JP3973351B2

JP3973351B2 - Signal receiving device

Info

Publication number: JP3973351B2
Application number: JP2000256065A
Authority: JP
Inventors: 善生和田
Original assignee: Kenwood KK
Current assignee: Kenwood KK
Priority date: 2000-08-25
Filing date: 2000-08-25
Publication date: 2007-09-12
Anticipated expiration: 2020-08-25
Also published as: JP2002077002A

Description

【０００１】
【発明の属する技術分野】
本発明は、最尤系列推定型等化器を用いた信号受信装置に関する。
【０００２】
【従来の技術】
従来から、受信性能劣化対策として、信号受信装置にインパルスレスポンス推定器と最尤系列推定型等化器を備え、最尤系列推定の原理により最適なデータ列を検出し、受信性能の向上を図ることが行われている。
【０００３】
図８は、従来の信号受信装置の構成例を示すブロック図である。同図に示す信号受信装置５０２は、アンテナ５０４、乗算器５０６、局発信号発生器５０８、インパルスレスポンス推定器５１０、最尤系列推定型等化器５１２を備えて構成される。なお、変調方式には２値位相変調方式（ＢＰＳＫ：Binary Phase Shift Keying ）が用いられているものとする。
【０００４】
信号送信装置（図示せず）からは所定のデータ列が送信される。信号受信装置５０２は、このデータ系列を受信するものであるが、受信信号には、直接波の他に、信号伝搬路の状況に応じて、該直接波に対して所定のシンボル時間長遅延し、且つ振幅が減少した遅延波も含まれている。このため、そのまま各シンボルの判定を行うと、判定に誤りが生じる場合がある。そこで、信号受信装置５０２では、最尤系列推定の原理により、受信信号に直接波と遅延波が含まれている場合であっても、受信信号から元のデータ列を復元可能とする。
【０００５】
詳細な説明は、例えば、文献「笹岡秀一編、移動通信、オーム社」に記載されているので省略するが、要するに、乗算器５０６は、アンテナ５０４が受信した信号に、局発信号発生器５０４からの基準周波数信号を乗算し、ベースバンド信号に変換する。インパルスレスポンス推定器５１０は、このベースバンド信号に基づいて、インパルスレスポンス推定値を導出する。
【０００６】
最尤系列推定型等化器５１２は、乗算器５０６からのベースバンド信号とインパルスレスポンス推定器５１０からのインパルスレスポンス推定値に基づいて、後述するメトリック計算を行い、ビタビアルゴリズムによる最適なデータ列を検出する。
【０００７】
【発明が解決しようとする課題】
しかしながら、従来の信号受信装置では、最尤系列推定型等化器５１２においてメトリック計算とビタビアルゴリズムにより最適なデータ列を得るものであったため、その精度には原理的に限界があり、受信性能を向上させることにも限界があった。このため、近年信号受信装置に対して更に受信性能を向上させてほしいという要求が高まりつつあるが、それに応えることができないという問題があった。
【０００８】
本発明は、上記従来の問題点を解決するものであり、その目的は、受信性能を向上させた信号受信装置を提供することにある。
【０００９】
【課題を解決するための手段】
上記目的を達成するため、本発明の信号受信装置は、受信信号から直接波のみを取り出す第１及び第２の受信機と、判定手段とを有する信号受信装置であって、前記第１の受信機は、受信信号をベースバンド信号に変換する第１の信号変換手段と、前記第１の信号変換手段からのベースバンド信号に基づいて、インパルスレスポンス推定値を導出する第１のインパルスレスポンス推定手段と、前記第１の信号変換手段からのベースバンド信号と、前記第１のインパルスレスポンス推定手段からのインパルスレスポンス推定値とに基づいて、メトリック計算を行い、ビタビアルゴリズムによる生き残りパスの検出を行うとともに、ｎ−１番目のタイミングにおける受信シンボルの状態がＡであるという条件下で、ｎ番目のタイミングにおける受信シンボルの状態がＢであるという事後確率を、各ブランチに対するブランチメトリックを、そのブランチに対する受信シンボルの真値とベースバンド信号の雑音を含む受信シンボルの値との差の２乗値として、ＡからＢへのブランチのブランチメトリックを、Ａから各受信シンボルの状態へのブランチのブランチメトリックの総和によって除算した値により算出することによって、ｎ番目の受信シンボルに対応する第１の事後確率を導出する第１の最尤系列推定型等化手段と、を備え、前記第２の受信機は、受信信号をベースバンド信号に変換する第２の信号変換手段と、前記第２の信号変換手段からのベースバンド信号に基づいて、インパルスレスポンス推定値を導出する第２のインパルスレスポンス推定手段と、前記第２の信号変換手段からのベースバンド信号を遅延させる第１の遅延手段と、前記第１の遅延手段を介して導かれる前記第２の信号変換手段からのベースバンド信号、前記第２のインパルスレスポンス推定手段からのインパルスレスポンス推定値、及び前記第１の最尤系列推定型等化手段からの第１の事後確率に基づいて、メトリック計算を行い、ビタビアルゴリズムによる生き残りパスの検出を行うとともに、ｎ−１番目のタイミングにおける受信シンボルの状態がＡであるという条件下で、ｎ番目のタイミングにおける受信シンボルの状態がＢであるという事後確率を、各ブランチに対するブランチメトリックを、そのブランチに対する受信シンボルの真値と前記第１の遅延手段を介して導かれるベースバンド信号の雑音を含む受信シンボルの値との差の２乗値に第１の事後確率を乗算した値として、ＡからＢへのブランチのブランチメトリックを、Ａから各受信シンボルの状態へのブランチのブランチメトリックの総和によって除算した値により算出することによって、ｎ番目の受信シンボルに対応する第２の事後確率を導出する第２の最尤系列推定型等化手段と、を備え、前記判定手段は、前記第２の最尤系列推定型等化手段からの第２の事後確率を比較し、小さい方の値に対応する状態を、ｎ番目の受信シンボルに対応するデータとして検出する。
【００１０】
この場合において、前記第１の信号変換手段からのベースバンド信号を遅延させる第２の遅延手段と、前記第２の遅延手段を介して導かれる前記第１の信号変換手段からのベースバンド信号、前記第１のインパルスレスポンス推定手段からのインパルスレスポンス推定値、及び前記第２の最尤系列推定型等化手段からの第２の事後確率に基づいて、メトリック計算を行い、ビタビアルゴリズムによる生き残りパスの検出を行うとともに、ｎ−１番目のタイミングにおける受信シンボルの状態がＡであるという条件下で、ｎ番目のタイミングにおける受信シンボルの状態がＢであるという事後確率を、各ブランチに対するブランチメトリックを、そのブランチに対する受信シンボルの真値と前記第２の遅延手段を介して導かれるベースバンド信号の雑音を含む受信シンボルの値との差の２乗値に第２の事後確率を乗算した値として、ＡからＢへのブランチのブランチメトリックを、Ａから各受信シンボルの状態へのブランチのブランチメトリックの総和によって除算した値により算出することによって、ｎ番目の受信シンボルに対応する第３の事後確率を導出する第３の最尤系列推定型等化手段と、を更に備え、前記判定手段は、前記第３の最尤系列推定型等化手段からの第３の事後確率を比較し、小さい方の値に対応する状態を、ｎ番目の受信シンボルに対応するデータとして検出することが好ましい。
【００１１】
また、複数段に接続された最尤系列推定型等化手段と、前記複数段に接続された最尤系列推定型等化手段の各段に対応して、前記第２の遅延手段からのベースバンド信号を遅延させる偶数段の遅延手段と、前記第１の遅延手段からのベースバンド信号を遅延させる奇数段の遅延手段と、を更に備え、奇数段目の第（ｍ：ｍ＝３、５、・・）の最尤系列推定型等化手段は、対応する第（ｍ−１）の遅延手段を介して導かれる前記第１の信号変換手段からのベースバンド信号、前記第１のインパルスレスポンス推定手段からのインパルスレスポンス推定値、及び前段の偶数段目の第（ｍ−１）の最尤系列推定型等化手段からの第（ｍ−１）の事後確率に基づいて、メトリック計算を行い、ビタビアルゴリズムによる生き残りパスの検出を行うとともに、ｎ−１番目のタイミングにおける受信シンボルの状態がＡであるという条件下で、ｎ番目のタイミングにおける受信シンボルの状態がＢであるという事後確率を、各ブランチに対するブランチメトリックを、そのブランチに対する受信シンボルの真値と第（ｍ−１）の遅延手段を介して導かれるベースバンド信号の雑音を含む受信シンボルの値との差の２乗値に第（ｍ−１）の事後確率を乗算した値として、ＡからＢへのブランチのブランチメトリックを、Ａから各受信シンボルの状態へのブランチのブランチメトリックの総和によって除算した値により算出することによって、ｎ番目の受信シンボルに対応する第（ｍ）の事後確率を導出し、偶数段目の第（ｍ＋１）の最尤系列推定型等化手段は、対応する第（ｍ）の遅延手段から導かれる前記第２の信号変換手段からのベースバンド信号、前記第２のインパルスレスポンス推定手段からのインパルスレスポンス推定値、及び前段の奇数段目の第（ｍ）の最尤系列推定型等化手段からの第（ｍ）の事後確率に基づいて、メトリック計算を行い、ビタビアルゴリズムによる生き残りパスの検出を行うとともに、ｎ−１番目のタイミングにおける受信シンボルの状態がＡであるという条件下で、ｎ番目のタイミングにおける受信シンボルの状態がＢであるという事後確率を、各ブランチに対するブランチメトリックを、そのブランチに対する受信シンボルの真値と第（ｍ）の遅延手段を介して導かれるベースバンド信号の雑音を含む受信シンボルの値との差の２乗値に第（ｍ）の事後確率を乗算した値として、ＡからＢへのブランチのブランチメトリックを、Ａから各受信シンボルの状態へのブランチのブランチメトリックの総和によって除算した値により算出することによって、ｎ番目の受信シンボルに対応する第（ｍ＋１）の事後確率を導出し、前記判定手段は、最終段の最尤系列推定型等化手段からの第（ｍ）又は第（ｍ＋１）の事後確率を比較し、小さい方の値に対応する状態を、ｎ番目の受信シンボルに対応するデータとして検出することが好ましい。
【００１２】
また、第３の受信機を更に備え、該第３の受信機は、受信信号をベースバンド信号に変換する第３の信号変換手段と、前記第３の信号変換手段からのベースバンド信号に基づいて、インパルスレスポンス推定値を導出する第３のインパルスレスポンス推定手段と、前記第３の信号変換手段からのベースバンド信号を遅延させる第３の遅延手段と、前記第３の遅延手段を介して導かれる前記第３の信号変換手段からのベースバンド信号、前記第３のインパルスレスポンス推定手段からのインパルスレスポンス推定値、及び前記第２の受信機における第２の最尤系列推定型等化手段からの第２の事後確率に基づいて、メトリック計算を行い、ビタビアルゴリズムによる生き残りパスの検出を行うとともに、ｎ−１番目のタイミングにおける受信シンボルの状態がＡであるという条件下で、ｎ番目のタイミングにおける受信シンボルの状態がＢであるという事後確率を、各ブランチに対するブランチメトリックを、そのブランチに対する受信シンボルの真値と前記第３の遅延手段を介して導かれるベースバンド信号の雑音を含む受信シンボルの値との差の２乗値に第２の事後確率を乗算した値として、ＡからＢへのブランチのブランチメトリックを、Ａから各受信シンボルの状態へのブランチのブランチメトリックの総和によって除算した値により算出することによって、ｎ番目の受信シンボルに対応する第３の事後確率を導出する第３の最尤系列推定型等化手段と、を備え、前記判定手段は、前記第３の最尤系列推定型等化手段からの第３の事後確率を比較し、小さい方の値に対応する状態を、ｎ番目の受信シンボルに対応するデータとして検出することが好ましい。
【００１３】
【発明の実施の形態】
以下、図示した一実施形態に基いて本発明を詳細に説明する。図１は、本発明に係る信号受信装置の構成例を示すブロック図である。同図に示す信号受信装置２は、２段に接続された第１の受信機４及び第２の受信機６と、判定部８とを備えて構成される。
【００１４】
１段目の受信機（第１の受信機）４は、アンテナ１２、局発信号発生器１４、乗算器１６、インパルスレスポンス推定器１８、最尤系列推定型等化器２０を備えて構成される。一方、２段目の受信機（第２の受信機）６は、アンテナ２２、局発信号発生器２４、乗算器２６、インパルスレスポンス推定器２８、遅延器２９、最尤系列推定型等化器３０を備えて構成される。
【００１５】
なお、信号の送信元である信号送信装置（図示せず）は、０と１からなる所定のデータ列を送信しており、その送信シンボルは、データが０のときに−１、１のときに１の値をとるものとする。また、伝搬路の特性により、信号受信装置２によって受信される受信信号には、直接波の他に、該直接波に対して例えば１シンボル時間遅延し、且つ振幅が１／２に減少するような遅延波が含まれているものとする。
【００１６】
受信機４の乗算器１６は、アンテナ１２が受信した信号に、局発信号発生器１４からの基準周波数信号を乗算し、ベースバンド信号に変換する。
【００１７】
インパルスレスポンス推定器１８は、このベースバンド信号に基づいて、インパルスレスポンス推定値を導出するものである。具体的には、信号送信装置（図示せず）は、図２に示す伝送フレームのトレーニング信号にインパルス信号を設定して送信し、インパルスレスポンス推定器１８は、この信号送信装置からの直接波として受信したトレーニング信号と遅延波として受信したトレーニング信号とのずれと振幅の差を検出し、これらをインパルスレスポンス推定値として導出する。
【００１８】
最尤系列推定型等化器２０は、乗算器１６からのベースバンド信号と、インパルスレスポンス推定器１８からのインパルスレスポンス推定値とに基づいて、後述するメトリック計算を行い、ビタビアルゴリズムによる生き残りパスの検出を行うとともに、事後確率（第１の事後確率）を導出する。
【００１９】
以下、最尤系列推定型等化器２０による最尤系列推定の詳細を説明する。上述の通り、受信信号には、直接波の他に、該直接波に対して所定時間遅延した遅延波が含まれているため、受信信号のシンボル（以下、「受信シンボル」と称する）は、その時刻に送信されたシンボルと、それ以前に送信されたシンボルの遅延波の成分とが重畳された信号となる。なお、以下においては、説明を簡単にするために、遅延波は、直接波に対して、遅延が１シンボル時間、振幅が１／２の場合を想定して説明する。
【００２０】
従って、ある時刻に送信されたシンボルが−１（状態０）で、１つ前に送信されたシンボルが−１（状態０）であった場合には、遅延波が直接波の１／２の振幅であることを考慮すると、受信シンボルの値は−１．５になる。同様に、ある時刻に送信されたシンボルが−１（状態０）で、１つ前に送信されたシンボルが１（状態１）であった場合には、受信シンボルの値は−０．５になる。また、ある時刻に送信されたシンボルが１（状態１）で、１つ前に送信されたシンボルが−１（状態０）であった場合には、受信シンボルの値は０．５になり、ある時刻に送信されたシンボルが１（状態１）で、１つ前に送信されたシンボルが１（状態１）であった場合には、受信シンボルの値は１．５になる。
【００２１】
このように、受信シンボルは、−１．５、−０．５、０．５、１．５の何れかの値となるはずである。しかし、実際には受信シンボルには雑音等が含まれているため、必ずしもこれら４つの値にはならない。最尤系列推定では、これら４つの値（以下、「受信シンボルの真値」と称する）のそれぞれと、雑音を含む受信シンボルの値との差の２乗値をブランチメトリックとして算出するとともに、そこに至るまでのブランチメトリックの累積値（以下、「メトリック」と称する）を算出する。最適なパス（生き残りパス）は、このメトリックが最小のものであることが知られている。
【００２２】
図３は、最尤系列推定型等化器２０による生き残りパス検出の一例を示す図である。同図において、ｎ＋３番目の受信シンボルの状態０に着目すると、この状態０には１つ前のｎ＋２番目の受信シンボルの状態０から遷移する場合（経路Ａ１）と、状態１から遷移する場合（経路Ａ３）とがある。上述した通り、状態０から状態０に遷移する場合には、受信シンボルの真値は−１．５である。従って、ｎ＋３番目の受信シンボルにおける、経路Ａ１に対応するメトリックＳ00(n+3) は、ｎ＋３番目の受信シンボルの値と−１．５との差の２乗値（ブランチメトリック）に、ｎ＋２番目のシンボルの状態０に至るまでのメトリックを加算して得られる。また、状態１から状態０に遷移する場合には、受信シンボルの真値は−０．５である。従って、ｎ＋３番目の受信シンボルにおける、経路Ａ３に対応するメトリックＳ01(n+3) は、ｎ＋３番目の受信シンボルの値と０．５との差の２乗値（ブランチメトリック）に、ｎ＋２番目のシンボルの状態１に至るまでのメトリックを加算して得られる。そして、メトリックＳ00(n+3)、Ｓ01(n+3)を比較し、小さい方に対応する経路Ａ１、Ａ３の何れか一方を選択する。
【００２３】
同様に、ｎ＋３番目の受信シンボルの状態１に着目すると、この状態０には１つ前のｎ＋２番目の受信シンボルの状態０から遷移する場合（経路Ａ２）と、状態１から遷移する場合（経路Ａ４）とがある。上述した通り、状態０から状態１に遷移する場合には、受信シンボルの真値は０．５である。従って、ｎ＋３番目の受信シンボルにおける、経路Ａ２に対応するメトリックＳ10(n+3) は、ｎ＋３番目の受信シンボルの値と０．５との差の２乗値（ブランチメトリック）に、ｎ＋２番目のシンボルの状態０に至るまでのメトリックを加算して得られる。また、状態１から状態１に遷移する場合には、受信シンボルの真値は１．５である。従って、ｎ＋３番目の受信シンボルにおける、経路Ａ４に対応するメトリックＳ11(n+3) は、ｎ＋３番目の受信シンボルの値と１．５との差の２乗値（ブランチメトリック）に、ｎ＋２番目のシンボルの状態１に至るまでのメトリックを加算して得られる。そして、メトリックＳ10(n+3)、Ｓ11(n+3)を比較し、小さい方に対応する経路Ａ２、Ａ４の何れか一方を選択する。
【００２４】
このようにして選択された２つの経路がいずれもｎ＋２番目の受信シンボルの状態０から遷移するものであった場合、すなわち経路Ａ１、Ａ２が選択されている場合には、ｎ＋２番目の受信シンボルの状態０が生き残りパスとして選択される。同様に、選択された２つの経路がいずれもｎ＋２番目の受信シンボルの状態１から遷移するものであった場合、すなわち経路Ａ３、Ａ４が選択されている場合には、ｎ＋２番目の受信シンボルの状態１が生き残りパスとして選択される。
【００２５】
一方、選択された２つの経路の一方がｎ＋２番目の受信シンボルの状態０から遷移するものであり、他方が状態１から遷移するものである場合には、ｎ＋２番目の受信シンボルにおける生き残りパスは決定されない。この場合には、更にｎ＋４番目以降の受信シンボルにおいて、上述したｎ＋３番目の受信シンボルにおける処理と同様に、ブランチメトリック及びメトリックの算出と、算出したメトリックに基づく経路選択を行うことにより、ｎ＋２番目の受信シンボルにおける生き残りパスが決定されることになる。
【００２６】
上述の算出処理は、ビタビアルゴリズムと称されるものであり、各受信シンボルにおいて、このビタビアルゴリズムによる算出処理を行うことにより、生き残りパス、すなわち、受信シンボルの状態が決定される。
【００２７】
このような生き残りパスの検出は、従来の最尤系列推定型等化器においても行われているが、本実施形態の最尤系列推定型等化器２０では、更に第１の事後確率を導出する。以下においては、ｍ段目の受信機内の最尤系列推定型等化器で導出される、ｎ番目の受信シンボルに対応する第１の事後確率をＰ0(m,n)、Ｐ1(m,n)と表す。これら第１の事後確率は、Ｐ0(m,n)がｎ番目の受信シンボルが状態０でない確率を示し、第１の事後確率Ｐ1(m,n)がｎ番目の受信シンボルが状態１でない確率を示す。
【００２８】
具体的には、最尤系列推定型等化器２０は、ｎ−１番目の受信シンボルの状態を０、ｎ番目の受信シンボルの状態を０と決定した場合には、図４に示すように、ｎ−１番目の受信シンボルの状態０からｎ番目の受信シンボルの状態０へのブランチメトリック、すなわちｎ番目の受信シンボルの値と−１．５との差の２乗値Ｍ00(n) と、ｎ−１番目の受信シンボルの状態０からｎ番目の受信シンボルの状態１へのブランチメトリック、すなわちｎ番目の受信シンボルの値と０．５との差の２乗値Ｍ10(n) とに基づいて、ｎ番目の受信シンボルに対応する第１の事後確率Ｐ0(1,n)、Ｐ1(1,n)を
【００２９】
Ｐ0(1,n)＝Ｍ00(n)／（Ｍ00(n)＋Ｍ10(n)）（１）
【００３０】
Ｐ1(1,n)＝Ｍ10(n)／（Ｍ00(n)＋Ｍ10(n)）（２）
により導出する。
【００３１】
また、最尤系列推定型等化器２０は、ｎ−１番目の受信シンボルの状態を０、ｎ番目の受信シンボルの状態を１と決定した場合には、図４に示すように、ｎ−１番目の受信シンボルの状態０からｎ番目の受信シンボルの状態０へのブランチメトリック、すなわちｎ番目の受信シンボルの値と−１．５との差の２乗値Ｍ00(n) と、ｎ−１番目の受信シンボルの状態０からｎ番目の受信シンボルの状態１へのブランチメトリック、すなわちｎ番目の受信シンボルの値と０．５との差の２乗値Ｍ10(n) とに基づいて、ｎ番目の受信シンボルに対応する第１の事後確率Ｐ0(1,n)、Ｐ1(1,n)を
【００３２】
Ｐ0(1,n)＝Ｍ00(n)／（Ｍ00(n)＋Ｍ10(n)）（３）
【００３３】
Ｐ1(1,n)＝Ｍ10(n)／（Ｍ00(n)＋Ｍ10(n)）（４）
により導出する。
【００３４】
同様に、最尤系列推定型等化器２０は、ｎ−１番目の受信シンボルの状態を１、ｎ番目の受信シンボルの状態を０と決定した場合には、図４に示すように、ｎ−１番目の受信シンボルの状態１からｎ番目の受信シンボルの状態０へのブランチメトリック、すなわちｎ番目の受信シンボルの値と−０．５との差の２乗値Ｍ01(n) と、ｎ−１番目の受信シンボルの状態１からｎ番目の受信シンボルの状態１へのブランチメトリック、すなわちｎ番目の受信シンボルの値と１．５との差の２乗値Ｍ11(n) とに基づいて、ｎ番目の受信シンボルに対応する第１の事後確率Ｐ0(1,n)、Ｐ1(1,n)を
【００３５】
Ｐ0(1,n)＝Ｍ01(n)／（Ｍ01(n)＋Ｍ11(n)）（５）
【００３６】
Ｐ1(1,n)＝Ｍ11(n)／（Ｍ01(n)＋Ｍ11(n)）（６）
により導出する。
【００３７】
また、最尤系列推定型等化器２０は、ｎ−１番目の受信シンボルの状態を１、ｎ番目の受信シンボルの状態を１と決定した場合には、図４に示すように、ｎ−１番目の受信シンボルの状態１からｎ番目の受信シンボルの状態０へのブランチメトリック、すなわちｎ番目の受信シンボルの値と−０．５との差の２乗値Ｍ01(n) と、ｎ−１番目の受信シンボルの状態１からｎ番目の受信シンボルの状態１へのブランチメトリック、すなわちｎ番目の受信シンボルの値と０．５との差の２乗値Ｍ11(n) とに基づいて、ｎ番目の受信シンボルに対応する第１の事後確率Ｐ0(1,n)、Ｐ1(1,n)を
【００３８】
Ｐ0(1,n)＝Ｍ01(n)／（Ｍ01(n)＋Ｍ11(n)）（７）
【００３９】
Ｐ1(1,n)＝Ｍ11(n)／（Ｍ01(n)＋Ｍ11(n)）（８）
により導出する。
【００４０】
このようにして導出された第１の事後確率Ｐ0(1,n)、Ｐ1(1,n)は、後述する２段目の受信機６の最尤系列推定型等化器３０に送られる。
【００４１】
受信機６における乗算器２６は、アンテナ２２が受信した信号に、局発信号発生器２４からの基準周波数信号を乗算し、ベースバンド信号に変換する。
【００４２】
インパルスレスポンス推定器２８は、このベースバンド信号に基づいて、インパルスレスポンス推定値を導出するものである。具体的な導出方法は、受信機４のインパルスレスポンス推定器１８と同様であるのでその説明は省略する。
【００４３】
遅延器２９は、最尤系列推定型等化器３０に入力される、ベースバンド信号、インパルスレスポンス推定器２８からのインパルスレスポンス推定値、及び第１の受信機４の最尤系列推定型等化器２０からの第１の事後確率の入力タイミングを一致させるべく、乗算器２６からのベースバンド信号を所定時間遅延させて出力する。
【００４４】
最尤系列推定型等化器３０は、遅延器２９からのベースバンド信号、インパルスレスポンス推定器２８からのインパルスレスポンス推定値、及び受信機４の最尤系列推定型等化器２０からの第１の事後確率Ｐ0(1,n)、Ｐ1(1,n)に基づいて、上述のメトリック計算を行い、ビタビアルゴリズムによる生き残りパスの検出を行うとともに、第２の事後確率Ｐ0(2,n)、Ｐ1(2,n)を導出する。
【００４５】
最尤系列推定型等化器３０による最尤系列推定は、基本的には、第１の受信機４における最尤系列推定型等化器２０と同様であるが、ブランチメトリックの算出方法が異なる。すなわち、最尤系列推定型等化器３０では、４つの受信シンボルの真値のそれぞれと、雑音を含む受信シンボルの値との差の２乗値に、受信機４の最尤系列推定型等化器２０からの第１の事後確率を乗算し、その値をブランチメトリックとする。
【００４６】
具体的には、ｎ−１番目の受信シンボルの状態０からｎ番目の受信シンボルの状態０へのブランチメトリックは、ｎ番目の受信シンボルの値と−１．５との差の２乗値Ｍ00(n) に、第１の事後確率Ｐ0(1,n)を乗算して得られる。また、ｎ−１番目の受信シンボルの状態１からｎ番目の受信シンボルの状態０へのブランチメトリックは、ｎ番目の受信シンボルの値と−０．５との差の２乗値Ｍ01(n) に、第１の事後確率Ｐ0(1,n)を乗算して得られる。
【００４７】
同様に、ｎ−１番目の受信シンボルの状態０からｎ番目の受信シンボルの状態１へのブランチメトリックは、ｎ番目の受信シンボルの値と０．５との差の２乗値Ｍ10(n) に、第１の事後確率Ｐ1(1,n)を乗算して得られ、ｎ−１番目の受信シンボルの状態１からｎ番目の受信シンボルの状態１へのブランチメトリックは、ｎ番目の受信シンボルの値と０．５との差の２乗値Ｍ11(n) に、第１の事後確率Ｐ1(1,n)を乗算して得られる。
【００４８】
このようにして各ブランチメトリックを算出すると、最尤系列推定型等化器３０は、ｎ番目の受信シンボルに対応するメトリックを算出し、生き残りパスの検出を行うとともに、第２の事後確率Ｐ0(2,n)、Ｐ1(2,n)を導出する。これら生き残りパスの検出方法と、第２の事後確率Ｐ0(2,n)、Ｐ1(2,n)の導出方法は、上述した受信機４の最尤系列推定型等化器２０と同様であるので、その説明は省略する。
【００４９】
最尤系列推定型等化器３０によって導出された第２の事後確率Ｐ0(2,n)、Ｐ1(2,n)は、判定部８に送られる。判定部８は、これら第２の事後確率Ｐ0(2,n)、Ｐ1(2,n)を比較し、小さい方の値に対応する状態を、ｎ番目の受信シンボルに対応するデータとして検出する。
【００５０】
このように、本実施形態の信号受信装置２では、第１の受信機４及び第２の受信機６を２段に接続し、１段目の受信機４の最尤系列推定型等化器２０で導出された第１の事後確率Ｐ0(1,n)、Ｐ1(1,n)を、２段目の受信機６の最尤系列推定型等化器３０による生き残りパスの検出と第２の事後確率Ｐ0(2,n)、Ｐ1(2,n)の導出に用いるとともに、判定部８は、これら第２の事後確率Ｐ0(2,n)、Ｐ1(2,n)に基づいて、ｎ番目の受信シンボルに対応するデータを検出しており、事後確率を導出、利用することにより、データ検出の正確性の向上、換言すれば、受信性能の向上を図ることができる。
【００５１】
ところで、図１に示した信号受信装置２に、最尤系列推定型等化器を更に接続するようにしてもよい。図５は、最尤系列推定型等化器を更に接続した信号受信装置の構成例を示すブロック図である。同図に示す信号受信装置１０２は、２段に接続された受信機４、６と、最尤系列推定型等化器１０４と、判定部８とを備えて構成される。なお、受信機４には遅延器１９が追加されている。
【００５２】
最尤系列推定型等化器１０４には、受信機４のインパルスレスポンス推定器１８からのインパルスレスポンス推定値、受信機６の最尤系列推定型等化器３０からの第２の事後確率Ｐ0(2,n)、Ｐ1(2,n)、及び受信機４の遅延器１９からのベースバンド信号が入力される。受信機４の遅延器１９は、これら入力される信号の入力タイミングを一致させるべく、乗算器１６からのベースバンド信号を所定時間遅延させるものである。
【００５３】
最尤系列推定型等化器１０４は、これら入力される信号に基づいて、上述のメトリック計算を行い、ビタビアルゴリズムによる生き残りパスの検出を行うとともに、第３の事後確率Ｐ0(3,n)、Ｐ1(3,n)を導出する。具体的な動作は、図１に示した信号受信装置２の受信機６内の最尤系列推定型等化器３０と同様であるので、その説明は省略する。判定部８は、これら第３の事後確率Ｐ0(3,n)、Ｐ1(3,n)を比較し、小さい方の値に対応する状態を、ｎ番目の受信シンボルに対応するデータとして検出する。
【００５４】
また、図１に示した信号受信装置２に、複数段の最尤系列推定型等化器を更に接続するようにしてもよい。図６は、最尤系列推定型等化器を更に接続した信号受信装置の構成例を示すブロック図である。同図に示す信号受信装置２０２は、２段に接続された受信機４、６と、３段に接続された最尤系列推定型等化器２０４、２０６、２０８と、遅延器２１０、２１２と、判定部８とを備えて構成される。なお、第１の受信機４には遅延器１９が追加されている。
【００５５】
最尤系列推定型等化器２０４には、受信機４のインパルスレスポンス推定器１８からのインパルスレスポンス推定値、受信機６の最尤系列推定型等化器３０からの第２の事後確率Ｐ0(2,n)、Ｐ1(2,n)、及び受信機４の遅延器１９からのベースバンド信号が入力される。最尤系列推定型等化器２０４は、これら入力される信号に基づいて、上述のメトリック計算を行い、ビタビアルゴリズムによる生き残りパスの検出を行うとともに、第３の事後確率Ｐ0(3,n)、Ｐ1(3,n)を導出する。最尤系列推定型等化器２０６には、受信機６のインパルスレスポンス推定器１８からのインパルスレスポンス推定値、最尤系列推定型等化器２０４からの第３の事後確率Ｐ0(3,n)、Ｐ1(3,n)、及び遅延器２１０からのベースバンド信号が入力される。遅延器２１０は、最尤系列推定型等化器２０６に入力される、ベースバンド信号、インパルスレスポンス推定器２８からのインパルスレスポンス推定値、最尤系列推定型等化器２０４からの事後確率の入力タイミングを一致させるべく、受信機６の遅延器２９からのベースバンド信号を所定時間遅延させるものである。
【００５６】
最尤系列推定型等化器２０４は、これら入力される信号に基づいて、上述のメトリック計算を行い、ビタビアルゴリズムによる生き残りパスの検出を行うとともに、第４の事後確率Ｐ0(4,n)、Ｐ1(4,n)を導出する。
【００５７】
最尤系列推定型等化器２０８には、受信機６のインパルスレスポンス推定器１８からのインパルスレスポンス推定値、最尤系列推定型等化器２０６からの第４の事後確率Ｐ0(4,n)、Ｐ1(4,n)、及び遅延器２１２からのベースバンド信号が入力される。遅延器２１２は、最尤系列推定型等化器２０６に入力される、ベースバンド信号、インパルスレスポンス推定器１８からのインパルスレスポンス推定値、最尤系列推定型等化器２０６からの事後確率の入力タイミングを一致させるべく、受信機４の遅延器１９からのベースバンド信号を所定時間遅延させるものである。
【００５８】
最尤系列推定型等化器２０８は、これら入力される信号に基づいて、上述のメトリック計算を行い、ビタビアルゴリズムによる生き残りパスの検出を行うとともに、第５の事後確率Ｐ0(5,n)、Ｐ1(5,n)を導出する。
【００５９】
判定部８は、これら第５の事後確率Ｐ0(5,n)、Ｐ1(5,n)を比較し、小さい方の値に対応する状態を、ｎ番目の受信シンボルに対応するデータとして検出する。
【００６０】
また、受信機を３段以上接続して信号受信装置を構成するようにしてもよい。図７は、受信機を３段に接続した信号受信装置の構成例を示すブロック図である。同図に示す信号受信装置３０２は、３段に接続された受信機４、受信機６及び受信機３０４と、判定部８とを備えて構成される。なお、受信機４、受信機６は、図１に示した信号受信装置２の受信機４、受信機６と同様の構成であるので、その説明は省略する。
【００６１】
３段目の受信機３０４は、アンテナ３１２、局発信号発生器３１４、乗算器３１６、インパルスレスポンス推定器３１８、最尤系列推定型等化器３２０を備えて構成される。
【００６２】
乗算器３１６は、アンテナ３１２が受信した信号に、局発信号発生器１４からの基準周波数信号を乗算し、ベースバンド信号に変換する。インパルスレスポンス推定器３１８は、上述した如くこのベースバンド信号に基づいて、インパルスレスポンス推定値を導出する。遅延器３１９は、最尤系列推定型等化器３２０に入力される、ベースバンド信号、インパルスレスポンス推定器３１８からのインパルスレスポンス推定値、及び受信機６の最尤系列推定型等化器３０からの事後確率の入力タイミングを一致させるべく、乗算器３１６からのベースバンド信号を所定時間遅延させて出力する。
【００６３】
最尤系列推定型等化器３２０は、遅延器３１９からのベースバンド信号、インパルスレスポンス推定器３１８からのインパルスレスポンス推定値、及び受信機６の最尤系列推定型等化器３０からの第２の事後確率Ｐ0(2,n)、Ｐ1(2,n)に基づいて、上述のメトリック計算を行い、ビタビアルゴリズムによる生き残りパスの検出を行うとともに、第３の事後確率Ｐ0(3,n)、Ｐ1(3,n)を導出する。具体的な動作は、図１に示した信号受信装置２の受信機６内の最尤系列推定型等化器３０と同様であるので、その説明は省略する。判定部８は、これら第３の事後確率Ｐ0(3,n)、Ｐ1(3,n)を比較し、小さい方の値に対応する状態を、ｎ番目の受信シンボルに対応するデータとして検出する。
【００６４】
以上、本発明の一実施形態を図面に沿って説明した。しかしながら本発明は前記実施形態に示した事項に限定されず、特許請求の範囲の記載に基いてその変更、改良等が可能であることは明らかである。
【００６５】
【発明の効果】
以上の如く本発明によれば、事後確率を導出、利用することにより、データ検出の正確性の向上、換言すれば、受信性能の向上を図ることができるという著しい効果を奏する。
【図面の簡単な説明】
【図１】本発明に係る信号受信装置の構成例を示すブロック図である。
【図２】伝送フレームの一例を示す図である。
【図３】最尤系列推定型等化器による生き残りパス検出の一例を示す図である。
【図４】最尤系列推定型等化器による事後確率の導出の一例を示す図である。
【図５】最尤系列推定型等化器を更に接続した信号受信装置の構成例を示すブロック図である。
【図６】２段の最尤系列推定型等化器を更に接続した信号受信装置の構成例を示すブロック図である。
【図７】受信機を３段に接続した信号受信装置の構成例を示すブロック図である。
【図８】従来の信号受信装置の構成例を示すブロック図である。
【符号の説明】
２信号受信装置
４、６受信機
８判定部
１２アンテナ
１４局発信号発生器
１６乗算器
１８インパルスレスポンス推定器
１９遅延器
２０最尤系列推定型等化器
２２アンテナ
２４局発信号発生器
２６乗算器
２８インパルスレスポンス推定器
２９遅延器
３０最尤系列推定型等化器
１０２信号受信装置
１０４最尤系列推定型等化器
２０２信号受信装置
２０４、２０６、２０８最尤系列推定型等化器
２１０、２１２遅延器
３０２信号受信装置
３０４受信機
３１２アンテナ
３１４局発信号発生器
３１６乗算器
３１８インパルスレスポンス推定器
３１９遅延器
３２０最尤系列推定型等化器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a signal receiving apparatus using a maximum likelihood sequence estimation type equalizer.
[0002]
[Prior art]
Conventionally, as a countermeasure against reception performance degradation, the signal receiver has been equipped with an impulse response estimator and a maximum likelihood sequence estimation type equalizer to detect the optimal data sequence based on the principle of maximum likelihood sequence estimation and improve reception performance. Things have been done.
[0003]
FIG. 8 is a block diagram illustrating a configuration example of a conventional signal receiving apparatus. The signal receiving apparatus 502 shown in the figure includes an antenna 504, a multiplier 506, a local oscillation signal generator 508, an impulse response estimator 510, and a maximum likelihood sequence estimation type equalizer 512. It is assumed that a binary phase modulation method (BPSK: Binary Phase Shift Keying) is used as the modulation method.
[0004]
A predetermined data string is transmitted from a signal transmission device (not shown). The signal receiving apparatus 502 receives this data series. In addition to the direct wave, the received signal is delayed by a predetermined symbol time length with respect to the direct wave according to the condition of the signal propagation path. In addition, a delayed wave having a reduced amplitude is also included. For this reason, if each symbol is determined as it is, an error may occur in the determination. Therefore, the signal receiving apparatus 502 makes it possible to restore the original data string from the received signal, even when the received signal includes a direct wave and a delayed wave, based on the principle of maximum likelihood sequence estimation.
[0005]
The detailed description is omitted because it is described in, for example, the document “Shuichi Okaoka, Mobile Communications, Ohmsha”. In short, the multiplier 506 converts the signal received by the antenna 504 into the local signal generator 504. Is multiplied by the reference frequency signal from, and converted to a baseband signal. The impulse response estimator 510 derives an impulse response estimated value based on the baseband signal.
[0006]
Maximum likelihood sequence estimation type equalizer 512 performs metric calculation to be described later based on the baseband signal from multiplier 506 and the impulse response estimation value from impulse response estimator 510, and generates an optimal data sequence by the Viterbi algorithm. To detect.
[0007]
[Problems to be solved by the invention]
However, in the conventional signal receiving apparatus, the maximum likelihood sequence estimation type equalizer 512 obtains an optimal data string by metric calculation and the Viterbi algorithm, so its accuracy is theoretically limited, and reception performance is limited. There was a limit to improvement. For this reason, in recent years, there has been an increasing demand for signal reception devices to further improve reception performance, but there has been a problem that it is impossible to meet such demands.
[0008]
The present invention solves the above-described conventional problems, and an object of the present invention is to provide a signal receiving apparatus with improved reception performance.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a signal receiving apparatus of the present invention is a signal receiving apparatus having first and second receivers that extract only a direct wave from a received signal, and determination means, wherein the first receiving A first signal converting means for converting the received signal into a baseband signal, and a first impulse response estimating means for deriving an impulse response estimated value based on the baseband signal from the first signal converting means. And based on the baseband signal from the first signal conversion means and the impulse response estimation value from the first impulse response estimation means, The metric calculation is performed to detect the surviving path by the Viterbi algorithm, and the state of the received symbol at the nth timing is B under the condition that the state of the received symbol at the (n-1) th timing is A. The posterior probability is the branch metric for each branch, and the branch metric for the branch from A to B is the square of the difference between the true value of the received symbol for that branch and the value of the received symbol including the noise of the baseband signal. , By dividing by the sum of the branch metrics of the branches from A to the state of each received symbol, first maximum likelihood sequence estimation type equalization means for deriving a first posterior probability corresponding to the nth received symbol, and the second receiver converts the received signal into a baseband signal. 2 signal conversion means, second impulse response estimation means for deriving an impulse response estimation value based on the baseband signal from the second signal conversion means, and baseband from the second signal conversion means A first delay means for delaying a signal, a baseband signal from the second signal conversion means guided through the first delay means, an impulse response estimation value from the second impulse response estimation means, And a first posterior probability from the first maximum likelihood sequence estimation type equalization means, The metric calculation is performed to detect the surviving path by the Viterbi algorithm, and the state of the received symbol at the nth timing is B under the condition that the state of the received symbol at the (n-1) th timing is A. The posterior probability, the branch metric for each branch, the true value of the received symbol for that branch and Guided through said first delay means As a value obtained by multiplying the square value of the difference from the received symbol value including the noise of the baseband signal by the first posterior probability, the branch metric of the branch from A to B is changed from A to the state of each received symbol. By calculating by the value divided by the sum of the branch metrics of the branch, second maximum likelihood sequence estimation type equalization means for deriving a second posterior probability corresponding to the nth received symbol, and the determination means includes the second maximum likelihood sequence estimation type equalization means. Second posterior confirmation Rate Compare the state corresponding to the smaller value with the data corresponding to the nth received symbol. Detect as .
[0010]
In this case, a second delay means for delaying the baseband signal from the first signal conversion means, and a baseband signal from the first signal conversion means guided through the second delay means, Based on the impulse response estimation value from the first impulse response estimation means and the second posterior probability from the second maximum likelihood sequence estimation type equalization means, The metric calculation is performed to detect the surviving path by the Viterbi algorithm, and the state of the received symbol at the nth timing is B under the condition that the state of the received symbol at the (n-1) th timing is A. The posterior probability, the branch metric for each branch, the true value of the received symbol for that branch and Guided through the second delay means As a value obtained by multiplying the square value of the difference from the received symbol value including the noise of the baseband signal by the second posterior probability, the branch metric of the branch from A to B is changed from A to the state of each received symbol. By calculating by the value divided by the sum of the branch metrics of the branch, and third maximum likelihood sequence estimation type equalization means for deriving a third posterior probability corresponding to the nth received symbol, wherein the determination means is the third maximum likelihood sequence estimation type equalization means. Third posterior confirmation from Rate Compare the state corresponding to the smaller value with the data corresponding to the nth received symbol. Detect as It is preferable.
[0011]
A base from the second delay means corresponding to each stage of the maximum likelihood sequence estimation type equalization means connected to a plurality of stages and the maximum likelihood sequence estimation type equalization means connected to the plurality of stages. An even-numbered delay means for delaying the band signal and an odd-numbered delay means for delaying the baseband signal from the first delay means, and the odd-numbered (m: m = 3, 5) The maximum likelihood sequence estimation type equalization means includes a baseband signal from the first signal conversion means guided through a corresponding (m−1) th delay means, and the first impulse response. Based on the impulse response estimation value from the estimation means and the (m−1) th maximum likelihood sequence estimation type equalization means in the even numbered stage in the previous stage, The metric calculation is performed to detect the surviving path by the Viterbi algorithm, and the state of the received symbol at the nth timing is B under the condition that the state of the received symbol at the (n-1) th timing is A. The posterior probability, the branch metric for each branch, the true value of the received symbol for that branch and Led through the (m-1) th delay means To the square value of the difference from the received symbol value including noise of the baseband signal The (m-1) posterior probability By calculating the branch metric of the branch from A to B by the sum of the branch metric of the branch from A to the state of each received symbol, The (m) posterior probability corresponding to the nth received symbol is derived, and the (m + 1) th (M + 1) th maximum likelihood sequence estimation type equalizing means is derived from the corresponding (m) delay means. The baseband signal from the second signal conversion means, the impulse response estimation value from the second impulse response estimation means, and the (m) maximum likelihood sequence estimation type equalization means at the odd-numbered stage in the previous stage. Based on the (m) posterior probability, The metric calculation is performed to detect the surviving path by the Viterbi algorithm, and the state of the received symbol at the nth timing is B under the condition that the state of the received symbol at the (n-1) th timing is A. The posterior probability, the branch metric for each branch, the true value of the received symbol for that branch and Led through the (m) delay means To the square value of the difference from the received symbol value including noise of the baseband signal The (m) posterior probability By calculating the value obtained by multiplying the branch metric of the branch from A to B by the sum of the branch metrics of the branch from A to the state of each received symbol as a multiplied value, An (m + 1) th posterior probability corresponding to the nth received symbol is derived, and the determination means is the (m) or (m + 1) th posterior probability from the maximum likelihood sequence estimation type equalization means in the final stage. Rate Compare the state corresponding to the smaller value with the data corresponding to the nth received symbol. Detect as It is preferable.
[0012]
The third receiver further includes a third signal converting means for converting a received signal into a baseband signal, and a baseband signal from the third signal converting means. The third impulse response estimating means for deriving the impulse response estimated value, the third delay means for delaying the baseband signal from the third signal converting means, and the third delay means. The baseband signal from the third signal conversion means, the impulse response estimation value from the third impulse response estimation means, and the second maximum likelihood sequence estimation type equalization means in the second receiver. Based on the second posterior probability, The metric calculation is performed to detect the surviving path by the Viterbi algorithm, and the state of the received symbol at the nth timing is B under the condition that the state of the received symbol at the (n-1) th timing is A. The posterior probability, the branch metric for each branch, the true value of the received symbol for that branch and Guided through the third delay means As a value obtained by multiplying the square value of the difference from the received symbol value including the noise of the baseband signal by the second posterior probability, the branch metric of the branch from A to B is changed from A to the state of each received symbol. By calculating by the value divided by the sum of the branch metrics of the branch, and third maximum likelihood sequence estimation type equalization means for deriving a third posterior probability corresponding to the nth received symbol, and the determination means includes the third maximum likelihood sequence estimation type equalization means. The third posterior confirmation Rate The state corresponding to the smaller value is compared with the data corresponding to the nth received symbol. To detect It is preferable.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on the illustrated embodiment. FIG. 1 is a block diagram showing a configuration example of a signal receiving apparatus according to the present invention. The signal receiving apparatus 2 shown in FIG. 1 includes a first receiver 4 and a second receiver 6 connected in two stages, and a determination unit 8.
[0014]
The first-stage receiver (first receiver) 4 includes an antenna 12, a local signal generator 14, a multiplier 16, an impulse response estimator 18, and a maximum likelihood sequence estimation type equalizer 20. The On the other hand, the second-stage receiver (second receiver) 6 includes an antenna 22, a local oscillator generator 24, a multiplier 26, an impulse response estimator 28, a delay unit 29, and a maximum likelihood sequence estimation type equalizer. 30.
[0015]
Note that a signal transmission apparatus (not shown) that is a signal transmission source transmits a predetermined data string consisting of 0 and 1, and the transmission symbol is -1 when the data is 0 and 1 The value of 1 is assumed to be taken as 1. In addition to the direct wave, the received signal received by the signal receiving device 2 is delayed by, for example, one symbol time with respect to the direct wave and the amplitude is reduced to ½ due to the characteristics of the propagation path. It is assumed that a delayed wave is included.
[0016]
The multiplier 16 of the receiver 4 multiplies the signal received by the antenna 12 by the reference frequency signal from the local signal generator 14 and converts it to a baseband signal.
[0017]
The impulse response estimator 18 derives an impulse response estimated value based on the baseband signal. Specifically, the signal transmission device (not shown) sets an impulse signal to the training signal of the transmission frame shown in FIG. 2 and transmits the impulse signal, and the impulse response estimator 18 transmits the direct wave from this signal transmission device. A deviation and an amplitude difference between the received training signal and the training signal received as a delayed wave are detected, and these are derived as impulse response estimation values.
[0018]
The maximum likelihood sequence estimation type equalizer 20 performs a metric calculation to be described later based on the baseband signal from the multiplier 16 and the impulse response estimation value from the impulse response estimator 18, and the survival path of the Viterbi algorithm is calculated. While performing detection, a posterior probability (first posterior probability) is derived.
[0019]
Details of maximum likelihood sequence estimation by the maximum likelihood sequence estimation equalizer 20 will be described below. As described above, since the received signal includes a delayed wave delayed for a predetermined time with respect to the direct wave in addition to the direct wave, the symbol of the received signal (hereinafter referred to as “received symbol”) is: This is a signal in which the symbol transmitted at that time and the delayed wave component of the symbol transmitted before that are superimposed. In the following, in order to simplify the description, the delayed wave is described assuming that the delay is one symbol time and the amplitude is ½ with respect to the direct wave.
[0020]
Therefore, when the symbol transmitted at a certain time is -1 (state 0) and the symbol transmitted one time before is -1 (state 0), the delayed wave is 1/2 of the direct wave. Considering the amplitude, the value of the received symbol is −1.5. Similarly, when the symbol transmitted at a certain time is -1 (state 0) and the symbol transmitted one time before is 1 (state 1), the value of the received symbol is -0.5. Become. In addition, when the symbol transmitted at a certain time is 1 (state 1) and the symbol transmitted immediately before is -1 (state 0), the value of the received symbol is 0.5, When the symbol transmitted at a certain time is 1 (state 1) and the symbol transmitted immediately before is 1 (state 1), the value of the received symbol is 1.5.
[0021]
Thus, the received symbol should have a value of -1.5, -0.5, 0.5, or 1.5. However, since the received symbol actually includes noise and the like, these four values are not necessarily obtained. In the maximum likelihood sequence estimation, the square value of the difference between each of these four values (hereinafter referred to as “true value of received symbol”) and the value of the received symbol including noise is calculated as a branch metric. The cumulative value of the branch metric up to (hereinafter referred to as “metric”) is calculated. The optimal path (surviving path) is known to have the smallest metric.
[0022]
FIG. 3 is a diagram illustrating an example of surviving path detection by the maximum likelihood sequence estimation type equalizer 20. In the figure, focusing on the state 0 of the n + 3th received symbol, the state 0 transitions from the previous n + 2th received symbol state 0 (path A1) and the state 1 transitions ( There is a route A3). As described above, in the case of transition from state 0 to state 0, the true value of the received symbol is −1.5. Therefore, the metric S00 (n + 3) corresponding to the path A1 in the (n + 3) th received symbol is n + 2th as the square value (branch metric) of the difference between the value of the (n + 3) th received symbol and −1.5. It is obtained by adding the metrics up to the state 0 of the symbols. Further, when the state transits from state 1 to state 0, the true value of the received symbol is −0.5. Therefore, the metric S01 (n + 3) corresponding to the path A3 in the (n + 3) th received symbol is the square value (branch metric) of the difference between the value of the (n + 3) th received symbol and 0.5, and the (n + 2) th It is obtained by adding the metrics up to symbol state 1. Then, the metrics S00 (n + 3) and S01 (n + 3) are compared, and one of the routes A1 and A3 corresponding to the smaller one is selected.
[0023]
Similarly, paying attention to the state 1 of the n + 3th received symbol, the state 0 transitions from the previous n + 2th received symbol state 0 (path A2) to the state 0 (path A2). A4). As described above, in the case of transition from state 0 to state 1, the true value of the received symbol is 0.5. Therefore, the metric S10 (n + 3) corresponding to the path A2 in the (n + 3) th received symbol is the square value (branch metric) of the difference between the value of the (n + 3) th received symbol and 0.5, and the (n + 2) th It is obtained by adding the metrics up to symbol state 0. When the state 1 changes to the state 1, the true value of the received symbol is 1.5. Therefore, the metric S11 (n + 3) corresponding to the path A4 in the (n + 3) th received symbol is the square value (branch metric) of the difference between the value of the (n + 3) th received symbol and 1.5, and the (n + 2) th It is obtained by adding the metrics up to symbol state 1. Then, the metrics S10 (n + 3) and S11 (n + 3) are compared, and one of the routes A2 and A4 corresponding to the smaller one is selected.
[0024]
When both of the two paths selected in this way are transitions from the state 0 of the (n + 2) th received symbol, that is, when the paths A1 and A2 are selected, the n + 2th received symbol State 0 is selected as the surviving path. Similarly, if both of the two selected paths are transitions from state 1 of the (n + 2) th received symbol, that is, if paths A3 and A4 are selected, the state of the (n + 2) th received symbol 1 is selected as the survival path.
[0025]
On the other hand, if one of the two selected paths transitions from state 0 of the n + 2 received symbol and the other transitions from state 1, the surviving path in the n + 2 received symbol is determined. Not. In this case, in the n + 4th and subsequent received symbols, the branch metric and the metric are calculated, and the path selection based on the calculated metric is performed in the same manner as in the above-described processing of the n + 3th received symbol. The surviving path in the received symbol will be determined.
[0026]
The calculation process described above is called a Viterbi algorithm, and the survival path, that is, the state of the received symbol is determined by performing the calculation process using the Viterbi algorithm for each received symbol.
[0027]
Such detection of surviving paths is also performed in the conventional maximum likelihood sequence estimation type equalizer, but the maximum likelihood sequence estimation type equalizer 20 of the present embodiment further derives the first posterior probability. To do. In the following, the first posterior probabilities corresponding to the nth received symbol derived by the maximum likelihood sequence estimation equalizer in the m-th receiver are P0 (m, n) and P1 (m, n). ). These first posterior probabilities indicate the probability that P0 (m, n) is the nth received symbol is not in state 0, and the first posterior probability P1 (m, n) is the probability that the nth received symbol is not in state 1 Indicates.
[0028]
Specifically, when the maximum likelihood sequence estimation equalizer 20 determines that the state of the (n−1) th received symbol is 0 and the state of the nth received symbol is 0, as shown in FIG. , The branch metric from the state 0 of the (n−1) th received symbol to the state 0 of the nth received symbol, that is, the square value M00 (n) of the difference between the value of the nth received symbol and −1.5 , Branch metric from state 0 of the (n-1) th received symbol to state 1 of the nth received symbol, that is, the square value M10 (n) of the difference between the value of the nth received symbol and 0.5 Based on the first posterior probabilities P0 (1, n) and P1 (1, n) corresponding to the nth received symbol.
[0029]
P0 (1, n) = M00 (n) / (M00 (n) + M10 (n)) (1)
[0030]
P1 (1, n) = M10 (n) / (M00 (n) + M10 (n)) (2)
Derived by
[0031]
When the maximum likelihood sequence estimation type equalizer 20 determines that the state of the (n−1) th received symbol is 0 and the state of the nth received symbol is 1, as shown in FIG. The branch metric from state 0 of the first received symbol to state 0 of the nth received symbol, that is, the square value M00 (n) of the difference between the value of the nth received symbol and −1.5, and n− Based on the branch metric from state 0 of the first received symbol to state 1 of the nth received symbol, ie, the square value M10 (n) of the difference between the value of the nth received symbol and 0.5, The first posterior probabilities P0 (1, n) and P1 (1, n) corresponding to the nth received symbol are
[0032]
P0 (1, n) = M00 (n) / (M00 (n) + M10 (n)) (3)
[0033]
P1 (1, n) = M10 (n) / (M00 (n) + M10 (n)) (4)
Derived by
[0034]
Similarly, the maximum likelihood sequence estimation type equalizer 20 determines that the state of the (n−1) th received symbol is 1 and the state of the nth received symbol is 0, as shown in FIG. The branch metric from the state 1 of the -1st received symbol to the state 0 of the nth received symbol, that is, the square value M01 (n) of the difference between the value of the nth received symbol and -0.5, and n Based on the branch metric from state 1 of the first received symbol to state 1 of the nth received symbol, ie, the square value M11 (n) of the difference between the value of the nth received symbol and 1.5 , The first posterior probabilities P0 (1, n) and P1 (1, n) corresponding to the nth received symbol are
[0035]
P0 (1, n) = M01 (n) / (M01 (n) + M11 (n)) (5)
[0036]
P1 (1, n) = M11 (n) / (M01 (n) + M11 (n)) (6)
Derived by
[0037]
When the maximum likelihood sequence estimation equalizer 20 determines that the state of the (n−1) th received symbol is 1 and the state of the nth received symbol is 1, as shown in FIG. The branch metric from state 1 of the first received symbol to state 0 of the nth received symbol, that is, the square value M01 (n) of the difference between the value of the nth received symbol and −0.5, and n− Based on the branch metric from state 1 of the first received symbol to state 1 of the nth received symbol, that is, the square value M11 (n) of the difference between the value of the nth received symbol and 0.5, The first posterior probabilities P0 (1, n) and P1 (1, n) corresponding to the nth received symbol are
[0038]
P0 (1, n) = M01 (n) / (M01 (n) + M11 (n)) (7)
[0039]
P1 (1, n) = M11 (n) / (M01 (n) + M11 (n)) (8)
Derived by
[0040]
The first posterior probabilities P0 (1, n) and P1 (1, n) derived in this way are sent to the maximum likelihood sequence estimation equalizer 30 of the second-stage receiver 6 described later.
[0041]
The multiplier 26 in the receiver 6 multiplies the signal received by the antenna 22 by the reference frequency signal from the local signal generator 24 and converts it into a baseband signal.
[0042]
The impulse response estimator 28 derives an impulse response estimated value based on the baseband signal. Since the specific derivation method is the same as that of the impulse response estimator 18 of the receiver 4, the description thereof is omitted.
[0043]
The delay unit 29 receives the baseband signal, the impulse response estimation value from the impulse response estimator 28, and the maximum likelihood sequence estimation type equalization of the first receiver 4 that are input to the maximum likelihood sequence estimation type equalizer 30. In order to match the input timing of the first posterior probability from the multiplier 20, the baseband signal from the multiplier 26 is delayed by a predetermined time and output.
[0044]
The maximum likelihood sequence estimation type equalizer 30 includes a baseband signal from the delay unit 29, an impulse response estimation value from the impulse response estimator 28, and a first likelihood sequence estimation type equalizer 20 from the receiver 4. Based on the posterior probabilities P0 (1, n) and P1 (1, n), the survivor path is detected by the Viterbi algorithm, and the second posterior probabilities P0 (2, n), P1 (2, n) is derived.
[0045]
The maximum likelihood sequence estimation by the maximum likelihood sequence estimation type equalizer 30 is basically the same as the maximum likelihood sequence estimation type equalizer 20 in the first receiver 4, but the branch metric calculation method is different. . That is, the maximum likelihood sequence estimation type equalizer 30 sets the maximum likelihood sequence estimation type of the receiver 4 to the square value of the difference between the true value of each of the four received symbols and the value of the received symbol including noise. The first posterior probability from the generator 20 is multiplied and the value is set as a branch metric.
[0046]
Specifically, the branch metric from the state 0 of the (n-1) th received symbol to the state 0 of the nth received symbol is the square value M00 of the difference between the value of the nth received symbol and -1.5. It is obtained by multiplying (n) by the first posterior probability P0 (1, n). The branch metric from state 1 of the (n-1) th received symbol to state 0 of the nth received symbol is the square value M01 (n) of the difference between the value of the nth received symbol and -0.5. And the first posterior probability P0 (1, n).
[0047]
Similarly, the branch metric from state 0 of the (n-1) th received symbol to state 1 of the nth received symbol is the square value M10 (n) of the difference between the value of the nth received symbol and 0.5. And the branch metric from state 1 of the (n−1) th received symbol to state 1 of the nth received symbol is obtained by multiplying the first posterior probability P1 (1, n) by the nth received symbol. Is obtained by multiplying the square value M11 (n) of the difference between this value and 0.5 by the first posterior probability P1 (1, n).
[0048]
When each branch metric is calculated in this way, the maximum likelihood sequence estimation equalizer 30 calculates a metric corresponding to the nth received symbol, detects a surviving path, and also has a second posterior probability P0 ( 2, n) and P1 (2, n) are derived. The survivor path detection method and the second posterior probabilities P0 (2, n) and P1 (2, n) are derived in the same manner as the maximum likelihood sequence estimation equalizer 20 of the receiver 4 described above. Therefore, the description is omitted.
[0049]
The second posterior probabilities P 0 (2, n) and P 1 (2, n) derived by the maximum likelihood sequence estimation type equalizer 30 are sent to the determination unit 8. The determination unit 8 compares the second posterior probabilities P0 (2, n) and P1 (2, n), and detects a state corresponding to the smaller value as data corresponding to the nth received symbol. .
[0050]
Thus, in the signal receiving device 2 of the present embodiment, the first receiver 4 and the second receiver 6 are connected in two stages, and the maximum likelihood sequence estimation type equalizer of the first stage receiver 4 is used. The first a posteriori probabilities P 0 (1, n) and P 1 (1, n) derived at 20 are used to detect the surviving path by the maximum likelihood sequence estimation equalizer 30 of the second-stage receiver 6 and Are used to derive the posterior probabilities P0 (2, n) and P1 (2, n), and the determination unit 8 uses the second posterior probabilities P0 (2, n) and P1 (2, n) as follows. By detecting the data corresponding to the nth received symbol and deriving and using the posterior probability, it is possible to improve the accuracy of data detection, in other words, to improve the reception performance.
[0051]
By the way, a maximum likelihood sequence estimation type equalizer may be further connected to the signal receiving apparatus 2 shown in FIG. FIG. 5 is a block diagram showing a configuration example of a signal receiving apparatus further connected with a maximum likelihood sequence estimation type equalizer. The signal receiving apparatus 102 shown in the figure includes receivers 4 and 6 connected in two stages, a maximum likelihood sequence estimation type equalizer 104, and a determination unit 8. Note that a delay device 19 is added to the receiver 4.
[0052]
The maximum likelihood sequence estimation equalizer 104 includes an impulse response estimation value from the impulse response estimator 18 of the receiver 4, and a second posterior probability P 0 (from the maximum likelihood sequence estimation equalizer 30 of the receiver 6. 2, n), P1 (2, n), and the baseband signal from the delay unit 19 of the receiver 4 are input. The delay device 19 of the receiver 4 delays the baseband signal from the multiplier 16 for a predetermined time in order to match the input timings of these input signals.
[0053]
The maximum likelihood sequence estimation type equalizer 104 performs the above-described metric calculation based on these input signals, detects a surviving path by the Viterbi algorithm, and has a third posterior probability P0 (3, n), P1 (3, n) is derived. The specific operation is the same as that of the maximum likelihood sequence estimation equalizer 30 in the receiver 6 of the signal receiving apparatus 2 shown in FIG. The determination unit 8 compares the third posterior probabilities P0 (3, n) and P1 (3, n), and detects a state corresponding to the smaller value as data corresponding to the nth received symbol. .
[0054]
Further, a plurality of stages of maximum likelihood sequence estimation equalizers may be further connected to the signal receiving device 2 shown in FIG. FIG. 6 is a block diagram showing a configuration example of a signal receiving apparatus further connected with a maximum likelihood sequence estimation type equalizer. The signal receiving apparatus 202 shown in the figure includes receivers 4 and 6 connected in two stages, maximum likelihood sequence estimation equalizers 204, 206, and 208 connected in three stages, delay elements 210 and 212, and And a determination unit 8. Note that a delay device 19 is added to the first receiver 4.
[0055]
The maximum likelihood sequence estimation type equalizer 204 includes an impulse response estimation value from the impulse response estimator 18 of the receiver 4, and a second posterior probability P 0 (from the maximum likelihood sequence estimation type equalizer 30 of the receiver 6. 2, n), P1 (2, n), and the baseband signal from the delay unit 19 of the receiver 4 are input. The maximum likelihood sequence estimation type equalizer 204 performs the above-described metric calculation based on these input signals, detects a surviving path by the Viterbi algorithm, and also has a third posterior probability P0 (3, n), P1 (3, n) is derived. The maximum likelihood sequence estimation type equalizer 206 includes an impulse response estimation value from the impulse response estimator 18 of the receiver 6, and a third posterior probability P 0 (3, n) from the maximum likelihood sequence estimation type equalizer 204. , P1 (3, n), and the baseband signal from the delay unit 210 are input. The delay unit 210 inputs the baseband signal, the impulse response estimation value from the impulse response estimator 28, and the posterior probability from the maximum likelihood sequence estimation type equalizer 204, which are input to the maximum likelihood sequence estimation type equalizer 206. In order to match the timing, the baseband signal from the delay device 29 of the receiver 6 is delayed for a predetermined time.
[0056]
The maximum likelihood sequence estimation type equalizer 204 performs the above-described metric calculation based on these input signals, detects a surviving path by the Viterbi algorithm, and has a fourth posterior probability P0 (4, n), P1 (4, n) is derived.
[0057]
The maximum likelihood sequence estimation type equalizer 208 includes an impulse response estimation value from the impulse response estimator 18 of the receiver 6, and a fourth posterior probability P 0 (4, n) from the maximum likelihood sequence estimation type equalizer 206. , P1 (4, n), and the baseband signal from the delay unit 212 are input. The delay unit 212 inputs the baseband signal, the impulse response estimation value from the impulse response estimator 18, and the posterior probability from the maximum likelihood sequence estimation type equalizer 206, which are input to the maximum likelihood sequence estimation type equalizer 206. In order to match the timing, the baseband signal from the delay device 19 of the receiver 4 is delayed for a predetermined time.
[0058]
The maximum likelihood sequence estimation equalizer 208 performs the above-described metric calculation based on these input signals, detects a surviving path by the Viterbi algorithm, and has a fifth posterior probability P0 (5, n), P1 (5, n) is derived.
[0059]
The determination unit 8 compares the fifth posterior probabilities P0 (5, n) and P1 (5, n), and detects a state corresponding to the smaller value as data corresponding to the nth received symbol. .
[0060]
Further, the signal receiving apparatus may be configured by connecting three or more receivers. FIG. 7 is a block diagram illustrating a configuration example of a signal receiving apparatus in which receivers are connected in three stages. The signal receiving apparatus 302 shown in the figure includes a receiver 4, a receiver 6, and a receiver 304 that are connected in three stages, and a determination unit 8. The receiver 4 and the receiver 6 have the same configuration as the receiver 4 and the receiver 6 of the signal receiving apparatus 2 shown in FIG.
[0061]
The third-stage receiver 304 includes an antenna 312, a local signal generator 314, a multiplier 316, an impulse response estimator 318, and a maximum likelihood sequence estimation equalizer 320.
[0062]
The multiplier 316 multiplies the signal received by the antenna 312 by the reference frequency signal from the local signal generator 14 and converts the signal into a baseband signal. The impulse response estimator 318 derives an impulse response estimated value based on the baseband signal as described above. The delay unit 319 inputs the baseband signal, the impulse response estimation value from the impulse response estimator 318, and the maximum likelihood sequence estimation type equalizer 30 of the receiver 6 which are input to the maximum likelihood sequence estimation type equalizer 320. The baseband signal from the multiplier 316 is output after being delayed by a predetermined time in order to match the input timings of the posterior probabilities.
[0063]
The maximum likelihood sequence estimation type equalizer 320 includes a baseband signal from the delay unit 319, an impulse response estimation value from the impulse response estimator 318, and a second likelihood sequence from the maximum likelihood sequence estimation type equalizer 30 of the receiver 6. Based on the posterior probabilities P0 (2, n) and P1 (2, n), the above-mentioned metric calculation is performed to detect the surviving path by the Viterbi algorithm, and the third posterior probability P0 (3, n), P1 (3, n) is derived. The specific operation is the same as that of the maximum likelihood sequence estimation equalizer 30 in the receiver 6 of the signal receiving apparatus 2 shown in FIG. The determination unit 8 compares the third posterior probabilities P0 (3, n) and P1 (3, n), and detects a state corresponding to the smaller value as data corresponding to the nth received symbol. .
[0064]
The embodiment of the present invention has been described with reference to the drawings. However, the present invention is not limited to the matters shown in the above-described embodiments, and it is obvious that changes, improvements, etc. can be made based on the description of the scope of claims.
[0065]
【The invention's effect】
As described above, according to the present invention, it is possible to improve the accuracy of data detection, in other words, to improve reception performance by deriving and using the posterior probability.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration example of a signal receiving apparatus according to the present invention.
FIG. 2 is a diagram illustrating an example of a transmission frame.
FIG. 3 is a diagram illustrating an example of surviving path detection by a maximum likelihood sequence estimation type equalizer;
FIG. 4 is a diagram illustrating an example of derivation of posterior probabilities by a maximum likelihood sequence estimation type equalizer.
FIG. 5 is a block diagram showing a configuration example of a signal receiving apparatus to which a maximum likelihood sequence estimation type equalizer is further connected.
FIG. 6 is a block diagram illustrating a configuration example of a signal receiving apparatus to which a two-stage maximum likelihood sequence estimation type equalizer is further connected.
FIG. 7 is a block diagram illustrating a configuration example of a signal receiving apparatus in which receivers are connected in three stages.
FIG. 8 is a block diagram illustrating a configuration example of a conventional signal receiving apparatus.
[Explanation of symbols]
2 signal receiver
4, 6 Receiver
8 judgment part
12 Antenna
14 Local signal generator
16 multiplier
18 Impulse response estimator
19 Delay device
20 Maximum likelihood sequence estimation equalizer
22 Antenna
24 Local signal generator
26 multiplier
28 Impulse response estimator
29 Delay device
30 Maximum likelihood sequence estimation equalizer
102 Signal receiving apparatus
104 Maximum likelihood sequence estimation equalizer
202 Signal receiver
204, 206, 208 Maximum likelihood sequence estimation equalizer
210, 212 delay unit
302 signal receiving apparatus
304 receiver
312 antenna
314 Local signal generator
316 multiplier
318 Impulse response estimator
319 Delayer
320 Maximum likelihood sequence estimation equalizer

Claims

A signal receiving apparatus having first and second receivers that extract only a direct wave from a received signal, and a determination means,
The first receiver
First signal converting means for converting a received signal into a baseband signal;
First impulse response estimating means for deriving an impulse response estimated value based on a baseband signal from the first signal converting means;
Based on the baseband signal from the first signal conversion means and the impulse response estimation value from the first impulse response estimation means, metric calculation is performed, and a surviving path is detected by the Viterbi algorithm, and n -Under the condition that the state of the received symbol at the 1st timing is A, the posterior probability that the state of the received symbol at the nth timing is B, the branch metric for each branch, and the received symbol of the received symbol for that branch As the square value of the difference between the true value and the value of the received symbol including the noise of the baseband signal, the branch metric of the branch from A to B is calculated by the sum of the branch metric of the branch from A to the state of each received symbol. by calculating the dividing value, n-th First maximum likelihood sequence estimation type equalization means for deriving a first posterior probability corresponding to a received symbol;
With
The second receiver is
Second signal converting means for converting the received signal into a baseband signal;
Second impulse response estimating means for deriving an impulse response estimated value based on the baseband signal from the second signal converting means;
First delay means for delaying a baseband signal from the second signal conversion means;
A baseband signal from the second signal conversion means guided through the first delay means, an impulse response estimation value from the second impulse response estimation means, the first maximum likelihood sequence estimation type, etc. On the condition that the metric calculation is performed based on the first posterior probability from the converting means, the surviving path is detected by the Viterbi algorithm, and the state of the received symbol at the (n-1) th timing is A. The posterior probability that the state of the received symbol at the second timing is B, the branch metric for each branch, the true value of the received symbol for that branch and the noise of the baseband signal derived through the first delay means. As a value obtained by multiplying the square value of the difference from the value of the received symbol including the first posterior probability, from A to B Lunch branch metric by calculating the value obtained by dividing by the sum of the branch metrics of the branches of the status of each received symbol from A, the second deriving a second posterior probability corresponding to the n-th received symbol Maximum likelihood sequence estimation type equalization means;
With
The determination means compares the second post probabilities from the second maximum likelihood sequence estimation equalization means, the state corresponding to the smaller value, detected as data corresponding to the n-th received symbol signal receiving apparatus, characterized by.

Second delay means for delaying a baseband signal from the first signal conversion means;
A baseband signal from the first signal conversion means guided through the second delay means, an impulse response estimation value from the first impulse response estimation means, a second maximum likelihood sequence estimation type, etc. On the condition that the metric calculation is performed based on the second posterior probability from the converting means, the surviving path is detected by the Viterbi algorithm, and the state of the received symbol at the (n-1) th timing is A. th posterior probability that the state of the received symbol is B in timing, the branch metric for each branch, the noise of the baseband signal derived via the true value and the second delay means of the received symbol for that branch a second calculation value squared a posteriori probability to the square value of the difference between the value of the received symbol, including, from a to B Lunch branch metric by calculating the value obtained by dividing by the sum of the branch metrics of the branches of the status of each received symbol from A, the third of deriving a third a posteriori probability corresponding to the n-th received symbol Maximum likelihood sequence estimation type equalization means;
Further comprising
The determination means compares the third post-probability from the third MLSE equalization means, the state corresponding to the smaller value, detected as data corresponding to the n-th received symbol signal receiving apparatus according to claim 1, characterized in that.

Maximum likelihood sequence estimation type equalization means connected in multiple stages;
Corresponding to each stage of the maximum likelihood sequence estimation type equalization means connected to the plurality of stages, the even number delay means for delaying the baseband signal from the second delay means, and the first delay means An odd number of stages of delay means for delaying the baseband signal from
Further comprising
The odd-numbered (m: m = 3, 5,...) Maximum likelihood sequence estimation type equalizing means provides the first signal conversion guided via the corresponding (m−1) delay means. Baseband signal from the means, impulse response estimation value from the first impulse response estimation means, and (m−) th (m−1) maximum likelihood sequence estimation type equalization means from the even-numbered stage in the previous stage. Based on the posterior probability of 1), the metric calculation is performed, the surviving path is detected by the Viterbi algorithm, and the condition of the received symbol at the (n-1) th timing is A. the posterior probability that the state of the received symbol is B, and the branch metric for each branch is guided via the delay means of the true value of the received symbol and the (m-1) th for that branch As a value obtained by multiplying the posterior probability of the (m-1) to the square value of the difference between the value of the received symbol including noise of the baseband signal, the branch metric of the branch to get from A to B, or each received symbol from A by calculating the branch branch metric to the state of the value obtained by dividing the sum of, and derive the posterior probability of the (m) corresponding to the n-th received symbol,
The even-numbered (m + 1) th maximum likelihood sequence estimation type equalization means includes a baseband signal from the second signal conversion means derived from the corresponding (m) delay means, and the second impulse response. Based on the impulse response estimation value from the estimation means and the (m) maximum likelihood sequence estimation type equalization means of the odd numbered stage in the previous stage, the metric calculation is performed, and the Viterbi algorithm is used. The detection of the surviving path is performed, and the posterior probability that the state of the received symbol at the nth timing is B under the condition that the state of the received symbol at the (n−1) th timing is A is set as the branch for each branch. the metric, receiving a noisy baseband signals derived via the delay means of the true value of the received symbol and the (m) for that branch As a value obtained by multiplying the posterior probability of the (m) to the square value of the difference between the value of the symbol, a branch branch metric to get from A to B, or the sum of the branch metrics of the branches of the status of each received symbol from A To derive the (m + 1) th posterior probability corresponding to the nth received symbol by calculating by the value divided by
Said determination means, a state of comparing the posterior probability of the from MLSE equalization means in the final stage of the (m) or the (m + 1), corresponding to the smaller value, n-th received symbol The signal receiving device according to claim 2, wherein the signal receiving device is detected as data corresponding to.

A third receiver, the third receiver comprising:
Third signal converting means for converting the received signal into a baseband signal;
Third impulse response estimation means for deriving an impulse response estimation value based on the baseband signal from the third signal conversion means;
Third delay means for delaying a baseband signal from the third signal conversion means;
A baseband signal from the third signal converting means guided through the third delay means, an impulse response estimated value from the third impulse response estimating means, and a second in the second receiver Based on the second posterior probability from the maximum likelihood sequence estimation type equalization means, the metric calculation is performed, the surviving path is detected by the Viterbi algorithm, and the state of the received symbol at the (n-1) th timing is A. under the condition that the posterior probability that the state of the received symbol in the n-th timing is B, and the branch metric for each branch is guided via the true value and the third delay means received symbols for that branch A value obtained by multiplying the square value of the difference from the received symbol value including the noise of the baseband signal by the second posterior probability. To the branch metric of the branch to get from A to B, or by calculating the value obtained by dividing by the sum of the branch metrics of the branches into the status of each received symbol from A, the third corresponding to the n-th received symbol A third maximum likelihood sequence estimation type equalization means for deriving a posteriori probability;
With
The determination means compares the third post-probability from the third MLSE equalization means, the state corresponding to the smaller value, detected as data corresponding to the n-th received symbol signal receiving apparatus according to claim 1, characterized in that.