WO2014122850A1

WO2014122850A1 - Base station device, pre-coding method, integrated circuit, and radio communication system

Info

Publication number: WO2014122850A1
Application number: PCT/JP2013/082996
Authority: WO
Inventors: 宏道留場; 毅小野寺; 窪田　稔
Original assignee: シャープ株式会社
Priority date: 2013-02-06
Filing date: 2013-12-09
Publication date: 2014-08-14
Also published as: JP2016066827A

Abstract

This base station device is provided with a plurality of antennas, and is capable of performing radio transmission by using spatial multiplexing after applying nonlinear pre-coding to a signal addressed to a plurality of terminal devices. A first linear filter generated for a data signal addressed to the terminal devices and a second linear filter generated for a demodulation-use reference signal addressed to the terminal devices are differentiated from each other on the basis of information about a propagation channel between the base station device and the terminal devices, pre-coding is applied to the data signal and the demodulation-use reference signal on the basis of the first linear filter and the second linear filter, and a transmission is made.

Description

Base station apparatus, precoding method, integrated circuit, radio communication system

The present invention relates to a technique for performing multiuser multiple input multiple output transmission.

In wireless communication systems, it is always desired to improve the transmission speed in order to provide various broadband information services. Although the transmission speed can be improved by expanding the communication bandwidth, since the usable frequency band is limited, it is essential to improve the frequency utilization efficiency. Multiple input multiple output (MIMO) technology, which performs radio transmission using multiple transmission / reception antennas, is attracting attention as a technology that can greatly improve frequency utilization efficiency, such as cellular systems and wireless LAN systems. In practical use. The amount of improvement in frequency utilization efficiency by the MIMO technology is proportional to the number of transmission / reception antennas. However, the number of receiving antennas that can be arranged in the terminal device is limited. Therefore, multi-user MIMO (Multi User-MIMO (MU-MIMO)) that spatially multiplexes transmission signals from the base station apparatus to each terminal apparatus is regarded as a virtual large-scale antenna array. It is effective for improving the utilization efficiency.

In MU-MIMO, transmission signals destined for each terminal apparatus are received by the terminal apparatus as inter-user interference (IUI), so it is necessary to suppress IUI. For example, in the Long term evolution adopted as one of the 3.9th generation mobile radio communication systems, the base station device pre-multiplies a linear filter calculated based on the propagation path information notified from each terminal device. Thus, linear precoding that suppresses the IUI is employed.

Also, as a method for realizing MU-MIMO that can be expected to further improve the frequency utilization efficiency, MU-MIMO technology using nonlinear precoding in which nonlinear processing is performed on the base station apparatus side is attracting attention. When a terminal device can perform a modulo operation, a perturbation vector having a complex number (perturbation term) obtained by multiplying an arbitrary Gaussian integer by a constant real number can be added to a transmission signal. It becomes.

Therefore, if the perturbation vector is appropriately set according to the propagation path state between the base station apparatus and the plurality of terminal apparatuses, it is possible to significantly reduce the required transmission power compared to linear precoding. Become. As nonlinear precoding, Vector perturbation (VP) described in Non-Patent Document 1 and Tomlinson Harashima precoding (THP) described in Non-Patent Document 2 are well known.

In order to perform precoding in the base station apparatus, the base station apparatus needs propagation path information (Channel state information (CSI)) with each terminal apparatus. FIG. 13 is a sequence chart showing a state of communication between the base station apparatus that performs nonlinear precoding and the terminal apparatus. First, the base station apparatus generates a reference signal for estimating CSI for the terminal apparatus (step S101). Next, the base station apparatus generates transmission data and a demodulation reference signal (step S102). Next, the base station apparatus transmits a reference signal for estimating CSI to the terminal apparatus (step S103). Note that, depending on the radio frame configuration, the base station apparatus may simultaneously transmit a data signal and a demodulation length reference signal associated with a reference signal for estimating another CSI to the base station apparatus. Shall be sent separately. Since the reference signal for estimating CSI is known between the base station apparatus and the terminal apparatus, the terminal apparatus can estimate CSI based on the received reference signal (step S104).

The terminal device converts the estimated CSI into information that can be notified to the base station device (step S105), and notifies the base station device (step S106). Examples of information that can be notified include information obtained by directly quantizing estimated information into digital information, and a number indicating a code described in a code book shared by a base station device and a terminal device. Thereafter, the base station apparatus performs precoding on the data and the demodulation reference signal based on the restored CSI (step S107), and transmits it to the terminal apparatus (step S108).

When the terminal apparatus receives the data and the demodulation reference signal from the base station apparatus, the terminal apparatus performs propagation path estimation based on the demodulation reference signal (step S109). Equalization (spatial signal detection processing) is performed (step S110).
Here, when the precoding performed by the base station apparatus is nonlinear precoding, the terminal apparatus needs to perform a modulo operation (step S111) on the channel-equalized signal. The modulo operation is signal processing in which the real part and the imaginary part of the input complex signal are within [−δ, δ] with respect to a given real constant 2δ. Here, 2δ is called a modulo width. The terminal apparatus demodulates transmission data from the signal after the modulo calculation (step S112).

Here, since the modulo width of the modulo operation performed on the receiving side depends on the propagation path state, the terminal device needs to estimate based on the demodulation reference signal. However, depending on the precoding performed in the base station apparatus, an error may occur between the modulo width estimated by the terminal apparatus based on the demodulation reference signal and the true optimum modulo width.

In order to solve this problem, Non-Patent Document 3 discloses a method for correcting a modulo width estimated based on a demodulation reference signal. However, in the disclosed method, it is necessary to optimize parameters for correction in accordance with the propagation path environment. Therefore, parameter calibration is required for each propagation path environment, and optimal transmission characteristics cannot be realized in a propagation path environment where calibration is not possible.

In a radio communication system in which a base station apparatus performs MU-MIMO transmission based on nonlinear precoding, when a terminal apparatus estimates a modulo width based on a demodulation reference signal, the terminal apparatus estimates a modulo based on a demodulation reference signal. An error occurs between the width and the optimum modulo width, and transmission characteristics are greatly degraded. However, the method of realizing this error suppression without performing prior calibration is still unclear.

The present invention has been made in view of such circumstances, and in a wireless communication system in which a base station apparatus performs MU-MIMO transmission based on nonlinear precoding, a terminal apparatus can accurately perform a process based on a demodulation reference signal. It is an object of the present invention to provide a base station apparatus, a wireless communication system, and an integrated circuit that can estimate a modulo width.

In order to achieve the above object, the present invention has taken the following measures. That is, the base station apparatus of the present invention is a base station apparatus that includes a plurality of antennas, performs non-linear precoding on a signal addressed to a plurality of terminal apparatuses, performs spatial multiplexing, and performs radio transmission. A channel information acquisition unit for acquiring channel information, a mapping unit for multiplexing the data signals addressed to the plurality of terminal devices and a demodulation reference signal, and the data signal and the demodulation reference signal based on the channel information A precoding unit that performs precoding on the first linear filter that multiplies the data signal based on the propagation path information, and a second that multiplies the reference signal for demodulation. And a linear filter generation unit that generates different linear filters.

Also, the precoding method of the present invention can be applied to data signals and demodulation reference signals transmitted from a base station apparatus having a plurality of antennas to a plurality of terminal apparatuses, and to propagation path information between the plurality of terminal apparatuses. A precoding method for performing preliminary processing based on the propagation path information, calculating a first linear filter, a second linear filter and a feedback filter based on the propagation path information; A process of performing interference suppression and modulo operation on the data signal to calculate a transmission code; a process of calculating a transmission data signal and a power normalization coefficient based on the transmission code and the first linear filter; Calculating a demodulation reference signal based on the demodulation reference signal, the second linear filter, and the power normalization coefficient; A process of adjusting the transmit power of the serial transmission data signal and said transmission demodulation reference signal, and having a.

Also, the precoding method of the present invention can be applied to data signals and demodulation reference signals transmitted from a base station apparatus having a plurality of antennas to a plurality of terminal apparatuses, and to propagation path information between the plurality of terminal apparatuses. A precoding method for performing preliminary processing based on the propagation path information, a step of calculating a first linear filter and a second linear filter, the data signal, and the first signal Searching a perturbation vector based on a linear filter, calculating a transmission data signal and a power normalization coefficient based on the data signal, the first linear filter and the perturbation vector, and the demodulation reference A step of calculating a transmission demodulation reference signal based on the signal, the second linear filter, and the power normalization coefficient; and the transmission data signal and the transmission demodulation reference It characterized by having a a process of adjusting the transmit power of the No..

The integrated circuit of the present invention includes a plurality of antennas, is mounted in a base station apparatus that performs non-linear precoding and spatial multiplexing on signals addressed to a plurality of terminal apparatuses, and performs a plurality of radio transmissions on the base station apparatus. An integrated circuit that exhibits a function, a function of acquiring propagation path information with the terminal device, a function of multiplexing data signals addressed to the plurality of terminal devices and a demodulation reference signal, and the propagation path information A function of precoding the data signal and the demodulation reference signal based on the function, and the function of performing the precoding multiplies the data signal based on the propagation path information. Different linear filters of a first linear filter and a second linear filter that multiplies the demodulation reference signal are generated.

According to the present invention, in a wireless communication system in which a base station apparatus performs MU-MIMO transmission based on nonlinear precoding, a terminal apparatus can estimate a modulo width with high accuracy based on a demodulation reference signal. The characteristic deterioration due to the width estimation error is suppressed, which can contribute to a significant improvement in frequency utilization efficiency.

It is a figure which shows an example of the outline of the radio | wireless communications system which concerns on the 1st Embodiment of this invention. It is a block diagram which shows one structural example of the base station apparatus which concerns on the 1st Embodiment of this invention. It is a block diagram which shows one structural example of the precoding part 27 which concerns on the 1st Embodiment of this invention. It is a flowchart which shows an example of the signal processing in the precoding part 27 which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the example of 1 structure of the antenna part 29 which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the example of 1 structure of the terminal device 2 which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the example of 1 structure of the terminal antenna part 51 which concerns on the 1st Embodiment of this invention. It is a block diagram which shows one structural example of the precoding part 35 which concerns on the 2nd Embodiment of this invention. It is a flowchart which shows an example of the signal processing in the pre-coding part 35 which concerns on the 2nd Embodiment of this invention. It is a figure which shows an example of the outline of the radio | wireless communications system which concerns on the 3rd Embodiment of this invention. It is a figure which shows the example of 1 structure of the precoding part 37 which concerns on the 3rd Embodiment of this invention. It is a block diagram which shows the example of 1 structure of the terminal device 3 which concerns on the 3rd Embodiment of this invention. It is a sequence chart which shows the mode of communication between the conventional base station apparatus and a terminal device.

Hereinafter, an embodiment in a case where a wireless communication system of the present invention is applied will be described with reference to the drawings. In addition, the matter demonstrated in this embodiment is an aspect for understanding invention, and the content of invention is not interpreted limited to embodiment. Unless otherwise specified, ^AT is a transposed matrix of matrix A, A ^H is an adjoint (Hermitian transposed) matrix of matrix A, A ⁻¹ is an inverse matrix of matrix A, and diag (A) is a diagonal of matrix A Diagonal matrix from which only components are extracted or diagonal matrix in which elements in parentheses are arranged as diagonal components, I _N is an N × N unit matrix, 0 _N is an N × N zero matrix, floor (c) Is the floor function that returns the largest Gaussian integer whose real part and imaginary part do not exceed the values of the real part and imaginary part of the complex number c respectively, E [x] is the ensemble average of the random variable x, and || a || Represents the norm of each. [A, B] represents a matrix obtained by combining the matrices A and B in the column direction. Z [i] represents a set of all Gaussian integers. The Gaussian integer is a complex number in which the real part and the imaginary part are each represented by an integer.

[1. First Embodiment]
FIG. 1 is a diagram illustrating an example of an outline of a wireless communication system according to the first embodiment of the present invention. In the first embodiment, N _t has transmit antennas, relative to the non-linear precoding capable base station apparatus 1 (also referred to as a wireless transmitting device), the terminal apparatus 2 having the receive antennas N _r the The target is MU-MIMO transmission in which U (also referred to as radio receiving apparatuses) are connected (four terminals 4-1 to 2-4 in FIG. 1). It is assumed that L data is simultaneously transmitted to each terminal device 2 (the number of data transmitted simultaneously is also referred to as a rank number), and U × L = N _t and L = N _r .

In the following, for the sake of simplicity, the number of reception antennas and the number of ranks of each terminal device 2 are all the same, and L = N _r = 1 will be described. However, the number of reception antennas and the number of ranks differ for each terminal device 2. It doesn't matter. Further, as long as U × L ≦ _Nt and L ≦ _Nr are satisfied, the number of ranks and the number of reception antennas do not need to be the same between the terminal apparatuses 2.

As a transmission scheme, orthogonal frequency division multiplexing (OFDM) having _Nc subcarriers (subcarriers) is assumed. However, unless otherwise specified, signal processing described below is performed for each subcarrier. The base station apparatus 1 obtains CSI from the base station apparatus 1 to each terminal apparatus 2 based on the control information notified from each terminal apparatus 2, and precodes transmission data for each subcarrier based on the propagation path information. Shall be performed. In the following, the duplex scheme is assumed to be frequency division duplex, but time division duplex is also included in this embodiment.

First, CSI between the base station device 1 and the terminal device 2 is defined. In the present embodiment, a quasi-static frequency selective fading channel is assumed. Here, quasi-static means that the propagation path does not vary within one OFDM signal. The k-th sub-signal in the t-th OFDM signal between the n-th transmitting antenna (n = 1 to N _t ) and the m-th receiving antenna (m = 1 to N _r ) of the u-th terminal apparatus 2-u (u = 1 to U). When the complex channel gain of the carrier is set to _{hu, m, n} (k, t), the propagation path matrix H (k, t) is defined as in Expression (1).

h _u (k, t) represents an N _r × N _t matrix composed of complex channel gains observed by the u-th terminal apparatus 2-u. In the present embodiment, unless otherwise specified, CSI refers to a matrix composed of complex channel gains. However, a spatial correlation matrix or a matrix in which linear filters described in a code book shared in advance between the base station apparatus 1 and each terminal apparatus 2 are regarded as CSI, and signal processing described later can be performed. . Further, when the eigenvector obtained by performing singular value decomposition (or eigenvalue decomposition) on the propagation path matrix estimated by the terminal device 2 is notified to the base station device 1, the base station device 1 displays a matrix in which eigenvectors are arranged as CSI. May be considered. In the following description, the u-th terminal apparatus 2-u estimates h _u (k, t ₁ ) that is CSI at time t _1, performs quantization, and notifies the base station apparatus 1 of it.

Here, the CSI actually notified to the base station apparatus 1 by the u-th terminal apparatus 2-u is defined as h _{FB, u} (k, t ₁ ). In the following, it is assumed that h _{FB, u} (k, t ₁ ) is a matrix of N _r × N _t like h _u (k, t ₁ ), but it is not necessarily required to be N _r × N _t. Absent. For example, the u terminal device 2-u to a receiving antenna of the _{N r} this is _considered the case so as to notify only CSI about _(N r -1) receive antennas. In this case, naturally h _{FB, u} (k, t ₁ ) is a matrix of (N _r −1) × N _t . At this time, the base station apparatus 1 may perform transmission signal processing such as precoding, which will be described later, assuming that the number of reception antennas provided in the u-th terminal apparatus 2-u is (N _r −1).

In addition, not only h _u (k, t ₁ ) itself but also an eigenvector obtained by performing singular value decomposition on h _u (k, t ₁ ) or both eigenvector and singular value may be notified. . In this case, the eigenvectors will be a column vector of the element number N _t is the N _t exist. However, the eigenvector calculated here includes a vector that can be a linear filter that directs a null beam to the u-th terminal apparatus 2-u. The u-th terminal device 2-u can also perform control so as to notify an arbitrary number of column vectors among a plurality of eigenvectors. For example, if the u-th terminal apparatus 2-u notifies Q eigenvectors among the eigenvectors, the base station apparatus 1 assumes that the u-th terminal apparatus 2-u has Q reception antennas. Transmission signal processing such as precoding described later may be performed.

In the present embodiment, the method by which the u-th terminal apparatus 2-u notifies h _{FB, u} (k, t ₁ ) to the base station apparatus 1 is not limited to anything. In the following, it is assumed that the u-th terminal apparatus 2-u directly quantizes h _u (k, t ₁ ) and notifies the base station apparatus 1. At this time, an error occurs between h _u (k, t ₁ ) and h _{FB, u} (k, t ₁ ) according to the number of quantization bits. However, since the method itself of the present embodiment is not affected by the magnitude of the error, in the following description, h _u (k, t ₁ ) = h _{FB, u} (k, t ₁ ) Will be described.

[1.1. Base station apparatus 1]
FIG. 2 is a block diagram showing a configuration example of the base station apparatus 1 according to the first embodiment of the present invention. As shown in FIG. 2, the base station apparatus 1 includes a channel encoding unit 21, a data modulation unit 23, a mapping unit 25, a precoding unit 27, an antenna unit 29, a control information acquisition unit 31, and a propagation. And a road information acquisition unit 33. The precoding unit 27 exists as many as the number of subcarriers N _c , and the antenna unit 29 exists as many as the number of transmission antennas N _t .

First, the control information acquisition unit 31 acquires control information notified from each connected terminal device 2, and outputs information associated with the propagation path information to the propagation path information acquisition unit 33. . The propagation path information acquisition unit 33 acquires h _{FB, u} (k, t ₁ ) notified from each terminal device 2 based on the information input from the control information acquisition unit 31. Then, based on h _{FB, u} (k, t ₁ ), a quantized propagation path matrix H _FB (k, t ₁ ) represented by Expression (2) is calculated.

However, as already described, in the description of the present embodiment, since h _u (k, t ₁ ) = h _{FB, u} (k, t ₁ ) is assumed, H _FB (k, t ₁ ) = H (k, t ₁ ). In the present embodiment, since N _r = 1 is assumed, H _FB (k, t ₁ ) is a U × N _t matrix. The propagation path information acquisition unit 33 outputs the calculated H _FB (k, t ₁ ) to the precoding unit 27.

Next, after the channel coding unit 21 performs channel coding on the transmission data sequence addressed to each terminal device 2, the data modulation unit 23 performs QPSK (Quadrature Phase Shift Keying), 16QAM (Quadrature Amplitude).
digital data modulation such as ude Modulation). The data modulation unit 23 inputs the data signal subjected to data modulation to the mapping unit 25.

The mapping unit 25 performs mapping (also referred to as scheduling or resource allocation) in which each data is allocated to a specified radio resource (also referred to as resource element or simply resource). Here, the radio resource mainly refers to frequency, time, code, and space. The radio resource to be used is determined based on the reception quality observed by the terminal apparatus 2, the orthogonality of the propagation path between the spatially multiplexed terminals, and the like. In the present embodiment, it is assumed that radio resources to be used are determined in advance and can be grasped by both the base station apparatus 1 and each terminal apparatus 2. The mapping unit 25 also performs multiplexing of a known reference signal sequence for performing propagation path estimation in each terminal device 2.

The reference signals addressed to the terminal devices 2 are multiplexed so as to be orthogonal to each other so that they can be separated in the received terminal device 2. The reference signal includes two reference signals: a CSI-reference signal (CSI-RS) that is a reference signal for channel estimation, and a demodulation reference signal (DMRS) that is a demodulation reference signal (also referred to as a unique reference signal). Is multiplexed, but another reference signal may be further multiplexed. CSI-RS is for estimating CSI observed in each terminal apparatus 2. That is, the u-th terminal apparatus 2-u estimates h _u (k, t ₁ ) based on CSI-RS. On the other hand, DMRS is for estimating propagation path information reflecting the result of precoding described later. In the present invention, the mapping unit 25 performs mapping so that the data signal, DMRS, and CSI-RS are transmitted at different times, frequencies, or codes, respectively. The mapping unit 25 arranges the CSI-RS so as to be orthogonal between the transmission antennas. In addition, the mapping unit 25 arranges DMRSs so as to be orthogonal between terminal apparatuses and associated data streams. The mapping unit 25 inputs the mapped data information or the like to the corresponding subcarrier precoding unit 27.

FIG. 3 is a block diagram showing an example of a device configuration of the precoding unit 27 according to the first embodiment of the present invention. As shown in FIG. 3, the precoding unit 27 includes a switch unit 27-1, a linear filter generation unit 27-2, a THP unit 27-4, a transmission data signal generation unit 27-5, and a transmission DMRS generation unit 27-6. And a transmission signal generator 27-7. In the following, only the signal processing for the data signal and the DMRS among the signals input to the precoding unit 27 will be described. The CSI-RS is not subjected to precoding processing based on propagation path information in the precoding unit, and only transmission power control is performed, and thus the description thereof is omitted.

The signal input to the precoding unit 27 is first divided into a data signal and a DMRS in the switch unit 27-1. Next, the linear filter generation unit 27-2 generates a linear filter W (k, t ₁ ) based on the propagation path information H _FB (k, t ₁ ) input from the propagation path information acquisition unit 33. In the following description, it is assumed that H _FB (k, t ₁ ) = H (k, t ₁ ), and a sufficiently high correlation exists in the propagation path of the radio resource in which the data signal and DMRS are transmitted. It is assumed that the time and frequency indexes are omitted. In addition, since there is time selectivity in the actual propagation path, even if the base station apparatus 1 performs precoding, the IUI cannot be completely removed. However, the method of the present embodiment itself has a size of the residual IUI. In the following description, this effect is ignored.

In the present embodiment, the precoding performed by the precoding unit 27 assumes THP based on the MMSE (Minimum Mean Square Error) standard that minimizes the mean square error between the transmission data signal and the reception data signal of each terminal apparatus 2. Other norms of THP (eg, Zero-forcing norms that minimize IUI) are also included in this embodiment. The linear filter used in MMSE-THP basically converts a propagation path matrix into a lower triangular matrix. There are several methods for generating a linear filter. In this embodiment, a method based on QR decomposition is assumed.

In the method based on QR decomposition, an expanded channel matrix G given by G = [H, αI] is used. Here, α is an interference control term, and may be set to the square root of the reciprocal of the received signal-to-interference + noise power ratio (SINR) observed by each terminal device 2, for example. Linear filter generating unit 27-2 by performing relative ^{G H,} QR ^{decomposition,} decompose ^{G H} as G H = QR. Here, it can be expressed as Q = [Q ₁₁ , Q ₁₂ ; Q ₂₁ , Q ₂₂ ], and Q ₁₁ , Q ₁₂ , Q _21, and Q ₂₂ are each a matrix of U rows and U columns. Hereinafter, it is expressed as Q ₁₁ = Q _L. R = [R _L ; 0 _U ] can be expressed, and R _L is a lower triangular matrix of U rows and U columns. In the following, the Hermitian transposed matrix of _{R L} and _{L L.} That is, L _L is a lower triangular matrix of U rows and U columns.

In the conventional MMSE-THP, it is assumed that W = Q _L {diag (HQ _L )} ⁻¹ is a linear filter. In other words, this linear filter is a filter that converts the expanded propagation path matrix G into a lower triangular matrix, but is also a filter that uses H, which is an actual propagation path matrix, as a lower triangular matrix according to the MMSE standard. Here, {diag (HQ _L )} ⁻¹ is a power distribution control term for making the received SINR for the data signal of each terminal apparatus 2 constant, and may not be multiplied depending on the precoding technique. .

In the present embodiment, the linear filter generation unit 27-2 calculates W _d = Q _L {diag (L _L )} ⁻¹ as the linear filter W _d for the data signal. Unlike the conventional method, the linear filter generation unit 27-2 calculates a power distribution control term using L _L instead of (HQ _L ). Note that L _L may be obtained based on LQ decomposition for H _L.

In the conventional method, the linear filter used for the data signal (also referred to as the first linear filter) and the linear filter for multiplying the DMRS (to be described later) (also referred to as the second linear filter) are the same. I was trying. In the conventional method, W _d is also used for DMRS, but in this embodiment, different linear filters are used for the data signal and DMRS.

Specifically, the linear filter generation unit 27-2 sets the linear filter W _p for DMRS to W _p = Q _L {diag (HW _d )} ⁻¹ . The diagonal component of HW _d is information associated with the amplitude information of the desired signal included in the received signal of each terminal device 2. Hereinafter, {diag (HW _d )} ⁻¹ is also referred to as a first diagonal matrix. Linear filter generating unit 27-2 while the output to the _{W p} the transmission DMRS generating unit 27-6, a _{W d} is outputted to the THP unit 27-4 and the transmission data signal generating unit 27-5.

Next, signal processing in the THP unit 27-4 will be described. In the THP section 27-4, a data signal among the signals input from the mapping section 25 is input, and a part of inter-user interference (IUI) included in the received signal received by each terminal apparatus 2 is suppressed. Interference suppression is performed. In the following, it is assumed that the terminal devices 2-1 to 2-4 are connected to the base station device 1 as shown in FIG. 1, and the data addressed to each terminal device 2 is stored in the THP section 27-4. It is assumed that a transmission data vector d = [d ₁ , d ₂ , d ₃ , d ₄ ] ^T composed of signals is input.

THP portion 27-4 is, for the input data signal d, is multiplied by the linear filter W _d inputted from the linear filter generation unit 27-2, consider that to be transmitted to each terminal device 2. If the received signal of the u terminal device 2-u and _{r u,} received signals of the entire system vector _{_{_{r = [r 1, r 2}}} , r 3, r 4] T is given by r = HW _{d d.} Note that power normalization (to be described later) is performed on the actual transmission signal vector, and noise is applied to the reception signal, which is omitted here. The received signal of each terminal device 2 includes an IUI in addition to a desired signal addressed to the own device. For example, the received signal of the second terminal device 2-2 is given by equation (3).

Here, W _d = [w _{d, 1} , w _{d, 2} , w _{d, 3} , w _{d, 4} ], and w _{d, u} is multiplied by the data signal addressed to the u-th terminal device 2-u. This is an eigenlinear filter of N _t rows and 1 column. The second term and the third term on the right side of Equation (3) are IUI. Here, since W _d is a filter that converts the propagation path matrix H into a lower triangular matrix based on the MMSE norm, the IUI of the third term, that is, the third terminal apparatus 2-3 and the fourth terminal apparatus 2- While the IUI caused by the data signal addressed to 4 is sufficiently suppressed, the IUI caused by the data signal addressed to the first terminal device 2-1 is not suppressed at all.

Therefore, THP unit 27-4 performs interference suppression processing for previously suppressed IUI not suppressed by _{W d} to the data signals for each terminal device 2 addressed. First, signal processing in the conventional MMSE-THP will be described. For example, when the interference suppression signal after the second terminal device destined 2-2 (referred to as transmission code) was x _2, x ₂ is given by equation (4).

If the base station apparatus 1 transmits the transmission code given by the equation (4) to the second terminal apparatus 2-2, the second terminal apparatus 2-2 is caused by the transmission signal addressed to the first terminal apparatus 2-1. Therefore, the generated IUI is not received. However, depending on the state of the propagation path information H, the magnitude of x ₂ may be much larger than d _2, which may require enormous transmission power. Therefore, performing nonlinear signal processing called modulo operation on _{x 2} in THP unit 27-4. The modulo operation is also performed by the THP unit 27-4 of the present embodiment described below.

The modulo operation Mod _2δ (x) is such that, for a certain input signal x, the real part and the imaginary part of its output fall within −δ and less than δ, respectively. Here, δ is called a modulo width, and is set according to the modulation method of the input signal. For example, when a QPSK modulation signal is input, 2δ = 2 × ^2½ is set. Note that 2δ is also called a basic unit of a perturbation vector. Indeed, when subjected to modulo operation on the signal _{x 2} of the formula (4), its output is given by equation (5).

Here, z ₂ is a Gaussian integer, and by using z ₂ given by the second expression of Equation (5), the real part and the imaginary part of the right side of the first expression are each greater than −δ, and δ Fits below. This z ₂ or 2δz ₂ is called a perturbation term in the present invention. by performing modulo arithmetic, regardless of the state of the propagation path information H, it is possible to always make constant the size of x _2. The calculated x ₂ (including the modulo calculation) is the transmission code addressed to the second terminal device 2-2.

In the same manner, the THP unit 27-4 performs interference suppression and modulo calculation on the data signals addressed to the third terminal apparatus 2-3 and the fourth terminal apparatus 2-4. Note that the IUI received by the first terminal device 2-1 is all suppressed by the linear filter W _d , so that the THP unit 27-4 does not perform any signal processing on d ₁ (ie, x ₁ = d ₁ ). A vector z = [z ₁ , z ₂ , z ₃ , z ₄ ] ^{T in} which perturbation terms obtained by the sequential signal processing described above are collected is referred to as a perturbation vector in this embodiment. Using the perturbation vector z, the transmission code vector x = [x ₁ , x ₂ , x ₃ , x ₄ ] ^T is given by x = (IF) ⁻¹ (d + 2δz). Here, F is a feedback filter. That is, the interference suppression process performed by the THP unit 27-4 is performed based on the data signal and the feedback filter F. F is given by the lower triangular matrix portion of I- (diag (HW _d )) ⁻¹ HW _{d in} the conventional MMSE-THP.

In the conventional MMSE-THP, based on the calculated linear filter _{W d,} it performs THP treatment to calculate the feedback filter F. In this case, since the interference suppression by the interference suppression and THP by linear filter W _d are both MMSE criterion can be realized averagely good transmission characteristics. By the way, in non-linear precoding in which modulo operation is performed on the receiving side, transmission characteristic deterioration called modulo loss occurs. The modulo loss is particularly noticeable in a low received signal power to noise power ratio (SNR) environment. Therefore, in order to suppress the influence of the modulo loss, it may be more effective that the base station apparatus 1 performs precoding close to the MRC standard that maximizes the reception SNR instead of the MMSE standard.

Therefore, in the present embodiment, the THP unit 27-4 removes the diagonal component of the lower triangular matrix L _L calculated based on the QR decomposition on the expanded propagation path matrix G as a feedback filter necessary for THP. It is assumed that the triangular matrix part is used. That is, the linear filter generation unit 27-2 in the present embodiment generates a feedback filter given by F = I− (diag (L _L )) ⁻¹ L _L , and the THP unit 27-4 Interference suppression by THP is performed. Note that the linear filter generation unit 27-2 may calculate F based only on the lower triangular matrix component that does not include the diagonal component of L _L.

According to the method of the present embodiment, an error occurs between the IUI grasped by the THP unit 27-4 and the IUI actually observed by each terminal device 2. This means that the received SINR is degraded. On the other hand, since the signal processing is performed assuming that the amplitude of the desired signal in the received signal of each terminal device 2 is given by the diagonal component of L _L , the received signal vs. noise is compared with the conventional MMSE-THP. The power ratio (SNR) can be improved. Therefore, in the low SNR environment, the method according to this embodiment has better transmission characteristics. The signal processing in the THP unit 27-4 of this embodiment is the same as that of the conventional THP except that the shape of the feedback filter is different. The THP unit 27-4 outputs the calculated transmission code vector x to the transmission data signal generation unit 27-5.

The transmission data signal generation unit 27-5 multiplies the transmission code vector x input from the THP unit 27-4 by the linear filter W _d input from the linear filter generation unit 27-2 to obtain the transmission data signal vector s _d . Generate. At this time, power normalization is performed to keep the transmission power constant. In the present embodiment, the transmission data signal generating unit 27-5 performs power normalized by multiplying the power normalization term β in the transmission data signal vector s _d. The transmission data signal vector s _d is given by equation (6).

Here, P _x is a covariance matrix of transmission code vectors. The transmission data signal generation unit 27-5 outputs s _d to the transmission signal generation unit 27-7, and outputs the calculated power normal term β to the transmission DMRS generation unit 27-6.

Next, signal processing in the transmission DMRS generating unit 27-6 will be described. Among the signals input from the mapping unit 25, the DMRS is input to the transmission DMRS generation unit 27-6. Here, the base station apparatus 1 shall transmit DMRS addressed to each terminal device 2 in order to each terminal device 2 in a continuous radio | wireless resource. When the DMRS addressed the u terminal device 2-u and _{p u,} which is transmitted DMRS of the u terminal device destined 2-u to calculate the transmission DMRS generating unit 27-6 _{s p, u} is _{s p,} u = It is given by μβw _{p, u} p _u . _{_{_{_{Incidentally, s p = [s p,}}}} 1, s p, 2, s p, 3, s p, 4] T, W p = [w p, 1, w p, 2, w p, 3, w p, ₄ ]. W _p is input from the linear filter generation unit 27-2, and the power normalization term β is input from the transmission data signal generation unit 27-5. μ is a power adjustment term of DMRS and is given as an arbitrary real number, but basically needs to be shared between the base station apparatus 1 and each terminal apparatus 2. In the following description, μ = 1. Transmitting DMRS generating unit 27-6 transmits the calculated _{s p} the transmission signal generation unit 27-7.

Transmission signal generating unit 27-7, after giving a proper transmission power to the transmission signal vector _{s d} and _{s p} is inputted from the transmit data signal generating unit 27-5 and transmitting DMRS generating section 27-6, the antenna portion Output to 29. Note that the transmission power may be controlled so as to be adjusted by a wireless transmission unit 29-3 of the antenna unit 29 described later.

FIG. 4 is a flowchart illustrating an example of signal processing in the precoding unit 27 according to the first embodiment of the present invention. First, the switch unit 27-1 divides a signal input from the mapping unit into a data signal and a DMRS (step S201). Next, the linear filter generation unit 27-2 calculates the first linear filter _Wd , the second linear filter _Wp, and the feedback filter F based on the propagation path information input from the propagation path information acquisition unit 33 ( Step S202). Next, the THP unit 27-4 performs interference suppression and modulo operation on the data signal based on the feedback filter F, and calculates a transmission code vector x (step S203). Next, the transmission data signal generation unit 27-5 calculates the power normalization coefficient β and the transmission data signal vector s _d based on the transmission code vector x and the first linear filter W _d (step S204). Then, transmitting DMRS generating unit 27-6, DMRS and based on a second linear filter _{W p} and power normalization coefficient β and the power adjustment term, to calculate the _{s p} is the transmission DMRS (step S205). Finally, the transmission signal generation unit 27-7 adjusts the transmission power of _{s d} and _{s p,} is output to the antenna unit 29 (step S206).

In the above description, it is assumed that the precoding process performed by the precoding unit 27 is performed for each subcarrier, but the precoding unit 27 performs the precoding process for each subband including a plurality of subcarriers and OFDM signals. May be applied. For example, the linear filter generation unit 27-2 calculates one each of the first and second linear filters and the feedback filter for each subband, and applies them to each subcarrier in the subband. You may control.

Further, the transmission data signal generation unit 27-5 may perform control so as to obtain the power normalization coefficient β so that the transmission power becomes constant for each subband.

In addition, the precoding unit 27 may perform a series of signal processing after preliminarily performing preliminary processing on the channel information (propagation channel matrix) input from the channel information acquisition unit 33. As the preliminary processing, for example, an ordering (order change) technique for the propagation path matrix and a lattice base reduction technique can be considered. When preliminary processing is performed on the propagation path matrix, the precoding unit 27 performs processing corresponding thereto on the data signal input from the mapping unit and the demodulation reference signal. For example, when the ordering is performed on the channel matrix, the same ordering process is performed on the data signal and the demodulation reference signal (the demodulation reference signal may not be performed).

FIG. 5 is a block diagram illustrating an example of a device configuration of the antenna unit 29 according to the first embodiment of the present invention. As shown in FIG. 5, the antenna unit 29 includes an IFFT unit 29-1, a GI insertion unit 29-2, a wireless transmission unit 29-3, a wireless reception unit 29-4, and an antenna 29-5. It consists of In each antenna unit 29, first, the IFFT unit 29-1 performs N _c -point inverse fast Fourier transform (IFFT) or inverse discrete Fourier transform (IDFT) on the signal output from the corresponding precoding unit 27. ) To generate an OFDM signal having _Nc subcarriers, and input it to the GI insertion unit 29-2. Here, the number of subcarriers and the number of points of IFFT are described as being the same, but when a guard band is set in the frequency domain, the number of points is larger than the number of subcarriers. The GI insertion unit 29-2 gives a guard interval to the input OFDM signal, and then inputs it to the radio transmission unit 29-3. The radio transmission unit 29-3 converts the input baseband transmission signal into a radio frequency (RF) transmission signal and inputs it to the antenna 29-5. The antenna 29-5 transmits the input transmission signal in the RF band.

On the other hand, a signal transmitted from each terminal apparatus 2 to the base station apparatus 1 is input to the wireless reception unit 29-4. The radio reception unit 29-4 performs a process of demodulating the transmission signal from each terminal apparatus 2 from the received signal, and a signal related to the control information is output to the control information acquisition unit 31. Will be.

[1.2. Terminal device 2]
FIG. 6 is a block diagram illustrating a configuration example of the terminal device 2 according to the first embodiment of the present invention. As shown in FIG. 6, the terminal device 2 includes a terminal antenna unit 51, a propagation path estimation unit 53, a feedback information generation unit 55, a channel equalization unit 57, a demapping unit 59, a data demodulation unit 61, a channel And a decoding unit 63. Among them, the terminal antenna unit 51 exists by the number of receiving antennas _Nr . However, in the following description, it is assumed that the number of reception antennas is N _r = 1.

FIG. 7 is a block diagram showing a configuration example of the terminal antenna unit 51 according to the first embodiment of the present invention. As shown in FIG. 7, the terminal antenna unit 51 includes a radio reception unit 51-1, a radio transmission unit 51-2, a GI removal unit 51-3, an FFT unit 51-4, and a reference signal separation unit 51-. 5 and an antenna 51-6. The transmission signal transmitted from the base station apparatus 1 is first received by the antenna 51-6 of the terminal antenna unit 51 and then input to the radio reception unit 51-1. The radio reception unit 51-1 converts the input signal into a baseband signal and inputs the signal to the GI removal unit 51-3. The GI removal unit 51-3 removes the guard interval from the input signal and inputs it to the FFT unit 51-4. The FFT unit 51-4 applies N _c -point fast Fourier transform (FFT) or discrete Fourier transform (DFT) to the input signal, converts it to N _c subcarrier components, and then separates the reference signal Input to section 51-5. The reference signal separation unit 51-5 separates the input signal into a data signal component, a CSI-RS component, and a DMRS component. The reference signal separation unit 51-5 inputs the data signal component to the channel equalization unit 57, and inputs the CSI-RS and DMRS to the propagation path estimation unit 53. The signal processing described below is basically performed for each subcarrier.

The propagation path estimation unit 53 performs propagation path estimation based on the input known reference signals CSI-RS and DMRS. First, propagation path estimation using CSI-RS will be described.

Since the CSI-RS is transmitted without applying precoding, the CSI-RS corresponds to the u-th terminal apparatus 2-u in the channel matrix H (k, t ₁ ) represented by the equation (1). It is possible to estimate the matrix h _u (k, t ₁ ). Normally, since CSI-RS is periodically multiplexed with respect to radio resources, propagation path information of all subcarriers cannot be estimated directly. However, if the CSI-RS is transmitted at a time interval and a frequency interval that satisfy the sampling theorem, the terminal device 2 can estimate the propagation path information of all subcarriers by appropriate interpolation. A specific propagation path estimation method is not particularly limited. For example, two-dimensional MMSE propagation path estimation may be used.

The propagation path estimation unit 53 of the u-th terminal apparatus 2-u inputs the propagation path information h _u (k, t ₁ ) estimated based on the CSI-RS to the feedback information generation unit 55. The feedback information generation unit 55 provides information to be fed back to the base station apparatus 1 according to the input propagation path information and the propagation path information format fed back by each terminal apparatus 2, that is, h _{FB, u} (k, t ₁ ). Is generated. In the present invention, the propagation path information format is not limited to anything. For example, a method may be considered in which each element of the estimated propagation path information h _u (k, t ₁ ) is quantized with a finite number of bits and the quantization information is fed back. Further, feedback may be performed based on a code book that has been agreed with the base station apparatus 1 in advance.

Further, h _u (k, t ₁ ) may not be directly quantized, but may be quantized after some signal conversion. As signal conversion, for example, a method of performing singular value decomposition is conceivable. In this case, the feedback information generation unit 55 generates information to be notified to the base station apparatus 1 by quantizing the eigenvector obtained by the singular value decomposition or both the eigenvector and the singular value.

Next, the propagation path estimation unit 53 performs propagation path estimation based on the DMRS. This will be described later, and signal processing in the channel equalization unit 57 will be described first. Received signal r _u received by the u terminal device 2-u is input to the channel equalizer 57 is given by Equation (7).

Here, P _r is the average received power in consideration also the long-term variation component of the path loss, etc., the eta _u is the noise that is applied to the u terminal device 2-u. The second equation of Equation (7) assumes that the IUI is ideally suppressed by nonlinear precoding in the base station apparatus 1. As described above, when the base station apparatus 1 performs nonlinear precoding, a modulo operation is necessary on the receiving side. In this embodiment, the modulo width to be estimated by the propagation path estimation unit 53 is (2P _r ) ^1/2 β2δ, and h _u w _{d, u} is not included. This modulo width can be estimated by channel estimation based on DMRS in the channel estimation unit 53.

The propagation path estimation based on DMRS in the propagation path estimation unit 53 will be described. DMRSr _{p, u} currently received by the u-th terminal apparatus 2- _u is given by equation (8).

The propagation path estimation unit 53 performs inverse modulation on r _{p, u} using a known reference signal p _u . When the influence of noise can be ignored, the inverse modulation output becomes r _{p, u} / p _u = (2P _r ) ^1/2 β, and 2δ is a value shared between the base station apparatus 1 and the terminal apparatus 2. Therefore, the terminal device 2 can obtain a desired modulo width.

On the other hand, let us consider a case where the base station apparatus 1 multiplies DMRS by the same linear filter W _d as the data signal as in the prior art. At this time, the received signal rp _{, u} is given by equation (9).

When the propagation path estimation unit 53 performs inverse modulation based on _pu on this r _{p, u} , the output is (2P _r ) ^1/2 βh _u w _{d, u} . This means that the terminal device 2 estimates the modulo width as (2P _r ) ^1/2 βh _u w _{d, u} 2δ, and the estimated value does not match the desired modulo width. I understand. If the terminal device 2 estimates a modulo width different from the desired value, a large error occurs in the modulo calculation result, and the transmission characteristics are greatly degraded. As this embodiment has been targeted, it is possible to avoid such deterioration of transmission characteristics by using different linear filters for the DMRS and the data signal.

The propagation path estimation unit 53 outputs the inverse modulation output obtained based on the above-described method to the channel equalization unit 57 as a propagation path estimation value. In the above description, the channel estimation method is based on simple inverse modulation. However, in this embodiment, the channel estimation method applied to the DMRS by the channel estimation unit 53 is limited to something. Instead, the channel estimation value may be obtained based on another channel estimation method as in the channel estimation method for CSI-RS.

Channel equalizer 57 for the received signal r _u, subjected to channel equalization based on the channel estimation value input from channel estimator 53. For example, the received signal r _u input from the terminal antenna portion may be divided by the input from the channel estimator 53 channel estimates. The channel equalization unit 57 performs a modulo operation with a modulo width of 2δ on the received signal after channel equalization, and outputs the result to the demapping unit 59.

In the demapping unit 59, the terminal device 2 extracts transmission data addressed to itself from radio resources used for transmission of transmission data addressed to itself. The output of the reference signal separation unit 51-5 may be input to the demapping unit 59 first, and only the radio resource component corresponding to the own device may be input to the channel equalization unit 57. The output of the demapping unit 59 is then input to the data demodulating unit 61 for data demodulation, and the data demodulation result is input to the channel decoding unit 63 for channel decoding.

Note that depending on the channel decoding method performed by the channel decoding unit 63, it is also possible to perform direct decoding using a signal to which a perturbation term has been added. In this case, the channel equalizer 57 may not perform the modulo operation.

In this embodiment, it is assumed that OFDM signal transmission is performed and precoding is performed for each subcarrier, but there is no limitation on the transmission scheme (or access scheme) and the precoding application unit. For example, the present embodiment is also applicable when precoding is performed for each resource block in which a plurality of subcarriers are grouped, and similarly, a single carrier based access scheme (for example, single carrier frequency division multiple access (SC−) (FDMA) system).

In the present embodiment, the number of reception antennas N _r of each terminal device 2 is provided with 1, but the number of transmission rank L had a 1, also the present embodiment when the number of receive antennas and the transmission rank number L were multiple included. In this case, each terminal apparatus 2 estimates an apparent MIMO channel based on the demodulation reference signal transmitted from the base station apparatus, and based on the obtained MIMO channel estimated value, A space separation process may be performed. At this time, each terminal device 2 may use only the demodulation reference signal addressed to its own device, or may also use the demodulation reference signal addressed to another device, but this embodiment includes both cases.

As described above, the terminal device 2 can estimate the modulo width with high accuracy based on the demodulation reference signal, and realizes better transmission characteristics than the conventional MMSE-THP in a low SNR environment. Possible non-linear MU-MIMO transmission can be realized.

[2. Second Embodiment]
In the first embodiment, the non-linear precoding performed by the base station apparatus 1 is assumed to be MMSE-THP. The second embodiment is directed to the case where the base station apparatus 1 performs MMSE-VP as nonlinear precoding.

[2.1. Base station apparatus 1]
One configuration example of the base station apparatus 1 according to the second embodiment of the present invention is the same as that of FIG. However, the precoding unit 27 is configured to replace the precoding unit 35. Since the signal processing in each component device other than the precoding unit 35 to be replaced is the same as that in the first embodiment, the description thereof will be omitted, and the signal processing in the precoding unit 35 will be described below.

FIG. 8 is a block diagram showing an example of a device configuration of the precoding unit 35 according to the second embodiment of the present invention. As shown in FIG. 8, the precoding unit 35 includes a switch unit 35-1, a linear filter generation unit 35-2, a perturbation vector search unit 35-3, a transmission data signal generation unit 35-5, and a transmission DMRS generation unit 35. -6 and a transmission signal generator 35-7. The signal processing of the switch unit 35-1, the transmission DMRS generation unit 35-6, and the transmission signal generation unit 35-7 is the same as that of the switch unit 27-1 of the precoding unit 27 of FIG. 3 in the first embodiment. Since this is the same as the transmission DMRS generator 27-6 and the transmission signal generator 27-7, a description thereof will be omitted.

The linear filter generation unit 35-2 calculates a linear filter. In the first embodiment, the linear filters W _d and W _p generated by the linear filter generation unit 27-2 are both filters that convert the channel matrix H into a lower triangular matrix based on the MMSE norm, and each terminal A part of the IUI received by the device 2 can be suppressed. In this embodiment, the linear filter calculated by the linear filter generation unit 35-2 suppresses all IUIs received by each terminal apparatus 2. In this embodiment, a linear filter based on the MMSE standard is used. The linear filter W _d that multiplies the data signal generated by the linear filter generation unit 35-2 is given by Expression (10).

In the conventional MMSE-VP, the same linear filter W _p that multiplies DMRS as W _d is used. In the present embodiment, as in the first embodiment, the linear filter that multiplies the data signal is different from the linear filter that multiplies the DMRS. In this embodiment, the linear filter W _p generated by the linear filter generation unit 35-2 and multiplied by DMRS is given by Expression (11).

Linear filter generating unit 35-2 inputs the _{W d} perturbation vector search unit 35-3 to the transmission data signal generating unit 35-5 inputs the _{W p} in transmitting DMRS generating unit 35-6.

The perturbation vector search unit 35-3 searches for a perturbation vector z to be added to the data signal d. In the MMSE-THP targeted by the first embodiment, the perturbation vector z is obtained using a modulo operation. In the MMSE-VP targeted by this embodiment, the perturbation vector is searched by solving the minimization problem given by equation (12), not by the modulo operation.

Equation (12) suggests that the desired perturbation vector minimizes the transmission power of the transmission signal after the linear filter multiplication. However, since the perturbation terms constituting the perturbation vector are given by arbitrary Gaussian integers, it is not realistic to examine all combinations. Therefore, even in the study on the conventional MMSE-VP, it is assumed that a calculation amount reduction technique such as Sphere encoding is used.

The method of the present embodiment is not affected by the perturbation vector search method. Therefore, in the present embodiment, the perturbation vector search method is not limited to anything. Further, it does not have to be a norm that minimizes transmission power. For example, the perturbation vector search unit 35-3 searches for a perturbation vector based on the minimum mean square error norm, the minimum interference power norm, or the maximum transmission to interference + noise power ratio (SLNR) norm, not the minimum transmit power norm. The perturbation vector may be searched based on the lattice basis reduction technique. In addition, in an extreme case, the present embodiment includes a case where the perturbation vector search unit 35-3 randomly selects a perturbation vector. In the following description, it is assumed that the perturbation vector search unit 35-3 searches for the perturbation vector z based on some standard and search method, and outputs it to the transmission data signal generation unit 35-5.

In the transmission data signal generation unit 35-5, the data signal vector d input from the switch unit 35-1, the linear filter W _d input from the linear filter generation unit 35-2, and the perturbation vector search unit 35-3. A transmission data signal vector s _d is generated based on the input perturbation vector z. s _d is given by equation (13).

The transmission data signal generation unit 35-5 outputs the calculated transmission data signal vector s _d to the transmission signal generation unit 35-7, while the power normalization term β is output to the transmission DMRS generation unit 35-6. Output.

FIG. 9 is a flowchart illustrating an example of signal processing in the precoding unit 35 according to the second embodiment of the present invention. First, the switch unit 35-1 divides the signal input from the mapping unit 25 into a data signal and a DMRS (step S301). Then, the linear filter generation unit 35-2, based on the channel information inputted from the propagation path information acquiring unit 33 calculates a first linear filter W _d and the second linear filter W _p (step S302). Next, the perturbation vector search unit 35-3 searches for the perturbation vector z based on the data signal and the first linear filter (step S303). Next, the transmission data signal generator 35-5 calculates a power normalization coefficient β and a transmission data signal vector s _d based on the data signal, the first linear filter, and the perturbation vector (step S304). Then, transmitting DMRS generating unit 35-6, DMRS and based on a second linear filter _{W p} and power normalization coefficient β and the power adjustment term, to calculate the _{s p} is the transmission DMRS (step S305). Finally, the transmission signal generation unit 35-7 adjusts the transmission power of _{s d} and _{s p,} is output to the antenna unit 29 (step S306).

The above is the description of the signal processing in the precoding unit 35 according to the present embodiment. Since the signal processing in the other constituent devices of the base station device 1 is the same as that in the first embodiment, the description thereof is omitted.

[2.2. Terminal device 2]
The device configuration of the terminal device 2 in this embodiment is the same as that of the first embodiment. Since the signal processing in the other constituent devices is the same, the description thereof is omitted.

As described above, in the present embodiment, the case where the base station apparatus 1 uses MMSE-VP as a precoding method is targeted. In the first embodiment, the method of the present invention was effective in a low SNR environment, whereas the MMSE-VP targeted by the present embodiment is better than the conventional method regardless of the SNR value. Transmission characteristics can be realized, which can contribute to improvement of frequency utilization efficiency of the radio communication system.

[3. Third Embodiment]
In the first and second embodiments, it is assumed that all terminal devices 2 connected to the base station device 1 can perform modulo arithmetic. However, in an actual wireless communication system, there may be a case where terminal devices 3 that do not perform a modulo calculation coexist. In addition, in nonlinear precoding transmission based on modulo computation, there is a specific transmission characteristic deterioration factor called modulo loss. Therefore, depending on the propagation path environment, the frequency utilization efficiency may be improved when the base station apparatus generates a transmission signal that does not require the terminal apparatus to perform a modulo operation. The third embodiment is directed to a case where a terminal device 2 that performs a modulo operation and a terminal device 3 that does not perform a modulo operation coexist.

FIG. 10 is a diagram illustrating an example of an outline of a wireless communication system according to the third embodiment of the present invention. In the third embodiment, a base station apparatus 1b having N _t transmission antennas is compared with a terminal apparatus 2 having N _r reception antennas (in FIG. 10, terminal apparatuses 2-1 to 2-2 are connected). and two), two of the terminal device 3 (in FIG. 10 the terminal devices 3-1 to 3-2 having a reception antenna of the _{N r} present) is directed to a wireless communication system for multiple connections. Note that wireless parameters such as the number of transmission ranks are the same as those in the first embodiment unless otherwise specified. The terminal device 2 is a terminal device (also referred to as a non-linear terminal device) that performs a modulo operation on the received signal targeted in the first and second embodiments, and the terminal device 3 that does not perform a modulo operation on the received signal ( Also called a linear terminal device).

As in the second embodiment, even if all the terminal devices connected to the base station device 1b are terminal devices that can perform a modulo operation on the received signal, some terminal devices receive The base station apparatus 1b can control so as not to perform a modulo operation on the signal. The present embodiment includes such a case.
[3.1. Base station apparatus 1b]
The structure of the base station apparatus 1b which concerns on the 3rd Embodiment of this invention is the same as that of FIG. However, the precoding unit 27 is configured to replace the precoding unit 37. Since the signal processing in each component device other than the precoding unit 37 to be replaced is the same as that in the first embodiment, the description thereof will be omitted, and the signal processing in the precoding unit 37 will be described below.

FIG. 11 is a block diagram showing an example of a device configuration of the precoding unit 37 according to the third embodiment of the present invention. As shown in FIG. 11, the precoding unit 37 includes a switch unit 37-1, a linear filter generation unit 37-2, a perturbation vector search unit 37-3, a transmission data signal generation unit 37-5, and a transmission DMRS generation unit 37. −6 and a transmission signal generator 37-7. The signal processing in each component device except the linear filter generation unit 37-2 and the perturbation vector search unit 37-3 is performed by the corresponding component device (for example, the switch unit 37) in the precoding unit 35 according to the second embodiment. −1 is the same as the signal processing in the switch unit 35-1), and thus the description thereof is omitted. Hereinafter, signal processing in the linear filter generation unit 37-2 and the perturbation vector search unit 37-3 will be described.

Based on the propagation path information H input from the propagation path information acquisition section 33, the linear filter generation section 37-2 calculates a linear filter W _d that multiplies the data signal and a linear filter W _p that multiplies the DMRS. In the following, as in the second embodiment, the precoding unit 37 considers that MMSE-VP is applied to each data signal, but other nonlinear precoding such as MMSE-THP targeted by the first embodiment. Is also included in this embodiment. The linear filter W _d in MMSE-VP is already given by equation (10).

Next, W _p will be described. In the second embodiment, the linear filter generation unit 35-2 corrects W _d so that the error between the modulo width estimated by each terminal apparatus 2 based on DMRS and the desired modulo width becomes small. by performing, I had to calculate the W _p. However, in the present embodiment, the linear terminal device is included in the plurality of terminal devices connected to the base station device 1b. Since the linear terminal device does not perform a modulo operation on the received signal, it is not necessary to estimate the modulo width. Therefore, the linear filter generation unit 37-2 in the present embodiment can use the same linear filter that multiplies the data signal as the linear filter that multiplies the DMRS addressed to the linear terminal device, as in the conventional method. .

Assume that there are four terminal devices connected to the base station device 1b, of which the first and second terminal devices are the terminal device 3-1 and the terminal device 3-2 which are linear terminal devices. The third and fourth terminal devices are assumed to be a terminal device 2-1 and a terminal device 2-2 that are nonlinear terminal devices. Since the linear filter W _d for multiplying the data signal can be represented by a matrix of N _t rows and 4 columns, W _d = [w _{d, 1} , w _{d, 2} , w _{d, 3} , w _{d, 4} ]. In this way, it is expressed by four matrices of N _t rows and 1 column. Here, W _{d, u} is a linear filter by which the data signal addressed to the u-th terminal device is multiplied.

Similarly, it can be expressed as a linear filter _{W p} also _W p ₌ multiplying the _{DMRS [w p, 1, w} p, 2, w p, 3, w p, 4]. W _p calculated by the linear filter generation unit 37-2 is given by Expression (14).

That is, for the linear filter that is multiplied by the DMRS addressed to the linear terminal device, the same linear filter that is multiplied by the data signal is used, while the linear filter that is multiplied by the DMRS addressed to the nonlinear terminal device is the first one. Similarly to the second embodiment, a linear filter that is multiplied by the data signal is used. The linear filter generation unit 37-2 outputs the calculated linear filter W _d to the perturbation vector search unit 37-3 and the transmission data signal generation unit 37-5, and outputs the linear filter W _p to the transmission DMRS generation unit 37-6. Output toward.

In the perturbation vector search unit 37-3 calculates the perturbation vector z on the basis of the transmission data vector d to be inputted from the linear filter W _d and the switch 37-1 is input from the linear filter generating unit 37-2. The perturbation vector searched by the perturbation vector search unit 37-3 searches for the one that minimizes the transmission power, as in the case of the perturbation vector search unit 35-3 in the second embodiment (see Expression (12)). However, in the present embodiment, the first terminal device 3-1 and the second terminal device 3-2 do not perform a modulo operation on the received signal. Therefore, when a perturbation term is added to d ₁ and d ₂ , the first terminal device 3-1 and the second terminal device 3-2 cannot remove the perturbation term included in the received signal and transmit The characteristics are greatly degraded.

Therefore, in the perturbation vector search unit 37-3 in the present embodiment, the perturbation term added to the data signals addressed to the first terminal device 3-1 and the second terminal device 3-2 is always 0. Search for perturbation vectors. That is, the perturbation vector search unit 37-3 searches for the perturbation vector by solving the minimization problem given by the equation (15).

The perturbation vector search unit 37-3 outputs the perturbation vector searched based on the equation (15) to the transmission data signal generation unit 37-5. Note that the perturbation vector search unit 37-3 searches for the perturbation vector, assuming that all the terminal devices connected to the base station device 1 are nonlinear terminal devices, as in the second embodiment. Of the perturbation vectors z thus obtained, only the perturbation term to be added to the data signal addressed to the linear terminal device may be controlled to be replaced with zero.

In the above description, all perturbation terms added to the data signal addressed to the linear terminal device are set to zero. However, a perturbation term other than 0 may be added as long as it does not affect the demodulation processing for the received signal of the linear terminal device. For example, consider a case where the modulation method is QPSK modulation and a modulation symbol in the first quadrant is transmitted as a data signal addressed to the linear terminal apparatus. At this time, it is considered that the base station apparatus 1b adds a perturbation term given by a Gaussian integer (for example, (1 + j)) in the first quadrant as a perturbation term to the data signal. At this time, even if the linear terminal device cannot perform the modulo operation, the transmission characteristics do not deteriorate, and conversely, good transmission characteristics may be realized. That is, in the case of QPSK modulation, the base station device 1b may add the perturbation term to the data signal addressed to the linear terminal device as far as the perturbation term exists in the same quadrant.

In multi-level quadrature amplitude modulation, even when the base station apparatus 1b transmits modulation symbols whose four sides are not surrounded by a signal determination plane to the linear terminal apparatus, it is possible to add some perturbation terms. For example, in 16QAM, a perturbation term existing in the first quadrant can be added if the modulation symbol is given by ^3/10 ^1/2 + j × ^{3/10 1/2} ). Further, in the case of a modulation symbol given by 3/10 ^1/2 + j × 1/10 ^1/2 , perturbation terms given by positive real numbers (for example, 2δ, 4δ, etc.) can be added. This is based on the property that the error rate does not deteriorate even if the signal point is shifted in the direction not surrounded by the signal determination plane in each modulation symbol.
[3.2. Terminal device 3]
Since the device configuration and signal processing of the terminal device 2 that is a nonlinear terminal device are the same as those in the first and second embodiments, the description thereof is omitted. Below, the terminal device 3 which is a linear terminal device is demonstrated.

FIG. 12 is a block diagram showing a configuration example of the terminal device 3 according to the third embodiment of the present invention. As shown in FIG. 12, the configuration of the terminal device 3 is almost the same as the configuration of the terminal device 2 shown in FIG. 6, except that the channel equalization unit 57 is replaced with a channel equalization unit 67.

The difference between the channel equalization unit 57 and the channel equalization unit 67 will be described. The channel equalization unit 57 performs channel equalization on the received data signal based on the channel estimation value estimated by the channel estimation unit 53 based on DMRS. The channel equalization unit 57 performs a modulo operation on the channel-equalized signal, and then outputs the signal to the demapping unit 59. On the other hand, the channel equalization unit 67 outputs the channel equalization output to the demapping unit 59 without performing a modulo operation.

The terminal device 2 can remove the influence of the perturbation term by performing demodulation with the perturbation term in the channel decoding unit without performing the modulo operation in the channel equalization unit 57. Has already been described in the first embodiment. In this case, the difference between the terminal device 2 and the terminal device 3 is signal processing in the channel decoding unit 63. The terminal device 2 performs channel decoding taking into account the perturbation term, whereas the terminal device 3 uses the perturbation term. Channel decoding without consideration is performed.

Since the signal processing in other constituent devices except the channel equalization unit 67 is the same as that of the terminal device 2, the description thereof is omitted. Note that the signal processing in other constituent devices may be different between the terminal device 2 and the terminal device 3. For example, the case where the terminal device 2 and the terminal device 3 differ in the control information generation method associated with the propagation path information generated by the feedback information generation unit 55 is also included in the present embodiment.

In the present embodiment, as a terminal device connected to the base station device 1, there are a non-linear terminal device that performs a modulo operation on a received signal and a linear terminal device that does not perform a modulo operation on the received signal. Targeted for mixed cases. According to the method of the present embodiment, it is possible to multiplex terminals having different signal processing that can be performed on a received signal with high efficiency, so communication while reducing the burden of user scheduling and the like. It becomes possible to improve the frequency utilization efficiency of the system.

[4. Common to all embodiments]
The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to the embodiment, and the design and the like within the scope not departing from the gist of the present invention are also claimed. include.

Note that the present invention is not limited to the above-described embodiment. The terminal device 2 and the terminal device 3 of the present invention are not limited to application to a terminal device such as a cellular system, but are stationary or non-movable electronic devices installed indoors and outdoors, such as AV devices. Needless to say, it can be applied to kitchen equipment, cleaning / washing equipment, air conditioning equipment, office equipment, vending machines, and other daily life equipment.

A program that operates on the terminal device 2, the terminal device 3, the base station device 1, and the base station device 1b according to the present invention is a program (computer) that controls the CPU and the like so as to realize the functions of the above-described embodiments according to the present invention Is a program that functions). Information handled by these devices is temporarily stored in the RAM at the time of processing, then stored in various ROMs and HDDs, read out by the CPU, and corrected and written as necessary. As a recording medium for storing the program, a semiconductor medium (for example, ROM, nonvolatile memory card, etc.), an optical recording medium (for example, DVD, MO, MD, CD, BD, etc.), a magnetic recording medium (for example, magnetic tape, Any of a flexible disk etc. may be sufficient. In addition, by executing the loaded program, not only the functions of the above-described embodiment are realized, but also based on the instructions of the program, the processing is performed in cooperation with the operating system or other application programs. The functions of the invention may be realized.

Also, when distributing to the market, the program can be stored and distributed on a portable recording medium, or transferred to a server computer connected via a network such as the Internet. In this case, the storage device of the server computer is also included in the present invention. Moreover, you may implement | achieve part or all of the terminal device 2, the terminal device 3, the base station apparatus 1, and the base station apparatus 1b in embodiment mentioned above as LSI which is typically an integrated circuit. Each functional block of the terminal device 2, the terminal device 3, the base station device 1, and the base station device 1b may be individually made into a processor, or a part or all of them may be integrated into a processor. Further, the method of circuit integration is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. In addition, when an integrated circuit technology that replaces LSI appears due to progress in semiconductor technology, an integrated circuit based on the technology can also be used.

[Summary]
(1) In order to achieve the above object, the present invention takes the following measures. That is, the base station apparatus of the present invention is a base station apparatus that includes a plurality of antennas, performs non-linear precoding on a signal addressed to a plurality of terminal apparatuses, performs spatial multiplexing, and performs radio transmission. A channel information acquisition unit for acquiring channel information, a mapping unit for multiplexing the data signals addressed to the plurality of terminal devices and a demodulation reference signal, and the data signal and the demodulation reference signal based on the channel information A precoding unit that performs precoding on the first linear filter that multiplies the data signal based on the propagation path information, and a second that multiplies the reference signal for demodulation. And a linear filter generation unit that generates different linear filters.

Such a base station apparatus can use a linear filter different from the first linear filter that multiplies the data signal addressed to the terminal apparatus as the second linear filter that multiplies the demodulation reference signal addressed to the terminal apparatus. . Therefore, the terminal apparatus can estimate the modulo width with high accuracy based on the demodulation reference signal transmitted from the base station apparatus. As a result, frequency utilization efficiency can be improved.

(2) Further, in the base station apparatus of the present invention, the first linear filter is a mean square between a reception signal received by each of the plurality of terminal apparatuses and the data signal addressed to the plurality of terminal apparatuses. It is calculated based on a standard that minimizes the error.

In such a base station apparatus, the first station is based on a standard that minimizes a mean square error between received signals respectively received by the plurality of terminal apparatuses and the data signals addressed to the plurality of terminal apparatuses. A linear filter can be generated. Therefore, the terminal device can demodulate the data signal transmitted from the base station device with high accuracy. As a result, frequency utilization efficiency can be improved.

(3) Further, in the base station apparatus of the present invention, the linear filter generation unit calculates a first diagonal matrix based on the first linear filter and the propagation path information, and The second linear filter is generated based on a diagonal matrix and the first linear filter.

Such a base station apparatus calculates a first diagonal matrix based on the first linear filter and the propagation path information, and adds the first diagonal matrix and the first linear filter to the first diagonal filter. Based on this, the second linear filter can be generated. Therefore, the terminal apparatus can estimate the modulo width with high accuracy based on the demodulation reference signal transmitted from the base station apparatus. As a result, frequency utilization efficiency can be improved.

(4) In the base station apparatus of the present invention, the first diagonal matrix is configured by an inverse of a diagonal component of a matrix represented by a product of the first linear filter and the propagation path matrix. It is a diagonal matrix.

Such a base station apparatus uses, as the first diagonal matrix, a diagonal matrix composed of the inverse of the diagonal component of the matrix represented by the product of the first linear filter and the propagation path matrix. And the second linear filter can be generated based on the first diagonal matrix. Therefore, the terminal apparatus can estimate the modulo width with high accuracy based on the demodulation reference signal transmitted from the base station apparatus. As a result, frequency utilization efficiency can be improved.

(5) Further, in the base station apparatus of the present invention, the linear filter generation unit includes the feedback filter and the first filter based on LQ decomposition or QR decomposition on the expanded channel matrix calculated based on the channel information. A linear filter is generated, and the precoding unit further includes a THP unit that performs interference suppression and modulo operation on the data signal based on the feedback filter.

Such a base station device generates a feedback filter and the first linear filter based on LQ decomposition or QR decomposition on the expanded channel matrix calculated based on the channel information, and based on the feedback filter The data signal can be subjected to interference suppression and modulo arithmetic. Therefore, the terminal device can demodulate the data signal transmitted from the base station device with high accuracy. As a result, frequency utilization efficiency can be improved.

(6) In the base station apparatus of the present invention, the precoding unit further includes a perturbation vector search unit that searches for a perturbation vector based on the first linear filter and the data signal. The base station apparatus described in (1).

Such a base station apparatus can search for a perturbation vector based on the first linear filter and the data signal. Therefore, the required transmission power of the base station device can be reduced. As a result, frequency utilization efficiency can be improved.

(7) In the base station apparatus of the present invention, the precoding unit adds a perturbation vector to a non-linear terminal apparatus that can remove a perturbation vector from a received signal among the plurality of terminal apparatuses to be spatially multiplexed. The base station apparatus according to (4), wherein the base station apparatus generates a data signal that does not add a perturbation vector to a linear terminal apparatus that generates a processed data signal and cannot remove the perturbation vector from the received signal. And

Such a base station apparatus generates a data signal obtained by adding a perturbation vector to a non-linear terminal apparatus that can remove a perturbation vector from a received signal among a plurality of spatially multiplexed terminal apparatuses, and generates a perturbation vector from the received signal. It is possible to generate a data signal that does not add a perturbation vector to a linear terminal device that cannot be removed. Therefore, the base station apparatus can flexibly determine a combination of a plurality of terminal apparatuses that transmit the data signal and the demodulation reference signal. As a result, frequency utilization efficiency can be improved.

(8) Moreover, the base station apparatus of the present invention is the base station apparatus according to (7), wherein the precoding unit adds a perturbation vector to a part of the data signal addressed to the linear terminal apparatus. It is characterized by.

Such a base station device can add a perturbation vector to a part of the data signal addressed to the linear terminal device. Therefore, the required transmission power of the base station apparatus can be reduced. As a result, frequency utilization efficiency can be improved.

(9) In addition, the precoding method of the present invention is a method of propagating data signals and demodulation reference signals transmitted from a base station apparatus having a plurality of antennas to a plurality of terminal apparatuses between the plurality of terminal apparatuses. A precoding method for performing preliminary processing based on path information, a step of calculating a first linear filter, a second linear filter and a feedback filter based on the propagation path information, Based on the transmission signal and the first linear filter, the transmission data signal and the power normalization coefficient are calculated based on the process of calculating the transmission code by performing interference suppression and modulo arithmetic on the data signal. And a process for calculating a transmission demodulation reference signal based on the demodulation reference signal, the second linear filter, and the power normalization coefficient. When, characterized by having a a process of adjusting the transmission power of the transmission data signal and said transmission demodulation reference signal.

Such a precoding method is based on data signals and demodulation reference signals transmitted from a base station apparatus having a plurality of antennas to a plurality of terminal apparatuses based on propagation path information between the plurality of terminal apparatuses. Preliminary processing can be performed. Therefore, the terminal apparatus can estimate the modulo width with high accuracy based on the demodulation reference signal transmitted from the base station apparatus. Further, the terminal device can demodulate the data signal transmitted from the base station device with high accuracy. As a result, frequency utilization efficiency can be improved.

(10) In addition, the precoding method of the present invention propagates data signals and demodulation reference signals transmitted from a base station apparatus having a plurality of antennas to a plurality of terminal apparatuses between the plurality of terminal apparatuses. A precoding method for performing preliminary processing based on path information, a process of calculating a first linear filter and a second linear filter based on the propagation path information, the data signal, Searching a perturbation vector based on a first linear filter; calculating a transmission data signal and a power normalization coefficient based on the data signal, the first linear filter and the perturbation vector; A process of calculating a reference signal for transmission demodulation based on the demodulation reference signal, the second linear filter, and the power normalization coefficient, and the transmission data signal and the transmission recovery signal A process of adjusting the transmit power of the use reference signals, that has the features.

Such a precoding method is based on data signals and demodulation reference signals transmitted from a base station apparatus having a plurality of antennas to a plurality of terminal apparatuses based on propagation path information between the plurality of terminal apparatuses. Preliminary processing can be performed. Therefore, the base station apparatus can reduce the required transmission power. Further, the terminal apparatus can estimate the modulo width with high accuracy based on the demodulation reference signal transmitted from the base station apparatus. As a result, frequency utilization efficiency can be improved.

(11) Further, an integrated circuit according to the present invention is mounted on a base station apparatus that includes a plurality of antennas, performs non-linear precoding on signals addressed to a plurality of terminal apparatuses, performs spatial transmission, and performs radio transmission. An integrated circuit that exhibits a plurality of functions, a function of acquiring propagation path information between the terminal devices, a function of multiplexing data signals and demodulation reference signals addressed to the terminal devices, A function of performing precoding on the data signal and the demodulation reference signal based on propagation path information, and the function of performing the precoding is based on the propagation path information. The first linear filter for multiplying and the second linear filter for multiplying the demodulation reference signal are generated differently.

Such an integrated circuit includes a plurality of antennas, is implemented in a base station apparatus that performs non-linear precoding on signals addressed to a plurality of terminal apparatuses and performs spatial transmission and performs wireless transmission, and the base station apparatus has a plurality of functions. It can be demonstrated. Therefore, the terminal apparatus can estimate the modulo width with high accuracy based on the demodulation reference signal transmitted from the base station apparatus. Further, the terminal device can demodulate the data signal transmitted from the base station device with high accuracy. As a result, frequency utilization efficiency can be improved.

(12) In addition, the wireless communication system of the present invention includes the base station device described in (1) above and a plurality of terminal devices that respectively receive signals transmitted from the base station device.

Such a wireless communication system can include the base station apparatus described in (1) above and a plurality of terminal apparatuses that respectively receive signals transmitted from the base station apparatus. Therefore, the terminal apparatus can estimate the modulo width with high accuracy based on the demodulation reference signal transmitted from the base station apparatus. Further, the terminal device can demodulate the data signal transmitted from the base station device with high accuracy. As a result, frequency utilization efficiency can be improved.

The present invention is suitable for use in base station apparatuses, precoding methods, integrated circuits, and wireless communication systems.

1, 1b Base station apparatus 2, 2-1, 2-2, 2-3, 2-4, 2-u, 3-1, 3-2 Terminal apparatus 21 Channel encoding unit 23 Data modulation unit 25 Mapping Units 27, 35, 37 precoding units 27-1, 35-1, 37-1 switch units 27-2, 35-2, 37-2 linear filter generation unit 27-4 THP units 27-5, 35-5, 37-5 Transmission Data Signal Generation Units 27-6, 35-6, 37-6 Transmission DMRS Generation Units 27-7, 35-7, 37-7 Transmission Signal Generation Unit 29 Antenna Unit 29-1 IFFT Unit 29-2 GI Insertion unit 29-3 Wireless transmission unit 29-4 Wireless reception unit 29-5 Antenna 31 Control information acquisition unit 33 Propagation path information acquisition unit 35-3, 37-3 Perturbation vector search unit 51 Terminal antenna unit 51-1 Radio reception unit 51-2 Wireless Transmitter 51-3 G I removing unit 51-4 FFT unit 51-5 reference signal separating unit 51-6 antenna 53, 71 propagation path estimating unit 55 feedback information generating unit 57, 67 channel equalizing unit 59 demapping unit 61 data demodulating unit 63 channel decoding unit

Claims

A base station apparatus that includes a plurality of antennas, performs non-linear precoding on signals addressed to a plurality of terminal apparatuses, performs spatial transmission, and performs radio transmission.
A propagation path information acquisition unit for acquiring propagation path information with the terminal device;
A mapping unit that multiplexes a data signal addressed to the plurality of terminal devices and a demodulation reference signal;
A precoding unit that precodes the data signal and the demodulation reference signal based on the propagation path information,
The precoding unit generates different linear filters of a first linear filter that multiplies the data signal and a second linear filter that multiplies the demodulation reference signal based on the propagation path information. A base station apparatus comprising a linear filter generation unit.
The first linear filter is calculated based on a norm that minimizes a mean square error between received signals respectively received by the plurality of terminal devices and the data signals addressed to the plurality of terminal devices. The base station apparatus according to claim 1.
The linear filter generation unit calculates a first diagonal matrix based on the first linear filter and the propagation path information,
The base station apparatus according to claim 2, wherein the second linear filter is generated based on the first diagonal matrix and the first linear filter.
The first diagonal matrix is a diagonal matrix composed of reciprocals of diagonal components of a matrix represented by a product of the first linear filter and a propagation path matrix. The base station apparatus as described in.
The linear filter generation unit generates a feedback filter and the first linear filter based on LQ decomposition or QR decomposition on an expanded channel matrix calculated based on the channel information,
The base station apparatus according to claim 4, wherein the precoding unit further includes a THP unit that performs interference suppression and modulo arithmetic on the data signal based on the feedback filter.
The base station apparatus according to claim 4, wherein the precoding unit further includes a perturbation vector search unit that searches for a perturbation vector based on the first linear filter and the data signal.
The precoding unit includes:
Among the plurality of terminal devices that are spatially multiplexed,
For nonlinear terminal devices that can remove the perturbation vector from the received signal, generate a data signal with the addition of the perturbation vector,
The base station apparatus according to claim 4, wherein a data signal without adding a perturbation vector is generated for a linear terminal apparatus that cannot remove a perturbation vector from a received signal.
The precoding unit includes:
The base station apparatus according to claim 7, wherein a perturbation vector is added to a part of the data signal addressed to the linear terminal apparatus.
Precoding for performing preliminary processing on data signals and demodulation reference signals transmitted from a base station apparatus having a plurality of antennas to a plurality of terminal apparatuses based on propagation path information between the plurality of terminal apparatuses A method,
Calculating a first linear filter, a second linear filter and a feedback filter based on the propagation path information;
A step of performing interference suppression and modulo operation on the data signal based on the feedback filter and calculating a transmission code;
Calculating a transmission data signal and a power normalization coefficient based on the transmission code and the first linear filter;
Calculating a transmission demodulation reference signal based on the demodulation reference signal, the second linear filter, and the power normalization coefficient;
Adjusting the transmission power of the transmission data signal and the transmission demodulation reference signal. A precoding method comprising:
Precoding for performing preliminary processing on data signals and demodulation reference signals transmitted from a base station apparatus having a plurality of antennas to a plurality of terminal apparatuses based on propagation path information between the plurality of terminal apparatuses A method,
Calculating a first linear filter and a second linear filter based on the propagation path information;
Searching for a perturbation vector based on the data signal and the first linear filter;
Calculating a transmission data signal and a power normalization coefficient based on the data signal, the first linear filter and the perturbation vector;
Calculating a transmission demodulation reference signal based on the demodulation reference signal, the second linear filter, and the power normalization coefficient;
Adjusting the transmission power of the transmission data signal and the transmission demodulation reference signal. A precoding method comprising:
An integrated circuit that includes a plurality of antennas, is mounted on a base station apparatus that performs non-linear precoding on signals addressed to a plurality of terminal apparatuses and performs spatial transmission and performs wireless transmission, and allows the base station apparatus to perform a plurality of functions. ,
A function of acquiring propagation path information with the terminal device;
A function of multiplexing data signals and demodulation reference signals addressed to the plurality of terminal devices;
A function of precoding the data signal and the demodulation reference signal based on the propagation path information, and exhibiting a series of functions,
The precoding function includes different linear filters of a first linear filter that multiplies the data signal and a second linear filter that multiplies the demodulation reference signal based on the propagation path information. An integrated circuit characterized by generating.
A wireless communication system comprising: the base station apparatus according to claim 1; and a plurality of terminal apparatuses that respectively receive signals transmitted from the base station apparatus.