KR101362270B1 - Methods for managing power of base station in cellular networks - Google Patents

Abstract

Disclosed is a method for base station power management in a cellular network. The base station controller receives channel and interference information of at least one terminal from each base station, selects a terminal for each cell based on the received channel and interference information, and then considers a power limitation parameter of each base station and power parameters considering interference between adjacent cells. Next, the terminal is reselected for each cell by using the determined power limitation parameter and a power parameter considering interference between adjacent cells. Therefore, it is possible to maximize the power usage efficiency of the base station while reducing the complexity.

Description

METHODS FOR MANAGING POWER OF BASE STATION IN CELLULAR NETWORKS}

The present invention relates to a cellular network, and more particularly, to a base station power management method in a cellular network that can use energy efficiently.

Recently, interest in energy consumption is increasing in the information and communication industry. In particular, attention is focused on cellular networks, which are a large part of the information and communication industry. Since the base station consumes 60 to 80% of the power of the entire cellular network, efforts are being made to reduce the power of the base station in terms of government, network operators, or mobile operators. There is a need for use.

The transmission power of the base station is about 10 to 20W, which is considerably less than the total operating power of the base station (about 500 to 2000W). However, according to a recent study, the transmission power of the base station affects the total operating power proportionally, and it is known that the total operating power can be reduced by more than 200W only by reducing the transmission power by 10W.

Techniques for reducing the power of the base station have been directed to improving the performance of the hardware constituting the base station and to design the system to minimize the operating power of the base station in a given base station infrastructure environment.

Examples of methods for improving the performance of the hardware constituting the base station include a technique of increasing the efficiency of the power amplifier provided in the base station or using solar power generation.

Base station power saving methods in terms of system design are being studied under different time scales. For example, the base station may be installed at the most efficient position in terms of power considering the power of the base station operation in a time scale of several years or months, or the traffic may be changed in consideration of the change of user traffic on a time scale of several hours. It has been studied how to reduce the operating power of the entire base station by stopping the operation of some base stations in a small amount of time and extending the service area to the service area of the base station which has been stopped by the remaining base stations. In addition, only the transmission power fixedly allocated to each base station has been proposed to determine transmission power and user scheduling for every time slot in consideration of interference of adjacent cells.

However, the techniques for reducing the transmission power of the base station as described above are mostly based on the performance in terms of achievable throughput without using the method of improving hardware performance or considering the total operating power of the base station. Since the transmission power is determined, there is a disadvantage in that the transmission power is reduced.

Also, recently, a method of improving performance of a network using multiple antennas has been used. In order to reduce power of a base station in a cellular network environment using multiple antennas, power allocation, user scheduling, and beamforming for each antenna are used. Efforts are being made, but this method has a disadvantage of low effectiveness because of its high complexity.

SUMMARY OF THE INVENTION An object of the present invention for solving the above problems is to provide a base station power management method in a cellular network capable of maximizing power usage efficiency of a base station while reducing complexity for base station power management.

The base station power management method according to an embodiment of the present invention for achieving the above object of the present invention, the base station controller receiving the channel and interference information of at least one terminal from each base station, the received channel and Selecting a terminal for each cell based on the interference information, determining a power limitation parameter of each base station and a power parameter considering interference between adjacent cells, and using the power limitation parameter and a power parameter considering the interference between adjacent cells Reselecting the terminal for each cell.

Here, in the step of selecting a terminal for each cell based on the received channel and interference information, the weight for each terminal is set based on the received channel information and the interference information, and the set weight and transmission of each base station are set. The terminal may be selected for each cell based on the power and the data rate of each terminal.

The determining of the power limitation parameter of each base station and the power parameter considering the interference between adjacent cells may include determining the power limitation parameter corresponding to the instantaneous base station power limitation of the cell level and the network level, and the user terminal of the neighbor cell. And determining the power parameter reflecting the power of the interfering base station.

Here, the step of reselecting the terminal for each cell by using the power limitation parameter and the power parameter considering the interference between adjacent cells may be performed when terminal selection of all base stations is finally determined or a predetermined number of terminal selection processes are performed. Can be performed repeatedly.

Here, the power management method of the base station may be repeatedly performed every time slot.

In addition, the base station power management method according to another embodiment of the present invention for achieving the object of the present invention, the base station controller receiving the channel and interference information of at least one terminal from each base station, n (where n If the UE scheduling and beamforming vector is not determined for the th time slot, the UE scheduling and beamforming for the n + 1 th time slot is performed using the received channel and interference information of the UE. Determining a vector and when the user terminal scheduling and beamforming vector is not determined for the nth time slot, the n + 1 using the user terminal scheduling and beamforming vector determined for the n + 1 th time slot. Determining the number of antennas of each base station for the first time slot.

Here, in the power management method of the base station, when the user terminal scheduling and the beamforming vector are determined for the nth time slot, the n + 1 using the user terminal scheduling and the beamforming vector determined for the nth time slot. The method may further include determining the number of antennas of each base station for the first time slot.

According to the base station power management method according to the embodiment of the present invention as described above, by sharing the power resources of all base stations spatially by base station, and by sharing the average power resources in time, it is possible to share the spatial and temporal power between base stations In this way, it is possible to make full use of the total power resources.

In addition, it is possible to improve the performance in the entire power resources of the fixed base station, not only can achieve power saving effect under the same performance, but also achieve greening efficiency.

In addition, in the multi-antenna system, by sharing the power budget of the entire base station to determine the number of antennas to be used in each base station, and to determine the user terminal scheduling and beamforming function to reduce the complexity while increasing the network performance under a given power budget You can.

1 is a conceptual diagram illustrating a method of sharing power of a base station in a base station power management method according to an embodiment of the present invention.
2 is a flowchart illustrating an operation performed in each base station in the base station power management method according to an embodiment of the present invention.
3 is a flowchart illustrating an operation performed by a central base station controller in a base station power management method according to an embodiment of the present invention.
4 is a graph illustrating a performance evaluation result of the base station power management method according to an embodiment of the present invention.
5 is a flowchart illustrating an operation performed in each base station in the base station power management method according to another embodiment of the present invention.
6 is a flowchart illustrating an operation performed by a central base station controller in a base station power management method according to another embodiment of the present invention.

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

The terms first, second, A, B, etc. may be used to describe various elements, but the elements should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. And / or < / RTI > includes any 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 to or connected to that other component, but it may be understood that other components may be present in between. Should be. On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "having" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or 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 commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

The term 'terminal' used in the present application includes a mobile station (MS), a mobile terminal (MT), a user terminal, a user equipment (UE), a user terminal (UT) An access terminal (AT), a subscriber unit, a subscriber station (SS), a wireless device, a wireless communication device, a wireless transmit / receive unit (WTRU) Or < / RTI > other terms.

A 'base station' used in the present application generally refers to a fixed point for communicating with a terminal, and includes a base station, a Node-B, an eNode-B, a BTS (Base Transceiver System), an access point (Access Point), and the like.

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

The transmission power management method of a base station according to an embodiment of the present invention shares the transmission power between base stations in time or space so as to minimize the amount of interference between adjacent cells by maximizing a given power resource, based on a cellular network currently established. By performing the scheduling of the present invention provides a method for efficiently using the base station under the same network resources.

In addition, the transmission power management method of the base station according to an embodiment of the present invention determines the number of antennas to be used and the number of antennas not to be used among the plurality of antennas provided by each base station, and the complexity of the user terminal through scheduling and beamforming It provides a way to reduce power usage of base stations while improving the performance of cellular networks.

1 is a conceptual diagram illustrating a method of sharing power of a base station in a base station power management method according to an embodiment of the present invention.

First, a method of sharing spatially and / or temporally the power resources of a given entire base station will be described with reference to FIG. 1. Here, all base stations may be used to include all of a plurality of base stations included in the cellular network, or may be used to include a predetermined number of base stations selected as a power management target among all base stations.

The objective function for maximizing the average data rate of the user terminal under a given power resource can be expressed as Equation 1.

In Equation 1, U _k (x _k ) means the average utility function of the user terminal k, R (β) means the range of the average transmission rate that the user terminal can actually achieve, β is the power of the entire base station The controllable ratio of resources.

Under the overall objective function as shown in Equation 1, the method of sharing the power of the base station can be divided into four methods as shown in FIG.

First, as shown in (a) of FIG. 1, the power of the base station is not shared at all in temporal (T: temporal) and spatial (S: spatial), and (S, T) = (0,0 In this case, the power resource limit can be expressed as in Equation 2.

은 시간 t에서 기지국의 n의 서브채널(subchannel) s에서의 전송 전력을 의미하고,

는 하나의 기지국 n의 순간 전체전력의 최대값을 의미한다.In Equation 2, A _n means a constant proportional to the transmission power of the base station n, B _n means a constant independent of the transmission power of the base station n. Also,

Is the transmit power in subchannel s of n of the base station at time t,

Denotes a maximum value of the instantaneous total power of one base station n.

Second, as shown in FIG. 1 (b), the power of the base station is shared only in time, and is represented by (S, T) = (0,1), and the power resource limitation in this case is expressed by the following equation. It can be expressed as

은 하나의 기지국 n의 평균 전체전력의 최대값을 의미한다.In Equation 3,

Denotes a maximum value of the average total power of one base station n.

Third, as shown in (c) of FIG. 1, the power of the base station is shared only spatially, and is represented by (S, T) = (1,0), and the power resource limitation in this case is expressed by the following equation. It can be expressed as 4.

Fourth, as shown in (d) of FIG. 1, the power of the base station is shared in time and space, and is expressed as (S, T) = (1,1), and the power resource limitation in this case is represented by mathematics. It can be expressed as Equation 5.

Under the framework as described above, the base station power management method according to an embodiment of the present invention allocates power to every time slot and selects a user terminal through the following method.

First, a method of selecting a user terminal may be expressed as in Equation 6.

=1은 기지국 n이 서브채널 s상에서 사용자 단말 k를 스케줄링함을 의미하고,

=0는 그 이외의 경우를 나타낸다. 또한, k(n,s)는 기지국 n에 의해 서브채널 s에 스케줄된 사용자 단말을 의미하고,

은 기지국 n과 연관된 사용자 단말의 집합을 의미한다.

는 각 사용자 단말별로 할당되는 가중치를 의미하는 것으로

로 정의되며,

는 기지국 n에 의해 서브채널 s에서 서비스를 제공받기 위해 사용자 단말 k가 선택된 경우 사용자 단말 k의 의미있는(meaningful) 데이터 레이트를 의미한다.In Equation (6)

= 1 means that the base station n schedules the user terminal k on the subchannel s,

= 0 indicates otherwise. In addition, k (n, s) means a user terminal scheduled on the sub-channel s by the base station n,

Denotes a set of user terminals associated with the base station n.

Denotes a weight assigned to each user terminal.

Lt; / RTI >

Denotes a meaningful data rate of the user terminal k when the user terminal k is selected to receive a service in the subchannel s by the base station n.

Meanwhile, a method of allocating power to a base station every time slot can be expressed as shown in Equation (7).

은 사용자 단말 m으로부터 기지국 n까지의 서브채널 s에 대한 채널 이득을 나타내며,

은 기지국 n의 서브채널 s에 대한 열 잡음(thermal noise)을 의미한다.

는 인접 셀의 사용자 단말에 간섭을 미칠 수 있는 서브채널 s에 대한 기지국 n의 전력을 반영하는 택스 항(taxation term)을 의미한다. λ_n 및 μ은 각각 셀 레벨 및 네트워크 레벨의 순시 기지국 전력 제한과 연관된 음이 아닌 라그랑주 승수(non-negative Lagrange multipliers)를 의미한다.

및

는 평균 전력 자원에 수렴하는 시간과 정확성을 결정하는 상수값을 의미한다.In Equation (7)

Denotes a channel gain for subchannel s from user terminal m to base station n,

Denotes thermal noise for subchannel s of base station n.

Denotes a taxation term reflecting the power of the base station n for the subchannel s that may interfere with the user terminal of the neighbor cell. λ _n and μ mean non-negative Lagrange multipliers associated with instantaneous base station power limitations at cell level and network level, respectively.

And

Denotes a constant value that determines the time and accuracy to converge to the average power resource.

및

는 각각 가상 큐를 의미하며, 각각 하나의 기지국 당 평균전력자원, 기지국 전체의 평균전력자원을 나타내고, 매 타임 슬롯 마다 수학식 8과 같이 갱신된다.

And

Denote virtual queues, and each represents an average power resource per one base station and an average power resource of the entire base station, and is updated as shown in Equation 8 in every time slot.

2 is a flowchart illustrating an operation performed in each base station in the base station power management method according to an embodiment of the present invention.

Referring to FIG. 2, first, each base station measures a channel gain with each terminal and an interference amount of each terminal for each of a plurality of terminals belonging to a region in which the base station provides a service (S210).

Then, each base station transmits the channel gain and interference information measured for each terminal to the central base station controller (S220).

Subsequently, each base station receives transmission power and user terminal selection information for each time slot from the central base station controller (S230), selects a predetermined user terminal using the received user terminal selection information, and determines the selected user terminal. Data is transmitted using the transmission power (S240).

The operation S210 to S240 of each base station as described above is repeated every time slot.

3 is a flowchart illustrating an operation performed by a central base station controller in a base station power management method according to an embodiment of the present invention, wherein the central base station controller includes a channel gain of each terminal included in a service area of the corresponding base station from each base station; Assume receiving interference amount information.

)과 사용자 단말별 가중치(

) 그리고 택스 항(

)을 초기화하고, 가상 큐(

,

)들을 각 전력자원별로 갱신한다(S310).First, the central base station controller

) And weights by user terminal (

) And Tax terms (

), The virtual queue (

,

) Are updated for each power resource (S310).

Thereafter, the central base station controller selects a user terminal to provide a service for each cell using Equation 6 based on the information of each terminal received from each base station (S320). Here, the central base station controller determines the weight for each user terminal and the transmission power of each base station based on the channel information and the interference information of each user terminal received from each base station, and the user for each cell based on the data rate of each terminal. The terminal can be selected.

The central base station controller then determines the parameters [lambda] _n and [mu] associated with instantaneous base station power limitations at the cell level and network level through a bisection search, such as a water-filling algorithm, and receives from each base station. A tax term is calculated based on the channel information and the interference amount information (S330).

The central base station controller determines the transmission power of each base station based on the power limit parameter and the tax term as described above, and repeats the user terminal selection by reflecting the determined transmission power (S340). Here, the user terminal selection process may be repeated until the user terminal selection of all base stations converges or a predetermined maximum number of user terminal selection processes are performed.

Thereafter, the central base station controller transmits finally determined user selection information and transmission power to all base stations (S350).

The operations S310 to S350 of the central base station controller as described above are repeated every time slot.

4 is a graph illustrating a performance evaluation result of the base station power management method according to an embodiment of the present invention.

In (a), (b), (c) and (d) of FIG. 4, the meaning of each line is as follows. EQ + (S, T) = (0,0) indicates the case where each base station uses the same transmit power and does not share power, and IM + (S, T) = (0,0) manages the transmit power in each base station However, it represents a case where power sharing is not performed, and IM + (S, T) = (0,1) represents a case in which transmission power management is performed at each base station, but power sharing is performed at each base station, and IM + (S, T ) = (1,0) indicates power management at each base station, but only power sharing is performed between base stations, and IM + (S, T) = (1,1) indicates power management at each base station. This is a case where power sharing is performed temporally and spatially.

4 (a) and 4 (b) show GAT (Geometric Average User Throughput) and Greening Efficiency (β) for β values when the distance between base stations is set to be constant. Here, the greening efficiency is a value obtained by dividing the average performance of the user by the frequency band and the power used, and is an indicator of how efficiently the power is used in terms of performance. 4 (c) and 4 (d) show the GAT and greening efficiency for the β value when simulated under an actual base station topology, respectively.

As shown in FIG. 4, when each base station has a budget for time, space, and space and time compared to when each base station has a separate operating power budget, first, performance is improved, and second, power saving effect under the same performance (Power In terms of savings, and third, Greening efficiency, we can see better.

Hereinafter, a transmission power management method of a base station according to another embodiment of the present invention will be described.

The transmission power management method of a base station according to another embodiment of the present invention is a method for spatially maximizing the total power resources given to a base station having a plurality of antennas, by allowing each base station to share the power budget of all base stations. By determining the number of antennas to be used in each base station and determining the user terminal scheduling and beamforming functions, it is possible to reduce complexity while increasing network performance under a given power budget.

An objective function for maximizing the average utility of a user terminal under a controllable given power resource may be expressed as Equation (9).

는 사용자 단말 k의 평균 효용함수를 의미한다.In Equation 9, x _k denotes an average throughput that user terminal k can achieve, and R denotes a set of average throughputs that all user terminals can achieve. Also,

Denotes an average utility function of the user terminal k.

In addition, the given power resource limit may be expressed as Equation 10.

In Equation 10, P _T denotes a power resource given to the entire base station, a denotes a parameter proportional to a transmission power of an antenna used in all antennas of the base station, and b denotes a parameter that is not proportional to the transmission power. Means. P _max means transmit power used by one antenna, and N _n means the number of antennas used by the base station n.

Under the objective function as described above, there is an overall power limitation of all base stations, and the number of antennas used for each time slot is determined for each base station. Here, the number of antennas used in each base station may be determined by the central base station controller that controls the entire base station.

In addition, the data rate that can be achieved by the user terminal in each time slot can be expressed by Equation (11).

In Equation 11, W denotes a bandwidth of a system, P _{s, max} denotes a maximum transmit power used in a subcarrier s, and l _k denotes a path loss of a channel transmitted to the user terminal k. Where h _{s, k} denotes a fast fading channel when the user terminal k uses the subcarrier s, and f _{s, k} denotes a beamforming channel for the user terminal k.

Next, converting the objective function into the objective function of each time slot, as shown in Equation 12, converts the transmission power, the beamforming function, and the user terminal scheduling for each time slot.

In Equation 12, p , I , and B denote a pattern of the number of antennas allocated to each base station, a user terminal scheduling vector, and a beamforming vector, respectively.

In Equation 12, a method of determining the transmission power, the beamforming vector, and the user scheduling that are close to the optimum when the transmission power of each base station is limited has been proposed in a recent study. However, recent research suggests that transmission power is limited for each base station, and it is proposed to solve scheduling, beam pome, and power allocation through iterative, and the complexity is considerably high because it assumes a multi-cell environment. There is this.

The transmission power management method of the base station according to another embodiment of the present invention considers the total power used by the base station rather than the transmission power of the base station to overcome the above-mentioned disadvantages, and the distribution of user terminals or the number of user terminals for each base station. Sharing power in the same situation can improve the performance of the entire network. In addition, for each base station, the power allocation problem for each antenna is considered on / off (that is, using maximum power or not using at all), thereby reducing the complexity of power allocation.

5 is a flowchart illustrating an operation performed at each base station in the base station power management method according to another embodiment of the present invention, which is illustrated in the multi-antenna cellular system. Hereinafter, it is assumed that the beamforming vector is determined using the maximum ratio transmission (MRT) for the determined user terminal scheduling.

Referring to FIG. 5, first, each base station measures a channel gain with each terminal and an interference amount of each terminal for each of a plurality of terminals belonging to a region in which the base station provides a service (S510).

Thereafter, each base station transmits the channel gain and interference information measured for each terminal to the central base station controller (S520).

Subsequently, each base station receives a number of antennas used for each time slot, a user terminal selection vector, and a beamforming function from the central base station controller (S530), selects a predetermined user terminal using the received user terminal selection vector, and selects The data is transmitted through beamforming using the antenna determined to the user terminal (S540).

As described above, operations of each base station (S510 to S540) are repeated every time slot.

FIG. 6 is a flowchart illustrating an operation performed by a central base station controller in a base station power management method according to another embodiment of the present invention, showing a base station power management method of a multi-antenna cellular system.

First, the central base station controller receives channel gain and interference information of each terminal included in the service area of each base station from the plurality of base stations (S610).

The central base station controller determines whether the previous time slot is a time slot for which power management is performed for a predetermined time slot (S620), and when the previous time slot is a time slot for which no power management is performed, the received channel gain and interference information Determining a user terminal scheduling and a beamforming vector according to the current time slot arbitrarily. In addition, the number of antennas of each base station that satisfies the objective function of each time slot shown in Equation 12 is determined using the determined user terminal scheduling and the beamforming vector (S630).

Thereafter, the central base station controller transmits the determined user terminal scheduling, beamforming vector, and antenna number information to each base station (S640).

Meanwhile, if it is determined in step S620 that the time slot immediately before the predetermined time slot is the time slot where power management is performed, the central base station controller assumes a user terminal scheduling and beamforming vector determined in the immediately previous time slot and satisfies Equation 12. The number of antennas to be determined is determined (S650).

The operation of the central base station controller as described above is repeated every time slot.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention as defined by the following claims It can be understood that

Claims (7)

In the base station power management method performed in the base station controller,
Receiving channel and interference information of at least one terminal from each base station;
Selecting a terminal for each cell based on the received channel and interference information;
Determining a power parameter considering power limitation parameters of each base station and interference between adjacent cells; And
And reselecting a terminal for each cell by using the power limitation parameter and a power parameter considering the interference between adjacent cells. The method according to claim 1,
Selecting a terminal for each cell based on the received channel and interference information,
A base station power may be set based on the received channel information and interference information, and a terminal is selected for each cell based on the set weight, the transmission power of each base station, and the data transmission rate of each terminal. How to manage. The method according to claim 1,
Determining a power parameter considering the power limitation parameter of each base station and interference between adjacent cells,
Determining the power limit parameter corresponding to an instantaneous base station power limit at a cell level and a network level; And
And determining the power parameter reflecting the power of the base station interfering with the user terminal of the neighboring cell. The method according to claim 1,
Re-selecting the terminal for each cell using the power limitation parameter and the power parameter considering the interference between adjacent cells,
A method for power management of a base station, characterized in that it is repeatedly performed until the terminal selection of all base stations is finally determined or a predetermined number of terminal selection processes are performed. The method according to claim 1,
The power management method of the base station, the power management method of the base station characterized in that it is repeatedly performed every time slot. In the base station power management method performed in the base station controller,
Receiving channel and interference information of at least one terminal from each base station;
If the user terminal scheduling and beamforming vector is not determined for the n th time slot, where n is a natural number of 1 or more, the user for the n + 1 th time slot using the received channel and interference information of the terminal Determining a terminal scheduling and beamforming vector; And
If a user terminal scheduling and beamforming vector is not determined for an n th time slot, each of the n + 1 th time slots is determined using the user terminal scheduling and beamforming vector determined for the n + 1 th time slot. Determining a number of antennas of the base station. The method of claim 6,
The power management method of the base station
If the user terminal scheduling and beamforming vector is determined for the n th time slot, the antenna of each base station for the n + 1 th time slot using the user terminal scheduling and beamforming vector determined for the n th time slot And determining the number further.

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