KR20070102164A - Apparatus and method for transmitting/receiving a signal in a beam forming/multiple input multiple output-orthogonal frequency division multiple access communication system - Google Patents

Abstract

A method and an apparatus for transmitting/receiving signals in a beam forming MIMO(Multiple Input Multiple Output) OFDMA(Orthogonal Frequency Division Multiple Access) communication system are provided to reduce an uplink load of the communication system by minimizing amount of feedback information. A base station transmitter includes M transmission antenna processors(300-1-300-M) and a controller(350). The transmission antenna processors include resource selectors(311-1-311-M), beam forming processors(313-1-313-M), IFFT(Inverse Fast Fourier Transform) units(315-1-315-M), P/S converters(317-1-317-M), guard interval insertion units(319-1-319-M), transmission processors(321-1-321-M), and transmission antennas(323-1-323-M). The resource selector selects some of sub-carriers and transmits data symbols using the selected sub-carriers. The beam forming processor multiplies weights for the sub-carriers and outputs the result to the IFFT unit under the control of the controller.

Description

Beamforming-Multiple Input Multiple Output / Orthogonal Frequency Division Multiple Access Communication System and Apparatus and Method for Signal Transmitting

1 schematically illustrates segment allocation in a beamforming-MIMO / OFDMA communication system in accordance with an embodiment of the present invention.

FIG. 2 schematically illustrates types of segments supported in a beamforming-MIMO / OFDMA communication system according to an embodiment of the present invention.

3 is a diagram illustrating a structure of an apparatus for transmitting a base station when using a fourth type segment in a beamforming-MIMO / OFDM communication system according to an exemplary embodiment of the present invention.

4A-4C schematically illustrate a resource selection operation of the controller 350 of FIG. 3.

5 is a diagram illustrating a signal receiving device structure of a user terminal when using a fourth type segment in a beamforming-MIMO / OFDMA communication system according to an embodiment of the present invention;

6 is a flowchart illustrating an operation of a base station when using a fourth type segment in a beamforming-MIMO / OFDMA communication system according to an embodiment of the present invention.

7 is a flowchart illustrating an operation process of a user terminal when using a fourth type segment in a beamforming-MIMO / OFDMA communication system according to an embodiment of the present invention.

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an apparatus and method for transmitting and receiving signals in a communication system, and in particular, beam forming-multiple input multiple output (MIMO) / orthogonal frequency division multiple access (OFDMA: Orthogonal Frequency Division Multiple Access, hereinafter referred to as "OFDMA") relates to an apparatus and method for transmitting and receiving signals in a communication system (hereinafter referred to as "beamforming-MIMO / OFDMA communication system").

The next generation communication system has been developed to transmit a large amount of data at a high speed to a large number of user terminals, and in order to transmit a large amount of data at a high speed, peak throughput must be optimized as well as average throughput. do. In addition, for high speed large data transmission, it is important to increase data rate and improve transmission reliability, and a method that is actively being studied as a method of increasing data rate and improving transmission reliability is multiple antenna. That's the way. The multi-antenna scheme is a method of overcoming the limitation of bandwidth resources in the frequency domain by using a space domain.

On the other hand, the smart antenna (smart antenna) method is a method of performing a beam forming by receiving a signal corresponding to a preset direction of arrival (DOA) in the signal receiving apparatus when there is a correlation between the receiving antennas. That is, the smart antenna scheme is a reception beamforming scheme, and the smart antenna scheme is generally suitable for receiving an uplink signal from a base station (BS) rather than a user terminal. In the case of a user terminal, it is difficult to include a plurality of receive antennas in various aspects such as hardware minimization or manufacturing cost. On the contrary, since the base station is easier to have a plurality of receiving antennas than the user terminal, the smart antenna method is preferably applied to the base station rather than the user terminal.

In addition, the transmission beamforming method is a method in which a signal transmission apparatus actively uses a signal when transmitting a signal using a plurality of transmission antennas. In general, the transmission beamforming method is preferably applied to a base station as compared to a user terminal, and using the transmission beamforming method may improve reliability of a downlink signal transmitted from the base station to the user terminal. In addition, when using the transmission beamforming method based on the Maximum Ratio Combining (MRC) method, Signal to Interference and Noise Ratio (SINR) is referred to as 'SINR'. It is well known that it is optimal in terms of In this case, the MRC method is optimal in terms of maximizing a signal-to-noise ratio (SNR).

In the transmission beamforming method, diversity gain and array gain are performed only under the assumption that an accurate channel estimation is performed in the signal receiving apparatus and no error occurs in a signal fed back from the signal receiving apparatus to the signal transmitting apparatus. gain), and it is possible to maximize the reliability of data transmission. However, even if the transmission beamforming method satisfies the assumption that the signal transmission apparatus performs accurate channel estimation, it is referred to as a high complexity eigen-decomposition (hereinafter referred to as 'eigen-decomposition') in the signal transmission apparatus or the signal transmission apparatus. And the like, and have to feed back channel quality information (CQI: hereinafter referred to as 'CQI') from the signal receiving apparatus to the signal transmitting apparatus.

In particular, next-generation communication systems are actively considering using a multi-carrier modulation (MCM) method, for example, an OFDMA method, for high-speed large data transmission. When the OFDMA scheme is used, the amount of CQI that the signal receiver must feed back to the signal transmitter increases according to the number of sub-carriers used in the OFDMA scheme. Therefore, in the beamforming-MIMO / OFDM communication system, the amount of fed back CQI increases according to the number of subcarriers, the number of transmit antennas and the number of receive antennas. Increasing the amount of CQI fed back will result in a reduction in the amount of resources available in the beamforming-MIMO / OFDM communication system, thereby reducing resource efficiency, as well as increasing the uplink load due to CQI feedback. do.

Accordingly, an object of the present invention is to provide an apparatus and method for transmitting and receiving signals in a beamforming-MIMO / OFDMA communication system.

The apparatus of the present invention for achieving the above object; Beamforming multiple-input multiple-output (MIMO: Multiple Input Multiple Output) / orthogonal frequency division multiple access: in (OFDMA Orthogonal Frequency Division Multiple Access) system for transmitting and receiving signals at the base station of the communication system, N _c of used by the base station information on the subcarriers of the first desired the first resource selection information and the second user terminal to use and which includes information for the desired user terminal is using N _s subcarriers N _s subcarriers and receiving a second resource selection information including the receiver, the first resource selection information, and a second with reference to the resource selection information with the N _c sub-carriers in the first N _s subcarriers user terminal to use during the A controller for selecting the N _s subcarriers to be used by the second user terminal and M one to one connection to each of the M transmit antennas And transmitting antenna processing units, wherein each of the M transmitting antenna processing units targets the first user terminal, and N _s data symbols to be transmitted identically through each of the M transmitting antennas used in the base station. Receiving a second data symbol stream including a first data symbol stream including the first data symbol stream and N _s data symbols intended to be transmitted through each of the M transmit antennas. And transmitting data symbols included in the first data symbol stream through N _s subcarriers selected by the first user terminal, and transmitting data symbols included in the second data symbol stream to the second user terminal. a characterized in that the transmission on the N _s subcarriers chosen to use .

Another apparatus of the present invention for achieving the above object; A device for transmitting and receiving a signal in a user terminal of a beamforming-multiple input multiple output (MIMO) / orthogonal frequency division multiple access (OFDMA) communication system, comprising: N _c subs from a base station A receiver for receiving resource selection result information including information about N _s subcarriers to be used by the user terminal among carriers, N reception antenna processing units connected one to one to each of N reception antennas, and N selecting the N _s subcarriers that of the _c sub-carriers to use the user terminal, and to generate the resource selection information containing the information for the selected N _s subcarriers of the N reception antennas, respectively N _s corresponding to the resource selection result information among N _c subcarrier signals generated by A resource selection information generator for classifying subcarrier signals and N _s Maximum Ratio Combining (MRC) detectors, each of the N _s MRC detectors being configured by the N receive antennas in the resource selection generator. Each of the N _s subcarrier signals classified for each of the signals is detected as a data symbol mapped thereto using a maximum ratio combining (MRC) method.

The method of the present invention for achieving the above object; Beamforming multiple-input multiple-output (MIMO: Multiple Input Multiple Output) / orthogonal frequency division multiple access: A method for transmitting and receiving signals at the base station of the (OFDMA Orthogonal Frequency Division Multiple Access) communication system, N _c of used by the base station information on the subcarriers of the first desired the first resource selection information and the second user terminal to use and which includes information for the desired user terminal is using N _s subcarriers N _s subcarriers Receiving a second resource selection information that includes, and a target comprising the N _s data symbols to target the first user terminal, and to transmit the same through each of the M transmit antennas used in the base station Targeting one data symbol stream and the second user terminal, the same through each of the M transmit antennas N _s data symbols second data symbols with reference to the process of receiving a stream, the first resource selection information and the second resource selection information, wherein the N _c sub-carriers of the first user terminal of including to be transmitted is by the N _s subcarriers to the process and, the group of the M transmit antennas to the second user terminal selects N _s subcarriers for use, wherein the data symbols including the first data symbol stream And transmitting through the N _s subcarriers selected by the user terminal and transmitting the data symbols included in the second data symbol stream through the N _s subcarriers selected by the second user terminal. Characterized in that it comprises a.

Another method of the present invention for achieving the above object is; A method for transmitting and receiving a signal at a user terminal of a beamforming-multiple input multiple output (MIMO) / orthogonal frequency division multiple access (OFDMA) communication system, comprising: N _c subs from a base station Receiving resource selection result information including information about N _s subcarriers to be used by the user terminal among carriers, and for each of the N reception antennas, by fast Fourier transforming the received signal, the N _c subcarriers selecting the process and the N _c subcarriers of wishing to use the user terminal, N _s subcarriers, generated with the signal, the resource selection information containing the information for the selected N _s subcarriers process, and the N reception antennas, a N _c subcarriers for each new generation for generating a S of the resource selection result information corresponding N _s subcarriers signal process, and the N reception antennas, the maximum ratio combining for each of the N _s subcarriers signal classification for each classifying to the (MRC: Maximum And a process of detecting data symbols mapped thereto using a Ratio Combining) method.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that in the following description, only parts necessary for understanding the operation according to the present invention will be described, and descriptions of other parts will be omitted so as not to obscure the subject matter.

The present invention proposes an apparatus and method for transmitting and receiving signals in a communication system. Hereinafter, for convenience of description, beam forming-multiple input multiple output (MIMO) / orthogonal frequency division multiple access (OFDMA) A communication system (hereinafter referred to as a 'beamforming-MIMO / OFDMA communication system') will be described as an example of the communication system. The beamforming-MIMO / OFDMA communication system as well as other communication systems are of course applicable. Here, the 'beam forming-MIMO / OFDMA communication system' refers to a communication system using a beam forming method, a MIMO method, and an OFDMA method together.

1 is a diagram schematically illustrating segment allocation in a beamforming-MIMO / OFDMA communication system according to an embodiment of the present invention.

개의 변조된 OFDM 심벌들을 송신할 수 있게 된다. 상기 세그먼트를 구성하는 OFDM 심볼 구간들의 개수 N_t와 서브 캐리어 주파수 대역들의 개수 N_f는 상기 빔 포밍-MIMO/OFDMA 통신 시스템의 시스템 상황에 따라 가변적으로 설정될 수 있음은 물론이다.Referring to FIG. 1, the horizontal axis represents the time domain and the vertical axis represents the frequency domain. The beamforming-MIMO / OFDMA communication system divides the entire bandwidth into a plurality of sub-carrier frequency bands. As shown in FIG. 1, N _t orthogonal frequency division multiplexing (OFDM) symbol intervals preset in the time domain are occupied, and are preset in the frequency domain. An area occupying one N _f subcarrier frequency bands will be defined as a 'segment'. Thus, one segment

Two modulated OFDM symbols can be transmitted. The number N _t of the OFDM symbol intervals constituting the segment and the number N _f of the subcarrier frequency bands may be variably set according to a system situation of the beamforming-MIMO / OFDMA communication system.

Next, the types of segments supported by the beamforming-MIMO / OFDMA communication system according to an embodiment of the present invention will be described with reference to FIG. 2.

2 is a diagram schematically illustrating types of segments supported by a beamforming-MIMO / OFDMA communication system according to an embodiment of the present invention.

Referring to FIG. 2, the beamforming-MIMO / OFDMA communication system implements a differential segment structure by differentiating segments according to priority and a signal processing scheme applied thereto. Here, the priority is according to a delay tolerance condition, that is, according to a Quality of Service (QoS) level condition and a distance from a base station (BS). It is generated according to (distance from BS) conditions, that is, considering channel quality. Here, the QoS level condition is a condition for distinguishing whether a real time (RT) service or a non real time (NRT) service is used, and the channel quality condition is a cell center area or a cell boundary. (cell boundary) A condition that distinguishes whether it is a region. In the present invention, the type of the segment is divided into four types, that is, the first type (type I) to the fourth type (type IV) according to the priority. The first type segment is a segment for supporting a non-real time service targeting a terminal located in a cell center area, and the second type segment is a segment for real time service support targeting a terminal located in a cell center area. The third type segment is a segment for supporting a non-real time service targeting a terminal located in a cell boundary region, and the fourth type segment is a segment for real time service targeting a user terminal located in a cell boundary region. . In the present invention, since the signal transmission / reception operation in the beamforming-MIMO / OFDMA communication system will be described by using the fourth type segment as an example, only the fourth type segment will be described in detail.

First, the fourth type segment is a segment for real-time service support targeting a user terminal located in a cell boundary region, and a transmission scheme based on non-opportunistic scheduling is applied to the fourth type segment. . That is, since the base station supports transmission based on link level diversity scheme and uses a relatively low order modulation scheme such as Quadrature Phase Shift Keying (QPSK) scheme, the base station codes in the fourth type segment. Code Division Multiplexing (CDM) may be used. In addition, the base station determines a low speed adaptive modulation and coding (AMC) scheme and a hybrid automatic retransmission request (HARQ) scheme for the fourth type segment. HARQ ') may be applied simultaneously.

Therefore, the combination of the signal processing schemes applied to the fourth type segment is a combination of the following six signal processing schemes.

(1) Traffic / User Type: Real Time Traffic / Cell-Centric Area

(2) Scheduling method: non-planning method, scheduling method according to QoS level

(3) Link adaptation method: low speed AMC method, HARQ method with synchronous exponential IR (Incremental Redundancy)

(4) MIMO scheme: Space Time Coding (STC) scheme (ST-BICM (Space Time-Bit Interleaved Coded Modulation) scheme, antenna hopping scheme)

(5) Transmission Method: Frequency Hopping (FH), CDM

(6) Channel State Information (CSI) Estimation Method: Channel Estimation Method + Interpolation Method

Next, referring to FIG. 3, a structure of a signal transmission apparatus of a base station (BS) when using a fourth type segment in a beamforming-MIMO / OFDM communication system according to an embodiment of the present invention is illustrated.

3 is a diagram illustrating a structure of an apparatus for transmitting a base station when using a fourth type segment in a beamforming-MIMO / OFDM communication system according to an embodiment of the present invention.

Referring to FIG. 3, the base station signal transmission apparatus includes a plurality of transmission antennas, for example, M transmission antennas, that is, transmission antenna # 1 323-1 to transmission antenna #M 323 -M. User terminals, i.e., user terminal # 1 and user terminal # 2, use two fourth type segments, namely fourth type segment # 1 and fourth type segment # 2, and the two fourth type segments occupy It is assumed that the number of subcarriers is N _c, and each of the two user terminals transmits a data symbol stream by selecting only N _s subcarriers among the N _c subcarriers. . Where N _c = 2N _s .

The base station signal transmission apparatus includes M transmit antenna processing units, that is, transmit antenna processing unit # 1 (300-1) to transmit antenna processing unit #M (300-M), to transmit a signal through each of the M transmit antennas; Controller 350. Although not shown in FIG. 3, the apparatus includes a base station signal receiving apparatus for receiving resource selection information transmitted from each of the two user terminals. Here, the resource selection information indicates information indicating which subcarriers of the N _c subcarriers use which subcarriers and which subcarriers are selected not to be used. In the embodiment of the present invention, since the same data symbol streams are transmitted through each of the transmit antenna # 1 323-1 to the transmit antenna #M 323-M, the resource selection information is transmitted to the transmit antenna # 1 323-1. ) And only the selection information on whether to use the subcarrier without separately considering each of the transmission antennas #M 323 -M. Since the operation of generating the resource selection information will be described in detail below, the detailed description thereof will be omitted.

As described above, each of the transmit antenna processing unit # 1 300-1 to the transmit antenna processing unit #M 300 -M processes the same data symbol streams, but may be different only in that it transmits through different transmit antennas. It is only. That is, the first transmit antenna processing unit # 1 (300-1) transmits a resource selector # 1 311-1, a beamforming processor # 1 (313-1), and an inverse fast Fourier transform (IFFT: Inverse). Fast Fourier Transform, hereinafter referred to as IFFT processor # 1 315-1, parallel to serial converter (P / S) # 1 317-1, and guard interval ( guard interval) Includes inserter # 1 319-1, transmit processor # 1 321-1, and transmit antenna # 1 323-1. The transmit antenna processor #M (300-M), which is the Mth transmit antenna processor, includes a resource selector #M (311-M), a beam forming processor #M (313-M), and an IFFT processor #M (315-M). ), Parallel / serial converter #M 317-M, guard interval inserter #M 319-M, transmission processor #M 321-M, and transmission antenna #M 323-M. Include. Therefore, for convenience of description, the operation of the base station signal transmission apparatus will be described using the transmission antenna processing unit # 1 300-1 as an example, and it should be noted that the remaining transmission antenna processing units are not described separately.

First, it is assumed that data symbol stream # 1 targeting user terminal # 1 and data symbol stream # 2 targeting user terminal # 2 are input to the resource selector # 1 311-1. In addition, it is assumed that each of the data symbol stream # 1 and the data symbol stream # 2 includes N _s data symbols, and one data symbol includes at least one data bit. Here, N _s of which the data symbol stream # 1 is referred to as N data symbols _s a _{s 1 (1), ...,} s 1 (N s) comprising the, further comprising if the data symbol stream # 2 Data symbols will be referred to as s ₂ (1), ..., s ₂ (N _s ).

The resource selector # 1 311-1 selects N _s subcarriers among the N _c subcarriers under the control of the controller 350 to select the data symbols s ₁ (1),. s ₁ (N _S ) is mapped to be transmitted on the selected N _s subcarriers, and the data symbols s ₂ (1),..., s ₂ (N _s ) are transmitted on the remaining N _s subcarriers. After mapping to be transmitted through the remaining N _s subcarriers, the signal is output to the beamforming processor # 1 313-1. The beamforming processor # 1 313-1 performs beamforming on each of the N _c subcarriers to which data symbols are mapped in the resource selector # 1 311-1 under the control of the controller 350. After multiplying the weights, the result is output to the IFFT processor # 1 315-1. Here, the operation of the controller 350 will be described in detail.

The controller 350 corresponds to resource selectors, that is, resource selectors # 1 311-1 to resource selectors #M 311 -M corresponding to the resource selection information received from the user terminal # 1 and the user terminal # 2. Selects which user terminal each of the N _c subcarriers is to be used for data symbol transmission, and selects a result of the selection from the resource selector # 1 311-1 to the resource selector # M 311 -M, respectively. Output Here, each of the resource selector # 1 311-1 to the resource selector # M 311-M may be used to transmit data symbols of the user terminal # 2 and subcarriers to be used for data symbol transmission of the user terminal # 1. The subcarriers are selected identically. 4A to 4C, an operation of selecting the subcarriers to be used for data symbol transmission of the user terminal # 1 and the user terminal # 2 will be described.

4A to 4C schematically illustrate a resource selection operation of the controller 350 of FIG. 3.

First, it is assumed that the base station signal receiving apparatus receives resource selection information from each of user terminal # 1 and user terminal # 2 (411, 413). In this way, the received resource selection information 411 of the user terminal # 1 and the resource selection information 413 of the user terminal # 2 is transmitted to the controller 350, the controller 350 is a resource of the user terminal # 1 With reference to each of the selection information 411 and the resource selection information 413 of the user terminal # 2, the primary resource selection is performed considering only subcarriers in which the subcarriers are selected and no collision has occurred (415). In this case, the controller 350 selects a subcarrier so that a user terminal which selects the subcarriers for the subcarriers selected by one user terminal and the collision does not occur. For example, the controller 350 selects the first subcarrier to be used only by the user terminal # 2, as shown in FIG. 4A, and selects the first subcarrier to be used by the user terminal # 2. The subcarrier and the third subcarrier are selected by both the user terminal # 1 and the user terminal # 2 so that a collision occurs, so the primary resource selection is excluded and the fourth subcarrier is selected to use only the user terminal # 1. Therefore, the fourth subcarrier selects to use only user terminal # 1.

As such, after performing the primary resource selection, the controller 350 refers to each of the resource selection information 411 of the user terminal # 1 and the resource selection information 413 of the user terminal # 2, and the subcarrier is selected. At the same time, secondary resource selection is performed considering only subcarriers having collisions (417). Here, the controller 350 gives priority to user terminals to be selected by both user terminals and to receive more subcarriers after the primary resource selection result for each of the subcarriers in which collision occurs. And the subcarrier is selected so that the user terminal selecting the subcarriers uses the subcarrier. In addition, when two user terminals are selected as the same subcarriers as a result of the primary resource selection, the controller 350 allocates the corresponding subcarriers to the corresponding user terminals in a round robin manner.

As shown in FIG. 4B, since the second subcarrier is selected to be used by both the user terminal # 1 and the user terminal # 2, the controller 350 selects more subcarriers in consideration of the primary resource selection result. The user terminal to receive selects to use the second subcarrier. In FIG. 4B, it is assumed that the user terminal # 2 receives more subcarriers than the user terminal # 1 as a result of the primary selection. Therefore, the controller 350 uses the second sub carrier by the user terminal # 1. Choose to. However, assuming that the number of subcarriers selected by the user terminal # 1 and the user terminal # 2 is the same after selecting the second subcarrier to be used by the user terminal # 1, the controller 350 uses a round robin method. Select the third subcarrier for use by user terminal # 2. In FIG. 4B, the controller 350 applies the round robin method based on the user terminal # 2. When the round robin method is applied based on the user terminal # 1, the controller 350 uses the third subcarrier # as the user terminal #. Of course 1 chooses to use it.

As such, after performing the secondary resource selection, the controller 350 does not select the subcarrier by referring to each of resource selection information 411 of the user terminal # 1 and resource selection information 413 of the user terminal # 2. The third resource selection is performed considering only subcarriers that are not present (419). In this case, the controller 350 randomly targets user terminals to which additional subcarriers are to be additionally selected after the secondary resource selection result for each of the subcarriers not selected by both user terminals. Choose. For example, the controller 350 randomly selects the sixth subcarrier to be used by the user terminal # 2 as illustrated in FIG. 4C.

Meanwhile, '1' and '2' indicated in the resource selection information of the user terminal # 1 and the user terminal # 2 shown in FIGS. 4A to 4C indicate that the subcarrier is selected to be used. However, the actual resource selection information is marked only with '1' or '0', '1' indicates that the subcarrier is selected to be used, and '0' indicates that the subcarrier is selected not to be used. Accordingly, '1' and '2' in the resource selection information of the user terminal # 1 and the user terminal # 2 shown in FIGS. 4A to 4C are used by the user terminal # 1 to use the corresponding subcarrier. And the user terminal # 2 has selected to use the corresponding subcarrier.

Also, the IFFT processor # 1 315-1 inputs the signal output from the beamforming processor # 1 313-1 to perform an N _c point-IFFT operation and then performs the parallel / serial converter #. Outputs 1 (317-1). The parallel / serial converter # 1 317-1 inputs the signal output from the IFFT processor # 1 315-1 to perform serial conversion and outputs the signal to the guard interval inserter # 1 319-1. The guard interval inserter # 1 319-1 inputs the signal output from the parallel / serial converter # 1 317-1 to insert a guard interval and then outputs the guard interval to the transmission processor # 1 321-1. do. The transmission processor # 1 321-1 receives a signal output from the guard interval inserter # 1 319-1 and transmits the received signal to the user terminal through the transmission antenna # 1 323-1. do. Since the transmission processing operation performed by the transmission processor # 1 321-1 is the same as the transmission processing operation of a general communication system, a detailed description thereof will be omitted.

Meanwhile, although not separately illustrated in FIG. 3, the controller 350 generates and transmits resource selection result information indicating the subcarrier selection result to the user terminal # 1 and the user terminal # 2.

Next, a structure of a signal receiving apparatus of a user terminal in a beamforming-MIMO / OFDMA communication system according to an embodiment of the present invention will be described with reference to FIG. 5.

FIG. 5 is a diagram illustrating a signal receiving device structure of a user terminal when using a fourth type segment in a beamforming-MIMO / OFDMA communication system according to an embodiment of the present invention.

Referring to FIG. 5, the user terminal signal reception apparatus includes a plurality of reception antennas, for example, N reception antennas, that is, reception antennas # 1 511-1 to RN-N 511-N, and N. _It is assumed that _c subcarriers are used and a data symbol stream is recovered through only N _s subcarriers among the N _c subcarriers.

The user terminal signal receiving apparatus includes N receiving antenna processing units, that is, receiving antenna processing unit # 1 (500-1) to receiving antenna processing unit #N (500-N), for receiving signals through each of the N receiving antennas. Resource selection information generator 520 and N _s Maximum Ratio Combining (MRC) detectors, that is, MRC detectors # 1 530-1 to MRC detector #. M 530 -N _s and parallel / serial converter 540. Although not shown in FIG. 4, the user terminal includes a user terminal signal transmission apparatus for transmitting resource selection information to a base station corresponding to the user terminal. Each of the receiving antenna processing unit # 1 500-1 to the receiving antenna processing unit # N 500 -N differs only in receiving signals through different receiving antennas, and processes the received signals in the same manner. That is, the reception antenna processing unit # 1 (500-1), which is the first reception antenna processing unit, receives the reception antenna # 1 (511-1), the reception processor # 1 (513-1), and the guard interval remover # 1 (515-1). ), Serial to Parallel (S / P) Converter # 1 (517-1), and Fast Fourier Transform (FFT) processor # 1 (519-). It includes 1). In addition, the reception antenna processing unit #N (500-N), which is the Nth reception antenna processing unit, has a reception antenna #N (511-N), a reception processor #N (513-N), and a guard interval remover #N (515-N). ), Serial-to-parallel converter #N (517-N), and FFT processor #N (519-N). Therefore, for convenience of description, the operation of the user terminal signal receiving apparatus will be described using the reception antenna processing unit # 1 500-1 as an example, and it should be noted that the remaining reception antenna processing units are not described separately.

First, when a signal is received through the receiving antenna # 1 511-1, the received signal is transmitted to the receiving processor # 1 513-1. The receiving processor # 1 513-1 receives the received signal and outputs the received signal to the guard interval remover # 1 515-1. Since the reception processing operation performed by the reception processor # 1 513-1 is the same as the reception processing operation of the general communication system, a detailed description thereof will be omitted. The guard interval remover # 1 515-1 removes the guard interval by inputting the signal output from the reception processor # 1 513-1 and outputs the guard interval to the serial / parallel converter # 1 517-1. The serial / parallel converter # 1 517-1 inputs the signal output from the guard period remover # 1 515-1 and converts the signal into N _c signals in parallel, and then converts the FFT processor # 1 (519-1) into a parallel signal. ) The FFT processor # 1 519-1 inputs the signal output from the serial / parallel converter # 1 517-1 to perform an N _c -point FFT operation, and then outputs the result to the resource selection information generator 520. do.

The resource selection information generator 520 inputs a signal output from each of the FFT processor # 1 519-1 to the FFT processor # N 519-N, and then outputs an average signal band of the first subcarrier to the N _s subcarrier. Signal to Noise Ratio (SNR) hereinafter referred to as 'SNR' is detected. Here will be described an operation of the resource selection information generator 520 detects the average SNR for each of the N _s subcarriers as follows.

The resource selection information generator 520 is a channel matrix of a first subcarrier signal output from the FFT processor # 1 519-1 to a first subcarrier signal output from the FFT processor #N 519 -N ( considering the channel matrix (SNR) of the first subcarrier signal, and in this way, the N _c subcarrier signal output from the FFT processor # 1 519-1 to the FFT processor #N (519-N). in consideration of a channel matrix of N _c-th subcarrier output signal and detects the SNR of N _c-th sub-carrier signal. In this case, the resource selection information generator 520 detects an SNR of the c-th subcarrier signal as an example.

First, it is assumed that the beamforming vector applied to the data symbol s (c) mapped to the c-th subcarrier in the base station signal transmission apparatus is expressed by Equation 1 below.

In Equation 1, w _m (c) represents a weight to be applied to the c th subcarrier transmitted through the m th transmit antenna, and T represents a transpose.

In addition, it is assumed that the combining vector is represented by Equation 2 in the user terminal signal receiving apparatus.

In this case, a signal obtained by combining the c-th subcarrier signals received through the N reception antennas may be represented by Equation 3 below.

는

의 허미시안(Hermitian)을 나타내고,

는 c번째 서브 캐리어에 적용된 잡음 성분을 나타낸다. In Equation 3,

Is

Hermitian of,

Denotes a noise component applied to the c-th subcarrier.

Then, the SNR of the c-th subcarrier may be expressed by Equation 4 below.

는 효율적 채널 이득(effective channel gain)을 나타낸다. In Equation 4

Denotes an effective channel gain.

는 하기 수학식 5와 같이 나타낼 수 있다.Thus, a combining vector that maximizes SNR for a given w (c)

Can be expressed as Equation 5 below.

는 c번째 서브 캐리어를 위한 컴바이닝 벡터가 되며, 이는 하기 수학식 6과 같이 나타낼 수 있다.In addition, in Equation 5

Is the combining vector for the c-th subcarrier, which can be expressed by Equation 6 below.

In Equation 6, w _i (c) represents a weight applied to the c-th subcarrier transmitted through the i-th transmit antenna, and therefore, the SNR of the c-th subcarrier may be expressed as Equation 7 below.

Thus, the resource selection information generator 520 includes a total of N _s as detecting the SNR for each of the N _c subcarriers, and wherein the N _c sub-carriers from sub-carriers having the maximum SNR of the SNR is greater sequence choose to use sub-carriers, and generates the information for the selected N _s subcarriers in the resource selection information. Here, the resource selection information generator 520 may generate the resource selection information periodically or as needed, and buffer the generated resource selection information in an internal buffer. In addition, although not separately illustrated in FIG. 5, the resource selection information generator 520 previously receives resource selection result information selected by the user terminal from a base station, and thus actual data among N _c subcarriers received. The N _s subcarriers to which the symbol is mapped may be selected to recover data symbols therefrom. Accordingly, the resource selection information generator 520 corresponds to the resource selection information of N _c subcarriers output from the FFT processor # 1 519-1 to the FFT processor # N 519 -N. _s subcarriers are selected, and the selected N _s subcarriers are sequentially output to MRC detector # 1 530-1 to MRC detector # N 530 -N _s .

라고 가정하기로 한다. 상기 MRC 검출기#2(530-2)는 수신 안테나 처리부#1(500-1) 내지 수신 안테나 처리부#N(500-N)에서 출력한 N개의 서브 캐리어 신호들을 입력하여 MRC 방식으로 두 번째 데이터 심볼을 검출한 후 상기 병렬/직렬 변환기(540)로 출력한다. 여기서, 상기 MRC 검출기#2(530-2)에서 검출한 두 번째 데이터 심볼을

라고 가정하기로 한다. 이런 식으로, 마지막 MRC 검출기인 MRC 검출기#N_s(530-N_s)는 수신 안테나 처리부#1(500-1) 내지 수신 안테나 처리부#N(500-N)에서 출력한 N개의 서브 캐리어 신호들을 입력하여 MRC 방식으로 N_s 번째 데이터 심볼을 검출한 후 상기 병렬/직렬 변환기(540)로 출력한다. 여기서, 상기 MRC 검출기#N_s(530-N_s)에서 검출한 N_s 번째 데이터 심볼을

라고 가정하기로 한다.The MRC detector # 1 530-1 inputs N subcarrier signals output from the reception antenna processing unit # 1 500-1 to the reception antenna processing unit # N 500 -N to receive the first data symbol in an MRC scheme. Is detected and then output to the parallel / serial converter 540. Here, the first data symbol detected by the MRC detector # 1 530-1 is determined.

Let's assume. The MRC detector # 2 530-2 inputs N subcarrier signals output from the reception antenna processing unit # 1 500-1 to the reception antenna processing unit # N 500 -N to receive a second data symbol in an MRC manner. Is detected and then output to the parallel / serial converter 540. In this case, the second data symbol detected by the MRC detector # 2 530-2 is obtained.

Let's assume. In this way, the last MRC detector, MRC detector #N _s (530-N _s ), receives N subcarrier signals output from receive antenna processor # 1 500-1 to receive antenna processor #N 500-N. The N _s th data symbol is detected by the MRC method and then output to the parallel / serial converter 540. Here, the N _s- th data symbol detected by the MRC detector #N _s (530-N _s ) is obtained.

Let's assume.

,

, ... ,

)으로 복원한다. The P / S converter 540 converts a serial data symbol stream by the signal output from the MRC detector # 1 (530-1) to MRC detector #N _s (530 _s-N), respectively (

,

, ...,

Restore to).

Next, an operation process of the base station when using the fourth type segment in the beamforming-MIMO / OFDMA communication system according to an embodiment of the present invention will be described with reference to FIG. 6.

6 is a flowchart illustrating an operation process of a base station when using a fourth type segment in a beamforming-MIMO / OFDMA communication system according to an embodiment of the present invention.

Referring to FIG. 6, first, in step 611, the base station receives resource selection information from two user terminals, namely, user terminal # 1 and user terminal # 2, and proceeds to step 613. In step 613, the base station selects a user terminal to use each of the N _c subcarriers according to the received resource selection information, and assigns a data symbol to each of the N _c subcarriers according to the selection result. Map and proceed to step 615. In step 615, the base station performs beamforming by multiplying each of the N _c subcarriers to which the data symbols are mapped by a corresponding weight, and then proceeds to step 617. In step 617, the base station performs an N _c -point IFFT operation on the beamformed signal and proceeds to step 619. A base station group in the step 619 is the N _c - it proceeds to point IFFT operation is performed by the signal 621. After step-serial conversion. In step 621, the base station inserts a guard interval in the serialized signal and proceeds to step 623. In step 623, the base station transmits the guard interval-inserted signal to user terminals. In this case, steps 613 to 623 may be performed for each of the M transmit antennas as described with reference to FIG. 3.

 Next, an operation process of a user terminal when using the fourth type segment in the beamforming-MIMO / OFDMA communication system according to an embodiment of the present invention will be described with reference to FIG. 7.

7 is a flowchart illustrating an operation process of a user terminal when using a fourth type segment in a beamforming-MIMO / OFDMA communication system according to an embodiment of the present invention.

Referring to FIG. 7, in step 711, the user terminal receives and processes a received signal and proceeds to step 713. In step 713, the user terminal removes the guard interval from the received signal and proceeds to step 715. In step 715, the user terminal converts the guard interval-removed signal into N _c signals in parallel and proceeds to step 717. In step 717, the user terminal performs an N _c -point FFT operation on the parallel-converted signals. Here, the steps 711 to 717 are performed for each of the N reception antennas as described with reference to FIG. 5. In step 719, the user terminal detects an SNR of each of the N _c subcarriers, which are corresponding subcarrier signals FFT computed for each of the N receive antennas, and has an SNR having a maximum value among the detected SNRs. to a large magnitude of the SNR value from the sub-carriers corresponding to selects N _s subcarriers. In operation 721, the user terminal generates resource selection information indicating that the selected N _s subcarriers will be used.

In step 721, the user terminal selects N _s subcarriers from the N _c subcarriers FFT-calculated for each of the N receive antennas using the resource selection result information received from the base station. _{The s} subcarriers are detected from the data symbol using the MRC scheme, and the process proceeds to step 723. In step 723, the user terminal transmits the generated resource selection information to the base station and ends.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by the equivalents of the claims.

The present invention as described above, in the beamforming-MIMO / OFDMA communication system, by allowing the user terminal to feed back only the resource selection information indicating whether to use the subcarrier, not the CQI for all the subcarriers to the base station. In an OFDM communication system, an increase in the amount of CQI feedback caused by the use of the beamforming scheme can be prevented. In this way, by minimizing the information fed back to the resource selection information, not only does it increase the resource efficiency of the beamforming-MIMO / OFDM communication system, but also reduces the uplink load.

Claims (18)

A method of transmitting and receiving a signal at a base station of a beamforming-multiple input multiple output (MIMO) / orthogonal frequency division multiple access (OFDMA) communication system, It wants to have N _c subcarriers of a first resource selection information, and a second user terminal that includes information on a desired user terminal is using N _s subcarriers used used by the base station N _s of Receiving second resource selection information including information on subcarriers; A first data symbol stream targeted to the first user terminal and including N _s data symbols to be transmitted identically through each of the M transmit antennas used in the base station, and to the second user terminal. Receiving a second data symbol stream including N _s data symbols to be transmitted identically through each of the M transmit antennas; Wherein the first resource selection information and the second resource selection information by referring to the N _c sub-carriers of the first user terminal has N _s sub-carriers and the N _s subcarriers wherein the second user terminal is used for The process of choosing, For each of the M transmit antennas, transmit data symbols included in the first data symbol stream through N _s subcarriers selected by the first user terminal, and include the second data symbol stream. method for transmitting and receiving signals at the base station, characterized in that it comprises the step of transmitting on the N _s subcarriers choose to use the second user terminal, the data symbol. The method of claim 1, The process of the second user terminal selects N _s subcarriers used with claim 1 wherein the N _s subcarriers, the user terminal is available; Wherein the N _s subcarriers and the second resource selection information N _s subcarriers of subcarrier collisions have not occurred, including a are chosen to use the sub-carrier user terminals including the first resource selection information, Performing a primary resource selection operation so that it is used as is; The first resource selection information N _s subcarriers and the second resource selection information subcarrier is a conflict among the N _s subcarriers generated comprising a comprising a are more sub-after the primary resource selection operation result Performing a secondary resource selection operation for use by a user terminal that should receive carriers; After performing the secondary resource selection operation, subcarriers not selected to use any user terminal randomly perform a tertiary resource selection operation for use by the corresponding user terminal. How to send and receive. The method of claim 2, Allocating the corresponding subcarriers to the corresponding user terminals by applying a round robin method when the number of subcarriers selected by the first user terminal and the second user terminal is the same while performing the secondary resource selection operation; Method for transmitting and receiving a signal in the base station further comprises. The method of claim 1, The information about the N _s subcarriers included in the first resource selection information and the second resource selection information has a maximum signal-to-noise ratio detected by the first user terminal and the second user terminal among the N _c subcarriers. And information about N _s subcarriers sequentially selected from the sub-carrier to the signal-to-noise ratio magnitude order. The method of claim 1, The N _c subcarriers are subcarriers in which two segments occupy in a frequency domain, and the segments are segments for real-time service support targeting user terminals located in a cell boundary region. How to send and receive. The method of claim 1, Resource selection result information including N _s subcarriers to be used by the selected first user terminal and N _s subcarriers to be used by the second user terminal to the first user terminal and the second user terminal. Transmitting and receiving a signal in the base station further comprising the step of transmitting. A method for transmitting and receiving signals at a user terminal of a beamforming-multiple input multiple output (MIMO) / orthogonal frequency division multiple access (OFDMA) communication system, Receiving resource selection result information including information on N _s subcarriers to be used by the user terminal among N _c subcarriers from a base station; Generating, by the N Four receive antennas, fast Fourier transforming the received signal into the N _c subcarrier signals; Selecting N _s subcarriers that the user terminal wants to use among the N _c subcarriers, and generating resource selection information including information on the selected N _s subcarriers; Classifying N _s subcarrier signals corresponding to the resource selection result information among N _c subcarrier signals generated for each of the N reception antennas; Characterized in that it comprises the step of using: (Maximum Ratio Combining MRC) method detects the data symbols mapped thereto maximum ratio combining of the N reception antennas, the N _s subcarriers signal classification for each of the respective Method of transmitting and receiving signals in the user terminal. The method of claim 7, wherein The resource selection information, information on the N _s subcarriers, including a is the N _c sub-carriers of the detected signal-to-noise ratio is up to the sub-carrier from the signal-to-noise ratio an order of magnitude, as sequentially selected N _s subcarriers that Method for transmitting and receiving a signal in a user terminal characterized in that the information about the. The method of claim 7, wherein The N _c subcarriers are subcarriers in which two segments occupy in a frequency domain, and the segments are segments for real-time service support targeting user terminals located in a cell boundary region. How to send and receive. An apparatus for transmitting and receiving signals at a base station of a beamforming-multiple input multiple output (MIMO) / orthogonal frequency division multiple access (OFDMA) communication system, It wants to have N _c subcarriers of a first resource selection information, and a second user terminal that includes information on a desired user terminal is using N _s subcarriers used used by the base station N _s of A receiver for receiving second resource selection information including information on subcarriers; Wherein the first resource selection information and the second resource selection information by referring to the N _c sub-carriers of the first user terminal has N _s sub-carriers and the N _s subcarriers wherein the second user terminal is used for Controller to select, M transmit antenna processing units connected one to one to each of the M transmit antennas, Each of the M transmit antenna processing units targets the first user terminal and includes a first data symbol stream including N _s data symbols to be transmitted identically through each of the M transmit antennas used in the base station. And a second data symbol stream targeted to the second user terminal and including N _s data symbols to be transmitted identically through each of the M transmit antennas. transmitted through the N _s subcarriers choose to use the first user terminal, the data symbols comprises, and choose to use the second user terminal, the data symbol comprising the second data symbol streams N _s of An apparatus for transmitting and receiving signals at a base station characterized in that the transmission on the subcarriers. The method of claim 10, The controller; Wherein the N _s subcarriers and the second resource selection information N _s subcarriers of subcarrier collisions have not occurred, including a are chosen to use the sub-carrier user terminals including the first resource selection information, Performs the primary resource selection operation so that The first resource selection information N _s subcarriers and the second resource selection information subcarrier is a conflict among the N _s subcarriers generated comprising a comprising a are more sub-after the primary resource selection operation result Perform a secondary resource selection operation for use by a user terminal that should receive carriers; And after the secondary resource selection operation, subcarriers that are not selected for use by any user terminal randomly perform a tertiary resource selection operation for use by the corresponding user terminal. The method of claim 11, The controller; If the number of subcarriers selected for use by the first user terminal and the second user terminal is the same while performing the secondary resource selection operation, the corresponding subcarriers are allocated to the corresponding user terminals by applying a round robin method. Device for transmitting and receiving signals at the base station characterized in that. The method of claim 10, The information about the N _s subcarriers included in the first resource selection information and the second resource selection information has a maximum signal-to-noise ratio detected by the first user terminal and the second user terminal among the N _c subcarriers. And information about N _s subcarriers sequentially selected from the sub-carrier to the signal-to-noise ratio magnitude order. The method of claim 10, The N _c subcarriers are subcarriers in which two segments occupy in a frequency domain, and the segments are segments for real-time service support targeting user terminals located in a cell boundary region. Device for sending and receiving. The method of claim 10, The apparatus; Resource selection result information including N _s subcarriers to be used by the selected first user terminal and N _s subcarriers to be used by the second user terminal to the first user terminal and the second user terminal. Apparatus for transmitting and receiving signals at the base station further comprising a transmitter for transmitting. An apparatus for transmitting and receiving signals at a user terminal of a beamforming-multiple input multiple output (MIMO) / orthogonal frequency division multiple access (OFDMA) communication system, A receiver for receiving resource selection result information including information on N _s subcarriers for use by the user terminal among N _c subcarriers; N reception antenna processing units connected one to one to each of the N reception antennas, Select N _s subcarriers to be used by the user terminal among N _c subcarriers, generate resource selection information including information on the selected N _s subcarriers, and generate the N receive antennas. of N _c sub-carrier signals generated by the respective resource selection for classifying N _s of sub-carrier signals corresponding to the resource selection result information and the information generator, Includes N _s Maximum Ratio Combining (MRC) detectors, Each of the N _s MRC detectors uses the Maximum Ratio Combining (MRC) scheme for each of the N _s subcarrier signals classified for each of the N receive antennas in the resource selection generator. Apparatus for transmitting and receiving signals in a user terminal characterized in that detected by the mapped data symbols. The method of claim 16, The resource selection information, information on the N _s subcarriers, including a is the N _c sub-carriers of the detected signal-to-noise ratio is up to the sub-carrier from the signal-to-noise ratio an order of magnitude, as sequentially selected N _s subcarriers that Device for transmitting and receiving a signal from the user terminal, characterized in that the information about the. The method of claim 16, The N _c subcarriers are subcarriers in which two segments occupy in a frequency domain, and the segments are segments for real-time service support targeting user terminals located in a cell boundary region. Device for transmitting and receiving.

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