JP2004235916A - Ofdm signal receiver, ofdm signal transmitter receiver, and ofdm signal receiving method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve an error rate characteristic in an OFDM receiver using a combination of MIMO (multiple-input/multiple-output) and OFDM (orthogonal frequency division multiplexing). <P>SOLUTION: Each reception signal of an N system obtained by spatially multiplexing OFDM signals of the N system is subjected to multiplication type interference cancel by multiplication of a transmission coefficient inverse matrix, and subtraction type interference cancel by subtraction of a replica of mutual interference components. An error quantity is detected for a demodulated signal after the multiplication type and subtraction type interference cancel, and a demodulation signal having less error for each system from a demodulation signal of the N system after the multiplication type interference cancel and a demodulation signal of the N system after the subtraction type interference cancel. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００１１】
ただし、（１）式におけるｈ^ｉ _ｊ，ｋは、ｊ番目の送信アンテナとｋ番目の受信アンテナとの間のサブキャリアｉに対する伝達係数である。ｋ番目の受信アンテナのサブキャリアｉに対して付加される熱雑音をｎ^ｉ _ｋとして、サブキャリアｉに対するＮ個の熱雑音をベクトルｎ^ｉ＝（ｎ^ｉ _１ ｎ^ｉ _２・・・ｎ^ｉ _Ｎ）で表すと、送信信号と受信信号との関係は以下の（２）式で表される。
【００１２】
【数２】

【００１３】
伝達係数行列Ｈ^ｉの逆行列である伝達係数逆行列（Ｈ^ｉ）^−１が伝達係数行列演算器９−３によって誤差なく推定された場合、乗算型干渉キャンセラ９−４においてサブキャリアｉのＮ系統の受信信号ｒ^ｉに伝達係数逆行列（Ｈ^ｉ）^−１を乗算した結果である乗算型干渉キャンセラ出力信号ｕ^ｉ（＝（ｕ^ｉ _１ ｕ^ｉ _２・・・ｕ^ｉ _Ｎ））は、以下の（３）式で表される。ここで、ｕ^ｉ _ｋはｋ番目の送信アンテナのサブキャリアｉによって送信される信号ｔ^ｉ _ｋに対応する乗算型干渉キャンセル後の信号である。
【００１４】
【数３】

【００１５】
例えばＮ＝２の場合、乗算型干渉キャンセラ出力信号ｕ^ｉは、以下の（数４）で表される。
【００１６】
【数４】

【００１７】
乗算型干渉キャンセルが行われた後の信号は通信路の逆特性が乗算され正規化されているため、送信信号の系統間およびサブキャリア間の振幅の信頼度が失われている。したがって、この信号を用いて誤り訂正復号を行うと、信号の尤度に基づく判定が行えないため、良好な誤り率特性を得ることができない。そこで、重み付け器９−５−１〜９−５−Ｎにおいて、相互干渉成分がキャンセルされた乗算型干渉キャンセラ出力信号に対し、非特許文献１に記載された方法を用いて伝達係数に基づく重み付けを行う。重み付け後の乗算型干渉キャンセラ出力信号ｕ´^ｉおよび重み付けを与える行列Ｙ^ｉは、それぞれ（５）式および（６）式で表される。
【００１８】
【数５】

【００１９】
【数６】

【００２０】
ここで、（６）式において、Ｃは全サブキャリア共通の定数であり、ｈ´^ｉ _ｊ，ｋは伝達係数逆行列（Ｈ^ｉ）^−１のｋ行ｊ列（１≦ｋ≦Ｎ，１≦ｊ≦Ｎ）の要素である。
【００２１】
乗算型干渉キャンセル後の信号対雑音電力比の平均値すなわち平均ＳＮＲ（Ｓｉｇｎａｌ ｔｏ Ｎｏｉｓｅ ｐｏｗｅｒ Ｒａｔｉｏ）について、Ｎ＝２の場合を例にとって説明する。４つの伝達係数ｈ^ｉ _ｍ，ｎ（ｍ＝１，２，ｎ＝１，２）は、それぞれ統計的に独立であり、その位相は一様分布しており、その振幅はレイリー分布で平均値が｜ｈ｜とする。また、２つの加法性ガウス雑音（ＡＷＧＮ：Ａｄｄｉｔｉｖｅ Ｗｈｉｔｅ Ｇａｕｓｓｉａｎ Ｎｏｉｓｅ）成分ｎ^ｉ _１、ｎ^ｉ _２は、それぞれ統計的に独立であり、σ_ｖ ^２を分散値とする複素ガウス分布に従うものとする。この条件下において、乗算型サブキャリア干渉キャンセラ出力信号ｕ^ｉ _１の平均ＳＮＲは以下の式で表される。
【００２２】
【数７】

【００２３】
乗算型干渉キャンセラ出力信号ｕ^ｉ _２の平均ＳＮＲも同様の計算により下式で表される。
【００２４】
【数８】

【００２５】
一方、送信アンテナと受信アンテナを１ずつ使用するＯＦＤＭ送受信装置について考察すると、ｉ番目のサブキャリアの高速フーリエ変換後の受信信号ｒ^ｉは、逆高速フーリエ変換前の送信信号ｔ^ｉ、送信アンテナと受信アンテナとの間の伝達係数ｈ^ｉ、およびＡＷＧＮ成分ｎ^ｉを用いて次式で表される。
【００２６】
【数９】

【００２７】
このとき、高速フーリエ変換後の受信信号ｒ^ｉの平均ＳＮＲは次式で表される。
【００２８】
【数１０】

【００２９】
数式７（または数式８）と数式１０とから、アンテナあたりの平均送信電力（｜ｔ^ｉ _１｜^２に相当）が同一であれば、送受信アンテナが１本ずつの場合と２本ずつの場合とを比較すると、受信信号の平均ＳＮＲは同じであることが分かる。すなわち、伝達係数逆行列を用いた乗算型干渉キャンセルでは、送信信号を２本の受信アンテナで受信しているのにもかかわらず、ダイバーシチによる利得が得られないことが分かる。
【００３０】
そこで、ダイバーシチによる利得を得るために、特願２００２−１４９０１３に記載のＯＦＤＭ信号送受信装置では、乗算型干渉キャンセラ出力信号から送信信号のレプリカを生成し、当該レプリカを用いて系統間の相互干渉成分のレプリカを生成し、受信信号から当該レプリカを減算することによって高速フーリエ変換後の各受信信号を送信信号の各系統に対応する成分に分離し、当該各成分に対して伝達係数に基づく重み付けを行った後、送信信号の各系統に対応する成分同士を合成することとしている。
【００３１】
以下、図１１を参照して上記の減算型干渉キャンセルおよび重み付け合成について説明する。図１１において、サブキャリア再変調器９−７−１〜９−７−Ｎでは、送信側のサブキャリア変調器８−３−１〜８−３−Ｎと同一の変調方式により、第１の復調器９−６−１〜９−６−Ｎが出力する第１の復調信号を再変調する。減算型干渉キャンセラ９−９は、サブキャリア再変調器９−７−１〜９−７−Ｎの出力信号と伝達係数行列演算器９−３が出力するサブキャリア毎の伝達係数行列とを用いて、高速フーリエ変換後の受信信号に含まれる相互干渉成分を除去し、高速フーリエ変換後の各受信信号を送信信号の各系統に対応する信号成分に分離する。なお、減算型干渉キャンセラ９−９に入力される高速フーリエ変換後の受信信号は、Ｎ個の高速フーリエ変換器９−２−１〜９−２−Ｎの出力信号が受信信号遅延器９−８−１〜９−８−Ｎによって遅延させられたものである。ここで、受信信号遅延器９−８−１〜９−８−Ｎは、乗算型干渉キャンセラ９−４からサブキャリア再変調器９−７−１〜９−７−Ｎまでの処理時間に相当する遅延を発生させる。重み付け合成器９−１０は、減算型干渉キャンセラ９−９によって分離された信号成分を重み付け合成する。第２の復調器９−１１−１〜９−１１−Ｎは、重み付け合成器９−１０の出力信号を復調し、最終的なＮ系統の復調信号を出力する。
【００３２】
図１２は、上記の減算型干渉キャンセラ９−９および重み付け合成器９−１０の構成を示すブロック図である。ｉ番目のサブキャリアに着目すると、図１２の減算型干渉キャンセラ９−９おいて、受信信号行列演算器９−９−１は、受信信号遅延器９−８−１〜９−８−Ｎが出力する高速フーリエ変換後の受信信号から、受信信号行列Ｒ^ｉ
【００３３】
【数１１】

【００３４】
を計算する。
再変調信号行列演算器９−９−２は、サブキャリア再変調器９−７−１〜９−７−Ｎの出力信号から、再変調信号行列Ｔ´^ｉ
【００３５】
【数１２】

【００３６】
を計算する。レプリカ信号行列演算器９−９−３は、再変調信号行列演算器９−９−２が出力する再変調信号行列Ｔ´^ｉと伝達係数行列演算器９−３が出力する伝達係数行列Ｈ^ｉとからレプリカ信号行列（Ｔ´^ｉ・Ｈ^ｉ）を演算する。レプリカ減算器９−９−４は、以下の（１３）式に示されるとおり、受信信号行列演算器９−９−１が出力する受信信号行列Ｒ^ｉからレプリカ信号行列演算器が出力するレプリカ信号行列（Ｔ´^ｉ・Ｈ^ｉ）を減算して、レプリカ減算後信号行列Ｘ^ｉを計算する。
【００３７】
【数１３】

【００３８】
レプリカ減算後信号行列Ｘ^ｉは、減算型干渉キャンセラ９−９の出力として重み付け合成器９−１０に入力される。
重み付け合成器９−１０において、レプリカ減算後信号行列Ｘ^ｉに対して重み付けを行うために、レプリカ減算後重み付け行列演算器９−１０−１において、伝達係数行列演算器９−３が出力する伝達係数行列Ｈ^ｉからレプリカ減算後重み付け行列Ｗ^ｉを計算する。重み付け合成演算器９−１０−２では、レプリカ減算後重み付け行列演算器９−１０−１が出力するレプリカ減算後重み付け行列Ｗ^ｉと減算型干渉キャンセラ９−９の出力であるレプリカ減算後信号行列Ｘ^ｉとから重み付け合成後信号ｖ^ｉを算出する。ここで、行ベクトルｘ^ｉ _ｊ（１≦ｊ≦Ｎ）および列ベクトルｗ^ｉ _ｋ ^Ｔ（１≦ｋ≦Ｎ）を用いて、レプリカ減算後信号行列Ｘ^ｉおよびレプリカ減算後重み付け行列Ｗ^ｉをそれぞれ以下の式
【００３９】
【数１４】

【００４０】
で表すとき、重み付け合成後信号ｖ^ｉは以下の式で表される。
【００４１】
【数１５】

【００４２】
ただし、行ベクトルｘ^ｉ _ｊは（１１）式〜（１３）式より以下の式で得られる。
【００４３】
【数１６】

【００４４】
ここで、
【００４５】
【数１７】

【００４６】
である。従って、（ｘ^ｉ _ｊ，ｗ^ｉ _ｊ）は以下の式で表される。
【００４７】
【数１８】

【００４８】
重み付け合成後信号ｖ^ｉは、（１６）式および（１８）式を用いて、以下の式で表される。
【００４９】
【数１９】

【００５０】
ここで、行列Ｇ^ｉは、行列（Ｈ^ｉ・Ｗ^ｉ）とすべての対角成分が同一であって、すべての非対角成分が０である行列である。
以下、減算型干渉キャンセラ９−９による干渉キャンセル効果と重み付け合成器９−１０の出力信号である重み付け合成後信号ｖ^ｉの平均ＳＮＲについて考察する。（１９）式におけるレプリカ減算後重み付け行列Ｗ^ｉを
【００５１】
【数２０】

【００５２】
とすると、行列Ｇ^ｉは以下のように表される。
【００５３】
【数２１】

【００５４】
ここで、サブキャリア再変調器９−７−１〜９−７−Ｎによる再変調後の信号ｔ´^ｉが逆高速フーリエ変換前の送信信号ｔ^ｉと完全に一致すると仮定すると、（１９）式は以下のように表される。
【００５５】
【数２２】

【００５６】
ここで、ｎ^ｉ（＝（ｎ^ｉ _１ ｎ^ｉ _２・・・ｎ^ｉ _Ｎ））は、高速フーリエ変換後の受信信号ｒ^ｉに含まれるＡＷＧＮ成分である。（２２）式より、重み付け合成後信号ｖ^ｉにおいては相互干渉成分が除去されていることが分かる。
【００５７】
ここで、（Ｎ×Ｎ）個の伝達係数ｈ^ｉ _ｍ，ｎ（１≦ｍ≦Ｎ、１≦ｎ≦Ｎ）は、それぞれ統計的に独立であり、その位相は一様分布しており、その振幅はレイリー分布で平均値が｜ｈ｜とする。また、Ｎ個のＡＷＧＮ成分ｎ^ｉ _ｋ（１≦ｋ≦Ｎ）は、それぞれ統計的に独立であり、σ_ｖ ^２を分散値とする複素ガウス分布をとるものとする。この条件下において、重み付け合成後信号ｖ^ｉ _ｋの平均ＳＮＲは次式で表される。
【００５８】
【数２３】

【００５９】
上式より、重み付け合成後信号ｖ^ｉ _ｋの平均ＳＮＲがとりうる最大の値になるためには、
【００６０】
【数２４】

【００６１】
となることが必要である。これは、
【００６２】
【数２５】

【００６３】
であることを意味する。行列（Ｈ^ｉ）^＊Ｔは行列Ｈ^ｉの共役転置行列である。このとき（２３）式は以下のように表される。
【００６４】
【数２６】

【００６５】
上記（２６）式と（８）式とを比較すると、レプリカ減算後重み付け行列Ｗ^ｉとして行列（Ｈ^ｉ）^＊Ｔを用いれば、送信信号が同一の条件下で、重み付け合成後信号ｖ^ｉ _ｋの平均ＳＮＲは、送信アンテナと受信アンテナとがともに１つであるＯＦＤＭ信号送受信装置における高速フーリエ変換後の受信信号の平均ＳＮＲのＮ倍であることが分かる。すなわち、図１１のＯＦＤＭ信号送受信装置では、送信アンテナと受信アンテナとがともに１つであるＯＦＤＭ信号送受信装置に対して、平均ＳＮＲで比較して（１０・ｌｏｇＮ）ｄＢの利得を得ることができる。
【００６６】
【非特許文献１】
黒崎他、「ＭＩＭＯチャネルにより１００Ｍｂｉｔ／ｓを実現する広帯域移動通信用ＳＤＭ−ＣＯＦＤＭ方式の提案」、信学技報、ＲＣＳ２００１−１３５
【００６７】
【発明が解決しようとする課題】
上記の従来のＯＦＤＭ信号送受信装置では、乗算型干渉キャンセル後の復調信号を再変調し、送信信号のレプリカを生成してそれを高速フーリエ変換後の受信信号から減算することにより各受信信号を送信信号の各系統に対応する信号成分に分離し、次に所望信号成分同士を重み付け合成してダイバーシチ利得を得ている。この場合、送信信号のレプリカが誤りなく減算型干渉キャンセラに供給されたと仮定すれば、アンテナ数と同数倍だけ平均ＳＮＲを増大させることができる。しかし、実際には、送信信号のレプリカは、高速フーリエ変換後の受信信号に伝達係数逆行列を乗算することによって干渉キャンセルされた信号が復調されたものであるため、送信信号のレプリカに誤りが含まれることは避けられない。すなわち（１２）式で表される再変調信号行列Ｔ´^ｉの成分の一部に誤りが含まれる。
【００６８】
以下、再変調信号行列Ｔ´^ｉに誤りが含まれる場合の計算機シミュレーションによる特性評価を示す。このシミュレーションでは、アンテナ数は送受各２本であり、復調後に誤り訂正復号を行うこととしている。シミュレーション諸元は以下の表１に示されるとおりである。
【００６９】
【表１】

図１３は、シミュレーションの結果得られたパケット誤り率（ＰＥＲ：Ｐａｃｋｅｔ Ｅｒｒｏｒ Ｒａｔｅ）特性を示す図である。図１３において、破線は乗算型干渉キャンセラのみを用いた場合のＰＥＲ特性を示し、実線はさらに減算型干渉キャンセラを追加した場合のＰＥＲ特性を示す。また、○印で表される特性は、変調方式が６４ＱＡＭであって符号化率がＲ＝３／４の場合のものであり、△印で表される特性は、変調方式がＱＰＳＫであって符号化率がＲ＝１／２の場合のものである。図１３より、６４ＱＡＭ、Ｒ＝３／４の場合、減算型干渉キャンセラを用いた方が常に良好な特性を得ることができるが、その特性改善効果は１ｄＢ程度であることが分かる。この効果は、送信信号のレプリカが完全に正しく生成された場合の平均搬送波対雑音電力比（ＣＮＲ：ｃａｒｒｉｅｒ ｔｏ ｎｏｉｓｅ ｒａｉｏ）の増加量３ｄＢに比べて非常に小さい。また、ＱＰＳＫ、Ｒ＝１／２の場合、減算型干渉キャンセラを追加すると誤り率特性が逆に劣化してしまう。これは、誤ったレプリカを用いて減算型干渉キャンセルを行うからである。また、ＣＮＲが低いため、伝達係数の推定精度が低くなり、その結果、伝達係数を用いて算出されるレプリカ減算後重み付け行列Ｗ^ｉの推定精度が、ＣＮＲが高い６４ＱＡＭ、Ｒ＝３／４の場合よりも低くなるためである。
【００７０】
以上より、乗算型干渉キャンセル後さらに減算型干渉キャンセルおよび重み付け合成を行っても、常に乗算型干渉キャンセルのみの場合よりも良好な誤り率特性が得られるとは限らない。また、減算型干渉キャンセルの効果が得られる場合であっても、得られる特性改善効果は小さい。
【００７１】
本発明は上記事情に鑑みなされたものであり、その目的は、誤り率特性の向上を図ることができるＯＦＤＭ信号受信装置、ＯＦＤＭ信号送受信装置、およびＯＦＤＭ信号受信方法を提供することである。
【００７２】
【課題を解決するための手段】
上記した課題を解決し、目的を達成するための第１の発明は、各々誤り検出符号および既知のパイロット信号を含み、Ｎ本（Ｎは２以上の整数）の送信アンテナから同一周波数で送信されるＮ系統のＯＦＤＭ信号を受信するＯＦＤＭ信号受信装置であって、前記Ｎ系統のＯＦＤＭ信号が空間多重された信号を受信するＮ本の受信アンテナと、当該Ｎ本の受信アンテナで受信されたＮ系統の各受信信号を高速フーリエ変換してサブキャリア毎の受信信号に変換する高速フーリエ変換手段と、当該高速フーリエ変換後のＮ系統の受信信号に含まれるパイロット信号と前記既知のパイロット信号とを用いて、サブキャリア毎に、各送信アンテナと各受信アンテナとの間の伝達係数を要素とする伝達係数行列およびその逆行列である伝達係数逆行列を算出する伝達係数行列演算手段と、サブキャリア毎に、前記高速フーリエ変換後のＮ系統の受信信号に対して前記伝達係数逆行列を乗算し、前記高速フーリエ変換後のＮ系統の受信信号に含まれる系統間の相互干渉成分をキャンセルする乗算型干渉キャンセル手段と、当該乗算型干渉キャンセル手段のＮ系統の出力信号それぞれに対して、サブキャリア毎に、前記伝達係数に応じて重み付けする重み付け手段と、当該重み付け手段のＮ系統の出力信号それぞれを復調してＮ系統の第１の復調信号を出力する第１の復調手段と、当該Ｎ系統の第１の復調信号それぞれに対して送信時と同一のサブキャリア変調を行うサブキャリア再変調手段と、当該サブキャリア再変調手段のＮ系統の出力信号と前記伝達係数行列とを用いて、サブキャリア毎に、系統間の相互干渉成分のレプリカを生成し、当該レプリカを前記高速フーリエ変換後のＮ系統の受信信号から減算することによって当該各受信信号に含まれる系統間の相互干渉成分をキャンセルし、当該各受信信号を前記ＯＦＤＭ信号の各系統に対応する信号成分に分離する減算型干渉キャンセル手段と、当該減算型干渉キャンセル手段により分離された信号成分に対して、サブキャリア毎に、前記伝達係数に基づく重み付けを行い、前記ＯＦＤＭ信号の各系統に対応する信号成分同士を合成する重み付け合成手段と、当該重み付け合成手段のＮ系統の出力信号それぞれを復調してＮ系統の第２の復調信号を出力する第２の復調手段と、前記誤り検出符号を用いて前記Ｎ系統の第１および第２の復調信号それぞれの誤り量を検出する誤り検出手段と、当該誤り検出手段の検出結果に基づいて、前記Ｎ系統の第１および第２の復調信号のうち誤りの少ない復調信号を系統毎に選択する復調信号選択手段とを有することを特徴とする。
【００７３】
また、第２の発明は、各々誤り訂正符号化され、誤り検出符号および既知のパイロット信号を含み、Ｎ本（Ｎは２以上の整数）の送信アンテナから同一周波数で送信されるＮ系統のＯＦＤＭ信号を受信するＯＦＤＭ信号受信装置であって、前記Ｎ系統のＯＦＤＭ信号が空間多重された信号を受信するＮ本の受信アンテナと、当該Ｎ本の受信アンテナで受信されたＮ系統の各受信信号を高速フーリエ変換してサブキャリア毎の受信信号に変換する高速フーリエ変換手段と、当該高速フーリエ変換後のＮ系統の受信信号に含まれるパイロット信号と前記既知のパイロット信号とを用いて、サブキャリア毎に、各送信アンテナと各受信アンテナとの間の伝達係数を要素とする伝達係数行列およびその逆行列である伝達係数逆行列を算出する伝達係数行列演算手段と、サブキャリア毎に、前記高速フーリエ変換後のＮ系統の受信信号に対して前記伝達係数逆行列を乗算し、前記高速フーリエ変換後のＮ系統の受信信号に含まれる系統間の相互干渉成分をキャンセルする乗算型干渉キャンセル手段と、当該乗算型干渉キャンセル手段のＮ系統の出力信号それぞれに対して、サブキャリア毎に、前記伝達係数に応じて重み付けする重み付け手段と、当該重み付け手段のＮ系統の出力信号それぞれを復調する第１の復調手段と、当該第１の復調手段のＮ系統の出力信号それぞれに対し、誤り訂正復号を行いＮ系統の復号信号を出力する第１の復号手段と、当該Ｎ系統の復号信号それぞれについて前記誤り検出符号を用いて誤りの位置を検出する誤り検出手段と、当該誤り検出手段の検出結果を参照してＮ系統すべて正しく復号されたサブキャリアを選択し、当該サブキャリアに対応する復号信号について送信時と同一のサブキャリア変調を行う選択型再変調手段と、当該選択型再変調手段のＮ系統の出力信号と前記伝達係数行列とを用いて、選択されたサブキャリア毎に、系統間の相互干渉成分のレプリカを生成し、当該レプリカを前記高速フーリエ変換後のＮ系統の受信信号から減算することによって当該各受信信号に含まれる系統間の相互干渉成分をキャンセルし、当該各受信信号を前記ＯＦＤＭ信号の各系統に対応する信号成分に分離する減算型干渉キャンセル手段と、当該減算型干渉キャンセル手段により分離された信号成分に対して、選択されたサブキャリア毎に、前記伝達係数に基づく重み付けを行い、前記ＯＦＤＭ信号の各系統に対応する信号成分同士を合成する重み付け合成手段と、当該重み付け合成手段のＮ系統の出力信号と前記選択型再変調手段に選択されなかったサブキャリアについての前記重み付け手段のＮ系統の出力信号とを合成して復調する第２の復調手段と、当該第２の復調手段のＮ系統の出力信号それぞれに対し、誤り訂正復号を行う第２の復号手段と、を有することを特徴とする。
【００７４】
また、第３の発明は、各々誤り検出符号および既知のパイロット信号を含み、Ｎ本（Ｎは２以上の整数）の送信アンテナから同一周波数で送信されるＮ系統のＯＦＤＭ信号を受信するＯＦＤＭ信号受信装置であって、前記Ｎ系統のＯＦＤＭ信号が空間多重された信号を受信するＮ本の受信アンテナと、当該Ｎ本の受信アンテナで受信されたＮ系統の各受信信号を高速フーリエ変換してサブキャリア毎の受信信号に変換する高速フーリエ変換手段と、当該高速フーリエ変換後のＮ系統の受信信号に含まれるパイロット信号と前記既知のパイロット信号とを用いて、サブキャリア毎に、各送信アンテナと各受信アンテナとの間の伝達係数を要素とする伝達係数行列およびその逆行列である伝達係数逆行列を算出する伝達係数行列演算手段と、サブキャリア毎に、前記高速フーリエ変換後のＮ系統の受信信号に対して前記伝達係数逆行列を乗算し、前記高速フーリエ変換後のＮ系統の受信信号に含まれる系統間の相互干渉成分をキャンセルする乗算型干渉キャンセル手段と、当該乗算型干渉キャンセル手段のＮ系統の出力信号それぞれに対して、サブキャリア毎に、前記伝達係数に応じて重み付けする重み付け手段と、当該重み付け手段のＮ系統の出力信号それぞれを復調してＮ系統の第１の復調信号を出力する第１の復調手段と、当該Ｎ系統の第１の復調信号をもとに繰り返し減算型干渉キャンセルを行い複数のＮ系統の第２の復調信号を出力する減算型干渉キャンセル反復手段と、前記誤り検出符号を用いて前記Ｎ系統の第１の復調信号および複数のＮ系統の第２の復調信号それぞれの誤り量を検出する誤り検出手段と、当該誤り検出手段の検出結果に基づいて、前記Ｎ系統の第１の復調信号および複数のＮ系統の第２の復調信号の中から、最も誤りの少ない復調信号を系統毎に選択する復調信号選択手段とを有し、前記減算型干渉キャンセル反復手段は、前記Ｎ系統の復調信号それぞれに対して送信時と同一のサブキャリア変調を行うサブキャリア再変調手段と、当該サブキャリア再変調手段のＮ系統の出力信号と前記伝達係数行列とを用いて、サブキャリア毎に、系統間の相互干渉成分のレプリカを生成し、当該レプリカを前記高速フーリエ変換後のＮ系統の受信信号から減算することによって当該各受信信号に含まれる系統間の相互干渉成分をキャンセルし、当該各受信信号を前記ＯＦＤＭ信号の各系統に対応する信号成分に分離する減算型干渉キャンセル手段と、当該減算型干渉キャンセル手段により分離された信号成分に対して、サブキャリア毎に、前記伝達係数に基づく重み付けを行い、前記ＯＦＤＭ信号の各系統に対応する信号成分同士を合成する重み付け合成手段と、当該重み付け合成手段のＮ系統の出力信号それぞれを復調してＮ系統の第２の復調信号を出力する第２の復調手段と、を複数段備え、第１段目の前記サブキャリア再変調手段は前記Ｎ系統の第１の復調信号を変調し、第２段目以降の前記サブキャリア再変調手段はそれぞれ前段の前記Ｎ系統の第２の復調信号を変調することを特徴とする。
【００７５】
また、第４の発明は、各々誤り訂正符号化され、誤り検出符号および既知のパイロット信号を含み、Ｎ本（Ｎは２以上の整数）の送信アンテナから同一周波数で送信されるＮ系統のＯＦＤＭ信号を受信するＯＦＤＭ信号受信装置であって、前記Ｎ系統のＯＦＤＭ信号が空間多重された信号を受信するＮ本の受信アンテナと、当該Ｎ本の受信アンテナで受信されたＮ系統の各受信信号を高速フーリエ変換してサブキャリア毎の受信信号に変換する高速フーリエ変換手段と、当該高速フーリエ変換後のＮ系統の受信信号に含まれるパイロット信号と前記既知のパイロット信号とを用いて、サブキャリア毎に、各送信アンテナと各受信アンテナとの間の伝達係数を要素とする伝達係数行列およびその逆行列である伝達係数逆行列を算出する伝達係数行列演算手段と、サブキャリア毎に、前記高速フーリエ変換後のＮ系統の受信信号に対して前記伝達係数逆行列を乗算し、前記高速フーリエ変換後のＮ系統の受信信号に含まれる系統間の相互干渉成分をキャンセルする乗算型干渉キャンセル手段と、当該乗算型干渉キャンセル手段のＮ系統の出力信号それぞれに対して、サブキャリア毎に、前記伝達係数に応じて重み付けする重み付け手段と、当該重み付け手段のＮ系統の出力信号それぞれを復調する第１の復調手段と、当該第１の復調手段のＮ系統の出力信号それぞれに対し、誤り訂正復号を行いＮ系統の第１の復号信号を出力する第１の復号手段と、当該Ｎ系統の第１の復号信号を用いて繰り返し減算型干渉キャンセルを行いＮ系統の最終復号信号を出力する減算型干渉キャンセル反復手段とを有し、当該減算型干渉キャンセル反復手段は、Ｎ系統の復号信号それぞれについて前記誤り検出符号を用いて誤りの位置を検出する誤り検出手段と、当該誤り検出手段の検出結果を参照してＮ系統すべて正しく復号されたサブキャリアを選択し、当該サブキャリアに対応する復号信号について送信時と同一のサブキャリア変調を行う選択型再変調手段と、当該選択型再変調手段のＮ系統の出力信号と前記伝達係数行列とを用いて、選択されたサブキャリア毎に、系統間の相互干渉成分のレプリカを生成し、当該レプリカを前記高速フーリエ変換後のＮ系統の受信信号から減算することによって当該各受信信号に含まれる系統間の相互干渉成分をキャンセルし、当該各受信信号を前記ＯＦＤＭ信号の各系統に対応する信号成分に分離する減算型干渉キャンセル手段と、当該減算型干渉キャンセル手段により分離された信号成分に対して、選択されたサブキャリア毎に、前記伝達係数に基づく重み付けを行い、前記ＯＦＤＭ信号の各系統に対応する信号成分同士を合成する重み付け合成手段と、当該重み付け合成手段のＮ系統の出力信号と前記選択型再変調手段に選択されなかったサブキャリアについての前記重み付け手段のＮ系統の出力信号とを合成して復調する第２の復調手段と、当該第２の復調手段のＮ系統の出力信号それぞれに対し、誤り訂正復号を行いＮ系統の第２の復号信号を出力する第２の復号手段と、を複数段備え、第１段目の前記誤り検出手段は前記Ｎ系統の第１の復号信号の誤り検出を行い、第２段目以降の前記誤り検出手段はそれぞれ前段の前記Ｎ系統の第２の復号信号の誤り検出を行い、最終段の前記第２の復号手段は前記第２の復号信号を前記最終復号信号として出力することを特徴とする。
【００７６】
また、第５の発明は、ＯＦＤＭ信号送信装置とＯＦＤＭ信号受信装置とを備えるＯＦＤＭ信号送受信装置であって、前記ＯＦＤＭ信号送信装置は、入力されたＮ系統（Ｎは２以上の整数）の送信情報信号のそれぞれに対して誤り検出符号を付加する誤り検出符号付加手段と、前記Ｎ系統の送信情報信号のそれぞれに対してパイロット信号を付加するパイロット信号付加手段と、前記誤り検出符号およびパイロット信号が付加されたＮ系統の送信情報信号それぞれに対してサブキャリア変調を行うサブキャリア変調手段と、当該サブキャリア変調手段のＮ系統の出力信号それぞれに対して逆高速フーリエ変換を行う逆高速フーリエ変換手段と、当該逆高速フーリエ変換手段が出力するＮ系統のＯＦＤＭ信号を同一周波数で送信するＮ本の送信アンテナとを有し、前記ＯＦＤＭ信号受信装置は、前記Ｎ系統のＯＦＤＭ信号が空間多重された信号を受信するＮ本の受信アンテナと、当該Ｎ本の受信アンテナで受信されたＮ系統の各受信信号を高速フーリエ変換してサブキャリア毎の受信信号に変換する高速フーリエ変換手段と、当該高速フーリエ変換後のＮ系統の受信信号に含まれるパイロット信号と前記既知のパイロット信号とを用いて、サブキャリア毎に、各送信アンテナと各受信アンテナとの間の伝達係数を要素とする伝達係数行列およびその逆行列である伝達係数逆行列を算出する伝達係数行列演算手段と、サブキャリア毎に、前記高速フーリエ変換後のＮ系統の受信信号に対して前記伝達係数逆行列を乗算し、前記高速フーリエ変換後のＮ系統の受信信号に含まれる系統間の相互干渉成分をキャンセルする乗算型干渉キャンセル手段と、当該乗算型干渉キャンセル手段のＮ系統の出力信号それぞれに対して、サブキャリア毎に、前記伝達係数に応じて重み付けする重み付け手段と、当該重み付け手段のＮ系統の出力信号それぞれを復調してＮ系統の第１の復調信号を出力する第１の復調手段と、当該Ｎ系統の第１の復調信号それぞれに対して前記サブキャリア変調手段と同一のサブキャリア変調を行うサブキャリア再変調手段と、当該サブキャリア再変調手段のＮ系統の出力信号と前記伝達係数行列とを用いて、サブキャリア毎に、系統間の相互干渉成分のレプリカを生成し、当該レプリカを前記高速フーリエ変換後のＮ系統の受信信号から減算することによって当該各受信信号に含まれる系統間の相互干渉成分をキャンセルし、当該各受信信号を前記ＯＦＤＭ信号の各系統に対応する信号成分に分離する減算型干渉キャンセル手段と、当該減算型干渉キャンセル手段により分離された信号成分に対して、サブキャリア毎に、前記伝達係数に基づく重み付けを行い、前記ＯＦＤＭ信号の各系統に対応する信号成分同士を合成する重み付け合成手段と、当該重み付け合成手段のＮ系統の出力信号それぞれを復調してＮ系統の第２の復調信号を出力する第２の復調手段と、前記誤り検出符号を用いて前記Ｎ系統の第１および第２の復調信号それぞれの誤り量を検出する誤り検出手段と、当該誤り検出手段の検出結果に基づいて、前記Ｎ系統の第１および第２の復調信号のうち誤りの少ない復調信号を系統毎に選択する復調信号選択手段とを有することを特徴とする。
【００７７】
また、第６の発明は、ＯＦＤＭ信号送信装置とＯＦＤＭ信号受信装置とを備えるＯＦＤＭ信号送受信装置であって、前記ＯＦＤＭ信号送信装置は、入力されたＮ系統（Ｎは２以上の整数）の送信情報信号のそれぞれに対して誤り検出符号を付加する誤り検出符号付加手段と、前記Ｎ系統の送信情報信号のそれぞれに対して誤り訂正符号化を行う誤り訂正符号手段と、前記Ｎ系統の送信情報信号のそれぞれに対してパイロット信号を付加するパイロット信号付加手段と、前記誤り検出符号およびパイロット信号が付加されたＮ系統の送信情報信号それぞれに対してサブキャリア変調を行うサブキャリア変調手段と、当該サブキャリア変調手段のＮ系統の出力信号それぞれに対して逆高速フーリエ変換を行う逆高速フーリエ変換手段と、当該逆高速フーリエ変換手段が出力するＮ系統のＯＦＤＭ信号を同一周波数で送信するＮ本の送信アンテナとを有し、前記ＯＦＤＭ信号受信装置は、前記Ｎ系統のＯＦＤＭ信号が空間多重された信号を受信するＮ本の受信アンテナと、当該Ｎ本の受信アンテナで受信されたＮ系統の各受信信号を高速フーリエ変換してサブキャリア毎の受信信号に変換する高速フーリエ変換手段と、当該高速フーリエ変換後のＮ系統の受信信号に含まれるパイロット信号と前記既知のパイロット信号とを用いて、サブキャリア毎に、各送信アンテナと各受信アンテナとの間の伝達係数を要素とする伝達係数行列およびその逆行列である伝達係数逆行列を算出する伝達係数行列演算手段と、サブキャリア毎に、前記高速フーリエ変換後のＮ系統の受信信号に対して前記伝達係数逆行列を乗算し、前記高速フーリエ変換後のＮ系統の受信信号に含まれる系統間の相互干渉成分をキャンセルする乗算型干渉キャンセル手段と、当該乗算型干渉キャンセル手段のＮ系統の出力信号それぞれに対して、サブキャリア毎に、前記伝達係数に応じて重み付けする重み付け手段と、当該重み付け手段のＮ系統の出力信号それぞれを復調する第１の復調手段と、当該第１の復調手段のＮ系統の出力信号それぞれに対し、誤り訂正復号を行いＮ系統の復号信号を出力する第１の復号手段と、当該Ｎ系統の復号信号それぞれについて前記誤り検出符号を用いて誤りの位置を検出する誤り検出手段と、当該誤り検出手段の検出結果を参照してＮ系統すべて正しく復号されたサブキャリアを選択し、当該サブキャリアに対応する復号信号について前記サブキャリア変調手段と同一のサブキャリア変調を行う選択型再変調手段と、当該選択型再変調手段のＮ系統の出力信号と前記伝達係数行列とを用いて、選択されたサブキャリア毎に、系統間の相互干渉成分のレプリカを生成し、当該レプリカを前記高速フーリエ変換後のＮ系統の受信信号から減算することによって当該各受信信号に含まれる系統間の相互干渉成分をキャンセルし、当該各受信信号を前記ＯＦＤＭ信号の各系統に対応する信号成分に分離する減算型干渉キャンセル手段と、当該減算型干渉キャンセル手段により分離された信号成分に対して、選択されたサブキャリア毎に、前記伝達係数に基づく重み付けを行い、前記ＯＦＤＭ信号の各系統に対応する信号成分同士を合成する重み付け合成手段と、当該重み付け合成手段のＮ系統の出力信号と前記選択型再変調手段に選択されなかったサブキャリアについての前記重み付け手段のＮ系統の出力信号とを合成して復調する第２の復調手段と、当該第２の復調手段のＮ系統の出力信号それぞれに対し、誤り訂正復号を行う第２の復号手段とを有することを特徴とする。
【００７８】
また、第７の発明は、ＯＦＤＭ信号送信装置とＯＦＤＭ信号受信装置とを備えるＯＦＤＭ信号送受信装置であって、前記ＯＦＤＭ信号送信装置は、入力されたＮ系統（Ｎは２以上の整数）の送信情報信号のそれぞれに対して誤り検出符号を付加する誤り検出符号付加手段と、前記Ｎ系統の送信情報信号のそれぞれに対してパイロット信号を付加するパイロット信号付加手段と、前記誤り検出符号およびパイロット信号が付加されたＮ系統の送信情報信号それぞれに対してサブキャリア変調を行うサブキャリア変調手段と、当該サブキャリア変調手段のＮ系統の出力信号それぞれに対して逆高速フーリエ変換を行う逆高速フーリエ変換手段と、当該逆高速フーリエ変換手段が出力するＮ系統のＯＦＤＭ信号を同一周波数で送信するＮ本の送信アンテナとを有し、前記ＯＦＤＭ信号受信装置は、前記Ｎ系統のＯＦＤＭ信号が空間多重された信号を受信するＮ本の受信アンテナと、当該Ｎ本の受信アンテナで受信されたＮ系統の各受信信号を高速フーリエ変換してサブキャリア毎の受信信号に変換する高速フーリエ変換手段と、当該高速フーリエ変換後のＮ系統の受信信号に含まれるパイロット信号と前記既知のパイロット信号とを用いて、サブキャリア毎に、各送信アンテナと各受信アンテナとの間の伝達係数を要素とする伝達係数行列およびその逆行列である伝達係数逆行列を算出する伝達係数行列演算手段と、サブキャリア毎に、前記高速フーリエ変換後のＮ系統の受信信号に対して前記伝達係数逆行列を乗算し、前記高速フーリエ変換後のＮ系統の受信信号に含まれる系統間の相互干渉成分をキャンセルする乗算型干渉キャンセル手段と、当該乗算型干渉キャンセル手段のＮ系統の出力信号それぞれに対して、サブキャリア毎に、前記伝達係数に応じて重み付けする重み付け手段と、当該重み付け手段のＮ系統の出力信号それぞれを復調してＮ系統の第１の復調信号を出力する第１の復調手段と、当該Ｎ系統の第１の復調信号をもとに繰り返し減算型干渉キャンセルを行い複数のＮ系統の第２の復調信号を出力する減算型干渉キャンセル反復手段と、前記誤り検出符号を用いて前記Ｎ系統の第１の復調信号および複数のＮ系統の第２の復調信号それぞれの誤り量を検出する誤り検出手段と、当該誤り検出手段の検出結果に基づいて、前記Ｎ系統の第１の復調信号および複数のＮ系統の第２の復調信号の中から、最も誤りの少ない復調信号を系統毎に選択する復調信号選択手段とを有し、前記減算型干渉キャンセル反復手段は、前記Ｎ系統の復調信号それぞれに対して前記サブキャリア変調手段と同一のサブキャリア変調を行うサブキャリア再変調手段と、当該サブキャリア再変調手段のＮ系統の出力信号と前記伝達係数行列とを用いて、サブキャリア毎に、系統間の相互干渉成分のレプリカを生成し、当該レプリカを前記高速フーリエ変換後のＮ系統の受信信号から減算することによって当該各受信信号に含まれる系統間の相互干渉成分をキャンセルし、当該各受信信号を前記ＯＦＤＭ信号の各系統に対応する信号成分に分離する減算型干渉キャンセル手段と、当該減算型干渉キャンセル手段により分離された信号成分に対して、サブキャリア毎に、前記伝達係数に基づく重み付けを行い、前記ＯＦＤＭ信号の各系統に対応する信号成分同士を合成する重み付け合成手段と、当該重み付け合成手段のＮ系統の出力信号それぞれを復調してＮ系統の第２の復調信号を出力する第２の復調手段と、を複数段備え、第１段目の前記サブキャリア再変調手段は前記Ｎ系統の第１の復調信号を変調し、第２段目以降の前記サブキャリア再変調手段はそれぞれ前段の前記Ｎ系統の第２の復調信号を変調することを特徴とする。
【００７９】
また、第８の発明は、ＯＦＤＭ信号送信装置とＯＦＤＭ信号受信装置とを備えるＯＦＤＭ信号送受信装置であって、前記ＯＦＤＭ信号送信装置は、入力されたＮ系統（Ｎは２以上の整数）の送信情報信号のそれぞれに対して誤り検出符号を付加する誤り検出符号付加手段と、前記Ｎ系統の送信情報信号のそれぞれに対して誤り訂正符号化を行う誤り訂正符号手段と、前記Ｎ系統の送信情報信号のそれぞれに対してパイロット信号を付加するパイロット信号付加手段と、前記誤り検出符号およびパイロット信号が付加されたＮ系統の送信情報信号それぞれに対してサブキャリア変調を行うサブキャリア変調手段と、当該サブキャリア変調手段のＮ系統の出力信号それぞれに対して逆高速フーリエ変換を行う逆高速フーリエ変換手段と、当該逆高速フーリエ変換手段が出力するＮ系統のＯＦＤＭ信号を同一周波数で送信するＮ本の送信アンテナとを有し、前記ＯＦＤＭ信号受信装置は、前記Ｎ系統のＯＦＤＭ信号が空間多重された信号を受信するＮ本の受信アンテナと、当該Ｎ本の受信アンテナで受信されたＮ系統の各受信信号を高速フーリエ変換してサブキャリア毎の受信信号に変換する高速フーリエ変換手段と、当該高速フーリエ変換後のＮ系統の受信信号に含まれるパイロット信号と前記既知のパイロット信号とを用いて、サブキャリア毎に、各送信アンテナと各受信アンテナとの間の伝達係数を要素とする伝達係数行列およびその逆行列である伝達係数逆行列を算出する伝達係数行列演算手段と、サブキャリア毎に、前記高速フーリエ変換後のＮ系統の受信信号に対して前記伝達係数逆行列を乗算し、前記高速フーリエ変換後のＮ系統の受信信号に含まれる系統間の相互干渉成分をキャンセルする乗算型干渉キャンセル手段と、当該乗算型干渉キャンセル手段のＮ系統の出力信号それぞれに対して、サブキャリア毎に、前記伝達係数に応じて重み付けする重み付け手段と、当該重み付け手段のＮ系統の出力信号それぞれを復調する第１の復調手段と、当該第１の復調手段のＮ系統の出力信号それぞれに対し、誤り訂正復号を行いＮ系統の第１の復号信号を出力する第１の復号手段と、当該Ｎ系統の第１の復号信号を用いて繰り返し減算型干渉キャンセルを行いＮ系統の最終復号信号を出力する減算型干渉キャンセル反復手段とを有し、当該減算型干渉キャンセル反復手段は、Ｎ系統の復号信号それぞれについて前記誤り検出符号を用いて誤りの位置を検出する誤り検出手段と、当該誤り検出手段の検出結果を参照してＮ系統すべて正しく復号されたサブキャリアを選択し、当該サブキャリアに対応する復号信号について前記サブキャリア変調手段と同一のサブキャリア変調を行う選択型再変調手段と、当該選択型再変調手段のＮ系統の出力信号と前記伝達係数行列とを用いて、選択されたサブキャリア毎に、系統間の相互干渉成分のレプリカを生成し、当該レプリカを前記高速フーリエ変換後のＮ系統の受信信号から減算することによって当該各受信信号に含まれる系統間の相互干渉成分をキャンセルし、当該各受信信号を前記ＯＦＤＭ信号の各系統に対応する信号成分に分離する減算型干渉キャンセル手段と、当該減算型干渉キャンセル手段により分離された信号成分に対して、選択されたサブキャリア毎に、前記伝達係数に基づく重み付けを行い、前記ＯＦＤＭ信号の各系統に対応する信号成分同士を合成する重み付け合成手段と、当該重み付け合成手段のＮ系統の出力信号と前記選択型再変調手段に選択されなかったサブキャリアについての前記重み付け手段のＮ系統の出力信号とを合成して復調する第２の復調手段と、当該第２の復調手段のＮ系統の出力信号それぞれに対し、誤り訂正復号を行いＮ系統の第２の復号信号を出力する第２の復号手段と、を複数段備え、第１段目の前記誤り検出手段は前記Ｎ系統の第１の復号信号の誤り検出を行い、第２段目以降の前記誤り検出手段はそれぞれ前段の前記Ｎ系統の第２の復号信号の誤り検出を行い、最終段の前記第２の復号手段は前記第２の復号信号を前記最終復号信号として出力することを特徴とする。
【００８０】
また、第９の発明は、各々誤り検出符号および既知のパイロット信号を含み、Ｎ本（Ｎは２以上の整数）の送信アンテナから同一周波数で送信されるＮ系統のＯＦＤＭ信号を受信するＯＦＤＭ信号受信方法であって、前記Ｎ系統のＯＦＤＭ信号が空間多重された信号をＮ本の受信アンテナで受信する受信ステップと、当該Ｎ本の受信アンテナで受信されたＮ系統の各受信信号を高速フーリエ変換してサブキャリア毎の受信信号に変換する高速フーリエ変換ステップと、当該高速フーリエ変換後のＮ系統の受信信号に含まれるパイロット信号と前記既知のパイロット信号とを用いて、サブキャリア毎に、各送信アンテナと各受信アンテナとの間の伝達係数を要素とする伝達係数行列およびその逆行列である伝達係数逆行列を算出する伝達係数行列演算ステップと、サブキャリア毎に、前記高速フーリエ変換後のＮ系統の受信信号に対して前記伝達係数逆行列を乗算し、前記高速フーリエ変換後のＮ系統の受信信号に含まれる系統間の相互干渉成分をキャンセルする乗算型干渉キャンセルステップと、当該乗算型干渉キャンセルステップで相互干渉成分がキャンセルされたＮ系統の信号それぞれに対して、サブキャリア毎に、前記伝達係数に応じて重み付けする重み付けステップと、当該重み付けステップで重み付けされたＮ系統の信号それぞれを復調してＮ系統の第１の復調信号を得る第１の復調ステップと、当該Ｎ系統の第１の復調信号それぞれに対して送信時と同一のサブキャリア変調を行うサブキャリア再変調ステップと、当該サブキャリア再変調ステップでサブキャリア変調された信号と前記伝達係数行列とを用いて、サブキャリア毎に、系統間の相互干渉成分のレプリカを生成し、当該レプリカを前記高速フーリエ変換後のＮ系統の受信信号から減算することによって当該各受信信号に含まれる系統間の相互干渉成分をキャンセルし、当該各受信信号を前記ＯＦＤＭ信号の各系統に対応する信号成分に分離する減算型干渉キャンセルステップと、当該減算型干渉キャンセルステップで分離された信号成分に対して、サブキャリア毎に、前記伝達係数に基づく重み付けを行い、前記ＯＦＤＭ信号の各系統に対応する信号成分同士を合成する重み付け合成ステップと、当該重み付け合成ステップで得られた信号それぞれを復調してＮ系統の第２の復調信号を得る第２の復調ステップと、前記誤り検出符号を用いて前記Ｎ系統の第１および第２の復調信号それぞれの誤り量を検出する誤り検出ステップと、当該誤り検出ステップの検出結果に基づいて、前記Ｎ系統の第１および第２の復調信号のうち誤りの少ない信号を系統毎に選択する復調信号選択ステップとを有することを特徴とする。
【００８１】
また、第１０の発明は、各々誤り訂正符号化され、誤り検出符号および既知のパイロット信号を含み、Ｎ本（Ｎは２以上の整数）の送信アンテナから同一周波数で送信されるＮ系統のＯＦＤＭ信号を受信するＯＦＤＭ信号受信方法であって、前記Ｎ系統のＯＦＤＭ信号が空間多重された信号をＮ本の受信アンテナで受信する受信ステップと、当該Ｎ本の受信アンテナで受信されたＮ系統の各受信信号を高速フーリエ変換してサブキャリア毎の受信信号に変換する高速フーリエ変換ステップと、当該高速フーリエ変換後のＮ系統の受信信号に含まれるパイロット信号と前記既知のパイロット信号とを用いて、サブキャリア毎に、各送信アンテナと各受信アンテナとの間の伝達係数を要素とする伝達係数行列およびその逆行列である伝達係数逆行列を算出する伝達係数行列演算ステップと、サブキャリア毎に、前記高速フーリエ変換後のＮ系統の受信信号に対して前記伝達係数逆行列を乗算し、前記高速フーリエ変換後のＮ系統の受信信号に含まれる系統間の相互干渉成分をキャンセルする乗算型干渉キャンセルステップと、当該乗算型干渉キャンセルステップで相互干渉成分がキャンセルされたＮ系統の信号それぞれに対して、サブキャリア毎に、前記伝達係数に応じて重み付けする重み付けステップと、当該重み付けステップで重み付けされたＮ系統の信号それぞれを復調する第１の復調ステップと、当該第１の復調ステップで復調されたＮ系統の信号それぞれに対し、誤り訂正復号を行いＮ系統の復号信号を得る第１の復号ステップと、当該Ｎ系統の復号信号それぞれについて前記誤り検出符号を用いて誤りの位置を検出する誤り検出ステップと、当該誤り検出ステップの検出結果を参照してＮ系統すべて正しく復号されたサブキャリアを選択し、当該サブキャリアに対応する前記復号信号について送信時と同一のサブキャリア変調を行う選択型再変調ステップと、当該選択型再変調ステップでサブキャリア変調されたＮ系統の信号と前記伝達係数行列とを用いて、選択されたサブキャリア毎に、系統間の相互干渉成分のレプリカを生成し、当該レプリカを前記高速フーリエ変換後のＮ系統の受信信号から減算することによって当該各受信信号に含まれる系統間の相互干渉成分をキャンセルし、当該各受信信号を前記ＯＦＤＭ信号の各系統に対応する信号成分に分離する減算型干渉キャンセルステップと、当該減算型干渉キャンセルステップで分離された信号成分に対して、選択されたサブキャリア毎に、前記伝達係数に基づく重み付けを行い、前記ＯＦＤＭ信号の各系統に対応する信号成分同士を合成する重み付け合成ステップと、当該重み付け合成ステップで合成されたＮ系統の信号と前記選択型再変調ステップで選択されなかったサブキャリアについての前記重み付けステップで重み付けされたＮ系統の信号とを合成して復調する第２の復調ステップと、当該第２の復調ステップで復調されたＮ系統の信号それぞれに対し、誤り訂正復号を行う第２の復号ステップと、を有することを特徴とする。
【００８２】
また、第１１の発明は、各々誤り検出符号および既知のパイロット信号を含み、Ｎ本（Ｎは２以上の整数）の送信アンテナから同一周波数で送信されるＮ系統のＯＦＤＭ信号を受信するＯＦＤＭ信号受信方法であって、前記Ｎ系統のＯＦＤＭ信号が空間多重された信号をＮ本の受信アンテナで受信する受信ステップと、当該Ｎ本の受信アンテナで受信されたＮ系統の各受信信号を高速フーリエ変換してサブキャリア毎の受信信号に変換する高速フーリエ変換ステップと、当該高速フーリエ変換後のＮ系統の受信信号に含まれるパイロット信号と前記既知のパイロット信号とを用いて、サブキャリア毎に、各送信アンテナと各受信アンテナとの間の伝達係数を要素とする伝達係数行列およびその逆行列である伝達係数逆行列を算出する伝達係数行列演算ステップと、サブキャリア毎に、前記高速フーリエ変換後のＮ系統の受信信号に対して前記伝達係数逆行列を乗算し、前記高速フーリエ変換後のＮ系統の受信信号に含まれる系統間の相互干渉成分をキャンセルする乗算型干渉キャンセルステップと、当該乗算型干渉キャンセルステップで相互干渉成分がキャンセルされたＮ系統の信号それぞれに対して、サブキャリア毎に、前記伝達係数に応じて重み付けする重み付けステップと、当該重み付けステップで重み付けされたＮ系統の信号それぞれを復調してＮ系統の第１の復調信号を得る第１の復調ステップと、当該Ｎ系統の第１の復調信号をもとに繰り返し減算型干渉キャンセルを行い複数のＮ系統の第２の復調信号を得る減算型干渉キャンセル反復ステップと、前記誤り検出符号を用いて前記Ｎ系統の第１の復調信号および複数のＮ系統の第２の復調信号それぞれの誤り量を検出する誤り検出ステップと、当該誤り検出ステップの検出結果に基づいて、前記Ｎ系統の第１の復調信号および複数のＮ系統の第２の復調信号の中から、最も誤りの少ない復調信号を系統毎に選択する復調信号選択ステップとを有し、前記減算型干渉キャンセル反復ステップは、前記Ｎ系統の復調信号それぞれに対して送信時と同一のサブキャリア変調を行うサブキャリア再変調ステップと、当該サブキャリア再変調ステップでサブキャリア変調されたＮ系統の信号と前記伝達係数行列とを用いて、サブキャリア毎に、系統間の相互干渉成分のレプリカを生成し、当該レプリカを前記高速フーリエ変換後のＮ系統の受信信号から減算することによって当該各受信信号に含まれる系統間の相互干渉成分をキャンセルし、当該各受信信号を前記ＯＦＤＭ信号の各系統に対応する信号成分に分離する減算型干渉キャンセルステップと、当該減算型干渉キャンセルステップで分離された信号成分に対して、サブキャリア毎に、前記伝達係数に基づく重み付けを行い、前記ＯＦＤＭ信号の各系統に対応する信号成分同士を合成する重み付け合成ステップと、当該重み付け合成ステップで合成されたＮ系統の信号それぞれを復調してＮ系統の第２の復調信号を得る第２の復調ステップと、を複数回繰り返すステップであって、第１回目の前記サブキャリア再変調ステップでは前記Ｎ系統の第１の復調信号を変調し、第２回目以降の前記サブキャリア再変調ステップではそれぞれ前回の前記Ｎ系統の第２の復調信号を変調することを特徴とする。
【００８３】
また、第１２の発明は、各々誤り訂正符号化され、誤り検出符号および既知のパイロット信号を含み、Ｎ本（Ｎは２以上の整数）の送信アンテナから同一周波数で送信されるＮ系統のＯＦＤＭ信号を受信するＯＦＤＭ信号受信方法であって、前記Ｎ系統のＯＦＤＭ信号が空間多重された信号をＮ本の受信アンテナで受信する受信ステップと、当該Ｎ本の受信アンテナで受信されたＮ系統の各受信信号を高速フーリエ変換してサブキャリア毎の受信信号に変換する高速フーリエ変換ステップと、当該高速フーリエ変換後のＮ系統の受信信号に含まれるパイロット信号と前記既知のパイロット信号とを用いて、サブキャリア毎に、各送信アンテナと各受信アンテナとの間の伝達係数を要素とする伝達係数行列およびその逆行列である伝達係数逆行列を算出する伝達係数行列演算ステップと、サブキャリア毎に、前記高速フーリエ変換後のＮ系統の受信信号に対して前記伝達係数逆行列を乗算し、前記高速フーリエ変換後のＮ系統の受信信号に含まれる系統間の相互干渉成分をキャンセルする乗算型干渉キャンセルステップと、当該乗算型干渉キャンセルステップで相互干渉成分がキャンセルされたＮ系統の信号それぞれに対して、サブキャリア毎に、前記伝達係数に応じて重み付けする重み付けステップと、当該重み付けステップで重み付けされたＮ系統の信号それぞれを復調する第１の復調ステップと、当該第１の復調ステップで復調されたＮ系統の信号それぞれに対し、誤り訂正復号を行いＮ系統の第１の復号信号を得る第１の復号ステップと、当該Ｎ系統の第１の復号信号を用いて繰り返し減算型干渉キャンセルを行いＮ系統の最終復号信号を得る減算型干渉キャンセル反復ステップとを有し、当該減算型干渉キャンセル反復ステップは、Ｎ系統の復号信号それぞれについて前記誤り検出符号を用いて誤りの位置を検出する誤り検出ステップと、当該誤り検出ステップの検出結果を参照してＮ系統すべて正しく復号されたサブキャリアを選択し、当該サブキャリアに対応する復号信号について送信時と同一のサブキャリア変調を行う選択型再変調ステップと、当該選択型再変調ステップでサブキャリア変調されたＮ系統の信号と前記伝達係数行列とを用いて、選択されたサブキャリア毎に、系統間の相互干渉成分のレプリカを生成し、当該レプリカを前記高速フーリエ変換後のＮ系統の受信信号から減算することによって当該各受信信号に含まれる系統間の相互干渉成分をキャンセルし、当該各受信信号を前記ＯＦＤＭ信号の各系統に対応する信号成分に分離する減算型干渉キャンセルステップと、当該減算型干渉キャンセルステップで分離された信号成分に対して、選択されたサブキャリア毎に、前記伝達係数に基づく重み付けを行い、前記ＯＦＤＭ信号の各系統に対応する信号成分同士を合成する重み付け合成ステップと、当該重み付け合成ステップで合成されたＮ系統の信号と前記選択型再変調ステップで選択されなかったサブキャリアについての前記重み付けステップで重み付けされたＮ系統の信号とを合成して復調する第２の復調ステップと、当該第２の復調ステップで復調されたＮ系統の信号それぞれに対し、誤り訂正復号を行いＮ系統の第２の復号信号を得る第２の復号ステップと、を複数回繰り返すステップであって、第１回目の前記誤り検出ステップでは前記Ｎ系統の第１の復号信号の誤り検出を行い、第２回目以降の前記誤り検出ステップではそれぞれ前回の前記Ｎ系統の第２の復号信号の誤り検出を行い、最終回の前記第２の復号ステップでは前記第２の復号信号を前記最終復号信号として得ることを特徴とする。
【００８４】
【発明の実施の形態】
以下に添付図面を参照して、本発明に係るＯＦＤＭ信号受信装置、ＯＦＤＭ信号送受信装置、およびＯＦＤＭ信号受信方法についての好適な実施形態を第１の実施形態から第４の実施形態に分けて詳細に説明する。
【００８５】
（第１の実施形態）
本実施形態に係るＯＦＤＭ信号送受信装置は、ＯＦＤＭ信号受信装置において、乗算型干渉キャンセル後のＮ系統の復調信号と減算型干渉キャンセル後のＮ系統の復調信号とについて誤り量を検出し、より誤りの少ない復調信号を系統毎に選択することとしたものである。以下、本実施形態に係るＯＦＤＭ信号送受信装置の構成および動作について図面を参照して説明する。
【００８６】
図１は、本実施形態に係るＯＦＤＭ信号送受信装置の構成を示すブロック図である。図１において、ＯＦＤＭ信号送受信装置は、ＯＦＤＭ信号送信装置１とＯＦＤＭ信号受信装置２とを備えている。
【００８７】
ＯＦＤＭ信号送信装置１において、入力されたＮ系統（Ｎは２以上の整数）の送信情報信号Ｔ_１、Ｔ_２、・・・、Ｔ_Ｎは、各信号に対応するＮ個の誤り検出符号多重化器１−１−１〜１−１−Ｎにより、所定のブロック単位で誤り検出符号と多重化される。誤り検出符号多重化器１−１−１〜１−１−ＮのＮ系統の出力信号は、各信号に対応するＮ個のパイロット信号多重化器１−３−１〜１−３−Ｎにより、Ｎ個のパイロット信号生成器１−２−１〜１−２−Ｎによって生成された既知の伝達係数推定用のパイロット信号と多重化される。パイロット信号多重化器１−３−１〜１−３−ＮのＮ系統の出力信号は、各信号に対応するＮ個のサブキャリア変調器１−４−１〜１−４−Ｎにより、サブキャリア変調され、周波数領域すなわちサブキャリア毎の送信信号に変換される。サブキャリア変調器１−４−１〜１−４−Ｎから出力されるＮ系統の複数のサブキャリア信号からなる送信信号は、各信号に対応するＮ個の逆高速フーリエ変換器１−５−１〜１−５−Ｎにより、逆高速フーリエ変換され、時間領域のＮ系統の送信信号に変換される。逆高速フーリエ変換器１−５−１〜１−５−Ｎから出力されるＮ系統のＯＦＤＭ信号は、各信号に対応するＮ本の送信アンテナ１−６−１〜１−６−Ｎから同一周波数で送信される。
【００８８】
ＯＦＤＭ信号受信装置２において、Ｎ本の送信アンテナ１−６−１〜１−６−Ｎから送信され空間多重された信号は、Ｎ本の受信アンテナ２−１−１〜２−１−Ｎによって受信される。ここで、各受信アンテナは、Ｎ本の送信アンテナからのＮ系統のＯＦＤＭ信号を同時に受信するため、受信される各信号には系統間の相互干渉成分が含まれている。Ｎ本の受信アンテナ２−１−１〜２−１−Ｎによって受信されたＮ系統の受信信号は、各信号に対応するＮ個の高速フーリエ変換器２−２−１〜２−２−Ｎにより、高速フーリエ変換され、時間領域の受信信号から周波数領域すなわちサブキャリア毎の受信信号に変換される。以下、ｉ番目のサブキャリアの高速フーリエ変換後のＮ系統の受信信号をベクトルｒ^ｉ（＝（ｒ^ｉ _１ ｒ^ｉ _２・・・ｒ^ｉ _Ｎ））で表す。伝達係数行列演算器２−３は、Ｎ系統の高速フーリエ変換後の受信信号に含まれる受信パイロット信号の振幅および位相と、既知のパイロット信号の振幅および位相とを用いて、サブキャリア毎に、各送信アンテナと各受信アンテナとの間の伝達係数ｈ^ｉ _ｊ，ｋ（ｉはサブキャリアの番号、ｊは送信アンテナの番号、ｋは受信アンテナの番号）を算出し、当該伝達係数を要素とする伝達係数行列Ｈ^ｉとその逆行列である伝達係数逆行列（Ｈ^ｉ）^−１とを算出し、これらを記憶する。ここで、伝達係数行列Ｈ^ｉは（１）式で表される。
【００８９】
乗算型干渉キャンセラ２−４は、サブキャリア毎に、高速フーリエ変換後のＮ系統の受信信号のベクトルｒ^ｉと伝達係数逆行列（Ｈ^ｉ）^−１との積ｒ^ｉ・（Ｈ^ｉ）^−１を演算し、高速フーリエ変換後のＮ系統の受信信号に含まれる相互干渉成分をキャンセルする。すなわち、サブキャリア毎に、各系統の周波数領域すなわちサブキャリア毎の送信信号を推定する。乗算型干渉キャンセラ２−４により出力されるＮ系統の乗算型干渉キャンセラ出力信号ｕ^ｉ（＝（ｕ^ｉ _１ ｕ^ｉ _２・・・ｕ^ｉ _Ｎ））は、各信号に対応するＮ個の重み付け器２−５−１〜２−５−Ｎにより、サブキャリア毎に、伝達係数に応じて重み付けされる。具体的には、重み付け器２−５−１〜２−５−Ｎは、伝達係数逆行列に基づいて（６）式で表される重み付け行列Ｙ^ｉの対応する要素を算出し、当該要素を乗算型干渉キャンセラ出力信号に乗じ、重み付け器出力信号を算出する。Ｎ系統の重み付け器出力信号は、各信号に対応するＮ個の第１の復調器２−６−１〜２−６−Ｎにより、信号判定され、復調される。
【００９０】
ついで、Ｎ個の第１の復調器２−６−１〜２−６−Ｎから出力されるＮ系統の第１の復調信号は、各信号に対応するＮ個のサブキャリア再変調器２−７−１〜２−７−Ｎにより、送信時と同一の変調方式で、すなわちサブキャリア変調器１−４−１〜１−４−Ｎにおける変調と同一の変調方式で、サブキャリア変調される。
【００９１】
減算型干渉キャンセラ２−９は、サブキャリア再変調器２−７−１〜２−７−ＮのＮ系統の出力信号と伝達係数行列とを用いて、サブキャリア毎に、高速フーリエ変換後のＮ系統の受信信号に含まれる系統間の相互干渉成分をキャンセルし、高速フーリエ変換後の各受信信号をＯＦＤＭ信号の各系統に対応する信号成分に分離する。具体的には、減算型干渉キャンセラ２−９は、サブキャリア再変調器２−７−１〜２−７−ＮのＮ系統の出力信号と伝達係数行列とを用いて、高速フーリエ変換後のＮ系統の各受信信号に含まれる相互干渉成分のレプリカを生成し、当該レプリカを当該受信信号から減算することによって当該受信信号に含まれる相互干渉成分をキャンセルし、高速フーリエ変換後の各受信信号を、各系統のサブキャリア毎の送信信号に対応する信号成分に分離する。より具体的には、ｉ番目のサブキャリアに着目すると、以下の演算を行う。高速フーリエ変換後のＮ系統の受信信号から（１１）式に従って受信信号行列Ｒ^ｉを算出する。また、サブキャリア再変調器２−７−１〜２−７−ＮのＮ系統の出力信号ｔ´^ｉ（＝（ｔ´^ｉ _１ ｔ´^ｉ _２・・・ｔ´^ｉ _Ｎ））から（１２）式に従って再変調信号行列Ｔ´^ｉを計算する。そして、再変調信号行列Ｔ´^ｉと伝達係数行列Ｈ^ｉとからレプリカ信号行列（Ｔ´^ｉ・Ｈ^ｉ）を算出する。すなわち、高速フーリエ変換後の各受信信号に含まれる相互干渉成分のレプリカを生成する。ついで、（１３）式のとおり、受信信号行列Ｒ^ｉからレプリカ信号行列（Ｔ´^ｉ・Ｈ^ｉ）を減算して、レプリカ減算後信号行列Ｘ^ｉを出力する。このレプリカ減算後信号行列Ｘ^ｉの各要素は、高速フーリエ変換後のＮ系統の各受信信号に含まれる、ｉ番目のサブキャリアのＮ系統の各送信信号に対応する信号成分となっている。
【００９２】
なお、減算型干渉キャンセラ２−９に入力される高速フーリエ変換後の受信信号は、Ｎ個の高速フーリエ変換器２−２−１〜２−２−Ｎの出力信号が受信信号遅延器２−８−１〜２−８−Ｎによって遅延させられたものである。ここで、受信信号遅延器２−８−１〜２−８−Ｎは、乗算型干渉キャンセラ２−４からサブキャリア再変調器２−７−１〜２−７−Ｎまでの処理時間に相当する遅延を発生させる。
【００９３】
重み付け合成器２−１０は、サブキャリア毎に、減算型干渉キャンセラ２−９により分離された信号成分に対して伝達係数に基づく重み付けを行い、ＯＦＤＭ信号の各系統に対応する信号成分同士を合成する。具体的には、重み付け合成器２−１０は、伝達係数行列Ｈ^ｉの共役転置行列を求め、これをレプリカ減算後重み付け行列Ｗ^ｉとする。また、行列（Ｈ^ｉ・Ｗ^ｉ）とすべての対角成分が同一であって、かつ、すべての非対角成分が０である行列Ｇ^ｉを算出する。そして、（１９）式に従ってＮ系統の重み付け合成後信号ｖ^ｉを算出する。
【００９４】
このＮ系統の重み付け合成後信号ｖ^ｉは、各信号に対応するＮ個の第２の復調器２−１１−１〜２−１１−Ｎにより、復調される。
Ｎ個の第２の復調器２−１１−１〜２−１１−Ｎから出力されるＮ系統の第２の復調信号は、Ｎ系統の第１の復調信号とともに、後述するＮ個の復調信号選択回路２−１３−１〜２−１３−Ｎに供給される。なお、復調信号選択回路２−１３−１〜２−１３−Ｎに供給されるＮ系統の第１の復調信号は、Ｎ個の第１の復調器２−６−１〜２−６−Ｎから出力されるＮ系統の第１の復調信号が、Ｎ個の復調信号遅延器２−１２−１〜２−１２−Ｎによって遅延させられたものである。ここで、復調信号遅延器２−１２−１〜２−１２−Ｎは、Ｎ個の第１の復調器２−６−１〜２−６−ＮからＮ個の第２の復調器２−１１−１〜２−１１−Ｎまでの処理時間に相当する遅延を発生させる。
【００９５】
以上のとおり、本実施形態に係るＯＦＤＭ信号送受信装置は、特願２００２−１４９０１３に記載の従来のＯＦＤＭ信号送受信装置に、Ｎ個の誤り検出符号多重化器１−１−１〜１−１−Ｎ、Ｎ個の復調信号遅延器２−１２−１〜２−１２−Ｎ、およびＮ個の復調信号選択回路２−１３−１〜２−１３−Ｎを付加した構成となっている。
【００９６】
従来のＯＦＤＭ信号送受信装置では、Ｎ系統の第２の復調信号を常に最終的な出力としていた。これに対し、本実施形態に係るＯＦＤＭ信号送受信装置では、Ｎ個の復調信号選択回路２−１３−１〜２−１３−ＮによってＮ系統の第１の復調信号とＮ系統の第２の復調信号から誤りの少ない信号を系統毎に選択して最終的なＮ系統の復調信号とする。
【００９７】
図２は、第１番目の系統に対応する復調信号選択回路２−１３−１の構成を示すブロック図である。なお、他の系統に対応する復調信号選択回路２−１３−２〜２−１３−Ｎも全く同様の構成である。第１の復調器２−６−１の出力信号と第２の復調器２−１１−１の出力信号との出力の時間差に相当する遅延時間を、第１の復調器２−６−１の出力に対して復調信号遅延器２−１２−１を用いて与えているため、第１および第２の復調信号は同時刻で復調信号選択回路２−１３−１に供給される。図２において、復調信号遅延器２−１２−１から出力される第１の復調信号は第１の誤り検出回路３−１に供給され、第２の復調器２−１１−１から出力される第２の復調信号は第２の誤り検出回路３−２に供給される。第１の誤り検出回路３−１は第１の復調信号の誤り量を検出し、第２の誤り検出回路３−２は第２の復調信号の誤り量を検出する。ここで、第１および第２の誤り検出回路３−１、３−２は、送信側で付加された誤り検出符号を用いて誤り検出を行う。ここで、誤り検出符号は、パリティ検査、ＣＲＣ（Ｃｙｃｌｉｃ Ｒｅｄｕｎｄａｎｃｙ Ｃｈｅｃｋ）符号等、一般的に誤り検出で用いられている符号でよく、特に限定されない。誤り検出では、誤り検出の対象となるブロック内の全ての復調信号が参照される必要がある。このため、第１および第２の誤り検出回路３−１、３−２において、ブロック内に誤りが存在するかどうかの判定が終了するまでの処理時間が生ずる。この処理時間に相当する遅延が第１および第２の判定遅延補正器３−３、３−４によりそれぞれ第１および第２の復調信号に対して与えられ、第１および第２の復調信号、第１および第２の誤り検出回路３−１、３−２の検出結果が、それぞれ同期して信号選択回路３−５に供給される。信号選択回路３−５は、第１および第２の誤り検出回路３−１、３−２の検出結果を参照して、第１番目の系統の第１および第２の復調信号から、より誤りの少ない復調信号を選択し、最終的な第１番目の系統の復調信号として出力する。誤りの量に差がない場合には、予め設定されたどちらか一方の復調信号を選択すればよい。なお、誤り量の検出が２段階である場合、すなわち誤りの有無のみ検出される場合は、正しく復調された復調信号が選択されることとなる。
【００９８】
以上のとおり、本実施形態では、乗算型干渉キャンセラ２−４の出力の復調結果である第１の復調信号と、減算型干渉キャンセラ２−９の出力の復調結果である第２の復調信号とのうち、より誤りの少ない復調信号を系統毎に選択する。これにより、本実施形態によれば、従来の乗算型干渉キャンセラの出力の復調結果を用いるＯＦＤＭ信号送受信装置や、常に減算型干渉キャンセラの出力の復調結果を用いるＯＦＤＭ信号送受信装置に対して、誤り率特性の向上を図ることができる。特に、乗算型干渉キャンセラ２−４の出力の復調結果と減算型干渉キャンセラ２−９の出力の復調結果とのどちらかが正しければ、そのパケットの受信は成功することになる。
【００９９】
なお、誤り率向上の観点より、送信装置側にＮ系統の送信信号それぞれを誤り訂正符号化する誤り訂正符号化手段を設け、受信装置側にＮ系統の第１および第２の復調信号それぞれを誤り訂正復号する第１および第２の復号手段を設けるとよい。
【０１００】
以下、本実施形態の効果を具体的に示す。なお、以下の例では、復調後に復号することとしている。
乗算型干渉キャンセラの出力の復号結果を用いる装置、常に減算型干渉キャンセラの出力の復号結果を用いる装置、および本実施形態に係る装置について、計算機シミュレーションにより得られたパケット誤り率特性を図３に示す。アンテナの本数は送受各２本であり、シミュレーション諸元は表１のとおりとする。図３において、実線は本実施形態に係る装置の特性を示し、点線は乗算型干渉キャンセラの出力の復号結果を用いる装置の特性を示し、破線は常に減算型干渉キャンセラの出力の復号結果を用いる装置の特性を示す。また、○印で表される特性は、変調方式が６４ＱＡＭであって符号化率がＲ＝３／４の場合のものであり、△印で表される特性は、変調方式がＱＰＳＫであって符号化率がＲ＝１／２の場合のものである。図３より、本実施形態によれば、６４ＱＡＭ，Ｒ＝３／４の場合、ＰＥＲ≦１０^−２を満たすために必要となるＣＮＲで比較して、従来の常に減算型干渉キャンセラの出力の復号結果を用いた場合に対しては１ｄＢの利得が得られ、乗算型干渉キャンセラの出力の復号結果を用いた場合に対しては２．５ｄＢの利得が得られていることが分かる。また、ＱＰＳＫ、Ｒ＝１／２の場合、減算型干渉キャンセラの出力の復号結果を用いた場合の特性は乗算型干渉キャンセラの出力の復号結果を用いた場合の特性よりも悪かったが、誤り検出により復号結果を選択することにより、特性が改善されていることが分かる。
【０１０１】
送信アンテナ１、送信アンテナ２の送信信号に対応する乗算型干渉キャンセラ出力の復号信号をｄ_１ ^ＩＭ、ｄ_２ ^ＩＭとし、送信アンテナ１、送信アンテナ２の送信信号に対応する減算型干渉キャンセラ出力の復号信号をｄ_１ ^Ｒｅ、ｄ_２ ^Ｒｅとする。また、復号信号に誤りがない場合を「ｏ」、ある場合を「ｘ」と表記する。そして、例えば、送信アンテナ１、２の送信信号に対応する乗算型干渉キャンセラ出力の復号信号がそれぞれ誤り「あり」、誤り「なし」であって、送信アンテナ１、２の送信信号に対応する減算型干渉キャンセラ出力の復号信号がそれぞれ誤り「なし」、誤り「あり」である場合を、（ｄ_１ ^ＩＭ ｄ_２ ^ＩＭ ｄ_１ ^Ｒｅ ｄ_２ ^Ｒｅ）＝（ｏ ｘｘ ｏ）と表記することとする。上記の表記方法に従い、計算機シミュレーションによる乗算型干渉キャンセラ出力の復号信号と減算型干渉キャンセラ出力の復号信号との誤り事象の関係を以下の表２に示す。シミュレーション回数は１０，０００回であり、サブキャリア変調方式はＱＰＳＫ、符号化率はＲ＝１／２である。また、表中の数字は当該事象が発生した回数を示す。
【０１０２】
【表２】

表２において、（ｄ_１ ^ＩＭ ｄ_２ ^ＩＭ）＝（ｏ ｏ）となる行、すなわち乗算型干渉キャンセラの出力の復号結果がすべて正しい事象に該当する行に着目すると、（ｄ_１ ^ＩＭ ｄ_２ ^ＩＭ ｄ_１ ^Ｒｅ ｄ_２ ^Ｒｅ）＝（ｏ ｏ ｏ ｘ），（ｏ ｏ ｘ ｏ），（ｏ ｏ ｘ ｘ）となる事象、すなわち乗算型干渉キャンセラの出力の復号結果はすべて正しいが、減算型干渉キャンセラの出力の復号結果に誤りが含まれる事象が２０２回存在する。これは、乗算型干渉キャンセラの出力の復号結果が正しく、サブキャリア再変調器の作成したレプリカが正しいにもかかわらず、減算型干渉キャンセラの出力の復号結果が誤りを含んでしまう場合が存在することを示している。このような誤りは、伝達係数の推定誤差により減算型干渉キャンセル後の重み付けに誤差が生じていることによるものと考えられる。また、（ｄ_１ ^ＩＭｄ_２ ^ＩＭ）＝（ｏ ｏ）となる事象以外であって、乗算型干渉キャンセラの出力の復号結果よりも減算型干渉キャンセラの出力の復号結果の方が誤りの数が多い事象、すなわち（ｄ_１ ^ＩＭ ｄ_２ ^ＩＭ ｄ_１ ^Ｒｅ ｄ_２ ^Ｒｅ）＝（ｏ ｘ ｘ ｘ），（ｘ ｏ ｘ ｘ）となる事象は７回存在する。以上より、減算型干渉キャンセラを利用することにより、乗算型干渉キャンセラによって正しく復号された信号を誤って復号してしまう事象は２０９回存在することが分かる。
【０１０３】
一方、（ｄ_１ ^Ｒｅ ｄ_２ ^Ｒｅ）＝（ｏ ｏ）となる列、すなわち減算型干渉キャンセラの出力の復号結果がすべて正しい列に注目すると、（ｄ_１ ^ＩＭ ｄ_２ ^ＩＭ ｄ_１ ^Ｒｅ ｄ_２ ^Ｒｅ）＝（ｏ ｘ ｏ ｏ），（ｘ ｏ ｏ ｏ），（ｘ ｘ ｏ ｏ）となる事象、すなわち乗算型干渉キャンセラ出力の復号結果は誤りを含んでいるが、減算型干渉キャンセラ出力の復号結果はすべて正しいという事象が１９１回存在する。これは、乗算型干渉キャンセラ出力の復号結果が誤っていて、サブキャリア再変調器の作成したレプリカが誤っているのにもかかわらず、減算型干渉キャンセラの出力の復号結果が正しくなる、すなわち、減算型干渉キャンセラにより誤りが修正された事象である。また、（ｄ_１ ^Ｒｅ ｄ_２ ^Ｒｅ）＝（ｏ ｏ）となる事象以外での、減算型干渉キャンセラ出力の復号結果を用いることにより乗算型干渉キャンセラ出力の復号結果の誤りを修正した事象、すなわち（ｄ_１ ^ＩＭ ｄ_２ ^ＩＭ ｄ_１ ^Ｒｅ ｄ_２ ^Ｒｅ）＝（ｘ ｘ ｏ ｘ），（ｘ ｘ ｘ ｏ）となる事象は６回存在する。以上から、減算型干渉キャンセラを利用することにより、最初に誤って復号された信号が正しく復号し直された事象は１９７回存在することが分かる。
【０１０４】
以上のとおり、減算型干渉キャンセラを利用することにより誤りが増加する事象の回数（２０９回）の方が、誤りが減少する事象の回数（１９７回）を上回る。したがって、上記のシミュレーションの条件下においては、減算型干渉キャンセラを追加しても、常にその復号結果のみを利用した場合はパケット誤り率特性が劣化してしまう。
【０１０５】
これに対して、本実施形態によれば、乗算型干渉キャンセラの出力の復号結果と減算型干渉キャンセラの出力の復号結果のうち、少なくとも一方が正しく復号されていれば誤り事象とはならない。すなわち、事象（ｄ_１ ^ＩＭ ｄ_２ ^ＩＭ ｄ_１ ^Ｒｅ ｄ_２ ^Ｒｅ）＝（ｏ ｏ ｏ ｏ），（ｏ ｏ ｘ ｏ），（ｏ ｏ ｏ ｘ），（ｏ ｏ ｘ ｘ），（ｘ ｘ ｏ ｏ），（ｘ ｏ ｏ ｏ），（ｏ ｘ ｏ ｏ），（ｏ ｘ ｘ ｏ），（ｘ ｏ ｏ ｘ）は、誤りがなく復号されたことになる。
【０１０６】
乗算型干渉キャンセラ出力の復号結果が誤っていた場合において、減算型干渉キャンセルと誤り検出および復号結果の選択を行うことにより復号結果が正しくなる事象は、（ｄ_１ ^ＩＭ ｄ_２ ^ＩＭ ｄ_１ ^Ｒｅ ｄ_２ ^Ｒｅ）＝（ｘ ｘ ｏ ｏ），（ｘ ｏｏ ｏ），（ｏ ｘ ｏ ｏ），（ｏ ｘ ｘ ｏ），（ｘ ｏ ｏ ｘ）の５通りある。これらの事象は、上記のシミュレーションでは２０９回存在する。本実施形態によれば、これらの事象においては、パケット誤りを防ぐことが可能となる。したがって、本実施形態によるパケット誤り率特性の改善効果は非常に大きいといえる。
【０１０７】
（第２の実施形態）
本実施形態に係るＯＦＤＭ信号送受信装置は、第１の実施形態に係るＯＦＤＭ信号送受信装置とほとんど同じであるが、乗算型干渉キャンセル後のＮ系統の復号信号について誤り位置の検出を行い、Ｎ系統すべて正しく復号されたサブキャリアについては減算型干渉キャンセルおよび重み付け合成を行い、少なくとも１系統に誤りを含むサブキャリアについては乗算型干渉キャンセル後の出力信号を用いることを特徴とするものである。以下、図面を用いて本実施形態について説明するが、第１の実施形態と共通する部分については説明を省略する。
【０１０８】
本実施形態に係るＯＦＤＭ信号送受信装置は、ＯＦＤＭ信号送信装置４とＯＦＤＭ信号受信装置５とを備えている。
図４は、本実施形態に係るＯＦＤＭ信号送信装置４の構成を示すブロック図である。図４において、ＯＦＤＭ信号送信装置４は、図１に示される第１の実施形態のＯＦＤＭ信号送信装置１に対し、Ｎ個の誤り訂正符号器４−７−１〜４−７−Ｎを追加した構成となっている。このＮ個の誤り訂正符号器４−７−１〜４−７−Ｎは、入力されたＮ系統の送信情報信号のそれぞれに対して誤り訂正符号化を行うものである。この点以外は、第１の実施形態のＯＦＤＭ信号送信装置１と同じなので説明を省略する。
【０１０９】
図５は、本実施形態に係るＯＦＤＭ信号受信装置５の構成を示すブロック図である。図５において、受信アンテナ５−１−１〜５−１−Ｎから第１の復調器５−６−１〜５−６−Ｎまでの構成および動作は、図１に示されるＯＦＤＭ信号受信装置２と同様なので説明を省略する。
【０１１０】
第１の復調器５−６−１〜５−６−Ｎから出力されるＮ系統の第１の復調信号は、各信号に対応するＮ個の第１の復号器５−７−１〜５−７−Ｎにより、誤り訂正復号される。Ｎ個の第１の復号器５−７−１〜５−７−Ｎから出力されるＮ系統の復号信号に対し、各信号に対応するＮ個の誤り検出器５−８−１〜５−８−Ｎは、誤り検出符号を用いて誤りの位置を検出する。Ｎ個の選択型再変調器５−９−１〜５−９−Ｎは、誤り検出器５−８−１〜５−８−Ｎにより検出された誤りの位置を参照してＮ系統すべて正しく復号されたサブキャリアを選択し、当該サブキャリアに対応する復号信号について送信時と同一のサブキャリア変調を行う。ここで、サブキャリア変調前の信号における誤りの位置が分かれば、サブキャリア変調後にどのサブキャリアの信号に誤りが含まれることになるかを特定することができる。
【０１１１】
減算型干渉キャンセラ５−１１は、選択型再変調器５−９−１〜５−９−ＮのＮ系統の出力信号と伝達係数行列とを用いて、選択されたサブキャリアについてサブキャリア毎に、第１の実施形態と同様に、高速フーリエ変換後のＮ系統の受信信号に含まれる相互干渉成分をキャンセルし、高速フーリエ変換後の各受信信号をＮ系統の各ＯＦＤＭ信号に対応する信号成分に分離する。
【０１１２】
なお、減算型干渉キャンセラ５−１１に入力される高速フーリエ変換後の受信信号は、Ｎ個の高速フーリエ変換器５−２−１〜５−２−Ｎの出力信号が受信信号遅延器５−１０−１〜５−１０−Ｎによって遅延させられたものである。ここで、受信信号遅延器５−１０−１〜５−１０−Ｎは、乗算型干渉キャンセラ５−４から選択型再変調器５−９−１〜５−９−Ｎまでの処理時間に相当する遅延を発生させる。
【０１１３】
重み付け合成器５−１２は、選択されたサブキャリア毎に、第１の実施形態と同様に、減算型干渉キャンセラ５−１１により分離された信号成分に対して伝達係数に基づく重み付けを行い、Ｎ系統の各ＯＦＤＭ信号に対応する信号成分同士を合成する。重み付け合成器５−１２のＮ系統の出力信号は、Ｎ個の重み付け器出力信号遅延器５−１３−１〜５−１３−Ｎによって遅延させられた重み付け器５−５−１〜５−５−ＮのＮ系統の出力信号とともに、Ｎ個の干渉キャンセル信号多重化器５−１４−１〜５−１４−Ｎに供給される。ここで、重み付け器出力信号遅延器５−１３−１〜５−１３−Ｎは、第１の復調器５−６−１〜５−６−Ｎから重み付け合成器５−１２の出力までの処理時間に相当する遅延時間を発生させる。干渉キャンセル信号多重化器５−１４−１〜５−１４−Ｎにおいて、重み付け合成器５−１２の出力が存在するサブキャリアについての当該重み付け合成器５−１２のＮ系統の出力信号と、重み付け合成器５−１２の出力が存在しないサブキャリアについての重み付け器出力信号遅延器５−１３−１〜５−１３−ＮのＮ系統の出力信号とが、多重化される。干渉キャンセル信号多重化器５−１４−１〜５−１４−ＮのＮ系統の出力信号は、各信号に対応するＮ個の第２の復調器５−１５−１〜５−１５−Ｎにより、復調される。すなわち、Ｎ個の重み付け器出力信号遅延器５−１３−１〜５−１３−Ｎと、Ｎ個の干渉キャンセル信号多重化器５−１４−１〜５−１４−Ｎと、Ｎ個の第２の復調器５−１５−１〜５−１５−Ｎとにより、選択型再変調器５−９−１〜５−９−Ｎによって選択されたサブキャリアについての重み付け合成器５−１２のＮ系統の出力信号と、選択されなかったサブキャリアについての重み付け器５−５−１〜５−５−ＮのＮ系統の出力信号とが、合成された後、復調される。第２の復調器５−１５−１〜５−１５−ＮのＮ系統の出力信号は、各信号に対応するＮ個の第２の復号器５−１６−１〜５−１６−Ｎによって、誤り訂正復号され、最終的なＮ系統の復号信号として出力される。
【０１１４】
なお、乗算型干渉キャンセラ５−４の出力に対する重み付けと、減算型干渉キャンセラ５−１１の出力に対する重み付けとでは、演算が異なるため、各重み付け出力にはレベル差が発生する。これに対しては、乗算型干渉キャンセル後の重み付け係数、すなわち（６）式における行列の成分における定数Ｃの値を適切な値にすることにより、レベル差を補正すればよい。
【０１１５】
減算型干渉キャンセルを行う従来のＯＦＤＭ信号送受信装置では、乗算型干渉キャンセラの出力の復号結果は、当該結果の誤りの有無にかかわらず、再変調され、送信信号のレプリカとして減算型干渉キャンセルに用いられていた。これに対し、本実施形態のＯＦＤＭ信号送受信装置では、上述のとおり、Ｎ系統すべて正しく復号されたサブキャリアに関しては、減算型干渉キャンセルおよび重み付け合成により、乗算型干渉キャンセルよりも高精度に干渉キャンセルおよび重み付けを行う。一方、Ｎ系統のうち少なくとも１系統が誤って復号されたサブキャリアに関しては、誤ったレプリカが減算型干渉キャンセルおよび重み付け合成に用いられ復号結果が誤ることを防ぐために、減算型干渉キャンセルおよび重み付け合成を行わず、または、減算型干渉キャンセルおよび重み付け合成後の出力を用いずに乗算型干渉キャンセル後の出力を用いる。
【０１１６】
以上のとおり、本実施形態によれば、送信信号のレプリカがすべて正しく生成されたサブキャリアについては、減算型干渉キャンセルを行うことによって、より精度の高い干渉キャンセルおよび重み付け合成を行うことができる。一方、レプリカが正しく生成されなかったサブキャリアについては、誤ったレプリカを用いた減算型干渉キャンセラ出力を用いるのではなく乗算型干渉キャンセラ出力を利用することによって、誤ったレプリカを用いた減算型干渉キャンセルの出力が最終的な復号信号に含まれることを防止でき、信頼度の低い信号が含まれることを防ぐことができる。この結果、誤り率特性の向上を図ることができる。
【０１１７】
（第３の実施形態）
本実施形態に係るＯＦＤＭ信号送受信装置は、第１の実施形態に係るＯＦＤＭ信号送受信装置とほとんど同じであるが、繰り返し減算型干渉キャンセルおよび重み付け合成を行い、Ｎ系統の第１の復調信号および複数のＮ系統の第２の復調信号から、より誤りの少ない復調信号を系統毎に選択することを特徴とするものである。以下、図面を用いて本実施形態について説明するが、第１の実施形態と共通する部分については説明を省略する。
【０１１８】
本実施形態に係るＯＦＤＭ信号送受信装置は、第１の実施形態と同一のＯＦＤＭ信号送信装置１とＯＦＤＭ信号受信装置６とを備えている。
図６は、本実施形態に係るＯＦＤＭ信号受信装置６の構成を示すブロック図である。図６において、受信アンテナ６−１−１〜６−１−Ｎから第１の復調器６−６−１〜６−６−Ｎまでの構成および動作は、図１に示されるＯＦＤＭ信号受信装置２と同様なので説明を省略する。
【０１１９】
ＯＦＤＭ信号受信装置６は、それぞれ第１の実施形態と同様のサブキャリア再変調、減算型干渉キャンセル、重み付け合成、および復調を行う複数段（本実施形態ではＢ段とする）の減算型干渉キャンセル後復調器６−８−１〜６−８−Ｂを備え、これらによって、Ｎ系統の第１の復調信号をもとに繰り返し減算型干渉キャンセル等を行い複数の第２の復調信号を出力する。言い換えると、減算型干渉キャンセルおよび重み付け合成後の出力の復調結果を送信信号のレプリカとみなして、さらに減算型干渉キャンセルおよび重み付け合成を行う、という動作を複数回繰り返す。
【０１２０】
第１段目の減算型干渉キャンセル後復調器６−８−１の演算においては、乗算型干渉キャンセル出力の復調結果であるＮ個の第１の復調器６−６−１〜６−６−Ｎの出力信号、すなわちＮ系統の第１の復調信号を送信信号のレプリカとして用いる。第２段目以降、第ｂ段目（２≦ｂ≦Ｂ）の減算型干渉キャンセル後復調器６−８−ｂの演算においては、前段である第（ｂ−１）段目の減算型干渉キャンセル後復調器６−８−（ｂ−１）によって出力される第２の復調信号を送信信号のレプリカとして用いる。この演算を（ｂ−１）段行うことにより、合計でＢ回のサブキャリア再変調、減算型干渉キャンセル、重み付け合成、復調を繰り返す。
【０１２１】
ここで、第１段目の減算型干渉キャンセル後復調器６−８−１が演算を行うためには、第１の復調器６−６−１〜６−６−Ｎの処理が終了している必要がある。そこで、第１段目の減算型干渉キャンセル後復調器６−８−１に対しては、第１段目の受信信号遅延器６−７−１−１〜６−７−１−Ｎによって、乗算型干渉キャンセラ６−４、重み付け器６−５−１〜６−５−Ｎ、第１の復調器６−６−１〜６−６−Ｎにおける演算に必要となる時間と同じ遅延量を与えてから、Ｎ個の高速フーリエ変換器６−２−１〜６−２−Ｎの出力信号を供給する。また、第ｂ（２≦ｂ≦Ｂ）段目の減算型干渉キャンセル後復調器６−８−ｂが演算を行うためには、第（ｂ−１）段目の減算型干渉キャンセル後復調器６−８−（ｂ−１）の演算が終了している必要がある。そこで、高速フーリエ変換器６−２−１〜６−２−Ｎの出力信号に対し、Ｂ段のＮ個の受信信号遅延器６−７−１−１〜６−７−１−Ｎ、…、６−７−Ｂ−１〜６−７−Ｂ−Ｎにより遅延を与えてタイミング同期を取ることとしている。第ｂ段目のＮ個の受信信号遅延器６−７−ｂ−１〜６−７−ｂ−Ｎは、Ｎ個の高速フーリエ変換器６−２−１〜６−２−Ｎの出力信号を第ｂ段目の減算型干渉キャンセル後復調器６−８−ｂに同期させるものである。そして、第ｂ（２≦ｂ≦Ｂ）段目の減算型干渉キャンセル後復調器６−８−ｂに対しては、第ｂ段目のＮ個の受信信号遅延器６−７−ｂ−１〜６−７−ｂ−Ｎによって、第（ｂ−１）段目の減算型干渉キャンセル後復調器６−８−（ｂ−１）の処理時間に相当する遅延を与えてから、第（ｂ−１）段目のＮ個の受信信号遅延器６−７−（ｂ−１）−１〜６−７−（ｂ−１）−Ｎの出力信号を供給する。これにより、高速フーリエ変換器６−２−１〜６−２−Ｎの出力信号を第ｂ段目の減算型干渉キャンセル後復調器６−８−ｂに同期させることができる。以上に述べた遅延線構造を用いることにより、Ｎ系統の受信信号を連続して処理する場合において各減算型干渉キャンセル後復調器６−８−１〜６−８−Ｂ毎にパイプライン処理を行うことが可能となり、回路規模を削減することができる。
【０１２２】
以上のとおり、減算型干渉キャンセル、重み付け合成、および復調を繰り返すことにより、送信信号のレプリカに含まれる誤りビットの数が徐々に減少し、後段になればなるほどより品質の高い、すなわち誤りの少ない復調結果が得られることを期待できる。しかし、「発明が解決しようとする課題」の欄で述べたとおり、伝達係数行列の推定誤差が大きな場合は、必ずしも減算型干渉キャンセルの繰り返しがレプリカの精度向上に寄与するとは限らない。そこで、第１の実施形態と同様に、１個のＮ系統の第１の復調信号とＢ個のＮ系統の第２の復調信号との合計（Ｂ＋１）個のＮ系統の復調信号を復調出力選択回路６−１１−１〜６−１１−Ｎに供給して、（Ｂ＋１）個の復調信号の中から、最も誤りの少ない復調信号を系統毎に選択して最終的なＮ系統の復調信号として出力する。
【０１２３】
以下、減算型干渉キャンセル後復調器６−８−ｂ（１≦ｂ≦Ｂ）および復調出力選択回路６−１１−ｎ（１≦ｎ≦Ｎ）について、より詳しく説明する。
図７は、第ｂ段目の減算型干渉キャンセル後復調器６−８−ｂ（１≦ｂ≦Ｂ）の構成を示すブロック図である。図７において、Ｎ個の第１の復調器６−６−１〜６−６−Ｎが出力するＮ系統の第１の復調信号（ｂ＝１のとき）または前段の減算型干渉キャンセル後復調器６−８−（ｂ−１）が出力するＮ系統の第２の復調信号は、各信号に対応するＮ個のサブキャリア再変調器６−８−ｂ−１−１〜６−８−ｂ−１−Ｎにより、送信時と同一の変調方式でサブキャリア変調される。減算型干渉キャンセラ６−８−ｂ−２は、第１の実施形態と同様に、Ｎ個のサブキャリア再変調器６−８−ｂ−１−１〜６−８−ｂ−１−ＮのＮ系統の出力信号と伝達係数行列演算器６−３の出力する伝達係数行列を用いて、サブキャリア毎に、Ｎ個の受信信号遅延器６−７−ｂ−１〜６−７−ｂ−Ｎから供給されるＮ系統の高速フーリエ変換後の受信信号に含まれる相互干渉成分をキャンセルし、高速フーリエ変換後の各受信信号をＯＦＤＭ信号の各系統に対応する信号成分に分離する。重み付け合成器６−８−ｂ−３は、第１の実施形態と同様に、減算型干渉キャンセラ６−８−ｂ−２により分離された信号成分に対して、サブキャリア毎に、伝達係数行列演算器６−３からの伝達係数に基づく重み付けを行い、所望信号成分同士を合成する。この重み付け合成器６−８−ｂ−３から出力されるＮ系統の出力信号は、各信号に対応するＮ個の第２の復調器６−８−ｂ−４−１〜６−８−ｂ−４−Ｎにより、復調され、Ｎ系統の第２の復調信号として出力される。
【０１２４】
つぎに、ＯＦＤＭ信号の第ｎ番目の系統に対応する復調出力選択回路６−１１−ｎ（１≦ｎ≦Ｎ）について説明する。図６において、ＯＦＤＭ信号受信装置６は、ＯＦＤＭ信号の系統毎に復調信号を選択するため、Ｎ個の復調出力選択回路６−１１−１〜６−１１−Ｎを備えている。第ｎ番目の系統の復調出力を選択するための復調出力選択回路６−１１−ｎには、第ｎ番目の系統の第１の復調信号および複数（本実施形態ではＢ個）の第２の復調信号が供給される。ここで、第１の復調信号は、復調信号同士の同期をとるため、乗算型復調結果遅延器６−９−ｎにより、最終段（第Ｂ段目）の減算型干渉キャンセル後復調器６−８−Ｂの第２の復調信号が出力されるまで遅延させられる。また、第ｂ段目（１≦ｂ≦（ｂ−１））の減算型干渉キャンセル後復調器６−８−ｂが出力する第ｎ番目の系統の第２の復調信号は、復調信号同士の同期をとるため、減算型復調結果遅延器６−１０−ｂ−ｎにより、最終段の減算型干渉キャンセル後復調器６−８−Ｂの第２の復調信号が出力されるまで遅延させられる。なお、最終段の減算型干渉キャンセル後復調器６−８−Ｂが出力する第２の復調信号については、遅延器は設けられていない。
【０１２５】
図８は、復調出力選択回路６−１１−ｎ（１≦ｎ≦Ｎ）の構成を示すブロック図である。図８において、（Ｂ＋１）個の誤り検出器６−１１−ｎ−１−１〜６−１１−ｎ−１−（Ｂ＋１）は、（Ｂ＋１）個の復調信号に対応しており、各誤り検出器６−１１−ｎ−ｍ（１≦ｍ≦（Ｂ＋１））は、対応する復調信号の誤り量を検出する。（Ｂ＋１）個の判定遅延補正器６−１１−ｎ−２−１〜６−１１−ｎ−２−（Ｂ＋１）は、（Ｂ＋１）個の復調信号に対応している。各判定遅延補正器６−１１−ｎ−２−ｍ（１≦ｍ≦（Ｂ＋１））は、対応する復調信号に対して各誤り検出器６−１１−ｎ−ｍの処理時間に相当する遅延を与え、復調信号をセレクタ６−１１−ｎ−３に供給する。セレクタ６−１１−ｎ−３は、（Ｂ＋１）個の誤り検出器６−１１−ｎ−１−１〜６−１１−ｎ−１−（Ｂ＋１）からの検出結果を参照して、（Ｂ＋１）個の復調信号の中から、最も誤りの少ない復調信号を選択して、第ｎ番目の系統の最終的な復調信号として出力する。
【０１２６】
以上のとおり、本実施形態では、Ｎ系統の第１の復調信号とＢ個のＮ系統の第２の復調信号との合計（Ｂ＋１）個のＮ系統の復調信号の中から、最も誤りの少ない復調信号を系統毎に選択して最終的な１個のＮ系統の復調信号として出力するので、誤り率特性の向上を図ることができる。特に、複数の復調信号の中から最も誤りの少ない復調信号を選択するので、伝達係数行列の推定精度が低いことに起因する減算型干渉キャンセルおよび重み付け合成の繰り返しによる誤りの増加を回避することができる。
【０１２７】
（第４の実施形態）
本実施形態に係るＯＦＤＭ信号送受信装置は、第２の実施形態に係るＯＦＤＭ信号送受信装置とほとんど同じであるが、誤り検出、選択型再変調、減算型干渉キャンセル、重み付け合成、復調、復号からなるサイクルを複数回繰り返すことを特徴とするものである。以下、図面を用いて本実施形態について説明するが、第１または第２の実施形態と共通する部分については説明を省略する。
【０１２８】
本実施形態に係るＯＦＤＭ信号送受信装置は、第２の実施形態と同一のＯＦＤＭ信号送信装置４とＯＦＤＭ信号受信装置７とを備えている。
図９は、本実施形態に係るＯＦＤＭ信号受信装置７の構成を示すブロック図である。図９において、受信アンテナ７−１−１〜７−１−Ｎから第１の復号手段７−７−１〜７−７−Ｎまでの構成および動作は、図５に示されるＯＦＤＭ信号受信装置５と同様なので説明を省略する。
【０１２９】
ＯＦＤＭ信号受信装置７は、それぞれ第２の実施形態と同様の誤り検出、選択型再変調、減算型干渉キャンセル、重み付け合成、復調、および復号を行う複数段（本実施形態ではＢ段とする）の減算型干渉キャンセル後復号器７−８−１〜７−８−Ｂを備え、これらによって、Ｎ系統の第１の復号信号をもとに繰り返し減算型干渉キャンセル等を行いＮ系統の最終復号信号を出力する。ここで、減算型干渉キャンセル後復号器７−８−１〜７−８−Ｂの個数、すなわち減算型干渉キャンセル等の繰り返し回数Ｂは、回路規模の観点より、所望の品質が得られる最小限の数であることが望ましい。
【０１３０】
第１段目の減算型干渉キャンセル後復号器７−８−１は、乗算型干渉キャンセル後の復号結果であるＮ個の第１の復号器７−７−１〜７−７−Ｎの出力信号、すなわちＮ系統の第１の復号信号を用いて演算する。また、第２段目以降、第ｂ段目（２≦ｂ≦Ｂ）の減算型干渉キャンセル後復号器７−８−ｂは、前段である第（ｂ−１）段目の減算型干渉キャンセル後復号器７−８−（ｂ−１）によって出力される第２の復号信号を用いて演算する。
【０１３１】
ここで、第１段目の減算型干渉キャンセル後復号器７−８−１が演算を行うためには、第１の復号器７−７−１〜７−７−Ｎの処理が終了している必要がある。そこで、第１段目の減算型干渉キャンセル後復号器７−８−１に対しては、受信信号遅延器７−９−１−１〜７−９−１−Ｎによって、乗算型干渉キャンセラ７−４、重み付け器７−５−１〜７−５−Ｎ、第１の復調器７−６−１〜７−６−Ｎ、第１の復号器７−７−１〜７−７−Ｎにおける演算に必要となる時間と同じ遅延量を与えてから、Ｎ個の高速フーリエ変換器７−２−１〜７−２−Ｎの出力信号を供給する。また、第ｂ（２≦ｂ≦Ｂ）段目の減算型干渉キャンセル後復号器７−８−ｂが演算を行うためには、第（ｂ−１）段目の減算型干渉キャンセル後復号器７−８−（ｂ−１）の演算が終了している必要がある。そこで、高速フーリエ変換器７−２−１〜７−２−Ｎの出力信号に対し、Ｂ段のＮ個の受信信号遅延器７−９−１−１〜７−９−１−Ｎ、…、７−９−Ｂ−１〜７−９−Ｂ−Ｎにより遅延を与えてタイミング同期を取ることとしている。第ｂ段目のＮ個の受信信号遅延器７−９−ｂ−１〜７−９−ｂ−Ｎは、Ｎ個の高速フーリエ変換器７−２−１〜７−２−Ｎの出力信号を第ｂ段目の減算型干渉キャンセル後復号器７−８−ｂに同期させるものである。そして、第ｂ段目の減算型干渉キャンセル後復号器７−８−ｂに対しては、第ｂ段目のＮ個の受信信号遅延器７−９−ｂ−１〜７−９−ｂ−Ｎによって、第（ｂ−１）段目の減算型干渉キャンセル後復号器７−８−（ｂ−１）の処理時間に相当する遅延を与えてから、第（ｂ−１）段目の受信信号遅延器７−９−（ｂ−１）−１〜７−９−（ｂ−１）−Ｎの出力信号を供給する。これにより、高速フーリエ変換器７−２−１〜７−２−Ｎの出力信号を第ｂ段目の減算型干渉キャンセル後復号器７−８−ｂに同期させることができる。
【０１３２】
また、本実施形態では、第２の実施形態と同様に、Ｎ系統すべて正しく復号されたサブキャリア以外のサブキャリアについては、Ｎ個の重み付け器７−５−１〜７−５−ＮのＮ系統の出力信号を用いる。したがって、このＮ個の重み付け器７−５−１〜７−５−ＮのＮ系統の出力信号に対しても遅延を与える必要がある。そこで、第１段目の減算型干渉キャンセル後復号器７−８−１に対しては、第１段目の重み付け器出力信号遅延器７−１０−１−１〜７−１０−１−Ｎによって、第１の復調器７−６−１〜７−６−Ｎ、第１の復号器７−７−１〜７−７−Ｎにおける演算に必要となる時間と同じ遅延量を与えてから、Ｎ個の重み付け器７−５−１〜７−５−Ｎの出力信号を供給する。第２段目以降の第ｂ（２≦ｂ≦Ｂ）段目の減算型干渉キャンセル後復号器７−８−ｂについては次のとおりとする。第ｂ段目のＮ個の重み付け器出力信号遅延器７−１０−ｂ−１〜７−１０−ｂ−Ｎは、Ｎ個の重み付け器７−５−１〜７−５−Ｎの出力信号を第ｂ段目の減算型干渉キャンセル後復号器７−８−ｂに同期させるものである。そして、第ｂ（２≦ｂ≦Ｂ）段目の減算型干渉キャンセル後復号器７−８−ｂに対しては、第ｂ段目のＮ個の重み付け器出力信号遅延器７−１０−ｂ−１〜７−１０−ｂ−Ｎによって、第（ｂ−１）段目の減算型干渉キャンセル後復号器７−８−（ｂ−１）の処理時間に相当する遅延を与えてから、第（ｂ−１）段目のＮ個の重み付け器出力信号遅延器７−１０−（ｂ−１）−１〜７−１０−（ｂ−１）−Ｎの出力信号を供給する。これにより、重み付け器７−５−１〜７−５−Ｎの出力信号をそれぞれの減算型干渉キャンセル後復号器７−８−ｂに同期させることができる。
【０１３３】
以上に述べた遅延線構造を用いることにより、第３の実施形態と同様に、Ｎ系統の受信信号を連続して処理する場合において各減算型干渉キャンセル後復号器７−８−１〜７−８−Ｂ毎にパイプライン処理を行うことが可能となり、回路規模を削減することができる。
【０１３４】
以下、減算型干渉キャンセル後復号器７−８−ｂ（１≦ｂ≦Ｂ）について、より詳しく説明する。
図１０は、第ｂ段目の減算型干渉キャンセル後復号器７−８−ｂの構成を示すブロック図である。図１０において、Ｎ個の誤り検出器７−８−ｂ−１−１〜７−８−ｂ−１−Ｎは、Ｎ個の第１の復号器７−７−１〜７−７−Ｎが出力するＮ系統の第１の復号信号（ｂ＝１のとき）または前段の減算型干渉キャンセル後復号器７−８−（ｂ−１）が出力するＮ系統の第２の復号信号に対し、誤り検出符号を用いて誤りおよび誤りの位置を検出する。Ｎ個の選択型再変調器７−８−ｂ−２−１〜７−８−ｂ−２−Ｎは、第２の実施形態と同様に、誤り検出器７−８−ｂ−１−１〜７−８−ｂ−１−Ｎにより検出された誤りの位置を参照してＮ系統すべて正しく復号されたサブキャリアを選択し、当該サブキャリアに対応する復号信号について送信時と同一のサブキャリア変調を行う。減算型干渉キャンセラ７−８−ｂ−３は、選択型再変調器７−８−ｂ−２−１〜７−８−ｂ−２−ＮのＮ系統の出力信号と伝達係数行列とを用いて、選択されたサブキャリアについてサブキャリア毎に、受信信号遅延器７−９−ｂ−１〜７−９−ｂ−Ｎから供給される高速フーリエ変換後のＮ系統の受信信号に含まれる相互干渉成分をキャンセルし、高速フーリエ変換後の各受信信号をＯＦＤＭ信号の各系統に対応する信号成分に分離する。
【０１３５】
重み付け合成器７−８−ｂ−４は、選択されたサブキャリア毎に、減算型干渉キャンセラ７−８−ｂ−３により分離された信号成分に対して伝達係数に基づく重み付けを行い、ＯＦＤＭ信号の各系統に対応する信号成分同士を合成する。重み付け合成器７−８−ｂ−４のＮ系統の出力信号は、Ｎ個の乗算型干渉キャンセル信号遅延器７−１０−ｂ−１〜７−１０−ｂ−Ｎから供給されるＮ個の重み付け器８−５−１〜８−５−ＮのＮ系統の出力信号とともに、Ｎ個の干渉キャンセル信号多重化器７−８−ｂ−５−１〜７−８−ｂ−５−Ｎに供給される。干渉キャンセル信号多重化器７−８−ｂ−５−１〜７−８−ｂ−５−Ｎにおいて、重み付け合成器７−８−ｂ−４の出力が存在するサブキャリアについての当該重み付け合成器７−８−ｂ−４のＮ系統の出力信号と、重み付け合成器７−８−ｂ−４の出力が存在しないサブキャリアについての重み付け器出力信号遅延器７−１０−ｂ−１〜７−１０−ｂ−ＮのＮ系統の出力信号とが多重化される。干渉キャンセル信号多重化器７−８−ｂ−５−１〜７−８−ｂ−５−ＮのＮ系統の出力信号は、各信号に対応するＮ個の第２の復調器７−８−ｂ−６−１〜７−８−ｂ−６−Ｎにより復調され、ついで、第２の復号器７−８−ｂ−７−１〜７−８−ｂ−７−Ｎにより誤り訂正復号され、Ｎ系統の第２の復号信号として出力される。ここで、最終段の第２の復号器７−８−Ｂ−７−１〜７−８−Ｂ−７−Ｎは、Ｎ系統の第２の復号信号をＮ系統の最終復号信号として出力する。
【０１３６】
以上のとおり、本実施形態によれば、誤り検出、選択型再変調、減算型干渉キャンセル、重み付け合成、復調、および復号の操作を繰り返すことにより、より正確な減算型干渉キャンセルを行うことが可能となり、誤り率特性の向上を図ることができる。
【０１３７】
なお、本発明は、上記の各実施の形態に限定されないことは言うまでもない。
【０１３８】
【発明の効果】
第１、５、９の発明によれば、乗算型干渉キャンセル後のＮ系統の復調信号と、減算型干渉キャンセル後のＮ系統の復調信号とのうち、誤りの少ない復調信号を系統毎に選択するので、乗算型干渉キャンセル後の復調信号のみ、または、減算型干渉キャンセル後の復調信号のみを用いる場合に対して、誤り率特性の向上を図ることができる。
【０１３９】
第２、６、１０の発明によれば、乗算型干渉キャンセル後の復号信号がＮ系統すべて正しいサブキャリアについては、さらに減算型干渉キャンセルおよび重み付け合成を行うので、より精度の高い復号信号を得ることができる。一方、誤りを含むサブキャリアについては、乗算型干渉キャンセル後の信号を復号するので、誤った送信信号のレプリカを用いた減算型干渉キャンセルの出力が最終的な復号信号に含まれることを防止できる。この結果、誤り率特性の向上を図ることができる。
【０１４０】
第３、７、１１の発明によれば、乗算型干渉キャンセル後のＮ系統の復調信号および減算型干渉キャンセルを繰り返して得られる複数のＮ系統の復調信号の中から、最も誤りの少ない復調信号を系統毎に選択するので、減算型干渉キャンセルおよび重み付け合成を繰り返すことによる復号信号の精度向上を図りつつ、伝達係数行列の推定精度が低い場合に生じる繰り返しによる誤りの増加を回避することができる。この結果、誤り率特性の向上を図ることができる。
【０１４１】
第４、８、１２の発明によれば、復号信号がＮ系統すべて正しいサブキャリアについては、減算型干渉キャンセルおよび重み付け合成を繰り返し行うので、より精度の高い復号信号を得ることができる。一方、誤りを含むサブキャリアについては、乗算型干渉キャンセル後の信号を復号するので、誤った送信信号のレプリカを用いた減算型干渉キャンセルの出力が最終的な復号信号に含まれることを防止できる。この結果、誤り率特性の向上を図ることができる。
【図面の簡単な説明】
【図１】第１の実施形態に係るＯＦＤＭ信号送受信装置の構成を示すブロック図である。
【図２】第１の実施形態に係る復調信号選択回路２−１３−１の構成を示すブロック図である。
【図３】パケット誤り率特性を示す図である。
【図４】第２の実施形態に係るＯＦＤＭ信号送信装置の構成を示すブロック図である。
【図５】第２の実施形態に係るＯＦＤＭ信号受信装置の構成を示すブロック図である。
【図６】第３の実施形態に係るＯＦＤＭ信号受信装置の構成を示すブロック図である。
【図７】第３の実施形態に係る第ｂ段目の減算型干渉キャンセル後復調器６−８−ｂの構成を示す図である。
【図８】第３の実施形態に係る復調出力選択回路６−１１−ｎの構成を示す図である。
【図９】第４の実施形態に係るＯＦＤＭ信号受信装置の構成を示すブロック図である。
【図１０】第４の実施形態に係る第ｂ段目の減算型干渉キャンセル後復号器７−８−ｂの構成を示すブロック図である。
【図１１】従来のＯＦＤＭ信号送受信装置の構成を示すブロック図である。
【図１２】従来のＯＦＤＭ信号送受信装置に係る減算型干渉キャンセラおよび重み付け合成器の構成を示す図である。
【図１３】パケット誤り率特性を示す図である。
【符号の説明】
１ ＯＦＤＭ信号送信装置
１−１−１〜１−１−Ｎ 誤り検出符号多重化器
１−２−１〜１−２−Ｎ パイロット信号生成器
１−３−１〜１−３−Ｎ パイロット信号多重化器
１−４−１〜１−４−Ｎ サブキャリア変調器
１−５−１〜１−５−Ｎ 逆高速フーリエ変換器
１−６−１〜１−６−Ｎ 送信アンテナ
２ ＯＦＤＭ信号受信装置
２−１−１〜２−１−Ｎ 受信アンテナ
２−２−１〜２−２−Ｎ 高速フーリエ変換器
２−３ 伝達係数行列演算器
２−４ 乗算型干渉キャンセラ
２−５−１〜２−５−Ｎ 重み付け器
２−６−１〜２−６−Ｎ 第１の復調器
２−７−１〜２−７−Ｎ サブキャリア再変調器
２−８−１〜２−８−Ｎ 受信信号遅延器
２−９ 減算型干渉キャンセラ
２−１０ 重み付け合成器
２−１１−１〜２−１１−Ｎ 第２の復調器
２−１２−１〜２−１２−Ｎ 復調信号遅延器
２−１３−１〜２−１３−Ｎ 復調信号選択回路
３−１ 第１の誤り検出回路
３−２ 第２の誤り検出回路
３−３ 第１の判定遅延補正器
３−４ 第２の判定遅延補正器
３−５ 信号選択回路
４ ＯＦＤＭ信号送信装置
４−１−１〜４−１−Ｎ 検出符号多重化器
４−２−１〜４−２−Ｎ パイロット信号生成器
４−３−１〜４−３−Ｎ パイロット信号多重化器
４−４−１〜４−４−Ｎ サブキャリア変調器
４−５−１〜４−５−Ｎ 逆高速フーリエ変換器
４−６−１〜４−６−Ｎ 送信アンテナ
４−７−１〜４−７−Ｎ 誤り訂正符号化器
５ ＯＦＤＭ信号受信装置
５−１−１〜５−１−Ｎ 受信アンテナ
５−２−１〜５−２−Ｎ 高速フーリエ変換器
５−３ 伝達係数行列演算器
５−４ 乗算型干渉キャンセラ
５−５−１〜５−５−Ｎ 重み付け器
５−６−１〜５−６−Ｎ 第１の復調器
５−７−１〜５−７−Ｎ 第１の復号器
５−８−１〜５−８−Ｎ 誤り検出器
５−９−１〜５−９−Ｎ 選択型再変調器
５−１０−１〜５−１０−Ｎ 受信信号遅延器
５−１１ 減算型干渉キャンセラ
５−１２ 重み付け合成器
５−１３−１〜５−１３−Ｎ 重み付け器出力信号遅延器
５−１４−１〜５−１４−Ｎ 干渉キャンセル信号多重化器
５−１５−１〜５−１５−Ｎ 第２の復調器
５−１６−１〜５−１６−Ｎ 第２の復号器
６ ＯＦＤＭ信号受信装置
６−１−１〜６−１−Ｎ 受信アンテナ
６−２−１〜６−２−Ｎ 高速フーリエ変換器
６−３ 伝達係数行列演算器
６−４ 乗算型干渉キャンセラ
６−５−１〜６−５−Ｎ 重み付け器
６−６−１〜６−６−Ｎ 第１の復調器
６−７−１−（１〜Ｎ）〜６−７−Ｂ−（１〜Ｎ） 受信信号遅延器
６−８−１〜６−８−Ｂ 減算型干渉キャンセル後復調器
６−８−ｂ−１−１〜６−８−ｂ−１−Ｎ サブキャリア再変調器
６−８−ｂ−２ 減算型干渉キャンセラ
６−８−ｂ−３ 重み付け合成器
６−８−ｂ−４−１〜６−８−ｂ−４−Ｎ 第２の復調器
６−９−１〜６−９−Ｎ 乗算型復調結果遅延器
６−１０−１−（１〜Ｎ）〜６−１０−（ｂ−１）−（１〜Ｎ） 減算型復調結果遅延器
６−１１−１〜６−１１−Ｎ 復調出力選択回路
６−１１−ｎ−１−１〜６−１１−ｎ−１−（Ｂ＋１） 誤り検出器
６−１１−ｎ−２−１〜６−１１−ｎ−２−（Ｂ＋１） 判定遅延補正器
６−１１−ｎ−３ セレクタ
７ ＯＦＤＭ信号受信装置
７−１−１〜７−１−Ｎ 受信アンテナ
７−２−１〜７−２−Ｎ 高速フーリエ変換器
７−３ 伝達係数行列演算器
７−４ 乗算型干渉キャンセラ
７−５−１〜７−５−Ｎ 重み付け器
７−６−１〜７−６−Ｎ 第１の復調器
７−７−１〜７−７−Ｎ 第１の復号器
７−８−１〜７−８−Ｂ 減算型干渉キャンセル後復号器
７−８−ｂ−１−１〜７−８−ｂ−１−Ｎ 誤り検出器
７−８−ｂ−２−１〜７−８−ｂ−２−Ｎ 選択型再変調器
７−８−ｂ−３ 減算型干渉キャンセラ
７−８−ｂ−４ 重み付け合成器
７−８−ｂ−５−１〜７−８−ｂ−５−Ｎ 干渉キャンセル信号多重化器
７−８−ｂ−６−１〜７−８−ｂ−６−Ｎ 第２の復調器
７−８−ｂ−７−１〜７−８−ｂ−７−Ｎ 第２の復号器
７−９−１−（１〜Ｎ）〜７−９−Ｂ−（１〜Ｎ） 受信信号遅延器
７−１０−１−（１〜Ｎ）〜７−１０−Ｂ−（１〜Ｎ） 重み付け器出力信号遅延器[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an orthogonal frequency division multiplexing (OFDM) signal receiving apparatus, transmitting / receiving apparatus, and receiving method used in broadband mobile communication. In particular, the present invention relates to one that achieves high frequency use efficiency by using a plurality of transmitting antennas and a plurality of receiving antennas.
[0002]
[Prior art]
In broadband mobile communication, it is necessary to improve frequency utilization efficiency for achieving capacity increase using limited frequency resources, in addition to measures against frequency selective fading by multipath.
[0003]
As a countermeasure against frequency selective fading, a transmission signal is divided into subcarrier groups orthogonal to each other to generate a multicarrier signal, and a guard interval is inserted into a time signal, so that interference between adjacent symbols caused by a delayed wave is generated. An OFDM method for removing the noise is known and has been put to practical use in a wireless LAN or the like.
[0004]
On the other hand, as a measure for improving the frequency utilization efficiency, a multiple-input multiple-output (MIMO) channel is configured in the same frequency band using a plurality of transmission antennas and a plurality of reception antennas, and a plurality of transmission antennas are configured. A technique has been proposed in which a plurality of different systems of OFDM signals are transmitted to improve the frequency use efficiency by the number of transmission / reception antennas (for example, Non-Patent Document 1, Japanese Patent Application No. 2001-109679, Japanese Patent Application No. 2001-246408). reference). In this technique, transfer coefficients for all combinations of a transmission antenna and a reception antenna are estimated, and a plurality of inverse matrices of a transfer coefficient matrix (hereinafter, referred to as transfer coefficient inverse matrices) each having a transfer coefficient between antennas as an element. By multiplying the received signals of the systems, mutual interference components between the systems included in the received signals are canceled, and the transmitted OFDM signals of the plurality of systems are restored. Here, the inverse transfer coefficient matrix is calculated for each subcarrier based on the phase and amplitude of the known pilot signal and the received pilot signal included in the transmitted OFDM signal.
[0005]
However, in the method of performing interference cancellation by multiplication of an inverse transfer coefficient matrix, since the interference cancellation and the synthesis of the desired signal components included in the received signals of the respective receiving antennas are simultaneously performed, the weighting based on the reliability of each desired signal component is appropriate. Is not done. For this reason, there is a problem in that it is not possible to obtain diversity gain even though the signal is received by a plurality of receiving antennas. Therefore, first, a demodulated signal is generated by performing interference cancellation by multiplication of a transfer coefficient inverse matrix, and then a re-modulation is performed on the demodulated signal to generate a replica of the transmission signal, and interference of the received signal is generated using the replica. An interference canceller that obtains a diversity gain by canceling and separating each received signal into transmission signal components of each system, and performing weighting on the transmission signal components to combine the signals, has been proposed ( See Japanese Patent Application No. 2002-149013).
[0006]
FIG. 11 is a block diagram showing a configuration of an OFDM signal transmitting / receiving apparatus proposed in the above-mentioned Japanese Patent Application No. 2002-149013. In FIG. 11, the OFDM signal transmitting / receiving apparatus includes an OFDM signal transmitting apparatus 8 and an OFDM signal receiving apparatus 9.
[0007]
In the OFDM signal transmission device 8, the N transmitted (N is an integer of 2 or more) transmission information signals T₁, T₂, ... T_NAre respectively input to the pilot signal multiplexers 8-2-1 to 8-2-N. In the pilot signal multiplexers 8-2-1 to 8-2-N, transmission information signals of each system and known pilot signals input from the pilot signal generators 8-1-1 to 8-1-N are provided. Are multiplexed on the time axis. These multiplexed N-system signals are respectively modulated by subcarrier modulators 8-3-1 to 8-3-N, and converted into frequency domain transmission signals including a plurality of subcarrier signals. The transmission signal is input to inverse fast Fourier transformers 8-4-1 to 8-4-N, subjected to inverse fast Fourier transform, and converted into a time-domain transmission signal. The transmission signal in the time domain is input to each of the transmission antennas 8-5-1 to 8-5-N and transmitted to the OFDM signal receiving device 9.
[0008]
In the OFDM signal receiving device 9, a signal obtained by multiplexing in space N transmission signals of N systems transmitted from N transmission antennas 8-5-1 to 8-5-N is used for each of the N reception antennas 9-5-1. 1-1 to 9-1-N. Here, since each receiving antenna simultaneously receives transmission signals from a plurality of transmitting antennas, the received signal of each receiving antenna includes a mutual interference component between systems. The received signals received by each of the receiving antennas 9-1-1 to 9-1-N are subjected to fast Fourier transform in each of the fast Fourier transformers 9-2-1 to 9-2-N, and a plurality of signals are obtained from the signals in the time domain. Is converted into a frequency-domain received signal composed of The transfer coefficient matrix calculator 9-3 uses the pilot signal included in the output signal of each of the fast Fourier transformers 9-2-1 to 9-2-N and a known pilot signal to generate a transmission signal. An inverse transfer coefficient matrix for each subcarrier is estimated by a method described in 109679 or Japanese Patent Application No. 2001-246408. The multiplication type interference canceller 9-4 multiplies the output signals of the fast Fourier transformers 9-2-1 to 9-2-N by the inverse transfer coefficient matrix for each subcarrier to be included in the received signal. Cancel the mutual interference component. The output signal of the multiplication type interference canceller 9-4 is subjected to weighting based on the transfer coefficient by the weighting devices 9-5-1 to 9-5-N according to the method described in Non-Patent Document 1, and then to the first signal. Are demodulated by the demodulators 9-6-1 to 9-6-N.
[0009]
Hereinafter, multiplication type interference cancellation and weighting will be described. Here, the signal transmitted by subcarrier i of the j-th transmitting antenna is represented by tⁱ _jAnd the transmission signal of N systems transmitted by subcarrier i is represented by vector tⁱ= (Tⁱ ₁  tⁱ ₂... tⁱ _N). The received signal for the subcarrier i in the received signal after the fast Fourier transform of the k-th receiving antenna is represented by rⁱ _kAnd N received signals for subcarrier i are represented by vector rⁱ= (Rⁱ ₁  rⁱ ₂... rⁱ _N). The transfer coefficient matrix for the subcarrier i estimated by the transfer coefficient matrix calculator 9-3 is a matrix H expressed by the following equation (1).ⁱAnd
[0010]
(Equation 1)

[0011]
Where h in equation (1)ⁱ _{j, k}Is the transfer coefficient for subcarrier i between the j-th transmitting antenna and the k-th receiving antenna. The thermal noise added to subcarrier i of the k-th receiving antenna is represented by nⁱ _k, The N thermal noises for subcarrier i are taken as vector nⁱ= (Nⁱ ₁  nⁱ ₂... nⁱ _N), The relationship between the transmission signal and the reception signal is expressed by the following equation (2).
[0012]
(Equation 2)

[0013]
Transfer coefficient matrix HⁱTransfer matrix inverse matrix (Hⁱ)^-1Is estimated by the transfer coefficient matrix calculator 9-3 without error, the multiplication type interference canceller 9-4 receives the N-system received signals r of the subcarrier i.ⁱTo the inverse transfer coefficient matrix (Hⁱ)^-1Multiplication type interference canceller output signal uⁱ(= (Uⁱ ₁  uⁱ ₂... uⁱ _N)) Is represented by the following equation (3). Where uⁱ _kIs the signal t transmitted by subcarrier i of the kth transmit antennaⁱ _kIs a signal after multiplication-type interference cancellation corresponding to.
[0014]
(Equation 3)

[0015]
For example, when N = 2, the multiplication type interference canceller output signal uⁱIs represented by the following (Equation 4).
[0016]
(Equation 4)

[0017]
Since the signal after the multiplication-type interference cancellation is multiplied by the inverse characteristic of the communication channel and normalized, the reliability of the amplitude of the transmission signal between the systems and between the subcarriers is lost. Therefore, if error correction decoding is performed using this signal, it is not possible to make a determination based on the likelihood of the signal, so that good error rate characteristics cannot be obtained. Therefore, weighting units 9-5-1 to 9-5-N weight the multiplication interference canceller output signal from which the mutual interference component has been canceled based on the transfer coefficient using the method described in Non-Patent Document 1. I do. Multiplied interference canceller output signal u ′ after weightingⁱAnd a matrix Y for weightingⁱIs represented by the equations (5) and (6), respectively.
[0018]
(Equation 5)

[0019]
(Equation 6)

[0020]
Here, in Equation (6), C is a constant common to all subcarriers, and h ′ⁱ _{j, k}Is the inverse transfer coefficient matrix (Hⁱ)^-1Of k rows and j columns (1 ≦ k ≦ N, 1 ≦ j ≦ N).
[0021]
The average value of the signal-to-noise power ratio after the multiplication-type interference cancellation, that is, the average SNR (Signal to Noise power Ratio), will be described with an example of N = 2. Four transfer coefficients hⁱ _{m, n}(M = 1,2, n = 1,2) are statistically independent, their phases are uniformly distributed, and their amplitudes are Rayleigh distributions and the average value is | h |. Also, two additive white Gaussian noise (AWGN) components nⁱ ₁, Nⁱ ₂Are statistically independent, and σ_v ²Is assumed to follow a complex Gaussian distribution having a variance value. Under this condition, the multiplication type subcarrier interference canceller output signal uⁱ ₁Is represented by the following equation.
[0022]
(Equation 7)

[0023]
Multiplication type interference canceller output signal uⁱ ₂Is also expressed by the following formula by the same calculation.
[0024]
(Equation 8)

[0025]
On the other hand, when considering an OFDM transmission / reception apparatus using one transmission antenna and one reception antenna, the reception signal r after the fast Fourier transform of the i-th subcarrier is considered.ⁱIs the transmission signal t before the inverse fast Fourier transformⁱ, The transfer coefficient h between the transmitting and receiving antennasⁱ, And the AWGN component nⁱIs represented by the following equation.
[0026]
(Equation 9)

[0027]
At this time, the received signal r after the fast Fourier transformⁱIs represented by the following equation.
[0028]
(Equation 10)

[0029]
From Equation 7 (or Equation 8) and Equation 10, the average transmission power per antenna (| tⁱ ₁|²) Are the same, it can be seen that the average SNR of the received signal is the same when comparing the case of one transmission antenna and the case of two transmission antennas. That is, it can be seen that in the multiplication type interference cancellation using the inverse transfer coefficient matrix, a gain due to diversity cannot be obtained even though the transmission signal is received by two reception antennas.
[0030]
Therefore, in order to obtain a gain by diversity, the OFDM signal transmitting / receiving apparatus described in Japanese Patent Application No. 2002-149013 generates a replica of a transmission signal from a multiplication type interference canceller output signal, and uses the replica to generate a mutual interference component between systems. Is generated, and the received signal after fast Fourier transform is separated into components corresponding to each system of the transmission signal by subtracting the replica from the received signal, and weighting based on the transfer coefficient is applied to each component. After that, components corresponding to each system of the transmission signal are combined.
[0031]
Hereinafter, the subtraction-type interference cancellation and the weighting combination will be described with reference to FIG. In FIG. 11, the subcarrier re-modulators 9-7-1 to 9-7-N use the same modulation scheme as the subcarrier modulators 8-3-1 to 8-3-N on the transmitting side to perform the first modulation. The first demodulated signals output from the demodulators 9-6-1 to 9-6-N are re-modulated. The subtraction type interference canceller 9-9 uses the output signals of the subcarrier re-modulators 9-7-1 to 9-7-N and the transfer coefficient matrix for each subcarrier output by the transfer coefficient matrix calculator 9-3. Then, a mutual interference component included in the received signal after the fast Fourier transform is removed, and each received signal after the fast Fourier transform is separated into signal components corresponding to each system of the transmission signal. Note that the reception signals after the fast Fourier transform input to the subtraction type interference canceller 9-9 are the output signals of the N fast Fourier transformers 9-2-1 to 9-2-N. 8-1 to 9-8-N. Here, the reception signal delay units 9-8-1 to 9-8-N correspond to the processing time from the multiplication type interference canceller 9-4 to the subcarrier remodulators 9-7-1 to 9-7-N. Cause a delay. The weighting combiner 9-10 weights and combines the signal components separated by the subtraction interference canceller 9-9. The second demodulators 9-11-1 to 9-11-N demodulate the output signals of the weighting combiners 9-10 and output the final N-system demodulated signals.
[0032]
FIG. 12 is a block diagram showing a configuration of the subtraction type interference canceller 9-9 and the weighting combiner 9-10. Focusing on the i-th subcarrier, in the subtraction-type interference canceller 9-9 in FIG. 12, the reception signal matrix calculator 9-9-1 includes reception signal delayers 9-8-1 to 9-8-N. From the output received signal after the fast Fourier transform, a received signal matrix Rⁱ
[0033]
(Equation 11)

[0034]
Is calculated.
The remodulation signal matrix calculator 9-9-2 converts the output signals of the subcarrier remodulators 9-7-1 to 9-7-N from the remodulation signal matrix T '.ⁱ
[0035]
(Equation 12)

[0036]
Is calculated. The replica signal matrix calculator 9-9-3 outputs the remodulated signal matrix T ′ output from the remodulated signal matrix calculator 9-9-2.ⁱTransfer coefficient matrix H output from transfer coefficient matrix calculator 9-3ⁱAnd the replica signal matrix (T ′ⁱ・ Hⁱ) Is calculated. The replica subtractor 9-9-4 outputs the received signal matrix R output from the received signal matrix calculator 9-9-1 as shown in the following equation (13).ⁱFrom the replica signal matrix (T ′) output from the replica signal matrix calculatorⁱ・ Hⁱ) To obtain the signal matrix X after the replica subtraction.ⁱIs calculated.
[0037]
(Equation 13)

[0038]
Signal matrix X after replica subtractionⁱIs input to the weighting combiner 9-10 as the output of the subtraction type interference canceller 9-9.
In the weighting combiner 9-10, the signal matrix X after replica subtractionⁱTo perform weighting on the transfer coefficient matrix H output by the transfer coefficient matrix calculator 9-3 in the replica subtraction weight matrix calculator 9-10-1.ⁱWeighted matrix W after replica subtraction fromⁱIs calculated. In the weighting / combining arithmetic unit 9-10-2, the replica subtraction weight matrix W output from the replica subtraction weight matrix arithmetic unit 9-10-1 is output.ⁱAnd the signal matrix X after replica subtraction which is the output of the subtraction type interference canceller 9-9.ⁱFrom the weighted synthesized signal vⁱIs calculated. Where the row vector xⁱ _j(1 ≦ j ≦ N) and the column vector wⁱ _k ^TUsing (1 ≦ k ≦ N), the signal matrix X after replica subtractionⁱAnd replica subtraction weight matrix WⁱWith the following equations
[0039]
[Equation 14]

[0040]
, The weighted combined signal vⁱIs represented by the following equation.
[0041]
[Equation 15]

[0042]
Where the row vector xⁱ _jIs obtained from the equations (11) to (13) by the following equations.
[0043]
(Equation 16)

[0044]
here,
[0045]
[Equation 17]

[0046]
It is. Therefore, (xⁱ _j, Wⁱ _j) Is represented by the following equation.
[0047]
(Equation 18)

[0048]
Weighted synthesized signal vⁱIs expressed by the following equation using the equations (16) and (18).
[0049]
[Equation 19]

[0050]
Where the matrix GⁱIs the matrix (Hⁱ・ Wⁱ) And all diagonal components are the same, and all off-diagonal components are zero.
Hereinafter, the interference cancellation effect of the subtraction type interference canceller 9-9 and the weighted combined signal v which is the output signal of the weighted combiner 9-10 will be described.ⁱIs considered. Weight matrix W after replica subtraction in equation (19)ⁱTo
[0051]
(Equation 20)

[0052]
Then the matrix GⁱIs expressed as follows.
[0053]
(Equation 21)

[0054]
Here, signal t 'after remodulation by subcarrier remodulators 9-7-1 to 9-7-N.ⁱIs the transmission signal t before the inverse fast Fourier transformⁱAssuming that there is a perfect match, Equation (19) is expressed as follows.
[0055]
(Equation 22)

[0056]
Where nⁱ(= (Nⁱ ₁  nⁱ ₂... nⁱ _N)) Is the received signal r after the fast Fourier transform.ⁱIs an AWGN component contained in. From equation (22), the weighted and synthesized signal vⁱIt can be seen from FIG. 3 that the mutual interference component has been removed.
[0057]
Here, (N × N) transfer coefficients hⁱ _{m, n}(1 ≦ m ≦ N, 1 ≦ n ≦ N) are statistically independent of each other, their phases are uniformly distributed, and their amplitudes are Rayleigh distributions and the average value is | h |. Also, N AWGN components nⁱ _k(1 ≦ k ≦ N) are statistically independent, and σ_v ²Assume a complex Gaussian distribution with a variance of. Under this condition, the weighted combined signal vⁱ _kIs represented by the following equation.
[0058]
(Equation 23)

[0059]
From the above equation, the weighted combined signal vⁱ _kIn order for the average SNR to be the largest possible value,
[0060]
[Equation 24]

[0061]
It is necessary that this is,
[0062]
(Equation 25)

[0063]
It means that Matrix (Hⁱ)^{* T}Is the matrix HⁱIs the conjugate transpose of. At this time, equation (23) is expressed as follows.
[0064]
(Equation 26)

[0065]
Comparing the above equations (26) and (8), the replica subtraction weighting matrix WⁱAs a matrix (Hⁱ)^{* T}Is used, the weighted combined signal vⁱ _kIt can be understood that the average SNR of N is N times the average SNR of the received signal after the fast Fourier transform in the OFDM signal transmitting / receiving apparatus having one transmitting antenna and one receiving antenna. That is, in the OFDM signal transmission / reception apparatus of FIG. 11, a gain of (10 · logN) dB can be obtained by comparing the OFDM signal transmission / reception apparatus having one transmission antenna and one reception antenna with the average SNR. .
[0066]
[Non-patent document 1]
Kurosaki et al., "Proposal of SDM-COFDM System for Broadband Mobile Communication Realizing 100 Mbit / s by MIMO Channel," IEICE Technical Report, RCS 2001-135.
[0067]
[Problems to be solved by the invention]
In the above-mentioned conventional OFDM signal transmitting and receiving apparatus, each received signal is transmitted by remodulating the demodulated signal after the multiplication-type interference cancellation, generating a replica of the transmitted signal, and subtracting the replica from the received signal after the fast Fourier transform. The signal components are separated into signal components corresponding to the respective systems of the signal, and then the desired signal components are weighted and combined to obtain a diversity gain. In this case, assuming that the replica of the transmission signal is supplied to the subtraction-type interference canceller without error, the average SNR can be increased by the same number as the number of antennas. However, in practice, the replica of the transmission signal is a signal obtained by demodulating the signal that has been subjected to interference cancellation by multiplying the received signal after the fast Fourier transform by the inverse transfer coefficient matrix. Inclusion is inevitable. That is, the remodulated signal matrix T ′ represented by the equation (12)ⁱSome of the components of have an error.
[0068]
Hereinafter, the remodulated signal matrix T ′ⁱHere, the characteristic evaluation by computer simulation in the case where an error is included is shown. In this simulation, the number of antennas is two for transmission and reception, and error correction decoding is performed after demodulation. The simulation specifications are as shown in Table 1 below.
[0069]
[Table 1]

FIG. 13 is a diagram illustrating a packet error rate (PER) characteristic obtained as a result of the simulation. In FIG. 13, the broken line shows the PER characteristic when only the multiplication type interference canceller is used, and the solid line shows the PER characteristic when the subtraction type interference canceller is further added. In addition, the characteristics represented by ○ are those when the modulation method is 64 QAM and the coding rate is R = ３, and the characteristics represented by Δ are those when the modulation method is QPSK. This is for the case where the coding rate is R = 1/2. FIG. 13 shows that in the case of 64QAM and R = 3/4, the use of the subtraction type interference canceller can always obtain good characteristics, but the effect of improving the characteristics is about 1 dB. This effect is much smaller than the increase of the carrier-to-noise ratio (CNR) of 3 dB when the replica of the transmission signal is completely correctly generated. In addition, in the case of QPSK, R = す る と, the error rate characteristic deteriorates conversely when the subtraction type interference canceller is added. This is because subtractive interference cancellation is performed using an incorrect replica. Further, since the CNR is low, the estimation accuracy of the transfer coefficient is low, and as a result, the replica subtraction weighting matrix W calculated using the transfer coefficient is calculated.ⁱIs lower than that in the case of 64QAM having a high CNR and R = 3/4.
[0070]
As described above, even if the subtraction-type interference cancellation and the weighting synthesis are further performed after the multiplication-type interference cancellation, it is not always possible to obtain a better error rate characteristic than in the case of only the multiplication-type interference cancellation. Further, even when the effect of the subtraction type interference cancellation can be obtained, the obtained characteristic improvement effect is small.
[0071]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an OFDM signal receiving apparatus, an OFDM signal transmitting / receiving apparatus, and an OFDM signal receiving method capable of improving an error rate characteristic.
[0072]
[Means for Solving the Problems]
A first invention for solving the above-mentioned problems and achieving the object includes an error detection code and a known pilot signal, each of which is transmitted at the same frequency from N (N is an integer of 2 or more) transmission antennas. An OFDM signal receiving apparatus for receiving N systems of OFDM signals, comprising: N reception antennas for receiving signals obtained by spatially multiplexing the N systems of OFDM signals; and N reception antennas received by the N reception antennas. Fast Fourier transforming means for fast Fourier transforming each received signal of the system and converting it into a received signal for each subcarrier, and a pilot signal and the known pilot signal included in the received signals of the N systems after the fast Fourier transform. By using, for each subcarrier, a transfer coefficient matrix having a transfer coefficient between each transmitting antenna and each receiving antenna as an element and a transfer coefficient inverse matrix which is an inverse matrix thereof. And a transfer coefficient matrix calculating means for outputting, for each subcarrier, multiply the N-system received signal after the fast Fourier transform by the transfer coefficient inverse matrix, and include the N-system received signal after the fast Fourier transform. Interference canceling means for canceling mutual interference components between systems, and weighting means for weighting the output signals of the N systems of the multiplying interference cancellation means for each subcarrier in accordance with the transfer coefficient. The first demodulation means for demodulating each of the N-system output signals of the weighting means and outputting the N-system first demodulated signals; Using subcarrier remodulation means for performing subcarrier modulation of N, and output signals of N systems of the subcarrier remodulation means and the transfer coefficient matrix, for each subcarrier A replica of the mutual interference component between the systems is generated, and the replica is subtracted from the received signals of the N systems after the fast Fourier transform to cancel the mutual interference component between the systems included in each of the received signals. Subtraction-type interference cancellation means for separating a received signal into signal components corresponding to the respective systems of the OFDM signal; and for the signal components separated by the subtraction-type interference cancellation means, for each subcarrier, based on the transmission coefficient. Weighting / combining means for performing weighting and combining signal components corresponding to each system of the OFDM signal; and demodulating each of the N-system output signals of the weighting / combining means and outputting a second demodulated signal of N systems. Error detecting means for detecting an error amount of each of the first and second demodulated signals of the N systems by using a second demodulating means and the error detecting code; Means, and demodulated signal selecting means for selecting a demodulated signal having less error among the first and second demodulated signals of the N systems for each system based on a detection result of the error detecting means. I do.
[0073]
Further, the second invention is an N-system OFDM system which is error-correction-coded, includes an error detection code and a known pilot signal, and is transmitted at the same frequency from N (N is an integer of 2 or more) transmission antennas. An OFDM signal receiving apparatus for receiving a signal, comprising: N receiving antennas for receiving a signal obtained by spatially multiplexing the N OFDM signals; and N receiving signals received by the N receiving antennas. Is fast Fourier-transformed into a received signal for each subcarrier, and a pilot signal included in the N-system received signals after the fast Fourier transform and the known pilot signal, A transfer coefficient for calculating a transfer coefficient matrix having a transfer coefficient between each transmitting antenna and each receiving antenna as an element and a transfer coefficient inverse matrix which is an inverse matrix for each element A column operation unit, for each subcarrier, multiplying the N-system received signals after the fast Fourier transform by the inverse transfer coefficient matrix, and interpolating between the systems included in the N-system received signals after the fast Fourier transform; Multiplying interference canceling means for canceling mutual interference components, weighting means for weighting each of N output signals of the multiplying interference canceling means for each subcarrier according to the transfer coefficient, and the weighting means First demodulation means for demodulating each of the N output signals of the first system, and first decoding for performing error correction decoding on each of the N output signals of the first demodulation means and outputting a decoded signal of the N system Means, an error detection means for detecting an error position using the error detection code for each of the N-system decoded signals, and a detection result of the error detection means. Selecting re-modulation means for selecting the N sub-carriers which have been correctly decoded in the same way and performing the same sub-carrier modulation on the decoded signal corresponding to the sub-carrier as at the time of transmission; Using an output signal and the transfer coefficient matrix, for each selected subcarrier, generate a replica of the mutual interference component between the systems, and subtract the replica from the received signals of the N systems after the fast Fourier transform. Subtraction interference canceling means for canceling mutual interference components between systems included in each of the received signals, and separating each reception signal into signal components corresponding to each system of the OFDM signal, Is weighted based on the transfer coefficient for each of the selected subcarriers for the signal components separated by Weighting synthesizing means for synthesizing signal components corresponding to the systems, N-system output signals of the weighting-combining means, and N-system output signals of the weighting means for subcarriers not selected by the selective remodulation means And a second decoding unit that performs error correction decoding on each of the N output signals of the second demodulation unit.
[0074]
Further, a third invention is an OFDM signal for receiving N systems of OFDM signals transmitted at the same frequency from N (N is an integer of 2 or more) transmission antennas, each including an error detection code and a known pilot signal. A receiving apparatus, comprising: N receiving antennas for receiving signals obtained by spatially multiplexing the N systems of OFDM signals; and fast Fourier transforming each of the N systems of received signals received by the N receiving antennas. A fast Fourier transforming means for transforming into a received signal for each subcarrier, and a transmitting antenna for each subcarrier by using a pilot signal included in the N-system received signal after the fast Fourier transform and the known pilot signal. Transfer coefficient matrix calculating means for calculating a transfer coefficient matrix having a transfer coefficient between the antenna and each receiving antenna as an element and a transfer coefficient inverse matrix which is an inverse matrix thereof; For each carrier, the N received signals after the fast Fourier transform are multiplied by the inverse transfer coefficient matrix to cancel a mutual interference component between the systems included in the N received signals after the fast Fourier transform. Multiplying interference canceling means, weighting means for weighting each of the N output signals of the multiplying interference canceling means for each subcarrier in accordance with the transfer coefficient, and N output signals of the weighting means A first demodulation means for demodulating each of them and outputting an N-system first demodulated signal; and a plurality of N-system second demodulators for repeatedly performing subtractive interference cancellation based on the N-system first demodulated signals. Subtraction interference canceling and repeating means for outputting a demodulated signal of each of the first and second N-system demodulated signals using the error detection code. Error detection means for detecting an error amount, and demodulation having the least error among the N first demodulated signals and the plurality of N second demodulated signals based on the detection result of the error detection means. Demodulation signal selection means for selecting a signal for each system, wherein the subtraction-type interference cancellation repetition means performs subcarrier remodulation means for performing the same subcarrier modulation as at the time of transmission on each of the N system demodulation signals. And using the output signals of the N systems of the subcarrier remodulation means and the transfer coefficient matrix, for each subcarrier, generate a replica of the mutual interference component between the systems, and convert the replica after the fast Fourier transform. The mutual interference components between the systems included in each of the received signals are canceled by subtracting the received signals from the N systems, and the received signals are converted into signals corresponding to the respective systems of the OFDM signal. Subtraction-type interference canceling means for separating the signal into components, and weighting based on the transmission coefficient for each subcarrier for the signal component separated by the subtraction-type interference cancellation means, corresponding to each system of the OFDM signal. A plurality of stages of weighting combining means for combining signal components, and second demodulation means for demodulating each of the N-system output signals of the weighting-combining means and outputting a second N-system demodulated signal; The first-stage subcarrier remodulation means modulates the N-system first demodulated signal, and the second-stage and subsequent subcarrier remodulation means respectively modulates the preceding N-system second demodulated signal. It is characterized by modulation.
[0075]
In a fourth aspect of the present invention, an N-system of OFDM systems, each of which is error-correction coded, includes an error detection code and a known pilot signal, and is transmitted at the same frequency from N (N is an integer of 2 or more) transmission antennas An OFDM signal receiving apparatus for receiving a signal, comprising: N receiving antennas for receiving a signal obtained by spatially multiplexing the N OFDM signals; and N receiving signals received by the N receiving antennas. Is fast Fourier-transformed into a received signal for each subcarrier, and a pilot signal included in the N-system received signals after the fast Fourier transform and the known pilot signal, A transfer coefficient for calculating a transfer coefficient matrix having a transfer coefficient between each transmitting antenna and each receiving antenna as an element and a transfer coefficient inverse matrix which is an inverse matrix for each element A column operation unit, for each subcarrier, multiplying the N-system received signals after the fast Fourier transform by the inverse transfer coefficient matrix, and interpolating between the systems included in the N-system received signals after the fast Fourier transform; Multiplying interference canceling means for canceling mutual interference components, weighting means for weighting each of N output signals of the multiplying interference canceling means for each subcarrier according to the transfer coefficient, and the weighting means A first demodulating means for demodulating each of the N output signals of the N channels, and a second demodulating means for performing error correction decoding on each of the N output signals of the first demodulating means and outputting the N first decoded signals. Subtraction-type interference cancellation and iterative subtraction-type interference cancellation using the first decoding means and the N-system first decoded signals and outputting N-system final decoded signals And the subtraction-type interference cancellation repetition means refers to an error detection means for detecting an error position using the error detection code for each of the N-system decoded signals, and a detection result of the error detection means. Selecting re-modulation means for selecting the N sub-carriers which have been correctly decoded in the same way and performing the same sub-carrier modulation on the decoded signal corresponding to the sub-carrier as at the time of transmission; Using an output signal and the transfer coefficient matrix, for each selected subcarrier, generate a replica of the mutual interference component between the systems, and subtract the replica from the received signals of the N systems after the fast Fourier transform. Cancels the mutual interference components between the systems included in each of the received signals, and separates each of the received signals into signal components corresponding to each of the systems of the OFDM signal. Subtraction-type interference canceling means, and weighting based on the transmission coefficient for each selected subcarrier for the signal component separated by the subtraction-type interference cancellation means, and a signal corresponding to each system of the OFDM signal. Weighting / combining means for combining components; N-system output signals of the weighting / combining means; and N-system output signals of the weighting means for subcarriers not selected by the selective remodulation means. A plurality of second demodulating means for demodulating and a plurality of second decoding means for performing error correction decoding on each of the N-system output signals of the second demodulating means and outputting N-system second decoded signals are provided. A first stage, wherein the first stage error detection means performs an error detection of the first decoded signal of the N systems, and the second and subsequent stages of error detection means respectively perform the N system first detection signals. Performs error detection of the second decoding signals, the second decoding means at the last stage and outputs the second decoded signal as the final decoded signal.
[0076]
According to a fifth aspect of the present invention, there is provided an OFDM signal transmitting / receiving apparatus including an OFDM signal transmitting apparatus and an OFDM signal receiving apparatus, wherein the OFDM signal transmitting apparatus transmits N input signals (N is an integer of 2 or more). Error detection code adding means for adding an error detection code to each of the information signals, pilot signal addition means for adding a pilot signal to each of the N transmission information signals, the error detection code and the pilot signal Subcarrier modulation means for performing subcarrier modulation on each of the N transmission information signals to which N is added, and inverse fast Fourier transform for performing inverse fast Fourier transform on each of the N output signals of the subcarrier modulation means Means for transmitting N OFDM signals output from the inverse fast Fourier transform means at the same frequency. And an OFDM signal receiving apparatus comprising: an N number of receiving antennas for receiving a signal obtained by spatially multiplexing the N number of OFDM signals; and N number of receiving antennas received by the N number of receiving antennas. Fast Fourier transform means for transforming a signal into a received signal for each subcarrier by fast Fourier transform, and a pilot signal included in the N-system received signals after the fast Fourier transform and the known pilot signal, For each carrier, a transfer coefficient matrix calculating means for calculating a transfer coefficient matrix having a transfer coefficient between each transmitting antenna and each receiving antenna as an element and a transfer coefficient inverse matrix which is an inverse matrix thereof, and for each subcarrier, The N received signals after the fast Fourier transform are multiplied by the inverse transfer coefficient matrix, and a phase between the systems included in the N received signals after the fast Fourier transform is multiplied. A multiplication type interference canceling unit for canceling an interference component, a weighting unit for weighting each of the N-system output signals of the multiplication type interference canceling unit for each subcarrier in accordance with the transfer coefficient, First demodulation means for demodulating each of the N output signals and outputting N first demodulated signals; and the same sub-carrier modulation means for each of the N first demodulated signals. Subcarrier remodulation means for performing carrier modulation, and using the output signals of the N systems of the subcarrier remodulation means and the transfer coefficient matrix, for each subcarrier, to generate a replica of mutual interference components between systems, By subtracting the replica from the received signals of the N systems after the fast Fourier transform, mutual interference components between the systems included in each of the received signals are captured. Subtraction-type interference canceling means for canceling each received signal into signal components corresponding to each system of the OFDM signal, and a signal component separated by the subtraction-type interference cancellation means, for each subcarrier, Weighting and combining means for performing weighting based on the transfer coefficient and combining signal components corresponding to the respective systems of the OFDM signal, and demodulating each of the N-system output signals of the weighting / combining means to obtain a second N-system signal Second demodulation means for outputting a demodulated signal, error detection means for detecting an error amount of each of the N-system first and second demodulated signals using the error detection code, and a detection result of the error detection means And demodulated signal selecting means for selecting a demodulated signal having less error among the first and second demodulated signals of the N systems for each system based on
[0077]
Further, a sixth invention is an OFDM signal transmitting / receiving apparatus comprising an OFDM signal transmitting apparatus and an OFDM signal receiving apparatus, wherein the OFDM signal transmitting apparatus transmits N input systems (N is an integer of 2 or more). Error detection code adding means for adding an error detection code to each of the information signals; error correction code means for performing error correction coding on each of the N systems of transmission information signals; Pilot signal adding means for adding a pilot signal to each of the signals, subcarrier modulation means for performing subcarrier modulation on each of the N-system transmission information signals to which the error detection code and the pilot signal are added, Inverse fast Fourier transform means for performing inverse fast Fourier transform on each of the N output signals of the subcarrier modulation means; N transmission antennas for transmitting N-system OFDM signals output from the Fourier transform means at the same frequency, and the OFDM signal receiving apparatus receives a signal obtained by spatially multiplexing the N-system OFDM signals. Receiving antennas, fast Fourier transform means for fast Fourier transforming each of the N received signals received by the N receiving antennas to convert them into received signals for each subcarrier, and N after the fast Fourier transform. Using the pilot signal and the known pilot signal included in the received signal of the system, for each subcarrier, a transfer coefficient matrix having a transfer coefficient between each transmitting antenna and each receiving antenna as an element and an inverse matrix thereof. A transfer coefficient matrix calculating means for calculating an inverse transfer coefficient matrix, and for each subcarrier, the transfer coefficient matrix for the N-system received signals after the fast Fourier transform. Multiplying interference canceling means for multiplying the coefficient inverse matrix to cancel mutual interference components between the systems included in the N-system received signals after the fast Fourier transform, and N-system output signals of the multiplying interference canceling unit, respectively For each subcarrier, weighting means for weighting according to the transfer coefficient, first demodulation means for demodulating output signals of N systems of the weighting means, and N systems of the first demodulation means First decoding means for performing error correction decoding on each of the output signals and outputting N-system decoded signals, and error detection for detecting an error position using the error detection code for each of the N-system decoded signals Means and sub-carriers which have been correctly decoded for all N systems with reference to the detection result of the error detection means, and a decoded signal corresponding to the sub-carrier is selected. A selection-type remodulation unit that performs the same subcarrier modulation as the subcarrier modulation unit; and N output signals of the selection-type remodulation unit and the transfer coefficient matrix, for each selected subcarrier. Generating a replica of the mutual interference component between the systems, canceling the replica from the received signals of the N systems after the fast Fourier transform to cancel the mutual interference component between the systems included in each of the received signals, Subtraction-type interference cancellation means for separating each received signal into signal components corresponding to the respective systems of the OFDM signal; and for the signal components separated by the subtraction-type interference cancellation means, for each selected subcarrier, Weighting / combining means for performing weighting based on a transfer coefficient and combining signal components corresponding to respective systems of the OFDM signal with each other; Second demodulation means for combining and demodulating the N-system output signals of the means and the N-system output signals of the weighting means for the subcarriers not selected by the selective remodulation means; A second decoding unit that performs error correction decoding on each of the N-system output signals of the demodulation unit.
[0078]
Further, a seventh invention is an OFDM signal transmitting / receiving apparatus including an OFDM signal transmitting apparatus and an OFDM signal receiving apparatus, wherein the OFDM signal transmitting apparatus transmits N input (N is an integer of 2 or more) input N systems. Error detection code adding means for adding an error detection code to each of the information signals, pilot signal addition means for adding a pilot signal to each of the N transmission information signals, the error detection code and the pilot signal Subcarrier modulation means for performing subcarrier modulation on each of the N transmission information signals to which N is added, and inverse fast Fourier transform for performing inverse fast Fourier transform on each of the N output signals of the subcarrier modulation means Means for transmitting N OFDM signals output from the inverse fast Fourier transform means at the same frequency. And an OFDM signal receiving apparatus comprising: an N number of receiving antennas for receiving a signal obtained by spatially multiplexing the N number of OFDM signals; and N number of receiving antennas received by the N number of receiving antennas. Fast Fourier transform means for transforming a signal into a received signal for each subcarrier by fast Fourier transform, and a pilot signal included in the N-system received signals after the fast Fourier transform and the known pilot signal, For each carrier, a transfer coefficient matrix calculating means for calculating a transfer coefficient matrix having a transfer coefficient between each transmitting antenna and each receiving antenna as an element and a transfer coefficient inverse matrix which is an inverse matrix thereof, and for each subcarrier, The N received signals after the fast Fourier transform are multiplied by the inverse transfer coefficient matrix, and a phase between the systems included in the N received signals after the fast Fourier transform is multiplied. A multiplication type interference canceling unit for canceling an interference component, a weighting unit for weighting each of the N-system output signals of the multiplication type interference canceling unit for each subcarrier in accordance with the transfer coefficient, A first demodulation means for demodulating each of the N-system output signals and outputting N-system first demodulated signals; and performing a plurality of subtraction-type interference cancellations repeatedly based on the N-system first demodulated signals. Subtraction-type interference cancellation repetition means for outputting N second demodulated signals; and an error amount of each of the N first demodulated signals and the plurality of N second demodulated signals using the error detection code. And a plurality of N second demodulated signals among the N first demodulated signals and the plurality of N second demodulated signals based on the detection result of the error detecting means. Demodulation signal selecting means for selecting a small number of demodulated signals for each system, wherein the subtraction-type interference cancellation repetition means performs the same subcarrier modulation as the subcarrier modulation means on each of the N systems of demodulated signals. Subcarrier remodulation means, using the output signals of the N systems of the subcarrier remodulation means and the transfer coefficient matrix, for each subcarrier, generate a replica of the mutual interference component between the systems, the replica The mutual interference components between the systems included in each of the received signals are canceled by subtracting from the N-system received signals after the fast Fourier transform, and each of the received signals is separated into signal components corresponding to each of the OFDM signals. Subtraction-type interference canceling means, and the transmission component for each subcarrier with respect to the signal component separated by the subtraction-type interference cancellation means. Weighting and combining means for combining signal components corresponding to the respective systems of the OFDM signal, and demodulating each of the N-system output signals of the weighting / combining means to generate an N-system second demodulated signal. And a second demodulating means for outputting, the first sub-carrier re-modulating means modulating the N-system first demodulated signal, and the second and subsequent sub-carrier re-modulating means. The means modulates the N demodulated signals of the preceding N systems, respectively.
[0079]
Further, an eighth invention is an OFDM signal transmitting / receiving apparatus comprising an OFDM signal transmitting apparatus and an OFDM signal receiving apparatus, wherein the OFDM signal transmitting apparatus transmits N input systems (N is an integer of 2 or more). Error detection code adding means for adding an error detection code to each of the information signals; error correction code means for performing error correction coding on each of the N systems of transmission information signals; Pilot signal adding means for adding a pilot signal to each of the signals, subcarrier modulation means for performing subcarrier modulation on each of the N-system transmission information signals to which the error detection code and the pilot signal are added, Inverse fast Fourier transform means for performing inverse fast Fourier transform on each of the N output signals of the subcarrier modulation means; N transmission antennas for transmitting N-system OFDM signals output from the Fourier transform means at the same frequency, and the OFDM signal receiving apparatus receives a signal obtained by spatially multiplexing the N-system OFDM signals. Receiving antennas, fast Fourier transform means for fast Fourier transforming each of the N received signals received by the N receiving antennas to convert them into received signals for each subcarrier, and N after the fast Fourier transform. Using the pilot signal and the known pilot signal included in the received signal of the system, for each subcarrier, a transfer coefficient matrix having a transfer coefficient between each transmitting antenna and each receiving antenna as an element and an inverse matrix thereof. A transfer coefficient matrix calculating means for calculating an inverse transfer coefficient matrix, and for each subcarrier, the transfer coefficient matrix for the N-system received signals after the fast Fourier transform. Multiplying interference canceling means for multiplying the coefficient inverse matrix to cancel mutual interference components between the systems included in the N-system received signals after the fast Fourier transform, and N-system output signals of the multiplying interference canceling unit, respectively For each subcarrier, weighting means for weighting according to the transfer coefficient, first demodulation means for demodulating output signals of N systems of the weighting means, and N systems of the first demodulation means The first decoding means for performing error correction decoding on each of the output signals and outputting N systems of first decoded signals, and performing the subtraction interference cancellation repeatedly using the N systems of first decoded signals. And a subtraction-type interference cancellation repetition means for outputting a final decoded signal of the N systems, wherein the subtraction-type interference cancellation repetition means outputs the error for each of the N systems of decoded signals. Error detecting means for detecting the position of an error using a detection code, and selecting a subcarrier in which all N systems have been correctly decoded with reference to the detection result of the error detecting means, and for a decoded signal corresponding to the subcarrier, A selective remodulation means for performing the same subcarrier modulation as the subcarrier modulation means, and N output signals of the selective remodulation means and the transfer coefficient matrix, for each selected subcarrier, a system A replica of the mutual interference component between the signals is generated, and the replica is subtracted from the N systems of the received signals after the fast Fourier transform, thereby canceling the mutual interference components between the systems included in each of the received signals, and A subtraction-type interference canceling unit that separates the signal into signal components corresponding to the respective systems of the OFDM signal; Weighting means for weighting the signal component based on the transmission coefficient for each selected subcarrier, and combining signal components corresponding to the respective systems of the OFDM signal; and N systems of the weighting synthesis means A second demodulating means for combining and demodulating the output signal of the second demodulating means with the output signals of the N systems of the weighting means for the subcarriers not selected by the selective remodulating means; And N second decoding means for performing error correction decoding on each of the output signals of the respective systems and outputting N decoded signals of the N systems. The error detection of the first decoded signal is performed, the error detection means of the second and subsequent stages respectively perform the error detection of the second decoded signal of the N system of the previous stage, and the second decoding means of the last stage is The second The issue signals and outputs as the final decoded signal.
[0080]
A ninth invention is an OFDM signal for receiving N systems of OFDM signals transmitted at the same frequency from N (N is an integer of 2 or more) transmission antennas, each including an error detection code and a known pilot signal. A receiving method for receiving a signal obtained by spatially multiplexing the N systems of OFDM signals with N receiving antennas; and performing a fast Fourier transform on each of the N systems of received signals received by the N receiving antennas. Fast Fourier transform step of converting and converting to a received signal for each subcarrier, using the pilot signal and the known pilot signal included in the N-system received signal after the fast Fourier transform, for each subcarrier, A transfer coefficient row for calculating a transfer coefficient matrix having a transfer coefficient between each transmitting antenna and each receiving antenna as an element and a transfer coefficient inverse matrix as an inverse matrix thereof Calculating step: multiplying the N-system received signals after the fast Fourier transform by the inverse transfer coefficient matrix for each subcarrier, and interchanging between the systems included in the N-system received signals after the fast Fourier transform. A multiplying interference canceling step for canceling an interference component, and a weighting step for weighting each of the N systems of signals from which the mutual interference component has been canceled in the multiplying interference canceling step, for each subcarrier, according to the transfer coefficient. A first demodulation step of demodulating each of the N-system signals weighted in the weighting step to obtain an N-system first demodulated signal; and transmitting a signal to each of the N-system first demodulated signals. Sub-carrier re-modulation step for performing the same sub-carrier modulation as above, and sub-carrier modulation in the sub-carrier re-modulation step By using the obtained signal and the transfer coefficient matrix, a replica of the mutual interference component between the systems is generated for each subcarrier, and the replica is subtracted from the received signals of the N systems after the fast Fourier transform. A subtractive interference canceling step of canceling mutual interference components between systems included in each received signal and separating each received signal into signal components corresponding to each system of the OFDM signal; Weighting based on the transmission coefficient, for each subcarrier, for the subdivided signal components, and a weighting synthesis step of synthesizing signal components corresponding to each system of the OFDM signal, and a weighting synthesis step. A second demodulation step of demodulating each of the signals to obtain an N-system second demodulated signal; An error detecting step of detecting an error amount of each of the first and second demodulated signals of the system, and based on a detection result of the error detecting step, the first and second demodulated signals of the N systems having less errors. Demodulated signal selecting step of selecting a signal for each system.
[0081]
Further, a tenth aspect of the present invention is an N-system OFDM system which is error-correction coded, includes an error detection code and a known pilot signal, and is transmitted at the same frequency from N (N is an integer of 2 or more) transmission antennas. An OFDM signal receiving method for receiving a signal, comprising: a receiving step of receiving a signal obtained by spatially multiplexing the N-system OFDM signals with N receiving antennas; A fast Fourier transform step of fast Fourier transforming each received signal into a received signal for each subcarrier, and using the pilot signal and the known pilot signal included in the N-system received signals after the fast Fourier transform. , For each subcarrier, a transfer coefficient matrix having a transfer coefficient between each transmit antenna and each receive antenna as an element and a transfer coefficient inverse matrix thereof being an inverse matrix Calculating the transfer coefficient matrix, and for each subcarrier, multiply the received signal of the N systems after the fast Fourier transform by the transfer coefficient inverse matrix, and multiply the received signal of the N systems after the fast Fourier transform by A multiplication type interference canceling step for canceling a mutual interference component between the included systems, and a signal for each of the N systems in which the mutual interference component has been canceled in the multiplication type interference cancellation step, for each subcarrier, the transfer coefficient A first demodulation step of demodulating each of the N-system signals weighted in the weighting step, and an error correction for each of the N-system signals demodulated in the first demodulation step. A first decoding step of performing decoding to obtain N-system decoded signals; An error detection step of detecting an error position using an error detection code, and selecting a subcarrier in which all N systems are correctly decoded with reference to the detection result of the error detection step, and selecting the decoded signal corresponding to the subcarrier. For each of the selected subcarriers, using a selective remodulation step of performing the same subcarrier modulation as at the time of transmission, and the N-system signals subcarrier-modulated in the selective remodulation step and the transfer coefficient matrix. A replica of the mutual interference component between the systems is generated, and the mutual interference component between the systems included in each of the received signals is canceled by subtracting the replica from the received signals of the N systems after the fast Fourier transform, A subtractive interference canceling step of separating each of the received signals into signal components corresponding to each system of the OFDM signal; A weighting synthesis step of weighting the signal components separated in the cancellation step for each selected subcarrier based on the transfer coefficient, and synthesizing signal components corresponding to each system of the OFDM signal; A second demodulation step of combining and demodulating the N-system signals synthesized in the weighting synthesis step and the N-system signals weighted in the weighting step for the subcarriers not selected in the selective remodulation step; And a second decoding step of performing error correction decoding on each of the N systems of signals demodulated in the second demodulation step.
[0082]
An eleventh invention is an OFDM signal for receiving N systems of OFDM signals transmitted at the same frequency from N (N is an integer of 2 or more) transmission antennas, each including an error detection code and a known pilot signal. A receiving method for receiving a signal obtained by spatially multiplexing the N systems of OFDM signals with N receiving antennas; and performing a fast Fourier transform on each of the N systems of received signals received by the N receiving antennas. Fast Fourier transform step of converting and converting to a received signal for each subcarrier, using the pilot signal and the known pilot signal included in the N-system received signal after the fast Fourier transform, for each subcarrier, A transfer coefficient for calculating a transfer coefficient matrix having a transfer coefficient between each transmitting antenna and each receiving antenna as an element and a transfer coefficient inverse matrix as an inverse matrix thereof A column operation step, for each subcarrier, multiply the N-system received signal after the fast Fourier transform by the transfer coefficient inverse matrix, and perform multiplication between the systems included in the N-system received signal after the fast Fourier transform. A multiplication type interference canceling step for canceling the mutual interference component, and weighting for weighting each of the N systems of signals from which the mutual interference component has been canceled in the multiplication type interference cancellation step for each subcarrier in accordance with the transfer coefficient. Step, a first demodulation step of demodulating each of the N-system signals weighted in the weighting step to obtain an N-system first demodulated signal, and repeating based on the N-system first demodulated signal. A subtraction-type interference cancellation repetition step of performing subtraction-type interference cancellation to obtain a plurality of N-system second demodulated signals; An error detection step of detecting an error amount of each of the N-system first demodulated signal and the plurality of N-system second demodulated signals using the N-system first demodulated signal and a plurality of N-system second demodulated signals. A demodulation signal selection step of selecting a demodulation signal having the least error from among one demodulation signal and a plurality of N second demodulation signals for each system, wherein the subtraction-type interference cancellation repetition step comprises: A subcarrier remodulation step of performing the same subcarrier modulation as that at the time of transmission on each of the N systems of demodulated signals; and Then, a replica of the mutual interference component between the systems is generated for each subcarrier, and the replica is subtracted from the received signals of the N systems after the fast Fourier transform. Subtraction interference canceling step of canceling mutual interference components between systems included in the respective reception signals and separating the reception signals into signal components corresponding to the respective systems of the OFDM signal. The signal components separated in the step are weighted based on the transfer coefficient for each subcarrier, and a weighting combining step of combining signal components corresponding to each system of the OFDM signal, and a weighting combining step A second demodulation step of demodulating each of the combined N-system signals to obtain N-system second demodulated signals a plurality of times, wherein the first sub-carrier re-modulation step includes the step of: The first N demodulated signals of the N systems are modulated, and in the second and subsequent subcarrier remodulation steps, Characterized by modulating the demodulated signal.
[0083]
A twelfth invention is directed to N-system OFDM systems, each of which is error-correction coded, includes an error detection code and a known pilot signal, and is transmitted at the same frequency from N transmission antennas (N is an integer of 2 or more). An OFDM signal receiving method for receiving a signal, comprising: a receiving step of receiving a signal obtained by spatially multiplexing the N-system OFDM signals with N receiving antennas; A fast Fourier transform step of fast Fourier transforming each received signal into a received signal for each subcarrier, and using the pilot signal and the known pilot signal included in the N-system received signals after the fast Fourier transform. , For each subcarrier, a transfer coefficient matrix having a transfer coefficient between each transmit antenna and each receive antenna as an element and a transfer coefficient inverse matrix thereof being an inverse matrix Calculating the transfer coefficient matrix, and for each subcarrier, multiply the received signal of the N systems after the fast Fourier transform by the transfer coefficient inverse matrix, and multiply the received signal of the N systems after the fast Fourier transform by A multiplication type interference canceling step for canceling a mutual interference component between the included systems, and a signal for each of the N systems in which the mutual interference component has been canceled in the multiplication type interference cancellation step, for each subcarrier, the transfer coefficient A first demodulation step of demodulating each of the N-system signals weighted in the weighting step, and an error correction for each of the N-system signals demodulated in the first demodulation step. A first decoding step of performing decoding to obtain an N-system first decoded signal, and using the N-system first decoded signal. A subtraction-type interference cancellation repetition step of performing iterative subtraction-type interference cancellation to obtain N final decoded signals, wherein the subtraction-type interference cancellation repetition step uses the error detection code for each of the N types of decoded signals. An error detection step of detecting the position of the subcarrier, and selecting subcarriers that are correctly decoded in all N systems with reference to the detection result of the error detection step, and using the same subcarrier as that at the time of transmission for the decoded signal corresponding to the subcarrier. A mutual interference component between systems for each selected subcarrier by using a selective remodulation step of performing modulation, and N transmission signals and the transfer coefficient matrix subcarrier-modulated in the selective remodulation step. , And subtracting the replica from the N-system received signals after the fast Fourier transform, A subtractive interference canceling step of canceling a mutual interference component between systems included in each of the received signals and separating each of the received signals into signal components corresponding to each system of the OFDM signal; and a subtractive interference canceling step. A weighted combining step of performing weighting based on the transfer coefficient for each of the selected subcarriers on the separated signal components, and combining signal components corresponding to the respective systems of the OFDM signal; A second demodulation step of combining and demodulating the N-system signals combined in the above and the N-system signals weighted in the weighting step for the subcarriers not selected in the selective remodulation step; Error correction decoding is performed on each of the N systems of signals demodulated in the second demodulation step to perform N systems of second decoding. And a second decoding step of obtaining a signal, wherein the first error detection step performs error detection of the first decoded signal of the N systems, and performs the second and subsequent error detection. In the detection step, error detection is performed on the previous second decoded signal of the N systems, and in the final second decoding step, the second decoded signal is obtained as the final decoded signal.
[0084]
BEST MODE FOR CARRYING OUT THE INVENTION
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to the accompanying drawings, preferred embodiments of an OFDM signal receiving apparatus, an OFDM signal transmitting / receiving apparatus, and an OFDM signal receiving method according to the present invention are separately described in detail from a first embodiment to a fourth embodiment. Will be described.
[0085]
(1st Embodiment)
The OFDM signal transmitting and receiving apparatus according to the present embodiment detects an error amount of the N-system demodulated signal after the multiplication-type interference cancellation and the N-system demodulation signal after the subtraction-type interference cancellation in the OFDM signal receiving apparatus, and A demodulated signal having a small number is selected for each system. Hereinafter, the configuration and operation of the OFDM signal transmitting / receiving apparatus according to the present embodiment will be described with reference to the drawings.
[0086]
FIG. 1 is a block diagram illustrating a configuration of the OFDM signal transmitting / receiving apparatus according to the present embodiment. In FIG. 1, the OFDM signal transmitting / receiving apparatus includes an OFDM signal transmitting apparatus 1 and an OFDM signal receiving apparatus 2.
[0087]
In the OFDM signal transmitting apparatus 1, N input (N is an integer of 2 or more) transmission information signals T₁, T₂, ..., T_NAre multiplexed with an error detection code by a predetermined block unit by N error detection code multiplexers 1-1-1 to 1-1-N corresponding to each signal. Output signals of N systems of the error detection code multiplexers 1-1-1 to 1-1-N are output by N pilot signal multiplexers 1-3-1 to 1-3-N corresponding to the respective signals. , And N pilot signal generators 1-2-1 to 1-2-N and multiplexed with known pilot coefficients for transfer coefficient estimation. Output signals of N systems of pilot signal multiplexers 1-3-1 to 1-3-3-N are transmitted to N subcarrier modulators 1-4-1 to 1-4-N corresponding to each signal. Carrier modulation is performed, and the signal is converted into a transmission signal in the frequency domain, that is, for each subcarrier. The transmission signal composed of a plurality of N subcarrier signals output from the subcarrier modulators 1-4-1 to 1-4-N is composed of N inverse fast Fourier transformers 1-5 corresponding to each signal. Inverse fast Fourier transform is performed by 1 to 1-5-N, and is converted into N-system transmission signals in the time domain. N-system OFDM signals output from the inverse fast Fourier transformers 1-5-1 to 1-5-N are identical from N transmission antennas 1-6-1 to 1-6-N corresponding to each signal. Transmitted on frequency.
[0088]
In the OFDM signal receiving apparatus 2, signals transmitted from the N transmitting antennas 1-6-1 to 1-6-N and spatially multiplexed are transmitted by the N receiving antennas 2-1-1 to 2-1-N. Received. Here, since each receiving antenna simultaneously receives N OFDM signals from N transmitting antennas, each received signal contains a mutual interference component between the systems. The received signals of N systems received by the N receiving antennas 2-1-1 to 2-1-N are N fast Fourier transformers 2-2-1 to 2-2-N corresponding to each signal. , A fast Fourier transform is performed, and the received signal in the time domain is converted into a received signal in the frequency domain, that is, for each subcarrier. Hereinafter, the received signals of the N systems after the fast Fourier transform of the i-th subcarrier are represented by a vector rⁱ(= (Rⁱ ₁  rⁱ ₂... rⁱ _N)). The transfer coefficient matrix calculator 2-3 uses, for each subcarrier, the amplitude and phase of a received pilot signal included in the N-system fast Fourier-transformed received signal and the known pilot signal, Transfer coefficient h between each transmitting antenna and each receiving antennaⁱ _{j, k}(I is the number of the subcarrier, j is the number of the transmitting antenna, k is the number of the receiving antenna), and the transfer coefficient matrix H having the transfer coefficient as an element is calculated.ⁱAnd its inverse matrix, the transfer coefficient inverse matrix (Hⁱ)^-1And these are stored. Here, the transfer coefficient matrix HⁱIs represented by equation (1).
[0089]
The multiplication type interference canceller 2-4 is configured to perform, for each subcarrier, a vector r of the N-system received signal after the fast Fourier transform.ⁱAnd transfer coefficient inverse matrix (Hⁱ)^-1Product rⁱ・ (Hⁱ)^-1And cancel the mutual interference components included in the N-system received signals after the fast Fourier transform. That is, the frequency domain of each system, that is, the transmission signal for each subcarrier is estimated for each subcarrier. N-system multiplication type interference canceller output signal u output from multiplication type interference canceller 2-4ⁱ(= (Uⁱ ₁  uⁱ ₂... uⁱ _N)) Is weighted by N weighters 2-5-1 to 2-5-N corresponding to each signal in accordance with the transfer coefficient for each subcarrier. Specifically, the weighters 2-5-1 to 2-5-N determine the weighting matrix Y represented by the equation (6) based on the transfer coefficient inverse matrix.ⁱIs calculated, and the corresponding element is multiplied by the multiplication type interference canceller output signal to calculate a weighter output signal. The output signals of the N weighting devices are signal-determined and demodulated by N first demodulators 2-6-1 to 2-6-N corresponding to the respective signals.
[0090]
Next, the N first demodulated signals output from the N first demodulators 2-6-1 to 2-6-N are divided into N subcarrier remodulators 2 corresponding to each signal. According to 7-1 to 2-7-N, subcarrier modulation is performed in the same modulation scheme as that at the time of transmission, that is, in the same modulation scheme as the modulation in subcarrier modulators 1-4-1 to 1-4-N. .
[0091]
The subtraction-type interference canceller 2-9 uses the N-system output signals of the subcarrier re-modulators 2-7-1 to 2-7-N and the transfer coefficient matrix, and performs a fast Fourier transform after the fast Fourier transform for each subcarrier. Mutual interference components between the systems included in the N systems of received signals are canceled, and each received signal after the fast Fourier transform is separated into signal components corresponding to each system of the OFDM signal. Specifically, the subtraction type interference canceller 2-9 uses the N-system output signals of the subcarrier re-modulators 2-7-1 to 2-7-N and the transfer coefficient matrix to perform the fast Fourier transform. A replica of the mutual interference component included in each of the N-system received signals is generated, the mutual interference component included in the received signal is canceled by subtracting the replica from the received signal, and each of the received signals after the fast Fourier transform is performed. Is separated into signal components corresponding to transmission signals for each system of subcarriers. More specifically, focusing on the i-th subcarrier, the following operation is performed. The reception signal matrix R is obtained from the N-system reception signals after the fast Fourier transform according to the equation (11).ⁱIs calculated. Also, the N-system output signals t 'of the subcarrier remodulators 2-7-1 to 2-7-N.ⁱ(= (T 'ⁱ ₁  t 'ⁱ ₂... t 'ⁱ _N)) To remodulated signal matrix T ′ according to equation (12).ⁱIs calculated. Then, the remodulated signal matrix T 'ⁱAnd the transfer coefficient matrix HⁱAnd the replica signal matrix (T ′ⁱ・ Hⁱ) Is calculated. That is, a replica of the mutual interference component included in each received signal after the fast Fourier transform is generated. Then, as shown in equation (13), the received signal matrix RⁱFrom the replica signal matrix (T 'ⁱ・ Hⁱ) To obtain the signal matrix X after the replica subtraction.ⁱIs output. This signal matrix X after the replica subtractionⁱAre the signal components corresponding to the N transmission signals of the i-th subcarrier included in the N reception signals after the fast Fourier transform.
[0092]
The reception signal after the fast Fourier transform input to the subtraction type interference canceller 2-9 is obtained by converting the output signals of the N fast Fourier transformers 2-2-1 to 2-2-N into the reception signal delay unit 2-9. 8-1 to 2-8-N. Here, the received signal delay units 2-8-1 to 2-8-N correspond to the processing time from the multiplication type interference canceller 2-4 to the subcarrier remodulators 2-7-1 to 2-7-N. Cause a delay.
[0093]
The weighting combiner 2-10 weights the signal components separated by the subtraction type interference canceller 2-9 based on the transfer coefficient for each subcarrier, and combines the signal components corresponding to the respective systems of the OFDM signal. I do. Specifically, the weighting combiner 2-10 outputs the transfer coefficient matrix HⁱOf the conjugate transpose ofⁱAnd Also, the matrix (Hⁱ・ Wⁱ) And all the diagonal components are the same, and all off-diagonal components are zero.ⁱIs calculated. Then, according to equation (19), the N weighted combined signals vⁱIs calculated.
[0094]
This N-system weighted combined signal vⁱIs demodulated by N second demodulators 2-11-1 to 2-11-N corresponding to each signal.
The N second demodulated signals output from the N second demodulators 2-11-1 to 2-11-N are N demodulated signals to be described later together with the N first demodulated signals. The signals are supplied to the selection circuits 2-13-1 to 2-13-N. Note that the N first demodulated signals supplied to the demodulated signal selection circuits 2-13-1 to 2-13-N are N first demodulators 2-6-1 to 2-6-N Are delayed by N demodulated signal delay units 2-12-1 to 2-12-N. Here, the demodulated signal delay units 2-12-1 to 2-12-N include N first demodulators 2-6-1 to 2-6-N to N second demodulators 2-2-1 to 2-12-N. A delay corresponding to the processing time from 11-1 to 2-11-N is generated.
[0095]
As described above, the OFDM signal transmitting / receiving apparatus according to the present embodiment is different from the conventional OFDM signal transmitting / receiving apparatus described in Japanese Patent Application No. 2002-149013 in that N error detection code multiplexers 1-1-1 to 1-1-1. The configuration is such that N, N demodulated signal delay units 2-12-1 to 2-12-N and N demodulated signal selection circuits 2-13-1 to 2-13-N are added.
[0096]
In the conventional OFDM signal transmitting and receiving apparatus, the second demodulated signal of N systems is always used as the final output. On the other hand, in the OFDM signal transmitting and receiving apparatus according to the present embodiment, the N demodulated signal selection circuits 2-13-1 to 2-13-N use the N first demodulated signals and the N second demodulated signals. A signal having few errors is selected from the signals for each system to obtain a final N-system demodulated signal.
[0097]
FIG. 2 is a block diagram showing a configuration of the demodulated signal selection circuit 2-13-1 corresponding to the first system. The demodulated signal selection circuits 2-13-2 to 2-13-N corresponding to other systems have exactly the same configuration. The delay time corresponding to the time difference between the output signal of the first demodulator 2-6-1 and the output signal of the second demodulator 2-11-1 is determined by the delay time of the first demodulator 2-6-1. Since the output is given using the demodulation signal delay unit 2-12-1, the first and second demodulation signals are supplied to the demodulation signal selection circuit 2-13-1 at the same time. In FIG. 2, a first demodulated signal output from a demodulated signal delay unit 2-12-1 is supplied to a first error detection circuit 3-1 and output from a second demodulator 2-11-1. The second demodulated signal is supplied to a second error detection circuit 3-2. The first error detection circuit 3-1 detects an error amount of the first demodulated signal, and the second error detection circuit 3-2 detects an error amount of the second demodulated signal. Here, the first and second error detection circuits 3-1 and 3-2 perform error detection using an error detection code added on the transmission side. Here, the error detection code may be a code generally used in error detection, such as a parity check and a CRC (Cyclic Redundancy Check) code, and is not particularly limited. In error detection, it is necessary to refer to all demodulated signals in a block to be subjected to error detection. Therefore, the first and second error detection circuits 3-1 and 3-2 require a processing time until the determination as to whether an error exists in the block is completed. A delay corresponding to this processing time is given to the first and second demodulated signals by the first and second decision delay correctors 3-3 and 3-4, respectively, and the first and second demodulated signals, The detection results of the first and second error detection circuits 3-1 and 3-2 are supplied to the signal selection circuit 3-5 in synchronization with each other. The signal selection circuit 3-5 refers to the detection results of the first and second error detection circuits 3-1 and 3-2, and detects more errors from the first and second demodulated signals of the first system. And outputs the final demodulated signal of the first system. If there is no difference in the amount of error, one of the preset demodulated signals may be selected. When the error amount is detected in two steps, that is, when only the presence or absence of an error is detected, a demodulated signal that is correctly demodulated is selected.
[0098]
As described above, in the present embodiment, the first demodulated signal that is the demodulation result of the output of the multiplication interference canceller 2-4, and the second demodulation signal that is the demodulation result of the output of the subtraction interference canceller 2-9 Among them, a demodulated signal having less error is selected for each system. Thus, according to the present embodiment, an error occurs in an OFDM signal transmitting / receiving apparatus using the demodulation result of the output of the conventional multiplication type interference canceller or an OFDM signal transmitting / receiving apparatus always using the demodulation result of the output of the subtraction type interference canceller. The rate characteristics can be improved. In particular, if either the demodulation result of the output of the multiplication type interference canceller 2-4 or the demodulation result of the output of the subtraction type interference canceller 2-9 is correct, the reception of the packet is successful.
[0099]
From the viewpoint of improving the error rate, the transmitting apparatus is provided with error correction coding means for performing error correction coding on each of the N transmission signals, and the receiving apparatus is provided with N first and second demodulated signals. It is preferable to provide first and second decoding means for performing error correction decoding.
[0100]
Hereinafter, the effects of the present embodiment will be specifically described. In the following example, decoding is performed after demodulation.
FIG. 3 shows packet error rate characteristics obtained by computer simulation for an apparatus that uses the decoding result of the output of the multiplication type interference canceller, an apparatus that always uses the decoding result of the output of the subtraction type interference canceller, and the apparatus according to the present embodiment. Show. The number of antennas is two for transmission and reception, and the specifications of the simulation are as shown in Table 1. In FIG. 3, the solid line indicates the characteristic of the device according to the present embodiment, the dotted line indicates the characteristic of the device using the decoding result of the output of the multiplication type interference canceller, and the broken line always uses the decoding result of the output of the subtraction type interference canceller. This shows the characteristics of the device. In addition, the characteristics represented by ○ are those when the modulation method is 64 QAM and the coding rate is R = ３, and the characteristics represented by Δ are those when the modulation method is QPSK. This is for the case where the coding rate is R = 1/2. From FIG. 3, according to the present embodiment, when 64QAM, R = 3/4, PER ≦ 10^-2In comparison with the CNR required to satisfy the above, a gain of 1 dB is obtained when the decoding result of the output of the conventional subtractive interference canceller is always used, and the decoding result of the output of the multiplication interference canceller is obtained. It can be seen that a gain of 2.5 dB is obtained for the case of using. Also, in the case of QPSK, R = 1/2, the characteristic when using the decoding result of the output of the subtraction type interference canceller was worse than the characteristic when using the decoding result of the output of the multiplication type interference canceller. It can be seen that the characteristics are improved by selecting the decoding result by detection.
[0101]
The decoded signal of the multiplication type interference canceller output corresponding to the transmission signals of the transmission antennas 1 and 2 is represented by d₁ ^IM, D₂ ^IMAnd the decoded signal of the subtraction-type interference canceller output corresponding to the transmission signals of the transmission antennas 1 and 2 is represented by d.₁ ^Re, D₂ ^ReAnd In addition, a case where there is no error in the decoded signal is denoted as “o”, and a case where there is an error is denoted as “x”. Then, for example, the decoded signals of the multiplication type interference canceller outputs corresponding to the transmission signals of the transmission antennas 1 and 2 have an error “Yes” and an error “No”, respectively, and the subtraction corresponding to the transmission signals of the transmission antennas 1 and 2 respectively. In the case where the decoded signal of the type interference canceller output has an error “no” and an error “present”, respectively,₁ ^IM  d₂ ^IM  d₁ ^Re  d₂ ^Re) = (O xx o). Table 2 below shows the relationship between the error event between the decoded signal of the output of the multiplication type interference canceller and the decoded signal of the output of the subtraction type interference canceller by computer simulation according to the above notation method. The number of simulations is 10,000, the subcarrier modulation scheme is QPSK, and the coding rate is R = １ ／. The numbers in the table indicate the number of times the event has occurred.
[0102]
[Table 2]

In Table 2, (d₁ ^IM  d₂ ^IM) = (Oo), that is, rows in which the decoding results of the output of the multiplication type interference canceller are all correct events,₁ ^IM  d₂ ^IM  d₁ ^Re  d₂ ^Re) = (Ooox), (ooxo), (ooxx), that is, the decoding result of the output of the multiplication type interference canceller is all correct, but the decoding result of the output of the subtraction type interference canceller. There are 202 events that include an error. This is because there is a case where the decoding result of the output of the subtraction type interference canceller includes an error even though the decoding result of the output of the multiplication type interference canceller is correct and the replica created by the subcarrier remodulator is correct. It is shown that. It is considered that such an error is caused by an error in weighting after subtraction-type interference cancellation due to an error in estimating the transfer coefficient. Also, (d₁ ^IMd₂ ^IM) = (Oo), except that the decoding result of the output of the subtraction type interference canceller has a larger number of errors than the decoding result of the output of the multiplication type interference canceller, that is, (d)₁ ^IM  d₂ ^IM  d₁ ^Re  d₂ ^Re) = (Oxxx), (xoxx) events occur seven times. From the above, it can be seen that the use of the subtraction type interference canceller causes 209 times of incorrect decoding of a signal correctly decoded by the multiplication type interference canceller.
[0103]
On the other hand, (d₁ ^Re  d₂ ^Re) = (Oo), that is, when all the decoding results of the outputs of the subtraction type interference cancellers are correct, attention is paid to (d₁ ^IM  d₂ ^IM  d₁ ^Re  d₂ ^Re) = (Oxoo), (xooo), (xxoo), that is, the decoding result of the multiplication type interference canceller output includes an error, but the decoding of the subtraction type interference canceller output. There are 191 occurrences that all results are correct. This is because the decoding result of the multiplication type interference canceller output is incorrect, and the decoding result of the output of the subtraction type interference canceller is correct even though the replica created by the subcarrier remodulator is incorrect, that is, This is an event in which an error has been corrected by the subtraction type interference canceller. Also, (d₁ ^Re  d₂ ^Re) = (Oo), an event in which an error in the decoding result of the multiplication type interference canceller output is corrected by using the decoding result of the subtraction type interference canceller output, that is, (d)₁ ^IM  d₂ ^IM  d₁ ^Re  d₂ ^Re) = (Xxox), (xxxxo) events occur six times. From the above, it can be seen that by using the subtraction type interference canceller, there are 197 events in which the first erroneously decoded signal is correctly decoded again.
[0104]
As described above, the number of events in which the number of errors increases by using the subtraction interference canceller (209 times) is greater than the number of events in which the number of errors decreases (197 times). Therefore, under the conditions of the above simulation, even if a subtraction type interference canceller is added, the packet error rate characteristic deteriorates when only the decoding result is always used.
[0105]
On the other hand, according to the present embodiment, if at least one of the decoding result of the output of the multiplication type interference canceller and the decoding result of the output of the subtraction type interference canceller is correctly decoded, no error event occurs. That is, the event (d₁ ^IM  d₂ ^IM  d₁ ^Re  d₂ ^Re) = (Oooo), (ooxo), (ooxx), (ooxx), (xxoo), (xooo), (oxooo) , (Oxxo), (xox) are decoded without errors.
[0106]
When the decoding result of the output of the multiplication type interference canceller is erroneous, the event that the decoding result becomes correct by performing the subtraction type interference cancellation, the error detection, and the selection of the decoding result is (d)₁ ^IM  d₂ ^IM  d₁ ^Re  d₂ ^Re) = (Xxoo), (xooo), (oxoo), (oxxo), (xoox). These events occur 209 times in the above simulation. According to the present embodiment, it is possible to prevent packet errors in these events. Therefore, it can be said that the effect of improving the packet error rate characteristics according to the present embodiment is very large.
[0107]
(Second embodiment)
The OFDM signal transmitting / receiving apparatus according to the present embodiment is almost the same as the OFDM signal transmitting / receiving apparatus according to the first embodiment, but detects an error position in N decoded signals after multiplication-type interference cancellation, and performs N-system decoding. Subtractive interference cancellation and weighting synthesis are performed for all subcarriers that are correctly decoded, and output signals after multiplication interference cancellation are used for subcarriers that include errors in at least one system. Hereinafter, the present embodiment will be described with reference to the drawings, but description of parts common to the first embodiment will be omitted.
[0108]
The OFDM signal transmitting and receiving apparatus according to the present embodiment includes an OFDM signal transmitting apparatus 4 and an OFDM signal receiving apparatus 5.
FIG. 4 is a block diagram illustrating a configuration of the OFDM signal transmission device 4 according to the present embodiment. In FIG. 4, the OFDM signal transmitting apparatus 4 adds N error correction encoders 4-7-1 to 4-7-N to the OFDM signal transmitting apparatus 1 of the first embodiment shown in FIG. The configuration is as follows. The N error correction encoders 4-7-1 to 4-7-N perform error correction encoding on each of the input N transmission information signals. Except for this point, the configuration is the same as that of the OFDM signal transmission device 1 according to the first embodiment, and thus the description is omitted.
[0109]
FIG. 5 is a block diagram illustrating a configuration of the OFDM signal receiving device 5 according to the present embodiment. 5, the configuration and operation from receiving antennas 5-1-1 to 5-1-N to first demodulators 5-6-1 to 5-6-N are the same as those of the OFDM signal receiving apparatus shown in FIG. 2 and the description is omitted.
[0110]
The N first demodulated signals output from the first demodulators 5-6-1 to 5-6-N are N first decoders 5-7-1 to 5-5 corresponding to each signal. Error correction decoding is performed according to -7-N. For N decoded signals output from the N first decoders 5-7-1 to 5-7-N, N error detectors 5-8-1 to 5-8 corresponding to each signal are used. 8-N detects an error position using an error detection code. The N selective re-modulators 5-9-1 to 5-9-N refer to the positions of the errors detected by the error detectors 5-8-1 to 5-8-N, and correct all N systems. A decoded subcarrier is selected, and the same subcarrier modulation as that at the time of transmission is performed on a decoded signal corresponding to the subcarrier. Here, if the position of the error in the signal before subcarrier modulation is known, it is possible to identify which subcarrier signal contains an error after subcarrier modulation.
[0111]
The subtraction type interference canceller 5-11 uses the output signals of N systems of the selective re-modulators 5-9-1 to 5-9-N and the transfer coefficient matrix for each of the selected subcarriers for each subcarrier. As in the first embodiment, the mutual interference components included in the N-system received signals after the fast Fourier transform are cancelled, and the received signals after the fast Fourier transform are converted into signal components corresponding to the N-system OFDM signals. To separate.
[0112]
Note that the reception signals after the fast Fourier transform input to the subtraction type interference canceller 5-11 are the output signals of the N fast Fourier transformers 5-2-1 to 5-2-N. 10-1 to 5-10-N. Here, the reception signal delay units 5-10-1 to 5-10-N correspond to the processing time from the multiplication type interference canceller 5-4 to the selection type re-modulators 5-9-1 to 5-9-N. Cause a delay.
[0113]
The weighting combiner 5-12 weights the signal components separated by the subtraction-type interference canceller 5-11 based on the transfer coefficient for each of the selected subcarriers, as in the first embodiment. The signal components corresponding to the OFDM signals of the system are combined. The output signals of the N systems of the weighting combiner 5-12 are delayed by the N number of weighting device output signal delay units 5-13-1 to 5-13-N. Along with the -N output signals of the N systems, the signals are supplied to N interference cancellation signal multiplexers 5-14-1 to 5-14-N. Here, the weighting device output signal delay devices 5-13-1 to 5-13-N perform processing from the first demodulators 5-6-1 to 5-6-N to the output of the weighting synthesizer 5-12. Generate a delay time corresponding to time. In the interference cancellation signal multiplexers 5-14-1 to 5-14-N, the output signals of the N systems of the weighting combiner 5-12 for the subcarriers where the outputs of the weighting combiner 5-12 exist, and the weighting are performed. The weighting device output signal delay units 5-13-1 to 5-13-N for the subcarriers for which the output of the synthesizer 5-12 does not exist are multiplexed with the N output signals. Output signals of the N systems of the interference cancellation signal multiplexers 5-14-1 to 5-14-N are output by N second demodulators 5-15-1 to 5-15-N corresponding to each signal. Is demodulated. That is, N weighting device output signal delay units 5-13-1 to 5-13-N, N interference cancellation signal multiplexers 5-14-1 to 5-14-N, and N number of 2 demodulators 5-15-1 to 5-15-N and N of the weighting combiner 5-12 for the subcarriers selected by the selective remodulators 5-9-1 to 5-9-N. The output signal of the system and the output signals of the N systems of the weighters 5-5-1 to 5-5-N for the unselected subcarriers are combined and then demodulated. The output signals of the N systems of the second demodulators 5-15-1 to 5-15-N are output by N second decoders 5-16-1 to 5-16-N corresponding to the respective signals. Error-correction decoding is performed and output as a final decoded signal of N systems.
[0114]
Note that the weighting for the output of the multiplication type interference canceller 5-4 and the weighting for the output of the subtraction type interference canceller 5-11 are different from each other, and therefore, a level difference occurs between the weighted outputs. In order to cope with this, the level difference may be corrected by setting the weighting coefficient after the multiplication type interference cancellation, that is, the value of the constant C in the matrix component in the equation (6) to an appropriate value.
[0115]
In a conventional OFDM signal transmitting and receiving apparatus that performs subtraction-type interference cancellation, the decoding result of the output of the multiplication-type interference canceller is re-modulated regardless of the presence or absence of an error in the result, and is used as a replica of the transmission signal for subtraction-type interference cancellation. Had been. On the other hand, in the OFDM signal transmitting and receiving apparatus according to the present embodiment, as described above, subtraction-type interference cancellation and weighting synthesis are used for interference cancellation with higher precision than multiplication-type interference cancellation for subcarriers that are correctly decoded in all N systems. And weighting. On the other hand, with respect to subcarriers in which at least one of the N systems is erroneously decoded, subtractive interference canceling and weighting combining are performed in order to prevent an erroneous replica from being used for subtractive interference canceling and weighting combining and decoding results to be erroneous. Is performed, or the output after the multiplication-type interference cancellation is used without using the output after the subtraction-type interference cancellation and the weighted combination.
[0116]
As described above, according to the present embodiment, it is possible to perform more accurate interference cancellation and weighted combining by performing subtraction-type interference cancellation on subcarriers for which all replicas of transmission signals have been correctly generated. On the other hand, for a subcarrier for which a replica was not correctly generated, the subtraction-type interference canceller output using the erroneous replica is used instead of using the subtraction-type interference canceller output using the erroneous replica. It is possible to prevent the output of the cancellation from being included in the final decoded signal, and to prevent the signal having low reliability from being included. As a result, the error rate characteristics can be improved.
[0117]
(Third embodiment)
The OFDM signal transmitting / receiving apparatus according to the present embodiment is almost the same as the OFDM signal transmitting / receiving apparatus according to the first embodiment, but performs iterative subtraction-type interference cancellation and weighted synthesis to obtain N first demodulated signals and multiple signals. And selecting a demodulated signal having fewer errors for each of the N second demodulated signals. Hereinafter, the present embodiment will be described with reference to the drawings, but description of parts common to the first embodiment will be omitted.
[0118]
The OFDM signal transmitting / receiving apparatus according to the present embodiment includes the same OFDM signal transmitting apparatus 1 and OFDM signal receiving apparatus 6 as those in the first embodiment.
FIG. 6 is a block diagram illustrating a configuration of the OFDM signal receiving device 6 according to the present embodiment. 6, the configuration and operation from receiving antennas 6-1-1 to 6-N to first demodulators 6-6-1 to 6-6-N are similar to those of the OFDM signal receiving apparatus shown in FIG. 2 and the description is omitted.
[0119]
The OFDM signal receiving apparatus 6 includes a plurality of stages (in this embodiment, B stages) of subtraction-type interference cancellation for performing subcarrier remodulation, subtraction-type interference cancellation, weighting synthesis, and demodulation in the same manner as in the first embodiment. Post demodulators 6-8-1 to 6-8-B are provided, which repeatedly perform subtractive interference cancellation or the like based on the N first demodulated signals and output a plurality of second demodulated signals. . In other words, the operation of regarding the demodulation result of the output after the subtraction type interference cancellation and the weighted combination as a replica of the transmission signal and further performing the subtraction type interference cancellation and the weighted combination is repeated a plurality of times.
[0120]
In the operation of the demodulator 6-8-1 after the subtraction type interference cancellation in the first stage, N first demodulators 6-6-1 to 6-6 which are demodulation results of the multiplication type interference cancellation output are provided. The N output signals, that is, the first demodulated signals of the N systems are used as replicas of the transmission signal. In the calculation of the demodulator 6-8-b after the subtraction-type interference cancellation of the b-th stage (2 ≦ b ≦ B) in the second and subsequent stages, the subtraction-type interference of the (b-1) th stage, which is the preceding stage, is performed. The second demodulated signal output by the demodulator 6-8- (b-1) after cancellation is used as a replica of the transmission signal. By performing this operation in (b-1) stages, a total of B times of subcarrier remodulation, subtraction-type interference cancellation, weighted combining, and demodulation are repeated.
[0121]
Here, in order for the demodulator 6-8-1 after the first-stage subtraction-type interference cancellation to perform an operation, the processing of the first demodulators 6-6-1 to 6-6-N is completed. Need to be. Therefore, the first-stage received signal delay units 6-7-1-1 to 6-7-1-N provide the first-stage subtraction-type interference cancellation demodulator 6-8-1 with the first-stage received signal delay units 6-7-1-1 to 6-7-1-N. The same delay amount as the time required for the operations in the multiplication type interference canceller 6-4, the weighters 6-5-1 to 6-5-N, and the first demodulators 6-6-1 to 6-6-N Then, the output signals of the N fast Fourier transformers 6-2-1 to 6-2-N are supplied. In order for the demodulator 6-8-b of the b-th (2 ≦ b ≦ B) stage to perform the operation, the demodulator after the subtraction-type interference cancellation of the (b-1) -th stage is required. It is necessary that the operation of 6-8- (b-1) has been completed. Then, for the output signals of the fast Fourier transformers 6-2-1 to 6-2-N, N received signal delay units 6-7-1-1 to 6-7-1-N of B stages,. , 6-7-B-1 to 6-7-BN to provide a delay to achieve timing synchronization. The N received signal delay units 6-7-b-1 to 6-7-bN of the b-th stage are output signals of the N fast Fourier transformers 6-2-1 to 6-2-N. Is synchronized with the demodulator 6-8-b after the subtraction type interference cancellation at the b-th stage. Then, for the demodulator 6-8-b after the subtraction type interference cancellation at the b-th stage (2 ≦ b ≦ B), the N received signal delay units 6-7-b-1 at the b-th stage. 6-7-bN, a delay corresponding to the processing time of the demodulator 6-8- (b-1) after the subtraction-type interference cancellation of the (b-1) th stage is given, -1) The output signals of the N received signal delay units 6-7- (b-1) -1 to 6-7- (b-1) -N in the first stage are supplied. As a result, the output signals of the fast Fourier transformers 6-2-1 to 6-2-N can be synchronized with the demodulator 6-8-b after the subtraction-type interference cancellation at the b-th stage. By using the above-described delay line structure, pipeline processing is performed for each of the demodulators 6-8-1 to 6-8-B after each subtraction-type interference cancellation in the case of continuously processing received signals of N systems. And the circuit scale can be reduced.
[0122]
As described above, by repeating subtraction-type interference cancellation, weighting synthesis, and demodulation, the number of error bits included in the replica of the transmission signal is gradually reduced. It can be expected that a demodulation result can be obtained. However, as described in the section of “Problems to be Solved by the Invention”, when the estimation error of the transfer coefficient matrix is large, the repetition of the subtractive interference cancellation does not always contribute to the improvement of the replica accuracy. Therefore, similarly to the first embodiment, a total of (B + 1) N-system demodulated signals of one N-system first demodulated signal and B N-system second demodulated signals are demodulated and output. The demodulated signals are supplied to the selection circuits 6-11-1 to 6-11-N, and from among the (B + 1) demodulated signals, the demodulated signal having the least error is selected for each system, and the final demodulated signal of N systems is provided. Is output as
[0123]
Hereinafter, the demodulator 6-8-b (1 ≦ b ≦ B) and the demodulation output selection circuit 6-11-n (1 ≦ n ≦ N) after the subtraction type interference cancellation will be described in more detail.
FIG. 7 is a block diagram illustrating a configuration of the demodulator 6-8-b (1 ≦ b ≦ B) after the subtraction type interference cancellation at the b-th stage. In FIG. 7, N first demodulated signals (when b = 1) output from N first demodulators 6-6-1 to 6-6-N or demodulation after subtraction-type interference cancellation at the preceding stage. The N-system second demodulated signals output from the modulator 6-8- (b-1) are N subcarrier remodulators 6-8-b-1-1 to 6-8- corresponding to each signal. According to b-1-N, subcarrier modulation is performed using the same modulation scheme as that used for transmission. The subtraction-type interference canceller 6-8-b-2 includes N subcarrier remodulators 6-8-b-1-1-1 to 6-8-b-1-N, as in the first embodiment. Using N output signals and the transfer coefficient matrix output from the transfer coefficient matrix calculator 6-3, N received signal delay units 6-7-b-1 to 6-7-b- are provided for each subcarrier. Mutual interference components included in N-system fast Fourier-transformed received signals supplied from N are canceled, and each fast-Fourier-transformed received signal is separated into signal components corresponding to each system of the OFDM signal. The weighting combiner 6-8-b-3 provides, for each subcarrier, a transfer coefficient matrix for the signal components separated by the subtraction type interference canceller 6-8-b-2, as in the first embodiment. Weighting is performed based on the transfer coefficient from the arithmetic unit 6-3, and desired signal components are combined. The N output signals output from the weighting combiner 6-8-b-3 are N second demodulators 6-8-b-4-1 to 6-8-b corresponding to each signal. The signal is demodulated by -4-N and is output as an N-system second demodulated signal.
[0124]
Next, the demodulation output selection circuit 6-11-n (1 ≦ n ≦ N) corresponding to the n-th system of the OFDM signal will be described. In FIG. 6, the OFDM signal receiving device 6 includes N demodulation output selection circuits 6-11-1 to 6-11-N for selecting a demodulation signal for each OFDM signal system. The demodulation output selection circuit 6-11-n for selecting the demodulation output of the n-th system includes a first demodulation signal of the n-th system and a plurality of (B in this embodiment) second demodulation signals. A demodulated signal is provided. Here, the first demodulated signal is synchronized with the demodulated signals by a multiplication type demodulation result delay unit 6-9-n. It is delayed until the 8-B second demodulated signal is output. The second demodulated signal of the n-th system output from the demodulator 6-8-b after the subtraction type interference cancellation at the b-th stage (1 ≦ b ≦ (b-1)) For synchronization, the subtraction type demodulation result delay unit 6-10-bn delays the signal until the second demodulation signal of the demodulator 6-8-B after the subtraction type interference cancellation at the final stage is output. Note that no delay unit is provided for the second demodulated signal output from the demodulator 6-8-B after the subtraction-type interference cancellation in the final stage.
[0125]
FIG. 8 is a block diagram showing a configuration of the demodulation output selection circuit 6-11-n (1 ≦ n ≦ N). In FIG. 8, (B + 1) error detectors 6-11-n-1-1 to 6-11-n-1- (B + 1) correspond to (B + 1) demodulated signals, and The detector 6-11-nm (1 ≦ m ≦ (B + 1)) detects an error amount of the corresponding demodulated signal. (B + 1) decision delay correctors 6-11-n-2-1 to 6-11-n-2- (B + 1) correspond to (B + 1) demodulated signals. Each decision delay corrector 6-11-n-2-m (1 ≦ m ≦ (B + 1)) provides a delay corresponding to the processing time of each error detector 6-11-nm with respect to the corresponding demodulated signal. And supplies the demodulated signal to the selector 6-11-n-3. The selector 6-11-n-3 refers to the detection results from the (B + 1) error detectors 6-11-n-1-1 to 6-11-n-1- (B + 1), and selects (B + 1 ) The demodulated signal having the least error is selected from the demodulated signals and output as the final demodulated signal of the n-th system.
[0126]
As described above, in the present embodiment, among the (B + 1) N demodulated signals in total of the N first demodulated signals and the B N second demodulated signals, the least error is present. Since a demodulated signal is selected for each system and output as one final N-system demodulated signal, the error rate characteristics can be improved. In particular, since the demodulated signal with the fewest errors is selected from a plurality of demodulated signals, it is possible to avoid an increase in errors due to repeated subtraction-type interference cancellation and weighting synthesis due to low estimation accuracy of the transfer coefficient matrix. it can.
[0127]
(Fourth embodiment)
The OFDM signal transmitting / receiving apparatus according to the present embodiment is almost the same as the OFDM signal transmitting / receiving apparatus according to the second embodiment, but includes error detection, selective remodulation, subtractive interference cancellation, weighted combining, demodulation, and decoding. It is characterized by repeating a cycle a plurality of times. Hereinafter, the present embodiment will be described with reference to the drawings, but description of parts common to the first and second embodiments will be omitted.
[0128]
The OFDM signal transmitting / receiving apparatus according to the present embodiment includes the same OFDM signal transmitting apparatus 4 and OFDM signal receiving apparatus 7 as those in the second embodiment.
FIG. 9 is a block diagram illustrating a configuration of the OFDM signal receiving device 7 according to the present embodiment. In FIG. 9, the configuration and operation from receiving antennas 7-1-1 to 7-1-N to first decoding means 7-7-1 to 7-7-N are the same as those of the OFDM signal receiving apparatus shown in FIG. 5, the description is omitted.
[0129]
The OFDM signal receiving apparatus 7 performs a plurality of stages (in this embodiment, B stages) for performing error detection, selective re-modulation, subtraction-type interference cancellation, weighting synthesis, demodulation, and decoding in the same manner as in the second embodiment. , And performs subtractive interference cancellation or the like repeatedly based on the N first decoded signals, thereby performing final decoding of N systems. Output a signal. Here, the number of decoders 7-8-1 to 7-8-B after the subtraction-type interference cancellation, that is, the number of repetitions B of the subtraction-type interference cancellation or the like is a minimum value from which a desired quality can be obtained from the viewpoint of the circuit scale. Is desirably the number of
[0130]
The first-stage subtraction-type interference cancellation decoder 7-8-1 outputs the outputs of the N first decoders 7-7-1 to 7-7-N which are the decoding results after the multiplication type interference cancellation. The calculation is performed using the signal, that is, the first decoded signal of N systems. In addition, in the second and subsequent stages, the subtraction-type interference cancellation decoder 7-8-b of the b-th stage (2 ≦ b ≦ B) performs the subtraction-type interference cancellation of the preceding stage (b-1). The operation is performed using the second decoded signal output by the post-decoder 7-8- (b-1).
[0131]
Here, in order for the first-stage subtraction-type interference cancellation decoder 7-8-1 to perform an operation, the processing of the first decoders 7-7-1 to 7-7-N is completed. Need to be. Therefore, for the first-stage subtraction-type interference cancellation decoder 7-8-1, the multiplication type interference canceller 7 is provided by the reception signal delayers 7-9-1-1 to 7-9-1-N. -4, weighters 7-5-1 to 7-5-N, first demodulators 7-6-1 to 7-6-N, first decoders 7-7-1 to 7-7-N After giving the same delay amount as the time required for the operation in, the output signals of the N fast Fourier transformers 7-2-1 to 7-2-N are supplied. Also, in order for the b-th (2 ≦ b ≦ B) stage subtraction-type interference cancellation decoder 7-8-b to perform an operation, the (b-1) -th stage subtraction-type interference cancellation decoder The calculation of 7-8- (b-1) needs to be completed. Then, for the output signals of the fast Fourier transformers 7-2-1 to 7-2-N, N received signal delayers 7-9-1-1 to 7-9-1-N of B stages,. , 7-9-B-1 to 7-9-BN to provide a delay to achieve timing synchronization. The N received signal delay units 7-9-b-1 to 7-9-b-N of the b-th stage are output signals of the N fast Fourier transformers 7-2-1 to 7-2-N. Is synchronized with the decoder 7-8-b after the subtraction type interference cancellation at the b-th stage. Then, for the decoder 7-8-b after the subtraction type interference cancellation at the b-th stage, the N received signal delay units 7-9-b-1 to 7-9-b- at the b-th stage. N, a delay corresponding to the processing time of the (b-1) -th subtraction-type interference cancellation decoder 7-8- (b-1) is given, and then the (b-1) -th reception is performed. The output signals of the signal delay units 7-9- (b-1) -1 to 7-9- (b-1) -N are supplied. Thereby, the output signals of the fast Fourier transformers 7-2-1 to 7-2-N can be synchronized with the decoder 7-8-b after the subtraction type interference cancellation at the b-th stage.
[0132]
Further, in the present embodiment, as in the second embodiment, N sub-carriers other than the sub-carriers that have been correctly decoded in all of the N systems have N weighting units 7-5-1 to 7-5-N. Use the output signal of the system. Therefore, it is necessary to give a delay to the N output signals of the N weighters 7-5-1 to 7-5-N. Therefore, the first-stage weighting device output signal delay units 7-10-1-1 to 7-10-1-N are provided for the first-stage subtraction-type interference cancellation decoder 7-8-1. After giving the same delay amount as the time required for the operation in the first demodulators 7-6-1 to 7-6-N and the first decoders 7-7-1 to 7-7-N, , And N output signals of the weighters 7-5-1 to 7-5-N. The post-subtraction interference canceling decoder 7-8-b of the b-th (2 ≦ b ≦ B) stage after the second stage is as follows. The N-th weighting device output signal delay units 7-10-b-1 to 7-10-bN of the b-th stage output the N weighting devices 7-5-1 to 7-5-N. Is synchronized with the decoder 7-8-b after the subtraction-type interference cancellation at the b-th stage. Then, for the b-th (2 ≦ b ≦ B) stage subtraction-type interference canceling decoder 7-8-b, the b-th stage N weighting device output signal delay units 7-10-b After giving a delay corresponding to the processing time of the decoder 7-8- (b-1) after subtraction-type interference cancellation in the (b-1) th stage by -1 to 7-10-bN, The output signals of the N weighting device output signal delay units 7-10- (b-1) -1 to 7-10- (b-1) -N at the (b-1) stage are supplied. As a result, the output signals of the weighters 7-5-1 to 7-5-N can be synchronized with the respective decoders 7-8-b after subtraction-type interference cancellation.
[0133]
By using the above-described delay line structure, similarly to the third embodiment, in the case of continuously processing N-system received signals, each of the subtraction-type interference cancellation decoders 7-8-1 to 7-7-1 is used. Pipeline processing can be performed for each 8-B, and the circuit scale can be reduced.
[0134]
Hereinafter, the decoder 7-8-b (1 ≦ b ≦ B) after the subtraction-type interference cancellation will be described in more detail.
FIG. 10 is a block diagram showing the configuration of the decoder 7-8-b after the subtraction type interference cancellation at the b-th stage. In FIG. 10, N error detectors 7-8-b-1-1 to 7-8-b-1-N are N first decoders 7-7-1 to 7-7-N. Output from the N-system first decoded signal (when b = 1) or the N-system second decoded signal output from the preceding-stage subtraction-type interference cancellation decoder 7-8- (b-1) , The error and the position of the error are detected using the error detection code. The N selective remodulators 7-8-b-2-1-1 to 7-8-b-2-N are provided with error detectors 7-8-b-1-1 as in the second embodiment. 7-8-b-1-N, select subcarriers that are correctly decoded in all N systems with reference to the position of the error detected, and use the same subcarrier as the transmission signal for the decoded signal corresponding to the subcarrier. Perform modulation. The subtraction type interference canceller 7-8-b-3 uses the output signals of the N systems of the selective remodulators 7-8-b-2-1 to 7-8-b-2-N and the transfer coefficient matrix. Then, for each of the selected subcarriers, the mutual signals included in the N-system received signals after the fast Fourier transform supplied from the received signal delay units 7-9-b-1 to 7-9-bN are received. The interference component is canceled, and each received signal after the fast Fourier transform is separated into signal components corresponding to each system of the OFDM signal.
[0135]
The weighting combiner 7-8-b-4 weights the signal components separated by the subtraction type interference canceller 7-8-b-3 based on the transfer coefficient for each of the selected subcarriers, and outputs an OFDM signal. The signal components corresponding to the respective systems are synthesized. The N output signals of the weighting combiner 7-8-b-4 are output from N multiplication-type interference cancellation signal delay units 7-10-b-1 to 7-10-b-N. Together with the N output signals of the weighters 8-5-1 to 8-5-N, the N interference cancel signal multiplexers 7-8-b-5-1 to 7-8-b-5-N are used. Supplied. In the interference cancellation signal multiplexers 7-8-b-5-1 to 7-8-b-5-N, the weighted combiners for the subcarriers where the outputs of the weighted combiners 7-8-b-4 are present 7-8-b-4 N-system output signals and weighter output signal delayers 7-10-b-1 to 7-7 for subcarriers for which there is no output of weighting combiner 7-8-b-4 N output signals of 10-b-N are multiplexed. The N output signals of the interference cancellation signal multiplexers 7-8-b-5-1 to 7-8-b-5-N are N second demodulators 7-8- corresponding to each signal. demodulated by b-6-1 to 7-8-b-6-N, and then subjected to error correction decoding by second decoders 7-8-b-7-1 to 7-8-b-7-N. , N-system second decoded signals. Here, the second decoders 7-8-B-7-1 to 7-8-B-7-N at the final stage output the N-system second decoded signals as N-system final decoded signals. .
[0136]
As described above, according to the present embodiment, more accurate subtraction-type interference cancellation can be performed by repeating the operations of error detection, selective remodulation, subtraction-type interference cancellation, weighting synthesis, demodulation, and decoding. And the error rate characteristic can be improved.
[0137]
It is needless to say that the present invention is not limited to the above embodiments.
[0138]
【The invention's effect】
According to the first, fifth, and ninth aspects, a demodulated signal having few errors is selected for each system from the N-system demodulated signals after the multiplication-type interference cancellation and the N-system demodulated signals after the subtraction-type interference cancellation. Therefore, it is possible to improve the error rate characteristics in a case where only the demodulated signal after the multiplication-type interference cancellation or only the demodulation signal after the subtraction-type interference cancellation is used.
[0139]
According to the second, sixth, and tenth aspects of the invention, subtraction-type interference cancellation and weighting synthesis are further performed on subcarriers in which all of the N decoded signals after multiplication-type interference cancellation are correct, so that a more accurate decoded signal is obtained. be able to. On the other hand, for a subcarrier including an error, since the signal after the multiplication-type interference cancellation is decoded, the output of the subtraction-type interference cancellation using the replica of the erroneous transmission signal can be prevented from being included in the final decoded signal. . As a result, the error rate characteristics can be improved.
[0140]
According to the third, seventh, and eleventh aspects, the demodulated signal with the least error is selected from the N-system demodulated signal after the multiplication-type interference cancellation and the N-system demodulated signal obtained by repeatedly performing the subtraction-type interference cancellation. Is selected for each system, so that it is possible to improve the accuracy of a decoded signal by repeating subtraction-type interference cancellation and weighting synthesis, while avoiding an increase in errors due to repetition that occurs when the estimation accuracy of the transfer coefficient matrix is low. . As a result, the error rate characteristics can be improved.
[0141]
According to the fourth, eighth, and twelfth aspects, the subtraction-type interference cancellation and the weighting combination are repeatedly performed on the subcarriers in which the decoded signals are all N systems, so that a decoded signal with higher accuracy can be obtained. On the other hand, for a subcarrier including an error, since the signal after the multiplication-type interference cancellation is decoded, the output of the subtraction-type interference cancellation using the replica of the erroneous transmission signal can be prevented from being included in the final decoded signal. . As a result, the error rate characteristics can be improved.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an OFDM signal transmitting / receiving apparatus according to a first embodiment.
FIG. 2 is a block diagram illustrating a configuration of a demodulation signal selection circuit 2-13-1 according to the first embodiment.
FIG. 3 is a diagram illustrating a packet error rate characteristic.
FIG. 4 is a block diagram illustrating a configuration of an OFDM signal transmitting apparatus according to a second embodiment.
FIG. 5 is a block diagram illustrating a configuration of an OFDM signal receiving apparatus according to a second embodiment.
FIG. 6 is a block diagram illustrating a configuration of an OFDM signal receiving apparatus according to a third embodiment.
FIG. 7 is a diagram illustrating a configuration of a demodulator 6-8-b after subtraction type interference cancellation at the b-th stage according to the third embodiment.
FIG. 8 is a diagram illustrating a configuration of a demodulation output selection circuit 6-11-n according to a third embodiment.
FIG. 9 is a block diagram illustrating a configuration of an OFDM signal receiving apparatus according to a fourth embodiment.
FIG. 10 is a block diagram illustrating a configuration of a decoder 7-8-b after subtraction-type interference cancellation at the b-th stage according to the fourth embodiment.
FIG. 11 is a block diagram showing a configuration of a conventional OFDM signal transmitting / receiving apparatus.
FIG. 12 is a diagram illustrating a configuration of a subtractive interference canceller and a weighting combiner according to a conventional OFDM signal transmitting / receiving apparatus.
FIG. 13 is a diagram illustrating packet error rate characteristics.
[Explanation of symbols]
1 OFDM signal transmission device
1-1-1-1-1-N error detection code multiplexer
1-2-1 to 1-2-N Pilot signal generator
1-3-1 to 1-3-N Pilot signal multiplexer
1-4-1 to 1-4-N subcarrier modulator
1-5-1 to 1-5-N Inverse fast Fourier transformer
1-6-1 to 1-6-N transmitting antenna
2 OFDM signal receiver
2-1-1-2-1-N receiving antenna
2-2-1-2-2-2N Fast Fourier Transformer
2-3 Transfer coefficient matrix calculator
2-4 Multiplication type interference canceller
2-5-1 to 2-5-N weighting device
2-6-1 to 2-6-N First demodulator
2-7-1 to 2-7-N subcarrier remodulator
2-8-1 to 2-8-N Received signal delay unit
2-9 Subtraction interference canceller
2-10 Weighting synthesizer
2-11-1 to 2-11-N Second demodulator
2-12-1 to 2-12-N Demodulation signal delay unit
2-13-1 to 2-13-N Demodulated signal selection circuit
3-1 First error detection circuit
3-2 Second error detection circuit
3-3 First decision delay corrector
3-4 Second decision delay corrector
3-5 Signal selection circuit
4 OFDM signal transmission device
4-1-1 to 4-1-N detection code multiplexer
4-2-1 to 4-2-N Pilot signal generator
4-3-1 to 4-3-N Pilot signal multiplexer
4-4-1 to 4-4-N subcarrier modulator
4-5-1 to 4-5-N Inverse fast Fourier transformer
4-6-1 to 4-6-N transmitting antenna
4-7-1 to 4-7-N Error Correction Encoder
5 OFDM signal receiver
5-1-1 to 5-1-N receiving antenna
5-2-1 to 5-2-N Fast Fourier Transformer
5-3 Transfer coefficient matrix calculator
5-4 Multiplication type interference canceller
5-5-1 to 5-5-N Weighter
5-6-1 to 5-6-N First demodulator
5-7-1 to 5-7-N First Decoder
5-8-1 to 5-8-N Error Detector
5-9-1 to 5-9-N Selective Remodulator
5-10-1 to 5-10-N Receive signal delay unit
5-11 Subtraction interference canceller
5-12 Weighting synthesizer
5-13-1 to 5-13-N Weighting device output signal delay device
5-14-1 to 5-14-N interference canceling signal multiplexer
5-15-1 to 5-15-N Second Demodulator
5-16-1 to 5-16-N Second Decoder
6 OFDM signal receiver
6-1-1 to 6-1-N receiving antenna
6-2-1 to 6-2-N Fast Fourier Transformer
6-3 Transfer coefficient matrix calculator
6-4 Multiplication type interference canceller
6-5-1 to 6-5-N weighting device
6-6-1 to 6-6-N First demodulator
6-7-1- (1 to N) to 6-7-B- (1 to N) Received signal delay unit
6-8-1 to 6-8-B Demodulator after Subtraction Interference Cancellation
6-8-b-1-1 to 6-8-b-1-N subcarrier remodulator
6-8-b-2 Subtraction interference canceller
6-8-b-3 Weighting synthesizer
6-8-b-4-1 to 6-8-b-4-N Second Demodulator
6-9-1 to 6-9-N Multiplication Type Demodulation Result Delay Unit
6-10-1- (1 to N) to 6-10- (b-1)-(1 to N) Subtraction type demodulation result delay device
6-11-1 to 6-11-N Demodulation Output Selection Circuit
6-11-n-1-1 to 6-11-n-1- (B + 1) Error detector
6-11-n-2-1 to 6-11-n-2- (B + 1) decision delay corrector
6-11-n-3 selector
7 OFDM signal receiver
7-1-1 to 7-1-N receiving antenna
7-2-1 to 7-2-N Fast Fourier Transformer
7-3 Transfer coefficient matrix calculator
7-4 Multiplication type interference canceller
7-5-1 to 7-5-N weighting device
7-6-1 to 7-6-N First Demodulator
7-7-1 to 7-7-N First Decoder
7-8-1 to 7-8-B Decoder after Subtraction Interference Cancellation
7-8-b-1-1 to 7-8-b-1-N error detector
7-8-b-2-1-1 to 7-8-b-2-N Selective Remodulator
7-8-b-3 Subtraction interference canceller
7-8-b-4 Weighting synthesizer
7-8-b-5-1 to 7-8-b-5-N interference canceling signal multiplexer
7-8-b-6-1 to 7-8-b-6-N Second demodulator
7-8-b-7-1 to 7-8-b-7-N Second Decoder
7-9-1- (1 to N) to 7-9-B- (1 to N) Received signal delay unit
7-10-1- (1 to N) to 7-10-B- (1 to N) Weighting device output signal delay device

Claims (12)

OFDM signal receiving apparatus for receiving N systems of orthogonal frequency division multiplexing (OFDM) signals each including an error detection code and a known pilot signal and transmitted at the same frequency from N (N is an integer of 2 or more) transmission antennas And
N receiving antennas for receiving the spatially multiplexed signals of the N OFDM signals;
Fast Fourier transform means for fast Fourier transforming each of the N systems of received signals received by the N receiving antennas to convert the received signals into sub-carrier received signals;
By using a pilot signal included in the N-system received signals after the fast Fourier transform and the known pilot signal, a transmission having a transmission coefficient between each transmitting antenna and each receiving antenna as an element for each subcarrier. Transfer coefficient matrix calculating means for calculating a coefficient matrix and a transfer coefficient inverse matrix which is an inverse matrix thereof,
For each subcarrier, multiply the received signal of the N systems after the fast Fourier transform by the inverse transfer coefficient matrix, and cancel the mutual interference component between the systems included in the received signal of the N systems after the fast Fourier transform. Multiplication type interference canceling means,
Weighting means for weighting the output signals of the N systems of the multiplication type interference cancellation means for each subcarrier in accordance with the transfer coefficient;
First demodulation means for demodulating each of the N-system output signals of the weighting means and outputting N-system first demodulated signals;
Subcarrier re-modulation means for performing the same subcarrier modulation as at the time of transmission on each of the first demodulated signals of the N systems;
Using the output signals of the N systems of the subcarrier remodulation means and the transfer coefficient matrix, a replica of the mutual interference component between the systems is generated for each subcarrier, and the replica is converted into N systems after the fast Fourier transform. Subtraction-type interference canceling means for canceling the mutual interference component between the systems included in each of the received signals by subtracting from the received signals, and separating each of the received signals into signal components corresponding to the respective systems of the OFDM signal. ,
Weighting means for performing weighting based on the transfer coefficient for each subcarrier for the signal components separated by the subtraction-type interference canceling means, and combining signal components corresponding to each system of the OFDM signal;
Second demodulation means for demodulating each of the N-system output signals of the weighting and synthesizing means and outputting N-system second demodulated signals;
Error detection means for detecting an error amount of each of the N-system first and second demodulated signals using the error detection code;
An OFDM signal comprising: a demodulation signal selection unit that selects a demodulation signal having a small number of errors among the first and second demodulation signals of the N systems for each system based on a detection result of the error detection unit. Receiver. An N-system orthogonal frequency division multiplexing (OFDM) signal, each of which is error-correction coded, contains an error detection code and a known pilot signal, and is transmitted at the same frequency from N transmission antennas (N is an integer of 2 or more). An OFDM signal receiving apparatus for receiving,
N receiving antennas for receiving the spatially multiplexed signals of the N OFDM signals;
Fast Fourier transform means for fast Fourier transforming each of the N systems of received signals received by the N receiving antennas to convert the received signals into sub-carrier received signals;
By using a pilot signal included in the N-system received signals after the fast Fourier transform and the known pilot signal, a transmission having a transmission coefficient between each transmitting antenna and each receiving antenna as an element for each subcarrier. Transfer coefficient matrix calculating means for calculating a coefficient matrix and a transfer coefficient inverse matrix which is an inverse matrix thereof,
For each subcarrier, multiply the received signal of the N systems after the fast Fourier transform by the inverse transfer coefficient matrix, and cancel the mutual interference component between the systems included in the received signal of the N systems after the fast Fourier transform. Multiplication type interference canceling means,
Weighting means for weighting the output signals of the N systems of the multiplication type interference cancellation means for each subcarrier in accordance with the transfer coefficient;
First demodulation means for demodulating each of the N-system output signals of the weighting means;
First decoding means for performing error correction decoding on each of the N output signals of the first demodulation means and outputting N decoded signals;
Error detection means for detecting an error position using the error detection code for each of the N-system decoded signals;
A selection-type re-modulation unit that selects a subcarrier that is correctly decoded in all N systems with reference to the detection result of the error detection unit and performs the same subcarrier modulation as that at the time of transmission for a decoded signal corresponding to the subcarrier;
Using the output signals of the N systems of the selective remodulation means and the transfer coefficient matrix, a replica of a mutual interference component between the systems is generated for each selected subcarrier, and the replica is subjected to the fast Fourier transform. Subtraction from the N systems of received signals to cancel mutual interference components between systems included in each of the received signals, and separate each received signal into signal components corresponding to each system of the OFDM signal. Cancellation means,
Weighting combining for weighting the signal components separated by the subtraction type interference canceling means based on the transfer coefficient for each selected subcarrier, and combining signal components corresponding to each system of the OFDM signal. Means,
Second demodulation means for combining and demodulating the N-system output signals of the weighting / combining means and the N-system output signals of the weighting means for subcarriers not selected by the selective remodulation means;
A second decoding unit for performing error correction decoding on each of the N output signals of the second demodulation unit;
An OFDM signal receiving device comprising: OFDM signal receiving apparatus for receiving N systems of orthogonal frequency division multiplexing (OFDM) signals each including an error detection code and a known pilot signal and transmitted at the same frequency from N (N is an integer of 2 or more) transmission antennas And
N receiving antennas for receiving the spatially multiplexed signals of the N OFDM signals;
Fast Fourier transform means for fast Fourier transforming each of the N systems of received signals received by the N receiving antennas to convert the received signals into sub-carrier received signals;
By using a pilot signal included in the N-system received signals after the fast Fourier transform and the known pilot signal, a transmission having a transmission coefficient between each transmitting antenna and each receiving antenna as an element for each subcarrier. Transfer coefficient matrix calculating means for calculating a coefficient matrix and a transfer coefficient inverse matrix which is an inverse matrix thereof,
For each subcarrier, multiply the received signal of the N systems after the fast Fourier transform by the inverse transfer coefficient matrix, and cancel the mutual interference component between the systems included in the received signal of the N systems after the fast Fourier transform. Multiplication type interference canceling means,
Weighting means for weighting the output signals of the N systems of the multiplication type interference cancellation means for each subcarrier in accordance with the transfer coefficient;
First demodulation means for demodulating each of the N-system output signals of the weighting means and outputting N-system first demodulated signals;
Subtraction-type interference cancellation repetition means for repeatedly performing subtraction-type interference cancellation based on the first N-system demodulation signals and outputting a plurality of N-system second demodulation signals;
Error detection means for detecting an error amount of each of the N-system first demodulated signal and the plurality of N-system second demodulated signals using the error detection code;
A demodulation signal selection unit that selects a demodulation signal having the least error for each system from the N first demodulation signals and the plurality of N second demodulation signals based on the detection result of the error detection unit. Means,
The subtraction type interference cancellation repetition means,
Subcarrier re-modulation means for performing the same subcarrier modulation as at the time of transmission on each of the N-system demodulated signals;
Using the output signals of the N systems of the subcarrier remodulation means and the transfer coefficient matrix, a replica of the mutual interference component between the systems is generated for each subcarrier, and the replica is converted into N systems after the fast Fourier transform. Subtraction-type interference canceling means for canceling the mutual interference component between the systems included in each of the received signals by subtracting from the received signals, and separating each of the received signals into signal components corresponding to the respective systems of the OFDM signal. ,
Weighting means for performing weighting based on the transfer coefficient for each subcarrier for the signal components separated by the subtraction-type interference canceling means, and combining signal components corresponding to each system of the OFDM signal;
Second demodulation means for demodulating each of the N-system output signals of the weighting and synthesizing means and outputting N-system second demodulated signals;
With multiple stages,
The first-stage subcarrier remodulation unit modulates the N-system first demodulated signal, and the second-stage and subsequent subcarrier remodulation units respectively operate the N-system second demodulated signal in the preceding stage. An OFDM signal receiving apparatus, which modulates an OFDM signal. An N-system orthogonal frequency division multiplexing (OFDM) signal, each of which is error-correction coded, contains an error detection code and a known pilot signal, and is transmitted at the same frequency from N transmission antennas (N is an integer of 2 or more). An OFDM signal receiving apparatus for receiving,
N receiving antennas for receiving the spatially multiplexed signals of the N OFDM signals;
Fast Fourier transform means for fast Fourier transforming each of the N systems of received signals received by the N receiving antennas to convert the received signals into sub-carrier received signals;
By using a pilot signal included in the N-system received signals after the fast Fourier transform and the known pilot signal, a transmission having a transmission coefficient between each transmitting antenna and each receiving antenna as an element for each subcarrier. Transfer coefficient matrix calculating means for calculating a coefficient matrix and a transfer coefficient inverse matrix which is an inverse matrix thereof,
For each subcarrier, multiply the received signal of the N systems after the fast Fourier transform by the inverse transfer coefficient matrix, and cancel the mutual interference component between the systems included in the received signal of the N systems after the fast Fourier transform. Multiplication type interference canceling means,
Weighting means for weighting the output signals of the N systems of the multiplication type interference cancellation means for each subcarrier in accordance with the transfer coefficient;
First demodulation means for demodulating each of the N-system output signals of the weighting means;
First decoding means for performing error correction decoding on each of the N-system output signals of the first demodulation means and outputting N-system first decoded signals;
Subtraction-type interference cancellation repetition means for repeatedly performing subtraction-type interference cancellation using the first decoding signals of the N systems and outputting final decoding signals of the N systems,
The subtraction type interference cancellation repetition means,
Error detection means for detecting an error position using the error detection code for each of the N-system decoded signals;
A selection-type re-modulation unit that selects a subcarrier that is correctly decoded in all N systems with reference to the detection result of the error detection unit and performs the same subcarrier modulation as that at the time of transmission for a decoded signal corresponding to the subcarrier;
Using the output signals of the N systems of the selective remodulation means and the transfer coefficient matrix, a replica of a mutual interference component between the systems is generated for each selected subcarrier, and the replica is subjected to the fast Fourier transform. Subtraction from the N systems of received signals to cancel mutual interference components between systems included in each of the received signals, and separate each received signal into signal components corresponding to each system of the OFDM signal. Cancellation means,
Weighting combining for weighting the signal components separated by the subtraction type interference canceling means based on the transfer coefficient for each selected subcarrier, and combining signal components corresponding to each system of the OFDM signal. Means,
Second demodulation means for combining and demodulating the N-system output signals of the weighting / combining means and the N-system output signals of the weighting means for subcarriers not selected by the selective remodulation means;
A second decoding unit that performs error correction decoding on each of the N output signals of the second demodulation unit and outputs N second decoded signals;
With multiple stages,
The first-stage error detection means performs error detection on the N-system first decoded signal, and the second-stage and subsequent error detection means perform error detection on the N-system second decoded signal at the preceding stage, respectively. An OFDM signal receiving apparatus, wherein the detection is performed, and the second decoding means at the final stage outputs the second decoded signal as the final decoded signal. An OFDM signal transmitting / receiving apparatus comprising an orthogonal frequency division multiplexing (OFDM) signal transmitting apparatus and an OFDM signal receiving apparatus,
The OFDM signal transmission device,
Error detection code adding means for adding an error detection code to each of the input N transmission information signals (N is an integer of 2 or more);
Pilot signal adding means for adding a pilot signal to each of the N transmission information signals;
Subcarrier modulation means for performing subcarrier modulation on each of the N transmission information signals to which the error detection code and the pilot signal are added;
Inverse fast Fourier transform means for performing inverse fast Fourier transform on each of the N output signals of the subcarrier modulation means;
N transmission antennas for transmitting N-system OFDM signals output by the inverse fast Fourier transform means at the same frequency,
The OFDM signal receiving device includes:
N receiving antennas for receiving the spatially multiplexed signals of the N OFDM signals;
Fast Fourier transform means for fast Fourier transforming each of the N systems of received signals received by the N receiving antennas to convert the received signals into sub-carrier received signals;
By using a pilot signal included in the N-system received signals after the fast Fourier transform and the known pilot signal, a transmission having a transmission coefficient between each transmitting antenna and each receiving antenna as an element for each subcarrier. Transfer coefficient matrix calculating means for calculating a coefficient matrix and a transfer coefficient inverse matrix which is an inverse matrix thereof,
For each subcarrier, multiply the received signal of the N systems after the fast Fourier transform by the inverse transfer coefficient matrix, and cancel the mutual interference component between the systems included in the received signal of the N systems after the fast Fourier transform. Multiplication type interference canceling means,
Weighting means for weighting the output signals of the N systems of the multiplication type interference cancellation means for each subcarrier in accordance with the transfer coefficient;
First demodulation means for demodulating each of the N-system output signals of the weighting means and outputting N-system first demodulated signals;
Subcarrier re-modulation means for performing the same subcarrier modulation as the subcarrier modulation means for each of the first demodulated signals of the N systems;
Using the output signals of the N systems of the subcarrier remodulation means and the transfer coefficient matrix, a replica of the mutual interference component between the systems is generated for each subcarrier, and the replica is converted into N systems after the fast Fourier transform. Subtraction-type interference canceling means for canceling the mutual interference component between the systems included in each of the received signals by subtracting from the received signals, and separating each of the received signals into signal components corresponding to the respective systems of the OFDM signal. ,
Weighting means for performing weighting based on the transfer coefficient for each subcarrier for the signal components separated by the subtraction-type interference canceling means, and combining signal components corresponding to each system of the OFDM signal;
Second demodulation means for demodulating each of the N-system output signals of the weighting and synthesizing means and outputting N-system second demodulated signals;
Error detection means for detecting an error amount of each of the N-system first and second demodulated signals using the error detection code;
An OFDM signal comprising: a demodulation signal selection unit that selects a demodulation signal having few errors among the first and second demodulation signals of the N systems for each system based on a detection result of the error detection unit. Transceiver. An OFDM signal transmitting / receiving apparatus comprising an orthogonal frequency division multiplexing (OFDM) signal transmitting apparatus and an OFDM signal receiving apparatus,
The OFDM signal transmission device,
Error detection code adding means for adding an error detection code to each of the input N transmission information signals (N is an integer of 2 or more);
Error correction coding means for performing error correction coding on each of the N transmission information signals;
Pilot signal adding means for adding a pilot signal to each of the N transmission information signals;
Subcarrier modulation means for performing subcarrier modulation on each of the N transmission information signals to which the error detection code and the pilot signal are added;
Inverse fast Fourier transform means for performing inverse fast Fourier transform on each of the N output signals of the subcarrier modulation means;
N transmission antennas for transmitting N-system OFDM signals output by the inverse fast Fourier transform means at the same frequency,
The OFDM signal receiving device includes:
N receiving antennas for receiving the spatially multiplexed signals of the N OFDM signals;
Fast Fourier transform means for fast Fourier transforming each of the N systems of received signals received by the N receiving antennas to convert the received signals into sub-carrier received signals;
By using a pilot signal included in the N-system received signals after the fast Fourier transform and the known pilot signal, a transmission having a transmission coefficient between each transmitting antenna and each receiving antenna as an element for each subcarrier. Transfer coefficient matrix calculating means for calculating a coefficient matrix and a transfer coefficient inverse matrix which is an inverse matrix thereof,
For each subcarrier, multiply the received signal of the N systems after the fast Fourier transform by the inverse transfer coefficient matrix, and cancel the mutual interference component between the systems included in the received signal of the N systems after the fast Fourier transform. Multiplication type interference canceling means,
Weighting means for weighting the output signals of the N systems of the multiplication type interference cancellation means for each subcarrier in accordance with the transfer coefficient;
First demodulation means for demodulating each of the N-system output signals of the weighting means;
First decoding means for performing error correction decoding on each of the N output signals of the first demodulation means and outputting N decoded signals;
Error detection means for detecting an error position using the error detection code for each of the N-system decoded signals;
Selective remodulation that selects subcarriers that are correctly decoded in all N systems with reference to the detection result of the error detection means and performs the same subcarrier modulation as the subcarrier modulation means on a decoded signal corresponding to the subcarriers Means,
Using the output signals of the N systems of the selective remodulation means and the transfer coefficient matrix, a replica of a mutual interference component between the systems is generated for each selected subcarrier, and the replica is subjected to the fast Fourier transform. Subtraction from the N systems of received signals to cancel mutual interference components between systems included in each of the received signals, and separate each received signal into signal components corresponding to each system of the OFDM signal. Cancellation means,
Weighting combining for weighting the signal components separated by the subtraction type interference canceling means based on the transfer coefficient for each selected subcarrier, and combining signal components corresponding to each system of the OFDM signal. Means,
Second demodulation means for combining and demodulating the N-system output signals of the weighting / combining means and the N-system output signals of the weighting means for subcarriers not selected by the selective remodulation means;
An OFDM signal transmitting / receiving apparatus, comprising: a second decoding unit that performs error correction decoding on each of the N output signals of the second demodulation unit. An OFDM signal transmitting / receiving apparatus comprising an orthogonal frequency division multiplexing (OFDM) signal transmitting apparatus and an OFDM signal receiving apparatus,
The OFDM signal transmission device,
Error detection code adding means for adding an error detection code to each of the input N transmission information signals (N is an integer of 2 or more);
Pilot signal adding means for adding a pilot signal to each of the N transmission information signals;
Subcarrier modulation means for performing subcarrier modulation on each of the N transmission information signals to which the error detection code and the pilot signal are added;
Inverse fast Fourier transform means for performing inverse fast Fourier transform on each of the N output signals of the subcarrier modulation means;
N transmission antennas for transmitting N-system OFDM signals output by the inverse fast Fourier transform means at the same frequency,
The OFDM signal receiving device includes:
N receiving antennas for receiving the spatially multiplexed signals of the N OFDM signals;
Fast Fourier transform means for fast Fourier transforming each of the N systems of received signals received by the N receiving antennas to convert the received signals into sub-carrier received signals;
By using a pilot signal included in the N-system received signals after the fast Fourier transform and the known pilot signal, a transmission having a transmission coefficient between each transmitting antenna and each receiving antenna as an element for each subcarrier. Transfer coefficient matrix calculating means for calculating a coefficient matrix and a transfer coefficient inverse matrix which is an inverse matrix thereof,
For each subcarrier, multiply the received signal of the N systems after the fast Fourier transform by the inverse transfer coefficient matrix, and cancel the mutual interference component between the systems included in the received signal of the N systems after the fast Fourier transform. Multiplication type interference canceling means,
Weighting means for weighting the output signals of the N systems of the multiplication type interference cancellation means for each subcarrier in accordance with the transfer coefficient;
First demodulation means for demodulating each of the N-system output signals of the weighting means and outputting N-system first demodulated signals;
Subtraction-type interference cancellation repetition means for repeatedly performing subtraction-type interference cancellation based on the first N-system demodulation signals and outputting a plurality of N-system second demodulation signals;
Error detection means for detecting an error amount of each of the N-system first demodulated signal and the plurality of N-system second demodulated signals using the error detection code;
A demodulation signal selection unit that selects a demodulation signal having the least error for each system from the N first demodulation signals and the plurality of N second demodulation signals based on the detection result of the error detection unit. Means,
The subtraction type interference cancellation repetition means,
A subcarrier remodulation unit that performs the same subcarrier modulation as the subcarrier modulation unit on each of the N-system demodulated signals;
Using the output signals of the N systems of the subcarrier remodulation means and the transfer coefficient matrix, a replica of the mutual interference component between the systems is generated for each subcarrier, and the replica is converted into N systems after the fast Fourier transform. Subtraction-type interference canceling means for canceling the mutual interference component between the systems included in each of the received signals by subtracting from the received signals, and separating each of the received signals into signal components corresponding to the respective systems of the OFDM signal. ,
Weighting means for performing weighting based on the transfer coefficient for each subcarrier for the signal components separated by the subtraction-type interference canceling means, and combining signal components corresponding to each system of the OFDM signal;
Second demodulation means for demodulating each of the N-system output signals of the weighting and synthesizing means and outputting N-system second demodulated signals;
With multiple stages,
The first-stage subcarrier remodulation means modulates the N-system first demodulated signal, and the second-stage and subsequent subcarrier remodulation means respectively operate the N-system second demodulated signal in the preceding stage. An OFDM signal transmitting / receiving apparatus, which modulates an OFDM signal. An OFDM signal transmitting / receiving apparatus comprising an orthogonal frequency division multiplexing (OFDM) signal transmitting apparatus and an OFDM signal receiving apparatus,
The OFDM signal transmission device,
Error detection code adding means for adding an error detection code to each of the input N transmission information signals (N is an integer of 2 or more);
Error correction coding means for performing error correction coding on each of the N transmission information signals;
Pilot signal adding means for adding a pilot signal to each of the N transmission information signals;
Subcarrier modulation means for performing subcarrier modulation on each of the N transmission information signals to which the error detection code and the pilot signal are added;
Inverse fast Fourier transform means for performing inverse fast Fourier transform on each of the N output signals of the subcarrier modulation means;
N transmission antennas for transmitting N-system OFDM signals output by the inverse fast Fourier transform means at the same frequency,
The OFDM signal receiving device includes:
N receiving antennas for receiving the spatially multiplexed signals of the N OFDM signals;
Fast Fourier transform means for fast Fourier transforming each of the N systems of received signals received by the N receiving antennas to convert the received signals into sub-carrier received signals;
By using a pilot signal included in the N-system received signals after the fast Fourier transform and the known pilot signal, a transmission having a transmission coefficient between each transmitting antenna and each receiving antenna as an element for each subcarrier. Transfer coefficient matrix calculating means for calculating a coefficient matrix and a transfer coefficient inverse matrix which is an inverse matrix thereof,
For each subcarrier, multiply the received signal of the N systems after the fast Fourier transform by the inverse transfer coefficient matrix, and cancel the mutual interference component between the systems included in the received signal of the N systems after the fast Fourier transform. Multiplication type interference canceling means,
Weighting means for weighting the output signals of the N systems of the multiplication type interference cancellation means for each subcarrier in accordance with the transfer coefficient;
First demodulation means for demodulating each of the N-system output signals of the weighting means;
First decoding means for performing error correction decoding on each of the N-system output signals of the first demodulation means and outputting N-system first decoded signals;
Subtraction-type interference cancellation repetition means for repeatedly performing subtraction-type interference cancellation using the first decoding signals of the N systems and outputting final decoding signals of the N systems,
The subtraction type interference cancellation repetition means,
Error detection means for detecting an error position using the error detection code for each of the N-system decoded signals;
Selective remodulation that selects subcarriers that are correctly decoded in all N systems with reference to the detection result of the error detection means and performs the same subcarrier modulation as the subcarrier modulation means on a decoded signal corresponding to the subcarriers Means,
Using the output signals of the N systems of the selective remodulation means and the transfer coefficient matrix, a replica of a mutual interference component between the systems is generated for each selected subcarrier, and the replica is subjected to the fast Fourier transform. Subtraction from the N systems of received signals to cancel mutual interference components between systems included in each of the received signals, and separate each received signal into signal components corresponding to each system of the OFDM signal. Cancellation means,
Weighting combining for weighting the signal components separated by the subtraction type interference canceling means based on the transfer coefficient for each selected subcarrier, and combining signal components corresponding to each system of the OFDM signal. Means,
Second demodulation means for combining and demodulating the N-system output signals of the weighting / combining means and the N-system output signals of the weighting means for subcarriers not selected by the selective remodulation means;
A second decoding unit that performs error correction decoding on each of the N output signals of the second demodulation unit and outputs N second decoded signals;
With multiple stages,
The first-stage error detection means performs error detection on the N-system first decoded signal, and the second-stage and subsequent error detection means perform error detection on the preceding N-system second decoded signal, respectively. An OFDM signal transmitting and receiving apparatus, wherein the second decoding means in the final stage outputs the second decoded signal as the final decoded signal. OFDM signal receiving method for receiving N orthogonal frequency division multiplexing (OFDM) signals transmitted at the same frequency from N (N is an integer of 2 or more) transmission antennas each including an error detection code and a known pilot signal And
A receiving step of receiving a signal obtained by spatially multiplexing the N-system OFDM signals with N receiving antennas;
A fast Fourier transform step of fast Fourier transforming each of the N received signals received by the N receive antennas and converting the received signals into sub-carrier received signals;
By using a pilot signal included in the N-system received signals after the fast Fourier transform and the known pilot signal, a transmission having a transmission coefficient between each transmitting antenna and each receiving antenna as an element for each subcarrier. A transfer coefficient matrix calculating step of calculating a transfer coefficient inverse matrix which is a coefficient matrix and its inverse matrix,
For each subcarrier, multiply the received signal of the N systems after the fast Fourier transform by the inverse transfer coefficient matrix, and cancel the mutual interference component between the systems included in the received signal of the N systems after the fast Fourier transform. A multiplication-type interference cancellation step,
A weighting step of weighting each of the N-system signals whose mutual interference components have been canceled in the multiplication type interference cancellation step, for each subcarrier, according to the transfer coefficient;
A first demodulation step of demodulating each of the N-system signals weighted in the weighting step to obtain an N-system first demodulated signal;
A subcarrier remodulation step of performing the same subcarrier modulation as at the time of transmission on each of the first demodulated signals of the N systems;
Using the signal subjected to subcarrier modulation in the subcarrier remodulation step and the transfer coefficient matrix, a replica of a mutual interference component between systems is generated for each subcarrier, and the replica is subjected to the NFT after the fast Fourier transform. Subtraction interference canceling step of canceling mutual interference components between systems included in each of the received signals by subtracting from the received signals of the systems, and separating each of the received signals into signal components corresponding to each of the OFDM signals. When,
A weighting combining step of performing weighting based on the transfer coefficient for each subcarrier for the signal components separated in the subtraction-type interference cancellation step, and combining signal components corresponding to the respective systems of the OFDM signal,
A second demodulation step of demodulating each of the signals obtained in the weighting synthesis step to obtain N second demodulated signals;
An error detection step of detecting an error amount of each of the first and second demodulated signals of the N systems using the error detection code;
A demodulation signal selecting step of selecting a signal having a small number of errors among the first and second demodulated signals of the N systems for each system based on a detection result of the error detecting step. Method. An N-system orthogonal frequency division multiplexing (OFDM) signal, each of which is error-correction coded, contains an error detection code and a known pilot signal, and is transmitted at the same frequency from N transmission antennas (N is an integer of 2 or more). An OFDM signal receiving method for receiving,
A receiving step of receiving a signal obtained by spatially multiplexing the N-system OFDM signals with N receiving antennas;
A fast Fourier transform step of fast Fourier transforming each of the N received signals received by the N receive antennas and converting the received signals into sub-carrier received signals;
By using a pilot signal included in the N-system received signals after the fast Fourier transform and the known pilot signal, a transmission having a transmission coefficient between each transmitting antenna and each receiving antenna as an element for each subcarrier. A transfer coefficient matrix calculating step of calculating a transfer coefficient inverse matrix which is a coefficient matrix and its inverse matrix,
For each subcarrier, multiply the received signal of the N systems after the fast Fourier transform by the inverse transfer coefficient matrix, and cancel the mutual interference component between the systems included in the received signal of the N systems after the fast Fourier transform. A multiplication-type interference cancellation step,
A weighting step of weighting each of the N-system signals whose mutual interference components have been canceled in the multiplication type interference cancellation step, for each subcarrier, according to the transfer coefficient;
A first demodulation step of demodulating each of the N signals weighted in the weighting step;
A first decoding step of performing error correction decoding on each of the N-system signals demodulated in the first demodulation step to obtain N-system decoded signals;
An error detection step of detecting an error position using the error detection code for each of the N-system decoded signals;
A selection-type re-modulation step of selecting sub-carriers that are correctly decoded in all N systems with reference to the detection result of the error detection step, and performing the same sub-carrier modulation as at the time of transmission for the decoded signal corresponding to the sub-carrier; ,
Using the N-system signals subcarrier-modulated in the selective remodulation step and the transfer coefficient matrix, for each selected subcarrier, generate a replica of the mutual interference component between the systems, and The mutual interference component between the systems included in each of the received signals is canceled by subtracting from the received signals of the N systems after the fast Fourier transform, and the received signals are separated into signal components corresponding to the respective systems of the OFDM signal. Subtraction-type interference canceling step,
Weighting synthesis for weighting the signal components separated in the subtraction type interference cancellation step based on the transfer coefficient for each selected subcarrier, and synthesizing signal components corresponding to each system of the OFDM signal. Steps and
A second demodulation for combining and demodulating the N-system signals synthesized in the weighting synthesis step and the N-system signals weighted in the weighting step for the subcarriers not selected in the selective remodulation step; Steps and
A second decoding step of performing error correction decoding on each of the N signals demodulated in the second demodulation step;
A method of receiving an OFDM signal, comprising: OFDM signal receiving method for receiving N orthogonal frequency division multiplexing (OFDM) signals transmitted at the same frequency from N (N is an integer of 2 or more) transmission antennas each including an error detection code and a known pilot signal And
A receiving step of receiving a signal obtained by spatially multiplexing the N-system OFDM signals with N receiving antennas;
A fast Fourier transform step of fast Fourier transforming each of the N received signals received by the N receive antennas and converting the received signals into sub-carrier received signals;
By using a pilot signal included in the N-system received signals after the fast Fourier transform and the known pilot signal, a transmission having a transmission coefficient between each transmitting antenna and each receiving antenna as an element for each subcarrier. A transfer coefficient matrix calculating step of calculating a transfer coefficient inverse matrix which is a coefficient matrix and its inverse matrix,
For each subcarrier, multiply the received signal of the N systems after the fast Fourier transform by the inverse transfer coefficient matrix, and cancel the mutual interference component between the systems included in the received signal of the N systems after the fast Fourier transform. A multiplication-type interference cancellation step,
A weighting step of weighting each of the N-system signals whose mutual interference components have been canceled in the multiplication type interference cancellation step, for each subcarrier, according to the transfer coefficient;
A first demodulation step of demodulating each of the N-system signals weighted in the weighting step to obtain an N-system first demodulated signal;
A subtractive interference cancellation repetition step of repeatedly performing subtractive interference cancellation based on the first demodulated signals of the N systems to obtain a plurality of second demodulated signals of the N systems;
An error detection step of detecting an error amount of each of the first N demodulated signals and the plurality of second N demodulated signals using the error detection code;
A demodulation signal selection unit that selects a demodulation signal with the least error for each system from the first demodulation signal of the N systems and the second demodulation signals of a plurality of N systems based on the detection result of the error detection step. And
The subtractive interference cancellation repetition step,
A subcarrier remodulation step of performing the same subcarrier modulation as at the time of transmission on each of the N-system demodulated signals;
A replica of a mutual interference component between systems is generated for each subcarrier using the N-system signals subcarrier-modulated in the subcarrier remodulation step and the transfer coefficient matrix, and the replica is subjected to the fast Fourier transform. A subtraction type in which mutual interference components between systems included in each of the received signals are canceled by subtracting from the subsequent N systems of received signals, and each of the received signals is separated into signal components corresponding to each of the OFDM signals. An interference cancellation step;
A weighting combining step of performing weighting based on the transfer coefficient for each subcarrier for the signal components separated in the subtraction-type interference cancellation step, and combining signal components corresponding to the respective systems of the OFDM signal,
A second demodulation step of demodulating each of the N systems of signals synthesized in the weighting synthesis step to obtain N systems of second demodulated signals;
Is repeated a plurality of times,
In the first subcarrier remodulation step, the first demodulated signal of the N system is modulated, and in the second and subsequent subcarrier remodulation steps, the second demodulated signal of the previous N system is respectively modulated. A method for receiving an OFDM signal. An N-system orthogonal frequency division multiplexing (OFDM) signal, each of which is error-correction coded, contains an error detection code and a known pilot signal, and is transmitted at the same frequency from N transmission antennas (N is an integer of 2 or more). An OFDM signal receiving method for receiving,
A receiving step of receiving a signal obtained by spatially multiplexing the N-system OFDM signals with N receiving antennas;
A fast Fourier transform step of fast Fourier transforming each of the N received signals received by the N receive antennas and converting the received signals into sub-carrier received signals;
By using a pilot signal included in the N-system received signals after the fast Fourier transform and the known pilot signal, a transmission having a transmission coefficient between each transmitting antenna and each receiving antenna as an element for each subcarrier. A transfer coefficient matrix calculating step of calculating a transfer coefficient inverse matrix which is a coefficient matrix and its inverse matrix,
For each subcarrier, multiply the received signal of the N systems after the fast Fourier transform by the inverse transfer coefficient matrix, and cancel the mutual interference component between the systems included in the received signal of the N systems after the fast Fourier transform. A multiplication-type interference cancellation step,
A weighting step of weighting each of the N-system signals whose mutual interference components have been canceled in the multiplication type interference cancellation step, for each subcarrier, according to the transfer coefficient;
A first demodulation step of demodulating each of the N signals weighted in the weighting step;
A first decoding step of performing error correction decoding on each of the N-system signals demodulated in the first demodulation step to obtain N-system first decoded signals;
A subtractive interference cancellation repetition step of repeatedly performing subtractive interference cancellation using the first decoded signals of the N systems to obtain a final decoded signal of N systems.
The subtraction-type interference cancellation repetition step includes:
An error detection step of detecting an error position using the error detection code for each of the N decoded signals;
A selection-type re-modulation step of selecting sub-carriers that have been correctly decoded for all N systems with reference to the detection result of the error detection step, and performing the same sub-carrier modulation as at the time of transmission for a decoded signal corresponding to the sub-carrier;
Using the N-system signals subcarrier-modulated in the selective remodulation step and the transfer coefficient matrix, for each selected subcarrier, generate a replica of the mutual interference component between the systems, and The mutual interference component between the systems included in each of the received signals is canceled by subtracting from the received signals of the N systems after the fast Fourier transform, and the received signals are separated into signal components corresponding to the respective systems of the OFDM signal. Subtraction-type interference canceling step,
Weighting synthesis for weighting the signal components separated in the subtraction type interference cancellation step based on the transfer coefficient for each selected subcarrier, and synthesizing signal components corresponding to each system of the OFDM signal. Steps and
A second demodulation for combining and demodulating the N-system signals synthesized in the weighting synthesis step and the N-system signals weighted in the weighting step for the subcarriers not selected in the selective remodulation step; Steps and
A second decoding step of performing error correction decoding on each of the N-system signals demodulated in the second demodulation step to obtain N-system second decoded signals;
Is repeated a plurality of times,
In the first error detection step, error detection of the first decoded signal of the N systems is performed, and in the second and subsequent error detection steps, error detection of the previous second decoded signal of the N system is performed. Performing an OFDM signal receiving method, wherein the second decoded signal is obtained as the final decoded signal in the last second decoding step.

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