JP2006211210A - Base station apparatus and resource allocation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a base station apparatus and a resource assigning method capable of selecting an optimum MCS level by taking an amplifier margin obtained through the limitation applied to a frequency band into account in a system wherein the base station apparatus and a plurality of communication terminals carry out wireless communication adopting the OFDM system. <P>SOLUTION: A transmission destination selection section 401 selects a communication terminal being a data transmission destination according to received quality information outputted from a demodulation section 105. An MCS determining section 402 determines a frequency band used for data transmission on the basis of a result of the selection by the transmission destination selection section 401 and also determines a modulation system and a coding rate of the transmission data. A transmission power determining section 403 determines the transmission power on the basis of the frequency bandwidth determined by the MCS determining section 402. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a base station apparatus and resource allocation method used for OFDM wireless communication.

  In HSDPA (High Speed Downlink Packet Access) standardized by 3GPP, a communication terminal apparatus measures reception quality such as SIR (desired wave to interference wave ratio) for each subcarrier and reports it to the base station apparatus. The apparatus allocates radio resources based on reception quality received from a plurality of communication terminal apparatuses, QoS (Quality Of Service) information of the communication terminal apparatuses, and the like.

  In the case of OFDM wireless communication, there are hundreds to thousands of subcarrier resources in the frequency direction, so that the bandwidth of the signal transmitted from the base station apparatus to the communication terminal apparatus becomes very wide. When the base station device transmits a wideband signal, it is difficult to realize an amplifier that amplifies the wideband signal, which makes it difficult for the communication terminal device to secure a desired SIR. For example, in the case of 100 [MHz] bandwidth, if the SIR per 1 [Hz] is made equal to the 5 [MHz] bandwidth, amplification of 20 times that of the 5 [MHz] bandwidth is required.

Several proposals have been made to solve this problem. For example, in Non-Patent Document 1, a communication terminal device to be transmitted is limited to one, and a signal is transmitted not in the entire frequency band but in a part of the frequency band having high reception quality in the communication terminal device to be transmitted ing.
(RCS26) MC-CDMA system using frequency scheduling Yoshitaka Hara, Takashi Kawabata, Takamatsu Dan, Takashi Sekiguchi (Mitsubishi Electric)

  However, the method of Non-Patent Document 1 does not consider the margin of the amplifier obtained by limiting the frequency band.

  The present invention has been made in view of the above points, and in consideration of a margin of an amplifier obtained by limiting a frequency band, a base station apparatus capable of selecting an optimal MCS (Modulation and Coding Scheme) level, and An object is to provide a resource allocation method.

  In order to solve this problem, a base station apparatus of the present invention is a base station apparatus that performs OFDM wireless communication with a plurality of communication terminal apparatuses, and performs communication of data transmission destinations based on reception quality of each communication terminal apparatus A transmission destination terminal selection means for selecting one terminal device and a frequency band used for data transmission based on the reception quality of the communication terminal device of the data transmission destination, and a modulation method and a coding rate of transmission data are determined. A configuration comprising MCS determination means and transmission power determination means for determining transmission power based on the width of the frequency band determined by the MCS determination means is adopted.

  The resource allocation method of the present invention is a resource allocation method in a system in which one base station apparatus and a plurality of communication terminal apparatuses perform OFDM wireless communication, and the data transmission destination is based on the reception quality of each communication terminal apparatus. Selecting one communication terminal apparatus, determining a frequency band used for data transmission based on reception quality of the communication terminal apparatus of the data transmission destination, and determining a modulation scheme and a coding rate of transmission data; And a step of determining transmission power based on the determined width of the frequency band.

  According to the present invention, when transmitting by limiting the frequency band, the transmission power can be increased according to the width of the frequency band, and the MCS level is selected in consideration of the reception SIR that is improved by increasing the transmission power. Therefore, the optimum MCS level can be selected.

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

(Embodiment 1)
First, the configuration of the base station apparatus according to Embodiment 1 of the present invention will be described using the block diagram of FIG. The base station apparatus 100 of FIG. 1 performs wireless communication simultaneously with a plurality of communication terminal apparatuses. Each communication terminal apparatus measures reception quality for each subcarrier, averages reception quality for each subcarrier block in which a plurality of subcarriers are combined, and indicates information indicating an average reception quality of each subcarrier block (hereinafter, “ The reception quality information ”is reported to the base station apparatus 100.

  The duplexer 102 outputs the signal received by the antenna 101 to the wireless reception unit 103. The duplexer 102 wirelessly transmits the signal output from the wireless transmission unit 157 from the antenna 101.

  The radio reception unit 103 converts the radio frequency reception signal output from the duplexer 102 into a baseband signal and outputs the baseband signal to the FFT unit 104. FFT section 104 performs a Fourier transform on the received baseband signal and outputs the signal after the Fourier transform to demodulation section 105.

  As many demodulation units 105 as the number of communication terminal devices that perform wireless communication perform demodulation, error correction decoding, and other processing on the received baseband signal after Fourier transform to obtain received data. Demodulation section 105 also separates reception quality information included in the received signal and outputs it to scheduling section 151.

  Scheduling section 151 selects a data transmission destination communication terminal apparatus based on reception quality information, determines a frequency band used for data transmission, and determines transmission power, modulation scheme, and coding rate of transmission data (resource allocation). ). After performing resource allocation, scheduling section 151 outputs information (hereinafter referred to as “allocation information”) indicating subcarriers used for data transmission, modulation scheme, and coding rate to modulation section 154. In addition, the scheduling unit 151 instructs the transmission data selection unit 152 about the communication terminal device that is the data transmission destination, instructs the modulation unit and coding rate to the modulation unit 153, and instructs the radio transmission unit 157 about the transmission power. Details of the internal configuration of the scheduling unit 151 will be described later.

  The transmission data selection unit 152 selects transmission data to the data transmission destination communication terminal apparatus according to the instruction of the scheduling unit 151, and outputs the transmission data to the modulation unit 153.

  Modulation section 153 performs error correction coding and modulation on the transmission data output from transmission data selection section 152 in accordance with instructions from scheduling section 151, and outputs the result to multiplexing section 155. Modulation section 154 performs error correction coding and modulation on the allocation information and outputs the result to multiplexing section 155.

  The multiplexing unit 155 multiplexes the output signals of the modulation unit 153 and the modulation unit 154 and outputs the multiplexed signals to the IFFT unit 156. IFFT section 156 performs inverse Fourier transform on the output signal of multiplexing section 155 and outputs the signal after inverse Fourier transform to radio transmission section 157.

  The radio transmission unit 157 converts the baseband signal output from the IFFT unit 156 into a radio frequency signal, amplifies the transmission power instructed by the scheduling unit 151, and outputs the signal to the duplexer 102.

  Next, the configuration of the communication terminal apparatus according to the present embodiment will be described using the block diagram of FIG. 2 performs radio communication with the base station apparatus 100 shown in FIG. 1 and receives a radio signal including allocation information and block number information.

  The duplexer 202 outputs the signal received by the antenna 201 to the wireless reception unit 203. Further, the duplexer 202 wirelessly transmits the signal output from the wireless transmission unit 255 from the antenna 201.

  The radio reception unit 203 converts the radio frequency reception signal output from the duplexer 202 into a baseband signal and outputs the baseband signal to the FFT unit 204. FFT section 204 performs Fourier transform on the received baseband signal, and outputs the subcarrier signal indicated in the allocation information after Fourier transform to demodulation section 205.

  Demodulation section 205 performs processing such as demodulation and error correction decoding on the received baseband signal after Fourier transform to obtain received data. Demodulation section 205 also separates allocation information included in the received signal and outputs it to FFT section 204. Demodulation section 205 outputs information necessary for reception quality measurement such as desired wave power and interference wave power obtained in the process of demodulation processing to reception quality measurement section 206.

  Reception quality measurement section 206 measures reception quality for each subcarrier based on the information output from demodulation section 205 and outputs information indicating the measured reception quality to report value generation section 207.

  Report value generation section 207 summarizes a plurality of subcarriers into subcarrier blocks, averages the reception quality measured by reception quality measurement section 206 for each subcarrier block, and indicates the reception quality average value of each subcarrier block Receive quality information is generated. Report value generation section 207 outputs the generated reception quality information to modulation section 252.

  Modulation section 251 performs error correction coding and modulation on the data transmitted to base station apparatus 100 and outputs the result to multiplexing section 253. Modulation section 252 performs error correction coding and modulation on the received quality information and outputs the result to multiplexing section 253.

  The multiplexing unit 253 multiplexes the output signals of the modulation unit 251 and the modulation unit 252 and outputs the multiplexed signal to the IFFT unit 254. IFFT section 254 performs inverse Fourier transform on the output signal of multiplexing section 253, and outputs the signal after inverse Fourier transform to radio transmission section 255. Radio transmission section 255 converts the baseband signal output from IFFT section 254 into a radio frequency signal and outputs the signal to duplexer 202.

  Next, the operation sequence of the base station apparatus and communication terminal apparatus according to the present embodiment will be described using the sequence diagram of FIG. In FIG. 3, it is assumed that the base station apparatus (BTS) is communicating with two communication terminal apparatuses (MS # 1, MS # 2) simultaneously.

  First, the base station apparatus transmits a pilot signal to each communication terminal apparatus (S301, S302).

  Each communication terminal apparatus measures the reception quality of the received pilot signal (S303), averages the reception quality for each subcarrier block (S304), and receives the reception quality information indicating the reception quality average value of each subcarrier block as a base. The data is transmitted to the station device (S305).

  The base station apparatus performs resource allocation for each number of subcarrier blocks indicated in the block number information based on the reception quality information received from each communication terminal apparatus (S306). Specifically, the communication terminal device of the data transmission destination is selected, the frequency band used for data transmission is determined, the transmission power of the transmission data, the modulation method, and the coding rate are determined.

  Then, the base station apparatus transmits allocation information indicating the resource allocation result to each communication terminal apparatus (S307), and transmits data to the communication terminal apparatus (MS # 2 in FIG. 3) determined by resource allocation (S308, S309).

  The communication terminal apparatus (MS # 2) performs Fourier transform on the received signal and the subcarrier indicated in the allocation information to obtain received data (S310).

  Next, scheduling section 151 of base station apparatus 100 will be described in detail with reference to FIGS. FIG. 4 is a block diagram showing an internal configuration of the scheduling unit 151.

  The scheduling unit 151 mainly includes a transmission destination terminal selection unit 401, an MCS determination unit 402, and a transmission power determination unit 403.

  The transmission destination terminal selection unit 401 selects a data transmission destination communication terminal device based on the reception quality information output from the demodulation unit 105 and outputs information indicating the selection result to the transmission data selection unit 152 and the MCS determination unit 402. To do.

  The MCS determination unit 402 determines the frequency band used for data transmission based on the selection result of the transmission destination terminal selection unit 401, and determines the modulation method and coding rate of transmission data. MCS determination section 402 outputs information indicating the determined frequency band to transmission power determination section 403, and outputs information indicating the modulation scheme and coding rate of transmission data to modulation section 153 and modulation section 154.

  The transmission power determination unit 403 determines transmission power based on the frequency band width determined by the MCS determination unit 402, and outputs information indicating the determined transmission power to the wireless transmission unit 157 and the MCS determination unit 402.

  Hereinafter, a specific example of processing of the transmission destination terminal selection unit 401 will be described with reference to FIG. FIG. 5 is a diagram illustrating reception quality measurement results of two communication terminal apparatuses (MS # 1, MS # 2) with which the base station apparatus communicates. FIG. 5 shows a case where communication is performed with 40 subcarriers and 5 subcarrier blocks (SB1 to SB5). In FIG. 5, the horizontal axis indicates the frequency, the vertical axis indicates the reception SIR, the measurement value 511 is the reception SIR of MS # 1, the measurement value 521 is the reception SIR of MS # 2, and the average values 512-1 to 512-5 are MS. The average values and average values 522-1 to 522-5 of each subcarrier block of # 1 indicate the average values of reception SIR of each subcarrier block of MS # 2. MS # 1 and MS # 2 transmit average values 512-1 to 512-5 and average values 522-1 to 522-5, respectively, as reception quality information to base station apparatus 100. In the case of FIG. 5A, since the average value 522-3 is the highest in the reception quality information, the transmission destination terminal selection unit 401 selects MS # 2 as the data transmission destination.

  Next, specific examples of processing performed by the MCS determination unit 402 and the transmission power determination unit 403 will be described with reference to FIGS. FIG. 6 is a diagram illustrating an example of the MCS table held by the MCS determination unit 402. The MCS table indicates the range of SIR to which each MCS level (modulation scheme and coding rate) is assigned. For example, if the reception quality information is between α [dB] and β [dB], MCS2 (modulation method is QPSK and coding rate R is 3/4) is assigned. In the case of FIG.5 (b), since the average value 522-3 of subcarrier block SB3 is the highest, and only this average value exists in the range to which MCS3 is allocated, the MCS determination part 402 selects the frequency band used for data transmission. SB3.

FIG. 7 is a diagram illustrating an example of a table held by the transmission power determination unit 403. The table in FIG. 7 shows the relationship between the frequency bandwidth, transmission power, and improved reception SIR. For example, when the MCS determination unit 402 selects only SB3 as the frequency band used for data transmission, since the width of the frequency band, that is, the number of subcarriers is 8, the transmission power determination unit 403 determines the transmission power TP ₁ . . Further, from FIG. 7, the improved reception SIR when the transmission power TP ₁ is set is ΔdB ₁
Therefore, the transmission power determination unit 403 outputs ΔdB ₁ to the MCS determination unit 402.

Since the reception SIR is improved by increasing the transmission power, the MCS determination unit 402 calculates the reception SIR 531 by correcting by adding ΔdB ₁ to the average value 522-3. As a result, as shown in FIGS. 5B and 6, since the reception SIR 531 is larger than γ [dB], the MCS determination unit 402 sets the MCS level of the transmission data to MCS4 (modulation method is 16QAM, coding rate R Is 3/4).

  As described above, according to the present embodiment, when transmitting by limiting the frequency band, the transmission power can be increased according to the width of the frequency band, and the reception SIR improved by increasing the transmission power is considered. Since the MCS level can be selected, the optimum MCS level can be selected.

  When the correction value obtained by adding the improved reception SIR to the maximum value of the reception quality information is less than the minimum value of the MCS table (α [dB] in FIG. 6), the correction value of the reception quality information is equal to or greater than the minimum value of the MCS table. The frequency bandwidth may be narrowed until

  Conversely, when the correction value obtained by adding the improved reception SIR to the maximum value of the reception quality information is higher than the maximum value of the MCS table (γ [dB] in FIG. 6), the correction value of the reception quality information is less than the maximum value of the MCS table. The frequency bandwidth may be increased until

  FIG. 8 is a flowchart showing a processing flow of the MCS determination unit 402 and the transmission power determination unit 403 in this case. First, the MCS determination unit 402 determines the frequency band (S801), and the transmission power determination unit 403 determines the transmission power (S802).

  Then, the MCS determination unit 402 calculates the reception quality correction value by adding the improved reception SIR to the maximum value of the reception quality information (S803). If this correction value is less than the minimum MCS (S804: NO), the MCS determination is performed. The unit 402 narrows the frequency band (S805). On the other hand, when the correction value is larger than the maximum MCS (S806: YES), the MCS determination unit 402 widens the frequency band (S807). When this correction value is not less than the minimum MCS (S804: YES) and not more than the maximum MCS (S806: NO), the MCS determination unit 402 finally determines the MCS level.

  The present invention is suitable for use in base station apparatuses and communication terminal apparatuses that perform OFDM wireless communication.

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 which concerns on the said embodiment. The sequence diagram which shows the operation | movement order of the base station apparatus and communication terminal device which concern on the said embodiment The block diagram which shows the internal structure of the scheduling part of the base station apparatus which concerns on the said embodiment. The figure which shows an example of the reception quality measurement result of the two communication terminal devices with which the base station apparatus which concerns on the said embodiment communicates The figure which shows an example of the MCS table which the MCS determination part of the base station apparatus which concerns on the said embodiment hold | maintains. The figure which shows an example of the table which the transmission power determination part of the base station apparatus which concerns on the said embodiment hold | maintains. The flowchart which shows the flow of a process of the MCS determination part of the base station apparatus which concerns on the said embodiment, and a transmission power determination part

Explanation of symbols

100, 400, 600 Base station apparatus 104 FFT section 105 Demodulation section 151 Scheduling section 152 Transmission data selection section 153, 154 Modulation section 155 Multiplexing section 156 IFFT section 200, 500, 700 Communication terminal apparatus 204 FFT section 205 Demodulation section 206 Reception quality Measurement unit 207, 507, 707 Report value generation unit 251, 252 Modulation unit 253 Multiplexing unit 254 IFFT unit 401 Transmission destination terminal selection unit 402 MCS determination unit 403 Transmission power determination unit

Claims (5)

A base station device that performs OFDM wireless communication with a plurality of communication terminal devices,
A destination terminal selection means for selecting one communication terminal device as a data transmission destination based on the reception quality of each communication terminal device;
MCS determination means for determining a frequency band used for data transmission based on the reception quality of the communication terminal device of the data transmission destination, and determining a modulation scheme and a coding rate of transmission data;
A base station apparatus comprising: transmission power determination means for determining transmission power based on a frequency band width determined by the MCS determination means.   The MCS determination means corrects the reception quality of the communication terminal device of the data transmission destination by the reception quality improved by increasing the transmission power, and determines the modulation scheme and coding rate of the transmission data based on the reception quality correction value. The base station apparatus according to claim 1 to be determined.   The base station apparatus according to claim 2, wherein the MCS determination means narrows the width of the frequency band when the reception quality correction value is less than a predetermined first threshold value.   The base station apparatus according to claim 2 or 3, wherein the MCS determination means widens a frequency band when the reception quality correction value is larger than a predetermined second threshold value. A resource allocation method in a system in which one base station apparatus and a plurality of communication terminal apparatuses perform OFDM wireless communication,
Selecting one communication terminal device as a data transmission destination based on the reception quality of each communication terminal device;
Determining a frequency band to be used for data transmission based on the reception quality of the communication terminal device of the data transmission destination, and determining a modulation method and a coding rate of transmission data;
Determining a transmission power based on the width of the determined frequency band.

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