HK1210361B - Data transmission method and user equipment for the same - Google Patents

Abstract

A mobile communication technology, and, more particularly, a method for efficiently transmitting data stored in a message 3 (Msg3) buffer and a user equipment for the same is disclosed. The method of transmitting data by a user equipment in uplink includes receiving an uplink (UP) Grant signal from a base station on a specific message, determining whether there is data stored in a message 3 (Msg3) buffer when receiving the UL Grant signal on the specific message, determining whether the specific message is a random access response message, and transmitting the data stored in the Msg3 buffer to the base station using the UL Grant signal received on the specific message, if there is data stored in the Msg3 buffer when receiving the UL Grant signal on the specific message and the specific message is the random access response message.

Description

Data transmission method and user equipment for the same

The application is a divisional application, the corresponding original application is an international application with the application number of PCT/KR2009/004002 and the application date of 2009, 20 and 2010, 11 and 30, entering China, and the national application number of 200980120004.0.

Technical Field

The present invention relates to a mobile communication technology, and more particularly, to a method for efficiently transferring data stored in a message 3(Msg3) buffer and a user equipment for the same.

Background

As an example of a mobile communication system to which the present invention is applied, a third generation partnership project long term evolution (3GPP LTE) communication system will be schematically described.

Fig. 1 is a schematic diagram illustrating a network architecture of an evolved universal mobile telecommunications system (E-UMTS) as an example of a mobile communication system.

The E-UMTS is evolved from the existing UMTS and is currently standardized in 3 GPP. In general, E-UMTS may be referred to as an LTE system.

The E-UMTS may be generally divided into an evolved UMTS terrestrial radio Access network (E-UTRAN)101 and a Core Network (CN) 102. The E-UTRAN 101 may include User Equipments (UEs) 103, base stations (hereinafter referred to as "eNodeB" or "eNB") 104, and an Access Gateway (AG)105 located at a network end and connected to an external network. The AG105 may be divided into a part for processing user traffic and a part for processing control traffic. At this time, the AG for processing new user traffic and the AG for processing control traffic may communicate with each other using a new interface.

One or more cells may exist in one enode B. A plurality of enodebs may be connected through an interface for transmitting user traffic or control traffic. The CN 120 may include nodes for registering users of the UE 103 and the AG 105. An interface for distinguishing between the E-UTRAN 101 and the CN 102 may be used.

Layers of a radio interface protocol between the UE and the network may be classified into a first layer L1, a second layer L2, and a third layer L3, based on the lower three layers of an Open System Interconnection (OSI) reference model well known in the field of communication systems. The physical layer belonging to the first layer provides an information transfer service using a physical channel. A Radio Resource Control (RRC) layer belonging to the third layer is used to control radio resources between the UE and the network. The UE and the network exchange RRC messages via the RRC layer. The RRC layer may be allocated and provided at the network nodes of the enode B104 and the AG 105. Alternatively, the RRC layer may be provided only at the enode B104 or the AG 105.

Fig. 2 and 3 show the structure of a radio interface protocol between a UE and a UTRAN based on the 3GPP radio access network standard.

In the horizontal direction, the radio interface protocols of fig. 2 and 3 are formed of a physical layer, a data link layer, and a network layer. In the vertical direction, the radio interface protocol consists of a user plane for transmitting data information and a control plane for transmitting control signals. In particular, fig. 2 shows layers illustrating a radio protocol control plane, and fig. 3 shows layers illustrating a radio protocol user plane. The protocol layers of fig. 2 and 3 may be divided into a first layer (L1), a second layer (L2), and a third layer (L3) based on the lower three layers of the OSI reference model, which is well known in the art of communication systems.

The layers of the control plane of the radio protocol of fig. 2 and the user plane of the radio protocol of fig. 3 will be described below.

A Physical (PHY) layer of the first layer provides an information transfer service to an upper layer using a physical channel. The PHY layer is connected to an upper layer, such as a Medium Access Control (MAC) layer, via a transport channel. Data is transferred between the MAC layer and the PHY layer via a transport channel. At this time, the transport channel is largely divided into a dedicated transport channel and a common transport channel according to whether the channel is shared or not. Data is also transferred between different PHY layers, such as between a physical layer of a transmitting side and a physical layer of a receiving side, via a physical channel using radio resources.

Various layers are present in the second layer. First, the MAC layer serves to map various logical channels to different transport channels and to multiplex several logical channels into one transport channel. The MAC layer is connected to a Radio Link Control (RLC) layer, which is an upper layer, through a logical channel. The logical channel may be roughly divided into a control channel for transmitting information on a control plane and a traffic channel for transmitting information on a user plane according to the kind of transmitted information.

The RLC layer of the second layer serves to segment and concatenate data received from an upper layer in order to adjust the data size such that a lower layer transmits data in a radio sector. In addition, in order to guarantee various qualities of service (QoS) requested by the Radio Bearer (RB), the RLC provides three modes, i.e., a Transparent Mode (TM), a negative acknowledgement mode (UM), and a positive Acknowledgement Mode (AM). In particular, the AM RLC performs a retransmission function using an automatic repeat and request (ARQ) function for reliable data transmission.

A Packet Data Convergence Protocol (PDCP) layer of the second layer performs a header compression function to reduce the size of an Internet Protocol (IP) packet header, which includes unnecessary control information and has a considerable size, for efficient transmission in a radio sector having a relatively small bandwidth when transmitting IP packets, such as IPv4 packets or IPv6 packets. Therefore, only necessary information in the header portion of the data is transmitted in order to improve the transmission efficiency of the radio sector. In the LTE system, the PDCP layer also performs security functions including computation for preventing a third party from intercepting data and integrity protection for preventing the third party from processing data.

Radio Resource Control (RRC) located at the highest part of the third layer is defined only in the control plane. The RRC layer handles logical channels, transport channels, and physical channels for configuration, reconfiguration, and release of RBs. Here, the RB denotes a logical path provided by the first and second layers of the radio protocol for data transmission between the UE and the UTRAN, and the configuration of the RB denotes a procedure of defining characteristics of the radio protocol layers and channels required for providing a specific service and setting detailed parameters and operation methods. Each of the RBs is divided into a signaling RB and a data RB. SRB is used as a path for transmitting RRC messages in a control plane (C-plane), and DRB is used as a path for transmitting user data in a user plane (U-plane).

Downlink transport channels for transmitting data from the network to the UE may include a Broadcast Channel (BCH) for transmitting system information and a downlink Shared Channel (SCH) for transmitting user traffic or control messages. Traffic or control messages of a downlink multicast or broadcast service may be transmitted via the downlink SCH or via a separate downlink Multicast Channel (MCH). Uplink transport channels for transmitting data from the UE to the network may include a Random Access Channel (RACH) for transmitting an initial control message and an uplink SCH for transmitting user traffic or a control message.

In a radio sector between a network and a UE, downlink physical channels for transmitting information transmitted via downlink transport channels may include a Physical Broadcast Channel (PBCH) for transmitting information on the BCH, a Physical Multicast Channel (PMCH) for transmitting information on the MCH, a Physical Downlink Shared Channel (PDSCH) for transmitting information on the PCH and the downlink SCH, and a Physical Downlink Control Channel (PDCCH) (also referred to as DL L1/L2 control channel) for transmitting control information provided by the first and second layers, such as Downlink (DL) or Uplink (UL) scheduling grant information. In a radio sector between a network and a UE, uplink physical channels are used to transmit information transmitted via uplink transport channels, and may include a Physical Uplink Shared Channel (PUSCH) for transmitting information on an uplink SCH, a Physical Random Access Channel (PRACH) for transmitting information on a RACH, and a Physical Uplink Control Channel (PUCCH) for transmitting control information (e.g., HARQ ACK or NACK, Scheduling Request (SR), Channel Quality Indicator (CQI) report) provided by first and second layers

Hereinafter, a random access procedure provided by the LTE system is exemplarily described based on the above description.

First, the UE performs a random access procedure in the following case.

When the UE performs initial access, since there is no RRC connection with the eNodeB,

during handover, when the UE initially accesses the target unit,

when requesting a random access procedure by command of the enodeb,

-when there is uplink data transmission in case the uplink time synchronization is not aligned or in case no specific radio resource is allocated for requesting the radio resource, and

-when performing a recovery procedure in case of radio link failure or handover failure.

In the LTE system, two procedures are provided when selecting a random access preamble: one is a contention-based random access procedure, in which the UE randomly selects one preamble within a specific group for use; and the other is a non-contention based random access procedure in which the UE uses a random access preamble that the enodeb is allocated only to a specific UE. The non-contention based random access procedure may be used during a handover procedure or when requested by an instruction of the base station, as described above.

The random access procedure of the UE with a specific enodeb may generally include: step (1), at the UE, of transmitting a random access preamble to the enodeb (hereinafter referred to as "message 1" transmission step, in case such usage does not cause confusion); a step (2) of receiving a random access response corresponding to the transmitted random access preamble from the enode B (hereinafter referred to as "message 2" receiving step, in the case where such usage does not cause confusion); a step (3) of transmitting an uplink message using information received through the random access response message (hereinafter referred to as "message 3" transmission step, in the case where such usage does not cause confusion); and a step (4) of receiving a message corresponding to the uplink message from the enode B (hereinafter referred to as "message 4" receiving step, in the case where such usage does not cause confusion).

In the random access procedure, the UE stores data to be transmitted via message 3 in a message 3(Msg3) buffer, and transmits the data stored in the message 3 buffer corresponding to the reception of an Uplink (UL) grant signal. The UL grant signal indicates information on uplink radio resources that can be used when the UE transmits a signal to the enodeb, and is received on a random access response message received on a PDCCH or a PUSCH in the LTE system. According to the current LTE system standard, it is defined that if an UL grant signal is received in a case where data is stored in a message 3 buffer, the data stored in the message 3 buffer is transmitted regardless of a reception mode of the UL grant signal. As described above, a problem occurs if data stored in the message 3 buffer corresponding to the reception of all UL grant signals is transmitted. Therefore, research is required to solve these problems.

Disclosure of Invention

Accordingly, the present invention is directed to a data transmission method and user equipment for the same that substantially obviate one or more problems due to limitations and disadvantages of the related art.

An object of the present invention is to provide a data transmission method and a user equipment for the same, which can solve problems that may occur when transmitting data stored in a message 3(Msg3) buffer according to a reception mode of an Uplink (UL) grant signal.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a method of transmitting data by a user equipment through an uplink, the method comprising: receiving an uplink grant (UL grant) signal from a base station on a specific message; determining whether data is stored in a message 3(Msg3) buffer when an UL grant signal is received on a particular message; determining whether the specific message is a random access response message; and if the UL grant signal is received on the specific message and the specific message is a random access response message, transmitting the data stored in the message 3 buffer to the base station using the UL grant signal received on the specific message.

If no data is stored in the message 3 buffer or the specific message is not a random access response message when the UL grant signal is received on the specific message, new data is transmitted to the base station corresponding to the reception of the UL grant signal on the specific message.

The UL grant signal received on a particular message may be a UL grant signal received on a Physical Downlink Control Channel (PDCCH). In this case, the user equipment may transmit new data corresponding to the UL grant signal received on the PDCCH.

The UL grant signal received on the specific message may be a UL grant signal received on a random access response message received on a Physical Downlink Shared Channel (PDSCH). In this case, if data is stored in the message 3 buffer when the UL grant signal is received on the random access response signal, the user equipment may transmit the data stored in the buffer in the message 3 buffer using the UL grant signal received on the random access response message.

The data stored in the message 3 buffer may be a medium access control protocol data unit (MAC PDU) including a user equipment identifier, and if the user equipment starts a random access procedure for a Buffer Status Report (BSR), the data stored in the message 3 buffer further includes information on the BSR.

In another aspect of the present invention, a user equipment includes: a reception module that receives an uplink grant (UL grant) signal from a base station on a specific message; a transmission module transmitting data to the base station using the UL grant signal received on the specific message; a message 3(Msg3) buffer, the message 3 buffer storing UL data to be transmitted in a random access procedure; and a hybrid automatic repeat request (HARQ) entity determining whether data is stored in the message 3 buffer when the reception module receives the UL grant signal and the specific message is a random access response message; when the reception module receives the UL grant signal and the specific message is the random access response message, if there is data stored in the message 3 buffer, acquiring the data stored in the message 3 buffer; and controlling the transmission module to transmit the data stored in the message 3 buffer to the base station using the UL grant signal received on the specific message through the reception module.

The user equipment may also comprise a multiplexing and assembly entity for new data transmission. In this case, if no data is stored in the message 3 buffer or the received message is not a random access response message when the reception module receives the UL grant signal on the specific message, the HARQ entity may acquire new data to be transmitted from the multiplexing and assembling entity, and control the transmission module to transmit the new data acquired from the multiplexing and assembling entity using the UL grant signal received on the specific message by the reception module.

The user equipment may further include: one or more HARQ processes, and the HARQ buffer corresponds to the one or more HARQ processes, respectively. In this case, the HARQ entity transmits the data acquired from the multiplexing and assembling entity or the message 3 buffer to a specific HARQ process of the one or more HARQ processes, and controls the specific HARQ process to transmit the data acquired from the multiplexing and assembling entity or the message 3 buffer through the transmission module.

When a specific HARQ process transmits data stored in the message 3 buffer through the transmission module, the data stored in the message 3 buffer is controlled to be copied into the specific HARQ buffer corresponding to the specific HARQ process, and the data copied into the specific HARQ buffer is controlled to be transmitted through the transmission module.

The UL grant signal received on the specific message by the reception module may be a UL grant signal received on a Physical Downlink Control Channel (PDCCH). In this case, the HARQ entity may control new data transmission corresponding to the received UL grant signal received on the PDCCH.

The UL grant signal received on the specific message by the reception module may be a UL grant signal received on a random access response message received on a Physical Downlink Shared Channel (PDSCH), and when the reception module receives the UL grant signal on the random access response message, the HARQ entity may control to transmit data stored in a message 3 buffer using the UL grant signal received on the random access response message if there is data stored in the message 3 buffer.

According to the above-described embodiments of the present invention, data stored in the message 3 buffer can be transferred according to the reception mode of the UL grant signal without confusion.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings:

fig. 1 is a schematic diagram showing a network architecture of an evolved universal mobile telecommunications system (E-UMTS) as an example of a mobile communication system;

fig. 2 and 3 are views showing the structure of a radio interface protocol between a terrestrial UMTS radio access network (UTRAN) and a User Equipment (UE) based on a third generation partnership project (3GPP) radio access network standard;

fig. 4 is a view illustrating an operation procedure of a UE and a base station (enodeb) in a non-contention based random access procedure;

fig. 5 is a view illustrating an operation process of a UE and an enodeb in a contention-based random access procedure;

fig. 6 is a view illustrating an uplink hybrid automatic repeat request (HARQ) scheme;

fig. 7 is a view illustrating a method of transmitting a message 3 in a random access procedure when uplink radio resources are requested;

fig. 8 is a view illustrating a problem that may occur when data stored in a message 3 buffer is transmitted through an Uplink (UL) grant signal received on a message other than a random access response message;

fig. 9 is a flowchart illustrating a method of transmitting uplink data by a UE according to a preferred embodiment of the present invention;

fig. 10 is a view illustrating a method of transmitting uplink data when a Buffer Status Report (BSR) is triggered in a UE according to an embodiment of the present invention; and

fig. 11 is a diagram illustrating a configuration of a UE according to an embodiment of the present invention.

Detailed Description

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the detailed description disclosed in connection with the appended drawings is intended to describe exemplary embodiments of the present invention and is not intended to describe the only embodiments in which the present invention may be practiced. The following detailed description includes specific details for the purpose of providing a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without these specific details. For example, the following description is given under the assumption that the mobile communication system is a third generation partnership project long term evolution (3GPP LTE) system, but the present invention is applicable to other mobile communication systems than the 3GPP LTE system.

In some instances, well-known structures and devices are omitted to avoid obscuring the principles of the invention, and important functions of the structures and devices are shown in block diagram form. The same reference numbers will be used throughout the drawings to refer to the same or like parts.

In the following description it is assumed that the terminals comprise mobile or fixed user terminal devices, such as User Equipment (UE) and Mobile Stations (MS), and that the base stations comprise nodes of network terminals communicating with the terminals, such as node-B, e node B and base stations.

As described above, in the following description, a problem that may occur when data stored in a message 3(Msg3) buffer is transmitted according to a reception mode of an Uplink (UL) grant signal will be described in detail, and a method of solving the problem will be described. Transmission and reception of signals using a random access procedure and a hybrid automatic repeat request (HARQ) scheme will also be described in detail.

Fig. 4 is a view illustrating an operation procedure of a terminal (UE) and a base station (enodeb) in a non-contention based random access procedure;

(1) random access preamble assignment

As described above, the non-contention based random access procedure may be performed (1) in a handover procedure and (2) when a random access procedure is requested by an enodeb's command. Even in these cases, a contention-based random access procedure may be performed.

First, it is important to receive a specific random access preamble without a possibility of collision next from the enode B for the non-contention based random access procedure. The method of receiving the random access preamble may include a method using a handover command and a method using a Physical Downlink Control Channel (PDCCH) command. The UE receives an assigned random access preamble (S401).

(2) Message 1 transmission

As described above, upon receiving the assigned random access preamble from the enode B, the UE transmits the preamble to the enode B (S402).

(3) Message 2 transmission

After transmitting the random access preamble in step S402, the UE attempts to receive a random access response within a random access response reception window indicated by the enode B through a handover command or system information (S403). More specifically, the random access response information may be transmitted in the form of a Medium Access Control (MAC) Packet Data Unit (PDU), and the MAC PDU may be transmitted via a Physical Downlink Shared Channel (PDSCH). Further, in order for the UE to be able to appropriately receive information transmitted via the PDSCH, the UE preferably monitors the PDCCH. That is, the PDCCH may preferably include information on UEs that should receive the PDSCH, frequency and time information of radio resources of the PDSCH, a transmission format of the PDSCH, and the like. Here, if the PDCCH has been successfully received, the UE may appropriately receive a random access response transmitted on the PDSCH according to information of the PDCCH. The random access response may include a random access preamble identifier (e.g., a random access radio network temporary identifier (RA-RNTI)), an UL grant indicating uplink radio resources, a temporary C-RNTI, a Time Advance Command (TAC), and the like.

As described above, the reason why the random access response includes the random access preamble identifier is because a single random access response may include random access response information of at least one UE and thus report UEs for which UL grant, temporary C-RNTI, and TAC are valid. In this step, it is assumed that the UE selects a random access preamble identifier that matches the random access preamble selected by the UE in step 402.

In the non-contention based random access procedure, it is determined that the random access procedure is normally performed by receiving the random access response information, and the random access procedure may be completed.

Fig. 5 is a view illustrating an operation procedure of a UE and an enodeb in a contention based random access procedure.

(1) Message 1 transmission

First, the UE may randomly select a single random access preamble from a group of random access preambles indicated by system information or a handover command, and select and transmit a Physical Random Access Channel (PRACH) capable of transmitting the random access preamble (S501).

(2) Message 2 reception

The method of receiving the random access response information is similar to the non-contention based random access procedure described above. That is, after transmitting the random access preamble in step S501, the UE attempts to receive its own random access response within a random access response reception window indicated by the enode B through system information or a handover command and receives a Physical Downlink Shared Channel (PDSCH) using random access identifier information corresponding thereto (S502). Accordingly, the UE may receive the UL grant, the temporary C-RNTI, the TAC, and the like.

(3) Message 3 transmission

If the UE has received a random access response valid for the UE, the UE may process all information included in the random access response. That is, the UE applies the TAC and stores the temporary C-RNTI. Further, data corresponding to the reception of a valid random access response to be transmitted may be stored in the message 3 buffer. The process of storing data in the message 3 buffer and transmitting the data is described below with reference to fig. 7.

The UE transmits data (i.e., message 3) using the received UL grant (S503). Message 3 should include the UE identifier. In a content-based random access procedure, the enodeb may not determine which UEs are performing the random access procedure, but the UEs should be identified later for contention resolution.

Here, two different schemes including the UE identifier may be provided. The first scheme is that if the UE has received a valid cell identifier allocated by a corresponding unit before a random access procedure, the cell identifier of the UE is transmitted through an uplink transmission signal corresponding to an UL grant. In contrast, the second scheme is to transmit a unique identifier (e.g., S-TMSI or random ID) of the UE if the UE has not received a valid cell identifier before the random access procedure. Typically, the unique identifier is longer than the cell identifier. If the UE has transmitted data corresponding to the UL grant, the UE starts a Contention Resolution (CR) timer.

(4) Message 4 reception

After transmitting data with its identifier through the UL grant included in the random access response, the UE waits for an indication (instruction) from the enodeb for contention resolution. That is, the UE attempts to receive the PDCCH in order to receive a specific message (S504). Here, there are two schemes for receiving the PDCCH. As described above, if the message 3 transmitted corresponding to the UL grant is transmitted using the cell identifier of the UE, the UE makes the map receive the PDCCH with its own cell identifier, and if the identifier is its unique identifier, the UE attempts to receive the PDCCH using the temporary C-RNTI included in the random access response. Therefore, in the former scheme, if the PDCCH is received through its own cell identifier before the contention resolution timer expires, the UE determines that the random access procedure has been normally performed and completes the random access procedure. In the latter scheme, if the PDCCH is received through the temporary C-RNTI before the contention resolution timer expires, the UE checks data transmitted by the PDSCH indicated by the PDCCH. If the unique identifier of the UE is included in the data, the UE determines that the random access procedure has been normally performed and completes the random access procedure.

In the following, by way of example, an LTE system, an uplink hybrid automatic repeat request (HARQ) scheme of a MAC layer is described focusing on transmission of uplink data.

Fig. 6 is a view illustrating a HARQ scheme.

In order to transmit data to the enodeb through the HARQ scheme, the UE may receive UL grant information or UL scheduling information from the enodeb on the PDCCH (step S601). In general, the UL scheduling information may include a UE identifier (e.g., C-RNTI or semi-persistent scheduling C-RNTI), resource block assignments, transmission parameters (modulation, coding scheme, and redundancy version), and a New Data Indicator (NDI). In the LTE system, the UE has 8 HARQ processes, and the HARQ processes are simultaneously performed at a Transmission Time Interval (TTI). That is, specific HARQ processes may be sequentially assigned according to a time point when data is received in the following manner: after using the first HARQ process at TTI 1, the second HARQ process at TTI 2, …, and the eighth HARQ process at TTI 8, the first HARQ process is used at TTI 9, and the second HARQ process is used at TTI 10.

Further, since the HARQ process is synchronously designated as described above, the HARQ process related to the TTI in which the PDCCH for initial transmission of specific data is received is used for data transmission. For example, if it is assumed that the UE has received a PDCCH including UL scheduling information at the nth TTI, the UE transmits data at the (N +4) th TTI. In other words, the kth HARQ process assigned at the (N +4) th TTI is used for transmission of data. That is, after checking UL scheduling information transmitted to the UE by monitoring the PDCCH at every TTI, the UE may transmit data to the enodeb on the PUSCH according to the UL scheduling information (step S602).

When data has been received, the enode B stores the data in a soft buffer and attempts to decode the data. The enode B transmits an ACK signal if the data decoding is successful, and transmits a NACK signal if the data decoding fails. Fig. 6 shows an example in which data decoding fails and an enodeb transmits a NACK signal on a Physical HARQ Indicator Channel (PHICH) (step S603).

When having received the ACK signal from the enode B, the UE determines that transmission of data to the enode B is successful and transmits the next data. However, when the UE receives the NACK signal as shown in fig. 6, the UE may determine that data transmission to the enode B has failed and retransmit the same data through the same scheme or a new scheme (step S604).

HARQ retransmission of the UE may be performed through a non-adaptive scheme. That is, when a PDCCH including UL scheduling information should be received, initial transmission of specific data may be performed, but retransmission may be performed even when the PDCCH is not received. In non-adaptive HARQ retransmission, the data is retransmitted using the same UL scheduling information as the initial transmission at the TTI assigned the next HARQ process without receiving the PDCCH.

HARQ retransmission of the UE may be performed through an adaptive scheme. In this case, transmission parameters for retransmission are received on the PDCCH, but UL scheduling information included in the PDCCH may be different from that of the initial transmission according to a channel state. For example, if the channel state is better than that of the initial transmission, the transmission may be performed at a high bit rate. In contrast, if the channel state is worse than the initial transmission, the transmission may be performed at a lower bit rate than the initial transmission.

If the UE receives UL scheduling information on the PDCCH, it is determined whether data that should be transmitted this time is initially transmitted data or retransmitted previous data through an NDI field included in the PDCCH. The NDI field is toggled (toggle) in the order of 0, 1, … whenever new data is transmitted as described above, and the retransmitted NDI field has the same value as the NDI field of the initial transmission. Accordingly, the UE may compare the NDI field to a previously transmitted value to determine whether to retransmit the data.

The UE counts the number of transmissions (CURRENT _ TX _ NB) each time data is transmitted through the HARQ scheme, and deletes data stored in the HARQ buffer when the CURRENT _ TX _ NB has reached the maximum number of transmissions set in the RRC layer.

When receiving the retransmitted data, the enode B attempts to combine the received data with the data stored in the soft buffer due to a failure in decoding through various schemes, and decodes the combined data. If the decoding is successful, the enodeb transmits an ACK signal to the UE, and if the decoding fails, the enodeb transmits a NACK signal to the UE. The enode B repeats the process of transmitting the NACK signal and receiving the retransmitted data until the decoding of the data is successful. In the example of fig. 6, the enode B attempts to combine the data retransmitted in step S604 with the previously received and stored data and decode the combined data. If the decoding of the received data is successful, the enode B transmits an ACK signal to the UE on the PHICH (step S605). In order to report that the UL scheduling information is not for adaptive retransmission but for transmission of new data, the UE may transmit the UL scheduling information for transmission of next data to the UE on the PDCCH, and may transmit NDI with hop becoming 1 (step S606). The UE may transmit new data corresponding to the received UL scheduling information to the enodeb on the PUSCH (step S607).

The random access procedure may be triggered in the above-described case as described above. The case in which the UE requests UL radio resources will be described below.

Fig. 7 is a view illustrating a method of transmitting a message 3 in a random access procedure when requesting UL radio resources.

When new data is generated in a transmission buffer 601 (e.g., RLC buffer and PDCP buffer) of the UE, the UE should generally notify the enode B of information of data generation. More precisely, the UE is generated with data to the enodeb when the generation has a higher priority than the data stored in the UE's transmit buffer.

This indicates that the UE requests radio resources for the enodeb to transmit the generated data. Based on the above information, the enodeb may assign appropriate radio resources to the UE. Information on the generation of data is called a buffer status report (hereinafter referred to as "BSR"). Next, as described above, the request for transmission of the BSR is represented by triggering BSR transmission (S6100). If BSR transmission is triggered, the UE should transmit the BSR to the eNodeB. However, if there is no radio resource for transmitting the BSR, the UE may trigger a random access procedure and attempt to request radio resources (S6200).

As described above, if a random access procedure for requesting radio resources for the enode B is triggered, the UE may transmit a random access preamble to the enode B and receive a random access response message corresponding thereto, as described with reference to fig. 4 and 5. Further, in the MAC layer of the UE, message 3 (i.e., MAC PDU) including the UE identifier and the BSR may be generated through an UL grant signal included in the random access response message and stored in the message 3 buffer 602. Message 3 stored in message 3 buffer 602 may be copied and stored in HARQ process buffer 603 indicated by the UL grant information. For example, fig. 7 shows a case where HARQ process a is used for transmission of message 3. Thus, message 3 is copied into the HARQ buffer 603 corresponding to HARQ process a. Message 3 stored in HARQ buffer 603 may be transmitted to the enodeb on PUSCH.

Meanwhile, if the UE may perform a retry (retry) of the random access procedure due to a contention resolution failure, the UE may transmit a random access preamble to the enodeb again and receive a random access response (S6300). However, in the retried random access procedure, the UE uses again the message 3 stored in the message 3 buffer 602 without generating a new message 3. That is, the UE may copy and store the MAC PDU corresponding to message 3 stored in the message 3 buffer 602 of the HARQ buffer 604, and transmit the MAC PDU according to the UL grant signal included in the random access response received in the retried random access procedure. Fig. 7 shows a case of a random access procedure in which a retry is performed through HARQ process B. The data stored in the message 3 buffer 602 may be copied to the HARQ buffer B and transmitted.

As described above, if a random access response is received when a random access procedure is performed, the UE stores message 3 stored in the message 3 buffer in the HARQ buffer and transmits the message 3. As mentioned above, in the current LTE system standard for HARQ processes, it is defined that the transmission of data stored in the message 3 buffer is triggered by the reception of any UL grant signal. Therefore, the CR timer may be erroneously driven, so that an erroneous contention resolution process is performed. The BSR is not normally transmitted due to an erroneous contention resolution procedure, and the UE may enter a deadlock. This problem is described in detail below with reference to fig. 8.

Fig. 8 is a view illustrating a problem that may occur when data stored in a message 3 buffer is transmitted through an Uplink (UL) grant signal received on a message other than a random access response message.

As described with reference to fig. 7, the UE may trigger the BSR when generating high priority data, transmit a random access preamble in order to transmit the BSR to the enodeb (S801), and receive a random access response corresponding thereto (S802).

Thereafter, the UE may transmit a message 3 including a BSR via UL grant information included in the random access response message received in step S802 (S803). If message 3 is transmitted, the CR timer operates as described with reference to fig. 5.

If the random access procedure is completed before the CR timer expires, the UE determines that the random access procedure has not been successfully completed (S804). In this case, the UE may attempt to restart the random access procedure starting from the transmission of the random access preamble.

At this time, since the enodeb does not yet know that the UE is performing the random access procedure, the enodeb may transmit the UL grant signal on the masked PDCCH independently of the random access procedure (S805). In this case, according to the current LTE system standard, the UE transmits message 3 stored in the message 3 buffer according to the UL grant signal received on the PDCH in step S805 (S806). Further, when the message 3 is transmitted, the CR timer is restarted. That is, even if the UE does not perform transmission of the random access preamble and reception of the random access response message, the CR timer is restarted at step S806.

Although the CR timer starts when the UE transmits the message 3 in step S806, the enode B may not know that the UE is performing the random access procedure because the reception of the random access preamble and the transmission of the random access response message are not performed. If another UL grant signal including a UE identifier is accepted on the PDCCH (S807), the UE determines that the ongoing random access procedure is successfully completed. Accordingly, the UE may stop the ongoing CR time (S808).

If the message 3 transmitted to the enodeb in step S806 is not successfully received by the enodeb (a), the UE does not transmit the message 3 including the BSR any more. Accordingly, if additional data is not generated, the UE may not transmit the data generated in the transmission buffer to the enodeb.

The above problems are described as follows.

According to the current LTE system standard, if a stealing UL grant signal is received in a state in which data is stored in a message 3 buffer, the UE transmits the data stored in the message 3 buffer to the enode B. At this time, the UL grant signal may be transmitted through the enode B not for transmission of data stored in the message 3 buffer but for transmission of other data. Therefore, the CR timer may be started erroneously.

Further, if the enodeb does not know that the CR timer is erroneously started in the UE and transmits an UL grant signal for transmission of other data, as described with reference to fig. 8, information (e.g., BSR) to be transmitted through the message 3 may be lost.

Further, even with respect to the ongoing random access procedure, the UE may not receive the message 4 for completing the appropriate contention resolution procedure.

In a preferred embodiment of the present invention for solving the above-mentioned problems, the data stored in the message 3 buffer is transmitted restrictively only in case that the UL grant signal received from the enodeb is received on the random access response message, not in all cases in which the UL grant signal is received from the enodeb. If the UL grant signal is received on the masked PDCCH not through the random access response message but through the UE identifier (C-RNTI or semi-persistent scheduling radio network temporary identifier (SPS-RNTI)) in a state in which data is stored in the message 3 buffer, a method of acquiring and transmitting new data (MAC PDU) to the enodeb instead of the data stored in the message 3 buffer is suggested.

Fig. 9 is a flowchart illustrating a method of transmitting UL data by a UE according to a preferred embodiment of the present invention. In more detail, fig. 9 illustrates an operation of a HARQ entity of a UE according to an embodiment of the present invention at every TTI.

First, the HARQ entity of the UE may identify a HARQ process associated with a TTI (S901). If a HARQ process associated with a TTI is identified, the HARQ entity of the UE may determine whether reception of an UL grant signal from the eNodeB is indicated at the TTI (step S902). If there is no information about the received UL grant signal at the TTI, the UE may determine whether a HARQ buffer corresponding to the HARQ process is empty, and if there is data in the HARQ buffer, perform non-adaptive retransmission as described with reference to fig. 6 (S903).

Meanwhile, if there is a UL grant signal received from the enodeb at the TTI, it may be determined whether (1) the UL grant signal is not received on the PDCCH indicated by the temporary C-RNTI and the NDI hops from this value during transmission before the HARQ process; (2) whether there is a previous NDI and whether the transmission is an initial transmission of a HARQ process; (3) whether an UL grant signal is received on a PDCCH indicated by the C-RNTI and an HARQ buffer of the HARQ process is empty; or (4) whether an UL grant signal is received on the random access response message (S904). If any of the conditions (1) to (4) is satisfied in step S904(a), the method proceeds to step S906. In contrast, if any of the conditions (1) to (4) is not satisfied in step S904(B), the method proceeds to step S905 where adaptive retransmission is performed using the UL grant signal (S905).

Meanwhile, the UE determines whether there is data in the message 3 buffer (S906). Further, even if there is data in the message 3 buffer, the UE determines whether the received UL grant signal is received on the random access response message (S907). That is, the UE according to the present embodiment transmits data stored in the message 3 buffer only when there is data in the message 3 buffer when receiving the UL grant signal and the UL grant signal is received on the random access response message (S908). If there is no data in the message 3 buffer when the UL grant signal is received or no UL grant is received on the random access response message, the UE determines that the enode B does not make a request for transmission of data stored in the message 3 buffer but for transmission of new data, and performs new data transmission (S909). In more detail, the HARQ entity of the UE may be controlled such that acquiring the MAC PDU including new data from the multiplexing and assembling entity is acquired and transmitted through the HARQ process.

Next, an example of a procedure for a UE to transmit a BSR as shown in fig. 8, which is adapted to operate by the embodiment described with reference to fig. 9, will be described.

Fig. 10 is a view illustrating a method of transmitting UL data when a BSR is triggered in a UE according to an embodiment of the present invention.

As described above, new data may be generated in the RLC and PDCP buffers of the UE. It is assumed that the new data generated has a higher priority than the data already stored in the RLC and PDCP buffers. The UE may trigger BSR transmission in order to inform the enodeb of information on data generation (step 1).

The UE should transmit the BSR according to the BSR transmission trigger, but in a special case, there may be no radio resource for transmitting the BSR. In this case, the UE may trigger a random access procedure for transmitting the BSR. It is assumed that the random access procedure triggered in the present embodiment is a contention-based random access procedure, as described with reference to fig. 5.

The UE may transmit a random access preamble to the enode B according to the triggering of the random access procedure (step 2).

The enode B may receive the random access preamble transmitted by the UE and transmit a random access response message to the UE (step 3). The UE may receive a random access response message.

According to the UL grant signal included in the random access response message received in step 3, the UE may generate a message 3 including the BSR and the UE identifier, and store the message 3 in a message 3 buffer (step 4).

According to the UL grant information included in the random access response message received in step 3, the UE may select a HARQ process and copy and store the message 3 stored in the message 3 buffer in a buffer corresponding to the selected HARQ process. Thereafter, the data stored in the HARQ buffer is transmitted to the enode B according to the UL HARQ process described with reference to fig. 6 (step 5). The UE starts (or restarts) the CR timer through transmission of message 3.

When the CR timer expires, the UE may perform a retry of the random access procedure. That is, a random access preamble and PRACH resources may be prepared to be selected and transmitted to the enodeb. However, in a state in which the CR timer is not on, the UE may receive an UL grant signal from the enodeb on the PDCCH masked by the UE identifier (step 6).

When the UL grant signal has been received on the PDCCH in step 6, the UE generates new data different from the data stored in the message 3 buffer as a new MAC PDU according to the UL grant information received in step 6, unlike the procedure of the embodiment of fig. 8 for transmitting the message 3 stored in the message 3 buffer according to the UL grant information received in step 6 (step 7). In more detail, if the UE receives the UL grant signal in step 6, but does not receive the UL grant signal on the random access response message, the HARQ process corresponding thereto may be used to acquire and transmit a MAC PDU, which is not used to transmit data stored in the message 3 buffer but is used to transmit new data from the multiplexing and assembling entity.

After generating a new MAC PDU, the UE according to the present embodiment may select a HARQ process according to the UL grant signal received in step 6, store the newly generated MAC PDU in step 7 in a buffer corresponding to the HARQ process, and transmit the MAC PDU to the enodeb according to the UL HARQ process (step 8).

Thereafter, the UE may perform a random access procedure including transmission of a random access preamble and reception of a random access response, and transmit a BSR stored in the message 3 buffer to the enodeb.

According to the above-described embodiment, it is possible to prevent the enode B from erroneously operating the CR timer due to the UL grant signal transmitted not for the transmission of data stored in the message 3 buffer but for the transmission of new data. Therefore, the problem of the loss of the message 3 can be solved. In addition, the random access procedure of the UE with the enodeb may be performed normally.

Unlike the above-described embodiment, as another embodiment of the present invention, a method of performing a procedure can be implemented, in which if an UL grant signal is received from an enodeb on a PDCCH masked by a UE identifier during a random access procedure of a UE, the UL grant signal can be ignored. In this case, the UE may transmit the message 3 to the enodeb through a normal random access procedure, and after the random access procedure of the UE is completed, the enodeb may retransmit the UL grant signal for transmission of new data.

The configuration for realizing the above-described embodiment of the present invention will be described below.

Fig. 11 is a diagram illustrating a configuration of a UE according to an embodiment of the present invention.

As shown in fig. 11, the UE according to the present embodiment may include a reception (Rx) module 1101 for receiving an UL grant signal from an enodeb on a specific message, a Transmission (TX) module 1102 for transmitting data to the enodeb using the received UL grant signal, a message 3 buffer 1103 for storing UL data transmitted in a random access procedure, and a HARQ entity 1104 for controlling transmission of the UL data of the UE.

Specifically, the HARQ entity 1104 of the UE according to the present embodiment performs the following functions: when the receiving module 1101 receives the UL grant signal, it is determined whether data is stored in the message 3 buffer 1103 and it is determined whether the receiving module 1101 receives the UL grant signal on a random access response message. If data is stored in the message 3 buffer 1103 when the reception module 1101 receives the UL grant signal, and the reception module 1101 receives the UL grant signal on the random access response message, it controls the data stored in the message 3 buffer 1103 to be acquired and transmitted to the enode B. If no data is stored in the message 3 buffer 1103 when the reception module 1101 receives the UL grant signal, and the reception module 1101 does not receive the UL grant signal on the random access response message but on the PDCCH, the data stored in the message 3 buffer 1103 is not transmitted, but new data is acquired from the multiplexing and assembling entity in the form of a MAC PDU and transmitted to the enodeb.

Further, in order to perform the UL HARQ process, the UE according to the present embodiment may include one or more HARQ processes 1106 and a HARQ buffer 1107 corresponding to the HARQ processes 1106. In the current LTE system, 8 independent HARQ processes are defined for use, but the present invention is not limited thereto.

Meanwhile, the HARQ entity 1104 according to the present embodiment may transmit data acquired from the multiplexing and assembling entity 1105 or the message 3 buffer 1103 to a specific HARQ process 1106 using the above-described configuration, and control the specific HARQ process 1106 to transmit the data acquired from the multiplexing and assembling entity 1105 or the message 3 buffer 1103 through the transmission module 1102. As described above, if a specific HARQ process 1106 transmits data stored in the message 3 buffer 1103 through the transmission module 1102 as described above, the data stored in the message 3 buffer 1103 may be copied into the specific HARQ buffer 1107 corresponding to the specific HARQ process 1106 and the data copied into the specific HARQ buffer 1107 may be transmitted through the transmission module 1102.

At this time, the data stored in the message 3 buffer 1103 is a MAC PDU including a UE identifier and may further include information such as a BSR according to the purpose of a random access procedure.

In the configuration of the UE shown in fig. 11, the transmission module 1102 and the reception module 1101 may be configured as a physical layer processing module 1108, and the HARQ entity 1104, the multiplexing and assembling entity 1105, and one or more HARQ processes 1106 may be configured as a MAC layer module 1109. The present invention is not limited thereto. Further, message 3 buffer 1103 and HARQ buffer 1107 corresponding to HARQ process 1106 may be implemented using any storage medium.

Although the signal transmission or reception technology and the UE for the technology are applicable to the 3GPP LTE system, they are also applicable to various mobile communication systems having similar procedures in addition to the 3GPP LTE system.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Claims (7)

1. A method of transmitting data by a user equipment through an uplink channel in a mobile communication system, the method comprising:

receiving, at the user equipment, an uplink grant (UL grant) from a base station on a specific message; and is

Transmitting, by the user equipment, Msg3 buffer data to the base station in accordance with the UL grant received on the particular message when the UL grant is received on the particular message and the particular message is a random access response message with data stored in a Msg3 buffer of the user equipment,

transmitting, by the user equipment, new data to the base station when the UL grant is received on the specific message, and the specific message is not the random access response message and data is stored in the Msg3 buffer of the user equipment,

transmitting, by the user equipment, new data to the base station when the UL grant is received on the specific message, and the specific message is not the random access response message, and no data is stored in the Msg3 buffer of the user equipment, and

transmitting, by the user equipment, new data to the base station when the UL grant is received on the random access response message and the particular message is the random access response message and no data is stored in the Msg3 buffer of the user equipment.

2. The method of claim 1, further comprising:

receiving an additional UL grant signal on a Physical Downlink Control Channel (PDCCH); and

transmitting the new data to the base station corresponding to the additional UL grant signal.

3. The method of claim 2, wherein transmitting new data to the base station comprises:

obtaining a media access control protocol data unit (MAC PDU) from a multiplexing and assembly unit; and

transmitting the MAC PDU to the base station.

4. The method of claim 2, further comprising receiving the additional UL grant signal on a PDCCH related to one of a cell Radio Network Temporary Identifier (RNTI) and a temporary cell RNTI.

5. The method of claim 1, wherein the data stored in the Msg3 buffer is a media access control protocol data unit (MAC PDU) comprising a user equipment identifier.

6. The method of claim 5, wherein when a user equipment starts a random access procedure for a Buffer Status Report (BSR), then data stored in the Msg3 buffer further includes information about the BSR.

7. The method of claim 1, wherein the data is a medium access control protocol data unit (mac pdu).