JP2005033389A

JP2005033389A - Radio base station, communication terminal, and wireless radio system

Info

Publication number: JP2005033389A
Application number: JP2003194670A
Authority: JP
Inventors: Shigenori Fukuda; 茂紀福田; Masao Yamazawa; 昌夫山澤; Ichiro Iida; 一朗飯田; Shinji Fujino; 信次藤野
Original assignee: Fujitsu Ltd
Current assignee: Fujitsu Ltd
Priority date: 2003-07-09
Filing date: 2003-07-09
Publication date: 2005-02-03
Anticipated expiration: 2023-07-09
Also published as: JP4279068B2

Abstract

【課題】無線ＬＡＮ通信システムにおいて、通信量を増やしながら、ネットワーク全体の消費電力を抑制することを目的とする。
【解決手段】基地局１が、自局の通信トラフィック量の検出部２と、自局から発する電波強度の調整部３と、自局と通信中の端末に対する電波強度調整命令の送信部４とを備え、トラフィック量が増加した時、自局の下位のサブ基地局に稼動指示を送り、自局と通信中の端末の少なくとも一部にサブ基地局との通信に切り替えさせる指示を送り、自局、サブ基地局、及び端末の発する電波強度を低下させる。
【選択図】図２An object of the present invention is to suppress power consumption of the entire network while increasing the amount of communication in a wireless LAN communication system.
A base station includes a communication traffic amount detection unit, a radio wave intensity adjustment unit, a radio wave intensity adjustment command transmission unit for a terminal in communication with the local station, When the traffic volume increases, an operation instruction is sent to a sub-base station lower than its own station, and an instruction for switching to communication with the sub-base station is sent to at least a part of terminals communicating with the own station. The radio field intensity emitted from the station, the sub base station, and the terminal is reduced.
[Selection] Figure 2

Description

【０００１】
【発明の属する技術分野】
本発明は無線通信システムに係り、更に詳しくは無線ＬＡＮネットワークにおいて、無線基地局と、その管理下にあるサブ無線基地局とが相互に連携して通信電力の最適化を行う無線通信システムに関する。
【０００２】
【従来の技術】
インターネットの広範な利用に伴なって、ユーザはパソコン（ＰＣ）やパーソナルデジタルアシスタンツ（ＰＤＡ）等からネットワークに簡単にアクセスできるようになっているが、２０００年頃からＩＥＥＥの無線ＬＡＮ標準化仕様としてのＩＥＥＥ８０２．１１に基づく機器が普及し、無線によるローカルエリアネットワークが容易に構築できるようになっている。
【０００３】
図１３はそのようなローカルエリアネットワークの従来例である。同図において、３つのエリア１Ａ、１Ｂ、１Ｃにそれぞれ対応する基地局２Ａ、２Ｂ及び２Ｃは、有線のネットワークによって相互に結合され、例えば基地局２Ａはその周囲の多くの通信端末３Ａと通信を行っている。
【０００４】
図１３のような通信システムでは、無線ＬＡＮ方式によって基地局が通信端末とネットワークの間の仲介を行うことによって、通信端末をネットワークに接続することができる。１台の基地局は、複数の通信端末を同時にネットワークに接続することができ、無線ＬＡＮ通信端末は、煩雑な有線接続を行うことなく、ネットワークを利用することができる。
【０００５】
しかしながら現在利用されている仕様としてのＩＥＥＥ８０２．１１ｂでは、携帯電話やＰＨＳのシステムと異なり、細かい無線出力制御機能や、電波密度を検出してきめ細かな制御を行う機能が不足していた。また例えば移動端末は、必ずしも有線で電力を補給できるとは限らず、バッテリーによって駆動されることも多い。一般に移動端末の使用電力のうちで無線ＬＡＮ機器の使用電力が占める割合は多く、２割から３割となる場合があり、バッテリー駆動時間が少なくなるという問題点があった。
【０００６】
また一般的なインフラストラクチャーモード゛を利用する場合、図１３のエリア１Ａのように多くの通信端末３Ａが同時に基地局２Ａと通信するような環境では電波密度が上昇し、パケットの衝突やチャネルの枯渇が発生しやすく、通信品質が低下するという問題点があった。
【０００７】
この問題に対処するための仕様としてのＩＥＥＥ８０２．１１ｈでは、トランスミッティング・パワー・コントロールという機能があり、通信中の無線ＬＡＮ機器の距離が近い場合には電波出力を小さくする機能がある。この機能を活用することによって、基地局の近傍にある無線ＬＡＮ端末との通信が他の端末の通信に及ぼす影響は小さくなるが、通信領域の外周付近の端末は大きな電波出力を用いて通信を行わなければならず、無線ＬＡＮ通信の混雑は大きくは改善されないという問題点があった。
【０００８】
このような問題点を解決するための従来技術として次の文献がある。
【０００９】
【特許文献１】
特開平９−１６２７９８号公報「無線通信システム、無線通信システム用基地局および間欠電源投入型移動局」
【特許文献２】特開２００２−１８５４５８号公報「無線ＬＡＮシステムおよび端末」
【特許文献３】特開２００２−３００１７５号公報「無線通信システム」
【００１０】
特許文献１では、ビーコンを利用して通信時期を無線機器間で連絡し、無駄な消費電力を抑える無線通信システムが開示されている。
【００１１】
特許文献２では、基地局が接続可能な上限の端末数を設定し、この上限の数以上の端末に対しては、他の基地局に接続切り替えを行なわせることによって通信効率を向上させる無線ＬＡＮシステムが開示されている。
【００１２】
特許文献３では、リンクが確立されているネットワーク内の端末にデータ伝送を行うにあたって、データと共に次にデータを転送する時間を示すデータを送ることによって、自局宛以外のデータフレームを受信することがなくなり、受信動作における消費電力をおさえることができる無線通信システムが開示されている。
【００１３】
【発明が解決しようとする課題】
しかしながらこのようにデータ伝送時刻を送信したり、ビーコンを用いて受信待機電力を抑える手法では、送信する電波の密度は改善できず、むしろ追加データやビーコン通信用のために、電波の混雑度や発信電力は逆に増えてしまうという問題点があった。
【００１４】
また無線基地局の切替機能を用いても、各基地局に集中する通信量を制限することはできるが、空気中の電波密度は変わらず、やはり切替指示に要する通信の分だけ電波の混雑度や発信電力が増加してしまうといった問題点があった。
【００１５】
本発明の課題は、上述の問題点に鑑み、通信中の無線ＬＡＮ端末が増加して電波が混雑した状態の時には、サブ無線基地局を活用して通信領域を小さく分割し、各機器の電波出力を小さくして通信を行うことによって、一定領域内の通信量を増やしながらネットワーク全体の消費電力を小さくすることである。
【００１６】
【課題を解決するための手段】
図１は本発明の無線基地局の原理構成ブロック図である。同図において、基地局２はトラフィック量検出手段７、電波強度調整手段８、及び電波強度調整命令送信手段９を備える。
【００１７】
トラフィック量検出手段７は、例えば自局との間で通信を行っている通信端末の数によって通信のトラフィック量を検出するものであり、電波強度調整手段８は、検出されたトラフィック量がある所定の第１の値を超えたときに、自局から発射する電波の強度を低下させるものであり、電波強度調整命令送信手段９は自局と通信中の通信端末に対して、その通信端末が発射する電波の強度を低下させる命令を送るものである。
【００１８】
本発明において、後述するサブ無線基地局を使わないでシステムの運用を行う場合には、複数の無線基地局の通信領域を大きくとり、無線基地局同士の通信領域が重なるような形で運用されるような形態が考えられる。このような運用を行うことによって、後述するサブ無線基地局を用いる場合に比べて運用コストが小さくなることが期待される。
【００１９】
そして前述のように自局に対する通信のトラフィック量が大きくなった時には、自局自身の発射する電波の強度、及び自局と通信中の通信端末の電波強度を低下させることによって、全体の通信電力を低下させることが可能となる。
【００２０】
発明の実施の形態において、無線基地局２は、図１に図示しない稼動命令送信手段と、接続切替指示手段とを備えることもできる。稼動命令送信手段は、トラフィック量検出手段７がトラフィック量として所定の第２の値を超える値を検出したときに、自局の下位にあるサブ無線基地局に稼動命令を送るものであり、接続切替指示手段は現在自局と通信中の通信端末の一部に対して、サブ無線基地局との通信に切替させる指示を送るものである。
【００２１】
実施の形態としての無線基地局は、更に図示しないトラフィック量受信手段、及び待機状態指示手段を備えることもできる。
トラフィック量受信手段は、１つ以上のサブ無線基地局からの各サブ基地局のトラフィック量の通知を受け取るものであり、待機状態指示手段は、そのサブ基地局のトラフィック量と自局自身のトラフィック量との合計が所定の第３の値以下になった時、サブ基地局の少なくとも１つ以上に待機状態に移る指示を与えるものである。このとき電波強度調整手段８は、自局から発射する電波の強度を上げ、前述の接続切替指示手段はサブ無線基地局の中で待機状態に移るべきサブ無線基地局と通信していた通信端末に対して、自局との通信に切り替えるように指示を出す。
【００２２】
次に本発明において、上位の無線基地局によって稼動、又は待機の状態を指示され、稼動状態において通信端末との間で通信を行うサブ無線基地局は、通信接続手段と、トラフィック量通知手段を備える。
【００２３】
通信接続手段は、上位の無線基地局からの稼動指示に対応して、上位の無線基地局と通信を行っていた通信端末との間の通信を確立するものであり、トラフィック量通知手段は自局の通信トラフィック量を上位の無線基地局に通知するものである。
【００２４】
サブ無線基地局は、実施の形態において、更に接続切替指示手段と制御手段とを備えることもできる。接続切替指示手段は、上位の無線基地局から待機の指示が送られた時、自局と通信中の通信端末に対して電波強度を大きくさせ、上位無線基地局との間で通信を行わせる接続切替命令を送るものであり、制御手段は自局を待機状態に移すものである。
【００２５】
次に本発明の通信端末、すなわち無線基地局、またはその無線基地局の下位にあるサブ無線基地局との間で通信を行う通信端末は、無線基地局から送られる電波強度調整命令に従って、自端末から発する電波の強度を調整する電波強度調整手段を備える。
【００２６】
通信端末は更に接続変更手段を備えることもできる。通信端末が無線基地局との間で通信を行っている状態で無線基地局から電波強度を下げる命令を受け取った時、その命令に対応して、電波強度調整手段が自端末から発する電波の強度を下げると共に、接続変更手段が無線基地局からの指示に応じて、無線基地局との間で行っていた通信をサブ無線基地局との間の通信に切り替える。
【００２７】
また通信端末がサブ無線基地局との間で通信を行っている状態で無線基地局からの電波強度を上げる命令を受け取った時、その命令に対応して、電波強度調整手段が自端末から発する電波の強度を上げると共に、接続変更手段が無線基地局からの指示に応じて、サブ無線基地局との間で行っていた通信を無線基地局との間の通信に切り替える。
【００２８】
次に本発明の無線通信システムは、無線基地局、その無線基地局の下位にある１つ以上のサブ無線基地局、及び無線基地局またはサブ無線基地局との間で通信を行う通信端末によって構成される。
【００２９】
この通信システムにおいては、サブ無線基地局が待機状態にある時、無線基地局が自局と通信を行っている通信端末の数をチェックし、その数が所定の値、例えば後述する単独無線ＬＡＮ状態上限値を超えた時、無線基地局がサブ無線基地局に稼動状態への移行指示を送り、通信端末の一部にサブ無線基地局との通信に切り替えさせる接続変更指示を送り、自局、サブ無線基地局、及び通信端末の発する電波強度を小さくさせる動作が行われる。
【００３０】
またサブ無線基地局が稼動状態にある時、無線基地局が自局及び下位のサブ無線基地局との通信を行っている通信端末の数をチェックし、その数が所定の値、例えば後述するサブ無線ＬＡＮ管理状態下限値を下回った時、サブ無線基地局に待機状態への移行指示を送り、サブ無線基地局と通信していた通信端末に自局との通信に切り替えさせる接続変更指示を送り、自局及び通信端末の発する電波強度を大きくさせる動作が行われる。
【００３１】
以上のように本発明によれば、無線基地局の通信トラフィック量に応じてサブ無線基地局の稼動、又は待機の指示が行われ、通信システム全体としての消費電力の抑制が実現される。
【００３２】
【発明の実施の形態】
続いて図２以降を用いて本発明の実施形態について更に詳細に説明する。図２は、本実施形態における無線通信システムの構成図であり、各サブ無線基地局が待機状態にある場合を示す。すなわち従来例を示す図１３と異なり、各無線基地局２Ａ、２Ｂ、２Ｃのそれぞれ下位にあるサブ無線基地局として、例えば基地局２Ａに対しては３つのサブ無線基地局４Ａが、例えば有線によって接続されている。
【００３３】
図２においては、前述のようにサブ無線基地局の全ては待機状態であり、各無線基地局２Ａ、２Ｂ及び２Ｃは、それぞれ担当するエリア１Ａ、１Ｂ及び１Ｃの範囲内で通信を行うために十分な強度の通常強度の電波を利用している。またこれらの基地局と通信を行う通信端末３Ａ、３Ｂ及び３Ｃもそれぞれ通常強度の電波を利用している。なお例えば通信端末３Ａは移動端末であることも当然可能であり、端末３Ａがエリア１Ｂに移動した場合には基本的に基地局２Ｂとの間で通信を行うことになる。
【００３４】
図３は、例えば無線基地局２Ａに対応するエリア１Ａが、４つのエリア６Ａ_０〜６Ａ_３に分割され、各エリア内の通信端末は無線基地局２Ａ、３つのサブ無線基地局４Ａのいずれかとの間で通信を行っている状態を示す。この状態を本実施形態ではサブ無線ＬＡＮ管理状態、図２の状態を単独無線ＬＡＮ状態と呼ぶことにする。
【００３５】
図３において、基地局２Ａと３つの通信端末３Ａ_０とは、エリア６Ａ_０の範囲での通信に十分な電力を用いて通信を行っており、図２の単独無線ＬＡＮ状態よりも、自局または自端末から発する電波の強度を下げることができる。
【００３６】
またエリア６Ａ_１内の３つの通信端末３Ａ_１も、同様に電波強度を下げることができ、サブ無線基地局４Ａもそれに対応した電波強度で通信を行うことができる。
【００３７】
図４は本実施形態における無線ＬＡＮ基地局の構成ブロック図である。同図において基地局２は無線ＬＡＮによって接続された無線通信端末や、有線ＬＡＮによって接続された機器との通信を仲介するものであり、有線ＬＡＮ通信部１１、無線ＬＡＮ通信部１２、電波強度調節部１３、サブ無線ＬＡＮ基地局制御部１４、通信端末制御部１５、通信端末数管理部１６及び通信端末管理表１７を備え、通信端末管理表１７を除き、有線ＬＡＮ通信部１１から通信端末数管理部１６までは、バス１８によって相互に接続されているものとする。
【００３８】
有線ＬＡＮ通信部１１は、ＩＥＥＥ８０２．３や、その派生規格に準拠して、有線で接続されている通信機器との通信を行うものであり、無線ＬＡＮ通信部１２はＩＥＥＥ８０２．１１や、その派生規格に準拠して、無線で接続された通信端末との通信を行うものである。
【００３９】
電波強度調節部１３は、通信端末数管理部１６等の管理に対応して、無線ＬＡＮ通信部１２による通信強度の調節を行うものである。
サブ無線ＬＡＮ基地局制御部１４は、通信端末数管理部１６等の管理に従って、有線ＬＡＮ通信部１１を介して、自局の通信領域内、すなわち下位のサブ無線ＬＡＮ基地局に対して、待機命令や稼動命令を出すものである。
【００４０】
通信端末制御部１５は、通信端末数管理部１６等の管理に対応して、無線ＬＡＮ通信部１２を介して、無線通信端末への電波強度制御命令や通信基地局変更命令等を出すものである。
【００４１】
通信端末数管理部１６は、無線ＬＡＮ通信部１２やサブ無線ＬＡＮ基地局から報告される通信中の端末のデータを通信端末管理表１７に格納し、その管理を行うものである。前述の単独無線ＬＡＮの状態において、自局と通信を行っている端末の数が後述する単独無線ＬＡＮ状態上限値を超えた場合に、通信端末制御部１５や、サブ無線ＬＡＮ基地局制御部１４を介して、端末に対する電波強度制御命令等を出して、サブ無線ＬＡＮ管理状態に移行する。またサブ無線ＬＡＮ管理状態において、自局の管理下にある通信端末の数がサブ無線ＬＡＮ管理状態下限値を下回った場合には、端末に対して電波強度を上げさせる電波強度制御命令等を出して、単独無線ＬＡＮ状態に移行する。
【００４２】
なお、特許請求の範囲、請求項１〜３における電波強度調整手段は、例えば図４の電波強度調整部１３に、トラフィック量検出手段とトラフィック量受信手段は、例えば通信端末数管理部１６に相当する。また電波強度調整命令送信手段と接続切替指示手段は、例えば通信端末制御部１５に、稼動命令送信手段と待機状態指示手段は、例えばサブ無線ＬＡＮ基地局制御部１４に相当する。
【００４３】
図５は図４の通信端末管理表１７の格納内容の例である。同図において自局Ａ、及び自局の下位にあるサブ無線基地局Ａ１〜Ａ３のそれぞれと通信を行っている端末のＩＰアドレスが格納され、サブ無線ＬＡＮ管理状態下限値と、単独無線ＬＡＮ状態上限値とが指定されている。
【００４４】
図６はサブ無線ＬＡＮ基地局の構成を示すブロック図である。同図においてサブ基地局４は、無線ＬＡＮ基地局の指示に従って、無線ＬＡＮによって接続された無線通信端末や、有線ＬＡＮによって接続された通信機器との通信を仲介するものであり、有線ＬＡＮ通信部２１、無線ＬＡＮ通信部２２、電波強度調節部２３、無線ＬＡＮ基地局通信部２４及び通信端末制御部２５を備え、これらのすべてはバス２６によって接続されている。
【００４５】
有線ＬＡＮ通信部２１、無線ＬＡＮ通信部２２は、図４の基地局２内のものと同様の動作を行うものであり、電波強度調節部２３は無線ＬＡＮ基地局からの指示に従って、無線ＬＡＮ通信部２２による通信強度、すなわち電波強度を調節するものである。
【００４６】
無線ＬＡＮ基地局通信部２４は、無線ＬＡＮ基地局からの指示を受けて各部に指示を伝達するものであり、通信端末制御部２５は、無線ＬＡＮ基地局からの指示に従って、無線ＬＡＮ通信部２２を介して、無線通信端末への電波強度制御命令や基地局変更命令等を出すものである。
【００４７】
なお、請求項４、５における通信接続手段と接続切替指示手段とは、例えば図６の通信端末制御部２５に、トラフィック量通知手段は無線ＬＡＮ基地局通信部２４に、また自局を待機状態に移す制御手段は例えば無線ＬＡＮ通信部２２に相当する。
【００４８】
図７は無線ＬＡＮ通信端末の構成を示すブロック図である。同図において通信端末３は、無線ＬＡＮ通信部２７、電波強度調節部２８、無線ＬＡＮ基地局通信部２９を備えており、これらの各部はバス３０によって相互に接続されている。
【００４９】
無線ＬＡＮ通信部２７は、前述の規格に準拠して、無線ＬＡＮ基地局やサブ無線ＬＡＮ基地局との間で通信を行うものであり、電波強度調節部２８は基地局からの指示に従って無線ＬＡＮ通信部２７による通信強度を調節するものであり、無線ＬＡＮ基地局通信部２９は無線ＬＡＮ基地局やサブ無線ＬＡＮ基地局からの指示を各部に伝達するものである。
【００５０】
なお、請求項６〜８における電波強度調整手段は、例えば図７の電波強度調節部２８に、接続変更手段は無線ＬＡＮ通信部２７に相当する。
次に本実施形態における無線ＬＡＮ基地局、サブ無線ＬＡＮ基地局及び通信端末の動作について図８〜図１２を用いて説明する。図８及び図９は無線ＬＡＮ基地局の動作を示すものであり、図８は単独無線ＬＡＮ状態、図９はサブ無線ＬＡＮ管理状態における動作のフローチャートである。
【００５１】
図８において単独無線ＬＡＮ状態の動作が開始されると、まずステップＳ１で無線ＬＡＮ基地局として通信端末との間で通信が行われ、ステップＳ２で無線ＬＡＮ通信端末と新たに接続が開始したか、あるいは接続が終了したかが判定され、開始も終了もない場合にはステップＳ１に戻って通信が継続される。これらのステップの動作は図４の無線ＬＡＮ通信部１２によって行われる。
【００５２】
ステップＳ２で新たに接続が開始したか、あるいは接続していた通信が終了したと判定されると、ステップＳ３で管理中の無線ＬＡＮ端末数が増減される、すなわち図５の通信端末管理表１７に新たなデータが格納されるか、格納されていたデータが消去される。この動作は通信端末数管理部１６によって実行される。
【００５３】
続いてステップＳ４で、通信端末数管理部１６によって自局の管理する領域内の端末が単独無線ＬＡＮ状態上限値を超えたか否かが判定され、超えていない場合にはステップＳ１以降の処理が繰り返される。
【００５４】
ステップＳ４で単独無線ＬＡＮ状態上限値を超えたと判定されると、サブ無線ＬＡＮ管理状態に移行するために、ステップＳ５でサブ無線ＬＡＮ基地局制御部１４によって、自局の下位にあるサブ無線ＬＡＮ基地局が稼動状態とされ、ステップＳ６で通信端末制御部１５によって、自局と通信中の無線通信端末に対して電波強度を下げる指示と、サブ無線ＬＡＮ基地局との通信に切り替えるべきことを示す接続切替指示とが出され、ステップＳ７で電波強度調節部１３によって、自局から発する電波の強度が小さくされた後、サブ無線ＬＡＮ管理状態に移行する。
【００５５】
図９はサブ無線ＬＡＮ管理状態における基地局の動作を示すフローチャートである。同図において、まずステップＳ１１で無線ＬＡＮ通信部１２によって、無線ＬＡＮ基地局として通信端末との間で通信が行われ、ステップＳ１２でサブ無線ＬＡＮ基地局制御部１４によって、自局の管理下にあるサブ無線ＬＡＮ基地局から接続端末数の増加、あるいは減少の通知を受けたか否かが判定され、受けていない場合にはステップＳ１３で通信端末制御部１５によって、自局と通信している無線通信端末との間で新たな接続が開始、あるいは接続されていた通信が終了したかが判定され、開始も終了もしていない場合にはステップＳ１１に戻り、端末との通信を行う動作が続行される。
【００５６】
ステップＳ１２で自局の管理下にあるサブ基地局から接続端末数の増加、又は減少の通知を受けたと判定された場合、またはステップＳ１３で自局と無線通信端末との間で新たな接続が開始したか、接続されていた通信が終了したと判定されると、ステップＳ１４で通信端末数管理部１６によって、管理中の無線ＬＡＮ端末の数が増減され、通信端末管理表１７へのデータの格納、または消去が行われる。
【００５７】
続いてステップＳ１５で、通信端末数管理部１６によって、自局の管理下にある領域内の端末、すなわち自局と通信中の端末と、自局の下位にあるサブ基地局と通信中の端末の合計数がサブ無線ＬＡＮ管理状態下限値を下回ったか否かが判定され、下回っていないときにはステップＳ１１以降の動作が続行される。
【００５８】
下限値を下回っているときには、単独無線ＬＡＮ状態に移行するために、ステップＳ１６で、サブ無線ＬＡＮ基地局制御部１４によってサブ無線ＬＡＮ基地局に対して待機指示が出され、ステップＳ１７で電波強度調節部１３によって自局から発する電波の強度が大きくされ、ステップＳ１８で通信端末制御部１５によって自局と通信中の無線通信端末に電波強度を大きくする指示が出され、単独無線ＬＡＮ状態に移行する。
【００５９】
図１０はサブ無線ＬＡＮ基地局の動作を示すフローチャートである。同図においてサブ無線ＬＡＮ基地局は、最初待機状態にあるものとする。
まずステップＳ２１で無線ＬＡＮ基地局からの指示を待つ待機動作が行われ、ステップＳ２２で図６の無線ＬＡＮ基地局通信部２４によって、無線ＬＡＮ基地局側から稼動指示が送られたか否かが判定され、送られていない場合にはステップＳ２１に戻り、待機動作が続行される。
【００６０】
稼動指示が送られたと判定されると、ステップＳ２３で無線ＬＡＮ通信部２２によって、稼動状態における動作として、無線ＬＡＮサブ基地局としての通信が端末との間で行われ、ステップＳ２４で無線通信端末と新たに接続が開始したか、あるいは通信中の接続が終了したかが判定され、新たな開始または終了があった場合には、ステップＳ２５で無線ＬＡＮ基地局通信部２４によって、無線ＬＡＮ基地局に対して端末数の変化が通知された後に、また新たな開始、終了がない場合には直ちにステップＳ２６に移行する。
【００６１】
続いてステップＳ２６で無線ＬＡＮ基地局通信部２４によって、無線ＬＡＮ基地局から待機指示が送られたか否かが判定され、送られていない場合にはステップＳ２３以降の動作が続行される。待機指示が送られた場合には、待機状態に移行するために、ステップＳ２７で通信端末制御部２５によって通信中の無線通信端末に対して電波強度を大きくする指示と、通信先を無線ＬＡＮ基地局に切り替えさせる接続切替指示が出され、待機状態に戻る。
【００６２】
図１１，図１２は通信端末の動作を示すフローチャートであり、図１１は単独無線ＬＡＮ状態、図１２はサブ無線ＬＡＮ管理状態における動作を示す。
図１１の単独無線ＬＡＮ状態においては、ステップＳ３１で無線ＬＡＮ基地局通信部２９によって基地局から電波強度を小さくする指示を受けたか否かが判定され、受けていない場合には単独無線ＬＡＮ状態が続行される。
【００６３】
電波強度を小さくする指示を受けた場合には、ステップＳ３２で電波強度調節部２８によって電波強度が下げられ、ステップＳ３３で基地局から接続すべき基地局の変更指示を受けたか否かが無線ＬＡＮ基地局通信部２９によって判定され、受けた場合にはステップＳ３４で無線ＬＡＮ通信部２７によって接続する基地局が変更された後に、また変更指示を受けていない時には直ちにサブ無線ＬＡＮ管理状態に移行する。
【００６４】
図１２はサブ無線ＬＡＮ管理状態から単独無線ＬＡＮ状態への移行時の動作を示し、ステップＳ３６で電波強度を大きくする指示を受けた場合にはステップＳ３７で電波強度が上げられ、ステップＳ３８、Ｓ３９で図１２のステップＳ３３、Ｓ３４と同様の処理が行われた後に、単独無線ＬＡＮ状態に移行する。
【００６５】
【発明の効果】
以上詳細に説明したように、本発明によれば通信トラフィックの量に対応してサブ無線基地局の稼動、または待機の状態を切り替えることによって、無線通信システムの運用を効率的に行うことができる。
【００６６】
すなわち無線通信端末の数が増えて、電波が混雑した場合には、今までの通信領域を小さな領域に分割し、各通信機器の電波出力を小さくして通信を行うことによって、ネットワーク全体の消費電力を小さくすることができる。これに対して通信端末の数が少なくなった時には、複数の小さな通信領域を大きな１つの領域に統一し、稼動中のサブ基地局の数を減らすことによって、ネットワークの通信効率を向上させることが可能である。
【図面の簡単な説明】
【図１】本発明の無線基地局の原理構成を示すブロック図である。
【図２】本発明の実施形態における無線通信システムの構成（単独無線ＬＡＮ状態）を示す図である。
【図３】本実施形態における無線通信システムの構成（サブ無線ＬＡＮ管理状態）を示す図である。
【図４】無線ＬＡＮ基地局の構成を示すブロック図である。
【図５】通信端末管理表の格納内容の例を示す図である。
【図６】サブ無線ＬＡＮ基地局の構成を示すブロック図である。
【図７】無線通信端末の構成を示すブロック図である。
【図８】無線ＬＡＮ基地局の動作を示すフローチャート（その１）である。
【図９】無線ＬＡＮ基地局の動作を示すフローチャート（その２）である。
【図１０】サブ無線ＬＡＮ基地局の動作を示すフローチャートである。
【図１１】通信端末の動作を示すフローチャート（その１）である。
【図１２】通信端末の動作を示すフローチャート（その２）である。
【図１３】無線ＬＡＮ通信システムの従来例の構成を示す図である。
【符号の説明】
１，６エリア
２無線基地局
３通信端末
４サブ無線基地局
７トラフィック量検出手段
８電波強度調整手段
９電波強度調整命令送信手段
１１，２１有線ＬＡＮ通信部
１２，２２，２７無線ＬＡＮ通信部
１３，２３，２８電波強度調節部
１４サブ無線ＬＡＮ基地局制御部
１５，２５通信端末制御部
１６通信端末数管理部
１７通信端末管理表
１８，２６，３０バス
２４，２９無線ＬＡＮ基地局通信部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wireless communication system, and more particularly to a wireless communication system in a wireless LAN network in which a wireless base station and a sub wireless base station under its management cooperate with each other to optimize communication power.
[0002]
[Prior art]
With the widespread use of the Internet, users can easily access the network from personal computers (PCs), personal digital assistants (PDAs), etc. Devices based on IEEE 802.11 have become widespread, and a wireless local area network can be easily constructed.
[0003]
FIG. 13 shows a conventional example of such a local area network. In the figure, base stations 2A, 2B, and 2C respectively corresponding to three areas 1A, 1B, and 1C are coupled to each other by a wired network. For example, the base station 2A communicates with many surrounding communication terminals 3A. Is going.
[0004]
In the communication system as shown in FIG. 13, the base station can connect the communication terminal to the network by the intermediary between the communication terminal and the network by the wireless LAN method. One base station can simultaneously connect a plurality of communication terminals to the network, and the wireless LAN communication terminal can use the network without performing complicated wired connection.
[0005]
However, IEEE802.11b, which is currently used as a specification, differs from a mobile phone or PHS system in that it lacks a detailed wireless output control function and a function for detecting a radio wave density and performing fine control. In addition, for example, mobile terminals are not always replenished with power, and are often driven by batteries. In general, the proportion of power used by wireless LAN devices is large in the power used by mobile terminals, which may be 20% to 30%, and there is a problem that the battery driving time is reduced.
[0006]
When using a general infrastructure mode, the radio wave density increases in an environment where many communication terminals 3A communicate with the base station 2A at the same time as in the area 1A of FIG. There is a problem that the exhaustion is likely to occur and the communication quality is deteriorated.
[0007]
IEEE 802.11h as a specification for dealing with this problem has a function of transmitting power control, and a function of reducing radio wave output when the distance between wireless LAN devices in communication is short. By utilizing this function, the influence of communication with wireless LAN terminals in the vicinity of the base station on the communication of other terminals is reduced, but terminals near the outer periphery of the communication area can communicate using a large radio wave output. There is a problem that congestion of wireless LAN communication is not greatly improved.
[0008]
There are the following documents as conventional techniques for solving such problems.
[0009]
[Patent Document 1]
Japanese Patent Laid-Open No. 9-162798 “Wireless Communication System, Base Station for Wireless Communication System, and Intermittent Power-On Mobile Station”
[Patent Document 2] Japanese Patent Application Laid-Open No. 2002-185458 “Wireless LAN System and Terminal”
[Patent Document 3] Japanese Patent Laid-Open No. 2002-300195 “Wireless Communication System”
[0010]
Patent Document 1 discloses a wireless communication system that uses a beacon to communicate communication times between wireless devices and suppresses unnecessary power consumption.
[0011]
In Patent Document 2, a maximum number of terminals that can be connected to a base station is set, and a wireless LAN that improves communication efficiency by switching connections to other base stations for terminals that exceed this maximum number. A system is disclosed.
[0012]
In Patent Document 3, when data is transmitted to a terminal in a network where a link is established, data indicating the time for transferring data next is sent together with the data to receive a data frame other than that addressed to the own station. There is disclosed a wireless communication system capable of reducing power consumption in reception operation.
[0013]
[Problems to be solved by the invention]
However, the method of transmitting the data transmission time or suppressing the reception standby power using a beacon in this way cannot improve the density of the transmitted radio wave, but rather the radio wave congestion level for additional data and beacon communication. On the contrary, there was a problem that the transmission power increased.
[0014]
Even if the wireless base station switching function is used, the amount of communication concentrated on each base station can be limited, but the radio wave density in the air does not change, and the degree of radio wave congestion is the same as the communication required for the switching instruction. There is a problem that the transmission power increases.
[0015]
In view of the above-mentioned problems, the problem of the present invention is that when the number of wireless LAN terminals in communication increases and radio waves are congested, the sub radio base station is used to divide the communication area into small parts, and the radio waves of each device By reducing the output and performing communication, the power consumption of the entire network is reduced while increasing the amount of communication within a certain area.
[0016]
[Means for Solving the Problems]
FIG. 1 is a block diagram showing the basic configuration of a radio base station according to the present invention. In the figure, the base station 2 includes a traffic amount detection means 7, a radio wave intensity adjustment means 8, and a radio wave intensity adjustment command transmission means 9.
[0017]
The traffic volume detection means 7 detects the traffic volume of communication based on, for example, the number of communication terminals communicating with the own station, and the radio wave intensity adjustment means 8 has a predetermined traffic volume. When the first value is exceeded, the strength of the radio wave emitted from the own station is reduced, and the radio wave intensity adjustment command transmitting means 9 sends the communication terminal to the communication terminal communicating with the own station. It sends a command to reduce the intensity of the radio wave to be emitted.
[0018]
In the present invention, when the system is operated without using a sub-radio base station, which will be described later, the communication areas of a plurality of radio base stations are made large and the communication areas of the radio base stations overlap each other. Such a form can be considered. By performing such operation, it is expected that the operation cost is reduced as compared with the case where a sub radio base station described later is used.
[0019]
As described above, when the amount of communication traffic to the local station increases, the overall communication power is reduced by reducing the strength of the radio wave emitted by the local station itself and the radio field strength of the communication terminal communicating with the local station. Can be reduced.
[0020]
In the embodiment of the invention, the radio base station 2 can also include an operation command transmission means and a connection switching instruction means not shown in FIG. The operation command transmission means is for sending an operation command to a sub-radio base station below the own station when the traffic volume detection means 7 detects a value exceeding a predetermined second value as the traffic volume. The switching instruction means sends an instruction to switch to communication with the sub radio base station to a part of communication terminals currently communicating with the own station.
[0021]
The radio base station as an embodiment may further include a traffic amount receiving unit and a standby state instruction unit (not shown).
The traffic volume receiving means receives notification of the traffic volume of each sub base station from one or more sub radio base stations, and the standby state instructing means includes the traffic volume of the sub base station and its own traffic. When the total amount becomes equal to or less than a predetermined third value, an instruction to shift to a standby state is given to at least one of the sub base stations. At this time, the radio wave intensity adjusting means 8 increases the intensity of the radio wave emitted from the own station, and the above-mentioned connection switching instruction means communicates with the sub radio base station that should move to the standby state among the sub radio base stations. Is instructed to switch to communication with the local station.
[0022]
Next, in the present invention, a sub radio base station that is instructed by an upper radio base station to operate or is in a standby state and communicates with a communication terminal in the operating state includes a communication connection unit and a traffic amount notification unit. Prepare.
[0023]
The communication connection means establishes communication with the communication terminal that has been communicating with the upper radio base station in response to the operation instruction from the upper radio base station. The communication traffic amount of the station is notified to the upper radio base station.
[0024]
In the embodiment, the sub radio base station can further include connection switching instruction means and control means. When a standby instruction is sent from a higher-level radio base station, the connection switching instruction means increases the radio field strength of the communication terminal communicating with the own station and performs communication with the higher-level radio base station. A connection switching command is sent, and the control means shifts the own station to a standby state.
[0025]
Next, the communication terminal of the present invention, that is, a communication terminal that communicates with a radio base station or a sub radio base station that is subordinate to the radio base station, according to a radio wave intensity adjustment command sent from the radio base station. Radio wave intensity adjusting means for adjusting the intensity of radio waves emitted from the terminal is provided.
[0026]
The communication terminal can further include connection changing means. When the communication terminal receives a command to lower the radio field strength from the radio base station while communicating with the radio base station, the radio field strength adjustment means responds to the command by the radio field strength adjustment means. And the connection changing means switches the communication performed with the radio base station to the communication with the sub radio base station in response to an instruction from the radio base station.
[0027]
Also, when the communication terminal receives a command to increase the radio field strength from the radio base station while communicating with the sub radio base station, the radio field intensity adjustment means is issued from the own terminal in response to the command. While increasing the strength of the radio wave, the connection changing unit switches the communication performed with the sub-radio base station to the communication with the radio base station in response to an instruction from the radio base station.
[0028]
Next, a radio communication system according to the present invention includes a radio base station, one or more sub radio base stations subordinate to the radio base station, and a communication terminal that communicates with the radio base station or the sub radio base station. Composed.
[0029]
In this communication system, when the sub radio base station is in a standby state, the radio base station checks the number of communication terminals communicating with the own station, and the number is a predetermined value, for example, a single wireless LAN described later. When the state upper limit is exceeded, the radio base station sends an instruction to shift to the operating state to the sub radio base station, sends a connection change instruction to switch to communication with the sub radio base station to a part of the communication terminal, and Then, an operation for reducing the intensity of radio waves emitted from the sub radio base station and the communication terminal is performed.
[0030]
Also, when the sub radio base station is in operation, the radio base station checks the number of communication terminals communicating with the own station and lower sub radio base stations, and the number is a predetermined value, for example, described later. When the sub-wireless LAN management state lower limit value is not reached, the sub-wireless base station is instructed to enter a standby state, and the communication terminal that has been communicating with the sub-radio base station is instructed to switch to communication with the local station. The operation of increasing the intensity of the radio wave transmitted from the local station and the communication terminal is performed.
[0031]
As described above, according to the present invention, the operation of the sub radio base station or the standby instruction is performed according to the communication traffic amount of the radio base station, and the power consumption of the entire communication system is suppressed.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
Subsequently, the embodiment of the present invention will be described in more detail with reference to FIG. FIG. 2 is a configuration diagram of the radio communication system in the present embodiment, and shows a case where each sub radio base station is in a standby state. That is, unlike FIG. 13 showing the conventional example, as sub-radio base stations that are subordinate to each of the radio base stations 2A, 2B, and 2C, for example, three sub-radio base stations 4A are connected to the base station 2A, for example, by wire. It is connected.
[0033]
In FIG. 2, as described above, all of the sub radio base stations are in a standby state, and the radio base stations 2A, 2B, and 2C perform communication within the areas 1A, 1B, and 1C that they are responsible for, respectively. Uses normal strength radio waves with sufficient strength. Communication terminals 3A, 3B, and 3C that communicate with these base stations also use normal-intensity radio waves. For example, the communication terminal 3A can naturally be a mobile terminal. When the terminal 3A moves to the area 1B, communication is basically performed with the base station 2B.
[0034]
In FIG. 3, for example, the area 1A corresponding to the radio base station 2A has four areas 6A. ₀ ~ 6A ₃ The communication terminals in each area are in a state of performing communication with one of the radio base station 2A and the three sub radio base stations 4A. In this embodiment, this state is called a sub wireless LAN management state, and the state of FIG. 2 is called a single wireless LAN state.
[0035]
In FIG. 3, a base station 2A and three communication terminals 3A ₀ Is area 6A ₀ Communication is performed using sufficient power for communication in the range of (2), and the strength of radio waves emitted from the own station or the own terminal can be reduced as compared with the single wireless LAN state of FIG.
[0036]
Area 6A ₁ 3 communication terminals 3A ₁ Similarly, the radio field intensity can be reduced, and the sub radio base station 4A can communicate with the corresponding radio field intensity.
[0037]
FIG. 4 is a configuration block diagram of the wireless LAN base station in the present embodiment. In the figure, a base station 2 mediates communication with a wireless communication terminal connected by a wireless LAN or a device connected by a wired LAN, and includes a wired LAN communication unit 11, a wireless LAN communication unit 12, and radio wave intensity adjustment. Unit 13, sub wireless LAN base station control unit 14, communication terminal control unit 15, communication terminal number management unit 16, and communication terminal management table 17, except for communication terminal management table 17, the number of communication terminals from wired LAN communication unit 11 It is assumed that the management unit 16 is connected to each other by a bus 18.
[0038]
The wired LAN communication unit 11 communicates with a communication device connected by wire in accordance with IEEE 802.3 or a derivative standard, and the wireless LAN communication unit 12 is IEEE 802.11 or a derivative thereof. In accordance with the standard, communication is performed with a wirelessly connected communication terminal.
[0039]
The radio wave intensity adjustment unit 13 adjusts the communication intensity by the wireless LAN communication unit 12 in accordance with the management of the communication terminal number management unit 16 and the like.
The sub wireless LAN base station control unit 14 waits for the sub wireless LAN base station in its own communication area, that is, the lower sub wireless LAN base station via the wired LAN communication unit 11 according to the management of the communication terminal number management unit 16 and the like. An order or an operation order is issued.
[0040]
Corresponding to the management of the communication terminal number management unit 16 and the like, the communication terminal control unit 15 issues a radio wave intensity control command, a communication base station change command, etc. to the wireless communication terminal via the wireless LAN communication unit 12. is there.
[0041]
The communication terminal number management unit 16 stores the data of terminals in communication reported from the wireless LAN communication unit 12 and the sub wireless LAN base station in the communication terminal management table 17 and manages the data. In the state of the above-described single wireless LAN, when the number of terminals communicating with the own station exceeds the single wireless LAN state upper limit value described later, the communication terminal control unit 15 and the sub wireless LAN base station control unit 14 A radio wave intensity control command or the like is issued to the terminal via the terminal and shifts to the sub wireless LAN management state. Also, in the sub wireless LAN management state, when the number of communication terminals under the control of the local station falls below the lower limit value of the sub wireless LAN management state, a radio wave intensity control command or the like for increasing the radio field intensity is issued to the terminal. Thus, the state shifts to the single wireless LAN state.
[0042]
The radio wave intensity adjustment means in claims and claims 1 to 3 corresponds to, for example, the radio wave intensity adjustment section 13 in FIG. 4, and the traffic volume detection means and traffic volume reception means correspond to, for example, the communication terminal number management section 16. To do. The radio wave intensity adjustment command transmission unit and the connection switching instruction unit correspond to, for example, the communication terminal control unit 15, and the operation command transmission unit and the standby state instruction unit correspond to, for example, the sub wireless LAN base station control unit 14.
[0043]
FIG. 5 is an example of the contents stored in the communication terminal management table 17 of FIG. In the figure, the IP address of the terminal communicating with the own station A and each of the sub-radio base stations A1 to A3 subordinate to the own station is stored, the sub-radio LAN management state lower limit value, and the single radio LAN state An upper limit is specified.
[0044]
FIG. 6 is a block diagram showing the configuration of the sub wireless LAN base station. In the figure, the sub base station 4 mediates communication with a wireless communication terminal connected by a wireless LAN or a communication device connected by a wired LAN in accordance with an instruction from the wireless LAN base station. 21, a wireless LAN communication unit 22, a radio wave intensity adjustment unit 23, a wireless LAN base station communication unit 24, and a communication terminal control unit 25, all of which are connected by a bus 26.
[0045]
The wired LAN communication unit 21 and the wireless LAN communication unit 22 perform operations similar to those in the base station 2 of FIG. 4, and the radio wave intensity adjustment unit 23 performs wireless LAN communication in accordance with instructions from the wireless LAN base station. This adjusts the communication intensity by the unit 22, that is, the radio wave intensity.
[0046]
The wireless LAN base station communication unit 24 receives an instruction from the wireless LAN base station and transmits the instruction to each unit, and the communication terminal control unit 25 performs the wireless LAN communication unit 22 according to the instruction from the wireless LAN base station. A radio wave intensity control command, a base station change command, or the like is issued to the wireless communication terminal.
[0047]
The communication connection means and the connection switching instruction means in claims 4 and 5 are, for example, the communication terminal control section 25 in FIG. 6, the traffic amount notification means in the wireless LAN base station communication section 24, and the own station in a standby state. The control means to move to corresponds to, for example, the wireless LAN communication unit 22.
[0048]
FIG. 7 is a block diagram showing the configuration of the wireless LAN communication terminal. In the figure, the communication terminal 3 includes a wireless LAN communication unit 27, a radio wave intensity adjustment unit 28, and a wireless LAN base station communication unit 29, and these units are connected to each other by a bus 30.
[0049]
The wireless LAN communication unit 27 communicates with the wireless LAN base station and the sub wireless LAN base station in accordance with the above-mentioned standard, and the radio wave intensity adjustment unit 28 performs wireless LAN in accordance with an instruction from the base station. The communication strength by the communication unit 27 is adjusted, and the wireless LAN base station communication unit 29 transmits an instruction from the wireless LAN base station or the sub wireless LAN base station to each unit.
[0050]
The radio wave intensity adjusting means in claims 6 to 8 corresponds to, for example, the radio wave intensity adjusting section 28 in FIG. 7, and the connection changing means corresponds to the wireless LAN communication section 27.
Next, operations of the wireless LAN base station, the sub wireless LAN base station, and the communication terminal in the present embodiment will be described with reference to FIGS. 8 and 9 show the operation of the wireless LAN base station, FIG. 8 is a flowchart of the operation in the single wireless LAN state, and FIG. 9 is a flowchart of the operation in the sub wireless LAN management state.
[0051]
When the operation in the single wireless LAN state is started in FIG. 8, first, communication is performed with the communication terminal as a wireless LAN base station in step S1, and whether new connection with the wireless LAN communication terminal is started in step S2. Alternatively, it is determined whether or not the connection is completed, and if there is no start or end, the process returns to step S1 and communication is continued. The operations in these steps are performed by the wireless LAN communication unit 12 in FIG.
[0052]
If it is determined in step S2 that a new connection has been started or the connected communication has ended, the number of wireless LAN terminals being managed is increased or decreased in step S3, that is, the communication terminal management table 17 in FIG. The new data is stored in the memory or the stored data is erased. This operation is executed by the communication terminal number management unit 16.
[0053]
Subsequently, in step S4, it is determined by the communication terminal number management unit 16 whether or not the terminals in the area managed by the own station have exceeded the single wireless LAN state upper limit value. Repeated.
[0054]
If it is determined in step S4 that the single wireless LAN state upper limit has been exceeded, the sub wireless LAN base station control unit 14 in step S5 performs sub wireless LAN subordinate to the own station in order to shift to the sub wireless LAN management state. In step S6, the base station is set in an operating state, and the communication terminal control unit 15 switches the instruction to lower the radio field strength to the wireless communication terminal communicating with the own station and the communication with the sub wireless LAN base station. In step S7, the radio wave intensity adjusting unit 13 reduces the intensity of the radio wave emitted from the own station, and then shifts to the sub wireless LAN management state.
[0055]
FIG. 9 is a flowchart showing the operation of the base station in the sub wireless LAN management state. In the figure, first, in step S11, communication is performed with a communication terminal as a wireless LAN base station by the wireless LAN communication unit 12, and in step S12, the sub wireless LAN base station control unit 14 controls the local station. It is determined whether or not a notification of an increase or decrease in the number of connected terminals has been received from a certain sub wireless LAN base station. If not, the communication terminal control unit 15 performs wireless communication with the own station in step S13. It is determined whether a new connection with the communication terminal has started or the communication that has been connected has ended. If the communication terminal has not started or ended, the process returns to step S11 to continue the communication with the terminal. The
[0056]
If it is determined in step S12 that a notification of an increase or decrease in the number of connected terminals has been received from the sub-base station managed by the own station, or a new connection is established between the own station and the wireless communication terminal in step S13. If it is determined that the communication started or ended, the number of wireless LAN terminals being managed is increased or decreased by the communication terminal number management unit 16 in step S14, and the data stored in the communication terminal management table 17 is updated. Store or erase.
[0057]
Subsequently, in step S15, the communication terminal number management unit 16 uses a terminal in the area under the control of the own station, that is, a terminal communicating with the own station and a terminal communicating with the sub-base station below the own station. It is determined whether or not the total number of sub wireless LAN management state values is below the lower limit value of the sub wireless LAN management state.
[0058]
When the value is below the lower limit, in order to shift to the single wireless LAN state, in step S16, the sub wireless LAN base station control unit 14 issues a standby instruction to the sub wireless LAN base station, and in step S17, the radio wave intensity. The adjustment unit 13 increases the strength of the radio wave emitted from the own station, and in step S18, the communication terminal control unit 15 issues an instruction to increase the radio field strength to the wireless communication terminal communicating with the own station, and shifts to the single wireless LAN state. To do.
[0059]
FIG. 10 is a flowchart showing the operation of the sub wireless LAN base station. In the figure, it is assumed that the sub wireless LAN base station is initially in a standby state.
First, in step S21, a standby operation for waiting for an instruction from the wireless LAN base station is performed. In step S22, it is determined whether or not an operation instruction is sent from the wireless LAN base station side by the wireless LAN base station communication unit 24 of FIG. If it has not been sent, the process returns to step S21 to continue the standby operation.
[0060]
If it is determined that the operation instruction has been sent, the wireless LAN communication unit 22 performs communication as a wireless LAN sub-base station with the terminal as an operation in the operation state in step S23, and the wireless communication terminal in step S24. In step S25, the wireless LAN base station communication unit 24 causes the wireless LAN base station communication unit 24 to start the wireless LAN base station. If a change in the number of terminals is notified to the terminal and there is no new start or end, the process immediately proceeds to step S26.
[0061]
Subsequently, in step S26, the wireless LAN base station communication unit 24 determines whether or not a standby instruction is sent from the wireless LAN base station. If not, the operation after step S23 is continued. When the standby instruction is sent, in order to shift to the standby state, in step S27, the communication terminal control unit 25 instructs the wireless communication terminal in communication to increase the radio wave intensity, and sets the communication destination to the wireless LAN base. A connection switching instruction for switching to the station is issued, and the standby state is restored.
[0062]
11 and 12 are flowcharts showing the operation of the communication terminal. FIG. 11 shows the operation in the single wireless LAN state, and FIG. 12 shows the operation in the sub wireless LAN management state.
In the single wireless LAN state of FIG. 11, it is determined in step S31 whether or not the wireless LAN base station communication unit 29 has received an instruction to reduce the radio field intensity from the base station. Continued.
[0063]
If an instruction to reduce the radio field intensity is received, the radio field intensity is reduced by the radio field intensity adjustment unit 28 in step S32, and it is determined in step S33 whether or not an instruction to change the base station to be connected is received from the base station. If it is determined and received by the base station communication unit 29 and the base station to be connected is changed by the wireless LAN communication unit 27 in step S34, or if no change instruction is received, the state immediately shifts to the sub wireless LAN management state. .
[0064]
FIG. 12 shows the operation at the time of transition from the sub wireless LAN management state to the single wireless LAN state. When an instruction to increase the radio field intensity is received in step S36, the radio field intensity is increased in step S37, and steps S38 and S39 are performed. Then, after the processing similar to steps S33 and S34 in FIG.
[0065]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to efficiently operate the radio communication system by switching the operation or standby state of the sub radio base station corresponding to the amount of communication traffic. .
[0066]
In other words, when the number of wireless communication terminals increases and radio waves are congested, the conventional communication area is divided into smaller areas, and communication is performed by reducing the radio wave output of each communication device. Electric power can be reduced. On the other hand, when the number of communication terminals decreases, it is possible to improve the communication efficiency of the network by unifying a plurality of small communication areas into one large area and reducing the number of active sub-base stations. Is possible.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a principle configuration of a radio base station of the present invention.
FIG. 2 is a diagram showing a configuration (single wireless LAN state) of a wireless communication system in an embodiment of the present invention.
FIG. 3 is a diagram illustrating a configuration of a wireless communication system (sub wireless LAN management state) in the present embodiment.
FIG. 4 is a block diagram showing a configuration of a wireless LAN base station.
FIG. 5 is a diagram showing an example of stored contents of a communication terminal management table.
FIG. 6 is a block diagram showing a configuration of a sub wireless LAN base station.
FIG. 7 is a block diagram showing a configuration of a wireless communication terminal.
FIG. 8 is a flowchart (part 1) showing an operation of the wireless LAN base station.
FIG. 9 is a flowchart (part 2) illustrating the operation of the wireless LAN base station.
FIG. 10 is a flowchart showing an operation of a sub wireless LAN base station.
FIG. 11 is a flowchart (part 1) illustrating an operation of the communication terminal.
FIG. 12 is a flowchart (part 2) illustrating the operation of the communication terminal.
FIG. 13 is a diagram showing a configuration of a conventional example of a wireless LAN communication system.
[Explanation of symbols]
1,6 area
2 radio base stations
3 Communication terminal
4 sub-radio base stations
7 Traffic volume detection means
8 Radio field strength adjustment means
9 Radio wave intensity adjustment command transmission means
11, 21 Wired LAN communication section
12, 22, 27 Wireless LAN communication unit
13, 23, 28 Radio field intensity adjustment section
14 Sub wireless LAN base station controller
15, 25 Communication terminal control unit
16 Communication Terminal Number Management Department
17 Communication terminal management table
18, 26, 30 bus
24, 29 Wireless LAN base station communication section

Claims

In the radio base station that communicates with the terminal,
Traffic volume detection means for detecting the traffic volume of communication to the own station;
Radio wave intensity adjusting means for reducing the intensity of radio waves emitted from the own station when the detected traffic volume exceeds a predetermined first value;
A radio base station, comprising: a radio field intensity adjustment command transmitting unit that transmits a command to reduce the intensity of radio waves emitted by a communication terminal communicating with the local station.

When the traffic volume detection means detects a traffic volume exceeding a predetermined second value,
An operation command transmission means for transmitting an operation command to a sub-radio base station below the own station;
2. The radio according to claim 1, further comprising connection switching instruction means for sending an instruction to switch to communication with the sub radio base station to at least a part of communication terminals currently communicating with the own station. base station.

In the radio base station,
Traffic volume receiving means for receiving notification of the communication traffic volume of each sub radio base station from one or more sub radio base stations;
When the total of the traffic volume of each of the sub radio base stations and the traffic volume of the own station is equal to or less than a predetermined third value, at least one of the sub radio base stations is instructed to enter a standby state. A standby state instruction means for giving,
The radio wave intensity adjusting means increases the intensity of radio waves emitted from the own station,
3. The radio base station according to claim 2, wherein the connection switching instruction means issues an instruction to cause a communication terminal communicating with the sub radio base station to shift to the standby state to switch to communication with the own station.

In the sub radio base station that is instructed by the upper radio base station to operate or is in standby and communicates with the communication terminal in the active state.
Corresponding to the operation instruction from the upper radio base station, communication connection means for establishing communication with the communication terminal that was communicating with the upper radio base station;
A sub-radio base station comprising: a traffic amount notification means for notifying a higher-level radio base station of the communication traffic amount of the own station.

When a standby instruction is sent from the upper radio base station, a connection switching instruction is made to increase the radio field intensity for the communication terminal communicating with the own station and to communicate with the upper radio base station. 5. The sub-radio base station according to claim 4, further comprising: a connection switching instruction means for sending a message and a control means for moving the own station to a standby state.

In a communication terminal that communicates with a radio base station or a sub radio base station that is subordinate to the radio base station,
A communication terminal comprising: a radio field intensity adjusting unit that adjusts the intensity of a radio wave emitted from the terminal according to a radio field intensity adjustment command sent from the radio base station.

In response to an instruction to reduce the radio field intensity from the radio base station while the communication terminal is communicating with the radio base station, the radio field intensity adjustment means With lowering,
The communication terminal further comprises connection changing means for switching communication performed with the radio base station to communication with the sub radio base station according to an instruction from the radio base station. The communication terminal according to claim 6.

In response to a command to increase the radio field intensity from the radio base station in a state where the communication terminal is communicating with the sub radio base station, the radio field intensity adjustment means is the intensity of the radio wave emitted from the terminal itself As well as
The communication terminal further includes connection changing means for switching communication performed with the sub-radio base station to communication with the radio base station in response to an instruction from the radio base station. The communication terminal according to claim 6.

In a communication system including a radio base station, one or more sub radio base stations below the radio base station, and a communication terminal that communicates with the radio base station or the sub radio base station,
When the sub radio base station is in a standby state, the radio base station checks the number of communication terminals communicating with the own station,
When the number of terminals exceeds a predetermined first value, the radio base station sends an instruction to shift to an operating state to a sub radio base station, and a part of the communication terminal receives the sub A wireless communication system, wherein a connection change instruction for switching to communication with a wireless base station is sent to reduce the intensity of radio waves emitted from the own station, the sub wireless base station, and the communication terminal.

When the sub-radio base station is in operation, the radio base station checks the total number of communication terminals communicating with the own station and the sub-radio base station,
When the total number of the communication terminals falls below a predetermined second value, an instruction to shift to the standby state is sent to the sub radio base station, and the communication terminal communicating with the sub radio base station communicates with its own station. The communication system according to claim 9, wherein a connection change instruction to switch to is sent to increase the strength of radio waves emitted from the local station and the communication terminal.