KR20170004061A - Method and device for performing uplink time alignment - Google Patents

Method and device for performing uplink time alignment Download PDF

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Publication number
KR20170004061A
KR20170004061A KR1020150093891A KR20150093891A KR20170004061A KR 20170004061 A KR20170004061 A KR 20170004061A KR 1020150093891 A KR1020150093891 A KR 1020150093891A KR 20150093891 A KR20150093891 A KR 20150093891A KR 20170004061 A KR20170004061 A KR 20170004061A
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South Korea
Prior art keywords
random access
serving cell
base station
uplink
access preamble
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KR1020150093891A
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Korean (ko)
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KR101994235B1 (en
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김경숙
권동승
김대익
김성경
나지현
신무용
좌혜경
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한국전자통신연구원
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W56/00—Synchronisation arrangements
    • H04W56/004—Synchronisation arrangements compensating for timing error of reception due to propagation delay
    • H04W56/005—Synchronisation arrangements compensating for timing error of reception due to propagation delay compensating for timing error by adjustment in the receiver
    • H04W72/1294—
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W74/00—Wireless channel access
    • H04W74/08—Non-scheduled access, e.g. ALOHA
    • H04W74/0833—Random access procedures, e.g. with 4-step access

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  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

Various embodiments of the present invention relate to a method and an apparatus for performing uplink time synchronization. The method for performing uplink time synchronization may comprise the steps of: selecting, by a secondary timing advance group, a contention-based random access preamble when receiving a physical downlink control channel including information about uplink grant for a serving cell of the secondary timing advance group, from a base station, in an uplink asynchronous state; and performing a random access procedure by using the selected random access preamble.

Description

TECHNICAL FIELD [0001] The present invention relates to a method and apparatus for performing uplink time synchronization,

The present invention relates to a method for performing uplink time synchronization in a multi-carrier 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 order for a terminal to access a network, a random access process is performed. The random access procedure may be classified into a contention based random access procedure and a noncontention based random access procedure.

The BS allocates a dedicated preamble for the serving cell of the sTAG when the secondary timing advance group (sTAG) requires uplink scheduling from the asynchronous state to the sTAG serving cell, and allocates a dedicated preamble for the allocated preamble And transmits a random access order including information to the terminal. The MS may adjust the sTAG uplink transmission timing by transmitting a dedicated preamble to the BS according to the random access command to perform a random access procedure.

The number of available dedicated preambles of the base station is specified in the specification, and the base station can allocate a dedicated preamble for the random access procedure of the UE even in an event such as handover or DL data resume. Therefore, in a base station in which a mobile station moves frequently, a dedicated preamble resource may be insufficient. In a base station, a dedicated preamble resource may be preferentially allocated for a procedure with a high priority.

If there is no allocable dedicated preamble for time alignment of the sTAG of the UE, the BS can not issue a random access instruction for time alignment of the sTAG and wait until the dedicated preamble can be allocated. Also, the UE can immediately recognize the uplink asynchronous time of the sTAG by a time alignment timer (TAT) expiration event, but the base station determines the uplink synchronization status based on the uplink signal quality of the sTAG serving cell It is recognized later than the terminal.

Accordingly, the terminal has to wait for a random access instruction of the sTAG transmitted from the base station even when the time alignment timer of the sTAG expires and the number of uplink transmission data is large. In addition, if there is no available dedicated preamble resource, the base station must wait until a dedicated preamble can be allocated even in a situation where there are many uplink transmission data of the UE.

It is another object of the present invention to provide a method for solving a delay problem which may occur in uplink time adjustment of a secondary serving cell in a multi-carrier aggregation system and enabling data distribution to a secondary serving cell without delay .

A method for performing uplink time synchronization of a UE according to various embodiments of the present invention includes: performing uplink granting for a serving cell in a sub-time forward group from a base station in a secondary timing advance group in an uplink asynchronous state; selecting a contention-based random access preamble when a physical downlink control channel including uplink grant information is received, and performing a random access procedure using the selected random access preamble Step < / RTI >

Wherein the step of performing the random access procedure comprises: transmitting the selected random access preamble to a base station through a serving cell of the sub-time forward group; transmitting a random access response to the random access preamble from a base station adjusting a time of an uplink of a serving cell of the sub-time forward group according to a timing advance command included in the random access response when the response is received, And activating a time alignment timer.

Wherein the step of performing the random access procedure comprises: transmitting Msg3 based on a temporary cell radio network temporary identifier (C-RNTI) included in the random access response and uplink grant information; When a contention resolution timer is activated and a physical downlink control channel to a C-RNTI including uplink grant information for the serving cell is received while the contention resolution timer is operating, Step < / RTI >

The method may further comprise changing a state of the sub-time forward group to an uplink asynchronous state when the time alignment timer of the sub-time forward group expires.

Wherein the step of selecting the random access preamble comprises the steps of: when a secondary timing advance group is in an uplink asynchronous state and a physical uplink grant information Upon receiving the physical downlink control channel, the contention-based random access preamble may be selected.

A method for performing uplink time synchronization of a UE according to various embodiments of the present invention includes: providing a serving cell of a sub-time forward group including a preamble index indicating that there is no dedicated preamble available from the base station; Selecting a contention-based random access preamble when a physical downlink control channel for the random access preamble is received, and performing a random access procedure using the selected random access preamble .

Wherein the random access procedure comprises: transmitting the selected random access preamble to a base station; receiving a random access response for the random access preamble from the base station, Adjusting the uplink time of a serving cell of the sub-time forward group according to a timing advance command and operating a time alignment timer of the serving cell. have.

Wherein the step of performing the random access procedure comprises: transmitting Msg3 based on a temporary cell radio network temporary identifier (C-RNTI) included in the random access response and uplink grant information; When a contention resolution timer is activated and a physical downlink control channel to a C-RNTI including uplink grant information for the serving cell is received while the contention resolution timer is operating, The method comprising the steps of:

A UE according to various embodiments of the present invention includes a communication unit for performing communication with a base station and a communication unit for performing uplink acknowledgment for a serving cell of a sub-time forward group from a base station in a secondary timing advance group in an uplink asynchronous state, a random access preamble is selected when a physical downlink control channel including uplink grant information is received and a random access procedure is performed using the selected random access preamble And a control unit.

Wherein the control unit controls the selected random access preamble to be transmitted to a base station through a serving cell of the sub time forward group and receives a random access response for the random access preamble from the base station Time adjusts the uplink time of the serving cell of the sub-time forward group according to a timing advance command included in the random access response.

The control unit controls to transmit Msg3 based on a temporary cell radio network temporary identifier (C-RNTI) included in the random access response and uplink grant information, and when the Msg3 is transmitted, When a contention resolution timer is activated and a physical downlink control channel to a C-RNTI including uplink grant information for the serving cell is received while the contention resolution timer is operating, .

Wherein the controller is configured to transmit a physical downlink control channel physical uplink grant information including uplink grant information for a serving cell of a sub-time forward group from a base station in a secondary timing advance group in an uplink asynchronous state, downlink control channel is received, the contention-based random access preamble may be selected.

A terminal according to various embodiments of the present invention includes a communication unit for performing communication with a base station of the present invention and a sub-time forward group including a preamble index indicating that there is no dedicated preamble available from the base station Based random access preamble when a physical downlink control channel for the serving cell of the serving cell is received and a random access procedure using the selected random access preamble can do.

Wherein the control unit controls the selected random access preamble to be transmitted to the base station and transmits a timing advance command included in the random access response when a random access response to the random access preamble is received from the base station, the time of the uplink of the serving cell of the sub-time forward group can be adjusted according to the command.

According to various embodiments of the present invention, it is possible to solve the delay problem that may occur in the uplink time adjustment of the secondary serving cell in the multi-carrier aggregation system, and to enable the data distribution to the secondary serving cell without delay.

1 shows a wireless communication system according to an embodiment of the present invention.
2 illustrates a protocol structure for supporting multi-carrier according to an embodiment of the present invention.
3 illustrates a frame structure for a multi-carrier operation according to an embodiment of the present invention.
4 is a flowchart illustrating a method of performing uplink synchronization according to an embodiment of the present invention.
5 is a flowchart illustrating an uplink synchronization performing method according to an embodiment of the present invention.
6 is a block diagram illustrating a configuration of a terminal and a base station according to various embodiments 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 symbols as possible even if 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 describing the components of the present specification, terms such as first, second, A, B, (a), and (b) may be used. These terms are intended to distinguish the constituent elements from other constituent elements, and the terms do not limit the nature, order or order of the constituent elements. When a component is described as being "connected", "coupled", or "connected" to another component, the component may be directly connected or connected to the other component, Quot; may be "connected," "coupled," or "connected. &Quot;

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 according to an embodiment of the present invention.

Referring to FIG. 1, the wireless communication system 10 may provide various communication services such as voice, packet data, and the like. The wireless communication system 10 may include at least one base station 200 (BS). Each base station 200 provides communication services for specific cells (15a, 15b, 15c). A cell can be divided into multiple regions (or sectors).

A mobile station (MS) 100 may be fixed or mobile and may be a user equipment (UE), a mobileeterminal (MT), a user terminal (UT), a subscriber station (SS), a wireless device, a PDA a personal digital assistant, a wireless modem, a handheld device, and the like. The base station 200 may be referred to as another term 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 denote a partial region covered by the base station 200, and may be meant to encompass various coverage areas such as a megacell, a macrocell, a microcell, a picocell, and a femtocell.

The downlink means communication from the base station 200 to the terminal 100 and the uplink means communication from the terminal 100 to the base station 200. In the downlink, the transmitter may be a part of the base station 200, and the receiver may be a part of the terminal 100. In the uplink, the transmitter may be part of the terminal 100, and the receiver may be part of the base station 200. 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 (SC-FDMA), OFDM- Various multiple access schemes such as OFDM-CDMA can be used. 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 carriers and is also referred to as spectrum aggregation or bandwidth aggregation. The individual unit carriers tied by carrier aggregation are called component carriers (CCs). Each element carrier can be defined as a bandwidth and a center frequency. 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.

2 illustrates a protocol structure for supporting multi-carrier according to an embodiment of the present invention.

Referring to FIG. 2, a common Medium Access Control (MAC) entity 21 manages a physical layer 22 using a plurality of carriers. The MAC management message transmitted on a specific carrier may be applied to other carriers. That is, the MAC management message is a message capable of controlling other carriers including the specific carrier. The physical layer 22 may operate in a TDD (Time Division Duplex) and / or a FDD (Frequency Division Duplex).

There are a plurality of physical control channels used in the physical layer 22. The physical downlink control channel (PDCCH) can inform the UE of paging channel (PCH), resource allocation of downlink shared channel (DL-SCH), and hybrid automatic repeat request (HARQ) information related to DLSCH. The PDCCH may include uplink grant information indicating a resource allocation of an uplink transmission to the UE. The physical control format indicator channel (PCFICH) informs the UE of the number of OFDM symbols used for PDCCHs and can be transmitted every subframe. The physical Hybrid ARQ indicator channel (PHICH) can transmit the HARQ ACK / NAK signal in response to the uplink transmission. The physical uplink control channel (PUCCH) may include uplink control information such as a HARQ ACK / NAK for downlink transmission, a scheduling request, and a CQI. A physical uplink shared channel (PUSCH) may include an uplink shared channel (ULSCH). A physical random access channel (PRACH) may include a random access preamble.

3 illustrates a frame structure for a multi-carrier operation according to an embodiment of the present invention.

Referring to FIG. 3, a frame is composed of 10 subframes. The subframe includes a plurality of OFDM symbols. Each carrier may have its own control channel (e.g., PDCCH). The multi-carriers may or may not be adjacent to each other. The terminal may support one or more 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.

4 is a flowchart illustrating a method of performing uplink synchronization according to an embodiment of the present invention.

Referring to FIG. 4, when the time alignment timer of the secondary timing advance group (sTAG) has expired (S401), the UE 100 may change the uplink state of the sTAG to the asynchronous state (S403).

The base station 200 may allocate uplink radio resources for uplink data transmission to a serving cell of the sTAG (S405). According to one embodiment, the BS 200 can allocate uplink radio resources for uplink data transmission to the serving cell of the pTAG based on a buffer status report (BSR) received from the MS 100 have. According to an embodiment, the base station 200 may transmit uplink grant information of the pTAG to the UE 100 through the PDCCH. According to an embodiment, if the uplink buffer size remaining in the UE 100 is equal to or larger than the designated size after the uplink radio resource allocation of the pTAG, the base station 200 transmits uplink data to the serving cell of the sTAG for data distribution Uplink radio resources for the uplink. According to an embodiment, the base station 200 may transmit the uplink grant information of the sTAG to the terminal 100 through the PDCCH (S407).

If the PDCCH including the uplink grant information is received from the base station 200 in the uplink asynchronous state, the terminal 100 can select the contention-based random access preamble (S409). The UE 100 may transmit the selected random access preamble to the base station 200 through the serving cell of the sTAG (S411).

When the random access preamble is received, the base station 200 may transmit a random access response to the terminal 100 (S413). According to one embodiment, a random access response may be transmitted to the primary serving cell of the terminal 100 of the base station 200. The random access response can be transmitted to the UE through the physical downlink shared channel indicated by the PDCCH scrambled with the random access-radio network temporary identifier (RA-RNTI) of the UE 100. [ According to one embodiment, the random access response may include a timing advance command (TAC). The time advance command may indicate a change in the uplink time relative to the current uplink time. According to an exemplary embodiment, the random access response includes uplink grant information, a random access preamble identifier (RAPID) for identifying terminals performing random access, and a time slot for receiving a random access preamble Information and a temporary identifier of the UE, such as a temporary C-RNTI.

When the random access response is received, the UE 100 may adjust the uplink time of the serving cell of the sTAG according to the time advance command included in the random access response (S415). The terminal 100 may activate the time alignment timer when the uplink time is adjusted (S417).

When the random access response is received, the terminal 100 can transmit Msg3 (S419). According to one embodiment, the terminal 100 may transmit Msg3 based on the temporary C-RNTI and uplink grant information included in the random access response. After transmitting the Msg3, the UE 100 may activate a contention resolution timer for the serving cell that transmitted the random access preamble (S421).

The base station 200 may transmit a PDCCH including uplink grant information to the UE 100 when Msg3 is received (S423). According to one embodiment, the BS 200 can identify the MS 100 based on a C-RNTI MAC (Control Element) included in Msg3. According to one embodiment, the BS 200 may allocate uplink radio resources for a serving cell that transmitted a random access preamble to an identified UE, and may transmit a PDCCH to a C-RNTI including uplink grant information . The PDCCH to the C-RNTI may mean a PDCCH with a C-RNTI as a destination.

When the PDCCH to the C-RNTI including the uplink grant information for the serving cell that transmitted the random access preamble is received while the contention resolution timer is operating, the UE 100 may determine that the contention resolution procedure is successful (S425) .

According to the above-described embodiment, even if the base station 200 does not recognize the uplink asynchronous state of the terminal 100 and the random access instruction of the base station 200 is not issued, the terminal 100 can proceed with the random access procedure.

5 is a flowchart illustrating an uplink synchronization performing method according to an embodiment of the present invention.

Referring to FIG. 5, the base station 200 may change the state of the sTAG to the uplink asynchronous state (S501). According to an exemplary embodiment, the BS 200 measures the uplink signal quality of the sTAG serving cell received from the AT 100 and determines the uplink synchronization state of the sTAG serving cell of the AT 100. [ The base station 200 may change the uplink synchronization state of the sTAG serving cell of the UE 100 to the asynchronous state if the quality of the uplink signal of the sTAG serving cell is less than a reference time.

An uplink scheduling request may be generated from the base station 200 to the serving cell of the sTAG of the UE 100 in operation S503. According to one embodiment, the BS 200 can allocate uplink radio resources for uplink data transmission to the serving cell of the pTAG based on a buffer status report (BSR) received from the MS 100 have. According to an embodiment, the base station 200 may transmit uplink grant information of the pTAG to the UE 100 through the PDCCH. According to an embodiment, if the uplink buffer size remaining in the UE 100 is equal to or larger than the designated size after the uplink radio resource allocation of the pTAG, the base station 200 transmits uplink data to the serving cell of the sTAG for data distribution Uplink radio resources for the uplink.

The base station 200 can allocate a dedicated preamble for a random access procedure in the serving cell of the sTAG when an uplink scheduling request is generated from the uplink unsynchronized state of the SS 100 to the serving cell of the sTAG. If the dedicated preamble allocation fails because there is no available dedicated preamble (S505), the base station 200 may transmit a PDCCH including a random access order to perform a contention-based random access procedure (S507). The random access indication may include a preamble index indicating a preamble. According to one embodiment, the base station 200 may transmit a PDCCH including a preamble index (e.g., ra-preambledindex = 000000) indicating that there is no available dedicated preamble index if the dedicated preamble allocation fails.

If the PDCCH including the preamble index indicating that there is no dedicated preamble index available from the base station 200 is received, the UE 100 may select the contention-based random access preamble (S509). The terminal 100 may transmit the selected random access preamble to the base station 200 through the serving cell of the sTAG (S511).

When the random access preamble is received, the base station 200 may transmit a random access response to the terminal 100 (S513). According to one embodiment, a random access response may be transmitted to the primary serving cell of the terminal 100 of the base station 200. The random access response can be transmitted to the UE through the physical downlink shared channel indicated by the PDCCH scrambled with the random access-radio network temporary identifier (RA-RNTI) of the UE 100. [ According to one embodiment, the random access response may include a timing advance command (TAC). The time advance command may indicate a change in the uplink time relative to the current uplink time. According to an exemplary embodiment, the random access response includes uplink grant information, a random access preamble identifier (RAPID) for identifying terminals performing random access, and a time slot for receiving a random access preamble Information and a temporary identifier of the UE, such as a temporary C-RNTI.

When the random access response is received, the UE 100 may adjust the uplink time of the serving cell of the sTAG according to the time advance command included in the random access response (S515). The terminal 100 may activate the time alignment timer when the uplink time is adjusted (S517).

When the random access response is received, the terminal 100 can transmit Msg3 (S519). According to one embodiment, the terminal 100 may transmit Msg3 based on the temporary C-RNTI and uplink grant information included in the random access response. After transmitting the Msg3, the UE 100 may activate a contention resolution timer for the serving cell that transmitted the random access preamble (S521).

The base station 200 may transmit a PDCCH including uplink grant information to the UE 100 when Msg3 is received (S523). According to one embodiment, the BS 200 can identify the MS 100 based on a C-RNTI MAC (Control Element) included in Msg3. According to one embodiment, the BS 200 may allocate uplink radio resources for a serving cell that transmitted a random access preamble to an identified UE, and may transmit a PDCCH to a C-RNTI including uplink grant information . The PDCCH to the C-RNTI may mean a PDCCH with a C-RNTI as a destination.

When the PDCCH to the C-RNTI including the uplink grant information for the serving cell that transmitted the random access preamble is received while the contention resolution timer is operating, the UE 100 may determine that the contention resolution procedure is successful (S525) .

According to the above-described embodiment, the base station 200 can instruct the terminal 100 to perform random access even when there is no available dedicated preamble, so that the terminal 100 can proceed the random access procedure.

6 is a block diagram illustrating a configuration of a terminal and a base station according to various embodiments of the present invention.

Referring to FIG. 6, the AT 100 may include a communication unit 110 and a control unit 120.

The communication unit 110 can communicate with the base station 200 to transmit and receive information. According to an embodiment, the communication unit 110 may transmit the random access preamble and Msg3 to the base station 200. [ According to one embodiment, the communication unit 110 may receive a PDCCH, a random access response, from the base station 200. [ According to an exemplary embodiment, the PDCCH may include uplink grant information informing a UE of a resource allocation of an uplink transmission. According to one embodiment, the PDCCH may include a random access indication indicating a random access procedure. According to an exemplary embodiment, the PDCCH may include serving cell identifier information for transmitting uplink data using uplink grant information using a Carrier Indicator Field (CIF). According to an exemplary embodiment, the PDCCH may include serving cell identifier information for transmitting a random access preamble using a Carrier Indicator Field (CIF).

The control unit 120 can control the overall operation of the terminal 100. [ According to one embodiment, when the time alignment timer of the secondary timing advance group (sTAC) expires, the controller 120 may change the uplink state of the sTAG to the asynchronous state. According to one embodiment, when the sTAG is in the uplink asynchronous state and the PDCCH including the uplink grant information is received from the base station 200, the control unit 120 can select the contention-based random access preamble. According to an exemplary embodiment, the controller 120 may select a contention-based random access preamble when a PDCCH including a preamble index indicating no available dedicated preamble index is received from the base station 200.

The control unit 120 may control to transmit the selected random access preamble to the base station 200 through the serving cell of the sTAG. According to one embodiment, when the random access response is received from the base station 200, the control unit 120 may adjust the uplink time of the serving cell of the sTAG according to the time advance command included in the random access response. According to one embodiment, the controller 120 may operate the time alignment timer when the uplink time is adjusted.

According to one embodiment, the control unit 120 can control to transmit Msg3 when a random access response is received. For example, the control unit 120 may control to transmit Msg3 based on the temporary C-RNTI and uplink grant information included in the random access response. According to an exemplary embodiment, the controller 120 may activate a contention resolution timer for a serving cell that has transmitted a random access preamble after transmitting Msg3. According to one embodiment, when the PDCCH to the C-RNTI including the uplink grant information for the serving cell that transmitted the random access preamble is received while the contention resolution timer is operating, the controller 120 determines that the contention resolution procedure is successful can do.

Referring to FIG. 6, the base station 200 may include a communication unit 210 and a control unit 220.

The communication unit 210 can communicate with the terminal 110 to transmit and receive information. The communication unit 210 may receive an uplink signal including a random access preamble, Msg3, and a sounding reference signal from the terminal 100. [ According to one embodiment, the communication unit 210 may transmit a PDCCH, a random access response, According to an exemplary embodiment, the PDCCH may include uplink grant information informing a UE of a resource allocation of an uplink transmission. According to one embodiment, the PDCCH may include a random access indication indicating a random access procedure. According to an exemplary embodiment, the PDCCH may include serving cell identifier information for transmitting uplink data using uplink grant information using a Carrier Indicator Field (CIF). According to an exemplary embodiment, the PDCCH may include serving cell identifier information for transmitting a random access preamble using a Carrier Indicator Field (CIF).

The control unit 220 can control the overall operation of the base station 200. According to one embodiment, the controller 220 may measure the uplink signal quality of the sTAG serving cell received from the terminal 100 and determine the uplink synchronization state of the sTAG serving cell of the terminal 100. [ According to an exemplary embodiment, the control unit 220 may change the uplink synchronization state of the sTAG serving cell of the UE 100 to the asynchronous state if the signal quality is below a predetermined reference time.

According to one embodiment, the control unit 220 may allocate uplink radio resources for uplink data transmission to the serving cell of the pTAG based on a buffer status report (BSR) received from the AT 100 have. According to one embodiment, the controller 220 may transmit uplink grant information of the pTAG to the UE 100 through the PDCCH. According to one embodiment, if the uplink buffer size remaining in the UE 100 is greater than or equal to the designated size after the uplink radio resource allocation of the pTAG, the controller 220 transmits uplink data to the serving cell of the sTAG for data distribution Uplink radio resources for the uplink.

According to one embodiment, when an uplink scheduling request is generated from the sTAG of the UE 100 to the serving cell of the sTAG in the uplink asynchronous state, the controller 220 generates a dedicated preamble for the random access procedure in the serving cell of the sTAG Can be assigned. According to one embodiment, if the dedicated preamble allocation fails because there is no available dedicated preamble, the control unit 220 may transmit a PDCCH including a random access order to perform a contention-based random access procedure.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention.

100: terminal 200: base station

Claims (14)

A method for performing uplink time synchronization of a UE,
A secondary downlink control channel including uplink grant information for a serving cell of a sub-time forward group from a base station in a secondary timing advance group in an uplink asynchronous state, Selecting a contention-based random access preamble upon receipt of the contention-based random access preamble;
And performing a random access procedure using the selected random access preamble. The method according to claim 1,
Wherein the step of performing the random access procedure comprises:
Transmitting the selected random access preamble to a base station through a serving cell of the sub-time forward group;
When a random access response to the random access preamble is received from a base station, a serving cell of a sub-time forward group is uplinked according to a timing advance command included in the random access response Adjusting a time of the link; And
And activating a time alignment timer of the serving cell. 3. The method of claim 2,
Wherein the step of performing the random access procedure comprises:
Transmitting Msg3 based on a temporary cell radio network temporary identifier (C-RNTI) included in the random access response and uplink grant information;
Activating a contention resolution timer for the serving cell; And
And determining that the contention resolution procedure is successful if the physical downlink control channel to the C-RNTI including the uplink grant information for the serving cell is received while the contention resolution timer is operating. The method according to claim 1,
And changing the state of the sub-time forward group to an uplink asynchronous state when the time alignment timer of the sub-time forward group expires. The method according to claim 1,
Wherein the step of selecting the random access preamble comprises:
A secondary downlink control channel including uplink grant information for a serving cell of a sub-time forward group from a base station in a secondary timing advance group in an uplink asynchronous state, And selecting the contention-based random access preamble upon receipt of the contention-based random access preamble. A method for performing uplink time synchronization of a UE,
When a physical downlink control channel for a serving cell of a sub-time forward group including a preamble index indicating that there is no dedicated preamble available from the base station is received, Selecting a random access preamble;
And performing a random access procedure using the selected random access preamble. The method according to claim 6,
Wherein the step of performing the random access procedure comprises:
Transmitting the selected random access preamble to a base station;
When a random access response to the random access preamble is received from a base station, a serving cell of a sub-time forward group is uplinked according to a timing advance command included in the random access response Adjusting a time of the link; And
And activating a time alignment timer of the serving cell. 8. The method of claim 7,
Wherein the step of performing the random access procedure comprises:
Transmitting Msg3 based on a temporary cell radio network temporary identifier (C-RNTI) included in the random access response and uplink grant information;
Activating a contention resolution timer for the serving cell; And
And determining that the contention resolution procedure is successful if a physical downlink control channel including uplink grant information for the serving cell is received while the contention resolution timer is operating. A communication unit for performing communication with the base station; And
A secondary downlink control channel including uplink grant information for a serving cell of a sub-time forward group from a base station in a secondary timing advance group in an uplink asynchronous state, And a controller for selecting a contention based random access preamble and proceeding with a random access procedure using the selected random access preamble. 10. The method of claim 9,
Wherein,
Wherein the control unit controls the selected random access preamble to be transmitted to a base station through a serving cell of the sub-time forward group, and when a random access response for the random access preamble is received from the base station, And adjusts the uplink time of the serving cell of the sub-time forward group according to a timing advance command included in the response. 11. The method of claim 10,
Wherein,
(MCSG3) based on a temporary C-RNTI (Temporary Cell Radio Network Temporary Identifier) included in the random access response and uplink grant information. When the Msg3 is transmitted, a contention resolution timer, and determines that the contention resolution procedure is successful when the physical downlink control channel to the C-RNTI including the uplink grant information for the serving cell is received while the contention resolution timer is operating. 10. The method of claim 9,
Wherein,
A secondary downlink control channel including uplink grant information for a serving cell of a sub-time forward group from a base station in a secondary timing advance group in an uplink asynchronous state, The UE selects the contention-based random access preamble. A communication unit for performing communication with the base station; And
When a physical downlink control channel for a serving cell of a sub-time forward group including a preamble index indicating that there is no dedicated preamble available from the base station is received, And a controller for selecting a random access preamble and performing a random access procedure using the selected random access preamble. 14. The method of claim 13,
Wherein,
Wherein the control unit controls the selected random access preamble to transmit to the base station, and when a random access response to the random access preamble is received from the base station, the random access response is controlled according to a timing advance command included in the random access response. And adjusting the uplink time of a serving cell of the sub-time forward group.
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