Cooperative wireless communication device, wireless communication system, spatial multiplexing wireless transmission method, and program

Abstract

To utilize a null space expansion technique in each of a plurality of cooperating wireless communication devices.SOLUTION: A cooperative wireless communication device includes a shared information transmission unit that transmits, to the other associated wireless communication device by communication means different from the spatial multiplexing transmission, the shared information being information on a signal received from a non-associated wireless communication device by spatial multiplexing transmission or on a signal to be transmitted to the non-associated wireless communication device by spatial multiplexing transmission, the shared information being shared between the other associated wireless communication device, and a weight calculation unit that calculates a weight vector to be used during spatial multiplexing transmission on the basis of a channel matrix in which a first channel vector generated from channel information between an antenna element of the non-associated wireless communication device or a virtual antenna element obtained by combining the antenna elements and an antenna element of the associated wireless communication device including the non-associated wireless communication device itself, and one or more second channel vectors generated earlier than the first channel vector are arranged.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to an associated wireless communication device, a wireless communication system, a spatial multiplexing wireless transmission method, and a program. [Background technology]

[0002] In order to meet the ever-increasing demand for wireless communication, the implementation of MIMO (Multiple-Input Multiple-Output) technology, which multiplexes and transmits multiple stream signals on the same space, same time, and same frequency, is being promoted (see, for example, Non-Patent Document 1). For example, in order to cover a wide service area with one base station device, it is necessary to increase the line capacity, but the coherent transmission technology and the phased array antenna technology are basically technologies to improve the line gain, and are not technologies to increase the line capacity. To increase the line capacity, it is sufficient to widen the frequency band, but frequency resources are limited, and MIMO is used as a technology to increase the line capacity by using this limited frequency resource with high frequency utilization efficiency. In MIMO transmission, it is common to transmit signals by performing interference suppression processing (hereinafter also referred to as "null formation") on the transmitting side, the receiving side, or both, so that interference does not occur between multiple streams.

[0003] A multi-user MIMO system in which a base station device performs MIMO transmission to multiple terminal devices is also under consideration (see, for example, Non-Patent Document 2). In the case of a multi-user MIMO system, since the terminal devices cannot share information on the propagation path matrix, signal separation on the base station side is essential. In this case, stream separation between terminal antenna elements, which allows signal separation within one terminal device, is performed by the terminal, while stream separation between terminals, which is difficult to separate within one terminal device, is sometimes performed on the base station device side.

[0004] It is generally known that the performance of MIMO transmission improves as the number of antenna elements on the transmitting station side and the receiving station side increases relative to the number of spatially multiplexed signal sequences. This improvement in performance is utilized in the form of improving the SINR (Signal to Interference and Noise power Ratio) of each spatially multiplexed signal sequence and further increasing the number of spatial multiplexes. In recent years, the implementation of Massive MIMO technology, such as that disclosed in Non-Patent Document 3, in which the number of antenna elements on the base station side is expanded to an ultra-large number of 100 or more, is also progressing.

[0005] On the other hand, it is known that MIMO transmission is susceptible to interference between signal streams. For example, even if the signal separation processing shown in Non-Patent Document 1 is performed, if the accuracy of the channel information used in the signal separation processing is insufficient, interference between the signal streams occurs and the characteristics deteriorate. There are various factors that cause the accuracy of the channel information to decrease, but one major factor is fluctuations in the wireless propagation path. If the timing of acquiring the channel information by performing channel estimation differs from the timing of actually transmitting the signal, and the wireless propagation path changes during that time due to the movement of the wireless communication device or changes in the surrounding environment, the orthogonal condition between the channel information and the weights used in signal separation is lost, causing interference.

[0006] In particular, channel estimation is generally performed using a known signal, and since it is difficult to continuously transmit the known signal, it is difficult to continuously perform channel estimation, and therefore the accuracy of the channel information is reduced. This reduction in the accuracy of the channel information is a major issue in mobile communications. Among wireless communication devices, many terminal devices in particular are battery-powered devices, and communication overhead such as known signals needs to be reduced as much as possible to suppress battery consumption. Therefore, even if the opportunities for channel estimation are reduced, it is necessary to generate weights that are robust against deterioration of the accuracy of the channel information. As a technology capable of generating such weights, for example, the null space expansion technology disclosed in Patent Document 1 is being studied. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 6353375 [Non-patent literature]

[0008] [Non-Patent Document 1] Tomoaki Ohtsuki, "Overview of MIMO Technology", Journal of the Institute of Image Information and Television Engineers, 2016, Vol. 70, No. 1, pp. 2-5 [Non-Patent Document 2] Yasuji Takatori, Kentaro Nishimori, "Application of Downlink Multi-User MIMO Technology to Next-Generation High-Speed ​​Wireless Access Systems," IEICE Transactions on Information and Communication Engineers, Vol. J93-B, No. 9, September 2010, pp. 1127-1139 [Non-Patent Document 3] Kazuki Maruta et al., "Proposal of a Large-Scale Antenna Wireless Entrance System: Performance Evaluation by Computer Simulation", Technical Report of the Institute of Electronics, Information and Communication Engineers, April 2013, RCS2013-6, vol.113, no.8, pp.31-36 [Non-Patent Document 4] Eiichi Murata, Daisuke Umehara, "Terminal-Coordinated MIMO Reception Technology - Theory and Application to Mobile Devices -", ​​IEICE Fundamentals Review, Institute of Electronics, Information and Communication Engineers, January 2022, Vol. 15, No. 3, pp. 210-219 Summary of the Invention [Problem to be solved by the invention]

[0009] In the null space expansion technology disclosed in Patent Document 1, the remaining antenna degrees of freedom after the minimum necessary null formation are performed are used for additional null formation, thereby generating weights that are robust against fluctuations in the wireless propagation path. Therefore, a wireless terminal device that applies the null space expansion technology requires many antenna elements to increase the antenna degrees of freedom.

[0010] However, a wireless communication device on the terminal side usually has only a small number of antenna elements compared to a wireless communication device on the base station side, and even if it is attempted to have many antenna elements, it is difficult to realize due to restrictions on the size of the device, power consumption, etc. Therefore, it is more difficult to apply the null space expansion technology to a wireless communication device on the terminal side than to a wireless communication device on the base station side.

[0011] In response to this, Non-Patent Document 4 discloses a terminal-linked MIMO technology in which multiple terminal-side wireless communication devices cooperate to share received information, virtually increasing the number of antenna elements on the terminal side. By using this terminal-linked MIMO technology, it is possible to increase the degree of freedom of the terminal-side antenna.

[0012] However, when it is assumed that the null space expansion technique disclosed in Patent Document 1 is applied to each of the multiple wireless communication devices linked in Non-Patent Document 4, the following problem occurs. The technique disclosed in Patent Document 1 is a technique that utilizes the null space expansion technique closed within one base station device. In contrast, the technique disclosed in Non-Patent Document 4 links multiple wireless communication devices, and therefore has a problem that the null space expansion technique disclosed in Patent Document 1 cannot be applied as is to each of the multiple wireless communication devices linked in multiple ways.

[0013] The present invention has been made to solve the above problems, and its object is to provide a cooperative wireless communication device, a wireless communication system, a spatial multiplexing wireless transmission method, and a program that enable each of multiple cooperative wireless communication devices to utilize null space expansion technology. [Means for solving the problem]

[0014] In order to solve the above problem, one aspect of the present invention is an associated wireless communication device in a wireless communication system including an unassociated wireless communication device having a plurality of antenna elements and a plurality of associated wireless communication devices, in which the unassociated wireless communication device and the plurality of associated wireless communication devices perform spatial multiplexing transmission on the same frequency at the same time, the associated wireless communication device including the unassociated wireless communication device being provided with a shared information transmission unit that transmits shared information to the other associated wireless communication devices by a communication means different from the spatial multiplexing transmission, the shared information being information on a signal received from the unassociated wireless communication device by the spatial multiplexing transmission or on a signal to be transmitted to the unassociated wireless communication device by the spatial multiplexing transmission, and a weight calculation unit that calculates a weight vector to be used during the spatial multiplexing transmission based on a channel matrix in which a first channel vector is generated from channel information between an antenna element of the unassociated wireless communication device or a virtual antenna element obtained by combining the antenna elements of the unassociated wireless communication device and an antenna element of the associated wireless communication device including the associated wireless communication device itself, and one or more second channel vectors generated in the past relative to the first channel vector are arranged.

[0015] One aspect of the present invention is a wireless communication system including an uncooperative wireless communication device having a plurality of antenna elements and a plurality of cooperating wireless communication devices, in which the uncooperative wireless communication device and the plurality of cooperating wireless communication devices perform spatial multiplexing transmission at the same time on the same frequency, wherein the cooperating wireless communication device includes a shared information transmission unit that transmits shared information to the other cooperating wireless communication devices by a communication means different from the spatial multiplexing transmission, the shared information being information about a signal received from the uncooperative wireless communication device by the spatial multiplexing transmission or a signal to be transmitted to the uncooperative wireless communication device by the spatial multiplexing transmission, and a weight calculation unit that calculates a weight vector to be used during the spatial multiplexing transmission based on a channel matrix in which a first channel vector is generated from channel information between an antenna element of the uncooperative wireless communication device or a virtual antenna element obtained by combining the antenna elements and an antenna element of the cooperating wireless communication device including the uncooperative wireless communication device itself, and one or more second channel vectors generated in the past relative to the first channel vector are arranged.

[0016] One aspect of the present invention is a spatial multiplexing wireless transmission method executed by an associated wireless communication device in a wireless communication system including an unassociated wireless communication device having a plurality of antenna elements and a plurality of associated wireless communication devices, in which the unassociated wireless communication device and the plurality of associated wireless communication devices perform spatial multiplexing transmission on the same frequency at the same time. The spatial multiplexing wireless transmission method transmits shared information to the other associated wireless communication devices by a communication means different from the spatial multiplexing transmission, the shared information being information on a signal received from the unassociated wireless communication device by the spatial multiplexing transmission or on a signal to be transmitted to the unassociated wireless communication device by the spatial multiplexing transmission, and calculates a weight vector to be used during the spatial multiplexing transmission based on a channel matrix in which a first channel vector is generated from channel information between an antenna element of the unassociated wireless communication device or a virtual antenna element obtained by combining the antenna elements of the unassociated wireless communication device and an antenna element of the associated wireless communication device including the unassociated wireless communication device itself, and one or more second channel vectors generated in the past relative to the first channel vector.

[0017] One aspect of the present invention is a program for causing a computer that functions as the coordinated wireless communication device in a wireless communication system in which the uncooperative wireless communication device and the multiple coordinated wireless communication devices perform spatial multiplexing transmission on the same frequency at the same time, the program including: a shared information transmission step of transmitting shared information to the other coordinated wireless communication devices by a communication means different from the spatial multiplexing transmission, the shared information being information on a signal received from the uncooperative wireless communication device by the spatial multiplexing transmission or on a signal to be transmitted to the uncooperative wireless communication device by the spatial multiplexing transmission; and a weight calculation step of calculating a weight vector to be used during the spatial multiplexing transmission based on a channel matrix in which a first channel vector is generated from channel information between an antenna element of the uncooperative wireless communication device or a virtual antenna element obtained by combining the antenna elements of the uncooperative wireless communication device and an antenna element of the coordinated wireless communication device including the uncooperative wireless communication device itself, and one or more second channel vectors generated in the past before the first channel vector are arranged. Effect of the Invention

[0018] According to the present invention, the null space expansion technique can be used in each of a plurality of wireless communication devices working in cooperation with each other. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic diagram showing an example of the configuration of a general MIMO system. [Diagram 2] 1 is a flowchart showing a procedure for calculating a receiving weight matrix in a general MIMO system and regenerating a transmission signal using the calculated receiving weight matrix. [Diagram 3] FIG. 1 is a schematic block diagram showing an example of the configuration of a wireless communication device in a typical MIMO system. [Figure 4] 1 is a schematic block diagram showing an example of the configuration of a transmission unit included in a wireless communication device in a typical MIMO system. [Diagram 5]1 is a schematic block diagram showing an example of the configuration of a receiving section included in a wireless communication device in a typical MIMO system. [Figure 6] 1 is a flowchart showing a transmission process of a wireless communication device in a general MIMO system. [Figure 7] 1 is a flowchart showing a receiving process of a wireless communication device in a general MIMO system. [Figure 8] 1 is a schematic diagram illustrating a configuration example of a wireless communication system according to a first embodiment. [Figure 9] 2 is a schematic block diagram illustrating a configuration example of a receiving unit according to the first embodiment. FIG. [Figure 10] 2 is a schematic block diagram illustrating a configuration example of a reception weight processing unit according to the first embodiment. FIG. [Figure 11] FIG. 1 is a diagram illustrating an example of the configuration of a channel matrix used to calculate a receiving weight matrix in a general MIMO system. [Figure 12] 3 is a diagram showing an example of the configuration of an extended channel matrix used for calculating a receiving weight matrix in the first embodiment; FIG. [Figure 13] 5 is a flowchart showing an operation of a reception weight processing unit according to the first embodiment. [Figure 14] FIG. 11 is a schematic block diagram illustrating a configuration example of a reception weight processing unit according to a second embodiment. [Figure 15] 13 is a flowchart (part 1) showing the operation of a reception weight processing unit according to the second embodiment. [Figure 16] 13 is a flowchart (part 2) showing the operation of the reception weight processing unit according to the second embodiment. [Figure 17] 2 is a schematic block diagram illustrating a configuration example of a transmission unit according to the first embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] First, details of the MIMO technology, which is the premise of the embodiment according to the present invention, will be described.

[0021] <About MIMO Technology> (Overview of MIMO Technology) Figure 1 is a schematic diagram showing a configuration example of a general MIMO system. The MIMO system includes a wireless communication device 80BS and a wireless communication device 80T. In Figure 1, as an example, the wireless communication device 80BS is described as a base station device, and the wireless communication device 80T is described as a terminal device.

[0022] However, the wireless communication device 80BS may be a terminal device, and the wireless communication device 80T may be a base station device. When the wireless communication device 80BS is a base station device and the wireless communication device 80T is a terminal device, the MIMO system may include a plurality of wireless communication devices 80T. In this case, the wireless communication device 80BS, which is a base station device, performs spatial multiplexing transmission at the same time on the same frequency in the same space with a plurality of wireless communication devices 80T. Here, the same frequency does not mean exactly the same frequency value, but means the same frequency band (the same frequency channel) having a certain bandwidth centered on the center frequency assigned to MIMO transmission. Also, when the wireless communication device 80BS, which is a base station device, accommodates a plurality of wireless communication devices 80T, which are terminal devices, the wireless communication device 80BS may be configured to select some of the plurality of wireless communication devices 80T and perform MIMO transmission.

[0023] The wireless communication device 80BS forms a plurality of directional beams using a large number of antenna elements. For example, consider a case where three MIMO channels are assigned to the wireless communication device 80T and three signal sequences are transmitted. The separation processing of the three signals may be performed on the wireless communication device 80BS side, on the wireless communication device 80T side, or on both sides. In this case, either one or both of the wireless communication devices 80BS and 80T that perform the signal separation processing grasps the state of the wireless propagation path between the wireless communication device 80BS and the wireless communication device 80T, and performs the separation processing based on information indicating the state of the wireless propagation path. When the signal separation processing is performed on the transmitting side, the processing may be called precoding, and when the signal separation processing is performed on the receiving side, the processing may be called postcoding.

[0024] Signal separation processing in a MIMO channel is performed as follows. Here, as shown in FIG. 1, a case will be described in which each of the wireless communication device 80BS and the wireless communication device 80T has three antenna elements. For example, channel information between the jth (j=1, ..., 3) antenna element of the wireless communication device 80BS and the ith (i=1, ..., 3) antenna element of the wireless communication device 80T is expressed as h ij In this case, the column vector h1 corresponding to the first antenna element (j=1) of the wireless communication device 80BS is expressed as (h 11 ,h 21 ,h 31 ) T Let the column vector h2 corresponding to the second antenna element (j=2) of the wireless communication device 80BS be (h 12 ,h 22 ,h 32 ) T Let the column vector h3 corresponding to the third antenna element (j=3) of the wireless communication device 80BS be (h 13 ,h 23 ,h 33 ) TThat is, the number of column vectors is equal to the number of antenna elements of wireless communication device 80BS, and each of the column vectors is a vector having a number of dimensions equal to the number of antenna elements of wireless communication device 80T. Here, the symbol "T" on the right superscript represents the transpose of a vector or matrix.

[0025] The channel information is a value representing the state of the wireless propagation path, i.e., the actual propagation coefficient of the channel between the antenna element of the transmitting wireless communication device 80BS and the antenna element of the receiving wireless communication device 80T, estimated or acquired by the transmitting wireless communication device 80BS or the receiving wireless communication device 80T (strictly speaking, it includes the effects of the amplifiers and filters in the transmitting and receiving wireless communication devices 80BS, 80T).

[0026] The three signals transmitted by the wireless communication device 80BS are denoted as t1 to t3, and a column vector having these signals as components is denoted as T x =(t1,t2,t3) T The received signals received by the three antenna elements of the wireless communication device 80T are denoted as r1 to r3, and a column vector having these as components is denoted as R x =(r1,r2,r3) T A matrix having column vectors h1 to h3 as the first to third column components is denoted as a channel matrix H. Noise is denoted as n. In this case, the relationship of the following equation (1) holds for the entire MIMO system.

[0027]

number

[0028] Here, when signal separation processing, i.e., post-coding, is performed in the wireless communication device 80T on the receiving side, the received signal vector R x From the transmitted signal vector T x Specifically, the weight matrix W (receiving weight matrix) is calculated as shown in the following equation (2) and the receiving signal vector R x The process involves multiplying the value from the left.

[0029]

number

[0030] When the noise n is sufficiently small, the weight matrix W that follows the ZF (Zero-Forcing) criterion satisfies the following equation (3): ZF (receiving weight matrix), the following equation (4) holds, and the received signal vector R x From the transmitted signal vector T x In the formula (3), the matrix I is a unit matrix with 3 rows and 3 columns.

[0031]

number

[0032]

number

[0033] Weight matrix W ZF To calculate this, we use the weight matrix W ZF Any calculation method for calculating the weight matrix W can be applied. For example, when using the Moore-Penrose general inverse matrix, ZF is calculated by the following equation (5).

[0034]

number

[0035] In equation (5), the superscript "+" indicates a pseudo-inverse matrix, the superscript "-1" indicates an inverse matrix, and the superscript "H" indicates a conjugate transpose matrix. ij and the weight matrix W ZF Element w ij The following relationship holds between:

[0036]

number

[0037] That is, for a desired signal stream, i.e., when i=j, control is performed so that the energy does not become 0, and for a non-desired signal stream, i.e., when i≠j, control is performed so that the energy becomes 0. For the latter, control is performed to form a point (null) where no signal is received, for example, in a line-of-sight environment, control is performed so that the beam shape becomes a valley, and this control is called null formation.

[0038] In addition, the weight matrix W ZF The row vector of is a weight vector (receiving weight vector) corresponding to each antenna element of the wireless communication device 80BS. That is, the equation (6) expresses the weight matrix W ZF The row vector (w i1 ,w i2 ,w i3 ) and the j-th column vector (h 1j ,h 2j ,h 3j ) T This shows that null formation is performed by multiplying by i and j, so that if i ≠ j, the result is 0, and if i = j, the result is non-zero. MIMO transmission is performed by such orthogonalization processing.

[0039] 2 is a flowchart showing an example of a procedure for performing signal separation on the receiving side in a MIMO system. First, the wireless communication device 80T receives a known reference signal from the wireless communication device 80BS at a predetermined timing, and estimates a channel matrix H based on the received known reference signal (step S1). Next, the wireless communication device 80T estimates a receiving weight matrix, that is, a weight matrix W according to the ZF criterion. ZF (Step S2). The wireless communication device 80T calculates the received signal vector R x For the weight matrix WZF Multiplying the desired transmit signal vector T x (Step S3), and the process ends. Note that since channel information usually differs for each frequency component, in the case of a wideband signal, for example, a signal using an OFDM (Orthogonal Frequency Division Multiplexing) modulation method, a similar weight matrix W ZF The following calculation is made:

[0040] When transmitting from the wireless communication device 80T to the wireless communication device 80BS, the transmission weight matrix used in the signal separation process, i.e., precoding, in the wireless communication device 80T on the transmitting side can be calculated, for example, as follows. x ” and the transmission signal vector transmitted by the wireless communication device 80T is “T x ”, the channel matrix is ​​“H”, and the noise is “n”. Here, “R x =H W T x In this equation, it is possible to calculate the transmission weight matrix W such that "H·W" becomes the unit matrix I. If the noise n is sufficiently small, the equation can be expressed as R x ≒T x Therefore, in the wireless communication device 80T, the transmission signal vector T x is multiplied by the transmission weight matrix W from the left and transmitted, the result of which is the received signal vector R x Transmit signal vector T x Such a transmission weight matrix W can be regarded as the above-mentioned weight matrix W ZF In this case, the channel matrix H is a matrix in which the channel vectors h1, h2, and h3, which are column vectors, are converted into row vectors and arranged, so the transmission weight matrix W is a matrix in which the transmission weight vectors, which are column vectors, are arranged.

[0041] The above is the signal separation processing on the receiving side in a typical MIMO system. As described in Non-Patent Document 1, there are several variations of similar signal separation processing.

[0042] (Example of MIMO device configuration) 3 is a schematic block diagram showing an example of the internal configuration of a wireless communication device 80 in a MIMO system. An apparatus in which the wireless communication device 80 is a base station device is, for example, the wireless communication device 80BS in FIG. 1, and an apparatus in which the wireless communication device 80 is a terminal device is, for example, the wireless communication device 80T in FIG. 1. The wireless communication device 80 will be described as an apparatus having both a precoding configuration, i.e., a configuration in which a signal is separated on the transmitting side, and a postcoding configuration, i.e., a configuration in which a signal is separated on the receiving side. The wireless communication device 80 includes a transmitting unit 81, a receiving unit 85, an interface circuit 87, a MAC (Media Access Control) layer processing circuit 88, and a communication control circuit 820.

[0043] The wireless communication device 80 inputs and outputs data to and from an external device or its own software via the interface circuit 87. The external device may be directly connected to the interface circuit 87 via a wired connection line, or may be connected via a communication network. The interface circuit 87 detects data to be transferred over a wireless line from among the input data, and outputs the detected data to the MAC layer processing circuit 88.

[0044] The MAC layer processing circuit 88 performs processing related to the MAC layer according to instructions from a communication control circuit 820 that manages and controls the operation of the entire wireless communication device 80. Here, the processing related to the MAC layer includes conversion of data input / output to / from the interface circuit 87 and data transmitted / received over a wireless line, and addition of header information for the MAC layer. The processing related to the MAC layer includes various scheduling processes, and a circuit that performs the various scheduling processes is shown as a scheduling processing circuit 881 in FIG. 3. Here, the scheduling process is a process of determining which transmission resource (time-frequency resource) to allocate to a signal in data transmission, and in the case where the wireless communication device 80 is a base station device and is a multi-user MIMO transmission, it also includes a process of determining a combination of terminal devices that perform spatial multiplexing at the same time. The scheduling processing circuit 881 outputs the scheduling result to the communication control circuit 820. In MIMO transmission, signals are transmitted at once to multiple antenna elements of the opposing wireless communication device, so the MAC layer processing circuit 88 outputs multiple signal sequences to the transmission unit 81.

[0045] 4 is a schematic block diagram showing an example of the configuration of a transmitting unit 81 included in a wireless communication device 80. The transmitting unit 81 includes transmission signal processing circuits 811-1 to 811-L (L is an integer of 2 or more), additive synthesis circuits 812-1 to 812-K (K is an integer of 2 or more), IFFT (Inverse Fast Fourier Transform) & GI (Guard Interval) adding circuits 813-1 to 813-K, D / A (Digital / Analog) converters 814-1 to 814-K, a local oscillator 815, mixers 816-1 to 816-K, filters 817-1 to 817-K, HPAs (High Power Amplifiers) 818-1 to 818-K, antenna elements 819-1 to 819-K, and a transmission weight processing unit 830. The transmission signal processing circuits 811-1 to 811-L and the transmission weight processing unit 830 are connected to the communication control circuit 820 shown in FIG.

[0046] The transmission weight processing circuit 830 includes a channel information acquisition circuit 831, a channel information storage circuit 832, and a transmission weight calculation circuit 833. Here, the subscript L of the transmission signal processing circuits 811-1 to 811-L indicates the number of simultaneous spatial multiplexing operations. Also, the subscript K of the circuits from the additive synthesis circuits 812-1 to 812-K to the antenna elements 819-1 to 819-K indicates the number of antenna elements included in the wireless communication device 80.

[0047] If the signal separation process is not performed on the transmitting side, K=L and the transmission weight matrix is ​​a unit matrix, so the signal is transmitted without being multiplied by the transmission weight matrix. Therefore, in this case, there is no need to provide the transmission weight processor 830.

[0048] In MIMO, signals are transmitted simultaneously to multiple antenna elements of the opposing wireless communication device, so multiple signal sequences are input to the transmitter 81 via the MAC layer processing circuit 88. Each of the transmission signal processing circuits 811-1 to 811-L receives a corresponding signal sequence from the multiple signal sequences input to the transmitter 81. Therefore, in this case, the number of signal sequences input to the transmitter 81 is L. The transmission signal processing circuits 811-1 to 811-L generate data (data inputs #1 to #L) to be transmitted to each of the destination wireless communication devices, i.e., wireless packets to be transmitted over a wireless line from the received multiple signal sequences, and perform modulation processing.

[0049] Here, for example, if the OFDM modulation method is used, each of the transmission signal processing circuits 811-1 to 811-L performs modulation processing for each frequency component of the signal sequence that each of them takes in. The transmission signal processing circuits 811-1 to 811-L obtain a transmission weight matrix for each frequency component output by the transmission weight calculation circuit 833. The transmission signal processing circuits 811-1 to 811-L multiply the baseband signal for each frequency component that has been modulated by the transmission weight matrix corresponding to each frequency component. The transmission signal processing circuits 811-1 to 811-L perform the remaining signal processing as necessary on the signal multiplied by the transmission weight vector corresponding to each antenna element 819-1 to 819-K, and obtain sampling data of the transmission signal in the baseband. The transmission signal processing circuits 811-1 to 811-L output the sampling data of the transmission signal in the baseband to the addition and synthesis circuits 812-1 to 812-K.

[0050] The summing and combining circuits 812-1 to 812-K combine the signals output by the transmission signal processing circuits 811-1 to 811-L for each frequency component. The IFFT & GI adding circuits 813-1 to 813-K convert the signals combined by the summing and combining circuits 812-1 to 812-K from signals on the frequency axis to signals on the time axis. The IFFT & GI adding circuits 813-1 to 813-K insert guard intervals into the signals converted into signals on the time axis, and perform processes such as waveform shaping between OFDM symbols (between blocks of block transmission in the case of SC-FDE (Single-Carrier Frequency Domain Equalization)).

[0051] The D / A converters 814-1 to 814-K convert the digital sampling data output by the IFFT & GI adding circuits 813-1 to 813-K into baseband analog signals. The mixers 816-1 to 816-K multiply the analog signals output by the D / A converters 814-1 to 814-K by the local oscillation signal output by the local oscillator 815, and upconvert the analog signals into radio frequency signals. Here, the upconverted signals contain signals with frequency components outside the band of the channel to be transmitted. Therefore, the filters 817-1 to 817-K remove the frequency components outside the band from the signals output by the mixers 816-1 to 816-K to generate electrical signals to be transmitted. The HPAs 818-1 to 818-K amplify the signals output by the filters 817-1 to 817-K and transmit them via the antenna elements 819-1 to 819-K.

[0052] 4, after additive synthesis of the signals of the respective frequency components is performed by additive synthesis circuits 812-1 to 812-K, IFFT processing, guard interval insertion, waveform shaping, and other processing are performed. Alternatively, the transmission signal processing circuits 811-1 to 811-L may perform these processes and may not include the IFFT & GI adding circuits 813-1 to 813-K. In this case, the remaining signal processing as required after the multiplication of the transmission weight matrix in the transmission signal processing circuits 811-1 to 811-L is processing such as IFFT processing, guard interval insertion, waveform shaping, and the like.

[0053] In the transmission weight processing unit 830, the channel information acquisition circuit 831 separately acquires channel information for each opposing wireless communication device acquired by the receiving unit 85, or channel information fed back from each opposing wireless communication device via the communication control circuit 820. The channel information acquisition circuit 831 overwrites the channel information acquired successively in the channel information storage circuit 832, and updates the channel information stored in the channel information storage circuit 832 so that it becomes the most recent channel information. The transmission weight calculation circuit 833 reads out channel information corresponding to the wireless communication device of the transmission destination instructed by the communication control circuit 820 from the channel information storage circuit 832, and calculates a transmission weight matrix based on the read channel information. The transmission weight calculation circuit 833 outputs the calculated transmission weight matrix to the transmission signal processing circuits 811-1 to 811-L. Note that when the channel information acquisition circuit 831 acquires channel information for each frequency component, the transmission weight calculation circuit 833 calculates a transmission weight matrix for each frequency component.

[0054] The communication control circuit 820 manages control related to the entire communication, such as management of the wireless communication device of the transmission destination, overall timing control, etc. The communication control circuit 820 outputs information indicating the wireless communication device of the transmission destination, etc., to the transmission weight processing unit 830 that performs signal processing related to the calculation of the above-mentioned transmission weight matrix.

[0055] 5 is a schematic block diagram showing an example of the configuration of a receiving unit 85 included in the wireless communication device 80. The receiving unit 85 includes antenna elements 851-1 to 851-K, LNAs (Low Noise Amplifiers) 852-1 to 852-K, a local oscillator 853, mixers 854-1 to 854-K, filters 855-1 to 855-K, A / D (Analog / Digital) converters 856-1 to 856-K, FFT (Fast Fourier Transform) circuits 857-1 to 857-K, receiving signal processing circuits 858-1 to 858-L, and a receiving weight processing unit 860. The receiving signal processing circuits 858-1 to 858-L and the receiving weight processing unit 860 are connected to the communication control circuit 820 shown in FIG. The receiving weight processing circuit 860 includes a channel information estimation circuit 861 and a receiving weight calculation circuit 862 .

[0056] The LNAs 852-1 to 852-K amplify signals received via the antenna elements 851-1 to 851-K. The mixers 854-1 to 854-K multiply the radio frequency signals amplified by the LNAs 852-1 to 852-K by a local oscillation signal output by the local oscillator 853, and down-convert the radio frequency signals to baseband signals. Here, the down-converted signals also contain frequency components outside the frequency band to be received. Therefore, the filters 855-1 to 855-K remove the out-of-band components from the signals output by the mixers 854-1 to 854-K. The A / D converters 856-1 to 856-K convert the signals output by the filters 855-1 to 855-K into digital baseband signals. The FFT circuits 857-1 to 857-K convert the digital baseband signals output by the A / D converters 856-1 to 856-K from signals on the time axis to signals on the frequency axis (separate the signals into signals of each frequency component) at a predetermined symbol timing. The FFT circuits 857-1 to 857-K output the signals separated into each frequency component to the received signal processing circuits 858-1 to 858-L and the channel information estimation circuit 861.

[0057] In the receiving weight processing unit 860, the channel information estimation circuit 861 estimates channel information between the antenna element of the source wireless communication device and each of the antenna elements 851-1 to 851-K of the wireless communication device 80 for each frequency component based on a known signal for channel estimation (such as a preamble signal added to the beginning of a wireless packet) separated into each frequency component. The receiving weight calculation circuit 862 calculates a receiving weight matrix for each signal sequence and each frequency component based on the channel information estimated by the channel information estimation circuit 861. The receiving weight calculation circuit 862 outputs the receiving weight matrix for each frequency component corresponding to each of the calculated signal sequences to the receiving signal processing circuits 858-1 to 858-L corresponding to the signal sequence to be extracted.

[0058] 4 and 5, antenna elements 819-1 to 819-K that only perform transmission and antenna elements 851-1 to 851-K that only perform reception are shown separately. However, as described above, when the channel information acquisition circuit 831 of the transmission unit 81 acquires the channel information acquired by the reception unit 85 via the communication control circuit 820, the K antenna elements need to be antenna elements that are shared for transmission and reception. This is because the channel information acquired by the reception unit 85 is channel information between the antenna elements of the opposing wireless communication device and the antenna elements 851-1 to 851-K, and in order to use this as channel information between the antenna elements of the opposing wireless communication device and the antenna elements 819-1 to 819-K, the antenna elements need to be physically identical. In this case, the K antenna elements included in the wireless communication device 80 are branched into two and connected to the HPAs 818-1 to 818-K and the LNAs 852-1 to 852-K.

[0059] Each of the reception signal processing circuits 858-1 to 858-L multiplies the signal for each frequency component output by the FFT circuits 857-1 to 857-K by the reception weight matrix for each frequency component output by the reception weight calculation circuit 862. The reception signal processing circuits 858-1 to 858-L add and combine, for each frequency component, the signals corresponding to the antenna elements 851-1 to 851-K multiplied by the reception weight matrix for each frequency component. The reception signal processing circuits 858-1 to 858-L demodulate the added and combined signal, and output the regenerated data to the MAC layer processing circuit 88.

[0060] Here, different reception signal processing circuits 858-1 to 858-L each perform signal processing of a different signal sequence. MAC layer processing circuit 88 performs processing related to the MAC layer (for example, conversion between data input / output to / from interface circuit 87 and data transmitted / received over a wireless line, termination of header information of the MAC layer, etc.). MAC layer processing circuit 88 outputs the reception data that has been processed related to the MAC layer to an external device or software provided in itself via interface circuit 87.

[0061] The communication control circuit 820 manages the source wireless communication device and controls communication, such as timing control.

[0062] As for signal reception, similarly to the case of transmission, in a wideband system using the OFDM modulation method or the SC-FDE method, the multiplication of the above-mentioned receiving weight matrix is ​​performed for each frequency component. That is, the FFT circuits 857-1 to 857-K perform FFT on the signals output from the A / D converters 856-1 to 856-K to separate them into each frequency component, and the signal processing in the channel information estimation circuit 861 and the receiving signal processing circuits 858-1 to 858-L are performed for each separated frequency component.

[0063] (MIMO transmission processing) 6 is a flowchart showing a transmission process of a wireless communication device 80 in MIMO. When performing precoding, the wireless communication device 80 needs to acquire channel information of a wireless propagation path from which data will be transmitted. The channel information may be acquired by estimating it from a signal received by the wireless communication device 80, or by periodically receiving feedback from the opposing wireless communication device. Here, it is assumed that the channel information is periodically fed back from the opposing wireless communication device.

[0064] When the wireless communication device 80 starts the process of acquiring channel information (step S830), the channel information acquisition circuit 831 acquires channel information fed back from the opposing wireless communication device (step S831). The channel information acquisition circuit 831 overwrites the channel information of each frequency component for each antenna element of the opposing wireless communication device in the channel information storage circuit 832 (step S832). The processes of steps S831 and S832 are performed sequentially each time channel information is fed back from the opposing wireless communication device.

[0065] When the signal transmission process is started in the wireless communication device 80 (step S821), the communication control circuit 820 outputs information indicating the wireless communication device of the destination station to the transmission weight calculation circuit 833 (hereinafter, the wireless communication device of the destination station is referred to as the "destination station"). Note that the communication control circuit 820 may output information indicating multiple destination stations to the transmission weight calculation circuit 833, and in this case, the subsequent process is performed for each of the multiple destination stations.

[0066] When the transmission weight calculation circuit 833 receives information indicating the destination station from the communication control circuit 820, it reads out channel information of each frequency component corresponding to each antenna element of the destination station from the channel information storage circuit 832 (step S822). Based on the read channel information, the transmission weight calculation circuit 833 calculates a transmission weight vector corresponding to each antenna element of the destination station for each frequency component by the process described above. Based on the calculated transmission weight vector, the transmission weight calculation circuit 833 generates a transmission weight matrix for each frequency component corresponding to each destination station (step S823).

[0067] In parallel with the processing of steps S822 and S823, the transmission signal processing circuits 811-1 to 811-L take in data to be transmitted to each destination station, which is supplied from the MAC layer processing circuit 88. The transmission signal processing circuits 811-1 to 811-L perform transmission signal processing such as various modulation processes on the taken-in data, and generate transmission signals of each frequency component for each destination station (step S824).

[0068] The transmission signal processing circuits 811-1 to 811-L multiply the generated transmission signals of each frequency component for each destination station by the transmission weight matrix for each frequency component corresponding to each destination station calculated by the transmission weight calculation circuit 833 in step S823 so that the frequency components match (step S825). The transmission signal processing circuits 811-1 to 811-L perform the remaining signal processing on the transmission signals of each frequency component for each destination station multiplied by the transmission weight matrix, and output them to the summing circuits 812-1 to 812-K. The summing circuits 812-1 to 812-K sum and combine the transmission signals of each frequency component for each destination station for each antenna element 819-1 to 819-K. As a result, a transmission signal on the frequency axis for each destination station corresponding to each antenna element 819-1 to 819-K is obtained.

[0069] The IFFT & GI adding circuits 813-1 to 813-K convert the transmission signal on the frequency axis into a transmission signal on the time axis. The IFFT & GI adding circuits 813-1 to 813-K perform processing such as inserting guard intervals and shaping waveforms between OFDM symbols (between blocks in block transmission in the case of SC-FDE) on the converted transmission signals, and output the signals to the D / A converters 814-1 to 814-K (steps S826-1 to S826-K).

[0070] Predetermined processing is performed on the transmission signals output from the IFFT & GI adding circuits 813-1 to 813-K. Here, the predetermined processing on the transmission signals refers to the processing by the D / A converters 814-1 to 814-K, mixers 816-1 to 816-K, filters 817-1 to 817-K, and HPAs 818-1 to 818-K described above. Each of the HPAs 818-1 to 818-K transmits a transmission signal from the antenna elements 819-1 to 819-K connected thereto (steps S827-1 to S827-K), and the processing ends (steps S828-1 to S828-K).

[0071] (MIMO reception processing) 7 is a flowchart showing reception processing of wireless communication device 80 in MIMO. When reception processing is started in wireless communication device 80 (step S840), signals are received by first to K-th antenna elements 851-1 to 851-K, and predetermined processing is performed on the received signals (steps S841-1 to S841-K). Here, the predetermined processing on the received signals refers to the above-mentioned processing by LNAs 852-1 to 852-K, mixers 854-1 to 854-K, filters 855-1 to 855-K, and A / D converters 856-1 to 856-K, and subsequent signal processing is processing on the received signals digitized by A / D converters 856-1 to 856-K.

[0072] Next, the FFT circuits 857-1 to 857-K perform signal processing such as separation into each frequency component on the received signals digitized by the A / D converters 856-1 to 856-K (steps S842-1 to S842-K). The channel information estimation circuit 861 performs channel estimation of each frequency component from the reception state of the known signals for channel estimation separated into each frequency component output by the FFT circuits 857-1 to 857-K, for example, a preamble signal of a known pattern that was added to a wireless packet (steps S843-1 to S843-K). In other words, the channel information estimation circuit 861 grasps the attenuation of the signal on the wireless propagation path and the rotation state of the complex phase. In the channel estimation performed in steps S843-1 to S843-K, as shown individually in steps S843-1, S843-2, ..., S843-K, channel estimation is performed individually for each spatially multiplexed signal sequence.

[0073] This individual channel estimation needs to be performed in a state where the signals transmitted from each of the source wireless communication devices can be separated. In the case of the OFDM modulation method, for example, a preamble signal for channel estimation with the same number of symbols as the spatial multiplexing number is required. Each of the source wireless communication devices transmits a signal with the same number of symbols as the spatial multiplexing number (or a number of symbols equal to or greater than the same number) and with a preamble signal of a different pattern, and the channel information estimation circuit 861 performs individual channel estimation in steps S843-1 to S843-K by utilizing the difference in the patterns.

[0074] The receiving weight calculation circuit 862 calculates an individual receiving weight vector that satisfies Equation (6) by Equation (5) for each spatially multiplexed signal sequence and each frequency component using the channel information estimated by the channel information estimation circuit 861. The receiving weight calculation circuit 862 generates a receiving weight matrix for each signal sequence and each frequency component based on the calculated receiving weight vector. The receiving weight calculation circuit 862 groups the generated receiving weight matrices for each signal sequence and each frequency component for each signal sequence, and outputs the receiving weight matrices for each frequency component grouped for each signal sequence to the receiving signal processing circuits 858-1 to 858-L corresponding to each signal sequence (step S844).

[0075] Each of the reception signal processing circuits 858-1 to 858-L multiplies the signals separated into frequency components by the FFT circuits 857-1 to 857-K by the reception weight matrix for each frequency component output by the reception weight calculation circuit 862 so that the frequency components match (steps S845-1 to S845-K).

[0076] Here, the process of step S845-1 is specifically the following process. The signal received by the first antenna element 851-1 and subjected to the processes of steps S841-1 and S842-1 is separated into frequency components by the FFT circuit 857-1 and output to each of the reception signal processing circuits 858-1 to 858-L. Each of the reception signal processing circuits 858-1 to 858-L performs a process of multiplying the signal received by the first antenna element 851-1 and separated into frequency components by the FFT circuit 857-1 with a reception weight matrix for each frequency component output by the reception weight calculation circuit 862 so that the frequency components match. Similar processes are also performed in steps S845-2 to S845-K. As a result, each of the reception signal processing circuits 858-1 to 858-L obtains a number of multiplication results equal to K×L as a multiplication result obtained by multiplying the reception weight matrix. As described above, the receiving weight calculation circuit 862 calculates a receiving weight matrix for each spatially multiplexed signal sequence and for each frequency component, so that the K×L multiplication results calculated by each of the receiving signal processing circuits 858-1 to 858-L usually differ from each other.

[0077] Each of the reception signal processing circuits 858-1 to 858-L adds and combines the K×L multiplication results calculated by each circuit for each frequency component (steps S846-1 to S846-L). The reception signal processing circuit 858-1 performs reception signal processing of the first signal sequence, such as demodulation processing, on the first signal sequence that has been added and combined (step S847-1). Similarly, the reception signal processing circuits 858-2 to 858-L also perform reception signal processing for each of the signal sequences corresponding to each circuit (steps S847-2 to S847-L). The L signal sequences that have been subjected to reception signal processing by each of the reception signal processing circuits 858-1 to 858-L are output to the MAC layer processing circuit 88, and the processing ends (steps S848-1 to S848-L).

[0078] For simplicity, an example is shown in which a linear receiving weight matrix such as the ZF standard is used, but a non-linear receiving weight matrix such as MLD (Maximum Likelihood Detection) may be used for signal processing. In this case, the processes in steps S845-1 to S845-K, steps S846-1 to S846-L, and steps S847-1 to S847-L are integrated to perform non-linear signal detection processing. In addition, in addition to the receiving weight matrix calculated using the Moore-Penrose general inverse matrix (also called pseudo-inverse matrix) described above, it is also possible to use a receiving weight matrix calculated using MMSE for calculating the linear receiving weight matrix. In addition, in this example, the number of signal sequences to be spatially multiplexed is "L" for the number "K" of antenna elements 851-1 to 851-K used for reception, but "K" and "L" do not usually need to be the same. If the value of the spatial multiplexing number "L" is equal to or less than the value of the number "K" of antenna elements, signals of a large number of signal sequences can be spatially multiplexed.

[0079] The above is a description of the configuration of the MIMO technology. Based on the above description of the configuration of the MIMO technology, an embodiment of the present invention will be described below.

[0080] (First embodiment) 8 is a schematic diagram showing a configuration example of a wireless communication system 1 according to the first embodiment of the present invention. The wireless communication system 1 is a so-called MIMO system as described above. The wireless communication system 1 includes a base station device 80BS and a plurality of terminal devices 80aT-1 to 80aT-6. The base station device 80BS has the same configuration as the wireless communication device 80BS shown in FIG. 1 in terms of MIMO transmission, and is therefore denoted by the same reference numeral "80BS" as the wireless communication device 80BS in FIG. 1. Therefore, the base station device 80BS transmits three systems of signals (three streams of downstream signals) from three antennas, similar to the wireless communication device 80BS in FIG. 1.

[0081] Each of the terminal devices 80aT-1 to 80aT-6 has the same configuration, and hereinafter, when any one of the terminal devices 80aT-1 to 80aT-6 is indicated, it is described as a terminal device 80aT. Note that, in FIG. 8, six terminal devices 80aT-1 to 80aT-6 are shown as an example, but the number of the terminal devices 80aT-1 to 80aT-6 is required to be equal to or more than the number of streams that the base station device 80BS is to transmit when each of the terminal devices 80aT-1 to 80aT-6 has one antenna element as an antenna element for receiving a signal from the base station device 80BS and performs a signal stream separation process based on the ZF norm in the terminal device 80aT. Furthermore, when performing weight calculation based on an additional channel vector described in the embodiment of the present invention, the number of the terminal devices is equal to or more than the number of the signal streams plus the number of the additional channel vectors, so that the calculation of the Moore-Penrose general inverse matrix described above is possible. In the following description, it is assumed that "K" in the terminal device 80aT is an integer equal to or greater than the number of antenna elements included in the base station device 80BS, and that the wireless communication system 1 includes K terminal devices 80aT-1 to 80aT-K.

[0082] The terminal device 80aT has a configuration in which the receiving unit 85 in the configuration of the wireless communication device 80 shown in Fig. 3 is replaced with a receiving unit 85a shown in Fig. 9. The receiving unit 85a includes antenna elements 851, 951-1 to 951-(K-1), LNAs 852, 952-1 to 952-(K-1), mixers 854, 954-1 to 954-1-(K-1), local oscillators 853, 953-1 to 953-(K-1), filters 855, 955-1 to 955-(K-1), A / D converters 856, 956-1 to 956-(K-1), FFT circuits 857, 957-1 to 957-(K-1), receiving signal processing circuits 858-1 to 858-L, receiving weight processing units 860a, and a shared information transmitting unit 960. The reception signal processing circuits 858-1 to 858-L and the reception weight processing unit 860a are connected to the communication control circuit 820 shown in Fig. 3. The reception signal processing circuits 858-1 to 858-L have the same configuration as the reception signal processing circuits 858-1 to 858-L provided in the receiving unit 85.

[0083] The receiver 85a shown in FIG. 9 includes K antenna elements 851, 951-1 to 951-(K-1), LNAs 852, 952-1 to 952-(K-1), mixers 854, 954-1 to 954-1(K-1), filters 855, 955-1 to 955-(K-1), A / D converters 856, 956-1 to 956-(K-1), FFT circuits 857, 957-1 For ease of explanation, 957-(K-1) have different symbols from the antenna elements 851-1 to 851-K, LNAs 852-1 to 852-K, mixers 854-1 to 854-K, filters 855-1 to 855-K, A / D converters 856-1 to 856-K, and FFT circuits 857-1 to 857-K that the receiving unit 85 shown in FIG. 5 has, each of which is equipped with K units, but they have the same configuration.

[0084] The reason for using different reference numerals is that the antenna element 851 is an antenna element used to receive signals transmitted by the base station device 80BS, whereas the antenna elements 951-1 to 951-(K-1) are antenna elements used to receive signals transmitted by the other K-1 terminal devices 80aT. The antenna elements 951-1 to 951-(K-1), LNAs 952-1 to 952-(K-1), local oscillators 953-1 to 953-(K-1), mixers 954-1 to 954-1(K-1), filters 955-1 to 955-(K-1), A / D converters 956-1 to 956-(K-1), and FFT circuits 957-1 to 957-(K-1) correspond to the shared information transmitting unit 960 and are also referred to as a shared information receiving unit 950. Each of the K terminal devices 80aT is assigned K different frequencies other than the frequencies assigned for communication between each of the K terminal devices 80aT and the base station device 80BS so that each of the K terminal devices 80aT can transmit and receive signals to and from each other.

[0085] In the receiver 85 shown in FIG. 5, the frequencies of the signals received by the antenna elements 851-1 to 851-K are the same, so only one local oscillator 853 is required. In contrast, in the case of the receiver 85a, the antenna element 851 receives a signal transmitted by the base station device 80BS, and each of the antenna elements 951-1 to 951-(K-1) receives signals transmitted by the other K-1 terminal devices 80aT. Therefore, the frequencies of the radio frequency signals supplied to each of the mixers 854, 954-1 to 954-(K-1) are all different. Each of the mixers 854, 954-1 to 954-(K-1) needs to down-convert all of the supplied radio frequency signals to baseband signals. Therefore, each of the local oscillators 853, 953-1, 953-(K-1) outputs a local oscillation signal of a different frequency that down-converts the frequency of the radio frequency signal supplied to the mixers 854, 954-1 to 954-(K-1) connected to each of them to a baseband signal.

[0086] The shared information transmission unit 960 includes a local oscillator 961, a mixer 962, a filter 963, an HPA 964, and an antenna element 965. The mixer 962 is connected to the output of the filter 855. That is, the signal supplied to the mixer 962 is a signal transmitted by the base station device 80BS and received by the antenna element 851, and becomes a baseband analog signal that has been processed by the LNA 852, the mixer 854, and the filter 855. Information superimposed on this baseband analog signal becomes shared information to be shared with the other K-1 terminal devices 80aT.

[0087] The local oscillator 961 outputs a local oscillation signal of a frequency that up-converts the frequency of the signal supplied to the mixer 962 to a frequency assigned to the device itself. The filter 963 removes out-of-band frequency components from the signal output by the mixer 962 to generate an electrical signal to be transmitted. The HPA 964 amplifies the signal output by the filter 963 and transmits it via the antenna element 965.

[0088] As shown in Fig. 10, the receiving weight processing circuit 860a includes a channel information estimation circuit 861a, a channel information storage circuit 863, and a receiving weight calculation circuit 862a. The channel information estimation circuit 861a has the same configuration as the channel information estimation circuit 861 shown in Fig. 5, and further writes the estimated channel information to the channel information storage circuit 863. The channel information storage circuit 863 stores the channel information written by the channel information estimation circuit 861a in chronological order. The receiving weight calculation circuit 862a calculates a receiving weight vector to which the null space expansion technique is applied, as described below, to generate a receiving weight matrix.

[0089] <About Null Space Expansion Technology> First, a case where the null space expansion technique is not applied will be described with the wireless communication device 80BS in Fig. 1 as the base station device 80BS and the wireless communication device 80T as the terminal device 80T. In downlink transmission from the base station device 80BS to the terminal device 80T, MIMO transmission in which signal separation processing is performed on the terminal device 80T side is assumed. In this case, the terminal device 80T grasps channel information between all of its own antenna elements 851-1 to 851-K and all of the antenna elements 819-1 to 819-K of the base station device 80BS, and performs interference suppression processing on the received signals based on the grasped channel information so that interference does not occur between signal streams, thereby separating the signals.

[0090] As described above, there are a number of methods for interference suppression processing. However, all of these methods have in common that, in each of the antenna elements 819-1 to 819-K of the base station device 80BS, a reception process is added based on channel information related to antenna elements other than the antenna element transmitting the desired stream so that interference signals from antenna elements other than the antenna element transmitting the desired stream are not received. In other words, the reception process for preventing interference signals from antenna elements other than the antenna element transmitting the desired stream is a reception process for forming a null.

[0091] For simplicity, let us consider the case where K=L in the base station device 80BS, that is, the base station device 80BS does not perform signal separation during transmission, and L antenna elements 819-1 to 819-L transmit L streams. L (t) is a channel vector at time t corresponding to each antenna element 819-1 to 819-L of the base station device 80BS, and is a vector having a dimension of "K", which is the number of antenna elements of the terminal device 80T. Note that the channel vector h j (j=1,…,L) is, as mentioned above, (h 1j ,h 2j ,…,h ij ,…,h Kj ) T and h ij is channel information between the j-th antenna element 819-j of the base station device 80BS and the i-th antenna element 851-i of the terminal device 80T.

[0092] In the case of the MIMO transmission described with reference to Fig. 1 to Fig. 7, a matrix in which channel vectors corresponding to the number of antenna elements of base station device 80BS that simultaneously multiplex and transmit a plurality of signal sequences are arranged, that is, a matrix with K rows and L columns shown in Fig. 11 is used as the channel matrix. When extracting a stream from antenna element 819-1 of base station device 80BS, interference between streams is suppressed by using a receiving weight vector as shown below. That is, channel vectors h2(t) to h L (t)(=H1 sub ), the wireless signals cancel each other out to form a null. The conventional technique uses a receiving weight vector calculated from a channel matrix by processing such as orthogonalization.

[0093] For a more specific explanation, let us focus on the j-th antenna element of the base station device 80BS. In this case, a partial channel matrix H j subFor example, the channel matrix shown in FIG. 11 is a channel matrix when j=1. This channel matrix is ​​a partial channel matrix H1 main and a partial channel matrix H1 in which column vectors corresponding to antenna elements 819-2 to 819-L other than the first one are arranged. sub The channel matrix includes:

[0094] The reception weight calculation circuit 862 included in the reception weight processing unit 860 of the terminal device 80T calculates the partial channel matrix H j sub Here, the orthogonalization process performed by the reception weight calculation circuit 862 is to calculate a reception weight vector corresponding to an antenna element other than the j-th antenna element of the base station device 80BS. k sub Here, k ≠ j, k = 1 to L. The reception signal processing circuits 858-1 to 858-L of the terminal device 80T multiply a signal from the j-th antenna element of the base station device 80BS by a reception weight vector calculated by the reception weight calculation circuit 862 for the j-th antenna element of the base station device 80BS to perform interference suppression.

[0095] In this case, the receiving weight calculation circuit 862 calculates the receiving weight vector based on the most recent channel estimation result. That is, the receiving process is performed by forming nulls only for the latest channel vector. Therefore, if fluctuations occur in the wireless propagation path during this receiving process, inter-stream interference will occur.

[0096] In response to this, the receiving weight processing unit 860a to which the null space expansion technique is applied includes a channel information storage circuit 863 as shown in FIG. 10, and stores channel information in chronological order in the channel information storage circuit 863. The receiving weight calculation circuit 862a also performs null formation for previously estimated channel information stored in the channel information storage circuit 863. That is, as shown in FIG. 12, the receiving weight calculation circuit 862a calculates additional channel vectors "~h2" to "~h L " is inserted to generate a channel matrix. Note that the symbol "~" is the symbol placed above the letter "h" as shown in FIG. 12, but in the following text, it will be written before the letter "h" as described above.

[0097] The receiving weight calculation circuit 862a calculates the additional channel vectors "~h2" to "~h L By inserting ", the partial channel matrix H corresponding to all antenna elements 819-1 to 819-L of the base station device 80BS is obtained. j sub The receiving weight calculation circuit 862a expands the expanded partial channel matrix H' j sub Based on this, the receiving weight calculation circuit 862 performs an orthogonalization process similar to that of the above-mentioned receiving weight calculation circuit 862 to calculate receiving weight vectors corresponding to antenna elements other than the j-th antenna element of the base station device 80BS. In the receiving signal processing circuits 858-1 to 858-L, a receiving weight matrix in which the receiving weight vectors calculated by the receiving weight calculation circuit 862a are arranged is multiplied, making it possible to form nulls over a wide range.

[0098] As a result, in addition to the null in the direction that should be originally pointed, a new null is formed in another direction. Therefore, for example, when the channel related to an antenna element other than the j-th antenna element of the base station device 80BS fluctuates over time, even if it deviates from the initial null point, as long as the fluctuating destination is near the additional null point, the interference suppression effect can be obtained similarly, and thus a high inter-stream interference reduction effect can be obtained even in a time-varying environment.

[0099] When comparing the channel matrix used by the receiving weight calculation circuit 862a to which the null space expansion technique is applied and the channel matrix used by the receiving weight calculation circuit 862, as can be seen from FIGS. 11 and 12, the partial channel matrix H1 main is common. On the other hand, the partial channel matrix H'1 sub is the partial channel matrix H1 sub The nearest channel vectors h2(t) to h3(t) of the other antenna elements 819-2 to 819-L of the base station device 80BS in L For each of (t), the corresponding past channel vectors "~h2" to "~h L " will be added to expand the scope of the text.

[0100] Channel vector "~h2" ~ "~h L Each of "t-nT" is, for example, h2(t-nT) to h L (t-nT). The past channel vector h k (t-nT) means a channel vector acquired before time nT corresponding to the k-th antenna element 819-k of the base station device. T is the time period during which channel estimation of the wireless propagation path is performed, and n=1, 2,... is a positive integer. Therefore, the channel vector h k (t-nT) indicates a channel vector estimated n periods ago. However, if channel estimation of the wireless propagation path is not performed periodically, the "t-nT" portion is replaced with any past time at which channel estimation was performed. In addition, the number of past channel vectors to be extended may be multiple, or may be different for each antenna element 819-k of the base station device 80BS.

[0101] (Processing by the terminal device of the first embodiment) Here, the processing of the terminal device 80aT will be described when the wireless communication system 1 includes one base station device 80BS and K terminal devices 80aT-1 to 80aT-K. As described above, the base station device 80BS does not perform signal separation processing on the transmitting side, so the number of antenna elements of the base station device 80BS is "L". Note that L is an integer equal to or greater than 2. When the base station device 80BS transmits a signal, each of the K terminal devices 80aT-1 to 80aT-K receives the signal transmitted by the base station device 80BS by the antenna element 851 that each of the K terminal devices 80aT-1 to 80aT-K includes. Each of the terminal devices 80aT-1 to 80aT-K transfers the signal received from the base station device 80BS to the other K-1 terminal devices 80aT by its own shared information transmission unit 960.

[0102] The terminal device 80aT receives K-1 signals transferred by the other K-1 terminal devices 80aT by each of the K-1 antenna elements 951-1 to 951-(K-1). That is, the terminal device 80aT directly receives a signal transmitted by the base station device 80BS by the antenna element 851, and indirectly receives a signal transmitted by the base station device 80BS by the antenna elements 951-1 to 951-(K-1). Therefore, the received signals converted to baseband analog signals by the mixers 854, 954-1 to 954-(K-1) are theoretically the same signals as the received signals converted to baseband analog signals by the mixers 854-1 to 854-K in the receiving unit 85 shown in FIG. 5.

[0103] The received signals converted into baseband analog signals by the mixers 854, 954-1 to 954-(K-1) are processed by the filters 855, 955-1 to 955-(K-1) and the A / D converters 856, 956-1 to 956-(K-1). Then, the processes corresponding to steps S842-1 to S42-K shown in FIG. 7 are performed by the FFT circuits 857, 957-1 to 957-(K-1).

[0104] The channel information estimation circuit 861a of the receiving weight processing circuit 860a performs processing equivalent to steps S843-1 to 843-K in Fig. 7. In this processing, the channel information estimation circuit 861a outputs the estimated channel information to the receiving weight calculation circuit 862a, and also performs processing of additionally writing the estimated channel information in the channel information storage circuit 863 in chronological order.

[0105] At the timing of step S844, the receiving weight calculation circuit 862a receives the channel information output by the channel information estimation circuit 861a, and writes and stores the received channel information in an internal storage area as the most recent channel information. After that, the receiving weight calculation circuit 862a starts the process shown in Fig. 13. The receiving weight calculation circuit 862a provides a counter j in an internal storage area and initializes the counter j to "1" (step Sa1).

[0106] The reception weight calculation circuit 862a selects channel information corresponding to the j-th antenna element 819-j of the base station device 80BS from the most recent channel information stored in an internal storage area. The reception weight calculation circuit 862a uses the selected channel information to calculate the partial channel matrix H j main (Step Sa2).

[0107] The receiving weight calculation circuit 862a selects channel information corresponding to antenna elements other than the j-th antenna element 819-j of the base station device 80BS from the most recent channel information stored in an internal storage area. Here, the antenna elements other than the j-th antenna element 819-j of the base station device 80BS are the antenna elements 819-1 to 819-(j-1) and 819-(j+1) to 819-L.

[0108] The receiving weight calculation circuit 862a uses the selected channel information to generate channel vectors corresponding to each of the antenna elements other than the j-th antenna element 819-j of the base station device 80BS. The receiving weight calculation circuit 862a arranges the generated channel vectors to generate a partial channel matrix H j sub Generate.

[0109] Here, in the channel information storage circuit 863, the channel information stored at the top of the chronological order is the most recent channel information. Here, for example, it is assumed that the channel information to be added is the channel information immediately before the most recent channel information, i.e., the second channel information from the top in chronological order. Therefore, the receiving weight calculation circuit 862a reads out the channel information immediately before the most recent channel information from the channel information storage circuit 863. The receiving weight calculation circuit 862a generates channel vectors corresponding to each of the antenna elements other than the j-th antenna element 819-j of the base station device 80BS from the read channel information. The receiving weight calculation circuit 862a converts each of the generated channel vectors into a partial channel matrix H j sub After inserting the channel vectors corresponding to each of the subchannel matrices H' j sub (Step Sa3).

[0110] The receiving weight calculation circuit 862a calculates the partial channel matrix H j main and the partial channel matrix H' j sub The receiving weight calculation circuit 862a generates an extended channel matrix H (hereinafter referred to as an extended channel matrix) by arranging and extending the above-mentioned. The receiving weight calculation circuit 862a performs the above-mentioned orthogonalization process based on the generated extended channel matrix, and calculates a receiving weight vector corresponding to the j-th antenna element 819-j of the base station device 80BS (step Sa4).

[0111] The receiving weight calculation circuit 862a determines whether or not the receiving weight vectors corresponding to all antenna elements 819-1 to 819-L of the base station device 80BS have been calculated. Specifically, the receiving weight calculation circuit 862a determines whether or not the counter j matches "L" (step Sa5). If the receiving weight calculation circuit 862a determines that the counter j does not match "L" (step Sa5, No), it increments the value of the counter j stored in the internal storage area by 1 (step Sa6) and performs the processes from step Sa2 onwards again.

[0112] On the other hand, when the receiving weight calculation circuit 862a determines that the counter j matches "L" (step Sa5, Yes), it arranges the receiving weight vectors calculated for the antenna elements 819-1 to 819-L of the base station device 80BS to generate a receiving weight matrix. As described above, since channel information exists for each signal sequence and for each frequency component, the receiving weight calculation circuit 862a performs the processes of steps Sa2 to Sa7 on the channel information for each signal sequence and for each frequency component. Therefore, when the process of step Sa7 is completed, the receiving weight calculation circuit 862a generates a receiving weight matrix for each signal sequence and for each frequency component.

[0113] The receiving weight calculation circuit 862a organizes the calculated receiving weight matrices for each signal sequence and each frequency component for each signal sequence, and outputs the receiving weight matrices for each frequency component organized for each signal sequence to the receiving signal processing circuits 858-1 to 858-L corresponding to each signal sequence (step Sa7), and then terminates the processing.

[0114] Thereafter, the reception signal processing circuits 858-1 to 858-L perform the processes of steps S845-1 to 845-K, steps S846-1 to 846-L, steps S847-1 to S847-L, and steps S848-1 to S848-L in FIG. 7, and the L signal sequences are output to the MAC layer processing circuit 88.

[0115] In the first embodiment described above, the terminal device 80aT transmits and receives shared information between the other K-1 terminal devices 80aT by wireless communication using different frequencies assigned to each of them, which are frequencies other than those assigned to wireless communication with the base station device 80BS. The reason for this is to prevent the wireless communication from interfering with each other. That is, the communication means between the terminal device 80aT and the other K-1 terminal devices 80aT may be any communication means that is different from the spatial multiplexing transmission and does not interfere with the spatial multiplexing transmission between the terminal device 80aT and the base station device 80BS, and does not interfere with each other. For example, it may be a communication means using a different wireless communication method, or it may be a wired communication means. In the case of a wired communication means, each of the terminal devices 80aT will be provided with a signal processing circuit for wired communication in place of each of the K-1 sets including the antenna element 951-k, LNA 952-k, local oscillator 953-k, mixer 954-k and filter 955-k (where k is 1 to K-1) and in place of the shared information transmission unit 960.

[0116] (Effects of the first embodiment) The key to the null space expansion technique is the partial channel matrix H j sub The aim is to extend the partial channel matrix H j sub Using the receiving weight matrix calculated after expanding H' can suppress interference over a wider range than in the case of normal MIMO transmission. j sub By performing processing such as orthogonalization on the received signal, a beam is directed toward the desired antenna element 819-j of the base station device 80BS, and in addition to forming nulls for antenna elements other than the desired antenna element 819-j of the base station device 80BS, a receiving weight matrix in which additional null forming is performed can be generated, making it possible to suppress inter-stream interference in a time-varying environment.

[0117] In other words, the receiving weight calculation circuit 862a calculates a receiving weight vector that aligns the phase of the radio signals when multiplied by the channel vector of the desired antenna element 819-j of the base station device 80BS, and that cancels out the radio signals to become null when multiplied by the channel vector of an antenna element other than the desired antenna element 819-j of the base station device 80BS and a past channel vector.

[0118] The effect of the wireless communication system 1 of the first embodiment will be further considered by comparing it with the MIMO system shown in Fig. 1. Assume that the wireless communication device 80T in Fig. 1 has an antenna with 100 elements, the wireless communication device 80BS has an antenna with 10 elements, and simultaneously receives spatial multiplexing transmission of 10 streams from the wireless communication device 80BS. In this case, the channel vectors corresponding to the antenna elements of the wireless communication device 80BS are 100-dimensional vectors. Usually, 10 degrees of freedom are used for spatial multiplexing of 10 streams, i.e., interference suppression for 10 streams, and the remaining 90 (=100-10) degrees of freedom are used for improving the line gain of each stream by in-phase synthesis.

[0119] Here, when the null space expansion technique is applied to the wireless communication device 80T, the wireless communication device 80T performs a process of calculating a receiving weight matrix by assuming that there is another virtual antenna element of the wireless communication device 80BS in the vicinity of each of the antenna elements of the wireless communication device 80BS, the virtual antenna element being the antenna element that should suppress interference. Here, the virtual antenna element of the wireless communication device 80BS refers to an antenna element that exists at a destination where the antenna element of the wireless communication device 80BS is moved when it is assumed that the antenna element has moved virtually.

[0120] In the case of a wireless communication device 80T to which the null space expansion technology is not applied, when the channel fluctuates due to the movement of the wireless communication device 80T, the effect of interference suppression is weakened and interference increases significantly. In contrast, in the case of a wireless communication device 80T to which the null space expansion technology is applied, if the destination of the antenna element of the wireless communication device 80BS due to time fluctuation (including relative movement accompanying the movement of the wireless communication device 80T) coincides with the destination of the virtual movement, that position becomes the place where a null is formed, so it is expected that interference suppression will be realized.

[0121] However, by applying the null space expansion technique to the wireless communication device 80T, interference suppression is also performed for the antenna elements virtually added in the wireless communication device 80BS, and one additional degree of freedom is consumed for each stream. As a result, the degrees of freedom used for interference suppression become 20 in total, and the degrees of freedom available for line gain improvement by in-phase combining are reduced to 80. If the improvement rate of line gain is proportional to the first power of the degrees of freedom, the difference in the degrees of freedom used for line gain improvement between the cases where the degrees of freedom are 90 and 80 is 10Log(80 / 90)=-0.51···[dB], which is only a difference of about 0.5 dB.

[0122] In contrast, if the null space expansion technology is applied and the time fluctuation of the channel falls within the range of the additional interference suppression implemented as described above, the power of the inter-stream interference can be significantly suppressed. In other words, although there will be a degradation of about 0.5 dB in terms of SNR (Signal to Noise Ratio), a significant improvement in SIR (Signal to Interference power Ratio) is expected. Ultimately, the transmission capacity of MIMO is determined by the SINR, but in a time-varying environment, the SIR characteristic is considered to be more dominant than the SNR, so it can be said that the method of applying the null space expansion technology is effective.

[0123] However, as described above, when the wireless communication device 80T is a terminal device, it is difficult to provide an antenna with as many as 100 elements due to restrictions on the size of the device and power consumption. In contrast, in the first embodiment, by linking multiple terminal devices 80aT, it is possible to virtually increase the number of antenna elements while limiting the number of antenna elements provided in each terminal device 80aT for direct communication with the base station device 80BS, making it easy to realize the terminal device 80aT as an actual device. In addition, by applying a null space expansion technique to each terminal device 80aT, it is possible to suppress inter-stream interference due to wireless propagation path fluctuations, which is not disclosed in Non-Patent Document 4.

[0124] Second Embodiment FIG. 14 is a block diagram showing the internal configuration of a receiving weight processing unit 860b according to the second embodiment. The receiving weight processing unit 860b is used in place of the receiving weight processing unit 860a of the first embodiment. For convenience of explanation, the configuration in which the receiving weight processing unit 860a is replaced with the receiving weight processing unit 860b in the configuration of the receiving unit 85a of the first embodiment is referred to as a receiving unit 85b. Also, the configuration in which the receiving unit 85a is replaced with the receiving unit 85b in the configuration of the terminal device 80aT of the first embodiment is referred to as a terminal device 80bT. Also, the configuration in which the terminal device 80aT is replaced with the terminal device 80bT in the configuration of the wireless communication system 1 of the first embodiment is referred to as a wireless communication system 1a.

[0125] In the second embodiment, the following configuration is provided, taking into consideration that null formation in a wireless propagation path with small channel fluctuation results in null formation in nearby elementary waves, which reduces the interference suppression effect. Here, elementary waves refer to, for example, when a radio wave arrives that is generated by adding together a direct wave and multiple reflected waves generated by reflection from reflecting objects such as buildings and walls, and the direct wave before being added together and each of the multiple reflected waves.

[0126] Partial channel matrix H' j subIn the base station device 80BS, the nearest channel vector h k (t) and the past channel vector h k (t-nT), where k is not equal to j, and K=L and k=1 to L in base station device 80BS, as in the first embodiment.

[0127] In this case, the channel vector h k (t) and the channel vector h k (t-nT) is a similar vector, the channel fluctuation is small and the interference suppression effect is reduced, so the need to form nulls for each channel vector is reduced. Therefore, in the second embodiment, in the antenna elements 819-1 to 819-L of the base station device 80BS, the nearest channel vector h corresponding to an antenna element other than the desired antenna element 819-j is k (t) and the past channel vector h k An index of similarity between (t-nT) is introduced. Based on this index, combinations of channel vectors with low similarity are identified, and the identified channel vectors are used to calculate the receiving weight vector. This is expected to enable MIMO transmission using receiving weight matrices obtained based on channel vectors that are effective in suppressing interference.

[0128] As shown in FIG. 14, the receiving weight processing circuit 860b includes a channel information estimation circuit 861a, a receiving weight calculation circuit 862b, a channel information storage circuit 863, a channel similarity calculation circuit 864, and a channel information selection circuit 865. The channel information estimation circuit 861a and the channel information storage circuit 863 have the same configuration as the receiving weight processing circuit 860a of the first embodiment. The receiving weight calculation circuit 862b has the same configuration as the receiving weight calculation circuit 862a of the first embodiment, except for the configuration described below. The receiving weight calculation circuit 862a of the first embodiment selects past channel information stored in the channel information storage circuit 863 by itself, and calculates the past channel vector h kIn contrast, the receiving weight calculation circuit 862b of the second embodiment generates the past channel vector h k (t-nT) is not generated, and the past channel vector h k Processing is performed using (t-nT).

[0129] The channel similarity calculation circuit 864 calculates the nearest channel vector h k (t) and the past channel vector h k Based on the inner product with (t-nT), the nearest channel vector h k (t) and the past channel vector h k (t-nT) and calculate the mutual similarity. Hereinafter, the mutual similarity is expressed as γ k The absolute value of (n), i.e., |γ k It is expressed as (n)|.

[0130] For example, the channel similarity calculation circuit 864 calculates the nearest channel vector h k (t) and the past channel vector h k The correlation coefficient between (t-nT) is calculated using the following equation (7).

[0131]

number

[0132] Here, the vector with the superscript H is the conjugate transpose vector. The correlation coefficient calculated by Equation (7) is the most recent channel vector h k (t) and the past channel vector h k (t-nT) is the inner product. Here, the correlation coefficient is expressed as γ k (n), and the channel similarity calculation circuit 864 calculates the absolute value of the correlation coefficient, i.e., |γ k (n)| is calculated, and the calculated value is regarded as the mutual similarity.

[0133] The channel similarity calculation circuit 864 judges whether the mutual similarity is low or not based on the mutual similarity and a predetermined fixed value. For example, when the mutual similarity is equal to or less than a fixed value, the channel similarity calculation circuit 864 judges that the mutual similarity is low, that is, the similarity between the wireless propagation paths is low. The channel similarity calculation circuit 864 calculates the past channel vector h k The information specifying (t−nT), that is, the information combining “k” and “n”, is output to the channel information selection circuit 865 .

[0134] The channel information selection circuit 865 reads out channel information from the channel information storage circuit 863 based on the combined information of “k” and “n” output by the channel similarity calculation circuit 864. The channel information selection circuit 865 selects, from the read channel information, past channel vectors h k Generate (t-nT).

[0135] (Processing by the reception weight processing unit of the second embodiment) 15 and 16 are flowcharts showing the flow of processing by the receive weight processor 860b of the second embodiment. In Fig. 15 and Fig. 16, a connection point with the letter "A" in a circle indicates that the processing of step Sb20 is performed following the processing of step Sb10 in Fig. 15.

[0136] Before the process shown in Fig. 15 is started, the channel information estimation circuit 861a of the receiving weight processing circuit 860b performs processes corresponding to steps S843-1 to 843-K in Fig. 7. In the processes corresponding to steps S843-1 to 843-K, the channel information estimation circuit 861a outputs the estimated channel information to the receiving weight calculation circuit 862a and writes it in chronological order in the channel information storage circuit 863.

[0137] When the channel similarity calculation circuit 864 detects that new channel information has been written to the channel information storage circuit 863, it starts the process shown in Fig. 15. The channel similarity calculation circuit 864 provides a counter k and a counter n in an internal storage area.

[0138] The channel similarity calculation circuit 864 initializes a counter k to "0" (step Sb1). The channel similarity calculation circuit 864 increments the value of the counter k stored in an internal storage area by 1 (step Sb2), and initializes the value of the counter n stored in an internal storage area to "0" (step Sb3).

[0139] The channel similarity calculation circuit 864 increments the value of the counter n stored in the internal storage area by 1 (step Sb4). The channel similarity calculation circuit 864 calculates the most recent channel vector h k (t) and the past channel vector h k (t-nT). The channel similarity calculation circuit 864 generates the most recent channel vector h k (t) and the past channel vector h k Based on (t-nT), the correlation coefficient is calculated using equation (7). The channel similarity calculation circuit 864 calculates the absolute value of the calculated correlation coefficient, and regards the calculated value as the mutual similarity (step Sb5).

[0140] The channel similarity calculation circuit 864 determines whether the mutual similarity is equal to or less than a predetermined fixed value (step Sb6). If the channel similarity calculation circuit 864 determines that the mutual similarity is not equal to or less than the fixed value (step Sb6, No), the process proceeds to step Sb8. On the other hand, if the channel similarity calculation circuit 864 determines that the mutual similarity is equal to or less than the fixed value (step Sb6, Yes), the channel similarity calculation circuit 864 calculates the past channel vector h k The information combining "k" and "n" that identifies (t-nT) is written and stored in an internal memory area (step Sb7).

[0141] The channel similarity calculation circuit 864 determines whether n matches a predetermined upper limit value (step Sb8). If the channel similarity calculation circuit 864 determines that n matches the upper limit value (step Sb8, Yes), the process proceeds to step Sb10.

[0142] On the other hand, it is assumed that the channel similarity calculation circuit 864 has determined that n does not match the upper limit (step Sb8, No). In this case, the channel similarity calculation circuit 864 calculates the past channel vector h k It is determined whether (t-(n+1)T) is stored (step Sb9).

[0143] The channel similarity calculation circuit 864 calculates the past channel vector h k Assume that it is determined that (t-(n+1)T) is stored (Yes at step Sb9). In this case, the channel similarity calculation circuit 864 advances the process to step Sb4.

[0144] On the other hand, the channel similarity calculation circuit 864 calculates the past channel vector h k Assume that it is determined that (t-(n+1)T) is not stored (step Sb9, No). In this case, the channel similarity calculation circuit 864 advances the process to step Sb10.

[0145] The channel similarity calculation circuit 864 judges whether or not the process has been performed for all the antenna elements 819-1 to 819-L of the base station device 80BS, that is, whether or not the value of the counter k matches L (step Sb10). It is assumed that the channel similarity calculation circuit 864 has determined that the process has not been performed for all the antenna elements 819-1 to 819-L of the base station device 80BS. In other words, it is assumed that the channel similarity calculation circuit 864 has determined that the value of the counter k does not match L (step Sb10, No). In this case, the channel similarity calculation circuit 864 advances the process to step Sb2.

[0146] On the other hand, it is assumed that the channel similarity calculation circuit 864 has determined that the processing is being performed on all of the antenna elements 819-1 to 819-L of the base station device 80BS. In other words, it is assumed that the channel similarity calculation circuit 864 has determined that the value of the counter k matches L (step Sb10, Yes).

[0147] In this case, the channel similarity calculation circuit 864 outputs all of the information combining "k" and "n" stored in the internal storage area to the channel information selection circuit 865. The channel information selection circuit 865 reads out, from the channel information storage circuit 863, channel information corresponding to each of the information combining "k" and "n" output by the channel similarity calculation circuit 864.

[0148] The channel information selection circuit 865 selects past channel vectors h k The channel information selection circuit 865 extracts the past channel vectors h(t-nT) that are determined to have low mutual similarity. k The receiving weight calculation circuit 862b outputs the past channel vector h(t-nT) that is determined to have a low degree of similarity output by the channel information selection circuit 865 to the receiving weight calculation circuit 862b. k The reception weight calculation circuit 862b takes in the past channel vectors h(t-nT) that are determined to have low mutual similarity. k(t-nT) is written and stored in an internal memory area (step Sb20).

[0149] The receive weight calculation circuit 862b provides a counter j in an internal storage area and initializes the counter j to "1" (step Sb21).

[0150] 15 is started, the receiving weight calculation circuit 862b takes in the most recent channel information output by the channel information estimation circuit 861a and writes and stores it in an internal storage area. After the process of step Sb21, the receiving weight calculation circuit 862b selects channel information corresponding to the j-th antenna element 819-j of the base station device 80BS from the most recent channel information stored in the internal storage area. Using the selected channel information, the receiving weight calculation circuit 862a calculates the partial channel matrix H j main (Step Sb22).

[0151] The receiving weight calculation circuit 862b selects channel information corresponding to antenna elements other than the j-th antenna element 819-j of the base station device 80BS from the most recent channel information stored in an internal storage area. Here, the antenna elements other than the j-th antenna element 819-j of the base station device 80BS are the antenna elements 819-1 to 819-(j-1) and 819-(j+1) to 819-L.

[0152] The receiving weight calculation circuit 862b uses the selected channel information to generate channel vectors corresponding to each of the antenna elements other than the j-th antenna element 819-j of the base station device 80BS. The receiving weight calculation circuit 862a arranges the generated channel vectors to generate a partial channel matrix H j sub Generate.

[0153] The reception weight calculation circuit 862a calculates the past channel vectors h k(t-nT), where k≠j is the past channel vector h k (t-nT) from the internal storage area. The reception weight calculation circuit 862a reads out the past channel vector h k As shown in Fig. 12, (t-nT) is expressed as the partial channel matrix H j sub After inserting the channel vectors corresponding to each of the subchannel matrices H' j sub (Step Sb23).

[0154] The processing of steps Sb24 to Sb27 is the same as the processing of steps Sa4 to Sa7 in the first embodiment, except that the receiving weight calculation circuit 862a is replaced with the receiving weight calculation circuit 862b.

[0155] Thereafter, the reception signal processing circuits 858-1 to 858-L perform the processes of steps S845-1 to 845-K, steps S846-1 to 846-L, steps S847-1 to S847-L, and steps S848-1 to S848-L in FIG. 7, and the L signal sequences are output to the MAC layer processing circuit 88.

[0156] (Effects of the second embodiment) As described above, when a plurality of channel vectors used in calculating a receiving weight matrix are similar, the effect of interference suppression is reduced even if the similar channel vectors are used. Therefore, the terminal device 80bT in the second embodiment calculates the similarity between channel vectors, and uses only channel vectors whose similarity is equal to or less than a certain level in calculating a receiving weight matrix. This allows the terminal device 80bT to efficiently suppress inter-stream interference. That is, according to the terminal device 80bT in the second embodiment, only channel vectors effective for interference suppression can be extracted to calculate a receiving weight matrix, and this makes it possible to efficiently suppress interference with a low amount of calculation.

[0157] (Other methods for calculating mutual similarity) In the second embodiment described above, the channel similarity calculation circuit 864 determines the mutual similarity as the absolute value of the correlation coefficient calculated by equation (7). This correlation coefficient may be normalized by the norm of each channel vector. In this case, as shown in the following equation (8), the channel similarity calculation circuit 864 multiplies the correlation coefficient calculated by equation (7) by the nearest channel vector h of the antenna element 819-k of the base station device 80BS. k The norm of (t) and the past channel vector h k The channel similarity calculation circuit 864 divides the cross-correlation value obtained by the division by the product of the norm of (t-nT). k (n), and γ k Absolute value of (n)|γ k Let (n)| be the mutual similarity.

[0158]

number

[0159] In equation (8), each channel vector is normalized using the norm of each channel vector. Incidentally, the norm of the channel vector is expected to have a certain magnitude depending on the number of antenna elements 851 in the terminal device 80bT that communicate with the base station device 80BS. Therefore, in such a case, the channel similarity calculation circuit 864 may divide the correlation coefficient calculated by equation (7) by an approximate norm. Here, the approximate norm is the correlation coefficient of the nearest channel vector h of the antenna element 819-k of the base station device 80BS. k (t) and the past channel vector h k The channel similarity calculation circuit 864 calculates the approximate correlation value obtained by division by the approximate norm as γ k (n), and γ k Absolute value of (n)|γ k (n)| is the mutual similarity. Note that the following equation (9) is the nearest channel vector h k(t) is divided by the square of (t) as an approximate norm. The following equation (10) is the past channel vector h k This is the formula when dividing the square of (t-nT) as an approximate norm.

[0160]

number

[0161]

number

[0162] The difference vector between channel vectors used for null formation represents the difference in the direction of the null to be formed for that channel vector. Therefore, the norm of the difference vector can be evaluated as the similarity between the channel vectors. For example, the channel similarity calculation circuit 864 calculates the nearest channel vector h k (t) and the past channel vector h k The difference vector from (t-nT) is calculated using the following equation (11).

[0163]

number

[0164] The channel similarity calculation circuit 864 calculates the difference vector d k The norm of (n) is used as the mutual similarity. The channel similarity calculation circuit 864 calculates the difference vector d k The norm of (n) is expressed as the nearest channel vector h k (t) and the past channel vector h k The value obtained by dividing (t-nT) by one of the norms may be used as the mutual similarity.

[0165] Furthermore, when the channel similarity calculation circuit 864 calculates mutual similarities greater than a predetermined value more than a predetermined number of times, it may regard "n" as reaching the upper limit and terminate the process. That is, it may set step Sb8=Yes and start processing for the antenna element of the next base station device. In this way, it is possible to simplify the process of calculating the similarity for channel vectors that are not expected to have a large interference suppression effect, and it becomes possible for the receiving weight calculation circuit 862b to calculate the receiving weight matrix more efficiently.

[0166] In the second embodiment described above, the channel similarity calculation circuit 864 determines whether the mutual similarity is equal to or less than a certain value in the processing of step Sb6 in FIG. 15, but depending on how the certain value is defined, it may be configured to determine whether the mutual similarity is less than a certain value.

[0167] As described above, the first and second embodiments of the present invention relate to a null forming technique using multiple antenna elements that is applied to MIMO wireless communication and the like. As described above, null forming techniques for suppressing interference signals from other users, other beams, and other streams have been studied. However, due to fluctuations in wireless propagation paths, nulls collapse, interference occurs, and transmission characteristics deteriorate. In contrast, in the first and second embodiments, the terminal devices 80aT and 80bT form multiple nulls for each antenna element of the base station device 80BS, thereby calculating a receiving weight matrix that is resistant to fluctuations in wireless propagation paths and the associated interference, thereby making it possible to suppress deterioration of transmission characteristics and realize stable, large-capacity wireless communication.

[0168] (Other supplementary matters regarding the embodiment of the present invention) Although the embodiments of the present invention have been described above in detail with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention also includes designs that do not deviate from the gist of the present invention. Below, some supplementary points regarding the embodiments of the present invention are summarized.

[0169] In the first and second embodiments, the case of reception MIMO processing in downlink transmission from the base station device 80BS to the terminal devices 80aT and 80bT has been mainly described as an example. In contrast, the first and second embodiments can be similarly applied to uplink transmission from the terminal devices 80aT and 80bT to the base station device 80BS, i.e., transmission MIMO processing. For example, when applying the first embodiment, the transmission unit 81a shown in FIG. 17 is used instead of the transmission unit 81 in FIG. 4 in the terminal device 80aT.

[0170] The transmitting unit 81a includes an antenna element 819, an HPA 818, a filter 817, a mixer 816, a local oscillator 815, a D / A converter 814, an IFFT & GI adding circuit 813, an additive synthesis circuit 812, transmission signal processing circuits 811-1 to 811-L, a transmission weight processing unit 830a, a shared information transmitting unit 910, and a shared information receiving unit 970. The transmission signal processing circuits 811-1 to 811-L and the transmission weight processing unit 830a are connected to the communication control circuit 820 shown in Fig. 3. The transmission signal processing circuits 811-1 to 811-L have the same configuration as the transmission signal processing circuits 811-1 to 811-L included in the transmitting unit 81.

[0171] The shared information transmission unit 910 includes antenna elements 919-1 to 919-(K-1), HPAs 918-1 to 918-(K-1), filters 917-1 to 917-(K-1), mixers 916-1 to 916-(K-1), local oscillators 915-1 to 915-(K-1), D / A converters 914-1 to 914-(K-1), IFFT & GI adding circuits 913-1 to 913-(K-1), and additive synthesis circuits 912-1 to 912-(K-1).

[0172] The transmitter 81a shown in FIG. 17 includes K antenna elements 819, 919-1 to 919-(K-1), HPAs 818, 918-1 to 918-(K-1), filters 817, 917-1 to 917-(K-1), mixers 816, 916-1 to 916-(K-1), D / A converters 814, 914-1 to 914-(K-1), IFFT & GI adding circuits 813, 913-1 to 913-(K-1), and additive synthesis circuits 812, 913-1 to 913-(K-1). For ease of explanation, 12-1 to 912-(K-1) have the same configuration as the K antenna elements 819-1 to 819-K, HPAs 818-1 to 818-K, filters 817-1 to 817-K, mixers 816-1 to 816-K, D / A converters 814-1 to 814-K, IFFT & GI application circuits 813-1 to 813-K, and additive synthesis circuits 812-1 to 812-K that are provided in each of the transmitting units 81 shown in FIG. 4, although the symbols are different.

[0173] The reason why the reference symbols are changed is that the antenna element 819 is an antenna element used when transmitting a signal to the base station device 80BS, whereas the antenna elements 919-1 to 919-(K-1) are antenna elements used when transmitting signals to the other K-1 terminal devices 80aT. Each of the K terminal devices 80aT is assigned K different frequencies other than the frequency assigned for communication between each of the K terminal devices 80aT and the base station device 80BS so that each of the K terminal devices 80aT can transmit and receive signals to and from each other.

[0174] 4, the frequencies of the signals transmitted by the antenna elements 819-1 to 819-K are the same, so it is sufficient to have only one local oscillator 815. In contrast, in the case of the transmission unit 81a, the antenna element 819 transmits a signal to the base station device 80BS, and each of the antenna elements 919-1 to 919-(K-1) transmits a signal to the other K-1 terminal devices 80aT. Therefore, the frequencies of the radio frequency signals after up-conversion by each of the mixers 816, 916-1 to 916-(K-1) are all different. Therefore, each of the local oscillators 815, 915-1, 915-(K-1) outputs a local oscillation signal of a different frequency that upconverts the frequency of the baseband signal supplied to the mixers 816, 916-1 to 916-(K-1) to which it is connected, to a radio frequency assigned to the corresponding antenna element 819, 919-1 to 919-(K-1).

[0175] The shared information receiving unit 970 includes an antenna element 971, an LNA 972, a local oscillator 973, a mixer 974, and a filter 975. The output of the filter 975 is connected to the mixer 816. The antenna element 971 receives signals transmitted by the other K-1 terminal devices 80aT. The LNA 972 amplifies the signal received via the antenna element 971. The local oscillator 973 outputs a local oscillation signal of a frequency that down-converts the signal supplied to the mixer 974 to a baseband analog signal. The mixer 974 down-converts the signal amplified by the LNA 972 to a baseband analog signal. The filter 975 removes out-of-band frequency components from the signal output by the mixer 974.

[0176] The transmission weight processing unit 830a differs from the transmission weight processing unit 830 shown in Fig. 4 in the following respects. The channel information acquisition circuit 831 does not store only the most recent channel information in the channel information storage circuit 832, but writes the acquired channel information in chronological order. Based on the most recent channel information stored in the channel information storage circuit 832, the transmission weight calculation circuit 833 calculates, for example, a partial channel matrix H j main and the partial channel matrix H j sub The transmission weight calculation circuit 833 further generates past channel vectors ∼h2, ∼h3, ..., ∼h based on the past channel information stored in the channel information storage circuit 832. L and generate the past channel vectors ~h2, ~h3, …, ~h L , the partial channel matrix H j sub to obtain the partial channel matrix H' j sub is generated to calculate the transmission weight matrix.

[0177] With the above configuration, the terminal device 80aT uses K-1 signals out of the K signals to be transmitted as shared information to be shared with the other K-1 terminal devices 80aT, and transmits the K-1 signals to the other K-1 terminal devices 80aT by the shared information transmission unit 910. The terminal device 80aT combines the signals transmitted by the other K-1 terminal devices 80aT to itself and the signals transmitted to the base station device 80BS after being converted to analog signals by the D / A converter 814, and transmits the combined signals to the base station device 80BS. This makes it possible to perform transmission using a transmission weight matrix that is resistant to fluctuations in the wireless propagation path and the interference associated therewith, to which null formation is applied, even in the case of uplink transmission. In this case, as in the first embodiment described above, the communication means between the terminal device 80aT and the other K-1 terminal devices 80aT may be any communication means that is different from the spatial multiplexing transmission that does not interfere with the spatial multiplexing transmission between the terminal device 80aT and the base station device 80BS and does not interfere with each other. For example, the communication means may be a different wireless communication method, or may be a wired communication means.

[0178] When the second embodiment is applied, a transmission weight processing unit 830b may be used in which functional units corresponding to the channel similarity calculation circuit 864 and the channel information selection circuit 865 are added to the above-mentioned transmission weight processing unit 830a. This makes it possible to calculate a transmission weight matrix by narrowing down the channel vectors with a greater interference suppression effect.

[0179] In the first and second embodiments, the device indicated by the reference symbol 80BS should not be interpreted as a base station device and the devices indicated by the reference symbols 80aT and 80bT as terminal devices, but the device indicated by the reference symbol 80BS may be interpreted as a terminal device and the devices indicated by the reference symbols 80aT and 80bT as base station devices. That is, each may be interpreted as a wireless communication device performing MIMO transmission, as in the MIMO system shown in FIG. 1. In this case, the device indicated by the reference symbol 80BS is positioned as a "non-cooperative wireless communication device" that does not cooperate with other wireless communication devices, and the devices indicated by the reference symbols 80aT and 80bT can be regarded as "cooperative wireless communication devices" that cooperate with each other.

[0180] That is, the associated wireless communication device (e.g., terminal devices 80aT, 80bT) includes a shared information transmission unit (a shared information transmission unit 960, or a shared information transmission unit provided in addition to the above-mentioned transmission unit 81) that transmits shared information to be shared with other associated wireless communication devices to the other associated wireless communication devices by a communication means other than spatial multiplexing transmission, the shared information being information on a signal received from a non-associated wireless communication device (e.g., base station device 80BS) by spatial multiplexing transmission or on a signal to be transmitted to the non-associated wireless communication device by spatial multiplexing transmission, and includes a weight calculation unit (e.g., a reception weight vector or a transmission weight vector) that calculates a weight vector to be used when performing spatial multiplexing transmission with the non-associated wireless communication device based on a channel matrix in which a first channel vector generated from channel information between the antenna element of the non-associated wireless communication device and the antenna element of the associated wireless communication device including the non-associated wireless communication device itself is arranged, and one or more second channel vectors generated earlier than the first channel vector are arranged.

[0181] Furthermore, the weight calculation unit selects a second channel vector having a low similarity to the first channel vector from among the second channel vectors, and calculates a weight vector based on a channel matrix in which the first channel vector and the selected second channel vector are arranged. Here, the second channel vector is calculated based on the above-mentioned past channel vector h k (t-nT). The first channel vector may be interpreted as the channel vector corresponding to each of the antenna elements other than the desired antenna element of the base station device 80BS, as described above.

[0182] In the above-mentioned first and second embodiments, an example is shown in which the base station device 80BS includes L antenna elements 819-1 to 819-L, or an example in which L=3. However, when the number of signal sequences transmitted by the base station device 80BS is less than the number of the antenna elements 819-1 to 819-L included in the base station device 80BS, it is not necessarily necessary to orthogonalize the channel vectors corresponding to each of the antenna elements 819-1 to 819-L. In this case, for example, in regard to downstream transmission (downlink transmission), by combining the antenna elements 819-1 to 819-L of the base station device 80BS with some coefficient, the antenna elements included in the base station device 80BS are considered to form one or more virtual antenna elements, and this virtual antenna element is treated as an actual antenna element, and a channel vector corresponding to the virtual antenna element is generated, whereby the receiving weight vector can be calculated in the same manner as in the processing of the above-mentioned first and second embodiments. This is also true for upstream transmission (uplink transmission). In addition, synthesizing using some coefficient means, for example, generating a channel vector corresponding to a physical antenna element, estimating an antenna synthesizing coefficient (e.g., a receiving weight vector or a transmitting weight vector) on the base station device 80BS side, and sequentially obtaining a channel vector between the virtual antenna element and the channel vector generated using the estimated coefficient.

[0183] Any method may be applied as the channel estimation method in the first and second embodiments described above. For example, when the terminal devices 80aT and 80bT acquire channel information, the base station device 80BS may transmit a predetermined training signal, and the terminal devices 80aT and 80bT may perform channel estimation based on the training signal. Alternatively, the base station device 80BS may notify the terminal devices 80aT and 80bT of the channel information estimated based on the training signal using a wireless packet containing predetermined control information. That is, there may be various methods for realizing the channel information estimation circuit 861a, but the process described with reference to Figs. 13, 15, and 16 is a process performed after the channel information estimation circuit 861a completes the estimation of the channel information, so that there is no effect even if any channel information estimation method is applied in the channel information estimation circuit 861a. Therefore, any channel information estimation method can be applied to the process described with reference to Figs. 13, 15, and 16.

[0184] In the above description, for simplicity, the subscripts representing frequency components are omitted, and furthermore, the description of individual frequency components is omitted. In general, all signal processing in channel information, transmission and reception weight vectors, and further transmission and reception signals are all individually defined and processed for each frequency component on the frequency axis. Inside each signal processing circuit, for example, signal processing up to the stage before IFFT processing on the transmission side (bit sequence interleaving, signal point mapping, signal modulation, multiplication of transmission weight matrix, etc.) is all performed for each frequency component, and similarly, signal processing from FFT processing on the reception side (multiplication of reception weight matrix, signal detection processing, signal demapping, deinterleaving, etc.) is all performed for each frequency component. For this reason, acquisition of channel information is also performed for each frequency component, and prediction of future channel information is also performed for each frequency component.

[0185] However, although the estimation of channel information is basically performed individually for all frequency components, it is assumed that the accuracy of future channel prediction is lower than that of simple estimation of channel information. In this case, it is not necessary to perform channel prediction for all subcarriers, and it is assumed that the characteristics will not deteriorate so much even if the frequency components are thinned out to some extent and the predicted channel vector is used for the nearby frequency components. For example, when channel prediction is performed once for three frequency components, the predicted channel vector may be used for the frequency components before and after the frequency component for which the prediction is performed. If the correlation in the frequency direction is even stronger, it is also possible to perform channel prediction by thinning out even more.

[0186] In terms of circuit configuration, a separate circuit may be provided for each frequency component, or since the same processing is performed, the processing may be performed serially for each frequency component in order, and the circuit may be shared for the frequency components. Furthermore, as an intermediate step, multiple circuits may be prepared, the frequency components may be appropriately divided, and parallel processing may be performed serially by the multiple circuits. These are common to all embodiments.

[0187] In addition, in the OFDM modulation method, all subcarriers are used for communication with the same terminal device 80aT, 80bT, so the transmission and reception weights (averaged transmission and reception weight vector and real-time transmission and reception weight matrix) in a specific terminal device 80aT, 80bT use the transmission and reception weights calculated by the terminal device 80aT, 80bT over all subcarriers. However, in OFDMA (Orthogonal frequency-division multiple access), allocations to the terminal devices 80aT, 80bT in different combinations are collected in a patchwork pattern on the time axis and frequency axis, so the terminal devices 80aT, 80bT to which they are assigned must calculate the transmission and reception weights for each time (OFDM symbol) and frequency (subcarrier). However, apart from this difference, OFDM and OFDMA can be processed in exactly the same way, and although the present specification has been described mainly with respect to OFDM, the embodiment of the present invention can also be applied in exactly the same way to OFDMA.

[0188] In addition, there are various operational variations regarding SC-FDE, but in both the reception signal processing after the averaged transmission weight is multiplied on the transmitting side and the signals transmitted from each antenna element are spatially combined, and the reception signal processing after the averaged reception weight is multiplied on the receiving side and the signals of each antenna element are added and combined, the above-mentioned configuration examples are configured to apply the processing performed in normal SC-FDE as is, so that they can be applied to all variations of SC-FDE. In this case, after performing signal processing with a single carrier instead of signal processing with an OFDM modulation method, if it is uplink transmission from the terminal devices 80aT and 80bT to the base station device 80BS, FFT processing is performed on the signal on the time axis of the single carrier to generate signal components for each frequency component. Then, it is sufficient to multiply these signal components by the transmission weight matrix generated by the embodiment of the present invention, regarding them as signals of each subcarrier generated by the OFDM modulation method.

[0189] Similarly, in the case of downlink transmission from the base station device 80BS to the terminal devices 80aT and 80bT, the signal obtained by performing FFT processing on the received signal is treated in the same manner as in the case of the OFDM modulation method, and the signal is separated by multiplying it by the receiving weight matrix generated by the embodiment of the present invention. Then, the separated frequency component signal is converted into a single carrier signal on the time axis by performing IFFT processing. In this way, although there are differences between the OFDM modulation method and SC-FDE in some signal processing, the generation of the transmitting and receiving weight matrices and the multiplication processing are common, and the embodiment of the present invention can be applied to either of these signal methods.

[0190] Furthermore, although this specification is described assuming a wideband system such as OFDM or OFDMA, the embodiments of the present invention are also applicable to narrowband systems in the same manner.

[0191] Furthermore, for convenience of explanation, this specification sometimes makes no distinction between "row vectors" and "column vectors". In a strict mathematical notation that unifies the direction of vector arrangement, a symbol such as "transpose" should be used. However, the information required for implementing this invention is the value of each component of a vector, and whether the vector is a row vector or a column vector does not mean much. Therefore, in order to prioritize ease of understanding, sometimes the description does not make a distinction between "row vectors" and "column vectors".

[0192] For example, when calculating the above-mentioned receiving weight matrix, the channel vector h j is a column vector, and the receiving weight vectors included in the receiving weight matrix are row vectors. As shown in FIG. 12, the extended partial channel matrix H′ j sub is a matrix in which the most recent channel vectors and past channel vectors of antenna elements not included in the calculation of the receiving weight vector in the base station device 80BS are arranged in each column. That is, when calculating the receiving weight vector, the partial channel matrix H jsub The past channel vector of the column vector is added to

[0193] On the other hand, when calculating the transmission weight matrix, the channel vectors of the antenna elements of the base station device 80BS are row vectors, and the transmission weight vectors are column vectors. Therefore, the expanded partial channel matrix H' used to calculate the transmission weight vectors j sub is a matrix in which the most recent channel vectors and past channel vectors of antenna elements not included in the calculation of the transmission weight vector in the base station device 80BS are arranged in each row. That is, when calculating the transmission weight vector, the partial channel matrix H j sub The past channel vector of the row vector is added to

[0194] The above-mentioned processing may be performed by recording a program for implementing the functions of the base station device 80BS and the terminal devices 80aT and 80bT in the first and second embodiments on a computer-readable recording medium, and reading and executing the program recorded on the recording medium into a computer system. The term "computer system" as used herein includes hardware such as an OS and peripheral devices. The term "computer system" also includes a WWW system equipped with a homepage providing environment (or display environment). The term "computer-readable recording medium" refers to portable media such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, and a storage device such as a hard disk built into a computer system. The term "computer-readable recording medium" also refers to a storage device that holds a program for a certain period of time, such as a volatile memory (RAM) inside a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line.

[0195] The above program may also be transmitted from a computer system in which the program is stored in a storage device or the like to another computer system via a transmission medium, or by transmission waves in the transmission medium. Here, the "transmission medium" that transmits the program refers to a medium that has the function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The above program may also be one that realizes part of the above-mentioned functions. Furthermore, it may be a so-called difference file (difference program) that can realize the above-mentioned functions in combination with a program already recorded in the computer system. [Industrial Applicability]

[0196] The present invention can be used in a wireless communication system in which a base station apparatus having a plurality of antenna elements communicates with a plurality of terminal apparatuses using the same frequency channel. [Explanation of symbols]

[0197] 80...wireless communication device, 80BS...wireless communication device, base station device, 80T...wireless communication device, 80aT, 80bT...terminal device, 81...transmitter, 85, 85a...receiver, 87...interface circuit, 88...MAC layer processing circuit, 811-1 to 811-L...transmission signal processing circuit, 812-1 to 812-K...addition synthesis circuit, 813-1 to 813-K...IFFT & GI adding circuit, 814-1 to 814-K...D / A converter, 815...local oscillator, 816-1 to 816-K...mixer, 817-1 to 817-K...filters, 818-1 to 818-K...HPAs, 819-1 to 819-K...antenna elements, 820...communication control circuit, 830...transmission weight processing unit, 831...channel information acquisition circuit, 832...channel information storage circuit, 833...transmission weight calculation circuit, 851, 851-1 to 851-K...antenna elements, 852, 852-1 to 852-K...LNAs, 853...local oscillators, 854, 854-1 to 854-K...mixers, 855, 855-1 to 8 55-K...filter, 856, 856-1 to 856-K...A / D converter, 857, 857-1 to 857-K...FFT circuit, 858-1 to 858-L...receiving signal processing circuit, 860, 860a, 860b...receiving weight processing unit, 861...channel information estimation circuit, 862, 862a, 862b...receiving weight calculation circuit, 863...channel information storage circuit, 864...channel similarity calculation circuit, 865...channel information selection circuit, 881...scheduling processing circuit, 951- 1 to 951-(K-1)...antenna elements, 952-1 to 952-(K-1)...LNA, 953-1 to 953-(K-1)...local oscillator, 954-1 to 954-(K-1)...mixer, 955-1 to 955-(K-1)...filter, 956-1 to 956-(K-1)...A / D converter, 975-1 to 957-(K-1)...FFT circuit, 960...shared information transmission unit, 962...mixer, 961...local oscillator, 963...filter, 964...HPA, 965...antenna element

Claims

1. An associated wireless communication device in a wireless communication system including an unassociated wireless communication device having a plurality of antenna elements and a plurality of associated wireless communication devices, the unassociated wireless communication device and the plurality of associated wireless communication devices performing spatial multiplexing transmission at the same time on the same frequency, a shared information transmission unit that transmits shared information to the other associated wireless communication devices by a communication means different from the spatial multiplexing transmission, the shared information being information on a signal received from the unassociated wireless communication device by the spatial multiplexing transmission or a signal to be transmitted to the unassociated wireless communication device by the spatial multiplexing transmission, the shared information being shared between the other associated wireless communication devices and the unassociated wireless communication device by a communication means different from the spatial multiplexing transmission; a weight calculation unit that calculates a weight vector to be used during the spatial multiplexing transmission based on a channel matrix in which a first channel vector is generated from channel information between an antenna element of the unassociated wireless communication device or a virtual antenna element obtained by combining the antenna elements and an antenna element of the associated wireless communication device including itself, and one or more second channel vectors generated earlier than the first channel vector are arranged; A cooperative wireless communication device comprising:

2. The weight calculation unit selecting the second channel vector having a low degree of similarity to the first channel vector from among the second channel vectors, and calculating the weight vector based on a channel matrix in which the first channel vector and the selected second channel vector are arranged; The cooperative wireless communication device according to claim 1 .

3. The weight calculation unit calculating the mutual similarity between the first channel vector and the second channel vector based on an inner product of the first channel vector and the second channel vector; The cooperative wireless communication device according to claim 2 .

4. The weight calculation unit the absolute value of the inner product is set as the mutual similarity, or the absolute value of a cross-correlation value obtained by dividing the inner product by a product of the norm of the first channel vector and the norm of the second channel vector is set as the mutual similarity, or the absolute value of an approximate correlation value obtained by dividing the inner product by the norm of either the first channel vector or the second channel vector or by the square of the norm of the one of the first channel vector and the second channel vector is set as the mutual similarity. The cooperative wireless communication device according to claim 3 .

5. The weight calculation unit a norm of a difference vector between the first channel vector and the second channel vector is set as the mutual similarity, or a value obtained by dividing the norm of the difference vector by the norm of either the first channel vector or the second channel vector is set as the mutual similarity. The cooperative wireless communication device according to claim 2 .

6. A wireless communication system including an unassociated wireless communication device having a plurality of antenna elements and a plurality of associated wireless communication devices, the unassociated wireless communication device and the plurality of associated wireless communication devices performing spatial multiplexing transmission at the same time on the same frequency, The cooperative wireless communication device, a shared information transmission unit that transmits shared information to the other associated wireless communication devices by a communication means different from the spatial multiplexing transmission, the shared information being information on a signal received from the unassociated wireless communication device by the spatial multiplexing transmission or a signal to be transmitted to the unassociated wireless communication device by the spatial multiplexing transmission, the shared information being shared between the other associated wireless communication devices and the unassociated wireless communication device by a communication means different from the spatial multiplexing transmission; a weight calculation unit that calculates a weight vector to be used during the spatial multiplexing transmission based on a channel matrix in which a first channel vector is generated from channel information between an antenna element of the unassociated wireless communication device or a virtual antenna element obtained by combining the antenna elements and an antenna element of the associated wireless communication device including itself, and one or more second channel vectors generated earlier than the first channel vector are arranged; A wireless communication system comprising:

7. A spatial multiplexing wireless transmission method executed by an associated wireless communication device in a wireless communication system including an unassociated wireless communication device having a plurality of antenna elements and a plurality of associated wireless communication devices, the unassociated wireless communication device and the plurality of associated wireless communication devices performing spatial multiplexing transmission at the same time on the same frequency, transmitting shared information to the other associated wireless communication devices by a communication means different from the spatial multiplexing transmission, the shared information being information on a signal received from the unassociated wireless communication device by the spatial multiplexing transmission or information on a signal to be transmitted to the unassociated wireless communication device by the spatial multiplexing transmission, calculates a weight vector to be used during the spatial multiplexing transmission based on a channel matrix in which a first channel vector is generated from channel information between an antenna element of the unassociated wireless communication device or a virtual antenna element obtained by combining the antenna elements and an antenna element of the associated wireless communication device including the unassociated wireless communication device itself, and one or more second channel vectors generated earlier than the first channel vector; A spatial multiplexing wireless transmission method.

8. A computer that functions as the associated wireless communication device in a wireless communication system including an unassociated wireless communication device having a plurality of antenna elements and a plurality of associated wireless communication devices, the unassociated wireless communication device and the plurality of associated wireless communication devices performing spatial multiplexing transmission at the same time on the same frequency, a shared information transmission step of transmitting shared information to the other associated wireless communication device by a communication means different from the spatial multiplexing transmission, the shared information being information on a signal received from the unassociated wireless communication device by the spatial multiplexing transmission or a signal to be transmitted to the unassociated wireless communication device by the spatial multiplexing transmission, the shared information being shared between the other associated wireless communication device and the unassociated wireless communication device; a weight calculation step of calculating a weight vector to be used during the spatial multiplexing transmission based on a channel matrix in which a first channel vector is generated from channel information between an antenna element of the uncooperative wireless communication device or a virtual antenna element obtained by combining the antenna elements and an antenna element of the cooperating wireless communication device including the uncooperative wireless communication device itself, and one or more second channel vectors generated earlier than the first channel vector are arranged; A program for executing the above.

Images