Method and device for encoding in wireless communication system

The present disclosure relates to a 5th Generation (5G) or a pre-5G communication system provided to support a higher data transmission rate than a system beyond a 4th Generation (4G) communication system such as Long Term Evolution (LTE). The purpose of the present disclosure is to maximize adaptive transmission performance by designing a puncturing order and a repetition order individually in optimized order. An operation method of a transmission device for adaptive transmission of a codeword according to an embodiment of the present disclosure includes generating a codeword using a polar code and transmitting a packet including at least one codeword indicated by a repetition order when bit repetition is needed. The repetition order is determined based on at least one of channel polarization or channel quality information.

This application claims the priority under 35 U.S.C. § 119(a) to Korean Application Serial No. 10-2015-0184251, which was filed in the Korean Intellectual Property Office on Dec. 22, 2015, the entire content of which is hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to a method and device for encoding in a wireless communication system.

BACKGROUND

To meet the demand for wireless data traffic having increased since deployment of 4 G communication systems, efforts have been made to develop an improved 5G or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4 G Network’ or a ‘Post LTE System’.

An adaptive transmission system may be divided into initial transmission and retransmission after the initial transmission. The retransmission may be performed when an error has occurred in previous transmission and a Negative ACKnowledge (NACK) message is thus received from a reception terminal. When the initial transmission is performed, a transmission device performs transmission using a coding rate determined based on channel information. The transmission device may increase a decoding success rate when the retransmission is performed at the later time, by additionally transmitting a parity. A representative adaptive transmission system is a technology called a Hybrid Automatic Repeat-Request (HARQ).

The transmission device may be able to perform adaptive transmission through a circular buffer after applying interleaving to a codeword generated by polar coding. The interleaving may be available in an interleaver. The interleaver arranges bits to be punctured and puts them in a later order so as to enable the bits to be sequentially transmitted in the circular buffer. However, in a conventional system, the interleaver is designed to interleave a codeword in consideration of puncturing only. Therefore, there is a problem in which transmission optimized for repetition cannot be guaranteed when transmission is repeatedly performed after completion of transmission of punctured bits.

SUMMARY

To address the above-discussed deficiencies, it is a primary object to provide a device and method for data encoding in a wireless communication system.

Another embodiment provides a device and method for data encoding using a polar code in a wireless communication system.

Still another embodiment provides a transmission device and method for adaptive transmission of a codeword in a wireless communication system.

Still another embodiment provides a device and method for repeatedly transmitting a codeword when an error message is received from a reception device in a wireless communication system.

Still another embodiment provides a device and method for determining a repetition order for repeatedly transmitting a codeword in a wireless communication system.

Still another embodiment provides a device and method for determining a repetition order based on channel polarization in a wireless communication system.

Still another embodiment provides a device and method for determining a repetition turn based on channel quality information in a wireless communication system.

Still another embodiment provides a device and method for determining a repetition order through a bit-reversal calculation in a wireless communication system.

Still another embodiment provides a device and method for determining a repetition order based on a channel state in a wireless communication system.

An operation method of a transmission device in a wireless communication system according to various embodiments of the present disclosure includes: generating a codeword using a polar code; and transmitting a packet including at least one codeword indicated by a repetition order when bit repetition is needed, in which the repetition order is determined based on at least one of channel polarization and channel quality information.

An operation method of a reception device in a wireless communication system according to various embodiments of the present disclosure includes: receiving a packet including at least one bit indicated by a repetition order; and decoding the packet received based on the repetition order, in which the repetition order is determined based on at least one of channel polarization and channel quality information.

A transmission device in a wireless communication system according to various embodiments of the present disclosure includes: a communication unit configured to transmit or receive a signal; and a control unit configured to generate a codeword using a polar code, and control transmission of a packet including at least one codeword indicated by a repetition order when bit repetition is needed, in which the repetition order is determined based on at least one of channel polarization and channel quality information.

A reception device in a wireless communication system according to various embodiments of the present disclosure includes: a communication unit configured to receive a packet including at least one bit indicated by a repetition order; and a control unit configured to decode the packet based received on the repetition order, in which the repetition order is determined based on at least one of channel polarization and channel quality information.

A polar code designed based on puncturing and a repetition transmission pattern used when the polar code is designed based on repetition, after all punctured bits are retransmitted, can ensure excellent performance compared to a conventional technology through a method for determining the repetition transmission pattern to be used.

DETAILED DESCRIPTION

Hereinafter, the operating principle of the present disclosure will be described in detail with reference to the accompanying drawings. In describing the present disclosure below, a detailed description of related known configurations or functions incorporated herein will be omitted when it is determined that the detailed description thereof may unnecessarily obscure the subject matter of the present disclosure. The terms which will be described below are terms defined in consideration of the functions in the present disclosure, and may be different according to users, intentions of the users, or customs. Therefore, the definitions of the terms should be made based on the contents throughout the specification.

Hereinafter, the present disclosure will describe a technique for transmitting a codeword in a wireless communication system.

Hereinafter, a term referring to control information, a term referring to a state change, a term referring to a change state of a bit stream according to encoding, terms referring to network entities, terms referring to messages, terms referring to elements of a device, etc., are provided as examples for convenience of description. Therefore, the present disclosure is not limited to the following terms, and other terms having the equivalent technical meanings may be used.

In the present disclosure, an adaptive transmission system is considered. A transmission device may use a polar code for message encoding. The adaptive transmission system considered in the present disclosure may include initial transmission and retransmission after the initial transmission. The retransmission may be performed when an error has occurred in previous transmission and a Negative ACKnowledge (NACK) message is thus received from a reception terminal. When the initial transmission is performed, the transmission device may perform transmission using a coding rate determined based on channel information. When the retransmission is performed at the later time, the transmission device may use a scheme in which a parity is additionally transmitted so as to increase a decoding success rate. A representative adaptive transmission system is a technology called a Hybrid Automatic Repeat-Request (HARQ). An embodiment of the present disclosure describes a method and device for transmitting a polar code based on a HARQ, but such a description should not be understood as a limitation of the embodiment. Therefore, the embodiment of the present disclosure may include all transmission systems which the technical idea of the present disclosure may affect.

The present disclosure deals with adaptive transmission of a codeword which is encoded using a polar code and, particularly, proposes an effective retransmission method in which a design feature of the polar code is considered.

Before describing operating principles of various embodiments, a general operating principle of a polar encoder is described. An input of a polar encoder may be defined as Ma having K+α bits, and an output may be defined as X having N bits. Necessary symbols for describing polar encoding are defined in TABLE 1 below.

TABLE ISignMeaningGNA polar code generator matrix having the size of N × N, in whichN = 2n.Defined as GN= BN, in which BN is a bit-reversal matrixhaving the size of N × N proposed by Arikan, andF=[1011]⁢,⊗n⁢⁢means⁢⁢n⁢-⁢th⁢⁢operation⁢⁢of⁢⁢Kronecker⁢⁢product.GNNon−can be also used as a generator matrix of a polarcode.The meaning of BN matrix will be described using an example,hereinafter.In the present document, GN is mainly considered as a polar codegenerator matrix, and the proposed technology of the disclosure canbe also applied when GNNonis used as a generator matrix.IInformation set of a polar codeA set having the size of K + α, which is a subset of {0, 1, 2, . . . ,N − 1}I is a set generated based on a channel polarization phenomenon,and a detailed description of a method for generating I is omitted.GN(I)A sub-generator matrix of a polar code, having the size of(K + α) × N.With respect to all i ∈ I, a sub-generator matrix having (i + 1)throws in GNmatrix.U(I)U is a row vector (U = u0, u1, . . . , uN−1) having the size of N × 1.U(I) is defined as U (I) = (ui:i ∈ I), and is a sub-vector of U.The order of components within vector U(I) follows the order ofcomponents within vector U.

All polar codes having the code length of N may be expressed as generator matrix GN(I). With respect to information set I having the size of K+α, polar encoding may be indicated as EQUATION 1. In this case, multiplication is performed by a binary operation.
Mα×GN(I)=X[EQUATION 1]

In EQUATION 1, Mαis a row vector having the size of K+α, sub-generator matrix GN(I) has the size of (K+α)×N, and therefore X is a binary vector having the size of 1×N. The X is a codeword of a polar code and is modulated into a signal so as to pass through a channel.

In EQUATION 2, G8is a polar code generator matrix having the size of 8×8, and G8Nonis a matrix generated through a bit-reversal of G8.

Rearrangement of rows in a bit-reversal order is as follows. First, zero to seven are sequentially assigned, as indexes, to the first row to the last row of matrix G8Non. Since N=8, when each index is extended to a three-bit binary number, the outcome corresponds to (000), (001), (010), (011), (100), (101), (110), (111). When the order of the first and last bits of each index is reversed while maintaining the order of row indexes, the outcome corresponds to (000), (100), (010), (110), (001), (101), (011), (111). When these values extended to three-bit binary numbers are converted to integer values, the outcome corresponds to 0, 4, 2, 6, 1, 5, 3, 7. That is, matrix G8is generated by rearranging the rows of matrix G8Nonin 0, 4, 2, 6, 1, 5, 3, 7 row index order. In the same manner, matrix G8Nonis generated by rearranging the rows of matrix G8in the bit-reversal order.

As an embodiment of the present disclosure, G8is considered between the two matrices above. In matrix G8, a sub-generator matrix G8(I) is determined according to the size and elements of set I. If K+α=4 and I={3, 5, 6, 7} in which I is an information set of a polar code, rows used to generate the sub-generator matrix G8(I) in matrix G8are rows corresponding to values generated by adding one to each element of I. That is, fourth, sixth, seventh, and eighth rows are used to constitute matrix G8(I), and matrix G8(I) has the size of 4×8 like EQUATION 3.

In EQUATION 3, K+α information bits are polar encoded through matrix G8(I), and this process may be expressed like EQUATION 4 (information bits are expressed as bi).

FIG. 1illustrates a polar encoder for a polar encoding process described above.

InFIG. 1, the block130on the right indicates a polar encoder using G8. Reference numeral110inFIG. 1expresses an enlarged view of a data input unit of the polar encoder. Eight elements of U=(u0, u1, . . . , u7) are input from the left side of the polar encoder, and X which has been mentioned above corresponds to output. However, each element of U operates as a switch, and operates in a mode in which a fixed value is transmitted or in a mode in which an information bit is transmitted.FIG. 1is a case where the fixed value is zero as expressed in reference numeral110.

When I={3, 5, 6, 7} like an example described above, an electronic device always inputs a fixed value of zero through U(Ic)=(u0, u1, u2, u4) and transmits an information bit through remaining positions of U(I)=(u3, u5, u6, u7). Four information bits have one-to-one mapping relationship with u3, u5, u6, u7bits.

A transmission device may use a block coding technique in an encoding process using a polar code. Therefore, when a polar code for initial transmission is designed, the transmission device may design a codeword based on puncturing or repetition and perform transmission. The present disclosure proposes a scheme for determining an optimal repetition transmission pattern used for a repetition-based design and a repetition transmission pattern used after the polar code designed based on puncturing has retransmitted all the punctured bits according to a retransmission request of a reception side.

FIG. 2illustrates a transmission device according to the present disclosure. The terms including “- unit” and “- device” which will be used below mean a unit which processes at least one function or operation, and may be implemented by hardware, software, or a combination of hardware and software. Referring toFIG. 2, the transmission device includes a communication unit210, a storage unit220, and a control unit230.

The communication unit210performs functions for transmitting or receiving a signal through a wireless channel. For example, the communication unit210performs a function of conversion between a baseband signal and a bit stream according to a physical layer standard of the system. For example, when data is transmitted, the communication unit210generates complex symbols by encoding and modulating a transmission bit stream. Also, when data is received, the communication unit210reconstructs a reception bit stream by demodulating and decoding a baseband signal. Also, the communication unit210performs an uplink conversion of a baseband signal to a radio frequency (RF) band signal and then transmits the same through an antenna, and performs a downlink conversion of the RF band signal received through the antenna to a baseband signal. For example, the communication unit210may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a Digital to Analog Convertor (DAC), an Analog to Digital Convertor (ADC), and so on.

Also, the communication unit210may include a plurality of RF chains. Further, the communication unit210may perform beamforming. For beamforming, the communication unit210may adjust the size and phase of each of signals transmitted or received through a plurality of antennas or antenna elements. Further, the communication unit210may include a plurality of communication modules in order to support a plurality of wireless access technologies which are different from each other.

Also, the communication unit210may include different communication modules in order to process signals in different frequency bands. For example, different communication standards may include Bluetooth Low Energy (BLE), Wi-Fi Gigabyte (WiGig), a cellular network (e.g., Long Term Evolution (LTE)), and so on. Also, different frequency bands may include a Super High Frequency (SHF) (e.g., 2.5 GHz and 5 Ghz) and a millimeter wave (e.g., 60 GHz).

The communication unit210transmits and receives a signal as described above. Accordingly, the communication unit210may be referred to as a transmission unit, a reception unit, or a transmission or reception unit. Also, in description hereinafter, the meaning of transmission and reception performed through a wireless channel includes performing a process by the communication unit210in the same manner as described above.

The storage unit220stores data such as a basic program, an application program, and configuration information, for an operation of the transmission device. The storage unit220may include a volatile memory, a non-volatile memory, or a combination of a volatile memory and a non-volatile memory. Particularly, the storage unit220may store an interleaving address for determining a transmission order of a polar code according to an embodiment of the present disclosure. Specifically, the storage unit220may store an interleaving address for puncturing-based transmission when the polar code is designed based on puncturing, and an interleaving address for transmitting a repeated bit after all punctured bits have been transmitted. Alternatively, the storage unit220may store an interleaving address for repetition-based transmission when the polar code is designed based on repetition. In addition, the storage unit220provides stored data according to a request of the control unit230.

The control unit230controls overall operations of the transmission device. For example, the control unit230transmits or receives a signal through the communication unit210. Also, the control unit230records data in the storage unit220and reads the same. To this end, the control unit230may include at least one processor or a microprocessor, or may be a part of a processor. Also, a part of the communication unit210and the control unit230may be referred to as a Communication Processor (CP). Particularly, the control unit230controls the transmission device to generate an interleaving address according to various embodiments which will be described hereinafter. Alternatively, the control unit230may determine a repetition order based on a structured algorithm. According to the present disclosure, a repetition order may be referred to as a repetition transmission order, a repetition pattern or repetition transmission order, and so on. For example, the control unit230may control the transmission device to perform processes illustrated inFIGS. 5 to 10below.

The transmission device according to the present disclosure includes all devices which transmit a codeword using an adaptive transmission method. For example, the transmission device may include a smart phone, a computer, a cellular phone, a user equipment, a mobile station (MS), or a multimedia device capable of performing a communication function.

In some embodiments, the device ofFIG. 2may also operate as a reception device.

FIG. 3illustrates a flow diagram indicating an operation method of a transmission device for adaptive transmission of a polar code according to the present disclosure.

Referring toFIG. 3, the transmission device generates a polar code, in step301. Specifically, the transmission device may generate polar code X having N bits through a polar coder, using input Mαhaving K+α bits. For example, the transmission device may generate polar code X through the polar encoder presented throughFIG. 1. In a situation where K+α bits are encoded into N1bits and transmitted when N1is smaller than N, the transmission device may determine a codeword based on puncturing. Alternatively, in a situation where K+α bits are encoded into N1bits and transmitted when N1is greater than N, the transmission device may determine a codeword based on repetition.

In step303, the transmission device transmits a packet including at least one bit indicated by a repetition order. Specifically, when a codeword is designed based on repetition and transmitted, the transmission device may transmit a packet including at least one bit indicated by a repetition order. Alternatively, when a codeword is designed based on puncturing and transmitted, the transmission device may transmit a packet including at least one bit indicated by a repetition order in a retransmission process according to an error report of a reception side. The transmission device may determine the repetition order based on at least one of a channel polarization principle, channel quality information, and a bit-reversal calculation. The transmission device may store the repetition order through a scheme for addressing the same in a memory. For example, the transmission device may store, in a memory, the repetition order determined based on a channel polarization principle. Alternatively, the transmission device may store, in a memory, the repetition order determined based on channel quality information. Alternatively, the transmission device may store, in a memory, the repetition order determined based on a bit-reversal calculation. When a codeword is required to be repeatedly transmitted, the transmission device may determine a repetition order using the repetition order stored in the memory.

Although not illustrated inFIG. 3, the transmission device may transmit a message including information on the repetition order of the polar code to a reception device. For example, a repetition order may be transmitted as a part of resource allocation information, feedback information, or system information.

FIG. 4illustrates a flow diagram indicating an operation method of a reception device for receiving a polar code according to the present disclosure.

Referring toFIG. 4, a reception device may receive a packet including at least one bit indicated by a repetition order, in step401. Specifically, when a codeword is designed based on repetition and transmitted, the reception device may receive a packet including at least one bit indicated by a repetition order. Alternatively, when a codeword is designed based on puncturing and transmitted, the reception device may receive a packet including at least one bit indicated by a repetition order in a retransmission process according to an error report. The repetition order may be determined, by a transmission device, based on at least one of a channel polarization principle, channel quality information, and a bit-reversal calculation. The transmission device may receive a message including information on the repetition order from the reception device.

In step403, the reception device decodes the packet received based on the repetition order. Specifically, the reception device may decode the packet received based on information on the repetition order transmitted from the transmission device. That is, according to an embodiment, the reception device may decode the packet after receiving the message including information on the repetition order from the transmission device. According to another embodiment, a repetition order may be predefined. In this case, the repetition order may not be received from the transmission device. Although not illustrated inFIG. 4, the reception device may request retransmission of a codeword from the transmission device when decoding of a normally received packet fails.

FIGS. 5A to 5Cillustrate block diagrams for adaptive transmission of a polar code according to the present disclosure. According to an embodiment,FIG. 5indicates a method for adaptively transmitting a polar code, which is designed based on repetition or puncturing, on the basis of a puncturing order (PO) or a repetition order (RO) which are stored in an interleaving address storage unit. Although not illustrated inFIG. 5, the interleaving address storage unit, which is not displayed through a drawing, may be included in a part of a memory.

The transmission device may determine a repetition order based on at least one of a channel polarization principle, channel quality information, and a bit-reversal calculation. The transmission device may store the determined repetition order in the interleaving address storage unit.

Specifically,FIGS. 5A and 5Billustrate block diagrams for adaptive transmission when N is greater than N1in a transmission system. That is, a transmission method, in a situation where K+α bits are encoded into N1bits and transmitted when N1is smaller than N, is indicated.FIG. 5Aindicates a first transmission method andFIG. 5Bindicates a transmission method in which second transmission, third transmission, etc. are included, except for first transmission.

Referring toFIG. 5A, the transmission device may generate polar code X via a polar encoding process of message Mα, using a polar encoder510. According to an embodiment, message Mαmay be a row vector having the size of K+α, and polar code X may have the length of N. Here, the length of N of polar code “X” may be 2n(n is a positive integer). Therefore, the transmission device may use a puncturing technique or a repetition technique in order to design a polar code which supports various lengths. The transmission device may temporarily store codeword X in a buffer530for adaptive transmission. That is, the transmission device may temporarily store codeword X in the buffer530for transmission based on the puncturing order or the repetition order.

As described above, when N is greater than N1, the transmission device may use polar code X designed based on puncturing. The transmission device may rearrange codeword X temporarily stored in the buffer530in order to randomly disperse bit error occurrences. According to an embodiment of the present disclosure, the transmission device may transmit codeword X temporarily stored in the buffer530based on an interleaving address stored in the interleaving address storage unit550. When N is greater than N1, polar code X may be designed to be transmitted based on puncturing, and the transmission device may transmit codeword X based on an interleaving address551for the puncturing order according to the present disclosure. In other words, the transmission device may transmit bits located at address values indicated by an interleaving address551. Therefore, when a polar code punctured at initial transmission is transmitted and all punctured bits are transmitted according to a retransmission request, the transmission device may transmit codeword X based on the interleaving address551for the puncturing order. That is, the transmission device may transmit N1bit transmitted at first transmission and N−N1bits transmitted at second transmission according to the retransmission request, based on the interleaving address551for the puncturing order. Here, the N−N1bits transmitted at the second transmission may include bits punctured at the first transmission.

However, the puncturing order, in general, may not provide a repetition order optimized for repetition transmission. Therefore, according to an embodiment of the present disclosure, the transmission device may not use the puncturing order, as it stands, for repetition transmission performed after all punctured bits are transmitted, but determine a repetition order so as to perform repetition transmission according thereto. Specifically, the transmission device may perform repetition transmission based on repetition order one. Repetition order one may provide a repetition order of a polar code designed based on puncturing. The transmission device may determine repetition order one based on at least one of a channel polarization principle, channel quality information, and a bit-reversal calculation.

FIG. 5Billustrates a method for performing repetition transmission based on an interleaving address553for repetition order one when the transmission device performs repetition transmission after transmitting all punctured bits in a case where N is greater than N1. After all punctured bits have been transmitted, the transmission device may transmit codeword X stored in the buffer based on the interleaving address553for repetition order one in order to perform repetition transmission. For example, when an error has occurred at first transmission, that is, when an NACK message has been received from the reception device, the transmission device may perform a second transmission operation. The transmission device may preferentially include, at second transmission, bits punctured at first transmission according to the puncturing order and may repeatedly transmit remaining bits for satisfying transmission bit N1according to repetition order one. Alternatively, when an error has occurred at second transmission, the transmission device may perform repetition transmission based on repetition order one for third transmission.

Contrarily,FIG. 5Cillustrates a block diagram for adaptive transmission when N is smaller than N1in a transmission system. That is,FIG. 5Cindicates a transmission method when N1is greater than N in a situation where K+α bits are encoded into N1bits and transmitted. FIG.5C includes all transmission operations such as a first transmission operation, a second transmission operation, and so on.

Referring toFIG. 5C, the transmission device may generate codeword X via a polar encoding process of message Mα, using the polar encoder510. According to an embodiment, message Mαmay be a row vector having the size of K+α, and codeword X may have the length of N. The transmission device may temporarily store polar code X in the buffer530for adaptive transmission. That is, the transmission device may temporarily store codeword X in the buffer530in order to guarantee an optimal transmission order based on a puncturing order or a repetition order.

As described above, when N is smaller than N1, that is, when the transmission device should perform initial transmission using a lower coding rate than a code rate which a system supports, the transmission device may design polar code X based on repetition and transmit the same. The transmission device may rearrange codeword X temporarily stored in the buffer530in order to randomly disperse bit error occurrences. According to an embodiment of the present disclosure, the transmission device may transmit codeword X temporarily stored in the buffer based on an interleaving address stored in the interleaving address storage unit550. When N is smaller than N1, X is designed based on repetition. Therefore, the transmission device may transmit codeword X based on an interleaving address555for repetition order two according to an embodiment of the present disclosure. The repetition order two may be combined with a repetition-based polar code design so as to provide an optimal repetition order. Therefore, the transmission device may perform first transmission based on R0#1. That is, the transmission device may transmit N bits transmitted at the first transmission and repeated N−N1bits, according to repetition order two. Since all retransmissions such as second transmission and third transmission are for repetition transmission, when an error has occurred at the first transmission, the transmission device may perform retransmission based on repetition order two. The transmission device may determine repetition order two based on at least one of a channel polarization principle, channel quality information, and a bit-reversal calculation.

FIGS. 6A and 6Billustrate a design rule of a repetition order for adaptive transmission according to the present disclosure.FIG. 6provides a method for designing a repetition order using channel polarization according to an embodiment. The transmission device may use channel polarization which is a technique for synthesizing and separating channels having the same capacity for polar coding. An embodiment based on the channel polarization principle provides a method for determining a repetition order such that the capacities of the synthesized channels (W2, W4, . . . WN) are uniform.

InFIGS. 6A and 6B, reference numeral610indicates a polar encoder structure for N=8(=23) for the purpose of explanation, not limitation of the embodiment. Therefore, the embodiment of the present disclosure corresponds to N=2nand includes a polar encoder where the value of n is any integer.

FIG. 6Aillustrates a method for determining a repetition order when the number of repetition bits is two bits. Referring toFIG. 6A, the transmission device may generate polar code X={x0, x1, x2, x3, . . . , x7} through a polar encoder610. According to an embodiment, it may be assumed that the transmission device determines polar code X based on repetition and transmits the same. That is, the embodiment indicates a transmission method when N1is greater than N in a situation where K+α bits are encoded into N1bits and transmitted. For example, when N is eight and N1is 10, the transmission device may repeatedly transmit N1−N=2 bits at first transmission. In this case, the transmission device may determine a repetition order using channel polarization. For example, it may be assumed that one bit of x0to be transmitted through a first W4channel601is firstly repeated in a first transmission operation. In this case, the transmission device may secondly repeat, at the first transmission, one bit of x5to be transmitted through a second W4channel603for maintaining channel capacities uniform according to channel polarization. As a result, the transmission device may repeat two bits of x0and x5in the first transmission operation. The important point here is that the channel capacities are maintained uniform according to the channel polarization principle. Therefore, changing the repetition order of x0and x5is of no consequence as long as x5comes first and x0comes second. In addition, repetition of x0and x5is merely a simple example, and the transmission device may be able to perform repetition through a random combination for making channel capacities uniform in the first W4channel601and the second W4channel603.

According to another embodiment, it may be assumed that the transmission device has designed polar code X based on puncturing. That is, the embodiment indicates a transmission method when N1is smaller than N in a situation where K+α bits are encoded into N1bits and transmitted. In this case, the transmission device may transmit N1bits and puncture N−N1bits, in a first transmission operation. When a second transmission operation is requested according to a retransmission request of the reception device, the transmission device may preferentially include, in the second transmission operation, the N−N1bits punctured in the first transmission operation according to the puncturing order. Also, the transmission device may repeat N1−(N−N1)=2*N1−N bits using channel polarization, using the same method as that described above, so that N1bits are finally transmitted in the second transmission operation. However, in the second transmission operation, a coding rate may be changed according to a channel state and N1bits and other random bits may be transmitted as a result. In this case, the number of repeated bits using channel polarization may be changed. In embodiments hereinafter, it is assumed that all transmissions (i.e., initial transmission and all retransmissions) are performed using N1bits for the purpose of explanation. However, such an assumption does not exclude an embodiment in which data is transmitted using sizes other than N1bits.

FIG. 6Billustrates a method for designing a repetition order when the number of repetition bits is four bits.

Referring to6B, the transmission device may generate polar code X={x0, x1, x2, x3, . . . x7} using the polar encoder610. According to an embodiment, it may be assumed that the transmission device has designed polar code X based on repetition. That is, the embodiment indicates a transmission method when N1is greater than N in a situation where K+α bits are encoded into N1bits and transmitted. For example, when N is eight and N1is 12, the transmission device may repeatedly transmit N1−N=4 bits in a first transmission operation. In this case, the transmission device may use the channel polarization principle in order to design a repetition order. For example, it may be assumed that one bit of x0to be transmitted through a first W4channel601is firstly repeated at first transmission. In this case, the transmission device may secondly repeat, at the first transmission, one bit of x5to be transmitted through a second W4channel603for maintaining channel capacities uniform according to channel polarization. In addition, it may be assumed that one bit of x2to be transmitted through the first W4channel601is thirdly repeated at the first transmission. In this case, the transmission device may fourthly repeat, at the first transmission, one bit of x6to be transmitted through the second W4channel603for maintaining channel capacities uniform. Reference numeral630indicates a specified form of the first W4channel601. The first W4channel601may include a first W2channel605and a second W2channel607. Although not illustrated in a drawing, the second W4channel603includes two W2channels like the first W4channel601. The channel polarization principle may also be applied between the first W2channel605and the second W2channel607. Therefore, the transmission device may determine a repetition order using a method by which the capacities among W2channels are uniform. As a result, the transmission device may repeat four bits of x0, x2, x5, and x6in the first transmission operation. The important point here is that the channel capacities are maintained uniform according to the channel polarization principle. Therefore, changing the repetition order of x0, x2, x5, and x6is of no consequence. Also, the repetition of x0, x2, x5, and x6is merely a simple example, and the transmission device may be able to perform repetition through a random combination for making the channel capacities between the first W4channel601and the second W4channel603uniform. In addition, the transmission device may be able to perform repetition through a random combination for making the channel capacities of the first W2channel605and the second W2channel607uniform.

According to another embodiment, it may be assumed that the transmission device has designed polar code X based on puncturing. That is, the embodiment indicates a transmission method when N1is smaller than N in a situation where K+α bits are encoded into N1bits and transmitted. In this case, the transmission device may transmit N1bits and puncture N−N1bits, in a first transmission operation. When a second transmission operation is performed according to a retransmission request, the transmission device may preferentially transmit, in the second transmission operation, the N−N1bits punctured in the first transmission operation according to the puncturing order. Also, the transmission device may repeat N1−(N−N1)=2*N1−N bits using channel polarization, using the same method as that described above, so that N1bits are finally transmitted in the second transmission operation.

Through the method presented inFIG. 6, a repetition order of random K bits may be determined. That is, not only the repetition order of two bits and four bits but also the repetition order of random K bits may be determined by applying channel polarization.

FIG. 7illustrates a flow diagram indicating a method for determining a repetition order based on channel polarization according to the present disclosure.

Referring toFIG. 7, the transmission device may determine repetition transmission of N bits, in step701, where N may be any integer greater than zero presented for the purpose of explanation, not limitation of the embodiment. It may be assumed that the transmission device is required to repeatedly transmit N bits according to a situation when polar code X is designed based on repetition or puncturing and transmitted. For example, it may be assumed that codeword X is designed based on puncturing and transmitted. That is, a transmission method, when N1is smaller than N in a situation where K+α bits are encoded into N1bits and transmitted, is indicated. When an error message has been received from the reception device, the transmission device may preferentially transmit bits punctured in a previous transmission operation, and then repeatedly transmit remaining N bits. For another example, it may be assumed that codeword X is designed based on repetition and transmitted. That is, a transmission method, when N1is greater than N in a situation where K+α bits are encoded into N1bits and transmitted, is indicated. In this case, the transmission device may determine repetition transmission of N bits.

In step703, the transmission device may determine a repetition order of N bits based on a channel polarization principle. Specifically, the technical feature may use a structured algorithm through the channel polarization principle in order to determine a repetition order of N bits required to be repeatedly transmitted. The transmission device may use channel polarization which is a technique for synthesizing and separating channels having the same capacity for polar coding. The transmission device may determine the repetition order based on the channel polarization principle such that the capacities of the synthesized channels (W2, W4, . . . , WN) are uniform. Description through specific embodiments are presented throughFIGS. 6A and 6B.

A specific process for designing a repetition pattern likeFIGS. 6A and 6Baccording to the polarization principle may be variously defined. For example, a repetition pattern may be designed by bit-reversal likeFIGS. 8A and 8Bbelow.

FIGS. 8A and 8Billustrate a specific design method for a repetition order according to the present disclosure.FIGS. 8A and 8Bprovide a method for determining, by the transmission device, a repetition order through a structured algorithm.

Referring to the table on the left inFIGS. 8A and 8B, x1indicates a polar code generated through a polar encoder of N=8(=23), in reference numeral810. However, the technical idea of the present disclosure is not limited to the polar encoder of N=8(=23), and may include a polar encoder of random N=2n. Codeword index i of polar code xigenerated through the polar encoder of N=8(=23) includes indexes of zero to seven. That is, the transmission device may generate codeword X={x0, x1, x2, x3, . . . , x7} through a polar encoding process. Codeword index i may be expressed like reference numeral830when the same is extended to a three-bit binary number. That is, i may be expressed as {000} when i is zero, i may be expressed as {001} when i is one, . . . , and i may be expressed as {111} when i is seven.

Referring to the table on the right inFIGS. 8A and 8B, codeword index i extended to a three-bit binary number indicates the result of a bit-reversal calculation performed by the transmission device. Specifically, reference numeral850indicates the result of the bit-reversal calculation in reference numeral830, and reference numeral870indicates a codeword for repetition corresponding to the result of the bit-reversal calculation. For example, codeword index three of codeword x3in reference numeral810becomes {011} when the same is extended to a three-bit binary number. When a bit-reversal calculation is performed for {011}, {011} becomes {110} in reference numeral850. {110} becomes six when re-expressed in a decimal number, and indicates a repetition order of codeword x6.

According to the order of reference numeral870, the transmission device may determine a repetition order like the order of {x0, x4, x2, x6, x1, x5, x3, x7}. The repetition order of reference numeral870may be referred to as a bit-reversal transmission order. The bit-reversal transmission order satisfies the channel polarization principle described inFIG. 5. That is, when the number of repetition bits is two, the transmission device may firstly repeat x0and secondly repeat x4, according to the bit-reversal transmission order. Accordingly, the capacity of synthesized channel W4may be uniform. Alternatively, when the number of repetition bits is four, the transmission device may firstly repeat x0and secondly repeat x4, according to the bit-reversal transmission order. In addition, the transmission device may thirdly repeat x2and may fourthly repeat x6. As a result, the capacities of channels among synthesized channel W4may be uniform. Also, the capacities among synthesized channel W2may be uniform. The method for determining a repetition order presented throughFIGS. 8A and 8Bis an embodiment according to the technical idea of the present disclosure. Therefore, other embodiments are neither limited nor excluded thereby.

FIG. 9illustrates a result of repetition transmission based on a bit-reversal transmission order according to the present disclosure. Specifically,FIG. 9is a graph through which the effect of a conventional repetition transmission technique and the effect of a repetition transmission technique of the bit-reversal transmission order presented throughFIGS. 8A and 8Bare compared.

In reference numeral910ofFIG. 9, the effect of a conventional repetition transmission technique and the effect of the repetition transmission technique of the bit-reversal transmission order are compared in a condition where {N=256, K+α=88, and repetition bit=32}. In reference numeral930ofFIG. 9, the effect of a conventional repetition transmission technique and the effect of the repetition transmission technique of the bit-reversal transmission order are compared in a condition where {N=256, K+α=196, and repetition bit=75}. Referring toFIG. 9, it may be seen that the proposed technique indicates a performance gain of approximately 0.3 dB in a continuous removal decoding environment.

Unlike the method of determining a repetition order by using channel polarization and a bit-reversal calculation as described above,FIGS. 10 and 11present a method for determining a repetition order based on channel quality information.

FIG. 10illustrates a flow diagram for determining a repetition order based on channel quality information according to the present disclosure, where the channel quality information includes a signal-to-noise ratio (SNR), a carrier to interference plus noise ratio (CINR), and so on.

Referring toFIG. 10, the transmission device may determine repetition transmission of an N-bit codeword, in step1001. A repetition order (RO) for the N-bit codeword may be indicated as {r1, r2, r3, . . . , rN}, where N is any integer greater than zero presented for the purpose of explanation, not limitation of the embodiment. The transmission device may generate codeword X of N bits via a polar encoding process. When codeword X is designed based on repetition or puncturing and transmitted, it may be assumed that repetition transmission of N bits is required. For example, it may be assumed that the transmission device designs codeword X based on puncturing and transmits the same. The transmission device may preferentially include a bit punctured in a previous transmission operation, and may determine repetition transmission of the N-bit codeword when an error message has been received from the reception device. For another example, it may be assumed that codeword X is designed based on repetition and transmitted. In this case, the transmission device may determine repetition transmission of the N-bit codeword.

The transmission device may determine that i=1, in step1003, where i is any integer equal to or greater than one and may be gradually increased by one. i=1 indicates a one-bit codeword for first repetition transmission.

The transmission device may determine channel quality for (N−i+1) repetition transmission pattern candidate groups in order to determine r1, in step1005. For example, the transmission device may determine a required SNR for the (N−i+1) repetition transmission pattern candidate groups. For example, when i=1, the transmission device may determine a required SNR for (N−1+1)=N repetition transmission pattern candidate groups in order to determine r1. That is, the transmission device may determine the required SNR for all the N repetition transmission pattern groups in order to determine codeword index r1to be firstly repeated. Here, the required SNR may be determined using an absolute value of a difference between an approximated block error rate (BLER) and a target error rate. A method for determining a required SNR is described in detail through a flow diagram inFIG. 11.

The transmission device may determine, as r1, a bit index corresponding to a pattern having optimal channel quality, in step1007. For example, the transmission device may determine, as r1, a bit index corresponding to a pattern having a lowest required SNR. For example, when i=1, the transmission device may determine, as r1, a bit index corresponding to a pattern having a lowest required SNR among the N repetition transmission pattern groups in order to determine bit index r1.

The transmission device may determine whether i=N is satisfied, in step1009. When i=N is satisfied, it means that the repetition order is all determined so that the transmission device may terminate an operation. Contrarily, when i=N is not satisfied, that is, when i is smaller than N, the transmission device moves to step1011.

In step1011, the transmission device may perform i=i+1 calculation. The transmission device may perform a calculation of adding one to i in order to sequentially determine r1, r2, . . . , rn, in step1011. For example, when r1has been determined, the transmission device may perform a calculation of adding one to i in order to determine r2.

Later, the transmission device may move back to step1005and circularly repeat steps1005to1011. The transmission device may make a final determination of a repetition order==(r1, r2, r3, rN) through the circular repetition of steps1005to1011.

FIG. 11illustrates a flow diagram for determining a required Signal Noise Ratio (SNR) according to the present disclosure. The transmission device may determine a required SNR used for determining a repetition order inFIG. 11, through a flow diagram inFIG. 11.

Specifically, the transmission device may determine a target block error rate and a random SNR value, in step1101. The target block error rate may be determined according to an adaptive transmission system. For example, in a HARQ system, the transmission device may determine the target block error rate to be 1%. The transmission device may configure and use a random SNR value in order to determine a required SNR.

In step1103, the transmission device may determine an error rate of N bit channels, where N is any positive integer and is a value which may be changed according to a polar encoder. For example, it may be assumed that N=8. The transmission device may apply a given repetition transmission pattern, and determine an error rate of N bit channels by using the random SNR value configured in step1101. Each bit channel error rate is an error rate for u1bits (1<i<N, and u0is an empty bit) when u1to ui-1are precisely known and may be calculated using a density evolution technique and so on. For example, the transmission device may use a pre-determined four repetition transmission patterns of r1, r2, r3, and r4in order to determine a require SNR of bit index r5for fifth repetition transmission. The transmission device may apply the given repetition transmission patterns of r1, r2, r3, and r4so as to determine error rates of N bit channels. For example, the transmission device may apply a density evolution technique so as to determine error rates of N bit channels.

In step1105, the transmission device may determine an approximated block error rate. Specifically, the transmission device may add bit channel error rates for u bits corresponding to a given information set so as to determine an approximated block error rate. For example, when it is defined that an information set={0, 0, 0, 0, 0, u1, u2, u3}, the transmission device may add only bit channel error rates corresponding to u1, u2, and u3so as to determine an approximated block error rate.

In step1107, the transmission device may determine whether an absolute value of the difference between the approximated block error rate and the target block error rate value is smaller than threshold value a, where a is any sufficiently small value which corresponds to a value presented for the reason that the approximated block error rate and the target block error rate value are unable to be exactly matched. The value of a may be changed according to an adaptive transmission system, and/or corresponds to a very small value which may be randomly configured by a user.

When an absolute value of the difference between the approximated block error rate and the target block error rate value is smaller than a, the transmission device moves to step1109. In step1109, the transmission device may determine the random SNR value determined in step1101as a required SNR for a repetition transmission pattern to which a random bit index has been applied.

When an absolute value of the difference between the approximated block error rate and the target block error rate value is smaller than a, the transmission device moves to step1111. In step1111, the transmission device may adjust a random SNR value. Specifically, the technical feature may increase or decrease the random SNR value determined in step1101. For example, when the approximated block error rate is greater than the target block error rate value, the transmission device may adjust the random SNR value to be decreased. For another example, when the approximated block error rate is smaller than the target block error rate value, the transmission device may adjust the random SNR value to be increased.

Later, the transmission device may move to step1103and circularly repeat steps1103to1107so as to determine a final required SNR value.

Methods stated in claims and/or specifications according to various embodiments may be implemented by hardware, software, or a combination of hardware and software.

In the above-described detailed embodiments of the present disclosure, a component included in the present disclosure is expressed in the singular or the plural according to a presented detailed embodiment. However, the singular form or plural form is selected for convenience of description suitable for the presented situation, and various embodiments of the present disclosure are not limited to a single element or multiple elements thereof. Further, either multiple elements expressed in the description may be configured into a single element or a single element in the description may be configured into multiple elements.