KR102332508B1 - Signal transmission method of space-frequency block coded single side band single carrier frequency division multiple access system - Google Patents

Abstract

The present invention relates to a signal transmission method in a frequency space block-encoded single side-waveform single-carrier frequency division multiple access system, comprising the steps of: encoding a transmission bit for each user in a transmitter, inputting them into an interleaver, and then performing subchannel mapping; After performing the subchannel mapping, performing a Discrete Fourier Transform (DFT) operation corresponding to the allocated channel size, and after performing the Discrete Fourier Transform (DFT) operation, the single side-band waveform (SSB) method is below Transmitting a first transmission signal processed with a band (LSB) signal through a first transmission antenna, and after performing the discrete Fourier transform (DFT) operation, the lower band (LSB) signal is subjected to frequency space block coding ( By including the step of transmitting the second transmission signal processed by the SFBC) signal or the third transmission signal processing the upper band (USB) signal of the single side-band waveform (SSB) method through the second transmission antenna, system calculation It is possible to obtain a diversity gain for improving the performance of the transmission system as well as not significantly increasing the complexity.

Description

SIGNAL TRANSMISSION METHOD OF SPACE-FREQUENCY BLOCK CODED SINGLE SIDE BAND SINGLE CARRIER FREQUENCY DIVISION MULTIPLE ACCESS SYSTEM

The present invention applies a frequency space block coded single side band (SSB) modulation scheme to a single carrier-frequency division multiple access system (SC-FDMA), thereby reducing the system calculation complexity relatively. The present invention relates to a signal transmission method of a frequency-space block-coded single-side waveform single-carrier frequency division multiple access system, which can obtain a diversity gain for improving the performance of a transmission system as well as not significantly increasing it.

As is well known, an orthogonal frequency division multiplexing (OFDM) multi-carrier communication method has been adopted and used as a core technology of a wireless local area network (LAN) system based on 4G broadband mobile communication and IEEE 802.11.

This OFDM multi-carrier communication method can provide excellent performance in a frequency selective fading environment while having a simple transmission/reception structure and high frequency efficiency.

When describing the transmission system to which the OFDM multi-carrier communication method is applied as described above, the OFDMA (orthogonal frequency division multiple access) transmission system is an OFDM-based multi-user access system, where a plurality of users transmit subcarriers of the OFDM multi-carrier communication method. It can be divided and used to transmit and receive information.

In addition, the SC-FDE (single carrier-frequency domain equalization) single carrier communication scheme is similar to a structure in which a discrete fourier transform (DFT) module existing in the transmitter of the OFDM scheme is moved to the receiver, so that the system complexity and It is known to have reception performance.

In addition, the SC-FDMA (frequency division multiple access) transmission system is a multi-user access system in which the SC-FDE scheme is extended to a subcarrier scheme.

Based on the similarity between OFDM and SC-FDE as described above and OFDMA and SC-FDMA have similar system complexity and reception performance, they are widely studied as basic transmission methods for next-generation broadband mobile communication systems. Therefore, various technologies are being researched and developed to improve the performance of high-speed broadband wireless communication transmission systems.

1. Korea Patent No. 10-0866195 (Registered on Oct. 24, 2008)

The present invention applies a frequency space block coded single sideband waveform (SSB) modulation scheme to a single carrier frequency division multiple access system (SC-FDMA), thereby improving the performance of the transmission system as well as not significantly increasing the system computational complexity. An object of the present invention is to provide a signal transmission method of a frequency-space block-coded single-side waveform single-carrier frequency division multiple access system capable of obtaining a diversity gain for .

In addition, the present invention performs frequency-space block encoding by utilizing conjugate plural symmetry generated according to discrete Fourier transform (DFT) spreading of a pulse amplitude modulation (PAM) signal, and it is applied to a multiplexing antenna. An object of the present invention is to provide a signal transmission method of a frequency-space block-coded single-side waveform single-carrier frequency division multiple access system that can obtain a diversity gain and improve reception performance of a transmission system by applying it.

On the other hand, in the present invention, the transmitter performs a discrete Fourier transform (DFT) operation on the transmission bits for each user, and then transmits the first transmission signal obtained by processing the single side-band waveform (SSB) type lower-band (LSB) signal. The second transmission signal is transmitted through the antenna, and the second transmission signal obtained by performing frequency space block encoding (SFBC) on the lower band (LSB) signal or the third transmission signal obtained by performing frequency space block encoding (SFBC) on the upper band (USB) signal is transmitted to the second transmission antenna. An object of the present invention is to provide a signal transmission method of a frequency-space block-coded single side-to-waveform single carrier frequency division multiple access system that can effectively transmit a transmission signal for each user by transmitting through the

In addition, the present invention performs a fast Fourier transform (FFT) operation on a received signal in a receiver, decodes it corresponding to frequency space block coding (SFBC), performs an inverse discrete Fourier transform (IDFT) operation, By restoring the original signal bits using the log likelihood ratio (LLR) value of the signal bits obtained from the probability (MAP) detector, a frequency-space block-coded single side-band waveform that can receive and effectively restore the transmitted signal transmitted for each user An object of the present invention is to provide a signal transmission method in a carrier frequency division multiple access system.

The purpose of the embodiments of the present invention is not limited to the above-mentioned purpose, and other objects not mentioned will be clearly understood by those of ordinary skill in the art to which the present invention belongs from the description below. .

According to an embodiment of the present invention, the transmitter encodes a transmission bit for each user, inputs the data into an interleaver, and then performs subchannel mapping, and after performing the subchannel mapping, a discrete Fourier transform corresponding to the allocated channel size. After performing the (DFT) operation, and after performing the discrete Fourier transform (DFT) operation, the first transmission signal processed by the single side-band waveform (SSB) method of the lower-band (LSB) signal is transmitted to the first transmission antenna. and, after performing the discrete Fourier transform (DFT) operation, the second transmission signal obtained by performing frequency space block coding (SFBC) on the lower band (LSB) signal or the upper side of the single sideband waveform (SSB) method. A signal transmission method of a frequency space block-encoded single-side waveform single carrier frequency division multiple access system, comprising the step of transmitting a third transmission signal obtained by performing frequency space block encoding (SFBC) on a band (USB) signal through a second transmission antenna can be provided.

In addition, according to an embodiment of the present invention, the transmitting through the first transmit antenna includes selecting the lower band (LSB) signal to fill subchannels for other users with zeros, and setting the subchannels to zero. After the step of filling with , performing an Inverse Fast Fourier Transform (IFFT) operation corresponding to the overall system size, and after performing the Inverse Fast Fourier Transform (IFFT) operation, adding a cyclic prefix (CP) to the first There may be provided a signal transmission method of a frequency space block coded single side-to-waveform single carrier frequency division multiple access system comprising transmitting a transmission signal through the first transmission antenna.

In addition, according to an embodiment of the present invention, the step of transmitting through the second transmit antenna comprises selecting the lower band (LSB) signal and performing frequency space block coding (SFBC) by changing the signs of complex conjugate numbers and negative numbers. After the step, and after the frequency space block coding (SFBC) step, the step of filling the subchannels for other users with zeros, and after the step of filling the subchannels with zeros, the Inverse Fast Fourier Transform (IFFT) corresponding to the overall system size ) operation, and after performing the Inverse Fast Fourier Transform (IFFT) operation, adding a periodic prefix (CP) to transmit the second transmission signal through the second transmission antenna A method of transmitting a signal in a spatial block coded single side-waveform single carrier frequency division multiple access system may be provided.

In addition, according to an embodiment of the present invention, the step of transmitting through the second transmit antenna comprises the steps of selecting the upper band (USB) signal and performing frequency space block coding (SFBC) through relocation using complex conjugate symmetry; , after the frequency space block coding (SFBC) step, after the step of filling the subchannels for other users with zeros, and after the step of filling the subchannels with zeros, an Inverse Fast Fourier Transform (IFFT) operation corresponding to the overall system size and transmitting the third transmission signal through the second transmission antenna by adding a periodic prefix (CP) after performing the inverse fast Fourier transform (IFFT) operation. A method of transmitting a signal in a coded single side-to-waveform single carrier frequency division multiple access system may be provided.

In addition, according to an embodiment of the present invention, in the signal transmission method of the frequency space block-coded single side-waveform single-carrier frequency division multiple access system, after removing the cyclic prefix (CP) for the received signal at the receiver, the fast Fourier transform ( After performing the FFT) operation, and after performing the Fast Fourier Transform (FFT) operation, decoding corresponding to frequency space block coding (SFBC), and then performing signal restoration through an equalizer, the signal; After performing the restoration, performing an Inverse Discrete Fourier Transform (IDFT) operation by selecting a subchannel assigned to each user, and after performing the Inverse Discrete Fourier Transform (IDFT) operation, the maximum posterior probability ( MAP) inputting the log likelihood ratio (LLR) value of the signal bits obtained from the detector to the deinterleaver and the decoder to restore the original signal bits. A signal transmission method may be provided.

The present invention applies a frequency space block coded single sideband waveform (SSB) modulation scheme to a single carrier frequency division multiple access system (SC-FDMA), thereby improving the performance of the transmission system as well as not significantly increasing the system computational complexity. It is possible to obtain a diversity gain for

In addition, the present invention obtains a diversity gain by performing frequency-space block encoding by utilizing conjugate plural symmetry generated by Discrete Fourier Transform (DFT) spreading of a pulse amplitude modulation (PAM) signal, and applying it to a multiplexing antenna. Not only can it be done, but it can also improve the reception performance of the transmission system.

On the other hand, in the present invention, the transmitter performs a discrete Fourier transform (DFT) operation on the transmission bits for each user, and then transmits the first transmission signal obtained by processing the single side-band waveform (SSB) type lower-band (LSB) signal. The second transmission signal is transmitted through the antenna, and the second transmission signal obtained by performing frequency space block encoding (SFBC) on the lower band (LSB) signal or the third transmission signal obtained by performing frequency space block encoding (SFBC) on the upper band (USB) signal is transmitted to the second transmission antenna. By transmitting through , it is possible to effectively transmit a transmission signal for each user.

In addition, the present invention performs a fast Fourier transform (FFT) operation on a received signal in a receiver, decodes it corresponding to frequency space block coding (SFBC), performs an inverse discrete Fourier transform (IDFT) operation, By restoring the original signal bits using the log likelihood ratio (LLR) value of the signal bits obtained from the probability (MAP) detector, it is possible to receive and effectively restore the transmission signal transmitted for each user.

1 is a flowchart illustrating a process of transmitting a signal from a transmitter of a frequency space block coded single side-wave single carrier frequency division multiple access system according to an embodiment of the present invention;
2 is a flowchart illustrating a process of transmitting a first transmission signal in a transmitter according to an embodiment of the present invention;
3 is a flowchart illustrating a process of transmitting a second transmission signal in a transmitter according to an embodiment of the present invention;
4 is a flowchart illustrating a process of transmitting a third transmission signal from a transmitter according to an embodiment of the present invention;
5 is a flowchart illustrating a process of restoring a received signal in a receiver according to an embodiment of the present invention;
6 to 12 are diagrams for explaining a frequency-space block-coded single-side waveform single carrier frequency division multiple access system according to an embodiment of the present invention;
13 and 14 are diagrams illustrating performance test results of a frequency-space block-coded single-side waveform single-carrier frequency division multiple access system according to an embodiment of the present invention.

Advantages and features of embodiments of the present invention, and methods of achieving them, will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the art to which the present invention pertains It is provided to fully inform those who have the scope of the invention, and the present invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout.

In describing the embodiments of the present invention, if it is determined that a detailed description of a well-known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, the terms to be described later are terms defined in consideration of functions in an embodiment of the present invention, which may vary according to intentions or customs of users and operators. Therefore, the definition should be made based on the content throughout this specification.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a flowchart illustrating a process of transmitting a signal in a transmitter of a frequency space block coded single side-wave single carrier frequency division multiple access system according to an embodiment of the present invention, and FIG. 2 is a transmitter according to an embodiment of the present invention. is a flowchart illustrating a process of transmitting the first transmission signal in It is a flowchart illustrating a process of transmitting a third transmission signal by a transmitter according to an embodiment of the present invention, and FIG. 5 is a flowchart illustrating a process of restoring a received signal in a receiver according to an embodiment of the present invention.

1 to 5 , as shown in FIG. 1 , the transmitter may encode a transmission bit for each user and input it to the interleaver, and then perform subchannel mapping (step 110).

Next, after performing the subchannel mapping, a discrete Fourier transform (DFT) operation may be performed corresponding to the allocated channel size (step 120).

Then, after the step of performing the discrete Fourier transform (DFT) operation, the first transmission signal processed by the single side-band waveform (SSB) method of the lower band (LSB) signal may be transmitted through the first transmission antenna (step 130). ).

Here, in step 130, as shown in FIG. 2, a lower band (LSB) signal is selected, subchannels for other users are filled with zeros (step 131), and inverse fast Fourier transform (IFFT) is performed corresponding to the overall system size. The operation is performed (step 132), and a cyclic prefix (CP) is added to transmit the first transmission signal through the first transmission antenna (step 133).

In addition, a second transmission signal obtained by performing frequency space block encoding (SFBC) on a lower band (LSB) signal or a third transmission signal obtained by performing frequency space block encoding (SFBC) on an upper band (USB) signal of a single sideband waveform (SSB) method It can transmit through the second transmit antenna (step 140).

Here, in step 140, as shown in FIG. 3, a lower band (LSB) signal is selected and frequency-space block coding (SFBC) is performed by changing the sign to a complex conjugate number and a negative number (step 141a), and a sub-band for other users. The channels are filled with zeros (step 142a), an Inverse Fast Fourier Transform (IFFT) operation is performed corresponding to the overall system size (step 143a), and a cyclic prefix (CP) is added to transmit the second transmission signal to the second transmission antenna. can be transmitted through (step 144a).

In addition, in step 140, as shown in FIG. 4, the upper band (USB) signal is selected and frequency space block encoding (SFBC) is performed through relocation using complex conjugate symmetry (step 141b), and subchannels for other users are set to 0. (step 142b), perform an inverse fast Fourier transform (IFFT) operation corresponding to the overall system size (step 143b), and add a cyclic prefix (CP) to transmit the third transmission signal through the second transmission antenna. It can be done (step 144b).

Meanwhile, as shown in FIG. 5 , the receiver may perform a fast Fourier transform (FFT) operation after removing the cyclic prefix (CP) on the received signal (step 210).

And, after performing the fast Fourier transform (FFT) operation, after decoding corresponding to the frequency space block coding (SFBC), the signal can be restored through an equalizer (step 220).

Next, after performing signal restoration, an inverse discrete Fourier transform (IDFT) operation may be performed by selecting a subchannel allocated to each user (operation 230).

Then, after performing the inverse discrete Fourier transform (IDFT) operation, the log likelihood ratio (LLR) value of the signal bits obtained from the maximum posterior probability (MAP) detector is input to the deinterleaver and the decoder to restore the original signal bits. There is (step 240).

Meanwhile, FIGS. 6 to 12 are diagrams for explaining a frequency space block-coded single-side waveform single carrier frequency division multiple access system according to an embodiment of the present invention, and as described above, a frequency space according to an embodiment of the present invention. The block-coded single-side waveform single-carrier frequency division multiple access system will specifically describe signal transmission/reception and processing in the transmitter and receiver.

First, the single side band (SSB) modulation method is an analog communication method that doubles the transmission efficiency by transmitting only half of the signal in the frequency domain. is divided into a lower band signal (LSB: lower side band) and an upper band signal (USB: upper side band), and after transmitting only the lower band signal (LSB) or the upper band signal (USB), You can follow the procedure to acquire both the lower band signal (LSB) and the upper band signal (USB), and the analog method single sideband waveform (SSB) is digital using multi-level pulse amplitude modulation (PAM). It is possible to implement a frequency-efficient Discrete Fourier Transform (DFT) spread SSB-OFDM system by applying it to a transmission system.

In addition, in OFDMA and SC-FDMA wideband transmission systems, a transmit diversity technique can be applied by using multiple transmit antennas or multiple repeaters in order to improve reception performance in a fading channel. code) and space-frequency block code (SFBC) are representative transmit diversity techniques that theoretically have the same performance. By applying a block code between the repeater) and successive subchannels, a diversity gain can be obtained and reception performance can be greatly improved.

And, as shown in FIG. 6, the basic frequency space block code (SFBC) technique can apply an orthogonal block code over two transmit antennas and two neighboring frequency bands f ₀ and f _{1 in a specific symbol period t 0 .} , _{transmits s 0} and s ₁ signals in two neighboring frequency bands through the first antenna, and transmits s ₁ * and -s ₀ * signals in two neighboring frequency bands through the second antenna.

In this case, * means a complex conjugate operation, and if _{signals received in two neighboring frequency bands f 0 and f 1} of the receiving station are r ₀ and r ₁ , it can be expressed as in Equation 1 below.

Here, h _i,j represents the channel frequency response of _{the sub-channel f j} between the receiving antenna and the i-th transmit antenna, and nj represents the additional noise of the _{sub-channel f j .}

, i=0,1이면 전송신호 s₀과 s₁에 대한 추정 값은 아래의 수학식 2와 같은 결정 과정을 통해 쉽게 얻을 수 있다.And, if it is assumed that channels in two neighboring frequency bands are constant, that is,

, i = 0,1, the estimated values for the transmission signals s ₀ and s ₁ can be easily obtained through a determination process as in Equation 2 below.

In addition, by substituting Equation 1 into Equation 2, an estimated signal can be obtained as Equation 3 below as the sum of the original signal and the noise of the deformed form reflecting the diversity effect.

On the other hand, if the Discrete Fourier Transform (DFT) Spread Single Sided Waveform (SSB) method is described, when a Discrete Fourier Transform (DFT) operation is performed using real data as an input, both sides centering on the intermediate reference value as shown in FIG. There is a characteristic that the data value of is symmetrical in the form of a complex conjugate number. When 2M pieces of data are used, the lower band signal (LSB) consisting of M data of the front part (low band) and M data of the rear part (high band) are used. above can be separated by the band signal (USB), the remaining data other than the reference value (S _M) of the reference value (S ₀₎ and the upper band signal (USB) following the band signal (LSB) consisting of their expression under 4 It is possible to form a complex conjugate symmetric relationship as

As can be seen from Equation 4, the upper band signal (USB) can be obtained by reversing the order of the lower band signal (LSB) and taking the complex conjugate number, so the lower band signal (LSB) and the upper band signal (USB) in the transmitter Even if only one band signal is transmitted, the receiver can acquire all band signals (lower band signal (LSB) and upper band signal (USB)) using the complex conjugate relationship of Equation (4), and the transmission efficiency is increased can

_{However, since both the reference value S 0} of the lower-band signal (LSB) and the reference _{value S M} of the upper-band signal (USB) must be transmitted, (2M-2) pieces of data are spread by discrete Fourier transform (DFT), and among them, M data can be transmitted.

In addition, FIG. 8 shows a transceiver structure of an OFDM transmission system to which a single sideband waveform (SSB) method is applied. After spreading ((2M-2)-point DFT) data through discrete Fourier transform (DFT) operation, the lower-band signal ((M-1) including the lower-band signal reference value) and upper-band signal reference value are collected and Only M signals can be selected (LSB selection), and a cyclic prefix (CP) is added after inverse fast fourier transform (IFFT) (M-point IFFT) is performed on the selected M signals. CP) and can be transmitted through the transmitting antenna.

Then, in the receiver (FIG. 8(b)), the periodic prefix (CP) is removed from the received signal (remove CP), and fast Fourier transform (FFT) is performed on the M signals (M-point FFT). ), the M signals can be restored through the equalization process (1-tap EQ), and among the restored M signals, the rest ( By taking M-2) lower band signals (LSB) and taking the complex conjugate number, it is possible to additionally obtain (M-2) upper band signals (USB) that have not been transmitted (2M-2 reunion).

After such a reunion process, all (2M-2) signals are finally restored, and the (2M-2) restored signals are subjected to an Inverse Discrete Fourier Transform (IDFT) operation ((2M-2) )-point IDFT) to obtain raw data (bit stream).

Next, a single-side waveform single carrier frequency division multiple access system (SSB SC-FDMA system) as shown in FIG. 9 will be described. Discrete Fourier Transform (DFT) Spread OFDM scheme is a Discrete Fourier Transform (DFT) in the transmitter. It is known that it is similar to the SC-FDMA transmission system rather than the OFDMA transmission system in that it performs calculation and Inverse Fast Fourier Transform (IFFT) operation, and the receiver performs Fast Fourier Transform (FFT) and Inverse Discrete Fourier Transform (IDFT) operations. can

In the transmitter (FIG. 9(a)) of a general SC-FDMA transmission system, after inputting an information bit for each user to an encoder and an interleaver, subcarrier mapping is performed. , after performing a discrete Fourier transform (DFT) operation ((2M-2)-point DFT) according to the assigned channel size (M, for example, 64), and then selecting the lower band signal (LSB) Subchannels for other users are filled with zeros (zero padding) and an Inverse Fast Fourier Transform (IFFT) operation is performed (N-point IFFT) to fit the overall system size (N, for example, 1024), and finally a periodic prefix ( CP) and can be transmitted through the transmitting antenna.

On the other hand, in the receiver (FIG. 9 (b)), after removing the cyclic prefix (CP) from the received signal (remove CP), a Fast Fourier transform (FFT) operation is performed to fit the overall system size (N) ( N-point FFT), the signal is restored (2M-2 reunion) through an equalizer (1-tap EQ), and M subchannels assigned to each user are selected and an inverse discrete Fourier transform (IDFT) operation (size M) ) ((2M-2)-point IDFT) and then deinterleaver the log-likelihood ratio (LLR) value of the signal bit obtained from the maximum a posteriori (MAP) detector. (de-interleaver) and the decoder (SISO decoder) input to the original signal bit (decoded bit) can be restored.

Here, FIG. 9 shows the structure of a transceiver applying the SSB method to a general SC-FDMA transmission system. Like the Discrete Fourier Transform (DFT) spread SSB OFDM system as shown in FIG. 8, more than M data ( By applying (2M-2) discrete Fourier transform (DFT) operations to 2M-2) data units, applying a single sideband waveform (SSB) method to select only the lower band signal (LSB) and transmitting only M signals It is possible to increase the transmission efficiency of the existing SC-FDMA transmission system, and the receiver can restore (2M-2) data by using the complex conjugate relationship based on the M signals that have passed through the equalizer.

Next, a frequency space block-coded single side-wave single carrier frequency division multiple access system (SFBC SSB SC-FDMA system) according to an embodiment of the present invention will be described. Alternatively, in an embodiment of the present invention, a signal may be transmitted using two transmission antennas. The first transmission antenna selects and transmits the lower band signal (LSB) of the single sideband waveform (SSB) method, and the second transmission antenna Like the frequency space block code (SFBC) technique of FIG. 6 , can transmit a signal made to have an orthogonal block code relationship with the lower band signal (LSB) transmitted through the first transmit antenna.

For example, if the transmitter describes the transmission through the first transmission antenna, the transmitter (in FIG. Subcarrier mapping can be performed, a discrete Fourier transform (DFT) operation can be performed ((2M-2)-point DFT) corresponding to the allocated channel size, and a single sideband waveform (SSB) method Subchannels for other users are filled with zeros (zero padding) by selecting the lower band (LSB) signal of ), and by adding a periodic prefix (CP) (add CP), the first transmission signal may be transmitted through the first transmission antenna.

And, when the transmitter transmits an embodiment through the second transmit antenna, it selects a lower band (LSB) signal and performs frequency space block coding (SFBC) by changing the sign of a complex conjugate number and a negative number (SF block coding). w LSB), subchannels for other users are filled with zeros (zero padding), an inverse fast Fourier transform (IFFT) operation is performed corresponding to the overall system size (N-point IFFT), and a cyclic prefix (CP) is added. (add CP) to transmit the second transmission signal through the second transmission antenna.

In addition, in another embodiment in which the transmitter transmits through the second transmit antenna, the upper band (USB) signal is selected and frequency space block coding (SFBC) is performed through relocation using complex conjugate symmetry (SF block coding w USB). ), subchannels for other users are filled with zeros (zero padding), an inverse fast Fourier transform (IFFT) operation is performed in response to the sub-total system size (N-point IFFT), and a cyclic prefix (CP) is added ( add CP) to transmit the third transmission signal through the second transmission antenna.

On the other hand, when the receiver restores the received signal, after removing the cyclic prefix (CP) from the received signal in the receiver (FIG. 10 (b)), the fast Fourier transform (FFT) After performing an operation (N-point FFT) and decoding corresponding to frequency space block coding (SFBC) (SF block decoding), signal restoration is performed through an equalizer (1-tap EQ) (2M-2 reunion) After selecting a subchannel assigned to each user and performing an inverse discrete Fourier transform (IDFT) operation ((2M-2)-point IDFT), the signal obtained from the maximum posterior probability (MAP) detector The original signal bit can be restored (decoded bit) by inputting the log likelihood ratio (LLR) value of the bit to a de-interleaver and a decoder (SISO decoder).

The transmission signal for the second transmission antenna as described above can be generated by applying a frequency space block code (SFBC) using the lower band signal (LSB) as shown in FIG. 11. In a system with M=64, _{For example, S 1} and S ₂ of the lower band (LSB) are _{transmitted through the first transmit antenna, and S 2} * and -S ₁ * are generated by changing the sign to a complex conjugate number and negative number to generate the second transmit antenna. can be transmitted, and the remaining _{signals from S 3} to S ₆₂ can be performed in the same manner.

In addition, as shown in FIG. 12 by utilizing the complex conjugate relationship presented in Equation 4, the frequency space block code (SFBC) can be easily applied by rearranging the upper band signal (USB) discarded by the transmitter. Taking the system M=64 as an example, since S ₁ and S ₂ of the lower band (LSB) are the same as the complex conjugate numbers _{of S 125} and S ₁₂₄ of the upper band (USB), respectively _{, S 1} and S of the lower band (LSB) ₂ through the first transmit antenna, _{and S 124} and -S ₁₂₅ of the upper band (USB) having the same values as _{S 2} * and -S ₁ * through the second transmit antenna, simplifying the frequency space The block code (SFBC) can be applied, and the remaining _{signals from S 3} to S ₆₂ can be equally applied using the upper band signal (USB).

Meanwhile, FIGS. 13 and 14 are diagrams illustrating performance test results of a frequency-space block-encoded single-side waveform single-carrier frequency division multiple access system according to an embodiment of the present invention.

13 and 14, a total of 256 subchannels (N=256) were used for the performance experiment of the frequency space block-coded single side-wave single carrier frequency division multiple access system according to an embodiment of the present invention, 64 subchannels (M=64) were allocated to each user.

A binary phase shift keying (BPSK) modulation scheme was applied to each subchannel, and a bit signal was coded using a 1/2 ratio convolutional code having a limit length of 7 and an S-random interleaver (S=5).

In addition, the normalized Doppler frequency value was set to 0.001, a 6-tap TU (typical urban) radio channel model was used, and it was assumed that perfectly estimated channel information was used in the equalization process.

As a result of the performance experiment as described above, the bit error rate (BER) performance of the SSB SC-FDMA system as shown in FIG. 13 and the symbol error rate (SER: symbol error rate) performance, the solid square line in each figure indicates the performance of the SSB SC-FDMA system implemented based on a single transmit antenna like the transmission system of FIG. 8, and the solid triangle in each figure is As shown in FIG. 9, the performance of the SSB SC-FDMA system (ie, the embodiment of the present invention) to which SFBC is applied based on two transmit antennas is shown. At this time, as shown in FIG. 12 , SFBC was implemented using a method of relocating upper band signals (USB) discarded by the transmitter.

As described above, by obtaining a transmit diversity gain through a frequency space block coding (SFBC) technique, a frequency space block coded single side-waveform single carrier frequency division multiple access system (SFBC SSB SC-FDMA) according to an embodiment of the present invention system) showed that the signal-to-noise power ratio (SNR) performance was improved by more than 4dB at both the ^{10 -3} BER level and the 10 ^-2 SER level compared to the single-antenna-based SSB SC-FDMA transmission system. can be checked

As described above, in the present invention, a frequency space block-encoded single side-wave single carrier frequency division multiple access system (SFBC SSB SC-FDMA system) is presented. By implementing the frequency space block code by utilizing the complex conjugate symmetry generated according to It can be confirmed through experiments that it is improved by about 4 dB or more at the level of ^{10 -2} symbol error rate compared to the single antenna-based system.

Accordingly, the present invention applies a frequency space block coded single side-band waveform (SSB) modulation scheme to a single-carrier frequency division multiple access system (SC-FDMA), thereby not only not significantly increasing the system calculation complexity, but also A diversity gain for improving performance may be obtained.

In addition, the present invention obtains a diversity gain by performing frequency-space block encoding by utilizing conjugate plural symmetry generated by Discrete Fourier Transform (DFT) spreading of a pulse amplitude modulation (PAM) signal, and applying it to a multiplexed antenna. Not only can it be done, but it can also improve the reception performance of the transmission system.

On the other hand, in the present invention, the transmitter performs a discrete Fourier transform (DFT) operation on the transmission bits for each user, and then transmits the first transmission signal obtained by processing the single side-band waveform (SSB) type lower-band (LSB) signal. The second transmission signal is transmitted through the antenna, and the second transmission signal obtained by performing frequency space block encoding (SFBC) on the lower band (LSB) signal or the third transmission signal obtained by performing frequency space block encoding (SFBC) on the upper band (USB) signal is transmitted to the second transmission antenna. By transmitting through , it is possible to effectively transmit a transmission signal for each user.

In addition, the present invention performs a fast Fourier transform (FFT) operation on a received signal in a receiver, decodes it corresponding to frequency space block coding (SFBC), performs an inverse discrete Fourier transform (IDFT) operation, By restoring the original signal bits using the log likelihood ratio (LLR) value of the signal bits obtained from the probability (MAP) detector, it is possible to receive and effectively restore the transmission signal transmitted for each user.

In the above description, various embodiments of the present invention have been presented and described, but the present invention is not necessarily limited thereto. It will be readily appreciated that branch substitutions, transformations and alterations are possible.

Claims (5)

A step of encoding a transmission bit for each user in the transmitter, inputting the data into an interleaver, and performing subchannel mapping;
performing a discrete Fourier transform (DFT) operation corresponding to the allocated channel size after performing the subchannel mapping;
After performing the discrete Fourier transform (DFT) operation, transmitting a first transmission signal processed with a single side-band waveform (SSB) type lower-band (LSB) signal through a first transmission antenna;
After performing the discrete Fourier transform (DFT) operation, transmitting a second transmission signal obtained by performing frequency space block coding (SFBC) on the lower band (LSB) signal through a second transmission antenna;
performing a fast Fourier transform (FFT) operation after removing the cyclic prefix (CP) on the received signal at the receiver;
After performing the Fast Fourier Transform (FFT) operation, decoding corresponding to frequency space block coding (SFBC), and then performing signal restoration through an equalizer;
After performing the signal restoration, selecting a subchannel assigned to each user and performing an inverse discrete Fourier transform (IDFT) operation;
After performing the inverse discrete Fourier transform (IDFT) operation, the log-likelihood ratio (LLR) value of the signal bits obtained from the maximum posterior probability (MAP) detector is input to the deinterleaver and the decoder to restore the original signal bits. includes,
The step of transmitting through the first transmitting antenna,
filling subchannels for other users with zeros by selecting the lower band (LSB) signal;
After filling the subchannels with zeros, performing an Inverse Fast Fourier Transform (IFFT) operation corresponding to the overall system size;
After performing the Inverse Fast Fourier Transform (IFFT) operation, adding a cyclic prefix (CP) to transmit the first transmission signal through the first transmission antenna,
The step of transmitting through the second transmitting antenna,
selecting the lower band (LSB) signal and performing frequency space block coding (SFBC) by changing the sign to a complex conjugate number and a negative number;
after the frequency space block coding (SFBC), subchannels for other users are filled with zeros;
After filling the subchannels with zeros, performing an Inverse Fast Fourier Transform (IFFT) operation corresponding to the overall system size;
After performing the Inverse Fast Fourier Transform (IFFT) operation, adding a cyclic prefix (CP) to transmit the second transmission signal through the second transmission antenna,
Since both the reference value S0 of the lower band (LSB) signal and the reference value SM of the upper band signal (USB) need to be transmitted, (2M-2) pieces of data are distributed through discrete Fourier transform (DFT) and M data among them to send,
When the data (bit stream) to be transmitted is input in the transmitter, (2M-2) data is spread ((2M-2)-point DFT) through discrete Fourier transform (DFT) operation, and then the lower band signal (below (LSB selection) of total M signals by collecting (M-1) including band signal reference values and upper-band signal reference values,
After performing an inverse fast Fourier transform (IFFT) (M-point IFFT) on the selected M signals, a cyclic prefix (CP) is added (add CP) and transmitted through the first and second transmit antennas. ,
The receiver removes the cyclic prefix (CP) from the received signal (remove CP), performs a fast Fourier transform (FFT) on the M signals (M-point FFT), and then performs an equalization process (1- tap EQ) to restore M signals,
Among the restored M signals, the remaining (M-2) lower-band signals (LSB) excluding the reference value of the lower-band signal (LSB) and the reference value of the upper-band signal (USB) are taken and the complex conjugate is taken. Additional (M-2) upper band signals (USB) are obtained,
Finally, all (2M-2) signals are restored, and the restored (2M-2) signals are subjected to an Inverse DFT (IDFT) operation ((2M-2)-point IDFT) to obtain the original data (bit stream), characterized in that it is possible to obtain a signal transmission method of a frequency space block coded single side-wave single carrier frequency division multiple access system. delete delete delete delete

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