KR20070117125A - Appaturus and method for downlink power control of relay station in broadband wireless access communication systemem - Google Patents

Abstract

An apparatus and a method for controlling downlink power of a relay station in a broadband wireless access communication system are provided to reduce a load of transmission and reception of control signals in an overall system by fairly controlling transmission power of relay stations through information collected from the multiple relay stations. A relay station average downlink gain calculating unit(407) calculates a channel gain between a relay station(430) and a user terminal(440) based on a channel gain transmitted by the user terminal(440) under the relay station(430). An inter-relay station interference level detector(406) detects an interference level between the relay station(430) and an adjacent relay station. The information outputted by the relay station average downlink gain calculating unit(407) and the inter-relay station interference level detector(407) are transmitted to a base station(420). A transmission power control instruction, which has been calculated based on the received information by the base station(420) and then transmitted from the base station(420), is received to control the transmission power of the relay station(430).

Description

APPARATUS AND METHOD FOR DOWNLINK POWER CONTROL OF RELAY STATION IN BROADBAND WIRELESS ACCESS COMMUNICATION SYSTEMEM}

1 is a view schematically showing the structure of a general IEEE 802.16e communication system;

2 is a diagram schematically showing a structure of a broadband wireless communication system using a general relay station;

3 illustrates a communication link between a base station and a user terminal using a general relay station;

4 is a block diagram illustrating the structure of a base station, a relay station, and a user terminal according to an embodiment of the present invention;

5 illustrates a downlink frame from a relay station to a user terminal according to an embodiment of the present invention;

6 is a flowchart illustrating a process in a base station according to an embodiment of the present invention, and

7 is a flowchart illustrating a process in a relay station according to an embodiment of the present invention.

The present invention relates to a broadband wireless access communication system, and more particularly, to an apparatus and method for reducing an influence on a user terminal by adjusting a transmission power of a relay station in a broadband wireless access communication system in which a relay station exists.

In the 4th Generation (hereinafter, referred to as '4G') communication system, providing users with services having various quality of service (QoS) with a transmission rate of about 100 Mbps. Active research is in progress. In particular, in the current 4G communication system, broadband wireless access such as a wireless local area network (LAN) system and a wireless urban area network (MAN) system Access: Research is being actively conducted to support high-speed services in the form of guaranteeing mobility and quality of service (QoS) in a BWA communication system. Also, representative communication systems are the Institute of Electrical and Electronics Engineers (IEEE) 802.16a communication system and the IEEE 802.16e communication system.

The IEEE 802.16a communication system and the IEEE 802.16e communication system are orthogonal frequency division multiplexing (OFDM) for supporting a broadband transmission network on a physical channel of the wireless MAN system. (Orthogonal Frequency Division Multiple Access (hereinafter referred to as 'OFDMA')). The IEEE 802.16a communication system is a system currently considering only a single cell structure and a state in which a subscriber station (hereinafter referred to as SS) is fixed, that is, no mobility of the SS is considered. In contrast, the IEEE 802.16e communication system is a system considering mobility of the SS in the IEEE 802.16a communication system, and the SS having the mobility is called a mobile station. Hereinafter, the mobile terminal and the subscriber terminal will be referred to as a user terminal.

In the conventional IEEE 802.16e communication system, since a signal is transmitted and received through a direct link between a fixed base station and a user terminal, a reliable wireless communication link can be easily configured between the base station and the user terminal. However, the IEEE 802.16e communication system has a low flexibility in configuring a wireless network since the location of the base station is fixed, and thus, it is difficult to provide an efficient communication service in a wireless environment in which traffic distribution or call demands are severe. In order to overcome such drawbacks, a multi-hop relay data transmission scheme may be applied to a general cellular wireless communication system such as the 802.16e communication system by using a fixed relay station, a relay station having a mobility or general user terminals. Can be. The multi-hop relay method may have an effect of expanding the area of the base station. The structure of a general IEEE 802.16e communication system is as follows.

1 is a diagram schematically illustrating a structure of a general IEEE 802.16e communication system.

Referring to FIG. 1, the IEEE 802.16e communication system has a multi-cell structure, that is, a specific base station having a cell 150 different from a specific cell 100 and managing the specific cell 100. 110, another base station 140 that manages the other cell 150, and a plurality of user terminals 111, 113, 130, 151, and 153. Here, signal transmission and reception between the base stations 110 and 140 and the user terminals 111, 113, 130, 151, and 153 is performed using the OFDM / OFDMA scheme. When the specific user terminal 130 of the user terminals 111, 113, 130, 151, and 153 exists in a boundary area between the specific cell 100 and the other cell 150, the moving direction or other reasons Therefore, handover may be performed. That is, when the specific user terminal 130 moves to another cell 150 managed by the other base station 140 while transmitting and receiving a signal with the specific base station 110, a handover occurs and the specific user terminal The serving BS of 130 is changed from the specific base station 110 to the other base station 140.

In the general IEEE 802.16e communication system, as shown in FIG. 1, since a signaling transmission and reception is performed between a fixed base station and a user terminal, a reliable wireless communication link can be easily configured between the base station and the user terminal. However, the IEEE 802.16e communication system has a low flexibility in configuration of the wireless network because the location of the base station is fixed, and thus, it is difficult to provide an efficient communication service in a wireless environment in which traffic distribution or call demand is severely changed.

In order to overcome such drawbacks, a multi-hop relay data transmission scheme may be applied to a general cellular wireless communication system such as the 802.16e communication system by using a fixed relay station, a relay station having a mobility or general user terminals. Can be. As a result, the wireless communication system using the multi-hop relay method can quickly reconfigure the network in response to changes in the communication environment, and more efficiently operate the entire wireless network. A wireless communication system using the multi-hop relay scheme can expand a cell service area and increase system capacity. That is, when the channel state between the base station and the user terminal is poor, a relay station is installed between the base station and the user terminal to configure a multi-hop relay path through the relay station, thereby providing a wireless channel having a better channel state to the user terminal. Can be. In addition, by using the multi-hop relay method in a cell boundary region having a poor channel state from a base station, it is possible to provide a faster data channel and expand a cell service area.

2 schematically illustrates a structure of a broadband wireless communication system using a general relay station.

Referring to FIG. 2, the wireless communication system using the multi-hop relay method has a multi-cell structure, that is, has a cell 240 different from a specific cell 200, and manages the cells 200 and 240. Base station 210, 250, a plurality of user terminals (211, 213, 251, 253, 255) located in the area of the cell (200, 240) and the base station (210, 250) managed but the cell In the plurality of user terminals 221, 223, 261, and 263 existing in the other areas 230 and 270 outside the (200, 240) area, the base stations 210 and 240 and the other areas 230 and 270. It consists of relay stations 220, 260 which provide a multi-hop relay path between existing user terminals 221, 223, 261, 263.

Here, signal transmission and reception between the base stations 210 and 250, the relay stations 220 and 260, and the user terminals 211, 213, 221, 223, 251, 253, 255, 261 and 263 are performed in the OFDM / The OFDMA method is used. In this case, although the user terminals 211 and 213 and the specific relay station 220 included in the specific cell 200 area may directly transmit and receive a signal with the specific base station 210, the specific relay station 220 The user terminals 221 and 223 present in the area 230 may not directly transmit or receive a signal with the specific base station 210. Accordingly, the specific relay station 220 manages the area 230 of the specific relay station 220 and between the specific base station 210 and the user terminals 221 and 223 that cannot directly transmit or receive a signal as described above. Relay the transmission and reception signal. That is, the user terminals 221 and 223 may transmit and receive signals to and from the specific base station 210 through the specific relay station 220.

In addition, although the user terminals 251, 253, and 255 included in the area of the other cell 240 and the other RS 260 may directly transmit / receive signals to / from the other BS 250, the other RS 260 may be used. The user terminals 261 and 263 present in the region 270 of FIG. 2 do not directly transmit and receive signals with the other base station 250. Accordingly, the other relay station 260 manages the area of the other relay station 260 and the signal between the other base station 250 and the user terminals 261 and 263 that cannot directly transmit or receive a signal as described above. Relays That is, the user terminals 261 and 263 may transmit and receive signals to and from the other base station 250 through the other relay station 260. Although not illustrated, the base stations 210 and 250 may transmit and receive signals with a plurality of relay stations.

Signal link configuration between the relay station 220, 230, the base station (210, 250) and the user terminal (221, 223, 260, 263) is as follows.

3 illustrates a communication link between a base station and a user terminal using a general relay station.

3 shows two downlinks 302 and 304 and two uplinks 306 and 307. The first downlink 302 of the two downlinks is a case where the base station 301 transmits information to the relay station 303, and the second downlink 304 is the relay station 303 is connected to the user terminal 305. This is the case when the information is transmitted to the. During the transmission of the second downlink 304, the base station 301 stops transmitting information.

In the second downlink, all relay stations including the relay station 303 transmit information using the same frequency band, and a plurality of user terminals including the user terminal 305 receive the information. In this case, the user terminal 305 may receive interference from other relay stations except for the relay station 303 to which the user terminal 305 belongs. The cause of the interference may be the channel gain between the relay station 303 and the user terminal 306 as well as the transmission power of the relay station 303.

Therefore, in order to reduce the interference and increase the overall performance, the relay stations including the relay station 303 need to adjust the amount of transmission power to each other. As a result, there is a need for an apparatus and method capable of adjusting the magnitude of transmit power. This necessity is the same even when the relay station can move.

An object of the present invention is to provide an apparatus and method for downlink power control of a relay station that is movable in a broadband wireless access communication system.

Another object of the present invention is to provide an apparatus and method for calculating power quality from channel preamble information of a user terminal and a preamble of a neighboring relay station, which are generally received in a mobile station capable of moving a broadband wireless access communication system, and transmitting the information to the base station. In providing.

It is still another object of the present invention to provide an apparatus and method for calculating a power regulation direction and power regulation amount for a relay station from information reported by a relay station in a base station of a broadband wireless access communication system and instructing the corresponding relay station to adjust.

According to a first aspect of the present invention for achieving the above object, in the apparatus of the relay station for downlink power control in a broadband wireless access communication system, the relay station and the user based on the channel gain transmitted by the user terminal under the relay station And a relay station average downlink gain calculator for calculating channel gain between terminals and an interference level detector between the relay stations for detecting the degree of interference between the relay station and other adjacent relay stations.

According to a second aspect of the present invention for achieving the above object, in a device of a base station for downlink power control in a broadband wireless access communication system, information transmitted by each relay station belonging to the base station and previously stored information It characterized in that it comprises a relay station power control unit for calculating and indicating the transmission power adjustment for each of the relay station from.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

The present invention describes a power control apparatus and method for a relay station for improving overall performance in a broadband wireless access communication system using a mobile relay station.

In addition, the following description also describes a power regulation instruction from the base station to the relay station, but the same may be applied to power regulation between the upper relay station and the lower relay station.

In addition, the following description describes a broadband wireless access communication system as an example, but the technology of the present invention may be equally applicable to a cellular-based communication system using a relay station.

The structure of a base station, relay station, and user terminal using the technique of the present invention is as follows.

4 is a block diagram illustrating structures of a base station, a relay station, and a user terminal according to an embodiment of the present invention.

4 illustrates a base station 420, a relay station 430, and a user terminal 440, respectively. Although not shown in the present invention, it is assumed that the number of relay stations is R. The relay station 430 represents a specific relay station of one of the R relay stations. In addition, it is assumed that each of the R relay stations has K user terminals.

Brief description of each function is as follows.

The base station 420 transmits the data received from an upper network node, for example, (Acees Control Router) (ACR) to the relay station 430. The relay station 430 transmits the data received from the base station 420 to the user terminal 440. In addition, the relay station 420 calculates the degree of interference from other relay stations and transmits it to the base station 420.

The user terminal 440 transmits channel quality information (CQI) during communication to the relay station 440. The relay station 430 transmits the channel quality information transmitted from the user terminal 440 to the base station 420.

The base station 420 calculates the amount of power to be adjusted by the relay station 430 based on the information transmitted from the relay station 430, transmits the amount of power to the relay station 430, and receives the adjusted amount of power. ) Adjusts the power as indicated.

The building blocks of the base station 420, the relay station 430, and the user terminal 440 to perform the operation are as follows.

First, a configuration block of the base station 420 will be described.

The base station communication unit 401 transmits data received from an upper network node, for example, (Acees Control Router) (ACR) to the relay station 430.

The RS 402 controls the channel quality information of the user terminal 440 received from the RS 430 and the degree of interference from other RSs on the RS 420 (step 412). Information), a list of other relay stations (the information in step 412), and the like, to calculate the power size that the relay station 420 needs to adjust.

The base station 420 performs the above process for all connected relay stations. The calculated adjusted power size is transmitted to the relay station 430 through the base station communication unit 401, and changes the transmission power size of the relay station transmitter 405. Step 413 shows the object to which the calculated regulated power size affects.

The relay station receiver 403 of the building block of the relay station 430 receives the data transmitted by the base station 420. When the reception process is described in detail, the received radio frequency is changed to the baseband, analog / digital conversion is performed, and CP (Cycle Prefix) is removed. Then, after the serial / parallel transformation, FFT (Fast Fourier Tranform) transformation, channel estimation, demodulation process is performed.

The AF / DF processing unit 430 performs the AF method processing or the DF method processing on the signal provided by the relay station receiving unit 403 according to a predefined algorithm, and then the relay station transmitting unit 405. To provide.

The AF method is a method of receiving and then amplifying and transmitting a signal, and the DF method is a method of decoding and then re-coding a received signal and transmitting the same. The AF technique is greatly influenced by the signal noise from the transmitting side to the relay station, and the DF technique is greatly influenced by the accuracy of signal transmission from the transmitting side to the relay station.

The RS 405 transmits the information to the user terminal 440 after performing the reverse process of the RS receiver 401 on the information provided by the AF / DF processing unit 404.

The relay station average DL gain calculator 407 calculates an average downlink gain based on the channel quality information 410 provided by the user terminal 440 and provides the average downlink gain to the base station 402.

The inter-station interference level detector 406 calculates and provides the degree of interference between the relay stations to the base station 402.

The average downlink gain providing process (411 process) and the interference degree providing process (412 process) between RSs are provided through uplink. The information and the acquisition process provided by the inter-station interference level detector 406 to the base station 402 will be described with reference to FIG. 5.

The user terminal communication unit 440 of the building block of the user terminal 440 decodes the information transmitted from the relay station 430 or the base station 420 in accordance with the standard, and transfers it to the upper network layer.

The channel estimator 409 performs channel estimation on the information transmitted from the relay station 430 or the base station 420, and then transmits the channel quality information to the relay station 430 and the user terminal communication unit 440. (410 process). The channel quality information (provided in step 410) is provided through uplink.

5 illustrates a downlink frame from a relay station to a user terminal according to an embodiment of the present invention.

Referring to FIG. 5, data transmission of the RS is divided into transmission of the downlink frame 504 and transmission of the uplink frame 505 due to a time division duplex (TDD). The relay station uses the same frequency band or carrier. Each relay station may in turn receive the preamble channel of the other relay station.

That is, while relay station 2 and relay station 3 are transmitting the respective preambles 503A and 503B, the relay station 1 receives 501 without transmitting the preamble. Subsequently, RS 2 does not transmit the preamble 503A in the next timeslot and RS 3 does not transmit the preamble 503B in the subsequent timeslot.

If the change in the radio frequency channel environment used by the RS is small, the frequency of the preamble reception by the RS may be lowered.

Now, control messages exchanged between the base station, the relay station, and the user terminal will be described. Table 1 shows the control message.

Control message Sending node-> receiving node Contents

User terminal-> relay station Channel gain between the user station and the relay station measured at the user terminal

Relay station-> base station Average downlink channel gain between the relay station and the user terminal for all user terminals under a specific relay station (r)

Relay station-> base station Set of relay stations acting as interference sources for a particular relay station (r)

Relay station-> base station The degree to which each relay station in the set of relay stations acts as an interference source for a specific relay station (r)

Base station-> relay station Whether transmission power is increased or decreased for specific relay stations (r)

Base station-> relay station Degree of adjustment of the transmit power for a specific relay station (r)

The control message exchange process and operation algorithm for power control of the relay station between the base station, the relay station and the user terminal are as follows.

First, with reference to the user terminal, channel estimation is required for coherent detection or demodulation of received information. In most communication systems, channel information is fed back from the terminal and can be utilized in adaptive coding and modulation.

)이 상기 사용자 단말기에서 중계국으로 피드백된다고 가정한다.In the present invention, there are k user terminals per specific relay station, and the channel gain between the average relay station and the user terminal for the carrier assigned to the user terminal (

) Is fed back to the relay station from the user terminal.

And the present invention assumes that there are r relay stations and assumes that all r relay stations calculate the average channel gain for all user terminals existing under each relay station.

)은 하기 <수학식 1>과 같이 나타낼 수 있다.Average channel gain for all user terminals

) Can be expressed as Equation 1 below.

는 특정 사용자 단말기 k에 할당된 반송파에 대한 평균 중계국 대 사용자 단말기 사이의 채널이득을 나타낸다.Here, K is the number of user terminals included in a specific relay station,

Denotes the channel gain between the average relay station and the user terminal for the carrier assigned to the specific user terminal k.

)이라고 한다. 그리고 상기 활성집합에 포함되는 임의의 중계국으로부터 수신하여 측정한 프리앰블 세기를 활성집합 수신 프리앰블 전력수신(

) 이라고 한다. 상기 중계국은 상기

,

,

를 상기 기지국으로 피드백한다. Now, with reference to the relay station, the relay station receives the preambles of other relay stations and measures the size as described in FIG. A set of relay stations that a particular relay station (r) can receive and measure

It is called). The preamble strength received from any relay station included in the active set and measured by the active set receiving preamble power reception (

) Is called. The relay station is

,

,

Feeds back to the base station.

,

,

를 수신하여 간섭전력(

)을 계산한다. 상기

는 상기 특정 중계국(r)이 상기 활성집합(r)에 포함된 다른 중계국(r'이라고 나타내기로 한다.)(r')로부터의 간섭받는 전력를 나타내고 하기 <수학식 2>와 같이 정의된다. Now, with reference to the base station, the base station

,

,

Receives the interference power (

Calculate remind

The specific relay station r is represented by another relay station r 'included in the active set r. The interference power from the r' is represented by Equation 2 below.

은 특정 중계국(r)이 상기 다른 중계국(r')로부터 영향받는 총 간섭전력을 나타낸다. here

Denotes the total interference power at which a particular relay station r is affected by the other relay station r '.

)은 하기 <수학식 3>과 같이 정의된다. Further, the ratio of the interference that the other relay station r 'to the specific relay station r (

) Is defined as in Equation 3 below.

는 상기 특정 중계국(r)의 송신전력을 나타낸다.here,

Denotes the transmission power of the specific relay station r.

은 보다 간단한 계산을 위해

로 표시된 몇 개의 레벨로 정량화하면 하기 <수학식 4> 와 같이 나타낼 수 있다. 본 발명에서는 일 실시 예로 세개의 레벨로 표시하지만 상기 레벨의 범위는 고정된 것이 아니고, 구현상황 또는 기타 상황에 따라 변할 수 있다.remind

For a simpler calculation

When quantified at several levels indicated by Equation 4, Equation 4 may be represented. In the present invention, three levels are shown as an example, but the range of the levels is not fixed and may vary according to implementation or other situations.

는 구현시 해당 규격에서 설정되는 임계값이다.here,

Is the threshold set by the specification in the implementation.

Whether the specific relay station r needs to increase or decrease the transmission power depends on how much the specific relay station r operates as an interference source.

, 여기서 특정 중계국(r)은,

이다.)을 도입하여 설명한다. 상기 임의의 중계국은 상기 특정 중계국으로부터 간섭을 감지하는 임의의 중계국을 나타낸다. 즉, 상기 특정 중계국(r)이 간섭원으로 동작할 경우를 나타낸다.The present invention is directed to any relay station (

, Where a specific relay station (r)

Will be explained. The arbitrary relay station represents any relay station that detects interference from the specific relay station. That is, it shows the case where the specific relay station r operates as an interference source.

)과 상기 임의의 중계국에서의 총 간섭전력에 대한 상기 특정 중계국에 의한 간섭전력의 비율(

)은 하기 <수학식 5>와 같이 정의된다.Transmission power of the specific relay station (

) And the ratio of the interference power by the specific relay station to the total interference power at any relay station (

) Is defined as in Equation 5 below.

은 구현시 해당 규격에서 설정되는 값이다. 그리고 특정 중계국(r)의 최대, 최소 전송 전력을 나타낸다. 그리고

는 특정 중계국의 전송전력,

는 임의의 중계국에서의 총 간섭전력에 대한 상기 특정 중계국에 의한 간섭전력의 비율을 나타낸다.here,

Is the value set in the specification in the implementation. And the maximum and minimum transmit power of the specific relay station r. And

Is the transmit power of a particular relay station,

Denotes the ratio of the interference power by the specific relay station to the total interference power at any relay station.

의 크기는 일반화(normalized)된 전력으로 정의된다. 상기 특정 중계국이 더 큰 송신전력을 가지고 송신할수록, 상기

의 크기는 비례적으로 증가한다. 그리고

은 상기 임의의 중계국이 상기 특정 중계국(r)에 의해 영향받는 간섭의 비율을 나타내므로 상기 특정 중계국(r)이 많은 비율을 차지할수록, 상기

의 크기는 비례적으로 증가한다.

The magnitude of is defined as the normalized power. As the specific relay station transmits with greater transmission power,

The size of increases proportionally. And

Denotes the ratio of interference influenced by the specific relay station r, so that as the specific relay station occupies a large proportion,

The size of increases proportionally.

From the point of view of the arbitrary relay station, the specific relay station should lower the transmission power as the specific relay station transmits with higher power, and the specific relay station should lower the transmission power as more interference occurs from the specific relay station.

If the above case is defined using a specific probability, it may be expressed as in Equations 6 and 7 below.

는 구현시 해당 규격에서 설정되는 값이다. 그리고

범위인

는 유니폼 랜덤(uniform random) 변수이다.here,

Is the value set in the specification in the implementation. And

Range

Is a uniform random variable.

If it demonstrates from the viewpoint of said arbitrary relay station, it is as follows.

는 상기 임의의 중계국이 상기 특정 중계국으로부터 간섭을 받는 정도를 나타낸다. 그리고

은 상기 특정 중계국이 상기 임의의 중계국에 미치는 간섭정도에 따른 전력조절량을 나타낸다. 상기 특정 중계국으로부터의 간섭이 크지 않다면 간섭레벨은 0이 된다. 이 경우 상기 특 정 중계국은

정도 송신전력을 증가시킨다. 상기 특정 중계국로부터의 간섭이 크다면, 간섭레벨은 1 또는 2가 된다. 이 경우, 상기 특정 중계국은

정도 송신전력을 감소시켜야 한다. 상기 특정 중계국로부터의 간섭이 크지도 작지도 않은 경우, 상기 특정 중계국은 현재의 송신전력을 유지한다.

Denotes the extent to which any relay station is subject to interference from the specific relay station. And

Denotes a power control amount according to the degree of interference that the specific relay station affects the arbitrary relay station. If the interference from the specific relay station is not large, the interference level is zero. In this case, the specific relay station

Increase transmit power. If the interference from the specific relay station is large, the interference level is one or two. In this case, the specific relay station

The transmit power should be reduced. If the interference from the specific relay station is neither large nor small, the specific relay station maintains the current transmission power.

If the degree of each interference that the specific relay station exerts on all arbitrary relay stations is shown to be large, an average of weighted weights for the specific relay station is obtained to determine whether the power increases or decreases in power and the set amount thereof.

The degree of each interference the particular relay station exerts on all arbitrary relay stations may be normalized by the distance between the particular relay station and any relay station.

)는 평균 하향링크 채널이득 비율을 평균 간섭 경로 이득(average path gain)으로 나눈 것으로 정의하고 하기 <수학식 8>과 같다.Said "distance" (

) Is defined as the average downlink channel gain ratio divided by the average interference path gain and is expressed by Equation 8 below.

는 상기 특정 중계국에서 임의의 중계국까지 의 채널또는 링크이득을 나타낸다.

는 평균채널이득을 상기

로 나눈 값이다. 만약, 상기

이 크다면, 일반적 채널의 링크가 간섭링크보다 훨씬 더 품질이 좋은 것을 나타낸다. 따라서 상기 임의의 중계국은 상기 특정 중계국으로부터의 간섭의 영향이 작고 서로 멀리 떨어져 있다고 할 수 있다.here,

Denotes the channel or link gain from the specific relay station to any relay station.

Recall average channel gain

Divided by. If above

If this is large, then the link of the general channel is much better quality than the interfering link. Thus, any of the relay stations may be said to have a small effect of interference from the specific relay station and be far from each other.

이 작다면, 상기 일반적 채널의 링크가 간섭링크와 비슷하거나 나쁘다는 것을 나타낸다. 따라서 상기 임의의 중계국은 상기 특정 중계국으로부터의 간섭의 영향이 크고 서로 가깝다고 할 수 있다.If above

If this is small, it indicates that the link of the general channel is similar or worse than the interfering link. Therefore, it can be said that the arbitrary relay stations are large and close to each other by the influence of the interference from the specific relay station.

)은 하기 <수학식 9>를 이용하여 결정된다.Power control direction of the specific relay station (

) Is determined using Equation 9 below.

은 특정 중계국과 임의의 중계국 사이의 일반화된(Normalized) 거리이다. here,

Is the normalized distance between a particular relay station and any relay station.

When the power regulation direction of Equation 9 is +1, the power should be increased by a predetermined value. In the case of -1, the amount of power reduction is determined according to the interference level of any relay station closest to the vicinity.

)이 간섭을 받지 않고 있는 경우에는, 송신 전력의 크기는 변화가 없어도 가능하나, 간섭을 받고 있는 경우에는 기 정의된 방식에 의해 송신 전력의 크기를 감소한다. 상기 과정은 하기 <수학식 10>과 동일하다.If a predetermined relay station (

In the case where) is not interfered with, the magnitude of the transmission power can be changed without any change, but when the interference is not reduced, the magnitude of the transmission power is reduced by a predefined method. The process is the same as Equation 10 below.

은 구현시 해당 규격에서 설정된다. here,

Is set in the specification at implementation.

은 상기 소정의 중계국에 전달되고, 상기 소정의 중계국은 하기 <수학식 11>을 이용하여 송신전력을 조절한다.remind

Is transmitted to the predetermined relay station, and the predetermined relay station adjusts a transmission power using Equation 11 below.

The above process is summarized as follows from the standpoint of the base station.

6 is a flowchart illustrating a process at a base station according to an embodiment of the present invention.

), 활성집합(

), 활성집합수신 프리앰블 전력(

)을 수신한다.Referring to FIG. 6, in step 605, the base station obtains an average user terminal channel gain of a user terminal connected to the relay station from the relay station.

), Active set (

), Active set preamble power (

).

), 트래픽채널 송신전력 크기(

), 상기 605단계의 상기 중계국으로부터의 수신값들을 이용하여 각각의 중계국에 대한 평균 간섭레벨을 계산한다.In step 610, the base station determines the power level of the preamble transmission of the relay station.

), Traffic channel transmit power size (

In step 605, the average interference level for each relay station is calculated using the received values from the relay station.

)를 결정한다.Then, in step 615, the base station increases or decreases power for each relay station.

Is determined.

)을 결정한다.Then, in step 620, the base station determines the power control amount for each relay station.

Is determined.

Thereafter, in step 630, the base station transmits the power increase or decrease in step 615 and the power control amount in step 620 to each relay station, and terminates the algorithm according to the present invention.

The above process is summarized as follows from the point of view of the relay station.

7 is a flowchart illustrating a processing procedure in a relay station according to an embodiment of the present invention.

)을 수신한다. Referring to FIG. 7, in step 705, the RS receives a downlink gain from the user terminal.

).

)을 계산한다.Subsequently, in step 710, the RS in step 705 receives an average "channel gain between the RS and the user terminal" from the downlink gain.

Calculate

)을 검출한다.Subsequently, in step 715, the relay station sets an active set for neighboring relay stations.

).

)을 계산한다.Subsequently, in step 720, the RS may perform preamble power (active set reception preamble power) of the RS corresponding to the active set of the RS in step 715.

Calculate

In step 725, the RS transmits the active set received in step 715 and the active set received preamble power in step 720 to the base station.

) 및 전력조절량(

)을 수신한다.Subsequently, in step 730, the relay station determines whether the power increase decreases from the base station.

) And power control

).

Thereafter, in step 735, the RS adjusts the transmission power based on whether the power increase decreases and the power control amount acquired in step 730, and terminates the algorithm according to the present invention.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

As described above, according to the present invention, the base station determines whether to adjust the transmission power of the plurality of relay stations and the amount of adjustment from the information collected by the plurality of relay stations, thereby enabling fair control over all the relay stations and having high overall performance. In addition, the present invention can reduce the load on the transmission and reception of the control signal in the entire system because it is possible to adjust the transmission power of the fair relay station only by transmitting and receiving the control signal between the relay station and the base station without affecting the user terminal.

Claims (25)

In the apparatus of the relay station for downlink power control in a broadband wireless access communication system, A relay station average downlink gain calculator for calculating channel gain between the relay station and the user terminal based on channel gains transmitted by the user terminal under the relay station; And an interference level detector between relay stations for detecting a degree of interference between the relay station and another adjacent relay station. The method of claim 1, The apparatus is characterized in that for transmitting the information output from the relay station average downlink gain calculating unit and the inter-station interference level detector to the base station. The method of claim 2, And the apparatus receives the transmission power adjustment instruction calculated and transmitted from the information received by the base station to adjust the transmission power of the relay station. The method of claim 3, wherein The content of the transmission power adjustment instruction transmitted by the base station is a transmission power adjustment direction and a transmission power adjustment amount, characterized in that for calculating the amount of transmission power to be adjusted using the following equation (12).

Where Txpower is the transmit power of the relay station r, AdjustDirection is the power adjustment direction, and AdjustAmount is the power adjustment amount. The method of claim 2, The channel gain between the RS and the user terminal calculated by the RS average downlink gain calculator is as shown in Equation (13).

Here, K is the number of user terminals included in a specific relay station,

Denotes the channel gain between the average relay station and the user terminal for the carrier assigned to a specific user terminal k. The method of claim 2, The information output by the interlevel relay level detector is an active set, which is a set of relay stations that the relay station can receive and measure a preamble, and an active set reception preamble power which is a preamble reception power of each relay station included in the set of relay stations. Characterized in that the device. An apparatus of a base station for downlink power control in a broadband wireless access communication system, And a relay station power control unit for calculating and indicating a transmission power adjustment for each relay station from information transmitted by each relay station belonging to the base station and previously stored information. The method of claim 7, wherein And the apparatus determines the transmission power adjustment direction and the transmission power adjustment amount from the information transmitted from each relay station and previously stored information, and instructs each relay station to adjust power. The method of claim 8, The information transmitted from each relay station is included in an average user terminal channel gain for each user terminal belonging to the relay station, an active set which is a set of relay stations that the relay station can receive and measure a preamble, and a set of the relay stations. And an active set receive preamble power which is the preamble receive power of each relay station. The method of claim 9, The average user terminal channel gain for each user terminal belonging to the relay station is as shown in Equation (14).

Here, K is the number of user terminals included in a specific relay station,

Denotes the channel gain between the average relay station and the user terminal for the carrier assigned to the specific user terminal k. The method of claim 8, In the transmission power control direction, when the result value is +1 using Equation 15, the power is increased by a predefined value, and when the result value is -1, the interference of any relay station closest to the vicinity is determined. And determine the amount of power reduction according to the level.

here

Is the specific relay station (

) And any relay station (

Is the normalized distance between remind

May be represented by Equation 16 below.

here,

Denotes the channel or link gain from the specific relay station to any relay station.

Recall average channel gain

Divided by. The method of claim 11, The transmission power adjustment amount is determined by using the following equation (17) according to the rotation power adjustment direction.

here,

Is a predefined value. The method of claim 8, And the information previously stored by the base station is a transmission power of each relay station and a preamble transmission power. In the method of the relay station for downlink power control in a broadband wireless access communication system, Calculating a channel gain between the relay station and the user terminal based on the channel gain transmitted by the user terminal under the relay station; Detecting the degree of interference between the relay station and another relay station adjacent to the same as or after the channel gain calculation process; Transmitting the detected interference degree and the channel gain to a base station; And after the transmitting, receiving a transmission power adjustment instruction from the base station to adjust transmission power of the relay station. The method of claim 14, The channel gain between the relay station and the user terminal is characterized by the following equation (18).

Here, K is the number of user terminals included in a specific relay station,

Denotes the channel gain between the average relay station and the user terminal for the carrier assigned to the specific user terminal k. The method of claim 14, The information detected in the process of detecting the degree of interference between the relay station and another adjacent relay station, And an active set reception preamble power which is an active set which is a set of relay stations capable of receiving and measuring the preamble and a preamble reception power of each relay station included in the set of relay stations. The method of claim 14, The content of the transmission power adjustment instruction received from the base station is a transmission power adjustment direction and a transmission power adjustment amount, characterized in that to calculate the amount of transmission power to be adjusted using Equation (19).

Where Txpower is the transmit power of the relay station r, AdjustDirection is the power adjustment direction, and AdjustAmount is the power adjustment amount. A method of a base station for downlink power control in a broadband wireless access communication system, Receiving specific information necessary for transmission power adjustment from each relay station belonging to the base station; And calculating transmission power adjustment for each relay station from the received specific parameter and previously stored information. The method of claim 18, The method further comprises the step of issuing the transmission power adjustment instruction for each relay station after calculating the transmission power adjustment for each relay station. The method of claim 18, The information transmitted from each relay station is included in an average user terminal channel gain for each user terminal belonging to the relay station, an active set which is a set of relay stations that the relay station can receive and measure a preamble, and a set of the relay stations. The active set receive preamble power which is the preamble receive power of each relay station. The method of claim 20, The average user terminal channel gain for each user terminal belonging to the relay station is represented by Equation 20 below.

Here, K is the number of user terminals included in a specific relay station,

Denotes the channel gain between the average relay station and the user terminal for the carrier assigned to the specific user terminal k. The method of claim 18, The step of calculating the transmission power adjustment for each relay station from the received specific information and previously stored information, And determining a transmission power adjustment direction and a transmission power adjustment amount from the information transmitted from each relay station and previously stored information. The method of claim 22, When the result value is +1 using the following Equation 21, the transmission power control direction increases the power by a predefined value, and when the result value is -1, the interference of any relay station closest to the nearest Determining the amount of power reduction in accordance with the level.

here

Is the specific relay station (

) And any relay station (

Is the normalized distance between remind

May be represented as in Equation 22.

here,

Denotes the channel or link gain from the specific relay station to any relay station.

Recall average channel gain

Divided by. The method of claim 22, The transmission power control amount is determined using the following Equation (23) according to the rotation power control direction.

here,

Is a predefined value. The method of claim 22, And the information previously stored by the base station is a transmission power of each relay station and a preamble transmission power.

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