JP5928687B2 - Radio parameter control system, radio parameter control apparatus, radio base station, radio parameter control method, and program - Google Patents

Description

  The present invention relates to a radio parameter control system, a radio parameter control apparatus, a radio base station, a radio parameter control method, and a program.

  In a cellular radio communication network typified by a cellular phone, a wide service area is configured by distributing a plurality of radio base stations. Each radio base station forms a radio cell that is in a range where it can communicate with itself. Usually, about 1 to 6 radio cells are managed by one radio base station. In addition, by overlapping a part of the coverage between adjacent radio cells, communication can be continued by handover even when a radio terminal (User Equipment: UE) moves across the radio cells. .

  During the installation and operation of the radio base station, radio cell coverage optimization is performed for the purpose of reducing coverage areas and further improving UE communication quality, particularly throughput. In general, a running test using a dedicated measuring instrument is carried out locally. In the running test, radio wave reception power and interference status, abnormal disconnection of communication and handover failure, throughput, and the like are measured. Then, a place where the received power is insufficient (Week coverage), a place receiving strong interference (Pilot polarization), and the like are specified, and radio parameters are adjusted to solve these problems. As radio parameters to be adjusted, for example, antenna tilt angle, antenna azimuth angle, transmission power, and handover parameters of a radio cell are generally used.

  The optimization of the coverage of a wireless cell based on the above-described running test is accompanied by an increase in the operating cost of the wireless communication network because it involves manual measurement and wireless parameter tuning work. Therefore, in order to reduce the cost for optimizing the coverage of the radio cell, a technique for autonomously optimizing the coverage of the radio cell has been proposed.

  One technique for autonomously optimizing wireless communication network settings is SON (Self Organizing Network). SON is a technology that autonomously implements parameter setting and optimization of a wireless communication network that has been performed manually by analyzing quality measurement data collected from wireless terminals and wireless base stations. It is expected as a technology to reduce infrastructure CAPEX (Capital Expenditure) / OPEX (Operational Expenditure). One specific use mode of SON is CCO (Coverage and Capacity Optimization). This CCO collects measurement results of radio quality (for example, RSRP: Reference Signal Received Power, RSRQ: Reference Signal Received Quality, etc.) from the radio terminal, and radio parameters of the radio cell (eg, transmission power, antenna tilt angle, etc.) ) Is a technique for autonomously optimizing the coverage of a radio cell.

  Another technique is ICIC (Inter-Cell Interference Coordination). ICIC is a technique for avoiding interference by cooperating between base stations based on radio quality information reported from radio terminals to reduce transmission power and pause signal transmission.

  Furthermore, as another technique, there is a technique described in Patent Document 1. The technique of Patent Literature 1 is based on the assumption that radio quality measurement information is collected from a radio terminal connected to the own femto cell, and the transmission power of the own femto cell is changed using the collected radio quality measurement information. This is a technique for predicting the radio quality (communication quality) of the own femtocell and determining whether or not to change the transmission power of the own femtocell.

International Publication No. WO2009 / 023587 Pamphlet

  By the way, when the radio parameters such as the transmission power and the antenna tilt angle are changed with the change of the coverage of the radio cell, even if the radio terminal exists in the same place, the radio terminal before and after the change of the radio parameter is changed. There is a possibility that the wireless cell (serving cell) to which is connected will change.

  However, the technique of Patent Document 1 does not consider the change of the serving cell of the wireless terminal accompanying the change of the wireless parameter. For this reason, it is not possible to accurately evaluate the communication quality of the wireless terminal whose serving cell is switched by changing the wireless parameter, and as a result, the wireless parameter cannot be optimized.

  Furthermore, since only the communication quality of the radio cell to be controlled (control target radio cell) is considered, the change of the radio parameter of the control target radio cell causes the quality degradation of the radio cells existing around the control target radio cell. There was a fear.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a radio parameter control system and a radio parameter control apparatus that can optimize radio parameters when controlling radio parameters of a radio cell. It is to provide a radio base station, a radio parameter control method, and a program.

  The present invention is a radio parameter control system for controlling radio parameters of a radio cell using measurement information by a radio terminal, and assuming that the radio parameter of a control target radio cell has been changed, Predicting a connection destination change wireless terminal to be a radio cell other than the control target radio cell from the control target radio cell, and evaluating at least one or more of the connection destination change radio terminals for radio parameters of the control target radio cell A radio parameter control system comprising: an evaluation target radio terminal selection unit that selects the evaluation target radio terminal; and a radio parameter control unit that determines a radio parameter of the control target radio cell in consideration of the evaluation target radio terminal.

  The present invention is a radio parameter control apparatus for controlling radio parameters of a radio cell using measurement information by a radio terminal, and assuming that the radio parameter of a control target radio cell has been changed, Predicting a connection destination change wireless terminal to be a radio cell other than the control target radio cell from the control target radio cell, and evaluating at least one or more of the connection destination change radio terminals for radio parameters of the control target radio cell An evaluation target radio terminal selection unit that selects as an evaluation target radio terminal, and a radio parameter control unit that determines radio parameters of the control target radio cell in consideration of the evaluation target radio terminal.

  The present invention is a radio base station that controls radio parameters of a radio cell using measurement information by a radio terminal, and assuming that the radio parameter of the radio cell to be controlled has been changed, Predicting a connection destination change wireless terminal to be a radio cell other than the control target radio cell from the target radio cell, and evaluating at least one or more of the connection destination change radio terminals for radio parameters of the control target radio cell A radio base station comprising: an evaluation target radio terminal selection unit that selects as an evaluation target radio terminal; and a radio parameter control unit that determines radio parameters of the control target radio cell in consideration of the evaluation target radio terminal.

  The present invention is a radio parameter control method for controlling radio parameters of a radio cell using measurement information by a radio terminal, and assuming that the radio parameter of a control target radio cell is changed, Predicting a connection destination change wireless terminal to be a radio cell other than the control target radio cell from the control target radio cell, and evaluating at least one or more of the connection destination change radio terminals for radio parameters of the control target radio cell This is a radio parameter control method for selecting a radio parameter of the control target radio cell in consideration of the evaluation target radio terminal.

  The present invention is a program for controlling radio parameters of a radio cell using measurement information by a radio terminal, and assuming that the radio parameter of a control target radio cell is changed in a computer, Predicting a connection destination change radio terminal to be a radio cell other than the control target radio cell from a control target radio cell, and evaluating at least one or more of the connection destination change radio terminals for radio parameters of the control target radio cell A program for executing a process of selecting as an evaluation target radio terminal and a process of determining radio parameters of the control target radio cell in consideration of the evaluation target radio terminal.

  The present invention can optimize the radio parameter of the control target radio cell when controlling the radio parameter of the radio cell.

FIG. 1 is a diagram for explaining the outline of the present invention. FIG. 2 is a block diagram of the wireless parameter control system of the present invention. FIG. 3 is a configuration diagram of the wireless communication system according to the first embodiment. FIG. 4 is a block diagram of the wireless parameter control device 30. FIG. 5 is a flowchart of the wireless parameter control device 30. FIG. 6 is a flowchart of another example of the wireless parameter control device 30. FIG. 7 is a block diagram of a radio base station in the second embodiment.

  An outline of the present invention will be described.

  1 and 2 are diagrams for explaining the outline of the present invention.

  In the present invention, when it is assumed that a radio parameter of a radio cell for controlling a radio parameter (hereinafter referred to as a control target radio cell) is changed, a connection destination radio cell of a radio terminal having the control target radio cell as a serving cell is A connection destination change radio terminal that is a radio cell other than the control target radio cell is predicted, and at least one of the connection destination change radio terminals is selected as an evaluation target radio terminal for evaluating radio parameters of the control target radio cell. . Then, the radio parameter of the control target radio cell is determined in consideration of the evaluation target radio terminal.

  This will be specifically described with reference to FIG.

  In FIG. 1, a radio cell whose radio parameter is to be controlled (changed) is a control target radio cell 2. Here, the radio terminals that use the control target radio cell 2 as a serving cell are the radio terminals 1a to 1e. Next, as a radio parameter of the control target radio cell 2, for example, assuming that the transmission power is reduced, the radio cell coverage of the control target radio cell 2 changes, and the connection range of the control target radio cell 2 changes. Is predicted. Along with this, the connection destination radio cell of the radio terminal that uses the control target radio cell 2 as the serving cell is also changed depending on the location of the radio terminal.

  In FIG. 1, it is predicted that the connection destination radio cell of the radio terminal 1 a, the radio terminal 1 b, and the radio terminal 1 e serving as the control target radio cell 2 is changed to a radio cell 3 different from the control target radio cell 2. The wireless terminal 1a, the wireless terminal 1b, and the wireless terminal 1e are wireless terminals in which the connection destination wireless cell is a wireless cell other than the controlled wireless cell 2 when it is assumed that the wireless parameter of the controlled wireless cell 2 is changed. Such a wireless terminal is referred to as a connection destination change wireless terminal in the following description.

  On the other hand, the connection destination radio cell of the radio terminal 1c and the radio terminal 1d is the control target radio cell 2 without changing even if it is assumed that the transmission power is reduced. Such a wireless terminal is referred to as a connection destination maintaining wireless terminal in the following description.

  In the present invention, at least one of the connection destination changing radio terminals is selected as an evaluation target radio terminal for evaluating the radio parameter of the control target radio cell 2. Although the selection of the evaluation target wireless terminals, all of the connection destination changing wireless terminals may be selected as the evaluation target wireless terminals, or the connection target maintaining wireless terminals may be included in the evaluation target wireless terminals. That is, the selection method is not limited, and is determined within a range not departing from the present invention in a timely manner.

  Next, the wireless parameter control system of the present invention will be described with reference to the drawings.

  FIG. 2 is a block diagram of the wireless parameter control system of the present invention.

  The radio parameter control system of the present invention includes a radio terminal 10, an evaluation target radio terminal selection unit 11, and a radio parameter control unit 12. The wireless communication network 13 is a system that provides a wireless communication service to the wireless terminal 10 and includes a wireless base station, a wireless parameter control device, and the like. In the following description, the radio communication network 13 includes the evaluation target radio terminal selection unit 11 and the radio parameter control unit 12, but each unit may be in either the radio base station or the radio parameter control device.

  The wireless terminal 10 has a function of measuring measurement information, for example, wireless quality, based on an instruction from the wireless communication network 13, and transmits the wireless quality to the wireless communication network 13. Here, as an example of the radio quality measured by the radio terminal 10, in the case of LTE (Long Term Evolution), RSRP (Reference Signal Received Power) representing received power, RSRQ (Reference Signal Received Quality) representing received quality, SINR (Signal to Interference plus Noise Power Ratio) representing a signal-to-interference noise ratio, throughput, and similar information thereof.

  The evaluation target radio terminal selection unit 11 assumes that the radio parameter is changed to a candidate value without actually changing the radio parameter of the control target radio cell, and the connection of the radio terminal 10 that uses the control target radio cell as a serving cell. Predict the destination radio cell. Then, at least one or more of the connection destination change wireless terminals whose connection destination wireless cells are wireless cells other than the control target wireless cell are selected as evaluation target wireless terminals.

  The connection destination changing radio terminal performs prediction using the measurement information (radio quality) collected from the radio terminal 10 having the control target radio cell as a serving cell in the current radio parameter setting (before the radio parameter change). Specifically, the evaluation target radio terminal selection unit 11 assumes that the radio quality of each control target radio cell and surrounding radio cells collected as measurement information from the radio terminal 10 has changed the radio parameters of the control target radio cell. Predict how it will change. Of the predicted radio qualities for each radio cell, the radio cell with the highest radio quality is predicted as the connection destination radio cell of the radio terminal when it is assumed that the radio parameter of the control target radio cell is changed. Note that not only a radio cell with the highest radio quality but also a predetermined number of higher radio cells with higher radio quality may be included in the connected radio cell. If the predicted connection destination wireless cell is a wireless cell other than the control target wireless cell, the wireless terminal 10 is predicted to be a connection destination changed wireless terminal.

  The evaluation target wireless terminal selection unit 11 selects at least one of the predicted connection destination change wireless terminals as the evaluation target wireless terminal. As a method for selecting the evaluation target wireless terminals, all of the connection destination changing wireless terminals may be selected as evaluation target wireless terminals, or a part of them may be selected. Further, the connection destination maintaining wireless terminal may be included in the evaluation target wireless terminal.

  The radio parameter control unit 12 determines radio parameters in consideration of the evaluation target radio terminal selected by the evaluation target radio terminal selection unit 11. Specifically, for each wireless parameter candidate value, an evaluation target wireless terminal when it is assumed that the wireless parameter is changed to the candidate value is obtained, and the communication quality of the evaluation target wireless terminal is evaluated. Then, the wireless parameter is determined based on the communication quality evaluation result. For example, the throughput for each evaluation target wireless terminal when it is assumed that the wireless parameter is changed to each candidate value is obtained, and the wireless parameter is changed to a candidate value having the highest degree of improvement in throughput. In addition, when there are a plurality of candidate values in one wireless parameter, instead of selecting an evaluation target wireless terminal for each candidate value, a wireless terminal selected as an evaluation target wireless terminal in at least one candidate value It is also possible to use a common evaluation target wireless terminal among wireless parameter candidate values. In addition, when there are a plurality of types of radio parameters to be controlled (for example, the transmission power of the radio cell, the tilt angle of the antenna, the azimuth angle of the antenna, etc.), it is selected as an evaluation target radio terminal by controlling at least one radio parameter. The wireless terminal may be the evaluation target wireless terminal. In addition to the throughput described above, the communication quality of the evaluation target wireless terminal may be a handover failure rate, an abnormal disconnection rate, or wireless quality (reception power, reception quality, signal-to-interference noise ratio, etc.). Specific examples of the radio parameter include the maximum transmission power of the downlink signal of the radio cell, the transmission power of the pilot signal and the reference signal, the antenna tilt angle, or the antenna azimuth angle. In addition, CIO (Cell Individual Offset) or Qoffset may be used as the wireless parameter.

  In addition, the communication quality of all evaluation target wireless terminals may be evaluated equally, but the measurement information of the connection destination change wireless terminal or the measurement information of the connection destination maintenance wireless terminal is weighted and weighted. Communication quality may be evaluated based on the measurement information. For example, it is considered that the connection destination changing radio terminal exists near the boundary (cell edge) between the control target radio cell and the surrounding radio cell. Even if the radio terminal at the cell edge does not change the radio parameters of the radio cell and the radio terminal exists at the same location, the serving cell changes due to the influence of radio wave fluctuation due to shadowing or the like. Cheap. Therefore, measurement information is less likely to be collected than a wireless terminal that exists near the center of the control target wireless cell, for example, a connection destination maintaining wireless terminal. Therefore, weighting is performed so that the measurement information of the connection destination changing wireless terminal is emphasized so that the measurement information of the wireless terminal existing at the cell edge is not neglected, and the communication quality is evaluated based on the weighted measurement information. .

  As described above, when assuming that the radio parameter of the control target radio cell is changed, the present invention predicts a connection destination change radio terminal in which the serving cell becomes a radio cell other than the control target radio cell from the control target radio cell, At least one or more of the connection destination changing radio terminals are selected as evaluation target radio terminals for evaluating the radio parameters of the control target radio cell, and the radio parameters of the control target radio cell are determined in consideration of the evaluation target radio terminal. .

  Therefore, it is possible to evaluate the communication quality of the wireless terminal that is predicted to switch the serving cell due to the change of the wireless parameter, and to determine the optimal wireless parameter. Furthermore, the radio parameters of the control target radio cell can be determined without causing quality degradation of radio cells existing around the control target radio cell.

  Hereinafter, specific embodiments will be described.

<First Embodiment>
A first embodiment of the present invention will be described.

  FIG. 3 is a configuration diagram of the wireless communication system according to the first embodiment.

  The radio communication system according to the first embodiment includes a radio base station 20 that manages a control target radio cell 2, a radio base station 21 that manages another radio cell 3, a radio parameter control device 30, and a plurality of radio Terminal (hereinafter referred to as UE) 40.

  The UE 40 has a function of measuring measurement information (radio quality). The radio quality includes a measurement result of radio quality of a radio cell (serving cell) to which the UE 40 is connected. Furthermore, the radio quality may include a measurement result of radio quality of neighboring cells other than the serving cell of the UE 40. A typical example of the radio quality measured by the UE 40 is the reception quality of a radio signal (downlink signal) transmitted from the radio base station 20.

  The reception quality is, for example, a signal power to interference noise ratio such as downlink pilot signal, reception power of downlink reference signal, or SINR (Signal to Interference plus Noise Ratio). In the case of W-CDMA, the radio quality measured by the UE 40 is the received power (CPICH RSCP (Received Signal Code Power)) of a common pilot channel (CPICH) for each radio cell, or per chip of the CPICH. The ratio of energy to in-band received power density (Ec / No) may be used. In addition, in the case of LTE (Long Term Evolution), the radio quality measured by the UE 40 includes the reception power (RSRP: Reference Signal Received Power) of the downlink reference signal (Downlink Reference Signal) and the reception quality (RSRQ: Reference Receive Receive Signal). ).

  Further, the radio quality includes communication quality such as throughput and BLER (Block Error Rate), event information such as presence / absence of abnormal disconnection or handover failure, time when the UE measures the radio quality, and an identifier of a radio cell corresponding to each radio quality. , And information such as UE identifiers.

  The UE 40 transmits the measured radio quality to the radio base station 20.

  The radio base station 20 manages the control target radio cell 2 and performs bidirectional radio communication with a plurality of UEs 40. And it has a function which collects the radio | wireless quality measured by subordinate UE40, and notifies the information to the radio | wireless parameter control apparatus 30. FIG. In addition to the wireless quality, performance counter information (for example, the number of occurrences of communication, the number of handovers, the resource block usage rate, the traffic load, the abnormal disconnection rate, the handover failure rate, etc.) aggregated for each wireless cell is stored in the wireless parameter control device 30. You may be notified. Further, the radio base station 20 has a function of changing radio parameters of the radio cell managed by the radio base station 20 according to the radio parameter control apparatus 30 according to the radio parameter determination result. Although FIG. 3 illustrates an example in which each radio base station manages one radio cell, the present invention is not limited to this. That is, each wireless base station may take a form of managing a plurality of wireless cells.

  The radio parameter control device 30 determines radio parameters of the radio base station 20 and the control target radio cell 2 based on the radio quality and performance counter information reported from the radio base station 20, and uses the result as the radio base station 20. It has a function to notify.

  FIG. 4 is a block diagram of the wireless parameter control device 30.

  The radio parameter control device 30 determines radio parameters of the control target radio cell 20 based on measurement information (radio quality and the like) and performance counter information reported from the radio base station 20, and determines the radio cell as a result of the determination. It has a function of notifying the radio base station 20 to be managed.

  The radio parameter control apparatus 30 includes a measurement information database 31, a connection destination radio cell prediction unit 32, an evaluation target radio terminal selection unit 33, a communication quality prediction unit 34, and a radio parameter determination unit 35.

  Next, the configuration of the wireless parameter control device 30 will be described.

  The measurement information database 31 is a database in which the radio quality and performance counter information of radio terminals reported from the radio base station 20 are registered.

  The connection destination radio cell prediction unit 32 changes the radio parameter of the control target radio cell to a predetermined candidate value using the radio cell measurement information (radio quality) measured by the UE 40 registered in the measurement information database 31. When the assumption is made, a connection-destination radio cell of the UE 40 having the control target radio cell as a serving cell is predicted. Specifically, when it is assumed that the radio parameter of the control target radio cell is changed to a candidate value using the measurement information (radio quality) measured by the UE 40, the connection destination of the UE 40 having the control target radio cell as the serving cell Predict radio cells. Hereinafter, a specific example in which reception power (RSRP (Reference Signal Received Power)) for each radio cell is collected as measurement information and transmission power is controlled as a radio parameter of the radio cell will be described.

  First, out of the measurement information measured and reported by the UE 40, the measurement information of the UE 40 using the control target radio cell as a serving cell is (RSRPs, RSRPn1, RSRPn2,..., RSRPni). Here, RSRPs is RSRP [dBm] of the serving cell, and RSRPni is RSRP [dBm] of the radio cell i other than the serving cell. Assuming that the transmission power of the control target radio cell is changed from the current setting value Pr [dBm] to the candidate value Pc [dBm], only the RSRP of the control target radio cell transmits the RSRP for each radio cell. (RSRPs− (Pr−Pc), RSRPn1, RSRPn2,..., RSRPni) can be predicted. Then, for the radio cell having the highest RSRP among the predicted RSRPs for each radio cell, the transmission power of the control target radio cell is changed from the current setting value Pr [dBm] to the candidate value Pc [dBm]. When it assumes, it estimates as the connecting point radio | wireless cell which the said UE40 connects. At this time, not only the radio cell with the highest RSRP but also the upper predetermined number of radio cells such as the top three may be included in the connection destination radio cell. In addition, although the example of RSRP was demonstrated above, it is not restricted to this, RSRQ, SINR, throughput, these similar information, etc. may be sufficient.

  For each radio parameter candidate value, the evaluation target radio terminal selection unit 33 is a connection destination change radio terminal in which the connection destination radio cell of the UE 40 predicted by the connection destination radio cell prediction unit 32 is a radio cell other than the control target radio cell. And a connection destination maintaining radio terminal whose connection destination radio cell predicted by the connection destination radio cell prediction unit 32 is a control target radio cell, and at least one connection destination change radio terminal is set in the radio parameter It selects as an evaluation object radio | wireless terminal for evaluating a candidate value. In addition, when there are a plurality of candidate values in one wireless parameter, instead of selecting an evaluation target wireless terminal for evaluating the candidate value for each candidate value, the evaluation target wireless in at least one of the candidate values The wireless terminal selected as the terminal may be a common evaluation target wireless terminal among the wireless parameter candidate values. Here, it goes without saying that the connection destination maintaining wireless terminal may be included in the evaluation target wireless terminal. Further, when the measurement information of the evaluation target wireless terminal is used by the communication quality prediction unit 34, it goes without saying that the measurement information of the evaluation target wireless terminal may be directly selected instead of selecting the evaluation target wireless terminal. .

  The communication quality prediction unit 34 predicts the communication quality of the evaluation target wireless terminal for the wireless parameter candidate value. The communication quality to be evaluated includes the throughput of each evaluation target wireless terminal, the handover failure rate and the abnormal disconnection rate, the wireless quality (reception power, reception quality, signal-to-interference noise ratio, etc.), and the like.

  The radio parameter determination unit 35 determines the radio parameter of the control target radio cell 2 using the result of the communication quality evaluation of the evaluation target radio terminal. For example, the radio parameter determination unit 35 predicts communication quality (for example, throughput) for each measurement information (radio quality information) predicted by the communication quality prediction unit 34, and the control target radio cell 2 is improved so that the communication quality is improved. Determine the radio parameters. Specific examples of the radio parameter include the maximum transmission power of the downlink signal of the radio cell, the transmission power of the pilot signal and the reference signal, the antenna tilt angle, or the antenna azimuth angle. In addition, CIO (Cell Individual Offset) or Qoffset may be used as the wireless parameter.

  A specific example of the communication quality prediction and wireless parameter determination method of the evaluation target wireless terminal will be described below. Here, a case will be described in which reception power (RSRP) for each radio cell is included as measurement information, and transmission power of a control target radio cell is determined as a radio parameter. The communication quality prediction unit 34 estimates the throughput for each candidate value of transmission power for each measurement information by the following method for the evaluation target wireless terminal.

The received power (RSRP [dBm]) for each wireless cell included in the measurement information is
(RSRPs, RSRPn1, RSRPn2, ..., RSRPni)
far. Here, RSRPs represents RSRP of a control target radio cell for determining radio parameters. RSRPn1, RSRPn2,..., RSRPni represents the RSRP of each radio cell from the peripheral radio cell 1 to the peripheral radio cell i.

First, the RSRP for each radio cell is predicted when it is assumed that the transmission power of the control target radio cell is changed from the current Pr [dBm] to the candidate value Pc [dBm]. For example, assuming that only the RSRP (RSRPs) of the control target radio cell changes by the change amount of the transmission power,
(RSRPs- (Pr-Pc), RSRPn1, RSRPn2, ..., RSRPni)
Can be predicted as

Next, the prediction results are rearranged in descending order, and the RSRP unit is converted from a decibel value (dBm) to a real value (mW).
(S1, I1, I2, ..., Ini)
far. At this time, since the radio cell corresponding to S1 is the radio cell having the highest RSRP when it is assumed that the transmission power of the control target radio cell is changed, it is regarded as a connection destination radio cell when the transmission power is changed. be able to.

When assuming that the transmission power of the control target radio cell is changed to the candidate value Pc [dBm], the SINR of the measurement information is
SINR = S1 / (I1 + I2 +... + Ini + NOISE)
Can be predicted as Note that NOISE represents thermal noise [mW]. For the following explanation, the result of converting the above SINR into a decibel value (dB) is set as SINR ′.

Assuming that the transmission power of the control target radio cell is changed to the candidate value Pc [dBm], the throughput (TP) of the measurement information is calculated using the Shannon equation well known to those skilled in the art.
TP = B × log ₂ (1 + SINR ′) × α
Can be predicted as Here, B is the system bandwidth [Hz], and α is a constant representing the amount of deterioration from the theoretical limit that occurs depending on the implementation of the receiver.

  The radio parameter determination unit 35 predicts the throughput for each measurement information of the evaluation target radio terminal for each radio parameter candidate value as described above, and obtains the radio parameter candidate value that is most expected to improve the throughput. Good. The wireless parameter determination method shown here is merely an example, and does not limit the application target of the present invention.

  Next, as an example of the operation of the radio parameter control device 30 of the first embodiment, an evaluation target radio terminal is selected for each radio parameter candidate value of the control target radio cell 2, and the communication quality of the evaluation target radio terminal is determined. A case where the radio parameter is determined based on the prediction result will be described.

  FIG. 5 is an operation flowchart of the radio parameter control apparatus 30 in the first embodiment.

  First, the radio parameter control apparatus 30 collects measurement information of the UE 40 collected by the radio base station 20 (Step 1). The collected measurement information (such as radio quality) of the UE 40 is registered in the measurement information database 31.

  Next, the radio parameter control device 30 predicts the communication quality of the evaluation target radio terminal for each radio parameter candidate value of the control target radio cell 2 (Step 2 to Step 4).

  Specifically, the connection destination radio cell prediction unit 32 uses the measurement information of the UE 40 that uses the control target radio cell as a serving cell among the measurement information of the UE 40 registered in the measurement information database 31. A connection destination radio cell of each UE 40 when it is assumed that the radio parameter is changed to the candidate value is predicted (Step 2). Subsequently, the evaluation target wireless terminal selection unit 33 distinguishes between the connection destination change wireless terminal and the connection destination maintenance wireless terminal based on the connection destination wireless cell predicted by the connection destination wireless cell prediction unit 32, and at least one The connection destination changing wireless terminal is selected as an evaluation target wireless terminal (Step 3). And the communication quality prediction part 34 estimates the communication quality for every evaluation object radio | wireless terminal with respect to the candidate value of the radio | wireless parameter of the control object radio | wireless cell 2 (Step 4).

  Finally, the radio parameter determination unit 35 determines, as the radio parameter value, the candidate value that is most expected to improve the communication quality among the communication qualities for each evaluation target radio terminal with respect to each radio parameter candidate value ( Step 5). For example, the average throughput of the evaluation target wireless terminal is obtained for each wireless parameter candidate value, and the wireless parameter candidate value that improves the average throughput most is selected. Also, the lower 5% throughput of the evaluation target wireless terminal is obtained for each wireless parameter candidate value, and the wireless parameter candidate value that improves the lower 5% throughput most is selected.

  Next, another example of the first embodiment will be described.

  In another example of the first embodiment, instead of selecting the evaluation target radio terminal for each radio parameter candidate value as described above, the evaluation target is set in any one of the radio parameter candidate values of the control target radio cell 2. A wireless terminal to be a wireless terminal is set as an evaluation target wireless terminal. Here, the evaluation target wireless terminal is selected by selecting an evaluation target wireless terminal for each wireless parameter candidate value, and selecting a wireless terminal selected as an evaluation target wireless terminal using any one of the candidate values between the wireless parameter candidate values. A common wireless terminal to be evaluated. Further, a predetermined candidate value (for example, a candidate value that narrows the connection range of the control target radio cell 2) is selected from among the radio parameter candidate values, an evaluation target radio terminal is selected from the candidate values, and the selected evaluation is performed. The target wireless terminal may be a common evaluation target wireless terminal among wireless parameter candidate values. Then, the selected evaluation target wireless terminal is set as a common evaluation target wireless terminal among the wireless parameter candidate values, the communication quality of the evaluation target wireless terminal is predicted for each wireless parameter candidate value, and the wireless parameter is determined.

  FIG. 6 is an operation flowchart of the wireless parameter control device 30 of another example of the first embodiment.

  First, the radio parameter control device 30 collects measurement information of the UE 40 collected by the radio base station 20 (Step 10). The collected measurement information (such as radio quality) of the UE 40 is registered in the measurement information database 31.

  Next, the connection destination radio cell prediction unit 32 sets the control target radio cell as the serving cell in the current radio parameter setting (before the radio parameter change) among the measurement information of the UE 40 registered in the measurement information database 31. For each radio parameter candidate value of the radio cell 2 to be controlled, the connection destination radio cell of each UE 40 is predicted using the measurement information collected from (Step 11). Subsequently, the evaluation target radio terminal selection unit 33 distinguishes between the connection destination change radio terminal and the connection destination maintenance radio terminal based on the connection destination radio cell predicted by the connection destination radio cell prediction unit 32, and UE40 which becomes a connection destination change radio | wireless terminal by a candidate value is selected as an evaluation object radio | wireless terminal common among the candidate values of a radio | wireless parameter (Step 12).

  In addition, instead of selecting the UE 40 that becomes the connection destination change radio terminal with any one of the radio parameter candidate values as the evaluation target radio terminal as described above, a predetermined candidate value (for example, a control target) among the radio parameter candidate values is selected. A candidate value that narrows the connection range of the wireless cell 2 is selected, and the evaluation target wireless terminal selected in the candidate value may be set as a common evaluation target wireless terminal among the wireless parameter candidate values. Specifically, the connection destination radio cell prediction unit 32 sets the control target radio cell as the serving cell in the current radio parameter setting (before the radio parameter change) among the measurement information of the UE 40 registered in the measurement information database 31. Using the measurement information collected from the UE 40, the radio parameter of the control target radio cell 2 is assumed to be changed to a predetermined candidate value, for example, the lowest transmission power among the transmission power candidate values. A connection destination radio cell is predicted (Step 11). Subsequently, the evaluation target wireless terminal selection unit 33 distinguishes between the connection destination change wireless terminal and the connection destination maintenance wireless terminal based on the connection destination wireless cell predicted by the connection destination wireless cell prediction unit 32, and at least one The above connection destination change wireless terminal is selected as a common evaluation target wireless terminal among the wireless parameter candidate values (Step 12).

  Subsequently, the communication quality prediction unit 34 predicts the communication quality of the evaluation target wireless terminal selected in Step 12 for each wireless parameter candidate value (Step 13).

  Finally, the radio parameter determination unit 35 determines, as the radio parameter value, the candidate value that is most expected to improve the communication quality among the communication qualities for each evaluation target radio terminal with respect to each radio parameter candidate value ( Step 14).

  In the first embodiment, assuming that the radio parameter of the control target radio cell is changed, the serving cell predicts a connection destination change radio terminal that becomes a radio cell other than the control target radio cell from the control target radio cell, Select at least one or more of the connection destination changing radio terminals as the evaluation target radio terminal for evaluating the radio parameter of the control target radio cell, and determine the radio parameter of the control target radio cell in consideration of the evaluation target radio terminal doing. That is, the radio parameter of the control target radio cell is determined in consideration of the change of the radio cell to which the radio terminal is connected due to the radio parameter change.

  Therefore, the radio parameters of the control target radio cell can be determined without causing quality degradation of radio cells existing around the control target radio cell.

<Second Embodiment>
A second embodiment will be described.

  The connection-destination-change wireless terminal that is predicted to change the connection-destination radio cell from the control target radio cell to the neighboring cell due to a change in radio parameter, for example, a decrease in transmission power, is near the boundary between the control-target radio cell and the neighboring cell. (Cell edge). Even if the radio terminal at the cell edge does not change the radio parameters of the radio cell and the radio terminal exists at the same location, the serving cell changes due to the influence of radio wave fluctuation due to shadowing or the like. Cheap. For these reasons, when measurement information is collected from a wireless terminal connected to a wireless cell managed by the wireless base station and the wireless parameter is controlled using the collected measurement information, the wireless base station exists near the center of the controlled wireless cell. Measurement information is less likely to be collected from wireless terminals existing at the cell edge than the connection destination maintaining wireless terminal, and the quality of the cell edge may not be sufficiently taken into account when determining the radio parameters.

  Therefore, in the second embodiment, while including the connection destination change radio terminal and the connection destination maintenance radio terminal in the evaluation target radio terminal, the measurement information of the connection destination change radio terminal is emphasized, and the connection destination change radio terminal A case will be described in which the measurement information of the evaluation target wireless terminal is weighted so that the measurement information is not neglected compared to the measurement information of the connection destination maintaining wireless terminal. In addition, description is abbreviate | omitted about the part similar to 1st Embodiment, and a different part is demonstrated.

  The evaluation target radio terminal selection unit 33 is based on the connection destination radio cell of the UE 40 predicted by the connection destination radio cell prediction unit 32, and the connection destination change radio terminal in which the connection destination radio cell is a radio cell other than the control target radio cell. And a connection destination maintaining radio terminal whose connection destination radio cell is a control target radio cell. Then, at least one or more connection destination changing radio terminals and at least one connection destination maintaining radio terminal are selected as evaluation target radio terminals.

  The communication quality prediction unit 34 performs weighting so that the measurement information of the connection destination change wireless terminal among the evaluation target wireless terminals is emphasized.

  As an example, weighting may be performed on the number of measurement information reports of the connection destination changed wireless terminal, and the number of measurement information reports of the connection destination changed wireless terminal may be increased from the actual number of reports. Alternatively, the measurement information of the connection destination maintaining wireless terminal may be thinned out at a certain rate. As a result, it is possible to solve the above-described problem that it is difficult for measurement information to be gathered from wireless terminals existing at the cell edge. Further, the report value of the measurement information of the connection destination changing wireless terminal may be corrected. For example, when the reception power for each radio cell is included in the measurement information, the reception power of the control target radio cell is lowered by a predetermined amount with respect to the measurement information of the connection destination change radio terminal, and the radio other than the control target radio cell Modification is made so that the received power of the cell is increased by a predetermined amount. As a result, it is possible to virtually change the position where the wireless terminal is present in a direction away from the center of the control target wireless cell, and to determine the wireless parameter in consideration of the quality of the cell edge. With respect to the measurement information of the evaluation target wireless terminal thus weighted, communication quality is predicted for each wireless parameter candidate value.

  As another example, the communication quality predicted using the measurement information of the connection destination changing radio terminal and the communication quality predicted using the measurement information of the connection destination maintaining radio terminal are Weighting may be performed so that communication quality predicted using measurement information is emphasized. For example, with respect to a candidate value of a certain radio parameter, the average value of the communication quality predicted using the measurement information of the connection destination changing radio terminal is X, and the average of the communication quality predicted using the measurement information of the connection destination maintaining radio terminal When the value is Y, the overall communication quality in the candidate value is evaluated as α · X + β · Y. Here, by setting the parameter α to a value larger than the parameter β, it is possible to place importance on the measurement information of the connection destination changing wireless terminal.

  Note that the communication quality prediction and the radio parameter determination method are as described in the first embodiment.

  In the above description, the example in which the measurement information of the connection destination changing radio terminal is emphasized has been described. However, the present invention is not limited to this, and the measurement information of the connection destination maintaining radio terminal may be emphasized. In that case, the number of reports of the measurement information of the connection destination maintaining wireless terminal is increased from the actual number of reports. Alternatively, the measurement information of the connection destination changing wireless terminal may be thinned out at a certain rate. Further, the report value of the measurement information of the connection destination maintaining wireless terminal may be corrected.

  In the second embodiment, while emphasizing either the measurement information of the connection destination changing radio terminal or the measurement information of the connection destination maintaining radio terminal, the measurement information that is not emphasized is also used, so the effect of the first embodiment In addition, it is possible to determine a radio parameter considering the balance of the entire radio cell.

<Third Embodiment>
A third embodiment will be described.

  In the above-described embodiment, the radio parameter control device 30 includes the measurement information database 31, the connection destination radio cell prediction unit 32, the evaluation target radio terminal selection unit 33, the communication quality prediction unit 34, and the radio parameter determination unit 35. The case where it is provided was explained.

  However, it is not always necessary for the wireless parameter control device 30 to include all of them. For example, the radio base station 40 may have the function of the radio parameter control device 30. FIG. 7 shows a block diagram of the radio base station 20. Similarly to the radio parameter control device 30, the radio base station 20 includes a measurement information database 31, a connection destination radio cell prediction unit 32, an evaluation target radio terminal selection unit 33, a communication quality prediction unit 34, and a radio parameter determination unit. 35.

  In the present embodiment, each radio base station autonomously determines an evaluation target radio terminal, evaluates communication quality of the evaluation target radio terminal, and controls radio parameters. Therefore, an apparatus that centrally manages a plurality of radio base stations is unnecessary. In addition, since a series of processing is performed in the radio base station, it is suitable for finely controlling radio parameters in time.

  This is the end of the description of the embodiment of the present invention. As is apparent from the above description, each unit may be configured by hardware or may be realized by a computer program. In this case, functions and operations similar to those of the above-described embodiments are realized by a processor that operates according to a program stored in the program memory. Moreover, you may implement | achieve only a part of function of embodiment mentioned above with a computer program.

  Furthermore, although the present invention has been described with reference to embodiments, the present invention is not necessarily limited to the above embodiments, and various modifications may be made within the scope of the technical idea. Moreover, you may implement combining each embodiment suitably.

1a to 1e Radio terminal 2 Control target radio cell 3 Radio cell 10 Radio terminal 11 Evaluation target radio terminal selection unit 12 Radio parameter control unit 13 Radio communication network 20, 21 Radio base station 30 Radio parameter control device 31 Measurement information database 32 Connection destination Radio cell prediction unit 33 Evaluation target radio terminal selection unit 34 Communication quality prediction unit 35 Radio parameter determination unit 40 UE

Claims (29)

A radio parameter control system for controlling radio parameters of a radio cell using measurement information by a radio terminal,
When it is assumed that the radio parameter of the control target radio cell has been changed, the connection destination change radio terminal in which the connection destination radio cell becomes a radio cell other than the control target radio cell from the control target radio cell, and the connection destination radio cell Predicts a connection destination maintenance radio terminal that does not change from the control target radio cell, and sets at least one or more connection destination change radio terminals and at least one or more connection destination maintenance radio terminals to the control target radio. An evaluation target radio terminal selection means for selecting as an evaluation target radio terminal for evaluating the radio parameters of the cell;
When it is assumed that the radio parameter has been changed, the communication quality of the evaluation target radio terminal is evaluated using measurement information collected from the evaluation target radio terminal, and based on the result of the evaluation, the control target radio cell A radio parameter control system comprising: radio parameter control means for determining a radio parameter of the system. The evaluation target terminal selection means, before changing the radio parameter of the control target radio cell based on the measurement information collected from the wireless terminal to serving the control target radio cell, predicting the connection destination change wireless terminal The radio parameter control system according to claim 1. The evaluation target radio terminal selection means uses the measurement information including radio qualities of the control target radio cell and radio cells other than the control target radio cell collected from radio terminals having the control target radio cell as a serving cell, predicted radio quality of the wireless terminal when it is assumed that changes the wireless parameters to the candidate values, the predicted radio quality is higher the higher predetermined number of radio cells, according to claim 1 or claim to the connection target radio cell Item 3. The wireless parameter control system according to Item 2 .   The radio parameter control means uses the evaluation target radio terminal in common for a plurality of candidate values of radio parameters to be changed.
The radio | wireless parameter control system in any one of Claims 1-3. The radio parameter control system according to claim 4, wherein the radio quality includes at least one of reception power, reception quality, signal-to-interference and noise ratio, and throughput. The radio parameter control system according to any one of claims 1 to 5, wherein the evaluation target radio terminal selection unit predicts the connection destination change radio terminal for each radio parameter candidate value. The evaluation target wireless terminal selection unit predicts, as a connection destination change wireless terminal, a wireless terminal in which the connection destination wireless cell is a wireless cell other than the control target wireless cell in any candidate value of the wireless parameter. The wireless parameter control system according to any one of claims 1 to 5. The radio parameter control system according to any one of claims 1 to 7, wherein the communication quality is at least one of a throughput, a handover failure rate, an abnormal disconnection rate, and a radio quality. The radio parameter according to any one of claims 1 to 8 , wherein the radio parameter control means evaluates communication quality by focusing on measurement information of the connection destination changing radio terminal among measurement information of the evaluation target radio terminal. Control system. The wireless parameter determination unit is configured to set the measurement information of the connection-destination wireless terminal so that a ratio of the number of measurement information reports of the connection-destination wireless terminal to the number of measurement information reports of the evaluation-target wireless terminal is high. Change the number of reports or the number of reports of measurement information other than the connection destination change wireless terminal
The radio parameter control system according to claim 9 . The wireless parameter determining means changes communication information of the connection destination changing wireless terminal to evaluate communication quality
The radio parameter control system according to claim 9 or 10 . The radio parameter control system according to any one of claims 1 to 11 , wherein the evaluation target radio terminal selection unit and the radio parameter control unit are provided in a radio parameter control device connected to a radio base station. The radio parameter control system according to any one of claims 1 to 11 , wherein the evaluation target radio terminal selection unit and the radio parameter control unit are provided in a radio base station. A radio parameter control device for controlling radio parameters of a radio cell using measurement information by a radio terminal,
When it is assumed that the radio parameter of the control target radio cell has been changed, the connection destination change radio terminal in which the connection destination radio cell becomes a radio cell other than the control target radio cell from the control target radio cell, and the connection destination radio cell Predicts a connection destination maintenance radio terminal that does not change from the control target radio cell, and sets at least one or more connection destination change radio terminals and at least one or more connection destination maintenance radio terminals to the control target radio. An evaluation target radio terminal selection means for selecting as an evaluation target radio terminal for evaluating the radio parameters of the cell;
When it is assumed that the radio parameter has been changed, the communication quality of the evaluation target radio terminal is evaluated using measurement information collected from the evaluation target radio terminal, and based on the result of the evaluation, the control target radio cell A wireless parameter control means for determining a wireless parameter of The evaluation target terminal selection means, before changing the radio parameter of the control target radio cell based on the measurement information collected from the wireless terminal to serving the control target radio cell, predicting the connection destination change wireless terminal Do
The wireless parameter control device according to claim 14 . The evaluation target radio terminal selection means uses the measurement information including radio qualities of the control target radio cell and radio cells other than the control target radio cell collected from radio terminals having the control target radio cell as a serving cell, Predicting the radio quality of the radio terminal when it is assumed that the radio parameter has been changed to a candidate value, the upper predetermined number of radio cells with the high predicted radio quality are defined as the connection destination radio cells.
The radio | wireless parameter control apparatus of Claim 14 or Claim 15 .   The radio parameter control means uses the evaluation target radio terminal in common for a plurality of candidate values of radio parameters to be changed.
The radio parameter control device according to any one of claims 14 to 16. The radio quality includes at least one of reception power, reception quality, signal-to-interference / noise ratio, and throughput.
The wireless parameter control device according to claim 17 . The evaluation target wireless terminal selection unit predicts the connection destination changed wireless terminal for each candidate value of the wireless parameter candidate value.
The radio parameter control device according to any one of claims 14 to 18 . The evaluation target wireless terminal selection unit predicts a wireless terminal in which the connection destination wireless cell is a wireless cell other than the control target wireless cell as a connection destination change wireless terminal in any one of the candidate values of the wireless parameter.
The radio parameter control device according to any one of claims 14 to 18 . The communication quality is at least one of throughput, handover failure rate, abnormal disconnection rate, and wireless quality
The radio parameter control device according to any one of claims 14 to 20 . The wireless parameter control means evaluates communication quality by placing importance on the measurement information of the connection destination changing wireless terminal among the measurement information of the evaluation target wireless terminal.
The radio parameter control device according to any one of claims 14 to 21 . The wireless parameter determination unit is configured to set the measurement information of the connection-destination wireless terminal so that a ratio of the number of measurement information reports of the connection-destination wireless terminal to the number of measurement information reports of the evaluation-target wireless terminal is high. Change the number of reports or the number of reports of measurement information other than the connection destination change wireless terminal
The radio parameter control device according to claim 22 . The wireless parameter determining means changes communication information of the connection destination changing wireless terminal to evaluate communication quality
The radio parameter control apparatus according to claim 22 or 23 . A radio base station that controls radio parameters of a radio cell using measurement information by a radio terminal,
When it is assumed that the radio parameter of the control target radio cell has been changed, the connection destination change radio terminal in which the connection destination radio cell becomes a radio cell other than the control target radio cell from the control target radio cell, and the connection destination radio cell Predicts a connection destination maintenance radio terminal that does not change from the control target radio cell, and sets at least one or more connection destination change radio terminals and at least one or more connection destination maintenance radio terminals to the control target radio. An evaluation target radio terminal selection means for selecting as an evaluation target radio terminal for evaluating the radio parameters of the cell;
When it is assumed that the radio parameter has been changed, the communication quality of the evaluation target radio terminal is evaluated using measurement information collected from the evaluation target radio terminal, and the control target radio is based on the result of the evaluation A radio base station comprising radio parameter control means for determining radio parameters of a cell.   The radio parameter control means uses the evaluation target radio terminal in common for a plurality of candidate values of radio parameters to be changed.
The radio base station according to claim 25. A radio parameter control method for controlling radio parameters of a radio cell using measurement information by a radio terminal,
When it is assumed that the radio parameter of the control target radio cell has been changed, the connection destination change radio terminal in which the connection destination radio cell becomes a radio cell other than the control target radio cell from the control target radio cell, and the connection destination radio cell Predicts a connection destination maintenance radio terminal that does not change from the control target radio cell, and sets at least one or more connection destination change radio terminals and at least one or more connection destination maintenance radio terminals to the control target radio. Select as an evaluation target radio terminal for evaluating the radio parameters of the cell,
When it is assumed that the radio parameter has been changed, the communication quality of the evaluation target radio terminal is evaluated using measurement information collected from the evaluation target radio terminal, and based on the result of the evaluation, the control target radio cell A radio parameter control method for determining a radio parameter of the system.   The determination of the wireless parameter uses the evaluation target wireless terminal in common for a plurality of candidate values of the wireless parameter to be changed.
The radio parameter control method according to claim 27. A program for controlling radio parameters of a radio cell using measurement information by a radio terminal,
On the computer,
When it is assumed that the radio parameter of the control target radio cell has been changed, the connection destination change radio terminal in which the connection destination radio cell becomes a radio cell other than the control target radio cell from the control target radio cell, and the connection destination radio cell Predicts a connection destination maintaining radio terminal that does not change from the control target radio cell, and sets at least one or more of the connection destination change radio terminals and at least one or more of the connection destination maintenance radio terminals to the control target radio cell. A process of selecting as an evaluation target wireless terminal for evaluating the wireless parameter of
When it is assumed that the radio parameter has been changed, the communication quality of the evaluation target radio terminal is evaluated using measurement information collected from the evaluation target radio terminal, and based on the result of the evaluation, the control target radio cell A program for executing a process for determining a wireless parameter.

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