WO2011155360A1

WO2011155360A1 - Mobile terminal apparatus, base station apparatus, communication system, and communication method

Info

Publication number: WO2011155360A1
Application number: PCT/JP2011/062372
Authority: WO
Inventors: 寿之示沢; 智造野上; 公彦今村
Original assignee: シャープ株式会社
Priority date: 2010-06-10
Filing date: 2011-05-30
Publication date: 2011-12-15
Also published as: JP2011259257A

Abstract

This invention mainly relates to a feedback control and a precoding control in a communication system that transmits a plurality of transmission path status measurement reference signals, and allows adaptive controls to be efficiently performed. A mobile terminal measures, based on a first transmission path status measurement reference signal and a second transmission path status measurement reference signal that is different from the first transmission path status measurement reference signal, a first transmission path status and a second transmission path status, and generates, based on the first transmission path status and the second transmission path status, a plurality of pieces of precoding information as feedback information that is to be fed back to a base station.

Description

Mobile terminal apparatus, base station apparatus, communication system, and communication method

The present invention relates to a communication system including a base station device and a mobile terminal device, a mobile terminal device, a base station device, and a communication method.

For example, in a mobile radio communication system such as LTE (Long Term Evolution), LTE-Advanced, and WiMAX (Worldwide Interoperability for Microwave Access), a plurality of areas covered by a base station (transmitting station, transmitting device, eNodeB) are arranged in a cell shape. By adopting the cellular configuration to be arranged, the communication area can be expanded. In addition, by using different frequencies between adjacent cells (sectors), mobile terminals (receiving stations, mobile stations, receiving devices, UEs (User Equipment)) in the cell edge region can communicate without receiving interference. it can. However, when different frequencies are used between adjacent cells, there is a problem regarding frequency utilization efficiency. On the other hand, frequency utilization efficiency can be greatly improved by repeatedly using the same frequency in each cell (sector). However, in this case, it is necessary to take measures against interference with the mobile terminal in the cell edge (cell edge) region.

In such a situation, a method for reducing or suppressing interference with a mobile terminal in a cell edge region by performing inter-cell cooperative communication between neighboring cells is studied. For example, the following Non-Patent Document 1 discusses a CoMP (Cooperative Multipoint) transmission system as the system.

FIG. 19 is a diagram illustrating an example in which the mobile terminal 1603 located in the cell edge region communicates with the base station 1601 and the base station 1602. Referring to FIG. 19, mobile terminal 1603 is located in each cell edge region (boundary region) in base station 1601 and base station 1602. Base station 1601 and base station 1602 communicate with mobile terminal 1603 in cooperation. The mobile terminal 1603 receives a transmission path condition measurement reference signal 1604 from the base station 1601 and receives a transmission path condition measurement reference signal 1605 from the base station 1602.

The mobile terminal 1603 can estimate the transmission path condition between the base station 1601 and the base station 1602 and the mobile terminal 1603 by using the transmission path condition measurement reference signal 1604 and the transmission path condition measurement reference signal 1605. The mobile terminal 1603 determines the modulation scheme and coding rate (MCS (Modulation and Coding Scheme)), spatial multiplexing number (layer, rank), precoding weight (precoding matrix), etc. By adaptively controlling, more efficient data transmission can be realized. For example, the mobile terminal 1603 can perform control using the method described in Non-Patent Document 2 below.

FIG. 20 is a block diagram illustrating an example for performing adaptive control when considering a downlink (downlink, downlink) in which data transmission from the base station 1700 to the mobile terminal 1710 is considered. First, the base station 1700 uses the multiplexing unit 1702 to transmit a reference signal (RS (Reference Signal), pilot signal, known signal) specific to the base station to a data signal for the mobile terminal 1710 or other movement. It is multiplexed with the data signal for the terminal and transmitted from the transmission antenna 1703.

The mobile terminal 1710 separates the transmission path condition measurement reference signal from the signal received by the reception antenna 1711 in the separation unit 1712. Mobile terminal 1710 provides feedback for adaptively controlling the modulation scheme and coding rate, the number of spatial multiplexing, the precoding matrix, etc., based on the separated channel state measurement reference signal in feedback information generation section 1713. Generate information. The feedback information generation unit 1713 further transmits the generated feedback information from the transmission antenna 1714 through the uplink (uplink, uplink).

The base station 1700 uses the feedback information processing unit 1705 to identify the feedback information transmitted from the mobile terminal 1710 from the signal received by the receiving antenna 1704 and process the identified feedback information. The adaptive control unit 1701 performs adaptive control on the data signal for the mobile terminal 1710 based on the received feedback information.

FIG. 21 is a diagram showing data transmission by cooperative communication. Referring to FIG. 21, mobile terminal 1803 receives data signal 1804 by cooperative communication transmitted from base station 1801 and base station 1802.

In a communication system that transmits a plurality of channel state measurement reference signals, such as a communication system capable of performing cooperative communication, the mobile terminal returns feedback information based on the plurality of channel state measurement reference signals. Generate. In the communication system, particularly when performing cooperative communication, the mobile terminal needs to efficiently generate appropriate feedback information. In particular, in a communication system that performs cooperative communication, a base station needs to efficiently perform appropriate precoding control based on feedback information from a mobile terminal.

However, it has not been clarified that efficient generation of appropriate feedback information and appropriate precoding control as described above are efficiently performed in a communication system that transmits a plurality of channel state measurement reference signals. For this reason, in the communication system, generation of feedback information and precoding control are factors that hinder improvement in transmission efficiency.

The present invention has been made in view of such circumstances, and in a communication system that transmits a plurality of transmission path condition measurement reference signals, mainly relates to feedback control and precoding control, and performs adaptive control efficiently. An object of the present invention is to provide a mobile terminal device, a base station device, a communication system, and a communication method.

(1) According to an aspect of the present invention, the mobile terminal apparatus includes a first transmission path status measurement reference signal different from the first transmission path status measurement reference signal and the first transmission path status measurement reference signal. Based on the first transmission path situation and the second transmission path situation, and based on the first transmission path situation and the second transmission path situation, one or more precoding information is A generating unit that generates the feedback information to the station device.

(2) Preferably, the generation unit generates wideband precoding information and narrowband precoding information as the plurality of precoding information.

(3) Preferably, the generation unit generates long interval variable precoding information and short interval variable precoding information as the plurality of precoding information.

(4) Preferably, the generation unit generates one or a plurality of precoding information as feedback information based on a precoding matrix commonly used for the first transmission path condition and the second transmission path condition. To do.

(5) Preferably, the generation unit sets at least one of a plurality of precoding matrices for the first transmission path condition and the second transmission path condition as a precoding matrix defined in advance, and One or more precoding information is generated as the feedback information based on a precoding matrix other than the precoding matrix defined in advance.

(6) According to another aspect of the present invention, the mobile terminal apparatus receives the first transmission path condition measurement reference signal from the first base station apparatus and performs cooperative communication with the first base station apparatus. Based on the receiving unit that receives the second transmission path condition measurement reference signal from the second base station apparatus, the first transmission path condition measurement reference signal, and the second transmission path condition measurement reference signal. A measurement unit that measures the transmission path status and the second transmission path status, and a generation unit that generates one or more precoding information as feedback information based on the first transmission path status and the second transmission path status And a transmission unit that transmits one or more precoding information generated as feedback information to the first base station apparatus.

(7) According to still another aspect of the present invention, the communication system includes: a first base station apparatus that transmits a first transmission path condition measurement reference signal; and a first transmission path condition measurement reference signal. A second base station device that transmits a different second transmission path condition measurement reference signal, a first transmission based on the first transmission path condition measurement reference signal and the second transmission path condition measurement reference signal A mobile terminal apparatus that measures a path condition and a second transmission path condition and generates one or a plurality of precoding information as feedback information based on the first transmission path condition and the second transmission path condition.

(8) Preferably, the first base station apparatus performs precoding processing based on a plurality of precoding information.

(9) According to still another aspect of the present invention, the communication system performs a precoding process based on a first base station apparatus that performs a precoding process based on a plurality of precoding matrices, and a plurality of precoding matrices. A second base station apparatus to perform, and a mobile terminal apparatus in which cooperative communication is performed by the first base station apparatus and the second base station apparatus.

(10) According to still another aspect of the present invention, in the communication method, the mobile terminal apparatus performs second transmission different from the first transmission path condition measurement reference signal and the first transmission path condition measurement reference signal. The step of measuring the first transmission path situation and the second transmission path situation based on the reference signal for path situation measurement, and the mobile terminal apparatus based on the first transmission path situation and the second transmission path situation Generating one or a plurality of precoding information as feedback information to the base station apparatus.

(11) According to still another aspect of the present invention, the communication method includes a step in which the first base station apparatus transmits the first transmission path condition measurement reference signal, and the second base station apparatus A step of transmitting a second transmission path condition measurement reference signal different from the first transmission path condition measurement reference signal, and the mobile terminal device comprising: the first transmission path condition measurement reference signal and the second transmission path; A step of measuring the first transmission path situation and the second transmission path situation based on the situation measurement reference signal, and the mobile terminal device 1 based on the first transmission path situation and the second transmission path situation; Alternatively, the method includes a step of generating a plurality of precoding information as feedback information to at least the first base station apparatus.

(12) According to still another aspect of the present invention, the communication method includes a step in which the first base station apparatus performs precoding processing based on a plurality of precoding matrices, and a plurality of second base station apparatuses. A precoding process based on the precoding matrix, and a step in which the first base station apparatus and the second base station apparatus perform cooperative communication with the mobile terminal.

According to the present invention, adaptive control can be efficiently performed mainly in relation to feedback control and precoding control in a communication system that transmits a plurality of channel state measurement reference signals.

It is a schematic block diagram which shows the structure of the anchor base station which concerns on the 1st Embodiment of this invention. It is a figure which shows an example of the reference signal for a data signal demodulation, the 1st reference signal for channel condition measurement, an information data signal, or a control information signal which a layer mapping part and a resource element mapping part map. It is a schematic block diagram which shows the structure of the cooperation base station which concerns on the 1st Embodiment of this invention. It is a figure which shows an example of the reference signal for a data signal demodulation, the 2nd reference signal for channel condition measurement, an information data signal, or a control information signal which a layer mapping part and a resource element mapping part map. It is a schematic block diagram which shows the structure of the mobile terminal which concerns on the 1st Embodiment of this invention. It is a figure which shows an example of the wideband precoding matrix and narrowband precoding matrix which are used in the 1st Embodiment of this invention. It is a figure which shows an example of the wideband precoding information and narrowband precoding information which are used in the 1st Embodiment of this invention. It is a figure which shows an example of a system band and a bandwidth part. It is a flowchart of communication between the anchor base station used in the 1st Embodiment of this invention, a cooperation base station, and a mobile terminal. It is a figure which shows an example of the wideband precoding information and narrowband precoding information which are used in the 2nd Embodiment of this invention. It is a figure which shows an example of the wideband precoding information and narrowband precoding information which are used in the 3rd Embodiment of this invention. It is a figure which shows an example of the wideband precoding information and narrowband precoding information which are used in the 4th Embodiment of this invention. It is a figure which shows an example of the wideband precoding information and narrowband precoding information which are used in the 5th Embodiment of this invention. It is a figure which shows an example of the long section fluctuation precoding information and short section fluctuation precoding information which are used in the 6th Embodiment of this invention. It is a flowchart of communication between the anchor base station used in the 6th Embodiment of this invention, a cooperation base station, and a mobile terminal. It is an example of the code book used in the 1st Embodiment of this invention. It is an example of the code book used in the 1st Embodiment of this invention. It is the schematic of the precoding process used in the 1st Embodiment of this invention. It is a figure which shows an example in which the mobile terminal located in a cell edge area | region is communicating with a base station and another base station. It is a block diagram which shows an example which performs adaptive control at the time of considering the downlink (downlink, downlink) which performs the data transmission from a base station to a mobile terminal. It is a figure which shows the data transmission by cooperative communication.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described. The communication system in the first embodiment includes a mobile terminal (terminal device, receiving point, receiving terminal, receiving device, third communication device, receiving antenna group, receiving antenna port group, UE), and base station (transmitting device). , Cell, transmission point, transmission antenna group, transmission antenna port group, component carrier, eNodeB), anchor base station (first base station apparatus, first communication apparatus, serving base station, primary base station, first Component carrier, first transmission path condition measurement reference signal) and coordinated base station (second base station device, coordinated base station group, coordinated base station set, second communication device, secondary base station, second component) Carrier, second transmission path condition measurement reference signal).

FIG. 1 is a schematic block diagram showing a configuration of an anchor base station 100 according to the first embodiment of the present invention. The anchor base station 100 is a base station that receives feedback information from a mobile terminal, a base station that transmits control information for the mobile terminal 500 (for example, information transmitted through a PDCCH (Physical Downlink Control Channel), or the like). The anchor base station 100 is one of base stations that communicate with the mobile terminal 500 in cooperation with a cooperative base station 300 (see FIG. 3) described later. Hereinafter, communication with respect to the mobile terminal 500 by the anchor base station 100 and the coordinated base station 300 coordinated with the anchor base station 100 is referred to as “coordinated communication”.

Referring to FIG. 1, anchor base station 100 includes coding section 101, scramble section 102, modulation section 103, layer mapping section 104, precoding section 105 (first precoding section), and resource elements. Mapping section 106, OFDM signal generation section 107, transmission antenna 108 (transmission antenna port), data signal demodulation reference signal generation section 113, and transmission path condition measurement reference signal generation section 109 (first transmission path condition) A measurement reference signal generation unit), a reception antenna 110, a reception signal processing unit 111, and a feedback information processing unit 112.

The reception antenna 110 receives a data signal including feedback information transmitted from the mobile terminal 500 via an uplink (for example, PUCCH (Physical Uplink Control Channel), PUSCH (Physical Uplink Shared Channel), etc.).

The reception signal processing unit 111 receives reception of transmission processing performed by the mobile terminal 500 for transmission, such as OFDM (Orthogonal Frequency Division Multiplexing) demodulation processing, signal demodulation processing, and decoding processing, on the signal received by the reception antenna 110. Process. The received signal processing unit 111 identifies feedback information from the received signals and outputs the feedback information to the feedback information processing unit 112. When there are a plurality of mobile terminals 500 that communicate with the anchor base station 100, SC-FDMA (Single carrier-frequency division multiple access) is used as an uplink (that is, signal transmission from the mobile terminal 500 to the base station 200). ), Data signals of the mobile terminal 500 can be multiplexed using various multiple access schemes such as Clustered DFT-S-OFDM (Discrete Fourier Transform-Spread-OFDM), OFDMA, time division multiple access, code division multiple access.

Also, the anchor base station 100 can use various methods as a method for identifying feedback information for each mobile terminal 500. For example, the anchor base station 100 designates resources (elements for signal transmission divided by time, frequency, code, spatial domain, etc.) to which each mobile terminal 500 transmits feedback information. The mobile terminal 500 transmits feedback information using the specified resource. Thereby, the anchor base station 100 can identify feedback information for each mobile terminal 500. Also, identification of feedback information for each mobile terminal 500 can be realized by adding a unique identification number for each mobile terminal 500 to each feedback information.

The feedback information processing unit 112 generates adaptive control information for performing various adaptive controls on the data signal transmitted to the mobile terminal 500, based on the input feedback information. When feedback information for the anchor base station 100 is included in the received signal, the feedback information processing unit 112 generates adaptive control information in the anchor base station 100. Feedback information processing section 112 outputs the generated adaptive control information to coding section 101, modulation section 103, layer mapping section 104, precoding section 105, and resource element mapping section 106 in anchor base station 100. Further, the feedback information processing unit 112 may output the adaptive control information to an upper layer (not shown).

Furthermore, when feedback information for the coordinated base station 300 is included in the received signal, the feedback information processing unit 112 performs an encoding unit 601, a modulation unit 603, a layer mapping unit 604, and a resource element mapping unit 606 in the coordinated base station 300 described later. Adaptive control information for is generated. The feedback information processing unit 112 outputs the generated adaptive control information to the coordinated base station 300 through a line such as an X2 interface (preferably a wired line such as an optical fiber or a unique wireless line using a relay technology).

It should be noted that the line connecting the base stations can be used for various purposes other than when the adaptive control information is communicated from the anchor base station 100 to the cooperative base station 300. For example, a line connecting base stations can communicate base station information and / or control information for performing cooperative communication from the cooperative base station 300 to the anchor base station 100. Further, when the received signal does not include feedback information for each base station, the feedback information processing unit 112 may execute a predetermined process.

Next, an adaptive control method based on feedback information will be described. Various information can be used as feedback information. In the following, a case will be described in which recommended transmission format information (implicit transmission path status information) for the base station and information (explicit transmission path status information) indicating the transmission path status (transmission path status, transmission channel) are used. .

First, when the recommended transmission format information for the base station is used as feedback information, it is assumed that a known transmission format is indexed in advance for both the base station and the mobile terminal. Also, the mobile terminal feeds back information using the transmission format, and the base station performs adaptive control using the information.

Specifically, since CQI (Channel Quality Indicator) is information indicating a coding rate and a modulation scheme, feedback information processing section 112 can control the coding section and the modulation section by CQI. Since PMI (Precoding Matrix Index) is information indicating a precoding matrix (hereinafter also referred to as “precoding information PMI”), the feedback information processing unit 112 can control the precoding unit by the precoding information PMI. Since RI (Rank Indicator) is information indicating the number of layers, the feedback information processing unit 112 can control the layer mapping unit and the upper layer that generates the codeword by the RI. Further, when the received signal also includes feedback information related to mapping to resources, the feedback information processing unit 112 can also control the resource element mapping unit according to the feedback information. Here, the precoding information PMI can be divided into a plurality of types according to the data transmission method, purpose, and application. Details of the precoding information PMI will be described later.

Next, when information indicating the transmission path condition is used as feedback information, the mobile terminal feeds back information on the transmission path condition with the base station using a reference signal for transmission path condition measurement from the base station. At that time, the mobile terminal can also reduce the amount of information by using various methods such as eigenvalue decomposition and quantization. The base station controls the terminal device using the information on the fed back transmission path condition. For example, the base station can determine the coding rate and modulation scheme, the number of layers, and the precoding matrix so that the mobile terminal can perform suitable reception based on the fed back information. Further, the base station can use various methods as the determination method.

The encoding unit 101 receives one or more codewords (transmission data signal, information data signal) to be transmitted to the mobile terminal from a processing device in an upper layer of the transmission device (not shown). The encoding unit 101 encodes each code word with an error correction code such as a turbo code, a convolutional code, or an LDPC (Low Density Parity Check) code. The encoding unit 101 outputs each encoded code word to the scramble unit 102. The codeword may be a processing unit that performs retransmission control such as HARQ (Hybrid Automatic Repeat reQuest), a processing unit that performs error correction coding, or a combination of a plurality of these units.

The scramble unit 102 generates different scramble codes for each base station, each mobile terminal, and the like. The scrambler 102 performs a scramble process on the signal encoded by the encoder 101 using the generated scramble code.

The modulation unit 103 performs modulation processing on the scrambled signal using a modulation method such as BPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase Shift Keying), or QAM (Quadrature Amplitude Modulation). Modulation section 103 outputs the modulated signal to layer mapping section 104.

The data signal demodulation reference signal generation unit 113 uses a data signal demodulation reference signal (Dm-RS (Demodulation Reference Signal) that is orthogonal or quasi-orthogonal between layers as a reference signal for demodulating the information data signal in the mobile terminal 500. ), DRS (Dedicated Reference Signal), Precoded RS, user-specific reference signal, UE-specific RS). The data signal demodulation reference signal generation unit 113 outputs the generated data signal demodulation reference signal to the layer mapping unit 104.

The data signal demodulation reference signal is precoded together with the information data signal for the mobile terminal 500. Further, the reference signal generation unit 113 for data signal demodulation uses either code division multiplexing (CDM; Code Division Multiplexing) or frequency division multiplexing (FDM) using orthogonal codes such as Walsh codes, or code division. Multiplexing and frequency division multiplexing are used together to orthogonalize the data signal demodulation reference signals of each layer. In addition, the data signal demodulation reference signal generation unit 113 can change the data signal demodulation reference signal according to the number of layers for the mobile terminal 500. Specifically, when the number of layers is 1 or 2, the data signal demodulation reference signal generation unit 113 performs code division multiplexing using an orthogonal code having a code length of 2. When the number of layers is 3 or 4, the data signal demodulation reference signal generation unit 113 uses both code division multiplexing using an orthogonal code having a code length of 2 and frequency division multiplexing. When the number of layers is 5 to 8, the data signal demodulation reference signal generation unit 113 uses both code division multiplexing using an orthogonal code having a code length of 4 and frequency division multiplexing. Hereinafter, a group in which the reference signal for data signal demodulation is code division multiplexed is referred to as a “CDM group”.

The layer mapping unit 104 maps the data signal demodulation reference signal input from the data signal demodulation reference signal generation unit 113 to each layer that performs spatial multiplexing such as MIMO (Multi-Input Multi-Output). Further, the layer mapping unit 104 maps the signal output by each modulation unit 103 to the resource elements excluding the data signal demodulation reference signal for each layer. For example, assuming that the number of codewords is 2 and the number of layers is 8, the layer mapping unit 104 changes the number of layers to 8 by converting each codeword into four parallel signals. However, the present invention is not limited to this.

The precoding unit 105 converts the signal output from the layer mapping unit 104 into parallel signals of the number of antenna ports (transmission antennas, logical ports) by performing precoding processing. Here, in the precoding process, the mobile terminal 500 can receive efficiently (for example, the reception power is maximized, the interference from the adjacent cell is reduced, or the interference to the adjacent cell is reduced). It is preferable to perform phase rotation or the like on the signal output from the layer mapping unit 104 so as to be small. Also, processing based on pre-determined precoding matrix, CDD (Cyclic Delay Diversity), transmit diversity (SFBC (Spatial Frequency Block Code), STBC (Spatial Time Block Code), TSTD (Time Switched Transmission Diversity), FSTD (Frequency Switched) Transmission Diversity) etc. can be used. However, the present invention is not limited to this. Here, when the precoding information PMI divided into a plurality of types is fed back, the precoding unit 105 can perform precoding processing based on the plurality of precoding information PMI. Details thereof will be described later.

The transmission path condition measurement reference signal generation unit 109 is used by the anchor base station 100 and the mobile terminal 500 to measure the transmission path condition (first transmission path condition) between the anchor base station 100 and the mobile terminal 500. A first transmission path condition measurement reference signal (cell-specific reference signal, CRS (Common RS), Cell-specific RS, Non-precoded RS) known to each other is generated. The transmission path condition measurement reference signal generation unit 109 outputs the generated first transmission path condition measurement reference signal to the resource element mapping unit 106. At this time, if both the anchor base station 100 and the mobile terminal 500 are known signals, an arbitrary signal (sequence) can be used as the first transmission path condition measurement reference signal. For example, as the arbitrary signal (sequence), a random number or a pseudo-noise sequence based on parameters assigned in advance such as a number (cell ID) unique to the anchor base station 100 can be used. In addition, as a method of orthogonalizing between antenna ports, a method of making resource elements that map the first reference signal for transmission path condition measurement mutually null (zero) between antenna ports, code division multiplexing using a pseudo-noise sequence A method, a method combining them, or the like can be used.

The resource element mapping unit 106 maps the transmission data signal output from the precoding unit 105 and the transmission path condition measurement reference signal output from the transmission path condition measurement reference signal 109 to the resource element of each antenna port. . Note that the mobile terminal 500 may further generate a reference signal for demodulating the control information signal, and the resource element mapping unit 106 may perform mapping.

FIG. 2 is a diagram illustrating an example of a data signal demodulation reference signal, a first transmission path condition measurement reference signal, an information data signal, or a control information signal mapped by the resource element mapping unit 106. Specifically, FIG. 2 shows a case where each signal is mapped when the number of antenna ports of the anchor base station 100 is 8 and the number of CDM groups of the reference signal for data signal demodulation is 2. Referring to FIG. 2, two resource blocks are included in one subframe. One resource block includes 12 subcarriers in the frequency direction and 7 OFDM symbols in the time direction. Each subcarrier in one OFDM symbol is also called a resource element. Of each subframe, the seven OFDM symbols before and after in the time direction are also called slots.

Of the colored resource elements in the figure, the reference signals for data signal demodulation of

CDM group numbers

1 and 2 are represented as D1 and D2, respectively, and the reference signals for channel state measurement of antenna ports 1 through 8 are represented as C1 and C8, respectively. ing. Furthermore, the resource element mapping unit 106 maps the information data signal or the control information signal to resource elements other than the resource element to which the reference signal in the figure is mapped. In this example, the maximum number of layers of the information data signal or the control information signal can be eight. For example, the number of information data signal layers can be two, and the number of control information signal layers can be one.

The resource element mapping unit 106 can change the number of resource blocks according to the frequency bandwidth (system bandwidth) used by the communication system. For example, the resource element mapping unit 106 can use 6 to 110 resource blocks. Furthermore, the resource element mapping unit 106 can increase the total system bandwidth to 110 or more by frequency aggregation. Usually, a component carrier is composed of 100 physical resource blocks. By using five component carriers with a guard band between component carriers, the total system bandwidth can be made 500 physical resource blocks. Expressing this in terms of bandwidth, for example, the total system bandwidth can be set to 100 MHz by configuring the component carrier at 20 MHz and using five component carriers with a guard band between the component carriers. .

Referring again to FIG. 1, OFDM signal generation section 107 performs frequency-time conversion processing on the frequency domain signal output by resource element mapping section by inverse fast Fourier transform (IFFT) or the like. Thus, the signal is converted into a time domain signal. Furthermore, the OFDM signal generation unit 107 adds a guard interval (cyclic prefix) by cyclically extending a part of each OFDM symbol. The transmission antenna 108 performs a process of converting the signal (baseband signal) output from the OFDM signal generator 107 into a signal for a radio frequency band. The transmission antenna 108 transmits the signal after the conversion process.

FIG. 3 is a schematic block diagram showing the configuration of the coordinated base station 300. The coordinated base station 300 is a base station that excludes the anchor base station 100 described with reference to FIG. 1 among the base stations that perform coordinated communication with the mobile terminal 500.

Referring to FIG. 3, cooperative base station 300 includes coding section 301, scramble section 302, modulation section 303, layer mapping section 304, precoding section 305 (second precoding section), resource elements Mapping section 306, OFDM signal generation section 307, transmission antenna 308, transmission path condition measurement reference signal generation section 309, data signal demodulation reference signal generation section 313 (second transmission path condition measurement reference signal generation Part).

The difference between the coordinated base station 300 and the anchor base station 100 described with reference to FIG. 1 is that each unit for receiving feedback information from the mobile terminal 500 is omitted in the coordinated base station 300. Further, adaptive control information for adaptively controlling each of the encoding unit 301, the modulation unit 303, the layer mapping unit 304, the precoding unit 305, and the resource element mapping unit 306 is transmitted from the anchor base station 100 through a line such as an X2 interface. Input to the coordinated base station 300. Further, in a cooperative communication scheme (for example, Joint Transmission, Dynamic Cell Selection, etc.) in which an information data signal is also transmitted from the cooperative base station 300 to the mobile terminal 500, an information data signal from the anchor base station 100 to the mobile terminal 500 is also an X2 interface, etc. Are input to the coordinated base station 300 through this line.

Hereinafter, the operation of the coordinated base station 300 will be described with a focus on differences from the anchor base station 100 described with reference to FIG.

The precoding unit 305 can perform different operations depending on the cooperative communication scheme for the mobile terminal 500. First, in a cooperative communication scheme in which an information data signal is transmitted from the cooperative base station 300 to the mobile terminal 500, such as joint transmission or joint processing, the precoding unit 305 includes the anchor base station 100. It is preferable to perform the precoding process so that the mobile terminal 500 can perform appropriate reception in cooperation with the above. Further, in a cooperative communication scheme such as coordinated scheduling or coordinated beamforming, the precoding unit 305 reduces other interference from the coordinated base station 300 to the mobile terminal 500. Precoding processing (including transmission power control) is preferably performed on the information data signal of the mobile terminal.

The reference signal generator 309 for transmission path condition measurement is used by the coordinated base station 300 and the mobile terminal 500 to measure the transmission path condition (second transmission path condition) between the coordinated base station 300 and the mobile terminal 500. Second reference signals for measurement of transmission path conditions (cell-specific reference signal, CRS (Common RS), Cell-specific RS, Non-precoded RS) are generated. The transmission path condition measurement reference signal generation unit 309 outputs the generated second transmission path condition measurement reference signal to the resource element mapping unit 306. At this time, if both the coordinated base station 300 and the mobile terminal 500 are known signals, an arbitrary signal (sequence) can be used as the second transmission path condition measurement reference signal. For example, as the arbitrary signal (sequence), a random number or a pseudo noise sequence based on a parameter assigned in advance such as a number (cell ID) unique to the coordinated base station 300 can be used. In addition, as a method of orthogonalizing between antenna ports, a method of making resource elements that map the second transmission path condition measurement reference signal mutually null (zero) between antenna ports, code division multiplexing using a pseudo noise sequence A method or the like can be used.

FIG. 4 is a diagram illustrating an example of a data signal demodulation reference signal, a second transmission path condition measurement reference signal, an information data signal, or a control information signal mapped by the layer mapping unit 304 and the resource element mapping unit 306. Here, the precoding process described above is performed by the precoding unit 305 on the reference signal for data signal demodulation. The second transmission path condition measurement reference signal is mapped so as to be frequency-division multiplexed with respect to the first transmission path condition measurement reference signal described in FIG. In the example of FIG. 2, the shift is in the frequency direction for one subcarrier. The position where each transmission path condition measurement reference signal is mapped may be notified or notified to the mobile terminal 500 as control information (including RRC (Radio Resource Control) signaling). In addition, the position where each transmission path condition measurement reference signal is mapped may be identified by the mobile terminal 500 based on other control information such as a cell ID. Moreover, only the position where the reference signal for channel condition measurement for one antenna port is mapped can be notified, broadcasted, or identified, and other antenna ports can be identified based on the position. It can also be done.

In this case, the resource element mapping unit 306 includes the second transmission path condition measurement reference signal and the first transmission path out of the information data signal or the control information signal mapped by the anchor base station 100 and the coordinated base station 300. The resource elements to which the situation measurement reference signal is mapped may be muted (zero, null), respectively. That is, the resource element mapping unit 306 mutes the resource element of the second transmission path condition measurement reference signal mapped by the coordinated base station 300 among the information data signal or control information signal mapped by the anchor base station 100. May be. Also, the resource element mapping unit 306 mutes the resource element of the first transmission path condition measurement reference signal mapped by the anchor base station 100 among the information data signal or control information signal mapped by the coordinated base station 300. May be. Note that all or part of the resource elements to be muted may be used.

When the resource element mapping unit 306 performs muting, the mobile terminal 500 can efficiently estimate the transmission path status when performing cooperative communication. As a muting method, for example, after mapping an information data signal or a control information signal, there is a method of thinning out a signal of a resource element to which a reference signal for transmission path condition measurement of another cooperating base station is mapped ( Puncturing). As another method, there is a method of mapping an information data signal or a control information signal so as to avoid a resource element to which a reference signal for transmission path condition measurement of another base station in cooperation is mapped (rate matching).

FIG. 5 is a schematic block diagram showing the configuration of the mobile terminal 500. Referring to FIG. 5, mobile terminal 500 includes reception antenna 501 (reception antenna port), OFDM signal demodulation section 502, resource element demapping section 503, and filter section 504 (propagation fluctuation compensation section, equalization section). , Interference removal unit, interference reduction unit), layer demapping unit 505, demodulation unit 506, descrambling unit 507, decoding unit 508, propagation path estimation unit 509, and feedback information generation unit 510 (transmission path status) A measurement unit), a transmission signal generation unit 511, and a transmission antenna 512.

The mobile terminal 500 includes at least one reception antenna 501 having the number of reception antennas (the number of reception antenna ports). The receiving antenna 501 receives a signal transmitted by the anchor base station 100 and the coordinated base station 300 and passing through a transmission path (propagation path, channel). The receiving antenna 501 performs a process of converting a received signal (a radio frequency band signal) into a baseband signal.

The OFDM signal demodulator 502 removes the guard interval added from the baseband signal. The OFDM signal demodulator 502 converts the baseband signal from which the guard interval has been removed, into a frequency domain signal by performing a time-frequency conversion process using a Fast Fourier Transform (FFT) or the like.

The resource element demapping unit 503 demaps (separates) signals mapped by the anchor base station 100 and the coordinated base station 300. The resource element demapping unit 503 outputs the information data signal to the filter unit 504 by demapping. Resource element demapping section 503 outputs the first transmission path condition measurement reference signal and the second transmission path condition measurement reference signal to feedback information generation section 510. Further, the resource element demapping unit 503 outputs the data signal demodulation reference signal to the propagation path estimation unit 509. Further, the control information signal is shared by the entire mobile terminal 500 (including the upper layer). The control information signal is used for various controls in the mobile terminal 500 such as demodulation of the information data signal (not shown).

Based on the input data signal demodulation reference signal, the propagation path estimation unit 509 varies the amplitude and phase (frequency response, transmission) in each resource element for each layer (rank, spatial multiplexing) of each reception antenna 501. A channel estimation value is obtained by estimating (propagation channel). Note that the propagation path estimation unit 509 interpolates, in the frequency direction and the time direction, for resource elements to which the data signal demodulation reference signal is not mapped, based on the resource elements to which the data signal demodulation reference signal is mapped. To estimate the propagation path. As the interpolation method, various methods such as linear interpolation, parabolic interpolation, polynomial interpolation, Lagrange interpolation, spline interpolation, FFT interpolation, and minimum mean square error (MMSE) can be used.

The filter unit 504 performs channel compensation using the channel estimation value output by the channel estimation unit 509 on the data signal for each reception antenna 501 output by the resource element demapping unit 503, thereby performing layer-by-layer compensation. The information data signal is detected (restored). As the detection method, ZF (Zero Forcing) standard or MMSE standard equalization, interference removal, and the like can be used. As other detection methods, a method based on MLD (Maximum Likelihood Detection) (for example, QRM-MLD (QR decomposition and M-algorithm MLD)), a method based on SIC (Successive Interference Cancellation) (for example, Turbo SIC, A method based on MMSE-SIC, ZF-SIC, BLAST (Bell laboratories layered space-time architecture, etc.), PIC (Parallel Interference Cancellation), etc. can also be applied.

The layer demapping unit 505 performs a demapping process on the signal for each layer with respect to each codeword. Thereafter, processing is performed for each codeword. The demodulator 506 performs demodulation based on the modulation scheme used in the anchor base station 100 and / or the coordinated base station 300. The descrambling unit 507 performs descrambling processing based on the scramble code used in the anchor base station 100 and / or the coordinated base station 300. Decoding section 508 performs error correction decoding processing based on the encoding method performed by anchor base station 100 and / or cooperative base station 300, and outputs the processing result to a higher layer processing apparatus of mobile terminal 500.

On the other hand, the feedback information generation unit 510 generates feedback information based on the transmission path condition measurement reference signal from each base station output by the resource element demapping unit 503. A method for generating feedback information is as follows. Feedback information generation section 510 uses the received reference signal for transmission path status measurement to determine the transmission path status of receiving antenna 501 in mobile terminal 500 for each transmitting station in each base station (reference signal for transmission path status measurement). For each base station (each reference signal for transmission path condition measurement) to generate a transmission path condition measurement value. Next, feedback information generation section 510 generates feedback information based on the generated transmission path condition estimated value.

In addition, as a unit for generating feedback information, the frequency direction (for example, for each subcarrier, for each resource element, for each resource block, for each subband composed of a plurality of resource blocks), for the time direction (for example, for each OFDM symbol Sub-frames, slots, radio frames, etc.), spatial directions (for example, antenna ports, transmission antennas, reception antennas, etc.) can be used. Furthermore, as a unit for generating feedback information, two or more of the frequency direction, the time direction, and the spatial direction can be combined.

Further, when the feedback information generating unit 510 generates recommended transmission format information for the base station as feedback information, various methods can be used for generating the recommended transmission format information. For example, first, feedback information generation section 510 obtains the maximum number of layers that can be spatially multiplexed by using eigenvalue decomposition or the like based on the generated transmission path condition estimated value. The feedback information generation unit 510 generates an RI based on the determined maximum number of layers. Feedback information generation section 510 estimates a precoding matrix or the like that allows suitable reception based on the generated RI and transmission path state estimated value. Feedback information generating section 510 generates precoding information PMI based on the estimated precoding matrix. The feedback information generation unit 510 uses, for example, a precoding matrix that is suitable for cooperative communication by multiplying the generated channel state estimation value by generating a precoding matrix that is a candidate and generating precoding information PMI. Also good. Further, feedback information generation section 510 may select a suitable precoding matrix using eigenvalue decomposition or the like.

Next, feedback information generation section 510 selects a modulation scheme and coding rate for the information data signal based on the generated RI, precoding information PMI, and transmission path condition estimated value. Feedback information generating section 510 generates CQI based on the selected modulation scheme and coding rate. The feedback information generation unit 510 may, for example, (i) receive signal power to interference / noise power ratio (SINR (Signal to Interference plus Noise power Ratio)), receive signal power to interference power ratio (SIR (Signal to Interference power Ratio)). ), Received signal power to noise power ratio (SNR (Signal to Noise power Ratio)), path loss, etc., and (ii) presetting a CQI lookup table that satisfies the required quality for each measurement value Alternatively, (iii) SINR at the time of performing cooperative communication may be obtained, and (iv) CQI may be generated from the preset lookup table.

The transmission signal generation unit 511 performs transmission processing by performing encoding processing, signal modulation processing, OFDM signal generation processing, and the like in order to transmit (feedback) the feedback information output from the feedback information generation unit 510 to the anchor base station 400. Is generated. The transmission antenna 512 transmits a transmission signal including feedback information generated by the transmission signal generation unit 511 to the anchor base station 100 and / or the coordinated base station 300 via an uplink (PUCCH or PUSCH).

In addition, as a method of feeding back the generated feedback information as described above to the anchor base station 100 and / or the coordinated base station 300, for example, it is divided into a plurality of subframes through the PUCCH designated by the anchor base station 100 and transmitted. can do. Further, the mobile terminal 500 can also transmit all or part of the generated feedback information in one subframe through the PUSCH specified by the anchor base station 100. At that time, the mobile terminal 500 may transmit the generated feedback information together with the information data signal from the mobile terminal 500.

Hereinafter, feedback of precoding processing and precoding information PMI used in this embodiment will be described. In the present embodiment, precoding information PMI for each base station includes wideband precoding information (wideband PMI, first partial precoding information) PMI1 indicating a wideband precoding matrix (weight, vector) W1, and narrowband precoding. A case will be described in which two types of narrowband precoding information (narrowband PMI, second partial precoding information) PMI2 indicating the matrix W2 are divided.

FIG. 6 is a diagram illustrating an example of a wideband precoding matrix and a narrowband precoding matrix used in the present embodiment. Referring to FIG. 6, the wideband precoding matrix in anchor base station 100 (first transmission path condition measurement reference signal) is W1a, and the narrow band in anchor base station 100 (first transmission path condition measurement reference signal). The precoding matrix is W2a, the wideband precoding matrix at the coordinated base station 300 (second transmission path condition measurement reference signal) is W1b, and the narrowband pattern at the coordinated base station 300 (second transmission path condition measurement reference signal). Let the recording matrix be W2b.

When the precoding matrix as shown in FIG. 6 is set in each base station, the precoding unit in each base station performs operations based on the wideband precoding matrix and the narrowband precoding matrix (multiplication, division, addition, The precoding matrix W for the information data signal is determined by performing subtraction, Kronecker calculation, weighting calculation, selection, and the like. That is, the precoding unit in each base station is obtained by W = f (W1, W2). Here, f (x, y) represents a function of x and y.

Hereinafter, as an example of the calculation, a case where a precoding matrix for an information data signal is obtained by multiplying a narrowband precoding matrix by a wideband precoding matrix will be described. In other words, the case where W = W1 * W2 is used will be described as an example. The symbol “*” is an arithmetic operator indicating multiplication. When this calculation is performed, characteristics when the mobile terminal 500 is located at the cell edge are improved.

Specifically, the anchor base station 100 obtains the precoding matrix Wa of the precoding process performed by the precoding unit 105 using Wa = W1a * W2a. Also, cooperative base station 300 obtains precoding matrix Wb of precoding processing performed by precoding unit 305 by Wb = W1b * W2b. The obtained precoding matrices Wa and Wb are respectively used for operations such as multiplication on the information data signal. Note that the narrowband precoding matrix multiplied by the wideband precoding matrix may be a precoding matrix for the information data signal. That is, anchor base station 100 and cooperative base station 300 may obtain a precoding matrix for the information data signal by W = W2 * W1. In this calculation, the cell throughput is particularly improved.

Next, precoding information PMI generated by the feedback information generation unit 510 in the mobile terminal 500 in order to perform the precoding process as described above will be described. *

FIG. 7 is a diagram showing an example of wideband precoding information and narrowband precoding information used in the present embodiment. In FIG. 7, wideband precoding information PMI1 common to the anchor base station 100 and the cooperative base station 300 and narrowband precoding information PMI2 common to the anchor base station 100 and the cooperative base station 300 are shown.

In the present embodiment, the feedback information generation unit 510 in the mobile terminal 500 uses the first transmission path condition measurement reference signal from the anchor base station 100 and the second transmission path condition measurement reference signal from the coordinated base station 300. Based on this, broadband precoding information PMI1 and narrowband precoding information PMI2 as shown in FIG. 7 are generated.

Generation of broadband precoding information PMI1 and narrowband precoding information PMI2 will be described. Feedback information generation section 510 selects, for example, a combination of a candidate wideband precoding matrix and narrowband precoding matrix. Feedback information generation section 510 multiplies the channel state estimated value by a precoding matrix obtained by an operation based on the selected wideband precoding matrix and narrowband precoding matrix. Feedback information generation section 510 selects a precoding matrix that is suitable when anchor base station 100 and cooperative base station 300 perform cooperative communication, from among the combinations of candidate matrices. Feedback information generating section 510 generates wideband precoding information PMI1 and narrowband precoding information PMI2 corresponding to the selected precoding matrix. At this time, feedback information generation section 510 selects a combination of wideband precoding matrix and narrowband precoding matrix that is common to anchor base station 100 and cooperative base station 300, respectively.

At this time, the mobile terminal 500 can change the generation method of the wideband precoding information PMI1 and the narrowband precoding information PMI2 according to the cooperative communication scheme. First, in the cooperative communication scheme in which an information data signal is transmitted from the cooperative base station 300 to the mobile terminal 500 such as joint transmission and joint processing, when the anchor base station 100 and the cooperative base station 300 transmit jointly, The mobile terminal 500 preferably selects the precoding matrix so that the mobile terminal 500 can perform suitable reception. Further, in a cooperative communication scheme such as cooperative scheduling and cooperative beamforming, the mobile terminal 500 precodes information data signals of other mobile terminals so as to reduce interference from the cooperative base station 300 with respect to the mobile terminal 500. It is preferable to select a matrix (including transmission power control). At that time, the mobile terminal 500 may further consider the reception state of the information data signal for the mobile terminal 500 in the anchor base station 100.

Here, wideband precoding information and narrowband precoding information will be described. FIG. 8 is a diagram illustrating an example of the system bandwidth and the bandwidth part. Referring to FIG. 8, the system bandwidth is composed of 16 resource blocks. The system bandwidth is composed of four bandwidth parts (BW (Bandwidth) parts). Each of the four bandwidth parts is composed of four resource blocks. The wideband precoding information indicates one precoding information in the system bandwidth. The narrowband precoding information indicates one precoding information with a BW part width.

The feedback information generation unit 510 of the mobile terminal 500 may divide the BW part width into subbands and the like, and use precoding information in which one subband is selected from one BW part as narrowband precoding information. Further, even when the narrowband precoding information is generated for each BW part, the feedback information generation unit 510 may feed back all of the information or may feed back a part thereof. For example, the feedback information generation unit 510 can select and feed back one or more BW parts with good reception characteristics.

Also, if there is no BW part with good reception characteristics, feedback information generation section 510 does not need to feed back narrowband precoding information. In this case, the feedback information generation unit 510 can select a communication method such as a transmission diversity method. Further, feedback information generation section 510 can also use narrowband precoding information PMI2 as wideband feedback information. In this case, the feedback information generation unit 510 can improve scheduling flexibility and reception performance by frequency selectivity of the transmission path condition.

Next, precoding information and precoding processing based on precoding information will be described more specifically. The system determines that a suitable precoder F is expressed as F = A (i) B (j), and the mobile terminal 500 anchors i as wideband precoding information PMI1 and j as narrowband precoding information PMI2. Report to base station 100. Here, F is a matrix having a size of the number of layers × the number of antenna ports. A and B are matrices of a predetermined size. However, the matrix here is a concept including a vector or a scalar. As A and B, for example, any matrix uniquely determined by designating i and j as follows can be used.

(1) A (i) = Wi, B (j) = V1 + V2φj. Here, V1 and V2 are predetermined matrices composed of elements of 0 and 1, Wi is a matrix specified by a predetermined codebook, and φj is a scalar specified by a predetermined codebook.

(2) A (i) = Wi, B (j) = Φj. Wi and Φj are matrices specified by a predetermined code book.

(3) A (i) = [Wi Wi], B (j) = Φj. Wi and Φj are matrices specified by a predetermined code book.

(4) A (i) = K (U, Wi), B (j) = [IΦjT] T. U is a predetermined matrix, I is a unit matrix, and Wi and Φj are matrices specified by a predetermined codebook. K (X, Y) is a Kronecker product of the matrix X and the matrix Y, and XT is an operator representing a transposed matrix of the matrix X.

Thus, the preferred precoders represented by using the wideband precoding information PMI1 and the narrowband precoding information PMI2 are the precoders represented by the wideband precoding information PMI1 and the precoders represented by the narrowband precoding information PMI2. It can be expressed as a combined precoder. Here, a case will be described in which the system decides F = A (i) B (j) as a combination of precoders, but F = K (A (i), B (j)) and The same effect can be obtained even if other precoder connection methods are determined by the system, such as when expressing.

FIG. 16 is an example of a code book used in the present embodiment. The size of this code book is 16. By designating an index i that can be represented by 4 bits as the wideband precoding information PMI1, Wi corresponding to i is uniquely determined.

FIG. 17 is an example of a code book used in the present embodiment. The size of the code book shown in FIG. The mobile terminal 500 uniquely determines Φj corresponding to i by designating an index j that can be represented by 4 bits as the narrowband precoding information PMI2.

FIG. 18 is a schematic diagram of the precoding process used in this embodiment. Hereinafter, a case where the number of antenna ports is 4, the number of layers is 2, and F = WiΦj will be described. The signal point at each antenna port of each layer is displaced (here, the phase is rotated in the range of 0 to 2π) by Wi, which is the precoder represented by the wideband precoding information PMI1. Furthermore, the signal point at each antenna port of each layer is displaced (here, the phase is rotated in the range of 0 to 2π) by Φj, which is the precoder represented by the narrowband precoding information PMI2.

When the mobile terminal 500 first reports the wideband precoding information PMI1 to the anchor base station 100, the mobile terminal 500 uses a suitable precoder (from a codebook including a precoder group that gives a specific displacement to signal points at each antenna port of each layer. The precoder that is suitable for the signal point after applying the precoder is determined. Here, mobile terminal 500 uses a code book as shown in FIG. 16 as a code book used for determination of wideband precoding information PMI1. When mobile terminal 500 next reports narrowband precoding information PMI2 to anchor base station 100, mobile terminal 500 further applies the precoder to the signal point after applying the precoder represented by the reported wideband precoding information PMI1. From the code book, the precoder for which the signal point is suitable is determined. The mobile terminal 500 reports the determined precoder index as narrowband precoding information PMI2. Here, the mobile terminal 500 uses a code book as shown in FIG. 17 as a code book used to determine the narrowband precoding information PMI2. The signal point displacement shown in FIG. 18 is an example, and the present invention is not limited to this.

FIG. 9 is a flowchart of communication among the anchor base station 100, the cooperative base station 300, and the mobile terminal 500 used in the present embodiment. First, the anchor base station 100 notifies the mobile terminal 500 of one or more coordinated base stations 300 for performing coordinated communication (step S901). The anchor base station 100 can use various methods as the notification method. For example, the anchor base station 100 provides the mobile terminal 500 with the cell ID of the coordinated base station 300, the coordinated component carrier, information identifying frequency bands (including a list indicating information), and the like (including combinations thereof). You may be notified. In these notification methods, the anchor base station 100 directly designates the cooperative base station 300, so that flexible cooperative communication can be performed. Also, the anchor base station 100 may notify in association with other control information. In this case, since the anchor base station 100 does not directly specify the coordinated base station 300, the overhead of control information can be reduced. When the anchor base station 100 notifies the mobile terminal 500 of base stations that are candidates for cooperative communication with the mobile terminal 500 in advance and performs cooperative communication, the mobile terminal 500 selects the cooperative base station from the candidates. It can also be designated as station 300. In this case, flexible cooperative communication can be realized while reducing the overhead of control information. Further, the anchor base station 100 can dynamically perform these notifications as control information by PDCCH, or can perform semi-static (quasi-static) as RRC signaling.

Next, the anchor base station 100 transmits the first transmission path condition measurement reference signal CSIRSa to the mobile terminal 500 (step S902). The cooperative base station 300 transmits the second transmission path condition measurement reference signal CSIRSb (step S903). The mobile terminal 500 receives CSISa and CSIRSb. The mobile terminal 500 generates the wideband precoding information PMI1 and the narrowband precoding information PMI2 as described in FIG. 7 based on the received CSIRSa and CSIRSb. The mobile terminal 500 feeds back the generated wideband precoding information PMI1 and narrowband precoding information PMI2 to the anchor base station 100 (step S904).

Based on the wideband precoding information PMI1 and the narrowband precoding information PMI2 fed back from the mobile terminal 500, the anchor base station 100 uses the wideband precoding matrix W1a in the anchor base station 100 and the narrowband precoding matrix in the anchor base station 100. W2a, a wideband precoding matrix W1b in cooperative base station 300, and a narrowband precoding matrix W2b in cooperative base station 300 are generated. The anchor base station 100 notifies the cooperative base station 300 of the information data signal data, the wideband precoding matrix W1b, and the narrowband precoding matrix W2b for the mobile terminal 500 (step S905). At this time, the anchor base station 100 may notify the wideband precoding information PMI1 and the narrowband precoding information PMI2, or the precoding matrix obtained by calculating the wideband precoding matrix W1b and the narrowband precoding matrix W2b. You may be notified.

The anchor base station 100 calculates a signal (for example, g (W1a, w2a, data) calculated based on the wideband precoding matrix W1a, the narrowband precoding matrix W2a, and data, where g (x, y , Z) transmits a function having x, y, z as parameters to the mobile terminal 500 (step S906). For example, anchor base station 100 transmits to mobile terminal 500 a signal obtained by multiplying data by a precoding matrix obtained by multiplying wideband precoding matrix W1a and narrowband precoding matrix W2a. Also, using the same resource transmitted by the anchor base station 100 in step S906, the coordinated base station 300 uses the signals (for example, g (W1b) obtained based on the wideband precoding matrix W1b, the narrowband precoding matrix W2b, and data. , W2b, data) is transmitted to the mobile terminal 500 (step S907). For example, cooperative base station 300 transmits to mobile terminal 500 a signal obtained by multiplying data by a precoding matrix obtained by multiplying wideband precoding matrix W1b and narrowband precoding matrix W2b.

By using the method described in this embodiment, even when the anchor base station 100 and the coordinated base station 300 perform coordinated communication, the transmission quality is improved without increasing feedback information, compared with the case where the coordinated communication is not performed. Can be realized. Further, even when the anchor base station 100 and the cooperative base station 300 perform cooperative communication, the feedback method can be made the same as the feedback method when the cooperative communication is not performed. Therefore, the mobile terminal 500 can efficiently transmit data when transmitting feedback information.

In the above description, RI, wideband precoding information PMI1, narrowband precoding information PMI2, and CQI have been described as independent feedback information. However, all or part of them may be combined into one piece of information. For example, it can be realized by joint coding. Specifically, RI and wideband precoding information PMI1 may be combined into one piece of information by joint coding.

In the above description, the reference signal for demodulating the data signal has been described using a combination of CDM and FDM using orthogonal codes. However, the present invention is not limited to this. At this time, any signal (sequence) can be used as the reference signal for data signal demodulation as long as both the base station and the mobile terminal are known signals. For example, a random number or pseudo-noise sequence (for example, M) based on a pre-assigned parameter such as a number unique to the base station (cell ID) and a number unique to the mobile terminal (RNTI; Radio Network Temporary Identifier) (Maximum-length) sequences, Gold codes, orthogonal Gold codes, Walsh codes, OVSF (Orthogonal Variable Spreading Factor) codes, Hadamard codes, Barker codes, etc. can be used as reference signals for data signal demodulation. A sequence that is cyclically shifted or a sequence that is cyclically expanded can also be used as a reference signal for data signal demodulation, or a search for a sequence with excellent autocorrelation characteristics or cross-correlation characteristics using a computer, etc. Can be used as a reference signal for data signal demodulation. That. In addition, the data signal demodulation reference signal generation unit 113 sets the resource elements that map the data signal demodulation reference signal to null between layers as a method of orthogonalizing the data signal demodulation reference signal between layers. A method (for example, time division multiplexing or frequency division multiplexing), a code division multiplexing method using a pseudo noise sequence, or the like can be used.

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described. The communication system in the present embodiment includes an anchor base station 100, a coordinated base station 300, and a mobile terminal 500 similar to those in the communication system in the first embodiment. The processing in the precoding unit 305 and the feedback information generation unit 510 in the mobile terminal 500 is different. Below, it demonstrates centering on a different part from 1st Embodiment.

FIG. 10 is a diagram showing an example of wideband precoding information and narrowband precoding information used in the present embodiment. FIG. 10 shows wideband precoding information PMI1 common to the anchor base station 100 and the coordinated base station 300 and narrowband precoding information PMI2 of the anchor base station 100. It is assumed that the narrowband precoding matrix W2b of the cooperative base station 300 is defined (fixed) in advance.

In the present embodiment, the feedback information generation unit 510 in the mobile terminal 500 uses the first transmission path condition measurement reference signal from the anchor base station 100 and the second transmission path condition measurement reference signal from the coordinated base station 300. Based on this, broadband precoding information PMI1 and narrowband precoding information PMI2 as shown in FIG. 10 are generated.

Generation of broadband precoding information PMI1 and narrowband precoding information PMI2 will be described. The feedback information generation unit 510 selects, for example, a combination of a wideband precoding matrix and a narrowband precoding matrix that are candidates, and multiplies the channel state estimated value by a precoding matrix obtained by calculating them. Feedback information generation section 510 selects a precoding matrix that is suitable for cooperative communication among candidate combinations. Feedback information generating section 510 generates wideband precoding information PMI1 and narrowband precoding information PMI2 corresponding to the selected precoding matrix. In this case, feedback information generation section 510 selects the common wideband precoding matrix W1a and wideband precoding matrix W1b in anchor base station 100 and cooperative base station 300. Further, feedback information generation section 510 uses a precoding matrix defined in advance as narrowband precoding matrix W2b of cooperative base station 300.

Based on the wideband precoding information PMI1 and the narrowband precoding information PMI2 fed back from the mobile terminal 500, the anchor base station 100 uses the wideband precoding matrix W1a in the anchor base station 100 and the narrowband precoding matrix in the anchor base station 100. W2a, a wideband precoding matrix W1b in the cooperative base station 300 is generated. The anchor base station 100 notifies the precoding information regarding the cooperative base station 300 to the cooperative base station 300 through the X2 interface or the like. Precoding section 105 in anchor base station 100 determines a precoding matrix based on wideband precoding matrix W1a and narrowband precoding matrix W2a. Precoding section 305 in cooperative base station 300 determines a precoding matrix based on wideband precoding matrix W1b and narrowband precoding matrix W2b. Anchor base station 100 and cooperative base station 300 perform cooperative communication using the determined precoding matrix.

By using the method described in this embodiment, even when the anchor base station 100 and the coordinated base station 300 perform coordinated communication, the transmission quality is improved without increasing feedback information, compared with the case where the coordinated communication is not performed. Can be realized. Further, even when the anchor base station 100 and the cooperative base station 300 perform cooperative communication, the feedback method can be made the same as the feedback method when the cooperative communication is not performed. Therefore, the mobile terminal 500 can efficiently transmit data when transmitting feedback information. Also, the mobile terminal 500 can make the precoding process in the anchor base station 100 different from the precoding process in the cooperative base station 300. Therefore, the anchor base station 100 and the cooperative base station 300 can realize flexible precoding processing. Therefore, the anchor base station 100 and the cooperative base station 300 can improve the reception performance in the mobile terminal 500.

In the above description, the case where the narrowband precoding matrix of the cooperative base station 300 is defined in advance has been described. However, the present invention is not limited to this. Various methods can be used as a method for fixing the narrowband precoding matrix of the coordinated base station 300. For example, the precoding matrix to be fixed may be notified dynamically or semi-statically from the network side such as the anchor base station 100 to the mobile terminal 500. Further, a plurality of precoding matrices may be defined in advance, and the mobile terminal 500 may select from the plurality of precoding matrices. In this case, the mobile terminal 500 may select a precoding matrix in association with information identifying subframes, resource blocks, cell IDs, component carriers, and the like. Also, any of the precoding matrices that are candidates may be restricted, and the mobile terminal 500 may select from the restricted precoding matrices. In that case, the mobile terminal 500 can operate a part of the precoding matrices semi-fixed. Also, the mobile terminal 500 can dynamically or quasi-statically switch whether or not to fix. The switching method may be notified directly from the network side such as the anchor base station 100, or may be defined for each other parameter such as a feedback mode.

In the above description, the case where the narrowband precoding matrix of the cooperative base station 300 is defined in advance has been described. However, the present invention is not limited to this. For example, the narrowband precoding matrix of the anchor base station 100 may be defined in advance. Also, the wideband precoding matrix of anchor base station 100 or cooperative base station 300 may be defined in advance, in which case the wideband precoding information of anchor base station 100 and cooperative base station 300 is shared as narrowband precoding information PMI2. It may be.

[Third Embodiment]
Hereinafter, a third embodiment of the present invention will be described. The communication system in the present embodiment includes an anchor base station 100, a coordinated base station 300, and a mobile terminal 500 similar to those in the communication system in the first embodiment. The processing in the precoding unit 305 and the feedback information generation unit 510 in the mobile terminal 500 is different. Below, it demonstrates centering on a different part from 1st Embodiment.

FIG. 11 is a diagram showing an example of wideband precoding information and narrowband precoding information used in the present embodiment. FIG. 11 shows narrowband precoding information PMI2 that is common to the anchor base station 100 and the coordinated base station 300. The wideband precoding matrix W1a and the wideband precoding matrix W1b of the anchor base station 100 and the coordinated base station 300 are respectively defined (fixed) in advance.

In the present embodiment, the feedback information generation unit 510 in the mobile terminal 500 uses the first transmission path condition measurement reference signal from the anchor base station 100 and the second transmission path condition measurement reference signal from the coordinated base station 300. Based on this, narrowband precoding information PMI2 as shown in FIG. 11 is generated.

The generation of narrowband precoding information PMI2 will be described. The feedback information generation unit 510 selects, for example, a combination of a wideband precoding matrix and a narrowband precoding matrix that are candidates, and multiplies the channel state estimated value by a precoding matrix obtained by calculating them. Feedback information generation section 510 selects a precoding matrix that is suitable for cooperative communication among candidate combinations. Feedback information generating section 510 generates wideband precoding information PMI1 and narrowband precoding information PMI2 corresponding to the selected precoding matrix. In this case, feedback information generation section 510 selects a common narrowband precoding matrix W2a and narrowband precoding matrix W2b in anchor base station 100 and cooperative base station 300. Also, feedback information generation section 510 uses pre-defined precoding matrices as wideband precoding matrix W1a and wideband precoding matrix W1b in anchor base station 100 and cooperative base station 300, respectively.

The anchor base station 100 generates a narrowband precoding matrix W2a in the anchor base station 100 and a narrowband precoding matrix W2b in the coordinated base station 300 based on the narrowband precoding information PMI2 fed back from the mobile terminal 500. The anchor base station 100 notifies the precoding information regarding the cooperative base station 300 to the cooperative base station 300 through the X2 interface or the like. Precoding section 105 in anchor base station 100 determines a precoding matrix based on wideband precoding matrix W1a and narrowband precoding matrix W2a. Precoding section 305 in cooperative base station 300 determines a precoding matrix based on wideband precoding matrix W1b and narrowband precoding matrix W2b. Anchor base station 100 and cooperative base station 300 perform cooperative communication with mobile terminal 500 using the determined precoding matrix.

By using the method described in this embodiment, even when the anchor base station 100 and the coordinated base station 300 perform coordinated communication, the transmission quality is improved without increasing feedback information, compared with the case where the coordinated communication is not performed. Can be realized. Also, the mobile terminal 500 can make the feedback method the same as the feedback method of the system that feeds back only one type of information related to the precoding information PMI. Therefore, the mobile terminal 500 can efficiently transmit data when transmitting feedback information. Also, the mobile terminal 500 can make the precoding process in the anchor base station 100 different from the precoding process in the cooperative base station 300. Therefore, the anchor base station 100 and the cooperative base station 300 can realize flexible precoding processing. Therefore, the anchor base station 100 and the cooperative base station 300 can improve the reception performance in the mobile terminal 500.

In the above description, the case where the wideband precoding matrix W1a and the wideband precoding matrix W1b are respectively defined in advance has been described. However, the present invention is not limited to this. Various methods can be used to fix the wideband precoding matrix W1a and the wideband precoding matrix W1b. For example, the precoding matrix to be fixed may be notified dynamically or semi-statically from the network side such as the anchor base station 100 to the mobile terminal 500. Further, a plurality of precoding matrices may be defined in advance, and the mobile terminal 500 may select from the plurality of precoding matrices. In this case, the mobile terminal 500 may select a precoding matrix in association with information identifying subframes, resource blocks, cell IDs, component carriers, and the like. Also, any of the precoding matrices that are candidates may be restricted, and the mobile terminal 500 may select from the restricted precoding matrices. In that case, the mobile terminal 500 can operate with some precoding matrices being semi-fixed. Also, the mobile terminal 500 can dynamically or quasi-statically switch whether or not to fix. The switching method may be notified directly from the network side such as the anchor base station 100, or may be defined for each other parameter such as a feedback mode.

In the above description, the case where the wideband precoding matrix W1a and the wideband precoding matrix W1b are defined in advance has been described. However, the present invention is not limited to this. For example, the narrowband precoding matrix W2a and the narrowband precoding matrix W2b may be defined in advance, and in this case, the wideband precoding matrix W1a and the wideband precoding matrix W1b may be shared as the wideband precoding information PMI1. .

[Fourth Embodiment]
The fourth embodiment of the present invention will be described below. The communication system in the present embodiment includes an anchor base station 100, a coordinated base station 300, and a mobile terminal 500 similar to those in the communication system in the first embodiment. The processing in the precoding unit 305 and the feedback information generation unit 510 in the mobile terminal 500 is different. Below, it demonstrates centering on a different part from 1st Embodiment.

FIG. 12 is a diagram showing an example of wideband precoding information and narrowband precoding information used in the present embodiment. FIG. 12 shows wideband precoding information PMI1 of the anchor base station 100 and narrowband precoding information PMI2 of the anchor base station 100. It is assumed that the wideband precoding matrix W1b and the narrowband precoding matrix W2b of the coordinated base station 300 are respectively defined (fixed) in advance.

In the present embodiment, the feedback information generation unit 510 in the mobile terminal 500 uses the first transmission path condition measurement reference signal from the anchor base station 100 and the second transmission path condition measurement reference signal from the coordinated base station 300. Based on this, broadband precoding information PMI1 and narrowband precoding information PMI2 as shown in FIG. 12 are generated.

Generation of broadband precoding information PMI1 and narrowband precoding information PMI2 will be described. The feedback information generation unit 510 selects, for example, a combination of a wideband precoding matrix and a narrowband precoding matrix that are candidates, and multiplies the channel state estimated value by a precoding matrix obtained by calculating them. Feedback information generation section 510 selects a precoding matrix that is suitable for cooperative communication among candidate combinations. Feedback information generating section 510 generates wideband precoding information PMI1 and narrowband precoding information PMI2 corresponding to the selected precoding matrix. In this case, feedback information generating section 510 uses pre-defined precoding matrices as wideband precoding matrix W1b and narrowband precoding matrix W2b of cooperative base station 300.

Based on the wideband precoding information PMI1 and the narrowband precoding information PMI2 fed back from the mobile terminal 500, the anchor base station 100 uses the wideband precoding matrix W1a in the anchor base station 100 and the narrowband precoding matrix in the anchor base station 100. W2a is generated. In addition, since precoding regarding the coordinated base station 300 is known, the anchor base station 100 may not notify the coordinated base station 300 of the precoding regarding the coordinated base station 300, but may notify it. In this case, the reliability of cooperative communication can be improved. In addition, it is not necessary to define a mechanism for notifying and not notifying each. Precoding section 105 in anchor base station 100 determines a precoding matrix based on wideband precoding matrix W1a and narrowband precoding matrix W2a. Precoding section 305 in cooperative base station 300 determines a precoding matrix based on wideband precoding matrix W1b and narrowband precoding matrix W2b. Anchor base station 100 and cooperative base station 300 perform cooperative communication with mobile terminal 500 using the determined precoding matrix.

In addition, as a cooperative communication scheme, when transmission from the cooperative base station 300 is stopped (including power control such as lowering power), the mobile terminal 500 assumes that there is no signal from the cooperative base station 300. Feedback information (including RI and CQI) can be generated. Therefore, the mobile terminal 500 can efficiently transmit data when transmitting feedback information. Further, when a base station adjacent to the anchor base station performs transmission diversity with respect to other mobile terminals, the mobile terminal 500 can also assume such a base station as the cooperative base station 300.

In the above description, the case where the wideband precoding matrix W1b in the cooperative base station 300 and the narrowband precoding matrix W2b in the cooperative base station 300 are defined in advance has been described. However, the present invention is not limited to this. Various methods can be used to fix the wideband precoding matrix W1b and the narrowband precoding matrix W2b. For example, the precoding matrix to be fixed may be notified dynamically or semi-statically from the network side such as the anchor base station 100 to the mobile terminal 500. Further, a plurality of precoding matrices may be defined in advance, and the mobile terminal 500 may select from the plurality of precoding matrices. In this case, the mobile terminal 500 may select a precoding matrix in association with information identifying subframes, resource blocks, cell IDs, component carriers, and the like. Also, any of the precoding matrices that are candidates may be restricted, and the mobile terminal 500 may select from the restricted precoding matrices. In this case, the mobile terminal 500 can operate with some precoding matrices being semi-fixed. Also, the mobile terminal 500 can dynamically or quasi-statically switch whether or not to fix. The switching method may be notified directly from the network side such as the anchor base station 100, or may be defined for each other parameter such as a feedback mode.

In the above description, the case where the wideband precoding matrix W1b and the narrowband precoding matrix W2b are defined in advance has been described. However, the present invention is not limited to this. For example, the wideband precoding matrix W1a and the narrowband precoding matrix W2a may be defined in advance. When there are a plurality of cooperative base stations 300, the wideband precoding matrix W1b and the narrowband precoding matrix W2b of some of the base stations may be defined in advance.

[Fifth Embodiment]
The fifth embodiment of the present invention will be described below. The communication system in the present embodiment includes an anchor base station 100, a coordinated base station 300, and a mobile terminal 500 similar to those in the communication system in the first embodiment. The processing in the precoding unit 305 and the feedback information generation unit 510 in the mobile terminal 500 is different. Below, it demonstrates centering on a different part from 1st Embodiment.

FIG. 13 is a diagram showing an example of wideband precoding information and narrowband precoding information used in the present embodiment. FIG. 13 shows narrowband precoding information PMI2a in the anchor base station 100 and narrowband precoding information PMI2b in the coordinated base station 300. At this time, it is assumed that wideband precoding matrix W1a in anchor base station 100 and wideband precoding matrix W1b in cooperative base station 300 are defined (fixed) in advance.

In the present embodiment, the feedback information generation unit 510 in the mobile terminal 500 uses the first transmission path condition measurement reference signal from the anchor base station 100 and the second transmission path condition measurement reference signal from the coordinated base station 300. Based on this, narrowband precoding information PMI2a and narrowband precoding information PMI2b as shown in FIG. 13 are generated.

Generation of narrowband precoding information PMI2a and narrowband precoding information PMI2b will be described. The feedback information generation unit 510 selects, for example, a combination of a wideband precoding matrix and a narrowband precoding matrix that are candidates, and multiplies the channel state estimated value by a precoding matrix obtained by calculating them. Feedback information generation section 510 selects a precoding matrix that is suitable for cooperative communication among candidate combinations. Feedback information generating section 510 generates narrowband precoding information PMI2a and narrowband precoding information PMI2b corresponding to the selected precoding matrix. In this case, feedback information generation section 510 uses pre-defined precoding matrices as wideband precoding matrix W1a and wideband precoding matrix W1b in anchor base station 100 and cooperative base station 300.

Anchor base station 100 generates narrowband precoding matrix W2a and narrowband precoding matrix W2b based on narrowband precoding information PMI2a and narrowband precoding information PMI2b fed back from mobile terminal 500. The anchor base station 100 notifies the precoding information regarding the cooperative base station 300 to the cooperative base station 300 through the X2 interface or the like. Precoding section 105 in anchor base station 100 determines a precoding matrix based on wideband precoding matrix W1a and narrowband precoding matrix W2a. Precoding section 305 in cooperative base station 300 determines a precoding matrix based on wideband precoding matrix W1b and narrowband precoding matrix W2b. Anchor base station 100 and cooperative base station 300 perform cooperative communication with mobile terminal 500 using the determined precoding matrix.

By using the method described in this embodiment, even when the anchor base station 100 and the cooperative base station 300 perform cooperative communication, wideband precoding information and narrowband precoding information are compared with a case where cooperative communication is not performed. Can improve the transmission quality without increasing the feedback information. Further, even when the anchor base station 100 and the cooperative base station 300 perform cooperative communication, the feedback method can be made the same as the feedback method when the cooperative communication is not performed. Therefore, the mobile terminal 500 can efficiently transmit data when transmitting feedback information. Also, the mobile terminal 500 can make the precoding process in the anchor base station 100 different from the precoding process in the cooperative base station 300. Therefore, the anchor base station 100 and the cooperative base station 300 can realize flexible precoding processing. Therefore, the anchor base station 100 and the cooperative base station 300 can improve the reception performance in the mobile terminal 500.

In the above description, the case where the wideband precoding matrix W1a and the wideband precoding matrix W1b are defined in advance has been described. However, the present invention is not limited to this. Various methods can be used to fix the wideband precoding matrix W1a and the wideband precoding matrix W1b. For example, the precoding matrix to be fixed may be notified dynamically or semi-statically from the network side such as the anchor base station 100 to the mobile terminal 500. Further, a plurality of precoding matrices may be defined in advance, and the mobile terminal 500 may select from the plurality of precoding matrices. In this case, the mobile terminal 500 may select a precoding matrix in association with information identifying subframes, resource blocks, cell IDs, component carriers, and the like. Also, any of the precoding matrices that are candidates may be restricted, and the mobile terminal 500 may select from the restricted precoding matrices. In that case, the mobile terminal 500 can operate with some precoding matrices being semi-fixed. Also, the mobile terminal 500 can dynamically or quasi-statically switch whether or not to fix. The switching method may be notified directly from the network side such as the anchor base station 100, or may be defined for each other parameter such as a feedback mode.

In the above description, the case where the wideband precoding matrix W1a and the wideband precoding matrix W1b are defined in advance has been described. However, the present invention is not limited to this. For example, the narrowband precoding matrix W2a and the narrowband precoding matrix W2b may be defined in advance, and in this case, the wideband precoding information of the anchor base station 100 and the cooperative base station 300 is narrowband precoding information PMI2a and narrowband precoding information PMI2a, respectively. The band precoding information PMI2b may be used. Further, mobile terminal 500 may feed back wideband precoding matrix W1a and wideband precoding matrix W1b in addition to narrowband precoding matrix W2a and narrowband precoding matrix W2b. In this case, by coordinating the precoding matrix of the anchor base station 100 and the precoding matrix of the cooperative base station 300, the reception performance in the mobile terminal 500 can be further improved. Alternatively, the precoding matrix (W1a and / or W2a) of the anchor base station 100 and the precoding matrix (W1b and / or W2b) of the coordinated base station 300 may be generated independently of each other. Thereby, the cooperative communication (dynamic cell selection etc.) of the structure which the anchor base station 100 or the cooperation base station 300 selects the data transmission with respect to the mobile terminal 500 is realizable.

[Sixth Embodiment]
The sixth embodiment of the present invention will be described below. The communication system in the present embodiment includes an anchor base station 100, a coordinated base station 300, and a mobile terminal 500 similar to those in the communication system in the first embodiment, but the precoding unit 105 and the coordinated base station 300 in the anchor base station 100. The processing in the precoding unit 305 and the feedback information generation unit 510 in the mobile terminal 500 is different. Also, the precoding information PMI to be fed back is long-interval precoding information instead of the wideband precoding information PMI1, and short-interval precoding information instead of the narrowband precoding information PMI2. Below, it demonstrates centering on a different part from 1st Embodiment. In the following description, for convenience of explanation, the long interval variation precoding information is referred to as “long interval variation precoding information PMI1 ′”, and the short interval variation precoding information is referred to as “short interval variation precoding information PMI2 ′”.

Here, the long interval variation precoding information PMI1 'and the short interval variation precoding information will be described. The frequency with which the mobile terminal 500 feeds back to the anchor base station 100 differs between the long interval variable precoding information PMI1 'and the short interval variable precoding information. That is, the feedback period is different. In addition, both the long interval variable precoding information PMI1 'and the short interval variable precoding information PMI2' may be wideband precoding information or narrowband precoding information. In the following, as an example, the long interval variation precoding information PMI1 ′ has a longer feedback period than the short interval variation precoding information PMI2 ′, and the long interval variation precoding information PMI1 ′ and the short interval variation precoding information PMI2 ′ A case where the information is also wideband precoding information will be described.

FIG. 14 is a diagram showing an example of the long interval variable precoding information PMI1 'and the short interval variable precoding information PMI2' used in the present embodiment. Further, FIG. 14 shows long-period variable precoding information PMI1 ′ common to the anchor base station 100 and the coordinated base station 300 and short-period variable precoding information PMI2 ′ common to the anchor base station 100 and the coordinated base station 300. Show.

In the present embodiment, the feedback information generation unit 510 in the mobile terminal 500 uses the first transmission path condition measurement reference signal from the anchor base station 100 and the second transmission path condition measurement reference signal from the coordinated base station 300. Based on this, long section variation precoding information PMI1 ′ and short section variation precoding information PMI2 ′ as shown in FIG. 14 are generated.

FIG. 15 is a flowchart of the anchor base station 100, the cooperative base station 300, and the mobile terminal 500 used in the present embodiment. First, the anchor base station 100 notifies the mobile terminal 500 of one or more cooperative base stations 300 for performing cooperative communication with the mobile terminal 500 (step S1501). The anchor base station 100 transmits the first first transmission path condition measurement reference signal CSIRSa (1) to the mobile terminal 500 (step S1502). The coordinated base station 300 transmits the first second transmission path condition measurement reference signal CSIRSb (1) to the mobile terminal 500 (step S1503).

The mobile terminal 500 receives CSIRa (1) and CSIRSb (1). The mobile terminal 500 generates first long interval variable precoding information PMI1 '(1) and first short interval variable precoding information PMI2' (1) as precoding information as described in FIG. The mobile terminal 500 feeds back the generated first long interval variable precoding information PMI1 ′ (1) and first short interval variable precoding information PMI2 ′ (1) to the anchor base station 100 (step S1504 and step S1504). S1505). Note that the mobile terminal 500 may feed back the long interval variable precoding information PMI1 '(1) and the short interval variable precoding information PMI2' (1) simultaneously.

The anchor base station 100 determines the first wideband precoding information in the anchor base station 100 based on the long interval variable precoding information PMI1 ′ (1) and the short interval variable precoding information PMI2 ′ (1) fed back from the mobile terminal 500. Recording matrix W1a (1), first narrowband precoding matrix W2a (1) at anchor base station 100, first wideband precoding matrix W1b (1) at coordinated base station 300, first matrix at coordinated base station 300 A narrowband precoding matrix W2b (1) is generated. The anchor base station 100 notifies the cooperative base station 300 of the first information data signal data (1), the wideband precoding matrix W1b (1), and the narrowband precoding matrix W2b (1) for the mobile terminal 500. (Step S1506). At this time, the anchor base station 100 may notify the coordinated base station 300 of the long interval variable precoding information PMI1 ′ (1) and the short interval variable precoding information PMI2 ′ (1), or wideband precoding. The precoding matrix obtained by calculating the matrix W1b (1) and the narrowband precoding matrix W2b (1) may be notified to the coordinated base station 300.

The anchor base station 100 transmits signals obtained based on the wideband precoding matrix W1a (1), the narrowband precoding matrix W2a (1), and data (1) (for example, g (W1a (1), w2a (1), signal (1)), where g (x, y, z) is a function with x, y, z as parameters) is transmitted to the mobile terminal 500 (step S1507). For example, the anchor base station 100 transmits a signal obtained by multiplying data (1) by a precoding matrix obtained by multiplying a wideband precoding matrix W1a (1) and a narrowband precoding matrix W2a (1). Also, using the same resource transmitted by anchor base station 100 in step S1507, cooperative base station 300 is based on wideband precoding matrix W1b (1), narrowband precoding matrix W2b (1), and data (1). The obtained signal (for example, a signal calculated by g (W1b (1), w2b (1), data (1))) is transmitted to the mobile terminal 500 (step S1508). The coordinated base station 300 transmits, for example, a signal obtained by multiplying data (1) by a precoding matrix obtained by multiplying a wideband precoding matrix W1b (1) and a narrowband precoding matrix W2b (1) to the mobile terminal 500. To send.

Next, the anchor base station 100 transmits the second first transmission path condition measurement reference signal CSIRSa (2) to the mobile terminal 500 (step S1509). The coordinated base station 300 transmits the second second transmission path condition measurement reference signal CSIRSb (2) to the mobile terminal 500 (step S1510). The mobile terminal 500 receives CSISa (2) and CSIRSb (2). The mobile terminal 500 generates second short interval variation precoding information PMI2 '(2) based on CSIRa (2) and CSIRSb (2). The mobile terminal 500 feeds back the generated second short interval variation precoding information PMI2 '(2) to the anchor base station 100 (step S1511). In this case, the mobile terminal 500 sets the long-interval precoding matrix in the anchor base station 100 and the coordinated base station 300 as the wide-band precoding matrix W1a (1) and the wide-band precoding matrix W1b (1), respectively. Information PMI2 ′ (2) is generated.

The anchor base station 100 determines the second narrowband precoding matrix W2a (2) in the anchor base station 100, the coordinated base station 300 based on the short interval variation precoding information PMI2 ′ (2) fed back from the mobile terminal 500. Generates the second narrowband precoding matrix W2b (2). The anchor base station 100 notifies the cooperative base station 300 of the second information data signal data (2), the wideband precoding matrix W1b (1), and the narrowband precoding matrix W2b (2) for the mobile terminal 500. (Step S1512). Note that, when the wideband precoding matrix W1b (1) is known, the anchor base station 100 can omit the notification of the wideband precoding matrix W1b (1). If the mobile terminal 500 cannot correctly receive the data (1) transmitted in steps S1507 and S1508, the anchor base station 100 may retransmit data (1) as data (2).

The anchor base station 100 transmits a signal obtained based on the wideband precoding matrix W1a (1), the narrowband precoding matrix W2a (2), and data (2) to the mobile terminal 500 (step S1513). Also, using the same resource transmitted by anchor base station 100 in step S1513, coordinated base station 300 is based on wideband precoding matrix W1b (1), narrowband precoding matrix W2b (2), and data (2). The obtained signal is transmitted to mobile terminal 500 (step S1514).

By using the method described in this embodiment, even when the anchor base station 100 and the coordinated base station 300 perform coordinated communication, the transmission quality is improved without increasing feedback information, compared with the case where the coordinated communication is not performed. Can be realized. Further, even when the anchor base station 100 and the cooperative base station 300 perform cooperative communication, the feedback method can be made the same as the feedback method when the cooperative communication is not performed. Therefore, the mobile terminal 500 can efficiently transmit data when transmitting feedback information. In addition, the mobile terminal 500 can perform flexible scheduling while suppressing feedback overhead and improve reception performance in the mobile terminal 500 by using a plurality of precoding information with different feedback periods.

In the above description, the long interval variable precoding information PMI1 ′ and the short interval variable precoding information PMI2 ′ have been described as precoding information common to the anchor base station 100 and the coordinated base station 300. As described in the fifth to fifth embodiments, the present invention can be applied even when some precoding matrices are defined in advance. In that case, the same effect as described in the second to fifth embodiments can be obtained.

In each of the above embodiments, the case has been described in which the anchor base station and the cooperative base station perform communication in cooperation. Of course, the base station mentioned here may be a physical base station apparatus in a cellular system, but in addition to this, a set of transmitting apparatuses (including relay apparatuses) that cooperate while extending cells. (A first transmitter and a second transmitter), or a set of transmitters that cooperate while transmitting reference signals for transmission path status measurement using different antenna ports (a first port and a second port). For example, an anchor base station and a coordinated base station can be used. In these cases, the same effects as those in the above embodiments can be obtained.

For example, the anchor base station is a base station device in a cellular system, and the cooperative base station is a transmission device controlled by the anchor base station (for example, RRU (Remote Radio Unit), RRE (Remote Radio Equipment), and Distributed antenna). Conversely, the cooperative base station may be a base station apparatus in a cellular system, and the anchor base station may be a transmission apparatus controlled and operated by the cooperative base station. Alternatively, both the anchor base station and the coordinated base station may be transmission devices that are controlled and operated by a physical base station device in the cellular system.

In each of the above embodiments, the cooperative communication between the anchor base station and the cooperative base station has been described mainly in the case where the cooperative base station is adjacent to the anchor base station, but the present invention is not limited to this. For example, even when the communication area of the anchor base station and the communication area of the cooperative base station overlap all or partly as in a heterogeneous network, the same effects described in the above embodiments can be obtained. At that time, all or part of the component carriers (carrier frequencies) of the respective base stations may overlap. Specifically, the anchor base station is a macro cell, the cooperative base station is a pico cell or a femto cell (Home eNodeB), and the communication area of a pico cell or femto cell that is smaller than the macro cell communication area is a communication of the macro cell (anchor base station). Applicable even when overlapping in an area.

In each of the above embodiments, resource elements and resource blocks are used as mapping units for information data signals, control information signals, PDSCH, PDCCH, and reference signals, and subframes and radio frames are used as transmission units in the time direction. However, it is not limited to this. The same effect can be obtained even if a region and a time unit composed of an arbitrary frequency and an arbitrary time are used instead.

In each of the above embodiments, the case where demodulation is performed using the precoding-processed reference signal RS will be described, and a port equivalent to the MIMO layer is used as a port corresponding to the precoding-processed reference signal RS. However, the present invention is not limited to this. In addition, the same effect can be obtained by applying the present invention to ports corresponding to different reference signals. For example, Unprecoded RS is used instead of Precoded RS, and a port equivalent to an output end after precoding processing or a port equivalent to a physical antenna (or a combination of physical antennas) can be used as a port.

A program that operates in the anchor base station 100, the cooperative base station 300, and the mobile terminal 500 according to the present invention is a program that controls a CPU or the like (a program that causes a computer to function so as to realize the functions of the above-described embodiments according to the present invention. ). Information handled by these devices is temporarily stored in the RAM at the time of processing, then stored in various ROMs and HDDs, read out by the CPU, and corrected and written as necessary. As a recording medium for storing the program, a semiconductor medium (for example, ROM, nonvolatile memory card, etc.), an optical recording medium (for example, DVD, MO, MD, CD, BD, etc.), a magnetic recording medium (for example, magnetic tape, Any of a flexible disk etc. may be sufficient. In addition, by executing the loaded program, not only the functions of the above-described embodiment are realized, but also based on the instructions of the program, the processing is performed in cooperation with the operating system or other application programs. The functions of the invention may be realized.

Also, when distributing to the market, the program can be stored and distributed on a portable recording medium, or transferred to a server computer connected via a network such as the Internet. In this case, the storage device of the server computer is also included in the present invention. Moreover, you may implement | achieve part or all of the anchor base station 100 in the embodiment mentioned above, the cooperation base station 300, and the mobile terminal 500 as LSI which is typically an integrated circuit. Each functional block of the anchor base station 100, the cooperative base station 300, and the mobile terminal 500 may be individually chipped, or a part or all of them may be integrated into a chip. Further, the method of circuit integration is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. In addition, when an integrated circuit technology that replaces LSI appears due to progress in semiconductor technology, an integrated circuit based on the technology can also be used.

As described above, the embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design changes and the like without departing from the gist of the present invention.

100 anchor base station, 101, 301 coding section, 102, 302 scramble section, 103, 303 modulation section, 104, 304 layer mapping section, 105, 305 precoding section, 106, 306 resource element mapping section, 107, 307 OFDM signal Generator, 108, 308, 512, 1703, 1714, transmission antenna, 109, 309, transmission path condition measurement reference signal generator, 110, 501, 1704, 1711, reception antenna, 111, received signal processor, 112, 1705, feedback information processing , 113, 313, data signal demodulation reference signal generator, 300 cooperative base station, 500, 1603, 1710, 1803, mobile terminal, 502 OFDM signal demodulator, 503 resource element demapping Unit, 504 filter unit, 505 layer demapping unit, 506 demodulation unit, 507 descrambling unit, 508 decoding unit, 509 propagation path estimation unit, 510, 1713 feedback information generation unit, 511 transmission signal generation unit, 1601, 1602, 1700, 1801, 1802 base station, 1701 adaptive control unit, 1702 multiplexing unit, 1712 separation unit.

Claims

Based on a first transmission path status measurement reference signal and a second transmission path status measurement reference signal different from the first transmission path status measurement reference signal, the first transmission path status and the second transmission A measuring unit for measuring road conditions;
A mobile terminal apparatus comprising: a generation unit that generates one or more precoding information as feedback information to the base station apparatus (100) based on the first transmission path condition and the second transmission path condition; 500).
The mobile terminal apparatus according to claim 1, wherein the generation unit generates wideband precoding information and narrowband precoding information as the plurality of precoding information.
The mobile terminal apparatus according to claim 1, wherein the generation unit generates long section varying precoding information and short section varying precoding information as the plurality of precoding information.
The generation unit generates the one or a plurality of precoding information as the feedback information based on a precoding matrix commonly used for the first transmission path condition and the second transmission path condition. The mobile terminal device according to claim 1.
The generator is
At least one of a plurality of precoding matrices for the first transmission path situation and the second transmission path situation is a precoding matrix defined in advance,
2. The mobile terminal apparatus according to claim 1, wherein the one or more precoding information is generated as the feedback information based on a precoding matrix other than the predetermined precoding matrix among the plurality of precoding matrices. .
A second transmission from the second base station apparatus (300) that receives the first transmission path condition measurement reference signal from the first base station apparatus (100) and performs cooperative communication with the first base station apparatus. A receiving unit for receiving a road condition measurement reference signal;
A measurement unit for measuring the first transmission path status and the second transmission path status based on the first transmission path status measurement reference signal and the second transmission path status measurement reference signal;
A generating unit that generates one or more precoding information as feedback information based on the first transmission path condition and the second transmission path condition;
A mobile terminal apparatus (500) comprising: a transmission unit that transmits the one or more precoding information generated as the feedback information to the first base station apparatus.
A first base station apparatus (100) for transmitting a first transmission path condition measurement reference signal;
A second base station apparatus (300) that transmits a second transmission path condition measurement reference signal different from the first transmission path condition measurement reference signal;
Based on the first transmission path status measurement reference signal and the second transmission path status measurement reference signal, the first transmission path status and the second transmission path status are measured, and the first transmission path status is measured. And a mobile terminal device (500) that generates one or more precoding information as feedback information based on the second transmission path condition.
The communication system according to claim 7, wherein the first base station apparatus performs precoding processing based on the plurality of precoding information.
A first base station apparatus (100) that performs precoding processing based on a plurality of precoding matrices;
A second base station apparatus (300) that performs precoding processing based on a plurality of precoding matrices;
A communication system comprising: a mobile terminal device (500) in which cooperative communication is performed by the first base station device and the second base station device.
The mobile terminal apparatus (500) has a first transmission path condition measurement reference signal different from the first transmission path condition measurement reference signal and the first transmission path condition measurement reference signal. Measuring a transmission path condition and a second transmission path condition;
The mobile terminal apparatus (500) includes generating one or more precoding information as feedback information to the base station apparatus based on the first transmission path condition and the second transmission path condition. ,Communication method.
The first base station apparatus (100) transmitting a first transmission path condition measurement reference signal;
A second base station apparatus (300) transmitting a second transmission path condition measurement reference signal different from the first transmission path condition measurement reference signal;
The mobile terminal device (500)
Measuring the first transmission path condition and the second transmission path condition based on the first transmission path condition measurement reference signal and the second transmission path condition measurement reference signal;
A communication method, comprising: generating one or more precoding information as feedback information to the first base station apparatus based on the first transmission path condition and the second transmission path condition.
A first base station device performing precoding processing based on a plurality of precoding matrices;
A second base station apparatus performing precoding processing based on a plurality of precoding matrices;
The first base station apparatus and the second base station apparatus perform cooperative communication with a mobile terminal.