JP4167545B2

JP4167545B2 - Mobile communication system

Info

Publication number: JP4167545B2
Application number: JP2003160310A
Authority: JP
Inventors: 健箭本; 博文塩月; 孝宏坂本
Original assignee: NEC Communication Systems Ltd
Current assignee: NEC Communication Systems Ltd
Priority date: 2003-06-05
Filing date: 2003-06-05
Publication date: 2008-10-15
Anticipated expiration: 2023-06-05
Also published as: GB2404310A; JP2004363979A; GB0412561D0; GB2404310B

Description

【０００１】
【発明の属する技術分野】
本発明は移動体通信システムに係り、特に所定の場合にハンドオーバを行う時分割多元接続（ＣＤＭＡ：Code Division Multiple Access）方式の移動体通信システムに関する。
【０００２】
【従来の技術】
各々固有のサービスエリアを有する複数の無線基地局と、最寄りの基地局のサービスエリア内で該基地局と無線通信する移動体端末と、複数の無線基地局を制御する無線基地局制御装置とを備え、複数の移動体端末に通信サービスを提供する移動体通信システムでは、各無線基地局における無線回線等の無線リソースは限られたものである。
【０００３】
このような移動体通信システムにおいて、無線リソースが許容量に近くなった場合、該当サービスエリアへ移動してきた移動体端末のための無線回線が確保できずに呼が切断されてしまったり、該当サービスエリアでの新たな発呼処理を行うことができなくなってしまう。そこで、無線リソースの有効利用を図るための移動体通信システムが従来より知られている（例えば、特許文献１参照）。
【０００４】
すなわち、特許文献１記載の従来の移動体通信システムでは、移動体通信システムを構成する通信装置（移動体端末）及び基地局通信装置（無線基地局）のそれぞれを、無線同期外れ状態の一定期間の継続及び装置内の異常が発生した後に一定期間の異常状態を監視し、異常監視出力に基づいてコネクションを制御してコネクションを装置自ら開放する構成により、不要なコネクションを開放することで、無線リソースの有効利用を図るようにしている。
【０００５】
【特許文献１】
特開２００１−３３３００７号公報（第２−３頁）
【０００６】
【発明が解決しようとする課題】
しかるに、上記の特許文献１記載の従来の移動体通信システムでは、無線同期外れ等、使用不能になった無線回線のみを切断しているため、無線リソースが逼迫したときの無線リソースを確保することが困難であり、また、無線リソース確保と呼切断処理回避とを同時に行うことができない。
【０００７】
本発明は以上の点に鑑みなされたもので、無線リソースが逼迫した時に、移動体端末が使用している無線回線を品質が劣化している回線から段階的に切断して品質の良い回線を予め決められた本数だけ残すことによって無線回線数を制限し、効率的な無線リソースの運用を可能とする移動体通信システムを提供することを目的とする。
【０００８】
また、本発明は上記の目的を達成するため、無線リソース確保と呼切断処理回避とを同時に行うことが可能な移動体通信システムを提供することにある。
【０００９】
【課題を解決するための手段】
本発明は上記の目的を達成するため、第１の発明の移動体通信システムは、各々固有のサービスエリアを有する複数の無線基地局と、複数の無線基地局のうち最寄りの無線基地局のサービスエリア内で基地局と無線回線を介して無線通信する移動体端末と、複数の無線基地局を制御する無線リソースの管理を行うと共に、複数の無線基地局からの無線リソース使用状況報告とダイバーシティハンドオーバ制御部からの無線回線品質情報から必要に応じて、品質の劣化している無線回線を特定し解放する機能を有する無線基地局制御装置とを備えた構成の移動体通信システムであって、ダイバーシティハンドオーバ制御部は、複数の無線回線を介してマクロダイバーシティ状態の移動体端末から複数の無線基地局へ送信された上り方向のデータを受信し、受信した上り方向のデータのうち最も品質の良い上り方向のデータだけを選択する選択合成機能と、下り方向のデータを複数の無線基地局へ複製して分配する複製分配機能と、上り方向のデータの無線品質を無線回線単位で監視する機能を有し、複数の無線基地局の各々は、移動体端末から受信したデータに無線品質情報を付加して上り方向のデータとしてダイバーシティハンドオーバ制御部へ送信する送信手段を有し、無線基地局制御装置は、複数の無線基地局から送られた無線リソースの状態が所定の第１の閾値を越えたときに、ダイバーシティハンドオーバ制御部から全無線回線の無線品質情報の読み出しを行い、マクロダイバーシティ状態の移動体端末の複数の無線回線に対して、無線品質が良好な無線回線を最大無線回線制限数の最小値まで残し、残りの無線回線の切断処理を順次実行することを特徴とする。
【００１０】
この発明では、無線基地局制御装置内のダイバーシティハンドオーバ制御部は、複数の無線回線を介してマクロダイバーシティ状態の移動体端末から複数の無線基地局へ送信された上り方向のデータの無線品質を無線回線単位で監視する機能を有し、無線基地局制御装置は、複数の無線基地局から送られた無線リソースの状態が所定の第１の閾値を越えたときに、ダイバーシティハンドオーバ制御部から全無線回線の無線品質情報の読み出しを行い、マクロダイバーシティ状態の移動体端末の複数の無線回線に対して、無線品質が良好な無線回線を最大無線回線制限数の最小値まで残し、残りの無線回線の切断処理を順次実行するようにしたため、同期はずれ等により使用不能になっていない無線回線であっても、無線品質が劣化していると判断された無線回線は切断処理が実行される。また、各移動体端末毎に確保する最低無線リソースの数（最大無線回線制限数の最小値）を設定して、その最低無線リソースの数は無線回線の切断処理は行わない。
【００１１】
また、上記の目的を達成するため、第２の発明の移動体通信システムは、第１の発明のダイバーシティハンドオーバ制御部を、無線基地局からのデータに付与された無線品質情報を受信する毎に、無線品質情報を保持し、所定期間での無線品質情報の変化を平均化し、無線回線毎の品質を管理する構成としたことを特徴とする。
【００１２】
また、上記の目的を達成するため、第３の発明の移動体通信システムは、第１の発明の無線基地局制御装置を、無線回線数制限時に移動体端末が無線回線制限数を越える新規無線回線の確立を行おうとした場合は新たな無線回線の確立を拒否し、無線回線数制限実施中のハンドオーバについては、ハンドオーバ時のみ無線回線制限数＋1の無線回線数を許容し、ハンドオーバ先の無線回線確立後に、最も品質の劣化している無線回線の切断を実行する構成としたことを特徴とする。
【００１３】
また、上記の目的を達成するため、第４の発明の移動体通信システムは、第１の発明の無線基地局制御装置を、複数の無線基地局から送られた無線リソースの状態が無線回線数制限実施解除の第２の閾値を下回ったときは、無線回線制限数を一本増加させることを、無線リソース使用量が第２の閾値を上回るか、無線回線制限数が有効無線回線数の最大値になるまで、一定時間毎に繰り返す構成としたことを特徴とする。この発明では、無線リソースの状態が無線回線数制限実施解除の第２の閾値を下回ったときは、無線回線制限数を一本増加させるようにしたため、無線品質が良好な無線回線をマクロダイバーシティ状態の移動体端末にできるだけ多く設定できるので、できるだけ高い通信品質を保つことができる。
【００１４】
また、上記の目的を達成するため、第５の発明の移動体通信システムは、第１乃至第４の発明における無線品質情報を、無線回線上の通信品質を表す通信品質情報と所定の符号による照合結果の一方または両方を用いて表すことを特徴とする。
【００１５】
また、上記の目的を達成するため、第６の発明の移動体通信システムは、各々固有のサービスエリアを有する複数の無線基地局と、複数の無線基地局のうち最寄りの無線基地局のサービスエリア内で基地局と無線回線を介して無線通信する移動体端末と、複数の無線基地局を制御する無線リソースの管理を行うと共に、複数の無線基地局からの無線リソース使用状況報告とダイバーシティハンドオーバ制御部からの無線回線品質情報から必要に応じて、品質の劣化している無線回線を特定し解放する機能を有する無線基地局制御装置とを備えた構成の移動体通信システムであって、移動体端末は、マクロダイバーシティ状態の複数の無線回線から受信した無線信号の感度から無線品質を計算・保持する機能を持つ無線信号受信部と、無線基地局制御装置からの切断可能な無線回線通知要求を受信したときに無線信号受信部にて保持している値を基に無線品質が良好な無線回線を選び出して無線基地局制御装置に対して通知する送受信手段とを有し、複数の無線基地局は各々、無線リソースが不足しているかどうかをチェックし、不足しているようであれば無線基地局制御装置にその情報を通知する通知手段を有し、無線基地局制御装置は、複数の無線基地局から報告される無線リソース値が閾値を下回ったときに、該当の無線基地局のサービスエリア内にいる移動体端末に対して、切断可能な無線回線通知要求をし、該無線回線通知要求に応答した移動体端末から無線品質が良好な無線回線の通知を受け、その通知された内容を基に切断する無線回線を判断し、無線品質が良好な無線回線を最大無線回線制限数の最小値まで残し、残りの無線回線の切断処理を順次実行することを特徴とする。
【００１６】
この発明では、マクロダイバーシティ状態の移動体端末が、複数の無線回線から受信した下り方向の無線信号の感度から無線品質を計算・保持する機能を持つ無線信号受信部を有しており、無線基地局制御装置が、複数の無線基地局から報告される無線リソース値が閾値を下回ったときに、該当の無線基地局のサービスエリア内にいる移動体端末に対して、切断可能な無線回線通知要求をし、これにより該当の移動体端末がその無線信号受信部にて保持している値を基に無線品質が良好な無線回線を選び出して無線基地局制御装置に対して通知することにより、無線基地局制御装置により無線品質が良好な無線回線を最大無線回線制限数の最小値まで残し、残りの無線回線の切断処理を順次実行させるようにしたため、同期はずれ等により使用不能になっていない無線回線であっても、無線品質が劣化していると判断された無線回線は切断処理が実行される。また、各移動体端末毎に確保する最低無線リソースの数（最大無線回線制限数の最小値）を設定して、その最低無線リソースの数は無線回線の切断処理は行わない。
【００１７】
また、上記の目的を達成するため、第７の発明は第６の発明の無線基地局制御装置を、無線回線数制限時に移動体端末が無線回線制限数を越える新規無線回線の確立を行おうとした場合は新たな無線回線の確立を拒否し、無線回線数制限実施中のハンドオーバについては、ハンドオーバ時のみ無線回線制限数＋1の無線回線数を許容し、ハンドオーバ先の無線回線確立後に、最も品質の劣化している無線回線の切断を実行する構成としたことを特徴とする。
【００１８】
【発明の実施の形態】
次に、本発明の実施の形態について図面と共に説明する。図１は本発明になる移動体通信システムの一実施の形態のシステム構成図を示す。同図に示す移動体通信システムは、ＣＤＭＡ方式の移動体通信システムで、最寄りの基地局のサービスエリア内で基地局と無線通信する移動体端末１１と、各々固有のサービスエリアＡ１、Ａ２、Ａ３及びＡ４を有する無線基地局１３、１４、１５及び１６と、無線基地局１３、１４、１５及び１６を制御する無線基地局制御装置１２とを備えた構成である。
【００１９】
移動体端末１１は、無線回線１８を介して無線基地局１３と、無線回線１９を介して無線基地局１４と、無線回線２０を介して無線基地局１５と、無線回線２１を介して無線基地局１６と、それぞれ接続される。無線基地局１３、１４、１５、１６はＩｕｂ回線２２、２３、２４、２５を介して、無線基地局制御装置１２内のダイバーシティハンドオーバ制御部１７と各々接続される。無線基地局１３、１４、１５、１６は、無線回線１８、１９、２０、２１を介して移動体端末１１と通信を行うと共に、無線リソースの使用状況を無線基地局制御装置１２に報告する機能を有する。
【００２０】
ダイバーシティハンドオーバ制御部１７は、無線回線１８、１９、２０、２１を介して移動体端末１１から送信された上り方向のデータを受信し、最も品質の良いデータだけを選択する選択合成機能と、下り方向のデータを各無線基地局１３、１４、１５、１６へ複製して分配する複製分配機能と、各無線回線１８、１９、２０、２１からの上り方向のデータの無線品質を無線回線単位で監視する機能を有する。
【００２１】
無線基地局制御装置１２は、無線リソースの管理を行うと共に、無線基地局１３、１４、１５、１６からの無線リソース使用状況報告とダイバーシティハンドオーバ制御部１７からの無線回線品質情報から必要に応じて、品質の劣化している無線回線を特定し解放する機能を有する。
【００２２】
次に、本実施の形態の動作について説明する。図１において、移動体端末１１は４台の無線基地局１３、１４、１５、１６とそれぞれ無線回線１８、１９、２０、２１を介して同時に接続された状態、すなわち、４本のマルチパスを持ったマクロダイバーシティ状態にある。なお、ここでは、一台の移動体端末１１が保有する事ができる無線回線数の最大値は「６」とし、無線回線制限数の最小値を「２」とする。
【００２３】
各無線基地局１３、１４、１５、１６は、移動体端末１１から受信したデータをフレームデータに変換し、Ｉｕｂ回線２２、２３、２４、２５を介して無線基地局制御装置１２内のダイバーシティハンドオーバ制御部１７へ送信する。この時、無線基地局１３、１４、１５、１６は、無線回線上の通信品質を表すＱＥ（Quality Estimate）情報と、ＣＲＣ符号による照合結果ＣＲＣＩ（ＣＲＣ Indicator）をフレームデータに付加してダイバーシティハンドオーバ制御部１７へ送信する。
【００２４】
無線基地局制御装置１２のダイバーシティハンドオーバ制御部１７は、各無線基地局１３、１４、１５、１６からＩｕｂ回線２２、２３、２４、２５を介して送信されたフレームデータ及びＱＥ情報及びＣＲＣＩを受信し、最も通信品質の良いフレームデータのみ選択して合成し、上位ネットワーク側へ転送する。この時、ダイバーシティハンドオーバ制御部１７では各無線回線１８、１９、２０、２１毎の無線品質の監視を行う。
【００２５】
上記の無線品質の監視は、図３に示される無線回線毎の無線品質情報３３をもとに実施される。無線品質情報３３には、前述した無線回線上の通信品質を表すＱＥ情報と、ＣＲＣ符号による照合結果ＣＲＣＩがあり、これらをどのように用いて無線品質の判定を行ってもよい。ここではＱＥ情報を用いて無線品質を監視し、無線回線品質を判定する例を用いて記述する。
【００２６】
図３に示すように、移動体端末１１から無線基地局１３（又は１４、１５又は１６）ヘ上り方向の無線データ３１が送信され、無線基地局１３（又は１４、１５又は１６）はその無線データ３１をフレームデータ３２に変換し、これに無線品質情報３３を付加して無線基地局制御装置１２内のダイバーシティハンドオーバ制御部１７に送信する。
【００２７】
無線回線品質が劣化すると、無線データ３１を受信した無線基地局１３（又は１４、１５又は１６）によって無線品質情報３３にその内容が反映される。無線基地局制御装置１２内のダイバーシティハンドオーバ制御部１７では、無線基地局１３（又は１４、１５又は１６）からのフレームデータ３２に付与された無線品質情報３３を受信する毎に、無線品質情報を保持する。この無線品質情報は、任意の数だけ過去の情報を保持する事ができ、その期間での無線品質情報の変化を平均化し、無線回線毎の品質を管理する。
【００２８】
無線回線品質の計算方法は任意であるが、参考のためＱＥを用いた場合の計算結果を図４に示す。図４では、図３の無線品質情報３３に相当する無線品質情報IにＱＥを使用し、図３のダイバーシティハンドオーバ制御部１７にて計算された無線品質IIをグラフ化している。縦軸はＱＥの値、横軸は受信したフレームの番号とする。ＱＥの値は小さい方が品質は良好とする。
【００２９】
図４において、ｎ番目に受信したフレームの無線品質情報IをＱＥ_ｎ、ダイバーシティハンドオーバ制御部１７にて保持されている無線品質情報IIの履歴の個数をｍ、計算された無線品質IIをＭＡＱ（Managemented Air Quality）とした場合、ｎ番目の無線品質ＭＡＱｎを導き出す式は数１の通りとなる。
【００３０】
【数１】

このように計算した無線品質ＭＡＱｎを使用することにより、一つのフレームの無線品質情報Iの急激な値の変化に対して冗長性を持たせる事ができ、瞬間的な無線品質情報の値の変動によって誤った判定が行われる事を防いでいる。この計算結果を用いて、ダイバーシティハンドオーバ制御部１７は、全ての無線回線の品質を監視する事ができる。
【００３１】
次に、図１の実施の形態において、無線リソース不足が発生した場合の無線回線切断処理について説明する。図１の各無線基地局１３、１４、１５、１６は無線リソースの使用状況について無線基地局制御装置１２に対して報告する。無線基地局制御装置１２は各無線基地局１３、１４、１５、１６から送られた無線リソースの状態がある閾値を越えた場合、無線リソースが逼迫したと判断して、ダイバーシティハンドオーバ制御部１７から全無線回線の無線品質情報の読み出しを行い、１台の移動体端末１１で３つ以上の無線回線１８、１９、２０、２１を有するマクロダイバーシティ状態の通信に対して、無線品質が良好な回線を最大２つまで残し、残りの無線回線の切断処理を順次実行する。
【００３２】
１台の移動体端末１１で２つの無線回線を持つ通信においても一方の無線回線の品質がある閾値以下であれば、この無線回線を切断してもよい。図１の実施の形態において、移動体端末１１と接続される、無線基地局１３への無線回線１８と無線基地局１５への無線回線２０の品質が良好で、無線基地局１４への無線回線１９と無線基地局１６への無線回線２１の品質が劣化していたものとすると、無線基地局制御装置１２は、無線回線１９と無線回線２１の切断処理を実行する。
【００３３】
また、無線回線数制限実施中のハンドオーバについては、ハンドオーバ時のみ最大、無線回線制限数＋1の無線回線数（ここでは、３つ）の無線回線を許容し、ハンドオーバ先の無線回線確立後に、最も品質の劣化している無線回線の切断を実行する。各無線基地局１３、１４、１５、１６からの無線リソース報告である閾値以上の空きが確認された場合は、このマクロダイバーシティ状態における無線回線数の制限を解除する。
【００３４】
次に、上記の無線リソース不足が発生した場合の無線回線切断処理について、図２と共に更に詳細に説明する。１台の移動体端末１１が２つ以上の無線基地局１３、１４、１５、１６との間で無線回線を同時に形成しているマクロダイバーシティ状態の通信において無線基地局制御装置１２は、各無線回線１８、１９、２０、２１の通信品質状態と、各無線基地局１３、１４、１５、１６から報告を受けた無線リソース状態を図２での使用無線リソース量１１１として監視する。
【００３５】
ここで、１１２を残無線リソース数が逼迫した事を示す閾値α、１１３を残無線リソース数に余裕ができた事を示す閾値β、無線基地局制御装置１２によって行われる無線回線制限数の最小値をａ、一つの移動体端末１１が持つことができる最大の無線回線数をｂとする。無線基地局からの無線リソース状況報告に応じて監視している使用無線リソース量１１１が閾値α（１１２）を上回った場合、無線基地局制御装置１２は無線回数制限を行い移動体端末１１が保持できる無線回線数を１つ減らし、マクロダイバーシティ状態の移動体端末１１が有する無線回線１８、１９、２０、２１のうち一番品質が劣化している無線回線の切断処理を実行する。
【００３６】
その後、無線基地局１３、１４、１５、１６から報告される無線リソース使用量１１１が閾値α（１１２）を一定時間下回らない場合、移動体端末１１が保持できる無線回線数を更に１つ減らし、その時点で移動体端末１１が有する無線回線のうち一番品質の劣化している無線回線の切断処理を実行することにより、再度無線回線数制限を行う。この処理は、無線リソース使用量１１１が閾値α（１１２）を下回るか、移動体端末１１の残無線回線数がａ本になるまで、無線基地局制御装置１２によって続けられる。
【００３７】
また、無線回線数制限時のソフトハンドオーバにおいても、ハンドオーバ先の無線回線確立後、無線リソース使用量１１１が閾値α（１１２）を上回り、既無線回線数がａ回線より多く存在する場合、無線基地局制御装置１２は無線リソース使用量１１１が閾値α（１１２）を下回るか移動体端末１１の残無線回線数がａ本になるまで、無線回線を一本ずつ切断していく。
【００３８】
また、無線回線数制限時に移動体端末１１が無線回線制限数を越える新規無線回線の確立を行おうとした場合においても、無線基地局制御装置１２は新たな無線回線の確立を拒否する。ただし、無線回線数制限実施中のハンドオーバについては、ハンドオーバ時のみ無線回線制限数＋1の無線回線数を許容し、ハンドオーバ先の無線回線確立後に、最も品質の劣化している無線回線の切断を実行する。
【００３９】
無線基地局制御装置１２は、監視している無線リソース使用量１１１が閾値β（１１３）を下回った時点で、移動体端末１１に対して行っている無線回線数削減処理を停止する。また、無線基地局制御装置１２は、無線リソース使用量１１１が無線回線数制限実施解除の閾値β（１１３）を下回った時点で、無線回線制限数を一本増加させる。その後、無線リソース使用量１１１が閾値β（１１３）を一定時間上回らなかった場合、無線基地局制御装置１２は無線回線制限数を再度一本増加させる。
【００４０】
この処理は、無線リソース使用量１１１が閾値β（１１３）を上回るか、無線回線制限数が有効無線回線数の最大値であるb本になるまで、無線基地局制御装置１２によって続けられる。
【００４１】
ＣＤＭＡ方式の移動体通信システムでマクロダイバーシティ状態にある移動体端末１１では、一本〜複数本の無線回線があれば通信に十分な品質が確保できるため、移動体端末一台あたりの無線回線使用数を制限することにより、品質を落とすことなく、柔軟な無線リソース配分が可能となり、無線リソースの逼迫を緩和する事が可能となる。
【００４２】
このように、本実施の形態によれば、無線基地局制御装置１２のダイバーシティハンドオーバ制御部１７が、各無線基地局１３、１４、１５、１６からＩｕｂ回線２２、２３、２４、２５を介して送信された無線品質情報３３に基づき、各無線回線１８、１９、２０、２１毎の無線品質の監視を継続的に行い、同期外れが発生していない無線回線でも無線品質が劣化していると判断された無線回線は無線リソース確保のための切断対象とすることにより、切断対象とする無線回線の候補をより多く持つことができ、無線リソースが逼迫したことを示す閾値αを超えたときの無線リソース確保を行うことが容易にできる。
【００４３】
また、本実施の形態では、各移動体端末毎に確保する最低無線リソースの数（無線回線制限数の最小値ａ）を設定しているため、すべての無線品質が悪いと判断されている移動体端末においても、その中で無線品質が良い無線回線を残すようにしているため、無線リソース確保と呼切断回避とを同時に行うことができる。
【００４４】
このような無線リソースの使用状況に応じたマクロダイバーシティ状態にある移動体端末１１の無線回線数制限を行うことにより、本実施の形態によれば、無線品質を確保しつつ、無線リソースの効率的な配分を行い、無線リソースの有効利用を実現させることができる。
【００４５】
次に、本発明の他の実施の形態について説明する。図５は本発明になる移動体通信システムの他の実施の形態のシステム構成図を示す。同図に示す移動体通信システムは、ＣＤＭＡ方式の移動体通信システムで、最寄りの基地局のサービスエリア内で該基地局と無線通信する移動体端末４１と、各々固有のサービスエリアＡ１、Ａ２、Ａ３及びＡ４を有する無線基地局４３、４４、４５及び４６と、無線基地局４３、４４、４５及び４６を制御する無線基地局制御装置４２とを備えた構成である。
【００４６】
無線基地局制御装置４２はダイバーシティハンドオーバ制御部４７を持ち、ダイバーシティハンドオーバ制御部４７と無線基地局４３、４４、４５、４６がそれぞれＩｕｂ回線で接続されている。移動体端末４１は、無線基地局４３と無線基地局４５のサービスエリアＡ１とＡ３内に在圏する。
【００４７】
ここで、本実施の形態は、移動体端末４１が、無線回線から下り方向の無線信号を受信し、受信した無線信号の感度から無線品質を計算・保持する機能を持つ無線信号受信部５６を実装している点に特徴がある。また、無線基地局４３、４４、４５、４６は、無線リソースが不足しているかどうかをチェックし、不足しているようであれば無線基地局制御装置４２にその情報を通知する機能を有する。
【００４８】
図５の実施の形態では、一台の移動体端末４１が保有する事ができる無線回線数の最大値は「６」とし、無線回線制限数の最小値を「２」とする。移動体端末４１は無線基地局４３、４４、４５、４６のサービスエリアＡ１、Ａ２、Ａ３、Ａ４の淵にて移動しており、図５の時点では移動体端末４１は無線基地局４３，４５のサービスエリアＡ１、Ａ３内に在圏している。無線基地局制御装置４２は、無線基地局４３、４５と、移動体端末４１が過去に通ったサービスエリアをカバーしている無線基地局４４、４６に対して、それぞれ図５の通りに計４本の無線回線用リソースを割り当てている。
【００４９】
この時、無線品質の閾値を下回る無線回線を良好、無線品質の閾値を上回る無線回線を劣化、と定義した場合、移動体端末４１が送受信する無線品質は、無線回線４８が最も良好となっており、無線回線５０は良好、無線回線４９は劣化が見られ、無線回線５１では著しく劣化しているものとする。移動体端末４１は、下りの無線データを受信する毎に、無線信号受信部５６にて無線品質を算出し、その結果を保持する。
【００５０】
無線基地局制御装置４２は、無線基地局４３、４４、４５、４６から報告される無線リソース値が閾値を下回った際に無線リソースが不足していると判断し、該当の無線基地局のサービスエリア内にいる移動体端末４１に対して切断可能な無線回線を通知するように要求する。
【００５１】
移動体端末４１はこの要求を受けると、無線信号受信部５６にて保持している値を基に無線品質が良好な無線回線２つを選び出し、無線基地局制御装置４２に対して通知する。無線基地局制御装置４２は、通知された内容を基に切断する無線回線を判断し、該当の無線回線を順次切断する。
【００５２】
図５の場合、無線リソースが不足しているある無線基地局が無線リソース不足通知を無線基地局制御装置４２に送信すると、無線基地局制御装置４２は無線回線４８、５０を保持して無線回線４９、５１を切断する処理を順次実行する。
【００５３】
前記図１の実施の形態では上り無線信号の品質を判断基準として無線回線の切断可否を判定していたが、図５の実施の形態は下り無線信号の品質を判断基準として無線回線の切断可否を判定するという違いがあるが、本実施の形態も図１の実施の形態と同様に無線リソースの使用状況に応じたマクロダイバーシティ状態にある移動体端末４１の無線回線数制限を行うことにより、無線品質を確保しつつ、無線リソースの効率的な配分を行い、無線リソースの有効利用を実現させることができる。
【００５４】
【発明の効果】
以上説明したように、本発明によれば、無線回線品質が劣化していることを継続的に監視し、同期はずれ等により使用不能になっていない無線回線であっても、無線品質が劣化していると判断された無線回線は、無線リソース確保のための切断対象とするようにしたため、切断対象とする無線回線の候補をより多く持つことができ、これにより無線リソースが逼迫したことを示す閾値を超えた場合の無線リソース確保を行うことが容易にできる。
【００５５】
また、本発明によれば、各移動体端末毎に確保する最低無線リソースの数を設定しているため、すべての無線品質が悪いと判断されている移動体端末でも、その中で無線品質の良い無線回線を残すことでリソース確保と呼切断回避とを同時に行うことができる。
【００５６】
更に、本発明によれば、マクロダイバーシティ状態における無線回線数の制限を実施することにより、無線リソース逼迫時に特定の移動体端末への無線リソースの集中が緩和でき、他の移動体端末に無線リソースを割り当てる事ができるようになるため、より多くの呼を受け付ける事が可能になり、また、無線回線を切断された移動体端末も、品質が良好な無線回線を無線回線制限数の最小値までは維持できるので、ある一定の通信品質を保つことができる。
【００５７】
また更に、ＣＤＭＡ方式の通信では隣接チャネルの送信電力が干渉電力となり品質劣化を招くため、劣化したチャネルは所要利得を得るために送信電力をあげ、それが隣接チャネルヘの干渉電力となり更に送信電力増加を招き、結果的に無線リソースを枯渇させる要因ともなっているが、本発明によれば、無線リソース逼迫時に無線回線数自体を削減するため、このような干渉電力の増加を軽減する事が期待できる。
【図面の簡単な説明】
【図１】本発明の一実施の形態のシステム構成図である。
【図２】図１の無線リソース不足が発生した場合の無線基地局制御装置による無線回線切断処理説明図である。
【図３】無線品質計算と保存の過程について示す図である。
【図４】無線品質計算のシミュレーション結果の一例を示す特性図である。
【図５】本発明の他の実施の形態のシステム構成図である。
【符号の説明】
１１、４１移動体端末
１２、４２無線基地局制御装置
１３〜１６、４３〜４６無線基地局
１７、４７ダイバーシティハンドオーバ制御部
１８〜２１、４８〜５１無線回線
２２〜２５、５２〜５５Ｉｕｂ回線
５６無線信号受信部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mobile communication system, and more particularly to a time division multiple access (CDMA) type mobile communication system that performs handover in a predetermined case.
[0002]
[Prior art]
A plurality of radio base stations each having a unique service area; a mobile terminal that performs radio communication with the base station within the service area of the nearest base station; and a radio base station controller that controls the plurality of radio base stations In addition, in a mobile communication system that provides communication services to a plurality of mobile terminals, radio resources such as a radio channel in each radio base station are limited.
[0003]
In such a mobile communication system, when the radio resource is close to the allowable amount, the call is disconnected because the radio line for the mobile terminal that has moved to the corresponding service area cannot be secured, It becomes impossible to perform a new call processing in the area. Therefore, a mobile communication system for effectively using radio resources is conventionally known (see, for example, Patent Document 1).
[0004]
That is, in the conventional mobile communication system described in Patent Document 1, each of the communication device (mobile terminal) and the base station communication device (radio base station) constituting the mobile communication system is kept in a certain period of time out of radio synchronization. By monitoring the abnormal state for a certain period after the continuation of the system and the abnormality in the device, and controlling the connection based on the abnormality monitoring output and releasing the connection by the device itself, the unnecessary wireless connection is released. We try to make effective use of resources.
[0005]
[Patent Document 1]
JP 2001-333007 A (page 2-3)
[0006]
[Problems to be solved by the invention]
However, in the conventional mobile communication system described in Patent Document 1 described above, since only wireless channels that have become unusable, such as loss of radio synchronization, are disconnected, radio resources when radio resources are tight are secured. It is difficult to secure radio resources and avoid call disconnection processing at the same time.
[0007]
The present invention has been made in view of the above points, and when radio resources are tight, a radio line used by a mobile terminal is disconnected step by step from a line whose quality has deteriorated to obtain a good quality line. An object of the present invention is to provide a mobile communication system that limits the number of wireless lines by leaving only a predetermined number and enables efficient use of wireless resources.
[0008]
Another object of the present invention is to provide a mobile communication system capable of simultaneously securing radio resources and avoiding call disconnection processing in order to achieve the above object.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the mobile communication system according to the first aspect of the present invention includes a plurality of radio base stations each having a unique service area and a service of the nearest radio base station among the plurality of radio base stations. Manages mobile terminals that communicate wirelessly with base stations in the area via radio links, radio resources that control multiple radio base stations, and reports on radio resource usage status and diversity handover from multiple radio base stations A mobile communication system comprising a radio base station controller having a function of identifying and releasing a radio channel having degraded quality as needed from radio channel quality information from a control unit, The handover control unit transmits uplink data transmitted from a mobile terminal in a macro diversity state to a plurality of radio base stations via a plurality of radio channels. A selection / combination function that selects only the uplink data with the highest quality from the received uplink data, a replication distribution function that replicates and distributes downlink data to a plurality of radio base stations, Diversity handover control as uplink data by adding radio quality information to the data received from the mobile terminal and having the function of monitoring the radio quality of the direction data in units of radio channels The radio base station control device transmits a radio resource from the diversity handover control unit when a state of radio resources transmitted from a plurality of radio base stations exceeds a predetermined first threshold. The wireless quality information of the line is read out, and a wireless line with a good wireless quality is transmitted to the wireless terminals at the maximum number of times Leaving to the minimum value of the limit, characterized by sequentially executing disconnection processing of the remaining radio channel.
[0010]
In this invention, the diversity handover control unit in the radio base station control apparatus wirelessly transmits the radio quality of the uplink data transmitted from the mobile terminal in the macro diversity state to the plurality of radio base stations via the plurality of radio channels. The radio base station controller has a function of monitoring in units of lines, and the radio handover station control unit transmits all radio signals from the diversity handover control unit when the state of radio resources transmitted from a plurality of radio base stations exceeds a predetermined first threshold. Read the radio quality information of the line, leave the radio line with good radio quality up to the minimum limit of the maximum radio line limit for the multiple radio lines of the mobile terminal in the macro diversity state, Since the disconnection process is executed sequentially, even if the radio line is not disabled due to loss of synchronization, etc., the radio quality has deteriorated. Sectional wireless line disconnection process is executed. Further, the minimum number of radio resources to be secured for each mobile terminal (minimum value of the maximum radio channel limit number) is set, and the radio channel disconnection processing is not performed for the minimum radio resource number.
[0011]
In order to achieve the above object, the mobile communication system of the second invention is configured such that the diversity handover control unit of the first invention receives the radio quality information attached to the data from the radio base station each time The wireless quality information is held, changes in the wireless quality information over a predetermined period are averaged, and the quality of each wireless line is managed.
[0012]
In order to achieve the above object, a mobile communication system according to a third aspect of the present invention provides a wireless base station control apparatus according to the first aspect of the present invention, in which a new wireless device whose mobile terminal exceeds the wireless line limit number when the number of wireless lines is limited. When trying to establish a line, the establishment of a new wireless line is rejected, and for handovers that are in the process of limiting the number of wireless lines, the number of wireless lines + 1 is allowed only at the time of handover. It is characterized in that after the line is established, the wireless line with the lowest quality is disconnected.
[0013]
In order to achieve the above object, a mobile communication system according to a fourth aspect of the present invention provides a wireless base station controller according to the first aspect, wherein the state of the wireless resources transmitted from a plurality of wireless base stations is the number of wireless lines. If the restriction threshold is canceled below the second threshold, the number of wireless lines is increased by one, the amount of wireless resource usage exceeds the second threshold, or the number of wireless lines is the maximum number of effective wireless lines. It is characterized in that it is configured to repeat every certain time until it reaches a value. In the present invention, when the state of the radio resource falls below the second threshold for canceling the restriction on the number of wireless lines, the number of wireless lines is increased by one, so that the wireless line with good wireless quality is in the macro diversity state. Since as many mobile terminals as possible can be set, the highest possible communication quality can be maintained.
[0014]
In order to achieve the above object, a mobile communication system according to a fifth aspect of the present invention uses the wireless quality information in the first to fourth aspects of the communication quality information representing the communication quality on the wireless line and a predetermined code. It is characterized by using one or both of the verification results.
[0015]
In order to achieve the above object, a mobile communication system of a sixth invention includes a plurality of radio base stations each having a unique service area, and a service area of the nearest radio base station among the plurality of radio base stations. Mobile terminals that communicate wirelessly with a base station via a radio line within the network, manage radio resources that control multiple radio base stations, and report radio resource usage status and diversity handover control from multiple radio base stations A mobile communication system comprising a radio base station control device having a function of identifying and releasing a radio channel having deteriorated quality as required from radio channel quality information from a mobile station, The terminal includes a radio signal receiving unit having a function of calculating and maintaining radio quality from sensitivity of radio signals received from a plurality of radio channels in a macro diversity state, and a radio base When a disconnectable radio channel notification request is received from the control device, a radio channel with good radio quality is selected based on the value held in the radio signal receiving unit and notified to the radio base station control device Each of the plurality of radio base stations checks whether or not the radio resources are insufficient, and if not, the radio base station has notification means for notifying the radio base station controller of the information. Then, the radio base station control device can disconnect the mobile terminal in the service area of the corresponding radio base station when radio resource values reported from a plurality of radio base stations fall below a threshold value. Make a radio channel notification request, receive a radio channel notification of good radio quality from the mobile terminal responding to the radio channel notification request, determine the radio channel to be disconnected based on the notified content, No good Leaving a line to a minimum value of the maximum radio channel limit, characterized by sequentially executing disconnection processing of the remaining radio channel.
[0016]
In this invention, the mobile terminal in the macro diversity state has a radio signal receiving unit having a function of calculating and holding radio quality from the sensitivity of the downlink radio signal received from a plurality of radio channels, When the radio resource value reported from a plurality of radio base stations falls below a threshold value, the station controller can make a disconnection request to the mobile terminal in the service area of the corresponding radio base station. Thus, by selecting a radio channel with good radio quality based on the value held by the corresponding mobile terminal in its radio signal receiving unit and notifying the radio base station controller, the radio terminal The base station controller left the radio channel with good radio quality up to the minimum limit of the maximum radio channel limit, and the disconnection process for the remaining radio channels was sequentially executed. Even radio line not been disabled, the radio network it is determined that the radio quality is deteriorated disconnection process is executed. Further, the minimum number of radio resources to be secured for each mobile terminal (minimum value of the maximum radio channel limit number) is set, and the radio channel disconnection processing is not performed for the minimum radio resource number.
[0017]
In order to achieve the above object, the seventh aspect of the invention is to establish a wireless base station controller of the sixth aspect of the invention by establishing a new wireless line in which the mobile terminal exceeds the wireless line limit number when the number of wireless lines is limited. If this happens, the establishment of a new radio channel is rejected, and for handovers that are in the process of limiting the number of radio channels, the number of radio channels + 1 is allowed only at the time of handover. It is characterized in that it is configured to execute the disconnection of the wireless line in which the quality is deteriorated.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a system configuration diagram of an embodiment of a mobile communication system according to the present invention. The mobile communication system shown in the figure is a CDMA mobile communication system, and a mobile terminal 11 that wirelessly communicates with a base station within a service area of the nearest base station, and service areas A1, A2, and A3 that are unique to each. And A4, and a radio base station control device 12 that controls the

radio base stations

13, 14, 15 and 16.
[0019]
The mobile terminal 11 includes a radio base station 13 via a radio line 18, a radio base station 14 via a radio line 19, a radio base station 15 via a radio line 20, and a radio base station via a radio line 21. Station 16 is connected to each. The

radio base stations

13, 14, 15, and 16 are connected to the diversity handover control unit 17 in the radio base station control device 12 via

Iub lines

22, 23, 24, and 25, respectively. The

radio base stations

13, 14, 15, and 16 communicate with the mobile terminal 11 through the

radio lines

18, 19, 20, and 21, and report the usage status of radio resources to the radio base station controller 12. Have
[0020]
The diversity handover control unit 17 receives the uplink data transmitted from the mobile terminal 11 via the

radio lines

18, 19, 20, and 21, and selects and combines only the data with the highest quality, A duplication / distribution function for duplicating and distributing direction data to each

radio base station

13, 14, 15, 16 and the radio quality of uplink data from each

radio line

18, 19, 20, 21 in units of radio lines Has a monitoring function.
[0021]
The radio base station control device 12 manages radio resources, and uses radio resource usage status reports from the

radio base stations

13, 14, 15 and 16 and radio channel quality information from the diversity handover control unit 17 as necessary. , Has a function of identifying and releasing a wireless line having degraded quality.
[0022]
Next, the operation of the present embodiment will be described. In FIG. 1, a mobile terminal 11 is connected to four

radio base stations

13, 14, 15, and 16 through

radio lines

18, 19, 20, and 21 simultaneously, that is, four multipaths are connected. It is in a macro diversity state. Here, the maximum value of the number of radio channels that can be held by one mobile terminal 11 is “6”, and the minimum value of the radio channel limit number is “2”.
[0023]
Each

radio base station

13, 14, 15, 16 converts the data received from the mobile terminal 11 into frame data, and performs diversity handover in the radio base station controller 12 via the Iub lines 22, 23, 24, 25. It transmits to the control part 17. At this time, the

radio base stations

13, 14, 15, and 16 add QE (Quality Estimate) information indicating communication quality on the radio channel and a CRC result (CRC Indicator) based on a CRC code to the frame data to add diversity handover. It transmits to the control part 17.
[0024]
The diversity handover control unit 17 of the radio base station controller 12 receives frame data, QE information, and CRCI transmitted from the

radio base stations

13, 14, 15, and 16 via the Iub lines 22, 23, 24, and 25. Then, only the frame data with the best communication quality is selected and combined and transferred to the upper network side. At this time, the diversity handover control unit 17 monitors the radio quality for each

radio line

18, 19, 20, and 21.
[0025]
The monitoring of the wireless quality is performed based on the wireless quality information 33 for each wireless line shown in FIG. The radio quality information 33 includes the above-described QE information indicating the communication quality on the radio channel and the collation result CRCI using the CRC code, and the radio quality may be determined using any of them. Here, description will be made using an example in which the wireless quality is monitored using the QE information and the wireless channel quality is determined.
[0026]
As shown in FIG. 3, uplink radio data 31 is transmitted from the mobile terminal 11 to the radio base station 13 (or 14, 15 or 16), and the radio base station 13 (or 14, 15 or 16) Data 31 is converted into frame data 32, radio quality information 33 is added thereto, and transmitted to diversity handover control unit 17 in radio base station controller 12.
[0027]
When the wireless channel quality deteriorates, the content is reflected in the wireless quality information 33 by the wireless base station 13 (or 14, 15 or 16) that has received the wireless data 31. The diversity handover control unit 17 in the radio base station controller 12 receives the radio quality information 33 every time it receives the radio quality information 33 attached to the frame data 32 from the radio base station 13 (or 14, 15 or 16). Hold. This wireless quality information can hold any number of past information, and averages the changes in the wireless quality information during that period to manage the quality of each wireless line.
[0028]
Although the calculation method of the radio channel quality is arbitrary, the calculation result when QE is used for reference is shown in FIG. 4, QE is used for the radio quality information I corresponding to the radio quality information 33 in FIG. 3, and the radio quality II calculated by the diversity handover control unit 17 in FIG. 3 is graphed. The vertical axis is the QE value, and the horizontal axis is the number of the received frame. The smaller the QE value, the better the quality.
[0029]
In FIG. 4, the radio quality information I of the nth received frame is represented by QE. _n When the number of radio quality information II histories held in the diversity handover control unit 17 is m and the calculated radio quality II is MAQ (Management Air Quality), the equation for deriving the nth radio quality MAQn is It becomes as Formula 1.
[0030]
[Expression 1]

By using the wireless quality MAQn calculated in this way, it is possible to provide redundancy for a sudden change in the wireless quality information I of one frame, and instantaneous fluctuations in the wireless quality information value. Prevents incorrect judgments from being made. Using this calculation result, the diversity handover control unit 17 can monitor the quality of all radio channels.
[0031]
Next, in the embodiment of FIG. 1, a radio line disconnection process when a radio resource shortage occurs will be described. Each

radio base station

13, 14, 15, 16 in FIG. 1 reports the radio resource usage status to the radio base station controller 12. When the state of the radio resource transmitted from each

radio base station

13, 14, 15, 16 exceeds a certain threshold, the radio base station control device 12 determines that the radio resource is tight, and the diversity handover control unit 17 A channel with good radio quality for reading out radio quality information of all radio channels and having three or

more radio channels

18, 19, 20, and 21 in one mobile terminal 11 in a macro diversity state communication. Are left out, and the remaining wireless lines are disconnected sequentially.
[0032]
Even in communication with one wireless terminal 11 having two wireless lines, if the quality of one wireless line is below a certain threshold, the wireless line may be disconnected. In the embodiment of FIG. 1, the quality of the radio channel 18 to the radio base station 13 and the radio channel 20 to the radio base station 15 connected to the mobile terminal 11 is good, and the radio channel to the radio base station 14 19 and the quality of the radio channel 21 to the radio base station 16 have deteriorated, the radio base station control device 12 executes a disconnection process between the radio channel 19 and the radio channel 21.
[0033]
In addition, with regard to a handover in which the number of radio channels is being limited, the maximum number of radio channels is limited only at the time of handover, and the number of radio channels (here, three) is allowed. Disconnect the wireless line whose quality has deteriorated. When a vacant space equal to or greater than a threshold, which is a radio resource report from each

radio base station

13, 14, 15, 16, is confirmed, the restriction on the number of radio channels in the macro diversity state is released.
[0034]
Next, the wireless line disconnection process when the above-described shortage of wireless resources occurs will be described in more detail with reference to FIG. In a macro diversity communication in which one mobile terminal 11 forms a radio line with two or more

radio base stations

13, 14, 15, 16 at the same time, the radio base station control device 12 The communication quality status of the

lines

18, 19, 20, 21 and the radio resource status received from each

radio base station

13, 14, 15, 16 are monitored as the used radio resource amount 111 in FIG.
[0035]
Here, 112 is a threshold value α indicating that the number of remaining radio resources is tight, 113 is a threshold value β indicating that the number of remaining radio resources is sufficient, and the minimum number of radio channel limits performed by the radio base station control device 12 The value is a, and the maximum number of radio channels that one mobile terminal 11 can have is b. When the used radio resource amount 111 monitored according to the radio resource status report from the radio base station exceeds the threshold α (112), the radio base station control device 12 limits the radio frequency and holds the mobile terminal 11 The number of possible radio channels is reduced by one, and the radio channel having the lowest quality among the

radio channels

18, 19, 20, and 21 of the mobile terminal 11 in the macro diversity state is disconnected.
[0036]
Thereafter, if the radio resource usage 111 reported from the

radio base stations

13, 14, 15, 16 does not fall below the threshold value α (112) for a certain time, the number of radio channels that the mobile terminal 11 can hold is further reduced by one, At that time, the number of wireless lines is limited again by executing a disconnection process of the wireless line having the worst quality among the wireless lines of the mobile terminal 11. This process is continued by the radio base station controller 12 until the radio resource usage 111 falls below the threshold value α (112) or the number of remaining radio channels of the mobile terminal 11 reaches a.
[0037]
Also, in soft handover when the number of radio channels is limited, if the radio resource usage 111 exceeds the threshold value α (112) after the handover destination radio channel is established, The station control device 12 disconnects the radio lines one by one until the radio resource usage 111 falls below the threshold value α (112) or until the number of remaining radio channels of the mobile terminal 11 reaches a.
[0038]
Even when the mobile terminal 11 attempts to establish a new radio channel exceeding the radio channel limit number when the number of radio channels is limited, the radio base station controller 12 refuses to establish a new radio channel. However, for handovers where the number of radio channels is being limited, the number of radio channels + 1 is allowed only during handover, and the radio channel with the most degraded quality is disconnected after the handover destination radio channel is established. To do.
[0039]
The radio base station control device 12 stops the radio channel number reduction process performed for the mobile terminal 11 when the monitored radio resource usage 111 falls below the threshold β (113). Also, the radio base station control device 12 increases the radio channel limit number by one when the radio resource usage amount 111 falls below the threshold β (113) for canceling the radio channel number limit execution. Thereafter, when the radio resource usage amount 111 does not exceed the threshold β (113) for a certain period of time, the radio base station control device 12 increases the radio channel limit number by one again.
[0040]
This process is continued by the radio base station controller 12 until the radio resource usage amount 111 exceeds the threshold value β (113) or the radio channel limit number reaches b which is the maximum number of effective radio channels.
[0041]
In a mobile terminal 11 in a macro diversity state in a CDMA mobile communication system, if there is one to a plurality of wireless lines, sufficient quality for communication can be ensured. By limiting the number, it is possible to flexibly allocate radio resources without degrading quality, and it is possible to alleviate the tightness of radio resources.
[0042]
As described above, according to the present embodiment, the diversity handover control unit 17 of the radio base station control device 12 transmits the

radio base stations

13, 14, 15, 16 to the Iub lines 22, 23, 24, 25. Based on the transmitted radio quality information 33, the radio quality of each

radio channel

18, 19, 20, 21 is continuously monitored, and the radio quality is deteriorated even in the radio channel where no synchronization has occurred. The determined wireless line is subject to disconnection for securing radio resources, so that it can have more candidates for the disconnection target wireless line, and when the threshold α indicating that the radio resource is tight is exceeded. It is easy to secure radio resources.
[0043]
Further, in this embodiment, since the minimum number of radio resources to be secured for each mobile terminal (minimum value a of the radio channel limit number) is set, all radio quality determined to be poor Also in the body terminal, since a wireless line with good wireless quality is left in the body terminal, it is possible to simultaneously secure radio resources and avoid call disconnection.
[0044]
By limiting the number of radio channels of the mobile terminal 11 in the macro diversity state according to the usage status of radio resources, according to the present embodiment, it is possible to efficiently improve radio resources while ensuring radio quality. Effective allocation of radio resources can be realized.
[0045]
Next, another embodiment of the present invention will be described. FIG. 5 shows a system configuration diagram of another embodiment of a mobile communication system according to the present invention. The mobile communication system shown in the figure is a CDMA mobile communication system, and a mobile terminal 41 wirelessly communicating with the base station within the service area of the nearest base station, and service areas A1, A2, and The

radio base stations

43, 44, 45, and 46 having A3 and A4, and a radio base station control device 42 that controls the

radio base stations

43, 44, 45, and 46 are provided.
[0046]
The radio base station control device 42 has a diversity handover control unit 47, and the diversity handover control unit 47 and the

radio base stations

43, 44, 45, and 46 are connected via Iub lines, respectively. The mobile terminal 41 is located in the service areas A1 and A3 of the radio base station 43 and the radio base station 45.
[0047]
Here, in this embodiment, the mobile terminal 41 receives a radio signal in the downlink direction from the radio channel, and includes a radio signal receiving unit 56 having a function of calculating and holding radio quality from the sensitivity of the received radio signal. It is characterized in that it is implemented. Further, the

radio base stations

43, 44, 45, and 46 have a function of checking whether or not the radio resources are insufficient, and notifying the radio base station control device 42 of the information if it is insufficient.
[0048]
In the embodiment of FIG. 5, the maximum value of the number of radio channels that can be held by one mobile terminal 41 is “6”, and the minimum value of the radio channel limit number is “2”. The mobile terminal 41 moves at the base of the service areas A1, A2, A3, and A4 of the

radio base stations

43, 44, 45, and 46. At the time of FIG. In the service areas A1 and A3. As shown in FIG. 5, the radio base station control device 42 has a total of 4

radio base stations

43 and 45 and 4 radio base stations 44 and 46 covering the service area that the mobile terminal 41 has passed in the past. Allocating resources for wireless links.
[0049]
At this time, if it is defined that the radio channel that is lower than the radio quality threshold is good and the radio channel that exceeds the radio quality threshold is degraded, the radio quality transmitted and received by the mobile terminal 41 is the best for the radio channel 48. The wireless line 50 is good, the wireless line 49 is deteriorated, and the wireless line 51 is remarkably deteriorated. Each time the mobile terminal 41 receives downlink radio data, the radio signal reception unit 56 calculates the radio quality and holds the result.
[0050]
The radio base station control device 42 determines that radio resources are insufficient when the radio resource value reported from the

radio base stations

43, 44, 45, 46 falls below the threshold, and the service of the corresponding radio base station A request is made to notify the mobile terminal 41 in the area of a radio link that can be disconnected.
[0051]
Upon receiving this request, the mobile terminal 41 selects two radio lines with good radio quality based on the values held by the radio signal receiving unit 56 and notifies the radio base station control device 42 of them. The radio base station control device 42 determines a radio channel to be disconnected based on the notified contents, and sequentially disconnects the corresponding radio channel.
[0052]
In the case of FIG. 5, when a radio base station having a shortage of radio resources transmits a radio resource shortage notification to the radio base station control device 42, the radio base station control device 42 holds the radio channels 48 and 50 and maintains the radio channel. The process of cutting 49 and 51 is executed sequentially.
[0053]
In the embodiment of FIG. 1, whether or not the radio channel can be disconnected is determined based on the quality of the uplink radio signal. However, the embodiment of FIG. 5 determines whether or not the radio channel can be disconnected based on the quality of the downlink radio signal. However, in the present embodiment, as in the embodiment of FIG. 1, by limiting the number of radio channels of the mobile terminal 41 in the macro diversity state according to the usage status of radio resources, While ensuring radio quality, it is possible to efficiently allocate radio resources and realize effective use of radio resources.
[0054]
【The invention's effect】
As described above, according to the present invention, it is continuously monitored that the radio channel quality is deteriorated, and even if the radio channel is not disabled due to loss of synchronization or the like, the radio quality deteriorates. Since the wireless line determined to be disconnected is targeted for disconnection for securing wireless resources, it can have more candidates for the wireless line to be disconnected, which indicates that the wireless resources are tight. It is easy to secure radio resources when the threshold is exceeded.
[0055]
In addition, according to the present invention, since the minimum number of radio resources to be secured for each mobile terminal is set, even mobile terminals that are determined to have poor radio quality have radio quality of those terminals. By leaving a good wireless line, resources can be secured and call disconnection avoidance can be performed simultaneously.
[0056]
Furthermore, according to the present invention, by limiting the number of radio channels in the macro diversity state, concentration of radio resources on a specific mobile terminal can be alleviated when radio resources are tight, and radio resources can be transmitted to other mobile terminals. It is possible to accept more calls, and mobile terminals that are disconnected from the wireless line can also connect a good quality wireless line up to the minimum number of wireless line restrictions. Can maintain a certain communication quality.
[0057]
Furthermore, in CDMA communication, the transmission power of the adjacent channel becomes interference power and causes quality degradation. Therefore, the deteriorated channel increases the transmission power to obtain a required gain, which becomes interference power to the adjacent channel and further increases the transmission power. However, according to the present invention, since the number of radio lines itself is reduced when radio resources are tight, it is expected to reduce such an increase in interference power. .
[Brief description of the drawings]
FIG. 1 is a system configuration diagram of an embodiment of the present invention.
FIG. 2 is an explanatory diagram of a radio line disconnection process performed by the radio base station control device when a radio resource shortage occurs in FIG. 1;
FIG. 3 is a diagram showing a wireless quality calculation and storage process.
FIG. 4 is a characteristic diagram showing an example of a simulation result of wireless quality calculation.
FIG. 5 is a system configuration diagram of another embodiment of the present invention.
[Explanation of symbols]
11, 41 Mobile terminal
12, 42 Radio base station controller
13-16, 43-46 Wireless base station
17, 47 Diversity handover controller
18-21, 48-51 Wireless circuit
22-25, 52-55 Iub line
56 Radio signal receiver

Claims

A plurality of radio base stations each having a unique service area; and a mobile terminal that performs radio communication with the base station via a radio line within a service area of the nearest radio base station among the plurality of radio base stations; In addition to managing radio resources for controlling a plurality of radio base stations, the quality deteriorates as necessary from radio resource usage status reports from the plurality of radio base stations and radio channel quality information from the diversity handover control unit. A mobile communication system comprising a radio base station control device having a function of identifying and releasing a radio line,
The diversity handover control unit receives uplink data transmitted from the mobile terminal in a macro diversity state to the plurality of radio base stations via the plurality of radio channels, and receives the uplink data received. A selection / combination function that selects only the uplink data with the highest quality, a replication distribution function that replicates and distributes downlink data to the plurality of radio base stations, and wireless quality of the uplink data is wireless. It has a function to monitor on a line basis,
Each of the plurality of radio base stations has transmission means for adding radio quality information to data received from the mobile terminal and transmitting the data as uplink data to the diversity handover control unit,
When the state of the radio resources transmitted from a plurality of the radio base stations exceeds a predetermined first threshold, the radio base station control device receives the radio quality information of all radio channels from the diversity handover control unit. Read out, and for the plurality of radio channels of the mobile terminal in the macro diversity state, leave radio channels with good radio quality up to the minimum value of the maximum radio channel limit, and sequentially disconnect the remaining radio channels A mobile communication system, characterized by being executed.

The diversity handover control unit holds the radio quality information every time it receives the radio quality information attached to the data from the radio base station, averages the change of the radio quality information in a predetermined period, 2. The mobile communication system according to claim 1, wherein quality for each line is managed.

The radio base station controller rejects establishment of a new radio channel when the mobile terminal attempts to establish a new radio channel exceeding the radio channel limit when the number of radio channels is limited, and implements a limit on the number of radio channels For middle handover, only the number of radio channels + 1 is allowed only at the time of handover, and after establishment of the handover destination radio channel, disconnection of the radio channel with the most deteriorated quality is performed. Item 4. The mobile communication system according to Item 1.

The radio base station control device increases the radio channel limit number by one when the state of radio resources transmitted from a plurality of radio base stations falls below a second threshold for canceling the radio channel number limit implementation. 2. The mobile communication according to claim 1, wherein the mobile communication is repeated at predetermined time intervals until a radio resource usage amount exceeds the second threshold value or a radio channel limit number reaches a maximum value of the number of effective radio channels. system.

5. The wireless quality information is represented using one or both of communication quality information indicating communication quality on the wireless line and a matching result using a predetermined code. The mobile communication system according to the item.

A plurality of radio base stations each having a unique service area; and a mobile terminal that performs radio communication with the base station via a radio line within a service area of the nearest radio base station among the plurality of radio base stations; In addition to managing radio resources for controlling a plurality of radio base stations, the quality deteriorates as necessary from radio resource usage status reports from the plurality of radio base stations and radio channel quality information from the diversity handover control unit. A mobile communication system comprising a radio base station control device having a function of identifying and releasing a radio line,
The mobile terminal can be disconnected from a radio signal receiving unit having a function of calculating and maintaining radio quality from sensitivity of radio signals received from a plurality of radio channels in a macro diversity state, and the radio base station control device Transmission / reception means for selecting a radio channel with good radio quality based on a value held in the radio signal receiving unit when receiving a radio channel notification request and notifying the radio base station controller. And
Each of the plurality of radio base stations has a notifying unit for checking whether or not radio resources are insufficient, and notifying the radio base station control device of the information if it seems to be insufficient,
When the radio resource value reported from the plurality of radio base stations falls below a threshold value, the radio base station control device disconnects the mobile terminal in the service area of the corresponding radio base station. A wireless line notification request is made, a wireless line notification having a good wireless quality is received from the mobile terminal responding to the wireless line notification request, and a wireless line to be disconnected is determined based on the notified content A mobile communication system characterized in that a wireless channel having good radio quality is left to a minimum value of the maximum number of wireless channels and a disconnection process of the remaining wireless channels is sequentially executed.

The radio base station controller rejects establishment of a new radio channel when the mobile terminal attempts to establish a new radio channel exceeding the radio channel limit when the number of radio channels is limited, and implements a limit on the number of radio channels For middle handover, only the number of radio channels + 1 is allowed only at the time of handover, and after establishment of the handover destination radio channel, disconnection of the radio channel with the most deteriorated quality is performed. Item 7. The mobile communication system according to Item 6.