KR102049652B1 - Superposition transmission for uplink scma systems and codebook design thereof - Google Patents

Abstract

Disclosed are an overlapping transmission method of an uplink SCMA system and a mobile communication system using the same. In a UL SCMA system according to an embodiment, a method of transmitting data overlap by a user terminal includes: dynamically allocating an SCMA codebook to the user terminal; Performing SCMA encoding based on the SCMA codebook dynamically allocated to the user terminal; Identifying an SCMA codeword based on an SCMA codebook corresponding to each data layer as the SCMA encoding is performed; And overlapping the identified SCMA codeword and transmitting the same to the base station.

Description

Nested transmission method of uplink SCMA system and mobile communication system applying the same {SUPERPOSITION TRANSMISSION FOR UPLINK SCMA SYSTEMS AND CODEBOOK DESIGN THEREOF}

The following description relates to a transmission method and system for increasing the transmission rate of a super-connected terminal in an uplink mobile communication system to which SCMA-based non-orthogonal multiple access technology is applied.

In order to meet the increasing demand for wireless data traffic since the commercialization of 4G communication systems, efforts are being made to develop improved 5G communication systems or pre-5G communication systems. For this reason, a 5G communication system or a pre-5G communication system is called a system after a 4G network (Beyond 4G Network) or a system after a Long Term Evolution (LTE) system (Post LTE).

In order to achieve high data rates, 5G communication systems are being considered for implementation in the ultra-high frequency (mmWave) band (eg, such as the 60 Gigabit (60 GHz) band). In 5G communication system, beamforming, massive array multiple input / output (Full-Dimensional MIMO), and full dimensional multiple input / output (FD-MIMO) are used in 5G communication systems to increase path loss mitigation and propagation distance of radio waves in the ultra-high frequency band. Array antenna, analog beamforming, and large scale antenna techniques are discussed.

In addition, in order to improve the network of the system, in the 5G communication system, an evolved small cell, an advanced small cell, a cloud radio access network (cloud RAN), an ultra high density network (ultradense network), Device to Device communication (D2D), wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), and interference cancellation Technology development is taking place.

In addition, in 5G systems, Hybrid FSK and QAM Modulation (FQAM) and sliding window superposition coding (SWSC), Advanced Coding Modulation (ACM), and FBMC (Filter Bank Multi Carrier) and NOMA (non orthogonal multiple access), and sparse code multiple access (SCMA), and the like are being developed.

In particular, sparse code multiple access (SCMA) is a codebook-based non-orthogonal multiple access technology, which is more resource efficient than conventional technologies because multiple users transmit signals in overlapping time-frequency domains. In the uplink SCMA system, each layer transmits a codeword mapped with binary data to a base station based on a unique codebook, and the base station detects codewords superimposed on time-frequency resources by using codebook information of each user. In the uplink SCMA system, the user equipment (UE) must additionally use physical resources to transmit a plurality of data streams. In one example, the rate can be increased by utilizing more time-frequency resources. If more transmitting antennas are installed, the additional data layer (or SCMA codebook) may be allocated to increase the transmission rate through multi-stream transmission.

Meanwhile, the serial link SCMA system has limitations and limitations in supporting the requirements of the future Mmtc and IoT environments. Although a large number of SCMA codebook resources are secured in the system to support hyper-connected user terminals, each user terminal has a characteristic of generating traffic at a rare frequency. In other words, since the actual active user terminal occupies a small ratio to the total number of codebook resources, the use of system resources is inefficient when considering the total codebook resources secured in the system.

Accordingly, there is a need for a concept and transmission method for efficiently utilizing codebook resources that are not used by an active user terminal.

Reference: Korean Patent Publication No. 10-2017-0042680, Korean Patent Publication No. 10-2017-0015018

By efficiently utilizing codebook resources for an uplink SCMA system, a transmission method and an operation method supporting various ranges of transmission rates through overlapping transmission of a user equipment (UE) are proposed.

In the uplink SCMA system, a data superimposition transmission method by a user terminal may include dynamically allocating an SCMA codebook to the user terminal; Performing SCMA encoding based on the SCMA codebook dynamically allocated to the user terminal; Identifying an SCMA codeword based on an SCMA codebook corresponding to each data layer as the SCMA encoding is performed; And overlapping the identified SCMA codeword and transmitting the same to the base station.

Performing SCMA encoding based on the SCMA codebook dynamically allocated to the user terminal may include: a binary vector transmitted through each data layer by mapping the SCMA codebook dynamically allocated to the user terminal to at least one data layer generating a parent signal locus from ( b _j ); Spreading a complex multi-dimensional symbol corresponding to each data layer output based on the generated mother signal locus; And outputting a codebook consisting of the spread complex multidimensional symbols according to a layer operation set for each data layer.

Transmitting the identified SCMA codewords to the base station may include passing the overlapped SCMA codewords transmitted through the same antenna by the user terminal through the same channel.

Dynamically allocating an SCMA codebook to the user terminal includes allocating at least one codebook to the user terminal for a specific time-frequency domain to support an overlapping transmission mode for the user terminal. When the terminal requests a data rate higher than or equal to a predetermined reference value, a codebook having a predetermined number or more may be used. When the user terminal requests a data rate lower than or equal to a predetermined reference value, a codebook of a predetermined number or less may be used.

Performing SCMA encoding based on the SCMA codebook dynamically allocated to the user terminal may include deriving a layer operation in consideration of interference between the data layers.

Performing SCMA encoding based on the SCMA codebook corresponding to each data layer comprises: determining a tuple of rotation phase based on a tuple of a fixed permutation function; Determining a tuple of permutation functions based on a product of the metric calculated to determine the tuple of the rotational phase; And determining, by the layer operation, the determined rotation phase tuple with respect to the determined permutation function.

An uplink SCMA system for performing data overlapping transmission by a user terminal, comprising: an allocator for dynamically allocating an SCMA codebook to the user terminal; An encoder for performing SCMA encoding based on an SCMA codebook dynamically allocated to the user terminal; An identification unit for identifying an SCMA codeword based on the SCMA codebook corresponding to each data layer as the SCMA encoding is performed; And a transmitter / receiver for transmitting the identified SCMA codewords to the base station.

The encoder generates a mother signal locus from a binary vector b _j transmitted through each data layer by mapping an SCMA codebook dynamically allocated to the user terminal to at least one data layer, and generates the mother signal. Spreading a complex multidimensional symbol corresponding to each data layer output based on the constellation, and outputting a codebook composed of the spread complex multidimensional symbols according to a layer operation set in each data layer. .

The transceiver may allow overlapping SCMA codewords transmitted by the user terminal through the same antenna to pass through the same channel.

The allocator may include assigning at least one codebook to a specific time-frequency region to the user terminal in order to support an overlapping transmission mode to the user terminal. If a codebook with a predetermined number or more is used and the user terminal requests a data rate less than or equal to a preset reference, a codebook with a predetermined number or less may be used.

The encoder may derive a layer operation in consideration of the interference between the data layers.

The encoder determines a tuple of a rotational phase based on a tuple of a fixed permutation function, determines a tuple of the permutation function based on a product of a metric calculated to determine the tuple of the rotational phase, and determines the determined permutation function. The determined rotation phase tuple may be determined by a layer operation.

An SCMA encoding apparatus, comprising: at least one processor, and at least one transceiver operatively coupled to the at least one processor, wherein the at least one processor comprises: a user terminal Generating a mother signal locus for the binary vector b _j transmitted through each data layer by mapping the SCMA codebook dynamically allocated to the at least one data layer; Spreading a complex multi-dimensional symbol corresponding to each data layer output based on the generated mother signal locus; And outputting a codebook consisting of the spread complex multi-dimensional symbols according to a layer operation set in each data layer.

The outputting of the codebook composed of the spread complex multi-dimensional symbols by the SCMA codeword according to the layer operation set in each data layer may include deriving a layer operation in consideration of the interference between the data layers.

The process of outputting a codebook composed of the spread complex multidimensional symbols according to a layer operation set for each data layer may include determining a tuple of a rotation phase based on a tuple of a fixed permutation function and tuple of the rotation phase. The method may include determining a tuple of a permutation function based on a product of a metric calculated to determine a value, and determining the determined rotation phase tuple by a layer operation with respect to the determined permutation function.

The uplink SCMA system according to an embodiment can increase the efficiency of system resource usage by efficiently allocating and utilizing the entire codebook resource and data layer for a small number of active user terminals compared to the total number of available codebooks.

The uplink SCMA system according to an embodiment can improve the transmission rate of a user terminal through overlapping transmission using a codebook without additionally using physical multiple access resources (time, frequency, antenna).

The uplink SCMA system according to an embodiment may effectively remove interference between data layers by applying a codebook designed based on overlapping transmission.

In the uplink SCMA system according to an embodiment, the overlapping transmission on the codebook does not incur a large overhead additionally to the transmitter / receiver for uplink.

1 is a view for explaining the operation of the uplink SCMA system.
2 is a view for explaining the configuration and encoding process of the SCMA encoder.
3 is an example of a multiple access resource structure and multiple access operation supporting overlapping transmission on a codebook according to one embodiment.
4 is a diagram illustrating an operation of an uplink SCMA system according to an embodiment.
5 is a block diagram illustrating a configuration of an uplink SCMA system according to an embodiment.
6 is a flowchart illustrating an uplink SCMA method in an uplink SCMA system according to an embodiment.
7 is a flowchart illustrating a method of generating a codebook in an uplink SCMA system according to an embodiment.
8 is a graph comparing interference cancellation between codebook layers in an uplink SCMA system according to an embodiment.
9 is a graph comparing transmission rates of an uplink SCMA system according to an embodiment.

Hereinafter, exemplary embodiments will be described in detail with reference to the accompanying drawings.

1 is a view for explaining the operation of the uplink SCMA system.

An operation of a general uplink SCMA system will be described in FIG. 1. As an example, consider a content link SCMA system supporting J (J is a natural number) data layers. Typically, a single data stream is transmitted through one transmit antenna. In the prior art, it is assumed that a single data stream can be transmitted through a layer for each data. Accordingly, the UE can transmit the maximum number of data streams by the number of transmit antennas held.

단위인 이진 벡터이다. SCMA 부호화(SCMA encoding)은 이진 벡터 b _j 로부터 SCMA 코드북의 원소인 부호화 x _j 로의 사상/맵핑(mapping)을 의미한다. 다시 말해서, 1≤j≤J 번째 SCMA 코드북은 X _j ⊂C ^K , SCMA 코드북의 크기는 M=| X _j |, SCMA 부호어의 길이는 K, SCMA 부호어 x _j ∈ X _j 는 'sparse'하다는 특징을 갖는다. 이때, d _J 는 K개의 0이 아닌 원소를 가지고, 반대로, (K-d _J )개의 원소는 0으로 채워진 형태로 구성될 수 있다.1 ≤ j ≤ vector b _j transmitted through the J th data layer has a length

Binary vector as a unit. SCMA encoding means mapping / mapping from binary vector b _j to encoding x _j , which is an element of the SCMA codebook. In other words, 1≤ j ≤ J th SCMA codebook is X _j ⊂C ^K , SCMA codebook is M = | X _j |, SCMA codeword length is K , The SCMA codeword x _j ∈ X _j is characterized as being 'sparse'. In this case, d _J has K non-zero elements, on the contrary, ( K − d _J ) elements may be configured to be filled with zeros.

). Assume that the power of the SCMA protector is set to 1 (

).

, 1≤k≤K번째 무선 자원을 사용하는 데이터 레이어의 인덱스 집합은

와 같이 나타낼 수 있다. The structure of an SMMA codebook can be described by a set of integers defined as follows: 1≤ j ≤ index set of radio resources used by the J th data layer

, The index set of the data layer using the second wireless resource 1≤ k ≤ K

Can be expressed as:

The resource utilization efficiency may refer to a ratio of resources actually used to total codebook resources given to the uplink SCMA system, and is actually connected to an active UE for the number J of the total codebooks. The number of times may be defined as U < J , and the resource use efficiency of the conventional system may be expressed as U / J.

2 is a view for explaining the configuration and encoding process of the SCMA encoder. ( d _J = 2, M = 4, K = 4).

SCMA encoder performs mapping from binary vector b _j to SCMA codeword x _j based on a unique codebook assigned to the data layer. For example, a suboptimal codebook can be designed by dividing the SCMA encoding process into three steps.

Step 1: Mother constellation mapping-Design complex-domain multidimensional constellation and output complex multidimensional symbols for binary input

Step 2: resource mapping-spreading parent signal locus symbols to radio resources assigned to the data layer

Step 3: layer-specific operation-outputs a different codeword symbol for each data layer by applying a unique operation assigned to the data layer

)는 길이가

인 이진 벡터

의 입력에 대하여 복소

차원 신호성좌 심볼을 출력하는 함수이다.In step 1, the parent signal constellation mapping function (

) Is the length

Binary vector

Complex against the input of

Outputs the dimensional signal locus symbol.

과 같이 나타낼 수 있다.For example,

It can be expressed as

번째 자원 맵핑 행렬(

)은

차원 복소 심볼을 K-차원 벡터 v _j 로 변환하도록 0과 1로만 구성된 행렬을 의미한다(

). 맵핑 행렬에서 모든 원소가 0으로 구성된 (

) 개의 행을 제거 시 크기가

인 항등 행렬(identity matrix)이 되는 특징을 가지고, 각 데이터 레이어에는 고유의 자원 맵핑 행렬이 할당된다. In step 2

Resource mapping matrix (

)silver

Means a matrix of 0's and 1's only for converting a dimensional complex symbol to a K -dimensional vector v _j (

). In the mapping matrix, all elements consist of zeros (

Size when removing) rows

It has the characteristic of being an identity matrix, and each data layer is assigned a unique resource mapping matrix.

일 때,

와 같이 나타낼 수 있다.For example,

when,

Can be expressed as:

번째 레이어 연산은 단계 1에서 이미 설계된 모신호성좌의 특성을 변화시키지 않는 유니터리 연산(unitary operation)으로서 자원 맵핑 출력

에 대한 순열(permutation) 및 위상 회전(phase rotation) 연산을 고려한다.

를 구성하는 0이 아닌 원소에 대한 순열 함수

를

로 정의하고, 순서 집합(ordered set)

에 대하여 원소의 순서가 변경된 순서 집합

를 고려하고,

에 대하여 순열 함수

는

의 맵핑을 수행할 수 있다. 예를 들면,

와 같이 나타낼 수 있다. 또한, 각 원소에 대한 위상 회전을 고려할 수 있다. 위상에 대한 K- 튜플은

, 정수

에 대하여 위상의 후보 집합 W를 다음과 같이 정의할 수 있다.Performed in step 3

The second layer operation is a unitary operation that does not change the characteristics of the parent signal locus already designed in step 1, and outputs the resource mapping.

Consider permutation and phase rotation operations for.

Permutation function for nonzero elements that make up

To

Defined as an ordered set

An ordered set of elements with respect to

Consider,

Permutation function

Is

Can be mapped. For example,

Can be expressed as: Also, phase rotation for each element can be considered. K -tuple for phase

, essence

The candidate set W of phases can be defined as follows.

의

번째 원소를

로 정의할 수 있다. 이에 따라 SCMA 부호화기의 최종 출력인 부호어의

번째 원소를 다음과 같이 표현할 수 있다. K -tuple

of

Element

Can be defined as Accordingly, the codeword as the final output of the SCMA encoder

The second element can be expressed as

4 is a diagram illustrating an operation of an uplink SCMA system according to an embodiment.

The use of additional resources such as codebook, space, power, interleaver, etc. in addition to physical resources (time, frequency, antenna) is an important trend to support uplink superconnected UE. In the embodiment, a transmission operation capable of supporting various ranges of transmission rates through overlapping transmission of a UE by efficiently utilizing codebook resources for an uplink SCMA system will be described. Specifically, a method of increasing the use efficiency of system resources by efficiently allocating and utilizing entire codebook resources and data layers for a small number of active user terminals compared to the total number of available codebooks will be described. In addition, a method of improving the transmission rate of each user terminal by simultaneously transmitting a large number of data streams without additionally using physical multiple access resources (time, frequency, antenna) will be described.

Referring to FIG. 3, it is an example of a multiple access resource structure and a multiple access operation supporting overlapping transmission on a codebook.

The uplink SCMA system supports overlapping transmission. The multiple access resource is a basic resource unit considered in the uplink SCMA system and may be configured of time, frequency, and codebook. In this case, a plurality of J codebooks of the same size may be divided for a specific time-frequency domain.

The uplink SCMA system controls the user terminal to occupy a plurality of codebook resources in a specific time-frequency region in order to support the overlapped transmission mode of the user terminal (UE). In this case, a user terminal requesting a transmission rate higher than or equal to a predetermined reference may utilize more than a predetermined number of codebooks in order to utilize a plurality of multiple access resources, and a user terminal requesting a transmission rate lower than or equal to a predetermined reference may use a codebook equal to or less than a preset number. It can be utilized. In the embodiment, it is assumed in the prior art that the user terminal communicates with the base station BS using a single multiple access resource (codebook).

을 정의한다. Matrix consisting of codewords that can be transmitted through all data layers as columns

Define.

번째 사용자 단말기에게 할당된 데이터 레이어의 인덱스를 원소로 갖는 집합

을 정의한다. u번째 사용자 단말기에 대하여

의 크기를

로 표기한다(

). 모든 사용자 단말기에게 할당된 데이터 레이어의 수를 표현하기 위하여 U-튜플을

로 정의한다.

Set whose elements have the indices of the data layers allocated to the first user terminal

Define. About u th user terminal

Size

It is written as (

). U -tuples are used to represent the number of data layers allocated to all user terminals.

Defined as

에 대하여 L _u =L로써 동일한 경우(uniform allocation),As an example, an example of codebook allocation and distribution may be shown as follows. For example, all

If L _u = L, then uniform allocation,

■ K = 4, d _J = 2 , J = 6, U = 1, L = 6

K = 4, d _J = 2 , J = 6, U = 3, L = 2 (orthogonally allocated)

■ K = 4, d _J = 2 , J = 6, U = 2, L = 3

As another example, when each user terminal is assigned a different number of layers (non-uniform allocation),

A total of U user terminals may transmit information by fully utilizing the entire J data layers. In the prior art, the user terminal may use only as many data layers as the number of transmit antennas, but since the embodiment considers overlapping transmission, the user terminal may utilize more data layers than the transmit antennas held.

Referring to FIG. 4, the uplink SCMA system according to an embodiment may perform overlapping transmission on a codebook.

It is assumed that a user terminal (UE) 110 collectively refers to a mobile or fixed user terminal device such as a mobile station (MS) and an advanced mobile station (AMS). In addition, it is assumed that the base station collectively refers to any node of the network side that communicates with the terminal such as a Node B, an eNode B, a Base Station, and an Access Point (AP). The repeater may be referred to as a relay node (RN), a relay station (RS), a relay, or the like.

In the uplink SCMA system, the user equipment 110 may receive information from the base station through downlink, and the user terminal may also transmit information through uplink. Information transmitted or received by the user terminal 110 may include data and various control information, and various physical channels may exist according to the type and purpose of information transmitted or received by the user terminal 110.

The SCMA encoder 111 may perform mapping from a binary vector to an SCMA codeword based on a unique codebook assigned to a data layer.

The modulator may perform quadrature amplitude modulation (QAM) and orthogonal frequency division multiplexing (OFDM), for example.

Although the uplink SCMA system overlaps SCMA codewords corresponding to each data layer, the uplink SCMA system can identify the overlapped codewords through a unique codebook assigned to each data layer.

번째 사용자 단말기는 할당된

개의 데이터 레이어에 대한 부호어를 중첩하여 전송할 수 있다.

User terminal is assigned

Codewords for two data layers may be overlapped and transmitted.

를 전송할 수 있다. 다시 말해서, 중첩된

개의 부호어는 동일한 전력으로써 전송됨을 의미한다.The superimposed codeword (nested codeword) may be modulated via a single modulator and then transmitted via a single transmit antenna. At this time, each user terminal is a superimposed codeword as the power of P through a single transmit antenna

Can be transmitted. In other words, nested

Codewords are transmitted with the same power.

개의 부호어가 공통적으로 통과하는 주파수 영역 채널을

로 정의할 수 있다.In an uplink SCMA system, overlapped codewords transmitted through the same transmit antenna pass through the same channel. At this time,

Frequency domain channel through which two codewords pass in common

Can be defined as

Assuming that all codewords are received in synchronization, the received signal y in the frequency domain may be expressed as follows.

을 가지는 정규 분포를 따른다. Where n is the AWGN vector where each element has an average of 0 and variance

Follow a normal distribution with

을 기반으로 종래의 다중 사용자 단말기 검출 기법을 동일하게 적용할 수 있으며, 각 데이터 레이어를 통하여 전송된 사용자 단말기의 정보를 검출할 수 있다. 종래의 수신기는 모든 SCMA 부호어가 서로 다른 채널을 통과하였음을 고려하였으나, 실시예에서는

,

의 성질을 이용하여 종래의 수신기를 동일하게 활용 가능하다. The base station BS receives the received signal y and the channel vector.

Based on the above, the conventional multi-user terminal detection technique may be applied in the same manner, and information of the user terminal transmitted through each data layer may be detected. The conventional receiver considered that all SCMA codewords passed through different channels, but in the embodiment

,

By using the properties of the conventional receiver can be utilized in the same way.

7 is a flowchart illustrating a method of generating a codebook in an uplink SCMA system according to an embodiment.

The uplink SCMA system can design an SCMA codebook that maximizes transmission rate improvement based on overlapping transmission. The uplink SCMA system can control interference between data layers due to overlapping transmission by designing an optimal layer operation for a given mother signal locus and resource mapping in the SCMA encoding process.

, 회전 위상 튜플에 대한 J-튜플을

, 모든 데이터 레이어에 대하여 자원 맵핑 출력을 열로서 구성하는 행렬을

로 정의할 수 있다. At this point, we need to add the J -tuple

, J -tuple for rotating phase tuple

For every data layer, we construct a matrix of resource mapping outputs as columns.

Can be defined as

,

번째 자원에 대한 dimension-wise distance를

로 표현할 수 있다. 집합

는 dimension-wise distance가 0이 아닌 자원의 인덱스를 원소로 갖는 집합으로서

과 같이 표현할 수 있다. 여기서,

의 크기는

에 존재할 수 있다.In addition, the main parameters representing the codebook characteristics for different matrices V and V will be summarized. Squared product distance

,

Dimension-wise distance for the first resource

Can be expressed as set

Is a set whose elements are indices of resources whose dimension-wise distance is nonzero.

It can be expressed as here,

The size of

May exist in

) 영역에서의 상향링크 SCMA 시스템의 BER

의 상한 값은 다음과 같이 유도될 수 있다.Assuming that the base station applies ML detection, high SNR (

BER of Uplink SCMA System in

The upper limit of can be derived as follows.

이고,

는 다음의 식으로 계산되며 squared product distance에 대한 함수임. 즉, squared product distance가 큰 코드북을 설계함으로써

의 값이 커질 수 있다.In this case, the binary hamming distance between V and V is

ego,

Is a function of squared product distance That is, by designing a codebook with a large squared product distance

Can increase the value of.

The upper limit value will be described. The formula of ① is the term determined by the given parent signal locus, and the formulas ② and ③ are generated by the interference between data layers. Therefore, the term ② is greatly influenced by the overall upper limit compared to the term ③. Consider the problem of layer computational design in view. Also, the set E of error events considered in calculating the term of ② can be defined as follows.

The term ② can be expressed differently from the one described below.

An example of designing a codebook will be described.

과

을 다음의 식으로써 최적화시킬 수 있다.In step 710, the uplink SCMA system computes a data layer that minimizes the upper limit for term

and

Can be optimized by the equation

At 710, the uplink SCMA system can derive a layer operation that maximizes the minimum weighted squared product distance for a set of major error events causing inter-layer interference.

In addition, another example of designing a codebook will be described.

The uplink SCMA system may consider the following optimization step in terms of maximizing each of the factors constituting the squared product distance.

에 대하여 최소 weighted dimension-wise distance가 최대화되는 관점에서 회전 위상의 튜플을 결정할 수 있다.In step 711, the uplink SCMA system performs a tuple of fixed permutation functions.

We can determine the tuple of the rotational phase in terms of maximizing the minimum weighted dimension-wise distance.

The metric calculated at this time can be defined as the following function.

에 대하여 단계711을 반복 후, 계산된 메트릭의 곱을 최대화하는 관점에서 최적의 순열 함수의 튜플을 결정할 수 있다. In step 712, the uplink SCMA system is

After repeating step 711 for, it is possible to determine the tuple of the optimal permutation function in terms of maximizing the product of the calculated metric.

에 대하여 미리 결정된 회전 위상 튜플을 최적의 레이어 연산

으로서 결정할 수 있다.In step 713, the uplink SCMA is the permutation function determined in step 712.

Layer calculation of a predetermined rotational phase tuple for

Can be determined as

In the uplink SCMA system according to an embodiment, the overlapping transmission on the codebook does not incur a large overhead additionally to the transmitting / receiving end for the uplink. Specifically, it does not require additional channel information for the uplink channel, and does not require an additional device such as a channel encoder or a QAM / OFDM modulator in addition to the addition operation for the SCMA codeword generated at the transmitter. It does not change the structure of the conventional receiving end device.

5 is a block diagram illustrating a configuration of an uplink SCMA system according to an embodiment, and FIG. 6 is a flowchart illustrating an uplink SCMA method in an uplink SCMA system according to an embodiment.

The uplink SCMA system 100 may include an allocator 510, an encoder 520, an identifier 530, and a transceiver 540. The configuration of the uplink SCMA system is shown only as an example, and one unit may be divided into detailed units or at least one unit may be integrated with other units according to an operator's intention or embodiments. In addition, the components of the uplink SCMA system may control the uplink SCMA system to perform steps 610 to 640 included in the uplink SCMA method of FIG. 6.

In operation 610, the allocator 510 may dynamically allocate the SCMA codebook to the user terminal. The allocator 510 may allocate at least one codebook to the user terminal in a specific time-frequency region in order to support the overlapped transmission mode.

In operation 620, the encoder 520 may perform SCMA encoding based on the SCMA codebook dynamically allocated to the user terminal. The encoder 520 may perform SCMA encoding based on the SCMA codebook corresponding to each data layer by mapping the SCMA codebook dynamically allocated to the user terminal to at least one data layer. The encoder 520 may perform mapping from a binary vector b _j transmitted through each data layer to an SCMA codeword x _{j, which} is an element of the SCMA codebook. In detail, the encoder 520 generates a mother signal locus from the binary vector b _j transmitted through each data layer by mapping the SCMA codebook dynamically allocated to the user terminal to at least one data layer. Spreading a complex multidimensional symbol corresponding to each data layer output based on the generated mother signal locus, and applying a codebook including the spread complex multidimensional symbol to a SCMA codeword according to a layer operation set in each data layer. You can print

In operation 630, as the identifier 530 performs SCMA encoding, the identification unit 530 may identify the SCMA codeword based on the SCMA codebook corresponding to each data layer.

In step 640, the transceiver 540 may transmit the superimposed SCMA codeword to the base station. The transceiver 540 may allow overlapping SCMA codewords transmitted by the user terminal through the same antenna to pass through the same channel.

8 is a graph comparing interference cancellation between codebook layers in an uplink SCMA system according to an embodiment.

로 표현될 수 있다. 만약, 모든 데이터 레이어가 사용자 단말기에게 할당 및 분배된다면 상향링크 시스템에 주어진 가용 자원을 100% 활용 가능함을 의미한다. Uplink SCMA system has high resource usage efficiency.

It can be expressed as. If all data layers are allocated and distributed to user terminals, it means that 100% of available resources given to the uplink system can be utilized.

, (b)

, (c)

이다.Referring to FIG. 8, Conventional codebooks represent BERs when a conventional codebook is applied to an uplink SCMA according to an embodiment, and a single-layer BER is a BER for data transmission at the same power in an environment without interference. It is shown. Comparing the BER when different codebooks are applied to the uplink SCMA system, (a)

, (b)

, (c)

to be.

When the codebook proposed in the embodiment is applied, an SNR gain of 2 to 3 dB can be obtained compared to when the conventional codebook is applied based on a BER of 10 ^-5 . In addition, the application of the designed codebook by observing the convergence to the BER of the environment where there is no interference in the high SNR region is very effective in controlling the interference between data layers.

9 is a graph comparing transmission rates of an uplink SCMA system according to an embodiment.

의 코드북 자원 할당/분배의 경우를 고려한다. Operating the uplink SCMA system according to an embodiment on the LTE system to observe the average data rate of the system, and applied to the LTE turbo code having a code rate of 1/3, 1/2, 2/3 four resource blocks ( resource block)

Consider the case of codebook resource allocation / distribution.

Conv. SCMA is a conventional uplink SCMA system, Prop. SCMA w / Conv. CBs means a case where a conventional codebook is applied to an uplink SCMA system according to an embodiment. Accordingly, the rate evaluation result of the system applying the codebook designed through the uplink SCMA system according to an embodiment is (a) when applying 1/3 LTE turbo code, (b) when applying 1/2 LTE turbo code, (c ) It may appear as when 2/3 LTE turbo code is applied.

Accordingly, when the overlapped transmission is applied in the uplink SCMA system, the maximum data rate can be achieved up to 3 times as compared to the conventional one.In the case of using the codebook designed in the embodiment, the maximum transmission rate is additionally increased by 48%, (a). b) 76%, (c) 74% can be improved.

The apparatus described above may be implemented as a hardware component, a software component, and / or a combination of hardware components and software components. For example, the devices and components described in the embodiments are, for example, processors, controllers, arithmetic logic units (ALUs), digital signal processors, microcomputers, field programmable gate arrays (FPGAs). Can be implemented using one or more general purpose or special purpose computers, such as a programmable logic unit (PLU), a microprocessor, or any other device capable of executing and responding to instructions. The processing device may execute an operating system (OS) and one or more software applications running on the operating system. The processing device may also access, store, manipulate, process, and generate data in response to the execution of the software. For the convenience of understanding, a processing device may be described as one being used, but a person skilled in the art will appreciate that the processing device includes a plurality of processing elements and / or a plurality of types of processing elements. It can be seen that it may include. For example, the processing device may include a plurality of processors or one processor and one controller. In addition, other processing configurations are possible, such as parallel processors.

The software may include a computer program, code, instructions, or a combination of one or more of the above, and configure the processing device to operate as desired, or process it independently or collectively. You can command the device. Software and / or data may be any type of machine, component, physical device, virtual equipment, computer storage medium or device in order to be interpreted by or to provide instructions or data to the processing device. It can be embodied in. The software may be distributed over networked computer systems so that they may be stored or executed in a distributed manner. Software and data may be stored on one or more computer readable recording media.

The method according to the embodiment may be embodied in the form of program instructions that can be executed by various computer means and recorded in a computer readable medium. The computer readable medium may include program instructions, data files, data structures, etc. alone or in combination. The program instructions recorded on the media may be those specially designed and constructed for the purposes of the embodiments, or they may be of the kind well-known and available to those having skill in the computer software arts. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tape, optical media such as CD-ROMs, DVDs, and magnetic disks, such as floppy disks. Magneto-optical media, and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include not only machine code generated by a compiler, but also high-level language code that can be executed by a computer using an interpreter or the like.

Although the embodiments have been described by the limited embodiments and the drawings as described above, various modifications and variations are possible to those skilled in the art from the above description. For example, the described techniques may be performed in a different order than the described method, and / or components of the described systems, structures, devices, circuits, etc. may be combined or combined in a different form than the described method, or other components. Or even if replaced or substituted by equivalents, an appropriate result can be achieved.

Therefore, other implementations, other embodiments, and equivalents to the claims are within the scope of the claims that follow.

Claims (15)

In the uplink SCMA system, in the data overlapping transmission method by the user terminal,
Dynamically allocating an SCMA codebook to the user terminal;
Performing SCMA encoding based on the SCMA codebook dynamically allocated to the user terminal;
Identifying an SCMA codeword based on an SCMA codebook corresponding to each data layer as the SCMA encoding is performed; And
Superimposing the identified SCMA codewords and transmitting them to a base station
Including,
Dynamically allocating a SCMA codebook to the user terminal,
In order to support the overlapped transmission mode to the user terminal, at least one codebook is allocated to the user terminal in a specific time-frequency region, and when the user terminal requests a transmission rate higher than or equal to a preset criterion, a codebook of a predetermined number or more is used. And using the codebook of a predetermined number or less when the user terminal requests a transmission rate of a predetermined reference or less.
Including,
Performing SCMA encoding based on the SCMA codebook dynamically allocated to the user terminal,
1) Derivation of the upper limit of BER (

To minimize the upper limit for ②

2) design the codebook based on a method of determining a layer operation for controlling the inter-layer data interference through 2) outputting the resource mapping based on a tuple of a fixed permutation function for nonzero elements constituting the resource mapping output. Determine a tuple of rotational phases with respect to the rotational phase of each element constituting an element, determine a tuple of the permutation function based on a product of the metric calculated to determine the tuple of the rotational phase, and determine the determined permutation function and the determined The codebook is designed based on the method of determining the rotation phase tuple determined for the permutation function by the layer operation for controlling the inter-data layer interference.
A mother signal locus is generated from a binary vector b _j transmitted through each data layer by mapping an SCMA codebook dynamically allocated to the user terminal to at least one data layer, and based on the generated mother signal locus. Spread a complex multidimensional symbol corresponding to each output data layer into a resource mapping matrix allocated to each data layer, and output a codebook composed of the complex multidimensional symbols as an SCMA codeword according to a layer operation set in each data layer. Steps to
Including,
Superimposing the identified SCMA codeword and transmitting to the base station,
Steps for superimposing SCMA codewords transmitted through the same antenna by the user terminal through the same channel
Including,
The tuple of the rotating phase

To make a decision based on
The metric calculated to determine the tuple of the rotational phase is

Defined as
The tuple of the permutation function maximizes the metric product

Determined by
The resource mapping matrix is configured to convert the complex multidimensional symbol into a resource mapping output that is a vector for the K-dimensional,
Tuples for permutation functions for nonzero elements that make up the resource mapping output.

, A tuple for the rotational phase of each element constituting the resource mapping matrix

For a data layer, a matrix consisting of resource mapping outputs as columns (

),
Squared product distances for different matrices V and V

,

Dimension-wise distance for the first resource

Expressed as
set

Is a set whose elements are indices of resources whose dimension-wise distance is nonzero.

Expressed as

The size of

Exist in,
The binary hamming distance between V and V

sign
Nested transmission method in the uplink SCMA system. delete delete delete The method of claim 1,
Performing SCMA encoding based on the SCMA codebook dynamically allocated to the user terminal,
Deriving a layer operation in consideration of the interference between the data layers
Nested transmission method in an uplink SCMA system comprising a. delete In an uplink SCMA system performing data overlapping transmission by a user terminal,
An allocator for dynamically allocating an SCMA codebook to the user terminal;
An encoder for performing SCMA encoding based on an SCMA codebook dynamically allocated to the user terminal;
An identification unit for identifying an SCMA codeword based on the SCMA codebook corresponding to each data layer as the SCMA encoding is performed; And
Transmitter and receiver to superimpose the identified SCMA codeword and transmit to the base station
Including,
The allocation unit,
In order to support the overlapped transmission mode to the user terminal, at least one codebook is allocated to the user terminal in a specific time-frequency region, and when the user terminal requests a transmission rate higher than or equal to a preset criterion, a codebook of a predetermined number or more is used. And, if the user terminal requires a transmission rate of less than the predetermined reference, including using a codebook of a predetermined number or less,
The encoder,
1) Derivation of the upper limit of BER (

To minimize the upper limit for ②

2) design the codebook based on a method of determining a layer operation for controlling the inter-layer data interference through 2) outputting the resource mapping based on a tuple of a fixed permutation function for nonzero elements constituting the resource mapping output. Determine a tuple of rotational phases with respect to the rotational phase of each element constituting an element, determine a tuple of the permutation function based on a product of a metric calculated to determine the tuple of the rotational phase, and determine the determined permutation function and the determined The codebook is designed based on the method of determining the rotation phase tuple determined for the permutation function by a layer operation to control the inter-data interference.
A mother signal locus is generated from a binary vector b _j transmitted through each data layer by mapping the SCMA codebook dynamically allocated to the user terminal to at least one data layer, and based on the generated mother signal locus. Spread a complex multidimensional symbol corresponding to each output data layer into a resource mapping matrix allocated to each data layer, and output a codebook composed of the complex multidimensional symbols as an SCMA codeword according to a layer operation set in each data layer. Including doing it,
The transceiver unit,
The overlapping SCMA codewords transmitted through the same antenna by the user terminal pass through the same channel,
The tuple of the rotating phase

To make a decision based on
The metric calculated to determine the tuple of the rotational phase is

Defined as
The tuple of the permutation function maximizes the metric product

Determined by
The resource mapping matrix is configured to convert the complex multidimensional symbol into a resource mapping output that is a vector for the K-dimensional,
Tuples for permutation functions for nonzero elements that make up the resource mapping output.

, A tuple for the rotational phase of each element constituting the resource mapping matrix

For a data layer, a matrix consisting of resource mapping outputs as columns (

),
Squared product distances for different matrices V and V

,

Dimension-wise distance for the first resource

Expressed as
set

Is a set whose elements are indices of resources whose dimension-wise distance is nonzero.

Expressed as

The size of

Exist in,
The binary hamming distance between V and V

sign
Uplink SCMA System. delete delete delete The method of claim 7, wherein
The encoder,
Deriving a layer operation in consideration of the interference between each data layer
Uplink SCMA system, characterized in that. delete In the SCMA encoder,
At least one processor,
At least one transceiver operatively coupled to the at least one processor,
The at least one processor,
Generating a mother signal locus for the binary vector b _j transmitted through each data layer by mapping the SCMA codebook dynamically allocated to the user terminal to at least one data layer;
Spreading a complex multidimensional symbol corresponding to each data layer output based on the generated mother signal locus into a resource mapping matrix allocated to each data layer; And
Outputting a codebook consisting of the complex multidimensional symbols into an SCMA codeword according to a layer operation set for each data layer
Including,
The process of outputting the codebook consisting of the complex multi-dimensional symbols by the SCMA codeword according to the layer operation set in each data layer,
1) Derivation of the upper limit of BER (

To minimize the upper limit for ②

Determining a layer operation for controlling the interference between data layers through 2) or 2) each element constituting the resource mapping output based on a tuple of a fixed permutation function for nonzero elements constituting the resource mapping output. Determine a tuple of rotational phases relative to the rotational phase, determine a tuple of permutation functions based on a product of the metric calculated to determine the tuple of the rotational phases, and determine the rotations determined for the determined permutation function and the determined permutation function Determining a phase tuple by a layer operation for controlling interference between data layers;
The tuple of the rotating phase

To make a decision based on
The metric calculated to determine the tuple of the rotational phase is

Defined as
The tuple of the permutation function maximizes the metric product

Determined by
The resource mapping matrix is configured to convert the complex multidimensional symbol into a resource mapping output that is a vector for the K-dimensional,
Tuples for permutation functions for nonzero elements that make up the resource mapping output.

, A tuple for the rotational phase of each element constituting the resource mapping matrix

For a data layer, a matrix consisting of resource mapping outputs as columns (

),
Squared product distances for different matrices V and V

,

Dimension-wise distance for the first resource

Expressed as
set

Is a set whose elements are indices of resources whose dimension-wise distance is nonzero.

Expressed as

The size of

Exist in,
The binary hamming distance between V and V

sign
SCMA encoder. The method of claim 13,
The process of outputting the codebook consisting of the complex multi-dimensional symbols by the SCMA codeword according to the layer operation set in each data layer,
Deriving a layer operation in consideration of the interference between the data layers
SCMA encoding apparatus comprising a. delete

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