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 4th-Generation (4G) communication system such as Long Term Evolution (LTE). The present invention relates to a method and a device for efficiently shortening and puncturing a non-binary LDPC code, the method for a transmitter shortening and puncturing a non-binary code being capable of supporting various modulation methods by using a single non-binary code, and the method comprising the steps of: shortening, on the basis of a modulation method, at least one information bit in at least one information symbol constituting the non-binary code; encoding the at least one information symbol having a shortened information bit; and puncturing, on the basis of the modulation method, at least one parity code in at least one parity symbol obtained through the encoding step.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates a method and an apparatus for efficiently shortening and puncturing non-binary Low Density Parity Check (LDPC) code. 
       BACKGROUND ART 
       [0002]    To meet the demand for wireless data traffic having increased since deployment of 4th generation (4G) communication systems, efforts have been made to develop an improved 5th 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 LTE System’. 
         [0003]    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. 
         [0004]    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. 
         [0005]    In the 5G system, Hybrid FSK and QAM 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. 
         [0006]    A Low Density Parity Check (LDPC) code has an excellent performance for various channel states and modulation schemes. However, in the LDPC code, a length and a code rate of a code word are determined according to a parity check matrix. In order to overcome disadvantages of the LDPC that cannot support various code word lengths and code rates, information word shortening and parity puncturing are used to support a predetermined code word length and code rate. 
         [0007]    In general, a non-binary code has a gain in terms of a channel capacity compared to a binary code in various channel states and modulation schemes. However, the non-binary code has a modulation scheme and a demodulation scheme that change according to a relation between a q value of a non-binary finite field GF (q) in which the code is defined and an M value that is a modulation order of a M-Quadrature Amplitude Modulation (QAM) modulation scheme. That is, the system should have a plurality of encoders and decoders that can support all of them to make an optimum performance, but this is not efficient in consideration of system complexity. 
         [0008]    As a result, in various modulation schemes, using a single non-binary code may be a more efficient method. Accordingly, it may be required to provide a shortening and puncturing method using a single non-binary code in various modulation schemes. 
       DETAILED DESCRIPTION OF THE INVENTION 
     Technical Problem 
       [0009]    Accordingly, an embodiment of the present invention provides a method and an apparatus for efficiently shortening and puncturing a non-binary Low Density Parity Check (LDPC) code. 
         [0010]    Another embodiment of the present invention provides a method and an apparatus for performing shortening and puncturing to uniformly include modulation symbols in non-binary codes. 
         [0011]    Another embodiment of the present invention provides a method and an apparatus for performing shortening and puncturing in consideration of a modulation symbol corresponding to a modulation scheme by a transmitter. 
         [0012]    Another embodiment of the present invention provides a method and an apparatus for performing shortening and puncturing based on a code rate and/or a code length and a modulation scheme by a transmitter. 
       Technical Solution 
       [0013]    According to an embodiment of the present invention, a method of a transmission end for shortening and puncturing a non-binary code includes: shortening at least one information bit in at least one information symbol included in a non-binary code based on a modulation scheme; encoding at least one information symbol in which the information bits are shortened; and puncturing at least one parity code in at least one parity symbol acquired through the encoding based on the modulation scheme. 
         [0014]    According to an embodiment of the present invention, an apparatus of a transmission end for shortening and puncturing a non-binary code includes: an information bit shortening performing unit for shortening at least one information bit in at least one information symbol included in a non-binary code based on a modulation scheme; an encoding unit for encoding at least one information symbol in which the information bits are shortened; and a parity bit puncturing performing unit for puncturing at least one parity code in at least one parity symbol acquired through the encoding based on the modulation scheme. 
       Effects of the Invention 
       [0015]    In the present invention, a transmission end may shorten information bits to include bits corresponding to a modulation order in each of the information symbols included in a non-binary code as uniformly as possible, acquire at least one parity symbol by encoding the information symbols in which the information bits have been shortened, and then select and puncture parity bits to include bits corresponding to the modulation order in each of the parity symbols as uniformly as possible, thereby supporting various modulation schemes based on a single non-binary code. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a block diagram illustrating a transmission end in a communication system according to an embodiment of the present invention; 
           [0017]      FIG. 2  illustrates a non-binary code according to an embodiment of the present invention; 
           [0018]      FIG. 3  illustrates a process of shortening and puncturing bits of a non-binary code in a communication system according to an embodiment of the present invention; 
           [0019]      FIG. 4  illustrates an example of shortening information bits of a non-binary code in a communication system according to an embodiment of the present invention; 
           [0020]      FIG. 5  illustrates another example of shortening information bits of a non-binary code in a communication system according to an embodiment of the present invention; 
           [0021]      FIG. 6  illustrates a process of shortening and puncturing bits of a non-binary code in a communication system according to another embodiment of the present invention; 
           [0022]      FIG. 7  illustrates an example of shortening and puncturing information bits of a non-binary code in a communication system according to another embodiment of the present invention; 
           [0023]      FIG. 8  illustrates another example of shortening and puncturing information bits of a non-binary code in a communication system according to another embodiment of the present invention; and 
           [0024]      FIG. 9  illustrates an example of shortening and puncturing bits of a non-binary code in a communication system according to an embodiment of the present invention. 
       
    
    
     MODE FOR CARRYING OUT THE INVENTION 
       [0025]    Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. Further, in the following description of the present invention, a detailed description of known functions or configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. Further, terms described later are defined in consideration of functions of the present invention, but may vary according to the intention or convention of a user or operator. Therefore, the definitions of the terms should be made based on the contents throughout the specification. 
         [0026]    In an embodiment of the present invention, a method of shortening and puncturing information bits and parity bits constituting a non-binary code will be described to support various modulation schemes using a single non-binary LDPC code. 
         [0027]      FIG. 1  is a block diagram illustrating a transmission end in a communication system according to an embodiment of the present invention. 
         [0028]    At this time, the transmission end may be a device such as a base station, a terminal, or the like that transmits a signal. 
         [0029]    Referring to  FIG. 1 , a transmission end  100  may include a transceiver  101 , a controller  111 , and a storage unit  113 . 
         [0030]    The transceiver  101  controls and processes a function for transmitting and receiving a signal to and from a reception end according to a control of the controller  111 . Particularly, although the transceiver  101  according to an embodiment of the present invention may be configured as one module for convenience of the description, the transceiver  101  may be configured as a transmitter and a receiver separated from each other according to a design method. 
         [0031]    The transceiver  101  according to an embodiment of the present invention may include an information bit shortening performing unit  103 , an encoding unit  105 , a parity bit puncturing performing unit  107 , and a modulation unit  109 , and may shorten and encode information bits within the non-binary code and then perform a function for puncturing parity bits within the non-binary code. 
         [0032]    The information bit shortening performing unit  103  may select at least one bit to be shortened according to a modulation order corresponding to a modulation scheme in at least one information symbol constituting the non-binary code. At this time, the non-binary code may include an information symbol  201  including at least one information bit and a parity symbol  203  including at least one parity bit as illustrated in  FIG. 2 . The information bit shortening performing unit  103  may select and shorten the information bits such that bits corresponding to a modulation order are included in each information symbol constituting the non-binary code as uniformly as possible. The information bit shortening performing unit  101  according to an embodiment of the present invention may determine the number of bits to be shortened based on a code rate and/or a code length, select information bits to be shortened to most uniformly include bits corresponding to a modulation order in each information symbol constituting the non-binary code based on the number of bits and the modulation order, and shorten the selected information bits. The information bit shortening performing unit  103  according to another embodiment of the present invention may shorten other bits except for the bits corresponding to the modulation order within each information symbol constituting the non-binary code based on the modulation order. At this time, the information bit shortening performing unit  103  may check whether additional shortening is needed based on the code rate and/or the code length and, when the additional shortening is needed, perform shortening in the unit of information symbols according to the code rate and/or the code length. Here, the shortened bit refers to a bit considered to have a 1 chance of being 0 and a 0 change of being 1. According to an embodiment of the present invention, a method of shortening information bits to make bits corresponding to the modulation order included as uniformly as possible will be described in detail with reference to the following drawings. 
         [0033]    The encoding unit  105  may encode at least one information symbol having the information bits shortened by the information bit shortening performing unit  103 . More specifically, the encoding unit  105  may perform an LDPC encoding on at least one information symbol having the shortened information bits, so as to acquire an LDPC code word to which at least one parity symbol is added. 
         [0034]    The parity bit puncturing performing unit  107  may select at least one bit to be punctured according to a modulation order in at least one parity symbol within the LDPC code word acquired by the encoding unit  105 . The parity bit puncturing performing unit  107  may select and puncture parity bits such that bits corresponding to the modulation order are included in each parity symbol constituting the non-binary code as uniformly as possible. The parity bit puncturing performing unit  107  according to an embodiment of the present invention may select parity bits to be punctured such that bits corresponding to the modulation order are included in at least one parity symbol within the LDPC code word as uniformly as possible based on the number of shortened bits and the modulation order, and may puncture the selected parity bits. The parity bit puncturing performing unit  107  according to another embodiment of the present invention may puncture other bits except for the bits corresponding to the modulation order in at least one parity symbol within the LDPC code based on the modulation order. At this time, the parity bit puncturing performing unit  107  may check whether additional puncturing is needed based on the code rate and/or the code length and, when the additional puncturing is needed, perform puncturing in the unit of information symbols according to the code rate and/or the code length. Here, the punctured bit refers to a bit considered to have a ½ chance of being 0 and a ½ chance of being 1. At this time, a location of the punctured parity bit of the parity symbol may correspond to a location of the shortened information bit of the information symbol. 
         [0035]    The modulation unit  109  may modulate the shortened and punctured non-binary code according to a predetermined modulation scheme. 
         [0036]    The controller  111  may control and process a general operation of the transmission end  100  to shorten and puncture the non-binary code. 
         [0037]    The storage unit  113  may store various types of data and programs required for the operation of the transmission end. According to an embodiment of the present invention, the storage unit  111  may store information on a code rate and/or a code length required by the system in the information symbol. 
         [0038]      FIG. 3  illustrates a procedure of, when the number of bits to be shortened is predetermined in a communication system, shortening and puncturing bits of the non-binary code according to an embodiment of the present invention. 
         [0039]    Referring to  FIG. 3 , the transmission end  100  may determine the number of information bits to be shortened in step  301 . In other words, the transmission end  100  may determine the number of information bits to be shortened within the information symbol constituting the non-binary code based on the code rate and/or the code length required by the system. For example, the transmission end  100  may identify that 6 information bits within the information symbol should be shortened based on the code rate and/or the code length required by the system. 
         [0040]    Thereafter, the transmission end  100  may shorten the information bits according to a modulation order of the modulation scheme such that modulation bits are included in at least one information symbol as uniformly as possible in step  303 . For example, when the number of information bits to be shortened is 6 and the non-binary LDPC code designed in the non-binary finite field GF (64) supports 16 Quadrature Amplitude Modulation (QAM), the transmission end  100  may perform shortening three times  411  to  415 , by two bits each, in the information symbols  401  to  407  in order to include the lower four bits  421  to  427  corresponding to the modulation order 16 in each of the information symbols  401  to  407  as uniformly as possible. In another example, when the number of information bits to be shortened is 8 and the non-binary LDPC code designed in the non-binary finite field GF (64) supports 16 QAM, the transmission end  100  may perform shortening four times, by two bits each, in the information symbols in order to uniformly include the lower four bits corresponding to the modulation order 16 in each information symbol. In another example, when the number of information bits to be shortened is 3 and the non-binary LDPC code designed in the non-binary finite field GF (64) supports 32 QAM, the transmission end  100  may perform shortening three times, by one bit each, in the information symbols in order to uniformly include the lower five bits corresponding to the modulation order 32 in each information symbol in order to include lower four bits  421  to  427  in each of the information symbols  401  to  407  as uniformly as possible. In another example, when the number of information bits to be shortened is 4 and the non-binary LDPC code designed in the non-binary finite field GF (64) supports 32 QAM, the transmission end  100  may perform shortening four times, by one bit each, in the information symbols in order to uniformly include the lower five bits corresponding to the modulation order 32 in each information symbol. 
         [0041]    Thereafter, the transmission end  100  may identify whether the determined number of bits to be shortened is larger than the number of shortened bits in step  305 . 
         [0042]    When the predetermined number of bits to be shortened is larger than the number of shortened bits, the transmission end  100  may shorten the bits to minimize a channel capacity loss in step  307 . For example, when the number of information bits to be shortened is 12 and the non-binary LDPC code designed in the non-binary finite field GF (64) supports 16 QAM, the transmission end  100  performs shortening four times  511  to  517 , by two bits each, in the information symbols  501  to  507  in order to uniformly include the lower four bits  521  to  527  corresponding to the modulation order 16 in each of the information symbols  501  to  507 . However, in this event, 8 bits have been shortened, which are smaller than 12 bits corresponding to the number of bits to be shortened determined in step  301 , and thus, four more bits should be shortened. Accordingly, the transmission end  100  may perform shortening of 4 bits  519  in the unit of information symbols to minimize the channel capacity loss. Therefore, the transmission end  100  may perform the shortening such that as many bits corresponding to the modulation order as possible are included in each information symbol constituting the non-binary code. 
         [0043]    Thereafter, the transmission end  100  may acquire parity symbols by encoding the shortened information symbols in step  309 . For example, the transmission end  100  may acquire parity symbols including at least one parity bit by performing an LDPC encoding on the shortened information symbols. 
         [0044]    Thereafter, the transmission end  100  may puncture the parity bits according to the modulation order such that bits corresponding to the modulation order are included in at least one parity symbol acquired through the encoding as uniformly as possible in step  311 . At this time, the transmission end  100  may puncture the parity bits within the parity symbol in the same way as that of shortening the information bits within the information symbol. In other words, a location of the punctured parity bit of the parity symbol may correspond to a location of the shortened information bit. 
         [0045]    In contrast, when the number of bits to be shortened determined in step  305  is not larger than the number of shortened bits, the transmission end  100  may proceed to step  309  and perform the following steps. In other words, when the number of bits to be shortened, which is determined in step  301 , is the same the number of bits shortened in step  303 , the transmission end  100  may proceed to step  309  and perform the following steps. 
         [0046]    Thereafter, the transmission end  100  may end the procedure according to the embodiment of the present invention. 
         [0047]      FIG. 6  illustrates a procedure of, when the number of bits to be shortened is not predetermined, shortening and puncturing bits of the non-binary code in the communication system according to an embodiment of the present invention. 
         [0048]    Referring to  FIG. 6 , the transmission end  100  may select at least one information bit and at least one parity bit to be modulated according to a modulation order of a modulation scheme within at least one symbol in step  601 . More specifically, the transmission end  100  may determine at least one information bit to be modulated within at least one information symbol and determine at least one parity bit to be modulated within at least one parity symbol based on the modulation order. For example, the transmission end  100  may select bits corresponding to the modulation order within at least one information symbol as the bits to be modulated and determine the remaining bits except for the selected bits as the bits to be shortened. Further, the transmission end  100  may select bits corresponding to the modulation order within at least one parity symbol as the bits to be modulated and determine the remaining bits except for the selected bits as the bits to be punctured. 
         [0049]    Thereafter, the transmission end  100  may shorten and puncture the information bits and the parity bits that have not been selected within each symbol in step  605 . In other words, the transmission end  100  may shorten the remaining information bits except for the information bits to be modulated within at least one information symbol and puncture the remaining parity bits except for the parity bits to be modulated within at least one parity symbol. 
         [0050]    Thereafter, the transmission end  100  may end the procedure according to the embodiment of the present invention. 
         [0051]      FIG. 6  described above illustrates a method by which the transmission end  100  shortens and punctures the non-binary code in consideration of only the modulation order corresponding to the modulation scheme. For example, when the non-binary LDPC code designed in the non-binary finite field GF (64) supports 32 FQAM, the transmission end  100  may select lower 5 bits  701  and  707  corresponding to a modulation order 32 within the information symbol as information bits to be modulated and select lower 5 bits  711  and  711  corresponding to the modulation order 32 within the parity symbol as 5 bits of parity bits to be modulated, and may then shorten the remaining information bits  703  and  705  that have not been selected and puncture the remaining parity bits  713  and  715  that have not been selected as illustrated in  FIG. 7 . In another example, when the non-binary LDPC code designed in the non-binary finite field GF (64) supports 16 FQAM, the transmission end  100  may select lower 4 bits  801  and  807  corresponding to a modulation order 16 within the information symbol as information bits to be modulated and select lower 4 bits  801  and  807  corresponding to the modulation order 16 within the parity symbol as parity bits to be modulated, and may then shorten the remaining information bits  803  and  805  that have not been selected and puncture the remaining parity bits  813  and  815  that have not been selected as illustrated in  FIG. 8 . 
         [0052]    In addition, when the shortening and the puncturing are performed using the method of  FIG. 6 , the transmission end  100  may check whether additional shortening and puncturing are needed based on the code rate and/or the code length required by the system. That is, the transmission end  100  may check whether as many bits as the number of bits to be shorted and to be punctured determined according to the code rate and/or the code length required by the system have been shortened and punctured. When it is determined that the as many bits as the number of bits to be shorted and to be punctured determined according to the code rate and/or the code length required by the system have not been shortened and punctured, the transmission end  100  may further perform the shortening and puncturing based the number of bits that are required to be shortened and punctured. 
         [0053]      FIG. 9  illustrates an example of shortening and puncturing bits of the non-binary code in the communication system according to an embodiment of the present invention. 
         [0054]    As illustrated in  FIG. 9 , the transmission end  100  may select and shorten information bits such that bits corresponding to a modulation order are included in each information symbols as uniformly as possible based on the modulation order of a modulation scheme in information symbols including at least one information symbol. Thereafter, the transmission end  100  may acquire an LDPC code word to which a parity symbol for each information symbol is added through an encoding of the shortened information symbols. The transmission end  100  may select parity bits to be punctured such that bits corresponding to the modulation order are included in at least one parity symbol included in the acquired LDPC code word as uniformly as possible, and may puncture the selected parity bits. Thereafter, the transmission end  100  may modulate the shortened and punctured LDPC code word and then transmit the modulated LDPC code word to a reception end through an antenna. 
         [0055]    Embodiments and all functional operations described in the present invention may be carried out by computer software, firmware, hardware, or one or more combinations thereof, which include the structures disclosed in the present invention and equivalent structures thereof. Further, embodiments of the present invention described in the present invention may be executed by one or more computer program products, i.e. data processing devices, or carried out by one or more modules of computer program commands encoded in computer-readable media for controlling the operations of the devices. 
         [0056]    A computer-readable medium may be a machine-readable storage medium, a machine-readable storage substrate, a memory device, a configuration of a material influencing a machine-readable electric wave stream, or one or more combinations thereof. The term “data processing device” includes, for example, a programmable processor, a computer, or all nodes, devices, and machines, including a multi-processor or computer, for processing data. The node may include, in addition to hardware, a code that creates an execution environment for a computer program, for example, a code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or one or more combinations thereof. 
         [0057]    Although specific exemplary embodiments have been described in the detailed description of the present invention, various change and modifications may be made without departing from the spirit and scope of the present invention. Therefore, the scope of the present invention should not be defined as being limited to the embodiments, but should be defined by the appended claims and equivalents thereof.