KR20150110281A - Method and apparatus for transmitting/receiving signal in mobilre communication system supporting a plurality of carriers - Google Patents

Abstract

The present invention relates to an operation method of a terminal in a mobile communications system supporting a plurality of carriers, the invention including the steps of: inspecting, upon detecting an instruction of bearer reset, whether the bearer reset pertains to a secondary cell group (SCG) or to a multiple bearer; and performing, based on the inspection result, an operation of reporting a state of the packet data convergence protocol (PDCP).

Description

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

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for transmitting / receiving signals in a mobile communication system, and more particularly, to a method and apparatus for transmitting / receiving signals in a mobile communication system supporting a plurality of carriers.

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.

(LTE) system in a 3rd generation partnership project (3GPP) as one of the next generation mobile communication systems. The work on the specification is underway. The LTE system is a technology for realizing high-speed packet-based communication with a transmission rate of several hundred Mbps higher than the data transmission rate currently provided, and the standardization is almost completed.

Recently, the discussion about advanced LTE (LTE-advanced: LTE-A, hereinafter referred to as "LTE-A") communication system which improves the transmission speed by combining various new technologies with the LTE communication system is getting into full swing. A representative example of the newly introduced technology is carrier aggregation. Carrier aggregation is one in which a terminal uses a plurality of forward carriers and a plurality of reverse carriers, whereas a terminal conventionally transmits and receives data using only one forward carrier and one reverse carrier.

In LTE-A, only intra-ENB carrier aggregation is defined. This leads to a reduction in the applicability of the carrier aggregation function. In particular, in a scenario in which a plurality of picocells and one macrocell are overlapped with each other, the macrocell and the picocell can not be aggre- gated.

On the other hand, the above information is only presented as background information to help understand the present invention. No determination has been made as to whether any of the above content is applicable as prior art to the present invention, nor is any claim made.

An embodiment of the present invention proposes a method and apparatus for transmitting and receiving signals in a mobile communication system supporting a plurality of carriers.

Also, an embodiment of the present invention proposes a method and apparatus for transmitting / receiving signals based on an inter-ENB carrier aggregation scheme in a mobile communication system supporting a plurality of carriers.

A method proposed in an embodiment of the present invention comprises: A method of operating a terminal in a mobile communication system supporting a plurality of carriers, the method comprising the steps of: detecting whether bearer re-establishment is instructed, whether the bearer re-establishment is associated with a secondary cell group (SCG) And performing a packet data convergence protocol (PDCP) status reporting operation based on the result of the checking.

An apparatus proposed in an embodiment of the present invention comprises: In a mobile communication system supporting a plurality of carriers, if it is detected that bearer re-establishment is instructed, the UE checks whether the bearer re-establishment is related to a secondary cell group (SCG) bearer or a multi bearer, And a processor for performing a packet data convergence protocol (PDCP) status reporting operation based on the result of the checking.

One embodiment of the present invention is effective in that it is possible to aggregate a plurality of carriers between base stations and transmit / receive signals in a mobile communication system supporting a plurality of carriers.

In addition, in an embodiment of the present invention, in a mobile communication system supporting a plurality of carriers, it is possible to aggregate a plurality of carriers between base stations to transmit / receive signals, thereby improving the signal transmission / reception speed of the user terminal It is effective.

Further aspects, features and advantages of the present invention as set forth above in connection with certain preferred embodiments thereof will become more apparent from the following description, taken in conjunction with the accompanying drawings, in which:
1 schematically shows a structure of an LTE system according to an embodiment of the present invention,
2 is a diagram schematically illustrating a wireless protocol structure in an LTE system according to an embodiment of the present invention;
3 schematically illustrates a carrier aggregation operation in a base station in an LTE system according to an embodiment of the present invention;
4 is a diagram schematically illustrating inter-base station carrier aggregation operation in an LTE system according to an embodiment of the present invention;
5 is a schematic view illustrating a connection structure of a PDCP apparatus in an LTE system according to an embodiment of the present invention;
6 is a diagram schematically illustrating an operation procedure of a terminal and a network when a SeNB is set or released in an LTE system according to an embodiment of the present invention;
7 is a diagram schematically illustrating an example of a process of configuring terminal capability information related to a DC in an LTE system according to an embodiment of the present invention.
FIG. 8 is a diagram schematically illustrating another example of a process of configuring terminal capability information related to a DC in an LTE system according to an embodiment of the present invention.
9 schematically illustrates an example of DC basic performance in an LTE system according to an embodiment of the present invention;
10 schematically shows another example of DC basic performance in an LTE system according to an embodiment of the present invention, Fig.
11 is a diagram schematically illustrating a process of changing an SeNB in an LTE system according to an embodiment of the present invention,
FIG. 12 is a diagram schematically illustrating a terminal operation for triggering and transmitting a PDCP Status Report when an offload bearer is reset in an LTE system according to an embodiment of the present invention; FIG.
13 is a diagram schematically illustrating a format of a PDCP Status Report in an LTE system according to an embodiment of the present invention;
FIG. 14 is a diagram schematically illustrating an operation procedure of a base station for receiving a PDCP status report and retransmitting PDCP data in an LTE system according to an embodiment of the present invention; FIG.
15 is a diagram schematically illustrating an internal structure of a terminal apparatus for transmitting PDCP data in a multi-bearer in an LTE system according to an embodiment of the present invention;
16 is a diagram schematically illustrating an operation of transmitting a PDCP data packet and a PDCP control packet through a multi-bearer in an LTE system according to an embodiment of the present invention;
17 is a diagram schematically illustrating an internal structure of a UE in an LTE system according to an embodiment of the present invention,
18 is a view schematically showing an internal structure of a base station in an LTE system according to an embodiment of the present invention.
FIG. 19 is a diagram schematically illustrating an operation procedure when an RLC UM bearer is re-established from an MCG bearer to an SCG bearer in an LTE system according to an embodiment of the present invention and then re-established to an MCG bearer; FIG.
20 is a diagram schematically illustrating an operation procedure of a TA timer of a UE to which multiple connections are established in an LTE system according to an embodiment of the present invention;
21 is a diagram schematically illustrating another example of DC basic performance in an LTE system according to an embodiment of the present invention;
22 is a diagram schematically illustrating another example of DC basic performance in an LTE system according to an embodiment of the present invention;
Throughout the drawings, it should be noted that like reference numerals are used to illustrate the same or similar elements and features and structures.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that only the parts necessary for understanding the operation according to the embodiments of the present invention will be described below, and the description of the other parts will be omitted so as not to disturb the gist of the present invention. The following terms are defined in consideration of the functions in the embodiments of the present invention, and may be changed according to the intention of the user, the intention or the custom of the operator. Therefore, the definition should be based on the contents throughout this specification.

The present invention is capable of various modifications and various embodiments, and specific embodiments thereof will be described in detail with reference to the drawings. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

It is also to be understood that the singular forms "a" and "an" above, which do not expressly state otherwise in this specification, include plural representations. Thus, in one example, a " component surface " includes one or more component representations.

Also, terms including ordinal numbers such as first, second, etc. may be used to describe various elements, but the elements are not limited to these terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

Also, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, the terms "comprises" or "having" and the like refer to the presence of stated features, integers, steps, operations, elements, components, or combinations thereof, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Furthermore, in the embodiments of the present invention, all terms used herein, including technical or scientific terms, unless otherwise defined, are intended to be inclusive in a manner that is generally understood by those of ordinary skill in the art to which this invention belongs. Have the same meaning. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and, unless explicitly defined in the embodiments of the present invention, are intended to mean ideal or overly formal .

According to various embodiments of the invention, the electronic device may comprise a communication function. For example, the electronic device may be a smart phone, a tablet personal computer (PC), a mobile phone, a videophone, an e-book reader e a notebook PC, a netbook PC, a personal digital assistant (PDA), a portable personal computer (PC) A mobile multimedia device, a portable multimedia player (PMP), an MP3 player, a mobile medical device, a camera, a wearable device (e.g., a head- Electronic devices such as a head-mounted device (HMD), an electronic apparel, an electronic bracelet, an electronic necklace, an electronic app apparel, an electronic tattoo, or a smart watch ) And the like.

According to various embodiments of the present invention, the electronic device may be a smart home appliance having communication capabilities. For example, the smart home appliance includes a television, a digital video disk (DVD) player, audio, a refrigerator, an air conditioner, a vacuum cleaner, an oven, A microwave oven, a washer, a dryer, an air purifier, a set-top box, a TV box (for example, Samsung HomeSync ^™ , Apple TV ^™ or Google TV ^™ ) a gaming console, an electronic dictionary, a camcorder, an electrophotographic frame, and the like.

According to various embodiments of the present invention, the electronic device may be a medical device (e.g., magnetic resonance angiography (MRA) device, magnetic resonance imaging (CT) device, an imaging device, or an ultrasonic device), a navigation device, and a magnetic resonance imaging (MRI) , A global positioning system (GPS) receiver, an event data recorder (EDR), a flight data recorder a recorder: FDR (hereinafter referred to as FER), an automotive infotainment device, a navigation electronic device (for example, a navigation navigation device, A gyroscope, or a compass), an avionics device, a secure device, an industrial or consumer robot, and the like.

In accordance with various embodiments of the present invention, an electronic device includes a plurality of devices, including furniture, a portion of a building / structure, an electronic board, an electronic signature receiving device, a projector and various measurement devices (e.g., Water, electricity, gas or electromagnetic wave measuring devices), and the like.

According to various embodiments of the invention, the electronic device may be a combination of devices as described above. It should also be apparent to those skilled in the art that the electronic device according to the preferred embodiments of the present invention is not limited to the device as described above.

According to various embodiments of the present invention, a user equipment (hereinafter UE or terminal) may be, for example, an electronic device.

An embodiment of the present invention proposes a method and apparatus for transmitting and receiving signals in a mobile communication system supporting a plurality of carriers.

Also, an embodiment of the present invention proposes a method and apparatus for transmitting / receiving signals based on an inter-ENB carrier aggregation scheme in a mobile communication system supporting a plurality of carriers.

The apparatus and method proposed in an embodiment of the present invention may be applied to a long-term evolution (LTE) mobile communication system and an advanced long term evolution (LTE-A) (LTE-A) mobile communication system, a high-speed downlink packet access (HSDPA) mobile communication system, and a high-speed downlink packet access , A high speed uplink packet access (HSUPA) mobile communication system, and a 3rd generation project partnership 2 (3GPP2, hereinafter referred to as 3GPP2) A high rate packet data (HRPD) mobile communication system of 3GPP2 and a wideband code division multiple access (WCDMA) mobile communication system of 3GPP2, (CDMA) mobile communication system of the 3GPP2, an Institute of Electrical and Electronics Engineers (IEEE), and the Institute of Electrical and Electronics Engineers an IEEE 802.16m communication system, an evolved packet system (EPS), a mobile internet protocol (hereinafter referred to as " mobile IP " (Hereinafter referred to as " Mobile IP ") system.

First, the structure of an LTE system according to an embodiment of the present invention will be described with reference to FIG.

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

Referring to FIG. 1, the radio access network of the LTE system includes an evolved Node B (hereinafter, referred to as an ENB, a Node B or a base station) 105 and a mobility management entity (MME) 125 and a serving-gateway (S-GW), as shown in FIG. A user equipment 135 connects to the external network via the ENBs 105, 110, 115, 120 and the S-GW 130. The user equipment (UE)

1, the ENBs 105, 110, 115, and 120 correspond to an existing node B of a universal mobile telecommunications system (UMTS) system. The ENBs 105, 110, 115, and 120 are connected to the UE 135 through a wireless 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 VoIP (Voice over IP) service through the Internet protocol is served through a shared channel, the state of the UE's buffer status, available transmission power state, An apparatus for collecting and scheduling information is needed, and the ENBs 105, 110, 115, and 120 are responsible for the apparatuses. One ENB normally controls a plurality of cells. In order to realize a transmission rate of 100 Mbps, the 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 in accordance with a channel state of the AT 135, AMC (hereinafter referred to as "AMC") scheme.

The S-GW 130 is a device for providing 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 base stations as an apparatus for performing various control functions as well as a mobility management function for the terminal 135.

FIG. 1 illustrates a structure of an LTE system according to an embodiment of the present invention. Referring to FIG. 2, a radio protocol structure in an LTE system according to an embodiment of the present invention will be described.

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

2, a wireless protocol of an LTE system includes a packet data convergence protocol (PDCP) layers 205 and 240, a radio link control (RLC) layers 210 and 235, and media access control (MAC) layers 215 and 230. The radio access control (RLC) .

The PDCP layers 205 and 240 perform operations such as Internet Protocol (IP) header compression / decompression and perform radio link control (RLC) The RLC layers 210 and 235 reconstruct a PDCP packet data unit (PDU) to an appropriate size to generate an automatic repeat request (ARQ) request (hereinafter, referred to as " ARQ ") operation.

The MAC layers 215 and 230 are connected to a plurality of RLC layer devices included in a UE, multiplex RLC PDUs into MAC PDUs, demultiplex the MAC PDUs, and generate RLC PDUs. The physical layers 220 and 225 channel-code and modulate the upper layer data, generate the OFDM symbols through the wireless channel, demodulate the OFDM symbols received through the wireless channel, perform channel decoding, and transmit the OFDM symbols to the upper layer And performs an operation.

FIG. 2 illustrates a wireless protocol structure in an LTE system according to an embodiment of the present invention. Referring to FIG. 3, a description will now be made of a carrier aggregation operation in a base station in an LTE system according to an embodiment of the present invention. .

3 is a schematic diagram illustrating a carrier aggregation operation in a base station in an LTE system according to an embodiment of the present invention.

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, conventionally, one terminal transmits one of the two carriers And transmitted / received data.

However, a terminal having carrier aggregation capability can transmit / receive data through several carriers at the same time. The base station 305 may increase the transmission rate of the terminal 330 by allocating more carriers to the terminal 330 having the carrier aggregation capability depending on the situation. The aggregation of the forward and uplink carriers transmitted and received by one base station is referred to as " carrier aggregation in the base station ". However, in some cases it may be necessary to aggregate forward and uplink carriers and uplink carriers transmitted and received in different base stations, unlike that shown in FIG.

FIG. 3 illustrates a carrier aggregation operation in a base station in an LTE system according to an embodiment of the present invention. Referring to FIG. 4, in an LTE system according to an exemplary embodiment of the present invention, The operation will be described below.

4 is a diagram schematically illustrating a carrier aggregation operation between base stations in an LTE system according to an embodiment of the present invention.

4, when the base station 1 405 transmits / receives a carrier having a center frequency f1 and the base station 2 415 transmits / receives a carrier having a center frequency f2, the terminal 430 transmits / The result of aggregating the carriers with f1 and the forward center frequency f2 carriers leads to the aggregation of carriers that are transmitted / received from one or more base stations, and in one embodiment of the present invention This is called "inter-ENB carrier aggregation" (or carrier aggregation). In an embodiment of the present invention, carrier aggregation between base stations is referred to as dual connectivity (DC). For example, the fact that the DC is set means that carrier aggregation between base stations is established, that one or more cell groups are set, and that a secondary cell group (SCG) That at least one secondary cell (hereinafter referred to as " SCell ") under the control of a base station other than the serving base station is set, that a primary SCell (pSCell: primary SCell) It means that a MAC entity for a serving eNB (SeNB) is set, that two MAC entities are set in the terminal, and so on.

Hereinafter, terms to be frequently used in explaining embodiments of the present invention will be schematically described as follows.

In the conventional sense, when one forward carrier transmitted by one base station and one uplink carrier received by the base station constitute one cell, carrier aggregation means that a terminal simultaneously transmits and receives data through several cells . At this time, the maximum transmission rate and the number of carriers to be aggregated have a positive correlation.

Hereinafter, in the embodiments of the present invention, it is assumed that the UE receives data through an arbitrary forward carrier or transmits data through an arbitrary uplink carrier in a cell corresponding to a center frequency and a frequency band that characterize the carrier It has the same meaning as transmitting / receiving data using a control channel and a data channel. In the exemplary embodiments of the present invention, the carrier aggregation will be expressed as 'a plurality of serving cells are set', and a basic serving cell (hereinafter referred to as PCell) and a secondary serving cell (hereinafter referred to as SCell) Will be used. The terms have the same meaning as they are used in an LTE mobile communication system. It should be noted that in the embodiments of the present invention, terms such as a carrier, a component carrier, a serving cell and the like are mixed.

In the embodiments of the present invention, 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 refers to a set of serving cells controlled by a base station (hereinafter referred to as " MeNB ") that controls a PCell, and the SCG refers to a base station that controls only PCs, A base station, and a SeNB). The base station informs the UE whether the particular serving cell belongs to the MCG or the SCG in the process of setting the serving cell.

One MCG and one or more SCGs may be set in one terminal. In the embodiments of the present invention, only one SCG is set for convenience of description. However, even if more than one SCG is set, This 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 embodiments of the present invention mean PCell and SCell defined in LTE standard 36.331 or 36.321.

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

Referring again to FIG. 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 a serving cell belonging to the SCG.

In the following description, other terms may be used instead of MCG and SCG for the sake of understanding. For example, terms such as primary set and secondary set, or primary carrier group and secondary carrier group can be used. Although these terms may be used differently, they should be noted that the terms used are different only, 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 embodiments of the present invention, it is assumed that at most one SCG can be set for convenience of explanation. An SCG can contain multiple SCells, one of which has a special attribute. In a typical intra-base station CA, a UE transmits a hybrid automatic repeat request (HARQ) request to a PCell through a physical uplink control channel (PUCCH) (Hereinafter referred to as "HARQ") feedback and channel state information (CSI), as well as HARQ feedback and CSI for the SCell. This is to apply the CA operation to terminals that can not perform uplink simultaneous transmission. In case of inter-base station CA operation, it may be practically impossible to transmit HARQ feedback and CSI of CSG SCell through PUCCH of PCell. The HARQ feedback should be delivered within a HARQ round trip time (RTT) (typically 8 ms), since the transmission delay between the MeNB and the SeNB may be longer than the HARQ RTT. Due to the above problem, a PUCCH transmission resource is set in one of the SCells 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. Hereinafter, a connection structure of the PDCP apparatus in the LTE system according to an embodiment of the present invention will be described with reference to FIG.

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

5, generally, one user service is served by one evolved packet system (EPS) bearer, one EPS bearer is served by one radio bearer (radio bearer). The radio bearer is composed of PDCP and RLC. In the inter-base transceiver station CA, the efficiency of data transmission and 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.

For example, in the case of a large data service, the user service can send and receive data with both MeNB and SeNB by forming two RLC devices, such as 510. If the quality of service (QoS) requirement is strict such as VoLTE, the user service can transmit / receive data using only the serving cell of the MeNB by placing the RLC device in the MeNB only as in 505 . Alternatively, the bearer may be set to transmit / receive data only to the serving cells of the SeNB, such as 535.

For the sake of convenience in the following description, a bearer that transmits / receives data only to MeNB serving cells is referred to as MCG bearer, a bearer such as 510 is referred to as a bearer, and a bearer that transmits / receives data only to SeNB serving cells is referred to as SCG bearer. The PDCP apparatus of the MCG bearer and the SCG bearer are connected to one RLC apparatus, and the PDCP apparatus of the multi bearer is connected to two RLC apparatuses. MCG RLCs 507 and 515 for transmitting / receiving data through MCG (or connected to a MAC device associated with MCG serving cells), and RLC devices for transmitting / receiving data via SCG to SCG RLC 520, 540). MACs 509 and 525 related to data transmission / reception through MCG are referred to as MCG-MAC, and MACs 530 and 545 related to data transmission / reception through SCG are referred to as SCG-MAC. The logical channel between the MCG RLC and the MCG-MAC is the MCG logical channel, and the logical channel between the SCG RLC and the SCG-MAC is the SCG logical channel. do. For convenience of explanation, it is assumed that a macro cell area means an area where only a macro cell signal is received without receiving a small cell signal, and a small cell area means an area where a macro cell signal and a small cell signal are received together do. A small cell can be additionally set to the terminal when the terminal having a large amount of downlink data demand moves from the macro cell area to the small cell area and the amount of downlink data such as a file transfer protocol (FTP) This many bearers can be re-established from the MCG bearer to the multi-bearer or SCG bearer.

In other words, when the UE moves from the macro cell area to the small cell area and then from the small cell area to the macro cell area, the predetermined bearer is re-set from MCG bearer to MCB bearer again as a multiple bearer / SCG bearer. For convenience of explanation, when SCG / SeNB is not set, data is transmitted / received through the MCG, but when the SCG / SeNB is set, the bearer in which a part or all of the data is transmitted / offload bearer. "The bearer re-establishment procedure may occur when the SeNB is set to the UE (SeNB addition), when the SeNB is released (SeNB release), or when the SeNB is changed (SeNB change). When the SeNB is set, the offload bearer is reset from the MCG bearer to the SCG bearer or the multi bearer, and when the SeNB is released, the offload bearer is reset from the SCG bearer or the multi bearer to the MCG bearer. , It is changed to another SCG bearer or a multiple bearer.

Table 1 and Table 2 show specific operations of each device when the bearer is reset for each case. In the following Tables 1 and 2, " previous ENB " refers to an ENB that transmits / receives all or a part of the data of the offload bearer before the reset occurs. The " new ENB " Indicates an ENB that transmits / receives a part.

Table 1 above shows operations related to SCG bearer resetting.

In Table 1 above, the previous ENB resets the MAC means that it releases the logical channel for the offload bearer and releases the mapping relationship between the logical channel and the transport channel managed by the MAC layer. In Table 1, it means that the new ENB resets the MAC to newly set the logical channel for the offload bearer and to set the mapping relationship between the logical channel and the transport channel managed by the MAC layer. In Table 1, re-establishing the RLC layer of the offload bearer by the UE means specifically performing the following operations.

[Terminal operation in re-establishment of RLC]

. Operation of receiving device

- Assemble assembled data among the data stored in the receive buffer and transmit it to the upper layer

- Discard the remaining data stored in the receive buffer, and initialize timers and variables. The timers and parameters of the RLC layer are as specified in Recommendation 36.322.

. Operation of transmitting apparatus

- Discard all data stored in the transmit buffer and initialize timers and variables

The fact that the UE re-establishes the PDCP of the offload bearer implies specifically the following operation.

[Terminal operation in PDCP re-establishment]

. Operation of receiving device

- Decryption of the data transmitted according to RLC re-establishment using the previous security key.

- When the decryption of the data is completed, the decryption apparatus is set to use a new security key

. Operation of transmitting apparatus

- Set up an encryption device to use the new secret key

When the SeNB is set, the MS reestablishes the MCG-MAC by releasing the logical channel of the offload bearer and releasing the mapping relationship between the logical channel and the transport channel. It means that a selective buffer flush is performed in the HARQ buffer. The selective buffer flush will be described later. When the SeNB is set up, the UE establishes the SeNB by creating a logical channel of the offload bearer, forming a mapping relationship between the logical channel and the transport channel, and generating a buffer status report and an available transmission report headroom report, and transmits the control information when uplink transmission to the SCG becomes possible in the future. When the SeNB is released, the UE releases the SCG-MAC by releasing the downlink buffer and the uplink buffer of the SCG-MAC, and performs a random access process, a buffer status report process, an available transmission output And an operation of canceling the reporting process and the like.

Table 2 shows the operations associated with multi-bearer re-establishment.

5, a connection structure of a PDCP apparatus in an LTE system according to an embodiment of the present invention is described. Referring to FIG. 6, when a SeNB is set or released in an LTE system according to an embodiment of the present invention, And the operation of the network will be described.

6 is a diagram schematically illustrating operations of a terminal and a network when a SeNB is established or released in an LTE system according to an embodiment of the present invention. Referring to FIG. 6, the LTE system includes a UE 605, a MeNB 607, and a SeNB 610.

In the LTE system including the UE 605, the MeNB 607 and the SeNB 610, the UE 605 performs radio resource control (RRC) with the MeNB 607 And reports the performance of the terminal 605 itself according to an instruction from the MeNB 607 (step 611). The performance information message includes information indicating in which frequency bands the UE 605 supports carrier aggregation. The information is SupportedBandCombination information, and the terminal 605 reports information on all band combinations related to the carrier aggregation supported by the terminal 605 in the SupportedBandCombination. Information indicating whether DC is supported in the band combination, and whether the SCG bearer / multiplex bearer is supported is also reported for each band combination reported in the SupportedBandCombination. The DC support is reported for each band combination angle that satisfies a predetermined condition. Therefore, the performance report message may include a plurality of DC support information. The SCG bearer / multiplex bearer support information is included only in the performance report message. For example, it is assumed that the terminal 605 reports band combinations using SupportedBandCombination as shown in Table 3 below.

The UE constructs 1-bit information indicating whether or not the DC support is supported for each band combination as shown in Table 4 and includes it in the control message. At this time, it is possible to exclude a band combination in which DC is not likely to be applied (for example, a band combination in which only one serving cell is set or a band combination in which a plurality of serving cells are set in the same band).

Since the DC support may be different for each band combination, it is reported separately for each band combination, but bearer support related information may be applied to all band combinations in which DC is supported. As described above, a UE to which bearer support is applied for all band combinations in which DC is supported constructs only one bearer support related information as shown in Table 5 and includes it in the control message. In other words, in the information of Table 5, the UE supporting the DC for at least one band combination includes the following information in the performance report message separately from the information indicating the DC support. The information shown in Table 5 below is composed of 2 bits or 2 bits of information, indicating whether to support SCG bearer setting and whether to support multi-bearer setting.

If only one of the two bits as shown in Table 5 is set to " YES ", it means that the terminal only supports the corresponding bearer setting, and if both bits are set to YES, This means that both bearer configurations are supported.

On the other hand, information indicating bearer setup support can be used to indicate whether the terminal supports SCG bearer setup or multi bearer setup. The information indicating whether the terminal supports the SCG bearer setup or the multi bearer setup may be composed of 1 bit, for example.

The UE reporting that DC is supported in at least one of the band combinations reports the bearer setup support indication information if it supports only the SCG bearer or only supports the multi bearer.

On the other hand, if the UE supporting the DC in at least one band supports both the SCG bearer and the multi bearer, the UE does not report the bearer setup support indication information.

Therefore, a combination of DC support information and bearer setup support information for each band combination indicates the following UE performance.

≪ Terminal performance indication based on a combination of DC support information and bearer setting support information per band combination >

The UE supports the SCG bearer setup by using two security keys, the first security key performs an encryption and decryption operation on the MCG bearer data, the second security key encrypts and decrypts the SCG bearer data, It is the ability to perform sharable operations.

The UE supports multi-bearer setup by connecting one PDCP device to two RLC devices to transmit / receive data.

A UE supporting both the SCG bearer and the multi bearer is referred to as an inter-operability test (IOT) for a bearer among the SCG bearer and the bearer bearer for each band combination supporting DC to the base station Quot;) has been completed. The IOT is an interworking test between a terminal and a network, and it is preferable that only the function that has passed the IOT is used. Since the IOT requires both a terminal and a network implemented at a commercial level, in a state where arbitrary functions are not widely implemented, the terminal may fail to perform the IOT even though it implements the function.

In particular, in the case of a DC applied to each band combination, if there is not yet a network that actually uses the band combination, or if only a SCG bearer and a multiple bearer are supported even if there is a network actually using the band combination, It is impossible to perform perfectly. Therefore, even if the UE supports both the multi-bearer and the SCG bearer, the IOT is performed only for one of the multi-bearer and the SCG bearer in an arbitrary combination of bands, and in the other bands combination, Band combination may perform only the IOT for the other bearer on which the IOT has been performed and another band combination may perform the IOT for both the multiplex bearer and the SCG bearer. At this time, if the UE does not separately report the IOT status according to the bearer setting to the BS, the BS can not know exactly which IOT for the bearer setup has been performed, so that there is a limitation in applying the DC operation.

Therefore, the UE can configure the performance information as follows by reflecting the IOT situation.

<Performance information reflecting IOT situation>

Also, the UE may report information indicating whether or not to support the asynchronous network operation together with the performance information through a performance report message. DC operation is limited by the constraint on the distance between sub-frame boundaries of the asynchronous network (the sub-frame boundary of the downlink signal between the serving cells is less than the predetermined reference, about 30 ms) So that the subframe boundaries of the two serving cells can be spaced up to 500 ms). In the synchronous network, the capacity of the signal receiving apparatus of the receiving RF circuit of the terminal can be designed considering a relatively small time difference, i.e., about 30 microseconds, but in the asynchronous network, Network, or may be operable in both synchronous and asynchronous networks. Therefore, the support of the asynchronous network by the UE means that it is possible to perform the multiple connection operation even if the difference of the subframe boundaries of the downlink signals of the serving cells is different by a predetermined time.

All terminals supporting DC operation should basically support operation in a synchronous network. Therefore, it is not necessary to separately report information indicating whether or not the synchronous network is supported to the base station.

Alternatively, the UE may not support the asynchronous network, so it is necessary to separately report the information indicating whether or not the asynchronous network is supported to the base station. The terminal can associate the information indicating whether the asynchronous network is supported or not with the IOT and display it for each band combination.

Hereinafter, an exemplary procedure for configuring terminal capability information related to DCs in an LTE system according to an embodiment of the present invention will be described with reference to FIG.

FIG. 7 is a diagram schematically illustrating an exemplary process of configuring terminal capability information related to a DC in an LTE system according to an embodiment of the present invention. Referring to FIG.

Referring to FIG. 7, the UE capability information includes information indicating whether a multi bearer is supported, information indicating whether the SCG bearer is supported, and the like.

The terminal capability information includes information on a band combination supported by the terminal (SupportedBandCombinationList) 708, a DCbandcombinationParameter 735 of the terminal, and dualConnectivityCapability 730.

The SupportedBandCombinationList includes at least one band combination parameter (BCP) 710, 715, 720, and 725. The BCP is information on each band combination supported by the UE. The BCP includes one or more band parameters (hereinafter referred to as BPs). The BP includes information indicating a band (FreqBandIndicator), a downlink band parameter bandParametersDL (hereinafter referred to as BPDL), and an uplink band parameter bandParametersUL (hereinafter referred to as BPUL). The BPDL includes a bandwidth class (bandwidthClass) indicating the number of serving cells supported by the corresponding band and antenna performance information. Here, the bandwidth class A represents performance capable of setting one serving cell using the maximum bandwidth of 20 MHz at maximum, the bandwidth class B represents the performance in which two serving cells can be set, and the total bandwidth is 20 MHz at maximum, Bandwidth class C indicates that the serving is capable of configuring two cells and the total bandwidth is up to 40 MHz.

The dualConnectivityCapability information includes information indicating whether the terminal supports SCG bearer setup (ScgBearerSupport), information indicating whether the terminal supports multi-bearer setup (SplitBearerSupport), information indicating whether the terminal supports operation in an asynchronous network (unsyncDeploySupport) .

Also, the unsyncDeploySupport may be configured such that the UE can receive a downlink subframe (hereinafter referred to as 'subframe x') of an arbitrary serving cell and a downlink subframe of a serving cell other than the arbitrary serving cell (For example, 0.5 ms) between the subframe x of the cell and the subframe nearest on the time axis (hereinafter, referred to as 'subframe y') becomes a predetermined value Can be performed. That is, even if the distance between the subframe boundary of the subframe x and the subframe boundary of the subframe y becomes maximum 0.5 ms, it indicates whether or not the terminal can perform the DC operation in the subframe x and the subframe y.

Also, the DCbandcombinationParameter includes at least one DCsupproted, and the number of DCsupproted is equal to the number of BCPs in the SupportedBandCombinationList. Any DCsupported is mapped on a one-to-one basis in order with the BCP. As an example, the first DCsupproted 740 is information about the first BCP 710. If the DCsupproted indicates 'Yes', it indicates that the terminal supports the DC in the band combination of the BCP corresponding to the DCsupproted and has completed the IOT for the DC operation in the band. At this time, specific details of the DC operation are as indicated in dualConnectivityCapability. That is, if dualConnectivityCapability supports SCG bearer setup and supports operation in an asynchronous network, then the band combination also supports the operation and means that the IOT for the operation is complete.

As another example, the number of DCsupproted may be equal to the number of BCPs that meet certain conditions. The condition is related to carrier aggregation, wherein a BCP satisfying a predetermined condition includes at least two band parameters or band entries, and at least two band entries are set uplink BCP. Alternatively, the BCP satisfying the predetermined condition may include one band entry, and the bandwidth class of the band entry may be a BCP indicating that the uplink configures at least two serving cells.

7, an example of a process of configuring terminal capability information related to a DC in an LTE system according to an embodiment of the present invention is described. Next, referring to FIG. 8, in an LTE system according to an embodiment of the present invention, Another example of the process of configuring the terminal capability information related to the DC will be described.

FIG. 8 is a diagram schematically illustrating another example of a process of configuring terminal capability information related to a DC in an LTE system according to an embodiment of the present invention. Referring to FIG.

Referring to FIG. 8, information indicating whether a multi-bearer is supported, information indicating whether a SCB bearer is supported or the like is signaled for each band combination.

The terminal capability information includes information on a band combination supported by the terminal (SupportedBandCombinationList) 708, and dual connection capability information (dualConnectivityCapability) 830.

The multiple connection capability information 830 includes at least one multiple connection capability (DCCapability) 845, 850. Here, the number of DCCapabilities included in the multiple connection capability information 830 is equal to the number of BCPs satisfying a predetermined condition. Wherein the predetermined condition is related to carrier aggregation, the BCP satisfying a predetermined condition includes at least two band parameters (BandParameters) or at least two band entries, and the BCP satisfying the predetermined condition is at least The two band entries may be a BCP with an uplink set. Alternatively, a BCP that satisfies the predetermined condition may include one band entry, which indicates that the bandwidth class of the band entry indicates at least two serving cells to which the uplink is set. Further, the BCP satisfying the predetermined condition is a BCP including at least two band entries.

On the other hand, the DCCapability is corresponded one-to-one according to the order in which the BCP satisfying the above conditions and the BCP are received. For example, DCCapability 845 corresponds to BandCombinationParameters 720 and DCCapability 850 corresponds to BandCombinationParameters 725.

The DCCapability includes at least three pieces of information, the first information includes information indicating whether the SCG bearer setting is supported and information indicating whether the IOT is performed, the second information includes information indicating whether the multi-bearer setting is supported, And the third information includes information indicating whether the operation is supported in the asynchronous network and information indicating whether to perform the IOT. That is, if the first information indicates the SCG bearer setup support and indicates the IOT performance, the UE supports the SCG bearer setup in the corresponding band combination and the IOT has been completed.

On the other hand, the DC operation includes transmitting the PUCCH in two serving cells. If DC is supported in any combination of bands, the terminal shall report to the base station which serving cell of the band combination it can transmit the PUCCH. As the number of band entries included in the band combination increases, the higher the bandwidth class, the more various band combinations are possible. To report which band combination supports the various band combinations, the signaling overhead may become extreme. For example, there is a band combination in which two serving cells can be set in band X, a band combination in which two serving cells can be set in band Y, and a band combination in which one serving cell can be set in band Z The number of cases of selecting two serving cells out of the five serving cells is 20 in total. 20 bits are required to indicate which band combination of the 20 band combinations the terminal supports PUCCH transmission. Considering that a terminal reports up to 128 band combinations, this overhead may be difficult to accommodate in terms of the terminal.

In one embodiment of the present invention, a band combination which can be most commonly used is defined without considering all the band combinations, and whether or not the band operation support is associated with the band combination support is determined. That is, if the UE reports that it supports the DC operation in an arbitrary combination of bands, the UE generates PUCCHs in the serving cells corresponding to 'two serving cell combinations' among 'two serving cell combinations' (Or PUCCH can be set). If another band combination other than the 'two serving cell basic combination' supports PUCCH transmission, it reports that the band combination other than the 'two serving cell basic combination' supports PUCCH transmission using new signaling.

The basic combination of two serving cells (hereinafter, referred to as 'basic combination') may be defined differently depending on the number of band entries, and will be described as follows.

(1) Basic combination for band combination with one band entry: All two serving cell combinations are the basic combination. For example, if an arbitrary BCP contains one band entry and the bandwidth class of the band entry indicates that it can support a maximum of three serving cells, then the possible band combination is [cell 1 + cell 2], [cell 1 + cell 3], and [cell 2 + cell 3], and the PUCCH can be set in all three band combinations.

(2) Basic combination of band combinations having two or more band entries: all band combinations including a serving cell of one band entry and a serving cell of a band entry other than the band entry are included in the basic combination. For example, in the band combination including the band X and the band Y, all two serving cell combinations including the serving cell of the band X and the serving cell of the band Y are the basic combination. That is, all the band combinations other than the band combination including only the serving cells belonging to one band entry are basic band combinations.

As described above, when there is one band entry, the basic performance is to transmit PUCCH in two serving cells formed in one band (or PUCCH is set in two serving cells), and if more than two band entries The basic performance for the band combination is that in one band, the PUCCH is transmitted in only one serving cell (or the PUCCH is set in one serving cell).

Meanwhile, in order to perform the DC operation, two groups of the serving cells must be configured. If DC is supported in any combination of bands, the UE shall report to the base station which serving cells of the band combination can be configured into the same serving cell group.

On the other hand, a message for defining all possible band combinations and reporting support for each of the possible band combinations may be remarkably large. Therefore, in one embodiment of the present invention, Define performance. The fact that an arbitrary terminal supports a DC in a predetermined band combination means that the DC supports the basic performance while supporting the DC.

Meanwhile, the basic performance can be defined differently for one band entry or for two or more band entries, which will be described in detail as follows.

(1) Basic performance for band combination with one band entry: all cases where serving cells are composed of two groups are supported. For example, if an arbitrary BCP includes a band entry and the bandwidth class of the band entry indicates that it can support a maximum of three serving cells, cell 1 is created as a group, cell 2 and cell 3 is created as another group (hereinafter, referred to as '[cell 1, cell 2 + cell 3]'), cell 1 and cell 2 are created as one group, and cell 3 is created as another group In case of generating, cell 1 and cell 3 are created as one group, and cell 2 is created as another group. That is, the basic performance for a band combination with one band entry means that it supports setting two cell groups within one band entry.

(2) Basic performance for band combinations with more than one band entry: All other cases are supported except that the serving cells of one band entry are set to two serving cell groups. For example, the basic performance of a band combination including band x, band y, and band z is as follows. One cell group is set as the serving cells of band x, and the remaining cell groups are set as the serving cells of band y and band z , One cell group is set as the serving cell of the band x and the band y, a remaining cell group is set as the serving cell of the band z, and one cell group is set as the serving cell of the band x and the band z , It is possible to set up a remaining cell group with the serving cells of the band y, but one cell group is set as a part of the serving cells of the band x and the rest of the serving cells of the band x and the remaining cells of the band y and the band z, When setting a group, etc. are not supported.

On the other hand, it is also possible to set the serving cell group and to transmit the two PUCCHs to one unit capability.

For example, if the terminal reports DC support in an arbitrary combination of bands, for example, if it reports terminal capability information including DC supported 740 for a corresponding band combination, the terminal determines DC basic performance .

The DC basic performance means a capability of the UE to form two cell groups satisfying a predetermined condition and to transmit PUCCH in each cell group.

The DC basic performance for any combination of bands may be defined differently depending on the number of band entries of the band combination.

(1) Multiple connections for a combination of bands having one band entry Basic performance: The UE can form two cell groups based on a combination of cells satisfying the condition A, and the uplink among the serving cells included in each cell group The PUCCH can be set and transmitted in any serving cell in which the link is established. The condition A can be satisfied if a serving cell group is formed such that at least one serving cell is set uplink.

Hereinafter, an example of DC basic performance in an LTE system according to an embodiment of the present invention will be described with reference to FIG.

9 is a diagram schematically illustrating an example of DC basic performance in an LTE system according to an embodiment of the present invention.

Referring to FIG. 9, it is assumed that supporting all seven cases of forming two serving cell groups as shown in FIG. 9, for example, a band entry that can be set up to four serving cells is DC basic performance . In FIG. 9, it is assumed that uplink is set in all serving cells. For example, in FIG. 17, it is assumed that the downlink bandwidth class and the uplink bandwidth class are both bandwidth classes indicating that four serving cells are supported.

(2) DC basic performance for a band combination having at least two band entries: In forming two cell groups, it represents the ability to form a cell group for all band combinations satisfying the following condition.

A) Serving cells included in the same band are not included in different cell groups. That is, one cell group is associated with one or more band entries, and a bend entry associated with one cell group is not associated with another cell group.

B) The uplink is set up in at least one serving cell of each cell group. That is, when one cell group is associated with n band entries, at least one band entry is a band entry in which BPUL is set.

C) PUCCH setup / transmission is possible in one serving cell of each cell group.

On the other hand, the DC basic performance for any combination of bands can be defined as follows.

(1) If DCsupported is included for any combination of bands (or DCsupported is signaled), and if the arbitrary combination of bands is composed of one band entry, the basic performance of the terminal for the arbitrary band combination is Lt; RTI ID = 0.0 &gt; D &lt; / RTI &gt; That is, the UE supports two cell groups set to satisfy the condition D. Here, the above condition D can be defined as follows.

<Condition D>

Two cell groups are set for the corresponding band entry (or the band indicated by the corresponding band entry), and the condition D is satisfied when the serving cells included in each cell group are continuous with each other in the frequency domain.

The serving cell 1 and the serving cell 2 are continuous with each other in the frequency domain, and thus the frequency band of the serving cell 1 and the serving cell 1 are the same, The frequency band of cell 2 is continuous except for the guard band.

Hereinafter, another example of DC basic performance in an LTE system according to an embodiment of the present invention will be described with reference to FIG.

21 is a diagram schematically illustrating another example of DC basic performance in an LTE system according to an embodiment of the present invention.

21, setting two cell groups as shown in reference numeral 2105, for example, setting cell 1 as one cell group, and setting cells 2, 3, and 4 as another cell group, Setting cell group 2 to one cell group, and setting cells 1, 3, and 4 to another cell group satisfy condition D Do not.

(2) if the DC combination is included for any combination of bands (or DC supported is signaled), and if the arbitrary band combination is composed of two band entries, Two cell groups are set so that condition E is satisfied for an arbitrary combination of bands. That is, the UE supports two cell groups set to satisfy the condition E. Here, the above condition E can be defined as follows.

<Condition E>

When one cell group is set per one band entry (or a band indicated by the band entry), the condition E is satisfied.

Hereinafter, another example of DC basic performance in an LTE system according to an embodiment of the present invention will be described with reference to FIG.

22 is a diagram schematically illustrating another example of DC basic performance in an LTE system according to an embodiment of the present invention.

Referring to FIG. 22, two cell groups are set as shown in reference numeral 2205. For example, cell 1 and cell 2 included in band 1 are set as one cell group, and cell 3 And cell 4 to another cell group satisfies condition E, but setting two cell groups as reference numeral 2210, for example, setting cell 1 as one cell group, and setting cells 2, 3, Setting 4 to another cell group does not satisfy condition E.

A description will now be made of a method in which a UE reports cell group performance when the number of band entries is two or more.

First, when the number of band entries is two or more, the serving cell or carrier of one band entry belongs to only one cell group. That is, the serving cell / carrier of one band entry does not belong to two or more serving cell groups. Thus, for example, if the number of band entries is two, then the number of possible cell group combinations is one. Alternatively, if the number of band entries is three or more, for example, the number of possible cell group combinations is two or more, that is, a plurality, and the terminal may support only a part of the plurality of possible cell group combinations. If the terminal only supports the synchronous operation in the band combination, the terminal supports all the cell group combinations. Alternatively, if the terminal supports the asynchronous operation in the corresponding band combination, the terminal may support only a part of the cell group combinations.

Meanwhile, the terminal uses an indicator or a bitmap to indicate whether asynchronous operation is supported for each band combination in which DC is supported. For the sake of convenience of explanation, the indicator for indicating whether or not to support the asynchronous operation is referred to as an 'asynchronous operation support indicator', and the asynchronous operation support indicator may be implemented as one bit, for example. Here, the bit map may be embodied to include at least two bits, and the number of bits included in the bit map is not limited.

Hereinafter, the asynchronous operation support indicator will be described in detail as follows.

In order to indicate whether or not to support an asynchronous operation for an arbitrary combination of bands, the asynchronous operation support indicator is included in the band combination having one or two band entries, or the asynchronous operation support indicator is included This indicates whether the band combination supports asynchronous operation. For example, the asynchronous operation is supported in the case of a combination of bands including the asynchronous operation support indicator, and the asynchronous operation is not supported in the case of a band combination in which the asynchronous operation support indicator is not included.

Next, for a band combination having three or more band entries, the asynchronous operation support indicator is included to indicate that all possible cell group combinations are supported in the corresponding band combination, or the bit map is included to indicate that the corresponding band combination Indicates that only a part of possible cell group combinations are supported, or does not include both the asynchronous operation support indicator and the bitmap, thereby indicating that the corresponding band combination does not support the asynchronous operation. This will be described in detail as follows.

First, if a terminal supports only a part of all possible cell group combinations for a combination of bands having three or more band entries, the terminal determines all possible cell group combinations based on a bit map defined according to a predetermined rule Indicating which cell group combination is supported.

For example, for a band combination comprising three band entries including band A, band B, and band C, the possible cell group combinations are as follows.

Possible cell group combination 1: [a cell group including a carrier / serving cell of band A, a cell group including a carrier / serving cell of band B and band C]

Possible cell group combination 2: [cell group including carrier / serving cell of band A and band B, cell group including carrier / serving cell of band C]

Possible cell group combination 3: [cell group including carrier / serving cell of band B, cell group including carrier / serving cell of band A and band C]

In this case, the terminal indicates which cell group combination among the possible cell group combinations is supported based on the bit map implemented with 3 bits.

If the number of the band entries is 4, there are seven possible cell group combinations as shown below, and the UE indicates which cell group combination among the possible cell group combinations is supported based on the bit map implemented with 7 bits .

Possible cell group combination 1: [cell group including carrier / serving cell of band A, cell B including band B, band C and band D carrier / serving cell]

Possible cell group combination 2: [configured cell group including carrier / serving cell of band A and band B, carrier / serving cell of band C and band D]

Possible cell group combination 3: [configured cell group comprising carrier / serving cell of band A and band C, composed cell group comprising carrier / serving cell of band B and band D]

Possible cell group combination 4: [configured cell group including carrier / serving cell of band A and band D, carrier / serving cell of band B and band C]

Possible cell group combination 5: [configured cell group including carrier / serving cell of band A, band B and band C, cell / group of carrier of band band D]

Possible cell group combination 6: [Cell group including carrier / serving cell of band A, band B and band D, constituted cell group including carrier / serving cell of band B]

Possible cell group combination 7: [Cell group including carrier / serving cell of band A, band C and band D, carrier / serving cell of band band B]

Also, if the number of band entries is 5, there are 15 possible cell group combinations as below, and the UE indicates which cell group combination is supported based on the bit map implemented with 15 bits.

Possible cell group combination 1: [Cell group including carrier / serving cell of band A, band B, band C, band D, and cell E containing carrier / serving cell of band E]

Possible cell group combination 2: [cell group including carrier / serving cell of band A and band B, carrier group / serving cell of band C, band D and band E]

Possible cell group combination 3: [cell group including carrier / serving cell of band A and band C, band B, cell group containing carrier / serving cell of band D and band E]

Possible cell group combination 4: [Cell group including carrier / serving cell of band A and band D, band B, carrier group of band C and band E]

Possible cell group combination 5: [Cell group including carrier / serving cell of band A and band E, band B, cell group containing carrier / serving cell of band C and band D]

Possible cell group combination 6: [Cell group including carrier / serving cell of band A, band B and band C, cell group containing carrier / serving cell of band D and band E]

Possible cell group combination 7: [cell group including carrier / serving cell of band A, band B and band D, cell group including carrier / serving cell of band C and band E]

Possible cell group combination 8: [cell group including carrier / serving cell of band A, band B and band E, cell group including carrier / serving cell of band C and band D]

Possible cell group combination 9: [Cell group including carrier / serving cell of band A, band C and band D, carrier / serving cell of band B and band E]

Possible cell group combination 10: [cell group including carrier / serving cell of band A, band C and band E, carrier group / serving cell of band B and band D]

Possible cell group combination 11: [cell group including carrier / serving cell of band A, band D and band E, cell group including carrier / serving cell of band B and band C]

Possible cell group combination 12: [cell group including carrier / serving cell of band A, band C, band D and band E, carrier group / serving cell of band B]

Possible cell group combination 13: [cell group including carrier / serving cell of band A, band B, band D and band E, carrier group / serving cell of band C]

Possible cell group combination 14: [cell group including carrier / serving cell of band A, band B, band C and band E, carrier group / serving cell of band D]

Possible cell group combination 15: [cell group including carrier / serving cell of band A, band B, band C and band D, carrier group / serving cell of band E]

In summary, the UE generates performance information according to the number of band entries as shown in the following table, and reports the generated performance information to the BS.

<Indication whether cell group combination is supported according to the number of band entries>

Hereinafter, another example of DC basic performance in an LTE system according to an embodiment of the present invention will be described with reference to FIG.

10 is a diagram schematically illustrating another example of DC basic performance in an LTE system according to an embodiment of the present invention.

10, cases 4, 5, 6, 10, 11, 12 and 13 are not included in the DC basic performance in the case of a band combination including three bands and four serving cells, .

As described above, the DC basic performance for a band combination having a single band entry is the ability to set / transmit a PUCCH in two serving cells formed in the band, and a band combination of two or more band entries (Or a combination of bands composed of two or more bands) can set / transmit a PUCCH in one serving cell formed in each band entry (or band) (i.e., PUCCH , And can set / transmit PUCCH in two band entries (or bands) in total.

If DCsupported is marked as 'True' for any combination of bands, DC basic performance is supported for that band combination. The number of DCsupported corresponds to the BandCombinationParameters (see Specification 36.331) of supportedBandCombination (see Specification 36.331) and BandCombinationParameters (see Specification 36.331) of supportedBandCombinationAdd (see Specification 36.331), and DCsupported corresponds first to the BandCombinationParameters of supportedBandCombination and the supportedBandCombinationAdd Corresponds later with BandCombinationParameters. For example, if supportedBandCombination consists of n BandCombinationParameters and supportedBandCombinationAdd consists of m BandCombinationParameters, the first DCsupported corresponds to the first band combination of supportedBandCombination and the nth DCsupported corresponds to the last band combination of supportedBandCombination. [n + 1] th DCsupported corresponds to the first band combination of supportedBandCombinationAdd, and [n + m] th DCsupported corresponds to the last band combination of supportedBandCombinationAdd.

Meanwhile, the terminal capability information is transmitted according to the request of the base station. When an arbitrary terminal establishes an RRC connection, the base station attempts to acquire performance information of the terminal from the MME once.

If the MME does not acquire the capability information of the UE, it transmits a predetermined control message to the UE and instructs the UE to transmit a performance report message to the UE. The control message includes information indicating whether a performance report for a radio access technology (RAT) is required, and the terminal has an advanced general-purpose terrestrial wireless access (E-UTRA: (hereinafter, referred to as &quot; E-UTRA &quot;), a performance report control message including information on supported band such as DC support is generated and transmitted to a base station (Step 611).

After that, the base station sets E-UTRA communication of the terminal appropriately and performs data transmission / reception with reference to the performance of the terminal. If the terminal is sufficiently close to the small cell at a certain point in time and it is determined that the traffic demand of the terminal is sufficiently high, the base station determines to additionally set the small cell to the terminal.

The MeNB 607 transmits a SeNB addition / modification indication control message to the SeNB 610 in step 612. The control message includes current configuration information of the terminal (AS-config, refer to Specification 36.331), EPS bearer setup information set in the terminal, setup information requested to the SeNB, and the like. The configuration information requested to the SeNB includes, for example, information indicating which bearer among the currently set EPS bearers is to be offloaded to the SeNB, information indicating the type of the bearer desirable for the offload bearer among the SCB bearer and the multi bearer have.

The SeNB 610 receiving the control message determines whether to accept the request. The current load situation and the nature of the bearer for which the offload is requested can be used to determine whether to accept the request. The SeNB 610 selects the serving cells to be allocated to the UE 605 and transmits information related to the serving cell such as frequency information of the serving cell (EARFCN, see 36.331) (For example, downlink bandwidth information, downlink HARQ feedback channel setting information (hereinafter, referred to as &quot; downlink bandwidth &quot;) information of a serving cell, information on a physical cell identification (PCI) Etc.), uplink related information of the serving cell (e.g., uplink bandwidth information, PUCCH setting information, etc.). In addition, the SeNB 610 performs operations related to the offload bearer (step 614). If the offload bearer is to be set up as an SCG bearer, the SeNB 610 generates a PDCP device and an RLC device for the SCG bearer. If the offload bearer is to be set to a multiple bearer, then the SeNB 610 creates an RLC entity for the multiple bearer. The SeNB 610 also generates a MAC device for the offload bearer.

The SeNB 610 generates and transmits a SeNB modification request message to the MeNB 607 (step 616). The SeNB change request message includes information related to a serving cell to be added to the MS 605, information related to an offload bearer setup, and the like.

Upon receipt of the SeNB change request message, the MeNB 607 determines whether or not to perform scheduling according to the type of the offload bearer. If the offload bearer is an SCG bearer, the MeNB 607 stops downlink data transmission to the bearer. If the offload bearer is a multi-bearer, the MeNB 607 continues to perform downlink data transmission to the bearer without stopping.

In step 620, the MeNB 607 transmits an RRC connection reconfiguration message to the UE 605 to add a small cell to the UE 605 and to reset the offload bearer. SCR setting information and offload bearer information are stored in the RRC connection re-establishment message. 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 offload bearer information is information on a radio bearer which is reset from the MCG bearer to the SCG bearer or the multi bearer, and the identifier information of the radio bearer, the type of the offload bearer (SCG bearer or multiplex bearer) It contains the same information.

The off-load bearer resetting information is shown in Table 6. The terminal 605 receiving the RRC connection re-establishment message performs an off-load bearer re-setting operation (step 625). In particular, the UE supporting both the SCG bearer and the multi bearer performs one of the two operations as shown in Table 7 according to whether the bearer is reset in the RRC connection reestablishment message.

Table 7 describes the offload bearer reset operation 1, i.e., the offload bearer reset operation performed by the UE supporting both the SCG bearer and the multiple bearer, depending on whether the bearer is reset in the RRC connection reestablishment message The terminal 605 transmits an RRC control message, i.e., an RRC connection reconfiguration complete message, to the MeNB 607 when the reloading operation of the offload bearer and the SCell adding operation are completed 627). Upon receiving the RRC connection reconfiguration completion message, the MeNB 610 forwards the data of the offload bearer to the SeNB 610 in step 630. In the case of re-establishment to the SCG bearer and re-establishment to the multi-bearer, the MeNB 607 forwards the first downlink PDCP SDU that the RLC entity has not confirmed successful transmission to the SeNB 610. In the case of re-establishment to the SCG bearer, the MeNB 607 also forwards the uplink PDCP SDUs successfully received in the RLC device to the SeNB 610. [

In step 635, the UE 605 performs a random access operation in the PSCell of the newly added SCG SCell separately from the completion report procedure. Through the random access operation, the UE 605 establishes uplink synchronization with the newly added SCG SCell and sets an uplink transmission output. When the random access operation is completed, the terminal 605 sets the PSCell to the active state and performs the offload bearer data transmission / reception operation (Step 637). The terminal 605 performs one of two operations as shown in Table 8 according to the type of bearer set.

Table 8 shows the offload bearer data transmission / reception operation performed according to the offload bearer data transmission / reception operation 1, that is, the type of the set bearer.

Thereafter, the UE 605 transmits and receives a part of the MCG bearer data and the multi-bearer data through the MCG, and transmits a part of the SCG bearer and the multi-bearer data through the SCG (Step 640).

The MeNB 607 or the SeNB 610 reconfigures the SCG bearer or the multiple bearer of the UE 605 as an MCG bearer when the UE 605 moves out of the small cell area or does not need to apply the DC operation , And decides to release the SCG serving cells. If the MeNB 607 makes the decision, the MeNB 607 transmits a SeNB addition / modification indication control message to the SeNB 610 to request release of the SCG serving cells . If the SeNB 610 directly makes the decision, the SeNB 610 proceeds directly to step 643. [

In step 643, the SeNB 610 generates and transmits a SeNB modification request control message to the MeNB 607. The SeNB change request control message includes information indicating the SCG removal. The SeNB 610 may deactivate the SCG serving cells and stop the downlink transmission of the offload bearer before transmitting the SeNB change request control message.

In step 645, the MeNB 610 performs an offload bearer-related operation 2. The MeNB 610 resets the offload bearer if all of the SCG serving cells are to be released. If the offload bearer is an SCG bearer, the SCG bearer is reset to the MCG bearer, the MCG bearer is connected to the MAC device, and if the offload bearer is a bearer, a predetermined timer is driven to stop the PDCP reordering operation .

In step 650, the MeNB 610 generates an RRC control message instructing the release of the SCG serving cell, that is, an RRC connection re-establishment message, and transmits the RRC control re-establishment message to the UE 605. If the SCN serving cell is completely released (or the SeNB is released) by the RRC connection re-establishment message, the SCG bearer and the multiple bearer are reset to the MCG bearer even if there is no separate control information indicating the bearer re-establishment in the SeNB change request message . Specifically, the terminal 605 proceeds to step 655 to perform the offload bearer reset operation 2. The terminal 605 performs one of the following two operations according to the kind of the bearer to be reset as shown in Table 9 below.

In Table 9, the offload bearer reset operation 2, that is, the offload bearer reset operation performed according to the type of the bearer to be reset, is described. In step 660, the terminal 605 transmits a predetermined RRC control message, an RRC connection reconfiguration completion message To the MeNB 607 to report the release of the SCG serving cells and the completion of the bearer reset. In step 647, the SeNB 610 forwards the data of the offload bearer to the MeNB 607. The reordering from the SCG bearer to the MCG bearer and the re-establishment from the multi bearer to the MCG bearer Both the SeNB 610 forwards the successfully received uplink PDCP SDUs to the MeNB 607. In the case of re-establishment from the SCG bearer to the MCG bearer, the SeNB 610 forwards the first downlink PDCP SDU to the MeNB 607 that the RLC entity has not confirmed successful transmission.

In step 665, the terminal 605 performs the offload bearer data transmission / reception operation 2. The terminal 605 performs one of two operations as shown in Table 10 according to the type of the bearer to be reset.

Table 10 shows the operation 2 of the offload bearer data transmission / reception.

The operation of operation 660 and operation of operation 665 may be performed independently of each other, and the temporal relationship between the operations may be mutually changed.

6, the UE 605 performs a single connectivity operation to transmit and receive all data through the MCG in step 670. Meanwhile, in the LTE system according to an embodiment of the present invention, It should be understood that various modifications may be made to FIG. 6, even though the operation of the terminal and the network is shown when set or released. As an example, although successive steps are shown in FIG. 6, it is understood that the steps described in FIG. 6 may overlap, occur in parallel, occur in different orders, or occur multiple times.

FIG. 6 illustrates operations of a terminal and a network when the SeNB is set or released in the LTE system according to an embodiment of the present invention. Referring to FIG. 11, in the LTE system according to an embodiment of the present invention, Will be described.

11 is a diagram schematically illustrating a process of changing an SeNB in an LTE system according to an embodiment of the present invention.

Referring to FIG. 11, the LTE system includes a terminal 605, a MeNB 607, a previous SeNB 610, and a new SeNB 1109.

First, since a terminal performing a dual connectivity with one SeNB is physically moved, it may be necessary to change multiple connections with a new SeNB. For example, if the UEs performing the multiple connection through the MeNB 607 and the SeNB 610 are out of coverage of the current SeNB 610 at any point in time, And notifies the user of this. Based on the measurement result of the UE, MeNB recognizes the channel quality deterioration of the current SCG and decides to establish a connection with the new SeNB 1109 and the SCG.

The MeNB 607 transmits an SeNB addition / change indication control message requesting the SCN addition and the bearer setup to the new SeNB 1109 (step 1115). The SeNB addition / change display control message includes a control message as described in step 612 including the current configuration information of the terminal (AS-config, specification 36.331), EPS bearer setup information set in the terminal, and configuration information requested to the SeNB And includes the same kind of information.

Upon receiving the SeNB addition / change display control message, the new SeNB 1109 determines whether to accept the SeNB addition request. The current load condition and the nature of the bearer for which the offload is requested. If the SeNB addition request is to be accepted, the new SeNB selects the serving cells to be allocated to the UE and transmits information related to the serving cell, for example, frequency information of the serving cell (EARFCN, see 36.331) (for example, downlink bandwidth information, downlink HARQ feedback channel setting information, etc.), uplink-related information of a serving cell (e.g., uplink bandwidth information, PUCCH setting information, etc.). Also, the SeNB performs an operation related to the offload bearer (step 1117). If the offload bearer is an SCG bearer, the SeNB creates a PDCP device and an RLC device for the SCG bearer. If the offload bearer is a multiple bearer, the SeNB creates an RLC device for the multiple bearer. SeNB creates a MAC device for the offload bearer of the UE. The new SeNB 1109 generates and transmits a SeNB modification request control message to the MeNB 607 in step 1120. The SeNB change request control message includes information related to a serving cell to be added to the UE, information related to an offload bearer setup, and the like.

The MeNB 607 that has completed the process of adding the new SeNB 1109 and the SCG addition and offload bearer transmits SeNB 610 to the previous SeNB 610 in order to release the SCG and the offload bearer of the previous SeNB 610 (SeNB addition / modification indication) control message (step 1125).

Upon receiving the SeNB addition / change display control message, the previous SeNB 610 generates and transmits a SeNB modification request control message to the MeNB 607 (step 1130). The SeNB change request control message includes information requesting to remove the serving cell. The previous SeNB 610 may deactivate the SCG serving cells and stop the downlink transmission of the offload bearer before transmitting the SeNB change request control message in step 1127.

The previous SeNB 610 forwards the data to the MeNB 607 (step 1131). Both the SCG bearer to MCG bearer re-establishment and the re-establishment from the multi bearer to the MCG bearer forward the uplink PDCP SDUs successfully received from the RLC device to the MeNB. In the case of re-establishment from the SCG bearer to the MCG bearer, the previous SeNB 610 forwards the first downlink PDCP SDU to the MeNB 607 that the RLC entity has not confirmed successful transmission.

The MeNB 607 forwards the data received from the previous SeNB 610 to the new SeNB 1109 (step 1133).

The MeNB 607 releases the current SCG / SeNB to the terminal 605, adds a new SCG / SeNB, and transmits an RRC connection re-establishment control message to the UE for instructing the re-establishment of the offload bearer in step 1135. The RRC connection re-establishment message includes information indicating the current SCG / SeNB release and information indicating a new SCG / SeNB setting. The information indicating the current SCG / SeNB release may be, for example, information for releasing all the SCells belonging to the SCG among the currently set SCells, the information indicating the new SCG / SeNB setting may be information for indicating a new SCell setting And information indicating that the new SCell belongs to the SCG. The control message may also include offload bearer information. The offload bearer information is information instructing to reset the offload bearer from the SCN bearer of the previous SeNB to the new SeNB's SCG bearer or to re-establish from the multiple bearer of the previous SeNB to the new bearer of the new SeNB, Lt; / RTI &gt; can be signaled. The terminal 605 resets the offload bearer according to the reset information if offloaded bearer reset information is included, and if the offloaded bearer reset information is not included, applies the previous bearer setting to reset the offloaded bearer (Step 1137). Off-load bearer reset operation 3 is as shown in Table 11 below.

The terminal 605 performs one of two operations as shown in Table 11 according to the resetting state.

In Table 11, the offload bearer reset operation 3 is described.

Upon completion of the reloading operation of the offload bearer and the SCell addition operation, the UE 605 transmits an RRC control message, i.e., an RRC connection reconfiguration completion message, to the MeNB 607 in step 1145.

The UE 605 performs random access in the PSCell of the newly added SCG SCell independent of the completion report procedure (step 1140). Through the random access procedure, the UE 605 establishes uplink synchronization with the newly added SCG SCell and sets an uplink transmission output. Upon completion of the random access procedure, the UE 605 sets the PSCell to an active state and performs an off-load bearer data transmission / reception operation 3 as shown in Table 12 (Step 1147).

The terminal 605 performs one of the following two operations as shown in Table 12 according to the state in which the terminal 605 is reset.

The UE 605 transmits and receives part of the MCG bearer data and the multi bearer data through the MCG, and transmits the data and the data of the SCG bearer through the SCG to the UE 605. [ And performs a DC operation of transmitting and receiving a part of the multi-bearer data (step 1150).

Although FIG. 11 illustrates a process of changing the SeNB in the LTE system according to an embodiment of the present invention, various modifications may be made to FIG. In one example, although the sequential steps are shown in FIG. 11, it is understood that the steps described in FIG. 11 may overlap, occur in parallel, occur in different orders, or occur multiple times.

FIG. 11 illustrates a process of changing the SeNB in the LTE system according to an embodiment of the present invention. Referring to FIG. 12, in the LTE system according to an embodiment of the present invention, Will be described below.

FIG. 12 is a diagram schematically illustrating a UE operation for triggering and transmitting a PDCP status report when an offload bearer is reset in an LTE system according to an embodiment of the present invention. Referring to FIG.

Prior to description of FIG. 12, the PDCP status report transmitted from the terminal to the base station reports the reception status of the downlink PDCP SDU, and the base station retransmits the PDCP SDU with reference to the PDCP status report. Therefore, the format of the PDCP status report in the LTE system according to an embodiment of the present invention will be described with reference to FIG.

13 is a diagram schematically illustrating a format of a PDCP status report in an LTE system according to an embodiment of the present invention.

Referring to FIG. 13, the PDCP status report includes a D / C field 1305, a PDU type field 1310, an FMS field 1315, and a BITMAP field 1320. The D / C field 1305 is a field indicating whether the PDCP packet is a data packet or a control packet.

The PDU type field 1310 is included only in the control packet and indicates the type of the control packet. If the field value of the PDU type field 1310 is '000', it indicates a PDCP status report. The FMS field 1315 indicates a serial number of a first non-receiving PDCP service data unit (SDU).

The BITMAP field 1320 indicates whether or not PDCP SDUs corresponding to a subsequent sequence number are received based on the FMS field 1315. The bit position of the corresponding bitmap is information on a PDCP SDU of a predetermined serial number, and if the bit is 0, it indicates that the corresponding PDCP SDU is not present in the receiving apparatus,

Referring back to FIG. 12, in step 1205, the UE receives an RRC control message for instructing a bearer reset, and proceeds to step 1210.

In step 1210, the UE checks whether the bearer reset is related to the SCG bearer or the multi bearer. Here, the reset associated with the SCG bearer means that the MCG bearer is reset to the SCG bearer, the SCG bearer is reset to the MCG bearer, or the SCG bearer is reset to the SCG bearer. Also, the reset associated with the multi-bearer means that the MCG bearer is reset to a multi-bearer, a multi-bearer is reset to an MCG bearer, or a multi-bearer is reset to a multi-bearer.

If it is determined in step 1210 that the SCG bearer is associated with the SCG bearer, the MS proceeds to step 1215. Otherwise, the MS proceeds to step 1240. In step 1240,

In step 1215, the UE waits until the PDCP is re-established in accordance with the re-establishment. When the PDCP is re-established and the RLC device delivers the PDCP packet, the UE processes the PDCP packets as a PDCP SDU, And stores the SDUs in the PDCP buffer. The UE triggers a PDCP status report and generates a PDCP status report in consideration of PDCP SDUs transferred to an upper layer in order with PDCP SDUs stored in the PDCP buffer.

In step 1220, the UE determines whether the bearer re-establishment corresponds to one of the following four cases.

. When a bearer reset and SeNB addition are performed together: a reset is performed with respect to the SCG bearer by one control message, and SeNB is added. Adding SeNB means adding the first SCG serving cell.

. If the bearer reset and SeNB release are performed together: a reset is performed with respect to the SCG bearer by one control message, and SeNB is released. Disabling SeNB means that the last SCG serving cell is released.

. If the bearer reset and the SeNB change proceed together: a reset is performed with respect to the SCG bearer by one control message, and the SeNB is changed. The change of SeNB means that all the serving cells of one SCG are released and the serving cell of the new SCG is added.

. If the bearer is reset but the SeNB is maintained: only a reset associated with the SCG bearer is performed by one control message, and SeNB or SCG add / release / change are not performed.

If it is determined in step 1220 that the SeNB is released, the MS proceeds to step 1225. If the SeNB is maintained, the BS proceeds to step 1230. If the SeNB is added or changed,

In step 1225, when the UE is enabled to transmit a new uplink in the MCG serving cell, the UE transmits a PDCP status report through the MCG serving cell.

In step 1230, when the UE is enabled to transmit a new uplink in the SCG serving cell, the UE transmits a PDCP status report through the SCG serving cell.

In step 1235, after receiving at least the random access response message during the random access procedure in the PSCell, the UE transmits a PDCP status report through the SCG serving cell. The PDCP status report is transmitted using an uplink grant allocated in a random access response message or an uplink grant allocated on a physical downlink control channel (PDCCH).

In step 1240, the UE checks whether the bearer reset corresponds to any of the four cases.

If the SeNB is changed, the MS proceeds to step 1245. If the SeNB is released, the MS proceeds to step 1255. If the SeNB is added or maintained, the MS proceeds to step 1260.

First, if the SeNB is changed and the process proceeds to step 1245, a PDCP status report is triggered because it is necessary to receive a PDCP SDU that has not been received in the previous SeNB. When the SeNB is changed, the UE re-establishes the SCG-RLC, and the UE triggers a PDCP status report when one of the RLCs associated with the PDCP is re-established (or when the SCG-RLC is re-established). After processing the PDCP packets transmitted from the SCG-RLC into the PDCP SDUs, the PDCP SDUs of the order are delivered to the upper layer and the PDCP SDUs of the unordered PDCP SDUs are stored in the PDCP buffer. In step 1245, the UE generates a PDCP status report in consideration of the PDCP SDUs transferred to the upper layer by aligning the order with the PDCP SDUs stored in the PDCP buffer.

In step 1250, when the UE is enabled to transmit a new uplink in the MCG serving cell, the UE transmits a PDCP status report through the MCG serving cell. When SeNB is changed, random access is performed in the new PSCell. And the multiplex bearer transmission in the SCG serving cell is possible after the random access procedure is completed. The UE does not wait until the random access of the PSCell is completed, but transmits the PDCP status report in the MCG serving cell. Alternatively, it is also possible to transmit a PDCP status report in a serving cell in which a new uplink transmission to the multi-bearer is possible, out of the MCG serving cell and the SCG serving cell.

On the other hand, if the SeNB is released and the terminal proceeds to step 1255, the PDCP status report is triggered because it is necessary to receive a PDCP SDU that was not received by the SeNB. When the SeNB is released, the UE releases the SCG-RLC, and the UE triggers a PDCP status report when one of the RLCs associated with the PDCP is released (or the SCG-RLC is released). After processing the PDCP packets transmitted from the released SCG-RLC into the PDCP SDUs, the PDCP SDUs with the ordered PDUs are delivered to the upper layer, and the unordered PDCP SDUs are stored in the PDCP buffer. In step 1255, the UE generates a PDCP status report in consideration of the PDCP SDUs transmitted to the upper layer by aligning the order with the PDCP SDUs stored in the PDCP buffer.

In step 1260, when the UE is enabled to transmit a new uplink in the MCG serving cell, the UE transmits a PDCP status report through the MCG serving cell.

If SeNB is maintained or SeNB is added, the PDCP packet retransmission requesting process is not required and the UE does not trigger the PDCP status report in step 1265. [

Meanwhile, although FIG. 12 illustrates a terminal operation for triggering and transmitting a PDCP Status Report when an offload bearer is reset in an LTE system according to an embodiment of the present invention, various modifications may be made to FIG. In one example, although the sequential steps are shown in FIG. 12, it is understood that the steps described in FIG. 12 may overlap, occur in parallel, occur in different orders, or occur multiple times.

Referring to FIG. 14, a description will now be made of an operation procedure of a base station for receiving a PDCP status report and retransmitting PDCP data in an LTE system according to an embodiment of the present invention.

FIG. 14 is a diagram schematically illustrating an operation procedure of a base station for receiving a PDCP status report and retransmitting PDCP data in an LTE system according to an embodiment of the present invention. Referring to FIG.

Prior to describing FIG. 14, as described above, the base station starts retransmission from the first unconfirmed packet even before receiving the PDCP status report. This early retransmission scheme is useful in terms of seamless data transmission.

However, robust header compression (ROHC) (hereinafter referred to as 'ROHC') may also be reset while an arbitrary bearer is re-established from a multi-bearer to a multi-bearer. A representative example thereof is a case where a reconfiguration from a multi-bearer to a multi-bearer and a handover are simultaneously performed. In this case, the base station may include the ROHC initialization packet (IR) (see RFC 3095) in the first unconfirmed packet for transmission. If the UE has already received the first non-affirmation packet, the UE may discard the first non-affirming packet and thus the ROHC initialization may fail.

According to an embodiment of the present invention, in order to prevent the above-described situation from occurring, it is proposed that when a predetermined condition is satisfied, a retransmission operation is started after receiving a PDCP status report without performing an early retransmission method, This will be described in detail with reference to FIG.

14, it is assumed that the PDCP transmitting apparatus is a base station, but it is needless to say that the PDCP transmitting apparatus may be a terminal.

First, the PDCP transmitting apparatus detects that it is time to transmit data for the first time after the handover is started in step 1405, and proceeds to step 1410. A time point at which data can be transmitted for the first time after the handover is initiated is a point of time when a random access is completed in a target cell in the case of a UE and a dedicated preamble is received from a UE in a case of a BS. May be received.

In step 1410, the PDCP transmitting apparatus checks whether ROHC initialization occurs in the target cell. Here, if the handover is a normal handover, ROHC initialization is performed. If the source base station and the target base station can exchange ROHC contexts, the ROHC context may be used without being initialized. If it is determined that the ROHC initialization is not performed, the PDCP transmitting apparatus proceeds to step 1415. In step 1415, the PDCP transmitting apparatus starts an early retransmission operation.

If it is determined in step 1410 that the ROHC initialization has occurred, the PDCP transmitting apparatus proceeds to step 1420. In step 1420, the PDCP transmitting apparatus checks whether the corresponding bearer is a multiple bearer. If it is determined that the corresponding bearer is a multi-bearer, the PDCP transmitting apparatus proceeds to step 1425 because the PDCP receiving apparatus performs the reordering and discards the duplicated received packets, so that it is not suitable to perform the early retransmission operation.

Meanwhile, if it is determined in step 1420 that the corresponding bearer is a single bearer, the UE applies the header recovery operation to the PDCP receiving apparatus, and then discards the packet. In this case, even if an early retransmission operation is performed, The flow advances to step 1415 to start the early retransmission operation.

In step 1425, the PDCP transmitting apparatus does not start the PDCP packet transmission and retransmission operations until a PDCP status report is received from the PDCP receiving apparatus. When the PDCP status report is received, a retransmission operation or a transmission operation is started in accordance with the PDCP SN from the packet requiring retransmission. In step 1425, the PDCP transmitting apparatus initiates the early retransmission, and the ROHC feedback control PDCP control packet (PDCP Control PDU), which is a control packet for storing only the ROHC control information, for interspersed ROHC feedback packets (see Specification 36.323). This is because the PDCP sequence number is not used for the ROHC feedback PDCP control packet, and thus the problem due to the duplicated reception discard does not occur.

Meanwhile, FIG. 14 illustrates an operation procedure of a base station for receiving a PDCP status report and retransmitting PDCP data in an LTE system according to an embodiment of the present invention, but various modifications may be made to FIG. In one example, although the sequential steps are shown in FIG. 14, it is understood that the steps described in FIG. 14 may overlap, occur in parallel, occur in different orders, or occur multiple times.

14, an operation procedure of a base station for receiving a PDCP status report and retransmitting PDCP data in an LTE system according to an embodiment of the present invention is described. Next, an operation procedure of an LTE system according to an embodiment of the present invention will be described with reference to FIG. An internal structure of a terminal apparatus for transmitting PDCP data in a multi-bearer in a system will be described.

15 is a diagram schematically illustrating an internal structure of a terminal apparatus for transmitting PDCP data in a multi-bearer in an LTE system according to an embodiment of the present invention.

15, the terminal apparatus includes a PDCP transmission buffer 1015, an encryption apparatus 1520, a PDCP control apparatus 1525, a PDCP header attaching apparatus 1530, a multi-bearer distribution apparatus 1535, An MCG-RLC transmission apparatus 1540, and an SCG-RLC transmission apparatus 1545.

First, a multi-bearer transmits and receives data through two RLC devices. When a multi-bearer is set up, MeNB transmits a predetermined rate of uplink data to the MCG-RLC device (or via MCG, or through the MCG- MeNB), and another rate of uplink data may be transmitted to the SCG-RLC device (or via SCG, or via the MCG-MAC device, or MeNB). This is referred to as a split ratio. In some cases, all data may be transmitted to the MCG or all data may be transmitted to the SCG.

The PDCP control packet, such as the PDCP status report, is preferably transmitted as soon as possible. Therefore, for example, even if all the uplink data is set to be transmitted to the SCG, it is preferable that the PDCP status report is transmitted to the MCG exceptionally if the uplink transmission opportunity is given first through the MCG.

A multi-bearer includes one PDCP device and two RLC devices.

The PDCP apparatus includes a PDCP transmission buffer 1515, an encryption apparatus 1520, a PDCP header attaching apparatus 1530, a PDCP control apparatus 1525, and a multi-bearer distribution apparatus 1535.

The PDCP transmission buffer 1515 stores a PDCP data packet (or PDCP SDU) generated in an upper layer. The encryption apparatus 1520 is an apparatus for performing an encryption operation on a PDCP data packet. The PDCP header attaching device 1530 attaches a PDCP header to a PDCP data packet or a PDCP control packet. The multi bearer distribution device 1535 is a device for distributing the PDCP packet to one of the MCG-RLC transmission device 1540 and the SCG-RLC transmission device 1545.

The PDCP controller 1525 receives the multiplex bearer setup information from the RRC and controls the PDCP. The PDCP controller 1525 receives a timer value related to a period in which the PDCP data packet is stored in the PDCP transmission buffer 1515 from the RRC layer and updates the corresponding packet of the PDCP transmission buffer 1515 every time the timer expires Lt; / RTI &gt; The PDCP controller 1525 receives the secret key from the RRC device and delivers it to the encryption device 1520. The PDCP controller 1525 receives the control information associated with the PDCP header format from the RRC apparatus and sets the PDCP header attaching apparatus 1530. The PDCP controller 1525 obtains distribution ratio information from the RRC apparatus and sets up the multi-bearer distribution apparatus using the information. For example, if the distribution ratio is [0: 100], all PDCP packets are set to be transmitted through the SCG. If [50:50], 50% PDCP packets are transmitted through the MCG and 50% PDCP packets are transmitted through the SCG . The multi-bearer distribution device 1535 determines which PDCP packet is to be delivered to which RLC transmission device according to the distribution ratio. If the distribution ratio is [0: 100], all the PDCP data packets are transmitted to the SCG-RLC transmitting apparatus 1545. If the distribution ratio is [30:70], a PDCP data packet with a probability of 30% is transmitted to the MCG-RLC transmitting device 1540, and a PDCP data packet with 70% is transmitted to the SCG-RLC transmitting device 1545.

On the other hand, when a predetermined condition is satisfied, the PDCP controller 1515 generates a PDCP control packet. For example, one of the MCG-RLC receiver and the SCG-RLC receiver may be re-established or released.

The PDCP control unit 1515 transfers the PDCP control packet to the multi-bearer distribution unit 1535. In the multi-bearer distribution unit 1535, the PDCP control packet is transmitted at the earliest time without considering the distribution ratio To a possible cell group (or to an RLC unit).

The MCG-RLC transmission apparatus 1540 and the SCG-RLC transmission apparatus 1545 are connected to the MCG-MAC 1550 and the SCG-MAC 1555, respectively. The PDCP packets transmitted from the PDCP are processed into RLC packets, Device.

15, the PDCP transmission buffer 1515, the encryption apparatus 1520, the PDCP control apparatus 1525, the PDCP header attaching apparatus 1530, the multi-bearer distribution apparatus 1535, the MCG-RLC The transmission apparatus 1540 and the SCG-RLC transmission apparatus 1545 are implemented as separate units, the PDCP transmission buffer 1515, the encryption apparatus 1520, the PDCP control apparatus 1525, At least two of the PDCP header attaching apparatus 1530, the multiple bearer distributing apparatus 1535 and the MCG-RLC transmitting apparatus 1540 and the SCG-RLC transmitting apparatus 1545 may be integrated.

15, an internal structure of a terminal apparatus for transmitting PDCP data in a multi-bearer in the LTE system according to an embodiment of the present invention has been described. Next, referring to FIG. 16, in an LTE system according to an embodiment of the present invention, An operation of transmitting a PDCP data packet and a PDCP control packet through a multi-bearer will be described.

16 is a diagram schematically illustrating an operation of transmitting a PDCP data packet and a PDCP control packet through a multi-bearer in an LTE system according to an embodiment of the present invention.

FIG. 16 illustrates an operation of performing transmission over a predetermined cell group according to a distribution ratio according to the type of a PDCP packet or transmission based on a transmission opportunity without considering a cell group.

First, in step 1605, the terminal receives the multiplex bearer setup information and proceeds to step 1610. [ The multiplex bearer setup information may include distribution ratio information.

In step 1610, the UE applies the allocation ratio information, sets a multi-bearer distributor so that the PDCP packet is transmitted according to the distribution ratio, and proceeds to step 1615.

If a new PDCP packet is generated in step 1615, the MS proceeds to step 1620 and determines whether the new PDCP packet is a PDCP data packet or a PDCP control packet.

If the new PDCP packet is a PDCP data packet (i.e., a PDCP SDU delivered from an upper layer), the terminal proceeds to step 1625. [ If it is determined in step 1615 that the new PDCP packet is a PDCP control packet (that is, if the control information generated in the PDCP control apparatus is a received packet), the mobile station proceeds to step 1630.

In step 1625, the UE determines a cell group to which the packet is to be transmitted according to the distribution ratio for the new PDCP packet, and transmits the PDCP packet according to the order in which packets to be transmitted through the cell group are generated.

In step 1630, the UE determines a cell group in which a transmission opportunity occurs first as a cell group to which the packet is to be transmitted without considering the distribution ratio. And transmits the PDCP packet by bypassing other data packets determined to be transmitted through the cell group (i.e., before any other data packet, without considering the occurrence time). For example, when a PDCP status report is triggered at t0, uplink transmission to the bearer is possible at t1 through the MCG serving cell, and uplink transmission to the bearer is possible at t2 through the SCG serving cell If t1 is earlier than t2, the PDCP status report is transmitted through the MCG. If t2 is earlier than t1, the PDCP status report is transmitted through the SCG.

If the PDCP status report is generated due to the SeNB change, the uplink transmission through the SCG can be performed only after the random access is completed in the PSCell, and if it occurs due to the SeNB release, the uplink transmission through the SCG is no longer possible. Therefore, it is possible to simplify the terminal operation to always transmit the PDCP status report through the MCG. That is, even if the distribution ratio is set to [0: 100], the PDCP status report is transmitted through the MCG.

The transmission of the PDCP control packet is not controlled by the distribution ratio, and the transmission of the PDCP control packet does not affect the distribution ratio. (For example, even if a PDCP control packet is transmitted through an arbitrary cell group, it does not affect the probability that an arbitrary PDCP data packet is transmitted through the cell group. On the other hand, when an arbitrary PDCP data packet is transmitted , It affects by reducing the probability that other PDCP data packets will be transmitted through the cell group.)

16 illustrates an operation of transmitting a PDCP data packet and a PDCP control packet through a multi-bearer in an LTE system according to an embodiment of the present invention, various modifications may be made to FIG. As an example, although successive steps are shown in FIG. 16, it is understood that the steps described in FIG. 16 may overlap, occur in parallel, occur in different orders, or occur multiple times.

16, an operation of transmitting a PDCP data packet and a PDCP control packet through a multi-bearer in an LTE system according to an embodiment of the present invention has been described. Next, referring to FIG. 17, The internal structure of the terminal device in the system will now be described.

17 is a diagram schematically illustrating an internal structure of a terminal apparatus in an LTE system according to an embodiment of the present invention.

17, the terminal includes an MCG-MAC unit 1710, a control message processor 1765, various upper layer processors 1770, 1775 and 1785, a controller 1780, an SCG-MAC unit 1715, And includes an MCG-MAC device 1710, a transceiver 1705, PDCP devices 1745, 1750, 1755 and 1760, and RLC devices 1720, 1725, 1730, 1735 and 1740.

The transceiver 1705 receives data and a predetermined control signal on a downlink channel of a serving cell, and transmits data and a predetermined control signal to the uplink channel. When a plurality of serving cells are set, the transceiver 1705 performs data transmission / reception and control signal transmission / reception through the plurality of serving cells.

The MCG-MAC unit 1710 multiplexes data generated in the RLC unit or demultiplexes data received from the transceiver 1705 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 processor 1765 is an RRC layer apparatus and processes a control message received from a base station to perform necessary operations. For example, receives an RRC control message and transmits various setting information to the control unit.

The upper layer processing unit may be configured for each service. And processes data generated in a user service such as a file transfer protocol (FTP) or a voice over Internet protocol (VoIP), and transfers the processed data to the PDCP device.

The control unit 1780 controls the transceiver 1705 and the multiplexing and demultiplexing unit so that the scheduling command received through the transceiver 1705, for example, the reverse grants, is checked and the reverse transmission is performed to the appropriate transmission resource at an appropriate time. The control unit 1780 also performs various terminal functions as described with reference to FIGS. 6 to 16 and various terminal functions as described with reference to FIG. For the sake of convenience, the controller 1780 is shown as a separate apparatus from the PDCP apparatus, but some functions of the controller may be integrated into the PDCP apparatus.

The PDCP apparatus performs various terminal operations shown in FIGS. 6 to 16 and a terminal operation described in FIG. 19 below.

17, a control message processor 1765, various upper layer processors 1770, 1775 and 1785, a controller 1780, an SCG-MAC device 1715, an MCG-MAC device 1710, 1750, 1755, and 1760 and the RLC devices 1720, 1725, 1730, 1735, and 1740 are implemented as separate units, the MCG 1710, the transceiver 1705, the PDCP devices 1745, MAC device 1710, a control message processing unit 1765, various upper layer processing units 1770, 1775 and 1785, a control unit 1780, an SCG-MAC unit 1715, an MCG-MAC unit 1710, a transceiver 1705 , At least two of the PDCP apparatuses 1745, 1750, 1755 and 1760 and the RLC apparatuses 1720, 1725, 1730, 1735 and 1740 can be integrated.

17, an internal structure of a terminal in an LTE system according to an embodiment of the present invention is described. Next, an internal structure of a base station in an LTE system according to an embodiment of the present invention will be described with reference to FIG. .

18 is a diagram schematically illustrating an internal structure of a base station in an LTE system according to an embodiment of the present invention.

18, the base station includes a MAC device 1810, a control message processor 1865, a controller 1880, a transceiver 1805, PDCP devices 1845, 1850, 1855, 1860, RLC devices 1820, 1825, 1830, 1835, 1840, and a scheduler 1890.

The transceiver 1805 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 transceiver 1805 performs data transmission / reception and control signal transmission / reception with the plurality of carriers.

The MAC unit 1810 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 processor 1865 processes a control message transmitted from the mobile station to perform a required operation or generates a control message to be transmitted to the mobile station and delivers the control message to a lower layer.

The scheduler 1890 allocates transmission resources to the terminal at an appropriate time in consideration of the buffer state of the terminal, the channel state, and the like, processes the signal transmitted from the terminal to the transceiver, or transmits a signal to the terminal. The PDCP apparatus is divided into MCG bearer PDCPs 1845, 1850 and 1860 and a multi-bearer PDCP 1855. The MCG bearer PDCP transmits and receives data only through the MCG, and is connected to one RLC transceiver. Multi-bearer PDCP transmits and receives data through MCG and SCG. The control unit 1880 controls the operations shown in FIGS. 6 to 16 and the operations shown in FIG. 19 performed by the MeNB.

18, the MAC device 1810, the control message processor 1865, the controller 1880, the transceiver 1805, the PDCP devices 1845, 1850, 1855 and 1860, the RLC devices 1820, 1825, 1830, The control message processor 1865, the controller 1880, the transceiver 1805, the PDCP apparatus 1810, and the scheduler 1890 are implemented as separate units, although the MAC unit 1810, the control message processor 1865, At least two of the RLC devices 1820, 1825, 1830, 1835, and 1840 and the scheduler 1890 may be integrated.

FIG. 18 illustrates the internal structure of a base station in an LTE system according to an embodiment of the present invention. Referring to FIG. 19, in an LTE system according to an embodiment of the present invention, an RLC UM bearer transmits an SCG bearer And resetting the MCG bearer to the MCG bearer will be described.

19 is a diagram schematically illustrating an operation procedure when an RLC UM bearer is reconfigured from an MCG bearer to an SCG bearer in an LTE system according to an embodiment of the present invention and then re-established to an MCG bearer.

Referring to FIG. 19, a handover or a bearer reset is accompanied by a PDCP re-establishment operation, and the HFN and the PDCP SN are initialized to 0 upon re-establishment of the PDCP of the PDCP apparatus connected to the RLC UM bearer. This is because it is not necessary to maintain the HFN and the PDCP SN because the RLC UM bearer does not apply the procedure for retransmission of non-received packets by the PDCP status report.

However, as the UE moves from the macro cell area to the small cell area, the RLC UM MCG bearer is reset to the RLC UM SCG bearer so that the RLC UM SCG bearer is moved to the macro cell area after transmitting / receiving data in the small cell, When the HFN and the PDCP SN are initialized to 0 when changed, a phenomenon occurs in which one or more pieces of data are coded using the same security key and the same COUNT, which may cause security problems.

Therefore, in an embodiment of the present invention, in order to solve the above problem, the UE determines whether to initialize the HFN and the COUNT upon re-establishment of the PDCP, according to the state of the UE.

For example, if the PDCP of the RLC UM bearer is re-established by entering / advancing an arbitrary small cell area while maintaining the RRC connection in the same macro cell, instead of initializing the HFN and the PDCP SN, And the PDCP SN are applied as they are. At this time, MeNB and SeNB inform the other HFN and PDCP SN to each other, so that the HFN and the PDCP SN are synchronized between the terminal and the base station. Alternatively, the PDCP SN is initialized to 0, and the HFN is incremented by a predetermined value so that the HFN mismatch does not occur.

It should be noted that the operation procedure when the RLC UM bearer shown in FIG. 19 is re-established from the MCG bearer to the SCG bearer and then re-established to the MCG bearer is the UE operation process in re-establishing the PDCP of the RLC UM bearer.

First, in step 1905, the upper layer of the UE instructs the PDCP layer of the UE to re-establish the PDCP. Here, the PDCP re-establishment may be indicated in the case of handover, SeNB addition / release, and the like.

In step 1910, the PDCP apparatus that has been instructed to re-establish the upper layer restores the header of the PDCP PDUs transmitted due to the re-establishment of the lower layer by applying the current header compression protocol, and uses the current non- After decrypting (ie, after processing with the PDCP SDU), it is forwarded to the upper layer.

In step 1915, the PDCP apparatus indicating re-establishment from the upper layer determines whether the control message instructing the re-establishment includes drb-Continue ROHC (control information indicating whether to reset the ROHC, see specifications 36.323 and 36.331) Or whether drb-ContinueROHC is set to true in the control message) to determine whether to reset the header compression protocol, and does not reset or reset the header compression protocol based on the determination result.

If the PDCP re-establishment is related to the SCG bearer re-establishment in step 1920 and the PDCP re-establishment is related to the SCG bearer re-establishment in step 1920, the MS proceeds to step 1925. If the PDCP re-establishment is not related to the SCG bearer re- RRC connection re-establishment. If the PDCP re-establishment is performed according to the RRC connection re-establishment procedure, the process proceeds to step 1930. Here, re-establishment of the PDCP related to the SCG bearer re-establishment means re-establishment of the PDCP caused by the MCG bearer being reset to the SCG bearer, or the SCG bearer being reset to the MCG bearer, or the SCG bearer being reset to the SCG bearer. Alternatively, re-establishment of the PDCP associated with the SCG bearer re-establishment implies re-establishment of the PDCP caused by setting the SCG / SeNB, releasing the SCG / SeNB, or changing the SCG / SeNB.

In step 1925, the UE resets Next_PDCP_RX_SN, RX_HFN, Next_PDCP_TX_SN, and TX_HFN of the PDCP apparatus to the scheme 1 (the definition of the above parameters conforms to the standard 36.323). Then, a related operation (for example, an operation of determining a COUNT of a packet to be transmitted, an operation of determining an HFN of a received packet, etc.) is performed by applying the following determined parameters to the PDCP SDU and the receiving PDCP PDU do.

[Next_PDCP_RX_SN / RX_HFN / Next_PDCP_TX_SN / TX_HFN Setting method 1]

Next_PDCP_RX_SN and Next_PDCP_TX_SN are initialized to 0

RX_HFN and TX_HFN are incremented by a predetermined integer n

The predetermined integer n may be an arbitrary integer fixed so that the terminal and the base station can use the same HFN. The reason for increasing RX_HFN and TX_HFN as described above is that the receiving apparatus can re-receive the PDCP PDU already received due to retransmission after re-establishing the PDCP, which causes HFN mismatch between the transmitting apparatus and the receiving apparatus. For example, when SeNB is released, SeNB can continue data transmission until the UE completely leaves the SeNB area even after initiating data forwarding to the MeNB. In this case, the terminal can re-receive the packet received by the SeNB to the MeNB.

In step 1930, the UE resets Next_PDCP_RX_SN, RX_HFN, Next_PDCP_TX_SN, and TX_HFN of the PDCP device in the following manner 2

[Next_PDCP_RX_SN / RX_HFN / Next_PDCP_TX_SN / TX_HFN Setting method 2]

Initialize Next_PDCP_RX_SN and Next_PDCP_TX_SN to 0

Initialize RX_HFN and TX_HFN to 0

In step 1935, the terminal initiates the application of the ciphering algorithm and the non-ciphering key indicated by the upper layer. Then, after the packet which has not yet been transmitted to the lower layer, the new algorithm / non-transmission key and the new HFN are applied to reconstruct the PDCP PDU and then transmit the PDCP PDU. The UE may initiate transmission from the m most recently transmitted packets to the lower layer to prevent loss of uplink data. That is, the UE reconfigures the PDCP PDU by applying a new algorithm / non-key and a new HFN from the PDCP SDU that has already been transmitted to the lower layer, and then transmits the PDCP PDU.

If the retransmission technique is not applied, the UE can determine Next_PDCP_RX_SN, RX_HFN, Next_PDCP_TX_SN, and TX_HFN by using the following scheme 3 instead of the scheme 1 in step 1925. [

[Next_PDCP_RX_SN / RX_HFN / Next_PDCP_TX_SN / TX_HFN setting method 3]

Maintain Next_PDCP_RX_SN and Next_PDCP_TX_SN as current values

Maintain RX_HFN and TX_HFN as current values

It goes without saying that, in step 1920, the UE may determine whether to proceed to step 1925 or step 1930 according to an instruction from the BS without determining on its own. For example, the BS transmits a control message instructing the RLC UM bearer to re-establish the RLC UM bearer, and determines whether the Next_PDCP_RX_SN, Next_PDCP_TX_SN, RX_HFN, and TX_HFN are maintained at the current value (i.e., , It may include control information instructing to initialize the variables to 0 (i.e., proceed to step 1930).

The control information may be applied to all the RLC UM bearers set in the UE at the same time, or may be information applied to each RLC UM bearer. In the former case, one piece of control information (for example, 1 bit information) is included in the control message, and in the latter case, a plurality of pieces of control information are included as many as the number of RLC UM bearers.

FIG. 19 illustrates the operation of the LTE system according to an embodiment of the present invention when the RLC UM bearer is reconfigured from the MCG bearer to the SCG bearer and then to the MCG bearer again. Referring to FIG. 20, A description will be made of a timing advance (TA) timer related operation of a terminal in which multiple connections are established in an LTE system according to an embodiment of the present invention.

20 is a flowchart schematically illustrating an operation procedure of a TA timer related to a UE having multiple connections in an LTE system according to an exemplary embodiment of the present invention.

Prior to describing FIG. 20, a timing advance group (TAG) will be described below.

First, TAG represents a set of serving cells sharing the same uplink transmission timing. The type of the TAG includes a primary TAG (P-TAG) and a secondary TAG (S-TAG) The P-TAG indicates a TAG to which PCell or PSCell belongs, and the S-TAG indicates a TAG including only TAGs other than the P-TAG, that is, SCells. The fact that an arbitrary serving cell belongs to a certain TAG means that the uplink transmission timing of the serving cell is the same as the uplink transmission timing of other serving cells belonging to the TAG, .

The reverse transmission timing of an arbitrary TAG is set by performing a random access procedure in a predetermined serving cell belonging to the TAG, and is maintained by receiving a TA command (TA command). The terminal drives or restarts the TA timer of the corresponding TAG whenever it receives a TA command for an arbitrary TAG. When the TA timer expires, the terminal determines that the uplink transmission synchronization of the corresponding TAG is lost, and does not perform the uplink transmission operation until the random access procedure is performed again.

In addition, a TAG identifier is assigned to each TAG, and the TAG identifier can be an arbitrary integer between 0 and 3, for example.

In addition, at least two TAGs may be set for a terminal in which multiple connections are established. Here, since the TAG operates independently for each BS, it is impossible to set all the serving cells to one TAG.

In one embodiment of the present invention, MeNB and SeNB assign TAGs such that PCell and PSCell belong to different TAGs, and always assign an arbitrary integer, for example, 0 as an identifier of the TAG to which the PCell belongs and the TAG to which the PSCell belongs .

In addition, when the terminal operates the TA timer for each TAG and receives the TA command through an arbitrary serving cell, the terminal applies the TA command to the TAG indicated by the TAG identifier indicated in the TA command and sets the TA timer of the corresponding TAG Re-drive. At this time, the UE determines which TAG the TA command is for, considering the serving cell group to which the serving cell in which the TA command is received belongs. For example, if the TA command is received at the SCG, the TA command is applied to a TAG having a TAG identifier that matches the TAG identifier included in the TA command among TAGs including SCG serving cells. For example, if the TA command having the TAG identifier of 0 is received through the MCG, the TA command is for the TAG to which the PCell belongs. If the TA command having the TAG identifier of 0 is received through the SCG, It belongs to the TAG to which it belongs.

On the other hand, if the TA timer of the P-TAG is not in operation, the UE does not perform the PUCCH signal transmission operation in the serving cell belonging to the P-TAG. In particular, if a resource for transmission of a PUCCH signal has already been allocated but a random access procedure has not been completed immediately after the terminal has handed over, there may be a situation where a valid PUCCH transmission resource exists but a TA timer is stopped. At this time, When performing a reverse transmission operation in the corresponding TAG through the PUCCH, it may cause uplink interference to other terminals, and thus it may be desirable to prohibit the PUCCH transmission operation for the corresponding terminal.

Referring to FIG. 20, a TA timer related operation of a terminal having multiple connections in an LTE system according to an embodiment of the present invention will be described.

First, in step 2005, the terminal receives a control message instructing to set a TAG from the base station and proceeds to step 2010. [ The control message may be implemented, for example, as an RRC connection reset message. The control message is a control message for setting one or more SCells, and may include a TAG identifier indicating which TAG the newly set SCell belongs to. In addition, the UE determines a TAG to which the corresponding SCell belongs according to the following rules for each newly set SCell.

(1) When no TAG identifier is indicated for a predetermined serving cell and there is no information indicating which cell group the serving cell belongs to

The UE determines that the serving cell belongs to P-TAG 1.

(2) when a TAG identifier is indicated for a predetermined serving cell and there is no information indicating which cell group the serving cell belongs to:

The UE determines that the serving cell belongs to the S-TAG specified by the TAG identifier among the TAGs set in the MCG.

(3) if no TAG identifier is indicated for a given serving cell and the serving cell is indicated to belong to the SCG:

The UE determines that the serving cell belongs to P-TAG2.

(4) if a TAG identifier is indicated for a given serving cell and the serving cell is indicated to belong to the SCG:

The UE determines that the serving cell belongs to the S-TAG specified by the TAG identifier among the TAGs set in the SCG.

Here, the P-TAG 1 indicates a TAG to which the PCell belongs, and the P-TAG 2 indicates a TAG to which the PSCell belongs.

In step 2010, the UE sets a serving cell and a TAG on the basis of the indication indicated by the control message, transmits an RRC control message indicating that the setting is completed to the BS through the MCG, and proceeds to step 2015.

In step 2015, the MS manages a TA timer for each TAG, and proceeds to step 2020. In step 2020, That is, when the UE successfully completes the random access in one of the serving cells of the corresponding TAG, the UE starts driving the TA timer, and when the TA command is received for the TAG, the UE restarts the TA timer .

In step 2020, the MS detects that the first type PUCCH transmission operation is required in the PCcell or the PSCell, and proceeds to step 2025. Here, the PUCCH transmission resources are periodic transmission resources and can be allocated in advance for each UE through the RRC control message. The PUCCH resource is divided into a scheduling request transmission resource, a channel status information (CSI) transmission resource, and a HARQ feedback transmission resource. The first type PUCCH transmission operation includes a scheduling request operation and a CSI feedback operation , And does not include the HARQ feedback operation. Herein, the CSI is also referred to as channel quality information (CQI).

On the other hand, the fact that the first type PUCCH transmission operation is detected means that there is a need to transmit a scheduling request signal through PCell, a PUCCH transmission resource for transmitting a scheduling request is allocated to PCell, or a CSI transmission resource And a PUCCH transmission resource for transmitting a scheduling request is allocated to the PSCell or a CSI of a PSCell is allocated to the PUCCH of the PSCell, Indicates that a transmission resource is allocated and the CSI transmission resource has arrived at a usable subframe.

In step 2025, the UE determines whether the serving cell for which the first type PUCCH transmission operation is detected is PCell or PSCell. If it is determined that the serving cell in which the first type PUCCH transmission operation is detected is PCell, the MS proceeds to step 2030. Otherwise, if the serving cell in which the first type PUCCH transmission operation is detected is a PSCell, The process proceeds to step 2040. [

In step 2030, the UE determines whether a TA timer of P-TAG 1 is being operated or a TA timer whose TAG identifier is 0 among the TA timers managed by the MAC device of the MCG, It is checked whether the TA timer of the P-TAG is being driven. If it is determined that the TA timer of the P-TAG 1 is running or the TA timer whose TAG identifier is 0 among the TA timers managed by the MAC device of the MCG is running or the TA If the TA timer of the P-TAG among the timers is in operation, the terminal proceeds to step 2035. [ On the contrary, when the TA timer of P-TAG 1 is not running and the TA timer whose TAG identifier is 0 is not running among the TA timers managed by the MAC device of the MCG and P If the TA timer of the -TAG is not in operation, the terminal proceeds to step 2050.

In step 2035, the UE performs a PUCCH transmission operation in the PCcell.

Meanwhile, in step 2050, the UE does not perform the PUCCH transmission operation in the PCell because the TA timer of P-TAG 1 is not in operation. Herein, the MS may perform an additional procedure according to the type of the PUCCH to which the transmission is omitted. For example, if transmission of the scheduling request signal through the PUCCH of the PCell is omitted, the UE initiates a random access operation in the PCell.

In step 2040, the UE determines whether a TA timer of P-TAG 2 is being operated or a TA timer whose TAG identifier is 0 among the TA timers managed by the MAC device of the SCG is running, The TA timer of the P-TAG is being driven. If it is determined that the TA timer of the P-TAG 2 is in operation or a TA timer whose TAG identifier is 0 among the TA timers managed by the MAC device of the SCG is running or the TA When the TA timer of the P-TAG among the timers is in operation, the terminal proceeds to step 2045. [ On the other hand, if the TA timer of the P-TAG 2 is not running and the TA timer whose TAG identifier is 0 is not running among the TA timers managed by the MAC device of the SCG, If the TA timer of the P-TAG is not in operation, the terminal proceeds to step 2050.

Meanwhile, in step 2045, the UE performs a PUCCH transmission operation in the PSCell.

In step 2050, the UE does not perform the PUCCH transmission operation in the PSCell because the TA timer of the P-TAG 2 is not in operation. Herein, the MS may perform an additional procedure according to the type of the PUCCH to which the transmission is omitted. For example, if the transmission of the scheduling request signal through the PUCCH of the PSCell is omitted, the terminal initiates a random access operation in the PSCell.

Meanwhile, although FIG. 20 illustrates a TA timer related operation procedure of a UE having multiple connections in an LTE system according to an embodiment of the present invention, various modifications may be made to FIG. As an example, although successive steps are shown in FIG. 20, it is understood that the steps described in FIG. 20 may overlap, occur in parallel, occur in different orders, or occur multiple times.

Certain aspects of the invention may also be implemented as computer readable code in a computer readable recording medium. The computer readable recording medium is any data storage device capable of storing data that can be read by a computer system. Examples of the computer-readable recording medium include read only memory (ROM), random access memory (RAM), CD-ROMs, magnetic tapes, floppy Floppy disks, optical data storage devices, and carrier waves (such as data transmission over the Internet). The computer readable recording medium may also be distributed over networked computer systems, and thus the computer readable code is stored and executed in a distributed manner. Also, functional programs, code, and code segments for accomplishing the present invention may be readily interpreted by programmers skilled in the art to which the invention applies.

It will also be appreciated that the apparatus and method according to an embodiment of the present invention may be implemented in hardware, software, or a combination of hardware and software. Such arbitrary software may be stored in a memory such as, for example, a volatile or non-volatile storage device such as a storage device such as ROM or the like, or a memory such as a RAM, a memory chip, a device or an integrated circuit, , Or a storage medium readable by a machine (e.g., a computer), such as a CD, a DVD, a magnetic disk, or a magnetic tape, as well as being optically or magnetically recordable. The method according to an embodiment of the present invention can be implemented by a computer or a mobile terminal including a control unit and a memory and the memory is suitable for storing a program or programs including instructions embodying the embodiments of the present invention It is an example of a machine-readable storage medium.

Accordingly, the invention includes a program comprising code for implementing the apparatus or method as claimed in any of the claims herein, and a storage medium readable by a machine (such as a computer) for storing such a program. In addition, such a program may be electronically transferred through any medium, such as a communication signal carried over a wired or wireless connection, and the present invention appropriately includes equivalents thereof

Also, an apparatus according to an embodiment of the present invention may receive and store the program from a program providing apparatus connected by wire or wireless. The program providing apparatus includes a memory for storing a program including instructions for causing the program processing apparatus to perform a predetermined content protection method, information necessary for the content protection method, and the like, and a wired or wireless communication with the graphics processing apparatus And a control unit for transmitting the program to the transceiver upon request or automatically by the graphic processing apparatus.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Therefore, the scope of the present invention should not be limited by the illustrated embodiments, but should be determined by the scope of the appended claims and equivalents thereof.

Claims (2)

A method of operating a terminal in a mobile communication system supporting a plurality of carriers,
Checking whether the bearer re-establishment is related to a secondary cell group (SCG) bearer or a multi-bearer if the bearer re-establishment is instructed;
And performing a Packet Data Convergence Protocol (PDCP) status reporting operation on the basis of the result of the checking.
In a mobile communication system supporting a plurality of carriers,
The mobile subscriber station checks whether the bearer re-establishment is related to a secondary cell group (SCG) bearer or a multi bearer, and transmits a packet data convergence protocol (PDCP) convergence protocol state reporting operation in a mobile communication system supporting a plurality of carriers.

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