KR102144266B1 - Decoding method and apparatus based on polar code in communication system - Google Patents

Abstract

Disclosed are a method for decoding based on a polar code in a communication system and an apparatus thereof. According to the present invention, an operation method of a first communication node comprises the steps of: receiving a signal from a second communication node; obtaining soft bits by performing a demodulation operation on the signal; determining whether pruning is possible for a decoding tree configured based on the soft bits; and if the pruning is not possible, obtaining decoded bits by performing an N-parallel successive cancellation (SC) decoding operation on the soft bits. Therefore, the performance of the communication system can be increased.

Description

A decoding method and apparatus based on a polar code in a communication system {DECODING METHOD AND APPARATUS BASED ON POLAR CODE IN COMMUNICATION SYSTEM}

The present invention relates to a decoding technology in a communication system, and more particularly, to a decoding technology based on a polar code.

For the processing of rapidly increasing radio data, a frequency band higher than the frequency band of LTE (long term evolution) (or LTE-A) (eg, a frequency band of 6 GHz or less) (eg, a frequency band of 6 GHz or higher) A communication system using (for example, a new radio (NR) communication system) is being considered. The NR communication system can support not only a frequency band of 6 GHz or less but also a frequency band of 6 GHz or more, and can support various communication services and scenarios compared to the LTE communication system. For example, the usage scenario of the NR communication system may include enhanced Mobile BroadBand (eMBB), Ultra Reliable Low Latency Communication (URLLC), and Massive Machine Type Communication (mMTC).

In an NR communication system, a communication node (eg, a base station or a terminal) may perform communication using a polar code. For example, the transmitting communication node may generate coded bits by encoding bits (eg, information bits) using a polar code, and Modulated symbols may be generated by performing a modulation operation for, and modulated symbols may be transmitted through radio resources.

The receiving communication node may obtain demodulated symbols by performing a demodulation operation on the received signal, and demodulated symbols (eg, soft bits) based on the polar code. bits)) to obtain information bits. The decoding operation based on the polar code may be performed using a successive cancellation (SC) scheme. In this case, since the SC operation is sequentially performed in all nodes constituting the decoding tree, a delay in the SC decoding operation may occur and the complexity of the SC decoding operation may increase.

An object of the present invention for solving the above problems is to provide a method and apparatus for reducing delay and complexity of a polar code-based successive cancellation (SC) decoding operation in a communication system.

In order to achieve the above object, a method of operating a first communication node according to a first embodiment of the present invention includes: receiving a signal from a second communication node; Obtaining soft bits by performing a demodulation operation on the signal; Dividing the soft bits into N soft bit groups; Constructing N sub-decoding trees for the N soft bit groups; Determining whether pruning is possible for the N sub-decoding trees; And when the pruning is not possible, obtaining decoded bits by performing an N-parallel SC decoding operation in the N sub-decoding trees, wherein the signal is a polar code at the second communication node. Is encoded based on, where N is a power of 2.

Here, when the (32, 16) polar code is used in the communication system, the size of the soft bits may be 32 × Q bits, the N may be 8, and each of the eight soft bit groups is 4 × It may be composed of Q bits, and the size of the decoded bits may be 16 bits.

Here, the obtaining of the decoded bits may include merging results of the N-parallel SC decoding operation; Determining an operation method based on a pattern of nodes belonging to a last layer in the N sub-decoding trees; And obtaining the decoded bits by applying the operation method to results of the N-parallel SC decoding operation.

Here, when N is 8, the pattern may be a pattern of 8 nodes among 32 nodes belonging to the last layer in 8 sub-decoding trees, and the 8 nodes are in different sub-decoding trees. Can belong.

Here, the operation method may be determined differently for each pattern of nodes belonging to the last layer in the N sub-decoding trees.

Here, the method of operating the first communication node may include performing pruning on the N sub-decoding trees when the pruning is possible; And obtaining the decoded bits by performing an SC decoding operation on the pruned N sub-decoding trees.

In order to achieve the above object, a first communication node according to a second embodiment of the present invention includes an antenna for receiving a signal from the second communication node; A demodulator for obtaining soft bits by performing a demodulation operation on the signal; And dividing the soft bits into N soft bit groups, configuring N sub-decoding trees for the N soft bit groups, and determining whether pruning is possible for the N sub-decoding trees. And a decoder that obtains decoded bits by performing an N-parallel SC decoding operation on the N sub-decoding trees when the pruning is not possible, wherein the signal is a polar code at the second communication node. Is encoded based on, where N is a power of 2.

Here, the decoder includes N DUs for performing the N-parallel SC decoding operation; An MU that merges the results of the N DUs; A PU performing pruning on the N sub-decoding trees and performing an SC decoding operation on the pruned N sub-decoding trees; And an output unit that outputs the decoded bits based on the result of the MU or the result of the PU.

Here, each of the N DUs includes an LLR storage unit; Partial sum register; And PE groups, each of the PE groups generating one new soft bit based on two soft bits obtained from the LLR storage unit and one partial sum obtained from the partial sum register. I can.

Here, in the step of obtaining the decoded bits, the decoder may merge the results of the N-parallel SC decoding operation, and operate based on a pattern of nodes belonging to the last layer in the N sub-decoding trees. A method may be determined, and the decoded bits may be obtained by applying the operation method to results of the N-parallel SC decoding operation.

Here, when N is 8, the pattern may be a pattern of 8 nodes among 32 nodes belonging to the last layer in 8 sub-decoding trees, and the 8 nodes are in different sub-decoding trees. Can belong.

Here, when the pruning is possible, the decoder may perform pruning on the N sub-decoding trees, and the decoded by performing an SC decoding operation on the pruned N sub-decoding trees. You can get bits.

According to the present invention, the SC decoding operation in a receiving communication node (eg, a base station or a terminal) can be performed in parallel. For example, when the size of soft bits resulting from demodulation in the receiving communication node is 32×Q bits, 8 sub-decoding trees may be configured in units of 4×Q bits, and 8 sub- In the decoding trees, the SC decoding operation may be performed in parallel. Accordingly, the delay and complexity of the SC decoding operation may be reduced, and the performance of the communication system may be improved.

1 is a conceptual diagram showing a first embodiment of a communication system.
2 is a block diagram showing the first embodiment of a communication node constituting a communication system.
3 is a flow chart showing a first embodiment of a method of transmitting and receiving signals in a communication system.
4 is a conceptual diagram showing a first embodiment of an existing SC decoding scheme in a communication system.
5 is a conceptual diagram illustrating a first embodiment of a pruning-based SC decoding scheme in a communication system.
6 is a flowchart showing a first embodiment of a decoding method in a communication system.
7 is a conceptual diagram illustrating first embodiments of four sub-decoding trees according to four soft bit groups in a communication system.
8 is a conceptual diagram illustrating first embodiments of eight sub-decoding trees according to eight soft bit groups in a communication system.
9 is a block diagram showing a first embodiment of a decoder in a communication system.
10 is a block diagram showing a first embodiment of a DU in a communication system.
11 is a block diagram showing a first embodiment of a PE in a communication system.
12 is a block diagram showing a first embodiment of an MU in a communication system.
13 is a conceptual diagram showing a first embodiment of a 4-parallel SC decoding scheme in a communication system.
14 is a graph showing error correction performance of an SC decoding scheme in a communication system.

Terms such as first and second may be used to describe various elements, but the elements should not be limited by the terms. These terms are only used for the purpose of distinguishing one component from another component. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may be referred to as a first component. The term and/or includes a combination of a plurality of related listed items or any of a plurality of related listed items.

When a component is referred to as being "connected" or "connected" to another component, it is understood that it is directly connected to or may be connected to the other component, but other components may exist in the middle. Should be. On the other hand, when a component is referred to as being "directly connected" or "directly connected" to another component, it should be understood that there is no other component in the middle.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present application, terms such as "comprise" or "have" are intended to designate the presence of features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, but one or more other features. It is to be understood that the presence or addition of elements or numbers, steps, actions, components, parts, or combinations thereof does not preclude in advance.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms as defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning in the context of the related technology, and should not be interpreted as an ideal or excessively formal meaning unless explicitly defined in this application. Does not.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings. In describing the present invention, in order to facilitate an overall understanding, the same reference numerals are used for the same elements in the drawings, and duplicate descriptions for the same elements are omitted.

A communication system to which embodiments according to the present invention are applied will be described. The communication system to which the embodiments according to the present invention are applied is not limited to the contents described below, and the embodiments according to the present invention can be applied to various communication systems. Here, the communication system may be used with the same meaning as a communication network.

1 is a conceptual diagram showing a first embodiment of a communication system.

Referring to FIG. 1, the communication system 100 includes a plurality of communication nodes 110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, 130-6). A plurality of communication nodes are 4G communication (e.g., long term evolution (LTE), LTE-A (advanced)), 5G communication (e.g., new radio) specified in the 3rd generation partnership project (3GPP) standard. ), etc. 4G communication may be performed in a frequency band of 6 GHz or less, and 5G communication may be performed in a frequency band of 6 GHz or more as well as a frequency band of 6 GHz or less.

For example, for 4G communication and 5G communication, a plurality of communication nodes may include a code division multiple access (CDMA) based communication protocol, a wideband CDMA (WCDMA) based communication protocol, a time division multiple access (TDMA) based communication protocol, Frequency division multiple access (FDMA)-based communication protocol, OFDM (orthogonal frequency division multiplexing)-based communication protocol, Filtered OFDM-based communication protocol, CP (cyclic prefix)-OFDM-based communication protocol, DFT-s-OFDM (discrete) Fourier transform-spread-OFDM)-based communication protocol, OFDMA (orthogonal frequency division multiple access)-based communication protocol, SC (single carrier)-FDMA-based communication protocol, NOMA (Non-orthogonal Multiple Access), GFDM (generalized frequency) Division multiplexing)-based communication protocol, filter bank multi-carrier (FBMC)-based communication protocol, universal filtered multi-carrier (UFMC)-based communication protocol, and space division multiple access (SDMA)-based communication protocol can be supported. .

In addition, the communication system 100 may further include a core network. When the communication system 100 supports 4G communication, the core network may include a serving-gateway (S-GW), a packet data network (PDN)-gateway (P-GW), a mobility management entity (MME), and the like. have. When the communication system 100 supports 5G communication, the core network may include a user plane function (UPF), a session management function (SMF), an access and mobility management function (AMF), and the like.

Meanwhile, a plurality of communication nodes 110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130- constituting the communication system 100 4, 130-5, 130-6) Each may have the following structure.

2 is a block diagram showing the first embodiment of a communication node constituting a communication system.

Referring to FIG. 2, the communication node 200 may include at least one processor 210, a memory 220, and a transmission/reception device 230 connected to a network to perform communication. The transmission/reception device 230 may be an antenna. In addition, the communication node 200 may further include an input interface device 240, an output interface device 250, and a storage device 260. Each of the components included in the communication node 200 may be connected by a bus 270 to perform communication with each other.

However, each of the components included in the communication node 200 may be connected through an individual interface or an individual bus centered on the processor 210, not through the common bus 270. For example, the processor 210 may be connected to at least one of the memory 220, the transceiver 230, the input interface device 240, the output interface device 250, and the storage device 260 through a dedicated interface. .

The processor 210 may execute a program command stored in at least one of the memory 220 and the storage device 260. The processor 210 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor in which methods according to embodiments of the present invention are performed. Each of the memory 220 and the storage device 260 may be configured with at least one of a volatile storage medium and a nonvolatile storage medium. For example, the memory 220 may be composed of at least one of a read only memory (ROM) and a random access memory (RAM).

Referring back to FIG. 1, the communication system 100 includes a plurality of base stations 110-1, 110-2, 110-3, 120-1, 120-2, and a plurality of terminals 130- 1, 130-2, 130-3, 130-4, 130-5, 130-6). Base stations (110-1, 110-2, 110-3, 120-1, 120-2) and terminals (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) The containing communication system 100 may be referred to as an “access network”. Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 may form a macro cell. Each of the fourth base station 120-1 and the fifth base station 120-2 may form a small cell. The fourth base station 120-1, the third terminal 130-3, and the fourth terminal 130-4 may belong to the cell coverage of the first base station 110-1. The second terminal 130-2, the fourth terminal 130-4, and the fifth terminal 130-5 may belong to the cell coverage of the second base station 110-2. The fifth base station 120-2, the fourth terminal 130-4, the fifth terminal 130-5, and the sixth terminal 130-6 may belong within the cell coverage of the third base station 110-3. have. The first terminal 130-1 may belong to the cell coverage of the fourth base station 120-1. The sixth terminal 130-6 may belong to the cell coverage of the fifth base station 120-2.

Here, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 is a NodeB, an evolved NodeB, gNB, and a base transceiver station (BTS). ), a radio base station, a radio transceiver, an access point, an access node, and the like. Each of the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 is a user equipment (UE), a terminal, an access terminal, and a mobile device. It may be referred to as a mobile terminal, a station, a subscriber station, a mobile station, a portable subscriber station, a node, a device, and the like.

Meanwhile, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may operate in a different frequency band or may operate in the same frequency band. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to each other through an ideal backhaul link or a non-ideal backhaul link, , Information can be exchanged with each other through an ideal backhaul link or a non-ideal backhaul link. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to the core network through an ideal backhaul link or a non-ideal backhaul link. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 transmits a signal received from the core network to the corresponding terminal 130-1, 130-2, 130-3, 130 -4, 130-5, 130-6), and the signal received from the corresponding terminal (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) Can be transferred to.

In addition, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 transmits MIMO (e.g., single user (SU)-MIMO, multi-user (MU)- MIMO, massive MIMO, etc.), coordinated multipoint (CoMP) transmission, carrier aggregation (CA) transmission, transmission in an unlicensed band, direct communication between terminals (device to device communication, D2D) (or, ProSe ( proximity services)). Here, each of the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 is a base station 110-1, 110-2, 110-3, 120-1 , 120-2) and operations supported by the base stations 110-1, 110-2, 110-3, 120-1, and 120-2. For example, the second base station 110-2 may transmit a signal to the fourth terminal 130-4 based on the SU-MIMO scheme, and the fourth terminal 130-4 can transmit a signal to the fourth terminal 130-4 by the SU-MIMO scheme. A signal may be received from the second base station 110-2. Alternatively, the second base station 110-2 may transmit a signal to the fourth terminal 130-4 and the fifth terminal 130-5 based on the MU-MIMO method, and the fourth terminal 130-4 And each of the fifth terminal 130-5 may receive a signal from the second base station 110-2 by the MU-MIMO method.

Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 may transmit a signal to the fourth terminal 130-4 based on the CoMP scheme, and The terminal 130-4 may receive signals from the first base station 110-1, the second base station 110-2, and the third base station 110-3 by the CoMP method. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 has terminals 130-1, 130-2, 130-3, and 130-4 belonging to their cell coverage. , 130-5, 130-6) and the CA method can transmit and receive signals. Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 can control D2D between the fourth terminal 130-4 and the fifth terminal 130-5. In addition, each of the fourth terminal 130-4 and the fifth terminal 130-5 may perform D2D under the control of the second base station 110-2 and the third base station 110-3. .

Next, decoding methods based on a polar code in a communication system will be described. Even when a method performed in the first communication node (for example, transmission or reception of a signal) among communication nodes is described, the second communication node corresponding thereto is a method corresponding to the method performed in the first communication node (e.g. For example, signal reception or transmission) may be performed. That is, when the operation of the terminal is described, the base station corresponding thereto may perform the operation corresponding to the operation of the terminal. Conversely, when the operation of the base station is described, a terminal corresponding thereto may perform an operation corresponding to the operation of the base station.

3 is a flow chart showing a first embodiment of a method of transmitting and receiving signals in a communication system.

Referring to FIG. 3, the communication system may include a first communication node and a second communication node. The first communication node may transmit a signal/channel to the second communication node, and may be referred to as a “transmission communication node”. The second communication node may receive a signal/channel from the first communication node, and may be referred to as a “receiving communication node”. When the first communication node is the base station shown in FIG. 1, the second communication node may be the terminal shown in FIG. 1. Alternatively, when the first communication node is the terminal shown in FIG. 1, the second communication node may be the base station or the terminal shown in FIG. 1. Each of the first communication node and the second communication node may be configured in the same or similar to the communication node 200 illustrated in FIG. 2.

The first communication node may generate coded bits by performing an encoding operation on information bits based on the polar code (S310). Step S310 may be performed by an encoder included in the first communication node, and the operation of the encoder is performed by a processor included in the first communication node (for example, the processor 210 shown in FIG. 2). Can be controlled. The first communication node may generate modulated symbols by performing a modulation operation on the coded bits (S320). Step S320 may be performed by a modulator included in the first communication node, and the operation of the modulator is performed by a processor included in the first communication node (for example, the processor 210 shown in FIG. 2). Can be controlled. The first communication node may transmit the modulated symbols (eg, a signal and/or a channel generated based on the modulated symbols) through a radio resource (S330). The second communication node may receive signals and/or channels from the first communication node.

Here, the signal is a reference signal (for example, a channel state information-reference signal (CSI-RS), a demodulation-reference signal (DM-RS), a phase tracking-reference signal (PT-RS), etc.)). I can. The channel can be a physical downlink control channel (PDCCH), a physical downlink shared channel (PDSCH), a physical uplink control channel (PUCCH), a physical uplink shared channel (PUSCH), a phsyical broadcast channel (PBCH), or a sidelink channel. have.

The second communication node may obtain demodulated symbols by performing a demodulation operation on the received signal and/or the received channel (S340). Step S340 may be performed by a demodulator included in the second communication node, and the operation of the demodulator is performed by a processor included in the second communication node (for example, the processor 210 shown in FIG. 2). Can be controlled. Here, the demodulated symbols may be soft bits (eg, log likelihood ratio (LLR) values). The second communication node may acquire information bits by performing a successive cancellation (SC) decoding operation on soft bits (S350). Step S350 may be performed by a decoder included in the second communication node, and the operation of the decoder is performed by a processor included in the second communication node (for example, the processor 210 shown in FIG. 2). Can be controlled. The SC decoding operation may be performed through one of the following methods.

-Method #1: pruning-based SC decoding method

-Method #2: Parallel SC decoding method

"Pruning-based SC decoding scheme" and "parallel SC decoding scheme" may be modified schemes based on "existing SC decoding scheme". The "existing SC decoding scheme" can be performed as follows.

4 is a conceptual diagram showing a first embodiment of an existing SC decoding scheme in a communication system.

Referring to FIG. 4, a (N, K) polar code may be used in a communication system. N may indicate the number of bits of the polar code (eg, the coded bits generated in step S310 shown in FIG. 3 ), and K may indicate the number of information bits included in the polar code. The number of frozen bits included in the polar code may be "N-K". Here, (16, 8) polar codes may be used.

The decoding tree may be composed of a plurality of nodes V _i,j . i may indicate the layer to which the corresponding node V _i,j belongs _{, and j} may be an index of the node V _i,j belonging to each layer. Soft bits input to the node V _i,j may be referred to as A _i,j . A _i,j can be defined as in Equation 1 below.

으로 표시된 노드 V_i,j에서 출력되는 B_i,j는 프로즌 비트에 기초하여 생성될 수 있고,

으로 표시된 노드 V_i,j에서 출력되는 B_i,j는 정보 비트에 기초하여 생성될 수 있고,

으로 표시된 노드 V_i,j에서 출력되는 B_i,j는 정보 비트 및 프로즌 비트를 포함할 수 있다.

B _i,j output from the node V _i,j denoted by may be generated based on the frozen bit,

B _i,j output from the node V _i,j indicated by can be generated based on the information bit,

B _i,j output from the node V _i,j indicated by may include information bits and frozen bits.

Soft bits A _0,0 resulting from step S340 shown in FIG. 3 may be input to nodes V _{0 and 0} . Soft bits input to the nodes V _{0 and 0} may be referred to as A _0,0 , and the size of the soft bits input to the nodes V _{0 and 0} may be 16 bits. And node V _0,0 A _0,0 A _1,0 and A _1,1 basis to the in can be _created, A _{1, 0} may be transmitted by node V _1,0, A _1,1 to node Can be transmitted to V _1,1 . Each size of A _1,0 and A _1,1 may be 1/2 of the size of A _0,0 . For example, each size of A _1,0 and A _1,1 may be 8 bits. A _1,0 may be referred to as F(x,y), and A _1,1 may be referred to as G(x,y,u). F(x,y) and G(x,y,u) may be defined as in Equation 2 below.

The above operations can be performed on all nodes V _i,j belonging to the decoding tree. In this case, the size of A _2,j input to nodes V _2,j belonging to the third layer of the decoding tree may be 4 bits, and nodes V _3,j belonging to the fourth layer of the decoding tree are inputted. The size of A _3,j may be 2 bits, and the size of A _4,j input to nodes V _4,j belonging to the fifth layer of the decoding tree may be 1 bit.

After A _i,j is transmitted to all nodes V _i,j belonging to the decoding tree, the decoding result (e.g., V _4,j ) from the node V _{i, j} (e.g., V _4,j ) belonging to the last layer in the decoding tree For example, hard decisions) can be created. The decoding result may be generated based on A _i,j , and may be referred to as B _i,j . B _i,j can be defined as in Equation 3 below.

B _i,j generated in node V _i,j may be transmitted to a parent node (eg, an upper node). The decoding result transmitted from node V _4,0 to node V _3,0 may be referred to as B _4,0 , and the decoding result transmitted from node V _4,1 to node V _3,0 is referred to as B _4,1 Can be. Node V _3,0 may generate B _3,0 based on Equation 4 below, and may transmit B _3,0 to V _2,0 .

The above operations can be performed on all nodes V _i,j belonging to the decoding tree, and a decoding operation when B _0,0 is generated based on B _1,0 and B _1,1 at node V _0,0 . This can be done.

Meanwhile, the "pruning-based SC decoding scheme" may be performed as follows.

5 is a conceptual diagram illustrating a first embodiment of a pruning-based SC decoding scheme in a communication system.

Referring to FIG. 5, a (16, 8) polar code may be used in a communication system. In order to reduce the processing delay of the decoding operation in the embodiment shown in FIG. 4, the number of nodes V _i,j belonging to the decoding tree in the embodiment shown in FIG. 5 may be reduced. The lower nodes of the node V _i,j composed of only frozen bits may be excluded from the decoding tree. For example, sub-nodes of node V _2,0 can be excluded from the decoding tree, sub-nodes of node V _3,2 can be excluded from the decoding tree, and sub-nodes of nodes V _3,4 are excluded from the decoding tree. May be excluded.

In addition, lower nodes of the node V _i,j composed of only information bits may be excluded from the decoding tree. For example, sub-nodes of nodes V ₃ and ₃ can be excluded from the decoding tree, sub-nodes of nodes V ₃ and ₅ can be excluded from the decoding tree, and sub-nodes of nodes V ₂ and ₃ are excluded from the decoding tree. May be excluded. In this case, the processing delay of the decoding operation in the embodiment shown in FIG. 5 may be reduced compared to the processing delay in the decoding operation in the embodiment shown in FIG. 4. The "pruning-based SC decoding scheme" may be used when pruning is possible according to a pattern of nodes V _i,j belonging to a lower layer of the decoding tree.

Referring back to FIG. 3, a detailed embodiment of step S350 may be as follows, and may be performed by a decoder included in the second communication node.

6 is a flowchart showing a first embodiment of a decoding method in a communication system.

Referring to FIG. 6, the second communication node may divide soft bits into N soft bit groups (S351). The second communication node may configure N soft bit groups in consideration of the pattern of nodes V _i,j belonging to the last layer of the decoding tree. N can be a power of 2. For example, N can be 4, 8, 16, or 32. When the size of the soft bits is 16×Q bits and N is 4, 4 soft bit groups may be generated, and the size of each of the 4 soft bit groups may be 4×Q bits. Here, the soft bits may be divided into N soft bit groups according to a predefined rule. Q can represent the degree of quantization. When N is 4, a 4-parallel SC decoding method may be performed, and when N is 8, an 8-parallel SC decoding method may be performed.

7 is a conceptual diagram illustrating first embodiments of four sub-decoding trees according to four soft bit groups in a communication system.

Referring to FIG. 7, the size of the soft bits may be 16×Q bits, and four soft bit groups (A(0) _0,0 , A(1) _0,0 , A(2) _0,0 , Each of A(3) _0,0 ) may have a size of 4×Q bits. A sub-decoding tree for each of the four soft bit groups (A(0) _0,0 , A(1) _0,0 , A(2) _0,0 , A(3) _0,0 ) can be created. In addition, the SC decoding operation may be performed in parallel in the four sub-decoding trees. Here, k may be an index of the sub-decoding tree.

8 is a conceptual diagram illustrating first embodiments of eight sub-decoding trees according to eight soft bit groups in a communication system.

Referring to FIG. 8, the size of soft bits may be 32×Q bits, and 8 soft bit groups (A(0) _0,0 , A(1) _0,0 , A(2) _0,0 , A(3) _0,0 , A(4) _0,0 , A(5) _0,0 , A(6) _0,0 , A(7) _0,0 ) Each size can be 4×Q bits have. 8 soft bit groups (A(0) _0,0 , A(1) _0,0 , A(2) _0,0 , A(3) _0,0 , A(4) _0,0 , A(5) ) _0,0 , A(6) _0,0 , A(7) _0,0 ) Sub-decoding trees can be generated for each, and SC decoding operations are performed in parallel in 8 sub-decoding trees Can be. Here, k may be an index of the sub-decoding tree.

Referring back to FIG. 6, the second communication node may determine whether pruning of N sub-decoding trees is possible (S352). When pruning of N sub-decoding trees is possible, the second communication node performs an SC decoding operation at nodes V _{i, j} belonging to the pruned N sub-decoding trees, thereby performing a decoding result (e.g., decoded bits) can be obtained (S353). The second communication node may determine whether the decoding operation for all soft bits has been completed (S354). When the decoding operation for all soft bits is completed, the second communication node may obtain information bits from the decoding result. Also, the second communication node may update a partial sum register using the decoded bits (S357). For example, the second communication node may store a value (eg, partial sum) obtained in the decoding operation in the partial sum register, and the partial sum is u shown in FIG. 11 (for example, in Equation 4). Some value).

Meanwhile, when pruning of all sub-decoding trees is not possible, the second communication node may perform an N-parallel SC decoding operation on N sub-decoding trees according to N soft bit groups (S355). ). For example, an N-parallel SC decoding operation may be performed in a decoder included in the second communication node, and a decoder performing an 8-parallel SC decoding operation may be configured as follows.

9 is a block diagram showing a first embodiment of a decoder in a communication system.

9, the decoder 900 includes a controller 910, a decoding part 920, a decision part 930, and an output part 940. Can include. Operations of the controller 910, the decoding unit 920, the determination unit 930, and the output unit 940 may be performed by the processor 210 illustrated in FIG. 2.

The controller 910 may determine whether pruning is possible for sub-decoding trees. That is, the controller 910 may perform step S351 shown in FIG. 6. When pruning for sub-decoding trees is possible, pruning for sub-decoding trees may be performed in a pruning unit (PU) included in the determination unit 930. The result of the PU (B _i,j ) may be transmitted to the output unit 940. If pruning for all sub-decoding trees is not possible, the decoding unit 920 may perform an 8-parallel SC decoding operation.

The decoding unit 920 may include 8 decoding units (DUs), and each of the 8 DUs may include a memory. The SC decoding operation may be performed in parallel on 8 DUs. For example, DU ₀ may perform an SC decoding operation in the sub-decoding tree according to A(0) _{0,0 shown} in FIG. 8, and DU ₁ is A(1) _0,0 shown in FIG. The SC decoding operation can be performed in the sub-decoding tree according to, and DU ₂ can perform the SC decoding operation in the sub-decoding tree according to A(2) _0,0 shown in FIG. 8, and DU ₃ is The SC decoding operation may be performed in the sub-decoding tree according to A(3) _0,0 shown in FIG. 8. DU ₄ can perform an SC decoding operation in the sub-decoding tree according to A(4) _{0,0 shown} in FIG. 8, and DU ₅ is a sub-decoding according to A(5) _0,0 shown in FIG. The SC decoding operation can be performed in the decoding tree, and DU ₆ can perform the SC decoding operation in the sub-decoding tree according to A(6) _{0,0 shown} in FIG. 8, and DU ₇ is shown in FIG. The SC decoding operation can be performed in the sub-decoding tree according to A(7) _0,0 . Each of the eight DUs included in the decoding unit 920 may be configured as follows.

10 is a block diagram showing a first embodiment of a DU in a communication system.

Referring to FIG. 10, the DU 1000 may include an LLR storage unit 1010, a partial sum register 1020, and a processing element (PE) group 1030. PE group 1030 may include 32 PEs. Parallel processing can be performed on 32 PEs. Here, F may be F(x,y) in Equation 2, and G may be G(x,y,u) in Equation 2. One PE can consist of:

11 is a block diagram showing a first embodiment of a PE in a communication system.

Referring to FIG. 11, two soft bits and one partial sum generated from a previously determined bit may be input to an input terminal of a PE. The PE may generate 1 new soft bit based on the 2 soft bits and 1 partial sum.

Meanwhile, the result R _i,j of the decoding unit 920 illustrated in FIG. 9 may be input to a merging unit (MU) included in the determination unit 930. The MU may output T _j by merging the result of the decoding unit 920 (R _i,j ) (eg, output of DU _0-7 ). When the 8-parallel SC decoding operation is performed, the size of the output of the MU may be 8 bits. The result of the MU (T _j ) may be transmitted to the output unit 940. The output unit 940 may store the result of the PU (B _i,j ) or the result of the MU (T _j ), and may output decoded bits when the SC decoding operation is completed.

Meanwhile, since the result of 8 DUs (R _i,j ) is not a bit, an additional operation of determining a bit using the result of 8 DUs (R _i,j ) may be required. Additional operations may be performed at the node V _i,j belonging to the last layer of the sub-decoding tree. The additional operation may be performed by the MU included in the determination unit 930, and the MU may be configured as follows.

12 is a block diagram showing a first embodiment of an MU in a communication system.

Referring to FIG. 12, a function for a major pattern may be performed using 8 soft bits obtained from the decoding unit 920 shown in FIG. 9. When an 8-parallel SC decoding operation is performed, the number of functions is 256, and functions for 9 major patterns may be prepared. The function for the corresponding pattern may be determined from W _j obtained from the controller 910 illustrated in FIG. 9. In 8-parallel decoding, the result of the function can be 8 bits.

In the case of a non-major pattern, two 4-parallel MUs may be configured for an operation on a minor pattern. In the case of a 4-parallel MU, a total of 16 simple functions are required, so all cases can be covered. Eight results obtained from the decoding unit 920 shown in FIG. 9 may be stored in a buffer in the MU. The value stored in the buffer can be transferred to two 4-parallel MUs. The buffer in the MU can output 4 Fs (i.e., F(x,y) of Equation 2) out of the 8 results as a 4-parallel MU, and the remaining 4 Gs (i.e., Equation 2) G(x,y,u)) can be output as a 4-parallel MU. The processing result of 4 Fs in the 4-parallel MU can be combined with the processing result of 4 Gs in the 4-parallel MU. That is, 8 bits can be determined using two 4-parallel MUs.

The MU operation may vary according to the pattern of 32 nodes V _i,j belonging to the last layer in the 8 sub-decoding trees. Table 1 below may represent the pattern ratio of 8 nodes among 32 nodes V _i,j belonging to the last layer in 8 sub-decoding trees. That is, the pattern may be a pattern of N nodes in N sub-decoding trees, and N nodes may belong to different sub-decoding trees. For example, in the embodiment shown in FIG. 13, the pattern is a second node belonging to the last layer of the first sub-decoding tree, a second node belonging to the last layer of the second sub-decoding tree, and the third sub-decoding It may be determined according to a second node belonging to the last layer of the tree and a second node belonging to the last layer of the fourth sub-decoding tree.

In Table 1, each value may be a ratio indicating how much a corresponding pattern occurs for all code rates in a corresponding code length (N). In Table 1, the sum of columns in each code length (N) may be 1.

Pattern Ox00, pattern 0x01, pattern 0x03, pattern 0x07, pattern 0x17, pattern 0x1F, pattern 0x3F, pattern 0x7F, and pattern 0xFF may occur frequently, and others may be patterns that rarely occur. Among 32 nodes V _i,j belonging to the last layer in the 8 sub-decoding trees, the definition of the MU operation according to the pattern of 8 nodes may be as shown in Table 2 below. In other cases, a general SC decoding operation may be performed once more. For example, in other cases the decoding operation may be performed using two N/2 merge operators.

That is, block M illustrated in FIG. 12 may be determined according to a pattern of 8 nodes among 32 nodes V _i,j belonging to the last layer in 8 sub-decoding trees. For example, block M _Ox00 , block M _Ox01 , block M _Ox03 , block M _Ox07 , block M _Ox17 , block M _Ox1F , block M _Ox3F , block M _Ox7F , and block M _OxFF, respectively, are pattern Ox00, pattern described in Table 1 It may correspond to 0x01, pattern 0x03, pattern 0x07, pattern 0x17, pattern 0x1F, pattern 0x3F, pattern 0x7F, and pattern 0xFF. 256 blocks are required to consider all patterns, but in this case, implementation complexity of hardware may increase. Therefore, 9 blocks can be set in consideration of frequently occurring patterns.

Meanwhile, referring again to FIG. 6, when the N-parallel SC decoding operation (ie, step S356) is completed in the decoding unit 920 shown in FIG. 9, the second communication node performs the N-parallel SC decoding operation. The execution results may be merged (S356). Step S356 may be performed by the MU shown in FIG. 12, and the result T _j of step S356 may be determined based on Tables 1 and 2. When step S356 is completed, the second communication node may determine whether decoding is completed (S354). When decoding of all soft bits is completed, the second communication node may output the decoded bits. In addition, the second communication node may update the partial sum register using the decoded bits (S357). For example, the second communication node may store a value (eg, partial sum) obtained in the decoding operation in the partial sum register, and the partial sum is u shown in FIG. 11 (eg, in Equation 4). Some value).

The above-described embodiments can be applied not only to an 8-parallel SC decoding method but also to a 4-parallel SC decoding method. The 4-parallel SC decoding method may be as follows.

13 is a conceptual diagram showing a first embodiment of a 4-parallel SC decoding scheme in a communication system.

Referring to FIG. 13, when the (16, 8) polar code is used, the soft bits (A _0,0 ) are 4 soft bit groups (A(0) _0,0 , A(1) _0,0 ). , A(2) _0,0 and A(3) _0,0 ). Accordingly, four sub-decoding trees can be constructed, and four bits can be simultaneously determined by combining decoding results in four sub-decoding trees.

When the (1024, 512) polar code is used, the decoding performance may be as shown in Table 3 below. The processing delay according to the N-parallel SC decoding method specified in the present invention may be smaller than the processing delay according to the existing SC decoding method (eg, sequential decoding method).

In Table 3, [1] is "KK Parhi. et al. Low-latency successive-cancellation polar decoder architectures using 2-bit decoding. IEEE Trans. Circuits Syst. I Reg . Papers , vol . 61, no. 4, pp. 1241-1254, Apr. 2014" may be decoding performance according to the technology. In Table 3, [2] refers to "C. Leroux. et al. A semi-parallel successive-cancellation decoder for polar codes. IEEE Trans. Signal Process. , vol. 61, no. 2, pp. 289-299, Jan. It may be decoding performance according to the technology specified in "2013". In Table 3, [3] is "P. Giard. et al. Fast low-complexity decoders for low-rate polar codes. J. Signal Process. Syst., vol. 90, no. 5, pp. 675-685, May. It may be decoding performance according to the technology specified in "2018". [4] in Table 3 is "F. Ercan. et al. Reduced-memory high-throughputfast-ssc polar code decoder architecture. in 2017 IEEE International Workshop on Signal Processing Systems (SiPS), Oct. 2017, pp. 1-6 It may be decoding performance according to the technique specified in ".

14 is a graph showing error correction performance of an SC decoding scheme in a communication system.

Referring to FIG. 14, "serial SC" may be a result according to an existing SC decoding method, and "8-parallel SC" may be a result according to an 8-parallel SC decoding method defined in the present invention. According to the present invention, a frame error rate (FER) compared to a signal to noise ratio (SNR) can be maintained, and at least 8 bits can be simultaneously decoded regardless of a pattern of nodes V _i,j . In addition, since the pruning technique can also be applied to the embodiment according to the present invention, the decoding processing delay can be further reduced.

The methods according to the present invention may be implemented in the form of program instructions that can be executed through various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like alone or in combination. The program instructions recorded on the computer-readable medium may be specially designed and configured for the present invention, or may be known and usable to those skilled in computer software.

Examples of computer-readable media include hardware devices specifically configured to store and execute program instructions, such as roms, rams, flash memories, and the like. Examples of program instructions include not only machine language codes such as those produced by a compiler but also high-level language codes that can be executed by a computer using an interpreter or the like. The above-described hardware device may be configured to operate as at least one software module to perform the operation of the present invention, and vice versa.

Although described with reference to the above embodiments, those skilled in the art will understand that various modifications and changes can be made to the present invention without departing from the spirit and scope of the present invention described in the following claims. I will be able to.

Claims (13)

As a method of operating a first communication node in a communication system,
Receiving a signal from a second communication node;
Obtaining soft bits by performing a demodulation operation on the signal;
Dividing the soft bits into N soft bit groups;
Constructing N sub-decoding trees for the N soft bit groups;
Determining whether pruning is possible for the N sub-decoding trees; And
If the pruning is not possible, obtaining decoded bits by performing an N-parallel successive cancellation (SC) decoding operation on the N sub-decoding trees,
The signal is encoded based on a polar code in the second communication node,
When the (32, 16) polar code is used in the communication system, the size of the soft bits is 32 × Q bits, the N is 8, each of the eight soft bit groups is composed of 4 × Q bits. , The size of the decoded bits is 16 bits, and the Q is a degree of quantization of the soft bits. delete The method according to claim 1,
The step of obtaining the decoded bits,
Merging the results of the N-parallel SC decoding operation;
Determining an operation method based on a pattern of nodes belonging to a last layer in the N sub-decoding trees; And
The method of operating a first communication node, further comprising the step of obtaining the decoded bits by applying the operation method to results of the N-parallel SC decoding operation. The method of claim 3,
When N is 8, the pattern is a pattern of 8 nodes among 32 nodes belonging to the last layer in 8 sub-decoding trees, and the 8 nodes belong to different sub-decoding trees. How the communication node operates. The method of claim 3,
The operation method of the first communication node is determined differently for each pattern of nodes belonging to a last layer in the N sub-decoding trees. The method according to claim 1,
The operating method of the first communication node,
If the pruning is possible, performing pruning on the N sub-decoding trees; And
The method of operating a first communication node, further comprising obtaining the decoded bits by performing an SC decoding operation on pruned N sub-decoding trees. As a first communication node in a communication system,
An antenna for receiving a signal from a second communication node;
A demodulator for obtaining soft bits by performing a demodulation operation on the signal; And
Dividing the soft bits into N soft bit groups, constructing N sub-decoding trees for the N soft bit groups, and pruning the N sub-decoding trees It includes a decoder that determines whether (pruning) is possible, and when pruning is not possible, obtains decoded bits by performing an N-parallel successive cancellation (SC) decoding operation on the N sub-decoding trees, and ,
The signal is encoded based on a polar code in the second communication node,
When the (32, 16) polar code is used in the communication system, the size of the soft bits is 32 × Q bits, the N is 8, and each of the eight soft bit groups is composed of 4 × Q bits. , The size of the decoded bits is 16 bits, and the Q is a degree of quantization of the soft bits. The method of claim 7,
The decoder,
N decoding units (DUs) performing the N-parallel SC decoding operation;
A merging unit (MU) for merging the results of the N DUs;
A pruning unit (PU) for performing pruning on the N sub-decoding trees and performing an SC decoding operation on the pruned N sub-decoding trees; And
The first communication node comprising an output unit for outputting the decoded bits based on the result of the MU or the result of the PU. The method of claim 8,
Each of the N DUs,
A log likelihood ratio (LLR) storage;
Partial sum register; And
Contains PE (processing element) groups,
Each of the PE groups generates one new soft bit based on two soft bits obtained from the LLR storage unit and one partial sum obtained from the partial sum register. The method of claim 7,
In the step of obtaining the decoded bits, the decoder merges results of the N-parallel SC decoding operation, determines an operation method based on a pattern of nodes belonging to the last layer in the N sub-decoding trees, and And obtaining the decoded bits by applying the calculation scheme to results of the N-parallel SC decoding operation. The method according to claim 10,
When N is 8, the pattern is a pattern of 8 nodes among 32 nodes belonging to the last layer in 8 sub-decoding trees, and the 8 nodes belong to different sub-decoding trees. Communication node. The method of claim 7,
When the pruning is possible, the decoder performs pruning on the N sub-decoding trees, and obtains the decoded bits by performing an SC decoding operation on the pruned N sub-decoding trees. , The first communication node. As a method of operating a first communication node in a communication system,
Receiving a signal from a second communication node;
Obtaining soft bits by performing a demodulation operation on the signal;
Dividing the soft bits into N soft bit groups;
Constructing N sub-decoding trees for the N soft bit groups;
Determining whether pruning is possible for the N sub-decoding trees; And
When the pruning is not possible, obtaining decoded bits by performing an N-parallel successive cancellation (SC) decoding operation on the N sub-decoding trees,
The signal is encoded based on a polar code in the second communication node,
When the (16, 8) polar code is used in the communication system, the size of the soft bits is 16 × Q bits, the N is 4, and each of the four soft bit groups is composed of 4 × Q bits. , The size of the decoded bits is 8 bits, and Q is a degree of quantization of the soft bits.

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