KR20150051091A - Method and apparatus for performing random access in wireless communication system using dual connectivity - Google Patents

Abstract

The present specification relates to a method for performing random access via a terminal in a wireless communications system using a dual connectivity method, and an apparatus thereof. Disclosed in the present specification are a step of transmitting a random access preamble, and a step of receiving, in response to the random access preamble, a random access response message via a physical downlink shared channel (PDSCH). A terminal is configured to have dual connectivity through a master base station (master eNB) and a secondary base station (secondary eNB). The random access response message is received over at least one of a primary serving cell (PCell) within a master cell group provided by the master base station, or over secondary serving cells (SCell) which are instructed to receive the random access response message within a secondary cell group provided by the secondary base station. According to the present invention, it is possible to improve receiving efficiency of random access preamble when a terminal attempts to perform random access in the state of double connectivity.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method and apparatus for performing random access in a wireless communication system using a dual-

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to wireless communication, and more particularly, to an apparatus and method for performing random access in a wireless communication system.

In a typical wireless communication system, although a bandwidth between an uplink and a downlink is set to be different from each other, only one carrier is mainly considered. In the 3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution), the number of carriers constituting the uplink and the downlink is 1 based on a single carrier, and the bandwidths of the UL and the DL are generally symmetrical to be. In this single carrier system, random access is performed using one carrier. However, as a multi-carrier system has been recently introduced, random access can be implemented through a plurality of component carriers.

A multi-carrier system refers to a wireless communication system capable of supporting carrier aggregation. Carrier aggregation is a technique for efficiently using a fragmented small band so as to achieve the same effect as using a logically large band by bundling a plurality of physically non-continuous bands in the frequency domain.

In a wireless communication system, a terminal can perform wireless communication through two or more base stations among the base stations constituting at least one serving cell. This is called dual connectivity. In other words, a dual connection is an operation in which a terminal set to an RRC connection state with at least two different network points consume radio resources provided by the network points can do. At least two or more different network points may be physically or logically divided into a plurality of base stations, one of which is a master eNB (MeNB) and the other base stations are a secondary eNodeB (SeNB) Lt; / RTI >

In the dual connection, each base station transmits downlink data through a bearer configured for one terminal and receives uplink data. At this time, one bearer may be configured through one base station, or may be configured through two or more different base stations. Also, in the dual connection, each base station may have at least one serving cell (Serving Cell), and each serving cell may be operated in an activated or deactivated state. In this case, a primary serving cell (PCell: Primary cell) configured in a conventional CA (Carrier Aggregation) scheme is configured in the master base station, a secondary serving cell (SCell: Cell). In some cases, different main serving cells may be configured for each of the master base station and the secondary base station. Here, carrier aggregation is a technique for efficiently using a fragmented small band, in which one base station bundles a plurality of physically continuous or non-continuous bands in the frequency domain to form a logically large band So as to have the same effect as using a band.

In order for a terminal to access a network, a random access process is performed. The random access procedure may be divided into a contention based random access procedure and a non-contention based random access procedure. The major difference between the contention based random access procedure and the non-contention based random access procedure is whether the random access preamble is dedicated to one UE. In the non-contention-based random access procedure, since the UE uses a dedicated random access preamble assigned only to itself, contention (or collision) with other UEs does not occur. Here, the contention means that two or more UEs attempt a random access procedure using the same random access preamble through the same resource. In the contention-based random access procedure, there is a possibility of contention because the UE uses randomly selected random access preamble.

The purpose of the terminal performing the random access procedure to the network may be initial access, handover, scheduling request, timing alignment, and the like.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and an apparatus for performing random access by a terminal in a wireless communication system using a dual connection scheme in which a terminal is dual-connected through two or more different base stations.

It is another object of the present invention to provide a method and apparatus for receiving a random access response message in a wireless communication system using a dual connection scheme.

According to an aspect of the present invention, there is provided a method for performing random access by a terminal in a wireless communication system using a dual connection scheme. The method includes transmitting a dummy access preamble and receiving a random access response message on a physical downlink shared channel (PDSCH) in response to the random access preamble, A dual connection is established by a master base station (master eNB) and a secondary base station (eNB), and the random access response message includes a primary serving cell (PCell) in a master cell group provided by the master base station And a secondary serving cell (SCell) instructed to receive the random access response message in the secondary cell group provided by the secondary base station.

According to another aspect of the present invention, there is provided a method of performing random access by a base station in a wireless communication system using a dual connection scheme. The method includes receiving a random access preamble and transmitting a random access response message on a physical downlink shared channel (PDSCH) in response to the random access preamble, A dual connection is established between a master eNB and a secondary eNB and a dual connection is established between a master eNB and a secondary eNB. , A primary serving cell (PCell) in a master cell group provided by the master base station, and a secondary serving cell in a secondary cell group provided by the secondary base station, the secondary serving cell being instructed to receive the random access response message and a serving cell (SCell).

According to another aspect of the present invention, there is provided a terminal performing random access in a wireless communication system using a dual connection scheme. The UE includes a transmitter for transmitting a random access preamble and a receiver for receiving a random access response message on a physical downlink shared channel (PDSCH) in response to the random access preamble, A dual connection by a master base station (master eNB) and a secondary base station (eNB) is configured, and the random access response message includes a primary serving cell (PCell) in a master cell group provided by the master base station, And a secondary serving cell (SCell) instructed to receive the random access response message in the secondary cell group provided by the secondary base station.

According to another aspect of the present invention, there is provided a base station performing random access in a wireless communication system using a dual connection scheme. The base station includes a receiver for receiving a random access preamble and a transmitter for transmitting a random access response message through a physical downlink shared channel (PDSCH) in response to the random access preamble, A dual connection is established by a master base station (master eNB) and a secondary base station (eNB), and the random access response message includes a primary serving cell (PCell) in a master cell group provided by the master base station Is transmitted through at least one of secondary serving cells (SCells) instructed to transmit the random access response message in the secondary cell group provided by the secondary base station.

It is possible to improve the reception efficiency of the response message to the random access preamble when the UE desires to perform random access in the dual connection state and to monitor the response message to the random access preamble and efficiently determine the effectiveness of the random access can do.

1 shows a wireless communication system to which the present invention is applied.
FIG. 2 shows an example of a protocol structure for supporting a multi-element carrier wave to which the present invention is applied.
3 shows a structure of a subframe to which the present invention is applied.
4 shows an example of a frame structure for a multi-component carrier wave operation to which the present invention is applied.
FIG. 5 shows a linkage between a downlink component carrier and an uplink component carrier in a multi-component carrier system to which the present invention is applied.
6 is a diagram illustrating a structure of a bearer service in a wireless communication system.
7 is a view showing a structure of a user plane for a double connection.
8A to 8E are diagrams illustrating a protocol structure of base stations in downlink transmission of user plane data.
9 is a flowchart illustrating an operation of a Node B and a UE performing random access in a dual connection wireless communication system according to an embodiment of the present invention.
FIG. 10 shows an example of transmitting and receiving a random access preamble and a response message thereto in a dual connection wireless communication system according to an embodiment of the present invention.
11 shows an example in which a response message of a random access preamble according to an embodiment of the present invention is mapped to a physical downlink data area.
FIG. 12 shows an example in which a response message of a random access preamble according to another embodiment of the present invention is transmitted in the form of a RAR MAC CE.
13 shows a MAC PDU structure for a random access response message to which the present invention is applied.
14 shows an R / R / E / LCID subheader to which the present invention is applied.
15A to 15E show an example of a RAR MAC CE according to an embodiment of the present invention.
16 shows an example of configuring parameters for a random access procedure through a PS cell (PUCCH SCell) of a main serving cell and a secondary cell group of a master cell group according to an embodiment of the present invention.
FIG. 17 shows an operation for determining whether or not random access is successful according to the first embodiment of the present invention.
FIG. 18 shows an operation for determining whether or not the random access is successful according to the second embodiment of the present invention.
FIG. 19 shows an operation for determining whether or not random access is successful according to the third embodiment of the present invention.
FIG. 20 shows an operation for determining whether or not random access is successful according to the fourth embodiment of the present invention.
21 is a block diagram illustrating a base station and a terminal for performing random access according to an exemplary embodiment of the present invention.

Hereinafter, some embodiments will be described in detail with reference to exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference numerals even though they are shown in different drawings. In the following description of the embodiments of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present disclosure rather unclear.

In addition, the present invention will be described with respect to a wireless communication network. The work performed in the wireless communication network may be performed in a process of controlling a network and transmitting data by a system (e.g., a base station) Work can be done at a terminal connected to the network.

1 shows a wireless communication system to which the present invention is applied.

Referring to FIG. 1, a wireless communication system 10 is widely deployed to provide various communication services such as voice, packet data, and the like. The wireless communication system 10 includes at least one base station 11 (BS). Each base station 11 provides communication services to specific cells (15a, 15b, 15c). The cell may again be divided into multiple regions (referred to as sectors).

A user equipment (UE) 12 may be fixed or mobile and may be a mobile station (MS), a mobile terminal (MT), a user terminal (UT), a subscriber station (SS) , A personal digital assistant (PDA), a wireless modem, a handheld device, and the like. The base station 11 may be called by other terms such as an evolved-NodeB (eNB), a base transceiver system (BTS), an access point, a femto base station, a home node B, . The cell should be interpreted in a generic sense to indicate a partial area covered by the base station 11 and is meant to cover various coverage areas such as a megacell, a macro cell, a microcell, a picocell, and a femtocell.

Hereinafter, downlink refers to communication from the base station 11 to the terminal 12, and uplink refers to communication from the terminal 12 to the base station 11. In the downlink, the transmitter may be part of the base station 11, and the receiver may be part of the terminal 12. In the uplink, the transmitter may be part of the terminal 12, and the receiver may be part of the base station 11. There are no restrictions on multiple access schemes applied to wireless communication systems. (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier-FDMA , OFDM-CDMA, and the like. A TDD (Time Division Duplex) scheme in which uplink and downlink transmissions are transmitted using different time periods, or an FDD (Frequency Division Duplex) scheme in which they are transmitted using different frequencies can be used.

A carrier aggregation (CA) supports a plurality of element carriers and is also referred to as spectral aggregation or bandwidth aggregation. The individual unit carriers tied by carrier aggregation are called component carriers (CCs). Each element carrier is defined as the bandwidth and center frequency. Carrier aggregation is introduced to support increased throughput, prevent cost increases due to the introduction of wideband radio frequency (RF) devices, and ensure compatibility with existing systems. For example, if five elementary carriers are allocated as the granularity of a carrier unit having a bandwidth of 20 MHz, it can support a bandwidth of up to 100 MHz.

Carrier aggregation can be divided into contiguous carrier aggregation between successive element carriers in the frequency domain and non-contiguous carrier aggregation between discontinuous element carriers. The number of carriers aggregated between the downlink and the uplink may be set differently. The case where the number of downlink element carriers is equal to the number of uplink element carriers is referred to as symmetric aggregation and the case where the number of downlink element carriers is different is referred to as asymmetric aggregation.

The size (i.e. bandwidth) of the element carriers may be different. For example, assuming that five element carriers are used for a 70 MHz band configuration, a 5 MHz element carrier (CC # 0) + 20 MHz element carrier (CC # 1) + a 20 MHz element carrier (CC # (CC # 3) + 5MHz element carrier (CC # 4).

Hereinafter, a multiple component carrier system refers to a system that supports carrier aggregation. In a multi-element carrier system, adjacent carrier aggregation and / or non-adjacent carrier aggregation may be used, and either symmetric aggregation or asymmetric aggregation may be used.

When the terminal forms a carrier aggregation, the terminal has one RRC connection with the network. This is the same when a dual connection is configured. When establishing / re-establishing / handing over an RRC connection, a particular serving cell provides non-access stratum (NAS) mobility information (e.g., TAI: Tracking Area ID). The cell is defined as a primary serving cell (PCS). The PCell is composed of a DL Primary PCC (Downlink Primary Component Carrier) and a UL PCC (Uplink Primary Component Carrier).

Secondary Serving Cells (SCell) may be configured with a PCcell in the form of a serving cell set according to the UE capability of the UE. The SCell may be composed only of a DL SCC (Downlink Secondary Component Carrier) or may be paired with a UL SCC (Uplink Secondary Component Carrier).

The serving cell set is always composed of one PCell and at least one SCell. PCell can only be changed through the handover procedure. PCell is used for PUCCH transmission. PCell can not transition to the inactive state. SCell can be transitioned to the inactive state. The RRC reset procedure is triggered when it experiences a Radio Link Failure (RLF) in PCell. SCell's RLF is not triggered.

SCell add / remove / reconfigure is done through RRC reconfiguration procedure which is dedicated signaling. When a new SCell is added, system information about the SCell is also included in the RRC reconfiguration message. Therefore, SCell does not need monitoring operation for changing the system information.

FIG. 2 shows an example of a protocol structure for supporting a multi-element carrier wave to which the present invention is applied.

Referring to FIG. 2, a common Medium Access Control (MAC) entity 210 manages a physical layer 220 that uses a plurality of element carriers. A MAC management message sent on a specific element carrier may be applied to another element carrier. That is, the element MAC management message is a message that can control other element carriers including the specific element carrier. The physical layer 220 may operate as a time division duplex (TDD) and / or a frequency division duplex (FDD).

There are several physical control channels used in the physical layer 220. The physical downlink control channel (PDCCH) informs the UE of paging channel (PCH), resource allocation of downlink shared channel (DL-SCH), and hybrid automatic repeat request (HARQ) information related to the DL-SCH. The PDCCH may carry an uplink grant informing the UE of the resource allocation of the uplink transmission. A physical control format indicator channel (PCFICH) informs the UE of the number of OFDM symbols used for PDCCHs and is transmitted every subframe. PHICH (Physical Hybrid ARQ Indicator Channel) carries HARQ ACK / NAK signal in response to uplink transmission. A physical uplink control channel (PUCCH) carries uplink control information such as HARQ ACK / NAK, scheduling request and CQI for downlink transmission. A physical uplink shared channel (PUSCH) carries an uplink shared channel (UL-SCH). A physical random access channel (PRACH) carries a random access preamble.

3 shows a structure of a subframe to which the present invention is applied.

Referring to FIG. 3, a subframe includes two consecutive slots. The maximum 3 OFDM symbols preceding the first slot in the subframe are the control regions to which the PDCCH is allocated and the remaining OFDM symbols are the data regions to which the PDSCH is allocated. Control channels such as PCFICH and PHICH may be allocated to the control area in addition to the PDCCH. The UE can decode the control information transmitted through the PDCCH and read the data information transmitted through the PDSCH. Here, it is only an example that the control region includes 3 OFDM symbols. The number of OFDM symbols included in the control region in the subframe can be known through the PCFICH.

The control area consists of a logical CCE sequence, which is a plurality of control channel elements (CCE). Hereinafter, the CCE sequence is a set of all CCEs constituting a control region in one subframe. The CCE corresponds to a plurality of resource element groups. For example, a CCE may correspond to nine resource element groups. A resource element group is used to define the mapping of control channels to resource elements. For example, one resource element group may be composed of four resource elements.

A plurality of PDCCHs may be transmitted within the control domain. The PDCCH carries control information such as scheduling assignment and the like. The PDCCH is transmitted on an aggregation of one or several consecutive control channel elements (CCEs). The format of the PDCCH and the number of possible PDCCH bits are determined according to the number of CCEs constituting the CCE aggregation unit. Hereinafter, the number of CCEs used for PDCCH transmission is referred to as a CCE aggregation level. Also, the CCE aggregation unit is a CCE unit for searching PDCCH. The size of a CCE aggregation unit is defined by the number of adjacent CCEs. For example, a CCE aggregation unit may be an element of {1, 2, 4, 8}.

The following table shows an example of the format of the PDCCH according to the CCE aggregation unit, and the number of bits of the possible PDCCH.

PDCCH format CCE aggregation unit Number of resource element groups Number of PDCCH bits 0 One 9 72 One 2 18 144 2 4 36 288 3 8 72 576

The control information transmitted through the PDCCH is referred to as downlink control information (DCI). DCI transmits uplink or downlink scheduling information, uplink power control command, control information for paging, control information for indicating a random access response (RA response), and the like. In the DCI format, format 0 for PUSCH scheduling, format 1 for scheduling one PDSCH codeword, format 1A for compact scheduling of one PDSCH codeword, format 1C for very simple scheduling of DL-SCH A format 2 for PDSCH scheduling in a closed-loop spatial multiplexing mode, a format 2A for PDSCH scheduling in an open-loop spatial multiplexing mode, a TPC for an uplink channel Control < RTI ID = 0.0 > commands. ≪ / RTI >

4 shows an example of a frame structure for a multi-component carrier wave operation to which the present invention is applied.

Referring to FIG. 4, a frame is composed of 10 subframes. Each element carrier may have its own control channel (e.g. PDCCH). The terminal may support one or more element carriers according to its capabilities.

Element carriers can be divided into Primary Component Carrier (PCC) and Secondary Component Carrier (SCC) depending on whether they are active or not. The primary carrier is always the active carrier, and the sub-carrier is the carrier that is activated / deactivated according to certain conditions. Activation means that the transmission or reception of traffic data is performed or is in a ready state. Deactivation means that transmission or reception of traffic data is impossible and measurement or transmission / reception of minimum information is possible. The terminal may use only one major carrier or use one or more sub-carrier with carrier. A terminal may be allocated a primary carrier and / or secondary carrier from a base station.

FIG. 5 shows a linkage between a downlink component carrier and an uplink component carrier in a multi-component carrier system to which the present invention is applied.

Referring to FIG. 5, the downlink component carriers D1, D2, and D3 are aggregated in the downlink, and the uplink component carriers U1, U2, and U3 are aggregated in the uplink. Where Di is the index of the downlink component carrier and Ui is the index of the uplink component carrier (i = 1, 2, 3). At least one downlink element carrier is a dominant carrier and the remainder is a subordinate element carrier. Similarly, at least one uplink component carrier is a dominant carrier and the remainder is a subindent carrier. For example, D1, U1 are the dominant carriers, and D2, U2, D3, U3 are the subelement carriers.

In the FDD system, the downlink component carrier and the uplink component carrier are set to be 1: 1. For example, D1 is connected to U1, D2 to U2, and D3 to 1: 1 respectively. The UE establishes a connection between downlink component carriers and uplink component carriers through the system information transmitted by the logical channel BCCH or the dedicated terminal RRC message transmitted by the DCCH. Each connection may be cell specific or UE specific.

5 illustrates only the 1: 1 connection setup between the downlink component carrier and the uplink component carrier, but it is needless to say that the connection setup of 1: n or n: 1 can also be established. The index of the element carrier does not match the order of the element carriers or the position of the frequency band of the corresponding element carrier.

In a wireless communication environment, a propagation delay is propagated while a transmitter propagates and propagates in a receiver. Therefore, even if the transmitter and the receiver both know the time at which the radio wave is propagated correctly, the arrival time of the signal to the receiver is influenced by the transmission / reception period distance and the surrounding propagation environment. If the receiver does not know exactly when the signal transmitted by the transmitter is received, it will receive the distorted signal even if it fails to receive or receive the signal.

Therefore, in a wireless communication system, synchronization between a base station and a mobile station must be established in order to receive an information signal regardless of a downlink / uplink. Types of synchronization include frame synchronization, information symbol synchronization, and sampling period synchronization. Sampling period synchronization is the most basic motivation to distinguish physical signals.

The downlink synchronization acquisition is performed in the UE based on the signal of the base station. The base station transmits a mutually agreed specific signal for facilitating downlink synchronization acquisition at the terminal. The terminal must be able to accurately identify the time at which a particular signal sent from the base station is transmitted. In case of downlink, since one base station simultaneously transmits the same synchronization signal to a plurality of terminals, each of the terminals can acquire synchronization independently of each other.

In case of uplink, the base station receives signals transmitted from a plurality of terminals. When the distance between each terminal and the base station is different, signals received by each base station have different transmission delay times. When uplink information is transmitted on the basis of the acquired downlink synchronization, Is received at the corresponding base station. In this case, the base station can not acquire synchronization based on any one of the terminals. Therefore, uplink synchronization acquisition requires a procedure different from downlink.

On the other hand, the need for uplink synchronization acquisition may vary for each multiple access scheme. For example, in the case of a CDMA system, the BS can separate the uplink signals even if the BS receives the uplink signals of the other terminals at different times. However, in a wireless communication system based on OFDMA or FDMA, a base station simultaneously receives uplink signals of all terminals and demodulates them at a time. Therefore, as the uplink signals of a plurality of terminals are received at the correct time, the reception performance is improved. As the difference of the reception time of each terminal signal becomes larger, the reception performance drastically deteriorates. Therefore, uplink synchronization acquisition may be essential.

A random access procedure is performed for uplink synchronization acquisition. During the random access procedure, the UE adjusts the uplink time based on a time alignment value transmitted from the base station to acquire uplink synchronization do. It is necessary to determine whether the acquired uplink synchronization is valid after a predetermined time elapses after obtaining the uplink synchronization based on the time alignment value. To this end, the terminal defines a time alignment timer (TAT) configurable by the base station. When the time alignment timer is in operation, the terminal and the base station are in a state in which uplink synchronization is performed. If the time alignment timer expires or does not operate, the terminal and the base station are not synchronized with each other and must start the uplink synchronization acquisition procedure. In this case, the UE does not perform uplink transmission other than the transmission of the random access preamble. The time alignment timer specifically operates as follows.

i) If the terminal receives a time advance command from the base station via the MAC control element, the terminal applies the time alignment value indicated by the received time advance command to the uplink synchronization. The terminal then starts or restarts the time alignment timer.

ii) If the terminal receives a time advance command via a random access response message from the base station and does not select a random access response message in the MAC layer of the terminal (a), the terminal generates a time alignment value indicated by the time advance command Applies to uplink synchronization, and starts or restarts the time alignment timer. Alternatively, if the terminal receives a time advance command via a random access response message from the base station, selects a random access response message in the MAC layer of the terminal, and the time alignment timer is not operating (b) Applies the time alignment value indicated by the command to the uplink synchronization, starts the time alignment timer, and stops the time alignment timer if the contention resolution, which is a random access phase in the future, fails. Otherwise, in cases other than (a) and (b), the terminal ignores the time advancing command.

iii) When the time alignment timer expires, the UE flushes the data stored in all the HARQ buffers. Then, the UE informs the RRC layer of the release of the PUCCH / SRS. At this time, the type SRS (periodic SRS) is released and the type 1 SRS (aperiodic SRS) is not released. The UE clears all downlink and uplink resource allocations configured.

6 is a diagram illustrating a structure of a bearer service in a wireless communication system.

FIG. 6 shows a path in which an end-to-end service is provided between a terminal and an Internet network. Here, the term end-to-end service refers to a service (UE Bearer) between the UE and the P-GW, a P-GW, and an external bearer to the outside for an Internet network and data service . Here, the external path is a bearer between the P-GW and the Internet network.

When the UE transmits data to the external Internet network, the UE transmits eNB data through the RB. Then, the base station transmits the data received from the terminal to the S-GW through the S1 bearer. The S-GW carries the data received from the base station through the S5 / S8 bearer to the P-GW, and finally the data is transmitted to the destination existing in the P-GW and the external internet network through the external bearer.

Likewise, in order for data to be transmitted from the external Internet network to the mobile station, the mobile station can transmit data to the mobile station via the bearers in the reverse direction.

As described above, in the wireless communication system, each bearer is defined for each interface to ensure independence between interfaces. The bearer at each interface will be described in more detail as follows.

The bearer provided by the wireless communication system is collectively referred to as an evolved packet system (EPS) bearer. The EPS bearer is a delivery path established between the UE and the P-GW to transmit IP traffic with a specific QoS. The P-GW may receive IP flows from the Internet or may transmit IP flows over the Internet. Each EPS bearer is set with QoS decision parameters indicating the characteristics of the propagation path. An EPS bearer may be configured for one or more UEs per UE, and one EPS bearer uniquely represents a concatenation of one E-RAB and one S5 / S8 bearer.

The radio bearer (RB) exists between the UE and the base station and delivers the packets of the EPS bearer. A specific RB has a one-to-one mapping relationship with the corresponding EPS Bearer / E-RAB (E-UTRAN Radio Access Bearer).

The S1 bearer carries the E-RAB packet as a bearer existing between the S-GW and the base station.

The S5 / S8 bearer is the bearer of the S5 / S8 interface. Both S5 and S8 are bearers present at the interface between the S-GW and the P-GW. S5 interface exists when the S-GW and P-GW belong to the same service provider. The S8 interface belongs to the Visited PLMN roaming S-GW and the P- RTI ID = 0.0 > PLMN). ≪ / RTI >

The E-RAB uniquely represents the concatenation of the S1 bearer and its corresponding RB. When there is one E-RAB, a one-to-one mapping is established between the corresponding E-RAB and one EPS bearer. That is, one EPS bearer corresponds to one RB, S1 bearer, and S5 / S8 bearer, respectively. The S1 bearer is the bearer at the interface between the base station and the S-GW.

RB means two kinds of data RB (data radio bearer) and signaling RB (signaling radio bearer). However, in the present invention, RB is a DRB provided in a Uu interface to support a user service . Therefore, the RB that is expressed separately is distinguished from the SRB. RB is a path through which user plane data is transmitted, and SRB is a path through which control plane data such as an RRC layer and a NAS control message are transmitted. There is a one-to-one mapping between RB, E-RAB and EPS bearer. The base station maps DRBs and S1 bearers to one-to-one and stores them in order to generate a DRB that bundles both uplink and downlink. The S-GW maps the S1 bearer to the S5 / S8 bearer one-to-one and stores it in order to create the S1 bearer and the S5 / S8 bearer that bind both the uplink and downlink.

EPS bearer types include a default bearer and a dedicated bearer. When the terminal accesses the wireless communication network, the terminal is allocated an IP address and generates a PDN connection and a default EPS bearer at the same time. That is, the default bearer is first created when a new PDN connection is created. If a user uses a service (eg, the Internet) via a default bearer and uses a service (eg, VoD, etc.) that is not properly provided with QoS as the default bearer, A dedicated bearer is created. In this case, the dedicated bearer can be set to a different QoS from the bearer that has already been set. The QoS decision parameters applied to the dedicated bearer are provided by the Policy and Charging Rule Function (PCRF). When generating the dedicated bearer, the PCRF can receive the subscription information of the user from the Subscriber Profile Repository (SPR) and determine QoS determination parameters. Up to 15 dedicated bearers can be created, for example, up to 15, and in the LTE system, four out of the 15 are not used. Therefore, up to 11 dedicated bearers can be created.

The EPS bearer includes QoS Class Identifier (QCI) and Allocation and Retention Priority (ARP) as basic QoS decision parameters. EPS bearer is divided into GBR (Guaranteed Bit Rate) bearer and non-GBR bearer according to QCI resource type. The default bearer is always set to a non-GBR bearer, and the dedicated bearer can be set to a GBR or non-GBR bearer. In addition to QCI and ARP, the GBR type bearer has GBR and MBR (Maximum Bit Rate) as QoS decision parameters. After QoS defined by the wireless communication system as a whole is defined as an EPS bearer, QoS is determined for each interface. Each interface establishes a bearer according to the QoS it should provide.

7 is a view showing a structure of a user plane for a double connection.

Referring to FIG. 7, a dual connection is composed of an arbitrary terminal, a master base station MeNB, and at least one secondary base station SeNB. The double connection can be divided into three options as shown in FIG. 7 according to the method of dividing the user plane data. In Fig. 7, the concept of the above three options for downlink transmission of user plane data is shown as an example.

The first option is when the S1-U interface has an end point not only in the master base station but also in the secondary base station. In this case, each of the base stations MeNB and SeNB transmits downlink data through an EPS bearer (EPS bearer # 1 for the master base station and EPS bearer # 2 for the secondary base station) configured for one UE. Since the user plane data is splitted in the core network (CN), this is called a CN split.

Second option: The case where the S1-U interface has an end point only in the master base station. In this case, the S1-U interface has an end point only at the master base station, but the bearer does not differentiate and only one bearer is mapped for each base station.

Option 3: The S1-U interface has an endpoint only in the MeNB. In this case, since the bearer is differentiated, it is called a bear split. The bearer split is divided into two flows (or more flows) because one bearer is differentiated into a plurality of base stations. We call bearer splits as multi-flow, multiple-node (eNB) transmission, inter-eNB carrier aggregation, etc. in that information is transmitted through multiple flows. Also.

On the other hand, if the end point of the S1-U interface is the master base station (i.e., the second or third option) in terms of the protocol structure, the protocol layer in the secondary base station must support the segmentation or refinement process. This is because the physical interface and subdivision processes are closely related to each other, and when using non-ideal backhaul, the subdivision or subdivision process must be the same as the node transmitting the RLC PDU. Therefore, considering the protocol structures for dual connection in the RLC layer and above, the following is considered.

A. It is the case that the PDCP layer exists independently in each base station. This is also referred to as an independent PDCP type. In this case, each base station can use the operation of the existing LTE layer 2 protocol in the bearer as it is. This can be applied to both the first option and the third option.

B. The case where the PDCP layer exists in a master-slave form.

C. It is the case that the RLC layer exists independently in each base station. This is also referred to as an independent RLC type. In this case, the S1-U interface makes the master base station an end point, and the PDCP layer exists only in the master base station. In the case of the bearer split (third option), the RLC layer is separated in both the network and the UE side, and there exists an independent RLC bearer for each RLC layer.

D. The RLC layer is divided into the 'master RLC' layer of the master base station and the 'slave RLC' layer of the secondary base station. This is also referred to as master-slave RLC type. In this case, the S1-U interface has a master base station as an end point. In the master base station, a part of the PDCP layer and the RLC layer (the master RLC layer) exists and the secondary base station has a part of the RLC layer (the slave RLC layer). In the UE, there is only one RLC layer forming a pair with the master RLC layer and the slave RLC layer.

Thus, the double connection can be distinguished as shown in FIG. 7 by the combination of the above-described options and types. For example, 1A indicates a dual connection in which the CN splits and the PDCP layer exists independently in each base station. The term " 2A " means a dual connection in which two bearers are differentiated from the master base station and the PDCP layer exists independently. 2C means a dual connection in which the PDCP layer exists only in the master base station while the two bearers are differentiated from the master base station.

8A and 8B are diagrams illustrating a protocol structure of base stations in downlink transmission of user plane data.

Referring to FIG. 8A, an S1-U interface has an end point not only in a master base station but also in a secondary base station, and a PDCP layer exists independently in each base station (1A dual connection). In this case, the PDCP layer, the RLC layer and the MAC layer exist in the master base station and the secondary base station, respectively, and each base station transmits downlink data through each EPS bearer configured for the terminal.

In this case, the master base station does not need to buffer or process packets transmitted by the secondary base station, and has the advantage that there is little or no impact on the RDCP / RLC and GTP-U / UDP / IP. Since there is no need for backhaul link between the master base station and the secondary base station and there is no need to control the flow between the master base station and the secondary base station, the master base station does not need to route all the traffic, Can support local break-out and content caching at the same time.

Referring to FIG. 8B, there is shown a case where the S1-U interface has an end point only in the master base station, a bearer split, and an RLC layer is independently present in each base station (3C dual connection). In this case, the master base station has the PDCP layer, the RLC layer, and the MAC layer, and only the RLC layer and the MAC layer exist in the secondary base station. The PDCP layer, the RLC layer, and the MAC layer of the master base station are separated into bearer levels, and one PDCP layer is connected to one of the RLC layers of the master base station and is connected to the RLC layer of the secondary base station through the Xn interface.

In this case, there is no security effect that the mobility of the secondary base station is hidden in the core network, encryption is required in the master base station, and data forwarding between the secondary base stations is not necessary when the secondary base station is changed. In addition, the master base station can transfer RLC processing to the secondary base station, and can utilize radio resources through the master base station and the secondary base station for the same bearer when there is no or little influence on the RLC, There is an advantage in that the requirement for the mobility of the secondary base station is small since it is possible to use the master base station.

9 is a flowchart illustrating an operation of a base station 910 and a terminal 920 performing random access in a dual connection wireless communication system according to an embodiment of the present invention.

In this embodiment, the base station 910 can include at least one base station, and when it includes a plurality of base stations, it can be assumed that it is a master base station and a secondary base station. It can also be assumed that a main serving cell is configured in a secondary base station in a network or a secondary serving cell in which a physical uplink control channel is configured exists. At this time, the MS 920 performs a monitoring operation to receive a response MSG2 to the random access preamble MSG1 transmitted through one of the serving cells in the secondary base station. The MS 920 can receive the response message MSG2 through a secondary serving cell or a secondary serving cell that forms a physical uplink control channel. This process is described in detail as follows.

9, the base station 910 transmits the dual connection configuration information of the main serving cell and the secondary serving cell configured in the terminal 920 to the terminal 920 (S910). The dual connection configuration information includes information related to a master cell group (MSG) provided by the master base station currently configured in the corresponding terminal 920 and a secondary cell group (SCG) provided by the secondary base station . The dual connection configuration information may include information related to the main serving cell and the secondary serving cell included in the master cell group and information related to the primary serving cell and the secondary serving cell included in the secondary cell group. Since procedures such as handover may be different according to the dual connection structure, the terminal 920 receiving the dual connection configuration information operates based on the double connection configuration information.

The base station 910 transmits a PDCCH indication (order) indicating the start of the random access procedure for the secondary serving cell configured in the terminal 920 to the terminal (S920). The random access procedure may be contention-based or non-contention-based.

For example, in the case of a non-contention-based random access procedure, the base station 910 may select one of the dedicated random access preambles previously reserved from all available random access preambles, And transmits preamble allocation information (RA Preamble assignment) including time / frequency resource information to the UE 920 through a PDCCH indication. This is because for the random access procedure based on the non-contention, the UE 920 must be allocated a dedicated random access preamble from the Node B 910 that has no possibility of collision.

For example, if the random access procedure is performed during the handover procedure, the UE 920 may obtain a dedicated random access preamble from the handover command message. Or, for example, if a random access procedure is performed by a request (PDCCH order) of the base station 910, the terminal 920 may obtain a dedicated random access preamble via a PDCCH, i.e., physical layer signaling. In this case, the physical layer signaling may include fields as shown in Table 2 as downlink control information (DCI) format 1A.

bits. 모든 비트들이 1로 설정됨
- 프리앰블 인덱스(Preamble Index) - 6 bits
- PRACH 마스크 인덱스(Mask Index) - 4 bits
- 하나의 PDSCH 부호어의 간이 스케줄링 할당을 위한 포맷 1A의 모든 남은 비트들이 0으로 설정됨Carrier indicator field (CIF) - 0 or 3 bits.
- Flag for format 0 / 1A identification - 1 bit (0 indicates format 0, 1 indicates format 1A)
If the Format 1A CRC is scrambled by the C-RNTI and the remaining fields are set as follows, Format 1A is used for the random access procedure initiated by the PDCCH command (order).
-bottom-
- Localized / Distributed VRB allocation flag - 1 bit. Set to 0
- Resource block allocation -

bits. All bits set to 1
- Preamble Index - 6 bits
- PRACH mask index (Mask Index) - 4 bits
All remaining bits of format 1A for simple scheduling assignment of one PDSCH codeword are set to zero

Referring to Table 2, the preamble index is an index indicating a selected one preamble among pre-reserved random access preambles reserved for a non-contention-based random access procedure, and the PRACH mask index is usable time / frequency resource information. The available time / frequency resource information is again indicated by the frequency division duplex (FDD) system and the time division duplex (TDD) system as shown in Table 3.

PRACH
Mask index Allowed PRACH (FDD) Allowed PRACH (TDD) 0 all all One PRACH resource index 0 PRACH resource index 0 2 PRACH resource index 1 PRACH resource index 1 3 PRACH Resource Index 2 PRACH Resource Index 2 4 PRACH Resource Index 3 PRACH Resource Index 3 5 PRACH Resource Index 4 PRACH Resource Index 4 6 PRACH Resource Index 5 PRACH Resource Index 5 7 PRACH Resource Index 6 Reserved 8 PRACH Resource Index 7 Reserved 9 PRACH Resource Index 8 Reserved 10 PRACH Resource Index 9 Reserved 11 All the even PRACH opportunities in the time domain, the first PRACH resource index in the subframe All even PRACH opportunities in the time domain,
The first PRACH resource index in the subframe 12 All odd PRACH opportunities in the time domain,
The first PRACH resource index in the subframe All odd PRACH opportunities in the time domain,
The first PRACH resource index in the subframe 13 Reserved The first PRACH resource index in the subframe 14 Reserved The second PRACH resource index in the subframe 15 Reserved The third PRACH resource index in the subframe

As another example, in the case of a contention-based random access procedure, the base station 910 sets the preamble index in the preamble allocation information to '000000' and transmits it to the terminal 920. The UE 920 randomly selects one of the contention-based random access preambles and sets the PRACH mask index value to '0', and proceeds to a contention-based procedure. Also, the preamble allocation information may be transmitted to the terminal 920 through a higher layer message such as RRC (e.g., mobility control information (MCI) in the handover command).

The terminal 920 transmits a random access (RA) preamble to the base station 910 (S930). At this time, the UE 920 can transmit a random access preamble to either the dual-connected master base station or the secondary base station. The random access preamble may be transmitted via the representative serving cell. The representative serving cell may be a main serving cell in the cell group associated with the master base station and the secondary base station configured in the terminal 920 or a secondary serving cell selected to transmit the random access preamble. For example, the secondary serving cell selected to transmit the random access preamble may be a secondary serving cell (PUCCH SCell: PSCell) constituting the PUCCH. Representative serving cells may be selected per time alignment group. Also, the terminal 920 may transmit a random access preamble on a representative serving cell in any one of the plurality of time alignment groups, or may transmit a random access preamble on each representative serving cell in two or more time alignment groups The preamble may also be transmitted. For example, if the time alignment group configured in the UE 920 is TAG1 and TAG2, and TAG1 = {the first serving cell, the second serving cell, the third serving cell}, TAG2 = {the fourth serving cell, }. If the representative serving cell of TAG1 is the second serving cell and the representative serving cell of TAG2 is the fifth serving cell, the terminal 920 transmits the allocated dedicated random access preamble to the base station through the second serving cell or the fifth serving cell .

If the base station 910 successfully receives the random access preamble, the base station 910 can check which serving cell has transmitted the random access preamble through which base station 910 based on the received random access preamble and time / frequency resources. In particular, if the terminal 920 initiates a random access procedure for a secondary serving cell in response to a PDCCH indication from the base station, the terminal 920 has already received a unique identifier of the terminal 920, And has secured a Cell-Radio Network Temporary Identifier (RNTI). Therefore, the base station 910 can use the C-RNTI of the UE 920 as needed, and can transmit downlink information to the UE using the C-RNTI. For example, the downlink information includes a random access response message that is a response to reception of a random access preamble.

The base station 910 may send a random access response message to the terminal 920 (S940). The base station 910 can transmit the PDCCH scrambled with the C-RNTI of the UE 920 and the PDSCH to which the random access response message is mapped to the UE.

In this case, as an example, the BS 910 transmits a random access response message in the form of a RAR MAC PDU for a non-contention-based and contention-based random access procedure. However, when there is a main serving cell in a corresponding cell group according to each cell group, for example, a master cell group (MCG) and a secondary cell group (SCG), the base stations 910 associated with each cell group A random access response message may be transmitted through the main serving cell for the random access preamble received through the serving cell. Alternatively, if there is a serving cell indicated to be able to transmit a random access response message in the corresponding cell group, the serving cell is notified via the serving cell indicated to be able to transmit the random access response message A random access response message for the random access preamble may be transmitted. Accordingly, it is possible to efficiently receive the random access response message and to prevent the resources from becoming insufficient due to the transmission of the random access response message of the plurality of terminals 920 to one serving cell.

Also, downlink control information (DCI) is mapped to the PDCCH. The DCI includes HARQ information. The HARQ information includes a new data indicator (NDI) and a transport block (TB) size. For downlink shared channel (DL-SCH) transmission, the HARQ information includes the HARQ process ID. Meanwhile, for transmission of an uplink shared channel (UL-SCH), the HARQ information includes a redundancy version (RV).

The random access response message may be mapped to the PDSCH alone, or may be multiplexed with other data in a single MAC PDU and mapped to the PDSCH.

When the UE 920 detects the PDCCH, the HARQ entity of the UE 920 can perform a HARQ process related to the random access response message. Therefore, when the terminal 920 monitors the PDCCH and the PDCCH instructs downlink transmission, the terminal 920 starts a HARQ round trip time (RTT) timer.

The HARQ RTT timer specifies the minimum number of subframes before downlink retransmission that the terminal 920 expects. For example, for an FDD system, the HARQ RTT timer is set to 8 subframes. On the other hand, in the TDD system, the HARQ RTT timer is set to k + 4 subframes, where k is defined as the interval between the downlink transmission and the transmission of the HARQ feedback. The HARQ RTT timer is defined for each downlink HARQ process. During the HARQ RTT timer, the UE 920 determines that there is no retransmission of downlink data for the corresponding HARQ process. Therefore, the UE 920 does not perform a reception operation for the HARQ process. For example, if the UE 920 does not perform any downlink data reception operation other than the HARQ process and the corresponding subframe is not included in the active time, the UE 920 maintains a state for PDCCH reception You do not have to do.

If the terminal 920 does not detect the PDCCH itself, the HARQ RTT timer can not be started. On the other hand, if the terminal 920 succeeds in receiving the PDSCH to which the random access response message is mapped, the terminal 920 can transmit the corresponding ACK signal to the base station. In addition, if the terminal 920 fails to receive the PDSCH to which the random access response message is mapped, the terminal 920 can transmit the NACK signal corresponding thereto to the base station. The ACK / NACK signal may be transmitted after four subframes from the subframe receiving the PDSCH. The channel through which the ACK / NACK signal is transmitted may be the PUCCH of the main serving cell. Or the channel through which the ACK / NACK signal is transmitted may be the PUSCH of the primary serving cell or the secondary serving cell.

After receiving the ACK / NACK signal from the terminal 920, the base station 910 can retransmit the random access response message to the terminal 920 at a predetermined timing. The transmission of the random access response message in step S940 may be a new transmission in response to step S930, or may be a retransmission by a HARQ process.

The case where the transmission of the random access response message is a retransmission is also a transmission of a valid random access response message. Accordingly, when determining that the random access response message is successfully received, the terminal 920 may consider the time delay due to the retransmission. The terminal 920 determines whether the random access procedure is successful within the RA valid reception duration (not shown). This will be explained later.

FIG. 10 shows an example of transmitting and receiving a random access preamble and a response message thereto in a dual connection wireless communication system according to an embodiment of the present invention.

10, a UE 1010 having a dual connection to a master base station (MeNB) and a secondary base station (SeNB) can perform a random access procedure on the master cell group 1020 and the secondary cell group 1030. The master cell group 1020 may be a cell group constituted by the master base station and the secondary cell group 1030 may be a cell group constituted by the secondary base station. Master cell group 1020 may include cell 1 1022, cell 2 1024 and cell 3 1026 and secondary cell group 1030 may include cell 4 1032, cell 5 1034, 6 1036 < / RTI > At this time, cell 1 1022 and cell 4 1032 may be the main serving cell of the master cell group 1020 and the secondary cell group 1030.

The UE 1010 may transmit a random access preamble to each of the master cell group 1020 and the secondary cell group 1030 when performing a random access procedure in a dual connection state. That is, the random access random access preamble 1 may be transmitted to the master cell group 1020 and the random access preamble 2 may be transmitted to the secondary cell group 1030. At this time, the random access preamble 1 may be transmitted to the cell 1 1022 which is the main serving cell in the master cell group 1020, and the random access preamble 2 may be transmitted to the cell 4 1032, which is the main serving cell in the secondary cell group 1030, Lt; / RTI > At this time, the random access preamble does not necessarily have to be transmitted to the main serving cell of each cell group but may be transmitted to another serving cell designated to receive the random access preamble in the corresponding cell group. The base station of each cell group receiving the random access preamble generates a random access response message for the received random access preamble. The base station of each cell group may transmit the random access response message to the terminal 1010 through a secondary serving cell or a secondary serving cell designated to transmit a random access response message. Here, the secondary serving cell designated to transmit the random access response message may be a secondary serving cell (PUCCH SCell: PSCell) configured with a PUCCH. 10, a random access preamble 1 is received in cell 1 1022, which is the main serving cell of the master cell group 1020, and a random access response message 1 is transmitted in cell 1 1022, which is a main serving cell, do. On the other hand, in the case of the secondary cell group 1030, the random access preamble 2 is received in the cell 4 1032 serving as the main serving cell, but the random access response message 2 is transmitted through the cell 5 1034 serving as the secondary serving cell.

Although not shown in the drawings, the following situation may be assumed. When the random access preamble is received in the cell 5 1034 serving as the secondary serving cell of the secondary cell group 1030, the response message of the random access preamble is transmitted to the cell 4 1032 serving as the main serving cell of the secondary cell group 1030 Lt; / RTI > Or, as the case may be, a response message may be sent to cell 5 1034 that has received the random access preamble. At this time, the cell 5 1034 may be a PSCell. Since random access preamble and random access response messages are transmitted and received independently for each cell group, the success or failure of the random access procedure can be independently determined. This will be described below with reference to FIG.

Also, the maximum value of the random access procedure in progress for each cell group can not exceed 1. That is, if a random access procedure has been started via any serving cell in a particular cell group and the random access procedure has not been terminated due to success or failure, then a new random access procedure can not be started within the same cell group. However, if the random access procedure is in progress in another cell group, the random access procedure can be started through any serving cell in the cell group.

11 shows an example in which a response message of a random access preamble according to an embodiment of the present invention is mapped to a physical downlink data area.

FIG. 11 illustrates transmission of a random access response message on a time / frequency plane. The terminal has a master cell group (MCG 1100) and a secondary cell group (SCG 1102), and transmits and receives a random access preamble and a random access response message through the cell group. A subframe for transmitting and receiving a random access preamble and a random access response message may include a control region 1110 and a data region 1112. [

First, with respect to the master cell group 1100, when the random access preamble 1 is transmitted through the main serving cell (PCell), the random access response message 1 1120 for the random access preamble 1 is transmitted to the main serving cell (PCell) Lt; / RTI > (Case 1). Alternatively, even if the random access preamble 1 is transmitted in the main serving cell (PCell), the random access response message 1 1122 for the random access preamble 1 is transmitted to the serving cell (SCell 1) instructed to transmit the random access response message Can be mapped to the data area (Case 2).

Next, with respect to the secondary cell group 1102, when the random access preamble 2 is transmitted from the secondary serving cell SCell 1 other than the main serving cell PCell, the random access response message 2 ( 1130 may be mapped to the data area of the main serving cell PCell (Case 3). Alternatively, when the random access preamble 2 is transmitted in the serving cell (SCell 1), the random access response message 2 1132 for the random access preamble 2 is transmitted to the serving cell (SCell 1) instructed to transmit the random access response message. Lt; RTI ID = 0.0 > (Case 4). ≪ / RTI > At this time, the secondary serving cell (SCell 1) may be the PSCell constituting the PUCCH.

FIG. 12 shows an example in which a response message of a random access preamble according to another embodiment of the present invention is transmitted in the form of a RAR MAC CE.

12, the transmission step S1210, the preamble transmission instruction step S1220 and the random access preamble transmission step S1230 of the double connection configuration information may be the same as the steps S910, S920 and S930 of FIG. 9 .

In this embodiment, after receiving the random access preamble, the base station 1210 may configure the RAR MAC CE (S1240).

If the RAR is transmitted using the RA-RNTI, a common search space is used to transmit the RAR. In this case, the random access procedure can not be efficiently achieved due to the lack of common search space resources. Therefore, in the non-contention-based random access procedure, the embodiment changes the structure of the message for transmitting the RAR so that the UE-specific search interval can be utilized.

In the case of a non-contention-based random access procedure, the master base station or the secondary base station transmits a primary serving cell (PCell) in a master cell group or a secondary cell group or a serving cell (e.g., The MAC PDU including the RAPID in the MAC PDU corresponding to the subheader including the logical control ID (LCID) value indicating the random access response message for the non-contention-based random access preamble. At this time, the C-RNTI of the UE 1220 may be used as the RNTI used when scrambling the PDCCH used to indicate the PDCCH including the RAR.

Then, the BS 1210 may transmit the MAC PDU including the information to the SS 1220 through the serving cell designated to receive the main serving cell or the random access response message (S1250). Here, the secondary base station may transmit the MAC PDU through one of the serving cells in the secondary cell group, and transmit the MAC PDU to the terminal 1220 through a secondary serving cell (PSCell) constituting a main serving cell or a PUCCH in the secondary cell group. PDU. ≪ / RTI >

At this time, the random access response message may be mapped to the PDSCH alone, or may be multiplexed with other data in a single MAC PDU and mapped to the PDSCH. The PDSCH to which the random access response message is mapped is indicated by the PDCCH scrambled with the C-RNTI. The random access response message may optionally be transmitted on the serving cell. The resource used for transmission of the PDSCH to which the random access response message is mapped is indicated by the resource block allocation field in the DCI.

As described above, a PDCCH scrambled by RA (random access) -RNTI is allocated to the common search space. However, since the common search space is not defined in the secondary serving cell and only the UE-specific search space can be defined, the terminal 1220 allocates the PDCCH scrambled by the RA-RNTI on the secondary serving cell and the PDCCH scrambled by the RA- I can not receive an access response message. Accordingly, in order to receive the random access response message in the secondary serving cell, the UE 1220 can only use the UE-specific search space and the PDCCH scrambled by the C-RNTI is allocated in the UE- And indicates the PDSCH for the random access response message with the PDCCH scrambled by the RNTI.

The MS 1220 receiving the MAC PDU decodes the physical downlink shared channel including the received MAC PDU using the C-RNTI of the MS itself (S1260). As a result of decoding, if the MAC CE including the RAPID indicated for the non-contention-based random access is confirmed, it can be confirmed that the non-contention-based random access procedure in progress through the main serving cell or the PSCell configured in the master base station or the secondary base station is successful.

13 shows a MAC PDU structure for a random access response message to which the present invention is applied.

13, the MAC PDU 1300 includes a MAC header 1310, at least one MAC control element 1320, ..., 1325, at least one MAC SDU (Service Data Unit) 1330-1, ..., 1330-m, and padding 1340.

The MAC header 1310 includes at least one sub-header 1310-1, 1310-2, ..., 1310-k, and each sub-header 1310-1, 1310-2, ..., ., 1310-k correspond to one MAC SDU or one MAC control element 1320, ..., 1325 or padding 740, respectively. The order of the subheaders 1310-1, 1310-2, ..., 1310-k corresponds to the corresponding MAC SDU, MAC control element 1320, ..., 1325 or padding 1340 in the MAC PDU 1300 ). Each of the subheaders 1310-1, 1310-2, ..., and 1310-k may have a structure as shown in FIG.

14 shows an R / R / E / LCID sub-header.

Referring to FIG. 14, each of the subheaders 1310-1, 1310-2, ..., and 1310-k may include four fields of R, R, E, and LCID. Here, R denotes a reserved bit and E denotes an extended bit. The LCID is logical channel identification information (Logical Channel ID). A subheader including four fields is a subheader corresponding to MAC control elements 1320, ..., 1325 or padding 1340. This does not indicate MAC RAR as a MAC PDU suitable for data transmission, but it can change the LCID included in the MAC RAR so that MAC RAR can be transmitted through a MAC PDU structure suitable for data transmission.

The Logical Channel ID (LCID) field is an identification field that identifies a logical channel corresponding to a MAC SDU or identifies a MAC control element 1320, ..., 1325 or a type of padding, When each subheader 1310-1, 1310-2, ..., 1310-k has an octet structure, the LCID field may be 5 bits.

For example, the LCID field indicates whether the MAC control element 1320, ..., 1325 is a MAC control element for instructing activation / deactivation of a serving cell, a contention resolution identifier for contention resolution Resolution Identity) Identifies whether it is a MAC control element or a MAC control element for a time advance command. The MAC control element for the time advance command is a MAC control element used for time alignment in random access.

LCID Index LCID value 00000 CCCH 00001-01010 Identifier of the logical channel 01011-11010 Reserved 11011 Enable / Disable 11100 The terminal contention resolution identifier 11101 Time advance command (TAC) 11110 DRX command 11111 padding

Referring to Table 4, if the value of the LCID field is 11101, the corresponding MAC control element is the MAC control element for the time advance command.

According to an embodiment of the present invention, when the random access response message having the MAC PDU structure is transmitted through one of the serving cells of the secondary cell group, the LCID field may be given as shown in Table 5.

LCID Index LCID value 00000 CCCH 00001-01010 Identifier of the logical channel 01011-11001 Reserved 11010 RAR for SeNB 11011 Enable / Disable 11100 The terminal contention resolution identifier 11101 Time advance command (TAC) 11110 DRX command 11111 padding

Referring to Table 5, if the value of the LCID field is 11010, the corresponding MAC control element is the MAC control element for the random access response. Using this LCID value, a random access response message can also be transmitted through a MAC PDU including a MAC CE and MAC SDUs for data transmission. That is, the terminal-specific search space other than the common search space can be utilized as a space for the random access response message.

13, a subheader including six fields of R, R, E, LCID, F and L as well as four subheaders of R, R, E and LCID can be transmitted. And a subheader including six fields is a subheader corresponding to a MAC SDU.

Next, the MAC control elements 1320, ..., and 1325 are control messages generated by the MAC layer. A padding 1340 is a predetermined number of bits added to make the size of the MAC PDU constant. The MAC control elements 1320 to 1325, the MAC SDUs 1330-1 to 1330-m and the padding 1340 are collectively referred to as a MAC payload.

Examples of the MAC control element for transmitting the random access preamble response message are shown in FIGS. 15A to 15D.

15A to 15E show an example of a RAR MAC CE according to an embodiment of the present invention.

Referring to FIG. 15A, a RAR MAC control element for transmitting a random access preamble response message may include only a random access preamble identifier (RAPID) field and a reserved bit. The RAPID is an identifier for identifying terminals performing random access. When the RAR MAC control element for transmitting a random access preamble response message is an octet structure, the RAPID field is 6 bits and the reserved bits are 2 bits. For example, if there are three RAPIDs and the RAPID index is 1, 2, or 3, the RAPID field may be displayed as {00, 01, 10}. If the RAPID index is 2, at least one of the 2-bit RAPID index fields may be set to a reserved bit R. [ The number of bits of the RAPID field and the number of bits of the reserved field in the present embodiment are merely examples, and they are not necessarily limited to six and two, respectively.

Referring to FIG. 15B, a RAR MAC control element for transmitting a random access preamble response message may include a RAPID field, a time advance command field, and a reserved bit. When the RAR MAC control element for transmitting the random access preamble response message is an octet structure, the RAPID field may have 6 bits, the reserved bits may have 4 bits, and the time advance command field may have 6 bits. At this time, the RAPID field occupies the right 6 bits of the first octet, the time advance command field occupies the right 6 bits of the second octet, and the remaining bits can occupy the reserved bits. However, the present invention is not limited thereto.

Referring to FIG. 15C, the RAR MAC control element for transmitting a random access preamble response message may include only a RAPID field and a time advance command field. When the RAR MAC control element for transmitting a random access preamble response message is an octet structure, the RAPID field may have 6 bits and the time advance command field may have 10 bits. At this time, the RAPID field occupies the right 6 bits of the second octet, and the time advance command field can occupy both the 8 bits of the first octet and the left 2 bits of the second octet. However, the present invention is not limited thereto.

Referring to FIG. 15D, the RAR MAC control element for transmitting a random access preamble response message may include only a time advance command field. When the RAR MAC control element for transmitting the random access preamble response message is an octet structure, the reserved bit may have 5 bits and the time advance command field may have 11 bits. At this time, the reserved bits occupy the left 1 bit of the first octet and the right 4 bits of the second octet, the time advance command field occupies 7 bits excluding the left 1 bit of the first octet and the left 4 bits of the second octet . However, the present invention is not limited thereto. Since the UE recognizes that only one random access procedure is in progress for each cell group, the UE determines whether the RAR MAC control element is a response to a random access preamble based on the cell group including the serving cell that received the RAR MAC control element It can be recognized without RAPID information. However, the spare bits of the left 1 bit of the first octet may be configured as a cell group indicator in order to prevent a reception error of the UE receiving the information. In this case, '0' indicates MCG and '1' indicates SCG.

Referring to FIG. 15E, the RAR MAC control element for transmitting the random access preamble response message may include a RAPID field, a time advance command field, an UL grant field, and a reserved bit. When the RAR MAC control element for transmitting a random access preamble response message is an octet structure, the RAPID field is 6 bits, the reserved bits are 11 bits, the time advance command field is 11 bits, and the UL grant field is 20 bits Lt; / RTI > At this time, the RAPID field occupies the right 6 bits of the fifth octet, the time advance command field occupies the right 7 bits of the first octet and the left 4 bits of the second octet, and the UL grant field occupies the right 4 bits of the second octet And all of the third and fourth bits, and the remaining bits can be occupied by the reserved bits. However, the present invention is not limited thereto.

16 illustrates an example of configuring parameters for a random access procedure through the PSCell of the main serving cell and the secondary cell group of the master cell group according to an embodiment of the present invention.

16, when a main serving cell is configured in a plurality of base stations configured in the mobile station, that is, when different master serving cells are included in each of the master cell group MCG and the secondary cell group SCG, When a secondary serving cell (PSCell) 1620 is present in the secondary cell group, a method for configuring parameters for a random access procedure is as follows.

Before the random access procedure is initiated, information about the serving cell concerned is considered available. At this time, the main serving cell 1610 of the master cell group MCG and the PSCell 1620 of the secondary cell group SCG are allocated random access preambles 1632 and 1634, A set of access preambles can be used. The preambles included in the random access preamble group A 1632 and the preambles included in the random access preamble group B 1634 are random access group A size parameters sizeOfRA -PreamblesGroupA and random access preamble number parameters numberOfRA - Preambles . Lt; / RTI >

When the size parameter ( sizeOfRA - PreamblesGroupA ) of the random access group A is equal to the number parameter ( numberOfRA - Preambles ) of the random access preamble, the random access preamble B 1634 is not present.

If random access preamble B 1634 is present, various information (info 1 to info N) required to select one of the two groups of random access preambles may be needed. The information is a random access window size (ra -ResponseWindowSize), a power-preamble based on the offset between the ramp factor (powerRampingStep), maximum number of preamble transmission (preambleTransMax), the preamble initial power (preambleInitialReceivedTargetPower), a preamble and a message 3 (Msg3) Format information ( DELTA _ PREAMBLE ), and the like.

The maximum number of times of message 3 (Msg3) HARQ transmission ( maxHARQ - Msg3Tx ) and the contention resolution timer information ( mac - ContentionResolutionTimer ) are stored in the main serving cell 1610 of the master cell group MCG ) And the PSCell 1620 of the secondary cell group (SCG).

FIG. 17 shows an operation for determining whether or not random access is successful according to the first embodiment of the present invention. As shown in FIG. 17, the contention-based random access procedure for the secondary base station is possible only in the PSCell in the secondary cell group. This is as follows.

Referring to FIG. 17, the UE performs a contention-based random access procedure in a secondary cell group (S1710). During the UE performing the random access procedure, the random access preamble may be retransmitted in a situation such as a contention occurrence or the like. The number of transmissions of the random access can be calculated through a counter. The MS calculates the number of retransmissions of the random access preamble and determines whether the number of retransmissions exceeds the threshold (S1720). If the number of retransmissions is smaller than the threshold, it is determined whether a suitable RAR is received (S1722). If a suitable RAR is received, the random access procedure is considered successful and the procedure is terminated (S1726). At this time, whether or not a suitable RAR has been received can be determined based on whether the RAR is decoded through the RNTI of the corresponding terminal. Specifically, when the following common requirements are satisfied, it can be determined that a suitable RAR has been received. The common requirement is that i) the UE will receive the PDSCH within the random access valid reception interval, ii) the UE will succeed in decoding the PDSCH, and iii) the random access response message will be mapped to the PDSCH. In this case, iii) determination of the requirement may be made by checking whether the MAC layer has mapped the MAC PDU including the random access response message to the PDSCH or checking whether a random access response (RAR) MAC control element (CE) Lt; / RTI >

If it is determined that the RAR is not received, the RAR preamble is retransmitted (S1724). At this time, the number of retransmissions increases and a determination is made as to whether the number of retransmissions is greater than the threshold.

If the number of retransmissions of the random access preamble is larger than the threshold value, that is, if the number of times of retry of the random access preamble has increased beyond the limit value in step S1720, the UE determines whether the random access preamble has been transmitted in the PSCell (S1730). If it is not PSCell, the random access procedure is considered to have failed and the procedure is terminated (S1732). If the PSCell is PSCell, the report is made to the upper layer (e.g., RRC layer) (S1734) And terminates the procedure (S1732).

FIG. 18 shows an operation for determining whether or not the random access is successful according to the second embodiment of the present invention.

The success or failure of the random access may be determined according to whether or not the contention resolution is made. Contention resolution is a downlink shared channel (DL-SCH) on the UE contention resolution identifier (UE Contention Resolution Identity: UE CR I _D), or, for a random access procedure in PSCell or master cell group for a random access procedure on the secondary cell group Lt; / RTI > on the PDCCH of the primary serving cell. As shown in FIG. 18, if a contention-based random access procedure initiated by a terminal directly or by a secondary base station proceeds in the PSCell, the success or failure of the random access procedure can be determined through the following procedure.

Referring to FIG. 18, in step S1810, the UE directly starts or performs a contention-based random access procedure indicated by the secondary base station in the PSCell of the secondary base station. The MS may transmit the message 3 (Msg3) including the C-RNTI to the secondary base station at least once (S1920). At this time, notification of reception of the PDCCH transmission can be received from the lower layer. Here, if the random access procedure is initiated by the MAC sublayer and the UE receives through the PSCell using the PDCCH scrambled with the same value as the C-RNTI (S1830), the UE determines that the contention resolution is successful (S1840). Then, the terminal considers that the random access procedure is successful (S1850).

FIG. 19 shows an operation for determining whether or not random access is successful according to the third embodiment of the present invention. In this embodiment, the success or failure of the random access can be determined according to whether or not the contention is resolved, and the contention resolution can be determined based on the contention resolution identifier on the downlink shared channel (DL-SCH), the PSCell Or a C-RNTI on the PDCCH of the primary serving cell for the random access procedure in the master cell group. The determination of conflict resolution and the success or failure of the random access procedure of the present embodiment may be performed as follows.

Referring to FIG. 19, if the UE receives a PDCCH scrambled with the same C-RNTI as the UL grant for new data transmission through one of the serving cells in the secondary cell group (S1910) (S1920). Then, it can be determined that the random access procedure is successful based on the success of the contention resolution (S1930).

FIG. 20 shows an operation for determining whether or not random access is successful according to the fourth embodiment of the present invention.

As shown in FIG. 20, the success or failure of the random access may be determined according to whether or not the contention resolution is performed, and the contention resolution may be performed as follows.

20, the UE may perform: i) a PSCell 2024 for a random access procedure in a secondary cell group 2020 or a C-PDCCH 209 on a PDCCH of a main serving cell 2012 for a random access procedure in a master cell group 2010, RNTI 2030 or a serving cell for a random access procedure in the secondary cell group 2020 (Scell 3 2026 in this embodiment) or a master cell group 2010 Based on any one of the UE contention resolution identifiers (UE CR I _D : 2040) on the downlink common channel (DL-SCH) of the SCELL 2016 (in some embodiments, the main serving cell 2012) It can be judged whether or not the conflict resolution is solved.

Here, the terminal contention resolution identifier 2040 may be the C-RNTI 2030 or may be another identifier. In addition, the terminal combination resolution identifier 2040 may be assigned a different value for each cell group. Therefore, the success or failure of the random access procedure may be determined independently with respect to each cell group by using the terminal resolution identifier 2040. As a result, success or failure of the contention-based random access procedure in the corresponding group according to the received cell group of the downlink shared channel (DL-SCH) including the same terminal contention resolution identifier can be independently determined.

21 is a block diagram illustrating a base station and a terminal for performing random access according to an exemplary embodiment of the present invention.

The terminal 2100 includes a receiving unit 2105, a terminal processor 2110, and a transmitting unit 2120. The terminal processor 2110 includes an HARQ performing unit 2111 and a random access processing unit 2112.

The receiving unit 2105 receives from the base station 2150 a PDCCH indication indicating the start of the random access procedure configured in the UE 2100. [ Here, the base station 2150 may be a plurality of base stations, and the plurality of base stations may include a master base station (MeNB) and a secondary base station (SeNB). Also, the receiver 2105 can receive the PDCCH scrambled with the C-RNTI and the PDSCH to which the random access response message is mapped, from the BS 2150. The receiving unit 2105 may receive the random access response message through a secondary serving cell or a secondary serving cell instructed to receive a random access response message in a cell group associated with the master base station MeNB and the secondary base station SeNB. At this time, the secondary serving cell designated to receive the LAN access response message may be a secondary serving cell constituting the PUCCH.

The receiving unit 2105 monitors the PDCCH using the C-RNTI related to the UE 2100, descrambles the PDCCH, and extracts the DCI. Downlink control information (DCI) is mapped to the PDCCH. The DCI includes HARQ information. The HARQ information includes a new data indicator (NDI), a transport block (TB) size. For downlink shared channel (DL-SCH) transmission, the HARQ information includes the HARQ process ID. Meanwhile, for transmission of an uplink shared channel (UL-SCH), the HARQ information includes a repeated version (RV).

When the receiving unit 2105 receives the PDSCH including the random access response message, the HARQ performing unit 2111 drives the HARQ RTT timer. When the receiving unit 2105 successfully decodes the PDSCH, the HARQ performing unit 2111 generates an ACK signal indicating successful decoding of the PDSCH, and the transmitting unit 2120 transmits the generated ACK signal to the base station 2150 do. The receiving unit 2105 receives a primary serving cell for a random access procedure or a logical channel identification information (LCID) indicating a random access response message through a secondary serving cell instructed to receive a random access response message in a cell group associated with the secondary base station, The MAC PDU corresponding to the MAC subheader including the value of the MAC PDU can be received. Here, the reception of the MAC PDU may be performed in a contention-free random access procedure.

The MAC PDU may include a MAC control element including a random access preamble identifier. At this time, the MAC control element may further include at least one of a timing advance command (TAC) and an uplink grant in addition to the random access preamble identifier. The receiver 2105 can perform decoding using a cell radio network temporary identifier (C-RNTI) that identifies the UE. If the receiver 2105 does not successfully decode the PDSCH, the HARQ processor 2111 generates a NACK signal indicating a decoding failure of the PDSCH by the HARQ process, and the transmitter 2120 transmits the generated NACK signal to the base station 2150).

The random access processing section 2112 judges whether or not the random access procedure is successful. The random access processing unit 2112 determines whether or not the random access procedure performed in the corresponding cell group independently depends on the cell group on which the downlink shared channel including the same terminal contention resolution identifier (UE CR _ID ) is received . At this time, the random access processing unit 2112 can determine whether or not the random access procedure is successful based on whether or not to resolve the contention. This can be accomplished by associating a main serving cell for a random access procedure in the cell group associated with the master base station, (C-RNTI) on a physical downlink control channel of a serving cell for a random access procedure in a cell group or a serving cell for a random access procedure in a cell group associated with the master base station, And a contention resolution identifier on a downlink shared channel (DL-SCH) of a serving cell for a random access procedure in a cell group associated with the cell group.

When the contention-based random access procedure for the secondary base station is performed in the PSCell in the secondary cell group and the number of preamble retries is increased beyond the limit value, the random access processing unit 2112 transmits the contention-based random access procedure to the upper layer (for example, the RRC layer) Can be reported. The random access processing unit 2112 regards the random access procedure as unsuccessful for all the SCells other than the PSCell and does not report it.

The random access processing unit 2112 determines whether the MS has directly started the contention-based random access procedure or the message 3 (MSG3) including the C-RNTI MAC CE is transmitted at least once, When the UL grant for new data transmission is received through the PSCell using the PDCCH scrambled with the same value as the C-RNTI, it is determined that the contention resolution has succeeded and it can be determined that the random access procedure has succeeded. If a PDCCH scrambled with the same C-RNTI as the UL grant for new data transmission is received through one of the serving cells in the secondary cell group, it is determined that the contention resolution is successful, It can be determined that the access procedure is successful.

First, the random access processing section 2112 primarily determines whether the random access (RA) procedure is successful in the random access window. In the random access window, the receiving unit 1705 successfully decodes the PDCCH scrambled with the C-RNTI, the new data indicator indicates 'new transmission' to the DCI of the PDCCH, and the receiving unit 2105 instructs The PDSCH is successfully received and decoded, and if it is satisfied that the PDSCH includes the random access response message, the random access processing unit 2112 confirms the success of the random access procedure. If any one of them is not satisfied, the random access processing section 2112 confirms the failure of the random access procedure.

If the random access procedure is successful, the random access processing unit 2112 adjusts the uplink time of the secondary serving cell based on the time alignment value included in the random access response message. If the random access procedure fails, the random access processing section 2112 triggers a retransmission of the random access preamble (RAP). When the HARQ RTT timer expires, the terminal can drive a DRX retransmission timer. At this time, the UE can monitor the PDCCH and receive and decode the retransmitted data.

The random access processing unit 2112 secondarily determines the success or failure of the random access (RA) procedure within the DRX retransmission timer. During the progress of the DRX retransmission timer, the receiver 2105 successfully decodes the PDCCH scrambled with the C-RNTI, the receiver 2105 successfully receives and decodes the PDSCH indicated by the PDCCH, and the PDSCH receives a random access response Message is satisfied, the random access processing section 2112 confirms the success of the random access procedure. If any one of them is not satisfied, the random access processing section 2112 confirms the failure of the random access procedure. Here, the random access response message may be retransmitted.

If the random access procedure is successful, the random access processing unit 2112 adjusts the uplink time of the secondary serving cell based on the time alignment value in the random access response message. The random access processing unit 2112 drives a time alignment timer (TAT).

On the other hand, when the time alignment timer is already in progress in the subframe in which the random access preamble is retransmitted, the random access processing unit 2112 can cancel the retransmission of the random access preamble. If the random access procedure fails, the random access processing section 21212 regenerates the random access preamble and controls the regenerated random access preamble to transmit the random access preamble in the predetermined subframe.

The base station 2150 includes a transmitting unit 2155, a receiving unit 2160, and a base station processor 2170. The base station processor 2170 includes an HARQ performing unit 2171 and a random access processing unit 2172.

The transmitting unit 2155 transmits a PDCCH indication indicating the start of the random access procedure regarding the secondary serving cell configured in the UE 2100, a PDCCH scrambled with the C-RNTI regarding the UE 2100, and a PDCCH scrambled with the C- And transmits a PDSCH indicated by the PDCCH and including a random access response message to the UE 2100.

The receiving unit 2160 receives the random access preamble from the terminal 2100 in response to the PDCCH indication. The receiving unit 2160 receives an ACK / NACK signal from the UE 2100 in response to the PDSCH transmission.

The HARQ performing unit 2171 generates the DCI including the HARQ information. The process of generating a DCI includes setting a value of a new data indicator, generating a DCI including HARQ information, adding a cyclic redundancy check (CRC) parity bit to the DCI, And scrambling with a C-RNTI.

The random access processing unit 2172 sets parameters necessary for a random access procedure such as a PRACH mask index allocated to the UE and generates a random access response message when the random access preamble is successfully received and sends the random access response message to the HARQ performing unit 2171. The HARQ performing unit 2171 generates an MAC PDU including the random access response message, maps the generated MAC PDU to the PDSCH, and sends the MAC PDU to the transmitting unit 2155. At this time, the base station 2150 receiving the contention-based random access preamble can transmit the RAR information through the common search space (CSS) using the RA-RNTI as in the conventional RAR MAC PDU. However, in case of non-contention-based random access, a MAC PDU corresponding to a subheader including an LCID value indicating a RAR for a non-contention-based random access through a SCell (PSCell) configured with a PCell or PUCCH in a secondary cell group includes a RAPID (CE), including the MAC address, to be transmitted. In this case, the RNTI used when scrambling the PDCCH used to indicate the PDSCH including the RAR can use the C-RNTI of the corresponding UE. The MAC PDU including the information may be transmitted through one of the serving cells in the secondary cell group or may be transmitted through a secondary serving cell in the secondary cell group or a secondary serving cell constituting the PUCCH. The transmitting unit 2155 transmits the PDSCH to the terminal 2100.

If the receiving unit 2160 receives the NACK signal for the PDSCH, the HARQ performing unit 2111 controls retransmission of the data mapped to the PDSCH.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions as defined by the following claims It will be understood that various modifications and changes may be made thereto without departing from the spirit and scope of the invention.

Claims (20)

A method for performing random access by a terminal in a wireless communication system using a dual connection method,
Transmitting a random access preamble; And
Receiving a random access response message on a physical downlink shared channel (PDSCH) in response to the random access preamble,
The terminal is configured with a dual connection by a master base station (master eNB) and a secondary base station (secondary eNB)
The random access response message includes an instruction to receive the random access response message in a primary cell (PCell) in a master cell group provided by the master base station and in a secondary cell group provided by the secondary base station And a secondary serving cell (SCell) serving as a secondary serving cell. The method according to claim 1,
Wherein the secondary serving cell designated to receive the random access response message is a secondary serving cell on which the physical uplink control channel is configured. The method of claim 1, wherein the random access response message comprises:
Wherein the random access preamble is received through the same serving cell as the serving cell in which the random access preamble was transmitted. 2. The method of claim 1, further comprising determining whether the random access procedure is successful,
In accordance with the determination of the success or failure of the random access procedure, a downlink shared channel (DLSCH) including the same UE Contention Resolution Identity is independently allocated to a corresponding cell group Is judged as to whether or not the random access procedure proceeding is successful. 5. The method of claim 4,
The success or failure of the random access procedure may be determined based on whether contention resolution is to be performed,
Whether or not the conflict is resolved,
A cell-radio network temporary identifier (C-RNG) on a physical downlink control channel of a serving cell for a random access procedure in a primary serving cell or a secondary serving cell for a random access procedure in the master cell group, RNTI)
A serving cell for a random access procedure in the master cell group or a cell contention resolution identifier on a downlink shared channel (DL-SCH) of a serving cell for a random access procedure in the secondary cell group,
Wherein the random access is performed based on any one of the plurality of random access times. 2. The method of claim 1, wherein the random access response message is a structure of a medium access control (MAC) protocol data unit (PDU)
The MAC PDU includes a MAC subheader and a MAC control element,
Wherein the MAC subheader includes a logical channel ID (LCID) indicating that the MAC control element is for the random access response. 7. The apparatus of claim 6,
Wherein the random access preamble identifier comprises a random access preamble identifier (RAPID). 7. The method of claim 6, wherein receiving the random access response message comprises:
Further comprising the step of decoding the physical downlink shared channel using a cell radio network temporary identifier (C-RNTI) that identifies the UE. 8. The apparatus of claim 7, wherein the MAC control element comprises:
A timing advance command (TAC), and an uplink grant. ≪ Desc / Clms Page number 19 > The method according to claim 6,
Wherein the reception of the MAC PDU is performed in a contention-free random access. A method for performing random access by a base station in a wireless communication system using a dual connection scheme,
Receiving a random access preamble; And
Transmitting a random access response message on a physical downlink shared channel (PDSCH) in response to the random access preamble,
A terminal is configured with a dual connection by a master base station (master eNB) and a secondary base station (secondary eNB)
Wherein the random access response message includes an instruction to transmit the random access response message in a primary cell (PCell) in a master cell group provided by the master base station and in a secondary cell group provided by the secondary base station And a secondary serving cell (SCell) serving as a secondary serving cell. 12. The method of claim 11,
Wherein the secondary serving cell designated to transmit the random access response message is a secondary serving cell on which the physical uplink control channel is configured. The method of claim 11, wherein the random access response message is a structure of a medium access control (MAC) protocol data unit (PDU)
The MAC PDU includes a MAC subheader and a MAC control element,
Wherein the MAC subheader includes a logical channel ID (LCID) indicating that the MAC control element is for the random access response. In a terminal performing random access in a wireless communication system using a dual connection scheme,
A transmitting unit for transmitting a random access preamble; And
And a receiver for receiving a random access response message through a physical downlink shared channel (PDSCH) in response to the random access preamble,
The terminal is configured with a dual connection by a master base station (master eNB) and a secondary base station (secondary eNB)
The random access response message includes an instruction to receive the random access response message in a primary cell (PCell) in a master cell group provided by the master base station and in a secondary cell group provided by the secondary base station And a secondary serving cell (SCell) serving as a serving cell. 15. The method of claim 14,
Wherein the secondary serving cell designated to receive the random access response message is a secondary serving cell on which the physical uplink control channel is configured. 16. The method of claim 15,
Further comprising a random access processing section for determining whether or not the random access procedure is successful,
It is determined whether or not the random access procedure in the corresponding cell group is successfully performed according to the cell group on which the DL Shared Channel (DLSCH) including the same UE Contention Resolution Identity is received . 16. The method of claim 15, wherein the random access response message is a structure of a medium access control (MAC) protocol data unit (PDU)
The MAC PDU includes a MAC subheader and a MAC control element,
Wherein the MAC subheader includes a logical channel ID (LCID) indicating that the MAC control element is for the random access response. A base station performing random access in a wireless communication system using a dual connection scheme,
A receiver for receiving a random access preamble; And
And a transmitter for transmitting a random access response message through a physical downlink shared channel (PDSCH) in response to the random access preamble,
A terminal is configured with a dual connection by a master base station (master eNB) and a secondary base station (secondary eNB)
Wherein the random access response message includes an instruction to transmit the random access response message in a primary cell (PCell) in a master cell group provided by the master base station and in a secondary cell group provided by the secondary base station And a secondary serving cell (SCell) serving as a serving cell. 19. The method of claim 18,
Wherein the secondary serving cell indicated to transmit the random access response message is a secondary serving cell on which the physical uplink control channel is configured. 19. The method of claim 18, wherein the random access response message is a structure of a medium access control (MAC) protocol data unit (PDU)
The MAC PDU includes a MAC subheader and a MAC control element,
Wherein the MAC subheader comprises a logical channel ID (LCID) indicating that the MAC control element is for the random access response.

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