RU2455765C2 - Method for phase shift based precoding and transducer for its supporting - Google Patents

Abstract

FIELD: information technology.

SUBSTANCE: matrix for phase shift based precoding can be generalised and defined in spatial domain by product of diagonal matrix for phase shift by unitary matrix for supporting orthogonality. Diagonal matrix can be expanded by product of precoding matrix for power multiplication in the channel by the mentioned diagonal matrix for phase shift.

EFFECT: higher efficiency of communications and generalisation and extension of phase shift based precoding.

17 cl, 8 dwg

Description

Technical field

[1] The present invention relates to a generalized phase shift based precoding method or an advanced phase shift based precoding method in a multi-antenna system using multiple subcarriers (frequencies), and to a transceiver for supporting it.

State of the art

[2] Currently, when information and communication services have been popularized, many multimedia services have appeared and high-quality services have appeared, the requirements for radio services are increasing rapidly. In order to quickly cope with this trend, a method of increasing communication throughput in a radio communication environment may include a method of finding new available frequency bands and a method of increasing the efficiency of using a limited resource. In the most modern methods, multi-antenna transmission / reception technologies with placing multiple antennas in a transmitter / receiver and further providing an area for using resources to obtain diversity gain or parallel data transmission through antennas to increase transmission bandwidth attract a lot of attention and actively are being developed.

[3] Among the multi-antenna transmission / reception technologies, the basic structure of a multi-input and multi-output system using orthogonal frequency division multiplexing (OFDM) will now be described with reference to FIG.

[4] In the transmitter, the channel encoder 101 adds redundant bits to the transmission data bits to reduce the influence associated with the channel or noise, the display device 103 converts the data bits into data symbol information, the serial / parallel converter 105 converts the data symbols into parallel data symbols to be transmitted by multiple subcarriers, and multi-antenna encoder 107 converts the symbols of parallel data into space-time signals. A multi-antenna decoding device 109, a parallel / serial converter 111, a reverse display device 113, a channel decoder 115 included in the receiver, perform the functions inverse to the functions of the multi-antenna channel encoder 107, the serial / parallel converter 105, the display device 103 and the channel encoder 101, respectively .

[5] In OFDM systems with many antennas, many technologies are required to improve the reliability of data transmission. Among them, a scheme for increasing spatial diversity gain includes space-time coding (STC) and cyclic delay diversity (CDD), and a scheme for increasing signal to noise ratio (SNR) includes beamforming (BF) and preliminary coding. Time-space coding (STC) and cyclic delay diversity (CDD) are used to increase transmission reliability in open loop systems in which the transmitter cannot use feedback information and beamforming (BF) and precoding are used to maximize the ratio signal-to-noise ratio (SNR) using feedback information in closed loop systems in which the transmitter can use feedback information.

[6] Among these schemes, a scheme for increasing spatial diversity gain and a scheme for increasing signal to noise ratio (SNR), and more specifically, cyclic delay diversity (CDD) and precoding, will be explained below.

[7] In cyclic delay diversity (CDD), a system having multiple transmit antennas transmits orthogonal frequency division multiplexing symbols (OFDM symbols) having different delays or different levels through all antennas so that the receiver benefits from the frequency explode. Figure 2 shows the configuration of a multi-antenna system using cyclic delay diversity (CDD).

[8] OFDM symbols are separated and transmitted to the antennas through a serial / parallel converter and encoder for many antennas, and added to the cyclic prefix to prevent inter-channel interaction (inter-channel interference) during transmission to the receiver. Moreover, the data sequence sent to the first antenna is transmitted unchanged, and the data sequence sent to the next antenna is cyclically delayed with respect to the sequence sent to the previous antenna by predetermined bits and then transmitted to the receiver.

[9] Meanwhile, if cyclic delay diversity (CDD) is implemented in the frequency domain, cyclic delay can be expressed as the result of phase sequences. In this case, as shown in FIG. 3, data sequences in the frequency domain are multiplied by predetermined different phase sequences (from phase sequence 1 to phase sequence M) with respect to the antennas, undergo inverse fast Fourier transform (IFFT), and thus transmitted to the receiver. This is called phase shift diversity.

[10] If phase shift diversity is used, it is possible to change the flat fading channel to a frequency selective channel and provide gain from frequency diversity by channel coding, or to provide diversity gain to many users through frequency selective scheduling.

[11] Meanwhile, precoding includes codebook based precoding, which is used in a closed loop system when the feedback information is finite, and a circuit for quantizing and power (power) information of the feedback channel. Among them, in codebook-based precoding, the precoding matrix index, which is known to the transmitter / receiver in advance, is transmitted to the transmitter as feedback information to benefit from an increase in signal-to-noise ratio (SNR).

[12] FIG. 4 shows a transmitter / receiver configuration of a multi-antenna system using codebook based precoding. The transmitter and receiver have finite precoding matrices from P ₁ to P _L. The receiver feedbacks the optimum precoding matrix index 1 using channel information, and the transmitter applies the precoding matrix corresponding to the feedback index to the transmission data from X ₁ to X _Mt. Table 1 shows an example of a codebook that is applicable when 3-bit feedback information is used in the IEEE 802.16e system, which supports spatial multiplexing coefficient 2 and has two transmit antennas.

[13] Table 1

[Table 1] Matrix Index (binary) Column 1 Column 2 000 one 0 0 one 001 0.7940 -0.5801-j0.1818 -0.5801 + j0.818 -0.7940 010 0.7940 -0.0576-j0.6051 -0.0576 + j0.6051 -0.7940 011 0.7941 -0.2978 + j0.5298 -0.2978-j0.5298 -0.7941 one hundred 0.7941 0.6038-j0.0689 0.6038 + j0.0689 -0.7941 101 0.3289 0.6614-j0.6740 0.6614 + j0.6740 -0.3289 110 0.5112 0.4754 + j0.7160 0.4754-j0.7160 -0.5112 111 0.3289 -0.8779 + j0.3481 -0.8779-j0.3481 -0.3289

[14] Phase shift diversity (PSD) is attracting more attention because the frequency selective diversity gain can be obtained in an open-loop system, and the frequency selective planning gain can be obtained in a closed-loop system in addition to the advantages discussed above. . However, with a spatial multiplexing factor of 1, a high data rate cannot be obtained. In addition, when the allocation of resources is fixed, it is difficult to obtain the gains discussed above.

[15] Furthermore, since the codebook-based precoding discussed above can use a high spatial multiplexing rate while still requiring a small amount of feedback information (index information), it is possible to efficiently transmit data. However, since a stable feedback channel must be provided, codebook-based precoding is not suitable for environments in which channel changes are excessive, and is only applicable to a closed loop system.

Disclosure of invention

Technical solution

[16] The present invention is directed to a phase shift based precoding method and a transceiver that substantially eliminate one or more problems due to limitations or disadvantages of the prior art.

[17] An object of the present invention is to provide a phase shift based precoding method capable of solving the disadvantages of a conventional cyclic delay diversity (CDD) method, phase shift diversity and a precoding scheme, and to various applications of a phase based precoding method shift to generalize or expand the phase shift-based precoding matrix.

[18] Additional advantages, objects, and features of the invention will be set forth in part in the description that follows, and in part will become apparent to those skilled in the art after studying the following description, or may be learned from carrying out the invention. The objectives and other advantages of the invention can be realized and achieved by the structure shown in more detail here in the description and claims along with the accompanying drawings.

[19] In order to achieve these objectives and other advantages, and in accordance with an object of the invention, as implemented and widely described herein, a phase shift based precoding method for transmitting in a multi-subcarrier multi-antenna system includes selecting a precoding matrix from the codebook as part of a phase shift-based precoding matrix; determining a diagonal matrix for the phase shift as part of a precoding matrix based on the phase shift; determining a unitary matrix as part of a phase shift-based precoding matrix; and multiplying the product of the precoding matrix, the diagonal matrix, and the unitary matrix by the symbol of the corresponding subcarrier to perform precoding.

[20] In another aspect of the present invention, a transceiver for transmitting data and performing phase shift-based precoding in a multi-subcarrier multi-antenna system includes a precoding matrix determining unit selecting a precoding matrix from a first codebook, as part of a phase shift-based precoding matrix defining a diagonal matrix for phase shift, as part of a pre-matrix Nogo coding based on the phase shift, selecting a unitary matrix from a second codebook, as part of a precoding matrix based on the phase shift, and receiving the product of the precoding matrix, the diagonal matrix and unitary matrix to determine the precoding matrix based on the phase shift; and a precoding unit multiplying a specific phase shift based precoding matrix by a symbol of the corresponding subcarrier.

[21] In another aspect of the present invention, a phase shift based precoding method of transmitting data in a multi-subcarrier multi-antenna system includes determining a diagonal matrix for phase shift as part of a phase based precoding matrix shift, the choice of a unitary matrix from the codebook as part of a precoding matrix based on a phase shift, and multiplication of the product of the diagonal matrix and unit a matrix per symbol of the corresponding subcarrier to perform precoding. The phase shift based precoding matrix according to the product of the unitary matrix and the diagonal matrix includes columns having identical phases.

[22] In another aspect of the present invention, a method for transmitting data using phase shift-based precoding in a multi-subcarrier multi-antenna system includes determining a first and second diagonal matrix for phase shift as part of a precoding matrix based on a phase shift, selecting a unitary matrix from the codebook as part of a precoding matrix based on a phase shift, and multiplying the product of the first an agonal matrix, a unitary matrix, and a second diagonal matrix per symbol of the corresponding subcarrier.

[23] In the mentioned aspects of the present invention, said unitary matrix can be selected from the codebook using a modulo (MOD) index k of the corresponding subcarrier with size N.

[24] In the mentioned aspects of the present invention, at least one of the matrices: a precoding matrix, a diagonal matrix (including the first diagonal matrix and the second diagonal matrix), and the unitary matrix can change over time.

[25] In aspects of the present invention, at least one of the matrices: a precoding matrix and a unitary matrix can be selected based on feedback information from the receiver. Moreover, the feedback information may contain a matrix index for at least one codebook.

[26] It is understood that both the foregoing general description and the following detailed description of the present invention are illustrative and explanatory and are intended to provide a further explanation of the invention as claimed.

Brief Description of the Drawings

[27] The accompanying drawings, which are included to provide a further understanding of the invention, and which are included in the relevant section of this application, illustrate embodiments of the invention and, together with the description, serve to explain the principle of the invention. In the drawings:

[28] FIG. 1 is a block diagram showing an orthogonal frequency division multiplexing (OFDM) system including transmit / receive antennas;

[29] FIG. 2 is a block diagram showing a transmitter of a conventional multi-antenna system using a cyclic delay diversity scheme;

[30] FIG. 3 is a block diagram showing a transmitter of a conventional multi-antenna system using phase shift diversity;

[31] FIG. 4 is a block diagram showing a conventional multi-antenna system using precoding;

[32] FIG. 5 is a block diagram showing a basic configuration of a transmitter / receiver for phase shift based precoding;

[33] FIG. 6 is a graph illustrating examples of the application of precoding based on phase shift and phase shift diversity;

[34] FIG. 7 is a block diagram showing an embodiment of a transmitter using orthogonal frequency division multiplexing (OFDM) with a single codeword (SCW) using phase shift based precoding with respect to an embodiment of the present invention ; and

[35] Fig. 8 is a block diagram showing an embodiment of a transmitter using orthogonal frequency division multiplexing (OFDM) with multiple codeword (MCW) with respect to an embodiment of the present invention.

Examples of carrying out the invention

[36] Reference will now be made to a detailed description of preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. In this case, if possible, the same reference numbers will be used in all drawings to refer to the same or similar parts.

[37] Embodiment 1

[38] Phase-shift-based precoding matrix

[39] FIG. 5 is a block diagram illustrating a basic transmitter / receiver configuration for performing phase shift based precoding.

[40] In phase shift-based precoding, all streams are for transmission through all antennas. Moreover, these flows are multiplied by different phase sequences. Typically, when a phase sequence is generated using a small cyclic delay, the channel value increases or decreases depending on the frequency domain, while the frequency is selected in the channel, from the point of view of the receiver.

[41] As shown in FIG. 5, the transmitter assigns the user terminal to a high frequency to stabilize the state of the channel in the frequency band, which varies depending on the relatively small cyclic delay. Here, a phase shift-based precoding matrix is used for applying a cyclic delay to each antenna that is constantly increasing or decreasing.

[42] The phase shift-based precoding matrix P can be expressed by equation 1.

[43] Equation 1

[44]

[45] Where k denotes a subcarrier index or an index of a particular frequency band, and

denotes the complex weight value determined by k. In addition, N denotes the number of transmitting (physical or virtual) antennas and R denotes the spatial multiplexing coefficient. The said complex weight value may vary depending on the subcarrier index and the specific frequency band that is multiplied for each antenna. Mentioned complex weight value may be determined by at least one of the following: the state of the channel and the availability of feedback information.

[46] In addition, the precoding matrix P in equation 1 is preferably developed by a unitary matrix in order to reduce channel throughput losses in a multi-antenna system. In order to verify the condition for configuring the unitary matrix, the aforementioned throughput of an open-loop system with many antennas is determined by equation 2.

[47] Equation 2

[48]

[49] where H denotes a matrix of dimension

N _r × N _t

channel system with many antennas and N _r denotes the number of receiving antennas. Equation 3 is obtained using said phase shift precoding matrix P in equation 2.

[50] Equation 3

[51]

[52] As can be seen from Equation 3, in order to prevent loss of throughput, the product of the matrices PP ^H must become the identity matrix (identity transformation matrix). Accordingly, the phase shift-based precoding matrix P should satisfy equation 4.

[53] Equation 4

[54]

PP ^H = I _N

[55] In order to allow the phase shift-based precoding matrix P to become a unitary matrix, two types of conditions must be satisfied simultaneously, namely, a degree restriction and an orthogonality restriction. The degree restriction allows the level of each column of the matrix to become 1, and the restriction of orthogonality allows the columns of the matrix to have orthogonal characteristics. These limitations are expressed in equations 5 and 6.

[56] Equation 5

[57]

[58] Equation 6

[59]

[60] The following is an example of a generalized equation for a 2 × 2 phase shift-based precoding matrix, and equations are obtained to satisfy two constraints. Equation 7 shows a generalized phase shift-based precoding matrix equation when the number of transmit antennas is 2 and the spatial multiplexing coefficient is 2.

[61] Equation 7

[62]

[63] where α _i and β _i (i = 1, 2) are real numbers, θ _i (i = 1, 2, 3, 4) is the phase value, and k is the subcarrier index or a specific subband index of the OFDM signal (multiplexing with orthogonal frequency division). In order to implement a precoding matrix with a unitary matrix, the degree constraint in Equation 8 and the orthogonality constraint in Equation 9 must be satisfied.

[64] Equation 8

[65]

[66] Equation 9

[68] where the superscript “*” denotes a complex conjugate. The following is an example of a phase-shift precoding matrix of dimension 2 by 2, which satisfies equations 7-9.

[69] Equation 10

[70]

[71] where θ ₂ and θ ₃ have the ratio expressed by equation 11, in accordance with the restriction of orthogonality.

[72] Equation 11

[73]

kθ ₃ = -kθ ₂ + π

[74] The precoding matrix may be stored in the memory of the transmitter and receiver in the form of a codebook, and the codebook may contain a plurality of precoding matrices generated using different finite values of θ ₂ . The value of θ ₂ can be correctly set in accordance with the state of the channel and the presence of feedback information. If the feedback information of the channel is such that the precoding matrix index is used, then the values of θ ₂ are small in order to gain frequency scheduling gain, and if the feedback information of the channel is not available, the values θ ₂ are large, thus providing high frequency diversity gain.

[75] Meanwhile, the frequency diversity gain or the frequency scheduling gain can be obtained in accordance with the delay reference value applied to the phase shift-based precoding. 6 is a graph showing examples of applying phase shift based precoding and phase shift diversity in accordance with a delay count value.

[76] As shown in FIG. 6, since the frequency selective period is short, if a large delay count value (or a large cyclic delay) is used, the frequency selectivity increases, and channel coding easily uses the frequency diversity gain. This is preferably used in an open loop system in which the channel value varies greatly over time and the reliability of the feedback information is degraded.

[77] If a small delay count value is used, the part in which the channel value increases and the part in which the channel value decreases are included in the frequency selective channel changed from the plane fading channel. Thus, the channel value of one subband (subcarrier region) of the OFDM symbol increases and the channel value of the other subcarrier region decreases.

[78] In an orthogonal frequency multiplexing (OFDMA) multiple access system that can support multiple users, when a signal is transmitted to each user in a frequency band in which the channel value increases, the signal-to-noise ratio (SNR) can increase. Since the degree of distribution of the frequency band in which the channel value increases can vary for each user, the system provides multi-user scheduling gain.

[79] The delay (or cyclic delay) count value for precoding based on a phase shift may be a value that is predetermined at the transmitter / receiver or feedback information from the receiver. The spatial multiplexing coefficient R may be a value that is predefined at the transmitter / receiver. Alternatively, the receiver can periodically check the state of the channel, calculate the spatial multiplexing coefficient and feed back the value of the spatial multiplexing coefficient to the transmitter, or the transmitter can calculate and change the spatial multiplexing coefficient using channel information from the receiver.

[80] Embodiment 2

[81] Generalized phase shift diversity matrix

[82] The phase shift-based precoding matrix described above can be expressed by equation 12 with respect to a system in which the number (physical or virtual) N _t (N _t is a positive number of 2 or more) antennas and the spatial multiplexing coefficient equal to R (R is a positive number 1 or greater). Since the equation is obtained by generalizing traditional phase shift diversity, the multi-antenna pattern expressed by equation 12 is also called generalized phase shift diversity (GPSD).

[83] Equation 12

[84]

обозначает матрицу GPSD (матрица обобщенного разнесения с фазовым сдвигом) k-й субполосы или поднесущей сигнала MIMO (много входов - много выходов)-OFDM (мультиплексирование с ортогональным частотным разделением), имеющего коэффициент пространственного мультиплексирования R и N_t передающих (физических или виртуальных) антенн, и

обозначает унитарную матрицу, удовлетворяющую условию[85] where

denotes a GPSD matrix (phase shift generalized diversity matrix) of the kth subband or subcarrier of a MIMO signal (many inputs - many outputs) -OFDM (orthogonal frequency division multiplexing) having a spatial multiplexing coefficient R and N _t transmitting (physical or virtual) antennas, and

denotes a unitary matrix satisfying the condition

,

,

удовлетворяет условию унитарной матрицы. В уравнении 12, соотношение между фазовым углом θ_i (i=1,…, N_t) частотной области и временем задержки t_i (i=1,…, N_t) временной области выражается уравнением 13.which is used to minimize intersymbol interactions between the signals (symbols) of the subcarrier corresponding to each antenna. In particular, in order to provide the characteristics of the unitary matrix of the diagonal matrix for the phase shift, it is preferable that

satisfies the condition of the unitary matrix. In equation 12, the relationship between the phase angle θ _i (i = 1, ..., N _t ) of the frequency domain and the delay time t _i (i = 1, ..., N _t ) of the time domain is expressed by equation 13.

[86] Equation 13

[87]

,

,

[88] where N _fft , denotes the number of subcarriers of the OFDM signal.

[89] As a modified example of equation 12, the GPSD matrix can be determined as follows.

[90] Equation 14

[92] When the matrix for Generalized Phase Shift Diversity (GPSD) is obtained according to Equation 14, the symbols of the data streams (or OFDM subcarriers) are shifted using the same phase, and thus the matrix structure is provided. Namely, while the GPSD matrix of Equation 12 has rows having the same phase, the GPSD matrix of Equation 14 has columns having the same phase. Subcarrier symbols are shifted in the same phase. When equation 14 expands, the GPSD matrix can be obtained as follows, expressed in equation 15.

[93] Equation 15

[94]

[95] According to Equation 15, since the rows and columns of the GPSD matrix have independent phases, a large variability in frequency diversity gain can be obtained.

[96] As an example of equations 12, 14 and 15, the GPSD matrix of a system using a 1-bit codebook and having two transmit antennas is expressed by equation 16.

[97] Equation 16

, α²+β²=1

, α ² + β ² = 1

[99] In equation 16, if the value of α is determined, then the value of β is easily determined. Accordingly, the value of α can be set to have two values, and information about the value of α can be transmitted as a feedback codebook index. For example, after mutual agreement between the transmitter and the receiver, the value of α is set to 0.2 if the feedback index is 0, the value of α is set to 0.8 if the feedback index is 1.

[100] In equations 12, 14 and 15, as an example of a unitary matrix

,

,

a predetermined precoding matrix may be used to obtain a signal to noise ratio (SNR) gain. As a precoding matrix, a Walsh-Hadarmard matrix or a DFT (discrete Fourier transform) matrix can be used. Among them, when the Walsh-Hadamard matrix is used, the GPSD matrix sample of Equation 12 is expressed by Equation 17.

[101] Equation 17

[102]

[103] Equation 17 is obtained based on a system having a spatial multiplexing coefficient of 4 and four transmit antennas. By appropriately reconfiguring the unitary matrix, a specific transmit antenna can be selected or the spatial multiplexing coefficient can be set.

[104] In addition, the unitary matrix

in equations 12, 14 and 15 may be included in the transmitter and the receiver in the form of a codebook. In this case, the transmitter receives the codebook index information transmitted from the receiver, selects the unitary index matrix included in the codebook, and configures the phase shift based precoding matrix using one of equations 12, 14 and 15.

для уравнений 12, 14 и 15, будут следующие[105] Examples of GPSD matrices using Walsh codes 2 × 2 and 4 × 4 as unitary matrices

for equations 12, 14 and 15, there will be the following

[106] table 2 [107] 2 transmit antennas Coefficient 1 Coefficient 2

[108] Table 3 [109] 4 transmit antennas Coefficient 1 Coefficient 2 Coefficient 4

[110] Embodiment 3

[111] Generalized phase shift diversity with time variation

[112] In GPSD (phase shift generalized) matrices according to Equations 12, 14, and 15, the phase angle θ _{i of the} diagonal matrix and / or unitary matrix U can change over time. For example, for equation 12, the GPSD matrix with a change in time can be expressed by equation 18.

[113] Equation 18

[114]

[115] where

denotes the GPSD matrix of the kth subcarrier or subband of the MIMO-OFDM system having a spatial multiplexing coefficient R and N _t transmitting (physical or virtual) antennas at a specific time t, and

denotes a unitary matrix (fourth matrix) to satisfy the condition

,

,

which is used to minimize intersymbol interaction (interference) of the subcarrier corresponding to each antenna. In particular, in order to maintain the characteristics of the unitary matrix of the diagonal matrix (third matrix) for the phase shift, it is preferable that

satisfies the condition of the unitary matrix. In equation 18, the relationship between the phase angle θ _i (i = 1, ..., N _t ) and the delay time θ _i (i = 1, ... N) is expressed by equation 19.

[116] Equation 19

[117]

[118] where N _ffl denotes the number of subcarriers of the OFDM signal.

[119] As can be seen from equations 18 and 19, the value of the time delay reference and the unitary matrix can vary in time. The unit of time may be an OFDM symbol unit or a predetermined unit of time.

[120] Examples of GPSD matrices using Walsh codes 2 × 2 and 4 × 4 as unitary matrices to obtain a GPSD matrix with time variation are shown in Tables 4 and 5.

[121] Table 4 [122] 2 transmit antennas Coefficient 1 Coefficient 2

[123] Table 5 [124] 4 transmit antennas Coefficient 1 Coefficient 2 Coefficient 4

[125] Although the time-varying GPSD matrix in Equation 12 is described in Embodiment 3, the diagonal matrix and the unitary matrix of Equations 14 and 15 can be used. Accordingly, although Equation 12 is described in the following embodiments, those skilled in the art will recognize that equations 14 and 15 can be similarly extended and used.

[126] Embodiment 4

[127] Extension of generalized phase shift diversity

[128] In the second embodiment, the expanded GPSD matrix can be configured by adding a third matrix corresponding to the precoding matrix to a GPSD matrix composed of a diagonal matrix and a unitary matrix. This is expressed in equation 20.

[129] Equation 20

[131] The expanded GPSD matrix is characterized in that an N _t × R precoding matrix P is added in front of the diagonal matrix of equation 12 and the size of the diagonal matrix is used in the region (N _t = R) of the virtual antennas, thus changed to R × R. Added precoding matrix

, если информация обратной связи доступна.may vary depending on a particular frequency band or symbol of a particular subcarrier, and may preferably be mounted on a unitary matrix. It is possible to get a more optimized gain in signal-to-noise ratio (SNR) by adding a precoding matrix

if feedback information is available.

[132] Preferably, the transmitter and receiver include a codebook containing a plurality of precoding matrices P.

[133] Furthermore, in the expanded GPSD matrix, at least one of the matrices: the precoding matrix P, the phase angle 9 of the diagonal matrix, and the unitary matrix U can change in time. When the index of the next precoding matrix P is transmitted to a predetermined unit of time or a predetermined subcarrier block, a specific precoding matrix P corresponding to the index can be selected in a predetermined codebook.

[134] An expanded GPSD matrix in accordance with the present embodiment may be expressed by equation 21.

[135] Equation 21

[136]

[137] Examples of an expanded GPSD matrix, a multi-antenna system matrix having two transmitting antennas can be used, and a multi-antenna system matrix having four transmitting antennas are expressed by equations 22 and 23. The DFT (discrete Fourier transform) matrix can be used as a unitary matrix U, but the present invention is not limited to this. Any matrix can be used as long as the matrix satisfies a condition, such as a Walsh-Hadamard code.

[138] Equation 22

[139]

[140] Equation 23

[141]

[142] Embodiment 5

[143] A transmitter / receiver for performing phase shift based precoding.

[144] Typically, a communication system includes a transmitter and a receiver. The transmitter and receiver may be a transceiver (transceiver), which can carry out the transmission function and the reception function. In order to make the feedback description clear, a device for transmitting data is called a transmitter, and a device for sending data in feedback back to a transmitter is called a receiver.

[145] In the downlink, the transmitter may be part of a base station, and the receiver may be part of a terminal. On the uplink, the transmitter may be part of a terminal, and the receiver may be part of a base station. A base station may include multiple receivers and multiple transmitters, and a terminal may include multiple receivers and multiple transmitters. In general, since the configuration of the receiver has functions that are inverse to those of the transmitter, only the transmitter will be described in detail.

[146] FIG. 7 is a block diagram illustrating an embodiment of a single codeword (SCW) OFDM transmitter (orthogonal frequency division multiplexing) using phase shift based precoding in accordance with an embodiment of the present invention, and Fig. 8 is a block diagram showing an embodiment of a multi-codeword (MCW) OFDM transmitter using phase shift based precoding in accordance with an embodiment of the present invention. the last invention.

[147] Since configurations including channel encoders 510 and 610, interleavers 520 and 620, inverse fast Fourier transform (IFFT) units 550 and 650, and analog converters 560 and 660 are similar to the elements in FIG. 1, a description thereof will be omitted. Only the preliminary encoder 540 and 640 will be described in detail.

[148] The precoder 540 and 640 includes precoding matrix determination units 541 and 641 and precoding units 542 and 642.

[149] The precoding matrix determination blocks 541 and 641 determine the phase shift based precoding matrices using one of equations 12, 14, 15, 20, and 21. Since the method for determining the precoding matrix is described in detail in embodiments of the invention with second to fourth, so its description will be omitted here. The phase shift-based precoding matrix defined by one of equations 12, 14, 15, 20 and 21 can be changed to a precoding matrix to reduce the interaction between subcarriers, to the phase angle of the diagonal matrix, and / or the unitary matrix, in accordance over time, as expressed by equation 18.

[150] The precoding matrix determination units 541 and 641 may select at least one of the following matrices: a precoding matrix and a unitary matrix based on feedback information from the receiver. Here, it is preferable that the feedback information comprises a matrix index for a predetermined codebook.

[151] Pre-coding units 542 and 642 multiply this specific phase-shift-based precoding matrix by the OFDM symbol (orthogonal frequency division multiplexing) of the corresponding subcarrier to perform precoding.

[152] It will be apparent to those skilled in the art that various modifications and changes can be made to the present invention without departing from the gist of the inventions. Therefore, it is intended that the present invention covers the modifications and variations of this invention within the scope of the appended claims and their equivalents.

Industrial applicability

[153] According to embodiments of the present invention, it is possible to implement efficient communication using phase shift-based precoding that will solve the disadvantages of conventional cyclic delay diversity, phase shift diversity and precoding schemes, and further improve communication efficiency or simplify development of a transmitter / receiver using generalized or advanced phase shift based precoding.

Claims (17)

1. A method of transmitting data by a transmitter using phase shift-based precoding in a multi-antenna system using multiple subcarriers, comprising:
selecting a precoding matrix from the codebook as part of a phase shift-based precoding matrix;
determining a diagonal matrix for the phase shift as part of a precoding matrix based on the phase shift;
determining a unitary matrix as part of a precoding matrix based on a phase shift;
multiplying, in the transmitter precoding module, the product of the precoding matrix, the diagonal matrix, and the unitary matrix by the symbol of the corresponding subcarrier or subband to create a precoded symbol; and transmitting this pre-coded symbol to the receiver. 2. The method according to claim 1, wherein said unitary matrix is selected using a modulo codebook index k for the corresponding subcarrier with size N. 3. The method according to claim 1, wherein said product of the precoding matrix, the diagonal matrix, and the unitary matrix has the form

where k is the index of a subcarrier or subband, θ _i (i = 1, ..., R) is the phase angle, and R is the spatial multiplexing coefficient. 4. The method of claim 3, wherein at least one of said matrices: a precoding matrix, a diagonal matrix, and a unitary matrix changes with time. 5. The method of claim 1, wherein said precoding matrix is selected based on feedback information from a receiver. 6. The method of claim 5, wherein said feedback information comprises a matrix index for a codebook. 7. A transceiver for transmitting data and performing phase shift-based precoding in a multi-antenna system using multiple subcarriers, comprising:
a precoding matrix determination unit for selecting a precoding matrix from the codebook as part of a phase shift-based precoding matrix, for determining a diagonal matrix for phase shift as a part of said phase-shift precoding matrix, for determining a unitary matrix as part of said precoding matrix phase shift coding, and to obtain a product of said precoding matrix, iagonalnoy matrix and the unitary matrix to determine said precoding matrix based on the phase shift; and
a precoding unit to multiply said specific phase shift-based precoding matrix by the symbol of the corresponding subcarrier or subband index to create a pre-encoded symbol,
wherein the transmitter transmits this pre-coded symbol to the receiver. 8. The transceiver according to claim 7, in which said unitary matrix is selected using a modulo codebook index k for the corresponding subcarrier with size N. 9. The transceiver according to claim 7, in which the product of the precoding matrix, the diagonal matrix and the unitary matrix has the form

where k is the index of the subcarrier or subband, θ _i (i = 1, ..., R) is the phase angle and R is the spatial multiplexing coefficient. 10. The transceiver according to claim 9, in which at least one of said matrices: a precoding matrix, a diagonal matrix, and a unitary matrix changes with time. 11. The transceiver according to claim 7, in which said precoding matrix is selected based on feedback information from the receiver. 12. The transceiver according to claim 11, wherein said feedback information comprises a matrix index for a codebook. 13. A method of transmitting data by a transmitter using phase shift-based precoding in a multi-antenna system using multiple subcarriers, comprising:
determining a diagonal matrix for the phase shift as part of a precoding matrix based on the phase shift;
determining a unitary matrix as part of said precoding matrix based on a phase shift; and
multiplying, in the transmitter precoding module, the product of said diagonal matrix and the unitary matrix by the symbol of the corresponding subcarrier or subband to perform precoding to create a precoded symbol; and
transmitting this pre-encoded character to the receiver,
wherein said phase shift-based precoding matrix according to said product of a unitary matrix and a diagonal matrix includes columns having an identical phase. 14. The method according to item 13, in which said product of the diagonal matrix and the unitary matrix has the form

where k is the subcarrier or subband index, θ _i (i = 1, ..., N _t ) is the phase angle and R is the spatial multiplexing coefficient. 15. The method according to item 13, in which said product of the diagonal matrix and the unitary matrix has the form

where k is the index of a subcarrier or subband, θ _i (i = 1, ..., R) is the phase angle, and R is the spatial multiplexing coefficient. 16. A method of transmitting data by a transmitter using phase shift-based precoding in a multi-antenna system using multiple subcarriers, comprising:
determining the first and second diagonal matrices for the phase shift as part of the precoding matrix based on the phase shift;
selection from the codebook of the unitary matrix as part of said phase shift pre-coding matrix;
multiplying in the transmitter precoding module the product of the first diagonal matrix, said unitary matrix, and the second diagonal matrix by the symbol of the corresponding subcarrier to create a precoded symbol; and
transmitting this pre-encoded character to the receiver. 17. The method according to clause 16, in which said product of the first diagonal matrix, the said unitary matrix, and the second diagonal matrix has the form

where, k denotes the index of the subcarrier or subband, θ _i (i = 1, ..., N _t ) and

denote the phase angle, and R denotes the spatial multiplexing coefficient.

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