KR20150090808A - Method and apparatus for transmitting and receiving data using a plurality of carriers in mobilre communication system - Google Patents

Abstract

The present invention relates to a mobile communication system and, more specifically, to a method and an apparatus for transmitting and receiving data by using multiple carriers in a mobile communication systems. A method for resetting bearer in a mobile communication system supporting multi bearer according to an embodiment of the present invention comprises processes of: receiving a first control message for bearer resetting; and converting PDCP PDUs into PDCP SDUs, when bearer-resetting from a single bearer into the multi bearer based on the first control message, and delivering the PDCP SDUs having aligned sequences to an upper layer.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method and apparatus for transmitting / receiving data using a plurality of carriers in a mobile communication system,

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

Generally, a mobile communication system is developed for providing communication while securing the mobility of a user. Such a mobile communication system has reached a stage where it can provide high-speed data communication services as well as voice communication owing to the remarkable development of the technology.

Recently, as one of the next generation mobile communication systems, LTE (Long Term Evolution) system is being provided in 3GPP (Third Generation Partnership Project) in a number of countries. The LTE system is a technology for implementing high-speed packet-based communication with a transmission rate of about 100 Mbps.

Recently, commercialization of the advanced LTE communication system (LTE-Advanced, LTE-A) which improves the transmission speed by combining various new technologies with the LTE communication system is underway. Carrier aggregation is one of the newly introduced technologies. Carrier integration is one in which a terminal uses a plurality of forward carriers and a plurality of reverse carriers, as opposed to a conventional method in which a terminal transmits and receives data using only one forward carrier and one reverse carrier.

LTE-A currently defines only intra-ENB carrier aggregation in the base station. This leads to a reduction in the applicability of the carrier integration function. In particular, in a scenario in which a plurality of picocells and one macro cell are overlapped with each other, the macrocell and the picocell can not be integrated. The picocell may be referred to as a micro cell, a small cell, or the like in other terms.

The present invention provides a method and apparatus for efficiently transmitting and receiving data using a plurality of carriers in a mobile communication system.

The present invention also provides a method and apparatus for inter-ENB carrier aggregation between different base stations.

The present invention also provides a PDCP operation switching method and apparatus in a mobile communication system supporting a multi-bearer.

The present invention also provides a PDCP reordering method and apparatus in a mobile communication system supporting a multi-bearer.

In a mobile communication system supporting a multi-bearer according to an exemplary embodiment of the present invention, a bearer re-establishment method includes: receiving a first control message for re-establishing a bearer; When the bearer is re-established, converting the PDCP PDUs into PDCP SDUs and delivering the ordered PDCP SDUs to the upper layer.

The method may further include receiving a second control message for bearer re-establishment, and re-establishing a bearer to the single bearer in the multi-bearer based on the second message, PDUs corresponding to COUNT to PDCP SDUs, and storing all SDUs after the first missing SDU in a buffer.

According to various embodiments of the present invention, the transmission / reception speed of the terminal can be further improved by integrating carriers between different base stations.

Also, according to various embodiments of the present invention, PDCP reordering can be efficiently performed in a bearer re-establishment between a single bearer and a multi bearer in a communication environment using a multi-bearer such as carrier aggregation.

1 is a diagram showing a structure of an LTE system to which an embodiment of the present invention is applied,
2 is a diagram illustrating a wireless protocol structure in an LTE system to which an embodiment of the present invention is applied;
3 is a diagram for explaining carrier integration in a base station in an LTE system,
4 is a diagram for explaining carrier aggregation among base stations in an LTE system according to an embodiment of the present invention;
5 is a diagram illustrating a connection structure of a PDCP apparatus in an LTE system according to an embodiment of the present invention;
6 is a diagram for explaining a process of switching a PDCP operation in an LTE system according to an embodiment of the present invention;
FIG. 7 is a diagram for illustrating resetting of an RLC apparatus when a PDCP operation is switched in an LTE system according to an embodiment of the present invention;
8 is a diagram for explaining operations of a UE in a bearer reset in an LTE system according to an embodiment of the present invention;
9 is a diagram for explaining an upper layer delivery condition of a PDCP operation in an LTE system according to an embodiment of the present invention;
10 is a diagram for explaining the operation of a PDCP receiving apparatus in an LTE system according to an embodiment of the present invention,
11 is a diagram for explaining an operation when the timer 1 expires in the PDCP receiving apparatus of FIG. 10,
12 is a diagram for explaining an operation of a terminal for setting a PBR for a multi-bearer according to an embodiment of the present invention;
13 is a diagram illustrating the format of a status PDU according to an embodiment of the present disclosure;
FIG. 14 is a diagram for explaining an operation of an RLC receiving apparatus for generating a status PDU according to an embodiment of the present invention;
15 is a diagram for explaining an operation of an RLC transmitting apparatus for receiving a status PDU according to an embodiment of the present invention;
16 is a block diagram illustrating a configuration of a terminal device in an LTE system according to an embodiment of the present invention;
17 is a block diagram illustrating a configuration of a base station apparatus in an LTE system according to an embodiment of the present invention.
18 is a diagram illustrating operations of a terminal reporting three categories according to an embodiment of the present invention and a base station performing downlink data transmission / reception with the terminal;
19 is a diagram illustrating a terminal operation according to an embodiment of the present invention;
20 is a diagram illustrating a terminal operation when a bearer is reset according to an embodiment of the present invention;
21 is a diagram illustrating an operation of a PDCP receiving apparatus operating as a multiple bearer according to an embodiment of the present invention;
22 is a diagram illustrating an operation of a PDCP receiving apparatus for switching to a PDCP operation 5 upon resetting from a multi bearer to an MCG bearer according to an embodiment of the present invention;
23 is a diagram illustrating an operation of a PDCP receiving apparatus when a timer 3 expires according to an embodiment of the present invention;
24 is a diagram illustrating a terminal operation when a bearer is reset according to an embodiment of the present invention;
FIG. 25 is a diagram illustrating a PDCP operation 7 of a PDCP receiving apparatus operating as a multi-bearer according to an embodiment of the present invention;
26 shows an operation of the PDCP receiving apparatus when the timer 3 expires according to the embodiment of the present invention,
FIG. 27 is a diagram illustrating an operation for determining whether a UE receives a PDCP PDU according to an exemplary embodiment of the present invention. FIG.
28 is a diagram illustrating a terminal operation when a bearer is reset according to an embodiment of the present invention;

In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The LTE system and carrier integration will be briefly described below before describing this specification. In the embodiments of the present invention, the LTE system will be understood to mean the LTE-A system.

1 is a diagram showing the structure of an LTE system to which an embodiment of the present invention is applied.

Referring to FIG. 1, a radio access network of an LTE system includes an Evolved Node B (hereinafter, referred to as an ENB, a Node B or a base station) 105, a Mobility Management Entity (MME) 125, (130, Serving-Gateway). A user equipment (hereinafter UE or terminal) 135 connects to an external network (not shown) via the ENBs 105, 110, 115, 120 and the S-GW 130.

In FIG. 1, the ENBs 105, 110, 115, and 120 correspond to the existing Node B of the UMTS system. The ENBs 105, 110, 115, and 120 are connected to the UE 135 through a radio channel and perform a more complex role than the existing Node B. In the LTE system, since all user traffic including a real-time service such as Voice over IP (VoIP) over the Internet protocol is serviced through a shared channel, status information such as buffer status, available transmission power status, And the ENBs 105, 110, 115, and 120 take charge of scheduling. One ENB 105, 110, 115, 120 typically controls a number of cells. For example, in order to realize a transmission rate of 100 Mbps, an LTE system uses Orthogonal Frequency Division Multiplexing (OFDM) as a radio access technology in a 20 MHz bandwidth. In addition, the ENBs 105, 110, 115, and 120 may perform adaptive modulation and coding (AMC) to determine a modulation scheme and a channel coding rate according to a channel state of the AT 135. [ ) Method is used. The S-GW 130 is a device that provides a data bearer and generates or removes a data bearer under the control of the MME 125. [ The MME 125 is connected to a plurality of ENBs as an apparatus for performing various control functions as well as a mobility management function for the terminal 135.

2 is a diagram illustrating a wireless protocol structure in an LTE system to which an embodiment of the present invention is applied.

Referring to FIG. 2, the wireless protocol structure of the LTE system includes PDCP (Packet Data Convergence Protocol 205, 240), Radio Link Control (RLC) 210, and MAC (Medium Access Control) 215 and 230 in the UE and the ENB, respectively.

The PDCP (Packet Data Convergence Protocol) 205 and 240 are responsible for operations such as IP header compression / decompression and Radio Link Control (RLC) 210 and 235 are PDCP PDU ) To an appropriate size to perform an ARQ (Automatic Repeat reQuest) operation or the like. The MACs 215 and 230 are connected to a plurality of RLC layer devices configured in one UE, multiplex RLC PDUs into MAC PDUs, and demultiplex RLC PDUs from MAC PDUs. The physical layers 220 and 225 perform channel coding and modulation on the upper layer data, transmit them to a wireless channel by making OFDM symbols, demodulate OFDM symbols received through a wireless channel, channel-decode and transmit the OFDM symbols to an upper layer .

3 is a diagram for explaining carrier integration in a base station in an LTE system.

Referring to FIG. 3, one base station can generally transmit and receive multiple carriers over several frequency bands. For example, when a carrier 315 having a forward center frequency f1 and a carrier 310 having a forward center frequency f3 are transmitted from the base station 305, one terminal is conventionally one of the two carriers f1 and f3 Data was transmitted and received using one carrier. However, the terminal 330 having the carrier integration capability can simultaneously transmit and receive data through a plurality of carriers. The base station 305 can increase the transmission speed of the terminal 330 by allocating more carriers to the terminal 330 having the carrier integration capability depending on the situation. The integration of forward and uplink carriers transmitted and received by one base station is called carrier aggregation in the base station. However, in some cases, it may be necessary to integrate forward and uplink carriers that are transmitted and received in different base stations, unlike the example shown in FIG.

4 is a diagram for explaining carrier integration between base stations, which is a carrier integration method according to the embodiment of the present invention.

4, when the base station 1 405 transmits and receives data through a carrier having a center frequency f1 and the base station 2 415 transmits and receives data through a carrier having a center frequency f2, Convergence of a carrier with a forward center frequency of f1 and a forward center frequency of f2 carriers results in one carrier accumulating carriers from two or more base stations and is referred to herein as an inter-ENB, Called carrier aggregation (or base station CA). In this specification, the carrier integration between the base stations is referred to as a Dual Connectivity (DC), and for example, a DC is set. This means that carrier aggregation between the base stations is established, that one or more cell groups are set up, At least one secondary serving cell SCell under the control of a base station other than the serving base station SeNB is set; that the primary serving cell (PCell or pSCell) is set; A MAC entity is set, and two MAC entities are set in the terminal.

Hereinafter, terms used in this specification will be described.

In the conventional sense, one forward carrier transmitted by one base station and one uplink carrier received by the base station constitute one cell. Carrier integration means that a terminal simultaneously transmits and receives data through a plurality of cells It may be understood. At this time, the maximum transmission rate and the number of integrated carriers have a positive correlation.

Hereinafter, in the present specification, a terminal receives data through an arbitrary forward carrier or transmits data through an arbitrary uplink carrier means that a control channel and data provided by a cell corresponding to a center frequency and a frequency band, Has the same meaning as transmitting and receiving data using a channel. In this specification, in particular, the carrier aggregation will be expressed as 'a plurality of serving cells are set', and terms such as a primary serving cell (hereinafter referred to as PCell) and a secondary serving cell (hereinafter referred to as SCell) or an activated serving cell will be used. The terms have the same meaning as they are used in an LTE mobile communication system. In the present invention, terms such as a carrier, a component carrier, and a serving cell are mixed.

In this specification, a set of serving cells controlled by the same base station is defined as a cell group or a carrier group (CG). The cell group is divided into a master cell group (MCG) and a secondary cell group (SCG). The MCG is a set of serving cells controlled by a base station (hereinafter, referred to as MeNB) that controls a PCell. The SCG is a base station that controls only the SCell, that is, a slave base station, SeNB). ≪ / RTI > The base station informs the UE whether the predetermined serving cell belongs to the MCG or the SCG in the process of setting the corresponding serving cell. One MCG and one or more SCGs may be set in one terminal. In the present invention, only one SCG is set for convenience of description. However, even if more than one SCG is set, Can be applied as it is. PCell and SCell are terms indicating the type of serving cell to be set in the UE. There are some differences between PCell and SCell, for example PCell is always active, but SCell repeats the activation and deactivation according to the base station's instructions. The mobility of the terminal is controlled by PCell, and the SCell can be understood as an additional serving cell for data transmission and reception. PCell and SCell in the present specification mean PCell and SCell defined in 3GPP LTE standard TS36.331 or TS36.321.

In the present invention macro cells and picocells are considered. The macro cell is a cell controlled by the macro base station and provides a service in a relatively large area. The picocell, on the other hand, is a cell controlled by SeNB and provides service in a significantly narrower area than a conventional macrocell. Although there is no strict criterion for distinguishing a macro cell from a picocell, for example, it can be assumed that a macro cell region has a radius of about 500 m and a picocell region has a radius of several tens of m. In this specification, a picocell and a small cell are mixed.

4, if the first base station 405 is MeNB and the second base station 415 is SeNB, the serving cell 410 having the center frequency f1 is the serving cell belonging to the MCG and the serving cell 420 having the center frequency f2 is the SCG Lt; / RTI >

In the following description, other terms may be used instead of MCG and SCG for the sake of understanding. For example, terms such as MCG and secondary set, or primary carrier group and secondary carrier group can be used. However, it should be noted that the terminology is different in this case, and the meaning is the same. The main purpose of these terms is to distinguish which cell is under the control of the base station controlling the PCs of a specific terminal, and when the cell is under the control of the base station controlling the PCell of the specific terminal, And the operation mode of the corresponding cell may be changed.

One or more SCGs may be set in the terminal, but in the present invention, it is assumed that only one SCG can be set for convenience of explanation. An SCG can consist of multiple SCell's, one of which has a special attribute.

In a conventional intra-base-station CA, a UE transmits HARQ feedback and CSI for SCell, as well as HARQ feedback and CSI for a PCell, through the PCUC's PUCCH. This is because CA is applied to terminals that can not perform uplink simultaneous transmission.

In the case of inter-base station CA, it may be practically impossible to transmit HARQ feedback and CSI of CSG SCell through PUCCH, which is an uplink control channel of PCell. The HARQ feedback should be delivered within the HARQ RTT (Round Trip Time, typically 8 ms) because the transmission delay between the MeNB and the SeNB may be longer than the HARQ RTT. Due to the above-mentioned problem, a PUCCH transmission resource is set in one cell of the SCs belonging to the SCG, and HARQ feedback and CSI for the SCG SCell are transmitted through the PUCCH. The special SCell is named pSCell (primary SCell). In the following description, the inter-base-station CA mixes the dual connectivity.

In general, one user service is served by one EPS (Evolved Packet System) bearer, and one EPS bearer is connected to one radio bearer. The radio bearer is composed of PDCP and RLC. In the inter-base transceiver station CA, the efficiency of data transmission / reception can be increased by locating the PDCP device and the RLC device of one radio bearer in different base stations. Different approaches are needed depending on the type of user service.

5 is a diagram illustrating a connection structure of a PDCP apparatus in an LTE system according to an embodiment of the present invention.

Referring to FIG. 5, for example, in the case of a large capacity data service, the user service may transmit and receive data with both MeNB and SeNB by forming two RLC devices as shown in reference numeral 510. If the QoS requirement is strict service such as VoLTE, the user service can transmit / receive data using only MeNB serving cell by placing the RLC device in the MeNB only as shown in reference numeral 505. For the sake of convenience of explanation, the bearer such as reference numeral 505 is referred to as a single bearer, and the bearer such as reference numeral 510 is referred to as a multi-bearer. A single bearer PDCP device is connected to one RLC device, and a multi bearer PDCP device is connected to two RLC devices. MCG RLC 515 refers to an RLC device in which data is transmitted / received through MCG (or connected to a MAC device related to serving cells of MCG), and RLC device to which data is transmitted / received through SCG is referred to as SCG RLC 520. The MAC 525 related to data transmission / reception through the MCG is referred to as an MCG-MAC, and the MAC 530 related to data transmission / reception through the SCG is referred to as an SCG-MAC. The logical channel between the MCG RLC and the MCG-MAC is referred to as the MCG logical channel, and the logical channel between the SCG RLC and the SCG-MAC is referred to as the SCG logical channel.

For convenience of explanation, the macro cell area means an area in which only a macro cell signal is received without receiving a small cell signal, and a small cell area means an area in which a macro cell signal and a small cell signal are received together. When a mobile station with a large downlink data demand moves from a macro cell area to a small cell area, a small cell can be additionally set to the mobile station. A bearer having a large amount of downlink data such as a file transfer protocol (FTP) It can be reset from a single bearer to a multiple bearer. In other words, when a mobile station moves from a macro cell area to a small cell area back to a macro cell area, a predetermined bearer is reset from a single bearer to a multiple bearer again to a single bearer. Since the PDCP device of a single bearer is connected to one RLC and the RLC delivers the ordered packets to the PDCP, the PDCP device processes the packets delivered by the RLC in order. On the other hand, the PDCP device of the multi-bearer is connected to two RLCs, and each RLC carries the ordered packets, but since the order may not be aligned among the RLC devices, the PDCP processes the packets after arranging the order . Therefore, when the PDCP device is reset from a single bearer to a multi-bearer or from a multi-bearer to a single bearer, the action taken by the PDCP device is also changed at an appropriate time.

In the embodiment of the present invention, the operation of the terminal is divided into PDCP operation 1, PDCP operation 2, and PDCP operation 3.

PDCP operation 1 is an operation to be applied to the PDCP of a single bearer. The details of the above operation are in accordance with 5.1.2 of 3GPP TS36.323. PDCP device operation 2 is another operation to apply to the PDCP of a single bearer, and PDCP device operation 1 is applied to a general case.

PDCP device operation 2 is applied in an exceptional case where the lower layer device can not perform the reordering, for example, in a handover situation or an RRC connection reestablishment procedure. The details of the above operation are also in accordance with 5.1.2 of Specification TS36.323. When the PDCP device operates in operation 1, the PDCP performs a necessary process on the assumption that the received packets are in the correct order, and then delivers the packets having the serial number lower than the received packet and the received packet to the upper layer. On the other hand, if the PDCP device operation 2 does not carry out the order reordering in the lower layer device, for example, the received packets may not be correctly ordered. Therefore, the packets are not transferred to the upper layer but are stored in the reordering buffer. Then, when the lower layer device becomes a point of time to re-order reordering (that is, when the handover is completed or the RRC connection re-establishment process is completed), the PDCP device operation 1 is switched to the newly received PDCP SDU SDUs to the upper layer. The switching between the PDCP operation 1 and the operation 2 occurs immediately, for example, at the moment of receiving the control message indicating the handover, and the PDCP operation 2 is applied for a short time immediately after the handover occurs. In the embodiment of the present invention, the PDCP operation 3 is newly introduced.

The PDCP operation 3 is an operation applied to the PDCP of the multi-bearer. The PDCP operation 3 receives a PDCP PDU (Protocol Data Unit) from two RLC apparatuses connected to the PDCP apparatus. But the order is not aligned between PDCP PDUs received from different RLC devices. In the PDCP operation 1 and operation 2, the received PDCP PDUs are once processed as a PDCP SDU (Service Data Unit), and then it is checked whether the PDCP PDUs are reordered. In the PDCP operation 3, Only PDCP PDUs whose order is aligned are processed as PDCP SDUs and transmitted to the upper layer. In PDCP operation 3, it is also possible to rearrange PDCP PDUs to PDCP SDUs before performing reordering. Details of the PDCP operation 1, the PDCP operation 2, and the PDCP operation 3 will be described later. As described above, PDCP operation 2 is temporarily applied in a handover situation, but PDCP operation 3 is continuously applied while operating as a multi-bearer. PDCP operation 1 for a single bearer, and PDCP operation 3 for a multi-bearer. The PDCP operation is switched from the operation 1 to the operation 3, or from the operation 3 to the operation 1 when an arbitrary bearer is switched from a single bearer to a multi-bearer, or vice versa. At this time, an unnecessary delay may occur when the PDCP apparatus transfers data to the upper hierarchical apparatus at a point in time when the operation is switched, and data loss may occur if the operation switching is delayed.

6 is a diagram for explaining a PDCP operation change process in an LTE system according to an embodiment of the present invention. 6, the operation of the UE and the BS related to the bearer reset including the process of switching the PDCP operation by the UE at an appropriate time will be described in detail.

6, the MeNB 610 at a certain point in the mobile communication system including the UE 605, the MeNB 610 and the SeNB 615 transmits the serving cell of the SeNB 615 to the UE 605 in step 620, And performs the procedure for adding the serving cell to the SeNB 615. [ If the SCN of the SeNB 615 is to be set for the first time (that is, the first SCG SCell is set), the MeNB 610 and the SeNB 615 transmit a certain bearer to the MeNB 610 It determines which bearer SeNB 615 will service. The MeNB 610 and the SeNB 615 can re-establish a bearer conforming to a predetermined condition, for example, a bearer that requires high-speed data transmission in the downlink to a multi-bearer. For convenience of explanation, it is assumed that bearer x has been reset from a single bearer to a multiple bearer.

In step 625, the MeNB 610 transmits a predetermined RRC control message to the UE 605. In the RRC control message, SCell setting information and multi-bearer information are stored. The SCell setting information is for a newly added SCell, and includes information indicating whether the SCell is an MCG SCell or an SCG SCell. The multi-bearer setup information is information on a radio bearer that is reset from a single bearer to a multi-bearer, and may include the identifier of the radio bearer, the SCG RLC setting information, and the like.

In step 630, when the UE 605 receives the control message, the UE 605 generates an SCG RLC for the bearer indicated by the bearer identifier, connects the SCCP RLC with the PDCP device, and connects the SCG RLC device with the MAC device for the SCG. The UE switches from the PDCP operation 1 to the PDCP operation 3 at the time when the configuration of the multi bearer is completed or when the random access is completed as described above. In the conventional RLC apparatus of the bearer, that is, the MCG RLC, normal data transmission and reception, for example, PDCP PDUs with ordered PDCP PDUs are transmitted to the PDCP apparatus during the reconfiguration procedure, PDCP PDUs of unordered PDCP PDUs are stored in the RLC buffer, And performs an operation of attempting to recover an unreceived PDU. As will be described later, unlike a single bearer-to-multiple-bearer reconfiguration, in the process of resetting from a multi-bearer to a single bearer, the MCG RLC unit also stops the RLC receiving operation and performs the RLC reset process.

In step 635, the terminal 605 performs random access in the newly added SCG SCell. Through the random access procedure, the UE 605 establishes uplink synchronization with the newly added SCG SCell and sets an uplink transmission output. When the random access procedure is completed, the UE 605 switches the operation of the PDCP apparatus reset to the multi bearer from the PDCP apparatus operation 1 to the PDCP apparatus operation 3 in step 640. The random access procedure is completed when a terminal receives a valid random access response message when a dedicated preamble is used and when a random preamble is used, Radio Network Temporary Identifier) and receives the uplink grant or downlink assignment indicating the new transmission. Other matters related to the random access are in conformity with specification TS36.321.

In step 645, the UE 605 transmits a predetermined RRC control message to the MeNB 610 to report that the SCell setting and the multi-bearer re-establishment are completed. In step 650, the MeNB 610 forwards the downlink data of the multi-bearer to the SeNB 615 upon receiving the reported information, and the SeNB initiates the downlink data transmission through the SCG RLC of the multi-bearer to the UE .

In step 655, the UE 605 receives the downlink data of the bearer from the MCG RLC apparatus and the SCG RLC apparatus after transmitting the predetermined RRC control message in step 655, and performs PDCP operation 3 on the received PDCP PDUs To be applied.

In step 670, the MeNB 610 or the SeNB 615 decides to release the SCG SCell at an arbitrary point in time. The MeNB 610 and the SeNB 61 perform a procedure for releasing the SCG SCell. In step 675, the MeNB 610 transmits a predetermined RRC control message to the terminal 605 to instruct the SCG SCell to be released.

In step 680, upon receiving the control message, the terminal 605 releases the SCG SCell according to the instruction. If the control message indicates the cancellation of the last SCG SCell (i.e., the SCG SCell is released according to the control message indication, the UE 605 does not have any more SCG SCell) Perform the necessary procedures for resetting to the bearer. When the control message explicitly indicates a re-establishment from a multi-bearer to a single bearer, it also performs an operation for re-setting from a multi-bearer to a single bearer.

[Resetting operation from a multi-bearer to a single bearer]

1) Disable the SCG RLC of the directed bearer

2) Reset the MCG RLC receiver of the directed multicast bearer

3) Discarding downlink HARQ buffer data of MCG-MAC

4) Trigger PDCP status report

In the process of releasing the SCG RLC, the UE 605 reconfigures the downlink RLC PDUs stored in the SCG RLC into the RLC SDUs, transfers the PDUs to the PDCP, and discards the uplink RLC PDUs and the uplink RLC SDUs stored in the SCG RLC. The RLC SDU / PDCP PDUs delivered in the SCG RLC are RLC SDU / PDCP PDUs whose order is not aligned (i.e., RLC SDUs transmitted before the RLC SDU but not yet received).

The resetting of the MCG RLC receiving apparatus by the UE initializes the receiving window, initializes the receiving sequence number, and transmits to the PDCP those that can be reconfigured as RLC SDUs among the downlink RLC PDUs stored in the receiving buffer. PDUs are discarded. The UE does not discard the uplink RLC PDUs and the RLC SDUs stored in the transmission buffer.

The PDCP status report may be triggered for each radio bearer and the UE 605 checks the sequence number of the PDCP packet stored in the buffer of the bearer PDCP of the bearer that has been reset to the single bearer in the multi bearer, And generates a PDCP status report including relevant information. PDCP PDUs delivered from the SCG RLC and PDCP PDUs delivered from the MCG RLC are stored in the PDCP buffer.

The PDCP status report is control information used to prevent PDCP packet loss during handover or RRC connection reestablishment. The handover and the RRC connection re-establishment process involve re-establishment of all RLC devices set in the UE 605 (re-establishment of a lower layer in the context of the PDCP device). When the handover or the RRC connection re-establishment process is started, the UE 605 triggers a PDCP status report for all DRBs satisfying the PDCP status report generation condition 1 described below. When the last SCG SCell is released, the terminal 605 triggers a PDCP status report for all DRBs that satisfy the PDCP status report generation condition 2 below. When a bearer is re-established from a multi-bearer to a single bearer, the UE checks whether the bearer meets the following PDCP status report generation condition 3 to determine whether to generate a PDCP status report.

[PDCP status report generation condition 1]

Of DRBs with RLC AM set, DRBs with statusReportRequired set

[PDCP status report generation condition 2]

Of the DRBs in which RLC AM and statusReportRequired are set,

[PDCP status report generation condition 3]

At least one of SCG RLC and MCG RLC of the corresponding multi bearer operates as RLC AM

The statusReportRequired is as described in specifications TS36.331 and TS36.323.

In step 685, the UE switches the PDCP operation of the re-established bearer from the PDCP operation 3 to the PDCP operation 2 when the UE resets the multi bearer to a single bearer. In the PDCP, unordered PDCP SDUs transmitted in the MCG RLC and unordered PDCP SDUs transmitted in the SCG RLC are stored. The PDCP SDUs transferred in the process of resetting the MCG RLC and the PDCP SDUs transferred in the process of releasing the SCG RLC are stored in the PDCP buffer in the order of COUNT, and the reception state of the PDCP SDUs delivered from the MCG RLC and the PDCP SDUs delivered from the SCG RLC, Generates a PDCP status report reflecting all the reception states of the SDUs and transmits them to the MeNB.

In step 690, the UE 605 transmits a predetermined RRC control message to the MeNB 610 to report that the process has been completed successfully. The UE 605 and the MeNB 610 transmit the uplink data And transmits and receives downlink data.

The UE not only releases the SCG RLC device but also resets the MCG RLC device in the process of resetting, in particular, from a multi-bearer to a single bearer. In principle, it is not necessary to reset the MCG RLC device because the MCG RLC device is not affected by the resetting process from the multi-bearer to the normal bearer.

However, in the embodiment of the present invention, the MCG RLC apparatus is reset artificially in order to efficiently switch the PDCP operation as in the example of FIG.

7 is a diagram for explaining the resetting of the RLC apparatus when the PDCP operation is switched in the LTE system according to the embodiment of the present invention.

Referring to FIG. 7, for example, when a reordering from a multi-bearer to a single bearer is instructed, PDCP PDU [10] and PDCP PDU [11] that are not ordered are stored in the MCG RLC 710 PDCP PDU [7], PDCP PDU [8], PDCP PDU [12], PDCP PDU [13], and PDCP PDU [14] are not arranged in the SCG RLC 715, Is stored. For reference, it is assumed that the RLC sequence number of the PDCP PDU [10] is 5 and the RLC sequence number of the PDCP PDU [11] is 6, and the former part of the corresponding square represents the RLC sequence number. If the PDCP PDU [10] and [11] are transmitted in the MCG RLC, the PDCP PDU [12] is transmitted in the order of the following packets Another order reordering operation must be introduced since it is difficult for the PDCP to determine reordering. In an embodiment of the present invention, when the multi bearer is reset to a single bearer in order to solve the above problem, the MCG RLC apparatus is also reset so that all the PDCP SDUs whose order is not aligned at that time are stored in the PDCP buffer. In addition, the PDCP operation 2 is applied immediately without immediately applying the PDCP operation 1 so that the PDCP SDUs whose order is not aligned are not immediately transferred to the upper layer. That is, after releasing the SCG RLC apparatus and resetting the MCG RLC apparatus, the UE switches the operation of the PDCP apparatus from the operation 3 to the operation 2, and when the first PDCP PDU is received after being reset to the single bearer, the UE switches from the PDCP operation 2 to the PDCP operation 1 do.

8 is a diagram for explaining operations of a UE in a bearer reset in an LTE system according to an embodiment of the present invention. In the embodiment of FIG. 8, the operation of the UE for resetting a bearer x from a normal bearer to a multi-bearer and then re-establishing a bearer x to a bearer will be described.

Referring to FIG. 8, in step 805, the UE applies PDCP operation 1 to bearer x, which is a single bearer. In step 810, a control message for resetting the bearer x to a multi-bearer is received. In step 815, the UE generates an SCG RLC apparatus to be connected to the multi bearer according to the setup information indicated in the control message, and then connects the PDCP with the SCG RLC apparatus. The MS proceeds to step 820 and switches the operation of the PDCP apparatus from the operation 1 to the operation 3. [ In other words, after the UE resets to the multi-bearer, it checks whether the PDCP PDU is received from the first PDCP PDU, and then applies the PDCP operation 3 to determine whether the PDCP PDU is re-ordered or not. After that, the UE converts the PDCP PDUs into PDCP SDUs by applying the PDCP operation 3 to the PDCP PDUs of the re-established bearer, and delivers the PDCP SDUs in order to the upper layer.

In step 825, upon receiving a control message indicating that the multi bearer should be re-established as a single bearer, the UE proceeds to step 830 and releases the SCG RLC and re-establishes the MCG RLC. At this time, the SCG RLC releases both the transmitting device and the receiving device, and the MCG RLC re-establishes only the receiving device. That is, the RLC SDUs and RLC PDUs stored in the MCG RLC transmission apparatus are processed without being discarded, and the RLC PDUs stored in the RLC receiving apparatus are assembled into RLC SDUs and assembled into RLC SDUs, And discards the remaining RLC PDUs.

In step 835, the UE does not immediately switch the operation of the PDCP apparatus from the operation 3 to the operation 1, but switches to the operation 2 once. That is, the UE processes the PDCP PDUs delivered from the MCG RLC and the SCG RLC according to COUNT, converts the PDCP PDUs into PDCP SDUs, and stores all SDUs after the first non-receiving SDU in the buffer.

In step 840, the UE applies the operation 1 from the first PDCP PDU received after the re-establishment to the single bearer. That is, after converting the first PDCP PDU into the SDU, the UE determines that the order of the SDUs is lower than COUNT of the last SDU even if there is an unreceived SDU among the SDUs, SDUs are forwarded to higher layers.

Steps 830, 835, and 840 may be modified as follows. In step 830, the MS releases the SCG RLC and retains the MCG RLC. In step 835, the PDCP device operation is changed from the operation 3 to the operation 2. That is, the UE processes the PDCP PDUs delivered from the SCG RLC and stores the unordered PDCP SDUs in the PDCP buffer instead of the upper layer. In step 840, the UE drives a predetermined timer 2 upon completion of switching to a single bearer or after receiving a first PDCP PDU after switching to a single bearer. The terminal maintains the operation 2 while the timer 2 is driven and switches from the operation 2 to the operation 1 when the timer expires. In other words, while the timer 2 is being driven, the sequence occurring due to the release of the SCG RLC waits for the order of unordered PDCP PDUs to be aligned. The timer 2 should be set to a sufficiently long time to be able to solve the order intermixing. The value of the timer 1 and the timer 2 is notified to the UE by the base station using a predetermined RRC control message.

It is to be understood that the PDCP operation 1, operation 2 and operation 3 are variously arranged in a series of various operations to be applied to the PDCP PDU delivered from the RLC entity. Table 1 below lists the detailed operations that constitute these operations and their order. The following detailed operations are performed in the order from top to bottom.

PDCP operation 1 PDCP operation 2 PDCP operation 3 PDCP PDU reception PDCP PDU reception PDCP PDU reception Determines the HFN / COUNT of the PDCP PDU. Discard duplicated PDUs Determines the HFN / COUNT of the PDCP PDU. Discard duplicated PDUs Determines the HFN / COUNT of the PDCP PDU. Discard duplicated PDUs PDCP PDU to PDCP SDU PDCP PDU to PDCP SDU PDCP PDU to PDCP SDU And delivers PDCP SDUs that satisfy the PDCP SDU and upper layer delivery condition 1 to the upper layer. Store the rest in a buffer Transmits PDCP SDUs satisfying upper layer transfer condition 2 to upper layer. The remaining SDUs are stored in the PDCP buffer Store the PDCP SDU in the PDCP buffer. Transmits PDCP SDUs satisfying upper layer transfer condition 3 to upper layer. The remaining SDUs are stored in the PDCP buffer.

A method of determining the HFN / COUNT of the received PDCP PDU described in Table 1 will be described below. COUNT is a 32-bit integer that starts at 0 and increments by 1. COUNT is assigned to each PDCP packet and is used for security related operations such as non-correspondence / non-correspondence of PDCP packets. The COUNT increases monotonically according to the order in which the PDCP packets are delivered to the lower layer. In principle, the PDCP SDUs are allocated in the order from the upper layer. COUNT consists of HFN and PDCP SN. The PDCP SN is included in the header of the PDCP packet and transmitted, but the HFN is not explicitly transmitted. Therefore, the PDCP receiving apparatus should determine the HFN of the received packet by itself. When the PDCP transmitting apparatus observes a predetermined condition (transmission such that the order shift of the PDCP SN is smaller than half of the total number of the sequence numbers that can be indicated by the PDCP SN) in transmitting the packet, the PDCP receiving apparatus receives the most recently received A sequence number (a received PDCP SN, see Specification 36.323) of one PDCP packet, a highest sequence number (Next_PDCP_RX_SN, see Specification 36.323), a window having a predetermined size (see Reordering_Window, Specification 36.323) (Last_Submitted_PDCP_RX_SN, refer to Specification 36.323) among the serial numbers transmitted to the upper layer up to the last HFN. If a packet having a higher sequence number than the received packet has already been delivered to the upper layer (i.e., the received packet has already been received or is a delayed received packet), header decompression is performed on the received packet Perform and discard. More specifically, when a packet is received redundantly or received in a delayed manner for reasons that can not be specified, the packet may contain useful information for updating the header decompression context, so that header decompression is performed and then discarded. The process of determining the HFN is as described in Section 5.1.2.1.2 of 36.323.

The processing of the PDCP PDU with the HFN and the COUNT determined as the PDCP SDU means that the PDCP PDU is reversed and the header of the IP packet stored in the PDCP PDU is restored and the details are described in the standard 36.323.

For convenience of explanation, COUNT corresponding to Last_Submitted_PDCP_RX_SN is referred to as Last_Submitted_PDCP_RX_COUNT, COUNT corresponding to the received PDCP SN is referred to as received PDCP COUNT, and COUNT corresponding to Next_PDCP_RX_SN is designated as Next_PDCP_RX_COUNT. Last_Submitted_PDCP_RX_COUNT is the highest COUNT (or highest ordered COUNT) delivered to the upper layer, received PDCP COUNT is the COUNT of the PDCP packet received, and Next_PDCP_RX_COUNT is the sum of the highest COUNT I suppose.

The upper layer transfer condition 1 of PDCP operation 1 is as follows.

[Upper layer transmission condition 1 of PDCP operation 1]

When the processing for any PDCP SDU [X] is completed in the PDCP operation 1, the UE extracts PDCP SDUs stored in the buffer from 'SDUs having COUNT lower than X' and ' SDUs of COUNT lower than COUNT 'satisfy Condition 1 and transmit them to the upper layer. For example, when PDCP SDU [100] is received, PDCP SDU [90] to PDCP SDU [99], PDCP SDU [101] to PDCP SDU [110], PDCP [112] PDCP SDU [100] which is the first non-received PDCP SDU among PDCP SDUs having a COUNT higher than PDCP SDU [100] and PDCP SDU [100] which are PDCP SDUs [90] PDCP SDU [101] to PDCP SDU [110] which are PDCP SDUs before SDU [111] satisfy condition 1 and are transferred to the upper layer and PDCP SDU [112] to PDCP SDU [115] . In the PDCP operation 1 triggered by receiving an arbitrary PDCP PDU, the received PDCP SDU is unconditionally transferred to the upper layer, and PDCP SDUs satisfying the condition 1 are also transmitted to the upper layer.

The upper layer transfer condition 2 of PDCP operation 2 is as follows.

[Upper layer transfer condition 2 of PDCP operation 2]

In the PDCP operation 2 triggered by receiving an arbitrary PDCP PDU, if the received PDCP SDU is an unreceived PDCP SDU having the lowest COUNT (i.e., Received PDCP COUNT is equal to Last_Submitted_PDCP_RX_COUNT plus 1) And delivers the next missing PDCP SDUs to the upper layer. If the received PDCP SDU is not the received PDCP SDU having the lowest COUNT, the PDCP SDU is stored in the PDCP buffer. In the PDCP operation 3 triggered by receiving any PDCP PDU, it is checked whether there are any SDUs satisfying condition 3 among the PDCP SDUs stored in the PDCP buffer including the processed PDCP SDU, and only SDUs satisfying the condition 3 .

The PDCP operation 3 and the upper layer transfer condition 3 will be described below.

[Upper layer transmission condition 3 of PDCP operation 3]

9, in a single bearer 905 in which one logical channel is set, the PDCP transmitting apparatus 910 transmits an RLC (RLC) message in the order of packet [1], packet [2], packet [ And transmits the packet to the transmitting apparatus 915. The packets are received by the RLC receiving device 920 via the MAC device and the wireless channel. At this time, if an error occurs in the radio channel, retransmission / error recovery is performed through HARQ and ARQ. In this case, the order of the packets received by the RLC receiving apparatus 920 is the order of the packets transmitted by the PDCP transmitting apparatus 915 ≪ / RTI > The RLC receiver 920 rearranges the above-described shift order and delivers it to the PDCP receiver 925. For example, the RLC receiving apparatus 920 delivers a packet to the PDCP receiving apparatus 925 in the order of packet [1], packet [2], packet [3], and packet [4].

In the case of a multi-bearer 930 with two logical channels, the PDCP transmitter 935 forwards the packet to the two RLC transmitters 940 and 845. For example, the PDCP transmitting apparatus 935 transmits packets [1] and [3] to the first RLC transmitting apparatus 940 and transmits packets [2] and [4] to the second RLC transmitting apparatus 945 do. The first RLC transmitting device 940 transmits the packet to the first RLC receiving device 950 and the second RLC transmitting device 945 transmits the packet to the second RLC receiving device 955. [ The first RLC receiving device 950 rearranges the order of the received packets in the order that the first RLC transmitting device 940 receives the packet from the PDCP transmitting device 935. That is, the first RLC receiving device 950 delivers the packets to the PDCP receiving device 960 in the order of packet [1] and packet [3]. Likewise, the second RLC receiver 955 rearranges the order of the packets received by the second RLC transmitter 945 in the order of receipt of the packet from the PDCP transmitter 935. That is, the second RLC transmitting apparatus 945 delivers the packets to the PDCP receiving apparatus 960 in the order of packet [2] and packet [4]. However, the order of the packets transmitted by the first RLC receiving device 950 and the second RLC receiving device 955 is not aligned. For example, the packets transmitted by the first RLC receiving device 950 and the second RLC receiving device 955 may be transmitted in the order of packet [1], packet [2], packet [4], packet [3] The packet [2], the packet [4], the packet [1], and the packet [3]. Therefore, the PDCP receiving apparatus 960 needs to rearrange the order of the packets transmitted by the two or more RLC receiving apparatuses 950 and 855 once again.

In the embodiment of the present invention, it is determined whether the order reordering of any non-received PDCP SDU [x] is satisfied or not. Condition 3 can be summarized as follows.

[Order reordering condition of arbitrary PDCP SDU [x] 3]

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

The timer 1 is driven when a PDCP SDU of COUNT higher than x is received from the RLC SCG and is for coping with out-of-sequence reception between MeNB and SeNB.

The fact that the order of any non-received PDCP SDU [x] is rearranged in the following description means that the SDU [x] is assumed to be received as it is received and performs subsequent operation since there is no possibility of receiving the missing SDU [x] . If the order of the missing SDU [x] is rearranged, the PDU of the receiving PDUs having a COUNT higher than x is transmitted to the upper layer with COUNT between [x + 1] and y, and the Last_Submitted_PDCP_RX_COUNT is updated with y. Y is a value obtained by subtracting 1 from the COUNT of the first non-received PDCP SDU higher than x. For example, Table 2 below shows the order reordering and related operations in the PDCP receiving apparatus.

MCG RLC SCG RLC Last_submitted_PDCP_RX_COUNT T1 timer PDCP operation t ₀ 10 t ₁ 11 11 11 to upper layer t ₂ 13 11 [13] is stored in the buffer; [12] does not receive SDU t ₃ 15 11 [15] related to T1 timer driving [13], [15] Save to buffer t ₄ 14 11 [13], [14], [15] Save to buffer t ₅ 15 T1 timer expired [12] is considered to be no longer received. The first non-received COUNT higher than 12 is 16, so SDUs between 12 and 16 are passed to upper layer

For example, when an SDU [11] is received from the MCG RLC at an arbitrary time t1, the SDU is transmitted to the upper layer because the SDU is ordered SDU, and the related variable is updated to 11.

Upon receiving SDU [13] from the MCG RLC at an arbitrary time t2, an unreceived RLC SDU [12] is generated, and the terminal stores SDU [13] in the PDCP buffer.

And then receives SDU [15] from the SCG RLC at an arbitrary time t3. Since the COUNT of the SDU received from the SCG RLC is higher than the COUNT not received, the terminal drives the T1 timer. If an unreceived PDU is not received before the T1 timer expires, the unreceived PDU is not received at least by the SCG RLC.

After that, SDU [14] is received from the SCG RLC at an arbitrary time t4 and thereafter the T1 timer associated with the SDU [15] (or associated with SDU [12]) expires at an arbitrary time t5. Since the COUNT higher than the unreceived COUNT has been received from both the MCG RLC and the SCG RLC and the associated T1 timer has expired, the UE receives the PDCP SDU [13], which is the SDUs of the COUNT of the next unreceived SDU, 14] and [15] to the upper layer and updates Last_submitted_PDCP_RX_COUNT to 15.

When it is found that any PDCP SDU is not received as described above, the timer 1 is the first one among the COUNT higher than the 'Not Received COUNT' and the COUNT higher than the 'Lowest COUNT received from the SCG RLC' or 'Not Received COUNT'Quot; received " or " not received COUNT ". In the above example, the serial number of the missing SDU is 12, and the first COUNT received from the SCG RLC among the COUNTs higher than 12 is 15, so that the timer 1 is the timer 1 related to 12 or 15. The size of the timer 1 is large enough to cope with a sequence of possible occurrences between the MeNB and the SeNB, that is, a packet transmitted by the MeNB at an arbitrary point in time at the SeNB arrives at the SeNB before the packet transmitted immediately before the packet , The size of the timer 1 is determined so as to correspond to the maximum possible value of the difference in the reception timing of two packets in which the sequence intermixing occurs.

FIG. 10 is a view for explaining the operation of a PDCP receiving apparatus in an LTE system according to an embodiment of the present invention, when a PDCP receiving apparatus of a multi-bearer receives a PDCP PDU from an RLC receiving apparatus.

Referring to FIG. 10, in step 1005, the PDCP receiving apparatus receives PDCP PDU [x] from the RLC receiving apparatus. In step 1010, the terminal despreads the PDCP PDU [x] and reconstructs (or converts or restores) the header of the IP packet stored in the PDCP PDU [x] into PDCP SDU [x]. If the PDCP SDU [x] is redundantly received, it is discarded and waits until the next PDU is received. If the PDCP SDU [x] is not duplicated, the UE proceeds to step 1015 and stores the PDCP SDU [x] in the PDCP buffer according to the COUNT sequence. In step 1020, it is determined whether the PDCP SDU [x] is received from the SCG RLC apparatus. If so, the procedure proceeds to step 1020; In step 1025, the UE determines whether there is an unreceived SDU having a sequence number lower than the SDU [x] and the SDU [x] is the SDU first received from the SCG RLC device after the unreceived SDU is generated If the condition is satisfied, the process proceeds to step 1030. Otherwise, the process proceeds to step 1035. In step 1030, the timer 1 is driven and the timer is associated with a value associated with a COUNT associated with the missing SDU, for example, a received COUNT, an unreceived COUNT, or a received COUNT.

In step 1035, the PDCP receiving apparatus checks whether there is an ordered SDU among the SDUs stored in the PDCP buffer. For example, if the SDU [x] is an unreceived SDU, the above condition can be satisfied. In step 1040, the SDUs arranged in the order are transmitted to the upper layer. Ordered SDUs may refer to SDUs between the highest COUNT delivered to the upper layer or the highest COUNT ordered and the lowest COUNT received, before receiving SDU [x]. have. In step 1040, the PDCP receiving apparatus sequentially transmits the SDUs arranged in order to the upper layer.

In steps 1045 and 1050, the UE determines SDUs that are not likely to be received among the SDUs that are not received yet, and transmits SDUs whose order is sorted among the SDUs that are not likely to be received to the upper layer It is judged whether condition 3 is established. First, the UE checks whether there is an unreceived SDU having the highest COUNT received from the SCG RLC and the lowest COUNT received from the MCG RLC among the unreceived SDUs. For example, if the COUNT of the missing SDU is 10 and the highest COUNT received from the MCG RLC is A, and the highest COUNT received from the SCG RLC is B, then the condition is true if both A and B are higher than 10, The condition is not established. If the condition is satisfied, step 1050 is performed. If the condition is not satisfied, step 1060 is performed. For the sake of convenience in the following description, the not-received COUNT satisfying the above condition is referred to as Y.

In step 1050, the UE checks whether Timer 1 associated with the Not Received SDU or associated with Y has already expired, and if so, proceeds to Step 1055, otherwise proceeds to Step 1060. In step 1055, the terminal forwards predetermined SDUs to an upper layer, and then proceeds to step 1060. The predetermined SDU is the SDU between '[Y + 1'] and the lowest COUNT of the non-received COUNTs higher than 'Y'. SDU [12], SDU [13], and SDU [14] are transferred to the upper layer, and the rest are stored in the PDCP buffer if Y is 10 and the unreceived COUNTs higher than 10 are 15, 20, I will. At least SDUs [14] are considered to be ordered. In step 1060, the UE waits until the next PDU is received or Timer 1 expires.

11 is a diagram for explaining an operation when the timer 1 expires in the PDCP receiving apparatus of FIG.

Referring to FIG. 11, Timer 1 associated with any missing PDCP SDU [z] expires in step 1105. The MS considers that the PDCP SDU [z] at this time is lost due to the sequence of intermixing between MeNB and SeNB. That is, if a COUNT higher than z is received from the MCG RLC, the SDU [z] performs subsequent operations as if it were received.

In step 1110, the UE checks whether the highest COUNT received from the SCG RLC and the highest COUNT received from the MCG RLC are higher than z. Timer 1 associated with an unreceived SDU z starts when a PDCP SDU of COUNT higher than z is received from the SCG RLC, so that in step 1110, the highest COUNT received by the MCG RLC may be checked to be higher than z. If the condition is satisfied in step 1110, it is determined that there is no possibility that the unreceived SDU [z] is no longer received, and the next unreceived SDU of COUNT higher than z among the SDUs having COUNT higher than z is transmitted to the upper layer, It is regarded that the order is aligned until the highest COUNT among the SDUs transmitted to the upper layer. In step < RTI ID = 0.0 > 1120, < / RTI > the UE waits until the next PDU is received or timer 1 associated with another missing SDU expires.

In the present invention, the PDCP receiving PDCP PDU from the MCG RLC is equivalent to receiving the reconfigured PDCP PDU from the MCG serving cell or from the data received from the MCG-MAC. The PDCP receiving PDCP PDU from the SCG RLC has the same meaning as receiving the reconstructed PDCP PDU from the SCG serving cell or from the data received from the SCG-MAC.

Another operation for rearranging the order of the PDCP PDUs according to the embodiment of the present invention is that when a single bearer to a multiple bearer is reconfigured to perform timer-based reordering while a multi-bearer is reconfigured to a single bearer, And a method of using the same timer as the two timers for performing the order reordering and for determining the stopping time.

20 is a diagram illustrating a terminal operation when a bearer is reset according to an embodiment of the present invention.

Referring to FIG. 20, in step 2005, a UE applies PDCP operation 1 to bearer x, which is a single bearer. In step 2010, a control message for resetting the bearer x to a multi-bearer is received. In step 2015, the UE generates an SCG (Secondary Cell Group) RLC apparatus to be connected to the multi bearer according to the setup information indicated in the control message, and then connects to the PDCP apparatus. The MS proceeds to step 2020 and switches the operation of the PDCP apparatus from the operation 1 to the operation 4. [ In other words, after the UE resets to the multi-bearer, it checks whether to reorder the PDCP PDUs from the first PDCP PDU received, and then applies the PDCP operation 4 to determine whether the PDCP PDUs are forwarded to the upper layer. After that, the UE converts the PDCP PDUs into PDCP SDUs by applying the PDCP operation 4 to the PDCP PDUs of the re-established bearer, and delivers the PDCP SDUs of the order to the upper layer. In determining the order, the terminal uses a timer 3.

In step 2025, upon receiving a control message instructing to reset the multi bearer to a single bearer, the UE proceeds to step 2030, releases the SCG RLC, switches PDCP operation 4 to PDCP operation 5, and drives timer 3. The UE performs the PDCP operation 5 while the timer 3 is driven and stops the PDCP operation 5 and switches to the PDCP operation 1 when the timer 3 expires in step 2035. [

It is understood that the PDCP operation 1, the operation 4, and the operation 5 are performed in a sequence of various operations to be applied to the PDCP PDU delivered from the RLC entity. Table 3 below lists the detailed operations that make up these operations and their order. The following detailed operations are performed in the order from top to bottom.

PDCP operation 1 PDCP operation 4 PDCP operation 5 PDCP PDU reception PDCP PDU reception PDCP PDU reception Determines the HFN / COUNT of the PDCP PDU. Discard duplicated PDUs Determines the HFN / COUNT of the PDCP PDU. Discard duplicated PDUs Determines the HFN / COUNT of the PDCP PDU. Discard duplicated PDUs PDCP PDU to PDCP SDU PDCP PDU to PDCP SDU PDCP PDU to PDCP SDU And delivers PDCP SDUs that satisfy the PDCP SDU and upper layer delivery condition 1 to the upper layer. Store the rest in a buffer Transmits PDCP SDUs satisfying the upper layer transmission condition 4 to the upper layer. The remaining SDUs are stored in the PDCP buffer Store the PDCP SDU in the PDCP buffer. Transmits PDCP SDUs satisfying the upper layer transmission condition 5 to the upper layer. The remaining SDUs are stored in the PDCP buffer.

[Upper layer delivery condition 5 of PDCP operation 5]

In the PDCP operation 5 applied while the timer 3 is driven, if the serial number of the received PDCP SDU is an unreceived PDCP SDU having the lowest serial number / COUNT (i.e., the Received PDCP SN is equal to 1 added to Last_Submitted_PDCP_RX_SN) SDUs of consecutive serial numbers / COUNT up to the next unreceived PDCP SDU, including the SDU, to the upper layer. If the received PDCP SDU is not an unsuccessful PDCP SDU having the lowest sequence number, the PDCP SDU is stored in the PDCP buffer. When Timer 3 expires, all PDCP SDUs stored in the current PDCP buffer are delivered to the upper layer in COUNT order, and the serial number of the last transmitted PDCP SDU is stored in Last_Submitted_PDCP_RX_SN.

For ease of explanation, the serial numbers below are used in combination with COUNT.

[Upper layer transfer condition 4 of PDCP operation 4]

If the serial number of the received PDCP SDU is an unreceived PDCP SDU of the lowest sequence number (i.e., if the Received PDCP SN is equal to 1 added to Last_Submitted_PDCP_RX_SN), the successive received SDUs up to the next non-received PDCP SDU including the received PDCP SDU To the upper layer. If the received PDCP SDU is not an unsuccessful PDCP SDU having the lowest sequence number, the PDCP SDU is stored in the PDCP buffer. If timer 3 is in operation, it waits until the next PDCP PDU is received. If timer 3 is not in operation, it drives timer 3 and stores COUNT in Reordering_PDCP_RX_COUNT which is one higher than the highest COUNT of PDCP SDUs received at that time. When Timer 3 expires, PDCP SDUs with COUNT lower than Reordering_PDCP_RX_COUNT and PDCP SDUs associated with consecutive COUNT higher than Reordering_PDCP_RX_COUNT are delivered to the upper layer. For example, if PDCP SDUs with Reordering_PDCP_RX_COUNT of N and COUNT of N + M are not received and all PDCP SDUs between N and [N + M] are stored in the PDCP buffer, when timer 3 expires, All PDCP SDUs of COUNT lower than N among the stored SDUs and all PDCP SDUs of COUNT including N and [N + M-1] are transmitted to the upper layer. Then, the serial number of the last transmitted PDCP SDU is stored in Last_Submitted_PDCP_RX_SN.

21 is a diagram illustrating an operation of a PDCP receiving apparatus operating as a multi-bearer according to an embodiment of the present invention. This shows the operation of the PDCP receiving apparatus that has received the packet from the RLC receiving apparatus.

Referring to FIG. 21, in step 2105, the PDCP receiving apparatus receives PDCP PDU [x] from the RLC receiving apparatus. In step 2110, the PDCP receiving apparatus determines the HFN (Hyper Frame Number) of the received packet by using the received packet's serial number (Received PDCP SN), Next_PDCP_RX_SN, Reordering_Window, Last_Submitted_PDCP_RX_SN, The PDCP receiving apparatus concatenates the determined HFN with the Received PDCP SN to calculate a COUNT associated with the PDCP packet. Then, the COUNT is applied to the PDCP PDU [x], and the header of the IP packet stored in the PDCP PDU [x] is restored and reconstructed (or converted or restored) into the PDCP SDU [x]. If the PDCP SDU [x] is redundantly received, it is discarded and waits until the next PDU is received. If the PDCP SDU [x] is not duplicated, the UE proceeds to step 2115 and stores the PDCP SDU [x] in the PDCP buffer according to the COUNT order.

In step 2120, the PDCP receiving apparatus checks whether the received packet is a non-received packet having the lowest COUNT. If the following conditions are satisfied, the process proceeds to step 2130 where the lowest COUNT is not received. If the following condition is not satisfied, the process proceeds to step 2125 and waits until the next PDCP PDU is received.

[Condition for judging whether the received packet is the non-received packet having the lowest COUNT]

Received PDCP SN = Last_Submitted_PDCP_RX_SN + 1; or

received PDCP SN = Last_Submitted_PDCP_RX_SN - Maximum_PDCP_SN

In step 2130, the PDCP receiving apparatus transmits PDCP SDUs associated with consecutive COUNT starting from the COUNT of the received PDCP SDUs stored in the PDCP buffer to the upper layer in order of COUNT, and transmits Last_Submitted_PDCP_RX_SN last Set to the serial number of the PDCP SDU. For example, it is assumed that PDCP SDUs with COUNT of [M], [M + 1], [M + 2], [M + 4], and [M + 5] are stored in the PDCP buffer and COUNT is [ If the SDU is received, the PDCP receiving device delivers PDCP SDUs of COUNT [M-1], [M], [M + 1], and [M + 2] to the upper layer.

In step 2135, the PDCP receiving apparatus checks whether at least one PDCP SDU is still stored in the PDCP buffer in an unordered order after performing the above operation. If yes, proceed to step 2140, otherwise proceed to step 2125.

In step 2140, the PDCP receiving apparatus checks whether the timer 3 is being driven, and if so, proceeds to step 2125. Otherwise, it proceeds to step 2145.

In step 2145, the PDCP receiving apparatus drives timer 3 and sets Reordering_PDCP_RX_COUNT to a value obtained by concatenating RX_HFN and Next_PDCP_RX_SN. In other words, a value higher than the highest COUNT received so far by 1 is stored in Reordering_PDCP_RX_COUNT, and the PDCP receiving apparatus proceeds to step 2125.

22 is a diagram illustrating an operation of a PDCP receiving apparatus for switching to a PDCP operation 5 upon reestablishing an MCG bearer from a multi bearer according to an embodiment of the present invention.

A Master Cell Group (MCG) bearer is a bearer that transmits and receives data only through MCG among a single bearer. When the PDCP receiving apparatus that has performed the dual connectivity operation releases the SeNB and the SCG due to a reason such as leaving the area of the serving base station (SeNB), the multi bearer can be reset to the MCG bearer.

Referring to FIG. 22, in step 2205, the PDCP receiving apparatus receives a control message instructing to reset the multi bearer to the MCG bearer. The control message may be, for example, to explicitly reset the multi bearer to the MCG bearer, or may be a control message that is not an explicit reset command but releases the last SCG cell.

In step 2210, the PDCP receiving entity cancels the SCG-RLC of the multi-bearer, assembles all PDCP PDUs among the RLC packets stored in the RLC into PDCP PDUs, and transmits the assembled PDCP PDUs to the PDCP receiving device.

In step 2215, the PDCP receiving apparatus checks whether the current timer 3 is being driven. Step 2215 may be performed as soon as the analysis of the control message indicating the MCG bearer switching is completed, or may be performed when the PDCP PDU is received from the released SCG-RLC.

If the timer 3 is not in operation, the process proceeds to step 2225. If the timer 3 is already in operation, In step 2220, various operations are possible. The PDCP receiving apparatus performs one of the following operations 1) to 3).

1) Stop current timer 3, restart timer 3, and proceed to 2230

2) Wait for Timer 3 currently running to expire, then restart Timer 3 and proceed to 2230

3) If a PDCP PDU is received from the released SCG-RLC, stop timer 3 currently being driven, restart timer 3, and proceed to 2230. If the PDCP PDU is not received from the released SCG-RLC, the currently active timer 3 is maintained as it is and the process proceeds to step 2230. However,

In step 2225, various operations are possible. The PDCP receiving apparatus performs one of the following operations a) and b).

a) Run timer 3 and proceed to 2230

b) If a PDCP PDU is received from the released SCG-RLC, then timer 3 is driven and proceed to 2230. If the PDCP PDU is not received from the released SCG-RLC, the UE does not proceed to step 2230 and immediately switches to the PDCP operation 1

In step 2230, the PDCP receiving apparatus waits until the timer 3 expires. When the timer 3 expires, the PDCP receiving apparatus transmits all the PDCP SDUs stored in the current PDCP buffer to the upper layer in the COUNT order, Set Last_Submitted_PDCP_RX_SN as the number. Switch to PDCP operation 1.

23 is a diagram illustrating an operation of the PDCP receiving apparatus when the timer 3 expires according to the embodiment of the present invention.

Referring to FIG. 23, in step 2305, the timer 3 of the PDCP receiving apparatus of any bearer expires.

In step 2310, the PDCP receiving apparatus checks whether the bearer is a multi-bearer or an MCG bearer. If it is a multi-bearer, the process proceeds to step 2315, and if it is an MCG bearer, the process proceeds to step 2320. [ Step 2320 means that the bearer is reconfigured as an MCG bearer in the multi bearer. Since Timer 3 has expired, all PDCP SDUs stored in the current PDCP buffer are retransmitted to the upper layer .

Proceeding to step 2315 means that the PDCP operation unit 4 is operating as PDCP operation 4. The PDCP receiving apparatus sequentially transmits Reordering_PDCP_RX_COUNT to all PDCP SDUs of COUNT lower than Reordering_PDCP_RX_COUNT based on Reordering_PDCP_RX_COUNT among the PDCP SDUs stored in the PDCP buffer, And transmits PDCP SDUs associated with COUNT to the upper layer. In other words, the PDCP SDUs corresponding to the conditions shown in Table 4 are transmitted to the upper layer.

- all stored PDCP SDUs (s) with an associated COUNT value less than Reordering_PDCP_RX_COUNT;
- all stored PDCP SDU (s) with consecutively associated COUNT value (s) starting from Reordeing_PDCP_RX_COUNT;

In step 2325, the PDCP receiving apparatus updates Last_Submitted_PDCP_RX_SN and proceeds to step 2330. [ In step 2330, the PDCP receiving apparatus checks whether there is at least one PDCP SDU remaining in the PDCP buffer. If the PDCP receiving apparatus has left at least one PDCP SDU, step 2335 is performed. Otherwise, step 2340 is performed.

In step 2335, the PDCP receiving apparatus drives timer 3 and sets Reordering_PDCP_RX_COUNT to a value obtained by concatenating RX_HFN and Next_PDCP_RX_SN.

And waits until the next PDCP PDU arrives in step 2340. [

As shown in the above embodiment, the PDCP receiving apparatus uses a variable managed by the PDCP SDU serial number in determining whether the received PDCP SDU is an unreceived SDU, determines a PDCP SDU to be transmitted to the upper layer after the expiration of the timer 3 We use variables managed by COUNT.

In another operation of rearranging the order of PDCP PDUs according to the embodiment of the present invention, when the bearer configuration is reconfigured from a single bearer to a multiple bearer, the timer is reordered based on the timer. A method of using the amount of data stored in the order reordering buffer and re-establishment of a lower layer is used for determining the point of time when the sequence reordering operation is stopped.

24 is a diagram illustrating a terminal operation when a bearer is reset according to an embodiment of the present invention.

Referring to FIG. 24, in step 2405, the UE applies the PDCP operation 6 to bearer x, which is a single bearer. In step 2410, a control message for resetting the bearer x to the multi-bearer is received. In step 2415, the UE generates an SCG (Secondary Cell Group) RLC apparatus to be connected to the multi bearer according to the setup information indicated in the control message, and then connects to the PDCP apparatus. The MS proceeds to step 2420 and switches the operation of the PDCP apparatus from the operation 6 to the operation 7. [ Operation 6 will be described later. In other words, the UE applies the PDCP operation 7 in order from the first received PDCP PDU after being reset to the multi-bearer, and the operation 7 will be described later. After that, the UE checks whether the PDCP PDUs received by applying the PDCP operation 7 to the PDCP PDUs of the bearer resumed to the multi bearer are reordered, converts the ordered PDCP PDUs into PDCP SDUs, . In determining the order, the terminal uses a timer 3.

In step 2425, when the UE receives a control message instructing to re-establish the multi bearer to a single bearer, the UE proceeds to step 2430 and releases the SCG RLC. PDCP PDUs whose order has not been aligned due to the SCG RLC release are delivered to the PDCP device, and the PDCP device continues to apply the operation 7 to the PDCP PDUs. If the sequence reordering suspension condition is satisfied, the operation proceeds to step 2435. In step 2435, the sequence reordering suspension condition is determined as " lower order reordering " . If it is determined that there is an unordered packet in the sequence, the process proceeds to step 2440 to switch to the PDCP device operation 6 and ends the process. If the lower layer is re-established, the process proceeds to step 2445. The lower layer is an MCG-RLC device. Or since the UE has already switched to a single bearer, the PDCP apparatus is connected to only one RLC apparatus, and the only RLC apparatus is re-established. In step 2445, the UE aligns the PDCP PDUs stored in the current reordering buffer and the PDCP PDUs delivered in the lower layer reordering in the order of COUNT, processes the PDCP PDUs in the order of COUNT into PDCP SDUs, And ends the post-process. At this time, the PDCP apparatus processes the PDCP PDUs stored in the order reordering buffer as if they are PDCP PDUs transferred due to re-establishment of the lower layer.

It is understood that the PDCP operation 6 and the operation 7 are performed in a sequence of various operations to be applied to the PDCP PDU delivered from the RLC entity. Table 5 below lists the detailed operations that make up these operations and their order. The following detailed operations are performed in the order from top to bottom.

PDCP operation 6 PDCP operation 7 PDCP PDU reception PDCP PDU reception Determines the HFN / COUNT of the PDCP PDU. Process duplicated PDUs as PDCP SDUs and discard Determines the HFN / COUNT of the PDCP PDU. PDCP PDU to PDCP SDU Process PDCP PDUs satisfying upper layer transfer condition 7 as PDCP SDUs and transfer them to upper layer. The remaining PDUs are stored in PDCP buffer And delivers PDCP SDUs that satisfy the PDCP SDU and upper layer delivery condition 1 to the upper layer. Store the rest in a buffer

In the PDCP operation 6, it is judged whether or not the reception is performed redundantly. However, in the PDCP operation 7, the reception is not checked. This is because, if the PDCP operation 6 is applied, there is a possibility that duplicate packets already received after the handover are received, but there is no such possibility in the PDCP operation 7. Duplicate received PDUs are processed by the SDU prior to discarding, in order to update the header recovery context. In the situation where PDCP operation 7 is applied, it is not necessary to perform an operation of determining a duplicated received packet, disposing it in the SDU, and discarding it.

In the PDCP operation 6, the received PDUs are once processed as SDUs, the unordered SDUs are stored in the buffer, and the ordered SDUs are transferred to the upper layer. In the PDCP operation 7, First, SDUs are processed only when PDUs whose order is aligned, and PDUs whose order is not sorted are stored in the buffer in the PDU state.

If the PDCP operation 6 is applied, if the packet [X] is received, the packet with the serial number lower than the packet [X] is no longer received. However, if the PDCP operation 7 is applied, since the packets whose order is not aligned can be received at any time, it is necessary to process the SDUs after arranging the order once.

The upper layer delivery condition 7 of the PDCP operation 7 is for the PDCP PDU instead of the PDCP SDU, and the upper layer delivery condition 4 and the upper layer delivery condition 5 are the same except that the packet satisfying the condition is transmitted to the PDCP PDU processing apparatus, same.

[Upper layer transfer condition 7 of PDCP operation 7]

If the sequence number of the received PDCP PDU is an unreceived PDCP PDU of the lowest sequence number (that is, if the Received PDCP SN is equal to 1 added to Last_Submitted_PDCP_RX_SN), the consecutively received PDUs including the received PDCP PDU including the received PDCP PDU To a processing device (for example, a header decompressing device, an inverting device). The de-interleaver means a device for dechiping the received PDCP PDU. The PDUs are processed by the processing unit into an SDU and then transferred to an upper layer. If the received PDCP PDU is not an unsuccessful PDCP PDU of the lowest sequence number, the PDCP PDU is stored in the PDCP buffer. If timer 3 is in operation, it waits until the next PDCP PDU is received. If timer 3 is not in operation, it drives timer 3 and stores COUNT in Reordering_PDCP_RX_COUNT, which is one higher than the highest COUNT of PDCP PDUs received at that time. When Timer 3 expires, PDCP PDUs with COUNT lower than Reordering_PDCP_RX_COUNT and PDCP PDUs associated with consecutive COUNT higher than Reordering_PDCP_RX_COUNT are delivered to the processing unit. Then, the serial number of the last transmitted PDCP SDU is stored in Last_Submitted_PDCP_RX_SN.

When the multi-bearer is re-established to a single bearer, the PDCP operation should be switched from operation 7 to operation 6. [ In the embodiment of the present invention, the PDCP apparatus continues to apply the PDCP operation 7 until the order reordering suspension condition is satisfied after the UE is reset to the single bearer, but switches to the PDCP operation 6 when the order reordering suspension condition is satisfied. The order reordering condition is met if the lower layer reestablishment or the PDU to reorder is no longer present.

The lower layer re-establishment may occur, for example, when a terminal operating as a single bearer is instructed to perform a handover. In this case, all PDCP PDUs whose order has not been sorted stored in the MCG-RLC apparatus are transferred to the PDCP receiving apparatus, and the UE transmits PDCP PDUs of unordered order stored in the current PDCP buffer and PDCP PDUs PDCP PDUs are sequentially processed into PDCP SDUs according to the COUNT order, and then the SDUs in order are transferred to the upper layer, the unordered SDUs are stored in the buffer, and the PDUs received in the newly set lower layer To the PDCP apparatus operation 6 for judging the SDUs to be transferred to the upper layer based on the serial number.

The fact that the PDU to be reordered no longer exists means that as a result of the reordering operation using the timer 3, the timer 3 associated with the non-received PDUs expires and the PDUs regarded as unordered by the non-received PDUs SDUs, and then transmitted to the upper layer, it may be the case that no more PDUs are not received yet. For example, if the value obtained by adding 1 to Last_Submitted_PDCP_RX_SN is equal to Next_PDCP_RX_SN, it means that there are no more unreceived PDUs, or there are no more unordered PDUs. The fact that the above condition is satisfied means that no more PDUs are stored in the PDCP buffer, so the PDCP receiving apparatus immediately switches to the PDCP apparatus operation 6 immediately.

The PDCP operation 7 is the same as the PDCP operation 4 shown in FIG. 25 except for the following matters, and a detailed description thereof will be omitted.

25 is a diagram illustrating a PDCP operation 7 of a PDCP receiving apparatus operating as a multi-bearer according to an embodiment of the present invention. The embodiment of FIG. 25 shows the operation of a PDCP receiving apparatus that has received a packet from an RLC receiving apparatus. Referring to FIG. 25, in step 2505, the PDCP receiving apparatus receives PDCP PDU [x] from the RLC receiving apparatus. In step 2510, the PDCP receiving apparatus determines the HFN (Hyper Frame Number) of the received packet using the received packet's serial number (Received PDCP SN), Next_PDCP_RX_SN, Reordering_Window, Last_Submitted_PDCP_RX_SN, The PDCP receiving apparatus concatenates the determined HFN with the Received PDCP SN to calculate a COUNT associated with the PDCP packet. And checks whether the packet received by applying the COUNT is an unreceived packet having the lowest COUNT.

In step 2520, if the following conditions are satisfied, the PDCP receiving apparatus proceeds to step 2530. In step 2525, the PDCP receiving apparatus waits until the next PDCP PDU is received.

[Condition for judging whether the received packet is the non-received packet having the lowest COUNT]

Received PDCP SN = Last_Submitted_PDCP_RX_SN + 1; or

received PDCP SN = Last_Submitted_PDCP_RX_SN - Maximum_PDCP_SN

In step 2530, the PDCP receiving apparatus processes the PDCP PDUs associated with consecutive COUNT starting from the COUNT of the received PDCP PDU among the PDCP PDUs stored in the PDCP buffer into the PDCP SDU in the order of COUNT, , Last_Submitted_PDCP_RX_SN is set to the serial number of the PDCP SDU last transmitted. For example, in the PDCP buffer, PDCP PDUs whose COUNT is [M], [M + 1], [M + 2], [M + 4], and [M + 5] are stored and COUNT is [ The PDCP receiving apparatus transmits the PDCP PDUs of COUNT [M-1], [M], [M + 1], and [M + 2] to the next processing apparatus, converts the PDCP PDUs into PDCP SDUs, . In step 2535, the PDCP receiving apparatus checks whether at least one PDCP PDU is still stored in the PDCP buffer in an unordered state after performing the above operation. If so, proceed to step 2540; otherwise, proceed to step 2525.

In step 2540, the PDCP receiving apparatus checks whether the timer 3 is being driven, and if so, proceeds to step 2525, otherwise proceeds to step 2545. In step 2545, the PDCP receiving apparatus drives timer 3 and sets Reordering_PDCP_RX_COUNT to a value obtained by concatenating RX_HFN and Next_PDCP_RX_SN. In other words, the value of Reordering_PDCP_RX_COUNT is set to 1 higher than the highest COUNT received so far. The PDCP receiving apparatus proceeds to step 2525.

26 is a diagram illustrating an operation of the PDCP receiving apparatus when timer 3 expires according to an embodiment of the present invention.

Referring to FIG. 26, in step 2605, the timer 3 of the PDCP receiving apparatus of any bearer expires. In step 2615, the PDCP receiving apparatus sequentially transmits PDCP PDUs of COUNT lower than Reordering_PDCP_RX_COUNT and Reordering_PDCP_RX_COUNT to PDCP PDUs associated with consecutive COUNT, based on Reordering_PDCP_RX_COUNT, among the PDCP PDUs stored in the PDCP buffer, After processing with SDU, it transfers to upper layer. In other words, the PDCP PDUs corresponding to the conditions shown in Table 6 are processed as PDCP SDUs and then transmitted to the upper layer.

- all stored PDCP PDUs (s) with an associated COUNT value less than Reordering_PDCP_RX_COUNT;
- all stored PDCP PDUs (s) with consecutively associated COUNT value (s) starting from Reordeing_PDCP_RX_COUNT;

In step 2625, the PDCP receiving entity updates Last_Submitted_PDCP_RX_SN and proceeds to step 2630. [ In step 2630, the PDCP receiving apparatus checks whether there is at least one PDCP PDU remaining in the PDCP buffer, and proceeds to step 2635. If not, the PDCP receiving apparatus proceeds to step 2640. In step 2635, the PDCP receiving apparatus drives timer 3 and transmits RX_HFN and Next_PDCP_RX_SN And sets Reordering_PDCP_RX_COUNT to a value that is concatenated. And waits until the next PDCP PDU arrives in step 2640.

In another operation of rearranging the order of the PDCP PDUs according to the embodiment of the present invention, a method is proposed in which the bearer configuration is reconfigured from a single bearer to a multiple bearer to operate as a multiple bearer. In this embodiment, when the UE is re-established as a multi-bearer, the PDCP PDUs whose order is aligned among the received PDCP PDUs are processed as PDCP SDUs and transferred to the upper layer, and PDCP PDUs of unordered order are processed as half PDCP SDUs , And stores them in the buffer until the order is sorted. When the order of the PDCP PDUs stored in the buffer is aligned, the UE converts the half PDCP SDU into a PDCP SDU and transfers the PDCP SDU to the upper layer. The PDCP processing operation includes deciphering and header decompression. Upon completion of the above procedure, received PDCP PDUs become PDCP SDUs. Herein, the half PDCP SDU means a packet to which only a part of the PDCP processing operation is applied to the PDCP PDU, but the packet is not decoded but the header is not recovered.

Packets received from a multiple bearer are discarded and stored in the reordering buffer. If the SCG of the UE is changed, the discarding key may be changed. In this case, the PDCP PDUs that have not yet been re- The complexity of applying different security keys to the old PDCP PDU and the newly received PDCP PDU occurs.

28 is a diagram illustrating a terminal operation when a bearer is reset according to an embodiment of the present invention.

Referring to FIG. 28, in step 2805, the UE applies PDCP operation 6 to bearer x, which is a single bearer. In step 2810, the UE receives a control message for resetting the bearer x to the multi-bearer. In step 2815, the UE generates an SCG (Secondary Cell Group) RLC apparatus to be connected to the multi bearer according to the setup information indicated in the control message, and then connects to the PDCP apparatus. The MS proceeds to step 2820 and switches the operation of the PDCP apparatus from the operation 6 to the operation 8. [ In other words, the UE applies the PDCP operation 8 in order from the first received PDCP PDU after being reset to the multi-bearer.

Specifically, the UE applies the PDCP operation 8 to the PDCP PDUs of the bearer resumed to the multi bearer, processes the PDCP PDUs of the ordered PDCP PDUs, which have been sorted among the received PDCP PDUs, as the PDCP SDUs to the upper layer, PDCP PDUs are converted into the half PDCP SDUs and stored in the PDCP sequence reordering buffer, and timer 3 is started if necessary.

Thereafter, in step 2825, when the UE receives a control message instructing to reset the multi bearer to a single bearer, the UE proceeds to step 2830 and releases the SCG RLC. PDCP PDUs whose order is not aligned due to the SCG RLC release are delivered to the PDCP device, and the PDCP device continues to apply the operation 8 to the PDCP PDUs. The operation 8 is applied until the order reordering suspension condition is satisfied, and if the sequence reordering suspension condition is satisfied, the sequence proceeds to step 2835 and the sequence reordering suspension condition is referred to as 'lower layer reordering' . If it is determined in step 2835 that the sequence reordering discontinuance condition is due to an unsequenced unacknowledged packet, the UE proceeds to step 2840 to switch to the PDCP operation 6 and terminates the process. If it is determined in step 2835 that the order reordering suspension condition is a lower layer re-establishment, the UE proceeds to step 2845. The lower layer is, for example, an MCG-RLC device. Or since the UE has already switched to a single bearer, the PDCP apparatus is connected to only one RLC apparatus, and the only RLC apparatus may be the lower layer. In step 2845, the UE checks whether there is a PDCP PDU or a half PDCP SDU whose order is aligned by referring to the sequence number or COUNT of the PDCP PDUs transferred to the lower layer re-establishment and the half PDCP SDUs stored in the reordering buffer , If there is a PDCP PDU or a half PDCP SDU whose order is aligned, the necessary PDCP processing operation is applied and converted into a PDCP SDU, and the PDCP SDU is transferred to the upper layer according to the COUNT sequence. The unordered half PDCP SDUs and PDCP PDUs are converted into PDCP SDUs and stored in the PDCP sequence reordering buffer according to the COUNT sequence. At this time, the PDCP SDUs of unordered order may be stored in the PDCP sequence reordering buffer where the half PDCP SDUs were stored. In some cases, the half PDCP SDU and the PDCP SDU may be stored in the same storage space. In this case, the half PDCP SDU is stored for each half PDCP SDU, and the PDCP SDU is not stored for each PDCP SDU. And switches to PDCP operation 6.

In step 2845, a PDCP PDU or a half PDCP SDU having an ordered sequence is the same as a PDCP PDU or a half PDCP SDU having a sequence number higher than Last_Submitted_PDCP_RX_SN among the PDCP PDU or half PDCP SDUs.

It is understood that the PDCP operation 6 and the operation 8 are variously arranged in a sequence of various operations to be applied to the PDCP PDU delivered from the RLC entity. Table 7 below illustrates the detailed operations and the procedure of configuring the PDCP operation 6 and the operation 8. In Table 7 below, the detailed operations proceed from top to bottom.

PDCP operation 6 PDCP operation 8 PDCP PDU reception PDCP PDU reception Determines the HFN / COUNT of the PDCP PDU. Process duplicated PDUs as PDCP SDUs and discard Determines the HFN / COUNT of the PDCP PDU. Discard duplicated PDUs without processing them as PDCP SDUs PDCP PDU to PDCP SDU Process PDCP PDUs as half PDCP SDUs And delivers PDCP SDUs that satisfy the PDCP SDU and upper layer delivery condition 1 to the upper layer. Store the rest in a buffer Transfer the half PDCP SDU that satisfies the upper layer transfer condition 8 to the upper layer by processing the PDCP SDU to the upper layer. The remaining half PDCP SDUs are stored in the PDCP buffer

In the PDCP operation 6, the UE processes the received PDUs as SDUs once, stores the unordered SDUs in the buffer, and delivers the ordered SDUs to the upper layer. In the PDCP operation 8, (E.g., dechiping) of the PDCP SDU, and determines whether or not the PDCP SDUs are rearranged after being converted into the half PDCP SDUs. In addition, only the half-PDCP SDUs whose order is aligned are processed by the remaining PDCP processing (for example, header decompression) into PDCP SDUs and transferred to the upper layer, and half PDCP SDUs whose order is not aligned are placed in the half PDCP SDU state Buffer.

The upper layer forwarding condition 8 of the PDCP operation 8 is a half PDCP SDU instead of a PDCP SDU, and a packet satisfying the condition is not forwarded to the first PDCP processing device (deciphering device) Device), except that it is delivered to the higher layer delivery condition 7. In some cases, the PDCP receiving apparatus may store not only unordered half PDCP SDUs but also unordered PDCP SDUs. In this case, the PDCP receiving apparatus considers not only the half PDCP SDU but also the PDCP SDU in applying the upper layer transfer condition 8.

[Upper layer transfer condition 8 of PDCP operation 8]

If the sequence number of the received PDCP PDU is the serial number of the non-received PDCP PDU of the lowest sequence number (i.e., if the Received PDCP SN is equal to the Last_Submitted_PDCP_RX_SN plus 1), the terminal transmits the received PDCP PDU (or its corresponding half PDCP SDU) to the next PDCP processing unit (e.g., a header decompression unit) to the next unreceived PDCP PDU (or its corresponding half PDCP SDU). The half PDCP SDUs are processed by the next PDCP processing unit into a PDCP SDU and then transferred to an upper layer. If the received PDCP PDU is not a non-received PDCP PDU of the lowest sequence number, the PDCP PDU is processed as a half PDCP SDU and stored in the PDCP buffer. If the timer 3 is in operation, the UE waits until the next PDCP PDU is received. If the timer 3 is not in operation, the UE drives the timer 3 and stores COUNT in the Reordering_PDCP_RX_COUNT, which is one higher than the highest COUNT among the received PDCP PDUs do. When timer 3 expires, half PDCP SDUs of COUNT lower than Reordering_PDCP_RX_COUNT and half PDCP SDUs higher than Reordering_PDCP_RX_COUNT and associated with consecutive COUNT are delivered to the next PDCP processing device (e.g., a header decompressor). Then, the PDCP SDUs processed by the header decompressor are transferred to the upper layer, and the serial number of the last transmitted PDCP SDU is stored in Last_Submitted_PDCP_RX_SN.

If the multi-bearer is re-established to a single bearer, then the PDCP operation should be switched from operation 8 to operation 6. In the exemplary embodiment of the present invention, the PDCP processing apparatus continues to apply the PDCP operation 8 until the order reordering suspension condition is satisfied after the reordering to the single bearer, but switches to the PDCP operation 6 when the sequence reordering suspension condition is satisfied. The order reordering condition is met if the lower layer reestablishment or the PDU to reorder is no longer present.

The lower layer re-establishment may occur, for example, when a terminal operating as a single bearer is instructed to perform a handover. In this case, all the unordered PDCP PDUs stored in the MCG-RLC apparatus are transmitted to the PDCP receiving apparatus, and the UE stores the unordered half PDCP SDUs stored in the current PDCP buffer and the lower- The PDCP PDUs sequentially processed are processed as PDCP SDUs in accordance with the COUNT order, and then the SDUs in order are transferred to the upper layer, the unordered SDUs are stored in the buffer, and the PDUs received in the newly set lower layer To the PDCP apparatus operation 6 for judging the SDUs to be transferred to the upper layer based on the serial number of the PDCP apparatus.

On the other hand, the fact that the PDU to be reordered no longer exists means that as a result of the reordering operation using the timer 3, the timer 3 associated with the non-received PDUs has expired and the half PDCP SDUs are processed as SDUs and then transmitted to an upper layer, it may be the case that no more PDUs are not received yet. Or that there is no more PDU to be reordered may be the case where the PDCP PDU delivered in the lower layer is an unreceived PDCP PDU with the lowest sequence number. For example, after resetting from a multi bearer to a single bearer, if the serial number of the received PDCP PDU is equal to the sum of 1 in Last_Submitted_PDCP_RX_SN and Last_Submitted_PDCP_RX_SN is equal to Next_PDCP_RX_SN, then no more unreceived PDUs exist Means that there is no half PDCP SDU in the unordered order. The fact that the above-described conditions are satisfied means that no more half PDCP SDUs are stored in the PDCP buffer, and the PDCP receiving apparatus immediately switches to the PDCP apparatus operation 6 immediately.

In another embodiment of the present invention, a PDCP receiving apparatus proposes an operation of processing a PDCP PDU received from a lower layer.

In this embodiment, when a PDCP PDU is received from a lower layer, the PDCP receiving apparatus determines whether the PDU satisfies a predetermined " duplicate reception condition " and performs a predetermined action on the PDU satisfying the " Take it. At this time, the PDCP receiving apparatus performs different operations according to whether the PDCP receiving apparatus is connected to a single bearer or a multi-bearer.

&Quot; Duplicate reception condition " for any PDU is defined as shown in Table 8 below.

if received PDCP SN - Last_Submitted_PDCP_RX_SN> Reordering_Window or
0? Last_Submitted_PDCP_RX_SN - received PDCP SN <Reordering_Window:

The &quot; duplicate reception condition &quot; is not a determination of whether any PDCP PDU has been previously received, but rather whether the serial number of the received PDU is lower than Last_Submitted_PDCP_RX_SN (or a number allocated before Last_Submitted_PDCP_RX_SN, Whether or not the serial number is lower than the lowest serial number already transmitted to the upper layer.

The fact that the "duplicate reception condition" is satisfied with respect to any PDCP PDU is because it is very likely that the payload of the PDCP PDU has already been delivered to the upper layer, and therefore it is highly likely that unnecessary malfunction will occur when PDCP SDUs are transmitted to the upper layer it means. Therefore, in the present embodiment, the PDCP receiving apparatus discards PDCP PDUs satisfying the &quot; duplicate reception condition &quot; without delivering them to the upper layer.

If the PDCP PDU satisfying the duplicate reception condition is received from the single bearer, the UE processes the PDCP PDU in the PDCP SDU and updates the ROHC context (see RFC 3095) before discarding the PDCP PDU, Discard the SDU. On the other hand, if the PDCP PDU satisfying the duplicate reception condition is received from the multi-bearer, the UE discards the PDCP PDU immediately without processing it as an SDU. The reason for applying the differential operation as described above is as follows.

Even if a PDCP PDU received from a single bearer is a duplicated PDU, an important packet related to the ROHC may be included in the PDU. This phenomenon may occur when the ROHC is reset in a process such as a handover. Therefore, even if the PDCP PDU received from the single bearer is duplicated, the UE processes the PDCP SDU once and discards the PDCP SDU after updating the ROHC context.

In the multi-bearer operation, since the ROHC is not reset, there is no need to perform the operation of updating the ROHC context by processing the duplicated packets as described above. Accordingly, the UE discards the PDCP PDU as soon as it is determined that the PDCP PDU is duplicated.

27 is a diagram illustrating an operation of a PDCP receiving apparatus according to an embodiment of the present invention.

Referring to FIG. 27, in step 2705, the PDCP receiving apparatus receives a PDCP PDU from a lower layer. In step 2710, the PDCP receiving apparatus checks whether the SN of the PDCP PDU satisfies the &quot; overlapping reception condition &quot;, and if the overlapping reception condition is not satisfied, the PDCP receiving apparatus proceeds to step 2715; In step 2715, the PDCP receiving apparatus determines whether the received PDCP PDU is received from a multi-bearer or a single bearer. If the PDCP PDU is received from a multi-bearer, the PDCP receiving apparatus proceeds to step 2719. If the PDCP PDU is received from a single bearer, .

In step 2717, the UE processes the received PDCP PDUs and constructs PDCP SDUs without considering order reordering, and then transmits the PDCP SDUs to the upper layer. In step 2719, if the received PDCP PDUs are ordered, the UE processes the PDCP PDUs immediately, configures them into PDCP SDUs, and transfers the PDCP PDUs to an upper layer. If the PDCP PDUs are not in an ordered state, After completion, the PDCP SDU is processed and transmitted to the upper layer. That is, in step 2719, the UE processes only the PDCP PDUs with the reordering sequence in the PDCP SDUs and delivers the PDCP SDUs to the upper layer. The processing of the PDCP PDU into the PDCP SDU means that the PDCP PDU is converted into the PDCP SDU by performing operations such as reversing the PDCP PDU and restoring the header.

On the other hand, if it is determined in step 2710 that the PDCP PDU is a single bearer or a multiple bearer, the PDCP receiving apparatus proceeds to step 2725. If the PDCP PDU is a bearer, . In step 2725, the PDCP receiving apparatus processes the PDCP PDU as a PDCP SDU and discards the PDCP SDU. In step 2730, the PDCP receiving entity discards the PDCP PDU without processing the PDCP PDU as a PDCP SDU.

27, when a PDCP PDU, a half PDCP SDU, or a PDCP SDU having the same sequence number as that of the received PDCP PDU is already stored in the reception buffer of the PDCP in the operation of another terminal, It is possible to perform differential operations with respect to the bearer.

For example, if the PDCP SDU having the same sequence number as the received PDCP PDU is already stored in the PDCP receiving buffer of the single bearer, the UE despreads the PDCP PDU, and recovers the header after discarding the PDCP PDU. The reason why the header is recovered and discarded is that the header decompression context is updated by restoring the header because the redundantly transmitted PDCP PDU is likely to be a header compressed packet with a more recent header compression context.

Also, if a PDCP SDU or a half PDCP SDU or PDCP PDU having the same sequence number as the received PDCP PDU is already stored in the PDCP receiving buffer of the multi-bearer, the UE despreads the PDCP PDU, processes the PDCP SDU into a half PDCP SDU, (PDCP PDU, half PDCP SDU, or PDCP SDU) of the same serial number currently stored, and stores the half PDCP SDU.

In the case of a multi-bearer, restoring the header of the unordered half PDCP SDU may adversely affect header restoration of the subsequent half PDCP SDUs. Therefore, the header of the redundantly received packet is not restored, Until it is sorted.

Hereinafter, a method of setting a PBR for a multi-bearer according to an embodiment of the present invention will be described.

In transmitting data using the uplink grant allocated by the base station, the terminal determines which data to transmit in consideration of the priority of the logical channel. If data is continuously generated in a high-priority logical channel, data of a low-priority logical channel may not be served for a long time. This may cause a problem that the minimum data transmission / reception for maintaining the data session becomes impossible. To solve this problem, the concept of Prioritized Bit Rate (PRB) has been introduced. When the PBR is set in the logical channel, the terminal increases Bj, which is a PBR related token, by PBR for each TTI for the logical channel. The terminal preferentially considers Bj in deciding the data to be transmitted. For example, if Bj of the logical channel x is 0, data of a logical channel whose priority is low but Bj is not 0 is preferentially transmitted by at least Bj even if there is data that can be transmitted to the logical channel x having a high priority. The operation is as described in Section 5.7 of 36.321.

The PBR is allocated and managed for each logical channel. However, in the case of a logical channel connected to a multi-bearer, it is preferable to operate the PBR in consideration of all the related logical channels rather than independently operating the PBR on the logical channel. The purpose of the PBR is to guarantee a minimum transmission bandwidth for any data service, and in the case of multiple bearers, one service is associated with two logical channels.

In the conventional signaling system, the parameters related to PBR are prioritizedBitRate and bucketSizeDuration and are signaled by logical channels. Bj is initially initialized to zero, then increases by prioritizedBitRate for every TTI, and the maximum size of Bj is limited to the product of prioritizedBitRate and bucketSizeDuration. In general, a particular radio bearer is set up as a single bearer that is only associated with one logical channel. If the UE moves to the macro cell area after the difference, the single bearer can be reset to the multi-bearer, and the UE properly allocates the PBR of the multi-bearer to the SCG logical channel and the MCG logical channel according to a predetermined rule.

FIG. 12 is a diagram for explaining an operation of a terminal for setting a PBR for a multi-bearer according to another embodiment of the present invention.

Referring to FIG. 12, in step 1205, the UE receives a control message instructing to re-establish a single bearer to a multi-bearer. In step 1210, the UE adjusts the PBR of the MCG logical channel and the PBR of the SCG logical channel to an appropriate value by referring to the PBR information of the control message 1 and the control message 2. The control message 2 refers to a control message for resetting a single bearer to a multi-bearer, and the control message 1 refers to a control message for accommodating PBR information for the single bearer. Normally control message 1 is generated first and control message 2 is generated later. There are a number of ways to adjust the PBR of an MCG logical channel and an SCG logical channel, and one of the methods shown below can be used.

[Method of setting PBR of random multiple bearer x 1]

When A is set to PBR of bearer x's logical channel in control message 1 and PBR of SCG LCH of bearer x is set to B in control message 2, the PBR of SCG LCH is set to signaled B and the PBR of MCG LCH Is adjusted to AB.

[PBR setting method of arbitrary multi-bearer x 2]

If there is PBR information in control message 2, apply PBR to SCG LCH. If there is no PBR information, apply PBR to MCG LCH; That is, when A is set to PBR of bearer x's logical channel in control message 1 and PBR of SCG LCH of bearer x is set to B in control message 2, the PBR of SCG LCH is set to signaled B and the MCG LCH PBR is adjusted to zero. Otherwise, if PBR for bearer x's SCG LCH is not set in control message 2, PBR of MCG LCH is kept as A, and PBR of SCG LCH is set to 0.

[PBR setting method of arbitrary multi-bearer x 3]

Control message 2 specifies to which LCH the PBR is to be applied. For example, PBR is set as shown in Table 9 below.

PBR of LCH of bearer x of control message 1 PBR of LCH of bearer x of control message 2 PBR indicator of control message 2 MCG LCH and SCG LCH PBR A B SCG MCG LCH PBR = 0
SCG LCH PBR = B A B MCG MCG LCH PBR = B
SCG LCH PBR = 0 A Absent Absent MCG LCH PBR = A
SCG LCH PBR = 0 A Absent SCG MCG LCH PBR = 0
SCG LCH PBR = A

For example, if A is reported to PBR of bearer x's logical channel in control message 1 and B is set to PBR of bearer x's logical channel in control message 2, the UE adjusts the PBR of MCG LCH to B if the PBR indicator is set to MCG And the PBR of SCG LCH is set to zero. In step 1215, the UE moves a predetermined amount of Bj of the existing MCG LCH to the SCG LCH.

If PBR setting method 1 is used, Bj of a predetermined ratio of Bj of MCG LCH is subtracted from MCG LCH and added to SCG LCH. Therefore, the Bj of the SCG LCH is not initialized to 0 but is initialized to Bj which is shifted from the MCG LCH.

If PBR setting method 2 or 3 is used, if PBR is applied to SCG, Bj of MCG LCH is all moved to SCG LCH. If PBR is applied to MCG, Bj of MCG LCH is maintained.

In step 1220, the coordinated PBR and adjusted Bj are applied to perform operations related to PBR on the MCG LCH and the SCG LCH. That is, increasing Bj every TTI as much as PBR and decreasing Bj by the amount of data transmission.

Hereinafter, a method for requesting retransmission of a packet that the RLC apparatus of the UE can not receive according to the embodiment of the present invention will be described.

When an event occurs, the RLC receiving entity generates an RLC STATUS PDU, reports the serial number of the RLC PDU that has been in good working order, and requests retransmission of a part of the RLC PDU or RLC PDU segment requiring retransmission (RLC PDU segment). The general operation of the RLC is compliant with 3GPP TS36.322 and the RLC PDU is mixed with the AMD PDU.

The RLC STATUS PDU may be significantly increased depending on the radio channel conditions, and the RLC STATUS PDU may not be transmitted as it is for a given transmission resource. In this case, the UE can selectively report only reportable information on a given transmission resource.

For example, it is assumed that the reception state of the terminal is as follows.

- the highest RLC serial number received so far = 100

- RLC PDUs not received = 90, 95

- 100th byte to 150th byte of RLC PDU segment = 93 that did not receive

The STATUS PDU consists of one ACK_SN, one or more NACK_SN, zero, one or more than one SOstart / SOend pair per NACK_SN as shown in FIG. 13 illustrating the format of the STATUS PDU. The STATUS PDU to be configured in the above situation is as follows, and the size of the STATUS PDU is 101 bits.

- ACK_SN = 101

- NACK_SN = 90

- NACK_SN = 93; SOstart = 100; SOend = 150

- NACK_SN = 95

If the amount of transmission resources allocated to the RLC apparatus is, for example, 16 bits, the UE configures a STATUS PDU according to an amount that can be transmitted.

- ACK_SN = 90

That is, up to serial number 89, only information indicating that it is well received is reported, and the remaining RLC PDUs are not reported.

In some cases, reporting only some of the above information may lead to inaccurate information. As shown in FIG. 13, a plurality of SOstart / SOend pairs may be accommodated for one NACK_SN. If only some information is included because of the amount of transmission resources, the RLC entity receiving the STATUS PDU may make a wrong decision. For example, the reception state of the RLC receiving apparatus at a certain point of time is as follows.

- the highest RLC serial number received so far = 100

- The RLC PDU segment that has not been received from the 100th byte to the 150th byte of the segment = 93, the remaining bytes from the 180th byte of 93

That is, some of the RLC PDUs of the serial number 93 (1st to 99th bytes and 151 to 179th bytes) are correctly received, and other parts (100th to 150th bytes and 180th to last bytes) are not correctly received.

If the amount of transmission resources available to the UE at the time the RLC STATUS PDU is triggered is only an amount that can include ACK_SN, NACK_SN and one SOstart / SOend, the UE generates and transmits the following STATUS PDU.

- ACK_SN = 100

- NACK_SN = 93; SOstart = 100; SOend = 150

The RLC entity receiving the STATUS PDU may mistakenly receive the 180th to last byte of the sequence number 93 as well received by the terminal and discard the portion from the buffer. Therefore, the operation of the RLC receiving apparatus to solve this problem will be described with reference to FIG.

14 is a view for explaining the operation of an RLC receiving apparatus for generating a status PDU according to an embodiment of the present invention.

Referring to FIG. 14, in step 1405, an RLC STATUS PDU is triggered. The RLC STATSU PDU is triggered when the first transmission opportunity occurs after the t-Reordering timer has expired or the poll bit has been set and the t-StatusProhibit has not been activated .

In step 1410, it is checked whether or not a STATUS PDU including ACK_SN, NACK_SN, and SOstart / SOend that reflects the current reception status can be generated in the transmission opportunity (or, if STATUS REPORT If so, proceed to step 1415, otherwise proceed to step 1420.

In step 1415, the terminal writes ACK_SN, NACK_SN, and SOstart / SOend to generate a STATSU PDU so as to reflect the reception state at that point in time.

If it is determined in step 1420 that the < condition > below is satisfied, the process proceeds to step 1425; otherwise, the process proceeds to step 1430.

<Condition>

When generating a STATUS PDU according to the amount of a given transmission resource (or the size of an RLC PDU advertised in a lower layer), is only a part of one or more SOstart / SOend pairs for one NACK_SN included in the STATUS PDU? Is it possible to report the reception status of only some segments to RLC PDUs that are not received (ie, can only include some SOstart / SOend among multiple SOstarts / SOend)?

In step 1425, the RLC receiver sets the SOend value of the last SOstart / SOend pair included in the NACK_SN to a predetermined value, for example, "111111111111111 ". If SOend is set to the above value, it indicates that the byte from the indicated byte to the last byte in the corresponding SOstart has not been received. That is, by setting the value of the last SOend to the value as described above, the retransmission is requested also for the successfully received segment, and at least the RLC transmission apparatus can be prevented from discarding the segment that has not yet received. In the above example, the following STAUTS PDU is generated.

- ACK_SN = 100

- NACK_SN = 93; SOstart = 100; SOend = predetermined value

The transmitting apparatus that has received the STATUS PDU will not discard the 151 th through 179 th bytes of the RLC PDU of the serial number 93.

Another operation may cancel the STATUS PDU triggered in step 1425 and trigger the STATUS PDU again on the next transmission opportunity. That is, more transmission resources are allocated to the next transmission opportunity, so that all necessary information can be included.

In step 1430, the UE determines to which RLC PDU segment the NACK information is to be reported according to the size of the RLC PDU, writes the sequence number of the RLC PDU next to the last RLC PDU segment in the ACK_SN, Or NACK information for the RLC PDU segment in order to generate a STATUS PDU. Therefore, the operation of the RLC transmitting apparatus for solving this will be described with reference to FIG.

FIG. 15 is a view for explaining the operation of an RLC transmitting apparatus for receiving a status PDU according to an embodiment of the present invention; FIG. Referring to FIG. 15, in step 1505, a STATUS PDU is received.

In step 1510, it is determined which RLC PDU and RLC PDU segments are transmitted using the ACK_SN, NACK_SN, SOstart, and SOend of the STATSU PDU, and the well-transmitted ones are discarded in the transmission buffer and those retransmitted are prepared for retransmission. At this time, the transmitting apparatus determines data to be discarded and data to be retransmitted in the transmission buffer as follows. For convenience of explanation, NACK information composed of one NACK_SN and one or more SOstart / SOend pairs is referred to as partial NACK information. ACK_SN, NACK_SN, NACK_SN, and SOstart / SOend are named STATUS elements.

- It is judged that RLC PDUs indicated only by NACK_SN in the STATUS PDU should retransmit the entire RLC PDU

- The RLC PDU segments reported as 'lost' by the partial NACK information included in the STATUS PDU are determined to be retransmitted

- The remaining NACK information included in the STATUS PDU excluding the RLC PDU segments reported as 'lost' by the partial NACK information other than the last STATUS element is judged to be correctly received and discarded

If the last STATUS element of the STATUS PDU is partial NACK information, the remaining segments except the RLC PDU segments reported as 'lost' by the partial NACK information do not determine whether to receive. In other words, it is neither discarded nor retransmitted.

Hereinafter, a method for performing a HARQ operation by reporting a plurality of categories according to an embodiment of the present invention and applying one of the categories will be described.

In order for the terminal and the base station to perform data transmission and reception, the base station must recognize the performance of the terminal. For example, information such as the maximum downlink data rate of the UE and the performance of the HARQ buffer of the UE is information that the BS should know in order to transmit downlink data to the UE. Performance information related to downlink data transmission / reception of the terminal is reported to the base station in a terminal category format. The following table is the 'terminal category' as defined in Specification 36.306. The category 1 is 10 Mbps, the category 2 is 50 Mbps, the category 3 is 100 Mbps, the category 4 is 150 Mbps, the categories 5, 6 and 7 are 300 Mbps, and the category 8 is 3 Gbps.

UE Category If the terminal can receive within one TTI (1 ms)
Maximum number of bits Total number of soft channel bits (buffer size) Maximum number of layers available for downlink Category 1 10296 250368 One Category 2 51024 1237248 2 Category 3 102048 1237248 2 Category 4 150752 1827072 2 Category 5 299552 3667200 4 Category 6 301504 3667200 2 Category 6 ' 301504 3667200 4 Category 7 301504 3667200 2 Category 7 ' 301504 3667200 4 Category 8 2998560 35982720 8

In Table 10, the categories 1 to 5 are introduced in the LTE specification release 8, and the categories 6 to 8 are introduced in the LTE specification release 10. In other words, Release 8 base stations do not understand categories 6-8. In addition to the above categories, it may be necessary to introduce categories corresponding to different data rates. For example, in LTE Specification Release 12, the introduction of new categories 9 and 10 of 450 Mbps was determined. For convenience of explanation, the categories 1 to 5 are referred to as a first category, the categories 6 to 8 as a second category, and the categories 9 to 10 as a third category. Base stations in Release 8 and Release 9 do not understand the second and third categories, base stations in Release 10 and Release 11 do not understand the third category, and Release 12 or later base stations understand all categories. Since the terminal does not recognize the release of the base station, it reports several categories in some cases. For example, the terminal of the second category not only reports the second category but also the first category. The terminals of the third category report not only the third category but also the second category and the first category. Since the category has a close relationship with the size of the soft buffer as described below, the terminal and the base station must apply the same category to each other. Therefore, there is a need for a method in which a terminal and a base station apply the same category to terminals reporting a plurality of categories. Each item of the above table will be described in more detail below.

If the maximum number of bits that can be received within one TTI (1 ms) of the terminal is multiplied by 1000 in the above table, the maximum transmission rate per second of the system can be converted.

In the above table, the 'total number of soft channel bits' is related not only to the buffer size of the UE but also to the rate matching operation. If the total number of soft channel bits is N _soft , the transport block soft buffer size is N _IR , and the code block soft buffer size is N _cb , there is a relation of Equation (1).

Here, K _MIMO has a value of 2 or 1 depending on a transmission mode, and a value of min (M _{DL_HARQ} , M _limit ) generally has a value of 8. Further, C is the number of code blocks, K _W has a relationship of _W = K represents the length of the circular buffer 3K _{Π, Π} K has a length of 6144 bits to the interleaver size of the sub-blocks. That is, as shown in the formula for the N _soft values affects the N _IR value, N when _IR / C value is less than K _W, In other words, high-speed data when the transmission is in progress, the value of N _IR value of N _cb In the case of the present invention. Puncturing / repetition pattern affects the value of N _cb , it is understood that if the N _soft value between the terminal and the ENB is misunderstood, it affects the erroneous operation. Other requirements related to rate matching are specified in Specification 36.212.

18 is a diagram illustrating operations of a terminal reporting three categories according to an embodiment of the present invention and a base station performing downlink data transmission / reception with the terminal.

Referring to FIG. 18, in a mobile communication system including a terminal 1805, a base station 1810, and an MME 1815, a terminal is powered on (1820). When the UE performs a cell search and an accessible cell is found, the UE performs an RRC connection establishment procedure (refer to specification 36.331) with the base station through the cell (1825). The UE transmits a predetermined control message to the MME through the established RRC connection (1830). The control message may be, for example, a service request message (SERVICE REQUEST) or an initial registration request message (ATTACH REQUEST). The MME determines whether to accept the request of the terminal through a predetermined procedure, accepts the request, and when it is determined to provide the mobile communication service to the terminal, the MME transmits a control message containing information related to the terminal to the base station (1835). The control message may include information necessary for the base station to transmit and receive data with the terminal, for example, security key information, service profile information of the terminal, and the like. If the MME has the capability information of the UE, the MME includes the capability information of the UE in the control message. If the MME does not have the capability information of the UE, the capability information is not transmitted, and the BS transmits a predetermined RRC control message to the UE to acquire performance information of the UE (1840). The control message is referred to as a UE capability information request message (UE capability information), and a field indicating which radio access technology performance information is requested is stored in the control message. The LTE base station sets the field to request performance information for E-UTRA. Upon receiving the control message, the UE checks which RAT performance information has been requested. If the UE has requested performance information on the E-UTRA, the UE transmits a UE capability information message containing performance information related to the E-UTRA. And transmits it to the base station (1845). In particular, the control message includes at least one category information.

If the performance of the terminal corresponds to one of the categories 1 to 5, the terminal reports only the first category corresponding to the performance of the terminal.

If the performance of the terminal corresponds to one of the categories 6 to 8, the terminal reports the second category corresponding to its performance and the first category most similar to the second category. For example, a Category 6 or 7 terminal reports Category 4 to a first category, and a Category 8 terminal reports Category 5 to a first category.

If the performance of the terminal is category 9 or 10, the terminal reports the third category corresponding to its performance and the second category and the first category most similar to the third category. For example, a Category 9 terminal reports category 9 as a third category, category 6 as a second category, and category 4 as a first category.

Upon receiving the performance information of the terminal, the base station determines the setting of the terminal with reference to the performance information, and determines which category to apply (1850).

The base station can set an antenna, a transmission mode, a carrier integration, and the like, and determines a category to be applied in connection with the setting according to a predetermined rule. The above rule will be described in more detail with reference to FIG. The base station transmits an RRC connection reset message containing the setting information to the mobile station (1855). The control message includes information for determining which category the base station has applied. The terminal applies the configuration information of the control message to set the antenna, the transmission mode, the carrier integration, and the like. And determines which category to apply by referring to the information of the control message. And resets the downlink HARQ soft buffer according to the determined category.

The base station constructs a downlink HARQ buffer by applying Nsoft of the determined category, and transmits downlink data to the terminal using the HARQ buffer (1865). For example, the UE determines N _IR by applying Nsoft of the determined category, and determines the size of the HARQ soft buffer according to N _IR . If Nsoft and N _IR change, change the size of the soft buffer accordingly. If the size of the reset soft buffer is smaller than the size of the previous soft buffer, the terminal discards the data stored in the soft buffer larger than the reset soft buffer and retains only the data smaller than the reset soft buffer do. This operation is called data management operation upon soft buffer reset.

The MS receives the downlink data from the BS using the re-established soft buffer (1865).

At a certain point in time, the base station changes the setting of the terminal. Accordingly, categories to be applied may be changed. For example, when a mobile station handover to a new base station, if the version of the new base station is lower than that of the previous base station and does not understand some of the categories of the terminal, a new category should be applied. In the handover, for example, the target BS determines configuration information to be applied after handover by the MS, and transmits the configuration information to the source BS. In step 1875, the source BS transmits an RRC connection reestablishment message containing the configuration information to the MS. A control message indicating handover is stored in the RRC connection re-establishment message, and the UE establishes downlink synchronization with the target cell indicated in the control message. The terminal also uses the information stored in the RRC connection reset message to determine a category to be applied in the target cell. The downlink soft buffer is reset according to the category (1880). The UE receives the downlink data from the target cell using the re-established downlink soft buffer (1885). In particular, if the downlink synchronization with the target cell is established, the terminal performs a random access procedure in the target cell and starts using the downlink soft buffer when the random access procedure is completed.

19 is a diagram illustrating a terminal operation according to an embodiment of the present invention.

Prior to starting the operation of FIG. 19, the terminal determines its category. The category of the terminal may be determined in the production stage and stored in a nonvolatile internal memory or the like. As described above, the terminal has at least one category. The UEs belonging to the third category have a second category and a first category that can be recognized by the old base station in connection with the connection with the old base station. Then, when the terminal is powered on, an appropriate cell to 'camp on' through a cell search operation or the like is selected, and a network connection process is performed through the cell (2005). The UE determines the size of the downlink soft buffer by applying Nsoft of the first category until receiving the first RRC connection reconfiguration message (RRC CONNECTION RECONFIGURATION) and performs the HARQ operation.

Referring to FIG. 19, in step 1910, the terminal reports its category while reporting performance information. The terminal can report the first category, the second category, and the third category. The terminal can report the category 9 as the third category, the category 6 as the second category, the category 4 as the first category, Category 7 as the second category, and category 4 as the first category.

Upon receiving the RRC connection reestablishment message in step 1915, the MS re-establishes the connection by applying the configuration information stored in the control message and proceeds to step 1920. In step 1920, the terminal checks whether the information stored in the control message satisfies the second category selection condition or the third category selection condition. If either of the two conditions is not satisfied, the process proceeds to step 1925. If the second category selection condition is satisfied, the process proceeds to step 1930. If the third category selection condition is satisfied, the process proceeds to step 1935.

In step 1925, the terminal determines Nsoft by applying the first category. For example, if the terminal reports category 9 as the third category, category 6 as the second category, and category 4 as the first category, the terminal applies category 4. If the new Nsoft determines a different value from Nsoft that is currently in use, or if a different NIR than the currently used NIR is determined, data management is performed during soft buffer reset.

In step 1930, the terminal determines Nsoft by applying the second category. For example, if the terminal reports category 9 as the third category, category 6 as the second category, and category 4 as the first category, the terminal applies category 6. If the new Nsoft determines a different value from Nsoft that is currently in use, or if a different NIR than the currently used NIR is determined, data management is performed during soft buffer reset.

 In step 1930, the terminal determines Nsoft by applying the third category. For example, if the terminal reports category 9 as the third category, category 6 as the second category, and category 4 as the first category, the terminal applies category 9. If the new Nsoft determines a different value from Nsoft that is currently in use, or if a different NIR than the currently used NIR is determined, data management is performed during soft buffer reset.

Various examples of the second category selection condition and the third category selection condition in this embodiment may be as follows.

[Second category selection condition (1)]

There is at least one serving cell in which no TM 10 is set in the serving cell and TM 9 is set

[Third category selection condition (1)]

At least one serving cell in which the TM 10 is set among the serving cells

That is, the category is selected based on the transmission mode set in the terminal.

TM 9 and TM 10 are the forward transmission modes defined in Specification 36.213. TM 9 is a mode supporting a single user-multi-input multi-output (SU-MIMO) having up to 8 ranks and TM10 is a mode supporting Coordinated Multi Point transmission (CoMP). A transmission mode with a high data rate likely to be applied is pre-associated with a high data rate category to determine which category to apply.

That is, if TM 9 is set, the second category is set to TM 10, the third category is applied, and if neither TM nor 10 is set, the first category is applied.

[Second category selection condition (2)]

At most two serving cells are set in the UE and at least one serving cell in which TM 9 is set

[Third category selection condition (2)]

At least three serving cells are set in the terminal.

That is, the category is determined in consideration of the carrier accumulation state of the terminal and the transmission mode of the terminal.

A 450 Mbit / s data rate is likely to be achieved if at least three serving cells are integrated. Therefore, it is possible to define that the third category is applied when the number of set serving cells is three or more.

That is, if at least three serving cells are set, a third category, a maximum of two serving cells are set, a TM9 is set, a second category, a maximum of two serving cells are set, and a TM9 is set, To be applied.

[Second category selection condition (3)]

At least one serving cell in which TM 9 is set is set, and the RRC re-establishment control message does not include 'terminal category' control information to be applied.

[Third category selection condition (3)]

The RRC re-establishment control message includes 'application category category' control information.

In short, it explicitly indicates which category to apply to the RRC Reset Control message. In particular, only the application of the third category is explicitly applied, and the second category can alleviate the signaling overhead by associating with the use of TM 9. That is, if the category information to be applied is included, the third category is applied. If the information is not available and TM 9 is set, the second category is applied. If the information is not TM 9, the first category is applied do.

16 is a block diagram illustrating a configuration of a terminal apparatus in an LTE system according to an embodiment of the present invention.

16, the terminal apparatus includes an MCG-MAC unit 1610, a control message processing unit 1665, various higher layer processing units 1670, 1775 and 1785, a control unit 1680, an SCG-MAC unit 1615, A MAC device 1610, a transceiver 1605, PDCP devices 1645, 1750, 1755 and 1760, and RLC devices 1620, 1725, 1730, 1735 and 1740.

The transceiving unit 1605 receives data and a predetermined control signal on the downlink channel of the serving cell, and transmits data and a predetermined control signal to the uplink channel. When a plurality of serving cells are set, the transmitting and receiving unit performs data transmission and reception and control signal transmission and reception through the plurality of serving cells.

The MCG-MAC unit 1610 multiplexes data generated in the RLC unit or demultiplexes data received from the transmission / reception unit 1605 and transmits the data to an appropriate RLC unit. The MCG-MAC device also processes the BSR or PHR triggered for the MCG.

The control message processing unit 1665 is an RRC layer apparatus and processes the control message received from the base station to take necessary actions. For example, receives an RRC control message and transmits various setting information to the control unit.

The upper layer processing units 1670, 1775, and 1785 can be configured for each service. And processes data generated in user services such as FTP (File Transfer Protocol) and VoIP (Voice over Internet Protocol), and transfers the processed data to the PDCP device.

The control unit 1680 controls the transmission / reception unit 1605 and the multiplexing and demultiplexing unit so that the scheduling command received through the transmission / reception unit 1605, for example, the reverse grants, . The control unit also performs various control functions for the terminal operation shown in FIG.

The PDCP devices 1645, 1750, 1755, and 1760 are divided into a single bearer PDCP 1645, 1750, and 1760 and a multi-bearer PDCP 1755. A single bearer PDCP transmits and receives data only through MCG or SCG, and is connected to one RLC transceiver. Multi-bearer PDCP transmits and receives data through MCG and SCG. The RLC devices 1620, 1725, 1730, 1735, and 1740 perform the operations described in FIGS. 14 and 15. The multi-bearer PDCP performs the PDCP operation shown in FIG. 5 to FIG. 7, and the controller 1680 collectively controls the various control operations shown in FIG. 5 to FIG. The control unit 1680 also collectively controls the various control operations shown in Figs. 18 to 28. Fig.

17 is a block diagram illustrating a configuration of a base station apparatus in an LTE system according to an embodiment of the present invention.

17, the base station includes a MAC device 1710, a control message processor 1765, a controller 1780, a transceiver 1705, PDCP devices 1745, 1850, 1855 and 1860, RLC devices 1720, 1825, 1830, 1835, 1840, and a scheduler 1790.

Transmitter / receiver 1705 transmits data and a predetermined control signal to a forward carrier and receives data and a predetermined control signal to a reverse carrier. When a plurality of carriers are set, the transmitting and receiving unit performs data transmission and reception and control signal transmission and reception with the plurality of carriers.

The MAC unit 1710 multiplexes data generated in the RLC unit or demultiplexes data received from the transmission / reception unit and transmits the data to an appropriate RLC unit or a control unit. The control message processing unit processes the control message transmitted by the mobile station to perform a required operation or generates a control message to be transmitted to the mobile station and transmits the control message to a lower layer.

The scheduler 1790 allocates transmission resources to the mobile station at an appropriate point in consideration of a buffer state of the mobile station, a channel state, and the like, processes the signal transmitted from the mobile station to the transmission / reception unit, or transmits a signal to the mobile station.

The PDCP devices 1745, 1850, 1855 and 1860 are divided into a single bearer PDCP 1745, 1750 and 1760 and a multi-bearer PDCP 1755. A single bearer PDCP transmits and receives data only through MCG or SCG, and is connected to one RLC transceiver. Multi-bearer PDCP transmits and receives data through MCG and SCG. The multi-bearer PDCP performs the PDCP operation shown in FIG. 5 to FIG. 7, and the control unit 1780 collectively controls the various control operations shown in FIG. 5 to FIG. The control unit 1780 also collectively controls the various control operations shown in Figs. 18, 19 and 21 to 28. Fig. The RLC apparatus performs the operations shown in FIG. 14 and FIG.

Claims (2)

A method for re-establishing a bearer in a mobile communication system supporting a multi-bearer,
Receiving a first control message for re-establishing a bearer; And
In a mobile communication system including a step of converting PDCP PDUs into PDCP SDUs and transferring ordered PDCP SDUs to an upper layer upon a bearer re-establishment from a single bearer to the multi-bearer based on the first control message, Way.
The method according to claim 1,
Receiving a second control message for re-establishing a bearer;
Processing the PDCP PDUs transferred from the MCG RLC and the SCG RLC according to COUNT and converting the PDCP PDUs into a PDCP SDU when the bearer is re-established from the multi bearer to the single bearer based on the second message; And
And storing all SDUs after the first missing SDU in a buffer.

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