KR101132620B1 - Method and apparatus for scheduling in orthogonal frequency division multiple access system - Google Patents

Abstract

In the conventional Orthogonal Frequency Division Multiple Access (OFDMA) system, the subchannel allocation technique uses the same method as the downlink allocation scheme in the uplink subchannel allocation, resulting in an increase in Peak-to-Average Power Ratio (PAPR). There is a performance degradation, and even if the constraints are assigned to uplink subchannels in order to minimize PAPR, there is a limitation that subchannels having good discrete characteristics cannot be allocated to a specific user. Accordingly, the present invention proposes a scheduling scheme that can maximize the capacity of an uplink system under the condition of continuously allocating subchannels to the same user. In the present invention, while allocating subchannels to users having the best channel quality, the loss in the case of being unable to allocate other spaced channels can be considered at the same time, thereby improving the overall system gain while allocating consecutive subchannels to the same user. can do.

Description

Scheduling apparatus and method in orthogonal frequency division multiple access system {METHOD AND APPARATUS FOR SCHEDULING IN ORTHOGONAL FREQUENCY DIVISION MULTIPLE ACCESS SYSTEM}

The present invention relates to an Orthogonal Frequency-Division Multiple Access (OFDMA) system, and more particularly, to efficiently allocate subchannels in uplink in an orthogonal frequency-division multiple access system. An apparatus and method for scheduling in an orthogonal frequency division multiple access system suitable for maximization.

At present, the most standard organization, ^{3GPP LTE (3 rd Generation Partnership Project} Long-Term Evolution), (Institute of Electrical & Electronics Engineers) IEEE 802.16 -based next generation mobile communication system, an orthogonal frequency division multiple access (Orthogonal Frequency-Division Multiple Access, OFDMA) is selected as a next generation mobile communication technology because the OFDMA method is easy to transmit and receive large data traffic even in a mobile communication environment and is suitable for various multimedia services. The characteristic of the OFDMA scheme is that the wideband frequency band is divided into several subchannels for communication, and it is easy to modulate and demodulate, and the structure of the equalizer is very simple. Many discussions have been made on an effective scheduling method for allocating various subchannels to users under the OFDMA system in consideration of capacity increase and fairness. In particular, in downlink, system capacity can be maximized by a scheduling method of allocating a specific subchannel having the best channel characteristic to a specific user.

However, when the downlink allocation scheme is applied to uplink scheduling as it is, performance degradation may occur due to an increase in Peak to Average Power Ratio (PAPR). In particular, since the PAPR is directly related to power amplification of the transmitter, it has a greater adverse effect on the uplink transmission of the terminal whose life is determined by the battery than the base station which is easy to receive power.

Therefore, various schemes are currently considered to reduce PAPR, and among them, Single Carrier Frequency Division Multiple Access (SC-FDMA), which is a modified form of OFDMA that allows one user to be assigned only consecutive subchannels Is the typical way. In this case, rather than directly allocating all uplink subchannels to increase complexity, one subchannel block is formed by grouping a certain number of subchannels, and the subchannel blocks are allocated to each user.

In the SC-FDMA scheme, since any user must be continuously allocated a subchannel block, the general OFDMA downlink scheduling scheme cannot be used, and under such constraints, efficiency of finite frequency resources (ie, capacity increase) can be prevented. There is a need for a method for more efficiently allocating subchannel blocks.

Accordingly, in the proposed conventional scheduling scheme, the number of subchannel blocks is kept equal to the number of users, thereby preventing the assignable user from being excessively restricted and reducing the overhead of the subchannel block-allocated user mapping information. have. In addition, the system capacity can be increased by preferentially selecting a subchannel block having a relatively good channel quality state.

However, calculating and comparing only gains of a specific user in selecting a subchannel block to be allocated is unreasonable to consider as an optimal choice when a plurality of subchannel blocks are allocated to a plurality of users.

For example, as shown in FIG. 7, in a situation where there are three users and three subchannel blocks, the subchannel block (a) having the maximum data rate according to the conventional scheme is allocated to user 1, and then the secondary channel. Assuming that channel block (b) is assigned to user 2, since subchannel block (c) is contiguous with subchannel block (b), assignable users are user 2 and user 3, based on subchannel block (c). User 2 having a high data rate is allocated a frequency block (c).

At this time, the optimal allocation for maximizing the total system capacity is that user 1 is allocated the subchannel block (c), and user 2 is allocated the subchannel blocks (a) and (b) in succession. This is because the existing scheme does not consider the prerequisite gains and losses of the system when allocating subchannel blocks of multiple users. In addition, when the subchannel blocks are spaced apart from each other, the allocation is not limited to the user having the best channel quality in the corresponding subchannel block, but is also considered in consideration of the channel quality of another user. If not assigned to the user with the highest channel quality, it is assigned to the user with the next lowest channel quality in the selected subchannel block, resulting in loss in terms of system gain.

Therefore, in order to maximize the capacity of the uplink system, a scheduling algorithm is required that simultaneously considers subchannel allocation of multiple users and effectively sets an assignable user set while complying with the constraints of SC-FDMA.

Accordingly, in the present invention, orthogonal frequency-division multiple access (OFDM) system in the orthogonal frequency-division multiple access (OFDMA) system under the constraint of allocating subchannels to the same user continuously, orthogonal frequency division multiple access that can maximize the capacity of the uplink system We propose a scheduling technique in the system.

According to a scheduling apparatus in an orthogonal frequency-division multiple access (OFDMA) system for solving the problems of the present invention, the uplink frequency band of the client terminal is divided into a predetermined number of subchannel blocks, A subchannel block constituting unit constituting the divided subchannel block, a channel quality measuring unit for measuring channel quality of the subchannel blocks, and temporarily storing the measured channel quality by data, and the subchannel block Selects an allocated subchannel block, selects a client terminal having the maximum channel quality from the selected subchannel block as an assigned client terminal, and determines whether to allocate the allocated subchannel block and the assigned client terminal. It may include a scheduling unit for determining.

Here, the subchannel block may be a subchannel allocation unit during scheduling, and the total number of subchannel blocks may be set equal to the total number of users.

In addition, the channel quality may include a signal-to-interference ratio (SINR).

The channel quality measuring unit may periodically update the channel quality of the client terminal with respect to an uplink subchannel block.

The scheduling unit may calculate an allocation rank for an unallocated subchannel block that has been allocated at a subchannel allocation time, and select the subchannel block having the largest allocation rank as the allocated subchannel block. .

The scheduling unit may calculate a subchannel block selection criterion value, select the allocation subchannel block and the client terminal, and determine whether to allocate the subchannel block, and determine whether to allocate the subchannel block and the client terminal according to the determined allocation. Can be selected.

In addition, the determination of whether to allocate the information may include determining whether to allocate a continuous subchannel block by determining whether to allocate a single subchannel block and then calculating a continuous allocation discrimination reference value.

The scheduling apparatus in the orthogonal frequency division multiple access system may further include an updater configured to perform an update operation for sequential subchannel block allocation on the allocation result determined by the scheduling unit.

In addition, the updater updates the assignable subchannel block, the pre-allocated subchannel block set, and the unassigned subchannel block set for each client terminal by reflecting the allocation result of the current time point for subchannel block allocation at the next time point. It can be characterized.

According to a scheduling method in an orthogonal frequency division multiple access system for solving the problems of the present invention, a process of configuring an uplink frequency band into subchannel blocks corresponding to the number of users, and the allocation subchannel in the subchannel block Selecting a block; selecting a client terminal having a maximum channel quality as the allocated client terminal in the selected subchannel block; and determining whether to allocate the selected subchannel block and the allocated client terminal. It may include the process of doing.

The selecting of the allocated subchannel block may include calculating a subchannel block selection reference value by obtaining a difference value of possible transmission rates in each unallocated subchannel block.

In addition, the selecting of the allocated subchannel block may include selecting a subchannel block having a maximum difference value of the possible data rates as a candidate.

The selecting of the allocation client terminal may include selecting the maximum channel quality client terminal of the subchannel block having the maximum difference value of the possible transmission rates as the allocation client terminal.

The determining of the allocation may include determining whether a pre-allocated subchannel block exists in the allocating client terminal, and if the pre-allocated subchannel block exists, assigning the allocated subchannel block to the allocating client terminal. Allocating to a single channel, calculating a successive allocation discrimination reference value if the pre-allocated subchannel block does not exist, and if the calculated successive allocation discrimination reference value is greater than or equal to the difference of the possible transmission rates, the allocated subchannel block. It may include the step of sequentially assigning to the pre-allocated subchannel block.

In addition, the scheduling method in the orthogonal frequency division multiple access system may further include updating a subchannel block range for sequential subchannel block allocation after the determining of the allocation.

The updating may include updating an allocable subchannel block range for each client terminal, updating an allocable subchannel block client terminal, and checking whether there is an unassigned subchannel block. Can be.

In addition, in the orthogonal frequency division multiple access system, the scheduling method includes: calculating the subchannel block selection reference value when the unassigned subchannel block exists in the process of checking whether the unassigned subchannel block exists. The process may further include.

According to the present invention, there is an effect of increasing the total data traffic capacity in a single carrier frequency division multiple access (SC-FDMA) system applicable to uplink of an orthogonal frequency-division multiple access (OFDMA) system. . Specifically, uplink capacity can be maximized by comparing channel quality difference values in various subchannel blocks by first assigning a user having the maximum channel quality to a subchannel block having the maximum channel quality difference value. The algorithm proposed in the present invention is not only applied between orthogonal frequency division multiple access based systems for providing voice and data services to individual users, but also applied to dynamic spectrum allocation between other broadcasting systems or arbitrary systems.

1 is a block diagram schematically illustrating a scheduling apparatus in an orthogonal frequency division multiple access system according to an embodiment of the present invention;
2 is a flowchart illustrating a scheduling method in an orthogonal frequency division multiple access system according to an embodiment of the present invention;
3 is a detailed flowchart of an update process for subchannel block allocation of FIG. 2;
4 and 5 are comparison graphs according to range update of an unallocated subchannel block to which user u can be allocated and a previously allocated subchannel block set;
6 is a diagram in which a subchannel block allocation gain is compared between a conventional scheduling method and a scheduling method according to an embodiment of the present invention;
7 is a graph illustrating a channel quality pattern in a conventional multi-cell multi-user environment, for example, when there are three users and three subchannel blocks.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be embodied in various different forms, and the present embodiments merely make the disclosure of the present invention complete, and are common in the art to which the present invention pertains. It is provided to fully inform those skilled in the art of the scope of the invention, which is to be defined only by the scope of the claims. Like numbers refer to like elements throughout.

In describing the embodiments of the present invention, if it is determined that a detailed description of a known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, terms to be described below are terms defined in consideration of functions in an embodiment of the present invention, which may vary according to intention or custom of a user or an operator. Therefore, the definition should be made based on the contents throughout the specification.

Also, each block or each step may represent a module, segment, or portion of code that includes one or more executable instructions for executing the specified logical function (s). It should also be noted that in some alternative embodiments the functions noted in the blocks or steps may occur out of order. For example, two blocks or steps shown in succession may in fact be performed substantially concurrently, or the blocks or steps may sometimes be performed in reverse order according to the corresponding function.

Prior to the description of the embodiments, an object of the present invention is based on uplink Orthogonal Frequency-Division Multiple Access (OFDMA), which requires contiguous subchannel blocks to each of the multiple users who wish to allocate resources. The present invention provides a resource allocation algorithm that maximizes capacity in a single carrier frequency division multiple access (FDMA) system. Thereby, based sizing the ^{3GPP LTE (3 rd Generation Partnership Project} Long-Term Evolution), IEEE (Institute of Electrical & Electronics Engineers) , and other OFDMA based possible flexibility for the uplink standard, user subchannel blocks more efficiently We propose a scheduling scheme for allocating them to effectively maximize uplink resources.

In an embodiment of the present invention, the number of subchannel blocks to be allocated can be selected while the number of all subchannel blocks is the same as the total number of users, and a user to be assigned the selected subchannel block can be determined. In determining the order of subchannel blocks to be allocated, the difference between the highest transmittable quality and the highest rank transmittable quality in each subchannel block may be based on a difference value. That is, in each frequency block, the difference between the channel quality of the user whose channel quality is the first and the channel quality of the user whose channel quality is the second is calculated, and the subchannel block having the largest value is selected first. User can be assigned. As a result, it is possible to expect an improvement in overall system capacity by using a method that reflects mutual gain and loss for multiple user allocation of a plurality of subchannel blocks, rather than simply comparing the system gains of individual subchannel block units.

Further, according to an embodiment of the present invention, when the subchannel block to be additionally allocated is spaced apart from the pre-assigned subchannel block, the subchannel block to be allocated between the subchannel block to be allocated by the user who has been allocated the subchannel and the subchannel block to be allocated. System capacity performance can be improved by determining whether to allocate the corresponding subchannel block in consideration of channel quality. This has the advantage of additionally reflecting the gain in the case of allocation including subchannel blocks having good discretely located characteristics.

Due to the selection of the allocated subchannel blocks and the selection of assignable user sets, when allocating only the maximum value of the aforementioned subchannel blocks while satisfying the SC-FDMA constraint of allocating the subchannel blocks continuously. It is possible to prevent the degradation of the total capacity of the system.

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

1 is a schematic configuration diagram of a scheduling apparatus in an OFDMA system according to an embodiment of the present invention. The channel quality measurement unit 102, the subchannel block configuration unit 104, the scheduling unit 106, and the updating unit ( 108) and the like.

As illustrated in FIG. 1, the channel quality measurement unit 102 may determine channel quality (or signal-to-interference ratio (SINR)) for subchannel blocks of the entire uplink frequency band of a client terminal (not shown). It measures the quality of the measured channel and can be temporarily stored in a separate storage media by measuring the channel quality. The channel quality measurement unit 102 may periodically update the channel quality of all client terminals for all uplink subchannel blocks.

The subchannel block configuration unit 104 may serve to configure a subchannel block of the divided uplink frequency band by dividing the entire uplink frequency band into a predetermined number of subchannel blocks. In this case, the configured subchannel block becomes a subchannel allocation unit during scheduling, and the total number of subchannel blocks may be set equal to the total number of users.

According to an embodiment of the present invention, the scheduling unit 106 calculates an allocation rank for an unallocated subchannel block that has been allocated at every subchannel allocation time, and allocates a subchannel block having a maximum value to the subchannel block. The user who has the maximum channel quality in the selected allocated subchannel block is selected as the assigning user, and whether to assign the selected subchannel block and the user is determined through a discriminant (described below). have. The function of selecting the allocation subchannel block and the allocation user of the scheduling unit 106 may include a subchannel block selection reference value calculation function, an allocation subchannel block and a user selection function, an allocation determination function, an allocation function, and the like in detail. Can be. Here, the allocation determination function may include a single subchannel block allocation determination function, a continuous allocation determination reference value calculation function, a continuous subchannel block allocation determination function, and the like.

The updater 108 may perform an update operation for sequential subchannel block allocation on the allocation result determined by the scheduling unit 106. In detail, the updater 108 may allocate an assignable subchannel block, a pre-assigned subchannel block set, and an unassigned subchannel block set for each user by reflecting an allocation result of the current time point for subchannel block allocation at a next time point. It can play a role of updating.

2 is a flowchart illustrating a scheduling process in an OFDMA system according to an embodiment of the present invention.

The embodiment of FIG. 2 illustrates an overall operation process when applied to an SC-FDMA-based system, assuming that all uplink frequency bands are pre-divided into a predetermined number of subchannel blocks as in the 3GPP LTE standard. do. In addition, the base stations (BSs) and the central system all know in advance the SINR values or the channel quality of the subchannel blocks of the entire uplink frequency band of all client terminals through the channel quality measurement unit 102. The client terminal periodically reports corresponding SINR values or channel quality of all subchannel blocks to the corresponding base station, and it is assumed that the entire system can properly update the transmission rates of all users for all uplink subchannel blocks periodically.

1) Subchannel Block Configuration Process (S200)

, 사용자 수를

이라고 가정하면, 부채널 블록 수는 사용자 수와 동일하게 형성된다. 이때, 각 부채널 블록에 속하는 부채널 수를 동일하게

로 구성하였다고 가정하면,

는

보다 작지 않은 최소의 정수가 되고, 부채널 블록

에 속하는 부채널 집합

에 속하는 부채널 인덱스(index)는 다음 [수학식 1]과 같이 표현될 수 있다.The subchannel block becomes a subchannel allocation unit during scheduling, and the total number of subchannel blocks can be set equal to the number of users. Therefore, the total number of subchannels

, The number of users

Is assumed, the number of subchannel blocks is formed equal to the number of users. At this time, the number of subchannels belonging to each subchannel block is equal.

Suppose we configured with

Is

Is the smallest integer that is not less than, and the subchannel block

Set of subchannels belonging to

A subchannel index belonging to may be expressed as Equation 1 below.

2) Allocation Subchannel Block and User Decision Process ((S202) to (S214))

An allocation rank is calculated for an unallocated subchannel block that has been allocated at every subchannel allocation time, and the subchannel block having the largest value is selected as the allocated subchannel block. The maximum user can be selected as the assigning user.

Subsequently, whether to allocate the selected subchannel block and the user may be determined through a discrimination equation. The allocation subchannel block and the user selection process may be specifically performed in the subchannel block selection reference value calculation process (S202), the allocated subchannel block and the user. The selection process (S204), whether or not the allocation process (S206) (S210) (S212), the allocation process (S208) (S214) and the like.

, 임의의 사용자

에 할당된 부채널 블록을

, 각 사용자에 최대로 허용된 사용 전력을

, 부채널 블록

에서

번째 높은 채널 품질을 갖는 사용자를

로 각각 가정하면, 아직까지 할당되지 않은 부채널 블록

에서 현재시점까지 할당받은 부채널 블록이 없는(즉,

일 경우) 사용자

의 가능 전송률

는 다음 [수학식 2]와 같이 표현될 수 있다.First, in the subchannel block selection reference value calculation process (S202), a set of subchannel blocks other than the pre-allocated subchannel block is determined.

, Any user

Subchannel block assigned to

, The maximum allowed power for each user

, Subchannel block

in

Users with the highest channel quality

Assuming that each is a subchannel block that has not yet been allocated

Has no subchannel blocks allocated to the current point in time (i.e.

User)

Possible bitrate of

May be expressed as Equation 2 below.

는 미 할당된 부채널 블록

의 대역폭(bandwidth),

는 사용자

에 인가된 최대 전력,

는 사용자

의 부채널 블록

채널 함수이며,

은 부채널 블록

의 잡음 전력이다.In [Equation 2]

Is an unallocated subchannel block

Bandwidth,

Is a user

Maximum power applied to,

Is a user

Subchannel Block of

Channel function,

Is a subchannel block

Is the noise power.

는 임의의 부채널 블록

에서 할당 가능한 사용자 집합으로서, 사용자

에 할당된 또는 할당 가능한 부채널 블록 집합

를 이용하면 다음 [수학식 3]과 같이 표현될 수 있다.here,

Is any subchannel block

The set of users assignable by

Set of subchannel blocks assigned or assignable to

By using Equation 3, Equation 3 can be expressed.

에 할당된 부채널 블록이 있을 경우(즉,

일 경우),

는 다음 [수학식 4]와 같이 표현될 수 있다.User in [Equation 3]

If there is a subchannel block assigned to

),

May be expressed as Equation 4 below.

는 다음 [수학식 5]와 같이 표현될 수 있다.In [Equation 4]

May be expressed as Equation 5 below.

은 최소 인덱스를 갖는 부채널 블록,

는 최대 인덱스를 갖는 부채널 블록,

는 사용자

에 할당된 부채널 블록 집합

의 원소를 각각 나타낼 수 있다.In [Equation 5]

Is the subchannel block with the smallest index,

Is the subchannel block with the largest index,

Is a user

Set of subchannel blocks assigned to

Each element of can be represented.

에서 최고 가능 전송률과 차순위 가능 전송률의 차

는 다음 [수학식 6]과 같이 계산될 수 있다.Unallocated Subchannel Block

The difference between the highest possible rate and the next highest possible rate in

May be calculated as shown in Equation 6 below.

로

가 최대인 부채널 블록을 선정할 수 있으며, 다음 [수학식 7]에서 구할 수 있다.Next, in the allocation subchannel block and the user selection process (S204), the subchannel block to be allocated

in

A subchannel block having a maximum can be selected, and can be obtained from Equation 7 below.

에 대해 다음 [수학식 8]과 같이 최대의 가능 전송률을 갖는 사용자를 할당 사용자로 결정할 수 있다.Selected Subchannel Block

For Equation 8, a user having the maximum possible transmission rate may be determined as an allocated user as shown in Equation 8 below.

에

를 할당하는 방법으로

를 단독적으로 할당하는 경우와

가 포함된 연속적인 부채널 블럭을 할당하는 경우로 구분할 수 있다.For example, the allocation process determining step 206 (S210) (S212) is, for example,

on

By assigning

Assigning to

It can be classified as a case of allocating a contiguous subchannel block including.

에 기 할당된 부채널 블록이 존재하지 않는지(조건1)를 확인할 수 있다. 조건1이 만족되면 후술하는 과정(S208)을 통해

를

에 단독적으로 할당할 수 있는데, 이때의 조건1은 다음 [수학식 9]와 같이 표현될 수 있다.First, in the process of determining whether to allocate a single subchannel block (S206), for example,

It can be checked whether there is no subchannel block previously allocated (condition 1). If condition 1 is satisfied, the following process (S208)

To

In this case, condition 1 may be expressed as Equation 9 below.

If it is not condition 1, it corresponds to a case of continuous allocation instead of single allocation, and the process of calculating the reference value for determining successive allocation can be performed as follows.

를 사용자에게 단독적으로 할당하지 않는 대신에 기 할당된 부채널 블록

와

사이의 모든 부채널 블록을 연속적으로 할당할 경우 이득에 따라 해당 범위의 부채널 블록을 연속적으로 할당할 지를 판별할 수 있다.If condition 1 is not satisfied

Instead of assigning to the user alone, the pre-allocated subchannel block

Wow

When all subchannel blocks in between are continuously allocated, it is possible to determine whether to sequentially allocate subchannel blocks of the corresponding range according to the gain.

와

를 포함하지 않은

와

사이의 부채널 블록 집합을

라 하고,

를 모두

에 할당할 경우의 가능 전송률과

를

를 제외한 사용자 중 최대 전송률을 갖는 할당 가능 사용자에게 할당할 경우의 가능 전송률의 차이

는 다음 [수학식 10]과 같이 표현될 수 있다.At this time,

Wow

Does not contain

Wow

Subchannel block set between

,

All of

Is available when you assign to

To

Difference in Available Bit Rate when Allocating to Assignable User with Maximum Transfer Rate Among Users

May be expressed as Equation 10 below.

는 다음 [수학식 11]과 같이 계산될 수 있다.In Equation 10,

May be calculated as shown in Equation 11 below.

는

에 속하는 부채널 블록 인덱스

의 대역폭,

는

에 속하는 부채널 블록 인덱스

에서 사용자

의 채널 함수,

은

에 속하는 부채널 블록 인덱스

에서의 잡음 전력을 각각 나타낸다. 또한,

는 [수학식 5]로 계산된 사용자

가

,

와

에 해당하는 모든 부채널 블록 각각에 할당 가능한 인가 전력을 나타낸다.In Equation 11

Is

Subchannel block index belonging to

Bandwidth,

Is

Subchannel block index belonging to

From

Channel function,

silver

Subchannel block index belonging to

Denotes the noise power at. Also,

Is the user calculated by [Equation 5]

end

,

Wow

Represents an applied power that can be allocated to each subchannel block corresponding to

는 다음 [수학식 12]와 같이 표현될 수 있다. Also,

May be expressed as Equation 12 below.

는

에 속하는 부채널 블록 인덱스

에서 사용자

의 채널 함수를 나타내며, 사용자

는 각 부채널 블록에서

를 인가하는 것으로 가정하기로 한다.In Equation 12,

Is

Subchannel block index belonging to

From

Represents a channel function of

In each subchannel block

It is assumed to apply.

의

값이

의 값보다 더 클 경우(조건2),

를 포함한

를

로 정의하고 이에 속하는 부채널 블록을

에 할당하는 것으로 판별할 수 있다. 조건2는 다음 [수학식 13]과 같이 예시될 수 있다.In the continuous subchannel block allocation determining process (S212), when it is determined that a gain occurs during continuous allocation, the corresponding subchannel block may be allocated. Subchannel block selected at this time

of

Value is

Is greater than the value of (condition2),

Including

To

Subchannel block

It can be determined by assigning to. Condition 2 may be exemplified by Equation 13 below.

를

로 갱신한 후 다음 시점의 할당 부채널 블록을 선정하기 위해 과정(S204)으로 피드백할 수 있다.If (Condition 2) is not satisfied, do not allocate the corresponding subchannel block at this time and use the following [Equation 14].

To

After updating to, it may be fed back to the process (S204) to select the allocation subchannel block of the next time.

의

값이 미 할당 미 할당 부채널 블록 중 최대값이므로,

보다

의 값이 더 크거나 같을 경우,

의

역시 미 할당 부채널 블록 중 최대 이득값이 될 수 있다.

값이

보다 크거나 같을 경우(조건3),

에 속하는 부채널 블록을

에 할당하는 것으로 판별할 수 있다. 조건3은 다음 [수학식 15]와 같이 표현될 수 있다.If it is determined that a gain occurs during continuous allocation, the corresponding range subchannel block may be allocated. Subchannel block selected at this time

of

Since the value is the maximum value among unallocated subchannel blocks,

see

Is greater than or equal to

of

It may also be the maximum gain value among unallocated subchannel blocks.

Value is

Greater than or equal to (condition 3)

Subchannel blocks belonging to

It can be determined by assigning to. Condition 3 may be expressed as in Equation 15 below.

를

로 갱신한 후 다음 시점의 할당 부채널 블록을 선정하기 위해 과정(S204)으로 피드백할 수 있다.If condition 3 is not satisfied, the subchannel block is not allocated at this point and the following [Equation 16] is used.

To

After updating to, it may be fed back to the process (S204) to select the allocation subchannel block of the next time.

또는

에 속한 부채널 블록을

에 할당할 수 있다. 이는 각 경우에 대해

에 할당된 부채널 블록 집합에 새롭게 할당된 부채널 블록을 포함시키는 것으로 구현될 수 있다. 또한, 미할당 부채널 블록 집합에서 할당된 부채널 블록을 다음 할당 시점 이동 전에 제외시킬 수 있다.On the other hand, in the assigning process (S208) (S214), according to the above-mentioned assignment determination result.

or

Subchannel blocks belonging to

Can be assigned to For each case

It may be implemented by including the newly allocated subchannel block in the subchannel block set assigned to the. In addition, the subchannel block allocated in the unassigned subchannel block set may be excluded before the next allocation time shift.

를

의 원소에 포함시킬 수 있으며, 또한

를 아래와 같이 변경할 수 있다.First, in the single assignment process (S208), as shown in Equation 17 below.

To

Can be included in the element of

Can be changed to

를

에 연속하여 할당하고

,

를 다음 [수학식 18]과 같이 각각 갱신할 수 있다.In the continuous allocation process (S214),

To

Assign consecutively to

,

Each can be updated as shown in [Equation 18].

3) Update process for sequential subchannel block allocation (S216)

와 미 할당된 부채널 블록 집합

를 갱신할 수 있다. 모든 부채널 블록 할당이 완료된 경우 할당 절차를 종료할 수 있다.
In the updating process for allocating the next time point (S216), the assignable subchannel block and the pre-assigned subchannel block set for each user are reflected to reflect the result of the current time point for the next time subchannel block assignment.

And unallocated subchannel block set

Can be updated. If all subchannel block allocation is completed, the allocation procedure can be terminated.

3 is a flowchart illustrating a detailed operation of the update process S216 for sequential subchannel block allocation of FIG. 2.

As illustrated in FIG. 3, the update process S216 may include an assignable subchannel block range update process S218 for each user, an assignable subchannel block user update process S220, and an unassigned subchannel block presence check process S222. ) May be included.

갱신 시 아직까지 할당받은 부채널 블록이 없는 사용자인 경우와, 도 5에 도시한 바와 같은 기 할당된 부채널 블록이 있는 사용자인 경우로 나누어 수행할 수 있다. 이때, 아직까지 할당받은 부채널 블록이 없는 사용자의 경우

는

와 동일하며, 기 할당된 부채널 블록이 있는 사용자인 경우

는

혹은

를 제외하는 연속적인 부채널 블록의 집합으로 구성된다.First, a user-assignable subchannel block range update process (S218) may be performed as illustrated in FIG. 4.

This may be performed by dividing into a case in which the user does not have a subchannel block allocated yet at the time of updating and a case in which the user has a previously allocated subchannel block as shown in FIG. 5. In this case, the user who does not have a subchannel block allocated yet

Is

Is the same as that of the user who has a pre-allocated subchannel block

Is

or

It consists of a set of consecutive subchannel blocks excluding.

① Unassigned user

에 할당된 부채널 블록이 없을 경우(즉,

), 미 할당된 모든 부채널 블록은 사용자

에 할당할 수 있으므로,

는

와 동일하며, 다음 [수학식 19]와 같이 갱신할 수 있다.user

If no subchannel block is assigned to

), All unassigned subchannel blocks

Can be assigned to,

Is

The same as, and can be updated as shown in Equation 19.

② Assigned User

, 현 시점에서 연속으로 부채널 블록을 할당받은

와 그 전 시점에서 부채널 블록을 할당받은 사용자

를 구분하여 갱신할 수 있다.At this time, the subchannel block is allocated by itself.

In this case, subchannel blocks are allocated consecutively at this point.

User assigned subchannel block at and before

Can be updated separately.

사용자가

를 할당받은 경우②-1:

User

Is assigned

에 할당된 부채널 블록

를 포함하는 미 할당 연속 부채널 블록으로

가 축소될 수 있다. 이때,

를

보다 작은 인덱스를 갖는 기 할당된 부채널 블록 중에서 최대 인덱스를 갖는 부채널 블록으로 정의하고,

를

보다 큰 인덱스를 갖는 기 할당된 부채널 블록 중에서 최소 인덱스를 갖는 부채널 블록으로 각각 정의했을 때,

는 다음 [수학식 20]과 같이 갱신될 수 있다.

Subchannel Blocks Assigned to

To an unallocated contiguous subchannel block containing

Can be reduced. At this time,

To

Defined as a subchannel block having the maximum index among the pre-allocated subchannel blocks having a smaller index,

To

When each of the subchannel blocks having the larger index is defined as the subchannel block having the smallest index,

May be updated as shown in Equation 20 below.

사용자가

를 할당받은 경우②-2:

User

Is assigned

를

에 할당하는 경우,

로 인하여,

의 변화가 발생하지 않으므로

는 그대로 유지될 수 있다.At this point

To

If you assign to

Due to

Change does not occur

May remain as it is.

사용자 경우②-3: Gi Allocation

User case

혹은

가 기 할당

의

에 포함되는 경우,

혹은

와 해당하는 미 할당 부채널 블록을 제외시킨다. 이때,

과

는

와

모두를 포함할 수 있다.Subchannel block allocated at this time

or

Top assignment

of

If included in

or

And the corresponding unallocated subchannel block are excluded. At this time,

and

Is

Wow

It can include everything.

This may be expressed as Equation 21 below.

혹은

가 기 할당

의

에 포함되지 않은 경우,

의 변화가 발생하지 않으므로

는 그대로 유지될 수 있다.Subchannel block allocated at this time

or

Top assignment

of

If not included in

Change does not occur

May remain as it is.

에 대한 갱신 과정(S220)을 수행할 수 있다.When the assignable subchannel block range update process (S218) is completed, the assignable subchannel block range user, for example

An update process (S220) may be performed.

의 할당 가능한 사용자 집합

는

가

의 원소가 아닌 경우 제외하며, 다음 [수학식 22]와 같이 갱신할 수 있다.Unallocated subchannel block

Assignable user set of

Is

end

Except when it is not an element of, it can be updated as shown in [Equation 22].

When the assignable subchannel block user is updated, it may be determined whether an unallocated subchannel block exists (S222).

Specifically, after checking whether there is an unallocated subchannel block, if the existence condition (condition 4) is satisfied, the process returns to step S202, and if the condition 4 is not satisfied, the subchannel allocation procedure may be terminated. Condition 4 may be expressed as Equation 23 below.

Next, a case in which a scheduling method in an OFDMA system according to an embodiment of the present invention is applied will be described with reference to FIG. 6.

For example, assume a simple SC-FDMA system with a total of four users and four subchannel blocks. FIG. 6 is a diagram illustrating a difference between an allocation method using a scheduling method and an allocation method according to a conventional scheduling method. Referring to FIG.

값이 5로서 전체 주파수 대역에서 가장 큰 차이가 난다. 따라서, 부채널 블록(c)를 이용자 2에게 할당할 수 있다.First, when a subchannel block is allocated by the scheduling method according to an embodiment of the present invention, the subchannel block (c) between user 2 and user 1

The value 5 is the largest difference over the entire frequency band. Therefore, the subchannel block c can be allocated to the user 2.

값을 가지는 부채널 블록을 검색하면, 이용자 2가 부채널 블록(a)에서 최대값인 4를 가지고 있으나, 부채널 블록(c)와 연결하여 할당하여야 하므로 새로운

값을 구하기 위해 상술한 [수학식 7]을 적용할 수 있다. 이때,

가 3으로 변경되고 이 값으로 부채널 블록(a)의

을 갱신할 수 있다.After, up again

When a subchannel block having a value is searched for, user 2 has a maximum value of 4 in the subchannel block (a), but a new channel is allocated in connection with the subchannel block (c).

Equation 7 described above may be applied to obtain a value. At this time,

Is changed to 3 and this is the value of the subchannel block (a).

Can be updated.

을 가지므로, 부채널 블록 (a)를 이용자 2에게 할당하고, 연결되는 부채널 블록(b) 역시 이용자 2에게 할당할 수 있다. 따라서, 이용자 2는 부채널 블록(a), (b), (c)를 연속적으로 할당받게 되며, SC-FDMA 제한조건을 위반하지 않는다. 마지막으로 부채널 블록 (d)에서 최대

을 가지는 이용자 (c)을 할당하고 본 발명의 실시예에 따른 스케줄링 과정을 종료하며, 이때 시스템 전체 이득은 29로 될 수 있다.Subchannel block (a) is the maximum in all unallocated subchannel blocks even after updating.

Since the subchannel block (a) is assigned to the user 2, the subchannel block (b) to be connected can also be assigned to the user 2. Thus, User 2 is allocated subchannel blocks (a), (b) and (c) consecutively and does not violate the SC-FDMA constraint. Finally, in subchannel block (d),

Allocating a user (c) having a and terminates the scheduling process according to an embodiment of the present invention, wherein the system overall gain may be 29.

However, when the subchannel block is allocated by the conventional scheduling method, the user 2 can be assigned only the subchannel block (a) having the maximum value, and the user 1 is the subchannel block (b) and (c), the user 3 Each of these subchannel blocks d is allocated. Therefore, the system overall gain by the conventional scheduling method is 25, which means that the system overall gain is lower than the scheduling method according to the embodiment of the present invention.

As described above, in the embodiment of the present invention, a method of efficiently allocating subchannels in uplink in an OFDMA system, specifically, compares channel quality difference values of various subchannel blocks to select a user having a maximum channel quality. It is implemented to maximize uplink capacity by applying a method of first assigning a subchannel block having a maximum channel quality difference value.

102: channel quality measurement unit
104: subchannel block configuration
106: scheduling unit
108: update unit

Claims (17)

delete delete delete delete delete delete delete delete delete delete Configuring an uplink frequency band into subchannel blocks corresponding to the number of users;
Selecting an allocated subchannel block from the configured subchannel block;
Selecting a client terminal having a maximum channel quality as the assigned client terminal in the assigned subchannel block;
Determining whether to allocate the allocated subchannel block and the assigned client terminal to be selected;
The process of selecting an allocated subchannel block may include obtaining a difference value between a possible transmission rate of a first unallocated subchannel block and a possible transmission rate of a second unallocated subchannel block in a plurality of unassigned subchannel blocks. Involving the process of calculating
Scheduling in Orthogonal Frequency Division Multiple Access Systems.
The method of claim 11,
The selecting of the allocated subchannel block includes selecting as a candidate a subchannel block having a maximum difference between a possible data rate of the first unallocated subchannel block and a possible data rate of the second unassigned subchannel block. doing
Scheduling in Orthogonal Frequency Division Multiple Access Systems.
The method of claim 11,
The selecting of the assigned client terminal may include: assigning a maximum channel quality client terminal of a subchannel block having a maximum difference between a possible transmission rate of the first unallocated subchannel block and a possible transmission rate of the second unassigned subchannel block. Including selecting a client terminal
Scheduling in Orthogonal Frequency Division Multiple Access Systems.
The method of claim 11,
The process of determining whether to assign the,
Determining whether a pre-allocated subchannel block exists in the allocating client terminal;
Allocating the allocated subchannel block solely to the allocating client terminal when the pre-allocated subchannel block exists;
Calculating a reference value for determining successive allocation if the pre-allocated subchannel block does not exist;
The allocated subchannel block is assigned to the pre-allocated subchannel block if the calculated continuous allocation discrimination reference value is equal to or greater than a difference between a possible transmission rate of the first unallocated subchannel block and a possible transmission rate of the second unassigned subchannel block. Including the process of assigning consecutively
Scheduling in Orthogonal Frequency Division Multiple Access Systems.
The method of claim 11,
Scheduling in the orthogonal frequency division multiple access system,
The method may further include updating a subchannel block range for sequential subchannel block allocation after the determining of the allocation.
Scheduling in Orthogonal Frequency Division Multiple Access Systems.
The method of claim 15,
The updating process,
Updating the assignable subchannel block range for each client terminal;
Updating the assignable subchannel block client terminal;
Including checking for the presence of unassigned subchannel blocks
Scheduling in Orthogonal Frequency Division Multiple Access Systems.
17. The method of claim 16,
Scheduling in the orthogonal frequency division multiple access system,
And in the process of checking whether or not the unassigned subchannel block exists, feeding back to the process of calculating the subchannel block selection reference value when the unassigned subchannel block exists.
Scheduling in Orthogonal Frequency Division Multiple Access Systems.

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