KR20120132286A - Apparatus and method for performing random access in wireless communication system - Google Patents

Abstract

PURPOSE: A random access apparatus in a wireless communication system and method thereof are provided to reduce overhead according to random access attempts by acquiring a time alignment value for a plurality of serving cells according to one random access procedure. CONSTITUTION: A terminal transmits classification supporting information to a BS(base station)(S500). The BS configures a TAG(timing alignment group) by classifying serving groups(S505). The base station transmits TAG configuration information to the terminal(S510). The terminal executes a random access procedure for the BS(S515). A time forwarding command field controls the uplink time of the serving cells. [Reference numerals] (AA) Terminal; (BB) Base station; (S500) Classification support information; (S505) Time alignment group configuration; (S510) Time alignment group configuration information; (S515) Random access procedure

Description

Apparatus and method for performing random access in a wireless communication system {APPARATUS AND METHOD FOR PERFORMING RANDOM ACCESS IN WIRELESS COMMUNICATION SYSTEM}

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, even though the bandwidth between uplink and downlink is set differently, only one carrier is 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, with the recent introduction of multiple carrier systems, random access can be implemented through multiple component carriers.

The multi-carrier system refers to a wireless communication system capable of supporting carrier aggregation. Carrier aggregation is a technique for efficiently using fragmented small bands in order to combine physically non-continuous bands in the frequency domain and to have the same effect as using logically large bands.

In order to access the network, the UE goes through a random access process. The random access process may be divided into a contention based random access procedure and a non-contention based random access procedure. The biggest difference between the contention-based random access process and the non- contention-based random access process is whether a random access preamble is assigned to one UE. In the contention-free random access process, since the terminal uses a dedicated random access preamble designated only to the terminal, contention (or collision) with another terminal does not occur. Here, contention refers to two or more terminals attempting a random access procedure using the same random access preamble through the same resource. In the contention-based random access process, there is a possibility of contention because the terminal uses a randomly selected random access preamble.

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

An object of the present invention is to provide an apparatus and method for performing random access in a wireless communication system.

Another technical problem of the present invention is to provide an apparatus and method for performing random access to obtain a time alignment value commonly applied to a plurality of secondary serving cells in one random access procedure.

Another technical problem of the present invention is to provide an apparatus and method for classifying secondary serving cells to which a same time alignment value is applied.

Another technical problem of the present invention is to provide an apparatus and method for transmitting a random access response message including a time alignment value for each secondary serving cell group.

According to an aspect of the present invention, a terminal for performing random access in a wireless communication system is provided. The terminal receives a time alignment group configuration information for classifying at least one serving cell configured in the terminal into a timing alignment group (TAG) from the base station, and a random on one representative serving cell in the time alignment group And a transmitter for transmitting an access preamble to the base station.

The receiver receives a random access response message including a time forward command field from the base station in response to the random access preamble, and the time forward command field equals uplink time of all serving cells in the time alignment group. Indicates the time alignment value to be adjusted.

According to another aspect of the present invention, a method of performing random access by a terminal in a wireless communication system is provided. The random access method may include receiving, from a base station, time alignment group configuration information for classifying at least one serving cell configured in a terminal into a time alignment group, and receiving a random access preamble on one representative serving cell in the time alignment group. Transmitting to the base station, and receiving a random access response message from the base station in response to the random access preamble, the random access response message comprising a time forward command field.

The time forward command field indicates a time alignment value for equally adjusting uplink times of all serving cells in the time alignment group.

According to another aspect of the present invention, there is provided a base station for performing random access in a wireless communication system. The base station includes an RRC processor for generating time alignment group configuration information for classifying at least one serving cell configured in a terminal into a time alignment group, a transmitter for transmitting the time alignment group configuration information to the terminal, and one of the time alignment group. Receiving unit for receiving a random access preamble from the terminal on a representative serving cell of the time advance, indicating a time alignment value for equally adjusting the uplink time of all the serving cells in the time alignment group in response to the random access preamble And a random access processor for generating a random access response message including a command field, and a transmitter for transmitting the random access response message to the terminal.

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. The random access method may include transmitting, to the terminal, time alignment group configuration information for classifying at least one serving cell configured in a terminal into a time alignment group, and generating a random access preamble on one representative serving cell in the time alignment group. A random access response including a time forward command field indicating a time alignment value for equally adjusting an uplink time of all serving cells in the time alignment group in response to receiving from the terminal and in response to the random access preamble And transmitting a message to the terminal.

According to the present specification, a procedure for acquiring a time alignment value for a serving cell undergoing a random access procedure for securing and maintaining uplink time synchronization becomes clear, and a time for acquiring uplink synchronization for a serving cell can be reduced. In addition, the overhead of excessive random access attempts can be reduced by obtaining time alignment values for a plurality of serving cells in one random access procedure.

1 shows a wireless communication system to which the present invention is applied.
2 shows an example of a protocol structure for supporting multiple carriers to which the present invention is applied.
3 shows an example of a frame structure for multi-carrier operation to which the present invention is applied.
4 shows a linkage between a downlink component carrier and an uplink component carrier in a multi-carrier system to which the present invention is applied.
5 is a flowchart illustrating a method of performing random access according to an embodiment of the present invention.
6 is a flowchart illustrating a random access procedure according to an embodiment of the present invention. This is a contention free random access procedure.
7 shows a MAC PDU structure for a random access response message to which the present invention is applied.
8 is a block diagram illustrating a structure of a MAC control element for a time forward command according to an embodiment of the present invention.
9A is a block diagram illustrating a structure of a MAC control element for a time forward command according to another example of the present invention.
9B is a block diagram illustrating a structure of a MAC control element for a time forward command according to another example of the present invention.
10 is a flowchart illustrating a non-contention based random access procedure according to another example of the present invention.
11 is an explanatory diagram illustrating a method of configuring a time alignment group and a method of determining a time alignment value in a multicarrier system according to the present invention.
12 is a flowchart illustrating a method of performing random access according to another embodiment of the present invention.
13 is a flowchart illustrating a method of performing random access according to another embodiment of the present invention.
14 is a flowchart illustrating a method of performing random access according to another example of the present invention.
15 is a flowchart illustrating operations of a terminal performing random access according to an embodiment of the present invention.
16 is a flowchart illustrating operations of a base station performing random access according to an embodiment of the present invention.
17 is a block diagram illustrating a base station and a terminal for performing random access according to an embodiment of the present invention.
18 is an example of a MAC subheader according to an embodiment of the present invention.
19 illustrates a MAC control element for TAG according to an embodiment of the present invention.
20 illustrates a MAC control element for TAG according to another embodiment of the present invention.
21 shows an example in which DCI is mapped to an extended physical downlink control channel according to the present invention.
22 shows another example in which DCI is mapped to an extended physical downlink control channel according to the present invention.
23 shows another example in which DCI is mapped to an extended physical downlink control channel according to the present invention.
24A and 24B are another block diagrams illustrating the structure of a MAC control element for a time forward command according to an embodiment of the present invention.

Hereinafter, some embodiments will be described in detail with reference to exemplary drawings. In adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are assigned to the same components as much as possible 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 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 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 mobile station (MS) 12 may be fixed or mobile and may be a user equipment (UE), a mobile terminal (MT), a user terminal (UT), a subscriber station (SS), a wireless device, (personal digital assistant), 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.

Carrier aggregation (CA) supports a plurality of carriers, also referred to as spectrum aggregation or bandwidth aggregation. Individual unit carriers bound 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, if five element carriers are used for a 70 MHz band configuration, then 5 MHz element carrier (carrier # 0) + 20 MHz element carrier (carrier # 1) + 20 MHz element carrier (carrier # 2) + 20 MHz element carrier (carrier # 3) + 5 MHz element carrier (carrier # 4).

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

2 shows an example of a protocol structure for supporting multiple carriers to which the present invention is applied.

Referring to FIG. 2, the common medium access control (MAC) entity 210 manages a physical layer 220 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 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 resource allocation of a paging channel (PCH), a 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 a HARQ ACK / NAK signal in response to uplink transmission. 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 an example of a frame structure for multi-carrier operation to which the present invention is applied.

Referring to FIG. 3, the frame consists of 10 subframes. The subframe includes a plurality of OFDM symbols. Each carrier may have its own control channel (eg, PDCCH). The multicarriers may or may not be adjacent to each other. The terminal may support one or more carriers according to its capability.

The component carrier may be divided into a primary component carrier (PCC) and a secondary component carrier (SCC) according to activation. The major carriers are always active carriers, and the subcarrier carriers are carriers that are activated / deactivated according to specific 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 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 shows a linkage between a downlink component carrier and an uplink component carrier in a multi-carrier system to which the present invention is applied.

Referring to FIG. 4, 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 configured to be 1: 1. For example, D1 is connected to U1, D2 is U2, and D3 is U1 1: 1. The terminal establishes a connection between the downlink component carriers and the uplink component carriers through system information transmitted by a logical channel BCCH or a terminal-specific RRC message transmitted by a DCCH. Each connection configuration may be set cell specific or UE specific.

4 illustrates only a 1: 1 connection setup between the downlink component carrier and the uplink component carrier, but it is needless to say that a 1: n or n: 1 connection setup can also be established. In addition, the index of the component carrier does not correspond to the order of the component carrier or the position of the frequency band of the component carrier.

The primary serving cell refers to one serving cell that provides security input and NAS mobility information in an RRC connection or re-establishment state. Depending on the capabilities of the terminal, at least one cell may be configured to form a set of serving cells together with a main serving cell, said at least one cell being referred to as a secondary serving cell.

Therefore, the set of serving cells configured for one terminal may consist of only one main serving cell, or may consist of one main serving cell and at least one secondary serving cell.

The downlink component carrier corresponding to the main serving cell is referred to as a downlink principal carrier (DL PCC), and the uplink component carrier corresponding to the main serving cell is referred to as an uplink principal carrier (UL PCC). In the downlink, the element carrier corresponding to the secondary serving cell is referred to as a downlink sub-element carrier (DL SCC), and in the uplink, an elementary carrier corresponding to the secondary serving cell is referred to as an uplink sub-element carrier (UL SCC) do. Only one DL serving carrier may correspond to one serving cell, and DL CC and UL CC may correspond to each other.

Therefore, the communication between the terminal and the base station through the DL CC or the UL CC in the carrier system is a concept equivalent to the communication between the terminal and the base station through the serving cell. For example, in the method of performing random access according to the present invention, transmitting a preamble by using a UL CC may be regarded as a concept equivalent to transmitting a preamble using a main serving cell or a secondary serving cell. In addition, the UE receiving the downlink information by using the DL CC, can be seen as a concept equivalent to receiving the downlink information by using the primary serving cell or secondary serving cell.

On the other hand, the main serving cell and the secondary serving cell has the following characteristics.

First, the primary serving cell is used for transmission of the PUCCH. On the other hand, the secondary serving cell can not transmit the PUCCH but may transmit some of the information in the PUCCH through the PUSCH.

Second, the main serving cell is always activated, while the secondary serving cell is a carrier that is activated / deactivated according to a specific condition. The specific condition may be when the activation / deactivation MAC CE message of the eNB is received or the deactivation timer in the UE expires.

Third, when the primary serving cell experiences RLF, RRC reconnection is triggered, but when the secondary serving cell experiences RLF, RRC reconnection is not triggered. Radio link failure occurs when downlink performance is maintained below a threshold for more than a certain time, or when the RACH has failed a number of times above the threshold.

Fourth, the main serving cell may be changed by a security key change or a handover procedure accompanied by the RACH procedure. However, in the case of a content resolution message, only a downlink control channel indicating a CR (hereinafter referred to as a 'PDCCH') should be transmitted through the primary serving cell, and the CR information may be transmitted through the primary serving cell or the secondary serving cell. Can be sent through.

Fifth, non-access stratum (NAS) information is received through the main serving cell.

Sixth, the main serving cell always consists of DL PCC and UL PCC in pairs.

Seventh, a different CC may be set as a primary serving cell for each terminal.

Eighth, procedures such as reconfiguration, adding, and removal of the secondary serving cell may be performed by the radio resource control (RRC) layer. In addition to the new secondary serving cell, RRC signaling may be used to transmit the system information of the dedicated secondary serving cell.

Ninth, the main serving cell transmits PDCCH (e.g., downlink allocation information) assigned to a UE-specific search space set for transmitting control information for a specific UE in a region for transmitting control information Or PDCCH (e.g., system information (e.g., uplink information) allocated to a common search space set for transmitting control information to all terminals in the cell or to a plurality of terminals conforming to a specific condition, SI), a random access response (RAR), and transmit power control (TPC). On the other hand, only the UE-specific search space can be set as the serving cell. That is, since the UE can not confirm the common search space through the secondary serving cell, it can not receive the control information transmitted only through the common search space and the data information indicated by the control information.

The technical spirit of the present invention with respect to the features of the primary serving cell and the secondary serving cell is not necessarily limited to the above description, which is merely an example and may include more examples.

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 terminal must be made in advance in order to receive an information signal regardless of downlink and 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 be different for each multiple access scheme. For example, in the case of a CDMA system, even if the base station receives uplink signals of different terminals at different times, the uplink signals may be separated. However, in a wireless communication system based on OFDMA or FDMA, the base station simultaneously receives and demodulates uplink signals of all terminals. Therefore, as uplink signals of a plurality of terminals are received at the correct time, reception performance increases, and as the difference in reception time of each terminal signal increases, the reception performance deteriorates rapidly. Therefore, uplink synchronization acquisition may be essential.

A random access procedure is performed to obtain uplink synchronization, and the terminal acquires uplink synchronization based on a timing alignment value transmitted from the base station during the random access procedure. When uplink synchronization is obtained, the terminal starts a time alignment timer. When the time alignment timer is in operation, the terminal and the base station are in a state of uplink synchronization with each other. If the time alignment timer expires or does not operate, the UE and the base station report that they are not synchronized with each other, and the UE does not perform uplink transmission other than the transmission of the random access preamble.

Meanwhile, in a multi-carrier system, one terminal communicates with a base station through a plurality of component carriers or a plurality of serving cells. If the signals of the plurality of serving cells configured in the terminal all have the same time delay, the terminal may acquire uplink synchronization for all the serving cells with only one time alignment value. On the other hand, if the signals of the plurality of serving cells have different time delays, different time alignment values are required for each serving cell. That is, multiple timing alignment values are required. If the UE performs random access for each serving cell in order to obtain multi-time alignment values, overhead may be generated for limited uplink resources, and complexity of random access may increase. There is a need for a method of performing random access in a multi-carrier system that reduces such overhead and complexity.

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

Referring to FIG. 5, the terminal transmits classification assistant information to the base station (S500). The classification support information provides information or criteria necessary for classifying at least one serving cell configured in the terminal into a timing alignment group (TAG). For example, the classification support information may include at least one of geographical location information of the terminal, neighbor cell measurement information of the terminal, network deployment information, and serving cell configuration information. The geographic location information of the terminal indicates a location that can be expressed by latitude, longitude, height, etc. of the terminal. The neighbor cell measurement information of the terminal includes a reference signal received power (RSRP) or a reference signal received quality (RSRQ) of the reference signal transmitted from the neighbor cell. The network configuration information is information indicating an arrangement of a base station, a frequency selective repeater (FSR) or a remote radio head (RRH). The serving cell configuration information is information about a serving cell configured in the terminal. Step S500 indicates that the terminal transmits the classification assistance information to the base station, but the base station may know the classification assistance information separately or may retain it. In this case, random access according to the present embodiment may be performed with step S500 omitted.

The base station classifies the serving cells to form a time alignment group (S505). Serving cells may be classified or configured into each time alignment group according to classification support information. The time alignment group is a group including at least one serving cell, and the same time alignment value is applied to the serving cells in the time alignment group. For example, when the first serving cell and the second serving cell belong to the same time alignment group TAG1, the same time alignment value TA ₁ is applied to the first serving cell and the second serving cell. On the other hand, when the first serving cell and the second serving cell belong to different time alignment groups TAG1 and TAG2, different time alignment values TA ₁ and TA ₂ are applied to the first serving cell and the second serving cell, respectively. The time alignment group may include a main serving cell, may include at least one secondary serving cell, and may include a primary serving cell and at least one secondary serving cell.

As an example, the base station may configure a time alignment group specific to the terminal. Since the serving cell configuration information is configured individually and independently for each terminal, when this is used as classification support information, a time alignment group may also be configured individually and independently for each terminal. For example, the time alignment groups for the first terminal are TAG1_UE1 and TAG2_UE1, and the time alignment groups for the second terminal are TAG1_UE2 and TAG2_UE2. TAG1_UE1 = {first serving cell}, TAG2_UE1 = {second serving cell} when the first and second serving cells are configured in the first terminal, whereas TAG1_UE2 = when the first to fourth serving cells are configured in the second terminal. {First serving cell, second serving cell}, TAG2_UE2 = {third serving cell, fourth serving cell}.

As another example, the base station may configure a time alignment group specific to the cell. Since the network configuration information is determined irrespective of the terminal, when this is used as the classification support information, the time alignment group may be configured cell-centric regardless of the terminal. For example, assume that a first serving cell of a specific frequency band is always served by a frequency selective repeater or a remote radio head, and a second serving cell is served by a base station. In this case, the first serving cell and the second serving cell are classified into different time alignment groups for all the terminals in the service area of the base station.

The base station transmits time alignment group configuration information (TAG configuration) to the terminal (S510). At least one serving cell configured in the terminal is classified into a time alignment group. That is, the time alignment group configuration information describes a state in which the time alignment group is configured. As an example, the time alignment group setting information may include a number field of the time alignment group, an index field of each time alignment group, and an index field of a serving cell included in each time alignment group, and these fields may include a time alignment group. Describe the configured state.

As another example, the time alignment group configuration information may further include representative serving cell information in each time alignment group. The representative serving cell is a serving cell capable of performing a random access procedure for maintaining and configuring uplink synchronization in each time alignment group. The representative serving cell may be referred to as a special SCell or a reference SCell. Unlike the above embodiment, if the time alignment group configuration information does not include a representative serving cell, the terminal may select a representative serving cell in each time alignment group by itself.

The terminal performs a random access procedure on the base station (S515). The random access procedure may be performed on a contention-free or contention-based basis. Since the procedure differs depending on whether contention-based or contention-based, the random access procedure will be described with reference to the drawings. Step S515 follows the procedure of FIG. 6 in the case of non-contention based, and the procedure of FIG. 10 in the case of contention-based.

6 is a flowchart illustrating a random access procedure according to an embodiment of the present invention. This is a contention free random access procedure.

Referring to FIG. 6, the base station selects one of dedicated random access preambles previously reserved for a non-contention based random access procedure among all available random access preambles, and the index and available time / of the selected random access preamble / The preamble assignment information including the frequency resource information is transmitted to the terminal (S600). The UE needs to be allocated a dedicated random access preamble with no possibility of collision from the base station for a non-contention based random access procedure.

As an example, when the random access procedure is performed during the handover procedure, the UE may obtain a dedicated random access preamble from the handover command message. As another example, when the random access procedure is performed at the request of the base station, the terminal may obtain a dedicated random access preamble through PDCCH or porphysical layer signaling. In this case, the physical layer signaling is downlink control information (DCI) format 1A and may include fields shown in Table 1 below.

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 to identify format 0 / 1A-1 bit (format 0 if 0, format 1A if 1)
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 order.
-bottom-
Localized / Distributed VRB allocation flag-1 bit. Set to 0
Resource block allocation

bits. All bits are set to 1
Preamble Index-6 bits
PRACH Mask Index-4 bits
All remaining bits of format 1A for simple scheduling allocation of one PDSCH codeword are set to 0.

Referring to Table 1, the preamble index is an index indicating a preamble selected from among dedicated random access preambles reserved for the contention-free random access procedure, and the PRACH mask index is available time / frequency resource information. The available time / frequency resource information is indicated again according to a frequency division duplex (FDD) system and a time division duplex (TDD) system, as shown in Table 2 below.

PRACH
Mask index PRACH (FDD) allowed PRACH (TDD) allowed 0 all all One PRACH resource index 0 PRACH resource index 0 2 PRACH resource index1 PRACH resource index1 3 PRACH resource index2 PRACH resource index2 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 index7 Reserved 9 PRACH resource index8 Reserved 10 PRACH resource index9 Reserved 11 All even PRACH opportunities in the time domain,
First PRACH Resource Index in Subframe All even PRACH opportunities in the time domain,
First PRACH Resource Index in Subframe 12 All odd PRACH opportunities in the time domain,
First PRACH Resource Index in Subframe All odd PRACH opportunities in the time domain,
First PRACH Resource Index in Subframe 13 Reserved First PRACH Resource Index in Subframe 14 Reserved Second PRACH Resource Index in Subframe 15 Reserved Third PRACH Resource Index in Subframe

The terminal transmits the allocated dedicated random access preamble to the base station through the representative serving cell (S605). The representative serving cell is a serving cell selected to transmit a random access preamble in a time alignment group configured in the terminal. The representative serving cell may be selected for each time alignment group. In addition, the UE may transmit a random access preamble on a representative serving cell in any one time alignment group among a plurality of time alignment groups, or may transmit a random access preamble on each representative serving cell in two or more time alignment groups. . For example, suppose that the time alignment groups configured in the terminal are TAG1 and TAG2, and TAG1 = {first serving cell, second serving cell, third serving cell}, and TAG2 = {fourth serving cell, fifth 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 transmits the allocated dedicated random access preamble to the base station through the second serving cell or the fifth serving cell. In other words, the random access preamble is not transmitted in the serving cell other than the representative serving cell in each time alignment group.

The random access preamble may proceed after the representative serving cell is activated. In addition, the random access procedure for the secondary serving cell may be initiated by the PDCCH order (order) transmitted by the base station. In the present embodiment, a non-contention-based random access procedure will be described based on the present invention, but may be applied to a contention-based random access procedure by the base station.

If only the time alignment value (hereinafter, the representative time alignment value) regarding the representative serving cell is obtained, the terminal may use the representative time alignment value as the time alignment value of another serving cell. This is because the same time alignment value is applied to the serving cells belonging to the same time alignment group. By blocking unnecessary random access procedures in a specific serving cell, duplication, complexity, and overhead of the random access procedure can be reduced.

The base station transmits a random access response message to the terminal (S610). As an example, the random access response message includes a timing advance command (TAC) field. The time forward command field indicates a change in the uplink time relative to the current uplink time and may be an integer multiple of the sampling time T _s , for example, 16T _s . The time advance command field indicates a time alignment value for equally adjusting the uplink time of all serving cells in the time alignment group. The time alignment value can be given by a specific index. An example of a method of determining a time alignment value is described in FIG. 11. As another example, the random access response message includes an index of a time alignment group that includes a time forward command and a representative serving cell. The data structure for the time advance command is described in Figures 7-9.

The UE checks the time advance command and / or time alignment group index in the random access response message, and adjusts uplink time for all serving cells in the identified time alignment group by the time alignment value according to the time advance command. Examples of the uplink time adjusted by the time alignment value are shown in Equations 1 to 4. If there is a time advance command and / or a time alignment group index for a plurality of time alignment groups in the random access response message, the UE transmits an uplink time for the serving cell (s) of each time alignment group to the corresponding time advance command. Adjust by time alignment value accordingly.

The base station may determine which terminal transmits the random access preamble through which serving cell based on the received random access preamble and time / frequency resources. Accordingly, the random access response message is transmitted to the terminal through a physical downlink control channel (PDSCH) indicated by a PDCCH scrambled with a Cell-Radio Network Temporary Identifier (C-RNTI) of the terminal. The random access response message may be transmitted through a scheduling cell for the representative serving cell.

Downlink control in PDCCH in which information of the physical layer (L1) indicating which radio resource (RB) is allocated to the PDCCH order indicating the random access procedure and a random access response message which is a MAC layer message is allocated. Downlink control information (DCI) information may be transmitted through a lower layer control channel defined as EPDCCH (Extended PDCCH). The EPDCCH is composed of a resource block (RB) pair. Herein, the RB pair may be defined as an RB for each of two slots constituting one subframe, and may be defined as a pair when each RB is configured as one pair. Here, each RB constituting the RB pair may not be configured with slots having the same time. In addition, it may be composed of RBs existing in the same frequency band or may be composed of RBs existing in different frequency bands. This is illustrated in Figures 21-23.

21 shows an example in which DCI is mapped to an extended physical downlink control channel according to the present invention.

Referring to FIG. 21, a downlink subframe includes a control region 2100 and a data region 2105. The PDCCH 2110 is mapped to the control region 2100 and has a length of 2 to 4 OFDM symbols in the time domain. EPDCCH (Extended PDCCH) 2115 and PDSCH 2120 are mapped in the data region 2105. Referring to the indication relationship between each downlink physical channel, the PDCCH 2110 indicates the region where the EPDCCH 2115 is transmitted, and the EPDCCH 2115 indicates the PDSCH 2120 including user information actually transmitted. At this time, the EPDCCH 2115 is limited to the resources indicated by the PDCCH 2110 and mapped. In addition, the EPDCCH 2115 and the PDCCH 2110 may be mapped to different DL CCs and may be cross carrier scheduling by the PDCCH 2110. However, in the EPDCCH 2115, the PDSCH 2120 must always exist in the same DL CC.

The EPDCCH transmits a DCI for physical layer (L1) information of a PDCCH order and a random access response message.

22 shows another example in which DCI is mapped to an extended physical downlink control channel according to the present invention.

Referring to FIG. 22, a PDCCH 2210 mapped to a control region 2200 indicates a search space 2215 of an EPDCCH mapped to a data region 2205. The UE uses the blind decoding scheme used to receive the PDCCH 2210, that is, the EPDCCH in the search space 2215 of the EPDCCH using a data detection scheme based on a cyclic redundancy check (CRC) scheme. Should be detected. In addition, the EPDCCH and the PDCCH 2210 may be mapped to different DL CCs, and the inter-carrier scheduling may be performed by the PDCCH 2210. The EPDCCH includes physical layer (L1) information of a PDCCH order and a random access response message.

23 shows another example in which DCI is mapped to an extended physical downlink control channel according to the present invention.

Referring to FIG. 23, the EPDCCH 2305 is present in the PDSCH region 2310 regardless of the PDCCH. Information about the search space 2310 of the EPDCCH is provided in the upper layer (RRC) for the information about the different search space (for example, search space bandwidth information) for each terminal, or in the search space shared by a plurality of terminals Information is provided by RRC signaling or broadcasting scheme. In this case, the control area 2300 may not exist. That is, it may be removed.

In this case, the UE should blind decode the search space 2310 of the EPDCCH to obtain the EPDCCH 2305. If the search space 2310 of the EPDCCH is 1, that is, if the search space 2310 of the EPDCCH is defined as a space to which only one EPDCCH can be mapped, a data detection method using C-RNTI assigned to each UE is performed. A method of determining whether to receive its own EPDCCH may be used. In addition, the EPDCCH 2305 and the PDSCH 2315 must always exist in the same DL CC.

The base station determines whether the UE receives the EPDCCH 2305 or the PDCCH in the corresponding serving cell, which may be configured for each serving cell through higher layer (RRC) signaling. Therefore, when the terminal is configured to receive the EPDCCH (2115, 2223, 2305) in any serving cell, the terminal does not receive the UE-specific PDCCH transmitted (UE specific). Accordingly, the UE may receive a random access initiation indicator including preamble allocation information only through the EPDCCHs 2115, 2223, and 2305 in the random access procedure performed in the arbitrary serving cell. In addition, the UE may receive random access response information in the PDSCHs 2120, 2205, and 2315 indicated by the EPDCCHs 2115, 2223, and 2305.

Referring back to FIG. 6, in comparison to the contention-based random access process, the non- contention-based random access process receives a random access response message, thereby determining that the random access process is normally performed, and ends the random access process. If the preamble index in the preamble allocation information received by the UE is '000000', the UE randomly selects one of the contention-based random access preambles and sets the PRACH mask index value to '0' and then proceeds to the contention-based procedure. do. In addition, the preamble allocation information may be transmitted to the terminal through a message of a higher layer such as RRC (for example, mobility control information (MCI) in a handover command).

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

Referring to FIG. 7, the MAC PDU 700 includes a MAC header 710, at least one MAC control element 720,..., 725, at least one MAC service data unit 730-1, ..., 730-m) and padding 740.

The MAC header 710 includes at least one sub-header 710-1, 710-2, ..., 710-k, each subheader 710-1, 710-2, ... .710-k corresponds to one MAC SDU or one MAC control element 720,..., 725 or padding 740. The order of subheaders 710-1, 710-2,..., 710-k is the corresponding MAC SDU, MAC control element 720,..., 725 or padding 740 in MAC PDU 700. Are arranged in the same order.

Each subheader 710-1, 710-2, ..., 710-k contains four fields: R, R, E, LCID or R, R, E, LCID, F, L Field may be included. Subheaders containing four fields are subheaders corresponding to MAC control elements 720, ..., 725 or padding 740, and subheaders containing six fields are subheaders corresponding to MAC SDUs. .

The logical channel identification information (LCID, Logical Channel ID) field is an identification field for identifying a logical channel corresponding to the MAC SDU, or for identifying a MAC control element (720, ..., 725) or a type of padding. When each subheader 710-1, 710-2,..., 710-k has an octet structure, the LCID field may be 5 bits.

For example, as shown in Table 3, the LCID field indicates whether the MAC control elements 720, ..., 725 are MAC control elements for indicating activation / deactivation of the serving cell, or contention resolution identifiers for contention resolution between terminals. Resolution Identity) Identifies whether it is a MAC control element or MAC control element for time advance command. The MAC control element for the time forward command is the MAC control element used for time alignment in random access.

LCID Index LCID value 00000 CCCH 00001-01010 Logical channel identifier 01011-11010 Reserved 11011 Activation / deactivation 11100 UE contention resolution identifier 11101 Time Forward Command (TAC) 11110 DRX command 11111 padding

Referring to Table 3, if the value of the LCID field is 11101, the corresponding MAC control element is a MAC control element for the time forward command.

Meanwhile, when a time advance command is given to a plurality of serving cells because a plurality of serving cells are configured in a terminal, an LCID field may be given as shown in Table 4.

LCID Index LCID value 00000 CCCH 00001-01010 Logical channel identifier 01011-11001 Reserved 11010 Extended Timing Advance Command 11011 Activation / deactivation 11100 UE contention resolution identifier 11101 Time Forward Command (TAC) 11110 DRX command 11111 padding

Referring to Table 4, if the value of the LCID field is 11010, the corresponding MAC control element is a MAC control element for the time advance command for the plurality of serving cells.

Next, MAC control elements 720,..., 725 are control messages generated by the MAC layer. Padding 740 is a predetermined number of bits added to make the size of the MAC PDU constant. The MAC control elements 720,..., 725, MAC SDUs 730-1,..., 730-m, and padding 740 together may also be referred to as MAC payloads.

When the terminal transmits the random access preamble to the base station on the representative serving cell of the specific time alignment group, the base station transmits an index of the specific time alignment group and a time forward command commonly applied to the specific time alignment group to the terminal. MAC control elements for time forward commands may be used. Examples of the MAC control element for the time forward command are the same as in FIG. 8 or 9A, 9B.

8 is a block diagram illustrating a structure of a MAC control element for a time forward command according to an embodiment of the present invention.

Referring to FIG. 8, the MAC control element for the time advance command includes an index field G ₁ , G ₀ and a timing advance command (TAC) field of a time alignment group TAG. When the MAC control element for the time advance command has an octet structure, the index field of the time alignment group is 2 bits, and the time forward command field is 6 bits. The time alignment group index is defined in the time alignment group configuration information. For example, if there are four time alignment groups and the time alignment group indexes are 1, 2, 3, and 4, G ₁ and G ₀ may be represented as {00, 01, 10, 11}. If the maximum number of time alignment groups is two, one of the two bit time alignment group index fields, for example, G ₁ is set to a reserved bit R, or the time alignment group index field defines only one bit. The time forward command field may be defined as 7 bits. The number of bits of the time alignment group index field and the number of bits of the time advance command field are merely examples, and are not necessarily limited to two and six, respectively. In addition, the index value of the time alignment group including the main serving cell may be fixed to '00' or '0'.

24A and 24B are another block diagrams illustrating the structure of a MAC control element for a time forward command according to an embodiment of the present invention.

Referring to FIG. 24A, a MAC control element for a time advance command includes an index field (G ₁ , G ₀ ) and a timing advance command (TAC) field of a time alignment group TAG. When the MAC control element for the time advance command is composed of two octets, the reserved bits are 3 bits, the index field of the time alignment group is 2 bits, and the time forward command field is 11 bits. Can be. If the index field of the time alignment group is 1 bit or 3 bits, the reserved bits may be 4 bits or 2 bits, respectively. Here, as shown in FIG. 24B, one of the reserved bits may be set to a bit X that does not use the most significant bit similarly to a format in a random access response message used in the existing LTE system.

When a plurality of time alignment groups are configured in the terminal, the terminal transmits a random access preamble on the representative serving cell of each time alignment group. That is, when the terminal transmits a plurality of random access preambles to the base station in the same subframe on a plurality of serving cells, the base station should send a time alignment value (or time saving command) for each time alignment group to the terminal. Therefore, a MAC control element for reporting time alignment values for a plurality of time alignment groups is also required.

9A is a block diagram illustrating a structure of a MAC control element for a time forward command according to another example of the present invention.

Referring to FIG. 9A, the MAC control element for the time forward command includes octet 1 (Oct 1), ..., octet N (Oct N). Each octet includes an index field (G ₁ , G ₀ ) and a timing advance command (TAC) field of a time alignment group (TAG).

For example, suppose that the terminal transmits a random access preamble to a base station in a first representative serving cell designated in TAG1 and a second representative serving cell designated in TAG2. The base station generates a random access response (RAR) message in response to the random access preamble, wherein the random access response message includes a MAC control element for a time forward command of two octets. Here, the first octet includes an index field of the first time alignment group indicating the index of TAG1 and a first time forward command field indicating the time alignment value of TAG1. The second octet includes an index field of the second time alignment group indicating the index of TAG2 and a second time forward command field indicating the time alignment value of TAG2.

The terminal performs time alignment by applying the time alignment value of TAG1 to all serving cells belonging to TAG1, and performs time alignment by applying the time alignment value of TAG2 to all serving cells belonging to TAG2.

9B is a block diagram illustrating a structure of a MAC control element for a time forward command according to another example of the present invention.

Referring to FIG. 9B, the MAC control element for the time forward command includes octet 1 (Oct 1), ..., octet N (Oct N). Octet 1 contains an indicator for each serving cell (or CC). This indicator may indicate the presence or absence of a time forward command field for the serving cell. For example, G0 is the time forward command field for TAG0, ie the TAG containing the main serving cell, G1 is the time forward command field for TAG1, G7 is the time forward for TAG7 It is an indicator that indicates whether a command field exists. Therefore, G0, G1, and G3 indicating TAG0, TAG1, and TAG3 are set to 1, and other G2, G4 to G7 are set to 0. The TAC values for TAG0, TAG1, and TAG3 are mapped in order. Using the configuration of FIG. 9B, a TAC value may be set for a corresponding TAG requiring an update for a specific TAG. The remaining octets 2, ..., octet N include a reserved field R and a time advance command (TAC) field.

10 is a flowchart illustrating a random access procedure according to another example of the present invention. This is a contention based random access procedure. The terminal needs uplink synchronization to transmit and receive data with the base station. The terminal may proceed with receiving information necessary for synchronization from the base station for uplink synchronization. The random access procedure may be applied to the case where the UE newly joins the network through a handover or the like. After the UE joins the network, the random access process may be performed in various situations such as synchronization or RRC state changing from RRC_IDLE to RRC_CONNECTED.

Referring to FIG. 10, the UE randomly selects one preamble signature from a random access preamble signature set, and selects a random access preamble according to the selected preamble signature through a representative serving cell using a PRACH resource. To transmit (S1000). The representative serving cell is a serving cell selected to transmit a random access preamble in a time alignment group configured in the terminal. The representative serving cell may be selected for each time alignment group. In addition, the UE may transmit a random access preamble on a representative serving cell in any one time alignment group among a 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 random access preamble may proceed after the representative serving cell is activated. In addition, the random access procedure for the secondary serving cell may be initiated by the PDCCH order (order) transmitted by the base station.

Information on the configuration of the random access preamble set may be obtained from a base station through a part of system information or a handover command message. Here, the UE may recognize a random access-radio network temporary identifier (RA-RNTI) in consideration of a frequency resource and a transmission time temporarily selected for preamble selection or RACH transmission.

The base station transmits a random access response message to the terminal as a response to the received random access preamble (S1005). The channel used at this time is PDSCH. The random access response message is transmitted in the form of MAC PDU according to FIGS. 7 to 9. The random access response message includes a time forward command for uplink synchronization of the terminal, uplink radio resource allocation information, a random access preamble identifier (RAPID) for identifying terminals performing random access, and a random access of the terminal. It includes information on the time slot for receiving the preamble and a temporary identifier of the terminal, such as a temporary C-RNTI. The random access preamble identifier is for identifying the received random access preamble.

The terminal transmits uplink data including the random access identifier to the base station through the PUSCH at the scheduling time determined based on the time alignment value according to the time advance command (S1010). The uplink data may include an RRC connection request, a tracking area update, a scheduling request, or a buffer status reporting on data transmitted by the UE on the uplink. have. The random access identifier may include a temporary C-RNTI, a C-RNTI (state included in the UE), or terminal identifier information (UE contention resolution identify). As the time alignment value is applied, the UE starts or restarts the time alignment timer. If the time alignment timer was previously running and restarts the time alignment timer, start the time alignment timer if the time alignment timer was not previously running.

In operations S1000 to S1010, since random access preamble transmission of various terminals may collide, the base station transmits a contention resolution message indicating that the random access is successfully terminated to the terminal (S1015). The contention resolution message may include a random access identifier. Contention in a contention-based random access process occurs because the number of possible random access preambles is finite. Since the UE cannot assign a unique random access preamble to all UEs in the cell, the UE randomly selects and transmits one random access preamble from the random access preamble set. Accordingly, two or more terminals may select and transmit the same random access preamble through the same PRACH resource.

At this time, transmission of the uplink data all fails, or the base station successfully receives only the uplink data of a specific terminal according to the location or transmission power of the terminals. When the uplink data is successfully received by the base station, the base station transmits a contention resolution message using the random access identifier included in the uplink data. Upon receiving its random access identifier, the UE may know that contention resolution is successful. In the contention-based random access process, it is called contention resolution to allow the UE to know whether contention fails or succeeds.

Upon receiving the contention resolution message, the terminal checks whether the contention resolution message is its own. If the result of the check is correct, the terminal sends an ACK to the base station, and if the terminal of the other terminal does not send response data. Of course, even if the DL allocation is missed or the message cannot be decoded, no response data is sent. In addition, the contention resolution message may include C-RNTI or terminal identifier information.

11 is an explanatory diagram illustrating a method of configuring a time alignment group and a method of determining a time alignment value in a multicarrier system according to the present invention.

Referring to FIG. 11, a reference time means a time that is a reference of synchronization of downlink or uplink. Here, it is assumed that the reference time is set to a point in time when the downlink frame is received by the terminal and confirmed after synchronization. The terminal includes a serving cell 1 (SCell 1), a serving cell 2 (SCell 2), a serving cell 3 (SCell 3), a serving cell 4 (SCell 4), and a serving cell 5 (SCell 5).

Based on the classification assistance information, the base station configures the serving cell 1, the serving cell 3, and the serving cell 4 into one time alignment group 1 (TAG1), and the serving cell 2 and the serving cell 5 into the other time alignment group 2 ( TAG2). Since the current uplink time of the serving cells of TAG1 is delayed by TA1 time compared to the reference time, the base station sets the first time alignment value N _TA1 to advance the uplink time of the serving cells of TAG1 by TA1 time. This is indicated in the first time forward command field and transmitted to the terminal.

In addition, since the uplink time of the serving cells of TAG2 is delayed by TA2 time than the present time, the base station sets a second time alignment value N _TA2 to advance the uplink time of the serving cells of TAG2 by TA2 time than the present time. Indicated in the second time forward command field and transmitted to the terminal. The MAC control element including the first and second time forward command fields may have a structure as shown in FIG. 9.

The terminal may calculate time TA1 and TA2 to be adjusted using N _TA1 and N _TA2 provided by the base station and adjust uplink time. The adjusted time TA may be obtained as in Equation 1 below.

Here, N _TA is a time alignment value, which is variably controlled by a time advance command of a base station, and N _{TA offset} is a fixed value by the frame structure. T _s is the sampling period. In this case, when the time alignment value N _TA is positive, it indicates adjusting to advance the uplink time, and when it is negative, it adjusts to delaying the uplink time.

On the other hand, the time alignment value (N _TA) is currently set N _TA value _- the new N _TA value by value of index from the (N _{TA old) -} is adjusted by (N _{TA new),} the new N _TA value is obtained as equation (2) Can be done.

Referring to Equation 2, T _i is an index value, and 0, 1, 2, ..., 63.

Alternatively, the time alignment value N _TA may be determined as a difference value with respect to the time alignment value of the TAG included in the main serving cell as shown in Equation 3 below.

Referring to Equation _{3, N TA - TAG (Sn} ) but does not contain a primary serving cell (PCell) and the time alignment value for time alignment group with an index value of n is, N _{TA - TAG (p)} is a primary serving A time alignment value for a time alignment group including a cell (PCell). T _{i -n} is the T _i value for the time alignment group whose index value is n.

When the UE first receives the time alignment value for the serving cell, since there is no target value to prepare, the time alignment value N _TA may be determined as shown in Equation 4.

As another example, when the propagation delay time of the downlink transmission is the same as the propagation delay time of the uplink transmission, the terminal may adjust the uplink time for all serving cells using the propagation delay time of the downlink transmission.

12 is a flowchart illustrating a method of performing random access according to another embodiment of the present invention.

Referring to FIG. 12, if a UE in Radio Resource Control (RRC) idle mode cannot aggregate component carriers, only a UE in RRC connected mode may perform component carrier aggregation. If there is, the UE selects a cell for RRC connection prior to component carrier aggregation and performs an RRC connection establishment procedure for the base station through the selected cell (S1200). The RRC connection establishment procedure is performed by the terminal transmitting the RRC connection request message to the base station, the base station transmitting the RRC connection setup to the terminal, and the terminal transmitting the RRC connection setup complete message to the base station. The RRC connection setup procedure includes the setup of SRB1.

Meanwhile, a cell for RRC connection is selected based on the following selection conditions.

(i) The most suitable cell for attempting a radio resource control connection may be selected based on the information measured by the terminal. As measurement information, the UE defines an RSRP for measuring reception power based on a cell-specific reference singal (CRS) of a specific cell received and an RSRQ defined as a ratio of RSRP values (denominators) for a specific cell to total reception power (molecule). Consider all. Accordingly, the UE acquires RSRP and RSRQ values for each of the distinguishable cells and selects a suitable cell based on the obtained RSRP and RSRQ values. For example, both the RSRP and RSRQ values have a value greater than 0 dB and the weight is set for each cell having the maximum RSRP value or the maximum RSRQ value or each of the RSRP and RSRQ values (for example, 7: 3) and the weight is considered. To select a suitable cell based on the average value.

(ii) Radio resources using information on a service provider (PLMN) or downlink center frequency information or cell identification information (eg PCI (Physical cell ID)) fixedly set in a system stored in the terminal internal memory. A control connection can be attempted. The stored information may be configured with information on a plurality of service providers and cells, and priority or priority weight may be set for each information.

(iii) The terminal may attempt to establish a radio resource control connection by receiving the system information transmitted through the broadcasting channel from the base station and confirming the information in the received system information. For example, the terminal should check whether or not a specific cell (eg, a closed subscribe group, a non-allowed Home base station, etc.) requiring membership for cell access. Accordingly, the terminal checks the CSG ID information indicating whether or not the CSG by receiving the system information transmitted by each base station. If it is confirmed that it is a CSG, it checks whether the CSG is accessible. In order to confirm the accessibility, the UE may use its own membership information and unique information of the CSG cell (for example, (E) CGI ((envolved) cell grobal ID) or PCI information in the system information). If it is confirmed that the base station is inaccessible through the checking procedure, no radio resource control connection is attempted.

(iv) A radio resource control connection may be attempted through valid component carriers stored in the terminal internal memory (for example, component carriers configurable within a frequency band supported by the terminal in implementation). .

Of the four selection conditions, the conditions (ii) and (iv) are optional but the conditions (i) and (iii) must be mandatory.

In order to attempt a radio resource control connection through a cell selected for RRC connection, the UE must identify an uplink band for transmitting an RRC connection request message. Accordingly, the terminal receives system information through a broadcasting channel transmitted through downlink of the selected cell. System information block 2 (SIB2) includes bandwidth information and center frequency information for a band to be used as an uplink. Therefore, the UE attempts RRC connection through an uplink band configured through downlink, downlink and information in SIB2 of the selected cell. In this case, the terminal may transmit the RRC connection request message as uplink data to the base station within the random access procedure. If the RRC connection procedure is successful, the RRC connected cell may be called a main serving cell, and the main serving cell includes a DL PCC and a UL PCC.

When the base station needs to allocate to the terminal of more radio resources by the request of the terminal or the request of the network or the base station itself, the RRC connection reconfiguration for additional configuration of at least one secondary cell (SCell) to the terminal ) And performs the procedure (S1205). The RRC connection reconfiguration procedure is performed by the base station transmitting an RRC connection reconfiguration message to the terminal and the terminal transmitting an RRC connection reconfiguration complete message to the base station.

Steps S500, S505, S510, and S515 are equally applied to the following steps S1210, S1215, S1220, and S1225. On the other hand, the classification support information may be included in the RRC connection reconfiguration complete message in step S1205, in which case, step S1210 may be omitted. In addition, performing a random access procedure (S1225) may be performed on a contention-free or contention-based basis. The random access procedure differs depending on whether it is based on contention-free or contention-based and follows the procedure of FIG. 6 in the case of non-contention-based, and the procedure of FIG. 10 in case of contention-based.

13 is a flowchart illustrating a method of performing random access according to another embodiment of the present invention.

Referring to FIG. 13, the terminal and the base station perform an RRC connection establishment procedure for the base station through the selected cell (S1300). The terminal transmits classification support information to the base station (S1305). The classification support information provides information or criteria necessary for classifying at least one serving cell configured in the terminal into a time alignment group. Meanwhile, the base station may know the classification support information separately or may already have it. In this case, random access according to the present embodiment may be performed with step S1305 omitted.

The base station classifies the serving cells to form a time alignment group (S1310). Serving cells may be classified or configured into each time alignment group according to classification support information.

The base station performs an RRC connection reconfiguration procedure for additionally configuring at least one secondary serving cell to the terminal when it is necessary to allocate to the terminal of more radio resources by the request of the terminal or the request of the network or the self-determination of the base station (S1315). ). In the RRC connection reconfiguration procedure, the base station may transmit time alignment group configuration information in the RRC connection reconfiguration message to the terminal. The time alignment group configuration information describes a state in which the time alignment group is configured. As an example, the time alignment group setting information may include a number field of the time alignment group, an index field of each time alignment group, and an index field of a serving cell included in each time alignment group, and these fields may include a time alignment group. Describe the configured state.

Thereafter, the UE performs a random access procedure (S1320), which may be performed based on contention-free or contention-based. The random access procedure differs depending on whether it is based on contention-free or contention-based and follows the procedure of FIG. 6 in the case of non-contention-based, and the procedure of FIG. 10 in case of contention-based.

The UE checks the time advance command and / or time alignment group index in the random access response message, and adjusts uplink time for all serving cells in the identified time alignment group by the time alignment value according to the time advance command. Examples of the uplink time adjusted by the time alignment value are shown in Equations 1 to 4. If there is a time advance command and / or a time alignment group index for a plurality of time alignment groups in the random access response message, the UE transmits an uplink time for the serving cell (s) of each time alignment group to the corresponding time advance command. Adjust by time alignment value accordingly.

14 is a flowchart illustrating a method of performing random access according to another example of the present invention.

Referring to FIG. 14, the terminal and the base station perform an RRC connection establishment procedure for the base station through the selected cell (S1400). The selected cell becomes the main serving cell. The base station performs an RRC connection reconfiguration procedure for additionally configuring at least one secondary serving cell to the terminal when it is necessary to allocate to the terminal of more radio resources by the request of the terminal or the request of the network or the self determination of the base station (S1405). ).

The terminal configures one or more secondary serving cells and performs a random access procedure (S1410). The terminal transmits a random access preamble to the base station in order to secure time synchronization for the secondary serving cell for which synchronization is not secured or the newly added / modified secondary serving cell. In this case, the random access procedure may be performed only after the representative serving cell is activated. The random access procedure for the secondary serving cell may be initiated by a PDCCH order transmitted by the base station. The random access procedure may be performed on a contention-free basis or a contention-based contention by the base station.

The base station classifies the serving cells configured in the terminal based on the random access preamble received in step S1410 to form a time alignment group (S1415). The time alignment group is a group including at least one serving cell, and the same time alignment value is applied to the serving cells in the time alignment group. As an example, the base station may configure a time alignment group specific to the terminal. As another example, the base station may configure a time alignment group specific to the cell.

The base station transmits time alignment group configuration information to the terminal (S1420). The time alignment group configuration information describes a state in which the time alignment group is configured. As an example, the time alignment group setting information may include a number field of the time alignment group, an index field of each time alignment group, and an index field of a serving cell included in each time alignment group, and these fields may include a time alignment group. Describe the configured state.

As another example, the time alignment group configuration information may further include representative serving cell information in each time alignment group. The representative serving cell is a serving cell capable of performing a random access procedure for maintaining and configuring uplink synchronization in each time alignment group. Unlike the above embodiment, if the time alignment group configuration information does not include a representative serving cell, the terminal may select a representative serving cell in each time alignment group by itself.

15 is a flowchart illustrating operations of a terminal performing random access according to an embodiment of the present invention.

Referring to FIG. 15, the terminal transmits classification assistance information to the base station (S1500). The classification support information provides information or criteria necessary for classifying at least one serving cell configured in the terminal into a time alignment group. Meanwhile, the base station may know the classification support information separately or may already have it. In this case, random access according to the present embodiment may be performed with step S1500 omitted.

If the UE in the idle mode cannot aggregate the component carriers, and only the UE in the RRC connected mode can perform the component carrier aggregation, the terminal in the idle mode selects a cell for RRC connection prior to the component carrier aggregation before step S1500, An RRC connection establishment procedure may be performed for the base station through the selected cell.

The terminal receives time alignment group configuration information from the base station (S1505). The time alignment group is a group including at least one serving cell, and the same time alignment value is applied to the serving cells in the time alignment group. As an example, the base station may configure a time alignment group specific to the terminal. As another example, the base station may configure a time alignment group specific to the cell.

The time alignment group configuration information describes a state in which the time alignment group is configured. As an example, the time alignment group setting information may include a number field of the time alignment group, an index field of each time alignment group, and an index field of a serving cell included in each time alignment group, and these fields may include a time alignment group. Describe the configured state.

As another example, the time alignment group configuration information may further include representative serving cell information in each time alignment group. The representative serving cell is a serving cell capable of performing a random access procedure for maintaining and configuring uplink synchronization in each time alignment group. Unlike the above embodiment, if the time alignment group configuration information does not include a representative serving cell, the terminal may select a representative serving cell in each time alignment group by itself.

Thereafter, the terminal performs a random access procedure (S1510). In this step, the terminal transmits the random access preamble to the base station on the representative serving cell, and receives a MAC control element for the time advance command from the base station. This can be done on a contention-free or contention-based basis. The random access procedure differs depending on whether it is based on contention-free or contention-based and follows the procedure of FIG. 6 in the case of non-contention-based, and the procedure of FIG. 10 in case of contention-based.

The UE checks the time advance command and / or time alignment group index in the random access response message, and adjusts uplink time for all serving cells in the identified time alignment group by the time alignment value according to the time advance command. Examples of the uplink time adjusted by the time alignment value are shown in Equations 1 to 4. If there is a time advance command and / or a time alignment group index for a plurality of time alignment groups in the random access response message, the UE transmits an uplink time for the serving cell (s) of each time alignment group to the corresponding time advance command. Adjust by time alignment value accordingly.

16 is a flowchart illustrating operations of a base station performing random access according to an embodiment of the present invention.

Referring to FIG. 16, the base station receives classification support information from the terminal (S1600). The classification support information provides information or criteria necessary for classifying at least one serving cell configured in the terminal into a time alignment group. Meanwhile, the base station may know the classification support information separately or may already have it. In this case, random access according to the present embodiment may be performed with step S1600 omitted.

 The base station configures a time alignment group based on the classification assistance information (S1605), and transmits time alignment group configuration information to the terminal (S1610). The time alignment group is a group including at least one serving cell, and the same time alignment value is applied to the serving cells in the time alignment group. As an example, the base station may configure a time alignment group specific to the terminal. As another example, the base station may configure a time alignment group specific to the cell. The time alignment group configuration information describes a state in which the time alignment group is configured.

Thereafter, the base station performs a random access procedure with the terminal. In this step, the base station receives a random access preamble from the terminal on a representative serving cell and transmits a MAC control element for a time advance command to the terminal. This can be done on a contention-free or contention-based basis. The random access procedure differs depending on whether it is based on contention-free or contention-based and follows the procedure of FIG. 6 in the case of non-contention-based, and the procedure of FIG. 10 in case of contention-based.

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

Referring to FIG. 17, the terminal 1700 includes a terminal receiver 1705, a terminal processor 1710, and a terminal transmitter 1720. The terminal processor 1710 also includes an RRC processor 1711 and a random access processor 1712.

The terminal receiver 1705 receives preamble allocation information, time alignment group configuration information, a random access response message, an RRC connection configuration message, an RRC connection reconfiguration message, or a contention resolution message from the base station 1750. The time alignment group configuration information describes a state in which the time alignment group is configured.

The RRC processing unit 1711 generates classification support information, an RRC connection message, and an RRC connection reconfiguration complete message. The classification support information may be included in the RRC connection reconfiguration complete message. The RRC processor 1711 identifies at least one of the number of time alignment groups configured in the terminal 1700, the index of each time alignment group, the index of the serving cell in each time alignment group, and the representative serving cell information from the time alignment group configuration information. Can be. The representative serving cell is a serving cell selected to transmit a random access preamble in a time alignment group configured in the terminal. The representative serving cell may be selected for each time alignment group.

The random access processor 1712 processes a non-contention based or contention based random access procedure. The random access processing unit 1712 generates a random access preamble to secure uplink time synchronization for the serving cell. The generated random access preamble may be a dedicated random access preamble assigned by the base station 1750. When a plurality of time alignment groups are configured in the terminal 1700, the random access processor 1712 may generate random access preambles to be transmitted on a representative serving cell of each time alignment group.

Meanwhile, the random access processor 1712 checks the time advance command and / or the time alignment group index in the random access response message, and time-aligns the uplink time for all the serving cells in the identified time alignment group according to the time advance command. Adjust by value. Examples of the uplink time adjusted by the time alignment value are shown in Equations 1 to 4. If there are time advance commands and / or time alignment group indexes for the plurality of time alignment groups in the random access response message, the random access processor 1712 may determine an uplink time for the serving cell (s) for each time alignment group. Adjust the time alignment value according to the time advance command.

The terminal transmitter 1720 transmits classification support information, an RRC connection message, an RRC connection reconfiguration complete message, or a random access preamble to the base station 1750. For example, suppose that the time alignment groups configured in the terminal are TAG1 and TAG2, and TAG1 = {first serving cell, second serving cell, third serving cell}, and TAG2 = {fourth serving cell, fifth 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 transmitter 1720 transmits the first random access preamble on the second serving cell, and transmits the second random access preamble. Transmit on the fifth serving cell.

The base station 1750 includes a base station transmitter 1755, a base station receiver 1760, and a base station processor 1770. The base station processor 1770 also includes an RRC processing unit 1773 and a random access processing unit 1772.

The base station transmitter 1755 transmits preamble allocation information, time alignment group configuration information, a random access response message, an RRC connection complete message, an RRC connection reconfiguration message, or a contention resolution message to the terminal 1700.

The base station receiver 1760 receives classification support information, a random access preamble, an RRC connection establishment related message, or an RRC connection reconfiguration related message from the terminal 1700.

The RRC processor 1775 generates an RRC connection complete message or an RRC connection reconfiguration message. In addition, the RRC processing unit 1773 configures a time alignment group, and generates time alignment group configuration information. The time alignment group is a group including at least one serving cell configured in the terminal 1700, and the same time alignment value is applied to the serving cells in the time alignment group. As an example, the RRC processing unit 1773 may configure a time alignment group specifically for the terminal 1770. As another example, the RRC processing unit 1773 may configure a time alignment group specific to a cell.

The random access processing unit 1772 selects one of the reserved random access preambles previously reserved for the non-contention based random access procedure among all available random access preambles, and indexes and usable time / frequency of the selected random access preamble. Generates preamble allocation information including resource information.

In addition, the random access processing unit 1772 generates a random access response message or a contention resolution message. The random access processing unit 1772 identifies the representative serving cell to which the random access preamble is transmitted, and identifies a time alignment group including the representative serving cell. In addition, the random access processing unit 1772 determines a time alignment value to be applied to the identified time alignment group, and generates a random access response message including a time advance command (TAC) indicating the determined time alignment value.

The time advance command indicates a change in the uplink time relative to the current uplink time, and may be an integer multiple of the sampling time T _s , for example, 16T _s . The temporal advance command may be expressed as a time alignment value of a specific index.

Alternatively, the random access processing unit 1772 may generate a random access response message including a time advance command and an index of the identified time alignment group. The data structure for the time advance command is described in Figures 7-9B.

Hereinafter, the time alignment group setting information will be described in detail. As an example, the base station may transmit time alignment group configuration information to the terminal using an RRC message. For example, the time alignment group configuration information may be transmitted in an RRC connection reconfiguration message used in an RRC connection reconfiguration procedure. Table 5 is an example of an RRC connection reconfiguration message including time alignment group configuration information.

TAG-ConfigDedicated :: = SEQUENCE {
pTAG SCellListOfTAG,
sTAG SCellListOfTAG,
sTAG-referenceCell INTEGER (1..7)
}

SCellListOfTAG :: = SEQUENCE (SIZE (1..7)) OF Serv-index

Referring to Table 5, the RRC connection reconfiguration message includes time alignment group configuration information (TAG-ConfigDedicated). pTAG indicates a time alignment group including the main serving cell, and sTAG indicates a time alignment group not including the main serving cell. The representative serving cell index (referenceCell) in the sTAG has a value of 1 to 7, which corresponds to the serving cell index. The serving cell list information SCellListOfTAG of the temporal alignment group has a value of 1 to 7, which corresponds to the serving cell index.

Table 6 is another example of an RRC connection reconfiguration message including time alignment group configuration information.

TAG-ConfigDedicated :: = SEQUENCE {
pTAG BIT STRING (SIZE (7)),
sTAG BIT STRING (SIZE (7)),
sTAG-referenceCell INTEGER (1..7)
}

Referring to Table 6, the RRC connection reconfiguration message includes time alignment group configuration information (TAG-ConfigDedicated). Unlike Table 5, Table 6 shows the serving cells included in the pTAG and sTAG as a bit string. The size of the bit string is 7 bits, and one serving cell corresponds to only one bit of the bit string. Of course, the size of the 7-bit bit string is exemplary and may be smaller or larger.

As another example, the base station may transmit time alignment group configuration information to the terminal using a MAC message. The MAC message including the time alignment group configuration information may have the MAC PDU structure of FIG. 7. In particular, the time alignment group configuration information may be included in a MAC control element, and a value of an LCID field indicating such a MAC control element may be defined as shown in Table 7.

LCID Index LCID value 00000 CCCH 00001-01010 Logical channel identifier 01011-11001 Reserved 11010 Time alignment group setting information 11011 Activation / deactivation 11100 UE contention resolution identifier 11101 Time Forward Command (TAC) 11110 DRX command 11111 padding

Referring to Table 6, the LCID field having the value 11010 indicates that the corresponding MAC control element is a MAC control element (hereinafter referred to as MAC control element for TAG) including time alignment group configuration information. The MAC subheader corresponding to the MAC control element for the TAG includes six fields such as R / R / E / LCID / F / L, where the MAC control element for the TAG may have a variable length. The L field indicates the length of a MAC control element for a TAG in bytes. The length of the L field is indicated by the F field. For example, the F field is 1 bit and '1' indicates that the MAC control element for the TAG is smaller than 128 bytes. In this case, the MAC subheader is the same as the first embodiment of FIG. In addition, if the F field is '0', the length of the MAC control element for the TAG is 128 bytes or more, and the MAC subheader in this case is the same as the second embodiment of FIG.

19 illustrates a MAC control element for TAG according to an embodiment of the present invention.

Referring to FIG. 19, octet 1 (Oct 1) in 8-bit units corresponds to a pTAG and represents a serving cell included in the pTAG in a bitmap format or a binary format. R, C ₇ , C ₆ , C ₅ , C ₄ , C ₃ , C ₂ , and C ₁ of octet 1 are sequentially assigned to the serving cell index 1, the serving cell index 2,. Corresponding to the serving cell index 7, R is a reserved field. That is, C _n corresponds to the serving cell index n. For example, if C _n = 1, it may indicate that a serving cell having an index n is included in the pTAG, and if C _n = 0, it may indicate that a serving cell having an index n is not included in the pTAG. In pTAG, the main serving cell always becomes the representative serving cell.

Octet 2 is an area corresponding to the first sTAG and represents a serving cell included in the sTAG in a bitmap form or a binary form. R, C ₇ , C ₆ , C ₅ , C ₄ , C ₃ , C ₂ , and C ₁ of octet 2 sequentially serve cell index 1, serving cell index 2,... Corresponding to the serving cell index 7, R is a reserved field. The next octet 3 indicates a representative serving cell in the sTAG indicated by octet 2, which is the previous octet. That is, octet 3 includes a cell index field indicating a representative serving cell of the first sTAG. Since seven serving cells can be represented by 3 bits, the cell index field is 3 bits, and the remaining 5 bits of octet 3 are represented. Is set to a preliminary field (R field).

Similarly, octet 2 (N-1) is an area corresponding to the Nth sTAG, and octet 2N-1 is an area indicating a representative serving cell in the Nth sTAG.

In each octet, the R field is shown as being located in the leftmost bit, but this is only an example and the R field may be located in the rightmost bit.

20 illustrates a MAC control element for TAG according to another embodiment of the present invention.

Referring to Fig. 20, each octet 1, 2, 3,... , n + 1 is sequentially pTAG, sTAG1, sTAG2,... , which corresponds to sTAGn, represents a serving cell included in a time alignment group in a bitmap form or a binary form. 19 is different from the cell index field indicating the representative serving cell of each time alignment group. The representative serving cell of each TAG may be predefined between the terminal and the base station or may be known to the terminal by separate signaling. In each octet, the R field is shown as being located in the leftmost bit, but this is only an example and the R field may be located in the rightmost bit.

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and changes without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas falling within the scope of the same shall be construed as falling within the scope of the present invention.

Claims (18)

A terminal for performing random access in a wireless communication system,
A receiver for receiving, from a base station, time alignment group configuration information for classifying at least one serving cell configured in a terminal into a timing alignment group (TAG); And
A transmitter for transmitting a random access preamble to the base station on one representative serving cell in the time alignment group,
The receiver receives a random access response message including a time forward command field from the base station in response to the random access preamble, and the time forward command field equals uplink time of all serving cells in the time alignment group. And indicating a time alignment value to be adjusted. The method of claim 1,
And a random access processing unit for adjusting uplink times of all of the serving cells in the time alignment group based on the time alignment value. The method of claim 1,
And the receiving unit receives a radio resource control (RRC) connection reconfiguration message from the base station indicating that the at least one serving cell is configured in the terminal. The method of claim 1,
And an RRC processing unit for generating classification support information for providing information necessary for classifying the time alignment group.
The transmitter is characterized in that for transmitting the classification support information to the base station. A method of performing random access by a terminal in a wireless communication system,
Receiving time alignment group configuration information for classifying at least one serving cell configured in a terminal into a time alignment group from a base station;
Transmitting a random access preamble to the base station on one representative serving cell in the time alignment group; And
In response to the random access preamble, receiving a random access response message from the base station including a time forward command field,
And the time forward command field indicates a time alignment value for equally adjusting uplink times of all serving cells in the time alignment group. The method of claim 5, wherein
The time alignment group configuration information includes at least one of a number field of a time alignment group, an index field of a time alignment group, an index field of a serving cell included in the time alignment group, and information of the representative serving cell. How to perform random access. The method of claim 5, wherein
The random access response message further comprises an index field indicating the time alignment group, random access method. The method of claim 5, wherein
And adjusting the uplink times of all the serving cells in the time alignment group equally based on the time alignment value. A base station performing random access in a wireless communication system,
An RRC processing unit for generating time alignment group configuration information for classifying at least one serving cell configured in a terminal into a time alignment group;
A transmitter for transmitting the time alignment group configuration information to the terminal;
A receiver which receives a random access preamble from the terminal on one representative serving cell in the time alignment group;
A random access processor configured to generate a random access response message including a time forward command field indicating a time alignment value for equally adjusting uplink times of all serving cells in the time alignment group in response to the random access preamble; And
And a transmitter for transmitting the random access response message to the terminal. The method of claim 9,
And the receiving unit receives classification support information from the terminal, which provides information necessary for classifying the time alignment group. The method of claim 9,
The RRC processing unit generates an RRC connection reconfiguration message indicating to configure the at least one serving cell in the terminal,
The transmitter is characterized in that for transmitting the RRC connection reconfiguration message to the terminal. The method of claim 9,
The time alignment group configuration information includes at least one of a number field of a time alignment group, an index field of a time alignment group, an index field of a serving cell included in the time alignment group, and information of the representative serving cell. Base station. A method of performing random access by a base station in a wireless communication system,
Transmitting time alignment group configuration information for classifying at least one serving cell configured in the terminal into a time alignment group;
Receiving a random access preamble from the terminal on one representative serving cell in the time alignment group; And
In response to the random access preamble, transmitting a random access response message including a time forward command field indicating a time alignment value for equally adjusting uplink times of all serving cells in the time alignment group to the terminal. Method for performing random access, characterized in that it comprises a. The method of claim 13,
The time alignment group configuration information includes at least one of a number field of a time alignment group, an index field of a time alignment group, an index field of a serving cell included in the time alignment group, and information of the representative serving cell. How to perform random access. The method of claim 13,
The random access response message further comprises an index field indicating the time alignment group, random access method. The method of claim 13,
And receiving classification support information from the terminal that provides information necessary for classifying the time alignment group. The method of claim 13,
The time alignment group configuration information is transmitted in an RRC connection reconfiguration message.
The time alignment group configuration information is defined by distinguishing between a time alignment group including a primary serving cell (primary serving cell) and a time alignment group not including the primary serving cell, random access method. The method of claim 13,
The time alignment group configuration information is transmitted in a MAC control element.
The time alignment group configuration information indicates an entire octet of the serving cell in the time alignment group in octets of 8 bits.

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