Abstract:
The present disclosure relates to a pre-5 th -Generation (5G) or 5G communication system to be provided for supporting higher data rates Beyond 4 th -Generation (4G) communication system such as Long Term Evolution (LTE). Various exemplary embodiments of the present disclosure include: performing Fourier transform with respect to a plurality of modulation signals; dividing the plurality of transformed signals into at least two groups; generating FBMC symbols corresponding to the groups; transmitting the FBMC symbols.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) AND CLAIM OF PRIORITY 
       [0001]    The present application is related to and claims priority under 35 U.S.C. §119 to an application filed in the Korean Intellectual Property Office on Nov. 10, 2015 and assigned Serial No. 10-2015-0157458, the contents of which are incorporated herein by reference. 
       TECHNICAL FIELD 
       [0002]    Exemplary embodiments of the present disclosure relate to controlling a Peak to Average Power Ratio (PAPR) of a signal in a wireless communication system. 
       BACKGROUND 
       [0003]    To meet the demand for wireless data traffic having increased since deployment of 4 th  generation (4G) communication systems, efforts have been made to develop an improved 5 th  generation (5G) or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post Long Term Evolution (LTE) System’. 
         [0004]    The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems. 
         [0005]    In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, coordinated multi-points (CoMP), reception-end interference cancellation and the like. 
         [0006]    In the 5G system, Hybrid frequency shift keying (FSK) and quadrature amplitude modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed. 
         [0007]    An FBMC transmission system includes a filtering process, a multi carrier modulation process using an inverse fast fourier transform (IFFT) block, and a process of overlapping modulated symbol blocks. The FBMC transmission system may be classified by an offset quadrature amplitude modulation (OQAM) method, and a quadrature amplitude modulation (QAM) method. 
         [0008]    A discrete fourier transform (DFT) spreading technique has been considered as a technique for reducing the PAPR in an orthogonal frequency division multiplexing (OFDM) transmission system. The OFDM transmission system performs DFT prior to performing IFFT, thereby obtaining a PAPR reduction effect. In the DFT spreading technique, the size of DFT is equal to the number of carriers allocated to a transmitting apparatus. The DFT size may be smaller than or equal to the IFFT size. A signal which is pre-processed by the DFT method is modulated by the IFFT block. The above-described method is classified into a localized frequency division multiple access (LFDMA) and an interleaved frequency division multiple access (IFDMA) according to a method for allocating a carrier location of an IFFT block. 
         [0009]    Since the FBMC transmission system overlaps signals to transmit the signals unlike the OFDM transmission system, the PAPR reduction effect is weak when the DFT spreading technique is applied in the same way as in the OFDM transmission system. 
       SUMMARY 
       [0010]    To address the above-discussed deficiencies, it is a primary object to provide a reduction effect of a PAPR which is generated from an overlapping structure by applying a DFT spreading technique of an LFDMA method in an FBMC transmission system. 
         [0011]    An exemplary embodiment of the present disclosure may provide an operating method of a transmitting apparatus. The operating method includes: performing Fourier transform with respect to a plurality of modulation signals; dividing the plurality of transformed signals into at least two groups; generating FBMC symbols corresponding to the groups; transmitting the FBMC symbols. 
         [0012]    Another exemplary embodiment of the present disclosure may provide an operating method of a receiving apparatus. The operating method includes: dividing a plurality of received signals into at least two groups; generating FBMC symbols corresponding to the at least two divided groups; performing inverse Fourier transform with respect to the signals of the at least two generated groups simultaneously; and generating a plurality of restored signals by performing channel estimation and equalization with respect to the plurality of transformed signals. 
         [0013]    Another exemplary embodiment of the present disclosure may provide a transmitting apparatus. The transmitting apparatus includes: a transmitter configured to transmit signals; and a modulator functionally combined with the transmitter, and the modulator is configured to: perform Fourier transform with respect to a plurality of modulation signals; divide the plurality of transformed signals into at least two groups; and generate FBMC symbols corresponding to the groups. 
         [0014]    Another exemplary embodiment of the present disclosure may provide a receiving apparatus. The receiving apparatus includes: a receiver configured to receive a plurality of signals; and a demodulator functionally combined with the receiver, and the demodulator is configured to: divide the plurality of received signals into at least two groups; generate FBMC symbols corresponding to the at least two divided groups; perform inverse Fourier transform with respect to the signals of the at least two generated groups simultaneously; and generate a plurality of restored signals by performing channel estimation and equalization with respect to the plurality of transformed signals. 
         [0015]    Various exemplary embodiments provide an effective DFT spreading technique which can enhance a PAPR reduction effect in an FBMC transmission system. 
         [0016]    Before undertaking the DETAILED DESCRIPTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term “controller” means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts: 
           [0018]      FIG. 1  illustrates an example of a wireless communication system in which signals are transmitted and received; 
           [0019]      FIG. 2  illustrates a transmitting apparatus according to an exemplary embodiment; 
           [0020]      FIG. 3  illustrates a receiving apparatus according to exemplary embodiments; 
           [0021]      FIG. 4  illustrates an operation of transmitting and receiving signals in a filter bank multi carrier (FBMC) transmission system according to exemplary embodiments; 
           [0022]      FIG. 5  illustrates another example of the operation of transmitting and receiving signals in an FBMC transmission system according to exemplary embodiments; 
           [0023]      FIG. 6  illustrates a transmission signal processing according to exemplary embodiments; 
           [0024]      FIG. 7  illustrates another transmission signal processing according to exemplary embodiments; 
           [0025]      FIG. 8  illustrates a reception signal processing according to exemplary embodiments; 
           [0026]      FIG. 9  illustrates another reception signal processing according to exemplary embodiments; 
           [0027]      FIG. 10  illustrates a flowchart of a transmission signal processing according to an exemplary embodiment; 
           [0028]      FIG. 11  illustrates another flowchart of a transmission signal processing according to exemplary embodiments; 
           [0029]      FIG. 12  illustrates yet another flowchart of a transmission signal processing according to exemplary embodiments; 
           [0030]      FIG. 13  illustrates a flowchart of a reception signal processing according to exemplary embodiments; 
           [0031]      FIG. 14  illustrates a another flowchart of a reception signal processing according to exemplary embodiments; 
           [0032]      FIG. 15  illustrates yet another flowchart of a reception signal processing according to exemplary embodiments; 
           [0033]      FIG. 16  illustrates an interleaving operation according to exemplary embodiments; 
           [0034]      FIG. 17  illustrates a peak to average power ration (PAPR) performance according to exemplary embodiments; and 
           [0035]      FIG. 18  illustrates another PAPR performance according to exemplary embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0036]      FIGS. 1 through 18 , discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged electronic device. 
         [0037]    Exemplary embodiments of the present disclosure will be described herein below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. Also, the terms used herein are defined according to the functions of various exemplary embodiments. Thus, the terms may vary depending on user&#39;s or operator&#39;s intension and usage. Therefore, the terms used herein must be understood based on the descriptions made herein. 
         [0038]    Hereinafter, technology for an effective DFT spreading technique which can enhance a PAPR reduction effect in a wireless communication system according to the present disclosure will be described. 
         [0039]    In the following description, the term indicating modulation, the term indicating demodulation, the term indicating filtering, the term indicating offset, the term indicating signals, and the term indicating an element of an apparatus are merely examples for the convenience of explanation. Therefore, the present disclosure is not limited to the terms described below and other terms having the same technical meaning may be used. 
         [0040]      FIG. 1  illustrates an example of a wireless communication system  100  in which signals are transmitted and received. 
         [0041]    Referring to  FIG. 1 , the system  100  includes a transmitting apparatus  110  and a receiving apparatus  120 . The transmitting apparatus  110  and the receiving apparatus  120  may correspond to a user device or a network device. The user device may include a terminal, a mobile station, user equipment, or the like. The network device may include a base station, a node B (nodeB), an evolved node B (enodeB), or the like. For example, both the transmitting apparatus  110  and the receiving apparatus  120  may correspond to terminals. In another example, the transmitting apparatus  110  may correspond to a terminal and the receiving apparatus  120  may correspond to a base station. 
         [0042]    The transmitting apparatus  110  may transmit signals to the receiving apparatus  120 . For example, the transmitting apparatus  110  may transmit at least one symbol which is modulated in an FBMC method. The receiving apparatus  120  may receive signals. Although the transmitting apparatus  110  is illustrated as being able to transmit signals and the receiving apparatus  120  is illustrated as being able to receive signals for the convenience of explanation, the receiving apparatus  120  may also transmit signals and the transmitting apparatus  110  may also receive signals. 
         [0043]      FIG. 2  illustrates a transmitting apparatus  110  according to exemplary embodiments. The term “unit” and the term ending the suffix “-er” or “-or” which are used herein may refer to a unit which processes at least one function or operation, and these terms may refer to hardware, software, or a combination of hardware and software. 
         [0044]    Referring to  FIG. 2 , the transmitting apparatus  110  includes a communication interface  210 , a storage  220 , and a controller  230 . The communication interface  210  may include a modulator  212  and a transmitter  214 . The modulator  212  may provide a series of functions for generating transmission signals. For example, the modulator  212  may perform a function of converting between a baseband signal and a bit string according to a physical layer standard of the system. In addition, the modulator  212  may generate complex symbols by encoding and modulating a transmission bit string. The modulator  212  may include a transmission filter bank. The transmission filter bank may obtain a waveform in a desired form by filtering the modulated complex symbols. The filtering operation may be performed in a frequency domain or may be performed in a time domain. For example, the modulated symbols may be filtered in the frequency domain and may be transformed into the time domain by performing Inverse Fast Fourier Transform (IFFT). In another example, the modulated symbols may be transformed into the time domain by performing IFFT and may be filtered. 
         [0045]    The transmitter  214  may perform a series of functions for transmitting signals. For example, the transmitter  214  may up-convert a baseband signal into a radio frequency (RF) band signal and then may transmit the signal through an antenna. 
         [0046]    The storage  220  may store a basic program for the operation of the transmitting apparatus  110 , an application program, and data such as setting information or the like. The storage  220  may include a volatile memory, a non-volatile memory, or a combination of a volatile memory and a non-volatile memory. 
         [0047]    The controller  230  may control the overall operations of the transmitting apparatus  110 . For example, the controller  230  may transmit and receive signals through the communication interface  210 . In addition, the controller  230  may write or read data on or from the storage  220 . The controller  230  may include at least one of a processor or a micro processor, or may be a part of the processor. In particular, the controller  230  may control a function of reducing the PAPR of a signal transmitted from the communication interface  210 . For example, the controller  230  may control the communication interface  210  to perform operations for reducing the PAPR, which will be described below. 
         [0048]      FIG. 3  illustrates a receiving apparatus  120  according to exemplary embodiments. The term “unit” and the term ending the suffix “-er” or “-or” which are used herein may refer to a unit which processes at least one function or operation, and these terms may refer to hardware, software, or a combination of hardware and software. 
         [0049]    Referring to  FIG. 3 , the receiving apparatus  120  may include a communication interface  310 , a storage  320 , and a controller  330 . The communication interface  310  may include a demodulator  312  and a receiver  314 . The receiver  314  may perform a series of functions for receiving signals through an antenna. For example, the receiver  314  down-converts an RF band signal received through the antenna into a baseband signal. 
         [0050]    The demodulator  312  may perform a series of functions for restoring received signals. For example, the demodulator  312  performs a function of converting between a baseband signal and a bit string according to a physical layer standard of the system. For example, when receiving data, the demodulator  312  restores a reception bit string by demodulating and decoding the baseband signal. The demodulator  312  may include a reception filter bank. The reception filter bank may obtain a waveform in a desired form by filtering the demodulated symbols. The filtering operation may be performed in a frequency domain or may be performed in a time domain. For example, the demodulated symbols may be filtered in the time domain and may be transformed into the frequency domain by performing Fast Fourier Transform (TFT). In another example, the demodulated symbols may be transformed into the frequency domain by performing FFT and may be filtered. 
         [0051]    The storage  320  may store a basic program for the operation of the receiving apparatus  120 , an application program, and data such as setting information or the like. The storage  320  may include a volatile memory, a non-volatile memory, or a combination of a volatile memory and a non-volatile memory. 
         [0052]    The controller  330  may control the overall operations of the receiving apparatus  120 . For example, the controller  330  may receive signals through the communication interface  310 . In addition, the controller  330  may write or read data on or from the storage  320 . The controller  330  may include at least one of a processor or a micro processor, or may be a part of the processor. In particular, the controller  330  may control a function for reducing the PAPR of a signal received at the communication interface  310 . For example, the controller  330  may control the communication interface  310  to perform operations for reducing the PAPR, which will be described below. 
         [0053]      FIG. 4  illustrates an example of an operation of transmitting and receiving signals in an FBMC transmission system.  FIG. 4  illustrates an example of an operation of filtering in a frequency domain. 
         [0054]    Referring to  FIG. 4 , the transmitting apparatus  110  includes a transmission filter bank  412 , an IFFT  414 , an overlapping and addition circuit  416 . The transmission filter bank  412  may correspond to the transmission filter bank  212  of  FIG. 2 . The transmission filter bank  412  may oversample data symbols D 1  to Dm. In an exemplary embodiment,  FIG. 4  illustrates that an oversampling factor is 5. When the oversampling is performed, the transmission filter bank  412  may perform filtering using a filter order K. In an exemplary embodiment,  FIG. 4  illustrates that the filter order K is 2. That is, the oversampling factor is determined by 5=2K+1. Although the oversampling factor is 5 and the filter order is 2 in  FIG. 4  for the convenience of explanation, other values may be determined for the oversampling factor and the filter order. For example, the transmission filter bank  412  may generate the five (5) same D 1  by oversampling D 1 . Similarly, the transmission filter bank  412  may oversample D 2  to Dm and multiply each of the oversampled symbols by a filter coefficient. In this case, some of the filtered samples of neighbor data symbols are added. For example, two of the samples of the filtered D 1  may be added with two of the samples of the filtered D 2 . In order for the added samples to be separated in the receiving apparatus  120 , different filters may be applied to neighbor data symbols. In addition, in order for the added samples to be separated in the receiving apparatus  120 , the neighbor data symbols may be divided into at least two different groups. For example, in the case of the OQAM method, the neighbor data symbols may be divided into a real value and an imaginary value. 
         [0055]    The IFFT  414  may perform an IFFT operation with respect to the data symbols outputted from the transmission filter bank  412 . That is, the IFFT  414  may generate FBMC symbols using the IFFT operation. The length of the FBMC symbols is longer than the number M of existing data symbols because of the oversampling performed in the transmission filter bank  412 . Accordingly, the overlapping and addition circuit  416  may partially overlap and add the FBMC symbols generated by the IFFT  414 . The FBMC symbols may not be transmitted independently from one another in the time domain, and may be transmitted, partially overlapping one another. More specifically, the rear end of the first FBMC symbol and the front end of the second FBMC symbol may overlap each other. That is, the overlapping and addition circuit  416  may arrange the FBMC symbols at predetermined intervals, and generate a transmission signal by adding the samples of the FBMC symbols located in the same time zone. 
         [0056]    Although not shown in  FIG. 4 , the transmitting apparatus  110  may further include at least one circuit to transmit the transmission signal generated by the overlapping and addition circuit  416 . The transmission signal generated by the overlapping and addition circuit  416  is a digital baseband signal. Accordingly, the transmission apparatus  110  may further include at least one circuit to convert the transmission signal into an analogue signal and up-convert the analogue signal into a signal of an RF band. 
         [0057]    The transmission signal may be transmitted to the antenna of the receiving apparatus  120 . An FFT  422  may perform an FFT operation with respect to the reception signal. The FFT  422  may extract as many samples as the length of a single FBMC symbol from the reception signal which has been generated by overlapping and adding the FBMC symbols, and may perform the FFT operation. A reception filter bank  424  may filter the samples corresponding to the single FBMC symbol, which are provided from the FFT  422 , and may perform downsampling. The samples may be restored to D 1  to Dm by the downsampling. For example, the reception filter bank  424  may multiply five (5) samples of the samples of the reception signal which has undergone the FFT operation by filter coefficients, and may add the samples. 
         [0058]      FIG. 5  illustrates another example of the operation of transmitting and receiving signals in the FBMC transmission system.  FIG. 5  illustrates an example of an operation of filtering in a time domain. 
         [0059]    Referring to  FIG. 5 , the transmitting apparatus  110  includes an IFFT  512 , a transmission filter bank  514 , and an overlapping and addition circuit  516 . The IFFT  512  may perform an IFFT operation with respect to data symbols. The length of data symbols which has undergone the IFFT operation is equal to M. The transmission filter bank  514  may filter the result outputted from the IFFT  512  in the time domain. The transmission filter bank  514  may generate the same output as the IFFT  414  of  FIG. 4 . The operation of the transmission filter bank  412  of  FIG. 4  corresponds to a convolution operation in the frequency domain, and a corresponding operation in the time domain may be implemented by signal repetition and filtering. More specifically, the transmission filter bank  514  may duplicate the result value outputted from the IFFT  512  as many as a filter order, and may perform multiplication with the transmission filter of the time domain corresponding to the frequency domain filter of the transmission filter bank  412  of  FIG. 4 . 
         [0060]    The overlapping and addition circuit  516  may partially overlap and add the FBMC symbols which are generated by the multiplication. The FBMC symbols may not be transmitted independently from one another in the time domain, and may be transmitted, partially overlapping one another. More specifically, the rear end of the first FBMC symbol and the front end of the second FBMC symbol may overlap each other. That is, the overlapping and addition circuit  516  may arrange the FBMC symbols at predetermined intervals, and generate a transmission signal by adding the samples of the FBMC symbols located in the same time zone. 
         [0061]    Although not shown in  FIG. 5 , the transmitting apparatus  110  may further include at least one circuit to transmit the transmission signal generated by the overlapping and addition circuit  516 . The transmission signal generated by the overlapping and addition circuit  516  is a digital baseband signal. Accordingly, the transmitting apparatus  110  may further include at least one circuit to convert the transmission signal into an analogue signal and up-convert the analogue signal into a signal of an RF band. 
         [0062]    The transmission signal may be transmitted to the antenna of the receiving apparatus  120 . A reception filter bank  522  may perform time domain filtering using a reception filter corresponding to the transmission filter used in the transmission filter bank  514 . In this case, the reception filter bank  522  may extract as many samples as the length of a single FBMC symbol from the reception signal which has been generated by overlapping and adding the FBMC symbols, and may perform reception filtering. In addition, the reception filter bank  522  may divide the signal according to a repetition order, and add the divided signals. Accordingly, the signal is restored to the signal before transmission filtering (for example, IFFT {D}). An FFT  522  may perform an FFT operation with respect to the signal provided from the reception filter bank  522 . Accordingly, the data symbols D 1  to Dm may be restored. 
         [0063]      FIG. 6  illustrates a transmission signal processing in the wireless communication system according to exemplary embodiments.  FIG. 6  illustrates a process of FBMC modulating symbols which are modulated by the OQAM method in the transmitting apparatus  110 . 
         [0064]    Referring to  FIG. 6 , M refers to a data length. In addition, M may refer to the number of complex data symbols. N refers to an IDFT size in relation to whole carriers. That is, the transmitting apparatus  110  may transmit M complex data symbols using N carriers. 
         [0065]    In block  610 , the transmitting apparatus  110  may convert the M complex symbols which are modulated by OQAM from a series arrangement to a parallel arrangement. In block  620 , the transmitting apparatus  110  may perform a DFT operation with respect to each of the converted symbols. When the DFT operation is performed, an offset interference may occur while the plurality of symbols undergoes an IFFT operation and is overlapped and added. The plurality of symbols may cause a low PAPR due to the offset interference. It may be noted that the transmitting apparatus  110  may perform the DFT operation before the plurality of symbols are divided into two groups. While the complex symbols are divided into two groups, the symbols included in each of the groups are divided in a single dimension (for example, into a real number part and an imaginary number part). However, when the transmitting apparatus  110  performs the DFT operation with respect to each of the symbols included in the two divided groups, the symbols are outputted in a complex dimension again and thus a mutual interference may occur. Accordingly, the DFT operation may be performed before the plurality of symbols are divided into two groups. 
         [0066]    The transmitting apparatus  110  may divide the complex symbols which have undergone the DFT operation into a first group  630   a  including the real number part of the complex symbols and a second group  630   b  including the imaginary number part of the complex symbols. Even when the number of symbols included in the two divided groups increase by oversampling and then the symbols are overlapped and added, the influence of the interference may be reduced. That is, a PAPR may be reduced by overlapping and addition. 
         [0067]    There is still a correlation between the two divided groups. Since the symbols included in the two divided groups that interfere each other while the symbols are overlapped and added, the PAPR may be still on the increase. Accordingly, according to an exemplary embodiment of the present disclosure, the transmitting apparatus  110  may perform interleaving and phase rotation with respect to each of the first group and the second group in blocks  640   a  and  640   b  and blocks  650   a , and  650   b . The interleaving and the phase rotation may cause an offset interference between two symbols when the symbols included in the two divided groups are added. The added symbols may reduce the PAPR due to the offset interference. The interleaving operation will be described in detail with reference to  FIG. 16 . 
         [0068]    The transmitting apparatus  110  may generate FBMC symbols corresponding to the first group and the second group which have undergone the interleaving and the phase rotation. The FBMC modulation may correspond to the processing process which is performed by the transmitting apparatus  110  in  FIG. 5 . For example, referring to  FIG. 6 , the FBMC modulation may include blocks  660   a  and  660   b  to perform an IDFT operation, blocks  670   a  and  670   b  to perform parallel-to-serial (P/S) conversion, and blocks  680   a  and  680   b  to perform filtering. In  FIG. 6 , blocks  660   a  and  660   b  may perform the same or similar function as or to the IFFT  512  of  FIG. 5 . In addition, blocks  680   a  and  680   b  of  FIG. 6  may perform the same or similar function as or to the transmission filter bank  514  of  FIG. 5 . When the second group  630   b  is filtered, the transmitting apparatus  110  may perform offsetting by M/2 in block  690 . The offsetting is applied to synchronize at least two groups which are not synchronized in the time domain. For example, the first group including the real number part and the second group including the imaginary number part are transmitted at an interval of time of M/2 not to overlap each other. 
         [0069]    Although not shown in  FIG. 6 , the transmitting apparatus  110  may overlap and add the symbols included in the two groups when the filtering is performed. The overlapping and adding is the same as or similar to the process which is performed in the overlapping and addition circuit  516  of  FIG. 5 . However, unlike in the overlapping and adding process shown in  FIG. 5 , the symbols processed by the interleaving and the phase rotation in  FIG. 6  may cause a lower PAPR due to the offset interference. 
         [0070]    According to an exemplary embodiment of  FIG. 6 , the operation of applying the DFT spreading technique in the transmitting apparatus  110  of the FBMC transmission system may be expressed in the form of a matrix as follows: 
         [0000]        s=FV   M   −1   WLV   N   x   r   =Tx   r   (1)
 
         [0071]    Equation 1 indicates a process of generating a signal in which two FBMC symbols overlap each other with respect to M complex data symbols. Herein, s indicates a signal which is modulated in the time domain. F indicates a matrix form of filtering. V M   −1  indicates a matrix of IDFT having a size of M. W indicates a phase rotation matrix. L indicates an interleaving matrix. V N  indicates a DFT matrix having a size of N. x r  indicates a matrix of symbols having real values in the frequency domain. 
         [0072]    According to an exemplary embodiment of the present disclosure, the phase rotation may perform multiplication by 
         [0000]    
       
         
           
             
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         [0000]    Herein, n refers to a symbol block index and m refers to a carrier index. In addition, n+m mod 2 refers to a remainder after the sum of n and m is divided by 2. 
         [0073]      FIG. 7  illustrates a transmission signal processing process in the wireless communication system according to exemplary embodiments.  FIG. 7  illustrates a process of FBMC modulating symbols which are modulated by the QAM method in the transmitting apparatus  110 . 
         [0074]    Referring to  FIG. 7 , M refers to a data length. In addition, M may refer to the number of complex data symbols. N refers to an IDFT size in relation to whole carriers. That is, the transmitting apparatus  110  may transmit M complex data symbols using N carriers. 
         [0075]    In block  710 , the transmitting apparatus  110  may convert the M complex symbols which are modulated by QAM from a series arrangement to a parallel arrangement. In block  720 , the transmitting apparatus  110  may perform a DFT operation with respect to each of the converted symbols. When the DFT operation is performed, an offset interference may occur even when the plurality of symbols are overlapped and added after the IFFT operation is performed. The plurality of symbols may cause a low PAPR due to the offset interference. It may be noted that the transmitting apparatus  110  may perform the DFT operation before the plurality of symbols is divided into two groups because there occurs a correlation between a first group  730   a  and a second group  730   b  when the plurality of symbols is divided into the two groups after the DFT operation is performed. 
         [0076]    The transmitting apparatus  110  may divide the complex symbols which have undergone the DFT operation into the first group  730   a  and the second group  730   b  including the same number of symbols. For example, the first group  730   a  may include symbols having an odd number index from among the M symbols which have undergone the DFT operation, and the second group  730   b  may include symbols having an even number index. While the number of symbols increases by oversampling and then the symbols are overlapped and added, the overlapped and added symbols may reduce the influence of the interference. That is, a PAPR may be reduced by overlapping and addition. 
         [0077]    The transmitting apparatus  110  may generate FBMC symbols corresponding to the first group and the second group. The FBMC modulation may correspond to the processing process which is performed by the communication interface  210  in  FIG. 5 . For example, referring to  FIG. 7 , the FBMC modulation may include blocks  740   a  and  740   b  to perform an IDFT operation, blocks  760   a  and  760   b  to perform parallel-to-serial (P/S) conversion, and blocks  770   a  and  770   b  to perform filtering. In  FIG. 7 , blocks  730   a  and  730   b  may perform the same or similar function as or to the IFFT  512  of  FIG. 5 . In addition, blocks  770   a  and  770   b  of  FIG. 7  may perform the same or similar function as or to the transmission filter bank  514  of  FIG. 5 . In block  750 , the transmitting apparatus  110  may perform phase rotation with respect to the symbols included in the second group  730   b . The phase rotation may cause the offset interference while the symbols included in the two groups are overlapped and added. 
         [0078]    Although not shown in  FIG. 7 , the transmitting apparatus  110  may overlap and add the symbols included in the first group and the second group when the filtering is performed. The overlapping and adding is the same as or similar to the process which is performed in the overlapping and addition circuit  516  of  FIG. 5 . However, unlike in the overlapping and adding process shown in  FIG. 5 , the symbols processed in  FIG. 7  may cause the offset interference and thus may generate a lower PAPR. 
         [0079]    According to an exemplary embodiment of  FIG. 7 , the operation of applying the DFT spreading technique in the transmitting apparatus  110  of the FBMC transmission system may be expressed in the form of a matrix as follows: 
         [0000]        s=FWV   M/2   −1   V   N   x=Tx   (2)
 
         [0080]    Equation 2 indicates a process of generating a signal in which an even numbered symbol and an odd numbered symbol, that is, two FBMC symbols overlap each other with respect to M complex data symbols. 
         [0081]    Herein, s indicates a signal which is modulated in the time domain. F indicates a matrix form of filtering. W indicates a phase rotation matrix. V M/2   −1  indicates a matrix of IDFT having a size of M/2. V N  indicates a DFT matrix having a size of N. x indicates a matrix of symbols having complex values in the frequency domain. 
         [0082]    According to an exemplary embodiment of the present disclosure, the phase rotation may perform multiplication by 
         [0000]    
       
         
           
             
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         [0000]    Herein, n refers to a sample index in the time domain and x(n) refers to an output value of an odd sub-carrier IDFT. 
         [0083]      FIG. 8  illustrates a reception signal processing process in the wireless communication system according to exemplary embodiments.  FIG. 8  illustrates a process of FBMC demodulating received symbols in the receiving apparatus  120 . The received symbols include symbols which are modulated in the transmitting apparatus  110  by the OQAM method. A series of operations illustrated in  FIG. 8  are symmetrical to the series of operations performed in the transmitting apparatus  110  of  FIG. 6 . 
         [0084]    Referring to  FIG. 8 , M refers to a data length. In addition, M may refer to the number of complex data symbols. N refers to an IDFT size in relation to whole carriers. That is, the receiving apparatus  120  may receive N carriers and restore M complex data symbols. 
         [0085]    In blocks  810   a  and  810   b , the receiving apparatus  120  may divide the N received data symbols into a first group and a second group. The two divided groups may include the data symbols corresponding to the first group and the second group which are divided in  FIG. 6 . In blocks  820   a  and  820   b , the receiving apparatus  120  performs multiplication by a filter coefficient with respect to each of the first group and the second group. In blocks  830   a  and  830   b , the receiving apparatus  120  may convert each of the first group and the second group which have undergone the multiplication from a series arrangement to a parallel arrangement. In blocks  840   a  and  840   b , the receiving apparatus  120  may perform a DFT operation of an N size with respect to each of the converted first group and second group. The DFT operation performed in blocks  840   a  and  840   b  of  FIG. 8  is symmetrical to the IFFT operation which is performed in blocks  660   a  and  660   b  of  FIG. 6 . In blocks  850   a  and  850   b , the receiving apparatus  120  performs phase rotation with respect to each of the first group and the second group which have undergone the DFT operation. A plurality of symbols included in the two groups which have undergone the phase rotation correspond to real values as shown in blocks  855   a  and  855   b . That is, each of the blocks  855   a  and  855   b  indicates real values corresponding to the plurality of symbols included in the two groups. In blocks  860   a  and  860   b , the receiving apparatus  120  deinterleaves each of the two groups which have undergone the phase rotation. When the deinterleaving is completed, the receiving apparatus  120  performs multiplication by a j value with respect to the group corresponding to the imaginary number part in the transmitting apparatus  110  (block  870 ). For example, it is assumed that the symbols of the second group generated in block  630   b  correspond to the real number. The symbols of the second group generated in block  810   b  of  FIG. 8  correspond to the symbols of the second group generated in block  630   b  of  FIG. 6 . Accordingly, the receiving apparatus  120  performs the multiplication by the j value with respect to the symbols of the second group generated in block  810   b  of  FIG. 8 . When the multiplication is performed in block  870 , the first group and the second group may include data symbol values corresponding to the real number part and the imaginary number part, respectively. In block  880 , the receiving apparatus  120  performs an IDFT operation of an M size with respect to the two groups. The IDFT operation is symmetrical to the DFT operation performed in block  620  of  FIG. 6 . Similarly, it may be noted that the IDFT operation may be performed after the symbols included in the first group and the second group are added to make complex symbols. When the IDFT operation is performed, the receiving apparatus  120  converts the plurality of complex symbols from a parallel arrangement to a series arrangement in block  890 . 
         [0086]    Although not shown in  FIG. 8 , the receiving apparatus  120  may generate restored symbols by performing channel estimation and equalization with respect to the plurality of complex symbols which have been converted into the series arrangement in block  890 . 
         [0087]      FIG. 9  illustrates a reception signal processing process in the wireless communication system according to exemplary embodiments.  FIG. 9  illustrates a process of FBMC demodulating received symbols in the receiving apparatus  120 . The received symbols include symbols which are modulated in the transmitting apparatus  110  by the QAM method. A series of operations illustrated in  FIG. 9  are symmetrical to the series of operations performed in the transmitting apparatus  110  of  FIG. 7 . 
         [0088]    Referring to  FIG. 9 , M refers to a data length. In addition, M may refer to the number of complex data symbols. N refers to an IDFT size in relation to whole carriers. That is, the receiving apparatus  120  may receive N carriers and restore M complex data symbols. 
         [0089]    In blocks  910   a  and  910   b , the receiving apparatus  120  may divide the N received data symbols into a first group and a second group. The two divided groups include the same number of symbols. In addition, neighbor symbols are divided into different groups. For example, the receiving apparatus  120  may divide the plurality of data symbols into symbols having an even number index and symbols having an odd number index. In blocks  920   a  and  920   b , the receiving apparatus  120  may perform multiplication by a filter coefficient with respect to each of the first group and the second group. In blocks  930   a  and  930   b , the receiving apparatus  120  converts each of the first group and the second group which have undergone the multiplication from a series arrangement to a parallel arrangement. In block  940 , the receiving apparatus  120  performs phase rotation with respect to one of the converted first group and second group. For example, in block  940 , the receiving apparatus  120  performs the phase rotation with respect to the second group including the symbols having the odd number index, whereas, in block  950   a , the receiving apparatus  120  performs a DFT operation of an N/2 size with respect to the first group including the symbols having the even number index without performing the phase rotation. In blocks  950   a  and  950   b , the receiving apparatus  120  performs the DFT operation of the N/2 size with respect to each of the first group and the second group. The reason why the DFT operation of the N/2 size is applied is that the N received data symbols are divided into groups including N/2 symbols in blocks  910   a  and  910   b . The DFT operation performed in blocks  950   a  and  950   b  of  FIG. 9  is symmetrical to the IFFT operation performed in blocks  740   a  and  740   b  of  FIG. 7 . In block  960 , the receiving apparatus  120  performs an IDFT operation of an M size with respect to the first group and the second group which have undergone the DFT operation. The IDFT operation is symmetrical to the DFT operation performed in block  720  of  FIG. 7 . Similarly, it may be noted that the IDFT operation may be performed after the first group and the second group each including N/2 symbols are added. In block  970 , the receiving apparatus  120  converts the M data symbols which have undergone the IDFT operation from a parallel arrangement to a series arrangement. 
         [0090]    Although not shown in  FIG. 9 , the receiving apparatus  120  may generate restored symbols by performing channel estimation and equalization with respect to the plurality of symbols which have been converted into the series arrangement. 
         [0091]      FIG. 10  illustrates a flowchart of a transmission signal processing in the wireless communication system according to exemplary embodiments.  FIG. 10  illustrates the transmission signal processing process in the transmitting apparatus  110 . 
         [0092]    Referring to  FIG. 10 , in step  1020 , the transmitting apparatus  110  performs Fourier transform with respect to a plurality of modulation symbols. When the Fourier transform is performed, a probability that a random signal is generated while IFFT is performed is reduced. Therefore, a PAPR may further be reduced while overlapping and addition are performed. In step  1040 , the transmitting apparatus  110  may divide the symbols which have undergone the Fourier transform into two groups. For example, the transmitting apparatus  110  may divide the symbols which are OQAM modulated into a real number part and an imaginary number part. In another example, the transmitting apparatus  110  may divide the symbols which are QAM modulated into symbols corresponding to an even number index and symbols corresponding to an odd number index. In step  1060 , the transmitting apparatus  110  generates FBMC modulation symbols corresponding to the two divided groups. For example, the FBMC modulation may include an IFFT operation, a filtering process, and an overlapping and adding process. In another example, the FBMC modulation may perform the IFFT operation after performing the filtering. 
         [0093]      FIG. 11  illustrates another flowchart of a transmission signal processing in the wireless communication system according to exemplary embodiments.  FIG. 11  illustrates the transmission signal processing process in the transmitting apparatus  110 . In addition,  FIG. 11  illustrates a flowchart of an operation of applying a DFT spreading technique to symbols which are modulated by the OQAM method. 
         [0094]    Referring to  FIG. 11 , in step  1110 , the transmitting apparatus  110  performs Fourier transform with respect to a plurality of modulation symbols. When the Fourier transform is performed, a probability that a random signal is generated while IFFT is performed is reduced. Therefore, a PAPR may further be reduced while overlapping and addition are performed. In step  1120 , the transmitting apparatus  110  may divide the symbols which have undergone the Fourier transform into a real number part and an imaginary number part. In step  1130 , the transmitting apparatus  110  interleaves each of the symbols included in the divided groups. In step  1140 , the transmitting apparatus  110  performs phase rotation with respect to each of the symbols included in the divided groups. In step  1150 , the transmitting apparatus  110  generates FBMC symbols corresponding to the divided groups. For example, the FBMC modulation may include an IFFT operation, a filtering process, and an overlapping and adding process. In another example, the FBMC modulation may perform the IFFT operation after performing the filtering. 
         [0095]      FIG. 12  illustrates yet another flowchart of a transmission signal processing in the wireless communication system according to exemplary embodiments.  FIG. 12  illustrates the transmission signal processing process in the transmitting apparatus  110 . In addition,  FIG. 12  illustrates a flowchart of an operation of applying a DFT spreading technique to symbols which are modulated by the QAM method. 
         [0096]    Referring to  FIG. 12 , in step  1210 , the transmitting apparatus  110  performs Fourier transform with respect to a plurality of modulation symbols. When the Fourier transform is performed, a probability that a random signal is generated while IFFT is performed is reduced. Therefore, a PAPR may further be reduced while overlapping and addition are performed. In step  1220 , the transmitting apparatus  110  may divide the symbols which have undergone the Fourier transform into two groups. For example, the transmitting apparatus  110  may divide the plurality of symbols into symbols corresponding to an odd number index and symbols corresponding to an even number index. In step  1230 , the transmitting apparatus  110  may perform inverse Fourier transform with respect to the symbols included in each of the divided groups. When the inverse Fourier transform is performed, the symbols in the frequency domain may be transformed into the symbols in the time domain. In step  1240 , the transmitting apparatus  110  may perform phase rotation with respect to symbols included in one of the two divided groups. For example, the transmitting apparatus  110  may perform phase rotation with respect to the first group including the symbols corresponding to the odd number index. In step  1250 , the transmitting apparatus  110  may perform multiplication by a filter coefficient with respect to each of the symbols included in the two divided groups. 
         [0097]      FIG. 13  illustrates a flowchart of a reception signal processing process in the wireless communication system according to exemplary embodiments.  FIG. 13  illustrates the reception signal processing process in the receiving apparatus  120 . 
         [0098]    Referring to  FIG. 13 , in step  1320 , the receiving apparatus  120  divides received symbols into at least two groups. For example, the receiving apparatus  120  may divide the symbols which have been OQAM modulated in the transmitting apparatus into a real number part and an imaginary number part. In another example, the receiving apparatus  120  may divide the symbols which have been QAM modulated in the transmitting apparatus into symbols corresponding to an even number index and symbols corresponding to an odd number index. In step  1340 , the receiving apparatus  120  demodulates each of the at least two divided groups in the FBMC method. In step  1360 , the receiving apparatus  120  may perform inverse Fourier transform with respect to the plurality of symbols included in the at least two demodulated groups. The inverse Fourier transform is performed by a single inverse Fourier transform operation. In step  1380 , the receiving apparatus  120  generates a plurality of restored symbols by performing channel estimation and equalization with respect to the plurality of symbols which have undergone the inverse Fourier transform. For example, the restored symbols may correspond to the symbols which are modulated in the transmitting apparatus by the OQAM method. In another example, the modulation symbols may correspond to the symbols which are modulated in the QAM method. 
         [0099]      FIG. 14  illustrates another flowchart of a reception signal processing process in the wireless communication system according to exemplary embodiments.  FIG. 14  illustrates the reception signal processing process in the receiving apparatus  120 . In addition,  FIG. 14  illustrates a flowchart of an operation of applying a DFT spreading technique to symbols which are modulated in the OQAM method. 
         [0100]    In step  1410 , the receiving apparatus  120  divides a plurality of received symbols into two groups corresponding to a real number part and an imaginary number part. In step  1420 , the receiving apparatus  120  demodulates each of the two divided groups in the FBMC method. In step  1430 , the receiving apparatus  120  may perform phase rotation with respect to each of the two divided groups. In step  1440 , the receiving apparatus  120  deinterleaves each of the two divided groups. In step  1450 , the receiving apparatus  120  may perform inverse Fourier transform with respect to the plurality of symbols included in the two divided groups. The inverse Fourier transform is performed by a single inverse Fourier transform operation. In step  1460 , the receiving apparatus  120  generates a plurality of restored symbols by performing channel estimation and equalization with respect to the plurality of transformed symbols. 
         [0101]      FIG. 15  illustrates yet another flowchart of a reception signal processing in the wireless communication system according to exemplary embodiments.  FIG. 15  illustrates the reception signal processing process in the receiving apparatus  120 . In addition,  FIG. 15  illustrates a flowchart of an operation of applying a DFT spreading technique to symbols which are modulated by the QAM method. 
         [0102]    Referring to  FIG. 15 , in step  1510 , the receiving apparatus  120  divides a plurality of received symbols into a first group and a second group. The first group and the second group include the same number of symbols. For example, when the number of received symbols is M, each of the first group and the second group includes M/2 symbols. In step  1520 , the receiving apparatus  120  generates a third group by multiplying the first group by a filter coefficient, and generates a fourth group by multiplying the second group by a filter coefficient. The filter coefficient by which the first group is multiplied and the filter coefficient by which the second group is multiplied have the same factor. That is, the third group and the fourth group include the same number of symbols. In step  1530 , the receiving apparatus  120  performs phase rotation with respect to one of the third group and the fourth group. In step  1540 , the receiving apparatus  120  performs Fourier transform with respect to each of the third group and the fourth group. In step  1550 , the receiving apparatus  120  may perform inverse Fourier transform with respect to the plurality of symbols included in the third group and the fourth group. The inverse Fourier transform is performed by a single inverse Fourier transform operation. In step  1560 , the receiving apparatus  120  generates a plurality of restored signals by performing channel estimation and equalization with respect to the plurality of transformed symbols. For example, the plurality of restored signals may correspond to signals which are modulated in the QAM method. 
         [0103]      FIG. 16  illustrates an interleaving operation in the wireless communication system according to exemplary embodiments. 
         [0104]    Referring to  FIG. 16 , the length of data symbols may be N and the number of blocks to interleave may be X. For example,  FIG. 16  illustrates that the length of data symbols N=8 and the number of blocks X=2. The N value and the X value are defined as described above for the convenience of explanation, but other values may be substituted for the N value and the X value. 
         [0105]    In step  1620 , eight (8) data symbols have indexes 1 to 8. The data symbols are arranged according to a predetermined order of the indexes. For example, the symbols having the indexes 1-8 may correspond to 1, j, −1, −j, 1, j, 1, j. 
         [0106]    In step  1640 , the data symbols may be rearranged in two block lines. For example, as shown in  FIG. 16 , symbols having indexes 1 to 4 from among the data symbols may form one line and symbols having indexes 5 to 8 may form the other line. That is, four (4) data symbols are arranged in one line. 
         [0107]    In step  1660 , the data symbols rearranged as described above may be rearranged in a single line according to a predetermined regulation. For example, the data symbols may be rearranged in an order as illustrated in the lower drawing. In this case, the symbol having index 5 is arranged next to the symbol having index 1. Next, when the symbol having index 2 is arranged, the symbol having index 6 is arranged thereafter. 
         [0108]    Since an inter-signal offset interference occurs while the data symbols are overlapped and added by the above-described block interleaving operation, a low PAPR may be caused. 
         [0109]      FIG. 17  illustrates a PAPR performance in the wireless communication system according to exemplary embodiments. In  FIG. 17 , a PAPR performance in the operation of applying the DFT spreading technique in the OQAM method and a PAPR performance in other methods are compared. 
         [0110]    Referring to  FIG. 17 , the x-axis refers to a PAPR value. In addition, the y-axis refers to a complementary cumulative distribution function (CCDF) value. The CCDF means a probability that a random signal is generated with respect to the same PAPR value. For example, in  FIG. 17 , graph  1710  indicates that a probability that a random signal is generated while the PAPR value reaches about 8.5 dB is 1/10. In another example, graph  1710  indicates that a probability that a random signal is generated while the PAPR value reaches about 9.5 dB is 1/100. 
         [0111]    Graph  1710  shows a PAPR performance when the DFT spreading technique is not applied in an existing FBMC transmission system. Graph  1720  shows a PAPR performance when only the DFT spreading technique is applied in the existing FBMC transmission system and interleaving and phase rotation are not applied. Graph  1730  shows a PAPR performance when the DFT spreading technique according to the above-described method is applied in the FBMC transmission system, but related-art phase rotation is applied. Graph  1740  shows a PAPR performance when the DFT spreading technique according to the above-described method is applied in the FBMC transmission system and phase rotation according to the above-described method is applied. Graph  1750  shows a PAPR performance when the DFT spreading technique is applied in the related-art OFDM method. For example, when the probability that the random signal is generated is 1/10, graph  1710  shows that the PAPR value of about 8.5 dB is generated, whereas graph  1730  shows that the PAPR value of about 7.5 dB is generated. 
         [0112]      FIG. 18  illustrates another PAPR performance in the wireless communication system according to exemplary embodiments. In  FIG. 18 , a PAPR performance in the operation of applying the DFT spreading technique in the QAM method and a PAPR performance in other methods are compared. 
         [0113]    Referring to  FIG. 18 , the x-axis refers to a PAPR value. In addition, the y-axis refers to a CCDF value. The CCDF means a probability that a random signal is generated with respect to the same PAPR value. For example, in  FIG. 18 , graph  1810  indicates that a probability that a random signal is generated while the PAPR value reaches about 8.5 dB is 1/10. In another example, graph  1810  indicates that a probability that a random signal is generated while the PAPR value reaches about 9.5 dB is 1/100. 
         [0114]    Graph  1810  shows a PAPR performance when the DFT spreading technique is not applied in an existing FBMC transmission system. Graph  1820  shows a PAPR performance when only the DFT spreading technique is applied in the existing FBMC transmission system and interleaving and phase rotation are not applied. Graph  1830  shows a PAPR performance when the DFT spreading technique according to the above-described method is applied in the FBMC transmission system, but related-art phase rotation is applied. Graph  1840  shows a PAPR performance when the DFT spreading technique according to the above-described method is applied in the FBMC transmission system and phase rotation according to the above-described method is applied. Graph  1850  shows a PAPR performance when the DFT spreading technique is applied in the related-art OFDM method. For example, when the probability that the random signal is generated is 1/10, graph  1810  shows that the PAPR value of about 8.5 dB is generated, whereas graph  1840  shows that the PAPR value of about 7 dB is generated. 
         [0115]    The methods according to exemplary embodiments described in the claims or descriptions of the present disclosure may be implemented by hardware, software, or a combination of hardware and software. 
         [0116]    The software may be stored in a computer readable storage medium. The computer readable storage medium may store at least one program (software module) and at least one program including instructions for the electronic device to perform the method of the present disclosure when being executed by at least one processor in the electronic device. 
         [0117]    The software may be stored in a volatile storage device or a non-volatile storage device such as a read only memory (ROM), a memory such as a Random Access Memory (RAM), a memory chip device, or an integrated circuit, or an optical or magnetic readable medium such as a compact disc-ROM (CD-ROM), digital versatile discs (DVDs), a magnetic disk, or a magnetic tape. 
         [0118]    The storage device and the storage medium are exemplary embodiments of a machine readable storing means which is appropriate to store a program or programs including the instructions for implementing the embodiments when being executed. The exemplary embodiments provide a program including a code for implementing the apparatus or method as claimed in any one of the claims of the specification, and a machine readable storage medium for storing such a program. Furthermore, these programs may be electronically transmitted by a certain means such as a communication signal which is transmitted through wired or wireless connection, and the exemplary embodiments appropriately include the equivalents. 
         [0119]    In the above-described exemplary embodiments, the elements included in the present disclosure are expressed in singular forms or plural forms according to a detailed exemplary embodiment. However, the singular or plural expression is appropriately selected according to a suggested situation for the convenience of explanation, and the above-described exemplary embodiments are not limited to the singular or plural elements. An element expressed in the plural form may be configured as a single element or an element expressed in the singular form may be configured as a plurality of elements. 
         [0120]    Although the present disclosure has been described with an exemplary embodiment, various changes and modifications may be suggested to one skilled in the art. It is intended that the present disclosure encompass such changes and modifications as fall within the scope of the appended claims.