JP4071097B2 - Decoding device and code identification method - Google Patents

Description

【００３１】
次に、シンドロームＳ_ｋが０か否かを判定する（ステップＳＴ１４）。ここで、シンドロームＳ_ｋが０である場合を統計量として記憶する。例えば、予め統計量を記憶するテーブルを用意しておき、シンドロームＳ_ｋ＝０になった場合、そのとき処理していたサンプルの原始多項式ｐ（ｘ）と符号長ｎとｋの値との組み合わせをアドレスとしてテーブルに記憶されている統計量をカウントアップする（ステップＳＴ１５）。ここまで処理したサンプルの番号ｊがサンプル数Ｋに達したか否かを判定し（ステップＳＴ１６）、サンプル番号ｊがサンプル数Ｋに達していれば相関値計算処理を終了し、達していなければ次に処理するサンプル番号ｊをｊ＝ｊ＋１としてインクリメントし（ステップＳＴ１７）、次のサンプルに対してステップＳＴ１２の受信語（Ｘ_ｎ−１，Ｘ_ｎ−２，…Ｘ_１，Ｘ_０）を抽出する処理過程から繰り返す。
【００３２】
ステップＳＴ１４において、シンドロームＳ_ｋが０ではないと判定された場合は、評価処理したサンプル数がＫに達したか否かを判定する（ステップＳＴ１６）。評価処理したサンプルのサンプル番号ｊがサンプル数Ｋに達していれば相関値計算処理を終了し、サンプル番号ｊがサンプル数Ｋに達していなければ次に処理するサンプル番号ｊのインクリメントｊ＝ｊ＋１を行い（ステップＳＴ１７）、次のサンプルについてステップＳＴ１２の受信語（Ｘ_ｎ−１，Ｘ_ｎ−２，…Ｘ_１，Ｘ_０）を抽出する処理過程から繰り返す。
【００３３】
図３に示した処理を全て終了した後、カウントアップして記憶されている統計量から誤り訂正に用いるパラメータを推定する。図３のステップＳＴ１５において符号長ｎ、原始多項式ｐ（ｘ）等に対応させて記憶した統計量が予め設定された閾値より大きな値になった場合は、例えば、連続するｋからｋ＋ｄの範囲において符号長ｎ，原始多項式ｐ（ｘ）から次の式（２）で表される生成多項式ｇ（ｘ）が推定される。なお、ここでｄは設計距離、最小距離を示すものである。
【数２】

【００３４】
このようにして推定された生成多項式ｇ（ｘ）を誤り訂正に用いるパラメータとして誤り訂正手段７へ設定する。
【００３５】
以上のように、実施の形態２によれば、所定の演算によって求めたシンドロームＳ_ｋが０になる受信語の数を統計量として求めるようにしたので、ブロック符号の符号パラメータである生成多項式ｇ（ｘ）が推定できるという効果がある。
【００３６】
実施の形態３．
実施の形態３による符号識別方法は、ブロック符号が用いられた受信語の相関に関する統計量を求めるもので、図１に示した復号装置の符号識別手段５と同一または相当するものに用いられる。ここでは実施の形態３による符号識別方法を用いた符号識別手段５の動作を説明し、その他各手段の構成及び動作説明を省略する。
【００３７】
次に、動作について説明する。
図４は、この発明の実施の形態３による符号認識方法の処理過程を示すフローチャートである。なお、図４のフローチャートは、図２に示したステップＳＴ２の受信語の先頭の識別処理とステップＳＴ３の予め定められたサンプル数の受信語を取り出す処理に相当するものを省略し、受信系列を構成する各サンプルの先頭位置が識別されているものとして、それ以降に行われる相関計算の処理部分のみを示したものである。各サンプルの先頭位置の識別がなされていることを前提として、実施の形態３による符号識別方法を図４のフローチャートを用いて説明する。
【００３８】
図４に示した実施の形態３による符号識別方法は、図３のステップＳＴ１０〜ステップＳＴ１３の処理過程と同様に行われ、また、ステップＳＴ１４の判定過程にステップＳＴ２０の判定過程を付加したものである。図４のフローチャートに図３と同様な処理について同じステップ符号を付し、各処理過程の詳細説明を省略する。
【００３９】
ステップＳＴ１０〜ステップＳＴ１３までの処理過程を図３を用いて説明したように行い、ステップＳＴ１３において求めた各シンドロームＳ_ｋの値が０と等しいか否かを判定する（ステップＳＴ１４）。シンドロームＳ_ｋが０に等しい場合は、実施の形態２において一例を示して説明したように処理して統計量をカウントアップし、シンドロームＳ_ｋ＝０となる受信語の数を記憶する（ステップＳＴ１５）。次に、ここまで処理したサンプルの番号ｊがサンプル数Ｋに達したか否かを判定し（ステップＳＴ１６）、サンプル番号ｊがサンプル数Ｋに達していれば相関値計算処理を終了し、達していなければ次に処理するサンプル番号ｊをｊ＝ｊ＋１としてインクリメントし（ステップＳＴ１７）、次のサンプルに対してステップＳＴ１２の受信語（Ｘ_ｎ−１，Ｘ_ｎ−２，…Ｘ_１，Ｘ_０）を抽出する処理過程から繰り返す。
【００４０】
ステップＳＴ１４において、シンドロームＳ_ｋが０ではないと判定された場合は、連続する３つのシンドロームＳ_ｋ−１，Ｓ_ｋ，S_ｋ＋１に対して、Ｓ_ｋ ^２＋Ｓ_ｋ−１Ｓ_ｋ＋１＝０が成り立つか否かを判定する（ステップＳＴ２０）。ステップＳＴ２０において、Ｓ_ｋ ^２＋Ｓ_ｋ−１Ｓ_ｋ＋１＝０であると判定した場合は、前述のステップＳＴ１５の動作説明と同様に統計量をカウントアップし、シンドロームＳ_ｋ＝０となる受信語の数を記憶する（ステップＳＴ１５）。また、ステップＳＴ２０において、Ｓ_ｋ ^２＋Ｓ_ｋ−１Ｓ_ｋ＋１＝０ではないと判定した場合は、ここまで処理したサンプルの番号ｊがサンプル数Ｋに達したか否かを判定し（ステップＳＴ１６）、サンプル番号ｊがサンプル数Ｋに達していれば相関値計算処理を終了し、達していなければ次に処理するサンプル番号ｊをｊ＝ｊ＋１としてインクリメントし（ステップＳＴ１７）、次のサンプルに対してステップＳＴ１２の受信語（Ｘ_ｎ−１，Ｘ_ｎ−２，…Ｘ_１，Ｘ_０）を抽出する処理過程から繰り返す。
【００４１】
図４に示した処理を全て終了した後、カウントアップして記憶されている統計量から、実施の形態２において例示説明したように、例えば、式（２）のような生成多項式ｇ（ｘ）を推定し、この生成多項式ｇ（ｘ）を誤り訂正に用いるパラメータとして誤り訂正手段７へ設定する。実施の形態３による符号識別方法は、このようにして誤り訂正に用いるパラメータ、即ち未知の符号パラメータを推定する。
【００４２】
以上のように、実施の形態３によれば、シンドロームＳ_ｋが０である受信語の数、またはシンドロームＳ_ｋ及び隣接するシンドロームＳ_ｋ−１，Ｓ_ｋ＋１に対して、Ｓ_ｋ ^２＋Ｓ_ｋ−１Ｓ_ｋ＋１＝０の関係式が成り立つ受信語の数を統計量としてカウントするようにしたので、誤りが生起した場合でも統計量を的確にカウントすることができ、さらに確かなブロック符号の符号パラメータを推定することができるという効果がある。
【００４３】
実施の形態４．
実施の形態４による符号識別方法は、畳込み符号が用いられた受信語の相関に関する統計量を求めるもので、図１に示した復号装置の符号識別手段５と同一または相当するものに用いられる。ここでは実施の形態４による符号識別方法を用いた符号識別手段５の動作を説明し、その他各手段の構成及び動作説明を省略する。
【００４４】
次に、動作について説明する。
図５は、この発明の実施の形態４による符号識別方法の処理過程を示すフローチャートである。なお、図５のフローチャートは、図２に示したステップＳＴ２の受信語の先頭の識別処理とステップＳＴ３の予め定められたサンプル数の受信語を取り出す処理に相当するものを省略し、受信系列を構成する各サンプル、即ち受信語の先頭位置は識別されているものとして、それ以降に行われる受信語の相関計算の処理部分のみを示したものである。各受信語の先頭位置が識別されていることを前提として、実施の形態４による符号識別方法を図５のフローチャートを用いて説明する。
【００４５】
初めに、各サンプルの統計量を算出するパラメータとして、符号化率１／ｎを既知のものと想定し、パンクチャはないものと想定する。また、受信系列から抽出する受信語として、時点Ｋ１においてｎＫ１ビットの受信データをサンプリングすると想定する。さらに、ｎ組の生成多項式ｇ０（ｘ），ｇ１（ｘ）…ｇｎ−１（ｘ）を設定する（ステップＳＴ３０）。次に、パスメトリックを計算する時点ｊの初期値を１に設定する（ステップＳＴ３１）。
【００４６】
時点ｊにおいて、サンプリングを行う受信系列の先頭位置から順にｎビットの受信データを抽出する（ステップＳＴ３２）。抽出されたｎビットの受信データについて、時点ｊ−１から時点ｊに推移するトレリスのブランチメトリックを計算する（ステップＳＴ３３）。ステップＳＴ３３において計算されたブランチメトリックを利用してＡＣＳ演算を行い、時点ｊにおける各状態、即ち各生成多項式ｇ０（ｘ），ｇ１（ｘ）…ｇｎ−１（ｘ）をそれぞれ組み合わせてパスメトリックを計算する（ステップＳＴ３４）。
【００４７】
次に、時点ｊの値が予め設定された時点Ｋ１であるか否かを判定する（ステップＳＴ３５）。時点ｊが時点Ｋ１に達していなければ、時点ｊをｊ＝ｊ＋１としてインクリメントし（ステップＳＴ３６）、受信系列から次にブランチメトリックを計算するｎビットの受信データを抽出して（ステップＳＴ３２）、ステップＳＴ３２〜ステップＳＴ３５の処理過程を繰り返す。
【００４８】
ステップＳＴ３５において、時点ｊの値が時点Ｋ１に達した場合は、時点Ｋ１における各状態のうち、パスメトリック値が最大となった生成多項式の組み合わせと共に当該パスメトリックの最大値を統計量として記憶する（ステップＳＴ３７）。
【００４９】
このようにして生成多項式ｇ０（ｘ），ｇ１（ｘ）…ｇｎ−１（ｘ）の想定されるすべての組み合わせについて統計量を求め、これらについて求めた統計量を記憶し、記憶された統計量であるパスメトリックの最大値の中で最も大きな値となったときの生成多項式の組み合わせを、畳込み符号の符号パラメータとして推定する。なお、こうして推定された符号パラメータは誤り訂正に用いるパラメータとして誤り訂正手段７へ設定される。
【００５０】
以上のように、実施の形態４によれば、複数の生成多項式ｇ０（ｘ），ｇ１（ｘ）…ｇｎ−１（ｘ）をそれぞれ組み合わせ、所定の時点Ｋ１におけるパスメトリックを求め、各生成多項式の組み合わせについて求めたパスメトリックの最大値を統計量としたので、統計量が最大値となる生成多項式の組み合わせから畳込み符号の符号パラメータである生成多項式が推定できるという効果がある。
【００５１】
実施の形態５．
実施の形態５による符号識別方法は、畳込み符号が用いられた受信語の相関に関する統計量を求めるもので、図１に示した復号装置の符号識別手段５と同一または相当するものに用いられる。ここでは実施の形態５による符号識別方法を用いた符号識別手段５の動作を説明し、その他各手段の構成及び動作説明を省略する。
【００５２】
次に、動作について説明する。
図６は、この発明の実施の形態５による符号識別方法の処理過程を示すフローチャートである。なお、図６のフローチャートは、図２に示したステップＳＴ２の受信語の先頭の識別処理とステップＳＴ３の予め定められたサンプル数の受信語を取り出す処理に相当するものを省略し、受信系列を構成する各サンプル、即ち受信語の先頭位置の識別はできているものとして、それ以降に行われる受信語の相関計算の処理部分のみを示したものである。各受信語の先頭位置が識別されていることを前提として、実施の形態５による符号識別方法を図６のフローチャートを用いて説明する。
【００５３】
初めに各受信語の統計量を算出するパラメータとして、符号化率は未知と想定する。ただし最小の符号化率は１／ｎと限定する。また、ｍ≦ｎの条件を満たすｍ組の生成多項式ｇ０（ｘ），ｇ１（ｘ）…ｇｍ−１（ｘ）を設定する。また、時点Ｋ１においてパンクチャされるビット数ｐを設定する。つまり、時点Ｋ１において、受信系列から抽出される受信語として、ｍＫ１−ｐビットの受信データがサンプリングされる。これらのことからパンクチャパターンを想定する（ステップＳＴ４０）。次に、パスメトリックを計算する時点ｊの初期値を１に設定する（ステップＳＴ４１）。
【００５４】
時点ｊにおいて、受信系列の先頭位置から順にｍ−ｔｊ（ｔｊは時点ｊにおいてパンクチャされるビット数）ビットの受信データを抽出する（ステップＳＴ４２）。抽出されたｍ−ｔｊビットの受信データについて、時点ｊ−１から時点ｊに推移するトレリスのブランチメトリックを計算する（ステップＳＴ４３）。ステップＳＴ４３において計算されたブランチメトリックを利用してＡＣＳ演算を行い、時点ｊにおける各状態、即ち各生成多項式ｇ０（ｘ），ｇ１（ｘ）…ｇｎ−１（ｘ）をそれぞれ組み合わせてパスメトリックを計算する（ステップＳＴ３４）。
【００５５】
次に、時点ｊの値が予め定められた時点Ｋ１に達したか否かを判定する（ステップＳＴ４５）。時点ｊが時点Ｋ１に達していない場合は、時点ｊをｊ＝ｊ＋１としてインクリメントし（ステップＳＴ４６）、次にブランチメトリックを計算するｍ−ｔｊビットの受信データを受信系列から抽出して（ステップＳＴ４２）、ステップＳＴ４２〜ステップＳＴ４５の処理過程を繰り返す。
【００５６】
ステップＳＴ４５において、時点ｊが時点Ｋ１に達した場合は、時点Ｋ１における各状態、即ち各生成多項式ｇ０（ｘ），ｇ１（ｘ）…ｇｎ−１（ｘ）のそれぞれの組み合わせにおいて求められたパスメトリック値の中から最大値Ｐｍａｘを選択する（ステップＳＴ４７）。次にパスメトリックの最大値Ｐｍａｘを符号化率及びパンクチャパターンに応じて補正する（ステップＳＴ４８）。例えば、符号化率による補正は最大値Ｐｍａｘにｎ／ｍを乗算し、前述のパンクチャパターンに応じた補正は符号化率によって補正された最大値Ｐｍａｘ＊ｎ／ｍに対して、ｍＫ１／（ｍＫ１−ｐ）を乗算してパスメトリックの最大補正値Ｐｍｏｄを計算する。
【００５７】
ステップＳＴ４８において求めた最大補正値Ｐｍｏｄを統計量として、当該最大補正値Ｐｍｏｄが求められた生成多項式の組み合わせ，パンクチャパターン，符号化率と共に記憶する（ステップＳＴ４９）。
【００５８】
このようにして想定される全ての生成多項式の組み合わせ，符号化率，パンクチャパターンについて統計量を求め、これらについて求めた最大補正値Ｐｍｏｄを記憶し、記憶された最大補正値Ｐｍｏｄの中で最も大きな値となったときの生成多項式の組み合わせ及びパンクチャパターンを畳込み符号の符号パラメータとして推定する。なお、こうして推定された符号パラメータは誤り訂正に用いるパラメータとして誤り訂正手段７へ設定される。
【００５９】
以上のように、実施の形態５によれば、複数の生成多項式ｇ０（ｘ），ｇ１（ｘ）…ｇｎ−１（ｘ）の組み合わせについて所定の時点Ｋ１におけるパスメトリックを求め、各生成多項式の組み合わせについて求めたパスメトリックの最大値Ｐｍａｘを符号化率，パンクチャパターンに応じた補正を行って最大補正値Ｐｍｏｄを求め、当該最大補正値Ｐｍｏｄを統計量としたので、当該統計量から畳込み符号の符号パラメータとして生成多項式の組み合わせ，符号化率，パンクチャパターンが推定できるという効果がある。
【００６０】
実施の形態６．
図７は、この発明の実施の形態６による符号識別方法が用いられる復号装置の構成及び通信システムの構成を示すブロック図である。図１に示したものと同様あるいは相当する部分に同じ符号を付し、その説明を省略する。外符号符号化手段１０は、図示を省略した情報源等から入力した情報ビット系列の送信データに所定の符号化を行うと共に外符号の誤り訂正符号を付加する。インタリーバ１１は、外符号符号化手段１０によって外符号に符号化された送信データの順序を入れ替えて内符号符号化手段１２へ出力する。内符号符号化手段１２は、インタリーバ１１から入力した送信データについて所定の符号化を行うと共に内符号の誤り訂正符号を付加して変調手段２へ出力する。変調手段２は内符号符号化手段１２から入力した送信データを変調して通信路３へ送出する。変調手段２から送出された符号系列には通信路３上を伝送する際に誤りが生起し、受信系列として復号装置へ入力される。
【００６１】
図７において、復調手段４、内符号識別手段１３、内符号誤り訂正手段１４、デインタリーバ１５、外符号識別手段１６、外符号誤り訂正手段１７によって復号装置が構成される。復調手段４は、受信した受信系列をベースバンド信号に復調して内符号識別手段１３へ出力する。内符号識別手段１３は、受信系列について所定の要素の抽出処理及び演算を行い、内符号の未知の誤り訂正パラメータを推定する。内符号誤り訂正手段１４は、内符号識別手段１３によって推定された誤り訂正パラメータ等に基づいて受信系列の内符号の復号及び誤り訂正を行い、デインタリーバ１５へ出力する。デインタリーバ１５は、受信系列の受信データをインタリーバ１１で並び替えられた順序から元の順序に戻して外符号識別手段１６へ出力する。外符号識別手段１６は、外符号の未知の誤り訂正パラメータを推定する。外符号誤り訂正手段１７は、外符号識別手段１６によって推定された誤り訂正パラメータ等に基づいて受信系列の外符号の復号及び誤り訂正を行い、推定された情報ビット系列を出力する。
【００６２】
次に動作について説明する。
ここでは、実施の形態６による符号識別方法が用いられる内符号識別手段１３、内符号誤り訂正手段１４、デインタリーバ１５、外符号識別手段１６、及び外符号誤り訂正手段１７の動作について説明し、その他の各手段の動作説明を省略する。なお、ここでは外符号符号化手段１０によってブロック符号化が行われ、内符号符号化手段１２によって畳込み符号化が行われた場合を例示して説明する。
【００６３】
図８は、この発明の実施の形態６による符号識別方法の処理過程を示すフローチャートである。前述のように受信系列の受信語、即ち受信データは、外符号としてブロック符号、内符号として畳込み符号が用いられたもので、インタリーブパターンは既知として当該受信系列を受信した場合の動作を図８のフローチャートを用いて説明する。
【００６４】
内符号識別手段１３は、復調手段４によってベースバンド信号に復調された受信系列に対して、例えば、実施の形態４または実施の形態５において説明した符号識別方法を用いて畳込み符号の未知の符号パラメータ、即ち誤り訂正に用いる未知のパラメータを推定する（ステップＳＴ５０）。内符号誤り訂正手段１４は、既知の誤り訂正符号のパラメータや内符号識別手段１３によって推定された誤り訂正に用いるパラメータに基づいて受信系列の畳込み符号の復号と共に誤り訂正を行う（ステップＳＴ５１）。ここでは、硬判定、軟判定いずれによって復号化されても差し支えない。
【００６５】
デインタリーバ１５は、内符号誤り訂正手段１４において畳込み復号された受信系列の順序を既知のインタリーブパターンに基づいて並べ替えるデインタリーブ操作を行い（ステップＳＴ５２）、外符号が符号化されたときの順序に戻す。外符号識別手段１６は、ブロック符号の符号パラメータのうち、未知の符号パラメータを例えば実施の形態２または実施の形態３において説明した符号識別方法を用いて推定する（ステップＳＴ５３）。この後、外符号誤り訂正手段１７は、既知の誤り訂正符号のパラメータや外符号識別手段１３によって推定されたブロック符号の符号パラメータ、即ち誤り訂正に用いるパラメータに基づいてブロック符号の復号を行うと共に受信系列の誤り訂正を行う（ステップＳＴ５４）。
【００６６】
なお、ここでは内符号として畳込み符号が用いられ、外符号としてブロック符号が用いられた場合について説明したが、内符号としてブロック符号が用いられ、外符号として畳込み符号が用いられた場合も、内符号識別手段１３で用いられる符号識別方法と外符号識別手段１６で用いられる符号識別方法とを入れ換えることで同様な作用効果が得られる。
【００６７】
以上のように、実施の形態６によれば、内符号識別手段１３で用いる符号識別方法と外符号識別手段１６で用いる符号識別方法が異なるようにしたので、畳込み符号の符号パラメータの推定とブロック符号の符号パラメータの推定とを組み合わせることが可能になり、連接符号の符号パラメータを推定することができるという効果がある。
【００６８】
【発明の効果】
以上のように、この発明によれば、符号識別手段が、想定される符号パラメータの組み合わせについて統計量をそれぞれ算出し、その中から所定の条件を満たしたものを抽出して、抽出した統計量が求められた符号パラメータから誤り訂正に用いる符号パラメータを推定するようにしたので、未知の符号パラメータを推定して誤り訂正が行えるという効果がある。
【００６９】
この発明によれば、内符号識別手段が、想定される全ての内符号の符号パラメータの組み合わせについて統計量をそれぞれ算出した後、その中から所定の条件を満たしたものを抽出して内符号の誤り訂正に用いる符号パラメータを推定し、また外符号識別手段が、想定される全ての外符号の符号パラメータの組み合わせについて統計量をそれぞれ算出した後、その中から所定の条件を満たしたものを抽出して外符号の誤り訂正に用いる符号パラメータを推定するようにしたので、畳込み符号のパラメータ推定とブロック符号のパラメータ推定とを組み合わせることが可能になり、連接符号のパラメータを推定して誤り訂正が行えるという効果がある。
【図面の簡単な説明】
【図１】 この発明の実施の形態１による符号識別方法が用いられる復号装置の構成及び通信システムの構成を示すブロック図である。
【図２】 この発明の実施の形態１による符号識別方法の処理過程を示すフローチャートである。
【図３】 この発明の実施の形態２による符号識別方法の処理過程を示すフローチャートである。
【図４】 この発明の実施の形態３による符号識別方法による処理過程を示すフローチャートである。
【図５】 この発明の実施の形態４による符号識別方法の処理過程を示すフローチャートである。
【図６】 この発明の実施の形態５による符号識別方法の処理過程を示すフローチャートである。
【図７】 この発明の実施の形態６による符号識別方法が用いられる復号装置の構成及び通信システムの構成を示すブロック図である。
【図８】 この発明の実施の形態６による符号識別方法の処理過程を示すフローチャートである。
【符号の説明】
１ 誤り訂正符号化手段、２ 変調手段、３ 通信路、４ 復調手段、５ 符号識別手段、６ パラメータ設定手段、７ 誤り訂正手段、１０ 外符号符号化手段、１１ インタリーバ、１２ 内符号符号化手段、１３ 内符号識別手段、１４ 内符号誤り訂正手段、１５ デインタリーバ、１６ 外符号識別手段、１７ 外符号誤り訂正手段。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a decoding apparatus and a code identification method for estimating a parameter of an error correction code of a received sequence when a transmitted code format is unknown.
[0002]
[Prior art]
The conventional decoding apparatus and code identification method estimate only the transport block length of the code transmitted from the path metric value. As a decoding apparatus using such a code identification method, for example, there is a W-CDMA transmission rate estimation method and apparatus described in Patent Document 1.
[0003]
Next, the operation will be described.
When the encoded data is received, first, the first bit length combination, that is, the transport format combination is selected, and the rate is adjusted by deinterleaving each transport channel based on this combination. Then, a maximum path metric calculation process for the bit string of the received data is performed. These processes are sequentially performed for each combination of transport formats.
[0004]
Next, the maximum path metric calculation process will be described. First, in the trellis diagram showing the state transition of this process, the first node time is selected and a branch metric is generated. Then, an ACS operation is performed to select and store the maximum one from the path metrics of each state at the time of the node.
[0005]
While sequentially shifting the node time points on the trellis diagram until the node time point determined by the threshold is reached, branch metric generation and path metric generation are performed at each node point, and the maximum path metric at each node point is selected. The stored maximum path metric is updated for each node time, and the maximum path metric is stored in the combination of the transport formats. Note that the threshold value indicating the predetermined node time point of the trellis diagram is generally set to a value that is four to five times the constraint length of the convolutional code.
[0006]
When the node point on the trellis diagram is sequentially shifted to reach the node point for which a predetermined threshold is set, it is determined whether or not another transport format combination remains, and other transport format combinations. Is left, the next transport block combination is selected, and the deinterleaver, rate adjustment, and maximum path metric calculation processing are repeatedly executed. When these processes are completed for all the transport block combinations, the maximum path metric values obtained for each transport format combination are compared with each other, and the maximum path metric value is obtained from them. The transport block combination is selected, and the estimated transmission rate, that is, the code length of the transmitted code is estimated from the content of the transport block combination.
[0007]
[Patent Document 1]
JP 2001-320347 A (pages 4 to 7, FIGS. 3 to 10)
[0008]
[Problems to be solved by the invention]
Since the conventional decoding apparatus and code identification method are configured as described above, code parameters such as generator polynomials can be obtained only by estimating the code transmission rate, that is, the code length, using a statistic such as a path metric. There is a problem that estimation cannot be performed and code parameters relating to block codes cannot be estimated.
[0009]
The present invention has been made to solve the above-described problems, and an object thereof is to estimate error correction code parameters such as code length and generator polynomial for a block code.
[0010]
Another object of the convolutional code is to enable estimation of error correction code parameters for a generator polynomial and a puncture pattern.
[0011]
[Means for Solving the Problems]
In the decoding device according to the present invention, the code identifying means sets a plurality of code parameters in combination, extracts a received word from the received sequence, and obtains predetermined statistics on the correlation between the set code parameter combination and the received word. Calculate the statistic for all possible combinations of code parameters, extract the statistic that satisfies a predetermined condition, and extract the extracted statistic from the obtained code parameter A code parameter used for error correction is estimated.
[0012]
A decoding apparatus according to the present invention inputs a multiplex-encoded received sequence demodulated by a demodulator, sets a plurality of code parameters for an inner code of the received sequence, and extracts a received word from the received sequence , Calculate a predetermined statistic regarding the correlation between the combination of the code parameters set for the inner code and the received word, calculate the statistic for all possible combinations of the code parameters of the inner code, and The inner code identifying means for extracting the code satisfying a predetermined condition from the code parameters, and estimating the code parameter used for error correction of the inner code from the code parameter for which the extracted statistic is obtained, and the reception rearranged by the deinterleaver Enter a sequence and set the outer sequence code of the received sequence by combining the code parameters of multiple outer codes. A predetermined statistic regarding the correlation between the combination of the code parameters set for the outer code and the received word, and calculating the statistic for all possible combinations of the code parameters of the outer code Outer code identification means for extracting code parameters used for error correction of outer codes from the code parameters for which the extracted statistics satisfying a predetermined condition are obtained, and for which the extracted statistics are obtained, The means inputs the code parameters used for error correction of the inner code estimated by the inner code identifying means and performs error correction of the inner code, and the outer code error correcting means performs the correction of the outer code estimated by the outer code identifying means. A code parameter used for error correction is inputted to perform error correction of the outer code.
[0013]
In the code identification method according to the present invention, a process in which the code identification unit sets a plurality of code parameters in combination, a process of extracting a received word from the received sequence, and a correlation between the set combination of the code parameters and the received word After repeating the process of calculating the predetermined statistic and the process of setting the combination of code parameters to the process of calculating the statistic, calculating the statistics for all possible combinations of code parameters, A process of extracting a quantity satisfying a predetermined condition from the quantity, and estimating a code parameter used for error correction from the code parameter for which the extracted statistic is obtained.
[0014]
The code identification method according to the present invention includes a process in which an inner code identification unit that receives a multiplex-encoded reception sequence demodulated by a demodulation unit sets a combination of a plurality of code parameters for an inner code of a reception sequence; Statistics from the process of extracting the received word from the sequence, the process of calculating a predetermined statistic regarding the correlation between the combination of the code parameters set for the inner code and the received word, and the process of setting the code parameter combination of the inner code After repeating the process of calculating the quantity, calculating the statistic for each possible combination of code parameters of the inner code, extracting the statistic satisfying a predetermined condition, and extracting the statistic A process of estimating a code parameter used for error correction of an inner code from a code parameter for which a statistic is obtained, Therefore, the inner code error correction means that has input the code parameters used for the error correction of the estimated inner code performs the process of correcting the error of the inner code and the received sequence that has been corrected by the inner code error correction means. A combination of a process in which the input outer code identifying means sets a combination of code parameters of a plurality of outer codes for the outer code of the received sequence, a process of extracting a received word from the received sequence, and a code parameter set for the outer code The process of calculating a predetermined statistic relating to the correlation between the received code and the received code and the process of setting a combination of code parameters of the outer code to the process of calculating the statistic are repeated, After calculating the statistic for each combination, the statistic that satisfies the specified condition is extracted, and the extracted statistics A process of estimating a code parameter used for error correction of the outer code from the code parameter for which the quantity is obtained, and an outer code error correcting means for inputting the code parameter used for error correction of the outer code estimated by the outer code identifying means, And a process of performing error correction of the outer code using code parameters used for error correction of the outer code.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described below.
Embodiment 1 FIG.
FIG. 1 is a block diagram showing a configuration of a decoding apparatus and a configuration of a communication system in which the code recognition method according to Embodiment 1 of the present invention is used. The error correction encoding means 1 encodes transmission data of an information bit series input from an information source (not shown) in a predetermined format and adds an error correction code. The modulation means 2 modulates the transmission data output from the error correction coding means 1 and sends it to the communication path 3. An error occurs in the code sequence transmitted from the modulation means 2 when it is transmitted on the communication path 3, and is input to the decoding device as a reception sequence.
[0016]
In FIG. 1, the demodulating means 4, the code identifying means 5, the parameter setting means 6, and the error correcting means 7 constitute a decoding device. The demodulating means 4 demodulates the received received sequence into a baseband signal and outputs it to the code identifying means 5. The code identifying means 5 performs extraction processing and calculation of predetermined elements on the received sequence, and estimates error correction code parameters such as an unknown generator polynomial. The parameter setting unit 6 sets the parameter of each error correction code estimated by the code identification unit 5 in the error correction unit 7. The error correction unit 7 performs an error correction decoding process on the reception sequence input from the demodulation unit 4 based on the parameters of the error correction code set by the parameter setting unit 6, and the decoded reception data is omitted from illustration, for example. Output to the data processing means.
[0017]
Next, the operation will be described.
Here, the description of the operation for generating the code sequence from the information bit sequence by the error correction encoding unit 1 and the modulation unit 2 and transmitting it to the communication path 3 is omitted, and the processing operation performed on the received sequence will be described. As described above, the demodulator 4 converts the received sequence in which an error has occurred when transmitting the communication path 3 into a baseband signal. The code identification means 5 acquires information such as the code length from the received sequence demodulated into the baseband signal, and estimates an unknown parameter used for error correction of the received sequence. The parameter setting means 6 stores the parameters of the known error correction code and the unknown parameters estimated by the code identification means 5 and sets each parameter in the error correction means 7.
[0018]
The error correction means 7 inputs the reception sequence output from the demodulation means 4, performs error correction based on each parameter set by the parameter setting means 6, and outputs an estimated information bit sequence.
[0019]
FIG. 2 is a flowchart showing the process of the code identification method according to Embodiment 1 of the present invention. The operation process of the code identifying means 5 according to the first embodiment will be described with reference to the flowchart of FIG.
[0020]
The code identifying means 5 inputs the demodulated received sequence from the demodulating means 4 and sets the first parameter combination (step ST1). The combination of parameters set here is a combination of parameters such as primitive polynomial, generator polynomial, code length, etc. when the received word is a block code, and generator polynomial, puncture when the received word is a convolutional code. It is a combination of unknown parameters such as patterns.
[0021]
After setting the first combination of parameters, the head of the received word is identified from the received sequence (step ST2). As a method for identifying a code at the head of a received word, for example, there is a method for identifying the code by finding a synchronization bit. In addition, when the received data is a convolutional code, synchronization may be obtained by calculating a path metric from the set generator polynomial, and the head position of the received word may be identified.
[0022]
From the position of the received word whose head is identified in step ST2, a predetermined number of received words are extracted (step ST3). Next, a correlation value between the combination of parameters set in step ST1 and the received word extracted from the reception sequence in step ST3 is calculated, and the value is stored as a statistic (step ST4).
[0023]
It is determined whether or not there is a combination of parameters for which statistics are not calculated in step ST4 (step ST5). If a combination of parameters that has not yet been subjected to statistical calculation processing remains, the combination of the unprocessed parameters is set (step ST6), and the processing process of steps ST2 to ST4 is performed for this parameter combination. Do. In this manner, the calculation processing for the statistics relating to the correlation of the received words shown in step ST4 is performed for all parameter combinations, and the statistics for each parameter combination are stored.
[0024]
If it is determined in step ST5 that the statistic is calculated for all parameter combinations, among the statistics related to the correlation calculated in step ST4, for example, the parameter whose statistic is larger than a predetermined threshold value. The combination is determined as a parameter used for error correction (step ST7), and is output from the code identifying means 5 to the parameter setting means 6. Thereafter, using the determined parameter and the parameter of the known error correction code, the error correction processing of the reception sequence is performed as described above.
[0025]
As described above, according to the invention of the first embodiment, since the code identification unit 5 calculates the statistics related to the correlation, not only the code length of the received word but also a generator polynomial, a primitive polynomial, a puncture pattern, etc. Code parameter, that is, a parameter used for error correction can be estimated, and an unknown parameter used for error correction can be obtained.
[0026]
In addition, since code parameters such as generator polynomials, primitive polynomials, and puncture patterns can be estimated, even when the code parameters of the code sequence sent to the communication path 3 are changed, reception suitable for the changed code parameters is received. There is an effect that a decoder capable of correcting a sequence error can be obtained.
[0027]
Embodiment 2. FIG.
The code identification method according to the second embodiment obtains a statistic relating to the correlation of received words using block codes, and is used for the same or equivalent code identification means 5 of the decoding apparatus shown in FIG. Here, the operation of the code identifying means 5 using the code identifying method according to the second embodiment will be described, and the configuration and operation description of each other means will be omitted.
[0028]
Next, the operation will be described.
FIG. 3 is a flowchart showing a process of a code recognition method according to Embodiment 2 of the present invention. Note that the flowchart of FIG. 3 omits the processing corresponding to the identification processing of the beginning of the received word in step ST2 and the processing of extracting the received word of a predetermined number of samples in step ST3 shown in FIG. Only the processing part of the correlation calculation performed thereafter is shown assuming that the head position of each sample to be configured is identified. The code identification method according to the second embodiment will be described with reference to the flowchart of FIG. 3 on the assumption that the head position of each sample has been identified.
[0029]
First, for example, a code length n and a primitive polynomial p (x) are assumed as parameters for calculating the statistic of each sample. Further, it is assumed that the root of the primitive polynomial p (x) = 0 is α, the degree of the primitive polynomial p (x) is m, and the number of received word samples is K (step ST10). Next, the initial value of the sample number j for identifying each sample is set to 1 (step ST11).
[0030]
For the jth sample with the sample number, received data of n symbols in order from the head position, that is, received words (X_n-1, X_n-2, ... X₁, X₀) Is extracted (step ST12). Syndrome S from extracted received words_k(K = 0, 1, ... 2^m-1) is calculated using the following equation (1) (step ST13).
[Expression 1]

[0031]
Next, Syndrome S_kIs determined to be 0 (step ST14). Where Syndrome S_kIs stored as a statistic. For example, a table for storing statistics in advance is prepared, and the syndrome S_kWhen = 0, the statistics stored in the table are counted up with the combination of the primitive polynomial p (x) of the sample being processed at that time and the values of the code lengths n and k as an address (step ST15). ). It is determined whether or not the number j of samples processed so far has reached the number of samples K (step ST16). If the number of samples j has reached the number of samples K, the correlation value calculation process is terminated. The sample number j to be processed next is incremented as j = j + 1 (step ST17), and the received word (X_n-1, X_n-2, ... X₁, X₀) Is repeated from the process of extracting.
[0032]
In step ST14, syndrome S_kIf it is determined that is not 0, it is determined whether or not the number of samples subjected to the evaluation process has reached K (step ST16). If the sample number j of the sample subjected to the evaluation process has reached the sample number K, the correlation value calculation process is terminated. If the sample number j has not reached the sample number K, an increment j = j + 1 of the sample number j to be processed next is set. (Step ST17), the received word (X in step ST12) for the next sample_n-1, X_n-2, ... X₁, X₀) Is repeated from the process of extracting.
[0033]
After all the processes shown in FIG. 3 are completed, the parameters used for error correction are estimated from the statistics that are counted up and stored. When the statistic stored in association with the code length n, the primitive polynomial p (x), etc. in step ST15 in FIG. 3 becomes larger than a preset threshold value, for example, in a continuous range from k to k + d A generator polynomial g (x) represented by the following equation (2) is estimated from the code length n and the primitive polynomial p (x). Here, d represents the design distance and the minimum distance.
[Expression 2]

[0034]
The generator polynomial g (x) estimated in this way is set in the error correction means 7 as a parameter used for error correction.
[0035]
As described above, according to the second embodiment, syndrome S obtained by a predetermined calculation is used._kSince the number of received words for which becomes 0 is obtained as a statistic, the generator polynomial g (x), which is the code parameter of the block code, can be estimated.
[0036]
Embodiment 3 FIG.
The code identification method according to the third embodiment obtains a statistic relating to the correlation of received words using block codes, and is used for the same or equivalent code identification means 5 of the decoding apparatus shown in FIG. Here, the operation of the code identification means 5 using the code identification method according to the third embodiment will be described, and the configuration and operation description of each other means will be omitted.
[0037]
Next, the operation will be described.
FIG. 4 is a flowchart showing a process of a code recognition method according to Embodiment 3 of the present invention. The flowchart of FIG. 4 omits the processing corresponding to the identification processing of the beginning of the received word in step ST2 and the processing of extracting the received word of the predetermined number of samples in step ST3 shown in FIG. Only the processing part of the correlation calculation performed thereafter is shown assuming that the head position of each sample to be configured is identified. The code identification method according to the third embodiment will be described with reference to the flowchart of FIG. 4 on the assumption that the head position of each sample has been identified.
[0038]
The code identification method according to the third embodiment shown in FIG. 4 is performed in the same manner as the processing steps in steps ST10 to ST13 in FIG. 3, and the determination process in step ST20 is added to the determination process in step ST14. is there. Steps similar to those in FIG. 3 are denoted by the same step symbols in the flowchart of FIG. 4, and detailed description of each processing step is omitted.
[0039]
The process from step ST10 to step ST13 is performed as described with reference to FIG. 3, and each syndrome S obtained in step ST13 is processed._kIt is determined whether or not the value of is equal to 0 (step ST14). Syndrome S_kIs equal to 0, the processing is performed as described with reference to the example in the second embodiment to count up the statistics, and the syndrome S_kThe number of received words with = 0 is stored (step ST15). Next, it is determined whether or not the number j of samples processed so far has reached the number of samples K (step ST16). If the number of samples j has reached the number of samples K, the correlation value calculation process is terminated and reached. If not, the sample number j to be processed next is incremented as j = j + 1 (step ST17), and the received word (X_n-1, X_n-2, ... X₁, X₀) Is repeated from the process of extracting.
[0040]
In step ST14, syndrome S_kIf it is determined that is not 0, three consecutive syndromes S_k-1, S_k, S_{k + 1}Against S_k ²+ S_k-1S_{k + 1}It is determined whether or not 0 holds (step ST20). In step ST20, S_k ²+ S_k-1S_{k + 1}If it is determined that = 0, the statistic is counted up in the same manner as in the description of the operation in step ST15 described above, and the syndrome S_kThe number of received words with = 0 is stored (step ST15). In step ST20, S_k ²+ S_k-1S_{k + 1}If it is determined that it is not = 0, it is determined whether or not the number j of the samples processed so far has reached the number of samples K (step ST16), and if the sample number j has reached the number of samples K, the correlation value The calculation process is terminated. If not reached, the sample number j to be processed next is incremented as j = j + 1 (step ST17), and the received word (X_n-1, X_n-2, ... X₁, X₀) Is repeated from the process of extracting.
[0041]
After all the processes shown in FIG. 4 are completed, the generator polynomial g (x) represented by the equation (2), for example, is calculated from the statistics counted up and stored as described in the second embodiment. And the generator polynomial g (x) is set in the error correction means 7 as a parameter used for error correction. In this way, the code identification method according to the third embodiment estimates a parameter used for error correction, that is, an unknown code parameter.
[0042]
As described above, according to the third embodiment, the syndrome S_kNumber of received words for which is 0, or syndrome S_kAnd adjacent syndrome S_k-1, S_{k + 1}Against S_k ²+ S_k-1S_{k + 1}Since the number of received words satisfying the relational expression = 0 is counted as a statistic, the statistic can be accurately counted even when an error occurs, and a more reliable code parameter of the block code is estimated. There is an effect that can be.
[0043]
Embodiment 4 FIG.
The code identification method according to the fourth embodiment calculates a statistic relating to the correlation of received words using convolutional codes, and is used for the same or equivalent code identification means 5 of the decoding apparatus shown in FIG. . Here, the operation of the code identification means 5 using the code identification method according to the fourth embodiment will be described, and the configuration and operation description of each other means will be omitted.
[0044]
Next, the operation will be described.
FIG. 5 is a flowchart showing a process of a code identification method according to Embodiment 4 of the present invention. The flowchart of FIG. 5 omits the processing corresponding to the identification processing of the beginning of the received word in step ST2 and the processing of extracting the received word of the predetermined number of samples in step ST3 shown in FIG. Only the processing part of the correlation calculation of the received word performed after that is shown assuming that each sample, that is, the head position of the received word is identified. The code identification method according to the fourth embodiment will be described with reference to the flowchart of FIG. 5 on the assumption that the head position of each received word is identified.
[0045]
First, it is assumed that the coding rate 1 / n is known as a parameter for calculating the statistic of each sample, and that there is no puncturing. Further, it is assumed that nK1-bit received data is sampled at a time point K1 as a received word extracted from the received sequence. Further, n sets of generator polynomials g0 (x), g1 (x)... Gn-1 (x) are set (step ST30). Next, the initial value of the time point j for calculating the path metric is set to 1 (step ST31).
[0046]
At time point j, n-bit received data is extracted in order from the head position of the reception sequence to be sampled (step ST32). For the extracted n-bit received data, a trellis branch metric that transitions from time point j-1 to time point j is calculated (step ST33). ACS calculation is performed using the branch metric calculated in step ST33, and the path metric is obtained by combining each state at time point j, that is, each generator polynomial g0 (x), g1 (x)... Gn-1 (x). Calculate (step ST34).
[0047]
Next, it is determined whether or not the value of the time point j is a preset time point K1 (step ST35). If the time point j does not reach the time point K1, the time point j is incremented as j = j + 1 (step ST36), and n-bit received data for calculating a branch metric next is extracted from the received sequence (step ST32). The process from ST32 to ST35 is repeated.
[0048]
In step ST35, when the value of the time point j reaches the time point K1, the maximum value of the path metric is stored as a statistic together with the combination of the generator polynomials having the maximum path metric value among the states at the time point K1. (Step ST37).
[0049]
In this way, statistics are obtained for all possible combinations of the generator polynomials g0 (x), g1 (x)... Gn-1 (x), the statistics obtained for these are stored, and the stored statistics are stored. The combination of generator polynomials when the maximum value of the path metric is the largest is estimated as the code parameter of the convolutional code. The code parameter estimated in this way is set in the error correction means 7 as a parameter used for error correction.
[0050]
As described above, according to the fourth embodiment, a plurality of generator polynomials g0 (x), g1 (x)... Gn−1 (x) are combined to obtain a path metric at a predetermined time point K1, and each generator polynomial is obtained. Since the maximum value of the path metric obtained for each combination is used as the statistic, there is an effect that the generator polynomial that is the code parameter of the convolutional code can be estimated from the combination of generator polynomials having the maximum statistic.
[0051]
Embodiment 5. FIG.
The code identification method according to the fifth embodiment obtains a statistic relating to correlation of received words using convolutional codes, and is used for the same or equivalent code identification means 5 of the decoding apparatus shown in FIG. . Here, the operation of the code identifying means 5 using the code identifying method according to the fifth embodiment will be described, and the configuration and operation description of each other means will be omitted.
[0052]
Next, the operation will be described.
FIG. 6 is a flowchart showing a process of a code identification method according to the fifth embodiment of the present invention. Note that the flowchart of FIG. 6 omits the processing corresponding to the identification processing of the beginning of the received word in step ST2 and the processing of extracting the received word of a predetermined number of samples in step ST3 shown in FIG. Only the processing part of the correlation calculation of the received word performed after that is shown on the assumption that each constituent sample, that is, the head position of the received word has been identified. The code identification method according to the fifth embodiment will be described with reference to the flowchart of FIG. 6 on the assumption that the head position of each received word is identified.
[0053]
First, it is assumed that the coding rate is unknown as a parameter for calculating the statistic of each received word. However, the minimum coding rate is limited to 1 / n. In addition, m generator polynomials g0 (x), g1 (x)... Gm−1 (x) satisfying the condition of m ≦ n are set. Also, the number of bits punctured at time K1 is set. That is, at time K1, mK1-p-bit received data is sampled as a received word extracted from the received sequence. From these, a puncture pattern is assumed (step ST40). Next, the initial value of the time point j for calculating the path metric is set to 1 (step ST41).
[0054]
At time j, reception data of m-tj (tj is the number of bits punctured at time j) bits is extracted in order from the head position of the reception sequence (step ST42). For the extracted m-tj-bit received data, the branch metric of the trellis that transitions from time point j-1 to time point j is calculated (step ST43). An ACS operation is performed using the branch metric calculated in step ST43, and the path metric is obtained by combining each state at time point j, that is, each generator polynomial g0 (x), g1 (x)... Gn-1 (x). Calculate (step ST34).
[0055]
Next, it is determined whether or not the value of time point j has reached a predetermined time point K1 (step ST45). If the time point j does not reach the time point K1, the time point j is incremented as j = j + 1 (step ST46), and m-tj-bit received data for calculating the branch metric is extracted from the received sequence (step ST42). ), The process of step ST42 to step ST45 is repeated.
[0056]
In step ST45, when the time point j reaches the time point K1, the paths obtained in the respective states at the time point K1, that is, the respective combinations of the generator polynomials g0 (x), g1 (x)... Gn−1 (x). The maximum value Pmax is selected from the metric values (step ST47). Next, the maximum value Pmax of the path metric is corrected according to the coding rate and the puncture pattern (step ST48). For example, the correction by the coding rate multiplies the maximum value Pmax by n / m, and the correction according to the puncture pattern described above is mK1 / (mK1) with respect to the maximum value Pmax * n / m corrected by the coding rate. Multiply -p) to calculate the maximum correction value Pmod of the path metric.
[0057]
The maximum correction value Pmod determined in step ST48 is stored as a statistic along with the combination of generator polynomials, puncture pattern, and coding rate for which the maximum correction value Pmod is determined (step ST49).
[0058]
Statistics are obtained for all combinations, coding rates, and puncture patterns assumed in this way, the maximum correction value Pmod obtained for these is stored, and the largest among the stored maximum correction values Pmod. A combination of generator polynomials and a puncture pattern when the value is reached are estimated as code parameters of the convolutional code. The code parameter estimated in this way is set in the error correction means 7 as a parameter used for error correction.
[0059]
As described above, according to the fifth embodiment, a path metric at a predetermined time point K1 is obtained for a combination of a plurality of generator polynomials g0 (x), g1 (x). The maximum value Pmax of the path metric obtained for the combination is corrected according to the coding rate and the puncture pattern to obtain the maximum correction value Pmod, and the maximum correction value Pmod is used as a statistic. As a code parameter, the combination of generator polynomials, coding rate, and puncture pattern can be estimated.
[0060]
Embodiment 6 FIG.
FIG. 7 is a block diagram showing a configuration of a decoding apparatus and a configuration of a communication system in which the code identification method according to the sixth embodiment of the present invention is used. Parts that are the same as or correspond to those shown in FIG. 1 are given the same reference numerals, and descriptions thereof are omitted. Outer code encoding means 10 performs predetermined encoding on transmission data of an information bit sequence input from an information source (not shown) and adds an error correction code of the outer code. The interleaver 11 changes the order of the transmission data encoded into the outer code by the outer code encoding means 10 and outputs it to the inner code encoding means 12. The inner code encoding unit 12 performs predetermined encoding on the transmission data input from the interleaver 11 and adds an error correction code of the inner code to output to the modulation unit 2. The modulation means 2 modulates the transmission data input from the inner code encoding means 12 and sends it to the communication path 3. An error occurs in the code sequence transmitted from the modulation means 2 when it is transmitted on the communication path 3, and is input to the decoding device as a received sequence.
[0061]
In FIG. 7, the demodulating unit 4, the inner code identifying unit 13, the inner code error correcting unit 14, the deinterleaver 15, the outer code identifying unit 16, and the outer code error correcting unit 17 constitute a decoding device. The demodulating means 4 demodulates the received received sequence into a baseband signal and outputs it to the inner code identifying means 13. The inner code identification means 13 performs extraction processing and calculation of predetermined elements on the received sequence, and estimates an unknown error correction parameter of the inner code. The inner code error correcting means 14 decodes the inner code of the received sequence and corrects the error based on the error correction parameter estimated by the inner code identifying means 13 and outputs the result to the deinterleaver 15. The deinterleaver 15 returns the received data of the received sequence from the order rearranged by the interleaver 11 to the original order, and outputs it to the outer code identifying means 16. The outer code identifying means 16 estimates an unknown error correction parameter of the outer code. Outer code error correcting means 17 performs decoding and error correction of the outer code of the received sequence based on the error correction parameter estimated by outer code identifying means 16 and outputs an estimated information bit sequence.
[0062]
Next, the operation will be described.
Here, operations of the inner code identifying means 13, the inner code error correcting means 14, the deinterleaver 15, the outer code identifying means 16 and the outer code error correcting means 17 in which the code identifying method according to the sixth embodiment is used will be described. Description of the operation of each other means is omitted. Here, a case where block coding is performed by the outer code coding unit 10 and convolutional coding is performed by the inner code coding unit 12 will be described as an example.
[0063]
FIG. 8 is a flowchart showing the process of the code identification method according to the sixth embodiment of the present invention. As described above, the received sequence received word, that is, the received data uses a block code as the outer code and a convolutional code as the inner code, and shows the operation when the received sequence is received with the interleave pattern known. This will be described with reference to the flowchart of FIG.
[0064]
The inner code identifying unit 13 uses the code identifying method described in the fourth or fifth embodiment, for example, for the reception sequence demodulated into the baseband signal by the demodulating unit 4. A code parameter, that is, an unknown parameter used for error correction is estimated (step ST50). The inner code error correcting unit 14 performs error correction together with decoding of the convolutional code of the received sequence based on the parameters of the known error correcting code and the parameters used for error correction estimated by the inner code identifying unit 13 (step ST51). . Here, it may be decoded by either hard decision or soft decision.
[0065]
The deinterleaver 15 performs a deinterleaving operation for rearranging the order of the reception sequences convolutionally decoded by the inner code error correction means 14 based on a known interleave pattern (step ST52), and when the outer code is encoded. Return to order. Outer code identification means 16 estimates an unknown code parameter among the code parameters of the block code using, for example, the code identification method described in the second embodiment or the third embodiment (step ST53). Thereafter, the outer code error correction means 17 decodes the block code based on the parameters of the known error correction code and the code parameters of the block code estimated by the outer code identification means 13, that is, parameters used for error correction. Error correction of the reception sequence is performed (step ST54).
[0066]
Here, a case where a convolutional code is used as an inner code and a block code is used as an outer code has been described. However, a case where a block code is used as an inner code and a convolutional code is used as an outer code is also possible. By replacing the code identification method used by the inner code identification means 13 and the code identification method used by the outer code identification means 16, the same effect can be obtained.
[0067]
As described above, according to the sixth embodiment, since the code identification method used by the inner code identification unit 13 and the code identification method used by the outer code identification unit 16 are different from each other, It becomes possible to combine the estimation of the code parameter of the block code, and there is an effect that the code parameter of the concatenated code can be estimated.
[0068]
【The invention's effect】
As described above, according to the present invention, the code identification unit calculates the statistics for each possible combination of the code parameters, extracts those satisfying the predetermined condition, and extracts the extracted statistics Since the code parameter used for error correction is estimated from the code parameter obtained from the above, there is an effect that error correction can be performed by estimating an unknown code parameter.
[0069]
According to the present invention, the inner code identifying means calculates the statistic for each of the assumed combinations of code parameters of the inner code, and then extracts the one satisfying the predetermined condition from the statistics. Estimate the code parameters used for error correction, and the outer code identification means calculates the statistics for all possible combinations of code parameters of the outer code, and then extracts the one that satisfies the predetermined condition Since the code parameters used for error correction of the outer code are estimated, it is possible to combine the parameter estimation of the convolutional code and the parameter estimation of the block code, and the error correction is performed by estimating the parameters of the concatenated code. There is an effect that can be performed.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a decoding apparatus and a configuration of a communication system in which a code identification method according to Embodiment 1 of the present invention is used.
FIG. 2 is a flowchart showing a process of a code identification method according to Embodiment 1 of the present invention.
FIG. 3 is a flowchart showing a process of a code identification method according to Embodiment 2 of the present invention.
FIG. 4 is a flowchart showing a process performed by a code identification method according to Embodiment 3 of the present invention.
FIG. 5 is a flowchart showing a process of a code identification method according to Embodiment 4 of the present invention.
FIG. 6 is a flowchart showing a process of a code identification method according to Embodiment 5 of the present invention.
FIG. 7 is a block diagram showing a configuration of a decoding device and a configuration of a communication system in which a code identification method according to Embodiment 6 of the present invention is used.
FIG. 8 is a flowchart showing a process of a code identification method according to Embodiment 6 of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Error correction coding means 2 Modulation means 3 Communication path 4 Demodulation means 5 Code identification means 6 Parameter setting means 7 Error correction means 10 Outer code coding means 11 Interleaver 12 Inner code coding means , 13 inner code identifying means, 14 inner code error correcting means, 15 deinterleaver, 16 outer code identifying means, 17 outer code error correcting means.

Claims (12)

Demodulating means for demodulating the received received sequence, code identifying means for estimating the code parameter of the received sequence, and error correcting means for correcting the error of the received sequence using the code parameter estimated by the code identifying means A decoding device comprising:
The code identifying means sets a plurality of code parameters in combination, extracts a received word from the received sequence, and calculates a predetermined statistic regarding a correlation between the set code parameter combination and the received word. , Calculating the statistic for all possible combinations of the code parameters, extracting the statistic satisfying a predetermined condition, and correcting the extracted statistic from the obtained code parameter The decoding apparatus characterized by estimating the code | cord parameter used for. Demodulating means for demodulating received sequences multiplexed with different received codes, inner code error correcting means for correcting errors of inner codes of the received sequences, and rearranging received data constituting the received sequences In a decoding apparatus comprising a deinterleaver and outer code error correction means for correcting an error of an outer code of the received sequence that has been rearranged,
The multiplex-encoded received sequence demodulated by the demodulating means is input, a plurality of code parameters are set in combination for the inner code of the received sequence, a received word is extracted from the received sequence, and the inner code is Calculate a predetermined statistic regarding the correlation between the set code parameter combination and the received word, calculate the statistic for all possible combinations of the code parameters of the inner code, and calculate from the statistic An inner code identifying means for extracting a code that satisfies a predetermined condition and estimating a code parameter used for error correction of the inner code from the code parameter for which the extracted statistic is obtained;
Input the received sequence rearranged by the deinterleaver, set a combination of code parameters of a plurality of outer codes for the outer code of the received sequence, extract a received word from the received sequence, and set the outer code A predetermined statistic regarding the correlation between the received code parameter combination and the received word is calculated, the statistic is calculated for all possible combinations of the code parameters of the outer code, and a predetermined statistic is calculated from the statistic And an outer code identifying means for estimating a code parameter used for error correction of the outer code from the code parameter for which the extracted statistic is obtained,
The inner code error correcting means inputs code parameters used for error correction of the inner code estimated by the inner code identifying means, performs error correction of the inner code,
The decoding apparatus according to claim 1, wherein the outer code error correction means inputs a code parameter used for error correction of the outer code estimated by the outer code identification means and performs error correction of the outer code. In the code identification method for estimating the code parameter of the received sequence when the code identifying unit decodes the received sequence for the received sequence received by the demodulating unit,
A process in which the code identification means sets a plurality of code parameters in combination;
Extracting received words from the received sequence;
Calculating a predetermined statistic relating to the correlation between the set code parameter combination and the received word;
After repeating the process of setting the combination of the code parameters to the process of calculating the statistic, calculating the statistic for all possible combinations of the code parameters, and then calculating a predetermined condition from the statistic And a process of estimating a code parameter used for error correction from a code parameter for which the extracted statistic is obtained. The process of setting the code parameter combination performed by the code identification means sets the combination of the code length and the primitive polynomial,
The process of calculating a statistic calculates a syndrome using a combination of the code length and the primitive polynomial for a received word and obtains a statistic of the received word for which the syndrome has a predetermined value,
In the process of estimating the code parameter, the statistic satisfying a predetermined condition is extracted from the statistic obtained for all the assumed code lengths and the primitive polynomial, and the code length for which the statistic is obtained. The code identification method according to claim 3, wherein a predetermined generator polynomial is estimated from the primitive polynomial and the primitive polynomial. 5. The code identification method according to claim 4, wherein the step of calculating the statistic performed by the code identification means obtains the statistic of the received word including when the calculated continuous syndrome satisfies a predetermined condition. A process of calculating a branch metric at a predetermined time after the code identifying means extracts the received signal from the received sequence;
Calculating a plurality of path metrics using the branch metrics,
The process of setting the combination of sign parameters is to set a combination of multiple generator polynomials,
The step of calculating the statistic stores the maximum path metric among the plurality of path metrics obtained in the step of calculating the path metric as a statistic together with the combination of generator polynomials for which the maximum path metric is obtained,
In the process of estimating the sign parameter, after the maximum path metric is obtained for all possible combinations of the generator polynomials, the largest path metric is extracted from the stored maximum path metrics, and the extraction is performed. 4. The code identification method according to claim 3, wherein a code parameter is estimated from a combination of generator polynomials for which the obtained path metrics are obtained. A process of calculating a branch metric at a predetermined time after the code identification means extracts a received word from the received sequence;
Calculating a plurality of path metrics using the branch metrics;
Selecting a maximum path metric from the plurality of path metrics;
Correcting the maximum path metric and obtaining a maximum correction value of the path metric,
In the process of setting a combination of code parameters, a combination of a plurality of generator polynomials, a coding rate, and the number of bits to be punctured are set and a puncture pattern is assumed based on these settings.
The process of obtaining the maximum correction value of the path metric performs correction according to the coding rate and the puncture pattern,
In the process of calculating the statistic, the maximum correction value of the path metric is stored as a statistic together with the combination of generator polynomials for which the maximum correction value of the path metric is obtained, the coding rate, and the puncture pattern,
In the process of estimating the sign parameter, after the maximum correction value of the path metric is obtained for all possible combinations of the generator polynomials, the largest path metric among the stored maximum correction values of the path metric is obtained. 4. The code according to claim 3, wherein a maximum correction value is extracted, and a code parameter is estimated from a combination of a generating polynomial, a coding rate, and a puncture pattern from which the maximum correction value of the extracted path metric is obtained. Identification method. In a code identification method for estimating a code parameter of the reception sequence when the code identification unit decodes a reception sequence multiplexed with different codes received by the demodulation unit,
Inner code identifying means that has received the multiplex-encoded received sequence demodulated by the demodulating means sets a combination of a plurality of code parameters for the inner code of the received sequence;
Extracting received words from the received sequence;
Calculating a predetermined statistic relating to a correlation between a combination of code parameters set for the inner code and the received word;
After repeating the process from setting the code parameter combination of the inner code to the process of calculating the statistic, calculating the statistic for all possible combinations of the code parameters of the inner code, and then calculating the statistic Extracting a code satisfying a predetermined condition from the above, and estimating a code parameter used for error correction of the inner code from the code parameter for which the extracted statistic is obtained;
A process in which an inner code error correction unit that inputs code parameters used for error correction of the inner code estimated by the inner code identification unit performs error correction of the inner code;
The outer code identifying means that has input the received sequence that has been subjected to error correction of the inner code by the inner code error correcting means, and setting a combination of code parameters of a plurality of outer codes for the outer code of the received sequence;
Extracting received words from the received sequence;
Calculating a predetermined statistic relating to a correlation between a combination of code parameters set for the outer code and the received word;
After repeating the process of setting the code parameter combination of the outer code to the process of calculating the statistic, calculating the statistic for all possible combinations of code parameters of the outer code, and then calculating the statistic Extracting a code that satisfies a predetermined condition from among the code parameters for which the extracted statistic is obtained, and estimating a code parameter used for error correction of the outer code;
A process in which an outer code error correction unit that has input a code parameter used for error correction of an outer code estimated by the outer code identification unit performs error correction of the outer code using a code parameter used for error correction of the outer code A code identification method comprising: The process of setting the combination of outer code parameters or the process of setting the combination of inner code parameters performed by the inner code identifying means or the outer code identifying means sets the combination of code length and primitive polynomial,
The process of calculating a statistic calculates a syndrome using a combination of the code length and the primitive polynomial for a received word and obtains a statistic of the received word for which the syndrome has a predetermined value,
In the process of estimating the inner code parameter or the process of estimating the outer code parameter, a statistic satisfying a predetermined condition is extracted from all the calculated code lengths and the statistic obtained for the primitive polynomial, 9. The code identification method according to claim 8, wherein a predetermined generator polynomial is estimated from the code length for which a statistic is obtained and the primitive polynomial. 10. The process of calculating a statistic performed by an inner code identifying unit or an outer code identifying unit calculates a statistic of a received word including when the calculated continuous syndrome satisfies a predetermined condition. Code identification method. A process of calculating a branch metric at a predetermined time after the inner code identifying means or the outer code identifying means extracts a received word from the received sequence;
Calculating a plurality of path metrics using the branch metrics,
The process of setting a combination of inner code parameters or a process of setting a combination of outer code parameters sets a combination of generator polynomials,
The step of calculating the statistic stores the maximum path metric among the plurality of path metrics obtained in the step of calculating the path metric as a statistic together with the combination of generator polynomials for which the maximum path metric is obtained,
The process of estimating the inner code parameter or the process of estimating the outer code parameter is performed by calculating the maximum path metric for all possible combinations of the generator polynomials, and then determining the largest of the stored maximum path metrics. 9. The code identification method according to claim 8, wherein a large path metric is extracted, and an inner code parameter or an outer code parameter is estimated from a combination of generator polynomials for which the extracted path metric is obtained. A process of calculating a branch metric at a predetermined time after the inner code identifying means or the outer code identifying means extracts a received word from the received sequence;
Calculating a plurality of path metrics using the branch metrics;
Selecting a maximum path metric from the plurality of path metrics;
Correcting the maximum path metric and obtaining a maximum correction value of the path metric,
The process of setting a combination of inner code parameters or the process of setting a combination of outer code parameters is performed by setting a combination of a plurality of generator polynomials, a coding rate, and the number of bits to be punctured and puncturing patterns based on these settings. Assuming
The process of obtaining the maximum correction value of the path metric performs correction according to the coding rate and the puncture pattern,
In the process of calculating the statistic, the maximum correction value of the path metric is stored as a statistic together with the combination of generator polynomials for which the maximum correction value of the path metric is obtained, the coding rate, and the puncture pattern,
The process of estimating the inner code parameter or the process of estimating the outer code is performed by determining a maximum correction value of the path metric for all possible combinations of the generator polynomials, and then storing the maximum correction of the path metric stored. The maximum correction value of the largest path metric is extracted from the values, and the maximum correction value of the extracted path metric is estimated, and the code parameter is estimated from the combination of the generating polynomial, the coding rate, and the puncture pattern. The code identification method according to claim 8.

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