KR20220074706A - Method and appratus for transmission control of access node in communication system - Google Patents

Abstract

A transmission control technique of an access node in a communication system is disclosed. A method of operating a central processing unit of a communication system, comprising: classifying access nodes into activated access nodes and inactive access nodes based on the number of connected terminals by identifying connection states of access nodes with terminals; distributing terminals connected to each of the inactive access nodes to other activated access nodes; deactivating the inactive access nodes; and adjusting the maximum transmit power of the activated access nodes. A method of operating a central processing unit may be provided.

Description

Transmission control method and apparatus of an access node in a communication system

The present invention relates to a transmission control technology of an access node in a communication system, and more particularly, a transmission control technology of an access node in a communication system that selects an access node to be activated in an ultra-high-density network and adjusts the power of the selected access node is about

In order to accommodate the increasing mobile traffic, recent communication technologies use high-frequency (eg, millimeter wave, terahertz) bands that can secure a wider bandwidth, use more antennas to increase frequency efficiency, and use high-density base stations. placement may be considered. Here, there may be an ultra-dense network (UDN) as a deployment technology of a high-density base station. In such an ultra-dense network, the distance between base stations may be reduced. Accordingly, in the ultra-dense network, the received signal strength of the terminal may increase due to a decrease in the distance between the terminal and the adjacent base station. However, in the ultra-dense network, inter-cell interference may also increase due to a decrease in the distance between the terminal and the adjacent base station.

In such an ultra-high-density network, access nodes (ANs) and terminals distributed in a coverage area are simultaneously serviced by the control of a central processing unit (CP) for adaptive interference control and cooperative communication support. The system can be configured in the form of distributed massive multiple-input and multiple-output (MIMO). In such a distributed large-scale multiple input/output system, a cell-free massive MIMO (CFmMIMO) system may be in a form in which access nodes are distributed, and distributed access nodes are installed in the front. It can be synchronized through a fronthaul/backhaul link to provide services to all terminals through the same resource Frequency efficiency of such a CFmMIMO system can increase as the number of access nodes participating in cooperative transmission increases However, power consumption may increase accordingly, so that the CFmMIMO system restricts some access nodes to cooperative transmission to the UE to improve energy efficiency.

An object of the present invention to solve the above problems is to provide a method and apparatus for controlling transmission of an access node in a communication system that selects an access node to be activated in an ultra-high density network and adjusts the power of the selected access node. .

In order to achieve the above object, a transmission control method of an access node in a communication system according to a first embodiment of the present invention for achieving the above object is a method of operating a central processing unit of a communication system. classifying into activated access nodes and inactive access nodes based on the number of distributing terminals connected to each of the inactive access nodes to other activated access nodes; deactivating the inactive access nodes; and adjusting the maximum transmit power of the activated access nodes.

In the ultra-dense network, the central processing unit may inactivate the corresponding access node by distributing terminals providing communication services to the access node to other access nodes.

In addition, the central processing unit may satisfy the quality requirement of the terminal by changing the maximum transmit power by adjusting the maximum transmit power constraint when selecting access nodes to distribute the terminals.

In addition, the central processing unit can improve energy efficiency by deactivating the access nodes to lower the overall power consumption of the network.

1 is a conceptual diagram for explaining a first embodiment of a cell-free large-scale antenna system (CFmMIMO).
2 is a block diagram illustrating a first embodiment of a communication node;
3 is a flow diagram illustrating a first embodiment of a method for optimizing an active access node;
4 is a conceptual diagram illustrating a first embodiment of a method for controlling transmission of an access node in a communication system.
5 is a flowchart illustrating a first embodiment of a method for controlling transmission of an access node in a communication system.
6 is a flowchart illustrating a first embodiment of a process for selecting inactive candidate access nodes of FIG. 5 .
7 is a flowchart illustrating a first embodiment of a process of distributing terminals to active access nodes in FIG. 5 .

Since the present invention can have various changes and can have various embodiments, specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the present invention to specific embodiments, and it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention.

Terms such as first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component. and/or includes a combination of a plurality of related listed items or any of a plurality of related listed items.

When a component is referred to as being “connected” or “connected” to another component, it may be directly connected or connected to the other component, but it is understood that other components may exist in between. it should be On the other hand, when it is said that a certain element is "directly connected" or "directly connected" to another element, it should be understood that the other element does not exist in the middle.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present application, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning in the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present application. does not

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings. In describing the present invention, in order to facilitate the overall understanding, the same reference numerals are used for the same components in the drawings, and duplicate descriptions of the same components are omitted.

1 is a conceptual diagram for explaining a first embodiment of a cell-free large-scale antenna system (CFmMIMO)

Referring to FIG. 1 , in the cell-free large-scale antenna system, large-scale distributedly arranged large-scale access nodes 110 are connected to one central processing unit (CP) 100 and are much more than access nodes (ANs) 110 . A communication service may be provided to a small number of all terminals 120 through the same time/frequency resource. The central processing unit 100 may be connected to the distributed access nodes 110 through a fronthaul (FH) 130 . In this case, the cell-leaving large-scale antenna system may have K terminals 120 and M access nodes 110 . The density of the access nodes 110 may be similar to that of the terminals 120 , or a high-density environment higher than the density of the terminals 120 may be considered (M?K). Each of the distributed access nodes 110 may use a large-scale array antenna. However, each of the distributed access nodes 110 may use radio frequency (RF) chains smaller than the number of antenna elements of the array antenna for cost-effective implementation. The terminals 120 may simultaneously receive a communication service through cooperative communication of a plurality of access nodes 120 . Here, the central processing unit 100 , the access nodes 110 , and the terminals 120 may be communication nodes. Each of the communication nodes may have the following structure.

2 is a block diagram illustrating a first embodiment of a communication node;

Referring to FIG. 2 , the communication node 200 may include at least one processor 210 , a memory 220 , and a transceiver 230 connected to a network to perform communication. In addition, the communication node 200 may further include an input interface device 240 , an output interface device 250 , a storage device 260 , and the like. Each of the components included in the communication node 200 may be connected by a bus 270 to communicate with each other. However, each of the components included in the communication node 200 may not be connected to the common bus 270 but to the processor 210 through an individual interface or an individual bus. For example, the processor 210 may be connected to at least one of the memory 220 , the transceiver 230 , the input interface device 240 , the output interface device 250 , and the storage device 260 through a dedicated interface. .

The processor 210 may execute a program command stored in at least one of the memory 220 and the storage device 260 . The processor 210 may mean a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which methods according to embodiments of the present invention are performed. Each of the memory 220 and the storage device 260 may be configured as at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 220 may be configured as at least one of a read only memory (ROM) and a random access memory (RAM).

Referring back to FIG. 1 , the CFmMIMO system may use cooperative transmission between the access nodes 110 in order to efficiently manage interference and provide a more uniform service to each of the terminals 120 . In addition, the CFmMIMO system may use power allocation for each terminal and power control for each terminal in order to efficiently manage interference and provide a more uniform service to each of the terminals 120 . The CFmMIMO system may require a fronthaul/backhaul link capable of providing a low delay and high capacity in order to support cooperative transmission between the access nodes 110 . In order to alleviate the requirements for such a fronthaul/backhaul link, the CFmMIMO system may consider a method of limiting service provision to individual terminals 120 to some access nodes 110 . As such, the CFmMIMO system can select the access nodes 110 participating in cooperative transmission based on distance (within a certain distance from the terminal) during cooperative transmission by limiting the number of access nodes 110 . In addition, the CFmMIMO system may consider a method of establishing an association (AN-UE association) between the selected access nodes 110 and the terminals 120 . In contrast, the CFmMIMO system is limited to some of the access nodes 110 and the access nodes 110 participating in cooperative transmission based on large-scale channel gain information of the access node and the terminal during cooperative transmission. can be selected. In addition, the CFmMIMO system may consider a method of establishing a connection between the selected access nodes 110 and the terminals 120 .

Most of the existing power allocation/control methods for such a CFmMIMO system may equally allocate transmit power or receive power of all terminals 120 to reduce complexity. In contrast, existing power allocation/control methods may allocate transmission power so that the channel capacity determined by the average channel condition is maximized. Also, most existing methods may assume that all access nodes 110 in the CFmMIMO system participate in cooperative transmission of terminals 120 .

Meanwhile, energy efficiency (EE) of a radio access network system may be determined by spectral efficiency (SE) and network power consumption. Frequency efficiency of the CFmMIMO system may increase as the number of access nodes 110 participating in cooperative transmission increases. However, power consumption of the CFmMIMO system may increase accordingly. In addition, the CFmMIMO system may simultaneously provide a service to all terminals 120 through all access nodes 110 connected to the central processing unit 100 . In this case, the transmission of some of the access nodes 110 of the CFmMIMO system may contribute to an increase in a data rate, thereby contributing to an increase in frequency efficiency. Accordingly, the CFmMIMO system may consider a scheme for cooperative transmission between the access nodes 110 by limiting to some access nodes 110 in order to alleviate the requirements for the fronthaul/backhaul link in order to improve energy efficiency. That is, the CFmMIMO system may consider an access node selection procedure for cooperative transmission by allocating some access nodes 110 , which have a high contribution to an actual increase in the transmission rate, to the terminals 120 , in terms of energy efficiency. Accordingly, a method of selecting the access nodes 110 participating in cooperative transmission in the CFmMIMO system may require consideration of fronthaul/backhaul restrictions. In addition, the method of selecting the access nodes 110 participating in the cooperative transmission in the CFmMIMO system may include a method of selecting the access nodes 110 to be deactivated to maximize energy efficiency. In addition, the method of selecting the access nodes 110 participating in the cooperative transmission in the CFmMIMO system may include an appropriate method of selecting the access nodes to be activated. These methods may usually correspond to NP-hard problems, and methods for finding a sub-optimal solution in consideration of a trade-off between complexity and performance may be mainly presented.

3 is a flow diagram illustrating a first embodiment of a method for optimizing an active access node;

을

으로 초기화할 수 있다(S300). 이후에 중앙 처리 장치는 이전 단계(i-1,i=1,2…) 활성 액세스 노드 집합

에서 활성화되는 액세스 노드들을 순차적으로 선택하여 에너지 효율

을 계산할 수 있다(S301). 중앙 처리 장치는 활성 액세스 노드 집합을 새롭게 조정하여 현 단계(i) 활성 액세스 노드 집합

를 설정할 수 있다(S302). 그리고, 중앙 처리 장치는 새롭게 설정된 현 단계 활성 액세스 노드 집합에서 순차적으로 액세스 노드들을 선택하여 에너지 효율

을 계산할 수 있다(S303). 중앙 처리 장치는 새로 계산한 현 단계 에너지 효율과 이전 단계의 에너지의 효율을 비교하여(S304), 새로 계산한 현 단계 에너지 효율이 이전 단계의 에너지 효율보다 크면 에너지 효율이 개선된 것으로 판단하여 현 단계 활성 액세스 노드 집합을 대상으로 단계 S301부터 반복할 수 있다. 이와 달리, 중앙 처리 장치는 새로 계산한 에너지 효율이 이전 단계의 에너지 효율보다 크지 않으면 에너지 효율이 개선되지 않은 것으로 판단하여 이전 단계의 활성 액세스 노드 집합을 최적 활성 액세스 노드 집합으로 결정할 수 있다(S305).Referring to FIG. 3 , in the method of optimizing an active access node, a central processing unit sets an active access node

second

can be initialized to (S300). Afterwards, the central processing unit sets the active access node in the previous step (i-1,i=1,2…)

Energy efficiency by sequentially selecting the access nodes activated in

can be calculated (S301). The central processing unit newly adjusts the set of active access nodes, so that the current step (i) set of active access nodes

can be set (S302). Then, the central processing unit sequentially selects the access nodes from the newly set current stage active access node set to achieve energy efficiency.

can be calculated (S303). The central processing unit compares the newly calculated current stage energy efficiency with the energy efficiency of the previous stage (S304), and if the newly calculated current stage energy efficiency is greater than the energy efficiency of the previous stage, it is determined that the energy efficiency is improved, It can be repeated from step S301 for the active access node set. On the other hand, if the newly calculated energy efficiency is not greater than the energy efficiency of the previous step, the central processing unit determines that the energy efficiency is not improved, and determines the active access node set of the previous step as the optimal active access node set ( S305 ) .

As described above with reference to FIG. 3 , the previously proposed methods may consist of selecting the number of activated access nodes and optimizing the activated access nodes. Existing methods may repeatedly compare energy efficiency according to selection of activated access nodes for optimal energy efficiency. In addition, existing methods may consider quality of service (QoS) requirements of terminals and maximum transmission power restrictions of access nodes in order to guarantee uniform performance of terminals when selecting access nodes. As a result, the existing methods can select active access nodes capable of obtaining optimal energy efficiency and optimize the number of active access nodes. However, the existing methods may exclude a specific access node from deactivation target according to the maximum transmission power constraint of the access nodes and the service quality requirement of the terminals, thereby limiting further improvement in energy efficiency. Such a case may occur when the corresponding access node cannot be deactivated when there is only one connectable access node of a specific terminal in the maximum transmit power constraint of a given access node.

In order to solve such a problem, the CFmMIMO system may require a method of controlling the transmission mode of the access nodes to improve energy efficiency by improving frequency efficiency and lowering overall network power consumption by access nodes in an ultra-dense base station environment. That is, the CFmMIMO system may need a method of additionally selecting access nodes to be deactivated from active access nodes to perform cooperative communication. Specifically, the CFmMIMO system may adjust the maximum transmit power constraints of the access nodes to additionally select access nodes to be deactivated so that energy efficiency is improved while satisfying the service quality constraints of the terminals. As a result, the CFmMIMO system may further change the transmission mode of some activated access nodes by adjusting the maximum transmission power constraint of the access nodes to improve the energy efficiency while satisfying the service quality of the terminals.

4 is a conceptual diagram illustrating a first embodiment of a method for controlling transmission of an access node in a communication system.

은 각각의 액세스 노드의 소모 전력

의 합, 각각의 액세스 노드별 프론트홀의 소모 전력

의 합 및 중앙 처리 장치의 소모 전력

으로 구분할 수 있다.Referring to FIG. 4 , in the method for controlling transmission of the access node, the third access node AN3 may provide a communication service to the third terminal UE3. At this time, if the third access node AN3 can find another access node capable of providing the communication service to the third terminal UE3 because the only terminal providing the communication service is the third terminal UE3, the third access By deactivating the node AN3, power consumption may be reduced. In this case, the central processing unit may select the first access node AN1 from among the first access node AN1 , the second access node AN2 , and the fourth access node AN4 . In addition, the central processing unit may increase the maximum transmission power of the first access node AN1 , and accordingly, the first access node AN1 may provide a communication service to the third terminal UE3 . Accordingly, the central processing unit may change the connection between the third access node AN3 and the third terminal UE3 to the connection between the first access node AN1 and the third terminal UE3. In this case, the central processing unit may limit the degree of increase in the maximum transmission power of the first access node AN1 within a range in which overall network power consumption does not increase. To this end, the central processing unit may consider a network power consumption model as in Equation (1). Total network power consumption in the network power consumption model considered by the central processing unit

is the power consumption of each access node

sum of , the power consumption of the fronthaul for each access node

Sum of and power consumption of central processing unit

can be distinguished as

과 각각의 액세스 노드의 활성 소모 전력

으로 구성될 수 있다. And, the power consumption of each access node is fixed power consumption of each access node as shown in Equation 2 below

and active power consumption of each access node

can be composed of

과 무선 전송 시에 소비되는 전력량인 각각의 액세스 노드의 전송 소모 전력

으로 구성될 수 있다. Here, the fixed power consumption of each access node may mean an amount of power that is fixedly consumed regardless of whether each access node is activated. In addition, the active power consumption of each access node may be an amount of power consumed in an activated state of each access node. The active power consumption of each access node is the amount of power consumed in related circuits such as an RF chain and an amplifier as shown in Equation 3, and the circuit consumption power of each access node is

and transmission power consumption of each access node, which is the amount of power consumed during wireless transmission.

can be composed of

의 합일 수 있다.In this case, the transmission power consumption of each access node is the transmission consumption power for each terminal of each access node consumed when each access node provides a communication service to each terminal as shown in Equation 4 below.

can be the sum of

과 트래픽과 관련된 소비 전력인 각각의 액세스 노드별 프론트홀의 트래픽 소모 전력

의 합으로 구성될 수 있다.On the other hand, the power consumption of the fronthaul for each access node is the fixed power consumption of the fronthaul for each access node, which is fixed power consumption regardless of traffic.

Traffic consumption power of the fronthaul for each access node, which is the power consumption related to traffic

It can be composed of the sum of

은 다음 수학식 6과 같이 각각의 액세스 노드별 프론트홀의 트래픽 기본 단위당 소모 전력

에 단말별 트래픽량

의 합을 곱한 전력량일 수 있다.Here, the traffic consumption power of the fronthaul for each access node

is the power consumption per basic traffic unit of the fronthaul for each access node as shown in Equation 6 below.

traffic volume per terminal

It may be the amount of power multiplied by the sum of .

로 정의할 수 있다. 이와 같은 활성 액세스 노드 집합에 포함되는 액세스 노드들에 의한 네트워크 소모 전력을 활성 네트워크 소모 전력

으로 정의할 수 있다. 이와 같은 활성 네트워크 소모 전력

은 다음 수학식 7과 같이 표현할 수 있다. 여기서, 활성 액세스 노드 집합

는

과 같이 전체 액세스 노드 집합

의 부분 집합일 수 있다. 활성 액세스 노드 집합의 수는

일 수 있다. 전체 액세스 노드 집합의 수는

일 수 있다.In a CFmMIMO system, the central processing unit may select only some access nodes to be active to maximize energy efficiency. At this time, the set consisting of the access nodes selected by the central processing unit is set as the active access node set.

can be defined as Network consumption power by the access nodes included in such an active access node set is the active network power consumption.

can be defined as This active network consumes power

can be expressed as in Equation 7 below. where the set of active access nodes

Is

Full access node set as

may be a subset of The number of active access node sets is

can be The total number of access node sets is

can be

가 아래 수학식 8과 같이 단말별 트래픽 최소 요구

보다 크거나 같을 수 있는 조건을 가정할 수 있다. 또한, 중앙 처리 장치는 각각의 액세스 노드의 단말별 전송 소모 전력

의 합이 아래 수학식 9와 같이 허용 최대 전송 전력

보다 작거나 같을 수 있는 조건을 가정할 수 있다. 그리고, 중앙 처리 장치는 전체 단말 트래픽량

을 활성 네트워크 소모 전력으로 나누는 것으로 정의되는 에너지 효율을 최대로 하기 위해 수학식 8과 수학식 9를 만족하는 수학식 10의 최적화 문제를 풀어 최적 액세스 노드 집합

을 구할 수 있다. 또한, 중앙 처리 장치는 최적 액세스 노드 집합에 포함되는 최적 액세스 노드들의 각각의 단말별 전송 소모 전력인 각각의 최적 액세스 노드의 단말별 소모 전력

를 구할 수 있다. 여기서, 수학식 8은 단말의 트래픽 요구 사항이라고 할 수 있고, 수학식 9는 각각의 액세스 노드의 최대 전송 전력 제약 사항이라고 할 수 있다. In the CFmMIMO system, the central processing unit determines the amount of traffic per terminal.

is the minimum traffic requirement for each terminal as shown in Equation 8 below

Conditions that can be greater than or equal to can be assumed. In addition, the central processing unit transmits power consumption for each terminal of each access node.

The sum of the allowable maximum transmit power as in Equation 9 below

Conditions that can be less than or equal to can be assumed. And, the central processing unit is the total amount of terminal traffic

In order to maximize energy efficiency, which is defined by dividing

can be obtained In addition, the central processing unit transmits power consumption for each terminal of each of the optimal access nodes included in the set of optimal access nodes, the power consumption for each terminal of each optimal access node.

can be obtained Here, Equation 8 may be referred to as a traffic requirement of the terminal, and Equation 9 may be referred to as a maximum transmission power constraint of each access node.

s.t. [Equation 8], [Equation 9]

Meanwhile, the central processing unit may allow other access nodes to provide communication services to the corresponding terminals when there are few terminals to which some access nodes provide communication services. And, the central processing unit may deactivate the corresponding access nodes. As such, when some access nodes are additionally deactivated, a set consisting of the remaining activated access nodes may be defined as a coordinating access node set. In this case, the maximum transmit power allowed for the coordinating access nodes may be defined as the coordinating maximum transmit power. In this case, since there is no change in the terminal receiving the communication service, the central processing unit may maintain the traffic requirement of the terminal in Equation (8). However, the central processing unit may change the maximum transmit power constraint of the access nodes as in Equations 9 to 11 because there is a change in activated access nodes that provide communication services. That is, the central processing unit may obtain a solution satisfying Equation 12 by re-solving the optimization problem for maximizing energy efficiency satisfying the conditions of Equation 8 and the changed Equation 11.

s.t. [Equation 8], [Equation 11]

는 조정 액세스 노드 집합일 수 있다. 그리고,

는 조정 액세스 노드 집합에게 허용되는 조정 최대 전송 전력일 수 있다. 이러한 변경을 이해하기 위해 도 4를 참조하면, 도 4의 왼쪽의 도면은 수학식 10에 의해 얻어진 결과일 수 있고, 오른쪽의 도면은 수학식 12에 의해 얻어진 결과일 수 있다. 수학식 10에 의하면, 활성 액세스 노드 집합

는

={1,2,3,4}일 수 있다. 이와 달리, 수학식 12에 의하면, 조정 활성 액세스 노드 집합

은

={1,2,4}일 수 있다. 도 4에서 점선에서 실선으로의 변경은 최대 전송 전력이 허용 최대 전송 전력에서 조정 최대 전송 전력으로 변경으로 인해 서비스 영역이 넓어지는 것을 나타낼 수 있다. 한편, 이처럼 중앙 처리 장치가 수학식 11로 변경된 조건에서 수학식 12를 사용하여 조정 액세스 노드 집합을 구하는 과정은 도 5와 같을 수 있다.here,

may be a coordinating access node set. and,

may be the coordinated maximum transmit power allowed for the coordinating access node set. Referring to FIG. 4 to understand this change, the figure on the left of FIG. 4 may be a result obtained by Equation 10, and the figure on the right may be a result obtained by Equation 12. FIG. According to Equation 10, the set of active access nodes

Is

={1,2,3,4}. On the other hand, according to Equation (12), the coordinating active access node set

silver

={1,2,4}. The change from the dotted line to the solid line in FIG. 4 may indicate that the service area is widened due to the change in the maximum transmit power from the allowable maximum transmit power to the adjusted maximum transmit power. On the other hand, the process of obtaining the coordinating access node set by using Equation 12 under the condition that the central processing unit is changed to Equation 11 may be as shown in FIG. 5 .

5 is a flowchart illustrating a first embodiment of a method for controlling transmission of an access node in a communication system.

Referring to FIG. 5 , in the method for controlling transmission of an access node, the central processing unit may select deactivable candidate access nodes that can be additionally deactivated ( S510 ). The central processing unit may select deactivation candidate access nodes that can be deactivated based on the number of terminals connected to the access nodes as a reference condition.

6 is a flowchart illustrating a first embodiment of a process for selecting inactive candidate access nodes of FIG. 5 .

를 정의할 수 있다(S511). 이때, 중앙 처리 장치는 비활성화 후보 액세스 노드 집합

의 초기값을

=0으로 설정할 수 있고, 이후 과정을 통하여 업데이트할 수 있다. 이후에, 중앙 처리 장치는 각각의 액세스 노드에 대하여 연결된 단말 수를 파악할 수 있다(S512). 이때, 중앙 처리 장치는 K개의 단말들과 M개의 액세스 노드들의 연결 정보를 이미 알고 있을 수 있다. 중앙 처리 장치는 K개의 단말들과 M개의 액세스 노드들의 연결 정보를 행렬 형태로 저장하고 있을 수 있으며, 일예로 연결 정보 행렬

로 저장하고 있을 수 있다. 이러한 연결 정보 행렬에서

가 0이면 m번째 액세스 노드와 k번째 단말이 연결되어 있지 않을 수 있고,

가 1이면 m번째 액세스 노드와 k번째 단말이 연결되어 있을 수 있다. 중앙 처리 장치는 단말들의 서비스 품질 요구 사항과 액세스 노드들의 최대 전송 전력 제약 사항 (

)에서 에너지 효율 최대화에 의해 얻은 해(

)에 의해

를 형성할 수 있다. 이때, 중앙 처리 장치는 m번째 액세스 노드의 k번째 단말에 대한 전송 소모 전력

가 0보다 크면 m번째 액세스 노드와 k번째 단말이 연결되어 있어

을 1로 설정할 수 있다. 그리고, 중앙 처리 장치는 각 액세스 노드에 연결된 단말들로 이루어진 집합인 연결 단말 집합

을

와 같이 형성할 수 있다. 이에 따라, 활성 액세스 노드 집합은 연결 단말 집합의 단말 수

가 1보다 같거나 큰 액세스 노드들의 집합

일 수 있다. 이와 관련되어 도 4를 참조하면, 왼쪽 그림에서

는

일 수 있다. 그리고, 각 액세스 노드와 연결되어 있는 연결 단말 집합은

={1,2}.

={1,2},

={3},

={1,2}일 수 있다, 연결 단말 집합의 수는

=2,

=2,

=1,

=2일 수 있고,

={1,2,3,4}일 수 있다.Referring to FIG. 6 , in the process of selecting deactivation candidate access nodes, the central processing unit sets a set of deactivation candidate access nodes.

can be defined (S511). At this time, the central processing unit sets the deactivation candidate access node

the initial value of

It can be set to =0, and can be updated through a subsequent process. Thereafter, the central processing unit may determine the number of terminals connected to each access node (S512). In this case, the central processing unit may already know the connection information of the K terminals and the M access nodes. The central processing unit may store connection information of K terminals and M access nodes in the form of a matrix, for example, the connection information matrix

may be stored as In this connection information matrix

If is 0, the m-th access node and the k-th terminal may not be connected,

If is 1, the m-th access node and the k-th terminal may be connected. The central processing unit determines the service quality requirements of the terminals and the maximum transmit power constraints of the access nodes (

) from the solution obtained by maximizing energy efficiency (

) by

can form. At this time, the central processing unit transmits power consumption for the k-th terminal of the m-th access node.

is greater than 0, the m-th access node and the k-th terminal are connected

can be set to 1. And, the central processing unit is a set of connected terminals, which is a set consisting of terminals connected to each access node.

second

can be formed as Accordingly, the set of active access nodes is the number of terminals in the set of connected terminals.

A set of access nodes where is greater than or equal to 1

can be Referring to FIG. 4 in this regard, in the figure on the left

Is

can be And, the set of connection terminals connected to each access node is

={1,2}.

={1,2},

={3},

= {1,2}, the number of connected terminal sets is

=2,

=2,

=1,

=2,

={1,2,3,4}.

가 제1 임계치

이하인(즉,

) 액세스 노드들로 비활성 후보 액세스 노드 집합을 구성하여 비활성 후보 액세스 노드 집합을 업데이트할 수 있다(S513).Again, referring to FIG. 6 , the central processing unit determines the number of terminals in the connected terminal set identified for each access node.

is the first threshold

less than (i.e.,

) by configuring the inactive candidate access node set with the access nodes, the inactive candidate access node set may be updated (S513).

Referring again to FIG. 5 , the central processing unit may distribute the terminals in which the deactivation candidate access nodes are providing communication services to other active access nodes ( S520 ). A process in which the central processing unit distributes terminals to other active access nodes may be the same as in FIG. 7 .

7 is a flowchart illustrating a first embodiment of a process of distributing terminals to different active access nodes in FIG. 5 .

를 선택할 수 있다(S521). 여기서,

는

일 수 있다. 이때, 비활성화 후보 액세스 노드

가 통신 서비스를 제공하는 단말은

라고 표시할 수 있고,

일 수 있다. 이에 따라, 중앙 처리 장치는 비활성화 후보 액세스 노드

의 연결 단말 집합

에서 어느 하나의 단말

을 선택하여(S522) 다른 활성화 액세스 노드들에 연결할 수 있는지를 판단할 수 있다(S523). 이처럼, 중앙 처리 장치는 단말

을 다른 활성화 액세스 노드들에 연결할 수 있으면, 연결할 수 있는 후보 활성화 액세스 노드들

에서 최종 액세스 노드

를 선정할 수 있다(S524). 일예로, 중앙 처리 장치는 수학식 13과 같은 제2 임계치와 관련된 조건을 만족하는 후보 활성화 액세스 노드들에서 수학식 14와 같이 단말

와 가장 좋은 채널 상태

를 가지는 액세스 노드를 최종 액세스 노드로 선정할 수 있다. 여기서, ε은 임의의 실수일 수 있다.Referring to FIG. 7 , in the process of distributing terminals to other active access nodes, the central processing unit performs a deactivation candidate access node with the smallest number of connections with a terminal in a set of deactivation candidate access nodes.

can be selected (S521). here,

Is

can be At this time, the deactivation candidate access node

The terminal that provides the communication service is

can be indicated as

can be Accordingly, the central processing unit is a deactivation candidate access node

a set of connected terminals of

any one terminal in

By selecting (S522), it is possible to determine whether it is possible to connect to other active access nodes (S523). In this way, the central processing unit is

can connect to other active access nodes, then the connectable candidate active access nodes

last access node in

can be selected (S524). As an example, the central processing unit is a terminal as in Equation 14 in the candidate activated access nodes that satisfy the condition related to the second threshold as in Equation 13.

with the best channel conditions

An access node having ? may be selected as the final access node. Here, ε may be any real number.

를 다른 활성화 액세스 노드들에 연결할 수 있으면, 연결 단말 집합

에서 단말

을 제외할 수 있다(S525). 그리고, 중앙 처리 장치는 비활성화 후보 액세스 노드

의 연결 단말 집합의 수를 파악할 수 있다(S526). 이후에, 중앙 처리 장치는 파악된 연결 단말 집합의 수가 0인지를 판단하여(S527), 0이 아니면 단계 S522부터 반복하여 연결 단말 집합에 포함되는 모든 단말에 대하여 다른 활성화 단말 노드에 분배할 수 있는지 확인한다. 이와 달리, 중앙 처리 장치는 연결 단말 집합의 수가 0이면 비활성 후보 액세스 노드 집합에서 해당 비활성 후보 액세스 노드를 제외할 수 있다(S528). 이후에, 중앙 처리 장치는 비활성 후보 액세스 노드 집합의 수를 파악하여(S529), 파악된 비활성 후보 액세스 노드 집합의 수가 0인지를 판단하여(S530), 0이 아니면 S521부터 반복 수행할 수 있고, 0이면 종료할 수 있다. And, the central processing unit determines the result of the terminal

If it can connect to other active access nodes, the set of connected terminals

terminal in

can be excluded (S525). And, the central processing unit is a deactivation candidate access node

It is possible to determine the number of connected terminal sets of (S526). Thereafter, the central processing unit determines whether the number of the identified connected terminal sets is 0 (S527), and if not 0, repeats from step S522 to see if all terminals included in the connected terminal set can be distributed to other active terminal nodes Check it. Alternatively, if the number of connected terminal sets is 0, the central processing unit may exclude the corresponding inactive candidate access node from the inactive candidate access node set (S528). Thereafter, the central processing unit determines the number of inactive candidate access node sets (S529), determines whether the number of inactive candidate access node sets is 0 (S530), and if not 0, repeats from S521; If it is 0, it can be terminated.

을 다른 활성화 액세스 노드들에 연결할 수 없으면, 단말

에 대한 다른 활성화 액세스 노드들에게 허용되는 허용 최대 전송 전력을 조정하여 새롭게 다른 활성화 액세스 노드들에게 허용되는 조정 최대 전송 전력

을 설정할 수 있다(S531). 그리고, 중앙 처리 장치는 조정 최대 전송 전력 이내에서 단말

에 대한 다른 활성화 액세스 노드들의 최대 전송 전력

을 단계적으로 양의 실수인

를 증가시킬 수 있다(S532). 이처럼 중앙 처리 장치는 수학식 15와 같이 최대 전송 전력

에 0보다 큰 양의 실수인

를 누적하여 최대 전송 전력을 증가시킬 수 있다.On the other hand, the central processing unit determines the result of S523, the terminal

If it cannot connect to other active access nodes, the terminal

By adjusting the allowable maximum transmit power allowed to other active access nodes for

can be set (S531). And, the central processing unit adjusts the terminal within the maximum transmit power

Maximum transmit power of other active access nodes to

Step by step positive real number

can be increased (S532). As such, the central processing unit has the maximum transmit power as shown in Equation 15.

is a positive real number greater than 0 in

It is possible to increase the maximum transmit power by accumulating .

에 대한 다른 활성화 액세스 노드들의 최대 전송 전력

가 조정 최대 전송 전력 미만인지를 판단할 수 있다(S533). 중앙 처리 장치는 판단 결과 최대 전송 전력이 조정 최대 전송 전력 미만이 아니면 단말

를 다른 활성화 액세스 노드에 할당할 수 없다. 그 결과, 중앙 처리 장치는 비활성화 후보 액세스 노드를 비활성화시킬 수 없다. 이에 따라, 중앙 처리 장치는 단계 S528을 수행하여 해당 비활성 액세스 노드를 비활성화 후보 액세스 노드 집합에서 제거하여 불필요한 동작이 반복되지 않도록 할 수 있다. 이와 달리, 중앙 처리 장치는 판단 결과 최대 전송 전력이 조정 최대 전송 전력 미만이면, 단말

을 다른 활성화 액세스 노드들에 연결할 수 있는지를 판단할 수 있다(S534). 이때, 중앙 처리 장치는 단말

을 다른 활성화 액세스 노드들에 연결할 수 없으면 최대 전송 전력을 증가시키면서 연결 여부를 알아보기 위해 단계 S532부터 반복 수행할 수 있다. 이와 달리, 중앙 처리 장치는 단말

을 다른 활성화 액세스 노드들에 연결할 수 있으면, S524 단계를 수행할 수 있다.Afterwards, the central processing unit

Maximum transmit power of other active access nodes to

It may be determined whether is less than the adjusted maximum transmission power (S533). If the central processing unit determines that the maximum transmission power is not less than the adjusted maximum transmission power, the terminal

cannot be assigned to another active access node. As a result, the central processing unit cannot deactivate the deactivation candidate access node. Accordingly, the central processing unit may perform step S528 to remove the inactive access node from the set of inactive candidate access nodes to prevent unnecessary operations from being repeated. On the other hand, if the central processing unit determines that the maximum transmission power is less than the adjusted maximum transmission power, the terminal

It can be determined whether it can be connected to other active access nodes (S534). At this time, the central processing unit is the terminal

If it is not possible to connect to other active access nodes, it may be repeatedly performed from step S532 to check whether the connection is established while increasing the maximum transmission power. In contrast, the central processing unit is

can connect to other active access nodes, step S524 may be performed.

Referring again to FIG. 5 , the central processing unit may connect terminals in which inactive access nodes provide communication services to other active access nodes ( S540 ). Then, the central processing unit may adjust the maximum transmission power of the active access nodes newly established connection with the terminals (S550). Next, the central processing unit may deactivate the corresponding access nodes by turning off the power of the access nodes to be deactivated ( S560 ).

The methods according to the present invention may be implemented in the form of program instructions that can be executed by various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions recorded on the computer-readable medium may be specially designed and configured for the present invention, or may be known and available to those skilled in the art of computer software. Examples of computer-readable media may include hardware devices specially configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions may include not only machine language codes such as those generated by a compiler, but also high-level language codes that can be executed by a computer using an interpreter or the like. The hardware device described above may be configured to operate as at least one software module to perform the operations of the present invention, and vice versa.

In addition, the above-described method or apparatus may be implemented by combining all or part of its configuration or function, or may be implemented separately.

Although the above has been described with reference to the preferred embodiment of the present invention, those skilled in the art can variously modify and change the present invention within the scope without departing from the spirit and scope of the present invention as described in the claims below. You will understand that it can be done.

Claims (1)

A method of operating a central processing unit of a communication system, comprising:
classifying the access nodes into activated access nodes and inactive access nodes based on the number of connected terminals by identifying a connection state of the access nodes with the terminals;
distributing terminals connected to each of the inactive access nodes to other activated access nodes;
deactivating the inactive access nodes; and
and adjusting the maximum transmit power of the activated access nodes.

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