JP2003037555A - Transmission power control method and mobile communication system in radio base station for mobile communication system and radio base station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission power control method and a system in a CS (radio base station) for a mobile communication system which can rationally save transmission power in a CS and reduce interference with other CSs without complicating the mobile communication system. SOLUTION: In the transmission power control method which controls transmission power in the radio base station for the mobile communication system by which radio communications is made between radio base stations in each region in plural service areas and mobile stations, the above problem is solved by information communication state of other radio base stations obtained from transmission signals received from other radio base stations and the transmission power control method of the radio base station for the mobile communication system which controls transmission power of the own station based on the relation of received power of the other radio base stations.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission power control method for a radio base station in a mobile communication system, and more specifically, in a mobile communication system, a radio base station transmits a transmission signal transmitted from another radio base station. The present invention relates to a transmission power control method and system for receiving traffic and monitoring traffic, and controlling the transmission power of its own radio base station in accordance with traffic fluctuations.

The present invention also relates to a radio base station for controlling transmission power according to such a transmission power control method.

[0003]

2. Description of the Related Art Recently, one of digital mobile communication systems has been developed.
As one of them, voice / non-voice service is actively provided by a simple mobile phone system (hereinafter, abbreviated as PHS) using a micro cell. This PHS is composed of a radio base station (hereinafter, abbreviated as CS) provided in the service area and a mobile station (hereinafter, abbreviated as PS) located in the service area, where PS is CS. It is possible to receive the provision of a predetermined service by wirelessly communicating with.

[0004] Conventionally, in CS used in PHS, some techniques for avoiding interference and some techniques for power saving have been proposed.

For example, as techniques for avoiding interference, Japanese Patent Laid-Open Nos. 8-19031 and 2000-17524.
2 and the like are proposed. These are techniques for installing a device as a control station, monitoring the radio field intensity or traffic of surrounding base stations, and increasing or decreasing the CS to be activated depending on the monitoring situation.

[0006] As a technique for saving power,
Japanese Unexamined Patent Publication No. 9-65427 has been proposed. These are techniques in which a device, which is a relay station, is installed and the transmission signals of neighboring CSs are relayed by the relay station, so that the CSs can monitor each other's signal strength and avoid interference.

[0007]

As described above, the techniques proposed in Japanese Patent Laid-Open Nos. 8-19031 and 2000-175242 require the design of base station groups in addition to the usual area design. Therefore, it lacks flexibility in area design. In addition, there is a problem that one base station is always in a standby state as a control station, or a control station has to be installed for each base station group, and the system becomes complicated.

Further, the technique proposed in Japanese Patent Application Laid-Open No. 9-65247 is incapable of being handled by a fixed relay station when the traffic changes drastically, such as when the traffic areas are different between night and day. There was a problem.

Therefore, a first object of the present invention is to more rationally save the transmission power of CS without complicating the mobile communication system and reduce the interference with neighboring CSs. It is possible to provide a transmission power control method and system for a wireless base station in a mobile communication system that can be used.

A second object of the present invention is to provide a radio base station (= CS) capable of controlling transmission power according to such a transmission power control method.

[0011]

In order to solve the above-mentioned first problem, the present invention, as set forth in claim 1, comprises a radio base station arranged in each of a plurality of service areas, and a mobile station. In a transmission power control method for controlling transmission power at a radio base station in a mobile communication system for performing radio communication with a station, the radio base station receives a transmission signal transmitted from another radio base station. , Configured to control the transmission power at its own station based on the relationship between the information related to the communication status at the other radio base station obtained from the received transmission signal and the reception power from the other radio base station To be done.

In such a transmission power control method for a wireless base station, the wireless base station monitors the communication status (= traffic status) of the surrounding wireless base stations and the received power from the surrounding wireless base stations. If the traffic of another radio base station that provides the required reception power in the local station is in a low traffic state, the transmission power of the local station is controlled to be weakened. That is, even if this wireless base station weakens the transmission power, if the received power from another wireless base station satisfies the required standard, the mobile station communicating with the local station can hand over to another wireless base station. Therefore, it will not be a call loss. Therefore, according to the transmission power control method of the radio base station of the present invention, each radio base station can control the transmission to be stopped or started according to the surrounding state, so that it is flexible to traffic fluctuations. It is possible to achieve power saving while responding. Further, according to the present invention, since it is not necessary to install a control station, a relay station, etc., which has been a problem in the past, the system is not complicated.

Further, according to the present invention, in the transmission power control method in the radio base station in the mobile communication system, the radio base station can be assigned in its own radio base station. When the number of wireless channels is greater than or equal to a predetermined number, the number of wireless channels that can be assigned by the other wireless base station is greater than or equal to the predetermined number from the information included in the transmission signal received from the other wireless base station. If it is determined that the number of assignable wireless channels in the other wireless base station is greater than or equal to a predetermined number, the received power from the other wireless base station is determined in advance. If the value is equal to or more than a predetermined value, the transmission power of the own wireless base station is controlled to be weakened.

From the viewpoint that call relief can be surely performed by giving a handover instruction to the mobile station,
The present invention provides the transmission power control method in a radio base station in the mobile communication system as set forth in claim 3, wherein the radio base station receives from another radio base station a value equal to or more than a predetermined value. When the power is obtained, an arbitrary wireless channel is determined based on the information related to the wireless channel that can be assigned by the other wireless base station included in the transmission signal received from the other wireless base station, and the determined wireless Instructing a mobile station that is in communication with its own radio base station to communicate with another radio base station using a channel, and the mobile station establishes communication with the other radio base station according to the instruction. later,
It is configured to control the transmission power of its own radio base station to be weakened.

From the viewpoint that the transmission power of the radio base station can be saved more, the present invention provides a transmission power control method in the radio base station in the mobile communication system as described in claim 4. In the above, the radio base station is configured to weaken the transmission power of the radio base station and control the radio base station to stop.

The present invention is described in claim 5, from the viewpoint that a radio base station in a sleep state can automatically shift to a normal operating state in response to traffic fluctuations of peripheral radio base stations. As described above, in the transmission power control method in the radio base station in the mobile communication system,
The radio base station, after controlling to reduce or weaken the transmission power of its own radio base station as described above,
When the information to reject the allocation of the wireless channel is obtained by the transmission signal from the other wireless base station, if the received power from the other wireless base station is equal to or more than the predetermined value, the other wireless base station uses it. The wireless channel other than the specified wireless channel is determined as the wireless channel to be used by the own wireless base station, and when there is a channel allocation request from a mobile station located in another wireless base station, it is determined. It is configured to select and allocate an arbitrary wireless channel from the wireless channels.

In such a power control method for a wireless base station, a wireless base station in a sleep state monitors a channel used by another wireless base station to obtain a required received power (eg, maximum received power). ) Is received from another radio base station, the mobile station automatically shifts to the operating state and rescues the mobile station that cannot be accommodated in the area. At this time, since a radio channel of a frequency other than the frequency used by the other radio base station is selected and assigned to the mobile station, it is possible to avoid interference with surrounding radio base stations when the normal operation is restored. it can.

According to a sixth aspect of the present invention, in the transmission power control method in the radio base station in the mobile communication system, the transmission signal transmitted from the other radio base station is controlled. It is configured to be at least one of a control signal transmitted by a channel or a communication signal transmitted by a communication channel.

From the viewpoint of being able to monitor the reception power from another radio base station, the present invention provides the transmission power control method in the radio base station in the mobile communication system, as described in claim 7. The radio base station is configured to receive a transmission signal transmitted from another radio base station and obtain reception power.

In order to solve the above first problem, the present invention provides, as described in claim 8, between a radio base station and a mobile station arranged in each of a plurality of service areas. In a mobile communication system in which transmission power is controlled by a wireless base station when performing wireless communication, the wireless base station is
Receives transmission signals transmitted from other wireless base stations,
A communication status information acquisition unit for acquiring information on a communication status at another wireless base station from the received transmission signal, and a reception power acquisition unit for acquiring reception power from another wireless base station, It is configured to have a transmission power control unit that controls the transmission power based on the relationship between the information about the communication status thus obtained and the reception power from another wireless base station.

Further, in order to solve the above-mentioned second problem, the present invention provides any one of a plurality of radio base stations arranged in a plurality of service areas in a mobile communication system as described in claim 15. Then, in the wireless base station that controls the transmission power when performing wireless communication with the mobile station,
Receives transmission signals transmitted from other wireless base stations,
A communication status information acquisition unit for acquiring information on a communication status at another wireless base station from the received transmission signal, and a reception power acquisition unit for acquiring reception power from another wireless base station, It is configured to have a transmission power control unit that controls the transmission power based on the relationship between the information related to the communication status thus obtained and the reception power from another wireless base station.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

A mobile communication system to which a transmission power control method in a radio base station according to an embodiment of the present invention is applied is
For example, it is a simple mobile phone system configured as shown in FIG.

In FIG. 1, this simplified portable telephone system (hereinafter abbreviated as PHS) has four transmission systems.
Channel-multiplexed multi-carrier TDMA (Time Division M
Ultimate Access) / TDD (Time Division Duplex) method is adopted. The TDMA / TDD system is a system in which a radio frequency is time-divided, a specific time zone (slot) is assigned to a caller, and communication is performed in the assigned slot. In this TDMA / TDD system, as shown in FIG. 2, 5 digital signals on one radio carrier are transmitted.
It is divided into frames every ms, and one frame is divided into 8
Divide into slots. The slots thus divided are 4 slots # 1T to # 4T in the downlink (CS → PS).
Are allocated, and 4 slots # 1R for uplink (PS → CS)
~ # 4R are assigned. In addition, of the 8 slots, one uplink and one downlink slot (# 1T, # 1R) are
It is assigned as a control channel for transmitting and receiving control signals, and the other six slots are assigned as communication channels for transmitting and receiving voice signals.

Returning to FIG. 1, the PHS according to the embodiment.
As shown in the figure, the configuration of the wireless base station (hereinafter abbreviated as CS) 11 ₁ arranged in the cell 13 ₁ and the mobile station 12 ₁ (hereinafter abbreviated as PS) located in the cell 13 ₁ are as shown in FIG. to) and, and a CS11 ₂ in a corresponding cell 13 _2, and PS12 ₂ residing in the cell 13 _2.

PS12 ₁ has a communication slot of radio frequency f1 (example) with CS11 _1, and PS12 _1
2 is able to perform voice communication and non-speech communications by performing wireless communication using a communication slot of the radio frequency f2 (Example) with the CS11 _2. Further, control for exchanging control signals for link establishment and position registration or call setup using the control channel (= control physical slot) of the control frequency f3 (example) between each PS and CS. Signals are exchanged.

The CS 11 ₁ has a reception function of receiving a transmission signal (eg, a control channel transmitted at the radio frequency f3) from another CS 11 ₂ . In the present embodiment, for the purpose of simplifying the description of the present invention, the following description will be given assuming that the reception function is included in _one of the CSs 11 ₁ .

The CS11 ₁ is receiving a transmission signal from another CS11 ₂ (= monitor) by, in addition to the allocation status of the self CS11 ₁ communication slot, assignment status of communication slots in the other CS11 _2, in other words, it is possible to know the traffic situation in other CS11 _2. Since the CS of the present invention is designed to stop or start the transmission of its own station (= CS11 ₁ ) according to the traffic situation of the surrounding CS obtained as described above, the control channel reception It is possible to realize reasonable power saving of transmission power while minimizing call loss due to failure.

[0029] The CS11 ₁ is configured as shown in FIG.

[0030] In FIG. 3, the CS11 ₁ includes a base station antenna 14, a mobile station antenna 15, a base station transceiver 16, a mobile station transceiver 17, a base station transceiver control unit 18, the mobile station transceiver The device control unit 19, the call processing control unit 20, the frequency channel control unit 21, and the base station power supply control unit 22. Incidentally, CS11 _1, the network 31: connected (eg switching device, etc.), performed call setup or the like between PS12 ₁ being in landline and cell 13 ₁ which is connected to the public network via the network 31 It also plays a role in establishing calls.

The base station transceiver 16 includes a base station antenna 1
4 has a function of demodulating a radio signal received from A4, and modulates and amplifies a digital signal of an information source,
Has a function of supplying to. Base station transceiver controller 18
Has a function of controlling the transmission timing and the reception timing of the base station transceiver 16. Frequency channel control unit 2
1 has a channel assignment function of a wireless channel.

Further, the CS11 ₁ of the present invention, PS and similar transceivers and (= mobile station transceiver 17), the mobile station transceiver controller 19 responsible for control of the transceiver provided,
The mobile station transceiver 17 can receive and monitor a transmission signal from another CS.

Next, referring to FIG. 4, the CS11 _{1 of} the present invention will be described.
The operation concept of is explained.

Referring to FIG. 4, the CS11 of the present invention.₁Against
And become another station CS11_Two() Indicates the physical slot for communication.
P in the area using the transmission slots T2 to T4
Signals are transmitted to S1 () to PS3 ().
On the other hand, each PS1 () to PS3 () is assigned respectively.
In the received slots (R2 to R4) that have been set, CS11
_Two() Receives signals transmitted from slots T2 to T4
Make a belief. Also, CS11 _Two() Is the physical slot for control
A packet (T1) to each PS1 () to PS3 ()
Believe that PS1 () to PS3 ()
By receiving the control physical slot, control information, such as
For example, system information, call information, channels
Obtain information such as rejection of allocation requests. Also, CS
11_TwoIs transmitted from each PS1 () to PS3 ()
Control for requesting location registration and channel allocation
For the physical slot (R1) for reception.

The CS11 ₁ () of the present invention is the CS1
Similar to 1 ₂ (), in addition to the function of operating as a normal base station, the mobile station transceiver 17 is used to receive (A) the control physical slot transmitted from CS 11 ₂ (). Thus, CS11 ₁ (), by receiving the control physical slot from the CS11 _2, the CS11 ₂
It is possible to obtain control information related to () (eg, information related to system, information related to calling, information such as refusal to a channel allocation request). That is, a feature of the present invention is that CS11 ₁ has a function of operating as PS.

For example, CS11 ₁ () is CS11 ₂
When the control information for denying the channel allocation for PS is obtained from the transmission signal transmitted from (), CS11 ₁
() Is able to know that the traffic situation in the area of the information from the CS11 2 ₍₎ is high. That is, for the PS CS11 2 ₍₎ makes a channel allocation request, that is sending a "Channel Assignment denied" means that there is no available radio channels can be allocated in the local station.
In other words, it can be seen from this that the traffic in CS11 ₂ () is congested and the wireless channel cannot be assigned.

[0037] Thus, CS11 ₁ of the present invention, other C
It is possible to know the status of the traffic of another station by obtaining information included in the transmission signal from S11 _2, will allow the transmission power control of its own station in consideration of the traffic conditions. For example, the following transmission power of the own station (CS11 ₁ ) can be controlled according to the traffic situation of the other station (CS11 ₂ ).

(Example) CS11₁Is the traffic condition of your own station
The state is low and the other station (CS
11_Two) Is in a low traffic state
And my station (CS11₁) Weakens the transmission power and stops
The transmission power is controlled so that it is in At this time,
CS11₁Is another station (CS11_Two) Received power from
Confirm that the required standards are met before controlling the transmission power
I will keep it in my station (CS11 ₁) Was communicating with
PS is the required received power (or required received field strength
Other stations (CS11)_Two) Is housed in. That
Therefore, my station (CS11₁), Other stations (CS11_Two) Both low
When in the traffic state, one of the base stations (in this example, C
S11₁) Makes it possible to stop transmission.
Therefore, according to the present invention, low traffic can be achieved without causing call loss.
It is possible to save the transmission power of the CS in the locked state. Well
In addition, CS in the sleep state (CS11₁) From the
Since the wave is not transmitted, the interference to the surrounding CS is low.
It is possible to reduce. Furthermore, CS is equivalent to PS
Hardware just to provide the functionality of
Therefore, it is not necessary to provide a control station or a relay station. That
Therefore, the system cost does not have to be complicated, so the device cost
It is possible to reduce the burden of.

Next, specific cases CS11 ₁ of the present invention is the transition from the normal state (state in which by usual radio base station operates) the sleep state (not out transmission wave from the radio base station) An example of such operation will be described with reference to FIG. Incidentally, since this, a transmission signal transmitted from CS11 _2: to (eg control signal), information relating to the number of radio channels unused be described as being included as control information. This unused radio channel is a CS
In, the wireless channels that can be assigned but are not assigned because there are no users are indicated.

[0040] (Embodiment 1) FIG. 5 is a flowchart showing the operation when the CS11 ₁ transitions from the normal state to the sleep state.

[0041] In FIG. 5, CS11 ₁ is own station (CS
In 11 ₁ ), the number of unused wireless channels that can be assigned to the PS is known, and the number of unused wireless channels is C which is a predetermined number of unused wireless channels.
First, it is determined whether the value is 1 or more (S1). This C
1 is a predetermined value, and if it is determined in the above determination (S1) that the number of free wireless channels is C1 or more, C
It can be seen that the number of users using S11 ₁ is sufficiently small and the traffic within the service area of CS 11 ₁ is small.

When it is determined in the above determination (S1) that the number of unused wireless channels grasped by CS11 ₁ is C1 or more (YES in S1), the process proceeds to the next step (S2) to move. station number of unused radio channels other CS11 ₂ included in the information of the control signal received by the transceiver 17 to determine (S1) determines if an unused radio channel number C2 than the predetermined. By performing this determination (S2), if the number of free wireless channels in the other CS11 ₂ is C2 or more, it is possible to sufficiently accommodate the PS user even if the PS under the control of CS11 ₁ is handed over to another CS11 _2. .

In the above determination (S2), the mobile station transceiver 17
When it is determined that the number of unused wireless channels of the other CS11 ₂ received in step S1 is equal to or greater than the predetermined number C2 of unused wireless channels (YES in S2), the CS11 ₁ moves to the next step (S3). and, determine whether the power of the transmission signal from the other CS11 ₂ received at the mobile station transceiver 17 is P1 or more predetermined (S3) is performed. The (S3) determined by performing, if the power of the transmitted signal from another CS11 ₂ is CS11 ₁ reception power P1 or received by, PS12 ₁ which are in the cell 13 _1, the other CS1
It can be seen that the reception of the transmission signal from the 1 ₂ are possible.

In the above judgment (S3), the mobile station transceiver 17
In the case where the power of the transmission signal from the other CS11 ₂ received is determined to be the received power P1 more (YES in S3),
The process proceeds to the next step (S4), the transmission power from the base station transceiver 16 is gradually weakened and stopped (base station transceiver 16
The transmission power control is performed stepwise or continuously so as to turn off the power supplied to the device) and the sleep state is entered. In this case, the base station transceiver 16 follows the power OFF instruction from the base station power controller 22.

On the other hand, if it is determined in (S1) that the number of unused wireless channels managed by CS11 ₁ is smaller than C1 (NO in S1), or (S2).
Then, when it is determined that the number of unused wireless channels of the other CS11 ₂ received by the mobile station transceiver 17 is smaller than the number of unused wireless channels C2 (NO in S2), or in the above (S3), the mobile station transmission / reception is performed. Others received by machine 17 CS11
_When it is determined that the transmission signal power from ₂ is smaller than the reception power P1 (NO in S3), the CS11 ₁ continues the normal base station operation (S5).

As described above, in the first embodiment, C
In S11 ₁ , the number of unused wireless channels in the other CS 11 ₂ is determined in advance by monitoring the signal output by the other CS 11 ₂ using the mobile station transceiver 17 installed in the own station (CS11 ₁ ). Whether there are more than the specified number, other CS1
1 received power from ₂ can perform determination of whether at least the required value.

In CS11 ₁ , the number of channels used by its own station (CS11 ₁ ) is reduced (= the number of unused wireless channels is equal to or more than a predetermined number), and the number of channels used by other CS11 ₂ is reduced. (A state in which the number of unused wireless channels is equal to or more than a predetermined number), and its own station (CS1
The transmission power of 1 ₁ ) is gradually weakened and stopped (the stopped state is called a sleep state). At this time, CS11
_{Since 1} confirms that the received power from the other station (CS11 ₂ ) satisfies the required standard before controlling the transmission power, the PS communicating with the own station (CS11 ₁ ) is
In its own station (CS11 ₁ ), it is accommodated in another station (CS11 ₂ ) that gives a required reception level. As a result, according to the first embodiment, power saving of the transmission power of the CS in the low traffic state can be realized without causing a call loss. Further, since the transmission wave from the CS in the sleep state is not transmitted, it is possible to reduce the interference given to the peripheral CS.

In the first embodiment described above, one mode in which the transmission power of the CS under the condition of low traffic is controlled so that the transmission power of the CS is gradually weakened and stopped is described. The PS with which the incoming CS is communicating
Can be handed over to another CS in a low traffic state. next,
An embodiment in such a case will be described with reference to FIG.

[0049] (Embodiment 2) FIG. 6 is a flowchart showing the operation when the CS11 ₁ in a low traffic state transitions from the normal state to the sleep state.

In FIG. 6, the processing from (S11) to (S13) is performed as described in the first embodiment. Above (S11) ~ (YES in S13) positive determination when the result is obtained (YES in S11) and (YES at S12) and the determination of the (S13), CS11 ₁ is proceeds to the next step (S14) and, the information contained in the transmission signal transmitted from the other CS11 _2: other C from (eg control information)
S11 obtains information about ₂ unused radio channel,
An unused wireless channel based on the information is selected (S14). Here, it is assumed that Ch1 is determined.

The unused radio channel Ch as described above
When 1 is determined, the CS 11 ₁ sends the determined wireless channel Ch to the PS 12 ₁ currently communicating in the area.
Instruct PS12 ₁ to perform handover to ₁ (S15)
To do. The determination of the Ch1, the other CS which has been found by the transmission signal of the base station 11 ₂ received by the mobile station transceiver 17
11 ₂ available, and the user shall be determined from among the radio channels are unused to not.

PS12 ₁ sends to CS11 ₂ a request for handover to the channel (= Ch1) instructed by CS11 ₁ . CS11 ₂ (if this, Ch1 request allocation of) the channel assignment request from PS12 ₁ to establish a link based on the, to initiate communication by performing a predetermined call setup.

In CS11 ₁ , PS12 ₁ is other CS11 ₂
To confirm whether the handover is normally performed (S16),
When it is confirmed in this confirmation (S16) that the PS12 ₁ has normally handed over to another CS11 ₂ (YES in S16), the process proceeds to the next step (S18) to gradually increase the transmission power from the base station transceiver 16. Then, the transmission power control is performed stepwise or continuously so as to weaken and stop (turn off the power supply to the base station transceiver 16) to enter the sleep state. In this case, the base station transceiver 16 follows the power OFF instruction from the base station power control unit 22 as in the first embodiment.

On the other hand, if it is determined in (S11) that the number of unused wireless channels managed by CS11 ₁ is smaller than C1 (NO in S11), or (S1)
When it is determined in 2) that the number of unused wireless channels of the other CS 11 ₂ received by the mobile station transceiver 17 is smaller than the number of unused wireless channels C2 (NO in S12), or the above (S13) Others received by station transceiver 17 C
S11 when the transmission signal power from the ₂ is determined to be smaller than P1 (NO in S13), or in (16),
When it cannot be confirmed that PS12 ₁ has handed over to another CS11 ₂ (including handover failure) (S1
(NO in 6), the CS 11 ₁ continues the normal base station operation (S17).

[0055] As described above, according to the second embodiment, CS11 ₁ recognizes an unused radio channel in another CS11 ₂ based on the signal that is out of the other CS11 _2, unused and recognition An arbitrary wireless channel is determined from the wireless channels and notified to the handover target PS. That is, the CS 11 ₁ instructs the PS to be handed over to which radio channel of the other station (CS 11 ₂ ) to perform handover before putting its own station into the sleep state. You can go to sleep with.

In the above-described first and second embodiments, the operation example when the CS shifts from the normal state to the sleep state has been described. The operation when shifting to the normal state will be described with reference to FIG.

[0057] Figure 7 is a flowchart showing the operation when the CS11 ₁ shifts from the sleep state to the normal state.

(Third Embodiment) In FIG. 7, CS11
_1, CS11 ₂ information of the transmission signal being sent from: receives (eg control information), whether or not the determination (S21) information representative of the radio channel assignment refusal from the information being delivered. In this determination, (YES at S21) if the information representative of the radio channel assignment reject from CS11 ₂ is determined to be delivered, the other moves to the next step (S22), and received by the mobile station transceiver 17 CS11 _It is determined whether or not the power of the transmission signal from ₂ is equal to or higher than the predetermined reception power P2 (S22). This (S22)
When the mobile station transceiver 17 of CS11 ₁ receives the power of the transmission signal from another CS11 _{2 according} to the determination of P2,
If there is the above received power, the PS 12 in the cell 13 _2
2 can receive the transmitted signal from CS11 ₁ .

In the above determination (S22), the mobile station transceiver 1
Others received in 7 CS11_TwoThe power of the transmission signal from P2
If it is determined that the above is the case (YES in S22), CS
11 ₁Other CS11_TwoRadio channel used in
Other than the wireless channel other than CS11₁To use
Determine the wireless channel (Ch2-Chn in this case) (S
23) and then the power supplied to the base station transceiver 16 is
The source is turned on (S24). In this case, base station transmission / reception
The machine 16 follows the power ON instruction from the base station power control unit 22.
U

When the power supplied to the base station transceiver 16 of the CS 11 ₁ is turned on as described above, the CS 11 ₁
11 ₁ determines whether or not there is a wireless channel allocation request from PS 12 ₁ that has been handed over to CS 11 ₂ in Embodiment 2 above (S25). In this determination (S25),
When it is determined that there is a wireless channel allocation request from PS12 ₁ (YES in S25), CS11 ₁ selects PS1 as an arbitrary wireless channel from Ch2 to Chn.
It is determined as a wireless channel to be assigned to 2 ₁ (S26),
The determined wireless channel is used to establish a communication path with the PS 12 ₁ and start predetermined communication. But,
In the above determination (S25), if there is no wireless channel allocation request from PS12 ₁ (NO in S25), CS11
₁ enters a standby state (S28) and waits for a wireless channel allocation request from PS12 ₁ .

[0061] Further, in the above (S21), if not received a radio channel assignment refusal from CS11 ₂ (S2
NO 1), or in the above (S22), if the power of the transmission signal from the other CS11 ₂ received at the mobile station transceiver 17 is determined to be smaller than P2 (NO at S22), the
CS11 ₁ maintains the sleep state (S27).

As described above, in the third embodiment, C
S11 ₁ monitors whether the other CS11 ₂ has issued a radio channel assignment reject, if other CS11 ₂ is known that has issued a radio channel assignment reject, the CS1
It can be seen traffic in the 1 ₂ area is high traffic.

The CS11 ₁ is the other CS1 as described above.
1 the _second traffic it can be seen in a high traffic state, the state of the own station (CS11 ₁₎ is returned from the sleep state to the normal state, the other station is a high traffic (CS
11 ₂ ) covers PS that cannot be accommodated. When CS11 ₁ covers PS, other CS11
_Since the radio channel other than the frequency used in _{No. 2} is used by the own station (CS11 ₁ ), it is possible to avoid interference with other CSs.

[0064] In the above example, the reception processing function communication status information acquisition means CS11 ₁ mobile station transceiver 17, RF receiving function aircraft 17 corresponds to the reception power acquisition unit, the base station transceiver control unit 18 The base station transmission / reception power control function corresponds to the transmission power control means. In addition, the frequency channel management function of the frequency channel control unit 21 functions as the first unused wireless channel number monitoring means and the second unused wireless channel number monitoring means, and the channel selection function of the same unit 21 functions as the wireless channel determination means and self It corresponds to station radio channel determination means and radio channel allocation means. Further, the base station transceiver control unit 1
The received power determination function of 8 corresponds to the received power determination means, the channel notification function of the same section 18 corresponds to the handover instructing means, and the transceiver power supply control function of the base station power supply control section 22 corresponds to the transceiver power OFF means. .

[0065]

As described above, according to the first aspect of the present invention.
According to the present invention described in No. 4, since the radio base station monitors the transmission signal transmitted from the other radio base station, it is possible to know the traffic status and the received power of the other radio base station. Therefore, the wireless base station can stop the transmission of the own station or start the transmission in consideration of the traffic situation and the received power of other wireless base stations, so that it is possible to realize a reasonable power saving. . As a result, it is possible to reduce the number of base stations operating at low traffic and reduce interference with surrounding wireless base stations.

Further, according to the invention of the fifteenth to twenty-first aspects, it is possible to realize a radio base station capable of performing the transmission power control as described above.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a simplified mobile phone system to which a transmission power control method for a wireless base station according to an embodiment of the present invention is applied.

FIG. 2 is a diagram showing a mechanism of operation of a TDMA / TDD system.

FIG. 3 is a block diagram showing a configuration example of a radio base station according to the present invention.

FIG. 4 is a diagram showing an operation concept of the radio base station of the present invention.

FIG. 5 is a flowchart showing an operation in which the wireless base station of the present invention shifts from a normal state to a sleep state (when there is no handover instruction to a mobile station).

FIG. 6 is a flowchart showing the operation of the radio base station of the present invention for shifting from a normal state to a sleep state (when a handover instruction to a mobile station is issued).

FIG. 7 is a flowchart showing an operation in which the wireless base station of the present invention shifts from a sleep state to a normal state.

[Explanation of symbols]

11 _{1 to} 11 ₂ Radio Base Station (CS) 12 _{1 to} 12 ₂ Mobile Station (PS) 13 _{1 to} 13 ₂ Cell 14 Base Station Antenna 15 Mobile Station Antenna 16 Base Station Transceiver 17 Mobile Station Transceiver 18 Base Station Transceiver Control unit 19 Mobile station transceiver control unit 20 Call processing control unit 21 Frequency channel control unit 22 Base station power supply control unit 31 Network

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Osamu Nakamura             2-11-1, Nagatacho, Chiyoda-ku, Tokyo Stock             Ceremony company NTT Docomo F term (reference) 5K060 BB05 BB07 CC04 CC12 DD04                       EE05 FF06 LL01 LL25                 5K067 AA03 AA43 BB04 CC04 EE02                       EE10 GG08 GG09 HH22 JJ02                       JJ13

Claims (21)

[Claims] 1. A transmission power control method for controlling transmission power in a radio base station in a mobile communication system for performing radio communication between a radio base station arranged in each of a plurality of service areas and a mobile station. , The radio base station receives a transmission signal transmitted from another radio base station, information related to the communication status at the other radio base station obtained from the received transmission signal, and the other radio base station A transmission power control method in a radio base station in a mobile communication system for controlling transmission power in the local station based on a relationship with received power from the mobile station. 2. The transmission power control method in a radio base station in a mobile communication system according to claim 1, wherein the radio base station has the number of radio channels that can be allocated in its own radio base station is a predetermined number or more. In some cases, it is determined from the information included in the transmission signal received from another wireless base station whether the number of assignable wireless channels in the other wireless base station is equal to or more than a predetermined number, and the determination is made. If the received power from the other wireless base station is equal to or more than a predetermined value when it is determined that the number of assignable wireless channels in the other wireless base station is equal to or more than a predetermined number, A transmission power control method in a radio base station in a mobile communication system for controlling so that the transmission power of a station is weakened. 3. The transmission power control method in a radio base station in a mobile communication system according to claim 2, wherein the radio base station receives from another radio base station a reception power equal to or higher than a predetermined value. In addition, an arbitrary wireless channel is determined based on the information related to the wireless channel that can be assigned by the other wireless base station, which is included in the transmission signal received from the other wireless base station, and the other wireless channel is determined using the determined wireless channel. The mobile station that is in communication with its own radio base station to communicate with the other radio base station, and after the mobile station establishes communication with the other radio base station according to the instruction, A transmission power control method in a radio base station in a mobile communication system for controlling so that the transmission power of a station is weakened. 4. A transmission power control method in a radio base station in a mobile communication system according to claim 2, wherein the radio base station controls to weaken the transmission power of its own radio base station and stop the mobile communication. A transmission power control method in a radio base station in a system. 5. The transmission power control method for a radio base station in a mobile communication system according to claim 2, wherein the radio base station controls the transmission power of its own radio base station as described above. After controlling to stop weakly or weakly,
When the information to reject the allocation of the wireless channel is obtained by the transmission signal from the other wireless base station, if the received power from the other wireless base station is equal to or more than the predetermined value, the other wireless base station uses it. Radio channels other than the specified radio channel are determined as the radio channels that should be used by the own radio base station, and when there is a channel allocation request from a mobile station located in another radio base station, the decision is made. A transmission power control method in a radio base station in a mobile communication system for selecting and allocating an arbitrary radio channel from radio channels. 6. A transmission power control method in a radio base station in a mobile communication system according to claim 1, wherein a transmission signal transmitted from the other radio base station is transmitted by a control channel. And a transmission power control method in a radio base station in a mobile communication system, which is at least one of a control signal or a communication signal transmitted by a communication channel. 7. The transmission power control method for a radio base station in a mobile communication system according to claim 1, wherein the radio base station receives a transmission signal transmitted from another radio base station. A transmission power control method in a radio base station in a mobile communication system for receiving and obtaining reception power. 8. A mobile communication system in which transmission power is controlled by a wireless base station when wireless communication is performed between a wireless base station and a mobile station arranged in each of a plurality of service areas. The station receives a transmission signal transmitted from another wireless base station, and obtains information on the communication state of the other wireless base station from the received transmission signal, and a communication status information acquiring unit, and another wireless base station. A reception power acquisition unit for acquiring reception power from the station, and controls the transmission power based on the relationship between the information related to the communication status obtained as described above and the reception power from another radio base station. A mobile communication system having a transmission power control means. 9. The mobile communication system according to claim 8, wherein the radio base station determines whether or not the number of radio channels that can be assigned by the radio base station is equal to or more than a predetermined number. The number of used wireless channels monitoring means and the information contained in the transmission signal received from the other wireless base station determine whether or not the number of assignable wireless channels in the other wireless base station is greater than or equal to a predetermined number. When the second unused radio channel number monitoring means and the determination result in that the number of assignable radio channels in the other radio base station is equal to or more than a predetermined number, the other radio base station determines Reception power determining means for determining whether or not the reception power of is greater than or equal to a predetermined value, and the reception power determining means determines that the reception power from another wireless base station is greater than or equal to a predetermined value. To myself Mobile communication system and a transmission power control means for controlling so as to weaken the transmission power of the line base station. 10. The mobile communication system according to claim 9, wherein the radio base station receives from another radio base station when receiving radio power more than a predetermined value from the other radio base station. Using a radio channel determining means for determining an arbitrary radio channel based on information about a radio channel that can be assigned by the other radio base station included in the transmission signal, and a radio channel determined by the radio channel determining means Handover instruction means for instructing a mobile station that is in communication with its own radio base station to communicate with another radio base station, and the mobile station establishes communication with the other radio base station according to the instruction. A mobile communication system having a transmission power control means for controlling the transmission power of its own radio base station to be weakened later. 11. The mobile communication system according to claim 9 or 10, wherein said radio base station has a transceiver power supply OFF means for controlling so as to weaken and stop transmission power of its own radio base station. 12. The mobile communication system according to claim 9, wherein the radio base station is controlled to weaken or weaken the transmission power of its own radio base station as described above to stop the transmission power. ,
When the information to reject the allocation of the wireless channel is obtained by the transmission signal from the other wireless base station, if the received power from the other wireless base station is equal to or more than the predetermined value, the other wireless base station uses it. There is a channel allocation request from the local station's wireless channel determining means that determines a wireless channel other than the existing wireless channel as the wireless channel to be used by the own wireless base station, and the mobile station located in another wireless base station. At this time, a mobile communication system having a radio channel assigning means for selecting and assigning an arbitrary radio channel from among the radio channels determined by the own station radio channel determining means. 13. The mobile communication system according to claim 8, wherein the transmission signal transmitted from the other radio base station is transmitted by a control signal transmitted by a control channel or a communication channel. A mobile communication system which is at least one of communication signals. 14. The mobile communication system according to claim 8, wherein the radio base station receives a transmission signal transmitted from another radio base station and obtains reception power. Mobile communication system having means. 15. A wireless base station, which is any of a plurality of wireless base stations arranged in a plurality of service areas in a mobile communication system, and which controls transmission power when performing wireless communication with a mobile station. , A communication status information acquisition unit that receives a transmission signal transmitted from another wireless base station and obtains information related to the communication status at the other wireless base station from the received transmission signal, and from another wireless base station And a reception power acquisition unit that acquires the reception power of the transmission power, and controls the transmission power based on the relationship between the information related to the communication status obtained as described above and the reception power from another radio base station. A radio base station having a control means. 16. The wireless base station according to claim 15, wherein the first unused wireless channel number monitoring means determines whether or not the number of assignable wireless channels in the own wireless base station is equal to or more than a predetermined number. And a second unused radio for judging from the information contained in the transmission signal received from the other radio base station whether or not the number of assignable radio channels in the other radio base station is a predetermined number or more. When the number of channels monitoring means determines that the number of wireless channels that can be assigned by the other wireless base station is equal to or greater than a predetermined number, the reception power from the other wireless base station is determined in advance. Reception power determining means for determining whether or not the reception power from another radio base station is greater than or equal to a predetermined value. Transmit power of The radio base station and a transmission power control means for controlling so as to weaken. 17. The radio base station according to claim 16, wherein when the radio base station receives a reception power of a predetermined value or more from another radio base station, the radio base station includes the transmission signal received from the other radio base station. Radio channel determining means for deciding an arbitrary radio channel based on information on radio channels assignable by another radio base station, and another radio base station using the radio channel decided by the radio channel deciding means Handover instruction means for instructing a mobile station that is in communication with its own radio base station to perform communication, and its own radio base station after the mobile station establishes communication with the other radio base station according to the instruction. And a transmission power control means for controlling so that the transmission power of the radio base station is weakened. 18. The radio base station according to claim 16 or 17, further comprising a transceiver power supply OFF means for controlling so as to weaken the transmission power of the radio base station and stop the radio base station. 19. The radio base station according to any one of claims 16 to 18, wherein after the transmission power of its own radio base station is controlled to be weakened or weakened to stop as described above, another radio base station. If the received signal from another wireless base station is equal to or more than a predetermined value when the information to reject the wireless channel allocation is obtained from the transmission signal from the wireless channel other than the wireless channel used by the other wireless base station. Radio channel determining means for deciding the radio channel of this station as the radio channel to be used by the own radio base station, and when there is a channel allocation request from a mobile station located in another radio base station, the own station A radio base station having radio channel assigning means for selecting and assigning an arbitrary radio channel from the radio channels determined by the radio channel determining means. 20. The radio base station according to claim 15, wherein the transmission signal transmitted from the other radio base station is transmitted by a control signal transmitted by a control channel or a communication channel. A radio base station serving as at least one of communication signals. 21. The radio base station according to claim 15, further comprising a reception power acquisition unit that receives a transmission signal transmitted from another radio base station and obtains reception power. .