KR102041996B1 - Method for communicating in mobile communication system and apparatus for the same - Google Patents

Abstract

A method of operating a terminal in a mobile communication system is disclosed. Driving a T310 timer when a physical layer out-of-sync of the downlink PDCCH transmitted from a first base station occurs; and when the physical layer in-sync state of the downlink PDCCH is not reached until the T310 timer expires, a radio link confirming that a failure has occurred, performing PDCP layer and radio link control (RLC) layer reset for all radio bearers except SRB0, stopping all radio bearers except SRB0, and performing cell selection Performing RRC connection reestablishment to the selected second base station and resuming all radio bearers if the RRC connection reestablishment with the second base station succeeds.

Description

TECHNICAL FOR COMMUNICATING IN MOBILE COMMUNICATION SYSTEM AND APPARATUS FOR THE SAME

The present invention relates to a mobile communication system, and more particularly, to a low latency data transmission and reception technique in a mobile communication system.

The fifth generation mobile communication, which aims to support Gbps (Giga bps), at least 10 to 100 times the data rate than the fourth generation mobile communication, includes not only the existing mobile communication frequency band but also several tens of GHz (Giga Herz) frequency bands. . The fifth generation of mobile communication is not only enhanced mobile broadband (eMBB) for ultra-high data rate support, but also massive machine type communication (MMTC) and ultra-reliable low latency communication (URLLC) for IoT support. We aim to support.

The use of a shorter transmission time interval (TTI) and a technique for reducing transmission delay time are required to support URLLC, and frequency / time / spatial dimensional diversity is used to achieve high reliability. Technique is needed.

An object of the present invention for solving the above problems is to provide a method for operating a terminal for minimizing data transmission delay and ensuring improved data transmission reliability in a mobile communication system.

A method of operating a terminal in a mobile communication system according to an embodiment of the present invention for achieving the above object, T310 when the physical layer out-of-sync of the downlink physical downlink control channel (PDCCH) transmitted from the first base station Driving a timer, confirming that a radio link failure (RLF) occurs when the physical layer in-sync state of the downlink PDCCH does not occur until the expiration of the T310 timer, and all except signaling radio bearer0 (SRB0) Performing packet data convergence protocol (PDCP) layer and radio link control (RLC) layer reconfiguration for the radio bearer, suspending all radio bearers except SRB0, and performing cell selection to a second base station selected Performing an RRC connection reestablishment of the RRC connection and resuming all radio bearers upon successful RRC connection reestablishment with the second base station. .

Here, the method may further include transferring the data transmitted from the first base station to the RLC upper layer at a point in time determined through control of a radio resource control (RRC) layer, and optionally to the PDCP upper layer.

Here, if data is not normally received even in a retransmission request according to a predetermined criterion to the first base station, transferring the data transmitted from the first base station to a higher layer of RLC, and optionally transmitting to a higher layer of PDCP. It may include.

The method may further include transmitting information indicating the RLF generation to the first base station through the second base station when the RLF occurs with the first base station.

Here, the method may further include transmitting information indicating an identifier (ID) for the second base station selected through the cell selection to the first base station.

The method may further include transmitting information indicating the RLF generation to the first base station through a second cell carrier, wherein the first base station may be a master base station of carrier aggregation.

The method may further include transmitting information indicating the occurrence of the RLF to the first base station through a second cell group, wherein the first base station is a master base station of dual connectivity. Can be.

Performing a PDCP layer and RLC layer reconfiguration for all radio bearers except for the master base station and SRB0; And

The method may further include performing data transmission / reception with the master base station without suspending all radio bearers except the SRB0.

A method of operating a terminal in a mobile communication system according to another embodiment of the present invention for achieving the above object, the first RLC receiver and the second RLC to the same data transmitted from the first RLC transmitter and the second RLC transmitter of the base station; Receiving each of the receivers, and if at least one of the first RLC receiver and the second RLC receiver normally receives the data, transmitting normal reception information to the first RLC transmitter that has transmitted the data and the normal At least one of the first RLC receiving unit and the second RLC receiving unit receives an RLC PDU including a sequence number of an RLC PDU discarded from at least one of the first RLC transmitting unit and the second RLC transmitting unit that has not received the reception information. Steps.

Here, a first RLC receiver and a first RLC PDU comprising only an RLC header from at least one of the first RLC transmitter and the second RLC transmitter that do not receive the normal reception information, and the first RLC receiver that do not transmit the normal reception information; The method may further include receiving by at least one of the 2 RLC receiving units.

Here, the packet data convergence protocol (PDCP) layer of the base station informs the first RLC transmitter and the second RLC transmitter that the PDCP PDUs of the PDCP layer are duplicated, and polls the RLC PDU including the PDCP PDU. ) Bit setting method.

In accordance with still another aspect of the present invention, there is provided a method of operating a terminal in a mobile communication system, comprising: a PDCP protocol data unit (PDU) including importance determination information for each IP packet; Transmitting to a radio link control (RLC) layer, transmitting an RLC PDU including importance determination information for each IP packet to a medium access control (MAC) layer, and a buffer status report (BSR) to a base station; Transmitting, and receiving an uplink grant from the base station; if the PDCP PDU to be transmitted through an uplink radio resource allocated through the uplink grant grant is not transmitted for a predetermined time, the IP And performing discarding of the RLC PDU on a predetermined basis according to the importance of the packet.

Here, quality of service (QoS) may be differentially applied according to the importance determination information for each IP packet.

In this case, the MAC layer may immediately trigger the buffer status report when there is high importance data.

Here, when there are a plurality of acknowledgment (ACK) packets for one transmission control protocol (TCP) connection to be transmitted to the base station, the PDCP layer selects the remaining ACK packets except for the most recently generated ACK packet. Can be discarded.

Here, a subchannel may be allocated for each QoS for a logical channel for the IP packet to which QoS is differentially assigned according to the importance determination information for each IP packet.

Here, different priority and discard timers may be set for each subchannel.

According to the present invention, high reliability and low latency communication can be performed through data transmission and reception of a mobile communication system reflecting efficient management of redundant transmission and data transmission priority setting.

1 is a conceptual diagram showing the structure of a communication system.
2 is a block diagram illustrating an embodiment of a communication node constituting a communication system.
3 is a conceptual diagram illustrating a structure of a radio interface protocol between a terminal and a base station in a 3GPP LTE and LTE-A mobile communication system according to the prior art.
4 is a conceptual diagram illustrating an RRC state and an RRC connection method according to the prior art.
5 is a flowchart illustrating a RRC connection reconfiguration procedure according to the prior art.
6 is a flowchart illustrating an RRC connection resetting procedure according to an embodiment of the present invention.
7 is a conceptual diagram illustrating data transmission through RRC connection reconfiguration of a redundant connection support terminal according to an embodiment of the present invention.
8 is a conceptual diagram illustrating data transmission through RRC connection reconfiguration of a carrier aggregation support terminal according to an embodiment of the present invention.
9 is a conceptual diagram illustrating PDCP PDU redundant transmission according to the prior art.
10 is a conceptual diagram illustrating PDCP PDU redundant transmission according to an embodiment of the present invention.
11 is a conceptual diagram illustrating data transmission using a QoS setting for each IP flow according to the prior art.
12 is a conceptual diagram illustrating data transmission using QoS setting for each IP flow according to an embodiment of the present invention.
13A is a conceptual diagram illustrating slot-based PDCCH monitoring according to the prior art.
13B is a conceptual diagram illustrating PDCCH monitoring when a minislot according to the prior art is applied.
14 is a flowchart illustrating a mini slot-based PDCCH according to an embodiment of the present invention.

As the present invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component. The term and / or includes a combination of a plurality of related items or any item of a plurality of related items.

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

Hereinafter, with reference to the accompanying drawings, it will be described in detail a preferred embodiment of the present invention. In the following description of the present invention, the same reference numerals are used for the same elements in the drawings and redundant descriptions of the same elements will be omitted.

1 is a conceptual diagram showing the structure of a communication system.

Referring to FIG. 1, the communication system 100 includes a plurality of communication nodes 110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, 130-6). Here, a communication system may be referred to as a "communication network." Each of the plurality of communication nodes may support at least one communication protocol. For example, each of the plurality of communication nodes may include a code division multiple access (CDMA) based communication protocol, a wideband CDMA (WCDMA) based communication protocol, a time division multiple access (TDMA) based communication protocol, and a frequency division multiple (FDMA) based communication protocol. access based communication protocol, orthogonal frequency division multiplexing (OFDM) based communication protocol, orthogonal frequency division multiple access (OFDMA) based communication protocol, single carrier (SC) -FDMA based communication protocol, non-orthogonal multiple An access based communication protocol and a space division multiple access (SDMA) based communication protocol may be supported. Each of the plurality of communication nodes may have a structure as follows.

2 is a block diagram illustrating an embodiment of a communication node constituting a communication system.

Referring to FIG. 2, the communication node 200 may include at least one processor 210, a memory 220, and a transceiver 230 that communicates with a network. In addition, the communication node 200 may further include an input interface device 240, an output interface device 250, a storage device 260, and the like. Each component included in the communication node 200 may be connected by a bus 270 to communicate with each other. However, each component included in the communication node 200 may be connected through a separate interface or a separate bus around the processor 210, instead of the common bus 270. For example, the processor 210 may be connected to at least one of the memory 220, the transceiver 230, the input interface device 240, the output interface device 250, and the storage device 260 through a dedicated interface. .

The processor 210 may execute a program command stored in at least one of the memory 220 and the storage device 260. The processor 210 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which methods according to embodiments of the present invention are performed. Each of the memory 220 and the storage device 260 may be configured as at least one of a volatile storage medium and a nonvolatile storage medium. For example, the memory 220 may be configured as at least one of a read only memory (ROM) and a random access memory (RAM).

Referring back to FIG. 1, the communication system 100 includes a plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2, and a plurality of user equipments. ) 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6. Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 may form a macro cell. Each of the fourth base station 120-1 and the fifth base station 120-2 may form a small cell. The fourth base station 120-1, the third terminal 130-3, and the fourth terminal 130-4 may belong to the coverage of the first base station 110-1. The second terminal 130-2, the fourth terminal 130-4, and the fifth terminal 130-5 may belong to the coverage of the second base station 110-2. The fifth base station 120-2, the fourth terminal 130-4, the fifth terminal 130-5, and the sixth terminal 130-6 may belong to the coverage of the third base station 110-3. . The first terminal 130-1 may belong to the coverage of the fourth base station 120-1. The sixth terminal 130-6 may belong to the coverage of the fifth base station 120-2.

Here, each of the base stations 110-1, 110-2, 110-3, 120-1, and 120-2 is a NodeB, an evolved NodeB, a base transceiver station (BTS), Radio base station, radio transceiver, access point, access node, road side unit (RSU), digital unit (DU), cloud digital unit (CDU) , May be referred to as a radio remote head (RRH), a radio unit (RU), a transmission point (TP), a transmission and reception point (TRP), a relay node, and the like. Each of the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 is a terminal, an access terminal, a mobile terminal, It may be referred to as a station, a subscriber station, a mobile station, a portable subscriber station, a node, a device, or the like.

A plurality of communication nodes 110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, 130-6 Each may support cellular communication (eg, long term evolution (LTE), LTE-A (advanced, etc.) as defined in the 3rd generation partnership project (3GPP) standard). Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may operate in different frequency bands, or may operate in the same frequency band. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to each other through an ideal backhaul or a non-ideal backhaul, and an ideal backhaul. Alternatively, information can be exchanged with each other via non-ideal backhaul. Each of the base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to a core network (not shown) through an ideal backhaul or a non-idal backhaul. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 receives a signal received from the core network, corresponding terminal 130-1, 130-2, 130-3, 130. -4, 130-5, 130-6, and the signal received from the corresponding terminal (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) core network Can be sent to.

Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may support downlink transmission based on OFDMA and uplink based on SC-FDMA. Can support transport. In addition, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may transmit multiple input multiple output (MIMO) (eg, single user (SU) -MIMO, Multi-user (MU) -MIMO, massive MIMO), CoMP (coordinated multipoint) transmission, carrier aggregation transmission, transmission in unlicensed band, device to device, D2D Communication (or, ProSeimity services (ProSe), etc.) Here, each of the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 may be a base station. Operations corresponding to (110-1, 110-2, 110-3, 120-1, 120-2), by the base stations 110-1, 110-2, 110-3, 120-1, 120-2 Supported operations can be performed.

For example, the second base station 110-2 may transmit a signal to the fourth terminal 130-4 based on the SU-MIMO scheme, and the fourth terminal 130-4 may transmit the signal based on the SU-MIMO scheme. The signal may be received from the second base station 110-2. Alternatively, the second base station 110-2 may transmit a signal to the fourth terminal 130-4 and the fifth terminal 130-5 based on the MU-MIMO scheme, and the fourth terminal 130-4 may be used. And each of the fifth terminals 130-5 may receive a signal from the second base station 110-2 by the MU-MIMO scheme. Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 may transmit a signal to the fourth terminal 130-4 based on a CoMP scheme, and a fourth The terminal 130-4 may receive a signal from the first base station 110-1, the second base station 110-2, and the third base station 110-3 by the CoMP scheme. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 includes terminals 130-1, 130-2, 130-3, 130-4, which belong to its own coverage. 130-5 and 130-6) and a signal may be transmitted and received based on the CA scheme. Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 coordinates D2D communication between the fourth terminal 130-4 and the fifth terminal 130-5. The fourth terminal 130-4 and the fifth terminal 130-5 may each perform D2D communication by coordination of each of the second base station 110-2 and the third base station 110-3. Can be performed.

Next, low latency data transmission techniques in a mobile communication system will be described. Here, even when a method (for example, transmission or reception of a signal) is performed among the communication nodes is described, the corresponding second communication node corresponds to the method performed in the first communication node. (E.g., receiving or transmitting a signal). That is, when the operation of the terminal is described, the base station corresponding thereto may perform an operation corresponding to the operation of the terminal. In contrast, when the operation of the base station is described, the terminal corresponding thereto may perform an operation corresponding to the operation of the base station.

3 is a conceptual diagram illustrating a structure of an air interface protocol in a 3GPP LTE and LTE-A mobile communication system according to the prior art.

Referring to FIG. 3, a layer of a radio interface protocol between a terminal and a base station (including a core network) is based on the lower three layers of an open system interconnection (OSI) model well known in a communication system. , It is divided into a second layer (L2: layer 2) and a third layer (L3: 1ayer 3). The air interface protocol between the terminal and the base station may be horizontally divided into a physical layer, a data link layer and a network layer, and vertically, a protocol stack for transmitting control information. It may be divided into a control plane and a user plane, which is a protocol stack for transmitting data (also called user data or traffic) information.

L1 is a physical layer (PHY) 310. The physical layer 310 provides a service for transmitting information (data and control information) to a higher layer through a physical channel. The physical layer 310 is connected to the upper layer media access control (MAC) layer 320 through a transport channel (that is, the physical channel is mapped to the transport channel). Data and control information may be transmitted between the MAC layer 320 and the physical layer 310 through a transport channel. Data and control information between different physical layers, that is, between the physical layer 310/370 of the transmitting device and the physical layer 370/310 of the receiving device may be transmitted using a radio resource through a physical channel.

The physical layer 310 may use a physical control channel to transmit control information in addition to data. For example, a physical downlink control channel (PDCCH) delivers information on resource allocation of a paging channel (PCH) and a downlink shared channel (DL-SCH), and hybrid automatic repeat request (HARQ) information related to the DL-SCH to the UE. It is used to The PDCCH also includes an UL grant, which is information on resource allocation for uplink transmission. The physical control format indicator channel (PCFICH) delivers the number of OFDM symbols used for the PDCCH to the UE. A physical hybrid ARQ indicator channel (PHICH) is used to deliver HARQ acknowledgment (ACK) / non-acknowledgement (NACK) information for uplink shared channel (UL-SCH) transmission. A physical uplink control channel (PUCCH) transmits UL control information such as HARQ ACK / NACK, scheduling request, and channel quality indicator (CQI) for downlink transmission.

The physical channel includes a plurality of subframes in the time domain and a plurality of subcarriers in the frequency domain. One subframe consists of a plurality of resource blocks (RBs). One resource block includes a plurality of symbols (one subframe consists of a plurality of symbols in the time domain) and a plurality of subcarriers. In addition, each subframe may use specific subcarriers of specific symbols of the corresponding subframe for PDCCH transmission. In one example, the first symbol of the subframe may be used for PDCCH transmission. A transmission time interval (TTI), which is a unit time for transmitting data, may be equal to the length of one subframe, and the length of one subframe may be 1 ms.

As described above, the physical layer 310 is connected to the upper layer MAC layer 320 through a transport channel. Transport channels are classified into a common transport channel and a dedicated transport channel according to whether the channels are shared. The downlink transport channel includes a broadcast channel (BCH) for transmitting system information, a paging channel (PCH) for transmitting a paging message, a DL-SCH for transmitting user data or control information, and the like. . The DL-SCH supports dynamic link adaptation and dynamic / semi-static resource allocation by HARQ, change in transmit power, potential modulation and coding. Traffic or control information of a multimedia broadcast / multicast service (MBMS) is transmitted through a multicast channel (MCH).

The uplink transport channel includes a random access channel (RAC) used for initial control message transmission and initial access to a cell, a UL-SCH for transmitting user data or control information, and the like. UL-SCH supports dynamic link adaptation by HARQ, change in transmit power, potential modulation and coding change. RACH is generally used for initial connection to a cell.

The MAC layer 320 corresponding to L2 (layer 2) provides a service to a radio link control (RLC) layer, which is a higher layer, through a logical channel. The MAC layer 320 provides a mapping function from the plurality of logical channels to the plurality of transport channels (ie, the logical channel is located above the transport channel and mapped to the transport channel). In addition, the MAC layer 320 provides a logical channel multiplexing function by mapping from a plurality of logical channels to one transport channel. The logical channel may be divided into a control logical channel for information transmission of a control plane and a traffic logical channel for information transmission of a user plane according to the type of information to be transmitted. That is, the type of logical channel is defined for each transmission service provided by the MAC layer 320.

In particular, the control logical channel is used only for information transfer of the control plane. The control logical channel provided by the MAC layer 320 includes a broadcast control channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH), a multicast control channel (MCCH), and a dedicated control channel (DCCH). . BCCH is a logical channel for broadcasting system control information. The PCCH is a logical channel used to transmit paging information and to page a terminal whose cell unit location is unknown to the base station. CCCH is used by the terminal when the terminal does not have a radio resource control (RRC) connection with the base station. MCCH is a one-to-many downlink logical channel used for transmitting MBMS control information from a base station to a terminal. DCCH is a one-to-one bidirectional logical channel used by the terminal for transmitting dedicated control information between the terminal and the network in an RRC connection state.

The traffic logical channel is used only for conveying information in the user plane. The traffic logical channel provided by the MAC layer 310 includes a dedicated traffic channel (DTCH) and a multicast traffic channel (MTCH). DTCH is used for transmission of user information of one UE in a one-to-one channel and may exist in both uplink and downlink. MTCH is a one-to-many downlink logical channel for transmitting data (traffic) from the base station to the terminal.

RLC layer 330 belongs to L2. The function of the RLC layer 330 includes scaling of data by segmentation / concatenation of data received from the upper layer so that the lower layer is suitable for transmitting data. In order to guarantee various quality of service (QoS) required by a radio bearer (RB), the RLC layer 330 is a transparent mode (TM), an unacknowledged mode (UM) and an acknowledgment mode. It provides three modes of operation (AM; acknowledged mode). AM RLC provides retransmission through automatic repeat request (ARQ) for reliable data transmission. Meanwhile, the function of the RLC layer 330 may be implemented as a functional block inside the MAC layer 310, in which case the RLC layer 330 may not exist.

The packet data convergence protocol (PDCP) layer 340 also belongs to the L2 layer. The PDCP layer 340 introduces an Internet Protocol (IP) packet such as Internet Protocol Version 4 (IPv4) or Internet Protocol Version 6 (IPv6) over a relatively low bandwidth wireless interface to efficiently transmit data. It provides header compression to reduce unnecessary control information. Header compression improves the transmission efficiency in the radio channel section by transmitting only the information necessary for the header of the data. In addition, the PDCP layer 340 provides a security function. Security functions include encryption to prevent third party inspection and integrity protection to prevent third party data manipulation.

RRC layer 350 belongs to L3. The RRC layer 350, located at the bottom of L3, is defined only in the control plane. The RRC layer 350 serves to control radio resources between the terminal and the base station. To this end, the UE and the network exchange RRC messages through the RRC layer 350. The RRC layer 350 is responsible for controlling logical channels, transport channels, and physical channels in connection with configuration, re-configuration, and release of RBs. RB is a logical path provided by L1 and L2 for data transmission between the terminal and the base station. That is, RB means a service provided by L2 for data transmission between the terminal and the base station. Setting up an RB means defining the characteristics of the radio protocol layer and channel to provide a particular service, and determining each specific parameter and method of operation. RBs may be classified into two types: signaling RBs (SRBs) and data RBs (DRBs). The SRB is used as a path for transmitting RRC messages in the control plane, and the DRB is used as a path for transmitting user data in the user plane.

The non-access stratum (NAS) layer 360 located above the RRC layer 350 performs functions such as session management and mobility management.

Referring back to FIG. 3, the RLC layer 330 and the MAC layer 320 of the control plane may perform functions such as scheduling, ARQ, and HARQ. The RRC layer 350 may perform functions such as broadcasting, paging, RRC connection management, RB control, mobility function, and terminal measurement report / control. The NAS control protocol of the NAS layer 360 may perform functions such as system architecture evolution (SAE) bearer management, authentication, LTE_IDLE mobility handling, paging initiation in LTE_IDLE, and security control for signaling between the terminal and the gateway. (The detailed description is omitted). The RLC layer and the MAC layer of the user plane may perform the same functions as those in the control plane (in FIG. 3, the air interface protocol of the control plane). The PDCP layer can perform user plane functions such as header compression, integrity protection, and encryption. Next, the RRC state and the RRC connection method of the UE will be described.

4 is a conceptual diagram illustrating an RRC state and an RRC connection method according to the prior art.

Referring to Figure 4, it shows a change in the RRC state according to the power-on (410) of the terminal power.

The RRC state indicates whether the RRC layer of the terminal is logically connected to the RRC layer of the base station (including the core network). The RRC state may be divided into two types, such as an RRC connected state (RRC_CONNECTED) 430 and an RRC idle state (RRC_IDLE) 420. When the RRC connection between the RRC layer of the terminal and the RRC layer of the base station is established, the terminal is in the RRC connection state 430, otherwise the terminal is in the RRC idle state 420. Since the terminal of the RRC connection state 430 and the RRC connection is established with the base station, the base station can determine the existence of the terminal of the RRC connection state 430, and can effectively control the terminal. On the other hand, the base station can not determine the terminal of the RRC idle state 420, the core network (CN) manages the terminal in units of a tracking area (tracking area), the area larger than the cell (CN). That is, the terminal of the RRC idle state 420 is only identified as a unit of a larger area, and in order to receive a normal mobile communication service such as voice or data communication, the terminal must transition to the RRC connected state 430.

In the RRC idle state 420, while the terminal designates a discontinuous reception (DRX) set by the NAS, the terminal may receive a broadcast of system information and paging information. In addition, the terminal may be assigned an identification (ID) that uniquely designates the terminal in the tracking area, and perform public land mobile network (PLMN) selection and cell reselection.

In the RRC connection state 430, the terminal is capable of receiving data from the base station and / or transmitting data to the base station by bringing the base station RRC connection and RRC context from the base station. In addition, the terminal may report channel quality information and feedback information to the base station. In the RRC connection state 430, the base station can know the cell to which the terminal belongs. Therefore, the base station may transmit data to the terminal and / or receive data from the terminal. In the RRC idle state 420, the UE designates a paging discontinuous reception (DRX) cycle. In more detail, the UE monitors a paging signal during a specific paging occasion for each UE specific paging DRX cycle. Paging opportunity is the time interval during which the paging signal is transmitted. The terminal has its own paging opportunity. The paging message is sent across all cells belonging to the same tracking area.

When the user first turns on the power of the terminal (410), the terminal first searches for the appropriate cell and then stays in the RRC idle state in the cell (410). When it is necessary to establish an RRC connection, the terminal staying in the RRC idle state may make an RRC connection with the RRC layer of the base station through the RRC connection procedure and may transition to the RRC connection state 430. The UE staying in the RRC idle state 420 is connected to establish an RRC connection with the base station when uplink data transmission is needed due to a user's call attempt, or when a paging message is received from the base station and a response message is required. A connection establishment 440 is performed to switch from the RRC idle state 420 to the RRC connection state 430. In contrast, a connection release 450 is performed to switch from the RRC connected state 430 to the RRC idle state 420. As described above, the air interface protocol and the RRC state change, which are the basis of data transmission between the base station and the terminal, have been described. Next, the RRC connection reestablishment to overcome the radio link failure (RLF) due to physical layer error, etc. will be described. Next, an RRC connection reestablishment procedure according to the prior art will be described.

5 is a flowchart illustrating a RRC connection reconfiguration procedure according to the prior art.

Referring to FIG. 5, when the PDCCH BLER becomes greater than or equal to a certain criterion, the RLF timer T310 is operated to determine that an RLF is generated if the PDCCH BLER (block error rate) does not meet a predetermined criterion until the T310 timer expires. Indicates that the RRC reset procedure is in progress. A radio link failure (RLF) may occur in a situation in which a radio link is already established between the terminal and the source base station (S505). In another case, even if the base station (or terminal) RLC does not receive the RLC PDU from the terminal (or base station) normally even if the RLC PDU retransmission is performed for the maximum number of RLC automatic repeat request (ARQ) retransmissions for a specific PDU, the RLC protocol It may be determined that an error has occurred, and the RRC resetting procedure may proceed as in the case of the RLF. The determination of the downlink RLF according to the prior art is performed by a radio link monitor (RLM) of the terminal. When the RLM of the UE enters the Qout state, it determines that a physical layer problem out-of-sync has occurred and drives a T310 timer (generally, Qout means PDCCH BLER 10% or more). At this time, the source base station and the target base station prepares for handover (S510) from the source base station to the target base station (S510) when the terminal determines the downlink RLF generation during the handover from the terminal to the target base station, the target is the target The RRC connection reconfiguration procedure may be performed to the base station so that the RLF recovery procedure may be successfully performed. If the terminal enters the Qin state after driving the T310 timer, the T310 timer is stopped by determining that the physical layer problem is solved (generally, Qin means less than 2% of the PDCCH BLER).

On the other hand, if the Q310 state does not enter until the preset T310 timer expires, the RLM of the terminal determines that an RLF has occurred (S515) (also called RLF detection).

When the RLF is detected, all radio bearers (RBs) except for signaling radio bearer 0 (SRB0) are suspended (S520). SRBs are used for RRC signaling messages and non-access stratum (NAS) message transfers. The RRC message is used for signaling between the terminal and the base station, and the NAS message is used for signaling between the terminal and the mobility management entity (MME).

After stopping all radio bearers (RBs) except for SRB0, the UE selects a cell after attempting cell searching for an optimal cell (S525). If cell selection is successfully completed, the terminal may receive a master information block (MIB) and a system information block (SIB) from a newly selected cell (target base station). Thereafter, the terminal performs a random access procedure with the new cell using the received MIB and SIB (S530). The terminal transmits an RRCConncectionReestablishmentRequest to the target base station (S535). If the target base station has context information of the terminal, the terminal receives an RRCConncectionReestablishment (or RRCConncectionReestablishmentReject if the RRC connection reestablishment request is rejected from the base station) from the target base station (S540).

Upon receiving the RRCConncectionReestablishment, the UE performs the radio resource setup procedure and resumes the SRB1 while re-establishing the PDCP layer and the RLC layer for the SRB1 (S545). Next, the terminal configures a lower layer to activate integrity protection and ciphering, and reactivates AS (access stratum) security (S550). Thereafter, the terminal transmits the RRCConncectionReestablishmentComplete to the target base station (S555), and receives the RRCConncectionReconfiguration from the target base station (S560). Next, the terminal resets and resumes SRB2 and DRB (data radio bearer) (S565).

On the other hand, when the terminal receives the RRCConncectionReestablishmentReject (not shown) from the target base station, it resets the medium access control (MAC) while leaving the RRC_CONNECTED state. In addition, the UE stops all running timers except T320, T325, and T330, releases all radio resources including the RLC entity and the associated PDCP entity for MAC setup and all established RBs, and puts them into the RRC_IDLE state. Enter.

On the other hand, during the RRC connection resetting procedure in 3GPP LTE and LTE-A, the data transmission and reception disconnection time between the terminal and the base station is generally (), the DRB resumes after the successful RRC connection resetting procedure from the time when the T310 timer starts (Qout occurs). up to the point where it was resumed (typically the T310 timer is set to 1 second). In the RRC connection resetting procedure, the data transmission and reception disconnection time is known to be about 0.8 seconds (800 ms), and the received data may become obsolete because the received data cannot be delivered to the upper layer during this time, resulting in increased data transmission delay. Can be.

At this time, even if the DRB is re-established and delivers the data received from the terminal to the upper layer, the data transmitted out of order in the PDCP layer is not delivered to the PDCP upper layer, so that all the data received from the terminal is useless. There is a problem that is thrown away. In addition, when the DRB is reset and resumed, the PDCP layer of the terminal receiving the data out of order may be implemented to deliver the corresponding data to the upper layer of the PDCP layer, but in this case, the data transmission and reception disconnection time is hardly reduced. Next, a description will be given of the RRC connection resetting according to an embodiment of the present invention for solving this long data transmission and reception disconnection problem.

6 is a flowchart illustrating an RRC connection resetting procedure according to an embodiment of the present invention.

Referring to FIG. 6, when the RLF generation acknowledgment timer T310 expires and becomes an RLF state, it indicates that the PDCP layer and the RLC layer of all RB except SRB0 are re-establishment and suspend. When the RLM of the UE confirms the occurrence of the Qout of the downlink PDCCH, it determines that a physical layer problem out-of-sync has occurred and drives the T310 timer. According to an embodiment of the present invention, the data received while the T310 is driven may be transmitted to a higher layer of the terminal even if the data does not match the transmission order.

Specifically, a radio link failure (RLF) may occur in a situation in which a radio link is already established between the terminal and the source base station (first base station) (S605).

Alternatively, as described above, even if the base station (or terminal) RLC does not normally receive the RLC PDU from the terminal (or base station) even if the RLC PDU retransmission is performed for the maximum number of RLC automatic repeat request (ARQ) retransmissions for a specific PDU, It may be determined that an RLC protocol error has occurred, and the RRC resetting procedure may proceed as in the case where the RLF has occurred.

When the RLM of the UE enters the Qout state, it determines that a physical layer problem out-of-sync has occurred and drives the T310 timer. At this time, the source base station and the target base station prepares for handover (S610) from the source base station to the target base station (second base station) (S610) to determine the downlink RLF generation during the handover from the terminal to the target base station later In this case, the UE may perform the RLF recovery procedure successfully by performing the RRC connection reconfiguration procedure to the target base station. When the RLF is detected, all radio bearers (RBs) except for signaling radio bearer 0 (SRB0) are suspended (S620-1). In addition, re-establishment may be performed for all RBs (S620-2).

After stopping all radio bearers (RBs) except for SRB0, the UE selects a cell after attempting cell searching for an optimal cell (S625). If cell selection is successfully completed, the terminal may receive a master information block (MIB) and a system information block (SIB) from a newly selected cell (target base station). Thereafter, the terminal performs a random access procedure with the new cell using the received MIB and SIB (S630). The terminal transmits an RRCConncectionReestablishmentRequest to the target base station (S635). After the target base station has the context (context) information of the terminal, the terminal receives the RRCConncectionReestablishment (or RRCConncectionReestablishmentReject if the RRC connection reset request is rejected from the base station) from the target base station (S640).

Upon receiving the RRCConncectionReestablishment, the UE performs a radio resource setup procedure and resumes SRB1 while re-establishing the PDCP layer and the RLC layer for SRB1 (S645). Next, the terminal configures a lower layer to activate integrity protection and ciphering, and reactivates AS (access stratum) security (S650). Thereafter, the terminal transmits the RRCConncectionReestablishmentComplete to the target base station (S655), and receives the RRCConncectionReconfiguration from the target base station (S660). The UE resumes SRB2 and DRB (data radio bearer) (S665).

In the case of using the RRC connection resetting according to the embodiment of the present invention described above, the data communication disconnection time between the UE and the base station is determined by resetting the PDCP layer and the RLC layer of the DRB after the T310 timer expires. This is until the DRB resumes after the successful connection reset procedure. Data received during the operation of the T310 timer can be delivered to the upper layer to reduce the data communication delay time, thereby reducing the data transmission delay. To this end, the RRC layer of the UE may inform the lower PDCP layer or the RLC layer when the data that does not match the order to the upper layer. That is, the data transmitted from the source base station to the terminal may be delivered to the RLC upper layer at a point in time determined through control of a radio resource control (RRC) layer, and may also be selectively transmitted to the PDCP upper layer. For example, data that is relatively sensitive to delay may need to be delivered to the upper layer quickly, in which case it may be delivered to the PDCP upper layer.

Meanwhile, the RLC PDU transmitted by the base station may be lost in the radio channel section or may not be received by the terminal for a predetermined time. Alternatively, the RLC PDU may not be normally received even after the UE requests retransmission from the base station more than a preset number of times for the RLC PDU having the same sequence number. In this case, the UE may determine that the RLC PDU of the corresponding sequence number cannot be received. In general, even when the transmitting side (the transmitting side means a base station or a terminal) RLC performs RLC PDU retransmission for a specific number of RLC automatic repeat request (ARQ) maximum retransmissions, the receiving side (means a terminal or a base station) normally If the RLC PDU is not received, it is determined that an RLC protocol error has occurred, and the RRC resetting procedure may proceed as in the case of the RLF. In this case, if normal data is not received even though the terminal makes a request for retransmission to the source base station according to a predetermined criterion, the data received from the source base station may be delivered to the upper layer of the RLC, and may also be selectively delivered to the higher layer of PDCP. For example, data that is relatively sensitive to delay may need to be delivered to the upper layer quickly, in which case it may be delivered to the PDCP upper layer.

Next, a description will be given of the RRC connection reconfiguration in the case that the terminal supports a dual (or dual connectivity) (DC) according to an embodiment of the present invention.

7 is a conceptual diagram illustrating data transmission through RRC connection reconfiguration of a redundant connection support terminal according to an embodiment of the present invention.

Referring to FIG. 7, when the terminal 730 supports dual connectivity (DC), an RLF is generated in a cell 710 (first base station) of a master cell group (MCG: master cell group). If the radio link state of the cell 720 (second base station) of the secondary cell group (SCG) is good, it indicates that the terminal 730 reports that the MCG RLF is generated to the SCG cell 720.

When the RLF is generated in the terminal 730 set up with the radio link with the MCG cell 710, the terminal 730 is the PDCP layer and RLC layer of all RBs when there is a radio link in which no RLF is generated among the neighboring SCG cells 720. Can be reset and not suspend all RBs.

Specifically, when the terminal 730 supports DC, when the RLF occurs in the radio link between the MeNB (Master eNode B) (710) which is an MCG cell and the UE, the UE is a secondary eNode B, which is an SCG cell. (Second Base Station) 720 The connection 740 may inform the MeNB that an RLF has occurred (the MeNB and SeNB are connected in an X2 interface manner).

That is, the MeNB 710 may transmit data to be transmitted to the terminal 730 through the SeNB 720 connected through the X2 interface, and the SeNB 720 may transmit the corresponding data to the terminal 730. In this case, since the terminal supports the DC, the terminal may transmit data to the upper layer through the additional radio link processing protocol path 730-2 instead of the radio link processing protocol path 730-1 with the MeNB 710. Can be.

In addition, the terminal 730 may reset the PDCP layer and RLC layer of all the RB except SRB0, or may continuously transmit and receive data between the terminal and the SeNB without stopping all RBs. In addition, the terminal 730 transmits a PDCP status report to the MeNB 710 via the SeNB 720, and the MeNB 710 reviews the received PDCP status report to retransmit the PDCP SDU (service data). unit) may be retransmitted to the terminal 730.

That is, the UE performs RLF detection or selects a cell (second base station) to perform RRC connection reconfiguration by selecting a cell in an RRC connection reconfiguration procedure, and then the MeNB (first base station) 710 in which the RLF is generated. It is possible to inform that RLF is generated through a good wireless link that is not a wireless link. The MeNB 710, which is the source base station that is reported that the RLF is generated, can continuously exchange data with the terminal through the radio link (the radio link through the SeNB 720) where the RLF has not occurred, thereby reducing the data transmission / reception time. I can eliminate it.

In addition, the UE 730 may report a cell ID (identifier) of the cell SeNB 720 to perform RLF generation and reconfiguration to the MeNB 710 after determining a cell to be reset in the cell selection step in the RRC connection reconfiguration procedure. . Through this procedure, the MeNB 710 can perform SN Status Transfer and data forwarding faster to the SeNB 720, which is a target base station corresponding to the reported cell ID. In other words, the terminal can receive data more quickly.

Next, a description will be given of the RRC connection reconfiguration in the case that the terminal supports carrier aggregation (CA) according to an embodiment of the present invention.

8 is a conceptual diagram illustrating data transmission through RRC connection reconfiguration of a carrier aggregation support terminal according to an embodiment of the present invention.

Referring to FIG. 8, when an RLF occurs between a terminal 840 supporting a CA and a primary cell 820 of the base station 810, the terminal 840 is a secondary of the base station 810. Cell 830 indicates the notification of the occurrence of the RLF. The base station 910 may transmit data to be transmitted to the terminal 840 through the secondary cell 830.

RRC connection reconfiguration of the terminal supporting CA can be configured in various ways.

In the first method, the PDCP layer and the RLC layer may be re-established for all the DRBs after the RRC connection reestablishment is successfully established between the terminal 840 and the secondary cell 830 of the base station.

In a second method, the secondary cell 830 of the terminal 840 and the base station re-establishes the PDCP layer and the RLC layer of all RBs including the SRB and the DRB, and does not suspend all the RBs. Can send and receive

In a third method, the secondary cell 830 of the terminal 840 and the base station may reset the remaining SRB except for the SRB0, and may continuously transmit and receive data without resetting the PDCP layer and the RLC layer for all the DRBs.

In addition, the terminal 840 may transmit a PDCP status report to the base station 810, and the base station 810 may receive the PDCP SDU requiring retransmission to the terminal 840 based on the corresponding PDCP status report.

Next, as another method for implementing high reliability low latency communication, PDCP PDU duplication transmission according to an embodiment of the present invention will be described.

9 is a conceptual diagram illustrating PDCP PDU redundant transmission according to the prior art.

Referring to FIG. 9, two methods of redundantly transmitting PDCP PDUs to a UE are shown. When redundant transmission is established for a specific radio bearer by the RRC layer, another RLC entity and logical channel are added to the corresponding radio bearer to coordinate overlapping PDCP PDUs. Therefore, redundancy in the PDCP layer means sending the same PDCP PDU twice (the first means sent through the original RLC entity and the second sent by the added RLC entity). Through these independent transmission paths, the reliability of packet transmission is improved, and transmission delay in packet transmission is greatly reduced, thus playing a significant role in implementing the URLLC function.

When PDCP redundant transmission, PDCP PDUs and duplicate PDCP PDUs are not transmitted on the same carrier. Two different logical channels may belong to the same single MAC entity or may belong to different MAC entities. In the case of the terminal 930 supporting DC, the PDCP PDU can be repeatedly transmitted through different base stations 920-1 and 920-2 when the PDCP PDU is redundantly transmitted. In the case of the terminal supporting CA, different carriers 910 can be used. PDCP PDUs may be transmitted through -1,910-2. In this way, you can meet the reliability and latency requirements of URLLC implementation.

However, in the case of such PDCP PDU redundant transmission, if data is normally received by the UE through one RLC entity, duplication of data transmission through another RLC entity causes radio resource waste and data transmission delay. Next, a description will be given of PDCP PDU redundant transmission according to an embodiment of the present invention to prevent data transmission delay due to such data redundant transmission.

10 is a conceptual diagram illustrating PDCP PDU redundant transmission according to an embodiment of the present invention.

Referring to FIG. 10, a control signal and data transmission / reception process for reducing radio resource waste and data transmission delay when a PDCP PDU is redundantly transmitted from a base station to a user equipment is shown. PDCP PDU redundant transmission according to an embodiment of the present invention relates to a situation in which a PDCP transmitter of a base station repeatedly transmits a PDCP PDU to a first RLC transmitter and a second RLC transmitter (but this is an embodiment of the present invention. The invention is not limited thereto). First, the first RLC transmitter of the base station may transmit PDCP PDUs corresponding to sequential numbers 1 through 4 of the PDCP PDUs to the first RLC receiver of the UE (transmitted in the form of RLC PDUs). Commonly applied in one embodiment of the present invention 10) (S1010-1). In the present embodiment, it is assumed that PDCP PDUs (SN 1 to SN 4) transmitted in the form of four RLC PDUs transmitted from the base station first RLC transmitter to the first RLC receiver of the terminal are successfully received by the first RLC receiver of the terminal. . The second RLC transmitter of the base station may also transmit PDCP PDUs corresponding to sequential numbers 1 through 4 to the second RLC receiver of the terminal (transmitted in the form of an RLC PDU as described above). (S1010-2).

In the present embodiment, the four PDCP PDUs (SN 1 to SN 4) (transmitted in the form of RLC PDUs as described above) transmitted from the base station second RLC transmitter to the second RLC receiver of the terminal are the terminal for reasons such as a radio channel state. Assume that it is not received by the second RLC receiver and is missing. At this time, the PDCP transmitter of the base station may notify the lower layer RLC (first RLC layer and the second RLC layer) when the PDCP PDU is duplicated transmission, the RLC layer is configured to poll for the duplicated RLC PDU By doing so, the RLC receiver of the terminal can quickly transmit a status PDU to the base station.

The first RLC receiver of the UE that normally receives the PDCP PDUs (transmitted in the form of an RLC PDU as described above) corresponding to four consecutive sequences is transmitted to the first RLC transmitter of the base station using a status PDU. The PDUs SN 1 to SN 4 (transmitted in the form of an RLC PDU as described above) may be notified to the first RLC receiving unit (S1020).

The first RLC transmitter of the base station receiving the status PDU from the terminal corresponds to an upper layer of the base station indicating that the PDCP PDUs (SN 1 to SN 4) (received in the form of an RLC PDU as described above) are normally transmitted to the first RLC receiver. The PDCP transmitter may be informed (S1030). Since the PDCP transmitter of the base station knows that it is not necessary to transmit the PDCP PDUs (SN 1 to SN 4) (transmitted in the form of an RLC PDU as described above) through the second RLC transmitter through the PDCP Tx, The RLC transmitter may request to discard the PDCP PDUs (SN 1 to SN 4) (S1040). In this case, when the second RLC transmitter has not yet transmitted the corresponding RLC PDU (the RLC PDU corresponding to the PDCP PDU ranging from SN 1 to SN 4 as described above) to the UE, an RLC SDU (service data unit) for the corresponding RLC PDU ) Is discarded.

On the other hand, even if the base station transmits the RLC PDU corresponding to the PDCP PDU ranging from SN 1 to SN 4 to the UE, the base station may discard the related RLC SDU and stop transmitting the RLC PDU. In this case, since the out-of-order sequence is generated in the receiving terminal to perform the reordering operation, data transmission to the upper layer of the terminal may be delayed. In order to prevent this, the related RLC SDU may be discarded to transmit the RLC PDU using a minimum radio resource, and the RLC PDU may be transmitted without payload data (where the payload may be an RLC SDU). Alternatively, an RLC control PDU including information indicating that the RLC PDU is discarded may be transmitted. In this case, the RLC control PDU may include the SN of the discarded PDU.

To this end, the second RLC transmitter may transmit the RLC PDU configured with only the RLC header without payload data to the second RLC receiver of the terminal (S1050). The second RLC receiver that receives the RLC PDU consisting of only the RLC header without the payload data may know that the corresponding RLC SDU has been discarded.

Next, as another method for implementing high reliability low latency communication, data transmission using differential quality of service (QoS) settings according to an embodiment of the present invention will be described.

11 is a conceptual diagram illustrating data transmission using a QoS setting for each IP flow according to the prior art.

Referring to FIG. 11, a terminal 1110 transmits and receives data to and from a PDN gateway (PDN-GW) 1140 via a base station 1120 and a serving gateway (SGW) 1130. Indicate the process.

A collection of IP packets having the same transmit / receive IP address, transport protocol, and transmit / receive port is called one IP flow.

Each IP flow is mapped to one bearer, and one or more IP flows are mapped to one bearer. The bearer is a virtual concept as described above and defines how data and signaling of the terminal are handled while being transmitted and received through the network. Networks handle data according to their characteristics. RB is divided into a signaling radio bearer (SRB) and a data radio bearer (DRB). As mentioned above, SRBs are used to carry control plane traffic such as RRC signaling messages and NAS messages, and DRBs are used to carry user plane traffic (user plane traffic is also referred to as user data). do). DRB is used to carry IP packets.

 IP flow is mapped to one bearer in the RRC layer, and one bearer is mapped to one logical channel in the RLC / MAC layer. At this time, the same QoS is applied to all IP packets of a bearer and a logical channel associated with one IP flow. In 3GPP LTE and LTE-A mobile communication systems, the MAC layer determines transmission priority and amount of data according to logical channel priority. The uplink TFT (traffic flow template) of the terminal and the downlink TFT of the PDN-GW may separate the IP packet for each IP flow through a packet filter and transmit the IP packet to the counterpart communication node in the form of a bearer (the bearer is a terminal It is transmitted in the form of RB between the 1110 and the base station 1120, in the form of an S1 bearer between the base station 1120 and the SGW 1130, and in the form of an S5 / S8 bearer between the SGW 1130 and the PDN-GW 1140. do).

In the case of FIG. 11, the first uplink traffic flow aggregate 1105-1 is a PDN-GW 1140 in the form of an RB 1150 via a packet filter 1110-1 associated with a terminal uplink TFT. (In the form of an S1 bearer between base station 1120 and SGW 1130 and between SGW 1130 and PDN-GW 1140 in the form of an S5 / S8 bearer). The second uplink traffic flow aggregate 1105-2 is delivered to the PDN-GW 1140 in the form of an RB 1160 via a packet filter 1110-2 associated with the terminal uplink TFT ( A S1 bearer between the base station 1120 and the SGW 1130 and between the SGW 1130 and the PDN-GW 1140 in the form of an S5 / S8 bearer.

The TFT rules used in the conventional uplink and downlink TFTs are used to process IP packets on the IP flow (source IP address, destination IP address, transport protocol, source transport port). port and 5 tuples of destination transport port, and all the IP packets in one IP flow are subject to the same QoS and if congestion occurs during the IP flow. From the earliest (ie, oldest) IP packet to generation time in time, it is discarded by the RLC layer (which is at the request of the PDCP layer).

However, if more important IP packets are discarded in one IP flow, the overall performance can be greatly affected. As such, when congestion occurs and the IP packet is discarded without considering the importance of the IP packet, the overall communication service quality may be degraded and the data transmission delay may increase. Next, data transmission using differential QoS settings according to an embodiment of the present invention for preventing data transmission delay will be described.

12 is a conceptual diagram illustrating data transmission using QoS setting for each IP flow according to an embodiment of the present invention.

Referring to FIG. 12, in case of an IP packet to which different QoS is applied in one IP flow, an IP packet to which different QoS is applied in one bearer is classified and processed. When IP packets are mapped to different bearers and logical channels within one IP flow, data may be delivered to an upper layer of a counterpart communication node in an out-of-order order, which may cause performance degradation. Therefore, in order to solve this problem, different QoS can be applied to IP packets in one bearer for IP packets that need to apply different QoS in one IP flow.

To this end, for the IP packet transmitted from the terminal upper layer to the lower PDCP layer, it is possible to determine the importance of the delivered IP packet according to a predetermined importance determination criterion. The PDCP layer may include the discrimination information that meets the criteria according to the importance determination criterion and transmit the information to the RLC layer (S1210). For example, if there is a two-step importance criterion (distinguishing important data by setting the critical data flag bit, etc.), the PDCP PDU is delivered to the RLC layer by marking it as critical data for important IP packets. Can be.

The RLC layer which has received this may transmit the RLC PDU including the importance determination information to the MAC layer (S1220). For example, if the above-described two-step importance determination criterion is marked as critical data, the MAC layer may be notified that the RLC PDU is waiting to be transmitted to the RLC buffer.

Next, when the MAC layer of the UE receives data indicated as important data according to the importance determination information to be transmitted from the upper layer, a buffer status report (BSR) is sent to the base station for rapid data communication according to separate processing criteria. Resource allocation for uplink transmission may be requested by transmitting (S1230) (in case of important data, the BSR may be immediately triggered). The base station receiving the BSR from the terminal may allow an uplink grant to allow uplink important data to be transmitted (S1240).

According to this procedure, the UE is allocated an uplink radio resource and transmits a PDCP PDU to a base station, but there may be a PDCP PDU not transmitted for a predetermined time. At this time, depending on the importance of the PDCP PDU that has not been transmitted for a certain time, the PDCP layer may request the RLC layer to discard the associated RLC SDU (S1250). That is, even if a request for discarding an RLC SDU related to an IP packet that is not important is discarded by discarding an IP packet that has caused transmission congestion, the important data is not discarded according to the importance of the IP packet. It can reduce the delay and prevent the quality of communication service provision. The importance determination criteria may be set in advance and provided to the terminal from the base station, or the terminal may decide for itself.

As a processing method for an IP packet that needs to apply different QoS in one IP flow, in another embodiment of the present invention, different QoS may be applied by mapping to different bearers and logical channels for each packet. In addition to the 5 tuples of the above-described TFT rules (source IP address, destination IP address, transport protocol, source transport port, destination transport port), a separate protocol header field may be added and configured. For example, an IP packet having an acknowledgment (ACK) bit set in a TCP flag of a transmission control protocol (TCP) header may be mapped to a logical channel having a high priority.

In another embodiment of the present invention, a plurality of sub-channels are applied in one logical channel to apply different QoS in a method of processing IP packets that require different QoS in one IP flow. The packets that need to be classified can be processed. That is, subchannels for logical channels associated with each QoS may be allocated differently. Through this, the MAC layer can transmit data from the subchannel to which the packet with the highest priority among the data in the RLC buffer is allocated. The information on the subchannel is an internal operation of the terminal, and the base station does not need to know the corresponding information separately.

In relation to the packets that need to apply different QoS, the priority and discard timer for each IP packet according to QoS difference may be different (that is, apply QoS parameters differentially). For example, different priority and different discard timers may be set for each subchannel for a logical channel and applied to IP packets allocated to the subchannel (the setting of QoS parameters may be controlled by the RRC layer). .

Specifically, in the case of TCP packets, if there are a plurality of ACK packets to be transmitted, discarding old ACK packets except for the latest (late) generated ACK packet in time, and transmitting a new ACK packet may improve TCP performance. Can be. If necessary, the PDCP layer may request the RLC layer to discard the old TCP ACK packet by requesting the RLC SDU to discard before the discard timer expires. Next, a mini-slot PDCCH monitoring method according to an embodiment of the present invention for preventing data transmission delay will be described.

13A is a conceptual diagram illustrating slot-based PDCCH monitoring according to the prior art, and FIG. 13B is a conceptual diagram illustrating PDCCH monitoring when a minislot according to the prior art is applied.

Referring to FIGS. 13A and 13B, unlike the conventional slot-based transmission time interval (TTI), when transmitting a physical downlink control channel (PDCCH) through a mini slot-based transmission time interval in symbol units It shows an increase in the number of PDCCH monitoring due to an increase in PDCCH candidates.

As described above, in the fifth generation mobile communication system, unlike the conventional 20 MHz maximum bandwidth and 15 kHz single subcarrier spacing, the goal is to support a wide bandwidth from 5 MHz to 400 MHz. It is difficult. Therefore, a method of differentially applying subcarrier spacing for each frequency bandwidth has been studied. In this regard, a method of applying slots and mini-slots according to subcarrier spacing has been studied. Using a wide subcarrier spacing shortens the length of one slot in inverse proportion, thereby reducing the transmission delay in the wireless section. This is essential for the implementation of the URLLC required by the fifth generation mobile communication system as described above. In addition to the conventional scheduling of slots, the scheduling of mini slots (slots consisting of 2 OFDM symbols, 4 OFDM symbols, and 7 OFDM symbols) is studied. It is becoming.

13A and 13B, mini slot-based PDCCH monitoring is conventional slot-based PDCCH monitoring (one PDCCH 1310 per slot includes downlink control information for one or more resource blocks 1320, 1330). Unlike the PDCCHs 1340 and 1360 for one or more mini slots, a PDCCH occasion for receiving downlink control information occurs more frequently, and thus the UE monitors the PDCCH more frequently (first mini slot PDCCH ( 1340 includes downlink control information for the first resource block 1350, and the second mini slot PDCCH 1360 includes downlink control information for the second resource block 1370 and the third resource block 1380. Containing).

Mini-slot-based PDCCH monitoring reduces data transmission delay, but terminal power consumption increases due to an increase in the number of PDCCH monitoring of the terminal. In addition, as described above, since the fifth generation mobile communication system needs to support several tens of times the frequency bandwidth, the PDCCH candidate is also increased in the frequency domain, thereby increasing the number of blind decoding operations of the UE. Done. Next, a mini slot based PDCCH monitoring method according to an embodiment of the present invention for solving the problem of mini slot based PDCCH monitoring according to the prior art will be described.

14 is a flowchart illustrating a mini slot-based PDCCH according to an embodiment of the present invention.

Referring to FIG. 14, a terminal performing mini-slot-based PDCCH monitoring requests PDCCH occasion pattern information from a base station and, in response, indicates that the base station transmits pattern information of PDCCH occasion to the terminal. The base station may have information on a control resource set (CORESET) pattern to which the PDCCH occasion is to be allocated in advance.

The CORESET pattern may have information about various PDCCH occasion allocations by combining them using information on N resource sets in the frequency domain and M resource sets in the time domain. The UE can monitor the PDCCH occasion only for a portion of the region not the entire PDCCH allocation region by referring to the information on the CORESET pattern received from the base station, thereby reducing power consumption by not performing blind decoding on an unnecessary region. In more detail, the terminal may request CORESET pattern information from the base station (S1410). A base station receives it can transmit the CORESET pattern information assigned to the UE to the UE (S1420) (the one embodiment of the present invention, to F _1, F ₂ frequency domain, and T _1, T ₂ the terminal shown in Figure 14 It is assumed that a CORESET pattern consisting of a time domain is allocated, but is not limited thereto. In this case, the CORESET pattern request information and the CORESET Pattern information may be transmitted through an RRC signaling message and / or MAC CE (ontrol element).

When the UE receives the information on the CORESET pattern, it can only monitor the PDCCH occasion corresponding to the corresponding CORESET. The base station may set a CORESET pattern and transmit it to the terminal, but the terminal may request the base station to the desired CORESET pattern. The base station receiving such a request may allocate a CORESET pattern to the UE as it is, or may notify the UE of the CORESET pattern based on the CORESET pattern allocation situation to other terminals.

In addition, the base station and the terminal may enable (on) or deactivate (off) the mini slot-based PDCCH occasion in the frequency domain and time domain. For example, the base station may deactivate (mini) the mini-slot based PDCCH occasion monitoring as needed and inform the terminal of the related information (relevant allocation information on all frequency domains and time domains in the CORESET pattern information received by the terminal is deactivated). (off), the UE may determine that the mini slot-based PDCCH occasion is inactivated). In addition, the terminal may request the base station to disable the mini slot-based PDCCH occasion (off), if necessary, the base station receiving the request may deactivate the mini-slot based PDCCH monitoring and inform the terminal of the result.

In addition, a physical downlink shared channel (PDSCH) and / or a physical uplink shared channel (PUSCH) may also apply a resource set in the same manner as a PDCCH. In this case, the PDSCH and / or PUSCH resource set pattern may be allocated at the request of the UE, and uplink data transmission / reception may be performed using the PDSCH on the specific frequency domain and the time domain and / or the PUSCH resource on the specific frequency domain and the time domain. .

Meanwhile, switching may be performed from a mini slot-based TTI operation to a slot-based TTI operation, and conversely, may be switched from a slot-based TTI operation to a mini slot-based TTI operation. When switching from the mini slot based TTI operation to the slot based TTI operation, the number of hybrid automatic repeat request (HARQ) processes being performed in the mini slot based TTI operation may be greater than the number of HARQ processes of the slot based TTI. In this case, even though HARQ retransmission is required, HARQ retransmission cannot be performed using the HARQ process in the slot-based TTI operation, thereby degrading data communication performance. To prevent this problem, if the number of HARQ processes in the mini slot-based TTI operation that is being performed at the time of switching is larger than the number of HARQ processes in the slot-based TTI operation, the slot-based TTI after switching for data requiring HARQ retransmission before switching When the HARQ process of operation becomes available, HARQ retransmission may be performed in the form of initial transmission using this.

The methods according to the invention can be implemented in the form of program instructions that can be executed by various computer means and recorded on a computer readable medium. Computer-readable media may include, alone or in combination with the program instructions, data files, data structures, and the like. The program instructions recorded on the computer readable medium may be those specially designed and constructed for the present invention, or may be known and available to those skilled in computer software.

Examples of computer readable media include hardware devices that are specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code, such as produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware device described above may be configured to operate with at least one software module to perform the operations of the present invention, and vice versa.

Although described with reference to the embodiments above, those skilled in the art will understand that the present invention can be variously modified and changed without departing from the spirit and scope of the invention as set forth in the claims below. Could be.

Claims (17)

As an operation method of a terminal in a mobile communication system,
Driving a T310 timer when a physical layer out-of-sync of a downlink physical downlink control channel (PDCCH) transmitted from a first base station occurs;
Confirming that a radio link failure (RLF) occurs when the physical layer in-sync state of the downlink PDCCH does not occur until the T310 timer expires;
In order to establish a new radio link when the RLF occurs, a packet data convergence protocol (PDCP) layer and a radio link control (RLC) layer for all radio bearers except for signaling radio bearer 0 (SRB0) between the terminal and the second base station. Performing a reset;
Suspending all radio bearers except for SRB0;
Performing RRC connection reconfiguration to the selected second base station through cell selection; And
And resuming all radio bearers if the RRC connection reestablishment with the second base station succeeds. The method according to claim 1,
And transmitting the data transmitted from the first base station to an RLC upper layer at a point in time determined through control of a radio resource control (RRC) layer, and optionally to the PDCP upper layer. The method according to claim 1,
If data is not normally received even in a retransmission request according to a predetermined criterion to the first base station, forwarding the data transmitted from the first base station to an RLC upper layer, and optionally forwarding the PDCP higher layer , The operation method of the terminal. The method according to claim 1,
And transmitting information indicating the occurrence of the RLF to the first base station through the second base station when the RLF occurs with the first base station. The method according to claim 4,
And transmitting information indicating an identifier for the second base station selected through the cell selection to the first base station. The method according to claim 1,
And transmitting information indicating the occurrence of the RLF to the first base station through a second cell carrier, wherein the first base station is a master base station of carrier aggregation. Way. The method according to claim 1,
Transmitting information indicating the occurrence of the RLF to the first base station through a second cell group, wherein the first base station is a dual connectivity master base station; Method of operation of the terminal. The method according to claim 7,
Performing PDCP layer and RLC layer reconfiguration for all radio bearers except for the master base station and SRB0; And
And performing data transmission / reception with the master base station without suspending all radio bearers except the SRB0. As an operation method of a terminal in a mobile communication system,
Receiving, by a first RLC receiver of the terminal, original data from a first RLC transmitter of a base station;
Receiving, by the second RLC receiver of the terminal, duplicated data generated based on the raw data from the second RLC transmitter of the base station;
When the raw data is successfully received, transmitting, by the first RLC receiver, first information indicating that the raw data is successfully received to the first RLC transmitter; And
Receiving, by the second RLC receiver, second information indicating that the duplicated data is discarded at the base station from the second RLC transmitter;
The RLC connection between the first RLC transmitter and the first RLC receiver is used for transmission and reception of the raw data, and the RLC connection between the second RLC transmitter and the second RLC receiver is used for transmission and reception of the duplicate data. Method of operation. The method according to claim 9,
The second information is included in an RLC PDU configured only with an RLC header, and the RLC PDU transmitted from the second RLC transmitter is received at the second RLC receiver. The method according to claim 9,
The packet data convergence protocol (PDCP) layer of the base station notifies the first RLC transmitter and the second RLC transmitter that the PDCP PDUs of the PDCP layer are duplicated, and polls an RLC PDU including the PDCP PDU. Method of operating a terminal to set the bit. delete delete delete delete delete delete

Images