JP2006303698A - Base station apparatus and modulation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely improve the transmission efficiency, while decreasing the feedback information amount. <P>SOLUTION: A transmission mode selection section 205 compares the maximum Doppler frequency with a prescribed threshold, decides that fading variations between a mobile station apparatus and a base station apparatus are rapid and the reception quality is rapidly varying, when the maximum Doppler frequency is the prescribed threshold or higher, and selects hierarchy modulation as a transmission mode. The transmission mode selection section 205 decides that fading variations between the mobile station apparatus and the base station apparatus are slow, and the reception quality does not vary so much, when the maximum Doppler frequency is lower than the prescribed threshold, and selects adaptive modulation as the transmission mode. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a base station apparatus and a modulation method, and more particularly to a base station apparatus and a modulation method in a wireless communication system in which a coding rate and a modulation multi-level number are variable.

  Conventionally, for example, Patent Document 1 and the like have studied the introduction of hierarchical modulation as a modulation method in a wireless communication system. Hierarchical modulation is a technique in which a plurality of bits assigned to one symbol are hierarchized into bits that are easy to error and bits that are hard to error, and bits in the same layer are used as a unit for error correction coding. That is, for example, when the modulation multi-level number is 16QAM (Quadrature Amplitude Modulation), the transmission side performs gray mapping for assigning, for example, 4 bits as shown in FIG. Error correction coding is separately performed on the lower layer and the lower 2 bits that are likely to be erroneous, and the receiving side performs threshold determination on the received symbol and retransmits only the bits of the layer that cannot be accurately demodulated to the transmitting side. Request.

  More specifically, for example, in 16QAM, 4 bits are allocated to each of 16 signal points on the IQ plane and modulated, but the transmitting side that performs hierarchical modulation only has 1 bit out of 4 bits at adjacent signal points. Are modulated by assigning different bit sequences. By performing such modulation, all the first bits are 0 in the region where the I component is positive, and all the first bits are 1 in the region where the I component is negative. In the area where the Q component is positive, all the second bits are 0, and in the area where the Q component is negative, all the second bits are 1. Similarly, in the region including the four signal points in the Q-axis direction, the third bit is 0 in the region including the inner two columns close to the Q axis, and the third bit is 1 in the region including the outer two columns. Become. Further, among the areas including the four signal points in the I-axis direction, the fourth bit is 0 in the area including the two inner lines close to the I axis, and the fourth bit is 1 in the area including the outer two lines. .

  Using such a property, the reception side performs threshold determination on the IQ plane of the reception symbol position. In other words, for example, by using the Q axis and the I axis as the determination axes, it is determined whether the first bit and the second bit are 0 or 1, and the inner rows and columns in the Q axis direction and the I axis direction, respectively. It is determined whether the third bit and the fourth bit are 0 or 1 by using the center line between the first row and the outer row / column as a determination axis.

  At this time, the third and fourth bits are likely to be erroneous when the received symbol position is closer to the determination axis than the first and second bits, and the reception quality is poor. When the reception quality is poor and only the third and fourth bits are wrong, the receiving side requests the transmitting side to retransmit only the third and fourth bit layers. This is equivalent to the transmission of 2 bits in one symbol, and the transmission efficiency is the same as when QPSK modulation is performed on the transmission side.

  As described above, in the hierarchical modulation, if the reception quality is poor, the transmission efficiency is equal to or lower than that in the case of modulation with a modulation multilevel number (for example, QPSK) smaller than the actual modulation multilevel number (for example, 16QAM). However, if the reception quality is good, transmission efficiency commensurate with the actual modulation multilevel number (for example, 16QAM) can be realized. Even when reception quality is poor, information is reliably transmitted by retransmission in bit units of the same layer. Therefore, in hierarchical modulation, by making the modulation multi-level number relatively large, it is possible to transmit bits with a transmission efficiency corresponding to the reception quality without feeding back the reception quality information from the reception side to the transmission side. Will be done.

Therefore, the amount of feedback information is reduced to reduce the burden on the line from the reception side to the transmission side, compared to adaptive modulation in which the reception quality information is fed back from the reception side to the transmission side as needed to switch the modulation level. Can do.
JP 2000-31944 A

  However, in general, when the power per symbol is the same, the larger the modulation multi-value number, the closer the distance between the signal point position and the determination axis on the receiving side, so when the reception quality is poor, When the modulation multi-level number is increased, there is a problem that transmission efficiency may be lowered. That is, for example, as shown in FIG. 7A, when a symbol modulated by 16QAM corresponding to the bit string “0010” is received at the position of a white point in the figure due to the influence of fading, this symbol is I Since it fluctuates across the axes, demodulation of the second bit, which is the upper bit, is not accurately performed. However, when symbols modulated by QPSK corresponding to the bit string “00” are transmitted in the same propagation environment, the symbol position at the time of reception is within the same region as at the time of transmission, as shown in FIG. Demodulation is performed accurately.

  In 16QAM, 3 points out of 4 points that are in the positive region for both the I component and Q component are the I axis that is the determination axis for the higher 2 bits than one point in the positive region for both the I component and Q component in QPSK. Or it is close to the Q axis, and it is easy to make an error when the reception quality is poor. Therefore, as a whole, when the reception quality is poor, even in hierarchical modulation, 16QAM is more likely to cause errors than QPSK, and the transmission efficiency is likely to decrease.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a base station apparatus and a modulation method capable of reliably improving transmission efficiency while reducing the amount of feedback information.

  A base station apparatus according to the present invention is obtained by being modulated with modulation means for modulating a signal for the mobile station apparatus in a transmission mode of either hierarchical modulation or adaptive modulation in accordance with variation in reception quality in the mobile station apparatus. And a transmission means for transmitting the received signal.

  The modulation method according to the present invention includes a step of selecting a transmission mode of either hierarchical modulation or adaptive modulation according to a change in reception quality in a mobile station device, and modulating a signal for the mobile station device in the selected transmission mode And a step of performing.

  According to these, since the signal is modulated in a transmission mode according to the variation in reception quality in the mobile station device, when the variation in reception quality is large, hierarchical modulation that does not require reception quality feedback from the mobile station device is performed. On the other hand, when the variation in reception quality is small, adaptive modulation can be performed by extending the feedback period of reception quality from the mobile station apparatus. As a result, it is possible to reliably improve transmission efficiency while reducing the amount of feedback information.

  According to the present invention, it is possible to reliably improve transmission efficiency while reducing the amount of feedback information.

  The gist of the present invention is that, when it is determined that the maximum Doppler frequency is large and fading fluctuation is abrupt, the transmission mode using hierarchical modulation is selected as the modulation method, and it is determined that the maximum Doppler frequency is small and fading fluctuation is slow. If so, it is to select a transmission mode that uses adaptive modulation as the modulation scheme.

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

  FIG. 1 is a block diagram showing a main configuration of a mobile station apparatus according to an embodiment of the present invention. The mobile station apparatus shown in the figure includes an RF (Radio Frequency) reception unit 101, a demodulation unit 102, an error correction decoding unit 103, a separation unit 104, a CRC (Cyclic Redundancy Check) check unit 105, a reception It has a quality measurement unit 106, a reception quality information generation unit 107, a maximum Doppler frequency measurement unit 108, a maximum Doppler frequency information generation unit 109, a multiplexing unit 110, an error correction encoding unit 111, a modulation unit 112, and an RF transmission unit 113. ing.

  The RF receiving unit 101 receives a signal from a base station apparatus (to be described later) via an antenna, and performs predetermined radio reception processing (down-conversion, A / D conversion, etc.) on the received signal.

  Demodulation section 102 demodulates the received signal with reference to transmission parameter information notified from the base station apparatus, and obtains the demodulated data obtained by error correction decoding section 103, reception quality measurement section 106, and maximum Doppler frequency measurement section 108. Output to.

  Error correction decoding section 103 performs error correction decoding on the demodulated data with reference to transmission parameter information notified from the base station apparatus, and outputs the obtained decoded data to demultiplexing section 104.

  Separating section 104 extracts the received data from the decoded data and outputs it, and also outputs transmission parameter information included in the decoded data to demodulation section 102 and error correction decoding section 103, and performs CRC check on the CRC bits included in the decoded data And outputs the reception quality report cycle information included in the decoded data to reception quality information generation section 107.

  The CRC check unit 105 performs error detection of the decoded data using the CRC bits, generates retransmission request information according to the error detection result, and outputs the retransmission request information to the multiplexing unit 110. Note that the CRC check unit 105 generates retransmission request information for requesting retransmission in bit units when the base station apparatus performs hierarchical modulation.

  Reception quality measuring section 106 measures reception quality using demodulated data. Reception quality measuring section 106 measures reception quality as needed, and outputs the measurement result to reception quality information generating section 107.

  Reception quality information generation section 107 generates reception quality information for reporting the reception quality to the base station apparatus for each reception quality report period in accordance with the reception quality report period information output from demultiplexing section 104, and to multiplexing section 110 Output. The reception quality information includes an instantaneous value of reception quality for each reception quality report period or an average value of reception quality for a predetermined period. The reception quality information is used when transmission parameters for each mobile station apparatus are determined in the base station apparatus.

  The maximum Doppler frequency measurement unit 108 measures the maximum Doppler frequency every predetermined period using the demodulated data. The maximum Doppler frequency is an indicator of fading fluctuations. That is, if the maximum Doppler frequency is large, the fading fluctuation is considered to be abrupt, while if the maximum Doppler frequency is small, the fading fluctuation is considered to be slow. The period in which the maximum Doppler frequency measurement unit 108 measures the maximum Doppler frequency is sufficiently longer than the reception quality report period.

  Maximum Doppler frequency information generation section 109 generates maximum Doppler frequency information for reporting the maximum Doppler frequency measured by maximum Doppler frequency measurement section 108 to the base station apparatus, and outputs the maximum Doppler frequency information to multiplexing section 110. The maximum Doppler frequency information is used in the base station apparatus when determining whether the transmission mode is hierarchical modulation or adaptive modulation.

  Multiplexer 110 multiplexes retransmission request information, reception quality information, maximum Doppler frequency information, and transmission data, and outputs the obtained multiplexed data to error correction encoder 111. Note that the multiplexed transmission data includes information related to a reception quality measurement error in the reception quality measurement unit 106.

  The error correction encoding unit 111 performs error correction encoding on the multiplexed data and outputs the obtained encoded data to the modulation unit 112.

  Modulation section 112 modulates the encoded data and outputs the obtained modulated data to RF transmission section 113.

  The RF transmission unit 113 performs predetermined radio transmission processing (D / A conversion, up-conversion, etc.) on the modulated data, and transmits the modulated data to the base station apparatus via the antenna.

  FIG. 2 is a block diagram showing a main configuration of the base station apparatus according to one embodiment. The base station apparatus shown in the figure includes an RF reception unit 201, a demodulation unit 202, an error correction decoding unit 203, a separation unit 204, a transmission mode selection unit 205, a reception quality report cycle determination unit 206, a resource allocation unit 207, and a buffer unit 208. A transmission parameter setting unit 209, a multiplexing unit 210, an error correction coding unit 211, a modulation unit 212, and an RF transmission unit 213.

  The RF receiving unit 201 receives a signal from the mobile station apparatus via an antenna and performs predetermined radio reception processing (down-conversion, A / D conversion, etc.) on the received signal.

  Demodulation section 202 demodulates the received signal and outputs the obtained demodulated data to error correction decoding section 203.

  The error correction decoding unit 203 performs error correction decoding on the demodulated data and outputs the obtained decoded data to the separation unit 204.

  Separating section 204 extracts and outputs received data from decoded data, and outputs maximum Doppler frequency information and reception quality measurement error information included in the decoded data to transmission mode selecting section 205 to receive the received data included in the decoded data. The quality information is output to the resource allocation unit 207.

  The transmission mode selection unit 205 selects either hierarchical modulation or adaptive modulation as the transmission mode according to the information on the maximum Doppler frequency information and the reception quality measurement error. Specifically, the transmission mode selection unit 205 compares the maximum Doppler frequency with a predetermined threshold, and when the maximum Doppler frequency is equal to or higher than the predetermined threshold, fading fluctuation between the mobile station apparatus and the base station apparatus is abrupt. Therefore, it is determined that the reception quality fluctuates drastically, and hierarchical modulation is selected as the transmission mode. Hierarchical modulation can achieve transmission efficiency according to reception quality without feedback of reception quality information from the mobile station apparatus to the base station apparatus even when the reception quality changes abruptly. It can be said that this is a suitable transmission mode when there is a severe situation. Further, while the reception quality is good even for a short time, the transmission efficiency can be improved to the maximum by selecting the hierarchical modulation in which the modulation multi-level number is set larger as the transmission mode.

  On the other hand, when the maximum Doppler frequency is less than the predetermined threshold, the transmission mode selection unit 205 determines that the fading fluctuation between the mobile station apparatus and the base station apparatus is slow and the reception quality does not fluctuate so much. To select adaptive modulation. In adaptive modulation, reception quality information is fed back from the mobile station apparatus to the base station apparatus, and the modulation multi-level number is finely controlled. Therefore, modulation is performed with the modulation multi-level number optimal for the reception quality, and an error occurs. The transmission efficiency can be improved reliably. If the reception quality does not fluctuate so much, feedback of reception quality information may be performed in a relatively long period even in adaptive modulation, and even if adaptive modulation is selected as the transmission mode, an increase in the amount of feedback information is suppressed. .

  Also, the transmission mode selection unit 205 considers not only the maximum Doppler frequency but also the reception quality measurement error, and when the reception quality measurement error is equal to or greater than a predetermined threshold, the reception quality error reported from the mobile station apparatus. In order to absorb this, hierarchical modulation is selected as the transmission mode. On the other hand, if the reception quality measurement error is less than a predetermined threshold, adaptive modulation is selected as the transmission mode. Note that the transmission mode selection unit 205 may select the transmission mode based on threshold determination of only one of the maximum Doppler frequency and the reception quality measurement error.

  Then, transmission mode selection section 205 notifies the selected transmission mode to reception quality report cycle determination section 206 and resource allocation section 207.

  Reception quality reporting period determining section 206 determines a period for causing the mobile station apparatus to report reception quality based on the transmission mode and the maximum Doppler frequency. Specifically, the reception quality report cycle determination unit 206 shortens the reception quality report cycle when the transmission mode is adaptive modulation than when the transmission mode is hierarchical modulation, and when the transmission mode is adaptive modulation, When the maximum Doppler frequency is larger than when it is small, the reception quality reporting period is shortened. That is, the reception quality report cycle determination unit 206 shortens the reception quality report cycle the shortest when the maximum Doppler frequency is slightly smaller than the predetermined threshold and adaptive modulation is selected as the transmission mode. This reception quality report period is determined to be less than the time when the reception quality fluctuates to the extent that the modulation multi-level number and the coding rate should be changed in the transmission modes of hierarchical modulation and adaptive modulation. Therefore, when hierarchical modulation that does not depend much on reception quality is selected as the transmission mode, the reception quality report cycle may be set to a relatively long cycle. Reception quality report cycle determining section 206 then outputs the reception quality report cycle information to multiplexing section 210.

  Resource allocation section 207 selects a mobile station apparatus as a signal transmission destination according to reception quality information reported from a plurality of mobile station apparatuses, and encodes and modulates multi-levels corresponding to each selected mobile station apparatus Determine transmission parameters such as number. Specifically, as shown in FIG. 3, the resource allocation unit 207 includes a mobile station selection unit 2071, a transmission parameter determination unit 2072, an MCS (Modulation Coding Scheme) table 2073, and a maximum modulation multilevel number table 2074. ing.

  The mobile station selection unit 2071 refers to reception quality information reported from all the mobile station devices in the cell covered by the base station device shown in FIG. 2, selects a mobile station device with good reception quality, and selects it. It is determined that a signal is transmitted to the received mobile station apparatus. Note that the mobile station selection unit 2071 may select a mobile station apparatus having a reception quality equal to or higher than a predetermined level, or may select a predetermined number of mobile station apparatuses in order of good reception quality.

  Transmission parameter determination section 2072 determines transmission parameters corresponding to the transmission mode and reception quality for each mobile station apparatus selected as the signal transmission destination. That is, when the transmission mode is adaptive modulation, transmission parameter determination section 2072 refers to MCS table 2073 to determine the coding rate and modulation multilevel number (MCS) corresponding to the reception quality. In addition, when the transmission mode is hierarchical modulation, the transmission parameter determination unit 2072 refers to the maximum modulation multilevel number table 2074 to determine the modulation multilevel number (maximum modulation multilevel number) in hierarchical modulation corresponding to the reception quality. decide. Transmission parameter determination section 2072 outputs transmission parameter information indicating the determined transmission parameter and allocation information indicating the selected mobile station apparatus to buffer section 208 and transmission parameter setting section 209.

  The MCS table 2073 stores a coding rate and a modulation multilevel number (MCS) corresponding to reception quality when the transmission mode is adaptive modulation.

  The maximum modulation multilevel number table 2074 stores a modulation multilevel number (maximum modulation multilevel number) corresponding to the reception quality when the transmission mode is hierarchical modulation.

  Referring to FIG. 2 again, buffer section 208 temporarily accumulates transmission data to each mobile station apparatus, and transmits to each mobile station apparatus as a signal transmission destination at a rate according to transmission parameter information and allocation information. The data is output to the multiplexing unit 210.

  The transmission parameter setting unit 209 refers to the transmission parameter information and the allocation information, and transmits the transmission parameters (that is, the coding rate, the modulation multi-level number, etc.) corresponding to each mobile station apparatus as the signal transmission destination to the error correction coding unit. 211 and the modulation unit 212.

  Multiplexing section 210 multiplexes reception quality report cycle information, transmission parameter information, allocation information, and transmission data, and outputs the obtained multiplexed data to error correction encoding section 211.

  Error correction coding section 211 performs error correction coding on the multiplexed data at the coding rate set by transmission parameter setting section 209, and outputs the obtained coded data to modulation section 212.

  Modulation section 212 modulates the encoded data with the modulation multilevel number set by transmission parameter setting section 209 and outputs the obtained modulated data to RF transmission section 213.

  The RF transmission unit 213 performs predetermined wireless transmission processing (D / A conversion, up-conversion, etc.) on the modulated data, and transmits it via an antenna.

  Next, operations of the mobile station apparatus and base station apparatus configured as described above will be described with reference to the sequence diagram shown in FIG. 4 and the flowchart shown in FIG.

  In general, a base station apparatus always transmits a pilot signal using a common pilot channel or the like. This pilot signal is received via the antenna of the mobile station apparatus shown in FIG. 1, and a predetermined radio reception process is performed by the RF receiving unit 101.

  The received signal is demodulated by the demodulator 102, and the maximum Doppler frequency measurement unit 108 measures the maximum Doppler frequency (301). The maximum Doppler frequency is large when fading fluctuation is abrupt, such as when the moving speed of the mobile station apparatus is fast, and small when fading fluctuation is slow. When the maximum Doppler frequency is measured, the maximum Doppler frequency information generation unit 109 generates maximum Doppler frequency information, and the maximum Doppler frequency information is multiplexed with transmission data such as reception quality measurement error information by the multiplexing unit 110. At this time, retransmission request information generated by the CRC check unit 105 and reception quality information generated by the reception quality information generation unit 107 may be multiplexed by the multiplexing unit 110.

  Multiplexed data including maximum Doppler frequency information and reception quality measurement error is subjected to error correction coding by the error correction coding unit 111, modulated by the modulation unit 112, and transmitted from the RF transmission unit 113 to the base station apparatus via the antenna. (302).

  A signal including maximum Doppler frequency information and reception quality measurement error information is received via the antenna of the base station apparatus shown in FIG. 2, and predetermined radio reception processing is performed by the RF reception unit 201. Although omitted in FIG. 4, the base station apparatus shown in FIG. 2 receives signals including maximum Doppler frequency information and reception quality measurement error information from all mobile station apparatuses in the cell covered by the base station apparatus.

  The received signal is demodulated by demodulator 202, error-correction-decoded by error correction decoder 203, and maximum Doppler frequency information and reception quality measurement error information are output to transmission mode selector 205 by separator 204. At this time, if reception quality information is included in the received signal, the separation unit 204 outputs it to the resource allocation unit 207.

  The maximum Doppler frequency information and reception quality measurement error information are used by the transmission mode selection unit 205 to select a transmission mode. That is, the processing shown in the flowchart of FIG. 5 is performed by the transmission mode selection unit 205, and the transmission mode of each mobile station apparatus is determined to be either hierarchical modulation or adaptive modulation (303).

  Specifically, as shown in FIG. 5, first, the maximum Doppler frequency is compared with a predetermined threshold Th1 (ST1000). As a result of the comparison, when the maximum Doppler frequency is equal to or higher than the threshold Th1, fading fluctuation is abrupt, and reception quality information needs to be frequently fed back in order to perform adaptive modulation. Therefore, hierarchical modulation is selected as the transmission mode. (ST1300).

  On the other hand, if the maximum Doppler frequency is less than the threshold value Th1 as a result of the comparison in ST1000, it is determined that the fading fluctuation is slow, and the reception quality measurement error is compared with a predetermined threshold value Th2 (ST1100). As a result of the comparison, when the reception quality measurement error is equal to or greater than the threshold Th2, the reliability of the reception quality information fed back from the mobile station apparatus is low, and it is difficult to determine an appropriate transmission parameter in adaptive modulation. Hierarchical modulation is selected as ST1300.

  Further, if the reception quality measurement error is less than the predetermined threshold Th2 as a result of the comparison in ST1100, the reliability of the reception quality information fed back from the mobile station apparatus is high, and fine transmission parameters can be determined by adaptive modulation. Therefore, adaptive modulation is selected as the transmission mode (ST1200).

  Then, it is determined whether or not the above processing has been completed for all mobile station apparatuses in the cell (ST1400), and if not completed, the processing is repeated again from ST1000.

  When the transmission mode for each mobile station apparatus is determined in this way, this transmission mode is notified to the reception quality report period determining unit 206 and the resource allocating unit 207 together with the maximum Doppler frequency. Then, reception quality reporting period determining section 206 determines a reception quality reporting period T by each mobile station apparatus (304), and outputs reception quality reporting period information to multiplexing section 210. Here, the reception quality report period T is long when the transmission mode is hierarchical modulation and short when it is adaptive modulation. Further, when the transmission mode is adaptive modulation, the reception quality reporting period T is longer as the maximum Doppler frequency is smaller and shorter as it is larger.

  As described above, the hierarchical modulation is transmitted preferentially from the upper bits with the transmission efficiency corresponding to the reception quality regardless of whether the reception quality is reported. For this reason, when the transmission mode is hierarchical modulation, it is not necessary to shorten the reception quality reporting period T. Further, when the maximum Doppler frequency is small, fading fluctuation is slow and reception quality does not fluctuate so much, so that it is not necessary to shorten the reception quality reporting period T. In the present embodiment, the transmission mode is adaptive modulation only when the maximum Doppler frequency is small. Therefore, even when the transmission mode is adaptive modulation, it is not necessary to excessively shorten the reception quality report period T. Therefore, the reception quality reporting cycle T can be lengthened as a whole, and an increase in the amount of feedback information can be suppressed.

  The reception quality report cycle information is transmitted from the multiplexing unit 210 via the RF transmission unit 213 via the antenna (305). This transmission signal includes reception quality report cycle information for each mobile station apparatus in the cell.

  A signal including reception quality report cycle information is received via the antenna of the mobile station apparatus shown in FIG. 1, and predetermined radio reception processing is performed by the RF reception unit 101. The received signal is output to separation section 104 via demodulation section 102 and error correction decoding section 103, and reception quality report cycle information is output to reception quality information generation section 107 by separation section 104.

  Then, the reception quality information generating unit 107 generates reception quality information for each reporting period specified by the reception quality reporting period information (306). The reception quality measurement unit 106 always measures reception quality using the above-described pilot signal and the like, and outputs the measurement result to the reception quality information generation unit 107. Therefore, reception quality information generation section 107 outputs an instantaneous value of reception quality or an average value of reception quality from the previous reporting time to the current reporting time, etc., as reception quality information for each reporting period to multiplexing section 110. The reception quality information is multiplexed with retransmission request information and transmission data as required by the multiplexing unit 110, and the obtained multiplexed data is transmitted from the error correction encoding unit 111 via the RF transmission unit 113 via the antenna. It is transmitted to the base station apparatus (307).

  A signal including reception quality information is received via the antenna of the base station apparatus shown in FIG. 2, and a predetermined radio reception process is performed by the RF reception unit 201. Although omitted in FIG. 4, the base station apparatus shown in FIG. 2 receives signals including reception quality information from all mobile station apparatuses in the cell.

  The received signal is output from demodulating section 202 via demultiplexing section 204 and reception quality information is output to mobile station selecting section 2071 in resource allocating section 207. Also, the transmission parameter determination unit 2072 in the resource allocation unit 207 is already notified of the transmission mode of each mobile station apparatus from the transmission mode selection unit 205. Thus, the resource allocation unit 207 determines the transmission parameters and the like to be allocated to each mobile station apparatus, and performs resource allocation (308).

  Specifically, the mobile station selection unit 2071 selects a mobile station device with good reception quality as the mobile station device that is the signal transmission destination, and notifies the transmission parameter determination unit 2072 of the selected mobile station device. . Then, the transmission parameter determination unit 2072 refers to the MCS table 2073 or the maximum modulation multilevel number table 2074 according to the transmission mode and reception quality for each mobile station apparatus, and encodes and modulates the coding rate and modulation corresponding to each mobile station apparatus. Transmission parameters such as multi-value numbers are determined. At this time, the MCS corresponding to the reception quality is determined from the MCS table 2073 for the mobile station apparatus whose transmission mode is adaptive modulation, and the mobile station apparatus whose transmission mode is hierarchical modulation is received from the maximum modulation multilevel number table 2074. The maximum modulation multi-value number according to the quality is determined.

  Then, transmission parameter information indicating the transmission parameter determined by transmission parameter determining section 2072 and allocation information indicating the mobile station apparatus to which the resource is allocated are output to buffer section 208 and transmission parameter setting section 209. When the transmission parameter information and the allocation information are output to the buffer unit 208, these information are transmitted from the multiplexing unit 210 via the RF transmission unit 213 via the antenna (309).

  A signal including transmission parameter information and allocation information is received by each mobile station apparatus in the cell, and each mobile station apparatus determines whether or not a signal is transmitted to the own apparatus, and the signal is transmitted. In this case, the modulation multi-level number in the demodulation unit 102 and the coding rate in the error correction decoding unit 103 are appropriately set according to the transmission parameter information.

  On the other hand, after transmitting the transmission parameter information and the allocation information, the base station apparatus performs transmission processing on the transmission data (310). That is, transmission parameter setting section 209 sets the coding rate in error correction coding section 211 and the modulation multi-level number in modulation section 212 based on transmission parameter information and allocation information. Then, the transmission parameter information and the allocation information are referred to by the buffer unit 208, and the amount of transmission data corresponding to the transmission parameter for each mobile station apparatus is output to the multiplexing unit 210, and the error correction encoding unit 211 performs error correction encoding. Then, the signal is modulated by the modulation unit 212 and transmitted from the RF transmission unit 213 via the antenna (311). This transmission signal is processed with an appropriate transmission mode of either hierarchical modulation or adaptive modulation, an appropriate coding rate, and a modulation multi-value number selected from the maximum Doppler frequency and reception quality of each mobile station apparatus. .

  The transmission signal is received via the antenna of the mobile station apparatus shown in FIG. 1 and subjected to predetermined radio reception processing by the RF receiving unit 101. Then, the received signal is subjected to reception processing by the demodulation unit 102 and the error correction decoding unit 103 in which the modulation multi-level number and the coding rate are set by the transmission parameter information and the allocation information received in advance (312). Received data is output from the separation unit 104.

  After the reception quality report from the mobile station device to the base station device, the process from resource allocation (308) by the base station device to reception processing (312) by the mobile station device until the reception quality reporting period T elapses. Repeatedly, when the reception quality report period T elapses, reception quality information is again generated by the mobile station apparatus and transmitted to the base station apparatus.

  As described above, according to the present embodiment, using the maximum Doppler frequency in the mobile station apparatus, hierarchical modulation is selected as the transmission mode when the reception quality varies drastically, and transmission is performed when the reception quality does not vary much. Select adaptive modulation as the mode. For this reason, when reception quality fluctuates drastically, hierarchical modulation that does not require reception quality feedback and sets a large modulation multi-level number maximizes transmission efficiency while reception quality is good even in a short time. Can be improved. If reception quality does not fluctuate much, adaptive modulation that finely controls the optimal coding rate and modulation multi-level according to the reception quality should reduce the occurrence of errors and reliably improve transmission efficiency. Can do. In addition, when the adaptive modulation is in the transmission mode, the reception quality does not fluctuate so much, so the frequency of feedback of the reception quality can be reduced, and the amount of feedback information can be reduced.

  In the present embodiment, the base station apparatus selects the transmission mode based on the maximum Doppler frequency measured by the mobile station apparatus. However, the mobile station apparatus performs the selection up to the transmission mode and the base station apparatus. You may make it alert | report to.

  For example, in multicarrier transmission such as OFDM (Orthogonal Frequency Division Multiplex), a transmission mode of either hierarchical modulation or adaptive modulation is selected for each of a plurality of carriers or carrier groups. Also good.

  The base station apparatus according to the first aspect of the present invention includes a modulation unit that modulates a signal for the mobile station apparatus in a transmission mode of either hierarchical modulation or adaptive modulation according to a change in reception quality in the mobile station apparatus; And a transmission means for transmitting a signal obtained by modulation.

  According to this configuration, since the signal is modulated in the transmission mode according to the variation in reception quality in the mobile station apparatus, when the variation in reception quality is large, hierarchical modulation that does not require feedback of the reception quality from the mobile station apparatus is performed. On the other hand, when the fluctuation of the reception quality is small, the adaptive modulation can be performed by extending the feedback period of the reception quality from the mobile station apparatus. As a result, it is possible to reliably improve transmission efficiency while reducing the amount of feedback information.

  The base station apparatus according to a second aspect of the present invention is the base station apparatus according to the first aspect, wherein the modulation means selects a transmission mode according to the maximum Doppler frequency in the mobile station apparatus, and the selected transmission mode. And assigning means for assigning the modulation multi-level number corresponding to the mobile station apparatus to the mobile station apparatus.

  According to this configuration, the transmission mode corresponding to the maximum Doppler frequency in the mobile station apparatus is selected, and the modulation multi-value number is assigned to the mobile station apparatus from the selected transmission mode. It is possible to accurately estimate the variation in reception quality and improve the transmission efficiency by the optimum number of modulation multi-levels reflecting the variation in reception quality.

  The base station apparatus according to a third aspect of the present invention is the base station apparatus according to the second aspect, wherein the selecting means selects hierarchical modulation as a transmission mode when the maximum Doppler frequency is equal to or higher than a predetermined threshold, while the maximum Doppler frequency is selected. Adopts a configuration in which adaptive modulation is selected as the transmission mode when is less than a predetermined threshold.

  According to this configuration, the hierarchical modulation is selected when the maximum Doppler frequency is large, and the adaptive modulation is selected when the maximum Doppler frequency is small. Therefore, the hierarchical modulation is selected when the fading variation is large, and the fading variation is small. In this case, adaptive modulation is selected, and an appropriate transmission mode can be selected according to the variation in reception quality due to fading variation.

  The base station apparatus according to a fourth aspect of the present invention is the base station apparatus according to the second aspect, wherein the selecting means is configured such that the maximum Doppler frequency is less than a predetermined threshold and the reception quality measurement error in the mobile station apparatus is a predetermined threshold. If it is less than this, a configuration is adopted in which adaptive modulation is selected as the transmission mode.

  According to this configuration, since the adaptive modulation is selected when the maximum Doppler frequency and the reception quality measurement error in the mobile station apparatus are small, the reliability of the reception quality information fed back from the mobile station apparatus is high and the variation in the reception quality is small. Only in this case will adaptive modulation be performed. Therefore, when adaptive modulation is selected as the transmission mode, the transmission efficiency can be reliably improved.

  The base station apparatus according to a fifth aspect of the present invention is the base station apparatus according to the second aspect, wherein the selection means is configured to determine whether the reception quality measurement error in the mobile station apparatus is equal to or greater than a predetermined threshold value regardless of the maximum Doppler frequency. A configuration is adopted in which hierarchical modulation is selected as the transmission mode.

  According to this configuration, since the hierarchical modulation is selected when the reception quality measurement error in the mobile station apparatus is large, the transmission mode that does not depend on the reception quality information when the reliability of the reception quality information fed back from the mobile station apparatus is low. Will be selected. Therefore, the reception quality measurement error is absorbed by the hierarchical modulation, and a decrease in transmission efficiency can be prevented.

  The base station apparatus according to a sixth aspect of the present invention provides the base station apparatus according to the second aspect, wherein the modulating means determines a reception quality report period by the mobile station apparatus in accordance with the selected transmission mode. Furthermore, the structure which has is taken.

  According to this configuration, since the reception quality report period is determined according to the transmission mode, it is possible to determine the reception quality feedback period from the mobile station apparatus suitable for each of the hierarchical modulation and the adaptive modulation, and the amount of feedback information Reduction can be achieved.

  The modulation method according to the seventh aspect of the present invention includes a step of selecting either a hierarchical modulation mode or an adaptive modulation transmission mode according to a variation in reception quality in a mobile station apparatus, and the mobile station in the selected transmission mode. Modulating a signal to the device.

  According to this method, the signal is modulated in the transmission mode according to the reception quality fluctuation in the mobile station apparatus. Therefore, when the reception quality fluctuation is large, hierarchical modulation that does not require the reception quality feedback from the mobile station apparatus On the other hand, when the fluctuation of the reception quality is small, the adaptive modulation can be performed by extending the feedback period of the reception quality from the mobile station apparatus. As a result, it is possible to reliably improve transmission efficiency while reducing the amount of feedback information.

  The base station apparatus and modulation method of the present invention can reliably improve the transmission efficiency while reducing the amount of feedback information. This is useful as a modulation method.

The block diagram which shows the principal part structure of the mobile station apparatus which concerns on one embodiment of this invention The block diagram which shows the principal part structure of the base station apparatus which concerns on one Embodiment The block diagram which shows the internal structure of the resource allocation part which concerns on one embodiment The sequence diagram which shows operation | movement of the mobile station apparatus and base station apparatus which concern on one embodiment The flowchart which shows the example of the transmission mode selection method which concerns on one embodiment The figure which shows an example of the signal point arrangement | positioning of hierarchical modulation (A) Diagram showing an example of symbol propagation path variation in 16QAM (b) Diagram showing an example of symbol propagation channel variation in QPSK

Explanation of symbols

101, 201 RF reception unit 102, 202 Demodulation unit 103, 203 Error correction decoding unit 104, 204 Separation unit 105 CRC check unit 106 Reception quality measurement unit 107 Reception quality information generation unit 108 Maximum Doppler frequency measurement unit 109 Maximum Doppler frequency information generation Unit 110, 210 multiplexing unit 111, 211 error correction coding unit 112, 212 modulation unit 113, 213 RF transmission unit 205 transmission mode selection unit 206 reception quality report cycle determination unit 207 resource allocation unit 2071 mobile station selection unit 2072 transmission parameter determination Section 2073 MCS table 2074 Maximum modulation multi-level number table 208 Buffer section 209 Transmission parameter setting section

Claims (7)

Modulation means for modulating a signal for the mobile station device in a transmission mode of either hierarchical modulation or adaptive modulation according to a variation in reception quality in the mobile station device;
Transmitting means for transmitting a signal obtained by modulation;
A base station apparatus comprising: The modulating means includes
Selection means for selecting a transmission mode according to the maximum Doppler frequency in the mobile station device;
Allocating means for allocating a modulation multi-level number corresponding to the selected transmission mode to the mobile station device;
The base station apparatus according to claim 1, further comprising: The selection means includes
The hierarchical modulation is selected as the transmission mode when the maximum Doppler frequency is equal to or higher than a predetermined threshold, and the adaptive modulation is selected as the transmission mode when the maximum Doppler frequency is less than the predetermined threshold. Base station device. The selection means includes
The base station apparatus according to claim 2, wherein adaptive modulation is selected as a transmission mode when a maximum Doppler frequency is less than a predetermined threshold and a reception quality measurement error in the mobile station apparatus is less than a predetermined threshold. The selection means includes
3. The base station apparatus according to claim 2, wherein hierarchical modulation is selected as a transmission mode regardless of the maximum Doppler frequency when a reception quality measurement error in the mobile station apparatus is equal to or greater than a predetermined threshold. The modulating means includes
The base station apparatus according to claim 2, further comprising a determining unit that determines a reception quality report period by the mobile station apparatus according to the selected transmission mode. Selecting either a hierarchical modulation mode or an adaptive modulation transmission mode according to a change in reception quality in the mobile station device;
Modulating a signal for the mobile station device in a selected transmission mode;
A modulation method characterized by comprising:

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