JP2004221704A - Wireless system, server, and mobile station - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless position detection system for correcting a synchronizing error between base stations due to a measurement error of transmission reception times so as to enhance the positioning accuracy. <P>SOLUTION: The wireless position detection system evaluates and records a measurement error of transmission reception times of a signal between base stations in advance. The system evaluates and records a time error due to processing delay of the signal transmission reception or the like on the basis of transmission/reception times t1, t2 between the base stations 3, 4 and a signal propagation time T depending on the distance between the base stations. Or the system evaluates and records the measurement time error of the transmission signal between the base stations while a common clock is given to the base stations 3, 4. The system corrects a measurement result of times between the base stations by using the recorded error at positioning. <P>COPYRIGHT: (C)2004,JPO&amp;NCIPI

Description

【特許文献１】特開平７−１８１２４２号公報
【特許文献２】特表平１１−５１３４８２号公報
【発明が解決しようとする課題】
計測時間誤差や計測から送受信までの回路配線、処理遅延等により送信信号５の計測・記録時刻ｔ１、ｔ２と実際の送受信時刻とに差が生じる。図２に、図１の系内の信号送受信図を示す。時刻ｔ１に、δｔ、時刻ｔ２にδｒの誤差が生じるとする。数１で表される時刻のずれＯは数２の通り誤差（δｒ−δｔ）を持つこととなる。ここで誤差（δｒ−δｔ ）は信号を送受信する基地局の組合せに依らず一定であるとする。一般に誤差が信号を送受信する基地局の組合せに依る場合には、誤差を（δｒ_ｉ−δｔ_ｊ ）と記述する。ここでδｒ_ｉとは信号を受信する基地局ｉで記録された信号受信時刻と真の受信時刻との差であり、δｔ_ｊとは信号を送信する基地局ｊで記録された信号送信時刻と真の送信時刻との差であるとする。
【０００６】
【数２】

基地局（位置測定専用の信号送受信機器も含む）間で信号送受信時間を計測・記録し、該基地局間の時刻のずれを補正するシステムにおいて、計測時刻と実際の送受信時刻の差分を較正し、同期精度を上げることが本発明の課題である。
【０００７】
【課題を解決するための手段】
機器間で信号送受信時間を計測し、該機器間の時刻のずれを補正するシステムにおいて、計測時刻と実際の送受信時刻との差分を補正する。予め基地局間の通信の送受信時刻を測定する。サーバーもしくは移動局において該送受信時刻と基地局間距離で決まる信号伝搬時間とから信号送受信の処理遅延等による時刻のずれの誤差の算出を行い記録する。基地局間の時刻のずれの測定結果に対して前記記録した誤差値を用いて補正を行う。
【０００８】
【発明の実施の形態】
図３に本発明のシステム構成図の一例を示す。それぞれの基地局は有線（１５、１６、１７）でＬＡＮ２に接続されている。Ｔ_ｉ （ｉ＝２， ３， ２３）は信号伝搬時間である。Ｔ_ｉは既知である基地局間距離Ｌ_ｉ （ｉ＝２， ３， ２３）と信号伝搬の速さｃから既知である。基地局間距離Ｌ_ｉは、例えばサーバーが保持する基地局アンテナ座標から既知である。
【０００９】
図８に基地局の構成図の一例を示す。基地局９５は９、１０、１１のいずれであっても良い。ＬＡＮ Ｉ／Ｆ部８７はＬＡＮ２に対するインタフェースである。 時間測定部９２でメモリー８８に記録された受信情報と既知の情報との相関を相関器８９で計算する。既知の信号とは例えば、無線パケット先頭のプリアンブルや同期ワードであって良い。ＣＰＵ８６が相関器８９の出力が最大となる時刻をメモリ８４に記録する。ＣＰＵ８６は相関器８９出力を補間した結果が最大となる時刻をメモリ８４に記録しても良い。基地局間相互の送受信タイミングをそろえる為に外部から各基地局に共通のクロックを供給しても良い。このため基地局９５は外部クロックの入力端子９１を備えても良い。
ＲＦ部８０はＤＡＣ８２からのベースバンド信号を無線周波数にアップコンバートしてアンテナに出力する。またＲＦ部８０はアンテナの受信信号をベースバンドにダウンコンバートしてＡＤＣ８１に出力する。ＡＤＣ８１はアナログ信号を入力してデジタル信号に変換して出力する。ＤＡＣ８２はデジタル信号を入力してアナログ信号に変換し出力する。ベースバンド部８３はＡＤＣ８１からの入力信号に復調やデスクランブルやＣＲＣ（Ｃｙｃｌｉｃ Ｒｅｄｕｎｄａｎｃｙ Ｃｈｅｃｋ ｃｏｄｅ）等の各種復号化の信号処理を行う。ＣＰＵ８６は復号された情報をメモリ８４に書き込む。またＣＰＵ８６は送信する信号をメモリから読み出し、ベースバンド部８３に入力する。ベースバンド部８３は無線送信する情報の符号化、変調を行いＤＡＣ８２に出力する。
【００１０】
基地局相互の時刻のずれの誤差が送受信する基地局の組に依らず一定として該時刻のずれの誤差を測定および記録し、該誤差を用いて基地局間相互の時刻のずれを補正する例を説明する。各基地局が移動局からの到来信号の受信時刻を測定し測位に用いる場合で、基地局間で双方向に送信される信号を用いて基地局相互の時刻のずれの誤差を測定する場合の例を示す。本実施例によると、後述の、誤差が送受信する基地局の組合せに依存する場合と比較して、より簡単に誤差補正ができる。また処理は複雑になるが、後述の他の例に示す通り、誤差が送受信する基地局の組合せに依存する場合でも誤差補正が可能である。
【００１１】
以下に複数基地局間の信号送受信時間の測定から該送受信時間の誤差（δｒ−δｔ ）を求める原理を説明する。基地局１から信号を送信し送受信時間を記録する場合の、基地局間の信号の送受信図を図４に示す。時刻ｔ１に基地局１が信号を送信し、時刻ｔ２に基地局２が信号を受信する。また時刻ｔ３に基地局３が信号を受信する。ｔ１、ｔ２、ｔ３は記録された時間である。記録された送信時間と実際の送信時間との間の差をδｔとする。また、記録された受信時間と実際の受信時間との間の差をδｒとする。このとき、基地局１を基準とした基地局ｉ （ｉ＝２， ３）の時刻のずれをＯ_ｉとすると数３、数４の関係がある。
【００１２】
【数３】

【数４】

基地局３から信号を送信し送受信時間を記録する場合の、基地局間の信号の送受信図を図５に示す。時刻ｔ４に基地局３が信号を送信し、時刻ｔ５に基地局２が信号を受信する。また時刻ｔ６に基地局１が信号を受信する。ｔ１、ｔ２、ｔ３は記録された時間である。記録された送信時間と実際の送信時間との間の差をδｔとし、記録された受信時間と実際の受信時間との間の差をδｒとする。このとき、基地局１を基準とした基地局ｉ （ｉ＝２， ３）の時刻のずれをＯ_ｉとすると数５、数６の関係がある。
【００１３】
【数５】

【数６】

以下に、前記関係式を変形して時間の誤差（δｒ−δｔ ）を計算する例を示す。まず数３から数４を辺々減じて数７が得られる。
【００１４】
【数７】

さらに数５、数７より送信時間と受信時間の誤差の差分が数８で表される。右辺は測定により求まる量である。ｔ２、ｔ３、ｔ４、ｔ５は基地局で送受信時間を計測して得られる。Ｔ_２、Ｔ_３，、Ｔ _２３はそれぞれ基地局１と基地局２、基地局１と基地局３、基地局２と基地局３のアンテナ間距離を測定、もしくは基地局座標から計算し、信号伝搬の早さで割って求められる。
【００１５】
【数８】

以下に基地局相互の時刻のずれの誤差が送受信する基地局の組に依って異なる場合に該時刻のずれの誤差を測定および記録し、該誤差を用いて基地局間相互の時刻のずれを補正する実施例を説明する。本実施例によれば、時刻のずれの誤差が基地局に依存しないとする前述の方法に比べ、より精度良く誤差測定及び位置測定を行うことができる。
【００１６】
基地局１から信号を送信し送受信時間を記録する場合の、基地局間の信号の送受信図を図１０に示す。時刻ｔ１に基地局１が信号を送信し、時刻ｔ２に基地局２が信号を受信する。また時刻ｔ３に基地局３が信号を受信する。ｔ１、ｔ２、ｔ３は記録された時間である。基地局１において記録された送信時間と実際の送信時間との間の差をδｔ_１とする。また、基地局ｉで記録された受信時間と実際の受信時間との間の差をδｒ_ｉとする。このとき、基地局１を基準とした基地局ｉ （ｉ＝２， ３）の時刻のずれをＯ_ｉとすると数９、数１０の関係がある。
【００１７】
【数９】

【数１０】

基地局３から信号を送信し送受信時間を記録する場合の、基地局間の信号の送受信図を図１１に示す。時刻ｔ４に基地局３が信号を送信し、時刻ｔ５に基地局２が信号２３を受信する。また時刻ｔ６に基地局１が信号２４を受信する。ｔ４、ｔ５、ｔ６は記録された時間である。基地局３において記録された送信時間と実際の送信時間との間の差をδｔ_３とする。また、基地局ｉで記録された受信時間と実際の受信時間との間の差をδｒ_ｉとする。このとき、基地局１を基準とした基地局ｉ （ｉ＝２， ３）の時刻のずれをＯ_ｉとすると数１１、数１２の関係がある。
【００１８】
【数１１】

【数１２】

基地局２から信号を送信し送受信時間を記録する場合の、基地局間の信号の送受信図を図１２に示す。時刻ｔ７に基地局２が信号を送信し、時刻ｔ８に基地局３が信号１０１を受信する。また時刻ｔ９に基地局１が信号１０２を受信する。
ｔ７、ｔ８、ｔ９は記録された時間である。基地局２において記録された送信時間と実際の送信時間との間の差をδｔ_２とする。また、基地局ｉで記録された受信時間と実際の受信時間との間の差をδｒ_ｉとする。このとき、基地局１を基準とした基地局ｉ （ｉ＝２， ３）の時刻のずれをＯ_ｉとすると数１３、数１４の関係がある。
【００１９】
【数１３】

【数１４】

図９の構成により基地局を共通のクロックで動作させて測定した場合、基地局１を基準とした基地局ｉ （ｉ＝２， ３）の時刻のずれＯ_ｉはゼロである。数９、数１０、数１１、数１２、数１３、数１４よりそれぞれ以下の関係が求まる。ここで、誤差値Δ_ｊｉとは、送信基地局ｉ、受信基地局ｊの組合せについて測定された誤差（δｒ_ｊ−δｔ_ｉ ）である。
【００２０】
【数１５】

【数１６】

【数１７】

【数１８】

【数１９】

【数２０】

サーバーは数１５、数１６、数１７、数１８、数１９、数２０を計算し、記録する。サーバーは、時間のずれ測定時に数１５、数１６、数１７、数１８、数１９、数２０の値をそれぞれ数９、数１０、数１１、数１２、数１３、数１４に代入し、Δ_ｊｉを補正する。
【００２１】
サーバーは送信基地局ｉ、受信基地局ｊの組合せに対して誤差値Δ_ｊｉを記録する。記録フォーマット例を図１４に示す。１２１は送信基地局を特定する識別子である。１２２は通信チャンネルを特定する識別子である。１２３は送信基地局のアンテナ座標である。１２４は基地局間の時刻のずれである。例えば、前記基地局１を基準とする基地局ｉ （ｉ＝２， ３）の時刻のずれＯ_ｉを格納する。一般に１２４は特定の基地局を基準とする必要は無く、基地局間の相対的な時刻のずれの情報であれば良い。１２５は送受信処理遅延等に依る時間時刻のずれの誤差である。
送信基地局と受信基地局の組合せに対して決まる値である。例えば、送信基地局識別子ｉで特定される基地局および受信基地局識別子ｊで特定される基地局に対してΔ_ｊｉを格納する。
【００２２】
サーバーが送受信時間および基地局座標から誤差（δｒ−δｔ ）を計算し記録する。図６に、誤差（δｒ−δｔ ）を計測・記録し位置計算で補正に用いる場合の信号の送受信の例を示す。サーバーが時刻誤差測定要求４６、４７、４８を基地局１，２，３に送る。各基地局は他局からの信号の受信待機をする。基地局１は時刻ｔ１に信号２１，２２を送信し、それぞれ基地局２，３が、それぞれ時刻ｔ２、ｔ３に受信する。基地局１、２，３はそれぞれ時刻ｔ１、ｔ２、ｔ３を計測、記録する。ここで計測、記録された時刻は図４に示すように誤差を含む。基地局３は時刻ｔ４に信号２３，２４を送信し、それぞれ基地局２，１が、それぞれ時刻ｔ５、ｔ６に受信する。基地局３、２，１はそれぞれ時刻ｔ４、ｔ５、ｔ６を計測、記録する。計測、記録された時刻は図５に示すように誤差を含む。信号２１、２２、２３、２４は、例えばサーバーからの制御信号によって基地局が送信しても良く、また例えば各基地局が時刻誤差測定要求受信時刻から一定時間経過したことによって送信しても良い。基地局１，２、３は、記録した時刻をそれぞれ信号２５、２６、２７によってサーバーに伝送する。
【００２３】
図１３に信号２５、２６、２７のフォーマット例を示す。１１０は時間測定を行った基地局の識別子である。１１１は、信号２５、２６、２７に含まれる測定回数を表す。１１２は送受を表すフラグである。１１３は測定した送信時刻もしくは受信時刻である。信号２５、２６、２７は送受フラグと測定時刻の組を測定順に１１５で指定される測定回数分格納する。例えば、信号２５は、１１０に基地局１の識別子を格納する。１１１に測定回数２を格納する。１１２に送信フラグを格納し、１１３に送信時刻ｔ１を格納する。１１４に受信フラグを格納し、１１５に受信時刻ｔ６を格納する。サーバーは測定回数毎に送受フラグ１１２と基地局識別子１１１を解析することにより、送信基地局および受信基地局を特定する。
【００２４】
サーバーは数８によって誤差（δｒ−δｔ ）を計算し記録する。サーバーはチャンネル監視要求４１，４２，４３を、それぞれ基地局１，２，３に送信する。
サーバーは移動局１８に送信要求４４を送信する。移動局１８は測位のため信号２８、２９、３０を送信する。基地局１，２，３は、それぞれ信号２８、２９、３０を受信し、それぞれ受信時刻ｔ８、ｔ９、ｔ１０を記録する。基地局１は時刻のずれを測定するため、時刻ｔ１１に信号３１，３２を送信する。基地局２、基地局３はそれぞれ時刻ｔ１２に信号３１を、ｔ１３に信号３２を受信し時刻を記録する。時刻ｔ１１、ｔ１２、ｔ１３は図２及び数２で表したのと同様に誤差（δｒ−δｔ ）を含む。基地局１，２、３は、記録した時刻をそれぞれ信号３４、３５、３６によってサーバーに伝送する。サーバは信号２１，２２，２３，２４の送受信時刻を用いて時刻のずれを求めても良い。
【００２５】
数３、数４に、前記記録された誤差（δｒ−δｔ ）を代入し、それぞれ時刻のずれＯ_２、Ｏ_３を求めることが出来る。時刻のずれが時間の経過によらず一定の場合、本方法により信号３１、３２を送受信すること無く時刻のずれを求めることが出来る。
【００２６】
一方、時刻のずれが時間の経過と供に変化する場合には、時刻のずれを測定した時点での基地局間の時刻のずれの関係が測位の時点では最早成り立たなくなる。そこで測位に用いる信号２８，２９，３０の送信時刻に近い時刻に、時刻のずれを測定することが望ましい。この場合には信号２８，２９，３０の直後に送信される信号３１，３２を用いて時刻のずれを求める。サーバーは次のように誤差（δｒ−δｔ ）の補正を行う。信号３１，３２の送受信時間、ｔ１１、ｔ１２、ｔ１３と、基地局１と基地局ｉ （ｉ＝２， ３）間の伝搬時間Ｔ_ｉと、基地局１を基準とする基地局ｉ （ｉ＝２， ３）の時刻のずれＯ_ｉとの間には数２１、数２２の関係がある。
【００２７】
【数２１】

【数２２】

サーバーは数２１、数２２の（δｒ−δｔ ）に数８より求めて記録した値を代入しＯ_ｉの補正を行う。さらにサーバーは補正したＯ_ｉを記録し、位置計算に用いる。サーバーは補正した時刻のずれＯ_ｉを用いて次のように位置計算を行う。
【００２８】
基地局ｉ （ ｉ ＝１，２，３ ） のアンテナ位置座標を（ｘｉ， ｙｉ）、移動局位置を（ ｘｍ，ｙｍ ）とする。基地局のアンテナ位置座標は既知でサーバーが保持しているものとする。基地局間距離と、基地局が記録した信号受信時刻と、基地局間の時間のずれとの間に以下の関係がある。
【００２９】
【数２３】

【数２４】

サーバーは、数２３、数２４を（ｘｍ， ｙｍ ）について解き、移動局の位置座標を計算する。サーバーは信号３７で位置計算結果を移動局１８に送信する。
【００３０】
図７にサーバーが保持する情報のフォーマットの例を示す。７１は基地局を特定する識別子である。７２は通信チャンネルを特定する識別子である。７３はアンテナ座標である。７４は基地局間の時刻のずれである。例えば、前記基地局１を基準とする基地局ｉ （ｉ＝２， ３）の時刻のずれＯ_ｉを格納する。一般に７４は特定の基地局を基準とする必要は無く、基地局間の相対的な時刻のずれの情報であれば良い。７５は送受信処理遅延等に依る時間時刻のずれの誤差である。例えば、７５には前記（δｒ−δｔ ）を格納する。
【００３１】
基地局間で相互に送信される信号を用いて各基地局相互の時刻のずれの誤差を測定し、移動局で受信した各基地局からの信号の受信時刻を測位に用いる実施例を以下に示す。
【００３２】
図１５に、誤差（δｒ−δｔ ）を計測・記録し位置計算で補正に用いる場合の信号の送受信の他の例を示す。本例は各基地局からの送信信号を移動局１８が受信し、移動局の受信時間を測位に用いる例である。システムの構成は図３に示すものと同様である。サーバーが時刻誤差測定要求４６、４７、４８を基地局１，２，３に送る。各基地局は他局からの信号の受信待機をする。基地局１は時刻ｔ１に信号２１，２２を送信し、それぞれ基地局２，３が、それぞれ時刻ｔ２、ｔ３に受信する。基地局１、２，３はそれぞれ時刻ｔ１、ｔ２、ｔ３を計測、記録する。ここで計測、記録された時刻は図４に示すように誤差を含む。基地局３は時刻ｔ４に信号２３，２４を送信し、それぞれ基地局２，１が、それぞれ時刻ｔ５、ｔ６に受信する。基地局３、２，１はそれぞれ時刻ｔ４、ｔ５、ｔ６を計測、記録する。計測、記録された時刻は図５に示すように誤差を含む。信号２１、２２、２３、２４は、例えばサーバーからの制御信号によって基地局が送信しても良く、また例えば各基地局が時刻誤差測定要求受信時刻から一定時間経過したことによって送信しても良い。基地局１，２、３は、記録した時刻をそれぞれ信号２５、２６、２７によってサーバーに伝送する。
【００３３】
サーバーは数８によって誤差（δｒ−δｔ ）を計算し記録する。サーバーは、測位に用いる信号の送信要求１５０，１５１，１５２、およびチャンネル監視要求１５３を、それぞれ基地局１，２，３、移動局１８に送信する。基地局１，２，３は、それぞれ信号１３０、１３１、１３２を送信し、それぞれ送信時刻ｔ１６、ｔ１８、ｔ２０を測定する。移動局１８は測位のため信号１３０、１３１、１３２を受信し、それぞれ受信時刻ｔ１７、ｔ１９、ｔ２１を測定する。基地局１，２，３と移動局１８は測定した送受信時刻をそれぞれ信号１５４、１５５、１５６、１５７でサーバーに伝送する。サーバは信号２１，２２，２３，２４の送受信時刻を用いて時刻のずれを求めても良い。数３、数４に、前記記録された誤差（δｒ−δｔ ）を代入し、それぞれ時刻のずれＯ_２、Ｏ_３を求めることが出来る。時刻のずれが時間の経過によらず一定の場合、本方法により信号３１、３２を送受信すること無く時刻のずれを求めることが出来る。
【００３４】
一方、時刻のずれが時間の経過と供に変化する場合には、時刻のずれを測定した時点での基地局間の時刻のずれの関係が測位の時点では最早成り立たなくなる。そこで測位に用いる信号１３０，１３１，１３２の送信時刻に近い時刻に、時刻のずれを測定することが望ましい。この場合には信号１３０，１３１，１３２の後に送信される信号３１，３２を用いて時刻のずれを求める。時刻のずれを測定した時刻と測位の時刻を近くすることによって、時刻のずれをより正しく求めることが出来る。
【００３５】
基地局１は時刻のずれを測定するため、時刻ｔ１１に信号３１，３２を送信する。基地局２、基地局３はそれぞれ時刻ｔ１２に信号３１を、ｔ１３に信号３２を受信し時刻を記録する。時刻ｔ１１、ｔ１２、ｔ１３は図２及び数２で表したのと同様に誤差（δｒ−δｔ ）を含む。基地局１，２、３は、記録した時刻をそれぞれ信号３８、３９、４０によってサーバーに伝送する。
【００３６】
サーバーは誤差（δｒ−δｔ ）の補正を行う。ｔ１１、ｔ１２、ｔ１３と、基地局１と基地局ｉ （ｉ＝２， ３）間の伝搬時間Ｔ_ｉと、基地局１を基準とする基地局ｉ （ｉ＝２， ３）の時刻のずれＯ_ｉとの間には数２１、数２２の関係がある。
【００３７】
サーバーは数２１、数２２の（δｒ−δｔ ）に数８より求めて記録した値を代入しＯ_ｉの補正を行う。さらにサーバーは補正したＯ_ｉを記録し、位置計算に用いる。サーバーは補正した時刻のずれＯ_ｉを用いて次のように位置計算を行う。
【００３８】
基地局ｉ （ ｉ ＝１，２，３ ） のアンテナ位置座標を（ｘｉ， ｙｉ）、移動局位置を（ ｘｍ，ｙｍ ）とする。基地局のアンテナ位置座標は既知でサーバーが保持しているものとする。基地局間距離と、基地局が記録した信号受信時刻と、基地局間の時間のずれとの間に以下の関係がある。
【００３９】
【数２５】

【数２６】

サーバーは、数２５、数２６を（ｘｍ， ｙｍ ）について解き、移動局の位置座標を計算する。サーバーは信号５０で位置計算結果を移動局１８に送信する。
【００４０】
上記例は、サーバーが計測時間を集めて基地局間の時間のずれを補正するが、移動局が計測時間を集めて時間のずれの補正を行っても良い。この場合、移動局１８が図１４のフォーマットの情報を保持する。またこの場合、図１５において、フローは例えば以下の通り変更される。信号２５、２６、２７はサーバーではなく、移動局１８に送信される。移動局１８で前記例と同様に時刻のずれを計算し記録する。測位のための測定時刻を含む信号３４，３５，３６は移動局１８に送信される、信号３７は不要である。基地局間の時刻のずれ算出のための測定時刻を含む信号３８、３９、４０が移動局１８に送信される。移動局１８が誤差補正および位置計算を行う。サーバーからの位置計算結果の通知のための信号５０は不要である。また、フェ−ジング等無線環境による時間測定の精度劣化の影響を防ぐ為に、基地局間時刻のずれの誤差の測定を有線で行っても良い。例えば（δｒ−δｔ ）およびΔ_ｊｉの測定は、図３、図９の構成において基地局アンテナを信号線に換えて基地局間を結線し、有線で行っても良い。このとき前記例のＴ_ｉ（ｉ＝２， ３， ２３）は、それぞれ基地局１と基地局２間、基地局１と基地局３間、基地局２と基地局３間の信号線の信号伝搬時間とすれば、前記例と同様に誤差測定が可能である。
【００４１】
各基地局相互の時刻のずれの誤差を測定および記録し、記録された該誤差を用いて前記検出された基地局間相互の時刻のずれを補正する他の例を説明する。各基地局が移動局からの到来信号の受信時刻を測定し測位に用いる場合で、各基地局に共通のクロックを供給し基地局間で一方向に送信される信号を用いて各基地局相互の時刻のずれの誤差を測定する場合の例を以下に示す。
【００４２】
基地局１，２，３が外部から共通のクロック９９を、外部クロックの入力端子９１から入力する場合のシステム構成を図９に示す。信号線９６、９７、９８の長さを揃え、９９から各基地局までの信号伝搬時間を一定とする。
【００４３】
基地局１，２，３で共通のクロックのため、数３、数４、数５、数６、数２１、数２２においてＯ_ｉがゼロとなる。数３より、誤差（δｒ−δｔ ）は数２７で表される。送信時刻ｔ１と、受信時刻ｔ２と、基地局１，２間距離より求めた信号伝播時間Ｔ_２との測定により誤差（δｒ−δｔ ）が求められる。図３の構成で基地局間が非同期で運用するシステムでも、実際に運用するシステム構築前に図９の構成として基地局間時刻のずれの誤差測定および記録を行っても良い。時刻のずれの誤差は基地局位置に依存しない為、図９と図３とで基地局位置が異なっていても良い。また、図９は３基地局からなるシステムの例であるが、一般に２基地局以上なら良い。例えば基地局ｉと基地局ｊの２局に共通のクロックを供給し誤差（δｒ−δｔ ）の測定を行っても良い。数２７は基地局１と基地局２との２基地局のみを共通のクロックとしても成り立つ。この場合も、前記と同様にサーバーへ情報を伝達し、サーバーで数２７より（δｒ−δｔ ）を計算し図７のフォーマットで記録できる。図３の構成において運用時の誤差（δｒ−δｔ ）の補正方法は前記例と同様である。
【００４４】
【数２７】

【発明の効果】
本発明のシステムは、各基地局が無線信号の送信時刻および受信時刻を計測して基地局間相互の時刻のずれを検出し、前記各基地局相互の時刻のずれを用いて移動局の位置を検出する。さらに本発明のシステムは各基地局が信号の送信時刻および受信時刻を計測して基地局間相互の時刻のずれの誤差を測定および記録する。本発明のサーバーもしくは移動局は、該送受信時刻と基地局間距離で決まる信号伝搬時間とから信号送受信の処理遅延等による時刻のずれの誤差の算出を行い記録する。記録された該誤差を用いて前記検出された基地局間相互の時刻のずれを補正する。本発明のシステムは基地局間の時刻のずれの測定結果に対して前記記録した誤差値を用いて補正を行うので、基地局間の時刻のずれを精度良く測定出来る。
【００４５】
本発明のシステムは、各基地局相互の時刻のずれを用いて移動局の位置を検出する、また、計測時刻と実際の送受信時刻との差分を補正するので、基地局間の同期精度を上げることが出来る。結果として位置検出の精度を上げることが出来る。
【図面の簡単な説明】
【図１】同期補正系構成の一例の図。
【図２】系内の信号送受信の一例の図。
【図３】本発明によるシステム構成の一例の図。
【図４】本発明による基地局間信号送受信の一例の図。
【図５】本発明による基地局間信号送受信の一例の図。
【図６】本発明による測位フローの一例の図。
【図７】本発明によるデータフォーマットの一例の図。
【図８】基地局構成の一例の図。
【図９】本発明によるシステム構成の一例の図。
【図１０】本発明による基地局間信号送受信の一例の図。
【図１１】本発明による基地局間信号送受信の一例の図。
【図１２】本発明による基地局間信号送受信の一例の図。
【図１３】本発明による信号フォーマットの一例の図。
【図１４】本発明によるデータフォーマットの一例の図。
【図１５】本発明による測位フローの一例の図。
【符号の説明】
１：サーバ、２：ＬＡＮ、３、４、９、１０、１１：基地局、５：送信信号、６：受信時刻情報、７：送信時刻情報、１８：移動局、２１、２２、２３、２４、２５、２６、２７、３４、３５、３６：信号、３７：位置計算結果、４１、４２、４３：チャンネル監視要求、４４：送信要求、４６、４７、４８：時刻誤差測定要求
７１：基地局識別子、７２：チャンネル識別子、７３、アンテナ座標、７４：時刻のずれ、７５：時刻のずれの誤差
８０：ＲＦ部、８１：ＡＤＣ、８２：ＤＡＣ、８３：ベースバンド部、８４、８８：メモリ、８６：ＣＰＵ、８７：ＬＡＮ Ｉ／Ｆ部、８９：相関器、９０、９９：クロック、９１：外部クロックの入力端子、９２：時間測定部
１１０：基地局識別子、１１１：測定回数、１１２：送受フラグ、１１３：送受時刻、
１２１：送信基地局識別子、１２２：チャンネル識別子、１２３：送信基地局アンテナ座標、１２４：時刻のずれ、１２５：時刻のずれの誤差
１５０、１５１、１５２：測位信号送信要求、１５３：チャンネル監視要求、１５４、１５５、１５６、１５７：送受信時刻信号。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a position detection technique in a wireless communication system.
[0002]
[Prior art]
A system is disclosed in which a distance difference between a plurality of base stations and a mobile station is measured, and a mobile station position is obtained by using the measurement results and the base station position. Since a propagation delay time difference is measured in order to obtain a distance difference between a plurality of base stations and a mobile station, time alignment between the base stations is required. For example, Patent Literature 1 discloses a system that obtains a signal propagation delay time difference by subtracting a transmission time difference predetermined for each base station from signals from a plurality of base stations. In this example, the base stations are synchronized and transmit a signal at a timing determined for each base station.
[0003]
Patent Document 2 discloses that a signal from a plurality of base stations (BTS) is simultaneously received and compared by both a mobile station and a fixed station at a known position, and a delay between signals received by both stations is determined. A system is disclosed. In this example, the base stations are asynchronous, and the time difference between the transmission signals from each base station to the mobile station is corrected using the signal reception time from each base station at a fixed station installed at a known position. is there.
[0004]
Japanese Patent Application No. 2002-260772, filed earlier by the same applicant, discloses a synchronization correction between base stations described below. In this example, each base station measures a transmission time or a reception time of a radio signal to detect a time lag between the base stations, and corrects the time of each base station using the lag, or performs position calculation. At this time, taking into account the clock skew, a state equivalent to synchronization between base stations is created in calculation. FIG. 1 shows a conventional example in which the synchronization between the base stations 3 and 4 is corrected. The transmission signal 5 is transmitted from the base station 3 to the base station 4. The base station 3 measures and records the transmission time t1 of the signal 5, and the base station 4 measures and records the reception time t2 of the signal 5. The base stations i and j transmit the times t1 and t2 and the identifiers of the base stations i and j to the server 1 by means of 7 and 6, respectively. It is assumed that the distance L between the base stations i and j or the coordinates of the antenna positions of the base stations i and j are measured in advance and registered in the server 1. The server 1 calculates the time difference O of the time of the base station j with respect to the base station i by Expression 1. Further, the time lag O is used for synchronization correction between the base station i and the base station j. Here, T is the signal propagation time between base stations, and c is the signal propagation speed.
[0005]
(Equation 1)

[Patent Document 1] JP-A-7-181242
[Patent Document 2] Japanese Patent Publication No. 11-513482
[Problems to be solved by the invention]
Due to a measurement time error, circuit wiring from measurement to transmission and reception, processing delay, and the like, a difference occurs between the measurement and recording times t1 and t2 of the transmission signal 5 and the actual transmission and reception times. FIG. 2 shows a signal transmission / reception diagram in the system of FIG. It is assumed that an error of δt occurs at time t1 and an error of δr occurs at time t2. The time lag O represented by Equation 1 has an error (δr−δt) as shown in Equation 2. Here, it is assumed that the error (δr−δt) is constant irrespective of the combination of base stations that transmit and receive signals. Generally, when the error depends on the combination of base stations that transmit and receive signals, the error is calculated as (δr _i -Δt _j ). Where δr _i Is the difference between the signal reception time recorded at the base station i that receives the signal and the true reception time, and δt _j Is the difference between the signal transmission time recorded at the base station j transmitting the signal and the true transmission time.
[0006]
(Equation 2)

In a system for measuring and recording signal transmission / reception time between base stations (including signal transmission / reception devices dedicated to position measurement) and correcting a time lag between the base stations, a difference between the measured time and the actual transmission / reception time is calibrated. It is an object of the present invention to improve synchronization accuracy.
[0007]
[Means for Solving the Problems]
In a system for measuring a signal transmission / reception time between devices and correcting a time difference between the devices, a difference between a measured time and an actual transmission / reception time is corrected. The transmission / reception time of communication between base stations is measured in advance. The server or mobile station calculates and records a time deviation error due to a signal transmission / reception processing delay or the like from the transmission / reception time and the signal propagation time determined by the distance between base stations. The measurement result of the time lag between the base stations is corrected using the recorded error value.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 3 shows an example of a system configuration diagram of the present invention. Each base station is connected to LAN2 by wire (15, 16, 17). T _i (I = 2, 3, 23) is the signal propagation time. T _i Is a known distance L between base stations. _i (I = 2, 3, 23) and the signal propagation speed c. Base station distance L _i Is known from the base station antenna coordinates held by the server, for example.
[0009]
FIG. 8 shows an example of a configuration diagram of a base station. The base station 95 may be any one of 9, 10, and 11. The LAN I / F unit 87 is an interface for LAN2. The correlator 89 calculates the correlation between the received information recorded in the memory 88 and the known information in the time measuring unit 92. The known signal may be, for example, a preamble or a synchronization word at the head of a wireless packet. The CPU 86 records the time when the output of the correlator 89 becomes maximum in the memory 84. The CPU 86 may record the time at which the result of interpolation of the correlator 89 becomes maximum in the memory 84. A common clock may be externally supplied to each base station in order to align the transmission and reception timings between the base stations. Therefore, the base station 95 may include an input terminal 91 for an external clock.
The RF unit 80 up-converts the baseband signal from the DAC 82 to a radio frequency and outputs the radio frequency to the antenna. Further, the RF unit 80 down-converts the received signal of the antenna to a baseband and outputs the signal to the ADC 81. The ADC 81 receives an analog signal, converts the signal into a digital signal, and outputs the digital signal. The DAC 82 receives a digital signal, converts the signal into an analog signal, and outputs the analog signal. The baseband unit 83 performs demodulation, descrambling, and various kinds of decoding signal processing such as CRC (Cyclic Redundancy Check code) on the input signal from the ADC 81. The CPU 86 writes the decrypted information into the memory 84. Further, the CPU 86 reads out a signal to be transmitted from the memory and inputs the signal to the baseband unit 83. The baseband unit 83 encodes and modulates information to be wirelessly transmitted, and outputs the result to the DAC 82.
[0010]
An example of measuring and recording an error of a time difference between base stations, regardless of a set of transmitting and receiving base stations, and measuring and recording the error of the time difference, and correcting the time difference between the base stations using the error. Will be described. When each base station measures the reception time of the incoming signal from the mobile station and uses it for positioning, and when measuring the error of the time difference between the base stations using the signal transmitted bidirectionally between the base stations. Here is an example. According to the present embodiment, error correction can be performed more easily as compared with a case where an error depends on a combination of transmitting and receiving base stations, which will be described later. Further, although the processing becomes complicated, as shown in another example described later, error correction can be performed even when the error depends on a combination of transmitting and receiving base stations.
[0011]
Hereinafter, the principle of obtaining the error (δr−δt) of the transmission / reception time from the measurement of the signal transmission / reception time between a plurality of base stations will be described. FIG. 4 shows a signal transmission / reception diagram between base stations when a signal is transmitted from the base station 1 and the transmission / reception time is recorded. At time t1, base station 1 transmits a signal, and at time t2, base station 2 receives the signal. At time t3, the base station 3 receives a signal. t1, t2, and t3 are recorded times. Let the difference between the recorded transmission time and the actual transmission time be δt. The difference between the recorded reception time and the actual reception time is denoted by δr. At this time, the time lag of the base station i (i = 2, 3) with respect to the base station 1 is represented by O _i Then, there is a relationship of Equations 3 and 4.
[0012]
[Equation 3]

(Equation 4)

FIG. 5 shows a signal transmission / reception diagram between base stations when a signal is transmitted from the base station 3 and the transmission / reception time is recorded. At time t4, the base station 3 transmits a signal, and at time t5, the base station 2 receives the signal. At time t6, base station 1 receives the signal. t1, t2, and t3 are recorded times. The difference between the recorded transmission time and the actual transmission time is δt, and the difference between the recorded reception time and the actual reception time is δr. At this time, the time lag of the base station i (i = 2, 3) with respect to the base station 1 is represented by O _i Then, there is a relationship of Expressions 5 and 6.
[0013]
(Equation 5)

(Equation 6)

Hereinafter, an example of calculating the time error (δr−δt) by modifying the relational expression will be described. First, Equation 7 is obtained by subtracting Equation 4 from Equation 3 everywhere.
[0014]
(Equation 7)

Further, from Expressions 5 and 7, the difference between the error between the transmission time and the reception time is expressed by Expression 8. The right side is an amount obtained by measurement. t2, t3, t4, and t5 are obtained by measuring the transmission / reception time at the base station. T ₂ , T _3, , T ₂₃ Is obtained by measuring the distance between the antennas of the base station 1 and the base station 2, the base station 1 and the base station 3, the base station 2 and the base station 3, or calculating from the base station coordinates, and dividing by the signal propagation speed. .
[0015]
(Equation 8)

If the time difference error between the base stations is different depending on the set of transmitting and receiving base stations, the time difference error is measured and recorded, and the time difference between the base stations is calculated using the error. An embodiment for correction will be described. According to the present embodiment, the error measurement and the position measurement can be performed more accurately than the above-described method in which the error of the time difference does not depend on the base station.
[0016]
FIG. 10 shows a signal transmission / reception diagram between base stations when a signal is transmitted from the base station 1 and the transmission / reception time is recorded. At time t1, base station 1 transmits a signal, and at time t2, base station 2 receives the signal. At time t3, the base station 3 receives a signal. t1, t2, and t3 are recorded times. The difference between the transmission time recorded at the base station 1 and the actual transmission time is δt ₁ And Also, the difference between the reception time recorded at the base station i and the actual reception time is δr _i And At this time, the time lag of the base station i (i = 2, 3) with respect to the base station 1 is represented by O _i Then, there is the relationship of Expression 9 and Expression 10.
[0017]
(Equation 9)

(Equation 10)

FIG. 11 shows a signal transmission / reception diagram between base stations when a signal is transmitted from the base station 3 and the transmission / reception time is recorded. At time t4, the base station 3 transmits a signal, and at time t5, the base station 2 receives the signal 23. At time t6, the base station 1 receives the signal 24. t4, t5, and t6 are the recorded times. The difference between the transmission time recorded at the base station 3 and the actual transmission time is δt ₃ And Also, the difference between the reception time recorded at the base station i and the actual reception time is δr _i And At this time, the time lag of the base station i (i = 2, 3) with respect to the base station 1 is represented by O _i Then, there is the relationship of Expression 11 and Expression 12.
[0018]
[Equation 11]

(Equation 12)

FIG. 12 shows a signal transmission / reception diagram between base stations when a signal is transmitted from the base station 2 and the transmission / reception time is recorded. At time t7, the base station 2 transmits a signal, and at time t8, the base station 3 receives the signal 101. At time t9, base station 1 receives signal 102.
t7, t8, and t9 are the recorded times. The difference between the recorded transmission time at base station 2 and the actual transmission time is δt ₂ And Also, the difference between the reception time recorded at the base station i and the actual reception time is δr _i And At this time, the time lag of the base station i (i = 2, 3) with respect to the base station 1 is represented by O _i Then, there is a relationship of Expressions 13 and 14.
[0019]
(Equation 13)

[Equation 14]

When the measurement is performed by operating the base station with a common clock by the configuration of FIG. _i Is zero. The following relationships can be obtained from Expression 9, Expression 10, Expression 11, Expression 12, Expression 13, and Expression 14, respectively. Here, the error value Δ _ji Is the error (δr) measured for the combination of the transmitting base station i and the receiving base station j. _j -Δt _i ).
[0020]
(Equation 15)

(Equation 16)

[Equation 17]

(Equation 18)

[Equation 19]

(Equation 20)

The server calculates and records Equation 15, Equation 16, Equation 17, Equation 18, Equation 19, and Equation 20. The server substitutes the values of Equation 15, Equation 16, Equation 17, Equation 18, Equation 19, and Equation 20 into Equations 9, 9, 10, 11, 12, 13, and 14 when measuring the time lag, Δ _ji Is corrected.
[0021]
The server determines the error value Δ for the combination of the transmitting base station i and the receiving base station j. _ji Record FIG. 14 shows an example of the recording format. Reference numeral 121 denotes an identifier for specifying a transmission base station. An identifier 122 specifies a communication channel. 123 is the antenna coordinates of the transmitting base station. Reference numeral 124 denotes a time lag between base stations. For example, the time lag O of the base station i (i = 2, 3) with respect to the base station 1 _i Is stored. In general, reference numeral 124 does not need to be based on a specific base station, but may be any information on the relative time lag between base stations. Reference numeral 125 denotes an error of a time / time shift due to a transmission / reception processing delay or the like.
This value is determined for a combination of the transmitting base station and the receiving base station. For example, for the base station specified by the transmitting base station identifier i and the base station specified by the receiving base station identifier j, Δ _ji Is stored.
[0022]
The server calculates and records the error (δr−δt) from the transmission / reception time and the base station coordinates. FIG. 6 shows an example of signal transmission / reception when an error (δr−δt) is measured and recorded and used for correction in position calculation. The server sends the time error measurement requests 46, 47, 48 to the base stations 1, 2, 3. Each base station waits for reception of a signal from another station. The base station 1 transmits signals 21 and 22 at time t1, and the base stations 2 and 3 receive the signals at times t2 and t3, respectively. The base stations 1, 2, and 3 measure and record the times t1, t2, and t3, respectively. Here, the time measured and recorded includes an error as shown in FIG. The base station 3 transmits signals 23 and 24 at time t4, and the base stations 2 and 1 receive the signals at times t5 and t6, respectively. The base stations 3, 2, and 1 measure and record times t4, t5, and t6, respectively. The time measured and recorded includes an error as shown in FIG. The signals 21, 22, 23, and 24 may be transmitted by the base station according to a control signal from a server, for example, or may be transmitted when each base station has passed a certain time from the time error measurement request reception time. . The base stations 1, 2, and 3 transmit the recorded times to the server by signals 25, 26, and 27, respectively.
[0023]
FIG. 13 shows a format example of the signals 25, 26, and 27. 110 is an identifier of the base station that performed the time measurement. 111 represents the number of measurements included in the signals 25, 26, and 27. A flag 112 indicates transmission / reception. Reference numeral 113 denotes a measured transmission time or reception time. Signals 25, 26, and 27 store sets of transmission / reception flags and measurement times for the number of measurements specified by 115 in the measurement order. For example, the signal 25 stores the identifier of the base station 1 in 110. The number of measurements 2 is stored in 111. The transmission flag is stored in 112, and the transmission time t1 is stored in 113. The reception flag is stored in 114, and the reception time t6 is stored in 115. The server specifies the transmitting base station and the receiving base station by analyzing the transmission / reception flag 112 and the base station identifier 111 for each measurement count.
[0024]
The server calculates and records the error (δr-δt) according to equation (8). The server sends channel monitoring requests 41, 42, 43 to base stations 1, 2, 3, respectively.
The server sends a transmission request 44 to the mobile station 18. The mobile station 18 transmits signals 28, 29, 30 for positioning. The base stations 1, 2, and 3 receive the signals 28, 29, and 30, respectively, and record the reception times t8, t9, and t10, respectively. The base station 1 transmits signals 31 and 32 at time t11 to measure the time lag. Base station 2 and base station 3 receive signal 31 at time t12 and signal 32 at t13, respectively, and record the time. Times t11, t12, and t13 include an error (δr−δt) as shown in FIG. The base stations 1, 2, and 3 transmit the recorded times to the server by signals 34, 35, and 36, respectively. The server may determine the time lag using the transmission / reception times of the signals 21, 22, 23, and 24.
[0025]
The recorded error (δr−δt) is substituted into Equations 3 and 4, and the time difference O ₂ , O ₃ Can be requested. If the time lag is constant over time, the method can determine the time lag without transmitting and receiving the signals 31 and 32.
[0026]
On the other hand, when the time lag changes with the passage of time, the relationship of the time lag between the base stations at the time when the time lag is measured is no longer established at the time of positioning. Therefore, it is desirable to measure the time lag at a time close to the transmission time of the signals 28, 29, 30 used for positioning. In this case, the time lag is determined using the signals 31, 32 transmitted immediately after the signals 28, 29, 30. The server corrects the error (δr−δt) as follows. The transmission and reception times of the signals 31 and 32, t11, t12 and t13, and the propagation time T between the base station 1 and the base station i (i = 2, 3) _i And the time difference O of the base station i (i = 2, 3) with respect to the base station 1 _i And the relationship of Expression 21 and Expression 22.
[0027]
(Equation 21)

(Equation 22)

The server substitutes the value obtained from Equation 8 and recorded in (δr-δt) of Equations 21 and 22 to obtain O _i Is corrected. In addition, the server corrected O _i Is recorded and used for position calculation. The server corrects the time difference O _i Is used to calculate the position as follows.
[0028]
Assume that the antenna position coordinates of the base station i (i = 1, 2, 3) are (xi, yy) and the mobile station position is (xm, ym). It is assumed that the antenna position coordinates of the base station are known and are held by the server. The following relationship exists between the distance between base stations, the signal reception time recorded by the base station, and the time lag between base stations.
[0029]
[Equation 23]

(Equation 24)

The server solves Equations 23 and 24 for (xm, ym) and calculates the position coordinates of the mobile station. The server transmits the position calculation result to the mobile station 18 by a signal 37.
[0030]
FIG. 7 shows an example of the format of information held by the server. 71 is an identifier for identifying the base station. 72 is an identifier for specifying a communication channel. 73 is an antenna coordinate. 74 is a time lag between base stations. For example, the time lag O of the base station i (i = 2, 3) with respect to the base station 1 _i Is stored. Generally, 74 does not need to be based on a specific base station, but may be any information on the relative time lag between base stations. Reference numeral 75 denotes an error of a time and time shift due to a transmission / reception processing delay or the like. For example, the above (δr−δt) is stored in 75.
[0031]
An example in which the error of the time difference between each base station is measured using signals mutually transmitted between the base stations and the reception time of the signal from each base station received by the mobile station is used for positioning is described below. Show.
[0032]
FIG. 15 shows another example of signal transmission / reception when the error (δr−δt) is measured and recorded and used for correction in position calculation. In this example, a mobile station 18 receives a transmission signal from each base station and uses the reception time of the mobile station for positioning. The configuration of the system is the same as that shown in FIG. The server sends the time error measurement requests 46, 47, 48 to the base stations 1, 2, 3. Each base station waits for reception of a signal from another station. The base station 1 transmits signals 21 and 22 at time t1, and the base stations 2 and 3 receive the signals at times t2 and t3, respectively. The base stations 1, 2, and 3 measure and record the times t1, t2, and t3, respectively. Here, the time measured and recorded includes an error as shown in FIG. The base station 3 transmits signals 23 and 24 at time t4, and the base stations 2 and 1 receive the signals at times t5 and t6, respectively. The base stations 3, 2, and 1 measure and record times t4, t5, and t6, respectively. The time measured and recorded includes an error as shown in FIG. The signals 21, 22, 23, and 24 may be transmitted by the base station according to a control signal from a server, for example, or may be transmitted when each base station has passed a certain time from the time error measurement request reception time. . The base stations 1, 2, and 3 transmit the recorded times to the server by signals 25, 26, and 27, respectively.
[0033]
The server calculates and records the error (δr-δt) according to equation (8). The server transmits a transmission request 150, 151, 152 and a channel monitoring request 153 of a signal used for positioning to the base stations 1, 2, 3 and the mobile station 18, respectively. The base stations 1, 2, and 3 transmit signals 130, 131, and 132, respectively, and measure transmission times t16, t18, and t20, respectively. The mobile station 18 receives the signals 130, 131, and 132 for positioning, and measures reception times t17, t19, and t21, respectively. The base stations 1, 2, 3, and the mobile station 18 transmit the measured transmission / reception times to the server as signals 154, 155, 156, and 157, respectively. The server may determine the time lag using the transmission / reception times of the signals 21, 22, 23, and 24. The recorded error (δr−δt) is substituted into Equations 3 and 4, and the time difference O ₂ , O ₃ Can be requested. If the time lag is constant over time, the method can determine the time lag without transmitting and receiving the signals 31 and 32.
[0034]
On the other hand, when the time lag changes with the passage of time, the relationship of the time lag between the base stations at the time when the time lag is measured is no longer established at the time of positioning. Therefore, it is desirable to measure the time lag at a time close to the transmission time of the signals 130, 131, 132 used for positioning. In this case, the time lag is determined using the signals 31, 32 transmitted after the signals 130, 131, 132. By making the time at which the time difference is measured close to the time of the positioning, the time difference can be obtained more correctly.
[0035]
The base station 1 transmits signals 31 and 32 at time t11 to measure the time lag. Base station 2 and base station 3 receive signal 31 at time t12 and signal 32 at t13, respectively, and record the time. Times t11, t12, and t13 include an error (δr−δt) as shown in FIG. The base stations 1, 2, and 3 transmit the recorded times to the server by signals 38, 39, and 40, respectively.
[0036]
The server corrects the error (δr−δt). propagation times T11, t12, and t13 between the base station 1 and the base station i (i = 2, 3) _i And the time difference O of the base station i (i = 2, 3) with respect to the base station 1 _i And the relationship of Expression 21 and Expression 22.
[0037]
The server substitutes the value obtained from Equation 8 and recorded in (δr-δt) of Equations 21 and 22 to obtain O _i Is corrected. In addition, the server corrected O _i Is recorded and used for position calculation. The server corrects the time difference O _i Is used to calculate the position as follows.
[0038]
Assume that the antenna position coordinates of the base station i (i = 1, 2, 3) are (xi, yy) and the mobile station position is (xm, ym). It is assumed that the antenna position coordinates of the base station are known and are held by the server. The following relationship exists between the distance between base stations, the signal reception time recorded by the base station, and the time lag between base stations.
[0039]
(Equation 25)

(Equation 26)

The server solves the equations (25) and (26) for (xm, ym) and calculates the position coordinates of the mobile station. The server transmits the position calculation result to the mobile station 18 by a signal 50.
[0040]
In the above example, the server collects the measurement time and corrects the time lag between the base stations. However, the mobile station may collect the measurement time and correct the time lag. In this case, the mobile station 18 holds the information in the format of FIG. In this case, in FIG. 15, the flow is changed as follows, for example. The signals 25, 26, 27 are transmitted to the mobile station 18, not to the server. The mobile station 18 calculates and records the time lag in the same manner as in the above example. The signals 34, 35 and 36 including the measurement time for positioning are transmitted to the mobile station 18, and the signal 37 is unnecessary. Signals 38, 39, and 40 including the measurement time for calculating the time difference between the base stations are transmitted to the mobile station 18. The mobile station 18 performs error correction and position calculation. The signal 50 for notifying the position calculation result from the server is unnecessary. Further, in order to prevent the influence of the accuracy of the time measurement from deteriorating due to the radio environment such as fading, the error of the time difference between the base stations may be measured by wire. For example, (δr−δt) and Δ _ji 3 and FIG. 9, the base station antenna may be replaced with a signal line in the configuration of FIG. At this time, T _i (I = 2, 3, 23) is the signal propagation time between the base station 1 and the base station 2, between the base station 1 and the base station 3, and between the base station 2 and the base station 3, respectively. Error measurement is possible as in the example.
[0041]
Another example of measuring and recording a time difference error between the base stations, and correcting the detected time difference between the base stations using the recorded error will be described. When each base station measures the reception time of an incoming signal from a mobile station and uses it for positioning, it supplies a common clock to each base station and uses signals transmitted in one direction between base stations to allow each base station to communicate with each other. An example of the case of measuring the error of the time lag is shown below.
[0042]
FIG. 9 shows a system configuration in which the base stations 1, 2, and 3 externally input a common clock 99 from an external clock input terminal 91. The lengths of the signal lines 96, 97 and 98 are made uniform, and the signal propagation time from 99 to each base station is made constant.
[0043]
Since the clocks are common to the base stations 1, 2, and 3, O in Equations 3, 4, 4, 5, 6, 21, and 22 _i Becomes zero. From Equation 3, the error (δr−δt) is expressed by Equation 27. The transmission time t1, the reception time t2, and the signal propagation time T calculated from the distance between the base stations 1 and 2. ₂ , An error (δr−δt) is obtained. Even in a system in which the base stations operate asynchronously in the configuration of FIG. 3, the error measurement and recording of the time lag between the base stations may be performed as the configuration of FIG. 9 before constructing the system to actually operate. Since the error of the time shift does not depend on the base station position, the base station position may be different between FIG. 9 and FIG. FIG. 9 shows an example of a system composed of three base stations. For example, a common clock may be supplied to the two base stations i and j to measure the error (δr−δt). Equation 27 holds even when only two base stations, base station 1 and base station 2, are used as a common clock. Also in this case, information can be transmitted to the server in the same manner as described above, and (δr−δt) can be calculated from Equation 27 by the server and recorded in the format shown in FIG. In the configuration of FIG. 3, the method of correcting the error (δr−δt) during operation is the same as in the above example.
[0044]
[Equation 27]

【The invention's effect】
In the system of the present invention, each base station measures a transmission time and a reception time of a radio signal to detect a time difference between the base stations, and uses the time difference between the base stations to determine a position of the mobile station. Is detected. Further, in the system of the present invention, each base station measures a transmission time and a reception time of a signal, and measures and records an error of a time difference between the base stations. The server or the mobile station of the present invention calculates and records a time deviation error due to a signal transmission / reception processing delay or the like from the transmission / reception time and the signal propagation time determined by the distance between base stations. Using the recorded error, the detected time lag between the base stations is corrected. The system of the present invention corrects the measurement result of the time lag between the base stations using the recorded error value, so that the time lag between the base stations can be accurately measured.
[0045]
The system of the present invention detects the position of the mobile station using the time lag between the respective base stations, and corrects the difference between the measured time and the actual transmission / reception time, thereby increasing the synchronization accuracy between the base stations. I can do it. As a result, the accuracy of position detection can be improved.
[Brief description of the drawings]
FIG. 1 is a diagram of an example of a configuration of a synchronization correction system.
FIG. 2 is a diagram showing an example of signal transmission / reception in a system.
FIG. 3 is a diagram showing an example of a system configuration according to the present invention.
FIG. 4 is a diagram showing an example of signal transmission and reception between base stations according to the present invention.
FIG. 5 is a diagram showing an example of signal transmission / reception between base stations according to the present invention.
FIG. 6 is a diagram showing an example of a positioning flow according to the present invention.
FIG. 7 is a diagram showing an example of a data format according to the present invention.
FIG. 8 is a diagram of an example of a base station configuration.
FIG. 9 is a diagram showing an example of a system configuration according to the present invention.
FIG. 10 is a diagram showing an example of signal transmission / reception between base stations according to the present invention.
FIG. 11 is a diagram showing an example of signal transmission and reception between base stations according to the present invention.
FIG. 12 is a diagram showing an example of signal transmission and reception between base stations according to the present invention.
FIG. 13 is a diagram showing an example of a signal format according to the present invention.
FIG. 14 is a diagram showing an example of a data format according to the present invention.
FIG. 15 is a diagram showing an example of a positioning flow according to the present invention.
[Explanation of symbols]
1: server, 2: LAN, 3, 4, 9, 10, 11: base station, 5: transmission signal, 6: reception time information, 7: transmission time information, 18: mobile station, 21, 22, 23, 24 , 25, 26, 27, 34, 35, 36: signal, 37: position calculation result, 41, 42, 43: channel monitoring request, 44: transmission request, 46, 47, 48: time error measurement request
71: base station identifier, 72: channel identifier, 73, antenna coordinates, 74: time deviation, 75: time deviation error
80: RF unit, 81: ADC, 82: DAC, 83: baseband unit, 84, 88: memory, 86: CPU, 87: LAN I / F unit, 89: correlator, 90, 99: clock, 91: External clock input terminal, 92: time measurement unit
110: base station identifier, 111: number of measurements, 112: transmission / reception flag, 113: transmission / reception time,
121: transmitting base station identifier, 122: channel identifier, 123: transmitting base station antenna coordinates, 124: time deviation, 125: time deviation error
150, 151, 152: positioning signal transmission request, 153: channel monitoring request, 154, 155, 156, 157: transmission / reception time signal.

Claims (9)

A plurality of base stations having different times, measuring a transmission time or a reception time of a first radio signal transmitted between the base stations, detecting a time difference between the base stations, A wireless system that detects a position of the mobile station using a reception time of a second wireless signal transmitted between a station and a mobile station and a time difference between the respective base stations,
Using the difference between the transmission time and the reception time of the first radio signal and the distance between the base stations, calculate the error of the time difference between the base stations, record the error, and use the error. A mobile station that detects the position of the mobile station by correcting the detected time lag between the base stations. 2. The radio system according to claim 1, wherein each of the base stations measures a reception time of a first radio signal transmitted from the mobile station, and a reception time of an incoming signal from the mobile station and each of the base stations. A wireless system for detecting a position of a mobile station using a time difference between each other and a position of each of the base stations. 2. The radio system according to claim 1, wherein the mobile station measures a reception time of a second radio signal transmitted from each of the base stations, and determines a reception time of an incoming signal from each of the base stations and the base station. A wireless system for detecting a position using a time difference between stations and a position of each of the base stations. 4. The wireless system according to claim 1, wherein the calculation of the time difference error between the base stations supplies a common clock to each base station, and the base stations transmit based on the common clock. A wireless system is performed using the first wireless signal. 4. The wireless system according to claim 1, wherein the calculation of the time difference error between the base stations is performed using two or more of the first wireless signals transmitted between the base stations. A wireless system, characterized in that: In a system in which a plurality of base stations have different times, a difference between a transmission time measured at the transmission base station and a reception time measured at the reception base station of a signal transmitted between the base stations, A server which calculates an error of a time difference between base stations using an inter-distance and records an error of a time difference between base stations. 7. The server according to claim 6, wherein the calculated time difference error between the base stations is recorded in association with the transmitting base station and the receiving base station. In a system in which a plurality of base stations have different times, a difference between a transmission time measured at the transmission base station and a reception time measured at the reception base station of a signal transmitted between the base stations, A mobile station which calculates an error of a time difference between base stations using an inter-distance and records an error of a time difference between base stations. 9. The mobile station according to claim 8, wherein the calculated time difference error between the base stations is recorded in association with the transmitting base station and the receiving base station.

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