Apparatus for transmitting and receiving data to provide high-speed data comunication and method thereof

Technical field of the invention [0001] The present invention relates to an apparatus for transmitting and receiving data in a radio communication network. More specifically, the present invention relates to a device compatible with a conventional wireless local area network communication system for transmitting and receiving data at a high speed and a method for this. In addition, the present invention relates to a wireless communication system for increasing the data rate from 54Mbps (megabits per second), which was the maximum data rate in a conventional wireless local area network communication system, to hundreds of megabits per second.

(b) Description of the Related Art [0002] In the conventional IEEE 802.11a wireless local area network (LAN) system, using the orthogonal frequency multiplexing method, a 20MHz bandwidth is divided between 64 subcarriers and 52 subcarriers among these 64 subcarriers are used to transmit data symbols and pilots. That is, data is transmitted at a maximum speed of 54Mbps using a single antenna and a 20MHz bandwidth.

[0003] The present invention provides an apparatus for transmitting and receiving data while maintaining compatibility with the conventional IEEE 802.11 method and orthogonal frequency division multiplexing (OFDM). The device uses multiple antennas and a number of 20MHz bands to achieve high data rates. [0004] Various practical applications demanding a bandwidth of over 100Mbps have been developed in response to the demand for high speed multimedia transmission. However, even the highest-bandwidth wireless LAN system among current wireless communication systems does not offer bandwidths above 25Mbps. Therefore, the present invention proposes a system offering a data rate that is four or more times higher than the conventional IEEE 802.11a system.

[0005] More specifically, the present invention proposes a configuration in which a number of antennas and bands are systematically controlled and the maximum data rate is controlled according to the characteristics of the system. The present invention also proposes a method of ensuring compatibility with a conventional system.

[0006] FIG. 1 is a block diagram representing a system for transmitting and receiving data in a conventional wireless LAN.

[0007] In the conventional IEEE 802.11a system, shown in FIG. 1, the 20MHz bandwidth is divided between 64 subcarriers. Of these 64 subcarriers, 48 ​​subcarriers are used for data transmission, 4 subcarriers are used for pilot symbol transmission, while the fixed subcarrier and the remaining 11 subcarriers are not used.

[0008] For data transmission, spi code with 1/2, 2/3 and 3/4 efficiency, binary phase shift keying (BPSK) modulation, quadrature phase keying (QPSK) quaternary phase shift keying), 16-state quadrature amplitude modulation (QAM) and 64-state quadrature amplitude modulation (QAM).

[0009] In the system shown in FIG. 1, when the source module 101 generates binary data, these binary data is provided to the scrambler 102 for randomization of binary data permutation.

[0010] The convolutional encoder 103 performs channel coding according to the code efficiency and modulation determined by the desired data rate, and the mapper 105 performs modulation to map the previous data permutation to the permutation of complex symbols.

[0011] The interleaver 104 provided between the convolutional encoder 103 and the mapper 105 interleaves the data permutation according to a predetermined rule. Maper 105 establishes the permutation of a group of 48 complex numbers, while the subcarrier allocator 107 forms 48 data components and 4 pilot components.

[0012] The 64-sample inverse fast Fourier transform (64-IFFT) module performs inverse fast Fourier transform on these 48 data components and 4 pilot components to form an OFDM symbol.

[0013] The cyclic prefix adding module 109 adds the cyclic prefix, which is the guard period for the OFDM symbol.

[0014] The radio frequency transmitting (RF) module 110 transmits a transmission frame formed by the above configuration on a carrier frequency. The RF receiving module 112 receives the transmission signal (transmission frame transmitted on the carrier frequency) via radio channel 111. Radio channel 111 includes a channel with multi-path fading and Gaussian noise introduced from the receiving terminal.

[0015] The receiving terminal RF 112 of the receiving terminal receives the disturbed signal passing through the radio channel 111 and subjects the signal transmitted on the carrier frequency to down-converting the signal in the baseband in a manner opposite to that performed by the transmitting terminal RF 110.

[0016] The cyclic prefix eliminator 113 eliminates the cyclic prefix added at the transmitter. The 64 sample fast Fourier transform module (64-FFT) converts the received OFDM symbol into a frequency domain signal by performing an FFT operation.

[0017] The subcarrier extractor 115 sends 48 complex symbols, corresponding to the subcarriers of the 64 received, to the correction and tracking module 117 and sends 4 subcarriers, corresponding to pilots, to the correction and tracking parameter estimator 116.

[0018] The correction and tracking parameter estimator 116 estimates the phase change caused by frequency and time errors by using known symbols and sends the estimation result to the correction and tracking module 117.

[0019] The correction and tracking module 117 uses the above estimation result to perform the tracking operation. Corrective Tracker 117 also performs frequency domain channel correction operation for frequency domain channel interference correction in addition to the tracking process. [0020] Demaper 118 performs a hard decision operation to convert the output complex number after the correction and channel tracking operation to binary data, or performs a soft decision to convert this output complex number to a real number. De-interlacing module 119 removes

Reverse interleaving the data for the pusher module 104, and the Viterbi decoder 120 performs convolutional code decoding for error correction and restoration of transmitted data.

[0021] Deskrambier 121 randomizes data transmitted from the source module in a similar manner as Scrambler 102 and sends the received data to the receiving module 122.

[0022] The conventional wireless LAN system shown in FIG. 1, has data rate and bit rate limitations, and therefore this system is difficult to use in a service requiring high data rate, such as a high quality moving picture service.

[0023] Systems using multiple bands and antennas to provide high data rates previously were not compatible with conventional transceivers [0024] For example, in the article "Preamble Design for Multiple-Antenna OFDM-based WLANs with Nuli Subcarriers" in proc, of IEEE Signal Processing letter, vol. 8, no, 11, November 2001, Erik G. Larsson and Jian Li propose to provide the transmitter and receiver with moistened antennas to meet the requirements of increased data rates in WLANs and are considering an optimal preamble pattern for such a system with two transmitting antennas and multiple receiving antennas. It is proposed to modify these preambles so that the preambles transmitted from these two transmit antennas differ from each other and meet certain conditions. Thus, such a system is not backward compatible with a conventional system having only one transmit antenna.

[0025] In the article "A MIMO system with backward compatibility for OFDM based WLANs" in proc, of 4th IEEE workshop on Signal processing Advances in Wireless Communication, 2003, Jianhua Liu and others are considering doubling the data rate of the IEEE 802.11 system by using the system with multiple inputs and multiple outputs (MIMO, multi-input multi-output), equipped with two transmit antennas and two receive antennas, and propose a preamble formula for the system under consideration, which is backwards compatible with its counterpart, namely a single-input single-output system (SISO) as defined by the IEEE 802.11 a standard. In detail, the same T1 and T2 preambles as for the system SISO is used for all multiplied transmit antennas before the SIGNAL field, and thus the SISO receiver can effectively detect up to the SIGNAL field in which some reserved bits indicate whether MIMO transmission is still occurring. In addition, different preambles are transmitted over the SIGNAL field by each of the multiple transmit antennas for use by the MIMO receiver for channel estimation.

[0026] However, the system proposed by Jianhua Liu et al. Is not efficient in the sense that preambles before the SIGNAL field cannot be used to efficiently estimate the MIMO channel because all the multiplied transmit antennas broadcast the same preambles.

[0027] Accordingly, the present invention provides a transmit and receive device to ensure compatibility with a conventional wireless communication system, high data rate and efficient channel estimation and a suitable method.

SUMMARY OF THE INVENTION

TECHNICAL PROBLEM [0028] The present invention provides a device that transmits and receives data to provide high data rates and compatibility with a conventional wireless communication system, and a method that allows this.

TECHNICAL SOLUTION [0029] The present invention provides a data transmission device according to claim 1. 1 for providing high data rate and compatibility with a conventional wireless communication system, the method of claim 7. which enables and the method of reception according to claim 12.

[0030] The data transmission device includes a band distributor, encoder, maper, antenna distributor, subcarrier allocator, inverse Fourier transform module, preamble generator and frame generator.

[0031] The bandwidth distributor separates the data generated in the source module into at least one band. The encoder performs encoding of split data to perform data error correction. The maper performs mapping of the encoded data to the complex number symbol. An antenna distributor splits this complex symbol to at least one antenna. The subcarrier allocator allocates the subcarrier for orthogonal frequency multiplexing to the separated symbol and complex number. The inverse Fourier transform module performs the inverse Fourier transform of the OFDM signal to which the subcarrier is allocated. The preamble generator generates the short preamble, the first long preamble and the second long subcarrier preamble. The frame generator generates frames in the order of the short preamble, first long preamble, symbol signal, second long preamble and data field. At this time, one of the first long preambles of the second antenna can be used as the second long preamble to perform subcarrier channel estimation that is not used by the first antenna when two or more antennas are used.

[0032] The signal symbol generated by the frame generator includes a transmission mode identifier for determining whether the transmission mode is single-antenna transmission mode or multiple-input / multiple-output (MIMO) mode.

[0033] The transmit mode identifier uses the signal symbol bit R4 in the IEEE 802.16a frame.

[0034] The reserved signal symbol bit is used as a bit to determine whether the transmit mode uses the spatial division muitipiexing method (SDM) or the space-time block code (STBC).

[0035] The data transmission device according to an example of the present invention further comprises a scraper, an interleaver, a cyclic prefix adding module and an RF transmitting module.

[0036] The scrambler is connected between the band distributor and the encoder and performs the scrambling operation. The interleaver is enabled between the encoder and the rem map and performs the interleaving operation. The cyclic prefix adding module adds the cyclic prefix to the inverted Fourier transform signal with orthogonal frequency multiplexing (OFDM). The RF transmitter module transmits the frame over a radio channel. The antenna distributor separates the mapped symbols into the antennas or codes with the STBC code.

[0037] The data receiving apparatus comprises an RF receiving module, a channel mixer, a pre-synchronizer, a Fourier transform module, a signal symbio demodulator, a channel estimator and a detector.

[0038] The RF receiving module receives the frame via a radio channel. The channel mixer performs the channel mixing operation for extracting the short 20MHz preamble and the first 20MHz long preamble from the received frame. The pre-synchronizer performs the pre-synchronization operation by using the extracted short preamble and the first long preamble. The Fourier transform module performs the Fourier transform of the frame operation, the signal symbol demodulator demodulates the signal symbo and demodulates the transmission mode information. The channel estimator performs the first estimation

Channel by using the first long preamble and performs a second channel estimation by using the transmission of the second long preamble after the signal symbol when the information about the transmission mode is MIMO-OFDM transmission mode. The detector detects a complex number symbol corresponding to the given in relation to the estimated channel and the demodulated signal symbol. We detect the transmission mode identifier set in the signal symbol and determine whether the transmission mode is single-antenna transmission mode or MIMO-OFDM transmission mode.

[0039] The channel estimator uses a second long preamble to perform a second subcarrier channel estimation that is not used by the first antenna.

[0040] The data receiving apparatus further includes a cyclic prefix eliminator, subcarrier extractor, demaper, deinterlacing module and error correction decoder.

[0041] The cyclic prefix eliminator eliminates the cyclic prefix of the signal received from the RF receiving module. The subcarrier extractor extracts subcarriers from a Fourier transform signal and combines these subcarriers. The demaper performs mapping the demodulated signal to a complex signal into a binary data signal. The deinterlacing module deinterlaces the demapped signal. The error correction decoder performs the signal error correction decoding operation after deinterlacing. The detector is an SDM detector or an STBC decoder.

ADVANTAGE EFFECT [0042] According to the present invention, an increased data rate is provided by using multiple bands and antennas in a wireless communication system.

[0043] Due to compatibility with a conventional system, this increased data rate is provided without modifying the existing device and design.

BRIEF DESCRIPTION OF THE FIGURES [0044] FIG. 1 is a block diagram representing a conventional transceiver system in a wireless LAN.

FIG. 2 is a block diagram representing a transmitter configuration according to an exemplary embodiment of the present invention.

FIG. 3 is a block diagram representing a receiver configuration according to an exemplary embodiment of the present invention.

FIG 4 shows an allocation method of OFDM sub-carriers supporting a single band and an allocation method of OFDM sub-carriers to support multiplex bands.

FIG. 5 is a diagram representing the configuration of the IEEE 802.16a standard frame.

FIG. 6 is a diagram representing a frame configuration according to an exemplary embodiment of the present invention.

FIG. 7 is a block diagram representing the configuration for initial synchronization of a receiver according to an exemplary embodiment of the present invention.

FIG. 8 is a block diagram representing a data transmission method according to an exemplary embodiment of the present invention.

FIG. 9 is a block diagram representing a method of receiving data according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION [0045] In the following detailed description, only the preferred embodiment of the invention is shown and described, simply as an illustration of the best mode of implementation of the invention contemplated by the inventor (s). It will be appreciated that the invention may be modified in various obvious respects in its entirety without departing from the invention. Accordingly, figures and descriptions will be regarded as naturally illustrative rather than restrictive. For explanations of the present invention, parts that are not described in the specification are omitted, and parts for which the same descriptions are provided have the same reference numerals.

[0046] Although this invention is described in connection with what is now considered to be the most practical and preferred embodiment, it should be understood that the invention is not limited to the disclosed embodiment, but on the contrary is intended to cover various modifications and equivalent systems contained in the idea and scope of the attached patent claims.

[0047] FIG. 2 is a block diagram representing a transmitter configuration according to an exemplary embodiment of the present invention.

[0048] This transmitter includes the source module 201, band distributor 202, scrambler / convolutional encoders 2031 to 203L, interleaver 204, maper 205, pilots module 206, antenna distributor 207, subcarriers afocators 2081 to 208M, modules IFFT 2091 to 209M, modules adding 2101 to 21 OM cyclic prefix, 2301 to 230M preamble generators, 2311 to 231M frame generators and RF 2111 to 211M transmission modules.

[0049] When the binary data generated in the source module 201 is sent to the band distributor 202, this band distributor 202 splits this binary data into L bands according to the number (L) of 20MHz bands for use in the 202 band distributor.

[0050] The scrambler / convolutional encoders 2031 to 203L perform stall operations and convolutional coding for individual bands.

[0051] The interleaver 204 receives file coded data. At this time, two types of 204 interleaver modules are available. One interleaver performs interleaving of each of the OFDM symbols of individual bands in a similar manner to scrambler / convolutional encoders 2031 to 203L, and the other interleaver performs interleaving the L number of OFDM symbols in each band. The first interleaver is simple and easy to understand, and the second interleaver is complex in implementation and is expected to gain profit in action from the gain of diversity, [0052] Maper 205 converts binary data to complex symbols. The transformed complex symbols are separated to the number of M transmitting antennas by the antenna distributor 207. The subcarrier allocators 2081 to 208L use pilot symbols from pilot module 206 and separated complex data symbols for subcarrier allocation for OFDM modulation. The allocation of subcarriers will be described later.

[0053] Frequency domain OFDM symbols corresponding to the allocated M number of transmit antennas are transformed by inverse Fourier transform to time domain OFDM symbols by (L * 64) -IFFT modules 2091 to 209M. Modules for adding 2101 to 210M cyclic prefix add cyclic prefixes corresponding to OFDM symbols from each path.

[0054] Frame generators 2311 to 231M generate the appropriate frames for the system shown in FIG. 2. As in the conventional IEEE 802.16a frame configuration, the frame configuration according to the exemplary embodiment of the present invention comprises a short preamble, a first long preamble,

Signal symbol and data, In addition, this frame configuration includes a second long preamble in preamble generators 2301 to 230M. The second long preamble is the long preamble used in another antenna, and the MIMO channel estimation on the subcarriers is performed at the second long preamble.

[0055] Preamble generators 2301 to 230M generate short preamble, first long preamble and second long preamble and provide frame generators 2311 to 231M.

[0056] The frame used in the exemplary embodiment of the present invention will be described below.

[0057] FIG. 3 is a block diagram representing a receiver according to an exemplary embodiment of the present invention.

[0058] The receiver shown in FIG. 3 performs the reverse operation to that of the transmitter on the signal transmitted from the transmitter shown in FIG. 2.

[0059] The signal transmitted through the channel 212 from the transmitter is received by the number N of receiving antennas in the number N of RF receiving modules 2131 to 213N. The received signal is processed back to the signal transmitted while passing through the 2141 to 214N cyclic prefix eliminators, (L * 64) -point FFT modules 2151 to 215N, subcarrier extractors 2161 to 216L, channel estimation and tracking module, MIMO 218 detector, demaper 219, deinterlacing module 220, Viterbi deskrambler / decoders 2211 to 221L and a link module in the base band 222, and data is sent to the receiving module 223.

[0060] The demodulation process for the receiver shown in FIG 3 is similar to that for the receiver shown in FIG. 1. However, the channel estimation module 217 at the receiver shown in FIG. 3 estimates the MIMO channel, which is different from the system shown in FIG. 1. In addition, the correction module 117 shown in FIG. 1 is replaced by the MIMO 218 detector in the system shown in FIG. 3. The deinterlacing block configuration must be changed according to the changed interlacing block configuration.

[0061] A baseband merger module 222, added in the system shown in FIG. 3, performs the reverse operation to that of the band distributor 202 at the transmitter shown in FIG. 2.

[0062] Although (L * 64) -point IFFT and (L * 64) -point FFT are used in FIG. 2 and FIG. 3, the number of L 64-point FFT and 64-point IFFT can be used, and one (L * 64) -point IFFT and one (L * 64) -point FFT can be used. These modifications are obvious to those skilled in the art.

[0063] FIG. 3 illustrates the reception and demodulation configuration corresponding to the MIMO transmitter shown in FIG. 2, and the receiver configuration for performing initial synchronization and channel estimation will be described later.

[0064] In FIG. 2, a spatia! Division multiplexing (SDM) method is described for increasing the data rate by using multiple transmit / receive antennas. [0065] The SDM multiplexing method, one of the MIMO methods, increases the data rate by transmitting independent data through individual transmit antennas.

[0066] If the system is designed for extending the service area and increasing the signal to noise ratio (SNR) instead of for increasing the data rate, a time-space block code (STBC) may be used in the exemplary embodiment of the present invention. space-time Błock codę) to achieve the profit of diversity.

[0067] If the STBC code is used in the exemplary embodiment of the present invention, the antenna distributor 207 is replaced by the STBC encoder and the MIMO 218 detector is replaced by the STBC decoder.

[0068] For convenience of description, to describe the frame configuration in an exemplary embodiment of the present invention, an example of a system comprising two transmit antennas and covering two bands will be given. That is, L is 2 and M is 2 in the system shown in FIG. 2, In this example embodiment of the present invention, conventional frame configuration and OFDM symbol configuration are used to provide compatibility with the prior art IEEE 802.11a system.

[0069] With respect to the OFDM symbol configuration, in an exemplary embodiment of the present invention, the 40MHz bandwidth is divided into 128 subcarriers, which are generated by combining two 20MHz bandwidths, each of which is divided into 64 subcarriers known in the art. Accordingly, 128-point IFFT is used to perform OFDM modulation in 20MHz and 40MHz bandwidths.

[0070] FIG. 4 shows the method of allocating OFDM subcarriers supporting a single band and the method of allocating OFDM subcarriers to support multiplexed bands.

[0071] The subcarrier allocation configuration (a) is formed if the signal is transmitted through one antenna in one band of the conventional IEEE 802.11a standard. Configuration (b) according to an exemplary embodiment of the present invention corresponds to that of the conventional IEEE 802 11a standard, when the signal fills the desired band, 0 fills other bands, and the signal is transmitted through a single antenna.

[0072] That is, data and pilots are allocated on 52 subcarriers between 0 and 63, and 0 are filled between -64 and -1 when using a lower frequency band on one side in a signal configuration (b) using two the subcarrier allocation configuration band shown in FIG. 4. Accordingly, the system according to an exemplary embodiment of the present invention is compatible with the conventional IEEE 802.11a system because a conventional frame configuration is broadcast in the new system.

[0073] A frame configuration according to an exemplary embodiment of the present invention will be described.

[0074] FIG. 5 is a diagram representing the configuration of an IEEE 802.11a frame.

[0076] The IEEE 802.11a frame configuration shown in FIG. 5 includes short t1 to t10 preambles, long T1 and T2 preambles, guard periods G1 and G2, signal symbol SIGNAL and data. Short preamble and long preamble are symbols for channel synchronization and estimation in the case of demodulation. The signal symbol contains information about data rate, length and parity. [0076] The short preamble is a symbol generated by the Fourier transform of the OFDM signal in the frequency domain given in expression 1, and the long preamble is a symbol generated by the Fourier transform of the OFDM signal in the frequency domain given in expression 2.

[Expression 1]

<img file="PL2363987T3_D0001.tif" />

-9 [Expression 2]

Α₂₆,26 = {1,1-1-1,1,1-1,1-1,1,1,1,1,1,1,-1,-1,1,1-1,1-1,1,1,1,1,0,

1, -1, -1.1, 1.1, -1.1, -1.1, -1, -1, -1, -1, -1.1.1, -1, -1.1, - 1,1, -11,1,1,1}} [0077] The signal symbol contains information about the length of the data section (0 to 4.095 bytes), code efficiency (1/2, 2/3 and 3/4) and methods mapping (BPSK, QPSK, 16-QAM and 64-QAM).

[0078] To ensure compatibility with the IEEE 802.11 a standard, in an exemplary embodiment of the present invention, the frame configuration shown in FIG. 5 is slightly modified for the characteristics of the multiple antennas when the signals are transmitted according to the conventional OFDM mode (IEEE 802.11 a).

[0079] When two transmit antennas are used, 52 subcarriers from preambles are equally divided into 26 transmit subcarriers. In addition, a second long preamble is provided after the signal symbol for estimating the subcarrier channel that is not used in the first long preamble.

[0080] The MIMO subcarrier channel estimation is performed by transmitting the first long preamble used as the second long preamble by the second antenna. Accordingly, the length of the long preamble is increased by the number of transmit antennas.

[0081] The signal in the preamble short frequency domain to be transmitted by two antennas is given in expression 3. S⁽⁰⁾.₂6.26 is transmitted by antenna 0, while S ^. 26.26 is transmitted by antenna 1.

[0082] The signal in the frequency domain of the first long preamble provided by the signal symbol is given in expression 4. L⁽⁰⁾.26i26 is transmitted by antenna 0, while L⁽¹⁾.26i26 is transmitted by antenna 1.

[Expression 3]

S⁽ 26.26 = V (²⁶/⁶) · +7,0,0,0,0,0,0,0,1 + /,0,0,0,0,0,0,0,-1 - 7,0,0,0,0,0,0,0,0,

0,0,0,-1-/,0,0,0,0,0,0,0,1 + /,0,0,0,0,0,0,0,1 + /,0,0,0,0,0,0}

S-26.26 = {0.0.0.0.0.0, -1 - /, 0.0.0.0.0.0.0, -1-7.0.0.0.0 , 0.0.0.1 + /, 0.0.0.0,

0.0,0,0,0,0,0, -1 - /, 0,0,0,0,0,0,0,1 +. /, 0,0,0,0,0,0, 0.1 +.7,0.0} [Expression 4] ^ 6.26 = &amp; {1.0, -1.0, 1.0, -1.0, -1.0, 1.0.1 , 0,1,0, -1,0,1,0,1,0,1,0,1,0,0,

0, -1,0,1,0, -1,0, - 1,0, -1,0, -1,0, -1,0,1,0, -1,0, -1,0, -1,0,1,0,1} ⁿ-26.26 {0.1.0, -1.0, 1.0, 1.0, 1.0, 1.0, 1.0, -1.0, 1.0, -1.0, -1.0, 1.0, 1.0, 1.0, -1.0, 1.0, 1.0, 1.0, -1.0, -1.0, 1.0, -1 , 0,1,0,1,0,1,0,1,0} [0083] For the second long preamble following the signal symbol, the location of the first long preamble is changed so that L⁽¹⁾.26i26 is transmitted by antenna 0, while Lⁱ⁰⁾.2Si26 is broadcast by

-10anthena 1.

[0084] FIG. 6 is a diagram representing a frame configuration according to an exemplary embodiment of the present invention.

[0085] As shown in FIG. 6, the frame transmitted by the first antenna (antenna 0) uses even subcarriers to transmit the frame, and this frame is formed using the first long preamble of odd subcarriers as the second long preamble.

[0086] The preamble and signal symbol configuration are staggered to support multiple bands. For example, the short preamble and long preamble for the conventional mode (dual band IEEE 802.11 a) using two bands are represented by expression 5 and expression 6 when these two bands are used.

[Expression 5]

<img file="PL2363987T3_D0002.tif" />

[Expression 6]

L__58&gt;58 UJ, 1.1, -1, -1.1, 1.1, -1.1, -1.1, 1.1, 1.0,

1, -1, -1,1,1, -1,1, -1,1,-1,-1,-1,-1,-1,1,1, -1,-1,1,-1,1, -1,1,1,1,1,

0,0,0,0,0,0,0,0,0,0,0,

1,1,-1,-1,1,1,-1,1,-1,1,1,1,1,1,1,-1,-1,1,1,-1,1,-1,1,1,1,1,0,

1, -1, -1.1, 1.1, -1.1, -1.1, -1, -1, -1, -1, -1.1.1, -1, -1.1, - 1,1, -1,1,1,1,1} [0087] When these two bands and two antennas are used, the short preamble and long preamble transmitted by the individual antennas are given in Expression 7 and Expression 8.

[Expression 7]

- 11 &lt;8 = {Ο, Ο, Ι + ΥΑΟΑΟ, ΟΑθ, Ι ν&gt; θ, 0Α0,0Α0, -1-7, Ο, Ο, 0,0, Ο, ΟΑ0, 0,0,0, -1 - / ο, ο, ο, ο, ο, ο, ο, ι + / ο, ο, ο, ο, ο, ο, ο, ι + / 0,0,0,0,0,0, ο, ο, ο, ο, ο, ο, ο, ο, ο, ο, ο,

0,0,1 + / 0,0,0,0,0,0,04 + 7,0,0,0,0,0,0,0, -1-7,0,0,0,0, 0.0.0.0, 0.0.0, -1 - / 0.0.0.0.0.0.0.1 + / 0.0.0.0.0.0.0.1 + j, 0,0,0,0,0,0}

4.58 = ^^ · {θΑθΑθΑ-ΐ- / ΑθΑθΑθΑ-ΐ-7ΑθΑθ, ο, ο, θΛ + Λθ, ο, θ, θ, 0,0,0,0,0,0,0, -1- / 0 , 0,0,0,0,0,0,1 + / 0,0,0,0,0,0,0,1 + / 0,0, ο, ο, ο, ο, ο, ο, ο , ο, ο, ο, ο,

0,0,0,0,0,0-1 - /, 0,0,0,0,0,0,0, -1 -./0,0,0,0,0,0,0,1 + / 0.0,0,0, Ο, Ο, Ο, Ο, Ο, Ο, Ο, -1- / 0,0,0,0,0,0,0,1 + 7,0, 0,0,0,0,0,1 + / 0.0}

4.58 = V2 · {1.0, -1.0, 1.0, -1.0, -1.0, 1.0, 1.0, 1.0, -1.0, 1.0 , 1,0,1,0,1,0,0,

0, -1,0,1,0, -1,0, -1,0, -1,0, -1,0, -1,0,1,0, -1,0, -1,0- 1,0,1,0,1, ο, ο, ο, ο, ο, ο, ο, ο, ο, ο, ο,

1,0,-1,0,1,0,-1,0-1,0,1,0,1,0,1,0,-1,0,1,0,1,0,1,0,1,0,0,

0,-1,0,1,0,-1,0,-1,0,-1,0,-1,0-1,0,1,0,-1,0,-1,0,-1,0,1,0,1} /(1)

-58,58 · {0,1,0-1,0,1,0,1,0,1,0,1,0,1,0,-1,0,1,0,-1,0 -1,0,1,0,1,0, 1,0, -1,0,1,0,1,0,1,0, - 1,0, -1,0,1,0, -1,0,1,0,1,0,1,0,1,0,

0,0,0,0,0,0,0,0,0, ο, ο,

0,1,0, -1,0,1,0,1,0,1,0,1,0,1,0, -1,0,1,0, -1.0, -1.0, 1.0, 1.0, 1.0, -1.0, 1.0, 1.0, 1.0, -1.0, -1.0, 1.0, -1.0.1, 0,1,0,1,0,1,0} [0088] As described above, S⁽⁰⁾.68i58 is transmitted by the O antenna, while the S⁽¹\ 58i58 is transmitted by antenna 1. It is transmitted by antenna O, while L⁽¹\_58i58 is transmitted by antenna 1. However,

The second long preamble, following the signal symbol, is transmitted in reverse order.

[0089] According to the configuration described above, the receiving terminal performs channel estimation of the subcarriers further by performing channel estimation using the second long preamble without determining which antenna in the system transmits the signal using the multiple bands and the multiple antennas.

[0090] Accordingly, the long preamble is generated in a manner similar to the generation of the long preamble by the preamble generators 2301 to 230M shown in FIG. 2, and preamble generators 2301 to 230M additionally insert a second long preamble after the signal symbol for frame generation.

[0091] The frame generator modifies the signal symbols to ensure compatibility with a conventional system.

[0092] A bit that, as a reserved bit, was not used in the conventional symbol configuration, is redefined as the antenna bit A and this bit is used to distinguish between SDM and STBC modes. [0093] The R4 bit of the four RATES bits is used to distinguish between the conventional IEEE 802.11 mode and the multi-antenna OFDM mode. Accordingly, the frame generator allocates RATA bits R1 to R4 and antenna bit A as shown in Table 1.

[Table 1]

<td>Bit allocation RATATA, ANTENNA, (R1 R4, AND).</td><td>Speed data,</td><td>Way mapping,</td><td>Efficiency code</td><td>Mode broadcasting</td>

<td>1101Χ,</td><td> 6,</td><td>BPSK</td><td> 1/2,</td><td>1EEE802 11a,</td>

<td>1111Χ,</td><td> 9,</td><td>BPSK</td><td> 3/4,</td><td>IEEE802 11a,</td>

<td>0101Χ,</td><td> 12,</td><td>QPSK,</td><td> 1/2,</td><td>IEEE802 11a,</td>

<td>0111Χ,</td><td> 18,</td><td>QPSK,</td><td> 3/4,</td><td>ΪΕΕΕ802 11a,</td>

<td>1001Χ,</td><td> 24,</td><td>16GAM,</td><td> 1/2,</td><td>IEEE802 11a,</td>

<td>1011Χ,</td><td> 36,</td><td>160AM,</td><td> 3/4,</td><td>IEEE802 11a,</td>

<td>0001X,</td><td> 48,</td><td>64OAM,</td><td> 2/3,</td><td>IEEE802 11a,</td>

<td>0011Χ,</td><td> 54,</td><td>64OAM,</td><td> 3/4,</td><td>IEEE802 11a,</td>

<td> 11000,</td><td> 6,</td><td>BPSK</td><td> 1/2,</td><td>STSC-OFDM</td>

<td> 11100,</td><td> 9,</td><td>BPSK</td><td> 3/4,</td><td>STBC-OFDM</td>

<td> 01000,</td><td> 12,</td><td>QPSK,</td><td> 1/2,</td><td>STBC-OFDM</td>

<td> 01100,</td><td> 18,</td><td>GPSK,</td><td> 3/4,</td><td>STBC-OFDM</td>

<td> 10000,</td><td> 24,</td><td>16QAM,</td><td> 1/2,</td><td>STBC-OFDM</td>

<td> 10100,</td><td> 36,</td><td>160AM,</td><td> 3/4,</td><td>STBC-OFDM</td>

<td> 00000,</td><td> 48,</td><td>64OAM,</td><td> 2/3,</td><td>STBC-OFDM</td>

<td> 00100,</td><td> 54,</td><td>64OAM,</td><td> 3/4,</td><td>STBC-OFDM</td>

<td> 11001,</td><td> 12,</td><td>BPSK</td><td> 1/2,</td><td>SDM-OFDM</td>

<td>Bit allocation RATATA, ANTENNA, (R1 R4, AND).</td><td>Speed data,</td><td>Way mapping,</td><td>Efficiency code</td><td>Mode broadcasting</td>

<td> 11101,</td><td> 18,</td><td>BPSK</td><td> 3/4,</td><td>OFM SDM,</td>

<td> 01001,</td><td> 24,</td><td>QPSK,</td><td> 1/2,</td><td>OFM SDM,</td>

<td> 01101,</td><td> 36,</td><td>QPSK,</td><td> 3/4,</td><td>SDM, OFDM,</td>

<td> 10001,</td><td> 48,</td><td>16QAM,</td><td> 1/2,</td><td>OFM SDM,</td>

<td> 10101,</td><td> 72,</td><td>16QAM.</td><td> 3/4,</td><td>OFM SDM,</td>

<td> 00001,</td><td> 96,</td><td>64QAM,</td><td> 2/3,</td><td>OFM SDM,</td>

<td> 00101,</td><td> 108,</td><td>64QAM,</td><td> 3/4,</td><td>OFM SDM,</td>

[0094] As shown in Table 1, when R4 bit is set to 1, data is received by the IEEE 802.16a standard method. When the R4 bit is 1, because the transmission mode is IEEE 802.16a mode, the antenna bit value is not affected, and the signal symbol configuration corresponds to that of the IEEE 802.16a standard.

[0095] However, when bit R4 is set to 0, the system is a MIMO system. At this time, it is determined whether the transmission mode is SDM or STBC mode by reference to antenna bit A.

[0096] Bits R1 to R3 correspond successively to information about eight data rates, mapping methods and code performances.

[0097] Accordingly, the signal symbol is configured by combining 24 bits in a manner similar to a conventional signal symbol. These 24 bits contain a 12-bit field, 1 parity bit and 6 end bits. Data is transmitted on 64 or repeated 128 (64 + 64) subcarriers in the conventional IEEE 802.11 a mode and data is separately transmitted on even subcarriers and odd subcarriers in multi-antenna mode, according to expression 4 and expression 8.

[0098] With respect to the output signal of the transmit antenna, pre-set configurations of the preamble and the signal symbol are formed regardless of the number of transmit antennas and bands.

[0099] With the above frame configuration, a process for maintaining compatibility by a conventional system and system according to an exemplary embodiment of the invention in a receiving terminal will be described.

[0100] When data is transmitted in a conventional IEEE 802.11a system, the conventional receiver can perform demodulation of the short preamble, the first long preamble and the signal symbol field. In contrast, when the signal symbol is interpreted, the data following the signal symbol are demodulated because the frame corresponds to a conventional frame, when the R4 bit from RATA bits is 1, data demodulation is not performed before the end of the frame because the frame is not demodulated by a conventional demodulator when bit R4 is 0. Accordingly, compatibility is ensured in a network formed by combining a conventional system and a system according to an exemplary embodiment of the present invention.

[0101] The system receiver according to an exemplary embodiment of the present invention starts performing demodulation of the data following the signal symbol when the receiver recognizes that the frame is an IEEE 802.11 a frame when the signal symbol R4 bit is 1. However, when the R4 bit is 0, the receiver performs channel estimation using a second long preamble,

- following the signal symbol, it checks the antenna bit A, determines whether the transmission mode is SDM-OFDM or STBC-OFDM and recovers the transmitted data after a proper demodication process in accordance with the specified mode.

[0102] Accordingly, the same system according to an exemplary embodiment of the present invention may be compatible with the conventional IEEE 802.16a system.

[0103] FIG. 7 is a block diagram representing the configuration for initial synchronization of a receiver according to an exemplary embodiment of the present invention.

[0104] In FIG. 7 the receiver includes constant component compensators 300a and 300b as well as synphase and quadrature compensators (I / G, inphase and quadrature) 31 Oa and 31 Ob for compensation of l / Q mismatch for individual antenna paths. The constant component compensators 300a and 300b eliminate the constant component in the paths of individual antennas, which can be generated in analog and RF circuits. The I / Q 31 Oa and 31 Ob compensators compensate for the I / Q mismatch that can be generated in analog and RF circuits.

[0105] The data before the signal symbol, which is part of the short preamble and part of the first long preamble, is input to the channel mixer 400. In the channel mixer 400, the frequency is shifted by + 10MHz and by -10MHz for a corresponding split of 40MHz bandwidth signals occupying two bands on channel 0 20MHz wide and channel 1 20MHz wide. Accordingly, two output signals are generated from individual antenna paths. These signals pass through the Iow pass filter (LPF) 410 and these signals are determined by 1/2 to transform these signals into signals with a bandwidth of 20MHz. The initial synchronization is performed using the short preamble and the first long preamble for the 20MHz bandwidth.

[0106] Carrier frequency offset estimator (CFO) 430 estimates carrier frequency offset using short preamble and first long preamble autocorrelation.

[0107] The frame synchronizer 420 performs frame synchronization using the cross correlation of the short preamble and the first long preamble. The band detector 440 performs band detection for determining the bandwidth using the autocorrelation of the first long preamble.

[0108] The signal symbol including the first long preamble and some data is introduced into the FFT modules 330a and 330b after initial synchronization. At this time channel estimation takes place and the signal symbol is demodulated using the first long preamble FFT output samples.

[0109] The signal symbol is demodulated without transmission mode information, because the method of transmitting the signal symbol is always the same. After the signal symbol is demodulated, information on the transmission mode, bandwidth, frame length, demodulation method and code efficiency is provided.

[0110] As described above, when the R4 bit is 1 (i.e. when the transmission mode is MIMO-OFDM mode), the channel estimator 450 further performs channel estimation using a second long preamble.

[0111] The data field is demodized with respect to information determined from the signal symbol when performing channel estimation.

[0112] Phase compensators 340a and 340b estimate and compensate for remaining frequency and phase shifts using pilot subcarriers.

[0113] The signal is detected according to the transmit mode by the detector 300, and the receiver combines the data processed by the demaper, deinterlacing module, Viterbi decoder and deskrambier and sends the combined data to the media access control layer (MAC) !).

[0114] Thus, this multiplied support system facilitates channel estimation and ensures compatibility with a conventional system.

[0115] FIG. 8 is a block diagram representing a data transmission method according to an exemplary embodiment of the present invention.

[0116] Binary data generated in the source module is split into a number of bands in step S100. Data speed can be increased with the separation of binary data into a number of bands. [0117] The data separated into individual bands is appropriately encoded in step S110 using, for example, a convolutional code for better correction of data errors. In addition, an encryption operation may be performed before the encoding operation.

[0118] An interleaving operation is performed to prevent packet transmission errors and the binary data is mapped to a number of complex symbols in step S120 when the data is encoded. The mapping method includes BPSK, QPSK, 16QAM, and 64QAM modulations. [0119] Data mapped to complex number symbols is separated into antennas, and subcarriers allocated for individual antennas are allocated for separated complex symbols in step S140. OFDM signals formed by the allocation of individual subcarriers carry out an inverse fast Fourier transform for transforming a signal in the frequency domain to a signal in the time domain.

[0120] When subcarriers are allocated, the signal fills the desired bands and 0 fills the remaining bands. The subcarriers can also be allocated so that the subcarrier used by the antenna cannot be used by another antenna.

[0121] In steps S100 and S130, not only multiplied bands and antennas can be used, but also a single band and a single antenna.

[0122] When a single band and antenna are used, the data modulation process corresponds to that of the conventional IEEE 802.16a standard.

[0123] Accordingly, in step S150, it is determined whether the OFDM signal is to be transmitted according to the MIMO transmission method, using multiple bands and antennas. Information for determining MIMO status is determined by configuration search and previous transmitter operation.

[0124] When the OFDM signal is to be transmitted according to the MIMO transmission method, using multiplied antennas, in step S160 preambles are generated for individual subcarriers. The preamble includes the long preamble of operating antennas and subcarriers. The long preamble includes the first long preamble for channel estimation for operating subcarriers and the second long preamble for channel estimation of subcarriers that are not used.

[0125] At this time, the first long preamble that was used for the carrier by the antenna can be used as the second long preamble.

[0126] A signal symbol with data demodication information is generated in step S161. The signal symbol is generated by mapping information about the transmission mode, data rate, mapping method and code efficiency into bits R1 to R4 and the antenna bit as shown in Table 1.

[0127] The data field and frame for the MIMO antenna are generated using the generated short preamble, first long preamble and second long preamble in step S162. The frame is collated in

- 16 sequences of short preamble, first long preamble, signal symbol, second long preamble and data retrieval.

[0128] When it is determined that the OFDM signal is not to be transmitted according to the MiMO transmission method, in S170 a frame is generated for a single antenna in a similar manner as in a conventional system. The frame for a single antenna also includes a short preamble, a long preamble, a signal symbol and a data link. The description of generating a frame for a single antenna described above will be omitted. [0129] The frame generated in the above configuration is transmitted to the receiver via an RF transmitter module in step S180.

[0130] F (G. 9 is a block diagram representing a method of receiving data according to an exemplary embodiment of the present invention.

[0131] In this method of receiving data, the OFDM signal received on the radio channel is pre-synchronized in step S210. In addition, the constant component using the filter is eliminated and the I / Q discrepancy is compensated in step S210. The short preamble and the first long preamble before the signal symbol are used to perform the initial synchronization of the compensated signal, [0132] The subcarrier frequency offset is estimated using the autocorrelation of the short preamble and the first long preamble, and frame synchronization is performed using the cross correlation of the short preamble and the first long preambles in step S220.

[0133] Bandwidth detection is performed to determine the bandwidth, using the autocorrelation of the first long preamble in step S230.

[0134] The first channel estimation is performed using the fast Fourier transform of the first long preamble in step S240. The methods for initial time synchronization, frequency synchronization and channel estimation can be easily selected by those skilled in the art because the preamble in the physical layer convergence procedure (PLCP) , physical layer convergence procedure), which is the training sequence for synchronization, has been defined in the IEEE 802.11a standard.

[0135] The receiver demodises the signal symbol and determines the information in the signal symbol in step S250. The signal symbol contains information about the transmission mode, data rate, mapping method and code efficiency. [0136] The receiver determines whether the demodulated signal symbol is transmitted from the MiMO system, referring to the transmission mode information in step S260. information about the transmission mode is given based on the determined value of bit R4 in the signal symbols.

[0137] When the transmission mode is MIMO-OFDM mode, channel estimation is performed using a second long preamble, transmitted after the signal symbol. The first long subcarrier preamble, which is not used by another antenna, is used as the second long preamble. Therefore, the MIMO-OFDM signal channel estimation is complete when the second estimation is performed. [0138] The phase shift is compensated using a pifot subcarrier, and the data demodulation is performed according to the data rate, mapping method and code efficiency of the signal symbol. Data demodulation has been described with reference to FIG. 3.

[0139] When in the previous step S260 the transmission mode is not the MIMO-OFDM mode, phase compensation and data demodulation are performed without performing the second channel estimation.

[0140] According to an exemplary embodiment of the present invention, high data rate

- 17 is provided by the MIMO-OFDM system, and compatibility with the conventional system is also ensured, because in this exemplary embodiment of the present invention most of the frame configuration of the conventional one-antenna OFDM system is retained.

[0141] Although the present invention has been described in detail with respect to preferred embodiments, those skilled in the art will recognize that various modifications and changes may be made thereto without departing from the scope of the present invention as set out in the appended claims.