KR101506171B1 - Device and method for controlling random access process of ue in wireless communication system - Google Patents

Abstract

The terminal random access control method of the mobile communication system adjusts the N_TA to 0 in random access and transmits the preamble, adjusts the uplink transmission timing in accordance with the TA command of the message received by the base station, and then restarts the TA timer Waiting for reception of a contention solving message of the base station, and stopping the TA timer when the contention resolution is unsuccessful upon receiving the contention resolution message, and resuming the random access procedure while transmitting the preamble.

LTE (Long Term Evolution), TA (Timing Advance)

Description

TECHNICAL FIELD [0001] The present invention relates to a device and a method for controlling random access in a mobile communication system,

The present invention relates to an apparatus and method for controlling random access in a mobile communication system, and more particularly, to an apparatus and method for controlling an uplink transmission timing and a TA timer.

The Universal Mobile Telecommunication Service (UMTS) system is based on Global System for Mobile Communications (GSM) and General Packet Radio Services (GPRS), which are European mobile communication systems, and includes a Wideband Code Division Multiple Access (CDMA) Is a third-generation asynchronous mobile communication system using a mobile station.

In the 3rd Generation Partnership Project (3GPP), which is in charge of standardization of UMTS, a discussion on LTE (Long Term Evolution) is underway as a next generation mobile communication system of UMTS system. LTE is a technology that implements high-speed packet-based communication with a transmission rate of up to 100 Mbps and aims to commercialize it in about 2010. Various schemes are being discussed for this purpose. For example, there are discussions to reduce the number of nodes located on the communication path by simplifying the structure of the network, and to approach the wireless protocols as much as possible to the wireless channel.

1 is a diagram illustrating a structure of an LTE mobile communication system.

1, an Evolved Radio Access Network (hereinafter referred to as E-RAN) 110 and 112 is a next-generation base station (hereinafter, referred to as an ENB or a Node B) 120, 122, 124, 126, and 128, and an upper node (referred to as an Access Gateway) 130 and 132, respectively. A User Equipment (UE) 101 accesses an Internet Protocol (IP) network by an E-RAN 110 or 112.

The ENBs 120-128 correspond to the existing Node B of the UMTS system. The ENB is connected to the UE 101 via a radio channel, and plays a more complex role than the existing Node B. In LTE, all user traffic, including real-time services such as Voice over IP (VoIP) via the Internet protocol, is serviced through a shared channel. Therefore, a device for collecting and scheduling situation information of UEs is needed. (120 to 128). One ENB typically controls multiple cells. In order to realize a transmission rate of up to 100 Mbps, LTE uses Orthogonal Frequency Division Multiplexing (OFDM) as a radio access technology in a bandwidth of up to 20 MHz. In addition, Adaptive Modulation and Coding (AMC) scheme is used to determine a modulation scheme and a channel coding rate in accordance with a channel state of a UE.

In the LTE mobile communication system, random access is used for various purposes. The terminal sets the reverse transmission timing to a desired timing by the base station through the random access and transmits the predetermined data in the reverse direction. 2 is a diagram illustrating a random access procedure in an LTE mobile communication system.

Referring to FIG. 2, if the UE starts a random access procedure for some reason in step 215, it randomly selects one of predetermined code sets in step 220 and transmits a preamble on a predetermined transmission resource. At this time, since the preamble is used to determine how to adjust the uplink transmission timing, the terminal transmits the initial transmission timing of the preamble in accordance with the forward frame boundary. The reverse transmission timing of the UE is managed by a variable named N_TA, and N_TA = 0 means an uplink transmission timing coinciding with the forward frame boundary.

Upon receiving the preamble, the BS determines how much the MS should adjust the uplink transmission timing based on the reception time of the preamble. The reverse timing adjustment value is referred to as a TA (Timing Adjustment) command. In step 225, the BS transmits a message containing the TA command and the reverse transmission resource information to the UE. The message is referred to as message 2 (UL grant, TA command). In step 230, the terminal transmits the reverse data through the allocated transmission resource by applying the received TA command. And a message 3 is transmitted. In the first upling message, various types of information are stored according to the purpose of random access. Upon receiving the message 3, the BS transmits data including the contents stored in the message 3 to the MS in step 235, thereby enabling the MS to determine whether the random access procedure has been successfully completed. This is called a contention resolution message.

The reason for the contention resolution is that when a plurality of terminals simultaneously transmit the same preamble, transmission and reception of messages 2 and 3 proceed normally, but random access is successful only for a maximum one of the plurality of terminals. The contention resolution process will be described in more detail. The UE transmits a message 3, drives a predetermined timer called a contention timer (CR timer), and if the contention resolution message is not received until the timer expires, And returns to the preamble transmission process.

The reverse transmission timing of the UE having completed the random access procedure is synchronized with the base station, and the UE performs the reverse transmission using the set uplink transmission timing. When the UE moves to another cell or moves a lot in the same cell, the uplink transmission timing may not be valid anymore. In other words, even if the UE performs the uplink transmission in accordance with the predetermined uplink transmission timing, the uplink signal may not be received within the desired region of the base station. Therefore, the UE determines that the existing reverse transmission timing is no longer valid after a predetermined period of time elapses. More specifically, each time the terminal successfully receives a TA command, it drives or restarts a predetermined timer, called a timer (Timing Adjustment timer), and if a new TA command is not received until the TA timer expires, The UE determines that the synchronization of the uplink transmission timing is corrupted and does not perform the uplink transmission except for the preamble transmission.

A typical random access procedure is often performed in a state where the TA timer of the terminal is not driven. If the terminal in exceptional connection status performs a random access procedure for buffer status reporting, the TA timer of the terminal may be running. That is, the random access procedure is performed in a state in which the reverse transmission timing is already synchronized. The random access procedure involves adjustment of the uplink transmission timing of the user equipment, but it is unclear how to adjust the uplink transmission timing of the user equipment that has already been synchronized with the uplink transmission timing.

An embodiment of the present invention proposes a method and apparatus for adjusting a timer variable N_TA and a TA timer when a UE operating a TA timer performs a random access procedure in a mobile communication system.

The UE random access method of the mobile communication system according to the first embodiment of the present invention adjusts the N_TA to 0 in random access and transmits the preamble by adjusting the reverse transmission timing in accordance with the TA command of the message received by the base station A step of restarting the TA timer and awaiting reception of a contention solving message of the base station; and a step of resuming the random access procedure while stopping the TA timer and transmitting the preamble if the contention resolution fails upon receiving the contention resolution message .

The UE random access method of the mobile communication system according to the second embodiment of the present invention includes the steps of checking whether a TA timer is running during random access, checking whether a dedicated preamble is in use during the operation of the TA timer, Setting N_TA to 0 when using a preamble and transmitting a preamble; and stopping the TA timer and adjusting an uplink transmission timing according to a TA command of a message transmitted from the base station.

The UE random access method of the mobile communication system according to the third embodiment of the present invention includes the steps of checking whether a TA timer is running during random access, checking whether a dedicated preamble is in use during the operation of the TA timer, If the preamble is not used, adjusting the N_TA to a value stored in the variable TIME_ADVANCE to restore the original reverse transmission timing and ignoring the TA command of the message transmitted from the base station and performing the remaining random access procedure, TIME_ADVANCE updates the TIME_ADVANCE of the TA command of the message transmitted from the base station, and updates the TIME_ADVANCE to a value obtained by adding the value to the value stored in the current TIME_ADVANCE when the TA command is received via the TA MAC CE.

The UE random access method of the mobile communication system according to the fourth embodiment of the present invention includes the steps of checking whether a maximum number of transmissions has been reached during an uplink transmission in an HARQ process, And discarding data stored in the HARQ buffer and terminating the reverse transmission.

According to a first embodiment of the present invention, a terminal apparatus for performing random access in a mobile communication system includes a transceiver for transmitting and receiving a MAC PDU over a wireless channel and for transmitting a preamble, An MAC PDU reception processing unit for processing the MAC PDUs transmitted from the transmitter / receiver and generating upper layer data, a message 2 including a TA command, and a TA MAC CE, At the beginning of the process, N_TA is set to 0 and the TA timer is stopped. Upon receipt of the new TA command via the message 2, the N_TA is renewed and the TA timer is driven. When the TA timer is stopped or expired, And controls the transmission / reception unit to adjust the uplink transmission timing of the transmission / reception unit every time the N_TA is changed, , Selects a preamble at the start of the random access procedure, and instructs the transmission / reception unit to transmit it to the reverse transmission timing control unit. Upon receiving the TA command through the message 2, the reverse transmission timing control unit transmits the TA command to the C- And a random access control unit for controlling the backoff process so that the backoff is not applied when the message 3 including the message 3 is received.

According to a second embodiment of the present invention, a terminal apparatus for performing random access in a mobile communication system includes a transceiver for transmitting and receiving a MAC PDU over a wireless channel and for transmitting a preamble, A MAC PDU reception processing unit for processing the MAC PDUs transmitted from the transmitter / receiver and generating a message 2E including upper layer data and a TA command; If the preamble is not used, the N_TA is not changed in the random access procedure. If a dedicated preamble is used even if the TA timer is not running or the TA timer is running, the N_TA is set to 0 and the TA timer is stopped. Upon expiration, the transmitter / receiver is controlled so as not to transmit the reverse signal, and whenever the N_TA is changed, the transmitter / When a random access procedure is started, a preamble is selected and a transmission is instructed to the transmission / reception unit, and the reverse transmission timing control unit is notified to the reverse transmission timing control unit. When a TA command is received through the message 2, And a random access control unit for transmitting the random access control signal to the transmission timing control unit.

According to a third exemplary embodiment of the present invention, a terminal apparatus for performing random access in a mobile communication system includes a transceiver for transmitting and receiving a MAC PDU over a wireless channel and for transmitting a preamble, An MAC PDU reception processing unit for processing the MAC PDUs transmitted from the transmitter and the receiver to generate a message 2E including upper layer data and TA commands, N_TA is set to 0. When the TA timer is in operation and the dedicated preamble is not used, the N_TA is set to the value stored in TIME_ADVANCE after transmitting the preamble. When the TA timer is stopped or expired, the transmission / And when the N_TA is changed, the transmission / reception section controls the reverse transmission timing to be adjusted. A random access controller for selecting a preamble at the start of the random access procedure and instructing the transmission and reception section to transmit the notification to the reverse transmission timing control section and transmitting the TA command to the reverse transmission timing control section, .

According to a fourth exemplary embodiment of the present invention, a terminal apparatus for performing random access in a mobile communication system includes a transceiver for transmitting and receiving a MAC PDU over a wireless channel and for transmitting a preamble, An MAC PDU reception processing unit for processing the MAC PDUs transmitted from the transmission and reception unit and generating a message 2E including upper layer data and a TA command, And transmits a TA command to the reverse transmission timing controller. Upon reception of the TA command through the message 2, the reverse transmission timing controller controls the reverse transmission timing When the maximum number of transmissions is reached in the HARQ process and the message 3 is transmitted And a random access controller for discarding the temporary identifier and the HARQ buffer data of the UE and terminating the HARQ process.

According to the present invention, when a terminal under operation of a TA timer performs a random access procedure, it reduces a case of performing a reverse transmission at a wrong reverse transmission timing.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that, in the drawings, the same components are denoted by the same reference symbols as possible. Further, the detailed description of well-known functions and constructions that may obscure the gist of the present invention will be omitted.

In the present invention, a method and apparatus for adjusting a N_TA and a TA timer in a terminal in which a TA timer is running perform a random access procedure.

In the first embodiment of the present invention, when the terminal on which the TA timer is operating starts a random access procedure for some reason, the terminal adjusts N_TA to 0 and transmits a preamble when it is time to transmit the preamble. Upon receiving the message 2 (UL grant, TA command) from the base station, the terminal that has transmitted the preamble stops the TA timer, adjusts the reverse transmission timing in accordance with the TA command of the message 2, and restarts the TA timer. Then, the UE transmits a first upling message and waits until it receives a contention resolution message. At this time, if the contention fails (CR failure), the UE stops the TA timer and does not apply the backoff, and resumes the random access process while transmitting the preamble at the nearest time.

In the second embodiment of the present invention, the UE, which is operating the TA timer, starts the random access procedure and maintains the uplink transmission timing currently being used even if the preamble is transmitted. In this case, since the TA command received in the message 2 (UL grant, TA command) is information calculated on the assumption that the terminal transmits N_TA by setting it to 0, the terminal ignores the TA command. However, even if the TA timer is in operation, if a random access procedure is performed using a dedicated preamble, a contention failure does not occur, and it is possible to readjust the uplink transmission timing through the random access procedure. Therefore, even if the TA timer is running, the UE using the dedicated preamble sets the N_TA to 0 and adjusts the uplink transmission timing according to the TA command received through the message 2 in the future.

The third embodiment of the present invention proposes a method of restoring the N_TA to the previous value immediately after the preamble transmission is completed by setting the N_TA to 0 while the terminal in operation with the TA timer is transmitting the preamble. To this end, the terminal has a variable TIME_ADVANCE, and stores the accumulated value of the TA command applied up to that point in the TIME_ADVANCE variable. The UE adjusts N_TA to 0 before transmitting the preamble, and after transmitting the preamble, if the TA timer is in operation and the dedicated preamble is not used, the UE adjusts the N_TA to the value stored in the TIME_ADVANCE variable, The TA command that restores the timing and then receives via message 2 is ignored.

The fourth embodiment of the present invention proposes a method of discarding the temporary identifier when the terminal is at a point in time when it is impossible to retransmit the message 3 so that the reverse grant transmitted by the temporary identifier is no longer received. The UE in the connected state monitors its own unique identifier and temporary identifier until the contention is resolved at the start of the message 3 transmission or until it is recognized that the contention has failed for the adaptive retransmission of the message 3 . This operation of the terminal unnecessarily monitors the temporary identifier until it is recognized that the contention resolution has failed at the point of time when the retransmission of the message 3 is impossible, and when the temporary identifier is allocated to another terminal, It can cause the problem of misinterpreting the reverse grant as a reverse grant assigned to it. According to the fourth embodiment of the present invention, when a message 3 is transmitted in a state in which the maximum number of transmissions has been reached when the HARQ process is performed, the UE determines that retransmission of the message 3 is impossible and discards the temporary identifier And does not receive the reverse grant transmitted by the temporary identifier.

≪ Embodiment 1 >

The BS sets the TA command on the assumption that the UE sets the reverse transmission timing to the boundary of the forward frame, i.e., sets the N_TA to 0 and transmits the TA command. Therefore, in the first embodiment, it is necessary to adjust the reverse transmission timing through the random access procedure The preamble transmission is performed after the N_TA is adjusted to 0, even if the terminal does not have the TA timer. After that, the terminal stops the TA timer of the terminal because the terminal can not transmit any signal in the reverse direction until the N_TA is held at 0, that is, before the terminal receives the message 2. When a contention failure occurs, the UE stops the TA timer so that the uplink transmission can not be performed until the synchronization of the uplink transmission timing is restored. The base station may instruct to apply back-off to terminals that perform random access, for example, if the random access channel is congested or momentary overload occurs. The backoff command is stored in the message 2, and the terminal that has failed the contention waits for a period corresponding to the value indicated by the backoff, and resumes the random access procedure. However, if backoff is applied in a state in which the terminal in which the TA timer is running fails the contention and the TA timer is stopped, the terminal can not perform normal communication during the backoff period. If the TA timer is running before performing the random access procedure, the UE immediately restarts the random access procedure without applying back-off in restarting the random access procedure due to a contention failure.

3 is a diagram showing the entire operation of the first embodiment of the present invention.

Referring to FIG. 3, the terminal on which the TA timer is running starts a random access procedure for some reason. As described above, a terminal on which a TA timer is running can perform a random access procedure to transmit a buffer status report. If the N_TA of the UE is? (305), the UE keeps N_TA until? Before transmitting the preamble. That is, the uplink transmission timing of the UE is spaced apart from the forward frame boundary by a. When it is time to transmit the preamble (315), the UE adjusts N_TA to 0 and transmits a preamble.

The terminal that has transmitted the preamble stops the TA timer (320), and upon receiving the message 2, adjusts the reverse transmission timing in accordance with the TA command of the message 2. That is, if the TA command is? (TA command =?) (325), the terminal sets N_TA to? (N_TA =?) And the terminal adjusts the TA command and restarts the TA timer. The terminal waits until it sends message 3 and receives a contention resolution message. Successfully receiving the contention resolution message terminates the process, but if the contention resolution fails (CR failure) (345), the TA timer is stopped (330). Even if the base station instructs the terminal to apply the backoff, the terminal ignores backoff (335), transmits the preamble at the nearest time point, resumes the random access procedure while initializing the N_TA (N_TA = 0) (340).

4 is a diagram illustrating a terminal operation according to the first embodiment of the present invention.

Referring to FIG. 4, when the random access procedure starts in step 405, the UE waits until the closest point at which the preamble can be transmitted, and then proceeds to step 410 to set the N_TA to 0 and transmit a preamble. Hereinafter, setting N_TA to x means that the reverse transmission timing is set to a time point spaced by x from the forward frame boundary. The terminal stops the TA timer in step 415 and waits until message 2 transmitted from the base station is received. At this time, if the BS transmits a message, the MS receives the message 2 transmitted to itself in step 420, and adjusts the N_TA and the reverse transmission timing in accordance with the TA command of the message 2 in step 425.

Then, the terminal proceeds to step 430 and drives a TA timer. The MS transmits a message 3 to the BS according to a predetermined procedure, and analyzes the contention resolution message transmitted from the BS in step 435 to determine whether to resolve the contention. If it is determined in step 435 that the contention is resolved, the process proceeds to step 440 and ends.

However, if it is determined in step 435 that the contention is unsuccessful, the MS proceeds to step 445 and checks whether the MS is in a connection state by checking the message 3. That is, in step 445, the MS determines whether a C-RNTI MAC CE (Control Element) has been stored in the message 3 to determine whether to apply backoff before resuming the random access procedure in step 445. The C-RNTI is an identifier for identifying a terminal in a cell, and is given to a connected state terminal. The C-RNTI MAC CE refers to C-RNTI information to be inserted into a packet in the MAC layer, and the UE performing the random access in the connected state stores the C-RNTI MAC CE in the message 3. That is, the reception of the C-RNTI MAC CE in the message 3 means that the terminal performing the random access is the terminal in the connected state. The reverse link resource or the forward link resource may be allocated to the terminal in the connected state at any time. However, if the TA timer of the terminal is stopped, even if the transmission resource is allocated, the terminal can not use the TA resource. That is, it is preferable that the state in which the TA timer of the connection state terminal is stopped is canceled as soon as possible. In the embodiment of the present invention, if the UE has stored the C-RNTI MAC CE in the message 3, the UE proceeds directly to step 455 without applying a backoff, waits until the time when the preamble transmission is possible nearest to the UE, The process returns to step 410 to resume the random access procedure. However, the UE that has not stored the C-RNTI MAC CE in the message 3 waits for a period corresponding to the backoff in step 450 and then proceeds to step 455. [

≪ Embodiment 2 >

When the UE operating the TA timer performs a random access procedure, the UE changes the N_TA to 0 at the moment of transmitting the preamble and adjusts the N_TA according to the TA command received via the message 2, 3 may be transmitted with wrong reverse transmission timing. In addition, if the UE is allocated an uplink transmission resource before recognizing that the contention has failed, the situation becomes worse because the UE performs another uplink transmission at the wrong uplink transmission timing.

In order to solve the above problem, in the second embodiment of the present invention, the UE, which is operating the TA timer, starts the random access procedure and maintains the uplink transmission timing being used even if the preamble is transmitted. In this case, since the TA command received in message 2 is information calculated on the assumption that the terminal transmits N_TA by setting it to 0, the terminal ignores the TA command. However, even if the TA timer is in operation, if a random access procedure is performed using a dedicated preamble, a contention failure does not occur, so that the reverse transmission timing can be readjusted through a random access procedure. Therefore, even if the TA timer is running, the UE using the dedicated preamble sets the N_TA to 0 and adjusts the uplink transmission timing according to the TA command received through the message 2 in the future. For reference, a base station can allocate a specific preamble to a terminal in a connected state, which is referred to as a dedicated preamble. If a dedicated preamble is used, there is an advantage that a contention failure does not occur in the random access procedure. Therefore, the base station can allocate the dedicated preamble to a terminal performing the handover.

5 is a flowchart illustrating an operation procedure of the UE according to the second embodiment of the present invention.

Referring to FIG. 5, when the UE starts the random access procedure in step 505, it proceeds to step 510 and checks whether the current TA timer is being driven. At this time, if the TA timer is in operation, the terminal proceeds to step 515 and checks whether a dedicated preamble is allocated. As described above, the dedicated preamble is a preamble dedicated for allocating a specific preamble to a terminal in a connected state, as described above. If the dedicated preamble is used, a contention failure does not occur in the random access procedure. Accordingly, if the UE detects that the dedicated preamble is allocated, the UE should adjust the uplink transmission timing in the random access procedure even if the TA timer is running (TA timer running). Accordingly, if it is detected in step 515 that the dedicated preamble has been allocated, the UE proceeds to step 525 to adjust the N_TA value to 0 (N_TA = 0), transmit the preamble, and stop the TA timer in step 530. However, if it is detected in step 515 that the dedicated preamble is not allocated, the MS proceeds to step 520 and transmits a preamble while maintaining the current uplink transmission timing. That is, the preamble is transmitted while maintaining the N_TA at the current value. The terminal then ignores the TA command of message 2 and maintains the reverse transmission timing.

If it is determined in step 510 that the TA timer is not in operation, the terminal initializes N_TA to 0 and transmits a preamble in step 525. In step 530, Lt; / RTI > The UE then adjusts the uplink transmission timing according to the TA command of the message 2.

≪ Third Embodiment >

For a base station, the N_TA may not properly detect the transmitted preamble without being set to 0. In the third embodiment of the present invention, a method is disclosed in which a terminal on which a TA timer operates transmits a preamble and sets N_TA to 0 and restores the N_TA to its previous value immediately after the preamble transmission is completed. To this end, the terminal has a variable TIME_ADVANCE, and stores the accumulated value of the TA command applied up to that point in the TIME_ADVANCE variable. The UE adjusts N_TA to 0 before transmitting the preamble, and after transmitting the preamble, if the TA timer is in operation and the dedicated preamble is not used, the UE adjusts the N_TA to the value stored in the TIME_ADVANCE variable, The TA command that restores the timing and then receives via message 2 is ignored.

6 is a flowchart illustrating an operation procedure of a terminal according to the third embodiment of the present invention.

Referring to FIG. 6, when the random access procedure starts in step 605, the UE waits until the closest point at which the preamble can be transmitted, and then sets the N_TA to 0 in step 607 and transmits a preamble. After the preamble transmission is completed, the terminal checks in step 610 whether the current TA timer is being driven. If it is determined in step 610 that the TA timer is active, the terminal checks if a dedicated preamble is used in step 615. If it is determined in step 615 that the dedicated preamble is not used, the UE proceeds to step 620 to recover the uplink transmission timing used before the random access procedure. In step 620, the UE transmits the uplink transmission timing stored in the TIME_ADVANCE . That is, N_TA is set to the value stored in TIME_ADVANCE. When the base station transmits the message 2, the terminal receives the TA message in step 625, ignores the TA command received in the received message 2, and proceeds to step 640 to perform the remaining random access procedure.

However, if it is determined in step 610 that the TA timer is not in operation, the terminal proceeds to step 635 and receives the message 2. The UE adjusts the uplink transmission timing in accordance with the TA command stored in the message 2, and proceeds to step 640 to perform the remaining random access procedure. If it is determined in step 615 that the dedicated preamble is used even if the TA timer is in operation, the terminal proceeds to step 630 to stop the ongoing TA timer and proceeds to step 635 to receive the message 2. Then, the uplink transmission timing is adjusted according to the TA command stored in the message 2, and the remaining random access procedure is performed in step 640.

7 is a diagram showing an operation procedure for the terminal to update the TIME_ADVANCE.

As described above, the accumulated value of the TA command applied up to that point is stored in TIME_ADVANCE. The TA command is delivered via the TA MAC Advance MAC Control Element (TA MAC) or via message 2. Since the TA MAC CE transmits the C-RNTI of the corresponding terminal to the terminal in the connected state, there is no problem that a wrong TA command is delivered due to a contention failure or the like. Therefore, the terminal always follows the TA command received through the TA MAC CE. In addition, TA MAC CE transmits a timing adjustment value relative to the current reverse transmission timing of the UE. Therefore, the timing is adjusted by the indicated value based on the current reverse transmission timing. On the other hand, the TA command transmitted through the message 2 is a transmission timing adjustment value for the reverse signal transmitted from the terminal at N_TA = 0. Therefore, TIME_ADVANCE is reset to the TA command received via the message 2.

In summary, when the TA receives the TA command via the message 2, the terminal updates the TIME_ADVANCE with the value, and upon receiving the TA command via the TA MAC CE, updates the TIME_ADVANCE with the value summed with the value stored in the current TIME_ADVANCE.

Referring to FIG. 7, when the terminal receives the TA command in step 705, it determines in step 710 whether the TA command is received through the TA MAC CE. At this time, if it is determined that the TA command is received via the TA MAC CE, the terminal proceeds to step 715 and updates the TIME_ADVANCE to a value obtained by adding the value stored in the current TIME_ADVANCE and the value instructed by the TA command. Wait until.

However, if it is determined that the TA command received in step 710 is not received through the TA MAC CE, i.e., received through the message 2, the terminal proceeds to step 720 and determines that the current TA timer is not in operation or a dedicated preamble Check if it is used. If both conditions are satisfied, step 725 is reached. If both conditions are not satisfied, that is, if the TA timer is in operation and the dedicated preamble is not used, step 730 is performed. In step 725, the terminal updates TIME_ADVANCE to the value indicated in the TA command received. In step 730, the terminal maintains TIME_ADVANCE at the current value.

<Fourth Embodiment>

As described above, the random access procedure is completed after the contention is resolved. Until the contention is resolved, the UE receives the reverse grant through a Temporary C-RNTI (Temporary C-RNTI). For example, if it is intended to instruct the retransmission of the message 3 with a new transmission resource, the base station transmits the reverse grant using the temporary identifier of the terminal, and when the terminal receives the reverse grant indicated by the temporary identifier, Retransmit.

As described above, the random access procedure may be performed by a terminal already in a connected state, and the terminal has its own unique identifier (C-RNTI). The UE in the connected state may check the unique identifier and the temporary identifier together until the contention is resolved at the beginning of the message 3 transmission or the contention is not recognized for the adaptive retransmission of the message 3, do. This operation of the terminal unnecessarily monitors the temporary identifier until it is recognized that the contention resolution has failed at the point of time when the retransmission of the message 3 is impossible, and when the temporary identifier is allocated to another terminal, It can cause the problem of misinterpreting the reverse grant as a reverse grant assigned to it.

In the fourth embodiment of the present invention, when the UE becomes unable to retransmit the message 3, the temporary identifier is discarded so that the reverse grant transmitted by the temporary identifier is not received.

8 is a flowchart illustrating a terminal operation according to the fourth embodiment of the present invention.

Referring to FIG. 8, if an HARQ process is performed in an HARQ process in step 805, the UE proceeds to step 810 and checks whether the number of transmissions reaches a maximum number of transmissions. The number of transmissions of a specific HARQ process is managed by a variable CURRENT_TX_NB, and the UE can recognize the HARQ maximum number of transmissions through the system information or through the control message in the call setup process. The reason why the HARQ maximum transmission count is required is to prevent the HARQ retransmission from being repeated infinitely when the HARQ retransmission continues to fail. Since CURRENT_TX_NB is initialized to 0, the condition in step 810 is satisfied when CURRENT_TX_NB is equal to a value obtained by subtracting 1 from the maximum number of transmissions. If the CURRENT_TX_NB is less than the value obtained by subtracting 1 from the maximum transmission number, that is, if the maximum transmission number has not yet been reached, the UE detects this in step 810 and waits until the next transmission time of the HARQ process in step 815.

However, if CURRENT_TX_NB is greater than the value obtained by subtracting 1 from the maximum number of transmissions, i.e., the maximum number of transmissions has been reached, the terminal detects this in step 810 and proceeds to step 820. [ In step 820, the UE determines whether the message transmitted through the HARQ process is a message 3. If the MAC PDU transmitted through the HARQ process is acquired from the message 3 buffer, the MAC PDU transmitted through the HARQ process is message 3, and not the message 3. If the message transmitted through the HARQ process is message 3, the UE proceeds to step 825; otherwise, the UE proceeds to step 830. If it is determined in step 920 that the message 3 has been transmitted, it means that the message 3 is not to be retransmitted any more. Therefore, the UE discards the temporary C-RNTI in step 825, Eliminates the possibility of performing erroneous reverse transmission due to the identifier. In step 830, the UE discards the data stored in the HARQ buffer and completes the HARQ transmission. However, if it is determined in step 920 that the message 3 is not transmitted, the MS proceeds to step 803 to discard the data stored in the HARQ buffer and terminate the HARQ transmission.

As described above, when the HARQ process is performed and the message 3 is transmitted when the maximum number of transmissions has been reached, the UE determines that retransmission of the message 3 is impossible, discards the temporary ID, Do not receive the reverse grant being transmitted.

9 is a diagram illustrating a structure of a terminal device performing a random access procedure according to the first to fourth embodiments of the present invention.

9, the terminal apparatus includes an upper layer apparatus 905, a random access control unit 910, a MAC PDU transmission processing unit 915, an reverse transmission timing control unit 920, an MAC PDU reception processing unit 925, and a transmission / reception unit 930.

The upper layer device 905 collectively refers to a device that generates data to be transmitted / received through a wireless channel of the LTE. The upper layer device 905 includes both the terminal application and the control message processing device. The random access controller 910 is an apparatus for controlling the overall operation of the random access procedure according to the first to fourth embodiments of the present invention. The random access controller is triggered when new data is generated in the upper layer. When the random access controller needs to start the random access procedure, the random access controller instructs the transmission and reception unit to select and transmit a preamble, and the MAC PDU reception processor 925 receives Interpret one message 2 and perform the required action. When the random access starts, the random access controller 910 notifies the reverse transmission timing controller 920 of the random access. When the random access controller 910 receives the TA command via the message 2, the random access controller 910 transmits the TA command to the reverse transmission timing controller 920. In the first embodiment, the random access controller 910 controls the backoff process so that backoff is not applied if a message 3 including C-RNTI CE is transmitted. In the fourth embodiment of the present invention, when the transmission of the message 3 is completed, that is, when the HARQ transmission of the message 3 is performed for the maximum number of transmissions, the random access controller 810 allocates the Temporary C-RNTI Discard.

The reverse transmission timing controller 920 drives the TA timer and controls the transmission / reception unit 930 so as not to transmit the reverse signal when the TA timer is stopped or expired. The reverse transmission timing controller 920 manages the N_TA and notifies the transmission / reception unit 930 whenever the N_TA is changed so that the transmission / reception unit 930 adjusts the reverse transmission timing. In the first embodiment of the present invention, when the random access procedure starts, the reverse transmission timing controller 920 sets N_TA to 0 and stops the TA timer. Upon receiving a new TA command via message 2, it updates N_TA and drives the TA timer. In the second embodiment of the present invention, when the TA timer is in operation and the dedicated preamble is not used, the reverse transmission timing controller 920 does not change the N_TA in the random access procedure, and if the TA timer is not running or the TA timer is running If a dedicated preamble is used, set N_TA to 0 and stop the TA timer. In the third embodiment of the present invention, the reverse transmission timing controller 920 manages the TIME_ADVANCE variable. The N_TA is set to 0 when the random access procedure is started. If the TA timer is running and a dedicated preamble is not used, the N_TA is set to the value stored in TIME_ADVANCE after transmitting the preamble.

The MAC PDU transmission processing unit 915 configures MAC PDUs (Protocol Data Units) transmitted from the upper layer device 905 and transmits the data to the transmission / reception unit 930. The MAC PDU reception processing unit 925 processes the MAC PDUs transmitted by the transmission / reception unit 930, and transfers the upper layer data to the upper layer device 905, the message 2 to the random access control unit 910, and the A MAC CE to the reverse transmission timing control unit 920. The transceiver transmits / receives the MAC PDU over the LTE radio channel or transmits the preamble.

As described above, in the first embodiment of the present invention, when the random access procedure starts, the N_TA is set to 0 and the TA timer is stopped. When receiving the new TA command through the message 2, the N_TA is updated And drives the TA timer. In the second embodiment of the present invention, when the TA timer is in operation and the dedicated preamble is not used, the reverse transmission timing controller 920 does not change the N_TA in the random access procedure, and if the TA timer is not running or the TA timer is running If a dedicated preamble is used, set N_TA to 0 and stop the TA timer. In the third embodiment of the present invention, the reverse transmission timing controller 920 sets N_TA to 0 when the random access procedure is started. If the TA timer is in operation and the dedicated preamble is not used, the preamble is transmitted and the N_TA is stored in the TIME_ADVANCE Setting. In the fourth embodiment of the present invention, when the message 3 is transmitted when the maximum number of transmissions has been reached when the HARQ process is performed, the random access controller 910 determines that retransmission of the message 3 is impossible and discards the temporary identifier And does not receive the reverse grant transmitted by the temporary identifier.

The embodiments of the present invention disclosed in the present specification and drawings are merely illustrative of specific embodiments of the present invention and are not intended to limit the scope of the present invention in order to facilitate understanding of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention are possible in addition to the embodiments disclosed herein.

1 is a diagram showing a structure of an LTE mobile communication system;

2 is a diagram showing a random access procedure in an LTE mobile communication system

3 is a diagram showing a random access operation procedure according to the first embodiment of the present invention

4 is a diagram showing a terminal operation according to the first embodiment of the present invention

5 is a flowchart illustrating an operation procedure of a terminal according to a second embodiment of the present invention.

6 is a flowchart illustrating an operation procedure of a terminal according to a third embodiment of the present invention.

7 is a diagram showing an operation procedure of the terminal updating the TIME_ADVANCE in Fig. 6

8 is a flowchart illustrating an operation procedure of the UE according to the fourth embodiment of the present invention.

9 is a diagram showing a structure of a terminal device performing a random access procedure according to an embodiment of the present invention

Claims (16)

A random access method of a terminal in a mobile communication system, Synchronizing an uplink transmission time with a base station in a first random access procedure; Adjusting the TA (timing advance) obtained in the synchronization step to a preset value and stopping the timer driven in the synchronization step when the terminal initiates the second random access; Transmitting the preamble after adjusting the TA; Adjusting the TA based on a first message including TA adjustment information received from the base station; And And if the contention solving message is received from the base station, completing the second random access procedure successfully. The method according to claim 1, Wherein the predetermined value includes zero. The method according to claim 1, When the timer is stopped, Wherein the terminal does not perform reverse transmission. The method according to claim 1, The step of adjusting the TA comprises: Restarting the timer; And And transmitting a second message including the reverse data to the base station. The method according to claim 1, And returns to the preamble transmission process if the second random access procedure fails. The method according to claim 1, Determining whether a dedicated preamble is assigned to the terminal; And Wherein the second random access procedure is performed when the dedicated preamble is allocated to the terminal. The method according to claim 1, The step of adjusting the TA comprises: And adjusts the TA with an accumulated value of the TA stored in the TA storage unit. The method according to claim 1, Upon receiving the contention resolution message, Determining whether the number of transmissions of the HARQ process has reached a maximum number of transmissions; Determining whether a second message has been transmitted through the HARQ process when the number of transmissions of the HARQ process has reached a maximum number of transmissions; And discarding the temporary identifier and the data stored in the buffer of the HARQ if the second message is determined to have been transmitted. In a terminal performing random access, A communication unit for communicating with other network entities; A step of synchronizing an uplink transmission time with a base station in a first random access procedure and adjusting a timing advance (TA) obtained in the synchronization step to a preset value when starting a second random access, Adjusts the TA based on a first message including TA adjustment information received from the base station, and adjusts the TA based on a first message received from the base station, and when a contention resolution message is received from the base station, And controlling the second random access procedure to be completed successfully. 10. The method of claim 9, Wherein the predetermined value includes zero. 10. The method of claim 9, Wherein, And controls the terminal not to perform the reverse transmission when the timer is interrupted. 10. The method of claim 9, Wherein, Restarts the timer, and transmits a second message including reverse data to the base station. 10. The method of claim 9, Wherein, And to return to the preamble transmission process if the second random access procedure fails. 10. The method of claim 9, Wherein, Determines whether a dedicated preamble has been allocated to the terminal, and controls the terminal to perform the second random access procedure if the dedicated preamble is allocated to the terminal. 10. The method of claim 9, Wherein, And controls the TA to be adjusted to an accumulated value of the TA stored in the TA storage unit. 10. The method of claim 9, Wherein, Determining whether the number of transmissions of the HARQ process has reached the maximum number of transmissions, determining whether a second message has been transmitted through the HARQ process if the number of transmissions of the HARQ process has reached the maximum number of transmissions, And to discard the temporary identifier and the data stored in the buffer of the HARQ if it is determined that the second message has been transmitted.

Images