KR20090101796A - Method and apparatus for checking transmission success or failure of medium access control protocal data unit in mobile communication system - Google Patents

Abstract

PURPOSE: A method and an apparatus for checking transmission success or failure of a medium access control protocol data unit in a mobile communication system are provided to prevent the unnecessary operation of a terminal by judging the transmission success or failure of an MAC PDU(Medium Access Control Protocol Data Unit). CONSTITUTION: A method for checking the transmission success or failure of a MAC PDU(Medium Access Control Protocol Data Unit) in a mobile communication system comprises the steps of: inspecting whether or not transmission resources for initial transmission are allocated in the retransmission point of an MAC PDU(515); judging the success or failure of transmission by inspecting whether the feedback of an HARQ(Hybrid Automatic Retransmission reQuest) feedback is an ACK response or NACK response(520); and judging the success or failure of the transmission by inspecting whether the last HARQ feedback is the ACK response or the NACK response for the MAC PDU(525).

Description

METHOD AND APPARATUS FOR CHECKING TRANSMISSION SUCCESS OR FAILURE OF MEDIUM ACCESS CONTROL PROTOCAL DATA UNIT IN MOBILE COMMUNICATION SYSTEM}

The present invention relates to a mobile communication system, and more particularly, to a method and apparatus for determining whether transmission of a MAC PDU is successful in a mobile communication system.

In a mobile communication system including Long Term Evolution (LTE), various control messages may be retransmitted or a control procedure may be restarted based on a timer. For example, in order to transition to a connected state, a radio resource control (RRC) layer device of an idle mode terminal transmits an RRC connection request message (hereinafter, referred to as an RRC CONNECTION REQUEST message) to a lower layer. do. If the lower layer confirms the successful transmission of the RRC CONNECTION REQUEST message to the RRC layer, the RRC layer starts a timer at the time when the successful transmission is confirmed. The RRC layer retransmits the RRC CONNECTION REQUEST message if a response message to the RRC CONNECTION REQUEST message is not received until the timer expires. In addition, there are many cases in which successful transmission of a specific message from a lower layer serves as a trigger of a specific procedure.

In a mobile communication system in which a hybrid automatic retransmit request (HARQ) is not driven, the transmission completion point of a specific message is a point in time at which a packet containing the message is transmitted through a wireless channel.

On the other hand, in a mobile communication system in which HARQ is driven, it is not clear at which point in time when a successful transmission is to be determined based on which event, especially when HARQ, which allows adaptive retransmission, is driven. That is, when a typical HARQ is driven in a mobile communication system, when HARQ ACK (ACKnowledge) is received for the transmitted data, it is determined that the data is successfully transmitted, but when HARQ is allowed to be adaptively retransmitted, Completion of data transmission cannot be determined only by receiving the HARQ ACK.

Accordingly, there is a need for a method for determining whether data is successfully transmitted when HARQ, which is capable of adaptive retransmission, is driven in a mobile communication system.

The present invention provides a method and apparatus for determining whether transmission of a MAC PDU is successful in a mobile communication system.

In addition, the present invention provides a method and apparatus for determining the success or failure of the transmission of the MAC PDU when HARQ is allowed to be adaptively retransmitted in the mobile communication system.

In the mobile communication system according to the present invention, a method for determining whether a medium access control protocol data unit (MAC PDU) is successfully transmitted includes checking whether an initial transmission resource is allocated at the time of retransmission of the MAC PDU, and transmitting the initial transmission resource. If is allocated, the first step of determining whether the transmission success by checking whether the last HARQ (Hybrid Automatic Retransmission reQuest) feedback for the MAC PDU is a normal response (ACK) or a negative response (NACK), and the transmission resource for the first transmission If not assigned, check whether the last retransmission feedback time has elapsed, and if the last retransmission feedback time has passed, check whether the last HARQ feedback for the MAC PDU is the normal response or the negative acknowledgment. It includes a second process of determining.

In addition, in the mobile communication system according to the present invention, the apparatus for determining success of transmission of a medium access control protocol data unit (MAC PDU), a transceiver for receiving PDCCH control information and HARQ feedback information through a wireless channel and transmitting the MAC PDU And checking whether the transmission resource for initial transmission is allocated among the received PDCCH control information at the time of retransmission of the MAC PDU, and if the transmission resource for the first transmission is allocated, the last hybrid automatic retransmission reQuest (HARQ) feedback for the MAC PDU is received. Check whether the transmission is successful by checking whether it is a normal response (ACK) or a negative response (NACK). If the transmission resource for the first transmission is not allocated, it is checked whether the last retransmission feedback time has elapsed, and the last retransmission feedback time has elapsed. If the last HARQ feedback for the MAC PDU is the normal response (ACK) or the negative response (NACK) Used by a controller to determine whether the transmission success.

The present invention can prevent the UE from taking unnecessary operations by inaccurately determining the success or failure of the MAC PDU (2 layer data).

1 is a view showing the structure of an LTE mobile communication system,

2 is a diagram illustrating a radio protocol structure of an LTE mobile communication system;

3 is a diagram illustrating an example of a synchronous HARQ transmission scheme in an LTE mobile communication system;

4 is a diagram showing an adaptive synchronous HARQ transmission scheme in an LTE mobile communication system;

5 is a flowchart illustrating a terminal operation according to a first embodiment of the present invention;

6 is a diagram illustrating an example of a terminal operation according to a first embodiment of the present invention;

7 is a block diagram of a terminal according to a first embodiment of the present invention;

8 is a flowchart illustrating another example of a terminal operation according to the first embodiment of the present invention;

9 is a view illustrating a transmission time point, a retransmission grant time point in another example of a terminal operation according to the first embodiment of the present invention;

10 is a diagram illustrating a process of transmitting reverse data during a DRX operation according to a second embodiment of the present invention;

11 is a view showing an example of a terminal operation according to a second embodiment of the present invention;

12 is a flowchart illustrating a terminal operation according to a second embodiment of the present invention;

13 is a block diagram of a terminal according to a second embodiment of the present invention;

14 is a flowchart illustrating an example of a terminal operation according to a third embodiment of the present invention;

15 is a flowchart illustrating another example of a terminal operation according to the third embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intention or custom of a user or an operator. Therefore, the definition should be made based on the contents throughout the specification.

In the present invention, when the HARQ is allowed to be adaptive retransmission in the mobile communication system is driven, the HARQ ACK can also be used for the purpose of simply stopping the retransmission. Then, the transmission success / failure of the data is determined based on the most recent HARQ feedback information on the data.

Hereinafter, the structure of the LTE mobile communication system applied to the present invention will be briefly described with reference to FIGS. 1 to 4 before describing the present invention.

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

Referring to FIG. 1, as illustrated, a next-generation radio access network (Evolved Radio Access Network: E-RAN) 110, 112 in an LTE system is an Evolved Node B: ENB or Node B. (120, 122, 124, 126, 128) and the upper node (Access Gateway) (130, 132) two node structure is simplified. The user equipment 101 (hereinafter referred to as UE) 101 connects to the Internet Protocol (hereinafter referred to as IP) network 114 by the E-RANs 110 and 112.

The ENBs 120 to 128 correspond to existing Node Bs of the UMTS system and are connected to the UE 101 by a radio channel. Unlike the existing Node B, the ENBs 120 to 128 play a more complex role. In LTE, all user traffic including a real-time service such as Voice over IP (VoIP) through the Internet protocol is serviced through a shared channel, and therefore, an apparatus for collecting and scheduling situation information of UEs is needed. The ENBs 120-128 are in charge. In order to realize a transmission rate of up to 100 Mbps, LTE uses Orthogonal Frequency Division Multiplexing (hereinafter, referred to as OFDM) in a maximum 20 MHz bandwidth as a wireless access technology. In addition, an adaptive modulation & coding (AMC) scheme that determines a modulation scheme and a channel coding rate according to the channel state of the terminal is applied.

2 is a diagram illustrating a radio protocol structure of an LTE mobile communication system.

Referring to FIG. 2, the wireless protocol of the LTE mobile communication system includes PDCP layers (205, 240), RLC layers (210, 235), and MAC layer (Medium Access Control Layer). ) 215 and 230, and physical layers 220 and 225.

The PDCP layers 205 and 240 are in charge of operations such as IP header compression / restore and secret / de-secret. The RLC layers 210 and 235 reconfigure PDCP PDUs (hereinafter referred to as PDUs of the protocol) to a proper size to perform an ARQ operation. The MAC layers 215 and 230 are connected to several RLC devices configured in one UE, and perform an operation of multiplexing the RLC PDUs into the MAC PDU and demultiplexing the RLC PDUs from the MAC PDU. The physical layers 220 and 225 channel-code and modulate higher layer data and form orthogonal frequency division multiplexing (OFDM) symbols to transmit them in a wireless channel, or demodulate and channel decode OFDM symbols received through the wireless channel to a higher layer. It acts to deliver.

In the LTE mobile communication system, HARQ is applied to all traffic except for some control messages. HARQ is a technique of retransmitting data according to HARQ feedback information of a physical layer. The HARQ is a technique of increasing reception success rate by storing previously received data in a soft buffer and softly combining the retransmitted data with previous data. In the reverse direction of the LTE mobile communication system, the synchronous HARQ transmission scheme as shown in FIG. 3, which performs transmission and retransmission for the same data with a certain time difference, is applied.

3 is a diagram illustrating an example of a synchronous HARQ transmission scheme in an LTE mobile communication system.

The reverse transmission resource is essentially a frequency / time resource. In the LTE mobile communication system, a unit transmission resource is a frequency band of a predetermined size during a time slot of a predetermined length.

In FIG. 3, one square 305 is a unit transmission resource, and the unit transmission resource is called a resource block. The size of the resource block on the time axis is 1 msec and is called a subframe or transmission time interval (TTI).

The base station scheduler allocates uplink transmission resources to the UE through a control channel called a physical downlink control channel (PDCCH), and the allocated transmission resources are assigned to the same packet at a time point spaced apart by a HARQ RTT (Round Trip Time, 310) on a time axis. It can be used for transmission and retransmission.

The terminal first transmits reverse data through the allocated transmission resource 320, and analyzes HARQ feedback information received at a predetermined time to determine whether to retransmit the HARQ. If HARQ feedback information is HARQ NACK (Negative ACKnowledgment) in step 345, the terminal retransmits data using the same transmission resource 325 at the next HARQ retransmission time. The retransmission of the data as in step 345 is repeated until the HARQ ACK is received. That is, if HARQ feedback information is HARQ NACK in step 350, the UE retransmits data using the same transmission resource 330 at the next HARQ retransmission time.

After that, if the HARQ ACK is received in step 355, the reverse data transmission process ends. As described above, in the synchronous HARQ operation, when the HARQ NACK is received, the uplink transmission resource is automatically allowed. However, since retransmission of the same data more than a certain number of times is not preferable in terms of transmission efficiency, retransmission of one data is limited by the maximum number of retransmissions. For example, if the maximum number of retransmissions is three times, the terminal determines that the allocated transmission resource is no longer valid after completing three retransmissions even if the UE does not receive the HARQ ACK. That is, if HARQ NACK is continuously received, the UE performs retransmission using the transmission resources 325, 330, and 335, but after performing the last retransmission 335 determined by the maximum number of retransmissions, the transmission resource 340. This is no longer considered valid. The initial transmission and retransmission proceed through the same HARQ process. The HARQ process is a soft buffer that stores HARQ data. The HARQ process stores data to be transmitted at the transmitting side and data received at the receiving side. When the receiving side receives retransmission data for any HARQ process, the receiving side flexibly combines the data stored in the process with the received retransmission data. The HARQ process is assigned an identifier. In the synchronous HARQ, the identifier of the HARQ process corresponds to a time when data is transmitted and received, and transmission and retransmission are always performed through a process indicated by the same identifier. For example, in transmitting data through the transmission resource allocated in step 315, the time point at which the data is transmitted through the transmission resource 320 is replaced by a specific HARQ identifier, for example, process 4, and retransmission of the data. Is performed at the time points 360, 365, 370, 375, and 380 corresponding to process 4. In the conventional HARQ operation, when the HARQ ACK is received, it is determined that the corresponding data is successfully transmitted, and the successful transmission is confirmed to the upper layer.

In the LTE mobile communication system, reverse retransmission may be performed using a transmission resource different from the previous transmission as shown in FIG. 4, which is called an adaptive synchronous HARQ transmission scheme.

4 is a diagram illustrating an adaptive synchronous HARQ transmission scheme in an LTE mobile communication system.

Referring to FIG. 4, one square 405 is a unit transmission resource, and the unit transmission resource is called a resource block. The terminal first transmits reverse data through the allocated transmission resource 420 in step 415, interprets HARQ feedback information received at a predetermined time, and determines whether to retransmit the HARQ. If the HARQ feedback information is HARQ NACK in step 445, the UE retransmits data using the same transmission resource 425 at the next HARQ retransmission time.

On the other hand, if it is desired to perform retransmission using a transmission resource different from the previous transmission for any reason at any time, in step 465, the base station allocates a reverse transmission resource for retransmission through the PDCCH. When the terminal receives the retransmission reverse transmission resource, the terminal performs retransmission using the newly allocated transmission resources 430, 435, and 440 instead of the conventional transmission resources 420 and 425. When the base station executes the adaptive retransmission as described above, the reverse transmission resource allocation information for retransmission is lost, so that the terminal allocates the reverse transmission resource for retransmission in order to prevent the terminal from using the transmission resource other than its own transmission resource. The HARQ ACK 450 may be transmitted as the previous HARQ feedback information. The HARQ ACK does not indicate that data has been successfully received, but is to prevent the UE from retransmitting the same transmission resource as the transmission resource used in the previous transmission. If the UE determines the HARQ ACK as a successful transmission of data and executes a subsequent procedure, for example, driving a predetermined timer, retransmission is resumed through an adaptive retransmission process, and the retransmission may have failed. At the same time, it has to accept the inefficiency of canceling all the actions taken since it was determined that the transmission was successful.

Therefore, in the present invention, in order to solve the problem caused by pseudo ACK (received ACK) that can be received in the adaptive retransmission process, the determination on whether or not the successful transmission until the time when no further adaptive retransmission occurs, and further When the time when the above adaptive retransmission does not occur, the transmission success / failure of the data is determined based on the HARQ feedback information received last.

<First embodiment>

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

Referring to FIG. 5, in step 505, a UE is allocated an uplink transmission resource for initial transmission to a HARQ process. In step 510, the UE configures a MAC PDU to be transmitted using the backward transmission resource, and transmits the MAC PDU through a transmission resource allocated at a predetermined time. In step 515, the UE checks whether a transmission resource for initial transmission is allocated to the HARQ process in which the MAC PDU is transmitted. In other words, it is checked whether a transmission resource for initial transmission is allocated at the time of retransmission of the MAC PDU. The allocation of a transmission resource for initial transmission to the HARQ process means that the base station will stop the ongoing HARQ retransmission, which means that adaptive retransmission will no longer occur. Therefore, in step 515, if the first transmission resource is allocated to the HARQ process that has not yet passed the last retransmission time, the UE proceeds to step 525 to determine the success / failure of MAC PDU transmission. On the other hand, in step 515, if the first transmission resource is not allocated to the HARQ process, the terminal proceeds to step 520 and checks whether the last retransmission feedback time has elapsed. The last retransmission feedback time point is a time point at which feedback for the last retransmission of the MAC PDU can be received, and is calculated by Equation 1 below.

Last retransmission feedback time = initial transmission time + HARQ RTT ⅹ Maximum number of retransmissions + ㅿ

In Equation 1, 상기 is a time interval between backward transmission and feedback information transmission and has a fixed value. For example, if the initial transmission time is the x-th subframe, HARQ RTT is 8 subframes, the maximum number of retransmissions is 4, ㅿ is 2 subframes, the last retransmission feedback time is the x + 34th subframe.

In step 520, if the last retransmission time point has not passed, the terminal returns to step 515 and monitors whether a new transmission resource is allocated. On the other hand, in step 520, if the last retransmission time has passed as a result of the check whether the last retransmission feedback time has elapsed, the terminal proceeds to step 525 to determine whether the MAC PDU is successful or failed.

In step 525, the UE checks whether the last HARQ feedback for the corresponding HARQ process or for the MAC PDU to determine transmission success / failure is HARQ ACK or HARQ NACK. In step 525, the UE determines whether the last HARQ feedback for the MAC PDU is HARQ ACK or HARQ NACK. If the last HARQ feedback is HARQ ACK, the terminal proceeds to step 530, and if it is HARQ NACK, proceeds to step 540.

Proceeding to step 530 means that the last HARQ feedback is HARQ ACK. In step 530, the UE considers that the MAC PDU has been successfully transmitted or the transmission of the MAC PDU is completed, and proceeds to step 535 to perform the necessary subsequent procedure. For example, if a predetermined control message is stored in the MAC PDU, a predetermined timer is started or a new procedure triggered by successful transmission of the control message is started.

Proceeding to step 540 means that the last HARQ feedback is HARQ NACK. In step 540, the UE considers that the MAC PDU has not been successfully transmitted or deems that transmission of the MAC PDU is not completed, and proceeds to step 545 to perform the necessary subsequent procedure. For example, if a predetermined control message is stored in the MAC PDU, the retransmission procedure of the control message is started.

6 is a diagram illustrating an example of a terminal operation according to a first embodiment of the present invention.

Referring to FIG. 6, if a reverse transmission resource for initial transmission for the HARQ process x is allocated in step 605, the terminal transmits data in the reverse direction using the allocated transmission resource in step 610. When the UE receives the HARQ NACK for the first transmission in step 615, the UE transmits data using the same transmission resource at the next transmission time in step 617, and receives the HARQ ACK for the transmission in step 620.

In general, the time point at which HARQ ACK is received is the time point at which data transmission is successful, but in the present invention, the terminal does not determine that data transmission is successful at this time point. After that, if the UE is allocated the uplink transmission resource for the first HARQ process x at a point before the last retransmission feedback point in step 625, the UE checks the most recent HARQ feedback for the HARQ process x. Since the last HARQ feedback was ACK, the terminal determines that the transmission of the MAC PDU was successful at this point and performs the necessary subsequent operation.

As another example, if the reverse transmission resource for the initial transmission for the HARQ process x is allocated in step 630, the terminal transmits data in the reverse direction using the allocated transmission resource in step 635. When the UE receives the HARQ NACK for the first transmission in step 640, the UE transmits data using the same transmission resource at the next transmission time in step 645, and receives HARQ ACK for the transmission in step 650.

In the normal case, the terminal determines that the data transmission is successful at the time, but the terminal continuously monitors the control channel to monitor whether the retransmission resource or the initial transmission resource for the process x is allocated. After the last retransmission feedback time has elapsed, the last HARQ feedback is examined in step 655. If the last HARQ feedback is ACK, the terminal determines that the transmission of the MAC PDU is successful and performs the necessary subsequent operation.

7 is a block diagram of a terminal according to the first embodiment of the present invention.

Referring to FIG. 7, the terminal includes a higher layer device 705, a HARQ process 710, a transceiver 725, and a controller 720.

The controller 720 receives the PDCCH control information through the transceiver 725 and controls the transceiver 725 to transmit the packet through a transmission resource recognized through the PDCCH control information. The packet transmission includes HARQ initial transmission, retransmission, and adaptive retransmission.

In addition, when the HARQ transmission of the packet starts, the controller 720 calculates a time of receiving the last feedback of the packet, and for the first transmission of the HARQ process of the packet even after the time elapses or before the time elapses. When the transmission resource is allocated, it is determined whether the packet is successfully transmitted by referring to the last HARQ feedback for the packet and notifies the upper layer device 705 of this.

The transceiver 725 is a device that receives PDCCH control information (first transmission backward transmission resource and initial transmission transmission resource) or HARQ feedback information through a wireless channel and transmits a packet.

The HARQ process 710 is a set of soft buffers configured to perform an HARQ operation and is identified by an HARQ process identifier.

The higher layer apparatus 705 receives a packet successfully received in the HARQ process 710 to perform a predetermined operation or generates a packet to be transmitted through the HARQ process 710 and the transceiver 725. In addition, the higher layer device 705 may perform a predetermined operation such as driving a retransmission timer after the packet is successfully transmitted according to the type of generated packet.

8 is a flowchart illustrating another example of a terminal operation according to the first embodiment of the present invention.

Referring to FIG. 8, in step 805, the UE is allocated an uplink transmission resource for initial transmission to the HARQ process. In step 810, the UE configures a MAC PDU to be transmitted using the backward transmission resource, and transmits the MAC PDU through a transmission resource allocated at a predetermined time. In step 815, HARQ feedback information is received at a predetermined time. In step 815, if the received HARQ feedback is NACK, the terminal proceeds to step 820. If the received HARQ feedback is ACK, the terminal proceeds to step 850.

In step 820, the UE increases the variable called CURRENT_TX_NB by one. The CURRENT_TX_NB will be described later. In step 825, the UE checks whether the CURRENT_TX_NB has reached a predetermined maximum number of transmissions. If the maximum number of transmissions is not reached in step 825, the terminal proceeds to step 830 and retransmits the MAC PDU again. If the maximum number of transmissions is reached, the terminal proceeds to step 835.

Proceeding to step 835, the UE has already performed the maximum number of transmissions and means that no further HARQ retransmission is allowed. In step 835, the UE discards the data stored in the buffer of the HARQ process. In step 840, the UE recognizes that the transmission of the MAC PDU is unsuccessful. In step 845, the UE performs the necessary subsequent procedure. For example, if a predetermined control message is stored in the MAC PDU, the retransmission procedure of the control message is started.

In step 815, if the received HARQ feedback is ACK, the terminal proceeds to step 850 and determines whether a transmission resource for adaptive retransmission is allocated, that is, a grant message indicating adaptive retransmission is received. In step 850, if the grant message indicating the adaptive retransmission has not been received, the terminal proceeds to step 855, and if the grant message is received, proceeds to step 865.

Proceeding to step 855, the HARQ ACK is received but the grant indicating the adaptive retransmission is not received. In a typical HARQ operation in which adaptive retransmission is not considered, when the HARQ ACK is received, data stored in the corresponding HARQ buffer is discarded. However, in the present invention, since adaptive retransmission is considered, the UE does not generate any further adaptive retransmission. The data stored in the HARQ buffer is not discarded until it is not.

In step 855, the UE waits until the next transmission occasion, and increases the CURRENT_TX_NB by 1 at the transmission possible time, and proceeds to step 860. It should be noted that step 855 is a situation after the UE receives the ACK with HARQ feedback, and thus, backward transmission is not performed at the transmittable time. In the present invention, in order to determine when adaptive retransmission will no longer occur, the CURRENT_TX_NB is increased by one regardless of whether or not backward transmission occurs whenever a transmission possible time elapses. In the CURRENT_TX_NB, a value indicating how many HARQ transmissions the UE has performed on a certain MAC PDU is usually stored, but in the present invention, the CURRENT_TX_NB indicates how many transmission time points have elapsed since the UE started initial transmission of any MAC PDU. Is stored. The time point at which transmission is possible will be described in more detail with reference to FIG. 9.

FIG. 9 is a diagram illustrating a transmittable time point and a retransmission grant time point in another example of a terminal operation according to the first embodiment of the present invention.

Receiving an initial transmission grant message for any HARQ process x at any point in time (905), the UE uses the allocated transmission resource in a TTI that is 4 TTIs away from the TTI that received the initial transmission grant message. Initial transmission is performed (910). For example, if the time point at which the first transmission grant message is received is an arbitrary y-th TTI, the actual time point at which the first transmission is performed is the (y + 4) th TTI. The UE may then perform HARQ retransmission for the MAC PDU every eighth TTI. The HARQ retransmission is allowed until the CURRENT_TX_NB reaches the maximum number of transmissions. In the present invention, the TTIs capable of performing HARQ transmission or retransmission by the UE are referred to as transmission occassion. Assuming the maximum number of transmissions as 4, in FIG. 9, 910, 920, 930, and 940 correspond to transmission time points. When the UE receives the NACK at the previous feedback time point or receives a grant message indicating the adaptive retransmission at the previous retransmission grant occassion, the UE performs backward transmission at the time at which transmission is possible; Do not perform reverse transmission. The feedback time point is a time point spaced apart by 4 TTIs from when the backward transmission is performed. In FIG. 9, 915, 925, 935, and 945 may be feedback points or not depending on whether backward transmission is performed at the time at which transmission is possible. The retransmission grant time point is a time point at which a grant message indicating adaptive retransmission can be received, and between the time point 905 at which the grant indicating the first transmission is received and the last time point 940 at which the first transmission is received, the first transmission is received. TTIs spaced apart by a multiple of 8 from the time point. That is, 915, 925, and 935 correspond to retransmission grant points. Note that in most cases, the retransmission grant time and the feedback time point are the same. This is because the feedback time point is followed by 4 TTIs from any backward transmission, and the retransmission grant time is preceded by 4 TTIs from any backward transmission.

As shown in FIG. 9, the terminal receiving the grant message indicating the initial transmission may determine a transmission possible time and a retransmission grant time based on the time point as follows. In the following equation, y is the time point at which the grant message indicating the first transmission is received, and n is the maximum number of transmissions.

Sendable time point = (y + 4) th TTI, (y + 4 + 1 x 8) th TTI, (y + 4 + 2 x 8) th TTI, .., (y + 4 + (n-1) x 8 ) TTI

Retransmission grant time = (y + 1 x 8) th TTI, (y + 2 x 8) th TTI, .., (y + (n-1) x 8) th TTI

In the present invention, the UE increases CURRENT_TX_NB by 1 whenever the transmittable time calculated as described above passes and checks whether a grant message indicating adaptive retransmission is received by checking the PDCCH at each retransmission grant time.

In step 860 of FIG. 8, the UE checks whether the CURRENT_TX_NB has reached the maximum number of transmissions. When the CURRENT_TX_NB has reached the maximum number of transmissions, it means that the adaptive retransmission will no longer be performed, and the ACK received in step 815 is not a pseudo ACK.

In step 875, the UE discards the data stored in the HARQ buffer and proceeds to step 880 to determine that the MAC PDU transmission is successful. Thereafter, in step 885, the UE takes necessary follow-up actions, for example, driving a timer related to a control message stored in the MAC PDU.

In step 860, if the CURRENT_TX_NB has not reached the maximum number of transmissions, it means that there is a possibility that adaptive retransmission is performed in the future. After the UE waits until the next retransmission grant time, the UE proceeds to step 850 and is adaptive. Check that a grant message indicating retransmission is received. When the grant message indicating the adaptive retransmission is received in step 850, the terminal proceeds to step 865 to increase the CURRENT_TX_NB by 1 and proceeds to step 870 when the grant message is spaced apart by 4 TTIs from the time when the grant message is received. The MAC PDU is retransmitted using the transmission resource indicated in the grant message. In step 815, the HARQ feedback is checked.

Second Embodiment

In the second embodiment of the present invention, DRX (Discontinuous Reception) is applied in LTE to prolong the battery life of the terminal. In the DRX process, the UE receives the PDCCH only for a predetermined period of time, thereby minimizing power consumption generated when the receiver is kept on. When transmitting reverse data, the UE performs an operation for reverse data transmission even during the DRX process.

10 is a diagram illustrating a process of transmitting reverse data during a DRX operation according to a second embodiment of the present invention.

Referring to FIG. 10, when backward data occurs during a period (after a sleep period) defined in the terminal in the DRX operation to turn off the receiver in step 1005, the terminal may refer to a scheduling request as a predetermined reverse transmission resource. Send 1 bit information. The terminal maintains an activation period until a grant message for allocating backward transmission resources is received at the time when the scheduling request is transmitted.

In step 1010, when the terminal receives the grant message for allocating the uplink transmission resource, the UE drives a predetermined timer called an inactivity timer (1010). The timer is restarted each time the grant message is received, and when the timer expires in step 1015, the terminal turns off the receiver. For convenience of description below, terms related to DRX are defined as follows.

Active period: A period of time defined to receive a PDCCH during DRX operation. Typically, the period during which the activity measurement timer is running is included in the activation period.

Sleep period: A period of time defined during which DRX operation does not require receiving a PDCCH. Sleep period is the rest of the period except the activation period.

According to the second embodiment of the present invention, if the reverse MAC PDU in which HARQ transmission is not completed at the time when an activity timer expires, HARQ process in which HARQ transmission of the MAC PDU is performed until transmission of the MAC PDU is completed The receiver is turned on at each retransmission grant time and the channel on which the grant message is transmitted is monitored. Hereinafter, for convenience of description, a channel on which a grant message is transmitted is referred to as a physical downlink control channel (PDCCH).

The UE also performs backward transmission when receiving a NACK with previous HARQ feedback or a grant message indicating adaptive retransmission. At this time, the PDCCH of the forward subframe positioned on the time axis among the forward subframes overlapping the reverse subframe in which the backward transmission is performed is received.

In other words, if there is a reverse MAC PDU for which HARQ transmission is not yet completed at the time when the activity measurement timer expires, the following TTIs are added to the activation period, and the UE receives the PDCCH in the lower TTI.

1. TTI corresponding to retransmission grant time of reverse MAC PDU in which HARQ transmission is not completed.

2. A TTI located backward in time among forward TTIs that overlap with the reverse TTI in which the retransmission is performed when retransmission of the reverse MAC PDU in which HARQ transmission is not completed.

11 is a diagram illustrating an example of a terminal operation according to a second embodiment of the present invention.

In FIG. 11, reference numerals 1150 to 1180 denote high receivers as shown in FIG. 10, and low receivers indicate a receiver off state.

Referring to FIG. 11, when the activity measurement timer expires in step 1105, there is one reverse MAC PDU for which HARQ transmission is not completed. HARQ transmission of any reverse MAC PDU is not complete corresponds to case 1 and case 2 below.

Case 1. The last HARQ feedback for any MAC PDU was ACK, and the last retransmission grant time has not passed.

Case 2. The last HARQ feedback for any MAC PDU was NACK, and the last transmittable time has not elapsed.

If the reverse MAC PDU in which the HARQ transmission is not completed when the activity measurement timer expires corresponds to case 1, the UE turns on the receiver at the next retransmission grant time point 1130 and receives the PDCCH to indicate adaptive retransmission. Determine if it works.

If the adaptive retransmission is not indicated, the UE maintains the sleep period until the next retransmission grant time point 1135 and transitions to the activation period 1160 at the next retransmission grant time point 1135 to receive the PDCCH. If a grant message indicating adaptive retransmission is not received at the retransmission grant time point 1135, the UE proceeds to the last retransmission grant time point 1140, and when the last retransmission grant time point 1140 elapses, Discard the data stored in the buffer, it is determined that the transmission of the MAC PDU successfully completed. Then start the sleep section.

If the reverse MAC PDU in which HARQ transmission is not completed when the activity measurement timer expires corresponds to case 2, the terminal performs backward transmission at the next transmission possible time 1115. In operation 1155, the PDCCH is received at the forward TTI located later in time among the forward TTIs overlapping with the uplink transmission time. The terminal repeats the process until receiving the HARQ ACK or until the last transmission possible time 1125 elapses.

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

When the activity measurement timer expires in step 1205, the UE proceeds to step 1210 and checks whether there is a reverse MAC PDU for which HARQ operation is not completed. If there is a reverse MAC PDU, the UE proceeds to step 1215. Proceed to step 1235. In step 1235, since the UE has completed the operation of all HARQ processes, the UE recognizes that the activation period due to backward transmission no longer exists, and performs an appropriate operation such as transitioning to the sleep period.

As described above, if there is a reverse MAC PDU corresponding to case 1 or case 2, HARQ operation of the corresponding reverse HARQ process is not completed.

After waiting until the next transmittable point in step 1215, the UE determines whether to perform retransmission of the reverse MAC PDU, and when retransmitting the reverse MAC PDU, in a forward subframe associated with a reverse subframe in which reverse transmission is performed. Receive the PDCCH. In this case, the UE performs retransmission of the MAC PDU when the last HARQ feedback is HARQ NACK or when a grant message indicating adaptive retransmission is received at a previous retransmission grant time.

The forward subframe associated with the reverse subframe in which retransmission is performed refers to a forward subframe located in time later among the forward subframes overlapping with the reverse subframe in which backward transmission is performed, as described with reference to FIG. 11.

In step 1220, the UE checks whether the last transmittable time has elapsed, and if the last transmittable time has elapsed, since the transmission of the MAC PDU or the HARQ operation of the HARQ process is completed, the UE returns to step 1210 to complete the HARQ operation. Check if there is another HARQ process that is not present.

If the last transmittable time has not passed in step 1220, the terminal proceeds to step 1225 and receives a PDCCH at a next retransmission grant time. In step 1230, the UE checks whether the retransmission grant time was the last retransmission grant time, and returns to step 1215 when the retransmission grant time is not the last retransmission grant time, and when the last retransmission grant time is HARQ operation of the corresponding HARQ process Since it is completed, the process returns to step 1210 to check whether there is another HARQ process for which the HARQ operation is not completed.

13 is a block diagram of a terminal according to a second embodiment of the present invention.

Referring to FIG. 13, the terminal includes a higher layer device 1305, an HARQ process 1310, a transceiver 1325, and a DRX controller 1320.

When the activity measurement timer expires, the DRX controller 1320 checks whether there is a reverse HARQ process in which HARQ operation is not completed and receives and transmits a PDCCH at every retransmission grant time of HARQ processes in which HARQ operation is not completed. ). When retransmission is performed to HARQ processes for which the HARQ operation is not completed, the transceiver 1325 controls the transceiver 1325 to receive a PDCCH in a forward subframe associated with a reverse subframe in which the retransmission is performed.

The transceiver 1325 receives PDCCH control information or HARQ feedback information through a wireless channel and transmits a packet.

The HARQ process 1310 is a set of soft buffers configured to perform an HARQ operation and is identified by an HARQ process identifier.

The higher layer apparatus 1305 receives a packet successfully received in the HARQ process 1310 to perform a predetermined operation or generates a packet to be transmitted through the HARQ process 1310 and the transceiver 1325.

Third Embodiment

In the third embodiment of the present invention, when the terminal transmits a reverse packet through a predetermined transmission resource, the battery life of the terminal is further extended by not monitoring the PDCCH at the time of the retransmission grant.

Recently, various methods for efficiently supporting VoIP have been studied in a mobile communication system that has recently been standardized, such as LTE. For example, a semi-permanent transmission resource allocation scheme (Semi-Permanent Scheduling, SPS). When an arbitrary transmission resource is allocated as a semi-persistent transmission resource, the SPS transmits a packet having a predetermined size by applying a predetermined MCS through the transmission resource at regular intervals. In this case, since synchronous HARQ is applied, when the UE receives the HARQ NACK for the transmitted packet, the UE retransmits the packet using the same transmission resource when the HARQ RTT (Round Trip Time) has elapsed. Even if the UE receives the HARQ ACK after transmitting the VoIP packet through the SPS transmission resource, the terminal monitors the PDCCH every time a reverse grant can be received until the maximum retransmission time of the packet elapses. This substantially causes the UE to monitor the PDCCH every 4 msec, which is a factor in reducing the DRX efficiency.

According to the third embodiment of the present invention, when a packet is transmitted through an SPS transmission resource, the UE preliminarily prohibits adaptive retransmission at the time of retransmission grant after HARQ ACK is transmitted and received, so that the UE frequently monitors the PDCCH. Eliminate inefficiency.

14 is a diagram illustrating an example of a terminal operation according to a third embodiment of the present invention.

Referring to FIG. 14, in step 1405, a UE to which an SPS transmission resource is allocated starts MAC PDU transmission. That is, in step 1405, the UE is allocated an SPS transmission resource or a general reverse transmission resource through a predetermined path, and transmits a MAC PDU for the first time through the SPS transmission resource or the general reverse transmission resource. In step 1410, the UE checks whether the MAC PDU is transmitted as an SPS transmission resource. If the MAC PDU is transmitted to the SPS transmission resource in step 1410, the flow proceeds to step 1415. If the MAC PDU is transmitted to the general transmission resource instead of the SPS transmission resource, the flow proceeds to step 1420.

In step 1415, when the UE transmits the MAC PDU using the SPS transmission resource, it is determined that the adaptive retransmission is not indicated at the retransmission grant time after receiving the HARQ ACK for the MAC PDU. The reverse grant indicative of adaptive retransmission is included in the activation period until the HARQ ACK is received and no HARQ ACK is received. In other words, the UE transitions to an activation period at the retransmission grant times to monitor the PDCCH. The retransmission grant time point may be defined as a time point at which a reverse grant for a current HARQ retransmission can be transmitted and received. HARQ retransmission for any HARQ process is currently in progress means that the last transmission time of the MAC PDU stored in the HARQ process has not yet passed.

In general, since a subframe in which HARQ ACK / NACK is received and a retransmission grant time point are the same subframe, the UE may receive only HARQ ACK in an arbitrary subframe or simultaneously receive a reverse grant indicating HARQ ACK and adaptive retransmission. . The reverse grant indicative of adaptive retransmission for any MAC PDU includes all retransmission grant times up to the time of activation until only HARQ ACK is received without being received.

On the other hand, if the SPS transmission resource is not used to transmit the MAC PDU in step 1410, as in the second embodiment of the present invention, the UE checks all retransmission grant points until the last transmission point of the MAC PDU passes in step 1420. Include in the activation period.

In order to simplify the operation of the terminal, the determination process of step 1410 may be based on whether there is an SPS transmission resource allocated to the terminal at the corresponding time. That is, in step 1410, if the UE has an SPS transmission resource set in a certain subframe, it may proceed to step 1415, and if it does not have an SPS transmission resource, it may proceed to step 1420.

If the terminal does not store data in any HARQ buffer, retransmission for the HARQ process is impossible, and the terminal does not need to monitor the retransmission grant time for the HARQ process. Therefore, in the present invention, by adjusting the time point at which the UE flushes the HARQ buffer, it is possible to eliminate the inefficiency of the UE to monitor the PDCCH frequently.

15 is a diagram illustrating another example of the operation of the terminal according to the third embodiment of the present invention. It was.

Referring to FIG. 15, in step 1505, a UE does not receive a reverse grant indicating adaptive retransmission and receives a HARQ ACK for a MAC PDU.

In step 1510, the UE checks whether the MAC PDU is transmitted through an SPS transmission resource. In step 1510, if the MAC PDU is transmitted through the SPS transmission resources, the UE proceeds to step 1515 to remove the MAC PDU from the HARQ buffer, so that the future retransmission grant time of the MAC PDU is included in the activation time of the UE prevent.

In contrast, in step 1510, if the MAC PDU is transmitted through a general transmission resource rather than an SPS transmission resource, the terminal proceeds to step 1520 to prepare for future retransmission without removing the MAC PDU stored in a HARQ buffer.

In the third embodiment of the present invention, when the SPS transmission resource is used, only the retransmission grant time point until the HARQ ACK is received is included in the activation period or the HARQ buffer is flushed at the time when only the HARQ ACK is received. Proposed ways to extend the

In order to further provide an adaptive retransmission opportunity, the operation of the third embodiment includes the activation period until the nth, for example, the first, retransmission grant time after the time when only the HARQ ACK is received, or only the HARQ ACK is received. If a reverse grant indicating adaptive retransmission is not received until the nth, for example, first, retransmission grant point after the time point, it may be modified to flush the corresponding HARQ buffer.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the appended claims, but also by the equivalents of the claims.

Claims (7)

In the method of determining whether the transmission of the MAC PDU (Medium Access Control Protocal Data Unit) in the mobile communication system, Check whether the transmission resource for the first transmission is allocated at the time of retransmission of the MAC PDU, and if the transmission resource for the first transmission is allocated, whether the last Hybrid Automatic Retransmission reQuest (HARQ) feedback for the MAC PDU is a normal response (ACK) or a negative response. A first process of determining whether the transmission is successful by checking whether or not the packet is NACK; If the transmission resource for the first transmission is not allocated, it is checked whether the last retransmission feedback time has elapsed, and when the last retransmission feedback time has passed, whether the last HARQ feedback for the MAC PDU is the normal response or the negative response. And a second process of determining whether the transmission is successful by determining whether the transmission is successful. The method of claim 1, wherein before the first process, a MAC PDU to be transmitted is configured by using an uplink transmission resource allocated for the HARQ process, and the MAC PDU is transmitted through the allocated first transmission reverse transmission resource. And determining whether the MAC PDU is successfully transmitted in the mobile communication system. The method of claim 1, wherein if the last retransmission feedback time has not elapsed in the second process, the mobile station returns to the first process. The method of claim 1, wherein the last retransmission feedback time point is calculated by Equation 2 below. <Equation 2> Last retransmission feedback time = initial transmission time + HARQ RTT ⅹ Maximum number of retransmissions + ㅿ In Equation 2, k is a time interval between backward transmission and feedback information transmission and has a fixed value. In the apparatus for determining whether the transmission of the MAC Medium Access Control Protocol Data Unit (PDU) in the mobile communication system, A transceiver for receiving PDCCH control information and HARQ feedback information through a wireless channel and transmitting the MAC PDU; At the time of retransmission of the MAC PDU, it is checked whether the transmission resource for the first transmission is allocated among the received PDCCH control information. If the transmission resource for the first transmission is allocated, the last Hybrid Automatic Retransmission reQuest (HARQ) feedback on the MAC PDU is normal. (ACK) or NACK to determine whether the transmission was successful, If the transmission resource for the first transmission is not allocated, it is checked whether the last retransmission feedback time has elapsed, and when the last retransmission feedback time has elapsed, is the last HARQ feedback for the MAC PDU the normal response (ACK) or the negative response ( And a control unit for determining whether the transmission is successful by checking whether it is NACK). The method of claim 5, wherein the control unit, And if the last retransmission feedback time has not elapsed, checking whether the first transmission resource is allocated again at the time of retransmission of the MAC PDU. 6. The apparatus of claim 5, wherein the last retransmission feedback time point is calculated by Equation 3 below. 7. <Equation 3> Last retransmission feedback time = initial transmission time + HARQ RTT ⅹ Maximum number of retransmissions + ㅿ In Equation 3, ㅿ is a time interval between backward transmission and feedback information transmission and has a fixed value.