JP4786413B2 - Control station apparatus and radio communication control method - Google Patents

Control station apparatus and radio communication control method Download PDF

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JP4786413B2
JP4786413B2 JP2006141518A JP2006141518A JP4786413B2 JP 4786413 B2 JP4786413 B2 JP 4786413B2 JP 2006141518 A JP2006141518 A JP 2006141518A JP 2006141518 A JP2006141518 A JP 2006141518A JP 4786413 B2 JP4786413 B2 JP 4786413B2
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浩輔 山崎
健也 米澤
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KDDI Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To avoid or reduce the interferences of frequency channels among the cells of base stations while allowing the base stations to be installed or removed at an arbitrary and uneven locations. <P>SOLUTION: A central control station 1 decides if interferences occur among the cells of the base stations 2, based on a list in the base stations 2 relating to the mobile stations 3 created, based on the received electric waves. Based on the decision result, the central control station 1 also decides, if it is possible to assign a frequency channel from a predetermined number of frequency channels with respect to each of the base station 2, with which the interference between the cells can be avoided, and determines a priority sequence for interference avoidance for each combination of the base stations 2, based on the decision result. The central control station 1 decides the frequency channel to be assigned to the each base station 2, in accordance with the priority sequence. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

本発明は、制御局装置及び無線通信制御方法に関する。 The present invention, control related control station apparatus location and radio communications control method.

従来より、無線接続サービスにおいて広域をカバーする広域セル方式の無線通信システムが知られている。広域セル方式の無線通信システムでは、少数の基地局で広域の通信エリアを実現できる反面、局所的な電波の不感地帯が散在する可能性がある、又、１基地局当たりで収容するユーザ数が多く、基地局の処理能力がボトルネックとなる可能性がある、などの問題がある。これらの問題に対処するために基地局数を増加させることが考えられるが、広域セル方式の基地局装置は高コストである点、又、基地局の新規設置時において干渉増大の抑制のための綿密な置局設計が必要とされる点、などから柔軟な対応が困難である。   2. Description of the Related Art Conventionally, a wide area cellular radio communication system that covers a wide area in a wireless connection service is known. In a wide area cellular radio communication system, a wide area communication area can be realized with a small number of base stations, but local insensitive zones may be scattered, and the number of users accommodated per base station is small. There are many problems such as the possibility that the processing capability of the base station may become a bottleneck. In order to cope with these problems, it is conceivable to increase the number of base stations. However, a wide-area cell base station device is expensive, and is used to suppress an increase in interference when a new base station is installed. It is difficult to respond flexibly because of the need for careful design.

そのような状況下において、広域セルに比べてセルサイズが極小であるピコセルを用いた無線通信システムが検討されている。ピコセル方式の無線通信システムでは、基地局装置が広域セル方式に比べて安価であるので、基地局装置の増加にも比較的対応がしやすい。また、ピコセル方式によれば、適切に基地局の配置を行えば、周波数利用効率の向上が望めるという利点もある。但し、広域セル方式と同様に、干渉増大の抑制のための綿密な置局設計を行わなければ、周波数チャネルが基地局間で互いに干渉し、所望の伝送性能が得られない事態が発生し得る。しかし、ピコセル方式の基地局は簡易に設置することができることから、基地局の設置自由度が大きいことがピコセル方式の利点でもあり、綿密な置局設計を行って設置者の意向に反して指定の場所に基地局を設置するよう強制することは本望ではない。このため、できるだけ任意の場所に基地局を設置できるように置局設計は簡易化し、その分、置局後の基地局間で生じる周波数チャネルの干渉を回避もしくは軽減する方が好ましい。   Under such circumstances, a wireless communication system using a pico cell whose cell size is extremely small compared to a wide area cell has been studied. In a pico cell wireless communication system, base station devices are cheaper than wide area cell methods, and therefore, it is relatively easy to cope with an increase in base station devices. Further, according to the picocell system, if base stations are appropriately arranged, there is an advantage that improvement in frequency use efficiency can be expected. However, as in the wide-area cell system, if careful placement is not performed to suppress an increase in interference, frequency channels may interfere with each other between base stations, and a situation in which desired transmission performance cannot be obtained may occur. . However, since a picocell base station can be easily installed, it is also an advantage of the picocell system that the degree of freedom of base station installation is large, and it is specified against the intention of the installer by careful placement design It is not my desire to force a base station to be installed in the location. For this reason, it is preferable to simplify the station placement design so that the base station can be installed in an arbitrary place as much as possible, and to avoid or reduce the interference of the frequency channel generated between the base stations after the station placement.

セルラシステムにおける従来のセル設計技術では、例えば非特許文献１に記載されるように、セル形状を三角形、四角形、六角形などの多角形で近似することを想定している。そのように想定した環境下における従来の周波数チャネル割当て方法としては、例えば特許文献１に記載の方法が知られている。特許文献１記載の方法では、多角形の形状を想定したセルを間断なく配置した環境において、セル間の干渉をトラヒック量等から推定し、複数のセル間における干渉が大きい場合には同一周波数帯域が割り当てられるセルの距離間隔を大きくし、逆に干渉が小さい場合には同一周波数帯域が割り当てられるセルの距離間隔を小さくしている。
奥村・進士監修、「移動通信の基礎」、第8章、（社）電子情報通信学会 特開２００５−２７１８９号公報 In the conventional cell design technique in the cellular system, as described in Non-Patent Document 1, for example, it is assumed that the cell shape is approximated by a polygon such as a triangle, a quadrangle, or a hexagon. As a conventional frequency channel assignment method under such an assumed environment, for example, a method described in Patent Document 1 is known. In the method described in Patent Document 1, in an environment in which cells assuming a polygonal shape are arranged without interruption, interference between cells is estimated from the traffic amount and the like, and when the interference between a plurality of cells is large, the same frequency band If the interference is small, the distance between cells to which the same frequency band is assigned is reduced.
Supervised by Okumura and Shinji, “Basics of Mobile Communications”, Chapter 8, The Institute of Electronics, Information and Communication Engineers JP 2005-27189 A

しかし、上述した従来の周波数チャネル割当て方法では、多角形のセルが規則的に間断なく配置された環境を想定しており、例えばピコセル方式において基地局が任意の場所に設置されることにより、セルが複雑に重複配置されるような環境に対しては、適用することが難しい。   However, the above-described conventional frequency channel allocation method assumes an environment in which polygonal cells are regularly arranged without interruption. For example, a base station is installed in an arbitrary place in a pico cell system, so that the cell However, it is difficult to apply to an environment where the two are arranged in a complicated manner.

本発明は、このような事情を考慮してなされたもので、その目的は、基地局が任意の場所に、かつ、不規則に設置及び廃止されることを許容しつつ、各基地局のセル間で生じる周波数チャネルの干渉を回避もしくは軽減することのできる無線通信システム、制御局装置、移動局装置及び無線通信制御方法を提供することにある。   The present invention has been made in view of such circumstances, and its purpose is to allow each base station cell to be installed and abolished at an arbitrary location and irregularly. An object of the present invention is to provide a radio communication system, a control station apparatus, a mobile station apparatus, and a radio communication control method that can avoid or reduce interference between frequency channels generated between them.

上記した課題を解決するために、本発明の一態様に係る制御局装置は、複数の基地局の各々に対して移動局との間の通信用の周波数チャネルを割り当てる制御局装置において、 前記移動局毎に受信電波に基づいて作成された基地局のリストに基づき、各基地局のセル間の重複の有無を判断する重複判断手段と、前記判断結果に基づき、所定数の周波数チャネルで、各基地局に対してセル間干渉を回避できる周波数チャネルの割当てが可能か判定する判定手段と、前記判定結果に応じて、基地局の組合せ毎の干渉回避の優先順位を決定する優先順位決定手段と、前記優先順位に従って、各基地局に割り当てる周波数チャネルを決定する周波数チャネル決定手段と、基地局を表すノードと、セル間の干渉のあり得る基地局間に対応するノード間を接続する枝と、から構成される無線基地局グラフを作成する無線基地局グラフ作成手段と、前記無線基地局グラフに応じた彩色多項式を生成する彩色多項式生成手段と、を備え、前記判定手段は、前記無線基地局グラフが前記所定数で彩色可能ならば、所定数の周波数チャネルで、各基地局に対してセル間干渉を回避できる周波数チャネルの割当てが可能であると判定し、前記優先順位決定手段は、前記無線基地局グラフにおいて、セル間の干渉の影響が小さいノード間の枝を前記優先順位が低いノードとして切断する際に、前記移動局毎に受信電波に基づいて算出された基地局の組み合わせ毎の搬送波対干渉波電力比に基づき、基地局の組み合わせ毎の搬送波対干渉波電力比の逆数の総和を求め、前記無線基地局グラフにおいて、前記総和がより小さい値となるノード間の枝を切断し、前記周波数チャネル決定手段は、枝で接続された２つのノードに対応する各基地局に対し、異なる周波数チャネルを割り当てるよう周波数チャネルを決定することを特徴とする。 In order to solve the above-described problem, a control station apparatus according to an aspect of the present invention provides a control station apparatus that assigns a frequency channel for communication with a mobile station to each of a plurality of base stations. Based on a list of base stations created based on received radio waves for each station, duplication judgment means for judging the presence or absence of duplication between cells of each base station, and based on the judgment result, a predetermined number of frequency channels, Determining means for determining whether a frequency channel capable of avoiding inter-cell interference can be assigned to a base station; and priority order determining means for determining a priority order of interference avoidance for each combination of base stations according to the determination result; A frequency channel determining means for determining a frequency channel to be assigned to each base station according to the priority, a node representing the base station, and a node corresponding to a base station where interference between cells is possible Comprising a branch connecting a radio base station graph creation means for creating a radio base station graph composed, and a color polynomial generating means for generating a color polynomial corresponding to the radio base station graph, said determining means If the radio base station graph can be colored with the predetermined number, it is determined that the frequency channel capable of avoiding inter-cell interference can be assigned to each base station with the predetermined number of frequency channels, and the priority order In the wireless base station graph, the determining means determines the base calculated based on the received radio wave for each mobile station when disconnecting a branch between nodes having a small influence of inter-cell interference as a node having a low priority. Based on the carrier-to-interference power ratio for each combination of stations, find the sum of the reciprocal of the carrier-to-interference power ratio for each combination of base stations, and in the radio base station graph, Cutting the branch between the smaller value becomes the node, the frequency channel determination means, for each base station corresponding to the two nodes connected by branches, determining a frequency channel to assign different frequency channels Features.

上記制御局装置において、前記干渉の判断結果に応じて、基地局の送信電力を制御する送信電力制御手段を備えてもよい。 The control station apparatus may include transmission power control means for controlling the transmission power of the base station in accordance with the interference determination result .

上記制御局装置において、前記干渉の判断結果に応じて、基地局の適応変調を制御する適応変調制御手段を備えてもよい。 The control station apparatus may include adaptive modulation control means for controlling adaptive modulation of the base station in accordance with the interference determination result .

本発明の他の態様に係る無線通信制御方法は、複数の基地局の各々に対して移動局との間の通信用の周波数チャネルを割り当てる制御局の無線通信制御方法であって、前記移動局毎に受信電波に基づいて作成された基地局のリストに基づき、各基地局のセル間の重複の有無を判断する過程と、前記判断結果に基づき、所定数の周波数チャネルで、各基地局に対してセル間干渉を回避できる周波数チャネルの割当てが可能か判定する過程と、前記判定結果に応じて、基地局の組合せ毎の干渉回避の優先順位を決定する過程と、前記優先順位に従って、各基地局に割り当てる周波数チャネルを決定する過程と、基地局を表すノードと、セル間の干渉のあり得る基地局間に対応するノード間を接続する枝と、から構成される無線基地局グラフを作成する過程と、前記無線基地局グラフに応じた彩色多項式を生成する過程と、を備え、前記周波数チャネルの割当てが可能か判定する過程は、前記無線基地局グラフが前記所定数で彩色可能ならば、所定数の周波数チャネルで、各基地局に対してセル間干渉を回避できる周波数チャネルの割当てが可能であると判定し、前記優先順位を決定する過程は、前記無線基地局グラフにおいて、セル間の干渉の影響が小さいノード間の枝を前記優先順位が低いノードとして切断する際に、前記移動局毎に受信電波に基づいて算出された基地局の組み合わせ毎の搬送波対干渉波電力比に基づき、基地局の組み合わせ毎の搬送波対干渉波電力比の逆数の総和を求め、前記無線基地局グラフにおいて、前記総和がより小さい値となるノード間の枝を切断し、前記周波数チャネルを決定する過程は、枝で接続された２つのノードに対応する各基地局に対し、異なる周波数チャネルを割り当てるよう周波数チャネルを決定することを特徴とする。 A radio communication control method according to another aspect of the present invention is a radio communication control method of a control station that allocates a frequency channel for communication with a mobile station to each of a plurality of base stations, the mobile station A process of determining whether or not there is duplication between cells of each base station based on a list of base stations created based on received radio waves for each, and based on the determination result, each base station is assigned a predetermined number of frequency channels. A process for determining whether it is possible to assign a frequency channel capable of avoiding inter-cell interference, a process for determining a priority level of interference avoidance for each combination of base stations according to the determination result, and according to the priority level, Create a radio base station graph consisting of the process of determining the frequency channel to be assigned to the base station, the node representing the base station, and the branch connecting the nodes corresponding to each other between the base stations where interference between cells is possible The steps that, the and a process of generating a color polynomial corresponding to the radio base station graph, the process determines whether allocation can of the frequency channel, if the radio base station graph can colored with the predetermined number In the radio base station graph, it is determined that it is possible to assign a frequency channel that can avoid inter-cell interference to each base station with a predetermined number of frequency channels and the priority order is determined in the radio base station graph. Based on the carrier-to-interference wave power ratio for each combination of base stations calculated based on the received radio wave for each mobile station, when the branch between nodes having a small influence of interference is cut as the node having the low priority , the total sum of the reciprocals of the carrier-to-interference power ratio of each combination of base station, in the radio base station graph, cutting the branch between nodes the sum becomes a value smaller than the previous The process of determining a frequency channel for each base station corresponding to the two nodes connected by branches, and determines a frequency channel to assign different frequency channels.

上記無線通信制御方法において、前記干渉の判断結果に応じて、基地局の送信電力を制御する過程を備えてもよい。The radio communication control method may include a step of controlling transmission power of the base station according to the interference determination result.

上記無線通信制御方法において、前記干渉の判断結果に応じて、基地局の適応変調を制御する過程を備えてもよい。The wireless communication control method may include a step of controlling adaptive modulation of the base station in accordance with the interference determination result.

本発明によれば、基地局が任意の場所に、かつ、不規則に設置及び廃止されることを許容しつつ、各基地局のセル間で生じる周波数チャネルの干渉を回避もしくは軽減することができる。   According to the present invention, it is possible to avoid or reduce frequency channel interference that occurs between cells of each base station, while allowing the base station to be randomly installed and abolished in an arbitrary place. .

以下、図面を参照し、本発明の一実施形態について説明する。
図１は、本発明の一実施形態に係る無線通信システムの構成を示すブロック図である。図１において、集中制御局１は、各無線基地局２に通信回線を介して接続されている。各無線基地局２は、それぞれの無線接続サービスエリアであるセル１００を形成している。移動局３は、在圏しているセル１００の無線基地局２と無線接続することができる。 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of a wireless communication system according to an embodiment of the present invention. In FIG. 1, a centralized control station 1 is connected to each radio base station 2 via a communication line. Each radio base station 2 forms a cell 100 which is a respective radio connection service area. The mobile station 3 can wirelessly connect to the radio base station 2 of the cell 100 in which the mobile station 3 is located.

図１の例では３つのセル１００は互いに重複して配置されている。このため、各無線基地局２のセル間で周波数チャネルの干渉が生じる可能性があり、干渉対策を講じることが望ましい。そこで、本実施形態では、集中制御局１が周波数チャネルの割当を調整し、各無線基地局２のセル間で生じ得る周波数チャネルの干渉を回避もしくは軽減することを図る。   In the example of FIG. 1, the three cells 100 are arranged overlapping each other. For this reason, there is a possibility that frequency channel interference may occur between cells of each radio base station 2, and it is desirable to take measures against interference. Therefore, in the present embodiment, the central control station 1 adjusts the frequency channel assignment to avoid or reduce frequency channel interference that may occur between cells of each radio base station 2.

以下、本実施形態に係る周波数チャネル割当て方法について詳細に説明する。   Hereinafter, the frequency channel allocation method according to the present embodiment will be described in detail.

ピコセル方式の無線通信システムのように基地局が任意に設置及び廃止される場合には、全ての基地局間の位置関係を正確に把握することができないので、セル同士が重複して配置されていたとしても、その重複しているセル間の位置関係を基地局間の位置関係から知ることは難しい。そのため、本実施形態では、移動局３がアクセス可能な無線基地局２をアクセス可能局リストとしてリスト化し、集中制御局１はそのアクセス可能局リストを取得して参照することにより、各無線基地局２のセル間のエリアの重複関係を推定し、同一周波数チャネルを用いた場合に周波数チャネル干渉が発生し得るか判定する。   When base stations are arbitrarily installed and abolished as in a pico-cell wireless communication system, it is impossible to accurately grasp the positional relationship between all base stations, so the cells are placed overlapping each other. Even so, it is difficult to know the positional relationship between the overlapping cells from the positional relationship between the base stations. Therefore, in this embodiment, the wireless base station 2 accessible by the mobile station 3 is listed as an accessible station list, and the centralized control station 1 acquires and refers to the accessible station list so that each wireless base station 1 The overlapping relationship between the areas of the two cells is estimated, and it is determined whether frequency channel interference can occur when the same frequency channel is used.

図２は、図１に示す集中制御局１の構成を示すブロック図である。
図２において、集中制御局１は、制御開始通知部１１と干渉報告受信部１２と周波数チャネル割当て制御部１３と使用周波数チャネル通知部１４とを有する。 FIG. 2 is a block diagram showing the configuration of the centralized control station 1 shown in FIG.
In FIG. 2, the centralized control station 1 includes a control start notification unit 11, an interference report reception unit 12, a frequency channel allocation control unit 13, and a used frequency channel notification unit 14.

集中制御局１において制御開始通知部１１は、自集中制御局１の配下の無線基地局２に対して周波数チャネル割当て動作の開始を通知する。この通知によって、無線基地局２は接続中の移動局３に対してアクセス可能局リストを要求する。この要求によって、移動局３は、受信電波に基づき、無線基地局２のリストを作成する。そのリスト作成処理では、現時点で通信可能である無線基地局２を記載したアクセス可能局リストを作成する。移動局３は、アクセス可能局リストを接続中の無線基地局２に送信する。無線基地局２は、移動局３からのアクセス可能局リストを集中制御局１に送信する。   In the central control station 1, the control start notification unit 11 notifies the start of the frequency channel assignment operation to the radio base station 2 under the control of the central control station 1. By this notification, the radio base station 2 requests an accessible station list from the connected mobile station 3. In response to this request, the mobile station 3 creates a list of the radio base stations 2 based on the received radio waves. In the list creation process, an accessible station list describing the wireless base stations 2 that can communicate at the present time is created. The mobile station 3 transmits the accessible station list to the connected radio base station 2. The radio base station 2 transmits an accessible station list from the mobile station 3 to the central control station 1.

図３には、アクセス可能局リストの例が示されている。図３に示される無線通信システムの例（図３には集中制御局１は図示していない）では、４つの無線基地局２Ａ、２Ｂ、２Ｃ、２Ｄが存在し、それぞれ対応するセル１００Ａ、１００Ｂ、１００Ｃ、１００Ｄが形成されている。それらセル１００Ａ、１００Ｂ、１００Ｃ、１００Ｄは重複して配置されている。具体的には、セル１００Ａ、１００Ｂ、１００Ｃは互いに重複して配置されている。また、セル１００Ｂ、１００Ｃ、１００Ｄは互いに重複して配置されている。セル１００Ａと１００Ｄは重複していない。また、図３の例では、３台の移動局３ａ、３ｂ、３ｃが存在している。移動局３ａはセル１００Ａと１００Ｂの重複エリアに在圏している。移動局３ｂはセル１００Ａと１００Ｂと１００Ｃの重複エリアに在圏している。移動局３ｃはセル１００Ｃと１００Ｄの重複エリアに在圏している。   FIG. 3 shows an example of the accessible station list. In the example of the radio communication system shown in FIG. 3 (the central control station 1 is not shown in FIG. 3), there are four radio base stations 2A, 2B, 2C, and 2D, and the corresponding cells 100A, 100B, respectively. , 100C, 100D are formed. The cells 100A, 100B, 100C, and 100D are arranged in an overlapping manner. Specifically, the cells 100A, 100B, and 100C are arranged overlapping each other. Further, the cells 100B, 100C, and 100D are arranged overlapping each other. Cells 100A and 100D do not overlap. In the example of FIG. 3, there are three mobile stations 3a, 3b, and 3c. The mobile station 3a is located in an overlapping area between the cells 100A and 100B. The mobile station 3b is located in the overlapping area of the cells 100A, 100B, and 100C. The mobile station 3c is located in an overlapping area between the cells 100C and 100D.

図３においては、移動局３ａは無線基地局２Ａと２Ｂとに通信可能であるので、無線基地局２Ａと２Ｂを記載したアクセス可能局リスト２００ａを作成する。移動局３ｂは無線基地局２Ａと２Ｂと２Ｃとに通信可能であるので、無線基地局２Ａと２Ｂと２Ｃを記載したアクセス可能局リスト２００ｂを作成する。移動局３ｃは無線基地局２Ｃと２Ｄとに通信可能であるので、無線基地局２Ｃと２Ｄを記載したアクセス可能局リスト２００ｃを作成する。各アクセス可能局リスト２００ａ、２００ｂ、２００ｃは、それぞれの移動局が接続中の無線基地局を介して集中制御局１に送られる。   In FIG. 3, since the mobile station 3a can communicate with the radio base stations 2A and 2B, an accessible station list 200a describing the radio base stations 2A and 2B is created. Since the mobile station 3b can communicate with the radio base stations 2A, 2B, and 2C, an accessible station list 200b that describes the radio base stations 2A, 2B, and 2C is created. Since the mobile station 3c can communicate with the radio base stations 2C and 2D, an accessible station list 200c describing the radio base stations 2C and 2D is created. Each accessible station list 200a, 200b, 200c is sent to the centralized control station 1 via the radio base station to which each mobile station is connected.

集中制御局１において干渉報告受信部１２は、アクセス可能局リストを受信する。干渉報告受信部１２は、アクセス可能局リストに基づき、各無線基地局２のセル間の重複の有無を判断する。また、干渉報告受信部１２は、各無線基地局２のセル間において干渉が発生する可能性の有無を表す無線基地局グラフを作成する。図４には、図３に例示される３つのアクセス可能局リスト２００ａ、２００ｂ、２００ｃに基づいて作成された無線基地局グラフ３００が示されている。無線基地局グラフ３００において、ノードＡ、Ｂ、Ｃ、Ｄは、それぞれ無線基地局２Ａ、２Ｂ、２Ｃ、２Ｄを表す。ノード間を接続する枝は、接続している２つのノードに対応する各無線基地局２のセル間で干渉が発生し得ることを表し、当該２つの無線基地局２のセルの重複エリアに対応している。   In the centralized control station 1, the interference report receiving unit 12 receives the accessible station list. The interference report receiving unit 12 determines whether there is duplication between cells of each radio base station 2 based on the accessible station list. Further, the interference report receiving unit 12 creates a radio base station graph indicating whether or not interference may occur between cells of each radio base station 2. FIG. 4 shows a radio base station graph 300 created based on the three accessible station lists 200a, 200b, and 200c illustrated in FIG. In the radio base station graph 300, nodes A, B, C, and D represent radio base stations 2A, 2B, 2C, and 2D, respectively. The branch connecting the nodes indicates that interference may occur between the cells of each radio base station 2 corresponding to the two connected nodes, and corresponds to the overlapping area of the cells of the two radio base stations 2 is doing.

干渉報告受信部１２は、同一アクセス可能局リスト中に記載された各無線基地局２のセル間には干渉が発生し得るものとして、当該ノード間を枝で接続する。これにより、図４の無線基地局グラフ３００では、アクセス可能局リスト２００ａ中に記載された無線基地局２Ａと２Ｂ間、アクセス可能局リスト２００ｂ中に記載された無線基地局２Ａと２Ｂと２Ｃの各間、アクセス可能局リスト２００ｃ中に記載された無線基地局２Ｃと２Ｄ間のそれぞれ対応するノード間が枝で接続される。   The interference report receiving unit 12 assumes that interference may occur between the cells of each radio base station 2 described in the same accessible station list, and connects the nodes with branches. As a result, in the radio base station graph 300 of FIG. 4, the radio base stations 2A, 2B, and 2C described in the accessible station list 200b, and between the radio base stations 2A and 2B described in the accessible station list 200a. Between the nodes, the corresponding nodes between the radio base stations 2C and 2D described in the accessible station list 200c are connected by branches.

なお、無線基地局グラフは、実質的に図４に例示されるようにノードと枝とから構成されればよく、その表現方法には限定されない。例えば、図５に例示されるように、行列形式で無線基地局グラフを構成してもよい。図５には、図４に示される無線基地局グラフ３００が行列形式で構成されている。図５において、各行及び各列はノードＡ、Ｂ、Ｃ、Ｄに対応している。そして、ノードの組み合わせに対応する行列要素は当該ノード間の枝の有無を表し、行列要素“１”は枝有りを表し、行列要素“０”は枝無しを表す。例えば、ノードＡとノードＢの組み合わせに対応する１行２列の行列要素は“１”であり、当該ノードＡ、Ｂ間には枝が有ることを表す。一方、ノードＡとノードＤの組み合わせに対応する１行４列の行列要素は“０”であり、当該ノードＡ、Ｄ間には枝が無いことを表す。   Note that the radio base station graph may be composed of nodes and branches substantially as illustrated in FIG. 4 and is not limited to the expression method. For example, as illustrated in FIG. 5, the radio base station graph may be configured in a matrix format. In FIG. 5, the radio base station graph 300 shown in FIG. 4 is configured in a matrix format. In FIG. 5, each row and each column corresponds to nodes A, B, C, and D. A matrix element corresponding to a combination of nodes represents the presence or absence of a branch between the nodes, a matrix element “1” represents presence of a branch, and a matrix element “0” represents absence of a branch. For example, the 1-by-2 matrix element corresponding to the combination of node A and node B is “1”, indicating that there is a branch between the nodes A and B. On the other hand, the 1 × 4 matrix element corresponding to the combination of node A and node D is “0”, indicating that there is no branch between the nodes A and D.

干渉報告受信部１２が作成した無線基地局グラフにおいては、枝の両端の各ノードに対応する各無線基地局２のセル間で干渉発生の可能性ありが示されると共に、その干渉によって通信に悪影響の及ぶ移動局３が存在することが示されている。従って、その干渉を回避もしくは軽減するためには、無線基地局グラフ中の枝で接続された２つのノードに対応する各無線基地局２に対しては異なる周波数チャネルを割り当てればよい。   The radio base station graph created by the interference report receiving unit 12 shows that interference may occur between cells of each radio base station 2 corresponding to each node at both ends of the branch, and the interference adversely affects communication. It is shown that there is a mobile station 3 covered by Therefore, in order to avoid or reduce the interference, different frequency channels may be assigned to the radio base stations 2 corresponding to the two nodes connected by the branches in the radio base station graph.

集中制御局１において周波数チャネル割当て制御部１３は、セル間の重複の有無の判断結果に基づき、所定数の周波数チャネルで、各無線基地局２に対してセル間干渉を回避できる周波数チャネルの割当てが可能か判定する。この判定処理では、干渉報告受信部１２が作成した無線基地局グラフを使用する。周波数チャネル割当て制御部１３は、その判定結果に応じて、無線基地局２の組合せ毎の干渉回避の優先順位を決定する。この優先順位決定処理では、現在の無線基地局グラフの状況では周波数チャネルの割り当てが成功しない場合に、セル間の干渉の影響が小さいノード間の枝を切断する。   In the centralized control station 1, the frequency channel allocation control unit 13 allocates frequency channels that can avoid inter-cell interference for each radio base station 2 using a predetermined number of frequency channels based on the determination result of whether there is overlap between cells. Judge whether or not is possible. In this determination process, the radio base station graph created by the interference report receiving unit 12 is used. The frequency channel allocation control unit 13 determines the priority order of interference avoidance for each combination of the radio base stations 2 according to the determination result. In this priority determination process, when the frequency channel assignment is not successful in the situation of the current radio base station graph, a branch between nodes having a small influence of interference between cells is cut.

周波数チャネル割当て制御部１３は、その優先順位に従って、各無線基地局に割り当てる周波数チャネルを決定する。この周波数チャネル決定処理では、優先順位が反映された無線基地局グラフ（つまり、枝切断後の無線基地局グラフ）において、枝で接続された２つのノードに対応する各無線基地局２に対しては異なる周波数チャネルを割り当てる。例えば、図４の無線基地局グラフ３００では、枝の両端の２つのノードの組として、ノードＡとＢ、ノードＡとＣ、ノードＢとＣ、ノードＣとＤの４つの組がある。これら４つの組の全てにおいて、組中の２つのノードに対応する各無線基地局２に対しては異なる周波数チャネルを割り当てるようにする。   The frequency channel allocation control unit 13 determines a frequency channel to be allocated to each radio base station according to the priority order. In this frequency channel determination processing, in each radio base station 2 corresponding to two nodes connected by branches in the radio base station graph reflecting the priority order (that is, the radio base station graph after branch cutting). Assign different frequency channels. For example, in the radio base station graph 300 of FIG. 4, there are four sets of nodes A and B, nodes A and C, nodes B and C, and nodes C and D as sets of two nodes at both ends of the branch. In all these four sets, different frequency channels are assigned to the respective radio base stations 2 corresponding to the two nodes in the set.

使用周波数チャネル通知部１４は、その割当て結果の各無線基地局２の使用周波数チャネルの情報を各無線基地局２に通知する。   The used frequency channel notification unit 14 notifies each radio base station 2 of information on the used frequency channel of each radio base station 2 as a result of the allocation.

次に、上記した集中制御局１の周波数チャネル割当て制御部１３が行う周波数チャネルの割当てに係る動作を詳細に説明する。   Next, operations related to frequency channel assignment performed by the frequency channel assignment control unit 13 of the centralized control station 1 will be described in detail.

始めに、図６を参照して、周波数チャネルの割当てに係る全体動作を説明する。
図６は、本実施形態に係る周波数チャネル割当て処理の手順を示すフローチャートである。図６において、ステップＳ１では、集中制御局１は、各移動局３が作成したアクセス可能局リストを収集し、各無線基地局２のセル間の重複を把握する。ステップＳ２では、その収集したアクセス可能局リストに基づき、無線基地局グラフを作成する。 First, with reference to FIG. 6, the overall operation related to frequency channel allocation will be described.
FIG. 6 is a flowchart showing a procedure of frequency channel assignment processing according to the present embodiment. In FIG. 6, in step S <b> 1, the central control station 1 collects the accessible station list created by each mobile station 3 and grasps the overlap between cells of each radio base station 2. In step S2, a radio base station graph is created based on the collected accessible station list.

ステップＳ３〜Ｓ６では、周波数チャネル割当て制御部１３が、無線基地局グラフに基づき、無線基地局２に対する周波数チャネルの割当てを行う。ここで、上記したように、所定数の周波数チャネルで、各無線基地局２に対してセル間干渉を回避できる周波数チャネルの割当てが可能か判定する。本実施形態では、この問題をグラフ理論における彩色問題として扱う。つまり、無線基地局グラフ中の枝の両端の各ノードを異なる色で彩色する問題として扱う。彩色に使用可能な色の数は、利用可能な周波数チャネルの数である。利用可能な周波数チャネルの数は予め定められている。   In steps S3 to S6, the frequency channel assignment control unit 13 assigns frequency channels to the radio base station 2 based on the radio base station graph. Here, as described above, it is determined whether it is possible to assign a frequency channel that can avoid inter-cell interference to each radio base station 2 with a predetermined number of frequency channels. In this embodiment, this problem is treated as a coloring problem in graph theory. That is, each node at both ends of the branch in the radio base station graph is treated as a problem of coloring with different colors. The number of colors available for coloring is the number of available frequency channels. The number of available frequency channels is predetermined.

先ず、ステップＳ３では、無線基地局グラフに応じた彩色多項式P(k)を生成する。kは彩色に使用可能な色の数である。彩色多項式P(k)は、任意のグラフをk色で彩色する場合に、その塗り方の数を与える関数（彩色関数）である。与えられたグラフが単純グラフ（各ノード間を接続する枝が必ず１本のみであるグラフ）であれば、彩色関数は必ずkの多項式となる。また、彩色多項式P(k)の値が「k＝R」の条件で必ず１以上であることが保証されるのであれば、与えられたグラフはR色で彩色可能である。   First, in step S3, a chromatic polynomial P (k) corresponding to the radio base station graph is generated. k is the number of colors available for coloring. The chromatic polynomial P (k) is a function (coloring function) that gives the number of painting methods when an arbitrary graph is colored with k colors. If the given graph is a simple graph (a graph in which there is always only one branch connecting each node), the coloring function is always a polynomial of k. If it is guaranteed that the value of the chromatic polynomial P (k) is always 1 or more under the condition of “k = R”, the given graph can be colored with the R color.

本実施形態の無線基地局グラフは単純グラフであるので、必ず彩色多項式P(k)が生成可能である。従って、利用可能な周波数チャネルの数がRであるとき、「k＝R」の条件で彩色多項式P(k)の値が１以上になれば、少なくとも１つの塗り方が存在するので、無線基地局グラフはR色で彩色可能である。そして、無線基地局グラフがR色で彩色可能ならば、所定数Rの周波数チャネルで、各無線基地局２への周波数チャネルの割り当てを成功させることができると判定することができる。   Since the radio base station graph of the present embodiment is a simple graph, a chromatic polynomial P (k) can always be generated. Therefore, when the number of available frequency channels is R, if the value of the chromatic polynomial P (k) is 1 or more under the condition of “k = R”, there is at least one painting method. The station graph can be colored in R color. If the radio base station graph can be colored with R color, it can be determined that the frequency channel can be successfully assigned to each radio base station 2 with a predetermined number R of frequency channels.

ステップＳ４では、「k＝R」の条件での彩色多項式P(k)の値P(R)が１以上であるか判断する。この結果、値P(R)が１未満ならば、無線基地局グラフの枝を切断する（ステップＳ５）。このとき、切断する枝は、セル間の干渉の影響が小さいノード間の枝である。その枝切断後にステップＳ３に戻り、彩色多項式P(k)を生成し直す。   In step S4, it is determined whether the value P (R) of the chromatic polynomial P (k) under the condition of “k = R” is 1 or more. As a result, if the value P (R) is less than 1, the branch of the radio base station graph is cut (step S5). At this time, the branch to be cut is a branch between nodes that is less affected by interference between cells. After the branch cut, the process returns to step S3 to regenerate the chromatic polynomial P (k).

ステップＳ４の判断の結果、値P(R)が１以上ならば、無線基地局グラフはR色で彩色可能であるので、当該無線基地局グラフに基づき、各無線基地局２への周波数チャネルの割り当てを行う（ステップＳ６）。このとき、無線基地局グラフ中の枝で接続された２つのノードに対応する各無線基地局２に対しては、異なる周波数チャネルを割り当てる。   If the value P (R) is equal to or greater than 1 as a result of the determination in step S4, the radio base station graph can be colored in R color. Therefore, based on the radio base station graph, the frequency channel to each radio base station 2 is determined. Allocation is performed (step S6). At this time, different frequency channels are assigned to the respective radio base stations 2 corresponding to the two nodes connected by the branches in the radio base station graph.

ステップＳ７では、各無線基地局２に対して、割り当てられた周波数チャネルを通知する。   In step S7, the assigned frequency channel is notified to each radio base station 2.

次に、彩色多項式P(k)の生成方法を説明する。   Next, a method for generating the chromatic polynomial P (k) will be described.

図７には、グラフの例として、簡単なグラフＧ１、Ｇ２が示されている。図７（１）のグラフＧ１をk色で彩色する場合の彩色多項式PＧ１(k)は、（１）式となる。
PＧ１(k)＝k(k-1)2 ・・・（１）
また、図７（２）のグラフＧ２をk色で彩色する場合の彩色多項式PＧ２(k)は、（２）式となる。
PＧ２(k)＝k(k-1)(k-2) ・・・（２）
従って、例えばグラフＧ１の場合、kが２以上ならば、（１）式の値は必ず１以上になることが保証される。これにより、グラフＧ１は２色で彩色可能であることが分かる。同様にグラフＧ２の場合、kが３以上ならば、（２）式の値は必ず１以上になるので、グラフＧ２は３色で彩色可能であることが分かる。このように、ある無線基地局グラフに対して、その彩色多項式を生成することにより、何色で彩色可能であるかを判定することが可能になる。 FIG. 7 shows simple graphs G1 and G2 as graph examples. The chromatic polynomial P G1 (k) when the graph G1 in FIG. 7A is colored with k colors is expressed by equation (1).
P G1 (k) = k (k-1) 2 (1)
Further, the chromatic polynomial P G2 (k) when the graph G2 in FIG. 7B is colored with k colors is expressed by equation (2).
P G2 (k) = k (k-1) (k-2) (2)
Therefore, for example, in the case of the graph G1, if k is 2 or more, it is guaranteed that the value of the expression (1) is always 1 or more. Thereby, it can be seen that the graph G1 can be colored with two colors. Similarly, in the case of the graph G2, if k is 3 or more, the value of the expression (2) is always 1 or more, so it can be seen that the graph G2 can be colored with three colors. In this way, by generating a chromatic polynomial for a certain radio base station graph, it is possible to determine how many colors can be colored.

以下、任意の無線基地局グラフに対して彩色多項式を生成する方法を説明する。なお、ここで挙げる方法は一般に知られているものである。
本生成方法では、次の定理を用いる。
［定理］
単純グラフＧから枝ｅを除去して得られるグラフ「Ｇ−ｅ」と、単純グラフＧから枝ｅを縮約して得られるグラフ「Ｇ＼ｅ」との間には、（３）式の関係が成立する。
PＧ(k)＝PＧ−ｅ(k)−PＧ＼ｅ(k) ・・・（３）
但し、PＧ(k)は単純グラフＧの彩色多項式、PＧ−ｅ(k)はグラフ「Ｇ−ｅ」の彩色多項式、PＧ＼ｅ(k)はグラフ「Ｇ＼ｅ」の彩色多項式である。
また、枝の除去とは、枝を取り除くことを指す。
また、枝の縮約とは、枝を取り除き、その両端のノードを一つのノードに合成することを指す。このとき、重複する枝が発生する場合には一本の枝として再記述する。 Hereinafter, a method of generating a chromatic polynomial for an arbitrary radio base station graph will be described. The methods listed here are generally known.
In this generation method, the following theorem is used.
[theorem]
Between the graph “Ge” obtained by removing the branch e from the simple graph G and the graph “G \ e” obtained by reducing the branch e from the simple graph G, the equation (3) A relationship is established.
P G (k) = P G−e (k) −P G \ e (k) (3)
Where P G (k) is a chromatic polynomial of the simple graph G, P G-e (k) is a chromatic polynomial of the graph “G-e”, and P G \ e (k) is a chromatic polynomial of the graph “G \ e”. It is.
Further, removal of a branch refers to removing a branch.
Branch reduction refers to removing a branch and combining nodes at both ends into one node. At this time, if an overlapping branch occurs, it is rewritten as a single branch.

この定理を用いて、任意のグラフの彩色多項式を次のアルゴリズムにより生成することができる。
ステップＳ１１；任意の枝を選択し、その選択した枝を除去したグラフと、その選択した枝を縮約したグラフとを生成する。そして、上述の定理を適用する。
ステップＳ１２；ステップＳ１１で生成した二つのグラフにおいてさらに任意の枝を選択し、それぞれのグラフにおいて、その選択した枝を除去したグラフと、その選択した枝を縮約したグラフとを生成する。そして、上述の定理を適用する。
ステップＳ１３；上記の工程を、当初のグラフが空グラフ（枝が０本のグラフ）または所定の形のグラフ（例えば図７のグラフＧ１、Ｇ２など）のみで表されるまで繰り返す。
ステップＳ１４；最終的に得られたグラフ群に含まれる各グラフを、空グラフの彩色多項式または所定の形のグラフの彩色多項式に置換し、当初のグラフの彩色多項式を得る。 Using this theorem, a chromatic polynomial of an arbitrary graph can be generated by the following algorithm.
Step S11: An arbitrary branch is selected, a graph from which the selected branch is removed, and a graph in which the selected branch is contracted are generated. Then, the above theorem is applied.
Step S12: An arbitrary branch is further selected in the two graphs generated in step S11, and in each graph, a graph from which the selected branch is removed and a graph in which the selected branch is contracted are generated. Then, the above theorem is applied.
Step S13: The above steps are repeated until the initial graph is represented only by an empty graph (a graph having zero branches) or a graph of a predetermined shape (for example, the graphs G1 and G2 in FIG. 7).
Step S14: Each graph included in the finally obtained graph group is replaced with a chromatic polynomial of an empty graph or a chromatic polynomial of a graph of a predetermined shape to obtain a chromatic polynomial of the original graph.

具体的に、図８を参照して、上述のアルゴリズムを説明する。
図８において、（Ａ）式の左辺のグラフが当初のグラフＧである。
先ず、当初グラフＧから、枝ｅを除去したグラフ（（Ａ）式の右辺第一項のグラフ）と、枝eを縮約したグラフ（（Ａ）式の右辺第二項のグラフ）とを生成する。ここで、上述の定理により、左辺のグラフの彩色多項式は右辺に示す二つのグラフの彩色多項式の差となる。これにより、（Ａ）式が得られる（ステップＳ１１）。 Specifically, the above algorithm will be described with reference to FIG.
In FIG. 8, the graph on the left side of the formula (A) is the initial graph G.
First, a graph obtained by removing the branch e from the initial graph G (a graph of the first term on the right side of the formula (A)) and a graph obtained by reducing the branch e (a graph of the second term on the right side of the formula (A)). Generate. Here, according to the above theorem, the chromatic polynomial of the graph on the left side is the difference between the chromatic polynomials of the two graphs shown on the right side. Thereby, (A) Formula is obtained (step S11).

次いで、（Ａ）式の右辺第一項のグラフの枝eを、除去したグラフと縮約したグラフとを生成する。また、（Ａ）式の右辺第二項のグラフの枝eを、除去したグラフと縮約したグラフとを生成する。そして、上述の定理を適用する。これにより、（Ｂ）式の右辺が得られる（ステップＳ１２）。   Next, a graph in which the branch e of the graph of the first term on the right side of the equation (A) is removed and a contracted graph are generated. In addition, a graph in which the branch e of the graph in the second term on the right side of the equation (A) is removed and a contracted graph are generated. Then, the above theorem is applied. Thereby, the right side of the equation (B) is obtained (step S12).

次いで、そのステップＳ１２の処理を（Ｂ）式の右辺に対してもう一度繰り返すことによって、（Ｃ）式の右辺が得られる（ステップＳ１２）。   Next, the process in step S12 is repeated once more on the right side of equation (B) to obtain the right side of equation (C) (step S12).

次いで、（Ｃ）式の右辺に含まれる各グラフを彩色多項式に置換する。（Ｃ）式の右辺には５つのグラフが含まれており、その種類は４種類である。（Ｃ）式の右辺において、左から順番に各グラフの彩色多項式を示すと、
k(k-1)4、
k(k-1)3、
k(k-1)3、
k(k-1)2、
k(k-1)(k-2)、
となる。なお、空グラフの彩色多項式は、図９に示される（４）式である。 Next, each graph included in the right side of the equation (C) is replaced with a chromatic polynomial. The right side of the equation (C) includes five graphs, and there are four types. In the right side of equation (C), the chromatic polynomial of each graph is shown in order from the left.
k (k-1) 4 ,
k (k-1) 3 ,
k (k-1) 3 ,
k (k-1) 2 ,
k (k-1) (k-2),
It becomes. Note that the chromatic polynomial of the sky graph is the equation (4) shown in FIG.

（Ｃ）式の右辺の各グラフを、それぞれ対応する彩色多項式に置換する。これにより、図８の当初グラフＧの彩色多項式PＧ(k)は、（５）式として得られる。
PＧ(k)＝k(k-1)4−k(k-1)3−２（k(k-1)3−k(k-1)2）＋k(k-1)(k-2)
＝k(k-1)4−３k(k-1)3＋２k(k-1)2＋k(k-1)(k-2)
＝k(k-1)(k-2)3 ・・・（５） Each graph on the right side of the equation (C) is replaced with a corresponding chromatic polynomial. Thereby, the chromatic polynomial P G (k) of the initial graph G of FIG. 8 is obtained as the equation (5).
P G (k) = k (k−1) 4 −k (k−1) 3 −2 (k (k−1) 3 −k (k−1) 2 ) + k (k−1) (k−2 )
= K (k-1) 4 -3k (k-1) 3 + 2k (k-1) 2 + k (k-1) (k-2)
= K (k-1) (k-2) 3 (5)

（５）式から、kが3以上の場合に彩色多項式PＧ(k)の値は１以上になることが保証される。これにより、３色あれば、図８の当初グラフＧは彩色可能であることが分かる。 From equation (5), it is guaranteed that the value of the chromatic polynomial P G (k) is 1 or more when k is 3 or more. Accordingly, it can be seen that the initial graph G in FIG. 8 can be colored with three colors.

次に、無線基地局グラフの枝の切断方法を説明する。   Next, a method for cutting a branch of the radio base station graph will be described.

利用可能な周波数チャネルの数がRであるとき、「k＝R」の条件で彩色多項式P(k)の値が１未満でありR色で彩色不可能であった場合には、無線基地局グラフの枝を一本選択して切断し、無線基地局グラフの近似を行う。図１０に枝切断の例を示す。   When the number of available frequency channels is R, if the value of the coloring polynomial P (k) is less than 1 under the condition of “k = R” and cannot be colored with the R color, the radio base station One branch of the graph is selected and cut to approximate the radio base station graph. FIG. 10 shows an example of branch cutting.

図１０の例では、使用可能な色の数（利用可能な周波数チャネルの数）は３である。先ず、図１０（Ａ）に示される最初の無線基地局グラフＧａが生成される。図１０（Ａ）の無線基地局グラフＧａの彩色多項式PＧａ(k)は、（６）式である。
PＧａ(k)＝k(k-1)(k-2)(k-3)(k-4) ・・・（６） In the example of FIG. 10, the number of usable colors (the number of available frequency channels) is three. First, the first radio base station graph Ga shown in FIG. 10A is generated. The chromatic polynomial P Ga (k) of the radio base station graph Ga in FIG.
P Ga (k) = k (k-1) (k-2) (k-3) (k-4) (6)

（６）式から、値PＧａ(3)は１未満であるので、無線基地局グラフＧａは３色では彩色することができない。このため、枝を一本切断し、図１０（Ｂ）の無線基地局グラフＧｂに変形する。なお、ここでは、切断する枝は説明の便宜上の枝である。 Since the value P Ga (3) is less than 1 from the equation (6), the radio base station graph Ga cannot be colored with three colors. For this reason, one branch is cut and transformed into the radio base station graph Gb of FIG. Here, the branches to be cut are branches for convenience of explanation.

図１０（Ｂ）の無線基地局グラフＧｂの彩色多項式PＧｂ(k)は、（７）式である。
PＧａ(k)＝k(k-1)(k-2)(k-3)2 ・・・（７）
（７）式から、値PＧｂ(3)は１未満であるので、無線基地局グラフＧｂでも３色では彩色することができない。このため、さらに枝を一本切断し、図１０（Ｃ）の無線基地局グラフＧｃに変形する。 The chromatic polynomial P Gb (k) of the radio base station graph Gb in FIG. 10B is an expression (7).
P Ga (k) = k (k-1) (k-2) (k-3) 2 (7)
Since the value P Gb (3) is less than 1 from the equation (7), the radio base station graph Gb cannot be colored with three colors. For this reason, one branch is further cut and transformed into the radio base station graph Gc of FIG.

図１０（Ｃ）の無線基地局グラフＧｃの彩色多項式PＧｃ(k)は、（８）式である。
PＧａ(k)＝k(k-1)2(k-2)2 ・・・（８）
（８）式から、値PＧｃ(3)は１以上であるので、無線基地局グラフＧｃならば３色で彩色することができる。これにより、無線基地局グラフＧｃに基づき、各無線基地局２への周波数チャネルの割り当てを行う。このとき、無線基地局グラフＧｃ中の枝で接続された２つのノードに対応する各無線基地局２に対しては、異なる周波数チャネルを割り当てる。 The chromatic polynomial P Gc (k) of the radio base station graph Gc in FIG.
P Ga (k) = k (k-1) 2 (k-2) 2 (8)
From the equation (8), since the value P Gc (3) is 1 or more, the radio base station graph Gc can be colored with three colors. Thereby, the frequency channel is assigned to each radio base station 2 based on the radio base station graph Gc. At this time, different frequency channels are allocated to the respective radio base stations 2 corresponding to the two nodes connected by the branches in the radio base station graph Gc.

無線基地局グラフ中の枝を切断することは、セルが重複している複数の無線基地局２に、同一の周波数チャネルを割り当てることを許容することに相当する。セルが重複している複数の無線基地局２に同一の周波数チャネルが割り当てられると、その重複しているセル間で干渉が発生し得る。従って、そのセル間の干渉の影響が小さい無線基地局２間（ノード間）の枝を切断することが好ましい。以下、セル間の干渉の影響が小さい無線基地局２間（ノード間）の枝を選択する方法を説明する。   Cutting a branch in the radio base station graph corresponds to allowing the same frequency channel to be assigned to a plurality of radio base stations 2 having overlapping cells. When the same frequency channel is assigned to a plurality of radio base stations 2 having overlapping cells, interference may occur between the overlapping cells. Therefore, it is preferable to cut a branch between the radio base stations 2 (between nodes) that is less affected by interference between the cells. Hereinafter, a method for selecting a branch between wireless base stations 2 (between nodes) that is less affected by interference between cells will be described.

［第１の枝選択方法］
第１の枝選択方法では、移動局３毎に受信電波に基づいて算出された無線基地局２の組み合わせ毎の搬送波対干渉波電力比（Carrier to Interference Ratio：ＣＩＲ）に基づき、無線基地局２の組み合わせ毎のＣＩＲの最低値を求め、無線基地局グラフにおいて、該最低値がより高い値となるノード間の枝を切断する。 [First branch selection method]
In the first branch selection method, based on the carrier-to-interference ratio (CIR) for each combination of the radio base stations 2 calculated based on the received radio wave for each mobile station 3, the radio base station 2 The lowest CIR value for each combination is obtained, and in the radio base station graph, a branch between nodes where the lowest value is higher is cut.

移動局３は、受信電波に基づき、無線基地局２の組み合わせ毎のＣＩＲを求める計測手段を備える。移動局３は、通信可能な全ての無線基地局２を一つずつ所望局にして、それぞれのＣＩＲを測定する。なお、そのＣＩＲ測定において、ＣＩＲの測定対象となる無線基地局２間が同一の周波数チャネルを使用していない場合には、それぞれの無線基地局２からの受信信号強度（Received Signal Strength Indicator：ＲＳＳＩ）を測定し、該ＲＳＳＩ測定値を同一の周波数チャネルの値として想定のＣＩＲを算出する。本実施形態では、この想定のＣＩＲも含めてＣＩＲとする。   The mobile station 3 includes measurement means for obtaining CIR for each combination of the radio base stations 2 based on the received radio waves. The mobile station 3 sets all the radio base stations 2 that can communicate with each other as desired stations, and measures each CIR. In the CIR measurement, when the same frequency channel is not used between the radio base stations 2 to be measured by CIR, the received signal strength (Received Signal Strength Indicator: RSSI) from each radio base station 2 is used. ) And the assumed CIR is calculated using the RSSI measurement value as the value of the same frequency channel. In the present embodiment, the CIR including the assumed CIR is used.

移動局３で測定された無線基地局２の組み合わせ毎のＣＩＲは、集中制御局１に送られる。例えば、アクセス可能局リストと同時に集中制御局１に送られる。   The CIR for each combination of the radio base stations 2 measured by the mobile station 3 is sent to the central control station 1. For example, it is sent to the centralized control station 1 simultaneously with the accessible station list.

集中制御局１において周波数チャネル割当て制御部１３は、各移動局３から報告されたＣＩＲに基づき、無線基地局２の組み合わせ毎のスコアを決定し記録する。具体的には、無線基地局２の同一組み合わせに関するＣＩＲの中で最低値を当該無線基地局２の組み合わせの、つまり該当する枝のスコアに決定する。   In the centralized control station 1, the frequency channel assignment control unit 13 determines and records a score for each combination of the radio base stations 2 based on the CIR reported from each mobile station 3. Specifically, the lowest value among the CIRs related to the same combination of the radio base stations 2 is determined as the score of the combination of the radio base stations 2, that is, the corresponding branch.

ここで、スコアの高い枝に対応する干渉エリアの方が、他のスコアの低い枝に対応する干渉エリアよりも、高いＣＩＲを提供可能である。このことから、スコアの高い枝に対応する干渉エリアの方が、他のスコアの低い枝に対応する干渉エリアよりも、干渉の影響が少ないと考えられる。従って、スコアの最も高い枝を切断対象とする。   Here, an interference area corresponding to a branch having a high score can provide a higher CIR than an interference area corresponding to a branch having another low score. From this, it is considered that the interference area corresponding to the branch having a high score has less influence of the interference than the interference area corresponding to the other branch having a low score. Therefore, the branch with the highest score is the cutting target.

［第２の枝選択方法］
第２の枝選択方法では、アクセス可能局リストにより報告された無線基地局２の組み合わせ毎の報告数を求め、無線基地局グラフにおいて、該報告数が最も少ない値となるノード間の枝を切断する。 [Second branch selection method]
In the second branch selection method, the number of reports for each combination of the radio base stations 2 reported by the accessible station list is obtained, and in the radio base station graph, the branch between the nodes having the smallest report number is cut. To do.

集中制御局１において周波数チャネル割当て制御部１３は、アクセス可能局リストにより報告された無線基地局２の組み合わせ毎の報告数を算出する。ある２つの無線基地局２の組がｎ個のアクセス可能局リスト中に記載されていた場合は、当該２つの無線基地局２の組の報告数はｎとなる。例えば、ある２つの無線基地局２の組が３つのアクセス可能局リスト中にのみ記載されていた場合は、当該２つの無線基地局２の組の報告数は３である。各無線基地局２の組のスコアは、無線基地局グラフ中の対応する枝のスコアとして記録する。   In the centralized control station 1, the frequency channel allocation control unit 13 calculates the number of reports for each combination of the radio base stations 2 reported by the accessible station list. When a set of two radio base stations 2 is described in the list of n accessible stations, the number of reports of the set of the two radio base stations 2 is n. For example, when a set of two radio base stations 2 is described only in three accessible station lists, the number of reports of the set of the two radio base stations 2 is three. The score of each wireless base station 2 set is recorded as the score of the corresponding branch in the wireless base station graph.

本報告数が少ない方が干渉の影響を与えている移動局３の数が少ない。従って、スコアの最も低い枝を切断対象とする。   The smaller the number of reports, the smaller the number of mobile stations 3 affecting the interference. Therefore, the branch with the lowest score is the cutting target.

［第３の枝選択方法］
第３の枝選択方法では、移動局３毎に受信電波に基づいて算出された無線基地局２の組み合わせ毎のＣＩＲに基づき、無線基地局２の組み合わせ毎のＣＩＲの逆数の総和を求め、無線基地局グラフにおいて、該総和がより小さい値となるノード間の枝を切断する。 [Third branch selection method]
In the third branch selection method, based on the CIR for each combination of the radio base stations 2 calculated based on the received radio wave for each mobile station 3, the sum of the reciprocals of the CIR for each combination of the radio base stations 2 is obtained. In the base station graph, a branch between nodes having the smaller sum is cut.

上述の第１の枝選択方法と同様に、移動局３で測定された無線基地局２の組み合わせ毎のＣＩＲは、集中制御局１に送られる。   Similar to the first branch selection method described above, the CIR for each combination of the radio base stations 2 measured by the mobile station 3 is sent to the centralized control station 1.

集中制御局１において周波数チャネル割当て制御部１３は、各移動局３から報告されたＣＩＲに基づき、無線基地局２の組み合わせ毎のスコアを決定し記録する。具体的には、無線基地局２の同一組み合わせに関するＣＩＲの逆数の総和を算出し、該総和を当該無線基地局２の組み合わせの、つまり該当する枝のスコアに決定する。   In the centralized control station 1, the frequency channel assignment control unit 13 determines and records a score for each combination of the radio base stations 2 based on the CIR reported from each mobile station 3. Specifically, the sum of the reciprocal of the CIR for the same combination of the radio base stations 2 is calculated, and the sum is determined as the score of the combination of the radio base stations 2, that is, the corresponding branch.

ここで、スコアの低い枝に対応する干渉エリアの方が、他のスコアの高い枝に対応する干渉エリアよりも、高いＣＩＲを提供可能である。このことから、スコアの低い枝に対応する干渉エリアの方が、他のスコアの高い枝に対応する干渉エリアよりも、干渉の影響が少ないと考えられる。従って、スコアの最も低い枝を切断対象とする。   Here, an interference area corresponding to a branch having a low score can provide a higher CIR than an interference area corresponding to a branch having another high score. From this, it is considered that the interference area corresponding to the branch having a low score has less influence of the interference than the interference area corresponding to another branch having a high score. Therefore, the branch with the lowest score is the cutting target.

なお、一般にＣＩＲにはデシベル単位が使用されるが、「ＣＩＲの逆数」の算出には、デシベル単位に換算しない、次式で表されるＣＩＲを用いることが好ましい。
ＣＩＲ＝搬送波の受信電力／干渉波の受信電力 In general, decibel units are used for CIR. However, it is preferable to use CIR represented by the following formula, which is not converted to decibel units, in calculating “reciprocal of CIR”.
CIR = received power of carrier wave / received power of interference wave

上述したように本実施形態によれば、移動局毎に受信電波に基づいて作成された無線基地局のリスト（アクセス可能局リスト）から、セル間の重複の有無が判断される。その結果から、所定数の周波数チャネルで、各無線基地局に対してセル間干渉を回避できる周波数チャネルの割当てが可能かが判定され、不可能である場合には無線基地局の組合せ毎の干渉回避の優先順位を決定し、その優先順位に従って、各無線基地局に割り当てる周波数チャネルが決定される。これにより、例えばピコセル方式において無線基地局が任意の場所に、かつ、不規則に設置及び廃止されることにより、セルが複雑に重複配置されるような環境であっても、各無線基地局のセル間で生じる周波数チャネルの干渉を回避もしくは軽減することができる。   As described above, according to the present embodiment, whether or not there is an overlap between cells is determined from a list of wireless base stations (accessible station list) created based on received radio waves for each mobile station. From the result, it is determined whether it is possible to assign a frequency channel that can avoid inter-cell interference to each radio base station with a predetermined number of frequency channels, and if this is not possible, interference for each combination of radio base stations is determined. A priority order of avoidance is determined, and a frequency channel to be assigned to each radio base station is determined according to the priority order. Thereby, for example, even in an environment where cells are complicatedly overlapped due to radio base stations being randomly installed and abolished in a pico cell system, the radio base stations Frequency channel interference occurring between cells can be avoided or reduced.

また、各無線基地局のセル間の干渉の判断結果として、各無線基地局のセル間において干渉が発生する可能性の有無を表す無線基地局グラフを作成するので、所定数の周波数チャネルで、各無線基地局への周波数チャネルの割り当てを行う処理が簡単になる。   In addition, as a result of determining the interference between the cells of each radio base station, a radio base station graph indicating whether or not interference may occur between the cells of each radio base station is created, so with a predetermined number of frequency channels, The process of assigning frequency channels to each radio base station is simplified.

さらに、無線基地局グラフに応じた彩色多項式を生成するので、グラフ理論における彩色問題として、所定数の周波数チャネルで、各無線基地局に対してセル間干渉を回避できる周波数チャネルの割当てが可能かの判定を行うことができる。これにより、周波数チャネル割当て処理がさらに簡単になる。   In addition, since a chromatic polynomial is generated according to the radio base station graph, it is possible to assign a frequency channel that can avoid inter-cell interference to each radio base station with a predetermined number of frequency channels as a chromatic problem in graph theory. Can be determined. This further simplifies the frequency channel assignment process.

以上、本発明の実施形態を図面を参照して詳述してきたが、具体的な構成はこの実施形態に限られるものではなく、本発明の要旨を逸脱しない範囲の設計変更等も含まれる。
例えば、各無線基地局のセル間の重複の有無の判断結果に応じて、無線基地局の送信電力を制御するようにしてもよい。その重複の有無の判断結果としては、無線基地局グラフが利用可能である。 The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design changes and the like within a scope not departing from the gist of the present invention.
For example, you may make it control the transmission power of a radio base station according to the judgment result of the presence or absence of duplication between the cells of each radio base station. A wireless base station graph can be used as the determination result of the presence or absence of duplication.

また、各無線基地局のセル間の重複の有無の判断結果に応じて、無線基地局の適応変調を制御するようにしてもよい。その重複の有無の判断結果としては、無線基地局グラフが利用可能である。   Moreover, you may make it control the adaptive modulation of a radio base station according to the judgment result of the presence or absence of duplication between the cells of each radio base station. A wireless base station graph can be used as the determination result of the presence or absence of duplication.

なお、本発明は、ピコセル方式など、各種セル方式の無線通信システムに適用可能である。   Note that the present invention is applicable to radio communication systems of various cell systems such as a pico cell system.

本発明の一実施形態に係る無線通信システムの構成を示すブロック図である。It is a block diagram which shows the structure of the radio | wireless communications system which concerns on one Embodiment of this invention. 図１に示す集中制御局１の構成を示すブロック図である。It is a block diagram which shows the structure of the centralized control station 1 shown in FIG. 本発明の一実施形態に係るアクセス可能局リストの例を示す図である。It is a figure which shows the example of the accessible station list which concerns on one Embodiment of this invention. 本発明の一実施形態に係る無線基地局グラフの例を示す図である。It is a figure which shows the example of the radio base station graph which concerns on one Embodiment of this invention. 本発明の一実施形態に係る無線基地局グラフの他の例を示す図である。It is a figure which shows the other example of the wireless base station graph which concerns on one Embodiment of this invention. 本発明の一実施形態に係る周波数チャネル割当て処理の手順を示すフローチャートである。It is a flowchart which shows the procedure of the frequency channel allocation process which concerns on one Embodiment of this invention. 本発明の一実施形態に係る彩色多項式の生成方法を説明するためのグラフの例を示す図である。It is a figure which shows the example of the graph for demonstrating the production | generation method of the chromatic polynomial which concerns on one Embodiment of this invention. 本発明の一実施形態に係る彩色多項式の生成方法を説明するための説明図である。It is explanatory drawing for demonstrating the generation method of the chromatic polynomial which concerns on one Embodiment of this invention. 本発明の一実施形態に係る彩色多項式の生成方法を説明するためのグラフ及び彩色多項式の例を示す図である。It is a figure which shows the example for generating the coloring polynomial which concerns on one Embodiment of this invention, and the example of a coloring polynomial. 本発明の一実施形態に係る無線基地局グラフの枝の切断方法を説明するための説明図である。It is explanatory drawing for demonstrating the cutting method of the branch of the wireless base station graph which concerns on one Embodiment of this invention.

符号の説明Explanation of symbols

１…集中制御局、２…無線基地局、３…移動局、１１…制御開始通知部、１２…干渉報告受信部、１３…周波数チャネル割当て制御部、１４…使用周波数チャネル通知部、１００…セル、３００…無線基地局グラフ

DESCRIPTION OF SYMBOLS 1 ... Central control station, 2 ... Wireless base station, 3 ... Mobile station, 11 ... Control start notification part, 12 ... Interference report receiving part, 13 ... Frequency channel allocation control part, 14 ... Used frequency channel notification part, 100 ... Cell , 300 ... Wireless base station graph

Claims (6)

複数の基地局の各々に対して移動局との間の通信用の周波数チャネルを割り当てる制御局装置において、
前記移動局毎に受信電波に基づいて作成された基地局のリストに基づき、各基地局のセル間の重複の有無を判断する重複判断手段と、
前記判断結果に基づき、所定数の周波数チャネルで、各基地局に対してセル間干渉を回避できる周波数チャネルの割当てが可能か判定する判定手段と、
前記判定結果に応じて、基地局の組合せ毎の干渉回避の優先順位を決定する優先順位決定手段と、
前記優先順位に従って、各基地局に割り当てる周波数チャネルを決定する周波数チャネル決定手段と、
基地局を表すノードと、セル間の干渉のあり得る基地局間に対応するノード間を接続する枝と、から構成される無線基地局グラフを作成する無線基地局グラフ作成手段と、
前記無線基地局グラフに応じた彩色多項式を生成する彩色多項式生成手段と、
を備え、
前記判定手段は、
前記無線基地局グラフが前記所定数で彩色可能ならば、所定数の周波数チャネルで、各基地局に対してセル間干渉を回避できる周波数チャネルの割当てが可能であると判定し、
前記優先順位決定手段は、前記無線基地局グラフにおいて、セル間の干渉の影響が小さいノード間の枝を前記優先順位が低いノードとして切断する際に、前記移動局毎に受信電波に基づいて算出された基地局の組み合わせ毎の搬送波対干渉波電力比に基づき、基地局の組み合わせ毎の搬送波対干渉波電力比の逆数の総和を求め、前記無線基地局グラフにおいて、前記総和がより小さい値となるノード間の枝を切断し、
前記周波数チャネル決定手段は、
枝で接続された２つのノードに対応する各基地局に対し、異なる周波数チャネルを割り当てるよう周波数チャネルを決定する
ことを特徴とすることを特徴とする制御局装置。 In a control station apparatus that assigns a frequency channel for communication with a mobile station to each of a plurality of base stations,
Based on a list of base stations created based on received radio waves for each mobile station, a duplication judgment means for judging whether or not there is duplication between cells of each base station;
Based on the determination result, determination means for determining whether or not it is possible to assign a frequency channel that can avoid inter-cell interference to each base station with a predetermined number of frequency channels;
In accordance with the determination result, priority determining means for determining the priority of interference avoidance for each combination of base stations,
Frequency channel determining means for determining a frequency channel to be assigned to each base station according to the priority order;
A radio base station graph creating means for creating a radio base station graph composed of a node representing a base station and a branch connecting nodes corresponding to each other between base stations where interference between cells is possible;
A chromatic polynomial generating means for generating a chromatic polynomial corresponding to the radio base station graph;
With
The determination means includes
If the radio base station graph can be colored with the predetermined number, it is determined that it is possible to assign a frequency channel that can avoid inter-cell interference to each base station with a predetermined number of frequency channels,
The priority order determining means calculates, based on the received radio wave for each mobile station, when a branch between nodes having a small influence of inter-cell interference is cut as the low priority node in the radio base station graph. Based on the carrier-to-interference wave power ratio for each combination of base stations, the sum of the reciprocal of the carrier-to-interference wave power ratio for each combination of base stations is obtained, and the sum is smaller in the radio base station graph. branches between becomes nodes were cut,
The frequency channel determining means includes
A control station apparatus, wherein a frequency channel is determined so that different frequency channels are allocated to each base station corresponding to two nodes connected by branches . 前記干渉の判断結果に応じて、基地局の送信電力を制御する送信電力制御手段を備えたことを特徴とする請求項１に記載の制御局装置。 The control station apparatus according to claim 1 , further comprising transmission power control means for controlling transmission power of a base station according to the determination result of the interference. 前記干渉の判断結果に応じて、基地局の適応変調を制御する適応変調制御手段を備えたことを特徴とする請求項１に記載の制御局装置。 The control station apparatus according to claim 1 , further comprising: an adaptive modulation control unit that controls adaptive modulation of a base station in accordance with the interference determination result. 複数の基地局の各々に対して移動局との間の通信用の周波数チャネルを割り当てる制御局の無線通信制御方法であって、
前記移動局毎に受信電波に基づいて作成された基地局のリストに基づき、各基地局のセル間の重複の有無を判断する過程と、
前記判断結果に基づき、所定数の周波数チャネルで、各基地局に対してセル間干渉を回避できる周波数チャネルの割当てが可能か判定する過程と、
前記判定結果に応じて、基地局の組合せ毎の干渉回避の優先順位を決定する過程と、
前記優先順位に従って、各基地局に割り当てる周波数チャネルを決定する過程と、
基地局を表すノードと、セル間の干渉のあり得る基地局間に対応するノード間を接続する枝と、から構成される無線基地局グラフを作成する過程と、
前記無線基地局グラフに応じた彩色多項式を生成する過程と、
を備え、
前記周波数チャネルの割当てが可能か判定する過程は、
前記無線基地局グラフが前記所定数で彩色可能ならば、所定数の周波数チャネルで、各基地局に対してセル間干渉を回避できる周波数チャネルの割当てが可能であると判定し、
前記優先順位を決定する過程は、前記無線基地局グラフにおいて、セル間の干渉の影響が小さいノード間の枝を前記優先順位が低いノードとして切断する際に、前記移動局毎に受信電波に基づいて算出された基地局の組み合わせ毎の搬送波対干渉波電力比に基づき、基地局の組み合わせ毎の搬送波対干渉波電力比の逆数の総和を求め、前記無線基地局グラフにおいて、前記総和がより小さい値となるノード間の枝を切断し、
前記周波数チャネルを決定する過程は、
枝で接続された２つのノードに対応する各基地局に対し、異なる周波数チャネルを割り当てるよう周波数チャネルを決定する
ことを特徴とすることを特徴とする無線通信制御方法。 A wireless communication control method of a control station that assigns a frequency channel for communication with a mobile station to each of a plurality of base stations,
Based on a list of base stations created based on received radio waves for each mobile station, determining whether there is overlap between cells of each base station;
Determining whether it is possible to assign a frequency channel capable of avoiding inter-cell interference to each base station with a predetermined number of frequency channels based on the determination result;
In accordance with the determination result, determining a priority order of interference avoidance for each combination of base stations,
Determining a frequency channel to be assigned to each base station according to the priorities;
A process of creating a radio base station graph composed of nodes representing base stations and branches connecting nodes corresponding to each other between base stations where interference between cells is possible;
Generating a chromatic polynomial according to the radio base station graph;
With
The process of determining whether the frequency channel can be allocated includes:
If the radio base station graph can be colored with the predetermined number, it is determined that it is possible to assign a frequency channel that can avoid inter-cell interference to each base station with a predetermined number of frequency channels,
The step of determining the priority order is based on the received radio wave for each mobile station when a branch between nodes having a small influence of inter-cell interference is cut as the node having a low priority order in the radio base station graph. Based on the carrier-to-interference wave power ratio for each combination of base stations calculated in this way, the sum of the reciprocal of the carrier-to-interference wave power ratio for each combination of base stations is obtained, and the sum is smaller in the radio base station graph. Cut the branch between the value nodes ,
The process of determining the frequency channel includes:
A radio communication control method characterized by deciding a frequency channel so that different frequency channels are allocated to each base station corresponding to two nodes connected by branches . 前記干渉の判断結果に応じて、基地局の送信電力を制御する過程を備えたことを特徴とする請求項４に記載の無線通信制御方法。5. The radio communication control method according to claim 4, further comprising a step of controlling transmission power of the base station according to the interference determination result. 前記干渉の判断結果に応じて、基地局の適応変調を制御する過程を備えたことを特徴とする請求項４に記載の無線通信制御方法。The radio communication control method according to claim 4, further comprising a step of controlling adaptive modulation of a base station in accordance with the interference determination result.
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