KR101054738B1 - Method for allocating transmit power to a plurality of subchannels and wireless communication device using same - Google Patents

Abstract

A method of allocating transmit power to a plurality of subchannels and a wireless communication device using the same are disclosed. According to one or more exemplary embodiments, there is provided a method comprising: (a) performing communication by allocating transmission power to each of a plurality of subchannels according to a water filling algorithm having a limitation that a total transmission power is less than or equal to a preset threshold; (b) adjusting the threshold based on a minimum required transmission rate, a previously achieved subchannel-specific transmission rate, and a previously allocated subchannel transmission power; And (c) allocating transmission power to each of the plurality of subchannels according to a water filling algorithm, which limits the total transmission power to be less than or equal to the adjusted threshold.

Description

Method for allocating transmit power to subchannels and wireless communication device using the same}

The disclosed technique relates to a resource allocation method for a plurality of subchannels, and more particularly, but not exclusively, each of the wireless communication devices in a multichannel communication system transmits to its subchannels. A method of allocating power to perform communication.

In a multi-channel communication system, a wireless communication device can communicate using a plurality of subchannels. In one example, such a wireless communication device determines a transmission power to be used in each subchannel, a modulation scheme (eg, BPSK, QPSK, 16-QAM, etc.), and performs communication according to the determined result.

A representative example of the multi-channel communication system may include a multi-carrier communication system using at least one subcarrier as a subchannel, but is not limited thereto. Examples of the multi-carrier communication system include an orthogonal frequency division multiple access (OFDMA) system and an orthogonal frequency division multiplexing (OFDM) system. In the former communication system, the wireless communication device uses subcarriers allocated from the base station and the like, and in the latter system, the wireless communication device can perform communication using all subcarriers belonging to the OFDM system.

Examples of methods for determining transmit power for each subchannel include a water-filling technique, a channel inversion technique that allocates transmit power inversely proportional to the channel gain, and uniformity for each subchannel. And a technique of allocating a transmission power. In particular, the water filling technique is a power allocation technique for maximizing a transmission rate within a preset maximum allowable power (maximum value of total allowable transmission power allowed) in a wireless communication device, and has been applied to various systems.

However, since the proposed water filling technique is designed based on a single cell network model, the effect of intercell interference has not been fully considered. For example, when applying an existing water filling technique to a multi-cell network, a power war between wireless communication devices (e.g., mobile stations) occurs and is in a channel state that is advantageous in such a power war (e.g., base station). Wireless communication devices that are in close proximity to each other and have a relatively good state of the corresponding subchannels will always win, resulting in radios that are in an unfavorable channel state (e.g., located at cell boundaries and having relatively poor state of the corresponding subchannels). The problem arises that the communication device cannot achieve the required quality of service (QoS).

Disclosure of Invention The technical problem to be solved by the disclosed technology is to provide a transmission power allocation method for increasing the achievement rate compared to the number and power consumption of wireless communication devices that satisfy a required QoS in a multi-channel communication system, and a wireless communication device using the same.

One aspect of the disclosed technology to achieve the above technical problem is a method for allocating transmit power to a plurality of subchannels in a wireless communication device, (a) water filling with a limit condition that the total transmit power is below a preset threshold; Performing communication by allocating transmit power to each of the plurality of subchannels according to an algorithm; (b) adjusting the threshold based on a minimum required transmission rate, a previously achieved subchannel-specific transmission rate, and a previously allocated subchannel transmission power; And (c) allocating transmit power to each of the plurality of subchannels according to a water filling algorithm with a limiting condition that a total transmit power is less than or equal to the adjusted threshold.

In one embodiment, the step (b) comprises the steps of: calculating a first parameter that is proportional to the transfer rate previously achieved (b1) and inversely proportional to the minimum required transfer rate; (b2) calculating a second parameter proportional to a deviation of a ratio between the previously achieved subchannel transmission rate and the previously allocated subchannel transmission power; And (b3) multiplying the predetermined threshold by a value inversely proportional to the calculated first and second parameters to obtain the adjusted threshold.

Another aspect of the disclosed technology to achieve the above technical problem is in a wireless communication device using a plurality of subchannels, the minimum required transmission rate, previously achieved subchannel transmission rate, and previously allocated subchannel transmission power Adjusting unit for adjusting the maximum allowable power on the basis; An allocating unit for allocating transmission power to each of the plurality of subchannels according to a water filling algorithm with a condition that a total transmission power is less than or equal to the adjusted maximum allowable power; And a communication unit configured to perform communication using the allocated transmission power.

Another aspect of the disclosed technology to achieve the above technical problem provides a computer readable recording medium containing a program for realizing a method of the disclosed technology on a computer.

Embodiments of the present invention presented above may have an effect including the following advantages. However, all the embodiments of the present invention are not meant to include them all, and thus the scope of the present invention should not be understood as being limited thereto.

According to an embodiment, it is possible to provide a multi-channel communication system capable of increasing the achievement rate compared to the number and power consumption of wireless communication devices that satisfy a required QoS. According to one embodiment, a problem of power warfare caused by applying a water filling algorithm to a multi-cell environment that derives maximum performance in a single cell (e.g., unevenly allocated transmit power to multiple wireless communication devices due to inter-cell interference) Problem can be solved. According to one embodiment, the inter-cell interference can be effectively controlled without incurring additional overhead in the network, thereby increasing the number of wireless communication devices that satisfy the required QoS on the entire network.

Since descriptions of embodiments of the present invention are merely illustrated for structural to functional descriptions of the present invention, the scope of the present invention should not be construed as limited by the embodiments described in the present invention. That is, the embodiments of the present invention may be variously modified and may have various forms, and thus, it should be understood to include equivalents that may realize the technical idea of the present invention.

On the other hand, the meaning of the terms described in the present invention will be understood as follows.

Terms such as "first" and "second" are intended to distinguish one component from another component, and the scope of the present invention should not be limited by these terms. For example, the first component may be named a second component, and similarly, the second component may also be named a first component.

The term “and / or” should be understood to include all combinations that can be presented from one or more related items. For example, "first item, second item, and / or third item" means "at least one or more of the first item, second item, and third item", and means first, second, or third item. A combination of all items that can be presented from two or more of the first, second and third items as well as the third item.

Singular expressions described herein are to be understood to include plural expressions unless the context clearly indicates otherwise, and the terms "comprise" or "having" include elements, features, numbers, steps, operations, and elements described. It is to be understood that the present invention is intended to designate that there is a part or a combination thereof, and does not exclude in advance the possibility of the presence or addition of one or more other features or numbers, steps, actions, components, parts or combinations thereof. .

Each step described in the present invention may occur out of the stated order unless the context clearly dictates the specific order. That is, each step may occur in the same order as specified, may be performed substantially simultaneously, or may be performed in the reverse order.

Unless otherwise defined, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art, and shall be interpreted as having ideal or overly formal meanings unless expressly defined in this application. Can't be.

In the present specification, the disclosed technology will be described mainly for an OFDMA-based cellular communication system for convenience, but it can be fully understood by those skilled in the art that the disclosed technology can be applied to various multi-channel communication systems without being limited thereto. .

An optimization problem that maximizes the transmission rate within a given maximum allowable power may be represented by Equation 1, and the solution to this optimization problem may be obtained by a water filling algorithm.

은 m번째 셀에 있는 i번째 무선 통신 기기에 할당된 부반송파들의 집합을 나타내며,

는 m번째 셀의 i번째 무선 통신 기기가 k번째 부반송파에 할당하는 송신 전력을 나타내며,

는 m번째 셀의 i번째 무선 통신 기기의 최대 허용 전력을 나타낸다. 이러한 최대 허용 전력은 여러 가지 파라미터(예컨대, 무선 통신 기기의 배터리 소모량, PAPR 등)를 고려하여 미리 설정될 수 있다.here,

Denotes a set of subcarriers assigned to the i th wireless communication device in the m th cell,

Denotes transmit power allocated to the k th subcarrier by the i th wireless communication device of the m th cell,

Denotes the maximum allowable power of the i-th wireless communication device of the m-th cell. This maximum allowable power may be preset in consideration of various parameters (eg, battery consumption of a wireless communication device, PAPR, etc.).

는 m번째 셀의 i번째 무선 통신 기기가 k번째 부반송파를 통하여 성취할 수 있는 전송률로서, 일실시예에 있어서 수학식 2로 구할 수 있으나, 반드시 이에 한정되는 것은 아니다.

Is a data rate that the i-th wireless communication device of the m-th cell can achieve through the k-th subcarrier, which can be obtained by Equation 2 in one embodiment, but is not limited thereto.

는 k번째 부반송파의 대역폭을 나타내며,

는 m번째 셀의 i 번째 무선 통신 기기 입장에서 바라본 k번째 부반송파의 신호대간섭잡음비(Signal to Interference and Noise Ratio : 이하, SINR)를 나타낸다. here,

Denotes the bandwidth of the kth subcarrier,

Denotes a Signal to Interference and Noise Ratio (SINR) of the k th subcarrier viewed from the i th wireless communication device of the m th cell.

에 속하는 부반송파들) 각각에 대한 SINR(예컨대,

)을 추정한 후, 추정된 결과를 기초로 최대 허용 전력(예컨대,

)을 상기 해당 부반송파들에 분배하는 방식으로 송신 전력 할당을 수행한다. According to the water filling algorithm, each wireless communication device (e.g., the i-th wireless communication device of the m-th cell) uses various estimation algorithms to determine corresponding subcarriers (e.g.,

SINR for each of the subcarriers belonging to

) Is estimated and then the maximum allowable power (e.g.,

Transmit power allocation in a manner of distributing a) to the corresponding subcarriers.

FIG. 1 is a diagram for conceptually explaining a method of allocating transmission power according to a water filling algorithm.

를 재번호(renumber)한 버전의 부반송파 인덱스를 나타내며, 세로축은 해당 무선 통신 기기의 n번째 부반송파가 가지는 SINR의 역수를 나타낸다.In FIG. 1, the horizontal axis represents indexes of subcarriers allocated to a corresponding wireless communication device, and the vertical axis represents an inverse of SINR of the corresponding subcarrier. For example, when the wireless communication device is the i-th wireless communication device in the m-th cell, n in FIG.

The subcarrier index of the renumbered version represents a subcarrier index, and the vertical axis represents the inverse of the SINR of the nth subcarrier of the wireless communication device.

는 수면의 높이를 나타낸다. 또한, 도 1에서 음영 부분은 워터 필링에 따라 최대 허용 전력이 분배된 영역을 나타낸다.In FIG. 1, the dotted line represents the surface of the water filling,

Represents the height of the water surface. In addition, the shaded portion in FIG. 1 represents an area where the maximum allowable power is distributed according to water filling.

,

의 송신 전력이 할당됨을 알 수 있다.Referring to FIG. 1, no transmission power is allocated to the first subcarrier, and the second and third subcarriers are allocated.

,

It can be seen that the transmit power of is allocated.

및 수면의 높이에 관여하는

는 수학식 3으로 구할 수 있다.That is, the transmission power allocated to each subcarrier

And involved in the height of sleep

Can be obtained from equation (3).

은 n번째 부반송파의 SINR을 나타낸다.In Equation 3, x ⁺ represents the operation of max (x, 0),

Denotes the SINR of the nth subcarrier.

Meanwhile, the above-described water filling may be repeatedly performed, and the water filling performed repeatedly may be referred to as IWF (Iterative Water-Filling). In one example, the wireless communication device performs communication while repeatedly performing water filling until the transmission rate and / or transmission power converges, and then transmits a subsequent period (e.g., the subchannels of the corresponding wireless channels) with the transmission power according to the repeated performance. Communication may be performed for a period of time before being newly assigned to the communication device) .In another example, the wireless communication device performs communication while repeatedly performing the water peeling a predetermined number of times, and then according to the result of the repeated operation. Communication may be performed for subsequent periods at transmit power.

)를 고정적으로 사용할 경우, 상술한 전력 전쟁이 발생되어, 일부의 무선 통신 기기(예컨대, 셀 경계에 위치하여 해당 부채널들의 상태가 상대적으로 열악한 무선 통신 기 기)가 요구 QoS를 달성할 수 없게 된다. 이러한 현상은, 특히, 1의 값을 가진 주파수 재사용율을 사용하는 셀룰러 통신 시스템에서 두드러지게 발생될 수 있다.On the other hand, the total transmit power to be distributed according to the water filling algorithm (eg,

), The above-mentioned power war occurs and some wireless communication devices (e.g., wireless communication devices located at the cell boundary and having relatively poor state of the corresponding subchannels) cannot achieve the required QoS. do. This phenomenon can occur particularly prominently in cellular communication systems using frequency reuse rates with a value of one.

In order to solve this problem, the method according to an embodiment is a PIWF (Penalized iterative Water-Filling) that can penalize a kind of penalty to a wireless communication device having a relatively favorable channel state among a plurality of wireless communication devices using the same subchannel ).

2 illustrates a method of allocating transmission power in a wireless communication device to perform communication.

The wireless communication device 300 having the structure illustrated in FIG. 3 includes a frame including a channel allocation period T ₁ and a plurality of unit communication periods T ₁ , T ₂ ,..., T _N as shown in FIG. 4. According to the structure of 400, one embodiment will be described on the premise of operating.

Referring to FIG. 3, the adjusting unit 312 adjusts the maximum allowable power based on a minimum required transmission rate, a previously achieved subchannel transmission rate, and a previously allocated subchannel transmission power, and the allocation unit 314. Allocates transmission power to each of the plurality of subchannels according to a water filling algorithm that restricts a total transmission power to be less than or equal to the adjusted maximum allowable power, and the communication unit 320 communicates using the allocated transmission power. Do this. The adjusting unit 312 and the allocating unit 314 may be implemented as one control unit 310 as shown in FIG. 3.

The operation of the above-described wireless communication device 300 will be described in more detail with reference to FIGS. 2 to 4 as follows.

In S210, during the channel allocation period T ₁ , the wireless communication device 300 is allocated a plurality of subchannels from the base station. For example, the communication unit 320 may receive channel allocation information from the base station during the channel allocation period T ₁ , and the control unit 310 may prepare for transmission power allocation according to the received channel allocation information. .

In S220, the wireless communication device 300 estimates SINRs for the allocated subchannels, and in S230, the allocator 314 determines that the total transmission power is set to a preset threshold (eg, maximum allowable based on the estimated result). According to a water filling algorithm with a limiting condition of less than power), the transmission power is allocated to each of the corresponding subchannels (the subchannels allocated in S210), and the communication unit 320 uses the allocated transmission power to determine the unit communication period ( T ₁ ) to communicate. Since the water filling in S230 is as described above with reference to Equations 1 to 3 and FIG. 1, a description thereof will be omitted.

In step S240, the controller 310 determines whether the repetition termination condition is satisfied.

In one embodiment, the repetition end condition is satisfied when the water filling according to S230 is performed twice. For example, when a repetition end condition of the repetition number 2 is set, the wireless communication device 300 also performs S220 and S230 for communication for the unit communication period T ₂ . That is, the wireless communication device 300 may maintain its performance (for example, the channel state is relatively good to maintain good performance with only the first two water fillings), or the channel ecology is relatively poor to satisfy the required QoS. Etc.), the wireless communication device 300 according to an embodiment uses the magnetic state prediction periods T ₁ and T ₂ . Penalty parameters to be described below may be calculated based on information obtained during the magnetic state prediction periods T ₁ and T ₂ .

 When the repetition termination condition is satisfied (S240), in S250, the controller 312 calculates the achievement rate penalty parameter and the deviation penalty parameter and adjusts the maximum allowable power based on the calculated result.

The achievement rate penalty parameter is a parameter for indicating the degree of selfishness according to the achieved rate, which is generally proportional to the rate previously achieved and generally inversely proportional to the minimum required rate, and in one embodiment, may be represented by Equation 4. have.

는 m번째 셀의 i번째 무선 통신 기기의 성취 전송률 페널티 파라미터이고,

는 m번째 셀의 i번째 무선 통신 기기의 최대 허용 전송률을 나타내며,

은 이전에 성취한 부채널별 전송률을 나타내며,

는 m번째 셀의 i번째 무선 통신 기기의 최소 요구 전송률을 나타낸다.In Equation 4,

Is the achieved transfer rate penalty parameter of the i th wireless communication device of the m th cell,

Represents the maximum allowable transmission rate of the i th wireless communication device of the m th cell,

Indicates the bit rate for each subchannel that was previously achieved.

Denotes a minimum required data rate of the i-th wireless communication device of the m-th cell.

과 이전에 할당한 부채널별 송신 전력

간의 비율에 대한 편차에 대체로 비례하며, 일실시예에 있어서, 수학식 5로 표현될 수 있다.The deviation penalty parameter is the bit rate for each subchannel that was previously achieved.

And previously allocated subchannel transmit power

It is generally proportional to the deviation with respect to the ratio of, and in one embodiment, may be represented by Equation 5.

는 m번째 셀의 i번째 무선 통신 기기의 편차 전송률 페널티 파라미터이고,

는 k번째 부반송파에 대한 m번째 셀의 i번째 무선 통신 기기의 품질 변수를 나타내며,

는 m번째 셀의 i번째 무선 통신 기기의 품질 변수의 평균을 나타내며,

는 부반송파 집합

의 원소 개수를 나타낸다.In Equation 5,

Is the deviation rate penalty parameter of the i th wireless communication device of the m th cell,

Denotes a quality variable of the i th wireless communication device of the m th cell for the k th subcarrier,

Represents the average of the quality variables of the i th wireless communication device of the m th cell,

Subcarrier set

It represents the number of elements of.

In one embodiment, the maximum allowable power may be adjusted by multiplying a predetermined maximum allowable power by a value that is generally inversely proportional to the achieved transfer rate penalty parameter and the deviation penalty parameter, and this adjusting method may be represented by Equation 6.

는 페널티 함수

와 S230의 워터 필링에 사용된 최대 허용 전력

을 곱하여 얻어지는 새로운 최대 허용 전력(즉, 조절된 최대 허용 전력)을 나타내며, S270의 워터 필링에 사용된다. 수학식 6에서

는 min[max(x,a),b]의 연산을 나타내며,

는

가 최소한 가져야 하는 값이며, 설계 파라미터로서 미리 설정될 수 있다.In Equation 6,

Penalty function

Permissible power used for water filling

Denotes the new maximum allowable power (ie, the adjusted maximum allowable power) obtained by multiplying and used for water filling of S270. In equation (6)

Represents the operation of min [max (x, a), b],

Is

Is a minimum value and may be preset as a design parameter.

S250 may be performed between the communication units or performed during the period (T _3), a communication unit time period (T ₂₎ and a communication unit time period (T _3). In the former case, the communication according to S270 may be started from the unit communication period T ₄ , and in the latter case, the communication according to S270 may be started from the unit communication period T ₃ . Hereinafter, it will be described on the premise of the former case.

In S260, the controller 310 estimates SINRs for the allocated subchannels, and in S270, the allocation unit 314 sets the total transmission power to be less than or equal to the adjusted threshold based on the estimated result. Transmission power is allocated to each of the plurality of subchannels according to the water filling algorithm, and the communication unit 320 performs communication during the unit communication period T ₄ using the allocated transmission power.

In S280, the controller 310 determines whether the repetition termination condition is satisfied.

In one embodiment, an example of the repetition termination condition may be a case where a preset number of repetitions is performed when the transmission rate and / or transmission power are sufficiently converged. Since there are various methods used in the already known IWF algorithm for determining whether to converge, the following description is omitted.

When the repetition end condition is satisfied (S280), in S290, the communication unit 320 performs communication using the transmission power determined last (that is, the transmission power allocated through the last S270) during the subsequent period. For example, the unit of communication time period (T ₁₀₎ when the water filling the rate is converged, the communication unit 320 at S290 is the remaining unit communication period from (T _10, T _11, ..., T _N) is used to end the determined transmission power To communicate.

The present invention can also be embodied as computer-readable codes on a computer-readable recording medium. Computer-readable recording media include all kinds of recording devices that store data that can be read by a computer system. Examples of the computer-readable recording medium include a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, and the like, and may be implemented in the form of a carrier wave (for example, transmission via the Internet) . The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. In addition, functional programs, codes, and code segments for implementing the present invention can be easily inferred by programmers in the art to which the present invention belongs.

The inventors of the present invention have been described with reference to the embodiments shown in the drawings for clarity, but this is merely exemplary, and those skilled in the art may various modifications and other equivalent embodiments therefrom. Will understand. Therefore, the true technical protection scope of the present invention will be defined by the appended claims.

Embodiments of the present invention presented above may have an effect including the following advantages. However, all the embodiments of the present invention are not meant to include them all, and thus the scope of the present invention should not be understood as being limited thereto.

According to an embodiment, it is possible to provide a multi-channel communication system capable of increasing the achievement rate compared to the number and power consumption of wireless communication devices that satisfy a required QoS. According to one embodiment, a problem of power warfare caused by applying a water filling algorithm to a multi-cell environment that derives maximum performance in a single cell (e.g., unevenly allocated transmit power to multiple wireless communication devices due to inter-cell interference) Problems can be solved. According to one embodiment, the inter-cell interference can be effectively controlled without incurring additional overhead in the network, thereby increasing the number of wireless communication devices that satisfy the required QoS on the entire network.

FIG. 1 is a diagram for conceptually explaining a method of allocating transmission power according to a water filling algorithm.

2 illustrates a method of allocating transmission power in a wireless communication device to perform communication.

3 is a block diagram illustrating a configuration of a wireless communication device according to an exemplary embodiment.

4 is a frame structure according to an embodiment.

Claims (11)

A method of allocating transmit power to a plurality of subchannels in a wireless communication device, the method comprising: (a) performing communication by allocating transmission power to each of the plurality of subchannels according to a water filling algorithm having a limit condition that a total transmission power is less than or equal to a preset threshold; (b) adjusting the threshold based on a minimum required transmission rate, a previously achieved subchannel-specific transmission rate, and a previously allocated subchannel transmission power; And (c) allocating transmission power to each of the plurality of subchannels according to a water filling algorithm, which limits the total transmission power to be less than or equal to the adjusted threshold to perform communication. According to claim 1, wherein step (b), (b1) calculating a first parameter that is proportional to the rate previously achieved and inversely proportional to the minimum required rate; (b2) calculating a second parameter proportional to a deviation of a ratio between the previously achieved subchannel transmission rate and the previously allocated subchannel transmission power; And (b3) multiplying the predetermined threshold by a value inversely proportional to the calculated first and second parameters to obtain the adjusted threshold. The method of claim 1, wherein step (c) comprises: (c1) allocating transmit power to each of the plurality of subchannels according to a water filling algorithm with a condition that a total transmit power is less than or equal to the adjusted threshold; And (c2) performing communication using the allocated transmit power. The method of claim 1, wherein step (a) Characterized in that it is performed repeatedly. The method of claim 4, wherein step (a) Characterized in that it is repeated twice. The method of claim 1, Step (c) is repeated; and (d) performing communication according to the result of the repeated transmission power allocation in step (c). The method of claim 1, Step (c) is repeated until the previously achieved transmission rate converges, and (d) performing communication according to the result of the repeated transmission power allocation in step (c). The method of claim 1, The wireless communication device comprises a mobile station belonging to a cellular communication system, And the plurality of subchannels includes a plurality of subcarriers allocated from a base station belonging to the cellular communication system. The system of claim 8, wherein the cellular communication system is Using a frequency reuse with a value of one. In a wireless communication device using a plurality of subchannels, An adjusting unit for adjusting a maximum allowable power based on a minimum required transmission rate, a previously achieved subchannel transmission rate, and a previously allocated subchannel transmission power; An allocating unit for allocating transmission power to each of the plurality of subchannels according to a water filling algorithm with a condition that a total transmission power is less than or equal to the adjusted maximum allowable power; And And a communication unit for performing communication using the allocated transmission power. A computer-readable recording medium containing a program for implementing the method of claim 1 on a computer.

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