KR102198010B1 - Methods for load management of ran nodes and apparatueses thereof - Google Patents

Abstract

The present disclosure relates to a technology for managing a load on a base station node in a 5G network. In an embodiment, in a method for a master base station to manage a load of a secondary base station, the steps of configuring dual connectivity with the secondary base station, receiving a secondary base station status indication message from the secondary base station through an X2 interface, and a secondary base station status indication message It provides a method and apparatus, comprising the step of determining whether to perform a load reduction operation for the secondary base station based on the value of the secondary base station load information parameter included in.

Description

BACKGROUND OF THE INVENTION Method and apparatus for load management of a base station TECHNICAL FIELD [Methods for Load Management

The present disclosure relates to a technology for managing a load on a base station node in a 5G network.

Next-generation mobile communication technologies are being studied in accordance with the demand for large-capacity data processing and high-speed data processing. For example, in a mobile communication system such as LTE (Long Term Evolution), LTE-Advanced, and 5G of the current 3GPP series, a high-speed and large-capacity communication system capable of transmitting and receiving various data such as video and wireless data beyond voice-oriented services. Is being demanded.

In order to handle this request, the terminal and the base station need a technology for transmitting and receiving data using a plurality of carriers. For example, a carrier aggregation technology in which one base station merges a plurality of carriers to communicate with a terminal, or a dual connection technology in which a plurality of base stations communicate with a terminal using a plurality of carriers, has been studied.

However, although next-generation wireless access technology is being developed, it is expected that a certain period of time is required to provide communication service only to base stations using the same. Accordingly, even in a situation in which an LTE base station using a conventional radio access technology and an NR base station using a next-generation radio access technology coexist, it is necessary to provide a service through the aforementioned carrier aggregation or dual connection.

In addition, technology for base station load management is becoming important in a situation in which the data usage of the terminal increases rapidly. In particular, in the case of base stations using heterogeneous access technology, or when a single base station transmits data using a plurality of cells, a technology for managing the load of an individual base station or an individual cell by accurately recognizing the situation of each base station is required.

In the above-described background, the present disclosure intends to propose a method and apparatus for load management of individual base stations when different base stations configure dual connectivity in a terminal.

In addition, the present disclosure is intended to propose a load management method and apparatus for each node when a plurality of logical nodes are configured in a base station.

An embodiment devised to solve the above-described problem is a method for a master base station to manage the load of a secondary base station, the step of configuring dual connectivity with the secondary base station, and sending a secondary base station status indication message from the secondary base station through the X2 interface. It provides a method comprising the step of receiving and determining whether to perform a load reduction operation for the secondary base station based on the value of the secondary base station load information parameter included in the secondary base station status indication message.

In addition, an embodiment includes a control unit for configuring dual connectivity with the secondary base station in a master base station for managing a load of a secondary base station, and a receiving unit for receiving a secondary base station status indication message from the secondary base station through an X2 interface, and the control unit It provides a master base station, characterized in that determining whether to perform a load reduction operation for the secondary base station based on a value of the secondary base station load information parameter included in the secondary base station status indication message.

In addition, in an embodiment, in a method for a central unit to manage a load of a distributed unit, receiving a distribution unit status indication message from the distribution unit through an F1 interface, and a distribution unit status indication It provides a method comprising the step of determining whether to perform a load reduction operation for the distribution unit based on the value of the distribution unit load information parameter included in the message.

In addition, in one embodiment, in the central unit that manages the load of the distributed unit, the receiving unit receiving the distribution unit status indication message from the distribution unit through the F1 interface and the distribution unit status indication message It provides a central unit, characterized in that it comprises a control unit for determining whether to perform a load reduction operation for the distribution unit based on the value of the included distribution unit load information parameter.

The present disclosure provides an effect of efficiently managing the load of individual base stations when different base stations configure dual connectivity in a terminal.

In addition, the present disclosure provides an effect of efficiently managing a load for each node when a plurality of logical nodes are configured in a base station.

1 is a diagram schematically illustrating a structure of an NR wireless communication system to which the present embodiment can be applied.
2 is a diagram for explaining a frame structure in an NR system to which this embodiment can be applied.
3 is a diagram for explaining a dual connectivity structure to which the present embodiment can be applied.
4 is a flowchart illustrating an operation of a master base station according to an embodiment.
5 is a flowchart illustrating an operation of a master base station according to another embodiment.
6 is a signal diagram illustrating a procedure for transmitting a secondary base station status indication message according to an embodiment.
7 and 8 are signal diagrams for explaining a procedure for transmitting a secondary base station status indication message according to another embodiment.
9 and 10 are signal diagrams for explaining a procedure when transmission of a secondary base station status indication message fails according to another embodiment.
11 is a diagram for explaining a resource state update procedure between different base stations.
12 is a diagram illustrating a dual connectivity structure in which a central unit and a distribution unit are divided according to an exemplary embodiment.
13 is a flowchart illustrating an operation of a central unit according to an embodiment.
14 is a signal diagram illustrating a procedure for transmitting a distribution unit status indication message according to an embodiment.
15 and 16 are signal diagrams for explaining a procedure for transmitting a distribution unit status indication message according to another embodiment.
17 and 18 are signal diagrams for explaining a procedure when transmission of a distribution unit base station status indication message fails according to another embodiment.
19 is a diagram for explaining a resource state update procedure between a distribution unit and a central unit.
20 is a diagram illustrating a configuration of a master base station according to an embodiment.
21 is a diagram showing a configuration of a central unit according to another embodiment.

Hereinafter, the embodiments will be described in detail through exemplary drawings. In adding reference numerals to elements of each drawing, it should be noted that the same elements are assigned the same numerals as possible even if they are indicated on different drawings. In addition, in describing the present embodiment, if it is determined that a detailed description of a related known configuration or function may obscure the subject matter of the present embodiment, a detailed description thereof will be omitted.

In the present specification, a wireless communication system refers to a system for providing various communication services such as voice and packet data. The wireless communication system includes a user equipment (UE) and a base station (BS).

A user terminal is a generic concept that refers to a terminal in wireless communication, as well as UE (User Equipment) in WCDMA, LTE, HSPA, and IMT-2020 (5G or New Radio), as well as MS (Mobile Station) and UT in GSM. It should be interpreted as a concept that includes all of (User Terminal), SS (Subscriber Station), and wireless device.

A base station or cell generally refers to a station that communicates with a user terminal, and Node-B (Node-B), evolved Node-B (eNB), gNB (gNode-B), LPN (Low Power Node) ), Sector, Site, various types of antennas, BTS (Base Transceiver System), Access Point, Points (e.g., Transmit Point, Receiving Point, Transceiver Point), Relay Node ( Relay Node), mega cell, macro cell, micro cell, pico cell, femto cell, RRH (Remote Radio Head), RU (Radio Unit), small cell, etc.

In the various cells listed above, since there is a base station controlling each cell, the base station can be interpreted in two meanings. 1) In relation to the radio area, the device itself may provide a mega cell, a macro cell, a micro cell, a pico cell, a femto cell, and a small cell, or 2) the radio area itself may be indicated. In 1), all devices that are controlled by the same entity that provide a predetermined wireless area are controlled by the same entity, or all devices that interact to form a wireless area in collaboration are instructed to the base station. Points, transmission/reception points, transmission points, reception points, etc. are an embodiment of the base station according to the configuration method of the wireless area. In 2), it is possible to instruct the base station to the radio region itself that receives or transmits a signal from the viewpoint of the user terminal or the viewpoint of a neighboring base station.

In the present specification, a cell refers to a component carrier having coverage of a signal transmitted from a transmission/reception point or a coverage of a signal transmitted from a transmission/reception point, and the transmission/reception point itself. I can.

In the present specification, the user terminal and the base station are two (Uplink or Downlink) transmission/reception subjects used to implement the technology or technical idea described in this embodiment, and are used in a comprehensive sense, and are limited by a term or word specifically referred to. It doesn't work.

Here, the uplink (Uplink, UL, or uplink) refers to a method of transmitting and receiving data to the base station by the user terminal, and the downlink (Downlink, DL, or downlink) is transmitting and receiving data to the user terminal by the base station. It means the way to do it.

For uplink transmission and downlink transmission, a Time Division Duplex (TDD) scheme transmitted using different times may be used, and a frequency division duplex (FDD) scheme transmitted using different frequencies, a TDD scheme and an FDD scheme Mixed use methods can be used.

In addition, in a wireless communication system, a standard is configured by configuring uplink and downlink based on one carrier or carrier pair.

In the uplink and downlink, control information is transmitted through a control channel such as Physical Downlink Control CHannel (PDCCH), Physical Uplink Control CHannel (PUCCH), and the like, and It is configured with the same data channel to transmit data.

Downlink may refer to a communication or communication path from multiple transmission/reception points to a terminal, and uplink may refer to a communication or communication path from a terminal to multiple transmission/reception points. In this case, in the downlink, the transmitter may be a part of the multiple transmission/reception points, and the receiver may be a part of the terminal. In addition, in the uplink, the transmitter may be a part of the terminal, and the receiver may be a part of the multiple transmission/reception points.

Hereinafter, a situation in which signals are transmitted/received through channels such as PUCCH, PUSCH, PDCCH, and PDSCH may be expressed in the form of “transmitting and receiving PUCCH, PUSCH, PDCCH, and PDSCH”.

Meanwhile, high layer signaling described below includes RRC signaling that transmits RRC information including RRC parameters.

The base station performs downlink transmission to the terminals. The base station is a physical downlink for transmitting downlink control information such as scheduling required for reception of a downlink data channel, which is a main physical channel for unicast transmission, and scheduling approval information for transmission in an uplink data channel. Can transmit a control channel. Hereinafter, transmission and reception of signals through each channel will be described in the form of transmission and reception of the corresponding channel.

There are no restrictions on the multiple access scheme applied in the wireless communication system. Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Code Division Multiple Access (CDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Non-Orthogonal Multiple Access (NOMA), OFDM-TDMA, OFDM-FDMA, Various multiple access techniques such as OFDM-CDMA can be used. Here, NOMA includes Sparse Code Multiple Access (SCMA) and Low Density Spreading (LDS).

An embodiment of this embodiment is used for resource allocation in asynchronous wireless communication evolving to LTE/LTE-Advanced, IMT-2020 through GSM, WCDMA, HSPA, and synchronous wireless communication field evolving to CDMA, CDMA-2000 and UMB. Can be applied.

In this specification, a machine type communication (MTC) terminal may mean a terminal supporting low cost (or low complexity) or a terminal supporting coverage enhancement. Alternatively, in this specification, the MTC terminal may mean a terminal defined as a specific category for supporting low cost (or low complexity) and/or coverage enhancement.

In other words, in this specification, the MTC terminal may mean a newly defined 3GPP Release-13 low cost (or low complexity) UE category/type that performs an LTE-based MTC-related operation. Or, in this specification, the MTC terminal supports improved coverage compared to the existing LTE coverage, or the UE category/type defined in the existing 3GPP Release-12 or lower supporting low power consumption, or a newly defined Release-13 low cost (or low complexity) may mean UE category/type. Or, it may mean a further enhanced MTC terminal defined in Release-14.

In the present specification, a NB-IoT (NarrowBand Internet of Things) terminal means a terminal that supports wireless access for cellular IoT. The objectives of the NB-IoT technology include improved indoor coverage, support for large-scale low-speed terminals, low latency sensitivity, ultra-low cost terminals, low power consumption, and an optimized network structure.

3GPP develops 5G (5th-Generation) communication technology to meet the requirements of ITU-R's next-generation wireless access technology after research on 4G (4th-Generation) communication technology. Specifically, 3GPP develops a new NR communication technology separate from 4G communication technology and LTE-A pro, which has improved LTE-Advanced technology as a 5G communication technology to meet the requirements of ITU-R. LTE-A pro and NR both refer to 5G communication technology.

In this specification, frequencies, frames, subframes, resources, resource blocks, regions, bands, subbands, control channels, data channels, synchronization signals, various reference signals, various signals, and various messages related to NR (New Radio) Can be interpreted as a meaning used in the past or present, or in various meanings used in the future.

Meanwhile, the terms NR or 5G hereinafter will be described as encompassing new next-generation network technologies that satisfy the 5G requirements described above. In addition, a radio access technology that is distinguished from NR is described as a conventional LTE technology.

The 5G network is divided into a 5G core network (hereinafter referred to as 5GC, 5G CN, NGC, etc.) and a 5G radio access network (hereinafter referred to as NG-RAN, 5G-RAN, etc.). The NG-RAN may consist of a set of 5G NBs (gNB), which are one or more 5G base station nodes. In addition, an entity constituting the above-described core network may be referred to as a core network entity.

Meanwhile, a base station to which 5G radio access technology is applied is described as a 5G base station, a base station or an NR base station, NG-RAN, gNB, etc., but is not limited to such terms. In addition, a base station to which the conventional LTE radio access technology is applied is described and described as a 4G base station, another base station or an LTE base station, an eNB, etc., but is not limited to these terms.

The operation scenario in NR defined various operation scenarios by adding considerations to satellites, automobiles, and new verticals from the existing 4G LTE scenario.In terms of service, eMBB (Enhanced Mobile Broadband) scenario, high terminal density, but wide It is deployed in the range and supports the mMTC (Massive Machine Communication) scenario that requires a low data rate and asynchronous connection, and the URLLC (Ultra Reliability and Low Latency) scenario that requires high responsiveness and reliability and supports high-speed mobility. .

In order to satisfy this scenario, NR discloses a wireless communication system to which a new waveform and frame structure technology, a low latency technology, a mmWave support technology, and a forward compatible provision technology are applied. In particular, in the NR system, various technological changes are proposed in terms of flexibility to provide forward compatibility. The main technical features of the NR will be described below with reference to the drawings.

<NR system general>

1 is a diagram schematically showing a structure of an NR system to which this embodiment can be applied.

1, the NR system is divided into 5GC (5G Core Network) and NG-RAN parts, and the NG-RAN controls the user plane (SDAP/PDCP/RLC/MAC/PHY) and UE (User Equipment). It is composed of gNB and ng-eNB that provide plane (RRC) protocol termination. The gNB or gNB and ng-eNB are interconnected through an Xn interface. The gNB and ng-eNB are each connected to 5GC through the NG interface. The 5GC may include an Access and Mobility Management Function (AMF) in charge of a control plane such as a terminal access and mobility control function, and a User Plane Function (UPF) in charge of a control function for user data. NR includes support for both frequency bands below 6GHz (FR1, Frequency Range 1) and frequencies above 6GHz (FR2, Frequency Range 2).

gNB means a base station that provides NR user plane and control plane protocol termination to a terminal, and ng-eNB means a base station that provides E-UTRA user plane and control plane protocol termination to a terminal. The base station described in the present specification should be understood in a sense encompassing gNB and ng-eNB, and may be used as a means to distinguish between gNB or ng-eNB as necessary.

<NR wave form, numer roller and frame structure>

In NR, a CP-OFDM waveform using a cyclic prefix is used for downlink transmission, and CP-OFDM or DFT-s-OFDM is used for uplink transmission. OFDM technology is easy to combine with MIMO (Multiple Input Multiple Output), and has the advantage of being able to use a low complexity receiver with high frequency efficiency.

On the other hand, in NR, since the requirements for data rate, delay rate, and coverage are different for each of the three scenarios described above, it is necessary to efficiently satisfy the requirements for each scenario through a frequency band constituting an arbitrary NR system. . To this end, a technique for efficiently multiplexing a plurality of different numerology-based radio resources has been proposed.

값이 2의 지수 값으로 사용되어 지수적으로 변경된다.Specifically, the NR transmission neuron is determined based on sub-carrier spacing and CP (Cyclic prefix), and is based on 15khz as shown in Table 1 below.

The value is used as an exponential value of 2 and changes exponentially.

Subcarrier spacing Cyclic prefix Supported for data Supported for synch 0 15 Normal Yes Yes One 30 Normal Yes Yes 2 60 Normal, Extended Yes No 3 120 Normal Yes Yes 4 240 Normal No Yes

As shown in Table 1 above, the NR neuron can be classified into 5 types according to the subcarrier interval. This is different from LTE, one of 4G communication technologies, where the subcarrier spacing is fixed at 15 kHz. Specifically, subcarrier intervals used for data transmission in NR are 15, 30, 60, and 120 kHz, and subcarrier intervals used for synchronization signal transmission are 15, 30, 12, and 240 kHz. Also, the extended CP is applied only to the 60kHz subcarrier interval. On the other hand, a frame structure in NR is defined as a frame having a length of 10 ms consisting of 10 subframes having the same length of 1 ms. One frame can be divided into 5 ms half frames, and each half frame includes 5 subframes. In the case of a 15 kHz subcarrier interval, one subframe consists of 1 slot, and each slot consists of 14 OFDM symbols. 2 is a diagram for explaining a frame structure in an NR system to which the present embodiment can be applied.

Referring to FIG. 2, in the case of a normal CP, a slot is fixedly composed of 14 OFDM symbols, but the length in the time domain of the slot may vary according to the subcarrier interval. For example, in the case of a newer roller with a 15 kHz subcarrier interval, a slot is 1 ms long and has the same length as the subframe. In contrast, in the case of a newer roller with a 30 kHz subcarrier interval, a slot consists of 14 OFDM symbols, but two slots may be included in one subframe with a length of 0.5 ms. That is, the subframe and the frame are defined with a fixed time length, and the slot is defined by the number of symbols, and the time length may vary according to the subcarrier interval.

Meanwhile, NR defines a basic unit of scheduling as a slot, and introduces a mini-slot (or sub-slot or non-slot based schedule) in order to reduce the transmission delay of the radio section. If a wide subcarrier spacing is used, the length of one slot is shortened in inverse proportion, so that transmission delay in the radio section can be reduced. The mini-slot (or sub-slot) is for efficient support for the URLLC scenario, and scheduling is possible in units of 2, 4, or 7 symbols.

In addition, unlike LTE, NR defines uplink and downlink resource allocation as a symbol level within one slot. In order to reduce HARQ delay, a slot structure capable of transmitting HARQ ACK/NACK directly within a transmission slot has been defined, and this slot structure is named and described as a self-contained structure.

NR is designed to support a total of 256 slot formats, of which 62 slot formats are used in 3GPP Rel-15. In addition, a common frame structure constituting an FDD or TDD frame is supported through a combination of various slots. For example, a slot structure in which all symbols of a slot are set to downlink, a slot structure in which all symbols are set to uplink, and a slot structure in which a downlink symbol and an uplink symbol are combined are supported. In addition, NR supports that data transmission is distributed and scheduled in one or more slots. Accordingly, the base station may inform the UE of whether the slot is a downlink slot, an uplink slot, or a flexible slot using a slot format indicator (SFI). The base station can indicate the slot format by indicating the index of the table configured through UE-specific RRC signaling using SFI, and dynamically indicates through Downlink Control Information (DCI) or statically or through RRC. It can also be quasi-static.

In this specification, it can be applied to both a base station using an LTE radio access technology and a base station using an NR radio access technology. In particular, a dual connectivity situation between base stations using different radio access technologies will be described. Therefore, the base station below may be an LTE base station or an NR base station, and if necessary, each of them will be described separately.

This embodiment is a 5G wireless access network, NSA (Non-standalone) network, SA (Standalone) network, base station interworking interface, X2 interface/protocol, F1 interface/protocol, dual connectivity, EN-DC (E- UTRA-NR Dual Connectivity), base station and RAN load management, 5G user and control plane interfaces, NR and LTE protocols, and network Multi-Vendor Interoperability (MVI).

Conventionally, a load and overload management method for various user resources between base station nodes supporting heterogeneous radio access technology or between nodes within a base station has not been considered. In particular, with the introduction of a new 5G network, the NR base station is essential to interwork with the existing LTE base station in the NSA structure, and the NR base station in the SA structure. In addition, interworking between a central unit (CU) and a distributed unit (DU), which is a node inside the NR base station, and between CU-CP and CU-UP are also supported.

Since information about the load and overload conditions associated with the 5G base station node cannot be informed to other nodes, proper load control becomes difficult. Therefore, a malfunction of the base station system may occur and seriously affect the stability. Therefore, it is necessary to change the design of the X2 and F1 control interfaces to enable optimal load management even in 5G base stations.

In particular, dual connectivity means that different base stations transmit and receive data using radio resources to a terminal, and can be applied to a 5G network.

3 is a diagram for explaining a dual connectivity structure to which the present embodiment can be applied.

Referring to FIG. 3, a master base station 310 and a secondary base station 320 are interlocked through an X2 interface to provide radio resources to a terminal, respectively. In a dual connectivity situation, the secondary base station 320 provides only user plane data to the terminal. Therefore, the connection with the core network is made through the S1-MME interface between the master base station 310 and the core network entity (ex, MME, 300).

That is, in the dual connectivity structure, the master base station 310 is associated with the core network entity 300, and the secondary base station 320 provides only user plane data to the terminal. As described above, in this case, the master base station 310 has a problem that it is difficult to know the load state of the secondary base station 320. In particular, as described above, in the case of the NSA of the 5G network, the radio access technology of the master base station 310 and the secondary base station 320 is different, or a different technology may be used in the case of the core network. Since the 5G terminal is likely to consume a large amount of data, when data is transmitted and received to the terminal through a dual connectivity configuration, load management for the secondary base station 320 may be more important.

Accordingly, the following describes a procedure and a specific embodiment for load management of other base stations in a dual connectivity structure.

4 is a flowchart illustrating an operation of a master base station according to an embodiment.

Referring to FIG. 4, in a method of managing the load of the secondary base station, the master base station may perform the step of configuring dual connectivity with the secondary base station (S410). For example, the master base station may configure dual connectivity for the secondary base station and the terminal.

In the present specification, the master base station and the secondary base station may be configured to use different radio access technologies. In addition, both the master base station and the secondary base station may be configured as 5G base stations. In addition, the master base station may be connected to the core network, the control plane, and the user plane, and the secondary base station may be configured to connect only the core network and the user plane.

As an example, the master base station may be an eNB using LTE radio access technology, and the secondary base station configuring dual connectivity between the eNB and the terminal may be a gNB using NR radio access technology. As another example, the master base station may be a gNB using NR radio access technology, and the secondary base station configuring dual connectivity between the gNB and the terminal may be an eNB using LTE radio access technology. As another example, the master base station and the secondary base station may be configured to use the same radio access technology. For example, both base stations may be LTE base stations or NR base stations.

Meanwhile, the core network may be an EPC linked to an LTE base station or a 5GC linked to an NR base station.

A detailed method of configuring dual connectivity with a secondary base station by a master base station using different radio access technologies will be described again below.

The master base station may perform the step of receiving the secondary base station status indication message from the secondary base station through the X2 interface (S420). For example, the master base station may receive a secondary base station status indication message from the secondary base station using the X2 protocol.

The secondary base station status indication message may be periodically received. Alternatively, transmission of the secondary base station status indication message may be triggered by the secondary base station when a preset trigger condition is satisfied. Alternatively, the secondary base station status indication message may be transmitted by the secondary base station at the request of the master base station and received by the master base station.

The secondary base station status indication message may include a message type parameter and a secondary base station load information parameter. The message type parameter may include a unique value specifying the procedure of the message, and the same message type parameter is applied in the same procedure. The secondary base station load information parameter may include any one of a value indicating an overload and a value indicating no overload.

For example, when the secondary base station is in an overloaded state, the secondary base station load information parameter may be set to a value indicating overload (ex, overloaded). Alternatively, when the secondary base station is in a normal state (not an overload state), the secondary base station load information parameter may be set to a value indicating that the secondary base station is not overloaded (ex, not-overloaded). If necessary, the secondary base station load information parameter may be additionally designated as a value indicating another state in addition to the above two values. For example, the secondary base station load information parameter may be set to any one of a normal state, a low load state, and an overload state. The value set in the secondary base station load information parameter is not limited, and may be set to any one of values for classifying N (N is a natural number of 2 or more) states.

The master base station may perform a step of determining whether to perform a load reduction operation for the secondary base station based on the value of the secondary base station load information parameter included in the secondary base station status indication message (S430).

When the master base station receives the secondary base station status indication message, the master base station checks the value of the secondary base station load information parameter. If the secondary base station load information parameter is set to a value indicating an overload, the master base station may determine to start a load reduction operation for the secondary base station. In contrast, when the secondary base station load information parameter is set to a value indicating that there is no overload, the master base station does not start a load reduction operation for the secondary base station.

The load reduction operation can be variously set by the base station operator, and there is no limitation. For example, the load reduction operation may be an operation of reducing the amount of data transmitted to the secondary base station. Alternatively, the load reduction operation may be an operation of limiting the number of dual connectivity radio bearers allocated to the secondary base station. Alternatively, the load reduction operation may be an operation of deactivating or releasing the dual connectivity configuration of the secondary base station.

Meanwhile, when the start of the load reduction operation is determined, the master base station may maintain the load reduction operation on the secondary base station to be performed until a secondary base station status indication message including a value indicating that there is no overload is received. For example, if the first secondary base station status indication message is set to a value indicating overload, the master base station starts a load reduction operation. The master base station monitors the M-th secondary base station status indication message received after the above-described first secondary base station status indication message, and stops the load reduction operation when a secondary base station status indication message set to a value indicating that there is no overload is received. .

Through this operation, the master base station can quickly and accurately acquire the load level of the secondary base station on the X2 interface, and based on this, even when different radio access technologies are used, the load of the secondary base station can be efficiently managed.

5 is a flowchart illustrating an operation of a master base station according to another embodiment.

Referring to FIG. 5, a master base station may configure dual connectivity with a secondary base station. Here, steps S510 and S520 may be included in step S410 or may be sequentially performed.

Specifically, the master base station transmits an X2 interface setup request message including a list of all serving cells of the master base station to the secondary base station (S510). The master base station transmits an X2 interface setup request message for configuring dual connectivity to a candidate secondary base station for configuring dual connectivity to the terminal. In this case, list information on all serving cells provided by the master base station may be included in the X2 interface setup request message.

The master base station performs a step of receiving an X2 interface setup response message including a list of all serving cells of the secondary base station from the secondary base station (S520). After transmitting the X2 interface setup request message, the master base station receives an X2 interface setup response message including information on a list of all serving cells of the secondary base station from the candidate secondary base station.

Thereafter, the master base station determines a secondary base station to configure dual connectivity to the terminal based on the received X2 interface setup response message, and configures dual connectivity by transmitting configuration information necessary for configuring dual connectivity to the secondary base station (S410).

Through this, the master base station may configure dual connectivity by selecting a specific secondary base station to configure dual connectivity in the terminal among candidate secondary base stations.

Hereinafter, more various embodiments of a procedure for receiving the secondary base station state indication information will be described separately. For convenience of explanation, the following embodiments will be described focusing on the case where the master base station is the eNB and the secondary base station is the gNB, but as described above, the same can be applied to the case of a base station having the same radio access technology or opposite to each other.

6 is a signal diagram illustrating a procedure for transmitting a secondary base station status indication message according to an embodiment.

Referring to FIG. 6, the eNB 310 may receive a GNB STATUS INDICATION message from the gNB 320 through the X2 interface (S600). The GNB STATUS INDICATION message may include a message type parameter and a gNB load information parameter indicating load information of the gNB.

As described above, the gNB load information parameter may include any one of an overload and a value indicating that the overload is not. Alternatively, the gNB load information parameter may include a value of any one of normal, overload and underload.

As shown in FIG. 6, the GNB STATUS INDICATION message may be received even without a separate request from the eNB 310. For example, the GNB STATUS INDICATION message may be transmitted and received according to a preset period. Alternatively, the GNB STATUS INDICATION message may be transmitted according to a result of the gNB 320 checking whether a transmission trigger is satisfied.

7 and 8 are signal diagrams for explaining a procedure for transmitting a secondary base station status indication message according to another embodiment.

Referring to FIG. 7, the eNB 310 may transmit a resource status request message to the gNB 320 through the X2 interface (S700). That is, if necessary, the eNB 310 may transmit a message for requesting load information of the gNB 320.

When the resource status request message is received, the gNB 320 transmits a resource status response message to the eNB 310 (S710). The resource status response message is transmitted through the X2 interface, and may include a message type parameter and a gNB load information parameter indicating load information of the gNB.

As described above, the gNB load information parameter may include any one of an overload and a value indicating that the overload is not. Alternatively, the gNB load information parameter may include a value of any one of normal, overload and underload.

Referring to FIG. 8, the gNB 320 may transmit a resource status request message to the eNB 310 through the X2 interface (S800). That is, if necessary, the gNB 320 may transmit a message for requesting load information of the gNB 310.

When the resource status request message is received, the eNB 310 transmits a resource status response message to the gNB 320 (S810). The resource status response message is transmitted through the X2 interface, and may include a message type parameter and an eNB load information parameter indicating load information of the eNB. The eNB load information parameter may include any one of an overload and a value indicating that the overload is not. Alternatively, the eNB load information parameter may include any one of normal, overload and underload.

In this case, the gNB 320 may be a master base station. Alternatively, the gNB 320 may be a secondary base station or a case where load state information of a master base station is required.

9 and 10 are signal diagrams for explaining a procedure when transmission of a secondary base station status indication message fails according to another embodiment.

Referring to FIG. 9, the eNB 310 may transmit a resource status request message to the gNB 320 through the X2 interface (S900). That is, if necessary, the eNB 310 may transmit a message for requesting load information of the gNB 320.

When the resource status request message is received, the gNB 320 checks whether a response to the request message is possible. If the resource status information according to the request message cannot be provided, the gNB 320 transmits a resource status failure message to the eNB 310 (S910). The resource status failure message is transmitted through the X2 interface, and may include a message type parameter and a cause parameter that cannot provide load information of the gNB.

Referring to FIG. 10, the gNB 320 may transmit a resource status request message to the eNB 310 through the X2 interface (S1000). That is, if necessary, the gNB 320 may transmit a message for requesting load information of the gNB 310.

When the resource status request message is received, the eNB 310 checks whether it is possible to provide resource status information. If the resource status information according to the request message cannot be provided, the eNB 310 transmits a resource status failure message to the gNB 320 (S1010). The resource status failure message is transmitted through the X2 interface, and may include a message type parameter and a cause parameter that cannot provide load information of the eNB.

11 is a diagram for explaining a resource state update procedure between different base stations.

Referring to FIG. 11, the eNB 310 may receive a resource status update message from the gNB 320 through the X2 interface (S1100). The resource status update message may include a message type parameter and a gNB load information parameter indicating load information of the gNB.

Conversely, the gNB 320 may receive a resource status update message from the eNB 310 through the X2 interface (S1110). The resource state update message may include a message type parameter and an eNB load information parameter indicating load information of the eNB.

As described above, the eNB load information parameter and the gNB load information parameter may include any one of overload and a value indicating that there is no overload. Alternatively, the eNB load information parameter and the gNB load information parameter may include any one of normal, overload and underload.

In the case of FIG. 11, it is shown that the process of FIG. 6 is performed by each of the base stations 310 and 320. That is, steps S1100 and S1110 may be individually performed regardless of the order. Alternatively, when the message according to step S1100 is received, the eNB 310 may perform step S1110. Alternatively, when the message according to step S1110 is received, the gNB 320 may transmit the message in the same manner as in step S1100. That is, each of the base stations 310 and 320 may transmit their own load information when receiving load information of the other base stations 320 and 310.

The name of each message and the name of the parameter described with reference to FIGS. 6 to 11 are exemplary and are not limited thereto. In the following, various embodiments of the above-described operation and parameters will be further described in terms of each message.

1) Resource status request message

As described above, the eNB may transmit a RESOURCE STATUS REQUEST message to the gNB (or the gNB to the eNB). The RESOURCE STATUS REQUEST message may include an eNB Measurement ID and a gNB Measurement ID, which are load measurement identifiers for eNB and gNB, as parameters.

gNB-CU Measurement ID, gNB-CU-CP Measurement ID, gNB-CU-UP Measurement ID, gNB-DU Measurement ID, gNB-RU, which are load measurement identifiers for CU, CU-CP, CU-UP, DU, and RU Each Measurement ID may be used. Similarly, eNB-DU Measurement ID and eNB-RU Measurement ID, which are load measurement identifiers for the eNB DU and RU, may be used, respectively.

Measurement IDs of the eNB and gNB may be separated/divided into IDs corresponding to a load associated with an LTE terminal and a load associated with an NSA terminal, respectively. For example, it may be classified into four types: eNB Measurement ID for LTE and eNB Measurement ID for NSA, gNB Measurement ID for LTE, and gNB Measurement ID for NSA.

Alternatively, only the measurement IDs of the eNB may be separated/divided into IDs corresponding to the load associated with the LTE terminal and the load associated with the NSA terminal, respectively. For example, it may be classified into an eNB Measurement ID for LTE and an eNB Measurement ID for NSA.

The RESOURCE STATUS REQUEST message includes LTE cell or NR cell information, cell frequency and bandwidth, used LTE and NR component carriers, available throughput (or data rate) per cell, and available throughput (or data rate) rate. And it may include at least one of information indicating whether a licensed (licensed) / unlicensed (unlicensed) / shared (shared) band.

The load information of each base station can be measured by all connected bearers or by bearer type. For example, each base station can calculate the load for each MCG bearer, SCG split bearer, and SCG bearer type. Alternatively, the load information can be measured for each frequency or all frequencies used in the NR gNB. For example, it is possible to calculate the load for each 3.5 GHz frequency and 28 GHz frequency. Alternatively, in the case of simultaneous use for LTE and NR in the same frequency band, it is possible to measure the load for the sum of these frequencies.

2) Resource status response message

If the gNB can provide the load status and information requested from the eNB (or the eNB is from the gNB), it measures/calculates the information and reports it through the RESOURCE STATUS RESPONSE message.

For example, through a resource status response message, each base station may inform whether all or part of the requested load information can be provided, and transmits including a list of available information and a list of impossible.

In addition, the resource status response message may include calculated load information or information indicating whether an overload is present as described above.

3) Resource status failure message

If the gNB is unable to provide the load status and information requested from the eNB (or the eNB is from the gNB), each base station notifies the eNB (or gNB) through a RESOURCE STATUS FAILURE message. The RESOURCE STATUS FAILURE message may include information indicating the cause of failure to provide load information.

4) Resource status update message

The gNB updates the load status and information provision to the eNB (or from the eNB to the gNB) through a RESOURCE STATUS UPDATE message. It can be updated or periodically updated according to a specific event, and in the case of periodic update, an update period is set.

The load information used by the NSA's base stations (eNB and gNB) includes all or part of the following:

5) NR gNB related load information

The load information transmitted by the gNB may include at least one of the following information.

-Cell unit load (DL, UL, DU+UL, SUL) information

-Frequency unit load information

-Terminal unit load (NSA terminal, SA terminal) information

-NR CA connection count and NR CA load information

-At least one of gNB total load information, CP processing load information, UP processing load information, and VM load information

-Information of at least one of the total load, CP processing load, UP processing load, and VM load of the gNB CU. However, if the CU is divided into CU-CP and CU-UP, CU-CP load, CU-UP load, CU-CP VM load, and CU-CP VM load can be added/replaced.

-Information of at least one of the total load of the gNB DU, CP processing load, UP processing load, and VM load. However, load information is available when RU is included in DU and when RU is not included.

-Information on at least one of gNB RU's total load, CP processing load, UP processing load, and VM load

-At least one of transmission network load and transmission delay information between the gNB and the eNB

-At least one of transmission network load and transmission delay information between gNB and gNB

-At least one information of transmission network load and transmission delay information between gNB CU-DUs

-At least one of gNB DU-RU transmission network load and transmission delay information

-Information of at least one of the start time, end time, and duration time of each load state

6) LTE eNB related load information

The load information transmitted by the eNB may include at least one of the following information.

-Cell unit load (DL, UL, DU+UL, SUL) information

-Frequency unit load information

-Terminal unit load (NSA terminal, SA terminal) information

-LTE CA connection number and LTE CA load information

-Information of at least one of the total load of the eNB, CP processing load, UP processing load, and VM load

-Information of at least one of the total load of the eNB DU, CP processing load, UP processing load, and VM load. However, load information is available when RU is included in DU and when RU is not included.

-Information on at least one of the total load of the eNB RU, CP processing load, UP processing load, and VM load

-At least one information of transmission network load and transmission delay between eNB and eNB

-At least one information of transmission network load and transmission delay between eNB DU-RUs

-Information of at least one of the start time, end time, and duration time of each load state

On the other hand, the above-described load state can be classified qualitatively or quantitatively as follows, and may be configured by a combination of some/all of them.

1) Low, Medium, High, and Critical

2) Normal, Overloaded

3) Not Overloaded, Overloaded

4) Underloaded, Normal, Overloaded

5) Relative level value of load (e.g., no load 0 ~ maximum load 100)

6) Relative percentage of the load (e.g. 0% min to 100% max)

7) Value of the corresponding status value (eg, number of CA connections, number of VMs, etc.)

Through the operation described above, the master base station can perform efficient load management by acquiring load information of the secondary base station. Hereinafter, an embodiment in which the above-described operation is applied to load management between logical nodes of a 5G base station (gNB) will be described.

12 is a diagram illustrating a dual connectivity structure in which a central unit and a distribution unit are divided according to an exemplary embodiment.

Referring to FIG. 12, a 5G network is divided into a core network (CN, 300), an NR and/or an LTE radio access network (RAN). The terminal assumes a dual-mode terminal that can be connected to both the NR base station 1220+1250 and the LTE base station 310.

The core network 300 is divided into control plane (CP, 1210) and user plane (UP, 1215) functions, respectively, CN-CP (1210, ex, MME/AMF/SMF) and CN- It is composed of UP(1215, ex, SGW/PGW/UPF) devices. The interface between the CN-CP 1210 and the CN-UP 1215 device is connected through a standardized interface.

In addition, the interface between the CN 300 and the NR/LTE base station is linked to an upgraded S1 interface to enable NSA support or an NG (or N2) interface capable of SA support.

The NR base station 1220+1250 or the LTE base station 310 may be the master base station according to the operator's wireless network construction scenario and the frequency characteristics used. As described above, it is assumed that the eNB 310 is the master base station. The master base station 310 is connected to the CN-CP 1210 device through the S1-C/NG-C interface, and the CN-UP 1215 device through the S1-U/NG-U interface, respectively.

Meanwhile, an interface directly connected for interworking between the NR base station 1220+1225 and the LTE base station 310 is defined and described as X2 (or X2 EN-DC). The X2 interface can be viewed as an Inter-RAT interworking interface between NR and LTE base stations, and is required to support mobility in radio sections and multiple connections between NR and LTE base stations.

The CU node 1220 of the NR base station can be further divided into a CU-CP node 1222 and a CU-UP node 1221, which are interlocked with an E1 control interface. In addition, the NR base station is divided into a CU node 1220 and a DU node 1250, which are interlocked with F1-C and F1-U interfaces. Here, the NR gNB DU 1250 may be a node including all of the RLC, MAC, and PHY, or may be separated from the RU node and include only a part of the RLC, MAC, and PHY. For example, DU 1250 may be configured to include RLC and MAC, and RU may be configured to include PHY. In addition, the LTE eNB 310 may have a digital unit (DU) and a radio unit (RU) node integrated or separated.

Meanwhile, the 5G NSA network consists of an LTE base station 310 and an NR base station 1220+1225 supporting various frequencies. That is, when a cell and a base station node with a low load can be selected, the throughput of the terminal can be improved and stable network operation is possible.

In addition, when the configuration base station function is installed and operated on the virtualization system, the processing performance is affected by the VM (Virtual Machine) load, CP processing load, UP processing load, and transmission network load between nodes. It is also possible to improve performance through load balancing.

Accordingly, load management between the gNB CU 1220 and the DU 1250 may be additionally required. In this case, it can be applied by changing the state indication operation on the X2 interface described above. The terms of the status indication message and each parameter below are illustrative and are not limited thereto, and may be variously modified as necessary.

13 is a flowchart illustrating an operation of a central unit according to an embodiment.

Referring to FIG. 13, in a method of managing a load of a distributed unit, a central unit may perform the step of receiving a distribution unit status indication message from a distribution unit through an F1 interface. (S1310).

As described above, the base station may consist of one central unit and one or more distribution units. In addition, the central unit is a logical node that hosts Radio Resource Control (RRC) and Packet Data Convergence Protocol (PDCP) of the base station. The distribution unit is a logical node that hosts Radio Link Control (RLC), Medium Access Control (MAC), and Physical (PHY) layers of the base station.

The distribution unit status indication message may be periodically received. Alternatively, transmission of the distribution unit status indication message may be triggered by the distribution unit when a preset trigger condition is satisfied. Alternatively, the distribution unit status indication message may be transmitted by the distribution unit at the request of the central unit and received by the central unit.

The distribution unit status indication message may include a message type parameter, a transaction identification parameter, and a distribution unit load information parameter. The message type parameter indicates the type of the message. The Transaction ID IE uniquely identifies a procedure among all ongoing parallel procedures of the same type initiated by the same protocol peer. same type initiated by the same protocol peer). Messages belonging to the same procedure shall use the same Transaction ID. The Transaction ID is determined by the initiating peer of a procedure.

The distribution unit load information parameter may include any one of a value indicating an overload and a value indicating no overload.

For example, when the distribution unit is in an overload state, the distribution unit load information parameter may be set to a value indicating an overload (ex, overloaded). Alternatively, when the distribution unit is in a normal state (not overloaded), the distribution unit load information parameter may be set to a value (ex, not-overloaded) indicating that there is no overload. If necessary, the distribution unit load information parameter may be designated as a value indicating another state in addition to the above two values. For example, the distribution unit load information parameter may be set to any one of a normal state, a low load state, and an overload state. The value set in the distribution unit load information parameter is not limited, and may be set to any one of values for distinguishing N (N is a natural number of 2 or more) states.

The central unit may perform a step of determining whether to perform a load reduction operation for the distribution unit based on the value of the distribution unit load information parameter included in the distribution unit status indication message (S1320).

When the central unit receives the distribution unit status indication message, the central unit checks the value of the distribution unit load information parameter. If the distribution unit load information parameter is set to a value indicating overload, the central unit may determine to start the load reduction operation for the distribution unit. In contrast, when the distribution unit load information parameter is set to a value indicating that there is no overload, the central unit does not start a load reduction operation for the distribution unit.

The load reduction operation can be variously set by the base station operator, and there is no limitation. For example, the load reduction operation may be an operation of reducing the amount of data transmitted to the distribution unit. Alternatively, the load reduction operation may be an operation of limiting the number of radio bearers allocated to the distribution unit. Alternatively, the load reduction operation may be an operation of deactivating or releasing the configuration of the distribution unit.

Meanwhile, when the start of the load reduction operation is determined, the central unit may maintain the load reduction operation for the distribution unit to be performed until a distribution unit status indication message including a value indicating that there is no overload is received. For example, when the first distribution unit status indication message is set to a value indicating overload, the central unit starts a load reduction operation. The central unit monitors the M-th distribution unit status indication message received after the above-described first distribution unit status indication message, and stops the load reduction operation when a distribution unit status indication message set to a value indicating that there is no overload is received. .

Through this operation, the central unit can quickly and accurately acquire the load level of the distribution unit on the F1 interface, and manage the load of the distribution unit efficiently.

14 is a signal diagram illustrating a procedure for transmitting a distribution unit status indication message according to an embodiment.

Referring to FIG. 14, the gNB-DU 1250 may transmit a GNB-DU STATUS INDICATION message to the gNB-CU 1220 through the F1 interface (S1400). The GNB-DU STATUS INDICATION message may include a message type parameter, a transaction ID parameter, and a distribution unit load information parameter indicating load information of the gNB-DU.

As described above, the distribution unit load information parameter may include any one of an overload and a value indicating that the overload is not. Alternatively, the distribution unit load information parameter may include any one of normal, overload, and underload.

As shown in FIG. 14, the GNB-DU STATUS INDICATION message may be received even without a separate request from the gNB-CU 1220. For example, the GNB-DU STATUS INDICATION message may be transmitted and received according to a preset period. Alternatively, the GNB-DU STATUS INDICATION message may be transmitted according to a result of checking whether the gNB-DU 1250 satisfies a transmission trigger.

15 and 16 are signal diagrams for explaining a procedure for transmitting a distribution unit status indication message according to another embodiment. Here, the distribution unit status indication message is described as a resource status response message.

Referring to FIG. 15, the gNB-CU 1220 may transmit a resource status request message to the gNB-DU 1250 through the F1 interface (S1500). That is, the gNB-CU 1220 may transmit a message for requesting load information of the gNB-DU 1250, if necessary.

When the resource status request message is received, the gNB-DU 1250 transmits a resource status response message to the gNB-CU 1220 (S1510). The resource status response message is transmitted through the F1 interface, and may include a message type parameter, a transaction identification parameter, and a distribution unit load information parameter indicating load information of the gNB-DU.

As described above, the distribution unit load information parameter may include any one of an overload and a value indicating that the overload is not. Alternatively, the distribution unit load information parameter may include any one of normal, overload, and underload.

Referring to FIG. 16, the gNB-DU 1250 may transmit a resource status request message to the gNB-CU 1220 through the F1 interface (S1600). That is, the gNB-DU 1250 may transmit a message for requesting load information of the gNB-CU 1220 if necessary.

When the resource status request message is received, the gNB-CU 1220 transmits a resource status response message to the gNB-DU 1250 (S1610). The resource status response message is transmitted through the F1 interface, and may include a message type parameter, a transaction identification parameter, and a central unit load information parameter indicating load information of the eNB-CU. The central unit load information parameter may include any one of an overload and a value indicating that there is no overload. Alternatively, the eNB central unit information parameter may include any one of normal, overload and underload.

17 and 18 are signal diagrams for explaining a procedure when transmission of a distribution unit base station status indication message fails according to another embodiment.

Referring to FIG. 17, the gNB-CU 1220 may transmit a resource status request message to the gNB-DU 1250 through the F1 interface (S1700). That is, the gNB-CU 1220 may transmit a message for requesting load information of the gNB-DU 1250, if necessary.

When the resource status request message is received, the gNB-DU 1250 checks whether a response to the request message is possible. If the resource status information according to the request message cannot be provided, the gNB-DU 1250 transmits a resource status failure message to the gNB-CU 1220 (S1710). The resource status failure message is transmitted through the F1 interface, and may include a message type parameter, a transaction identification parameter, and a cause parameter that cannot provide load information of the gNB-DU 1250.

Referring to FIG. 18, the gNB-DU 1250 may transmit a resource status request message to the gNB-CU 1220 through the F1 interface (S1800). That is, the gNB-DU 1250 may transmit a message for requesting load information of the gNB-CU 1220 if necessary.

When the resource status request message is received, the gNB-CU 1220 checks whether resource status information can be provided. If the resource status information according to the request message cannot be provided, the gNB-CU 1220 transmits a resource status failure message to the gNB-DU 1250 (S1810). The resource status failure message is transmitted through the F1 interface, and may include a message type parameter, a transaction identification parameter, and a cause parameter that cannot provide load information of the gNB-CU 1220.

19 is a diagram for explaining a resource state update procedure between a distribution unit and a central unit.

Referring to FIG. 19, the gNB-CU 1220 may receive a resource status update message from the gNB-DU 1250 through the F1 interface (S1900). The resource status update message may include a message type parameter, a transaction identification parameter, and a distribution unit load information parameter indicating load information of the gNB-DU 1250.

Conversely, the gNB-DU 1250 may receive a resource status update message from the gNB-CU 1220 through the F1 interface (S1910). The resource status update message may include a message type parameter, a transaction identification parameter, and a central unit load information parameter indicating load information of the gNB-CU 1220.

As described above, the central unit load information parameter and the distribution unit load information parameter may include any one of an overload and a value indicating no overload. Alternatively, the central unit load information parameter and the distribution unit load information parameter may include any one of normal, overload, and low load.

In the case of FIG. 19, it is shown that the process of FIG. 14 is performed by each of the nodes 1220 and 1250. That is, steps S1900 and S1910 may be individually performed regardless of the order. Alternatively, when the message according to step S1900 is received, the gNB-CU 1220 may perform step S1910. Alternatively, when the message according to step S1910 is received, the gNB-DU 1250 may transmit the message in the same manner as in step S1900. That is, each node 1220 and 1250 may transmit its own load information when receiving load information of another node 1250 and 1220.

The name of each message and the name of the parameter described with reference to FIGS. 14 to 19 are exemplary and are not limited thereto. Hereinafter, the above-described operation and various embodiments will be further described in terms of each message and parameter.

1) Resource status request message

The CU requests the DU (or the DU to the CU) to report the load status and information of the DU (or CU) by sending a RESOURCE STATUS REQUEST message.

gNB-CU Measurement ID, gNB-CU-CP Measurement ID, gNB-CU-UP Measurement ID, gNB-DU Measurement ID, gNB-RU, which are load measurement identifiers for CU, CU-CP, CU-UP, DU, RU Each measurement ID is used. Also, the measurement IDs of the gNB presented above may be separated/divided into IDs corresponding to a load associated with the SA terminal and a load associated with the NSA terminal, respectively. For example, it may be classified into gNB Measurement ID for SA and gNB Measurement ID for NSA.

The RESOURCE STATUS REQUEST message includes NR cell information, cell frequency and bandwidth, used NR component carrier, available throughput (or data rate) per cell, available throughput (or data rate) rate and licensed It may include at least one of information on whether the /unlicensed/shared band is available.

Load information can be measured for all connected bearers or for each bearer type. For example, it is possible to calculate the load for each type of MCG bearer, SCG split bearer, and SCG bearer. Alternatively, the load information can be measured for each frequency or all frequencies used in the NR gNB. For example, it is possible to calculate the load for each 3.5GHz frequency and 28GHz frequency. In addition, in the case of simultaneous use of LTE and NR in the same frequency band, it is possible to measure the load for the sum of these frequencies.

2) Resource status response message (distribution unit status indication message)

If the load status and information requested from the CU (or the CU is the DU) can be provided, the DU measures/calculates the information and reports it to the CU (or DU) through the RESOURCE STATUS RESPONSE message.

The RESOURCE STATUS RESPONSE message may include information indicating whether all or part of the requested load information can be provided, and may include a list of information that can be provided and a list that cannot be provided.

3) Resource status failure message

If the load status and information requested by the CU (or the CU from the DU) cannot be provided, the DU notifies the CU (or DU) through a RESOURCE STATUS FAILURE message. The RESOURCE STATUS FAILURE message may include a cause parameter indicating a load status and a reason for failure to provide load information.

4) Resource status update message

DU updates the load status and information provision through the RESOURCE STATUS UPDATE message to the CU (or from CU to DU). It can be updated or periodically updated according to a specific event, and in the case of periodic update, an update period is set.

The above-described messages are F1 interface-based load management methods between the gNB CU and the DU, and can be applied equally to the SA network.

5) NR gNB related load information

The load information transmitted by the gNB-DU or gNB-CU may include at least one of the following information.

-Cell unit load (DL, UL, DU+UL, SUL) information

-Frequency unit load information

-Terminal unit load (NSA terminal, SA terminal) information

-NR CA connection count and NR CA load information

-At least one of gNB total load information, CP processing load information, UP processing load information, and VM load information

-Information of at least one of the total load, CP processing load, UP processing load, and VM load of the gNB CU. However, if the CU is divided into CU-CP and CU-UP, CU-CP load, CU-UP load, CU-CP VM load, and CU-CP VM load can be added/replaced.

-Information of at least one of the total load of the gNB DU, CP processing load, UP processing load, and VM load. However, load information is available when RU is included in DU and when RU is not included.

-Information on at least one of gNB RU's total load, CP processing load, UP processing load, and VM load

-At least one of transmission network load and transmission delay information between the gNB and the eNB

-At least one of transmission network load and transmission delay information between gNB and gNB

-At least one information of transmission network load and transmission delay information between gNB CU-DUs

-At least one of gNB DU-RU transmission network load and transmission delay information

-Information of at least one of the start time, end time, and duration time of each load state

On the other hand, the above-described load state can be classified qualitatively or quantitatively as follows, and may be configured by a combination of some/all of them.

1) Low, Medium, High, and Critical

2) Normal, Overloaded

3) Not Overloaded, Overloaded

4) Underloaded, Normal, Overloaded

5) Relative level value of load (e.g., no load 0 ~ maximum load 100)

6) Relative percentage of the load (e.g. 0% min to 100% max)

7) Value of the corresponding status value (eg, number of CA connections, number of VMs, etc.)

As described above, according to the present disclosure, it is possible to perform efficient load management between base stations or between base station nodes in a 5G radio access network supporting heterogeneous radio technologies. In addition, it is possible to provide more stable connectivity and transmission speed through such load management, and to significantly reduce the cost of building and operating a wireless network.

Hereinafter, the configuration of the master base station and the central unit will be described with reference to the drawings.

20 is a diagram illustrating a configuration of a master base station according to an embodiment.

Referring to FIG. 20, the master base station 2000 includes a control unit 2010 for configuring dual connectivity with the secondary base station, and a receiving unit 2030 for receiving a secondary base station status indication message from the secondary base station through an X2 interface. The control unit 2010 may determine whether to perform a load reduction operation for the secondary base station based on a value of the secondary base station load information parameter included in the secondary base station status indication message.

For example, the master base station 2000 may configure dual connectivity for the secondary base station and the terminal. As an example, the master base station 2000 may be an eNB using LTE radio access technology, and the secondary base station configuring dual connectivity between the eNB and the terminal may be a gNB using NR radio access technology. As another example, the master base station 2000 may be a gNB using NR radio access technology, and the secondary base station configuring dual connectivity between the gNB and the terminal may be an eNB using LTE radio access technology. As another example, the master base station 2000 and the secondary base station may be configured to use the same radio access technology.

The secondary base station status indication message may be periodically received. Alternatively, transmission of the secondary base station status indication message may be triggered by the secondary base station when a preset trigger condition is satisfied. Alternatively, the secondary base station status indication message may be transmitted by the secondary base station at the request of the master base station 2000 and received by the receiving unit 2030.

The secondary base station status indication message may include a message type parameter and a secondary base station load information parameter. The message type parameter may include a unique value specifying the procedure of the message, and the same message type parameter is applied in the same procedure. The secondary base station load information parameter may include any one of a value indicating an overload and a value indicating no overload.

For example, when the secondary base station is in an overloaded state, the secondary base station load information parameter may be set to a value indicating overload (ex, overloaded). Alternatively, when the secondary base station is in a normal state (not an overload state), the secondary base station load information parameter may be set to a value indicating that the secondary base station is not overloaded (ex, not-overloaded). If necessary, the secondary base station load information parameter may be additionally designated as a value indicating another state in addition to the above two values.

When the secondary base station status indication message is received, the control unit 2010 checks the value of the secondary base station load information parameter. If the secondary base station load information parameter is set to a value indicating an overload, the control unit 2010 may determine to start a load reduction operation for the secondary base station. On the contrary, when the secondary base station load information parameter is set to a value indicating that there is no overload, the control unit 2010 does not start a load reduction operation for the secondary base station.

The load reduction operation can be variously set by the base station operator, and there is no limitation. For example, the load reduction operation may be an operation of reducing the amount of data transmitted to the secondary base station. Alternatively, the load reduction operation may be an operation of limiting the number of dual connectivity radio bearers allocated to the secondary base station. Alternatively, the load reduction operation may be an operation of deactivating or releasing the dual connectivity configuration of the secondary base station.

Meanwhile, when the start of the load reduction operation is determined, the controller 2010 may maintain the load reduction operation for the secondary base station to be performed until a secondary base station status indication message including a value indicating that there is no overload is received.

Also, the transmitter 2020 transmits an X2 interface setup request message including a list of all serving cells of the master base station to the secondary base station. The transmitter 2020 transmits an X2 interface setup request message for configuring dual connectivity to a candidate secondary base station for configuring dual connectivity in the terminal. In this case, list information on all serving cells provided by the master base station 2000 may be included in the X2 interface setup request message.

The reception unit 2030 receives an X2 interface setup response message including a list of all serving cells of the secondary base station from the secondary base station. After transmitting the X2 interface setup request message, the receiving unit 2030 receives an X2 interface setup response message including information on a list of all serving cells of the secondary base station from the candidate secondary base station.

Thereafter, the control unit 2010 determines the secondary base station to configure dual connectivity to the terminal based on the received X2 interface setup response message, and controls the secondary base station to transmit configuration information necessary for dual connectivity configuration to configure dual connectivity. .

In addition to this, the control unit 2010 generally controls the operation of the master base station 2000 required to perform the operation for load management of the secondary base station according to the present embodiment described above.

In addition, the transmission unit 2020 and the reception unit 2030 are used to transmit and receive signals, messages, and data necessary for performing the above-described embodiments with other base stations and terminals.

21 is a diagram showing a configuration of a central unit according to another embodiment.

Referring to FIG. 21, a central unit 2100 that manages the load of a distributed unit includes a receiving unit 2130 for receiving a distribution unit status indication message from the distribution unit through an F1 interface, and the distribution unit status. It may include a control unit 2110 that determines whether to perform a load reduction operation for the distribution unit based on the value of the distribution unit load information parameter included in the indication message.

Referring to FIG. 21, the base station may be composed of one central unit 2100 and one or more distribution units. In addition, the central unit 2100 is a logical node that hosts Radio Resource Control (RRC) and Packet Data Convergence Protocol (PDCP) of the base station. The distribution unit is a logical node that hosts Radio Link Control (RLC), Medium Access Control (MAC), and Physical (PHY) layers of the base station.

The receiving unit 2130 may periodically receive a distribution unit status indication message. Alternatively, transmission of the distribution unit status indication message may be triggered by the distribution unit when a preset trigger condition is satisfied. Alternatively, the distribution unit status indication message may be transmitted by the distribution unit at the request of the central unit 2000 and received by the central unit 2000.

The distribution unit status indication message may include a message type parameter, a transaction identification parameter, and a distribution unit load information parameter. The message type parameter indicates the type of the message. The Transaction ID IE uniquely identifies a procedure among all ongoing parallel procedures of the same type initiated by the same protocol peer. same type initiated by the same protocol peer). Messages belonging to the same procedure shall use the same Transaction ID. The Transaction ID is determined by the initiating peer of a procedure.

The distribution unit load information parameter may include any one of a value indicating an overload and a value indicating no overload. For example, when the distribution unit is in an overload state, the distribution unit load information parameter may be set to a value indicating an overload (ex, overloaded). Alternatively, when the distribution unit is in a normal state (not overloaded), the distribution unit load information parameter may be set to a value (ex, not-overloaded) indicating that there is no overload. If necessary, the distribution unit load information parameter may be designated as a value indicating another state in addition to the above two values.

When the distribution unit status indication message is received, the control unit 2110 checks the value of the distribution unit load information parameter. If the distribution unit load information parameter is set to a value indicating an overload, the controller 2110 may determine to start a load reduction operation for the distribution unit. In contrast, when the distribution unit load information parameter is set to a value indicating that there is no overload, the control unit 2110 does not start a load reduction operation for the distribution unit. The load reduction operation can be variously set by the base station operator, and there is no limitation. Meanwhile, when the start of the load reduction operation is determined, the controller 2110 may maintain the load reduction operation for the distribution unit to be performed until a distribution unit status indication message including a value indicating that there is no overload is received.

In addition, the control unit 2110 generally controls the operation of the central unit 2100 required to perform the operation for managing the load of the distribution unit according to the present embodiment described above.

In addition, the transmission unit 2120 and the reception unit 2130 are used to transmit and receive signals, messages, and data necessary for performing the above-described embodiments with a distribution unit, a core network entity, and other base stations and terminals.

The above-described embodiments may be supported by standard documents disclosed in at least one of IEEE 802, 3GPP and 3GPP2 wireless access systems. That is, steps, configurations, and parts not described in order to clearly reveal the present technical idea among the embodiments may be supported by the aforementioned standard documents. In addition, all terms disclosed in the present specification can be described by the standard documents disclosed above.

The above-described embodiments can be implemented through various means. For example, the present embodiments may be implemented by hardware, firmware, software, or a combination thereof.

In the case of implementation by hardware, the method according to the embodiments includes one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), and FPGAs. (Field Programmable Gate Arrays), a processor, a controller, a microcontroller, or a microprocessor.

In the case of implementation by firmware or software, the method according to the embodiments may be implemented in the form of an apparatus, procedure, or function that performs the functions or operations described above. The software code may be stored in a memory unit and driven by a processor. The memory unit may be located inside or outside the processor, and may exchange data with the processor through various known means.

In addition, terms such as "system", "processor", "controller", "component", "module", "interface", "model", or "unit" described above generally refer to computer-related entity hardware, hardware and software. It may mean a combination of, software or running software. For example, the above-described components may be, but are not limited to, a process driven by a processor, a processor, a controller, a control processor, an object, an execution thread, a program, and/or a computer. For example, both the controller or processor and the application running on the controller or processor can be components. One or more components may reside within a process and/or thread of execution, and the components may be located on one device (eg, a system, a computing device, etc.) or distributed across two or more devices.

The above description is merely illustrative of the technical idea of the present disclosure, and those of ordinary skill in the technical field to which the present disclosure pertains will be able to make various modifications and variations without departing from the essential characteristics of the technical idea. In addition, the present embodiments are not intended to limit the technical idea of the present disclosure, but to explain the technical idea, and thus the scope of the technical idea is not limited by these embodiments. The scope of protection of the present disclosure should be construed by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present disclosure.

Claims (20)

In the method for the master base station to manage the load of the secondary base station,
Configuring dual connectivity with the secondary base station;
Receiving a secondary base station status indication message from the secondary base station through an X2 interface; And
Determining whether to perform a load reduction operation for the secondary base station based on a value of a secondary base station load information parameter included in the secondary base station status indication message,
The step of determining whether to perform a load reduction operation for the secondary base station,
When the secondary base station load information parameter includes a value indicating an overload, it is determined to start a load reduction operation for the secondary base station,
The master base station,
When it is determined that the start of the load reduction operation is determined, the load reduction operation is performed on the secondary base station until a secondary base station status indication message including a value indicating that there is no overload is received. The method of claim 1,
The master base station and the secondary base station,
A method of using different radio access technologies, wherein the master base station has a core network, a control plane, and a user plane connected, and the secondary base station performs only connection between the core network and the user plane. The method of claim 1,
The step of configuring the dual connectivity,
Transmitting an X2 interface setup request message including a list of all serving cells of the master base station to the secondary base station; And
And receiving an X2 interface setup response message including a list of all serving cells of the secondary base station from the secondary base station. The method of claim 1,
The secondary base station load information parameter,
And a value indicating the overload and not the overload. delete In the master base station managing the load of the secondary base station,
A control unit for configuring dual connectivity with the secondary base station; And
Including a receiving unit for receiving a secondary base station status indication message from the secondary base station through the X2 interface,
The control unit,
Determine whether to perform a load reduction operation for the secondary base station based on a value of a secondary base station load information parameter included in the secondary base station status indication message,
The control unit,
When the secondary base station load information parameter includes a value indicating an overload, it is determined to start a load reduction operation for the secondary base station,
When the start of the load reduction operation is determined, the master base station performs a load reduction operation on the secondary base station until a secondary base station status indication message including a value indicating that there is no overload is received. The method of claim 6,
The master base station and the secondary base station,
The master base station uses different radio access technologies, the master base station has a core network, a control plane, and a user plane connected, and the secondary base station performs only connection between the core network and the user plane. The method of claim 6,
Further comprising a transmitter for transmitting an X2 interface setup request message including a list of all serving cells of the master base station to the secondary base station,
The receiving unit,
And receiving an X2 interface setup response message including a list of all serving cells of the secondary base station from the secondary base station. The method of claim 6,
The secondary base station load information parameter,
And a value indicating the overload and not the overload. delete In a method for a central unit to manage the load of a distributed unit,
Receiving a distribution unit status indication message from the distribution unit through the F1 interface; And
Determining whether to perform a load reduction operation for the distribution unit based on a value of a distribution unit load information parameter included in the distribution unit status indication message,
The step of determining whether to perform a load reduction operation for the distribution unit,
When the distribution unit load information parameter includes a value indicating an overload, it is determined to start a load reduction operation for the distribution unit,
The central unit,
When the start of the load reduction operation is determined, the load reduction operation for the distribution unit is performed until a distribution unit base station status indication message including a value indicating that there is no overload is received. The method of claim 11,
The base station,
Consisting of one said central unit and one or more said distribution units,
The central unit is a logical node that hosts Radio Resource Control (RRC) and Packet Data Convergence Protocol (PDCP) of the base station, and the distribution unit is a Radio Link Control (RLC), Medium Access Control (MAC) and PHY of the base station. (Physical) A method, characterized in that the logical node hosting the layer. The method of claim 11,
The distribution unit status indication message,
And a message type parameter, a transaction identification parameter, and the distribution unit load information parameter. The method of claim 11,
The distribution unit load information parameter,
And a value indicating the overload and not the overload. delete In the central unit (Central Unit) that manages the load of the distributed unit,
A receiving unit for receiving a distribution unit status indication message from the distribution unit through the F1 interface; And
A control unit for determining whether to perform a load reduction operation for the distribution unit based on a value of a distribution unit load information parameter included in the distribution unit status indication message,
The control unit,
When the distribution unit load information parameter includes a value indicating an overload, it is determined to start a load reduction operation for the distribution unit,
When the start of the load reduction operation is determined, the central unit performs a load reduction operation on the distribution unit until a distribution unit base station status indication message including a value indicating that there is no overload is received. The method of claim 16,
The base station,
Consisting of one said central unit and one or more said distribution units,
The central unit is a logical node that hosts Radio Resource Control (RRC) and Packet Data Convergence Protocol (PDCP) of the base station, and the distribution unit is a Radio Link Control (RLC), Medium Access Control (MAC) and PHY of the base station. (Physical) Central unit, characterized in that the logical node hosting the layer. The method of claim 16,
The distribution unit status indication message,
And a message type parameter, a transaction identification parameter, and the distribution unit load information parameter. The method of claim 16,
The distribution unit load information parameter,
And a value indicating the overload and the non-overload. delete

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