JP3634806B2

JP3634806B2 - Wireless LAN system connection device, wireless LAN connection method, wireless LAN system program, and wireless LAN system recording medium

Info

Publication number: JP3634806B2
Application number: JP2002040457A
Authority: JP
Inventors: 亮太美濃越
Original assignee: NTT Comware Corp
Current assignee: NTT Comware Corp
Priority date: 2002-02-18
Filing date: 2002-02-18
Publication date: 2005-03-30
Anticipated expiration: 2022-02-18
Also published as: JP2003244161A

Description

【０００１】
【発明の属する技術分野】
本発明は、送信電力によって定まった通信エリア（セル）内の端末（コンピュータ）と関連付けを行うことにより、この端末と無線通信を行う無線ＬＡＮシステム用接続装置（ＡＰ：ＡｃｃｅｓｓＰｏｉｎｔ）、無線ＬＡＮ接続方法、無線ＬＡＮシステム用プログラム、無線ＬＡＮシステム用記録媒体に関する。
【０００２】
【従来の技術】
企業や大学などの情報化に伴い、ＬＡＮ（ＬｏｃａｌＡｒｅａＮｅｔｗｏｒｋ：ローカルエリアネットワーク）が多数構築されている。しかしながら、部屋のレイアウトの変更が生ずると配線をやり直す必要があったり、古い貴重な建物などでは新たに配線を行うことが難しい場合がある。これらの問題に対処するために、配線の一部或いはほとんどを無線に置き換えた無線ＬＡＮが注目され、標準化が行なわれるようになってきた。
【０００３】
ＬＡＮを利用してデータをどのような方法で媒体（無線ＬＡＮではケーブルではなく、空間）上に送信するかを制御するＭＡＣ（ＭｅｄｉａＡｃｃｅｓｓＣｏｎｔｒｏｌ：媒体アクセス制御）層の分散型アクセス制御方式としては、ＣＳＭＡ（ＣａｒｒｉｅｒＳｅｎｓｅＭｕｌｔｉｐｌｅＡｃｃｅｓｓ）方式がある。このＣＳＭＡ方式では、ＬＡＮ上の各機器は、チャネル上のキャリアの有無を検知して、キャリアが無い場合にフレームを送信する。この方式では、伝送遅延等によりキャリアを検出できず、フレームを送信してしまった場合にフレームの衝突が起こる。有線ＬＡＮについては、ＩＥＥＥ８０２．３で、ＣＳＭＡ方式に送信中のフレーム衝突検出機能とフレーム送信中断機能を付加したＣＳＭＡ／ＣＤ（ＣａｒｒｉｅｒＳｅｎｓｅＭｕｌｔｉｐｌｅＡｃｃｅｓｓｗｉｔｈＣｏｌｌｉｓｉｏｎＤｅｔｅｃｔｉｏｎ：搬送波感知多重アクセス／衝突検出）方式が標準化されている。しかし、無線ＬＡＮでは、送信中にフレームの衝突検出を行うことが困難であるため、ＣＳＭＡ方式に衝突回避機能を付加したＣＳＭＡ／ＣＡ（ＣａｒｒｉｅｒＳｅｎｓｅＭｕｌｔｉｐｌｅＡｃｃｅｓｓｗｉｔｈＣｏｌｌｉｓｉｏｎＡｖｏｉｄａｎｃｅ：搬送波感知多重アクセス／衝突回避）方式が提案・検討されてきた。このＣＳＭＡ／ＣＡ方式によれば、端末から近傍のＡＰ（ＡｃｃｅｓｓＰｏｉｎｔ：接続装置）に対してフレームを送信し、一定期間経過してもＡＰから返信がなければ再びフレームを送信する。
【０００４】
ところが、特定のエリアにのみ多数の端末が集中しり、端末が大量のデータ通信を行った場合にはチャネル負荷が高まり、端末の総要求量がチャネル容量を逼迫し、チャネル内の通信効率や通信品質の低下につながる。そのため、一般に、ＡＰはチャネル負荷が高くなると、接続する端末数を制限したり、各端末との通信レートを下げるといった対策をとる。このような接続端末数を制限する方法としては、端末の新規関連付け要求を拒否したり、既に関連付けされた端末に対して関連付けの強制切断を行う。この方法では、個々のＡＰのチャネル負荷を抑えることは可能であるが、ネットワーク全体の可用性を改善もしくは維持することには必ずしもつながらない。高負荷となったＡＰとの関連付けを拒否又は強制切断された端末は、通信可能な別のチャネル（ＡＰ）を探索し、最大のＲＳＳＩ（ＲｅｃｅｉｖｅＳｉｇｎａｌＳｔｒｅｎｇｔｈＩｎｄｉｃａｔｏｒ：受信電波強度）が得られるチャネルを選択するが、この探索時にＡＰとの距離が遠い場合や電波伝播状況等によりＲＳＳＩが不足し、十分な品質の通信が行えないことがある。特にＡＰの近くに端末が位置した場合に、こうした状況が起こりやすい。このような状況は、図１３を用いて説明することができる。即ち、図１３に示すように、ＡＰ_Ａの通信エリア内に端末α、βが位置し、しかも端末αはＡＰ_Ａから離れた位置、端末βはＡＰ_Ａに近い位置にある場合を考える。このような場合でＡＰ_Ａとの通信が切断されてしまうと、端末αはＡＰ_Ｅのセル内にも位置しているため、ＡＰ_Ｅを探索することによりＡＰ_Ｅと無線通信を行うことができる。しかし、端末βは他のどのＡＰのセル内にも位置していないため、その後の通信を行うことができない。このような端末βは、電波の届く範囲より無線端末間の距離が長い場合や、間に電波を遮る障害物がある場合のように、互いの送信信号を受信できない、いわゆる「隠れ端末」と実質的に同じ状態ということができる。そのため、ＣＳＭＡ／ＣＡ方式では、「隠れ端末」の問題が生じた場合には、通信できない端末は何度も同じフレームを送信することになり、更にチャネル負荷が増加するという悪循環になってしまう。
【０００５】
この「隠れ端末」問題の対策としては、ＣＳＭＡ／ＣＡ方式にＲＴＳ／ＣＴＳ（ＲｅｑｕｅｓｔＴｏＳｅｎｄ／ＣｌｅａｒＴｏＳｅｎｄ）方式による通信権制御の仕組みを加える方法が一般的に知られている。このＲＴＳ／ＣＴＳ方式は、ＩＥＥＥ８０２．１１規格で定義されており、送信許可を要求する信号（ＲＴＳ）と、送信許可に応答する信号（ＣＴＳ）を組み合わせて用いている。即ち、端末が、ＲＴＳを加えて送信許可の有無を確かめ、ＡＰより送信許可のＣＴＳフレームを受け取った場合に送信を行うことができる。この方式では、ＡＰが送信した送信許可のＣＴＳフレームは、ＲＴＳを送信した端末以外の端末へも送信されるため、その時点で他の端末がＡＰと通信を行っていることが分かり、ＣＳＭＡ／ＣＡ方式のように何度も同じＲＴＳフレームを送信するという問題を解決することができる。
【０００６】
【発明が解決しようとする課題】
しかしながら、ＲＴＳ／ＣＴＳ方式では、上記のような再送信を繰り返すことによる悪循環の問題を解決することはできるが、送受信できないという「隠れ端末」の直接的な問題を解決している訳ではない。そのため、ネットワーク全体の可用性が制限されることに変わりはない。
【０００７】
また、上記のように送信方式に着目するのではなくＡＰの送信電力に着目し、図１４に示すように、ＡＰの送信電力を大きくすることによってセルを大きくし、端末βを他のＡＰのセル内にも位置させるようにすれば、「隠れ端末」の直接的な問題を解決することは可能である。即ち、図１４に示すように各ＡＰのセルを大きくすると、端末βは隣のＡＰ_Ｄ，ＡＰ_Ｅのセル内に入るため、ＡＰ_Ａと通信できなくても、ＡＰ_Ｄ又はＡＰ_Ｅと通信することが可能である。しかし、セルを大きくすることによって、送信電力が大きくなるため、ＡＰの低消費電力化の観点から好ましくない。しかも、送信電力を大きくさせ過ぎると、ＡＰ間の電波干渉が発生する可能性もある。
【０００８】
そこで、本発明は上述した事情を鑑みてなされたものであり、ＡＰの消費電力を極力抑えつつ「隠れ端末」の問題を解決することを目的としたものである。
【０００９】
【課題を解決するための手段】
上記目的を達成するため、第１の態様に係る発明は、送信電力によって定まった通信エリア内の端末と関連付けを行うことにより、前記端末と無線通信を行う無線ＬＡＮシステム用接続装置において、自己の接続装置の負荷状態を判定する負荷状態判定手段と、前記負荷状態判定手段によって判定した負荷状態を近傍の接続装置に通知する負荷状態通知手段と、前記近傍の接続装置から通知された前記近傍の接続装置の負荷状態を受信する負荷状態受信手段と、前記負荷状態判定手段によって判定した自己の負荷状態と、前記負荷状態受信手段によって受信した近傍の負荷状態とに基づいて、前記送信電力を制御する送信電力制御手段と、を有することを特徴とする無線ＬＡＮシステム用接続装置である。
【００１０】
第２の態様に係る発明は、前記送信電力制御手段による送信電力の制御は、自己の負荷状態が一定値よりも低い場合であって、近傍の負荷状態が前記一定値よりも高い場合には、送信電力値を上げることであることを特徴とする第１の態様の無線ＬＡＮシステム用接続装置である。
【００１１】
第３の態様に係る発明は、前記送信電力制御手段による送信電力の制御は、自己の負荷状態が一定値よりも高い場合には、前記近傍の負荷状態とは無関係に送信電力値を維持又は下げることであることを特徴とする第１の態様の無線ＬＡＮシステム用接続装置である。
【００１２】
第４の態様に係る発明は、第１の態様の無線ＬＡＮシステム用接続装置であって、更に、前記負荷状態判定手段によって判定した自己の負荷状態に基づいて、自己の通信エリア内における関連付けしていない端末との新規関連付け、及び既に関連付けしている端末とのその後の関連付けを決定する関連付決定手段と、前記関連付決定手段によって決定した関連付けを実行する関連付実行手段と、を有することを特徴とする無線ＬＡＮシステム用接続装置である。
【００１３】
第５の態様に係る発明は、前記関連付決定手段は、既に関連付けしている端末との関連付けを切断する場合には、端末からの受信電力が小さい方から優先に切断することを特徴とする第４の態様の無線ＬＡＮシステム用接続装置である。
【００１４】
第６の態様に係る発明は、送信電力によって定まった通信エリア内の端末と関連付けを行うことにより、前記端末と無線通信を行う無線ＬＡＮシステム用接続装置を利用した無線ＬＡＮ接続方法において、自己の接続装置の負荷状態を判定する負荷状態判定処理と、前記負荷状態判定処理によって判定した負荷状態を近傍の接続装置に通知する負荷状態通知処理と、前記近傍の接続装置から通知された前記近傍の接続装置の負荷状態を受信する負荷状態受信処理と、前記負荷状態判定処理によって判定した自己の負荷状態と、前記負荷状態受信手段によって受信した近傍の負荷状態とに基づいて、前記送信電力を制御する送信電力制御処理と、を実行することを特徴とする無線ＬＡＮ接続方法である。
【００１５】
第７の態様に係る発明は、前記送信電力制御処理による送信電力の制御は、自己の負荷状態が一定値よりも低い場合であって、近傍の負荷状態が前記一定値よりも高い場合には、送信電力値を上げることであることを特徴とする第６の態様の無線ＬＡＮ接続方法である。
【００１６】
第８の態様に係る発明は、前記送信電力制御処理による送信電力の制御は、自己の負荷状態が一定値よりも高い場合には、前記近傍の負荷状態とは無関係に送信電力値を維持又は下げることであることを特徴とする第６の態様の無線ＬＡＮ接続方法である。
【００１７】
第９の態様に係る発明は、第６の態様の無線ＬＡＮ接続方法であって、更に、前記負荷状態判定処理によって判定した自己の負荷状態に基づいて、自己の通信エリア内における関連付けしていない端末との新規関連付け、及び既に関連付けしている端末とのその後の関連付けを決定する関連付決定処理と、前記関連付決定処理によって決定した関連付けを実行する関連付実行処理と、を実行することを特徴とする無線ＬＡＮ接続方法である。
【００１８】
第１０の態様に係る発明は、前記関連付決定処理は、既に関連付けしている端末との関連付けを切断する場合には、端末からの受信電力が小さい方から優先的に切断することを特徴とする第９の態様の無線ＬＡＮ接続方法である。
【００１９】
第１１の態様に係る発明は、送信電力によって定まった通信エリア内の端末と関連付けを行うことにより、前記端末と無線通信を行う無線ＬＡＮシステム用接続装置で用いられる無線ＬＡＮシステム用プログラムにおいて、自己の接続装置の負荷状態を判定する負荷状態判定手段と、前記負荷状態判定手段によって判定した負荷状態を近傍の接続装置に通知する負荷状態通知手段と、前記近傍の接続装置から通知された前記近傍の接続装置の負荷状態を受信する負荷状態受信手段と、前記負荷状態判定手段によって判定した自己の負荷状態と、前記負荷状態受信手段によって受信した近傍の負荷状態とに基づいて、前記送信電力を制御する送信電力制御手段と、を無線ＬＡＮ用接続装置に機能させることを特徴とする無線ＬＡＮシステム用プログラムである。
【００２０】
ここで、本発明における「プログラム」とは、無線ＬＡＮシステム用接続装置（コンピュータ）による処理に適した命令の順番付けられた列からなるものをいい、コンピュータのＨＤＤ、ＣＤ−ＲＷ等にインストールされているものや、ＣＤ−ＲＯＭ、ＤＶＤ、ＦＤ、コンピュータのＨＤＤ等の各種記録媒体に記録されているものも含まれる。
【００２１】
第１２の態様に係る発明は、前記送信電力制御手段による送信電力の制御は、自己の負荷状態が一定値よりも低い場合であって、近傍の負荷状態が前記一定値よりも高い場合には、送信電力値を上げることであることを特徴とする第１１の態様の無線ＬＡＮシステム用プログラムである。
【００２２】
第１３の態様に係る発明は、前記送信電力制御手段による送信電力の制御は、自己の負荷状態が一定値よりも高い場合には、前記近傍の負荷状態とは無関係に送信電力値を維持又は下げることであることを特徴とする第１１の態様の無線ＬＡＮシステム用プログラムである。
【００２３】
第１４の態様に係る発明は、第１１の態様の無線ＬＡＮシステム用プログラムであって、更に、前記負荷状態判定手段によって判定した自己の負荷状態に基づいて、自己の通信エリア内における関連付けしていない端末との新規関連付け、及び既に関連付けしている端末とのその後の関連付けを決定する関連付決定手段と、前記関連付決定手段によって決定した関連付けを実行する関連付実行手段と、を無線ＬＡＮシステム用接続装置に機能させることを特徴とする無線ＬＡＮシステム用プログラムである。
【００２４】
第１５の態様に係る発明は、前記関連付決定手段は、既に関連付けしている端末との関連付けを切断する場合には、端末からの受信電力が小さい方から優先に切断することを特徴とする第１４の態様の無線ＬＡＮシステム用プログラムである。
【００２５】
第１６の態様に係る発明は、第１１乃至第１５の態様の少なくとも１態様の無線ＬＡＮシステム用プログラムを記録したことを特徴とする無線ＬＡＮシステム用接続装置で読み取り可能な無線ＬＡＮシステム用記録媒体である。
【００２６】
ここで、本発明における「記録媒体」とは、無線ＬＡＮシステム用接続装置（コンピュータ）で各手段を機能させるためのプログラムの読み取りに使用することができればよく、情報を媒体の物理的特性を利用してどのように記録するか等の物理的な記録方法には依存しない。例えば、ＦＤ、ＣＤ−ＲＯＭ（Ｒ、ＲＷ）、ＤＶＤ−ＲＯＭ（ＲＡＭ、Ｒ、ＲＷ）、ＭＯ、ＭＤ、磁気テープ等が該当する。
【００２７】
【発明の実施の形態】
以下に、図面を用いて本発明に係る一実施形態を説明する。
【００２８】
図１は、本実施形態に係る無線ＬＡＮシステム１の全体構成を示す図である。図１に示すように、無線ＬＡＮシステム１は、有線ＬＡＮ２を介して通信可能な接続装置としてのＡＰ_Ａ並びに近傍ＡＰ（ＡＰ_Ｂ等）と、各ＡＰと無線ＬＡＮを利用して通信可能なコンピュータ端末（ここでは、端末α）により構築されている。尚、ＡＰの構成は全て同じであるため、以下ではＡＰ_Ａの構成を説明する。また、本実施形態においては、ＡＰ_Ａが端末αと無線通信を行う場合について説明する。
【００２９】
ＡＰ_Ａは、このＡＰ_Ａ全体の制御を行う主制御部（ＣＰＵ）１０と、この主制御部を含めたＡＰ_Ａ全体の動作に必要なプログラム（ｐ）が記憶されているプログラム記憶部１１を備えている。このプログラム（ｐ）は、ＡＰ_Ａに後述する機能（処理）を実行させるためのプログラムである。
【００３０】
また、ＡＰ_Ａは、端末αと無線通信するためのアンテナ１２と、このアンテナ１２に接続されたスイッチ１３を備えると共に、このスイッチ１３の切り換えにより電波を送信する送信部１４及び電波を受信する受信部１５を備えている。更に、ＡＰ_Ａは、送信部１４及び受信部１５の動作を制御する送受信制御部１７を備えている。また、ＡＰ_Ａは、送信部１４の送信電力を制御する送信電力制御部１６を備えており、更に送信電力制御部１６は主制御部１０によって動作が制御される。更に、ＡＰ_Ａは、受信部１５で受信した電波の電力を計測する受信電力計測部１８を備えている。また、ＡＰ_Ａは、主制御部１０で後述の３つの負荷状態を判定するために、自己ＡＰ_Ａの負荷計測を行う負荷計測部１９を備えている。更に、ＡＰ_Ａは、主制御部１０と外部の設定端末３及び有線ＬＡＮ２を接続するための外部インターフェース２０を備えている。
【００３１】
また、ＡＰ_Ａには、送信電力値テーブル２１、受信電力値テーブル２２、負荷閾値テーブル２３、及び隣接ＡＰ定義テーブル２４が構築されている。
【００３２】
このうち、送信電力値テーブル２１は、図２に示すように、送信電力レベル毎に電力値が設定されており、送信電力制御部１６で送信部１４の送信電力を変化させるために用いるテーブルである。
【００３３】
また、受信電力値テーブル２２は、図３に示すように、各端末の端末ＭＡＣアドレス毎にＲＳＳＩを管理するためのテーブルであり、受信電力計測部１８で計測された電力値（最新値）を管理する。尚、受信電力計測部１８は、自己ＡＰ_Ａに関連付けられた端末毎に電力値を計測し、端末との通信が行われるたびに、この端末のエントリが無い場合は追加し、既に端末のエントリがある場合は値を更新する。
【００３４】
また、負荷閾値テーブル２３は、図４に示すように、自己ＡＰ_Ａのチャネル負荷の状態を決定する負荷閾値（％）を管理するためのテーブルである。
【００３５】
また、近傍ＡＰ定義テーブル２４は、図５に示すように、自己ＡＰ_Ａの近傍のＡＰのＭＡＣアドレスを管理するためのテーブルである。この近傍ＡＰ定義テーブル２４で管理している近傍ＡＰは、自己ＡＰ_Ａの近傍に設置された１つ以上のＡＰであって、自己ＡＰ_Ａのセルと重なるセルを有するＡＰである。この近傍ＡＰは、ＡＰ配置トポロジー、電波伝播状況を考慮して設定する。
【００３６】
尚、送信電力値テーブル２１、負荷閾値テーブル２３、及び隣接ＡＰ定義テーブル２４に管理されている値は、設定端末２を利用して入力することが可能であり、各テーブル２１，２３，２４にはＡＰ_Ａの始動前にデータを入力しておく。
【００３７】
続いて、本実施形態の特徴部分を更に詳細に説明する。尚、本実施形態の特徴的な機能は、大きく分けて（１）自己ＡＰ_Ａの負荷状態の判定、（２）判定した負荷情報に基づいた端末の関連付けの変更、（３）自己ＡＰ_Ａと近傍ＡＰの負荷状態に基づいた自己ＡＰ_Ａの送信電力の変更、の３つであるため、以下ではこれらの特徴を分けて説明する。
【００３８】
（１）自己ＡＰ_Ａの負荷状態の判定
負荷計測部１９では、チャネルビジー率、自己ＡＰ_Ａが関連付けする端末数、ＡＰ_ＡのＣＰＵ使用率などを個別に採用するか、若しくはこれらを組み合わせて採用することによって自己ＡＰ_Ａの負荷値を計測する。また、主制御部１０では、負荷計測部１９で計測した負荷計測値に基づいて、自己ＡＰ_Ａの負荷状態を判定する。この判定方法は、負荷計測部１９で計測した負荷計測値を図４に示す負荷閾値テーブル２３に照らし合わせて、４つの負荷閾値（Ｌ_ＨｔｏＬ、Ｌ_ＬｔｏＨ、Ｌ_ＥｔｏＨ、Ｌ_ＨｔｏＥ）の中から一つを選択し、この選択した負荷閾値を図６に示すＡＰの負荷状態の状態遷移概念に基づいて、３つの負荷状態（低負荷、高負荷、極高負荷）の中のいずれの状態であるかを判定するものである。尚、図４に示す負荷閾値は、一例であって、これに限定するものではない。
【００３９】
また、図４に示す負荷閾値は、負荷状態に対してヒステリシス的に遷移するように設定しておく必要がある。このように設定するのは、ＡＰ_Ａの負荷状態が短い間隔で頻繁に遷移すると、次のような問題が生じるからである。即ち、ＡＰ_Ａ側では、主制御部１０による後述の関連付け処理や送信電力制御が頻繁に行われ、ＡＰ_Ａの処理増加を引き起こし、端末α側では、ＡＰの切り換えを頻繁に行うことにより、通信のオーバヘッドが増加し、チャネル負荷が増加するという問題である。
【００４０】
また、主制御部１０により、自己ＡＰ_Ａの負荷状態が遷移する度に、外部インターフェース２０及び有線ＬＡＮ２を介して、全ての近傍ＡＰに対し、上記判定した自己の負荷状態を通知する。また逆に、近傍ＡＰの負荷状態が遷移する度に、近傍ＡＰから有線ＬＡＮ２を介して通知された近傍ＡＰの負荷状態通知を受信する。
【００４１】
（２）判定した負荷状態に基づいた端末の関連付けの変更
主制御部１０は、上記判定した自己ＡＰ_Ａの負荷状態に基づいて、図７に示すように、端末との関連付けを決定する。例えば、自己ＡＰ_Ａが低負荷の場合には、端末からの新規関連付けの要求（送信許可要求）を許可すると共に、既に関連付けしている端末との関連付けを維持する。また、自己ＡＰ_Ａが高負荷の場合には、端末からの新規関連付けの要求を拒否するが、既に関連付けしている端末との関連付けは維持する。更に、自己ＡＰ_Ａが極高負荷の場合には、端末からの新規関連付けの要求を拒否すると共に、既に関連付けしている端末との関連付けを強制切断する。
【００４２】
また、関連付けの強制切断に関しては、図３に示す受信電力値テーブル２２を参照し、受信電力が小さい端末から優先的に一つずつ所定の時間間隔（ｔ_{ｔｒａｎｓ}）をおいて切断するように制御する。これにより、端末の位置がセルの周縁部に近い順（ＡＰ_Ａから遠い順）に切断することになるため、ＡＰ_Ａの近くで発生し易い隠れ端末の出現の可能性を低く抑えながら関連付けの切断を行うことができる。但し、電波伝播状況や端末の移動によって、切断順序が前後することはあり得る。
【００４３】
尚、上記所定の時間間隔（ｔ_{ｔｒａｎｓ}）、つまり、関連づけの切断間隔については、端末の関連付け切断により自己ＡＰ_Ａの負荷状態が変化する際に、軽減された新たな負荷定常値に遷移するまでの時間が確保されるように設定する。
【００４４】
（３）自己ＡＰ_Ａと近傍ＡＰの負荷状態に基づいた自己ＡＰ_Ａの送信電力の変更
送信電力制御部１６は、自己ＡＰ_Ａ又は近傍ＡＰの負荷状態が遷移する度に、図８に示す主制御部１０からの送信電力レベルの指示（Ｂｏｏｓｔレベル／通常レベル）に従い、図２に示す送信電力テーブル２１に管理された電力値（Ｂｏｏｓｔレベルの値／通常レベルの値）に基づいて送信電力値（ｍＷ）を変化させる。即ち、送信電力制御部１６は、上記自己の負荷状態と受信した近傍の負荷状態に基づいて、図８に示すように、通常レベルとＢｏｏｓｔレベル（通常レベルの電力＜Ｂｏｏｓｔレベルの電力）のどちらかに自己ＡＰ_Ａの送信電力を変更させるように制御する。ここで、上記図７との違いは、図７では、自己ＡＰ_Ａの負荷状態のみに基づいて端末との関連付けを変更させるのに対して、図８では、自己ＡＰ_Ａと近傍ＡＰの両方の負荷状態に基づいて自己ＡＰ_Ａの送信電力レベルを制御させる点である、例えば、図８に示すように、自己ＡＰ_Ａが極高負荷の場合には、たとえ近傍ＡＰが極高負荷であっても、ＡＰ_Ａは近傍ＡＰの負荷状態とは無関係に、送信電力レベルを通常のレベルのままに維持することになる。一方、近傍ＡＰが極高負荷であって、自己ＡＰ_Ａが低負荷の場合には、自己ＡＰ_Ａと近傍ＡＰを含めた無線ＬＡＮシステム１全体として負荷分散を行い、ＡＰ_Ａは送信電力レベルをＢｏｏｓｔレベルに上げて近傍ＡＰを補助する。
【００４５】
尚、Ｂｏｏｓｔレベルは、近傍ＡＰのセル内に位置する隠れ端末に十分な強度で電波が届くように設定するが、送信電力の増加によるＡＰ間の電波干渉を考慮して、同じ周波数帯の電波が干渉しない範囲となるように送信電力を設定する必要がある。
【００４６】
続いて、本実施形態に係る無線ＬＡＮシステム１の動作について説明する。尚、ここでは、各ＡＰが図９（ａ）に示すように低負荷状態の場合から、図９（ｂ）に示すように、ＡＰ_Ａが極高負荷状態（又は高負荷状態）になったが、近傍ＡＰは低負荷状態のままである場合について説明する。図９（ａ）は、ＡＰ_Ａ及び近傍ＡＰ（ＡＰ_Ｂ，ＡＰ_Ｃ，ＡＰ_Ｄ，ＡＰ_Ｅ，ＡＰ_Ｆ，ＡＰ_Ｇ）からなる無線ＬＡＮシステム１において、ＡＰ_Ａのセル内に端末α、端末β、端末γが存在している場合を示している。尚、ＡＰ_Ａと端末β間の実線矢印は、既に関連付けしている状態（同期済み状態）を示している。即ち、この時点では、ＡＰ_Ａと端末α、端末γの関連付けは行われていない。
【００４７】
図８（ａ）に示す状態で、端末βが大量のデータ通信等を行った結果、ＡＰ_Ａのチャネル負荷が高まると、端末α、γは実質的な隠れ端末の状態となる。この場合において、ＡＰ_Ａの負荷計測部１９では自己ＡＰ_Ａの負荷値を計測する。また、主制御部１０では、負荷計測部１９で計測した負荷計測値に基づいて、自己ＡＰ_Ａの負荷状態を判定する。ここでは、高負荷状態になったと判定している。
【００４８】
次に、主制御部１０は、上記判定した自己ＡＰ_Ａの負荷状態に基づいて、図７に示すように、端末βとの関連付けを決定する。この決定に基づいて、主制御部１０は、関連付けを実行する。ここでは、高負荷状態であるため、主制御部１０は、端末α及び端末γからの新規関連付けの要求を拒否するが、既に関連付けられた端末βとの関連付けを維持する。
【００４９】
一方、自己ＡＰ_Ａの負荷状態が低負荷状態から高負荷状態に遷移しているため、主制御部１０は、外部インターフェース２０及び有線ＬＡＮ２を介して、全ての近傍ＡＰに対し、自己ＡＰ_Ａの負荷状態を通知する。これにより、近傍ＡＰでは、ＡＰ_Ａからの通知を受信する。
【００５０】
次に、各近傍ＡＰでは、図８に示すそれぞれの主制御部１０からの指示（Ｂｏｏｓｔレベル／通常レベル）に従い、図２に示すそれぞれの送信電力テーブル２１に格納された電力値（Ｂｏｏｓｔレベルの値／通常レベルの値）に基づいて、送信電力値（ｍＷ）を変化させる。ここでは、各近傍ＡＰは低負荷状態であり、近傍ＡＰ_Ｂ等から見た近傍ＡＰとしてのＡＰ_Ａは高負荷状態であるため、各近傍ＡＰでは、送信電力を上げてＢｏｏｓｔレベルに変更する。図９（ｂ）は、このように各近傍ＡＰでＢｏｏｓｔレベルに変更した結果、各近傍ＡＰのセルが大きくなった状態を示している。これにより、端末αは、ＡＰ_Ａと関連付けを行うことができなくても、新規接続先ＡＰを探索することにより、ＡＰ_Ｅ又はＡＰ_Ｄと関連付けを行うことができる。また、端末γは、同じくＡＰ_Ａと関連付けを行うことができなくても、新規接続先ＡＰを探索することにより、ＡＰ_Ｃと関連付けを行うことができる。
【００５１】
以上説明したように、本実施形態によれば、隠れ端末としての端末α，γは、近傍ＡＰと通信を行うことができるため、隠れ端末の問題を解決することができる。しかも、近傍ＡＰは、通常は送信電力レベルを通常レベルにしておき、ＡＰ_Ａの通信を補助するときだけＢｏｏｓｔレベルに上げるため、各ＡＰの送信電力を極力抑えることができる。
【００５２】
尚、図７の負荷状態に応じた関連付け処理のマッピング、及び、図８の負荷状態に応じた送信電力のマッピングは、運用ポリシーに合わせてカスタマイズ可能である。例えば、図１０に示すように、負荷状態として負荷が低負荷状態よりさらに低い「極低負荷状態」を追加し（同時に、対応する負荷閾値を追加し、関連付け処理のマッピングも変更する）、出力レベルとしてＳａｖｅレベル、通常レベル、Ｂｏｏｓｔレベルを設定することも可能である。また、自己ＡＰ_Ａの負荷状態のみに着目して、自己ＡＰ_Ａが極高負荷時には、図１１に示すように、通常レベルより低い「Ｓａｖｅレベル」を設定することも可能である。このように負荷状態に応じた関連付け処理のマッピング、及び、負荷状態に応じた送信出力レベルのマッピングのカスタマイズにより、運用ポリシーに応じて細かな負荷分散制御設定が可能になる。但し、「Ｓａｖｅレベル」は、電力低下により信号対雑音比が低下することを考慮して、通信品質が良好に保たれる範囲内に設定する必要がある。
【００５３】
以上のような負荷状態及び送信出力の細分化により、以下に示すような無線ＬＡＮシステム１’の動作が可能となる。
【００５４】
ここでは、各ＡＰが図１２（ａ）に示すように低負荷状態の場合から、図１２（ｂ）に示すように、ＡＰ_Ａが極高負荷状態になったが、近傍ＡＰは低負荷状態のままである場合について説明する。図１２（ａ）は、ＡＰ_Ａ及び近傍ＡＰからなる無線ＬＡＮシステム１’において、ＡＰ_Ａのセル内に端末α、端末β、端末γが存在している場合を示している。尚、ＡＰ_Ａと端末β間の実線矢印は、既に関連付けしている状態（同期済み状態）を示している。即ち、この時点では、ＡＰ_Ａと端末α、端末γの関連付けは行われていない。
【００５５】
図１２（ａ）に示す状態で、端末βが大量のデータ通信等を行った結果、ＡＰ_Ａのチャネル負荷が非常に高まると、図１０に示すように、ＡＰ_Ａは端末α，γの新規関連付けを拒否するため、端末α，γは実質的な隠れ端末の状態となる。しかも、図１０に示すように、ＡＰ_Ａは既に関連付けられている端末βとの関連付けを切断する。しかし、図１１に示すように、自己ＡＰ_Ａは送信電力をＳａｖｅレベルに下げると共に、近傍ＡＰは送信電力をＢｏｏｓｔレベルに上げる。このように無線ＬＡＮシステム１’全体として負荷分散を行うことにより、図１２（ｂ）に示すように、端末αはＡＰ_Ｄ又はＡＰ_Ｅと通信可能となり、端末βはＡＰ_Ｆ又ＡＰ_Ｇと通信可能となり、端末γはＡＰ_Ｂ、ＡＰ_Ｃ又はＡＰ_Ｄと通信可能となる。
【００５６】
以上説明したように、Ｓａｖｅレベルまで送信電力を細分化することによって、自己ＡＰ_Ａが既に関連付けしていた端末βとの関連付けを切断しなければならないような極高負荷状態になった場合でも、自己ＡＰ_Ａを保護することが可能である。
【００５７】
また、上記実施形態において、近傍ＡＰが高負荷となった場合に、ＡＰ_Ａのアンテナ１２を指向性を有するものとし、近傍ＡＰの方向へだけ送信出力を増加させるように制御してもよい。これにより、少ない消費電力で負荷分散を行え、また、出力を増加させた際の近傍ＡＰとの電波干渉を少なく抑えることができる。この組み合わせた方式を実現するためには、近傍ＡＰ定義テーブルに各近傍ＡＰに対して方位情報を付加し、指向性アンテナ毎の送信電力制御を行えばよい。
【００５８】
また、上記実施形態に係る発明に対して、更に自己ＡＰ_Ａの負荷に応じて各端末との通信レートを変化させる機能を付加することにより、上記実施形態における関連付けの方法を修正又は変更する必要はない。
【００５９】
更に、上記実施形態におけるプログラム記憶部１１へのプログラム（ｐ）の記憶作業は、プログラム（ｐ）が記録されているＣＤ−ＲＯＭ等の記録媒体を利用することによって行うことも可能である。
【００６０】
【発明の効果】
以上説明したように、本発明によれば、複数のＡＰが自己の負荷状態を互いに送受信して把握し、自己ＡＰの負荷状態と近傍ＡＰの負荷状態に基づいて、送信電力を制御することにより、近傍ＡＰが高負荷状態で自己ＡＰが低負荷状態の場合には、近傍ＡＰの通信を補助すべく送信出力を上げる等の制御を行うことができる。このように、無線ＬＡＮシステム全体として負荷分散を行うことによって、実質的な「隠れ端末」の問題を解決することができる。しかも、近傍ＡＰは、通常は送信電力レベルを通常レベルにしておき、ＡＰ_Ａの通信を補助するときだけ上げる等の送信電力の制御を行うことで、各ＡＰの送信電力をできるだけ抑えることもできる。
【図面の簡単な説明】
【図１】本発明の一実施形態に係る無線ＬＡＮシステム１の全体構成を示す図。
【図２】本発明の送信電力値テーブル２１の概念図。
【図３】本発明の受信電力値テーブル２２の概念図。
【図４】本発明の負荷閾値テーブル２３の概念図。
【図５】本発明の近傍ＡＰ定義テーブル２４の概念図。
【図６】ＡＰの負荷状態の状態遷移を示した概念図。
【図７】実施形態に係る自己ＡＰの負荷状態に応じた端末との関連付けの処理を示した概念図。
【図８】実施形態に係る自己ＡＰと近傍ＡＰの負荷状態に応じた自己ＡＰの送信電力レベルを示した概念図。
【図９】各ＡＰが低負荷状態の場合（ａ）から、ＡＰ_Ａが極高負荷状態（又は高負荷状態）になったが、近傍ＡＰは低負荷状態のままである場合（ｂ）のセルの大きさ（通信エリアの範囲）を示した図。
【図１０】他の実施形態に係る自己ＡＰの負荷状態に応じた端末との関連付けの処理を示した概念図。
【図１１】他の実施形態に係る自己ＡＰと近傍ＡＰの負荷状態に応じた自己ＡＰの送信電力レベルを示した概念図。
【図１２】各ＡＰが低負荷状態の場合（ａ）から、ＡＰ_Ａが極高負荷状態になったが、近傍ＡＰは低負荷状態のままである場合（ｂ）のセルの大きさ（通信エリアの範囲）を示した図。
【図１３】従来の無線ＬＡＮシステムにおける各ＡＰのセルの大きさ（通信エリアの範囲）を示した図。
【図１４】従来の無線ＬＡＮシステムにおける各ＡＰのセルの大きさ（通信エリアの範囲）を示した図。
【符号の説明】
１無線ＬＡＮシステム
２有線ＬＡＮ
３設定端末
１０主制御部
１１プログラム記憶部
１２アンテナ
１３スイッチ
１４送信部
１５受信部
１６送信電力制御部
１７送受信制御部
１８受信電力計測部
１９負荷計測部
２０外部インターフェース
２１送信電力値テーブル
２２受信電力値テーブル
２３負荷閾値テーブル
２４近傍ＡＰ定義テーブル
（ｐ）プログラム（無線ＬＡＮシステム用プログラム）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wireless LAN system connection device (AP: Access Point) that performs wireless communication with a terminal (computer) in a communication area (cell) determined by transmission power, and wireless LAN connection. The present invention relates to a method, a wireless LAN system program, and a wireless LAN system recording medium.
[0002]
[Prior art]
Along with informatization of companies and universities, many LANs (Local Area Networks) are constructed. However, if the room layout is changed, it may be necessary to redo the wiring, or it may be difficult to newly perform wiring in an old valuable building. In order to cope with these problems, a wireless LAN in which a part or most of the wiring is replaced with wireless is attracting attention and standardization has been performed.
[0003]
As a distributed access control method of a MAC (Media Access Control) medium that controls how data is transmitted on a medium (a space rather than a cable in a wireless LAN) using a LAN. And CSMA (Carrier Sense Multiple Access). In this CSMA system, each device on the LAN detects the presence or absence of a carrier on the channel, and transmits a frame when there is no carrier. In this method, when a carrier cannot be detected due to a transmission delay or the like and a frame is transmitted, a frame collision occurs. For wired LANs, IEEE 802.3 is a CSMA / CD (Carrier Sense Multiple Access Collision Detection) method in which a frame collision detection function during transmission and a frame transmission interruption function are added to the CSMA system. Has been standardized. However, in a wireless LAN, it is difficult to detect a collision of a frame during transmission. Therefore, CSMA / CA (Carrier Sense Multiple Access Collision Avidance): a carrier sense-sensitive multiple access / collision avoidance. ) Method has been proposed and studied. According to this CSMA / CA system, a frame is transmitted from a terminal to a nearby AP (Access Point), and if there is no response from the AP even after a certain period of time, the frame is transmitted again.
[0004]
However, when a large number of terminals are concentrated only in a specific area and a terminal performs a large amount of data communication, the channel load increases, and the total required amount of terminals imposes the channel capacity, and the communication efficiency and communication within the channel It leads to quality degradation. Therefore, generally, when the channel load becomes high, the AP takes measures such as limiting the number of terminals to be connected or lowering the communication rate with each terminal. As a method for limiting the number of such connected terminals, a new association request for a terminal is rejected, or the association is forcibly disconnected for an already associated terminal. This method can reduce the channel load of individual APs, but does not necessarily improve or maintain the availability of the entire network. The terminal rejected or forcibly disconnected from the AP having a high load searches for another communicable channel (AP), and selects a channel from which the maximum RSSI (Receive Signal Strength Indicator) can be obtained. Although it is selected, there may be a case where the RSSI is insufficient due to a long distance from the AP or a radio wave propagation state during the search, and communication with sufficient quality may not be performed. Such a situation is likely to occur particularly when the terminal is located near the AP. Such a situation can be described with reference to FIG. That is, as shown in FIG. _A Terminals α and β are located within the communication area of _A Away from, terminal β is AP _A Consider the case where the position is close to. In such a case, AP _A If the communication with the terminal α is disconnected, the terminal α _E AP is also located in the cell _E By searching for AP _E Wireless communication. However, since the terminal β is not located in the cell of any other AP, subsequent communication cannot be performed. Such terminals β are so-called “hidden terminals” that cannot receive each other's transmission signals, such as when the distance between wireless terminals is longer than the reach of radio waves, or when there are obstacles that block radio waves between them. It can be said that it is substantially the same state. Therefore, in the CSMA / CA system, when the problem of “hidden terminal” occurs, a terminal that cannot communicate transmits the same frame over and over, resulting in a vicious circle in which the channel load further increases.
[0005]
As a countermeasure for the “hidden terminal” problem, a method of adding a communication right control mechanism based on an RTS / CTS (Request To Send / Clear To Send) method to the CSMA / CA method is generally known. This RTS / CTS method is defined in the IEEE 802.11 standard, and uses a combination of a signal requesting transmission permission (RTS) and a signal responding to transmission permission (CTS). That is, the terminal can confirm the presence / absence of transmission permission by adding RTS, and can perform transmission when receiving a transmission-permitted CTS frame from the AP. In this scheme, the transmission-permitted CTS frame transmitted by the AP is also transmitted to a terminal other than the terminal that transmitted the RTS, so that it is understood that the other terminal is communicating with the AP at that time. The problem that the same RTS frame is transmitted many times as in the CA method can be solved.
[0006]
[Problems to be solved by the invention]
However, although the RTS / CTS method can solve the problem of vicious circle caused by repeating retransmission as described above, it does not solve the direct problem of “hidden terminal” that cannot be transmitted and received. Therefore, the availability of the entire network is still limited.
[0007]
In addition, paying attention to the transmission power of the AP instead of focusing on the transmission method as described above, as shown in FIG. 14, the cell is enlarged by increasing the transmission power of the AP, and the terminal β is set to another AP. If it is also located in the cell, it is possible to solve the direct problem of “hidden terminal”. That is, when the cell of each AP is enlarged as shown in FIG. _D , AP _E AP to enter the cell of _A Even if you can not communicate with AP _D Or AP _E It is possible to communicate with. However, increasing the cell increases the transmission power, which is not preferable from the viewpoint of reducing the power consumption of the AP. Moreover, if the transmission power is increased too much, radio wave interference between APs may occur.
[0008]
Therefore, the present invention has been made in view of the above-described circumstances, and an object thereof is to solve the “hidden terminal” problem while suppressing the power consumption of the AP as much as possible.
[0009]
[Means for Solving the Problems]
To achieve the above objective, First aspect The present invention relates to a load state determination for determining a load state of its own connection device in a connection device for a wireless LAN system that performs wireless communication with the terminal by associating with a terminal in a communication area determined by transmission power. Means, a load state notifying unit for notifying a nearby connection device of the load state determined by the load state determination unit, and a load state reception for receiving the load state of the nearby connection device notified from the nearby connection device And a transmission power control means for controlling the transmission power based on the own load state determined by the load state determination means and a nearby load state received by the load state reception means. This is a connection device for a wireless LAN system.
[0010]
Second aspect In the invention according to the present invention, the transmission power control by the transmission power control means is performed when the own load state is lower than a certain value, and the neighboring load state is higher than the certain value, the transmission power value It is characterized by raising First aspect This is a connection device for a wireless LAN system.
[0011]
Third aspect In the invention according to claim 1, the transmission power control by the transmission power control means is to maintain or lower the transmission power value regardless of the neighboring load state when its own load state is higher than a certain value. It is characterized by First aspect This is a connection device for a wireless LAN system.
[0012]
Fourth aspect The invention according to First aspect The wireless LAN system connection apparatus according to claim 1, further comprising: a new association with an unassociated terminal in the own communication area based on the own load state determined by the load state determination unit; A connection device for a wireless LAN system, comprising: association determining means for determining subsequent association with a terminal that is present; and association executing means for executing association determined by the association determining means.
[0013]
Fifth aspect The association determining means is characterized in that, when disconnecting the association with a terminal that has already been associated, the association determination unit preferentially disconnects the received power from the terminal in ascending order. Fourth aspect This is a connection device for a wireless LAN system.
[0014]
Sixth aspect In the wireless LAN connection method using the wireless LAN system connection device that performs wireless communication with the terminal by associating with the terminal in the communication area determined by the transmission power, the invention according to A load state determination process for determining a state, a load state notification process for notifying a nearby connection device of the load state determined by the load state determination process, and a load of the nearby connection device notified from the nearby connection device Transmission power control for controlling the transmission power based on a load state reception process for receiving a state, a self load state determined by the load state determination process, and a nearby load state received by the load state reception means A wireless LAN connection method.
[0015]
Seventh aspect In the invention according to the present invention, the transmission power control by the transmission power control process is performed when the own load state is lower than a certain value, and when the neighboring load state is higher than the certain value, the transmission power value is It is characterized by raising Sixth aspect This is a wireless LAN connection method.
[0016]
Eighth aspect In the invention according to the present invention, the transmission power control by the transmission power control process is to maintain or lower the transmission power value regardless of the neighboring load state when its own load state is higher than a certain value. It is characterized by Sixth aspect This is a wireless LAN connection method.
[0017]
Ninth aspect The invention according to Sixth aspect The wireless LAN connection method according to claim 1, further comprising: a new association with an unassociated terminal in the own communication area and an already associated terminal based on the own load state determined by the load state determination process The wireless LAN connection method is characterized by executing an association determination process for determining a subsequent association with and an association execution process for executing the association determined by the association determination process.
[0018]
Tenth aspect The invention according to claim is characterized in that, in the association determination process, when the association with a terminal that has already been associated is disconnected, the association determination process preferentially disconnects from a terminal having a lower reception power. Ninth aspect This is a wireless LAN connection method.
[0019]
Eleventh aspect In the wireless LAN system program used in the wireless LAN system connection device that performs wireless communication with the terminal by associating with the terminal in the communication area determined by the transmission power, the invention according to A load state determining unit for determining a load state, a load state notifying unit for notifying a nearby connection device of the load state determined by the load state determination unit, and the nearby connection device notified from the nearby connection device. Transmission power for controlling the transmission power based on a load condition receiving means for receiving a load condition, a self load condition determined by the load condition determining means, and a nearby load condition received by the load condition receiving means A program for a wireless LAN system, characterized by causing a wireless LAN connection device to function as a control means. .
[0020]
Here, the “program” in the present invention refers to an ordered sequence of instructions suitable for processing by a wireless LAN system connection device (computer), and is installed in a computer HDD, CD-RW, or the like. And those recorded on various recording media such as CD-ROM, DVD, FD, and computer HDD.
[0021]
12th aspect In the invention according to the present invention, the transmission power control by the transmission power control means is performed when the own load state is lower than a certain value, and the neighboring load state is higher than the certain value, the transmission power value It is characterized by raising Eleventh aspect This is a program for the wireless LAN system.
[0022]
13th aspect In the invention according to claim 1, the transmission power control by the transmission power control means is to maintain or lower the transmission power value regardless of the neighboring load state when its own load state is higher than a certain value. It is characterized by Eleventh aspect This is a program for the wireless LAN system.
[0023]
14th aspect The invention according to Eleventh aspect The wireless LAN system program of the present invention is further related to a new association with an unassociated terminal in its own communication area based on the own load status determined by the load status determination means, and has already been associated A wireless LAN system that causes a connection device for a wireless LAN system to function associating determining means for determining subsequent association with a terminal and associating execution means for executing the association determined by the association determining means; This is a system program.
[0024]
15th aspect The association determining means is characterized in that, when disconnecting the association with a terminal that has already been associated, the association determination unit preferentially disconnects the received power from the terminal in ascending order. 14th aspect This is a program for the wireless LAN system.
[0025]
16th aspect The invention according to At least one of the eleventh to fifteenth aspects A wireless LAN system recording medium readable by a wireless LAN system connection device, wherein the wireless LAN system program is recorded.
[0026]
Here, the “recording medium” in the present invention only needs to be used for reading a program for causing each means to function in a connection device (computer) for a wireless LAN system, and information uses physical characteristics of the medium. Thus, it does not depend on a physical recording method such as how to record. For example, FD, CD-ROM (R, RW), DVD-ROM (RAM, R, RW), MO, MD, magnetic tape, etc. are applicable.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0028]
FIG. 1 is a diagram showing an overall configuration of a wireless LAN system 1 according to the present embodiment. As shown in FIG. 1, the wireless LAN system 1 includes an AP as a connection device that can communicate via a wired LAN 2. _A And neighboring APs (AP _B Etc.) and a computer terminal (here, terminal α) that can communicate with each AP using a wireless LAN. Since all AP configurations are the same, AP _A The structure of will be described. In the present embodiment, AP _A A case will be described in which performs wireless communication with the terminal α.
[0029]
AP _A This AP _A Main control unit (CPU) 10 that performs overall control, and AP including this main control unit _A A program storage unit 11 in which a program (p) necessary for the entire operation is stored is provided. This program (p) _A Is a program for executing a function (processing) described later.
[0030]
AP _A Includes an antenna 12 for wireless communication with the terminal α, a switch 13 connected to the antenna 12, and a transmission unit 14 that transmits radio waves by switching the switch 13 and a reception unit 15 that receives radio waves. ing. In addition, AP _A Includes a transmission / reception control unit 17 that controls operations of the transmission unit 14 and the reception unit 15. AP _A Includes a transmission power control unit 16 that controls transmission power of the transmission unit 14, and the operation of the transmission power control unit 16 is controlled by the main control unit 10. In addition, AP _A Includes a received power measuring unit 18 that measures the power of the radio wave received by the receiving unit 15. AP _A In order to determine the three load states to be described later in the main control unit 10, the self-AP _A The load measurement unit 19 that performs the load measurement is provided. In addition, AP _A Includes an external interface 20 for connecting the main control unit 10 to the external setting terminal 3 and the wired LAN 2.
[0031]
AP _A A transmission power value table 21, a reception power value table 22, a load threshold table 23, and an adjacent AP definition table 24 are constructed.
[0032]
Among these, the transmission power value table 21 is a table in which a power value is set for each transmission power level as shown in FIG. 2 and is used for changing the transmission power of the transmission unit 14 by the transmission power control unit 16. is there.
[0033]
Further, the received power value table 22 is a table for managing RSSI for each terminal MAC address of each terminal, as shown in FIG. 3, and the power value (latest value) measured by the received power measuring unit 18. to manage. The received power measuring unit 18 is connected to the own AP. _A The power value is measured for each terminal associated with the terminal, and every time communication with the terminal is performed, if there is no entry for this terminal, it is added. If there is already an entry for the terminal, the value is updated.
[0034]
In addition, the load threshold table 23 includes a self-AP as shown in FIG. _A It is a table for managing the load threshold value (%) for determining the channel load state of.
[0035]
In addition, as shown in FIG. _A Is a table for managing the MAC addresses of APs in the vicinity of. Neighboring APs managed by this neighboring AP definition table 24 are self APs. _A One or more APs installed in the vicinity of the self-AP _A AP having a cell that overlaps the cell. This neighboring AP is set in consideration of the AP arrangement topology and the radio wave propagation situation.
[0036]
The values managed in the transmission power value table 21, the load threshold table 23, and the adjacent AP definition table 24 can be input using the setting terminal 2, and each table 21, 23, 24 can be input. Is AP _A Data is input before starting.
[0037]
Subsequently, the characteristic part of the present embodiment will be described in more detail. The characteristic functions of this embodiment can be broadly divided into (1) self AP. _A (2) change of terminal association based on the determined load information, (3) self AP _A And self AP based on the load state of neighboring AP _A Therefore, these characteristics will be described separately below.
[0038]
(1) Self AP _A Load status
In the load measuring unit 19, the channel busy rate, self AP _A Number of terminals associated with the AP _A Adopting the CPU usage rate of each of them individually or combining them to adopt the self AP _A Measure the load value. Further, the main control unit 10 determines the self AP based on the load measurement value measured by the load measurement unit 19. _A Determine the load state. This determination method is performed by comparing the load measurement value measured by the load measurement unit 19 with the load threshold value table 23 shown in FIG. _HtoL , L _LtoH , L _EtoH , L _HtoE ), And the selected load threshold is selected from among the three load states (low load, high load, and extremely high load) based on the state transition concept of the load state of the AP shown in FIG. Which state is determined. The load threshold shown in FIG. 4 is an example, and the present invention is not limited to this.
[0039]
Further, the load threshold shown in FIG. 4 needs to be set so as to transition in a hysteresis manner with respect to the load state. This setting is for AP _A This is because the following problems occur if the load state frequently changes at short intervals. That is, AP _A On the side, the association processing and transmission power control described later by the main control unit 10 are frequently performed, and the AP _A In the terminal α side, frequent switching of APs causes an increase in communication overhead and an increase in channel load.
[0040]
In addition, the main controller 10 _A Each time the load state changes, the determined self load state is notified to all neighboring APs via the external interface 20 and the wired LAN 2. Conversely, every time the load state of the neighboring AP changes, a load state notification of the neighboring AP notified from the neighboring AP via the wired LAN 2 is received.
[0041]
(2) Changing terminal association based on the determined load state
The main control unit 10 determines the self AP determined above. _A As shown in FIG. 7, the association with the terminal is determined based on the load state. For example, self AP _A When the load is low, a request for a new association (transmission permission request) from the terminal is permitted and the association with the already associated terminal is maintained. Self AP _A Is a heavy load, the request for new association from the terminal is rejected, but the association with the already associated terminal is maintained. In addition, self AP _A Is extremely heavy, the request for new association from the terminal is rejected, and the association with the already associated terminal is forcibly disconnected.
[0042]
Further, regarding the forced disconnection of the association, the received power value table 22 shown in FIG. 3 is referred to, and a predetermined time interval (t _trans ) To control cutting. As a result, the position of the terminal is closer to the edge of the cell (AP _A AP will be disconnected in order of distance from the _A The association can be cut while suppressing the possibility of the appearance of a hidden terminal that is likely to occur near the terminal. However, the cutting order may be changed depending on the state of radio wave propagation and the movement of the terminal.
[0043]
The predetermined time interval (t _trans ) That is, for the disconnection interval of association, the self-AP _A When the load state changes, the time until the transition to the new reduced steady load value is secured.
[0044]
(3) Self AP _A And self AP based on the load state of neighboring AP _A The transmission power of
The transmission power control unit 16 uses the self AP _A Alternatively, every time the load state of the neighboring AP changes, the power value managed in the transmission power table 21 shown in FIG. 2 according to the instruction (Boost level / normal level) from the main control unit 10 shown in FIG. The transmission power value (mW) is changed based on (Boost level value / normal level value). That is, the transmission power control unit 16 determines whether the normal level or the boost level (normal level power <boost level power), as shown in FIG. 8, based on the self load state and the received nearby load state. Crab self AP _A The transmission power is controlled to be changed. Here, the difference from FIG. 7 is that in FIG. _A While the association with the terminal is changed based on only the load state of FIG. _A And self AP based on the load state of both AP and neighboring AP _A For example, as shown in FIG. _A Is extremely high load, even if the neighboring AP is extremely high load, AP _A Will maintain the transmission power level at the normal level regardless of the load state of the neighboring AP. On the other hand, the neighboring AP has a very high load and the self AP _A If the load is low, the self-AP _A And load distribution as a whole for the wireless LAN system 1 including neighboring APs. _A Increases the transmission power level to the Boost level to assist neighboring APs.
[0045]
The Boost level is set so that the radio wave reaches the hidden terminal located in the cell of the neighboring AP with sufficient strength. It is necessary to set the transmission power so as to be in a range where no interference occurs.
[0046]
Next, the operation of the wireless LAN system 1 according to this embodiment will be described. Here, from the case where each AP is in a low load state as shown in FIG. 9 (a), the AP is changed as shown in FIG. 9 (b). _A A case will be described in which the extremely high load state (or the high load state) is reached, but the neighboring AP remains in the low load state. FIG. 9A shows AP. _A And neighboring APs (AP _B , AP _C , AP _D , AP _E , AP _F , AP _G In the wireless LAN system 1 consisting of _A In this case, terminal α, terminal β, and terminal γ exist in the cell. AP _A The solid line arrow between the terminal β and the terminal β indicates the already associated state (synchronized state). That is, at this point, AP _A Are not associated with terminal α and terminal γ.
[0047]
As a result of the terminal β performing a large amount of data communication or the like in the state shown in FIG. _A When the channel load increases, the terminals α and γ become substantially hidden terminals. In this case, AP _A The load measurement unit 19 of the self-AP _A Measure the load value. Further, the main control unit 10 determines the self AP based on the load measurement value measured by the load measurement unit 19. _A Determine the load state. Here, it is determined that a high load state has been reached.
[0048]
Next, the main control unit 10 determines the self AP determined above. _A As shown in FIG. 7, the association with the terminal β is determined based on the load state. Based on this determination, the main control unit 10 executes association. Here, because of the high load state, the main control unit 10 rejects the request for new association from the terminal α and the terminal γ, but maintains the association with the already associated terminal β.
[0049]
On the other hand, self AP _A Since the load state of the transition is from the low load state to the high load state, the main control unit 10 transmits the self AP to all neighboring APs via the external interface 20 and the wired LAN 2. _A Notify the load status of. As a result, in the neighboring AP, AP _A Receive notifications from.
[0050]
Next, in each neighboring AP, in accordance with an instruction (Boost level / normal level) from each main control unit 10 shown in FIG. 8, the power value (Boost level of the Boost level) stored in each transmission power table 21 shown in FIG. Value / normal level value), the transmission power value (mW) is changed. Here, each neighboring AP is in a low load state, and the neighboring AP _B AP as a neighboring AP seen from _A Is in a high load state, each neighboring AP increases its transmission power and changes it to the Boost level. FIG. 9B shows a state in which the cell of each neighboring AP has become larger as a result of changing to the boost level at each neighboring AP. As a result, the terminal α _A Even if it is not possible to associate with the AP, by searching for a new connection destination AP, AP _E Or AP _D Can be associated with. The terminal γ is also AP _A Even if it is not possible to associate with the AP, by searching for a new connection destination AP, AP _C Can be associated with.
[0051]
As described above, according to the present embodiment, since the terminals α and γ as hidden terminals can communicate with neighboring APs, the problem of hidden terminals can be solved. Moreover, the neighboring AP normally sets the transmission power level to the normal level, and the AP _A The transmission power of each AP can be suppressed as much as possible because it is raised to the Boost level only when assisting the communication.
[0052]
Note that the mapping of the association process according to the load state of FIG. 7 and the mapping of the transmission power according to the load state of FIG. 8 can be customized according to the operation policy. For example, as shown in FIG. 10, a “very low load state” in which the load is lower than the low load state is added as a load state (at the same time, a corresponding load threshold is added and mapping of the association process is also changed), and output It is also possible to set a save level, a normal level, and a boost level as the level. Self AP _A Focusing only on the load state of the self AP _A When the load is extremely high, as shown in FIG. 11, it is possible to set a “Save level” lower than the normal level. As described above, the mapping of the association process according to the load state and the customization of the mapping of the transmission output level according to the load state enable fine load distribution control setting according to the operation policy. However, it is necessary to set the “Save level” within a range in which the communication quality is kept good in consideration of the decrease in the signal-to-noise ratio due to the power reduction.
[0053]
The above-described load state and transmission output subdivision enable operation of the wireless LAN system 1 ′ as described below.
[0054]
Here, from the case where each AP is in a low load state as shown in FIG. 12 (a), the AP is changed as shown in FIG. 12 (b). _A A case will be described in which the extremely high load state is reached, but the neighboring AP remains in the low load state. FIG. 12A shows AP. _A And a wireless LAN system 1 'composed of neighboring APs, _A In this case, terminal α, terminal β, and terminal γ exist in the cell. AP _A The solid line arrow between the terminal β and the terminal β indicates the already associated state (synchronized state). That is, at this point, AP _A Are not associated with terminal α and terminal γ.
[0055]
As a result of the terminal β performing a large amount of data communication or the like in the state shown in FIG. _A When the channel load of the AP increases significantly, as shown in FIG. _A Rejects the new association between the terminals α and γ, so that the terminals α and γ are substantially hidden. Moreover, as shown in FIG. _A Disconnects from the already associated terminal β. However, as shown in FIG. _A Decreases the transmission power to the Save level, and the neighboring AP increases the transmission power to the Boost level. As shown in FIG. 12B, by performing load distribution as a whole of the wireless LAN system 1 ′, the terminal α becomes AP _D Or AP _E Terminal β can communicate with AP _F AP _G And the terminal γ is AP _B , AP _C Or AP _D It becomes possible to communicate with.
[0056]
As explained above, by subdividing the transmission power to the Save level, the self AP _A Even if it becomes an extremely high load state in which the association with the terminal β that has already been associated must be disconnected, _A It is possible to protect.
[0057]
In the above embodiment, when a nearby AP is heavily loaded, the AP _A The antenna 12 may have directivity and may be controlled so that the transmission output is increased only in the direction of the neighboring AP. Thereby, load distribution can be performed with low power consumption, and radio wave interference with neighboring APs when the output is increased can be reduced. In order to realize this combined method, it is only necessary to add azimuth information to each neighboring AP in the neighboring AP definition table and perform transmission power control for each directional antenna.
[0058]
Further, in addition to the invention according to the embodiment, the self-AP _A It is not necessary to modify or change the association method in the above embodiment by adding a function of changing the communication rate with each terminal according to the load of the user.
[0059]
Further, the storage operation of the program (p) in the program storage unit 11 in the above embodiment can be performed by using a recording medium such as a CD-ROM in which the program (p) is recorded.
[0060]
【The invention's effect】
As described above, according to the present invention, a plurality of APs can grasp their own load state by transmitting and receiving each other, and control transmission power based on the load state of the own AP and the load state of neighboring APs. When the neighboring AP is in a high load state and the self AP is in a low load state, it is possible to perform control such as increasing the transmission output to assist the communication of the neighboring AP. In this way, by performing load distribution as the entire wireless LAN system, the substantial “hidden terminal” problem can be solved. Moreover, the neighboring AP normally sets the transmission power level to the normal level, and the AP _A The transmission power of each AP can be suppressed as much as possible by controlling the transmission power, such as increasing only when assisting the communication.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall configuration of a wireless LAN system 1 according to an embodiment of the present invention.
FIG. 2 is a conceptual diagram of a transmission power value table 21 of the present invention.
FIG. 3 is a conceptual diagram of a received power value table 22 of the present invention.
FIG. 4 is a conceptual diagram of a load threshold table 23 according to the present invention.
FIG. 5 is a conceptual diagram of a neighborhood AP definition table 24 according to the present invention.
FIG. 6 is a conceptual diagram showing state transition of a load state of an AP.
FIG. 7 is a conceptual diagram showing a process of associating with a terminal according to the load state of the self AP according to the embodiment.
FIG. 8 is a conceptual diagram showing transmission power levels of the self AP according to the load states of the self AP and the neighboring AP according to the embodiment.
FIG. 9 shows the case where each AP is in a low load state (a) and then AP _A The figure which showed the magnitude | size (range of a communication area) of (b) when near AP became a very high load state (or high load state), but neighboring AP is still in a low load state.
FIG. 10 is a conceptual diagram showing a process of associating with a terminal according to a load state of a self AP according to another embodiment.
FIG. 11 is a conceptual diagram showing the transmission power level of the self AP according to the load states of the self AP and the neighboring AP according to another embodiment.
FIG. 12 shows the case where each AP is in a low load state from (a) to AP _A The figure which showed the magnitude | size (range of a communication area) of the cell of (b) when near AP became a very high load state, but neighboring AP remains in a low load state.
FIG. 13 is a diagram showing the cell size (communication area range) of each AP in a conventional wireless LAN system.
FIG. 14 is a diagram showing the cell size (communication area range) of each AP in a conventional wireless LAN system.
[Explanation of symbols]
1 Wireless LAN system
2 Wired LAN
3 Setting terminal
10 Main control unit
11 Program storage
12 Antenna
13 switch
14 Transmitter
15 Receiver
16 Transmission power control unit
17 Transmission / reception controller
18 Received power measurement unit
19 Load measurement section
20 External interface
21 Transmission power value table
22 Received power value table
23 Load threshold table
24 Neighborhood AP definition table
(P) Program (program for wireless LAN system)

Claims

In the wireless LAN system connection device that performs wireless communication with the terminal by associating with a terminal in a communication area determined by transmission power,
Load state determination means for determining the load state of the own connection device;
Load state notifying means for notifying a nearby connection device of the load state determined by the load state determining means;
Load state receiving means for receiving the load state of the nearby connection device notified from the nearby connection device;
Based on the own load state determined by the load state determining unit and the nearby load state received by the load state receiving unit, if the own load state is lower than a certain value, the nearby load state is If it is higher than a certain value, it increases its own transmission power value, and if its own load state is higher than a certain value, it maintains or lowers its own transmission power value regardless of the neighboring load state. Transmission power control means for controlling power;
A connection device for a wireless LAN system, comprising:

The load state determination means includes
  Using a first load threshold, a second load threshold smaller than the first load threshold, a third load threshold smaller than the second load threshold, a fourth load threshold smaller than the third load threshold,
  If the self load value is greater than the first load threshold, the self load state is determined as an extremely high load state,
  When the self load value is smaller than the second load threshold and larger than the third load threshold, the self load state is determined as a high load state,
  When the self load value is smaller than the fourth load threshold, the self load state is determined as a low load state,
  The transmission power control means includes
  When the self load state is a low load state, if the nearby load state is a high load state or an extremely high load state, the self transmission power value is set as the first transmission power value, and the nearby load state is a low load state. Then, the self transmission power value is set as a second transmission power value smaller than the first transmission power value,
  The self-transmission power value is set as the second transmission power value regardless of a nearby load state when the self-load state is a high load state or an extremely high load state. Wireless LAN system connection device.

The load state determination means includes
  The first load threshold, the second load threshold smaller than the first load threshold, the third load threshold smaller than the second load threshold, the fourth load threshold smaller than the third load threshold, and the fifth smaller than the fourth load threshold. Using a sixth load threshold smaller than the load threshold and the fifth load threshold,
  If the self load value is greater than the first load threshold, the self load state is determined as an extremely high load state,
  When the self load value is smaller than the second load threshold and larger than the third load threshold, the self load state is determined as a high load state,
  When the self load value is smaller than the fourth load threshold and larger than the fifth load threshold, the self load state is determined as a low load state,
  When the self load value is smaller than the sixth load threshold, the self load state is determined as an extremely low load state,
  The transmission power control means includes
  When the self load state is an extremely low load state, if the nearby load threshold is a high load state or an extremely high load state, the self transmit power value is set as the first transmit power value, and the near load threshold is low. If it is a load state or an extremely low load state, the self transmission power value is set to a second transmission power value smaller than the first transmission power value,
  When the self load state is a low load state, if the nearby load threshold is an extremely high load state, the self transmission power value is the first transmission power value, and the nearby load threshold is a high load state or low. If it is a load state or an extremely low load state, its own transmission power value is the second transmission power value,
  If your load is high,
Regardless of the load state in the vicinity, the self transmission power value is the second transmission power value,
  If your load is very high,
2. The wireless LAN system connection device according to claim 1, wherein the transmission power value thereof is set to a third transmission power value smaller than the second transmission power value regardless of a nearby load state.

The wireless LAN system connection device according to claim 1, further comprising:
Association determination for determining a new association with an unassociated terminal in the own communication area and a subsequent association with an already associated terminal based on the own load state determined by the load state determining means Means,
Association executing means for executing association determined by the association determining means;
A connection device for a wireless LAN system, comprising:

5. The wireless LAN system according to claim 4, wherein, when disconnecting the association with a terminal that has already been associated, the association determination unit preferentially disconnects the received power from the terminal in ascending order. Connection device.

In a wireless LAN connection method using a wireless LAN system connection device that performs wireless communication with the terminal by associating with a terminal within a communication area determined by transmission power,
A load state determination process for determining a load state of the own connection device;
A load state notification process for notifying a nearby connection device of the load state determined by the load state determination process;
A load state reception process for receiving a load state of the nearby connection device notified from the nearby connection device;
Based on the load state determined by the load state determination process and the nearby load state received by the load state reception process , if the load state is lower than a certain value, If it is higher than a certain value, it increases its own transmission power value, and if its own load state is higher than a certain value, it maintains or lowers its own transmission power value regardless of the neighboring load state. A transmission power control process for controlling power;
The wireless LAN connection method characterized by performing.

The load state determination process includes:
  Using a first load threshold, a second load threshold smaller than the first load threshold, a third load threshold smaller than the second load threshold, a fourth load threshold smaller than the third load threshold,
  If the self load value is greater than the first load threshold, the self load state is determined as an extremely high load state,
  When the self load value is smaller than the second load threshold and larger than the third load threshold, the self load state is determined as a high load state,
  When the self load value is smaller than the fourth load threshold, the self load state is determined as a low load state,
  The transmission power control process includes:
  When the self load state is a low load state, if the nearby load state is a high load state or an extremely high load state, the self transmission power value is set as the first transmission power value, and the nearby load state is a low load state. Then, the self transmission power value is set as a second transmission power value smaller than the first transmission power value,
  The self-transmission power value is set as the second transmission power value regardless of a nearby load state when the self-load state is a high load state or an extremely high load state. Wireless LAN connection method.

The load state determination process includes:
  The first load threshold, the second load threshold smaller than the first load threshold, the third load threshold smaller than the second load threshold, the fourth load threshold smaller than the third load threshold, and the fifth smaller than the fourth load threshold. Using a sixth load threshold smaller than the load threshold and the fifth load threshold,
  If the self load value is greater than the first load threshold, the self load state is determined as an extremely high load state,
  When the self load value is smaller than the second load threshold and larger than the third load threshold, the self load state is determined as a high load state,
  When the self load value is smaller than the fourth load threshold and larger than the fifth load threshold, the self load state is determined as a low load state,
  When the self load value is smaller than the sixth load threshold, the self load state is determined as an extremely low load state,
  The transmission power control process includes:
  When the self load state is an extremely low load state, if the nearby load threshold is a high load state or an extremely high load state, the self transmit power value is set as the first transmit power value, and the near load threshold is low. If it is a load state or an extremely low load state, the self transmission power value is set to a second transmission power value smaller than the first transmission power value,
  When the self load state is a low load state, if the nearby load threshold is an extremely high load state, the self transmission power value is the first transmission power value, and the nearby load threshold is the high load state or low. If it is a load state or an extremely low load state, its own transmission power value is the second transmission power value
  When the self load state is a high load state, the self transmission power value is set as the second transmission power value regardless of the nearby load state,
  The self-transmission power value is set to a third transmission power value smaller than the second transmission power value regardless of a nearby load state when the self-load state is an extremely high load state. 7. The wireless LAN connection method according to 6.

The wireless LAN connection method according to claim 6, further comprising:
Association determination for determining a new association with an unassociated terminal in the own communication area and a subsequent association with an already associated terminal based on the own load state determined by the load state determination process Processing,
An association execution process for executing the association determined by the association determination process;
The wireless LAN connection method characterized by performing.

10. The wireless LAN according to claim 9, wherein in the association determination process, when the association with a terminal that has already been associated is disconnected, the wireless LAN according to claim 9 is preferentially disconnected from a terminal having a lower reception power. Connection method.

By associating with a terminal in a communication area determined by transmission power, a wireless LAN system program used in a wireless LAN system connection device that performs wireless communication with the terminal,
Load state determination means for determining the load state of the own connection device;
Load state notifying means for notifying a nearby connection device of the load state determined by the load state determining means;
Load state receiving means for receiving the load state of the nearby connection device notified from the nearby connection device;
Based on the own load state determined by the load state determining unit and the nearby load state received by the load state receiving unit, if the own load state is lower than a certain value, the nearby load state is It is higher than a certain value increases the own transmission power value, when its load state is higher than the constant value, the transmission by maintaining or lowering the own transmission power value regardless of the load state of the neighboring Transmission power control means for controlling power;
A wireless LAN system program that causes a wireless LAN connection device to function.

The load state determination means,
  Using a first load threshold, a second load threshold smaller than the first load threshold, a third load threshold smaller than the second load threshold, a fourth load threshold smaller than the third load threshold,
  If the self load value is greater than the first load threshold, the self load state is determined as an extremely high load state,
  When the self load value is smaller than the second load threshold and larger than the third load threshold, the self load state is determined as a high load state,
  When the self load value is smaller than the fourth load threshold, the self load state is made to function as a low load state,
  The transmission power control means;
  When the self load state is a low load state, if the nearby load state is a high load state or an extremely high load state, the self transmission power value is set as the first transmission power value, and the nearby load state is a low load state. Then, the self transmission power value is set as a second transmission power value smaller than the first transmission power value,
  When the self load state is a high load state or an extremely high load state, the self-transmission power value is made to function as the second transmission power value regardless of a nearby load state. Item 12. A program for a wireless LAN system according to Item 11.

The load state determination means,
  The first load threshold, the second load threshold smaller than the first load threshold, the third load threshold smaller than the second load threshold, the fourth load threshold smaller than the third load threshold, and the fifth smaller than the fourth load threshold. Using a sixth load threshold smaller than the load threshold and the fifth load threshold,
  If the self load value is greater than the first load threshold, the self load state is determined as an extremely high load state,
  When the self load value is smaller than the second load threshold and larger than the third load threshold, the self load state is determined as a high load state,
  When the self load value is smaller than the fourth load threshold and larger than the fifth load threshold, the self load state is determined as a low load state,
  When the self load value is smaller than the sixth load threshold, the self load state is made to function as an extremely low load state,
  The transmission power control means;
  When the self load state is an extremely low load state, if the nearby load threshold is a high load state or an extremely high load state, the self transmit power value is set as the first transmit power value, and the near load threshold is low. If it is a load state or an extremely low load state, the self transmission power value is set to a second transmission power value smaller than the first transmission power value,
  When the self load state is a low load state, if the nearby load threshold is an extremely high load state, the self transmission power value is the first transmission power value, and the nearby load threshold is the high load state or low. If it is a load state or an extremely low load state, its own transmission power value is the second transmission power value,
  When the self load state is a high load state, the self transmission power value is set as the second transmission power value regardless of the nearby load state,
  When the self-load state is an extremely high load state, the self-transmission power value is made to function as a third transmission power value smaller than the second transmission power value regardless of a nearby load state. The wireless LAN system program according to claim 11.

The wireless LAN system program according to claim 11, further comprising:
Association determination for determining a new association with an unassociated terminal in the own communication area and a subsequent association with an already associated terminal based on the own load state determined by the load state determining means Means,
Association executing means for executing association determined by the association determining means;
For a wireless LAN system connection device.

15. The wireless LAN system according to claim 14, wherein, when disconnecting the association with a terminal that has already been associated, the association determination unit disconnects the communication with priority from the one having the lower reception power from the terminal. Program.

16. A wireless LAN system recording medium readable by a wireless LAN system connection device, wherein the wireless LAN system program according to claim 11 is recorded.