JP2017092641A - Base station antenna and antenna control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve throughput as an entire area through antenna control even if terminal distribution is uniform or biased.SOLUTION: The present invention relates to a base station antenna comprising a plurality of antenna elements. The base station antenna controls a mechanical tilt for changing a tilt angle by controlling a physical inclination of the plurality of antenna elements and a phase shifted tilt for changing a tilt angle by controlling a phase difference between the plurality of antenna elements in accordance with traffic volume or a radio resource use rate in a communication by the base station antenna.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a base station antenna and an antenna control method.

  In a wireless communication system represented by a cellular system, a large number of base stations are installed in a service area, and the service area is divided into a plurality of cells according to the communication area (coverage area) of each base station. The base station may have a communication function corresponding to a plurality of cells, and each cell may be further divided into sectors by a plurality of base station antennas having directivity in the horizontal direction. Further, both are sometimes called cells without distinguishing between cells and sectors. Hereinafter, cells and sectors are not distinguished unless explicitly mentioned.

  In order to reduce interference with adjacent cells, the base station antenna generally has directivity in the vertical direction, and the vertical angle at which the radio wave radiation intensity is maximum is inclined downward from the horizontal direction. This tilt angle is called a tilt angle or a down tilt angle. Here, the tilt angle is assumed to be 0 degrees in the horizontal direction of the base station antenna and 90 degrees in the direction directly below the base station antenna.

  The tilt angle is determined by various factors such as the antenna height of the base station antenna, the reach of the base station radio wave (also called the cell radius), the distance to the adjacent base station, the density of the base station, and surrounding buildings. The However, even after the base station and the base station antenna are installed, it is necessary to change the tilt angle due to various factors.

  Patent Document 1 states that an antenna corresponding to a communication area of its own station, which is a base station provided with the antenna capable of controlling a tilt angle, which is an angle formed between a vertically downward direction and a main beam of the antenna. A command for adjusting the transmission timing of a signal transmitted from a station is transmitted, and the number of mobile stations existing in the communication area is monitored using the command, and the number of mobile stations is the communication area. In the disclosure of the present application, the tilt angle is an angle formed between the vertical downward direction and the main beam of the antenna. It is described.

JP 2014-96772 A

  If the technique disclosed in Patent Document 1 is used, the tilt angle can be controlled so that the number of mobile stations accommodated is equalized between a plurality of base stations. However, it is difficult to improve the communication quality and throughput over the entire area only by increasing the general tilt angle according to the increase in the number of mobile stations (decreasing the tilt angle in Patent Document 1). . Also, it did not adaptively respond to traffic that fluctuates greatly with time and place.

  The present invention has been made in view of the above points, and an object of the present invention is to improve the throughput of the entire area by antenna control regardless of whether the terminal distribution is uniform or biased.

  The outline of typical ones of the inventions disclosed in the present application will be described as follows. A base station antenna having a plurality of antenna elements, wherein a tilt angle is changed by controlling a physical inclination of the plurality of antenna elements according to a traffic amount or a radio resource usage rate of communication by the base station antenna. A base station antenna that controls a mechanical tilt and a phase shift tilt that changes a tilt angle by controlling a phase difference between the plurality of antenna elements.

  According to the present invention, it is possible to perform antenna control according to traffic conditions, and it is possible to improve the throughput of the entire area regardless of whether the terminal distribution is uniform or uneven.

  Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments.

It is a figure which shows the example of the tilt angle control with respect to a coverage hole. It is a figure which shows the example of the tilt angle control for load balancing. It is a figure which shows the example of the relationship between traffic amount, communication quality, and a throughput. It is a figure which shows the example of a phase shift type tilt. It is a figure which shows the example of a mechanical tilt. It is a figure which shows the example of communication quality distribution of a phase shift type tilt and a mechanical tilt. It is a figure which shows the example of a system configuration. It is a figure which shows the example of the relationship between traffic amount or a radio | wireless resource usage rate, and transmission power. It is a figure which shows the example of the operation | movement procedure of the traffic analyzer which switches a tilt control system. It is a figure which shows the example of the tilt angle when the amount of traffic is large. It is a figure which shows the example of the tilt angle when the amount of traffic is small. It is a figure which shows the example of the tilt angle when there is deviation in the traffic amount. It is a figure which shows the example of the operation | movement procedure of the traffic analyzer which controls a tilt angle. It is a figure which shows the example of the system configuration | structure which provided the traffic analyzer separately. It is a figure which shows the example of a system configuration which acquires a radio | wireless resource usage rate etc. from a base station. It is a figure which shows the example of the operation | movement procedure of the traffic analyzer which controls a tilt angle in steps. It is a figure which shows the example of the table which shows the relationship between transmission power and a radio | wireless resource usage rate. It is a figure which shows the example of the table which shows the relationship between the wireless resource usage rate, the tilt angle of mechanical tilt, and the tilt angle of phase shift tilt. It is a figure which shows the example of the table which shows the relationship between a radio | wireless resource usage rate and a tilt angle.

  FIG. 1A is a diagram illustrating an example of tilt angle control for coverage optimization. There may be an area incapable of communication between the coverage area 31a of the signal radiated from the base station antenna 11a and the coverage area 31b of the signal radiated from the base station antenna 11b. Such an incommunicable area is generally called a dead zone or a coverage hole.

  In order to eliminate such a coverage hole 35, the coverage angle 31b of the base station antenna 11b is changed to the coverage area 31d by reducing the tilt angle of the base station antenna 11b covering the vicinity of the coverage hole 35 (facing upward). Can be enlarged.

  FIG. 1B is a diagram illustrating an example of tilt angle control for load leveling. Since the terminals are moving between the coverage areas of the base station antennas, many terminals are concentrated in the specific coverage area 31f at a specific time, and the load is concentrated. Thus, the terminals 21a and 21b in the coverage area 31f, etc. Throughput may be reduced.

  In order to eliminate such load concentration, the coverage area 31f is reduced to the coverage area 31h by increasing the tilt angle of the base station antenna 11d in the coverage area 31f with many terminals (directed downward), and the adjacent cell By handing over the terminals, the terminals in the coverage area 31h can be reduced and the load can be reduced.

  Alternatively, the tilt angle of the base station antenna 11c in the coverage area 31e with few terminals adjacent to the coverage area 31f with many terminals is reduced, the coverage area 31e is expanded to the coverage area 31g, and the terminal is changed from a cell with many terminals to a cell with few terminals. Can be handed over.

  Further, by reducing the coverage area 31f to the coverage area 31h and expanding the coverage area 31e to the coverage area 31g, the terminal 21a can be handed over, and load leveling (load balancing) can be realized.

  Next, the relationship among communication quality, traffic volume, and throughput in a wireless communication system will be described. FIG. 2 is a diagram illustrating an example of the relationship among communication quality, traffic volume, and throughput. Graph A shows a cumulative distribution of communication quality of two systems (system A and system B). For example, the system A and the system B have different antenna parameters as will be described later. Here, in the graph A, SINR (Signal to Interference plus Noise power Ratio), which is a ratio of signal power and the sum of noise and interference power, is used as an index of communication quality.

  Further, the cumulative distribution may be a cumulative distribution of SINR for each location in the service area. Or it is good also as a cumulative distribution of SINR for every terminal when a plurality of terminals exist in a service area. However, the SINR shown in the graph A is the SINR when the traffic amount is sufficiently large.

  System A is an example of a system in which the variation in communication quality between places or terminals is small. On the other hand, the system B is an example of a system in which the communication quality varies greatly depending on the location or terminal. That is, in the system B, the communication quality value at the peak or the cell center is large, while the communication quality value at the cell boundary is small.

  At this time, when the traffic amount, the number of terminals, or the radio resource usage rate in each of the systems A and B is large, the cumulative distribution of throughput of each terminal is as shown in the graph B. When the amount of traffic is large, radio resources are allocated to each terminal almost equally, so that throughput corresponding to the communication quality of graph A can be obtained.

  Therefore, the system A has a small variation in throughput between terminals. In other words, a stable throughput can be obtained. On the other hand, the system B has a large variation in throughput between terminals, and the throughput near the peak or cell center is large, but the throughput of terminals near the cell boundary is small. If the throughput near the cell boundary is small, the available applications are limited and the communication quality experienced by the user is lowered. Therefore, assuming that there is no significant difference in the average throughput (or capacity of traffic that can be accommodated) between system A and system B, overall, system A is more suitable when there is a large amount of traffic. I can say that.

  On the other hand, when the traffic volume, the number of terminals, or the radio resource usage rate in each of the systems A and B is small, the cumulative distribution of throughput of each terminal is as shown in the graph C. As shown in the graph C, when the traffic is low, the system B having a high peak communication quality or a cell-centered communication quality has a high throughput as a whole including a region where the throughput is small.

  This is because when the traffic is low, a terminal with high communication quality terminates communication early, and as a result, the effect of increasing the resources of other terminals and the effect of reducing interference with other cells are obtained. Because it is. Therefore, it can be said that the system B having higher peak communication quality is more suitable when the traffic is low.

  As described above, in the wireless communication system, the distribution of suitable communication quality differs depending on the traffic volume. For example, when the tilt angle of the base station antenna is increased, the communication quality at the cell center is improved, but the communication quality at the cell boundary is decreased. That is, the effect of antenna parameter control has a trade-off relationship between the cell center and the cell boundary.

  Furthermore, as will be described later, the same phenomenon occurs even when other antenna parameters such as a tilt control method are changed. That is, depending on the antenna parameter, there may be a case where the communication quality similar to that of the system A in the graph A can be obtained or a communication quality similar to that of the system B can be obtained. Therefore, in a conventional wireless communication system that does not control antenna parameters according to the traffic volume, it is difficult to improve the throughput of the entire area.

  However, since the distribution of communication quality suitable for the amount of traffic (radio resource usage rate) varies, even if the effect of antenna parameter control is a trade-off, if the traffic is low, the system B in the graph C As a result, overall throughput can be improved. Therefore, the present invention provides a base station antenna, a wireless communication system, and an antenna control method that can improve throughput as a whole area by adaptively controlling antenna parameters according to the traffic volume.

  Specifically, when the traffic amount is large, an antenna parameter having the same characteristics as the system A in FIG. 2 is applied, and when the traffic amount is small, the antenna having the same characteristics as the system B in FIG. Apply parameters. Specific antenna parameters to be controlled, their implementation methods, system configurations, etc. will be described below.

  In the first embodiment, the tilt control method is switched according to the traffic amount. As shown in FIGS. 3A and 3B, there are roughly two types of base station antenna tilt control methods. Here, in FIGS. 3A and 3B, a three-sector base station antenna is shown as an example. The base station antennas 11e-1 to 11e-3 and 11f-1 to 11f-3 are shown in perspective views so that the positional relationship is easy to see, but the directivity of radio waves is easy to understand the operation of the tilt control method. Expressed in the vertical plane (vertical direction), the difference in directivity due to the directivity of the horizontal plane is omitted.

  3A and 3B, each of the base station antennas 11e-1 to 11e-3, 11f-1 to 11f-3 transmits and receives signals corresponding to one sector. The base station antennas 11e-1 and 11f-1 have directivity in the left direction of the drawing, and the base station antennas 11e-2 and 11f-2 have directivity in the right direction of the drawing. It is assumed that the antennas 11e-3 and 11f-3 have directivity in the back side of the drawing. Terminals 21c and 21d are located in a sector formed by the directivities of base station antennas 11e-2 and 11f-2.

  The first tilt control method is a method called phase shift tilt or electronic tilt shown in FIG. 3A. In the phase-shifting tilt, a phase difference is provided in signals radiated from different antenna elements of the base station antennas 11e-1 to 11e-3, thereby changing the direction in which the radio wave intensity is electronically increased, that is, the main beam direction. In phase-shifting tilt, the greater the phase difference between antenna elements, the greater the tilt angle.

  Since this phase difference occurs only in the vertical direction, as shown in FIG. 3A, the phase-shift tilt operation is performed by using the vertical angles of the base station antennas 11e-1 to 11e-3 as viewed from the terminal 21c (that is, If the elevation angle is the same, the antenna gain is the same regardless of the horizontal angle (that is, the azimuth angle) of the terminal 21c viewed from the base station antennas 11e-1 to 11e-3. That is, the antenna gain is the same if the vertical height is the same regardless of the azimuth.

  As shown in FIG. 3A, when the terminal 21c is positioned in the main beam direction as the vertical direction of the base station antenna 11e-2 (that is, when the elevation angle of the terminal 21c with respect to the base station antenna 11e-2 is the same as the tilt angle), Since the terminal 21c is located at the same angle as the main beam direction as the vertical direction for the base station antennas 11e-1 and 11e-3 of other sectors, the inter-sector interference is not suppressed by the directivity in the vertical direction. Since there is directivity in the horizontal direction (horizontal plane), it is suppressed by the directivity in the horizontal direction. On the other hand, in phase-shift tilt, generally, the elevation angle decreases as the distance between the terminal and the base station antenna increases. Therefore, since the terminal 21c deviates from the main beam direction of the base station antenna of another base station having a large distance, interference between the base stations is small.

  The second tilt control method is a method called mechanical tilt shown in FIG. 3B. As shown in FIG. 3B, the mechanical tilt is a method in which the main beam direction is changed by physically tilting the base station antennas 11f-1 to 11f-3 with respect to the vertical direction (vertical direction). The base station antennas 11f-1 to 11f-3 are tilted in the same direction as the directivity in the horizontal direction.

  The directivity in the vertical direction (vertical plane) of the base station antenna in the mechanical tilt is a main beam direction perpendicular to the base station antenna formed by a plurality of antenna elements. In other words, the tilt angle as the phase shift tilt is 0 degree. The physical tilt becomes the tilt angle as it is.

  In the mechanical tilt, as shown in FIG. 3B, the tilt angle is downward with respect to the direction in which the base station antennas 11f-1 to 11f-3 are inclined (referred to as the front), but the direction in which the antenna is inclined For the reverse direction (referred to as the rear), the tilt angle is upward. For example, with respect to the base station antenna 11f-2, since the tilt angle is as indicated by the solid line arrow 33-2, the terminal 21d is positioned in the main beam direction as the vertical direction.

  However, with respect to the forward directional broken line 32-1 inclined by the base station antenna 11f-1, it is located behind the inclined line and has an angular difference as shown by a double-dashed broken line 34-1. Is larger than the base station antenna 11f-2 and deviates from the main beam direction as the vertical direction.

  Similarly, the terminal 21d deviates from the main beam direction as the vertical direction of the base station antenna 11f-3, but the terminal 21d is located in the lateral direction of the direction in which the base station antenna 11f-3 is tilted (back side direction). Apparently, the tilt angle of the base station antenna 11f-3 viewed from the terminal 21d is around 0 degree. That is, it becomes like a directional dotted line 32-3, and has an angle difference like a double-pointed dotted line 34-3.

  Since there is horizontal directivity, in addition to suppression due to horizontal directivity, in mechanical tilt, the apparent elevation angle seen from the terminal 21d differs from sector to sector, so interference between different sectors causes vertical interference. It is suppressed by directivity. As a result, in the mechanical tilt, interference between sectors of the same base station is smaller than in the phase shift tilt.

  On the other hand, in the lateral direction with respect to the inclination of each of the base station antennas 11f-1 to 11f-3 (for example, the directional dotted line 32-3 of the base station antenna 11f-3), the tilt angle is near 0 degrees, and the vertical direction Since the position in the main beam direction is far from the phase shift tilt, the interference with other base stations (not shown) is larger than the phase shift tilt.

  As described above, the phase shift tilt and the mechanical tilt have different characteristics, and the distribution of communication quality in the area is different even at the same tilt angle. FIG. 4 is a diagram illustrating an example of a cumulative distribution of SINR (communication quality) of phase-shifting tilt and mechanical tilt when the amount of traffic is large. As can be seen from FIG. 4, the phase shift tilt has a small variation in communication quality depending on the location or the terminal, whereas the mechanical tilt has a large variation in communication quality depending on the location or the terminal. That is, in the mechanical tilt, the communication quality at the peak or cell center is higher than the phase-shifted tilt, but the communication quality near the cell boundary is low. This is due to the following reason.

  As described above, in the phase-shift tilt, interference between different sectors of the same base station is suppressed only by the directivity in the horizontal direction, so that the interference between sectors is larger than that of the mechanical tilt. On the other hand, in the phase shift tilt, interference between different base stations is smaller than that of the mechanical tilt. Since interference between base stations is small near the center of the cell, interference between sectors of the same base station determines communication quality. Therefore, the communication quality of the mechanical tilt is higher than that of the phase shift tilt. On the other hand, in the vicinity of the cell boundary, since the distance to the adjacent base station is small, the interference between the base stations determines the communication quality. Therefore, the communication quality of the phase shift tilt is higher than that of the mechanical tilt. As described above, the phase shift tilt and the mechanical tilt have different communication quality distributions as shown in FIG. 4 even if the tilt angle is the same.

  4 and FIG. 2 are compared, it can be seen that the phase-shift tilt has the characteristics of the system A in the graph A of FIG. 2 and the mechanical tilt has the characteristics of the system B. Therefore, phase shift tilt is suitable in an environment with a large traffic volume, and mechanical tilt is suitable in an environment with a small traffic volume.

  Therefore, phase shift tilt is applied when the traffic amount or radio resource usage rate is large, and mechanical tilt is applied when the traffic amount or radio resource usage rate is small.

  FIG. 5 is a diagram illustrating an example of a system configuration. The base station antenna 11g is the base station antennas 11e-1 to 11e-3 and 11f-1 to 11f-3 described with reference to FIGS. 3A and 3B. For example, the base station antenna 11g is mechanically coupled with the base station antenna 11e-1 having a phase shift tilt. This is a base station having both structures of the tilt base station antenna 11f-1. You may provide the structure of base station antenna 11a-11d demonstrated using FIG. 1A and 1B.

  The base station antenna 11g is connected to the base station 10g and transmits a downlink signal input from the base station 10g. Moreover, the base station antenna 11g receives the uplink signal transmitted from the terminal, and outputs it to the base station 10g. The base station 10g and the base station antenna 11g may be connected by a coaxial cable, and a radio frequency (RF) signal may flow between them.

  Alternatively, the RRH and the base station antenna 11g may be connected by a coaxial cable via an RRH (Remote Radio Head) (not shown) from the base station 10g. In that case, the base station 10g and the RRH are connected by an optical fiber or the like, a baseband signal flows, and an RF signal flows between the RRH and the base station antenna 11g.

  Alternatively, the base station 10g and the base station antenna 11g may be connected by an optical fiber, and the base station antenna 11g may have an active antenna configuration. In that case, a baseband signal flows between the base station 10g and the base station antenna 11g, and the base station antenna 11g has an analog-digital converter (A / D converter) or a digital-analog converter (D) (not shown). / A converter), a radio frequency converter, a signal amplifier, and the like. Alternatively, the base station 10g and the base station antenna 11g may be connected by a wireless line.

  The base station antenna 11g includes a power measurement device 12, a traffic analysis device 13g, a tilt control device 14, variable phase shifters 15a to 15d, a movable portion 16, and antenna elements 17a to 17d. The movable unit 16 is a drive unit that physically tilts the variable phase shifters 15a to 15d and the antenna elements 17a to 17d by a tilt angle based on the control of the tilt control device 14. A structure in which only the antenna elements 17a to 17d are physically tilted may be employed.

  Each of the variable phase shifters 15 a to 15 d is based on the control of the tilt control device 14, so that the phase difference of the signal between the antenna element 17 a, the antenna element 17 b, the antenna element 17 c, and the antenna element 17 d is due to the phase shift tilt. Is generated. The power measurement device 12 measures the transmission power of the radio frequency signal input from the base station 10g, and notifies the traffic analysis device 13g of the measurement result. The traffic analysis device 13g uses the transmission power notified from the power measurement device 12 to execute an operation procedure described with reference to FIG.

  Before describing the operation procedure, transmission power will be described. FIG. 6 is a diagram illustrating an example of the relationship between transmission power and traffic volume or radio resource usage rate. In general, in a wireless communication system, transmission power increases as the traffic amount or the radio resource usage rate increases.

  When the amount of traffic is small, the data of the terminal to be transmitted is small. Therefore, the base station needs to transmit only a pilot signal, a reference signal, a synchronization signal, a broadcast signal for broadcasting system information, and the like, and other radio resources Is in an unused state, the total transmission power during a predetermined period of the signal to be transmitted is small.

  On the other hand, when the traffic volume is large, the amount of data to be transmitted increases, so that radio resources that are available when the traffic volume is small are used, and the transmission frequency increases, so that transmission power increases. When the radio resource usage rate reaches 100%, the transmission power is saturated.

  Since the relationship as shown in FIG. 6 is established, the traffic analysis device 13g may calculate the traffic amount from the notified transmission power with reference to the relationship of FIG. Instead, the radio resource usage rate may be calculated. The traffic amount may be an amount related to data to be communicated, and the wireless resource may be a wireless bandwidth.

  FIG. 7 is a diagram illustrating an example of an operation procedure of the traffic analysis device 13g. The traffic analysis device 13g determines whether or not the transmission power notified from the power measurement device 12 is equal to or greater than a preset threshold value (step 71). Since this determination has the relationship described with reference to FIG. 6, it is equivalent to determining whether the traffic amount or the radio resource usage rate is equal to or greater than a predetermined threshold. That is, the determination that the transmission power is small in the traffic analysis device 13g is equivalent to the determination that the traffic amount is small, and the determination that the transmission power is large is equivalent to the determination that the traffic amount is large.

  When the traffic analysis device 13g determines that the transmission power notified from the power measurement device 12 is equal to or greater than a preset threshold value (when Step 71 is Yes), the traffic analysis device 13g applies the phase shift tilt. Therefore, the traffic analyzer 13g sets the tilt angle of the mechanical tilt to 0 degree and sets the phase shift tilt angle to T degrees (step 72).

  On the other hand, when it is determined that the transmission power is smaller than a preset threshold value (No in step 71), mechanical tilt is applied. For this reason, the traffic analyzer 13g sets the tilt angle of the mechanical tilt to T degrees and sets the tilt angle of the phase shift tilt to 0 degrees (step 73). That is, in the example of FIG. 7, the magnitude of the tilt angle is the same when the mechanical tilt is used and when the phase shift tilt is used, and the sum of the tilt angle of the phase shift tilt and the tilt angle of the mechanical tilt is the same. The value is the same value regardless of the transmission power. The angle T degree is set in advance.

  Then, the tilt control device 14 is notified of the tilt angle set in step 72 or step 73 (step 74). For example, the traffic analysis device 13g may notify the tilt control device 14 of information indicating whether the applied tilt control method is a phase shift tilt or a mechanical tilt, and the tilt angle.

  Alternatively, the tilt angle of each of the phase shift tilt and the mechanical tilt may be notified, and when one of the tilt angles is 0 degrees, it may indicate that the other tilt control method is used. Alternatively, only the information indicating either mechanical tilt or phase shift tilt may be notified, and the tilt control device 14 may store the T degree in advance.

  Here, the preset threshold value used for the determination in step 71 is based on the use of phase shift tilt, and when mechanical tilt is used only when the traffic amount is small, for example, the radio resource usage rate is 20 The transmission power value may be about 30% to 30%. Alternatively, the threshold of step 71 is based on the use of mechanical tilt, and when the phase shift tilt is used only when the traffic volume is large, for example, the radio resource usage rate is about 70% to 80%. It is good also as a value of transmission power. If there is no particular priority in mechanical tilt and phase shift tilt, the threshold value in step 71 may be a transmission power value at which the radio resource usage rate is about 50%.

  The tilt control device 14 performs switching control between a phase shift tilt and a mechanical tilt in response to a notification from the traffic analysis device 13g. When the notification from the traffic analysis device 13g is a phase shift tilt, the tilt control device 14 controls the movable portion 16 to release the tilt of the antenna elements 17a to 17b, that is, the tilt angle of the mechanical tilt is 0 degree. Control to be. Then, the tilt control device 14 controls the phase differences of the variable phase shifters 15a to 15d connected to the antenna elements 17a to 17b so that the tilt angle of the phase shift tilt becomes T degrees.

  On the other hand, when the notification from the traffic analysis device 13g is a mechanical tilt, the tilt control device 14 controls the movable portion 16 so that the tilts of the antenna elements 17a to 17b and the tilt angle of the mechanical tilt become T degrees. To control. Then, the tilt control device 14 controls the phase difference between the variable phase shifters 15a to 15d and controls the phase difference between the antenna elements 17a to 17b to be zero. That is, the tilt angle of the phase shift tilt is set to 0 degree.

  The movable part 16 generates a physical tilt of the antenna elements 17a to 17d in order to realize a mechanical tilt. The tilt of the antenna elements 17 a to 17 d, that is, the operation amount of the movable portion 16 is controlled by the tilt control device 14.

  The variable phase shifters 15a to 15d change the phase difference between signals radiated or received from the antenna elements 17a to 17d. The variable phase shifters 15a to 15d may be configured to change the amount of phase shift by changing the length of the transmission line from the feeding point to each of the antenna elements 17a to 17d.

  Alternatively, in the case where the base station antenna 11g has an active antenna configuration, the variable phase shifters 15a to 15d may be multipliers, and are input from the base station 10g or the antenna elements 17a to 17d. The amount of phase shift may be changed by multiplying the signal to be expressed by exp (jθn). Here, j is an imaginary unit, and θn is the amount of phase shift of the nth antenna element.

  Multiplication in the variable phase shifters 15a to 15d may be performed on a digital signal or an analog signal. For example, when the phase difference between the antenna elements 17a to 17d is 0, the gain by the antenna elements 17a to 17d is maximized in a direction perpendicular to the surface of the antenna elements 17a to 17d (a direction where the elevation angle is 0 degree). At this time, the tilt angle by the phase-shifting tilt is 0 degree.

  Further, when the phase of the upper antenna element 17a is advanced as compared with the lower antenna element 17d, the gains of the antenna elements 17a to 17d are lower than the direction perpendicular to the plane of the antenna elements 17a to 17d. Maximum. This means that a positive angle phase-shift tilt is applied.

  Since the relationship described with reference to FIG. 6 has been described, it has been described that the determination of the transmission power in step 71 is equivalent to the determination of the traffic amount or the radio resource usage rate. The traffic amount or the radio resource usage rate is calculated from the notified transmission power with reference to the relationship of FIG. 6 set and stored in advance. In step 71, the traffic amount or the radio resource usage rate is preset. You may determine whether it is more than a threshold value.

  By utilizing the fact that the communication quality distribution suitable for the amount of traffic differs according to the first embodiment described above, switching the tilt control method (mechanical tilt and phase-shifting tilt) according to the traffic amount allows traffic to be reduced. When there is a large amount, a stable throughput like the system A in the graph B shown in FIG. 2 can be obtained, and when there is little traffic, a throughput like the system B in the graph C can be obtained, and a single tilt control is performed. Throughput can be improved as compared with the case of using the method.

  In addition, the switching of the tilt control method according to the traffic volume does not use whether or not the traffic between cells is biased as a criterion for control, so traffic or a terminal in an area composed of a plurality of cells Even if the distribution is uniform or biased, it can be applied. Further, since the distribution of communication quality within the area is changed, as a result of the control, the effect of improving the throughput can be obtained even if the cell or base station to which the terminal is connected is not changed.

  However, the tilt angle of the phase shift tilt used when the traffic is large may be made larger than the tilt angle of the mechanical tilt used when the traffic is small. As a result, switching between mechanical tilt and phase shift tilt according to the traffic volume or radio resource usage rate provides the effect of improving throughput by changing the distribution of communication quality, and the same effect as load balancing Can also be obtained.

  In the first embodiment, the tilt control method is switched according to the traffic amount, but in the second embodiment, the tilt angle is switched according to the traffic amount. When the tilt angle is increased, the direction in which the vertical main beam faces is downward. In other words, when the tilt angle is increased, the position of the main beam is closer to the base station antenna. Therefore, when the tilt angle is increased, the radio field intensity near the cell center increases, while the radio field intensity near the cell boundary decreases.

  As a result, when the tilt angle is increased in the state where the communication quality like the system A in the graph A of FIG. 2 is obtained when the tilt angle is small, the distribution of the communication quality is the distribution of the system B in the graph A of FIG. It becomes like this. Therefore, in the second embodiment, when the traffic amount of a certain sector or cell is small, the communication quality distribution similar to that of the system B in the graph A of FIG. 2 is increased by increasing the tilt angle of the sector or the sector to which the cell belongs. And the throughput is improved like the system B in the graph C of FIG.

  FIG. 8A is a diagram illustrating an example of setting the tilt angle when the traffic amount or the radio resource usage rate is large for the entire area. The tilt angle in this example may be determined similarly to the tilt angle of the conventional wireless communication system and the base station antenna. For example, the tilt angle is determined according to general cell design criteria based on base station antenna height, cell radius, distance to neighboring base stations, base station density, frequency transmitted by the base station antenna, etc. The

  On the other hand, when the traffic amount or the radio resource usage rate is small as a whole area, as shown in FIG. 8B, the tilt angle is increased as compared with the tilt angle in FIG. 8A. As a result, the communication quality value at the cell center increases, the termination of communication of terminals located near the cell center is accelerated, radio resources available to other terminals increase, or interference with other cells occurs. Decreasing effect is obtained.

  Therefore, the throughput of the entire area can be improved as in the system B in the graph C of FIG. Thus, in the example of FIG. 8B, although the tilt angle is controlled according to the traffic amount, even when there is no bias in the traffic amount between cells, between sectors, or between base stations, the number of terminals, or the radio resource usage rate. Throughput can be improved.

  On the other hand, for example, as shown in FIG. 8C, when the traffic volume is large in a certain cell and the traffic volume is small in another cell, the tilt angle of the cell having a small traffic volume is increased. However, when the traffic amount is small, instead of increasing the tilt angle of the cell, the same effect may be realized by decreasing the tilt angle of an adjacent cell whose traffic amount is not small. Alternatively, both of increasing the tilt angle of a cell having a small traffic volume and decreasing the tilt angle of an adjacent cell having a small traffic volume adjacent to the cell may be executed.

  Here, in the conventional wireless communication system, when there is a cell with a large traffic volume and a cell with a small traffic volume, the tilt angle of the cell with a large traffic volume is increased (area is reduced) or the traffic is small. The operation was to reduce the tilt angle of the cell (enlarge the area). However, in the second embodiment, the operation is reverse to that of the conventional wireless communication system.

  The control of the tilt angle in the second embodiment may be performed by mechanical tilt or may be performed by phase shift tilt. The system configuration of the second embodiment is almost the same as that shown in FIG. However, when the tilt angle is controlled only by the phase-shifting tilt, the mechanical tilt movable unit 16 in FIG. 5 may not exist. On the other hand, when the control of the tilt angle is realized only by the mechanical tilt, the variable phase shifters 15a to 15d in FIG. 5 may not exist. Further, the operation procedure of the traffic analyzer 13g is different.

  FIG. 9 is a diagram illustrating an example of an operation procedure of the traffic analysis device 13g that controls the tilt angle. The traffic analysis device 13g determines whether or not the transmission power notified from the power measurement device 12 is equal to or greater than a preset threshold value (step 81). Since the traffic analysis apparatus 13g has the relationship described with reference to FIG. 6 similarly to the description in FIG. 7, the determination that the transmission power is small is equivalent to the determination that the traffic amount or the radio resource usage rate is small. The determination that the transmission power is high is equivalent to the determination that the traffic amount or the radio resource usage rate is large.

  Therefore, when the traffic analysis device 13g determines that the transmission power notified from the power measurement device 12 is equal to or greater than a preset threshold value (when Step 81 is Yes), the traffic angle is set to a preset value. Set (step 82). Here, in order to compare with the case where the traffic amount is small, the tilt angle set in step 82 is set to Tmin degree.

  On the other hand, when it is determined that the transmission power is smaller than a preset threshold value (when Step 81 is No), the tilt angle is set to Tmax degrees (Step 83). Here, when Tmin <Tmax and the amount of traffic is smaller, the tilt angle is larger, and the Tmin degree and the Tmax degree may be set in advance. Then, the traffic analyzer 13g notifies the tilt controller 14 of the tilt angle set in step 82 or step 83 (step 84).

  For example, the tilt control device 14 may be notified of the set tilt angle from the traffic analysis device 13g. Alternatively, the amount of increase or decrease in tilt angle may be notified. Or you may notify only the information which shows whether the increase of a tilt angle is applied, ie, a tilt angle is Tmin degree or Tmax degree. In this case, the tilt control device 14 may be set in advance to set the tilt angle to Tmin degrees when the increase in the tilt angle is not applied and to Tmax degrees when the increase in the tilt angle is applied.

  In the first and second embodiments, the traffic analysis device 13g is included in the base station antenna 11g and distributed control is shown. However, in the third embodiment, the traffic analysis device is not a base station antenna but an operation management (Operation and). (Maintenance: O & M, OAM) An example of a configuration included in the apparatus side and centrally controlled is shown.

  FIG. 10 is a diagram illustrating an example of a system configuration in which the traffic analysis device 13h is outside the base station antenna 11h. Since the base station 10g is the same as that shown in FIG. The base station antenna 11h includes a power measurement device 12, a tilt control device 14, variable phase shifters 15a to 15d, a movable unit 16, antenna elements 17a to 17d, and the like. Since these are also the same as those in FIG.

  The traffic analysis device 13h is connected to the power measurement device 12 and the tilt control device 14 of the base station antenna 11h via an arbitrary network line. However, the traffic analysis device 13h is a device that is physically different from the base station antenna 11h, and is installed together with the operation management device of the wireless communication system, for example. Alternatively, the traffic analysis device 13h may be included in the operation management device as one of the functions of the operation management device.

  Therefore, when there are a plurality of base station antennas 11h, the traffic analysis device 13h may be connected to the power measurement devices 12 and the tilt control devices 14 of the plurality of base station antennas 11h. For example, when the base station 10g has a communication function of a plurality of cells or sectors, the base station antenna 11h of each cell or sector may be connected to one traffic analysis device 13h.

  The traffic analysis device 13g receives transmission power information measured by the power measurement device 12 from the power measurement device 12 of the base station antenna 11h. Then, based on the received transmission power information, the operation procedure described with reference to FIGS. 7 and 9 is executed, and the antenna parameters are transmitted to the tilt control device 14. Further, based on the notified power information, the traffic amount or radio resource usage rate of the cell, sector, or base station corresponding to the base station antenna 11h is calculated, and according to the calculated traffic amount or radio resource usage rate, The antenna parameter may be transmitted to the tilt control device 14.

  However, in a configuration in which one traffic analyzer 13h is connected to a plurality of base station antennas 11h, determination of traffic amount (transmission power, radio resource usage rate) and antenna parameters are individually made for each base station antenna 11h. May be determined, or information of a plurality of base station antennas 11h may be integrated to determine the traffic volume (transmission power, radio resource usage rate) in a certain area and to collectively determine antenna parameters. .

  For example, based on the average value of the radio resource usage rate (traffic amount) of a plurality of base station antennas 11h covering a predetermined area, it is determined whether the traffic amount (radio resource usage rate) in the predetermined area is large or small. Then, the antenna parameters of all the base station antennas 11h in the predetermined area are collectively set (that is, step 72 or step 73 in FIG. 7 or step 82 or step 83 in FIG. 9 is performed). Alternatively, it may be set based on the radio resource usage rate (traffic amount) of a preset number of base station antennas 11h.

  Alternatively, whether the traffic amount (transmission power, radio resource usage rate) is large or small is determined individually for each base station antenna 11h (sector), and all of the determination results of the determination results of the plurality of base station antennas 11h The antenna parameters of the base station antenna 11h may be determined collectively. Alternatively, whether the traffic amount (transmission power, radio resource usage rate) is large or small is individually determined for each base station antenna 11h (sector), and the transmission power (traffic) of any one base station antenna 11h (sector) is determined. When the amount and the radio resource usage rate) are smaller (or larger) than the threshold, the antenna parameters of all the base station antennas 11h may be determined collectively.

  FIG. 11 is a diagram illustrating an example of another system configuration in which the traffic analysis device 13k is outside the base station antenna 11k. The description using FIG. 10 shows an example in which the traffic amount or the radio resource usage rate is calculated using the relationship shown in FIG. 6 from the transmission power information obtained from the power measurement device 12 or the transmission power information. However, in the example shown in FIG. 11, the traffic amount or the radio resource usage rate is acquired from the statistical information reported from the base station 10k.

  In the example shown in FIG. 11, the traffic analysis device 13k is connected to the base station 10k and the tilt control device 14 in the base station antenna 11k via an arbitrary network line. The base station antenna 11k includes a tilt control device 14, variable phase shifters 15a to 15d, a movable portion 16, antenna elements 17a to 17d, and the like. Since these of the base station antenna 11k are the same as those of FIG. 5, the same reference numerals are given, and detailed description thereof is omitted. However, the base station antenna 11k does not include a power measurement device.

  The base station 10k measures the amount of traffic or the usage rate of radio resources for a certain period, and periodically transmits it to an operation management apparatus (not shown). Therefore, the traffic analysis device 13k acquires the same information as the transmitted information directly from the base station 10k via the network line, determines whether the traffic amount (the usage rate of radio resources) is large or small, and determines the antenna parameter. To decide. Further, the traffic analysis device 13k may be acquired from the operation management device without being acquired directly from the base station 10k via the network line.

  As described above, the antenna parameters can be determined without providing the base station antenna 11k with a traffic analysis device. In particular, since one traffic analyzer 13k can be shared by a plurality of base station antennas 11k, the cost can be reduced. Further, by acquiring the traffic amount information from the base station 10k, the power measuring device is not necessary, and the cost can be reduced.

  In the first to third embodiments, the control of antenna parameters (tilt control method or tilt angle) according to the traffic amount (radio resource usage rate, transmission power) is set in advance for the traffic amount (radio resource usage rate, transmission power). An example is shown in which the threshold value is larger or smaller than the threshold value. In the fourth embodiment, an example in which antenna parameters are determined in a stepwise manner according to the amount of traffic, the radio resource usage rate, or the magnitude of transmission power will be described.

  The system configuration of the fourth embodiment may be the same as the configuration described with reference to FIGS. 5, 10, and 11, and the operations of the traffic analyzers 13 g, 13 h, and 13 k are different. Here, any of the traffic analysis device 13g, the traffic analysis device 13h, and the traffic analysis device 13k may be used, and it is not necessary to distinguish between them. Therefore, the traffic analysis device 13 is representatively described.

  Further, when both the tilt angle of the mechanical tilt notified from the traffic analysis device 13 and the tilt angle of the phase shift tilt are not 0, the tilt control device 14 performs only the notified tilt angle of the mechanical tilt. The movable unit 16 is controlled to tilt the antenna elements 17a to 17d, and the tilt control device 14 further adjusts the phase shift by an amount corresponding to the notified tilt angle of the phase shift tilt. 15d is controlled. 5, 10, and 11, the description is omitted because there is no notification from the traffic analyzers 13 g, 13 h, and 13 k that both the tilt angle of the mechanical tilt and the tilt angle of the phase shift tilt are not zero. However, since the tilt control device 14 shown in FIGS. 5, 10, and 11 may operate for notifications in which both are not 0, they are referred to with the same reference numerals.

  FIG. 12 is a diagram illustrating an example of an operation procedure of the traffic analysis device 13. The traffic analysis device 13 calculates a traffic amount or a radio resource usage rate from the transmission power notified from the power measurement device 12 (step 91). For this calculation, the relationship between the transmission power and the radio resource usage rate is set in advance using information such as that shown in FIG. 13, for example, and the traffic analysis device 13 may hold the information shown in FIG.

  Here, when there is no terminal data to be transmitted in the base station 10g, the base station 10g transmits only a synchronization signal, a reference signal (or pilot signal), a broadcast signal for broadcasting system information, and the like. In this case, the radio resource usage rate is Rmin%, and the transmission power is Pmin [dBm]. Further, the transmission power when the traffic amount in the base station 10g is sufficiently large and the radio resource usage rate is 100% is Pmax [dBm].

  For example, referring to the information shown in FIG. 13, the traffic analysis device 13 has a radio resource usage rate R of 10% when the transmission power P notified from the power measurement device 12 is greater than Pmin and less than or equal to P1. You may determine that there is. Similarly, when the transmission power P is greater than P1 and less than or equal to P2, it may be determined that the radio resource usage rate R is 20%. Here, Pmin <P1 <P2 ... <Pmax. The numerical values shown in FIG. 13 are examples, and other preset values may be used.

  Next, the traffic analyzer 13 refers to the radio resource usage rate-tilt angle table from the radio resource usage rate calculated in step 91 to determine the mechanical tilt angle Tm degree and the phase shift tilt angle Te degree. (Step 92). The radio resource usage rate-tilt angle table is set in advance as shown in FIG. 14, for example, when both mechanical tilt and phase shift tilt are controlled as in the first embodiment.

  In the antenna parameter described in the first embodiment, a phase shift tilt is set when the traffic amount (radio resource usage rate) is large, and a mechanical tilt is set when the traffic amount (radio resource usage rate) is small. It was. Therefore, for example, when the radio resource usage rate R is Rmin% or more and the predetermined threshold value R0% or less, the traffic amount (radio resource usage rate) is sufficiently small, so that only the mechanical tilt is applied. The tilt angle is set to. That is, the tilt angle of the mechanical tilt is Tm = T degrees, and the tilt angle of the phase shift tilt is Te = 0 degrees.

  When the radio resource usage rate R is greater than R0% and equal to or less than R1%, the tilt angle of the mechanical tilt is reduced by α1 degrees from T degrees to Tm = T−α1 degrees, and the phase-shifted tilt tilt The angle is Te = α1 degree. Similarly, when the radio resource usage rate R is greater than R1% and less than or equal to R2%, the tilt angle Tm of the mechanical tilt is further reduced from α1 degrees to obtain Tm = T−α2 degrees (where α1 <α2) Then, the tilt angle of the phase-shifting tilt is increased from α1 degree to Te = α2 degrees.

  When the radio resource usage rate is larger than Rn% (and 100% or less), the traffic amount (radio resource usage rate) is sufficiently large, so the tilt angle is set to apply only the phase-shifting tilt. The That is, the tilt angle of the mechanical tilt is Tm = 0 degrees, and the tilt angle of the phase shift tilt is Te = T degrees.

  Referring to the information as shown in FIG. 14, the traffic analyzer 13 determines and sets the tilt angle, so that the smaller the radio resource usage rate, the closer to the state where only mechanical tilt is applied, and the radio As the resource usage rate increases, the tilt control device 14 can be controlled so as to approach the state where only the phase shift tilt is applied.

  In other words, by using the relationship shown in FIG. 14, the smaller the radio resource usage rate, the more the tilt angle of the mechanical tilt with respect to the total tilt angle of the tilt angle of the mechanical tilt and the tilt angle of the phase shift tilt. The tilt angle can be determined and set so that the ratio of the phase shift tilt angle increases as the ratio increases and the radio resource usage rate increases.

  Then, in step 92, the traffic analyzer 13 notifies the tilt controller 14 of the mechanical tilt angle Tm and / or the phase-shifted tilt angle Te that have been set (step 93). 13 and 14, the example of the radio resource usage rate has been described as information. However, the traffic amount may be used instead of the radio resource usage rate, and the table shown in FIG. 14 is a traffic amount-tilt angle table. May be.

  In this way, by changing the distribution of tilt angles between mechanical tilt and phase shift tilt, it is possible to appropriately control the balance between the communication quality increase effect at the cell center and the communication quality decrease effect at the cell boundary. Fine antenna parameters can be controlled according to traffic volume or radio resource usage rate, and throughput can be improved.

  However, in the example shown in FIG. 14, the total value of the tilt angle of the mechanical tilt and the tilt angle of the phase shift tilt is the same value T degrees irrespective of the value of the radio resource usage rate (traffic amount). However, as described above, when only the phase-shifting tilt is used (when the radio resource usage rate is Rn% or more), the tilt angle is used only when the mechanical tilt is used (when the radio resource usage rate is R0% or less). ) May be set to be larger than the tilt angle.

  As another example of the radio resource usage rate-tilt angle table referred to in step 92, depending on the traffic amount (transmission power, radio resource usage rate) using one of the tilt control methods of mechanical tilt or phase shift tilt. An example corresponding to the second embodiment for controlling the tilt angle will be described. FIG. 15 is a diagram illustrating an example of a radio resource usage rate-tilt angle table when the tilt angle is controlled by one tilt control method as in the second embodiment.

  In the second embodiment, since the tilt angle is controlled by one tilt control method, the tilt angle set in step 92 may be any one of the mechanical tilt angle Tm and the phase shift tilt angle Te. As the antenna parameter in Example 2, a larger tilt angle was set as the traffic amount was smaller.

  Therefore, in the radio resource usage rate-tilt angle table shown in FIG. 15, when the radio resource usage rate R is equal to or greater than Rmin% and equal to or less than R0%, the tilt angle has a maximum value Tmax. On the other hand, when the radio resource usage rate R is larger than Rn% (and 100% or less), the minimum tilt angle value Tmin is set.

  When the radio resource usage rate R is greater than R0% and less than or equal to Rn%, the tilt angle approaches Tmax degree as the radio resource usage rate R decreases, and the tilt angle increases as the radio resource usage rate R increases. Is a value that approaches Tmin degrees. That is, the tilt angle increases as the radio resource usage rate R decreases, and the tilt angle decreases as the radio resource usage rate R increases.

  Thus, for example, when the radio resource usage rate R is greater than R0% and equal to or less than R1%, the tilt angle T is set to T1 degrees that is less than Tmax degrees (where Tmax degree> T1). Every time). Similarly, when the radio resource usage rate R is greater than R1% and less than or equal to R2%, the tilt angle T is set to T2 degrees reduced from T1 degrees (where T1 degree> T2 degrees).

  Then, the traffic analysis device 13 notifies the tilt control device 14 of either the mechanical tilt angle Tm or the phase shift tilt angle Te set in step 92 (step 93). Although the example of the radio resource usage rate has been described as information in FIG. 15, the traffic amount may be used instead of the radio resource usage rate, and the table shown in FIG. 15 may be a traffic amount-tilt angle table. Good. Further, the radio resource usage rate-tilt angle table and the traffic amount-tilt angle table may be set in advance as described above.

  In this way, by controlling the tilt angle in a stepwise manner according to the amount of traffic or the value of radio resource usage, the balance between the effect of increasing the communication quality at the cell center and the effect of decreasing the communication quality at the cell boundary is appropriately adjusted. It is possible to control the throughput, and the throughput can be improved by finely controlling the antenna parameters according to the traffic amount or the radio resource usage rate.

  In the example described above, the stepwise distribution of the tilt angles of the mechanical tilt and the phase shift tilt, or the stepwise tilt angles in one tilt control method, according to the absolute value of the radio resource usage rate. An example of determination is shown. However, the stepwise distribution of the tilt angle between the mechanical tilt and the phase shift tilt, or the stepwise tilt angle in one tilt control method may be determined according to the relative value of the radio resource usage rate.

  For example, the values of the radio resource usage rate-tilt angle table shown in FIG. 14, the radio resource usage rate R, the mechanical tilt angle Tm, and the phase shift tilt angle Te are positive relative to each other centering on 0% and 0 degrees. A value and a negative relative value may be set in advance. The traffic analysis device 13 obtains a relative value by calculating a difference between an average value of the radio resource usage rate for a predetermined period set in advance and a value of the current radio resource usage rate, thereby obtaining a radio resource usage rate − Referring to the tilt angle table, if the current value has decreased with respect to the average value of the radio resource usage rate, it is decided to increase the tilt angle of the mechanical tilt and decrease the tilt angle of the phase shift tilt. Also good.

  Further, the traffic analysis device 13 refers to the radio resource usage rate-tilt angle table using the calculated relative value, and when the current value is increased with respect to the average radio resource usage rate, the mechanical tilt It may be determined that the tilt angle is decreased and the tilt angle of the phase shift tilt is increased.

  Note that the values in the radio resource usage rate-tilt angle table shown in FIG. 14 may be used as they are. For example, when the calculated relative value of the radio resource usage rate is (R2-R1), the difference between the two upper limit values in each of the two ranges is acquired for the radio resource usage rate R item shown in FIG. The difference between the upper limit values that coincide with the value (R2-R1) is detected, and (T-α2) and (T-α1) of the mechanical tilt angle Tm and α2 and α1 of the phase shift tilt angle Te are obtained. Alternatively, (α2−α1) degrees may be calculated as the relative value of the tilt angle.

  Further, when there is no change in the average value and the current value of the radio resource usage rate, the tilt angle may not be changed. Instead of the radio resource usage rate, the average value of the transmission power and the traffic amount and the current value may be used.

  Similarly, the radio resource usage rate R and the tilt angle T in the radio resource usage rate-tilt angle table shown in FIG. 15 have a positive relative value and a negative relative value centered on 0% and 0 degrees, respectively. It may be set. Then, the traffic analysis device 13 obtains a relative value by calculating the difference between the average value of the radio resource usage rate for a predetermined period set in advance and the value of the current radio resource usage rate, and uses the radio resource usage. With reference to the rate-tilt angle table, when the current value is decreasing with respect to the average value of the radio resource usage rate, it may be determined to increase the tilt angle.

  Further, the traffic analysis device 13 refers to the radio resource usage rate-tilt angle table using the calculated relative value, and when the current value increases with respect to the average value of the radio resource usage rate, the traffic analysis device 13 sets the tilt angle. You may decide to decrease. The values of the radio resource usage rate-tilt angle table shown in FIG. 15 may be used as they are, or instead of the radio resource usage rate, the average value of transmission power and traffic volume and the current value may be used.

  Further, in step 91 of FIG. 12, the traffic analysis device 13 has shown an example of calculating the radio resource usage rate from the transmission power notified from the power measurement device 12, but as in the system configuration shown in FIG. The operation of step 92 may be performed using the radio resource usage rate (traffic amount) notified from the base station 10k. In this case, step 91 may be omitted.

10g, 10k ... base stations 11a-11k ... base station antenna 12 ... power measuring devices 13, 13g, 13h, 13k ... traffic analyzer 14 ... tilt control devices 15a-15d ... variable phase shifter 16 ... movable parts 17a-17d ... Antenna elements 21a to 21d ... terminal

Claims (15)

A base station antenna having a plurality of antenna elements,
A mechanical tilt that changes a tilt angle by controlling a physical tilt of the plurality of antenna elements according to a traffic amount or a radio resource usage rate of communication by the base station antenna, and a position between the plurality of antenna elements. A base station antenna that controls phase-shifting tilt that changes a tilt angle by controlling a phase difference. The base station antenna according to claim 1,
The base station antenna is
A power measuring device for measuring power of communication by the base station antenna;
A base station antenna that performs control according to a traffic amount or a radio resource usage rate of communication by the base station antenna by performing control according to power measured by the power measuring device. The base station antenna according to claim 1,
The base station antenna is
A power measuring device for measuring power of communication by the base station antenna;
An analyzer that converts the power measured by the power measuring device into a traffic amount or a radio resource usage rate of communication by the base station antenna, and determines the converted traffic amount or radio resource usage rate;
The base station antenna, which is controlled according to a traffic amount or a radio resource usage rate of communication by the base station antenna by controlling according to a determination result of the analysis device. A base station antenna according to claim 3,
The analyzer is
When it is determined that the traffic volume of communication by the base station is equal to or greater than a threshold, a tilt angle by phase shift tilt is set,
A base station antenna characterized by setting a tilt angle by mechanical tilt when it is determined that a traffic volume of communication by the base station is smaller than the threshold value. A base station antenna according to claim 3,
The analyzer is
The tilt angle by the mechanical tilt and the tilt angle by the phase shift tilt are set in the tilt angle setting by the phase shift tilt and the tilt angle setting by the mechanical tilt according to the communication traffic amount or the radio resource usage rate by the base station. The base station antenna is set such that the total value of the base station is constant regardless of the traffic volume or the radio resource usage rate of communication by the base station. A base station antenna according to claim 3,
The analyzer is
When it is determined that the traffic volume of communication by the base station is equal to or greater than a threshold, a first tilt angle is set by either a phase shift tilt or a mechanical tilt,
When it is determined that the traffic volume of communication by the base station is smaller than the threshold, a second tilt angle larger than the first tilt angle is set instead of setting the first tilt angle. And base station antenna. A base station antenna according to claim 3,
The analyzer is
If the radio resource usage rate of communication by the base station is larger than the first value, set the tilt angle by phase shift tilt,
If the radio resource usage rate of communication by the base station is less than or equal to the second value smaller than the first value, set the tilt angle by mechanical tilt,
When the radio resource usage rate of communication by the base station is greater than the second value and less than or equal to the first value, a tilt angle is set by both phase shift tilt and mechanical tilt. Base station antenna. A base station antenna according to claim 7,
The analyzer is
When the radio resource usage rate of communication by the base station is greater than the second value and less than or equal to the first value, the tilt angle by mechanical tilt increases as the radio resource usage rate of communication by the base station increases. The base station antenna is characterized in that the angle is set to be small and the tilt angle by the phase-shift tilt is increased. A base station antenna according to claim 8,
The analyzer is
When the radio resource usage rate of communication by the base station is greater than the second value and less than or equal to the first value, the total value of the tilt angle by mechanical tilt and the tilt angle by phase shift tilt is Set to be constant regardless of the radio resource usage rate of communication by the base station,
When the radio resource usage rate of communication by the base station is larger than the first value, the tilt angle by the phase-shift tilt is used, and when the radio resource usage rate of communication by the base station is less than or equal to the second value, A base station antenna set to be larger than a tilt angle by mechanical tilt. The base station antenna according to claim 9, wherein
The analyzer is
It has information that records the relationship between the range of radio resource usage, the tilt angle by mechanical tilt and the tilt angle by phase shift tilt angle,
The range of the radio resource usage rate recorded in the information including the radio resource usage rate of communication by the base station is specified, and the tilt angle and the phase shift type by the mechanical tilt related to the range specified in the information A base station antenna that obtains and sets a tilt angle according to a tilt angle. An antenna control method for an analyzer and a plurality of base station antennas,
The analyzer is
Instructing the plurality of base station antennas according to the traffic volume or radio resource usage rate of communication by the plurality of base station antennas,
Each of the plurality of base station antennas each having a plurality of antenna elements,
Based on an instruction from the analyzer, a mechanical tilt that changes a tilt angle by controlling a physical tilt of the plurality of antenna elements, and a tilt angle that changes a phase difference between the plurality of antenna elements. An antenna control method comprising controlling phase-shifting tilt. The antenna control method according to claim 11, comprising:
The analyzer is
An antenna control method comprising: instructing each of the plurality of base station antennas according to a traffic amount or a radio resource usage rate of each of the plurality of base station antennas. The antenna control method according to claim 11, comprising:
The analyzer is
An antenna control method, wherein the same instruction is given to the plurality of base station antennas based on a traffic amount of each of the plurality of base station antennas or an average value of a radio resource usage rate. The antenna control method according to claim 11, comprising:
The analyzer is
An antenna control method comprising: determining a traffic amount or a radio resource usage rate of each of the plurality of base station antennas; and issuing the same instruction to the plurality of base station antennas based on a majority of the determination results. The antenna control method according to claim 11, comprising:
The analyzer is
An antenna control method comprising: giving the same instruction to the plurality of base station antennas based on any one of a traffic amount and a radio resource usage rate of each of the plurality of base station antennas.

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