JP2007019569A - Wireless communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem of a conventional wireless communication system in which the traffic reduction effect is insufficient though the conventional system reduces the traffic by controlling an antenna down-tilt angle or a pilot channel transmission power. <P>SOLUTION: Each of wireless base stations for configuring a wireless communication system disclosed herein calculates a load factor L by subtracting a maximum value among a load factor η<SB>UL</SB>in an uplink, a load factor η<SB>DL</SB>in a down link, a hardware resource utilization factor η<SB>HW</SB>of the wireless base station, and a resource utilization factor η<SB>OVSF</SB>of number of orthogonal codes of the wireless base station from "1", and informs a radio network controller about the load factor L (21 to 25). The radio network controller judges that the wireless base station whose load factor L is greater than an upper limit X of a specified range is in an overload state and controls the wireless base station to increase both the antenna down-tilt angle and the pilot channel transmission power (26, 27). The radio network controller carries out similar control when an SHO overhead value Z is greater than an upper limit β. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a radio communication system, and more particularly to a radio communication system that performs antenna downtilt angle and pilot channel transmission power control.

  A wireless communication system in which a service area is divided into a plurality of cells, each of which is a radio zone of a base station, and one base station existing in each cell wirelessly communicates signals via one or more antenna modules Is conventionally known (see, for example, Patent Document 1). In this conventional wireless communication system, the antenna module of the base station is configured to include at least one receiving antenna and one transmitting antenna, or is configured by a single transmitting / receiving antenna. The radiation pattern (mainly the main lobe) of the transmitting antenna or the transmitting / receiving antenna is inclined at an angle from the horizontal reference line of the antenna. This angle is called the antenna's down tilt angle, and the angle from the horizontal reference line of the antenna toward the ground is measured as positive.

  In addition, each base station transmits a pilot signal to the mobile station using a pilot channel with a constant transmission power, and the mobile station moving through each cell communicates with the base station transmitting the pilot signal having the highest received electric field strength. So that you can always communicate wirelessly. The downtilt angle of the antenna and the transmission power of the pilot channel directly affect the service area quality.

  The antenna downtilt angle affects the amount of interference with other cells and the cell coverage area, and thus greatly affects the capacity of the network. Increasing the downtilt angle of the antenna (directing the antenna main beam toward the own cell) reduces the amount of interference with other cells, but reduces the cell coverage area and generates a coverage hole.

  Also, the pilot channel is used as a reference for camp-on or handover operation to a cell, and therefore the pilot channel transmission power determines the cell coverage area. Increasing the pilot channel transmission power increases the amount of interference with other cells and affects the network capacity. However, if the pilot channel transmission power is decreased, a coverage hole occurs.

  In addition, the amount of interference increases as the cell load (load) increases due to the occurrence of a call, and the cell coverage area is reduced, greatly affecting the capacity of the network. In cell coverage in which calls occur intensively, a load sharing technique is adopted by changing the antenna downtilt angle and the transmission power of the pilot channel to change the boundary of cell dominance (power).

  As described above, the down tilt angle of the antenna and the transmission power of the pilot channel are closely related to the coverage and capacity. For this reason, in the conventional wireless communication system, the antenna downtilt angle and pilot channel transmission power of each base station are set at the time of initial introduction. And several field quality investigations etc. are carried out and the quality of the radio communication system is improved by changing these settings.

  However, since the change of the antenna downtilt angle and the change of the pilot channel transmission power are generally carried out by a worker, there are problems such as occurrence of work mistakes and costs such as time and labor costs. In addition, since these optimum setting values are determined after repeated quality surveys, once they are determined, they are not changed many times. Changes that adapt to changes in call volume were difficult to implement.

  Therefore, an adaptive antenna system that reconfigures a cylindrical antenna array based on the position of a mobile station and signal information (for example, transmission power information) as a cylindrical antenna array as a base station antenna is conventionally known (for example, Patent Document 2). In a conventional wireless communication system employing this adaptive antenna system, a cylindrical antenna array is first installed in a base station based on mathematical parameters, and the configuration of the antenna components of the cylindrical antenna array is adjusted by a controller to cause interference and call. And the effective range is maximized within one cell and between a plurality of adjacent cells.

  Also, by reducing the transmission power gain of the pilot signal at the base station of the cell where the traffic is concentrated and increasing the transmission power gain of the pilot signal at the base station of the surrounding cell, the traffic of the cell where the traffic is concentrated A wireless communication system for reducing the size is also known in the art (see, for example, Patent Document 3).

JP 2000-269723 A JP 2002-064427 A JP 2004-343807 A

  However, in the conventional wireless communication system adopting the adaptive antenna system described in Patent Document 2, the cylindrical antenna array installed in the base station is adjusted by the controller to adjust the configuration of the antenna component of the cylindrical antenna array, and the antenna downtilt angle is adjusted. It is a configuration to control, traffic reduction is not sufficient, and a special antenna called a cylindrical antenna array is required.

  Further, the wireless communication system described in Patent Document 3 has a problem that the effect of reducing traffic (load distribution effect) is not sufficient because only the pilot channel transmission power is changed according to the traffic volume.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a radio communication system capable of realizing a sufficient traffic reduction effect by simultaneously controlling the antenna downtilt angle and the pilot channel transmission power. .

  Another object of the present invention is that a high accuracy is obtained by calculating the load factor with a plurality of items (such as hardware resources and orthogonal codes) without requiring a special antenna such as a cylindrical antenna array. An object of the present invention is to provide an off-the-shelf remote electrical / mechanical tilt wireless communication system capable of improving quality by calculating the load factor.

In order to achieve the above object, the present invention provides a communication between a plurality of radio base stations each having an independent radio zone, and a radio base station in a radio zone within the radio zone of each of the plurality of radio base stations. In a wireless communication system having a mobile station for wireless communication and a base station controller connected to a plurality of wireless base stations and controlling the operation thereof,
Each of the plurality of radio base stations includes a load factor calculating means for calculating a load factor L including at least an uplink load factor and a downlink load factor, and an antenna downtilt angle based on control from the base station controller. Variable setting means for variably setting the pilot channel transmission power independently by a preset step width;
Based on the load factor L calculated in each of the plurality of radio base stations, the base station controller determines for each radio base station whether the load factor L is within a preset first specified value range. When the determination result that the load factor L is within the first specified value range is input from the first determination unit and the first determination unit, the antenna down of the radio base station that calculated the load factor L When the tilt angle and the pilot channel transmission power are both maintained in the current state, and the determination result that the load factor L is smaller than the lower limit value of the first specified value range is input, the load factor L is A first control means for outputting an instruction to change the calculated antenna downtilt angle of the radio base station and / or an instruction to change the pilot channel transmission power to the radio base station that has calculated the load factor L, and Radio base stations And calculation of the load factor in each repeating a judging operation and the control operation in the base station controller characterized.

  In the present invention, when the load factor L calculated by each of the plurality of radio base stations is smaller than the lower limit value of the first specified value range, the antenna down is performed with respect to the radio base station that calculated the load factor L. Since the tilt angle down change instruction and / or the pilot channel transmission power down change instruction are issued, the base station control apparatus can perform the optimal antenna down in which the load factor L at the radio base station satisfies the specified value range. Tilt angle, pilot channel transmit power can be found, cell dominance is reduced and dominance boundaries move. As a result, when a radio base station is changed down, a call that has been accommodated in the cell of the radio base station so far is under the control of an adjacent cell and is load-balanced. The load factor L may be calculated by the base station controller.

  In order to achieve the above object, the present invention provides a soft handover when the base station controller determines that the load factor L is within the first specified value range by the first determining means. A second determination unit that calculates an SHO overhead value Z indicating a necessary expense, and determines for each radio base station whether the SHO overhead value is within a second predetermined value range set in advance; When the determination result that the SHO overhead value Z is within the second specified value range is input from the determination means, the antenna downtilt angle of the radio base station that calculated the SHO overhead value Z, the pilot channel transmission power, Are both maintained in their current state, and when the determination result that the SHO overhead value Z is larger than the upper limit value of the second specified value range is input, A second control means for outputting an instruction to change the antenna downtilt angle of the radio base station for which the head value Z has been calculated and / or an instruction to change the pilot channel transmission power to the radio base station for which the SHO overhead value Z has been calculated; When the determination result that the load factor L is within the first specified value range is input from the first determination unit, the first control unit performs the determination operation by the second determination unit. It is made to perform.

  In the present invention, it is determined whether not only the load factor L but also the SHO overhead value Z is within the second specified value range, and the SHO overhead value Z is larger than the upper limit value of the second specified value range. Is input to the radio base station that has calculated the SHO overhead value Z, and / or to change the pilot channel transmission power down. Therefore, the base station controller can find the optimal antenna downtilt angle and pilot channel transmission power that satisfy the load factor L and SHO overhead value Z within the specified range in the radio base station, and the cell dominance is reduced. The dominance boundary moves. As a result, when a radio base station is changed down, a call that has been accommodated in the cell of the radio base station so far is under the control of an adjacent cell and is load-balanced.

  In order to achieve the above object, according to the present invention, the first control means determines from the first determination means that the load factor L is greater than the upper limit value of the first specified value range. Is input to the radio base station that has calculated the load factor L, an instruction to change the antenna downtilt angle of the radio base station that calculated the load factor L and / or an instruction to change the pilot channel transmission power. It is characterized by outputting. In the present invention, not only when the cell loading is overloaded, but also when the determination result that the load factor L is larger than the upper limit value of the first specified value range is input, it is determined that the load is low, and the antenna By increasing the down tilt angle or the pilot channel transmission power, the coverage can be expanded.

  In order to achieve the above object, according to the present invention, the second control means determines from the second determination means that the SHO overhead value Z is less than the lower limit value of the second specified value range. Is input, an instruction to change the antenna downtilt angle of the radio base station that calculated the SHO overhead value Z and / or an instruction to change the pilot channel transmission power up, and the radio base station that calculated the SHO overhead value Z It outputs to a station. In this invention, when the determination result that the SHO overhead value Z is less than the lower limit value of the second specified value range is input, it is determined that the load is low, and the antenna downtilt angle or the pilot channel transmission power is increased. By doing so, coverage can be expanded.

Furthermore, in order to achieve the above object, according to the present invention, the load factor calculating means includes the use of the load factor η _UL in the uplink, the load factor η _DL in the downlink, and the use of hardware resources of the radio base station. The load factor L is calculated by subtracting the maximum value among the rate η _HW and the utilization rate η _OVSF of the orthogonal code number resource of the radio base station from 1. Further, in the present invention, the second determination means is configured to calculate the number of mobile stations that are in communication in a zone in which cells of each of a plurality of radio base stations overlap each other. The SHO overhead value Z is calculated by dividing by the number of communicating mobile stations located in a zone that does not overlap with the cells of other radio base stations among the cells of the radio base station of It is a means for determining for each radio base station whether or not the SHO overhead value is within a preset second specified value range.

  According to the present invention, the change in cell load is determined by the load factor L calculated by the radio base station and / or the SHO overhead value Z calculated by the base station controller, and the antenna downtilt angle and the Since the load distribution is performed by automatically controlling the pilot channel transmission power at the same time, the optimal antenna downtilt angle and pilot channel transmission power can be set according to the maturity level of the network (traffic, system configuration, etc.). Compared to conventional systems that control only the antenna downtilt angle or pilot channel transmission power without the need for a large antenna array, it is possible to construct a high-quality wireless communication system, and there is a need for work at high places and tuning work. Costs can be reduced, for example, by eliminating them.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic system configuration diagram of an embodiment of a radio communication system according to the present invention. The radio communication system according to the present embodiment includes a mobile station 11, radio base stations 12 a and 12 b, and a base station control device 13. There are actually a plurality of mobile stations 11 and base station controllers 13 and three or more radio base stations 12a and 12b, but they are omitted here for convenience. This embodiment is applied to a CDMA mobile communication radio system intended for mobile objects such as automobiles, ships, and people (walking).

  The radio base stations 12a and 12b have their own radio zones (cells) Ca and Cb, and perform radio communication with the mobile stations 11 located in their own radio zones (cells) Ca and Cb. The control device 13 communicates with each other independently. The radio base stations 12a and 12b each have an antenna tilt control device and a pilot channel transmission power control device. The base station control device 13 controls the radio base stations 12 a and 12 b and supports communication with the mobile station 11. In addition, the base station control device 13 incorporates a device having an overload discrimination function based on cell load, and also includes an antenna tilt control device that controls the antenna downtilt angles of the radio base stations 12a and 12b, and A pilot channel transmission power control device that controls the pilot channel transmission power is provided, and load distribution is performed by optimizing the antenna downtilt angle and the pilot channel transmission power.

  In the wireless communication system shown in FIG. 1, for example, when the cell loading of the cell Ca increases, the base station controller 13 sets the set values of the wireless base station 12a and the surrounding wireless base stations 12b in order to perform load distribution. Control to change the antenna downtilt angle or pilot channel transmission power is performed.

Next, the operation of the present embodiment will be described with reference to the flowchart of FIG. First, the radio base stations 12a and 12b shown in FIG. 1 measure η _UL , η _DL , η _HW , and η _OVSF independently of each other (steps 21 to 24). Here, ηUL indicates a load factor in the uplink and is measured based on the following equation.

η _UL = ηtotal / ηplanned (1)
In equation (1), ηtotal represents the current uplink interference amount, and ηplanned represents the planned uplink interference amount.

The η _DL indicates the load factor in the downlink, and is measured based on the following equation.

η _DL = Ptxtotal / Ptxmax (2)
In equation (2), Ptxtotal represents the current transmission power amount in the radio base stations 12a and 12b, and Ptxmax represents the maximum transmission power capacity.

The η _HW indicates the usage rate of the hardware resources (channel cards) of the radio base stations 12a and 12b, and is measured based on the following equation.

η _HW = ηtotal1 / ηmax1 (3)
In equation (3), ηtotal1 represents the current number of hardware resources used, and ηmax1 represents the maximum number of hardware resources.

Further, η _OVSF indicates the usage rate of the orthogonal code number resources of the radio base stations 12a and 12b, and is measured based on the following equation.

η _OVSF = ηtotal2 / ηmax2 (4)
In equation (4), ηtotal2 indicates the current number of orthogonal code number resources used, and ηmax2 indicates the maximum upper limit number of orthogonal code number resources.

  Subsequently, the radio base stations 12a and 12b calculate the load factor L based on the measurement result (step 25). The load factor L is expressed by the following equation.

L = 1−max (η _UL , η _DL , η _HW , η _OVSF ) (5)
However, in the formula (5), max (η _UL , η _DL , η _HW , η _OVSF ) indicates the maximum value among the values of η _UL , η _DL , η _HW and η _OVSF .

  Subsequently, the load factor L separately calculated in the radio base stations 12a and 12b is transmitted to the base station control device 13, and the base station control device 13 loads the load factor L of the radio base stations 12a and 12b under its control. Is determined separately for each radio base station 12a, 12b (step 26). Whether the load factor L is within the specified value range is determined by providing a lower limit specified value X and an upper limit specified value Y that can be arbitrarily set as parameters, the load factor L is equal to or higher than the lower limit specified value X, and the upper limit. If it is equal to or less than the specified value Y, it is determined that it is within the specified value range (X ≦ L ≦ Y), and the routine proceeds to step 29.

  In step 29, it is determined for each of the radio base stations 12a and 12b whether the SHO overhead value Z is within a specified value range (α ≦ Z ≦ β) that is greater than or equal to the lower limit value α and less than or equal to the upper limit value β. To do. Here, the SHO Overhead value Z is the number of mobile stations in communication (SHO Link) in a soft handover state that are located in a zone where cells of a plurality of radio base stations overlap. This is a value divided by the number of mobile stations in communication (Best Server Link) in a zone that does not overlap with the cells of other radio base stations in the cell of one radio base station. Therefore, if the value of SHO Link is 1 and the value of Best Server Link is 2, Z = 0.5.

  Here, the SHO Overhead value Z represents the cost required for soft handover, and a low value indicates that the overlap between the cell Ca and the cell Cb is small. This is expected to increase the probability of coverage hole occurrence. Conversely, if the value Z is high, it indicates that the overlap between the cell Ca and the cell Cb is large, and an overload is expected. Usually, the SHO Overhead value Z is said to be 30 to 40% or less, but here, the SHO Overhead value Z is defined by providing defined values α and β that can be arbitrarily set as parameters.

  When it is determined in step 29 that it is within the specified value range, the base station controller 13 determines the antenna of the radio base station determined to be within the specified value range among the subordinate radio base stations 12a and 12b. The downtilt angle and pilot channel transmission power are determined to be current (step 30).

  On the other hand, when it is determined in step 26 that the load factor L is outside the specified value range N1 (L <X) that is less than the lower limit specified value X, the base station control device 13 determines that it is overloaded and the subordinate radio base An instruction to change the antenna downtilt angle of the radio base station determined to be N1 outside the above specified value range and / or to decrease the pilot channel transmission power among the stations 12a and 12b is issued (step 27). Receiving the change instruction, the radio base station 12a and / or 12b performs the measurement of the steps 21 to 25 and the calculation of the load factor L again.

  By repeating the loop of steps 21 to 27, the base station controller 13 can find the optimum antenna downtilt angle and pilot channel transmission power that satisfy the load factor L within the specified value range in the radio base station. it can. In the case of a down change, the cell dominance is reduced and the dominance boundary is moved. As a result, when the radio base station 12a is down-changed, the call that has been accommodated in the cell Ca so far is under the control of the adjacent cell Cb, and the load is distributed. In this case, the load factor L from the radio base station 12b satisfies the specified value range, or the load factor L is larger than the upper limit specified value Y in step 26, N2 (L> Y ).

  If it is determined in step 26 that the load factor L is outside the specified value range N2 (L> Y) where the load factor L is greater than the upper limit specified value Y, the base station control device 13 determines that the load is light and the subordinate radio The base station 12a, 12b issues an instruction to change the antenna downtilt angle of the radio base station that is determined to be N2 outside the above specified value range and / or to increase the pilot channel transmission power (step 28). Receiving the change instruction, the radio base station 12a and / or 12b performs the measurement of the steps 21 to 25 and the calculation of the load factor L again.

  By repeating the loop of steps 21 to 26 and 28, the base station controller 13 finds the optimum antenna downtilt angle and pilot channel transmission power that satisfies the load factor L within the specified value range in the radio base station. be able to. In the case of an up change, the cell dominance is expanded and the dominance boundary is moved. As a result, when the radio base station 12a is changed up, calls that have been accommodated in the cell Cb so far are under the control of the adjacent cell Ca and are load-balanced. Note that the antenna downtilt angle, the change step width of the pilot channel transmission power, and the lower limit value and the upper limit value are physically limited, and therefore are set to arbitrary parameters determined in advance.

  If it is determined in step 29 that the value is outside the specified value range, the antenna downtilt angle is changed and the pilot channel transmission power is changed in step 27 or step 28 described above. If the base station controller 13 determines in step 29 that the SHO Overhead value Z is outside the specified value range N3 (Z> β), which is larger than the upper limit specified value β, the capacity of DL decreases due to an excessive SHO probability. Therefore, the base station controller 13 determines that the load is overloaded, and of the subordinate radio base stations 12a and 12b, the antenna downtilt angle of the radio base station that is determined to be N3 outside the above specified value range and / or Alternatively, an instruction to change the pilot channel transmission power down is issued (step 27). Receiving the change instruction, the radio base station 12a and / or 12b performs the measurement of the steps 21 to 25 and the calculation of the load factor L again.

  On the other hand, if the base station controller 13 determines in step 29 that the SHO Overhead value Z is out of the specified value range N4 (Z <α) that is less than the lower limit specified value alpha, the SHO probability decreases and a coverage hole is generated. Since it is predicted, it is determined that the load is light, and of the subordinate radio base stations 12a and 12b, the antenna downtilt angle of the radio base station that is determined to be N4 outside the above specified value range and / or the pilot channel An instruction to change the transmission power is issued (step 28). Receiving the change instruction, the radio base station 12a and / or 12b performs the measurement of the steps 21 to 25 and the calculation of the load factor L again.

  As described above, in FIG. 1, when wireless communication with the mobile station 11 is concentrated (overloaded) in the cell Ca or Cb, the phenomenon of reducing the coverage area occurs, so steps 21 to 27 are repeated. As a result, the optimal antenna downtilt angle and pilot channel transmission power suitable for the cell load situation can be controlled and determined at the same time, the boundary of cell dominance can be changed, and load distribution can be implemented to achieve a sufficient traffic reduction effect, The quality of the communication system can be improved. Further, the radio base stations 12a and 12b do not require a special antenna such as a cylindrical antenna array, and load distribution can be realized.

  Further, in this embodiment, not only when the cell loading is overloaded, but also when the load is low, the steps 21 to 26 and 28 are repeated to increase the antenna downtilt angle or the pilot channel transmission power. The effect that can be expanded is obtained. Thereby, in this Embodiment, it operate | moves even at the time of low load, and the quality improvement of a radio | wireless communications system is obtained.

  The present invention is not limited to the above-described embodiment. For example, the load factor L may be calculated not by the radio base stations 12a and 12b but by the base station control device 13.

It is a system configuration figure of one embodiment of the invention. It is a flowchart for operation | movement description of FIG.

Explanation of symbols

11 Mobile station 12a, 12b Wireless base station 13 Base station controller

Claims (7)

A plurality of radio base stations each having an independent radio zone; a mobile station that performs radio communication with a radio base station in a radio zone within the radio zones of the plurality of radio base stations; and the plurality of radios In a wireless communication system having a base station controller connected to a base station and controlling its operation,
Each of the plurality of radio base stations
A load factor calculating means for calculating a load factor L including at least a load factor in the uplink and a load factor in the downlink;
Based on the control from the base station control device, variable setting means for variably setting the antenna downtilt angle and the pilot channel transmission power independently by a preset step width,
The base station controller is
Based on the load factor L calculated in each of the plurality of radio base stations, a first determination is made for each radio base station whether the load factor L is within a preset first specified value range. A determination means;
When the determination result that the load factor L is within the first specified value range is input from the first determination unit, the antenna downtilt angle of the radio base station that calculated the load factor L and Both the pilot channel transmission power and the current state are maintained, and when the determination result that the load factor L is smaller than the lower limit value of the first specified value range is input, the load factor L is calculated. And a first control means for outputting an instruction to change the antenna downtilt angle of the radio base station and / or an instruction to change the pilot channel transmission power to the radio base station that has calculated the load factor L. And
A wireless communication system, wherein the calculation of the load factor in each of the plurality of wireless base stations and the determination operation and control operation in the base station control device are repeated. A plurality of radio base stations each having an independent radio zone; a mobile station that performs radio communication with a radio base station in a radio zone within the radio zones of the plurality of radio base stations; and the plurality of radios In a wireless communication system having a base station controller connected to a base station and controlling its operation,
Each of the plurality of radio base stations
Based on the control from the base station controller, it has variable setting means for variably setting the antenna downtilt angle and the pilot channel transmission power independently by a preset step width,
The base station controller is
A load factor calculating means for calculating at least a load factor L including an uplink load factor and a downlink load factor in each of the plurality of radio base stations;
Based on the load factor L calculated in each of the plurality of radio base stations, a first determination is made for each radio base station whether the load factor L is within a preset first specified value range. A determination means;
When the determination result that the load factor L is within the first specified value range is input from the first determination unit, the antenna downtilt angle of the radio base station that calculated the load factor L and Both the pilot channel transmission power and the current state are maintained, and when the determination result that the load factor L is smaller than the lower limit value of the first specified value range is input, the load factor L is calculated. And a first control means for outputting an instruction to change the antenna downtilt angle of the radio base station and / or an instruction to change the pilot channel transmission power to the radio base station that has calculated the load factor L. And
A wireless communication system, wherein the calculation of the load factor and the determination operation and control operation are repeated. When the load factor L is determined to be within the first specified value range by the first determination unit, the base station controller calculates a SHO overhead value Z indicating a cost required for soft handover. Second determination means for determining for each radio base station whether or not the SHO overhead value is within a preset second specified value range;
When the determination result that the SHO overhead value Z is within the second specified value range is input from the second determination means, the antenna downtilt of the radio base station that calculated the SHO overhead value Z When both the angle and the pilot channel transmission power are maintained as they are, and when the determination result that the SHO overhead value Z is larger than the upper limit value of the second specified value range is input, the SHO overhead value Second control for outputting an instruction to change the antenna downtilt angle of the radio base station that has calculated Z and / or an instruction to change the pilot channel transmission power to the radio base station that has calculated the SHO overhead value Z And further comprising means
When the determination result that the load factor L is within the first specified value range is input from the first determination unit, the first control unit performs the determination operation by the second determination unit. The wireless communication system according to claim 1, wherein the wireless communication system is performed.   When the determination result that the load factor L is larger than the upper limit value of the first specified value range is input from the first determination unit, the first control unit calculates the load factor L. The calculated change instruction of the antenna downtilt angle of the radio base station and / or the change instruction of increase of the pilot channel transmission power is output to the radio base station from which the load factor L has been calculated. Item 3. The wireless communication system according to Item 1 or 2.   When the determination result that the SHO overhead value Z is less than the lower limit value of the second specified value range is input from the second determination unit, the second control unit receives the SHO overhead value Z An instruction to change the antenna downtilt angle and / or an instruction to change an increase in pilot channel transmission power of the radio base station for which the SHO overhead value Z has been calculated is output to the radio base station that has calculated the SHO overhead value Z. The wireless communication system according to claim 3. The load factor calculating means includes an uplink load factor η _UL , a downlink load factor η _DL , a hardware resource usage rate η _HW of the radio base station, and an orthogonal code number resource of the radio base station. 3. The wireless communication system according to claim 1, wherein the load factor L is calculated by subtracting the maximum value of the usage rate η _OVSF from 1 from 1. The second determination means determines the number of the mobile stations that are in communication in a zone in which cells of each of the plurality of radio base stations overlap with each other. The SHO overhead value Z is calculated by dividing the cell by the number of mobile stations that are in communication in a zone that does not overlap with the cell of another radio base station among the cells of 4. The radio communication system according to claim 3, wherein said radio communication system is means for determining for each radio base station whether or not the value is within a preset second specified value range.

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