WO2018131904A1

WO2018131904A1 - Method for controlling heterogeneous network handover and apparatus therefor

Info

Publication number: WO2018131904A1
Application number: PCT/KR2018/000518
Authority: WO
Inventors: 김하성
Original assignee: 주식회사 케이티
Priority date: 2017-01-12
Filing date: 2018-01-11
Publication date: 2018-07-19

Abstract

The present disclosure relates to a technique for controlling handover of a terminal between base stations using different networks. One embodiment provides a method for a source base station to control heterogeneous network handover of a terminal and an apparatus therefor, the method comprising the steps of: determining whether to handover to a target base station using a heterogeneous network for the terminal on the basis of measurement information received from the terminal; when it is determined to handover, transmitting, to a core network entity associated with the source base station, a handover request message including identification information of the target base station; receiving, from the core network entity, a handover instruction message including evolved packet system (EPS) bearer setup list information of the target base station; and transmitting, to the terminal, the handover instruction message.

Description

Heterogeneous network handover control method and device

The present disclosure relates to a technique for controlling handover of a terminal between base stations using different networks. More specifically, the present invention relates to a specific method and procedure when a terminal performs handover between a base station using 5G technology and a base station using LTE technology.

Existing LTE supports bearer management for interworking with the LTE base station linked to the core network EPC through the S1 interface and application protocol.

Meanwhile, with the introduction of 5G networks, it has become essential to provide mobility between 5G base stations. In particular, when the 5G base station uses the mmWave frequency (eg, 28 GHz) of the high frequency band, the coverage of the base station is expected to be smaller due to the characteristics of the frequency. Therefore, in this case, the frequency of the process of the user equipment to move the base station increases, and the handover (handover) procedure for this also becomes very important.

In addition, when the base station using the 5G radio access technology is constructed in the region where the base station using the existing LTE radio access technology is configured, there is a high possibility that the terminal handover between the LTE base station and the 5G base station occurs frequently due to the difference in coverage.

In this situation, unlike the LTE core network and base station-to-base station transmission in LTE, 5G quality control can be performed in units of Quality of Service (QoS) flow, and 5G core networks (hereinafter, referred to as 5G core and 5G). Between a Core Network, NGC or 5GC) and a 5G base station (hereinafter referred to as 5G NB, NR NB, NG-RAN or gNB) to establish a Packet Data Unit (PDU) session containing a QoS flow. Packet data can be transmitted via

As such, there is a high necessity for a terminal to perform handover in a heterogeneous network situation using different radio access technologies and different core systems, and development of a technology for smoothly controlling handover according to different network characteristics is difficult. It is required.

In the above background, the present disclosure intends to propose a specific method and apparatus for supporting handover of a terminal when a source base station and a target base station use heterogeneous network technology.

In addition, the present disclosure is to propose a specific control method and apparatus for supporting the handover of the terminal between different core network entities when the terminal performs heterogeneous network handover.

An embodiment devised to solve the above-described problem is a method for a source base station to control a heterogeneous network handover of a terminal, based on measurement information received from the terminal, to a target base station using a heterogeneous network for the terminal. If it is determined whether or not to perform the handover and the handover is determined, transmitting a handover request message including the identification information of the target base station to the core network entity associated with the source base station and the EPS of the target base station from the core network entity ( Evolved Packet System) Provides a method comprising the steps of receiving a handover command message including bearer setup list information and transmitting a handover command message to the terminal.

In addition, according to an embodiment, a core network entity controls a heterogeneous network handover of a terminal, wherein a handover type or a forward relocation request message is performed using identification information of a target base station included in the handover request message. Determining the core network entity associated with the target base station to which the target is to be transmitted, converting the stored terminal context into the Evolved Packet Core (EPC) terminal context for the handover performing terminal, and converting the target base station identification information and the EPC terminal context. A forward relocation message including transmitting a forwarding request message, including a forwarding request message, to a core network entity linked to the target base station and including Evolved Packet System (EPS) bearer setup list information of the target base station from the core network entity linked to the target base station. Receiving a response message and EPS bearer setup lease of the target base station A handover command message including information provides a method comprising transmitting to the source base station.

In addition, an embodiment is a source base station for controlling a heterogeneous network handover of a terminal, the control unit and the hand to determine whether to handover to a target base station using a heterogeneous network for the terminal based on the measurement information received from the terminal If it is determined to perform the over, Evolved Packet System (EPS) bearer setup list information of the target base station from the transmitting unit and the core network entity transmitting a handover request message including identification information of the target base station to the core network entity associated with the source base station. Includes a receiving unit for receiving a handover command message comprising a transmitter, the transmitter provides a source base station apparatus for further transmitting the handover command message to the terminal.

In addition, an embodiment provides a handover type or a forward relocation request message using identification information of a target base station included in a handover request message in a core network entity controlling heterogeneous network handover of a terminal. Determination of the core network entity associated with the target base station to be transmitted, and a control unit for converting the stored terminal context into the Evolved Packet Core (EPC) terminal context for the handover performing terminal, the forwarding including the target base station identification information and the EPC terminal context. Forward Relocation Response message including information on the Evolved Packet System (EPS) bearer setup list of the target base station from the transmitting unit for transmitting the request message to the core network entity associated with the target base station and the core network entity associated with the target base station. Includes a receiving unit for receiving, the transmitting unit EPS bear of the target base station It provides the core network operating object device that transmits a handover command message including the set-up information list to the source base station.

As described above, the present disclosure provides an effect that the UE can smoothly perform handover between base stations using different network technologies.

In addition, the present disclosure provides a specific procedure and method for supporting handover of a terminal between core network entities using different networks, thereby providing a user with mobility while maintaining the same quality of service.

FIG. 1 is a diagram exemplarily illustrating inter-system, inter-RAT mobility, and interworking structure between networks using different network technologies.

2 is a diagram illustrating an interworking interface between core network entities using different network technologies.

3 is a diagram illustrating an operation of controlling a heterogeneous network handover of a terminal by a source base station according to an embodiment.

4 is a diagram illustrating an operation of controlling a heterogeneous network handover of a terminal by a core network entity linked to a source base station according to an embodiment.

5 is a signal diagram exemplarily illustrating a heterogeneous network handover procedure of a terminal according to an embodiment.

6 is a flowchart exemplarily illustrating a message between core network entities for performing a heterogeneous network handover procedure of a terminal according to an embodiment.

7 is a flowchart illustrating a heterogeneous network handover procedure of a terminal according to an embodiment.

8 is a diagram illustrating a configuration of a source base station according to an embodiment.

9 is a diagram illustrating a configuration of a core network entity according to an embodiment.

Hereinafter, the present embodiments will be described in detail with reference to the accompanying drawings. In adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are assigned to the same components as much as possible even though they are shown in different drawings. In addition, in describing this embodiment, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present embodiment, the detailed description thereof will be omitted.

In the present specification, the 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 comprehensive concept of a terminal in a wireless communication, and includes a user equipment (UE) in WCDMA, LTE, HSPA, and IMT-2020 (5G or New Radio), as well as a mobile station (MS) and a UT in GSM. It should be interpreted as a concept that includes a user terminal, a subscriber station (SS), and a wireless device.

A base station or cell generally refers to a station that communicates with a user terminal, and includes a Node-B, an evolved Node-B, an eNB, a gNode-B, and a Low Power Node. ), Sector, site, various types of antennas, base transceiver system (BTS), access point, access point (for example, transmission point, reception point, transmission / reception point), relay node ( It is meant to encompass various coverage areas such as a relay node, a mega cell, a macro cell, a micro cell, a pico cell, a femto cell, a remote radio head (RRH), a radio unit (RU), and a small cell.

Since the various cells listed above have a base station for controlling each cell, the base station may be interpreted in two meanings. 1) the device providing the mega cell, the macro cell, the micro cell, the pico cell, the femto cell, the small cell in relation to the wireless area, or 2) the wireless area itself. In 1) all devices that provide a given radio area are controlled by the same entity or interact with each other to cooperatively configure the radio area to the base station. According to the configuration of the wireless area, a point, a transmission point, a transmission point, a reception point, and the like become one embodiment of a base station. In 2), the base station may indicate the radio area itself that receives or transmits a signal from the viewpoint of the user terminal or the position of a neighboring base station.

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

In the present specification, the user terminal and the base station are two types (uplink or downlink) transmitting and receiving subjects used to implement the technology or the technical idea described in this embodiment, and are used in a generic sense and limited by terms or words specifically referred to. It doesn't work

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

The uplink transmission and the downlink transmission may use a time division duplex (TDD) scheme that is transmitted using different times, and use a frequency division duplex (FDD) scheme, a TDD scheme, and an FDD scheme, which are transmitted using different frequencies. Mixed mode may be used.

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

The uplink and the downlink transmit control information through a control channel such as a physical downlink control channel (PDCCH), a physical uplink control channel (PUCCH), a physical downlink shared channel (PDSCH), a physical uplink shared channel (PUSCH), and the like. It is composed of the same data channel to transmit data.

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

Hereinafter, a situation in which a signal is transmitted and received through a channel such as a PUCCH, a PUSCH, a PDCCH, and a PDSCH may be described in the form of 'sending and receiving a PUCCH, a PUSCH, a PDCCH, and a PDSCH.'

Meanwhile, high layer signaling described below includes RRC signaling for transmitting RRC information including an RRC parameter.

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

There is no limitation 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, the NOMA includes a sparse code multiple access (SCMA) and a low density spreading (LDS).

One embodiment of the present embodiment is for resource allocation in the fields of asynchronous wireless communication evolving to LTE / LTE-Advanced, IMT-2020 via GSM, WCDMA, HSPA, and synchronous wireless communication evolving to CDMA, CDMA-2000 and UMB. Can be applied.

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

In other words, in the present specification, the MTC terminal may mean a newly defined 3GPP Release-13 low cost (or low complexity) UE category / type for performing LTE-based MTC related operations. Alternatively, in the present specification, the MTC terminal supports enhanced coverage compared to the existing LTE coverage, or UE category / type defined in the existing 3GPP Release-12 or lower, or newly defined Release-13 low cost (or supporting low power consumption). low complexity) can mean UE category / type. Or, it may mean a further Enhanced MTC terminal defined in Release-14.

In this specification, a NB-IoT (NarrowBand Internet of Things) terminal refers to a terminal that supports radio access for cellular IoT. The objectives of NB-IoT technology include improved Indoor coverage, support for large scale low speed terminals, low sensitivity, low cost terminal cost, low power consumption, and optimized network architecture.

As a typical usage scenario in New Radio (NR), which is recently discussed by 3GPP, enhanced Mobile BroadBand (eMBB), massive machine type communication (MMTC), and Ultra Reliable and Low Latency Communication (URLLC) are being raised.

5G technology means all network technologies satisfying ITU's 5G requirements, and includes NR newly developed by 3GPP and eLTE, which is a modification of conventional LTE technology to meet 5G requirements.

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). May be interpreted as meaning used in the past or present, or various meanings used in the future.

On the other hand, the term NR or 5G is described below to encompass a new network technology that satisfies the above-mentioned 5G requirements. In addition, a radio access technology distinguished from NR is described as a conventional LTE technology.

5G network is divided into 5G core network (hereinafter referred to as 5GC, 5G CN, NGC, etc.) and 5G radio access network (hereinafter referred to as NG-RAN, 5G-RAN, etc.). The NG-RAN may consist of a set of 5G NBs (gNBs) that are one or more 5G base station nodes. The entity configuring the aforementioned core network may be referred to as a core network entity. Core network entity may refer to 5GC-C or 5GC-U described below, and may also mean a collection of one or more 5GC-C and one or more 5GC-U.

Meanwhile, the 5G base station may be separately configured into a central unit (CU) and a distributed unit (DU) device, and one or more DUs may be connected to one CU.

The present disclosure relates to a procedure for performing handover to a base station using a conventional LTE network when the terminal is connected to a base station using a 5G network. Thus, the base station herein is a source base station (eg, gNB, 5G RAN, 5G base station) using 5G radio access technology and a target base station (eg, eNB, LTE RAN, using LTE radio access technology) LTE base station) will be described. In addition, if necessary, the base station may be named and a wireless access technology used by the base station may be described.

In addition, the core network entity may be a core network entity (5G CN, 5G core network entity, AMF) linked to a source base station using 5G network technology and a core network entity (LTE EPC, associated with a target base station using LTE network technology). LTE core network entity (MME) may be described separately, and may be named as a core network entity and the network technology used may be described.

As described above, in the present specification, in order to describe UE handover between different heterogeneous networks, the base station and the core network entity are distinguished and described, but the name is not limited thereto.

Hereinafter, a terminal handover procedure of the present disclosure will be described with reference to the drawings.

The conventional LTE wireless network supports handover between LTE base stations and handover between LTE-3G.

However, as new radio access technology and network technology (5G technology) that can satisfy various requirements are newly introduced, it is necessary to provide mobility with an existing LTE base station. In particular, it is expected that 5G base stations will be frequently collaborate with LTE base stations due to limited coverage in the early stages of deployment compared to LTE base stations, which are largely constructed in large scale. Therefore, a handover procedure between base stations using different network technologies is required to provide a service of a terminal. In particular, when the 5G base station uses the mmWave frequency (eg, 28 GHz frequency), the coverage is expected to be narrow depending on the frequency characteristics, and handover with the LTE base station having relatively wide coverage is expected to occur frequently. do.

In addition, since the LTE base station is connected to the EPC core network and the 5G base station is separately connected to the 5G-CN core network, efficient handover between the 5G base station and the existing LTE base station considering the interface between these core networks and the new 5G protocol function is also considered. A procedure is necessary.

The present disclosure is to provide a method for providing inter-RAT or inter-system mobility to provide service mobility between heterogeneous wireless networks 5G and LTE in such a situation.

Referring to FIG. 1, a 5G network is divided into a core network (CN) 125 and a radio access network (RAN) 115 and configured as an external network that is a data network (DN) 130. Connected with 5G core network 5G-CN 125 can support both 5G and eLTE base station 115, but the existing LTE base station 110 is connected only to the existing EPC (120). eLTE is a modification of the existing LTE technology to meet the 5G requirements, and can be connected between the 5G-CN 125 and the EPC 120 core network nodes through an NGx interface. Is optional.

In addition, the interface between the 5G-CN 125 and the 5G / eLTE RAN 115 are all linked to the NG interface, and the interface between the EPC 120 and the LTE RAN 110 is linked to the S1 interface.

The terminal 110 may be equipped with both 5G and LTE wireless transceiver and protocol.

2, the EPC 120 and the 5G CN 125 may exchange control information using a core network interworking interface (eg, NGx or N26) between heterogeneous networks (S210). That is, the EPC 120 and the 5G CN 125 may support heterogeneous network handover of the terminal by exchanging control information for supporting inter-system mobility in both directions through the corresponding interface.

As described above, since the 5G base station and the LTE base station are connected to different core networks, the direct connection interface between the 5G base station and the LTE base station may not be supported, so the inter-system and inter-RAT handover procedures are considered. need. In addition, since 5G and LTE are heterogeneous networks due to handover of the terminal, both core network control plane (CP) and user plane (UP) devices may be changed.

In contrast, both 5G base stations and eLTE base stations using NR technology are connected to the same 5G-CN (or AMF) core network, and a direct connection interface between 5G base stations and eLTE base stations is expected to be supported. Therefore, a handover procedure considering this is also necessary.

Therefore, hereinafter, the operations of a terminal, a source base station, a target base station, a source core network entity, and a target core network entity are proposed in performing heterogeneous network handover. Meanwhile, in the present disclosure, a case in which a terminal performs handover to an LTE base station in a state of being connected to a 5G base station will be described as an example. However, an operation subject and a message flow may be reversely applied.

Referring to FIG. 3, in a method of controlling heterogeneous network handover of a terminal, the source base station determines whether to handover to a target base station using a heterogeneous network for the terminal based on measurement information received from the terminal. It may be performed (S310). For example, the source base station may receive measurement information in which the terminal measures the radio state of at least one of a 5G cell and an LTE cell.

The source base station may determine whether the terminal needs Inter-RAT handover based on the received measurement information. For example, the source base station may determine the handover of the terminal in consideration of the required bandwidth information, radio latency information, slicing capability information, and the like. Specifically, the source base station may determine the handover of the terminal when the bandwidth additionally accommodated by the target base station is greater than the use bandwidth between the source base station and the terminal. Alternatively, the source base station may determine the handover of the terminal when the radio delay degree supported by the target base station is less than or equal to the radio delay degree of the source base station. Alternatively, the source base station may determine the handover of the terminal when the network system applied to the target base station supports network slicing or is superior to the network slicing capability of the source base station. In addition, the source base station may determine whether the terminal is heterogeneous network handover according to a predetermined determination criteria of the heterogeneous network handover.

On the other hand, it is assumed that the terminal is set to a single registration mode (single registration mode). For example, it is assumed that the terminal does not simultaneously register to two core networks. However, the present disclosure may be extended and applied to a dual-registration terminal. Further, hereinafter, the source base station and the target base station use different network technologies, the core network entity associated with the source base station is AMF (Core Access and Mobility Management Function), and the core network entity associated with the target base station is MME ( Mobility Management Entity). If the terminal performs handover to the 5G base station while connected to the LTE base station, the core network entity may be reversed.

In addition, when it is determined that the handover is performed, the source base station may perform a step of transmitting a handover request message including identification information of the target base station to the core network entity associated with the source base station (S320). For example, when the heterogeneous network handover of the terminal is determined, the source base station may transmit a handover request message requesting handover of the terminal to a core network entity (eg, AMF) controlling the source base station.

The handover request message may include at least one of target base station identification information which is a handover target and information indicating a bearer associated with a quality of service (QoS) flow for data forwarding of the terminal. For example, at least one of the target base station identification information and information indicating a bearer associated with a quality of service (QoS) flow for data forwarding of the terminal may be received from the terminal.

For example, when the source base station transmits a handover request message to the core network entity, the core network entity may determine the handover type using identification information of the target base station included in the handover request message. For example, the core network entity may determine the handover type by inter-system handover (handover for the E-UTRAN base station) when the identification information of the target base station uses heterogeneous network technology.

As another example, the core network entity may specify the target base station core network entity controlling the target base station using the target base station identification information of the handover request message. For example, the core network entity may determine and determine the MME controlling the target base station.

Meanwhile, the core network entity receives the handover request message, and when the heterogeneous network handover is determined, converts the terminal context for the corresponding terminal to be recognized by the heterogeneous network. For example, the core network entity may convert the terminal context into an Evolved Packet Core (EPC) terminal context and transmit the core context to the core network entity (eg, MME) associated with the target base station.

In addition, the source base station may perform a step of receiving a handover command message including Evolved Packet System (EPS) bearer setup list information of the target base station from the core network entity (S330). The handover command message may include EPS bearer setup list information. The EPS bearer setup list information may be included in the control information received from the target base station by the core network entity associated with the target base station and transmitted to the core network entity associated with the source base station. May be included.

The source base station may perform a step of transmitting a handover command message to the terminal (S340). The source base station may transmit a handover command message including EPS bearer setup list information to the terminal to perform the handover and information necessary for the terminal to access the target base station and perform the handover. For example, the source base station may receive from the target base station through the core network entity the applicable parameters required for the terminal to perform a handover to the LTE base station to the terminal.

The terminal performs a handover operation to the target base station based on the handover command message, and transmits a handover complete message to the target base station when the handover is completed. The target base station transmits the information on the handover completion to the core network entity linked to the target base station, and the core network entity linked to the target base station sequentially transmits the information on the handover completion to the core network entity linked to the source base station. By doing so, it is possible to efficiently complete the heterogeneous network handover of the terminal.

Referring to FIG. 4, the core network entity determines a core network entity linked to the target base station to which the handover type or the forward relocation request message is transmitted using identification information of the target base station included in the handover request message. In operation S410, the process may be performed. The core network entity may receive a handover request message from the source base station. For example, the handover request message may include at least one of a target base station identification that is a handover target and information indicating a bearer associated with a quality of service (QoS) flow for data forwarding of the terminal. In addition, at least one of the target base station identification information and information indicating a bearer associated with a Quality of Service (QoS) flow for data forwarding of the terminal may be information received from the terminal and transmitted to the source base station.

For example, the core network entity may determine the handover type using identification information of the target base station included in the handover request message. For example, the core network entity may determine the handover type by inter-system handover (handover for the E-UTRAN base station) when the identification information of the target base station uses heterogeneous network technology.

In addition, the core network entity may perform the step of converting the stored terminal context into the Evolved Packet Core (EPC) terminal context for the handover performing terminal (S420). For example, the core network entity may generate and convert the stored terminal context into an EPC terminal context. Alternatively, the core network entity may map and fall back the data flow to the EPS bearer. Alternatively, the core network entity may convert the 5G NAS message into the LTE NAS message. Alternatively, the core network entity may remove or fall back the 5G slice configuration information. Alternatively, the core network entity may convert 5G security context by mapping to EPS security context. In addition, the core network entity may perform at least one of each operation described above.

Meanwhile, the core network entity may perform a step of transmitting a forwarding request message including the target base station identification information and the EPC terminal context to the core network entity associated with the target base station (S430). For example, the core network entity generates a forwarding request message including at least one of the target base station ID information, EPS terminal context information, direct forwarding flag, and terminal usage type information to the core network entity associated with the target base station. Can transmit

Meanwhile, the core network entity associated with the target base station receiving the forwarding request message transmits a handover request message including a list of EPS bearer identification information that needs to be set up to the target base station. The target base station allocates the request resource based on the handover request message and transmits a handover request confirmation message including EPS bearer setup list information and applicable parameter information to the core network entity associated with the target base station.

In addition, the core network entity may perform a step of receiving a forward relocation response message including Evolved Packet System (EPS) bearer setup list information of the target base station from the core network entity linked to the target base station ( S440). The core network entity may receive a forward response message including the EPS bearer setup list information transmitted according to the handover request process between the core network entity associated with the target base station and the target base station from the core network entity associated with the target base station. have. The forward response message may include applicable parameters that the terminal can apply in performing the handover.

In addition, the core network entity may perform a step of transmitting a handover command message including EPS bearer setup list information of the target base station to the source base station (S450). Upon receiving the forward response message, the core network entity may transmit a handover command message to the source base station. For example, the handover command message may include at least one of EPS bearer setup list information and applicable parameter information for handover of the terminal.

On the other hand, it is assumed that the terminal is set to a single registration mode (single registration mode), the source base station and the target base station uses different network technology, the core network entity associated with the source base station is AMF (Core Access and Mobility Management) Function), and the core network entity linked to the target base station may mean a mobility management entity (MME).

Thereafter, the terminal performs a handover operation to the target base station based on the handover command message, and transmits a handover complete message to the target base station when the handover is completed. The target base station transmits the information on the handover completion to the core network entity linked to the target base station, and the core network entity linked to the target base station sequentially transmits the information on the handover completion to the core network entity linked to the source base station. By doing so, it is possible to efficiently complete the heterogeneous network handover of the terminal.

As described above, the source base station and the core network entity may control heterogeneous network handover of the terminal, the terminal, the source base station, the core network entity linked to the source base station, the core network entity linked to the target base station and the target base station The UE may prepare, proceed, and complete a heterogeneous network handover of the terminal through the above-described operations.

Hereinafter, the overall heterogeneous network handover procedure including operations of the source base station and the core network entity described with reference to FIGS. 3 and 4 will be described once again with reference to the signal diagram.

Herein, it is assumed that the terminal does not simultaneously register to two core networks, but the terminal may be extended and applied to a dual-registration terminal.

Referring to FIG. 5, the terminal 100 is communicating with the 5G-CN 125. Inter-RAT handover is initiated by the source base station 115, the source base station 115 provides the terminal 100 with the configuration information necessary for handover. Here, the source base station 115 is connected to the 5G-CN 125 and the target base station 110 is connected to the EPC 120 through the NG and S1 interfaces, respectively. Therefore, when a handover occurs according to the movement of the terminal 100, both the base station and the core network may be changed. As described above, the terminal provides only a single transmission / reception function. In particular, the handover procedure has an advantage of minimizing service interruption because the target base station can set up the radio resource guarantee for the terminal in advance. However, 5G and LTE differ in different CN contexts, different QoS frameworks, and slicing support, so this should be considered in the handover procedure.

The handover message flowchart in the opposite direction from the LTE base station to the 5G base station may be performed by changing 125 and 120 of FIG. 5, and detailed operations and message flows are performed similarly to FIG. 5.

Specifically, each step will be described.

The terminal 100 is single-registered with the 5G network to perform data communication.

The 5G base station 115 transmits configuration information related to radio measurement to the terminal 100 through an RRC message "RRCConnectionReconfiguration", and the terminal 100 measures quality of 5G and LTE radio links using the configuration information related to the measurement. When the Inter-RAT handover event (for example, similar to the B1 / B2 event of the LTE handover) occurs, the terminal 100 transmits the measurement information to the 5G base station 115 through the "Measurement Report" message. It transmits (S510). For example, the measurement information may be used frequency, frequency bandwidth, serving and neighbor cell list, RSRP / RSRQ of serving and neighboring cells, candidate beam list per serving and neighboring cell, RSRP / RSRQ of candidate beams, and terminal capability And LTE base station specifications (LTE or eLTE).

The source base station 115 checks whether the terminal 100 fulfills the inter-RAT handover execution condition based on the measurement report, and determines that handover to the target base station 110 is possible if the execution condition is satisfied (S520). ). For example, the source base station 115 determines the Inter-RAT handover by referring to the predetermined decision criteria for the 5G radio link and the LTE radio link, measurement information, and the state of the target base station 110.

If necessary, the source base station 115 may have a large difference between the frequency of the 5G and the LTE base station and the radio access technology (RAT) capability, and should be determined in consideration of this. For example, the source base station 115 may determine whether to accept Inter-RAT handover in consideration of all or some of the items disclosed in Table 1 below. The items of Table 1 may be changed according to the predefined items as described, for example, and may also be determined through a QoS comparison combining the items.

항목Item	핸드오버 수용 조건Handover Acceptance Conditions
요구 대역폭(Bandwidth)Required Bandwidth	타켓 기지국이 추가로 수용 가능한 대역폭이 소스 기지국과 단말 간 사용 대역폭 보다 큰 경우 Inter-RAT 핸드오버를 수용함.Inter-RAT handover is accepted when the target base station additionally accepts more bandwidth than the source base station and the terminal.
무선 지연도(Latency)Wireless Latency	타켓 기지국이 지원하는 지연도가 소스 기지국의 지연도 보다 작거나 같은경우, Inter-RAT 핸드오버를 수용함.If the delay supported by the target base station is less than or equal to the delay of the source base station, the Inter-RAT handover is accepted.
슬라이싱 역량(Slicing)Slicing Competence	타켓 시스템이 지원하는 네트워크 슬라이싱 역량이 소스 시스템의 네트워크 슬라이싱 역량과 같거나 우위인 경우 Inter-RAT 핸드오버를 수용함.단, LTE 시스템의 네트워크 슬라이싱 역량은 복수의 5G 네트워크 슬라이싱 역량 중 적어도 한 개의 값을 갖도록 매핑될 수 있음.Accepts Inter-RAT handover when the network slicing capability supported by the target system is equal to or superior to the network slicing capability of the source system, provided that the network slicing capability of the LTE system is the value of at least one of the multiple 5G network slicing capabilities. Can be mapped to have

When the inter-RAT handover is determined, the source base station 115 transmits a handover required message to the 5G-CN 125 (for example, AMF) to inform the inter-RAT handover (S530). For example, the handover request message may include at least one of a target base station ID, transmission control information of the target RAT, and information indicating a bearer associated with a quality of service (QoS) flow for data forwarding. Here, the 5G-CN 125 identifies the target core network entity 120 based on the target base station ID. In addition, the 5G-CN 125 may determine the handover type by using the target base station 110 identification information of the handover request message. For example, the 5G-CN 125 may determine the handover type as an inter-system handover.

Meanwhile, when the NGx interface between the 5G-CN 125 and the EPC 120 is supported, the 5G-CN 125 determines that Inter-System handover is possible (S535).

When the inter-system handover is possible, the 5G-CN 125 performs an operation of converting the 5G-CN UE context into the EPC UE context (S540). For example, the 5G-CN 125 may generate and convert the stored terminal context into an EPC terminal context. Alternatively, the 5G-CN 125 may map and fall back the data flow to the EPS bearer. Alternatively, the 5G-CN 125 may convert a 5G NAS message into an LTE NAS message. Alternatively, the 5G-CN 125 may remove or fall back the 5G slice configuration information. Alternatively, the 5G-CN 125 may map and convert the 5G security context to the EPS security context. In addition, the 5G-CN 125 may perform at least one of each operation described above. In this case, the corresponding conversion operation varies according to the handover direction, and may include the procedure of Table 2, respectively.

5G -> LTE 핸드오버5G-> LTE Handover	LTE -> 5G 핸드오버LTE-> 5G Handover
EPC UE Context 생성Create EPC UE Context		5G-CN UE Context 생성Create 5G-CN UE Context
5G 플로우를 EPS 베어러로 매핑 및 폴백(Fallback)Map and Fallback 5G Flows to EPS Bearers	EPS 베어러를 5G 플로우로 매핑Mapping EPS Bearer to 5G Flow

5G NAS 메시지를 LTE NAS 메시지로 변환Convert 5G NAS messages to LTE NAS messages	LTE NAS 메시지를 5G NAS 메시지로 변환Convert LTE NAS messages to 5G NAS messages
5G 슬라이스 구성정보 제거/폴백Remove / fall back 5G slice configuration information	5G 슬라이스 구성정보 생성5G slice configuration information generation

Thereafter, the 5G-CN 125 transmits information including the UE context converted for the EPC to the EPC 120 through a forward relocation request message (S545). The redirect request message may be transmitted through the NGx interface.

The EPC 120 requests the handover to be performed through the handover request message to the target base station 110 (S550). For example, the handover request message may include an EPS bearer identification list.

The target base station 110 allocates a radio resource based on at least one of EPS bearer identification information, DRB setup information, and EPC UE context, and includes at least one of EPS bearer setup list information and applicable parameter information. A handover request acknowledgment message is generated and transmitted to the EPC 120 (S555). For example, the handover request confirmation message may include UE RRC full configuration information including data radio bearer (DRB) setup.

The EPC 120 notifies the 5G-CN 125 that the preparation of the handover of the target base station 110 is completed through a forward relocation response message (S560). The forward response message may include information included in the aforementioned handover request confirmation message.

The 5G-CN 125 transmits a handover request confirmation message to the source base station 115 to indicate that preparation for handover is completed (S565). The handover request confirmation message may include a handover command message. If the NGx interface is not supported, the procedure S540 to S560 are not performed, and the source base station 115 is notified that the inter-system handover is not supported in the handover request confirmation message.

The source base station 115 performs a RAN QoS mapping operation (S570), and instructs the terminal 100 to handover to the target base station 110 through a Handover Command message (S575). For example, QoS mapping depends on the handover direction, and can be performed according to the procedure of Table 3, respectively.

5G -> LTE 핸드오버5G-> LTE Handover	LTE -> 5G 핸드오버LTE-> 5G Handover
LTE 기지국은 EPS 베어러를 LTE DRB로 매핑LTE base station maps EPS bearers to LTE DRB	5G 기지국은 QoS 플로우를 5G DRB로 매핑5G base station maps QoS flows to 5G DRB

If the inter-system handover is not supported, the source base station 115 may request the terminal 100 for a Release with Redirection procedure instead of a Handover Command message.

The terminal 100 accesses the target base station 110 using at least one of EPS bearer setup list information, DRB information, and bearer configuration information in the handover command message, and transmits a handover complete message to the target base station. Transmit to 110. The target base station 110 transmits a handover completion message to the EPC 120.

If the inter-system handover is not supported, the terminal 100 performs a attach operation by performing a new attach request to the target base station 110.

Meanwhile, each of the above-described steps may be omitted, addition of steps, and order change may be made as necessary.

As described above, when the UE proceeds with heterogeneous network handover, information required for handover is exchanged using an interface between 5G-CN and the EPC.

Referring to FIG. 6, the 5G-CN 125 transmits a forward request message to the EPC 120 (S610). As described above, the forwarding request message includes target base station identification information, EPC terminal context information, MM context information including EPS security context, SM EPS terminal context information including default and indicated GBR bearer information, The information may include at least one of direct forwarding flag information and terminal usage type information.

The EPC 120 confirms whether handover is possible with the target base station using the forwarding request message, and performs a handover preparation procedure. Thereafter, the EPC 120 transmits a forward response message to the 5G-CN 125 (S620). For example, the forward response message may include Cause information, List of Set Up RABs information, EPS Bearer setup list information, and MME tunnel endpoint identification information for the control plane. MME Tunnel Endpoint Identifier for Control Plane, RAN Cause Information, MME Address for Control Plane Information, Target to Source Transparent Container, Address Information and Data Forwarding It may include at least one information of TEID (TEID (s) for Data Forwarding) information for.

As such, the 5G-CN 125 and the EPC 120 may transmit and receive information necessary for heterogeneous network handover through the NGx interface. .

Referring to FIG. 7, the heterogeneous network handover procedure is once again summarized as follows. The terminal measures radio quality for 5G and LTE cells (or radio links), and reports the result to the source base station (S710). To this end, the terminal may receive measurement configuration information for measurement from the source base station.

The source base station determines whether to initiate the Inter-RAT handover based on the measurement report of the terminal (S720). In this case, the source base station may determine whether the preset Inter-RAT handover start condition is satisfied.

If it is determined that the Inter-RAT handover is necessary, the source base station sends a handover request message to the source core network entity (for example, AMF), and the source core network entity determines whether to initiate the inter-system handover ( S730). For example, the source core network entity may identify the target core network entity and determine the handover type.

When the inter-system handover is determined, the source core network entity converts the terminal context into an EPC terminal context, and performs an inter-system context mapping operation including the above-described transformation operation such as security context (S740).

The source core network entity transmits a heterogeneous network handover request to the target core network entity through a forwarding request message, and the target core network entity requests an inter-RAT handover to the target base station through the handover request message (S750). Through this, EPS bearer setup and radio resource allocation operation required for handover are performed.

Thereafter, the target core network entity transmits EPS bearer setup list information and parameters for DRB configuration through a forward response message to the source core network entity, and the source core network entity maps the RAN Qos using the target core network entity (S760). The source base station instructs the terminal to perform handover while transmitting information received from the target core network entity to the terminal through a handover command message.

The terminal may perform an inter-RAT handover to the target base station by performing a handover command message, or may perform a redirection procedure through an initial access to the target base station when receiving a command indicating that inter-RAT handover is impossible ( S770).

As described above, the terminal may provide service continuity to the user by performing a handover to the LTE base station using another radio access technology in a situation of communicating through the 5G base station.

Hereinafter, a configuration of a source base station and a core network entity capable of performing all or part of the embodiments described with reference to FIGS. 1 to 7 will be described with reference to the drawings.

Referring to FIG. 8, the source base station 800 determines whether to perform a handover with the controller 810 for determining whether to handover to a target base station using a heterogeneous network for the terminal based on the measurement information received from the terminal. If necessary, the transmission unit 820 transmits a handover request message including identification information of the target base station to the core network entity associated with the source base station, and Evolved Packet System (EPS) bearer setup list information of the target base station from the core network entity. The receiver 830 may receive a handover command message. Here, the handover request message may include at least one of target base station identification information serving as a handover target and information indicating a bearer associated with a quality of service (QoS) flow for data forwarding of the terminal.

In addition, the transmitter 820 may transmit a handover command message to the terminal. The handover command message may include EPS bearer setup list information. The EPS bearer setup list information may be included in the control information received from the target base station by the core network entity associated with the target base station and transmitted to the core network entity associated with the source base station. May be included. The receiver 830 may receive measurement information of a terminal measuring a radio state of at least one of a 5G cell and an LTE cell.

The controller 810 may determine whether the terminal requires an Inter-RAT handover based on the received measurement information. For example, the source base station may determine the handover of the terminal in consideration of the required bandwidth information, radio latency information, slicing capability information, and the like.

In addition, the controller 810 controls the overall operation of the source base station 800 necessary for controlling the heterogeneous network handover of the terminal, such as transmitting and receiving information with the core network entity, heterogeneous network handover decision, and handover command to the terminal. To control.

In addition, the transmitter 820 and the receiver 830 are used to transmit and receive signals, messages, and data necessary for performing the above-described embodiments with a core network entity linked to the terminal and the source base station.

Referring to FIG. 9, the core network entity 900 may use a core network associated with a target base station to transmit a handover type or a forward relocation request message using identification information of the target base station included in the handover request message. The control unit 910 for determining the entity and converting the stored terminal context into the Evolved Packet Core (EPC) terminal context for the handover performing terminal and the target base station for the forwarding request message including the target base station identification information and the EPC terminal context. Receive a forward relocation response message including EPS (Evolved Packet System) bearer setup list information of the target base station from the transmitting unit 920 and the core base station associated with the target base station to transmit to the core network entity associated with A receiver 930 may be included.

In addition, the transmitter 920 may transmit a handover command message including EPS bearer setup list information of the target base station to the source base station. The receiver 930 may receive a handover request message from a source base station. For example, the handover request message may include at least one of a target base station identification that is a handover target and information indicating a bearer associated with a quality of service (QoS) flow for data forwarding of the terminal.

In addition, the controller 910 may determine the handover type using identification information of the target base station included in the handover request message. For example, when the identification information of the target base station uses heterogeneous network technology, the control unit 910 may determine the handover type by inter-system handover (handover for the E-UTRAN base station).

Alternatively, the controller 910 may specify a target base station core network entity controlling the target base station by using the target base station identification information of the handover request message. For example, the controller 910 may determine and determine the MME controlling the target base station. Also, the controller 910 may generate the core network entity by converting the stored terminal context into an EPC terminal context. Alternatively, the controller 910 may map and fall back the data flow to the EPS bearer. Alternatively, the controller 910 may convert the 5G NAS message into the LTE NAS message. Alternatively, the controller 910 may remove or fall back the 5G slice configuration information. Alternatively, the controller 910 may map and convert the 5G security context to the EPS security context. In addition, the controller 910 may perform at least one of the operations described above.

The transmitting unit 920 may generate a forwarding request message including at least one information of target base station ID information, EPS terminal context information, direct forwarding flag, and terminal usage type information, and transmit the generated request message to a core network entity linked to the target base station. .

In addition, the controller 910 is capable of providing more stable connectivity and seamless service continuity by fully utilizing the existing LTE network through handover between 5G and LTE, which are heterogeneous wireless networks required to perform the above-described embodiment. Controls the operation of the overall core network entity 900.

In addition, the transmitter 920 and the receiver 930 are used to transmit and receive signals, messages, and data necessary for performing the above-described embodiments with the core network entity associated with the source base station and the target base station.

The standard contents or standard documents mentioned in the above embodiments are omitted to simplify the description of the specification and form a part of the present specification. Therefore, the addition of the contents of the standard and part of the standard documents to the specification or the description in the claims should be construed as falling within the scope of the present invention.

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and changes without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical spirit of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of the present invention.

CROSS-REFERENCE TO RELATED APPLICATIONCROSS-REFERENCE TO RELATED APPLICATION

This patent application is filed with the Korean Patent Application No. 10-2017-0005590, filed with Korea on Jan. 12, 2017, and Patent Application No. 10-2018-0002947, filed with Korea on Jan. 09, 2018. Priority is claimed under section (a) (35 USC § 119 (a)), all of which is incorporated by reference in this patent application. In addition, if this patent application claims priority for the same reason for countries other than the United States, all its contents are incorporated into this patent application by reference.

Claims

In the method for the source base station to control the heterogeneous network handover of the terminal,

Determining whether to handover to a target base station using a heterogeneous network for the terminal based on the measurement information received from the terminal;

If it is determined that the handover is performed, transmitting a handover request message including identification information of the target base station to a core network entity associated with the source base station;

Receiving a handover command message including Evolved Packet System (EPS) bearer setup list information of the target base station from the core network entity; And

Transmitting the handover command message to the terminal.
The method of claim 1,

The handover request message,

And indicating information indicating a bearer associated with a Quality of Service (QoS) flow for data forwarding.
The method of claim 1,

Core network entity associated with the source base station,

And determining a core network entity associated with the target base station to transmit a handover type or a forward relocation request message by using identification information of the target base station included in the handover request message.
The method of claim 1,

Core network entity associated with the source base station,

And converting the stored terminal context for the terminal into an Evolved Packet Core (EPC) terminal context and transmitting it to the core network entity associated with the target base station.
The method of claim 1,

The terminal is set to a single registration mode (single registration mode), the source base station and the target base station uses different network technology,

The core network entity associated with the source base station is a core access and mobility management function (AMF), and the core network entity associated with the target base station is a mobility management entity (MME).
In the core network entity to control the heterogeneous network handover of the terminal,

Determining a core network entity associated with the target base station to transmit a handover type or a forward relocation request message using identification information of the target base station included in the handover request message;

Converting the stored terminal context into an Evolved Packet Core (EPC) terminal context for the handover performing terminal;

Transmitting the redirect request message including the target base station identification information and the EPC terminal context to a core network entity associated with the target base station;

Receiving a forward relocation response message including Evolved Packet System (EPS) bearer setup list information of the target base station from a core network entity associated with the target base station; And

And sending a handover command message including EPS bearer setup list information of the target base station to the source base station.
The method of claim 6,

The handover request message,

And indicating information indicating a bearer associated with a Quality of Service (QoS) flow for data forwarding.
The method of claim 6,

Core network entity associated with the target base station,

And transmitting a handover request message to the target base station, the handover request message including a set of EPS bearer identification information required for setup.
The method of claim 8,

The target base station,

Allocate request resources based on the handover request message,

And sending a handover request confirmation message including the EPS bearer setup list information and applicable parameter information to a core network entity associated with the target base station.
The method of claim 6,

The terminal is set to a single registration mode (single registration mode), the source base station and the target base station uses different network technology,

The core network entity is a core access and mobility management function (AMF), and the core network entity associated with the target base station is a mobility management entity (MME).
In the source base station for controlling the heterogeneous network handover of the terminal,

A controller for determining whether to handover to a target base station using a heterogeneous network for the terminal based on the measurement information received from the terminal;

A transmitter configured to transmit a handover request message including identification information of the target base station to a core network entity associated with the source base station when the handover is determined to be performed; And

Including a receiving unit for receiving a handover command message including the Evolved Packet System (EPS) bearer setup list information of the target base station from the core network entity,

The transmitting unit,

And a source base station further transmitting the handover command message to the terminal.
The method of claim 11,

The handover request message,

The source base station further comprising information indicating a bearer associated with a Quality of Service (QoS) flow for data forwarding.
The method of claim 11,

Core network entity associated with the source base station,

A source base station for determining a core network entity associated with the target base station to transmit a handover type or a forward relocation request message using the identification information of the target base station included in the handover request message. .
The method of claim 11,

Core network entity associated with the source base station,

And converting the stored terminal context into the Evolved Packet Core (EPC) terminal context for the terminal and transmitting the converted context to the core network entity associated with the target base station.
The method of claim 11,

The terminal is set to a single registration mode (single registration mode), the source base station and the target base station uses different network technology,

And a core network entity linked to the source base station is a core access and mobility management function (AMF), and a core network entity linked to the target base station is a mobility management entity (MME).
In the core network entity that controls the heterogeneous network handover of the terminal,

Using the identification information of the target base station included in the handover request message, determine a core network entity associated with the target base station to transmit a handover type or a forward relocation request message;

A control unit for converting a stored terminal context into an Evolved Packet Core (EPC) terminal context for the handover performing terminal;

A transmitter for transmitting the forwarding request message including the target base station identification information and the EPC terminal context to a core network entity associated with the target base station; And

And a receiving unit for receiving a forward relocation response message including Evolved Packet System (EPS) bearer setup list information of the target base station from a core network entity associated with the target base station.

The transmitting unit,

A core network entity for transmitting a handover command message including EPS bearer setup list information of the target base station to the source base station.
The method of claim 16,

The handover request message,

The core network entity further comprising information indicating a bearer associated with a QoS flow for data forwarding.
The method of claim 16,

Core network entity associated with the target base station,

Core object according to claim 1, wherein the target base station transmits a handover request message including a list of EPS bearer identification information required for setup.
The method of claim 18,

The target base station,

Allocate request resources based on the handover request message,

And a handover request confirmation message including the EPS bearer setup list information and applicable parameter information to a core network entity associated with the target base station.
The method of claim 16,

The terminal is set to a single registration mode (single registration mode), the source base station and the target base station uses different network technology,

The core network entity is a core access and mobility management function (AMF), and the core network entity associated with the target base station is a mobility management entity (MME).