JP5640386B2 - Base station equipment - Google Patents

Description

  The present invention relates to a base station apparatus that performs wireless communication with a terminal apparatus.

  2. Description of the Related Art Conventionally, some wireless communication systems include a base station device and a movable terminal device that is wirelessly connected to the base station device. The base station device forms a communication area (cell) that can communicate with the terminal device. A terminal device located in a cell can perform wireless communication with a base station device that forms the cell (see, for example, Patent Document 1).

JP 2009-177532 A

In the above wireless communication system, when communication areas (cells) set by a plurality of base station devices overlap, a signal transmitted from a base station device is in a cell of another nearby base station device It may reach the terminal device and become an interference signal for the terminal device.
Furthermore, in the wireless communication system, as a base station device, for example, a macro base station device that forms a cell (macro cell) having a size of several kilometers, and a relatively small cell (about several tens of meters) installed in the macro cell ( Some have a femto base station apparatus that forms a femto cell) in the macro cell. In such a wireless communication system, it can be said that the femtocell formed by the femto base station apparatus is an environment in which interference is likely to occur because almost the entire area overlaps with the macrocell.

As a method for suppressing such interference, measures such as giving directivity to the signal by beam forming or adjusting transmission power so as not to give interference can be considered.
Of these, the method of adjusting the transmission power is effective in suppressing interference, but if the interference is not properly grasped, the transmission power is unnecessarily adjusted, There is a possibility that the inconvenience of lowering the communication quality in the wireless communication performed by itself may occur.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a base station apparatus that can effectively suppress interference by appropriately grasping the possibility of occurrence of interference. .

(1) The present invention is a base station device that is wirelessly connected to a terminal device, the acquisition unit acquiring downlink signal reception quality information related to the reception quality of the downlink signal received by the terminal device, and the acquisition unit And a control unit that controls transmission power of its own downlink signal based on the downlink signal reception quality information.

In the base station apparatus configured as described above, the radio resource allocated to the terminal apparatus connected to itself and the radio resource allocated to the other terminal apparatus overlap, so that When receiving the interference due to the downlink signal from the base station apparatus, the reception quality of the downlink signal indicated by the downlink signal reception quality information acquired by the acquisition unit decreases, and the own downlink signal is transmitted to other terminal apparatuses. There is a possibility of interference. That is, based on the reception quality, it can be determined whether or not the own downlink signal may cause interference to other terminal devices.
According to the base station apparatus of the present invention, since the control unit controls the transmission power of its own downlink signal based on the downlink signal reception quality information, for example, the reception quality of the downlink signal indicated by the downlink signal reception quality information From this, if it can be determined that there is a possibility that its own downlink signal may interfere with other terminal devices because its own terminal device has received interference due to downlink signals from other base station devices, By adjusting the transmission power of its own downlink signal, it is possible to suppress interference with other terminal devices connected to other base station devices. That is, the control unit can perform interference control for suppressing interference with other terminal apparatuses by performing power control on the own downlink signal based on the reception quality of the own downlink signal.
Thus, according to the base station apparatus of the present invention, interference can be effectively suppressed by appropriately grasping the possibility of occurrence of interference.

(2) More specifically, the control unit estimates the interfered power in the received downlink signal based on the downlink signal reception quality information, and determines the own downlink signal based on the estimated interfered power. Transmission power can be controlled.
In this case, if the estimated interfered power is relatively large, it can be determined that the terminal device of itself is receiving interference of downlink signals from other base station devices. Therefore, by adjusting the transmission power of the own downlink signal according to the interfered power, it is possible to suppress interference with the other terminal device.

(3) That is, when the own terminal device receives interference of a downlink signal from another base station device, the radio resource assigned to the other terminal device and the own terminal device are assigned. Since the radio resource overlaps, if the transmission power of the own downlink signal is increased, there is a possibility that the own downlink signal may cause interference to other terminal apparatuses connected to other base station apparatuses.
On the other hand, in the base station apparatus, when the interfered power is equal to or greater than a predetermined threshold, the control unit sets and controls a predetermined upper limit for the transmission power of the own downlink signal. Can be.
In this case, by setting the threshold to a value that can determine whether or not the interfered power is due to interference of a downlink signal of another base station apparatus, It is possible to determine whether or not there is downlink signal interference from the base station apparatus. Furthermore, when the interfered power is equal to or greater than the threshold, it can be determined that the terminal device of the own device is receiving interference from the downlink signal from another base station device. By setting the upper limit value so as to determine the range of power that can suppress interference, the transmission power can be controlled within the range of power that does not interfere with other terminal devices, thereby effectively preventing interference. Can be suppressed.

(4) When the interfered power is smaller than the threshold, it can be determined that the terminal device of the terminal device has not received interference from the downlink signal from another base station device. In this case, the control unit The transmission power of the own downlink signal may be controlled without setting the upper limit value.

(5) In the case where it is determined that the own terminal device is receiving downlink signal interference from another base station device based on the interfered power, if the interfered power is relatively large, for example, another terminal Since the device is located in the vicinity of itself, etc., it is highly probable to cause interference on both sides, and it can be determined that the possibility that the own downlink signal will cause interference to other terminal devices is also high. The upper limit value is preferably obtained based on the interfered power.

(6) In the base station apparatus, the control unit obtains a lower limit value required to secure communication with the terminal apparatus connected to the terminal, with respect to transmission power of the own downlink signal, and the lower limit value Is determined to be smaller than the upper limit, the transmission power of the own downlink signal is preferably controlled within the range from the upper limit to the lower limit.
In this case, based on the obtained upper limit value and lower limit value, the range of power that can ensure communication with the own terminal device while suppressing the transmission power of the own downlink signal from interfering with other terminal devices. Can be controlled.

(7) Further, in the base station apparatus, the control unit obtains a lower limit value required for ensuring communication with the terminal apparatus connected to the control unit for the transmission power of the downlink signal, When it is determined that the lower limit value is equal to or higher than the upper limit value, the transmission power of the own downlink signal is controlled so that communication with the own terminal device can be secured while suppressing interference with other terminal devices. Therefore, it is preferable that another radio resource different from the radio resource allocated to the terminal device is allocated to the terminal device.
As a result, it is possible to allocate radio resources that are not allocated to other terminal apparatuses to the terminal apparatus, and to ensure communication with the terminal apparatus without causing interference to the other terminal apparatuses. .

(8) The control unit may obtain the lower limit value based on a path loss value between itself and the terminal device of itself and / or the interfered power.
In this case, it is possible to suitably obtain the lower limit value that is the minimum transmission power necessary to ensure communication with the terminal device connected to itself.

(9) The information on the reception quality is transmitted from the own terminal apparatus when CINR when the downlink signal received by the own terminal apparatus is received or when predetermined data is transmitted to the own terminal apparatus. It is preferable that at least one of the ratios of the confirmation response and the negative response is included. In this case, it is possible to accurately grasp the reception quality of the downlink signal in its own terminal device.

(10) Further, the present invention provides a base station device that is wirelessly connected to a terminal device, wherein the acquisition unit acquires downlink signal reception quality information related to reception quality of a downlink signal received by the terminal device, and the acquisition unit includes: Based on the acquired downlink signal reception quality information, a determination unit that determines whether there is a possibility that the own downlink signal may interfere with another terminal device connected to another base station device, It is characterized by having.
According to the base station apparatus having the above configuration, it is possible to effectively suppress interference by appropriately determining the possibility of occurrence of interference by the determination unit.

(11) Further, the present invention is a base station apparatus that is wirelessly connected to a terminal device, an acquisition unit that acquires uplink signal reception quality information related to reception quality of an uplink signal from the terminal device, and the acquisition unit acquires And a control unit that controls the transmission power of the uplink signal of the terminal device connected to itself based on the uplink signal reception quality information.

According to the base station apparatus having the above configuration, the control unit controls the transmission power of the uplink signal of its own terminal device based on the uplink signal reception quality information. For example, the uplink signal reception quality information acquired by the acquisition unit Based on the reception quality of the uplink signal indicated by, it is possible to determine that the uplink signal from the other terminal apparatus has received interference, so that the uplink signal of its own terminal apparatus can interfere with the other base station apparatus When it can be determined that there is a possibility, it is possible to adjust the transmission power of the uplink signal of its own terminal device to suppress interference with the other base station device. That is, the control unit can perform interference control for suppressing interference with another base station device by performing power control on the uplink signal of its own terminal device based on the reception quality of the uplink signal.
Thus, according to the base station apparatus of the present invention, interference can be effectively suppressed by appropriately grasping the possibility of occurrence of interference.

(12) The control unit estimates interference power in the uplink signal based on the uplink signal reception quality information, and determines transmission power of the uplink signal of the terminal device based on the estimated interference power. Can be controlled.
In this case, if the estimated interfered power is relatively large, it can be determined that the device itself is receiving interference from an uplink signal from another terminal device. Therefore, by adjusting the transmission power of the uplink signal of its own terminal device according to this interfered power, it is possible to suppress interference with the other base station device.

(13) In the base station apparatus, when the interfered power is greater than or equal to a predetermined threshold, the control unit sets and controls a predetermined upper limit value for the transmission power of the uplink signal of the terminal apparatus of its own You may do.
In this case, by setting the threshold value to a value that can determine whether or not the interfered power is due to the interference of the uplink signal of another terminal device, the control unit can detect itself from the other terminal device. It is possible to determine whether or not there is interference from the upstream signal. Furthermore, if the interfered power is equal to or greater than the threshold, it can be determined that the device is receiving interference from an uplink signal from another terminal device. In this case, interference with other base station devices is suppressed. By setting an upper limit value so as to define a range of possible power, transmission power can be controlled within a range of power that does not interfere with other base station apparatuses, thereby effectively suppressing interference. be able to.

(14) If the interference power is smaller than the threshold value, it can be determined that the mobile station is not receiving interference from an upstream signal from another terminal device. You may control without setting the said upper limit about the transmission power of a signal.

(15) In the case where it is determined based on the interfered power that the self is receiving interference of an uplink signal from another terminal device, if the interfered power is relatively large, there is a possibility that both may cause interference. It is preferable that the control unit obtains the upper limit value based on the interfered power because it can be determined that the uplink signal of the terminal device of the terminal device is likely to cause interference with another base station device. .

(16) The uplink signal reception quality information includes at least one of a CINR of a known signal included in an uplink signal from the terminal device of the terminal received by itself and a BER of the uplink signal. In this case, it is possible to accurately grasp the reception quality of the uplink signal of its own terminal device.

(17) Further, the present invention is a base station apparatus that is wirelessly connected to a terminal device, an acquisition unit that acquires uplink signal reception quality information related to reception quality of an uplink signal from the terminal device, and the acquisition unit acquires A determination unit that determines whether or not the uplink signal of the terminal device of the own device may interfere with another base station device based on the received uplink signal reception quality information. It is characterized by.
According to the base station apparatus having the above configuration, it is possible to effectively suppress interference by appropriately determining the possibility of occurrence of interference by the determination unit.

  According to the base station apparatus of the present invention, interference can be more effectively suppressed according to various situations.

It is the schematic which shows the structure of the radio | wireless communications system provided with the base station apparatus which concerns on 1st embodiment of this invention. It is a figure which shows the structure of each uplink and downlink radio frame in LTE. It is a figure which shows the detailed structure of DL frame. It is a figure which shows the detailed structure of a UL frame. In FIG. 1, it is a block diagram which shows the structure of femto BS. It is a block diagram which shows the structure of an output control part. In FIG. 1, it is a block diagram which shows the structure of MS. It is a flowchart which shows the process about control of the transmission power of the downlink transmission signal (uplink transmission signal) which an output control part performs. In FIG. 1, it is a figure which shows the relationship of the interference in each of communication between macro BS and macro MS and communication between femto BS and femto MS. It is a flowchart which shows the process about control of the transmission power of the downlink transmission signal (uplink transmission signal) which the output control part of femto BS which concerns on 2nd embodiment of this invention performs. It is a block diagram of femto BS which concerns on 3rd embodiment of this invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
[First embodiment]
[1. Configuration of communication system]
FIG. 1 is a schematic diagram illustrating a configuration of a wireless communication system including a base station apparatus according to the first embodiment of the present invention.
The wireless communication system includes a plurality of base station devices 1 and a plurality of terminal devices 2 (mobile terminals) that can perform wireless communication with the base station device 1.
The plurality of base station apparatuses 1 are compared with a plurality of macro base station apparatuses (Macro Base Stations) 1a forming a communication area (macrocell) MC having a size of several kilometers, for example, and are installed in the macrocell MC. A plurality of femto base station apparatuses (Femto Base Stations) 1b forming a small femtocell FC.

Macro base station apparatus 1a (hereinafter also referred to as macro BS 1a) can perform radio communication with terminal apparatus 2 in its own macro cell MC.
Further, the femto base station apparatus 1b (hereinafter also referred to as a femto BS 1b) is arranged, for example, in a place where it is difficult to receive the radio wave of the macro BS 1a, such as indoors, and forms the femto cell FC. The femto BS 1b can wirelessly communicate with the terminal device 2 (hereinafter also referred to as MS2) in the femto cell FC formed by the femto BS 1b. In this system, a place where the radio wave of the macro BS 1a is difficult to receive, etc. However, by installing a femto BS 1b that forms a relatively small femto cell FC at that location, it is possible to provide services to the MS 2 with sufficient throughput.
In the following description, the MS 2 connected to the femto BS 1b is also referred to as a femto MS 2b, and the MS 2 connected to the macro BS 1a is also referred to as a macro MS 2a.

  The radio communication system according to the present embodiment is a system for mobile phones to which, for example, LTE (Long Term Evolution) is applied, and communication based on LTE is performed between each base station device and a terminal device. . In LTE, a frequency division duplex (FDD) scheme can be adopted. In the present embodiment, the communication system will be described as adopting an FDD scheme. Note that the communication system is not limited to the LTE and is not limited to the FDD system, and may be a TDD (Time Division Duplex) system, for example.

[2. LTE frame structure]
In the FDD scheme that can be adopted in LTE that the communication system according to the present embodiment complies with, an uplink signal (a transmission signal from the terminal device to the base station device) and a downlink signal (a transmission signal from the base station device to the terminal device) By assigning different use frequencies to each other, uplink communication and downlink communication are simultaneously performed.
In the present embodiment, OFDM (Orthogonal Frequency Division Multiplexing) is adopted for downlink radio communication, and SC-FDMA (Single Carrier-Frequency Multiple Access) is adopted for uplink radio communication.

  FIG. 2 is a diagram illustrating the structure of uplink and downlink radio frames in LTE. The radio frame (DL frame) and the uplink radio frame (UL frame), which are downlink basic frames in LTE, each have a time length of 10 milliseconds, from # 0 to # 9. It is composed of 10 subframes. These DL frames and UL frames are arranged in the time axis direction with their timings aligned.

FIG. 3 is a diagram illustrating a detailed structure of a DL frame. In the figure, the vertical axis direction represents frequency, and the horizontal axis direction represents time.
Each subframe constituting the DL frame is composed of two slots (for example, slots # 0 and # 1). One slot is composed of seven (# 0 to # 6) OFDM symbols (in the case of Normal Cyclic Prefix).
Also, in the figure, a resource block (RB: Resource Block) that is a basic unit area in data transmission is defined by 12 subcarriers in the frequency axis direction and 7 OFDM symbols (1 slot) in the time axis direction. Therefore, for example, when the frequency bandwidth of the DL frame is set to 5 MHz, 300 subcarriers are arranged, so that 25 resource blocks are arranged in the frequency axis direction.

  As shown in FIG. 3, a transmission area for the base station apparatus to allocate a control channel necessary for downlink communication to the terminal apparatus is secured at the head of each subframe. This transmission area is allocated with symbols # 0 to # 2 (three symbols at the maximum) of the slot located at the head side in each subframe, and PDSCH (PDSCH: Physical Downlink Shared Channel, where user data is stored) Control channel configuration indication channel for notifying downlink control channel (PDCCH: Physical Downlink Control Channel) including allocation information and the like of PUSCH (explained) and PUSCH (PDSCH: Physical Uplink Shared Channel, explained later) and information on PDCCH (PCFICH: Physical Control Format Indicator Channel), hive for PUSCH HARQ indication channel (PHICH: PhysicHididHardQ) for transmitting acknowledgment (ACK: Acknowledgement) and negative acknowledgment (NACK: Negative Acknowledgment) It has been.

  In addition to the allocation information, the PDCCH includes information related to uplink transmission power control information, which will be described later, and a report instruction for downlink CQI (Channel Quality Indicator).

Also, in the DL frame, a broadcast channel (PBCH: Physical Broadcast Channel) for notifying the terminal device of the system bandwidth and the like by broadcast transmission is assigned to the first subframe # 0. PBCH is arranged with four symbol widths at the positions of symbols # 0 to # 3 in the slot on the rear side in first subframe # 0 in the time axis direction, and in the frequency axis direction, the center of the bandwidth of the DL frame Are allocated for 6 resource block widths (72 subcarriers). This PBCH is configured to be updated every 40 milliseconds by transmitting the same information over four frames.
PBCH stores main system information such as a communication bandwidth, the number of transmission antennas, and a structure of control information.

  Of the 10 subframes constituting the DL frame, each of the first (# 0) and sixth (# 5) subframes is a signal for identifying a base station apparatus or a cell. One synchronization signal and second synchronization signal (P-SCH: Primary Synchronization Channel, S-SCH: Secondary Synchronization Channel) are assigned.

P-SCH is arranged with a single symbol width at the position of symbol # 6 which is the last OFDM symbol of the leading slot in each of subframe # 0 and subframe # 5 in the time axis direction, and in the frequency axis direction. , 6 resource block widths (72 subcarriers) are arranged at the center of the DL frame bandwidth.
S-SCH is arranged with a single symbol width at the position of symbol # 5, which is the second OFDM symbol from the end of the first slot in each of subframe # 0 and subframe # 5, in the time axis direction. In the axial direction, 6 resource block widths (72 subcarriers) are arranged at the center of the DL frame bandwidth.

By combining P-SCH and S-SCH, a plurality of patterns defined in advance in the communication standard are defined, and are known in each base station apparatus and each terminal apparatus. That is, P-SCH and S-SCH are known signals that can take a plurality of patterns, respectively.
P-SCH and S-SCH may be used as signals for synchronization between base stations that synchronize communication timing and / or frequency between base station apparatuses, in addition to the case where terminal apparatuses synchronize with base station apparatuses. Used.

Resource blocks in other areas to which the above-described channels are not allocated are used as the above-described downlink shared channel (PDSCH) for storing user data and the like. This PDSCH is an area shared and used by a plurality of terminal devices. In addition to user data, control information for each terminal device such as information indicating transmission power at the time of transmission of a downlink transmission signal necessary for CQI measurement, etc. Is also stored.
The allocation of user data stored in the PDSCH is notified to the terminal device by downlink allocation information regarding downlink radio resource allocation stored in the PDCCH allocated at the head of each subframe. This downlink allocation information is information indicating radio resource allocation for each PDSCH, and the terminal apparatus can determine whether or not data for itself is stored in the subframe based on this downlink allocation information.

FIG. 4 is a diagram illustrating a detailed structure of the UL frame. In the figure, the vertical axis direction represents frequency, and the horizontal axis direction represents time.
The structure of the UL frame is basically the same as that of the DL frame, and each subframe is composed of two slots (for example, slots # 0 and # 1), and one slot has seven (# 0 to # 6) OFDM symbols.
The same applies to a resource block (RB) as a basic unit area in data transmission, and is defined by 12 subcarriers in the frequency axis direction and 7 OFDM symbols (1 slot) in the time axis direction.

  A physical random access channel (PRACH) used for communication for the first access before the terminal apparatus connects to the base station apparatus is assigned to the UL frame. The PRACH has a frequency bandwidth of 6 resource blocks (72 subcarriers), and the allocation is notified to the terminal device by the PBCH (broadcast channel) of the DL frame.

An uplink control channel (PUCCH: Physical Uplink Control Channel) is allocated to both ends of each subframe in the frequency axis direction. PUCCH includes HARQ ACK and NACK information related to PDSCH received data, downlink CQI information for reporting CQI indicating reception quality when a terminal apparatus receives a downlink transmission signal, to the base station apparatus, and the like. Used for transmission. The allocation of the PUCCH is notified to the terminal device by the PBCH of the DL frame.
Also, a sounding reference signal (SRS) is assigned to the last symbol of each subframe. This SRS is a reference signal transmitted using known transmission power and phase, and is used by the received base station apparatus to measure the uplink CQI of the uplink signal for each frequency of each terminal apparatus.

Resource blocks in other areas to which the above-described channels are not allocated are used as the above-described uplink shared channel (PUSCH) for storing user data and the like. The PUSCH is an area shared and used by a plurality of terminal apparatuses, and stores control information and the like in addition to user data.
The user data allocation for the PUSCH is notified to the terminal apparatus by uplink allocation information related to uplink radio resource allocation stored in the PDCCH of the DL frame. The uplink allocation information is information indicating radio resource allocation for each PUSCH, and the terminal apparatus can recognize the PUSCH used for its own transmission by this uplink allocation information.

[3. Configuration of base station apparatus]
FIG. 5 is a block diagram showing a main configuration of the femto BS 1b in FIG. Here, the configuration of the femto BS 1b will be described, but the configuration of the macro BS 1a is also substantially the same as that of the femto BS 1b.
The femto BS 1b includes an antenna 3, a receiving unit 4 connected to the antenna 3, a demodulating unit 5 that demodulates an uplink reception signal given from the receiving unit 4 as uplink reception data, and outputs the demodulated signal to an upper layer. Modulation unit 6 that modulates various transmission data to be output and outputs it as a downlink transmission signal, transmission unit 7 that transmits the downlink transmission signal output from modulation unit 6 from antenna 3, and quality information that acquires information on CQI of uplink and downlink An acquisition unit 8 and an output control unit 9 that controls transmission power of the downlink transmission signal are provided.

The receiving unit 4 includes a filter, an amplifier, an A / D converter, and the like that allow only the frequency band of the upstream signal to pass through, acquires the upstream signal from the MS 2 from the received signal received by the antenna 3, and amplifies this At the same time, it is converted into a digital signal and output to the demodulator 5 as an upstream received signal.
The transmission unit 7 includes a D / A converter, a filter, an amplifier, and the like. The transmission unit 7 receives a downstream transmission signal output as a digital signal from the modulation unit 6, converts this into an analog signal, amplifies the signal, and amplifies It has a function of transmitting as a downlink signal.

The modulation unit 6 modulates the transmission data given from the higher layer by a predetermined method for each predetermined data unit based on a command such as a scheduler (not shown), and the modulated data for each resource block unit. It has a function of assigning DL frames and generating its own downlink transmission signal.
Further, when the modulation unit 6 generates its own downlink transmission signal, the uplink transmission power control information for causing the femto MS 2b connected to the modulation unit 6 to adjust the transmission power of the uplink transmission signal to the PDCCH of its own downlink transmission signal. It has a function of adjusting the transmission power of the femto MS 2b by storing and transmitting to the femto MS 2b.

Furthermore, the modulation unit 6 has a function of setting the transmission power of its own downlink transmission signal and the transmission power of the uplink transmission signal of the femto MS 2b connected to itself for each resource block. Based on the downlink transmission power control information, the transmission power of its own downlink transmission signal is adjusted for each resource block.
Similarly, the transmission power of the uplink transmission signal of the femto MS 2b also causes the MS 2 to adjust the transmission power of the uplink transmission signal for each resource block according to the uplink transmission power control information transmitted to the femto MS 2b.

The quality information acquisition unit 8 acquires downlink CQI information as downlink signal reception quality information included in the uplink reception data demodulated by the demodulation unit 5. Also, the quality information acquisition unit 8 receives the SRS separated from the uplink reception signal from the femto MS 2b from the reception unit 4, and based on this SRS, the reception quality of the uplink signal received by itself is determined by CINR (Carrier to Interference plus Noise). (Ratio), and the result is acquired as uplink CQI information as uplink signal reception quality information.
Moreover, the quality information acquisition part 8 calculates | requires the path loss value L between self and femto MS2b based on said SRS. The path loss value L is expressed as the following formula (1). In the following formula, the unit of the path loss value L is “dB”, and the unit of the parameter representing the other power is “dBm”. Hereinafter, in this specification, the unit of the parameter representing the power is all represented by “dBm”.
Path loss value L = Pu _ref −Pr (1)

In the above equation (1), Pu _ref indicates power at the time of SRS transmission, and Pr indicates power at the time of SRS reception. Since the power Pu _ref at the time of SRS transmission is known as described above, the quality information acquisition unit 8 obtains the power Pr when the self (own device) receives the SRS, so that the quality information acquisition unit 8 can determine the relationship between the self and the femto MS 2b. A path loss value L can be obtained.

  The quality information acquisition unit 8 outputs information related to the reception quality of the upper and lower signals, such as the downlink CQI information, the uplink CQI information, and the path loss value L, to the output control unit 9.

  From the downlink CQI information, the uplink CQI information, and the path loss value L given from the quality information acquisition unit 8, the output control unit 9 transmits the transmission power of its own downlink transmission signal, and the MS 2 connected to itself (hereinafter referred to as its own MS 2). Transmission power control information for adjusting the transmission power of the uplink transmission signal of the femto MS 2 b, which is also referred to as), is output to the modulation unit 6.

FIG. 6 is a block diagram showing a configuration of the output control unit 9. In the figure, the output control unit 9 estimates the downlink interfered power of the downlink signal received by its own MS 2 and the uplink interfered power of the uplink signal received by itself based on the information regarding the reception quality from the quality information acquisition unit 8. And determining whether or not the interference power estimation unit 9a is caused by interference of transmission signals by other BS1 and MS2 (hereinafter also referred to as other MS2) connected to other BS1. Unit 9b, and upper and lower limit value settings for setting an upper limit value and / or a lower limit value of the transmission power for the own downlink transmission signal and the own MS2 uplink transmission signal based on the determination result of the determination unit 9b and the both interference powers And a control unit 9d that causes the modulation unit 6 to perform processing related to adjustment of the transmission power of the both transmission signals within a range of power determined by the set upper and lower limit values.
The control unit 9d generates uplink transmission power control information and downlink transmission power control information for causing the modulation unit 6 to control transmission power, and outputs the information to the modulation unit 6 to control transmission power. Let it be done.

[4. Configuration of terminal device]
FIG. 7 is a block diagram showing the configuration of the MS 2 in FIG. The macro MS 2a and the femto MS 2b are different depending on whether the connection destination is the macro BS 1a or the femto BS 1b, and the configurations thereof are the same.
The MS 2 includes an antenna 21, a transmission / reception unit 22 that transmits / receives a downlink signal from the BS 1 connected to the antenna 21 and an uplink signal to be transmitted, and an input / output for inputting / outputting transmission / reception data including a keyboard and a monitor. In addition to controlling the output unit 23, the transmission / reception unit 22 and the input / output unit 23, a control unit 24 that performs processing necessary to perform communication with the BS 1 such as modulation / demodulation is provided.

  The control unit 24 has a function of receiving various control information included in the downlink signal from the BS 1 to which the control unit 24 is connected, and performing communication with the BS 1 according to the control information. The control information includes uplink assignment information indicating the frequency band assigned to the uplink signal of the MS 2, information on transmission power, and information on modulation scheme, and these pieces of information are given from BS1. That is, the BS 1 performs control related to the uplink signal of the MS 2 by transmitting various control information to the MS 2 connected to the BS 1.

When the control unit 24 receives an instruction to measure the CQI of the downlink signal from the BS 1 to which the control unit 24 is connected, the control unit 24 measures the CINR of the received downlink signal and transmits the result to the BS 1 as downlink CQI information. It also has a function. The control unit 24 uses a reference signal, which is a known signal arranged at a predetermined position, among a plurality of symbols constituting a radio frame in a downlink signal transmitted by the BS 1 to be connected, so that the CINR is used. Measure.
The control unit 24 also has a function for processing related to HARQ. In other words, the encoded data from the received BS1 is decoded and then subjected to error determination. If it is determined to be an error, a NACK is transmitted for the corresponding packet. Send ACK.
Next, the control process regarding the transmission power of the transmission signal of the self or its own femto MS 2b performed by the output control unit 9 of the femto BS 1b of the present embodiment will be described.

[5. Control of transmission power of own downlink transmission signal)
FIG. 8 is a flowchart showing a process for controlling transmission power of a downlink transmission signal (uplink transmission signal) performed by the output control unit 9. Note that the processing of transmission power control of the uplink transmission signal of the femto MS 2b connected to itself is almost the same as the processing of the own downlink transmission signal, and each of the parameter names for the downlink transmission signal shown in FIG. Indicates the names of parameters corresponding to uplink transmission signals in parentheses. Below, it demonstrates paying attention to control of the transmission power of a downlink transmission signal.

When the quality information acquisition unit 8 receives the downlink CQI information from the femto MS 2b and the path loss value L between itself and the femto MS 2b from the quality information acquisition unit 8, the output control unit 9 sends the downlink interference in the femto MS 2b to the interfered power estimation unit 9a. The interference power is estimated (step S101). Specifically, the interfered power estimation unit 9a obtains downlink interfered power based on the following equation (2).
Downlink interference power X = Pd _ref −L−CINR _d −N _d (2)

In the above equation (2), “Pd _ref ” is the power at the time of transmission of the above-mentioned reference signal that is a known signal included in the downlink signal, and “CINR _d ” is the downlink signal in the femto MS 2 b obtained from the downlink CQI information. The CINR, “N _d ”, of the reference signal at the time of reception is noise generated in the physical layer or the like, and other noise power that is unavoidably generated, and can be calculated in advance by a predetermined method.
That is, when the femto MS 2b receives its own downlink transmission signal, if there is no external interference factor in the transmission path between itself and the femto MS 2b, the above CINR _d , path loss value L, and noise power N are added. This value matches the power Pd _ref at the time of transmitting the reference signal. However, if CINR _d decreases due to external interference, the added value becomes smaller than the power Pd _ref . The value obtained by subtracting the added value from the power Pd _{ref at} this time is the interference power from the outside, and is obtained as the downlink interfered power X as shown in the above equation (2).

Next, the output control unit 9 causes the upper and lower limit value calculation unit 9c to calculate the lower limit value Pdmin of the transmission power for the own downlink transmission signal (step S102). The lower limit value Pdmin is expressed as the following formula (3).
Lower limit value Pdmin = CINR _dmin + X + L + N _d (3)

In the above equation (3), CINR _dmin is a minimum CINR value necessary for downlink communication between the femto BS 1b and the femto MS 2b, and the upper and lower limit value calculation unit 9c includes interference power, path loss value, In consideration of noise power and noise power in advance, by adding CINR _dmin , the minimum transmission power of the downlink transmission signal that can ensure communication with the femto MS 2b is determined as the lower limit value Pdmin.

Next, the output control unit 9 causes the determination unit 9b to determine whether or not the downlink interfered power X is greater than or _equal to a predetermined threshold value Xth (step S103).

FIG. 9 is a diagram showing the relationship of interference in communication between the macro BS 1a and the macro MS 2a and communication between the femto BS 1b and the femto MS 2b in FIG.
In the case of FIG. 9, in addition to receiving the downlink signal DL2 transmitted by the femto BS 1b, the femto MS 2b may receive the downlink signal DL1 transmitted to the macro MS 2a by the macro BS 1a as another BS 1 as the interference wave DL11. .
For example, when the range of the resource block of the downlink frame as the radio resource allocated to the femto MS 2b overlaps the range of the resource block of the downlink frame allocated to the macro MS 2a, the femto MS 2b The interference wave DL11 of the downlink signal DL1 transmitted toward the MS 2a is received.

When the femto MS 2b receives interference by receiving a downlink signal from another BS1, CINR _d that is the reception quality of the downlink signal in the femto MS 2b is reduced by the interference, and is expressed by the above equation (2). As described above, the downlink interfered power X in the femto MS 2b increases. Therefore, the femto BS 1b can determine whether or not the femto MS 2b has received interference from the downlink signal of another BS 1 based on the value of the downlink interfered power X. if the interference power X is long the threshold value X _th or more, it is judged that receiving interference by the downlink signals of the other BS1.

  Further, when the femto MS 2b receives interference due to a downlink signal from another BS1, as the other MS 2 to which the resource block is assigned overlapping with the range of the resource block assigned to the femto MS 2b. It can be recognized that the macro MS2a exists. Further, when the resource block of the downlink frame of the femto MS2b and the resource block of the downlink frame of another MS2 overlap, the macro MS2a transmits the interference signal DL21 of the downlink signal DL2 that the femto BS1b transmits to the femto MS2b. It can be recognized that the downlink signal DL2 of the femto BS 1b may interfere with the macro MS 2a.

  As described above, the femto BS 1b determines whether or not the femto MS 2b has received interference due to the downlink signal of another BS 1 based on the value of the downlink interfered power X, thereby allocating resources allocated to the femto MS 2b. It can also be determined whether or not there is another MS2 to which a resource block overlapping with the block range is allocated, and whether the downlink signal DL2 of the femto BS1b may cause interference to the other MS2 It can also be judged whether or not. As described above, the output control unit 9 has a function as a determination unit that determines whether or not the own downlink signal DL2 may cause interference to another MS2.

Threshold X _th in step S103 is a threshold for the downlink received interference power X to determine whether it is due to the interference of the downlink signal of another BS1 than self, when it comes to this value or more, It is set to a value that can be determined that there is a possibility that the downlink signal DL2 of the femto BS 1b that is the self is affected by the downlink signal of another BS1 and that it may cause interference to the other MS2.

The output control unit 9, in step S103, if the downlink received interference power X is determined to be a predetermined threshold value X _th or more, the transmission power of the own downlink transmission signal can suppress the interference to other MS2 The upper and lower limit value calculation unit 9c is made to obtain an upper limit value Pdmax for determining the power range (step S104).
The upper limit value Pdmax is obtained based on the following formula (4).
Upper limit value Pdmax = Pd _const −X + L + N _d (4)

The Pd _const is a fixed value, and the upper limit value Pdmax is a value suitable for suppressing interference with other MSs 2 with respect to the downlink interfered power X determined by the threshold value X _th . It is set by obtaining in advance by simulation or the like.
In the above equation (4), the downlink interfered power X is subtracted from each value including the fixed value Pd _const , and the upper limit value Pdmax is set to be smaller as the downlink interfered power X is larger. If the downlink interfered power X is large and it can be determined that the interference power from the other BS1 is relatively large, for example, the macro MS 2a may be located in the vicinity of its own femto BS 1b, and may cause interference on both sides. This is because it can be determined that there is a high possibility that the own downlink signal DL2 will interfere with the macro MS 2a.

  Next, the upper and lower limit value calculation unit 9c determines whether or not the lower limit value Pdmin obtained in step S102 is smaller than the upper limit value Pdmax (step S105). When it is determined that the lower limit value Pdmin is smaller than the upper limit value Pdmax, the process proceeds to step S106, and the output control unit 9 controls transmission power for the resource block allocated to the femto MS 2b in its own downlink transmission signal. Is performed within the range of power from the upper limit value Pdmax to the lower limit value Pdmin (step S106), and the process ends.

  When it can be determined that the femto MS 2b has received interference due to the downlink signal DL1 of the macro BS 1a, as described above, other resource blocks that are assigned to overlap the resource block range assigned to the femto MS 2b are assigned. Since the macro MS 2a that is the MS 2 exists, if the transmission power of its own downlink transmission signal is increased without any limitation, the macro MS 2a may be interfered by the own downlink transmission signal.

  Here, in general, the femto BS is preferably set so as to perform communication by giving priority to the communication by the macro BS forming the macro cell MC. This is because the communication performed by the macro BS that forms the macro cell, which is a wide communication area, is highly public.

  In this regard, in the femto BS 1b of the present embodiment, the output control unit 9 determines that the femto MS 2b is interfered by the downlink signal DL1 of the macro BS 1a on the basis of the downlink interfered power X. Communication with the femto MS 2b from the upper limit value Pdmax that can suppress interference with the other MS 2, when it is determined that there is a possibility of interference with the other MS 2 Is controlled within the range of the power of the lower limit value Pdmin, which is the minimum transmission power of the downlink transmission signal that can ensure the above. Therefore, the femto BS 1b can control the transmission power of its own downlink transmission signal within a range of power that does not interfere with the macro MS 2a, and can effectively suppress the interference with the macro MS 2a. Communication with the femto MS 2b can be secured while giving priority to the communication of the BS 1a.

On the other hand, if it is determined in step S105 that the lower limit value Pdmin is not smaller than the upper limit value Pdmax, the own downlink transmission signal can be secured so as to secure communication with the femto MS 2b while suppressing interference with the macro MS 2a. Since it is difficult to control the transmission power, the output control unit 9 assigns to the current femto MS 2b by outputting control information indicating that and the resource block allocated to the femto MS 2b to the modulation unit 6. Allocation processing for assigning another resource block different from the resource block being assigned to the femto MS 2b is caused to be performed by the modulation unit 6 (step S107), and the processing ends.
In this way, the output control unit 9 causes the modulation unit 6 to perform the allocation process for the resource block allocated to the femto MS 2b, thereby overlapping at least the resource block allocated to the macro MS 2a as the other MS 2. This can be avoided, and it is possible to suppress the own downlink transmission signal from interfering with the macro MS 2a. As a result, the femto BS 1b that is itself can ensure communication with the femto MS 2b without causing interference to the macro MS 2a.

Further, in step S103, when it is determined that the downlink the interference power X is not a predetermined threshold value X _th or more, since the femto MS2b it can be determined that it does not receive interference from the downlink signal DL1 of the macro BS1a, output control The unit 9 causes the control unit 9d to control the transmission power for the resource block allocated to the femto MS 2b in its own downlink transmission signal based on only the lower limit value Pdmin without setting the upper limit value Pdmax ( Step S108), the process ends.

  In this case, since it can be determined that the femto MS 2b has not received interference due to the downlink signal DL1 of the macro BS 1a, there is another MS 2 that is assigned overlapping with the resource block range assigned to the femto MS 2b. In addition, since it can be determined that the downlink signal DL2 of the femto BS 1b does not possibly interfere with the macro MS 2a, the femto BS 1b that is itself limits the transmission power of the downlink transmission signal by giving an upper limit value. Thus, transmission power can be controlled within a range of power that can be adjusted by itself.

[6. Control of transmission power of upstream transmission signal of own femto MS 2b]
As described above, the process for controlling the transmission power of the uplink transmission signal of the femto MS 2b is basically the same as the flowchart shown in FIG.
The output control unit 9 determines the uplink interfered power Y based on the uplink CQI information generated by the quality information acquisition unit 8 and the path loss value L. Uplink interference power Y is expressed as in the following equation (5).
Uplink received interference power _{Y = Pu ref - L - CINR} u - N u ··· (5)

In the above equation (5), “Pu _ref ” is the power at the time of SRS transmission as described above, and “CINR _u ” is the self obtained from the uplink CQI information and has received the uplink signal from the femto MS 2 b CIRS of the SRS, “N _u ”, is noise power that is unavoidable.

As shown in FIG. 9, the femto BS 1b receives the uplink signal UL2 transmitted from the femto MS2b, and the macro MS 2a, which is another MS2, may receive the uplink signal UL1 transmitted toward the macro BS 1a as the interference wave UL11. There is.
For example, if the range of the uplink frame resource block as the radio resource allocated to the femto MS 2b overlaps the range of the uplink frame resource block allocated to the macro MS 2a, the femto BS 1b The interference wave UL11 of the uplink signal UL1 transmitted toward the BS 1a is received.

When the femto BS 1b receives interference by receiving a downlink signal from another MS 2, the interference causes the CINR _u, which is the reception quality of the uplink signal, to decrease in the femto BS 1b. Thus, the uplink interfered power Y at the femto BS 1b increases. Therefore, the femto BS 1b can determine whether or not the femto BS 1b that is the femto BS 1b is subject to interference from the uplink signal of the other MS 2 based on the value of the uplink interfered power Y.

  Further, when the femto BS 1b receives interference due to an uplink signal from another MS2, the macro as the other MS 2 assigned overlapping with the range of the uplink frame resource block assigned to the femto MS 2b. It can be recognized that MS2a exists. Further, when the uplink frame resource block of the femto MS 2b overlaps the resource block of the uplink frame of another MS 2, the macro BS 1a transmits the interference wave UL 22 of the uplink signal UL 2 transmitted from the femto MS 2b to the femto BS 1b. It can be recognized that the uplink signal UL2 of the femto MS 2b may interfere with the macro BS 1a.

  As described above, the femto BS 1b determines whether or not the femto BS 1b is receiving interference due to the uplink signal of another MS 2 based on the value of the uplink interfered power Y, so that the resource block allocated to the femto MS 2b is determined. It can also be determined whether there is another MS2 to which a resource block that overlaps with the range is allocated, and whether or not the uplink signal UL2 of the femto MS2b may interfere with the macro BS1a. Can also be judged. As described above, the output control unit 9 has a function as a determination unit that determines whether or not the uplink signal UL2 of the femto MS 2b may cause interference with the macro BS 1a.

That is, the output control unit 9 determines whether or not the uplink interference power Y is greater than or equal to a predetermined threshold Y _th in step S103 in FIG. 8 for controlling the transmission power of the uplink transmission signal of the femto MS 2b. By doing so, it is determined whether or not the uplink transmission signal of the femto MS 2b may cause interference to the macro BS 1a.

  The following processing is the same as the transmission power control processing of the own downlink transmission signal, and the output control unit 9 appropriately obtains the upper limit value Pumax and the lower limit value Pumin according to the result of each determination, and sets the upper and lower limits. Based on the value, the modulation unit 6 is caused to control the transmission power of the uplink transmission signal for the femto MS 2b, and the process ends.

The threshold value Y _th is a threshold value for determining whether or not the uplink interfered power Y is caused by the interference of the uplink signal of the other MS 2, and is subject to interference caused by the uplink signal of the other MS 2. In addition, the uplink signal UL2 of the femto MS2b connected to itself is set to a value that can determine that there is a possibility of interference with other BS1.
Further, the upper limit value Pumax and the lower limit value Pumin are obtained based on the uplink interference power Y as shown in the following formulas (6) and (7).
Lower limit value Pumin = CINR _umin + Y + L + N _u (6)
Upper limit value Pumax = Pu _const −Y + L + N _u (7)

Note that Pu _const is a fixed value so that the upper limit value Pumax can be a value suitable for suppressing interference with another BS 1 with respect to the uplink interfered power Y determined by the threshold value Y _th. Further, it is set by obtaining in advance by simulation or the like.
In addition, CINR _umin in Equation (6) is the minimum CINR value necessary for uplink communication between the femto BS 1b and the femto MS 2b, and “N” is noise power that is unavoidably generated.

As described above, according to the femto BS 1b having the above-described configuration, the output control unit 9 determines its own power based on the interfered powers X and Y obtained from the CQI information that is information regarding the reception quality of the downlink signal and the uplink signal. Since the transmission power of the upstream signal of the femto MS 2b or the transmission power of its own downstream transmission signal can be adjusted, the upstream signal of its own femto MS 2b interferes with another BS 1 by the interfered powers X and Y. If it can be determined that there is a possibility that its own downlink transmission signal may interfere with another MS2, the transmission power of the uplink signal of its own femto MS2b, Alternatively, the transmission power of its own downlink transmission signal can be adjusted to suppress interference with other MS2s or other BS1s.
As a result, according to the femto BS 1b of the present embodiment, interference can be effectively suppressed by appropriately grasping the possibility of occurrence of interference.

[Second Embodiment]
FIG. 10 is a flowchart showing a process for controlling transmission power of a downlink transmission signal (uplink transmission signal) performed by the output control unit 9 of the femto BS 1b according to the second embodiment of the present invention. Also in this embodiment, the process for controlling the downlink transmission signal and the process for controlling the uplink transmission signal are almost the same, and therefore, the following description will be given with a focus on the control of the transmission power of the downlink transmission signal.

  The difference between the present embodiment and the first embodiment is that when the upper limit value Pdmax is obtained in the transmission power control performed by the output control unit 9, a new upper limit value Pdmax is obtained based on the upper limit value Pdmax obtained in the past. It is a point to ask for.

  In FIG. 10, steps S201 to S203 and S205 to S208 are respectively performed in the same manner as steps S101 to S103 and S105 to S108 shown in FIG. 8 of the first embodiment. Therefore, hereinafter, steps S200, S210 to S213, which are different from the first embodiment, will be described.

In the present embodiment, the output control unit 9 first sets the upper limit value Pdmax to “0” when starting the processing (step S200). Then, the process proceeds to step S201, S202, S203, in step S203, if it is determined that the downlink the interference power X is the threshold value X _th or more, the output control section 9 proceeds to step S210, the upper limit value Pdmax is "0 Is not determined (step S210).

  When the upper limit value Pdmax is “0”, the process proceeds to step S211, and the output control unit 9 causes the upper and lower limit value calculation unit 9c to obtain the upper limit value Pdmax as the initial value. In step S211, the upper limit value Pdmax is obtained by the method shown in step S104 of the first embodiment. Thereafter, the process proceeds to step S205.

On the other hand, if the upper limit value Pdmax is not “0”, the process proceeds to step S212, and the output control unit 9 causes the upper and lower limit value calculation unit 9c to determine a new upper limit value Pdmax based on the upper limit value Pdmax determined in the past ( The process proceeds to step S212) and step S205.
The upper and lower limit value calculation unit 9c calculates a new upper limit value Pdmax based on the following equation (8).
New upper limit value Pdmax = α × past Pdmax +
(1-α) × (Pd _const −X + L + N _d ) (8)

Here, the past Pdmax is the upper limit value Pdmax obtained by the calculation in the previous process, and α (where 0 ≦ α <1) is the interfered power X and the path loss acquired in the current process. This is a coefficient for adjusting the influence of the value L on the upper limit value Pdmax, and is adjusted and set to a suitable value in advance. The other coefficients are as shown in the first embodiment.
The output control unit 9 of the present embodiment obtains a new upper limit value Pdmax using the upper limit value Pdmax obtained in the past, as shown in the above equation (8).

  Steps S205 to S207 and Step S208 after Step S212 are the same as Steps S105 to S107 and Step S108 of the first embodiment, but the output control unit 9 uses the upper limit value Pdmax for control of transmission power. After step S207 and step S208 are completed, the process proceeds to step S213, the upper limit value Pdmax is set to “0”, the process ends, and the process returns to step S201.

  According to the femto BS 1b of the present embodiment, as shown in the above equation (8), when determining the upper limit value Pdmax, the influence of the interfered power X and the path loss value L acquired in the current process are considered. Since a new upper limit value Pdmax is obtained based on the upper limit value Pdmax obtained in the past, fluctuations in the upper limit value Pdmax obtained sequentially can be mitigated, and an interfered object that includes a large error due to a sudden interference wave, noise, or the like. Even if the electric power X is obtained, the influence can be suppressed as much as possible.

[Third embodiment]
FIG. 11 is a block diagram of a femto BS 1b according to the third embodiment of the present invention.
The difference between the present embodiment and the first and second embodiments is that the quality information acquisition unit 8 acquires information related to the received quality of the downlink signal from the HARQ processing unit 10 that performs processing related to HARQ.

The HARQ processing unit 10 has a function of performing processing related to HARQ, performs processing for error correction coding for each packet on transmission data given from an upper layer, and responds (ACK or NACK) from the femto MS 2b. Accordingly, a function of performing a process of retransmitting data in which an error has occurred is provided. The HARQ processing unit 10 acquires ACK or NACK that is a response from the MS 2 from the uplink reception data demodulated by the demodulation unit 5, and performs data retransmission processing based on these responses.
Further, the HARQ processing unit 10 counts the number of ACKs and NACKs of the target femto MS 2b for predetermined data of a predetermined capacity prepared for grasping the quality of the downlink signal, for example. It also has a function of outputting to the information acquisition unit 8.

The quality information acquisition unit 8 has a function of obtaining the ratio of NACK to ACK for the predetermined data from the count result information given from the HARQ processing unit 10 and estimating the CINR in the MS 2 from this ratio. Specifically, a CINR value corresponding to the ratio is grasped in advance, and a table indicating the relationship between the ratio and CINR is prepared and stored in advance. When obtaining the ratio, the quality information acquisition unit 8 can acquire the corresponding CINR as an estimated value by referring to the table.
The quality information acquisition unit 8 outputs the estimated CINR to the output control unit 9 as downlink signal reception quality information.

The output control unit 9 uses Pd _ref in the above formula (2) as the transmission power at the time of transmission of the predetermined data, and uses the CINR given from the quality information acquisition unit 8 based on the formula (2). The interference power X is obtained.

  In the present embodiment, since the CINR of the area where the predetermined data is arranged in the downlink radio frame can be measured, the degree of freedom of the area that can be measured is increased, and the CINR of the necessary area can be preferably measured.

  In this embodiment, downlink interference power X is estimated using CINR estimated from the ratio of NACK to ACK. However, CINR based on downlink CQI information from femto MS 2b can also be used together. In this case, CINR can be measured in many ways, and the measurement accuracy can be further improved.

The present invention is not limited to the above embodiments.
In each of the above embodiments, the CINR measured using the SRS is acquired as the uplink CQI information as the signal reception quality information for the uplink transmission signal from the femto MS 2b. For example, a plurality of symbols constituting a radio frame in the uplink signal CINR may be measured by using a plurality of known reference signals arranged at predetermined positions, or a predetermined capacity of predetermined data may be transmitted to the femto MS 2b with a predetermined transmission power, and the femto BS 1b The quality information acquisition unit 8 may measure the BER (Bit Error Rate) when the predetermined data is received, and estimate the CINR of the uplink signal from the BER. In addition, as a method for estimating CINR from BER, a table for CINR corresponding to BER is prepared in advance, as in the case of estimating CINR from the ratio of NACK to ACK described above. CINR can be estimated from

  In each of the above embodiments, the lower limit value Pdmin is set to the minimum CINR necessary for communication between itself and the femto MS 2b, the interference power X, and the lower limit value Pdmin as shown in the above formulas (3) and (6). For example, the transmission power is set as the lower limit value Pdmin such that the ratio of NACK to ACK when it transmits predetermined data is a value that can maintain the necessary minimum communication quality. Alternatively, the lower limit value Pdmin may be obtained using a CINR value that can achieve a predetermined throughput.

In the above embodiments, at step S103, when the downlink (uplink) the interference power X (Y) is the threshold value X _th or more, sets the upper limit value Pdmax (Pumax), when it is not the threshold value X _th or more, the upper limit a case has been exemplified for controlling the transmission power not set a value Pdmax (Pumax) setting, for example, when when the downlink (uplink) the interference power X (Y) is not the threshold value X _th or more, the threshold value X _th or The threshold value X _th is determined (whether there is a possibility of interference with other BS1 or MS2), such as setting an upper limit value Pdmax (Pumax) that is larger than the upper limit value Pdmax (Pumax) The transmission power may be controlled so as to adjust the upper limit value according to the determination.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the meanings described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Base station apparatus 1a Macro base station apparatus 1b Femto base station apparatus 2 Terminal apparatus 2a Macro terminal apparatus 2b Femto terminal apparatus 8 Quality information acquisition part 9 Output control part (determination part)

Claims (7)

A base station device wirelessly connected to a terminal device,
An acquisition unit for acquiring downlink signal reception quality information relating to reception quality of the downlink signal received by the terminal device;
Based on the downlink signal reception quality information acquired by the acquisition unit, and a control unit that controls transmission power of the own downlink signal ,
The control unit estimates interference power in the received downlink signal based on the downlink signal reception quality information, controls the transmission power of its own downlink signal based on the estimated interference power, and A base station apparatus characterized by setting and controlling a predetermined upper limit for transmission power of its own downlink signal when the interfered power is equal to or greater than a predetermined threshold . The base station apparatus according to claim 1 , wherein the control section controls the transmission power of its own downlink signal without setting the upper limit value when the interfered power is smaller than the threshold value. Wherein the control unit, the base station apparatus according to claim 1 or 2 wherein based on the interference power obtaining the upper limit value. The control unit obtains a lower limit value necessary for ensuring communication with its own terminal device connected to itself for transmission power of its own downlink signal, and determines that the lower limit value is smaller than the upper limit value. The base station apparatus as described in any one of Claims 1-3 which controls in the range from the said upper limit to the said lower limit about the transmission power of the said own downlink signal. The control unit obtains a lower limit value necessary for ensuring communication with the terminal device connected to the terminal device with respect to transmission power of the own downlink signal, and determines that the lower limit value is equal to or greater than the upper limit value. The base station apparatus as described in any one of Claims 1-3 which allocates another radio | wireless resource different from the radio | wireless resource allocated to the said own terminal device to the said own terminal device. The base station apparatus according to claim 4 or 5 , wherein the control unit obtains the lower limit value based on a path loss value between itself and the terminal apparatus of the self and / or the interfered power. The downlink signal reception quality information is a CINR when a downlink signal received by the terminal device is received, or a confirmation transmitted from the terminal device when predetermined data is transmitted to the terminal device. among ratio of negative acknowledgment response, the base station apparatus according to claim 1-6 comprising at least one.

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