JPWO2014136739A1 - Wireless communication system, control device, control method, and program - Google Patents

Abstract

An object of the present invention is to make it possible to optimize the coverage of a radio cell while suppressing the occurrence of a weak electric area and a dead zone associated with a change in antenna tilt angle based on a measurement result of radio quality from a radio terminal. That is. The present invention is an invention for controlling antenna parameters of a radio cell managed by a radio base station, based on measurement information on radio quality or radio communication status reported by a radio terminal capable of communicating with the radio base station, Estimating means for estimating the degree of change in the received signal strength of the signal from the radio base station after the change in the antenna tilt angle of the radio base station, and the antenna tilt angle based on the estimated degree of change in the received signal strength Control means for controlling.

Description

  The present invention relates to a wireless communication system, a control device, a control method, and a program.

  Generally, in a wireless communication system such as a cellular system, a wireless terminal communicates within a wireless cell managed by each installed wireless base station. Here, when a wireless terminal moves across a plurality of wireless cells, it is necessary to partially overlap the coverage of adjacent wireless cells in order to continue communication. Here, the coverage is a cover area where a wireless quality sufficient for the wireless terminal to perform communication is maintained. As a technique for adjusting the coverage, for example, a method using the antenna tilt angle of each wireless cell is conceivable. However, in general, it is necessary to be careful in coverage adjustment using the antenna tilt angle, and if an incorrect setting is made, it may cause a big problem.

  For example, when the antenna tilt angle between adjacent wireless cells is too large (too deep), a place where the coverage overlap area becomes insufficient occurs, and the handover quality of the wireless terminal moving between the cells deteriorates. Problems arise. In addition, an area with insufficient coverage occurs around the boundary between the cells, and communication of wireless terminals existing in the area may be disconnected or communication quality may deteriorate. Such an area with insufficient coverage is referred to as a weak power area, and an area where communication disconnection occurs is particularly referred to as a dead zone.

  On the other hand, when the antenna tilt angle between adjacent wireless cells is too small (too shallow), the area where the coverage overlaps becomes excessive, and the wireless terminal interferes with a signal from a wireless cell other than the staying wireless cell. And the communication quality (for example, throughput) deteriorates.

  Therefore, in the cellular system, it is necessary to appropriately set the antenna tilt angle of each radio cell so that good communication quality can be obtained without generating such a low power area or dead zone.

  In an environment where there are no terrain undulations or buildings, and base stations are laid uniformly, the coverage of each wireless cell is uniform, and the adjustment of the antenna tilt angle is relatively easy. However, in an actual environment, the coverage of a radio cell has a complicated shape due to the influence of topography and buildings of various sizes and due to location restrictions in laying radio base stations. For this reason, the above-described coverage adjustment of the radio cell is performed by a drive test using a radio wave measurement vehicle and a careful adjustment work of radio parameters by a skilled engineer, and a large operation cost is required.

In view of this, a technique for autonomously adjusting the antenna tilt angle of each wireless cell has been proposed for the purpose of reducing the cost for setting the antenna tilt angle. For example, in Patent Document 1, candidate values for antenna tilt angles of radio cells are set, and these are sequentially applied to actual radio cells. And a control method for measuring an uplink (uplink) interference at a radio base station and selecting an appropriate antenna tilt angle.
Patent No. 4220611

  In the above technique, since the candidate value of the antenna tilt angle is applied to an actual radio cell, the coverage may be insufficient depending on the candidate value, which may cause a weak electric area or a dead zone. In general, since the measurement information of the wireless terminal is collected from an area where communication is possible, in particular, there may be a case where a dead area once generated cannot be detected. For this reason, there is a possibility that the antenna tilt angle at which the dead zone actually occurs is selected. Therefore, it is necessary to control the antenna tilt angle autonomously so as to appropriately adjust the coverage while suppressing the occurrence of a low power area and a dead area.

  Therefore, the problem to be solved by the present invention is to solve the above-mentioned problems, and to suppress the generation of weak electric areas and dead areas accompanying the control of the antenna tilt angle.

  The present invention provides the following radio communication system, radio base station, and radio parameter control method in order to solve the above problems.

  The present invention is a radio communication system for controlling antenna parameters of radio cells managed by a radio base station, based on measurement information on radio quality or radio communication status reported by radio terminals that can communicate with the radio base station. , An estimation means for estimating a change level of the reception strength of the signal from the radio base station after the change of the antenna tilt angle of the radio base station, and the antenna tilt angle based on the estimated change level of the reception strength. Control means for controlling.

  The present invention is a control device for controlling antenna parameters of a radio cell managed by a radio base station, based on measurement information related to radio quality or radio communication status reported by a radio terminal capable of communicating with the radio base station, Estimating means for estimating a change level of the reception intensity of the signal from the radio base station after changing the antenna tilt angle of the radio base station, and controlling the antenna tilt angle based on the estimated change degree of the reception intensity Control means.

  The present invention is a control method for controlling antenna parameters of a radio cell managed by a radio base station, based on measurement information related to radio quality or radio communication status reported by a radio terminal capable of communicating with the radio base station, An estimation step for estimating the degree of change in the reception strength of the signal from the radio base station after the change in the antenna tilt angle of the radio base station, and the antenna tilt angle is controlled based on the degree of change in the estimated reception strength A control step.

  The present invention relates to a program for a control device that controls antenna parameters of a radio cell managed by a radio base station, and the program reports radio quality reported by a radio terminal capable of communicating with the radio base station. Alternatively, based on measurement information related to a radio communication state, an estimation unit that estimates a degree of change in reception intensity of a signal from the radio base station after changing an antenna tilt angle of the radio base station, and a change in the estimated reception intensity It functions as a control means for controlling the antenna tilt angle based on the degree.

  According to the present invention, it is possible to adjust the coverage of a radio cell while suppressing the generation of a weak electric area and a dead zone accompanying the change of the antenna tilt angle as much as possible. The reason is to determine whether or not the antenna tilt angle can be changed by estimating whether or not sufficient received signal strength can be obtained after changing the antenna tilt angle based on the measurement result of the wireless quality from the wireless terminal. .

It is a block diagram of the radio | wireless communications system in this invention. It is a figure which shows the structure of the wireless base station in this invention. It is a figure which shows the example of the content of the base station information table which the base station information storage device in this invention hold | maintains. It is a figure which shows the example of the content of the measurement information table from the radio | wireless terminal in this invention. It is a figure which shows the operation | movement flow of the received signal strength estimation part in this invention. It is a schematic diagram about the estimation method of the maximum variation | change_quantity of the received signal strength using the antenna gain pattern in this invention. It is a figure which shows the example of the content of the extraction information table in this invention. It is a figure which shows the operation | movement flow of the antenna parameter control determination part in this invention. It is a figure for demonstrating an example in 2nd Embodiment. It is a figure for demonstrating an example in 3rd Embodiment.

  The basic principle of the present invention is that wireless base stations or network operation management devices (also called SON (Self Organizing Network) servers) measure information related to wireless quality or wireless communication status reported by wireless terminals that can communicate with the wireless base station. On the basis of the antenna tilt angle of the radio base station, the degree of change in the reception strength of the signal transmitted by the radio base station is estimated, and the antenna tilt angle is controlled based on the estimated degree of change. is there.

  In controlling the antenna tilt angle, control is started after determining whether or not to change the antenna tilt angle before the control. As this determination method, the coverage change rate is calculated based on the estimated change level of the received strength, and it is determined whether the antenna tilt angle is controlled based on whether the coverage change rate is less than a predetermined coverage change rate. A method is conceivable. Here, as the coverage change rate, for example, the area rate at which the reception intensity of the signal transmitted by the radio base station is less than the required quality, or the area rate at which communication is impossible, is considered, and the coverage change rate (in this case, The antenna tilt angle is changed when the coverage deterioration rate is less than a predetermined coverage change rate. Further, the degree of change in reception strength is estimated by at least one of the antenna tilt angle, the antenna height, the antenna gain pattern, or the expected angle to the cell edge of the radio base station that manages the radio cell to be controlled by the antenna tilt angle. Use one. In addition, as the degree of change in the reception strength, the amount of change in reception strength or the maximum amount of change accompanying the change in antenna tilt angle is used. Note that the amount of change and the rate of change can be considered as the degree of change. Hereinafter, as an example of a wireless communication system, a 3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution) system will be described. However, GSM (Global System for Mobile communications: a registered trademark), UMTS (Universal Mobile Telecommunications System), CDMA2000 (Code Division Multiple Access 2000) and its development system (1xRTT, HRPD), WiMAX (Worldwide interoperability for Microwave Access), etc. Other communication systems may be used.

  Details of the present invention will be described below with reference to the drawings.

<First embodiment>
FIG. 1 shows the configuration of a wireless communication system as an embodiment of the present invention. The wireless communication system includes an external network 100, a core network 101, a wireless access network 102, a network management device 103, wireless base stations 120 and 121, and wireless terminals 130 to 132. The external network 100 and the core network 101 are connected to each other via a wired link 110, and the core network 101 and the wireless access network 102 are connected to each other via a wired link 111.

  The network management apparatus 103 is connected to the core network 101 via the wired link 113, and is connected to the wireless access network 102 via the wired link 112, manages the communication state of both networks, and performs maintenance and operation.

  The radio base stations 120 and 121 manage the radio cells 140 and 141, respectively. The radio terminals 130, 131, and 132 have radio links with the radio base stations 120 and 121 that manage the radio cells 140 and 141 to which the radio terminals are connected. Communicate through. In addition, although it demonstrates using the structure which has two of the wireless base stations 120 and 121, it is not necessary to limit the number in this invention.

  The wireless terminals 130, 131, and 132 have a wireless quality measurement function, and measure the wireless quality periodically or in response to an arbitrary measurement trigger. In addition, although it demonstrates using the structure which has the radio | wireless terminals 130-132, the number does not need to be limited in this invention.

  FIG. 2 shows an example of the configuration of network management apparatus 103 and radio base station 120 shown in FIG.

  The radio base station 120 includes a measurement control unit 211 and a transmission / reception unit 210.

  First, the measurement control unit 211 in the radio base station 120 collects radio quality measurement information from the radio terminal 132 using the transmission / reception unit 210 and notifies the network management apparatus 103 periodically or in accordance with an arbitrary trigger.

  Next, the network management apparatus 103 aggregates the measurement information notified from one or more radio base stations and stores it in the radio quality statistical information storage apparatus 201. Here, the measurement information of radio quality includes received power (RSRP: Reference Signal Received Power) of a reference signal from one or more radio base stations.

  Next, the received signal strength estimation unit 212 uses the antenna gain pattern to perform one or more of each of the one or more associated with the change of the antenna tilt angle in the radio cell (hereinafter referred to as the own cell) that is the object of antenna tilt angle control. The amount of change or the maximum amount of change in the reception strength of signals from the radio cell (here, RSRP is assumed) is estimated. Note that the change amount of the received signal strength or the estimated maximum change amount in the antenna tilt angle change candidate value includes the change history of one or more antenna tilt angles in the own cell and the measurement information corresponding to the history. You may use the estimated value obtained by the linear interpolation method using received signal strength. Further, the maximum change amount, the reception power and cell ID of the reference signal of the own cell and the radio cell adjacent to the own cell (hereinafter also referred to as an adjacent cell) included in the measurement result of the radio quality from the radio terminal 132. Based on this, the change degree of the received signal strength when the antenna tilt angle of the own cell is changed is estimated. In the following, the amount of change is assumed as the degree of change in received signal strength. Note that the reception strength is not necessarily RSRP, and may be another index such as RSSI (Received Signal Strength Indicator).

  Next, the antenna parameter control determination unit 213 calculates a coverage change rate based on the amount of change in received signal strength when the antenna tilt angle is changed, and determines whether the antenna change rate is less than a predetermined coverage change rate. It is determined whether or not to change the tilt angle. Here, as the coverage change rate, a coverage degradation rate that is an area rate at which the received signal strength is less than the required quality may be used. In this case, the antenna tilt angle is changed when the coverage degradation rate is less than the predetermined coverage degradation rate. To do. When the antenna tilt angle of the own cell is updated, the base station information storage device 200 is updated. Instead of estimating the maximum change amount of the received signal strength accompanying the change of the antenna tilt angle, the distribution of the received signal strength change amount is estimated, and a predetermined point of the distribution, for example, a cumulative distribution function (CDF: Cumulative Distributed) An arbitrary value of (Function) may be used instead of the maximum change amount.

  FIG. 3 shows the contents of the base station information 300 held by the base station information storage device 200.

  In this example, the station information 310 including the base station ID 301, the cell ID 302, and the installation point 303, the cell ID 302, the maximum transmission power 304, and the parameters including the antenna configuration 305 including the height, directivity pattern, azimuth angle, and elevation angle. Information 320 is defined. Here, the maximum transmission power 304 and the antenna configuration 305 are notified to the network management apparatus 103 when the setting values are changed. Similarly, operation information such as traffic load measured in each wireless cell per unit time is also notified to the network management apparatus 103.

  FIG. 4 shows the content of the measurement information 400 measured by the wireless terminal 132.

  In this example, Rank 401, RSRP value 402, and cell ID 403 are defined. The wireless terminal measures the RSRP of one or more wireless cells and reports it to the connected wireless base station. Based on the measurement information, the radio base station or the network management apparatus rearranges them by adding Ranks in descending order of the RSRP value, and associates them with the ID of the radio cell of the transmission source. Here, it is assumed that the wireless terminal is connected to the wireless cell X having the largest RSRP value. That is, the radio cell X corresponding to Rank # 1 is a Serving Cell, and the radio cells A to F corresponding to Rank # 2 to 7 after that are Neighbor Cells.

  Although the configuration of the embodiment has been described in detail above, the transmission / reception functions of radio base stations and radio terminals other than those described above are well known to those skilled in the art and are not directly related to the present invention. Is omitted.

<Description of operation>
First, the measurement control unit 211 operates as follows. The measurement control unit 211 in the radio base station 120 collects measurement information, which is information on radio quality or radio communication status, from radio terminals in communication in the radio cell 140 managed by the radio base station 120. Next, the collected measurement information is notified to the network management apparatus 103 periodically or according to an arbitrary trigger, and stored in the wireless quality statistical information storage apparatus 201.

  Next, the overall operation of the present embodiment will be described in detail with reference to FIGS. Note that the operation described below is performed for one or more candidate values of the antenna tilt angle. When actually changing the antenna tilt angle, it was determined that the antenna tilt angle can be changed. This is performed by selecting one of the candidate values.

  In FIG. 5, the received signal strength estimation unit 212 operates as follows. When a predetermined time has elapsed or sufficient measurement information has been collected, the received signal strength estimation unit 212 starts an estimation process. First, measurement information collected from a wireless terminal is acquired from the wireless quality statistical information storage device 201 (step S101), and the total number of collected measurement information is counted (step S102).

  Next, the distance to the cell edge 511 of the own cell is estimated (step S103). Here, the distance to the cell edge 511 of the own cell is estimated using the installation point 303 and the antenna configuration 305 in the base station information regarding the radio base stations of the own cell and the adjacent cells. For example, when the maximum transmission power, altitude, antenna height 512, and elevation angle of the own cell and adjacent cells are equal, the distance to the midpoint between the two cells may be used. Further, it may be obtained by utilizing actual measurement data obtained from a drive test or the like that can grasp the position of measurement information. In this case, the radio base station may execute processing associated with control of the antenna tilt angle. good.

  Next, using the distance to the cell edge and the antenna height 512 of the own cell, a prospective angle 513 to the cell edge is calculated (step S104). In general, the amount of change in the received signal strength associated with the downtilt is the largest at the cell edge 511, and therefore, the estimated angle 513 toward the cell edge is used here for estimating the maximum amount of change Δ520 in the received signal strength.

  Next, based on the antenna gain pattern at the current antenna tilt angle and the changed antenna tilt angle and the expected angle 513 toward the cell edge, the maximum change amount Δ520 of the received signal strength due to the change in the antenna tilt angle is estimated (step). S105).

  Here, FIG. 6 shows a schematic diagram of a method for estimating the maximum change amount of the received signal intensity using the antenna gain pattern. In FIG. 6, an antenna gain pattern (before change) 500 (dotted line portion) indicates an antenna gain pattern before the antenna tilt angle is changed, and an antenna gain pattern (after change) 501 (solid line portion) is the antenna gain pattern after change. Is shown. Here, the difference in antenna gain before and after the change is the largest at the cell end 511 of the radio cell 140, and the difference corresponds to the maximum change amount Δ520 of the received signal strength.

For example, when Antenna pattern (vertical) described in Table A.2.1.1.1-2 of Non-Patent Document 1 (3GPP TS36.814 V9.0.0) is used, it can be estimated from Equation 1. . In Equation 1, H _ant is the antenna height, D _edge is the distance from the antenna to the cell edge, θ _ant is the antenna tilt angle after change, θ _pre is the antenna tilt angle before change, θ _{3 dB} is the 3 dB beam width of the antenna, and Atn () is an arctangent function.

  Then, using the estimated maximum change amount of the received signal strength, for example, measurement information of a terminal that is expected to deteriorate in radio quality due to a change in antenna tilt angle of a terminal or the like at the cell edge is extracted. Specifically, the RSRP value of the own cell when the antenna tilt angle of the own cell is changed is less than the required quality necessary for satisfying the desired radio quality, and the RSRP value of the neighboring cell. Measurement information that is less than the RSRP value indicating the largest value is extracted (step S106). The extracted information includes the RSRP value of the own cell and the RSRP value of the neighboring cell indicating the largest value. Here, the RSRP value of the neighboring cell is extracted because the radio terminal that is expected to switch the connection to the neighboring cell by changing the antenna tilt angle can maintain sufficient radio quality after switching the connection. This is to determine whether or not.

  FIG. 7 shows an example of the contents of the extracted information. In this example, from the measurement information 410 of the wireless terminal 1 and the measurement information 420 of the wireless terminal 2, the RSRP value of the Serving Cell X and the RSRP values of the Cell A and Cell C indicating the largest RSRP value in the Neighbor Cell (Pal , Pc2). The RSRP value of Serving Cell X in the extracted information 600 reflects the maximum change amount Δ520 of the received signal strength estimated in step S105 (that is, a value obtained by subtracting Δ), and Px1-Δ and Px2-Δ are It is assumed that the quality is less than the required quality, or is less than Pal and Pc2, respectively.

  Next, in FIG. 8, the antenna parameter control determination unit 213 operates as follows. First, the reception signal strength of the own cell after changing the antenna tilt angle estimated from the reception signal strength estimation unit 212 (here, RSRP is assumed) and the extraction information of the reception signal strength of the adjacent cell are acquired (step S201).

  Next, the extracted information is selected one by one, and the RSRP value of the own cell after changing the antenna tilt angle is compared with the RSRP value of the neighboring cell, but first, is there an unselected (unselected) received signal strength? It is determined whether or not (step S202). If there is an unselected received signal strength (step 202: Yes), one of them is selected (step S203). Then, the RSRP value of the own cell after the antenna tilt angle change is compared with the RSRP value of the adjacent cell (step S204). If the RSRP value of the own cell is large (step S204: Yes), the RSRP value of the own cell is changed. The required quality is compared (step S205). Here, when the RSRP value of the own cell is less than the required quality (step S205: No), it is counted as the coverage deterioration number (step S207). If the RSRP value of the neighboring cell is larger than the RSRP value of the own cell in step S204 (step S204: No), the RSRP value of the neighboring cell is compared with the required quality (step S206). Similarly, if the RSRP value of the adjacent cell is less than the required quality, it is counted as the coverage deterioration number (step S207).

  On the other hand, when selection of all the extracted information is completed (step 202: No), the ratio of the coverage deterioration number to the total number of measurement information is calculated as the coverage deterioration rate (step S208). Next, the calculated coverage deterioration rate is compared with a predetermined coverage change rate (step S209). Here, when the coverage deterioration rate is less than the predetermined coverage change rate (step S209: Yes), the antenna tilt angle can be changed (step S210). On the other hand, when the coverage deterioration rate is equal to or higher than the predetermined coverage change rate (step S209: No), the change of the antenna tilt angle is denied (step S211).

  In addition, when the weak electric area or the place where the dead zone is generated is specified and the antenna tilt angle of the surrounding wireless cell is changed, the amount of change of the antenna tilt angle can be set using this embodiment. calculate. The basic operation is the same as the operation described with reference to FIGS. 5 to 8 except that the expected angle to the weak electric area or the dead area is used instead of the expected angle 513 to the cell edge. Thus, the maximum change amount of the received signal strength at one or more candidate antenna tilt angles is estimated. First, based on the antenna azimuth angle of each radio cell, a radio cell including the weak power area or the dead zone is extracted within a predetermined horizontal angle range from the antenna azimuth angle. Note that the following processing may be performed by extracting again a wireless cell whose distance between the extracted wireless cell and the weak power area or the dead zone is within a predetermined value. Next, for the extracted wireless cell, the distance attenuation amount of the received signal strength is estimated based on the distance from the weak power area or the dead zone. Here, a generally known radio wave propagation model is used for estimating the distance attenuation. Next, the maximum change amount of the received signal strength at one or more candidate antenna tilt angle values is estimated using the antenna gain pattern and the expected angle to the weak power area or the dead zone. Next, the received signal strength in the weak power area or the dead zone is calculated from the estimated distance attenuation amount, the maximum change amount of the received signal strength, and the transmission power value of the wireless cell. Further, by comparing the calculated received signal strength with the required value, a change value of the antenna tilt angle necessary for eliminating the low power area or the dead zone is calculated.

  Next, the effect of this embodiment will be described. In the present embodiment, the maximum change amount of the received signal strength accompanying the change of the antenna tilt angle is estimated based on the measurement information of the radio quality collected from the radio terminal and the base station information. Further, the coverage deterioration rate after changing the antenna tilt angle is estimated using the maximum change amount of the received signal strength, and whether or not the antenna tilt angle can be changed is determined. Thereby, it is possible to optimize the coverage while suppressing the generation of the weak electric area and the dead area due to the change of the antenna tilt angle.

  Another effect of the present embodiment will be described. By using the estimation process of the received signal strength in the present embodiment, for example, the occurrence location of the weak power area is specified, and when the response is made by changing the antenna tilt angle of the surrounding wireless cell, the corresponding weak power area is entered. From the expected angle and the antenna gain pattern, it is possible to estimate the amount of change in the antenna tilt angle necessary for eliminating the low power area. Based on the change amount of the antenna tilt angle, by selecting an appropriate radio cell and changing the antenna tilt angle, it is possible to contribute to improving the radio quality as a result.

  In the above description, it is assumed that the network management apparatus performs all the processes associated with the control of the antenna tilt angle. However, the radio base station may execute the processes associated with the control of the antenna tilt angle. In the case of such a configuration, there is an effect that signaling in collecting measurement results of radio quality from radio terminals is reduced.

(Second Embodiment)
Next, the best mode for carrying out the second invention of the present invention will be described in detail.

  The basic configuration of the second embodiment is the same as that of the first embodiment. Further, the basic operation is the same as in FIG. 5 and FIG. 8 in the first embodiment, but excludes all measurement information including wireless cells belonging to the same wireless base station in the Neighbor Cell. Specifically, in step S106 described in FIG. 5, information including IDs of other radio cells belonging to the same radio base station as the own cell is excluded, and other information belonging to other radio base stations different from the Serving Cell Measurement information indicating the maximum received signal strength among the received signal strengths of signals from the radio cell is extracted. This is because the change of the received signal strength due to the change of the antenna azimuth is dominant at the cell boundary with other radio cells belonging to the same radio base station, and the change of the received signal strength due to the change of the antenna tilt angle is small. It is because it is considered. As an example, FIG. 9 shows an example of extracted information when X, A, and C belong to the same radio base station.

  Further, in addition to the information including the ID of the radio cell belonging to the same radio base station, the information including the ID of another radio cell located outside the range of the predetermined horizontal angle from the antenna azimuth angle of the own cell in the Neighbor Cell ID May be excluded. That is, the received signal strength of a signal from a wireless cell existing within a predetermined horizontal angle may be calculated with reference to the antenna azimuth angle of the own cell, and measurement information indicating the highest received signal strength may be extracted. .

  Next, the effect of this embodiment will be described. In this embodiment, the extraction information is generated from the measurement information at the cell edge where the amount of change in the received signal strength due to the downtilt of the own cell is the largest, so the coverage degradation rate after changing the antenna tilt angle is more accurately determined. Can be estimated. As a result, it is possible to adjust the coverage without greatly degrading the radio quality in the radio terminal in the radio cell.

  Another effect of the present embodiment will be described. By limiting the extracted information in the present embodiment, the amount of information can be reduced. As a result, the present invention can be realized with a realistic processing amount even in a radio cell covering a high traffic area where a large amount of measurement information is collected or in a radio cell covering a wide area.

<Third embodiment>
Next, a third embodiment of the present invention will be described in detail.

  The basic configuration of the third embodiment is the same as that of the first embodiment. Further, the basic operation is the same as in FIG. 5 and FIG. 8 in the first embodiment, but after changing the antenna tilt angle of the own cell, the number of wireless terminals that switch connection to another adjacent wireless cell is estimated. The load of the own cell and the neighboring cell is estimated. Specifically, in step S203 described in FIG. 8, the ratio of terminals that switch the connection to the neighboring cell from the total number of measurement information by counting measurement information in which the RSRP value of the own cell is less than the RSRP value of the neighboring cell, or The number is estimated, and the load amount of the adjacent cell when the antenna tilt angle is changed is estimated based on the load information of the own cell and the adjacent cell. Then, when the estimated load on the adjacent cell is less than the predetermined load amount, the antenna tilt angle is changed. FIG. 10 shows an example of the ratio of wireless terminals that switch connections to adjacent cells when the antenna tilt angle of the wireless cell X is changed. In this example, when the antenna tilt angle of the wireless cell X is changed, 15% of the load of the wireless cell X is transferred to the adjacent wireless cell A. If 15% of the load of the radio cell X is allowable in the cell A (that is, less than a predetermined load amount), and a part of the load of the radio cell X can be allowed in other radio cells as well. The antenna tilt angle of the wireless cell X is changed.

  Next, the effect of this embodiment will be described. In the present embodiment, when the antenna tilt angle is changed based on the radio quality measurement information collected from the radio terminals and the base station information, the ratio or the number of radio terminals that switch the connection from the own cell to the adjacent cell is calculated. Estimated. Further, the load amount of the adjacent cell after changing the antenna tilt angle is estimated from the estimated value and the load of the own cell and the adjacent cell, and whether or not the antenna tilt angle can be changed is determined. Thereby, it is possible to suppress the occurrence of congestion in the adjacent cell due to the change of the antenna tilt angle of the own cell.

  As an application example of the present invention, in a wireless communication system, the present invention can be applied to applications such as a wireless base station or a network management device that controls an antenna tilt angle based on measurement information of a wireless terminal.

  In addition, as a second application example of the present invention, when the location of a weak power area and a dead area by a drive test or the like is made, or when a weak power area occurs due to a failure of a wireless base station or a power failure, The present invention can be applied to applications such as coverage adjustment in surrounding radio base stations.

(Appendix 1)
A wireless communication system for controlling antenna parameters of a wireless cell managed by a wireless base station,
Based on measurement information related to radio quality or radio communication state reported by a radio terminal capable of communicating with the radio base station, a change in signal reception intensity from the radio base station after changing the antenna tilt angle of the radio base station An estimation means for estimating the degree;
A wireless communication system comprising: control means for controlling the antenna tilt angle based on the estimated degree of change in received intensity.

(Appendix 2)
The control means calculates a coverage change rate of the radio base station based on the degree of change estimated by the estimation means, and calculates the antenna tilt angle based on the calculated coverage change rate and a predetermined coverage change rate. The wireless communication system according to supplementary note 1, wherein the wireless communication system is configured to control the antenna tilt angle when it is determined whether to control the antenna tilt angle.

(Appendix 3)
The control means calculates, as the coverage change rate, an area rate at which the received intensity of the signal from the radio base station is less than required quality, or a coverage deterioration rate that is an area rate at which communication is impossible, and the calculation The wireless communication system according to supplementary note 2, wherein the antenna tilt angle is changed when the coverage deterioration rate is less than a predetermined coverage change rate.

(Appendix 4)
The wireless communication according to any one of appendix 1 to appendix 3, wherein the estimation unit estimates the degree of change based on a change amount of an antenna gain after changing an antenna tilt angle of the radio base station and the measurement information. system.

(Appendix 5)
The estimation means uses at least one of the antenna tilt angle, the antenna height, the antenna gain pattern, and the expected angle to the cell edge of the radio base station, and the amount of change in reception intensity or the maximum with the change of the antenna tilt angle. The wireless communication system according to any one of appendix 1 to appendix 4, which estimates an amount of change.

(Appendix 6)
The estimation means estimates an antenna gain amount before control at the cell edge based on the antenna gain pattern using an antenna tilt angle before control of the radio base station and a prospective angle to the cell edge, and Using the antenna tilt angle after control of the base station and the estimated angle to the cell edge, the amount of antenna gain after control at the cell edge based on the antenna gain pattern is estimated, and the estimated before and after control The wireless communication system according to appendix 5, wherein the amount of change in reception strength at a cell edge, which is the maximum amount of change in reception strength, is estimated by comparing the amount of antenna gain of

(Appendix 7)
The estimation means estimates the signal reception strength of the cell when the antenna tilt angle of the radio base station is changed based on the maximum change amount of the reception strength, and the estimated reception strength is less than the required quality. The radio according to appendix 5 or appendix 6, wherein measurement information and measurement information whose estimated reception strength is lower than the maximum reception strength among the reception strengths of signals from adjacent radio base stations adjacent to the radio base station are extracted. Communications system.

(Appendix 8)
The control means compares the received quality of the signal from the radio base station when the antenna tilt angle of the radio base station is changed or the extracted received strength of the signal from the adjacent radio base station and the required quality. The wireless communication system according to appendix 7, wherein the coverage change rate is calculated, and the antenna tilt angle of the wireless base station is changed when the calculated coverage change rate is less than the predetermined coverage change rate.

(Appendix 9)
The control means calculates a reception strength of a signal from another radio base station different from the radio base station that manages a radio cell in which the radio terminal stays, and calculates the calculated reception strength and the required quality. The wireless communication system according to supplementary note 7 or supplementary note 8 to be compared.

(Appendix 10)
The control means calculates a reception strength of a signal from a radio base station existing within a predetermined horizontal angle on the basis of an antenna azimuth angle of the radio base station, and compares the calculated reception strength with the required quality. The wireless communication system according to any one of appendix 7 to appendix 9.

(Appendix 11)
The control means includes
Using the reception intensity of signals from the radio base station and at least one or more adjacent base stations and the maximum change amount of the reception intensity when the antenna tilt angle is changed, the antenna tilt angle is controlled after the control. Estimate the number of wireless terminals that switch connections to neighboring base stations,
Based on the load information of the radio base station and the adjacent base station, the antenna tilt angle is changed when the load of the radio base station and the adjacent base station after the control of the antenna tilt angle is less than a predetermined load amount. The wireless communication system according to any one of appendix 7 to appendix 10.

(Appendix 12)
The measurement information includes at least one of a reference signal received power (RSRP) that is a received power of a reference signal and a reference signal received quality (RSRQ) that is a received quality of the reference signal. The wireless communication system according to any one of Supplementary Note 1 to Supplementary Note 11, including:

(Appendix 13)
A control device for controlling antenna parameters of a radio cell managed by a radio base station,
Based on measurement information related to radio quality or radio communication state reported by a radio terminal capable of communicating with the radio base station, a change in signal reception intensity from the radio base station after changing the antenna tilt angle of the radio base station An estimation means for estimating the degree;
A control device comprising: control means for controlling the antenna tilt angle based on the estimated degree of change in received intensity.

(Appendix 14)
The control means calculates a coverage change rate of the radio base station based on the degree of change estimated by the estimation means, and calculates the antenna tilt angle based on the calculated coverage change rate and a predetermined coverage change rate. The control device according to supplementary note 13, which controls the antenna tilt angle when it is determined whether to control the antenna tilt angle.

(Appendix 15)
The control means calculates, as the coverage change rate, an area rate at which the received intensity of the signal from the radio base station is less than required quality, or a coverage deterioration rate that is an area rate at which communication is impossible, and the calculation 15. The control device according to supplementary note 14, wherein the antenna tilt angle is changed when the coverage deterioration rate is less than a predetermined coverage change rate.

(Appendix 16)
The control apparatus according to any one of appendix 13 to appendix 15, wherein the estimation means estimates the degree of change based on an amount of change in antenna gain after changing an antenna tilt angle of the radio base station and the measurement information. .

(Appendix 17)
The estimation means uses at least one of the antenna tilt angle, the antenna height, the antenna gain pattern, and the expected angle to the cell edge of the radio base station, and the amount of change in reception intensity or the maximum with the change of the antenna tilt angle. The control device according to any one of appendix 13 to appendix 16, which estimates a change amount.

(Appendix 18)
The estimation means estimates an antenna gain amount before control at the cell edge based on the antenna gain pattern using an antenna tilt angle before control of the radio base station and a prospective angle to the cell edge, and Using the antenna tilt angle after control of the base station and the estimated angle to the cell edge, the amount of antenna gain after control at the cell edge based on the antenna gain pattern is estimated, and the estimated before and after control 18. The control device according to appendix 17, wherein a change amount of the reception strength at the cell edge, which is a maximum change amount of the reception strength, is estimated by comparing the antenna gain amounts of the received antenna gains.

(Appendix 19)
The estimation means estimates the signal reception strength of the cell when the antenna tilt angle of the radio base station is changed based on the maximum change amount of the reception strength, and the estimated reception strength is less than the required quality. The control according to supplementary note 17 or supplementary note 18, wherein measurement information and measurement information whose estimated reception strength is lower than a maximum reception strength among reception strengths of signals from adjacent radio base stations adjacent to the radio base station are extracted. apparatus.

(Appendix 20)
The control means compares the received quality of the signal from the radio base station when the antenna tilt angle of the radio base station is changed or the extracted received strength of the signal from the adjacent radio base station and the required quality. The control apparatus according to supplementary note 19, wherein the coverage change rate is calculated, and the antenna tilt angle of the radio base station is changed when the calculated coverage change rate is less than the predetermined coverage change rate.

(Appendix 21)
The control means calculates a reception strength of a signal from another radio base station different from the radio base station that manages a radio cell in which the radio terminal stays, and calculates the calculated reception strength and the required quality. The control device according to supplementary note 19 or supplementary note 20 to be compared.

(Appendix 22)
The control means calculates a reception strength of a signal from a radio base station existing within a predetermined horizontal angle on the basis of an antenna azimuth angle of the radio base station, and compares the calculated reception strength with the required quality. The control device according to any one of appendix 19 to appendix 21.

(Appendix 23)
The control means includes
Using the reception intensity of signals from the radio base station and at least one or more adjacent base stations and the maximum change amount of the reception intensity when the antenna tilt angle is changed, the antenna tilt angle is controlled after the control. Estimate the number of wireless terminals that switch connections to neighboring base stations,
Based on the load information of the radio base station and the adjacent base station, the antenna tilt angle is changed when the load of the radio base station and the adjacent base station after the control of the antenna tilt angle is less than a predetermined load amount. The control device according to any one of appendix 19 to appendix 22.

(Appendix 24)
The measurement information includes at least one of a reference signal received power (RSRP: Reference Signal Received Power) that is a received power of a reference signal and a reference signal received quality (RSRQ: Reference Signal Received Quality) that is a received quality of the reference signal. The control device according to any one of appendix 13 to appendix 23, including:

(Appendix 25)
A control method for controlling antenna parameters of a radio cell managed by a radio base station,
Based on measurement information related to radio quality or radio communication state reported by a radio terminal capable of communicating with the radio base station, a change in signal reception intensity from the radio base station after changing the antenna tilt angle of the radio base station An estimation step for estimating the degree;
And a control step of controlling the antenna tilt angle based on the estimated degree of change in received intensity.

(Appendix 26)
The control step calculates a coverage change rate of the radio base station based on the degree of change estimated in the estimation step, and based on the calculated coverage change rate and a predetermined coverage change rate, the antenna tilt angle 26. The control method according to appendix 25, wherein the antenna tilt angle is controlled when it is determined whether to control the antenna tilt angle in the estimation step.

(Appendix 27)
The control step calculates, as the coverage change rate, an area rate at which the received intensity of a signal from the radio base station is less than a required quality, or a coverage deterioration rate that is an area rate at which communication is impossible, 27. The control method according to appendix 26, wherein the antenna tilt angle is changed when the coverage deterioration rate is less than a predetermined coverage change rate.

(Appendix 28)
28. The control method according to any one of appendix 25 to appendix 27, wherein the estimating step estimates the degree of change based on a change amount of an antenna gain after changing an antenna tilt angle of the radio base station and the measurement information. .

(Appendix 29)
The estimation step uses at least one of the antenna tilt angle, the antenna height, the antenna gain pattern, and the expected angle to the cell edge of the radio base station, and the received intensity change amount or the maximum with the change of the antenna tilt angle. The control method according to any one of appendix 25 to appendix 28, wherein the amount of change is estimated.

(Appendix 30)
The estimation step estimates an antenna gain amount before control at the cell edge based on the antenna gain pattern using an antenna tilt angle before control of the radio base station and a prospective angle to the cell edge, and Using the antenna tilt angle after control of the base station and the estimated angle to the cell edge, the amount of antenna gain after control at the cell edge based on the antenna gain pattern is estimated, and the estimated before and after control The control method according to supplementary note 29, wherein the amount of change in reception strength at the cell edge, which is the maximum amount of change in reception strength, is estimated by comparing the amount of antenna gain of each.

(Appendix 31)
The estimation step estimates the signal reception strength of the cell when the antenna tilt angle of the radio base station is changed based on the maximum change amount of the reception strength, and the estimated reception strength is less than the required quality. The control according to supplementary note 29 or supplementary note 30, wherein measurement information and measurement information whose estimated reception strength is lower than a maximum reception strength among reception strengths of signals from adjacent radio base stations adjacent to the radio base station are extracted. Method.

(Appendix 32)
The control step compares the required quality with the received strength of the signal from the radio base station or the extracted received strength of the signal from the adjacent radio base station when the antenna tilt angle of the radio base station is changed. The control method according to supplementary note 31, wherein the coverage change rate is calculated, and the antenna tilt angle of the radio base station is changed when the calculated coverage change rate is less than the predetermined coverage change rate.

(Appendix 33)
The control step calculates a reception strength of a signal from another radio base station different from the radio base station that manages a radio cell in which the radio terminal stays, and calculates the calculated reception strength and the required quality. The control method according to Supplementary Note 31 or Supplementary Note 32 to be compared.

(Appendix 34)
The control step calculates a reception strength of a signal from a radio base station existing within a predetermined horizontal angle with reference to an antenna azimuth angle of the radio base station,
The control method according to any one of Supplementary Note 31 to Supplementary Note 33, wherein the control step compares the calculated received intensity with the required quality.

(Appendix 35)
The control step includes
Using the reception intensity of signals from the radio base station and at least one or more adjacent base stations and the maximum change amount of the reception intensity when the antenna tilt angle is changed, the antenna tilt angle is controlled after the control. Estimate the number of wireless terminals that switch connections to neighboring base stations,
Based on the load information of the radio base station and the adjacent base station, the antenna tilt angle is changed when the load of the radio base station and the adjacent base station after the control of the antenna tilt angle is less than a predetermined load amount. The control method according to any one of Supplementary Note 31 to Supplementary Note 34.

(Appendix 36)
The measurement information is at least one of a reference signal received power (RSRP) that is a received power of a reference signal and a reference signal received quality (RSRQ) that is a received quality of the reference signal. The control method according to any one of supplementary note 25 to supplementary note 35 including:

(Appendix 37)
A program of a control device that controls antenna parameters of a radio cell managed by a radio base station, the program controlling the control device,
Based on measurement information related to radio quality or radio communication state reported by a radio terminal capable of communicating with the radio base station, a change in signal reception intensity from the radio base station after changing the antenna tilt angle of the radio base station An estimation means for estimating the degree;
A program that functions as a control unit that controls the antenna tilt angle based on the estimated degree of change in reception intensity.

  This application claims the priority on the basis of Japanese application Japanese Patent Application No. 2013-042369 for which it applied on March 4, 2013, and takes in those the indications of all here.

DESCRIPTION OF SYMBOLS 100 External network 101 Core network 102 Wireless access network 103 Network management apparatus 110-113 Wired link 120-121 Wireless base station 130-132 Wireless terminal 140-141 Wireless cell
200 Base station information storage device 201 Radio quality statistical information storage device 210 Transmission / reception unit 211 Measurement control unit 212 Received signal strength estimation unit 213 Antenna parameter control determination unit 300 Base station information 301 Base station ID
302 Cell ID
303 Installation point 304 Maximum transmission power 305 Antenna configuration 310 Station location information 320 Parameter information 400 Measurement information 401 Rank
402 RSRP value 403 Cell ID
410 Measurement information 420 of wireless terminal 1 Measurement information 500 of wireless terminal 2 Antenna gain pattern (before change)
501 Antenna gain pattern (after change)
511 Cell edge 512 Antenna height 513 Expected angle 520 to cell edge Maximum change amount Δ of signal strength Δ
600 Extraction information 601 Serving Cell RSRP value 602 Serving Cell ID
603 Neighbor Cell RSRP value 604 Neighbor Cell ID
610 Extracted information example 700 when X, A, and C belong to the same base station Example of ratio of wireless terminals that switch connection to neighboring wireless cells when antenna tilt angle of wireless cell X is changed

Claims (10)

A wireless communication system for controlling antenna parameters of a wireless cell managed by a wireless base station,
Based on measurement information related to radio quality or radio communication state reported by a radio terminal capable of communicating with the radio base station, a change in signal reception intensity from the radio base station after changing the antenna tilt angle of the radio base station An estimation means for estimating the degree;
A wireless communication system comprising: control means for controlling the antenna tilt angle based on the estimated degree of change in received intensity. The control means calculates a coverage change rate of the radio base station based on the degree of change estimated by the estimation means, and calculates the antenna tilt angle based on the calculated coverage change rate and a predetermined coverage change rate. The wireless communication system according to claim 1, wherein it is determined whether to control the antenna tilt angle, and when it is determined to control the antenna tilt angle, the antenna tilt angle is controlled. The control means calculates, as the coverage change rate, an area rate at which the received intensity of the signal from the radio base station is less than required quality, or a coverage deterioration rate that is an area rate at which communication is impossible, and the calculation The wireless communication system according to claim 2, wherein the antenna tilt angle is changed when the coverage deterioration rate is less than a predetermined coverage change rate. The said estimation means estimates the said change degree based on the variation | change_quantity of the antenna gain after changing the antenna tilt angle of the said radio base station, and the said measurement information. Wireless communication system. The estimation means uses at least one of the antenna tilt angle, the antenna height, the antenna gain pattern, and the expected angle to the cell edge of the radio base station, and the amount of change in reception intensity or the maximum with the change of the antenna tilt angle. The wireless communication system according to claim 1, wherein the amount of change is estimated. The estimation means estimates an antenna gain amount before control at the cell edge based on the antenna gain pattern using an antenna tilt angle before control of the radio base station and a prospective angle to the cell edge, and Using the antenna tilt angle after control of the base station and the estimated angle to the cell edge, the amount of antenna gain after control at the cell edge based on the antenna gain pattern is estimated, and the estimated before and after control The wireless communication system according to claim 5, wherein the amount of change in reception strength at the cell edge, which is the maximum amount of change in reception strength, is estimated by comparing the amount of antenna gain of the received signal. The estimation means estimates the signal reception strength of the cell when the antenna tilt angle of the radio base station is changed based on the maximum change amount of the reception strength, and the estimated reception strength is less than the required quality. 7. The radio according to claim 5, wherein measurement information and measurement information whose estimated reception strength is less than a maximum reception strength are extracted from reception strengths of signals from adjacent radio base stations adjacent to the radio base station. Communications system. A control device for controlling antenna parameters of a radio cell managed by a radio base station,
Based on measurement information related to radio quality or radio communication state reported by a radio terminal capable of communicating with the radio base station, a change in signal reception intensity from the radio base station after changing the antenna tilt angle of the radio base station An estimation means for estimating the degree;
A control device comprising: control means for controlling the antenna tilt angle based on the estimated degree of change in received intensity. A control method for controlling antenna parameters of a radio cell managed by a radio base station,
Based on measurement information related to radio quality or radio communication state reported by a radio terminal capable of communicating with the radio base station, a change in signal reception intensity from the radio base station after changing the antenna tilt angle of the radio base station An estimation step for estimating the degree;
And a control step of controlling the antenna tilt angle based on the estimated degree of change in received intensity. A program of a control device that controls antenna parameters of a radio cell managed by a radio base station, wherein the program includes the control device,
Based on measurement information related to radio quality or radio communication state reported by a radio terminal capable of communicating with the radio base station, a change in signal reception intensity from the radio base station after changing the antenna tilt angle of the radio base station An estimation means for estimating the degree;
A program that functions as a control unit that controls the antenna tilt angle based on the estimated degree of change in reception intensity.

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