KR20230044897A - Method and apparatus for notifying connection release in communication system - Google Patents

Abstract

Disclosed is a connection release notification technology in a communication system. An operation method performed in a terminal of a communication system, comprising: transmitting msg1 including a preamble to a base station; receiving msg2, which is a response signal to the msg1, from the base station; Transmitting msg3 including a cell radio network temporary identifier (C-RNTI) to the base station in response to the msg2; and receiving a message indicating that the connection between the base station and the terminal is released in response to the msg3 from the base station when the C-RNTI is not valid in the base station. this can be provided.

Description

Disconnect notification method and device in communication system {METHOD AND APPARATUS FOR NOTIFYING CONNECTION RELEASE IN COMMUNICATION SYSTEM}

The present invention relates to a connection disconnection notification technology in a communication system, and more particularly, to a connection disconnection notification technology in a communication system that allows a base station to notify a terminal of the mismatch when a terminal state is inconsistent between a terminal and a base station. .

Along with the development of information and communication technology, various wireless communication technologies may be developed. Representative wireless communication technologies may include long term evolution (LTE) and new radio (NR), which are defined in the 3rd generation partnership project (3GPP) standard. LTE may be one wireless communication technology among 4th generation (4G) wireless communication technologies, and NR may be one wireless communication technology among 5th generation (5G) wireless communication technologies.

For the processing of rapidly increasing wireless data after the commercialization of 4G communication systems (eg, communication systems supporting LTE), the frequency band (eg, frequency bands below 6 GHz) of the 4G communication system as well as the 4G communication system A 5G communication system (eg, a communication system supporting NR) using a frequency band higher than the frequency band of (eg, a frequency band of 6 GHz or higher) may be considered. The 5G communication system may support eMBB (enhanced Mobile BroadBand), URLLC (Ultra-Reliable and Low Latency Communication), and mMTC (massive machine type communication).

In such a communication system, a procedure initially performed by a terminal to establish a connection with a base station may be a random access procedure. Such a random access procedure can be classified into several procedures according to the triggering subject and the presence or absence of dedicated resources. Accordingly, the random access procedure can be divided into an initial random access procedure for initial access and a connected random access procedure performed by a terminal previously assigned a cell radio network temporary identifier (C-RNTI) from a base station.

On the other hand, when the terminal can temporarily move to a shadow area or the communication network is unstable, a case in which the terminal and the specific terminal state managed by the base station do not match may occur. That is, when the state that the terminal thinks (ie, radio resource control (RRC) connection state) may be different from the terminal state that the base station thinks (that is, RRC idle state), the terminal and the specific terminal state managed by the base station are inconsistent may occur. At this time, the connected random access procedure performed by the terminal in the idle state may fail because the base station does not have the context of the corresponding terminal. In this case, even if the terminal attempts connected random access as many times as the set maximum number of preamble transmissions, it may eventually fail. As such, the terminal may execute a procedure in which failure is obvious in the connected random access procedure.

An object of the present invention for solving the above problems is a connection disconnection notification method and apparatus in a communication system in which a base station informs a terminal of the mismatch when a terminal state is inconsistent between a terminal and a base station so that the terminal does not repeat unnecessary operations. is providing

To achieve the above object, a connection release notification method in a communication system according to a first embodiment of the present invention is an operation method performed in a terminal of the communication system, comprising: transmitting msg1 including a preamble to a base station; receiving msg2, which is a response signal to the msg1, from the base station; Transmitting msg3 including a cell radio network temporary identifier (C-RNTI) to the base station in response to the msg2; and receiving a message indicating that the connection between the base station and the terminal is released in response to the msg3 from the base station when the C-RNTI is not valid in the base station.

According to the present application, when the terminal states are inconsistent between the terminal and the base station, the base station informs the terminal of contention resolution failure so that the terminal does not repeat unnecessary operations.

In addition, the base station can enable efficient physical random access channel (PRACH) channel operation by preventing unnecessary preamble transmission of the terminal by allowing the terminal to recognize a random access procedure that is bound to fail.

In addition, the base station can minimize power consumption of the terminal by allowing the terminal to avoid retrying for connected random access failure that inevitably occurs.

1 is a conceptual diagram illustrating a first embodiment of a communication system.
2 is a block diagram showing a first embodiment of a communication node constituting a communication system.
3 is a flowchart illustrating a first embodiment of a random access procedure.
4 is a flow chart illustrating a second embodiment of a random access procedure.

Since the present invention can make various changes and have various embodiments, specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the present invention to specific embodiments, and 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. These terms are only used for the purpose of distinguishing one component from another. For example, a first element may be termed a second element, and similarly, a second element may be termed a first element, without departing from the scope of the present invention. The terms and/or include any combination of a plurality of related recited items or any of a plurality of related recited items.

In embodiments of the present application, “at least one of A and B” may mean “at least one of A or B” or “at least one of combinations of one or more of A and B”. Also, in the embodiments of the present application, “one or more of A and B” may mean “one or more of A or B” or “one or more of combinations of one or more of A and B”.

It is understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, but other elements may exist in the middle. It should be. On the other hand, when an element is referred to as “directly connected” or “directly connected” to another element, it should be understood that no other element exists in the middle.

Terms used in this application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, the terms "include" or "have" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

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 to which the present invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in this application, they should not be interpreted in an ideal or excessively formal meaning. don't

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in more detail. In order to facilitate overall understanding in the description of the present invention, the same reference numerals are used for the same components in the drawings, and redundant descriptions of the same components are omitted.

1 is a conceptual diagram illustrating a first embodiment of a communication system.

Referring to FIG. 1, a 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, the 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 is a communication protocol based on code division multiple access (CDMA), a communication protocol based on wideband CDMA (WCDMA), a communication protocol based on time division multiple access (TDMA), and a frequency division multiple (FDMA) access) based communication protocol, OFDM (orthogonal frequency division multiplexing) based communication protocol, OFDMA (orthogonal frequency division multiple access) based communication protocol, SC (single carrier)-FDMA based communication protocol, NOMA (non-orthogonal multiple access) access)-based communication protocol, space division multiple access (SDMA)-based communication protocol, and the like may be supported. Each of the plurality of communication nodes may have the following structure.

2 is a block diagram showing a first embodiment of a communication node constituting a communication system.

Referring to FIG. 2 , a communication node 200 may include at least one processor 210, a memory 220, and a transceiver 230 connected to a network to perform communication. 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 an individual interface or an individual bus centered on 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 transmission/reception device 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 include at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 220 may include 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, 120-2), a plurality of user equipment (UEs). ) (130-1, 130-2, 130-3, 130-4, 130-5, 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 UE 130-3, and the fourth UE 130-4 may belong to the coverage of the first base station 110-1. The second UE 130-2, the fourth UE 130-4, and the fifth UE 130-5 may belong within the coverage of the second base station 110-2. The fifth base station 120-2, the fourth UE 130-4, the fifth UE 130-5, and the sixth UE 130-6 may belong within the coverage of the third base station 110-3. . The first UE 130-1 may belong within the coverage of the fourth base station 120-1. The sixth UE 130-6 may belong within the coverage of the fifth base station 120-2.

Here, each of the plurality of 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, roadside unit (RSU), digital unit (DU), cloud digital unit (CDU) , 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 UEs 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 includes a terminal, an access terminal, a mobile terminal, It may be referred to as a station, subscriber station, mobile station, portable subscriber station, node, device, and 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), advanced (LTE-A), etc. specified 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 ideal backhaul or non-ideal backhaul, and ideal backhaul Alternatively, information may be exchanged with each other through non-ideal backhaul. Each of the plurality of 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-ideal backhaul. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 transmits a signal received from the core network to a corresponding UE 130-1, 130-2, 130-3, and 130. -4, 130-5, 130-6), and signals received from the corresponding UEs 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 are transmitted to the 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 OFDMA-based downlink transmission, and may support SC-FDMA-based uplink transmission. ) can support transmission. In addition, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 transmits multiple input multiple output (MIMO) (eg, single user (SU)-MIMO, MU (multi user)-MIMO, massive MIMO, etc.), CoMP (coordinated multipoint) transmission, carrier aggregation transmission, transmission in unlicensed band, device to device (D2D) ) communication (or proximity services (ProSe)), etc. Here, each of the plurality of UEs 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 is a base station Operations corresponding to (110-1, 110-2, 110-3, 120-1, 120-2) supported by base stations 110-1, 110-2, 110-3, 120-1, 120-2 action can be performed.

In such a communication system, a procedure initially performed by a terminal to establish a connection with a base station may be a random access procedure. Such a random access procedure can be classified into several procedures according to the triggering subject and the presence or absence of dedicated resources. For example, the random access procedure can be divided into initial random access for initial access and connected random access performed by a terminal previously allocated a C-RNTI from a base station. For this random access procedure, the terminal may receive PRACH resources for random access and variables for performing random access from the base station.

Here, the initial random access may be a random access for a terminal in an idle state to transition to a connected state. When the terminal succeeds in initial random access to the base station, it may be allocated a C-RNTI used to identify the terminal from the base station. Accordingly, the terminal can complete setting of a channel through which it can communicate with the base station. This initial random access procedure includes the step of transmitting a preamble signal (ie, msg1) to the PRACH resource available to the UE, allocating a temporary C-RNTI (TC-RNTI) that the UE can use temporarily, and radio resource control (RRC) Receiving a random access response signal (ie, msg2) including uplink (UL) grant information for transmission of the setup request signal (ie, msg3) from the base station; Transmitting an RRC setup request signal (ie, msg3) to the base station using the received uplink grant, and the terminal receiving a contention resolution ID (identifier) and an RRC setup signal (ie, msg4) from the base station It can be done in steps of When contention is resolved through these steps, the terminal can convert the TC-RNTI received through msg2 into a C-RNTI, and can then use the C-RNTI as an identifier for communication with the base station.

Meanwhile, the connected random access may be a random access procedure performed by a terminal in a connected state after being allocated a C-RNTI for the purpose of matching uplink synchronization. Such a connected random access procedure includes the steps of transmitting a preamble signal (i.e., msg1) to the base station on available PRACH resources by the UE, TC-RNTI allocation that the UE can temporarily use, and an RRC setup request signal (i.e., msg3 Receiving a random access response signal (ie, msg2) including uplink (UL) grant information for transmission of ) from the base station, and the terminal previously allocated using the uplink grant received in the previous step Transmitting an RRC setup request signal (ie, msg3) including C-RNTI and BSR (buffer status report) information to the base station, and uplink resource allocation for the terminal to resolve contention from the base station DCI (downlink control) information) 0 may be included.

In this connected random access procedure, the base station can confirm that the terminal is a terminal previously connected to itself through the C-RNTI received in msg3. When the base station determines that the terminal is a valid terminal, the base station may allocate uplink resources to the terminal when there are available resources. When contention is resolved through these steps, the terminal can transmit uplink data to the base station. In this state, when the terminal transitions to the idle state, the base station may delete the C-RNTI allocated to the terminal. Accordingly, in order for the terminal to transition to the connected state, the terminal may perform initial random access and re-allocate the C-RNTI from the base station.

Meanwhile, when a terminal may temporarily move to a shadow area or a communication network is unstable, a case in which a terminal and a specific terminal state managed by a base station do not match may occur. That is, the terminal can be considered as a radio resource control (RRC) connected state, and the base station can consider the terminal state as an RRC idle state, so that a case in which the terminal and a specific terminal state managed by the base station do not match may occur. That is, the terminal is in a connected state by being allocated a C-RNTI in an RRC connected state, and the base station considers the corresponding terminal to be in an RRC idle state and can release it and delete the related context.

3 is a flowchart illustrating a first embodiment of a random access procedure.

Referring to FIG. 3, in a random access procedure, a UE may transmit a preamble signal (ie, msg1) to a base station through PRACH (S301). The base station may receive a preamble signal from the terminal. Then, the base station can transmit scheduling information for the RAR signal through a physical downlink control channel (PDCCH) (S302) and transmit the RAR signal (ie, msg2) through a physical downlink shared channel (PDSCH) (S303). Scheduling information for the RAR signal may be included in a downlink control indicator (DCI) and transmitted from the base station to the terminal. Accordingly, the terminal may receive scheduling information for the RAR signal from the base station, and may receive the RAR signal using the received scheduling information. And, the terminal may transmit an RRC setup request signal (ie, msg3) to the base station (S304). Accordingly, the base station may receive the RRC setup request signal from the terminal. Then, the base station may transmit scheduling information for msg4 to the terminal (S305) and may transmit an RRC setup signal (ie, msg4) (S306). Scheduling information for Msg4 may be included in DCI and transmitted from the base station to the terminal. Accordingly, the terminal may receive scheduling information for the RRC setup signal from the base station, and may receive the RRC setup signal using the received scheduling information.

Thereafter, the terminal may transmit an RRC setup completion signal (ie, msg5) to the base station (S307). Accordingly, the base station may receive the RRC setup completion signal from the terminal. Then, the base station may transmit scheduling information for retransmission to the terminal (S308). Scheduling information for retransmission may be included in DCI and transmitted from the base station to the terminal. Then, the terminal can receive scheduling information for retransmission from the base station. As such, the base station and the terminal may perform an operation for retransmission by repeating these operations (S307 to S311). As such, the terminal can retransmit msg5 according to the retransmission policy provided by the base station. At this time, if even the retransmission fails, connected random access can be performed to request uplink resources from the base station. In this situation, when the base station cannot receive msg5 and the timer expires, it can delete the context of the corresponding terminal. Accordingly, when the terminal performs the connected random access procedure due to the failure of retransmission of msg5, it may fail because the base station does not have the context of the corresponding terminal.

Looking at this in more detail, the terminal may transmit a preamble signal (ie, msg1) to the base station for the connected random access procedure (S320). The base station may receive a preamble signal from the terminal. Then, the base station may transmit scheduling information for the RAR signal to the terminal through the PDCCH (S321), and may transmit the RAR signal (ie, msg2) through the PDSCH (S322). Scheduling information for the RAR signal may be included in DCI and transmitted from the base station to the terminal. Accordingly, the terminal may receive scheduling information for the RAR signal from the base station and receive the RAR signal according to the received scheduling information. Then, the UE may transmit an RRC setup request signal (ie, msg3) including previously allocated C-RNTI and BSR information to the base station using the uplink grant received in the previous step (S323). The base station may receive an RRC setup request signal including C-RNTI and BSR information from the terminal. At this time, the base station cannot transmit scheduling information for contention resolution to the terminal because the context for the terminal is deleted. In this way, when the terminal cannot receive scheduling information for contention resolution from the base station and the contention resolution timer expires, the connected random access procedure may be repeated a set number of times (S330 to S333). In this way, although the terminal performs the repeated connected random access procedure, it may fail because the base station does not have the context of the corresponding terminal. Accordingly, the terminal may repeatedly execute a procedure in which failure is obvious. Of course, if the connected random access fails, the terminal may be able to recover communication by performing cell search and initial random access procedures for link failure recovery, but unnecessary signaling may occur in the meantime. Such an unnecessary signaling procedure may reduce the efficiency of PRACH resources in a 5G communication network that must accommodate a very large number of terminals. In this case, if the UE can recognize the random access procedure that is bound to fail, unnecessary preamble transmission can be prevented and efficient PRACH channel management can be achieved.

4 is a flow chart illustrating a second embodiment of a random access procedure.

Referring to FIG. 4, in the random access procedure, the terminal may recognize that it is in an RRC connection state with the base station (S401). However, the base station may release the connection to the terminal and delete the context for the terminal due to various situations such as when the terminal moves to a shadow area (S402). In this way, the terminal can recognize its own state as an RRC connected state, and if it is determined that the C-RNTI allocated to it is valid, it can transmit a preamble signal (ie, msg1) to the base station to start a connected random access procedure. (S403). Accordingly, the base station can receive the preamble signal from the terminal. And, the base station may transmit scheduling information for the RAR signal through the PDCCH to the terminal (S404), and may transmit the RAR signal (ie, msg2) through the PDSCH scheduled according to the scheduling information (S405). Scheduling information for the RAR signal may be included in a downlink control indicator (DCI) and transmitted from the base station to the terminal. Accordingly, the terminal can receive the RAR signal from the base station.

Meanwhile, the terminal may transmit an RRC setup request signal (ie, msg3) including previously allocated C-RNTI and BSR information to the base station using the uplink grant received in the previous step (S406). The base station may receive an RRC setup request signal including C-RNTI and BSR information from the terminal. That is, the base station may inform the terminal of the C-RNTI and BSR information using the uplink grant in the RAR. Here, the C-RNTI can be used by the base station to identify the identity of the terminal. And, the BSR can be used to notify the amount of data to be transmitted by the UE through the uplink. At this time, the base station determines whether the received C-RNTI is valid and if it can confirm that the corresponding terminal is a terminal in a connected state, allocates uplink transmission resources based on the BSR information requested by the terminal and transmits scheduling information to the corresponding terminal. can Upon receiving this, the terminal may recognize that contention resolution has been successfully performed, and may resume communication in the future. If there is no uplink resource to allocate, the base station may not transmit scheduling information to the terminal. If the UE does not receive scheduling information until a contention resolution timer that starts running after transmission of msg3 expires, it may consider that contention resolution has failed. This is a general exception case that may occur when uplink resources are insufficient, and it may be a normal procedure for the terminal to perform the connected random access procedure by transmitting the preamble again.

Alternatively, the C-RNTI received by the base station from the terminal may not be a valid identifier because the terminal is released from the base station. In this way, if the terminal is released from the base station for some reason, that is, if the C-RNTI received by msg3 can be deleted from the base station and is not managed, if the terminal operates according to the general procedure, as mentioned above, the terminal resolves contention. Connected random access, of which failure is obvious, may be performed as many times as set by the base station. Accordingly, the base station may inform the terminal of the release state by transmitting a connection release state notification signal to the terminal (S407).

At this time, the base station may notify the terminal of the disconnection state by utilizing the DCI format for scheduling uplink data. DCI formats for scheduling uplink data may use format 0 in 4G systems and format 0_0, format 0_1, and format 0_2 in 5G. Each format may have different information depending on its use, but its purpose may be to include scheduling information for the terminal to transmit uplink data. That is, each format may include a DCI format identifier, time and frequency resources for transmitting uplink data, HARQ information, and the like. The base station may scramble this DCI information into an appropriate RNTI according to the state of the terminal and transmit it to the terminal. Here, DCI including scheduling information for uplink data transmission may be referred to as DCI0. In particular, the base station may set a parameter related to uplink scheduling among the fields of DCI0 to 0xFF (or other meaningless value), and transmit the address to the corresponding C-RNTI to the terminal.

At this time, since the user search space of the corresponding terminal does not exist because the context of the terminal is deleted, the base station may transmit DCI0 addressed by the C-RNTI to a common search space (CSS). As such, the base station may transmit DCI0 addressed to the C-RNTI to the terminal through CSS. After transmitting msg3 in performing the connected random access procedure, the terminal may monitor the common search space to decode DCI0 addressed to the C-RNTI in addition to the TC-RNTI. Accordingly, the terminal can obtain DCI0 with scheduling-related information set to 0xFF (or other meaningless value), the terminal can detect that it has been deleted from the base station at some point in the past, and the connected random access procedure is stopped. can do.

Thereafter, when communication with the network is still required, the terminal may immediately perform a cell search procedure, and operate to communicate with the corresponding cell through an initial random access procedure.

The methods according to the present invention may 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 program instructions, data files, data structures, etc. alone or in combination. Program instructions recorded on a computer readable medium may be specially designed and configured for the present invention or may be known and usable to those skilled in computer software. Examples of computer readable media may include hardware devices specially configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions may include not only machine language codes generated by a compiler but also high-level language codes that can be executed by a computer using an interpreter and 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. In addition, the above-described method or device may be implemented by combining all or some of its components or functions, or may be implemented separately.

Although the above has been described with reference to preferred embodiments of the present invention, those skilled in the art will variously modify and change the present invention within the scope not departing from the spirit and scope of the present invention described in the claims below. You will understand that it can be done.

Claims (1)

As an operation method performed in a terminal of a communication system,
Transmitting msg1 including a preamble to a base station;
receiving msg2, which is a response signal to the msg1, from the base station;
Transmitting msg3 including a cell radio network temporary identifier (C-RNTI) to the base station in response to the msg2; and
When the C-RNTI is not valid in the base station, receiving a message indicating that the connection between the base station and the terminal is released in response to the msg3 from the base station.

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