JP2004343807A - Cellular mobile communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cellular mobile communication system which is capable of dealing with traffic fluctuation and is economical because the number of cells is reduced. <P>SOLUTION: Each base station 801 comprises a variable gain power amplifier 112 for amplifying a pilot signal P and a power control circuit 107 for controlling a gain thereof. The power control circuit 107 controls the transmission power gain in accordance with a control signal 106 which is imparted from a radio repeater station 803 which monitors the traffic of each base station. The repeater station 803 issues a command to decrease the power gain of the base station of a cell where traffic is concentrated and to increase the power gain of the base stations of the peripheral cells, thereby reducing the size of a cell 800d where the traffic is concentrated. Thus, the transmission power of the base station is controlled in accordance with the traffic fluctuation on the basis of a place or time to change a cell radius or a cell area, so that the system is capable of dealing with the communication demand using a small number of cells. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a cellular mobile communication system.

A cellular mobile communication system divides a communicable area of a mobile station into a plurality of adjacent or partially overlapping sub-areas (cells) and arranges a plurality of mobile stations located in the cell for each cell. Multiple access to one base station enables communication between mobile stations and communication between mobile stations and fixed stations. In order to allow a large number of mobile stations in a cell to share one base station, in a cellular mobile communication system, it is important to avoid interference between communication lines. Conventionally, for example, (1) Frequency division multiple access (FDMA)
(2) Time division multiple access system (TDMA)
(3) Code division multiple access (CDMA)
(4) A system such as a hybrid system combining the above (1) to (3) has been proposed.

  In the FDMA system, a frequency band used for mobile communication is divided into a plurality of bands, and a base station allocates a used communication band to a plurality of mobile stations in a cell so that spectrums do not overlap each other, and mutually allocates the used communication band. Perform communication. In the TDMA system, a plurality of mobile stations communicate with a base station by transmitting signals in the same carrier frequency band so as not to overlap with each other over time. In the CDMA system, a specific code is assigned to each mobile station, and the transmitting side spreads a modulated wave of the same carrier frequency with this code and transmits the same, and the receiving side synchronizes with the code assigned to itself. Is a multiple access method for identifying a desired line.

  In general, radio waves emitted into the air are attenuated roughly in proportion to the power of the distance as they move away from the radio station, and are buried in noise at a distance. Therefore, in areas sufficiently separated from each other, independent communication can be performed for each area using radio waves of the same frequency. This is the principle of cell repetition employed in cellular mobile communication systems. In this case, since the maximum number of connections that can be multiple-accessed does not depend on the cell area, in a cellular mobile communication system, as a method for coping with an increase in traffic, a method of shortening the radius of each cell (microcelling) is used. Are known.

  The principle of cell repetition and the cellular mobile communication system are described in detail in, for example, Yoshihisa Okumura and Masaaki Shinji, "Basics of Mobile Communication", p188-p217, published by the Institute of Electronics, Information and Communication Engineers.

"Basics of Mobile Communication", pp.188-217, supervised by Yoshihisa Okumura and Masaaki Shinshi, published by IEICE

  However, one of the problems in the practical use of the above-described cellular mobile communication system is that the traffic volume of each cell greatly changes depending on the location and time. For example, in a residential area and a commercial area, there is a large difference in traffic even in areas (cells) having the same area. In addition, in the vicinity of stations and stadiums, traffic volume in the same area during commuting hours and other time zones, competition time zones and other time zones (or competition day and other days) There is a big difference.

  However, in the conventional cellular mobile communication system, the cell radius and the cell area under the control of each base station are all designed to be equal, and the microcellization is performed based on the area where the traffic is maximized. Was. For this reason, depending on the location and time, it is inevitable that the number of cells will be insufficient or excessive than the actual demand, and the number of base stations will increase, which will increase the maintenance cost of infrastructure equipment and the location registration of mobile terminals. The problem of complication of the system function occurred.

  An object of the present invention is to provide a cellular mobile communication system and a radio base station that can cope with a change in traffic volume due to a place or time.

  Another object of the present invention is to provide a cellular mobile communication system and a radio base station that can cover a wide range of service area with a smaller number of base stations as compared with a conventional system and can adapt to a change in traffic volume in each cell. It is in.

  In order to achieve the above object, the cellular mobile communication system of the present invention is formed around a base station by relatively changing the transmission power of a pilot signal between base stations in a positional relationship adjacent to each other. It is characterized in that the boundary of each cell is changed according to the traffic situation. For example, when the number of mobile stations (mobile terminals) increases in a certain cell and the multiple access capacity is full or in a traffic state close to the same, the base station of the cell and the base station of the cell are reduced in a direction to reduce the cell area. The cell boundary position is changed by relatively changing the pilot signal transmission power between adjacent base stations. As a result, of the mobile stations that are controlled by the base station, the mobile stations located around the cell are equivalently moved under the control of the adjacent base station, and the load is adjusted.

  Specifically, each base station constituting the cellular mobile communication system of the present invention includes a variable gain amplifying unit for amplifying a modulated pilot signal, a modulation unit for modulating transmission data, and a modulation unit for modulating the transmission data. Transmitting means for synthesizing the signal and emitting it in the air as a radio wave, and transmission gain control means for controlling the gain of the variable gain amplifying means, wherein the transmission gain control means responds to changes in traffic conditions. The transmission power of the pilot signal is controlled in response to a control signal provided accordingly. The pilot signal transmission gain control command is issued to each base station from a relay station for connecting a plurality of base stations to a network, for example.

      The cell boundary is determined by the received electric field strength of pilot signals emitted from two base stations having an adjacent positional relationship. For example, the mobile station receives a stronger signal from the base station A than the received signal from the base station B. During this time, the terminal communicates with another terminal via the base station A, and communicates with the other terminal via the base station B when the signal strength relationship is reversed. Therefore, as in the present invention, a mobile station to shift a cell boundary position by relatively changing transmission power of a pilot signal between adjacent base stations and to be controlled by a specific cell in which traffic is overcrowded. Can be adapted to the capabilities of the base stations by distributing the load to base stations in neighboring cells.

  As is apparent from the above description, according to the present invention, it is possible to change the cell size by controlling the transmission power of the pilot signal emitted from the base station according to the traffic amount that varies depending on the location or time. As a result, the same communication scale can be covered with a smaller number of cells than before.

  1 to 3 are diagrams showing a control method at a cell boundary in the present invention.

  FIG. 1 is a diagram showing a cell boundary in a normal state between two base stations A200 and B201 constituting the cellular mobile communication system of the present invention.

  The horizontal axis 202 indicates the distance between the base station and the mobile station, the vertical axis 203 indicates the received electric field intensity of the pilot signal received by the mobile station, RXa 204 indicates the received electric field intensity characteristic of the pilot signal emitted from the base station A200, RXb205 indicates the received electric field strength characteristic of the pilot signal emitted from base station B201.

  In the normal state, the transmission powers of the pilot signals emitted from the base station A200 and the base station B201 are set to be equal, and the reception field strength of the pilot signal from the base station A at the point a and the pilot power from the base station B at the point b. The value P is equal to the received electric field strength of the signal.

  In this state, the boundary between the cell under the control of the base station A200 and the cell under the control of the base station B201 is the point c where the received signal strengths of the pilot signals emitted from the two base stations are equal. In this case, the radius of the cell formed around the base station A200: R210 and the radius of the cell formed around the base station B201: R211 are equal to the radius R as long as the target is between these two base stations. Become. In cellular mobile communication, a mobile station receives pilot signals from a plurality of base stations, and the received electric field strength from a certain base station Y increases the reception field strength from the base station X to which the mobile station has been connected. When it becomes stronger than the electric field strength (when it reaches the cell boundary position), the base station to be connected is switched from X to Y.

  FIG. 2 shows a first embodiment of the cell boundary control for making a microcell in the cellular mobile communication system of the present invention.

  In this case, the cell of the base station B201 becomes a target cell for microfabrication due to an increase in traffic. The transmission power of the pilot signal emitted from the adjacent base station A200 is increased, and the reception electric field strength at the point a is increased. Is increased from P to P ′, and the reception field strength characteristic RXa of the pilot signal is changed from 204 to 300.

  Since the received electric field strengths RXa and RXb of the pilot signals from the two base stations A and B become equal at the point c ′, the radius of the cell of the base station A200 expands to X303, and the radius of the cell of the base station B201 becomes 2R−2. Reduced to X304 (micro cell). Therefore, among the mobile stations that existed before in the cell of the base station B, the mobile station that was in the area between the points c and c ′ becomes the cell of the base station A with the change of the cell boundary. , And the traffic in the cell of the base station B is alleviated.

  FIG. 3 shows a second embodiment of the cell boundary control for microcell formation according to the present invention.

  Here, the cell of the base station B201 is also a target cell for micronization. However, in the present embodiment, contrary to the first embodiment, the transmission power of the pilot signal emitted from the base station B201 is changed to the normal state. , The reception electric field strength at the point b is reduced from P to P ″, and the reception electric field strength characteristic RXb of the pilot signal is changed from 205 to 400. The reception field strength characteristic RXb of the pilot signal becomes equal to the reception field strength property RXa of the base station A200 at the point c ″, and as in the first embodiment, the cell radius of the base station A200 expands to X403, and the base station B201 Is reduced (microcell) to 2R-X404.

  The microcellization of the cell in the present invention is performed by combining the first embodiment and the second embodiment described above (third embodiment) on the base station B201 side of the cell to be microfabricated. The transmission power of the pilot signal may be made weaker than in the normal state, and the transmission power of the pilot signal may be made stronger on the base station B201 side of the adjacent cell than in the normal state.

  FIG. 4 shows a configuration of a cell when the transmission power of the pilot signal of each base station is in a normal state (normal mode) in the cellular mobile communication system according to the present invention. In this state, the radius or area of each adjacent cell 800 (800a to 800g) is basically the same.

  FIG. 5 shows a configuration of a cell in a state where one cell is micronized (degeneration mode) by transmission power control. In this example, the cell 800d is micronized, and accordingly, the adjacent peripheral cells 800a to 800c and 800e to 800g are macronized. By miniaturizing one cell 800d in this way, a mobile station in a cell peripheral area that has been connected to or has attempted to connect to the base station of cell 800d is handed over to a peripheral cell, and traffic in cell 800d is reduced. Be relaxed. In this case, since the maximum number of multiple connections per base station is unchanged, the allowable number of connections per unit area is equivalently increased in the micronized cell 800a, for example, as in the vicinity of a station in a commuting time zone. In a region where the traffic volume is temporarily high, communication with the mobile station can be normally processed.

  FIG. 6 shows, as a special application example of the present invention, a cell configuration of a cellular mobile communication system along a highway (or highway) 1103. In the figure, 1101a to 1101e,... Are cells on the main road 1103, and 1100a to 11100e,. The illustrated cell structure shows a state in which each base station is operating in the normal mode, and each cell has the same cell radius or cell area.

  FIG. 7 shows a configuration of a cell in a state where cells 1101a to 1101e,... Here, if the cells 1101a to 1101e,... On the main road 1103 are locally converted into microcells according to the traffic volume or the degree of congestion of the mobile station, the microcells can be placed in an area where the communication demand density is high. Position, and can easily cope with communication demands.

  FIG. 8 shows an example of a basic configuration of a cellular mobile communication system to which the present invention is applied.

  800 (800a to 800c,...) Indicate cells managed by the base station 801 (801a to 801c,...), And 803 indicates a relay station for connecting these base stations to the network 804. . The relay station 803 is, for example, an exchange, and each base station 801 is connected to the relay station by a wired or wireless transmission path 802 (802a to 802c,...).

  9 to 11 show an example of a traffic management table managed by the relay station 803. The management table stores, for each cell, the number of mobile stations that are connected to the base station (“the number of simultaneous connections”) and the state of the transmission mode control signal (“the control signal”). Is a mode control signal for instructing a base station to be microcellized and / or a base station of an adjacent cell to change the transmission power based on the information in the management table.

  The traffic management table shown in FIG. 9 indicates that the traffic of the cell 800b approaches the maximum multiple access number (for example, “10”), and the traffic of the cells 801b and 802b is sufficiently small.

  The relay station 803 monitors the traffic of the cell 800 under the control of each base station 801, and makes a cell whose traffic is equal to or more than a predetermined threshold (for example, “9”) a micro cell. In this example, the cell 800a is the target cell, and the relay station instructs the base station 801a that is in charge of this cell to reduce the transmission power amplification gain of the pilot signal by ΔdB (dB). Send "-Δ".

  In order to avoid a rapid change in the cell boundary and make the system operation relatively stable, it is desirable to set the value of “Δ” to a small value, for example, about 1 to 2 dB. In this example, for the base stations 801b and 801c that control the cells 800b and 800c with low traffic, a control method corresponding to the second embodiment in which the power amplification gain of the pilot signal is maintained at the current state is adopted. The base station that maintains the current state may be instructed to maintain the current state when instructing another base station to change the gain, or may be given a control signal at all until the station needs to change the gain. It may not be necessary.

  FIG. 10 shows an example in which a control method corresponding to the first embodiment is performed using the traffic management table.

  Relay station 803 is a control signal for instructing base stations 801b and 801c that control macro cells 800b and 800c adjacent to cell 800a to be converted into micro cells to increase the power amplification gain of the pilot signal. Send “+ Δ”. The base station 801a that controls the cell 800a maintains the power amplification gain of the pilot signal as it is. The determination as to which cells are to be macroscopically made is made, for example, by referring to a cell configuration information table for indicating the positional relationship of the cells prepared separately from the traffic management table.

  FIG. 11 shows an example in which a control method corresponding to the third embodiment is performed using the traffic management table.

  The relay station 803 sends a control signal “−Δ” for instructing the base station 801 a that controls the cell 800 a to be microcellized to reduce the power amplification gain of the pilot signal, A control signal “+ Δ” is transmitted to the base stations 801 b and 801 c that control the cells 800 b and 800 c to increase the power amplification gain of the pilot signal.

  FIG. 12 shows an example of the configuration of a base station according to the present invention having the above-described cell boundary control function.

  (A) is a configuration diagram of a transmission circuit system. A multiplexed data 100 composed of signals for a plurality of channels is converted by a demultiplexer 111 into a control signal 106 and transmission data 100a, 100b, and 100c for each channel corresponding to each mobile station. ,…. The transmission data corresponding to each mobile station is modulated into signals 102a, 102b, 102c,... By modulators 101a, 101b, 101c,. Pilot signal P is modulated into signal 102x by modulator 101x and then amplified by amplifier 112 to signal 112x. The modulated pilot signal 112x and the transmission data signals 102a, 102b, 102c,... For each mobile station are combined into one signal 104 by the addition circuit 103. The signal 104 synthesized by the addition circuit 103 is amplified into a signal 109 by an amplifier 105 and then emitted into the air via an antenna 110. Here, the modulation scheme used for the transmission data modulators 101x, 101a, 101b, 101c,... May be any of FDMA, TDMA, CDMA, etc., and is not particularly limited in the present invention. In addition, these transmission data modulators 101 are configured to be able to control the power gain for each channel so that, for example, a transmission output corresponding to the strength of a signal received from a mobile station (distance from a base station) can be obtained. You may.

  The control signal 106 separated from the multiplexed data by the separation device 111 is provided to the power control circuit 107. The power control circuit 107 generates a gain control signal 108 for determining the power amplification gain of the amplifier 112 for amplifying the pilot signal according to the input control signal. The amplifier 112 power-amplifies the modulated pilot signal 102x with a gain determined by the gain control signal 108. The control signal 106 is provided from the relay station 803 shown in FIG. However, as shown in FIG. 2, when the base station of the cell whose traffic has increased adopts a control method of increasing the transmission power, each base station is provided with a means for monitoring the amount of traffic, and the micro station is determined by its own station. Cellization and its release may be executed.

  (B) shows the configuration of the receiving circuit system. The radio signal 501 received by the antenna 500 is input to the input amplifier 502, and is amplified to a signal 503 in a level range in which the demodulators 504a, 504b, 504c,. The amplified signal 503 is converted into demodulated signals 505a, 505b, 505c,... By demodulators 504a, 504b, 504c,. These demodulated signals 505a, 505b, 505c,... Are multiplexed by a multiplexer 506 and transmitted as multiplexed data 507 to a relay station 803 by wire or wirelessly. As a result, communication between each mobile station and the relay station 803 is performed, and a call can be made to another mobile station or fixed station via the relay station and another base station or network.

  FIG. 13 is a block diagram showing a second embodiment of the transmitting section of the base station having a cell boundary control function. Circuit elements common to the embodiment shown in FIG. 12 are denoted by the same reference numerals. It is.

  In this embodiment, an auxiliary receiving antenna 600 is installed near the transmitting antenna 110, the signal 601 received by the auxiliary antenna 600 is amplified by the amplifier 602, and the amplified signal 603 is transmitted to the electric field intensity measuring device 604. You are typing. The electric field intensity measuring device 604 obtains a received electric field intensity signal 605 by obtaining a time average of, for example, envelope detection, and inputs the signal to the power control circuit 107.

  According to the configuration of the present embodiment, a signal proportional to the actual transmission power received by the auxiliary antenna 600 is fed back to the power control circuit 107, and the gain control signal 108 is corrected. The transmission power of the pilot signal can be more accurately controlled.

  Here, if the distance 606 between the transmitting antenna 110 and the auxiliary antenna 600 is standardized so as to be the same in each base station, the electric field strength measuring device 604 and / or the power control circuit 107 are connected to each base station. There is no need to specialize each time. If the distance 606 between the transmitting antenna 110 and the auxiliary antenna 600 cannot be set to a standard value for some reason, adjustment is made in the electric field strength measuring device 604 or the power control circuit 107 so that a feedback corresponding to the standard antenna distance is obtained. It may be modified to work.

  FIG. 14 shows a configuration diagram of a transmitting antenna having directivity that can be adopted in a base station in implementing the present invention. In this example, the transmission antenna is composed of a plurality of sector antennas 700, 701, 702,... Each having directivity in a specific direction, and each of the sector antennas communicates in a specific sector a 703, sector b 704, and sector c 705, respectively. To share. When such a plurality of sector antennas are employed, the transmission power gain control of the pilot signal described above is performed independently for each sector, so that the cell size can be expanded or reduced for each sector.

  Next, with reference to FIG. 15, the transmission power control of the base station and the mobile station for the channel data will be described. Here, an embodiment in which CDMA is used as a modulation method will be described. In addition, in order to simplify the explanation and facilitate understanding, here, the cellular mobile communication system is configured by two cells, base station A200 and base station B201, and the distance from position b of base station B is R / A model is a case where “N” traffic 1304, 1305, and 1306 are generated at points e, f, and g at 6, R / 2, and 5R / 6, respectively.

  When the transmission power of the pilot signal of each base station is in a normal state (normal mode), the boundary between the cells controlled by the two base stations is equidistant from the position a of the base station A and the position b of the base station B. It is formed at point c of R (broken line position on the left side). Now, it is assumed that the cell boundary has moved from the position c in the normal mode to a point d (position indicated by a broken line on the right) which is closer to the base station B by a distance R / 3 due to the transmission power gain control of the pilot signal.

First, the transmission power of the mobile station will be described. In this example, the reuse rates F _A and F _B of the frequencies corresponding to the base stations A and B assume that the radio wave attenuates in proportion to the square of the distance. Are given by Equations 1 and 2, respectively.

Here, σA and σB indicate the received power from the mobile station in the cell of the base station A and the cell of the base station B, respectively. Assuming that σA and σB are constant irrespective of the position of the mobile station in the cell by performing the transmission power control according to the position of each mobile station, the condition for maximizing the frequency use efficiency is as follows: The purpose is to make the frequency reuse rates F _A and F _B of each cell proportional to the amount of traffic. Equation 3 shows this condition.

Solving Equations 1 and 2 for σB / σA under the condition of Equation 3 gives
σB / σA = 11.24
It becomes. Thus, when the frequency reuse ratios F _A and F _B corresponding to the base stations A and _B are obtained, they become “0.43” and “0.85”, respectively.

In the normal mode state in which cell boundary is located at the point c, since in the cell of the base station A no mobile station, in the maximum communication state in the cell of the base station B, the frequency reuse factor F _A, F _B is “0” and “1”, respectively. Here, assuming that the maximum number of multiple access when the frequency reuse rate is “1” is 2.35N, in the normal mode state, 22% ((3N−2) of all the mobile stations in the cell of the base station A. .35N) / 3N × 100) cannot communicate.

  However, when the transmission power control of the base station according to the present invention is performed and the cell boundary is moved to the point d, N (2.35N × 0.43) traffics 1306 are connected to the base station A and the base station B Is connected to a total of 2N (2.35N × 0.85) traffic 1304 and 1305, so that a total of 3N traffic can be connected.

  Next, transmission power control for channel data of the base station will be described.

  The condition for maximizing the frequency use efficiency is to keep the signal-to-noise ratio at each mobile station constant. When the transmission power from the base station B to the traffic 1304 is “1”, the transmission power from the base station B to the traffic 1305 is “a”, and the transmission power from the base station A to the traffic 1306 is “b”, the frequency use efficiency is maximized. Is given by equation (4).

Solving the above equation for variables a, b, and γ gives:
a = 1.166, b = 3.551, γ = 0.455
It becomes. γ indicates the signal-to-noise ratio before spectrum despreading in the mobile station, and the signal-to-noise ratio before spectrum despreading in the normal mode state where the cell boundary is located at point c is 0.333. Since the signal-to-noise ratio is proportional to the maximum number of multiple accesses, in this case, the application of the present invention increases the maximum number of multiple accesses by about 37 percent (0.455 ÷ 0.333−1) × 100. Become.

  When FDMA or TDMA is used in place of the CDMA as the multiple access method, the transmission power of radio waves emitted from the base station and the mobile station can be reduced by the base station and the mobile station while ensuring the desired communication quality. The transmission power may be selected so that the base station and the mobile station can secure desired communication quality in a cell that repeats the frequency.

FIG. 4 is a diagram for explaining a cell boundary when transmission of a base station is in a normal mode state in the cellular mobile communication system of the present invention. FIG. 4 is a diagram for explaining a first embodiment of cell boundary control in the present invention. FIG. 7 is a diagram for explaining a second embodiment of the cell boundary control according to the present invention. FIG. 2 is a diagram showing a cell configuration in a normal mode of the cellular mobile communication system of the present invention. FIG. 3 is a diagram showing a cell configuration in a state where a cell boundary is changed in the cellular mobile communication system of the present invention. The figure which shows the other example of a cell structure in a cellular mobile communication system. FIG. 7 is a diagram showing changes in cells when the present invention is applied to the cell configuration in FIG. 6. FIG. 1 is a diagram illustrating an example of a configuration of a cellular mobile communication system according to the present invention. The figure which shows the content of the traffic management table corresponding to 1st Example of cell boundary control. The figure which shows the content of the traffic management table corresponding to the 2nd Example of cell boundary control. The figure which shows the content of the traffic management table corresponding to 3rd Example of cell boundary control. The figure which shows an example of a structure of the base station which comprises the communication system of this invention. The figure which shows the other example of a structure of the transmission part of the base station which comprises the communication system of this invention. The figure which shows the structure of the sector antenna which can be employ | adopted by this invention. FIG. 3 is a diagram for explaining an operation when CDMA is applied to the cellular mobile communication system of the present invention.

Explanation of reference numerals

100 multiplexed data, 101 modulator, 103 adder, 105, 112 amplifier, 107 power control circuit, 110 transmission antenna, 500 reception antenna, 502 amplifier, 504 demodulator, 507 multiplexing Data, 600: auxiliary antenna, 602: amplifier, 604: electric field strength measuring instrument, 700: segment antenna, 803: wireless relay station

Claims (10)

  In a cellular mobile communication system composed of a plurality of base stations, the transmission power of base stations in a positional relationship adjacent to each other is relatively changed, so that the boundary of each cell formed by each base station is changed according to the traffic situation. A cellular mobile communication system characterized in that the mobile communication system is changed.   When the connection traffic volume with the mobile station in a specific cell exceeds a predetermined threshold, by relatively changing the transmission power of the pilot signal at least one of the base station and the adjacent base station that control the specific cell, The cellular mobile communication system according to claim 1, wherein the size of the specific cell is reduced.   The relay station connected to the plurality of base stations monitors a traffic state of each cell, and controls the transmission power according to a command from the relay station. A cellular mobile communication system according to claim 1.   In a radio base station constituting a cellular mobile communication system, a variable gain amplifying means for amplifying a modulated pilot signal, a modulating means for modulating transmission data to a mobile station, and combining these modulated signals Transmitting means for emitting a radio wave into the air, and a transmission gain control means for controlling the power gain of the variable gain amplifying means, wherein the transmission gain control means responds to changes in traffic conditions. A radio base station characterized in that the power gain is controlled in response to a control signal provided in response to change a cell boundary with an adjacent base station.   The radio base station according to claim 4, wherein the transmitting means has a plurality of antenna members each having directivity in a different direction, and the power gain is controlled corresponding to the antenna members. Bureau.   An auxiliary receiving means for receiving the intensity of the radio wave emitted into the air by said transmitting means, and a means for returning a detection output by said auxiliary receiving means to said transmission gain control means. Item 5. The wireless base station according to item 4.   In a cellular mobile communication system comprising a plurality of base stations and traffic monitoring means connected to each base station, each base station transmits a pilot signal for identifying a base station in response to a command from the monitoring means. A cellular mobile communication system characterized by changing power.   8. The cellular mobile communication system according to claim 7, wherein the monitoring unit instructs a base station of a specific cell whose traffic has increased to increase transmission power of a pilot signal.   The monitoring means instructs a base station having at least one cell having a positional relationship adjacent to a specific cell having increased traffic to control a transmission power of a pilot signal to a base station. Item 8. The cellular mobile communication system according to Item 7. The monitoring means instructs the base station of a specific cell whose traffic has increased to increase the transmission power of a pilot signal, and issues a command to a base station having at least one cell adjacent to the specific cell as a service area. 8. The cellular mobile communication system according to claim 7, wherein a command is issued to reduce the transmission power of the pilot signal.

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