KR101077428B1 - Apparatus for communicating data - Google Patents

Abstract

A data communication apparatus of the present invention includes a modulator for modulating data to be transmitted according to a designated modulation method; A MIMO encoder for encoding data modulated by the modulator according to a MIMO scheme; An OFDM encoder for encoding data encoded according to the MIMO scheme according to the OFDM scheme; And an antenna output unit configured to output a signal output from the OFMD encoding unit to an antenna;

An antenna input unit configured to receive a signal received by the antenna; An OFDM decoding unit for decoding the signal output from the antenna input unit by an OFDM scheme; A MIMO decoding unit for decoding the data decoded according to the OFDM scheme according to the MIMO scheme; And a demodulator for demodulating the signal output from the MIMO decoder according to a specified demodulation method.

In accordance with the communication environment of the data receiving unit, AMC control unit for controlling the operation of the data transmission unit.

OFDM, MIMO, AMC, Modulation, Channel Coding, SNR

Description

Apparatus for communicating data

The present invention relates to a data communication apparatus for transmitting and receiving data in an OFDM scheme.

In the wireless mobile communication environment, the change of the channel state has a great effect on the overall transmission / reception process. Therefore, a link adaptation technique in which a transmission parameter is changed to compensate for an adverse effect of a change in channel state is required.

The existing link adaptation technique is a power control technique that maintains transmission quality by controlling power according to a radio link. The link adaptation technique is an efficient way for a system to guarantee the quality of a link in a fixed rate situation such as voice.

Adaptive Modulation and Coding (AMC) is one of such link adaptation techniques. It is basically a link adaptation technique that allows transmission power to be fixed by determining the appropriate transmission rate according to channel characteristics.

According to the AMC technique, the state of a channel is estimated and an appropriate modulation scheme and channel coding rate are selected according to the estimated state of the channel.

On the other hand, since multimedia data requires various transmission rates and various transmission qualities according to service types, a link adaptation technique having a different concept from that of a conventional voice-oriented service is required.

On the other hand, recent data communication technologies, such as the WiBro wireless Internet standard, apply Orthogonal Frequency Division Multiplexing (OFDM) technology. OFDM uses a plurality of orthogonal subcarriers, and uses orthogonality between an inverse fast fourier transform (IFFT) and a fast fourier transform (FFT).

At the transmitter, data is sent by performing an IFFT. The receiver performs FFT on the received signal to recover the original data. The transmitter uses an IFFT to combine multiple subcarriers, and the receiver uses a corresponding FFT to separate multiple subcarriers. According to the OFDM, the complexity of the receiver can be reduced in a frequency selective fading environment of a wideband channel, and the spectral efficiency can be increased through selective scheduling in the frequency domain by using different channel characteristics between subcarriers. .

OFDM uses multiple orthogonal subcarriers. OFDM uses orthogonality between inverse fast fourier transforms (IFFTs) and fast fourier transforms (FFTs). The transmitter performs IFFT on the data and transmits it. The receiver performs FFT on the received signal to recover the original data. The transmitter uses an IFFT to combine multiple subcarriers, and the receiver uses a corresponding FFT to separate multiple subcarriers.

In the wireless portable Internet system to which the OFDM is applied, the entire transmission frame on the wireless channel where data communication between one base station and a plurality of terminals is performed has a structure as shown in FIG. The illustrated frame is a time division scheme applied for a period of 5 ms, and is divided into an uplink section in which data is transmitted from the terminals to the base station, and a downlink section in which data is transmitted from the base station to the terminals.

In general, downlink (DL) means communication from the base station to the terminal, and uplink (UL) means communication from the terminal to the base station, but may have the opposite meaning depending on the implementation.

According to the IEEE 802.16e and 802.16d standard, a fast feedback signal is transmitted as a QPSK modulation signal distributed in 48 subcarriers constituting a subchannel allocated to each terminal (ACK / NACK signal is Defined as 24 subcarriers). The fast feedback subchannel uses QPSK modulation having 48 subcarriers and may carry 6 bits of fast feedback data. 48 subcarriers may be reserved from six OPUSC tiles or six PUSC tiles or other zones such as AMC.

1 illustrates an up / down link frame structure of the wireless portable Internet of the above standard. The illustrated frame is divided into an uplink frame and a downlink frame. The downlink frame includes a PUSC subchannel interval, a diversity subchannel interval, and an AMC subchannel interval, and the uplink frame includes an uplink control symbol interval and diversity. It consists of a subchannel section and an AMC section. Each section is used to transmit data or control signals for each terminal according to a predetermined use.

2 shows the structure of an encoder on the side of a mobile terminal constituting a wireless Internet system. The illustrated encoder includes an input buffer 620 for receiving 6-bit data to be encoded; And a mapping block 640 for encoding data latched in the input buffer 620 according to a predetermined algorithm. The 6-bit data is input from a predetermined control signal generator 720.

The 6-bit input value is symbol-mapped into six vector index columns that can fill six tiles. The output values of the six vector index strings according to the six bit input values may be represented by six tile values, and index numbers of '0' to '7' represented by each tile value may be represented by a set of vectors. Each vector is represented by four complex numbers each having a phase difference of 90 degrees, and is physically applied to the subcarriers.

An object of the present invention is to provide an AMC scheme for multiple antennas and a data communication apparatus employing OFDM techniques.

A data communication apparatus of the present invention includes a modulator for modulating data to be transmitted according to a designated modulation method; A MIMO encoder for encoding data modulated by the modulator according to a MIMO scheme; An OFDM encoder for encoding data encoded according to the MIMO scheme according to the OFDM scheme; And an antenna output unit configured to output a signal output from the OFMD encoding unit to an antenna;

An antenna input unit configured to receive a signal received by the antenna; An OFDM decoding unit for decoding the signal output from the antenna input unit by an OFDM scheme; A MIMO decoding unit for decoding the data decoded according to the OFDM scheme according to the MIMO scheme; And a demodulator for demodulating the signal output from the MIMO decoder according to a specified demodulation method.

In accordance with the communication environment of the data receiving unit, AMC control unit for controlling the operation of the data transmission unit.

According to the data communication apparatus of the present invention, it is possible to implement high throughput optimized for a channel environment, and to perform improved wireless communication through a strong combination of channel padding and noise.

The following detailed description is only illustrative, and merely illustrates embodiments of the present invention. In addition, the principles and concepts of the present invention are provided for the purpose of explanation and most useful.

Accordingly, various forms that can be implemented by those of ordinary skill in the art, as well as not intended to provide a detailed structure beyond the basic understanding of the present invention through the drawings.

The idea of the present invention relates to a data communication device to which AMC MIMO technology and OFDM technology are simultaneously applied. Before describing the preferred embodiment of the present invention, the AMC MIMO technology and the OFDM technology will be briefly described.

Multiple input multiple output (MIMO) system is to maximize the performance and communication capacity of the wireless communication system. MIMO technology is a method that can improve the transmission and reception data transmission efficiency by adopting multiple transmission antennas and multiple reception antennas, away from the use of one transmission antenna and one reception antenna. The MIMO system is also called a multiple antenna system. MIMO system in the description of the present invention, multiple input and output

(multiple-input multiple-output; MIMO) system, multiple input single output

It can be a concept including both a multiple-input single-output (MISO) system or a single-input multiple-output (SIMO) system.

MIMO technology is an application of a technique of gathering and completing fragmented pieces of data received from multiple antennas without relying on a single antenna path to receive one entire message. As a result, it is possible to improve the data transfer rate in a specific range or increase the system range for a specific data transfer rate.

MIMO techniques include transmit diversity, spatial multiplexing, beamforming, and the like. Transmit diversity is a technique of increasing transmission reliability by transmitting the same data in multiple transmit antennas. Spatial multiplexing includes spatial multiplexing for a single user and spatial multiplexing for multiple users.

Spatial multiplexing for a single user is also referred to as Single User MIMO (SU-MIMO), and spatial multiplexing for multiple users is called SDMA (Spatial Division Multiple Access) or MU-MIMO (MU-MIMO). The capacity of the MIMO channel increases in proportion to the number of antennas. The MIMO channel can be broken down into independent channels. When the number of transmitting antennas is Nt and the number of receiving antennas is Nr, the number Ni of independent channels is Ni ≦ min {Nt, Nr}. Each independent channel may be referred to as a spatial layer. The rank may be defined as the number of non-zero eigenvalues of the MIMO channel matrix and the number of spatial streams that can be multiplexed. Spatial multiplexing is a technology that allows high-speed data transmission without increasing the bandwidth of the system by simultaneously transmitting different data from multiple transmit antennas.

Beamforming is used to increase the signal to interference plus noise ratio (SINR) of a signal by applying weights according to channel conditions in multiple antennas. The weight may be represented by a weight vector, and two or more weight vectors may be represented by a weight matrix. The weight vector is called a precoding vector and the weight matrix is called a precoding matrix. A preprocessing method using weights according to channel conditions is called channel dependent precoding. Channel-based precoding uses weights that match the channel conditions in order to maximize the capacity of the transport channel. Channel information for channel-based precoding may be obtained through a sounding channel, a codebook, channel quantization, and the like. Among the various precoding methods, the system using codebook based precoding creates a codebook set that can reflect the channel status and selects a codebook that maximizes the capacity of the transport channel. do. In general, the more codebooks in a codebook set, the more the capacity of a transmission channel can be increased.

( Example )

3 is a block diagram illustrating a schematic structure of a data transmitting apparatus and a data receiving apparatus according to an embodiment of the present invention.

The illustrated data transmission device includes a modulator 220 for modulating data to be transmitted according to a designated modulation method; A MIMO encoder 240 for encoding data modulated by the modulator 220 according to a MIMO scheme; An OFDM encoder 260 for encoding data encoded according to the MIMO scheme according to the OFDM scheme; And an antenna output unit 280 for outputting a signal output from the OFMD encoding unit 260 to an antenna.

The illustrated data receiving apparatus includes an antenna input unit 480 for receiving a signal received by an antenna; An OFDM decoding unit 460 for decoding the signal output from the antenna input unit 480 by an OFDM method; A MIMO decoding unit 440 for decoding data decoded according to the OFDM scheme according to the MIMO scheme; And a demodulator 420 for demodulating the signal output from the MIMO decoding unit according to a specified demodulation method.

The illustrated data transmitting device and data receiving device may be a terminal or a base station device that performs data communication according to a wireless LAN standard of WiBro or Wi-Fi.

The signal output from the antenna output unit 280 of the illustrated data transmission apparatus is transmitted to the wireless channel 900 in the air through the antenna, and the signal carried on the wireless channel 900 is transmitted to the antenna of the illustrated data receiving apparatus. It is received and input to the antenna input unit 480.

4 is a block diagram showing a detailed configuration of the data transmission device of FIG.

The modulation unit 220 of the illustrated data transmission apparatus includes an input of data to be transmitted from an application unit 210, and the application unit 210 includes a data storage unit 212 for storing data to be transmitted; And the CRC encoder 214.

The modulator 220 may include a channel encoder 222 and a modulator 224.

The CRC encoder 214 adds a CRC parity to the data to be transmitted and encodes it as an information word, and the channel encoder 222 receives the information word and parity for error correction according to a predetermined code rate. ), That is, encoding to generate and print a codeword.

The modulator 224 may perform phase modulation on the codeword received from the channel encoder 222.

The modulation scheme performed by the modulator 224 is not limited, and may be m-Phase Shift Keying (m-PSK) or m-Quadrature Amplitude Modulation (m-QAM). For example, m-PSK may be BPSK, QPSK or 8-PSK. m-QAM may be 16-QAM, 64-QAM or 256-QAM. In some embodiments, the modulator 224 may select one of a plurality of modulation schemes under the control of an external AMC controller.

The layer mapper 244, 245 defines a hierarchy of input symbols so that the precoder 246, 247 can distribute antenna specific symbols to the path of each antenna. The layer is defined as an information path input to the precoders 246 and 247. The information path before the precoders 246 and 247 may be referred to as a virtual antenna or a layer.

The precoders 246 and 247 output the antenna specific symbol by processing the input symbol by the MIMO scheme according to the multiple transmit antenna. The precoders 246 and 247 may use codebook based precoding. The precoders 246 and 247 may use a codebook selected from a secondary codebookset including a codebook selected from a primary codebook set, which is a set of predefined codebooks, and a smaller number of codebooks than the primary codebookset. Precoders 246 and 247 distribute antenna specific symbols to subcarrier mappers 262 and 263 in the path of the antenna. Each information path sent by the precoder 246 and 247 through one subcarrier mapper to one antenna is called a stream. This may be referred to as a physical antenna.

The MIMO mode selector 242 determines how to send data in multiple streams. For example, the two streams shown may be determined to transmit the same data to each other in a transmit diversity mode, or may be determined to transmit different data in a spatial multiplexing mode. The criteria for determining the MIMO mode by the MIMO mode selector 242 may be based on a surrounding communication environment or communication service condition or control of an external AMC controller.

The illustrated OFDM encoding unit 260 includes a Parallel to Serial block (P / S block, 266, 267), a space adjuster (268, 269), an IFFT block (264, 265), subcarrier mapper (262, 263). can do.

The subcarrier mappers 262 and 263 assign antenna specific symbols to the appropriate subcarriers and multiplex them according to the user. The subcarrier mappers 262 and 263 output an OFDM symbol by modulating the antenna specific symbol by the OFDM scheme. The IFFT blocks 264 and 265 may perform an inverse fast fourier transform (IFFT) on an antenna specific symbol.

The illustrated parallel to serial blocks (P / S blocks) 266 and 267 and the space adjusters 268 and 269 may insert a cyclic prefix (CP) into a time domain symbol on which IFFT is performed. The OFDM symbol is transmitted through the antenna output unit 280.

The illustrated antenna output 220 includes up converters 282, 283, and an antenna subset selector 286.

Up converters 282 and 283 convert the OFDM symbols into signals that can be carried on an antenna. The antenna subset selector 286 designates an antenna for transmitting the converted signal according to the selection of the MIMO mode selector 242 and / or the control of an external AMC controller.

The illustrated data receiving apparatus includes an antenna input unit 480 for receiving a signal received by an antenna; An OFDM decoding unit 460 for decoding the signal output from the antenna input unit 480 by an OFDM method; A MIMO decoding unit 440 for decoding data decoded according to the OFDM scheme according to the MIMO scheme; And a demodulator 420 for demodulating the signal output from the MIMO decoding unit according to a specified demodulation method.

FIG. 5 is a block diagram illustrating a detailed configuration of the data receiving apparatus of FIG. 3.

The antenna input unit 480 of the illustrated receiver includes a communication mode detection unit 490 for detecting a MIMO mode and other communication environments; And down converters 482 and 484 for converting the signal received by the antenna. In addition, the communication mode detecting unit 490 may serve to designate an antenna to which each down converter 482 or 484 is connected upon reception so as to match the transmission antenna selection of the subset selector of the transmitter.

The illustrated OFDM decoding unit 460 uses a Serial to Parallel block (S / P block, 466, 467), a blank remover (468, 469), an FFT block (464, 465), and a subcarrier demapper (462, 463). It may include.

The S / P blocks 466 and 467 and the blank remover 468 and 469 sort data to remove a guard interval from the signals received from the down converters 482 and 484 and perform an FFT. do.

The FFT blocks 464 and 465 perform a fast fourier transform (FFT) on the aligned data.

The subcarrier demappers 462 and 463 extract data for a specific user from the multiplexed data by extracting data from a specific symbol of the FFT transformed data.

The illustrated MIMO decoding unit 440 may perform decoding in a manner opposite to the encoding performed by the MIMO encoding unit 240. In addition, when the MIMO mode detected by the communication mode detection unit 490 is a transmit diversity mode, it is possible to perform functions of error correction and data recovery using data transmitted in two streams. In the case of spatial multiplexing mode, a function of collecting data transmitted in two streams may be performed. According to an implementation, the MIMO decoding unit may perform MIMO decoding according to the MIMO mode determined under the control of an external controller.

The demodulator 420 may include a demodulator 424 and a channel decoder 422.

The demodulator 424 may generate a codeword by performing spatial phase demodulation on the signal received from the MIMO decoding unit 440.

The channel decoder 422 decodes a codeword received from the demodulator 424 in a manner opposite to the operation of checking parity for error correction and the encoding performed by the channel encoder 222. To generate an information word and transmit it to the application unit 410.

The illustrated CRC checker 414 of the application unit 410 checks the CRC attached to the information word and generates a data block 412 from which the CRC is removed.

FIG. 6 is a data communication device including the data transmitter of FIG. 4 and the data receiver of FIG. 5, further comprising an AMC controller 500 for controlling the MIMO mode by the AMC method. It is.

The AMC controller 500 receives the MIMO mode detected by the communication mode detection unit 490 of the receiver and information about the communication environment (for example, a value of a signal to noise ratio (SNR) signal fed back from the receiver). The controller 220 controls the operations of the transmitter 220, the MIMO encoder 240, and the antenna subset selector 286.

The illustrated antenna input unit 480 includes a communication mode detection unit 490 for detecting a MIMO mode and other communication environments; And down converters 482 and 483 for converting a signal received from an antenna, and the AMC controller 500 may receive a signal detected by the communication mode detector 490.

The demodulator 420 includes: a demodulator 424 for generating a codeword by performing phase demodulation on a signal received from the MIMO decoding unit 440; And a channel decoder 422 for generating an information word by decoding a codeword received from the demodulator.

The illustrated antenna output unit 280 includes: up converters 282 and 283 for converting a signal output from the OFDM encoding unit 260 into a signal that can be carried on an antenna; And an antenna subset selector 286 that designates an antenna to transmit the converted signal under the control of the AMC controller 500.

The illustrated MIMO encoding unit 240 includes: a layer mapper (244, 245) defining a layer of an input signal input from the modulation unit; A precoder (246, 247) for processing the input signal in a MIMO scheme according to a multiple transmit antenna and outputting the signal as a signal for a specific antenna; And a MIMO mode selector 242 for determining a method of transmitting data for a plurality of streams under the control of the AMC controller 500.

The modulator 220 shown in advance sets a plurality of channel coding rates in advance, and selects one channel coding rate under the control of the AMC control unit 500 to channel-encode the transmission data. ); And a modulator 224 that selects a modulation scheme under the control of the AMC controller 500 and modulates an output signal of the channel encoder 222 according to the selected modulation scheme.

According to an implementation, the illustrated data transmitter and data receiver may be located in the same device so that the data transmitter may transmit data to another counterpart data communication device, and the data receiver may receive data from the other counterpart data communication device. In this case, the data may be located in different devices to perform data communication with each other.

In the case of dual electrons, the illustrated data communication device may be a base station equipment or a terminal of a wireless Internet communication system. In this case, control of the transmitter of the AMC controller 500 and / or control of the receiver of the AMC controller 500 may be performed wirelessly.

According to the latter case implementation, when the data transmitter of the figure is a base station equipment in a wireless Internet communication system, the terminal communicating with the base station extracts and extracts an SNR signal according to the strength of the received signal while communicating with the base station. As the SNR signal is transmitted to the base station and fed back, the SNR signal fed back from the terminal may be input to the channel encoder 222, the modulator 224, and the MIMO mode selector 242.

Other components except for the AMC controller 500 are similar to the corresponding components of FIGS. 4 and 5.

For example, the OFDM encoder 260 may include a subcarrier mapper configured to generate an OFDM signal by modulating a signal output from the MIMO encoder by an OFDM scheme; And an IFFT block performing an inverse fast fourier transform (IFFT) on the generated OFDM signal.

In addition, the OFDM decoding unit 460, an FFT block for performing a Fast Fourier Transform (FFT) on the signal output from the antenna input unit; And a subcarrier demapper for demodulating the FFT-converted signal by the OFDM scheme.

Hereinafter, the control operation of the AMC control unit 500 will be described.

The illustrated channel encoder 222 sets 'turbo code 1/3' or 'turbo code 1/2' as the channel coding rate in advance, and selects one channel coding rate under the control of the AMC controller 500. And, the channel data is encoded by the externally input transmission data at the selected channel coding rate.

That is, the channel encoder 222 selects the 'turbo code 1/3' or 'turbo code 1/2' under the control of the AMC controller 500, and selects the 'turbo code 1/3' or 'turbo'. The code 1/2 'is channel encoded for externally input transmission data. The transmission data channel-encoded by the channel encoder 222 is input to the modulator 224.

The modulator 224 illustrated in advance sets Quadrature Phase Shift Keying (QPSK), 16 Quadrature Amplitude Modulation (16QAM), and 32 Quadrature Amplitude Modulation (32QAM) as a modulation method, and according to the control of the AMC controller 500. A modulation method is selected, and the output signal of the channel encoder 222 is modulated by the selected modulation method.

The illustrated MIMO mode selector 242 presets an Orthogonal Space Time Block Code (OSTBC) 4X2, a Space Time Block Code (STBC) 2X2, a Double Space Time Transmit Diversity (D-STTD) 4X2, and a Layered 4X2 as a MIMO mode. In this case, one MIMO mode may be selected under the control of the AMC controller 500, and the output signal of the modulator 224 may be processed in the selected one MIMO mode.

The illustrated antenna subset selector 286 outputs a high frequency signal received from the up converters 282 and 283 to a plurality of antennas 140 selected according to the MIMO scheme.

Table 1 below shows that the channel encoder 222, the modulator 224, and the MIMO mode selector 242 select a channel coding rate, a modulation scheme, and a MIMO mode according to a modulation and coding scheme (MCS) level. Table shows the data rates according to the modulation, modulation, and MIMO modes.

MCS Level MIMO technique Modulation method Channel coding rate Bit rate (kbps) One  STBC 4X2 QPSK Turbo Code 1/3   160 2   Layered 4X2 QPSK Turbo Code 1/3  320 3   Layered 4X2 QPSK Turbo Code 1/2  480 4   Layered 4X2 16QAM Turbo Code 1/3  640 5 Layered 4X2 16QAM Turbo Code 1/2  960 6 Layered 4X2 64QAM Turbo Code 1/2 1440

Referring to Table 1, in MCS level 1, channel encoder 222 uses turbo code 1/3 as the channel coding rate, modulator 224 uses quadrature phase shift keying (QPSK) as the modulation method, and MIMO mode. The selector 242 uses Space Time Block Code (STBC) 4X2 in MIMO mode, and the data rate is 160 kbps.

In MCS level 2, channel encoder 222 uses turbo code 1/3 as the channel coding rate, modulator 224 uses QPSK as the modulation scheme, and MIMO mode selector 242 uses STBC (Space Time) in MIMO mode. Block Code) Using 2X2, the data rate is 320kbps.

For MCS Level 3, channel encoder 222 uses turbo code 1/2 for channel coding rate, modulator 224 uses QPSK for modulation, and MIMO mode selector 242 uses Layered 4X2 for MIMO mode. The data rate is 480kbps.

In MCS level 4, channel encoder 222 uses turbo code 1/3 as the channel coding rate, modulator 224 uses 16 Quadrature Amplitude Modulation (16QAM) as the modulation scheme, and MIMO mode selector 242 uses MIMO. Using Layered 4X2 as the mode, the data rate is 640kbps.

For MCS level 5, channel encoder 222 uses turbo code 1/2 for channel coding rate, modulator 224 uses 16QAM for modulation, and MIMO mode selector 242 uses Layered 4X2 for MIMO mode. The data rate is 960 kbps.

For MCS level 6, channel encoder 222 uses turbo code 1/2 for channel coding rate, modulator 224 uses 64QAM for modulation, and MIMO mode selector 242 uses Layered 4X2 for MIMO mode. The data rate is 1440 kbps.

As such, the AMC controller 500 sets the six MCS levels, selects one MCS level according to the SNR signal fed back from the receiver, and selects the channel encoder 222 and the modulator according to the selected MCS level. 224 and the MIMO mode selector 242 may be selected to select a channel coding rate, a modulation scheme, and a MIMO mode.

7 is a graph showing the transmission rate in each case using a fixed MCS level according to the present invention. Referring to FIG. 7, for example, when the value of the feedback SNR signal is about 22 dB or more, the controller selects MCS level 6, and the channel encoder 222 sets the turbo to the channel coding rate according to the selected MCS level 6. Code 1/2 is used, modulator 224 uses 64QAM as the modulation scheme, and MIMO mode selector 242 controls the use of Layered 4X2 in MIMO mode to transmit data at a data rate of 1440 kbps.

When the value of the feedback SNR signal is in the range of about 17 to 22 Hz, the controller selects MCS level 5, and according to the selected MCS level 5, the channel encoder 222 uses the turbo code 1/2 as the channel coding rate. In addition, the modulator 224 uses 16QAM as a modulation scheme, and the MIMO mode selector 242 controls to use Layered 4X2 in the MIMO mode to transmit data at a data rate of 960 kbps.

If the value of the feedback SNR signal is in the range of about 14 to 17 kHz, the controller selects MCS level 4, and according to the selected MCS level 4, the channel encoder 222 uses the turbo code 1/3 as the channel coding rate. In addition, the modulator 224 uses 16QAM as a modulation method, and the MIMO mode selector 242 controls the use of Layered 4X2 in the MIMO mode to transmit data at a data rate of 640 kbps.

When the value of the feedback SNR signal is in the range of about 9 to 14 kHz, the controller selects MCS level 3, and according to the selected MCS level 3, the channel encoder 222 uses the turbo code 1/2 as the channel coding rate. The modulator 224 uses QPSK as a modulation method, and the MIMO mode selector 242 controls the use of Layered 4X2 in the MIMO mode to transmit data at a data rate of 480 kbps.

When the value of the feedback SNR signal is in the range of about 3 to 9 kHz, the controller selects MCS level 2, and according to the selected MCS level 2, the channel encoder 222 uses the turbo code 1/3 as the channel coding rate. The modulator 224 uses QPSK as a modulation scheme, and the MIMO mode selector 242 controls the use of Layered 4X2 in the MIMO mode to transmit data at a data rate of 320 kbps.

When the value of the feedback SNR signal is about 3 dB or less, the controller selects MCS level 1, and according to the selected MCS level 1, the channel encoder 222 uses the turbo code 1/3 as the channel coding rate, and modulator ( 224 uses Quadrature Phase Shift Keying (QPSK) as a modulation method, and the MIMO mode selector 242 controls to use Space Time Block Code (STBC) 4X2 in MIMO mode to transmit data at a data rate of 160 kbps.

The present invention transmits data by selecting a low MCS level when the value of the SNR signal fed back from the terminal is low, and by selecting a high MCS level as the value of the SNR signal is high.

The six MCS levels described above have been described, for example, and according to the present invention, data can be transmitted by adding an MCS level.

8 is a graph showing a transmission rate of a common platform combining a channel AMC scheme and a MIMO mode selection scheme in an OFDM communication system according to the present invention. Referring to FIG. 3, the present invention can transmit data at a high data rate by transmitting a data by selecting a MIMO scheme, a modulation scheme, and a channel coding rate according to the value of the SNR signal fed back from the terminal.

The present invention has been described in detail with reference to exemplary embodiments, but those skilled in the art to which the present invention pertains can make various modifications without departing from the scope of the present invention. I will understand.

Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims below and equivalents thereof.

1 is a timing diagram showing the structure of a data transmission interval frame in an OFDM wireless wireless Internet system.

2 is a block diagram showing a structure of a part of an OFDM encoder.

3 is a block diagram showing a structure of a data communication apparatus according to an embodiment of the present invention.

4 is a block diagram showing in detail the structure of a transmitting unit of the data communication apparatus of FIG.

5 is a block diagram illustrating in detail the structure of a receiver of the data communication apparatus of FIG. 3;

6 is a block diagram showing a detailed structure of a data communication apparatus according to another embodiment of the present invention.

7 is a graph showing the transmission rate in each case using a fixed MCS level in accordance with the present invention.

8 is a graph showing a transmission rate of a common platform combining the AMC scheme and the MIMO mode selection scheme in an OFDM communication system according to the present invention.

Claims (11)

A modulator for modulating data to be transmitted according to a designated modulation method; A MIMO encoder for encoding data modulated by the modulator according to a MIMO scheme; An OFDM encoder for encoding data encoded according to the MIMO scheme according to the OFDM scheme; And A data transmitter including an antenna output unit configured to output a signal output from the OFDM encoding unit to an antenna; An antenna input unit configured to receive a signal received by the antenna; An OFDM decoding unit for decoding the signal output from the antenna input unit by an OFDM scheme; A MIMO decoding unit for decoding the data decoded according to the OFDM scheme according to the MIMO scheme; And A data receiver comprising a demodulator for demodulating the signal output from the MIMO decoder according to a specified demodulation method; In accordance with the communication environment of the data receiving unit, AMC control unit for controlling the operation of the data transmission unit, The AMC control unit As shown in the diagram below, the MCS level for selecting the channel coding rate, modulation method and MIMO mode is set in advance, and one MCS level is selected according to the value of the SNR signal input from the data receiver, and according to the selected MCS level. And a data communication device controlling the modulation unit and the MIMO encoding unit. MCS Level MIMO technique Modulation method Channel coding rate One STBC 4X2 QPSK Turbo Code 1/3 2  Layered 4X2 QPSK Turbo Code 1/3 3  Layered 4X2 QPSK Turbo Code 1/2 4  Layered 4X2 16QAM Turbo Code 1/3 5 Layered 4X2 16QAM Turbo Code 1/2 6 Layered 4X2 64QAM Turbo Code 1/2 The method of claim 1, The antenna input unit, A communication mode detecting unit detecting a MIMO mode and other communication environments; And It includes a down converter for converting the signal received from the antenna, The AMC control unit, And a data communication device receiving a signal sensed by the communication mode detection unit. The method of claim 1, The antenna output unit, An up converter for converting a signal output from the OFDM encoding unit into a signal that can be carried on an antenna; And an antenna subset selector for designating an antenna to transmit the converted signal under the control of the AMC controller. The method of claim 1, The MIMO encoding unit, A layer mapper defining a layer of an input signal input from the modulator; A precoder for processing the input signal in a MIMO scheme according to a multiplexing antenna and outputting the signal as a signal for a specific antenna; And A MIMO mode selector for determining a method of transmitting data for a plurality of streams under the control of the AMC controller. Data communication device comprising a. The method of claim 1, The modulator, A channel encoder for presetting a plurality of channel coding rates, selecting one channel coding rate, and channel encoding the transmission data according to the control of the AMC controller; And A modulator for selecting a modulation method under control of the AMC controller and modulating an output signal of the channel encoder according to the selected modulation method Data communication device comprising a. delete The method of claim 1, wherein the selection of the MCS level comprises: And an MCS level having a higher transmission rate to process an output signal of the modulator as the value of the SNR signal is higher. The method of claim 1, The demodulation unit, A demodulator for generating a codeword by performing phase demodulation on the signal received from the MIMO decoding unit; And A channel decoder for generating an information word by decoding a codeword received from the demodulator Data communication device comprising a. The method of claim 1, The MIMO decoding unit, And a data communication device for performing MIMO decoding according to the MIMO mode determined by the control of the AMC controller. The method of claim 1, The OFDM encoding unit, A subcarrier mapper configured to generate an OFDM signal by modulating the signal output from the MIMO encoder by an OFDM scheme; And An IFFT block performing an inverse fast fourier transform (IFFT) on the generated OFDM signal Data communication device comprising a. The method of claim 1, The OFDM decoding unit, An FFT block for performing a fast fourier transform (FFT) on the signal output from the antenna input unit; And Subcarrier demapper for demodulating the FFT-converted signal by OFDM Data communication device comprising a.

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