WO2012014486A1

WO2012014486A1 - Base station device and transmitting power control method

Info

Publication number: WO2012014486A1
Application number: PCT/JP2011/004286
Authority: WO
Inventors: 継峰李; 将彦南里
Original assignee: パナソニック株式会社
Priority date: 2010-07-30
Filing date: 2011-07-28
Publication date: 2012-02-02
Also published as: JP2012034211A

Abstract

Disclosed is a base station device capable of suppressing interference applied to a peripheral base station device while maintaining a predetermined resource, and capable of preventing deterioration of control data quality of a control channel of the peripheral base station device. In the device, an IFFT unit (105) performs orthogonal frequency division multiplexing of control data and PDSCH data to generate an OFDM signal comprising control data allocated from the head of a sub-frame to N (N is an arbitrary positive integer) OFDM symbol, and PDSCH data allocated to OFDM symbols located rearward of the NOFDM symbol, with respect to each sub-frame. A transmitting power control unit (106) functions so that, in an OFDM signal, the PDSCH data transmitting power transmitted at the time overlapping the transmission time when the control data of the peripheral base station device is reduced compared to the PDSCH data transmitting power transmitted at the time other than the overlapping time.

Description

Base station apparatus and transmission power control method

The present invention relates to a base station apparatus and a transmission power control method, for example, when downlink control channel data of a base station apparatus forming a macro cell interferes with downlink data channel data transmitted from a small base station. The present invention relates to a base station apparatus and a transmission power control method for mitigating interference with respect to a signal.

LTE (Long Term Evolution), one of mobile communication standards, is characterized by improved frequency utilization efficiency and low delay compared to conventional communication standards. It is expected as a standard that supports the development of

The LTE downlink modulation scheme employs an OFDM (Orthogonal Frequency Division) Multiplexing (OFDM) scheme, and the minimum unit of information symbols in the frequency domain is one subcarrier. Twelve subcarriers are called one resource block (hereinafter referred to as “RB”), and this is an allocation unit for each downlink channel. In LTE, a downlink channel is configured by repeatedly and continuously arranging a 1 RB frame format in a predetermined frequency region. Note that the number of RBs repeatedly and continuously arranged is determined by the scheduler of the base station apparatus according to the amount of transmission information to the mobile station or the downlink propagation path environment.

When viewed in the time direction, the transmission allocation unit of each channel is called one subframe, and is composed of 14 OFDM symbols in normal CP (Cyclic Prefix). In Extended CP, it is composed of 12 OFDM symbols. Among these, a control channel (CCH: Control Channel) (hereinafter referred to as “CCH”) is assigned to 1 to 3 OFDM symbols from the top. A data channel, a synchronization channel, or a broadcast channel is assigned to the remaining OFDM symbols. In the following description, the data channel, the synchronization channel, and the broadcast channel are collectively described as a common channel (SCH) (hereinafter referred to as “SCH”). The number of OFDM symbols to which CCH is assigned differs depending on the amount of control information required per subframe, and is determined by CFI (Control Format Indicator). Further, a reference signal (RS: Reference Signal) is intermittently assigned for each transmission antenna in the time domain and the frequency domain.

In recent years, a small base station apparatus called a pico cell or a home eNB (hereinafter referred to as “small eNB”) has been developed in order to cover a dead zone of a mobile phone. The small eNB is mainly assumed to be installed in a home or a company, and the number of accommodated terminals is generally said to be several or at most about 100. The cell formed by the small eNB is smaller than the cell formed by the conventional macro base station apparatus (hereinafter referred to as “MeNB”).

Since the conventional MeNB is installed after the communication carrier performs an appropriate station location design in advance, inter-cell interference does not become a problem. On the other hand, since a small eNB has low transmission power and can be installed at an arbitrary location by an end user, interference with the MeNB becomes a big problem. In particular, the communication to the existing MeNB should not be hindered. In particular, when interference is provided to the downlink control channel, not only downlink data communication of the MeNB but also serious troubles in broadcast information or uplink communication to a mobile station (hereinafter referred to as “MUE”) under the MeNB. .

In order to prevent such interference, 3GPP (3rd Generation Generation Partnership Project), which is a standardization body for mobile communication standards, has made various technical proposals as described in Non-Patent Document 1 and Non-Patent Document 2. . Non-Patent Document 1 proposes a technique for puncturing a part of a control channel of MeNB. Further, in Non-Patent Document 2, the MeNB centrally schedules MUEs with low downlink propagation path loss in a specific subframe, thereby reducing the downlink transmission power of the subframe and reducing interference with a small eNB. Technology has been proposed.

However, in Non-Patent Document 1, since the control channel is punctured, there is a problem that the reception performance of the control channel is lowered and resources of MeNB shared by many MUEs are tight.

Further, in Non-Patent Document 2, since downlink transmissions to MUEs with high downlink propagation loss are concentrated in a specific subframe, the downlink transmission power becomes high in that subframe, and the small eNB causes large interference. There is a problem of receiving.

An object of the present invention is to provide a base station apparatus that can suppress interference given to neighboring base station apparatuses while securing predetermined resources, and can prevent quality deterioration of control data of control channels of neighboring base station apparatuses And a transmission power control method.

A base station apparatus according to the present invention is a base station apparatus that forms a cell having a size different from that of a cell formed by a neighboring base station apparatus and communicates using an OFDM scheme that is the same communication scheme as the neighboring base station apparatus. By performing orthogonal frequency division multiplex processing on the data of a plurality of channels, control data distributed to a predetermined number of symbols from the beginning of the transmission period and a symbol behind the predetermined number of symbols for each predetermined transmission period Orthogonal frequency division multiplexing means for generating an OFDM signal including transmitted data and transmission power of the transmission data at a transmission timing that overlaps a transmission timing of control data of the neighboring base station apparatus in the OFDM signal. Transmission power control for performing control to reduce the transmission power of the transmission data at a transmission timing other than the timing Take the stage, a configuration and a transmitting means for transmitting the OFDM signal at a controlled transmit power by the transmit power control unit.

According to the transmission power control method of the present invention, a cell having a size different from a cell formed by a neighboring base station apparatus is formed, and transmission is performed in a base station apparatus that communicates using an OFDM scheme that is the same communication scheme as the neighboring base station apparatus. A power control method, wherein control data distributed to a predetermined number of symbols from the beginning of the transmission period and the predetermined number of symbols for each predetermined transmission period by performing orthogonal frequency division multiplexing processing on data of a plurality of channels Generating an OFDM signal including transmission data distributed to symbols behind the transmission signal, and, in the OFDM signal, the transmission power of the transmission data at a transmission timing overlapping the transmission timing of the control data of the neighboring base station apparatus, Control to reduce the transmission power of the transmission data at a transmission timing other than the overlapping transmission timing. Cormorants and step, was to be equipped with.

According to the present invention, it is possible to suppress interference given to neighboring base station apparatuses while securing predetermined resources, and to prevent quality deterioration of control data of control channels of neighboring base station apparatuses.

The block diagram which shows the structure of the base station apparatus which concerns on Embodiment 1 of this invention. The block diagram which shows the structure of the communication terminal device in Embodiment 1 of this invention. The figure which shows the control method of the transmission power in the base station apparatus which concerns on Embodiment 1 of this invention, and the periphery base station of a base station apparatus The figure which shows the other control method of the transmission power in the base station apparatus which concerns on Embodiment 1 of this invention, and the periphery base station of a base station apparatus The block diagram which shows the structure of the base station apparatus which concerns on Embodiment 2 of this invention. The figure which shows the control method of the transmission power in the base station apparatus which concerns on Embodiment 2 of this invention, and the periphery base station of a base station apparatus The figure which shows the control method of the transmission power in the base station apparatus which concerns on Embodiment 3 of this invention, and the periphery base station of a base station apparatus

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

(Embodiment 1)
Hereinafter, the configuration of base station apparatus 100 according to Embodiment 1 of the present invention will be described in detail with reference to FIG. Moreover, since MeNB and small eNB are the same structures, in this Embodiment, base station apparatus 100 may be either MeNB or small eNB. However, the transmission timing of one of the MeNB and the small eNB is set in OFDM symbol units with respect to the transmission timing of the other so that the CCH symbol of the MeNB and the CCH symbol of the small eNB do not overlap on the time axis. Shift on the time axis. In the present embodiment, the above-described shift amount of the OFDM symbol on the time axis is 3 OFDM symbols, but the present invention is not limited to this, and may be N (N is an arbitrary positive integer) OFDM symbol. .

FIG. 1 is a block diagram showing a configuration of base station apparatus 100 according to the present embodiment.

Base station apparatus 100 includes CCH modulation section 101, SCH modulation section 102, channel selection section 103, resource mapping section 104, IFFT section 105, transmission power control section 106, addition section 107, and transmission timing adjustment. The unit 108, the RF unit 109, and the antenna 110 are mainly configured.

The CCH modulation unit 101 outputs a control channel symbol (hereinafter referred to as “CCH symbol”) obtained by modulating the input CCH control data (hereinafter referred to as “CCH data”) to the channel selection unit 103. Here, the CCH includes PDCCH (Physical Downlink Control Channel), PHICH (Physical Hybrid-ARQ Indicator Channel), and PCFICH (Physical Control Format Indicator Channel).

The SCH modulation unit 102 outputs a common channel symbol (hereinafter referred to as “SCH symbol”) obtained by modulating the input SCH data (hereinafter referred to as “SCH data”) to the channel selection unit 103. Here, the SCH includes PDSCH (Physical Downlink Shared Channel), P-SCH (Primary-Synchronization Channel), S-SCH (Secondary-Synchronization Channel), and PBCH (Physical Broadcast Channel).

The channel selection unit 103 selects the CCH symbol input from the CCH modulation unit 101 and the SCH symbol input from the SCH modulation unit 102 according to the input symbol number information for each subframe. Specifically, channel selection section 103 selects a CCH symbol when the symbol number of the input symbol number information is t0. Further, the channel selection unit 103 selects nothing when the symbol number of the input symbol number information is t1 to t2. Channel selection section 103 selects an SCH symbol corresponding to each symbol number when the symbol number of the input symbol number information is t3 to t13. Channel selection section 103 then outputs the selected CCH symbol and SCH symbol to resource mapping section 104. Note that the channel selection unit 103 outputs nothing to the resource mapping unit 104 when nothing is selected.

The resource mapping unit 104 arranges the CCH symbol or the SCH symbol input from the channel selection unit 103 on the frequency axis and outputs it to the IFFT unit 105.

Based on the input symbol number information, IFFT section 105 performs an inverse discrete Fourier transform process, which is an OFDM modulation process, on the CCH symbol or SCH symbol input from resource mapping section 104 to form an OFDM signal. Further, IFFT section 105 outputs the formed OFDM signal to transmission power control section 106. The OFDM signal is composed of, for example, 14 OFDM symbols for each subframe. Each OFDM symbol is composed of, for example, 12 subcarriers in a resource block that is a predetermined frequency band.

The transmission power control unit 106 performs transmission power control of PDSCH symbols (data channel symbols) among the SCH symbols of the OFDM signal input from the IFFT unit 105 according to the input symbol number information. At this time, based on the input timing information, transmission power control section 106 performs control to reduce the transmission power of PDSCH symbols that overlap the transmission timing of CCH symbols of neighboring base stations by a predetermined amount. Then, transmission power control section 106 outputs the OFDM signal subjected to transmission power control to addition section 107. Detailed operation in the transmission power control unit 106 will be described later.

The addition unit 107 duplicates the latter half of the OFDM signal input from the transmission power control unit 106 as a CP, and places the duplicated CP at the beginning of the OFDM signal. Further, the adding unit 107 multiplies the CP-added OFDM signal by a window function in order to maintain continuity between adjacent symbols. Further, adding section 107 outputs the OFDM signal multiplied by the window function to transmission timing adjusting section 108.

The transmission timing adjustment unit 108 monitors the timing of the subframe with reference to the input timing information as necessary, and based on the monitoring result, the OFDM signal input from the addition unit 107 is temporally measured in OFDM symbol units. shift. Also, the transmission timing adjustment unit 108 outputs the OFDM signal shifted on the time axis to the RF unit 109. However, when the own station is one of the MeNB and the small eNB, the transmission timing adjustment unit 108 shifts the transmission timing in time in the other one of the neighboring base station, the MeNB and the small eNB. Outputs the OFDM signal input from the adding unit 107 to the RF unit 109 without shifting in time.

The RF unit 109 converts the frequency of the OFDM signal input from the transmission timing adjustment unit 108 from a baseband signal to a high frequency signal and outputs the converted signal to the antenna 110.

The antenna 110 transmits the high-frequency signal input from the RF unit 109 to the communication terminal device 200 described later.

This completes the description of the configuration of the base station apparatus 100.

Next, the configuration of communication terminal apparatus 200 according to Embodiment 1 of the present invention will be described in detail with reference to FIG.

FIG. 2 is a block diagram showing a configuration of communication terminal apparatus 200 according to the present embodiment.

The communication terminal device 200 includes an antenna 201, an RF unit 202, a reception timing adjustment unit 203, a CP removal unit 204, an FFT unit 205, an equalization unit 206, a resource demapping unit 207, and a channel selection unit 208. And synthesizer 209, CCH demodulator 210, and SCH demodulator 211.

The antenna 201 receives a high frequency signal from the base station apparatus 100 and outputs it to the RF unit 202.

The RF unit 202 converts the high-frequency signal input from the antenna 201 into a baseband signal and outputs the baseband signal to the reception timing adjustment unit 203.

The reception timing adjustment unit 203 refers to the input timing information when the OFDM signal received from either the base station apparatus 100 in communication or the small eNB is shifted in time. The OFDM signal, which is a baseband signal input from the RF unit, is shifted on the time axis based on the monitoring result. Specifically, reception timing adjustment section 203 returns to the timing before shifting on the time axis by transmission timing adjustment section 108 of base station apparatus 100. Reception timing adjustment section 203 outputs the OFDM signal shifted in time to CP removal section 204. In addition, the reception timing adjustment unit 203 receives the OFDM signal input from the RF unit 202 when the OFDM signal received from the base station apparatus 100 of either the MeNB or the small eNB in communication is not shifted on the time axis. The signal is output to the CP removing unit 204 without shifting on the time axis.

CP removing section 204 removes the CP from the OFDM signal input from reception timing adjusting section 203 based on a predetermined symbol timing, and outputs the result to FFT section 205.

The FFT unit 205 subjects the OFDM signal input from the CP removal unit 204 to discrete Fourier transform, which is OFDM demodulation, and outputs the result to the equalization unit 206.

The equalization unit 206 extracts a reference signal from the OFDM signal input from the FFT unit 205. Further, the equalization unit 206 obtains a channel response of the propagation path using the extracted reference signal and a replica of the reference signal stored in advance, and obtains the channel estimation value from the obtained channel response of the propagation path. The equalization process is performed. Further, equalization section 206 outputs the OFDM signal after the equalization processing to resource demapping section 207. Here, as a method for obtaining the channel estimation value, various methods such as EGC (Equal Gain Combining) or MMSE (Minimum Mean Square Error) can be used.

The resource demapping unit 207 extracts data necessary for the own station from the OFDM signal input from the equalization unit 206 based on the input symbol number information. Specifically, the resource demapping section 207 extracts the CCH symbol assigned to the own station when the symbol number of the symbol number information is t0 mapping the CCH symbol. Further, when the symbol number of the symbol number information is t3 to t13 mapping the SCH symbol, the resource demapping unit 207 identifies the resource to which the SCH symbol addressed to the own station is allocated from the CCH symbol extracted in advance. Then, only the SCH symbol from the resource is extracted. Resource demapping section 207 then outputs the extracted CCH symbol and SCH symbol to channel selection section 208.

Based on the symbol number information, channel selection section 208 outputs the CCH symbol of symbol number t0 input from resource demapping section 207 to combining section 209, and the SCHs of symbol numbers t3 to t13 input from resource demapping section 207. The symbol is output to SCH demodulating section 211.

The combining unit 209 combines the CCH symbols input from the channel selection unit 208 based on the symbol number information, and outputs the combined CCH symbols to the CCH demodulation unit 210. Here, various synthesis methods such as a simple synthesis method or a weighted synthesis method can be used as the synthesis method.

The CCH demodulator 210 demodulates the CCH symbol input from the combiner 209 and outputs it as CCH data.

The SCH demodulator 211 demodulates the SCH symbol input from the channel selector 208 and outputs it as SCH data. At this time, by performing error correction decoding on the demodulated SCH data by a decoding unit (not shown), it is possible to minimize the deterioration of the PDSCH symbol that has caused the quality deterioration due to the reduction of the transmission power in the base station apparatus 100. it can.

This completes the description of the configuration of the communication terminal apparatus 200.

Next, a transmission power control method in the base station apparatus 100 and the base stations surrounding the base station apparatus 100 will be described with reference to FIG. FIG. 3 is a diagram illustrating a transmission power control method in the base station apparatus 100 and base stations surrounding the base station apparatus 100.

From FIG. 3, downlink frame # 301 is transmitted from the MeNB, and downlink frame # 302 is transmitted from the small eNB. In each frame, the reference signal (RS) (shaded area in FIG. 3) is assigned intermittently.

As shown in FIG. 3, the MeNB transmits the OFDM symbol without shifting in time. On the other hand, the small eNB performs transmission by delaying by 3 OFDM (delay time T) by shifting the time by 3 OFDM symbols with respect to the transmission timing of the MeNB. As a result, the SCH symbol # 320 of the symbol numbers t3 to t4 of the downlink frame # 301 transmitted from the MeNB overlaps with the CCH symbol # 321 of the symbol numbers t0 to t1 of the downlink frame # 302 transmitted from the small eNB on the time axis. .

Therefore, in this embodiment, transmission power control section 106 of MeNB performs PDSCH symbols (symbols in FIG. 3) in SCH symbols # 320 of symbol numbers t3 to t4 that overlap with CCH symbol # 321 on the time axis. Reduce the transmission power. Thereby, in this Embodiment, the quality degradation of the CCH symbol of the small eNB in the communication terminal device 200 can be suppressed.

Next, a method for controlling transmission power in transmission power control section 106 of base station apparatus 100 will be described.

The downlink transmission power control method described in the “Downlink 電力 power allocation” section of 3GPP TS 36.213 5.2 is changed as follows.

That is, when the number of PDSCH symbols for reducing the transmission power is K (K is an arbitrary positive integer), the control for reducing the transmission power with respect to the symbols of symbol numbers t3 to (t3 + K) by the expression (1). I do.

In addition, when the base station apparatus 100 performs MIMO communication, in the case of a 4-cell specific antenna, control to reduce transmission power is performed according to Equation (2).

Further, when the base station apparatus 100 performs MIMO communication, the transmission power is reduced according to the equation (3) when the base station apparatus 100 is other than the 4-cell specific antenna.

FIG. 4 is a diagram illustrating another method of controlling the transmission power between the base station apparatus 100 and the base stations surrounding the base station apparatus 100.

4, the MeNB may reduce the transmission power of the symbol numbers t3 to t5 instead of reducing the transmission power of the symbol numbers t3 to t4.

FIG. 4 shows a reduction in transmission power of 3 OFDM symbols with the maximum number of OFDM symbols that can be allocated to CCH symbols regardless of the number of OFDM symbols to which CCH symbols are actually allocated. As a result, the transmission power control process can be simplified.

As described above, according to the present embodiment, the transmission power of the PDSCH symbol at the transmission timing that overlaps the transmission timing of the CCH symbol of the neighboring base station apparatus is reduced, thereby preventing the quality deterioration of the CCH symbol of the neighboring base station apparatus. Can do. Further, according to the present embodiment, since CCH symbols are not punctured, predetermined resources can be secured. Further, according to the present embodiment, since PDSCH symbols with high transmission power are not concentrated on specific OFDM symbols, it is possible to suppress interference given to neighboring base station apparatuses.

In the present embodiment, the transmission power of the PDSCH symbol that overlaps the CCH symbol is reduced only in the transmission power control unit 106 of the MeNB. However, the present invention is not limited to this, and the CCH only in the transmission power control unit 106 of the small eNB. You may reduce the transmission power of the PDSCH symbol which overlaps with a symbol.

(Embodiment 2)
FIG. 5 is a block diagram showing a configuration of base station apparatus 500 according to Embodiment 2 of the present invention.

5 has a transmission power control unit 501 instead of the transmission power control unit 106. The base station apparatus 500 shown in FIG. In FIG. 5, parts having the same configuration as in FIG. In the present embodiment, the communication terminal apparatus has the same configuration as that shown in FIG.

Base station apparatus 500 includes CCH modulation section 101, SCH modulation section 102, channel selection section 103, resource mapping section 104, IFFT section 105, addition section 107, transmission timing adjustment section 108, and RF section 109. And an antenna 110 and a transmission power control unit 501.

The IFFT unit 105 performs an inverse discrete Fourier transform process, which is an OFDM modulation process, on the CCH symbol or SCH symbol input from the resource mapping unit 104 to form an OFDM signal. Further, IFFT section 105 outputs the formed OFDM signal to transmission power control section 501.

The transmission power control unit 501 performs transmission power control of PDSCH symbols among the SCH symbols of the OFDM signal input from the IFFT unit 105 according to the input symbol number information. At this time, based on the input timing information, transmission power control section 501 performs control to reduce the transmission power of PDSCH symbols that overlap the transmission timing of CCH symbols of neighboring base stations by a predetermined amount. Also, the transmission power control section 501 uses the number of OFDM symbols to reduce transmission power based on information (CFI) on the number of OFDM symbols to which CCH symbols are distributed in the peripheral base station apparatus included in the input peripheral base station information. Is adaptively changed. Then, transmission power control section 501 outputs the OFDM symbol subjected to transmission power control to adding section 107. The detailed operation in the transmission power control unit 501 will be described later.

The addition unit 107 duplicates the latter half of the OFDM signal input from the transmission power control unit 501 as a CP, and places the duplicated CP at the beginning of the OFDM signal. Further, the adding unit 107 multiplies the CP-added OFDM signal by a window function in order to maintain continuity between adjacent symbols. Further, adding section 107 outputs the OFDM signal multiplied by the window function to transmission timing adjusting section 108.

Next, a transmission power control method in the base station apparatus 500 and the base stations surrounding the base station apparatus 500 will be described with reference to FIG. FIG. 6 is a diagram illustrating a transmission power control method in the base station device 500 and base stations surrounding the base station device 500.

6, downlink frame # 601 is transmitted from the MeNB, and downlink frame # 602 is transmitted from the small eNB.

As shown in FIG. 6, the MeNB transmits the OFDM symbol without shifting on the time axis. On the other hand, the small eNB shifts by 3 OFDM symbols with respect to the transmission timing of the MeNB, thereby transmitting with a delay of 3 OFDM. As a result, SCH symbol # 630 of symbol numbers t3 to t4 of subframe # 610 transmitted from MeNB overlaps with CCH symbol # 631 of symbol numbers t0 to t1 of subframe # 620 transmitted from the small eNB on the time axis. .

Therefore, in the present embodiment, MeNB transmission power control section 501 uses PDSCH symbols (symbols in FIG. 6) in SCH symbols # 630 of symbol numbers t3 to t4 that overlap with CCH symbol # 631 on the time axis. Reduce the transmission power.

Also, SCH symbol # 632 of symbol number t3 of subframe # 611 transmitted from the MeNB overlaps with CCH symbol # 633 of symbol number t0 of subframe # 621 transmitted from the small eNB on the time axis.

At this time, in the present embodiment, the transmission power control unit 501 of the MeNB can know the symbol number to which the CCH symbol is mapped in the small eNB from the neighboring base station information. Therefore, the transmission power control unit 501 of the MeNB reduces the transmission power of the PDSCH symbol (the symbol of the shaded portion in FIG. 6) in the SCH symbol # 632 of the symbol number t3 that overlaps the CCH symbol # 633 of the small eNB on the time axis. To do.

The method for controlling the transmission power in transmission power control section 501 of base station apparatus 500 is the same as the method for controlling the transmission power in transmission power control section 106 in the first embodiment, and the description thereof is omitted. To do.

Thus, in the present embodiment, in addition to the effects of the above-described first embodiment, the number of OFDM symbols for reducing transmission power is adaptively set according to the number of OFDM symbols to which the CCH symbols of the neighboring base station apparatuses are allocated. Change. Thereby, according to this Embodiment, compared with the case where the number of OFDM symbols which reduces transmission power is fixed, the characteristic deterioration of the PDSCH symbol which the base station apparatus which reduces transmission power can transmit can be suppressed. .

(Embodiment 3)
FIG. 7 is a diagram illustrating a transmission power control method in the base station apparatus according to Embodiment 3 of the present invention and neighboring base stations of the base station apparatus.

In the present embodiment, the base station apparatus has the same configuration as in FIG. 1, and the communication terminal apparatus has the same configuration as in FIG. Moreover, in the following description, it demonstrates using the code | symbol of FIG.

The base station apparatus 100 according to the present embodiment is only the point that the transmission power control unit 106 always performs control to reduce the transmission power regardless of whether the own station is a MeNB or a small eNB. Different from 1.

7, downlink frame # 701 is transmitted from the MeNB, and downlink frame # 702 is transmitted from the small eNB.

As shown in FIG. 7, the MeNB transmits the OFDM symbol without shifting on the time axis. On the other hand, the small eNB transmits the signal with a delay of 3OFDM by shifting the transmission timing of the MeNB on the time axis by 3OFDM symbols. As a result, SCH symbol # 730 of symbol numbers t3 to t4 of subframe # 710 transmitted from the MeNB overlaps with CCH symbol # 731 of symbol numbers t0 to t1 of subframe # 720 transmitted from the small eNB on the time axis. .

Therefore, in the present embodiment, MeNB transmission power control section 106 uses PDSCH symbols (symbols in FIG. 7) in SCH symbols # 730 of symbol numbers t3 to t4 that overlap with CCH symbol # 731 on the time axis. Reduce the transmission power.

Also, SCH symbol # 732 with symbol number t3 in subframe # 711 transmitted from the MeNB overlaps with CCH symbol # 733 with symbol number t0 in subframe # 721 transmitted from the small eNB on the time axis.

Therefore, the transmission power control unit 106 of the MeNB reduces the transmission power of the PDSCH symbol (the symbol of the shaded portion in FIG. 7) in the SCH symbol # 732 of the symbol number t3 that overlaps the CCH symbol # 733 of the small eNB on the time axis. To do. Further, in this embodiment, in addition to SCH symbol # 732, the transmission power of the PDSCH symbol is also reduced in the SCH symbol of symbol number t4 in subframe # 711. In the case of FIG. 7, the transmission power of the PDSCH symbol does not have to be reduced in the SCH symbol of symbol number t4 in subframe # 711.

Further, SCH symbol # 734 of symbol numbers t11 to t13 of subframe # 720 transmitted from the small eNB overlaps with CCH symbol # 735 of symbol numbers t0 to t2 of subframe # 711 transmitted from the MeNB on the time axis.

Therefore, the transmission power control unit 106 of the small eNB transmits the transmission power of the PDSCH symbol (the symbol of the shaded portion in FIG. 7) in the SCH symbol # 734 of the symbol numbers t11 to t13 that overlaps the CCH symbol # 735 of the MeNB on the time axis. Reduce.

As described above, in the present embodiment, in addition to the effects of the first embodiment, the transmission power of the PDSCH symbol in which the transmission timing and the transmission timing of the CCH symbol of the neighboring base station apparatus overlap in both the MeNB and the small eNB. Reduce. Thereby, according to this Embodiment, the quality degradation of the CCH symbol of all the base station apparatuses can be suppressed.

In Embodiments 1 to 3 above, the transmission power is reduced. However, the present invention is not limited to this, and the PDSCH symbols addressed to communication terminal apparatuses having a low transmission power are sequentially selected, and the selected PDSCH symbols are converted to CCH. You may make it distribute to the OFDM symbol which overlaps with a symbol one by one. Further, in the above-described Embodiments 1 to 3, the transmission timing is shifted on the time axis by 3 OFDM. However, the present invention is not limited to this, and the control channel symbol of the MeNB and the control channel of the small eNB are timed. If mapping is performed so as not to overlap on the axis, there is no need to shift on the time axis.

In Embodiments 1 to 3, the OFDM symbol shift amount on the time axis is 3 OFDM symbols. However, the present invention is not limited to this, and N (N is an arbitrary positive integer). It may be an OFDM symbol.

The disclosure of the specification, drawings and abstract contained in the Japanese application of Japanese Patent Application No. 2010-172375 filed on July 30, 2010 is incorporated herein by reference.

The base station apparatus and transmission power control method according to the present invention provide a downlink control channel when, for example, downlink control channel data of a base station apparatus forming a macro cell interferes with downlink data channel data transmitted from a small base station. It is suitable for mitigating interference with respect to.

DESCRIPTION OF SYMBOLS 100 Base station apparatus 101 CCH modulation part 102 SCH modulation part 103 Channel selection part 104 Resource mapping part 105 IFFT part 106 Transmission power control part 107 Addition part 108 Transmission timing adjustment part 109 RF part 110 Antenna

Claims

A base station apparatus that forms a cell having a different size from a cell formed by a peripheral base station apparatus and communicates using an OFDM scheme that is the same communication scheme as the peripheral base station apparatus,
By performing orthogonal frequency division multiplexing on the data of a plurality of channels, the control data allocated to a predetermined number of symbols from the beginning of the transmission period and the symbols behind the predetermined number of symbols are allocated for each predetermined transmission period. Orthogonal frequency division multiplexing means for generating an OFDM signal including transmission data;
In the OFDM signal, control is performed to reduce the transmission power of the transmission data at a transmission timing overlapping with the transmission timing of the control data of the neighboring base station apparatus, compared to the transmission power of the transmission data at a transmission timing other than the overlapping transmission timing. Transmission power control means to perform,
Transmitting means for transmitting the OFDM signal with transmission power controlled by the transmission power control means;
A base station apparatus comprising:
The apparatus further comprises adjusting means for adjusting the transmission timing of the OFDM signal generated by the orthogonal frequency division multiplexing means so that the transmission timing of the control data in the OFDM signal and the control data of the neighboring base station apparatus do not overlap. ,
The transmission power control means performs the control when the transmission timing of control data of the neighboring base station apparatus overlaps the transmission timing of the transmission data in the OFDM signal whose transmission timing is adjusted by the adjustment means. Item 4. The base station apparatus according to Item 1.
The base station apparatus according to claim 1, wherein the transmission power control means performs the control in symbol units and fixes the number of symbols for reducing transmission power.
2. The base according to claim 1, wherein the transmission power control means performs the control on a symbol-by-symbol basis, and makes the number of symbols for reducing transmission power the same as the maximum number of symbols to which the peripheral base station apparatus can distribute control data. Station equipment.
The transmission power control means performs the control on a symbol-by-symbol basis, and adaptively changes the number of symbols for reducing transmission power according to the number of symbols to which the peripheral base station device distributes control data. Base station device.
The base station apparatus according to claim 1, wherein a cell having a size different from a macro cell formed by the neighboring base station apparatus is formed.
The base station apparatus according to claim 1, wherein a macro cell having a size different from a cell formed by the neighboring base station apparatus is formed.
A transmission power control method in a base station apparatus that forms a cell having a different size from a cell formed by a peripheral base station apparatus and communicates using an OFDM method that is the same communication method as the peripheral base station apparatus,
By performing orthogonal frequency division multiplexing on the data of a plurality of channels, the control data allocated to a predetermined number of symbols from the beginning of the transmission period and the symbols behind the predetermined number of symbols are allocated for each predetermined transmission period. Generating an OFDM signal including transmission data;
In the OFDM signal, control is performed to reduce the transmission power of the transmission data at a transmission timing overlapping with the transmission timing of the control data of the neighboring base station apparatus, compared to the transmission power of the transmission data at a transmission timing other than the overlapping transmission timing. Steps to do,
A transmission power control method comprising: