JP2014132763A - Method and device for transmitting uplink signal using muti-antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of maintaining good Peak to Average Power Ratio (PAPR) or Cubic Metric (CM) properties when an uplink signal is transmitted using a MIMO scheme.SOLUTION: A hierarchical mapper 1401 performs mapping to hierarchies having the number corresponding to a specific rank. A DFT module 1402 diffuses each hierarchy signal. A specific precoding matrix which is set so that each hierarchy signal is mapped to one antenna and transmitted at the time of precoding of a precoder 1403 is selected. A time region signal is generated and CP (Cyclic Prefix) is added by an IFFT module 1404, and the hierarchy signal is transmitted to a base station through a multi-antenna 1405.

Description

  The present invention relates to a radio mobile communication system, and more particularly to a system using a MIMO scheme.

  The multi-input multi-output (MIMO) method uses a plurality of transmitting antennas and a plurality of receiving antennas, and this method can improve data transmission / reception efficiency. That is, the capacity can be increased and the performance can be improved by using a plurality of antennas at the transmitting end or the receiving end of the wireless communication system. Hereinafter, MIMO is also referred to as “multiple antenna” in this document.

  In the multi-antenna technique, when one whole message is received, the data is completed by merging pieces of data received from a plurality of antennas into one without depending on a single antenna path. When the multi-antenna technology is used, it is possible to improve the data transfer rate in a cell region of a specific size, or to increase the system coverage while ensuring the specific data transfer rate. In addition, this technology can be widely used for mobile communication user apparatuses and repeaters. According to the multi-antenna technology, it is possible to overcome the limit of transfer amount in the mobile communication according to the conventional technology using a single antenna.

  FIG. 1 is a configuration diagram of a general multiple antenna (MIMO) communication system.

N _T transmitting antennas are installed at the transmitting end, and N _R receiving antennas are installed at the receiving end. Thus, when a plurality of antennas are used at both the transmitting end and the receiving end, theoretical channel transfer is performed as compared with the case where a plurality of antennas are used only at either the transmitting end or the receiving end. Capacity increases. The increase in channel transfer capacity is proportional to the number of antennas. Therefore, the transfer rate is improved and the frequency efficiency is improved. If the maximum transfer rate when using one antenna is R _o , the transfer rate when using multiple antennas is theoretically multiplied by the following rate increase rate R _i to the above R _o. It can be increased by the amount.

R _i = min (N _T , N _R ) (Formula 1)

  For example, in a MIMO communication system using four transmission antennas and four reception antennas, a transfer rate that is four times as high as that of a single antenna system can be theoretically obtained. Since the theoretical capacity increase of such a multi-antenna system was proved in the mid-90s, various techniques for substantially improving the data transfer rate have been actively researched until now. The technology is already reflected in various wireless communication standards such as 3rd generation mobile communication and next generation wireless LAN.

  The multi-antenna technology improves the transmission rate by simultaneously transmitting a large number of data symbols using a large number of transmission antennas and a spatial diversity or transmission diversity scheme that increases transfer reliability using symbols that have passed through various channel paths. It is roughly divided into the spatial multiplexing method to be performed. In addition, by appropriately combining both of these formulas, the respective advantages can be obtained appropriately.

  In connection with multi-antenna technology, research on information theory related to multi-antenna communication capacity calculation in various channel environments and multiple access environments, radio channel measurement and model derivation research of multi-antenna systems, and improvement of transmission reliability and transmission Active research is underway from various viewpoints, including spatio-temporal signal processing technology research to improve rates.

  Currently, in the third generation partnership project long-term evolution (3GPP LTE) system, the above MIMO scheme is applied only to downlink signal transfer. The MIMO scheme can also be used for uplink signal transfer. In this case, the transmission end structure must be changed to implement MIMO, and the peak power to average power ratio (PAPR) or third order metric (CM: The characteristic (cubic metric) may be deteriorated. Therefore, a technique for efficiently applying the MIMO scheme to uplink signal transfer is desired.

  An object of the present invention is to provide a technique for efficiently performing uplink signal transfer using a MIMO scheme.

  In one aspect of the present invention for solving the above problems, a method is provided in which a user equipment transmits uplink signals using multiple antennas.

  Other advantages, objects, and features of the present invention will be set forth in part in the description that follows, and will be apparent in part by those skilled in the art upon examination of the following description or learned by practicing the invention. Will. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the drawings.

  The method includes the steps of mapping an uplink signal to a predetermined number of layers, performing discrete Fourier transform (DFT) spreading on each of the predetermined number of layer signals, and a code table stored in advance. Selecting a specific precoding matrix configured to transmit one layer signal for each antenna, precoding each layer signal that has been DFT-spread, and a single signal for the precoded signal. Processing for carrier frequency division multiple access (SC-FDMA) symbol configuration and transferring to the base station through the multiple antennas.

  Here, the specific precoding matrix may be set so that the transfer powers of the multiple antennas are equal, or may be set so that the transfer powers of the predetermined number of layers are equal.

のような形態を有し、

の条件を満たす第１タイプのプリコーディング行列を含むことができる。 The code table is a rank 2 precoding matrix used when the number of the multiple antennas is 4 and the rank is 2.

Has a form like

A first type precoding matrix that satisfies the following condition may be included.

のような形態を有する第２タイプのプリコーディング行列、及び、

のような形態を有する第３タイプのプリコーディング行列をさらに含むことができる。 Further, the rank-2 precoding matrix is a precoding matrix of a type in which the position of each row of the first type precoding matrix is changed, specifically,

A second type of precoding matrix having the form

A third type precoding matrix having the following form may be further included.

  Here, each row of the precoding matrix corresponds to each of the four multiple antennas, and each column corresponds to each layer.

  In addition, the rank-2 precoding matrix may further include a precoding matrix in which the position of each column of the first type precoding matrix is changed.

のような形態を有し、

の条件を満たす第１タイプのプリコーディング行列を含むことができ、さらに、前記ランク３プリコーディング行列は、前記第１タイプのプリコーディング行列の、各行の位置が変更されたタイプのプリコーディング行列及び／又は前記第１タイプのプリコーディング行列の、各列の位置が変更されたタイプのプリコーディング行列をさらに含むことができる。すなわち、前記符号表は、前記多重アンテナの個数が４個であり、前記ランクが３の場合に用いられるランク３プリコーディング行列であって、第１階層が第１アンテナ及び第２アンテナに分散してマッピングされ、第２階層及び第３階層がそれぞれ第３アンテナ及び第４アンテナにマッピングされて転送されるように設計されたプリコーディング行列を含むことができる。 The code table is a rank 3 precoding matrix used when the number of the multiple antennas is 4 and the rank is 3.

Has a form like

The rank-3 precoding matrix may include a precoding matrix of a type in which the position of each row of the first type of precoding matrix is changed, and It may further include a precoding matrix of a type in which the position of each column of the first type precoding matrix is changed. That is, the code table is a rank 3 precoding matrix used when the number of the multiple antennas is 4 and the rank is 3, and the first layer is distributed to the first antenna and the second antenna. The second layer and the third layer may include a precoding matrix designed to be mapped and transferred to the third antenna and the fourth antenna, respectively.

の形をとる場合、第１列が一つの符号語にだけマップされる階層にマップされ、第２列及び第３列は残りの符号語にマップされる階層にマップされる。 When the number of antennas is 4, the rank is 3, and the number of codewords is 2, one of the codewords is mapped to one layer, and the remaining codewords are mapped to two layers. The precoding matrix may be configured such that the total transmission power from each layer is different in order to make the transmission power uniform among multiple antennas. In this case, a column of a precoding matrix having a larger transmission power is mapped to a hierarchy that is mapped to one codeword. In this way the precoding matrix is

The first column is mapped to a hierarchy that is mapped to only one codeword, and the second and third columns are mapped to the hierarchy that is mapped to the remaining codewords.

  The code table preferably includes a different number of precoding matrices for each rank.

  The uplink signal may be input in codeword units, and the layer mapping step may include a step of periodically changing a layer to which a specific codeword is mapped. In this case, the period may be 1 SC-FDMA symbol.

  On the other hand, in another aspect of the present invention for solving the above-described problem, a user apparatus for transferring a signal in uplink through multiple antennas is provided. The user apparatus includes: a signal transmission / reception multiplex antenna; a memory for storing a code table including a precoding matrix set to transfer one hierarchical signal for each of the multiplex antennas; the multiplex antenna and the memory And a processor for processing the uplink signal transfer, wherein the processor maps the uplink signal to a number of layers corresponding to the specific rank, and the predetermined number of layers. From a DFT module that performs DFT spreading for each signal and a code table stored in the memory, select a specific precoding matrix that is set so that one hierarchical signal is transferred for each of the multiple antennas. The respective DFT-spread hierarchical signals received from the DFT module Comprising a precoder for recoding, a transfer module for transferring to the base station via the multiple antennas the the precoded signal by performing processing for SC-FDMA symbols constituting the.

  Here, the memory stores the code table as described above, and the processor performs antenna shift and / or layer shift separately from the precoder precoding or in the matrix in the precoding. It can be configured to do by row and / or column replacement.

  It is understood that both the foregoing general description and the following detailed description of the invention are exemplary and explanatory and are intended to illustrate the invention as claimed in the claims in more detail. I want to be.

  According to the present invention, it is possible to maintain good PAPR or CM characteristics in uplink signal transfer using the MIMO scheme.

  It is also possible to obtain the maximum diversity gain while uniformly adjusting the antenna / layer transmission power and minimizing the signaling overhead required for precoding matrix information.

  The drawings accompanying the present application are provided and incorporated to provide a further understanding of the invention, and are a part of the application, illustrate the invention, and explain the principles of the invention.

1 is a configuration diagram of a general multiple antenna (MIMO) communication system. It is a figure which shows the general structure of the transmission end which uses MIMO. It is a figure which shows the general structure of the transmission end which uses MIMO. It is a figure which shows the process in which the information of each hierarchy is precoded and transmitted through an antenna. It is a figure for demonstrating a general SC-FDMA system. FIG. 3 is a diagram illustrating a method in which codewords are mapped to multiple hierarchies. FIG. 6 is a diagram illustrating a method of performing DFT for each layer after codeword layer mapping is performed in order to prevent an increase in CM value for each antenna according to an embodiment of the present invention. It is a figure which shows the method of replacing the position of the column or row of a precoding matrix. It is a figure for demonstrating the concept of a chord distance. It is a figure for demonstrating the structure of a general base station and a user apparatus. FIG. 3 is a diagram for explaining an SC-FDMA scheme for uplink signal transfer and an orthogonal frequency division multiple access (OFDMA) scheme for downlink signal transfer in a 3GPP LTE system. FIG. 3 is a diagram for explaining an SC-FDMA scheme for uplink signal transfer and an OFDMA scheme for downlink signal transfer in a 3GPP LTE system. It is a figure which shows the processor structure for a base station to transfer a downlink signal by a MIMO system in 3GPP LTE system. It is a figure which shows concretely the processor structure of the user apparatus by preferable one Embodiment of this invention.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like elements.

  The detailed description disclosed below in connection with the appended drawings is intended as a description of exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced. The following detailed description includes specific details in order to assist in a thorough understanding of the present invention. However, it will be understood by those skilled in the art that the present invention may be practiced without such specific details. For example, in the following description, explanation will be made mainly on certain terms, but the term is not limited to these terms, and the same meaning can be shown even when referred to by arbitrary terms. Throughout this specification, the same or similar components will be described using the same reference numerals.

  PAPR is a parameter indicating the characteristics of the waveform. This value is a dimensionless value obtained by dividing the maximum amplitude of the waveform by the time-averaged mean square root (RMS) value of the waveform. Mainly, the PAPR of a single carrier signal is better than the PAPR of a multicarrier signal.

  In LTE-Advanced, MIMO can be implemented using SC-FDMA in order to maintain good CM characteristics. When general precoding is used, signals including information corresponding to a number of layers are multiplexed and transferred through one antenna. Therefore, a signal transferred through the antenna is regarded as a kind of multi-carrier signal. be able to. The PAPR is associated with the dynamic range that the power amplifier must apply on the transmission side, and the CM value is another numerical value that can be substituted for the numerical value represented by the PAPR.

  FIG. 2 is a diagram illustrating a general structure of a transmission end using MIMO.

  One or a plurality of code words are mapped to a plurality of hierarchies. The mapped information is mapped and transferred to each physical antenna by precoding.

  FIG. 3 is a diagram showing in more detail the transmission end using the MIMO shown in FIG.

  “Codeword” refers to data coded with a specific coding scheme after cyclic redundancy check (CRC) bits are added to the data information. There are various coding schemes including a turbo code and a tail biting convolutional code. Each codeword is mapped to one or more (virtual) layers, and the number of all layers mapped at this time is a rank value. That is, if the transmission rank is 3, the total number of layers to be transmitted is 3. Information mapped to each layer undergoes a precoding process. Here, the data information mapped to the hierarchy is mapped to the physical hierarchy by precoding (here, “hierarchy” refers to a virtual hierarchy unless specifically referred to as a physical hierarchy). Information is transmitted to each antenna through each physical layer. Unless otherwise mentioned in FIG. 3, precoding is performed in the frequency domain, and orthogonal frequency division multiplexing (OFDM) information transfer scheme is used for information mapped to the physical layer. The information mapped to the physical layer is mapped to a specific frequency region, and then subjected to IFFT calculation. Thereafter, a cyclic prefix (CP) is added. Thereafter, information is transmitted to each antenna through a radio frequency (RF) circuit group.

Precoding can be performed by a matrix multiplication method. In this matrix, the number of rows is the same as the number of physical layers, that is, the number of antennas, and the number of columns is the same as the rank value. Since the rank value is the same as the number of layers, the number of columns is the same as the number of layers. Referring to Equation 2, the information mapped to the (virtual) layer is x ₁ and x ₂ , and each element p _ij of the 4 × 2 matrix is a weight value used for precoding. y ₁ , y ₂ , y ₃ , and y ₁₄ are information mapped to the physical layer, and are transferred for each antenna using an individual OFDM transfer method.

・・・ （式２）

... (Formula 2)

  Hereinafter, unless there is confusion, the virtual layer is abbreviated as “layer”, and the mapping of the virtual layer signal to the physical layer by precoding is expressed as “the layer is mapped to the antenna”.

  Precoding can be roughly divided into two methods. Wideband precoding and subband precoding are these.

  Wideband precoding refers to a method of using the same precoding matrix for all information transferred in the frequency domain when performing precoding in the frequency domain.

  FIG. 4 is a diagram illustrating a process in which information of each layer is precoded and transferred through an antenna.

  Referring to FIG. 4, it can be seen that information corresponding to a plurality of layers is precoded for each subcarrier in each frequency domain and transmitted through each antenna. At this time, in wideband precoding, the precoding matrix 'P' to be used is the same.

  Subband precoding is an extension of wideband precoding and refers to a method of using a plurality of precoding matrices for each subcarrier without using the same precoding matrix for all subcarriers. That is, a method of using precoding matrix 'P' for a specific subcarrier and using precoding matrix 'M' for other subcarriers is referred to as subband precoding. Here, P and M are matrices having different element values.

  Uplink signal transfer is relatively sensitive to PAPR or CM characteristics compared to downlink signal transfer. This is because an increase in the filter price accompanying an increase in PAPR or CM can be fatal relative to the user equipment. Therefore, the SC-FDMA scheme is mainly used for uplink signal transfer.

  FIG. 5 is a diagram for explaining a general SC-FDMA system.

  As shown in FIG. 5, both the OFDM scheme and the SC-FDMA scheme convert a serial signal in parallel, map the parallel signal to a subcarrier, and after IDFT or IFFT processing, convert the serial signal again to a serial signal. It is the same in the aspect of transferring the signal through the RF module after the addition. However, in the SC-FDMA system, after the parallel signal is converted into the serial signal, DFT spreading is performed, thereby reducing the influence of the subsequent IDFT or IFFT processing and maintaining the single signal characteristic at a certain level or more. It is characterized by.

  On the other hand, when the MIMO scheme is applied during uplink signal transfer, considering the reason why the CM value decreases, the CM value of the superimposed signal decreases when multiple single carrier signals with good CM are simultaneously superimposed. There are things to do. Therefore, in the SC-FDMA system, when information output from a plurality of layers is multiplexed and transmitted through as few single carrier signals as possible and one physical antenna, a transmission signal having a good CM is generated. be able to.

  Codeword hierarchy mapping can be performed before precoding the information to be transmitted. Since the SC-FDMA system is mainly used at 1 Tx, the number of layers is one. However, when MIMO is applied in SC-FDMA, there are a plurality of layers, and a codeword consisting of one transfer block can be mapped to a plurality of layers.

  FIG. 6 is a diagram illustrating a method in which codewords are mapped to multiple hierarchies.

  Referring to FIG. 6, when codeword layer mapping is performed after DFT for SC-FDMA is performed, the CM value can be increased. That is, the signal output from the DFT block may go through another process before being subjected to IFFT processing, that is, through a process of being separated into two layers, and thus the CM value may increase.

  FIG. 7 is an embodiment of the present invention, and proposes a method of performing DFT for each layer after codeword layer mapping is performed in order to prevent an increase in CM value for each antenna.

  Therefore, when the number of DFT blocks varies depending on the number of layers according to the rank value, the CM value can be kept low. That is, the signal output from the DFT block is directly input to the IFFT block without going through another processing process, so that the CM value can be kept low. When actually implemented, a plurality of layers may share one DFT block.

  Similarly, when a plurality of hierarchical signals are transferred to one antenna using the MIMO scheme in uplink signal transfer, the PAPR or CM characteristics may be similarly reduced. Therefore, in the embodiment of the present invention described below, it is proposed to design a code table so as to use a precoding matrix set so that only one layer is transferred to one antenna.

  In the following, for ease of explanation, a set of signals transmitted to the precoding block in the transmission system is x, and a set of precoded signals is y. In this case, if the precoding matrix is P, Equation 3 is established.

    y = P · x (Formula 3)

Here, the dimension of P is N _T × N _L , the dimension of x is N _L × 1, and the dimension of y is N _T × 1. Here, N _T represents the number of antennas, and N _L represents the number of layers.

Below,
I. First, the code table design principle that can be used when the user equipment applies the MIMO technique and the uplink signal is transferred is described.
II. A specific form of a code table selected in consideration of chordal distance among precoding matrices satisfying the principle described in I will be described.

I. Code table design principle
<2Tx code table>
Hereinafter, an embodiment of the present invention relating to the structure of a precoding matrix constituting a code table used in the 2Tx mode will be described.

  The present invention includes a step of mapping a codeword to a plurality of layers to generate a plurality of streams, and a step of precoding the generated plurality of streams to map to a plurality of antennas for transmission. Here, the code table can be configured as follows. The precoding matrix used for rank 1 and the precoding matrix used for rank 2 will be described separately.

For a 2Tx-Rank 1 precoding matrix 2Tx-Rank 1, according to one embodiment of the present invention, Equation 3 can be rewritten as Equation 4.

・・・ （式４）

... (Formula 4)

  In general, if wideband precoding is used, in rank 1 precoding, a signal of each layer is multiplied by a specific constant value. Therefore, the PAPR or CM value of a signal transferred through each antenna at 2Tx is 1Tx. It is the same as the PAPR or CM value of the transferred signal. Therefore, when using wideband precoding, PAPR and CM are not affected by the value of the 2Tx-rank 1 precoding matrix.

になりうる。 Precoding is a method of changing channels so that signals transferred through each channel are reinforced. This improves signal transmission performance. Therefore, in Equation 4, “a”, which is the first element of P, can be set to 1, and “b”, which is the second element, can be set to an arbitrary value. In addition, by making the power of signals transferred through each antenna the same, all power amplifiers provided in each antenna can be used to the maximum. For this purpose, the second element can be a complex value of absolute value 1. That is, in Equation 4,

Can be.

において

とすることができる。すなわち、

となりうる。 There is a limit to the number of precoding matrices included in the code table used for precoding. This is because both the transmitting end and the receiving end must have code tables, and in some cases, information related to a certain precoding matrix is exchanged. Therefore, only a limited number of precoding matrices must be used. For this purpose, for example, as each element of the precoding matrix, the absolute value is 1, and the phase is + 0 °, + 45 °, + 90 °, + 135 °, + 180 °, −135 °, −90 °, − A complex number corresponding to any one of 45 ° can be used. That is,

In

It can be. That is,

It can be.

In the case of 2Tx-rank 2 precoding matrix 2Tx-rank 2, Equation 3 can be rewritten as Equation 5.

・・・ （式５）

... (Formula 5)

The signal y _k transferred through the antenna as shown in Equation 5 is composed of a combination of a plurality of input signals x _i , and thus the CM value may increase.

Here, if p ₁₂ and p ₂₁ , or p ₁₁ and p ₂₂ are set to 0, only one signal can be transmitted for each antenna. Therefore, if a good CM value of a signal x _i, also becomes favorable CM value of the precoded signal. As described above with reference to FIG. 7, after codewords are mapped to layers, DFT spreading is performed on signals mapped to the layers, and precoding is performed so that only one layer signal is transferred for each antenna. Then, the effect of performing the IDFT or IFFT processing directly after the DFT processing can be obtained, and the PAPR or CM characteristics can be maintained well. This will be described in more detail later.

In this case, if p ₁₂ and p ₂₁ are 0, a signal corresponding to each layer is transmitted from each antenna after being multiplied by an arbitrary constant complex value, and thus the multiplied complex value is set to 1. Setting will not affect performance.

  Thus, according to one embodiment of the present invention, Equation 5 can be rewritten as Equation 6.

・・・ （式６）

... (Formula 6)

<4Tx code table>
Hereinafter, embodiments of the present invention relating to the structure of a precoding matrix constituting a code table used in the 4Tx mode will be described.

  The present invention includes a step of mapping a codeword to a plurality of layers to generate a plurality of streams, and a step of precoding the generated plurality of streams to map to a plurality of antennas for transmission. Here, the code table can be configured as follows. The precoding matrices used for rank 1, rank 2, rank 3, and rank 4 will be described separately.

In the case of 4Tx-rank 1 precoding matrix 4Tx-rank 1, Equation 3 can be rewritten as Equation 7.

・・・ （式７）

... (Formula 7)

  As in the case of 2Tx-Rank 1 code table, when wideband precoding is used, the CM of the signal transferred for each antenna by 4Tx-Rank 1 precoding is the same as the CM of the signal at 1Tx. Therefore, any precoding matrix can be used for CM.

In the case of 4Tx-rank 2 precoding matrix 4Tx-rank 2, Equation 3 can be rewritten as Equation 8.

・・・ （式８）

... (Formula 8)

  Similar to the 2Tx-Rank 2 code table, the 4Tx-Rank 2 code table also minimizes duplication of signals transferred for each antenna by setting a specific element of the precoding matrix to 0. Can be kept low.

In Equation 8, when p _k1 or p _k2 value is set to 0 in p _k1 x ₁ + p _k2 x ₂ which is a signal transferred for each antenna, a signal transferred for each antenna is transmitted from one layer. Therefore, the CM of the signal transferred for each antenna can be kept at a low value.

に設定することができる。この場合、式８は式９のように書き直すことができる。 In one embodiment of the present invention, in Equation 8,

Can be set to In this case, Equation 8 can be rewritten as Equation 9.

・・・ （式９）

(Equation 9)

  Referring to Equation 9, only one layer is mapped to a signal transferred for each antenna. From the standpoint of one layer, it can be considered that 2Tx-rank 1 precoding is used for information transferred through this one layer. Accordingly, a 4Tx-rank 2 precoding matrix can be generated using a 2Tx-rank 1 precoding matrix. That is, the 4Tx-rank 2 precoding matrix can be a super matrix of the 2Tx-rank 1 precoding matrix.

  For example, P according to an embodiment of the present invention may be given by Equation 10.

・・・ （式１０）

(Equation 10)

  The precoding matrix presented above is for a method of transferring information using two antennas for a signal of one layer. However, when four physical antennas are provided, the communication performance may change depending on which combination is used for transfer among various antenna combinations including two antennas. In this case, the combination of selected antennas may change according to the value of the precoding matrix P.

  For example, according to an embodiment of the present invention, the precoding matrix P may have various forms as shown in Equation 11, and each form represents a different antenna combination.

・・・ （式１１）

(Equation 11)

  When an appropriate value is selected as the precoding matrix P in Equation 11, the performance by precoding can be improved. When the precoding matrix is formed as described above, the signal corresponding to each layer uses two antennas out of a total of four antennas, so that the channel estimation performance between the layers can be made similar. The CM value can be minimized for each antenna.

  In general, even when a specific column vector of an arbitrary precoding matrix is multiplied by a constant value, the characteristics of the precoding matrix are not changed. Therefore, even if a specific column of the precoding matrix mentioned above is multiplied by a constant value, the characteristics of the precoding matrix are not changed. Therefore, multiplying a specific column vector of a precoding matrix according to an embodiment of the present invention by a constant value does not depart from the scope of the present invention.

  Also, the precoding matrix shown in the above equation 11 can be multiplied by a constant scaling coefficient, and can be expressed as the following equation 12.

・・・ （式１２）

... (Formula 12)

4Tx-Rank 3 precoding matrix (1)
In the case of 4Tx-Rank 3, Equation 3 can be rewritten as Equation 13.

・・・ （式１３）

(Equation 13)

  In substantially the same manner as the 4Tx-Rank 2 precoding matrix, in the 4Tx-Rank 3 precoding matrix, by setting the specific element of the precoding matrix to 0, the duplication of the signal transferred for each antenna is minimized, and thus , CM can be kept low.

In Equation 13, if p _k1 , p _k2 , or p _k3 value is set to 0 in p _k1 x ₁ + p _k2 x ₂ + p _k3 x ₃ which is a signal transferred for each antenna, it is transferred for each antenna. The signal CM can maintain a low value.

に設定することができる。この場合、式１３は式１４のように書き直すことができる。 In one embodiment of the invention, in Equation 12

Can be set to In this case, Equation 13 can be rewritten as Equation 14.

・・・ （式１４）

... (Formula 14)

  In rank 3, the number of layers to be transferred is 3, and the number of physical antennas is 4. In this case, each of the three antennas can be mapped independently to one layer. At this time, only one layer of signals can be mapped to the remaining one antenna, and signals of two or more layers can be mapped together. When only one specific layer signal is mapped to the remaining antenna, the CM of the signal transmitted through this antenna can exhibit good characteristics, but this specific one layer The communication performance of the information may be different from the communication performance of information in another layer. For example, when layer 1 information is mapped to antenna 1 and antenna 4, layer 2 information is mapped to antenna 2, and layer 3 information is mapped to antenna 3, communication performance with respect to layer 1 information is The communication performance of the layer 2 or layer 3 may be different.

In an embodiment of the present invention, the precoding matrix P may have one of the values P ₁ , P ₂ , and P ₃ of Equation 15 for the purpose of making the CM value as low as possible for each antenna in precoding. .

・・・ （式１５）

(Equation 15)

When using the above precoding matrices P ₁ , P ₂ , P ₃ , the number of antennas used for each layer is not the same. However, instead of using only _{one of} the precoding matrices P ₁ , P ₂ , and P ₃ when transferring certain information, when using P ₁ , P ₂ , and P ₃ equally, The number of antennas used for the hierarchy can be normalized. The precoding matrices P ₁ , P ₂ , P ₃ can be used alternately in the frequency domain, but according to this scheme, the single carrier characteristic of a signal already composed of a single carrier is damaged, and thus CM The value may increase. Therefore, an increase in CM can be prevented by alternately applying the precoding matrices P ₁ , P ₂ , and P ₃ for each SC-FDMA symbol. When transferring data, information can be decoded in units of one subframe. Accordingly, when the precoding matrices P ₁ , P ₂ , and P ₃ are alternately applied to each SC-FDMA symbol, the information of each layer is the same on average for the entire information transferred through one subframe. Can be transmitted through a number of antennas.

  In another embodiment of the present invention, performance can be improved by changing the position of the antenna used by each layer. Changing the position of the antenna can be done according to the flow of time, and in particular, can be changed for each SC-FDMA symbol. A specific method for changing the position of the antenna is as follows.

  That is, by changing the position of a value other than 0 in the precoding matrix within one row vector, the position of the antenna to which the signal of each layer is transferred can be changed. Alternatively, the method can be implemented by row / column permutation with a given precoding matrix.

  FIG. 8 is a diagram illustrating a method for replacing the positions of columns or rows of a precoding matrix.

  FIG. 8A shows a method for replacing row positions, and FIG. 8B shows a method for replacing column positions.

In the precoding matrix of Equation 15, the precoding matrix P ₂ or P ₃ can be generated by performing row replacement and / or column replacement on the precoding matrix P ₁ . Therefore, in a structure such as precoding matrices P ₁ , P ₂ , P ₃ , a unique new precoding matrix can be generated only by row replacement.

The order of the rows changed by possible row replacement in 4Tx is as follows:

{1, 2, 3, 4}, {1, 2, 4, 3}, {1, 3, 2, 4}, {1, 3, 4, 2},
{1, 4, 2, 3}, {1, 4, 3, 2}, {2, 1, 3, 4}, {2, 1, 4, 3},
{2, 3, 1, 4}, {2, 3, 4, 1}, {2, 4, 1, 3}, {2, 4, 3, 1},
{3, 2, 1, 4}, {3, 2, 4, 1}, {3, 1, 2, 4}, {3, 1, 4, 2},
{3, 4, 2, 1}, {3, 4, 1, 2}, {4, 2, 3, 1}, {4, 2, 1, 3},
{4, 3, 2, 1}, {4, 3, 1, 2}, {4, 1, 2, 3}, {4, 1, 3, 2}

Here, {w, x, y, z} means that when a precoding matrix P _k is given, the row vectors 1, 2, 3, and 4 of the precoding matrix are rearranged in the order in {}. Meaning.

  According to the row replacement, signals corresponding to a specific layer are mapped to different antennas, and according to the column replacement, information of different layers can be switched to each other. In particular, it is not necessary to classify the performance for each hierarchy, and in a system that requires similar performance for each hierarchy, there is no need to use the column replacement method. That is, the antenna selection effect can be obtained only by row replacement.

  On the other hand, each 4Tx-Rank 3 precoding matrix shown in Equation 15 can be multiplied by a fixed scaling factor, and the form is as shown in Equation 6 below.

・・・ （式１６）

(Equation 16)

4Tx-Rank 3 precoding matrix (2)
In the case of 4Tx-Rank 3, if each antenna transmits information corresponding to only one layer, the CM value of a signal transmitted through the antenna can be kept low, but information of one layer is 1 Since it is transmitted only through one specific antenna, the communication performance may deteriorate. Therefore, in the case of 4Tx-Rank 3, the communication performance is simultaneously reduced while minimizing the increase in CM by designing the signals of up to two layers to be multiplexed and transferred through one antenna. Can be increased.

According to an embodiment of the present invention, when transmitting information corresponding to two layers with one antenna, the precoding matrix P of Equation 13 is changed to P _{4 of} Equation 17 or P ₅ of Equation 18. Can be expressed as:

・・・ （式１７）

(Equation 17)

・・・ （式１８）

(Equation 18)

In Expression 17, to satisfy rank 3, the X value and Z value of the precoding matrix P ₄ must be different.

In the method using the precoding matrix P ₄ or P ₅ , two layers of signals are multiplexed and transferred by a specific antenna, but only one layer of signals is transferred by another antenna. There are drawbacks.

In one embodiment of the present invention, the precoding matrix P can have one of the values of P ₆ , P ₇ , and P ₈ of Equation 19 to compensate for this drawback.

・・・ （式１９）

(Equation 19)

Matrix permutation can be performed on the precoding matrices P ₄ , P ₅ , P ₆ , P ₇ , P ₈ as described above in connection with the 4Tx-Rank 3 precoding matrix. By performing matrix permutation, an antenna selection function that enables transmission of a signal in a specific layer through an arbitrary antenna can be realized by precoding.

  In one embodiment of the present invention, the column vectors of the precoding matrix can be configured to be orthogonal to each other.

  When each column vector of the precoding matrix is configured to have orthogonality, the precoding matrix satisfies the characteristics of a one-sided unitary matrix. That is, the precoding matrix P can have a characteristic as shown in Equation 20.

P ^H P = αI ≠ PP ^H (Equation 20)

  In one embodiment of the present invention, a rank 3 precoding matrix can be constructed as shown in Equation 21. The precoding matrix P that satisfies Equation 21 satisfies the relationship of Equation 20.

・・・ （式２１）

... (Formula 21)

満たすことから、プリコーディング行列Ｐが式２０を満たすということが確認できる。 In Equation 21

Since it satisfies, it can be confirmed that the precoding matrix P satisfies Expression 20.

4Tx-Rank 4 precoding matrix (1)
In the case of 4Tx-Rank 4, Equation 3 can be rewritten as Equation 22.

・・・ （式２２）

(Equation 22)

  In the case of 4Tx-rank 4, signals from four layers are multiplexed and transferred through each antenna.

  In one embodiment of the present invention, when the precoding matrix is configured by a unit matrix, only one signal corresponding to one layer is transferred by one antenna. In this case, Equation 22 can be rewritten as Equation 23.

・・・ （式２３）

(Equation 23)

4Tx-Rank 4 precoding matrix (2)
Communication performance can be improved by increasing the number of rank 4 precoding matrices in the 4Tx-rank 4 code table. As the number of precoding matrices constituting the code table increases, a precoding matrix closer to the actual channel can be selected. Therefore, as the number of precoding matrices increases, the performance can be improved. However, since selection of a precoding matrix in the code table becomes complicated, it is preferable to include an appropriate number of precoding matrices in the code table. However, in the case of 4Tx-Rank 4, in order to transfer only signals corresponding to one layer for each antenna, the precoding matrix must be a unit matrix, and a plurality of rank 4 precoding matrices are used. Then, there may be a case where signals corresponding to two or more layers must be transmitted through one antenna. Therefore, the specific element of the precoding matrix can be set to 0 in order to increase the number of rank 4 precoding matrices in the code table while minimizing the CM value. In Equation 22, two values of p _k1 , p _k2 , p _k3 and p _k4 are set to 0 in p _k1 x ₁ + p _k2 x ₂ + p _k3 x ₃ + p _k4 x ₄ which are signals transferred for each antenna. Then, the CM of the signal transferred for each antenna can maintain a low value.

In one embodiment of the present invention, the precoding matrix can be set as P ₉ in Equation 24, P ₁₀ in Equation 25, and P ₁₁ in Equation 26.

・・・ （式２４）

(Equation 24)

・・・ （式２５）

(Equation 25)

・・・ （式２６）

(Equation 26)

The precoding matrices P ₉ , P ₁₀ , and P ₁₁ are examples of precoding matrices that transfer signals of up to two layers for each antenna. As described above, by performing matrix replacement on the precoding matrices P ₉ , P ₁₀ , and P ₁₁ , signals in different layers can be transmitted through different antennas.

Since the precoding matrix P ₁₁ is a unitary matrix, the advantages of the unitary precoding matrix can be utilized.

4Tx-Rank 4 precoding matrix (3)
In the case of 4Tx-rank 4, only one element of the elements in each row of the precoding matrix can be set to zero. When this method is used, signals corresponding to three layers can be multiplexed and transmitted through one antenna, and communication performance can be improved. However, according to this method, the CM value is further increased, but has a smaller CM value than when all the elements of the precoding matrix are set to values other than 0. Therefore, this method can be used effectively in a good signal-to-noise ratio (SNR) that does not require transmission at the maximum transfer power on the transmission side.

In one embodiment the present invention, the precoding matrix P, P ₁₃ of P _12, Equation 28 of formula 27, P ₁₄ of formula 29, it can be expressed as P ₁₅ of formula 30.

・・・ （式２７）

(Equation 27)

・・・ （式２８）

(Equation 28)

・・・ （式２９）

(Equation 29)

・・・ （式３０）

(Equation 30)

Since the precoding matrix P ₁₅ of Equation 30 is a unitary matrix, the advantage of the unitary precoding matrix can be utilized.

  A matrix generated by multiplying a specific column of the above-described precoding matrix by a constant, or a matrix obtained by performing matrix replacement on the above-described precoding matrix can be used as a part of the code table.

から選択された。しかし、これは例示のためのもので、絶対値が１であり、その位相値が互いに異なる複素数から構成された集合から選択してもよい。例えば、プリコーディング行列の要素は、

（αは、任意の定数）から選択することができる。 All the elements of the precoding matrix described above have an absolute value of 1 and their phase values are + 0 °, + 45 °, + 90 °, + 135 °, + 180 °, −135 °, −90 °, −45 °. A complex number corresponding to any one was selected. That is, the elements of the precoding matrix are

Selected from However, this is for illustration, and the absolute value is 1, and the phase value may be selected from a set composed of different complex numbers. For example, the elements of the precoding matrix are

(Α is an arbitrary constant).

Power adjustment On the other hand, in the code table designed as described above, transmit power adjustment of transmit power adjustment and / or each layer of each antenna is also an important factor. If the transfer power per antenna is not adjusted as uniformly as possible, it will lead to a difference in performance for each transfer antenna. Similarly, if the power is not adjusted as uniformly as possible for each transfer layer, a performance difference will occur for each codeword.

  Therefore, in one embodiment of the present invention, the norm of all elements corresponding to each antenna in the precoding matrix (all elements in a specific row of the precoding matrix) is used to consider antenna power adjustment. We propose to design a precoding matrix. Specifically, it is proposed to use the precoding matrix represented by Equation 31 as a form in which antenna power adjustment is performed as in Equation 32.

・・・ （式３１）

... (Formula 31)

・・・ （式３２）

... (Formula 32)

  Also, in one embodiment of the present invention, a precoding matrix is designed in consideration of hierarchical power adjustment using the norm of all elements of each layer (all elements of a specific column of the precoding matrix). Propose that. Specifically, it is proposed to use the precoding matrix represented by Equation 33 as a form in which hierarchical power adjustment is performed as in Equation 34.

・・・ （式３３）

... (Formula 33)

・・・ （式３４）

... (Formula 34)

  Here, in the case of the 4Tx-rank 3 precoding matrix, the number of rows and the number of columns are different from the rank 2 precoding matrix and may not be suitable for performing the antenna power adjustment and the hierarchical power adjustment described above simultaneously. It is necessary to pay attention to the point. However, in a system using a layer shift method in which a layer used for transfer is changed according to a specific pattern at the time of transfer, for example, the effect that the performance difference is dispersed per layer can be obtained. The hierarchical power adjustment as described above may be relatively insignificant compared to the antenna power adjustment. Therefore, in an embodiment of the present invention, when antenna power adjustment and hierarchical power adjustment cannot be performed at the same time, it is proposed to use a precoding matrix in a form in which antenna power adjustment is prioritized.

  On the other hand, among the 4Tx-rank 3 precoding matrices described above, the following precoding matrix transfers two symbols for each layer, and thus it can be seen that antenna power control can be performed as follows.

・・・ （式３５）

... (Formula 35)

  Similarly, among the 4Tx-rank 3 precoding matrices described above, the following precoding matrix transfers only one symbol per antenna, and thus it can be seen that hierarchical power adjustment can be performed as follows.

・・・ （式３６）

... (Formula 36)

  Meanwhile, another embodiment of the present invention proposes that the following 4Tx-rank 3 precoding matrix includes the following precoding matrix from the viewpoint of simultaneously performing antenna power adjustment and hierarchical power adjustment.

・・・ （式３７）

... (Formula 37)

  That is, the 4Tx-Rank 3 precoding matrix uses a precoding matrix that is set so that no signal is transferred to one specific antenna.

  On the other hand, an example of a precoding matrix in which hierarchical power adjustment is performed on a 4Tx-rank 4 precoding matrix is as follows.

・・・ （式３８）

... (Formula 38)

<Code table pruning>
In the 4Tx system, a precoding matrix corresponding to rank 1, rank 2, rank 3, and rank 4 described above can be used as an element of a code table used on the transmission / reception side. However, when all the above-described precoding matrices are used, the code table is too large, and thus it is necessary to reduce the number of precoding matrices while maintaining performance to some extent. An embodiment for reducing the number of precoding matrices will be described below. The methods for constraining the precoding matrix described below can be used individually or together.

Code Table Element Alphabet Restriction All elements of the precoding matrix described above have an absolute value of 1, and their phase values are + 0 °, + 45 °, + 90 °, + 135 °, + 180 °, −135 °, −90 °, Selected from complex numbers corresponding to any one of -45 °.

  In one embodiment of the present invention, in order to reduce the number of precoding matrices, the elements of the matrix have an absolute value of 1, and the phase value is any of + 0 °, + 90 °, + 180 °, and −90 °. A complex number corresponding to one can be selected. That is, the elements of the precoding matrix can be selected from {1, j, −1, −j}.

  Alternatively, it can be used by extracting from an arbitrary N subset of 8 alphabets separated by an angle of 45 °.

When the column vectors in the limited precoding matrix are orthogonal to the unitary precoding matrix, the precoding matrix is a unitary matrix or a partial unitary matrix. If the precoding matrix has such features, additional gain can be obtained.

  Therefore, in one embodiment of the present invention, only a unitary matrix or a partial unitary matrix among all the precoding matrices described above can be collected to form a code table.

  As an example, a code table can be generated by arbitrarily combining a precoding matrix arranged in Expression 39 and a matrix obtained by performing matrix substitution on the precoding matrix arranged in Expression 40.

・・・ （式３９）

... (Formula 39)

When a restricted rank 1, rank 2, rank 3, and rank 4 precoding matrix is formed in a nested structure, a rank 2 or rank 3 precoding matrix is formed using a column vector of the rank 4 precoding matrix. This is called a precoding matrix having a nested structure. When a particular rank 4 precoding matrix is used as part of the precoding code table, the rank 3 precoding matrix must be configurable using the column vector of that rank 4 precoding matrix, There are constraints on the configuration. Therefore, the code table size can be limited by this norm.

  In one embodiment of the present invention, rank 1, rank 2, rank 3, and rank 4 precoding matrices may have a nested structure.

  For example, the code table can be configured by a combination of matrices obtained by performing matrix substitution on the precoding matrices listed in Equation 40.

・・・ （式４０）

... (Formula 40)

  In addition to the matrix expressed in the above equation, various types of applicable matrices can exist. It can be easily understood that these matrices are obtained by performing row substitution and / or column substitution on the above matrix. In the present invention, since an element having a value of 0 exists in the precoding matrix, a certain antenna may not be mapped to a specific input stream. This can also be grasped as an antenna selection function.

II. Specific form of code table The following is a method of designing a code table so as to satisfy the above-described code table design principles, and more specifically, precoding matrices for each rank in the code table are considered in consideration of chordal distance. A method of determining will be described.

  FIG. 9 is a diagram for explaining the concept of chord distance.

  Chord distance is a well-known norm that compares the performance of various codebook sets. Here, the “string” represents a straight line connecting two points located on the circumference. Accordingly, in terms of two dimensions, the chord distance represents the distance between two points on the circumference of the (unit) circle, as shown in FIG.

  In the case of a 4Tx code table, a four-dimensional chord distance must be considered, and the following equation can be used as a chord distance for selecting a code table set.

・・・ （式４１）

... (Formula 41)

は、行列のフロベニウスノルム（Ｆｒｏｂｅｎｉｕｓ ｎｏｒｍ）である。上記の弦距離は、下記のような式によっても測定可能である。 In the above equation 41, P = [v ₁ v ₂ ... V _N ], Q = [u ₁ u ₂ ... U _N ], (where v _i , u _i (i = 1, 2,... N, 4Tx In the case of an antenna, N = 4) is the basic vector of the matrices P and Q.

Is the Frobenius norm of the matrix. The chord distance can also be measured by the following equation.

・・・ （式４２）
ここで、Ａ及びＢはそれぞれＰ及びＱの正規直交生成行列（ｇｅｎｅｒａｔｉｏｎ ｍａｔｒｉｃｅｓ）である。

... (Formula 42)
Here, A and B are P and Q orthonormal generation matrices, respectively.

  Using the above chord distance concept, the above code table design will be more specific for a system using four transfer antennas (4Tx system). In the following description, for the sake of simplicity of description, the coefficient related to power adjustment is omitted.

Rank 2
First, assume the following three groups of code tables that maintain good CM performance for a 4Tx rank 2 system.

・・・ （式４３）

... (Formula 43)

Although the number of precoding matrices satisfying the above-described form is considerably large, it is preferable to design a code table including only a predetermined number of precoding matrices according to a reasonable norm. In the following, it is proposed to limit the number of precoding matrices per rank to a predetermined number or less using the following norm.
Norm 1: Chord distance Norm 2: Whether or not each group is selected uniformly (if the number of precoding matrices / vectors in the code table is not divisible by the number of groups, consider the norm 1 above and be as uniform as possible To select.)

  It is proposed that such a norm is applied equally to ranks 3 and 4 described below.

Specifically, in an embodiment of the present invention, it is proposed to select a precoding matrix set from a code table for a specific rank using the norm 1. As a first step, the chord distance is calculated using the above equation 42 for all precoding matrix pairs in one code table. For example, if there are four code table sets, the four minimum chord distance values can be calculated as follows:
d ¹ _{c, min} = 1, d ² _{c, min} = 0.56, d ³ _{c, min} = 0.71 and d ⁴ _{c, min} = 1

In this ^case, d _i ^c, _{min (i,} the code table set number) because higher system performance greater value is improved, it is preferable that first and fourth code table proceeds to the next selection round.

  As a second step, it is proposed to select a precoding matrix as equally as possible for each group for application in various radio channel environments. For example, if there are 3 code table groups and 16 precoding matrices are required as a rank 2 code table, 5 precoding matrices are selected from the 2 groups and 6 precoding matrices remain. Propose to be selected from one group. For example, it is proposed that 5 precoding matrices are selected from the first 2 groups and 6 precoding matrices are selected from the last 1 group. In the embodiment of the present invention, as described above, it is possible to consider restricting the element value (alphabet) of each precoding matrix (for example, limiting to X = 1, j, −1, −j). An example of a code table for 4Tx rank 2 that can be configured by the process as described above is as follows.

ランク２符号表セット２−１

ランク２符号表セット３−１

ランク２符号表セット４−１

ランク２符号表セット５−１

ランク２符号表セット６−１

ランク２符号表セット７−１

ランク２符号表セット８−１

ランク２符号表セット９−１

ランク２符号表セット１０−１

ランク２符号表セット１１−１

ランク２符号表セット１２−１

Table 1
Rank 2 code table set 1-1

Rank 2 code table set 2-1

Rank 2 code table set 3-1

Rank 2 code table set 4-1

Rank 2 code table set 5-1

Rank 2 code table set 6-1

Rank 2 code table set 7-1

Rank 2 code table set 8-1

Rank 2 code table set 9-1

Rank 2 code table set 10-1

Rank 2 code table set 11-1

Rank 2 code table set 12-1

  All of the code tables shown in Table 1 above are examples, and row substitution and / or column substitution can be applied to all or part of the precoding matrix.

  When the 4Tx rank 2 code table includes 15 precoding matrices, one precoding matrix can be removed from the group in which the most precoding matrices are selected from each precoding matrix group. An example of a 4Tx rank 2 code table configured in the above manner is as follows.

ランク２符号表セット２−２

ランク２符号表セット３−２

ランク２符号表セット４−２

ランク２符号表セット５−２

ランク２符号表セット６−２

ランク２符号表セット７−２

ランク２符号表セット８−２

ランク２符号表セット９−２

ランク２符号表セット１０−２

ランク２符号表セット１１−２

ランク２符号表セット１２−２

Table 2
Rank 2 code table set 1-2

Rank 2 code table set 2-2

Rank 2 code table set 3-2

Rank 2 code table set 4-2

Rank 2 code table set 5-2

Rank 2 code table set 6-2

Rank 2 code table set 7-2

Rank 2 code table set 8-2

Rank 2 code table set 9-2

Rank 2 code table set 10-2

Rank 2 code table set 11-2

Rank 2 code table set 12-2

  The code table shown in Table 2 is also exemplary, and row replacement and / or column replacement can be performed on all or part of each precoding matrix.

Rank 3-First Embodiment For a 4Tx rank 3 code table design that maintains the CM characteristics well, assume three precoding matrix groups as follows: In the following, similarly, the power adjustment related coefficient is omitted.

グループ２

グループ３

・・・ （式４４） Group 1

Group 2

Group 3

... (Formula 44)

  In the case of rank 3, as in rank 2, it is proposed that the code table be configured according to norm 1 and norm 2 described above. Specifically, after calculating the chord distance for all possible precoding matrix combinations in the code table using Equation 42 above, the minimum number of sets with the maximum chord distance can be selected. It is also proposed to select a precoding matrix from each group (groups 1, 2, 3) as evenly as possible. When the alphabet expressed by the precoding matrix components in each group is limited to (1, j, −1, −j), the following code table satisfying the minimum chord distance dc, = 0.007 is obtained. Can do.

ランク３符号表セット２−１

ランク３符号表セット３−１

ランク３符号表セット４−１

ランク３符号表セット５−１

ランク３符号表セット６−１

ランク３符号表セット７−１

ランク３符号表セット８−１

Table 3
Rank 3 code table set 1-1

Rank 3 code table set 2-1

Rank 3 code table set 3-1

Rank 3 code table set 4-1

Rank 3 code table set 5-1

Rank 3 code table set 6-1

Rank 3 code table set 7-1

Rank 3 code table set 8-1

  Similarly, the code table shown in Table 3 can perform row replacement and / or column replacement on a part or the whole precoding matrix.

  When only 15 precoding matrices are included in the rank 3 code table, the precoding matrix of the group in which the most precoding matrix is selected from each group in the code table of Table 3 above is removed, It can be configured as follows.

ランク３符号表セット２−２

ランク３符号表セット３−２

ランク３符号表セット４−２

ランク３符号表セット５−２

ランク３符号表セット６−２

ランク３符号表セット７−２

ランク３符号表セット８−２

Table 4
Rank 3 code table set 1-2

Rank 3 code table set 2-2

Rank 3 code table set 3-2

Rank 3 code table set 4-2

Rank 3 code table set 5-2

Rank 3 code table set 6-2

Rank 3 code table set 7-2

Rank 3 code table set 8-2

  Similarly in Table 4 above, row substitution and / or column substitution can be performed on the whole or part of the precoding matrix.

Rank 3—Second Embodiment In this embodiment, a method of constructing a code table using six precoding matrix groups that maintain good CM characteristics will be described. Six 4Tx-rank 3 precoding matrix groups that maintain good CM characteristics can be expressed as follows:

・・・ （式４５）

... (Formula 45)

  An example of a rank 3 code table including 24 precoding matrices from the 6 groups represented by the above Expression 45 is as follows. The following example corresponds to a case where the alphabet expressed as a precoding matrix component is limited to 1, j, -1, and -j for the purpose of reducing complexity.

Table 5

  As another example, a method is proposed in which the group 4 that can be generated by applying column replacement to the group 1 is excluded from the group represented by the above Expression 45. In general, when three column vectors are represented by [c1, c2, c3], [c1, c3, c2], [c2, c1, c3], [c2, c3, c1], [c3, c2, It is possible to generate six column permutation matrices such as [c1], [c3, c1, c2].

As described above, the motivation for not using the specific vector permutation matrix is that the encoded sequence is mapped to a specific column vector (or a specific hierarchy) of the precoding matrix. Assume that two independently encoded codewords in the group of precoding matrices are mapped to different hierarchies as follows.
(1) The first codeword is mapped to the first layer.
(2) The second codeword is mapped evenly distributed in the second and third layers.

  Given such codeword hierarchy mapping, certain column permutations do not result in an average SINR difference between different codewords. For example, when the column vector [c1, c2, c3] is replaced with [c1, c3, c2], it can be seen that only the hierarchy for the second codeword is swapped. In this way, swapping between two hierarchies where the same second codeword is evenly distributed and mapped does not cause a change in performance, and the column table replacement precoding matrix as described above is included separately in the code table. There is no need. Therefore, it is proposed to eliminate the group generated by replacing only the second and third column vectors from such logic and consider only the following precoding matrix group.

・・・ （式４６）

... (Formula 46)

  The following code table shows an example of a 4Tx rank 3 code table including 20 precoding matrices with the alphabet in the precoding matrix group limited to 1, j, -1, and -j.

Table 6

  On the other hand, in another embodiment of the present invention, the number of precoding matrices necessary for obtaining optimum performance at a high rank is equal to the number of precoding matrices necessary for obtaining optimum performance at a low rank. The rank 3 code table can be limited to include less than 24 precoding matrices. In this case, using the norm 2, the precoding matrix can be equally selected from the six precoding matrix groups as follows.

Table 7

Table 7 above shows that the number of precoding matrices in the code table is twelve because e ^−jθ is simply multiplied by a specific column vector or column replacement in the precoding matrix does not affect performance improvement. The example which restricts to is shown. On the other hand, in one embodiment of the present invention, antenna replacement can be performed to obtain antenna selection gain. This can be realized by row replacement of the precoding matrix in the code table described above.

Rank 3—Third Embodiment In this embodiment, it is assumed that the following six precoding matrix groups are considered as precoding matrices that maintain good CM performance.

・・・ （式４７）

... (Formula 47)

  Referring to group 1 in equation 47 above, [c1, c3, c2], [c2, c1, c3], [c2, c3, c1], [c1, c3], [c1, c3, c2], [c2, c3, c1], [c1, c3] It can be seen that three permutation matrices are selected from [c3, c2, c1] and [c3, c1, c2]. In the case of group 4, it can be seen that one constituent precoding matrix is excluded. This is because it is already included in group 1. This embodiment is preferably used particularly when the hierarchy movement operation is not performed. In the present embodiment, hierarchical movement can be implemented by using a code table including a precoding matrix set subjected to column replacement. This allows information sequences to be mapped to all layers, thus leveling signal-to-interference and noise ratio (SINR) differences that exist between layers.

  Also in this embodiment, a precoding matrix can be selected using the norm 1 and norm 2 described above.

Rank 3-Fourth Embodiment In the present embodiment, the following three groups are considered as precoding matrix groups that maintain good CM characteristics.

・・・ （式４８）

... (Formula 48)

は、ＤＦＴベースのプリコーディングベクトル／行列、又はハウスホールドベースのプリコーディングベクトル／行列のような異なるプリコーディング行列でありうる。例えば、３ＧＰＰ ＬＴＥシステム（リリース８システム）のランク１符号表がその一例である。好ましくは、

の直交性／部分ユニタリ特性を維持するために、行列

及び

はユニタリ特性を満たさなければならない。同様に、行列

の行列

及び

、そして

の行列

及び

は、ユニタリ特性を満たさなければならない。これは、パラメータが下記のような関係を満たすべきということを意味する。 The last vector in the precoding matrix group expressed in Equation 48 above.

May be a different precoding matrix such as a DFT-based precoding vector / matrix or a household-based precoding vector / matrix. For example, a rank 1 code table of 3GPP LTE system (release 8 system) is an example. Preferably,

In order to maintain the orthogonality / partial unitary property of

as well as

Must satisfy unitary characteristics. Similarly, matrix

Matrix of

as well as

And

Matrix of

as well as

Must satisfy unitary characteristics. This means that the parameters should satisfy the following relationship:

In group 1: a = 1, b = −X, and c = −d · Y ^*
In group 2: a ′ = 1, b ′ = − X, and c ′ = − d ′ · Y ^*
In group 3: a ″ = 1, b ″ = − X, and c ″ = − d ″ · Y ^*
... (Formula 49)

  Here, it is assumed that a, a ′, and a ″ are 1 because a column vector of a specific precoding matrix is regarded as representing the same precoding matrix even if it is multiplied by a certain complex constant.

  Preferably, this embodiment may be useful when hierarchical replacement operates. Hierarchy replacement operation means that the specific SINR performance difference is made uniform by setting a specific information sequence to be cyclically mapped and transferred to all layers. When the same power is used for different layers, the data sequence of the last layer corresponding to the last column not including 0 as a component has the highest power (in terms of the precoding output signal).

  If the serial interference cancellation (SIC) receiver algorithm is used without layer replacement, the layer to which the first codeword is mapped is a precoding vector sequence whose transmit power is relatively higher than other precoding vector sequences. It is preferable to correspond. For Equation 48, the third column has a higher transmit power than the others. If the first column is mapped to the first hierarchy, the third column is mapped to the third hierarchy, and equation 48a may be used instead of equation 48. This precoding matrix structure improves the probability that when a plurality of codewords are transmitted, the entire codeword is correctly decoded, thereby improving the performance when the SIC receiver is used without performing layer replacement. be able to.

・・・ （式４８ａ）

(Formula 48a)

Rank 3-5 Fifth Embodiment In this embodiment, the following groups are assumed as precoding matrix groups that maintain good CM performance.

・・・ （式５０）

... (Formula 50)

は、ＤＦＴベースのプリコーディングベクトル／行列又はハウスホールドベースのプリコーディングベクトル／行列のような、異なるプリコーディング行列でありうる。例えば、３ＧＰＰ ＬＴＥシステム（ｒｅｌｅａｓｅ ８システム）のランク１符号表がその一例である。 The precoding matrix group represented by the above equation 50 includes a version of the precoding matrix in which row or column permutation is performed in the fourth embodiment. Column vector with precoding matrix group of Equation 50

May be different precoding matrices, such as DFT based precoding vectors / matrixes or household based precoding vectors / matrixes. For example, the rank 1 code table of 3GPP LTE system (release 8 system) is an example.

  As in the fourth embodiment, the precoding matrix vectors are preferably orthogonal to each other, and the first non-zero element of all column vectors in the precoding matrix group is preferably 1.

  The code table according to the present embodiment includes a precoding matrix obtained by performing column replacement on the precoding matrix according to the fourth embodiment. As described above, the precoding matrix having the column vector [c1, c2, c3] is [c1, c3, c2], [c2, c1, c3], [c2, c3, c1], [c3, c2, c1]. ], [C3, c1, c2], and 5 column permutation precoding matrices.

  The reason for not including a specific column permutation precoding matrix is that, as described above, in the system in which the first codeword is mapped to the first layer and the second codeword is distributed and mapped to the second and third layers. This is because the replacement of the second column and the third column of the precoding matrix does not cause a performance difference.

Rank 3-Sixth Embodiment The precoding matrix according to the present embodiment has a form in which row replacement is performed on the precoding matrix of the code table according to the fourth embodiment. This is because gain can be obtained by antenna switching using row permutation.

  The precoding matrix group according to the present embodiment can be expressed as follows.

・・・ （式５１）

... (Formula 51)

又はこれらの行置換の形態は、ＤＦＴベースのプリコーディングベクトル／行列又はハウスホールドベースのプリコーディングベクトル／行列のような、異なるプリコーディング行列でありうる。例えば、３ＧＰＰ ＬＴＥシステム（リリース８システム）のランク１符号表がその一例である。 Column vector

Or, these forms of row permutation may be different precoding matrices, such as DFT-based precoding vectors / matrixes or household-based precoding vectors / matrixes. For example, a rank 1 code table of 3GPP LTE system (release 8 system) is an example.

  As in the fourth embodiment, the column vectors of the precoding matrix are preferably orthogonal to each other, and at the same time, a, a ′, and a ″ of the precoding matrix are preferably 1. The code table according to the present embodiment. An example of can be expressed as follows.

・・・ （式５２）

... (Formula 52)

Rank 3-Seventh Embodiment The code table according to this embodiment has a row replacement form of the code table according to the fifth embodiment. An example of the code table according to the present embodiment can be expressed as follows.

・・・ （式５３）

... (Formula 53)

又はこれらの行置換の形態は、ＤＦＴベースのプリコーディングベクトル／行列又はハウスホールドベースのプリコーディングベクトル／行列のような、異なるプリコーディング行列でありうる。例えば、３ＧＰＰ ＬＴＥシステム（リリース８システム）のランク１符号表がその一例である。 Column vector

Or, these forms of row permutation may be different precoding matrices, such as DFT-based precoding vectors / matrixes or household-based precoding vectors / matrixes. For example, a rank 1 code table of 3GPP LTE system (release 8 system) is an example.

  As in the fourth embodiment, the column vectors of the precoding matrix are preferably orthogonal to each other, and at the same time, a, a ′, and a ″ of the precoding matrix are preferably 1. The code table according to the present embodiment. Is preferably used when the antenna replacement operation is not performed, because the antenna replacement effect can be realized by using the precoding matrix subjected to row replacement by using the code table according to the present embodiment.

  An example of the code table according to the present embodiment can be expressed as follows.

・・・ （式５４）

... (Formula 54)

Additional Precoding Matrix Selection Criteria In this embodiment, in addition to the norm 1 and norm 2 described above, the components expressed by alphabets in each precoding matrix group are not selected from 8 values, Considering a method of reducing the number of precoding matrices included in the code table by limiting to 1, j, -1, and -j.

  According to such an embodiment, a code table set including 16 precoding matrices is considered. For example, a rank 1 DFT vector for a 4Tx antenna can be expressed as:

An N * N DFT matrix (or Fourier matrix) using a component given as F _N = e ^{−j 2π / N} normalized to 1 / √N so as to become a unitary matrix is expressed as follows: be able to.

・・・ （式５５）

... (Formula 55)

  A rank 1 DFT vector for a 4Tx antenna composed of 16 4 × 1 column vectors in the first to fourth rows of Equation 55 can be expressed as follows.

Table 8

  The 4Tx rank 1 household vector can be expressed as follows:

Table 9

As the restriction described above codebook size, it can be used to limit the number of precoding matrices contained in the codebook, at least one of the first norm to third norm. In the present embodiment, among the above description, the viewpoint of the size limit of the code table per rank, particularly the size limit for the rank 1 code table will be described.

  Currently, the downlink 4Tx code table of the 3GPP LTE system stipulates that there are 16 vectors / matrices identically for each rank. However, it is known from various studies that the number of precoding matrices required to obtain optimum performance at a high rank is smaller than the number of precoding matrices required at a low rank. From this point, in this embodiment, the number of precoding matrices for the lower rank is designed to be larger than the number of precoding matrices for the higher rank, and the number of precoding matrices is separately set according to each rank. Proposed code table form is proposed.

  On the other hand, various transfer modes can be applied in a mobile communication system. It is assumed that the user equipment (UE) located at the cell boundary uses the X-th transfer mode usefully to apply a closed loop operation using rank 1 PMI (Precoding Matrix Indicator). In such a case, the rank 1 PMI vector is simply composed of a precoding matrix for the entire rank to apply the Y-th transfer mode such as open-loop MIMO and closed-loop MIMO. Selected from the rank-1 precoding matrix in the entire code table. Here, it is assumed that the Xth transfer mode and the Yth transfer mode are different from each other. In the case of the Y-th transfer mode, the size of the code table for rank 1 can be set so as not to be a power of 2. Even if the code table size for rank 1 has a form of power of 2, only the code table size may be increased without significant performance improvement. Therefore, in this embodiment, it is proposed that the size of the code table is reasonably limited so that it can be expressed with a small amount of feedback information while having appropriate performance.

  First, it is assumed that the number of precoding matrices per rank for applying the Yth transfer mode is A-rank 1, B-rank 2, C-rank 3, and D-rank 4 (where D ≦ C ≦ B ≦ A). In this case, the size of the entire code table is the sum of A, B, C, and D. In order to apply such a code table size, m-bit signaling that satisfies the following conditions is required.

A + B + C + D ≦ 2 ^m (Formula 56)

If the UE is configured to use the Xth transfer mode, the UE will use rank-1 PMI information. Preferably, 2 ⁿ (n <m) rank 1 PMIs may be newly defined in order to reduce the number of bits required for signaling. There are the following methods that can be used to reduce the number of signaling bits in this way.
(1) Method 1 If possible, select even-numbered index (2) Method 2 If possible, select odd-numbered index (3) Method 3 Select first 2 ⁿ indexes (4) Method 4 Last 2 Select ⁿ indexes (5) Method 5 Select any index (6) Method 6 Configured by signaling

  For example, for the Y-th transfer mode, 33 precoding matrices can be provided for rank 1, 15 for rank 2, 15 for rank 3, and 4 for rank 4.

In this case, a method of constructing a rank 1 code table for representing only 16 precoding matrices is as follows.
(1) Method 1 Select even-numbered index (2) Method 2 Select odd-numbered index (3) Method 3 Select first 16 indexes (4) Method 4 Select last 16 indexes (5) Method 5 Select index arbitrarily (6) Method 6 Configured by signaling

On the other hand, a method of constructing a rank 1 code table for representing only 32 precoding matrices is as follows.
(1) Method 1 Select the first 32 indexes (2) Method 2 Select the last 32 indexes (3) Method 3 Select any index (4) Method 4 Configured by signaling

  When 16 downlink rank 1 vectors are included in a code table for rank 1 including 32 precoding matrices, a restriction scheme such as the following methods (I) and (II) can be used.

  The restriction method (I) corresponds to the case of constructing a rank-1 code table of size 16, and the details thereof are as follows.

(A) 16 downlink rank 1 vectors selected (B) 16 rank rank 1 code table selected regardless of downlink rank 1 vector (1) First 16 indexes selected (2) Last 16 (3) Arbitrarily select an index (4) Configure by signaling

    Another restriction method (II) corresponds to the case of constructing a rank 1 code table of size 32, and the details thereof are as follows.

(A) 16 downlink rank 1 vectors + additional vector selection (1) First 16 indexes are selected (2) Last 16 indexes are selected (3) Arbitrary index is selected (4) Configuration by signaling ( B) Select a rank 1 code table of 32 size regardless of the downlink rank 1 vector (1) Select the first 32 indexes (2) Select the last 32 indexes (3) Select any index ( 4) Configured by signaling

  The number of code tables for each rank can be efficiently configured by various methods as described above.

III. Device Configuration In the following, as described above, a configuration that a user apparatus should be provided for applying the MIMO scheme to uplink signal transfer while maintaining good PAPR or CM characteristics will be described.

  FIG. 10 is a diagram for explaining a configuration of a general base station and user apparatus.

  In general, the base station 10 includes a processor 11, a memory 12, and an RF module 13 as a transmission / reception module for receiving uplink signals and transferring downlink signals. The processor 11 controls downlink signal transfer using information stored in the memory 12 for downlink signal transfer, eg, a specific precoding matrix in a code table for downlink signal transfer, and Information stored in the memory 12 for reception of the uplink signal, for example, multiplying the uplink signal by a Hermite matrix having the same precoding matrix as the precoding matrix used by the user apparatus 20 as the reverse process of precoding The signal reception process can be controlled.

  Similarly, the user equipment 20 can include a processor 21, a memory 22, and an RF module 23 as a transmission / reception module for transferring uplink signals and receiving downlink signals. The processor 21 uses information stored in the memory 22 for uplink signal transfer, for example, a specific precoding matrix in the code table as described in the above-described embodiment for uplink signal transfer. Controls link signal transfer, and also stores information stored in the memory 22 for receiving downlink signals, for example, the same precoding matrix as the precoding matrix used by the user equipment 20 as a reverse process of precoding of downlink signals It is possible to control a signal reception process such as multiplication by a Hermitian matrix.

  On the other hand, among the above configurations, the configuration of the processor of the user apparatus 20 (or the base station 10), in particular, the configuration for transferring signals by the SC-FDMA scheme will be described in more detail. First, a description will be given of a processor configuration for SC-FDMA signal transfer and a general OFDM method signal transfer in 3GPP LTE system, and a user apparatus combines a MIMO scheme according to an embodiment of the present invention. The configuration of the processor for transferring the uplink signal by the SC-FDMA method will be described.

  11 and 12 are diagrams for explaining an SC-FDMA scheme for uplink signal transfer and an OFDMA scheme for downlink signal transfer in the 3GPP LTE system.

  First, referring to FIG. 11, the user equipment for uplink signal transfer and the base station for downlink signal transfer are both serial-to-parallel converter 401, subcarrier mapper 403, M-point IDFT module 404, And the parallel-serial converter 405 and the like. However, the user equipment for transferring a signal by the SC-FDMA scheme further includes an N-point DFT module 402, which cancels a certain part of the IDFT processing effect of the M-point IDFT module 404 so that the transfer signal becomes a single carrier wave. It is different to have the following characteristics.

  In FIG. 12, a block diagram for an uplink signal processing process shown in TS 36.211 defining the 3GPP LTE system standard, and a processor for transferring signals in the SC-FDMA scheme shown in FIG. The relationship with the configuration is shown. According to TS 36.211, for the uplink signal transfer, a scrambled transfer signal is scrambled for each user equipment using a specific scramble sequence, and the scrambled signal is modulated to generate a complex symbol. Thereafter, conversion precoding for performing DFT spreading processing on the complex symbol is performed. That is, the conversion precoder defined in TS 36.211 can correspond to the N-point DFT module. Thereafter, the DFT-spread signal is mapped to a specific resource element according to a resource block unit mapping rule by the resource element mapper, which corresponds to the subcarrier mapper in FIG. The signal mapped to the resource element in this way is subjected to M-point IDFT or IFFT processing by the SC-FDMA signal generation module, and after parallel-serial conversion, CP is added.

  On the other hand, FIG. 12 also shows a processor configuration of the base station for receiving a signal transferred to the base station through such a process.

  Thus, the processor configuration for SC-FDMA transfer in the 3GPP LTE system does not include a configuration for applying the MIMO scheme. Therefore, first, the processor configuration of the base station for MIMO transfer in the 3GPP LTE system will be described, and then, using this, the user apparatus combines the SC-FDMA scheme and the MIMO scheme to transfer an uplink signal. The configuration of the processor will be described.

  FIG. 13 is a diagram illustrating a processor configuration for a base station to transfer a downlink signal using a MIMO scheme in a 3GPP LTE system.

  In the 3GPP LTE system, a base station can transfer one or more codewords in the downlink. Accordingly, each of the one or more codewords can be processed as complex symbols by the scramble module 301 and the modulation mapper 302 as in the uplink of FIG. Each layer is mapped to a hierarchy and can be assigned to each transfer antenna by being multiplied by a predetermined precoding matrix selected according to the channel state in the precoding module 304. Each of the antenna-specific transfer signals processed in this way is mapped to a time-frequency resource element used for transfer by the resource element mapper 305, and then transferred from each antenna via the OFDM signal generator 306. it can.

  However, the downlink signaling method in the 3GPP LTE system as shown in FIG. 13 may lead to a problem that PAPR or CM characteristics deteriorate. Therefore, the user apparatus efficiently combines the SC-FDMA scheme for maintaining good PAPR and CM characteristics as described above with reference to FIGS. 11 and 12 and the MIMO scheme of FIG. As described in the above embodiment, a configuration for performing precoding using a precoding matrix capable of maintaining good PAPR and CM characteristics is required.

  First, according to a preferred embodiment of the present invention, it is assumed that a user equipment for transmitting a signal through an uplink through multiple antennas includes multiple antennas (not shown) for signal transmission / reception. Referring to FIG. 10, the user apparatus 20 includes a memory 22 for storing a code table including a precoding matrix set so that one hierarchical signal is transferred for each of the multiple antennas, a multiple antenna (not shown). And a processor 21 connected to the memory (22) for processing the uplink signal transfer. The configuration of the processor 21 of the user apparatus having such a configuration will be described more specifically.

  FIG. 14 is a diagram specifically illustrating a processor configuration of the user apparatus according to the preferred embodiment of the present invention.

  As shown in FIG. 14, the processor of the user apparatus 20 according to the preferred embodiment of the present invention includes a layer mapper 1401 that maps uplink signals to a number of layers corresponding to a specific rank, and a predetermined number of layer signals. A specific number of DFT modules 1402 that perform DFT spreading and a specific precoding matrix set so that one layer signal is transferred for each of the multiple antennas 1405 from the code table stored in the memory 22, It is proposed to include a precoder 1403 for precoding each of the DFT-spread layer signals received from the DFT module 1402. In particular, in this embodiment, the DFT module 1402 spreads each layer signal, and the DFT module 1402 that spreads each layer signal is positioned immediately before the precoder 1403, and each layer signal is precoded by the precoder 1403. It is characterized by maintaining a single carrier characteristic of each layer signal and maintaining a good PAPR / CM characteristic by being configured to be mapped and transferred to one antenna. On the other hand, the user apparatus 20 performs processing for SC-FDMA symbol configuration (for example, time domain signal generation by the IFFT module 1404 and CP addition) on the precoded signal in this manner, and performs base station through the multiple antenna 1405. It further includes a transfer module for transferring to the station.

  On the other hand, the precoder 1403 can select a precoding matrix to be used for signal transfer from a code table stored in the memory 22 and use it for precoding. It is preferable that the precoding matrix is set so that the transfer power of each layer is equal.

  The number of multiple antennas 1405 can be two or four. In addition, the processor of the user apparatus according to an embodiment of the present invention may include a layer moving function for periodically or aperiodically changing a layer to which a specific codeword is mapped and / or an antenna to which a specific layer signal is transferred. An antenna moving function that changes periodically or aperiodically can also be performed. The layer moving function may be performed separately from the precoding of the precoder 1403 by the layer mapper 1401 or may be performed by column replacement of a precoding matrix when the precoder 1403 performs precoding. Similarly, the antenna moving function can be performed separately from precoding or by row replacement of a precoding matrix.

  The embodiments described above are obtained by combining the constituent elements and features of the present invention in a predetermined form. Each component or feature should be considered optional unless stated otherwise. Each component or feature may be implemented in a form that is not combined with another component or feature. Also, some embodiments and / or features may be combined to form embodiments of the present invention. The order of operations described in the embodiments of the present invention can be changed. Some configurations or features of one embodiment may be included in another embodiment, or may replace a corresponding configuration or feature of another embodiment. It is obvious that claims that are not explicitly cited in the claims can be combined to constitute an embodiment, or can be included as a new claim by amendment after application.

  Embodiments according to the present invention can be implemented by various means such as hardware, firmware, software, or a combination thereof. When implemented in hardware, one embodiment of the invention includes one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs). , A field programmable gate array (FPGA), a processor, a controller, a microcontroller, a microprocessor, and the like.

  In the case of implementation by firmware or software, an embodiment of the present invention may be implemented in the form of a module, procedure, function, or the like that performs the functions or operations described above. The software code can be stored in a memory unit and driven by a processor. The memory unit is provided inside or outside the processor, and can exchange data with the processor by various known means.

  It will be apparent to those skilled in the art that the present invention can be embodied in other specific forms without departing from the technical idea and essential features of the present invention. Accordingly, the above detailed description should not be construed as limiting in any respect, and should be considered as exemplary. The scope of the invention should be determined by reasonable interpretation of the appended claims, and thus any changes that come within the equivalent scope of the invention are included in the scope of the invention.

  As is clear from the above description, the present invention can maintain PAPR or CM characteristics while transmitting an uplink signal using the MIMO scheme.

  Furthermore, the present invention can uniformly control or adjust the transmission power of the antenna / layer, minimize the amount of signal overhead required for precoding matrix information, and obtain the maximum diversity gain.

  The present invention can be used in a broadband wireless mobile communication system.

  It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Accordingly, the present invention includes modifications and variations of the present invention and equivalents that fall within the scope of the claims of this application.

DESCRIPTION OF SYMBOLS 10 Base station 20 User apparatus 301 Scramble 302 Modulation mapper 303 Hierarchical mapper 304 Precoding 305 Resource element mapper 306 OFDM signal generator 401 Serial-parallel conversion 402 N-point DFT
404 M-point IDFT
405 Parallel-serial conversion 406 CP addition 1401 Code word to layer mapping 1402 DFT
1403 Precoding 1404 IFFT
1405 Antenna

Claims (18)

A method in which a user equipment transmits an uplink signal using multiple antennas,
Mapping the uplink signal to a predetermined number of layers;
Performing discrete Fourier transform (DFT) diffusion on each of the predetermined number of hierarchical signals;
Select a specific precoding matrix set so that one layer signal is transferred for each of the multiple antennas from a code table stored in advance, and precode each layer signal that has been DFT-spread,
An uplink signal transfer method comprising: performing processing for single carrier frequency division multiple access (SC-FDMA) symbol configuration on the precoded signal and transferring the processed signal to a base station through the multiple antennas.   The uplink signal transfer method according to claim 1, wherein the specific precoding matrix is a precoding matrix set so that transfer powers of the multiple antennas are equalized.   The uplink signal transfer method according to claim 1, wherein the specific precoding matrix is a precoding matrix set so that transfer powers of the predetermined number of layers are equal. The code table is a rank 2 precoding matrix used when the number of the multiple antennas is 4 and the rank is 2.

Has a form like

Including a first type precoding matrix that satisfies the following condition:
The uplink signal transfer method according to claim 1, wherein each row of the precoding matrix corresponds to each of the four multiple antennas, and each column corresponds to each layer. The rank-2 precoding matrix is

A second type of precoding matrix having the form

A third type precoding matrix having a form such as
The second type precoding matrix and the third type precoding matrix are respectively

The uplink signal transfer method according to claim 4, wherein the condition is satisfied.   The rank-2 precoding matrix includes a precoding matrix in which the position of each row is changed, a precoding matrix in which the position of each column is changed, and each row of the first to third types of precoding matrices. The uplink signal transfer method according to claim 5, further comprising at least one of a type of precoding matrix in which a position of each column and a position of each column are changed. The code table is a rank 3 precoding matrix used when the number of the multiple antennas is 4 and the rank is 3.

Has a form like

Including a first type precoding matrix that satisfies the following condition:
The uplink signal transfer method according to claim 1, wherein each row of the precoding matrix corresponds to each of the four multiple antennas, and each column corresponds to each layer. The rank 3 precoding matrix is

A second type of precoding matrix having the form

A third type precoding matrix having a form such as
The second type precoding matrix and the third type precoding matrix are respectively

The uplink signal transfer method according to claim 7, wherein the condition is satisfied.   The rank-3 precoding matrix includes a precoding matrix in which the position of each row is changed, a precoding matrix in which the position of each column is changed, and each row of the first to third types of precoding matrices. The method of claim 8, further comprising a precoding matrix of a type in which the position of each column and the position of each column are changed. The code table is a rank 3 precoding matrix used when the number of the multiple antennas is 4 and the rank is 3.
A precoding matrix designed such that the first layer is distributed and mapped to the first antenna and the second antenna, and the second layer and the third layer are mapped and transferred to the third antenna and the fourth antenna, respectively. The uplink signal transfer method according to claim 1, further comprising:   The method of claim 1, wherein the code table includes a different number of precoding matrices for each rank. The uplink signal is input in codeword units,
The uplink signal transfer method according to claim 1, wherein the mapping to the layer includes periodically changing a layer to which a specific codeword is mapped.   The uplink signal transfer method according to claim 12, wherein the mapping to the layer includes changing a layer to which the specific codeword is mapped for each SC-FDMA symbol. A user equipment that transmits signals in uplink through multiple antennas,
Multiple antennas for signal transmission and reception;
A memory for storing a code table including a precoding matrix set to transfer one layer signal for each of the multiple antennas;
A processor connected to the multiple antennas and the memory for processing the uplink signal transfer;
Including
The processor is
A layer mapper for mapping the uplink signal to a number of layers corresponding to the specific rank;
A DFT module that performs discrete Fourier transform (DFT) spreading on each of the predetermined number of hierarchical signals;
The DFT spread received from the DFT module is selected from a code table stored in the memory by selecting a specific precoding matrix set to transfer one layer signal for each of the multiple antennas. A precoder for precoding a hierarchical signal;
A transfer module that performs processing for single carrier frequency division multiple access (SC-FDMA) symbol configuration on the precoded signal and forwards it to a base station through the multiple antennas;
Including user equipment. The code table stored in the memory is a rank 2 precoding matrix used when the number of the multiple antennas is 4 and the rank is 2.

Has a form like

Including a first type precoding matrix that satisfies the following condition:
The user apparatus according to claim 14, wherein each row of the precoding matrix corresponds to each of the four multiple antennas, and each column corresponds to each layer. The rank-2 precoding matrix is

A second type of precoding matrix having the form

A third type precoding matrix having a form such as
The second type precoding matrix and the third type precoding matrix are respectively

The user apparatus according to claim 15, wherein the condition is satisfied. The code table stored in the memory is a rank 3 precoding matrix used when the number of the multiple antennas is 4 and the rank is 3.

Has a form like

Including a first type precoding matrix that satisfies the following condition:
The user apparatus according to claim 14, wherein each row of the precoding matrix corresponds to each of the four multiple antennas, and each column corresponds to each layer. The rank 3 precoding matrix is

A second type of precoding matrix having the form

A third type precoding matrix having a form such as
The second type precoding matrix and the third type precoding matrix are respectively

The user apparatus according to claim 17, wherein the condition is satisfied.

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