KR101975205B1 - Method for Handover in Heterogeneous Network and User Equipment therefor - Google Patents

Abstract

The present invention can reduce the latency in performing handover between heterogeneous base stations in a heterogeneous network including a 5G base station and a 4G base station, and handover in a heterogeneous network capable of preventing a call drop of a terminal. A method and a user device therefor, the method is similar to the standby mode, but when the handover event occurs in the inactive mode in which the connection between the user device and the base station device is maintained without releasing the connection, the user device connects without confirmation of the base station device After canceling the configuration, the mobile station attempts to connect to a new base station device, thereby reducing latency caused by handover and preventing call drop of the terminal.

Description

Method for Handover in Heterogeneous Network and User Equipment therefor {Method for Handover in Heterogeneous Network and User Equipment therefor}

The present invention relates to a handover method between base station devices in a mobile communication network, and more particularly, to reduce latency when performing handover between heterogeneous base stations in a heterogeneous network including a 5G base station and a 4G base station. The present invention relates to a handover method in heterogeneous networks capable of preventing call drop and a user device therefor.

In the next generation mobile communication technology, 5G (5-Generation) NR (New Radio), standardization and research and development of various technologies to handle faster and more capacity with limited resources as mobile devices and data usage explode. This is in progress. Representative technologies of 5G NR include Massive MIMO (Multi Input Multi Output) technology, 3D beamforming technology, and small cell technology.

Among these, the small cell technology is a small cell such as pico and femto in a hot-spot or a building in which a large amount of traffic is generated within the cell area of an existing macro base station. As a technology for increasing network capacity per unit area by overlapping base stations, it was used for distributing data traffic through LTE and dissolving residential and shadow areas through Home eNB in LTE. As a result, its use has been extended to improve spectrum efficiency and to accommodate exploding data traffic.

Through such a small cell technology, a heterogeneous small cell base station and a macro base station overlap with each other is called a heterogeneous network (HetNet).

Figure 1 shows an example of HetNet, the first base station device 100 represents a small cell base station having a low power coverage 10 of several tens to hundreds of meters, the second base station device 200 is approximately a few kilometers A macro base station with broadband coverage 20 is shown. The first base station apparatus 100 may be divided into a femtocell, a picocell, a metrocell, and a microcell according to the size and use of the cell.

The user device 300 used by the user in the HeTNet moves from the broadband coverage 20 of the second base station apparatus 200 to the low power coverage 10 of the first base station apparatus 100 according to the movement of the user, or vice versa. In this case, the user device 300 needs to perform a handover between the first base station device 200 and the second base station device 100.

Particularly, in an environment in which Long Term Evolution (LTE), a fourth generation mobile communication system, is established, when 5G mobile communication is introduced, the first base station apparatus 200 is implemented as an eNB of LTE, and the first base station apparatus ( 100) may be implemented with a gNB defined in 5G mobile communication technology. In this case, the user device 300 must perform handover between the LTE E-UTRAN network and the NR (New Radio) network of 5G mobile communication.

However, in the E-UTRAN, which is a wireless access network of LTE, as shown in FIG. 2, an RRC CONNECTED mode (hereinafter referred to as a connection mode), a mode in which a connection between a base station device and a user device is established, and a mode in which the connection is released While only the RRC IDLE mode (hereinafter, referred to as standby mode) is defined, TS 38.331, which is currently defined in 3GPP, in TS 38.331, is the RRC INACTIVE mode (hereinafter, referred to as inactive mode) along with the connection mode and standby mode. The deactivation mode is a mode that transitions when there is no traffic after the RRC connection is established between the user equipment and the base station apparatus. The deactivation mode is similar to the standby mode, but mutual RRC information is transmitted between the terminal apparatus and the base station apparatus. Because it does not release, it does not need to proceed with the RRC setup procedure when transitioning to connected mode.

In addition, in 5G specification TS38.331, the transition from the connected mode and the standby mode of the 5G to the connected mode and the standby mode of the LTE is defined, but the LTE directly in the deactivation mode which is an intermediate step between the connected mode and the standby mode. The transition to connected mode is not described.

Accordingly, after the user device 300 is connected to the first base station device 100 corresponding to the 5NB gNB and has no traffic, the user device 300 transitions to the deactivation mode of FIG. 2 and thus the second base station device 200 corresponding to the eNB of LTE. When the handover event occurs by moving to the coverage 20 of the user equipment 300, the user equipment 300 first transitions from the inactive mode to the connected mode in association with the first base station apparatus 100, and then again the first base station apparatus ( Handover from the 100 to the second base station apparatus 200 should be performed.

However, if the wireless environment is changed drastically or if the coverage of the 5G mobile network is insufficient, and the user enters the 5G coverage hall, a call drop may occur before performing the above two steps, and even if the RRC reconnection is performed, the 5G mobile network There is a problem that it is difficult to successfully set up RRC reconnection.

Korean Patent Publication No. 10-2014-0106368, 2014.09.03. Disclosure (Name: Handover Method and Device in Heterogeneous Network)

The present invention can reduce the latency in performing handover between heterogeneous base stations in a heterogeneous network including a 5G base station and a 4G base station, and handover in a heterogeneous network capable of preventing a call drop of a terminal. It is intended to provide a method and a user device therefor.

In particular, the present invention is similar to the standby mode, but when the handover event occurs in a deactivation mode in which the connection between the user equipment and the base station apparatus is maintained without releasing the connection, after the user equipment releases the connection without confirmation of the base station apparatus In order to provide a handover method in a heterogeneous network that reduces latency due to handover and prevents a call drop of a terminal by attempting to connect to a new base station device, and a user device therefor.

As a means for solving the above problems, the present invention provides a first base station apparatus in which radio resource control is performed in an inactive mode, which is an intermediate step together with a standby mode and a connected mode, and a second base station in which radio resource control is performed in the standby mode and a connected mode. A handover method in a heterogeneous network comprising a device, comprising: transitioning to a deactivation mode after a user device is connected to the first base station device; Confirming whether a handover event occurs in the user device; When the handover event occurs in the deactivation mode, disconnecting, by the user device, the connection with the first base station device without confirmation or control of the first base station device; And after the connection is released from the first base station apparatus, the user equipment performing connection establishment with the second base station apparatus.

The handover method in a heterogeneous network according to the present invention further includes the step of checking, by the user equipment, whether or not data traffic to be transmitted and received occurs before releasing a connection to a first base station apparatus. When the handover event occurs while occurring, the connection to the first base station device may be released.

In the handover method in the heterogeneous network according to the present invention, in the step of performing connection establishment with the second base station apparatus, when the user equipment requests connection establishment to the second base station apparatus, it informs that the connection establishment request by handover. Tag, and transmit the tag so that the first base station apparatus releases the connection setting for the user equipment according to the report of the second base station apparatus.

A handover method in a heterogeneous network according to the present invention may include: activating radio resource control with the first base station apparatus before releasing the connection to the first base station apparatus; And transmitting a measurement report message to indicate that a handover has occurred to the first base station apparatus, so that the first base station apparatus releases the connection setting for the user equipment after receiving the measurement report message. Can be.

In the handover method in a heterogeneous network according to the present invention, the step of confirming whether the handover event is generated may include: base station signal strength of the first base station apparatus, base station signal strength of the second base station apparatus, The occurrence of a handover event may be determined by comparing one or more of a signal difference and a time between the base station signal and the second base station device.

In addition, as another solution to the above-described problem, the present invention provides a first base station apparatus in which radio resource control is performed in an inactive mode, which is an intermediate step together with a standby mode and a connection mode, and radio resource control in the standby mode and a connection mode. A wireless communication unit configured to access a second base station apparatus configured to establish and release a wireless connection, and to transmit and receive data through the connection; And interworking with the wireless communication unit, if the handover event occurs during the operation in the inactive mode after connecting to the first base station apparatus, disconnects the connection to the first base station apparatus without checking or controlling the first base station apparatus. After the release, by performing connection establishment with the second base station apparatus, the user equipment comprising a control unit for handing over from the first base station apparatus to the second base station apparatus.

In the user device according to the present invention, the controller further checks whether data traffic to be transmitted and received occurs before releasing the connection to the first base station device, and when the data traffic occurs and a handover event occurs, 1 may be controlled to release the connection to the base station device.

In addition, in the user device according to the present invention, the control unit transmits a tag indicating that the connection establishment request by handover is included in the request for connection establishment to the second base station apparatus, so that the first base station apparatus transmits the second base station. Enable to release the connection setting to the user device according to the report of the device, or activate radio resource control with the first base station device prior to releasing the connection to the first base station device. 1 A measurement report message may be transmitted to indicate that a handover has occurred to the base station apparatus, so that the first base station apparatus releases the connection setting for the user equipment after receiving the measurement report message.

The present invention is similar to the standby mode, but when the handover event occurs in a deactivation mode in which the connection between the user device and the base station device is maintained without releasing the connection, after the user device releases the connection without confirmation of the base station device, By attempting to connect to the base station apparatus, it is possible to reduce latency caused by handover between heterogeneous base stations and to prevent cold drop of the terminal.

In particular, when the user device moves from the 5G wireless access network in which the deactivation mode is defined to the 4G wireless access network in which the deactivation mode is not defined, the user device may perform a transition process from the deactivation mode to the connected mode. There is no need to perform the connection setup for the 4G wireless access network immediately, without having to try to exchange messages excessively when the possibility of normal message exchange between the user device and the base station device due to the change of the wireless environment, Handover can be performed, which reduces latency and prevents cold drop.

1 is a diagram illustrating an example of a mobile communication network to which the present invention is applied.
2 is a block diagram illustrating an interworking relationship between an LTE network and a 5G NR network defined in 3GPP.
3 is a flowchart illustrating a handover process between heterogeneous networks according to a first embodiment of the present invention.
4 is a flowchart illustrating a handover process between heterogeneous networks according to a second embodiment of the present invention.
5 is a configuration diagram of a user device for performing a handover method between heterogeneous networks according to the present invention.
6 is a flowchart illustrating a method for handover between heterogeneous networks by a user device according to a first embodiment of the present invention.
7 is a flowchart illustrating a method for handover between heterogeneous networks by a user device according to a second embodiment of the present invention.
8 is a flowchart illustrating in detail a process of determining handover triggering in a method for handover between heterogeneous networks according to the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, in the following description and the accompanying drawings, detailed descriptions of well-known functions or configurations that may obscure the subject matter of the present invention will be omitted. In addition, it should be noted that like elements are denoted by the same reference numerals as much as possible throughout the drawings.

The terms or words used in the specification and claims described below should not be construed as being limited to ordinary or dictionary meanings, and the inventors are appropriate as concepts of terms for explaining their own invention in the best way. It should be interpreted as meanings and concepts in accordance with the technical spirit of the present invention based on the principle that it can be defined. Therefore, the embodiments described in the present specification and the configuration shown in the drawings are only the most preferred embodiments of the present invention, and do not represent all of the technical ideas of the present invention, and various alternatives may be substituted at the time of the present application. It should be understood that there may be equivalents and variations.

In addition, terms including ordinal numbers, such as first and second, are used to describe various components, and are used only to distinguish one component from another component, and to limit the components. Not used. For example, without departing from the scope of the present invention, the second component may be referred to as the first component, and similarly, the first component may also be referred to as the second component.

In addition, when a component is referred to as being "connected" or "connected" to another component, it means that it may be connected or connected logically or physically. In other words, although a component may be directly connected or connected to other components, it should be understood that other components may exist in the middle, and may be connected or connected indirectly.

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

The present invention relates to a handover between heterogeneous base station devices in a heterogeneous network system including heterogeneous base station devices to which different communication technologies are applied as shown in FIG. 1.

For reference, handover refers to a function in which a service is connected to a call channel allocated to another base station apparatus by a terminal when the user equipment moves from the coverage of the previously connected base station apparatus to the coverage of another base station apparatus. According to the scheme, there is a soft handover scheme in which an existing circuit is connected to a new base station, followed by a soft handover scheme in which an existing circuit is disconnected, and an existing circuit is first disconnected and then connected to a new base station. Depending on the over subject, there are communication network control handover, mobile station control handover, and the like. In addition, a series of state transition processes of switching from the connection mode of the previous base station device to the connection mode of the new base station device may be defined as handover.

In the present specification, when the user equipment moves from the coverage of the pre-connected base station apparatus to the coverage of the other base station apparatus, the new base station apparatus as well as the function that the service is connected by tuning to the call channel allocated to the other base station apparatus by the terminal. It will be defined and described in a comprehensive sense including the process of transition to the connection mode of.

That is, in the handover method according to the present invention to be described below, since the state transition is made from the deactivation mode of the previously connected first base station apparatus 100 to the connection mode of the new second base station apparatus 200, the hand has a narrow meaning. Although it may be interpreted as not being over, in the present invention, as the user equipment 300 moves from the coverage of the previously connected first base station apparatus 100 to the coverage of the new second base station apparatus 200, the first base station apparatus Since the connection is switched from the 100 to the second base station apparatus 200, it may correspond to a handover technique in a broad sense.

Hereinafter, a heterogeneous network in which a handover method between heterogeneous networks according to the present invention is performed will be described with reference to FIG. 1.

In one embodiment of the present invention, one of the heterogeneous base station apparatuses for which handover is performed (for example, the first base station apparatus 100) is an RRC (processing setting and release for radio connection in a wireless access network). In the Radio Resource Control) layer, a connection setting between the user device 300 and the first base station device 100 as a relaying step of an RRC Idle mode, an RRC CONNECTED mode, and a standby mode and a connected mode. It operates in three stages, RRC INACTIVE mode, which operates similarly to the standby mode while maintaining the function without releasing it.

For example, in the present invention, the first base station apparatus 100 may be a base station apparatus (gNB) defined in the 5G mobile communication standard.

Meanwhile, another base station apparatus (for example, the second base station apparatus 200) where handover is performed from the first base station apparatus 100 is a base station apparatus according to a mobile communication standard different from the first base station apparatus 100. For example, it may be a base station apparatus (eNB) defined in the fourth generation mobile communication standard.

Since the second base station apparatus 200 has no deactivation mode unlike the first base station apparatus 100, the second base station apparatus 200 operates in two stages in the standby mode and the connected mode in the RRC layer.

For reference, in the mobile communication technology, the RRC layer is a cell system information broadcast, paging message delivery, RRC connection management (setting / maintenance / release), mobility management (handover), user equipment 130 required for the mode terminal in the cell As a layer performing measurement report and control thereof, these are achieved through exchange of RRC messages.

In addition, in the RRC state, the connected mode is a state in which a radio resource control channel is connected, and the user device 300 monitors the control channel to transmit and receive data with the first and second base station devices 100 and 200, and performs handover. Can be performed. In the standby mode, the radio resource control channel is disconnected, and the user device 300 monitors a paging channel to detect a signal transmitted from the first and second base station devices 100 and 200, and thereby the cell system. By acquiring the information, neighbor cell measurement and cell selection can be made.

In addition, the deactivation mode is a mode proposed to efficiently manage the user device 300, and when transitioning to the connected mode while performing a wireless control procedure in a form similar to the standby mode to reduce power consumption of the user device 300. In order to minimize the control procedure required for the connection, the connection state between the user device 300 and the first base station device 100 maintains a state similar to the connection mode. In the deactivation mode, the user device 300 only allows the transmission of the preamble signal and the reception of the paging channel, and stops the measurement procedure or the use of the data channel that consumes a lot of power. The first base station apparatus 100 controls the deactivation mode by referring to mobility information and channel state information of the user device 300 acquired in the connected mode.

In the heterogeneous network environment, the present invention relates to a handover method performed in a state where a user device 300 is connected to the first base station device 100 and then transitions to an inactive mode, and the handover method according to the present invention is deactivated. When the handover event occurs in the mode, the connection setup is canceled without exchanging a message with the first base station apparatus 100, and the connection setup with the adjacent second base station apparatus 200 is performed. At this time, the connection establishment release procedure for the first base station apparatus 100 may be performed in various manners independently of the connection establishment release procedure at the user device 300.

3 and 4 are flowcharts illustrating a handover process between heterogeneous networks according to an embodiment of the present invention, with reference to this, a handover method in a heterogeneous network according to the present invention will be described.

First, FIG. 3 is a flowchart illustrating a handover process between heterogeneous networks according to a first embodiment of the present invention.

Referring to FIG. 3, in the user device 300 according to the present invention, after the connection setting of the first base station device 100 and the radio resource control channel is completed, the data traffic does not occur for a predetermined time or more, so that the user device 300 transitions to the inactive mode. (S105). As described above, in the deactivation mode, the user device 300 is only allowed to transmit a preamble signal and receive a paging channel.

In this state, the user device 300 monitors a radio signal transmitted from the first base station apparatus 100 and the neighboring base station apparatus, for example, the second base station apparatus 200 through the paging channel to generate a handover event. And whether data traffic to be transmitted has occurred. Here, the handover event occurs when the wireless communication environment is lowered to a predetermined level or less as the distance from the first base station apparatus 100 currently connected due to the movement of the user apparatus 300. Specifically, the user apparatus ( 300 may be determined using one or more of the strength of the radio signal of the first base station apparatus 100 (for example, RSSI value) and the strength of the radio signal of the adjacent second base station apparatus 200. This will be described later in more detail.

As a result of the check, when a handover event occurs and data traffic to be transmitted is generated (S110), the user device 300 transmits a control message related to handover to the first base station device 100 or the first base station device 100. RRC connection is released without receiving the control message related to the handover from (S115). This is done without radio resource control of the first base station apparatus 100, also referred to as blind release.

The existing disconnection is performed by the user device 300 requesting a disconnection from the first base station apparatus 100 or receiving a disconnection request from the first base station apparatus 100. However, in step S115, the user is disconnected. RRC connection release of the user device 300 is performed in an independent operation without the device 300 interworking with the first base station device 100.

The user device 300 performs an RRC connection establishment procedure with a immediately adjacent base station device, that is, the second base station device 200. Specifically, the user device 300 moves to the second base station device 200. When the RRC connection request message is transmitted (S120), the second base station apparatus 200 receiving the RRC connection request message allocates radio resources to transmit the RRC connection configuration information to the user device 300 (S125). Is made by transmitting the completion report for the RRC connection establishment to the second base station apparatus 200 (S130). The data traffic is transmitted to the second base station apparatus 200 through the RRC connection.

In this case, the user device 300 performs a handover from the first base station device 100 when the RRC connection request is made in step S120 for RRC connection release processing for the user device 300 in the first base station device 100. It transmits the information including the information indicating that the over is made (for example, a handover notification tag). The handover notification tag may include identification information indicating the handover and identification information of the first base station apparatus 100 to which the user apparatus 300 has previously connected.

Upon receiving this, the second base station apparatus 200 checks the handover notification tag included in the RRC connection request, thereby confirming that the user apparatus 300 is handed over from another base station apparatus instead of the first connection. The handover of the user device 300 is reported to the corresponding first base station device 100 (S135).

When the first base station apparatus 100 receives the handover report message transmitted from the second base station apparatus 200, the first base station apparatus 100 performs an RRC connection release process for the corresponding user apparatus 300 (S140).

According to the first embodiment of the present invention, when the handover event and the data traffic occur at about the same time, the RRC connection is established to the adjacent second base station apparatus 200 immediately after the RRC connection is released from the user device 300. As a result, the mobile station can be handed over from the first base station apparatus 100 to the second base station apparatus 200 with a minimum delay to process data traffic through the second base station apparatus 200. In particular, the connection setting is made through the second base station apparatus 200 having better radio environment characteristics, rather than the first base station apparatus 100 having a low possibility of normal message transmission due to the deterioration of the wireless environment. It can be minimized.

In addition, the user device 300 does not directly inform the first base station apparatus 100 of the RRC connection release, but indirectly determines the disconnection state of the user device 300 through the second base station apparatus 200 in which the RRC connection is established. By transmitting, the RRC connection release of the first base station apparatus 100 may be normally processed.

4 is a flowchart illustrating a handover process between heterogeneous networks according to a second embodiment of the present invention.

Referring to FIG. 4, as described above, the user device 300 transitions to the inactive mode because data traffic does not occur for a predetermined time after the connection setting of the first base station device 100 and the radio resource control channel is completed. (S205).

In this state, the user device 300 monitors a radio signal transmitted from the first base station apparatus 100 and the neighboring base station apparatus, for example, the second base station apparatus 200 through the paging channel to generate a handover event. And whether data traffic to be transmitted has occurred.

Steps S205 and S210 may be the same as steps S105 and S110 according to the first embodiment.

As a result of the check, when a handover event occurs and data traffic to be transmitted is generated, the user device 300 activates an RRC connection that is currently idle (S215), and performs a MR (Measurement Report) through the activated RRC connection. The message is transmitted to the first base station apparatus 100 (S220). The MR message is a message for reporting a measurement value of the user device 300 in the RRC layer, and the user device 300 transmits the current state through the MR message, that is, the wireless environment of the first base station device 100. Send the measured value. In this case, the MR message may also include information of the second base station apparatus 200 to be handed over. In addition, the MR message is unilaterally transmitted from the user device 300 to the first base station device 100, and the user device 300 does not wait for a response thereto.

After the MR message is transmitted, the user device 300 releases the RRC connection by itself without exchanging a message with the first base station device 100 (S230).

At this time, the first base station apparatus 100 confirms the state of the user apparatus 300 by checking the MR message, so that the user equipment 300 of the user apparatus 300 is moved to the second base station apparatus 200 to which the user apparatus 300 is to be handed over. Report the handover (S225), and releases the RRC connection to the user device 300 (S230). Here, the RRC connection release of the first base station apparatus 100 is also performed by itself without interworking with the user apparatus 30.

That is, the RRC disconnection from the user device 300 and the RRC disconnection from the first base station device 100 are independently performed.

In this way, the user device 300 that has released the RRC connection with the first base station apparatus 100 performs an RRC connection establishment procedure with an adjacent base station apparatus, that is, the second base station apparatus 200 (S235 ˜ S245). As described above, when the user device 300 transmits an RRC connection request message to the second base station apparatus 200 (S235), the second base station apparatus 200 receiving the same allocates radio resources to establish an RRC connection. The information is transmitted to the user device 300 (S240), and the user device 300 reports the completion of the RRC connection establishment to the second base station device 200 (S245).

When the RRC connection setting is completed as described above, the RRC is activated between the user device 300 and the second base station device 200 to transmit data traffic (S250).

According to the above embodiment, when the handover event occurs in the inactive mode, the terminal device 300 releases the RRC connection by itself without control or confirmation of the first base station device 100, and then the neighboring agent. 2 By directly connecting to the base station apparatus 200, after the transition to the connection mode to the existing first base station apparatus 100, the latency is more than the method of performing a handover through the first base station apparatus 100 Can be reduced, and cold drop during handover processing can be prevented.

Next, FIG. 5 is a configuration diagram of a user device 300 performing a handover method between heterogeneous networks according to the present invention.

Referring to FIG. 5, the user device 300 according to the present invention basically communicates with the first and second base station devices 100 and 200 to establish or release an RRC connection, and transmit and receive data traffic through the connection. A wireless communication unit 310 and a control unit 320 for controlling the operation of the wireless communication unit 310. Of course, the present invention is not limited thereto, and further includes a storage unit 330, an input unit 340, an output unit 350, and the like as a normal user device. Here, the storage unit 330 is a memory for storing data and program modules, and may include both a random access memory (RAM) / ROM (Read Only Memory) and a storage medium such as a flash memory or a hard disk. 340 denotes an input interface device for user manipulation, and means various input means such as a touch pad, a touch screen, a keypad, and the like. The output unit 350 is a device for visually providing information to a user. It means the same display device. The storage unit 330, the input unit 340, and the output unit 350 are devices typically provided in the user device 300, but are not directly related to handover between heterogeneous networks according to the present invention. Description thereof is omitted.

Therefore, the wireless communication unit 310 and the control unit 320 which are the main components related to handover processing between heterogeneous networks according to the present invention will be described in detail.

The wireless communication unit 310 may include one or more mobile communication modules for processing wireless connection and data transmission and reception according to different frequencies or different communication technologies. Specifically, the wireless communication unit 310 may include a first base station apparatus 100. 5G based mobile communication module for accessing and allocating radio resources and transmitting and receiving data through the allocated radio resources, and accessing the second base station apparatus 200 to allocate radio resources and to transmit data through the allocated radio resources. It may include a 4G-based mobile communication module for transmitting and receiving. Each mobile communication module may include an antenna, an RF signal processing circuit for performing amplification / frequency conversion / filtering, a D-A converter for signal conversion, a digital signal processor, and the like.

The controller 320 is an apparatus for controlling overall operations of the user device 300 and hardware components of the user device 300, and includes one or more processors and an OS loaded and executed by the processor. System) program can be implemented. The controller 320 executes a program module stored in the storage 330 to process information or data to perform a predetermined function. For reference, the processor may be implemented as hardware, or software or a combination of hardware and software. For example, a CPU (Central Processing Unit) and a microprocessor, which are implemented in hardware, as well as an interpreter implemented in software, Comprehensive generalization of compiler and assembler.

The controller 320 controls the wireless communication unit 310 to perform the handover method according to the present invention, and the detailed operation thereof will be described with reference to the flowcharts of FIGS. 6 to 8.

6 is a flowchart illustrating a method for handover between heterogeneous networks by a user device 300 according to a first embodiment of the present invention.

Referring to FIG. 6, in the first embodiment of the present invention, when the user device 300 is located within the coverage 10 of the first base station device 100, the user device 300 may include a wireless communication unit 310. When the first base station apparatus 100 recognizes the first base station apparatus 100 and performs RRC connection with the first base station apparatus 100, when data traffic to be transmitted or received does not occur for a predetermined time or more, the user apparatus 300 may be used to reduce power consumption. ) Is operated in an inactive mode (S305).

In the deactivation mode of the RRC state, the control unit 320 of the user device 300 manages data traffic to be transmitted and received (S310), and determines whether to handover by measuring a wireless environment at a predetermined period (S315). The transmission and reception of the data traffic and the determination of handover may be independently performed in parallel, and the data traffic and the handover event occur at about the same time or at a predetermined time difference. That is, after the occurrence of the data traffic to be transmitted and received is confirmed first, it may be checked whether the handover, or as the occurrence of the handover event may be subsequently confirmed whether there is data traffic to be transmitted and received.

 In addition, the determination of whether the handover is performed in a predetermined period, by receiving the base station signal of the currently connected first base station apparatus 100 and the base station signal of the adjacent second base station apparatus 200 by measuring the reception strength The process may be performed as shown in FIG. 8.

That is, when data traffic occurs and a handover event occurs through the process as shown in FIG. 8, the user device 300 releases the RRC connection by itself without checking or controlling the currently connected first base station device 100. (S320).

The user device 300 accesses the adjacent second base station device 200 to perform RRC connection establishment (S325), and transmits and receives data traffic through the corresponding connection (S335). In this case, the user device 300 may transmit a RRC connection request message, including a handover notification tag indicating that the connection is set by the handover request, the second base station device 200 receives the handover When the over notification tag is included, the user equipment 300 may report to the corresponding first base station apparatus 100 that the user equipment 300 has requested a connection to itself, that is, a handover request has occurred. 100 may release the RRC connection setting for the user device 300.

On the other hand, if the data traffic occurs in step S315, but the handover event does not occur, the user device 300 exchanges a message with the first base station device 100, as in the usual procedure, to connect the RRC state Transition to the mode (S330), and transmits and receives data traffic through the activated RRC connection (S335).

Although not described in the above example, if a handover event occurs without generating data traffic, the handover may be performed after the transition to the connected mode as in the existing handover procedure, or the steps S320 to S325 may be performed. Can also be.

Next, FIG. 7 is a flowchart illustrating a method for handover between heterogeneous networks by a user device according to a second embodiment of the present invention.

Referring to FIG. 7, in the second embodiment of the present invention, after the user device 300 is located in the coverage 10 of the first base station device 100, the RRC connection with the first base station device 100 is performed. In the state of transition to the inactive mode (S405), when data traffic to be transmitted and received occurs (S410), as in the above-described first embodiment, the user device 300 checks whether a handover event occurs (S415). .

To this end, the user device 300 determines the handover by measuring the wireless environment at predetermined intervals while processing data traffic to be transmitted and received. As described above, the transmission and reception of the data traffic and the determination of handover may be independently performed in parallel, and the data traffic and the handover event may occur almost simultaneously or at a predetermined time difference. That is, after the occurrence of the data traffic to be transmitted and received is confirmed first, it may be checked whether the handover, or as the occurrence of the handover event may be subsequently confirmed whether there is data traffic to be transmitted and received.

 In addition, the determination of whether the handover is performed in a predetermined period, by receiving the base station signal of the currently connected first base station apparatus 100 and the base station signal of the adjacent second base station apparatus 200 by measuring the reception strength The process may be performed as shown in FIG. 8.

As described above, when data traffic occurs and a handover event occurs (S415), the user device 300 activates the deactivated RRC connection (S420) to prepare an MR message to confirm that a handover has occurred. 1 is transmitted to the base station apparatus 100 (S425). The MR message is transmitted from the user equipment 300 to the first base station apparatus 100 in one direction, and a response thereof is unnecessary. However, after confirming the handover state of the user device 300 through the MR message, the first base station device 100 transfers it to the second base station device 200 to be handed over, and then an RRC for the user device 300. Disconnect. This is also done without confirmation of the user device 300.

Subsequently, after transmitting the MR message, the user device 300 releases the RRC connection by itself without checking or controlling the currently connected first base station apparatus 100 (S430).

Subsequently, the user device 300 accesses the adjacent second base station device 200 to perform RRC connection establishment (S435), and transmits and receives data traffic through the corresponding connection (S445).

On the other hand, when the data traffic occurs in step S415, but the handover event does not occur, the user device 300 exchanges a message with the first base station device 100, as in the usual procedure, to connect the RRC state Transition to the mode (S440), and transmits and receives data traffic through the activated RRC connection (S445).

Although not described in the above example, if a handover event occurs without generating data traffic, the handover may be performed after the transition to the connection mode as in the existing handover procedure, or the steps S420 to S435 may be performed. Can also be.

Lastly, FIG. 8 is a flowchart illustrating a process of determining handover triggering in detail between handover methods between heterogeneous networks according to the present invention.

The process of FIG. 8 described below may be performed at step S315 shown in FIG. 6 and step S415 of FIG. 7.

That is, in steps S315 and S415 of FIG. 6, the user device 300 periodically determines whether to handover as described below.

In order to operate at a constant period, the period variable t_m is reset to 0 (S505), and then an up count of the period variable t_m is started (S510).

When the period variable t_m reaches the set period T_m (S515), the user device 300 may access the base station signal S_1 of the currently connected first base station apparatus 100 and / or the adjacent base station, that is, the second base station. The base station signal S_2 of the device 200 is received and its size (eg, RSSI) is measured (S520).

The user device 300 performs one or more of steps S525 to S535 to compare the measured strength of the base station signal.

In detail, in operation S525, the user device 300 compares whether the strength of the base station signal S_1 of the first base station device 100 is equal to or less than a first threshold value. The first threshold may be set to the lowest strength of the base station signal S_1 for stably communicating with the currently connected first base station apparatus 100. That is, when the strength of the base station signal S_1 is lower than the first threshold value, the radio environment characteristics are deteriorated and data transmission and reception are not smoothly performed.

In operation S530, the user device 300 compares whether the strength of the base station signal S_2 of the second base station device 200 is greater than or equal to a second threshold value. The second threshold is the lowest intensity for stably performing communication with the second base station apparatus 200.

In operation S535, the user device 300 may compare the strengths of the base station signal S_1 of the first base station apparatus 100 and the base station signal S_2 of the second base station apparatus 200.

Subsequently, the user device 300 determines whether a preset reference condition for generating a handover event is satisfied based on the comparison result of steps S525 to S535 (S540). In more detail, in step S540, the user device 300 may determine that the strength of the base station signal S_1 of the first base station device 100 is less than or equal to the first threshold value, or that the base station signal S_1 of the first base station device 100 is not included. The strength is less than or equal to the first threshold and the strength of the base station signal S_2 of the second base station apparatus 200 is greater than or equal to the second threshold, or the strength of the base station signal S_2 of the second base station apparatus 200 is greater than the first base station. The base station of the second base station apparatus 200 is greater than the offset value greater than the strength of the base station signal S_1 of the apparatus 100 or the intensity of the base station signal S_1 of the first base station apparatus 100 is less than or equal to the first threshold value. When the strength of the signal S_2 is more than the offset value of the strength of the base station signal S_1 of the first base station apparatus 100, it may be determined that the reference condition is satisfied.

In addition, when it is determined that the reference condition is satisfied, the user device 300 may further determine whether the maintenance time of the reference condition is counted to maintain the preset time T_S or more (S545).

In addition, the handover event may be generated when the reference condition is maintained for a predetermined time or more.

The reference condition of the handover event may be selectively applied as follows. In the following, t_s denotes a holding time of a corresponding condition, and T_S denotes a preset holding time.

① S_1 <first threshold

(S_1 <first threshold) AND (S_2> second threshold)

③ S_1 + Offset <S_2

④ (S_1 <first threshold) AND (S_1 + Offset <S_2)

(S_1 <first threshold) AND (t_s> T_s)

⑥ (S_1 <first threshold) AND (S_2> second threshold) AND (t_s> T_s)

⑦ (S_1 + Offset <S_2) AND (t_s> T_s)

⑧ (S_1 <first threshold) AND (S_1 + Offset <S_2) AND (t_s> T_s)

The above-described conditions are reference conditions for determining an appropriate handover time point from the first base station apparatus 100 to the second base station apparatus 200, and they may be changed according to a wireless environment.

The handover method in the heterogeneous network according to the present invention as described above is implemented in a software form readable through various computer means, recorded in the storage unit 330 of the user device 300, and then the control unit 320 It can be loaded and executed by the processor. Here, the storage unit 330 is. Program instructions, data files, data structures, and the like, may be included alone or in combination. Program instructions recorded on the recording medium may be those specially designed and constructed for the present invention, or they may be of the kind well-known and available to those having skill in the computer software arts. For example, the storage unit 330 may be an optical recording medium such as a magnetic media such as a hard disk, a floppy disk, or a magnetic tape, a compact disk read only memory (CD-ROM), or a digital video disk (DVD). , Specially configured to store and execute program instructions, such as magneto-optical media, such as floppy disks, and random access memory (RAM), flash memory, and the like. Device. Examples of program instructions may include high-level language code that can be executed by a computer using an interpreter as well as machine code such as produced by a compiler.

In addition, although the present specification and drawings disclose a preferred embodiment of the present invention, it is common in the technical field to which the present invention belongs that other modifications based on the technical idea of the present invention can be carried out even with the exceptions disclosed herein. It is self-evident to those who have knowledge. In addition, although specific terms are used in the specification and the drawings, they are only used in a general sense to easily explain the technical contents of the present invention and to help the understanding of the present invention, and are not intended to limit the scope of the present invention.

Although the specification includes numerous specific implementation details, these should not be construed as limiting to any invention or the scope of the claims, but rather as a description of features that may be specific to a particular embodiment of a particular invention. It must be understood. Certain features that are described in this specification in the context of separate embodiments may be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments individually or in any suitable subcombination. Furthermore, while the features may operate in a particular combination and may be initially depicted as so claimed, one or more features from the claimed combination may in some cases be excluded from the combination, the claimed combination being a subcombination Or a combination of subcombinations.

Likewise, although the operations are depicted in the drawings in a specific order, it should not be understood that such operations must be performed in the specific order or sequential order shown in order to obtain desirable results or that all illustrated operations must be performed. In certain cases, multitasking and parallel processing may be advantageous. Moreover, the separation of the various system components of the above-described embodiments should not be understood as requiring such separation in all embodiments, and the described program components and systems will generally be integrated together into a single software product or packaged into multiple software products. It should be understood that it can.

Specific embodiments of the subject matter described in this specification have been described. Other embodiments are within the scope of the following claims. For example, the actions recited in the claims can be performed in a different order but still achieve desirable results. As an example, the process depicted in the accompanying drawings does not necessarily require that particular illustrated or sequential order to obtain desirable results. In certain implementations, multitasking and parallel processing may be advantageous.

The present invention is applied to a wireless access network of a mobile communication system, and when the handover event occurs in a state similar to the standby mode but in an inactive mode in which the connection between the user equipment and the base station apparatus is maintained without releasing the connection setting, the user equipment is the base station apparatus. After releasing the connection setting without confirmation, attempting to connect to a new base station device can reduce latency caused by handover and prevent cold drop of the terminal.

In particular, when the user device moves from the 5G wireless access network in which the deactivation mode is defined to the 4G wireless access network in which the deactivation mode is not defined, the user device may perform a transition process from the deactivation mode to the connected mode. There is no need to perform the connection setting for the 4G wireless access network, and it is possible to quickly exchange the message without excessively attempting to exchange the message when the possibility of normal message exchange between the user device and the base station device due to the change of the wireless environment. Handover can be performed, which reduces latency and prevents cold drop.

100: first base station apparatus
200: second base station apparatus
300: user device
310: wireless communication unit
320: control unit

Claims (9)

A handover method in a heterogeneous network comprising a first base station apparatus in which radio resource control is performed in an inactive mode, which is an intermediate step together with a standby mode and a connected mode, and a second base station apparatus in which radio resource control is performed in the standby mode and a connected mode. To
Transitioning to the inactive mode after a user device is connected to the first base station device;
Confirming whether a handover event occurs in the user device;
When the handover event occurs in the deactivation mode, disconnecting, by the user device, the connection with the first base station device without confirmation or control of the first base station device; And
After the connection to the first base station apparatus is released, the user equipment performs connection establishment with the second base station apparatus;
Performing connection establishment with the second base station apparatus,
When the user device requests a connection establishment request to the second base station device, the user device includes a tag indicating that the connection establishment request by handover is transmitted,
And the first base station apparatus can release the connection setup for the user equipment according to the report of the second base station apparatus. The method of claim 1,
Checking, by the user device, whether or not data traffic to be transmitted and received occurs before releasing the connection to the first base station device;
When the handover event occurs while the data traffic occurs, disconnecting the connection to the first base station apparatus. delete The method of claim 1,
Prior to the step of releasing the connection to the first base station device,
Activating radio resource control with the first base station apparatus; And
Transmitting a measurement report message to indicate that a handover has occurred to the first base station apparatus;
And the first base station device releases the connection setting for the user device after receiving the measurement report message. The method of claim 1, wherein the determining whether the handover event is generated comprises:
Determining whether a handover event has occurred by comparing one or more of a base station signal strength of the first base station apparatus, a base station signal strength of the second base station apparatus, a signal difference between the base station signal of the first base station apparatus and the second base station apparatus, and time. Handover method in a heterogeneous network characterized by. Establishes and releases a wireless connection by accessing a first base station apparatus in which radio resource control is performed in an inactive mode, which is an intermediate step together with a standby mode and a connection mode, and a second base station apparatus in which radio resource control is performed in the standby mode and a connection mode, and Wireless communication unit for transmitting and receiving data through the connection; And
If the handover event occurs during the operation in the deactivation mode after connecting to the first base station apparatus in cooperation with the wireless communication unit, release the connection to the first base station apparatus without checking or controlling the first base station apparatus. And a controller for handing over from the first base station apparatus to the second base station apparatus by performing connection establishment with the second base station apparatus.
The control unit
When the connection establishment request to the second base station apparatus is included, a tag indicating that the connection establishment request is requested by handover is transmitted and transmitted, so that the first base station apparatus performs connection establishment for the user equipment according to the report of the second base station apparatus. And release the user device. The method of claim 6, wherein the control unit
Before releasing the connection to the first base station apparatus, further confirming whether data traffic to be transmitted and received occurs, and if the data traffic occurs and a handover event occurs, controlling to release the connection to the first base station apparatus. Characterized in that the user device. delete The method of claim 6, wherein the control unit
Before releasing the connection to the first base station apparatus, the radio resource control with the first base station apparatus is activated, and through this, a measurement report message is transmitted to indicate that a handover occurs to the first base station apparatus. And the first base station device releases the connection setting for the user device after receiving the measurement report message.

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