JP3639168B2

JP3639168B2 - Communication control method, mobile communication system, base station, and mobile station

Info

Publication number: JP3639168B2
Application number: JP37580299A
Authority: JP
Inventors: 成視梅田; 信三大久保; 泰山尾; 嬉珍佐藤
Original assignee: NTT Docomo Inc
Current assignee: NTT Docomo Inc
Priority date: 1999-12-28
Filing date: 1999-12-28
Publication date: 2005-04-20
Anticipated expiration: 2019-12-28
Also published as: JP2001189687A

Abstract

PROBLEM TO BE SOLVED: To provide a communication control method in a mobile communication system for satisfying the desired communication service quality of a mobile station while using effectively the transmitting power resources or facility resources. SOLUTION: In this communication control method that is available when the communication of information is carried out between a base station and a mobile station in a mobile communication system, the selective switching is carried out between a 1st communication means with which the base station performs the communication of information with the mobile station via an antenna having the fixed directivity and a 2nd communication means with which the base station performs the communication of information with the mobile station via an antenna whose directivity is variable for tracking the mobile station according to a requested transmission rate of information and the state of a radio transmission line set between the mobile station and the base station.

Description

【０００１】
【発明の属する技術分野】
本発明は、移動通信システムにおける通信制御方法、詳しくは、要求される情報の伝送速度に応じて移動局と基地局との間の通信態様を制御するようにした通信制御制御方法に関する。
本発明は、また、そのような通信制御方法が適用される移動通信システム、基地局及び移動局に関する。
【０００２】
【従来の技術】
セルラ方式の移動通信システムでは、移動局との間で無線通信を行う基地局が通信サービスエリア内に複数設置されており、各基地局は、移動局との無線通信が可能な範囲となるセル（無線ゾーン）を形成している。セル内に在圏する移動局は、そのセルの基地局と無線通信を行うことにより、種々の通信サービス（通話、データ配信など）を受ける。
【０００３】
ところで、近年、移動局と基地局間の情報伝送の高速化が要望されている。高速な情報伝送を行う場合、伝送方式が同じで、アンテナ利得などの伝送条件が同じであるとすると、より多くの送信電力が必要となる。そのことは、限られた送信電力にてより高速な情報伝送を行おうとすると、各基地局の無線可能領域、即ち、セルの半径が小さくなることを意味する。より高い周波数を用いて基地局と移動局との間で無線通信を行う場合、伝播損失が増大するので、更に、情報の高速伝送における移動局との無線通信可能範囲（セル）に関する条件は厳しくなる。
【０００４】
【発明が解決しようとする課題】
上述したような状況において、情報の高速伝送を可能にした移動通信システムによって安定した通信サービスを移動局のユーザに提供するためには、送信電力を増大させるか、あるいは、送信電力の増大を行わずに、通信サービスエリア内により多くの基地局を設置して小さい多くのセルにて当該通信サービスエリアをカバーすることになる。
【０００５】
しかし、移動局が基地局に比較的近い範囲に存在する場合には、比較的少ない送信電力であっても基地局と移動局との間において情報を高速に伝送することができる。また、情報の種類（例えば、音声情報）によっては、必ずしも高速伝送を行わなくても、十分な品質の通信サービスを提供することも可能な場合がある。これらの状況を考慮すると、一律に各基地局での送信電力を増大させるのでは、システム内における電力資源を効率的に利用されるものとはならない。
【０００６】
また、多くの基地局を通信サービスエリア内に設置しようとしても、特に、都市部などでは、設置場所の制限が多く、所望の位置に基地局をきめ細かく設置することは、困難である。そして、上述したように、必ずしも高速伝送を行わなくても十分な品質の通信サービスを提供しうる場合があることから、仮に、多くの基地局をきめ細かく設置したとしても、それらの基地局が有効に利用されるとは限らない。
【０００７】
そこで、本発明の第一の課題は、移動通信システムにおいて、送信電力資源や設備資源を効率的に利用しつつ、移動局において要望される通信サービスの質を満足できるようにした通信制御方法を提供することである。
本発明の第二の課題は、そのような通信制御方法が適用される移動通信システムを提供することである。
【０００８】
本発明の第三の課題は、そのような通信制御方法が適用される移動通信システムにおける基地局を提供することである。
更に、本発明の第四の課題は、そのような通信制御方法が適用される移動通信システムにおける移動局を提供することである。
【０００９】
【課題を解決するための手段】
上記第一の課題を解決するため、本発明は、請求項１に記載されるように、移動通信システムにおける基地局の第１の通信手段又は第２の通信手段と移動局との間において情報通信を行う際の通信制御方法において、移動局は、基地局の止まり木チャネルにて送信される報知情報から、送受信される情報に関する通信サービスの質に応じた閾値を受信し、無線伝送路の状態及び上記閾値に基づいて、第１の通信手段に対応する第１のセル又は、第２の通信手段に対応する第２のセルのうちいずれかのセルを選択し、上記選択されたセルの基地局に対して所定の信号を送信し、上記所定の信号を受信した基地局は、要求される情報の伝達速度と、移動局と基地局との間の無線伝送路の状態とに応じて、固定的な指向性を有するアンテナを用いて基地局が移動局と情報通信を行う第１の通信手段と、移動局を追尾するように指向性が可変となるアンテナを用いて基地局が移動局と情報通信を行う第２の通信手段とを選択的に切替えるように構成される。
【００１０】
このような通信制御方法では、上記第一の通信手段は固定的な指向性を有するアンテナを用いて基地局と移動局との間において情報通信を行い、上記第二の通信手段は、移動局を追尾するように指向性が可変となるアンテナを用いて基地局と移動局との間において情報通信を行うので、同じ送信電力のもとでは、上記第二の通信手段のほうが、上記第一の通信手段より、基地局からより遠方の移動局に対して情報通信を行うことができる。要求される通信速度と、基地局と移動局との間の無線伝送路の状態とに基づいて、それらの第一の通信手段と第二の通信手段を切替えることによって、種々の通信サービスの質を満足するような情報伝送が可能となる。
【００１１】
上記移動局と基地局との間の無線通信路の状態は、移動局と基地局との間の距離（無線伝送路の距離）、障害物での反射の状態、電波の減衰の状態、他の通信ノードからの電波の干渉状態などであって、例えば、信号の受信レベル、信号の誤り率、干渉波の受信レベル（受信ＣＩＲ：Carrier Interference Ratio）などにて表すことができる。
【００１２】
また、上記第一の通信手段にて用いられるアンテナの特性となる固定的な指向性には、所謂、無指向性も含まれる。
請求項２に記載されるように、上記通信方法において、基地局からの止まり木チャネルの受信レベルを移動局にて測定し、その測定結果を上記移動局と基地局との間の無線伝送路の状態として用いるように構成することができる。
【００１３】
上記第一の通信手段と第二の通信手段との切替え条件を具体的に提供するという観点から、本発明は、請求項３に記載されるように、上記各通信制御方法において、要求される情報の伝送速度条件に対して予め定められた基準となる無線伝送路の状態より移動局と基地局との間の無線伝送路の状態が良好な場合に、上記第一の通信手段が選択されるようにし、上記移動局と基地局との間の無線伝送路の状態が上記基準となる無線伝送路の状態より良好とならない場合に、上記第二の通信手段が選択されるように、上記第一の通信手段と上記第二の通信手段が切替えられるように構成することができる。
【００１４】
上記第一の通信手段のアンテナを具体的に提供するという観点から、本発明は、請求項４に記載されるように、上記各通信制御方法において、上記第一の通信手段のアンテナとして、送信電力に応じた移動局との通信可能エリアを固定的に形成するアンテナを用いるように構成される。
更に具体的には、本発明は、請求項５に記載されるように、上記各通信制御方法において、送信電力に応じた移動局との通信可能エリアを固定的に形成するアンテナとして、オムニアンテナまたはセクタアンテナを用いるように構成することができる。
【００１５】
また、第２の通信手段のアンテナを具体的に提供するという観点から、本発明は、請求項６に記載されるように、上記各通信制御方法において、上記第２の通信手段のアンテナとして、アダプティブアレイアンテナ(Adaptive Array Antenna : AAA)を用いるように構成することができる。
上記第二の課題を解決するため、本発明は、請求項７に記載されるように、基地局の第１の通信手段又は第２の通信手段と移動局との間において情報通信を行う移動通信システムにおいて、移動局は、基地局の止まり木チャネルにて送信される報知情報から、送受信される情報に関する通信サービスの質に応じた閾値を受信する閾値受信手段と、移動局と基地局との間の無線伝送路の状態を測定する伝送路状態測定手段と、無線伝送路の状態及び上記閾値に基づいて、第１の通信手段に対応する第１のセル又は、第２の通信手段に対応する第２のセルのうちいずれかのセルを選択するセル選択手段と、上記選択されたセルの基地局に対して所定の信号を送信する信号送信手段とを有し、上記所定の信号を受信した基地局は、固定的な指向性を有するアンテナを用いて移動局と情報通信を行う第１の通信手段と、移動局を追尾するように指向性が可変となるアンテナを用いて移動局と情報通信を行う第２の通信手段と、要求される情報の伝送速度と、上記伝送路状態測定手段にて測定された移動局と基地局との間の無線伝送路の状態に基づいて上記第１の通信手段と第２の通信手段とを選択的に切替える切替制御手段とを有するように構成される。
【００１６】
更に、上記第三の課題を解決するため、本発明は、請求項１４に記載されるように、基地局と移動局との間において情報通信を行う移動通信システムに用いられる基地局において、固定的な指向性を有するアンテナを用いて移動局と情報通信を行う第１の通信手段と、移動局を追尾するように指向性が可変となるアンテナを用いて移動局と情報通信を行う第２の通信手段と、止まり木チャネルにて送信される報知情報から、送受信される情報に関する通信サービスの質に応じた閾値を受信し、無線伝送路の状態及び上記閾値に基づいて、上記第１の通信手段に対応する第１のセル又は、上記第２の通信手段に対応する第２のセルのうちいずれかのセルを選択した移動局から送信された所定の信号に応じて、要求される情報の伝送速度と、移動局と基地局との間の無線伝送路の状態に基づいて上記第１の通信手段と第２の通信手段とを選択的に切替える切替え手段とを有するように構成される。
【００１７】
また、更に、上記第四の課題を解決するため、本発明は、請求項１９に記載されるように、基地局の第１の通信手段又は第２の通信手段と移動局との間において情報通信を行う移動通信システムに用いられる移動局において、基地局の止まり木チャネルにて送信される報知情報から、送受信される情報に関する通信サービスの質に応じた閾値を受信する閾値受信手段と、基地局との間の無線伝送路の状態を測定する伝送路状態測定手段と、無線伝送路の状態及び上記閾値に基づいて、第１の通信手段に対応する第１のセル又は、第２の通信手段に対応する第２のセルのうちいずれかのセルを選択するセル選択手段と、上記選択されたセルの基地局に対して所定の信号を送信する信号送信手段とを有し、上記セル選択手段は、上記伝送路状態測定手段での測定結果と、要求される情報の伝送速度に基づいて、固定的な指向性を有するアンテナを用いて基地局と移動局との間で情報通信を行う第１の通信手段と、移動局を追尾するように指向性が可変となるアンテナを用いて基地局と移動局との間で情報通信を行う第２の通信手段とのいずれを選択すべきかを判断し、該判断された第１の通信手段または第２の通信手段にて基地局と当該移動局との間において情報通信がなされるように構成される。
【００１８】
【発明の実施の形態】
以下、本発明の実施の形態を図面に基づいて説明する。
本発明の実施の一形態に係る複合セル切替え制御方法の提供される移動通信システムにおけるセル構成は、例えば、図１に示すようになっている。
図１において、通信サービスエリア内に複数の基地局１１、１２、１３、１４、１５、１６が設置されている。なお、図１では、便宜的に６つの基地局しか示されていない。
【００１９】
各基地局１１、１２、１３、１４、１５、１６は、所定の送信電力で情報の高速伝送を通常のアンテナ（例えば、オムニアンテナ、セクタアンテナ）を介して行える無線通信領域となるマイクロセルＣ１を構成する。この場合、高い伝送速度での無線通信が可能となるマイクロセルＣ１のセル半径は一般的に小さく、各基地局１１、１２、１３、１４、１５、１６の各マイクロセルＣ１だけでは、通信サービスエリア全体をカバーすることができない。ただし、比較的低い伝送速度で情報の無線通信を行う場合、このマイクロセルＣ１のセル半径は大きくなり、各マイクロセルＣ１にて通信サービスエリア全体をカバーすることができるようになる。
【００２０】
各基地局１１、１２、１３、１４、１５、１６は、更に、移動局の追尾機能を有する高利得アンテナ、例えば、アダプティブアレイアンテナを介して行える無線通信領域となるＡＡＡセルＣ２を形成する。このアダプティブアレイアンテナを用いた場合、指向性（電波のビーム）を絞ることができるので、限られた送信電力で、比較的広い範囲の移動局を追尾することができる。従って、ＡＡＡセルＣ２はマクロセルＣ１より広く、情報の高速伝送の際に上記マイクロセルＣ１にてカバーできなかった通信サービスエリアは、各基地局にて形成されるＡＡＡセルＣ２によってカバーされる。
【００２１】
また、制御チャネルに要求される伝送速度は、一般的に高速の通信チャネルほどには大きくないので、制御チャネルでの無線通信可能範囲（制御用セル）は比較的広くなる。この例では、各基地局の無線チャネルでの無線通信可能範囲は、情報の低速伝送の際に形成されるセル半径の大きいマイクロセルＣ１に対応し、通信サービスエリアを連続的にカバーできるものとする。
【００２２】
上記各基地局１１、１２、１３、１４、１５、１６は、例えば、図２に示すように構成される。
図２において、基地局は、制御部１００、アンテナアレイ１０１、送受分配器１０２、ウエイト制御・乗算部１０３（受信信号用）、ウエイト制御・乗算部１０４（送信信号用）、切替器１１０、復調回路１１１、復号回路１１２、変調回路１１３、符号化回路１１４、送受分配器１２０、送受分配器１３０、復調回路１３１、復号回路１３２、変調回路１３３及び符号化回路１３４を有している。
【００２３】
上記アレイアンテナ１０１、送受分配器１０２、ウエイト制御・乗算部１０３、１０４は、ＡＡＡセルＣ２内の移動端末機との間で、情報の高速伝送を行う際に用いられる（ＡＡＡセル系）。ウエイト制御・乗算部１０３は、移動局固有のパイロット信号を用いて、予め定められたアダプティブウエイト決定アルゴリズムに従ってアレイアンテナ１０１の各アンテナ素子に対するウエイトを決定し、各アンテナ素子からの信号に対して対応するウエイトを乗じることによって、受信信号を生成する。このウエイト制御・乗算部１０３（受信信号用）にて決定された各アンテナ素子に対するウエイトは、ウエイト制御・乗算部１０４（送信信号用）にリアルタイムで通知される。ウエイト制御・乗算部１０３にて生成された受信信号は、切替器１１０を介して復調回路１１１、復号回路１１２に順次供給され、復調、復号の処理にて得られた受信情報信号が制御部１００に供給される。
【００２４】
ウエイト制御・乗算部１０４（送信信号用）は、上記ウエイト制御・乗算部１０３（受信信号用）から通知された各ウエイトを送信信号に乗算し、その結果得られた各信号をアンテナアレイ１０１の対応するアンテナ素子から送信する。制御部１００からの送信情報信号は、符号化回路１１４、変調回路１１３に順次供給され、符号化、変調の処理にて得られた送信信号が切替器１１０を介してウエイト制御・乗算部１０４に供給される。
【００２５】
送受分配器１２０は、例えば、オムニアンテナを介して信号の送受信を行い、マイクロセルＣ１内の移動局と通信を行うために用いられる（マイクロセル系）。オムニアンテナにて受信された信号は、この送受分配器１２０、切替器１１０を介して復調回路１１１、復号回路１１２に順次供給される。これら復調回路１１１、復号回路１１２での処理にて得られた受信情報信号が制御部１１０に供給れる。また、制御部１００からの送信信号が符号化回路１１４、変調回路１１３に順次供給される。そして、それら符号化、変調の各処理にて得られた送信信号が切替器１１０を介して送受分配器１２０に供給され、オムニアンテナから送信される。
【００２６】
送受分配器１３０は、例えば、オムニアンテナを介して制御チャネルの信号の送受信を行うために用いられる（制御用セル系）。アンテナにて受信された制御信号は、この送受分配器１３０を介して復調回路１３１、復号回路１３２に順次供給される。復調、復号の各処理された制御チャネルの情報は、受信情報信号として制御部１００に供給される。また、制御部１００からの制御信号は、符号化回路１３４、変調回路１３３に順次供給される。そして、それら符号化、変調の各処理にて得られた制御信号が送受分配器１３０に供給され、アンテナから送信される。
【００２７】
切替器１１０は、制御部１００からの指示により、移動局に対して動作させるべき送受信系（ＡＡＡセル系またはマイクロセル系）を切替える。なお、この制御部１００による切替器１１０の切替制御の詳細については後述する。
なお、上記制御用セル系の通信ユニット（送受分配器１３０、復調回路１３１、復号回路１３２、変調回路１３３及び符号化回路１３４）は、マイクロセル系の通信ユニット（送受分配器１２０、復調回路１１１、復号回路１１２、変調回路１１３及び符号化回路１１４）にて代用することができる。また、図２において、送信系、受信系の双方に用いられる増幅器については、省略されている。
【００２８】
通信サービスエリア内で基地局と無線通信を行う移動局は、例えば、図３に示すように構成されている。
図３において、この移動局は、制御部２００、アンテナを介して信号の送受信を行う送受分配器２０１と、復調回路２０２、復号回路２０３、変調回路２０４、符号化回路２０５を有している。アンテナを介して受信した信号が送受分配器２０１を介して復調回路２０２、復号回路２０３に順次供給される。復調回路２０２、復号回路２０３での復調、復号処理にて得られた受信情報信号が制御部２００に供給される。また、制御部２００からの送信情報信号が符号化回路２０５、２０４に順次供給され、それらでの処理により得られた送信信号が送受分配器２０１を介してアンテナから送信される。
【００２９】
なお、図３において、送信系、受信系の双方に用いられる増幅器については、省略されている。
移動局と、基地局との間の通信の手順について説明する。
移動局からの起動により情報伝送が行われる場合、例えば、図４に示す手順に従って、移動局と基地局との間で通信が行われる。
【００３０】
図４において、移動局（ＭＳ）は、マイクロセルＣ１またはＡＡＡセルＣ２の選択を行う。このセルの選択は、次のようにしてなされる。
各基地局（ＢＳ）は、図５に示すように、前述した制御用セル系の通信ユニットにて止まり木チャネルセルを一定の送信電力で送信している。移動局（ＭＳ）は、制御部２００での制御のもと、周囲の基地局（ＢＳ）からの止まり木チャネルを走査し、その受信レベルを順次測定する（Ｓ１１）。そして、その測定された受信レベルのうち最大レベルとなる止まり木チャネルの基地局を当該移動局が在圏するセルの基地局と判定する（Ｓ１２）。この移動局が在圏するセルの基地局の判定処理は、移動局が待ち受け状態でも、また、通信状態のいずれの状態でも、一定時間毎など、予め定められた条件のもとで行われる。
【００３１】
その後、図６に示すように、その判定された基地局（ＢＳ）から止まり木チャネルにて送信される報知情報を受信した移動局（ＭＳ）は、その報知情報に含まれるマイクロセルＣ１とＡＡＡセルＣ２の切替条件となる閾値Ｓを取得する（Ｓ１３）。
この閾値Ｓは、送受信される情報に関する通信サービスの質に応じて異なる。例えば、画像情報などの情報を高速伝送することが要求される情報が送受信される場合の閾値Ｓ１は、比較的大きな値となる。また、通話情報などの情報のように特に高速伝送しなくても比較的高い通信品質を保つことのできる情報が送受信される場合の閾値Ｓ２は比較的小さな値となる。
【００３２】
上記のようにマイクロセルＣ１とＡＡＡセルＣ２の切替条件となる閾値を取得した移動局（ＭＳ）は、自局が在圏するセルの基地局からの止まり木チャネルの受信レベルＲを測定し（Ｓ１４）、その受信レベルと上記取得した閾値Ｓとの比較結果に基づいてマイクロセルＣ１とＡＡＡセルＣ２の選択を行うＳ１５）。
上記受信レベルＳが閾値Ｒ（Ｒ１またはＲ２）以上となる場合、マイクロセルＣ１が選択される。一方、上記受信レベルＳが閾値Ｒ（Ｒ１またはＲ２）より小さい場合、ＡＡＡセルＣ２が選択される。情報を高速伝送する場合、上記閾値Ｓ１が比較的大きな値となるため、受信レベルＲが、比較的高いレベルとならなければ、マイクロセルＣ１が選択されない。即ち、移動局（ＭＳ）と基地局（ＢＳ）との間の無線伝送路の状態が比較的良好な場合（移動局が基地局に比較的近い場合）にマイクロセルＣ１が選択される。一方、情報を高速伝送する必要がない場合には、上記閾値Ｓ２が比較的小さい値となるため、受信レベルＲが比較的低いレベルであっても、マイクロセルＣ１が選択される。即ち、移動局（ＭＳ）と基地局（ＢＳ）との間の無線伝送路の状態がそんなに良好でなくても（移動局が基地局より比較的遠くに位置していても）マイクロセルＣ１が選択される。
【００３３】
また、一方、上記閾値Ｓ（Ｓ１またはＳ２）を基準として、移動局（ＭＳ）と基地局（ＢＳ）との間の無線伝送路の状態が比較的悪い場合（移動局が基地局から上記基準に基づいて比較的遠くに位置する場合）には、ＡＡＡセル２が選択される。
図４に戻って、上記のようにして、移動局（ＭＳ）にてマイクロセルＣ１またはＡＡＡセルＣ２の選択がなされると、移動局（ＭＳ）は、制御チャネルを用いて発信信号及び無線状態報告信号を在圏すると判定されたセルの基地局（ＢＳ）に送信する。この無線状態報告信号には、選択されたセル種別（マイクロセルＣ１またはＡＡＡセルＣ２）の情報を含む。
【００３４】
これら発信信号及び無線状態報告信号を制御チャネルにて受信した基地局（ＢＳ）の制御部１００（図２参照）は、無線状態報告信号に含まれる選択されたセル種別の情報に基づいて切替器１１０に対する切替制御信号を生成し、その切替制御信号にて切替器１１０の切替制御が行われる（Ｓ２１）。移動局（ＭＳ）にてマイクロセルＣ１の選択が行われた場合、マイクロセル系の通信ユニットである送受分配器１２０が復調回路１１１及び変調回路１１３に接続されるように、切替器１１０が接続切替を行う。
【００３５】
このように通信ユニット（通信チャネル）の選択がなされると、その選択された通信ユニット（ＡＡＡセル系またはマイクロセル系）の送受信機の起動がなされる（Ｓ２２）。そして、基地局（ＢＳ）から制御チャネルを用いて通信チャネルの指定情報を含む信号が移動局に送信される。このとき、ＡＡＡセル系の通信ユニットが選択された場合、移動局（ＭＳ）に対して通信チャネルの通知と共に、アクティブアレイの動作に必要な情報（移動局のパイロット信号など）も通知される。
【００３６】
基地局（ＢＳ）から通信チャネルの指定情報を受信した移動局（ＭＳ）は、その指定された通信チャネル用の受信機を起動する（Ｓ３）。そして、その通信チャネルでの受信同期を確立するために同期用信号を基地局（ＢＳ）に送信する。基地局（ＢＳ）は、移動局（ＭＳ）から受信した同期用信号に基づいて当該通信チャネルでの受信同期を確立させる（Ｓ２３）。
【００３７】
この状態で移動局（ＭＳ）と基地局（ＢＳ）との間で情報伝送のための通信が所定の送信電力にて行われる。例えば、情報の高速伝送を行う場合、移動局（ＭＳ）が図１に示すマイクロセルＣ１内に在圏すれば、基地局（ＢＳ）のマイクロセル系の通信ユニットにより、基地局（ＢＳ）と移動局（ＭＳ）との間において、それぞれ所定の送信電力にて情報の高速伝送が行われる。また、移動局（ＭＳ）が上記マイクロセルＣ１の外に位置する場合、基地局（ＢＳ）のＡＡＡセル系の通信ユニットが、制御部１００での制御のもと、アダプティブアレイの動作に必要な情報（移動局固有のパイロット信号など）に基づいてアダプティブアレイアンテナを制御する( アンテナ素子のウエイトを制御する) ことによって移動局（ＭＳ）を追尾しつつ、上記所定の送信電力にてその移動局（ＭＳ）と情報の高速伝送を行う。
【００３８】
また、例えば、移動局（ＭＳ）が、位置的には、図１に示す高速伝送におけるＡＡＡセルＣ２内に存在する場合であっても、比較的低速にて情報転送を行う場合には、マイクロセルＣ１が比較的広くなるので、当該移動局（ＭＳ）がその比較的広いマイクロセルＣ１内に存在することになれば、基地局（ＢＳ）のマイクロセル系の通信ユニットにより移動局（ＭＳ）と基地局（ＢＳ）は、それぞれ所定の送信電力にて比較的低速での情報伝送を行う。
【００３９】
更に、移動局に対する着信により情報伝送が行われる場合、例えば、図７に示す手順に従って、移動局と基地局との間で通信が行われる。
図７において、基地局（ＢＳ）から制御用セル内に着信一斉呼出しがなされる。そのとき、その制御用セル内の移動局がその一斉呼出しを受信し、自局に対する呼出しであることを検出した移動局（ＭＳ）では、前述と同様に、マクロセルＣ１またはＡＡＡセルの選択を行う（Ｓ１）。そして、移動局（ＭＳ）は、マイクロセルＣ１及びＡＡＡセルＣ２のいずれかの選択を行った後に、着信応答と無線状態報告信号を所定の制御チャネルにて基地局（ＢＳ）に送信する。以後、移動局（ＭＳ）と基地局（ＢＳ）との間で上述したのと同様なニゴシエーションが行われる。そして、選択された通信チャネルを用いて、着信を受けた移動局（ＭＳ）と基地局（ＢＳ）は、それぞれ、所定の送信電力にて要求される伝送速度での情報伝送を、基地局（ＢＳ）におけるマイクロセル系の通信ユニットまたはＡＡＡセル系の通信ユニットを用いて行う。
【００４０】
上述した例では、情報の高速伝送を行う場合、移動局が比較的基地局の近くに位置して移動局と基地局との間の無線伝送路の状態が比較的よい状況（受信レベルが比較的高い状況）では、基地局がオムニアンテナを有するマイクロセル系の通信ユニットを用い、それぞれ所定の送信電力にて基地局と移動局は情報通信を行う。一方、移動局が基地局から比較的遠い位置に存在し移動局と基地局との間の無線伝送路の状態が比較的よくない状況（受信レベルが比較的低い状況）では、基地局がアダプティブアレイアンテナを有するＡＡＡセル系の通信ユニットを用い、それぞれ所定の送信電力にて基地局と移動局は情報通信を行う。また、情報を比較的低速で送信する場合には、移動局が基地局から比較的遠い位置に存在しても、基地局がオムニアンテナを有するマイクロセル系の通信ユニットを用い、それぞれ所定の送信電力にて基地局と移動局は情報通信を行う。
【００４１】
従って、上述した例によれば、常に情報の高速伝送に対応できるように、通信サービスエリア内に基地局をきめ細かく設置したり、高い送信電力にて情報伝送を行わなくても、要求される伝送速度に応じて、オムニアンテナを有するマイクロセル系の通信ユニットでの情報伝送とアダプティブアレイアンテナを有するＡＡＡセル系の通信ユニットでの情報伝送とを切替えることによって、所定の送信電力での基地局から移動局への情報通信が可能となる。
【００４２】
なお、上記の例では、マイクロセルＣ１とＡＡＡセルＣ２との切替え基準となる閾値Ｓを基地局からの報知情報から移動局が取得するようにしたが、移動局が在圏するセルに対応してそのような基準となる情報を知ることができれば、他のどのような方法でもよい。
また、上記例では、移動局においてマイクロセルＣ１とＡＡＡセルＣ２の判定を行っているが、移動局にて測定された各基地局の止まり木チャネルの受信レベルを在圏するセルの基地局に報告し、該基地局にてマイクロセルＣ１とＡＡＡセルＣ２の判定を行うことができる。
【００４３】
【発明の効果】
以上、説明してきたように、請求項１乃至６記載の本願発明によれば、要求される通信速度と、基地局と移動局との間の無線伝送路の状態とに基づいて、第一の通信手段と第二の通信手段を切替えることによって、種々の通信サービスの質を満足するような情報伝送が可能となる。即ち、移動通信システムにおいて、送信電力資源や設備資源を効率的に利用しつつ、移動局の要望される通信サービスの質を満足できるようにした通信制御方法を提供することができる。
【００４４】
また、請求項７乃至１３記載の本願発明によれば、上記のような通信制御方法が適用される移動通信システムを提供することができる。
更に、請求項１４乃至１８記載の本願発明によれば、上記のような通信制御方法が適用される移動通信システムにおける基地局を提供することができる。
また、更に、請求項１９及び２０記載の本願発明によれば、上記のような通信制御方法が適用される移動通信システムにおける移動局を提供することができる。
【図面の簡単な説明】
【図１】本発明の実施の一形態に係る通信方式が適用される移動通信システムのセル構成の例を示す図である。
【図２】基地局の構成例を示すブロック図である。
【図３】移動局の構成例を示すブロック図である。
【図４】移動局からの発信にて情報伝送がなされる場合の処理手順の一例を示すシーケンス図である。
【図５】移動局にて在圏セルの基地局を判定するための手順を示すフローチャートである。
【図６】移動局にてマイクロセルＣ１とＡＡＡセルＣ２の判定を行うための手順を示すフローチャートである。
【図７】移動局への着信にて情報転送がなされる場合の処理手順の一例を示すシーケンス図である。
【符号の説明】
１１、１２、１３、１４、１５、１６基地局
１００制御部
１０１アンテナアレイ
１０２送受分配器
１０３ウエイト制御・乗算部（受信信号用）
１０４ウエイト制御・乗算部（送信信号用）
１１０切替器
１１１復調回路
１１２復号回路
１１３変調回路
１１４符号化回路
１２０送受分配器
１３０送受分配器
１３１復調回路
１３２復号回路
１３３変調回路
１３４符号化回路
２００制御部
２０１送受分配器
２０２復調回路
２０３復号回路
２０４変調回路
２０５符号化回路[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a communication control method in a mobile communication system, and more particularly, to a communication control control method for controlling a communication mode between a mobile station and a base station according to a required transmission rate of information.
The present invention also relates to a mobile communication system, a base station, and a mobile station to which such a communication control method is applied.
[0002]
[Prior art]
In a cellular mobile communication system, a plurality of base stations that perform wireless communication with a mobile station are installed in a communication service area, and each base station is a cell in a range where wireless communication with the mobile station is possible. (Radio zone) is formed. A mobile station residing in a cell receives various communication services (call, data distribution, etc.) by performing wireless communication with the base station of the cell.
[0003]
In recent years, there has been a demand for speeding up information transmission between a mobile station and a base station. When performing high-speed information transmission, if the transmission method is the same and the transmission conditions such as antenna gain are the same, more transmission power is required. This means that the radio coverage area of each base station, that is, the radius of the cell, is reduced when higher-speed information transmission is performed with limited transmission power. When wireless communication is performed between a base station and a mobile station using a higher frequency, the propagation loss increases. Therefore, the conditions regarding the wireless communication possible range (cell) with the mobile station in high-speed information transmission are severe. Become.
[0004]
[Problems to be solved by the invention]
In the situation as described above, in order to provide a mobile station user with a stable communication service using a mobile communication system that enables high-speed transmission of information, the transmission power is increased or the transmission power is increased. Instead, more base stations are installed in the communication service area, and the communication service area is covered with many smaller cells.
[0005]
However, when the mobile station exists in a range relatively close to the base station, information can be transmitted between the base station and the mobile station at high speed even with a relatively small transmission power. Also, depending on the type of information (for example, voice information), it may be possible to provide a communication service with sufficient quality without necessarily performing high-speed transmission. Considering these situations, if the transmission power at each base station is uniformly increased, the power resources in the system cannot be used efficiently.
[0006]
Further, even if many base stations are to be installed in the communication service area, there are many restrictions on installation locations, particularly in urban areas, and it is difficult to finely install base stations at desired positions. As described above, there may be cases where it is possible to provide a communication service with sufficient quality without necessarily performing high-speed transmission. Even if many base stations are installed finely, these base stations are effective. It is not always used.
[0007]
Accordingly, a first problem of the present invention is to provide a communication control method in a mobile communication system that can efficiently use transmission power resources and facility resources while satisfying the quality of communication services required in mobile stations. Is to provide.
A second problem of the present invention is to provide a mobile communication system to which such a communication control method is applied.
[0008]
A third object of the present invention is to provide a base station in a mobile communication system to which such a communication control method is applied.
Furthermore, the fourth object of the present invention is to provide a mobile station in a mobile communication system to which such a communication control method is applied.
[0009]
[Means for Solving the Problems]
In order to solve the first problem, the present invention provides a base station in a mobile communication system as described in claim 1. First communication means or second communication means In a communication control method when performing information communication between a mobile station and a mobile station, The mobile station receives from the broadcast information transmitted on the perch channel of the base station a threshold value corresponding to the quality of the communication service related to information to be transmitted and received, and based on the state of the wireless transmission path and the threshold value, the first The first cell corresponding to the communication means or the second cell corresponding to the second communication means is selected, and a predetermined signal is transmitted to the base station of the selected cell The base station that has received the predetermined signal The base station performs information communication with the mobile station using an antenna having a fixed directivity according to the required transmission speed of information and the state of the wireless transmission path between the mobile station and the base station. 1 The base station performs information communication with the mobile station using the communication means of the above and an antenna whose directivity is variable so as to track the mobile station. 2 The communication means is configured to be selectively switched.
[0010]
In such a communication control method, the first communication means performs information communication between the base station and the mobile station using an antenna having fixed directivity, and the second communication means includes the mobile station. Since the information communication is performed between the base station and the mobile station using an antenna whose directivity is variable so as to track the second signal, the second communication means is more suitable for the first communication device under the same transmission power. With this communication means, information communication can be performed from a base station to a mobile station farther away. By switching between the first communication means and the second communication means based on the required communication speed and the state of the wireless transmission path between the base station and the mobile station, the quality of various communication services is improved. Can be transmitted.
[0011]
The state of the wireless communication path between the mobile station and the base station includes the distance between the mobile station and the base station (distance of the wireless transmission path), the state of reflection from an obstacle, the state of attenuation of radio waves, etc. The interference state of the radio wave from the communication node can be expressed by, for example, a signal reception level, a signal error rate, an interference wave reception level (reception CIR: Carrier Interference Ratio), and the like.
[0012]
The fixed directivity that is the characteristic of the antenna used in the first communication means includes so-called omnidirectionality.
3. The communication method according to claim 2, wherein a reception level of a perch channel from the base station is measured by the mobile station, and the measurement result is a wireless transmission path between the mobile station and the base station. It can be configured to be used as a state of
[0013]
From the viewpoint of specifically providing the switching condition between the first communication means and the second communication means, the present invention is required in each of the communication control methods as described in claim 3. The first communication means is selected when the state of the wireless transmission path between the mobile station and the base station is better than the state of the wireless transmission path that is a predetermined reference with respect to the information transmission rate condition. So that the second communication means is selected when the state of the wireless transmission path between the mobile station and the base station is not better than the state of the reference wireless transmission path. The first communication means and the second communication means can be switched.
[0014]
From the standpoint of specifically providing the antenna of the first communication means, the present invention provides a transmission as an antenna of the first communication means in each of the communication control methods as described in claim 4. An antenna that fixedly forms a communicable area with a mobile station according to power is configured to be used.
More specifically, as described in claim 5, the present invention provides an omni antenna as an antenna for fixedly forming a communicable area with a mobile station according to transmission power in each of the communication control methods. Or it can comprise so that a sector antenna may be used.
[0015]
The second 2 From the viewpoint of specifically providing the antenna of the communication means, the present invention provides the communication control method according to the sixth aspect, as described in claim 6. 2 As an antenna of the communication means, an adaptive array antenna (AA) can be used.
In order to solve the second problem, the present invention provides a base station as described in claim 7. First communication means or second communication means In a mobile communication system that performs information communication between a mobile station and a mobile station, The mobile station, from broadcast information transmitted on the perch channel of the base station, threshold receiving means for receiving a threshold according to the quality of the communication service related to information to be transmitted and received, Transmission path state measuring means for measuring the state of a wireless transmission path between a mobile station and a base station And a cell that selects either the first cell corresponding to the first communication means or the second cell corresponding to the second communication means based on the state of the wireless transmission path and the threshold value. The base station having a selection means and a signal transmission means for transmitting a predetermined signal to the base station of the selected cell, and receiving the predetermined signal, Communicate information with a mobile station using an antenna with fixed directivity 1 The first communication means and an antenna whose directivity is variable so as to track the mobile station. 2 Based on the state of the wireless transmission path between the mobile station and the base station measured by the transmission means, the transmission speed of the required information, and the transmission path state measuring means. 1 Communication means and the second 2 Switching control means for selectively switching between the communication means.
[0016]
Further, in order to solve the third problem, the present invention provides a fixed base station used in a mobile communication system that performs information communication between the base station and the mobile station. To communicate information with a mobile station using an antenna with specific directivity 1 The first communication means and an antenna whose directivity is variable so as to track the mobile station. 2 Communication means of A threshold value corresponding to the quality of the communication service related to information to be transmitted and received is received from the broadcast information transmitted on the perch channel, and corresponds to the first communication means based on the state of the wireless transmission path and the threshold value. In response to a predetermined signal transmitted from a mobile station that has selected either the first cell or the second cell corresponding to the second communication means, Based on the required information transmission rate and the state of the wireless transmission path between the mobile station and the base station, 1 Communication means and the second 2 Switching means for selectively switching the communication means.
[0017]
Furthermore, in order to solve the fourth problem, the present invention provides a base station as set forth in claim 19. First communication means or second communication means In a mobile station used in a mobile communication system that performs information communication between a mobile station and a mobile station, Threshold receiving means for receiving a threshold corresponding to the quality of communication service related to information to be transmitted and received from broadcast information transmitted on the perch channel of the base station; Transmission path state measuring means for measuring the state of the wireless transmission path between the base station, Cell selection means for selecting either the first cell corresponding to the first communication means or the second cell corresponding to the second communication means based on the state of the wireless transmission path and the threshold value. And signal transmission means for transmitting a predetermined signal to the base station of the selected cell, the cell selection means, Based on the measurement result in the transmission path state measuring means and the required information transmission speed, information communication is performed between the base station and the mobile station using an antenna having a fixed directivity. 1 Communication between the base station and the mobile station using an antenna whose directivity is variable so as to track the mobile station. 2 Which communication method should be selected Refusal , The judgment The second 1 Communication means or the second 2 The communication means is configured to perform information communication between the base station and the mobile station.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
A cell configuration in a mobile communication system provided with a composite cell switching control method according to an embodiment of the present invention is, for example, as shown in FIG.
In FIG. 1, a plurality of base stations 11, 12, 13, 14, 15, 16 are installed in a communication service area. In FIG. 1, only six base stations are shown for convenience.
[0019]
Each base station 11, 12, 13, 14, 15, 16 is a micro cell C 1 serving as a radio communication area where high-speed transmission of information can be performed with a predetermined transmission power via a normal antenna (for example, an omni antenna or a sector antenna). Configure. In this case, the cell radius of the microcell C1 capable of wireless communication at a high transmission rate is generally small, and the communication service is provided only by the microcell C1 of each base station 11, 12, 13, 14, 15, 16. The entire area cannot be covered. However, when information wireless communication is performed at a relatively low transmission rate, the cell radius of the microcell C1 becomes large, and the entire communication service area can be covered by each microcell C1.
[0020]
Each base station 11, 12, 13, 14, 15, 16 further forms an AAA cell C 2 that serves as a radio communication area that can be performed via a high-gain antenna having a mobile station tracking function, for example, an adaptive array antenna. When this adaptive array antenna is used, directivity (radio wave beam) can be narrowed down, so that a relatively wide range of mobile stations can be tracked with limited transmission power. Accordingly, the AAA cell C2 is wider than the macro cell C1, and a communication service area that cannot be covered by the micro cell C1 during high-speed transmission of information is covered by the AAA cell C2 formed at each base station.
[0021]
Further, since the transmission rate required for the control channel is generally not as great as that of a high-speed communication channel, the wireless communicable range (control cell) on the control channel is relatively wide. In this example, the wireless communication range of each base station on the wireless channel corresponds to the microcell C1 having a large cell radius formed at the time of low-speed transmission of information and can continuously cover the communication service area. To do.
[0022]
Each of the base stations 11, 12, 13, 14, 15, 16 is configured as shown in FIG. 2, for example.
In FIG. 2, a base station includes a control unit 100, an antenna array 101, a transmission / reception distributor 102, a weight control / multiplication unit 103 (for reception signals), a weight control / multiplication unit 104 (for transmission signals), a switch 110, and a demodulation. The circuit 111, the decoding circuit 112, the modulation circuit 113, the encoding circuit 114, the transmission / reception distributor 120, the transmission / reception distributor 130, the demodulation circuit 131, the decoding circuit 132, the modulation circuit 133, and the encoding circuit 134 are provided.
[0023]
The array antenna 101, the transmission / reception distributor 102, and the weight control / multiplication units 103 and 104 are used when performing high-speed information transmission with the mobile terminal in the AAA cell C2 (AAA cell system). The weight control / multiplication unit 103 uses the pilot signal specific to the mobile station to determine the weight for each antenna element of the array antenna 101 according to a predetermined adaptive weight determination algorithm, and responds to the signal from each antenna element The received signal is generated by multiplying the weight to be received. The weight for each antenna element determined by the weight control / multiplication unit 103 (for reception signal) is notified to the weight control / multiplication unit 104 (for transmission signal) in real time. The reception signal generated by the weight control / multiplication unit 103 is sequentially supplied to the demodulation circuit 111 and the decoding circuit 112 via the switch 110, and the reception information signal obtained by the demodulation and decoding processing is supplied to the control unit 100. To be supplied.
[0024]
The weight control / multiplication unit 104 (for transmission signal) multiplies the transmission signal by each weight notified from the weight control / multiplication unit 103 (for reception signal), and each signal obtained as a result is transmitted to the antenna array 101. Transmit from the corresponding antenna element. The transmission information signal from the control unit 100 is sequentially supplied to the encoding circuit 114 and the modulation circuit 113, and the transmission signal obtained by the encoding and modulation processing is sent to the weight control / multiplication unit 104 via the switch 110. Supplied.
[0025]
The transmission / reception distributor 120 is used, for example, to transmit and receive signals via an omni antenna and to communicate with a mobile station in the microcell C1 (microcell system). A signal received by the omni antenna is sequentially supplied to the demodulation circuit 111 and the decoding circuit 112 via the transmission / reception distributor 120 and the switch 110. The reception information signal obtained by the processing in the demodulation circuit 111 and the decoding circuit 112 is supplied to the control unit 110. A transmission signal from the control unit 100 is sequentially supplied to the encoding circuit 114 and the modulation circuit 113. Then, the transmission signals obtained by the encoding and modulation processes are supplied to the transmission / reception distributor 120 via the switch 110 and transmitted from the omni antenna.
[0026]
The transmission / reception distributor 130 is used, for example, for transmitting / receiving a control channel signal via an omni antenna (control cell system). The control signal received by the antenna is sequentially supplied to the demodulation circuit 131 and the decoding circuit 132 via the transmission / reception distributor 130. Information on the control channel subjected to the demodulation and decoding is supplied to the control unit 100 as a reception information signal. A control signal from the control unit 100 is sequentially supplied to the encoding circuit 134 and the modulation circuit 133. Then, control signals obtained by the encoding and modulation processes are supplied to the transmission / reception distributor 130 and transmitted from the antenna.
[0027]
The switcher 110 switches a transmission / reception system (AAA cell system or microcell system) to be operated with respect to the mobile station according to an instruction from the control unit 100. The details of the switching control of the switch 110 by the control unit 100 will be described later.
The control cell communication unit (transmission / reception distributor 130, demodulation circuit 131, decoding circuit 132, modulation circuit 133, and encoding circuit 134) is a microcell communication unit (transmission / reception distributor 120, demodulation circuit 111). The decoding circuit 112, the modulation circuit 113, and the encoding circuit 114) can be substituted. In FIG. 2, the amplifiers used for both the transmission system and the reception system are omitted.
[0028]
A mobile station that performs wireless communication with a base station within the communication service area is configured as shown in FIG. 3, for example.
In FIG. 3, the mobile station includes a control unit 200, a transmission / reception distributor 201 that transmits and receives signals via an antenna, a demodulation circuit 202, a decoding circuit 203, a modulation circuit 204, and an encoding circuit 205. A signal received via an antenna is sequentially supplied to a demodulation circuit 202 and a decoding circuit 203 via a transmission / reception distributor 201. Received information signals obtained by the demodulation and decoding processes in the demodulation circuit 202 and the decoding circuit 203 are supplied to the control unit 200. In addition, transmission information signals from the control unit 200 are sequentially supplied to the encoding circuits 205 and 204, and transmission signals obtained by the processing are transmitted from the antenna via the transmission / reception distributor 201.
[0029]
In FIG. 3, the amplifiers used for both the transmission system and the reception system are omitted.
A communication procedure between the mobile station and the base station will be described.
When information transmission is performed by activation from the mobile station, for example, communication is performed between the mobile station and the base station according to the procedure shown in FIG.
[0030]
In FIG. 4, the mobile station (MS) selects the micro cell C1 or the AAA cell C2. This cell selection is performed as follows.
As shown in FIG. 5, each base station (BS) transmits a perch channel cell with a constant transmission power in the control cell system communication unit described above. The mobile station (MS) scans the perch channel from the surrounding base station (BS) under the control of the control unit 200, and sequentially measures the reception level (S11). Then, the base station of the perch channel that is the maximum of the measured reception levels is determined as the base station of the cell where the mobile station is located (S12). The determination processing of the base station of the cell in which the mobile station is located is performed under a predetermined condition such as every predetermined time regardless of whether the mobile station is in a standby state or in a communication state.
[0031]
Thereafter, as shown in FIG. 6, the mobile station (MS) that has received the broadcast information transmitted from the determined base station (BS) through the perch channel, receives the microcell C1 and AAA included in the broadcast information. A threshold value S, which is a switching condition for the cell C2, is acquired (S13).
This threshold value S differs depending on the quality of the communication service related to information to be transmitted / received. For example, the threshold value S1 when information required to transmit information such as image information at high speed is transmitted and received is a relatively large value. In addition, the threshold value S2 when information that can maintain a relatively high communication quality even when information such as call information is not transmitted at a particularly high speed is transmitted and received is a relatively small value.
[0032]
As described above, the mobile station (MS) that has acquired the threshold value that is the switching condition between the micro cell C1 and the AAA cell C2 measures the reception level R of the perch channel from the base station of the cell in which the mobile station is located ( S14), the micro cell C1 and the AAA cell C2 are selected based on the comparison result between the reception level and the acquired threshold value S15).
When the reception level S is equal to or higher than the threshold value R (R1 or R2), the micro cell C1 is selected. On the other hand, if the reception level S is smaller than the threshold value R (R1 or R2), the AAA cell C2 is selected. When information is transmitted at high speed, the threshold value S1 is a relatively large value, and therefore the microcell C1 is not selected unless the reception level R is a relatively high level. That is, the micro cell C1 is selected when the state of the radio transmission path between the mobile station (MS) and the base station (BS) is relatively good (when the mobile station is relatively close to the base station). On the other hand, when it is not necessary to transmit information at a high speed, the threshold value S2 is a relatively small value, so that the microcell C1 is selected even if the reception level R is a relatively low level. That is, even if the state of the wireless transmission path between the mobile station (MS) and the base station (BS) is not so good (even if the mobile station is located relatively far from the base station), the micro cell C1 Selected.
[0033]
On the other hand, when the state of the wireless transmission path between the mobile station (MS) and the base station (BS) is relatively poor with the threshold S (S1 or S2) as a reference (the mobile station is AAA cell 2 is selected if it is located relatively far based on
Returning to FIG. 4, when the micro cell C1 or the AAA cell C2 is selected in the mobile station (MS) as described above, the mobile station (MS) uses the control channel to transmit signals and radio conditions. The report signal is transmitted to the base station (BS) of the cell determined to be in the service area. This radio status report signal includes information on the selected cell type (microcell C1 or AAA cell C2).
[0034]
The control unit 100 (see FIG. 2) of the base station (BS) that has received the transmission signal and the radio status report signal through the control channel, switches based on the information on the selected cell type included in the radio status report signal. A switching control signal for 110 is generated, and switching control of the switch 110 is performed by the switching control signal (S21). When the mobile station (MS) selects the microcell C1, the switch 110 is connected so that the transmission / reception distributor 120, which is a microcell communication unit, is connected to the demodulation circuit 111 and the modulation circuit 113. Switch.
[0035]
When the communication unit (communication channel) is thus selected, the transceiver of the selected communication unit (AAA cell system or microcell system) is activated (S22). Then, a signal including communication channel designation information is transmitted from the base station (BS) to the mobile station using the control channel. At this time, when an AAA cell-based communication unit is selected, the mobile station (MS) is notified of the communication channel and information necessary for the operation of the active array (such as a pilot signal of the mobile station).
[0036]
The mobile station (MS) that has received the communication channel designation information from the base station (BS) activates the receiver for the designated communication channel (S3). Then, a synchronization signal is transmitted to the base station (BS) in order to establish reception synchronization in the communication channel. The base station (BS) establishes reception synchronization in the communication channel based on the synchronization signal received from the mobile station (MS) (S23).
[0037]
In this state, communication for information transmission is performed with a predetermined transmission power between the mobile station (MS) and the base station (BS). For example, when performing high-speed transmission of information, if the mobile station (MS) is located in the micro cell C1 shown in FIG. 1, the base station (BS) and the base station (BS) High-speed transmission of information is performed with a predetermined transmission power between the mobile station (MS). When the mobile station (MS) is located outside the microcell C1, the AAA cell communication unit of the base station (BS) is necessary for the operation of the adaptive array under the control of the control unit 100. The mobile station (MS) is tracked by controlling the adaptive array antenna (controlling the weight of the antenna element) on the basis of information (such as a pilot signal unique to the mobile station), and the mobile station with the predetermined transmission power. (MS) and high-speed transmission of information.
[0038]
Further, for example, even when the mobile station (MS) is located in the AAA cell C2 in the high-speed transmission shown in FIG. Since the cell C1 is relatively wide, if the mobile station (MS) is present in the relatively wide microcell C1, the mobile station (MS) is transmitted by the microcell communication unit of the base station (BS). The base station (BS) performs information transmission at a relatively low speed with a predetermined transmission power.
[0039]
Furthermore, when information transmission is performed by an incoming call to the mobile station, for example, communication is performed between the mobile station and the base station according to the procedure shown in FIG.
In FIG. 7, an incoming call is called from the base station (BS) into the control cell. At that time, the mobile station in the control cell receives the simultaneous call and the mobile station (MS) that has detected that the call is for the own station selects the macro cell C1 or the AAA cell as described above. (S1). The mobile station (MS), after selecting one of the micro cell C1 and the AAA cell C2, transmits an incoming call response and a radio status report signal to the base station (BS) through a predetermined control channel. Thereafter, the same negotiation as described above is performed between the mobile station (MS) and the base station (BS). Then, using the selected communication channel, the mobile station (MS) and the base station (BS) that have received an incoming call each perform information transmission at a transmission rate required with a predetermined transmission power. This is performed using a microcell communication unit or an AAA cell communication unit in BS).
[0040]
In the example described above, when performing high-speed transmission of information, the mobile station is located relatively close to the base station, and the state of the radio transmission path between the mobile station and the base station is relatively good (the reception level is compared). In a high situation), the base station uses a microcell communication unit having an omni antenna, and the base station and the mobile station perform information communication with predetermined transmission power. On the other hand, in a situation where the mobile station is located relatively far from the base station and the state of the radio transmission path between the mobile station and the base station is relatively poor (a situation where the reception level is relatively low), the base station is adaptive. Using an AAA cell-based communication unit having an array antenna, the base station and the mobile station each perform information communication with a predetermined transmission power. Also, when transmitting information at a relatively low speed, even if the mobile station is located at a position relatively far from the base station, the base station uses a microcell communication unit having an omni antenna, and each of the predetermined transmissions. The base station and the mobile station perform information communication using power.
[0041]
Therefore, according to the above-described example, the required transmission can be performed without installing a base station in the communication service area finely or performing information transmission with high transmission power so as to always support high-speed transmission of information. By switching between information transmission in a microcell communication unit having an omni antenna and information transmission in an AAA cell communication unit having an adaptive array antenna according to the speed, the base station with a predetermined transmission power can Information communication to the mobile station becomes possible.
[0042]
In the above example, the mobile station obtains the threshold value S, which is a reference for switching between the micro cell C1 and the AAA cell C2, from the broadcast information from the base station. However, it corresponds to the cell where the mobile station is located. Any other method can be used as long as it can know the information that serves as the reference.
In the above example, the micro station C1 and the AAA cell C2 are determined in the mobile station, but the reception level of the perch channel of each base station measured by the mobile station is transmitted to the base station of the cell in the area. The base station can determine the micro cell C1 and the AAA cell C2.
[0043]
【The invention's effect】
As described above, according to the present invention described in claims 1 to 6, based on the required communication speed and the state of the wireless transmission path between the base station and the mobile station, the first By switching between the communication means and the second communication means, it is possible to transmit information that satisfies the quality of various communication services. That is, in the mobile communication system, it is possible to provide a communication control method capable of satisfying the quality of communication service requested by a mobile station while efficiently using transmission power resources and facility resources.
[0044]
Further, according to the present invention described in claims 7 to 13, it is possible to provide a mobile communication system to which the communication control method as described above is applied.
Furthermore, according to the present invention of claims 14 to 18, it is possible to provide a base station in a mobile communication system to which the communication control method as described above is applied.
Furthermore, according to the present invention of claims 19 and 20, it is possible to provide a mobile station in a mobile communication system to which the communication control method as described above is applied.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an example of a cell configuration of a mobile communication system to which a communication scheme according to an embodiment of the present invention is applied.
FIG. 2 is a block diagram illustrating a configuration example of a base station.
FIG. 3 is a block diagram illustrating a configuration example of a mobile station.
FIG. 4 is a sequence diagram showing an example of a processing procedure when information transmission is performed by transmission from a mobile station.
FIG. 5 is a flowchart showing a procedure for determining a base station of a serving cell in a mobile station.
FIG. 6 is a flowchart showing a procedure for determining a micro cell C1 and an AAA cell C2 in a mobile station.
FIG. 7 is a sequence diagram showing an example of a processing procedure when information transfer is performed when an incoming call arrives at a mobile station.
[Explanation of symbols]
11, 12, 13, 14, 15, 16 Base station
100 Control unit
101 Antenna array
102 Transmitter / receiver distributor
103 Weight control / multiplication unit (for received signal)
104 Weight control / multiplication unit (for transmission signal)
110 switcher
111 Demodulator
112 Decoding circuit
113 Modulation circuit
114 Coding circuit
120 Transceiver / distributor
130 Transmitter / Distributor
131 Demodulator
132 Decoding circuit
133 Modulation circuit
134 Coding circuit
200 Control unit
201 Transmitter / Distributor
202 Demodulator circuit
203 Decoding circuit
204 Modulation circuit
205 Coding circuit

Claims

In a communication control method when performing information communication between a first communication unit or a second communication unit of a base station in a mobile communication system and a mobile station,
The mobile station
From the broadcast information transmitted on the perch channel of the base station, receive a threshold according to the quality of the communication service related to the information transmitted and received,
Based on the state of the wireless transmission path and the threshold value, select either the first cell corresponding to the first communication means or the second cell corresponding to the second communication means,
A predetermined signal is transmitted to the base station of the selected cell,
The base station that has received the predetermined signal
The base station performs information communication with the mobile station using an antenna having a fixed directivity according to the required transmission speed of information and the state of the wireless transmission path between the mobile station and the base station. 1. A communication control method for selectively switching between one communication means and a second communication means in which a base station performs information communication with a mobile station using an antenna whose directivity is variable so as to track the mobile station .

The communication control method according to claim 1,
A communication control method in which a reception level of a perch channel from a base station is measured by a mobile station, and the measurement result is used as a state of a wireless transmission path between the mobile station and the base station.

The communication control method according to claim 1 or 2,
The first communication means when the state of the wireless transmission path between the mobile station and the base station is better than the state of the wireless transmission path that is a predetermined reference with respect to the transmission rate condition of the required information And the second communication means is selected when the state of the wireless transmission path between the mobile station and the base station is not better than the state of the reference wireless transmission path. And a communication control method in which the first communication means and the second communication means are switched.

The communication control method according to any one of claims 1 to 3,
A communication control method using an antenna that fixedly forms a communicable area with a mobile station according to transmission power as an antenna of the first communication means.

The communication control method according to claim 4, wherein
A communication control method using an omni antenna or a sector antenna as an antenna for fixedly forming a communicable area with a mobile station according to transmission power.

The communication control method according to any one of claims 1 to 5,
A communication control method using an adaptive array antenna as an antenna of the second communication means.

In a mobile communication system that performs information communication between a first communication unit or second communication unit of a base station and a mobile station,
The mobile station
Threshold receiving means for receiving a threshold corresponding to the quality of communication service related to information to be transmitted and received from broadcast information transmitted on the perch channel of the base station;
Transmission path state measuring means for measuring the state of the wireless transmission path between the mobile station and the base station ;
Cell selection means for selecting either the first cell corresponding to the first communication means or the second cell corresponding to the second communication means based on the state of the wireless transmission path and the threshold value. When,
Signal transmitting means for transmitting a predetermined signal to the base station of the selected cell;
Have
The base station that has received the predetermined signal
First communication means for performing information communication with a mobile station using an antenna having fixed directivity;
Second communication means for performing information communication with the mobile station using an antenna whose directivity is variable so as to track the mobile station;
The first communication means and the second communication means based on the transmission rate of the required information and the state of the wireless transmission path between the mobile station and the base station measured by the transmission path state measurement means And a switching control means for selectively switching between.

The mobile communication system according to claim 7,
A mobile communication system in which the transmission path state measuring means is provided in a mobile station.

The mobile communication system according to claim 8,
The transmission path state measuring means includes a reception level measuring means for measuring a reception level of a perch channel of a base station as a state of a wireless transmission path between the mobile station and the base station.

The mobile communication system according to any one of claims 7 to 9,
The switching control means is better in the state of the wireless transmission path measured by the wireless transmission path state measuring means than the state of the wireless transmission path which is a predetermined reference corresponding to the transmission rate condition of the required information. If the first communication means is selected and the state of the wireless transmission path measured by the wireless transmission path state measurement means is not better than the state of the reference wireless transmission path, the second communication is performed. A mobile communication system for selecting means.

The wireless communication system according to any one of claims 7 to 10,
The mobile communication system, wherein the antenna of the first communication means is an antenna that fixedly forms an area communicable with a mobile station according to transmission power.

The mobile communication system according to claim 11, wherein
The mobile communication system in which an antenna that forms a communicable area with a mobile station according to transmission power is an omni antenna or a sector antenna.

The mobile communication system according to any one of claims 7 to 11,
The mobile communication system, wherein the antenna of the second communication means is an adaptive array antenna.

In a base station used in a mobile communication system that performs information communication between a base station and a mobile station,
First communication means for performing information communication with a mobile station using an antenna having fixed directivity;
Second communication means for performing information communication with the mobile station using an antenna whose directivity is variable so as to track the mobile station;
From the broadcast information transmitted on the perch channel of the base station, a threshold value corresponding to the quality of the communication service related to the information to be transmitted and received is received, and the first communication means based on the state of the wireless transmission path and the threshold value Transmission of requested information in response to a predetermined signal transmitted from a mobile station that has selected either the first cell corresponding to the second cell or the second cell corresponding to the second communication means. Speed,
A base station comprising: switching means for selectively switching between the first communication means and the second communication means based on a state of a wireless transmission path between the mobile station and the base station.

The base station according to claim 14,
The switching control means is better in the state of the wireless transmission path measured by the wireless transmission path state measuring means than the state of the wireless transmission path which is a predetermined reference corresponding to the transmission rate condition of the required information. If the first communication means is selected and the state of the wireless transmission path measured by the wireless transmission path state measurement means is not better than the state of the reference wireless transmission path, the second communication is performed. A base station that selects the means.

The base station according to claim 14 or 15,
The antenna of said 1st communication means is a base station used as an antenna which forms the area which can communicate with the mobile station according to transmission power fixedly.

The base station according to claim 16, wherein
An antenna that forms a fixed communication area with a mobile station according to transmission power is an omni antenna or a sector antenna.

The base station according to any one of claims 14 to 17,
The antenna of said 2nd communication means is a base station used as an adaptive array antenna.

In a mobile station used in a mobile communication system that performs information communication between the first communication means or the second communication means of the base station and the mobile station,
Threshold receiving means for receiving a threshold corresponding to the quality of communication service related to information to be transmitted and received from broadcast information transmitted on the perch channel of the base station;
Transmission path state measuring means for measuring the state of the wireless transmission path between the base station ,
Cell selection means for selecting either the first cell corresponding to the first communication means or the second cell corresponding to the second communication means based on the state of the wireless transmission path and the threshold value. When,
Signal transmitting means for transmitting a predetermined signal to the base station of the selected cell;
Have
In the cell selection means, the base station performs information communication with the mobile station using an antenna having a fixed directivity based on the measurement result of the transmission path state measurement means and the required information transmission rate. determining a first communication means, the base station should be selected either with the second communication means for performing mobile station and information communication using the antenna directivity is variable so as to track the mobile station, A mobile station configured to perform information communication between the base station and the mobile station by the determined first communication means or second communication means.

The mobile station according to claim 19, wherein
The cell selecting means is in a case where the state of the wireless transmission path measured by the transmission path state measuring means is better than the state of the wireless transmission path that is a predetermined reference for the transmission rate condition of the required information If the first communication means is selected and the state of the wireless transmission path measured by the transmission path state measuring means is not better than the state of the reference wireless transmission path, the second communication is performed. A mobile station that determines that a means is selected.