JP2019068193A - Wireless communication system and handover method - Google Patents

Abstract

A handover is realized separately for uplink and downlink of a user plane. A small base station device (5) sends a measurement report to a macro base station device (3) that the uplink reception strength of a user plane between a terminal device (1) and a macro base station device (3) has changed from below a threshold to above a threshold. and the macro base station device 3 transmits a user plane uplink handover request to the small base station device 5 by the measurement report, and the small base station device 5 transmits a user plane uplink handover response to the macro base by the uplink handover request. The macro base station apparatus 3 transmits a user plane uplink handover instruction to the terminal apparatus 1 in response to an uplink handover response, and the terminal apparatus 1 transmits a user plane uplink base station in response to the uplink handover instruction. The device is switched from the macro base station device 3 to the small base station device 5. [Selection drawing] Fig. 6

Description

  The present invention relates to a wireless communication system and a handover method.

  Conventionally, a base station apparatus having a relatively large cell (hereinafter referred to as a macro cell) (hereinafter referred to as a macro base station apparatus) and a base station apparatus having a relatively small cell (hereinafter referred to as a small cell) (hereinafter referred to as A wireless communication system is known which arranges a macro cell and a small cell such that the macro cell includes all or a part of the small cell. In such a radio communication system, a user equipment (UE) performs radio communication of uplink of a user plane (U-plane) by a small cell, and a downlink of the user plane For example, Non-Patent Document 1 discloses a wireless communication method in which (Downlink) wireless communication is performed by a macro cell.

Federico Boccardi, Jeffrey Andrews, Hisham Elshaer, Mischa Dohler, Stefan Parkvall, Petar Popovski, Sarabjot Singh, “Why to Decouple the Uplink and Downlink in Cellular Networks and How to Do It”, IEEE Communications Magazine, Volume: 54, Issue: 3 , March 2016.

  In the above-described conventional wireless communication method, it has been one problem to realize handover separately for the uplink and downlink of the user plane.

  The present invention has been made in consideration of such circumstances, and an object thereof is to realize handover separately for uplink and downlink in the user plane.

(1) One aspect of the present invention includes a first base station apparatus, a second base station apparatus, and a terminal apparatus, and the cell of the first base station apparatus is all of the cells of the second base station apparatus. Alternatively, the second base station apparatus performs an uplink radio communication with the first base station apparatus in the user plane with the second base station apparatus, and the second base station of the uplink radio signal of the terminal apparatus. A measurement unit configured to measure a first reception strength in the station apparatus, and the terminal apparatus in which the measurement result of the first reception strength changes from less than the first threshold to exceed the first threshold with respect to a predetermined first threshold; (1) In response to an uplink handover request of the user plane of the terminal apparatus received from the first base station apparatus and a measurement report unit that transmits a measurement report to the first base station apparatus, the user plane of the terminal apparatus is up Link handover response A base station control unit that transmits the first base station apparatus to the first base station apparatus, and the first base station apparatus responds to the first measurement report on the terminal apparatus received from the second base station apparatus. When an uplink handover request of a user plane of a terminal apparatus is transmitted to the second base station apparatus and an uplink handover response to the uplink handover request is received from the second base station apparatus, the user plane is raised to the terminal apparatus. The terminal apparatus that includes a base station control unit that transmits a link handover instruction, and that performs uplink radio communication with the first base station apparatus in the user plane, is a user plane received from the first base station apparatus. In accordance with the uplink handover instruction, the base station apparatus of the other party performing uplink radio communication in the user plane Performs handover to switch from serial first base station apparatus to the second base station apparatus, and a terminal control unit to transmit the uplink handover complete user plane to the second base station apparatus, a wireless communication system.
(2) In one aspect of the present invention, in the wireless communication system according to the above (1), the measurement unit performs the radio communication of the user plane uplink with the own second base station apparatus. The measurement report unit performs measurement of the second reception strength of the uplink radio signal in the own second base station apparatus, and the measurement report unit determines that the measurement result of the second reception strength is greater than the first threshold from the first threshold The second measurement report on the terminal apparatus changed to less than one threshold is transmitted to the first base station apparatus, and the base station control unit of the second base station apparatus transmits the second measurement report to the first base station apparatus. An uplink handover request of a user plane of the terminal apparatus targeted for the second measurement report is transmitted to the first base station apparatus, and an uplink handover response to the uplink handover request is transmitted to the first base station apparatus. When it receives from the station apparatus, it transmits an uplink handover instruction of the user plane to the terminal apparatus, and the base station control unit of the first base station apparatus receives the above-mentioned terminal apparatus from the second base station apparatus. An uplink handover response of the user plane of the terminal device is transmitted to the second base station device in response to a second measurement report and an uplink handover request of the user plane of the terminal device received from the second base station device. The terminal control unit of the terminal device that performs uplink radio communication of a user plane with the second base station device is responsive to an uplink handover instruction of the user plane received from the second base station device. A second base station apparatus from the second base station apparatus, a base station apparatus of the other side which performs uplink radio communication in the user plane; Performs handover to switch the base station apparatus transmits the uplink handover complete user plane to the first base station apparatus, a wireless communication system.

(3) One aspect of the present invention includes a first base station apparatus, a second base station apparatus, and a terminal apparatus, and the cell of the first base station apparatus is all of the cells of the second base station apparatus. Or the terminal device which performs radio communication on the downlink of the user plane with the first base station device, including a part thereof, of the radio signal on the downlink of the user plane received from the second base station device A measurement unit that measures the third reception intensity in the own terminal device, and a third measurement that the measurement result of the third reception intensity changes from less than the second threshold to exceed the second threshold with respect to the predetermined second threshold. A measurement report unit that transmits a report to the first base station apparatus, and a base station that performs downlink radio communication on the user plane according to a downlink handover instruction of the user plane received from the first base station apparatus The device is said first A terminal control unit that performs handover to switch from a base station apparatus to the second base station apparatus and transmits a downlink handover completion of a user plane to the second base station apparatus, the first base station apparatus comprising A downlink handover request of the user plane of the terminal device is transmitted to the second base station device in response to the third measurement report received from the terminal device, and a downlink handover response to the downlink handover request is transmitted to the second base station. A base station control unit that transmits a downlink handover instruction of a user plane to the terminal device when received from the station device, and the second base station device receives the user plane of the terminal device received from the first base station device Down the user plane of the corresponding terminal according to the downlink handover request of It comprises a base station controller for transmitting a link handover response to the first base station apparatus, a wireless communication system.
(4) In one aspect of the present invention, in the wireless communication system according to (3), the measurement unit of the terminal device that performs downlink radio communication of a user plane with the second base station device The fourth reception strength of the downlink radio signal of the user plane received from the second base station apparatus is measured in the own terminal apparatus, and the measurement report unit of the terminal apparatus measures the fourth reception strength as the measurement result of the fourth reception strength. A fourth measurement report of change from exceeding the second threshold to less than the second threshold with respect to the second threshold is transmitted to the second base station apparatus, and the terminal control unit of the terminal apparatus is configured to transmit the second base station In accordance with the downlink handover instruction of the user plane received from the apparatus, the base station apparatus of the other party performing the downlink radio communication of the user plane is switched from the second base station apparatus to the first base station apparatus Handover is performed, and downlink handover completion of the user plane is transmitted to the first base station apparatus, and the base station control unit of the second base station apparatus responds to the fourth measurement report received from the terminal apparatus. When a downlink handover request of the user plane of the terminal apparatus is transmitted to the first base station apparatus and a downlink handover response to the downlink handover request is received from the first base station apparatus, the user plane to the terminal apparatus And the base station control unit of the first base station apparatus, in response to the user terminal downlink handover request of the terminal apparatus received from the second base station apparatus, the terminal apparatus User terminal downlink handover response to the second base station To a wireless communication system.

(5) One aspect of the present invention includes a first base station apparatus, a second base station apparatus, and a terminal apparatus, and the cell of the first base station apparatus is all of the cells of the second base station apparatus. Or a handover method of a wireless communication system including a part of the above, wherein the second base station apparatus performs uplink radio communication of a user plane with the first base station apparatus. Measuring the first reception strength of the radio signal in the second base station apparatus, and the second base station apparatus determines that the measurement result of the first reception strength is a first threshold with respect to a predetermined first threshold. Transmitting to the first base station apparatus a first measurement report for the terminal apparatus that has changed from less than the first threshold value to exceeding the first threshold value; and the terminal that the first base station apparatus receives from the second base station apparatus Said first measurement report on the device Transmitting in response to the second base station apparatus an uplink handover request of the user plane of the terminal apparatus in response, and the user plane of the terminal apparatus received by the second base station apparatus from the first base station apparatus Transmitting an uplink handover response of a user plane of the terminal apparatus to the first base station apparatus in response to an uplink handover request; and a terminal transmitted by the first base station apparatus to the second base station apparatus When an uplink handover response to an uplink handover request of a device is received from the second base station device, the step of transmitting an uplink handover instruction of a user plane to the terminal device, and a user with the first base station device The terminal device that performs uplink wireless communication on a plane is the first base According to the uplink plane handover instruction of the user plane received from the apparatus, handover is performed to switch the base station apparatus with which the user plane uplink radio communication is performed from the first base station apparatus to the second base station apparatus, Transmitting the user plane uplink handover completion to the second base station apparatus.
(6) One aspect of the present invention is the terminal method according to the above (5), wherein the second base station apparatus performs uplink radio communication of the user plane with the own second base station apparatus. Measuring the second reception strength of the uplink radio signal in the own second base station apparatus, the second base station apparatus measuring the second reception strength with respect to the first threshold Transmitting, to the first base station apparatus, a second measurement report on the terminal apparatus which has changed from exceeding the first threshold value to less than the first threshold value; and the second base station apparatus transmits the first base station apparatus Transmitting, to the first base station apparatus, an uplink handover request of a user plane of the terminal apparatus targeted for the second measurement report, the first base station apparatus receiving from the second base station apparatus Do An uplink handover response of the user plane of the terminal device according to the second measurement report for the terminal device and an uplink handover request of the user plane of the terminal device received from the second base station device; Transmitting to the base station apparatus, and the second base station apparatus receives, from the first base station apparatus, an uplink handover response to the uplink handover request of the terminal apparatus transmitted to the first base station apparatus; Transmitting an uplink handover instruction of a user plane to a terminal apparatus, and the terminal apparatus performing wireless communication of an uplink of the user plane with the second base station apparatus, receiving from the second base station apparatus In response to the user plane uplink handover instruction, Performing handover to switch a base station apparatus of the other party performing uplink wireless communication from the second base station apparatus to the first base station apparatus, and transmitting an uplink handover completion of a user plane to the first base station apparatus; And a handover method further including.

(7) One aspect of the present invention includes a first base station apparatus, a second base station apparatus, and a terminal apparatus, and the cell of the first base station apparatus is all of the cells of the second base station apparatus. Or a handover method of a wireless communication system including a part, wherein the terminal device performs downlink radio communication of a user plane with the first base station device; and the terminal device A step of performing measurement of a third reception strength in the own terminal of a user plane downlink radio signal received from a second base station apparatus, the terminal may measure the third reception strength as a predetermined second threshold And transmitting to the first base station apparatus a third measurement report that the second base station apparatus has changed from less than the second threshold value to exceeding the second threshold value, and the first base station apparatus receives the third measurement report from the terminal apparatus 3 According to the measurement report Transmitting a downlink handover request of a user plane of the terminal apparatus to the second base station apparatus; and a downlink of the user plane of the terminal apparatus received by the second base station apparatus from the first base station apparatus Transmitting the downlink handover response of the user plane of the terminal apparatus to the first base station apparatus in response to the handover request; and the terminal apparatus transmitting the second base station apparatus to the first base station apparatus When a downlink handover response to a downlink handover request is received from the second base station apparatus, transmitting a downlink handover instruction of a user plane to the terminal apparatus; and the terminal apparatus receives from the first base station apparatus User according to the downlink handover instruction of the user plane A handover is performed to switch the base station device with which the downlink radio communication of the plane is to be performed from the first base station device to the second base station device, and transmit the downlink handover completion of the user plane to the second base station device A handover method including the following steps:
(8) One aspect of the present invention is the handover method according to (7), wherein the terminal device performs downlink radio communication of a user plane with the second base station device, and the terminal device A fourth step of performing measurement of a fourth reception strength of a downlink radio signal of a user plane received from the second base station apparatus in the own terminal apparatus; and the terminal apparatus measures the fourth reception strength as the measurement result Transmitting, to the second base station apparatus, a fourth measurement report indicating that the second threshold value exceeds the second threshold value to less than the second threshold value, and the second base station apparatus receives from the terminal apparatus Transmitting, to the first base station apparatus, a downlink handover request of a user plane of the terminal apparatus according to the fourth measurement report, the first base station apparatus transmitting the second base station apparatus Transmitting, to the second base station apparatus, a downlink handover response of the user plane of the terminal apparatus in response to the downlink handover request of the user plane of the terminal apparatus received from the apparatus; and the second base station apparatus Receiving a downlink handover response to the first base station apparatus from the first base station apparatus in response to a downlink handover request for the terminal apparatus transmitted to the first base station apparatus, transmitting a downlink handover instruction of a user plane to the terminal apparatus; According to the user terminal downlink handover instruction received by the terminal device from the second base station device, the other base station device that performs downlink radio communication in the user plane is transmitted from the second base station device to the second base station device Perform handover to switch to one base station device, Transmitting a downlink handover completion of lane to the first base station apparatus that further include a handover method.

  According to the present invention, it is possible to achieve handover separately in the uplink and the downlink of the user plane.

It is a figure which shows the structural example of the radio | wireless communications system which concerns on one Embodiment. It is a block diagram showing an example of composition of terminal unit 1 concerning one embodiment. It is a block diagram which shows the structural example of the macro base station apparatus 3 which concerns on one Embodiment. FIG. 5 is a block diagram showing an example of configuration of a small base station apparatus 5 according to an embodiment. It is explanatory drawing of the handover method which concerns on one Embodiment. It is a sequence chart which shows Example 1 of the handover method of the uplink which concerns on one Embodiment. It is a sequence chart which shows Example 2 of the handover method of the uplink which concerns on one Embodiment. It is a sequence chart which shows Example 1 of the handover method of the downlink which concerns on one Embodiment. It is a sequence chart which shows Example 2 of the handover method of the downlink which concerns on one Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating an exemplary configuration of a wireless communication system according to an embodiment. In FIG. 1, the wireless communication system includes a terminal device 1 and a plurality of base station devices 3 and 5. The base station apparatus (macro base station apparatus) 3 has a relatively large cell (macro cell) CELM. The base station apparatus (small base station apparatus) 5 has a relatively small cell (small cell) CELS. As an example of the present embodiment, the macro cell CELM illustrated in FIG. 1 includes all of the small cells CELS. The macro cell CELM may include part of the small cell CELS. In the present embodiment, the macro base station apparatus 3 corresponds to the first base station apparatus, and the small base station apparatus 5 corresponds to the second base station apparatus.

  The terminal device 1 can perform wireless communication with the macro base station device 3 when located in the macro cell CELM. When the terminal device 1 is in the small cell CELS, the terminal device 1 can perform wireless communication with the small base station device 5. Hereinafter, when the macro base station apparatus 3 and the small base station apparatus 5 are not particularly distinguished from one another, they are referred to as a base station apparatus BS. The terminal device 1 can communicate with another communication device of the wireless communication network or access to another communication network such as the Internet through the base station device BS to which the terminal device 1 is connected.

  FIG. 2 is a block diagram showing a configuration example of the terminal device 1 according to the present embodiment. In FIG. 2, the terminal device 1 includes a wireless communication unit 11, a terminal control unit 12, a terminal storage unit 13, a measurement unit 21, and a measurement report unit 22. The wireless communication unit 11 performs wireless communication with the base station apparatus BS. The terminal control unit 12 controls the terminal device 1. The terminal storage unit 13 stores data such as the terminal information 14 and the like. The terminal information 14 is information of the terminal device 1 including information of a wireless communication method supported by the own terminal device 1 and wireless communication resources such as a radio frequency band. The measurement unit 21 measures the reception intensity of the downlink radio signal of the user plane received from the base station device BS in the own terminal device 1. The measurement report unit 22 transmits a measurement report (Measurement Report) on the measurement result of the reception intensity by the measurement unit 21 to the base station apparatus BS.

  The functions of the terminal control unit 12, the measurement unit 21, and the measurement report unit 22 are realized by execution of a computer program by a CPU (Central Processing Unit) included in the terminal device 1. The terminal device 1 may be, for example, a mobile communication terminal device such as a smartphone or a tablet computer (tablet PC).

  FIG. 3 is a block diagram showing a configuration example of the macro base station device 3 according to the present embodiment. In FIG. 3, the macro base station apparatus 3 includes a wireless communication unit 31, a communication unit 32, a base station control unit 33, and a base station storage unit 34. The wireless communication unit 31 performs wireless communication with the terminal device 1. The communication unit 32 communicates with another base station apparatus 3 or another apparatus (not shown) of the wireless communication system. The base station control unit 33 controls the macro base station device 3. The base station storage unit 34 stores data such as the terminal information 35 and the base station information 36. The terminal information 35 is information of the terminal device 1 including information of a wireless communication method supported by the terminal device 1 under the control of the macro base station device 3 and wireless communication resources such as a radio frequency band. The base station information 36 is information of the macro base station apparatus 3 including information of a radio communication system supported by the macro base station apparatus 3 of its own and radio communication resources such as a radio frequency band. The function of the base station control unit 33 is realized by the CPU of the macro base station apparatus 3 executing a computer program.

  FIG. 4 is a block diagram showing a configuration example of the small base station apparatus 5 according to the present embodiment. In FIG. 4, the small base station apparatus 5 includes a wireless communication unit 51, a communication unit 52, a base station control unit 53, a base station storage unit 54, a measurement unit 61, and a measurement report unit 62. The wireless communication unit 51 performs wireless communication with the terminal device 1. The communication unit 52 communicates with another base station apparatus 3 or another apparatus (not shown) of the wireless communication system. The base station control unit 53 controls the small base station apparatus 5. The base station storage unit 54 stores data such as the terminal information 55 and the base station information 56. The terminal information 55 is information of the terminal 1 including the wireless communication method supported by the macro base station 3 and the terminal 1 under the control of the own small base station 5 and information of a wireless communication resource such as a radio frequency band. . The base station information 56 is information of the base station apparatus 3 including information of a radio communication system supported by the macro base station apparatus 3 and its own small base station apparatus 5 and a radio communication resource such as a radio frequency band.

  The measurement unit 61 measures the reception strength of the wireless signal of the uplink of the user plane received from the terminal device 1 in the own small base station device 5. The measurement report unit 62 transmits a measurement report on the measurement result of the reception intensity by the measurement unit 61 to the macro base station apparatus 3. The functions of the base station control unit 53, the measurement unit 61, and the measurement report unit 62 are realized by the CPU of the small base station apparatus 5 executing a computer program.

  Next, the handover method according to the present embodiment will be described with reference to FIGS. 5 and 6 to 9. FIG. 5 is an explanatory diagram of a handover method according to the present embodiment. 6 to 9 are sequence charts showing an example of the handover method according to the present embodiment.

[Example 1 of uplink handover method]
An example 1 of the uplink handover method according to the present embodiment will be described with reference to FIGS. 5 and 6. FIG. 6 is a sequence chart showing an example 1 of the uplink handover method according to the present embodiment. The example 1 of the uplink handover method is an example of a method in which the terminal device 1 hands over a cell in which uplink radio communication in the user plane is performed from the macro cell CELM to the small cell CELS.

  In FIG. 5, first, the terminal device 1 exists at a position P1 in the macro cell CELM. The position P1 is a position within the range of the macro cell CELM and outside the range of the small cell CELS. The terminal device 1 performs uplink radio communication of the user plane with the macro base station device 3 by the macro cell CELM at the position P1. In addition, the terminal device 1 performs wireless communication of a control plane (C-plane) with the macro base station device 3 by the macro cell CELM at the position P1. Next, the terminal device 1 moves to the position P2 while continuing uplink radio communication of the user plane with the macro base station device 3 by the macro cell CELM. The position P2 is near the boundary of the small cell CELS. The terminal device 1 performs wireless communication of the control plane with the macro base station device 3 by the macro cell CELM at the position P2, and wireless communication of the control plane with the small base station device 5 by the small cell CELS. Do. The boundary of the small cell CELS corresponds to the boundary (UL boundary) for switching the cell performing uplink radio communication in the user plane. The terminal device 1 moved from the position P1 to the position P2 becomes a candidate terminal device 1 for performing handover of a cell performing uplink radio communication in the user plane from the macro cell CELM to the small cell CELS.

  Hereinafter, with reference to FIG. 6, an example 1 of an uplink handover method will be described. In FIG. 6, the macro base station apparatus 3 is a base station apparatus of a serving cell (a base station apparatus of a handover source). The small base station apparatus 5 is a base station apparatus of a target cell (a base station apparatus at a handover destination). Communication between the macro base station device 3 and the small base station device 5 is performed by the communication units 32 and 52. The macro base station device 3 and the small base station device 5 perform wireless communication with the wireless communication unit 11 of the terminal device 1 by the wireless communication units 31 and 51.

(Step S11) The measuring unit 61 of the small base station apparatus 5 receives the reception strength of the radio signal of the uplink of the user plane in the own small base station apparatus 5 (hereinafter referred to as “the terminal apparatus 1 under the macro base station apparatus 3”). 1) Measure the received signal strength). Information on the terminal device 1 subordinate to the macro base station device 3 is included in the terminal information 55. The measurement report unit 62 associates the measurement result UL_RX1 of the first reception intensity measured by the measurement unit 61 with the measurement time and holds it. The measurement report unit 62 determines whether or not the measurement result UL_RX1 of the first reception intensity changes from less than the first threshold to exceed the first threshold with respect to the predetermined first threshold TH1 for one terminal device 1. Measurement report unit 62 reports on measurement of terminal apparatus 1 in which measurement result UL_RX1 of the first reception intensity changes from less than the first threshold to exceed the first threshold with respect to first threshold TH1 (hereinafter referred to as first measurement report) ) To the macro base station apparatus 3. The first measurement report is information including terminal identification information that identifies the terminal device 1 in which the measurement result UL_RX1 of the first reception intensity changes from less than the first threshold to exceed the first threshold with respect to the first threshold TH1. The macro base station device 3 receives the first measurement report on the terminal device 1 from the small base station device 5.

(Step S12) The base station control unit 33 of the macro base station device 3 requests uplink handover of the user plane of the terminal device 1 according to the first measurement report on the terminal device 1 received from the small base station device 5. Send (UL-HO request) to the small base station apparatus 5. The small base station apparatus 5 receives the uplink handover request of the user plane of the terminal apparatus 1 from the macro base station apparatus 3.

(Step S13) In response to the uplink handover request of the user plane of the terminal device 1 received from the macro base station device 3, the base station control unit 53 of the small base station device 5 performs uplink of the user plane of the terminal device 1 A handover response (UL-HO Response) is returned to the macro base station device 3. The macro base station apparatus 3 receives the uplink handover response of the user plane of the terminal apparatus 1 from the small base station apparatus 5.

(Step S14) The base station control unit 33 of the macro base station device 3 receives the uplink handover response to the uplink handover request of the terminal device 1 transmitted to the small base station device 5 from the small base station device 5, The user terminal transmits an uplink handover instruction (UL-HO Command) of the user plane to the terminal device 1. The terminal device 1 receives an uplink handover instruction of the user plane from the macro base station device 3.

(Step S15) The terminal device 1 performs uplink radio communication of the user plane with the macro base station device 3 at the position P2. Next, when the terminal control unit 12 of the terminal device 1 receives an uplink handover instruction of the user plane from the macro base station apparatus 3, the terminal control unit 12 of the user plane performs uplink wireless communication in accordance with the uplink handover instruction of the user plane. A handover is performed to switch the base station apparatus of the other party to be performed from the macro base station apparatus 3 to the small base station apparatus 5. Next, the terminal control unit 12 transmits, to the small base station apparatus 5, uplink handover completion (UL-HO Confirm) of the user plane. The small base station apparatus 5 receives the uplink handover completion of the user plane from the terminal apparatus 1. The base station control unit 53 of the small base station apparatus 5 performs radio communication of uplink of the user plane with the terminal device 1 in response to completion of uplink handover of the user plane received from the terminal device 1. Take control.

  According to the above example 1 of the uplink handover method, for the terminal device 1 moved from the position P1 to the position P2, the cell performing the uplink radio communication in the user plane can be handed over from the macro cell CELM to the small cell CELS To be realized.

[Example 2 of uplink handover method]
Example 2 of the uplink handover method according to the present embodiment will be described with reference to FIGS. 5 and 7. FIG. 7 is a sequence chart showing an example 2 of the uplink handover method according to the present embodiment. Example 2 of the uplink handover method is an example of a method in which the terminal device 1 hands over a cell in which uplink radio communication in the user plane is performed from the small cell CELS to the macro cell CELM.

  In FIG. 5, first, the terminal device 1 exists at a position P5 in the small cell CELS. The position P5 is a position within the range of the macro cell CELM and within the range of the small cell CELS. The terminal device 1 performs uplink radio communication of the user plane with the small base station device 5 by the small cell CELS at the position P5. The terminal device 1 performs wireless communication of the control plane with the macro base station device 3 by the macro cell CELM at the position P5, and wirelessly of the control plane with the small base station device 5 by the small cell CELS. I am communicating. Next, the terminal device 1 moves to the position P7 while continuing uplink radio communication of the user plane with the small base station device 5 by the small cell CELS. The position P7 is near the boundary of the small cell CELS. The terminal device 1 performs wireless communication of the control plane with the macro base station device 3 by the macro cell CELM at the position P7, and wireless communication of the control plane with the small base station device 5 by the small cell CELS. Do. The boundary of the small cell CELS corresponds to the boundary (UL boundary) for switching the cell performing uplink radio communication in the user plane. The terminal device 1 that has moved from the position P5 to the position P7 becomes a candidate terminal device 1 that hands over a cell performing uplink wireless communication in the user plane from the small cell CELS to the macro cell CELM.

  Hereinafter, with reference to FIG. 7, an uplink handover method 2 will be described. In FIG. 7, the small base station apparatus 5 is a base station apparatus (serving as a handover source base station apparatus) of a serving cell. The macro base station apparatus 3 is a base station apparatus of a target cell (a base station apparatus at a handover destination). Communication between the macro base station device 3 and the small base station device 5 is performed by the communication units 32 and 52. The macro base station device 3 and the small base station device 5 perform wireless communication with the wireless communication unit 11 of the terminal device 1 by the wireless communication units 31 and 51.

(Step S21) The measurement unit 61 of the small base station apparatus 5 receives the reception strength of the radio signal of the uplink of the user plane in the own small base station apparatus 5 (hereinafter, the terminal apparatus 1 under the control of the own small base station apparatus 5). Measure the second reception strength). Information on the terminal device 1 subordinate to the small base station device 5 is included in the terminal information 55. The measurement report unit 62 associates the measurement result UL_RX2 of the second reception intensity by the measurement unit 61 with the measurement time and holds the result. The measurement report unit 62 determines, for one terminal device 1, whether or not the measurement result UL_RX2 of the second reception intensity changes from exceeding the first threshold to less than the first threshold with respect to the predetermined first threshold TH1. Measurement report unit 62 reports on measurement of terminal apparatus 1 in which measurement result UL_RX2 of the second reception intensity has changed from exceeding the first threshold to less than the first threshold with respect to first threshold TH1 (hereinafter referred to as second measurement report) ) To the macro base station apparatus 3. The second measurement report is information including terminal identification information for identifying the terminal device 1 in which the measurement result UL_RX2 of the second reception strength has changed from exceeding the first threshold to less than the first threshold with respect to the first threshold TH1. The macro base station device 3 receives the second measurement report on the terminal device 1 from the small base station device 5.

(Step S22) The base station control unit 53 of the small base station device 5 transmits the uplink handover request (UL-HO request) of the user plane of the terminal device 1 of the target of the second measurement report transmitted to the macro base station device 3. , And transmits to the macro base station apparatus 3. The macro base station device 3 receives, from the small base station device 5, an uplink handover request for the user plane of the terminal device 1.

(Step S23) The base station control unit 33 of the macro base station device 3 receives the second measurement report for the terminal device 1 received from the small base station device 5 and the user plane of the terminal device 1 received from the small base station device 5. In response to the uplink handover request, the uplink handover response (UL-HO Response) of the user plane of the terminal device 1 is returned to the small base station device 5. The small base station apparatus 5 receives, from the macro base station apparatus 3, an uplink handover response of the user plane of the terminal device 1.

(Step S24) The base station control unit 53 of the small base station device 5 receives the uplink handover response to the uplink handover request of the terminal device 1 transmitted to the macro base station device 3 from the macro base station device 3, The user terminal transmits an uplink handover instruction (UL-HO Command) of the user plane to the terminal device 1. The terminal device 1 receives an uplink handover instruction of the user plane from the small base station device 5.

(Step S25) At position P7, the terminal device 1 performs uplink radio communication of the user plane with the small base station device 5 by the small cell CELS. Next, when the terminal control unit 12 of the terminal device 1 receives the uplink handover instruction of the user plane from the small base station apparatus 5, the terminal control unit 12 of the user plane performs uplink wireless communication in accordance with the uplink handover instruction of the user plane. A handover is performed to switch the base station apparatus of the other party to be performed from the small base station apparatus 5 to the macro base station apparatus 3. Then, the terminal control unit 12 transmits, to the macro base station apparatus 3, uplink handover completion (UL-HO Confirm) of the user plane. The macro base station device 3 receives, from the terminal device 1, the uplink handover completion of the user plane. The base station control unit 33 of the macro base station device 3 performs radio communication of uplink of the user plane with the terminal device 1 in response to completion of uplink handover of the user plane received from the terminal device 1. Take control.

  According to the above example 2 of the uplink handover method, for the terminal device 1 moved from the position P5 to the position P7, the cell performing the uplink radio communication of the user plane can be handed over from the small cell CELS to the macro cell CELM To be realized.

[Example 1 of downlink handover method]
An example 1 of the downlink handover method according to the present embodiment will be described with reference to FIGS. 5 and 8. FIG. 8 is a sequence chart showing an example 1 of the downlink handover method according to the present embodiment. The example 1 of the downlink handover method is an example of a method in which the terminal device 1 hands over a cell in which user terminal downlink radio communication is performed from the macro cell CELM to the small cell CELS.

  In FIG. 5, first, the terminal device 1 exists at a position P1 in the macro cell CELM. The position P1 is a position within the range of the macro cell CELM and outside the range of the small cell CELS. The terminal device 1 performs downlink radio communication of the user plane with the macro base station device 3 by the macro cell CELM at the position P1. In addition, the terminal device 1 performs control plane radio communication with the macro base station device 3 by the macro cell CELM at the position P1. Next, the terminal device 1 moves to the position P3 while continuing downlink radio communication with the macro base station device 3 with the macro base station device 3 by means of the macro cell CELM. The position P3 is within the range of the small cell CELS, and is a position on the center side of the small cell CELS to some extent from the boundary of the small cell CELS. The terminal device 1 performs wireless communication of the control plane with the macro base station device 3 by the macro cell CELM at the position P3, and wireless communication of the control plane with the small base station device 5 by the small cell CELS. Do. The boundary corresponding to the position P3 corresponds to the boundary (DL boundary) for switching the cell performing downlink radio communication in the user plane. The terminal device 1 that has moved from the position P1 to the position P3 becomes a candidate terminal device 1 for performing handover of a cell that performs downlink radio communication in the user plane from the macro cell CELM to the small cell CELS.

  Hereinafter, with reference to FIG. 8, an example 1 of the handover method for the downlink will be described. In FIG. 8, the macro base station apparatus 3 is a base station apparatus (serving as a handover source base station apparatus) of a serving cell. The small base station apparatus 5 is a base station apparatus of a target cell (a base station apparatus at a handover destination). Communication between the macro base station device 3 and the small base station device 5 is performed by the communication units 32 and 52. The macro base station device 3 and the small base station device 5 perform wireless communication with the wireless communication unit 11 of the terminal device 1 by the wireless communication units 31 and 51.

(Step S31) At the position P3, the terminal device 1 performs downlink radio communication of the user plane with the macro base station device 3 by the macro cell CELM. The measurement unit 21 of the terminal device 1 measures the reception intensity (hereinafter, referred to as a third reception intensity) in the own terminal device 1 of the downlink radio signal of the user plane received from the small base station device 5. The measurement report unit 22 associates the measurement result DL_RX3 of the third reception intensity by the measurement unit 21 with the measurement time and holds the result. The measurement report unit 22 determines whether the measurement result DL_RX3 of the third reception intensity changes from less than the second threshold to exceeding the second threshold with respect to a predetermined second threshold TH2. The measurement report unit 22 macro-measures a measurement report (hereinafter referred to as a third measurement report) that the measurement result DL_RX3 of the third reception intensity changes from less than the second threshold to exceeding the second threshold with respect to the second threshold TH2 (hereinafter referred to as the third measurement report). Transmit to base station apparatus 3. The third measurement report is information including terminal identification information that identifies the terminal device 1 in which the measurement result DL_RX3 of the third reception strength changes from less than the second threshold to more than the second threshold with respect to the second threshold TH2. The macro base station device 3 receives the third measurement report from the terminal device 1.

(Step S32) In response to the third measurement report received from the terminal device 1, the base station control unit 33 of the macro base station device 3 receives a downlink handover request (DL-HO request) of the user plane of the terminal device 1. Transmit to the small base station device 5. The small base station apparatus 5 receives the downlink handover request of the user plane of the terminal apparatus 1 from the macro base station apparatus 3.

(Step S33) The base station control unit 53 of the small base station device 5 responds to the downlink handover request of the user plane of the terminal device 1 received from the macro base station device 3, the downlink of the user plane of the terminal device 1 A handover response (DL-HO Response) is returned to the macro base station apparatus 3. The macro base station device 3 receives the downlink handover response of the user plane of the terminal device 1 from the small base station device 5.

(Step S34) The base station control unit 33 of the macro base station device 3 receives the downlink handover response to the downlink handover request of the terminal device 1 transmitted to the small base station device 5 from the small base station device 5, Send a user plane downlink handover instruction (DL-HO Command) to the terminal device 1. The terminal device 1 receives the downlink handover instruction of the user plane from the macro base station device 3.

(Step S35) The terminal device 1 performs radio communication on the downlink of the user plane with the macro base station device 3 at the position P3. Next, when the terminal control unit 12 of the terminal device 1 receives the downlink handover instruction of the user plane from the macro base station device 3, the terminal control unit 12 of the user plane performs downlink wireless communication in accordance with the downlink handover instruction of the user plane. A handover is performed to switch the base station apparatus of the other party to be performed from the macro base station apparatus 3 to the small base station apparatus 5. Then, the terminal control unit 12 transmits the downlink handover completion (DL-HO Confirm) of the user plane to the small base station apparatus 5. The small base station apparatus 5 receives the downlink handover completion of the user plane from the terminal apparatus 1. The base station control unit 53 of the small base station apparatus 5 performs radio communication on the downlink of the user plane with the terminal device 1 in response to the completion of the downlink handover on the user plane received from the terminal device 1. Take control.

  According to the example 1 of the downlink handover method described above, for the terminal device 1 moved from the position P1 to the position P3, the cell performing the downlink radio communication of the user plane can be handed over from the macro cell CELM to the small cell CELS To be realized.

[Example 2 of downlink handover method]
An example 2 of the downlink handover method according to the present embodiment will be described with reference to FIGS. 5 and 9. FIG. 9 is a sequence chart showing an example 2 of the downlink handover method according to the present embodiment. The example 2 of the downlink handover method is an example of a method in which the terminal device 1 hands over a cell in which user terminal downlink radio communication is performed from the small cell CELS to the macro cell CELM.

  In FIG. 5, first, the terminal device 1 exists at a position P4 in the small cell CELS. The position P4 is a position within the range of the macro cell CELM and within the range of the small cell CELS. The terminal device 1 performs radio communication on the downlink of the user plane with the small base station device 5 by the small cell CELS at the position P4. Also, at position P4, the terminal device 1 performs radio communication of the control plane with the macro base station device 3 by the macro cell CELM, and radio of the control plane with the small base station device 5 by the small cell CELS. I am communicating. Next, the terminal device 1 moves to the position P6 while continuing the downlink radio communication of the user plane with the small base station device 5 by the small cell CELS. The position P6 is within the range of the small cell CELS, and is a position on the center side of the small cell CELS to some extent from the boundary of the small cell CELS. The terminal device 1 performs wireless communication of the control plane with the macro base station device 3 by the macro cell CELM at the position P6, and wireless communication of the control plane with the small base station device 5 by the small cell CELS. Do. The boundary corresponding to the position P6 corresponds to the boundary (DL boundary) for switching the cell performing downlink radio communication in the user plane. The terminal device 1 that has moved from the position P4 to the position P6 becomes a candidate terminal device 1 for handing over a cell that performs downlink radio communication in the user plane from the small cell CELS to the macro cell CELM.

  An example 2 of the downlink handover method will be described below with reference to FIG. In FIG. 9, the small base station apparatus 5 is a base station apparatus of a serving cell (a base station apparatus of a handover source). The macro base station apparatus 3 is a base station apparatus of a target cell (a base station apparatus at a handover destination). Communication between the macro base station device 3 and the small base station device 5 is performed by the communication units 32 and 52. The macro base station device 3 and the small base station device 5 perform wireless communication with the wireless communication unit 11 of the terminal device 1 by the wireless communication units 31 and 51.

(Step S41) At position P6, the terminal device 1 is performing downlink radio communication of the user plane with the small base station device 5 by the small cell CELS. The measurement unit 21 of the terminal device 1 measures the reception intensity (hereinafter, referred to as fourth reception intensity) in the own terminal device 1 of the downlink radio signal of the user plane received from the small base station device 5. The measurement report unit 22 associates the measurement result DL_RX4 of the fourth reception intensity by the measurement unit 21 with the measurement time and holds the result. The measurement report unit 22 determines whether or not the measurement result DL_RX4 of the fourth reception intensity changes from exceeding the second threshold to less than the second threshold with respect to the predetermined second threshold TH2. The measurement report unit 22 has a small measurement report (hereinafter, referred to as a fourth measurement report) that the measurement result DL_RX4 of the fourth reception intensity has changed from exceeding the second threshold to less than the second threshold with respect to the second threshold TH2. Transmit to base station apparatus 5. The fourth measurement report is information including terminal identification information that identifies the terminal device 1 in which the measurement result DL_RX4 of the fourth reception strength has changed from exceeding the second threshold to less than the second threshold with respect to the second threshold TH2. The small base station device 5 receives the fourth measurement report from the terminal device 1.

(Step S42) In response to the fourth measurement report received from the terminal device 1, the base station control unit 53 of the small base station device 5 transmits a downlink handover request (DL-HO request) of the user plane of the terminal device 1 concerned. Transmit to macro base station device 3. The macro base station apparatus 3 receives, from the small base station apparatus 5, a downlink handover request for the user plane of the terminal device 1.

(Step S43) The base station control unit 33 of the macro base station device 3 responds to the downlink handover request of the user plane of the terminal device 1 received from the small base station device 5, the downlink of the user plane of the terminal device 1 A handover response (DL-HO Response) is returned to the small base station apparatus 5. The small base station apparatus 5 receives the downlink handover response of the user plane of the terminal apparatus 1 from the macro base station apparatus 3.

(Step S44) The base station control unit 53 of the small base station device 5 receives the downlink handover response to the downlink handover request of the terminal device 1 transmitted to the macro base station device 3 from the macro base station device 3, Send a user plane downlink handover instruction (DL-HO Command) to the terminal device 1. The terminal device 1 receives the downlink handover instruction of the user plane from the small base station device 5.

(Step S45) At the position P6, the terminal device 1 performs downlink radio communication of the user plane with the small base station device 5 by the small cell CELS. Next, when the terminal control unit 12 of the terminal device 1 receives the downlink handover instruction of the user plane from the small base station apparatus 5, the terminal control unit 12 of the user plane performs downlink wireless communication in accordance with the downlink handover instruction of the user plane. A handover is performed to switch the base station apparatus of the other party to be performed from the small base station apparatus 5 to the macro base station apparatus 3. Then, the terminal control unit 12 transmits the downlink handover completion (DL-HO Confirm) of the user plane to the macro base station apparatus 3. The macro base station apparatus 3 receives the downlink handover completion of the user plane from the terminal apparatus 1. The base station control unit 33 of the macro base station device 3 performs radio communication on the downlink of the user plane with the terminal device 1 in response to the completion of the downlink handover on the user plane received from the terminal device 1. Take control.

  According to the example 2 of the downlink handover method described above, for the terminal device 1 moved from the position P4 to the position P6, the cell performing the downlink radio communication in the user plane can be handed over from the small cell CELS to the macro cell CELM To be realized.

As described above, according to this embodiment, handover can be realized separately for the uplink and downlink of the user plane. Thus, for example, uplink radio communication in the user plane can be performed by the small cell CELS, and downlink radio communication in the user plane can be performed by the macro cell CELM. By performing uplink radio communication of the user plane by the small cell CELS and performing downlink radio communication of the user plane by the macro cell CELM, for example, the following effects 1-3 can be obtained.
(Effect 1) The effect of improving the SNR (signal-to-noise ratio) of the uplink and reducing the transmission power of the terminal device 1 can be obtained.
(Effect 2) The effect of improving the radio environment relating to radio interference can be obtained.
(Effect 3) The effect of improving the uplink data rate can be obtained.

  Although the embodiments of the present invention have been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like within the scope of the present invention are also included.

Alternatively, a computer program for realizing the functions of the respective devices described above may be recorded in a computer-readable recording medium, and the computer system may read and execute the program recorded in the recording medium. Note that the “computer system” referred to here may include an OS and hardware such as peripheral devices.
The “computer readable recording medium” is a writable non-volatile memory such as a flexible disk, an optical magnetic disk, a ROM, a flash memory, etc., a portable medium such as a DVD (Digital Versatile Disc), etc. Storage devices such as hard disks.

Furthermore, the “computer-readable recording medium” is a volatile memory (for example, DRAM (Dynamic Memory) inside a computer system that becomes a server or client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line) As Random Access Memory), it is assumed that the program which holds the program for a fixed time is included.
The program may be transmitted from a computer system in which the program is stored in a storage device or the like to another computer system via a transmission medium or by transmission waves in the transmission medium. Here, the “transmission medium” for transmitting the program is a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line.
Further, the program may be for realizing a part of the functions described above. Furthermore, it may be a so-called difference file (difference program) that can realize the above-described functions in combination with a program already recorded in the computer system.

DESCRIPTION OF SYMBOLS 1 ... Terminal device, 3 ... Macro base station apparatus, 5 ... Small base station apparatus, 11, 31, 51 ... Radio | wireless communication part, 12 ... Terminal control part, 13 ... Terminal memory part, 21, 61 ... Measurement part, 22, 62 Measurement report unit 32, 52 Communications unit 33, 53 Base station control unit 34, 54 Base station storage unit

Claims (8)

A first base station apparatus, a second base station apparatus, and a terminal apparatus;
The cell of the first base station device includes all or a part of the cell of the second base station device,
The second base station apparatus
A measurement unit that measures a first reception intensity of the uplink radio signal of the terminal device that performs uplink radio communication of a user plane with the first base station device, in a second base station device;
A measurement report of transmitting to the first base station apparatus a first measurement report on the terminal apparatus whose measurement result of the first reception intensity has changed from less than the first threshold to exceed the first threshold with respect to a predetermined first threshold Department,
A base station control unit for transmitting, to the first base station apparatus, an uplink handover response of the user plane of the terminal apparatus in response to an uplink handover request of the user plane of the terminal apparatus received from the first base station apparatus; , And
The first base station apparatus
In response to the first measurement report on the terminal apparatus received from the second base station apparatus, an uplink handover request of the user plane of the terminal apparatus is transmitted to the second base station apparatus, and the uplink handover request is transmitted. And a base station control unit that transmits an uplink handover instruction of a user plane to the terminal when an uplink handover response is received from the second base station apparatus,
The terminal device which performs uplink radio communication of a user plane with the first base station device,
In accordance with the uplink plane handover instruction of the user plane received from the first base station apparatus, the base station apparatus of the other party performing the uplink radio communication of the user plane from the first base station apparatus to the second base station apparatus The terminal control unit performs handover to be switched, and transmits an uplink handover completion of a user plane to the second base station apparatus.
Wireless communication system. The measurement unit measures the second reception intensity of the uplink radio signal of the terminal device performing radio communication on the uplink of the user plane with the second base station device at the second base station device. Do,
The measurement report unit is configured to transmit a second measurement report of the terminal apparatus for which the measurement result of the second reception intensity has changed from exceeding the first threshold to less than the first threshold with respect to the first threshold as the first base station apparatus Send to
The base station control unit of the second base station apparatus transmits the uplink handover request of the user plane of the terminal apparatus of the target of the second measurement report transmitted to the first base station apparatus to the first base station apparatus When transmitting to the terminal apparatus and receiving an uplink handover response to the uplink handover request from the first base station apparatus, the terminal apparatus transmits an uplink handover instruction of the user plane to the terminal apparatus;
The base station control unit of the first base station apparatus receives the second measurement report for the terminal apparatus received from the second base station apparatus and the user plane of the terminal apparatus received from the second base station apparatus. In response to the uplink handover request, an uplink handover response of the user plane of the terminal apparatus is transmitted to the second base station apparatus,
The terminal control unit of the terminal apparatus that performs uplink radio communication of a user plane with the second base station apparatus is responsive to an uplink handover instruction of the user plane received from the second base station apparatus. A handover is performed to switch the base station apparatus with which the user plane uplink radio communication is to be performed from the second base station apparatus to the first base station apparatus, and the uplink handover completion of the user plane is sent to the first base station apparatus Send,
The wireless communication system according to claim 1. A first base station apparatus, a second base station apparatus, and a terminal apparatus;
The cell of the first base station device includes all or a part of the cell of the second base station device,
The terminal device which performs downlink radio communication of a user plane with the first base station device,
A measurement unit configured to measure a third reception intensity of the downlink radio signal of the user plane received from the second base station apparatus in the own terminal apparatus;
A measurement report unit that transmits, to the first base station apparatus, a third measurement report that the measurement result of the third reception intensity changes from less than the second threshold to exceed the second threshold with respect to a predetermined second threshold;
In response to the user plane downlink handover instruction received from the first base station apparatus, the other base station apparatus performing the downlink radio communication in the user plane from the first base station apparatus to the second base station apparatus A terminal control unit that performs handover to be switched and transmits downlink handover completion of a user plane to the second base station apparatus;
The first base station apparatus
A downlink handover request for the user plane of the terminal device is transmitted to the second base station device in response to the third measurement report received from the terminal device, and a downlink handover response to the downlink handover request is transmitted to the second base station device. And a base station control unit that transmits a downlink handover instruction of a user plane to the terminal device when received from the base station device,
The second base station apparatus
A base station control unit for transmitting a downlink handover response of a user plane of the terminal apparatus to the first base station apparatus in response to a downlink handover request of the user plane of the terminal apparatus received from the first base station apparatus; Prepare,
Wireless communication system. The measurement unit of the terminal device that performs downlink radio communication of a user plane with the second base station device is a terminal device of a radio signal of a downlink of the user plane received from the second base station device. Measure the fourth reception strength at
The measurement report unit of the terminal device is configured to transmit, to the second base station, a fourth measurement report that the measurement result of the fourth reception intensity changes from exceeding the second threshold to less than the second threshold with respect to the second threshold. Send to device,
The terminal control unit of the terminal apparatus, in response to the downlink handover instruction of the user plane received from the second base station apparatus, the base station apparatus of the other party performing the downlink radio communication of the user plane as the second base station Performing handover to switch from the station apparatus to the first base station apparatus, and transmitting a downlink handover completion of a user plane to the first base station apparatus;
The base station control unit of the second base station apparatus transmits a downlink handover request of a user plane of the terminal apparatus to the first base station apparatus according to the fourth measurement report received from the terminal apparatus, When a downlink handover response to the downlink handover request is received from the first base station apparatus, a user plane downlink handover instruction is transmitted to the terminal apparatus,
The base station control unit of the first base station apparatus receives the downlink handover response of the user plane of the terminal apparatus in response to the downlink handover request of the user plane of the terminal apparatus received from the second base station apparatus. Transmit to the second base station apparatus;
The wireless communication system according to claim 3. A first base station apparatus, a second base station apparatus, and a terminal apparatus;
The cell of the first base station apparatus is a handover method of a wireless communication system including all or part of the cell of the second base station apparatus,
First reception strength in the own second base station apparatus of the uplink radio signal of the terminal apparatus in which the second base station apparatus performs radio communication on the uplink of the user plane with the first base station apparatus Step of measuring
The first measurement report for the terminal apparatus in which the second base station apparatus changes the measurement result of the first reception strength from less than the first threshold to exceed the first threshold with respect to a predetermined first threshold is the first measurement report. Transmitting to the base station apparatus;
The first base station apparatus transmits, to the second base station apparatus, an uplink handover request of a user plane of the terminal apparatus according to the first measurement report on the terminal apparatus received from the second base station apparatus. Step to
In response to the uplink handover request of the user plane of the terminal device received from the first base station device, the second base station device transmits the uplink handover response of the user plane of the terminal device to the first base station device Sending to
When the first base station apparatus receives, from the second base station apparatus, an uplink handover response to the uplink handover request of the terminal apparatus transmitted to the second base station apparatus, uplink handover of a user plane to the terminal apparatus Sending instructions;
In response to the uplink handover instruction of the user plane received from the first base station apparatus, the terminal apparatus performing the uplink wireless communication with the first base station apparatus according to the uplink of the user plane Performing handover to switch the other base station apparatus performing the wireless communication from the first base station apparatus to the second base station apparatus, and transmitting an uplink handover completion of a user plane to the second base station apparatus;
Handover method including: Second reception strength at the own second base station apparatus of the uplink radio signal of the terminal apparatus in which the second base station apparatus performs uplink radio communication with the own second base station apparatus in the user plane Step of measuring
The second base station apparatus transmits a second measurement report for the terminal apparatus for which the measurement result of the second reception intensity has changed from exceeding the first threshold to less than the first threshold with respect to the first threshold as the first base Transmitting to the station apparatus;
The second base station apparatus transmitting, to the first base station apparatus, an uplink handover request of a user plane of the terminal apparatus targeted for the second measurement report transmitted to the first base station apparatus;
In response to the second measurement report for the terminal apparatus received from the second base station apparatus and the uplink handover request of the user plane of the terminal apparatus received from the second base station apparatus, the first base station apparatus receiving from the second base station apparatus Transmitting an uplink handover response of a user plane of the terminal apparatus to the second base station apparatus;
When the second base station apparatus receives, from the first base station apparatus, an uplink handover response to the uplink handover request of the terminal apparatus transmitted to the first base station apparatus, uplink handover of the user plane to the terminal apparatus Sending instructions;
In response to the uplink handover instruction of the user plane received from the second base station apparatus, the terminal apparatus performing the uplink wireless communication with the second base station apparatus according to the uplink of the user plane Performing handover to switch the other base station apparatus performing the wireless communication from the second base station apparatus to the first base station apparatus, and transmitting an uplink handover completion of the user plane to the first base station apparatus;
The handover method according to claim 5, further comprising A first base station apparatus, a second base station apparatus, and a terminal apparatus;
The cell of the first base station apparatus is a handover method of a wireless communication system including all or part of the cell of the second base station apparatus,
The terminal apparatus performs downlink radio communication of a user plane with the first base station apparatus;
The terminal device performs measurement of a third reception strength at its own terminal device of a downlink radio signal of a user plane received from the second base station device;
The terminal apparatus transmits, to the first base station apparatus, a third measurement report that the measurement result of the third reception strength changes from less than the second threshold to exceeding the second threshold with respect to a predetermined second threshold. Step and
The first base station apparatus transmitting, to the second base station apparatus, a downlink handover request of a user plane of the terminal apparatus according to the third measurement report received from the terminal apparatus;
The second base station apparatus receives the user terminal downlink user plane downlink handover response in response to the user terminal downlink user interface downlink handover request received from the first base station apparatus. Sending to
When the first base station apparatus receives, from the second base station apparatus, a downlink handover response to a downlink handover request of a terminal apparatus transmitted to the second base station apparatus, downlink handover of a user plane to the terminal apparatus Sending instructions;
The base station apparatus with which the terminal apparatus performs radio communication on the downlink of the user plane in response to the downlink handover instruction of the user plane received from the first base station apparatus from the first base station apparatus Performing handover to switch to a two base station apparatus, and transmitting downlink handover completion of a user plane to the second base station apparatus;
Handover method including: The terminal apparatus performs downlink radio communication of a user plane with the second base station apparatus;
The terminal device performs measurement of a fourth reception strength of the user plane downlink radio signal received from the second base station device in the own terminal device;
The terminal device transmits, to the second base station apparatus, a fourth measurement report that the measurement result of the fourth reception strength has changed from exceeding the second threshold to less than the second threshold with respect to the second threshold; When,
The second base station apparatus transmits, to the first base station apparatus, a downlink handover request of a user plane of the terminal apparatus according to the fourth measurement report received from the terminal apparatus;
In response to the downlink handover request of the user plane of the terminal apparatus received by the first base station apparatus from the second base station apparatus, the downlink handover response of the user plane of the terminal apparatus is the second base station apparatus Sending to
When the second base station apparatus receives, from the first base station apparatus, a downlink handover response to a downlink handover request of a terminal apparatus transmitted to the first base station apparatus, downlink handover of a user plane to the terminal apparatus Sending instructions;
According to the user terminal downlink handover instruction received by the terminal device from the second base station device, the other base station device that performs downlink radio communication in the user plane is transmitted from the second base station device to the second base station device Performing handover to switch to one base station apparatus, and transmitting downlink handover completion of a user plane to the first base station apparatus;
The handover method according to claim 7, further comprising

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