KR20110004567A - Cooperative management method of radio resource - Google Patents

Abstract

PURPOSE: A cooperative management method of radio resources is provided to allocate power, time, and a frequency. CONSTITUTION: An upper system receives signal to noise ratio information measured by a sub channel of each cell to which each base station belongs in a cooperative unit from the base station. The upper system allocates radio resources including a transmission power value using the received signal to noise ratio information and current average transmission rate information of each terminal. The transmission power value guarantees the minimum average transmission rate by each terminal. The upper system transmits the allocated radio resource information by each terminal to each base station.

Description

Collaborative radio resource management method {COOPERATIVE MANAGEMENT METHOD OF RADIO RESOURCE}

The present invention relates to a radio resource management method, and more particularly, to a method for managing radio resources by cooperating between base stations having a cooperative relationship.

Cellular system is a proposed concept to overcome the limitation of service area and subscriber capacity. It is spatially frequency by dividing the service area into several small areas, ie cells or sectors, and using the same frequency band in two cells which are far enough apart from each other. It is a system that can be reused. A cell refers to a service area by one wireless base station, and a plurality of cells gather to form a service area, which is a system.

Features of cellular systems include frequency reuse, cell partitioning techniques, handoff or handover. In order to maximize the subscriber capacity, the same frequency is used in different cells, and the frequency reuse distance depends on the topographical characteristics, antenna height, transmission power, and the like. Cell division is one way to maximize subscriber capacity. In a cellular system, cells have different channels in separate zones, creating a channel for subscribers' needs.

In a multi-cellular system, each cell allocates radio resources such as time, frequency, and power to each terminal in consideration of only its own cell. When the communication is performed between the base station and the terminal, the communication performance is degraded due to interference from adjacent cells using the same time and frequency band. In particular, the closer the terminal is to the cell boundary, the lower the performance.

This degradation can be a problem not only in current multi-cellular systems, but also in next-generation mobile communication systems, which are expected to continue to increase in the number of small- and medium-sized cells such as femto-cells and pico-cells. have. In order to stably provide a high-speed data service, it is necessary to effectively overcome interference from adjacent cells regardless of the position of the terminal or the channel condition.

Recently, researches on multi-cell cooperative communication have been actively conducted to solve the problem of communication performance deterioration. Representatively, MK Karakayali et al. Presented at the IEEE International Conference on Communications (ICC) in 2006, "The Maximum Common Baud Rate Achievable in Collaborative Networks." In the paper titled 'On the maximum common rate achievable in a coordinated network', base stations and terminals belonging to multiple cells that collaborate together are regarded as virtual MIMO (virtual multiple input and multiple output) systems. When transmitting a signal by performing Dirty Paper Coding (DPC: DPC), a technique for maximizing a minimum transmission rate of terminals has been proposed.

By implementing the method proposed in the paper, we can effectively reduce the influence of interference and at the same time obtain diversity diversity to maximize the efficiency of radio resource use and greatly improve the minimum transmission rate of UEs with poor channel environment. have.

Dirty paper coding is one of pre-interference signal cancellation techniques that can remove an interference signal from the transmitting end in advance so that the receiving end is not affected by the interference signal. This technology has received much attention recently as a technique for guaranteeing capacity in a Gaussian downlink environment with multiple users with multiple input multiple-output (MIMO).

Typically, two independent codes are used in the implementation of dirty paper encoding. One of them is an error correction code that restores the original information from the received signal damaged by the channel. The other is a shaping that minimizes the power consumption of the transmitter by making the shape of the transmitting signal close to a sphere. shaping) code. In the receiver, iterative decoding can be gradually increased by using an iterative decoding technique between two decoders corresponding to these two codes. The dirty paper coding system implemented in this way exhibits a performance very close to the Shannon limit.

Hereinafter, a method of maximizing a minimum transmission rate of terminals by performing conventional dirty paper encoding and transmitting a signal will be described.

Each cell selects a terminal according to an arbitrary scheduling scheme (step 1). Each base station is referred to as any base station or radio network controller (RNC: RNC) which performs current channel state information and transmission signal information with selected terminals on behalf of other base stations in the cooperative unit, dirty paper coding. (Step 2).

Each base station, any base station or RNC performing dirty paper encoding as a representative, uses the information received in step 2 to minimize the number of terminals in the virtual multi-antenna system environment formed between the base stations in the cooperative unit and the terminals selected in step 1. Perform dirty paper encoding to maximize the transmission rate (when any base station or RNC performs dirty paper encoding as a representative, the dirty paper encoding performance information is transmitted to each base station in the cooperative unit) (step 3). Thereafter, each base station transmits a signal according to the result of the scheduling and dirty paper encoding performed previously (step 4).

The above method assumes a communication system capable of joint processing (JP) between base stations in a cooperative unit in order to use dirty paper coding. Therefore, each base station should exchange excessive information amounts such as current channel state information, transmission signal information, and dirty paper encoding performance information with all terminals with other base stations or apparatuses performing dirty paper encoding in a cooperative unit as a representative. .

The amount of computation required to perform dirty paper coding for optimal radio resource management is very difficult and difficult to use because of its high complexity. In addition, by allocating terminals before performing the dirty paper encoding, there is a problem that the minimum transmission rates of all the terminals belonging to the cooperative unit cannot be simultaneously considered when there are a plurality of terminals for each cell.

So far, there is overhead and complexity that can be tolerated by realistic systems, and efficient cell-to-cell that meets the minimum transmission rate of all terminals belonging to the cooperative unit and at the same time allows for proportional fairness (PF). There is no proposal for a cooperative radio resource management method.

An object of the present invention is to provide a cooperative radio resource management method.

The technical problems to be solved by the present invention are not limited to the technical problems and other technical problems which are not mentioned can be understood by those skilled in the art from the following description.

In order to achieve the above technical problem, the cooperative radio resource management method according to the present invention receives signal-to-noise ratio information measured for each sub-channel of each cell in the cooperative unit from the base station in the cooperative unit. Making; Allocating a radio resource including a transmission power value for guaranteeing a minimum average transmission rate for each terminal by using the received signal-to-noise ratio information and the current average transmission rate information of each terminal; And transmitting the allocated radio resource information to each base station for each terminal.

In order to achieve the above technical problem, the cooperative radio resource management method according to the present invention comprises the steps of: receiving radio resource information that has previously performed radio resource management from another base station in the cooperative unit; Receiving signal-to-noise ratio information measured for each subchannel from each terminal in a cooperative unit or each terminal in a cell to which the base station itself in the cooperative unit belongs; Minimum of each terminal by using radio resource information of another base station in the received cooperative unit, signal to noise ratio information of each terminal in the cell to which the base station in the cooperative unit belongs, or the cell belonging to the base station itself in the cooperative unit Allocating a radio resource comprising transmit power to ensure an average rate; And transmitting the allocated radio resource information and average transmission rate information of the selected specific terminal to a base station to perform cooperative radio resource management in a preset order.

In accordance with an aspect of the present invention, there is provided a cooperative radio resource management method comprising: receiving signal-to-noise ratio information measured for each subchannel by each terminal from each terminal in a cell to which the base station belongs; Allocating a first radio resource including transmission power for guaranteeing a minimum average transmission rate for each terminal in a cell to which the base station itself belongs by using the received signal-to-noise ratio information; A second radio resource information including transmission power allocated by each other base station in the cooperative unit to guarantee a minimum average rate for the terminal in the cell to which the base station belongs, and a specific terminal in a cell to which the other base station in the cooperative unit belongs. Receiving average rate information on a terminal from another base station in the cooperative unit; And allocating a radio resource including a transmission power for guaranteeing a minimum average transmission rate of the specific terminal by using the average rate information, the first radio resource information, and the second radio resource information for the specific terminal.

According to the present invention, in a multi-cellular communication system performing cooperative communication between cells, a multi-operation operation required for dirty paper coding (DPC), etc. is unnecessary, and low overload is achieved by allocating power, time, and frequency through a cooperative radio resource management technique. The head and computation amount can effectively reduce the inter-cell interference effects.

In addition, according to the present invention, an inter-cell cooperative radio resource management scheme, a signal-to-noise ratio, and an average rate transmission period are dynamically selected according to a system and a channel environment, thereby reducing the overhead and complexity associated with cooperative radio resource management.

In addition, the present invention has the advantage that it is possible to ensure the minimum transmission rate of more terminals compared to the prior art by considering all the terminals at the same time.

Effects obtained in the present invention are not limited to the above-mentioned effects, and other effects not mentioned above may be clearly understood by those skilled in the art from the following description. will be.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The detailed description set forth below in conjunction with the appended drawings is intended to explain exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced. The following detailed description includes specific details to assist in a thorough understanding of the present invention. However, one of ordinary skill in the art appreciates that the present invention may be practiced without these specific details. For example, the following description will focus on certain terms, but need not be limited to these terms and may refer to the same meaning even when referred to as any term. In addition, the same or similar components throughout the present specification will be described using the same reference numerals.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, without excluding other components unless specifically stated otherwise.

The technique disclosed below may be used in various communication systems, which may provide various communication services such as voice, packet data, and the like. The technology of the communication system can be used for downlink or uplink. A base station may be replaced by terms such as a fixed station, a base station, a Node B, an eNode B (eNB), an access point, an ABS, and the like. In addition, a mobile station (MS) may be replaced with terms such as a user equipment (UE), a subscriber station (SS), a mobile subscriber station (MSS), an AMS, or a mobile terminal.

Also, the transmitting end refers to a node transmitting data or voice service, and the receiving end refers to a node receiving data or voice service. Therefore, in uplink, a terminal may be a transmitting end and a base station may be a receiving end. Similarly, in downlink, a terminal may be a receiving end and a base station may be a transmitting end.

On the other hand, the terminal of the present invention PDA (Personal Digital Assistant), cellular phone, PCS (Personal Communication Service) phone, GSM (Global System for Mobile) phone, WCDMA (Wideband CDMA) phone, MBS (Mobile Broadband System) phone This can be used.

Embodiments of the present invention may be supported by standard documents disclosed in at least one of the Institute of Electrical and Electronics Engineers (IEEE) 802 system, the 3GPP system, the 3GPP LTE system, and the 3GPP2 system, which are wireless access systems. That is, steps or parts which are not described to clearly reveal the technical spirit of the present invention among the embodiments of the present invention may be supported by the above documents. In addition, all terms disclosed in the present document can be described by the above standard document. In particular, embodiments of the present invention may be supported by documents such as standard documents of the IEEE 802.16 system, P802.16-2004, P802.16e-2005, and P802.16Rev2.

Specific terms used in the following description are provided to help the understanding of the present invention, and the use of such specific terms may be changed to other forms without departing from the technical spirit of the present invention.

The term base station used in the present invention may be used as a concept including a cell or a sector. In the present invention, one base station may provide a service for one cell. In addition, a higher system corresponds to a system that performs a higher function of each base station and controls data and control information transmission. Such a higher system may generally be referred to as a network entity.

A serving base station (cell) can be viewed as a base station that provides existing main services to a terminal, and can perform transmission and reception of control information on cooperative multiple transmission points. In this sense, the serving base station may be referred to as an anchor base-station (cell).

1 is a diagram illustrating an example of an inter-cell cooperative radio resource management scheme.

Referring to FIG. 1, the cooperative radio resource management scheme proposed by the present invention may be classified into three methods. The first cooperative radio resource management scheme is a method in which a cooperative radio resource management between cells is performed by an upper system connected to base stations in a cooperative unit at an upper layer. Optionally, one base station in the cooperative unit may perform radio resource management in the first cooperative radio resource management scheme.

In the second cooperative radio resource management scheme, each cell (base station) of a cooperative unit is assigned a random order, and each cell (base station) performs radio resource management in a predetermined order, and transmits the result to the next cell. to be.

In the third cooperative radio resource management scheme, each cell first performs radio resource management considering only terminals of its own cell, and then, as a result, the average data rate information of the selected terminals and the like are compared with all other base stations in the cooperative unit. By exchanging and using the information, each cell performs radio resource management on a secondary basis.

This cooperative radio resource management scheme may be determined in a suitable manner according to the system and channel environment. When the number of cells (or base stations) or the number of terminals in the cooperative unit is small, the amount of information exchange for cooperative radio resource management to be transmitted through a wired or wireless network is relatively low, or the amount of information exchange for cooperative radio resource management and the time required for the cooperative radio resource management. If this is not greatly restricted, it is preferable to apply the first cooperative radio resource management scheme. In this case, the overhead is large because all base stations in the cooperative unit must exchange signal-to-noise ratio (SNR), average transmission rate of each terminal, and cooperative radio resource management results with each other. There is an advantage in that an optimal inter-cell cooperative radio resource management result can be obtained.

On the contrary, when the number of cells (or base stations) or the number of terminals in the cooperative unit is large, the amount of information exchange for cooperative radio resource management to be transmitted through a wired or wireless network is relatively high, or the amount of information exchange for cooperative radio resource management and the like. If the time required is greatly limited, it is preferable to apply the second cooperative radio resource management scheme.

In this case, a random order is assigned to each cell (base station) of the cooperative unit, and each cell (base station) performs radio resource management in a predetermined order, and the result of the execution and average transmission rate information of the selected terminals are performed in the following order. It can deliver to the cell (base station). The second cooperative radio resource management scheme has less overhead and lower complexity than the first cooperative radio resource management scheme 1.

In addition, in the third cooperative radio resource management scheme, each cell (base station) performs primary radio resource management considering only its own cell (base station), and then transfers the result with all other base stations in the cooperative unit. The base station) performs the second radio resource management again in consideration of the result of the first radio resource management performed by the other cells. This results in a slightly lower performance than the optimal radio resource management result, but can significantly reduce the overhead required for cooperative radio resource management between cells.

The period at which each base station transmits a signal-to-noise ratio and a current average transmission rate of each terminal may be dynamically determined according to a cooperative radio resource method, a system, and a channel environment. In order to achieve optimal performance, it is desirable to make the signal-to-noise ratio and the average rate transmission period equal to the period for managing cooperative radio resources.However, in order to reduce the overhead, the system and channel environment are considered in consideration of the cooperative radio resource management period. You can set this long.

The signal-to-noise ratio transmission period is close to performance when the channel does not change rapidly with time, i.e. when the channel's time selectivity is not large, the period value is increased to reduce the significant amount of overhead and the period value is small. Can be obtained.

The cooperative radio resource management may be performed by a higher system in the first cooperative radio resource management scheme. In the second cooperative radio resource management scheme and the third cooperative radio resource management scheme, it may be performed by each base station in the cooperative unit.

2 illustrates a preferred embodiment of a first cooperative radio resource management scheme according to the present invention.

Referring to FIG. 2, the terminal may first measure a signal-to-noise ratio with the searchable base stations in the cooperative unit and transmit the signal-to-noise ratio to each base station. At this time, the terminal may transmit to each base station in the cooperative unit according to a predetermined period in consideration of the system and the channel environment in order to transmit the optimal signal-to-noise ratio and the average data rate.

This signal-to-noise ratio and average rate transmission period may be determined by one base station or higher system in the cooperative unit. This period can be determined dynamically.

The base stations can determine the channel gain of the corresponding channel in consideration of the dispersion of the noise by using the signal-to-noise ratio received from the terminal. The base stations can transmit the signal-to-noise ratio and the average data rate of all terminals in the cell to the higher-order system according to the signal-to-noise ratio and the average data rate transmission period. In this case, the transmission period of the base station to the upper system may be the same as the signal-to-noise ratio transmission period of the terminal to the base station. The higher level system may perform radio resource management using the signal-to-noise ratio and the current average rate of the terminals received from each base station in the cooperative unit. Hereinafter, a method of performing radio resource management by a higher system according to a first cooperative radio resource management method will be described.

Radio resource management may be performed in a direction in which proportional fairness (PF) is maximized while an average transmission rate of all terminals in the cooperative unit satisfies the minimum average transmission rate (). This can be formulated using the equations described below.

Equation 1 represents an instantaneous transmission rate that can be obtained when the k-th terminal is allocated to the t-th scheduling time in the n-th subchannel in the uplink.

는 n번째 부채널에서 k번째 단말의 t번째 스케줄링 시간에 서의 전송 전력,

는 협력단위 c에 속한 기지국 b의 단말들의 집합인

에서

번째 단말이 n번째 부채널에서 할당받는 경우의 t번째 스케줄링 시간에서의 전송 전력,

는 n번째 부채널에서 t번째 스케줄링 시간에 k번째 단말 및 기지국 b의 채널,

는

번째 단말과 기지국 b의 채널을 나타낸다.here

Is the transmit power at the t th scheduling time of the k th terminal in the n th subchannel,

Is a set of terminals of base station b belonging to cooperative unit c.

in

Transmission power at the t-th scheduling time when the first terminal is allocated in the n-th subchannel,

Is the channel of the k-th terminal and the base station b at the t-th scheduling time in the n-th subchannel,

Is

The channel of the first terminal and the base station b is shown.

Equation 2 represents an instantaneous data rate that can be obtained when the k-th terminal is allocated to the t-th scheduling time in the n-th subchannel in the downlink.

및

는 각각 n번째 부채널에서 t번째 스케줄링 시간에 각각 기지국 b와 기지국

의 전송 전력을 나타낸다.

은 n번째 부채널에서 t번째 스케줄링 시간에 각각 기지국 b와 k번째 단말 간의 채널을 나타내며,

는 기지국

와 k번째 단말 간의 채널을 나타낸다.here

And

Are respectively the base station b and the base station at the t th scheduling time in the n th subchannel.

Denotes the transmission power of.

Denotes a channel between the base station b and the k-th terminal at the t-th scheduling time in the n-th subchannel,

Is a base station

And a channel between the k-th terminal.

에 속한 k번째 단말의 t+1번째 스케줄링 시간에서의 평균 전송률을 나타낸 식이다.Equation 3 is a set of terminals of base station b belonging to cooperative unit c.

The average transmission rate at the t + 1 < th > scheduling time of the k < th >

는 부채널 수,

는 n번째 부채널에서 k번째 단말이 t번째 스케줄링 시간에서 할당을 받을 경우 1, 할당받지 않으면 0을 나타내는 함수이다.here

Is the number of subchannels,

Is a function representing 1 when the k-th terminal is allocated at the t-th scheduling time in the n-th subchannel and 0 when it is not allocated.

Equation 4 is an expression representing the total amount of each terminal in the cooperative unit does not satisfy the minimum average data rate.

Where R _min is the minimum average data rate, and the [] ⁺ symbol is 0 if the value of [] is less than 0, and the value represents the value if it is greater than 0.

In order to guarantee the minimum average data rate of the terminals, it is preferable to perform radio resource management to minimize the equation (4).

Equation 5 represents an equation considering proportional fairness in addition to guaranteeing the minimum average rate of the terminals.

는 단말들의 최소 평균 전송률 보장의 정도를 나타내는 상수이다. 이 값이 클수록 단말들의 최소 평균 전송률 보장을 우선적으로 고려하여 무선 자원 관리를 수행하게 된다. 상위 시스템은 단말에 대해 시간, 주파수 및 전송 전력 등의 무선 자원이 상기 수학식 5를 만족하도록 할당할 수 있다. 상위 시스템은 협력단위에 속하는 모든 기지국들 및 모든 단말들과의 신호대 잡음비뿐만 아니라 모든 단말들의 현재 평균 전송률을 알고 있으므로 상기 수학식 5를 만족하는 무선 자원 관리를 수행할 수 있다. here

Is a constant representing the degree of minimum average rate guarantee of the terminals. As this value increases, radio resource management is performed in consideration of guaranteeing minimum average data rates of terminals. The higher system may allocate radio resources such as time, frequency, and transmit power to the terminal to satisfy Equation 5. The higher-level system knows the signal-to-noise ratios of all the base stations and all the terminals belonging to the cooperative unit, as well as the current average data rates of all the terminals, thereby performing radio resource management that satisfies Equation 5 above.

For example, the upper system may perform cell selection and power allocation for each cell in a direction maximizing proportional fairness when all terminals in the cooperative unit maintain a transmission rate higher than the minimum average transmission rate. In addition, if there is at least one terminal that does not satisfy the minimum average data rate in the cooperative unit, first, the radio resource management may be performed in a direction of minimizing the equation (4). It is desirable to perform cooperative radio resource management so as to effectively overcome the communication performance degradation caused by the interference between cells and satisfy the minimum average data rate.

Then, the higher level system may transmit the cooperative radio resource information performed to each base station in the cooperative unit, and each base station may perform inter-cell cooperative communication using the received cooperative radio resource information.

When a base station in a cooperative unit, not a higher system, performs the first cooperative radio resource management scheme, one base station performing cooperative radio resource management may obtain signal-to-noise ratio and current average rate information of each terminal in the cooperative unit from a higher system. Can be received. The base station performing the cooperative radio resource management which has received this may perform radio resource management in the same manner as the above-described higher system. The cooperative radio resource management information, which is a result of the execution, may be transmitted to the upper system.

3 is a diagram illustrating a preferred embodiment of a second cooperative radio resource management scheme according to the present invention.

Referring to FIG. 3, UEs can measure a signal-to-noise ratio with base stations that can be searched in a cooperative unit and transmit the signal-to-noise ratio to each base station in the cooperative unit. Similar to the first cooperative radio resource management scheme, at this time, the terminal may transmit to another base station in the cooperative unit according to a predetermined period in consideration of the system and the channel environment for optimal signal-to-noise ratio and average rate information transmission. This signal-to-noise ratio and average rate transmission period can be determined by one base station in the cooperative unit. In addition, this period can be determined dynamically.

In the case of the second cooperative radio resource management scheme, each base station may sequentially perform radio resource management by determining the order for each cell (base station). For example, a base station belonging to a cell determined in a corresponding order in an arbitrary order may perform cooperative radio resource management by using cooperative radio resource information performed by the base station corresponding to the previous order, signal-to-noise ratio and average rate information of terminals. Can be. As a result of performing the cooperative radio resource management, the cooperative radio resource information and the average data rate information of the selected specific terminal may be transmitted to the base station belonging to the cell of the next order. In this case, the average rate information of the selected terminal may be transmitted according to a preset average rate transmission period.

For example, consider that the set c (m) of cells is constructed in the order of 1 to m in the cooperative unit c. In the cooperative unit c, it is preferable that the cooperative radio resource management is performed in such a manner that the average transmission rate of all terminals belonging to the set c (m) of the cells in order from 1 to m satisfies the minimum average transmission rate and maximizes the proportional fairness. This can be formulated using the following equations.

을 최소화하는 방향으로 무선 자원을 관리를 수행하여, 단말들이 최소 평균 전송률을 만족할 수 있도록 한다.In the second cooperative radio resource management scheme, a base station belonging to a cell of an m th order may allocate a radio resource to terminals belonging to a corresponding cell to satisfy Equation 5 above. When all terminals belonging to c (m) maintain a transmission rate equal to or greater than the minimum average transmission rate, the terminal is selected in a direction maximizing proportional fairness, and the transmission power of the terminal is allocated. In contrast, if there is at least one terminal that does not satisfy the minimum average data rate in c (m),

By managing the radio resources in a direction to minimize the, so that the terminals can satisfy the minimum average rate.

The base station may transmit the cooperative radio resource management result performed above to the base station belonging to the m + 1 th cell together with the average data rate of each specific terminal selected in c (m). After completion of radio resource management of all base stations in the cooperative unit, each base station may perform inter-cell cooperative communication based on its cooperative radio resource management result.

4 is a diagram illustrating a preferred embodiment of a third cooperative radio resource management scheme according to the present invention.

Referring to FIG. 4, as in the first and second cooperative radio resource management schemes, in the third cooperative radio resource management scheme, terminals measure a signal-to-noise ratio with the base stations searchable in the cooperative unit and transmit the same to each base station in the cooperative unit. Can be. In this case, the terminals may transmit to other base stations in the cooperative unit according to a predetermined period in consideration of the system and the channel environment for optimal signal-to-noise ratio and average transmission rate transmission.

This signal-to-noise ratio and average rate transmission period may be determined by one base station in the cooperative unit. One base station in the cooperative unit may determine the optimal signal-to-noise ratio and the average data rate transmission period in consideration of the system and the channel environment, and notify each other base station in the cooperative unit. At this time, this period may be determined dynamically.

In the third cooperative radio resource management scheme, each base station first performs radio resource management by considering only its own cell, and then transmits the result and average rate information of the selected terminals to other base stations in the cooperative unit. . In this case, the average rate information of the selected terminals may be transmitted according to a preset average rate transmission period. Subsequently, each base station in the cooperative unit may perform cooperative radio resource management by considering its own cell and other cells simultaneously using information received from each other base station.

Hereinafter, a method of allocating and managing radio resources by a base station belonging to an arbitrary cell according to a third cooperative radio resource management scheme will be described. For example, the base station b considers only its own cell and primarily performs radio resource management in a direction in which the average rate of terminals belonging to its own cell satisfies the minimum average rate while maximizing proportional fairness. Resource management can be formulated using the following equations.

에서 최소 평균 전송률을 만족하지 못하는 단말이 하나 이상 존재할 경우에는,

을 최소화하는 방향으로 무선 자원 관리를 수행하여 단말들이 최소 평균 전송률을 만족할 수 있도록 하는 것이 바람직하다. When allocating radio resources primarily in the third cooperative radio resource management scheme, when all terminals belonging to the base station b maintain a transmission rate higher than the minimum average transmission rate, the terminals may be selected in a direction to maximize proportional fairness. If, the set of terminals of base station b

If at least one terminal does not satisfy the minimum average data rate,

It is desirable to perform radio resource management in a direction to minimize the UE so as to satisfy the minimum average data rate.

Each base station in the cooperative unit may transmit the result of the primary radio resource management performed on the terminals belonging to its cell to another base station in the cooperative unit together with the average data rate of the specific terminal selected in the primary radio resource management. The other base station in the cooperative unit may perform the secondary radio resource management in such a way that the average transmission rate of the terminals satisfies the minimum average transmission rate while maximizing the proportional fair by considering other cells in the cooperative unit. And this can be formulated as the following equation.

는 기지국 b에서 1차 무선 자원 관리 때 선택된 특정 단말들을 나타낸다.here

Denotes specific terminals selected in the primary radio resource management in the base station b.

In the third cooperative radio resource management scheme, when secondly allocating radio resources, if there is one or more terminals that do not satisfy the minimum average data rate among specific terminals selected in the primary radio resource management in each base station of the cooperative unit, Radio resource management may be performed in a direction that minimizes Equation 7 so that terminals may satisfy a minimum average data rate. On the other hand, when all of the selected terminals in the primary radio resource management in the base station of the cooperative unit maintains a transmission rate of more than the minimum average data rate, power allocation may be performed in a direction to maximize proportional fairness using Equation (8). Can be.

는 다음 수학식 9와 같이 나타낼 수 있다.here

May be expressed as in Equation 9 below.

And, r _{n , k *} (t) can be expressed as in the following equation (10).

는 단말들의 최소 평균 전송률 보장의 정도를 나타내는 상수이다. 이 값이 클수록 단말들의 최소 평균 전송률 보장을 우선적으로 고려하여 무선 자원 관리를 수행하는 것이 바람직하다.here

Is a constant representing the degree of minimum average rate guarantee of the terminals. As this value increases, radio resource management is preferably performed in consideration of guaranteeing minimum average data rates of terminals.

Thereafter, each base station in the cooperative unit may perform secondary cooperative radio resource management and perform inter-cell cooperative communication based on the result.

FIG. 5 is a diagram illustrating an example of a signal in which a terminal transmits signal-to-noise ratio information for each subchannel of searchable cells required for inter-cell cooperative radio resource management to a base station.

Referring to FIG. 5, this signal may be transmitted from a terminal to a base station through a wireless channel. Each signal-to-noise ratio information may be quantized and transmitted in bit units. In this case, the number of bits required to represent the quantization level, that is, the signal-to-noise ratio information, may be determined in consideration of the system and the channel environment. Each terminal may arrange the signal-to-noise ratio of each searchable cell by subchannel in order of subchannels and transmit them to the base station.

FIG. 6 is a diagram illustrating an example of a signal transmitted from a base station to a higher system for cooperative radio resource management in a first cooperative radio resource method.

Referring to FIG. 6, in the case of the first cooperative radio resource management scheme, each base station in a cooperative unit may use an MS (Mobile Station Identity), an average transmission rate of a corresponding terminal, and a corresponding terminal for inter-cell cooperative radio resource management. The signal-to-noise ratio (SNR) for each subchannel of the searchable cells that have been measured and transmitted can be transmitted to an upper system. The signal may be transmitted from a base station to a higher system through a wired channel or a wireless channel, and the average rate information of each terminal may be quantized and transmitted in bit units. In this case, the number of bits required to represent average rate information may be determined differently according to a system and a channel environment.

FIG. 7 is a diagram illustrating an example of a signal transmitted by a higher system to each base station in a cooperative unit after the cooperative radio resource management is performed in the first cooperative radio resource management scheme.

Referring to FIG. 7, the upper system may transmit a signal including an ID (MS ID) and power allocation information (Pwr Lev: Power Level) of a terminal selected in a subchannel of each cell to each base station. This signal can be transmitted to each base station via a wired or wireless channel. In this case, the power allocation information is quantized and transmitted in units of bits, and the number of bits required to represent the power allocation information may be determined in consideration of a system and a channel environment.

FIG. 8 is a diagram illustrating an example of a signal transmitted from an m-th base station for cooperative radio resource management of an m + 1 th base station in a second cooperative radio resource management scheme.

Referring to FIG. 8, the base station of the m th order performs radio resource management of a cell to which it belongs, and then selects an ID (MS ID) and power allocation information of a terminal selected for each subchannel of each cell in a 1 th to m th order. (Pwr Lev) and the average rate (Avg Rate: Average Rate) of the terminals selected for each cell may be transmitted to the base station in the m + 1 th order. This signal can be transmitted over a wired channel or a wireless channel.

9 is a diagram illustrating an example of a signal for transmitting a result of a base station performing primary cooperative radio resource management to another base station in a third cooperative radio resource management scheme.

Referring to FIG. 9, each base station may transmit a result of performing primary cooperative radio resource management, that is, an ID (MS ID) of a selected terminal for each subchannel and an average avg rate of the selected terminals to other base stations in the cooperative unit. . In this case, the signal may be transmitted through a wired channel or a wireless channel.

10 is a diagram illustrating a signal-to-noise ratio and an average rate transmission period according to the present invention in comparison with a cooperative radio resource management period.

Referring to FIG. 10, the cooperative radio resource management period may be represented as a transmission time interval (TTI) as an example. In addition, the signal-to-noise ratio transmission period and the average rate transmission period may be represented in units of TTIs. The signal-to-noise ratio transmission period and the average transmission rate transmission period of the terminal may be determined by a separate cooperative radio resource management scheme determination apparatus in the first to third cooperative radio resource management schemes.

In addition, in the first cooperative radio resource management scheme, a base station in a higher system or a cooperative unit may decide. In the second cooperative radio resource management scheme, each base station or one base station in the cooperative unit may be determined. In addition, in the third cooperative radio resource management scheme, each base station or one base station in the cooperative unit may be determined.

In order to obtain optimal radio resource management performance, it may be preferable that the signal-to-noise ratio period and the average rate transmission period of the terminal are the same as the cooperative radio resource management period. However, in order to reduce the overhead and the amount of information exchange in a wired or wireless network, the signal-to-noise ratio and the average rate transmission period may be longer than the cooperative radio resource management period in consideration of the system and channel environment.

In the case of a signal-to-noise ratio transmission period, if the channel does not change rapidly with time, that is, if the channel's time selectivity is not large, the period value can be increased to reduce the amount of overhead and to achieve a performance close to that of the small period value. You can get it.

11 is a diagram illustrating a cumulative distribution function of average data rates according to a radio resource management scheme in a single subchannel system.

Referring to FIG. 11, a cooperative radio resource management scheme proposed in an uplink of a subchannel system of a terminal (first cooperative radio resource management scheme according to the present invention: O-CRRM (Optimal-Cooperative Radio Resource Management), according to the present invention). Third Cooperative Radio Resource Management Scheme: A cumulative distribution function (CDF) of average transmission rate according to 2-cooperative radio resource management (CCR) is illustrated through simulation. In this case, the performance of the technique of performing radio resource management independently for each cell without performing cooperative radio resource management between cells is also illustrated.

=4), 최소 요구 평균 전송률은 0.6bits/Hz (Rmin=0.6), 61개의 셀 들로 구성된 4-티어(tier)이며, 셀 별 단말 수는 3 (k=3), 셀 경계에서의 신호대 잡음비는 10dB(ρ_b=10dB), 전력 할당시 레벨은 4 (N_pwr=4), 클러스터 별 기지국 수는 3이라고 가정하였다. The simulation environment has a cell radius of 1 km (Db = 1 km) and a path attenuation index of 4 (

= 4), minimum required average rate is 0.6bits / Hz (Rmin = 0.6), 4-tier of 61 cells, number of terminals per cell is 3 (k = 3), signal band at cell boundary It is assumed that the noise ratio is 10dB (ρ _b = 10dB), the power level is 4 (N_pwr = 4), and the number of base stations per cluster is 3.

In a system that should consider quality of service (QoS) guarantee of the UE first, when performing cooperative radio resource management proposed by the present invention, it effectively reduces interference effects through efficient coordination between base stations. It can be seen from the graph shown in FIG. 11 that the QoS of more terminals can be guaranteed compared to the technique for performing radio resource management (S-RRM: Single-Radio Resource Management).

In addition, it can be seen that the third cooperative radio resource management scheme, which requires a relatively small amount of information exchange compared to the performance of the first cooperative radio resource management scheme, has a significant effect that is almost close to the performance of the first cooperative radio resource management scheme. Can be.

12 is a diagram illustrating a cumulative distribution function of an average data rate according to a radio resource management scheme in a multiple subchannel system.

Referring to FIG. 12, a cooperative radio resource management scheme proposed in the uplink of a multi-subchannel system (first cooperative radio resource management scheme in the present invention: O-CRRM, and third cooperative radio resource scheme in the present invention: 2- The cumulative distribution function of the average data rate according to CRRM) is shown through simulation. In addition, as shown in Figure 12, the performance of the technique (S-RRM) to perform radio resource management independently for each cell without cooperative radio resource management between cells is also shown.

In each cooperative radio resource management scheme, a scheduling technique performed without considering the allocation result of previous subchannels in a process of accumulating an average rate when selecting a terminal for each subchannel (PFS-S: Proportional Fair Scheduling-Single carrier) system (hereinafter referred to as PFS-S) and scheduling schemes (PFS-I: Proportional Fair Scheduling-Instantaneous, hereinafter referred to as PFS-I) which are performed in consideration of the allocation result in previous subchannels. 3 In the case of cooperative radio resource management, when the maximum value of power allocated to each subchannel is limited (peak power constraint) and the maximum value of sum of power allocated by all subchannels is limited ( Sum power constraints were considered respectively.

The simulation environment of the system and the channel is assumed to be the same as in the single subchannel system of FIG. 11, except that the number of subchannels is four. In the multi-subchannel system, when the cooperative radio resource management scheme proposed by the present invention is performed, it is confirmed that the QoS of more terminals can be guaranteed by effectively reducing the influence of intercell interference through inter-base station cooperation.

It can be seen that the use of the channel between subchannels using the sum power constraint condition shows better performance than the use of the peak power constraint condition. Also, in this simulation environment, PFS-S showed better performance than PFS-I.

As described above, in a multi-cellular communication system performing cooperative communication between cells, multi-operation operations required for dirty paper coding (DPC), etc. are unnecessary, and radio resources such as power, time, and frequency are interoperated with each other. By allocating through, it is possible to effectively reduce the inter-cell interference effect with low overhead and calculation amount compared with the prior art.

In addition, the inter-cell cooperative radio resource management scheme according to the present invention may be dynamically selected and performed according to a system and a channel environment. In addition, by determining the signal-to-noise ratio and the average rate transmission period suitable for the system and channel environment, it is possible to reduce the overhead and complexity associated with cooperative radio resource management compared to the prior art.

In addition, the cooperative radio resource management scheme according to the present invention has the advantage of ensuring the minimum transmission rate of more terminals compared to the prior art by considering all the terminals at the same time.

13 is a block diagram showing a configuration of a preferred embodiment of a base station apparatus for performing cooperative radio resource management according to the present invention.

Referring to FIG. 13, a base station apparatus according to the present invention includes a receiving module 1310, a processor 1320, a memory unit 1330, and a transmitting module 1340. The processor 1320 includes a cooperative radio resource management module 1321. The receiving module 1310 may receive a signal or information from another base station or each terminal in the cooperative unit.

The cooperative radio resource module 1321 in the processor 1320 is a module for performing cooperative radio resource management according to the present invention. In the case of the second cooperative radio resource management scheme, the cooperative radio resource module 1321 may perform cooperative radio resource management information performed by a previous base station, each terminal in the cooperative unit, or each terminal belonging to its own cell in the cooperative unit. By using the signal-to-noise ratio information and the current average rate information, it is possible to allocate a radio resource including the transmission power to ensure the minimum average rate of each terminal.

In the second cooperative radio resource management scheme, the cooperative radio resource module 1321 uses the signal-to-noise ratio information received from the terminal in the cell to which the base station belongs to guarantees the minimum average rate for each terminal in the cell to which the base station belongs. The first radio resource including the transmit power may be allocated.

The second radio resource information including the first radio resource information, transmission power allocated by each other base station in the cooperative unit to guarantee the minimum average transmission rate for the terminal in the cell to which the base station belongs, and the other base station itself in the cooperative unit A radio resource including a transmission power for guaranteeing the minimum average transmission rate of the specific terminal may be allocated using the average transmission rate information of the specific terminal among the terminals in the cell.

The memory unit 1330 may store cooperative radio resource management information received from another base station in the cooperative unit, and may store signal to noise ratio information received from the terminal in the cooperative unit.

The transmission module 1340 may transmit cooperative radio resource management information to another base station in the cooperative unit or a terminal in the cooperative unit.

The embodiments described above are the components and features of the present invention are combined in a predetermined form. Each component or feature is to be considered optional unless stated otherwise. Each component or feature may be implemented in a form that is not combined with other components or features. It is also possible to combine some of the components and / or features to form an embodiment of the invention. The order of the operations described in the embodiments of the present invention may be changed. Some configurations or features of certain embodiments may be included in other embodiments, or may be replaced with corresponding configurations or features of other embodiments. It is obvious that the claims may be combined to form an embodiment by combining claims that do not have an explicit citation relationship in the claims or as new claims by post-application correction.

Embodiments according to the present invention may be implemented by various means, for example, hardware, firmware, software, or a combination thereof. In the case of a hardware implementation, an embodiment of the present invention may include one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), FPGAs ( Field Programmable Gate Arrays), processors, controllers, microcontrollers, microprocessors, and the like.

In the case of implementation by firmware or software, an embodiment of the present invention may be implemented in the form of a module, procedure, function, etc. that performs the functions or operations described above. The software code may be stored in a memory unit and driven by a processor. The memory unit may be located inside or outside the processor, and may exchange data with the processor by various known means.

It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the above detailed description should not be interpreted as limiting in all aspects and should be considered as illustrative. The scope of the invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the invention are included in the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included as part of the detailed description in order to provide a thorough understanding of the present invention, provide an embodiment of the present invention and together with the description, illustrate the technical idea of the present invention.

1 is a diagram illustrating an example of an inter-cell cooperative radio resource management scheme;

2 illustrates a preferred embodiment of a first cooperative radio resource management scheme according to the present invention;

3 is a view showing a preferred embodiment of a second cooperative radio resource management scheme according to the present invention;

4 is a diagram showing a preferred embodiment of a third cooperative radio resource management scheme according to the present invention;

5 is a diagram illustrating an example of a signal in which a terminal transmits signal-to-noise ratio information for each subchannel of searchable cells required for inter-cell cooperative radio resource management to a base station;

6 illustrates an example of a signal transmitted from a base station to a higher system for cooperative radio resource management in a first cooperative radio resource method;

FIG. 7 is a diagram illustrating an example of a signal transmitted by a higher system to each base station in a cooperative unit as a result of a cooperative radio resource management in a first cooperative radio resource management scheme; FIG.

8 is a diagram illustrating an example of a signal transmitted by a base station in an m order for cooperative radio resource management of a base station in an m + 1 order in a second cooperative radio resource management scheme;

9 is a diagram illustrating an example of a signal for transmitting a result to another base station after a base station performs primary cooperative radio resource management in a third cooperative radio resource management scheme;

10 is a diagram illustrating a signal-to-noise ratio and an average rate transmission period in comparison with a cooperative radio resource management period according to the present invention;

11 is a view showing a cumulative distribution function of an average data rate according to a radio resource management scheme in a single subchannel system;

12 is a diagram illustrating a cumulative distribution function of an average data rate according to a radio resource management scheme in a multiple subchannel system.

13 is a block diagram showing a configuration of a preferred embodiment of a base station apparatus for performing cooperative radio resource management according to the present invention.

Claims (20)

In the method for the management of two or more base stations in the cooperative unit radio resource management, Receiving signal-to-noise ratio information measured for each subchannel of each cell to which each base station in the cooperative unit belongs from the base station in the cooperative unit; Allocating a radio resource including a transmission power value for guaranteeing a minimum average transmission rate for each terminal by using the received signal-to-noise ratio information and the current average transmission rate information of each terminal; And And transmitting the allocated radio resource information to each base station for each terminal. The method of claim 1, A radio resource including a transmission power value that guarantees the minimum average rate of each terminal is allocated to minimize the following equation C using the following equations A and B: Equation A

Equation B

Equation C

Where R _min is the minimum average bit rate, the [] ⁺ sign is a zero indicating if the value of [] is less than zero, and a sign indicating its value if greater than zero,

Is an instantaneous data rate that can be obtained when a k-th terminal is allocated at a t-th scheduling time in an uplink n-th subchannel,

Is the transmit power at the t-th scheduling time of the k-th terminal in the n-th subchannel,

Is a set of terminals of base station b belonging to cooperative unit c.

in

Transmission power at the t-th scheduling time when the first terminal is allocated in the n-th subchannel,

Is

The first terminal is a channel of base station b,

Is the variance of the noise,

Is the number of subchannels,

Is a function representing 1 when the k-th terminal is allocated at the t-th scheduling time in the n-th subchannel and 0 when it is not allocated. 3. The method of claim 2, Wherein the radio resource uses the equations (A) and (B) and is allocated to satisfy the following equation D to maximize proportional fairness: [Equation D]

here

Is a constant representing the degree of minimum average rate guarantee of the terminals. The method of claim 1, The measured signal-to-noise ratio information is quantized and transmitted in units of bits. The method of claim 1, The signal-to-noise ratio information is transmitted according to a preset period. The method of claim 1, The signal-to-noise ratio information measured for each subchannel of each cell to which each base station in the cooperative unit is measured by each terminal in the cooperative unit. In the method for the base station in the cooperative unit to perform the cooperative radio resource management sequentially, Receiving radio resource information which has previously performed radio resource management from another base station in the cooperative unit; Receiving signal-to-noise ratio information measured for each subchannel from each terminal in a cooperative unit or each terminal in a cell to which the base station itself in the cooperative unit belongs; Minimum average of each terminal using the received radio resource information of the other base station in the cooperative unit, the signal-to-noise ratio information of each terminal in the cell to which the base station in the cooperative unit or the base station itself in the cooperative unit belongs and the current average rate information Allocating a radio resource comprising a transmission power to guarantee a transmission rate; And And transmitting the allocated radio resource information and average transmission rate information of the selected specific terminal to a base station to perform cooperative radio resource management according to a preset order. The method of claim 7, wherein A radio resource including a transmission power value that guarantees the minimum average rate of each terminal is allocated to minimize the following equation C using the following equations A and B: Equation A

Equation B

Equation C

Where R _min is the minimum average bit rate, the [] ⁺ symbol is 0 if the value of [] is less than 0, and the symbol represents the value if it is greater than 0,

Is an instantaneous data rate that can be obtained when a k-th terminal is allocated at a t-th scheduling time in an uplink n-th subchannel,

Is the transmit power at the t-th scheduling time of the k-th terminal in the n-th subchannel,

Is a set of terminals of base station b belonging to cooperative unit c.

in

Transmission power at the t-th scheduling time when the first terminal is allocated in the n-th subchannel,

Is

The first terminal is a channel of base station b,

Is the variance of the noise,

Is the number of subchannels,

Is a function representing 1 when the k-th terminal is allocated at the t-th scheduling time in the n-th subchannel and 0 when it is not allocated. The method of claim 8, Wherein the radio resource is allocated to satisfy the following equation D based on equations A and B to maximize proportional fairness: Equation C

here

Is a constant representing the degree of minimum average rate guarantee of the terminals. The method of claim 7, wherein The signal-to-noise ratio information is quantized and transmitted in units of bits, cooperative radio resource management method. The method of claim 7, wherein The signal-to-noise ratio information is transmitted according to a preset period. In the method for the base station in the cooperative unit to perform cooperative radio resource management, Receiving signal-to-noise ratio information measured by each terminal for each subchannel from each terminal in a cell to which the base station belongs; Allocating a first radio resource including transmission power for guaranteeing a minimum average transmission rate for each terminal in a cell to which the base station itself belongs by using the received signal-to-noise ratio information; A second radio resource information including transmission power allocated by each other base station in the cooperative unit to guarantee a minimum average rate for the terminal in the cell to which the base station belongs, and a specific terminal in a cell to which the other base station in the cooperative unit belongs. Receiving average rate information on a terminal from another base station in the cooperative unit; And Allocating a radio resource including a transmission power for guaranteeing a minimum average transmission rate of the specific terminal by using the average data rate information, the first radio resource information, and the second radio resource information for the specific terminal; Collaborative radio resource management method. The method of claim 12, And transmitting the average rate information and the first radio resource information for a specific terminal among terminals belonging to the cell of the base station to another base station in the cooperative unit. The method of claim 12, Wherein the first radio resource and the second radio resource are allocated to minimize the following equation C using the following equations A and B: Equation A

Equation B

Equation C

Where R _min is the minimum average bit rate, the [] ⁺ symbol is 0 if the value of [] is less than 0, and the symbol represents the value if it is greater than 0,

Is an instantaneous data rate that can be obtained when a k-th terminal is allocated at a t-th scheduling time in an uplink n-th subchannel,

Is the transmit power at the t-th scheduling time of the k-th terminal in the n-th subchannel,

Is a set of terminals of base station b belonging to cooperative unit c.

in

Transmission power at the t-th scheduling time when the first terminal is allocated in the n-th subchannel,

Is

The first terminal is a channel of base station b,

Is the variance of the noise,

Is the number of subchannels,

Is a function representing 1 when the k-th terminal is allocated at the t-th scheduling time in the n-th subchannel and 0 when it is not allocated. 15. The method of claim 14, The first radio resource and the second radio resource utilize the equations A and B and are allocated to satisfy the following equation D to maximize proportional fairness. : [Equation D]

The method of claim 12, A cooperative radio resource management method for allocating a radio resource including a transmission power for guaranteeing a minimum average data rate of a specific terminal is allocated to minimize the following equation G using the following equation E and the following equation F: [Equation E]

Equation F

[Equation G]

here

Is selected terminal among the terminals in the cell to which the base station b belongs,

Is the average transmission rate at the t + 1st scheduling time of the selected terminal among the terminals belonging to the base station b own cell belonging to the cooperative unit c,

Is an instantaneous data rate that can be obtained if k ^* th UEs are allocated at the t th scheduling time in the nth subchannel of the uplink,

Is the transmit power at the t th scheduling time of the k ^* th UE in the n th subchannel,

Is a set of terminals of base station b belonging to cooperative unit c.

in

Transmission power at the t-th scheduling time when the first terminal is allocated in the n-th subchannel,

Is the channel of the k ^* -th terminal and the base station b at the t-th scheduling time in the n-th subchannel,

Is

Channel of the first terminal and the base station b,

Is the variance of the noise,

Is the number of subchannels,

Is a function representing 1 when the k-th terminal is allocated at the t-th scheduling time in the n-th subchannel and 0 when it is not allocated. The method of claim 16, The radio resource for the specific terminal uses the equation (E) and the equation (F), and is allocated to satisfy the following equation (H) to maximize the proportional fairness (proportional fairness): [Equation H]

here

Is a constant representing the degree of minimum average rate guarantee of the terminals. The method of claim 12, The signal-to-noise ratio information is quantized and transmitted in units of bits, cooperative radio resource management method. The method of claim 12, The signal-to-noise ratio information is transmitted according to a preset period. The method of claim 12, And wherein the specific terminal is selected to maximize proportional fairness.

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