WO2013171831A1 - Receiver, transmitter, receiving method, transmitting method, and wireless communication system - Google Patents

Abstract

In a terminal (20), a codebook selector (27), on the basis of the reception power of a base station (40) and the reception power of a base station (60), selects from among a first codebook and a second codebook, that comprises a portion of a plurality of codeword candidates included in the first codebook, a codebook to be used for both the base station (40) and the base station (60). For example, this selection is performed on the basis of the ratio of the reception power of the base station (40) and the reception power of the base station (60).

Description

Reception device, transmission device, reception method, transmission method, and wireless communication system

The present invention relates to a receiving device, a transmitting device, a receiving method, a transmitting method, and a wireless communication system.

Commercial service of LTE (Long Term Evolution) system (3GPP Release 8), a new mobile communication system, has started. In addition, LTE-Advanced (Release 10) whose functions have been greatly expanded has already been developed at the International Standards Organization 3GPP (Third Generation Partnership Project). Currently, active discussions are taking place to further expand the functionality in the next release, Release 11.

In particular, in order to improve the throughput characteristics of users existing at the cell edge, a CoMP (Coordinated Multi-Point) transmission / reception technique shown in FIG. 1 has been studied. In downlink coordinated transmission, which is a form of CoMP transmission / reception technology, downlink signals transmitted from a plurality of transmission points (Transmission Points: TP) are received by a UE (User Equipment) and then combined. Thereby, reception characteristics can be improved.

Also, in 3GPP LTE-advanced, spatial multiplexing (that is, MIMO: Multiple Input Multiple Output) technology is adopted in order to realize a faster information transmission rate.

In a MIMO system, the transmission side transmits signals with a plurality of antennas, and the reception side receives signals with a plurality of antennas. Further, by using pre-coding on the transmission side, it is possible to effectively improve the performance of the MIMO system. MIMO precoding is a closed-loop transmission technology, and is divided into two types, precoding based on codebook and non-codebook, depending on the type of information to be fed back. Divided.

In precoding based on a code book, the transmission side and the reception side set a code book including a plurality of code words (Codewords) in advance. Before the data signal is transmitted from the transmission side, the reception side selects the most preferable code word from the set code book based on the current channel characteristics, and an index corresponding to the selected code word ( Index) is fed back to the transmission side. The transmitting side selects a codeword corresponding to the index fed back in the codebook, and precodes the transmission signal using the selected codeword. By doing so, it is possible to improve reception characteristics on the reception side.

RP-110457, “Study on downlink MIMO enhancement for LTE-Advanced,” RAN1 # 51, Kansas City, USA, March 2011 3GPP TR 36.819, “Coordinated multi-point operation for LTE physical layer aspects (Release 11),” V0.1.0, 2011-05 R1-111248, “Feedback enhancements for CoMP,” New Postcom, RAN166, Athens, Grece, August 2011 R1-1112454, “Preliminary Study on Codebook Design for JT-CoMP,” ITRI, RAN166, Athens, Grece, August 2011

By the way, when applying MIMO using precoding to CoMP transmission, information indicating the codeword selected on the receiving side for each of a plurality of TPs performing cooperative transmission is transmitted to the TP of the “connected cell”. The And the information which shows the codeword with respect to TP of cells other than the connection cell of the some TP which performs coordinated transmission is transmitted to that TP via TP of a connection cell.

That is, when MIMO using precoding is applied to CoMP transmission, the overhead of feedback information becomes large.

The disclosed technique has been made in view of the above, and an object thereof is to provide a receiving apparatus, a transmitting apparatus, a receiving method, a transmitting method, and a wireless communication system that can reduce the overhead of feedback information.

According to an aspect of the disclosure, there is provided a receiving device that receives data signals transmitted by MIMO (Multiple Input Multiple Output) to which precoding is applied from a first transmitting device and a second transmitting device, Based on the received power for the transmitting device and the received power for the second transmitting device, the first code book and a part of a plurality of codeword candidates included in the first code book A first selection unit that selects a first usage codebook used in the first transmission device and a second usage codebook used in the second transmission device from the second codebook; It has.

According to the disclosed aspect, the overhead of feedback information can be reduced.

FIG. 1 is a diagram for explaining CoMP transmission / reception technology. FIG. 2 is a diagram illustrating an example of a communication system according to the first embodiment. FIG. 3 is a block diagram illustrating an example of the terminal according to the first embodiment. FIG. 4 is a block diagram illustrating an example of the base station according to the first embodiment. FIG. 5 is a diagram illustrating an example of operation processing of the terminal and the base station according to the first embodiment. FIG. 6 is a diagram illustrating a hardware configuration of the terminal. FIG. 7 is a diagram illustrating a hardware configuration of the base station.

Hereinafter, embodiments of a receiving device, a transmitting device, a receiving method, a transmitting method, and a wireless communication system disclosed in the present application will be described in detail with reference to the drawings. Note that the receiving device, the transmitting device, the receiving method, the transmitting method, and the wireless communication system disclosed in the present application are not limited by this embodiment. Moreover, the same code | symbol is attached | subjected to the structure which has the same function in an Example, and the overlapping description is abbreviate | omitted.

[Example 1]
[Outline of communication system]
FIG. 2 is a diagram illustrating an example of a communication system according to the first embodiment. In FIG. 2, the communication system 10 includes a terminal 20, a base station 40, a base station 60, and a base station 70.

The base station 40 and the base station 60 correspond to the base station of the connected cell and the base station of the cooperative cell, respectively, which cooperatively transmit data signals to the terminal 20 using MIMO. The base station 70 is a base station of a non-cooperative cell that does not participate in cooperative transmission.

The base station 40 and the base station 60 each transmit a reference signal to the terminal 20. Since the reference signal of the base station 40 and the reference signal of the base station 60 are different, the terminal 20 can determine whether the reference signal is transmitted from either the base station 40 or the base station 60.

Based on the ratio between the first received power of the reference signal transmitted from the base station 40 and the second received power of the reference signal transmitted from the base station 60, the terminal 20 performs the base station 40 and the base station 60. The codebook used for data transmission by each of the above is selected.

The candidate codebook to be selected includes the first codebook and the second codebook. The first codebook corresponds to a conventional “high-precision codebook”, and the second codebook corresponds to a “low-precision codebook” compared to the first codebook.

Here, the number of codeword candidates included in the first codebook is larger than the number of codeword candidates included in the second codebook. Specifically, a part of the code word candidate group constituting the first code book constitutes the second code book. That is, the second codebook is a subset of the first codebook.

The terminal 20 transmits information indicating the code book selected for each of the base station 40 and the base station 60 (hereinafter, simply referred to as “code book information”) to the base station 40 of the connected cell. To do.

The base station 40 transfers the information indicating the code book of the base station 60 transmitted from the terminal 20 to the base station 60.

As described above, the base station 40 and the base station 60 can specify a codebook used for determining a precoding matrix (PM) used for precoding.

Also, the terminal 20 selects an optimal codeword from the codebook selected for each of the base station 40 and the base station 60 based on the channel characteristics.

Then, the terminal 20 transmits information indicating the selected codeword to each of the base station 40 and the base station 60 to the base station 40 of the connected cell.

The base station 40 transfers information indicating the codeword of the base station 60 transmitted from the terminal 20 to the base station 60.

In this way, each of the base station 40 and the base station 60 identifies the PM corresponding to the codeword indicated by the received information, and performs precoding of the data signal using the identified PM. The information indicating the codeword transmitted from the terminal 20 in order to identify the PM in the base station 40 and the base station 60 may be referred to as PMI (Precoding Matrix Indicator).

Here, the frequency of transmission to the base station 40 and the base station 60 is higher for the information indicating the code word than for the information indicating the code book. That is, the second cycle in which the information indicating the code word is transmitted is shorter than the first cycle in which the information indicating the code book is transmitted.

[Terminal configuration]
FIG. 3 is a block diagram illustrating an example of the terminal according to the first embodiment. 3, the terminal 20, RF (Radio Frequency) and receiver 21-1 ~ _{N R,} a CP (Cyclic Prefix) removing section _{22-1 ~ N R, FFT (Fast} Fourier Transform) unit 23-1 ~ N _R , separation unit 24, channel estimation unit 25, reception power ratio calculation unit 26, codebook selection unit 27, PM selection unit 28, control signal generation unit 29, reference signal generation unit 30, and multiplexing Unit 31, IFFT (Inverse Fast Fourier Transform) unit 32, CP addition unit 33, RF transmission unit 34, and demodulation unit 35.

Each RF receiver 21-1 ~ _{N R,} receiving the transmitted OFDM (Orthogonal Frequency-Division Multiplexing) signal from the base station 40 or base station 60, radio reception processing (down-conversion, quadrature demodulation, A / D It applies transform, etc.) to the CP removal unit 22-1 ~ _{N R.} RF receiver 21-1 ~ _{N R} correspond respectively to the _{N R} receive antennas.

Each of the CP removal unit 22 - 1 ~ _{N R,} removing the CP from the OFDM signal after the reception processing received from the RF receiver 21-1 ~ _{N R,} FFT section 23-1 to the OFDM signal after CP removal Output to N _R.

Each of the FFT units 23-1 ~ _{N R,} into a frequency domain signal by performing FFT processing on the OFDM signal after CP removal received from CP removing section 22-1 ~ _{N R.}

Separation unit 24 separates the frequency domain signal received from FFT section 23-1 ~ N _R, into a reference signal and other signals contained therein. The reference signal is output to the channel estimation unit 25, and other signals are output to the demodulation unit 35.

The channel estimation unit 25 calculates the cross-correlation between the reference signal transmitted from each of the base station 40 and the base station 60 and the known reference signal replica of each base station. Thereby, the channel estimation value of the radio channel represented by a complex number is obtained for each base station. The channel estimation value calculated in this way is output to the reception power ratio calculation unit 26, the PM selection unit 28, and the demodulation unit 35.

Based on the channel estimation value for each base station calculated by the channel estimation unit 25, the reception power ratio calculation unit 26 calculates the received power for the first base station and the received power for the second base station. The ratio (that is, the reception power ratio) is calculated.

Specifically, the reception power ratio calculation unit 26 detects the amplitude of the channel estimation value of the base station 40 calculated by the channel estimation unit 25, and calculates reception power from the detected amplitude. Thereby, the received power for the base station 40 is calculated. The same processing is performed for the channel estimation value of the base station 60.

Then, the received power ratio calculation unit 26 calculates a received power ratio that is a ratio of the received power for the base station 60 to the received power for the base station 40. Here, the received power ratio is the ratio of the received power for the base station 60 to the received power for the base station 40, but conversely, the received power for the base station 40 to the received power ratio for the base station 60. Electric power may be used. The reception power ratio calculation unit 26 calculates the reception power ratio with a cycle that is the same as or shorter than the first selection cycle in the codebook selection unit 27.

Based on the reception power ratio calculated by the reception power ratio calculation unit 26, the code book selection unit 27 selects a code book to be used for each of the base station 40 and the base station 60 from the code book group. As described above, this selection is performed in the first selection cycle. The code book group includes a first code book and a second code book. The first codebook corresponds to a conventional “high-precision codebook”, and the second codebook corresponds to a “low-precision codebook” compared to the first codebook. Specifically, the first codebook includes a first codeword group. The second code book, the first code word group (e.g., S (1), S ( 2), ..., S (2 B1) 2 B1 codewords hereinafter) which is a part of the second code word group (e.g., S (1), S ( 2), ..., S (2 B2) of ^{2 B2} codewords) consists. Naturally, the relationship of B1> B2 is established. A codeword group satisfying the following condition among the codeword groups composed of arbitrary 2 ^B2 codewords in the first codeword group (that is, a subset of the first codebook) is 2 codebook. The condition is, for example, that the total sum of Euclidean distances calculated for each codeword in the codeword group is maximized. That is, any 2 ^B2 codewords are selected from the first codeword group, and 2 ^B2 codes that maximize the sum of the minimum Euclidean distances from other codewords calculated for each codeword The combination of words is the second codebook.

Specifically, when the received power ratio is within a predetermined range including 1, the codebook selection unit 27 uses the first codebook as the use codebook for both the base station 40 and the base station 60. select. On the other hand, when the received power ratio is out of the predetermined range, the code book selecting unit 27 selects the first code book as the used code book for the one having the larger received power among the base station 40 and the base station 60. . And the code book selection part 27 selects a 2nd code book as a use code book with respect to the one where received power is smaller among the base station 40 and the base station 60. FIG. Information indicating the use code book selected for the base station 40 and the base station 60 in this way is output to the PM selection unit 28 and the control signal generation unit 29.

The PM selection unit 28 specifies an optimal codeword from the used codebook selected by the codebook selection unit 27 based on the channel estimation value estimated by the channel estimation unit 25. The identification of the codeword is performed for each of the two usage codebooks selected for the base station 40 and the base station 60. The selection criterion for selecting the optimum code word from the used code book is that the reception characteristic at the terminal 20 of the data signal that has been precoded using the selected code word is the highest.

Then, the PM selection unit 28 outputs information indicating the codeword selected for each of the base station 40 and the base station 60 to the control signal generation unit 29. Here, the PM selection unit 28 selects a code word in the second selection cycle. The second selection cycle is shorter than the first selection cycle described above.

The control signal generation unit 29 uses the control data as an input signal and generates a control signal from the input control data. This control signal includes codebook information and precoding matrix information (PMI).

The reference signal generation unit 30 generates a reference signal and outputs it to the multiplexing unit 31.

The multiplexing unit 31 performs frequency multiplexing by mapping the reference signal received from the reference signal generating unit 30 and the control signal received from the control signal generating unit 29 on the frequency axis, and outputs the multiplexed signal to the IFFT unit 32.

The IFFT unit 32 performs IFFT processing on the multiplexed signal received from the multiplexing unit 31 to convert it into a time domain signal (that is, an OFDM signal), and outputs it to the CP adding unit 33.

CP adding section 33 adds a CP to the OFDM signal received from IFFT section 32, and outputs the OFDM signal after the CP addition to RF transmitting section 34.

The RF transmitter 34 performs radio transmission processing (D / A conversion, orthogonal modulation, up-conversion, etc.) on the OFDM signal received from the CP adding unit 33, and transmits the obtained radio signal via the antenna.

The demodulator 35 performs MIMO demodulation on the data signal received from the separator 24 and outputs the received data obtained thereby to the subsequent processing unit. MIMO demodulation includes a process of separating a spatially multiplexed signal into a plurality of streams using a channel estimation matrix.

FIG. 4 is a block diagram illustrating an example of the base station according to the first embodiment. In FIG. 4, the base station 40 includes an RF receiver 41, a CP remover 42, an FFT unit 43, a separation unit 44, a channel estimation unit 45, a demodulation unit 46, an inter-base station interface 47, and a PM. Setting unit 48, data signal generation unit 49, precoding unit 50, reference signal generation unit 51, multiplexing units 52-1 to _NT , IFFT units 53-1 to _NT , and CP addition unit 54- 1 to _NT and RF transmitters 55-1 to _NT . In addition, since the structure of the base station 60 and the base station 70 is also the same, the description is abbreviate | omitted.

The RF receiver 41 receives the OFDM signal transmitted from the terminal 20, performs radio reception processing (down-conversion, orthogonal demodulation, A / D conversion, etc.), and outputs it to the CP removal unit 42.

The CP removing unit 42 removes the CP from the OFDM signal after reception processing received from the RF receiving unit 41, and outputs the OFDM signal after the CP removal to the FFT unit 43.

The FFT unit 43 performs an FFT process on the OFDM signal after CP removal received from the CP removal unit 42 to convert it into a frequency domain signal.

The demultiplexing unit 44 demultiplexes the received OFDM signal received from the FFT unit 43 into a control signal, a reference signal, and a data signal included therein. The reference signal is output to the channel estimation unit 45, and the control signal is output to the demodulation unit 46.

The channel estimation unit 45 performs channel estimation between the terminal 20 and its own device using the reference signal transmitted from the terminal 20, and outputs the obtained channel estimation value to the demodulation unit 46.

The demodulation unit 46 performs channel compensation on the control signal using the channel estimation value, and restores the control information.

Here, the control information includes codebook information and precoding matrix information for the own device, and codebook information and precoding matrix information for the base station 60 that jointly transmits with the own device.

Then, the demodulation unit 46 outputs the code book information and precoding matrix information for the device itself to the PM setting unit 48. Further, the demodulator 46 transmits codebook information and precoding matrix information for the base station 60 to the base station 60 via the inter-base station interface 47.

PM setting section 48 sets a precoding matrix for precoding section 50 based on codebook information and precoding matrix information received from demodulation section 46.

Specifically, the PM setting unit 48 specifies a codeword corresponding to the precoding matrix information received from the demodulation unit 46 as a precoding matrix in the codebook corresponding to the codebook information received most recently from the demodulation unit 46. . Then, the PM setting unit 48 sets the specified code word in the precoding unit 50.

In addition, when the own apparatus is a base station of a cooperative cell, the PM setting unit 48 uses the precoding unit 50 based on the codebook information and precoding matrix information received from the connected cell via the inter-base station interface 47. A precoding matrix is set for.

The data signal generation unit 49 generates a data signal and outputs it to the precoding unit 50. Here, the data signal is MIMO-transmitted from _NT antennas. Therefore, the data signal generation unit 49 outputs a plurality of streams to the precoding unit 50 as transmission signals.

The precoding unit 50 performs precoding on the plurality of streams received from the data signal generation unit 49 using the set precoding matrix, and the plurality of precoded streams are multiplexed by the multiplexing units 52-1 to N _T. To each output. Thus, the plurality of streams are MIMO-transmitted via a plurality of antennas.

The reference signal generation unit 51 generates a reference signal and outputs it to the multiplexing units 52-1 to _NT .

Each of the multiplexing units 52-1 to _NT performs frequency multiplexing by mapping the data signal stream received from the precoding unit 50 and the reference signal received from the reference signal generation unit 51 on the frequency axis, and the multiplexed signal is IFFT. Output to the units 53-1 to _NT .

IFFT sections 53-1 to _NT perform IFFT processing on the multiplexed signals received from multiplexing sections 52-1 to _NT to convert them into time domain signals (that is, OFDM signals), and CP adding sections 54-1 to 54-1 Output to _NT .

CP adding section 54-1 ~ _{N T} adds a CP of the OFDM signal received from the IFFT unit 53-1 ~ _{N T,} and outputs the OFDM signal with a CP to the RF transmitting unit 55-1 ~ _{N T} .

RF transmitters 55-1 to _NT perform radio transmission processing (D / A conversion, orthogonal modulation, up-conversion, etc.) on the OFDM signal after CP addition received from CP addition units 54-1 to _NT , The obtained radio signal is transmitted via _NT antennas.

[Operation of base station and terminal]
Operations of the terminal 20, the base station 40, and the base station 60 having the above configuration will be described. FIG. 5 is a diagram illustrating an example of operation processing of the terminal and the base station according to the first embodiment.

<Codebook selection procedure>
The terminal 20, the base station 40, and the base station 60 execute a code book selection procedure (step S10).

Specifically, the base station 40 and the base station 60 transmit a reference signal to the terminal 20 (step S11).

In the terminal 20, the received power ratio calculation unit 26 is based on the ratio of the received power for the base station 60 to the received power for the base station 40 based on the received power of the reference signal transmitted from the base station 40 and the base station 60. A certain received power ratio is calculated (step S12).

The code book selection unit 27 selects a code book for each of the base station 40 and the base station 60 from the code book group based on the reception power ratio calculated by the reception power ratio calculation unit 26 (step S13). ).

Specifically, when the received power ratio is within a predetermined range including 1, the codebook selection unit 27 uses the first codebook as the use codebook for both the base station 40 and the base station 60. select. On the other hand, when the received power ratio is out of the predetermined range, the code book selecting unit 27 selects the first code book as the used code book for the one having the larger received power among the base station 40 and the base station 60. . And the code book selection part 27 selects a 2nd code book as a use code book with respect to the one where received power is smaller among the base station 40 and the base station 60. FIG.

Here, when the difference between the received power for the base station 40 and the received power for the base station 60 is small, the base station 40 and the base station 60 cooperate by applying a high-accuracy codebook. Improvement of reception characteristics by transmission can be expected. On the other hand, when the difference between the received power for the base station 40 and the received power for the base station 60 is large, both when the low-accuracy codebook is applied to the smaller received power It is considered that there is no significant difference in reception characteristics between when a high-precision codebook is applied. However, it is possible to expect an overhead reduction effect by reducing the number of bits required for feedback information by applying a low-accuracy codebook to those with lower received power.

The terminal 20 transmits codebook information about the base station 40 and the base station 60 to the base station 40 (step S14). Then, the base station 40 transfers the code book information of the base station 60 received from the terminal 20 to the base station 60 (step S15).

<Code word selection processing procedure>
The terminal 20, the base station 40, and the base station 60 execute a code word selection processing procedure (step S20).

Specifically, the base station 40 and the base station 60 transmit a reference signal to the terminal 20 (step S21).

In the terminal 20, the PM selection unit 28 selects an optimal codeword from the used codebook selected in step S13 based on the received power of the reference signal transmitted from the base station 40 and the base station 60 (step S22). ).

The terminal 20 transmits precoding matrix information for the base station 40 and the base station 60 to the base station 40 (step S23). Then, the base station 40 transfers the precoding matrix information of the base station 60 received from the terminal 20 to the base station 60 (step S24).

<Procedure for cooperative transmission of data signals>
The base station 40 and the base station 60 perform coordinated transmission of data signals (steps S30 and S31).

Specifically, the base station 40 and the base station 60 perform precoding on the data signal using the precoding matrix indicated by the precoding matrix information transmitted from the terminal 20, and perform cooperative transmission using MIMO. Do.

Next, in FIG. 5, the data signal cooperative transmission procedure and the code word selection procedure are repeated (steps S40, S50, S60, S70, S80, S90, S100).

Then, the code book selection processing procedure is performed again at intervals of the first selection cycle T1 from step S10 (step S110). Then, a code word selection processing procedure is performed (step S120).

Here, as shown in FIG. 5, the code book selection processing procedure is performed with an interval of the first selection cycle T1, while the code word selection processing procedure is performed at the interval of the second selection cycle T2 (T2 <T1). It is done with a gap. That is, the frequency at which the code book selection processing procedure is performed is lower than the frequency at which the code word selection processing procedure is performed. By doing so, it is possible to reduce the impact on the overhead of an increase of 1 bit necessary for feeding back a codebook selected from the two codebooks.

As described above, according to the present embodiment, in the terminal 20, the code book selection unit 27 uses the first code book and the first code book for the use code book for each of the base station 40 and the base station 60. Are selected from a second codebook consisting of a part of a plurality of codeword candidates included in the codeword. For example, this selection is performed based on the reception power ratio calculated by the reception power ratio calculation unit 26.

By doing this, it is possible to select a second codebook with a small number of codewords included, and therefore, it is possible to expect an overhead reduction effect by reducing the number of bits required for feedback information.

In addition, the second codebook includes other codewords calculated for each codeword candidate among a plurality of subsets, each of which includes a predetermined number of codeword candidates arbitrarily selected from the first codebook. Is the subset with the maximum sum of the minimum Euclidean distances between and.

In this way, codeword candidates with different precoding characteristics can be included in the second codebook in a well-balanced manner.

Also, the frequency with which codebook information is fed back is lower than the frequency with which precoding matrix information is fed back.

By doing so, it is possible to reduce the impact on the overhead of an increase of 1 bit necessary for feeding back information on the codebook used selected from the two codebooks.

Further, in the base station 40, the RF receiver 41 receives first information indicating the code book selected in the terminal 20 and second information indicating the code word selected in the terminal 20. Then, the PM setting unit 48 responds to the first information from the first code book and the second code book including a part of the plurality of code word candidates included in the first code book. Select the codebook to use. Then, the PM setting unit 48 specifies a use codeword based on the selected use codebook and the second information, and sets a precoding matrix corresponding to the specified use codeword in the precoding unit 50. To do.

In this way, the first information with a small number of bits can be received when a second code book with a small number of code words is selected.

[Other embodiments]
[1] The terminal and the base station according to the first embodiment can be realized by the following hardware configuration.

FIG. 6 is a diagram illustrating a hardware configuration of the terminal. As shown in FIG. 6, the terminal 20 includes a CPU (Central Processing Unit) 20a, a memory 20b, an RF circuit 20c having an antenna, and a display device 20d such as an LCD (Liquid Crystal Display). Have The memory 20b is composed of, for example, a RAM such as an SDRAM, a ROM, and a flash memory. The RF transmitter 34 and the RF receiver 21 are realized by the RF circuit 20c. Further, the CP removal unit 22, the FFT unit 23, the separation unit 24, the channel estimation unit 25, the reception power ratio calculation unit 26, the codebook selection unit 27, the PM selection unit 28, and the control signal generation unit 29. The reference signal generation unit 30, the multiplexing unit 31, the IFFT unit 32, the CP addition unit 33, and the demodulation unit 35 are realized by an integrated circuit such as the CPU 20a.

FIG. 7 is a diagram illustrating a hardware configuration of the base station. As shown in FIG. 7, the base station 40 includes, as hardware components, a DSP (Digital Signal Processor) 40a, an FPGA (Field Programmable Gate Array) 40b, a memory 40c, and an RF (Radio Frequency) circuit 40d. And a network interface (IF) 40e. The DSP 40a and the FPGA 40b are connected so that various signals and data can be input and output via a network IF 40e such as a switch. The RF circuit 40d has an antenna. The memory 40c includes, for example, a RAM such as SDRAM (Synchronous Dynamic Random Access Memory), a ROM (Read Only Memory), and a flash memory. CP removing unit 42, FFT unit 43, separating unit 44, channel estimating unit 45, demodulating unit 46, PM setting unit 48, data signal generating unit 49, precoding unit 50, and reference signal generating unit 51, and the multiplexing unit 52-1 ~ _{N T,} the IFFT section 53-1 ~ _{N T,} and CP adding section 54-1 ~ _{N T,} for example DSP40a, is realized by an integrated circuit such as FPGA40b. The RF receiver 41 and the RF transmitter 55 are realized by the RF circuit 40d. The inter-base station interface 47 is realized by a network IF 40e. The base station 60 and the base station 70 are similarly configured.

[2] In the first embodiment, the terminal 20 and the base stations 40, 60, and 70 have been described as examples. However, the present invention is not limited to this, and the above-described embodiment also holds for a plurality of transmission apparatuses that cooperatively transmit signals and a reception apparatus that receives signals transmitted from the plurality of transmission apparatuses.

DESCRIPTION OF SYMBOLS 10 Communication system 20 Terminal 21, 41 RF receiving part 22, 42 CP removal part 23, 43 FFT part 24, 44 Separation part 25, 45 Channel estimation part 26 Reception power ratio calculation part 27 Codebook selection part 28 PM selection part 29 Control Signal generators 30, 51 Reference signal generators 31, 52 Multiplexers 32, 53 IFFT units 33, 54 CP adding units 34, 55 RF transmitters 35, 46 Demodulators 40, 60, 70 Base station 47 Inter-base station interface 48 PM setting unit 49 Data signal generation unit 50 Precoding unit

Claims (10)

A receiving apparatus that receives a data signal transmitted from a first transmitting apparatus and a second transmitting apparatus by MIMO (Multiple Input Multiple Output) to which precoding is applied,
Based on the received power for the first transmitter and the received power for the second transmitter, the first codebook and the codeword candidates included in the first codebook A first selection code for selecting a first usage codebook used in the first transmission device and a second usage codebook used in the second transmission device from among a second codebook consisting of a part. Receiving device comprising the selection unit. The second codebook includes other codewords calculated for each codeword candidate among a plurality of subsets each of a predetermined number of codeword candidates arbitrarily selected from the first codebook. Is the subset with the largest sum of the minimum Euclidean distances between
The receiving device according to claim 1. A first codeword set in the first transmitting device is selected from the first used codebook, and a second codeword set in the second transmitting device is selected from the second used codebook. A second selection unit for selecting two codewords;
Information about the selected first codeword and second codeword and the selected first codebook and second codebook is fed back to the first transmission device and the second transmission device. A feedback section;
Comprising
The frequency with which the information about the selected first codebook and the second codebook is fed back is lower than the frequency with which the information about the selected first codeword and the second codeword is fed back.
The receiving device according to claim 1 or 2. The first selection unit is configured to determine the first usage codebook and the second usage code based on a ratio of reception power for the first transmission device and reception power for the second transmission device. Select a book,
The receiving device according to claim 1. A transmission apparatus that transmits data signals to a reception apparatus in cooperation with other transmission apparatuses by MIMO (Multiple Input Multiple Output) to which precoding is applied,
A precoding unit for precoding the data signal using a set precoding matrix;
A receiving unit that receives first information indicating a codebook selected in the receiving device and second information indicating a codeword selected in the receiving device;
A code book is selected in accordance with the first information from the first code book and a second code book comprising a part of a plurality of code word candidates included in the first code book. A setting unit that specifies a codeword based on the selected codebook and the second information, and sets a precoding matrix corresponding to the specified codeword in the precoding unit;
A transmission apparatus comprising: The second codebook includes other codewords calculated for each codeword candidate among a plurality of subsets each of a predetermined number of codeword candidates arbitrarily selected from the first codebook. Is the subset with the largest sum of the minimum Euclidean distances between
The transmission device according to claim 5. The frequency at which the first information is received is lower than the frequency at which the second information is received.
The transmission device according to claim 5 or 6. A reception method for receiving a data signal transmitted from a first transmitter and a second transmitter by MIMO (Multiple Input Multiple Output) to which precoding is applied,
Based on the received power for the first transmitter and the received power for the second transmitter, the first codebook and the codeword candidates included in the first codebook Selecting a first usage codebook used in the first transmission device and a second usage codebook used in the second transmission device from among a second codebook consisting of a part;
A first codeword set in the first transmitting device is selected from the first used codebook, and a second codeword set in the second transmitting device is selected from the second used codebook. Select 2 codewords,
Receiving method. A transmission method in which a plurality of transmission devices cooperate to transmit data signals to a reception device by MIMO (Multiple Input Multiple Output) to which precoding is applied,
Receiving first information indicating a codebook selected in the receiving device and second information indicating a codeword selected in the receiving device;
A codebook to be used is selected according to the first information from a first codebook and a second codebook consisting of a part of a plurality of codeword candidates included in the first codebook And specifying a use codeword based on the selected use codebook and the second information, and setting a precoding matrix corresponding to the specified use codeword,
Precoding the data signal using the set precoding matrix;
Transmission method. A wireless communication system in which a receiving device receives a data signal transmitted by MIMO (Multiple Input Multiple Output) to which precoding is applied from a first transmitting device and a second transmitting device,
The receiving device is:
A reception power for the first transmission device, a first codebook for the second transmission device, and a second code comprising a portion of a plurality of codeword candidates included in the first codebook A first selection unit that selects a first usage codebook used in the first transmission device and a second usage codebook used in the second transmission device from among the codebooks;
A first codeword set in the first transmitting device is selected from the first used codebook, and a second codeword set in the second transmitting device is selected from the second used codebook. A second selection unit for selecting two codewords;
A transmitter that transmits first information indicating a selected codebook and second information indicating a codeword selected in the receiving device;
Each of the first and second transmission devices is
A receiving unit for receiving the first information and the second information transmitted from the receiving device;
Wireless communication system.

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