JP4847548B2 - Base station apparatus and radio communication system - Google Patents

Description

  The present invention relates to a radio communication system that detects a position of a mobile terminal using a radio signal and a base station apparatus thereof.

In the cellular telephone system, a reception time difference between signals transmitted from the base station to the mobile terminal (signal propagation time differences T1-T2 and T3-T2 from each base station to the mobile terminal) is calculated, and the propagation time difference is multiplied by the speed of light. Thus, the difference in signal propagation distance from the mobile terminal to each base station D1-D2 = c (T1-T2)
And D3-D2 = c (T3-T2)
Has been proposed to detect the position of the mobile terminal (see, for example, Patent Document 1).

Further, in the wireless LAN system, a time difference at which a signal transmitted from the terminal is received by the base station (a difference in reception time Ti−T1 of each base station) is calculated, and the reception time difference is multiplied by the speed of light, so that Difference in signal propagation distance to base station {| P−Pi | − | P−P1 |} = c (Ti−T1), i = 2,..., N
Has been proposed (see, for example, Non-Patent Document 1).

  FIG. 9 is a diagram showing the arrangement of base stations in such a conventional wireless communication system.

  The base stations 1 to 3 communicate with terminals in the areas 11 to 13 in the uplink direction (the terminal transmits a signal and the base station receives the signal) and the downlink (base station). Can transmit the signal, and the terminal can receive the signal). Generally, in a wireless communication system, base stations are arranged so that communication with the terminal 20 can be realized with as few base stations as possible. That is, the base stations are arranged so that the overlap of the areas 11 to 13 is minimized.

  10 is a block diagram showing a configuration of a base station used in the wireless communication system shown in FIG. Note that, as shown in Non-Patent Document 1, the base station in the case where the position of the terminal is detected based on the time difference when the signal transmitted from the terminal is received by the base station is shown.

  A signal received by the antenna 100 is input to the wireless reception unit 102 via the circulator 101, converted into a baseband signal by the wireless reception unit 102, and demodulated, decoded, and decoded by the baseband signal processing unit 103. Error correction processing is performed. The position detection signal processing unit 106 performs signal processing necessary for position detection, such as capture of a received signal, delay profile generation, and path detection.

  FIG. 11 is a flowchart of a communication speed setting process used in the wireless communication system shown in FIG.

  In general, in a wireless communication system, communication speeds for uplink and downlink communications are set at the start of communication or during communication. The communication speed in the radio section using the communication speed required for the signal quality, traffic volume, communication contents (for example, voice, still image, moving image, data, etc.) in the radio section between the terminal and the base station. Is determined (step 310). Specifically, for example, when the signal quality is poor, when the amount of traffic is large, or when the required communication speed is low, the communication speed is set to a low speed. On the other hand, when the signal quality is good, when the traffic volume is small, or when the required communication speed is high, the communication speed is set to a high speed.

  This communication speed setting process is performed in the base station and the terminal. Note that different communication speeds may be set for uplink communication and downlink communication, or the same communication speed may be set for uplink communication and downlink communication.

JP-A-7-181242

Satoshi Sugano, 5 others, “Wireless LAN integrated access system (1) Study on location detection system”, Proceedings of the 2003 General Conference, IEICE, B-5-203, p. 662

  The conventional wireless communication system described above is designed such that the upstream communication area (signal reception area) and the downstream communication area (transmission signal arrival area) are equal. For example, when the terminal 20 exists at the position shown in FIG. 9, the terminal 20 exists in the uplink communicable area of the base station 1, but does not exist in the uplink communicable area of the base stations 2 and 3. . Therefore, the base station 2 and the base station 3 cannot receive the uplink signal transmitted by the terminal 20 (or the base stations 2 and 3 can receive only poor quality). As a result, only the base station 1 can receive the uplink signal transmitted by the terminal 20.

  In the above-described position detection method (see Non-Patent Document 1) for detecting the position of a terminal based on a time difference at which a signal transmitted from the terminal is received by the base station, the uplink signal transmitted by the terminal is transmitted to at least three bases. It is necessary to receive at the station. Therefore, in order to detect the position of the terminal 20 by such a position detection method using the uplink signal, for example, as shown in FIG. 12, the base station 4 including the position where the terminal 20 exists in the uplink communicable area. It is necessary to additionally install the base station 5.

  Specifically, an arbitrary position where a terminal may exist may be included in an uplink / downlink communicable area of one base station when only communication is performed, but when position detection is performed. It must be included in the uplink coverage area of three base stations. Therefore, the number of base stations required for the entire wireless communication system to realize the position detection of the terminal increases about three times as compared with the case where only the communication between the base station and the terminal is performed.

  For this reason, in a wireless communication system that detects the position of a terminal, the cost required for the equipment increases, and there is a problem that the cost of a location information service (service usage fee) that provides the position detection result of the terminal increases.

  In order to solve the above-described problems, the base station of the present invention includes means for making the signal receivable distance longer than the transmission signal reachable distance and making the uplink communicable area wider than the downlink communicable area. Specifically, the terminal and / or the base station includes means for controlling the transmission rate of the uplink signal used for terminal position detection to a low rate.

  In the present invention, the signal receivable distance is made longer than the transmission signal reachable distance, and the uplink communicable area is wider than the downlink communicable area, so the number of base stations is increased compared to the number of base stations necessary for communication. The position of the terminal can be detected without any problem. Thereby, the cost required for the equipment of the radio communication system can be reduced, and the cost of the location information service can be reduced.

It is a block diagram which shows the structure of the base station of the 1st Embodiment of this invention. It is a block diagram which shows the structure of the terminal of the 1st Embodiment of this invention. It is explanatory drawing of the communicable area of the up direction and the down direction of the base station of the 1st Embodiment of this invention. It is explanatory drawing of the communicable area of each base station of the radio | wireless communications system of the 1st Embodiment of this invention. It is a block diagram which shows the structure of the base station of the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the base station of the 3rd Embodiment of this invention. It is a flowchart of the communication speed setting process of the 4th Embodiment of this invention. It is a block diagram of the radio | wireless communications system which detects the position of a terminal using the base station of embodiment of this invention. It is explanatory drawing of arrangement | positioning of the base station of the conventional radio | wireless communications system. It is a block diagram which shows the structure of the base station of the conventional radio | wireless communications system. It is a flowchart of the communication speed setting process of the conventional radio | wireless communications system. It is explanatory drawing of arrangement | positioning of the base station of the conventional radio | wireless communications system.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a base station according to the first embodiment of this invention.

  The antenna 100 is connected to the wireless transmission unit 105 and transmits a wireless signal. The antenna 200 having a higher gain than the antenna 100 used on the transmission side is connected to the radio reception unit 102 and receives a radio signal. That is, the high gain antenna 200 used on the receiving side is an antenna having a higher gain than the antenna 100 used on the transmitting side, and for example, a multistage collinear antenna or an adaptive array antenna can be used. The antenna 100 and the high gain antenna 200 are provided separately and separately.

  When an adaptive array antenna is used, the antenna 100 and the high gain antenna 200 are controlled by changing the gain of the antenna so that the gain is high at the time of transmission and low at the time of reception. Can be realized.

  The wireless receiving unit 102 performs processing such as amplification and detection at high and intermediate frequencies, and converts the wireless signal into a baseband signal. The baseband signal processing unit 103 performs demodulation, decoding, and error correction processing on the baseband signal generated by the wireless reception unit 102.

  In addition, the baseband signal processing unit 103 performs encoding and modulation processing to generate a baseband transmission signal. The wireless transmission unit 105 performs processing such as amplification at an intermediate frequency and a high frequency on the baseband transmission signal generated by the baseband signal processing unit 103 to generate a transmission signal. The transmission signal generated by the wireless transmission unit 105 is transmitted from the antenna 100 via the circulator 101.

  The control unit 104 performs control of each unit of the base station, protocol control for wireless communication with a terminal, protocol control for communication with an external network, and the like. The communication speed setting process (FIG. 11) described above is executed by the control unit 104.

  The position detection signal processing unit 106 uses the result obtained by the baseband signal processing unit 103 to perform signal processing necessary for position detection, such as capture of a received signal, delay profile generation, and path detection.

  FIG. 2 is a block diagram illustrating a configuration of the terminal according to the first embodiment of this invention.

  The antenna 300 is connected to the radio reception unit 302 and the radio transmission unit 305 via the circulator 301, and the transmission signal and the reception signal are separated by the circulator 301.

  The wireless reception unit 302 performs processing such as amplification and detection at a high frequency and an intermediate frequency, and converts the wireless signal into a baseband signal. The baseband signal processing unit 303 performs demodulation, decoding, and error correction processing on the baseband signal generated by the wireless reception unit 302.

  The baseband signal processing unit 303 performs encoding and modulation processing to generate a baseband transmission signal. The wireless transmission unit 305 performs processing such as amplification at an intermediate frequency and high frequency on the baseband transmission signal generated by the baseband signal processing unit 303 to generate a transmission signal. A transmission signal generated by the wireless transmission unit 305 is transmitted from the antenna 300 via the circulator 301.

  The control unit 304 performs control of each unit of the terminal, protocol control for wireless communication with the base station, and the like. The communication speed setting process (FIG. 11) described above is executed by the control unit 304.

  FIG. 3 shows communication areas in the uplink and downlink directions of the base station shown in FIG.

  The uplink direction communicable area 31 of the base station 1 is wider than the downlink direction communicable area 11. This is because the base station 1 uses the high gain antenna 200 as an antenna on the receiving side, and therefore can receive an upstream signal transmitted from a farther terminal. That is, the base station 1 can include a terminal located far outside the downlink communicable area (transmission signal reachable area) within the uplink communicable area (signal receivable area).

  FIG. 4 shows a communicable area of each base station in the wireless communication system according to the first embodiment of this invention. In the example shown in FIG. 4, the base station is arranged at the same position as in the conventional example shown in FIG.

  As described above, in the base station according to the embodiment of the present invention, the uplink communicable area is wider than the downlink communicable area 11. Since the terminal 20 is included in the downlink communicable area of the base station 1, the terminal 20 can receive the downlink signal transmitted by the base station 1. On the other hand, since the terminal 20 is included in all the upstream communication possible areas 31 to 33 of the base station 1 to the base station 3, the upstream signal transmitted from the terminal 20 by any of the base stations 1 to 3 is transmitted. Can be received.

  Therefore, in the position detection method for detecting the position of the terminal by receiving the signal transmitted from the terminal, the position of the terminal 20 can be detected without increasing the number of base stations.

  Next, a second embodiment of the present invention will be described.

  FIG. 5 is a block diagram illustrating a configuration of a base station according to the second embodiment of this invention. In addition, the same code | symbol is attached | subjected to the component same as the base station (FIG. 1) of 1st Embodiment mentioned above, and the detailed description is abbreviate | omitted.

  The high gain antenna 200 is connected to the wireless reception unit 102 and the wireless transmission unit 105 via the circulator 101, and the transmission signal and the reception signal are separated by the circulator 101. Instead of the circulator, the separator may be a duplexer based on a combination of bandpass filters or a switch that switches the antenna connection in response to transmission / reception timing.

  The attenuator 210 attenuates the transmission signal output from the wireless transmission unit 105 and controls the transmission output from the high gain antenna 200 to be a predetermined value. Here, the predetermined value is, for example, transmission power or electric field strength value defined by laws and regulations such as the Radio Law, signal power or electric field transmitted from the antenna 100 of the base station (see FIG. 1) of the first embodiment. Use intensity values.

  When an adaptive array antenna is used for the high gain antenna 200, the transmission output becomes a predetermined value by changing the gain of the antenna between transmission and reception without providing the attenuator 210. It is possible to improve the reception sensitivity while adjusting to.

  As described above, in the base station of the second embodiment, the uplink communicable area (signal receivable area) is the downlink direction as in the base station (FIG. 1) of the first embodiment described above. It is wider than the communicable area (transmission signal arrival area) and can receive signals from terminals located outside the downlink communicable area (see FIG. 3). Therefore, similarly to the base station (FIG. 1) of the first embodiment described above, the position of the terminal 20 can be detected without increasing the number of base stations (see FIG. 4).

  Next, a third embodiment of the present invention will be described.

  FIG. 6 is a block diagram illustrating a configuration of the base station according to the third embodiment of this invention. In addition, the same code | symbol is attached | subjected to the component same as the base station (FIG. 1) of 1st Embodiment mentioned above, and the detailed description is abbreviate | omitted.

  The high gain antenna 200 is connected to the wireless reception unit 102 and the wireless transmission unit 105 via the circulator 101, and the transmission signal and the reception signal are separated by the circulator 101.

  The transmission power adjustment unit 211 provided in the control unit 104 sets the output level of the baseband signal processing unit 103 so that the transmission output from the antenna 200 becomes a predetermined value. Here, as the predetermined output, similarly to the second embodiment described above, the same signal power or electric field strength value as required by the law or the base station of the first embodiment may be used.

  As described above, in the base station of the third embodiment, as in the base station (FIG. 1) of the first embodiment described above, the uplink communicable area (signal receivable area) is the downlink direction. It is wider than the communicable area (transmission signal arrival area) and can receive signals from terminals located outside the downlink communicable area (see FIG. 3). Therefore, the position of the terminal 20 can be detected without increasing the number of base stations as in the base stations (FIGS. 1 and 5) of the first and second embodiments described above (see FIG. 4). ).

  Next, a fourth embodiment of the present invention will be described. In the fourth embodiment, the configuration of the base station is the same as that of the conventional base station (FIG. 10), but the communication speed setting process executed by the control unit 104 is different.

  FIG. 7 is a flowchart of communication speed setting processing according to the fourth embodiment of this invention.

  First, it is determined whether or not the uplink signal that is the target of communication speed setting is a signal used for position detection (step 311). As a result of the determination in step 311, if it is determined that the uplink signal is not used for position detection, the signal quality, traffic volume, communication content (for example, voice, still image, moving image, data, etc.) of the radio section between the terminal and the base station ) Is used to determine the communication speed in the wireless section (step 310). Specifically, for example, when the signal quality is poor, when the amount of traffic is large, or when the required communication speed is low, the communication speed is set to a low speed. On the other hand, when the signal quality is good, when the traffic volume is small, or when the required communication speed is high, the communication speed is set to a high speed.

  On the other hand, if it is determined in step 311 that the uplink signal is used for position detection, the uplink communication speed is set to the slowest communication speed that can be used in the wireless communication system (that is, the highest in the base station). A communication speed for position detection that is a low communication speed is set (step 312). Specifically, the communication speed is changed by changing the modulation method, the encoding parameter (encoding method), and the error correction method.

  According to the communication speed determined in the communication speed setting flow described above, the control unit 104 of the base station sets each part of the base station, and the control unit 304 of the terminal sets each part of the terminal.

  Whether or not this uplink signal is a signal used for position detection may be determined by the base station and notified to the terminal, and the speed of the signal transmitted from the terminal may be changed or determined by the terminal. The speed of the transmitted signal may be changed.

  In general, when the transmission power of uplink signals is the same, the energy per bit increases as the communication speed is slow, and the uplink signal transmitted by a terminal located farther is received by the base station. Is possible. Therefore, according to the communication speed setting method of the fourth embodiment described above, the uplink communicable area (signal receivable area) becomes wider than the downlink communicable area (transmission signal reachable area). A signal from a terminal located outside can be received (see FIG. 3). Therefore, as with the base stations (FIGS. 1, 5, and 6) of the first, second, and third embodiments described above, the position of the terminal 20 is detected without increasing the number of base stations. (See FIG. 4).

  Next, the distance between the uplink and downlink communicable areas and the base station when the base stations (FIGS. 1, 5, 6, and 7) of the first to fourth embodiments of the present invention are used. A specific example of the relationship will be described.

  As described in the background art, in a wireless communication system, in order to realize communication with the terminal 20 in the target area with as few base stations as possible, for example, as shown in FIG. 9, the overlap of communicable areas is minimized. Thus, each base station is arranged. Therefore, assuming that the communicable area is a circle, the radius (transmission signal reachable distance) of the downlink communicable area used for communication is about half of the distance between base stations.

  On the other hand, the radius of the communicable area (signal receivable distance) of the uplink signal used for terminal position detection needs to be the same distance as between base stations. This is because the base stations 2 and 3 need to receive an uplink signal transmitted by the terminal 20 existing near the base station 1 (see FIG. 4).

  Therefore, using the base stations of the first to fourth embodiments (FIGS. 1, 5, 6, and 7), the uplink communicable distance is approximately twice the downlink communicable distance. To do.

  In addition, the base station (FIGS. 1, 5, 6, and 7) of the first to fourth embodiments is used so that the uplink communicable distance is less than twice the downlink communicable distance, Further, a base station for detecting the position of the terminal may be added.

  Also, when the accuracy of position detection is improved by increasing the number of base stations that can be used for terminal position detection, the base station of the present invention is the base station of the first to fourth embodiments (FIG. 1). 5, 6, and 7), the signal from the terminal is received by four or more base stations so that the uplink communicable distance is larger than twice the downlink communicable distance. Good.

  FIG. 8 is a configuration diagram of a radio communication system that detects the position of a terminal using the base stations according to the first to fourth embodiments of the present invention.

  A plurality of base stations (in FIG. 8, three base stations 1, 2, and 3 are shown as an example) are connected to a server 7 via a network 6 including a public network and a mobile communication network. The terminal 20 exchanges information and signals with the server 6 via these base stations. In response to an instruction from the server 7, the base station 1 to the base station 3 instructs the terminal to change the antenna gain or change the communication speed in order to detect the position of the terminal.

  Then, the server 7 collects information on the arrival time difference of the signals transmitted from the terminals, which is obtained by the base stations 1 to 3, and the server 7 calculates the position of the terminals.

By using the base station according to the embodiment of the present invention in the system of FIG. 8, the position of the terminal 20 in the entire communicable area without increasing the number of base stations as compared with the number of base stations required for communication. Or, for example, when the location of the terminal is unnecessary in some areas, or when the location of the terminal is detected using a different method such as GPS in some areas, the location of the terminal A base station having a conventional configuration can be used for an area that does not require detection, and a base station according to the present invention can be used for an area that needs to detect the position of a terminal.

  As described above, in the position detection method in which the base station receives the uplink signal transmitted by the terminal and detects the position of the terminal, the uplink signal transmitted by the terminal needs to be received by the three base stations. is there. On the other hand, in order to perform communication in a wireless communication system, an uplink signal transmitted by a terminal may be received by one base station. Therefore, when a base station having a conventional configuration or a communication speed setting method is used, about three times as many base stations as the number of base stations necessary for communication are required to detect the position of the terminal. . However, by using the present invention, it is possible to detect the position of the terminal by the number of base stations equal to the number of base stations necessary for communication. Therefore, the number of base stations necessary for detecting the position of the terminal can be reduced to about 1/3 as compared with the conventional case.

The following are typical examples of aspects of the present invention other than those described in the claims.
(1) In a base station apparatus that detects the position of a terminal using a radio signal, in order to separate an antenna commonly used for transmission and reception of the radio signal and a radio signal to be transmitted and a radio signal to be received , A radio reception unit that generates a reception signal from the received radio signal, a signal processing unit that performs signal processing of the reception signal and generation of a transmission signal, and radio transmission that generates a radio signal from the transmission signal , A control unit that controls the operation of the base station apparatus, a position detection signal processing unit that performs signal processing for position detection of the terminal, and the strength of the radio signal transmitted from the antenna is received from the antenna Transmission output reduction means for making the radio signal intensity smaller than the intensity of the radio signal, and the transmission output reduction means transmits the intensity of the radio signal transmitted from the antenna to the terminal by the radio transmission unit. Signal reception distance from the terminal by the wireless transmission unit can be received from the transmission signal arrival distance to the terminal by the wireless transmission unit by making the signal reachable distance and the signal receivable distance from the terminal by the wireless reception unit equal. A base station apparatus characterized by increasing a distance.
(2) The base station apparatus according to (1), wherein the transmission output reduction means includes an attenuator that attenuates a radio signal to be transmitted.
(3) The transmission output reduction means includes a transmission power adjustment unit that is provided inside the control unit and reduces the output level of the transmission signal output from the signal processing unit to the wireless transmission unit. (1) The base station apparatus according to (1).
(4) In a radio communication system in which a base station receives a radio signal transmitted by a terminal to detect the position of the terminal, at least one of the base stations is commonly used for transmission and reception of the radio signal. An antenna to be used; a separator for separating a radio signal to be transmitted and a radio signal to be received; a radio reception unit that generates a reception signal from the received radio signal; and signal processing and transmission of the reception signal A signal processing unit that generates a signal, a wireless transmission unit that generates a radio signal from the transmission signal, a control unit that controls the operation of the base station, and a position detection signal process that performs signal processing for detecting the position of the terminal And a transmission output reducing means for making the intensity of the radio signal transmitted from the antenna smaller than the intensity of the radio signal received from the antenna, the transmission output reducing means By reducing the strength of the radio signal transmitted from the antenna less than the strength at which the transmission signal arrival distance to the terminal by the radio transmission unit is equal to the signal receivable distance from the terminal by the radio reception unit, A wireless communication system, wherein a signal receivable distance from the terminal by the wireless reception unit is made longer than a transmission signal arrival distance to the terminal by the unit.
(5) The apparatus further includes a server that controls the position detection of the terminal, the transmission output reduction unit includes an attenuator that attenuates a radio signal to be transmitted, and the base station is based on an instruction from the server, The radio communication system according to (4), wherein a radio signal to be transmitted is attenuated by the attenuator.
(6) a server for controlling the position detection of the terminal;
The transmission output reduction means includes a transmission power adjustment unit that is provided inside the control unit and reduces an output level of the transmission signal output from the signal processing unit to the radio transmission unit, and the base station (4) The output level of the transmission signal output from the signal processing unit to the wireless transmission unit is reduced by the transmission power adjustment unit based on an instruction from the server. Wireless communication system.

  The present invention can be applied to a radio communication system that detects the position of a mobile terminal using an uplink radio signal transmitted by the terminal, and is particularly applicable to a wireless LAN system or a mobile phone system (particularly, CDMA). Suitable for

1, 2, 3, 4, 5 Base station 6 Network 7 Server 11, 12, 13, 14, 15 Downlink communicable area 20 Terminal 31, 32, 33 Uplink communicable area 100, 300 Antenna 101 Circulator 102, 302 Wireless Receiving unit 103, 303 Baseband signal processing unit 104, 304 Control unit 105, 305 Wireless transmission unit 106 Position detection signal processing unit 200 High gain antenna 210 Attenuator 211 Transmission power adjustment unit

Claims (5)

In a base station device that detects the position of a terminal using a radio signal,
An antenna commonly used for transmission and reception of the radio signal;
A separator for separating a transmitted radio signal and a received radio signal;
A wireless receiver that generates a received signal from the received wireless signal;
A signal processing unit that performs signal processing of the received signal and generation of a transmission signal;
A wireless transmission unit for generating a wireless signal from the transmission signal;
A control unit for controlling the operation of the base station device;
A position detection signal processing unit for performing signal processing for terminal position detection;
A communication speed control unit for controlling the communication speed of the uplink radio signal transmitted from the terminal to the base station device,
The communication speed control unit is configured to transmit a downlink signal to the terminal by the wireless transmission unit by reducing a communication speed of a signal used for position detection of the uplink radio signal transmitted from the terminal. A base station apparatus that performs control to increase a signal receivable distance in an uplink direction from a terminal by the wireless reception unit from a signal reachable distance.   The base station apparatus according to claim 1, wherein the communication speed control unit controls a communication speed of a signal used for position detection of the terminal to a minimum speed in the base station. In a radio communication system that detects a position of the terminal by receiving a radio signal transmitted by the terminal by a base station,
At least one of the base stations is
An antenna commonly used for transmission and reception of the radio signal;
A separator for separating a transmitted radio signal and a received radio signal;
A wireless receiver that generates a received signal from the received wireless signal;
A signal processing unit that performs signal processing of the received signal and generation of a transmission signal;
A wireless transmission unit for generating a wireless signal from the transmission signal;
A control unit for controlling the operation of the base station;
A position detection signal processing unit for performing signal processing for terminal position detection;
A communication speed control unit for controlling the communication speed of the uplink radio signal transmitted from the terminal to the base station device,
The communication speed control unit is configured to transmit a downlink signal to the terminal by the wireless transmission unit by reducing a communication speed of a signal used for position detection of the uplink radio signal transmitted from the terminal. A radio communication system, characterized in that control is performed to increase a signal receivable distance in the uplink direction from a terminal by the radio reception unit from a signal reach distance.   The wireless communication system according to claim 3, wherein the communication speed control unit controls a communication speed of a signal used for position detection of the terminal to a minimum speed in the base station. A server that controls the location of the terminal,
The communication speed control unit controls, based on an instruction from the server, a communication speed of an uplink signal used for terminal position detection to a minimum speed in the base station. 3. The wireless communication system according to 3.