JP3836063B2

JP3836063B2 - Wireless communication system

Info

Publication number: JP3836063B2
Application number: JP2002276569A
Authority: JP
Inventors: 有一郎後藤; 知多佳真鍋; 吉人福本
Original assignee: Kobe Steel Ltd
Current assignee: Kobe Steel Ltd
Priority date: 2001-11-08
Filing date: 2002-09-24
Publication date: 2006-10-18
Anticipated expiration: 2022-09-24
Also published as: JP2003209586A

Description

【０００１】
【発明の属する技術分野】
本発明は，双方向ＣＡＴＶ等，親局と１又は複数の子局との間で双方向の無線データ通信を行う無線通信システムに関するものである。
【０００２】
【従来の技術】
近年，データ通信の急速な普及に伴い，高速な回線網への需要がますます増大している。しかしながら，有線により提供される高速回線は，各戸別に導入配線工事が必要である上，屋内のレイアウト変更時にも屋内配線工事が必要となる等，利用者にとって手間と金銭的負担を伴う場合が多い。そこで，煩雑な各戸別の配線工事が不要な無線通信ネットワークの普及が望まれている。
このようなニーズに対応するシステムとして，例えば特許文献１には，既存のＣＡＴＶ（ケーブルテレビ）網を用いて，そのネットワークの末端部分を無線に置き換えた双方向無線ＣＡＴＶシステムが提案されている。これは，１０ＧＨｚ以上のマイクロ波〜ミリ波を用いて親局装置（基地局）と複数の子局装置（加入者局）との間でデータの送受信を行う１対多（ＰＭＰ）双方向無線通信システムであり，インターネットへの接続サービスの他，映画等の映像データをオンデマンドで提供する等，ブロードバンドが必要な通信サービスに利用可能なものである。
【０００３】
図６（ａ）は特許文献１に示されるＰＭＰ双方向無線通信システムＺの概略構成を表すブロック図である。
親局１０ａは，親局本体部１１０ａと親局中継部１２０ａとから構成され，それらの間を通信ケーブル１３０ａにて接続することにより，前記親局中継部１２０ａのみを高所に設置する等，分離して設置可能としている。同様に，子局１０ｂも，子局本体部１１０ｂと子局中継部１２０ｂとから構成され，それらの間が通信ケーブル１３０ｂで接続されている。
前記親局１０ａから前記子局１０ｂへのデータ送信においては，前記親局１０ａの通信制御部１１１ａによって生成された子局１０ｂへの送信信号が，変調器１１２ａによって例えば６４値の直交変調が行われた後，通信ケーブル１３０ａでの伝送減衰が小さい低周波信号として前記親局中継部１２０ａの周波数変換器１２３ａへ伝送され，該周波数変換器１２３ａで無線通信用の高周波信号に変換された後，送信アンプ１２１ａによって増幅されて不図示のアンテナによって前記子局１０ｂへ無線信号として送信される。また，前記子局１０ｂでは，無線信号が不図示のアンテナで受信され，前記子局中継部１２０ｂのＬＮＡ（Low Noise Amplifier）１２２ｂで増幅された後，周波数変換器１２４ｂによって，低周波信号に変換される。さらに，該低周波信号のレベルが所定のレベルとなるように中継用受信ＡＧＣ（Auto Gain Controller）１２６ｂによってレベル調節された信号が，前記通信ケーブル１３０ｂを介して前記子局本体部１１０ｂの受信ＡＧＣ１１５ｂに伝送され，該受信ＡＧＣ１１５ｂにより，前記中継用受信ＡＧＣ１２６ｂでレベル調節しきれなかった分が補助的にレベル補正された後，復調器１１３ｂによって復調されて通信制御部１１１ｂに取り込まれる。
【０００４】
一方，前記子局１０ｂから前記親局１０ａへのデータ送信においては，前記通信制御部１１１ｂによって生成された前記親局１０ａへの送信信号が，変調器１１２ｂによって例えば１６値の直交変調が行われ，変調後の信号が送信ＧＣ（Gain Controller）１１４ｂによって後述するゲイン補正（増幅）が行われた後，前記通信ケーブル１３０ｂを介して前記子局中継部１２０ｂの送信ＧＣ１１４ｂに伝送され，さらに，前記送信ＧＣ１１４ｂにより，前記中継用受信ＡＧＣ１２６ｂでの調節レベルに比例したゲインで増幅される。前述したように，前記中継用受信ＡＧＣ１２６ｂでの調節レベルは，前記親局１０ａからの受信信号レベルに応じて調節されるため，結果として，前記中継用送信ＧＣ１２５ｂのゲイン（増幅量）も，前記親局１０ａからの受信信号レベルに応じて調節されることとなる。このようにしてレベル調節された信号は，さらに周波数変換器１２３ｂにより無線通信用の高周波信号に変換された後，送信アンプ１２１ｂで増幅されて不図示のアンテナから前記親局１０ａに対して無線信号として送信される。また，前記親局１０ａでは，前記子局１０ｂから送信された無線信号が不図示のアンテナで受信され，前記親局中継部１２０ａのＬＮＡ１２２ａで増幅された後，前記通信ケーブル１０３ａを介して前記親局本体部１１０ａの復調器１１３ａに伝送され，該復調器１１３ａによって復調された信号が，前記親局本体部１１０ａ側の前記通信制御部１１１ａに取り込まれる。
以上示したように，前記親局１０ａ及び子局１０ｂそれぞれにおいて，本体部１１０ａ，１１０ｂと中継部１２０ａ，１２０ｂとが分離されているので，無線通信を行う中継部１２０ａ，１２０ｂのみを，障害物の影響を受けにくい高所に設置する等，適切な設置が可能である。
【０００５】
（下り信号）
図６（ｂ）は，前記親局１０ａの前記変調器１１２ａから前記子局１０ｂの復調器１１３ｂへ至るまでの下り信号の信号レベルの遷移の一例を表すダイヤグラムである。
例えば，晴天下においては，図６（ｂ）の実線Ｓｄ０に示されるように，前記親局中継部１２０ａの前記送信アンプ１２１ａから出力される信号は，無線信号の減衰レベルが比較的小さいため，比較的高いレベルで前記子局中継部１２０ｂの前記ＬＮＡ１２２ｂに到達する。しかし，降雨が激しい天候下においては，無線信号の減衰レベルが大きいため，低いレベルで前記ＬＮＡ１２２ｂに到達する。この前記子局１０ｂにおける受信信号レベルの変化は，該変化に応じて前記中継用受信ＡＧＣ１２６ｂによってレベル調節されるため，通常は，前記子局本体部１１０ｂの前記受信ＡＧＣ１１５ｂに入力される信号は所定の一定レベルに維持される。このようにして，前記中継用受信ＡＧＣ１２６ｂの調節限界まで受信レベルを調節された結果が図６（ｂ）の細い破線Ｓｄ１に示される。
しかし，さらに降雨が激しくなり，前記中継用受信ＡＧＣ１２６ｂの調節限界を越えて無線信号の減衰レベルが大きくなると，図６（ｂ）の太い破線Ｓｄ２に示されるように前記受信ＡＧＣ１１５ｂの入力信号は所定のレベルよりも下がる。このような場合でも，前記子局本体部１１０ｂの前記復調器１１３ｂへの入力信号レベルは一定となるように，前記子局本体部１１０ｂの前記受信ＡＧＣ１１５ｂによってレベル補正される。
【０００６】
（上り信号）
以上示したのと同様なレベル調節が，前記子局１０ｂから前記親局１０ａへの上り信号においても行われる。図６（ｃ）は，前記上り信号の信号レベルの遷移の一例を表すダイヤグラムである。
前記子局中継部１２０ｂの前記送信アンプ１２１ｂの出力信号レベルは，例えば晴天下においては，図６（ｃ）の実線Ｓｕ０に示されるように比較的低いレベルで出力され，降雨が激しく無線信号の減衰レベルが大きい場合は，前記親局１０ａへの到達レベルが一定となるように，前記中継用送信ＧＣ１２５ｂによってより高いレベルにレベル調節される。該レベル調節は，前記親局１０ａからの受信信号のレベルに応じて，即ち，受信信号のレベルの低下分だけ増幅するように行われる。前記親局１０ａからの無線信号と，前記子局１０ｂからの無線信号とは通信経路が同じであり，それらの減衰レベルは同等であるため，結果として，前記親局１０ａへ到達する信号レベルは所定のレベルで一定に維持される。このようにして，前記中継用送信ＧＣ１２５ｂの調節限界まで送信レベルを高く調節された結果が，図６（ｃ）の細い破線Ｓｕ１で示されている。
【０００７】
しかし，さらに降雨が激しくなり，前記中継用送信ＧＣ１２５ｂの調節限界を越えて無線信号の減衰レベルが大きくなると，図６（ｃ）の太い破線Ｓｕ２で示されるように前記親局１０ａへ到達する信号レベルが下がり，前記親局本体部１１０ａの入力信号は所定のレベルＬ０（以下，親局目標受信レベルという）よりも下がる。このとき，前記親局１０ａ側の前記通信制御部１１１ａから前記子局１０ｂ側の前記通信制御部１１１ｂに対して所定の補正指令が送信され，これに従い前記子局１０ｂ側の前記通信制御部１１１ｂによって前記子局本体部１１０ｂの前記送信ＧＣ１１４ｂに制御信号が出力され，前記親局本体部１１０ａにおける入力信号と前記親局目標受信レベルＬ０との差分だけ，前記子局本体部１１０ｂの前記送信ＧＣ１１４ｂのゲインが補正される。これにより，図６（ｃ）の太い破線Ｓｕ３に示されるように，前記親局本体部１１０ａへの入力信号レベルは前記親局目標受信レベルＬ０に維持される。
【０００８】
しかし，無線通信の減衰レベルが特に大きく（降雨が非常に激しい等），図６（ｃ）の太い破線Ｓｕ３の状態にまで至ると，前記親局中継部１２０ｂの送信アンプ１２１ｂの出力レベルが，所定の上限レベルＢＯ（以下，バックオフレベルという）を越え，信号に歪みが生じることにより，通信のビット誤り率が高くなる。このようにしてビット誤り率が高くなると通信に著しい支障を生じる。
信号の歪みに起因するビット誤り率は，信号の変調方式によって異なるため，実際の通信に影響が現れる前記バックオフレベルＢＯは，信号の変調方式によって異なる。即ち，信号に同程度の歪みが生じている場合でも，多値化レベルの低い変調方式であるほどビット誤り率は低いため，多値化レベルの低い変調方式では前記バックオフレベルＢＯは高く，多値化レベルの高い変調方式では前記バックオフレベルＢＯは比較的低い。しかし，多値化レベルの高い変調方式ほど，単位時間当たりの通信容量は大きくなり，高速データ通信が可能となるため，より多値化レベルの高い変調方式で通信するほうが望ましい。
このような特性から，ビット誤り率の上昇を防止するものとして，特許文献２には，光による無線通信に関し，相手局からの受信信号のレベルが低下した場合や，ビット誤り率（エラー回数）が上昇した場合に，変調方式を切り替えるものが提案されている。これにより，通常は，通信容量の大きい変調方式で通信を行い，受信信号レベルが低下した場合は，前記ビット誤り率の低い変調方式で通信うことにより，全体として効率的な通信が行える。
【０００９】
ところで，前記親局目標受信レベルＬ０を下げれば，前記子局１０ｂにおける前記送信アンプ１２１ｂの出力レベルを下げることができ，前記バックオフレベルＢＯを越えないようにはできるが，前記親局目標受信レベルＬ０を下げると，前記親局１０ａにおける受信信号レベルが，ノイズレベル（ノイズフィギュア）に近づき，ＳＮ比（ＳＮＲ）が悪化して返ってビット誤り率が高くなる。このようなＳＮ比の悪化に起因するビット誤り率も，変調方式によって異なる。即ち，多値化レベルの低い変調方式では，比較的低いＳＮ比でも通信に支障を生じるようなビット誤り率にはならないが，多値化レベルの高い変調方式（即ち，通信容量の大きい方式）では，より高いＳＮ比を確保しないと，ビット誤り率が上昇する。このため，通常は，通信容量を確保するため，多値化レベルの高い変調方式に合わせた比較的高い前記親局目標受信レベルＬ０が設定されている。
【００１０】
【特許文献１】
特開２０００−２９９８４８号公報
【特許文献２】
特開平１１−１９１７９４号公報
【００１１】
【発明が解決しようとする課題】
しかしながら，図６（ｃ）に示したように，親局側の受信信号レベルが一定となるように子局側の送信レベルが制御される通信システムでは，特許文献１に示されるように，前記親局１０ａ側の受信信号レベルの低下を契機に変調方式を切り替えることができないという問題点があった。また，同じく特許文献２に示されるように，ビット誤り率によって変調方式を切り替える方式は，ビット誤り率の上昇により，多値化レベルの高い変調方式から小さい変調方式へ切り替える場合には有効であるが，多値化レベルの低い変調方式（ビット誤り率は低い）から多値化レベルの高い変調方式へ戻す場合の契機に用いることができないという問題点があった。
従って，本発明は上記事情に鑑みてなされたものであり，その目的とするところは，親局側の受信信号レベルを子局側で制御する無線通信システムにおいて，大容量の通信方式で可能な限り通信するとともに，無線通信の減衰レベルが大きく変化した場合でも，信号の歪み発生やＳＮ比の劣化によるビット誤り率の上昇を防止できる無線通信システムを提供することにある。
【００１２】
【課題を解決するための手段】
上記目的を達成するために本発明は，親局装置と１又は複数の子局装置との間で双方向の無線データ通信を行い，前記親局装置が前記子局装置から受信した信号レベルと所定の親局目標受信レベルとの比較に基づき前記子局装置に所定の補正指令を送信することにより，前記子局装置が前記親局装置に送信する信号の送信レベルを補正する無線通信システムにおいて，前記子局装置に設けられ，前記親局装置に送信する信号のレベルに関する送信レベル情報を前記親局装置に送信する送信レベル情報送出手段と，前記親局装置に設けられ，前記子局装置から受信した前記送信レベル情報に基づく所定の規則に従って，所定の変調方式切替え指令を前記子局装置に対して送信する変調方式切替え指令送出手段と，前記子局装置に設けられ，前記親局装置から受信した前記変調方式切替え指令に基いて，前記親局装置に送信する信号の変調方式を２以上の方式から選択して切り替える変調方式切替え手段と，前記親局装置に設けられ，前記変調方式切替え指令に対応させて，前記子局装置から受信した信号の復調方式を２以上の方式から選択して切り替える復調方式切替え手段と，を具備してなることを特徴とする無線通信システムである。
これにより，親局装置において子局装置の送信信号レベルに関する情報を知ることができるので，親局装置における受信信号レベルが一定に制御される通信システムにおいても，無線通信の減衰レベルの変化を捉えて適切な変調方式の切り替えが可能となる。
【００１３】
また，前記親局装置に設けられ，前記送信レベル情報に基づく所定の規則に従って，前記親局目標受信レベルを切替える親局目標受信レベル切替え手段を具備するものも考えられる。
これにより，信号の変調方式の切り替えに応じて親局の受信信号レベルを切り替えることもできるので，変調方式の切り替えと組み合わせてより柔軟な通信状態の切り替えが可能となる。
また，別の実現形態として，前記親局装置に設けられ，前記送信レベル情報に基づく所定の規則に従って，前記親局目標受信レベルを切替える旨を表すレベル切替え通知を前記子局装置に送信するレベル切替え通知送信手段と，前記子局装置に設けられ，前記親局装置から受信した前記レベル切替え通知に基づいて前記親局装置に送信する信号の送信レベルを補正する送信信号レベル補正手段と，前記親局装置に設けられ，前記レベル切替え通知に対応させて前記親局目標受信レベルを切替える親局目標受信レベル切替え手段と，を具備するものであってもよい。
【００１４】
また，前記子局装置における前記変調方式及びこれに対応する前記親局装置における前記復調方式の切り替えが，多値化レベルの異なる２以上の方式を切り替えるものが考えられる。
これにより，無線信号の減衰レベルが小さい（即ち，子局装置の送信信号レベルが低い）場合は，大容量通信が可能な多値化レベルの高い変調方式で通信を行い，無線信号の減衰レベルが大きい場合には，ビット誤り率の低い通信が可能な多値化レベルの低い変調方式で通信を行うことにより，無線信号の減衰レベルの広範囲の変化に対応可能な通信が可能となる。
【００１５】
また，前記送信レベル情報に基づく所定の規則が，前記子局装置が送信する送信信号のレベルと，該送信信号を前記子局装置において増幅する送信アンプの出力信号における，前記変調方式に対応する所定の上限レベルとの比較に基づくものであるものが考えられる。
【００１６】
また，前記送信レベル情報に基づく所定の規則により，前記変調方式が，所定の多値化レベルである第１の変調方式と，それより多値化レベルの低い第２の変調方式とから選択して切り替えられ，前記親局目標受信レベルが，前記第１の変調方式に対応する所定の第１の親局目標受信レベルと，前記第２の変調方式に対応し前記第１の親局目標受信レベルよりも低い第２の親局目標受信レベルとから選択して切り替えられるものが考えられる。
【００１７】
さらに，前記送信レベル情報に基づく所定の規則が，前記子局装置が送信する送信信号のレベルと，該送信信号を前記子局装置において増幅する送信アンプの出力信号における，前記変調方式に対応する所定の上限レベルとの比較に基づくものが考えられる。
これにより，送信アンプの出力信号レベルが上昇し過ぎることにより，子局装置の送信信号に歪みが生じてビット誤り率が上昇する前に，信号歪みの影響を受けにくい変調方式に切り替えることが可能となる。
【００１８】
また，前記送信レベル情報に基づく所定の規則が，前記子局装置の前記送信アンプの出力における信号レベルが，前記第１の変調方式に対応する第１の上限レベルを上回った際に，前記第１の変調方式から前記第２の変調方式へ切替えるとともに，前記親局目標受信レベルを前記第１の親局目標受信レベルから前記第２の親局目標受信レベルへ切り替え，前記子局装置の前記送信アンプの出力における信号レベルが，前記第１の上限レベルを前記第１及び第２の親局目標受信レベルの差分よりも下回った際に，前記第２の変調方式から前記第１の変調方式へ切り替えるとともに，前記第２の親局目標受信レベルから前記第１の親局目標受信レベルに切り替えるものが考えられる。
【００１９】
また，前記送信レベル情報に基づく所定の規則が異なるものとして，前記子局装置の前記送信アンプの出力における信号レベルが前記第１の変調方式に対応する第１の上限レベルを上回った際に，前記第１の変調方式から前記第２の変調方式へ切替え，前記子局装置の前記送信アンプの出力における信号レベルが前記第２の変調方式に対応し前記第１の上限レベルよりも高い第２の上限レベルを上回った際に，前記第１の親局目標受信レベルから前記第２の親局目標受信レベルへ切替え，前記子局装置の前記送信アンプの出力における信号レベルが前記第２の上限レベルよりも前記第１及び第２の親局目標受信レベルの差分だけ下回った際に，前記第２の親局目標受信レベルから前記第１の親局目標受信レベルへ切り替え，前記子局装置の前記送信アンプの出力における信号レベルが前記第１の上限レベルを下回った際に，前記第２の変調方式から前記第１の変調方式へ切り替えるものであってもよい。
このように，前記親局目標受信レベルを変調方式に応じて切り替えることにより，例えば，多値化レベルの低い変調方式では，比較的低いＳＮ比でもビット誤り率は小さく通信可能であるため，多値化レベルの高い変調方式の場合よりも前記親局目標受信レベルを低く設定する等により，子局装置の送信アンプの出力レベルが前記バックオフレベルを極力超えないように余裕を持たせることが可能となる。
【００２０】
また，前記子局装置が前記親局装置に送信する信号の送信レベルの補正を，前記子局装置の前記送信アンプの出力における信号レベルが，前記第２の変調方式に対応し前記第１の上限レベルよりも高い第２の上限レベル以下となる範囲で行うよう構成したものが考えられる。
これにより，子局装置の送信アンプの出力レベルを上げ過ぎることがなくなり，信号歪みによるビット誤り率の上昇を防止できる。
【００２１】
また，前記親局装置に設けられ，前記子局装置から受信したデータの誤りを検出するデータ誤り検出手段を具備し，前記変調方式切替え指令送出手段における前記所定の規則が，前記子局装置から受信した前記送信レベル情報と前記データ誤り検出手段によるデータ誤りの検出結果とに基くものであるものも考えられる。
これにより，例えば，ビット誤り率等のデータ誤りの検出結果によって多値化レベルの高い変調方式から小さい変調方式へ切り替え，多値化レベルの低い変調方式（ビット誤り率は低い）から高い変調方式へ戻す場合の契機としては，前記子局装置から受信した前記送信レベル情報を用いる等の切り替え制御が可能となる。
例えば，前記変調方式切替え指令送出手段における前記所定の規則が，前記データ誤り検出手段によるデータ誤りの検出数に関する値が前記第１の変調方式に対応する第１の上限検出値を上回った際に，前記第１の変調方式から前記第２の変調方式へ切替えるとともに，前記親局目標受信レベルを前記第１の親局目標受信レベルから前記第２の親局目標受信レベルへ切り替え，前記子局装置の前記送信アンプの出力における信号レベルが前記第１の変調方式に対応する第１の上限レベルを前記第１及び第２の親局目標受信レベルの差分よりも下回った際に，前記第２の変調方式から前記第１の変調方式へ切り替えるとともに，前記第２の親局目標受信レベルから前記第１の親局目標受信レベルに切り替えるもの等が考えられる。
また，別の例としては，前記変調方式切替え指令送出手段における前記所定の規則が，前記データ誤り検出手段によるデータ誤りの検出数に関する値が所定の第１の上限検出値を上回った際に，前記第１の変調方式から前記第２の変調方式へ切替え，前記データ誤り検出手段によるデータ誤りの検出数に関する値が所定の第２の上限検出値を上回った際に，前記第１の親局目標受信レベルから前記第２の親局目標受信レベルへ切替え，前記子局装置の前記送信アンプの出力における信号レベルが前記第２の変調方式に対応した第２の上限レベルよりも前記第１及び第２の親局目標受信レベルの差分だけ下回った際に，前記第２の親局目標受信レベルから前記第１の親局目標受信レベルへ切り替え，前記子局装置の前記送信アンプの出力における信号レベルが前記第１の変調方式に対応し前記第２の上限レベルよりも低い第１の上限レベルを下回った際に，前記第２の変調方式から前記第１の変調方式へ切り替えるものも考えられる。
【００２２】
また，前記親局装置が，前記子局装置から受信した信号の周波数を無線通信用周波数から有線通信用周波数へ変換し，前記子局装置へ送信する信号を有線通信用周波数から無線通信用周波数へ変換する親局装置中継部と，これと有線にて接続された親局装置本体部とから構成され，前記子局装置が，前記親局装置から受信した信号の周波数を無線通信用周波数から有線通信用周波数へ変換し，前記親局装置へ送信する信号を有線通信用周波数から無線通信用周波数へ変換するとともに，前記親局装置から受信した信号レベルに基づいて前記親局装置へ送信する信号レベルを調節する子局装置中継部と，これと有線にて接続された子局装置本体部とから構成されるものであってもよい。
これにより，親局装置及び子局装置において，無線通信を行う中継部を分離して設置することができ，中継部のみを障害物の影響を受けにくい高所に設置する等，適切な設置を行うことができる。
【００２３】
【発明の実施の形態】
以下添付図面を参照しながら，本発明の実施の形態及び実施例について説明し，本発明の理解に供する。尚，以下の実施の形態及び実施例は，本発明を具体化した一例であって，本発明の技術的範囲を限定する性格のものではない。
ここに，図１は本発明の実施の形態に係るＰＭＰ双方向無線通信システムＸの概略構成を表すブロック図，図２は本発明の実施の形態に係るＰＭＰ双方向無線通信システムＸにおける状態遷移図，図３は本発明の実施の形態に係るＰＭＰ双方向無線通信システムＸにおける上り信号の信号レベルの遷移を表すダイヤグラム，図４は本発明の実施例に係るＰＭＰ双方向無線通信システムＸ’における状態遷移図，図５は本発明の実施例に係るＰＭＰ双方向無線通信システムＸ’における上り信号の信号レベルの遷移を表すダイヤグラム，図６は従来のＰＭＰ双方向無線通信システムＺの概略構成を表すブロック図，図７は本発明の実施例に係るＰＭＰ双方向無線通信システムＹの概略構成を表すブロック図，図８は本発明の実施例に係るＰＭＰ双方向無線通信システムＹにおける状態遷移図，図９は本発明の実施例に係るＰＭＰ双方向無線通信システムＹ’における状態遷移図である。
【００２４】
まず，図１を用いて，本発明の実施の形態に係るＰＭＰ双方向無線通信システムＸの構成について説明する。
本ＰＭＰ双方向無線通信システムＸは，前述した図６（ａ）に示されるＰＭＰ双方向無線通信システムＺの一部について構成要素を追加・変更したものであるので，追加・変更部分についてのみ説明する。
まず，前記親局本体部１１０ａにおいては，前記通信制御部１１１ａ及び前記復調器１１３ａと通信可能に接続され，不図示のＣＰＵ，ＲＯＭ，ＲＡＭ等で構成された通信制御演算部１４０ａが追加されている。前記復調器１１３ａは，前記通信制御演算部１４０ａからの所定の切替え信号により，前記子局１０ｂからの受信信号の復調方式を１６値及び４値の２つの多値化レベルのいずれかに切り替え可能なものとしている。また，前記通信制御演算部１４０ａは，前記子局１０ｂからの受信信号に含まれる後述する子局送信レベル計算値（前記送信レベル情報の一例）を前記通信制御部１１１ａから取得し，該子局送信レベル計算値に基づく所定の規則に従って，次の２つの制御を行う。
その１つは，前記通信制御部１１１ａを介して前記子局１０ｂに対する所定の変調方式切替え指令を送信することにより，前記子局１０ｂに対し，その送信信号の変調方式を１６値又は４値の２つの多値化レベルのいずれかに切り替えさせる制御である。この際，前記変調方式切り替え指令を送信した後，該指令が反映された前記子局１０ｂからの信号が返信される所定のタイミングで，前記復調器１１３ａに対して前記切替え信号を出力することにより，前記復調器１１３ａの復調方式を切り替える。
２つ目は，前記親局目標受信レベルを切替える制御である。該親局目標受信レベルが切り替わると，切り替わり後の前記親局目標受信レベルと前記親局本体部１１０ａへの入力信号レベルとの間に，切り替わり前後の差分だけ偏差が生じる。すると，その偏差分の前記補正指令が，前記親局１０ａ側の前記通信制御部１１１ａから前記子局１０ｂ側の前記通信制御部１１１ｂに対して送信されるので，これに従い前記子局１０ｂ側の前記通信制御部１１１ｂによって前記子局本体部１１０ｂの前記送信ＧＣ１１４ｂに制御信号が出力され，前記子局本体部１１０ｂの前記送信ＧＣ１１４ｂのゲインが補正される。これにより，前記親局本体部１１０ａへの入力信号レベルは切替え後の前記親局目標受信レベルに維持される。
また，前記親局目標受信レベルを切替える旨を表すレベル切替え通知を，前記通信制御部１１１ａを介して前記子局１０ｂに送信することにより，前記親局目標受信レベルの切り替わり前後の差分だけ，前記子局１０ｂに対し，その送信信号のレベルを補正させる制御を行ってもよい。この場合の補正制御は，前記ＰＭＰ双方向無線通信システムＺにおいて，前記親局本体部１１０ａの入力信号レベルと前記親局目標受信レベルとの差に基づき行われる補正に加えて，別途行われるものである。
【００２５】
一方，前記子局本体部１１０ｂにおいては，前記通信制御部１１１ｂが，前記変調器１１２ｂ及び前記送信ＧＣ１１４ｂと通信可能に接続されている。前記通信制御部１１１ｂは，前記親局１０ａから前記変調方式切替え指令を受信した場合，前記変調器１１２ｂに対して所定の切替え信号を出力し，該切替え信号に従って，該変調器１１２ｂは前記親局への送信信号の変調方式を１６値又は４値の２つの多値化レベルのいずれかに切り替える。さらに，前記通信制御部１１１ｂは，前記親局１０ａから前記補正指令を受信した場合，前記送信ＧＣ１１４ｂに対して所定の補正信号を出力し，これに従い前記送信ＧＣ１１４ｂが前記親局目標受信レベルの切り替わり前後の差分だけ増幅ゲインの補正を行う。
また，前記送信ＧＣ１１４ｂは，該送信ＧＣ１１４ｂの出力信号レベルＣＭＴｘを前記通信制御部１１１ｂに対して所定の周期で送信する。該出力信号レベルＣＭＴｘに基づいて，前記通信制御部１１１ｂは，前記親局１０ａに送信する信号のレベルに関する情報である前記子局送信レベル計算値を算出し，該情報を定期的に前記親局１０ａに対して送信する。該子局送信レベル計算値ｋは，次式（１）によって算出される。
ｋ＝ＣＭＴｘ＋Ｇｃｌｉｐ …（１）
但し，Ｇｃｌｉｐは前記子局本体部１１０ｂの前記送信ＧＣ１１４ｂの出力端から前記子局中継部１２０ｂの前記送信アンプ１２１ｂの出力端までの最大レベル増加量，即ち，前記送信アンプ１２１ｂによる信号の増幅量及び前記周波数変換器１２３ｂによる信号の減衰量は常時一定であるので，前記中継用送信ＧＣ１２５ｂが調節限界（上限）に達したときのレベル増加量を表す定数である。これにより，前記子局送信レベル計算値ｋは，前記中継用送信ＧＣ１２５ｂが調節限界（上限）に達した場合の，前記子局１０ｂが送信する信号の送信レベルＬｏｕｔ（前記送信アンプ１２１ｂの出力信号レベル）を表すこととなる。即ち，前記子局送信レベル計算値ｋは，前記子局１０ｂが送信する信号の現在の前記送信レベルＬｏｕｔ（前記送信アンプ１２１ｂの出力信号レベル）を表すものではなく，現在の前記出力信号レベルＣＭＴｘの状態で前記中継用送信ＧＣ１２５ｂが調節限界に達した場合に，前記子局１０ｂが送信することになる信号の前記送信レベルＬｏｕｔ（前記送信アンプ１２１ｂの出力信号レベル）を表すものである。
ここでは，前記子局１０ｂ側（の前記通信制御部１１１ｂ）で前記子局送信レベル計算値ｋを計算し，前記親局１０ａに送信する信号のレベルに関する情報として前記子局送信レベル計算値ｋを前記親局１０ａに送信する構成について説明したが，前記子局１０ｂ側の演算負荷軽減やメモリ容量低減を図りたい場合等には，前記子局１０ｂ側（の前記通信制御部１１１ｂ）から，前記親局１０ａに送信する信号のレベルに関する情報として，例えば，現在の前記出力信号レベルＣＭＴｘ（前記送信レベル情報の他の一例）を前記親局１０ｂに送信し，該親局１０ａ側（例えば，前記通信制御部１１１ａ）で前記子局送信レベル計算値ｋを計算するよう構成すること等も考えられる。この場合，例えば前記親局１０ｂの前記通信制御部１１１ａ等に，前記子局１０ａそれぞれについての前記中継用送信ＧＣ１２５ｂの調節限界時レベル増加量Ｇｃｌｉｐを記憶させておけばよい。
【００２６】
次に，図２及び図３を用いて，前記親局１０ａの前記通信制御演算部１４０ａが，前記子局送信レベル計算値ｋに基づいてどのような規則で前記子局１０ｂ側の変調方式及び前記親局受信目標レベルの切替えを行うかについて説明する。
図２に示すように，前記通信制御演算部１４０ａは，前記子局送信レベル計算値ｋに基づいて，通信状態を第１及び第２の状態Ｓｔ１及びＳｔ２に切替える。ここで，前記第１の状態Ｓｔ１は，前記子局１０ｂからの送信信号の変調方式を「１６値の直交変調方式」（以下，単に１６値方式という）とするとともに，前記親局目標受信レベルを前記１６値方式に対応した第１の親局目標受信レベルＬ１（以下，単に第１の目標レベルという）とする通信状態である。一方，前記第２の状態Ｓｔ２は，前記子局１０ｂからの送信信号の変調方式を「４値の直交変調方式」（以下，単に４値方式という）とするとともに，前記親局目標受信レベルを前記４値方式に対応した第２の親局目標受信レベルＬ２（以下，単に第２の目標レベルという）とする通信状態である。前記４値方式では，前記１６値方式に比べて多値化レベルが低いため，比較的低いＳＮ比でもビット誤り率は小さく通信可能である。従って，前記第２の目標レベルＬ２は，ビット誤り率が上昇しないＳＮ比の範囲で，前記第１の目標レベルよりも小さい値に設定される（Ｌ１＞Ｌ２）。
【００２７】
前記通信制御演算部１４０ａは，図２に示すように，前記子局送信レベル計算値ｋが所定の第１のバックオフレベルＢＯ１を上回ったとき（ｋ＞ＢＯ１）に，前記第１の状態Ｓｔ１から前記第２の状態Ｓｔ２へ切り替え，前記子局送信レベル計算値ｋが前記第１のバックオフレベルＢＯ１から前記第１及び第２の目標レベルＬ１，Ｌ２の差分を差し引いた値を下回ったとき（ｋ＜ＢＯ１−（Ｌ１−Ｌ２））に，前記第２の状態Ｓｔ２から前記第１の状態Ｓｔ１へ切替える。ここで，前記第１のバックオフレベルＢＯ１は，前記１６値方式での通信において，前記子局１０ｂの送信信号レベルＬｏｕｔがそのレベルを超えると，信号歪みによるビット誤り率が上昇する前記バックオフレベルである。また，前記子局１０ｂが複数ある場合には，例えば，所定数以上或いは所定割合以上の数の前記子局１０ｂについて，図２に示す状態の切替え条件が該当したときに，前記第１及び第２の状態Ｓｔ１，Ｓｔ２の切替えを行うよう構成することが考えられる。
【００２８】
以下，前記第１及び第２の状態Ｓｔ１及びＳｔ２の間で通信状態が変化するときの，前記子局１０ｂから前記親局１０ａへの送信信号のレベルの遷移について，図３を用いて説明する。
図３において，無線信号の減衰レベルの小さい（天候が良好な）状態が信号Ｓ０である。このとき，前記中継用送信ＧＣ１２５ｂは調節限界に達していないので，前記子局送信レベル計算値ｋ＜ＢＯ１（ＣＭＴｘ＋Ｇｃｌｉｐ＜ＢＯ１）であり，初期状態（前記第１の状態Ｓｔ１）である。そして，降雨が激しくなり（無線信号の減衰レベルが大きくなり），前記中継用送信ＧＣ１２５ｂが調節限界に達すると，図中の信号Ｓ１の状態となる。この信号Ｓ１の状態でもまだ，前記子局送信レベル計算値ｋ＜ＢＯ１である。この信号Ｓ１の状態からさらに無線信号の減衰レベルが大きくなると，前記中継用送信ＧＣ１２５ｂではゲインが不足するので前記親局１０ａの受信信号レベルが前記第１の目標レベルＬ１より下がり，受信レベルの偏差が生じ始めるので，前述したように前記親局１０ｂから所定の補正指令が前記子局１０ｂに対して送信され，前記子局本体部１１０ｂの前記送信ＧＣ１１４ｂにより，その出力信号レベルＣＭＴｘが前記受信レベルの偏差分だけ補正（レベル上昇）される。これにより，前記親局１０ａの受信信号レベルは前記第１の目標レベルＬ１に維持される（信号Ｓ１と信号Ｓ２の間の状態）。
【００２９】
さらに無線通信の減衰レベルが大きくなり，前記受信レベルの偏差分による補正が所定レベルに達すると，図中の信号Ｓ２に示すように，前記子局１０ｂの送信信号レベルＬｏｕｔが前記第１のバックオフレベルＢＯ１に達し，前記子局送信レベル計算値ｋ＝ＢＯ１となる。即ち，これ以上送信信号のレベルが上昇すると，前記送信信号レベルＬｏｕｔが前記第１のバックオフレベルＢＯ１を上回り，前記１６値方式では信号歪みのために前記ビット誤り率が上昇してしまう。ここで，この信号Ｓ２の状態からさらに無線信号の減衰レベルが大きくなると，前記子局送信レベル計算値ｋ＞ＢＯ１となるので，前記状態Ｓｔ１から前記状態Ｓｔ２へ切り替わる。これにより，前記親局目標受信レベルの切り替わり前後の差分（Ｌ２−Ｌ１）だけ前記送信ＧＣ１１４ｂの出力信号レベルＣＭＴｘが補正（レベル下降）され，図中の信号Ｓ３の状態となる（図中，太線は前記状態Ｓｔ２を表す）。この状態は，前記信号Ｓ２の状態，即ち，ｋ＝ＢＯ１の状態から，前記第１及び第２の目標レベルＬ１，Ｌ２の差分だけ前記出力信号レベルＣＭＴｘが下がった状態であるので，前記子局送信レベル計算値ｋ＞ＢＯ１−（Ｌ１−Ｌ２）である。このように，前記第２の状態Ｓｔ２，即ち，多値化レベルの低い前記４値方式に切り替わると，信号歪に強い通信方式となるので，図中の信号Ｓ４に示すように，前記送信信号レベルＬｏｕｔが前記第１のバックオフレベルを越える前記４値方式での前記バックオフレベルＢＯ２（第２のバックオフレベル）まで上昇しても，安定した通信が確保できる。ここで，前記送信信号レベルＬｏｕｔが前記バックオフレベルＢＯ２を越えると，前記４値方式においてもビット誤り率が上昇してしまうので，前記送信ＧＣ１１４ｂによる送信信号の補正は，前記子局送信レベル計算値ｋ（即ち，前記送信信号レベルＬｏｕｔ）が前記バックオフレベルＢＯ２を越えない範囲として，（ＢＯ２−Ｇｃｌｉｐ）以下の範囲で行われるように設定されている。
【００３０】
逆に，前記第２の状態Ｓｔ２において，無線信号の減衰レベルが小さくなった場合，前記信号Ｓ３の状態より前記送信信号レベルＬｏｕｔが下回ったとき，即ち，ｋ＜ＢＯ１−（Ｌ１−Ｌ２）となったときに前記第１の状態Ｓｔ１へ切り替えれば，前記親局目標レベルの切り替わり（Ｌ２→Ｌ１）により，前記送信信号レベルＬｏｕｔが前記差分（Ｌ１−Ｌ２）だけ上昇しても，前記第１のバックオフレベルＢＯ１を越えることはなく，安定した通信が確保できる。
【００３１】
このような通信状態の切り替えを行うことにより，子局１０ｂ側の送信アンプ等のパワーアップ（消費電力増大化，高コスト化）を必要とせず，大容量の通信方式（前記１６値方式）で可能な限り通信するとともに，より広範囲な環境変化（無線信号の減衰レベルの変化）に対応して信頼性の高い無線通信が可能となる。即ち，変調方式を切り替えない場合に比べ，前記第１及び第２のバックオフレベルの差分（ＢＯ２−ＢＯ１）だけ大きい減衰レベル変化に対応できるのに加え，前記親局目標受信レベルを切り替えることによって，さらにその差分（Ｌ１−Ｌ２）だけ対応できる減衰レベルの変化幅を大きくすることができる。
【００３２】
【実施例】
（実施例１）
前記ＰＭＰ双方向無線通信システムＸは，通信状態を２つの状態Ｓｔ１，Ｓｔ２に切り替えるものであるが，前記子局送信信号計算値ｋに基づいて，以下に示す３つの状態Ｓｔ１０，Ｓｔ２０，Ｓｔ３０に切り替えるＰＭＰ双方向無線通信システムＸ’も考えられる。ここで，前記状態Ｓｔ１０及び前記状態Ｓｔ２０は，前記第１及び第２の状態Ｓｔ１及びＳｔ２とそれぞれ同じ状態，前記状態Ｓｔ２０は，変調方式のみを前記４値方式とし（復調方式も対応させる），前記親局目標受信レベルは前記第１の目標レベルＬ１のままとする状態である。
これら３つの状態Ｓｔ１０，Ｓｔ２０，Ｓｔ３０は，前記通信制御演算部１４０ａが，図４に示すように切り替える。即ち，前記子局送信レベル計算値ｋが前記第１のバックオフレベルＢＯ１を上回ったとき（ｋ＞ＢＯ１）に，前記状態Ｓｔ１０から前記Ｓｔ２０へ切り替え，前記子局送信レベル計算値ｋが前記第２のバックオフレベルＢＯ２を上回ったとき（ｋ＞ＢＯ２）に，前記状態Ｓｔ２０から前記状態Ｓｔ３０へ切り替え，前記子局送信レベル計算値ｋが前記第２のバックオフレベルＢＯ２に前記第１及び第２の目標レベルＬ１，Ｌ２の差分だけ減算したレベルを下回ったとき（ｋ＜ＢＯ２−（Ｌ１−Ｌ２））に，前記状態Ｓｔ３０から前記状態Ｓｔ２０へ切り替え，前記子局送信レベル計算値ｋが前記第１のバックオフレベルＢＯ１を下回ったとき（ｋ＜ＢＯ１）に，前記状態Ｓｔ２０から前記状態Ｓｔ１０へ切り替える。
【００３３】
以下，前記状態Ｓｔ１０，Ｓｔ２０，及びＳｔ３０の間で通信状態が変化するときの，前記子局１０ｂから前記親局１０ａへの送信信号のレベルの遷移について，図５を用いて説明する。
図５において，無線信号の減衰レベルの小さい（天候が良好な）状態が信号Ｓ０である。このとき，前記中継用送信ＧＣ１２５ｂは調節限界に達していないので，前記子局送信レベル計算値ｋ＜ＢＯ１（ＣＭＴｘ＋Ｇｃｌｉｐ＜ＢＯ１）であり，初期状態（前記状態Ｓｔ１０）である。そして，降雨が激しくなり（無線信号の減衰レベルが大きくなり），前記中継用送信ＧＣ１２５ｂが調節限界に達すると，図中の信号Ｓ１の状態となる。この信号Ｓ１の状態でもまだ，前記子局送信レベル計算値ｋ＜ＢＯ１である。この信号Ｓ１の状態からさらに無線信号の減衰レベルが大きくなると，前記中継用送信ＧＣ１２５ｂでは前記親局１０ａの受信信号レベルが前記第１の目標レベルＬ１より下がり，受信レベルの偏差が生じ始めるので，前述したように前記親局１０ｂから所定の補正指令が前記子局１０ｂに対して送信され，前記親局本体部１１０ｂの前記送信ＧＣ１１４ｂにより，その出力信号レベルＣＭＴｘが前記受信レベルの偏差分だけ補正（レベル上昇）される。これにより，前記親局１０ａの受信信号レベルは前記第１の目標レベルＬ１に維持される。
【００３４】
前記受信レベルの偏差分の補正が所定レベルに達すると，図中の信号Ｓ２に示すように，前記子局１０ｂの送信信号レベルＬｏｕｔが前記第１のバックオフレベルＢＯ１に達し，前記子局送信レベル計算値ｋ＝ＢＯ１となる。即ち，これ以上送信信号のレベルが上昇すると，前記送信信号レベルＬｏｕｔが前記第１のバックオフレベルＢＯ１を上回り，前記１６値方式では信号歪みのために前記ビット誤り率が上昇してしまう。ここで，この信号Ｓ２の状態からさらに無線信号の減衰レベルが大きくなると，前記子局送信レベル計算値ｋ＞ＢＯ１となるので，前記状態Ｓｔ１０から前記状態Ｓｔ２０へ切り替わる。これにより，多値化レベルの低い前記４値方式となるため，前記送信信号レベルＬｏｕｔが前記第１のバックオフレベルを越えてもビット誤り率の上昇は生じない。
【００３５】
ここからさらに無線通信の減衰レベルが大きくなると，図中Ｓ３に示すように，前記子局１０ｂの送信信号レベルＬｏｕｔが前記第２のバックオフレベルＢＯ２に達し，前記子局送信レベル計算値ｋ＝ＢＯ２となる（図中，太い実線は前記状態Ｓｔ２０を表す）。即ち，これ以上前記送信信号レベルＬｏｕｔが上昇すると，前記第２のバックオフレベルＢＯ２を上回り，前記４値方式でも信号歪みのために前記ビット誤り率が上昇してしまう。ここで，この信号Ｓ３の状態からさらに無線信号の減衰レベルが大きくなると，前記子局送信レベル計算値ｋ＞ＢＯ２となるので，前記状態Ｓｔ２０から前記状態Ｓｔ３０へ切り替わる。これにより，前記親局目標受信レベルの切り替わり前後の差分（Ｌ２−Ｌ１）だけ前記送信ＧＣ１１４ｂの出力信号レベルＣＭＴｘが補正（レベル下降）され，図中の信号Ｓ４の状態となる（図中，太い破線は前記状態Ｓｔ３０を表す）。この状態は，前記信号Ｓ３の状態，即ち，ｋ＝ＢＯ２の状態から，前記第１及び第２の目標レベルＬ１，Ｌ２の差分だけ前記出力信号レベルＣＭＴｘが下がった状態なので，前記子局送信レベル計算値ｋ＞ＢＯ２−（Ｌ１−Ｌ２）である。このように前記親局目標受信レベルを前記目標レベルＬ２に切り替えることにより，さらに無線信号の減衰レベルが大きくなった場合でも，図中Ｓ５で示すように，前記送信信号レベルＬｏｕｔを前記第２のバックオフレベルＢＯ２となるまで（ｋ＝ＢＯ２まで）上昇させても，安定した通信が確保できる。
【００３６】
逆に，前記状態Ｓｔ３０において，無線信号の減衰レベルが小さくなった場合，前記信号Ｓ４の状態より前記送信信号レベルＬｏｕｔが下回ったとき，即ち，ｋ＜ＢＯ２−（Ｌ１−Ｌ２）となったときに前記状態Ｓｔ２０へ切り替えれば，前記親局目標レベルの切り替わりにより，前記送信信号レベルＬｏｕｔが前記差分（Ｌ１−Ｌ２）だけ上昇しても，前記第２のバックオフレベルＢＯ２を越えることはなく，安定した通信が確保できる。
さらに，前記状態Ｓｔ２０において，前記信号Ｓ２の状態より前記送信信号レベルＬｏｕｔが下回ったとき，即ち，ｋ＜ＢＯ１となったときに前記状態Ｓｔ１０へ切り替えれば，最大限の範囲で多値化レベルの高い前記１６値方式の大容量通信が行えることとなる。
【００３７】
このような通信状態の切り替えを行うことにより，前記ＰＭＰ双方向無線通信システムＸと同様に，大容量の通信方式で可能な限り通信するとともに，より広範囲な環境変化（無線信号の減衰レベルの変化）に対応して信頼性の高い無線通信が可能となる。さらに，多値化レベルの低い前記４値方式においても，可能な限り前記親局目標受信レベルが高いレベル（ＳＮ比が高い状態）で維持されるので，よりノイズに強い（ビット誤り率を抑制できる）通信が可能となるとともに，前記親局目標受信レベルの切り替わり時に，前記親局本体部１１０ｂの前記送信ＧＣ１１４ｂによる送信信号レベルの制御が収束するまでに生じる一時的な通信の不安定化についても，その発生頻度を最小限にすることができる。
【００３８】
（実施例２）
前記ＰＭＰ双方向無線通信システムＸは，通信状態の切り替えを，前記子局送信信号計算値ｋに基づいて行うものであったが，該子局送信信号計算値ｋ（前記送信レベル情報の一例）と前記親局１０ａにおいて前記子局１０ｂから受信したデータの誤り検出結果とに基づいて通信状態の切り替えを行うＰＭＰ双方向無線通信システムＹも考えられる。以下，図７及び図８を用いて，このようなＰＭＰ双方向無線通信システムＹについて説明する。
図７にＰＭＰ双方向無線通信システムＹの概略構成を表す。
図７に示すように，ＰＭＰ双方向無線通信システムＹは，前記ＰＭＰ双方向無線通信システムＸにおける前記子局１０ｂの前記通信制御部１１１ｂと前記変調器１１２ｂとの間に，前記親局１０ａへ送信する通信データ（前記変調器１１２ｂによる変調前の通信データ）を符号化する手段であるＦＥＣ（Forward Error Correction）エンコーダ１１６ｂが，前記親局１０ａの前記復調器１１３ａと前記通信制御部１１１ａとの間に，前記子局１０ｂから受信した通信データ（前記復調器１１３ａによる復調後の通信データ）を復号化するとともに，該復号化を正常に行えない場合にその通信データに誤りが生じていることを検出（データ誤りを検出）する手段であるＦＥＣデコーダ１１６ａがそれぞれ追加挿入されたものであり，その他の構成は前記ＰＭＰ双方向無線通信システムＸと同じである。ここでは，前記ＦＥＣエンコーダ１１６ｂは，通信データのリードソロモン符号化を行うとともに，データ誤り検出用の冗長データを付加するものであり，前記ＦＥＣデコーダ１１６ａ（前記データ誤り検出手段の一例）は，リードソロモン符号化がなされた通信データを復号化する際に前記冗長データを用いて可能な範囲でデータ誤りを除去（復旧）するとともに，データ誤りの発生有無を検出するものである。
また，前記ＦＥＣデコーダ１１６ａは，前記通信制御演算部１４０ａと通信可能に接続されており，前記通信制御演算部１４０ａは，前記ＦＥＣデコーダ１１６ａから通信データのデータ誤り検出数に関する誤り情報を取得することが可能である。リードソロモン符号化では，ブロック単位での誤りの有無を検出することが可能であり，前記ＦＥＣデコーダ１１６ａにより，復号時に検出される誤りの数（検出数）を一定時間ごとに（例えば，１秒ごとに）積算して単位時間当たりの誤り率Ｅｒが計算され，該誤り率が前記誤り情報として前記通信制御演算部１４０ａに送信される。ここで，前記誤り率の計算に用いる前記誤りの数は，前記ＦＥＣデコーダ１１６ａによって誤り訂正ができなかった件数（誤り訂正後の誤りの数）としても，誤り訂正を行う前の全誤り検出数（誤り訂正に成功した件数＋誤り訂正に失敗した件数）としてもよいが，通信に支障をきたす前に兆候段階で早期に通信状態を検知するためには，誤り訂正を行う前の全誤り検出数を用いる方が望ましい。
【００３９】
本ＰＭＰ双方向無線通信システムＹも，前記ＰＭＰ双方向無線通信システムＸと同じく，前記親局１０ａの前記通信制御演算部１４０ａによる前記第１の状態Ｓｔ１と前記第２の状態Ｓｔ２との切替え（前記子局１０ｂ側の変調方式及び前記親局受信目標レベルの切替え）を行うが，前記ＰＭＰ双方向無線通信システムＸとは，その切替え規則が異なっている。その他の動作は，前記ＰＭＰ双方向無線通信システムＸと同じであるので説明を省略し，以下，図８を用いて，前記状態Ｓｔ１と前記状態Ｓｔ２との切替え規則について説明する。
図８に示すように，前記通信制御演算部１４０ａは，前記子局送信レベル計算値ｋと前記ＦＥＣデコーダ１１６ａから取得した前記誤り率Ｅｒ（データ誤り検出数に関する値）とに基づいて，通信状態を前記第１及び第２の状態Ｓｔ１及びＳｔ２に切替える。
具体的には，前記通信制御演算部１４０ａは，図８に示すように，前記ＦＥＣデコーダ１１６ａから取得した前記誤り率Ｅｒが所定の第１の上限検出値Ｅ１を上回ったとき（Ｅｒ＞Ｅ１）に，前記第１の状態Ｓｔ１から前記第２の状態Ｓｔ２へ切り替え（多値化レベルの高い変調方式から低い変調方式へ切替え），前記子局送信レベル計算値ｋが前記第１のバックオフレベルＢＯ１（図３参照）から前記第１及び第２の目標レベルＬ１，Ｌ２の差分を差し引いた値を下回ったとき（ｋ＜ＢＯ１−（Ｌ１−Ｌ２））に，前記第２の状態Ｓｔ２から前記第１の状態Ｓｔ１へ切替える（Ｓｔ２→Ｓｔ１の切替え規則は前記ＰＭＰ双方向無線通信システムＸと同じ）。
ここで，前記第１の上限検出値Ｅ１は，前記１６値方式での通信（前記状態Ｓｔ１０）において，前記子局１０ｂの送信信号レベルＬｏｕｔが前記第１のバックオフレベルＢＯ１を超えたときに生じる信号歪みに起因して，前記親局１０ａ側で検出される前記誤り率Ｅｒのしきい値（予め設定される定数）である。即ち，前記状態Ｓｔ１０にある場合に，前記誤り率Ｅｒが前記第１の上限検出値Ｅ１を超えた場合には，前記子局１０ｂの送信信号レベルＬｏｕｔが前記第１のバックオフレベルＢＯ１を超えたとほぼみなせるよう，前記第１の上限検出値Ｅ１が設定される。また，前記第１のバックオフレベルＢＯ１は，前述したように，前記１６値方式での通信において，前記子局１０ｂの送信信号レベルＬｏｕｔがそのレベルを超えると，信号歪みによるビット誤り率（前記誤り率Ｅｒ）が上昇する（前記第１の上限検出値Ｅ１を超えることが多い）前記バックオフレベルである。
また，前記子局１０ｂが複数ある場合には，例えば，所定数以上或いは所定割合以上の数の前記子局１０ｂについて，図８に示す状態の切替え条件が該当したときに，前記第１及び第２の状態Ｓｔ１，Ｓｔ２の切替えを行うよう構成することが考えられる。
また，前記状態Ｓｔ１から前記状態Ｓｔ２への切替え条件を，前記子局送信レベル計算値ｋと前記誤り率Ｅｒとの組み合わせとしたものであってもよい。例えば，（ｋ＞ＢＯ１）の条件と（Ｅｒ＞Ｅ１）の条件とのＡＮＤ又はＯＲを切替え条件とする等である。これにより，より適切な切替え制御が可能となる。
以上のような切り替え制御により，前記ＰＭＰ双方向無線通信システムＸにおける前記子局１０ｂから前記親局１０ａへの送信信号のレベルの遷移（図３）と同様に送信信号（子局１０ｂ→前記親局１０ａ）のレベルが遷移することになり，前記ＭＰ双方向無線通信システムＸと同様の効果を奏することになる。
【００４０】
（実施例３）
続いて，図９を用いて，前記ＰＭＰ双方向無線通信システムＹの応用例であるＰＭＰ双方向無線通信システムＹ’について説明する。
ＰＭＰ双方向無線通信システムＹ’は，前記ＰＭＰ双方向無線通信システムＹにおいて，前記ＰＭＰ双方向無線通信システムＸ’と同じく通信状態を３つの前記状態Ｓｔ１０，Ｓｔ２０，Ｓｔ３０に切り替えるものである。ここで，前記状態Ｓｔ１０，Ｓｔ２０，Ｓｔ３０は，前記ＰＭＰ双方向無線通信システムＸ’の場合と同じである。また，システム構成及び動作（前記状態Ｓｔ１０，Ｓｔ２０，Ｓｔ３０の切替え規則を除く）は前記ＰＭＰ双方向無線通信システムＹ（図７）と同じである。
前述の３つの状態Ｓｔ１０，Ｓｔ２０，Ｓｔ３０は，前記通信制御演算部１４０ａが，図９に示すように切り替える。即ち，前記状態Ｓｔ１０にある場合であって前記ＦＥＣデコーダ１１６ａから取得した前記誤り率Ｅｒが前記第１の上限検出値Ｅ１を上回ったとき（Ｅｒ＞Ｅ１）に，前記状態Ｓｔ１０から前記Ｓｔ２０へ切り替え（多値化レベルの高い変調方式から低い変調方式へ切替え），前記状態Ｓｔ２０にある場合であって前記誤り率Ｅｒが所定の第２の上限検出値Ｅ２を上回ったとき（Ｅｒ＞Ｅ２）に，前記状態Ｓｔ２０から前記状態Ｓｔ３０へ切り替え，前記子局送信レベル計算値ｋが前記第２のバックオフレベルＢＯ２に前記第１及び第２の目標レベルＬ１，Ｌ２の差分だけ減算したレベルを下回ったとき（ｋ＜ＢＯ２−（Ｌ１−Ｌ２））に，前記状態Ｓｔ３０から前記状態Ｓｔ２０へ切り替え，前記子局送信レベル計算値ｋが前記第１のバックオフレベルＢＯ１を下回ったとき（ｋ＜ＢＯ１）に，前記状態Ｓｔ２０から前記状態Ｓｔ１０へ切り替える。
ここで，前記第２の上限検出値Ｅ２は，前記４値方式での通信（前記状態Ｓｔ２０）において，前記子局１０ｂの送信信号レベルＬｏｕｔが前記第２のバックオフレベルＢＯ２を超えたときに生じる信号歪みに起因して，前記親局１０ａ側で検出される前記誤り率Ｅｒのしきい値（予め設定される定数）である。即ち，前記状態Ｓｔ２０にある場合に，前記誤り率Ｅｒが前記第２の上限検出値Ｅ２を超えた場合には，前記子局１０ｂの送信信号レベルＬｏｕｔが前記第１のバックオフレベルＢＯ２を超えたとほぼみなせるよう，前記第２の上限検出値Ｅ２が設定される。この第２の上限検出値Ｅ２及び前記第１の上限検出値の各値とその大小関係等は，使用環境や構成機器の特性，要求性能等によって定められるものである。また，前記第２のバックオフレベルＢＯ２は，前述したように，前記４値方式での通信において，前記子局１０ｂの送信信号レベルＬｏｕｔがそのレベルを超えると，信号歪みによるビット誤り率（前記誤り率Ｅｒ）が上昇する（前記第２の上限検出値Ｅ２を超えることが多い）前記バックオフレベルである。
以上のような切り替え制御により，前述したＰＭＰ双方向無線通信システムＸ’における前記子局１０ｂから前記親局１０ａへの送信信号のレベルの遷移（図５）と同様に送信信号（子局１０ｂ→前記親局１０ａ）のレベルが遷移することになり，前記ＭＰ双方向無線通信システムＸ’と同様の効果を奏することになる。
また，前記状態Ｓｔ１０から前記状態Ｓｔ２０への切替え条件や前記状態Ｓｔ２０から前記状態Ｓｔ３０への切替え条件を，前記子局送信レベル計算値ｋと前記誤り率Ｅｒとの組み合わせとしたものであってもよい。例えば，前記状態Ｓｔ１０から前記状態Ｓｔ２０への切替え条件を，（ｋ＞ＢＯ１）の条件と（Ｅｒ＞Ｅ１）の条件とのＡＮＤ又はＯＲを切替え条件とし，前記状態Ｓｔ２０から前記状態Ｓｔ３０への切替え条件を，（ｋ＞ＢＯ２）の条件と（Ｅｒ＞Ｅ２）の条件とのＡＮＤ又はＯＲを切替え条件とする等である。これにより，より適切な切替え制御が可能となる。
【００４１】
【発明の効果】
以上説明したように，本発明によれば，親局において子局の送信信号レベルに関する情報を知ることができるので，親局側の受信信号レベルを子局側で制御する無線通信システムにおいても，無線通信の減衰レベルの変化を捉えて適切な変調方式の切り替えが可能となり，可能な限り大容量の通信方式で通信するとともに，無線通信の減衰レベルが大きく変化した場合でも，信号の歪み発生やＳＮ比の劣化によるビット誤り率の上昇を防止することができる。しかも，子局側の送信アンプ等のパワーアップ（消費電力増大化，高コスト化）も必要としない。
また，親局において，子局から受信したデータの誤りを検出し，その検出結果も用いて変調方式を切り替えることにより，より適切な変調方式の切替えが可能となる。
【図面の簡単な説明】
【図１】本発明の実施の形態に係るＰＭＰ双方向無線通信システムＸの概略構成を表すブロック図。
【図２】本発明の実施の形態に係るＰＭＰ双方向無線通信システムＸにおけるにおける状態遷移図。
【図３】本発明の実施の形態に係るＰＭＰ双方向無線通信システムＸにおける上り信号の信号レベルの遷移を表すダイヤグラム。
【図４】本発明の実施例に係るＰＭＰ双方向無線通信システムＸ’における状態遷移図。
【図５】本発明の実施例に係るＰＭＰ双方向無線通信システムＸ’における上り信号の信号レベルの遷移を表すダイヤグラム。
【図６】従来のＰＭＰ双方向無線通信システムＺの概略構成を表すブロック図及び信号レベルの遷移を表すダイヤグラム。
【図７】本発明の実施例に係るＰＭＰ双方向無線通信システムＹの概略構成を表すブロック図。
【図８】本発明の実施例に係るＰＭＰ双方向無線通信システムＹにおける状態遷移図。
【図９】本発明の実施例に係るＰＭＰ双方向無線通信システムＹ’における状態遷移図。
【符号の説明】
１０ａ…親局
１０ｂ…子局
１１０ａ…親局本体部
１１０ｂ…子局本体部
１１１ａ，１１１ｂ…通信制御部
１１２ａ，１１２ｂ…変調器
１１３ａ，１１３ｂ…復調器
１１４ｂ…送信ＧＣ（Gain Controller）
１１５ｂ…受信ＡＧＣ（Auto Gain Controller）
１１６ａ…ＦＥＣ（Forward Error Correction）デコーダ
１１６ｂ…ＦＥＣエンコーダ
１２０ａ…親局中継部
１２０ｂ…子局中継部
１２１ａ，１２１ｂ…送信アンプ
１２２ａ，１２２ｂ…ＬＮＡ（Low Noise Amplifier）
１２３ａ，１２３ｂ，１２４ａ，１２４ｂ…周波数変換器
１２５ｂ…中継用送信ＧＣ
１２６ｂ…中継用受信ＡＧＣ
１３０ａ，１３０ｂ…通信ケーブル
１４０ａ…通信制御演算部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wireless communication system that performs bidirectional wireless data communication between a master station and one or more slave stations, such as bidirectional CATV.
[0002]
[Prior art]
In recent years, with the rapid spread of data communication, the demand for high-speed network is increasing. However, in many cases, high-speed lines provided by wire require installation and wiring work for each house, and indoor wiring work is also required when changing the indoor layout. . Therefore, it is desired to spread a wireless communication network that does not require complicated wiring work for each house.
As a system that meets such needs, for example, Patent Document 1 proposes a bidirectional wireless CATV system in which an existing CATV (cable television) network is used and the end portion of the network is replaced with radio. This is a one-to-many (PMP) bi-directional radio that transmits and receives data between a master station device (base station) and a plurality of slave station devices (subscriber stations) using microwaves to millimeter waves of 10 GHz or more. It is a communication system and can be used for communication services that require broadband, such as providing video data such as movies on demand in addition to Internet connection services.
[0003]
FIG. 6A is a block diagram illustrating a schematic configuration of the PMP bidirectional wireless communication system Z disclosed in Patent Document 1. In FIG.
The master station 10a is composed of a master station main body 110a and a master station relay section 120a, and by connecting them with a communication cable 130a, only the master station relay section 120a is installed at a high place, etc. It can be installed separately. Similarly, the slave station 10b includes a slave station main body 110b and a slave station relay unit 120b, which are connected by a communication cable 130b.
In data transmission from the master station 10a to the slave station 10b, a transmission signal to the slave station 10b generated by the communication control unit 111a of the master station 10a is subjected to, for example, 64-level quadrature modulation by the modulator 112a. After being transmitted, it is transmitted to the frequency converter 123a of the master station relay unit 120a as a low frequency signal with small transmission attenuation in the communication cable 130a, and after being converted into a high frequency signal for wireless communication by the frequency converter 123a, Amplified by the transmission amplifier 121a and transmitted as a radio signal to the slave station 10b by an antenna (not shown). In the slave station 10b, a radio signal is received by an antenna (not shown), amplified by an LNA (Low Noise Amplifier) 122b of the slave station relay unit 120b, and then converted into a low frequency signal by a frequency converter 124b. Is done. Further, a signal whose level is adjusted by a relay reception AGC (Auto Gain Controller) 126b so that the level of the low-frequency signal becomes a predetermined level is received by the reception AGC 115b of the slave station main body 110b via the communication cable 130b. Then, the reception AGC 115b supplementarily corrects the level that could not be adjusted by the relay reception AGC 126b, and then demodulated by the demodulator 113b and taken into the communication controller 111b.
[0004]
On the other hand, in data transmission from the slave station 10b to the master station 10a, a transmission signal to the master station 10a generated by the communication control unit 111b is subjected to, for example, 16-value quadrature modulation by the modulator 112b. The modulated signal is subjected to later-described gain correction (amplification) by a transmission GC (Gain Controller) 114b, and then transmitted to the transmission GC 114b of the slave station relay unit 120b via the communication cable 130b. The transmission GC 114b amplifies the gain with a gain proportional to the adjustment level in the relay reception AGC 126b. As described above, the adjustment level in the relay reception AGC 126b is adjusted according to the reception signal level from the master station 10a. As a result, the gain (amplification amount) of the relay transmission GC 125b is also increased. It is adjusted according to the received signal level from the master station 10a. The signal level-adjusted in this way is further converted into a high-frequency signal for wireless communication by the frequency converter 123b, then amplified by the transmission amplifier 121b, and transmitted from the antenna (not shown) to the master station 10a. As sent. In the master station 10a, a radio signal transmitted from the slave station 10b is received by an antenna (not shown), amplified by the LNA 122a of the master station relay unit 120a, and then transmitted via the communication cable 103a. A signal transmitted to the demodulator 113a of the station main body 110a and demodulated by the demodulator 113a is taken into the communication control unit 111a on the master station main body 110a side.
As described above, since the main unit 110a, 110b and the relay unit 120a, 120b are separated from each other in the master station 10a and the slave station 10b, only the relay units 120a, 120b that perform wireless communication are used as obstacles. Appropriate installation is possible, such as installation in high places where it is difficult to be affected by
[0005]
(Downlink signal)
FIG. 6B is a diagram showing an example of signal level transition of a downstream signal from the modulator 112a of the master station 10a to the demodulator 113b of the slave station 10b.
For example, under a clear sky, as indicated by the solid line Sd0 in FIG. 6B, the signal output from the transmission amplifier 121a of the master station relay unit 120a has a relatively low attenuation level of the radio signal. The LNA 122b of the slave station relay unit 120b is reached at a relatively high level. However, under severe weather, the attenuation level of the radio signal is large, so that the LNA 122b is reached at a low level. Since the change in the received signal level in the slave station 10b is adjusted by the relay reception AGC 126b in accordance with the change, the signal input to the receive AGC 115b in the slave station main body 110b is usually a predetermined signal. Maintained at a certain level. The result of adjusting the reception level to the adjustment limit of the relay reception AGC 126b in this way is shown by a thin broken line Sd1 in FIG.
However, if the rainfall further increases and the attenuation level of the radio signal increases beyond the adjustment limit of the relay reception AGC 126b, the input signal of the reception AGC 115b is predetermined as shown by the thick broken line Sd2 in FIG. Lower than the level. Even in such a case, the level of the signal input to the demodulator 113b of the slave station body 110b is corrected by the reception AGC 115b of the slave station body 110b.
[0006]
(Uplink signal)
Level adjustment similar to that described above is also performed in the upstream signal from the slave station 10b to the master station 10a. FIG. 6C is a diagram showing an example of signal level transition of the upstream signal.
The output signal level of the transmission amplifier 121b of the slave station relay unit 120b is output at a relatively low level as shown by a solid line Su0 in FIG. When the attenuation level is large, the relay transmission GC 125b adjusts the level to a higher level so that the arrival level at the master station 10a is constant. The level adjustment is performed in accordance with the level of the received signal from the master station 10a, that is, so as to amplify the level of the received signal. The radio signal from the master station 10a and the radio signal from the slave station 10b have the same communication path, and their attenuation levels are the same. As a result, the signal level reaching the master station 10a is It remains constant at a predetermined level. The result of adjusting the transmission level to the adjustment limit of the relay transmission GC 125b in this way is shown by a thin broken line Su1 in FIG. 6 (c).
[0007]
However, if the rainfall further increases and the attenuation level of the radio signal increases beyond the adjustment limit of the relay transmission GC 125b, the signal reaching the master station 10a as shown by the thick broken line Su2 in FIG. The level decreases, and the input signal of the master station main body 110a falls below a predetermined level L0 (hereinafter referred to as master station target reception level). At this time, a predetermined correction command is transmitted from the communication control unit 111a on the master station 10a side to the communication control unit 111b on the slave station 10b side, and the communication control unit 111b on the slave station 10b side is accordingly transmitted. As a result, a control signal is output to the transmission GC 114b of the slave station body 110b, and the transmission GC 114b of the slave station body 110b is equal to the difference between the input signal in the master station body 110a and the target reception level L0. The gain is corrected. As a result, as indicated by the thick broken line Su3 in FIG. 6C, the input signal level to the master station main body 110a is maintained at the master station target reception level L0.
[0008]
However, when the attenuation level of the wireless communication is particularly large (rainfall is very intense, etc.) and reaches the state of the thick broken line Su3 in FIG. 6C, the output level of the transmission amplifier 121b of the master station relay unit 120b is A bit error rate of communication is increased by exceeding a predetermined upper limit level BO (hereinafter referred to as a back-off level) and causing distortion in the signal. If the bit error rate is increased in this manner, communication is significantly hindered.
Since the bit error rate resulting from signal distortion varies depending on the signal modulation scheme, the back-off level BO that affects the actual communication varies depending on the signal modulation scheme. That is, even when the same degree of distortion occurs in the signal, the bit error rate is lower as the modulation scheme has a lower multilevel, so the backoff level BO is higher in the modulation scheme having a lower multilevel. The backoff level BO is relatively low in a modulation scheme with a high multilevel. However, the higher the multi-level modulation method, the larger the communication capacity per unit time and the higher speed data communication is possible. Therefore, it is desirable to perform communication using a higher multi-level modulation method.
In order to prevent the bit error rate from increasing due to such characteristics, Patent Document 2 discloses a case where the level of a received signal from a partner station is reduced or the bit error rate (number of errors) is related to optical wireless communication. Proposals have been made to switch the modulation method when the signal rises. As a result, communication is normally performed with a modulation method having a large communication capacity, and when the received signal level is lowered, communication is performed with a modulation method having a low bit error rate, so that efficient communication as a whole can be performed.
[0009]
By the way, if the master station target reception level L0 is lowered, the output level of the transmission amplifier 121b in the slave station 10b can be lowered and the back-off level BO cannot be exceeded. When the level L0 is lowered, the received signal level at the master station 10a approaches the noise level (noise figure), the SN ratio (SNR) deteriorates and returns, and the bit error rate increases. The bit error rate resulting from such a deterioration of the SN ratio also differs depending on the modulation method. That is, with a modulation scheme with a low multilevel level, a bit error rate that does not interfere with communication even at a relatively low signal-to-noise ratio is not obtained, but a modulation scheme with a high multilevel level (that is, a mode with a large communication capacity). If the higher S / N ratio is not secured, the bit error rate increases. For this reason, normally, in order to ensure communication capacity, a relatively high master station target reception level L0 is set in accordance with a modulation scheme having a high multilevel level.
[0010]
[Patent Document 1]
JP 2000-299848 A
[Patent Document 2]
JP 11-191794 A
[0011]
[Problems to be solved by the invention]
However, as shown in FIG. 6C, in a communication system in which the transmission level on the slave station side is controlled so that the reception signal level on the master station side is constant, There was a problem that the modulation method could not be switched when the received signal level on the master station 10a side decreased. Similarly, as disclosed in Patent Document 2, the method of switching the modulation method according to the bit error rate is effective when switching from a modulation method having a high multilevel to a smaller modulation method due to an increase in the bit error rate. However, there is a problem that it cannot be used as a trigger when returning from a modulation system with a low multilevel (low bit error rate) to a modulation system with a high multilevel.
Accordingly, the present invention has been made in view of the above circumstances, and the object of the present invention is to enable a large-capacity communication system in a wireless communication system that controls the reception signal level on the master station side on the slave station side. An object of the present invention is to provide a wireless communication system capable of performing as much communication as possible and preventing an increase in bit error rate due to signal distortion and SN ratio degradation even when the attenuation level of wireless communication changes greatly.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the present invention performs bidirectional wireless data communication between a master station device and one or more slave station devices, and a signal level received from the slave station device by the master station device In a wireless communication system for correcting a transmission level of a signal transmitted from the slave station device to the master station device by transmitting a predetermined correction command to the slave station device based on a comparison with a predetermined master station target reception level , Provided in the slave station device, and provided in the master station device, transmission level information transmitting means for transmitting to the master station device transmission level information relating to the level of a signal transmitted to the master station device, and the slave station device A modulation method switching command sending means for transmitting a predetermined modulation method switching command to the slave station device according to a predetermined rule based on the transmission level information received from the slave station device, Based on the modulation method switching command received from the station device, provided in the parent station device, modulation method switching means for selecting and switching the modulation method of the signal transmitted to the parent station device from two or more methods, A radio communication system, comprising: a demodulating system switching means for selecting and switching a demodulating system of a signal received from the slave station device from two or more systems in response to a modulation system switching command; is there.
As a result, since the master station device can know information on the transmission signal level of the slave station device, even in a communication system in which the received signal level in the master station device is controlled to be constant, the change in the attenuation level of the wireless communication is captured. Therefore, it is possible to switch the appropriate modulation method.
[0013]
Further, it may be considered that the master station apparatus includes a master station target reception level switching means for switching the master station target reception level according to a predetermined rule based on the transmission level information.
As a result, the received signal level of the master station can be switched in accordance with the switching of the signal modulation method, so that a more flexible communication state can be switched in combination with the switching of the modulation method.
Further, as another implementation mode, a level provided in the master station device and for transmitting a level switching notification indicating that the master station target reception level is switched according to a predetermined rule based on the transmission level information to the slave station device A switching notification transmission means, a transmission signal level correction means for correcting a transmission level of a signal provided in the slave station apparatus and transmitted to the master station apparatus based on the level switching notification received from the master station apparatus; And a master station target reception level switching means for switching the master station target reception level in response to the level switching notification.
[0014]
In addition, switching of the modulation method in the slave station device and the demodulation method in the master station device corresponding to the modulation method may switch between two or more methods having different multilevel levels.
As a result, when the attenuation level of the radio signal is small (that is, the transmission signal level of the slave station device is low), communication is performed using a modulation method with a high multilevel that enables large-capacity communication. If the signal is large, communication is possible with a wide range of changes in the attenuation level of the radio signal by performing communication using a modulation method with a low multilevel which enables communication with a low bit error rate.
[0015]
Further, the predetermined rule based on the transmission level information corresponds to the modulation method in the level of the transmission signal transmitted by the slave station device and the output signal of the transmission amplifier that amplifies the transmission signal in the slave station device. One based on a comparison with a predetermined upper limit level is conceivable.
[0016]
Further, according to a predetermined rule based on the transmission level information, the modulation method is selected from a first modulation method having a predetermined multi-value level and a second modulation method having a lower multi-value level. The master station target reception level corresponds to the predetermined first master station target reception level corresponding to the first modulation scheme and the first master station target reception corresponding to the second modulation scheme. A second master station target reception level lower than the level can be selected and switched.
[0017]
Further, the predetermined rule based on the transmission level information corresponds to the modulation scheme in the level of the transmission signal transmitted by the slave station device and the output signal of the transmission amplifier that amplifies the transmission signal in the slave station device. Based on a comparison with a predetermined upper limit level is conceivable.
This makes it possible to switch to a modulation method that is less susceptible to signal distortion before the bit error rate rises due to distortion in the transmission signal of the slave station device due to an excessive increase in the output signal level of the transmission amplifier. It becomes.
[0018]
Further, the predetermined rule based on the transmission level information indicates that when the signal level at the output of the transmission amplifier of the slave station device exceeds a first upper limit level corresponding to the first modulation method, the first rule Switching from the first modulation scheme to the second modulation scheme and switching the master station target reception level from the first master station target reception level to the second master station target reception level; When the signal level at the output of the transmission amplifier falls below the first upper limit level below the difference between the first and second master station target reception levels, the second modulation scheme to the first modulation scheme And switching from the second master station target reception level to the first master station target reception level.
[0019]
Further, assuming that the predetermined rule based on the transmission level information is different, when the signal level at the output of the transmission amplifier of the slave station device exceeds the first upper limit level corresponding to the first modulation method, Switching from the first modulation method to the second modulation method, a signal level at the output of the transmission amplifier of the slave station device corresponding to the second modulation method is higher than the first upper limit level. Is switched from the first master station target reception level to the second master station target reception level, and the signal level at the output of the transmission amplifier of the slave station device is the second upper limit level. When the difference between the first and second master station target reception levels falls below the level, the second master station target reception level is switched to the first master station target reception level, and the slave station device in front When the signal level at the output of the transmission amplifier is below the first upper limit level, it may be switched to the first modulation scheme from the second modulation scheme.
In this way, by switching the master station target reception level according to the modulation method, for example, in a modulation method with a low multilevel, the bit error rate is small and communication is possible even with a relatively low SN ratio. It is possible to provide a margin so that the output level of the transmission amplifier of the slave station apparatus does not exceed the back-off level as much as possible by setting the master station target reception level lower than in the case of a modulation system having a high value level. It becomes possible.
[0020]
The slave station device corrects the transmission level of the signal transmitted to the master station device, and the signal level at the output of the transmission amplifier of the slave station device corresponds to the second modulation method. A configuration in which the operation is performed in a range that is lower than the second upper limit level that is higher than the upper limit level is conceivable.
As a result, the output level of the transmission amplifier of the slave station apparatus is not increased too much, and an increase in bit error rate due to signal distortion can be prevented.
[0021]
In addition, the master station device includes data error detection means for detecting an error in data received from the slave station device, and the predetermined rule in the modulation method switching command sending means is determined from the slave station device. One based on the received transmission level information and the data error detection result by the data error detection means is also conceivable.
As a result, for example, depending on the detection result of data error such as bit error rate, switching from a modulation method with a high multilevel to a small modulation method, a modulation method with a low multilevel (low bit error rate) to a high modulation method. As a trigger for returning to the mobile station, switching control such as using the transmission level information received from the slave station device becomes possible.
For example, when the predetermined rule in the modulation method switching command sending means exceeds a first upper limit detection value corresponding to the first modulation method, a value related to the number of data errors detected by the data error detection means. , Switching from the first modulation scheme to the second modulation scheme, switching the master station target reception level from the first master station target reception level to the second master station target reception level, When the signal level at the output of the transmission amplifier of the apparatus falls below the first upper limit level corresponding to the first modulation scheme, below the difference between the first and second master station target reception levels, the second It is possible to switch from the first modulation method to the first modulation method and to switch from the second master station target reception level to the first master station target reception level.
As another example, when the predetermined rule in the modulation method switching command sending means exceeds a predetermined first upper limit detection value when a value related to the number of data errors detected by the data error detection means exceeds a predetermined first upper limit detection value, When the value of the number of data errors detected by the data error detection means exceeds a predetermined second upper limit detection value when the first modulation method is switched to the second modulation method, the first master station The target reception level is switched to the second master station target reception level, and the signal level at the output of the transmission amplifier of the slave station device is higher than the second upper limit level corresponding to the second modulation method. When the second master station target reception level falls below the second master station target reception level difference, the second master station target reception level is switched from the first master station target reception level to the output of the transmission amplifier of the slave station device. It is also conceivable to switch from the second modulation method to the first modulation method when the signal level falls below a first upper limit level corresponding to the first modulation method and lower than the second upper limit level. It is done.
[0022]
The master station device converts the frequency of the signal received from the slave station device from a wireless communication frequency to a wired communication frequency, and transmits a signal to be transmitted to the slave station device from the wired communication frequency to the wireless communication frequency. The base station device relay unit for converting to the base station device main body unit connected to the base station device by wire, the frequency of the signal received from the base station device by the slave station device from the frequency for wireless communication Converting to a frequency for wired communication and transmitting a signal to be transmitted to the parent station device from a frequency for wired communication to a frequency for wireless communication and transmitting the signal to the parent station device based on the signal level received from the parent station device It may be composed of a slave station relay unit that adjusts the signal level and a slave station main unit connected to the slave station by wire.
As a result, in the master station device and slave station device, it is possible to separately install the relay unit that performs wireless communication, and to install only the relay unit in a high place that is not easily affected by obstacles. It can be carried out.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments and examples of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. It should be noted that the following embodiments and examples are examples embodying the present invention, and do not limit the technical scope of the present invention.
FIG. 1 is a block diagram showing a schematic configuration of a PMP bidirectional wireless communication system X according to an embodiment of the present invention, and FIG. 2 is a state transition in the PMP bidirectional wireless communication system X according to an embodiment of the present invention. FIGS. 3 and 3 are diagrams showing signal level transitions of uplink signals in the PMP bidirectional radio communication system X according to the embodiment of the present invention, and FIG. 4 is a PMP bidirectional radio communication system X ′ according to the embodiment of the present invention. FIG. 5 is a diagram showing the transition of the signal level of the upstream signal in the PMP bidirectional wireless communication system X ′ according to the embodiment of the present invention. FIG. 6 is a schematic configuration of the conventional PMP bidirectional wireless communication system Z. FIG. 7 is a block diagram showing a schematic configuration of the PMP bidirectional wireless communication system Y according to the embodiment of the present invention, and FIG. 8 is a PMP duplex diagram according to the embodiment of the present invention. State transition diagram in a direction a wireless communication system Y, FIG. 9 is a state transition diagram in PMP two-way radio communication system Y 'according to an embodiment of the present invention.
[0024]
First, the configuration of the PMP bidirectional wireless communication system X according to the embodiment of the present invention will be described with reference to FIG.
Since the PMP bidirectional wireless communication system X is obtained by adding / changing components to a part of the PMP bidirectional wireless communication system Z shown in FIG. 6 (a), only the added / changed parts will be described. To do.
First, in the master station main body 110a, a communication control calculation unit 140a that is communicably connected to the communication control unit 111a and the demodulator 113a and includes a CPU, ROM, RAM, etc. (not shown) is added. Yes. The demodulator 113a can switch the demodulation method of the received signal from the slave station 10b to one of two multi-value levels of 16-value and 4-value by a predetermined switching signal from the communication control arithmetic unit 140a. It is supposed to be. Further, the communication control calculation unit 140a obtains a slave station transmission level calculation value (an example of the transmission level information) described later included in the received signal from the slave station 10b from the communication control unit 111a, and the slave station The following two controls are performed according to a predetermined rule based on the transmission level calculation value.
One of them is to transmit a predetermined modulation scheme switching command to the slave station 10b via the communication control unit 111a, thereby changing the modulation scheme of the transmission signal to the slave station 10b to 16 or 4 values. This is control for switching to one of two multilevel levels. At this time, after transmitting the modulation method switching command, by outputting the switching signal to the demodulator 113a at a predetermined timing when a signal from the slave station 10b reflecting the command is returned. , The demodulation method of the demodulator 113a is switched.
The second control is to switch the master station target reception level. When the master station target reception level is switched, there is a difference between the master station target reception level after switching and the input signal level to the master station main body 110a by the difference before and after switching. Then, the correction command corresponding to the deviation is transmitted from the communication control unit 111a on the master station 10a side to the communication control unit 111b on the slave station 10b side, and accordingly, on the slave station 10b side The communication control unit 111b outputs a control signal to the transmission GC 114b of the slave station main body 110b, and the gain of the transmission GC 114b of the slave station main body 110b is corrected. Thereby, the input signal level to the master station main body 110a is maintained at the master station target reception level after switching.
Further, by transmitting a level switching notification indicating switching of the master station target reception level to the slave station 10b via the communication control unit 111a, only the difference before and after the switching of the master station target reception level is obtained. Control for correcting the level of the transmission signal may be performed on the slave station 10b. In this case, correction control is performed separately in the PMP bidirectional wireless communication system Z in addition to correction performed based on the difference between the input signal level of the master station main body 110a and the master station target reception level. It is.
[0025]
On the other hand, in the slave station main body 110b, the communication control unit 111b is communicably connected to the modulator 112b and the transmission GC 114b. When the communication control unit 111b receives the modulation method switching command from the master station 10a, the communication control unit 111b outputs a predetermined switching signal to the modulator 112b, and the modulator 112b transmits the master station according to the switch signal. The modulation system of the transmission signal is switched to one of two multilevel levels of 16 values or 4 values. Further, when the communication control unit 111b receives the correction command from the master station 10a, the communication control unit 111b outputs a predetermined correction signal to the transmission GC 114b, and the transmission GC 114b switches the master station target reception level accordingly. The amplification gain is corrected by the difference between before and after.
The transmission GC 114b transmits the output signal level CMTx of the transmission GC 114b to the communication control unit 111b at a predetermined cycle. Based on the output signal level CMTx, the communication control unit 111b calculates the slave station transmission level calculation value, which is information related to the level of the signal transmitted to the master station 10a, and periodically transmits the information to the master station. 10a is transmitted. The slave station transmission level calculation value k is calculated by the following equation (1).
k = CMTx + Gclip (1)
However, Gclip is the maximum level increase from the output end of the transmission GC 114b of the slave station main body 110b to the output end of the transmission amplifier 121b of the slave station relay unit 120b, that is, the amount of amplification of the signal by the transmission amplifier 121b. Since the attenuation amount of the signal by the frequency converter 123b is always constant, it is a constant representing the level increase amount when the relay transmission GC 125b reaches the adjustment limit (upper limit). Thus, the slave station transmission level calculation value k is the transmission level Lout of the signal transmitted by the slave station 10b when the relay transmission GC 125b reaches the adjustment limit (upper limit) (the output signal of the transmission amplifier 121b). Level). That is, the slave station transmission level calculation value k does not represent the current transmission level Lout (the output signal level of the transmission amplifier 121b) of the signal transmitted by the slave station 10b, but the current output signal level CMTx. This represents the transmission level Lout (the output signal level of the transmission amplifier 121b) of the signal to be transmitted by the slave station 10b when the relay transmission GC 125b reaches the adjustment limit in this state.
Here, the slave station transmission level calculated value k is calculated on the slave station 10b side (the communication control unit 111b), and the slave station transmission level calculated value k is used as information regarding the level of the signal transmitted to the master station 10a. Is transmitted to the master station 10a. However, when it is desired to reduce the computation load or memory capacity on the slave station 10b side, the slave station 10b side (the communication control unit 111b) As information on the level of the signal transmitted to the master station 10a, for example, the current output signal level CMTx (another example of the transmission level information) is transmitted to the master station 10b, and the master station 10a side (for example, It is also conceivable that the communication control unit 111a) is configured to calculate the slave station transmission level calculation value k. In this case, for example, the communication controller 111a of the master station 10b may store the level increase amount Gclip at the time of adjustment limit of the relay transmission GC 125b for each of the slave stations 10a.
[0026]
Next, using FIG. 2 and FIG. 3, the communication control calculation unit 140a of the master station 10a determines the modulation scheme on the slave station 10b side according to what rule based on the slave station transmission level calculation value k. Whether to switch the master station reception target level will be described.
As shown in FIG. 2, the communication control calculation unit 140a switches the communication state between the first and second states St1 and St2 based on the slave station transmission level calculation value k. Here, in the first state St1, the modulation method of the transmission signal from the slave station 10b is set to "16-value orthogonal modulation method" (hereinafter simply referred to as 16-value method), and the master station target reception level Is a communication state in which the first master station target reception level L1 (hereinafter simply referred to as the first target level) corresponding to the 16-value system is used. On the other hand, in the second state St2, the modulation method of the transmission signal from the slave station 10b is set to “four-value orthogonal modulation method” (hereinafter simply referred to as “four-value method”), and the master station target reception level is set to This is a communication state in which the second master station target reception level L2 (hereinafter simply referred to as the second target level) corresponding to the quaternary method is used. In the quaternary method, since the multi-level is lower than that in the 16-value method, the bit error rate is small and communication is possible even with a relatively low SN ratio. Therefore, the second target level L2 is set to a value smaller than the first target level within a range of the SN ratio in which the bit error rate does not increase (L1> L2).
[0027]
As shown in FIG. 2, the communication control calculation unit 140a performs the first state St1 when the slave station transmission level calculation value k exceeds a predetermined first backoff level BO1 (k> BO1). When the slave station transmission level calculation value k falls below a value obtained by subtracting the difference between the first and second target levels L1 and L2 from the first back-off level BO1. (K <BO1- (L1-L2)) is switched from the second state St2 to the first state St1. Here, the first back-off level BO1 is the back-off level in which the bit error rate due to signal distortion increases when the transmission signal level Lout of the slave station 10b exceeds that level in communication in the 16-value scheme. Is a level. Also, when there are a plurality of the slave stations 10b, for example, when the switching condition of the state shown in FIG. It is conceivable that the second state St1, St2 is switched.
[0028]
Hereinafter, the transition of the level of the transmission signal from the slave station 10b to the master station 10a when the communication state changes between the first and second states St1 and St2 will be described with reference to FIG. .
In FIG. 3, a signal S0 is a state where the attenuation level of the radio signal is small (weather is good). At this time, since the relay transmission GC 125b has not reached the adjustment limit, the slave station transmission level calculation value k <BO1 (CMTx + Gclip <BO1) and the initial state (the first state St1). Then, when the rainfall becomes intense (the attenuation level of the radio signal becomes large) and the relay transmission GC 125b reaches the adjustment limit, the state of the signal S1 in FIG. Even in the state of this signal S1, the slave station transmission level calculation value k <BO1. When the attenuation level of the radio signal is further increased from the state of the signal S1, the relay transmission GC 125b has insufficient gain, so that the reception signal level of the master station 10a falls below the first target level L1, and the reception level deviation As described above, a predetermined correction command is transmitted from the master station 10b to the slave station 10b as described above, and the output signal level CMTx is set to the reception level by the transmission GC 114b of the slave station main body 110b. It is corrected (level rise) by the deviation. Thereby, the reception signal level of the master station 10a is maintained at the first target level L1 (a state between the signal S1 and the signal S2).
[0029]
When the attenuation level of the radio communication further increases and the correction due to the deviation of the reception level reaches a predetermined level, the transmission signal level Lout of the slave station 10b becomes the first back as shown by the signal S2 in the figure. The off-level BO1 is reached, and the slave station transmission level calculation value k = BO1. That is, when the transmission signal level further increases, the transmission signal level Lout exceeds the first back-off level BO1, and the bit error rate increases due to signal distortion in the 16-value scheme. Here, when the attenuation level of the radio signal further increases from the state of the signal S2, the slave station transmission level calculation value k> BO1 is satisfied, so that the state St1 is switched to the state St2. As a result, the output signal level CMTx of the transmission GC 114b is corrected (decreased) by the difference (L2−L1) before and after switching of the master station target reception level, and the state of the signal S3 in FIG. Represents the state St2). This state is a state in which the output signal level CMTx is lowered by the difference between the first and second target levels L1 and L2 from the state of the signal S2, that is, the state of k = BO1. The transmission level calculation value k> BO1- (L1-L2). As described above, when switching to the second state St2, that is, the quaternary system having a low multilevel, the communication system is resistant to signal distortion. Therefore, as shown in the signal S4 in FIG. Even if the level Lout rises to the backoff level BO2 (second backoff level) in the quaternary method exceeding the first backoff level, stable communication can be ensured. Here, if the transmission signal level Lout exceeds the back-off level BO2, the bit error rate also increases in the quaternary method. As a range in which the value k (that is, the transmission signal level Lout) does not exceed the back-off level BO2, it is set to be performed within the range of (BO2-Gclip) or less.
[0030]
Conversely, when the attenuation level of the radio signal is small in the second state St2, when the transmission signal level Lout is lower than the state of the signal S3, that is, k <BO1- (L1-L2). If the state is switched to the first state St1 at this time, even if the transmission signal level Lout increases by the difference (L1-L2) due to the switching of the master station target level (L2 → L1), the first state St1 Therefore, stable communication can be ensured without exceeding the back-off level BO1.
[0031]
By switching the communication state in this manner, it is not necessary to power up the transmission amplifier etc. on the slave station 10b side (increasing power consumption and cost), and using a large-capacity communication method (the 16-value method). Communication is possible as much as possible, and highly reliable wireless communication is possible in response to a wider range of environmental changes (changes in the attenuation level of wireless signals). That is, compared with the case where the modulation method is not switched, it is possible to cope with a change in attenuation level which is larger by a difference (BO2-BO1) between the first and second backoff levels, and by switching the master station target reception level. In addition, it is possible to increase the variation range of the attenuation level that can be handled by the difference (L1-L2).
[0032]
【Example】
Example 1
The PMP two-way wireless communication system X switches the communication state between two states St1 and St2, but based on the slave station transmission signal calculation value k, the following three states St10, St20, and St30 are displayed. A PMP bidirectional wireless communication system X ′ to be switched is also conceivable. Here, the state St10 and the state St20 are the same as the first and second states St1 and St2, respectively, and the state St20 has only the modulation method as the quaternary method (corresponding to the demodulation method), The master station target reception level remains in the first target level L1.
These three states St10, St20, and St30 are switched by the communication control calculation unit 140a as shown in FIG. That is, when the slave station transmission level calculation value k exceeds the first backoff level BO1 (k> BO1), the state is switched from St10 to St20, and the slave station transmission level calculation value k is changed to the first backoff level BO1. When the value exceeds the back-off level BO2 of 2 (k> BO2), the state St20 is switched to the state St30, and the slave station transmission level calculation value k is changed to the second back-off level BO2. When the level is lower than the level obtained by subtracting the difference between the target levels L1 and L2 of 2 (k <BO2- (L1-L2)), the state St30 is switched to the state St20, and the slave station transmission level calculation value k is When the level falls below the first back-off level BO1 (k <BO1), the state St20 is switched to the state St10.
[0033]
Hereinafter, the transition of the level of the transmission signal from the slave station 10b to the master station 10a when the communication state changes between the states St10, St20, and St30 will be described with reference to FIG.
In FIG. 5, the signal S0 is a state where the attenuation level of the radio signal is small (weather is good). At this time, since the relay transmission GC 125b has not reached the adjustment limit, the slave station transmission level calculation value k <BO1 (CMTx + Gclip <BO1) and the initial state (the state St10). Then, when the rainfall becomes intense (the attenuation level of the radio signal becomes large) and the relay transmission GC 125b reaches the adjustment limit, the state of the signal S1 in FIG. Even in the state of this signal S1, the slave station transmission level calculation value k <BO1. When the attenuation level of the radio signal is further increased from the state of the signal S1, the reception signal level of the master station 10a is lower than the first target level L1 in the relay transmission GC 125b, and a deviation of the reception level starts to occur. As described above, a predetermined correction command is transmitted from the master station 10b to the slave station 10b, and the output signal level CMTx is corrected by the deviation of the reception level by the transmission GC 114b of the master station main body 110b. (Level rise). As a result, the received signal level of the master station 10a is maintained at the first target level L1.
[0034]
When the correction for the deviation of the reception level reaches a predetermined level, the transmission signal level Lout of the slave station 10b reaches the first back-off level BO1, as shown by a signal S2 in the figure, and the slave station transmission The level calculation value k = BO1. That is, when the transmission signal level further increases, the transmission signal level Lout exceeds the first back-off level BO1, and the bit error rate increases due to signal distortion in the 16-value scheme. Here, when the attenuation level of the radio signal further increases from the state of the signal S2, the slave station transmission level calculation value k> BO1 is satisfied, so that the state St10 is switched to the state St20. As a result, the quaternary scheme with a low multilevel level is adopted, so that the bit error rate does not increase even if the transmission signal level Lout exceeds the first back-off level.
[0035]
If the attenuation level of the wireless communication further increases from here, as shown in S3 in the figure, the transmission signal level Lout of the slave station 10b reaches the second back-off level BO2, and the slave station transmission level calculation value k = It becomes BO2 (in the figure, the thick solid line represents the state St20). That is, if the transmission signal level Lout further increases, it exceeds the second back-off level BO2, and the bit error rate increases due to signal distortion even in the quaternary method. Here, when the attenuation level of the radio signal further increases from the state of the signal S3, the slave station transmission level calculation value k> BO2 is satisfied, so that the state St20 is switched to the state St30. As a result, the output signal level CMTx of the transmission GC 114b is corrected (the level is lowered) by the difference (L2−L1) before and after switching of the master station target reception level, resulting in the state of the signal S4 in FIG. The broken line represents the state St30). This state is a state in which the output signal level CMTx is lowered by the difference between the first and second target levels L1 and L2 from the state of the signal S3, that is, the state of k = BO2. Calculated value k> BO2- (L1-L2). As described above, even when the attenuation level of the radio signal is further increased by switching the master station target reception level to the target level L2, the transmission signal level Lout is set to the second level as indicated by S5 in the figure. Even if the level is increased until the back-off level BO2 is reached (up to k = BO2), stable communication can be ensured.
[0036]
Conversely, in the state St30, when the attenuation level of the radio signal becomes small, when the transmission signal level Lout is lower than the state of the signal S4, that is, when k <BO2- (L1-L2). If the state is switched to the state St20, even if the transmission signal level Lout increases by the difference (L1-L2) due to the switching of the master station target level, the second back-off level BO2 is not exceeded. Stable communication can be secured.
Further, in the state St20, when the transmission signal level Lout is lower than the state of the signal S2, that is, when k <BO1, the state St10 is switched to the state St10 in the maximum range. High 16-value high capacity communication can be performed.
[0037]
By switching the communication state in this way, as in the PMP bidirectional wireless communication system X, communication is performed as much as possible with a large-capacity communication system, and a wider range of environmental changes (changes in the attenuation level of the radio signal) ), Wireless communication with high reliability becomes possible. Furthermore, even in the four-value scheme with a low multilevel, the master station target reception level is maintained as high as possible (high signal-to-noise ratio) so that it is more resistant to noise (suppresses bit error rate). Communication is possible, and at the time of switching of the master station target reception level, temporary instability of communication that occurs until the control of the transmission signal level by the transmission GC 114b of the master station main body 110b converges Can be minimized.
[0038]
(Example 2)
In the PMP bidirectional wireless communication system X, the communication state is switched based on the slave station transmission signal calculation value k. The slave station transmission signal calculation value k (an example of the transmission level information) A PMP bidirectional wireless communication system Y that switches the communication state based on the error detection result of the data received from the slave station 10b in the master station 10a is also conceivable. Hereinafter, the PMP bidirectional wireless communication system Y will be described with reference to FIGS.
FIG. 7 shows a schematic configuration of the PMP bidirectional wireless communication system Y.
As shown in FIG. 7, the PMP bidirectional radio communication system Y is connected to the master station 10a between the communication control unit 111b of the slave station 10b and the modulator 112b in the PMP bidirectional radio communication system X. An FEC (Forward Error Correction) encoder 116b, which is means for encoding communication data to be transmitted (communication data before modulation by the modulator 112b), is connected between the demodulator 113a of the master station 10a and the communication control unit 111a. In the meantime, the communication data (communication data demodulated by the demodulator 113a) received from the slave station 10b is decoded, and if the decoding cannot be performed normally, an error has occurred in the communication data. FEC decoder 116a, which is means for detecting data (detection of data error), is additionally inserted. Is the same as the MP two-way wireless communication system X. Here, the FEC encoder 116b performs Reed-Solomon encoding of communication data and adds redundant data for data error detection. The FEC decoder 116a (an example of the data error detection means) When decoding communication data that has been subjected to Solomon encoding, the redundant data is used to remove (recover) data errors to the extent possible and to detect whether or not a data error has occurred.
The FEC decoder 116a is communicably connected to the communication control calculation unit 140a, and the communication control calculation unit 140a acquires error information regarding the number of detected data errors in communication data from the FEC decoder 116a. Is possible. In Reed-Solomon coding, it is possible to detect the presence or absence of errors in units of blocks, and the number of errors (number of detections) detected at the time of decoding by the FEC decoder 116a is set at regular intervals (for example, 1 second). The error rate Er per unit time is calculated by integrating the error rate, and the error rate is transmitted to the communication control calculation unit 140a as the error information. Here, the number of errors used for the calculation of the error rate is the number of errors detected by the FEC decoder 116a (the number of errors after error correction). (The number of successful error corrections + the number of failed error corrections), but in order to detect the communication status early in the symptom stage before it interferes with communication, all error detection before error correction is performed. It is better to use numbers.
[0039]
Similarly to the PMP bidirectional wireless communication system X, the present PMP bidirectional wireless communication system Y is switched between the first state St1 and the second state St2 by the communication control calculation unit 140a of the master station 10a ( Switching of the slave station 10b side modulation scheme and the master station reception target level) is different from that of the PMP bidirectional radio communication system X. Since other operations are the same as those of the PMP bidirectional wireless communication system X, description thereof will be omitted. Hereinafter, a switching rule between the state St1 and the state St2 will be described with reference to FIG.
As shown in FIG. 8, the communication control calculation unit 140a determines the communication state based on the slave station transmission level calculation value k and the error rate Er (value related to the number of detected data errors) obtained from the FEC decoder 116a. Are switched to the first and second states St1 and St2.
Specifically, as shown in FIG. 8, the communication control calculation unit 140a, when the error rate Er acquired from the FEC decoder 116a exceeds a predetermined first upper limit detection value E1 (Er> E1) Then, switching from the first state St1 to the second state St2 (switching from a modulation scheme having a high multilevel level to a low modulation scheme), and the slave station transmission level calculation value k is the first back-off level When the value is less than the value obtained by subtracting the difference between the first and second target levels L1 and L2 from BO1 (see FIG. 3) (k <BO1- (L1-L2)), the second state St2 Switching to the first state St1 (the switching rule of St2 → St1 is the same as the PMP bidirectional wireless communication system X).
Here, the first upper limit detection value E1 is obtained when the transmission signal level Lout of the slave station 10b exceeds the first back-off level BO1 in the communication by the 16-value method (the state St10). This is the threshold value (preset constant) of the error rate Er detected on the master station 10a side due to the signal distortion that occurs. That is, in the state St10, if the error rate Er exceeds the first upper limit detection value E1, the transmission signal level Lout of the slave station 10b exceeds the first back-off level BO1. The first upper limit detection value E1 is set so that it can be almost regarded as having occurred. Further, as described above, when the transmission signal level Lout of the slave station 10b exceeds the first backoff level BO1, the bit error rate due to signal distortion (the above-mentioned The error rate Er) increases (it often exceeds the first upper limit detection value E1) at the back-off level.
In addition, when there are a plurality of the slave stations 10b, for example, when the switching condition of the state shown in FIG. It is conceivable that the second state St1, St2 is switched.
Further, the switching condition from the state St1 to the state St2 may be a combination of the slave station transmission level calculation value k and the error rate Er. For example, the switching condition is AND or OR between the condition (k> BO1) and the condition (Er> E1). Thereby, more appropriate switching control can be performed.
By the switching control as described above, the transmission signal (slave station 10b → the master station) is changed in the same manner as the transition of the level of the transmission signal from the slave station 10b to the master station 10a in the PMP bidirectional radio communication system X (FIG. The level of the station 10a) will change, and the same effect as the MP bidirectional radio communication system X will be achieved.
[0040]
Example 3
Next, a PMP bidirectional wireless communication system Y ′, which is an application example of the PMP bidirectional wireless communication system Y, will be described with reference to FIG.
In the PMP bidirectional wireless communication system Y, the PMP bidirectional wireless communication system Y ′ switches the communication state to the three states St10, St20, St30 as in the PMP bidirectional wireless communication system X ′. Here, the states St10, St20, and St30 are the same as those in the PMP bidirectional wireless communication system X ′. The system configuration and operation (excluding the switching rules for the states St10, St20, and St30) are the same as those of the PMP bidirectional wireless communication system Y (FIG. 7).
The three states St10, St20, and St30 are switched by the communication control calculation unit 140a as shown in FIG. That is, when the error rate Er acquired from the FEC decoder 116a exceeds the first upper limit detection value E1 (Er> E1) in the state St10, the state St10 is switched to the St20. (Switching from a modulation scheme with a high multilevel level to a modulation scheme with a lower level), in the state St20, when the error rate Er exceeds a predetermined second upper limit detection value E2 (Er> E2) , The state St20 is switched to the state St30, and the slave station transmission level calculation value k falls below the level obtained by subtracting the second back-off level BO2 by the difference between the first and second target levels L1 and L2. When (k <BO2- (L1-L2)), the state St30 is switched to the state St20, and the slave station transmission level calculation value k is changed to the first buffer. When below the off-level BO1 to (k <BO1), switching from the state St20 to the state St10.
Here, the second upper limit detection value E2 is obtained when the transmission signal level Lout of the slave station 10b exceeds the second back-off level BO2 in the communication in the quaternary method (the state St20). This is the threshold value (preset constant) of the error rate Er detected on the master station 10a side due to the signal distortion that occurs. That is, in the state St20, when the error rate Er exceeds the second upper limit detection value E2, the transmission signal level Lout of the slave station 10b exceeds the first back-off level BO2. The second upper limit detection value E2 is set so that it can be almost regarded as having occurred. Each value of the second upper limit detection value E2 and the first upper limit detection value and the magnitude relationship thereof are determined by the use environment, the characteristics of the constituent devices, the required performance, and the like. Further, as described above, when the transmission signal level Lout of the slave station 10b exceeds the second back-off level BO2, the bit error rate due to signal distortion (the above-mentioned) The error rate Er) increases (it often exceeds the second upper limit detection value E2) at the back-off level.
Through the switching control as described above, the transmission signal (slave station 10b →) is transmitted in the same manner as the transition of the level of the transmission signal from the slave station 10b to the master station 10a in the PMP bidirectional radio communication system X ′ described above (FIG. The level of the master station 10a) will transition, and the same effect as the MP bidirectional radio communication system X ′ will be achieved.
The switching condition from the state St10 to the state St20 and the switching condition from the state St20 to the state St30 may be a combination of the slave station transmission level calculation value k and the error rate Er. Good. For example, the switching condition from the state St10 to the state St20 is the switching condition of AND or OR between the condition (k> BO1) and the condition (Er> E1), and the switching from the state St20 to the state St30. The condition is such that the switching condition is AND or OR between the condition (k> BO2) and the condition (Er> E2). Thereby, more appropriate switching control can be performed.
[0041]
【The invention's effect】
As described above, according to the present invention, since it is possible to know information related to the transmission signal level of the slave station in the master station, even in the radio communication system that controls the reception signal level on the master station side on the slave station side, It is possible to switch the appropriate modulation method by detecting the change in the attenuation level of wireless communication. Communication is performed with the largest possible communication method, and even if the attenuation level of the wireless communication changes greatly, It is possible to prevent the bit error rate from increasing due to the degradation of the SN ratio. In addition, it is not necessary to power up the transmitter amplifier on the slave station side (increasing power consumption and cost).
In addition, the master station detects an error in the data received from the slave station and switches the modulation system using the detection result, thereby enabling more appropriate switching of the modulation system.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of a PMP bidirectional radio communication system X according to an embodiment of the present invention.
FIG. 2 is a state transition diagram in the PMP bidirectional radio communication system X according to the embodiment of the present invention.
FIG. 3 is a diagram showing signal level transition of an uplink signal in the PMP bidirectional wireless communication system X according to the embodiment of the present invention.
FIG. 4 is a state transition diagram in the PMP two-way radio communication system X ′ according to the embodiment of the present invention.
FIG. 5 is a diagram showing the transition of the signal level of the upstream signal in the PMP bidirectional wireless communication system X ′ according to the embodiment of the present invention.
FIG. 6 is a block diagram showing a schematic configuration of a conventional PMP bidirectional wireless communication system Z and a diagram showing signal level transitions.
FIG. 7 is a block diagram showing a schematic configuration of a PMP bidirectional wireless communication system Y according to an embodiment of the present invention.
FIG. 8 is a state transition diagram in the PMP bidirectional wireless communication system Y according to the embodiment of the present invention.
FIG. 9 is a state transition diagram in the PMP bidirectional wireless communication system Y ′ according to an embodiment of the present invention.
[Explanation of symbols]
10a ... Master station
10b ... Slave station
110a ... Main unit of the master station
110b ... Slave unit body
111a, 111b ... communication control unit
112a, 112b ... modulator
113a, 113b ... demodulator
114b ... Transmission GC (Gain Controller)
115b: Reception AGC (Auto Gain Controller)
116a: FEC (Forward Error Correction) decoder
116b ... FEC encoder
120a ... Master station relay section
120b ... Slave station relay section
121a, 121b... Transmission amplifier
122a, 122b ... LNA (Low Noise Amplifier)
123a, 123b, 124a, 124b... Frequency converter
125b ... Relay transmission GC
126b ... Reception AGC for relay
130a, 130b ... communication cable
140a: Communication control calculation unit

Claims

Two-way wireless data communication is performed between the master station device and one or more slave station devices, and the master station device compares the signal level received from the slave station device with a predetermined master station target reception level. In a wireless communication system for correcting a transmission level of a signal transmitted from the slave station device to the master station device by transmitting a predetermined correction command to the slave station device based on:
Transmission level information sending means for transmitting to the master station device transmission level information relating to the level of the signal to be sent to the master station device, provided in the slave station device;
A modulation system switching command sending means for transmitting a predetermined modulation system switching command to the slave station apparatus according to a predetermined rule based on the transmission level information received from the slave station apparatus, provided in the master station apparatus;
A modulation method switching means provided in the slave station device, for selecting and switching a modulation method of a signal transmitted to the parent station device from two or more methods based on the modulation method switching command received from the master station device; ,
A demodulation method switching means provided in the master station device, and selecting and switching a demodulation method of a signal received from the slave station device from two or more methods in response to the modulation method switching command;
A wireless communication system comprising:

The wireless communication system according to claim 1, further comprising: a master station target reception level switching unit that is provided in the master station apparatus and switches the master station target reception level according to a predetermined rule based on the transmission level information.

3. The switching of the modulation scheme in the slave station device and the demodulation scheme in the master station device corresponding to the modulation scheme switches between two or more schemes having different multilevel levels. Wireless communication system.

According to a predetermined rule based on the transmission level information,
The modulation method is selected and switched between a first modulation method having a predetermined multi-value level and a second modulation method having a lower multi-value level,
The master station target reception level is lower than the first master station target reception level corresponding to the predetermined first master station target reception level corresponding to the first modulation scheme and the second modulation scheme. The radio communication system according to claim 3, wherein the radio communication system is selected and switched from the second master station target reception level.

The predetermined rule based on the transmission level information includes a predetermined level corresponding to the modulation method in a level of a transmission signal transmitted by the slave station device and an output signal of a transmission amplifier that amplifies the transmission signal in the slave station device. The wireless communication system according to claim 1, wherein the wireless communication system is based on a comparison with an upper limit level.

A predetermined rule based on the transmission level information is:
When the signal level at the output of the transmission amplifier of the slave station device exceeds the first upper limit level corresponding to the first modulation scheme, the first modulation scheme is switched to the second modulation scheme. , Switching the master station target reception level from the first master station target reception level to the second master station target reception level,
When the signal level at the output of the transmission amplifier of the slave station device falls below the first upper limit level below the difference between the first and second master station target reception levels, the second modulation scheme 6. The wireless communication system according to claim 5, wherein the wireless communication system switches to the first modulation method and switches from the second master station target reception level to the first master station target reception level.

A predetermined rule based on the transmission level information is:
Switching from the first modulation scheme to the second modulation scheme when the signal level at the output of the transmission amplifier of the slave station device exceeds a first upper limit level corresponding to the first modulation scheme;
When the signal level at the output of the transmission amplifier of the slave station device exceeds a second upper limit level corresponding to the second modulation method and higher than the first upper limit level, the first parent station target Switching from the reception level to the second master station target reception level,
When the signal level at the output of the transmission amplifier of the slave station device falls below the second upper limit level by the difference between the first and second master station target reception levels, the second master station target reception Switch from the level to the first master station target reception level,
6. The method according to claim 5, wherein when the signal level at the output of the transmission amplifier of the slave station device falls below the first upper limit level, the second modulation method is switched to the first modulation method. Wireless communication system.

The slave station apparatus corrects the transmission level of the signal transmitted to the master station apparatus. The signal level at the output of the transmission amplifier of the slave station apparatus corresponds to the second modulation method and the first upper limit level. The radio | wireless communications system in any one of Claim 6 or 7 comprised so that it may carry out in the range used as the 2nd upper limit level higher than this.

Provided in the master station device, comprising data error detection means for detecting an error in data received from the slave station device;
6. The predetermined rule in the modulation system switching command sending means is based on the transmission level information received from the slave station apparatus and a data error detection result by the data error detecting means. A wireless communication system according to claim 1.

The predetermined rule in the modulation system switching command sending means is:
When the value related to the number of data errors detected by the data error detection means exceeds the first upper limit detection value corresponding to the first modulation scheme, the first modulation scheme is switched to the second modulation scheme. And switching the master station target reception level from the first master station target reception level to the second master station target reception level,
When the signal level at the output of the transmission amplifier of the slave station device falls below the first upper limit level corresponding to the first modulation method, below the difference between the first and second master station target reception levels, The radio communication system according to claim 9, wherein the second modulation scheme is switched to the first modulation scheme, and the second master station target reception level is switched to the first master station target reception level. .

The predetermined rule in the modulation system switching command sending means is:
Switching from the first modulation scheme to the second modulation scheme when a value related to the number of data errors detected by the data error detection means exceeds a predetermined first upper limit detection value;
When the value relating to the number of data errors detected by the data error detection means exceeds a predetermined second upper limit detection value, the first master station target reception level is switched to the second master station target reception level;
When the signal level at the output of the transmission amplifier of the slave station apparatus falls below the second upper limit level corresponding to the second modulation method by the difference between the first and second master station target reception levels, Switching from the second master station target reception level to the first master station target reception level;
When the signal level at the output of the transmission amplifier of the slave station apparatus falls below a first upper limit level corresponding to the first modulation scheme and lower than the second upper limit level, the second modulation scheme The wireless communication system according to claim 9, wherein the wireless communication system is switched to the first modulation method.

The master station device converts the frequency of a signal received from the slave station device from a wireless communication frequency to a wired communication frequency, and converts a signal to be transmitted to the slave station device from a wired communication frequency to a wireless communication frequency. A master station device relay unit and a master station device main body connected to the master station device by wire,
The slave station device converts the frequency of a signal received from the master station device from a wireless communication frequency to a wired communication frequency, and converts a signal transmitted to the master station device from a wired communication frequency to a wireless communication frequency. And a slave station relay unit that adjusts a signal level to be transmitted to the master station device based on a signal level received from the master station device, and a slave station device main body connected to the master station device by wire The wireless communication system according to any one of claims 1 to 11.