JPWO2016038764A1 - Coverage control method, directivity control method, base station apparatus, radio communication system, and base station control program - Google Patents

Abstract

A small cell base station (1) having first and second cells using the first and second frequencies as carriers, and a mobile station (1) that communicates with at least one of the first and second cells ( 2), a small cell base station (1) includes a mobile station distribution estimation unit (12) for estimating a distribution of mobile stations 2 in the first cell and the second cell, One or more units including a mobile station communication state measuring unit (13) for measuring a communication state of the mobile station 2, and a mobile station (2) distributed in the second cell based on the distribution and the communication state A mobile station group specifying unit (14) for specifying a mobile station group composed of mobile stations, and a radio parameter control unit (15) for controlling the coverage of the first cell for the specified mobile station group, Is provided. Provided is a coverage control method capable of improving the throughput of a mobile station in a position where only one frequency can be selected in a small cell base station using a plurality of frequencies.

Description

  The present invention relates to a coverage control method, a directivity control method, a base station apparatus, a wireless communication system, and a non-transitory computer-readable medium storing a base station control program, and in particular, a multicarrier load by controlling the directivity of a transmission beam. As a dispersion method, in a base station apparatus corresponding to a plurality of frequency bands, a coverage control method for controlling the directivity of a transmission beam, a directivity control method, a base station apparatus, a wireless communication system, and a non-temporary storage for storing a base station control program Relates to a typical computer readable medium.

  In recent years, data traffic of mobile communication has increased remarkably due to the spread of smartphones and tablet terminals and the transmission and reception of a large amount of data such as moving images. As a countermeasure against traffic increase, in addition to a base station that covers a wide range with high transmission power (hereinafter referred to as “macro base station”), a small base station (hereinafter referred to as “macro base station”) that covers a narrow range with low transmission power. A base station installation method that locally installs a large number of small cell base stations) to increase communication capacity is considered promising. Here, the small cell base station includes a pico base station installed in a hot spot where users are crowded, a femto cell base station installed indoors where radio quality is poor. The communication area of the base station is called a cell.

  When installing small cell base stations, it is difficult to install a small cell base station in an appropriate location where hot spots occur or to install a large number of stations until the desired number of stations is reached due to restrictions on location and laws. There is. In order to increase the communication capacity under such restrictions, small cell base stations have a plurality of frequencies with different frequency bands, and a method of forming a plurality of cells with a small number of small cell base stations is an effective method. is there. By providing a plurality of frequencies, a wide communication area is secured in a relatively low frequency band (for example, a band of 2 GHz or less), and a communication capacity of a specific area in a relatively high frequency band (for example, a band of 3.5 GHz or more). Can be dramatically improved. In addition, traffic load can be distributed among a plurality of cells.

  On the other hand, when the small cell base station has a plurality of frequency bands (configures a plurality of cells), for each frequency, the coverage that is a boundary line of a cell that satisfies a predetermined communication quality is adjusted. Can do. As an example of a coverage adjustment method implemented in a base station having a plurality of frequencies, a technique described in Japanese Patent Application Publication No. 2011-523272 “Dynamic coverage adjustment in a multicarrier communication system” has been proposed. .

  In Patent Document 1, in a multi-carrier communication system including a plurality of frequencies (carriers) (for example, including first and second carriers), cell load is reduced in order to reduce interference and improve performance. The coverage is adjusted by adjusting the transmission power of each carrier based on (the number of active terminals in communication). Specifically, when the load on the second cell is low, the transmission power level of the second carrier is reduced to '0' or to a low level less than the transmission power of the first carrier. , Interference with the first cell is reduced. Note that the second carrier has a second coverage that is equal to or smaller than the first coverage of the first carrier.

  As an example of a method for adjusting coverage in each cell, a technique described in Japanese Patent Application Publication No. 2005-525041 “Antenna Adaptation in Time Division Duplexing System” of Patent Document 2 has been proposed. In Patent Document 2, the measurement value (interference power) of the quality evaluation index in the current directivity of the transmission beam is compared with the measurement value of the quality evaluation index in the experimental directivity that is sequentially changed. Dynamically determining the best beam direction. In addition, by monitoring the load status of the adjacent base station and considering the load, the directivity direction is determined so as to minimize the effective interference to the adjacent base station.

Special table 2011-523272 (page 7-8) JP 2005-525041 A (page 7-12)

  As described above, when the small cell base station includes a plurality of cells having different frequencies, the traffic load by the mobile station connected to the small cell base station fluctuates with time in addition to the coverage being different for each cell. As a result, the traffic load may be biased toward a specific cell. For example, there is a case where a mobile station in a place where only one specific frequency (for example, 2 GHz) can be selected due to a difference in coverage generates a lot of traffic. In such a case, the traffic load in the cell of the frequency becomes high, and a mobile station in a place where only the one frequency can be selected cannot select a plurality of frequencies. Compared with a mobile station in a place where it can do, the throughput is reduced.

  However, in the technique described in Patent Document 1, since the load is measured in units of cells, a mobile station that can select only one frequency cannot be specified, and transmission power control used for coverage adjustment is not possible. However, since the influence other than the target mobile station such as interference is exerted, the above-described problem of throughput reduction cannot be solved. In the technique described in Patent Document 2, although the target mobile station can be covered by the directivity control of the transmission beam, the adjustment of the experimental directivity is repeated, so the load on the mobile station It is impossible to follow the time variation of the above, and it is impossible to solve the problem of throughput reduction as described above.

(Object of the present invention)
The present invention has been made based on the above-described knowledge, and an object of the present invention is to provide a coverage control method and a directivity control method capable of improving the throughput of a mobile station that can select only one frequency. It is to provide a base station apparatus, a radio communication system, and a base station control program.

  In order to solve the above-described problems, the coverage control method, directivity control method, base station apparatus, radio communication system, and base station control program according to the present invention mainly adopt the following characteristic configuration. .

  (1) The coverage control method according to the present invention includes at least one first cell using a first frequency as a carrier, and at least one using a second frequency in a lower frequency band than the first frequency as a carrier. A coverage control method in a wireless communication system including a second cell, a base station apparatus, and a mobile station that communicates with at least one of the first cell and the second cell, Estimated in the mobile station distribution estimation step for estimating the distribution of the mobile station in the cell and the second cell, the mobile station communication state measurement step for measuring the communication state of the mobile station, and the mobile station distribution estimation step Distribution to the second cell based on the distribution of the mobile stations and the communication state of the mobile station measured in the mobile station communication state measurement step A mobile station group specifying step for specifying a mobile station group including one or more mobile stations including the mobile station, and controlling the directivity of the transmission beam of the first frequency, A coverage control step of controlling coverage of the first cell with respect to the mobile station group specified in the specifying step.

  (2) The directivity control method according to the present invention uses at least one first cell that uses the first frequency as a carrier and at least one that uses a second frequency in a lower frequency band than the first frequency as a carrier. In a wireless communication system including two second cells, a base station device, and a mobile station that communicates with at least one of the first cell and the second cell, the first frequency or the second A directivity control method for controlling the directivity of a transmission beam having a frequency of the mobile station, the mobile station distribution estimation step for estimating the distribution of the mobile stations in the first cell and the second cell, A mobile station communication state measurement step for measuring a communication state; a distribution of the mobile station estimated in the mobile station distribution estimation step; and a measurement in the mobile station communication state measurement step. A mobile station group specifying step for specifying a mobile station group including one or more mobile stations including the mobile stations distributed in the second cell, based on the communication state of the mobile station, A directivity control step for controlling directivity of the transmission beam of the first frequency with respect to the mobile station group specified in the mobile station group specifying step.

  (3) The base station apparatus according to the present invention uses at least one first cell that uses the first frequency as a carrier, and at least one second carrier that uses a second frequency that is lower than the first frequency as a carrier. A base station apparatus in a wireless communication system including a second cell, and a mobile station that communicates with at least one of the first cell and the second cell, wherein the first cell and the first cell Mobile station distribution estimating means for estimating the distribution of the mobile stations in two cells, mobile station communication state measuring means for measuring the communication state with the mobile station, and the mobile station estimated by the mobile station distribution estimating means One or more mobile stations including the mobile stations distributed in the second cell based on the distribution and the communication state with the mobile station measured by the mobile station communication state measuring means Mobile station group specifying means for specifying the mobile station group to be configured; and the first frequency for the mobile station group specified by the mobile station group specifying means by controlling the directivity of the transmission beam of the first frequency. Coverage control means for controlling the coverage of the cell.

  (4) The wireless communication system according to the present invention includes at least one first cell that uses the first frequency as a carrier, and at least one that uses a second frequency in a lower frequency band than the first frequency as a carrier. A wireless communication system including a second cell, a base station device, and a mobile station that communicates with at least one of the first cell and the second cell, wherein the first cell and the In mobile station distribution estimation means for estimating the distribution of the mobile stations in a second cell, mobile station communication state measurement means for measuring the communication state between the mobile station and the base station apparatus, and the mobile station distribution estimation means Based on the estimated distribution of the mobile stations and the communication state between the mobile station and the base station apparatus measured by the mobile station communication state measuring means, the distribution to the second cell Mobile station group specifying means for specifying a mobile station group composed of one or more mobile stations including a mobile station; and directivity of a transmission beam of the first frequency to control the mobile station group specifying means Coverage control means for controlling the coverage of the first cell for the group of mobile stations identified in (1).

  (5) The base station control program according to the present invention uses at least one first cell that uses the first frequency as a carrier, and at least one that uses a second frequency in a lower frequency band than the first frequency as a carrier. In a wireless communication system including two second cells, a base station device, and a mobile station that communicates with at least one of the first cell and the second cell, the base station device is implemented in the base station device. A base station control program to be executed as a computer control program, a mobile station distribution estimation process for estimating a distribution of the mobile stations in the first cell and the second cell, the mobile station and the base station A mobile station communication state measurement process for measuring a communication state with a device; a distribution of the mobile station estimated in the mobile station distribution estimation process; and the mobile station communication state A mobile station group including one or more mobile stations including the mobile stations distributed in the second cell based on a communication state between the mobile station and the base station apparatus measured in a fixed process. Coverage for controlling mobile station group identification processing to be identified and coverage of the first cell for the mobile station group identified in the mobile station group identification processing by controlling directivity of the transmission beam of the first frequency And a control process.

  According to the coverage control method, directivity control method, base station apparatus, radio communication system, and base station control program of the present invention, the following effects can be obtained.

  That is, in a wireless communication environment where at least two cells using different frequencies as carriers exist, even if a mobile station exists in an area where only one cell frequency can be selected, the throughput of the mobile station is reduced. Can be improved. The reason is that by identifying the mobile station and controlling the directivity of the transmission beam of the frequency of the other cell to the mobile station, the load of the mobile station is applied to the cell using the other frequency as a carrier. This is because it is possible to disperse.

1 is a system configuration diagram illustrating an example of a system configuration of a wireless communication system including a small cell base station and a mobile station according to a first embodiment of the present invention. It is a block diagram which shows an example of the internal structure of the small cell base station and mobile station which concern on the 1st Embodiment of this invention. It is a flowchart which shows the operation | movement procedure in the small cell base station for implement | achieving an example of the coverage control method which concerns on the 1st Embodiment of this invention. It is explanatory drawing for demonstrating an example of operation | movement of step S101 of the implementation procedure of the coverage control in the small cell base station which concerns on the 1st Embodiment of this invention. It is explanatory drawing for demonstrating an example of operation | movement of step S103 of the implementation procedure of the coverage control in the small cell base station which concerns on the 1st Embodiment of this invention. It is explanatory drawing for demonstrating an example of operation | movement of step S105 of the implementation procedure of the coverage control in the small cell base station which concerns on the 1st Embodiment of this invention. It is a flowchart which shows the operation | movement procedure in the small cell base station for implement | achieving an example of the coverage control method which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows an example of the internal structure of the small cell base station and mobile station which concern on the 3rd Embodiment of this invention. It is a flowchart which shows the operation | movement procedure in the small cell base station for implement | achieving an example of the coverage control method which concerns on the 3rd Embodiment of this invention. It is a block diagram which shows an example of the internal structure of the small cell base station and mobile station which concern on the 4th Embodiment of this invention. It is a flowchart which shows the operation | movement procedure in the small cell base station for implement | achieving an example of the coverage control method which concerns on the 4th Embodiment of this invention.

  Preferred embodiments of a coverage control method, directivity control method, base station apparatus, wireless communication system, and base station control program according to the present invention will be described below with reference to the accompanying drawings. In the following description, the coverage control method, directivity control method, base station apparatus, and radio communication system according to the present invention will be described. The coverage control method and directivity control method are executed by a computer in the base station apparatus. Needless to say, it may be implemented as a possible base station control program, or may be recorded on a computer-readable recording medium. In addition, it is needless to say that the drawing reference numerals attached to the following drawings are added for convenience to the respective elements as an example for facilitating understanding, and are not intended to limit the present invention to the illustrated embodiments. Yes. Note that in the following drawings, the same elements are denoted by the same reference numerals, and redundant description of the same elements is omitted unless necessary for clarifying the description.

(Features of the present invention)
Prior to the description of the embodiments of the present invention, an outline of the features of the present invention will be described first. The main feature of the present invention is that it is possible to improve the throughput of a user (mobile station) who can select only one frequency. Specifically, the present invention mainly includes the following five modes. It is made up of.

  The first aspect of the present invention is a coverage control method. The coverage control method according to the present invention includes at least one first cell using a first frequency as a carrier, and at least one second cell using a second frequency in a lower frequency band than the first frequency as a carrier. And a base station apparatus, and a mobile station that communicates with at least one of the first cell and the second cell. And a mobile station distribution estimation step for estimating the distribution of the mobile stations in the second cell, a mobile station communication state measurement step for measuring a communication state of the mobile station, and the movement estimated in the mobile station distribution estimation step. Based on the distribution of stations and the communication state of the mobile station measured in the mobile station communication state measurement step, before distribution to the second cell A mobile station group specifying step for specifying a mobile station group including one or more mobile stations including the mobile station; and a directivity of a transmission beam of the first frequency to control the mobile station group specifying step And a coverage control step for controlling the coverage of the first cell for the mobile station group specified in (1).

  The second aspect of the present invention is a directivity control method. The directivity control method according to the present invention includes at least one first cell using a first frequency as a carrier and at least one first cell using a second frequency in a lower frequency band than the first frequency as a carrier. The first frequency or the second frequency in a wireless communication system including two cells, a base station apparatus, and a mobile station that communicates with at least one of the first cell and the second cell. A directivity control method for controlling the directivity of a transmission beam of the mobile station, the mobile station distribution estimation step for estimating the distribution of the mobile stations in the first cell and the second cell, and the communication state of the mobile station Measured in the mobile station communication state measurement step, the mobile station distribution estimation step and the mobile station communication state measurement step. A mobile station group specifying step for specifying a mobile station group composed of one or more mobile stations including the mobile stations distributed in the second cell based on a communication state of the mobile station; And a directivity control step for controlling the directivity of the transmission beam of the first frequency with respect to the mobile station group specified in the station group specifying step.

  A third aspect of the present invention is a base station apparatus. The base station apparatus according to the present invention includes at least one first cell that uses a first frequency as a carrier, and at least one second cell that uses a second frequency in a frequency band lower than the first frequency as a carrier. A base station apparatus in a wireless communication system, including a mobile station that communicates with at least one of the first cell and the second cell, wherein the first cell and the second cell Mobile station distribution estimation means for estimating a distribution of the mobile stations in a cell; mobile station communication state measurement means for measuring a communication state with the mobile station; and distribution of the mobile stations estimated by the mobile station distribution estimation means; Consists of one or more mobile stations including the mobile stations distributed in the second cell based on the communication status with the mobile station measured by the mobile station communication status measuring means Mobile station group specifying means for specifying the mobile station group to be transmitted, and directivity of the transmission beam of the first frequency is controlled, and the first cell of the first cell for the mobile station group specified by the mobile station group specifying means is controlled. And a coverage control means for controlling the coverage.

  A fourth aspect of the present invention is a wireless communication system. The wireless communication system according to the present invention includes at least one first cell using a first frequency as a carrier and at least one second cell using a second frequency in a lower frequency band than the first frequency as a carrier. A wireless communication system including a base station apparatus, a mobile station that communicates with at least one of the first cell and the second cell, wherein the first cell and the second cell Estimated by the mobile station distribution estimation means for estimating the distribution of the mobile stations in the cell, the mobile station communication state measurement means for measuring the communication state between the mobile station and the base station apparatus, and the mobile station distribution estimation means The mobile station distributed in the second cell based on the distribution of the mobile station and the communication state between the mobile station and the base station apparatus measured by the mobile station communication state measuring means A mobile station group specifying means for specifying a mobile station group composed of one or more mobile stations including the mobile station group specifying means for controlling directivity of a transmission beam of the first frequency and specifying the mobile station group specifying means; And a coverage control unit that controls coverage of the first cell with respect to the mobile station group.

  A fifth aspect of the present invention is a base station control program. The base station control program according to the present invention includes at least one first cell that uses a first frequency as a carrier, and at least one first cell that uses a second frequency in a lower frequency band than the first frequency as a carrier. In a wireless communication system including two cells, a base station device, and a mobile station communicating with at least one of the first cell and the second cell, a computer implemented in the base station device A base station control program executed as a control program, a mobile station distribution estimation process for estimating a distribution of the mobile stations in the first cell and the second cell, the mobile station, the base station device, Mobile station communication state measurement processing for measuring the communication state of the mobile station, distribution of the mobile station estimated in the mobile station distribution estimation processing, and mobile station communication state measurement processing A mobile station group including one or more mobile stations including the mobile stations distributed in the second cell is identified based on the communication state measured between the mobile station and the base station apparatus A mobile station group specifying process and a coverage control process for controlling the directivity of the transmission beam of the first frequency to control the coverage of the first cell for the mobile station group specified in the mobile station group specifying process It has the main feature of having.

<First embodiment of the present invention>
Next, a first embodiment of a coverage control method to which the present invention is applied will be described in detail with reference to the drawings. In the coverage control method in the wireless communication system according to the first embodiment, a mobile station group that can select only one frequency is specified and specified in a wireless communication environment in which at least two cells having different frequencies exist. The case where the directivity of the transmission beam of the other frequency is controlled toward the mobile station group is described.

(Description of configuration example of first embodiment)
FIG. 1 is a system configuration diagram showing an example of a system configuration of a radio communication system including a small cell base station and a mobile station according to the first embodiment of the present invention. In the following description of the first embodiment, an LTE (Long Term Evolution) scheme is applied to a wireless communication system, and TDD (Time Division Duplex) in which the transmission time differs between the uplink and the downlink at the same frequency. A case where the method is applied will be described.

  As shown in FIG. 1, the wireless communication system according to the first embodiment includes a multicarrier-compatible small cell base station 1 including a plurality of transmission / reception antennas for each frequency of a plurality of frequencies, and the small cell base station 1. And at least a mobile station 2 that communicates with the mobile station 2. Further, the small cell base station 1 includes a plurality of cells 3 and relatively uses a cell 3-1 (first frequency carrier) using a 3.5 GHz carrier (first frequency carrier) having a high frequency and a wide band (for example, 40 MHz). 1 cell) and a cell 3-2 (second cell) using a relatively low frequency, narrow band (for example, 20 MHz) 2 GHz carrier (second frequency carrier). In FIG. 1, a mobile station 2-1 communicating with a 3.5 GHz carrier and a mobile station 2-2 communicating with a GHz carrier are located in a cell 3-1 and a cell 3-2, respectively. In the first embodiment, the mobile station 2 can communicate only with the cell 3 of one of the carriers. In FIG. 1, each of the mobile station 2-1 and the mobile station 2-2 is in communication (active) with the small cell base station 1 via the cell 3-1 and the cell 3-2. is there.

  In general, the higher the frequency, the higher the straightness of the radio wave and the less the wraparound, so the higher frequency side of the 3.5 GHz carrier cell 3-1 covers the lower frequency side of the 2 GHz carrier cell 3-2. Is often narrow. In addition, since the frequency resources are easily secured in a wider band as the frequency is higher, the throughput of the mobile station 2-1 that performs communication using 3.5 GHz on the high frequency side is higher than 2 GHz on the low frequency side. It is often higher than the mobile station 2-2 to perform. Note that, in the first embodiment, as described above, carrier aggregation (CA: communication) is performed between the cell 3-1 and the cell 3-2 shown in FIG. (Carrier Aggregation) is described on the assumption that it does not apply.

  A further supplement of FIG. 1 is as follows. As shown as white mobile stations in FIG. 1, only 2 GHz carriers can be selected where five mobile stations 2-2 are located. It will be accommodated in a cell 3-2 of a 2 GHz carrier. In addition, in a place where one mobile station 2-1 shown as a mobile station with hatching in FIG. 1 is located, both 3.5 GHz carrier and 2 GHz carrier can be selected. Since received power (RSRP: Reference Signal Received Power) is equal to or greater than a predetermined value, the single mobile station 2-1 is accommodated in the cell 3-1.

  Further, as shown in FIG. 1, there are five mobile stations 2-2 and one mobile station 2-1, and the cell 3-2 is more connected to the mobile station 2 being connected than the cell 3-1. Since the number is large, the cell 3-2 has a relatively high load based on the number of mobile stations 2. In addition, the number of each mobile station 2, the number of each cell 3, the size, and the frequency in FIG. 1 are examples, and it goes without saying that the present invention is not limited to FIG.

  Next, the internal configuration of the small cell base station 1 and the mobile station 2 shown in FIG. 1 will be described in detail with reference to FIG. FIG. 2 is a block diagram showing an example of internal configurations of the small cell base station 1 and the mobile station 2 according to the first embodiment of the present invention. The internal configurations of the mobile station 2-1 and the mobile station 2-2 shown in FIG. 1 are the same, and FIG. Hereinafter, the internal configuration of each apparatus will be described in order.

  First, the internal configuration of the small cell base station 1 will be described. As shown in FIG. 2, the small cell base station 1 includes a base station radio transmission / reception unit 10, a transmission / reception buffer unit 11, a mobile station distribution estimation unit 12, a mobile station communication state measurement unit 13, a mobile station group identification unit 14, and radio parameters. The control part 15 is comprised including at least.

  The base station radio transmission / reception unit 10 has a basic function of radio transmission / reception in the small cell base station 1 for performing radio communication with the mobile station 2. The basic functions include a function of transmitting a control signal and data signal including a downlink reference signal to the mobile station 2, a function of receiving a control signal and data signal including an uplink reference signal from the mobile station 2, and a downlink. The mobile station 2 to be the data transmission partner is selected, and data is transmitted to the selected mobile station 2 together with scheduling information such as the allocated frequency resource (PRB: Physical Resource Block) and MCS (Modulation and Coding Schemes). There is a scheduler function. In addition, the base station radio transmission / reception unit 10 includes a plurality of transmission / reception antenna elements (two in the first embodiment, 3.5 GHz and 2 GHz) for each frequency in order to perform radio transmission / reception. . The plurality of transmission / reception antenna elements are arranged in a linear array at intervals of half-waves of radio waves, for example, so that beam forming of a transmission beam and arrival angle estimation of a reception beam can be performed.

  The transmission / reception buffer unit 11 temporarily stores data transmitted to the mobile station 2 via the wireless network (or data transmitted from the mobile station 2 via the wireless network). The buffers constituting the transmission / reception buffer unit 11 are prepared for each user and for each QCI (QoS Class Identifier). Here, QCI means a QoS (Quality of Service) identification index indicating the quality of service provided in the wireless network.

  The mobile station distribution estimation unit 12 receives the uplink reference signal from each of the mobile stations 2 by the plurality of transmission / reception antenna elements of the base station radio transmission / reception unit 10, thereby determining the arrival angle of the radio wave from each mobile station 2. Then, the estimation results of the arrival angles are collected, and the angle distribution of the arrival angles with respect to all the mobile stations 2 is estimated. As a method for estimating the arrival angle of the radio wave from each mobile station 2, a general technique in the field related to the present invention, such as a MUSIC (Multiple Signal Classification) method using an eigenvalue / eigenvector of a correlation matrix, is applied. Note that one mobile station 2-1 communicating in the cell 3-1 (first cell) shown in FIG. 1 transmits a 3.5 GHz carrier on the high frequency (first frequency) side to the cell 3-2. Each of the five mobile stations 2-2 communicating in the (second cell) estimates the arrival angle by using the 2 GHz carrier on the low frequency (second frequency) side. In addition, the angular distribution is estimated without being distinguished for each carrier.

  The mobile station communication state measurement unit 13 measures traffic, reception quality, and the like for each mobile station 2 as a characteristic state in communication of the mobile station 2. In the first embodiment, for communication with the small cell base station 1, which cell 3 is connected is measured as the communication state of the mobile station 2. The connection destination cell 3 of each mobile station 2 can be acquired from the information of the connected cell managed by the base station radio transceiver 10 for each communication. Specifically, the mobile station 2 measures and reports PCI information (Physical Cell ID: information identifying the cell 3 at the radio wave level) transmitted from the small cell base station 1 at the time of cell selection such as handover. Therefore, the connected cell can be specified from the PCI information. For example, it can be specified that the mobile station 2-1 is connected to the cell 3-1 of the 3.5 GHz carrier, and the mobile station 2-2 is connected to the cell 3-2 of the 2 GHz carrier.

  The mobile station group identification unit 14 uses the angular distribution of each mobile station 2 estimated by the mobile station distribution estimation unit 12 and the communication state of each mobile station 2 measured by the mobile station communication state measurement unit 13. The distribution of mobile stations that can only select 2 GHz carriers is specified. In the first embodiment, for each mobile station 2, by combining information on the arrival angle and the connection destination cell, only the 2 GHz carrier on the low frequency (second frequency) side can be selected. The mobile station 2 located in is identified. When a plurality of mobile stations 2 are crowded, the plurality of mobile stations 2 are regarded as one mobile station group.

  The radio parameter control unit 15 controls radio parameters in order to adjust the coverage. In the first embodiment, the transmission beam including the downlink reference signal is transmitted with respect to the cell 3-1 of the 3.5 GHz carrier toward the angle at which the mobile station group specified by the mobile station group specifying unit 14 is located. Control the directivity of That is, the radio parameter control unit 15 controls at least the directivity of the transmission beam of the 3.5 GHz carrier on the high frequency (first frequency) side, and the mobile station group specifying unit 14 specifies the mobile station group. Coverage control means for controlling the coverage of the cell 3-1 (first cell) is provided.

  Next, the internal configuration of the mobile station 2 in FIG. 2 will be described. The mobile station 2 includes at least a mobile station radio transmission / reception unit 20. The mobile station radio transmission / reception unit 20 has a basic function of radio transmission / reception in the mobile station 2 for radio communication with the small cell base station 1. As the basic function, a function of transmitting a control signal and data signal including an uplink reference signal to the small cell base station 1, a function of receiving a control signal and data signal including a downlink reference signal from the small cell base station 1, and the like There is.

(Description of the operation of the first embodiment)
Next, an example of the coverage control operation of the small cell base station 1 in the first embodiment will be described in detail with reference to the flowchart of FIG. FIG. 3 is a flowchart showing an operation procedure in the small cell base station 1 for realizing an example of the coverage control method according to the first embodiment of the present invention, and a predetermined time interval in the small cell base station 1. Periodically.

  When the flowchart of FIG. 3 is activated, first, the mobile station distribution estimation unit 12 uses the arrival angle information of the uplink reference signal of each mobile station 2 to cover the coverage area including the cells 3-1 and 3-2. The distribution of the mobile station 2 is estimated (step S101). An example of the operation in step S101 is shown in FIG. 4A. 4A, 4B, and 4C are explanatory diagrams for explaining an example of an implementation procedure of coverage control in the small cell base station 1 according to the first embodiment of the present invention. FIG. 4B illustrates an example of the operation, FIG. 4B illustrates an example of the operation of step S103, and FIG. 4C illustrates an example of the operation of step S105.

  In step S101, as shown in FIG. 4A, for example, one mobile station 2-1 belonging to the cell 3-1 is set to 3.5 GHz carrier with reference to the vertical axis extending vertically from the small cell base station 1. In addition, the five mobile stations 2-2 belonging to the cell 3-2 each measure the arrival angle of the uplink reference signal indicated by the chain line arrow using the 2 GHz carrier. Here, as the environment between the small cell base station 1 and each mobile station 2 is closer to the line of sight, the obtained arrival angle indicates the geographical position of each mobile station 2 regardless of the frequency. It can be regarded as an angular direction, and the distribution of each mobile station 2 in the coverage area including the cells 3-1 and 3-2 can be estimated.

  Returning to the flowchart of FIG. 3, next, the mobile station communication state measuring unit 13 measures the communication state of each mobile station 2. Here, as described above, in the first embodiment, the communication state of each mobile station 2 indicates which cell 3 is connected to each mobile station 2 for communication with the small cell base station 1. I will consider it. In order to specify the mobile station 2 that can select only the 2 GHz carrier from the measurement result of the communication state like this, the mobile station 2-2 that has selected the cell 3-2 as the connection destination cell 3 is extracted ( Step S102).

  Thereafter, the mobile station group identification unit 14 can select only a 2 GHz carrier using the angular distribution of each mobile station 2 obtained in step S101 and the communication state of each mobile station 2 obtained in step S102. A distribution of a group (mobile station group) of at least one mobile station 2 that cannot be specified is specified (step S103). An example of the operation in step S103 is shown in FIG. 4B.

  As shown in FIG. 4B, the five mobile stations 2-2 that have selected the cell 3-2 that communicates with the 2 GHz carrier as the connection destination cell 3 are divided into predetermined angular ranges (see FIG. 4B). In the example, the vertical axis extending vertically from the small cell base station 1 is rotated by 20 ° in the clockwise direction by dividing each angle range of 0 ° to 19 °, 20 ° to 39 °,. The number of mobile stations 2-2 is counted for each angle range based on the arrival angles of the mobile stations 2-2.

  The number of mobile stations 2-2 counted for each angle range is a predetermined ratio threshold that is predetermined with respect to the total number of mobile stations 2 (the total number of mobile stations 2-1 and 2-2). In the above case, a plurality of mobile stations 2-2 belonging to the corresponding angle range (three mobile stations surrounded by dotted circles as mobile stations 2-2 belonging to an angle range of 20 ° to 39 ° in FIG. 4B) 2-2) is regarded as the same mobile station group. In the first embodiment, the predetermined ratio is set to 50% from the viewpoint of distributing the load as evenly as possible between the two cells 3-1 and 3-2.

  In the example shown in FIG. 4B, as described above, three mobile stations 2-2 are distributed in an angle range of 20 ° to 39 °, and three are 50, which is a total of six mobile stations 2. Therefore, the three mobile stations 2-2 belonging to the angle range are regarded as one mobile station group.

  Returning to the flowchart of FIG. 3, it is next determined whether or not the presence of the mobile station group has been specified by the operations from step S101 to step S103 (step S104). If the number of identified mobile station groups is a positive integer and it is determined that the mobile station group exists (YES in step S104), the process proceeds to step S105. On the other hand, if the number of identified mobile station groups is “0” and it is determined that there is no mobile station group (NO in step S104), the throughput of the user, that is, the mobile station 2 cannot be improved. Since this is the case, the operation of the flowchart of FIG.

  If it is determined that the mobile station group exists, the process proceeds to step S105 as described above, and the radio parameter control unit 15 causes the high frequency side 3.5 GHz carrier to go to the mobile station group specified in step S103. By controlling the directivity of the transmission beam including the downlink reference signal in the cell 3-1, the coverage of the cell 3-1 for the mobile station group is expanded (step S105). Here, to control the directivity of the transmission beam of the 3.5 GHz carrier, only the directivity of the transmission beam is used without changing the beam shape (width or gain) using the arrival angle of the specified mobile station group. Apply steering vector method to control. An example of the operation in step S105 is shown in FIG. 4C.

  As shown in FIG. 4C, control is performed so that the directivity of the transmission beam of the 3.5 GHz carrier is directed toward the representative angle θ of the specified mobile station group. Here, as the representative angle θ, an average value of the arrival angles of the mobile stations 2 constituting the identified mobile station group may be used, or the arrival angles of the mobile stations 2 constituting the identified mobile station group may be used. The median value between the maximum angle and the minimum angle may be used.

  As described in detail above, in the first embodiment, a high frequency (first frequency) is directed toward a mobile station group that can select only a 2 GHz carrier on the low frequency (second frequency) side. ) Side 3.5 GHz carrier transmission beam directivity is controlled, so that the mobile station group can use the high frequency (first frequency) side 3.5 GHz carrier, and the cell 3-1 ( The load can be distributed between the first cell) and the cell 3-2 (second cell). Thus, it is possible to improve the reduced throughput of the mobile stations 2 constituting the mobile station group.

  The control procedure shown in the flowchart of FIG. 3 can also be realized by causing a computer such as a microprocessor to execute a control program for controlling the base station apparatus. That is, the computer that executes the base station control program may be made to perform mobile station group identification, transmission beam directivity control, and the like.

  In the first embodiment, the case where only one mobile station group is specified has been described. However, the present invention is not limited to such a case, and a plurality of mobile station groups are specified. Cases are also targeted. When a plurality of mobile station groups are specified, for example, the directivity of the transmission beam of the 3.5 GHz carrier is set to one mobile station group in which the number of mobile stations 2 constituting the mobile station group is maximum. What is necessary is just to control. By controlling in this way, more mobile stations 2 can be selected at a time as mobile stations 2 that are the targets for realizing load distribution.

  Moreover, although the case where carrier aggregation is not applied between the cell 3-1 and the cell 3-2 has been described in the first embodiment, carrier aggregation may be applied. When applying carrier aggregation, the directivity of the transmission beam of the 3.5 GHz carrier on the high frequency side is first changed. Thereafter, the identified mobile station group uses the cell 3-2 of the 2 GHz carrier as the primary cell that first establishes a control RRC (Radio Resource Control) connection, and the cell 3-1 of the 3.5 GHz carrier. Is performed as a secondary cell additionally provided for data, so that carrier aggregation is performed. Therefore, in the carrier aggregation, load distribution between cells is realized by a scheduler straddling between cells of a plurality of carriers.

  In the first embodiment, only the distribution of the mobile station 2 that can select only the 2 GHz carrier on the low frequency side is used, but the mobile station 2 that has selected the 3.5 GHz carrier on the high frequency side is used. A distribution may also be used. That is, even if the directivity of the transmission beam of the 3.5 GHz carrier is changed so as to be directed to the specified mobile station group by estimating the distribution of the mobile station 2 that has selected the 3.5 GHz carrier on the high frequency side, 3 The mobile station 2 that has selected the .5 GHz carrier can determine whether or not it can continue to select the 3.5 GHz carrier.

  For example, as shown in FIG. 4C, if the mobile station group of 2 GHz carrier and the mobile station 2 of 3.5 GHz carrier exist in substantially the same angular distribution, the directivity of the transmission beam of the 3.5 GHz carrier Since there is no effect on the connection destination cell of the mobile station 2 of the 3.5 GHz carrier, the directivity of the transmission beam of the 3.5 GHz carrier can be changed so as to go to the mobile station group of the 2 GHz carrier. It can be judged that it is possible.

<Second embodiment of the present invention>
Next, a second embodiment of the coverage control method to which the present invention is applied will be described. About the structure of the radio | wireless communications system which concerns on this 2nd Embodiment, and the internal structure of the small cell base station 1 and the mobile station 2, the same system as the case of FIG. 1, FIG. 2 shown as 1st Embodiment Although it is a structure and an internal structure, a part of operation | movement of the coverage control method in the radio | wireless communications system which concerns on this 2nd Embodiment differs from the case of FIG. 3 shown as 1st Embodiment.

  That is, in the first embodiment, a cell that is in communication (connected) is used as the communication state of the mobile station 2, but in the second embodiment, the communication state of the mobile station 2 is used. In addition, a case is described in which not only a communication (connected) cell is used but also a transmission buffer size addressed to each mobile station 2 is used. Here, the transmission buffer size means the amount of transmission data that stays in a buffer provided in a base station apparatus interposed in the middle of communication between the mobile station 2 and the application server. By further using the transmission buffer size as the communication state of the mobile station 2, control according to the traffic load per mobile station 2 can be realized.

  An example of the coverage control operation of the small cell base station 1 in the second embodiment will be described in detail with reference to the flowchart of FIG. FIG. 5 is a flowchart showing an operation procedure in the small cell base station 1 for realizing an example of the coverage control method according to the second embodiment of the present invention, and the flowchart of FIG. 3 in the first embodiment. As in the case of, the small cell base station 1 is periodically implemented at predetermined time intervals. The only difference between the coverage control method shown in the flowchart of FIG. 5 and the case of FIG. 3 is that the operation related to the measurement of the communication state of each mobile station 2 described in step S102 of FIG. 3 is replaced with the operation of step S202. It is. Each operation of other steps (step S101, step S103 to step S105) of the flowchart of FIG. 5 is the same as that of the flowchart of FIG. 3, and the same step symbols as those of FIG. I will omit the explanation.

  In step S202 in the flowchart of FIG. 5, the mobile station communication state measurement unit 13 determines which cell 3 each mobile station 2 connects to communicate with the small cell base station 1 as the communication state of each mobile station 2. And whether or not the transmission buffer size addressed to each mobile station 2 is equal to or larger than a predetermined size threshold value determined in advance. Here, the transmission buffer size can be obtained by measuring the amount of data stored in the transmission / reception buffer unit 11. Based on the measurement result of the communication state of the mobile station 2, only a 2 GHz carrier can be selected, and in order to identify the mobile station 2 whose traffic load is higher than a predetermined load threshold, Data stored in the transmission / reception buffer unit 11 is the mobile station 2-2 that has selected the cell 3-2 (second cell) of the 2 GHz carrier on the low frequency (second frequency) side as the cell 3. The mobile station 2-2 whose amount is larger than the size threshold is extracted (step S202).

  By performing the operation shown in step S202 as described above, the coverage control method according to the second embodiment can select only the 2 GHz carrier on the low frequency (second frequency) side, Further, the directivity of the transmission beam of the 3.5 GHz carrier on the high frequency (first frequency) side is controlled toward the mobile station group including the mobile stations 2 having a traffic load higher than the load threshold. −2 (second cell) to cell 3-1 (first cell), the load distribution effect can be made larger than in the first embodiment. Thus, there is an effect that the reduced throughput of the mobile stations 2 constituting the mobile station group can be improved more reliably.

  When a plurality of mobile station groups are specified in the second embodiment, for example, one mobile station in which the total value of the transmission buffer sizes addressed to each mobile station 2 constituting the mobile station group is maximized. The directivity of the transmission beam of the 3.5 GHz carrier may be controlled for the group. Thus, the load distribution effect from the cell 3-2 (second cell) to the cell 3-1 (first cell) can be more reliably realized.

  In the second embodiment, the case where the transmission buffer size is used as the communication state related to traffic other than the cell being connected (connected) has been described. However, the present invention is limited to such a case. It is not a thing. For example, QoS (Quality of Service) indicating service quality provided in a wireless network may be used. For QoS, priority is defined from the viewpoint of required quality such as traffic type (real time, non-real time, etc.), packet transmission delay, packet loss rate, etc., and the priority is determined by QCI (QoS Class Identifier). ). In such a case, the transmission / reception buffer in the transmission / reception buffer unit 11 is prepared for each QCI.

  Therefore, when the mobile stations 2 constituting the mobile station group to be subjected to coverage control are specified, the transmission data is predetermined in the transmission buffer in which the QCI indicating the priority is higher than a predetermined priority level. By identifying the communication state of the mobile station 2 that has accumulated more than a predetermined amount as the communication state of the control target related to traffic, the mobile station 2 with a high priority is assigned 3. The directivity of the transmission beam of the 5 GHz carrier can be controlled, and the required quality of QoS can be satisfied more reliably.

<Third embodiment of the present invention>
Next, a third embodiment of the coverage control method to which the present invention is applied will be described. In the coverage control method in the radio communication system according to the third embodiment, the case of the radio communication system according to the first embodiment is the same as that in the second embodiment. The two communication states are different. That is, as the communication state of the mobile station 2 to be measured, in the first embodiment, the connected (communication) cell is used, whereas in the third embodiment, the connected state ( In addition to the cell in communication), the reception quality of each mobile station 2 is also used. Here, as the reception quality, for example, the received power (RSRP: Reference Signal Received Power) of a downlink reference signal in a connected (communication) cell is measured and used. By using the received power (RSRP), control according to the received power of the desired signal for the connected (during communication) cell can be performed.

(Description of Configuration Example of Third Embodiment)
The system configuration of the radio communication system including the small cell base station and the mobile station according to the third embodiment of the present invention is the same as the system configuration shown in FIG. 1 as the first embodiment. The LTE (Long Term Evolution) method is applied, and the TDD (Time Division Duplex) method with the same frequency and different transmission time is applied between the uplink and the downlink.

  Next, the internal configurations of the small cell base station 1 and the mobile station 2 in the third embodiment will be described in detail with reference to FIG. FIG. 6 is a block diagram showing an example of internal configurations of the small cell base station 1 and the mobile station 2 according to the third embodiment of the present invention. The internal configurations of the mobile station 2-1 and the mobile station 2-2 shown in FIG. 1 are the same, and FIG. 6 shows an example of the internal configuration of the mobile station 2. 6 differs from the first embodiment in FIG. 2 in that the mobile station 2 shown in FIG. 6 is connected to the mobile station in FIG. 2 in order to obtain the received power (RSRP) of each mobile station 2. In addition to the mobile station radio transmission / reception unit 20 similar to 2, a channel quality measurement unit 21 and a channel quality report unit 22 are additionally provided.

  Other constituent elements of the block configuration diagram of FIG. 6 (base station radio transmission / reception unit 10, transmission / reception buffer unit 11, mobile station distribution estimation unit 12, mobile station communication state measurement unit 13, mobile station group identification unit of small cell base station 1 14 and each part of the radio parameter control unit 15 and the part of the mobile station radio transmission / reception unit 20 of the mobile station 2) are the same as those in the block configuration of FIG. Detailed explanation here is omitted. Hereinafter, in the block configuration diagram of FIG. 6, the channel quality measurement unit 21 and the channel quality report unit 22 that are additionally provided in the mobile station 2 as components unique to the third embodiment will be described in order. To do.

  The channel quality measuring unit 21 is connected to the cell to which the mobile station 2 is connected (in the case of the mobile station 2-1, the cell 3-1 of the 3.5 GHz carrier, in the case of the mobile station 2-2, the cell 3 of the 2 GHz carrier. -2) Measure the received power (RSRP) of the downlink reference signal.

  The channel quality report unit 22 reports information on the received power (RSRP) measured by the channel quality measurement unit 21 to the small cell base station 1 as a period measurement report (Periodic Measurement Report) at a predetermined cycle. To do. Thus, the report value in the periodic measurement report regarding the received power (RSRP) is transmitted from the mobile station radio transceiver 20 of the mobile station 2 via the radio network, the base station radio transceiver 10 of the small cell base station 1. It is delivered to the mobile station communication state measuring unit 13 of the small cell base station 1.

(Description of the operation of the third embodiment)
Next, the coverage control operation of the small cell base station 1 in the third embodiment will be described with reference to the flowchart of FIG. FIG. 7 is a flowchart showing an operation procedure in the small cell base station 1 for realizing an example of the coverage control method according to the third embodiment of the present invention, and the flowchart of FIG. 3 in the first embodiment. As in the case of, the small cell base station 1 is periodically implemented at predetermined time intervals. The only difference between the coverage control method shown in the flowchart of FIG. 7 and the case of FIG. 3 is that the operation related to the measurement of the communication state of each mobile station 2 described in step S102 of FIG. 3 is replaced with the operation of step S302. It is. Each operation of the other steps (step S101, step S103 to step S105) of the flowchart of FIG. 7 is the same as that of the flowchart of FIG. 3, and the same step symbols as those of FIG. I will omit the explanation.

  In step S302 in the flowchart of FIG. 7, the mobile station communication state measurement unit 13 determines which cell 3 each mobile station 2 connects to communicate with the small cell base station 1 as the communication state of each mobile station 2. And whether or not the received power (RSRP) of each mobile station 2 is equal to or less than a predetermined power threshold determined in advance is measured. Based on the measurement result of the communication state of the mobile station 2, only the 2 GHz carrier can be selected, and the mobile station 2 is identified as having a reception quality that has deteriorated to a poor state below a predetermined quality threshold. Therefore, the mobile station 2-2 selects the cell 3-2 (second cell) of the 2 GHz carrier on the low frequency (second frequency) side as the connection destination cell 3, and each mobile station 2 extracts the mobile station 2-2 in which the report value related to the received power (RSRP) periodically transmitted as the periodic measurement report is reduced to the power threshold value or less (step S302).

  By performing the operation shown in step S302 as described above, the coverage control method according to the third embodiment can select only the 2 GHz carrier on the low frequency (second frequency) side, Furthermore, the directivity of the transmission beam of the 3.5 GHz carrier on the high frequency (first frequency) side toward the mobile station group including the mobile stations 2 whose reception quality has deteriorated to an inferior state below the quality threshold value. Therefore, the load distribution effect from the cell 3-2 (second cell) to the cell 3-1 (first cell) can be made larger than that of the first embodiment. Thus, there is an effect that the reduced throughput of the mobile stations 2 constituting the mobile station group can be improved more reliably.

  In the third embodiment, the case where reception power (RSRP) is used for the reception quality measured as the communication state of each mobile station 2 has been described. However, the reception quality of each mobile station 2 in the present invention is as follows. This is not the only case. For example, as reception quality of each mobile station 2, downlink reference signal received power (RSRP), downlink reference signal reception quality (RSRQ: Reference Signal Received Quality), received signal power to interference and noise power ratio (SINR: Any one or more of Signal to Interference plus Noise Ratio (SNR), channel quality indicator (CQI) based on SINR, and average transmission rate calculated by the scheduler of the base station may be used. Among these various reception qualities, RSRQ and CQI are measured by the mobile station 2 in the same manner as in the case of received power (RSRP), and the measurement results are periodically transmitted to the small cell base station 1 at a predetermined cycle. Report it.

<Fourth embodiment of the present invention>
Next, a fourth embodiment of a coverage control method to which the present invention is applied will be described. The radio communication system according to the fourth embodiment has a configuration in which components for measuring the cell load of each cell are further added to the radio communication system according to the first embodiment. . Then, as a result of measuring the cell load of each cell, if the difference in cell load between the cells is large, the mobile station group identification and directivity control of the transmission beam of the 3.5 GHz carrier in the first embodiment To implement. On the other hand, if the difference in cell load between cells is small, the possibility of the presence of a mobile station group is low, and the operations of specifying the mobile station group and directivity control of the transmission beam of the 3.5 GHz carrier are avoided. That is, coverage control is performed only when there is a large difference in cell load between cells and there is a high need for directivity control of a transmission beam of a 3.5 GHz carrier. In the fourth embodiment, the cell load of each cell to be measured is the number of mobile stations 2 in communication (in connection) (that is, the number of active mobile stations).

(Description of configuration example of fourth embodiment)
The system configuration of the radio communication system including the small cell base station and the mobile station according to the fourth embodiment of the present invention is the same as the system configuration shown in FIG. 1 as the first embodiment. The LTE (Long Term Evolution) method is applied, and the TDD (Time Division Duplex) method with the same frequency and different transmission time is applied between the uplink and the downlink.

  Next, the internal configurations of the small cell base station 1 and the mobile station 2 in the fourth embodiment will be described in detail with reference to FIG. FIG. 8 is a block diagram showing an example of internal configurations of the small cell base station 1 and the mobile station 2 according to the fourth embodiment of the present invention. The internal configurations of the mobile station 2-1 and the mobile station 2-2 shown in FIG. 1 are the same, and FIG. 8 shows an example of the internal configuration of the mobile station 2. The difference between the block configuration of FIG. 8 and the first embodiment of FIG. 2 is that the small cell base station 1 shown in FIG. In addition to each part similar to 1, the cell load measuring unit 16 is additionally provided.

  Other constituent elements of the block configuration diagram of FIG. 8 (base station radio transmission / reception unit 10, transmission / reception buffer unit 11, mobile station distribution estimation unit 12, mobile station communication state measurement unit 13, mobile station group identification unit of small cell base station 1 14 and each part of the radio parameter control unit 15 and the part of the mobile station radio transmission / reception unit 20 of the mobile station 2) are the same as those in the block configuration of FIG. Detailed explanation here is omitted. Hereinafter, in the block configuration diagram of FIG. 8, the cell load measurement unit 16 provided in addition to the small cell base station 1 as a component specific to the fourth embodiment will be described.

  The cell load measuring unit 16 measures the number of active mobile stations connected to each cell 3 as the cell load of each cell 3. The measured cell load is notified to the radio parameter control unit 15 in the small cell base station 1.

(Description of the operation of the fourth embodiment)
Next, an example of the coverage control operation of the small cell base station 1 in the fourth embodiment will be described in detail with reference to the flowchart of FIG. FIG. 9 is a flowchart showing an operation procedure in the small cell base station 1 for realizing an example of the coverage control method according to the fourth embodiment of the present invention, and the flowchart of FIG. 3 in the first embodiment. As in the case of, the small cell base station 1 is periodically implemented at predetermined time intervals. The only difference between the coverage control method shown in the flowchart of FIG. 9 and the case of FIG. 3 is that the operation of step S4-6 is added as the first step of FIG. Each operation of other steps (steps S101 to S105) of the flowchart of FIG. 9 is the same as that of the flowchart of FIG. 3, and the same step symbols as those of FIG. Omit.

  In step S406 in the flowchart of FIG. 9, the radio parameter control unit 15 first compares the cell loads of the cell 3-1 and the cell 3-2 measured by the cell load measurement unit 16 (step S406). When the cell load of the cell 3-1 is smaller than a value obtained by adding a predetermined difference threshold A determined in advance to the cell load of the cell 3-2, that is, the cell load of the cell 3-1 is -2 is smaller than a predetermined difference threshold A determined in advance (YES in step S406), the cell load of the cell 3-2 is relatively smaller than the cell load of the cell 3-1. Since it is regarded as large, the process proceeds to step S101 and subsequent steps in order to perform coverage control.

  On the other hand, when the cell load of the cell 3-1 is larger than the value obtained by adding a predetermined difference threshold A to the cell load of the cell 3-2 (NO in step S406), the cell load of the cell 3-2 9 is relatively small compared to the cell load of the cell 3-1, and there is a low possibility that there is a mobile station group subject to coverage control. Therefore, the flowchart of FIG. End the operation.

  By performing the operation shown in step S406 as described above, the coverage control method according to the fourth embodiment allows the cell 3-1 (the first frequency) using the 3.5 GHz carrier on the high frequency (first frequency) side. Cell) and the cell 3-2 (second cell) using the 2 GHz carrier on the low frequency (second frequency) side, if the cell load has a large deviation, the deviation is corrected. As described above, the directivity of the transmission beam of the 3.5 GHz carrier on the high frequency (first frequency) side is controlled toward the mobile station group that is the target of load distribution. Therefore, only when coverage control is required, load distribution to the cell 3-1 (first cell) is realized, and throughput can be reliably improved while reducing the processing load of coverage control. it can. In addition, since the cell load of the cell 3-1 (first cell) as a load distribution destination is also taken into consideration, the mobile station 2-1 already connected to the cell 3-1 (first cell) The load can be effectively distributed to the cell 3-1 (first cell) having a low cell load while suppressing the influence of the coverage control.

  In the fourth embodiment, the case where the number of active mobile stations is used as the cell load has been described. However, the cell load in the present invention is not limited to this case. For example, as the cell load, the number of active mobile stations, the number of active mobile stations per frequency band considering the difference in bandwidth of each frequency of the cell 3, the resource usage rate of the frequency resource, the mobile station 2 in each cell 3 That is, any one or a plurality of transmission buffer sizes destined for each active mobile station may be used.

<Other Embodiments of the Present Invention>
Next, another embodiment of the coverage control method to which the present invention is applied will be described. In each of the embodiments from the first embodiment to the fourth embodiment described above, the mobile station distribution estimation unit 12 performs uplink processing in order for the small cell base station 1 to estimate the distribution of each mobile station 2. Although the case of measuring the arrival angle of the channel reference signal has been described, the mobile station distribution estimation operation in the present invention is not limited to this case.

  For example, each mobile station 2 measures the reception quality for each arrival angle of the downlink reference signal, and information on the measured reception quality is used as precoding weight information (PMI: Precoding Matrix Indicator), and the small cell base station 1 May be reported to the mobile station distribution estimation unit 12. The arrival angle of the uplink reference signal is suitable for TDD using the same frequency in the downlink and uplink, whereas when reporting from the mobile station 2 side as precoding weight information PMI. Although feedback delay from the small cell base station 1 to each mobile station 2 occurs, not only in the case of TDD, but also in the case of FDD (Frequency Division Duplex) using different frequencies for the downlink and uplink. Can be applied.

  Further, in each of the embodiments from the first embodiment to the fourth embodiment described above, the cell 3-2 (second frequency) of the 2 GHz carrier on the low frequency (second frequency) side as the coverage control target. High frequency (first cell) used by the cell 3-1 (first cell) for a mobile station group consisting of a plurality of mobile stations 2-2 existing within a predetermined angle range of the second cell). By controlling the directivity of the transmission beam of the 3.5 GHz carrier on the (frequency) side, each mobile station 2-2 of the mobile station group accommodated in the cell 3-2 (second cell) is transferred to the cell 3- Although the case where the control is performed so as to be covered by 1 (first cell) has been described, the coverage control operation in the present invention is not limited to such a case.

  For example, a part of the mobile station 2-2 existing in the cell 3-2 (second cell) is located indoors where radio wave attenuation is large, and the 3.5 GHz carrier on the high frequency (first frequency) side May be difficult to reach. In preparation for such a case, a communication position state indicating whether the mobile station 2-2 is communicating indoors or outdoors is determined as a communication state of the mobile station 2-2, and the determination result is used to determine 3. You may make it control the directivity of the transmission beam of the cell 3-1 of a 5 GHz carrier. That is, as a result of determining the communication position state, the mobile station 2-2 determined to be located indoors is excluded from the coverage control target, while only the mobile station 2-2 determined to be located outdoors is subjected to coverage control. As a target, the directivity of the transmission beam of the cell 3-1 of the 3.5 GHz carrier may be controlled toward the mobile station 2-2. Here, as a method of determining the indoor communication state, for example, when it is determined that the reception level of a GPS (Global Positioning System) radio wave is smaller than a predetermined required level threshold value, or detection of a GPS satellite When it is determined that the number is less than a predetermined threshold number of detected satellites.

  Further, in each of the embodiments from the first embodiment to the fourth embodiment described above, the directivity of the transmission beam of the cell 3-1 of the 3.5 GHz carrier on the high frequency (first frequency) side. However, the directivity control operation of the transmission beam in the present invention is not limited to this case.

  For example, as a coverage control operation, the directivity of the transmission beam of the cell 3-2 of the 2 GHz carrier on the low frequency (second frequency) side may be controlled. In such a case, each mobile station 2-2 is not limited to the cell 3-2 (second cell) to which the mobile station 2-2 is connected, as described in the third embodiment. The reception quality of the cell 3-1 (first cell) is also measured.

  As a measurement result, the reception quality of the cell 3-1 (first cell) is equal to or lower than a predetermined first cell quality threshold, or the cell 3-1 (first cell) with respect to the reception quality of the cell 3-2 (second cell). If the relative value of the reception quality of the first cell) is equal to or lower than a predetermined threshold value, the directivity of the transmission beam of the 3.5 GHz carrier of the cell 3-1 (first cell) is controlled. Since it is determined that the mobile station 2-2 cannot be covered, the directivity of the transmission beam of the 2 GHz carrier in the cell 3-2 is controlled.

  As described above, by controlling the directivity of the transmission beam of the 2 GHz carrier of the cell 3-2, the reception quality of the connection destination cell 3 of the corresponding mobile station 2-2 can be improved, so that the throughput can be improved. You can expect.

  Alternatively, in the cell load determination operation in step S406 of FIG. 9 in the fourth embodiment described above, the cell 3-2 (second cell) is used instead of the 3.5 GHz carrier of the cell 3-1 (first cell). In order to perform the operation of determining the cell load in the case of controlling the directivity of the transmission beam of the 2 GHz carrier of the cell), the inequality sign in step S406 in FIG. It may be determined whether or not the cell load of the (cell) is larger than a value obtained by adding a predetermined difference threshold A determined in advance to the cell load of the cell 3-2 (second cell). When the cell load of the cell 3-1 (first cell) is larger than the value obtained by adding the predetermined difference threshold A to the cell load of the cell 3-2 (second cell), the cell 3-2 Since the cell load of the (second cell) is relatively smaller than the cell load of the cell 3-1 (first cell), the transmission beam of the 2 GHz carrier of the cell 3-2 (second cell) Even if directivity control is performed, the number of mobile stations 2-2 affected by the influence is small.

  In each of the embodiments from the first embodiment to the fourth embodiment described above, the 3.5 GHz carrier on the high frequency (first frequency) side and the low frequency (second frequency) side. The 2 GHz carrier has been described as being composed of one cell having one frequency band, but the system configuration in the present invention is not limited to such a case.

  For example, each of the 3.5 GHz carrier on the high frequency (first frequency) side and the 2 GHz carrier on the low frequency (second frequency) side is composed of a plurality of frequency bands, and may be composed of a plurality of cells. good. Each frequency band at this time is referred to as a component carrier (hereinafter abbreviated as CC), and each CC corresponds to a cell. For example, when the 3.5 GHz carrier is composed of a 40 MHz wide frequency band in total, it can be divided into 4 MHz (4 cells) with a 10 MHz width. Thus, in the case of a carrier composed of a plurality of CCs, the coverage control operation as shown in each of the embodiments from the first embodiment to the fourth embodiment is performed for each CC. Will be carried out. As a result, when a plurality of mobile station groups are specified, a plurality of mobile station groups existing in the 2 GHz carrier on the low frequency (second frequency) side are moved to the high frequency (first frequency) by the coverage control operation for each CC. 1 frequency) side 3.5 GHz carrier can be accommodated in each CC.

  Further, in each of the embodiments from the first embodiment to the fourth embodiment described above, the case of the same communication method in which the cell 3-1 and the cell 3-2 have different frequencies has been described. The cells 3-1 and 3-2 in the present invention are not limited to this case.

  For example, the cell 3-1 and the cell 3-2 may use different RATs (Radio Access Technology). That is, when the cell 3-1 uses the LTE system and the cell 3-2 uses the third generation UMTS (Universal Mobile Telecommunications System), the cell 3-1 uses the wireless LAN, and the cell 3-2 It is also possible to use a combination such as when LTE is used. However, when the RATs are different, the corresponding frequencies are also different, so that the frequencies of the cells 3-1 and 3-2 are different.

  In each of the first to fourth embodiments described above, the case where the present invention is applied to an LTE wireless communication system has been described. The wireless communication method is not limited to this case.

  For example, the present invention may be applied to a UMTS wireless communication system, an FDD wireless communication system that uses different frequencies for uplink and downlink simultaneously, or an LTE method such as WiMAX, IEEE802.16m, etc. The present invention may be applied to a different TDD wireless communication system.

  Further, in each of the embodiments from the first embodiment to the fourth embodiment described above, when the cell 3-1 and the cell 3-2 are provided in the same small cell base station 1 However, the cell configuration in the present invention is not limited to such a case.

  For example, the cell 3-1 and the cell 3-2 may be configured to be separately provided in different base station apparatuses connected to each other via a wired or wireless line. For example, when the cell 3-1 is provided in the femtocell base station and the cell 3-2 is provided in the pico base station, or the cell 3-1 is provided in the remote radio head (RRH) base station. 3-2 may be provided in each macro base station. In such a case, when the angular distribution of the mobile station 2 is estimated, the distribution of the mobile station 2 may be corrected by a method such as a three-point survey using position information between the mobile station 2 and each base station. Alternatively, the first cell 3-1 may be a small cell located within the coverage of the second cell 3-2 regardless of the same base station device or different base station devices.

  Further, in each of the embodiments from the first embodiment to the fourth embodiment described above, each mobile station 2 has a plurality of frequency bands between the cell 3-1 and the cell 3-2. Although the case where there is no In-Band CA to which carrier aggregation (CA: Carrier Aggregation) that communicates simultaneously is applied has been described, the present invention relates to any one of the cells 3-1 and 3-2. However, the present invention is not limited to the case where the communication is performed using the cell, and the case where there is an In-Band CA in which the communication is performed using both the cell 3-1 and the cell 3-2 may be used.

  Further, in each of the embodiments from the first embodiment to the fourth embodiment described above, by controlling the directivity of the transmission beam with respect to the carrier of the cell 3, the cell 3 with respect to the mobile station 2 is controlled. Although the coverage control method for controlling the coverage has been described, the present invention is not limited to the coverage control method as described above, but may be configured as a directivity control method for controlling the directivity of the transmission beam with respect to the carrier of the cell 3. I do not care.

  For example, at least one cell 3-1 (first cell) that uses the first frequency as a carrier and at least one cell 3- that uses a second frequency lower than the first frequency as a carrier 3- 2 (second cell), a base station device, and a mobile station 2 communicating with at least one of the cell 3-1 (first cell) and the cell 3-2 (second cell) , A directivity control method for controlling the directivity of the transmission beam of the first frequency or the second frequency in a wireless communication system including at least the cell 3-1 (first cell) ) And a mobile station distribution estimation step for estimating the distribution of the mobile station 2 in the cell 3-2 (second cell), a mobile station communication state measurement step for measuring a communication state of the mobile station 2, and the mobile Office Based on the distribution of the mobile station 2 estimated in the estimation step and the communication state of the mobile station 2 measured in the mobile station communication state measurement step, it is distributed at least in the cell 3-2 (second cell). A mobile station group specifying step for specifying a mobile station group including one or more mobile stations 2 including the mobile station 2, and at least the first for the mobile station group specified in the mobile station group specifying step A directivity control method characterized by comprising at least a directivity control step for controlling the directivity of a transmission beam having a predetermined frequency.

  In the directivity control method as described above, the cell 3-1 (first cell) and the cell 3-2 (second cell) may be mounted on the same base station apparatus. In addition, the cell 3-1 (first cell) may be a small cell located within the coverage of the cell 3-2 (second cell).

  In the directivity control method as described above, each of the cell 3-1 (first cell) and the cell 3-2 (second cell) is connected to each other by a wired line. For example, the cell 3-1 (first cell) is mounted on a femtocell base station, and the cell 3-2 (second cell) is mounted on a pico base station. Alternatively, the cell 3-1 (first cell) is a remote radio head (RRH) base station, and the cell 3-2 (second cell) is a macro base. It may be installed in each station.

  In the directivity control method as described above, the estimation operation of the distribution of the mobile station 2 in the mobile station distribution estimation step is performed using a base station apparatus that implements the first cell and a base that implements the second cell. You may make it implement in a station apparatus or another apparatus.

  In the directivity control method as described above, it is desirable that the first frequency is a frequency higher than 3.0 GHz and the second frequency is a frequency lower than 3.0 GHz. For example, as described above, the first frequency may be 3.5 GHz and the second frequency may be 2 GHz. Alternatively, in such a directivity control method, for example, the first frequency may be a frequency higher than 1.0 GHz, and the second frequency may be a frequency lower than 1.0 GHz. Absent.

  In the above-described embodiments, the present invention has been described as a hardware configuration, but the present invention is not limited to this. The present invention can also realize arbitrary processing by causing a CPU (Central Processing Unit) to execute a computer program. Further, the above-described program can be stored using various types of non-transitory computer readable media and supplied to a computer. Non-transitory computer readable media include various types of tangible storage media. Examples of non-transitory computer-readable media include magnetic recording media (for example, flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (for example, magneto-optical disks), CD-ROM (Read Only Memory) CD-R, CD -R / W, semiconductor memory (for example, mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (Random Access Memory)). The program may also be supplied to the computer by various types of transitory computer readable media. Examples of transitory computer readable media include electrical signals, optical signals, and electromagnetic waves. The temporary computer-readable medium can supply the program to the computer via a wired communication path such as an electric wire and an optical fiber, or a wireless communication path.

<Appendix>
As is apparent from the detailed description of the embodiments of the present invention, some or all of the above-described embodiments can be described as the following supplementary notes. However, it goes without saying that the present invention is not limited to such a case.

  (Supplementary note 1) At least one first cell using a first frequency as a carrier, at least one second cell using a second frequency lower than the first frequency as a carrier, and a base A coverage control method in a radio communication system including a station apparatus and a mobile station that communicates with at least one of the first cell and the second cell, wherein the first cell and the second cell A mobile station distribution estimation step for estimating a distribution of the mobile stations in the cell; a mobile station communication state measurement step for measuring a communication state of the mobile station; and a distribution of the mobile stations estimated in the mobile station distribution estimation step; One or more units including the mobile stations distributed in the second cell based on the communication state of the mobile station measured in the mobile station communication state measurement step A mobile station group specifying step for specifying a mobile station group composed of the mobile stations, and a directivity of the transmission beam of the first frequency are controlled to the mobile station group specified in the mobile station group specifying step. A coverage control step of controlling the coverage of the first cell.

  (Supplementary Note 2) In order to estimate the distribution of the mobile station in the mobile station distribution estimation step, the mobile station receives an uplink reference signal transmitted from each mobile station and measures the angle of arrival of the received uplink reference signal. The coverage control method according to Supplementary Note 1, wherein the angular distribution in which each mobile station is located is estimated.

  (Supplementary note 3) In order to estimate the distribution of the mobile station in the mobile station distribution estimation step, each mobile station measures the reception quality for each arrival angle of the downlink reference signal, and the information on the measured reception quality The coverage control method according to supplementary note 1, wherein the angular distribution in which each mobile station is located is estimated by reporting from each mobile station as precoding weight information (PMI: Precoding Matrix Indicator).

  (Supplementary note 4) In the mobile station communication state measurement step, in order to measure the communication state of the mobile station, at least whether or not the mobile station is connected to the second cell is measured. The coverage control method according to any one of 1 to 3.

  (Supplementary Note 5) In order to measure the communication state of the mobile station in the mobile station communication state measurement step, at least the mobile station is in a state of being connected to the second cell and addressed to the mobile station The coverage control method according to any one of appendices 1 to 3, which measures whether or not the transmission buffer size is equal to or greater than a predetermined size threshold.

  (Supplementary note 6) In order to measure the communication state of the mobile station in the mobile station communication state measurement step, at least the mobile station is in a state of being connected to the second cell, and the reception quality is predetermined. 4. The coverage control method according to any one of appendices 1 to 3, which measures whether or not the state has fallen to a state equal to or less than a predetermined quality threshold value.

  (Supplementary Note 7) As the reception quality measured in the mobile station communication state measurement step, the received power of the downlink reference signal (RSRP: Reference Signal Received Power), the received quality of the downlink reference signal (RSRQ: Reference Signal Received Quality) Appendix 6 using any one or more of received signal power to interference and noise power ratio (SINR), channel quality indicator (CQI), or average transmission rate The coverage control method described.

  (Supplementary Note 8) In order to measure the communication state of the mobile station in the mobile station communication state measurement step, at least the mobile station is in a state of being connected to the second cell and indicates a priority. Additional remarks 1 to 1 for measuring whether or not the amount of transmission data stored in a transmission buffer having a QCI (QoS Class Identifier) higher than a predetermined priority level has reached a predetermined amount or more. 4. The coverage control method according to any one of 3.

  (Supplementary note 9) In order to measure the communication state of the mobile station in the mobile station communication state measurement step, at least the mobile station is in a state of being connected to the second cell, and the mobile station 4. The coverage control method according to any one of appendices 1 to 3, which measures whether or not the vehicle is located outdoors.

  (Supplementary note 10) When measuring whether or not the mobile station is located outdoors, the reception level of GPS (Global Positioning System) radio waves in the mobile station is greater than a predetermined required level threshold, or The coverage control method according to supplementary note 9, wherein when the number of detected GPS satellites is greater than a predetermined threshold number of detected satellites, it is determined that the state is located outdoors.

  (Supplementary Note 11) In order to specify the mobile station group in the mobile station group specifying step, the mobile stations in a state of being connected to the second cell are divided into predetermined predetermined angular ranges. If there is an angle range in which the number of mobile stations present in the area has reached a predetermined ratio threshold or more with respect to the total number of mobile stations, the mobile station exists in the area of the angle range. The coverage control method according to any one of appendices 1 to 10, wherein the mobile station is identified as one mobile station group.

  (Additional remark 12) In order to control the directivity of the transmission beam of the first frequency in the coverage control step, it is directed to a representative angle representative of the distribution region of the mobile station group specified in the mobile station group specifying step. The coverage control method according to any one of appendices 1 to 11, wherein the directivity of the transmission beam of the carrier of the first cell is controlled.

  (Supplementary note 13) Each mobile station group that constitutes the mobile station group that is specified as the representative angle of the mobile station group that is controlled so that the directivity of the transmission beam of the carrier of the first cell is directed in the mobile station group specifying step 13. The coverage control method according to appendix 12, wherein an average value of arrival angles of the mobile stations or a median value of maximum angles and minimum angles of arrival angles of the mobile stations constituting the specified mobile station group is used.

  (Supplementary Note 14) The coverage control step further includes a cell load measurement step of measuring each cell load of the first cell and the second cell, and the coverage control step includes the cell load measurement step. As a measurement result of the cell load in Step 1, when it is determined that at least the cell load of the first cell is smaller than a predetermined difference threshold as compared with the cell load of the second cell, 14. The device according to any one of appendices 1 to 13, wherein the directivity of a transmission beam having a frequency of 1 is controlled to perform an operation of controlling the coverage of the first cell for the mobile station group specified in the mobile station group specifying step. Coverage control method.

  (Supplementary Note 15) As the cell load measured in the cell load measurement step, the number of active mobile stations in connection with the cells of the first cell or the second cell, and the active movement per frequency band 15. The coverage control method according to appendix 14, wherein one or more of the number of stations, the resource usage rate of frequency resources, and the total value of transmission buffer sizes addressed to each active mobile station are used.

  (Supplementary Note 16) In the coverage control step, instead of controlling the directivity of the transmission beam of the first frequency so as to go to the mobile station group, the directivity of the transmission beam of the second frequency is changed to the mobile station. The coverage control method according to any one of appendices 1 to 11, wherein control is performed so as to go to a group.

  (Supplementary Note 17) In the case where the directivity of the transmission beam of the second frequency is controlled to be directed to the mobile station group in the coverage control step, at least the first reception quality of the first cell is predetermined. The coverage control method according to supplementary note 16, wherein the cell quality threshold is equal to or lower than the cell quality threshold, or the relative value of the reception quality of the first cell with respect to the reception quality of the second cell is equal to or lower than a predetermined threshold.

  (Supplementary note 18) The coverage control step further includes a cell load measurement step of measuring a cell load of each of the first cell and the second cell, and in the coverage control step, the second frequency As a case where the directivity of the transmission beam is controlled so as to be directed to the mobile station group, at least the cell load of the first cell is larger than a difference threshold value determined in advance compared to the cell load of the second cell. The coverage control method according to appendix 16, wherein the coverage control method is determined to be large.

  (Supplementary note 19) The coverage control method according to any one of supplementary notes 1 to 18, wherein each of the mobile stations communicates using one of the first cell and the second cell.

  (Supplementary note 20) The coverage control method according to any one of Supplementary notes 1 to 18, wherein each of the mobile stations communicates using both the first cell and the second cell.

  (Supplementary note 21) Each of the first frequency used as a carrier of the first cell and the second frequency used as a carrier of the second cell is composed of a plurality of frequency bands, and the first cell 21. The coverage control method according to any one of appendices 1 to 20, wherein each of the second cells is divided into a plurality of cells corresponding to a plurality of the frequency bands.

  (Supplementary Note 22) At least one first cell using a first frequency as a carrier, at least one second cell using a second frequency lower than the first frequency as a carrier, and a base In a wireless communication system including a station apparatus and a mobile station that communicates with at least one of the first cell and the second cell, the directivity of the transmission beam of the first frequency or the second frequency A mobile station distribution estimation step for estimating a distribution of the mobile stations in the first cell and the second cell, and a mobile station for measuring a communication state of the mobile station A communication state measurement step, a distribution of the mobile station estimated in the mobile station distribution estimation step, and a communication of the mobile station measured in the mobile station communication state measurement step. A mobile station group specifying step for specifying a mobile station group including one or more mobile stations including the mobile stations distributed in the second cell based on a state; and in the mobile station group specifying step A directivity control step for controlling directivity of the transmission beam of the first frequency with respect to the identified mobile station group.

  (Supplementary note 23) The directivity control method according to supplementary note 22, wherein the first cell and the second cell are mounted on the same base station apparatus.

  (Supplementary note 24) The directivity control method according to supplementary note 22, wherein the first cell is a small cell located within the coverage of the second cell.

  (Supplementary note 25) The directivity control method according to supplementary note 22, wherein the first cell and the second cell are separately installed in different base station apparatuses connected to each other through a wired line.

  (Supplementary note 26) The directivity control method according to supplementary note 25, wherein the first cell is mounted on a femtocell base station and the second cell is mounted on a pico base station.

  (Supplementary note 27) The directivity control according to supplementary note 25, wherein the first cell is mounted on a remote radio head (RRH) base station, and the second cell is mounted on a macro base station. Method.

  (Supplementary Note 28) The mobile station distribution estimation operation in the mobile station distribution estimation step is performed by a base station device that implements the first cell, a base station device that implements the second cell, or another device. The directivity control method according to any one of appendices 22 to 27, implemented in any one of the above.

  (Supplementary note 29) The directivity control method according to any one of supplementary notes 22 to 28, wherein the first frequency is a frequency higher than 3.0 GHz, and the second frequency is a frequency lower than 3.0 GHz. .

  (Supplementary note 30) The directivity control method according to any one of the supplementary notes 22 to 28, wherein the first frequency is a frequency higher than 1.0 GHz and the second frequency is a frequency lower than 1.0 GHz. .

  (Supplementary note 31) at least one first cell using a first frequency as a carrier, at least one second cell using a second frequency lower than the first frequency as a carrier, and A base station apparatus in a radio communication system including at least a mobile station that communicates with at least one of the first cell and the second cell, wherein the first cell and the second cell Mobile station distribution estimation means for estimating the distribution of the mobile stations in the cell, mobile station communication state measurement means for measuring a communication state with the mobile station, and distribution of the mobile stations estimated by the mobile station distribution estimation means And one or more of the mobiles including the mobile stations distributed in the second cell based on the communication state with the mobile station measured by the mobile station communication state measuring means A mobile station group specifying means for specifying a mobile station group comprising: a first control unit for controlling the directivity of a transmission beam of the first frequency to the mobile station group specified by the mobile station group specifying means; And a coverage control means for controlling the coverage of the cell.

  (Supplementary note 32) The base station apparatus according to Supplementary note 31, wherein one or both of the first cell and the second cell are provided as constituent elements.

  (Supplementary Note 33) One of the first cell and the second cell is included as a component, and the other cell of the first cell and the second cell is configured 32. The base station apparatus according to Supplementary Note 31, wherein the base station apparatus is connected to another base station apparatus configured as an element by a wired or wireless line.

  (Supplementary Note 34) At least one first cell using a first frequency as a carrier, at least one second cell using a second frequency lower than the first frequency as a carrier, and a base A wireless communication system including a station apparatus and a mobile station that communicates with at least one of the first cell and the second cell, wherein the movement in the first cell and the second cell Mobile station distribution estimating means for estimating the distribution of stations, mobile station communication state measuring means for measuring the communication state between the mobile station and the base station apparatus, and the distribution of the mobile stations estimated by the mobile station distribution estimating means And one or more of the mobile stations including the mobile stations distributed in the second cell based on the communication state between the mobile station and the base station apparatus measured by the mobile station communication state measuring means Mobile station group specifying means for specifying a mobile station group composed of mobile stations, and directivity of the transmission beam of the first frequency to control the mobile station group specified by the mobile station group specifying means And a coverage control means for controlling the coverage of the first cell.

  (Supplementary Note 35) One of the first cell and the second cell is included as a constituent element, and the other cell of the first cell and the second cell is configured 35. The wireless communication system according to appendix 34, wherein the wireless communication system is connected to another wireless communication system configured as an element by a wired or wireless line.

  (Supplementary note 36) The wireless communication system according to supplementary note 34 or 35, wherein the first cell and the second cell have different radio access schemes (RATs).

  (Supplementary Note 37) As a radio access scheme between the first cell and the second cell, any one of LTE (Long Term Evolution) scheme, UMTS (Universal Mobile Telecommunications System) scheme, and Wireless LAN scheme is used. 37. The radio communication system according to appendix 36.

  (Supplementary note 38) At least one first cell using a first frequency as a carrier, at least one second cell using a second frequency lower than the first frequency as a carrier, and a base In a wireless communication system including a station apparatus and a mobile station that communicates with at least one of the first cell and the second cell, the program is executed as a computer control program installed in the base station apparatus A base station control program for measuring a mobile station distribution estimation process for estimating a distribution of the mobile station in the first cell and the second cell, and measuring a communication state between the mobile station and the base station apparatus The mobile station communication state measurement process, the mobile station distribution estimated in the mobile station distribution estimation process, and the mobile station communication state measurement process measured in the mobile station communication state measurement process. A mobile station group specifying process for specifying a mobile station group composed of one or more mobile stations including the mobile stations distributed in the second cell based on a communication state between a station and the base station device And a coverage control process for controlling the directivity of the transmission beam of the first frequency to control the coverage of the first cell with respect to the mobile station group specified in the mobile station group specifying process. Station control program.

  The application example of the present invention is implemented in an environment in which a plurality of types of base stations having cells of different frequencies are mixed in the same area in mobile communication, and is suitable as a technique for controlling cell coverage for mobile stations. Can be applied to. In particular, when there are many mobile stations located in places where the frequency that can be covered is small, by controlling the directivity of the transmission beam of the carrier to the mobile station, the coverage to the mobile station will be expanded and the throughput will be improved. It is effective for the use.

  The configuration of the preferred embodiment of the present invention has been described above. However, it should be noted that such embodiments are merely examples of the present invention and do not limit the present invention. Those skilled in the art will readily understand that various modifications and changes can be made according to a specific application without departing from the gist of the present invention.

  This application claims the priority on the basis of Japanese application Japanese Patent Application No. 2014-186736 for which it applied on September 12, 2014, and takes in those the indications of all here.

DESCRIPTION OF SYMBOLS 1 Small cell base station 10 Base station radio | wireless transmission / reception part 11 Mobile station distribution estimation part 12 Mobile station communication state measurement part 13 Mobile station group specification part 14 Radio parameter control part 15 Cell load measurement part 2 Mobile station 2-1 Mobile station 2- 2 Mobile station 20 Mobile station wireless transmission / reception unit 21 Channel quality measurement unit 22 Channel quality report unit 3 Cell 3-1 Cell 3-2 Cell

Claims (10)

At least one first cell that uses a first frequency as a carrier, at least one second cell that uses a second frequency lower than the first frequency as a carrier, a base station device, A coverage control method in a radio communication system including a mobile station that communicates with at least one of the first cell and the second cell,
A mobile station distribution estimation step for estimating a distribution of the mobile stations in the first cell and the second cell;
A mobile station communication state measurement step for measuring a communication state of the mobile station;
1 including the mobile stations distributed in the second cell based on the distribution of the mobile stations estimated in the mobile station distribution estimation step and the communication state of the mobile stations measured in the mobile station communication state measurement step. A mobile station group specifying step for specifying a mobile station group composed of more than one mobile station;
A coverage control step of controlling the directivity of the transmission beam of the first frequency to control the coverage of the first cell with respect to the mobile station group specified in the mobile station group specifying step. Coverage control method. In order to estimate the distribution of the mobile stations in the mobile station distribution estimation step,
Receiving an uplink reference signal transmitted by each of the mobile stations, and measuring an arrival angle of the received uplink reference signal to estimate an angular distribution in which each of the mobile stations is located;
Alternatively, each mobile station measures reception quality for each arrival angle of a downlink reference signal, and reports information on the measured reception quality as precoding weight information (PMI: Precoding Matrix Indicator) from each mobile station. The coverage control method according to claim 1, further comprising: estimating an angular distribution in which each mobile station is located. In order to measure the communication state of the mobile station in the mobile station communication state measurement step,
Measuring whether the mobile station is connected to the second cell;
Alternatively, it is determined whether the mobile station is in a state of being connected to the second cell and a transmission buffer size addressed to the mobile station is equal to or larger than a predetermined size threshold.
Or measuring whether the mobile station is in a state of being connected to the second cell and the reception quality is reduced to a state equal to or lower than a predetermined quality threshold;
Alternatively, the amount of transmission data stored in a transmission buffer in which the mobile station is connected to the second cell and the QCI (QoS Class Identifier) indicating the priority is higher than a predetermined priority level Measures whether or not it has reached a predetermined amount or more,
Or measuring whether or not the mobile station is connected to the second cell and the mobile station is located outdoors. Item 3. The coverage control method according to Item 1 or 2. In order to specify the mobile station group in the mobile station group specifying step,
Among the mobile stations in a state of being connected to the second cell, the number of the mobile stations existing in an area divided for each predetermined angle range is determined in advance with respect to the total number of the mobile stations. When there is an angle range that reaches or exceeds a predetermined ratio threshold, the mobile stations that exist in the area of the angle range are specified as one mobile station group. Item 4. The coverage control method according to any one of Items 1 to 3. In order to control the directivity of the transmission beam of the first frequency in the coverage control step,
The directivity of the transmission beam of the carrier of the first cell is controlled so as to be directed to a representative angle representing the distribution region of the mobile station group specified in the mobile station group specifying step. The coverage control method according to any one of 4 to 4. As the coverage control step,
A cell load measuring step of measuring a cell load of each of the first cell and the second cell;
In the coverage control step, as a measurement result of the cell load in the cell load measurement step, the cell load of the first cell is smaller than a predetermined difference threshold compared to the cell load of the second cell. The directivity of the transmission beam of the first frequency is controlled, and the operation of controlling the coverage of the first cell with respect to the mobile station group specified in the mobile station group specifying step is performed. The coverage control method according to claim 1, wherein: At least one first cell that uses a first frequency as a carrier, at least one second cell that uses a second frequency lower than the first frequency as a carrier, a base station device, Directivity for controlling directivity of a transmission beam of the first frequency or the second frequency in a wireless communication system including a mobile station that communicates with at least one of the first cell and the second cell. A sex control method,
A mobile station distribution estimation step for estimating a distribution of the mobile stations in the first cell and the second cell;
A mobile station communication state measurement step for measuring a communication state of the mobile station;
1 including the mobile stations distributed in the second cell based on the distribution of the mobile stations estimated in the mobile station distribution estimation step and the communication state of the mobile stations measured in the mobile station communication state measurement step. A mobile station group specifying step for specifying a mobile station group composed of more than one mobile station;
A directivity control step for controlling directivity of the transmission beam of the first frequency with respect to the mobile station group specified in the mobile station group specifying step. At least one first cell using a first frequency as a carrier, at least one second cell using a second frequency lower than the first frequency as a carrier, and the first cell; And a mobile station that communicates with at least one cell of the second cell, and a base station apparatus in a wireless communication system,
Mobile station distribution estimation means for estimating a distribution of the mobile stations in the first cell and the second cell;
Mobile station communication state measuring means for measuring a communication state with the mobile station;
Including the mobile stations distributed in the second cell based on the distribution of the mobile stations estimated by the mobile station distribution estimation unit and the communication state with the mobile station measured by the mobile station communication state measurement unit Mobile station group specifying means for specifying a mobile station group composed of one or more mobile stations;
Coverage control means for controlling the directivity of the transmission beam of the first frequency to control the coverage of the first cell for the mobile station group specified by the mobile station group specifying means; Base station equipment. At least one first cell that uses a first frequency as a carrier, at least one second cell that uses a second frequency lower than the first frequency as a carrier, a base station device, A wireless communication system including a mobile station that communicates with at least one of the first cell and the second cell,
Mobile station distribution estimation means for estimating a distribution of the mobile stations in the first cell and the second cell;
Mobile station communication state measuring means for measuring a communication state between the mobile station and the base station device;
Based on the distribution of the mobile station estimated by the mobile station distribution estimation means and the communication state between the mobile station and the base station apparatus measured by the mobile station communication state measurement means, the distribution is made to the second cell. Mobile station group specifying means for specifying a mobile station group composed of one or more mobile stations including the mobile station;
Coverage control means for controlling the directivity of the transmission beam of the first frequency to control the coverage of the first cell for the mobile station group specified by the mobile station group specifying means; Wireless communication system. At least one first cell that uses a first frequency as a carrier, at least one second cell that uses a second frequency lower than the first frequency as a carrier, a base station device, In a wireless communication system including a mobile station that communicates with at least one of the first cell and the second cell, a base station control program executed as a computer control program installed in the base station apparatus A non-transitory computer readable medium for storing
A mobile station distribution estimation process for estimating a distribution of the mobile stations in the first cell and the second cell;
A mobile station communication state measurement process for measuring a communication state between the mobile station and the base station device;
Based on the distribution of the mobile stations estimated in the mobile station distribution estimation process and the communication state between the mobile station and the base station apparatus measured in the mobile station communication state measurement process, the distribution is performed in the second cell. A mobile station group specifying process for specifying a mobile station group including one or more mobile stations including the mobile station;
And a coverage control process for controlling the directivity of the transmission beam of the first frequency to control the coverage of the first cell for the mobile station group specified in the mobile station group specifying process. A non-transitory computer-readable medium storing a base station control program to be executed.

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