Downlink beam forming method and device of time division code division multiple access system

DOWNLINK BEAM FORMING METHOD AND DEVICE OF TIME DIVISION CODE DIVISION MULTIPLE ACCESS SYSTEM

The present invention relates to mobile communication technology, and more particularly, to a method and apparatus for downlink beamforming in a time division code division multiple access system.

The smart antenna can expand the capacity of the system by lowering the multiple access interference of a CDMA (Code Division Multiple Access) system through beamforming. When the interference signal can be measured, a spatial covariance matrix of the interference signal can be obtained, and the optimal interference suppression effect is obtained by considering the interference suppression for the interference signal when calculating the beamforming weighting coefficient.

When a time division-code division multiple access system (TD-CDMA) receives a signal, the received desired signal and the interfering signal are both located in the same time slot, and the desired user signal and the interfering user signal received in the uplink are directly transmitted. can be used to calculate the receive beamforming weighting factor. When a TD-CDMA system performs downlink transmission beamforming, a downlink transmission beamforming weighting coefficient is generally estimated based on a desired user signal and an interfering user signal received from the uplink. Taking the downlink beamforming method shown in FIG. 1 as an example, in step S101, a spatial covariance matrix of a desired user signal and an interference signal based on a desired user signal received from an uplink and an interfering user signal in an uplink time slot in which the user signal is located. Estimate the spatial covariance matrix of Proceeding to step S102, based on the spatial covariance matrix of the desired signal and the spatial covariance matrix of the interference signal, the desired user's beam is determined by any kind of rule (for example, the maximum signal-to-noise ratio rule or the maximum signal-to-interference ratio rule). Calculate the shaping weighting factor. Finally, in step S103, transmission beamforming is transmitted based on the obtained desired user weighting coefficient.

However, the above method is based on the assumption that the upstream and downstream desired users and interfering users are completely symmetrical. That is, it is based on the assumption that the desired user and the interfering user in a certain uplink time slot are exactly the same as the desired user and the interfering user in the corresponding downlink time slot. Like the time slot structure shown in FIG. 2 and the user's uplink and downlink time slots allocation scheme, the interfering user can be regarded as a user of another cell, and the uplink of the desired users 1 and 2 and the interfering users 1', 2' and 3'. is placed in time slot 1, and its downlink is placed in time slot 4. That is, the uplink time slot 1 and the downlink time slot 4 are corresponding time slots.

In a TD-CDMA system having a symmetric relationship, of course, transmission beam shaping can be performed by a traditional method. However, there are cases where the services of the TD-CDMA system are not symmetrical. In this case, the number of uplink and downlink time slots should be flexibly arranged, and the uplink and downlink time slots should not be fixed according to a preset allocation method. Also, flexible channel allocation means sometimes do not allocate user's uplink and downlink time slots according to a fixed correspondence relationship. Under these circumstances, the application of the conventional beam forming method for suppressing interference is no longer possible.

An object of the present invention is to provide a downlink beamforming method of a time division-code division multiple access system, which enables the time division-code division multiple access system to realize beamforming of interference suppression under the situation of asymmetric service, have.

The present invention provides a downlink beamforming method of a time division-code division multiple access system, comprising the steps of: obtaining a spatial covariance matrix of all uplink time slot interfering user signals and downlink time slots in which the interfering user signals are located; obtaining an interference spatial covariance matrix of each downlink time slot based on the downlink time slot in which the interfering user signal is located and the spatial covariance matrix of the interfering user signal; determining a beamforming weighting coefficient of the downlink desired user signal based on the matrix; and performing beamforming based on the beamforming weighting coefficient of the downlink desired user signal.

Here, the step of obtaining the downlink time slot in which the interfering user signal is located is obtained from the correspondence between the uplink time slot and the downlink time slot in which the user signals of all cells are preset, or the base station interferes with the radio network controller (RNC). Obtaining the number of the downlink time slot in which the user signal is located or, when all the interfering user signals exist in a cell controlled by the same base station, the base station searches the table to obtain the number of the downlink time slot in which the interfering user signal is located am.

Here, the spatial covariance matrix of the interfering user signal obtained by performing channel estimation for all uplink time slot interfering user signals using the channel estimator is,

<img file="KR20080098610A_D0001.tif" />ego,

where m is the number of interfering user signals, M indicates that there are all M interfering user signals, <img file="KR20080098610A_D0002.tif" />denotes the multi-antenna channel estimation of the m-th interfering user, <img file="KR20080098610A_D0003.tif" />silver <img file="KR20080098610A_D0004.tif" />Displays the conjugate transpose operation of .

The formula for calculating the interference spatial covariance matrix of the downlink time slot is,

<img file="KR20080098610A_D0005.tif" />ego,

where m is the number of the interfering user signal, u<sb>m</sb>denotes the mth interfering user signal, t<sb>d</sb>(m) indicates the number of a downlink time slot in which the m-th interfering user signal is located, and n represents the number of an arbitrary downlink time slot. The above formula indicates that the interfering spatial covariance matrix of one downlink time slot is the sum of the spatial covariance matrices of all interfering user signals in this downlink time slot.

The formula for calculating the beamforming weighting factor of the downlink desired user signal is,

<img file="KR20080098610A_D0006.tif" />ego,

where k is a positive integer, w denotes an arbitrary variable, w<sp>H</sp>denotes the conjugate transpose operation of w, I denotes the identity matrix of the number of antenna dimensions, λ denotes the noise power or a constant factor that is proportional to the interference power, w<sp>(k)</sp>denotes the beamforming weighting coefficient of the k-th downlink desired user signal.

The method for performing beamforming includes determining a transmission sequence of a downlink desired user signal from all antennas, and the formula for calculating the transmission sequence is:

<img file="KR20080098610A_D0007.tif" />is,

here, <img file="KR20080098610A_D0008.tif" />denotes the transmission data sequence of the k-th downlink desired user signal, k<sb>a</sb>is k<sb>a</sb>indicates the second antenna, <img file="KR20080098610A_D0009.tif" />is k<sb>a</sb>A beamforming weighting coefficient of the kth downlink desired user signal in the th antenna is indicated.

The beam shaping step can be completed by a multi-user signal beam shaper.

The method of the present invention determines the downlink time slots in which all interfering user signals are located and calculates the interference spatial covariance matrix of all downlink time slots to obtain beamforming weighting coefficients of all downlink desired user signals to proceed with beam forming. The beam forming method of the present invention is applied to both cases where the time slots are symmetrical or asymmetrical.

Another object of the present invention is to provide a downlink beamforming apparatus of a time division-code division multiple access system, which enables the time division-code division multiple access system to realize beamforming of interference suppression under the situation of asymmetric service. is doing

The time division-code division multiple access system of the present invention comprises:

an interfering user information obtaining module for obtaining all uplink time slot interfering user signals and downlink time slots in which the interfering user signals are located;

A space for obtaining the spatial covariance matrix of the uplink interference user signal, obtaining the interference spatial covariance matrix of the downlink time slot based on the downlink time slot in which the uplink interference user signal is located, and obtaining the spatial covariance matrix of the downlink desired user signal a covariance matrix acquisition module;

a beamforming weighting coefficient obtaining module for determining a beamforming weighting coefficient of a downlink desired user signal based on the interference spatial covariance matrix of each downlink time slot and the spatial covariance matrix of the downlink desired user signal;

and a beamforming module that performs beamforming based on a beamforming weighting coefficient of the downlink desired user signal.

In addition, the method in which the interfering user information obtaining module obtains the downlink time slot in which the interfering user signal is located is

obtained from the correspondence between the uplink time slot and the downlink time slot in which the user signals of all preset cells are located, or

Obtaining the number of a downlink time slot in which the interfering user signal is located from a radio network controller (RNC), or

When all interfering user signals exist in a cell controlled by the same base station, the number of a downlink time slot in which the interfering user signal is located is obtained by searching a table.

In addition, the spatial covariance matrix acquisition module performs channel estimation for all uplink time slot interference user signals using a channel estimator,

<img file="KR20080098610A_D0010.tif" />

obtain the spatial covariance matrix of the interfering user signal,

where m is the number of interfering user signals, M indicates that there are all M interfering user signals, <img file="KR20080098610A_D0011.tif" />denotes the multi-antenna channel estimation of the m-th interfering user, <img file="KR20080098610A_D0012.tif" />silver <img file="KR20080098610A_D0013.tif" />Displays the conjugate transpose operation of .

In addition, the calculation formula used when the spatial covariance matrix acquisition module acquires the interference spatial covariance matrix of the downlink time slot is,

<img file="KR20080098610A_D0014.tif" />ego,

where m is the number of the interfering user signal, u<sb>m</sb>denotes the mth uplink time slot interference user signal, t<sb>d</sb>(m) denotes a downlink time slot in which the m-th interfering user signal is located, and n denotes the number of the downlink time slot.

In addition, the calculation formula used when the beamforming weighting factor obtaining module obtains the beamforming weighting factor of the downlink desired user signal is,

<img file="KR20080098610A_D0015.tif" />ego,

where k is a positive integer, w denotes an arbitrary variable, w<sp>H</sp>denotes the conjugate transpose operation of w, I denotes the identity matrix of the number of antenna dimensions, λ denotes the noise power or a constant factor that is proportional to the interference power, w<sp>(k)</sp>denotes the beamforming weighting coefficient of the k-th downlink desired user signal.

In addition, the beam forming module is used to determine the transmission sequence of the downlink desired user signal in all antennas, and the formula for calculating the transmission sequence is:

<img file="KR20080098610A_D0016.tif" />is,

here, <img file="KR20080098610A_D0017.tif" />denotes the transmission data sequence of the k-th downlink desired user signal, k<sb>a</sb>is k<sb>a</sb>indicates the second antenna, <img file="KR20080098610A_D0018.tif" />is k<sb>a</sb>A beamforming weighting coefficient of the kth downlink desired user signal in the th antenna is indicated. The beam shaping module is realized by a multi-user signal beam shaper.

The apparatus of the present invention performs beamforming by obtaining beamforming weighting coefficients of all downlink desired user signals by determining downlink time slots in which all interfering user signals are located and calculating the interference spatial covariance matrix of all downlink time slots. The beamforming method of is applied both when the time slot is symmetrical or asymmetrical.

1 is a flowchart of a conventional down-beam forming method.

FIG. 2 is a time slot structure diagram and an allocation table of uplink and downlink time slots corresponding to the method shown in FIG. 1 .

3 is a flowchart of a first embodiment of the down-beam forming method of the present invention.

Fig. 4 is a view showing the beam former used in the first embodiment.

5 is a time slot structure diagram and an allocation table of uplink and downlink time slots of the second embodiment of the downlink beamforming method.

6 is a flowchart of a second embodiment of the present invention.

7 is a view showing the structure of the down-beam forming apparatus of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An optimal embodiment of the present invention will be described in detail below with reference to the drawings. First of all, the meaning of the terms, words, and claims used in the present invention is not limited to understanding according to the literal meaning and general meaning, and in addition, includes meanings and concepts consistent with the description of the present invention. This is so that we as inventors properly define the term to better describe our invention. Therefore, the present description and arrangement of drawings are merely preferred embodiments selected by the present invention, and do not enumerate all technical characteristics of the present invention. We should also know that there are various equivalent technical solutions or improved technical solutions that can replace our technical solutions.

3 is a flowchart of a first embodiment of the present invention;

As shown in Fig. 3, in step S301, spatial covariance matrices of interfering user signals of all uplink time slots and downlink time slots in which the interfering user signals are located are obtained. In this process, channel estimation is performed for the interfering user signals in all uplink time slots to obtain a spatial covariance matrix of the interfering user signals, and the determination of the interfering user signals can be realized by the power threshold of the interfering signal. All M interfering user signals in all uplink time slots<img file="KR20080098610A_D0019.tif" />For example, if there is an interfering user signal u<sb>m</sb>The subscript m in (m=1,, M) indicates the number of the interfering user signal, and M spatial covariance matrices are performed by performing channel estimation on M interfering user signals. <img file="KR20080098610A_D0020.tif" />get

here, <img file="KR20080098610A_D0021.tif" />ego,

<img file="KR20080098610A_D0022.tif" />denotes the mathematical expectation of a random variable, i.e., an operation for averaging it. <img file="KR20080098610A_D0023.tif" />silver matrix <img file="KR20080098610A_D0024.tif" />Displays the conjugate transpose operation of .

<img file="KR20080098610A_D0025.tif" />denotes multi-antenna channel estimation for the m-th interfering user signal, and there are various channel estimation methods. For example, there is a basic Steiner channel estimator (a kind of cheap estimation method) or an improved version thereof. Here, the interfering user signal may be an interfering user signal of the same cell or an interfering user signal of an external cell, and whether a user signal occupying the same radio resource is regarded as an interfering user signal depends on a specific system and a physical layer algorithm. . For example, when beamforming is performed in a TD-SCDMA (Time Division-Synchronous Code Division Multiple Access) system using a joint detection technique, it can be considered that the signal interference of the present cell has already been eliminated by joint detection, and the external cell Only the interference of the user signal of can be considered.

And, in this step, a downlink time slot in which M interfering user signals are located <img file="KR20080098610A_D0026.tif" />should be confirmed The base station may provide a correspondence relationship between uplink and downlink time slots of user signals of the same cell, and a method for determining a downlink time slot in which an interfering user signal is located with respect to a user signal of an external cell includes a preset method, a signaling transmission method, and a table There is a search method.

(1) Pre-setting method: This is a kind of default method, and in the network initialization step, the correspondence between the uplink and downlink time slots in which the user signals of all cells are located can be set.

(2) Signaling transmission method: The base station requests the RNC (Radio Network Controller) to inform the number of the downlink time slot in which the interfering user signal is located.

(3) Table search method: When all interfering user signals exist in a cell controlled by the same base station, the base station can obtain the number of a downlink time slot in which the interfering user signal is located by searching the table.

Then, the flow advances to step S302 to obtain an interference spatial covariance matrix of each downlink time slot based on the downlink time slot in which the interfering user signal is located and the spatial covariance matrix of the interfering user signal. In this step, assuming that all N downlink time slots exist in one cell, the set of interference user signals in any downlink time slot n (n = 1, 2, ..., N) is,

<img file="KR20080098610A_D0027.tif" />am.

here, <img file="KR20080098610A_D0028.tif" />u<sb>m</sb>is any or all uplink time slot interfering user signal (u<sb>m</sb>) is indicated.

The spatial covariance matrix of the interfering signal in time slot n is,

<img file="KR20080098610A_D0029.tif" />am.

That is, the spatial covariance matrix of the interfering signal in time slot n is the sum of the spatial covariance matrices of all interfering user signals located in time slot n.

Thereafter, the flow advances to step S303 to determine the beamforming weighting coefficient of the downlink desired user signal based on the interference spatial covariance matrix of each downlink time slot and the spatial covariance matrix of the downlink desired user signal. Assuming that a time slot in which a desired downlink user k is located is n, the downlink beamforming weighting factor is,

<img file="KR20080098610A_D0030.tif" />am.

here, <img file="KR20080098610A_D0031.tif" />silver <img file="KR20080098610A_D0032.tif" />We denote W that maximizes . W may be a variable of any type. I is the identity matrix of the number of antenna dimensions. λ may indicate noise power or a constant factor that is in constant proportion to interference power.<img file="KR20080098610A_D0033.tif" />denotes the spatial covariance matrix of the k-th downlink desired user signal, which can be obtained through various methods in the prior art. One of them is a method obtained through measurement of the physical layer. That is, the channel estimation result (<img file="KR20080098610A_D0034.tif" />), and using the channel estimation result, the spatial covariance matrix of the desired user <img file="KR20080098610A_D0035.tif" />get Among them,<img file="KR20080098610A_D0036.tif" />denotes the mathematical expectation of a random variable, i.e., an operation for averaging it. <img file="KR20080098610A_D0037.tif" />silver matrix <img file="KR20080098610A_D0038.tif" />Displays the conjugate transpose operation of . W<sp>(k)</sp>(k=1,2, ...,K) denotes a downlink transmission beamforming weighting coefficient of a desired user signal. In addition,

<img file="KR20080098610A_D0039.tif" />

is, <img file="KR20080098610A_D0040.tif" />k<sb>a</sb>A beamforming weighting coefficient of the kth downlink desired user signal in the th antenna is indicated.

Finally, in step S304, beamforming is performed based on the beamforming weighting coefficient of the downlink desired user signal. The transmission data sequence of the desired user signal k<img file="KR20080098610A_D0041.tif" />Assuming that , antenna k<sb>a</sb>(k<sb>a</sb>=1,2,...,K<sb>a</sb>), the transmission sequence in

<img file="KR20080098610A_D0042.tif" />am.

In this step, you may proceed with beam shaping using the beam shaping machine shown in FIG. As shown in Fig. 4, the transmission data sequence of the k-th desired user signal<img file="KR20080098610A_D0043.tif" />to k<sb>a</sb>Beamforming weighting factors at the antennas <img file="KR20080098610A_D0044.tif" />Antenna k by performing an AND operation with and then performing an OR operation with the result of this operation of other user signals.<sb>a</sb>transmission sequence in <img file="KR20080098610A_D0045.tif" />can get

With reference to FIGS. 5 and 6, the beam forming method disclosed by the present invention will be described by taking the TD-SCDMA system as an example.

As shown in Fig. 5, there are all six service time slots (time slot 1 to time slot 6) in this embodiment. Among them, time slots 1 and 2 are used for the uplink, and time slots 3, 4, 5, and 6 are used for the downlink. In the uplink time slot 1, four interfering user signals are measured and displayed as interfering user signals 1', 2', 3', and 4', respectively. Five interfering user signals are measured in uplink time slot 2 and displayed as interfering user signals 5', 6', 7', 8', and 9', respectively.

As shown in FIG. 6, in step S601, channel estimation is performed on nine uplink time slot interfering user signals to obtain spatial covariance matrices of the nine interfering user signals. In this embodiment, the spatial covariance matrix of the interfering user signal obtained by estimating the interfering user signals 1' to 4' in the uplink time slot 1 and estimating the interfering user signals 5' to 9' in the uplink time slot 2 is<img file="KR20080098610A_D0046.tif" />am.

And, in this step, a downlink time slot in which 9 interfering user signals are located <img file="KR20080098610A_D0047.tif" />(here, m=1,2,...,9) needs to be further determined. In this embodiment, a downlink time slot in which an interfering user signal is located is obtained by using a signaling transmission method. The base station is the signaling of the Iub interface (the interface between the radio network controller [RNC] and the base station), the signaling of the Iur interface (the logical interface between two RNCs) (or the signaling of the Iu interface between the radio network and the core network) or operation maintenance (OM). ) to request the RNC to inform the downlink time slot allocation number of the interfering user signal through the channel.

The downlink time slot number of the interfering user signal obtained by the base station through signaling is as follows.

<img file="KR20080098610A_D0048.tif" />

Thereafter, the flow advances to step S602 to obtain an interference spatial covariance matrix of the downlink time slots 3-6 based on the downlink time slot in which the interfering user signal is located and the spatial covariance matrix of the interfering user signal.

<img file="KR20080098610A_D0049.tif" />

<img file="KR20080098610A_D0050.tif" />

<img file="KR20080098610A_D0051.tif" />

<img file="KR20080098610A_D0052.tif" />

Thereafter, the flow advances to step S603 to determine the beamforming weighting coefficients of the downlink desired user signals based on the interference spatial covariance matrix of the downlink time slots 3-6 and the spatial covariance matrices of the nine downlink desired user signals. Taking downlink user 6 as an example, if downlink user 6 has to transmit data in both the 5th and 6th time slots, the downlink user 6 can calculate beamforming weighting coefficients in time slot 5 and time slot 6, respectively. where λ=0.5.

<img file="KR20080098610A_D0053.tif" />

<img file="KR20080098610A_D0054.tif" />

Finally, the flow proceeds to step S604 to perform beamforming based on the beamforming weighting coefficients of the nine downlink desired user signals. The transmission data sequence of the desired user signal k (k=1, 2, , 9)<img file="KR20080098610A_D0055.tif" />Assuming that , antenna k<sb>a</sb>(k<sb>a</sb>=1,2,...,K<sb>a</sb>), the transmission sequence is as follows.

<img file="KR20080098610A_D0056.tif" />

here <img file="KR20080098610A_D0057.tif" />is k<sb>a</sb>A beamforming weighting coefficient of the kth downlink desired user signal in the th antenna is indicated.

7 is a diagram showing the configuration of a down-beam forming apparatus of a time division-code division multiple access system of the present invention. The apparatus includes an interfering user information obtaining module 71 , a spatial covariance matrix obtaining module 72 , a beamforming weighting coefficient obtaining module 73 , and a beam forming module 74 .

The interfering user information obtaining module is used to determine all uplink time slot interfering user signals, and to determine downlink time slots in which the interfering user signals are located. A specific implementation example of this module is as follows.

Determination of the uplink interfering user signal may be implemented by a power threshold of the interfering signal. Here, the interfering user signal may be an interfering user signal of the same cell or an interfering user signal of an external cell, and whether a user signal occupying the same radio resource is regarded as an interfering user signal depends on a specific system and a physical layer algorithm. For example, when beamforming is performed in a TD-SCDMA (Time Division-Synchronous Code Division Multiple Access) system using a joint detection technique, it can be considered that the signal interference of the present cell has been removed by joint detection, and the user of an external cell Only interference of signals can be considered.

Since the base station can provide the correspondence between uplink and downlink time slots of user signals of the same cell, the downlink time slots in which the interfering user signals of the same cell are located can be obtained through the base station. A method of determining a downlink time slot in which an interfering user signal is located for a user signal of an external cell includes a preset method, a signaling transmission method, and a table search method.

(1) Pre-setting method: This is a kind of default method, and in the network initialization step, the correspondence between the uplink and downlink time slots in which the user signals of all cells are located can be set.

(2) Signaling transmission method: The base station requests the RNC (Radio Network Controller) to inform the number of the downlink time slot in which the interfering user signal is located.

(3) Table search method: When all interfering user signals exist in a cell controlled by the same base station, the base station may search the table to obtain the number of a downlink time slot in which the interfering user signal is located.

The spatial covariance matrix obtaining module performs channel estimation on all uplink time slot interfering user signals acquired by the interfering user information obtaining module to obtain spatial covariance matrices of all uplink interfering user signals, and then the interfering user information obtaining module determines the An interference spatial covariance matrix of each downlink time slot is obtained based on the downlink time slot in which the interfering user signal is located and the spatial covariance matrix of the interfering user signal.

All M interfering user signals in all uplink time slots <img file="KR20080098610A_D0058.tif" />For example, there is First, channel estimation is performed for M interfering user signals. Channel estimation can be implemented using a basic Steiner channel estimator (a kind of inexpensive estimation method) or an improved form thereof. Then, the M spatial covariance matrices are computed<img file="KR20080098610A_D0059.tif" />get here,<img file="KR20080098610A_D0060.tif" />am.

<img file="KR20080098610A_D0061.tif" />denotes the multi-antenna channel estimation of the m-th interfering user signal, <img file="KR20080098610A_D0062.tif" />Is <img file="KR20080098610A_D0063.tif" />denotes the conjugate transpose operation of <img file="KR20080098610A_D0064.tif" />denotes the mathematical expectation of a random variable, i.e., an operation for averaging it.

Assuming that all N downlink time slots exist in one cell, an interfering user signal of any downlink time slot n (n = 1, 2, ..., N) is <img file="KR20080098610A_D0065.tif" />am.

Among them, <img file="KR20080098610A_D0066.tif" />u<sb>m</sb>is any or all uplink time slot interfering user signal (u<sb>m</sb>) is indicated.

The spatial covariance matrix of the interfering signal in time slot n is,

<img file="KR20080098610A_D0067.tif" />am.

That is, the spatial covariance matrix of the interfering signal in time slot n is the sum of the spatial covariance matrices of all interfering user signals located in time slot n.

The beamforming weighting coefficient obtaining module determines the beamforming weighting coefficient of the downlink desired user signal based on the interference spatial covariance matrix of each downlink time slot and the spatial covariance matrix of the downlink desired user signal. Assuming that a time slot in which a desired downlink user k is located is n, the downlink beamforming weighting factor is

<img file="KR20080098610A_D0068.tif" />am.

here, <img file="KR20080098610A_D0069.tif" />silver <img file="KR20080098610A_D0070.tif" />We denote W that maximizes . W may be any type of variable. I denotes the identity matrix of the number of antenna dimensions. λ may indicate noise power or a constant factor that is in constant proportion to interference power.<img file="KR20080098610A_D0071.tif" />denotes the spatial covariance matrix of the k-th downlink desired user signal, which can be obtained through measurement. W<sp>(k)</sp>(k=1,2,...,K) indicates the downlink transmission beamforming weighting coefficient of the desired user signal and is expressed as follows.

<img file="KR20080098610A_D0072.tif" />

is, <img file="KR20080098610A_D0073.tif" />is k<sb>a</sb>A beamforming weighting coefficient of the kth downlink desired user signal in the th antenna is indicated.

The beam shaping module performs beam shaping based on the beam shaping weighting factor of the downlink desired user signal. The transmission data sequence of the desired user signal k<img file="KR20080098610A_D0074.tif" />Assuming that , antenna k<sb>a</sb>(k<sb>a</sb>=1,2,...,K<sb>a</sb>), the transmission sequence is as follows.

<img file="KR20080098610A_D0075.tif" />

The beam shaping module may be implemented through the beam shaper of FIG. 4 . As shown in Fig. 4, the transmission data sequence of the k-th desired user signal<img file="KR20080098610A_D0076.tif" />to k<sb>a</sb>Beamforming weighting factors at the antennas <img file="KR20080098610A_D0077.tif" />Antenna k by performing an AND operation with and then performing an OR operation with the result of this operation of other user signals.<sb>a</sb>transmission sequence in <img file="KR20080098610A_D0078.tif" />can get

Here, the spatial covariance matrix acquisition module and the beam shaping weighting coefficient acquisition module may be realized through a general-purpose calculation facility or software in the device, or may be realized through a dedicated hardware facility.

The above is merely a preferred embodiment of the present invention, and a person skilled in the art can make some improvements and changes under the premise that does not deviate from the principles of the present invention, and these improvements and changes are also considered to be within the scope of protection of the present invention. do.