bearers, by using a control message.

In operation 2910, the UE may determine whether handover is indicated using the control message. The PDCP may perform a reconfiguration operation if a handover is indicated. PDCP reconfiguration may include specific operations such as applying a new security key and resetting a header compression operation, and may be performed during handover.

If a handover is not indicated, the UE may proceed to operation 2915, and if a handover is indicated, the UE may proceed to operation 2935.

In operation 2915, the UE may check the type of reconfiguration. If the reconfiguration type indicates reconfiguration from the MCG bearer to the multi-bearer, the UE may proceed to operation 2920. If the reconfiguration type indicates a reconfiguration from multi-bearer to multi-bearer, the UE may proceed to operation 2925. If the reconfiguration type indicates reconfiguration from a multi bearer to an MCG bearer, the UE may proceed to operation 2930.

In operation 2935, the UE may check the type of reconfiguration. If the reconfiguration type indicates reconfiguration from the MCG bearer to the multi-bearer, the UE may proceed to operation 2940. If the reconfiguration type indicates a reconfiguration from multi-bearer to multi-bearer, the UE may proceed to operation 2945. If the reconfiguration type indicates reconfiguration from a multi bearer to an MCG bearer, the UE may proceed to operation 2950.

In operation 2920, the UE may stop applying PDCP operation 9 and then apply PDCP operation 10. In other words, the UE has received the RRC connection reconfiguration message related to the multi-bearer, and when the reconfiguration is performed, if the PDCP is not reconfigured (i.e., the reconfiguration is not the reconfiguration performed in the handover case) and the MCG bearer is reconfigured to the multi-bearer, the UE may stop applying the PDCP operation 9 as an operation for the MCG bearer and then apply the PDCP operation 10 as an operation for the multi-bearer.

In operation 2925, the UE may continue to apply PDCP operations 10. In other words, the UE has received the RRC connection reconfiguration message related to the multi-bearer, and when the reconfiguration is performed, if the PDCP is not reconfigured (i.e., the reconfiguration is not a reconfiguration performed in case of handover) and the multi-bearer is reconfigured to be a multi-bearer, the UE may continue to apply the PDCP operation 10 as an operation for the multi-bearer.

In operation 2930, the UE may apply the PDCP operation 10 until a predetermined condition is satisfied. The predetermined condition may be satisfied when the PDCP is first reconfigured after bearer reconfiguration is complete. In other words, the UE has received the RRC connection reconfiguration message related to the multi-bearer, and when the reconfiguration is performed, if the PDCP is not reconfigured (i.e., the reconfiguration is not a reconfiguration performed in the handover case) and the multi-bearer is reconfigured to an MCG bearer, the UE may continue to apply the PDCP operation 10 as an operation for the multi-bearer even if the bearer is reconfigured to an MCG bearer. If PDCP is reconfigured, the UE may apply PDCP operation 9 as an operation for the MCG bearer (i.e., the UE may continue to apply PDCP operation 10 until a handover is indicated after reconfiguration of the MCG bearer is completed, and if a handover is indicated, the UE may apply PDCP operation 9).

The reason why the UE does not immediately apply the PDCP operation 9 in operation 2930 is because there may be out-of-order PDCP PDUs if the bearer is reconfigured from a multi-bearer to an MCS bearer, the UE should continue to apply the PDCP operation 10 until the out-of-order PDUs are sequential in order to prevent data loss.

In operation 2940, the UE may apply PDCP operation 9 for the th PDU and PDCP operation 10 for the second PDU as described above, the th PDU may refer to a PDCP PDU received from the source cell and degradation of reordering performance may occur if PDCP operation 10 is applied even for the th PDU, the second PDU may refer to a PDU received from the target cell and may be received after the st PDU is completely received, since the second PDU is received after reconfiguration to the multi-bearer is completed, the UE may apply PDCP operation 10 for the second PDU, in other words, the UE has received an RRC connection reconfiguration message related to the multi-bearer and, when reconfiguration is performed, the UE may apply PDCP operation 9 for a PDCP PDU that has been received through a lower layer/release and a PDCP operation 10 for a PDCP PDU that has not been received through a lower layer/release if the PDCP PDU is also re-configured (i.e., reconfiguration is reconfiguration performed in case of handover) and the multi-bearer is reconfigured to an MCG bearer.

In operation 2945, the UE may apply PDCP operation 9 for the th PDU and PDCP operation 10 for the second PDU like in operation 2940 in other words, the UE has received an RRC connection reconfiguration message related to a multi-bearer, and when reconfiguration is performed, if PDCP is also reconfigured by (i.e., reconfiguration is reconfiguration performed in case of handover) and the multi-bearer is reconfigured to a multi-bearer, the UE may apply PDCP operation 9 for PDCP PDUs which have been received through reconfiguration/release of the lower layer and apply PDCP operation 10 for PDCP PDUs which have not been received through reconfiguration/release of the lower layer.

In operation 2950, the UE may apply PDCP operation 9 for both the th PDU and the second PDU, in other words, the UE has received an RRC connection reconfiguration message related to the multi-bearer, and when the reconfiguration is performed, if the PDCP is also reconfigured by (i.e., the reconfiguration is a reconfiguration performed in the case of a handover) and the multi-bearer is reconfigured to an MCG bearer, the UE may apply PDCP operation 9 for PDCP PDUs that have been received through reconfiguration/release of a lower layer, and even apply PDCP operation 9 for PDCP PDUs that have not been received through reconfiguration/release of a lower layer.

In an embodiment of the present disclosure, an operation of the PDCP receiving apparatus processing the PDCP PDUs received from the lower layer may be proposed.

In this embodiment of the present disclosure, if a PDCP PDU is received from a lower layer, the PDCP receiving apparatus may determine whether the PDU satisfies a predetermined duplicate reception condition and take a predetermined action for the PDU satisfying the duplicate reception condition. The PDCP receiving apparatus may perform different operations according to whether the PDCP receiving apparatus is a device connected with a single bearer or a device connected with a multi bearer.

The duplicate reception condition for any PDU may be defined as shown in the following table 11.

TABLE 11

[ Table 11]

The duplicate reception condition is used to determine whether the sequence number of the received PDU is a lower number than Last _ received _ PDCP _ RX _ SN (or whether the sequence number of the received PDU is a number assigned earlier than Last _ received _ PDCP _ RX _ SN (e.g., an older number), rather than determining whether any PDCP PDU has been received, and may be used to determine whether the sequence number of the received PDU is a lower sequence number than the lowest sequence number that has been delivered to an upper layer.

The expression that the duplicate reception condition is satisfied for any PDCP PDU means that unnecessary misappropriation is likely to occur if the PDCP SDU is delivered to an upper layer because the payload of the PDCP PDU is likely to have already been delivered to the upper layer. Therefore, in this embodiment, the PDCP receiving apparatus can discard the PDCP PDU satisfying the repeated reception condition without delivering it to the upper layer.

If the PDCP PDU satisfying the duplicate reception condition is a PDCP PDU that has been received on a single bearer, the UE may perform an operation of processing the PDCP PDU into a PDCP SDU to update a robust header compression (ROHC) context (see RFC 3095) before discarding the PDCP PDU and then discard the PDCP SDU in another aspect, if the PDCP PDU satisfying the duplicate reception condition is a PDCP PDU that has been received on multiple bearers, the UE may immediately discard the PDCP PDU without processing the PDCP PDU into an SDU.

If the PDCP PDU satisfying the repeated reception condition is a PDCP PDU that has been received on a single bearer, important packets related to ROHC may be included in the PDCP PDU even if the PDCP PDU is a repeatedly received PDU. This phenomenon may occur if ROHC is reset in a process such as handover. Therefore, even if the PDCP PDUs received on a single bearer are the repeatedly received PDCP PDUs, the UE can first process the PDCP PDUs into PDCP SDUs to update the ROHC context and then discard the PDCP SDUs.

In the multi-bearer operation, since ROHC is not reset, the UE does not have to perform an operation of processing repeatedly received packets to update the ROHC context. Accordingly, if it is determined that the PDCP PDU is repeatedly received, the UE can immediately discard the PDCP PDU.

Referring to fig. 27, in operation 2705, the PDCP receiving apparatus may receive PDCP PDUs from a lower layer. In operation 2710, the PDCP receiving apparatus may determine whether the sequence number of the PDCP SDU satisfies a duplicate reception condition. The PDCP receiving apparatus may proceed to operation 2715 if the sequence number of the PDCP SDU does not satisfy the duplicate reception condition, and may proceed to operation 2720 if the sequence number of the PDCP SDU satisfies the duplicate reception condition. In operation 2715, the PDCP receiving apparatus may determine whether the received PDCP PDU is delivered from a multi-bearer or a single bearer. The PDCP receiving apparatus may proceed to operation 2719 if the received PDCP PDUs are delivered from multiple bearers, and may proceed to operation 2717 if the received PDCP PDUs are delivered from a single bearer.

In operation 2717, the UE may process the received PDCP PDUs into PDCP SDUs regardless of whether the received PDCP PDUs are reordered, and then deliver the PDCP SDUs to an upper layer. In operation 2719, if the received PDCP PDU is sequential, the UE may immediately process the PDCP PDU into a PDCP SDU and then deliver the PDCP SDU to an upper layer, and if the received PDCP PDU is not sequential (or out of sequence), the UE may process the PDCP PDU into a PDCP SDU after reordering of the PDCP PDU is completed and then deliver the PDCP SDU to an upper layer. In other words, the UE may process only its reordering-completed PDCP PDUs into PDCP SDUs and deliver the PDCP SDUs to an upper layer in operation 2719. Here, processing the PDCP PDUs into PDCP SDUs may mean converting the PDCP PDUs into PDCP SDUs by performing operations such as decoding the PDCP PDUs and decompressing the headers thereof.

If the duplicate reception condition is satisfied in operation 2710, the PDCP receiving apparatus may determine whether a bearer from which the PDCP PDU is delivered is a single bearer or a multi bearer in operation 2720. If the bearer is a single bearer, the PDCP receiving apparatus may proceed to operation 2725, and if the bearer is a multi bearer, the PDCP receiving apparatus may proceed to operation 2730. In operation 2725, the PDCP receiving apparatus may process the PDCP PDUs into PDCP SDUs and then discard the PDCP SDUs. In operation 2730, the PDCP receiving apparatus may discard the PDCP PDU without processing the PDCP PDU into PDCP SDUs.

In the example of fig. 27, as another operation of the UE, if PDCP PDUs, incomplete PDCP SDUs, or PDCP SDUs having the same sequence number as that of the received PDCP PDUs have been already stored in the PDCP reception buffer, the UE may perform different operations for a single bearer and a multi bearer.

For example, if a PDCP SDU having the same sequence number as that of the received PDCP PDU has been stored in the PDCP reception buffer of the single bearer, the UE may decode the PDCP PDU, decompress its header, and then discard the PDCP PDU. The reason why the PDCP PDU is discarded after the header thereof is decompressed is to update the header decompression context by decompressing the header, because the repeatedly transmitted PDCP PDU is likely to be a packet whose header is compressed into a more recent header compression context.

Further, if PDCP SDUs, incomplete PDCP SDUs, or PDCP PDUs having the same sequence number as that of the received PDCP PDUs have been stored in the multi-bearer PDCP reception buffer, the UE may decode the PDCP PDUs, process the decoded PDCP PDUs into incomplete PDCP SDUs, then discard the currently stored PDCP packets (e.g., PDCP PDUs, incomplete PDCP SDUs, or PDCP SDUs) having the same sequence number, and store the incomplete PDCP SDUs.

In the case of multi-bearer, if the header of an out-of-order incomplete PDCP SDU is decompressed, its subsequent header decompression of the incomplete PDCP SDU may be affected. Thus, as described above, the UE may store the repeatedly received packets until the repeatedly received packets are reordered without decompressing their headers.

Although not shown in the example of fig. 27, as another operation of the UE, if PDCP PDUs or PDCP SDUs having the same sequence numbers as those of the received PDCP PDUs have been already stored in the PDCP reception buffer of the multi-bearer, the UE may perform another different operation.

For example, if PDCP SDUs having the same count as that of the received PDCP PDUs have been stored in the multi-bearer PDCP receive buffer, the UE may decode the PDCP PDUs, decompress the headers thereof, and then discard the PDCP PDUs. The reason why the PDCP PDU is discarded after the header thereof is decompressed is to update the header decompression context by decompressing the header, because the repeatedly transmitted PDCP PDU is likely to be a packet whose header is compressed as a more recent header compression context.

Further, if PDCP PDUs having the same count as the count of the received PDCP PDUs have been stored in the PDCP receive buffer of the multi-bearer, the UE may discard the stored PDCP PDUs and store newly received PDCP PDUs in case of a single bearer, the reason for performing an operation different from the operation of discarding the repeatedly received PDCP PDUs is that in the multi-bearer structure, upon retransmission of a predetermined PDCP PDU, the UE may compress the header again to a more recent header compression context and then retransmit the PDCP PDU, as another operation of the UE, upon processing a PDCP packet (e.g., a PDCP PDU or a PDCP SDU) having the same count as the count of the received PDCP PDUs, the UE may perform different operations depending on whether the PDCP PDU or the PDCP PDU having the same count.

If a PDCP packet having the same count as the count of the received PDCP PDU has been stored, the UE may determine whether the stored PDCP packet is a PDCP PDU or a PDCP SDU, and if the stored PDCP packet is a PDCP PDU, the UE may discard the PDCP PDU without performing additional operations, in another aspect, if the stored PDCP packet is a PDCP SDU, the UE may decompress a header of the received PDCP PDU, decode the PDCP PDU, and then discard the PDCP PDU.

A description will now be made of a method for setting a Prioritized Bit Rate (PBR) for multiple bearers according to an embodiment of the present disclosure.

If PBR is set in a logical channel, the UE may increase a PBR-related token Bj. for the PBR of the logical channel in each Transmission Time Interval (TTI) when determining data to be transmitted, the UE may first consider Bj., for example, even if transmittable data exists in a high priority logical channel x, the UE may preferentially transmit data of a logical channel whose priority is low but whose Bj is not 0, by at least Bj, if Bj of the logical channel x is 0, the data following the logical channel whose priority is low but whose Bj is not 0.A description in section 5.7 of this operation standard TS36.321 is provided.

PBR may be assigned and managed for each logical channel however, if a logical channel is a logical channel connected to a multi-bearer, it is prioritized to operate PBR for all relevant logical channels rather than operating PBR independently for each logical channel, the reason being that PBR is intended to ensure a minimum transmission bandwidth for any data service and in the case of a multi-bearer, services are related to two logical channels.

In existing signaling systems, parameters related to PBR may include a PRIORITEDBITRate and a bucktSizeDuration, and these parameters may be signaled for each logical channel Bj is first initialized to zero (0) and then increased in each TTI with a PRIORITSedBITBITRate, the maximum size of Bj being limited to the product of PRIORITSedBITRate and bucktSizeDuration.

Fig. 12 illustrates an operation of a UE setting a PBR for a multi-bearer according to an embodiment of the present disclosure.

Referring to fig. 12, in operation 1205, a UE may receive a control message for indicating reconfiguration of a single bearer to a multi bearer, in operation 1210, the UE may adjust PBR of an MCG logical channel and PBR of an SCG logical channel to appropriate values with reference to PBR information of control message 1 and control message 2, control message 2 means a control message for reconfiguring a single bearer to a multi bearer, and control message 1 means a control message containing PBR information on a single bearer.

PBR setting method 1 for any multiple bearers x

If the PBR of the logical channel carrying x is set to A in control message 1 and the PBR of the SCG Logical Channel (LCH) carrying x is set to B in control message 2, the PBR of the SCG LCH can be set to signaled B and the PBR of the MCG LCH can be adjusted to A-B.

PBR setting method 2 for any multiple bearers x

If the PBR information exists in the control message 2, the PBR may be applied to the SCG LCH, and if the PBR information does not exist, the PBR may be applied to the MCG LCH. In other words, if the PBR of the logical channel carrying x is set to a in control message 1 and the PBR of the SCG LCH carrying x is set to B in control message 2, the PBR of the SCG LCH can be set to signaled B and the PBR of the MCG LCH can be adjusted to zero (0). Otherwise, if the PBR for the SCG LCH of bearer x is not set in the control message 2, the PBR of the MCG LCH can be kept as a and the PBR of the SCG LCH can be set to 0.

PBR setting method 3 for any multiple bearers x

The LCH to be applied with PBR can be specified by control message 2. For example, PBR may be set as shown in table 12 below.

TABLE 12

[ Table 12]

For example, if the PBR of the logical channel carrying x is notified as a in control message 1 and the PBR of the logical channel carrying x is set to B and the PBR indicator is set as MCG in control message 2, the UE may adjust the PBR of MCG LCH to B and set the PBR of SCG LCH to 0. In operation 1215, the UE may shift a predetermined amount of Bj of the existing MCG LCH to the SCG LCH.

If the PBR setting method 1 is used, the UE may subtract a predetermined ratio of Bj for the MCG LCH from the MCG LCH and add it to the SCG LCH. Thus, Bj of SCG LCH can be initialized to the amount of Bj shifted in MCG LCH, rather than to 0.

If the

PBR setting method

2 or 3 is used, the entirety of Bj of MCG LCH can be shifted to SCG LCH if PBR is applied to SCG. If PBR is applied to MCG, Bj of MCG LCH can be kept as it is.

In operation 1220, the UE may perform operations related to PBR in MCG LCH and SCG LCH by applying the adjusted PBR and the adjusted Bj in other words, the UE may perform operations of increasing Bj by PBR and decreasing Bj by as much as the amount of data transmitted in each TTI.

In a scenario where the UE is transmitting and receiving data using a different radio technology , PDCP devices may perform reordering on PDCP PDUs received by the different radio technologies and distribute the PDCP PDUs to lower layer devices using the different radio technologies, in which case the techniques presented throughout this specification (e.g., timer-based reordering techniques or reordering operation switching procedures) can be applied.

A description will now be made of methods in which the RLC device of the UE requests retransmission of missing packets according to an embodiment of the present disclosure.

For normal operation of the RLC, the RLC receiving device may comply with 3GPP standard TS36.322 and may use the RLC PDU interchangeably with Acknowledged Mode Data (AMD) PDUs.

The RLC status PDU may be significantly large in size depending on radio channel conditions, and the UE may not transmit the entire RLC status PDU with a given transmission resource. In this case, the UE may optionally report information that may only be reported in a given transmission resource.

For example, the reception state of the UE will be assumed as follows.

-highest RLC sequence number currently received 100

-missing RLC PDU 90 and 95

-missing RLC PDU segmentation from the 100 th byte to the 150 th byte of PDU [93]

As shown in the example of fig. 13 showing the format of the status PDU, the status PDU may be configured with ACK _ SNs, or more NACK _ SNs, zero (0) per NACK _ SN, and or more SOstart/SOend pairs.

-ACK_SN＝101

-ACK_SN＝90

-NACK_SN＝93；SOstart＝100；SOend＝150

-NACK_SN＝95

If the amount of transmission resources to be allocated to the RLC device is, for example, 16 bits, the UE may configure a status PDU as shown below according to the possible amount of transmission resources.

-ACK_SN＝90

In other words, the UE may report only information indicating that the UE has normally received up to the sequence number 89, and may not report on the remaining RLC PDUs.

In cases, incorrect information may be sent if the UE reports only pieces of information as above.

Fig. 13 illustrates a format of a status PDU according to an embodiment of the present disclosure.

Referring to fig. 13, several SOstart/SOend pairs may be contained for NACK _ SNs, and if only parts of this information are contained due to a given amount of transmission resources, an RLC device that has received a status PDU may make an erroneous determination.

-highest RLC sequence number currently received 100

-missing RLC PDU segments from the 100 th byte to the 150 th byte of PDU [93], and from the 180 th byte to the last byte of PDU [93 ].

In other words, (e.g., 1 st to 99 th bytes and 151 th to 179 th bytes) of the RLC PDUs having the sequence numbers 93 have been normally received, and other parts (e.g., 100 th to 150 th bytes and 180 th to last bytes) of the RLC PDUs having the sequence numbers 93 have not been normally received.

If the amount of transmission resources that the UE can use when the RLC status PDU is triggered is only sufficient to include ACK _ SN, NACK _ SN, and SOstart/SOend pairs, the UE may generate and transmit the following status PDU.

-ACK_SN＝100

-NACK_SN＝93；SOstart＝100；SOend＝150

The RLC device having received the status PDU may discard the portion of the 180 th to last bytes of the RLC PDU having the sequence number 93 from the buffer, thereby misjudging that the UE has even normally received the portion of the 180 th to last bytes. The operation of the RLC receiving apparatus for solving this problem will be described with reference to fig. 14. Referring to other fields in fig. 13, the D/C field indicates whether the PDU is a data PDU or a control PDU, the CPT (control PDU type) field indicates the type of the control PDU, the E1 (extension bit 1) field indicates whether a set of NACK _ SN, E1, and E2 follows, and the E2 (extension bit 2) field indicates whether a set of SOstart and SOend follows. Oct 1 to Oct 9 indicate octets.

Fig. 14 illustrates an operation in which an RLC receiving apparatus generates a status PDU according to an embodiment of the present disclosure.

Referring to fig. 14, an RLC status PDU may be triggered in operation 1405 if a t-Reordering timer expires in the case that t-StatusProhibit is not driven or th transmission opportunity occurs after receiving the RLC PDU with the polling bit set.

In operation 1410, the RLC receiving apparatus may determine whether it can generate a status PDU including all of ACK _ SN, NACK _ SN, and SOstart/SOend reflecting the current reception status in a transmission opportunity (e.g., determine whether the size of a status report in which all current statuses are reflected is smaller than the size of a transmittable RLC PDU). If so, the RLC receiving apparatus may proceed to operation 1415, and if not, the RLC receiving apparatus may proceed to operation 1420.

In operation 1415, the UE may generate a status PDU to reflect the reception status at that time by writing ACK _ SN, NACK _ SN, and SOstart/SOend therein

In operation 1420, the UE may determine whether the following conditions are satisfied. If the condition is satisfied, the UE may proceed to operation 1425, and if the condition is not satisfied, the UE may proceed to operation 1430.

Condition

When the UE generates a status PDU according to a given amount of transmission resources (or size of RLC PDU provided by lower layers), is only of or more SOstart/soond pairs for NACK _ SN included in the status PDU?

In operation 1425, the RLC receiving apparatus may set the SOend value of the last SOstart/SOend pair included in the NACK _ SN to a predetermined value (e.g., "111111111111111"). If SOend is set to the above value, it means that the RLC receiving apparatus has not received a portion from the byte indicated by SOstart to the last byte. In other words, by setting the value of the last SOend to the above value, the RLC receiving apparatus can request transmission even for a successfully received segment, and can prevent at least the RLC transmitting apparatus from discarding segments that the RLC transmitting apparatus has not yet received. In the above example, the following status PDU may be generated.

-ACK_SN＝100

-NACK _ SN 93; SOstart is 100; SOend is a predetermined value

The transmitting apparatus having received the status PDU may not discard the 151 th to 179 th bytes of the RLC PDU having the sequence number 93.

As another operation, in operation 1425, the RLC receiving device may cancel the triggered status PDU and send the status PDU again in the next transmission opportunities.

In operation 1430, the UE may determine up to which RLC PDU segments the UE will report NACK information according to the size of the RLC PDU, write the sequence number of the missing RLC PDU immediately after the last RLC PDU segment into ACK _ SN, and generate status PDU by sequentially writing NACK information given to report NACK information or for RLC PDU segments.

Fig. 15 illustrates an operation in which an RLC transmitting apparatus receives a status PDU according to an embodiment of the present disclosure.

Referring to fig. 15, the RLC transmitting apparatus may receive/trigger a status PDU in operation 1505.

In operation 1510, the RLC transmitting apparatus may determine which RLC PDU and RLC PDU segment have been normally transmitted using ACK _ SN, NACK _ SN, SOstart, and SOend of the status PDU, and may discard the normally transmitted packet from its transmission buffer and prepare to retransmit the packet requiring retransmission.

The RLC transmitting apparatus may determine that it should retransmit all RLC PDUs indicated with NACK _ SN only among the status PDUs.

The RLC transmitting apparatus may determine that it should retransmit an RLC PDU segment reported as missing by partial NACK information included in the status PDU.

The RLC transmission apparatus may determine that remaining segments other than the RLC PDU segment reported as missing by the partial NACK information (except for the last status element) among the partial NACK information included in the status PDU have been normally received, and discard the remaining segments.

If the last status element of the status PDU is partial NACK information, the RLC transmitting apparatus may not determine whether remaining segments other than the RLC PDU segment reported as missing by the partial NACK information have been received. In other words, the RLC transmitting apparatus may neither discard the remaining segments nor retransmit the remaining segments.

Now, a description will be made of a method in which a UE reports a plurality of categories and performs a HARQ operation by applying of the categories according to an embodiment of the present disclosure.

In order for the UE and the ENB to perform data exchange, the ENB should recognize the capability of the UE. For example, the information such as the maximum downlink data rate of the UE and the HARQ buffer performance of the UE may be information that the ENB should know in order to transmit downlink data to the UE. Capability information related to downlink data transmission/reception of the UE may be reported to the ENB in the form of a UE category. The following table shows the "UE categories" defined in standard 36.306. If the UE category is classified based on the downlink data reception capability of the UE, category 1 corresponds to 10Mbps, category 2 corresponds to 50Mbps, category 3 corresponds to 100Mbps, category 4 corresponds to 150Mbps, and

Claims

1, A method of a user equipment, UE, in a wireless communication system, the method comprising:

receiving a packet data convergence protocol data unit (PDCP PDU) from a lower layer;

determining a count value of the received PDCP PDUs;

decrypting the received PDCP PDU using a count value of the received PDCP PDU;

storing at least PDCP service data units SDUs corresponding to the decrypted PDCP PDU in a buffer, and

after performing header decompression on the stored at least PDCP SDUs, delivering at least PDCP SDUs after the header decompression to an upper layer based on a count value of the received PDCP PDU.

2. The method of claim 1, wherein the delivering comprises:

determining whether a count value of the received PDCP PDUs is equal to a lowest count value associated with the lost PDCP SDUs; and

after performing header decompression on the at least two PDCP SDUs stored in the buffer, delivering the header-decompressed at least two PDCP SDUs to an upper layer in an ascending order of at least two count values associated with the at least two PDCP SDUs in response to the count value of the received PDCP SDU being equal to the lowest count value associated with the missing PDCP SDU.

3. The method as claimed in claim 1, wherein the count value of the received PDCP PDUs is determined based on a hyper frame number HFN of the received PDCP PDUs and a sequence number SN of the received PDCP PDUs.

4. The method of claim 1, further comprising:

discarding the repeatedly received PDCP PDUs among the previously received at least PDCP PDUs.

5. The method of claim 2, wherein the delivering comprises:

updating a lowest count value associated with the missing PDCP SDUs to a count value associated with an th PDCP SDU, wherein the th PDCP SDU has not been delivered to an upper layer and the count value associated with the th PDCP SDU is greater than the lowest count value associated with the missing PDCP SDU.

6. The method of claim 2, wherein the delivering comprises:

after performing header decompression on all PDCP SDUs in the buffer having consecutive correlation count values from the lowest count value associated with the missing PDCP SDU, delivering all PDCP SDUs after header decompression to an upper layer in ascending order of the correlation count values.

7. The method of claim 1, further comprising:

reordering the at least PDCP SDUs using a reordering-related timer, and

when the timer expires, after performing header decompression on all PDCP SDUs having th associated count values in the buffer and all PDCP SDUs having consecutive second associated count values, delivering all PDCP SDUs after header decompression to an upper layer in ascending order of th associated count value and second associated count value, the th associated count value being smaller than a count value after the count value associated with the PDCP PDU triggering the timer, the second associated count value starting from a count value after the count value associated with the PDCP PDU triggering the timer.

8, A User Equipment (UE) in a wireless communication system, the UE comprising:

a transceiver; and

a controller configured to:

controlling the transceiver to receive a packet data convergence protocol data unit, PDCP PDU, from a lower layer;

determining a count value of the received PDCP PDUs;

decrypting the received PDCP PDU using a count value of the received PDCP PDU;

9. The UE of claim 8, wherein the controller is configured to:

determining whether a count value of the received PDCP PDUs is equal to a lowest count value associated with the missing PDCP SDUs; and

10. The UE of claim 8, wherein the count value of the received PDCP PDUs is determined based on a Hyper Frame Number (HFN) of the received PDCP PDUs and a Sequence Number (SN) of the received PDCP PDUs.

11. The UE of claim 8, wherein the controller is further configured to:

12. The UE of claim 9, wherein the controller is further configured to:

13. The UE of claim 9, wherein the controller is further configured to:

14. The UE of claim 9, wherein the controller is further configured to:

reordering the at least PDCP SDUs using a reordering-related timer, and

15, A method of a base station, BS, in a wireless communication system, the method comprising:

determining a count value of the received PDCP PDUs;

decrypting the received PDCP PDU using a count value of the received PDCP PDU;

16. The method of claim 15, wherein the delivering comprises:

17. The method as claimed in claim 15, wherein the count value of the received PDCP PDUs is determined based on a hyper frame number HFN of the received PDCP PDUs and a sequence number SN of the received PDCP PDUs.

18. The method of claim 15, further comprising:

19. The method of claim 16, wherein the delivering comprises:

20. The method of claim 16, wherein the delivering comprises:

21. The method of claim 15, further comprising:

reordering the at least PDCP SDUs using a reordering-related timer, and

when the timer expires, after performing header decompression on all PDCP SDUs having th associated count values in the buffer and all PDCP SDUs having consecutive second associated count values, delivering all PDCP SDUs after header decompression to an upper layer in ascending order of th associated count value and second associated count value, the th associated count value being smaller than a count value after the count value associated with the PDCP PDU triggering the timer, the second associated count value starting from the count value after the count associated with the PDCP PDU triggering the timer.

22, A base station, BS, in a wireless communication system, the BS comprising:

a transceiver; and

a controller configured to:

control the transceiver to receive a packet data convergence protocol data unit (PDCP PDU) from a lower layer;

determining a count value of the received PDCP PDUs;

decrypting the received PDCP PDU using a count value of the received PDCP PDU;

23. The BS of claim 22, wherein the controller is configured to:

24. The BS of claim 22, wherein the count value of the received PDCP PDUs is determined based on a hyper frame number HFN of the received PDCP PDUs and a sequence number SN of the received PDCP PDUs.

25. The BS of claim 22, wherein the controller is further configured to:

26. The BS of claim 23, wherein the controller is further configured to:

27. The BS of claim 23, wherein the controller is further configured to:

after performing header decompression on all PDCP SDUs in the buffer having consecutive correlation count values from the lowest count value associated with the missing PDCP SDU, all PDCP SDUs after header decompression are delivered to an upper layer in ascending order of the correlation count values after performing header decompression.

28. The BS of claim 22, wherein the controller is further configured to:

reordering the at least PDCP SDUs using a reordering-related timer, and