WO2008123713A1

WO2008123713A1 - Method for signal transmitting and apparatus for the same, method for signal receiving and apparatus for the same

Info

Publication number: WO2008123713A1
Application number: PCT/KR2008/001934
Authority: WO
Inventors: Woo Suk Ko; Sang Chul Moon
Original assignee: Lg Electronics Inc.
Priority date: 2007-04-05
Filing date: 2008-04-04
Publication date: 2008-10-16
Also published as: KR20080090707A

Abstract

A signal transmission/reception method and a signal transmission/reception apparatus are disclosed. The signal transmission method includes selecting symbol data farther than a coherence bandwidth from among symbol data mapped based on a given transmission scheme, precoding the selected symbol data to disperse the selected symbol data into two or more symbol data in a frequency domain, and MIMO-encoding the symbol data dispersed by the precoding such that the dispersed symbol data can be transmitted on multiple paths. Therefore, data can be robust to frequency-selective fading of each transmission channel, and signal reception performance of a receiver can be improved.

Description

METHOD FOR SIGNAL TRANSMITTING AND APPARATUS FOR THE SAME, METHOD FOR SIGNAL RECEIVING AND

APPARATUS FOR THE SAME

Technical Field

[1] The present invention relates to a signal transmission/reception method and a signal transmission/reception apparatus, and more particularly, to a signal transmission/ reception method and a signal transmission/reception apparatus which are robust to frequency- selective fading. Background Art

[2] With the advance of technologies, the size of data desired by the user is on an increasing trend; however, there is a certain limitation in extending transmission resources for transmission of the data to the user side. For this reason, various technologies have been developed to increase data transmission efficiency using limited transmission resources.

[3] Among these technologies, a Multi Input Multi Output (MIMO) scheme has been proposed as a digital data transmission scheme to increase data transmission efficiency using a plurality of transmission/reception antennas.

[4] On the other hand, a transmission channel with a long delay time is subject to frequency- selective fading, and the size of a signal is very severely distorted due to a delay spread of the channel. As a result, there is a problem that a Signal-to-Noise Ratio (SNR) differs at different transmission bands and a reception rate is reduced in a transmission channel where the SNR is very low.

[5] In the MIMO scheme, a plurality of antennas can be used to obtain an array gain so as to improve an average SNR. Also, a diversity gain can be obtained when fading of a transmission channel from each transmission antenna to each reception antenna is independent.

[6] However, the MIMO scheme is problematic in that, in terms of only one specific transmission channel, this channel cannot help being subject to frequency- selective fading resulting from a delay time thereof as ever. Disclosure of Invention

Technical Problem

[7] An object of the present invention devised to solve the problem lies on a signal transmission/reception method and a signal transmission/reception apparatus which are robust to frequency-selective fading. Technical Solution

[8] The object of the present invention can be achieved by providing a signal transmission apparatus comprising: a symbol mapper for mapping input data to symbol data based on a given transmission scheme; a block selector for selecting symbol data farther than a coherence bandwidth from among the mapped symbol data; a precoder for precoding the selected symbol data to disperse the selected symbol data into two or more symbol data in a frequency domain; and a Multi Input Multi Output (MIMO) encoder for MIMO-encoding the precoded data such that the precoded data can be transmitted on multiple paths.

[9] In another aspect of the present invention, provided herein is a signal transmission method comprising: selecting symbol data farther than a coherence bandwidth from among symbol data mapped based on a given transmission scheme; precoding the selected symbol data to disperse the selected symbol data into two or more symbol data in a frequency domain; and MIMO-encoding the symbol data dispersed by the precoding such that the dispersed symbol data can be transmitted on multiple paths.

[10] In another aspect of the present invention, provided herein is a signal reception apparatus comprising: a MIMO decoder for MIMO-decoding data received on multiple paths to output one symbol data stream; a precoding decoder for restoring symbol data dispersed in a frequency domain from the outputted symbol data stream; a block restorer for returning the restored symbol data to its original position farther than a coherence bandwidth; and a symbol demapper for demapping the symbol data returned to its original position to output bit data of a corresponding symbol.

[11] In a further aspect of the present invention, provided herein is a signal reception method comprising: MIMO-decoding data received on multiple paths to output one symbol data stream; decoding the symbol data stream to restore symbol data dispersed in a frequency domain from the symbol data stream; and returning the restored symbol data to its original position farther than a coherence bandwidth and demapping the returned symbol data.

Advantageous Effects

[12] According to a signal transmission/reception method and a signal transmission/ reception apparatus of the present invention, input data can be dispersed and transmitted in a frequency domain, so that it can be robust to frequency-selective fading of each transmission channel. Also, it is possible to improve signal reception performance of a receiver. Brief Description of the Drawings

[13] The accompanying drawings, which are included to provide a further understanding of the invention, illustrate embodiments of the invention and together with the de- scription serve to explain the principle of the invention. [14] In the drawings :

[15] FIG. 1 is a schematic block diagram of a signal transmission apparatus according to one embodiment of the present invention. [16] FIG. 2 is a schematic block diagram of a linear precoder according to one embodiment of the present invention. [17] FIG. 3 is a view showing a code matrix for dispersion of input data according to one embodiment of the present invention. [18] FIG. 4 is a view showing another code matrix for dispersion of input data according to one embodiment of the present invention. [19] FIG. 5 is a schematic block diagram of a signal transmission apparatus having a plurality of transmission paths according to one embodiment of the present invention. [20] FIGs. 6 to 10 are views showing examples of a 2x2 code matrix for dispersion of input symbols according to one embodiment of the present invention. [21] FIG. 11 is a schematic block diagram of a signal reception apparatus according to one embodiment of the present invention. [22] FIG. 12 is a block diagram schematically showing an example of a linear precoding decoder according to one embodiment of the present invention. [23] FIG. 13 is a block diagram schematically showing another example of the linear precoding decoder according to one embodiment of the present invention. [24] FIG. 14 is a schematic block diagram of a signal reception apparatus having a plurality of reception paths according to one embodiment of the present invention. [25] FIGs. 15 to 19 are views showing examples of a 2x2 code matrix for restoration of dispersed symbols according to one embodiment of the present invention. [26] FIG. 20 is a flowchart illustrating a signal transmission/reception method according to one embodiment of the present invention.

Best Mode for Carrying Out the Invention [27] Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the invention rather unclear. [28] Besides, although terms used in the present invention are possibly selected from the currently well-known ones, some terms are arbitrarily chosen by the inventor in some cases so that their meanings are explained in detail in the following description. Hence, the present invention should be understood with the intended meanings of the cor- responding terms chosen by the inventor instead of the simple names or meanings of the terms themselves.

[29] FIG. 1 is a schematic block diagram of a signal transmission apparatus according to one embodiment of the present invention. In this embodiment, the signal transmission apparatus employs a Multi Input Multi Output (MIMO) scheme for multiple input/ output.

[30] In the case where the signal transmission apparatus transmits video data of a broadcast signal, it may be a broadcast signal transmission system. The embodiment of the signal transmission apparatus according to the present invention will hereinafter be described with reference to FIG. 1.

[31] The embodiment of FIG. 1 comprises an outer coder 100, outer interleaver 110, inner coder 120, inner interleaver 130, symbol mapper 140, block selector 150, linear precoder 160, MIMO encoder 170, frame builder 180, modulator 190, and transmitting unit 195. The embodiment of FIG. 1 will be described centering around a signal processing process of the signal transmission apparatus under the condition that the number of transmission paths is not fixed.

[32] The outer coder 100 and the outer interleaver 110 code and interleave multiplexed data, respectively, to improve transmission performance of an input signal. For example, in a DVB-T system, a Reed-Solomon coding scheme may be used for the outer coding and a convolution interleaving scheme may be used for the interleaving.

[33] The inner coder 120 and the inner interleaver 130 again code and interleave a signal interleaved and outputted by the outer interleaver 110, respectively, to cope with an error which may occur in a signal to be transmitted. The inner coder 120 may employ a punctured convolution coding scheme to code the signal to be transmitted. The inner interleaver 130 may employ a native or in-depth interleaving scheme based on memory operations in 2k, 4k and 8k transmission modes in, for example, the DVB-T system. The types of the respective coders and interleavers may be different depending on coding and interleaving schemes used in the signal transmission apparatus.

[34] The symbol mapper 140 maps a signal to be transmitted to symbol data based on a mapping scheme such as 16QAM, 64QAM or QPSK in consideration of a transmission mode, transmission scheme, etc.

[35] The block selector 150 selects symbol data farther than a coherence bandwidth from among symbol data outputted from the symbol mapper 140 and sends the selected symbol data to the linear precoder 160. For example, assuming that the coherence bandwidth is 'd', symbol data distanced by more than 'd' is selected and outputted from among inputted symbol data, thereby making it possible to prevent all data within the coherence bandwidth from being lost due to deep fading. This selection distance may be different according to different embodiments. [36] The linear precoder 160 disperses symbol data inputted thereto into a plurality of output symbol data in a frequency domain to reduce the probability for all information to be lost due to fading when a frequency- selective fading channel is experienced.

[37] FIG. 2 is a schematic block diagram of the linear precoder according to one embodiment of the present invention. The precoder 160 includes a serial/parallel converter 162, encoder 164, and parallel/serial converter 166.

[38] The serial/parallel converter 162 converts symbol data inputted thereto into parallel data. The encoder 164 disperses the parallel symbol data into a plurality of data in a frequency domain through encoding matrixing. For example, in the case where the transmission scheme is OFDM, the encoder 164 disperses the parallel data inputted thereto to respective carriers to code the parallel data such that the parallel data can be robust to frequency-selective fading of a channel. Therefore, even when fading occurs at a specific frequency band on a frequency-selective fading channel, a sub-carrier of the frequency band has a dispersed data value, thereby reducing the influence of the fading.

[39] FIG. 3 is a view showing a code matrix for dispersion of input data according to one embodiment of the present invention. FIG. 3 shows an example of an encoding matrix for dispersing the input data into a plurality of output data, which is called a vanderMonde matrix. The input data can be arranged in parallel by a length corresponding to the number L of output data.

[40] _θ

of the matrix can be expressed by the following equation 1, and may be defined in a different way. The vanderMonde matrix can adjust the matrix components thereof using the equation 1. [41] The matrix reflects each input data in output data by rotating it by a corresponding phase of the equation 1. Thus, input values can be dispersed into at least two output values according to characteristics of the matrix. [42] [Equation 1]

[44] In the above equation 1, L represents the number of output data. Assuming that a group of data inputted to the encoder 164 in FIG. 2 is x and a group of data encoded and outputted by the encoder 164 through the matrix is y, y can be expressed by the following equation 2.

[45] [Equation 2] y — Θ x

[47] FIG. 4 is a view showing another code matrix for dispersion of input data according to one embodiment of the present invention. FIG. 4 shows an example of an encoding matrix for dispersing the input data into a plurality of output data, which is called a Hadamard matrix. The matrix of FIG. 4 has a general form extended to a size of L = 2 , and 'L' represents the number of output symbols into which each input symbol is to be dispersed.

[48] The output symbols of this matrix can be obtained from additions and subtractions of

L input symbols. In other words, each input symbol can be dispersed into L output symbols.

[49] Similarly, in the case of the matrix of FIG. 4, assuming that a group of data inputted to the encoder 164 in FIG. 2 is x and a group of data encoded and outputted by the encoder 164 through the matrix is y, y is a product of the matrix and x.

[50] The parallel/serial converter 166 again converts output data from the encoder 164 into serial data and outputs the converted serial data to the MIMO encoder 170.

[51] The MIMO encoder 170 performs MIMO encoding with respect to data precoded by the linear precoder 160 such that the precoded data can be transmitted through a plurality of transmission antennas, and outputs the resulting data to the frame builder 180.

[52] The MIMO encoding may be broadly classified into a spatial multiplexing scheme and a spatial diversity scheme. The spatial multiplexing scheme is a scheme where a transmitter and a receiver transmit different data simultaneously using multiple antennas, thereby enabling data to be transmitted at a higher speed with no further increase in system bandwidth. The spatial diversity scheme is a scheme where data of the same information is transmitted through multiple transmission antennas to obtain transmission diversity.

[53] Here, a space-time block code (STBC), a space-frequency block code (SFBC), a space-time trellis code (STTC), etc can be used for the MIMO encoder 170 of the spatial diversity scheme. A scheme for simply dividing and transmitting a data stream by the number of transmission antennas, a full-diversity full-rate (FDFR) code, a linear dispersion code (LDC), a Vertical-Bell Lab. layered space-time (V-BLAST), a diagonal-BLAST (D-BLAST), etc. can be used for the MIMO encoder 170 of the spatial multiplex scheme.

[54] The frame builder 180 enables the precoded and MIMO-encoded symbol data to be modulated based on a multi-carrier transmission scheme, for example, an OFDM transmission scheme. To this end, the frame builder 180 converts the precoded and MIMO-encoded symbol data into symbol data of a time domain, inserts a guard interval in a data period of the symbol data of the time domain to create an OFDM symbol, and then collects a plurality of OFDM symbols to build a transmission frame. For example, in a DVB-Terrestrial (T) system, each transmission frame includes 68 OFDM symbols. Each OFDM symbol includes 6817 carriers in an 8k mode and 1705 carriers in a 2k mode. Also, each transmission frame includes a dispersed pilot signal, a consecutive pilot signal, and a transmission parameter signal (TPS) carrier. The TPS includes all information about transmission parameters such as the number of carriers of an OFDM symbol being currently transmitted and the length of a guard interval of the OFDM symbol.

[55] The modulator 190 modulates the transmission frame outputted from the frame builder 180 such that the OFDM data in the transmission frame can be transmitted on respective sub-carriers, and outputs the modulated frame to the transmitting unit 195. The transmitting unit 195 converts each sub-carrier from the modulator 190 into an analog signal, up-converts the converted analog signal into a radio frequency (RF) signal and transmits the converted RF signal.

[56] FIG. 5 is a schematic block diagram of a signal transmission apparatus having a plurality of transmission paths according to one embodiment of the present invention. For the convenience of description, the case where the number of transmission paths is two will hereinafter be taken as an example.

[57] The embodiment of FIG. 5 comprises an outer coder 400, outer interleaver 410, inner coding & interleaving unit 420, symbol mapper 430, block selector 440, linear precoder 450, MIMO encoder 460, first frame builder 470, second frame builder 475, first modulator 480, second modulator 485, first transmitting unit 490, and second transmitting unit 495.

[58] The same signal processing process of FIG. 1 can be applied as a signal processing process from the outer coder 400 to the MIMO encoder 460.

[59] That is, the outer coder 400 and the outer interleaver 410 code and interleave input data, respectively. For example, a Reed-Solomon coding scheme may be used for the outer coding and a convolution interleaving scheme may be used for the interleaving.

[60] The inner coder and the inner interleaver again code and interleave an interleaved signal, respectively, to cope with an error which may occur in a signal to be transmitted.

[61] The symbol mapper 430 maps a signal to be transmitted to symbol data based on a mapping scheme in consideration of a transmission mode, transmission scheme, etc, and outputs the mapped symbol data to the block selector 440. The block selector 440 selects symbol data farther than a coherence bandwidth from among symbol data outputted from the symbol mapper 430 and outputs the selected symbol data to the linear precoder 450. This selection distance may be different according to different embodiments.

[62] The linear precoder 450 disperses symbol data inputted thereto into a plurality of output symbol data in a frequency domain to reduce the probability for all information to be lost due to fading when a frequency- selective fading channel is experienced.

[63] The linear precoder 450 includes a serial/parallel converter, encoder, and parallel/ serial converter.

[64] FIGs. 6 to 10 are views showing examples of a 2x2 code matrix for dispersion of input symbols according to one embodiment of the present invention. The code matrices of FIGs. 6 to 10 are applicable to the signal transmission apparatus as shown in FIG. 5, and disperse two data inputted to the encoder in the linear precoder 450 into two output data.

[65] The matrix of FIG. 6 is an example of the vanderMonde matrix described in FIG. 3.

[66] The matrix of FIG. 6 adds a first one of the two input data and a second one of the two input data rotated 45 degrees ( n

1^~

) in phase to provide first output data, and adds the first input data and the second input data rotated 225 degrees (

5 π

4

) in phase to provide second output data. Then, the matrix of FIG. 6 scales each output data by dividing it by

[67] The matrix of FIG. 7 is an example of the Hadamard matrix described in FIG. 4.

[68] The matrix of FIG. 7 adds a first one of the two input data and a second one of the two input data to provide first output data, and subtracts the second input data from the first input data to provide second output data. Then, the matrix of FIG. 7 scales each output data by dividing it by

[69] FIG. 8 shows another example of the input symbol dispersion code matrix applicable to FIG. 5 according to one embodiment of the present invention. The matrix of FIG. 8 is an example of another code matrix different from the matrices described in FIGs. 3 and 4. [70] The matrix of FIG. 8 adds a first one of the two input data rotated 45 degrees ( n

4

) in phase and a second one of the two input data rotated -45 degrees ( n

^~ T

) in phase to provide first output data, and subtracts the second input data rotated -45 degrees in phase from the first input data rotated 45 degrees in phase to provide second output data. Then, the matrix of FIG. 8 scales each output data by dividing it by

[71] FIG. 9 shows another example of the input symbol dispersion code matrix applicable to FIG. 5 according to one embodiment of the present invention. The matrix of FIG. 9 is an example of another code matrix different from the matrices described in FIGs. 3 and 4.

[72] The matrix of FIG. 9 adds a first one of the two input data multiplied by 0.5 to a second one of the two input data to provide first output data, and subtracts the second input data multiplied by 0.5 from the first input data to provide second output data. Then, the matrix of FIG. 9 scales each output data by dividing it by

1.25

[73] FIG. 10 shows another example of the input symbol dispersion code matrix applicable to FIG. 5 according to one embodiment of the present invention. The matrix of FIG. 10 is an example of another code matrix different from the matrices described in FIGs. 3 and 4. In FIG. 10, '*' means a complex conjugate of input data.

[74] The matrix of FIG. 10 adds a first one of the two input data rotated 90 degrees ( π 2

) in phase and a second one of the two input data to provide first output data, and adds a complex conjugate of the first input data and a complex conjugate of the second input data rotated -90 degrees ( π 2

) in phase to provide second output data. Then, the matrix of FIG. 10 scales each output data by dividing it by [75] The precoded data is outputted to the MIMO encoder 460. The MIMO encoder 460 encodes and outputs symbol data inputted thereto such that the symbol data can be transmitted on a plurality of transmission antennas. For example, in the case where the number of transmission paths is two, the MIMO encoder 460 outputs the encoded data to the first frame builder 470 and/or second frame builder 475.

[76] In the case where the encoding is performed in the spatial diversity scheme, data of the same information is outputted to the first frame builder 470 and second frame builder 475. In the case where the encoding is performed in the spatial multiplexing scheme, different data are outputted to the first frame builder 470 and second frame builder 475, respectively.

[77] Each of the first frame builder 470 and second frame builder 475 inserts a guard interval, etc. in the precoded and MIMO-encoded signal to create an OFDM symbol, and then collects a plurality of OFDM symbols to build a transmission frame. This transmission frame includes a dispersed pilot signal, a consecutive pilot signal, and a transmission parameter signal (TPS) carrier.

[78] The first modulator 480 and second modulator 485 modulate respective data outputted from the first frame builder 470 and second frame builder 475 such that the data can be transmitted on OFDM sub-carriers, respectively, and output the modulated data to the first transmitting unit 490 and second transmitting unit 495, respectively.

[79] The first transmitting unit 490 and second transmitting unit 495 convert respective digital signals outputted from the first modulator 480 and second modulator 485 into analog signals and transmit the analog signals, respectively.

[80] FIG. 11 is a schematic block diagram of a signal reception apparatus according to one embodiment of the present invention. The embodiment of FIG. 11 may be included in a broadcast reception apparatus, etc.

[81] The signal reception apparatus of FIG. 11 comprises a receiving unit 600, synchronizer 610, demodulator 620, frame parser 630, MIMO decoder 640, linear precoding decoder 650, block restorer 660, symbol demapper 670, inner deinterleaver 680, inner decoder 690, outer deinterleaver 695, and outer decoder 697. The embodiment of FIG. 11 will be described centering around a signal processing process of the signal reception apparatus under the condition that the number of reception paths is not fixed.

[82] The receiving unit 600 down-converts a frequency band of a received RF signal, converts the resulting analog signal into a digital signal and outputs the converted digital signal to the synchronizer 610. The synchronizer 610 acquires frequency- domain and time-domain synchronizations of the received signal outputted from the receiving unit 600. For the acquisition of the frequency-domain synchronization, the synchronizer 610 may use frequency-domain offset results of data outputted from the demodulator 620.

[83] The demodulator 620 demodulates received data outputted from the synchronizer

610 in the reverse of a transmission scheme of the transmission side and outputs the demodulated data to the frame parser 630. The frame parser 630 converts a demodulated signal into a signal of a frequency domain, parses a frame structure of the converted signal of the frequency domain to extract, therefrom, data in a data period except a guard interval, namely, valid data, and outputs the extracted data to the MIMO decoder 640.

[84] The MIMO decoder 640 receives and decodes the data outputted from the frame parser 630, and outputs the resulting one data stream to the precoding decoder 650. The MIMO decoder 640 decodes the received data in a scheme corresponding to the encoding scheme of the MIMO encoder 170 of FIG. 1 to output one data stream.

[85] The linear precoding decoder 650 restores the original data from data dispersed to be robust to frequency-selective fading. The linear precoding decoder 650 restores the original data by performing an inverse process of the data dispersion process of the signal transmission apparatus. In the case where the transmission scheme is OFDM, the linear precoding decoder 650 restores data values dispersed to sub-carriers of data outputted from the MIMO decoder 640 to values allocated respectively to the sub- carriers. That is, the linear precoding decoder 650 inverse-disperses data values dispersed to two or more sub-carriers into values allocated respectively to the sub- carriers.

[86] FIG. 12 is a block diagram schematically showing an example of the linear precoding decoder according to one embodiment of the present invention. The linear precoding decoder 650 includes a serial/parallel converter 652, first decoder 654, and parallel/ serial converter 656.

[87] The serial/parallel converter 652 converts input data into parallel data and outputs the converted parallel data to the first decoder 654. The first decoder 654 restores the original data from dispersed data by applying the parallel data to decoding matrixing. A decoding matrix for performing the decoding is an inverse matrix of the encoding matrix of the signal transmission apparatus. For example, in the case where the signal transmission apparatus performs the encoding using the vanderMonde matrix as shown in FIG. 3, the first decoder 654 restores the dispersed data to the original data using an inverse matrix of the vanderMonde matrix.

[88] The parallel/serial converter 656 again converts parallel data outputted from the first decoder 654 into serial data and outputs the converted serial data to the block restorer 660.

[89] FIG. 13 is a block diagram schematically showing another example of the linear precoding decoder according to one embodiment of the present invention. The linear precoding decoder 650 includes a serial/parallel converter 651, second decoder 653, and parallel/serial converter 655.

[90] The serial/parallel converter 651 converts input data into parallel data and outputs the converted parallel data to the second decoder 653. The parallel/serial converter 655 again converts parallel data decoded and outputted by the second decoder 653 into serial data and outputs the converted serial data to the block restorer 660.

[91] The second decoder 653 may restore the original data dispersed into the parallel data outputted from the serial/parallel converter 651 using Maximum Likelihood (ML) decoding. That is, the second decoder 653 may be an ML decoder considering a transmission scheme of a transmitter. In this case, the second decoder 653 restores the original data dispersed into received symbol data by ML-decoding the received symbol data correspondingly to the transmission scheme. The ML decoder ML-decodes the received symbol data in consideration of an encoding rule of a transmitting stage.

[92] The block restorer 660 returns symbol data inputted thereto to its original position farther than a coherence bandwidth. That is, the block restorer 660 returns the symbol data to its original position by performing an inverse process of the process of the block selector of the signal transmission apparatus selecting and outputting symbol data farther than the coherence bandwidth.

[93] The symbol demapper 670 demaps the symbol data returned to its original position by the block restorer 660 to a bit stream of a corresponding symbol and outputs the bit stream to the inner deinterleaver 680.

[94] The inner deinterleaver 680 performs an inverse process of the inner interleaving of the signal transmission apparatus with respect to the bit stream inputted thereto and outputs the deinterleaved data to the inner decoder 690. The inner decoder 690 is a decoder corresponding to the inner coder of the signal transmission apparatus, and decodes the deinterleaved data to correct an error included in the data. The output of the inner decoder 690 is provided to the outer deinterleaver 695. The outer deinterleaver 695 and the outer decoder 697 again perform the deinterleaving process and the error correction decoding process based on schemes corresponding to the outer interleaving and outer coding of the signal transmission apparatus, respectively.

[95] FIG. 14 is a schematic block diagram of a signal reception apparatus having a plurality of reception paths according to one embodiment of the present invention. For the convenience of description, the case where the number of reception paths is two will hereinafter be taken as an example.

[96] The signal reception apparatus of FIG. 14 comprises a first receiving unit 800, second receiving unit 805, first synchronizer 810, second synchronizer 815, first demodulator 820, second demodulator 825, first frame parser 830, second frame parser 835, MIMO decoder 840, linear precoding decoder 850, block restorer 860, symbol demapper 870, inner deinterleaver 880, inner decoder 890, outer deinterleaver 895, and outer decoder 897.

[97] Each of the first receiving unit 800 and second receiving unit 805 receives an RF signal, down-converts a frequency band of the received RF signal, converts the resulting analog signal into a digital signal and outputs the converted digital signal. The first synchronizer 810 and the second synchronizer 815 acquire frequency-domain and time-domain synchronizations of the received signals outputted from the first receiving unit 800 and second receiving unit 805, respectively. For the acquisition of the frequency-domain synchronizations, the first synchronizer 810 and the second synchronizer 815 may use frequency-domain offset results of data outputted from the first demodulator 820 and second demodulator 825, respectively.

[98] The first demodulator 820 demodulates received data outputted from the first synchronizer 810 in the reverse of the modulation process of the transmission side and outputs the demodulated data to the first frame parser 830. The second demodulator 825 demodulates received data outputted from the second synchronizer 815 in the reverse of the modulation process of the transmission side and outputs the demodulated data to the second frame parser 835.

[99] Each of the first frame parser 830 and second frame parser 835 converts a signal demodulated by a corresponding one of the first demodulator 820 and second demodulator 825 into a signal of a frequency domain, parses a frame structure of the converted signal of the frequency domain to extract, therefrom, data in a data period except a guard interval, namely, valid data, and outputs the extracted data to the MIMO decoder 840.

[100] The MIMO decoder 840 receives the data outputted respectively from the first frame parser 830 and second frame parser 835, decodes the received data in a scheme corresponding to the MIMO encoding scheme of the signal transmission apparatus and outputs the resulting one data stream to the linear precoding decoder 850.

[101] Hereinafter, the same signal processing process of FIG. 11 can be applied as a signal processing process from the MIMO decoder 840 to the outer decoder 897.

[102] The linear precoding decoder 850 restores the original data from data dispersed to be robust to frequency-selective fading. The linear precoding decoder 850 restores the original data by performing an inverse process of the data dispersion process of the signal transmission apparatus. In the case where the transmission scheme is OFDM, the linear precoding decoder 850 restores data values dispersed to sub-carriers of data outputted from the MIMO decoder 840 to values allocated respectively to the sub- carriers. That is, the linear precoding decoder 850 inverse-disperses data values dispersed to two or more sub-carriers into values allocated respectively to the sub- carriers.

[103] To this end, the linear precoding decoder 850 includes a serial/parallel converter, a first decoder or second decoder, and a parallel/serial converter.

[104] FIGs. 15 to 19 are views showing examples of a 2x2 code matrix for restoration of dispersed symbols according to one embodiment of the present invention. The code matrices of FIGs. 15 to 19 are applicable to the signal reception apparatus as shown in FIG. 14, and restore and output data dispersed into two data inputted to the decoder of the linear precoding decoder 850.

[105] The matrix of FIG. 15 is an example of a vanderMonde inverse matrix, which is a decoding matrix corresponding to the encoding matrix of FIG. 6.

[106] The matrix of FIG. 15 adds a first one of the two input data and a second one of the two input data to provide first output data, and adds the first input data rotated -45 degrees ( π

^~ T ) in phase and the second input data rotated -225 degrees (

_ I-L

4

) in phase to provide second output data. Then, the matrix of FIG. 15 scales each output data by dividing it by

[107] The matrix of FIG. 16 is an example of a Hadamard inverse matrix, which is a decoding matrix corresponding to the encoding matrix of FIG. 7.

[108] The matrix of FIG. 16 adds a first one of the two input data and a second one of the two input data to provide first output data, and subtracts the second input data from the first input data to provide second output data. Then, the matrix of FIG. 16 scales each output data by dividing it by

[109] FIG. 17 shows another example of the dispersed data restoration code matrix applicable to FIG. 14 according to one embodiment of the present invention. The matrix of FIG. 17 is a decoding matrix corresponding to the encoding matrix of FIG. 8.

[110] The matrix of FIG. 17 adds a first one of the two input data rotated -45 degrees ( π

^~ 7^~

) in phase and a second one of the two input data rotated -45 degrees ( π

) in phase to provide first output data, and subtracts the second input data rotated 45 degrees in phase from the first input data rotated 45 degrees in phase to provide second output data. Then, the matrix of FIG. 17 scales each output data by dividing it by

[111] FIG. 18 shows another example of the dispersed data restoration code matrix applicable to FIG. 14 according to one embodiment of the present invention. The matrix of FIG. 18 is a decoding matrix corresponding to the encoding matrix of FIG. 9.

[112] The matrix of FIG. 18 adds a first one of the two input data multiplied by 0.5 to a second one of the two input data to provide first output data, and subtracts the second input data multiplied by 0.5 from the first input data to provide second output data. Then, the matrix of FIG. 18 scales each output data by dividing it by

[113] FIG. 19 shows another example of the dispersed data restoration code matrix applicable to FIG. 14 according to one embodiment of the present invention. The matrix of FIG. 19 is a decoding matrix corresponding to the encoding matrix of FIG. 10. In FIG. 19, '*' means a complex conjugate of input data.

[114] The matrix of FIG. 19 adds a first one of the two input data rotated -90 degrees ( n 2

) in phase and a complex conjugate of a second one of the two input data to provide first output data, and adds the first input data and the complex conjugate of the second input data rotated -90 degrees ( π 2

) in phase to provide second output data. Then, the matrix of FIG. 19 scales each output data by dividing it by

VI [115] The block restorer 860 returns symbol data inputted thereto to its original position farther than a coherence bandwidth and outputs the returned symbol data to the symbol demapper 870. The symbol demapper 870 demaps the symbol data returned to its original position by the block restorer 860 to a bit stream of a corresponding symbol and outputs the bit stream to the inner deinterleaver 880. The inner deinterleaver 880 deinterleaves a data bit stream interleaved by the transmission apparatus through an inverse process of the interleaving, and the inner decoder 890 decodes the dein- terleaved data to correct an error included in the data. The outer deinterleaver 895 and outer decoder 897 again perform the deinterleaving process and the error correction decoding process with respect to data outputted from the inner decoder 890, respectively.

[116] FIG. 20 is a flowchart illustrating a signal transmission/reception method according to one embodiment of the present invention, which transmits/receives a signal in such a manner that the signal is robust to frequency- selective fading. Steps SlOOO to S 1030 in FIG. 20 constitute a processing process of a signal transmission apparatus and steps S 1040 to S 1070 in FIG. 20 constitute a processing process of a signal reception apparatus.

[117] That is, the signal transmission apparatus selects symbol data farther than a coherence bandwidth of a channel from among mapped symbol data (SlOOO). Therefore, it is possible to reduce the probability that all data within the coherence bandwidth will be lost due to deep fading. This selection distance may be different according to different embodiments.

[118] The signal transmission apparatus performs precoding to disperse the selected symbol data into a plurality of output symbol data in a frequency domain, so as to enable data to be transmitted to be robust to frequency- selective fading (SlOlO).

[119] Then, the signal transmission apparatus performs MIMO encoding with respect to the data precoded at step SlOlO such that the precoded data can be transmitted through a plurality of antennas (S 1020). The number of the antennas may be the number of available data transmission paths. In a spatial diversity scheme, data of the same information is transmitted along the respective paths. In a spatial multiplexing scheme, different data are transmitted along the respective paths.

[120] Then, the signal transmission apparatus inserts a guard interval in the encoded data to create an OFDM symbol, collects a plurality of OFDM symbols to build transmission frames based on the number of the MIMO transmission paths, and modulates and transmits the built transmission frames (S 1030).

[121] On the other hand, the signal reception apparatus receives signals transmitted at step S 1030 through a plurality of reception antennas and performs synchronization acquisition and demodulation with respect to the received signals (S 1040). [122] Then, the signal reception apparatus MIMO-decodes the demodulated data in a scheme corresponding to the MIMO encoding scheme to obtain one symbol data stream (S 1050).

[123] The signal reception apparatus decodes the symbol data stream obtained at step

S 1050 in the reverse of the precoding scheme of the transmission apparatus to restore the original data dispersed into the plurality of symbol data in the frequency domain (S 1060).

[124] Thereafter, the signal reception apparatus returns the restored symbol data to its original position farther than the coherence bandwidth (S 1070). For example, the signal reception apparatus may return the symbol data to its original position by performing an inverse process of the transmission symbol selection process of step SlOOO.

[125] The above-described signal transmission/reception method and signal transmission/ reception apparatus are not limited to the above-stated embodiments, and are applicable to all signal transmission/reception systems employing the MIMO scheme.

[126] It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Claims

[1] A signal transmission apparatus comprising: a symbol mapper for mapping input data to symbol data based on a given transmission scheme; a block selector for selecting symbol data farther than a coherence bandwidth from among the mapped symbol data; a precoder for precoding the selected symbol data to disperse the selected symbol data into two or more symbol data in a frequency domain; and a Multi Input Multi Output (MIMO) encoder for MIMO-encoding the precoded data such that the precoded data can be transmitted on multiple paths.

[2] The signal transmission apparatus according to claim 1, wherein the precoder comprises: a serial/parallel converter for converting input serial data into parallel data; an encoder for multiplying the parallel data by a predetermined encoding matrix to disperse the parallel data; and a parallel/serial converter for converting the dispersed parallel data into serial data.

[3] The signal transmission apparatus according to claim 2, wherein the encoding matrix is a vanderMonde matrix

&

, the vanderMonde matrix

being expressed by the following equation when the number of output data is L which is a natural number and a matrix component θ is

with respect to k which is a natural number:

[4] The signal transmission apparatus according to claim 2, wherein the encoding matrix is a Hadamard matrix

H-

, the Hadamard matrix

H₂^ being expressed by the following equation when the number of output data is L =

-.k

2 , where L is a natural number:

[5] The signal transmission apparatus according to claim 2, wherein the encoder, for dispersion of two input data into two output data, adds a first one of the two input data and a second one of the two input data rotated 45 degrees in phase to provide a first one of the two output data, adds the first input data and the second input data rotated 225 degrees in phase to provide a second one of the two output data, and scales each of the first and second output data by dividing it by

[6] The signal transmission apparatus according to claim 2, wherein the encoder, for dispersion of two input data into two output data, adds a first one of the two input data and a second one of the two input data to provide a first one of the two output data, subtracts the second input data from the first input data to provide a second one of the two output data, and scales each of the first and second output data by dividing it by

Λ/2

[7] The signal transmission apparatus according to claim 2, wherein the encoder, for dispersion of two input data into two output data, adds a first one of the two input data rotated 45 degrees in phase and a second one of the two input data rotated - 45 degrees in phase to provide a first one of the two output data, subtracts the second input data rotated -45 degrees in phase from the first input data rotated 45 degrees in phase to provide a second one of the two output data, and scales each of the first and second output data by dividing it by

V^

[8] The signal transmission apparatus according to claim 2, wherein the encoder, for dispersion of two input data into two output data, adds a first one of the two input data multiplied by 0.5 to a second one of the two input data to provide a first one of the two output data, subtracts the second input data multiplied by 0.5 from the first input data to provide a second one of the two output data, and scales each of the first and second output data by dividing it by

[9] The signal transmission apparatus according to claim 2, wherein the encoder, for dispersion of two input data into two output data, adds a first one of the two input data rotated 90 degrees in phase and a second one of the two input data to provide a first one of the two output data, adds a complex conjugate of the first input data and a complex conjugate of the second input data rotated -90 degrees in phase to provide a second one of the two output data, and scales each of the first and second output data by dividing it by

[10] A signal transmission method comprising: selecting symbol data farther than a coherence bandwidth from among symbol data mapped based on a given transmission scheme; precoding the selected symbol data to disperse the selected symbol data into two or more symbol data in a frequency domain; and

MIMO-encoding the symbol data dispersed by the precoding such that the dispersed symbol data can be transmitted on multiple paths.

[11] The signal transmission method according to claim 10, wherein the precoding step comprises: converting input serial data into parallel data; multiplying the parallel data by a vanderMonde matrix to disperse the parallel data; and converting the dispersed parallel data into serial data.

[12] The signal transmission method according to claim 10, wherein the precoding step comprises: converting input serial data into parallel data; multiplying the parallel data by a Hadamard matrix to disperse the parallel data; and converting the dispersed parallel data into serial data.

[13] A signal reception apparatus comprising: a MIMO decoder for MIMO-decoding data received on multiple paths to output one symbol data stream; a precoding decoder for restoring symbol data dispersed in a frequency domain from the outputted symbol data stream; a block restorer for returning the restored symbol data to its original position farther than a coherence bandwidth; and a symbol demapper for demapping the symbol data returned to its original position to output bit data of a corresponding symbol.

[14] The signal reception apparatus according to claim 13, wherein the precoding decoder comprises: a serial/parallel converter for converting input serial data into parallel data; a decoder for multiplying the parallel data by a predetermined decoding matrix to restore data dispersed into the parallel data in the frequency domain; and a parallel/serial converter for converting the restored parallel data into serial data.

[15] The signal reception apparatus according to claim 14, wherein the decoding matrix is an inverse matrix of a vanderMonde matrix.

[16] The signal reception apparatus according to claim 14, wherein the decoding matr ix is an inverse matrix of a Hadamard matrix.

[17] The signal reception apparatus according to claim 14, wherein the decoder, for restoration of two output data dispersed into two input parallel data, adds a first one of the two input data and a second one of the two input data to provide a first one of the two output data, adds the first input data rotated -45 degrees in phase and the second input data rotated -225 degrees in phase to provide a second one of the two output data, and scales each of the first and second output data by dividing it by

Λ/2

[18] The signal reception apparatus according to claim 14, wherein the decoder, for restoration of two output data dispersed into two input parallel data, adds a first one of the two input data and a second one of the two input data to provide a first one of the two output data, subtracts the second input data from the first input data to provide a second one of the two output data, and scales each of the first and second output data by dividing it by

[19] The signal reception apparatus according to claim 14, wherein the decoder, for restoration of two output data dispersed into two input parallel data, adds a first one of the two input data rotated -45 degrees in phase and a second one of the two input data rotated -45 degrees in phase to provide a first one of the two output data, subtracts the second input data rotated 45 degrees in phase from the first input data rotated 45 degrees in phase to provide a second one of the two output data, and scales each of the first and second output data by dividing it by

[20] The signal reception apparatus according to claim 14, wherein the decoder, for restoration of two output data dispersed into two input parallel data, adds a first one of the two input data multiplied by 0.5 to a second one of the two input data to provide a first one of the two output data, subtracts the second input data multiplied by 0.5 from the first input data to provide a second one of the two output data, and scales each of the first and second output data by dividing it by

[21] The signal reception apparatus according to claim 14, wherein the decoder, for restoration of two output data dispersed into two input parallel data, adds a first one of the two input data rotated -90 degrees in phase and a complex conjugate of a second one of the two input data to provide a first one of the two output data, adds the first input data and the complex conjugate of the second input data rotated -90 degrees in phase to provide a second one of the two output data, and scales each of the first and second output data by dividing it by

V2 [22] The signal reception apparatus according to claim 13, wherein the precoding decoder comprises: a serial/parallel converter for converting input serial data into parallel data; a decoder for Maximum Likelihood (ML) -decoding the parallel data based on a transmission scheme to restore data dispersed into the parallel data in the frequency domain; and a parallel/serial converter for converting the restored parallel data into serial data. [23] A signal reception method comprising:

MIMO-decoding data received on multiple paths to output one symbol data stream; decoding the symbol data stream to restore symbol data dispersed in a frequency domain from the symbol data stream; and returning the restored symbol data to its original position farther than a coherence bandwidth and demapping the returned symbol data. [24] The signal reception method according to claim 23, wherein the symbol data restoration step comprises: converting input serial data into parallel data; multiplying the parallel data by an inverse matrix of a vanderMonde matrix to restore data dispersed into the parallel data in the frequency domain; and converting the restored parallel data into serial data. [25] The signal reception method according to claim 23, wherein the symbol data restoration step comprises: converting input serial data into parallel data; multiplying the parallel data by an inverse matrix of a Hadamard matrix to restore data dispersed into the parallel data in the frequency domain; and converting the restored parallel data into serial data. [26] The signal reception method according to claim 23, wherein the symbol data restoration step comprises: converting input serial data into parallel data;

ML-decoding the parallel data based on a transmission scheme to restore data dispersed into the parallel data in the frequency domain; and converting the restored parallel data into serial data.