JP2004007670A - Primitive handshake in adsl (asymmetric digital subscriber line) annex c synchronized to ttr - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technology to establish TTR display, which can be detected on a long loop with large noise, in ADSL annex C type communication systems. <P>SOLUTION: In a synchronization method, which synchronizes an initial procedure to TTR, in an ADSL annex C type communication system that has a transmission node and a receiving node, which are connected so as to enable communication, a special definition signal is transmitted during the period of one or more sets of known FEXT symbols related to a first output hyper frame. When the signal is received at the receiving node, the synchronization to the TTR is established by the special definition signal to enable the initial procedure for synchronization. <P>COPYRIGHT: (C)2004,JPO

Description

具体例において、上記ｘ（ｎ）は時間領域のＲＥＶＥＲＢ３３〜６４信号であり、ｙ（ｎ）はｘ（ｎ）を送信機から送信し、チャンネルｈ（ｎ）に通し、受信機で受信した信号である。したがって、ｙ（ｎ）はｘ（ｎ）とｈ（ｎ）の畳み込みであり、次式で定義される。
【００２７】
【数２】

式（２）のｙ（ｎ）を式（１）に代入すると、次式が得られる。
【００２８】
ｒ_ｘｙ（ｌ）　＝　ｈ（ｌ）　　　　　　ｌ　＝　０，±１，±２，．．．　　　　　　　　　　（３）
式（３）はｘ（ｎ）が広帯域のＰＲＢＳ（擬似ランダム２進シーケンス）であるという事実に基づいている。この種の信号の例として、Ｇ．９９２．１ドキュメントに記載されるＲＥＶＥＲＢタイプの信号を考慮する。さらに、ｘ（ｎ）の自己相関はデルタ関数で近似される。図３は本発明の１つの実施の形態に基づき、相関信号の例を示したものである。この相関信号は、４つの連続するＲＥＶＥＲＢ３３〜６４信号がＤＭＴ受信機の受信信号に存在することを表している。５ｋｍの紙パルプループと受信機に付加される−１３０ｄＢｍ／ＨｚのＡＷＧＮを想定している。図示のように、ＤＭＴシンボル０〜３にＲＥＶＥＲＢ３３〜６４信号が存在することを示す、４つの明白なピークがある。
デシメーション
ナイキスト標本化定理によれば、最大帯域幅ｆ_ｍＨｚのローパスアナログ信号は、サンプリングレートｆ_０をｆ_ｍの２倍以上とすると、サンプルによって表現され、サンプルから完全に復元することができる。最大帯域幅ｆ_ｍＨｚのアナログ信号を２ｆ_ｍ以上、例えば、４ｆ_ｍのサンプリングレートでサンプリングした信号は、情報損失なしに２でデシメーション処理する（１つ置きにサンプルを捨てる）ことができる。オーバーサンプリングしたアナログ信号が使用帯域を超えた不必要な信号を含む場合、デシメーション後に不必要な信号が使用帯域内に折り返すのを避けるため、デシメーションに先立ちフィルタリングが必要である。この処理はデシメーションフィルタリングと呼ばれる。
【００２９】
特殊定義ＴＴＲ表示信号がシンボル０〜３の間送信されるＲＥＶＥＲＢ３３〜６４である場合において、検出器モジュール２２５ｂは、シンボル０、１、２、３を受信したことを示す、４つの連続するＲＥＶＥＲＢ３３〜６４信号を検出するまで、受信サンプルに対する線形相互相関処理を実行し続ける。ＤＭＴシンボルの受信毎に、相互相関信号が計算される。検出器モジュール２２５ｂで解析するために、受信サンプルを（検出器モジュールに結合されるか、その内部に置かれる、ＲＡＭ、その他の記憶装置に）バッファリングし、又はその他の方法で保持する。当初、受信信号にＲＥＶＥＲＢ３３〜６４信号が現れた時点では、相互相関のピーク位置は、その受信シンボルについて計算した相関信号のサンプル内部における任意の位置であり得る。この理由は、受信機のフレーム境界の位置がまだ送信機のフレーム境界と合っていないからである。ここに、相互相関信号のピーク位置は、ハイパーフレームの位置合わせを可能にする、送信機と受信機のフレーム境界のオフセットを示すものである。この意味で、シンボル０〜３はハイパーフレーム合わせの、予め決められた証印を有する。
【００３０】
ここで、検出器モジュール２２５ｂは相互相関信号のピーク位置に基づき、フレーム境界の位置合わせを実行し、再度相関処理を行って次のハイパーフレームのＮ個のＲＥＶＥＲＢ３３〜６４信号を探索する。最初の４つの連続するＲＥＶＥＲＢ３３〜６４信号の検出に基づきフレーム境界の位置合わせが適正になされたら、相互相関のピークが相互相関信号の既知のサンプル（例えば、最初のサンプル）の位置で生じるとして（次のハイパーフレームにおいて）次の４つのＲＥＶＥＲＢ３３〜６４信号を検出する。このようにして、送信機と受信機のフレーム境界間の既知のオフセットが決まる。特に、相互相関信号の既知のサンプルにピーク位置をもつ、４番目に検出されるＲＥＶＥＲＢ３３〜６４信号はハイパーフレーム内のＤＭＴシンボル３の境界を表す。このようにして受信機はハイパーフレーム合わせを達成する。
【００３１】
ここに、現在の標準によるトーン４８（慣用のＴＴＲ表示信号）について、検出器モジュールの機能に影響を与えることなく、その位相トグル動作を従来と同様に実行することができる。さらに、トーン６４（慣用のパイロット信号）がＲＥＶＥＲＢｘ〜ｙ信号に含まれている。したがって、本発明は後方互換性を有する。
実現の詳細
実施形態において、プロセッサモジュール２２５は、本発明に基づき、ハイパーフレーム合わせ又は初期ハンドシェイク同期化を実行するようにプログラムされた、デジタル信号プロセッサ（ＤＳＰ）又はその他の適当な処理環境である。代替的な実施形態において、プロセッサモジュール２２５はＡＳＩＣやチップセット等の専用シリコンで実現される。プロセッサモジュール２２５を実現するためにＤＳＰとＡＳＩＣ技術の組合せを使用してもよい。したがって、本発明は、例えばハイパーフレーム合わせを実行する方法としてＡＤＳＬサービスプロバイダーが使用することができる。代わりに、本発明はモデムやプログラム可能なＤＳＰ又は専用チップ／チップセット等の装置に組み込むことができる。代わりに、本発明は、一方又は両方の送受信機が、後述する、ハイパーフレーム合わせ又は初期ハンドシェイク同期化を実行するように構成される送受信機対のようなシステムに組み込むことができる。代替として、本発明は、サーバやディスク等のコンピュータ読取可能な媒体に具体化したコンピュータプログラム製品等として組み込むことができる。
【００３２】
また、図示しないモジュールについても用途に応じてモデムに組み込むことができる。例えば、モデムは重複スペクトル用途で動作し、エコーキャンセラを備えてよい。他のモジュール（例えば、送信機と受信機のクロック）や構成については本開示から明らかである。さらに、プロセッサモジュール２２５はリンク初期化手続きの一環としてハイパーフレーム合わせ処理を自ら起動することができる。代わりに、イベント（例えば、位置合わせの検出失敗）やホストからの制御信号（例えば、ハイパーフレーム合わせソフトウェアの呼出又は論理イネーブルライン）により位置合わせ処理を起動することができる。同様に、リモートモデムによる、ハイパーフレーム合わせの起動を検出した後、プロセッサモジュール２２５はハイパーフレーム合わせ処理を開始することができる。代表的には、ＡＴＵ−Ｃモデムがハイパーフレーム合わせ処理を起動する。しかしながら、所望であれば、ＡＴＵ−Ｒがこの処理を起動するように構成することができる。
方法論
図４に、本発明の実施の形態に基づきハイパーフレーム合わせ処理を実行する方法のフローチャートを示す。この方法は、一般に伝送媒体を介して通信可能に結合される２つのモデムを備える通信システム（例えば、ＡＤＳＬアネックスＣ）において実施される。特に、この方法はシステムの特定の通信方向に関連する送信ノードにおいて実行される。送信（例えばローカル）と受信（例えばリモート）の両ノードのモデムは、例えば、図２で説明したように構成される。しかしながら、その他の構成も本開示から明らかである。
【００３３】
この方法はハイパーフレーム合わせ手続きを起動すること（ステップ４０５）から始まる。実施形態において、ハイパーフレーム合わせ手続きは通信リンクの初期化（例えばトレーニング）の期間中にＡＴＵ−Ｃにより起動される。しかしながら、代替的実施形態では、その他の時間（例えばサービスの中断後）でも位置合わせ手続きを起動することができる。さらに、方法は特別定義信号を発生し（ステップ４１０）、リモートノードにこの特殊定義信号をデータフレームにおける１以上の既知の区間中に送信する（ステップ４１５）。
【００３４】
実施形態において、データフレームはＤＭＴシンボル０〜３４４を有する、ＡＤＳＬダウンストリームのハイパーフレームであり、データフレームにおける１以上の既知の区間はハイパーフレームにおけるＤＭＴシンボル０〜３である。このデータフレームの最初の送信により送信機と受信機のシンボル境界の相対位置を識別することが上述したように可能になる。２回目（又はそれ以降）のフレーム送信によりハイパーフレーム合わせの確認が可能になる。代わりに、データフレームにおける１以上の既知の区間はハイパーフレームにおけるシンボルＮ_１〜Ｎ_２（例えば１４０〜１４４）及びハイパーフレームにおけるシンボルＮ_３〜Ｎ_４（例えば２３７〜２４１）である。このような実施形態では、シンボルＮ_１〜Ｎ_２の期間中に送信した特殊定義信号により送信機と受信機のシンボル境界のオフセットを識別することが可能となり、シンボルＮ_３〜Ｎ_４の間に送信した特殊定義信号によりハイパーフレーム合わせの確認が可能になる。
【００３５】
例えば、特殊定義信号は、疑似ランダムデータシーケンス又はその他の固有に識別可能な信号である。実施形態において、特殊定義信号は上述したＲＥＶＥＲＢタイプの信号に含まれるトーンのサブセット（例えば、ＲＥＶＥＲＢ６〜３１、ＲＥＶＥＲＢ１６〜３１、ＲＥＶＥＲＢ３３〜６４又はＲＥＶＥＲＢｘ〜ｙ（ここにｘ〜ｙは長いループの情報伝送で使用可能なトーンのセットを表す））である。このような特殊定義信号をデータフレームの既知の区間で送信することにより、長いループのリモート端で受信できる強固なＴＴＲ表示信号を提供する。
【００３６】
さらに、この方法はハイパーフレーム合わせの確認のため、リモートノードからの応答）を受信し（ステップ４２０）、その応答に基づき位置合わせが達成されたか判定する（ステップ４２５）。応答がハイパーフレーム位置の合っていることを確認している場合、手続きを終了する。ついで通信システムは他の初期化手続きを完了させ、データモード（例えばショウタイム）に移行する。しかし、応答がハイパーフレーム位置の不一致を確認している場合、ステップ４１５から４２０を繰り返す。上述したように、何回かの試み（例えば、Ｎ個のハイパーフレームの送信）の後、肯定応答を受信しなかった場合、送信側の送受信機はエラーとして認識するように構成される。
【００３７】
図５に、本発明のもう１つの実施の形態に基づきハイパーフレーム合わせ処理を実行する方法のフローチャートを示す。特に、この方法はシステムの特定の通信方向に関連する受信ノードにおいて実行される。
【００３８】
この方法はハイパーフレーム合わせ手続きを（例えば通信リンクの初期化におけるトレーニングの期間中にＡＴＵ−Ｃにより）起動すること（ステップ５０５）から始まる。さらに、方法はリモートノード送信機からデータフレームのデータを受信し（ステップ５１０）、データフレームにおける１以上の既知の区間で特殊定義信号を検出する（ステップ５１５）。特殊定義信号と既知のシンボルに関する上記説明はここでも適用される。方法はステップ５２０に進み、送信機と受信機の区間境界間のオフセットを識別し、ステップ５２５でハイパーフレーム合わせが達成されたか判定する。これらのステップを実施する特定の実施形態について以下説明する。
【００３９】
説明の便宜上、データフレームにおける既知の区間で送信される特殊定義信号は、ハイパーフレームにおけるシンボル０〜３の間送信されるＲＥＶＥＲＢｘ〜ｙ信号であるとする。実施形態において、送信機と受信機の区間境界間のオフセットは、４つの連続するＲＥＶＥＲＢｘ〜ｙ信号が検出される（これによりシンボル０〜３が示される）まで受信機のサンプルに対し線形相互相関を実行し続けることにより識別される。ここに、送信機と受信機のフレーム境界のオフセットはＲＥＶＥＲＶｘ〜ｙ信号の相互相関信号ピークに基づいて識別される。線形相互相関処理は後続のハイパーフレーム（例えば次のハイパーフレーム）で繰り返され、次の４つの連続するＲＥＶＥＲＢｘ〜ｙ信号が検出される。相互相関のピークが相互相関信号の既知のサンプル（例えば最初のサンプル）に位置する状態で次の４つの連続するＲＥＶＥＲＢｘ〜ｙ信号を検出することによりハイパーフレーム合わせが達成される。
【００４０】
もう１つの実施形態において、送信機と受信機の区間境界間のオフセットは、ＤＭＴシンボルの受信毎に相互相関信号を計算し、相互相関信号中に予め決められた、ハイパーフレーム合わせの証印を有する、Ｎ個の連続するＤＭＴシンボルを識別することによって識別される。この予め決まられた証印は、例えば、疑似ランダムデータシーケンスにトーンのセット（ｘ〜ｙ）（例えば、ＲＥＶＥＲＢ信号のトーン３３〜６４）を含む。フレーム境界位置合わせはこの証印を有する相互相関信号のピーク位置に基づいて行われる。２回目の相互相関処理を実行してＮ個の連続するＤＭＴシンボルの第２のセットを識別する。予め決められた証印の２度目の検出によりフレーム境界位置合わせを確認して、ハイパーフレーム合わせが達成されたことを示す。なお、２回目の相互相関処理は同一のハイパーフレーム又は後続のハイパーフレームのいずれで実行してもよい。さらに、プロセスを３回、４回、５回等の回数繰り返し実行して適切な位置合わせを確保するようにしてもよい。
【００４１】
ハイパーフレーム合わせが達成されない場合、方法はリモートノードにハイパーフレーム合わせが達成されていないことを示す否定の応答を送信する（ステップ５３０）。このような応答は例えば、特別に定義した信号あるいは単なる無音の期間である。ここで、受信状態にある送受信機は、複数回の試み（例えば複数回のハイパーフレームの送信）の後、肯定応答が受信されない場合、エラーとして認知するように構成することができる。一方、ハイパーフレーム合わせを達成した場合、方法はリモートノードにハイパーフレーム位置の一致を確認する応答を送信する（ステップ５３５）。ついで、通信システムはその他の初期化手続き（例えばチャンネル解析や交換）を完了し、データモード（例えばショータイム）に移行する。
初期化プロセスの全体概要
図６に、本発明の１つの実施の形態に基づく、初期化プロセスの概要を表すタイム図を示す。初期化プロセスは、撚り銅線対又はその他の伝送媒体を介して通信可能に結合される１以上のＡＤＳＬ通信のペアを備える通信システムにおいて実行されるものと想定する。
【００４２】
各送受信機について示す初期化プロセスは、初期ハンドシェイク手続きの後、送受信機のトレーニングとチャンネル解析の手続きが後続する構成である。その後、トレーニングと解析の手続きで習得した情報が交換される。ハンドシェイク手続きにより、一般に、新たに結合された送受信機は機能（ｃａｐａｂｉｌｉｔｉｅｓ）を交換し、共通の動作モードを選択することが可能になる。この初期ハンドシェイク手続きは、代表的には、ＩＴＵ−Ｔ勧告Ｇ．９９４．１（Ｇ．ｈｓ）又はその他の適当なハンドシェイク手続きに基づき実行される。
【００４３】
しかしながら、Ｇ．９９４．１は、上述したＴＴＲに基づく時分割二重方式を適用する、ＴＣＭ−ＩＳＤＮには同期しない。したがって、Ｇ．９９４．１信号はＴＣＭ−ＩＳＤＮ又はアネックスＣのＦＢＭのＮＥＸＴと、特に長距離ループ（例えば５ｋｍ以上）で干渉する。その結果ハンドシェイク手続きは失敗に帰すおそれがある。したがって、Ｇ．９９２のアネックスＣモデムのためにＧ．９９４．１の信頼性を高め強力なものにするニーズがある。
【００４４】
本発明の１つの実施の形態によりＧ．９９４．１をＴＣＭ−ＩＳＤＮに同期させることが可能となり、同期化はハンドシェイク手続きの前部期間において達成される。これによりＧ．９９４．１信号を長距離ループ上で例えばＦＥＸＴタイムの期間で交換することができ、ＮＥＸＴタイムの期間での送信を回避することができる。したがってより強力で信頼性の高いハンドシェイク手続きが実現される。
アネックスＣ　 Ｇ．９９４．１ のＴＴＲへの同期化
図７は本発明の１つの実施の形態に基づく、複式の初期化手続きのフローチャートである。特に、Ｇ．９９４．１のハンドシェイク手続きをＴＴＲに同期させる。いったんハンドシェイク手続きがＴＴＲに同期すると、ＮＥＸＴとＦＥＸＴの期間は既知になる。これにより意図的にＧ．ｈｓ信号（所望であればトレーニング信号等の他の初期化信号も可能である）を他方のモデムのＦＥＸＴ期間中に送信して信頼の置ける交換を確保することができる。
【００４５】
ハンドシェイク手続きの間、通信モデムはそれぞれＨＳＴＵ−Ｃ、ＨＳＴＵ−Ｒと呼ばれる。既存のＨＳＴＵ−Ｒの起動信号（Ｒ−ＴＯＮＥＳ−ＲＥＱ）は１６ｍｓ毎に位相反転し、ＴＴＲは５×１６ｍｓである８０ｍｓの周期を有する。本発明の１つの実施の形態に基づき、ＨＳＴＵ−ＣのＴＴＲ表示信号は、位相反転がＴＴＲに同期してなくて１６ｍｓという短い周期毎の正確な受信を妨げるような信号である、Ｒ−ＴＯＮＥＳ−ＲＥＱを送信しているＨＳＴＵ−Ｒにより確実に受信されるように定められる。
ハンドシェイク手続きのＨＳＴＵ−Ｃ起動方式
図７を参照すると、ＨＳＴＵ−ＣはＣ−ＳＩＬＥＮＴ１からの移行により開始し、ＴＴＲハイパーフレームの開始時にＣ−ＩＮＩＴと呼ばれる特別に定義されたハンドシェイク信号を送信する。例えば、Ｃ−ＩＮＩＴはＲＥＶＥＲＢ１６〜３１又はその他の上述したような特殊定義信号である。実施形態において、Ｃ−ＩＮＩＴはＤＭＴのＦＥＸＴ_Ｒシンボル０〜３、３３〜３６、１０８〜１１１及び１４０〜１４４の間、送信される。この特殊定義信号によりＴＴＲとの同期が可能となり、これにより同期化Ｇ．ｈｓ手続きが可能となり、その手続きのなかでハンドシェイク信号は図７に示すようにＦＥＸＴシンボルの期間のみ送信される。所望であれば、後続する初期化手続きであるトレーニングやチャンネル解析や交換においてＴＴＲとの同期を保持してよい。代わりに、後続する初期化手続きのなかで初期化を再度確立するようにしてもよい。
【００４６】
ここに、このＤＭＴシンボルのシーケンスは、ＴＴＲ期間の任意の位相において１６ｍｓ間隔の位相反転が現れる状況下で、このシーケンスが堅牢さを有することから選択された。上述したように、その他のデータパターン及びシンボル組合せを本発明の原理に基づきここで使用して信頼性の高い送信と受信を達成することもできる。
【００４７】
Ｃ−ＩＮＩＴを検出すると（例えば上述したＴＴＲ検出器）、ＨＳＴＵ−ＲはそのＰＧＡをセットし、シンボル位置合わせとタイミングの回復を実行する。さらに、ＨＳＴＵ−Ｒは、シンボル６〜９から始まり、シンボル１６〜１９、２７〜３０、・・・２１０〜２１４、・・・３４０〜３４３と続く（図１ｂに示す）、ＦＥＸＴ_Ｃシンボルの間、Ｒ−ＴＯＮＥ１_Ｆを送信する。実施形態において、ＨＳＴＵ−ＲがＣ−ＴＯＮＥＳ（慣用ハンドシェイク信号）を検出したら、ＨＳＴＵ−Ｒは適切に応答する前に、タイムアウトＴ１を待機してＨＳＴＵ−Ｃが本発明の原理に基づくＧ．ｈｓ手続きをサポートするかを決定する。
【００４８】
Ｒ−ＴＯＮＥ１_Ｆを検出した後、ＨＳＴＵ−Ｃは、ＦＥＸＴ_Ｒシンボルの間のみ、ＴＴＲハイパーフレームの開始時に始まるＣ−ＧＡＬＦ１_Ｆを送信する。各ビットはサブフレーム（０〜３、１１〜１４、２２〜２５、３３〜３６、・・・１４０〜１４３、・・・３３５〜３３８）の最初の４つのＦＥＸＴ_Ｒシンボルで送信される。３２ビットが８０ｍｓのハイパーフレーム内で送信される。上述したようにＧ．９９２ハイパーフレームは３４５個のＤＭＴシンボルから成る。ハイパーフレームには３２個のサブフレームがあり、各サブフレームはＴＴＲタイミングに依存する、１０〜１１個の連続するＤＭＴシンボルである。
【００４９】
Ｃ−ＧＡＬＦ１_Ｆの受信後、ＨＳＴＵ−Ｒはシンボル６〜９から始まる（Ｒ−ＴＯＮＥ１_Ｆの場合と同様）、ＦＥＸＴ_Ｃシンボルの間Ｒ−ＦＬＡＧ１_Ｆを送信する。Ｒ−ＦＬＡＧ１_Ｆを受信すると、ＨＳＴＵ−Ｃは、任意のＴＴＲサブフレームから始まる、サブフレームにおける最初の４つのＦＥＸＴ_Ｒシンボルの間、Ｃ−ＦＬＡＧ１_Ｆを送信する。ＨＳＴＵ−ＲでＣ−ＦＬＡＧ１_Ｆを受信すると、ＨＳＴＵ−Ｒは任意のＴＴＲサブフレームから始まる、最初のハンドシェイクトランザクションを開始することができる。
ハンドシェイク手続きのＨＳＴＵ−Ｒ起動方式
ＨＳＴＵ−Ｒが最初からＴＴＲにロックされるのでＨＳＴＵ−Ｃがハンドシェイク手続きを起動（開始）することは有益である。これによりＮＥＸＴ期間中に信号は送信されない。しかしながら、Ｒ−ＳＩＬＥＮＴ０から移行してＲ−ＩＮＩＴを送信することによりＨＳＴＵ−Ｒがハンドシェイク手続きを起動することができる。実施形態において、Ｒ−ＩＮＩＴはＲＥＶＥＲＢ６〜１５であるが、上述した信号やその他の特別定義ＴＴＲ表示信号をここで使用することができる。Ｒ−ＩＮＴの受信後、ＨＳＴＵ−Ｃは、ＨＳＴＵ−Ｃ起動方式で述べたのと同様にして、ＴＴＲハイパーフレームの開始時に始まるＣ−ＩＮＩＴを送信する。
【００５０】
ここに、Ｒ−ＩＮＩＴは、ＴＴＲにロックされるＨＳＴＵ−Ｃから信号をＨＳＴＵ−Ｒが受信する前に送信される。隣接する対のモデムに影響を及ぼすＮＥＸＴを回避するために、ＨＳＴＵ−Ｒはノイズパターンを検出し、高ノイズレベル（ＦＥＸＴ_Ｃ期間）のときのみＲ−ＩＮＩＴを送信するように構成することができる。
フォールバック手続き／後方互換性
上述したように、本発明は慣用の初期化手続きとの間で後方互換性を有する。例えば、ＨＳＴＵ−ＣがＣ−ＩＮＩＴを送ってハンドシェイク手続きを起動したがＨＳＴＵ−Ｒが応答しない場合を想定してみる。応答のない理由は、例えば、ＨＳＴＵ−Ｒが接続されていない、それが本発明の原理に基づく初期化手続きをサポートしていない、あるいはそれが与えられたループについて慣用のＧ．９９４．１初期化手続きの方がベターであると決定した、等である。
【００５１】
タイムアウト後、フォールバック手続きに入ることができる。例えば、ＨＳＴＵ−ＣはＣ−ＴＯＮＥＳを送るように構成される。ここでＨＳＴＵ−ＲがＲ−ＴＯＮＥ１で応答するならば、送受信機対は慣用のＧ．９９４．１初期化手続きにフォールバックする。しかしながら、ＨＳＴＵ−ＲがＣ−ＴＯＮＥＳに応答しない場合、ＨＳＴＵ−Ｃはタイムアウト後、再びＣ−ＩＮＩＴを送るように構成される。この交互動作はＨＳＴＵ−Ｒが肯定的に応答するか、あるいは長いタイムアウトが経過するまで何回か続けられる。このような交互動作により、既存のＧ．９９４．１装置における相互動作性の問題を少なくすることができる。
【００５２】
交互動作の長さは予め又はその他の方法で定められ、これによりＨＳＴＵ−Ｒは、ＨＳＴＵ−Ｃが本発明の原理に基づいて構成されているかどうかの決定を下すため、どのくらい長く受信信号をモニターすべきか知っている。これにしたがってＨＳＴＵ−Ｒは応答する。なお、本発明の原理に基づくＴＴＲ表示信号を既存のＧ．９９４．１起動信号と並列して送ることもできる。
【００５３】
次に、ＨＳＴＵ−ＲがＲ−ＩＮＩＴを送ってハンドシェイク手続きを起動したが（何らかの理由で）ＨＳＴＵ−Ｃが応答しない場合を想定してみる。Ｔ２のタイムアウト後、ＨＳＳＴＵ−ＲはＲ−ＴＯＮＥＳ−ＲＥＱ（慣用のハンドシェイク信号）を送るように構成される。ＨＳＴＵ−ＣがＣ−ＴＯＮＥＳで応答したならば、送受信機対は慣用のＧ．９９４．１及び初期化手続きにフォールバックする。しかしながら、ＨＳＴＵ−ＣがＲ−ＩＮＩＴに対しＣ−ＩＮＩＴで応答し、ＨＳＴＵ−Ｒがその後（例えば、ＨＳＴＵ−Ｒがループはさほど長くなく慣用のＧ．９９４．１が好ましいと決定したために）慣用のＧ．９９４．１にフォールバックすると決定した場合、ＨＳＴＵ−Ｒは無音を返すことができる。これによりＨＳＴＵ−Ｃはタイムアウトし、慣用のＧ．９９４．１に交互に後退して、Ｃ−ＴＯＮＥＳを送る。
フラグとメッセージ
慣用のＧ．９９４．１は８つの連続するＤＭＴシンボル内で同じ情報ビットを繰り返す必要がある。（図１ａに示すように）各ＴＴＲサブフレームには、代表的に４〜５個のＦＥＸＴ_Ｒシンボルと６〜７個のＮＥＸＴ_Ｒシンボルがある。本発明の１つの実施の形態において、１サブフレーム内の最初の４個のＦＥＸＴ_Ｒを用いて１ビットを送信する。したがって各情報ビットは４個の連続するＦＥＸＴ_Ｒシンボル内で送信される。もう一つの実施の形態ではサブフレームにおける全てのＦＥＸＴシンボルを用いて１ビットを送信する。したがって各情報ビットは４個又は５個の連続するＦＥＸＴ_Ｒシンボル内で送信される。このような構成は３４５個のシンボルを用いて３２ビットの情報を送信し、Ｇ．ｈｓビット当たり平均１０．７８個のＤＭＴシンボルとなる。モデムは、ＡＤＳＬアネックスＣのＦＢＭモードと同様にＦＥＸＴシンボルのみを送信する。エコーが存在しないので受信機のアルゴリズムは簡単になる。
【００５４】
本発明の代替的実施の形態において、ＦＥＸＴ又はＮＥＸＴシンボルに関わらず、１ＴＴＲ周期内の全シンボルを使用して１ビット情報を送信する。受信ノードを、一方はＦＥＸＴシンボル用、他方はＮＥＸＴシンボル用の、２つの受信機で構成する。２つの受信機の検出結果を比較し、（例えばＣＲＣ検査に基づき）信頼性の高い方を使用する。ＴＣＭ−ＩＳＤＮのノイズ下で、ＦＥＸＴ検出器はより信頼性のある結果を出す。しかしながら、他のノイズ状況下では、信頼性を良くするのにＮＥＸＴ検出器が役立つ可能性がある。このような環境は受信機の構成を複雑にし、半二重モードの利点を失うことになる（例えば、エコーキャンセレーションが必要になる）。
【００５５】
なお、上記ハンドシェイク信号（例えば、Ｃ−ＩＮＩＴ、Ｒ−ＴＯＮＥ１_Ｆ、Ｒ−ＩＮＩＴ）とハンドシェイク用のメッセージ長は、８０ｍｓの長さであるＴＴＲハイパーフレーム又は２．５ｍｓの長さであるサブフレームの倍数である。Ｇ．ｈｓからアネックスＣ動作モードへの移行時におけるＴＴＲとの同期は保持、又は保持されない。アネックスＣは、ＴＴＲと同期しない既存のＧ．９９４．１手続きとともに動作する必要があるので、いずれにせよアネックスＣ自身によるＴＴＲとの同期を実行する必要がある。
【００５６】
初期同期化の後、ＨＳＴＵ−ＣとＨＳＴＵ−ＲはＴＴＲとの同期を維持する必要がある。ＴＴＲクロックはＨＳＴＵ−Ｃで利用できるので、ＨＳＴＵ−Ｃはその送信クロックをＴＴＲにロックすることができる。ついでＨＳＴＵ−ＲはＨＳＴＵ−Ｃから受信した信号からタイミングの回復を実行する。実施形態において、ＨＳＴＵ−Ｒにおけるタイミング回復はループバックタイミング方式のなかで受信ハンドシェイク信号に基づき実行される。例えば、ループバックタイミングの実行により、ＨＳＴＵ−Ｒ送信機のクロックはＨＳＴＵ−Ｒ受信機のクロックにロックされ、ＨＳＴＵ−Ｒ受信機のクロックはＨＳＴＵ−Ｃ送信機のクロックにロックされ、ＨＳＴＵ−Ｃ送信機のクロックはＴＴＲにロックされる。もう１つの実施形態において、タイミング回復を可能にするために専用のパイロットトーンがＨＳＴＵ−ＣからＨＳＴＵ−Ｒに送信される。このパイロットトーンは全てのＤＭＴシンボルのなかで送信することができる。例えば、トーン１６をパイロットトーンとして使用できる。
混合ＳＮＲ環境用並列復号化
上述したように、Ｇ．ｈｓ受信機はＮＥＸＴとＦＥＸＴビットマップにおける異なるノイズ状況下で受信情報を復号する。さらに、任意の単一ＴＴＲ周期内においてＮＥＸＴからＦＥＸＴノイズへの移行中に１〜２個のシンボルがある。このような単一ＴＴＲ周期中の混合ＳＮＲ環境に対し、Ｇ．ｈｓ情報ストリームの復号を最適化する必要がある。Ｎ個の連続するシンボルに亘り単一の情報ビットが送られるので、本発明の１つの実施の形態では各ビット時間中に最大Ｎ個の受信機を並列に動作させる（例えばＮ＝８）。Ｇ．ｈｓフレームの受信後に、各受信機についてエラーチェック（例えばＣＲＣ）を計算する。正しいＣＲＣをもつ受信機からのビットストリームを使用する。
【００５７】
本発明の実施の形態に関する上記の説明は例示と説明のために提示したものである。説明は包括的ではなく、本発明を開示した形態そのものに限定することを意図していない。本書の開示に照らして多くの変形、変更形態が可能である。
【００５８】
例えば、本書で説明した特定の応用では、ハイパーフレーム合わせを確立するため、又はＧ．ｈｓ手続きをＴＴＲにロックするために特殊定義ＴＴＲ表示信号を使用する。しかしながら、本発明の原理に基づく特殊定義証印信号は、一般に特定の手続き又はイベントを与えられた基準に同期させるのに使用することができる。いったん同期が確立すれば、同期関係に関連する既知の特性を使用することができる。本書における一例ではＧ．ｈｓ信号がＴＴＲに同期する。この同期に関連する既知の特性として識別可能なＦＥＸＴとＮＥＸＴタイムの期間が含まれる。この与えられた知識に基づき、強力で信頼性の高い通信を行うことができる。このような同期関係を有するその他の応用についても等しく本発明の恩恵を受ける。
【００５９】
本発明の範囲は、特許請求の範囲によるべきであり、詳細な説明により限定されないことを意図している。
【図面の簡単な説明】
【図１ａ】ダウンストリームのＡＤＳＬアネックスＣハイパーフレーム構造を示す図である。
【図１ｂ】上り方向のＡＤＳＬアネックスＣハイパーフレーム構造を示す図である。
【図２】本発明の実施の形態に基づき、ハイパーフレーム合わせを実行するように構成されるＡＤＳＬモデムのブロック図である。
【図３】本発明の実施の形態に基づく、相互相関信号の例を示す図である。
【図４】本発明の実施の形態に基づき、ハイパーフレーム合わせを実行する方法を示すフローチャートである。
【図５】本発明のもう１つの実施形態に基づき、ハイパーフレーム合わせを実行する方法を示すフローチャートである。
【図６】本発明の実施の形態に基づく、初期化処理の概要を示すタイム図である。
【図７】本発明の実施の形態に基づく、初期化処理を示すフロー図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to communication, and more particularly, to a TTR indication (TTR indication) technique in an ADSL Annex C (Annex @ C) type communication system, which enables communication of an ASDL Annex C transceiver to a communication network timing reference (TTR) signal. It is possible to synchronize.
[0002]
[Prior art]
The Telecommunication Standardization Sector (ITU-T) of the International Telecommunication Union has drafted recommendations to facilitate the interoperation of communication networks. Two of these recommendations are described in G. 992.1 and G.G. 992.2, which defines the transceiver technology for Asynchronous Digital Subscriber Line (ADSL).
[0003]
G. FIG. 992.1 and G.G. Both the 992.2 standards use a multicarrier modulation scheme called Discrete Multitone (DMT) modulation technology. The DMT modulation scheme uses a large number of carriers or "tones" for both uplink and downlink communications. For example, G. The downlink communication of G.992.1 uses indexes up to 255, while G.992.1. In the downlink communication of 992.2, only the index up to 127 is used. By using multiple carriers instead of a single carrier, the available channel capacity is maximized and transmission bandwidth performance is optimized.
[0004]
G. FIG. 992.1 and G.C. All 992.2 have Annex C, which defines special recommendations for ASDL transceivers under the noise environment of the Time Compression Multiplexed Integrated Digital Communication Services Network (TCM-ISDN). References to "Annex C" can be found in G.W. 992.1 and G.C. 992.2 or both. TCM-ISDN conforms to ITU-T Recommendation G. 961 Appendix III. Recommendation G. Appendix III of 961 describes a ping-pong system in which data transmission (and reception) between two transceivers is performed under the control of a 400 Hz clock called TCM-ISDN timing reference (TTR). G. FIG. 992.1 and G.G. In Annex C of 992.2, the central office transceiver transmits a TTR indication signal during training of the transceiver, and the customer transceiver can receive it, locking the receiver and the transmitter to the TTR clock. This TTR display signal is based on 992.1 and G.C. The current version of 992.2 is tone 48 with phase inversion. The central office transmitter (ATU-C) transmits the data stream basically in the first half of the TTR period, and the customer transceiver (ATU-R) transmits basically in the second half of the TTR period. Such a ping-pong system is used in a communication channel environment having a high level of crosstalk interference due to a low-quality insulator (eg, pulp insulation) or the like in a bundle of cables where simultaneous transmission by the central office and the customer's transceiver is difficult. Particularly useful.
Hyper-frame alignment based on TTR detection
The TTR is used to lock the ATU-C A / D and D / A sampling rates and the ATU-C local clock frequency that controls the transmitter and receiver symbol rates. The ATU-C transmitter checks the phase of the TTR and locks its hyperframe window to the TTR. On the ATU-R side, the receiver tracks the signal received from the ATU-C transmitter and locks the local clock to the ATU-C clock frequency. The ATU-R further detects a hyperframe pattern from the TTR display signal received from the ATU-C, and matches its symbol counter to the hyperframe pattern (generally called hyperframe alignment). The symbol counter is used to keep track of the symbol index and is incremented by one for each symbol. This counter is reset to zero when it reaches 345 (there are 345 symbols in the hyperframe). In this way, the transmitter and the receiver are synchronized with the hyperframe. This alignment process occurs during transceiver training of the communication link between the two ADSL modems.
[0005]
Annex C defines a Dual Bitmap Mode (DBM) coding technique that provides a dual bitmap that is switched in synchronization with a hyperframe pattern that is synchronized with the TTR to provide a data stream with a dual bit rate. This technique is based on the observation that for short to medium distance local loops (eg, about 3 km), the signal-to-noise ratio (SNR) of the channel is sufficiently high during NEXT interference to transmit data at low bit rates. ing. Thus, under certain conditions, the DBM allows the TCM-ISDN transceiver to operate at full duplex by using different bit rates under NEXT and FEXT interference. In this sense, the communication channels operating under the DBM in the TCM-ISDN environment are essentially two communication channels, one is the FEXT channel and the other is the NEXT channel. A single bitmap mode (SBM, especially called FEXT bitmap or FBM) coding technique is also defined. In this case, the central office and the remote transceiver transmit data only during the FEXT time and do not transmit data at the same time (half-duplex mode).
[0006]
In DBM coding, the bit rate can be changed by switching the bitmap used to encode the symbols to be transmitted. As will be appreciated by those skilled in the art, a "bitmap" determines the number of bits of a symbol that can be encoded in each subchannel. "Symbol" is a basic unit of information transmitted by the transceiver. The number of bits encoded in each subchannel of a symbol is limited by the quality of the communication channel. The quality of a communication channel can be represented by its SNR. Therefore, a system using DBM uses two bitmaps having different data rates, one bitmap for NEXT time and one bitmap for FEXT time. In a system using the FBM, data is not transmitted at the NEXT time, and therefore, only one bitmap (FEXT bitmap) is used. Since each bitmap used in DBM corresponds to a different bit rate, a bitmap transition from one to the other must be detected to ensure a compatible transmitter / receiver pair. Since the standardized frame rate is not a multiple of the 400 Hz TTR signal, it is not easy to identify the boundary between the NEXT channel and the FEXT channel.
[0007]
G. FIG. 992.1 and G.G. According to Annex C of 992.2, ATU-C indicates the transition between the NEXT and FEXT bitmaps by a phase change of a single tone (tone 48). More specifically, the transmitter changes the phase of the single tone by 90 degrees to indicate the bitmap transition. Here, the ATU-R receiver needs to detect this phase change, and then detects the 345 symbol patterns shown in FIG. 1a and aligns them with the transmitter hyperframe.
[0008]
However, if the loop is long and the noise is large, it is very difficult to detect the phase change of the tone 48, and TTR detection is a bottleneck for a long reach. Further, since the TTR indication signal by tone 48 only indicates a bitmap transition, the receiver needs to search for the underlying pattern in FIG. 1a to identify and align the hyperframe boundaries. . For this reason, the process of hyperframe alignment performed on the receiver side becomes complicated, and the possibility of failure in a long loop increases.
[0009]
[Problems to be solved by the invention]
Therefore, what is needed is a TTR display signal that can be detected on long, noisy loops. Generally speaking, there is a need for signal synchronization or procedures for TTR.
[0010]
[Means for Solving the Problems]
One embodiment of the present invention provides a synchronization method for synchronizing an initialization procedure with a timing reference signal in an ADSL Annex C communication system. In this synchronization method, a specially defined signal is transmitted during one or more known symbols associated with an output hyperframe. When received by the receiving node, the special definition signal establishes synchronization with the timing reference signal. This enables a synchronization initialization procedure. In an alternative embodiment, a specially defined signal is received during one or more sets of known FEXT symbols for an output hyperframe to establish synchronization with the timing reference, thereby establishing a synchronization initialization procedure. enable.
[0011]
Another embodiment of the present invention provides a synchronizer configured to synchronize transmission by an ADSL Annex C transceiver to a timing reference signal. Such a synchronizer comprises a signal generation module configured to generate a specially defined signal transmitted during one or more known DMT symbols included in the output hyperframe. When received by the receiving node, the special definition signal establishes synchronization with the timing reference signal to enable a synchronization procedure. An alternative embodiment comprises a detector module configured to detect a specially defined signal during one or more known DMT symbols included in the input hyperframe. This detection establishes synchronization with the timing reference signal and enables a synchronization procedure.
[0012]
Another embodiment of the present invention provides a signal for use in an ADSL Annex C communication system. This signal is, for example, a set of tones transmitted during a plurality of known DMT symbols included in a hyperframe. Detection of this signal can synchronize the transmission performed by the transceiver included in the communication system with the timing reference signal, thereby enabling hyperframe alignment and / or synchronization initialization procedures.
[0013]
The features and advantages described herein are not all-inclusive, ie, many additional features and advantages will be apparent to those skilled in the art from the drawings and detailed description. Further, the language used herein has been selected for readability and illustrative purposes, and is not intended to limit the scope of the inventive subject matter.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Generally, the invention is embodied in a communication system having a transceiver pair communicatively coupled by a transmission medium (eg, a stranded copper pair). Thus, there is a transceiver pair in each communication direction (up and down). A specially defined TTR indication signal is generated by the transmitter at the transmitting node and transmitted to the receiving node. The specially defined signal is reliably detected by the receiver, which allows the transceiver to synchronize the transmission to the TTR. Therefore, the hyperframe alignment can be performed together with the synchronization initialization procedure.
Specially defined TTR display signal
Instead of using 90 degree phase reversal with a single tone to label the FEXT and NEXT bitmap boundaries, one embodiment of the present invention employs symbols 0, 1,. Only during periods 2 and 3 are REVERV type tones 33-64 transmitted. The specially defined signals are hereinafter referred to as REVERBs 33 to 64. As will be apparent from the disclosure herein, other specially defined TTR indication signals may be used (e.g., inverted versions of REVERBx-y, where x-y represents a set of tones).
[0015]
For example, the processor modules included in the ATU-C are programmed or otherwise configured to provide REVERBs 33-64 in a plurality of transmitted hyperframes. The processor modules included in the ATU-R can be configured to detect the known patterns of REVERBs 33-64 in symbols 0-3. Once a pattern is detected from four consecutive symbols, the positions of known symbols 0-3 within the hyperframe are identified. The ATU-R processor module can confirm these identification positions by detecting the REVERB 33 to 64 signals again from four consecutive symbols in the subsequent hyperframe. In particular, upon the second detection of four consecutive symbols with a known pattern, the receiver knows that symbol 3 is being received, and thus the hyperframe boundary is known.
[0016]
To ensure robust communication, the ATU-C transmitter may further continue to transmit REVERB 33-64 signals until ATU-R responds by transmitting R-REVBRB1 (or other response signal or flag). Can be configured. Therefore, the REVERB 33 to 64 signals are transmitted for the necessary number of hyperframes until the receiving node returns an acknowledgment of the positioning. If the acknowledgment is not received after several attempts (e.g., five times), the transmitting transmitter is configured to recognize the error. Then, appropriate processing is performed, such as re-starting or performing a loop diagnostic procedure to check for problems with the current communication link or to switch to a new link.
Alternative TTR indication signal
The present invention is not intended to be limited to the embodiments described herein. Rather, the principles of the present invention can be applied to many specific configurations. For example, tones 33 to 64 of the DMT spectrum were selected because G. This is because it represents a low frequency downlink tone as defined in 992.1. Such low frequency tones can be transmitted over long distances, improving the "reach" of the present invention. However, other tones can be used, for example, any tone or any tone capable of transmitting detectable information over a subset of the tones 33-64 (e.g., 34-61) or a long distance loop (e.g., 5 km or more). Tone groups (tones 6-31 or a subset thereof in overlapping spectrum applications where tones 6-31 are also used in the downstream direction) can be used. Similarly, uniqueness can be imparted to the transmitted TTR signal using data patterns other than the REVERB type. In short, any signal that is uniquely detectable at the receiving end of the long distance loop can be used in accordance with the principles of the present invention.
[0017]
Further, symbols other than 0 to 3 can be used. For example, symbols 341-344 can be used, or any uniquely identifiable group of symbols or portions of frame data can be used to identify the transmitter and receiver frame boundary offsets. In one alternative embodiment, a known pattern (e.g., REVERB 33-64 or REVERB 6-31) is₁~ N₂(E.g., symbols 140, 141, 142, 143, 144) and again₃~ N₄(Eg, 237, 238, 239, 240, 241). In this case, the special definition signal is transmitted twice over the symbols of the group within one hyperframe. According to such a specific example, instead of using two or more hyperframes as described above, (Symbol N₁~ N₂Can be identified (while receiving the symbol N)₃~ N₄Can be confirmed).
[0018]
The more symbols that are associated with a specially defined signal, the less likely the receiver will have signal detection errors. Thus, transmitting a specially defined signal during a plurality of symbols (eg, two or more symbols) provides a robust TTR indication. However, by transmitting a specially defined signal during only one known symbol period (if the receiving node can accurately detect this signal due to the noise and interference characteristics of the communication link), a hyper-signal according to the principles of the present invention is achieved. Frame alignment can be achieved.
Transceiver unit
FIG. 2 is a block diagram of an ADSL modem configured to perform hyperframe alignment according to one embodiment of the present invention. A pair of such modems is communicatively coupled, one modem being used at a local node (eg, CO (central office)) and the other modem being used at a remote node (eg, CPE (customer terminal)). You.
[0019]
The illustrated embodiment includes a transformer 205, a hybrid 210, a line driver 215, an analog front end (AFE) 220, and a processor module 225. The system interface is, for example, coupled to a network operating in an asynchronous transmission mode or a synchronous transmission mode. The network operator or manager can communicate with the modem via the system interface. Alternatively, the system interface may be coupled to an application running on a device, such as a customer's personal computer. The transmission medium is typically a copper loop or twisted pair. However, the invention also works with other types of transmission media.
[0020]
Transformer 205 couples the transmission medium to the circuitry of the modem and provides electrical isolation and a balanced interface. Hybrid 210 performs a 2/4 wire conversion to convert a bidirectional two wire signal from the transmission medium into two pairs of one way transmissions. One pair is for reception and the other pair is for transmission. The AFE 220 typically includes a digital / analog (D / A) converter 220a and an analog / digital (A / D) converter 220b, and further includes a gain adjustment module for optimizing a signal supplied to the processor module 225. Including. The signal received from the 4-wire interface of the hybrid 210 via the AFE 220 is converted from analog to digital by the A / D converter module 220b. The digital signal is then provided to the processor module 225.
[0021]
Regarding the transmission direction, data received from the system interface is processed by the processor module 225. The digital output of the processor module 225 is converted to a corresponding analog by the D / A converter 220a. The analog output of AFE 220 is provided to a line driver 25 operatively coupled to the 4-wire interface of hybrid 210. The transmission signal is supplied to the communication medium via the transformer 205. In an alternative configuration, it is not necessary to include all the elements shown in FIG. 2; for example, a transformerless design may be used.
[0022]
Processor module 225 is programmed or otherwise configured to perform a hyperframe alignment process in accordance with the principles of the present invention. In the illustrated embodiment, processor module 225 includes a signal generation module 225a and a detector module 225b. The signal generation module 225a is configured to generate a specially defined TTR indication signal to be transmitted from the transmitting node to the receiving node, and the detector module 225b is configured to detect the specially defined TTR indication signal. Processor module 225 performs a number of other functions, such as modulation / demodulation, coding / decoding, scrambling / descrambling, error detection (eg, CRC checking), framing / deframing, and other algorithmic functions. May be.
[0023]
For convenience of description, it is assumed that the modem having the configuration shown in FIG. 2 is used in both the transmitting node and the receiving node that determine one direction of the communication link. The specially defined TTR indication signal is transmitted from the transmitting node and received by the receiving node.
TTR display signal generator
During initialization, the processor module 225 generates a specially defined TTR indication signal, and the uniquely identifiable signal is transmitted to the transmission medium during one or more known symbol periods. The signal generation module 225a may be integrated within the processor module 225 as shown, or may be a separate module communicatively coupled to the processor module 225. For example, the signal generation module 225a is a programmed, independent module that is activated by a request from the module 225, supplies a specially defined data pattern, scrambles and performs other processing with the module 225, and performs a predetermined number of processes. , Known DMT symbols. In a specific example, the characteristics of the specially defined TTR indication signal are programmed into signal generation module 225a. For example, the programmed characteristics specify a subset of tones included in a REVERB type data pattern.
[0024]
In another embodiment, the characteristics of the specially defined TTR display signal are stored in a storage unit (eg, an EEPROM, or other programmable storage device). When the hyperframe matching process starts, the signal generation module 225a accesses the signal characteristics from the storage unit and generates a corresponding TTR signal. In such an embodiment, the local host can access the storage characteristics and dynamically update or change the specially defined TTR indication signal. For example, the specially defined TTR indication signal is changed from REVERB 33-64 (for example, used in a non-overlapping spectrum scheme) to REVERB 6-31 (for example, used in a overlapping spectrum scheme), or vice versa. In any case, the specially defined TTR indication signal is transmitted during one or more symbol periods.
[0025]
At the receiving node, the specially defined TTR indication signal is separated from the transmission medium by transformer 205 and provided to processor module 225 via hybrid 210 and AFE 220. Based on the known properties of the specially defined TTR indication signal, the detector module 225a of the receiver can detect the signal and perform hyperframe alignment.
TTR detector
The detector module 225a at the receiving node detects the specially defined TTR indication signal for a predetermined period (for example, DMT symbols 0 to 3). In an embodiment, upon this detection, detector module 225a uses a linear cross-correlation. In addition, the detector module 225a can perform decimation on the received data before performing cross-correlation to reduce computational complexity.
Cross correlation
In general, the cross-correlation of two signal sequences x (n) and y (n) is represented by a sequence r defined by_xy(L).
[0026]
(Equation 1)

In a specific example, the x (n) is a REVERB 33-64 signal in the time domain, and y (n) is a signal transmitted by transmitting x (n) from a transmitter, passing through a channel h (n), and receiving by a receiver. It is. Therefore, y (n) is the convolution of x (n) and h (n) and is defined by the following equation.
[0027]
(Equation 2)

By substituting y (n) in equation (2) into equation (1), the following equation is obtained.
[0028]
r_xy(L) = {h (l) {l} = {0, ± 1, ± 2,. . . (3)
Equation (3) is based on the fact that x (n) is a wideband PRBS (pseudo-random binary sequence). As an example of this type of signal, G. Consider the REVERB type signal described in the 992.1 document. Further, the autocorrelation of x (n) is approximated by a delta function. FIG. 3 shows an example of a correlation signal according to one embodiment of the present invention. This correlation signal indicates that four consecutive REVERB 33-64 signals are present in the received signal of the DMT receiver. Assume a 5 km paper pulp loop and an AWGN of -130 dBm / Hz added to the receiver. As shown, there are four distinct peaks indicating the presence of the REVERB 33-64 signals in DMT symbols 0-3.
Decimation
According to the Nyquist sampling theorem, the maximum bandwidth f_mHz low-pass analog signal has a sampling rate f₀To f_mIf it is twice or more, it is represented by a sample and can be completely restored from the sample. Maximum bandwidth f_mHz analog signal 2f_mAbove, for example, 4f_mThe signal sampled at the sampling rate can be decimated by 2 (discard every other sample) without loss of information. When the oversampled analog signal includes an unnecessary signal exceeding the use band, filtering is necessary prior to the decimation in order to prevent the unnecessary signal from folding back into the use band after decimation. This process is called decimation filtering.
[0029]
In the case where the specially defined TTR indication signal is REVERB 33-64 transmitted during symbols 0-3, detector module 225b indicates that four consecutive REVERBs 33-64 indicate that symbol 0, 1, 2, 3 has been received. The linear cross-correlation processing is continuously performed on the received samples until 64 signals are detected. Each time a DMT symbol is received, a cross-correlation signal is calculated. The received samples are buffered (in RAM or other storage, coupled to or located within the detector module) or otherwise stored for analysis by the detector module 225b. Initially, when the REVERB 33 to 64 signals appear in the received signal, the peak position of the cross-correlation may be any position within the sample of the correlation signal calculated for the received symbol. The reason for this is that the position of the frame boundary of the receiver has not yet been aligned with the frame boundary of the transmitter. Here, the peak position of the cross-correlation signal indicates the offset of the frame boundary between the transmitter and the receiver, which enables the alignment of the hyperframe. In this sense, the symbols 0 to 3 have a predetermined indicium for hyperframe alignment.
[0030]
Here, based on the peak position of the cross-correlation signal, the detector module 225b performs the alignment of the frame boundary, performs the correlation process again, and searches for the N REVERB 33 to 64 signals of the next hyperframe. If the frame boundaries are properly aligned based on the detection of the first four consecutive REVERB 33-64 signals, the cross-correlation peak may occur at the location of a known sample of the cross-correlation signal (e.g., the first sample) ( Detect the next four REVERB 33-64 signals (at the next hyperframe). In this way, the known offset between the transmitter and receiver frame boundaries is determined. In particular, the fourth detected REVERB 33-64 signal having a peak position at a known sample of the cross-correlation signal represents the boundary of DMT symbol 3 in the hyperframe. In this way, the receiver achieves hyperframe alignment.
[0031]
Here, the phase toggle operation of the current standard tone 48 (a conventional TTR display signal) can be performed as before without affecting the function of the detector module. Further, tone 64 (a conventional pilot signal) is included in the REVERBx-y signals. Therefore, the present invention is backward compatible.
Implementation details
In an embodiment, the processor module 225 is a digital signal processor (DSP) or other suitable processing environment programmed to perform hyperframe alignment or initial handshake synchronization in accordance with the present invention. In an alternative embodiment, processor module 225 is implemented in dedicated silicon, such as an ASIC or chipset. A combination of DSP and ASIC technology may be used to implement processor module 225. Thus, the present invention can be used by ADSL service providers, for example, as a way to perform hyperframe alignment. Alternatively, the invention can be incorporated into devices such as a modem, a programmable DSP or a dedicated chip / chipset. Alternatively, the present invention can be incorporated into a system such as a transceiver pair in which one or both transceivers are configured to perform hyperframe alignment or initial handshake synchronization, as described below. Alternatively, the invention may be embodied as a computer program product embodied in a computer readable medium such as a server or a disk.
[0032]
Modules not shown can also be incorporated in the modem according to the application. For example, a modem may operate in an overlapping spectrum application and include an echo canceller. Other modules (eg, transmitter and receiver clocks) and configurations will be apparent from this disclosure. Further, the processor module 225 can itself start the hyperframe alignment process as part of the link initialization procedure. Alternatively, the registration process can be triggered by an event (e.g., registration failure) or a control signal from the host (e.g., hyperframe registration software call or logic enable line). Similarly, after detecting activation of hyperframe alignment by the remote modem, the processor module 225 can start the hyperframe alignment process. Typically, the ATU-C modem activates the hyperframe matching process. However, if desired, the ATU-R can be configured to invoke this process.
methodology
FIG. 4 shows a flowchart of a method for performing the hyperframe matching process according to the embodiment of the present invention. The method is typically implemented in a communication system (eg, ADSL Annex C) comprising two modems communicatively coupled via a transmission medium. In particular, the method is performed at a transmitting node associated with a particular communication direction of the system. The modems at both the transmitting (for example, local) and receiving (for example, remote) nodes are configured, for example, as described in FIG. However, other configurations will be apparent from the present disclosure.
[0033]
The method begins by invoking a hyperframe alignment procedure (step 405). In embodiments, the hyperframe alignment procedure is invoked by the ATU-C during communication link initialization (eg, training). However, in alternative embodiments, the alignment procedure may be triggered at other times (eg, after interruption of service). Further, the method generates a specially defined signal (step 410) and sends the specially defined signal to the remote node during one or more known intervals in the data frame (step 415).
[0034]
In an embodiment, the data frame is an ADSL downstream hyperframe having DMT symbols 0-344, and one or more known intervals in the data frame are DMT symbols 0-3 in the hyperframe. The first transmission of this data frame allows to identify the relative position of the transmitter and receiver symbol boundaries, as described above. The second (or later) frame transmission enables confirmation of hyperframe alignment. Alternatively, one or more known intervals in the data frame are represented by symbols N in the hyperframe.₁~ N₂(For example, 140 to 144) and the symbol N in the hyperframe.₃~ N₄(For example, 237 to 241). In such an embodiment, the symbol N₁~ N₂, The offset of the symbol boundary between the transmitter and the receiver can be identified by the specially defined signal transmitted during the period of symbol N.₃~ N₄The hyperframe alignment can be confirmed by the special definition signal transmitted during the period.
[0035]
For example, a specially defined signal is a pseudo-random data sequence or other uniquely identifiable signal. In the embodiment, the specially defined signal is a subset of the tones included in the above-mentioned REVERB type signal (for example, REVERB6 to 31, REVERB16 to 31, REVERB33 to 64 or REVERBx to y (where x to y are information transmissions of a long loop). Represents a set of tones that can be used in))). Transmitting such specially defined signals in known sections of the data frame provides a robust TTR indication signal that can be received at the remote end of a long loop.
[0036]
In addition, the method receives a response from the remote node to confirm the hyperframe alignment (step 420) and determines whether alignment has been achieved based on the response (step 425). If the response confirms that the hyperframe is aligned, the procedure ends. The communication system then completes other initialization procedures and transitions to data mode (eg, showtime). However, if the response confirms a hyperframe position mismatch, steps 415 through 420 are repeated. As described above, after several attempts (eg, transmission of N hyperframes), if no acknowledgment is received, the transmitting transceiver is configured to recognize as an error.
[0037]
FIG. 5 shows a flowchart of a method for performing a hyperframe alignment process according to another embodiment of the present invention. In particular, the method is performed at a receiving node associated with a particular communication direction of the system.
[0038]
The method begins by invoking a hyperframe alignment procedure (eg, by ATU-C during training during communication link initialization) (step 505). Further, the method receives data of the data frame from the remote node transmitter (step 510) and detects a specially defined signal in one or more known intervals in the data frame (step 515). The above description for specially defined signals and known symbols applies here as well. The method proceeds to step 520, where an offset between the transmitter and receiver interval boundaries is identified, and step 525 determines whether hyperframe alignment has been achieved. Specific embodiments for performing these steps are described below.
[0039]
For convenience of description, it is assumed that specially defined signals transmitted in a known section of a data frame are REVERBx to y signals transmitted during symbols 0 to 3 in a hyperframe. In an embodiment, the offset between the transmitter and receiver interval boundaries is a linear cross-correlation to the receiver samples until four consecutive REVERBx-y signals are detected (thus indicating symbols 0-3). Are identified by continuing to execute. Here, the offset of the frame boundary between the transmitter and the receiver is identified based on the cross-correlation signal peak of the REVERVx to y signals. The linear cross-correlation process is repeated in a subsequent hyperframe (e.g., the next hyperframe), and the next four consecutive REVERBx to y signals are detected. Hyperframe alignment is achieved by detecting the next four consecutive REVERB x-y signals with the cross-correlation peak located at a known sample of the cross-correlation signal (e.g., the first sample).
[0040]
In another embodiment, the offset between the interval boundaries of the transmitter and the receiver calculates the cross-correlation signal each time a DMT symbol is received, and has a predetermined indicia of hyperframe alignment in the cross-correlation signal. , N consecutive DMT symbols. The predetermined indicia includes, for example, a set of tones (x to y) in a pseudo-random data sequence (eg, tones 33 to 64 of the REVERB signal). The frame boundary alignment is performed based on the peak position of the cross-correlation signal having this indicium. A second cross-correlation operation is performed to identify a second set of N consecutive DMT symbols. The frame boundary alignment is confirmed by the second detection of the predetermined indicium, indicating that the hyperframe alignment has been achieved. Note that the second cross-correlation processing may be executed in either the same hyperframe or a subsequent hyperframe. Further, the process may be repeatedly performed three times, four times, five times, or the like, to ensure proper alignment.
[0041]
If hyperframe alignment is not achieved, the method sends a negative response to the remote node indicating that hyperframe alignment has not been achieved (step 530). Such a response is, for example, a specially defined signal or just a period of silence. Here, the transceiver in the receiving state can be configured to recognize as an error if no acknowledgment is received after multiple attempts (eg, multiple transmissions of a hyperframe). On the other hand, if hyperframe alignment has been achieved, the method sends a response to the remote node confirming the hyperframe position match (step 535). The communication system then completes other initialization procedures (eg, channel analysis and exchange) and transitions to data mode (eg, showtime).
Overview of the initialization process
FIG. 6 shows a time diagram outlining the initialization process according to one embodiment of the present invention. It is assumed that the initialization process is performed in a communication system comprising one or more pairs of ADSL communications communicatively coupled via twisted copper wire pairs or other transmission media.
[0042]
The initialization process shown for each transceiver consists of an initial handshake procedure followed by transceiver training and channel analysis procedures. After that, information acquired through training and analysis procedures is exchanged. The handshake procedure generally allows newly joined transceivers to exchange capabilities and select a common mode of operation. This initial handshake procedure is typically performed in accordance with ITU-T Recommendation G. 994.1 (G.hs) or other suitable handshake procedure.
[0043]
However, G. 994.1 does not synchronize with TCM-ISDN, which applies the time division duplex scheme based on TTR described above. Therefore, G. The 994.1 signal interferes with the TCM-ISDN or NEXT of the Annex C FBM, especially in long distance loops (eg, 5 km or more). As a result, the handshake procedure may fail. Therefore, G. G.992 for the Annex C modem There is a need to increase the reliability and power of 994.1.
[0044]
According to one embodiment of the present invention, G. 994.1 can be synchronized to the TCM-ISDN, and synchronization is achieved in the front period of the handshake procedure. Thereby, G. For example, the 994.1 signal can be exchanged on the long-distance loop during the FEXT time, and transmission during the NEXT time can be avoided. Therefore, a stronger and more reliable handshake procedure is realized.
Annex C G. FIG. 994.1 Synchronization to TTR
FIG. 7 is a flowchart of a dual initialization procedure according to one embodiment of the present invention. In particular, G. Synchronize the 994.1 handshake procedure with the TTR. Once the handshake procedure is synchronized with the TTR, the NEXT and FEXT periods are known. Thereby, G.P. The hs signal (other initialization signals, such as a training signal, if desired) can be transmitted during the other modem's FEXT period to ensure a reliable exchange.
[0045]
During the handshake procedure, the communication modems are called HSTU-C and HSTU-R, respectively. The start signal (R-TONES-REQ) of the existing HSTU-R is inverted every 16 ms, and the TTR has a period of 80 ms, which is 5 × 16 ms. In accordance with one embodiment of the present invention, the HSTU-C TTR indication signal is a signal such that the phase inversion is not synchronized with the TTR and prevents accurate reception every 16 ms. -Defined to be reliably received by the HSTU-R transmitting the REQ.
HSTU-C activation method of handshake procedure
Referring to FIG. 7, the HSTU-C starts with a transition from C-SILENT1 and sends a specially defined handshake signal called C-INIT at the start of a TTR hyperframe. For example, C-INIT is REVERB16-31 or other specially defined signal as described above. In an embodiment, C-INIT is FEXT of DMT._RIt is transmitted during symbols 0-3, 33-36, 108-111 and 140-144. The special definition signal enables synchronization with the TTR, thereby enabling the synchronization G. The hs procedure becomes possible, and in that procedure, the handshake signal is transmitted only during the period of the FEXT symbol as shown in FIG. If desired, synchronization with the TTR may be maintained in subsequent initialization procedures such as training, channel analysis and exchange. Alternatively, the initialization may be re-established in a subsequent initialization procedure.
[0046]
Here, this sequence of DMT symbols was chosen because of its robustness in situations where phase inversion at 16 ms intervals appears at any phase of the TTR period. As noted above, other data patterns and symbol combinations may also be used herein in accordance with the principles of the present invention to achieve reliable transmission and reception.
[0047]
Upon detecting C-INIT (eg, the TTR detector described above), the HSTU-R sets its PGA and performs symbol alignment and timing recovery. Further, the HSTU-R starts with symbols 6-9, and continues with symbols 16-19, 27-30, ... 210-214, ... 340-343 (shown in Figure 1b)._CR-TONE1 between symbols_FSend In an embodiment, if the HSTU-R detects a C-TONES (conventional handshake signal), the HSTU-R waits for a timeout T1 before responding properly, and the HSTU-C may use the G.T. Determine whether to support the hs procedure.
[0048]
R-TONE1_FHSTU-C detects FEXT_RC-GALF1 starting at the start of TTR hyperframe only during symbols_FSend Each bit is the first four FEXTs of a subframe (0-3, 11-14, 22-25, 33-36, ... 140-143, ... 335-338)._RSent by symbol. 32 bits are transmitted in an 80 ms hyperframe. As described above, G. A 992 hyperframe consists of 345 DMT symbols. There are 32 subframes in a hyperframe, each subframe being 10-11 consecutive DMT symbols depending on TTR timing.
[0049]
C-GALF1_F, The HSTU-R starts from symbols 6 to 9 (R-TONE1)._F), FEXT_CR-FLAG1 between symbols_FSend R-FLAG1_FHSTU-C receives the first four FEXTs in a subframe, starting from any TTR subframe._RBetween symbols, C-FLAG1_FSend C-FLAG1 with HSTU-R_F, The HSTU-R may initiate the first handshake transaction, starting from any TTR subframe.
HSTU-R activation method of handshake procedure
It is beneficial for the HSTU-C to initiate (start) the handshake procedure since the HSTU-R is locked to the TTR from the beginning. As a result, no signal is transmitted during the NEXT period. However, by transferring from R-SILENT0 and transmitting R-INIT, the HSTU-R can activate the handshake procedure. In an embodiment, R-INIT is REVERB 6-15, but the signals described above and other specially defined TTR indication signals can be used here. After receiving the R-INT, the HSTU-C sends a C-INIT that starts at the start of the TTR hyperframe, as described in the HSTU-C activation scheme.
[0050]
Here, the R-INIT is transmitted before the HSTU-R receives a signal from the HSTU-C locked to the TTR. To avoid NEXT affecting neighboring pairs of modems, the HSTU-R detects the noise pattern and uses a high noise level (FEXT)._CR-INIT is transmitted only during the period).
Fallback procedure / backward compatibility
As described above, the present invention is backward compatible with conventional initialization procedures. For example, suppose that HSTU-C sends a C-INIT to initiate a handshake procedure, but HSTU-R does not respond. The reason for no response may be, for example, that the HSTU-R is not connected, that it does not support the initialization procedure according to the principles of the present invention, or that it has the conventional G.264 for the given loop. 994.1 initialization procedure is determined to be better, and so on.
[0051]
After the timeout, the fallback procedure can be entered. For example, HSTU-C is configured to send C-TONES. Here, if the HSTU-R responds with R-TONE1, the transceiver pair will use the conventional G.264. Fall back to 994.1 initialization procedure. However, if the HSTU-R does not respond to the C-TONES, the HSTU-C is configured to send a C-INIT again after a timeout. This alternation is continued several times until the HSTU-R responds affirmatively or a long timeout elapses. By such an alternate operation, the existing G. The problem of interoperability in the 994.1 device can be reduced.
[0052]
The length of the alternating operation is predetermined or otherwise determined so that the HSTU-R monitors the received signal for how long to determine whether the HSTU-C is configured in accordance with the principles of the present invention. Know what to do. The HSTU-R responds accordingly. It should be noted that a TTR display signal based on the principle of the present invention is converted into an existing G.264 signal. It can be sent in parallel with the 994.1 start signal.
[0053]
Next, suppose the HSTU-R sends an R-INIT to initiate the handshake procedure, but the HSTU-C does not respond (for any reason). After a timeout of T2, the HSSTU-R is configured to send an R-TONES-REQ (conventional handshake signal). If the HSTU-C responds with a C-TONES, the transceiver pair will use the conventional Fall back to 994.1 and the initialization procedure. However, the HSTU-C responds with a C-INIT to the R-INIT, and the HSTU-R then responds (e.g., because the HSTU-R has determined that the loop is not too long and the conventional G.994.1 is preferred). G. If it decides to fall back to 994.1, the HSTU-R can return silence. As a result, the HSTU-C times out, and the conventional G.264 is used. Alternately move back to 994.1 and send C-TONES.
Flags and messages
Conventional G. 994.1 needs to repeat the same information bits within eight consecutive DMT symbols. Each TTR subframe typically has 4-5 FEXTs (as shown in FIG. 1a)._RSymbol and 6-7 NEXT_RThere are symbols. In one embodiment of the present invention, the first four FEXTs in one subframe_RIs used to transmit one bit. Therefore, each information bit consists of four consecutive FEXT_RSent in a symbol. In another embodiment, one bit is transmitted using all FEXT symbols in a subframe. Therefore, each information bit consists of four or five consecutive FEXT_RSent in a symbol. Such a configuration transmits 32 bits of information using 345 symbols, and An average of 10.78 DMT symbols per hs bit. The modem transmits only FEXT symbols as in the ADSL Annex C FBM mode. The absence of echoes simplifies the algorithm of the receiver.
[0054]
In an alternative embodiment of the present invention, one bit information is transmitted using all symbols within one TTR period, regardless of FEXT or NEXT symbols. The receiving node is composed of two receivers, one for FEXT symbols and the other for NEXT symbols. The detection results of the two receivers are compared and the more reliable one is used (eg based on a CRC check). Under TCM-ISDN noise, the FEXT detector gives more reliable results. However, under other noise situations, a NEXT detector may help improve reliability. Such an environment would complicate the configuration of the receiver and would lose the benefits of half-duplex mode (eg, would require echo cancellation).
[0055]
The handshake signal (for example, C-INIT, R-TONE1)_F, R-INIT) and the handshake message length is a multiple of a TTR hyperframe that is 80 ms long or a subframe that is 2.5 ms long. G. FIG. hs, the synchronization with the TTR at the time of transition to the Annex C operation mode is maintained or not maintained. Annex C uses the existing G.100 that is not synchronized with the TTR. In any case, it is necessary to perform synchronization with the TTR by Annex C itself, since it needs to operate together with the 994.1 procedure.
[0056]
After the initial synchronization, the HSTU-C and HSTU-R need to maintain synchronization with the TTR. Since the TTR clock is available on the HSTU-C, the HSTU-C can lock its transmit clock to the TTR. The HSTU-R then performs timing recovery from the signal received from the HSTU-C. In the embodiment, the timing recovery in the HSTU-R is performed based on a reception handshake signal in a loopback timing scheme. For example, the execution of loopback timing locks the clock of the HSTU-R transmitter to the clock of the HSTU-R receiver, the clock of the HSTU-R receiver is locked to the clock of the HSTU-C transmitter, and the clock of the HSTU-C The transmitter clock is locked to the TTR. In another embodiment, a dedicated pilot tone is transmitted from HSTU-C to HSTU-R to allow for timing recovery. This pilot tone can be transmitted in all DMT symbols. For example, tone 16 can be used as a pilot tone.
Parallel decoding for mixed SNR environment
As described above, G.A. The hs receiver decodes the received information under different noise conditions in the NEXT and FEXT bitmaps. Further, there are 1-2 symbols during the transition from NEXT to FEXT noise within any single TTR period. For a mixed SNR environment during such a single TTR cycle, The decoding of the hs information stream needs to be optimized. Since a single information bit is sent over N consecutive symbols, one embodiment of the present invention operates a maximum of N receivers in parallel during each bit time (eg, N = 8). G. FIG. After receiving the hs frame, an error check (eg, CRC) is calculated for each receiver. Use the bitstream from the receiver with the correct CRC.
[0057]
The foregoing description of the embodiments of the present invention has been presented for purposes of illustration and description. The description is not exhaustive and is not intended to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the present disclosure.
[0058]
For example, in the particular application described herein, to establish hyperframe alignment, or Use the specially defined TTR indication signal to lock the hs procedure to the TTR. However, specially defined indicia signals in accordance with the principles of the present invention can generally be used to synchronize a particular procedure or event to a given reference. Once synchronization is established, known properties associated with the synchronization relationship can be used. In one example in this document, G. The hs signal is synchronized with the TTR. A known characteristic associated with this synchronization includes a period of FEXT and NEXT time that can be identified. Powerful and highly reliable communication can be performed based on the given knowledge. Other applications having such synchronization relationships will equally benefit from the present invention.
[0059]
The scope of the present invention should be determined by the appended claims, and is not intended to be limited by the detailed description.
[Brief description of the drawings]
FIG. 1a shows a downstream ADSL Annex C hyperframe structure.
FIG. 1b is a diagram showing an ADSL Annex C hyperframe structure in the upstream direction.
FIG. 2 is a block diagram of an ADSL modem configured to perform hyperframe alignment according to an embodiment of the present invention.
FIG. 3 is a diagram illustrating an example of a cross-correlation signal according to the embodiment of the present invention.
FIG. 4 is a flowchart illustrating a method for performing hyperframe alignment according to an embodiment of the present invention.
FIG. 5 is a flowchart illustrating a method for performing hyperframe alignment according to another embodiment of the present invention.
FIG. 6 is a time chart showing an outline of an initialization process based on the embodiment of the present invention.
FIG. 7 is a flowchart showing an initialization process based on the embodiment of the present invention.

Claims (25)

A method for synchronizing an initialization procedure to a TTR in an ADSL Annex C communication system having a transmitting node and a receiving node communicatively coupled, the method comprising:
Transmitting a specially defined signal during one or more sets of known FEXT symbols for a first output hyperframe to establish synchronization with the TTR with the specially defined signal when received by the receiving node; A synchronization initialization procedure. The method of claim 1, wherein the specially defined signal includes a plurality of tones of a pseudo-random data sequence. The method according to claim 1, wherein the specially defined signal includes a plurality of tones. The first output hyperframe has a start, and the one or more sets of known FEXT symbols include a symbol at the start of the first output hyperframe. Synchronization method. The first output hyperframe includes symbols 0-344, and the one or more sets of known FEXT symbols include symbols 0-3, 33-36, 108-111, and 140-144. The synchronization method according to claim 1. The initialization procedure is described in G. 2. The synchronization method according to claim 1, wherein the synchronization method is an hs handshake procedure. 2. The synchronization method according to claim 1, wherein once synchronization with the TTR is established, the synchronization initialization procedure is started. The above synchronous initialization procedure
The method of claim 1, further comprising receiving a first response signal during one or more sets of FEXT symbols for a first input hyperframe to confirm that the receiving node has detected the specially defined signal. Synchronization method according to 1. The method according to claim 8, wherein a second signal is transmitted during a FEXT symbol of a second output hyperframe in response to the first response signal. The second output hyperframe includes a plurality of subframes consisting of FEXT and NEXT symbols, wherein bits of the second signal are transmitted in the first four FEXT symbols of each subframe. The method according to claim 9. Further, receiving a second response signal during one or more sets of FEXT symbols related to a second input hyperframe to confirm that a receiving node has detected the second signal. 10. The synchronization method according to claim 9. The method according to claim 11, further comprising transmitting a third signal during a FEXT symbol of a third output hyperframe in response to the second response signal. The third output hyperframe includes a plurality of subframes consisting of FEXT and NEXT symbols, wherein bits of the third signal are transmitted in the first four FEXT symbols of each subframe. 13. The synchronization method according to claim 12. The synchronization method is started by the remote transceiver of the receiving node, and as a preliminary step,
Receiving a second specially defined signal from the remote transceiver during one or more sets of known FEXT symbols for a first input hyperframe, and responsive to detecting the second specially defined signal, 2. The synchronization method according to claim 1, wherein transmission is performed. The method of claim 1, wherein the synchronization method enters a fallback procedure in response to the receiving node not responding to the transmitted specially defined signal. 2. The synchronization method according to claim 1, wherein the synchronization method repeatedly and alternately transmits the specially defined signal and a normal signal until an acknowledgment is received from the receiving node. The method of claim 1, wherein once synchronization with TTR is established, the synchronization method transmits a pilot tone to the receiving node to perform timing recovery. A method for synchronizing an initialization procedure to a TTR in an ADSL Annex C communication system having a transmitting node and a receiving node communicatively coupled, the method comprising:
A synchronization method comprising receiving a specially defined signal during one or more sets of known FEXT symbols for an input hyperframe to establish synchronization with the TTR and enable a synchronization initialization procedure. . 19. The method of claim 18, wherein once synchronization with the TTR is established, the method performs timing recovery. The timing recovery is based on a loopback timing scheme, where the transmission clock of the reception node is locked to the reception clock of the reception node, the reception clock of the reception node is locked to the transmission clock of the transmission node, and the transmission clock of the transmission node is the TTR. 19. The synchronization method according to claim 18, wherein the synchronization method is locked. A synchronizer for synchronizing transmission by an ADSL Annex C type transceiver with a timing reference signal,
Generating a specially defined signal transmitted during one or more known DMT symbols included in the output hyperframe, and when received by the receiving node, establishes synchronization with the timing reference signal by the specially defined signal. And a signal generating module configured to enable a synchronization procedure. A synchronizer for synchronizing transmission by an ADSL Annex C type transceiver with a timing reference signal,
A detection configured to detect a specially defined signal during one or more known DMT symbols included in the input hyperframe, thereby establishing synchronization with the timing reference signal and enabling a synchronization procedure; Synchronizing device including a detector module. A computer program product stored on a computer-readable medium for synchronizing transmission by an ADSL Annex C transceiver with a timing reference signal, comprising:
Generating a specially defined signal transmitted during one or more known DMT symbols included in the output hyperframe, and when received by the receiving node, establishes synchronization with the timing reference signal by the specially defined signal. , A computer program product comprising a signal generation module configured to enable a synchronization procedure. A computer program product for synchronizing transmission by an ADSL Annex C type transceiver with a timing reference signal,
A detection configured to detect a specially defined signal during one or more known DMT symbols included in the input hyperframe, and to establish synchronization with the timing reference signal by this detection to enable a synchronization procedure. Computer program product comprising a detector module. In a signal used in an ADSL Annex C communication system, the signal is a set of tones transmitted during a plurality of known DMT symbols included in a hyperframe. A signal characterized by being able to synchronize the transmission performed by an included transceiver with a timing reference signal, thereby enabling at least one of a hyperframe alignment and a synchronization initialization procedure.

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