KR102152922B1 - Noma system and its method for scheduling multi-user - Google Patents

Abstract

The present invention relates to a non-orthogonal multiple access system and a multi-user scheduling method thereof, which is performed by a non-orthogonal multiple access system that performs a non-orthogonal multiple access (NOMA) between a base station and a user terminal. In the multi-user scheduling method, a) the base station receives subband channel information and quality of service (QoS) request information from a user terminal, and calculates a resource allocation amount using the service quality request information of the user terminal. Setting a weight for each user terminal after calculation; b) calculating a cumulative distribution function (CDF) based on a channel gain using the weight and channel information for each user terminal; And c) scheduling a user set by selecting a plurality of user terminals for each subband using the channel gain-based CDF, and feeding back scheduling information to each user terminal.

Description

Non-orthogonal multiple access system and its multi-user scheduling method TECHNICAL FIELD [NOMA SYSTEM AND ITS METHOD FOR SCHEDULING MULTI-USER]

The present invention relates to a non-orthogonal multiple access system that enables fair resource allocation in a NOMA environment and a multi-user scheduling method thereof.

In recent years, research on next-generation mobile communication is being actively conducted, and 5G mobile communication is receiving a lot of attention. The core of 5G mobile communication technology is high data rate, low latency, and massive connectivity.

Among 5G mobile communication technologies, a non-orthogonal multiple access (NOMA) method has been proposed as a method for simultaneously connecting a plurality of devices and improving data rates. Existing orthogonal access methods, for example OFDMA, TDMA, etc., can communicate with only one user at a fixed time and frequency resource, but the NOMA method allows multiple users to communicate simultaneously using the same time and frequency resource. .

Due to this, the NOMA system can not only connect multiple devices at the same time, but also improve data rates. However, the NOMA system can communicate with multiple users at the same time, but resources are limited, and in an environment such as IoT, many users try to communicate, so only users who can support at the same time communicate selectively. Such a user selection method is called scheduling, and the appropriate scheduling technique is required because the data rate and faireness are greatly affected by which users are scheduled.

In the NOMA system, user scheduling techniques can be divided into data rate aspects and fairness aspects. Existing user scheduling algorithms have been proposed in the direction of maximizing the total user data rate. In this case, the cell edge user, that is, the user at the farthest from the center of the cell, is SNR due to path attenuation. Because this is very bad, the resource is not allocated. As a result, unfair resource allocation is performed in the NOMA system, and user scheduling techniques considering fairness are required.

Republic of Korea Patent Publication No. 10-2017-0006681 (Name of the invention: User terminal device of a multi-user relay system and its non-orthogonal multiple access method operation method)

In order to solve the above-described problem, an object of the present invention is to adjust the amount of resources allocated to each user terminal according to an embodiment of the present invention, and to adjust the data rate accordingly.

However, the technical problem to be achieved by the present embodiment is not limited to the technical problem as described above, and other technical problems may exist.

As a technical means for achieving the above technical problem, a multi-user scheduling method of a non-orthogonal multiple access system according to an embodiment of the present invention provides a non-orthogonal multiple access (NOMA) wireless connection between a base station and a user terminal. In the multi-user scheduling method performed by a non-orthogonal multiple access system performing a), a) the base station receives channel information of a subband and quality of service (QoS) request information from a user terminal, and the Calculating a resource allocation amount using the service quality request information of the user terminal and then setting a weight for each user terminal; b) calculating a cumulative distribution function (CDF) based on a channel gain using the weight and channel information for each user terminal; And c) scheduling a user set by selecting a plurality of user terminals for each subband using the channel gain-based CDF, and feeding back scheduling information to each user terminal.

A non-orthogonal multiple access system according to an embodiment of the present invention is a memory in which a program for performing a multi-user scheduling method between a base station and a user terminal in a non-orthogonal multiple access (NOMA) environment is recorded. ; And a controller for executing the program, wherein the controller receives subband channel information and quality of service (QoS) request information from the user terminal by executing the program, and the user After calculating the resource allocation amount using the service quality request information of the terminal, a weight is set for each user terminal, and a cumulative distribution function (CDF) based on a channel gain is calculated using the weight and channel information for each user terminal. The channel gain-based CDF is used to select a plurality of user terminals for each subband, schedule a user set, and feed back scheduling information to each user terminal.

According to the above-described problem solving means of the present invention, it is possible to adjust the amount of resources allocated to each user terminal according to the conditions of each user terminal by adjusting the weight for each user terminal, and the data rate accordingly.

In addition, in the present invention, when scheduling the allocation of user terminals to subbands, the weights of the user terminals are set equally so that all user terminals are selected with the same probability, so that resources are allocated fairly, and more resources are given to cell edge users. Can be allocated, and an optimal user set can be scheduled for each subband according to the channel state.

1 is a diagram illustrating a NOMA system according to an embodiment of the present invention.
FIG. 2 is a diagram functionally illustrating the configuration of the base station of FIG. 1.
3 is a flowchart illustrating a multi-user scheduling method of a non-orthogonal multiple access system according to an embodiment of the present invention.
4 is a graph comparing a multi-user scheduling method (CS), a proportional fairness (PF), and a time resource allocation amount by random selection in a non-orthogonal multiple access system according to an embodiment of the present invention.
5 is a graph comparing time resource allocation according to weights in a multi-user scheduling method of a non-orthogonal multiple access system according to an embodiment of the present invention.
6 is a graph illustrating an analysis of resource allocation amount and average speed according to weights of cell edge users by a multi-user scheduling method of a non-orthogonal multiple access system according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art can easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and similar reference numerals are assigned to similar parts throughout the specification.

Throughout the specification, when a part is said to be "connected" to another part, this includes not only "directly connected" but also "electrically connected" with another element interposed therebetween. . In addition, when a part "includes" a certain component, it means that other components may be further included, and one or more other features, not excluding other components, unless specifically stated to the contrary. It is to be understood that it does not preclude the presence or addition of any number, step, action, component, part, or combination thereof.

The following examples are detailed descriptions to aid understanding of the present invention, and do not limit the scope of the present invention. Accordingly, the invention of the same scope performing the same function as the present invention will also belong to the scope of the present invention.

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

1 is a diagram illustrating a NOMA system according to an embodiment of the present invention.

Referring to FIG. 1, a NOMA system 100 according to an embodiment of the present invention includes at least one base station 110. Each base station 110 provides a communication service for a specific geographic area, that is, a cell 101. The user terminals UE1 and UE2 typically belong to one cell.

The base station 110 informs the user terminal of the information on the subband allocated for the services provided by the current system and the numerology used in the subband, and each user terminal uses (or receives) Information on a subband through which a desired service is transmitted may be received from the base station 110.

The NOMA scheme supports multiple user terminals () using the same time and frequency resources. In the NOMA technique, a user terminal is classified by using a power domain different from the conventional one, a superposition coding scheme is used in the transmitter, and a sequential interference cancellation (SIC) scheme is used in the receiver. This NOMA technique is known as an optimized method to obtain the maximum data rate in a multi-user situation.

In the NOMA scheme, a transmission signal in downlink can be represented by Equation 1 below.

[Equation 1]

는 k번째 사용자 단말이 전송하는 데이터,

는 k번째 사용자 단말에게 할당된 송신 파워, U는 동시에 통신할 수 있는 사용자 단말 수이다. NOMA 시스템은

로 전체 파워를 각 사용자 단말에게 적절히 분배하게 된다. 이렇게 각 사용자 단말의 데이터를 중첩해서 보내는 방식을 중첩 코딩(superposition coding)이라 한다. here

Is the data transmitted by the kth user terminal,

Is the transmit power allocated to the k-th user terminal, and U is the number of user terminals that can communicate simultaneously. NOMA system

The total power is properly distributed to each user terminal. This method of sending data of each user terminal overlapping is called superposition coding.

만을 검출해야 하는데, 송신 신호에 다른 사용자 단말의 데이터도 섞여 있으므로

만 검출하는 것이 어렵다. 이때, 수신기에서는 SIC 기법을 사용하게 되는데, 먼저 채널이

로 배치(ordering) 되어 있다고 가정한다. 셀룰러 시스템에서는 경로 감쇄로 인해 거리가 멀수록 채널 이득이 작아지기 때문에 위의 채널 이득에 대한 가정은 타당하다고 볼 수 있다. 즉, U 번째 사용자 단말이 기지국(110)과 가장 먼 위치에 존재할 것이다. After the transmission signal passes through the channel of h _i , the i-th user terminal receives the corresponding signal. double

It needs to be detected, but because the transmitted signal is also mixed with data from other user terminals

It is difficult to detect only. At this time, the receiver uses the SIC technique. First, the channel

It is assumed to be ordered. In a cellular system, since the channel gain becomes smaller as the distance increases due to path attenuation, the above assumption about the channel gain can be considered reasonable. That is, the U-th user terminal will exist in the farthest position from the base station 110.

는 검출할 수 있고, 수학식 1에서

의 데이터는 빼주게 된다. 그 후, 상기에서 설명한바와 같이 U-1 번째 사용자 단말의 데이터를 검출하여 빼주게 된다. 이러한 과정을 반복하게 되면 i번째 사용자 단말의 데이터 검출은 하기한 수학식 2와 같이 나타낼 수 있다.In a situation in which each user terminal has the above channel gain, the receiver detects the optimal SIC order from the user terminal having a small channel gain. Therefore, the i-th user terminal first detects the data of the U-th user terminal. At this time, data from other user terminals is treated as noise. Data from other user terminals acts as interference, but if perfect detection is possible

Can be detected, and in Equation 1

Data is subtracted. After that, as described above, the data of the U-1 th user terminal is detected and subtracted. When this process is repeated, data detection of the i-th user terminal can be expressed as in Equation 2 below.

[Equation 2]

는 평균이 0이고 분산이

인 i번째 사용자의 가우시안 노이즈(Gaussian noise)가 된다. 이때, i번째 사용자 단말의 데이터를 검출하게 되면

의 항이 간섭으로 작용하게 된다. 따라서, i 번째 사용자 단말의 신호 대 간섭 잡음비 (Signal-to-Interference plus Noise Ratio, SINR)은 하기 수학식 3과 같이 표현할 수 있다.In Equation 2,

Has a mean of 0 and a variance of

It becomes Gaussian noise of the i-th user. At this time, when the data of the i-th user terminal is detected,

The term of will act as interference. Accordingly, the signal-to-interference plus noise ratio (SINR) of the i-th user terminal can be expressed as Equation 3 below.

[Equation 3]

Therefore, if the channel gain is not large, the effect of interference increases, and the SINR decreases, thereby reducing the data rate. Equation 3 is the SINR when there is no SIC error, and when a detection error occurs when performing SIC, the SINR is further reduced. Therefore, in reality, the case of U=2 is considered, and more complexities and practical application problems arise. Therefore, the NOMA system for a multi-user scheduling method considers a situation in which two users are simultaneously supported.

In the LTE system, resources are divided into resource blocks (RBs) and allocated. Each RB can be assigned to only one user terminal, but if the NOMA technique is applied, the RB can be assigned to two user terminals, so that twice as many user terminals can be simultaneously supported. Accordingly, the data rate of all user terminals can be increased. In addition, the OFDMA scheme, which is currently widely used, allocates user terminals for each subcarrier in the frequency domain, so that user terminals can be classified by frequency.

As shown in FIG. 1, the NOMA system 100 according to an embodiment of the present invention divides the usable frequency bands into M subbands and supports two user terminals for each subband as NOMA. . Accordingly, the NOMA system can simultaneously support 2M user terminals among a total of K (K≥2M) user terminals, and user scheduling for which user terminal is selected greatly affects performance.

FIG. 2 is a diagram functionally illustrating the configuration of the base station of FIG. 1.

Referring to FIG. 2, the base station 110 may include a receiver 111, a controller 112, and a transmitter 113, but is not limited thereto.

The base station 110 may use other well-known terms instead of the base station ("eNodeB" or "eNB"), such as "base station" or "access point (AP)", depending on the network type. . In the present invention, a base station may be used to mean network infrastructure components that provide wireless access to remote terminals for convenience of description. In addition, user equipment (UE) is "mobile station", "subscriber station", "remote terminal", "wireless terminal", depending on the network type. Alternatively, other well-known terms such as "user device" may be used.

The receiver 111 performs functions for transmitting and receiving signals through a wireless channel. For example, the receiver 111 converts between a radio frequency (RF) signal and a baseband signal according to the physical layer standard of the system. For example, when receiving data, the receiver 111 receives an RF signal through at least one antenna, processes the RF signal, down-converts it into a baseband signal, and converts it into a digital signal. The receiver 111 may receive channel information and service quality request information from a plurality of user terminals, respectively.

The controller 112 controls the entire process of providing a multi-user scheduling method using channel information and quality of service request information received through the receiver 111. Each step performed by the controller 112 will be described later with reference to FIG. 3.

Here, the controller 112 may include all types of devices capable of processing data, such as a processor. Here, the'processor' may refer to a data processing device embedded in hardware having a circuit physically structured to perform a function represented by a code or instruction included in a program. As an example of a data processing device built into the hardware as described above, a microprocessor, a central processing unit (CPU), a processor core, a multiprocessor, and an application-specific integrated (ASIC) circuit) and processing devices such as field programmable gate arrays (FPGAs), but the scope of the present invention is not limited thereto.

The transmitter 113 may transmit scheduling information generated through the controller 112 to each user terminal.

Meanwhile, the base station 110 may include a memory 114 in which a program for performing a multi-user scheduling method is recorded. The memory 114 temporarily or permanently stores data processed by the controller 112. Here, the memory 120 may include a volatile storage medium or a non-volatile storage medium, but the scope of the present invention is not limited thereto.

A proportional fair (PF) scheduling method is widely used as a user scheduling method used in a general NOMA system. The PF scheduling scheme is a method of selecting user terminals that can maximize data rates while satisfying fairness. The PF scheduling scheme has a disadvantage in that it is impossible to allocate resources fairly to each user terminal, and it is not possible to allocate as many resources as required by each user terminal.

Therefore, there is a CDF-based scheduling scheme as a scheduling scheme that can compensate for the disadvantages of the PF scheduling scheme. The existing CDF-based scheduling scheme can represent the user terminal selected at the current time t as shown in Equation 4.

[Equation 4]

는 k번째 사용자 단말의 가중치(weight),

는 시간 t에서 k번째 사용자 단말의 데이터 속도,

는 데이터 속도의 CDF이다. 따라서, 기존의 CDF 기반의 스케줄링 기법은 현재 시간 t에서 CDF가 최대인 사용자 단말을 선택하는 기법이다. In Equation 4,

Is the weight of the k-th user terminal,

Is the data rate of the k th user terminal at time t,

Is the CDF of the data rate. Therefore, the existing CDF-based scheduling scheme is a scheme for selecting a user terminal with the largest CDF at the current time t.

In the NOMA system, if a user terminal with the maximum data rate is simply selected, a cell edge user is not selected, so CDF is used. Here, the data rate is a random variable due to the channel, and by obtaining the CDF value of the current data rate, it can be seen whether the current data rate is better or worse than the average.

의 확률값을 가지므로 데이터 속도의 랜덤 변수 R이 현재 데이터 속도보다 클 확률이 작으면 작을수록 현재 데이터 속도가 충분히 크다는 의미이므로 확률값이 최소인 사용자 단말을 선택한다. 이러한 확률 값은 CDF와 연관이 있으므로 CDF 기반의 스케줄링 기법이라고 한다. 즉, CDF값이 클수록 현재 링크에서 얻을 수 있는 최대치의 데이터 속도에 가깝다는 의미이다. 따라서, CDF 기반의 스케줄링 기법은 각 사용자 단말마다 얻을 수 있는 최대 데이터 속도와 비교하여 가장 좋은 데이터 속도를 가지고 있는 사용자 단말을 선택하는 알고리즘이다. 또한 가중치를 조절하여 각 사용자 단말에게 할당되는 자원량을 조절할 수 있고 그에 따라 데이터 속도도 조절할 수 있게 된다.Referring to Equation 4,

Since it has a probability value of, the smaller the probability that the random variable R of the data rate is greater than the current data rate, the smaller it means that the current data rate is sufficiently large, so the user terminal with the minimum probability value is selected. Since this probability value is related to CDF, it is called a CDF-based scheduling technique. In other words, the larger the CDF value, the closer to the maximum data rate that can be obtained from the current link. Accordingly, the CDF-based scheduling scheme is an algorithm that selects a user terminal having the best data rate compared to the maximum data rate that can be obtained for each user terminal. In addition, by adjusting the weight, the amount of resources allocated to each user terminal can be adjusted, and the data rate can be adjusted accordingly.

The existing CDF-based scheduling scheme uses CDF information of the data rate of each user terminal, selects and communicates with the user terminal with the maximum CDF value, and sets a different weight for each user terminal for each CDF value. Speed and resource allocation can be adjusted with weights. However, the existing CDF-based scheduling scheme has a disadvantage in that it is difficult to apply to a NOMA system because CDF is used based on data rate and only one user terminal is selected for each resource. Referring to Equation 3, in the NOMA system, it is difficult to predict the data rate because the SINR varies depending on the number of times the channel gain of the NOMA system is the largest. Therefore, there is a need for a method to apply the existing CDF-based scheduling technique to the NOMA system.

3 is a flowchart illustrating a multi-user scheduling method of a non-orthogonal multiple access system according to an embodiment of the present invention.

Referring to FIG. 3, in the multi-user scheduling method of the non-orthogonal multiple access system, each user terminal feeds back channel information and service quality request information to a base station (S11).

The base station calculates the resource allocation amount using the service quality request information of each user terminal and then sets a weight for each user terminal (S12).

Thereafter, the base station determines the channel state through channel information and, in the case of a frequency flat fading channel (S13), calculates a channel gain-based CDF using the weight and channel information for each user terminal (S14). ), since the channel is the same for each subband, 2M user terminals having the maximum CDF value are selected (S15).

The base station determines the channel state through channel information, and in the case of a frequency selective fading channel, calculates a channel gain-based CDF for each subband (S16), and the CDF value for each subband is 2M. After the user selects the user terminal, the scheduling process of calculating the CDF and selecting the user terminal for each subband is repeatedly performed (S17).

The base station feeds back scheduling information to each user terminal, and each user terminal transmits data to the base station using the schedule information (S18).

The base station performs multi-user scheduling by using the CDF based on the channel gain, not the CDF based on the data rate, and at this time, the set of scheduled users can be expressed as Equation (5).

[Equation 5]

의 사용자 단말 중

명의 사용자 단말을 선택하는 모든 경우 집합, M은 서브밴드의 수,

째 사용자 단말의 채널 이득(

), F_i()는 채널 이득 기반의 CDF, S^*은 각 사용자 단말의 CDF 값의 합을 최대화시키는 집합을 각각 나타낸다. In Equation 5,

Of the user terminals of

In all cases of selecting user terminals, M is the number of subbands,

Channel gain of the user terminal (

), F _i () denotes a channel gain-based CDF, and S ^* denotes a set that maximizes the sum of CDF values of each user terminal.

As shown in Equation 5, the base station selects 2M user terminals having the best channel condition, and if the channel condition is good, the SINR increases by that amount, so that the total data rate increases.

Maximizing the sum of the channel gain-based CDF values in the frequency plane fading channel is to arrange the CDF values in order and select 2M in the order of having the maximum value. Accordingly, scheduled user terminals are selected in the order in which the CDF value has the maximum value. In the frequency plane fading channel, since all M subbands are the same channel, the base station selects a total of 2M user terminals and randomly allocates them to each subband by two.

On the other hand, in the frequency selective channel, since channels are different for each subband, a user terminal must be selected through user scheduling for each subband. The base station selects a user terminal having the first and second largest CDF values for each subband. The probability that an i-th user terminal is selected in this frequency selective channel situation can be expressed by Equation 6 below.

[Equation 6]

When each term is calculated in Equation 6, the following Equations 7 and 8 can be obtained.

[Equation 7]

[Equation 8]

Accordingly, the selection probability value to be selected by the i-th user terminal at the current time t can be expressed as Equation 9 below.

[Equation 9]

A probability value at which the user terminal will be selected can be calculated through Equation 9, and this selection probability value means a degree occupied by the resource allocated to the selected user terminal among all time resources. That is, since Equation 9 is the amount of resources allocated to the i-th user terminal among the total time resources, if the selection probability is adjusted by adjusting the weight of the corresponding user terminal, the resource allocation amount of each user terminal can be adjusted according to the user condition.

일 경우, 선택 확률값은

가 된다. 모든 사용자 단말이 동일한 확률로 선택됨으로써 공평하게 자원 할당이 될 수 있다. 따라서, 공평성을 고려하여 셀 에지 사용자에게 더 많은 자원을 할당할 수 있고, 시스템 성능을 향상시키기 위해 기지국과 가까운 사용자 단말에 더 많은 자원을 할당할 수 있다.Using Equation 9, when the same weight is set to all user terminals, resources can be allocated fairly. That is, in Equation 9

If, then the probability of selection is

Becomes. Resource allocation can be made fairly by selecting all user terminals with the same probability. Accordingly, in consideration of fairness, more resources may be allocated to cell edge users, and more resources may be allocated to user terminals close to the base station in order to improve system performance.

4 is a graph comparing a multi-user scheduling method (CS), a proportional fairness (PF), and a time resource allocation amount by random selection in a non-orthogonal multiple access system according to an embodiment of the present invention. A graph comparing time resource allocation according to weights in a multi-user scheduling method of a non-orthogonal multiple access system according to an embodiment, and FIG. 6 is a graph showing a multi-user scheduling method of a non-orthogonal multiple access system according to an embodiment of the present invention. This is a graph analyzing the resource allocation amount and average speed according to the weight of the cell edge user.

Referring to FIG. 4, assuming that the total number of user terminals is 10, and only 4 of them are selected to communicate, it can be seen that resource allocations of all user terminals are equal if the weights of all user terminals are the same. Here, the selection probability value is a probability that each user terminal is selected in each time slot, and can be viewed as a time resource allocation amount when viewed from the total time.

The proportional fairness algorithm (PF) allocates more resources to cell edge users because the SNR of the cell edge user is lower, but has a disadvantage in that the resource allocation amount of each user terminal cannot be adjusted.

,

이다. 기지국은 더 많은 가중치를 각 사용자 단말에 할당할수록 자원이 많이 할당되는 것을 확인할 수 있다. 따라서, 각 상황에 맞게 각 사용자 단말의 가중치를 조절하면 사용자가 요구하는 서비스 품질을 만족시킬 수 있다.As shown in Figure 5, looking at the resource allocation amount according to the weight change of each user terminal,

,

to be. As the base station allocates more weights to each user terminal, it can be seen that more resources are allocated. Accordingly, by adjusting the weight of each user terminal according to each situation, the quality of service required by the user can be satisfied.

As shown in FIG. 6, as the weight of the other user terminal is set to 1 and only the weight of the cell edge user is changed, the resource allocation amount and the average speed are changed. As the weight increases, more resources are provided to the cell edge user. Allocate, and you can see that the average speed increases accordingly. Accordingly, the base station can satisfy the minimum speed required for each user terminal by adjusting the weight of each user terminal.

delete

The multi-user scheduling method of the non-orthogonal multiple access system according to the embodiment of the present invention described above may also be implemented in the form of a recording medium including instructions executable by a computer, such as a program module executed by a computer. . Such recording media include computer-readable media, and computer-readable media may be any available media that can be accessed by a computer, and include both volatile and nonvolatile media, and removable and non-removable media. In addition, computer-readable media includes computer storage media, which are volatile and nonvolatile embodied in any method or technology for storage of information such as computer-readable instructions, data structures, program modules or other data. , Both removable and non-removable media.

The above description of the present invention is for illustrative purposes only, and those of ordinary skill in the art to which the present invention pertains can understand that it is possible to easily transform it into other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not limiting. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as being distributed may also be implemented in a combined form.

The scope of the present invention is indicated by the claims to be described later rather than the detailed description, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention. do.

100: NOMA system 110: base station
111: receiver 112: controller
113: transmitter 114: memory

Claims (11)

In a multi-user scheduling method performed by a non-orthogonal multiple access system that performs a non-orthogonal multiple access (NOMA) between a base station and a user terminal,
a) The base station receives subband channel information and quality of service (QoS) request information from the user terminal, calculates a resource allocation amount using the service quality request information of the user terminal, and then weights each user terminal. Setting up;
b) calculating a cumulative distribution function (CDF) based on a channel gain using the weight and channel information for each user terminal; And
c) scheduling a user set by selecting a plurality of user terminals for each subband using the channel gain-based CDF, and feeding back scheduling information to each user terminal,
The user set is represented by Equation 1 below. A multi-user scheduling method for a non-orthogonal multiple access system.
[Equation 1]

Of the user terminals of

Set all cases of selecting user terminals
K: Total number of user terminals requesting communication to the NOMA system
M is the number of subbands
W _i is the weight of the i-th user terminal

Channel gain of the user terminal
F _i () is the channel gain-based CDF
S ^* is a set that maximizes the sum of CDF values of each user terminal The method of claim 1,
The step c),
In the case of a frequency flat fading channel by checking the channel status through the channel information, after arranging the CDF value based on the channel gain in order of size, the 2M user terminals with the maximum CDF value are selected. Allocating for each subband, multi-user scheduling method of a non-orthogonal multiple access system. The method of claim 1,
The step c),
In the case of a frequency selective fading channel by checking the channel status through the channel information, two users with the maximum CDF value after arranging the channel gain-based CDF value for each subband in order of magnitude To select a terminal, multi-user scheduling method of a non-orthogonal multiple access system. The method of claim 3,
The selection probability value for the i-th user terminal to be scheduled at the current time t is represented by Equation 2 below.
[Equation 2]

The method of claim 4,
The multi-user scheduling method of a non-orthogonal multiple access system, wherein the resource allocation amount of each user terminal is differently adjusted by adjusting the weight (W _i ) of the selection probability value. The method of claim 4,
The multi-user scheduling method of a non-orthogonal multiple access system to provide fairness of resource allocation by setting the same weight (W _i ) for each user terminal so that the selection probability value of each user terminal becomes the same. A memory in which a program for performing a multi-user scheduling method between a base station and a user terminal in a non-orthogonal multiple access (NOMA) environment is recorded; And
It includes a controller for executing the program,
The controller, by executing the program,
Receives subband channel information and quality of service (QoS) request information from the user terminal, calculates a resource allocation amount using the service quality request information of the user terminal, and sets weights for each user terminal,
A cumulative distribution function (CDF) based on a channel gain is calculated using the weight and channel information for each user terminal,
Schedule a user set by selecting a plurality of user terminals for each subband using the channel gain-based CDF, and feedback scheduling information to each user terminal,
The user set is represented by Equation 1 below.
[Equation 1]

Of the user terminals of

Set all cases of selecting user terminals
M is the number of subbands
K: Total number of user terminals requesting communication to the NOMA system
W _i is the weight of the i-th user terminal

Channel gain of the user terminal
F _i () is the channel gain-based CDF
S ^* is a set that maximizes the sum of CDF values of each user terminal The method of claim 7,
The controller checks the channel status through the channel information and, in the case of a frequency flat fading channel, arranges the channel gain-based CDF value in order of magnitude, and then 2M users with the maximum CDF value A non-orthogonal multiple access system that selects a terminal and allocates it to each subband. The method of claim 7,
The controller checks the channel status through the channel information and, in the case of a frequency selective fading channel, arranges the channel gain-based CDF value for each subband in order of magnitude, and the CDF value is the maximum. To select two user terminals, non-orthogonal multiple access system. The method of claim 9,
The selection probability value for the i-th user terminal to be scheduled at the current time t is represented by Equation 2 below.
[Equation 2]

The method of claim 10,
To adjust the resource allocation amount of each user terminal by adjusting the weight (W _i ) of the selection probability value, non-orthogonal multiple access system.

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