KR20130031126A

KR20130031126A - Apparatus and method for performing random access procedure in multiple component carrier system

Info

Publication number: KR20130031126A
Application number: KR1020110094860A
Authority: KR
Inventors: 권기범; 안재현; 정명철
Original assignee: 주식회사 팬택
Priority date: 2011-09-20
Filing date: 2011-09-20
Publication date: 2013-03-28

Abstract

PURPOSE: A device for performing a random access process in a multiple component carrier system and a method thereof are provided to control the random access process in a wireless communication system which operates a plurality of component carriers corresponding to a property of a serving cell. CONSTITUTION: A terminal receiving unit(1505) receives a random access interruption indicator from a base station(1550). The random access interruption indicator indicates interruption of a random access process in a secondary serving cell of a terminal(1500). A random access processing unit(1510) determines whether or not an interruption condition, which interrupts the random access process, is satisfied based on the random access interruption indicator. When the interruption condition is satisfied, the random access processing unit interrupts the random access process in the secondary serving cell. When the interruption condition is not satisfied, a terminal transmission unit(1520) transmits preamble to the base station. [Reference numerals] (1505) Terminal receiving unit; (1510) Random access processing unit; (1520) Terminal transmission unit; (1555) Base station transmission unit; (1560) Stop requesting unit; (1565) Base station receiving unit; (AA) Random access stop indicator; (BB) RACH configuration information; (CC) Preamble

Description

Apparatus and method for performing random access procedure in multi-component carrier system {APPARATUS AND METHOD FOR PERFORMING RANDOM ACCESS PROCEDURE IN MULTIPLE COMPONENT CARRIER SYSTEM}

The present invention relates to wireless communication, and more particularly, to an apparatus and method for performing a random access procedure in a multi-component carrier system.

In order to access the network, the UE goes through a random access procedure. The random access procedure 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 procedure and the non- contention-based random access procedure is whether a random access preamble is designated as dedicated to one UE. In the non-contention based random access procedure, since the terminal uses a dedicated random access preamble designated only for itself, contention (or collision) with other terminals 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 procedure, there is a possibility of contention because the terminal uses a random access preamble selected by the UE.

The random access procedure can be applied to the case where the terminal newly joins the network through a handover or the like, and after joining the network, when the state of synchronization or RRC (Radio Resource Control) changes from RRC_IDLE to RRC_CONNECTED, or the terminal It may proceed in various situations, such as when uplink synchronization is required to transmit and receive data with the base station.

An object of the present invention is to provide an apparatus and method for performing a random access procedure in a multi-component carrier system.

Another object of the present invention is to provide an apparatus and method for controlling a random access procedure according to a characteristic of a serving cell in a wireless communication system operating a plurality of CCs.

Another technical problem of the present invention is to provide an apparatus and method for adjusting the maximum number of retransmissions of a preamble in a random access procedure.

Another technical problem of the present invention is to provide an apparatus and method for transmitting an indicator for stopping a random access procedure in a specific serving cell.

Another object of the present invention is to provide an apparatus and method for providing a function of instructing interruption of a random access procedure to downlink control information indicating initiation of a random access procedure.

Another technical problem of the present invention is to provide an apparatus and method for stopping a random access procedure in a specific serving cell based on an indicator indicating the interruption of the random access procedure.

According to an aspect of the present invention, a method of performing a random access procedure by a terminal in a multi-carrier system is provided. In the method of performing the random access procedure, receiving a random access stop indicator from the base station indicating the stop of the random access procedure in the secondary serving cell configured in the terminal, based on the random access stop indicator, stop the random access procedure Determining whether an abort condition is satisfied; and stopping the random access procedure in the secondary serving cell when the abort condition is satisfied.

According to another aspect of the present invention, a terminal for performing a random access procedure in a multi-carrier system. The terminal may receive a random access stop indicator from the base station indicating a random access stop indicator in the secondary serving cell configured in the terminal, the stop condition for stopping the random access procedure based on the random access stop indicator; And a random access processing unit for stopping the random access procedure in the secondary serving cell when the stopping condition is satisfied, and a terminal transmitting unit transmitting a preamble to the base station when the stopping condition is not satisfied. do.

According to another aspect of the present invention, there is provided a method of performing a random access procedure by a base station in a multi-carrier system. The method of performing the random access procedure may include: transmitting a random access command to the terminal instructing the start of a random access procedure in a secondary serving cell configured in the terminal, determining whether to request the suspension of the random access procedure; and If it is necessary to request the interruption of a random access procedure, and transmitting a random access interruption indicator indicating the interruption of the random access procedure to the terminal.

According to another aspect of the present invention, there is provided a base station performing a random access procedure in a multi-carrier system. The base station transmits a random access command for instructing the start of a random access procedure in the secondary serving cell configured in the terminal to the terminal, a stop request unit for determining whether to request the termination of the random access procedure, and the terminal It includes a base station receiving unit for receiving a preamble from.

If the stop requesting unit determines that it is necessary to request the suspension of the random access procedure, the base station transmitter includes transmitting a random access interruption indicator indicating the suspension of the random access procedure to the terminal.

The base station may forcibly stop the random access procedure in progress in a specific serving cell and initiate a random access procedure in another serving cell. This can reduce system performance degradation such as delay of random access occurring in an environment where parallel random access procedure is not supported.

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 diagram illustrating an example of time advance in a synchronization process to which the present invention is applied.
FIG. 6 is a diagram illustrating an uplink time alignment value applied using downlink time alignment values of a primary serving cell and a secondary serving cell.
7 is a flowchart illustrating a contention based random access procedure to which the present invention is applied.
8 is a flowchart illustrating a random access procedure according to an indication of a base station to which the present invention is applied.
9 is a flowchart illustrating a method of performing a random access procedure according to an embodiment of the present invention.
10 is a block diagram illustrating a subheader of a MAC control element to which the present invention is applied.
11 is a block diagram illustrating a random access stop indicator according to an embodiment of the present invention.
12 is a flowchart illustrating a method of performing a random access procedure according to another example of the present invention.
13 is a flowchart illustrating a random access procedure performed by a terminal according to an embodiment of the present invention.
14 is a flowchart illustrating a random access procedure performed by a base station according to an embodiment of the present invention.
15 is a block diagram illustrating a terminal and a base station for performing a random access procedure 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;

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.

A terminal in Radio Resource Control (RRC) idle mode cannot aggregate component carriers, and only a terminal in RRC connected mode can perform component carrier aggregation. Accordingly, the UE should select a cell for RRC connection prior to component carrier aggregation and perform an RRC connection establishment procedure for the base station through the selected cell. 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.

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 carry 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.

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 for uplink synchronization acquisition, and the UE 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.

5 is a diagram illustrating an example of time advance in a synchronization process to which the present invention is applied.

Referring to FIG. 5, an uplink radio frame 520 should be transmitted at the time of transmitting a downlink radio frame 510 for communication between a base station and a terminal. In consideration of the time difference caused by the propagation delay between the terminal and the base station, the terminal transmits the uplink radio frame 520 at a time earlier than when the downlink radio frame 510 is transmitted to synchronize with the base station and the terminal. You can apply time advance.

The uplink time TA adjusted by the UE can be obtained through 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.

For uplink synchronization, the terminal may receive a TA value provided by the base station and apply time advance based on the TA value, and the terminal may acquire synchronization for wireless communication with the base station.

Now, the application of multiple timing advance is described.

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 signals of a plurality of serving cells configured in the terminal have different time delays, it is required for the terminal to apply different TAs to each serving cell.

6 is a diagram illustrating a method of applying an uplink time alignment value using downlink time alignment values of a primary serving cell and a secondary serving cell according to an embodiment of the present invention. DL CC1 and UL CC1 are main serving cells, and DL CC2 and UL CC2 are secondary serving cells.

Referring to FIG. 6, when a base station transmits a frame through DL CC1 and DL CC2 at a T_Send time point (610), the UE receives a frame through DL CC1 and DL CC2 (620). The terminal receives the frame as late as the propagation delay time after the T_Send time point transmitted by the base station. In DL CC1, a propagation delay occurs by T1 and receives a frame as late as T1. In DL CC2, a propagation delay is generated by T2 and a frame is received as late as T2.

If it is assumed that the propagation delay time of the downlink transmission is the same as the propagation delay time of the uplink transmission, the terminal may transmit a frame to the base station by applying TAs as much as T1 and T2 to the UL CC1 and the UL CC2 (630). As a result, the base station can receive the frame transmitted by the terminal through the UL CC1 and UL CC2 at the time T_Receive configured for uplink synchronization (640).

When multi-time forward is applied in a situation where a plurality of serving cells are configured between the terminal and the base station, UL CC is configured for all or part of the secondary serving cells, and the TA value of the primary serving cell and the TA value of some secondary serving cells are It can be set differently from each other. However, the TA value for the UL CC of some other secondary serving cells may be the same as the TA value of the main serving cell. In addition, some of the secondary serving cells may require the same TA value while having a different TA value from the main serving cell.

Therefore, rather than operating TA values individually for each of the serving cells in which the UL CC is configured, serving cells having the same uplink synchronization may be configured as a group. Such a group is defined as a timing advanced group (TAG). Therefore, serving cells with different uplink synchronization belong to different TAGs. The TAG may have an index value and the index value of the TAG to which the main serving cell belongs may be fixedly set to zero. In addition, the secondary serving cell can change the TAG, but the main serving cell can not change the TAG. In addition, a timing advanced timer (TAT) may be set for each group, may have a different expiration value for each TAT, and operation at the time of TAT expiration may be different. For example, if the TAT of the TAG to which the main serving cell belongs expires, the UE flushes data in uplink HARQ buffers for all serving cells and releases RRC of PUCCH / SRS for all serving cells. Notifies the layer L3, releases the type 0 non-triggering base (SRS), does not release the type 1 triggering base (SRS), and initializes downlink and uplink resource allocations configured for all serving cells ( clear).

In addition, if the TAT of a TAG composed of only secondary serving cells expires, the UE discards data in uplink HARQ buffers for secondary serving cells in the corresponding TAG and discards PUCCH / SRS for secondary serving cells in the corresponding TAG. It does not release, stops SRS transmission through the uplink of the secondary serving cells in the TAG, and initializes all configured uplink resource allocations for the secondary serving cells in the TAG.

The base station may instruct the terminal of the progress of the random access procedure to secure or update the TA value for the TAG. For example, information about which serving cell a UE should proceed with a random access procedure using which time / frequency resource may be obtained through a random access command. The random access procedure in the secondary serving cell may not be initiated voluntarily by the UE and may be an indicator (eg, a cell indicator field (CIF) or serving cell index or secondary serving cell index) for the secondary serving cell transmitted by the base station. Etc.) may be initiated by signaling.

The terminal does not simultaneously perform two or more random access procedures (parallel random access procedures). That is, two or more random access procedures are not synchronized and proceed at the same time, nor do they proceed simultaneously at some time when the random access procedure is in progress. In addition, the UE does not simultaneously perform a random access procedure in two or more serving cells. This may cause a problem that the random access procedure cannot be started through the secondary serving cell while the UE waits for the random access response in the random access procedure through the main serving cell. On the contrary, when the random access procedure through the secondary serving cell is in progress, even if the base station transmits a signaling requesting to start the random access procedure through the main serving cell to the terminal, the terminal cannot start the random access procedure through the primary serving cell. Problems may also arise.

As another problem, delay of uplink data transmission may occur. In the random access procedure initiated by the UE voluntarily, when the UE needs to transmit data through UL, generation of UL data generation information is performed by the UE in order to receive buffer state reporting (BSR) information. It transmits to a base station, where a random access procedure is used. If the base station is in the process of proceeding with the first random access procedure for updating the TA for the TAG, the terminal may not start the second random access procedure for transmitting the buffer status report information. In addition, if the random access progress failure and retransmission is delayed by the maximum number of retransmissions during the progress of the first random access procedure, the second random access procedure is delayed and the transmission of uplink data is delayed as a result. This causes a decrease in the quality of service (QoS) of the uplink. The minimum number of retransmissions that can be set in the random access procedure is three times, and the time required for the random access procedure to proceed is about 10 to 64 ms. Therefore, even when the minimum number of retransmissions is set, a maximum delay time of 192ms may occur.

Accordingly, there is a need for a method of reducing the complexity of a random access procedure through a plurality of serving cells configured with a UL CC and solving a system performance degradation such as a delay of a random access occurring in an environment in which a parallel random access procedure is not supported. To this end, the base station may forcibly stop the random access procedure in progress in a specific serving cell and initiate a random access procedure in another serving cell. The terminal may determine whether the random access procedure is interrupted, and may follow up on the suspended random access procedure according to the determination result.

The random access procedure interrupted by the base station may include both the contention based random access procedure of FIG. 7 and the non-contention based random access procedure of FIG. 8. The random access procedure may include both a random access procedure according to an order of a base station and a spontaneous random access procedure of a terminal.

7 is a flowchart illustrating a contention based random access procedure to which the present invention is applied.

Referring to FIG. 7, the terminal randomly selects a preamble signature to generate a random access preamble (RAP). The selected preamble is transmitted to the base station (S700). When the preamble signature is selected, a random access procedure may be performed contention-based.

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 random access channel (RACH) transmission.

The base station performs a random access response (RAR) on the preamble of the received terminal, and at this time, transmits the random access response message through a physical downlink shared channel (PDSCH) (S705). ).

The information transmitted through the RAR message may include, for example, identification information of a terminal preamble received by a base station, an identifier (ID) of the base station, a temporary cell radio network temporary identifier (C-RNTI), and a time when the terminal preamble is received. The slot information and the TA information may be included. Accordingly, since timing information for uplink synchronization is received through the RAR message, the terminal may perform uplink synchronization with the base station.

The terminal performs scheduled transmission at a scheduling time determined using the TA information (S710). It transmits data synchronized through a physical uplink shared channel (PUSCH) and may perform a hybrid automatic repeat request (HARQ).

The message transmitted in step S710 may include, for example, an RRC connection request, a tracking area update, a scheduling request, and the like. In addition, one of the messages may include a temporary C-RNTI, a C-RNTI (state included in the terminal), or terminal identifier information.

Meanwhile, since collision may occur in steps S700 to S710, the base station transmits a contention resolution (CR) message to the terminal (S715), and the terminal ai) the message received by the terminal is itself. A-ii) confirms that the received message is that of the other terminal and does not send response data. Of course, even if the DL assignment is missed or the message cannot be decoded, the response data is not sent. In addition, the CR message may include C-RNTI or terminal identifier information.

8 is a flowchart illustrating a random access procedure according to an indication of a base station to which the present invention is applied.

Referring to FIG. 8, the base station selects one of random access preambles reserved for a contention-free procedure among all available random access preambles and informs the terminal of available time / frequency resource information (S800). This is called random access preamble assignment.

As an example, the random access preamble assignment may be delivered through an upper layer message. For example, the random access preamble allocation may be transmitted to the terminal through mobility control information (MCI) in the handover command. Or, it may be transmitted to the terminal through an RRC reconfiguration procedure for secondary serving cell configuration. Or, it may be transmitted to the terminal through an RRC reconfiguration procedure for transmitting TAG group information. In this case, the preamble configuration information for all serving cells in the TAG group should be the same.

As another example, the random access preamble allocation may be mapped to the PDCCH as physical layer signaling (for example, format 1A downlink control information (DCI)) and delivered to the terminal. The format 1A DCI may be defined as shown in the following table.

Carrier 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 random access procedure according to the indication of the base station according to the value of the preamble index may be contention-based or non- contention-based. As an example, if all 6 bits of the preamble index information are set to '0', a contention based random access procedure is performed. For example, if the preamble index is '000000', the UE selects a random preamble, sets the PRACH mask index value to '0', and then proceeds with a contention-based random access procedure. Upon receiving the preamble index information in which all 6 bits are set to '0', the terminal selects the preamble group based on the amount of uplink data to be transmitted and the transmission power necessary to cancel the path loss. The terminal randomly selects one of the preambles in the selected preamble group. The terminal transmits the selected preamble to the base station using one of the closest resources in time in the RACH time / frequency resources allocated for the RACH in the corresponding serving cell (S805).

As another example, if all 6 bits of the preamble index information are not '0', the terminal transmits the selected preamble to the base station based on the received preamble index information (S805). The base station may determine which terminal transmits the preamble based on the preamble and time / frequency resources. Therefore, since there is only one terminal having the same RA-RNTI, a contention resolution procedure is not necessary. The base station transmits the random access response message to the terminal (S810) to complete the random access procedure.

The UE may declare a failure of the random access procedure during the contention-based random access procedure or the non- contention-based random access procedure. For example, the UE cumulatively increases the PREAMBLE_TRANSMISSION_COUNTER value by 1 for every preamble transmission failure in the secondary serving cell. However, if the preamble is transmitted after the number of transmissions of the preamble reaches the maximum retransmission number (preambleTransMax) but is not successful, the UE declares a final failure of the random access procedure. That is, when PREAMBLE_TRANSMISSION_COUNTER = preambleTransMax + 1, the UE declares a final failure of the random access procedure in the secondary serving cell. At this time, the UE does not restart the random access procedure in the corresponding serving cell and does not perform all transmissions such as sounding reference signal (SRS) transmission and data transmission in the uplink.

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

9, the terminal performs a random access procedure in the secondary serving cell (S900). The random access procedure in the secondary serving cell may include the contention-based random access procedure described above, a non- contention based random access procedure, and a random access procedure by an order of the base station.

The base station determines whether to request the terminal to stop the random access procedure in progress in the secondary serving cell (S905).

As an example, the base station may request the terminal to stop the random access procedure when a predetermined time elapses without receiving a preamble after ordering the random access procedure in the secondary serving cell. The elapse of a predetermined time may mean, for example, a state in which a counter becomes equal to a predetermined size after a command of a random access procedure or a timer expires. The counter or timer may be, for example, 100 ms, 200 ms, 500 ms, or the like.

As another example, when the new random access procedure starts or is scheduled to start in a serving cell having a higher priority than the secondary serving cell in which random access is in progress, the base station may request the terminal to stop the random access procedure. For example, among the plurality of timing alignment groups (TAGs), the priority of the time alignment group including the most secondary serving cells is highest. Suppose that a random access is currently in progress in a first secondary serving cell belonging to a first time alignment group, and a random access procedure is to be started in a second secondary serving cell belonging to a second time alignment group. If the second time alignment group includes more secondary serving cells than the first time alignment group, the second time alignment group has a higher priority. Accordingly, the base station may request the terminal to stop the random access procedure in the first secondary serving cell. Here, the main serving cell may always be considered to have a higher priority than the secondary serving cell.

If it is determined that no interruption is necessary, the base station continues the ongoing random access procedure.

If it is determined that the suspension is necessary, the base station may request the terminal to stop the random access procedure in progress in the secondary serving cell. In order to request the suspension of the random access procedure, the base station transmits a random access interruption indicator requesting the suspension of the random access in the secondary serving cell to the terminal (S910).

As an example, the random access stop indicator may be a DCI of format 1A. The DCI is mapped to a PDCCH which is a physical channel and may include fields as shown in the following table.

Referring to Table 2, specific fields are set to specific values to indicate that the random access stop indicator. For example, when cross carrier scheduling is applied, a carrier indicator field indicates the specific carrier to indicate that the DCI is a DCI for a specific carrier. The local / distributed VRB allocation flag is set to all zeros and all bits of the resource block allocation field are set to one.

The PRACH mask index is usable 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 3 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

Referring to Table 3, when the preamble index indicates a dedicated random access preamble reserved in advance for the start of the random access procedure, the PRACH mask index indicates available time / frequency resource information.

Meanwhile, the preamble index may provide two functions. The first function of the preamble index indicates a dedicated random access preamble reserved in advance for the start of the random access procedure in a situation in which no random access procedure is performed in a specific serving cell. The second function of the preamble index is that in a situation in which a random access procedure is in progress in a particular serving cell, the preamble index indicates the interruption of the random access procedure. In this case, 6 bits corresponding to the preamble index may be set to a specific value, for example, '000000'. If the preamble index indicates the interruption of the random access procedure, the PRACH mask index is fixed to a specific value and may be a meaningless field.

The DCI has the same form as instructing the start of the random access procedure for the secondary serving cell, and the terminal recognizes the DCI as a request to stop the random access and stops the random access procedure in the secondary serving cell.

Alternatively, the DCI may have the same form as that indicating the start of the contention-based random access procedure for the secondary serving cell. At this time, the terminal recognizes the DCI as a request to stop the random access and stops the random access procedure in the secondary serving cell.

If only a contention-based random access procedure is allowed, the message requesting the contention-based random access procedure may have a function of a random access stop indicator. At this time, the random access procedure is stopped regardless of whether the random access procedure is performed in the secondary serving cell.

As such, the meaning of the preamble index may be defined differently according to the progress of the random access procedure of the UE. The terminal must determine the interruption condition as in step S915 to identify whether the preamble index included in the random access interruption indicator indicates the start of the random access procedure or the interruption of the random access procedure.

The terminal determines whether the suspension condition for stopping the random access procedure in the secondary serving cell is satisfied (S915). The suspension condition may include: i) receive a random access abort indicator; and ii) random access is in progress in the serving cell. Since condition i) is satisfied in step S910, it should be determined whether condition ii) is satisfied.

The random access is in progress means that the random access procedure is not completed. Condition ii) may be used to determine whether the preamble index included in the random access stop indicator indicates to stop the random access procedure in progress in the corresponding serving cell. For example, the preamble index indicates the termination of the random access procedure when random access is in progress in the corresponding serving cell, whereas the preamble index indicates the start of a new random access procedure when random access is not in progress in the serving cell. Therefore, the definition of 'random access procedure in progress' should be clearly defined.

It can be said that random access is in progress before the random access procedure is completed. In other words, when the random access procedure is completed, random access is no longer in progress. The state in which the random access procedure is completed may be defined differently depending on whether the random access procedure is contention-based or non- contention-based.

First, a case of a non-contention based random access procedure will be described. For example, in order to complete the random access procedure, a random access procedure is initiated by an instruction of the base station, a preamble indicated by the base station is received from the terminal through a designated time / frequency resource, and a random access response message is transmitted to the terminal. All of this must be completed. Herein, the random access response message is a MAC control element, and the subheader of the MAC control element includes a preamble indicated by the base station as shown in FIG.

Referring to FIG. 10, the subheader 1000 includes an E field 1005, a T field 1010, and a RAPID field. The E field 1005 is a bit indicating whether there is more MAC header field. If the value is '1', at least one header field is further present. If the value is '0', the MAC RAR or padding starts from the next byte. ) Means to start. The T field 1010 is a bit indicating whether the MAC subheader is for a random access preamble identifier (RAPID) or a backoff indicator. '0' means the backoff indicator BI and '1' means the random access preamble identifier.

As another example, the earliest frame (n + 1) after the time (3ms or 4ms) that the base station transmits a random access response message to the terminal in the n-th frame, and confirms that the terminal has received the random access response message Or n + 2), if it is confirmed that the preamble allocated to the terminal is not received from the terminal, the random access procedure is considered to have ended. In this case, it is assumed that the number of transmissions of the preamble is in a state of not reaching the maximum number of retransmissions. If it is determined that the number of transmissions of the preamble reaches the maximum number of retransmissions, it is determined that the random access procedure is terminated without the preamble acknowledgment procedure.

Next, a case of a contention based random access procedure will be described. For example, after the base station receives the scheduled data from the terminal and checks which terminal the preamble is transmitted from based on the Cell-Radio Network Temporary Identifier (C-RNTI) value in the scheduled data, the base station receives a contention resolution message When transmitting or transmitting the PDCCH scrambled by the C-RNTI in the secondary serving cell, the random access procedure is considered to be completed. In this case, it is assumed that the number of transmissions of the preamble is in a state of not reaching the maximum number of retransmissions.

As another example, if the base station receives ACK information for the PDCCH from the terminal after transmitting the scrambled PDCCH in the n-th subframe is considered to have been completed.

Except for the above three cases where the random access procedure is considered complete, the random access procedure is considered to be in progress, wherein condition ii) is satisfied. Of course, cases in which the random access procedure is considered complete may include not only the above three cases but also more cases.

In step S915 of FIG. 9 again, if all of the stopping conditions are satisfied, the terminal stops the random access procedure (S920). The interruption of the random access procedure may be the same as the operation when the random access procedure fails in the secondary serving cell. That is, the terminal does not restart the random access procedure in the corresponding secondary serving cell and does not perform any transmission such as sounding reference signal transmission and data transmission in uplink.

In step S915, if the stop condition is not satisfied, that is, if the random access procedure that is the stop condition ii) is not in progress, the random access stop indicator received from the base station can be ignored. Or, the terminal initiates a random access procedure by transmitting a random access preamble to the base station in the secondary serving cell (S925). In this case, the random access procedure may be contention based.

Various embodiments of the random access stop indicator are described below. The serving cell in which the random access procedure is interrupted by the random access stop indicator may be limited to the secondary serving cell. Therefore, if the UE receives signaling (for example, PDCCH order) for instructing the start of the random access procedure with respect to the primary serving cell, 1) proceed with the ongoing procedure as it is and ignore the signaling, or 2) stop the ongoing procedure. Start a new procedure. At this time, the selection criteria do not exist in particular and may be variously set according to the implementation manner of the terminal.

The random access stop indicator may be physical layer signaling or may be a message of a higher layer such as a MAC layer or an RRC layer.

As an example, when the random access stop indicator is physical layer signaling, the random access stop indicator is a DCI mapped to the PDCCH. The DCI has the same form as instructing the start of the random access procedure for the secondary serving cell, and the terminal recognizes the DCI as a request to stop the random access and stops the random access procedure in the secondary serving cell.

If only the contention-free random access procedure is allowed, the message requesting the contention-based random access procedure may have a function of _random access stop indicator. In this case, if the random access procedure in the secondary serving cell is in progress, the corresponding random access procedure is stopped. However, when the random access stop indicator is received when the random access procedure is not in progress, the indicator is ignored.

In terms of priority of the random access procedure, the primary serving cell takes precedence over the secondary serving cell. For example, when a UE undergoing a random access procedure in a secondary serving cell receives a DCI for performing contention or non-contention based random access procedure with respect to a primary serving cell through a PDCCH, the random progress in the secondary serving cell is performed. The access procedure is suspended (or failed) and a random access procedure is initiated in the main serving cell.

As another example, when the random access stop indicator is a message of the MAC layer, it may be expressed as shown in FIG. 11.

11 is a block diagram illustrating a random access stop indicator according to an embodiment of the present invention.

Referring to FIG. 11, the MAC PDU 1100 may include a MAC header 1110, at least one MAC control element 1120,..., 1125, and at least one MAC service data unit 1130-1. ... 1113-m) and padding 1140.

The MAC header 1110 includes at least one subheader 1110-1, 1110-2,..., 1110-k, and each subheader 1110-1, 1110-2 ... .1110-k corresponds to one MAC SDU or one MAC control element 1120,..., 1125 or padding 1140. The order of the subheaders 1110-1, 1110-2,..., 1110-k is the corresponding MAC SDU, MAC control element 1120,..., 1125, or padding 1140 in the MAC PDU 1100. Are arranged in the same order.

Each subheader 1110-1, 1110-2, ..., 1110-k contains four fields R, R, E, LCID or R, R, E, LCID, F, L 6 Field may be included. Subheaders containing four fields are subheaders corresponding to MAC control elements 1120, ..., 1125 or padding 1140, and subheaders containing six fields are subheaders corresponding to MAC SDUs. .

The Logical Channel ID (LCID) field may identify a logical channel corresponding to a MAC SDU, instruct initiation of random access, instruct to stop random access, or MAC control element 1120, ..., 1125) or an identification field for identifying a type of padding. When each subheader 1110-1, 1110-2,..., 1110-k has an octet structure, the LCID field may be 5 bits.

As an example, the LCID field identifies whether the MAC control element commands a random access procedure in the current serving cell as shown in Table 4.

LCID Index LCID value 00000 CCCH 00001-01010 Logical channel identifier 01011-11010 Reserved 11011 Activation / deactivation 11100 UE contention resolution identifier 11101 RA Procedure Initiation Order 11110 DRX command 11111 padding

Referring to Table 4, if the value of the LCID field is 11101, the corresponding MAC control element is a MAC control element for instructing initiation of a random access (RA) procedure. For example, the MAC control element 1125 is a MAC control element for instructing the initiation of the random access procedure and may include an R field, a preamble ID field, a cell index field, and a mask index field.

As another example, the LCID field may indicate that the random access procedure is stopped in the current serving cell as shown in Table 5.

LCID Index LCID value 00000 CCCH 00001-01010 Logical channel identifier 01011-11010 Reserved 11011 Activation / deactivation 11100 UE contention resolution identifier 11101 RA procedure abort order 11110 DRX command 11111 padding

Referring to Table 5, if the value of the LCID field is 11101, the command to stop the random access (RA) procedure in a particular serving cell. At this time, the payload corresponding to the LCID field may be set to 0 bits and may not exist.

Next, MAC control elements 1120, ..., 1125 are control messages generated by the MAC layer. Padding 1140 is a predetermined number of bits added to make the size of the MAC PDU constant. The MAC control elements 1120,..., 1125, MAC SDUs 1130-1,... 1110-m, and padding 1140 together are also referred to as MAC payloads.

As another example, when the random access stop indicator is a message of the RRC layer, it may be expressed as shown in Table 6.

RACH-ConfigDedicated :: = SEQUENCE {
SCellIndex INTEGER (1..7)
or
ServCellIndex INTEGER (0..7)
ra-PreambleIndex INTEGER (0..63),
ra-PRACH-MaskIndex INTEGER (0..15)
}

Referring to Table 6, RACH-configDedicated is a message used in the RRC reconfiguration procedure, and provides a function of random access abort. In particular, RACH-configDedicated includes a SCell index or a serving cell index, and the base station transmits the RACH-configDedicated to the UE on the serving cell indicated by the secondary serving cell index or the serving cell index. send. When the UE receives the RACH-configDedicated, the UE stops the random access procedure in the serving cell indicated by the secondary cell index or the serving cell index in the RACH-configDedicated.

12 is a flowchart illustrating a method of performing a random access procedure according to another example of the present invention. This is a method of adjusting the maximum number of retransmissions of the preamble in the random access procedure to prevent delay of the random access procedure.

Referring to FIG. 12, the base station sets the maximum number of retransmissions among the random access parameters to 0 (S1200) and transmits RACH configuration information to the terminal (S1205). The table below is RACH configuration information (RACH-ConfigCommon) for setting a random access parameter, and is generated in the RRC layer.

RACH-ConfigCommon :: = SEQUENCE {
....
ra-SupervisionInfo SEQUENCE {
preambleTransMax ENUMERATED {
n0, n3, n4, n5, n6, n7, n8, n10, n20, n50, n100, n200},
...
}
-ASN1STOP

Referring to Table 7, preambleTransMax is the maximum number of retransmissions of the preamble, and may have a value of 0, 3, 4, 5, 6, ..., 200. Here, nk means that preambleTransMax = k.

If the base station determines that it is necessary to start the random access procedure for the secondary serving cell, the DCI indicating the start of the random access procedure is mapped to the PDCCH and transmitted to the terminal (S1210). For example, a random access procedure may be required when the base station wants to update an uplink time forward value.

The base station checks whether the random access procedure in the secondary serving cell is completed within a maximum delay time preset by the base station (S1215). Here, the maximum delay time may be 50ms, 70ms, 100ms and the like.

If the random access procedure is not completed within the maximum delay time, the base station determines that the random access procedure for the secondary serving cell has failed, and determines whether to transmit a DCI indicating the start of the random access procedure for the secondary serving cell to the terminal ( S1220). Before determining whether to transmit the DCI, the base station may suspend transmission of the DCI for a preset time. At this time, the transmission hold time may be 10ms, 20ms, 40ms, 80ms, 160ms, and the like.

The terminal ignores the DCI indicating the start of the random access procedure for the secondary serving cell or starts the random access procedure in the secondary serving cell based on the random access procedure in the primary serving cell (S1225). For example, if the UE starts the random access procedure through the main serving cell within the transmission hold time and the random access procedure is in progress, the UE ignores the DCI. If the random access procedure ends after the terminal starts the random access procedure through the primary serving cell within the transmission hold time, the terminal starts the random access procedure in the secondary serving cell.

If the base station intends to indicate the start of the random access procedure for the serving cell having a higher priority, the DCI indicating the start of the random access procedure for the secondary serving cell in which the random access procedure has failed may not be transmitted. For example, among the plurality of time alignment groups, the priority of the time alignment group including the largest secondary serving cell is higher than that of other time alignment groups. Suppose that a random access is currently in progress in a first secondary serving cell belonging to a first time alignment group, and a random access procedure is to be started in a second secondary serving cell belonging to a second time alignment group. If the second time alignment group includes more secondary serving cells than the first time alignment group, the second time alignment group has a higher priority. The base station may request the terminal to stop the random access procedure in the first secondary serving cell. Here, the main serving cell may always be considered to have a higher priority than the secondary serving cell.

13 is a flowchart illustrating a random access procedure performed by a terminal according to an embodiment of the present invention.

Referring to FIG. 13, the terminal performs a random access procedure with a base station for a secondary serving cell (S1300). The random access procedure in the secondary serving cell includes the aforementioned contention-based random access procedure, a non-contention-based random access procedure, and a random access procedure by an order of the base station.

The terminal receives a random access stop indicator from the base station requesting to stop the random access in the secondary serving cell (S1305).

As an example, the random access stop indicator may be a DCI of format 1A, as shown in Table 2 above.

The terminal determines whether the suspension condition for stopping the random access procedure in the secondary serving cell is satisfied (S1310). The suspension condition may include: i) receive a random access abort indicator; and ii) random access is in progress in the serving cell. Since condition i) is satisfied in step S1305, it should be determined whether condition ii) is satisfied.

The random access is in progress means that the random access procedure is not completed. Condition ii) may be used to determine whether the preamble index included in the random access stop indicator indicates to stop the random access procedure in progress in the corresponding serving cell. For example, the preamble index indicates the termination of the random access procedure when random access is in progress in the corresponding serving cell, whereas the preamble index indicates the start of a new random access procedure when random access is not in progress in the serving cell.

If the stop condition is satisfied, the terminal stops the random access procedure in the secondary serving cell (S1315). The interruption of the random access procedure may be the same as the operation when the random access procedure fails in the secondary serving cell. That is, the terminal does not restart the random access procedure in the corresponding secondary serving cell and does not perform any transmission such as sounding reference signal transmission and data transmission in uplink.

In step S1310, if the stop condition is not satisfied, the UE initiates a random access procedure by transmitting a random access preamble to the base station in the secondary serving cell (S1320). In this case, the random access procedure may be contention based.

14 is a flowchart illustrating a random access procedure performed by a base station according to an embodiment of the present invention.

Referring to FIG. 14, the base station proceeds with a random access procedure with respect to a secondary serving cell (S1400). The random access procedure in the secondary serving cell includes the aforementioned contention-based random access procedure, a non-contention-based random access procedure, and a random access procedure by an order of the base station.

The base station determines whether to request the suspension of the random access procedure in progress in the secondary serving cell (S1405). As an example, the base station may request an interruption after a predetermined time elapses without receiving a preamble after ordering a random access procedure in the secondary serving cell.

As another example, the base station may request to stop when the random access procedure starts or is scheduled to start in the serving cell having a higher priority than the secondary serving cell. For example, among the plurality of time alignment groups, the priority of the time alignment group including the largest secondary serving cell is higher than that of other time alignment groups. Here, the main serving cell may always be considered to have a higher priority than the secondary serving cell.

If it is determined that the suspension is necessary, the base station may request the terminal to stop the random access procedure in the secondary serving cell. In order to request the suspension of the random access procedure, the base station transmits a random access interruption indicator requesting the suspension of the random access in the secondary serving cell to the terminal (S1410).

Upon receiving the random access stop indicator, the UE determines whether an interruption condition for stopping the random access procedure in the secondary serving cell is satisfied, and when the interruption condition is satisfied, the UE transmits a preamble to the base station. If the stop condition is not satisfied, the UE stops the random access procedure in the secondary serving cell that is currently in progress. Therefore, the base station receives the preamble from the terminal or does not receive any response (no response) (S1415).

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

Referring to FIG. 15, the terminal 1500 includes a terminal receiver 1505, a random access processor 1510, and a terminal transmitter 1515.

The terminal receiving unit 1505 receives a random access stop indicator from the base station 1550 requesting the suspension of random access in the secondary serving cell. As an example, the random access stop indicator may be a DCI of format 1A, as shown in Table 2 above.

The terminal receiver 1505 also receives, from the base station 1550, RACH configuration information in which the maximum number of retransmissions is set to 0 among random access parameters. The RACH configuration information may be as shown in Table 7, for example.

The random access processing unit 1510 generates a message necessary for the random access procedure, and interprets the random access related message received from the base station 1550 to stop or start the random access procedure. The random access procedure in the secondary serving cell includes the aforementioned contention-based random access procedure, a contention-free random access procedure, and a random access procedure by an order of the base station 1550. For example, the random access processor 1510 determines a time / frequency resource for transmitting the preamble, and controls the terminal transmitter 1515 to transmit the preamble. In addition, the random access processor 1510 determines whether a suspension condition for stopping the random access procedure in the secondary serving cell is satisfied. The suspension condition may include: i) receive a random access abort indicator; and ii) random access is in progress in the serving cell.

The random access is in progress means that the random access procedure is not completed. Condition ii) may be used to determine whether the preamble index included in the random access stop indicator indicates to stop the random access procedure in progress in the corresponding serving cell. This is because the preamble index indicates the suspension of the random access procedure when the random access is in progress in the serving cell, whereas the preamble index indicates the start of a new random access procedure when the random access is not in progress in the serving cell.

If the stop condition is satisfied, the random access processor 1510 stops the random access procedure in the secondary serving cell. The interruption of the random access procedure may be the same as the operation when the random access procedure fails in the secondary serving cell. That is, the random access processor 1510 does not restart the random access procedure in the corresponding secondary serving cell and does not perform all transmissions such as sounding reference signal transmission and data transmission in the uplink.

If the stop condition is not satisfied, the random access processor 1510 initiates a random access procedure by transmitting the random access preamble to the base station 1550 in the secondary serving cell. In this case, the random access procedure may be contention based.

The random access processing unit 1510 ignores the DCI indicating the start of the random access procedure for the secondary serving cell from the base station based on the random access procedure in the primary serving cell, or ignores the random access procedure in the secondary serving cell. To start. For example, when the random access processor 1510 starts the random access procedure through the main serving cell within the transmission hold time and the random access procedure is in progress, the random access processor 1510 ignores the DCI. If the random access procedure ends after the random access processor 1510 starts the random access procedure through the main serving cell within the transmission hold time, the random access processor 1510 starts the random access procedure in the secondary serving cell.

The terminal transmitter 1515 transmits the random access preamble to the base station 1550.

The base station 1550 includes a base station transmitter 1555, a stop requester 1560, and a base station receiver 1565.

The base station transmitter 1555 transmits a random access stop indicator to the terminal 1500 requesting the termination of the random access in the secondary serving cell. The base station transmitter 1555 sets the maximum number of retransmissions among the random access parameters to 0 and transmits the RACH configuration information shown in Table 7 to the terminal.

The suspension request unit 1560 determines whether to request the terminal 1500 to stop the random access procedure in progress in the secondary serving cell. As an example, the interrupt request unit 1560 may request the terminal 1500 to stop the service after a predetermined time elapses without receiving a preamble after ordering the random access procedure in the secondary serving cell to the terminal 1500.

As another example, when the random access procedure starts or is scheduled to start in the serving cell having a higher priority than the secondary serving cell, the interrupt request unit 1560 may request the terminal 1500 to stop. For example, among the plurality of time alignment groups, the priority of the time alignment group including the largest secondary serving cell is higher than that of other time alignment groups. Here, the main serving cell may always be considered to have a higher priority than the secondary serving cell.

If it is determined that no interruption is necessary, the interruption requester 1560 continues the random access procedure in progress.

If it is determined that the suspension is necessary, the suspension request unit 1560 may request the terminal 1500 to stop the random access procedure in the secondary serving cell. In order to request the suspension of the random access procedure, the interruption requester 1560 generates a random access interruption indicator requesting the interruption of the random access in the secondary serving cell and transmits the random access interruption indicator to the base station transmitter 1555.

If the stop requester 1560 determines that it is necessary to start the random access procedure for the secondary serving cell, it generates a DCI indicating the start of the random access procedure and transmits it to the base station transmitter 1555. For example, a random access procedure may be needed when the base station 1555 wants to update an uplink time forward value.

The abort request unit 1560 confirms whether the random access procedure in the secondary serving cell is completed within a preset maximum delay time. Here, the maximum delay time may be 50ms, 70ms, 100ms and the like. If the random access procedure is not completed within the maximum delay time, the interruption requester 1560 reports that the random access procedure for the secondary serving cell has failed, and sends a DCI indicating the start of the random access procedure for the secondary serving cell to the terminal ( 1500). Before determining whether to transmit the DCI, the interruption requester 1560 may suspend transmission of the DCI for a preset time. At this time, the transmission hold time may be 10ms, 20ms, 40ms, 80ms, 160ms, and the like.

If the stop condition is satisfied, the terminal 1500 transmits the preamble to the base station 1550. If the stop condition is not satisfied, the terminal 1500 stops the random access procedure in the previously serving secondary serving cell. Therefore, the base station 1500 receives the preamble from the terminal 1500 or does not receive any response (no response).

The various illustrative logic blocks, modules, and circuits described in connection with the embodiments disclosed herein may be general purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or It may be controlled with other programmable logic devices, discrete gate or transistor logic, discrete hardware components or any combination thereof designed to perform the functions described herein. Control steps of the method or algorithm described in connection with the embodiments disclosed herein may be implemented directly in hardware, in a software module executed by a processor, or in a combination thereof. In one or more illustrative embodiments, the described control functions may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored or transmitted as one or more instructions or code on a computer-readable medium.

Claims

In the method of performing a random access procedure by the terminal in a multi-carrier system,
Receiving a random access interruption indicator from the base station instructing the termination of the random access procedure in the secondary serving cell configured in the terminal;
Determining whether a suspension condition for stopping the random access procedure is satisfied based on the random access suspension indicator; And
And stopping the random access procedure in the secondary serving cell when the suspension condition is satisfied.

The method of claim 1,
And the random access stop indicator is downlink control information mapped to a physical downlink control channel.

The method of claim 2,
The downlink control information includes a preamble index, wherein all bits of the preamble index are set to zero.

The method of claim 1,
And the stopping condition is conditional that the random access procedure is in progress.

In a terminal performing a random access procedure in a multi-carrier system,
A terminal receiver configured to receive a random access interruption indicator from the base station indicating the interruption of the random access procedure in the secondary serving cell configured in the terminal;
A random access processing unit determining whether an interruption condition for stopping the random access procedure is satisfied based on the random access interruption indicator, and stopping the random access procedure in the secondary serving cell when the interruption condition is satisfied; And
And a terminal transmitter for transmitting a preamble to the base station when the stop condition is not satisfied.

6. The apparatus of claim 5,
And receiving the random access stop indicator, which is downlink control information mapped to a physical downlink control channel, from the base station.

The method according to claim 6,
The downlink control information includes a preamble index, and all bits of the preamble index are set to zero.

The method of claim 5, wherein
The stopping condition is conditional that the random access procedure is in progress.

In the method of performing a random access procedure by the base station in a multi-carrier system,
Transmitting a random access command to the terminal instructing the start of the random access procedure in the secondary serving cell configured in the terminal;
Determining whether to request termination of the random access procedure; And
If it is necessary to request the interruption of the random access procedure, transmitting a random access interruption indicator indicating the interruption of the random access procedure to the terminal.

The method of claim 9, wherein the determining of whether to request the suspension of the random access procedure comprises:
And in the random access procedure, if a predetermined time elapses without receiving a preamble from the terminal, determining that it is necessary to request the suspension of the random access procedure.

The method of claim 9,
The random access stop indicator is downlink control information mapped to a physical downlink control channel,
The downlink control information includes a preamble index,
And all bits of the preamble index are set to zero.

In the base station performing a random access procedure in a multi-carrier system,
A base station transmitter for transmitting a random access command for instructing the start of a random access procedure in the secondary serving cell configured in the terminal to the terminal; And
A stop request unit determining whether to request to stop the random access procedure; And
A base station receiving unit for receiving a preamble from the terminal,
When the stop request unit determines that it is necessary to request the suspension of the random access procedure, characterized in that the base station transmitter comprises transmitting to the terminal a random access stop indicator indicating the suspension of the random access procedure, Base station.

The method of claim 12, wherein the stop request unit,
In the random access procedure, if a predetermined time elapses without receiving a preamble from the terminal, it is determined that the need to request the suspension of the random access procedure, the base station.

13. The method of claim 12,
The random access stop indicator is downlink control information mapped to a physical downlink control channel,
The downlink control information includes a preamble index,
And all bits of the preamble index are set to zero.