JP3993060B2

JP3993060B2 - Wireless communication system

Info

Publication number: JP3993060B2
Application number: JP2002286639A
Authority: JP
Inventors: 茂山▲崎▼
Original assignee: Nippon Signal Co Ltd
Current assignee: Nippon Signal Co Ltd
Priority date: 2002-09-30
Filing date: 2002-09-30
Publication date: 2007-10-17
Anticipated expiration: 2022-09-30
Also published as: JP2004128635A

Description

【０００１】
【発明の属する技術分野】
本発明は、無線通信システムに関し、特に、端末局の構成の簡素化が可能で専用狭帯域通信（Dedicated Short Range Communications：以下、ＤＳＲＣと略す）システム等に有効な無線通信システムに関する。
【０００２】
【従来の技術】
基地局と端末局との間で無線信号により情報を送受信する無線通信システムにおいては、マルチパスフェージング等による伝播遅延によって符号間干渉が発生し通信エラーが発生する。この通信エラーを低減するため、従来、等化処理で信号波形を整形して符号間干渉を低減させる方法が一般的に用いられる。
【０００３】
かかる等化処理には、送信側で等化処理する送信端等化と受信側で等化処理する受信端等化がある。
送信端等化は、基地局と端末局が共に固定されている場合に用いられる。この場合には、基地局と端末局との間の通信環境は略一定と考えられ、信号伝播路の伝播特性は変化しないと見なせるので、伝播路で信号がどのように歪むかを測定して信号伝播路の伝播特性を予め測定し、その伝播特性に対して最適な等化処理用パラメータ（信号伝播路の伝播特性と逆特性を信号に与えるパラメータ）を決定して等化器に予め設定する。そして、送信側から等化処理した信号を送信する。送信された信号は伝播過程で歪むが送信時に逆特性の歪みが与えられているので、受信側では本来の送信信号と同じ信号形態に復元されて受信されるので、正しい情報が受信できる。
【０００４】
受信端等化は、端末局が携帯電話等のような移動可能な移動体通信の場合に用いられる。この場合は、基地局と端末局との間の伝播路が変化し伝播特性が変化するため送信端等化は適用できない。従って、通信の度に伝播路の伝播特性を推測し、受信側でその時の伝播特性と逆特性を信号に与える等化処理を行って受信信号を復元する受信端等化により符号間干渉を低減する。
【０００５】
即ち、基地局と端末局の両方に予め同一の教示信号データを保持させる。基地局から端末局に教示信号を送信し、端末局は受信した教示信号と予め保持した教示信号データを比較する。一致していれば歪みなしと判断して受信信号をそのまま送信信号として処理する。不一致の場合は、比較結果に基づいてその時の信号伝播路の伝播特性を推測し、推測した伝播特性と逆特性を信号に与える等化処理用パラメータを等化器に設定し、教示信号に続いて受信される送信情報を等化器で等化処理して本来の送信信号と同じ信号形態に復元することにより正しい情報が受信できる。
【０００６】
ところで、等化器は大規模なディジタルフィルタや積和演算器等を必要とするため、機器や消費電力が大きくなり、コストも高くなる。このため、移動体通信において従来のような受信端等化技術を採用すると、移動可能な端末局となる例えば携帯電話等に要求される性能（携帯性、低コスト等）が損なわれる。
そこで、等化処理技術により符号間干渉を低減すると共に移動局の小型化及び省電力を図るようにした無線通信システムが提案されている（例えば特許文献１参照）。
【０００７】
これは、基地局から符号間干渉が問題とならない程度の低速の通信速度で信号を送信し、移動局との間で初期接続処理を行う。基地局と接続できた移動局は、通常の通信速度（符号間干渉が問題となるような高速の通信速度）で教示信号を基地局に送信する。基地局は、受信した教示信号パターンと予め記憶した教示信号パターンを比較し、比較結果に基づいてその時の伝播特性を推測して等化処理用パラメータを決定し、その等化処理用パラメータ情報を符号間干渉が問題とならない低速の通信速度で移動局に送信する。移動局は、その情報を受信して等化処理用パラメータを等化器に設定し、受信端等化により通信エラーの低減を図るようにしている。このように、基地局側に信号伝播路の伝播特性に対して最適な等化処理用パラメータを決定する適応等化機構を持たせ、端末局には等化器だけを設ける構成とすることにより、移動端末局の構成の簡素化を図るようにしている。
【０００８】
【特許文献１】
特許第２７８８７８８号公報
【０００９】
【発明が解決しようとする課題】
しかしながら、上述の特許第２７８８７８８号公報に記載された無線通信システムは、受信信号の等化処理用等化器が移動局に残るため、端末局の構成簡素化の点で十分とは言えない。また、従来の受信端等化と同様に等化処理用パラメータを設定するために教示信号を使用するので、ＤＳＲＣシステムのような予め通信方式が規格化されていて教示信号が使用できないシステムには適用できないという問題がある。
【００１０】
尚、従来のＤＳＲＣシステムの場合、マルチパスフェージング等による符号間干渉を低減するために、周囲に電波吸収体を設ける等の方法が採用されているが、基地局の設定場所等が制約されるという欠点がある。
本発明は上記問題点に着目してなされたもので、マルチパスフェージング等による符号間干渉に起因する通信エラーを低減できると共に、通常の送受信機能だけを備えた簡素な構成の端末局を使用できる無線通信システムを提供することを目的とする。
【００１１】
【課題を解決するための手段】
このため、請求項１の発明は、固定の基地局と該基地局の通信エリア内の端末局とで、無線信号により情報の送受信を行う無線通信システムであって、前記基地局が、信号伝播路の伝播特性に対して最適な等化処理用パラメータが設定されて送信信号に対して等化処理を行う送信信号等化処理部と、該送信信号等化処理部からの処理信号を送信する送信部と、前記端末局からの信号を受信する受信部と、前記送信信号等化処理部と同一の等化処理用パラメータが設定されて前記受信部の受信した受信信号に対して等化処理を行う受信信号等化処理部と、前記伝播路について予め想定される複数の異なる伝播特性に対してそれぞれ最適な複数の等化処理用パラメータを記憶するパラメータ記憶部と、前記記憶された複数の等化処理用パラメータのいずれか１つを前記送信信号等化処理部及び受信信号等化処理部に順次設定し、送信信号に対する端末局からの応答信号の有無に基づいて最適な等化処理用パラメータを決定して通信を行う通信制御部と、を備える構成とした。
【００１２】
かかる構成では、通信制御部は、パラメータ記憶部に記憶された複数の等化処理用パラメータのいずれか１つを送信信号等化処理部及び受信信号等化処理部に設定し送信信号を発生する。そして、送信信号を送信信号等化処理部で等化処理し、その処理信号を送信部から端末局に対して送信する。設定した等化処理用パラメータが信号伝播路の伝播特性に対して最適なものでなければ、端末局で受信する受信信号は本来の送信信号ではないため端末局は応答せず、基地局は端末局からの応答信号を受信しないので、通信制御部は、設定した等化処理用パラメータが不適と判断し、別の等化処理用パラメータを設定して送信信号を送信する。基地局はこの動作を繰返す。そして、設定した等化処理用パラメータが信号伝播路の伝播特性に対して最適であれば、送信信号が端末局側で本来の形態に復元されて受信されるので、端末局は送信信号に対する応答信号を等化処理なしの本来の信号形態のまま基地局に対して送信する。基地局は、受信した応答信号を受信信号等化処理部において送信信号等化処理部と同一の等化処理用パラメータにより等化処理し、処理信号が端末局からの応答信号であれば端末局から応答ありと判断し、その時の設定パラメータが最適と判断する。このように、通信制御部は端末局からの応答があるまで等化処理用パラメータの設定動作を繰返し、その時の信号伝播路の伝播特性に対して最適な等化処理用パラメータを決定して送信信号等化処理部及び受信信号等化処理部に設定する。これにより、マルチパスフェージング等による符号間干渉が低減し通信エラーを低減できるようになると共に、端末局側は、送受信信号の等化処理を必要としないので、通常の送受信機能を設けるだけでよい。
【００１３】
前記通信制御部は、請求項２のように、前記記憶された複数の等化処理用パラメータの１つを設定する毎に送信信号を送信する動作を常時繰り返し行う構成とすればよい。
かかる構成では、基地局から、異なる等化処理用パラメータにより等化処理された信号が、常時周期的に通信エリアに送信されるようになる。
【００１４】
請求項３のように、前記基地局が、伝播路の伝播特性を測定し最適な等化処理用パラメータを決定して前記パラメータ記憶部に記憶する伝播特性測定部を備える構成とするとよい。
かかる構成では、基地局を設置した後、基地局自体で信号伝播路の伝播特性を測定できるようになる。
【００１５】
請求項４のように、前記端末局が、車両に搭載された移動端末局であり、前記基地局の通信エリアに前記移動端末局を搭載した車両が進入したときに、基地局からの送信信号に対して前記移動端末局から応答信号が送信される路車間通信システムに適用するとよい。
この場合、請求項５のように、前記端末局を搭載する予め想定される複数の車種毎に伝播路の伝播特性を測定し、それぞれの車種に対応した最適な等化処理用パラメータを決定して前記パラメータ記憶部に記憶する構成とするとよい。
【００１６】
また、請求項６のように、基地局が、通信エリアに進入する車両の車種を検出する車種センサを備え、該車種センサにより進入車両の車種が判明したときに、前記パラメータ記憶部に記憶された複数の等化処理用パラメータの中から、判明車種に関連する等化処理用パラメータを選択し、前記送信信号等化処理部及び受信信号等化処理部に設定する構成とするとよい。
【００１７】
かかる構成では、最適な等化処理用パラメータの選択動作を効率よくできるようになる。
【００１８】
【発明の実施の形態】
以下、本発明の実施形態を図面に基づいて説明する。
図１に、本発明の無線通信システムをＤＳＲＣシステムによる路車間通信システムに適用した場合の第１実施形態の構成図を示す。
図１において、本実施形態の無線通信システムは、例えば路側の適当な場所に固定設置される基地局としての路側器１と、車両に搭載され路側器１と無線通信する端末局としての車載器２とを備える。
【００１９】
路側器１は、制御部１１と、送信信号等化処理部としての送信端等化器１２と、受信信号等化処理部としての受信端等化器１３と、送信部１４と、受信部１５と、送受信用のアンテナ１６と、等化器制御部１７と、パラメータ記憶部１８と、伝播特性測定部１９と、伝播特性測定用のアンテナ２０とを備える。
前記制御部１１は、路側器１の各部の動作を制御し、送受信情報を処理する。送信端等化器１２は、後述のようにして等化器制御部１７により設定された等化処理用パラメータにより制御部１１からの送信信号を送信端等化処理する。送信部１４は、送信端等化器１２で等化処理された処理信号をダウンリンク信号としてアンテナ１６を介して外部に送信する。受信部１５は、アンテナ１６を介して受信した車載器２からのアップリンク信号を受信する。受信端等化器１３は、受信部１５で受信された受信信号を等化器制御部１７により設定された送信端等化器１２と同一の等化処理用パラメータにより受信端等化処理する。制御部１１は、受信端等化器１３からの受信信号を処理して車載器２からの応答信号か否かを判断し、設定されている等化処理用パラメータが最適か否かを判断し、この判断結果に基づいて等化器制御部１７のパラメータ設定動作を制御する。等化器制御部１７は、制御部１１からの指令に基づいてパラメータ記憶部１８に記憶されている複数の等化処理用パラメータのうちから１つを順次読出し送信端等化器１２及び受信端等化器１３に設定する。パラメータ記憶部１８には、伝播特性測定部１９により後述のようにして決定された予め想定される複数の異なる等化処理用パラメータが記憶されている。伝播特性測定部１９は、制御部１１からの指令に基づいて測定動作を実行する。ここで、前記制御部１１及び等化器制御部１７で通信制御部が構成される。
【００２０】
車載器２は、送受信のアンテナ３１と、送信部３２と、受信部３３と、制御部３４とを備え、基地局１からのダウンリンク信号をアンテナ３１を介して受信部３３で受信して制御部３４で処理し、受信情報に応じて制御部３４から出力される送信信号を送信部３２からアップリンク信号としてアンテナ３１を介して外部に送信する構成である。
【００２１】
次に、伝播特性の測定動作について説明する。
ＤＳＲＣシステムは非常に狭いエリアで通信するシステムであるので、伝播環境をある程度特定でき、路車間通信の場合には、伝播環境は車両の形状等により変化すると考えられる。そこで、各車種毎に伝播特性を測定する。また、後続車が存在する場合を想定し、後続車との組合せについても伝播特性を測定し、測定した各伝播特性に対して最適なパラメータを決定して記憶させる。
【００２２】
測定手順は、路側器１を設置場所に固定し、測定対象データ（車種データ、各車種の組合せデータ）を伝播特性測定部１９に入力する。そして、測定対象の車両を通信エリア内に配置し、路側器１の受信部１５に接続した測定用のアンテナ２０を車両の規定位置（例えばダッシュボード上等）に載置し、この状態で図２のフローチャートに示すような測定動作を開始する。
【００２３】
ステップ１（図中、Ｓ１で示し以下同様とする）で、伝播特性測定部１９の操作部（図示せず）で測定対象の指定操作を行う。これにより、測定が開始される。具体的には、伝播特性測定部１９から既知のパターンのビットデータ系列を送信部１４に出力して通信エリアに送信する。車両側に載置したアンテナ２０を介して受信部１５でビットデータ系列を受信し、伝播特性測定部１９に送る。伝播特性測定部１９は、受信したビットデータ系列を送信した既知のビットデータ系列と比較し、データの変化具合を測定する。この測定結果に基づいて伝播特性を算出し、算出した伝播特性に対して最適な等化処理用パラメータ（伝播特性と逆特性を送信信号に与えるようなパラメータ）を算出する。
【００２４】
ステップ２で、ステップ１で算出したパラメータを、パラメータ記憶部１８に測定対象データと対応付けて記憶する。
更に、通信エリアに隣接する位置（例えば後方）に他の全ての車種の車両を配置し、同様にして等化処理用パラメータを記憶する。
以後、他の異なる車種について車両単独の場合と後続車が存在する場合について等化処理用パラメータを決定して記憶する。
【００２５】
ステップ３では、指定された測定数が予め入力された測定対象データ数と一致したか否かを判定し、一致したら全ての測定が終了したと判断し伝播特性の測定動作を終了する。
このようにして、予め想定した複数の異なる伝播特性に対する最適な等化処理用パラメータを、測定対象データと対応付けてパラメータ記憶部１８に記憶し、等化処理用パラメータのデータベースを作成する。測定後は、伝播特性測定部１９を制御部１１から遮断して使用しない。また、受信部１５からアンテナ２０を外し格納しておけばよい。
【００２６】
次に、図３のフローチャートを参照して実際の路車間通信動作を説明する。
ステップ１１では、制御部１１からの指令に基づいて等化器制御部１７は、パラメータ記憶部１８に記憶された第１の等化処理用パラメータを選択して送信端等化器１２及び受信端等化器１３に設定する。
ステップ１２では、路側器１から車載器２と通信を開始するための通信開始スロットを送信する。具体的には、制御部１１が通信開始スロットを発生すると、送信端等化器１２で設定されている等化処理用パラメータ等化処理し、送信部１４に送る。送信部１４は、送信端等化器１２からの処理信号をダウンリンク信号として通信エリアに送信する。車載器２の受信部３３は、受信信号を復調して制御部３４に転送する。ここで、制御部３４が転送された信号が路側器１からの送信信号であると正常に判定できるのは、送信信号が伝播過程で歪むことなく本来の信号形態で受信された場合に限られる。即ち、送信端等化器１２の等化処理用パラメータが伝播路の伝播特性と逆特性を信号に与えるような最適なパラメータが設定されている場合である。この場合、送信信号は伝播路の伝播特性と逆の特性で予め歪んだ状態で送信され、伝播過程でその伝播特性による歪みを受けることにより本来の信号形態に復元されて車載器２側で受信される。従って、路側器１の送信端等化器１２の設定パラメータが不適であれば車載器２は応答せず路側器１は応答信号を受信できない。一方、路側器１の送信端等化器１２の設定パラメータが最適なものであれば、車載器２の制御部３４は、路側器１の送信信号であると判定し、ＡＣＫを含む応答スロットを発生し、そのままの状態で送信部３２からアップリンク信号として路側器１に対して送信する。
【００２７】
ステップ１３では、車載器２から応答があった否かを判定する。路側器１では、受信部１５で受信した信号を受信端等化器１３に転送し、設定パラメータで等化処理した後、制御部１１に転送する。受信端等化器１３の設定パラメータが不適であれば制御部１１は車載器２の本来の信号形態の応答スロットを受信できない。受信端等化器１３の設定パラメータが最適なものであれば、制御部１１は車載器２の本来の信号形態の応答スロットの受信によりＡＣＫを受信する。即ち、受信端等化器１３の等化処理用パラメータが伝播路の伝播特性と逆特性を信号に与える最適なパラメータが設定されている場合である。この場合、受信信号は伝播過程で伝播特性により歪んで受信されるが、伝播特性と逆特性を受信信号に与えるパラメータが設定された受信端等化器１３で本来の信号形態に復元される。従って、制御部１１では、所定時間内にＡＣＫを受信すれば車載器２から応答ありと判断し、所定時間内にＡＣＫが受信できなければ車載器２から応答なし判断する。応答ありと判断した場合は、ステップ１４に進み通信成立と判断して車載器２との間で情報の送受信を行い、通信が終了すればステップ１１に戻り、最初に設定した等化処理用パラメータを送信端等化器１２及び受信端等化器１３に設定する。一方、応答なしと判断した場合はステップ１５に進む。
【００２８】
ステップ１５では、パラメータ記憶部１８に記憶された全てのパラメータが設定されたか否かを判定し、判定がＮＯであればステップ１６に進み、次の等化処理用パラメータを送信端等化器１２及び受信端等化器１３に設定する。判定がＹＥＳであれば、ステップ１１に戻り、最初に設定した等化処理用パラメータを送信端等化器１２及び受信端等化器１３に再度設定する。
【００２９】
以上のように、路側器１では、パラメータ記憶部１８に記憶された等化処理用パラメータの１つを順次選択して送信端等化器１２及び受信端等化器１３に設定する。この動作を常時周期的に繰り返し行う。車載器２からの応答が合ったときは、その時の設定パラメータが伝播特性に対して最適なパラメータと判断してパラメータの切替え動作を停止して車載器２との通信を行い、通信の終了後は、パラメータの切替え動作を再開して車載器２からの応答を待つ。
【００３０】
かかる構成によれば、端末局である車載器に等化器等を設けることなく、通信エラーを低減できる。また、通信エラーの低減により実質的な通信速度の向上が可能となる。そして、端末局には通常の送受信機能だけを備えればよいので、端末局の構成を従来よりも簡素化でき、端末局の小型化及び軽量化を図ることが可能となる。従って、端末局を極力低コスト、省電力化、小型・軽量化することが要求される通信システム、例えばＤＳＲＣシステムによる路車間通信システムのような端末局が車両に搭載する移動端末となる通信システムに、特に有効な通信システムである。また、ＤＳＲＣシステムによる路車間通信システムのように、既に通信規格が制定され、車載器が大量生産され販売されて仕様や方式の変更が行い難い場合に、車載器の構成を変更しなくとも済むという効果もある。また、符号間干渉防止のための電波吸収体等を設ける必要がなく、ＤＳＲＣシステムを採用する場合の機器の設置場所の自由度を拡大できる。
【００３１】
図４に、本発明の第２実施形態の構成図を示す。尚、図１の第１実施形態と同一要素には同一符号を付してある。
図４において、第２実施形態は、第１実施形態の構成に車種センサ２１を付加する構成である。車種センサは、例えば複数の光センサで構成され、車両の高さ及び長さ等を判定して車種を特定するものである。また、車両検知センサも兼ねる。
【００３２】
図５のフローチャートに従って第２実施形態の通信動作を説明する。尚、伝播特性を測定して等化処理用パラメータを記憶させる方法は第１実施形態と同様であり、ここでは説明を省略する。
ステップ２１で、車種センサ２１から信号に基づいて通信エリア内に車両が進入したか否かを判定する。ＹＥＳであればステップ２２に進み、車種センサ１により車種が判明したか否かを判定する。ＹＥＳであればステップ２３に進む。一方、ステップ２１でＮＯと判定された場合及びステップ２２でＮＯと判定された場合、即ち、車両が通信エリア内に車載器２を搭載した車両が存在しない場合及び存在しても車種が判明しない場合は、ステップ２７〜ステップ３１の処理を実行し、記憶されている等化処理用パラメータを順次設定する動作を周期的に繰返す。従って第２実施形態は、通信エリアに車載器２を搭載した車両が存在しない場合は、第１実施形態と同様に設定パラメータを順次切換え送信信号を送信する動作を周期的に繰返し行っている。尚、ステップ２７〜３１の動作は、図３のステップ１１〜１６の動作においてステップ１３でＮＯと判定された場合と同様の動作である。
【００３３】
車種が判明してステップ２３に進んだ場合は、パラメータ記憶部１８内の等化処理用パラメータの中から、パラメータと対応付けて記憶されている測定対象データに基づいて判明した車種用の等化処理用パラメータを選択し、送信端等化器１２及び受信端等化器１３に設定する。
ステップ２４では、通信開始スロットの送信を行う。
【００３４】
ステップ２５では、車載器２からの応答スロットの受信の有無を判定し、応答があればステップ２６に進み、通信成立と判断して車載器２との間で情報の送受信を行い、通信が終了すればステップ２１に戻る。所定時間内に応答がなければ、ステップ２７に進み、ステップ２３で設定したパラメータを除いて第１パラメータから順次送信端等化器１２及び受信端等化器１３に設定する。そして、応答があればステップ２９の判定がＹＥＳとなり、ステップ２６に進み、車載器２との通信を行う。
【００３５】
以上にように第２実施形態の構成によれば、第１実施形態と同様の効果に加えて、車種を判別してその車種に関連する等化処理用パラメータを選択して設定することにより、等化処理用パラメータの設定を効率良くできるという効果を有する。
尚、本発明の無線通信システムは、路車間通信システムに限らず、その他の近距離或いは中距離の基地局−端末局間の通信システム、例えばＲＦＩＤ（Radio Frequency Identification）システム等にも適用できることは言うまでもない。
【００３６】
【発明の効果】
以上説明したように本発明によれば、符号間干渉の影響を抑制でき通信エラーを低減できることは勿論、端末局には等化器等が不要で通常の送受信機能だけでよいので、端末局の構成を簡素化でき、端末局の小型化、軽量化及び省電力化図ることができる。従って、端末局を極力低コスト、省電力化、小型・軽量化することが要求される通信システムに特に有効な通信システムである。
【００３７】
また、基地局に伝播特性の測定機能を備えることで、基地局を実際に設置した状態での通信環境で伝播特性を測定できるので、等化処理用パラメータの設定精度を高めることができ、符号間干渉の低減効果を向上できる。
また、路車間通信システムに適用した場合に、車種センサを設けて進入車種に応じて等化処理用パラメータを選択設定するようにすれば、等化処理用パラメータの設定動作を効率よくでき、最適なパラメータの決定を迅速にできるようになる。
【図面の簡単な説明】
【図１】本発明の第１実施形態のブロック構成図
【図２】第１実施形態の伝播特性の測定動作を説明するフローチャート
【図３】第１実施形態の通信動作を説明するフローチャート
【図４】本発明の第２実施形態のブロック構成図
【図５】第２実施形態の通信動作を説明するフローチャート
【符号の説明】
１路側器
２車載器
１１制御部
１２送信端等化器
１３受信端等化器
１４送信部
１５受信部
１６送受信用アンテナ
１７等化器制御部
１８パラメータ記憶部
１９伝播特性測定部
２０伝播特性測定用アンテナ
２１車種センサ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radio communication system, and more particularly to a radio communication system that can simplify the configuration of a terminal station and is effective for a dedicated short range communication (DSRC) system or the like.
[0002]
[Prior art]
In a wireless communication system in which information is transmitted and received between a base station and a terminal station using wireless signals, intersymbol interference occurs due to propagation delay due to multipath fading and the like, resulting in a communication error. In order to reduce this communication error, conventionally, a method of shaping signal waveforms by equalization processing to reduce intersymbol interference is generally used.
[0003]
Such equalization processing includes transmission end equalization performed on the transmission side and reception end equalization performed on the reception side.
Transmission end equalization is used when both the base station and the terminal station are fixed. In this case, the communication environment between the base station and the terminal station is considered to be substantially constant, and it can be assumed that the propagation characteristics of the signal propagation path do not change, so measure how the signal is distorted in the propagation path. Preliminarily measure the propagation characteristics of the signal propagation path, determine the optimum equalization processing parameters for the propagation characteristics (parameters that give the signal propagation path and reverse characteristics to the signal), and set them in the equalizer in advance. To do. Then, the equalized signal is transmitted from the transmission side. The transmitted signal is distorted in the propagation process, but is given distortion of reverse characteristics at the time of transmission. Therefore, the receiving side restores the same signal form as the original transmission signal and receives it, so that correct information can be received.
[0004]
The receiving end equalization is used when the terminal station is mobile communication such as a mobile phone. In this case, since the propagation path between the base station and the terminal station changes and the propagation characteristics change, the transmission end equalization cannot be applied. Therefore, the propagation characteristics of the propagation path are estimated every time communication is performed, and the reception end equalization that restores the received signal by performing equalization processing that gives the signal the propagation characteristic opposite to that at that time on the receiving side reduces intersymbol interference. To do.
[0005]
That is, the same teaching signal data is held in advance in both the base station and the terminal station. A teaching signal is transmitted from the base station to the terminal station, and the terminal station compares the received teaching signal with previously stored teaching signal data. If they match, it is determined that there is no distortion and the received signal is processed as it is as a transmission signal. In the case of discrepancy, the propagation characteristics of the signal propagation path at that time are estimated based on the comparison result, the equalization processing parameters that give the estimated propagation characteristics and inverse characteristics to the signal are set in the equalizer, and the teaching signal is followed. The correct information can be received by equalizing the transmission information received by the equalizer and restoring it to the same signal form as the original transmission signal.
[0006]
By the way, since an equalizer requires a large-scale digital filter, a product-sum calculator, etc., equipment, power consumption, and cost increase. For this reason, when a conventional receiving end equalization technique is employed in mobile communication, performance (portability, low cost, etc.) required for a mobile terminal, such as a mobile phone, is impaired.
In view of this, a radio communication system has been proposed in which intersymbol interference is reduced by an equalization processing technique and the mobile station is reduced in size and power consumption (see, for example, Patent Document 1).
[0007]
In this case, a signal is transmitted from the base station at a low communication speed that does not cause intersymbol interference, and an initial connection process is performed with the mobile station. A mobile station that can connect to the base station transmits a teaching signal to the base station at a normal communication speed (a high communication speed at which intersymbol interference causes a problem). The base station compares the received teaching signal pattern with the previously stored teaching signal pattern, estimates the propagation characteristics at that time based on the comparison result, determines an equalization processing parameter, and sets the equalization processing parameter information Transmit to the mobile station at a low communication speed where intersymbol interference does not matter. The mobile station receives the information and sets equalization processing parameters in the equalizer so as to reduce communication errors by equalizing the receiving end. In this way, the base station side has an adaptive equalization mechanism for determining the optimum equalization processing parameters for the propagation characteristics of the signal propagation path, and the terminal station is provided with only an equalizer. The configuration of the mobile terminal station is simplified.
[0008]
[Patent Document 1]
Japanese Patent No. 2788788 [0009]
[Problems to be solved by the invention]
However, the wireless communication system described in the above-mentioned Japanese Patent No. 2788788 is not sufficient in terms of simplification of the configuration of the terminal station because the equalizer for equalization processing of the received signal remains in the mobile station. In addition, since the teaching signal is used to set the equalization processing parameters in the same way as the conventional receiving end equalization, the communication system is standardized in advance, such as the DSRC system, and the teaching signal cannot be used. There is a problem that it cannot be applied.
[0010]
In the case of a conventional DSRC system, in order to reduce intersymbol interference due to multipath fading or the like, a method such as providing a radio wave absorber around is adopted, but the setting location of the base station is restricted. There is a drawback.
The present invention has been made paying attention to the above problems, and can reduce a communication error caused by intersymbol interference due to multipath fading and the like, and can use a terminal station having a simple configuration only having a normal transmission / reception function. An object is to provide a wireless communication system.
[0011]
[Means for Solving the Problems]
Therefore, the invention of claim 1 is a radio communication system in which information is transmitted and received by radio signals between a fixed base station and a terminal station in the communication area of the base station. A transmission signal equalization processing unit that sets an equalization processing parameter that is optimal for the propagation characteristics of the path and performs equalization processing on the transmission signal, and transmits a processing signal from the transmission signal equalization processing unit An equalization process for the reception signal received by the reception unit, in which the same parameter for equalization processing is set as the transmission unit, the reception unit that receives the signal from the terminal station, and the transmission signal equalization processing unit A reception signal equalization processing unit for performing, a parameter storage unit for storing a plurality of optimum equalization processing parameters for a plurality of different propagation characteristics assumed in advance for the propagation path, and the plurality of stored Parameters for equalization processing Any one of them is sequentially set in the transmission signal equalization processing unit and the reception signal equalization processing unit, and an optimal equalization processing parameter is determined based on the presence / absence of a response signal from the terminal station for the transmission signal. And a communication control unit for performing the above.
[0012]
In such a configuration, the communication control unit sets any one of a plurality of equalization processing parameters stored in the parameter storage unit in the transmission signal equalization processing unit and the reception signal equalization processing unit, and generates a transmission signal. . Then, the transmission signal is equalized by the transmission signal equalization processing unit, and the processed signal is transmitted from the transmission unit to the terminal station. If the set equalization processing parameters are not optimal for the propagation characteristics of the signal propagation path, the terminal station does not respond because the received signal received by the terminal station is not the original transmission signal, and the base station Since the response signal from the station is not received, the communication control unit determines that the set equalization processing parameter is inappropriate, sets another equalization processing parameter, and transmits a transmission signal. The base station repeats this operation. If the set equalization processing parameters are optimal for the propagation characteristics of the signal propagation path, the terminal station transmits the response to the transmission signal because the transmission signal is restored to the original form on the terminal station side and received. The signal is transmitted to the base station in the original signal form without equalization processing. The base station equalizes the received response signal with the same equalization processing parameters as the transmission signal equalization processing unit in the reception signal equalization processing unit, and if the processed signal is a response signal from the terminal station, the terminal station Therefore, it is determined that there is a response, and the setting parameter at that time is determined to be optimal. In this way, the communication control unit repeats the equalization processing parameter setting operation until there is a response from the terminal station, and determines and transmits the optimum equalization processing parameter for the propagation characteristics of the signal propagation path at that time. Set in the signal equalization processing unit and the received signal equalization processing unit. As a result, intersymbol interference due to multipath fading and the like can be reduced and communication errors can be reduced, and since the terminal station side does not require equalization processing of transmission / reception signals, it is only necessary to provide a normal transmission / reception function. .
[0013]
The communication control unit may be configured to always repeatedly perform an operation of transmitting a transmission signal every time one of the plurality of stored equalization processing parameters is set.
In such a configuration, signals that have been equalized by different equalization parameters are constantly transmitted from the base station to the communication area.
[0014]
According to a third aspect of the present invention, the base station may include a propagation characteristic measurement unit that measures propagation characteristics of a propagation path, determines an optimal equalization processing parameter, and stores the parameter in the parameter storage unit.
In such a configuration, after the base station is installed, the base station itself can measure the propagation characteristics of the signal propagation path.
[0015]
The transmission signal from the base station when the terminal station is a mobile terminal station mounted on a vehicle and the vehicle on which the mobile terminal station is mounted enters a communication area of the base station as in claim 4. However, it may be applied to a road-vehicle communication system in which a response signal is transmitted from the mobile terminal station.
In this case, as in claim 5, the propagation characteristics of the propagation path are measured for each of a plurality of vehicle types assumed to be installed in advance, and the optimum equalization processing parameter corresponding to each vehicle type is determined. In this case, the parameter storage unit may be used.
[0016]
According to a sixth aspect of the present invention, the base station includes a vehicle type sensor that detects a vehicle type of a vehicle entering the communication area, and is stored in the parameter storage unit when the vehicle type of the entering vehicle is determined by the vehicle type sensor. In addition, it is preferable that an equalization processing parameter related to a known vehicle type is selected from a plurality of equalization processing parameters and set in the transmission signal equalization processing unit and the reception signal equalization processing unit.
[0017]
With such a configuration, it is possible to efficiently select an optimum equalization processing parameter.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a configuration diagram of a first embodiment when the wireless communication system of the present invention is applied to a road-to-vehicle communication system using a DSRC system.
In FIG. 1, a wireless communication system according to the present embodiment includes, for example, a roadside device 1 as a base station fixedly installed at an appropriate place on the roadside, and an in-vehicle device as a terminal station mounted on a vehicle and wirelessly communicating with the roadside device 1. 2 is provided.
[0019]
The roadside device 1 includes a control unit 11, a transmission end equalizer 12 as a transmission signal equalization processing unit, a reception end equalizer 13 as a reception signal equalization processing unit, a transmission unit 14, and a reception unit 15 A transmission / reception antenna 16, an equalizer control unit 17, a parameter storage unit 18, a propagation characteristic measurement unit 19, and a propagation characteristic measurement antenna 20.
The said control part 11 controls operation | movement of each part of the roadside device 1, and processes transmission / reception information. The transmission end equalizer 12 performs transmission end equalization processing on the transmission signal from the control unit 11 using the equalization processing parameters set by the equalizer control unit 17 as described later. The transmission unit 14 transmits the processed signal equalized by the transmission end equalizer 12 to the outside through the antenna 16 as a downlink signal. The receiving unit 15 receives the uplink signal from the vehicle-mounted device 2 received via the antenna 16. The reception end equalizer 13 performs reception end equalization processing on the reception signal received by the reception unit 15 using the same equalization processing parameters as those of the transmission end equalizer 12 set by the equalizer control unit 17. The control unit 11 processes the received signal from the receiving end equalizer 13 to determine whether it is a response signal from the vehicle-mounted device 2, and determines whether the set equalization processing parameter is optimal. Based on the determination result, the parameter setting operation of the equalizer controller 17 is controlled. The equalizer control unit 17 sequentially reads out one of a plurality of equalization processing parameters stored in the parameter storage unit 18 based on a command from the control unit 11, the transmission end equalizer 12 and the reception end. Set to equalizer 13. The parameter storage unit 18 stores a plurality of different equalization processing parameters assumed in advance by the propagation characteristic measurement unit 19 as described later. The propagation characteristic measurement unit 19 performs a measurement operation based on a command from the control unit 11. Here, the control unit 11 and the equalizer control unit 17 constitute a communication control unit.
[0020]
The vehicle-mounted device 2 includes a transmission / reception antenna 31, a transmission unit 32, a reception unit 33, and a control unit 34. The downlink signal from the base station 1 is received by the reception unit 33 via the antenna 31 and controlled. The transmission signal processed by the unit 34 and output from the control unit 34 according to the received information is transmitted from the transmission unit 32 to the outside as an uplink signal via the antenna 31.
[0021]
Next, the propagation characteristic measurement operation will be described.
Since the DSRC system communicates in a very narrow area, the propagation environment can be specified to some extent, and in the case of road-to-vehicle communication, the propagation environment is considered to change depending on the shape of the vehicle. Therefore, the propagation characteristics are measured for each vehicle type. In addition, assuming that there is a subsequent vehicle, the propagation characteristics are also measured for the combination with the subsequent vehicle, and optimum parameters are determined and stored for each measured propagation characteristic.
[0022]
In the measurement procedure, the roadside device 1 is fixed at the installation location, and measurement target data (vehicle type data, combination data of each vehicle type) is input to the propagation characteristic measurement unit 19. Then, the vehicle to be measured is placed in the communication area, and the measurement antenna 20 connected to the receiving unit 15 of the roadside device 1 is placed at a specified position (for example, on the dashboard) of the vehicle. The measurement operation as shown in the flowchart of FIG.
[0023]
In step 1 (indicated by S1 in the figure, the same shall apply hereinafter), an operation unit (not shown) of the propagation characteristic measurement unit 19 is used to specify a measurement target. Thereby, measurement is started. Specifically, a bit data series having a known pattern is output from the propagation characteristic measurement unit 19 to the transmission unit 14 and transmitted to the communication area. The receiving unit 15 receives the bit data series via the antenna 20 placed on the vehicle side and sends it to the propagation characteristic measuring unit 19. The propagation characteristic measurement unit 19 compares the received bit data sequence with the transmitted known bit data sequence and measures the degree of data change. A propagation characteristic is calculated based on the measurement result, and an equalization processing parameter (a parameter that gives the transmission signal an opposite characteristic to the propagation characteristic) is calculated with respect to the calculated propagation characteristic.
[0024]
In step 2, the parameter calculated in step 1 is stored in the parameter storage unit 18 in association with the measurement target data.
Furthermore, vehicles of all other vehicle types are arranged at positions adjacent to the communication area (for example, rearward), and equalization processing parameters are stored in the same manner.
Thereafter, the parameters for equalization processing are determined and stored for the case where the vehicle is alone and the case where the following vehicle exists for other different vehicle types.
[0025]
In step 3, it is determined whether or not the designated number of measurements matches the number of measurement target data input in advance. If they match, it is determined that all measurements have been completed, and the propagation characteristic measurement operation is terminated.
In this way, optimal equalization processing parameters for a plurality of different propagation characteristics assumed in advance are stored in the parameter storage unit 18 in association with the measurement target data, and an equalization processing parameter database is created. After the measurement, the propagation characteristic measurement unit 19 is cut off from the control unit 11 and is not used. Further, the antenna 20 may be removed from the receiving unit 15 and stored.
[0026]
Next, the actual road-to-vehicle communication operation will be described with reference to the flowchart of FIG.
In step 11, the equalizer control unit 17 selects the first equalization processing parameter stored in the parameter storage unit 18 based on a command from the control unit 11, and transmits the transmission end equalizer 12 and the reception end. Set to equalizer 13.
In step 12, a communication start slot for starting communication with the vehicle-mounted device 2 is transmitted from the roadside device 1. Specifically, when the control unit 11 generates a communication start slot, the equalization processing parameter equalization process set by the transmission end equalizer 12 is performed and sent to the transmission unit 14. The transmission unit 14 transmits the processing signal from the transmission end equalizer 12 to the communication area as a downlink signal. The receiving unit 33 of the vehicle-mounted device 2 demodulates the received signal and transfers it to the control unit 34. Here, the control unit 34 can normally determine that the transferred signal is a transmission signal from the roadside device 1 only when the transmission signal is received in the original signal form without being distorted in the propagation process. . In other words, this is a case where the parameters for equalization processing of the transmission end equalizer 12 are set to the optimum parameters that give the signal the characteristics opposite to the propagation characteristics of the propagation path. In this case, the transmission signal is transmitted in a state distorted in advance with a characteristic opposite to the propagation characteristic of the propagation path, and is restored to the original signal form by receiving distortion due to the propagation characteristic in the propagation process, and is received by the vehicle-mounted device 2 side. Is done. Therefore, if the setting parameter of the transmission end equalizer 12 of the roadside device 1 is inappropriate, the vehicle-mounted device 2 does not respond and the roadside device 1 cannot receive a response signal. On the other hand, if the setting parameter of the transmission end equalizer 12 of the roadside device 1 is optimal, the control unit 34 of the vehicle-mounted device 2 determines that it is a transmission signal of the roadside device 1 and sets a response slot including ACK. It is generated and transmitted as it is to the roadside device 1 as an uplink signal from the transmission unit 32.
[0027]
In step 13, it is determined whether or not there is a response from the vehicle-mounted device 2. In the roadside device 1, the signal received by the receiving unit 15 is transferred to the receiving end equalizer 13, equalized with the setting parameters, and then transferred to the control unit 11. If the setting parameter of the receiving end equalizer 13 is inappropriate, the control unit 11 cannot receive the response slot of the original signal form of the vehicle-mounted device 2. If the setting parameter of the receiving end equalizer 13 is optimal, the control unit 11 receives the ACK by receiving the response slot in the original signal form of the vehicle-mounted device 2. In other words, this is a case where the parameter for equalization processing of the receiving end equalizer 13 is set to an optimum parameter that gives the signal the characteristics opposite to the propagation characteristics of the propagation path. In this case, the received signal is distorted due to the propagation characteristics in the propagation process, but is restored to the original signal form by the receiving end equalizer 13 in which parameters that give the received signal the characteristics opposite to the propagation characteristics are set. Therefore, the control unit 11 determines that there is a response from the vehicle-mounted device 2 if ACK is received within a predetermined time, and determines that there is no response from the vehicle-mounted device 2 if ACK cannot be received within the predetermined time. If it is determined that there is a response, the process proceeds to step 14 where it is determined that communication is established, information is transmitted to and received from the vehicle-mounted device 2, and when communication is completed, the process returns to step 11, and the equalization processing parameters set first Are set in the transmission end equalizer 12 and the reception end equalizer 13. On the other hand, if it is determined that there is no response, the process proceeds to step 15.
[0028]
In step 15, it is determined whether all parameters stored in the parameter storage unit 18 have been set. If the determination is NO, the process proceeds to step 16, and the next equalization processing parameter is transmitted to the transmission end equalizer 12. And the reception end equalizer 13 is set. If the determination is YES, the process returns to step 11 to set the equalization processing parameters set first in the transmission end equalizer 12 and the reception end equalizer 13 again.
[0029]
As described above, the roadside device 1 sequentially selects one of the equalization processing parameters stored in the parameter storage unit 18 and sets it in the transmission end equalizer 12 and the reception end equalizer 13. This operation is repeated periodically at all times. When the response from the OBE 2 matches, the setting parameter at that time is determined to be the optimum parameter for the propagation characteristics, the parameter switching operation is stopped, and the communication with the OBE 2 is performed. Resumes the parameter switching operation and waits for a response from the vehicle-mounted device 2.
[0030]
According to such a configuration, communication errors can be reduced without providing an equalizer or the like in the vehicle-mounted device that is the terminal station. Further, the communication speed can be substantially improved by reducing the communication error. Since the terminal station only needs to have a normal transmission / reception function, the configuration of the terminal station can be simplified as compared with the conventional one, and the terminal station can be reduced in size and weight. Accordingly, a communication system that requires a terminal station to be as low-cost, power-saving, and compact and lightweight as possible, for example, a communication system that is a mobile terminal mounted on a vehicle, such as a road-to-vehicle communication system using a DSRC system. It is a particularly effective communication system. In addition, as in the road-to-vehicle communication system using the DSRC system, it is not necessary to change the configuration of the vehicle-mounted device when the communication standard has already been established and the vehicle-mounted device is mass-produced and sold and it is difficult to change the specifications and methods. There is also an effect. Further, it is not necessary to provide a radio wave absorber for preventing intersymbol interference, and the degree of freedom of installation location of equipment when the DSRC system is adopted can be expanded.
[0031]
FIG. 4 shows a configuration diagram of the second embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the same element as 1st Embodiment of FIG.
In FIG. 4, 2nd Embodiment is a structure which adds the vehicle type sensor 21 to the structure of 1st Embodiment. The vehicle type sensor is composed of, for example, a plurality of optical sensors, and determines the vehicle type by determining the height and length of the vehicle. It also serves as a vehicle detection sensor.
[0032]
The communication operation of the second embodiment will be described with reference to the flowchart of FIG. Note that the method of measuring the propagation characteristics and storing the equalization processing parameters is the same as in the first embodiment, and the description thereof is omitted here.
In step 21, it is determined whether or not a vehicle has entered the communication area based on a signal from the vehicle type sensor 21. If YES, the process proceeds to step 22, and it is determined whether or not the vehicle type is found by the vehicle type sensor 1. If yes, go to step 23. On the other hand, if NO is determined in step 21 and NO is determined in step 22, that is, if the vehicle in which the vehicle-mounted device 2 is mounted is not present in the communication area, and the vehicle type is not determined even if it exists. In this case, the processing of step 27 to step 31 is executed, and the operation of sequentially setting the stored equalization processing parameters is repeated periodically. Therefore, in the second embodiment, when there is no vehicle on which the vehicle-mounted device 2 is mounted in the communication area, the operation of sequentially switching the setting parameters and transmitting the transmission signal is repeatedly performed as in the first embodiment. In addition, the operation | movement of step 27-31 is an operation | movement similar to the case where it determines with NO by step 13 in the operation | movement of step 11-16 of FIG.
[0033]
When the vehicle type is determined and the process proceeds to step 23, the vehicle type equalization determined based on the measurement target data stored in association with the parameter from the equalization processing parameters in the parameter storage unit 18 Processing parameters are selected and set in the transmission end equalizer 12 and the reception end equalizer 13.
In step 24, the communication start slot is transmitted.
[0034]
In step 25, it is determined whether or not a response slot has been received from the vehicle-mounted device 2, and if there is a response, the process proceeds to step 26, and it is determined that communication has been established, information is transmitted to and received from the vehicle-mounted device 2, and communication is completed. If it does, it will return to step 21. If there is no response within the predetermined time, the process proceeds to step 27, where the parameters set in step 23 are excluded and the first parameter is sequentially set in the transmission end equalizer 12 and the reception end equalizer 13. And if there exists a response, determination of step 29 will be YES, and it will progress to step 26 and will communicate with the onboard equipment 2.
[0035]
As described above, according to the configuration of the second embodiment, in addition to the same effects as those of the first embodiment, by determining the vehicle type and selecting and setting the equalization processing parameters related to the vehicle type, This has the effect that the equalization processing parameters can be set efficiently.
The radio communication system of the present invention is not limited to a road-to-vehicle communication system, but can be applied to other short-range or medium-range communication systems between base stations and terminal stations, such as an RFID (Radio Frequency Identification) system. Needless to say.
[0036]
【The invention's effect】
As described above, according to the present invention, the influence of intersymbol interference can be suppressed and communication errors can be reduced. Of course, the terminal station does not require an equalizer, and only a normal transmission / reception function is required. The configuration can be simplified, and the terminal station can be reduced in size, weight and power saving. Therefore, this is a communication system that is particularly effective for a communication system that requires the terminal station to be as low-cost, power-saving, small, and light as possible.
[0037]
Also, by providing the propagation characteristics measurement function in the base station, the propagation characteristics can be measured in the communication environment with the base station actually installed, so that the setting accuracy of the equalization processing parameters can be improved, The effect of reducing interfering interference can be improved.
In addition, when applied to a road-to-vehicle communication system, if the vehicle type sensor is provided and the parameters for equalization processing are selected and set according to the type of approaching vehicle, the setting operation of the parameters for equalization processing can be made efficient and optimal. It is possible to quickly determine the parameters.
[Brief description of the drawings]
FIG. 1 is a block diagram of a first embodiment of the present invention. FIG. 2 is a flowchart for explaining a propagation characteristic measurement operation of the first embodiment. FIG. 3 is a flowchart for explaining a communication operation of the first embodiment. 4 is a block diagram of the second embodiment of the present invention. FIG. 5 is a flowchart for explaining the communication operation of the second embodiment.
DESCRIPTION OF SYMBOLS 1 Roadside device 2 Onboard equipment 11 Control part 12 Transmission end equalizer 13 Reception end equalizer 14 Transmission part 15 Reception part 16 Transmission / reception antenna 17 Equalizer control part 18 Parameter memory | storage part 19 Propagation characteristic measurement part 20 Propagation characteristic measurement Antenna 21 Vehicle type sensor

Claims

A wireless communication system that transmits and receives information using a wireless signal between a fixed base station and a terminal station within the communication area of the base station,
The base station is
A transmission signal equalization processing unit configured to perform equalization processing on a transmission signal by setting an optimal equalization processing parameter for the propagation characteristic of the signal propagation path;
A transmission unit for transmitting a processing signal from the transmission signal equalization processing unit;
A receiving unit for receiving a signal from the terminal station;
A reception signal equalization processing unit configured to equalize the reception signal received by the reception unit with the same equalization processing parameter set as the transmission signal equalization processing unit;
A parameter storage unit that stores a plurality of parameters for equalization processing that are optimal for a plurality of different propagation characteristics assumed in advance for the propagation path;
One of the plurality of stored equalization processing parameters is sequentially set in the transmission signal equalization processing unit and the reception signal equalization processing unit, and based on the presence or absence of a response signal from the terminal station for the transmission signal A communication control unit that performs communication by determining an optimal equalization processing parameter;
A wireless communication system comprising:

2. The wireless communication system according to claim 1, wherein the communication control unit is configured to always repeat an operation of transmitting a transmission signal every time one of the plurality of stored equalization processing parameters is set.

3. The wireless communication according to claim 1, wherein the base station includes a propagation characteristic measurement unit that measures a propagation characteristic of a propagation path, determines an optimal equalization processing parameter, and stores the parameter in the parameter storage unit. system.

The terminal station is a mobile terminal station mounted on a vehicle, and the mobile terminal station responds to a transmission signal from a base station when a vehicle mounting the mobile terminal station enters a communication area of the base station. The wireless communication system according to any one of claims 1 to 3, which is applied to a road-to-vehicle communication system in which a response signal is transmitted from the vehicle.

A configuration in which the propagation characteristics of a propagation path are measured for each of a plurality of vehicle types assumed in advance equipped with the terminal station, and an optimum equalization processing parameter corresponding to each vehicle type is determined and stored in the parameter storage unit. The wireless communication system according to claim 4.

The base station includes a vehicle type sensor that detects a vehicle type of a vehicle entering the communication area, and when the vehicle type of the approaching vehicle is determined by the vehicle type sensor, a plurality of equalization processing parameters stored in the parameter storage unit 6. The radio communication system according to claim 5, wherein an equalization processing parameter related to a known vehicle type is selected from among the parameters and set in the transmission signal equalization processing unit and the reception signal equalization processing unit.