KR20100045860A - Method and user equipment of detecting problem of data transmission - Google Patents

Abstract

According to an embodiment of the present invention, a method for detecting a data transmission problem of a UM terminal includes transmitting data to a network, and when the data is successfully received through the network, a hybrid ARQ as a response signal for receiving the data. Receiving an acknowledgment (ACK) from the network as a response signal when the network fails to receive the data, and receiving the HARQ NACK due to a failure in transmitting and retransmitting the data. Determining that the transmission of the data has failed, increasing the counter value of the transmission failure counter, and detecting that there is a problem in the data transmission when the counter value reaches a threshold. do. If there is a problem with data transmission, you can quickly identify it.

Description

METHOD AND USER EQUIPMENT OF DETECTING PROBLEM OF DATA TRANSMISSION}

The present invention relates to wireless communication, and more particularly to a method for detecting a problem in data transmission.

The next generation wireless communication system aiming at providing various multimedia services is to guarantee a certain level or more of quality for each service provided by subscribers. Recently, wireless communication systems have been developed to satisfy high frequency efficiency and reliable communication requirements. Unfortunately, due to the fading channel environment and interference due to various causes, packet errors limit the capacity of the entire system.

Problems with data transmission often occur due to changes in the wireless environment or problems within the network or the terminal. In this situation, when data transmission is attempted, data is not normally received by the receiving end, and data transmission eventually fails. And data retransmission is performed repeatedly.

In order to solve the situation where only unconditional retransmission of data is repeated, and to solve the problem, a method of detecting data transmission failure by first evaluating a data transmission failure or repetitive retransmission status is required.

The present invention seeks to provide a method for discovering a problem in data transmission occurring in an unacknowledged mode (UM) terminal to guarantee a quality of service and to quickly solve a problem such as a data transmission failure.

According to an aspect of the present invention, a data transmission problem detection method includes transmitting data to a network, and when the data is successfully received through the network, a HARQ (Hybrid ARQ) ACK (ACK) as a response signal for receiving the data. Acknowledgment), if the network fails to receive the data, receiving a HARQ NACK (Negative-acknowledgement) from the network as a response signal; maximum HARQ NACK for the data due to a failure in transmitting and retransmitting the data. If it is received more than the number of times of transmission, it is determined that the transmission of the data has failed, and increasing the counter value of the transmission failure counter, and if the counter value reaches a threshold, detecting the problem of data transmission.

According to another aspect of the present invention, a data transmission problem detection terminal includes an RF unit for supporting an unacknowledged mode (UM) and transmitting and receiving a radio signal; And a processor connected to the RF unit, wherein the processor transmits data to a network and receives a HARQ NACK exceeding the maximum number of transmissions for the data indicating that the network has failed to receive the data. It is determined that the transmission failure, the counter value of the transmission failure counter is increased, and if the counter value exceeds the threshold, it is detected that a problem has occurred in the transmission of the data.

When a problem occurs in data transmission in a UM (Unacknowledged Mode) terminal, it is possible to quickly detect a problem in data transmission based on a predetermined criterion.

1 is a block diagram illustrating a wireless communication system. This may be a network structure of an Evolved-Universal Mobile Telecommunications System (E-UMTS). The E-UMTS system may be referred to as a Long Term Evolution (LTE) system. Wireless communication systems are widely deployed to provide various communication services such as voice, packet data, and the like.

Referring to FIG. 1, an Evolved-UMTS Terrestrial Radio Access Network (E-UTRAN) includes a base station (BS) 20 that provides a control plane and a user plane.

The UE 10 may be fixed or mobile and may be called by other terms such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), a wireless device, and the like. A base station (BS) 20 generally refers to a fixed station communicating with the terminal 10, and includes an evolved-NodeB (eNB), a base transceiver system (BTS), an access point, and the like. It may be called in other terms. One base station 20 may provide a service for at least one cell. The cell is an area where the base station 20 provides a communication service. An interface for transmitting user traffic or control traffic may be used between the base stations 20. Hereinafter, downlink means communication from the base station 20 to the terminal 10, and uplink means communication from the terminal 10 to the base station 20.

The base stations 20 may be connected to each other through an X2 interface. The base station 20 is connected to an Evolved Packet Core (EPC), more specifically, a Mobility Management Entity (MME) / Serving Gateway (S-GW) 30 through an S1 interface. The S1 interface supports a many-to-many-relation between base station 20 and MME / S-GW 30.

2 is a block diagram illustrating a functional split between an E-UTRAN and an EPC. The hatched box represents the radio protocol layer and the white box represents the functional entity of the control plane.

Referring to FIG. 2, the base station performs the following function. (1) Radio Resource Management such as Radio Bearer Control, Radio Admission Control, Connection Mobility Control, Dynamic Resource Allocation to UE RRM), (2) Internet Protocol (IP) header compression and encryption of user data streams, (3) routing of user plane data to S-GW, and (4) paging messages. Scheduling and transmission, (5) scheduling and transmission of broadcast information, and (6) measurement and measurement reporting settings for mobility and scheduling.

The MME performs the following functions. (1) Non-Access Stratum (NAS) signaling, (2) NAS signaling security, (3) Idle mode UE Reachability, (4) Tracking Area list management , (5) Roaming, (6) Authentication.

S-GW performs the following functions. (1) mobility anchoring, (2) lawful interception. P-GW (P-Gateway) performs the following functions. (1) terminal IP (allocation) allocation (allocation), (2) packet filtering.

3 is a block diagram illustrating elements of a terminal. The terminal 50 includes a processor 51, a memory 52, an RF unit 53, a display unit 54, and a user interface unit 55. . The processor 51 is implemented with layers of the air interface protocol to provide a control plane and a user plane. The functions of each layer may be implemented through the processor 51. The memory 52 is connected to the processor 51 to store a terminal driving system, an application, and a general file. The display unit 54 displays various information of the terminal, and may use well-known elements such as liquid crystal display (LCD) and organic light emitting diodes (OLED). The user interface unit 55 may be a combination of a well-known user interface such as a keypad or a touch screen. The RF unit 53 is connected to a processor and transmits and / or receives a radio signal.

4 is a block diagram illustrating an Open System Interconnection (OSI) model. The OSI model is a model for protocol structures that are well known in communication systems.

Referring to FIG. 4, the OSI model is composed of seven layers. The OSI model includes a data link layer, a network layer, a transport layer, a session layer, and a presentation layer from the first layer, a physical layer. And an application layer. The application layer belonging to the seventh layer provides access to the OSI environment of the user and provides distributed information services.

Layers of a radio interface protocol between the terminal and the network may be divided into L1 (first layer), L2 (second layer), and L3 (third layer) based on the lower three layers of the OSI model. have. Among them, the physical layer belonging to the first layer provides an information transfer service using a physical channel. The second layer is again divided into three modules. The three modules are a Medium Access Control (MAC) layer, a Radio Link Control (RLC) layer, and a Packet Data Convergence Protocol (PDCP) layer. A radio resource control (hereinafter referred to as RRC) layer located in a third layer plays a role of controlling radio resources between a terminal and a network. To this end, the RRC layer exchanges RRC messages between the UE and the network.

FIG. 5 is a block diagram illustrating a radio protocol architecture for the user plane. 6 is a block diagram illustrating a radio protocol structure for a control plane. This shows the structure of the air interface protocol between the terminal and the E-UTRAN. The user plane is a protocol stack for user data transmission, and the control plane is a protocol stack for control signal transmission.

5 and 6, a physical layer (PHY), which is a first layer, provides an information transfer service to a higher layer using a physical channel. The physical layer is connected to the upper MAC layer through a transport channel, and data between the MAC layer and the physical layer moves through the transport channel. Data moves between physical layers between physical layers, that is, between physical layers of a transmitting side and a receiving side.

The MAC layer of the second layer transmits uplink data through the UL-SCH. The MAC layer generates a MAC Protocol Data Unit (PDU) according to the uplink radio resource allocation information and transmits the MAC PDU through the UL-SCH using a HARQ process.

The HARQ retransmission scheme can be divided into synchronous and asynchronous. Synchronous HARQ retransmits data at a time point known to both the transmitter and the receiver, thereby reducing signaling required for data transmission such as a HARQ processor number. Asynchronous HARQ is a method of allocating resources at random times for retransmission, and requires overhead for data transmission.

HARQ may be classified into adaptive HARQ and nonadaptive HARQ according to transmission attributes such as resource allocation, modulation technique, transport block size, and the like. Adaptive HARQ is a method in which transmission attributes used for retransmission are changed in whole or in part compared to initial transmission according to a change in channel conditions. Non-adaptive HARQ is a method of continuously using the transmission attribute used for the initial transmission regardless of the change in channel conditions.

If an error is not detected in the received data, the receiver transmits a HARQ ACK (Acknowledgement) signal as a response signal to inform the transmitter of the reception success. When an error is detected in the received data, the receiver transmits a HARQ NACK (Negative-acknowledgement) signal as a response signal to inform the transmitter of the error detection. The transmitter may retransmit data when the HARQ NACK signal is received.

In addition, the MAC layer receives HARQ ACK / NACK corresponding to the transmitted MAC PDU. When the terminal receives the HARQ ACK corresponding to the transmission of the MAC PDU, the data transmission is completed. If the UE receives the HARQ NACK but does not reach the maximum number of transmissions, the MAC PDU is retransmitted. If the maximum number of transmissions is reached while receiving the HARQ NACK, the MAC of the UE notifies the RLC of the UE of the transmission failure. Here, the maximum number of transmissions refers to the maximum number of retransmissions performed until it is determined that transmission fails for one data. Therefore, the MAC of the terminal that fails to transmit data receives a HARQ NACK whenever the data is retransmitted up to the maximum number of transmissions. That is, the MAC layer provides a service to an RLC layer, which is a higher layer, through a logical channel. The RLC layer of the second layer supports reliable data transmission. In the RLC layer of the UE, there are three operating modes according to a data transmission method: TM (Transparent Mode), UM (Unacknowledged Mode), and AM (Acknowledged Mode).

Hereinafter, the RLC in the second layer will be described in more detail.

The basic function of the RLC layer is to guarantee the quality of service (QoS) of each radio bearer (RB) and to transmit data. Since the radio bearer service is a service provided by the second layer of the radio protocol to the upper level, the entire second layer affects the quality of service, and among them, the RLC is particularly affected.

RLC sets independent RLC entities for each radio bearer in order to guarantee unique quality of service of the radio bearer, and in order to support various quality of service, as described above, transparent mode (TM), non-responsive mode (UM) and Three modes of response mode (AM) are provided. Since the three RLC modes support different QoS, each of the three RLC modes has a different operation method, and its detailed functions are also different. Therefore, each operation mode (TM, UM and AM) of the RLC will be described in more detail.

TM RLC is a mode that does not add any overhead to the RLC SDU received from the upper layer when configuring the RLC PDU. That is, it is called TM RLC because the RLC transparently passes the SDU. With this characteristic, the TM RLC plays the following roles in the user plane and the control plane.

In general, TM RLC is mainly responsible for the transmission of real-time circuit data such as voice and streaming in the Circuit Service domain (CS domain), because the data processing time in the RLC is short in the user plane. Since there is no overhead, the uplink is responsible for the transmission of the RRC message from the unspecified terminal, and the downlink is responsible for the transmission of the RRC message broadcast to all terminals in the cell.

Unlike transparent mode (TM), a mode in which overhead is added in RLC is called non-transparent mode, and in non-transparent mode, UM (no response mode) and response without acknowledgment of transmitted data are provided. There is an AM (response mode). The UM RLC attaches a PDU header including a sequence number (SN) to each PDU (Protocol Data Unit), so that the receiver can know which PDU is lost during transmission.

Because of this feature, UM RLC is mainly responsible for the transmission of broadcast / multicast data in the user plane or for real-time packet data such as voice (eg VoIP) or streaming in the PS domain. It is responsible for transmitting an RRC message that does not need an acknowledgment response among RRC messages transmitted to a specific terminal or a specific terminal group within.

One of the non-transparent modes, the AM RLC, the AM RLC provides a bidirectional data transmission service, and supports retransmission when a transmission failure of the RLC Protocol Data Unit (PDU) occurs. Like the UM RLC, the PDU is configured by attaching a PDU header including an SN when configuring the PDU. However, unlike the UM RLC, there is a big difference in that the receiver responds to the PDU transmitted by the sender. The reason why the receiver responds in the AM RLC is to request the transmitter to retransmit the PDU that it did not receive.

The AM RLC aims to guarantee error-free data transmission through retransmission, and for this purpose, AM RLC is mainly intended for the transmission of non-real time packet data such as TCP / IP in the packet service area in the user plane. The control plane is responsible for the transmission of the RRC message that must receive an acknowledgment response among the RRC messages transmitted to a specific terminal in the cell.

In terms of directionality, the TM RLC and UM RLC are used for uni-directional communication, whereas the AM RLC is used for bi-directional communication because there is feedback from the receiving side. Since the bidirectional communication is mainly used in point-to-point communication, the AM RLC uses only a dedicated logical channel.

In addition, in terms of structure, TM RLC and UM RLC have a structure in which one RLC entity transmits or receives, whereas an AM RLC has both a transmitter and a receiver in one RLC entity.

Meanwhile, the PDCP layer of the second layer performs a header compression function to reduce the header size of the IP packet.

The radio resource control (RRC) layer of the third layer is defined only in the control plane. The RRC layer is responsible for controlling logical channels, transport channels, and physical channels in connection with configuration, re-configuration, and release of radio bearers (hereinafter, RBs). RB means a service provided by the second layer for data transmission between the UE and the E-UTRAN. If there is an RRC connection (RRC Connection) between the RRC of the terminal and the RRC of the network, the terminal is in the RRC Connected Mode, otherwise it is in the RRC Idle Mode.

The non-access stratum (NAS) layer located above the RRC layer performs functions such as session management and mobility management.

7 is a block diagram illustrating a data transmission method.

Referring to FIG. 7, the RRC of the base station transmits signaling data to the RRC of the terminal. The signaling data is an RRC Connection Setup message or an RRC Connection Reconfiguration message. The RRC Connection Setup message is used to establish a Signaling Radio Bearer (SRB). SRB is an RB used for RRC message or NAS message transmission.

The RRC connection reset message is a message for modifying an RRC connection. The RRC connection reconfiguration message may include a radio resource configuration message. The radio resource configuration message can be used to setup, modify or release the RB. The radio resource configuration message may include a PDCP configuration message, an RLC configuration message, and the like. The PDCP configuration message includes a PDCP configurable PDCP parameter required for PDCP entity formation. For example, the PDCP configuration parameter includes a discard timer (Discard_Timer) parameter. The discard timer parameter is information about an operation duration of the discard timer.

The RLC setup message contains the RLC setup parameters required for the RLC entity formation. For example, the RLC configuration parameter includes a sequence number (SN) field length (SN-FieldLength) parameter. The sequence number field length parameter is information about the length of the sequence number field included in the header of the RLC PDU.

The RRC of the terminal delivers a PDCP configuration request (PDCP_CONFIG_REQ) message, which is signaling data, to the PDCP of the terminal. The PDCP configuration request message may be delivered through a control-service access point (C-SAP). The PDCP configuration request message is a message requesting to configure PDCP according to the PDCP configuration parameter. PDCP generates a discard timer according to the PDCP configuration parameters. The operation interval of the discard timer is determined according to the PDCP configuration parameter. That is, the expiry time of the discard timer is determined according to the user data reception time and the PDCP configuration parameter.

The application of the terminal delivers user data to the PDCP of the terminal. User data is an IP packet. User data may be delivered via PDCP-SAP. The PDCP starts a discard timer upon receipt of user data. The user data is subjected to header compression and ciphering, and then a PDCP header is added to form an RLC Service Data Unit (SDU). The PDCP of the terminal delivers the RLC SDU to the RLC of the terminal. RLC SDU may be delivered via RLC-SAP. If the user data is not transmitted until the discard timer expires, the terminal discards the user data.

8 is a flowchart illustrating a method of transmitting user data.

Referring to FIG. 8, the application of the terminal transmits a first PDCP data request (PDCP_DATA_REQ_1) message to the PDCP of the terminal (S10). The first PDCP data request message includes first user data User Data_1. The PDCP of the terminal starts a first discard timer Disccard_Timer_1 for the first user data (S11). The PDCP of the terminal transmits first user data to the PDCP of the base station (S12). The PDCP of the base station delivers a first PDCP data indication (PDCP_DATA_IND_1) message to the application of the base station (S13). The first PDCP data indication message includes first user data.

The application of the terminal transmits an N-th PDCP data request (PDCP_DATA_REQ_N) message to the PDCP of the terminal (S14). The N-th PDCP data request message includes N-th user data (User Data_N). The PDCP of the terminal starts the N-th discard timer Disc_Timer_N for the N-th user data (S15). The first discard timer expires (S16). The N-th discard timer expires (S17). After expiration of the N-th discard timer, the terminal checks whether the N-th user data is transmitted. Since the N-th user data is not transmitted until the N-th discard timer expires, the terminal discards the N-th user data (S18).

The application of the terminal retransmits the N-th PDCP data request message to the PDCP of the terminal (S19). This is the first retransmission. The PDCP of the terminal starts an N-th discard timer for N-th user data (S20). The N-th discard timer expires (S21). Since the N-th user data is not transmitted until the N-th discard timer expires, the terminal discards the N-th user data (S22). The application of the terminal re-delivers the N-th user data to the PDCP of the terminal (S23). This is the second retransmission.

9 is a block diagram illustrating a data transmission / reception method between an RLC entity of a transmitter and an RLC entity of a receiver. Indicates operation in UM mode.

Referring to FIG. 9, an RLC of a transmitter receives an RLC Service Data Unit (SDU) from a higher layer. For example, the upper layer is an RRC layer or PDCP layer.

The RLC of the transmitter stores the received RLC SDU in a transmission buffer. The RLC of the transmitter forms an RLC PDU from the received RLC SDUs. The RLC of the transmitter divides and concatenates RLC SDUs according to a TB (Transport Block) size, and adds a header to form an RLC PDU.

In this case, the header may include a sequence number (SN) field. The sequence number field indicates the transmission order of the RLC PDU. The length of the sequence number field is 5 bits or 10 bits. The length of the sequence number field is determined according to the RLC configuration parameter transmitted by the base station to the terminal.

The RLC of the transmitter delivers an RLC PDU to a lower layer. For example, the lower layer is a MAC layer or a physical layer. The RLC of the transmitter may deliver the RLC PDU to the MAC layer through the logical channel.

The transmitter transmits an RLC PDU to a receiver via a radio interface, and the receiver receives the RLC PDU.

The RLC of the receiver receives an RLC PDU from a lower layer. The RLC of the receiver may receive an RLC PDU through a logical channel. The RLC of the receiver stores the received RLC PDU in a reception buffer. The RLC of the receiver reorders the received RLC PDUs in the order of transmission. The RLC of the receiver also detects the loss of the RLC PDU. At this time, the RLC of the receiver rearranges the received RLC PDUs using the reception buffer and the reordering window.

The RLC of the receiver removes the header from the RLC PDU. The RLC of the receiver reassembles the RLC SDUs from the reordered RLC PDUs, except for the missing RLC PDUs. The RLC of the receiver delivers the RLC SDU to the upper layer through the RLC-SAP.

10 is a flowchart illustrating a data transmission method between a conventional UM mode terminal and a base station.

Prior to starting data transmission, the base station requests an RRC connection reconfiguration to the terminal based on a previous PDU transmission failure number (S1010), and the terminal accordingly according to the RRC connection reconfiguration complete (RRC Connection Reconfiguration Complete) The message is transmitted to the base station (S1020). Here, the RRC connection reset request or the RRC connection reset complete message is transmitted between the RRC of the terminal and the RRC of the base station.

After the radio bearer setup, the RLC PDU of the UM mode terminal is delivered to the base station through the MAC of the terminal.

First, PDCP PDU 1 is transmitted from the PDCP of the terminal to the PLC of the terminal (S1031). Here, PDCP PDU 1 may be a data transmission request.

Then, the RLC of the terminal transfers the RLC PDU 1 to the MAC of the terminal (S1032). The MAC of the UE, which has received the RLC PDU 1 from the RLC of the UM mode UE, transmits the RLC PDU 1 to the network through a HARQ process. That is, the MAC of the terminal transmits RLC PDU 1 to the MAC of the base station (S1033). When the MAC transmits the RLC PDU 1 once (1st Tx, S1033) and receives the HARQ ACK (S1050), since the transmission of the RLC PDU 1 is successful, the RLC PDU 2, which is the next RLC PDU, may be transmitted (S1041 to S1042).

PDCP PDU 2 is transmitted from the PDCP of the terminal to the RLC of the terminal for the transmission of the RLC PDU 2 (S1060). The RLC of the UE, that is, the UM RLC, transfers the RLC PDU 2 to the MAC (S1061). If the MAC fails to transmit after transmitting RLC PDU 2 once (1st Tx, S1062), HARQ NACK is received (S1063).

The MAC transmits RLC PDU 2 once more (2nd Tx) (S1064). If transmission fails despite the second transmission (2nd Tx), HARQ NACK is received again (S1065). Subsequently, if HARQ NACK is continuously received, retransmission of the MAC is repeated accordingly (S1066 to S1067). As a result of repeated HARQ NACK reception and retransmission several times, the UE's MAC notifies the RLC of a Transmission Failure of PDU 2 (S1070). And another data (PDU N) is attempted to be transmitted (S1080 to S1081).

As such, when the UE is in the UM mode, when retransmission fails several times, another data transmission is attempted, and a problem solving scheme such as determining a problem detection or a wireless reconnection time due to the accumulation of retransmission times is performed. Is not currently defined.

11 is a flowchart illustrating a wireless reconnection method according to the prior art.

If a problem occurs in the data transmission in the terminal, the terminal detects it (S1101), the terminal performs the following procedure to establish a wireless reconnection.

If a problem is found in the data transmission from the terminal, the terminal immediately sends an RRC Connection Reestablishment Request message to the base station and requests the base station to establish a wireless reconnection (S1110).

Then, after receiving the RRC connection reestablishment request message, the base station resets the signaling radio bearer (SRB) and sends an RRC connection reestablishment message to the terminal (S1120).

The terminal that receives the RRC Connection Reestablishment message also resets the radio bearer. The terminal recovers the signaling radio bearer (S1130). In operation S1140, the UE transmits an RRC connection reestablishment complete message using the reset radio bearer.

The base station also recovers the signaling radio bearer upon receiving the RRC connection reestablishment complete message (S1150). In operation S1160, an RRC connection reconfiguration message is transmitted. The terminal resets the RRC connection to the recovered signaling radio bearer, and transmits an RRC connection reconfiguration complete message to the base station (S1170). As a result, radio bearer recovery and radio connection reconfiguration for data transmission between the terminal and the base station are completed (S1180).

The terminal receiving the RRC Connection Reconfiguration Message from the base station starts data transmission by transmitting an RRC Connection Reconfiguration Complete message to the base station according to the method described above.

However, if the radio state between the terminal and the base station is poor, the MAC of the base station allocates a small transport channel block when scheduling for the corresponding UE or transport channel block to satisfy the quality of service. The power of the base station to send a lot will be used.

Here, one of the methods for detecting a problem in data transmission is to set the maximum number of retransmissions, and to inform the RRC of the problem according to the number of retransmissions. If the RRC receives a problem report from the RLC, the RRC performs a radio reconnection procedure.

However, in the case of the UE of the UM mode, there is no RLC retransmission operation in the UM RLC, and does not detect a data transmission problem. Therefore, even if a data transmission problem occurs, when using UM RLC, the UE maintains data transmission in a state where sufficient quality of service is not guaranteed unless a radio link failure occurs in the physical layer.

Maintaining the data rate in such a state causes the application to discover quality of service problems. In this case, it takes a long time for the base station to take an appropriate operation and a service interruption may occur.

12 is a flowchart illustrating an operation of a transmission failure counter for detecting a data transmission problem according to an embodiment of the present invention.

According to an embodiment of the present invention, the terminal is in UM mode and uses a transmission failure counter to determine whether to reconnect by detecting a problem in data transmission. The transmission failure counter is included in the terminal.

The basic operation of the transfer failure counter is to lower the counter value if the transfer succeeds and to raise the counter value if the transfer fails. Decreasing the counter value by successful transmission may include transmitting a PDU in a layer in the terminal. The degree of raising or lowering the counter value may be variously set according to various embodiments. In addition, a critical value for detecting whether there is a data transmission problem may be set.

First, in order to transmit data, the RLC of the UE generates an RLC PDU (S1210). In operation S1220, the mobile station delivers the RLC PDU to the MAC.

If the transfer of the RLC PDU to the MAC succeeds, the counter value decreases by a predetermined amount (S1230). The MAC transmits an RLC PDU to the network (S1240). It is determined whether the RLC PDU has been successfully transmitted from the MAC to the network. Whether the transmission of the RLC PDU is successful is determined according to whether the MAC receives the HARQ ACK or the HARQ NACK.

If the UE fails to transmit the RLC PDU and receives the HARQ NACK and repeats the retransmission and failure of the RLC PDU (S1261), the MAC notifies the transmission failure to the RLC (Sice) and transmits (S1262). The failure counter value is increased (S1270). As more data passes through the transmission failure and retransmission, the counter value continues to increase.

Even though retransmission is repeated by HARQ NACK reception, as data transmissions notified of failure of transmission to the RLC are accumulated, the counter value reaches a threshold for detecting a data transmission problem (S1280). When the counter reaches a threshold, the RLC of the UE notifies the RRC that a data transmission problem is detected.

When the counter value reaches a threshold due to the transmission failure, a problem on data transmission is detected (S1270) and the operation of the transmission failure counter is terminated.

If data transmission is successful, another RLC PDU is generated for transmission of other data (S1260). Repeat the above process to transfer other data and accumulate the counter value again.

In the present invention, even if the data transmission is totally failed, if the transfer of the RLC PDU between layers in the terminal is successful, the counter value may be reduced, and thus the increase may be increased rather than the decrease of the counter value. That is, when the value subtracted from the counter value is a and the value added to the counter value is b, b is larger than a. The greater the value added than the subtracted value from the counter value, the more cumulative counter values can be increased as the transmission fails, and the counter value can be used as an indicator for detecting data transmission problems when the counter value increases and reaches a certain value. to be. For example, the counter value may change by one when decreasing and by two when increasing.

13A and 13B are flowcharts illustrating a method of detecting a data transmission problem according to an embodiment of the present invention.

Referring to FIGS. 13A and 13B, when detecting a radio data transmission problem in a UM RLC, the operation between the terminal and the base station will be described. In the embodiment described here, an example is described in which a, which is a number that decreases in the counter value when the data transfer is successful, is 1, and b, which is a number that increases in the counter value when the data transfer ends in failure, is 2. Of course, the values of a and b may be variously set according to embodiments.

Prior to starting data transmission, the base station requests an RRC connection reconfiguration to the terminal based on a previous PDU transmission failure count (S1301), and the terminal accordingly according to the RRC connection reconfiguration complete (RRC Connection Reconfiguration Complete) The message is transmitted to the base station (S1302). Here, the RRC connection reset request or the RRC connection reset complete message is transmitted between the RRC layer of the terminal and the base station.

After the radio bearer setup, the RLC PDU of the UM mode terminal is delivered to the base station through the MAC of the terminal.

PDCP PDU 1 is transmitted from the PDCP of the terminal to the RLC of the terminal (S1310). Here, PDCP PDU 1 may be a data transmission request.

Then, the RLC of the terminal transfers the RLC PDU 1 to the MAC of the terminal (S1311). When the RLC PDU 1 is transmitted from the RLC of the UM mode terminal to the MAC of the terminal, the counter value of the transmission failure counter is reduced by 1 (S1312).

The MAC of the UE receiving the RLC PDU 1 transmits the RLC PDU 1 to the network through the HARQ process. That is, the MAC of the terminal transmits the RLC PDU 1 to the MAC of the base station (S1313). When the MAC transmits the RLC PDU 1 once (1st Tx) and receives the HARQ ACK (S1314), since the transmission of the RLC PDU 1 is successful (S1315 to S1316), the UE may transmit the next RLC PDU, RLC PDU 2.

In order to transmit the RLC PDU 2, a request for transmitting second data (Data 2 REQ) is transmitted from the PDCP of the UE to the RLC of the UE (S1320). The RLC of the UE, that is, the UM RLC, transfers the RLC PDU 2 to the MAC (S1321). As a result, the counter value of the transmission failure counter is reduced by one (S1322). If the MAC fails to transmit after transmitting the RLC PDU 2 once (1st Tx, S1323), the HARQ NACK is received (S1324).

Upon reception of the HARQ NACK, the MAC of the UE transmits RLC PDU 2 once more (2nd Tx) (S1325). If the HARQ NACK is continuously received after the second transmission (2nd Tx) (S1326), retransmission of the MAC is repeated accordingly (S1327 to S1328). In addition, the MAC transmits a transmission failure of DATA 2 indicating the transmission failure of the second data to the RLC (S1330). Accordingly, the counter value is increased (S1331).

The transmission of the n-th data is attempted, and in the process, the counter value may reach a threshold value according to transmission failure and retransmission. For the transmission of the n-th data, the PDCP transmits an n-th data transmission request (Data n REQ) to the RLC (S1332), and the RLC transmits an RLC PDU n to the MAC (S1333). As a result, the counter value decreases (S1334). Transmission failure and retransmission are repeated in the nth data (S1335 to S1340). If the number of retransmissions by HARQ NACK in the MAC reaches the maximum number of transmissions (MAX Tx, Nth Tx), the MAC fails to transmit the nth data to the RLC. failure of DATA n) (S1341). The counter value is increased (S1350).

In the embodiment of the present invention, each time the RLC is notified of the data transmission failure, the counter value is increased by two. Of course, the counter value is increased and the counter value is decremented by 1 each time a data transmission request (Data 2 REQ to Data n REQ) is transmitted from the RLC of the UE to the MAC in the process of retransmission being repeated.

In this case, by failing to transmit the n-th data, the counter value reaches a critical value for problem detection. The terminal then determines that a wireless data transmission problem has occurred. Accordingly, the RLC informs the RRC that a lower layer problem detection has been detected (S1360).

If the RRC is informed that a problem is detected in the lower layer, the RRC requests a radio reconnection from the base station (S1370). To this end, the RRC may transmit an RRC Connection Reestablishment Request to the RRC of the base station. Then, the base station transmits an RRC connection recovery message to the terminal (S1380), and when the connection is restored according to the RRC connection recovery message, the terminal transmits an RRC connection recovery complete message to the base station (S1390).

When the UE uses the UM RLC, if there is a case in which the radio link failure does not occur in the physical layer and satisfies the quality of service according to the radio state, a radio data transmission problem may be detected. By doing so, by requesting the base station to set up the wireless reconnection, it is possible to quickly set up the wireless reconnection, it is possible to attempt data transmission recovery in the wireless section.

All the above-described methods may be performed by a processor such as a microprocessor, a controller, a microcontroller, an application specific integrated circuit (ASIC), or the like according to software or program code coded to perform the method, or a processor of a terminal shown in FIG. 3. have. The design, development and implementation of the code will be apparent to those skilled in the art based on the description of the present invention.

According to an embodiment of the present invention, the data transmission problem detection terminal may be a terminal that performs the data transmission problem detection method described with reference to FIG. 13. The data transmission problem detecting terminal is a terminal for wireless communication shown in FIG. 3, and may be a terminal in an unacknowledged mode (UM) including an RF unit for transmitting and receiving a radio signal and a processor connected to the RF unit.

Hereinafter, a data transmission problem detection terminal according to an embodiment of the present invention will be referred to as a "terminal" for convenience of explanation and understanding. If retransmission and subsequent reception of HARQ NACK is repeated more than the maximum number of transmissions, the terminal determines that the transmission has failed. In addition, a counter for raising or lowering a counter value according to a transmission failure is used to determine whether a problem occurs in data transmission. In addition, the terminal transmits data through a HARQ process (HARQ process) and receives the HARQ ACK / NACK in response thereto.

The counter may be included in the processor of the terminal. The processor of the terminal receives HARQ NACK from the network if the network does not successfully receive data after transmitting data to the network. The maximum number of transfers is determined for one data. Since the maximum number of transmissions has been described above, duplicate descriptions are omitted.

When the terminal receives the HARQ NACK more than the maximum number of transmissions, the terminal determines that the transmission of the data has failed. The counter value of the transmission failure counter is increased. After several data transfers, as the number of data transfers accumulates, the counter value continues to increase. When the number of failed transmissions of data accumulates so that the counter value reaches a threshold, the processor detects that a problem has occurred in the transmission of data.

When the processor detects a problem with the data transfer, it requests a wireless connection reset to the network. The radio connection reset request may be the RRC connection recovery request message described above.

Here, the processor may obtain a counter value by using the transmission failure counter described with reference to FIG. 13. In this case, the counter value is decreased by a when the data is transmitted, and the counter value is increased by b when it is determined that the data transmission has failed. Therefore, if a is set smaller than b, the counter value increases as transmission failure occurs.

Although the present invention has been described above with reference to the embodiments, it will be apparent to those skilled in the art that the present invention may be modified and changed in various ways without departing from the spirit and scope of the present invention. I can understand. Therefore, the present invention is not limited to the above-described embodiment, and the present invention will include all embodiments within the scope of the following claims.

1 is a block diagram illustrating a wireless communication system.

2 is a block diagram illustrating functional division between an E-UTRAN and an EPC.

3 is a block diagram illustrating elements of a terminal.

4 is a block diagram illustrating an open system interconnect model.

5 is a block diagram illustrating a radio protocol structure for a user plane.

6 is a block diagram illustrating a radio protocol architecture for a control plane.

7 is a block diagram illustrating a data transmission method.

8 is a flowchart illustrating a method of transmitting user data.

9 is a block diagram illustrating a data transmission / reception method between an RLC entity of a transmitter and an RLC entity of a receiver.

10 is a flowchart illustrating a data transmission method between a conventional UM mode terminal and a base station.

11 is a flowchart illustrating a wireless reconnection method according to the prior art.

12 is a flowchart illustrating operation of a transmission failure counter for detecting a data transmission problem according to an embodiment of the present invention.

13A and 13B are flowcharts illustrating a method of detecting a data transmission problem according to an embodiment of the present invention.

Claims (13)

A method for detecting data transmission problems when transmitting data in UM mode, Transmitting data to a network; HARQ (ACK) Acknowledgment (ACK) as a response signal for receiving the data when the data is successfully received through the network, and HARQ NACK (Negative) as a response signal when the network fails to receive the data. receiving an acknowledgment from the network; If the HARQ NACK is received more than the maximum number of transmissions for the data due to the transmission and retransmission failure of the data, determining that the transmission of the data has failed and increasing the counter value of the transmission failure counter; And detecting that there is a problem with data transmission when the counter value reaches a threshold. The method of claim 1, Transmitting a connection recovery request message to the network after detecting that there is a problem with the data transmission. The method of claim 1, And reducing the counter value when receiving the HARQ ACK. The method of claim 3, The number of decreasing in the counter value upon receiving the HARQ ACK is smaller than the number increasing according to the transmission failure. The method of claim 1, The data is an RLC Protocol Data Unit (PDU) which is generated in a Radio Link Control (RLC) layer of a terminal and delivered to a Medium Access Control (MAC) layer of the terminal, and is transmitted to the network by the MAC layer. To detect data transfer problems. The method of claim 5, The transmission failure counter is in the RLC layer; And the MAC layer notifies the RLC layer of the transmission failure as the reception of the HARQ NACK is repeated, and the RLC layer increases the counter value. The method of claim 5, The transmission failure counter is in the RLC layer; When the counter value increases as the transmission of a plurality of data fails and the threshold value is reached, the RLC layer detects that there is a problem in data transmission by notifying that the data transmission is detected to the RRC layer of the UE. To detect data transmission problems. The method of claim 7, wherein The RRC layer further comprises the step of transmitting an RRC connection recovery request message to the network. The method of claim 5, Decreasing the counter value by a each time the RLC PDU is delivered to the MAC layer, and increasing the counter value by b whenever it is determined that the data transmission has failed. 10. The method of claim 9, And a is smaller than b. In a terminal supporting an unacknowledged mode (UM), RF unit for transmitting and receiving a radio signal; And Including a processor connected to the RF unit, The processor transmits data to the network, and when the HARQ NACK indicating that the network has failed to receive the data exceeds the maximum number of transmissions for the data, the processor determines that the transmission has failed and determines the counter value of the transmission failure counter. And increasing the counter value and detecting that a problem has occurred in the transmission of the data when the counter value exceeds a threshold. The method of claim 11, The processor detects the problem, and requests for resetting the radio connection to the network. The method of claim 11, The processor decreases the counter value by a when transmitting the data, and increments the counter value by b whenever it is determined that the data transmission has failed, wherein a is smaller than b. Problem detection terminal.

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