JP5359331B2 - Base station, radio communication system, base station control method, radio communication method, computer program, and mobile station - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a base station, a wireless communication system, a method of controlling a base station, a wireless communication method, a computer program, and a mobile station, which are capable of suppressing power consumption in the base station and avoiding radio wave interference between the base stations. <P>SOLUTION: A base station has a communication means for communicating with a mobile station, and a changing means that changes a state of the base station depending on a predetermined condition. The changing means transits the state of the base station among an active state where communication with the mobile station is possible, a radio wave transmission and reception stopped state where communication with the mobile station is not carried out, and a radio wave reception measuring state where a transmission signal from the mobile station to the other base station is received to measure the reception condition of the transmission signal. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a base station, a radio communication system, a base station control method, a radio communication method, a computer program, and a mobile station.

  For example, a cellular system is known as a mobile communication system. A cellular system is a system that secures a wide communication range of a service area by laying cells (communication areas of base stations covering several hundred m to several km). By the way, in the case of a cellular system, measures are taken to increase the number of base stations in order to avoid communication failure due to an increase in the number of terminals in a dark place or service area. In that case, depending on the installation status of the base station, the coverage area of a cell and the coverage area of a cell adjacent to the cell may overlap, or the entire coverage area of a cell may be included in the coverage area of another cell. In some cases, the cover areas of three or more cells overlap each other.

  However, there is concern about the occurrence of radio wave interference between base stations due to the overlap or inclusion of the cover areas. Radio interference causes a reduction in line capacity. Also, with the increase in the number of base stations, there is a probability that there is a base station that has been activated even though there is no mobile station in the cell coverage area (ie, it is not used at all). Rise. Power is wasted by base stations that are not used at all and are activated wastefully.

  Thus, techniques for avoiding interference and saving power in mobile communication systems have been proposed. For example, in Patent Document 1, a radio base station monitors a transmission signal transmitted from another radio base station, and stops transmission of the base station in consideration of traffic status and received power of the other radio base station. In addition, a technique for reducing the number of base stations operating at low traffic and reducing interference to surrounding radio base stations by starting transmission or the like is disclosed.

  As a related technique, Patent Document 2 discloses an access point that stops a reception operation using a contention free period (CEP) in a wireless LAN system.

JP 2003-37555 A Japanese Patent Laid-Open No. 2004-364069

Keiji Tachikawa, “W-CDMA Mobile Communication System” Maruzen Publishing, June 25, 2001, p45-p47

  In the case of Patent Literature 1, the own base station is returned from the sleep state to the normal state only under the condition that the traffic of the adjacent base station becomes high traffic. In the case of a wireless communication system in which there is only one base station adjacent to a predetermined base station, there is no particular problem even with the technique of Patent Document 1. However, in the case of a general wireless communication system typified by a cellular system, there are usually a plurality of base stations adjacent to a predetermined base station. When the technique of Patent Document 1 is applied to such a system, when a predetermined base station becomes high traffic, all adjacent base stations adjacent to the base station are activated. However, the probability that the location of each mobile station is uniformly present in the coverage area of each neighboring base station that is activated is extremely low, and there is a high possibility that the location is usually unevenly distributed in the coverage area of a specific base station. Therefore, there is a high possibility that among the activated adjacent base stations, there is a base station that is far away from the mobile station and cannot communicate or cannot secure sufficient communication quality even if it can communicate. That is, it can be said that such a base station is a base station that has been activated in vain, having little or no contribution to traffic reduction of a predetermined base station. In other words, the technique disclosed in Patent Document 1 cannot sufficiently reduce the number of base stations that have been activated in spite of the low traffic state, resulting in interference between adjacent cells and power consumption. It cannot be reduced sufficiently.

  On the other hand, in the case of Patent Document 2, since the access point stops the reception operation during the non-contention period, the power consumption of the system may be suppressed. However, this “non-contention period” is basically a period in which packet collision is guaranteed not to occur, and is unique to the wireless LAN. Therefore, it is difficult to apply such a technique to a general wireless communication system represented by a cellular system. That is, the technique described in Patent Document 2 cannot sufficiently reduce the number of base stations that have been activated in spite of the low traffic state, resulting in interference between adjacent cells and power consumption. Cannot be reduced sufficiently.

  The present invention has been made to solve the above-described problems, and is capable of suppressing power consumption in a base station and avoiding radio wave interference between base stations, a radio communication system, and a base station It is an object to provide a control method, a wireless communication method, a computer program, and a mobile station.

  In order to solve the above problems, the base station of the present invention comprises a communication means for communicating with a mobile station, and a changing means for changing the state of the base station according to a predetermined condition, the changing means comprising: An active state in which communication with the mobile station is possible, a radio wave transmission / reception stop state in which communication with the mobile station is not performed, and a radio wave reception measurement for receiving a transmission signal from the mobile station to another base station and measuring the reception status of the transmission signal Transition the state of the base station between states.

  The wireless communication system of the present invention includes a first base station, a second base station, and at least one mobile station capable of communicating with the first base station and the second base station, The second base station determines whether the base station is in an active state capable of communicating with the mobile station, a radio wave transmission / reception stopped state in which communication with the mobile station is not performed, and another base station from the mobile station according to a predetermined condition. Transition between radio wave reception measurement states in which a transmission signal is received and the reception status of the transmission signal is measured.

  Further, the base station control method of the present invention includes a base station state in accordance with predetermined conditions, an active state in which communication with the mobile station is possible, a radio wave transmission / reception stop state in which communication with the mobile station is not performed, and a mobile station Transition is made between radio wave reception measurement states in which a transmission signal to another base station is received and the reception state of the transmission signal is measured.

  The radio communication method of the present invention is a radio comprising a first base station, a second base station, and at least one mobile station capable of communicating with the first base station and the second base station. A wireless communication method in a communication system, wherein a state of the second base station is set according to predetermined conditions, an active state in which communication with a mobile station is possible, a radio wave transmission / reception stop state in which communication with the mobile station is not performed, and mobile Transition is made between radio wave reception measurement states in which a transmission signal from a station to another base station is received and the reception state of the transmission signal is measured.

  Further, the computer program of the present invention sets the state of the base station according to a predetermined condition, an active state in which communication with the mobile station is possible, a radio wave transmission / reception stop state in which communication with the mobile station is not performed, and other bases from the mobile station The base station computer executes a process of transitioning between radio wave reception measurement states in which a transmission signal to the station is received and the reception status of the transmission signal is measured.

  According to the present invention, power consumption in a base station is suppressed, and radio wave interference between base stations is avoided.

It is a block diagram which shows an example of the radio | wireless communications system which concerns on the 1st Embodiment of this invention. It is a block diagram which shows an example of the 1st base station in 1st Embodiment. It is a block diagram which shows an example of the 2nd base station in 1st Embodiment. It is explanatory drawing about the state transition of a 2nd base station. In 1st Embodiment, it is a sequence chart which shows an example of operation | movement of the radio | wireless communications system in case a 2nd base station changes from an active state to a radio wave transmission / reception stop state. It is a flowchart explaining an example of operation | movement of the 2nd base station when changing from an active state to a radio wave transmission / reception stop state, and changing from an active state to a radio wave reception measurement state. (A) is a graph showing the relationship between the distance of each mobile station from the first base station and the received power of the transmission signal from each mobile station to the first base station in the first base station; b) is a graph showing the relationship between the distance of each mobile station from the second base station and the received power at the second base station of the transmission signal from each mobile station to the first base station. 5 is a flowchart illustrating an example of an operation of a second base station when transitioning from a radio wave reception measurement state to an active state in the first embodiment. It is a block diagram which shows an example of the radio | wireless communications system concerning the 2nd Embodiment of this invention. It is a block diagram which shows an example of the 2nd base station in 2nd Embodiment. In 2nd Embodiment, it is a flowchart which shows an example of operation | movement of the 2nd base station in the case of changing from a radio wave reception measurement state to an active state. It is a block diagram which shows an example of the radio | wireless communications system concerning the 3rd Embodiment of this invention. It is a block diagram which shows an example of the 1st base station in 3rd Embodiment. In 3rd Embodiment, it is a sequence chart which shows an example of operation | movement of the radio | wireless communications system in case the 2nd base station changes from a radio wave transmission / reception stop state to a radio wave reception measurement state. It is a block diagram which shows an example of the principal part of the base station concerning embodiment of this invention.

  FIG. 15 is a block diagram illustrating an example of a main part of the base station 20 according to the embodiment of the present invention. The base station 20 includes a communication unit 22 and a changing unit 24. The communication means 22 communicates with the mobile station. The changing unit 24 changes the state of the base station 20 according to a predetermined condition. This changing means 24 is in an active state in which communication with the mobile station is possible, a radio wave transmission / reception stop state in which communication with the mobile station is not performed, and a transmission signal from the mobile station to another base station The state of the base station is transitioned between the radio wave reception measurement states for measuring.

  Specifically, for example, the base station 20 in the active state transitions from the active state to the radio wave transmission / reception stopped state when the loads on the base station and other base stations are low. On the other hand, when the load on the base station is low and the load on other base stations is high, the base station 20 transitions from the active state to the radio wave reception measurement state. Further, when the load on other base stations is high, the base station 20 transitions from the radio wave transmission / reception stop state to the radio wave reception measurement state. Further, when the load at the other base station is low, the base station 20 transitions from the radio wave reception measurement state to the radio wave transmission / reception stop state. Further, when the load on the other base station is high and the reception power of the transmission signal to the other base station of the mobile station is higher than the threshold, the base station 20 transitions to the active state.

  As described above, since the base station 20 changes its own state between the above three states in a fine manner, power consumption in the base station 20 can be suppressed and radio wave interference between the base stations can be avoided. It becomes possible.

Hereinafter, a plurality of other embodiments of the present invention will be described in detail. In each of the following embodiments, a case will be described in which a pilot signal, which is a common control signal that continuously and repeatedly transmits a signal of a predetermined pattern, is used as an example of a control signal.
[First Embodiment]
FIG. 1 is a configuration diagram showing an example of a radio communication system according to the first embodiment of the present invention. This wireless communication system includes a base station 1 (also referred to as a first base station or another base station), a base station 2 (second base station), mobile stations 100 to 102, a wireless network control device ( (Hereinafter referred to as RNC (Radio Network Controller)) 200. The base station 1 transmits a pilot signal to the mobile stations in the cell 11, and the mobile stations 100 to 102 that have received the pilot signal respectively connect the base station 1 and the radio link 1100 to each based on the received pilot signal. Communication is performed at 1102. In the cell 12, the base station 2 can communicate with a mobile station (for example, the mobile station 100 in FIG. 1). Here, at least a part of each of the cell 11 and the cell 12 overlaps. The RNC 200 is connected to the base station 1 through the line 2001 and is connected to the base station 2 through the line 2002. The RNC 200 manages the base station 1 and the base station 2. Here, the lines 2001 and 2002 may be wired lines or wireless lines, and will be described as wired lines in the following description.

  FIG. 2 is a block diagram showing an example of the base station 1 as the first base station shown in FIG. The base station 1 includes a network communication unit 300, an RF (Radio Frequency) unit 302, a reception signal processing unit 304, a transmission signal processing unit 306, an antenna 308, and a load management unit 400. The network communication unit 300 communicates with the RNC 200 via the line 2001. The RF unit 302 communicates with the mobile stations 100 to 102 through the wireless links 1100 to 1102. The received signal processing unit 304 processes a signal received by the RF unit 302 from the mobile stations 100 to 102. The transmission signal processing unit 306 processes a signal for transmission to the mobile stations 100 to 102, and outputs the processed signal to the RF unit 302. The antenna 308 radiates radio waves into the space in order to perform wireless communication with the mobile stations 100 to 102 or captures radio waves that have traveled through the space. The load management unit 400 acquires the mobile station communication traffic and the number of mobile stations supported by the base station 1 from the reception signal processing unit 304 and the transmission signal processing unit 306 as load information.

  FIG. 3 is a block diagram showing an example of the base station 2 as the second base station shown in FIG. The base station 2 includes a network communication unit 350, an RF unit 352, a reception signal processing unit 354, a transmission signal processing unit 356, a state transition control unit 358, a power control unit 360, an antenna 362, and a mobile station signal. An estimation unit 364 and a load management control unit 369 are configured.

  Here, the changing unit 24 described above is a condition recognition unit (for example, the mobile station signal estimation unit 364 and the load management control unit 369) that recognizes a predetermined condition, and the state of the base station 2 according to the recognized predetermined condition. State transition control means (for example, a state transition control unit 358 and a power control unit 360) that transitions from one state to the other state among the above states is provided.

  The network communication unit 350 communicates with the RNC 200 via the line 2002. The RF unit 352 communicates with the mobile stations 100 to 102 through a wireless link. The reception signal processing unit 354 processes signals received by the RF unit 352 from the mobile stations 100 to 102. The transmission signal processing unit 356 processes a signal for transmission to the mobile stations 100 to 102, and outputs the processed signal to the RF unit 352. The antenna 362 radiates radio waves to the space in order to perform wireless communication with the mobile stations 100 to 102 or captures radio waves transmitted through the space.

  The state transition control unit 358 controls the state transition of the base station 2 based on information or instructions from the network communication unit 350, the mobile station signal estimation unit 364, or the load management control unit 369. Based on the command from the state transition control unit 358, the power control unit 360 turns on / off the power of the reception signal processing unit 354, the transmission signal processing unit 356, and the mobile station signal estimation unit 364, and controls the transmission power in the RF unit 352. The power on / off control is executed.

  The mobile station signal estimation unit 364 receives signals from the RF unit 352 when the base station 2 performs a procedure for shifting to a radio wave transmission / reception stop state or a radio wave reception measurement state in an active state as described later, and in a radio wave reception measurement state. The transmission signals of the surrounding mobile stations 100 to 102 are detected from the received signal (for example, radio wave). As an example of a transmission signal detection method, for example, there is a method of detecting a signal from received power.

  The load management control unit 369 acquires the communication traffic of the mobile station supported by the base station 2 and the number of mobile stations in the cell 12 from the received signal processing unit 354 and the network communication unit 350 as load information. Further, the load management control unit 369 acquires load information in the base station 1 from the RNC 200 or the base station 1 via the network communication unit 350.

  FIG. 4 is an explanatory diagram of the state transition of the base station 2 as the second base station. The base station 2 has three operation states as shown in FIG. The first state is an active state St_1 in which the base station 2 can transmit and receive radio signals to and from a mobile station (for example, the mobile station 100 in FIG. 1) located in the cell 12.

  The second state is a radio transmission / reception function in the base station 2, which stops the RF unit 352, the transmission signal processing unit 356, the reception signal processing unit 354, and the mobile station signal estimation unit 364, and transmits radio waves from the base station 2. In addition, the radio wave transmission / reception stop state St_2 in which radio waves are not received with respect to the transmission signal from the mobile station and radio communication with the mobile station in the cell 12 is not performed.

  The third state is a radio wave reception measurement state in which the ambient noise power is measured using the RF unit 352 and the mobile station signal estimation unit 364, which are wireless reception functions.

  For example, the base station 2 performs transition between the states based on conditions Tr_12, Tr_23, Tr_32, Tr_13, and Tr_31 described below. The condition Tr_12 for the base station 2 to transition from the active state St_1 to the radio wave transmission / reception stop state St_2 is, for example, that the communication of the mobile station (for example, the mobile station 100 in FIG. 1) in communication with the base station 2 is disconnected. No mobile station to connect to and no other base station (for example, base station 1 in FIG. 1) has a load equal to or lower than a threshold.

  The condition Tr_23 in which the base station 2 transitions from the radio wave transmission / reception stop state St_2 to the radio wave reception measurement state St_3 is, for example, when the load at another base station is equal to or greater than a threshold value. Conversely, the condition Tr_32 for transitioning from the radio wave reception measurement state St_3 to the radio wave transmission / reception stop state St_2 is, for example, when the load at another base station is equal to or less than a threshold value.

  The condition Tr_31 for the base station 2 to transition from the radio wave reception measurement state St_3 to the active state St_1 is, for example, set by another mobile station (for example, the mobile station 100 in FIG. 1) by the mobile station signal estimation unit 364 of the base station 2. This is a case where it is determined that the reception power at the base station 2 of the transmission signal to the station (for example, the base station 1 in FIG. 1) is higher than a predetermined threshold. Conversely, the condition Tr_13 for transitioning from the active state St_1 to the radio wave reception measurement state St_3 is, for example, that the communication of the mobile station in communication with the base station 2 (for example, the mobile station 100 in FIG. This is a case where there is no mobile station to be connected and the load on another base station (for example, base station 1 in FIG. 1) is equal to or greater than a threshold value.

  FIG. 5 is a sequence chart showing an example of the operation of the wireless communication system when the base station 2 as the second base station transitions from the active state St_1 to the radio wave transmission / reception stop state St_2 (condition Tr_12). Hereinafter, the sequence illustrated in FIG. 5 will be described with reference to FIGS. 1 to 3 as necessary.

  First, the base station 2 is communicating with the mobile station 100 in the cell 12 (step S1). Here, for some reason, the mobile station 100 executes communication disconnection processing for the base station 2 (step S2). Receiving the communication disconnection request from the mobile station 100, the base station 2 checks whether there is a mobile station in communication other than the mobile station 100 in the cell 12 of the base station (step S3).

  When it is confirmed that there is no mobile station in communication other than the mobile station 100, the base station 2 moves from the mobile station in the vicinity of the cell 12 (for example, the mobile stations 101 and 102 in FIG. 1) to the other base station 1. The received power at the base station 2 of the transmitted signal is measured, and a comparison process between the measured received power and a preset threshold value is executed (step S4). If the received power does not exceed the threshold and a certain time (for example, 5 seconds) has elapsed, the base station 2 gradually decreases the transmission power (for example, 1 dB every 0.1 seconds) (step S5).

  While the transmission power is being reduced, the base station 2 checks whether or not there is a new connection request from the mobile station in the cell 12 of the base station (step S6). Further, while the transmission power is being reduced, the base station 2 checks whether or not the reception power at the base station 2 of the transmission signal to the other base station of the mobile station has exceeded the threshold value (step S7). If there is no new connection request and the received power is below the threshold, the base station 2 keeps the transmission power down by a certain amount (for example, 20 dB) (that is, the transmission power is 1 / 100th of the power in the active state St_11). Steps S5 to S7 are repeated. When the transmission power is reduced to a predetermined threshold (step S8), the base station 2 transmits to the RNC 200 another base station registered in the measurement cell set in the base station (for example, the base station 1 in FIG. 1). ) Is requested (step S9). Here, the measurement cell set is a list of cells (base stations) to which the mobile station measures the received power of the pilot signal.

  The RNC 200 that has received the load information request in the base station 1 from the base station 2 instructs the base station 1 to measure the load (step S10). The base station 1 instructed to measure the load from the RNC 200 measures the load at the own base station (step S11), and reports the measurement result to the RNC 200 (step S12). The RNC 200 that has received the load information from the base station 1 transmits the load information in the base station 1 to the base station 2 (step S13). The base station 2 that has received the load information in the base station 1 compares the load information of the base station 1 with a predetermined threshold value, and determines whether there is a state transition of the base station 2 according to the comparison result (step S14). For example, when the load information of the base station 1 is lower than a predetermined threshold, the base station 2 reports to the RNC 200 that the base station 2 transitions to the radio wave transmission / reception stop state St_2 (step S15).

  And the base station 2 which transmitted the state transition report stops the above-mentioned radio | wireless transmission / reception function, and changes to radio wave transmission / reception stop state St_2 (step S16). The RNC 200 that has received the report transmits a notification that the status report of the base station 2 has been accepted by the RNC 200 to the base station 2 (step S17). Further, the RNC 200 instructs the base station 1 to delete the base station 2 from the measurement cell set (step S18). The base station 1 that has received the instruction updates the measurement cell set in the base station 1 and deletes the base station 2 (step S19).

  Next, an example of the operation of the wireless communication system when the base station 2 transitions from the active state St_1 to the radio wave reception measurement state St_3 (condition Tr_13) will be described. The transition from the active state St_1 to the radio wave reception measurement state St_3 is common except for steps S15 and S16 in FIG. Therefore, description of steps other than steps S15 and S16 in FIG. 5 is basically omitted. When the load information in the base station 1 is higher than the predetermined threshold in step S14, the base station 2 reports to the RNC 200 that the base station 2 transitions to the radio wave reception measurement state St_3 (step S15 ′ ). Then, the base station 2 that has transmitted the state transition report stops the transmission of radio waves to the mobile station (in this case, the above-described wireless reception function is activated), and transitions to the radio wave reception measurement state (step S16 ′). .

  FIG. 6 shows the state of the base station 2 as the second base station in the transition from the active state St_1 to the radio wave transmission / reception stop state St_2 (condition Tr_12) and from the active state St_1 to the radio wave reception measurement state St_3 (condition Tr_13). It is a flowchart explaining an example of operation | movement. Briefly, the transition from the active state St_1 to the radio wave transmission / reception stop state St_2 (or the transition from the active state St_1 to the radio wave reception measurement state St_3) in the process shown in the flow is one of the following two conditions: That is, (1) when communication of the mobile station 100 in communication within the cell 12 is completed (in other words, when there is no mobile station communicating with the base station 2), (2) the mobile station 100 This is executed when the reception power of the transmission signal to the other base station of the mobile station 100 in the base station 2 falls below the threshold and a certain time has elapsed after the communication is handed over to the adjacent base station when leaving the cell 12.

  First, the load management control unit 369 of the base station 2 determines whether or not there is a mobile station in communication with the base station 2 (whether the number of mobile stations is 0 or whether the communication traffic is 0) (step). S20). When the load management control unit 369 determines that the mobile station in communication with the base station 2 is “present” (No determination in step S20), the state transition control unit 358 changes the operation state of the base station 2 to the active state. It is maintained at St_1 (step S30). Thereby, the state transition control unit 358 instructs the power control unit 360 to keep the transmission power in the normal operation state, and the active state that is the normal communication state is maintained.

  When it is determined that the mobile station in communication is “none” (in the case of Yes determination in step S20), the mobile station signal estimation unit 364 transmits a transmission signal to other base stations of the mobile stations existing around the cell 12. The received power at the base station 2 is measured, and the received power is compared with a threshold value (step S21). If the received power exceeds the threshold value (Yes in step S21), the mobile station signal estimation unit 364 notifies the state transition control unit 358 to that effect. Thereby, the state transition control unit 358 maintains the operation state of the base station 2 in the active state St_1 (step S30). On the other hand, when the received power is below the threshold value (No determination in step S21), the mobile station signal estimation unit 364 notifies the state transition control unit 358 to that effect. Thereby, state transition control section 358 issues an instruction to gradually reduce the transmission power of the control signal including the pilot signal to power control section 360. Receiving the instruction to reduce the transmission power, the power control unit 360 outputs an instruction to gradually reduce the transmission power of the transmission signal processing unit 356 (step S22). Here, for example, the power control unit 360 decreases the transmission power of the transmission signal processing unit 356 by 1 dB every 0.1 seconds, for example, until it decreases by 20 dB (that is, the transmission power is 100 minutes of the power in the active state St_11). Until the transmission power reduction processing is stopped.

  While the transmission signal processing unit 356 reduces the transmission power under the control of the power control unit 360, the reception signal processing unit 354 determines whether or not there is a new connection request from the mobile station in the cell 12 of the own base station. Confirm (step S23). At the same time, the mobile station signal estimation unit 364 checks whether or not the reception power at the base station 2 of the transmission signal to the other base station of the mobile station exceeds the threshold (step S24). While the transmission power is being reduced, whether there is a new connection request from the mobile station in the cell 12 (in the case of Yes determination in step S23), or the base station of the transmission signal to another base station of the mobile station 2 exceeds the threshold (in the case of Yes determination in step S24), at least one of the reception signal processing unit 354 and the mobile station signal estimation unit 364 defines the transmission power for the state transition control unit 358. Output control information or instructions to increase the value. Based on this control information or instruction, state transition control section 358 issues an instruction to power control section 360 to increase the transmission power of the control signal including the pilot signal in transmission signal processing section 356 to a specified value. Thereby, the power control unit 360 controls the transmission signal processing unit 356 to increase the transmission power (step S29), and maintains the operation state of the base station 2 in the active state St_1 (step S30).

  On the other hand, while the transmission power is being reduced, there is no new connection request from the mobile station in the cell 12 (in the case of No determination in step S23), and the base station 2 of the transmission signal to the other base station of the mobile station If the received power is lower than the threshold (No in step S24), the power control unit 360 determines whether or not the transmission power has decreased to a predetermined threshold (step S25). The power control unit 360 notifies the state transition control unit 358 to that effect when it has decreased to the threshold value (in the case of Yes determination in step S25). Receiving the notification, the state transition control unit 358 instructs the load management control unit 369 to inquire the RNC 200 via the network communication unit 350 about load information in other base stations. The load management control unit 369 compares the load information of other base stations with a threshold value (step S26). When the load information of the other base station is smaller than the threshold (Yes in step S26), the base station 2 reports to the RNC 200 that the base station 2 transitions to the radio wave transmission / reception stop state St_2 ( Step S27). After reporting the state transition to the RNC 200, the state transition control unit 358 issues an instruction to stop the wireless transmission / reception function to the power control unit 360 (step S28). Thereby, the operation state of the base station 2 becomes a radio wave transmission / reception stop state St_2. On the other hand, if the load information of the other base station is larger than the threshold value in step S26 (in the case of No determination in step S26), the base station 2 reports to the RNC 200 that it will transition to the radio wave reception measurement state St_3. (Step S27 ′). After reporting the state transition to the RNC 200, the state transition control unit 358 issues an instruction to stop the transmission signal processing unit 356 to the power control unit 360 (step S28 '). Thereby, the operation state of the base station 2 becomes the radio wave reception measurement state St_3.

  6 can be changed to a process for determining whether or not the received power of the pilot signal of the base station 2 at the mobile station is lower than a predetermined threshold value. Specifically, the load management control unit 369 of the base station 2 transmits the base station 2 in the mobile station (for example, the mobile station 101 in FIG. 1) existing around the cell 12 to the RNC 200 via the network communication unit 350. The pilot signal reception power status (whether the reception power exceeds a threshold value) is inquired. When the received power of the pilot signal of the base station 2 at the mobile station is below the threshold, the network communication unit 350 receives a notification to that effect from the RNC 200. That is, when it is determined that the mobile station in communication is “none” (Yes in step S20), and there is no new connection request from the mobile station in the cell 12 while the transmission power is being reduced. In the case (in the case of No determination in step S23), “the received power at the base station 2 of the transmission signal to the other base station of the mobile station existing around the cell 12 is measured and the received power is compared with the threshold value” Instead of the processing, the above processing (processing for determining whether or not the received power of the pilot signal of the base station 2 at the mobile station is lower than a predetermined threshold value) can be executed.

  Moreover, the transmission power reduction process in the base station 2 is not limited to the above. For example, the power control unit 360 or the transmission signal processing unit 356 of the base station 2 can also reduce the transmission power to a predetermined value at a stretch rather than gradually. In that case, at least the process of step S23 in FIG. 6, and depending on the case, the process of step S24 can be omitted. Here, the “predetermined value” includes a state where no signal is output, that is, a “0” output (for example, “0” watts).

  Next, an example of the operation of the wireless communication system when the base station 2 transitions from the radio wave transmission / reception stop state St_2 to the radio wave reception measurement state St_3 (condition Tr_23) will be described. When the base station 2 is in the radio wave transmission / reception stop state St_2 and the load on another base station (for example, the base station 1 in FIG. 1) exceeds a predetermined threshold, the base station 1 informs the RNC 200 to that effect. To report. Receiving the report that the load at the base station 1 exceeds the threshold value, the RNC 200 instructs the base station 2 to transition to the radio wave reception measurement state St_3. Receiving the instruction from the RNC 200 to change to the radio wave reception measurement state St_3, the base station 2 changes its own state from the radio wave transmission / reception stop state St_2 to the radio wave reception measurement state St_3.

  Next, an example of the operation of the wireless communication system when the base station 2 transitions from the radio wave reception measurement state St_3 to the radio wave transmission / reception stop state St_2 (condition Tr_32) will be described. When the base station 2 is in the radio wave reception measurement state St_3, if the load at another base station (for example, the base station 1 in FIG. 1) falls below a predetermined threshold, the base station 1 notifies the RNC to that effect. To report. Receiving the report that the load in the base station 1 has fallen below the threshold, the RNC 200 instructs the base station 2 to transition to the radio wave transmission / reception stop state St_2. Receiving the instruction from the RNC 200, the base station 2 changes its own state from the radio wave reception measurement state St_3 to the radio wave transmission / reception stop state St_2.

  Next, an example of the operation of the wireless communication system when the base station 2 transitions from the radio wave reception measurement state St_3 to the active state St_1 (condition Tr_31) will be described. The base station 2 in the radio wave reception measurement state St_3 moves from the mobile station 100 in the uplink band (band used for signal transmission from the mobile station to the base station) (for example, the base station 1 in FIG. 1). ) To determine whether there is a mobile station in communication around the base station 2 by measuring the reception power of the transmission signal to the base station 2, and the determination result (for example, mobile station signal estimation unit) 364), the state of the base station 2 is changed from the radio wave reception measurement state St_3 to the active state St_1.

  Here, referring again to FIG. 1, in order to communicate with the base station 1, each of the mobile stations 100 to 102 receives the pilot signal of the base station 1, transmits a radio wave based on the pilot signal, and transmits each radio link 1100. ~ 1102 are formed.

  FIG. 7A is a graph showing the relationship between the distance of each mobile station from the base station 1 and the received power of the transmission signal from each mobile station to the base station 1 in the base station 1. At this time, each of the mobile stations 100 to 102 adjusts the transmission power so that the reception power at the base station 1 is uniform. For example, the mobile station 100 located far from the base station 1 transmits a signal with higher power than the nearby mobile stations 101 and 102. By the way, the signal transmitted from the mobile station to the base station is an omnidirectional signal. Therefore, for example, the base station 2 can receive a signal (the signal 1100 in FIG. 1) that the mobile station 100 originally transmits to communicate with the base station 1. In this case, signals that can be received by the base station 2 are not limited to transmission signals from the mobile station 100 but also include transmission signals from other mobile stations 101 and 102. The mobile station signal estimation unit 364 of the base station 2 receives radio waves from neighboring mobile stations (in the case of FIG. 1, mobile stations 100, 101, 102) in the base station 2 in the radio wave reception measurement state St_3.

  FIG. 7B is a graph showing the relationship between the distance of each mobile station from the base station 2 and the received power of the transmission signal from each mobile station to the base station 1 in the base station 2. In this case, it can be understood from FIG. 1 and FIG. 7B that, for example, in the base station 2, the received power of the signal from the mobile station 100 closest to the base station 2 is the highest.

  The mobile station signal estimation unit 364 of the base station 2 measures the received power of radio waves from the surrounding mobile stations, compares the measured received power value with a predetermined threshold, and if the received power is greater than the threshold, It is determined that a mobile station in communication exists around the base station 2. Here, this threshold value is a threshold value for determining whether or not the measured received power value is a level at which it can be recognized that there is a mobile station in communication in the vicinity of the base station 2. Based on the determination result from the mobile station signal estimation unit 364, the base station 2 transitions to the active state St_1 (in other words, starts transmission of a pilot signal with a predetermined power). The base station 2 reports to the RNC 200 that the base station 2 has transitioned to the active state St_1. Receiving the report, the RNC 200 instructs the base station 1 to add the base station 2 to the measurement cell set. The base station 1 that has received the addition instruction instructs the connected mobile station to measure the received power of the pilot signal including the cell added to the measurement cell set, and the mobile station follows the instruction. Measure the received power of the pilot signal.

  FIG. 8 is a flowchart illustrating an example of the operation of the base station 2 as the second base station when the radio wave reception measurement state St_3 transitions to the active state St_1 (condition Tr_31). The process shown in the flow is called when the base station 2 transitions to the radio wave reception measurement state St_3.

  Based on the signal from the RF unit 352, the mobile station signal estimation unit 364 of the base station 2 in the radio wave reception measurement state St_3 performs reception power measurement of radio waves from the surrounding mobile stations as described above (step S40). The mobile station signal estimation unit 364 determines whether or not the measured received power value is greater than a predetermined threshold (step S41). When the received power is less than the threshold, the mobile station signal estimation unit 364 continues to measure the received power. When the received power exceeds the threshold, the mobile station signal estimation unit 364 determines that there is a mobile station in communication around the base station 2. Based on the determination result from the mobile station signal estimation unit 364, the state transition control unit 358 causes the operating state of the base station 2 to transition to the active state St_1. Specifically, the state transition control unit 358 instructs the power control unit 360 to start transmission of a pilot signal with a predetermined power from the transmission signal processing unit 356 (step S42). Also, the state transition control unit 358 reports to the RNC 200 via the network communication unit 350 that the base station 2 has transitioned to the active state St_1 (step S43).

  As described above, in the wireless communication system according to the first embodiment, the base station 2 as the second base station includes a changing unit that changes the state of the base station 2 according to a predetermined condition. The changing means receives an active state St_1 communicable with the mobile station, a radio wave transmission / reception stop state St_2 not communicating with the mobile station, and a transmission signal from the mobile station to another base station. The state of the base station 2 is transitioned between the radio wave reception measurement states St_3 for measuring the reception status of.

  For example, in the radio wave reception measurement state St_3, the base station 2 receives a transmission signal from the mobile station to another base station, and starts transmission of a pilot signal with a predetermined power according to the reception state of the transmission signal. . Specifically, the mobile station signal estimation unit 364, which is one of the condition recognition means of the base station 2, measures the received power, compares the measured received power value with a predetermined threshold value, and the received power is the threshold value. If it is greater than the range, it is determined that a mobile station in communication exists around the base station 2. Then, the state transition control unit 358, which is one of the state transition control means of the base station 2, makes a transition to the active state St_1 based on this determination result (in other words, transmission of a pilot signal with a predetermined power). Start). That is, in the case of this wireless communication system, the base station 2 is currently communicating with another base station, but enters the active state St_1 only when there is a mobile station that can reliably communicate with its own base station. Transition is made, and transmission of a pilot signal with a predetermined power is started. Therefore, as in Patent Document 1, it is possible to eliminate a base station that starts wastefully even though there is no mobile station that can communicate, and as a result, more reliably suppress power consumption in the base station, and It is possible to avoid radio wave interference between stations.

  Further, in the base station 2 of the wireless communication system according to the first embodiment, when a predetermined condition is satisfied after transition to the active state St_1 (for example, when there is no mobile station communicating with the base station 2) When the reception power of the pilot signal of the base station 2 at the mobile station is lower than the threshold, or when the reception power at the base station 2 of the transmission signal to the other base station of the mobile station is below the threshold, etc. Means (for example, when recognized by the mobile station signal estimation unit 364 and the load management control unit 369), state transition control means (for example, the state transition control unit 358 and the power control unit 360), the operation state of the base station 2 Can be executed from the active state St_1 to the radio wave transmission / reception stop state St_2. That is, the base station 2 includes means (for example, a state transition control means 358 and a power control unit 360) that stops transmission of the pilot signal when the predetermined condition is satisfied after starting the transmission of the pilot signal. .

  In this way, the base station 2 changes its own state between the above three states in a fine manner, so that the power consumption in the base station can be more reliably suppressed and radio wave interference between the base stations can be avoided. It becomes possible.

  In the first embodiment described above, the base station 2 compares the measured received power value with a predetermined threshold, and when the received power is larger than the threshold, the operating state of the base station 2 is set to the active state St_1. Explained that the Here, the predetermined threshold does not necessarily need to be a fixed threshold, and can be a variation threshold. In this case, for example, the threshold value can be changed according to the load information of the base station 1. For example, when the load on the base station 1 is high, setting the threshold value low makes it easier for the base station 2 to transition to the active state, and the load on the base station 1 can be reduced.

  In addition, when the base station 2 is in the radio wave reception measurement state St_3 in the first embodiment, the measurement period may be limited, the interval may be provided, and the measurement may be performed periodically. By periodically performing the measurement, it is possible to reduce the load applied to the measurement process in the interval period, and it is possible to reduce power consumption.

  Moreover, according to the load information in the base station 1, a measurement period and its period can be changed. For example, when the load information in the base station 1 exceeds the threshold value, it becomes easy to detect the mobile station by lengthening the measurement period or shortening the interval. This makes it easier for the base station 2 to transition to the active state, and the load on the base station 1 can be reduced.

  The base station 2 includes storage means (not shown) for holding past received power measurement results, and performs a measurement in consideration of the past measurement results and the current measurement results, an interval period, and the threshold value. It is also possible to determine (change) at least one of the following.

  In the first embodiment, regarding the transition between the radio wave transmission / reception stop state St_2 and the radio wave reception measurement state St_3, the load management control unit 369 which is one of the condition recognition means of the base station 2 It has been described that the load information of (for example, the base station 1 in FIG. 1) is used. However, regarding the above transition, it is not always necessary to use the load information of the base station 1. For example, when the condition recognition unit detects that a certain time (for example, 1 minute) has elapsed after the base station 2 transitions to the radio wave transmission / reception stop state St_2, the state transition control unit determines the state of the base station 2 as the radio wave It is also possible to automatically transition from the transmission / reception stop state St_2 to the radio wave reception measurement state St_3. Alternatively, when the base station 2 transitions to the radio wave reception measurement state St_3 and a certain time (for example, 1 minute) has elapsed without transitioning to the active state St_1, the state transition control means changes the state of the base station 2 to It is also possible to make a transition from the radio wave reception measurement state St_3 to the radio wave transmission / reception stop state St_2.

  In the first embodiment, the base station 2 uses the load information of the base station 1 regarding the transition from the active state St_1 to the radio wave transmission / reception stop state St_2. However, regarding the above transition, it is not always necessary to use the load information of the base station 1. For example, when the condition recognition unit detects that a certain time (for example, 1 minute) has elapsed without a mobile station communicating with the base station 2 in the active state St_1, the state transition control unit Can be automatically transitioned from the active state St_1 to the radio wave transmission / reception stop state St_2.

  In the first embodiment described above, it has been described that the base station 2 determines whether or not to measure the received power based on the load information of the base station 1, but the determination is not necessarily performed by the base station 2. There is no need to be done. For example, it is possible to make the determination in the RNC 200 and receive only the result on the base station 2 side.

In the first embodiment, when the base station 2 transits from the active state St_1 to the radio wave transmission / reception stop state St_2, and when the base station 2 transits from the active state St_1 to the radio wave reception measurement state St_3, the base station 2 Explained that the condition is that there is no mobile station in communication. In this case, the transition can be performed even when a mobile station in communication with the base station 2 exists. For example, when the load information in the base station 2 is below the threshold, there is a mobile station that is communicating with the base station 2 by handing over these communications to another base station (for example, the base station 1 in FIG. 1). You can create a situation where you don't. Accordingly, the base station 2 can transition from the active state St_1 to the radio wave transmission / reception stop state St_2 or from the active state St_1 to the radio wave reception measurement state St_3.
[Second Embodiment]
FIG. 9 is a configuration diagram showing an example of a wireless communication system according to the second embodiment of the present invention. The overall configuration of this wireless communication system is the same as that of the wireless communication system of the first embodiment shown in FIG. The difference of the second embodiment from the first embodiment is the configuration of the second base station. Hereinafter, a base station as a second base station in the wireless communication system of the second embodiment is newly referred to as a base station 3. Accordingly, the base station as the first base station in the wireless communication system remains the base station 1 (see FIG. 2) of the first embodiment.

  FIG. 10 is a block diagram illustrating an example of the base station 3 as the second base station of the wireless communication system according to the second embodiment. The base station 3 includes a calling signal detection unit 500 (condition recognition means) instead of the mobile station signal estimation unit 364 of the base station 2 (second base station in the first embodiment) shown in FIG. Since the configuration of the base station 3 other than the call signal detection unit 500 is the same as the configuration of the base station 2, the description thereof is omitted.

  Here, in general, when a mobile station makes a call, the mobile station receives a pilot signal of the base station to obtain identification information unique to the base station and synchronization timing. The mobile station that has obtained synchronization makes a call by transmitting a connection request to the base station using the power ramping method. Here, the power ramping method is to increase the output gradually from a predetermined low power so that the mobile station does not interfere with the communication of other mobile stations by using power stronger than necessary, This is a method of increasing the output until a connection request arrives at the base station. When the base station receives the connection request of the mobile station, the base station transmits an acknowledgment to the mobile station and instructs the transmission power of the mobile station.

  The calling signal detection unit 500 is a signal when a mobile station (for example, the mobile station 100 in FIG. 9) calls another base station (for example, the base station 1 in FIG. 9), for example, PRACH (Physical Random Access Channel) signal is detected. That is, the call signal detection unit 500 confirms whether or not the received signal contains identification information unique to the base station 1, thereby making a connection request to the base station 1 (in other words, a call to the base station 1). The presence or absence of a call) is detected.

  Here, examples of identification information unique to the base station 1 include a scrambling code and signature in the W-CDMA system described in Non-Patent Document 1. The load management control unit 369 determines whether or not to perform call signal detection in the call signal detection unit 500 based on the load information of the base station 1 acquired from the RNC 200. Then, the calling signal detection unit 500 acquires identification information unique to the base station 1 that is information necessary for detecting the calling signal from the RNC 200 or the base station 1.

  In the wireless communication system of the second embodiment, the base station 3 as the second base station makes a transition other than the transition from the radio wave reception measurement state St_3 to the active state St_1 (condition Tr_31) (conditions Tr_12, Tr_23, (Tr_32, Tr_13) of the wireless communication system and the operation flow of the second base station in the transition from the active state St_1 to the radio wave transmission / reception stop state St_2 are the operation sequence of the wireless communication system in the first embodiment ( 5) and the operation flow of the second base station (see FIG. 6), the description thereof will be omitted.

  Hereinafter, the operation of the wireless communication system of this embodiment when the base station 3 as the second base station transitions from the radio wave reception measurement state St_3 to the active state St_1 (condition Tr_31) will be described.

  In this wireless communication system, the base station 3 confirms whether or not the received signal includes identification information unique to the base station 1, thereby making a connection request to the base station 1 (in other words, to the base station 1). Detect the presence or absence of a call. When the mobile station 100 detects a connection request to the base station 1, the base station 3 determines that the mobile station 100 has made a call around the base station 3, and changes the state of the base station to the active state St_1. The base station 3 obtains in advance a list of identification information used by the base station 1 in order to detect a connection request signal from the mobile station 100 to the base station 1. Specifically, the calling signal detection unit 500 acquires the list from the RNC 200 or the base station 1.

  The base station 3 in the radio wave reception measurement state St_3 detects whether the call signal of the mobile station 100 is included in the received signal using the identification information of the base station 1. When the base station 3 detects a call from the mobile station 100 in the received signal, the base station 3 transitions from the radio wave reception measurement state St_3 to the active state St_1 (in other words, the pilot signal with a predetermined power). Start sending). The base station 3 reports to the RNC 200 that the base station 3 has transitioned to the active state St_1. The RNC 200 transmits a response to the report to the base station 3. The mobile station 100 that has received the pilot signal of the base station 3 acquires identification information unique to the base station 3 and synchronizes. The synchronized mobile station 100 makes a call to the base station 3, makes a connection request, and starts communication with the base station 3.

  FIG. 11 is a flowchart illustrating an example of the operation of the base station 3 as the second base station when the radio wave reception measurement state St_3 transitions to the active state St_1. The condition for calling the process shown in the flow in the base station 3 is when the base station 3 transits to the radio wave reception measurement state St_3.

  The call signal detection unit 500 of the base station 3 in the radio wave reception measurement state St_3 performs call signal detection. The calling signal detection unit 500 determines whether or not the calling signal has been detected (step S50). If the call cannot be detected, the process of step S50 is executed again. When a call signal is detected by the call signal detection unit 500, it can be determined that a mobile station has made a call in the vicinity of the base station 3, and the state transition control unit 358 determines the operation state of the base station 3 as a radio wave. A transition is made from the reception measurement state St_3 to the active state St_1 (step S51). In other words, the state transition control unit 358 issues an instruction to start transmission of a pilot signal with a predetermined power from the transmission signal processing unit 356 to the power control unit 360. The state transition control unit 358 reports that the base station 3 has transitioned to the active state St_1 to the RNC 200 via the network communication unit 350 (step S52).

  In the wireless communication system according to the second embodiment described above, the call signal detection unit 500 of the base station 3 detects the connection request signal for the base station 1 of the mobile station 100, thereby It is determined that the mobile station 100 has made a call in the vicinity, and the state of the base station 3 is changed to the active state St_1 (in other words, transmission of a pilot signal with a predetermined power is started). That is, in the case of this wireless communication system, the base station 3 is currently communicating with another base station, but enters the active state St_1 only when there is a mobile station that can reliably communicate with its own base station. Transition. Therefore, as in Patent Document 1, it is possible to eliminate a base station that starts wastefully even though there is no mobile station that can communicate, and as a result, more reliably suppress power consumption in the base station, and It is possible to avoid radio wave interference between stations.

  In the second embodiment described above, the mobile station 100 that has received the pilot signal of the base station 3 has been described as changing the synchronization from the base station 1 to the base station 3, but the base station without changing the synchronization. The connection to the base station 3 can be handed over after once connecting to the base station 1. By doing in this way, time until communication start can be shortened.

  In the second embodiment described above, the base station 3 can also be provided with an association table (not shown) that associates the base station 3 with the unique ID of the mobile station. When the call signal detection unit 500 of the base station 3 detects the call of the mobile station 100 in the received signal, the call signal detection unit 500 of the base station 3, for example, The unique ID of the mobile station 100 is extracted from the connection request signal for the station 1. The calling signal detection unit 500 determines whether or not the extracted unique ID is registered in the association table.

  When the unique ID of the mobile station is registered in the association table (that is, when the mobile station that made the call is associated with the base station 3), the state transition control unit 358 of the base station 3 You may make a transition from the measurement state St_3 to the active state St_1. In this case, the base station 3 may transition to the active state St_1 unconditionally (for example, regardless of the load state of the base station 1). Further, in this case, the base station 3 may transition to the active state St_1 according to a predetermined condition (for example, when the base station 1 is highly loaded).

  On the other hand, when the mobile station unique ID is not registered in the association table (that is, when the mobile station that made the call is not associated with the base station 3), the base station 3 changes to the active state St_1. Can be prohibited. In this case, the base station 3 prohibits the transition to the active state St_1 if the mobile station that made the call is not associated with the base station 3 even if the base station 1 is in a high load state. Also good.

In the wireless communication systems according to the first and second embodiments described above, when the base station (second base station) is in the radio wave reception measurement state St_3, the mobile station transmits another base station (first base station). The transmission signal to the base station) is received, and the transmission of the pilot signal with a predetermined power is started according to the reception status of the transmission signal (transition to the active state). That is, in the case of the wireless communication system according to the first and second embodiments, the second base station is currently communicating with the first base station, but can reliably communicate with the second base station. The transition to the active state St_1 is made only when there is a possible mobile station. However, just because there is one “mobile station that is currently communicating with the first base station but can communicate with the second base station”, the second base station is always It is not always necessary to transition to the active state St_1. For example, the second base station may transition to the active state St_1 only when there are a predetermined plurality of mobile stations.
[Third Embodiment]
FIG. 12 is a configuration diagram illustrating an example of a wireless communication system according to the third embodiment of the present invention. The overall configuration of this wireless communication system is the same as that of the wireless communication system of the first embodiment shown in FIG. The difference of the third embodiment from the first embodiment is the configuration of the first base station. Hereinafter, a base station as a first base station in the wireless communication system according to the third embodiment is newly referred to as a base station 4. Accordingly, the base station as the second base station in the wireless communication system remains the base station 2 (see FIG. 3) of the first embodiment.

  FIG. 13 is a block diagram illustrating an example of the base station 4 as the first base station of the wireless communication system according to the third embodiment. The base station 4 further includes a position information acquisition unit 450 in addition to the configuration provided in the base station 1 as the first base station in the first embodiment shown in FIG. Other components, that is, the configuration and operation of the network communication unit 300, the RF unit 302, the reception signal processing unit 304, the transmission signal processing unit 306, the load management unit 308, and the antenna 310 are the same as those of the base station 1. Since they are the same, their description is omitted. The position information acquisition unit 450 acquires or detects the position of the mobile station located in the cell 11 of the base station 4 based on the information obtained from the received signal processing unit 304.

  In the wireless communication system according to the third embodiment, the second base station transitions (conditions Tr_12, Tr_32, Tr_13, Tr_31) other than the transition from the radio wave transmission / reception stop state St_2 to the radio wave reception measurement state St_3 (condition Tr_23). ) And the operation flow of the second base station in the case of transition from the active state St_1 to the radio wave transmission / reception stop state St_3 (condition Tr_13) are the operations of the wireless communication system in the first embodiment. Sequence (see FIG. 5) or operation of the wireless communication system in the second embodiment, and operation flow of the second base station in the first embodiment (see FIG. 6), or second in the second embodiment Since this is the same as the operation flow of the base station (FIG. 11), description thereof will be omitted.

  Hereinafter, the operation of the wireless communication system of the present embodiment when the base station 2 as the second base station transitions from the radio wave transmission / reception stop state St_2 to the radio wave reception measurement state St_3 (condition Tr_23) will be described with reference to FIG. explain.

  FIG. 14 is a sequence chart showing an example of the operation of the wireless communication system according to the present embodiment when transitioning from the radio wave transmission / reception stop state St_2 to the radio wave reception measurement state St_3 (condition Tr_23).

  In this wireless system, the base station 2 uses the load information of the base station 4 which is the first base station and the position information of the mobile station supported by the base station 4 to start the radio wave from the radio wave transmission / reception stop state St_2. The transition to the reception measurement state St_3 is controlled.

  Specifically, when the load information in another base station (for example, base station 4 in FIG. 12) exceeds the threshold (step S100), the base station 4 transmits the load information of the base station 4 to the RNC 200. (Step S101). The RNC 200 compares the load information of the base station 4 with a predetermined threshold (step S102). On the other hand, the base station 4 requests location information from the mobile station (for example, the mobile stations 100 to 102 in FIG. 12) in communication with the base station 4 (step S103). Each mobile station that has received the position information request from the base station 4 acquires the position information (step S104), and transmits the acquired position information to the base station 4 (step S105). The base station 4 that has acquired the position information from the mobile station transmits the position information of the mobile station to the RNC 200 (step S106). The RNC 200 that acquired the load information of the base station 4 and the position information of the mobile station that is communicating with the base station 4 receives the position of the base station 2 in the radio wave transmission / reception stop state St_2, and the acquired position information of each mobile station. Are compared (step S107). By comparing the position of the base station 2 and the position of the mobile station in communication with the base station 4, the RNC 200 can detect the second base station that can communicate with those mobile stations (ie, the radio wave transmission / reception stop state St_2 And a base station that should be shifted to the radio wave reception measurement state St_3 is selected (step S108).

  The RNC 200 issues an instruction to transition to the radio wave reception measurement state St_3 from the radio wave transmission / reception stop state St_2 to the selected base station 2 (step S109). The state transition control means (for example, the state transition control unit 358 and the power control unit 360 in FIG. 3) of the base station 2 that has received the instruction from the RNC 200 measures the state of the base station 2 from the radio transmission / reception stop state St_2. Transition to the state St_3.

  As described above, in the third embodiment, the load information of the first base station (for example, the base station 4 in FIG. 12) and the position information of the mobile station in communication with the first base station are obtained. By using, the transition from the radio wave transmission / reception stop state St_2 of the second base station to the radio wave reception measurement state St_3 is efficiently performed without waste. Because, when the distance between the second base station and the mobile station is long (for example, the positional relationship between the base station 2 and the mobile station 102 in FIG. 12), even if the base station 2 transitions to the radio wave reception measurement state St_3, this It is difficult to receive the transmission signal of the mobile station 102, and it is not possible to transition to the active state St_1 thereafter. However, when the distance between the second base station and the mobile station is short (for example, the positional relationship between the base station 2 and the mobile station 100 in FIG. 12), after the transition to the radio wave reception measurement state St_3, the base station 4 of the mobile station 100 The reception power at the base station 2 of the transmission signal to (other base stations) becomes equal to or greater than the threshold value, and it becomes easy to transition to the active state St_1.

  That is, in the case of the third embodiment, since the base station 2 transitions to the radio wave reception measurement state St_3 with high accuracy, power consumption in the base station is suppressed and radio wave interference between base stations is also avoided. .

  The acquisition and detection of the mobile station position information in the first base station position information acquisition unit 450 is, for example, GPS (Global Positioning System) information or AGPS (positioning based on GPS and base station information). Assisted GPS) information, AFLT (Advanced Forward Link Trilateration) information, and the like can be used.

  In the third embodiment described above, the second base station is the base station 2, but may be the base station 3 in the second embodiment.

Further, in the third embodiment described above, it has been described that the process of comparing the position of the base station 2 in the radio wave transmission / reception stop state St_2 and the position information of each mobile station is performed by the RNC 200. However, the comparison process can also be performed by the second base station. Specifically, the second base station (for example, base station 2) in the radio wave transmission / reception stop state St_2 has its cell range information (base station location information) stored in its own storage means (not shown). May be stored. Then, the second base station directly acquires the position information of the mobile station (for example, the mobile stations 100 to 102 in FIG. 12) in communication with the first base station (for example, the base station 4) directly from the base station 4. Alternatively, it is received via the RNC 200. Then, the second base station compares the range information read from the storage means with the received location information of the mobile station. As a result, the second base station can communicate with the mobile station by the second base station (that is, the base station that is currently in the radio wave transmission / reception stop state St_2 and should transition to the radio wave reception measurement state St_3). It can be judged by one's own power.
[Modification]
In the first to third embodiments described above, each of the insides of the first base station (for example, base station 1 and base station 4) and the second base station (for example, base station 2 and base station 3) The function distribution of the components is not necessarily limited to the above-described embodiment (see FIGS. 2, 3, 10, and 13). Thus, current components may be arbitrarily divided or integrated, or functions may be transferred between components. For example, in the base station 2 as the second base station shown in FIG. 3, the mobile station signal estimation unit 364 and the state transition control unit 358 can be integrated. That is, the integration unit includes a function of the mobile station signal estimation unit 364 (a function of detecting a transmission signal from a signal received from the RF unit 352 to other base stations in the surrounding mobile station) and a state transition control unit 358. (A function for controlling the state transition of the base station 2 based on predetermined information or instructions). That is, the base station including this integration unit exhibits the same performance as the base station 2 shown in FIG. As a repetitive explanation, the functional distribution of the components of each base station and their names in each of the above embodiments are merely examples, and can be arbitrarily changed without being bound by the above embodiments. is there.

  In the first to third embodiments described above, the description has been given using the pilot signal as the control signal. However, the signal is not limited to the pilot signal, and a signal for reporting cell-specific information or system-specific information is used. The form to be used may be used.

  Further, in the first to third embodiments described above, it has been described that the base station and the cell correspond one-to-one, but one base station may have a plurality of cells. In that case, the base station can perform state transition control for each cell.

  In the first to third embodiments described above, the first base station (for example, base station 1 and base station 4) and the second base station (for example, base station 2 and base station 3) are: He explained that each was equipped with a dedicated function and was a dedicated machine for each purpose. However, the functions of the first base station and the second base station are shared by installing a function that one base station has only the other base station. Therefore, by doing so, the second base station can serve as the first base station described above, and conversely, the first base station can serve as the second base station. is there.

  In the first to third embodiments described above, the RNC 200 is not necessarily an essential component. For example, each of the first base station and the second base station can include the RNC 200 function. In that case, the first base station and the second base station are directly connected via a predetermined communication network (for example, a wired communication network). In this case, for example, instead of reporting to the RNC 200 after the second base station is in the active state, the measurement cell set can be changed by notifying the first base station directly.

  Further, in the first to third embodiments described above, it has been described that each of the first base station and the second base station is controlled by dedicated hardware. However, the first base station and the second base station may be controlled and operated by a computer circuit (not shown) (for example, a CPU (Central Processing Unit)) based on a control program.

  In addition, the cell configurations of the first and second base stations of the wireless communication systems of the first to third embodiments described above can be a hierarchical cell (also referred to as overlapping cell) configuration. For example, the first base station is a macro cell, and the second base station is a small cell (eg, a micro cell, a micro cell, a nano cell, a femto cell, etc.) whose entire coverage area is included in the coverage area of the macro cell. You can also.

1-4, 20 Base station 11, 12 Base station cell 22 Communication means 24 Change means 100-102 Mobile station 200 RNC
358 State transition control unit 360 Power control unit 364 Mobile station signal estimation unit 369 Load management control unit 450 Location information acquisition unit 500 Call signal detection unit

Claims (25)

A communication means for communicating with the mobile station;
Changing means for changing the state of the base station according to a predetermined condition,
The change means includes an active state in which communication with the mobile station is possible, a radio wave transmission / reception stop state in which communication with the mobile station is not performed, and a transmission signal from the mobile station to another base station to receive the transmission signal. A base station that changes the state of a base station between radio wave reception measurement states to be measured. The changing means includes a condition recognition means for recognizing the predetermined condition, state transitioning the state of the base station in response to perceived predetermined condition from one state of said each state to the other state The base station according to claim 1, further comprising transition control means.   3. The base station according to claim 2, wherein the condition recognition means measures the received power of a transmission signal to another base station in the uplink band of the mobile station and compares the received power with a predetermined threshold value. .   When the base station is in a radio wave reception measurement state, when the condition recognition unit recognizes that the received power is equal to or greater than the predetermined threshold, the state transition control unit sets the state of the base station to a radio wave reception measurement state. The base station according to claim 3, wherein the base station is shifted to an active state.   The condition recognition means further recognizes a load of the base station, acquires load information of the other base station, and compares the load information with a predetermined threshold value. 4. The base station according to 4.   When the base station is in an active state, the condition recognizing means is configured such that the load on the base station is equal to or less than a certain amount, the received power is equal to or less than the predetermined threshold, and load information on the other base station 6. The base station according to claim 5, wherein the state transition control means transitions the state of the base station from an active state to a radio wave transmission / reception stop state when it is recognized that is below the predetermined threshold. When the base station is in an active state, when the condition recognition unit recognizes that a predetermined period has passed without a mobile station communicating with the base station, the state transition control unit The base station according to claim 5 or 6 , wherein the state of the station is changed from an active state to a radio wave transmission / reception stop state.   When the base station is in an active state, the condition recognizing means is configured such that the load on the base station is equal to or less than a certain amount, the received power is equal to or less than the predetermined threshold, and load information on the other base station The state transition control means transitions the state of the base station from the active state to the radio wave reception measurement state when it is recognized that is equal to or greater than the predetermined threshold value. The base station described in the section.   When the base station is in a radio wave transmission / reception stop state, when the condition recognition unit recognizes that the load information of the other base station is greater than or equal to the predetermined threshold, the state transition control unit The base station according to any one of claims 5 to 8, wherein the state is shifted from a radio wave transmission / reception stop state to a radio wave reception measurement state.   When the condition recognition unit recognizes that a predetermined period has elapsed after the base station has transitioned to the radio wave transmission / reception stop state, the state transition control unit measures the state of the base station from the radio wave transmission / reception stop state. The base station according to any one of claims 2 to 9, wherein transition is made to a state.   When a mobile station in communication with another base station is present at a position where it can communicate with a base station that is in a radio wave transmission / reception stop state, the state transition control means receives the radio wave from the radio wave transmission / reception stop state. The base station according to any one of claims 2 to 10, wherein a transition is made to a measurement state. When the base station is in a radio wave reception measurement state, when the condition recognition unit recognizes that the load information of the other base station is equal to or less than the predetermined threshold, the state transition control unit The base station according to any one of claims 5 to 9 , wherein the state is shifted from a radio wave reception measurement state to a radio wave transmission / reception stop state.   When the condition recognizing means recognizes that the predetermined period has passed without transitioning to the active state after the base station transitions to the radio wave reception measurement state, the state transition control means determines the state of the base station as a radio wave. The base station according to any one of claims 2 to 12, wherein a transition is made from a reception measurement state to a radio wave transmission / reception stop state.   The base station according to claim 2, wherein the condition recognition unit detects a call made to another base station of the mobile station.   When the base station is in a radio wave reception measurement state, when the condition recognition unit detects the call, the state transition control unit causes the state of the base station to transition from the radio wave reception measurement state to an active state. The base station according to claim 14. The mobile station that made the call has a predetermined correspondence with the predetermined base station,
When the condition recognition means recognizes that the mobile station that starts communication with the other base station and the base station having the correspondence with the mobile station exist, the base having the correspondence The base station according to claim 15, wherein the state transition control means of the station transitions the state of the base station from a radio wave reception measurement state to an active state.   The condition recognition means includes at least one of a period for performing a process of measuring received power of a transmission signal to another base station in an uplink band of the mobile station, a period of the period, and a predetermined threshold value to be compared with the received power. The base station according to claim 3, wherein the base station is changed. When the base station is in a radio wave reception measurement state, the condition recognizing means sets at least one of the period, a period of the period, and the predetermined threshold to be compared with the received power to a load of another base station. The base station according to claim 17, wherein the base station is changed according to information. The base station further comprises storage means for holding past received power measurement results,
The condition recognizing means changes at least one of the predetermined threshold to be compared with the period, the period of the period, and the received power in consideration of a past measurement result. 18. A base station according to 18. A first base station;
A second base station;
Comprising at least one mobile station capable of communicating with the first base station and the second base station;
The second base station determines whether the base station is in an active state capable of communicating with the mobile station, a radio wave transmission / reception stopped state in which communication with the mobile station is not performed, and another base station from the mobile station according to a predetermined condition. A radio communication system, wherein a transition is made between radio wave reception measurement states in which a transmission signal is received and a reception state of the transmission signal is measured.   When the load in the second base station in the active state is below a predetermined threshold and there is a mobile station in communication with the second base station, the second base station 21. The wireless communication system according to claim 20, wherein after the station is handed over to the first base station, the wireless communication system transits from an active state to a radio wave transmission / reception stop state or from an active state to a radio wave reception measurement state.   In response to a predetermined condition, the base station is in an active state in which communication with the mobile station can be performed, a radio wave transmission / reception stop state in which communication with the mobile station is not performed, and a transmission signal from the mobile station to another base station is received. A control method for a base station, wherein a transition is made between radio wave reception measurement states for measuring the reception status of the transmission signal. The base station recognizes the predetermined condition,
Control method for a base station of claim 22, wherein the transitioning the state of the base station in response to perceived predetermined condition from one state of said each state to the other state. A wireless communication method in a wireless communication system comprising a first base station, a second base station, and at least one mobile station capable of communicating with the first base station and the second base station,
The state of the second base station according to a predetermined condition is an active state in which communication with the mobile station is possible, a radio wave transmission / reception stop state in which communication with the mobile station is not performed, and a transmission signal from the mobile station to another base station And a transition between radio wave reception measurement states for measuring the reception status of the transmission signal.   In response to a predetermined condition, the base station is in an active state in which communication with the mobile station can be performed, a radio wave transmission / reception stop state in which communication with the mobile station is not performed, and a transmission signal from the mobile station to another base station is received. A computer program for causing a computer of a base station to execute a process of transitioning between radio wave reception measurement states for measuring a reception state of the transmission signal.

Images