Title of Invention: MOBILE COMMUNICATION METHOD AND RADIO BASE STATION
Abstract: 
Provided is a mobile communication method including a step A of transmitting, by a mobile station UE, “Measurement Report” including measurement results of radio qualities of neighboring cells #2 to #4 in a downlink to a radio base station eNB#1 that manages a cell #1 in which the mobile station UE is in communication, a step B of selecting, by the radio base station eNB#1, the cell #2 from among the neighboring cells #2 to #4 on the basis of the “Measurement Report”, and a step C of transmitting, by the radio base station eNB#1, “DL HI indication” indicating an influence of interference on the mobile station UE in a downlink direction being strong to a radio base station eNB#2 that manages the cell #2. 

Detailed Description: 

TECHNICAL FIELD
The present invention relates to a mobile communication method and a radio base station.
BACKGROUND ART
In an LTE (Long Term Evolution) scheme, in order to reduce inter-cell interference, it is discussed to use “eICIC (Enhanced Inter Cell Interference Coordination)”.
CITATION LIST
Non Patent Literature
[NPL 1] 3GPP contribution R1-105779
[NPL 2] 3GPP TS36.423
[NPL 3] 3GPP TS36.300
[NPL 4] 3GPP TS36.211
SUMMARY OF INVENTION
Technical Problem
Unfortunately, in a conventional LTE scheme, since a timing at which the “eICIC” is started is not defined, there is a problem in that the “eICIC” is not started at an appropriate timing.
Therefore, the present invention has been achieved in view of the above-described problem, and an object of the present invention is to provide a mobile communication method and a radio base station with which it is possible to start “eICIC” at an appropriate timing.
Solution to Problem
A first characteristic of the present invention is summarized in including: a step A of transmitting, by a mobile station, a measurement report including measurement results of radio qualities of neighboring cells in a downlink to a first radio base station that manages a first cell in which the mobile station is in communication; a step B of selecting, by the first radio base station, a second cell from among the neighboring cells on the basis of the measurement report; and a step C of transmitting, by the first radio base station, interference indication information indicating an influence of interference on the mobile station in a downlink direction being strong to a second radio base station that manages the second cell.
A second characteristic of the present invention is summarized as a radio base station that manages a cell in which a mobile station is in communication, including: a measurement report receiving unit that receives a measurement report including measurement results of radio qualities of neighboring cells in a downlink from the mobile station; a selection unit that selects a specific cell from among the neighboring cells on the basis of the measurement report; and an interference indication information transmission unit that transmits interference indication information indicating an influence of interference on the mobile station in a downlink direction being strong to a specific radio base station that manages the specific cell.
Advantageous Effects of Invention
As described above, according to the present invention, it is possible to provide a mobile communication method and a radio base station with which it is possible to start “eICIC” at an appropriate timing.



BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a diagram showing the entire configuration of a mobile communication system according to a first embodiment of the present invention.
FIG. 2 is a functional block diagram of a radio base station according to the first embodiment of the present invention.
FIG. 3 is a diagram illustrating an example of a format of “X2 Load Information” used in the mobile communication system according to the first embodiment of the present invention.
FIG. 4 is a diagram illustrating an example of a format of “eNB Configuration Update” used in the mobile communication system according to the first embodiment of the present invention.
FIG. 5 is a diagram illustrating an example of a format of “Served Cell Information” as an information element included in the “eNB Configuration Update”, etc., used in the mobile communication system according to the first embodiment of the present invention.
FIG. 6 is a diagram illustrating an example of a format of “X2 Setup Request” used in the mobile communication system according to the first embodiment of the present invention.
FIG. 7 is a diagram illustrating an example of a format of “X2 Setup Response” used in the mobile communication system according to the first embodiment of the present invention.
FIG. 8 is a sequence diagram illustrating an operation of the mobile communication system according to the first embodiment of the present invention.



DESCRIPTION OF EMBODIMENTS
Mobile Communication System According to First Embodiment of the Present Invention
A mobile communication system according to a first embodiment of the present invention is described with reference to FIG. 1 through FIG. 8. In the present embodiment, an LTE mobile communication system will be described as an example of the mobile communication system according to the present embodiment. However, the present invention is also applicable to mobile communication systems other than the LTE mobile communication system.
The mobile communication system according to the present embodiment is configured to perform “eICIC” using a “Time domain scheme”.
As illustrated in FIG. 1, the mobile communication system according to the present embodiment includes a radio base station eNB#1 configured to manage a cell #1, a radio base station eNB#2 configured to manage a cell #2, a radio base station eNB#3 configured to manage a cell #3, and a radio base station eNB#4 configured to manage a cell #4.
Here, the cells #1 to #4 may be micro cells, or may be CSG (Closed Subscriber Group) cells. In addition, the CSG cell may be called a Femto cell, a Micro cell, a Pico cell, or the like.
In the mobile communication system according to the present embodiment, a mobile station UE is assumed to be in a connected state in the cell #1, that is, to be in communication in the cell #1.
As illustrated in FIG. 2, the radio base station eNB#1 includes a radio interface 11, a selection unit 12, an X2 interface 13, and a scheduling unit 14.
The radio interface 11 is configured to perform radio communication with the mobile station UE through an RRC (Radio Resource Control) connection.
For example, the radio interface 11 is configured to receive “Measurement Report” including measurement results of radio qualities of neighboring cells #2 to #4 in a downlink from the mobile station UE.
The selection unit 12 is configured to select a specific cell (for example, the cell #2) from among the neighboring cells #2 to #4 on the basis of the “Measurement Report”, that is, on the basis of the measurement results included in the “Measurement Report”.
For example, the selection unit 12 may be configured to select a cell of which the radio quality in the downlink is the worst or a cell of which the radio quality in the downlink is worse than a predetermined radio quality from among the neighboring cells #2 to #4, as the specific cell.
The X2 interface 13 is configured to serve as an interface with the neighboring cells #2 to #4.
Here, the X2 interface 13 is configured to transmit “DL HI (High Interference) Indication” to a specific radio base station eNB (for example, the radio base station eNb#2) that manages the specific cell.
Here, the “DL HI Indication” is information indicating an influence of interference on the mobile station UE in a downlink direction being strong.
For example, the X2 interface 13 may be configured to transmit the “DL HI Indication” by using “X2 Load Information”.
Specifically, as illustrated in FIG. 3, the X2 interface 13 may be configured to transmit “DL HI Indication” within “Cell Information” as an information element within the “X2 Load Information”.
Alternatively, the X2 interface 13 may be configured to transmit the “DL HI Indication” by using “eNB Configuration Update”.
Specifically, as illustrated in FIGS. 4 and 5, the X2 interface 13 may be configured to transmit “DL HI Indication” within “Served Cell Information” as an information element within the “eNB Configuration Update”.
Otherwise, the X2 interface 13 may be configured to transmit the “DL HI Indication” by using “X2 Setup Request”.
Specifically, as illustrated in FIGS. 5 and 6, the X2 interface 13 may be configured to transmit “DL HI Indication” within “Served Cell Information” as an information element within the “X2 Setup Request”.
Alternatively, the X2 interface 13 may be configured to transmit the “DL HI Indication” by using “X2 Setup Response”.
Specifically, as illustrated in FIGS. 5 and 7, the X2 interface 13 may be configured to transmit “DL HI Indication” within “Served Cell Information” as an information element within the “X2 Setup Response”.
The scheduling unit 14 is configured to perform scheduling on the mobile station UE in the downlink on the basis of a subframe pattern received by the X2 interface 13 from the radio base station eNb#2.
Here, the subframe pattern indicates a subframe that does not transmit downlink data, for example, an ABS (Almost Blank Subframe) or an MBSFN (Multicast Broadcast Single Frequency Network) subframe.
For example, the scheduling unit 14 may be configured to perform scheduling on the mobile station UE in the downlink in the ABS or the MBSFN subframe designated by the subframe pattern.
Hereinafter, an operation of the mobile communication system according to the present embodiment will be described with reference to FIG. 8.
As illustrated in FIG. 8, in step S1001, the mobile station UE transmits the “Measurement Report” including the measurement results of the radio qualities of the neighboring cells #2 to #4 in the downlink to the radio base station eNB#1 that manages the cell #1 in which the mobile station UE is in communication.
In step S1002, the radio base station eNB#1 selects the cell #2 as the specific cell from among the neighboring cells #2 to #4 on the basis of the measurement results included in the “Measurement Report”.
In step S1003, the radio base station eNB#1 transmits the “DL HI Indication” to the radio base station eNB#2 that manages the cell #2.
In step S1004, the radio base station eNB#2 starts the “eICIC” using the “Time domain scheme” in response to the “DL HI Indication”, and sets the ABS or the MBSFN subframe, that is a subframe which does not transmit the downlink data.
Even when the “DL HI Indication” is received, the radio base station eNB#2 may not set the ABS or the MBSFN subframe, that is a subframe which does transmit the downlink data.
In step S1005, the radio base station eNB#2 transmits the subframe pattern indicating the subframe which does not transmit the set downlink data to the radio base station eNB#1.
In step S1006, the radio base station eNB#1 performs scheduling on the mobile station UE in the downlink on the basis of the subframe pattern.
In the mobile communication system according to the present embodiment, when the “DL HI Indication” indicating the influence of the interference on the mobile station UE in the downlink being strong is received from the radio base station eNB#1, since the radio base station eNB#2 is configured to start the “eICIC” using the “Time domain scheme”, it is possible to appropriately start the “eICIC”.
The characteristics of the present embodiment as described above may be expressed as follows.
A first characteristic of the present embodiment is summarized in that the mobile communication method including: a step A of transmitting, by a mobile station UE, “Measurement Report” including the measurement results of the radio qualities of neighboring cells #2 to #4 in a downlink to a radio base station eNB#1 (a first radio base station) that manages a cell #1 (a first cell) in which the mobile station UE is in communication; a step B of selecting, by the radio base station eNB#1, the cell #2 (a second cell) from among the neighboring cells #2 to #4 on the basis of the “Measurement Report”; and a step C of transmitting, by the radio base station eNB#1, “DL HI indication (interference indication information)” indicating the influence of the interference on the mobile station UE in a downlink direction being strong to a radio base station eNB#2 (a second radio base station) that manages the cell #2.
In the first characteristic of the present embodiment, the mobile communication method may further include a step of transmitting, by the radio base station eNB#2, a subframe pattern (subframe information) indicating the subframe (ABS/MBSFN subframe) that does not transmit downlink data in response to the “DL HI Indication” to the radio base station eNB#1.
In the first characteristic of the present embodiment, in the step C, the radio base station eNB#1 may transmit the “DL HI Indication” by using “X2 Load Information”.
In the first characteristic of the present embodiment, in the step C, the radio base station eNB#1 may transmit the “DL HI Indication” by using “eNB Configuration Update (updating information of a configuration of the radio base station).
In the first characteristic of the present embodiment, in the step C, the radio base station eNB#1 may transmit the “DL HI Indication” by using “X2 Setup Request/X2 Setup Response” as information on setting of an X2 connection between the radio base station eNB#1 and the radio base station eNB#2.
A second characteristic of the present embodiment is summarized in that a radio base station eNB managing a cell #1 in which a mobile station UE is in communication includes: a radio interface 11 (a measurement report reception unit) that receives “Measurement Report” including the measurement results of the radio qualities of neighboring cells #2 to #4 in a downlink from the mobile station UE; a selection unit 12 that selects the cell #2 (the specific cell) from among the neighboring cells #2 to #4 on the basis of the “Measurement Report”; and an X2 interface 13 (interference indication information transmission unit) that transmits “DL HI Indication” to a radio base station eNB#2 (the specific radio base station) that manages the cell #2.
In the second characteristic of the present embodiment, the radio base station eNB may further include a scheduling unit 14 that performs scheduling on the mobile station UE in the downlink on the basis of the subframe pattern when the subframe pattern indicating the subframe (ABS/MBSFN subframe) that does not transmit downlink data is received from the radio base station eNB#2.
In the second characteristic of the present embodiment, the X2 interface 13 may be configured to transmit the “DL HI Indication” by using “X2 Load Information”.
In the second characteristic of the present embodiment, the
X2 interface 13 may be configured to transmit the “DL HI Indication” by using “eNB Configuration Update”.
In the second characteristic of the present embodiment, the X2 interface 13 may be configured to transmit the “DL HI Indication” by using “X2 Setup Request/X2 Setup Response”.
It should be noted that the operation of the radio base station eNB, or the mobile station UE may be performed by hardware, a software module performed by a processor, or a combination thereof.
The software module may be arranged in a storage medium of an arbitrary format such as a RAM (Random Access Memory), a flash memory, a ROM (Read Only Memory), an EPROM (Erasable Programmable ROM), an EEPROM (Electronically Erasable and
Programmable ROM), a register, a hard disk, a removable disk, or a CD-ROM.
The storage medium is connected to the processor so that the processor can write and read information into and from the storage medium. Such a storage medium may also be accumulated in the processor. Such a storage medium and processor may be arranged in an ASIC. The ASIC may be arranged in the radio base station eNB, or the mobile station UE. Furthermore, such a storage medium and processor may be arranged in the radio base station eNB, or the mobile station UE as discrete components.
Thus, the present invention has been explained in detail by using the above-described embodiments; however, it is obvious that for persons skilled in the art, the present invention is not limited to the embodiments explained herein. The present invention can be implemented as a corrected and modified mode without departing the gist and the scope of the present invention defined by the claims. Therefore, the description of the specification is intended for explaining the example only and does not impose any limited meaning to the present invention.
REFERENCE SIGNS LIST


eNB . . . Radio base station
11 . . . Radio interface
12 . . . Selection unit
13 . . . X2 interface
14 . . . Scheduling unit
UE . . . Mobile station




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