KR101518184B1 - Method and Device for scheduling on Device to Device Communication System - Google Patents

Abstract

Disclosed are a distribution type scheduling method considering fairness and a channel status according to a data transfer rate between terminals of D2D, and a technique for a terminal for performing scheduling. The discloses scheduling method comprises the steps of: generating information on a data transfer rate of predetermined link; generating a fairness parameter which is updated according to a reference transfer rate and the date transfer rate of the link; generating a scheduling prior parameter for the link by using channel status information for the fairness parameter and the link; and performing the scheduling according to the scheduling prior parameter.

Description

TECHNICAL FIELD [0001] The present invention relates to a terminal for performing a scheduling method and a scheduling in a D2D communication system,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a UE performing a scheduling method and scheduling in a D2D communication system, and more particularly, to a distributed scheduling method according to fairness between D2D terminals and a terminal performing scheduling.

A typical example of D2D communication technology is the FlashLinQ communication technology announced by Qualcomm. FlashLinQ technology refers to a wireless network capable of communicating at a broadband speed using an authorized communication frequency (e.g., mobile communication frequency) without a relay network equipment in a peer-to-peer manner.

Such a FlashLinQ technique can schedule D2D links for transmitting data in a corresponding traffic slot through distributed scheduling without the assistance of a base station for each traffic slot. Through such distributed scheduling, FlashLinQ technology can minimize interference between D2D terminals and efficiently reuse the same resources.

In the case of the conventional D2D communication such as the FlashLinQ described above, the scheduling priority is simply allocated according to the random scheduling priority, and the scheduling algorithm is performed according to the priority. At this time, since the scheduling priority of each D2D link is randomly allocated, each D2D link can fairly acquire a probability of attempting scheduling for each subframe.

However, since the channel conditions of the D2D links are different from each other, there is a problem that it is difficult to obtain a high fairness among the actually required D2D terminals merely by equally allocating the probability that each D2D link attempts scheduling.

DISCLOSURE OF THE INVENTION The present invention provides a distributed scheduling method considering fairness and channel state according to a data rate between D2D terminals and a terminal performing scheduling.

According to an aspect of the present invention, there is provided a scheduling method in a D2D communication system, comprising: generating data rate information of a set link; Generating a fairness parameter that is updated according to a reference transmission rate and a data transmission rate for the link; Generating a scheduling priority parameter for the link using the fairness parameter and channel state information for the link; And scheduling according to the scheduling priority parameter.

According to another aspect of the present invention, there is provided a scheduling method in a D2D communication system, the method comprising: receiving a fairness parameter function; Generating a fairness parameter using the fairness parameter function; Generating a scheduling priority parameter using the fairness parameter and channel state information; And performing scheduling according to the scheduling priority parameter, wherein the fairness parameter is a parameter generated based on a data rate of a set link and a reference rate.

According to another aspect of the present invention, there is provided an apparatus for generating a fairness parameter, the apparatus comprising: a fairness parameter generator for generating a fairness parameter updated according to a reference data rate and a data rate for a set link; A priority parameter generator for generating a scheduling priority parameter for the link using the fairness parameter and the channel status information for the link; And a communication unit for transmitting and receiving data according to the scheduling priority parameter.

According to the present invention, it is possible to distribute the resources fairly to the D2D terminals and improve the performance of the entire system.

According to the present invention, the scheduling priority is determined according to the fairness parameter updated according to the data rate of each link and the channel status of each link, thereby ensuring fairness between the D2D terminals and improving the transmission rate of the system. A scheduling method can be provided.

1 is a diagram illustrating a D2D communication system according to an embodiment of the present invention.
2 is a diagram illustrating a link scheduling channel configuration according to an embodiment of the present invention.
3 is a diagram illustrating a D2D terminal in a D2D communication system according to an embodiment of the present invention.
4 is a diagram illustrating a scheduling method in a D2D communication system according to an embodiment of the present invention.
5 is a diagram for explaining a scheduling method in a D2D communication system according to another embodiment of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

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

FIG. 1 is a diagram illustrating a D2D communication system according to an embodiment of the present invention, and FIG. 2 is a diagram illustrating a link scheduling channel configuration according to an embodiment of the present invention.

As shown in FIG. 1, the D2D communication system includes a plurality of D2D terminals 110a, 110b, 110c, 120a, 120b, and 120c. Here, the D2D terminals 110a, 110b, 110c, 120a, 120b, and 120c may be the transmitting entity and the receiving entity, respectively. Hereinafter, the transmitting subject will be referred to as a transmitting terminal and the receiving subject will be referred to as a receiving terminal in order to facilitate understanding and explanation.

In the D2D communication system, each link is composed of one D2D transmitting terminal and one D2D receiving terminal pair. Referring to FIG. 1, for example, a first D2D transmitting terminal T ₁ is paired with a first D2D receiving terminal R ₁ , and a second D ₂ D transmitting terminal T ₂ ) 2 D2D receiving terminal R ₂ and the third D2D transmitting terminal T ₃ can be configured as a pair with the third D2D receiving terminal R ₃ .

D2D communication systems can use distributed scheduling based on signal-to-interference ratio (SIR) using a single-tone orthogonal frequency-division multiplexing (OFDM) channel. Accordingly, each D2D terminal can perform link scheduling by transmitting an analog signal to a single-tone OFDM channel used for scheduling.

The link scheduling channel structure is as shown in FIG. In the D2D communication technology, data transmission is performed in a traffic slot unit of 2 ms. As shown in FIG. 2, each traffic slot is divided into a total of four channels: Link Scheduling, Rate Scheduling, Data Segment, and Acknowledge.

The link scheduling channel is composed of first and second transmission blocks (1 ^st , 2 ^nd Tx-block) and first and second reception blocks (1 ^st , 2 ^nd Rx-block) Each block consists of 4 OFDM symbols and 28 frequency tones.

All links have link-specific identification information (ID, hereinafter referred to as link identification information), and the link identification information can be mapped to a specific single-tone of the transmission block. Accordingly, the D2D transmitting terminal can transmit a direct power signal (DPS) and an inverse power echo (IPS) signal using a single tone allocated to each link.

Referring back to FIG. 1, the D2D terminal according to the present invention generates and updates a fairness parameter for each link according to a data rate, determines a scheduling priority by using fairness parameters and channel states, .

Here, the fairness is related to how much data can be transmitted uniformly by each D2D terminal, and can be determined according to the data transmission rate of each link. In the present invention, the fairness parameter is a parameter indicating the difference between the data transmission rate of each link and the reference transmission rate, and the reference transmission rate represents a required data transmission rate for fairness acquisition.

In one embodiment, the fairness parameter value may be designed to be small when the data rate of each link is greater than the required data rate for fairness acquisition, and to be large when the data rate of each link is less than the required data rate for fairness acquisition .

On the other hand, when performing scheduling considering only fairness parameters, the overall performance of the system may decrease. Therefore, the present invention determines the scheduling priority by further considering the channel state.

As a result, according to the present invention, it is possible to distribute the resources fairly to the D2D terminals and improve the performance of the entire system.

3 is a diagram illustrating a D2D terminal in a D2D communication system according to an embodiment of the present invention.

As described above, in the D2D communication system, each link is composed of one D2D transmitting terminal and one D2D receiving terminal pair, and in FIG. 3, the case of performing the scheduling in the D2D receiving terminal will be described as an embodiment.

3, the D2D terminal 300 according to the present invention includes an equality parameter generator 310, a priority parameter generator 320, and a communication unit 330. According to an embodiment, the apparatus may further include an interface unit receiving the fairness parameter function.

The fairness parameter generator 310 generates the fairness parameter that is updated according to the reference data rate and the data rate for the set link. Here, the initial value for the reference transmission rate can be set by the user. Since the fairness parameter is changed because the fairness parameter is changed, the reference transmission rate for newly measuring the fairness also needs to be changed. In the present invention, the reference transmission rate can be updated according to the updated fairness parameter.

 The fairness parameter value becomes smaller when the data rate of each link is larger than the reference rate, and may increase when the data rate of each link is smaller than the reference rate. Alternatively, the fairness parameter value may be increased if the data rate of each link is greater than the reference rate, and may be less if the data rate of each link is less than the reference rate.

Also, the fairness parameter generator 310 may generate the fairness parameter using the fairness parameter function. More specifically, the fairness parameter generator 310 may calculate a data rate and a reference rate for each traffic slot using the transmission result of each traffic slot, and may generate an equality parameter using Equation (1) .

는 트래픽 슬롯 t에서 링크 k에 대한 공평성 파라미터를 나타낸다. 그리고

는 링크 k의 공평성 파라미터 함수를 나타내며,

는 링크 k의 기준 전송률을 나타낸다.Here, t represents a time index of a traffic slot,

Represents the fairness parameter for link k in traffic slot t. And

Represents the fairness parameter function of link k,

Represents the reference transmission rate of link k.

와 같은 컨케이브(concave) 함수 또는 컨벡스(convex) 함수일 수 있으며, 정책에 따라 다양한 타입의 공평성 파라미터 함수가 사용될 수 있다. 인터페이스부는 복수의 공평성 파라미터 함수를 입력받을 수 있으며, 공평성 파라미터 생성부(310)는 입력된 복수의 공평성 파라미터 함수 중에, 정책에 따라 선택된 공평성 파라미터 함수를 이용하여 공평성 파라미터를 생성할 수 있다. 정책은 사용자에 의해 결정될 수 있다.The fairness parameter function may, for example,

Or a convex function, and various types of fairness parameter functions may be used depending on the policy. The interface unit may receive a plurality of the fairness parameter functions, and the fairness parameter generation unit 310 may generate the fairness parameter using the fairness parameter function selected according to the policy among the plurality of the input fairness parameter functions. The policy can be determined by the user.

The fairness parameter generator 310 can update the fairness parameter for each traffic slot as in Equation (2). According to Equation (2), the fairness parameter value becomes smaller when the data transmission rate of each link is larger than the reference transmission rate, and becomes larger when the data transmission rate of each link is smaller than the reference transmission rate. When the fairness parameter is updated, the reference transmission rate can be updated by Equation (1) in the next traffic slot.

는 트래픽 슬롯 t에서 링크 k의 데이터 전송률을 나타내며, α는 스텝 사이즈(step size)로서, 다양하게 설정될 수 있다.here,

Denotes the data rate of link k in traffic slot t, and alpha is a step size, which can be set variously.

The priority parameter generator 320 generates a scheduling priority parameter for the link using the fairness parameter and the channel status information for the link. The channel state information may be a channel gain value, and the scheduling priority parameter may be proportional to the fairness parameter and the channel gain value.

The priority parameter generator 320 can generate a priority parameter using Equation (3).

는 채널 이득 값, V는 시스템 상수(system constant)를 나타낸다. 시스템 상수는 다양하게 설정될 수 있다.Here, p denotes a priority parameter function,

Is a channel gain value, and V is a system constant. System constants can be set to various values.

The communication unit 330 transmits and receives data according to the scheduling priority parameter. As the scheduling priority parameter value is larger, data can be transmitted and received according to a higher priority.

The scheduling priority parameter is shared among the D2D terminals included in the D2D communication system, and each D2D terminal variably determines the priority of link scheduling using the scheduling priority parameter.

As a result, according to the present invention, the scheduling priority is determined according to the fairness parameter updated according to the data rate of each link and the channel state of each link, thereby ensuring fairness between the D2D terminals and improving the transmission rate of the system. A scheduling method can be provided.

4 is a diagram illustrating a scheduling method in a D2D communication system according to an embodiment of the present invention. In FIG. 4, the case of performing scheduling in the D2D receiving terminal will be described as an embodiment.

The D2D receiving terminal generates the data rate information of the set link (S401). That is, the D2D receiving terminal calculates a data transmission rate for a link established with another D2D terminal.

Then, the D2D receiving terminal generates the fairness parameter updated in accordance with the reference data rate and the data rate for the set link (S403). The data rate may vary for each traffic slot, and the D2D receiving terminal updates the fairness parameter to reflect the changing data rate.

At this time, the D2D receiving terminal generates the fairness parameter using the fairness parameter function, and the fairness parameter function can be the concave function or the convex function. The D2D receiving terminal can receive the fairness parameter function using a separate interface.

The fairness parameter is, in one embodiment, smaller as the data rate is larger than the reference data rate, and may become larger as the data rate is smaller than the reference data rate. And the reference transmission rate can also be updated as the fairness parameter is updated.

The D2D receiving terminal generates a scheduling priority parameter for the set link using the fairness parameter and the channel status information for the set link (S405), and performs scheduling according to the scheduling priority parameter (S407). Here, the channel state information may be, for example, a channel gain value, and the scheduling priority parameter may be generated to be proportional to the fairness parameter and the channel gain value.

5 is a diagram for explaining a scheduling method in a D2D communication system according to another embodiment of the present invention. In FIG. 5, a case of performing scheduling in the D2D receiving terminal will be described as an embodiment.

The D2D receiving terminal selects the fairness parameter function (S501), and generates the fairness parameter using the fairness parameter function (S503). The fairness parameter may be generated based on the data rate of the established link and the reference rate.

Also, the D2D receiving terminal can receive a plurality of the fairness parameter functions, and can generate the fairness parameters using the selected fairness parameter function according to the policy. Here, the fairness parameter function may be a concave function or a convex function.

The D2D receiving terminal generates a scheduling priority parameter using the fairness parameter and channel state information (S505), and performs scheduling according to the scheduling priority parameter (S507). Here, the channel state information is a channel gain value, and the scheduling priority parameter may be proportional to the fairness parameter and the channel gain value.

The above-described technical features 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 medium may be those specially designed and constructed for the embodiments or may be available to those skilled in the art of computer software. Examples of computer-readable media include magnetic media such as hard disks, floppy disks and magnetic tape; optical media such as CD-ROMs and DVDs; magnetic media 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 machine language code such as those produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware device may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.

As described above, the present invention has been described with reference to particular embodiments, such as specific elements, and specific embodiments and drawings. However, it should be understood that the present invention is not limited to the above- And various modifications and changes may be made thereto by those skilled in the art to which the present invention pertains. Accordingly, the spirit of the present invention should not be construed as being limited to the embodiments described, and all of the equivalents or equivalents of the claims, as well as the following claims, belong to the scope of the present invention .

Claims (15)

A method for scheduling in a D2D communication system,
Generating data rate information of a set link;
Generating a fairness parameter that is updated according to a reference transmission rate and a data transmission rate for the link;
Generating a scheduling priority parameter for the link using the fairness parameter and channel state information for the link; And
Performing scheduling according to the scheduling priority parameter
/ RTI >
The method according to claim 1,
The step of generating the fairness parameter
Generating the fairness parameter using a fairness parameter function,
The fairness parameter function is a concave function
Scheduling method.
3. The method of claim 2,
Receiving the fairness parameter function
≪ / RTI >
The method according to claim 1,
The fairness parameter
The data rate is smaller as the reference data rate is larger, and as the data rate is smaller than the reference data rate,
Scheduling method.
The method according to claim 1,
The channel state information
Channel gain value
Scheduling method.
6. The method of claim 5,
The scheduling priority parameter
Wherein the gain parameter is proportional to the fairness parameter and the channel gain value
Scheduling method.
The method according to claim 1,
The reference transmission rate
And is updated according to the fairness parameter
Scheduling method.
A method for scheduling in a D2D communication system,
Selecting an equality parameter function;
Generating a fairness parameter using the fairness parameter function;
Generating a scheduling priority parameter using the fairness parameter and channel state information; And
And performing scheduling according to the scheduling priority parameter,
The fairness parameter
A parameter generated based on the data transmission rate of the established link and the reference transmission rate
Scheduling method.
9. The method of claim 8,
The fairness parameter function is a concave function
Scheduling method.
9. The method of claim 8,
The step of generating the fairness parameter
Among the inputted plurality of the fairness parameter functions, the fairness parameter is generated using the fairness parameter function selected in accordance with the policy
Scheduling method.
9. The method of claim 8,
Wherein the channel state information is a channel gain value,
The scheduling priority parameter
Wherein the gain parameter is proportional to the fairness parameter and the channel gain value
Scheduling method.
A fairness parameter generator for generating a fairness parameter that is updated according to a reference data rate and a data rate for a set link;
A priority parameter generator for generating a scheduling priority parameter for the link using the fairness parameter and the channel status information for the link; And
And a communication unit for transmitting and receiving data according to the scheduling priority parameter
.
13. The method of claim 12,
And an interface unit receiving the fairness parameter function,
The fairness parameter generator
Generating the fairness parameter using the fairness parameter function
D2D terminal.
14. The method of claim 13,
The fairness parameter function is a concave function
The D2D terminal further comprising:
14. The method of claim 13,
The fairness parameter generator
Among the inputted plurality of the fairness parameter functions, the fairness parameter is generated using the fairness parameter function selected in accordance with the policy
D2D terminal.

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