JP2012209698A - Radio communication system, radio communication method, communication device, and radio communication program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration in throughput in radio communication performing precoding by using channel information compressed and transmitted.SOLUTION: A communication device comprises: a channel information compression section for generating channel information compression data which is compressed channel information showing a characteristic of a propagation path from a base station device to the own device; a first channel information development section for developing the channel information from the channel information compression data by using development processing developing the channel information from the channel information compression data at the base station device; and a channel quality index calculation section for calculating a channel quality index for the propagation path by using the developed channel information. The base station device comprises a pre-transmission processing section for selecting a modulation system for transmission data to be transmitted to the communication device based on the channel quality index received from the communication device, and performing precoding on the transmission data modulated by the selected modulation system based on the channel information compression data.

Description

  The present invention relates to a wireless communication system, a wireless communication method, a communication apparatus, and a wireless communication program.

  A MIMO (Multiple-Input Multiple-Output) system that communicates using a plurality of transmission / reception antennas has attracted attention. In the MIMO system, a base station apparatus and a mobile station apparatus are provided with a plurality of antennas, and different transmission data are transmitted from the plurality of antennas at the same frequency and the same time. In the MIMO system, precoding is performed in which a transmission-side apparatus previously acquires channel information indicating changes (characteristics) that transmission data undergoes on a propagation channel, and performs linear processing on the transmission data according to changes received on the propagation channel. By doing so, transmission efficiency can be increased.

  By the way, in order to perform pre-transmission processing in communication using an FDD (Frequency Division Duplex) system, the frequency used for transmission is different from the frequency used for reception. There is a need to obtain channel information indicating the change that the data has received on the propagation channel. For example, the base station apparatus needs to receive channel information corresponding to the downlink channel from the base station apparatus to the mobile station apparatus from the mobile station apparatus.

  For example, Non-Patent Document 1 describes a method of reducing the information amount (feedback amount) of channel information transmitted from a mobile station device to a base station device. In Non-Patent Document 1, the amount of feedback from a mobile station apparatus to a base station apparatus is reduced by allowing deterioration of channel information to be fed back.

  FIG. 4 is a diagram illustrating a configuration example of the wireless communication system 9 that reduces the feedback amount. The wireless communication system 9 includes at least one mobile station device 91 and a base station device 12, and the mobile station device 91 and the base station device 12 perform transmission using SU-MIMO (Single User-MIMO) technology. Do. The mobile station device 91 includes a reception unit 111, a channel estimation unit 112, a post-reception processing unit 113, a channel information compression unit 114, a CQI calculation unit 916, and a transmission unit 117. In addition, the base station apparatus 12 includes a receiving unit 121, a channel information expanding unit 122, a transmission preprocessing unit 123, and a transmitting unit 124.

In mobile station apparatus 91, receiving section 111 has a plurality of antennas, receives signals transmitted from base station apparatus 12 using the plurality of antennas using the plurality of antennas, and receives the received signals as channel estimation section 112. And output to the post-reception processing unit 113.
The channel estimation unit 112 uses the signal input from the reception unit 111 to estimate channel information, thermal noise, and interference received from adjacent cells in the propagation channel from the base station apparatus 12 to the own apparatus, and outputs the estimated result To do. Here, the thermal noise is a noise signal generated in the receiving unit 111 of the own apparatus. Note that, when a known signal (such as a pilot signal) is transmitted from the base station apparatus 12, the channel estimation unit 112 estimates channel information, thermal noise, and interference using a known technique.

The post-reception processing unit 113 uses the channel information output by the channel estimation unit 112 to output received data obtained by demodulating and decoding the signal received by the reception unit 111 to an external or higher-level device.
The channel information compression unit 114 reduces the information amount of the channel information estimated by the channel estimation unit 112 using a predetermined irreversible data compression process in order to reduce the amount of information fed back to the base station apparatus 12. Compression is performed to generate channel information compressed data. When compressing channel information, for example, DCT (Discrete Cosine Transform), DFT (Discrete Fourier Transform), or the like is used.

The CQI calculation unit 916 calculates a precoding matrix from the channel information output by the channel estimation unit 112, and further, from the channel information, the precoding matrix, and information indicating thermal noise and interference estimated by the channel estimation unit 112. A channel quality indicator (CQI) is calculated. This channel quality indicator is information indicating the quality of the channel in the propagation channel from the base station apparatus 12 to the mobile station apparatus 91.
The transmission unit 117 transmits the channel information compressed data generated by the channel information compression unit 114 and the channel quality indicator calculated by the CQI calculation unit 916 to the base station apparatus 12.

In the base station apparatus 12, the reception unit 121 receives the channel quality indicator and the channel information compressed data transmitted from the mobile station apparatus 91. In addition, receiving section 121 outputs the received channel information compressed data to channel information expanding section 122 and outputs the received channel quality indicator to pre-transmission processing section 123.
The channel information expansion unit 122 calculates channel information from the input channel information compressed data using a data expansion process corresponding to the data compression process used by the channel information compression unit 114. Here, for example, when the channel information compression unit 114 compresses channel information using DCT, the data expansion processing corresponding to the data compression processing is inverse using IDCT (Inverse Discrete Cosine Transform). Become a conversion.
Further, the channel information expanding unit 122 outputs the calculated channel information to the pre-transmission processing unit 123.

The pre-transmission processing unit 123 includes channel quality indicators input from the reception unit 121, channel information input from the channel information expansion unit 122, and transmission data transmitted from an external device or a higher-level device to the mobile station device 91. Entered.
The pre-transmission processing unit 123 calculates a precoding matrix used for precoding based on the input channel quality indicator and channel information, and modulates transmission data to be transmitted to the mobile station apparatus 91 and error correction coding. The coding rate is selected. For the selection of the modulation scheme and coding rate, for example, the base station apparatus 12 is provided with a table in which the correspondence between the combination of the modulation scheme and coding rate and the combination of the channel quality indicator and channel information is stored in advance. The preprocessing unit 123 may read a combination of a modulation scheme and a coding rate corresponding to the input channel quality indicator and channel information combination from the table, and select the read modulation scheme and coding rate.

In addition, the transmission preprocessing unit 123 performs encoding and modulation on transmission data using the selected modulation scheme and coding rate, and performs transmission and coding on the transmission data encoded and modulated using the calculated precoding matrix. To perform pre-transmission processing. The transmission preprocessing unit 123 outputs the transmission data subjected to the transmission preprocessing to the transmission unit 124.
The transmission unit 124 transmits the transmission data input from the transmission preprocessing unit 123 to the mobile station device 91.

In the wireless communication system 9 having the above-described configuration, the channel response matrix H when transmitted from the base station apparatus 12 to the mobile station apparatus 91, the precoding matrix W calculated by the base station apparatus 12, and the noise signal vector N When the interference vector I ^InterSector received from the adjacent cell is used, the CQI (γ _Layer1 ^Conv , γ _Layer2 ^Conv ) calculated in the mobile station device 91 is expressed by the following equations (1-1) and (1-2). The

Here, each of the channel response matrix H, the precoding matrix W, the noise signal vector N, and the interference vector I ^InterSector is expressed by the following equations (2-1) to (2-4).

Yasuyuki Hatakawa, Satoshi Konishi, “Characteristic Evaluation of CSI Compression Method Considering Channel Estimation Error and Feedback Delay”, IEICE Technical Report RCS2009-227, pp. 115-120, January 2010

  However, in the wireless communication system 9 described above, the channel information used when the base station apparatus 12 generates the precoding matrix W causes information deterioration due to compression in the mobile station apparatus 91 and expansion in the base station apparatus 12. There is. In this case, there is a difference between the channel information used when the mobile station device 91 calculates the channel quality indicator and the channel information used when the base station device 12 calculates the precoding matrix. Further, in the base station apparatus 12, the developed channel information does not correspond to the received channel quality indicator.

  In such a case, in the base station apparatus 12, the channel quality in the propagation channel from the base station apparatus 12 to the mobile station apparatus 91 may be estimated higher than the actual channel quality. For this reason, the transmission preprocessing unit 123 selects a modulation scheme and coding rate with high frequency utilization efficiency, and noise resistance of transmission data to be transmitted to the mobile station device 91 is lowered. As a result, there is a problem that many errors occur in the mobile station device 91 and the throughput of the wireless communication system 9 deteriorates.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a wireless communication system and wireless communication that suppress degradation of throughput in wireless communication in which precoding is performed using compressed and transmitted channel information. A method, a communication apparatus, and a wireless communication program are provided.

  To solve the above problem, the present invention comprises at least one communication device and a base station device that performs MIMO transmission to the communication device, and transmits data from the communication device to the base station device. In a wireless communication system in which a frequency and a frequency at which data is transmitted from the base station apparatus to the communication apparatus are different, the communication apparatus has an information amount of channel information indicating characteristics in a propagation channel from the base station apparatus to the own apparatus Channel information compression unit that generates channel information compressed data with reduced channel information, and a decompression process used when decompressing channel information from the channel information compressed data in the base station apparatus, channel information from the channel information compressed data The first channel information expansion unit that expands the channel information and the channel information expanded by the first channel information expansion unit. A channel quality indicator calculating unit for calculating a channel quality indicator for the propagation channel, wherein the base station device modulates transmission data to be transmitted to the communication device based on the channel quality indicator received from the communication device. A transmission pre-processing unit is provided that selects a method and pre-codes transmission data modulated using the selected modulation method based on channel information compressed data received from the communication device. A wireless communication system.

  Further, the present invention is the above-described invention, wherein two or more communication devices are provided, and the base station device transmits different transmission data to the at least two communication devices at the same frequency and the same time. It is characterized by transmitting.

  Further, the present invention is the above-described invention, wherein the base station device expands channel information from channel information compressed data received from each of the communication devices, and the second channel information expansion. A channel quality indicator correction unit that performs correction on the channel quality indicator received from each of the communication devices, based on the channel information developed by the unit and reflecting the interference that the transmission data to be spatially multiplexed has on each other. The transmission pre-processing unit selects a modulation scheme for transmission data to be transmitted to each of the communication devices according to the channel quality index corrected by the channel quality index correction unit.

  In addition, the present invention includes at least one communication device and a base station device that performs MIMO transmission to the communication device, a frequency at which data is transmitted from the communication device to the base station device, and the base station A wireless communication method in a wireless communication system having a different frequency for transmitting data from a device to the communication device, wherein the communication device has an information amount of channel information indicating characteristics of a propagation channel from the base station device to the own device Channel information compression step for generating channel information compressed data in which the channel information is reduced, and the channel information using a decompression process used when the communication device decompresses channel information from the channel information compressed data in the base station device. A first channel information expansion step of expanding channel information from the compressed data; and A channel quality index calculating step for calculating a channel quality index for the propagation channel using the channel information expanded in the channel information expanding step, and the base station apparatus based on the channel quality index received from the communication apparatus, A pre-transmission processing step of selecting a modulation scheme for transmission data to be transmitted to the communication apparatus, and precoding the transmission data modulated using the selected modulation scheme based on channel information compressed data received from the communication apparatus A wireless communication method characterized by comprising:

  In addition, the present invention includes at least one communication device and a base station device that performs MIMO transmission to the communication device, a frequency at which data is transmitted from the communication device to the base station device, and the base station Channel information compression that is a communication device in a wireless communication system having a different frequency for transmitting data from the device to the communication device, and that reduces the amount of channel information indicating characteristics of a propagation channel from the base station device to the own device A channel information compression unit that generates data, and a first channel that expands channel information from the channel information compressed data using a decompression process used when decompressing channel information from the channel information compressed data in the base station apparatus Using the channel information developed by the information expansion unit and the first channel information expansion unit, the propagation channel A channel quality indicator calculating unit for calculating a channel quality indicator for the transmission data, transmission data modulated based on the channel quality indicator, and pre-coded transmission data based on the channel information compressed data from the base station device A communication apparatus comprising a receiving unit for receiving.

  In addition, the present invention includes at least one communication device and a base station device that performs MIMO transmission to the communication device, a frequency at which data is transmitted from the communication device to the base station device, and the base station Channel information obtained by reducing the amount of channel information indicating characteristics of a propagation channel from the base station apparatus to the own apparatus in a computer included in a communication apparatus in a wireless communication system having a different frequency for transmitting data from the apparatus to the communication apparatus A channel information compressing step for generating compressed data, and a decompression process used when decompressing the channel information from the channel information compressed data in the base station apparatus, to develop channel information from the channel information compressed data. Expanding in the channel information expanding step and the first channel information expanding step A channel quality indicator calculating step for calculating a channel quality indicator for the propagation channel using channel information; transmission data modulated based on the channel quality indicator, precoded based on the channel information compressed data And a reception step of receiving received transmission data from the base station apparatus.

  According to the present invention, the channel information used when the communication apparatus calculates the channel quality indicator and the channel information used by the base station apparatus for precoding can be made the same, and the base station apparatus can Channel information used for processing to be performed can be associated with a channel quality index. As a result, the radio communication system can reduce the possibility that the base station apparatus estimates the channel quality in the propagation channel between the own apparatus and the communication apparatus to be high, and can suppress the deterioration of the throughput.

It is a schematic block diagram which shows the structure of the radio | wireless communications system 1 in 1st Embodiment. It is a schematic block diagram which shows the structure of the radio | wireless communications system 2 in 2nd Embodiment. It is a schematic block diagram which shows the structure of the radio | wireless communications system 3 in 3rd Embodiment. It is a figure which shows the structural example of the radio | wireless communications system 9 which reduces the amount of feedback.

  Hereinafter, a wireless communication system, a wireless communication method, a communication device, and a wireless communication program according to embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic block diagram showing a configuration of a wireless communication system 1 in the first embodiment. The wireless communication system 1 includes at least one mobile station apparatus 11 and a base station apparatus 12, and the mobile station apparatus 11 and the base station apparatus 12 perform communication using the SU-MIMO technology. Hereinafter, in the mobile station apparatus 11 and the base station apparatus 12, the same parts as those in the wireless communication system 9 in FIG. In the present embodiment, the wireless communication system 9 includes one mobile station apparatus 11 and a base station apparatus 12, and the base station apparatus 12 having two antennas changes to the mobile station apparatus 11 having two antennas. A case where data is transmitted will be described.

The mobile station apparatus 11 includes a reception unit 111, a channel estimation unit 112, a post-reception processing unit 113, a channel information compression unit 114, a channel information expansion unit 115, and a CQI calculation unit 116.
The channel information expansion unit 115 expands channel information from the channel information compressed data generated by the channel information compression unit 114 using a data expansion process corresponding to the data compression process used by the channel information compression unit 114. Channel information expanding section 115 outputs the expanded channel information to CQI calculating section 116. That is, channel information expanding section 115 outputs the same channel information as channel information output from channel information expanding section 122 provided in base station apparatus 12 to CQI calculating section 116.
CQI calculation section 116 calculates a precoding matrix from the channel information output from channel information expansion section 115. Also, CQI calculation section 116 calculates a channel quality index (CQI) from the thermal noise estimated by channel estimation section 112, interference received from neighboring cells, and the calculated precoding matrix, and transmits the calculated channel quality index. Output to the unit 117.

  The CQI calculation unit 116 describes a precoding matrix ^ W (hereinafter, ^ (hat) is added to W above W. Further, ^ (hat) is added to other characters. As a method of calculating the same), for example, a ZF (Zero Forcing) method as shown in the following equation (3) can be used.

Here, the elements ^ w _Layer1 ⁽¹⁾ and ^ w _Layer2 ⁽¹⁾ of the precoding matrix ^ W are precoding vectors (^ w _Layer1 ⁽¹⁾ , ^ w _Layer2 ^{(1 )} for one antenna of the mobile station apparatus 11. ⁾ ), And elements ^ w _Layer1 ⁽²⁾ and ^ w _Layer2 ⁽²⁾ are precoding vectors (^ w _Layer1 ⁽²⁾ , ^ w _Layer2 ⁽²⁾ ) for the other antenna of the mobile station apparatus 11. . ^ H is a channel response matrix indicated by the channel information output by the channel information expansion unit 115.
Further, the CQI calculating unit 116 uses the precoding matrix ^ W shown in Equation (3) to obtain channel quality indicators (γ _Layer1 ^WE1 and γ _Layer2 ^WE1 ) for the mobile station apparatus 11 according to the following Equation (4-1): Calculate as in (4-2).

Here, h _Layer1 ⁽¹⁾ and h _Layer2 ⁽¹⁾ indicate changes (characteristics) experienced by transmission data in the propagation channel from the base station apparatus 12 to one of the two antennas of the mobile station apparatus 11. Value. Further, h _Layer1 ⁽²⁾ and h _Layer2 ⁽²⁾ are values indicating the characteristics of the propagation channel from the base station apparatus 12 to the other of the two antennas of the mobile station apparatus 11. n _Layer1 and n _Layer2 are noises for the first layer and the second layer in the mobile station apparatus 11. Also, i _Layer1 ^InterSector and i _Layer2 ^InterSector, in each layer, it is interference from adjacent cells.

  In mobile station apparatus 11, CQI calculation section 116 uses channel information input to pre-transmission processing section 123 by channel information expansion section 115 using the same data expansion processing as channel information expansion section 122 in base station apparatus 12. The same channel information can be obtained. At this time, the CQI calculation unit 116 calculates and calculates a precoding matrix ^ W that is the same as the precoding matrix ^ W used for transmission data by the transmission preprocessing unit 123 of the base station apparatus 12 from the expanded channel information. A channel quality indicator (CQI) can be calculated from the precoding matrix ^ W.

Thereby, the pre-transmission processing unit 123 can perform the pre-transmission processing using the channel information expanded in the channel information expansion unit 122 and the channel quality index corresponding to the channel information. In doing so, it is possible to prevent the channel quality from being estimated higher than the actual channel quality.
As a result, the radio communication system 1 allows the base station apparatus 12 to change from the mobile station apparatus 11 to the base station apparatus 12 by selecting a modulation scheme according to actual channel quality and a coding rate in error correction coding. While reducing the amount of channel information to be fed back, the mobile station apparatus 11 can reduce the error rate when receiving transmission data from the base station apparatus 12, and the degradation of throughput can be suppressed.

(Second Embodiment)
FIG. 2 is a schematic block diagram showing the configuration of the wireless communication system 2 in the second embodiment. The wireless communication system 2 includes at least two mobile station apparatuses 21 and a base station apparatus 22, and the base station apparatus 22 transmits transmissions using MU-MIMO (Multi-User MIMO) technology to each mobile station apparatus 21. Against. Here, the radio communication system 2 includes mobile station apparatuses 21-1 and 21-2 as the mobile station apparatus 21, each mobile station apparatus 21 has one antenna, and the base station apparatus 22 has two antennas. The case will be described. Further, the mobile station device 21-1 and the mobile station device 21-2 have the same configuration. Hereinafter, when one or both of the mobile station device 21-1 and the mobile station device 21-2 is shown, it is referred to as the mobile station device 21.

As shown in FIG. 2, the mobile station apparatus 21 includes a reception unit 211, a channel estimation unit 212, a post-reception processing unit 213, a channel information compression unit 214, a channel information expansion unit 215, and a CQI calculation unit 216. , And a transmission unit 217.
The receiving unit 211 receives signals transmitted from the base station device 22 using two antennas, and outputs the received signals to the channel estimation unit 212 and the post-reception processing unit 213.
The channel estimation unit 212 uses the signal input from the reception unit 211 to estimate channel information, thermal noise, and interference received from adjacent cells in the propagation channel from the base station apparatus 22 to the own apparatus, and outputs the estimated result To do. The channel estimation unit 212 estimates channel information, thermal noise, and interference using a known technique, like the channel estimation unit 112 of the first embodiment.

Similar to the post-reception processing unit 113 of the first embodiment, the post-reception processing unit 213 is obtained by demodulating and decoding the signal received by the reception unit 211 using the channel information output by the channel estimation unit 212. The received data is output to an external or host device.
The channel information compression unit 214 compresses the channel information estimated by the channel estimation unit 212 to generate compressed channel information data in order to reduce the amount of information fed back to the base station apparatus 22.
The channel information expansion unit 215 expands channel information from the channel information compressed data generated by the channel information compression unit 214 using a data expansion process corresponding to the data compression process used by the channel information compression unit 214. Further, channel information expanding section 215 outputs the expanded channel information to CQI calculating section 216.

CQI calculation section 216 calculates a precoding vector from the channel information output from channel information expansion section 215. Further, CQI calculation section 216 uses the thermal noise estimated by channel estimation section 212, the interference received from adjacent cells, and the calculated precoding vector, and the channel quality for the propagation channel between base station apparatus 22 and the own apparatus. An index (CQI) is calculated, and the calculated channel quality index is output to the transmission unit 217.
The transmission unit 217 transmits the channel information compressed data generated by the channel information compression unit 214 and the channel quality indicator calculated by the CQI calculation unit 216 to the base station apparatus 22.

As shown in FIG. 2, the base station apparatus 22 includes a reception unit 221, a channel information expansion unit 222, a pre-transmission processing unit 223, and a transmission unit 224.
The receiving unit 221 receives channel information compressed data and a channel quality indicator transmitted from each mobile station device 21. In addition, the reception unit 221 outputs the received channel information compressed data to the channel information expansion unit 222 and outputs the received channel quality indicator to the pre-transmission processing unit 223.

The channel information expansion unit 222 calculates channel information from the input channel information compressed data using a data expansion process corresponding to the data compression process used in the channel information compression unit 214 of each mobile station device 21. Further, the channel information expanding unit 222 outputs the calculated channel information to the pre-transmission processing unit 223.
In the pre-transmission processing unit 223, channel information corresponding to the propagation channel from the own apparatus to the mobile station apparatus 21-1 and channel information corresponding to the propagation channel from the own apparatus to the mobile station apparatus 21-2 are channel information expanded. Input from the unit 222.
In addition, the channel quality indicator in the mobile station device 21-1 and the channel quality indicator in the mobile station device 21-2 are input from the reception unit 221 to the transmission preprocessing unit 223. In addition, different transmission data to be transmitted to each mobile station device 21 is input to the pre-transmission processing unit 223. The transmission data transmitted to each mobile station device 21 may be the same.

The pre-transmission processing unit 223 calculates a precoding vector used for precoding for transmission data to be transmitted to each mobile station apparatus 21 based on the input two channel information and two channel quality indicators, and each mobile station A modulation scheme for each transmission data to be transmitted to the device 21 and a coding rate in error correction coding are selected.
In addition, the transmission preprocessing unit 223 performs encoding and modulation using the modulation scheme and coding rate selected for each transmission data, and for the transmission data encoded and modulated using the calculated precoding vector. Perform pre-transmission processing to pre-code. The transmission preprocessing unit 223 outputs the transmission data subjected to the transmission preprocessing to the transmission unit 224. Note that, in the selection of the modulation scheme and coding rate in the transmission preprocessing unit 223, the correspondence between the combination of the modulation scheme and coding rate and the combination of the channel quality indicator and channel information is determined in advance as in the transmission preprocessing unit 123. A stored table may be prepared and read from the table.
The transmission unit 224 transmits data for transmitting the transmission data input from the transmission preprocessing unit 223 to the mobile station apparatuses 21-1 and 21-2.

Here, a procedure in which the CQI calculation unit 216 calculates a channel quality index will be described. Hereinafter, channel information indicating a propagation channel from the base station apparatus 22 to the mobile station apparatus 21-1 and channel information indicating a propagation channel from the base station apparatus 22 to the mobile station apparatus 21-2 are represented by channel vectors h _UE1 , h _{This is UE2} . At this time, the channel response matrix H indicating the characteristics of the propagation channel between the base station device 22 and the mobile station devices 21-1 and 22-2 is expressed by the following equation (5).

Here, each element h _UE1 ⁽¹⁾ , h _UE1 ⁽²⁾ , h _UE2 ⁽¹⁾ , and h _UE2 ⁽²⁾ of the channel response matrix H includes two antennas of the base station device 22 and a mobile station device. It is a value indicating the characteristics of the propagation channel between the antennas 21-1 and 21-2.
Further, the precoding vector calculated by the CQI calculation unit 216 provided in the mobile station apparatus 21-1 is set as _wUE1, and the precoding vector calculated by the CQI calculation unit 216 provided in the mobile station apparatus 21-2 is set as w _UE1. w _UE2 . At this time, the precoding matrix W is expressed as the following equation (6).

Moreover, the noise vector N which shows the thermal noise in the mobile station apparatuses 21-1 and 21-2 is expressed by the following equation (7-1), and the interference received by the mobile station apparatuses 21-1 and 21-2 from adjacent cells is shown. The interference vector I ^InterSector is expressed by the following equation (7-2).

Here, thermal noise n _UE1 indicates thermal noise in the mobile station apparatus 21-1, and thermal noise n _UE2 indicates thermal noise in the mobile station apparatus 21-2. Interference i _UE1 ^InterSector indicates interference received from an adjacent cell in mobile station apparatus 21-1, and interference i _UE2 ^InterSector indicates interference received from an adjacent cell in mobile station apparatus 21-2.

In mobile station apparatus 21-1, channel information expansion section 215 expands the channel information compressed data generated by channel information compression section 214, and outputs the expanded channel information (channel vector ^ h _UE1 ) to CQI calculation section 216. . Here, the vector and the element with ^ (hat) on the top indicate the channel information expanded in the channel information expansion unit 215 and its elements.
CQI calculation section 216 calculates precoding vector ^ w _UE1 from the input channel information (channel vector ^ h _UE1 ) using the following equation (8).

Further, CQI calculation section 216 calculates channel quality indicator γ _UE1 ^WE2 using the following equation (9).

Although the mobile station device 21-1 is shown here, the channel quality index γ _UE2 ^WE2 can be calculated similarly in the mobile station device 21-2.

As described above, in the mobile station apparatuses 21-1 and 21-2, the CQI calculation unit 216 is similar to the CQI calculation unit 116 of the first embodiment in that the pre-transmission processing unit 223 of the base station apparatus 22 performs the precoding vector. ^ w _UE1, ^ channel information used to calculate the w _UE2 (channel vector ^ h _UE1, ^ h _UE2) the same channel information as the (channel vector ^ h _UE1, ^ h _UE2) from the channel quality indicator (gamma _UE1 ^WE2, γ _UE2 ^WE2 ) is calculated.
Thereby, the transmission preprocessing unit 223 can perform the transmission preprocessing using the channel information expanded in the channel information expansion unit 222 and the channel quality index corresponding to the channel information. In doing so, it is possible to prevent the channel quality from being estimated higher than the actual channel quality.
As a result, in the radio communication system 2 that performs MU-MIMO transmission, the base station apparatus 22 selects a modulation scheme according to the actual channel quality and a coding rate in error correction coding, so that the mobile station apparatus 21 Can reduce the error rate when the mobile station apparatus 21 receives transmission data from the base station apparatus 22 while reducing the amount of channel information fed back from the base station apparatus 22 to the base station apparatus 22, and suppress the degradation of throughput. be able to.

(Third embodiment)
FIG. 3 is a schematic block diagram showing the configuration of the wireless communication system 3 in the third embodiment. The wireless communication system 3 includes at least two mobile station apparatuses 21 and a base station apparatus 32, and the mobile station apparatus 21 and the base station apparatus 32 perform communication using MU-MIMO technology. That is, different transmission data transmitted from the base station apparatus 32 to each mobile station apparatus 21 is spatially multiplexed and transmitted, so that each transmission data is transmitted to each mobile station apparatus 21 in the same time and the same frequency band.
Hereinafter, in the mobile station apparatus 21 and the base station apparatus 32, the same parts as those in the wireless communication system 2 (FIG. 2) of the second embodiment are denoted by the same reference numerals, and description thereof is omitted.

As shown in FIG. 3, the wireless communication system 3 in the present embodiment is different from the second embodiment in that the base station device 32 includes a CQI correction unit 325.
In the base station device 32, the CQI correction unit 325 corrects the channel quality index received by the reception unit 221 from each mobile station device 21 using the channel information expanded by the channel information expansion unit 222. Further, the CQI correction unit 325 outputs the corrected channel quality indicator to the transmission preprocessing unit 223. The pre-transmission processing unit 223 uses the channel quality index corrected by the CQI correction unit 325 instead of the channel quality index input from the reception unit 221. The transmission preprocessing unit 223 selects a modulation scheme and a coding rate for transmission data to be transmitted to each mobile station apparatus 21 based on the corrected channel quality indicator and the expanded channel information, and also a precoding vector. Is calculated.

By the way, since the channel quality indicator transmitted from each mobile station apparatus 21 cannot obtain the precoding vector used for the transmission data transmitted to the other mobile station apparatus 21, The interference received from the signal to be transmitted is not considered (for example, Equation (9)).
Therefore, in this embodiment, the CQI correction unit 325 uses the channel information (channel vector (^ h _UE1 , ^ h _UE2 )) corresponding to each mobile station apparatus 21 to transmit data to other mobile station apparatuses 21. The channel quality indicator is corrected in consideration of the interference received from the channel. That is, the CQI correction unit 325 performs correction on the channel quality indicator to reflect the influence of the interference of the transmission data transmitted to each mobile station apparatus 21 on each other.
Specifically, CQI correcting section 325, using the following equation (10), from the channel quality indicator gamma _UE1 ^WE2 received from the mobile station apparatus 21-1 calculates the corrected channel quality indicator gamma _UE1 ^WE3 was.

Moreover, CQI correcting section 325, likewise, from the channel quality indicator gamma _UE2 ^WE2 received from the mobile station apparatus 21-2 calculates the corrected channel quality indicator gamma _UE2 ^WE3 was.

As described above, in the base station apparatus 32, by correcting the channel quality index received from each mobile station apparatus 21, the channel quality index considering the interference received from the data addressed to the other mobile station apparatus 21 that is spatially multiplexed. And the accuracy of estimating the channel quality can be improved.
As a result, the radio communication system 3 can reduce the error rate in each mobile station apparatus 21 by the base station apparatus 32 generating a precoding vector corresponding to the actual channel quality, and suppress the deterioration of the throughput. can do.

In the first to third embodiments described above, the configuration in which the wireless communication system includes the mobile station device and the base station device has been described. However, the present invention is not limited to this, and the wireless communication system can move both. Alternatively, a wireless communication system in which both are fixed at a predetermined position may be used.
In the first to third embodiments, the configuration in which the transmission preprocessing is performed in the base station apparatus has been described. However, the transmission preprocessing may be performed in both the base station apparatus and the mobile station apparatus.
The communication device described in the present invention corresponds to the mobile station device in the first to third embodiments. The channel quality indicator calculation unit described in the present invention corresponds to the CQI calculation unit in the first to third embodiments. The channel quality indicator correction unit described in the present invention corresponds to the CQI correction unit in the third embodiment.

  Note that a program for realizing the functions of the mobile station device and the base station device in the present invention is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into a computer system and executed. Thus, processing such as channel information estimation, channel quality index (CQI) calculation, compression, decompression, and correction may be performed. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer system” includes a WWW system having a homepage providing environment (or display environment). The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” refers to a volatile memory (RAM) in a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those holding programs for a certain period of time are also included.

  The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

DESCRIPTION OF SYMBOLS 1, 2, 3, 9 ... Wireless communication system 11, 21, 21-1, 21-22, 91 ... Mobile station apparatus 12, 22, 32 ... Base station apparatus 111, 121, 211, 221 ... Reception part 112,212 ... Channel estimation unit 113, 213 ... Post-reception processing unit 114, 214 ... Channel information compression unit 115, 122, 215, 222 ... Channel information expansion unit 116, 216, 916 ... CQI calculation unit 117, 124, 217, 224 ... Transmission Units 123, 223 ... Pre-transmission processing unit 325 ... CQI correction unit

Claims (6)

At least one communication device, and a base station device that performs MIMO transmission to the communication device, a frequency at which data is transmitted from the communication device to the base station device, and from the base station device to the communication device In a wireless communication system with a different frequency for transmitting data,
The communication device
A channel information compression unit that generates channel information compressed data in which the amount of channel information indicating characteristics in a propagation channel from the base station device to the own device is reduced;
A first channel information decompressing unit that decompresses channel information from the channel information compressed data using a decompression process used when decompressing channel information from the channel information compressed data in the base station device;
A channel quality indicator calculating unit that calculates a channel quality indicator for the propagation channel using the channel information developed by the first channel information developing unit;
The base station device
Based on a channel quality indicator received from the communication device, a modulation scheme for transmission data to be transmitted to the communication device is selected, and a channel received from the communication device for transmission data modulated using the selected modulation scheme. A wireless communication system, comprising: a pre-transmission processing unit that performs precoding based on information compression data. The communication device comprises two or more,
The radio communication system according to claim 1, wherein the base station apparatus spatially multiplexes and transmits different transmission data to be transmitted to at least two of the communication apparatuses. The base station device
A second channel information expansion unit that expands channel information from channel information compressed data received from each of the communication devices;
A channel quality index that is corrected by the second channel information expansion unit for the channel quality index received from each of the communication devices, based on the channel information and performing correction that reflects interference between the transmission data to be spatially multiplexed. A correction unit, and
3. The radio according to claim 2, wherein the pre-transmission processing unit selects a modulation scheme for transmission data to be transmitted to each of the communication devices, according to the channel quality index corrected by the channel quality index correction unit. Communications system. At least one communication device, and a base station device that performs MIMO transmission to the communication device, a frequency at which data is transmitted from the communication device to the base station device, and from the base station device to the communication device A wireless communication method in a wireless communication system having a different frequency for transmitting data,
A channel information compression step in which the communication device generates channel information compression data in which the amount of channel information indicating characteristics in a propagation channel from the base station device to the own device is reduced;
A first channel information expansion step in which the communication apparatus expands channel information from the channel information compressed data using a expansion process used when expanding the channel information from the channel information compressed data in the base station apparatus;
A channel quality index calculating step in which the communication apparatus calculates a channel quality index for the propagation channel using the channel information expanded in the first channel information expanding step;
Based on the channel quality indicator received from the communication device, the base station device selects a modulation scheme for transmission data to be transmitted to the communication device, and for the transmission data modulated using the selected modulation scheme, A wireless communication method comprising: a pre-transmission processing step of performing precoding based on channel information compressed data received from a communication device. At least one communication device, and a base station device that performs MIMO transmission to the communication device, a frequency at which data is transmitted from the communication device to the base station device, and from the base station device to the communication device A communication device in a wireless communication system having a different frequency for transmitting data,
A channel information compression unit that generates channel information compressed data in which the amount of channel information indicating characteristics in a propagation channel from the base station device to the own device is reduced;
A first channel information decompressing unit that decompresses channel information from the channel information compressed data using a decompression process used when decompressing channel information from the channel information compressed data in the base station device;
A channel quality indicator calculating unit that calculates a channel quality indicator for the propagation channel using the channel information developed by the first channel information developing unit;
A communication apparatus comprising: a reception unit that receives transmission data modulated based on the channel quality indicator and pre-coded based on the channel information compressed data from the base station apparatus. At least one communication device, and a base station device that performs MIMO transmission to the communication device, a frequency at which data is transmitted from the communication device to the base station device, and from the base station device to the communication device In a computer included in a communication device in a wireless communication system having a different frequency for transmitting data,
A channel information compression step for generating channel information compressed data in which the amount of channel information indicating characteristics in a propagation channel from the base station device to the own device is reduced;
A first channel information expansion step of expanding channel information from the channel information compressed data using a expansion process used when expanding the channel information from the channel information compressed data in the base station device;
A channel quality index calculating step for calculating a channel quality index for the propagation channel using the channel information expanded in the first channel information expanding step;
And a reception step of receiving transmission data modulated based on the channel quality indicator and pre-coded transmission data based on the channel information compressed data from the base station apparatus.

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