JP4480847B2 - Method and apparatus for multi-user transmission - Google Patents

Description

は、異なるアンテナで受信された単一の対応キャリア信号又はサブバンドと、等化器係数Ｅ［ｓ］とを下記の数１に従って、線形結合させることによって計算される。
【００５９】
【数１】

【００６０】
一実施形態では、この線形推定は最小２乗（ＬＳ）法に基づいて実行される。本発明のこの実施形態では、上記Ｅ［ｓ］は、数２で与えられる期待値を最小にするように計算される。所定の雑音エネルギー（シグマの２乗）と数３によって与えられるｘに対する条件とに関して、Ｅ［ｓ］は数４のＵ個のセットの線形方程式に従う。ここで、上付き文字Ｈは、エルミート転置行列を表す。
【００６１】
【数２】

【数３】

【数４】

【００６２】
本発明の一実施形態では、アップリンク通信に関するサブバンド毎のスカラー合成処理の方式は、線形ゼロ強制（ＺＦ）方式によって、コンポジットピア内の１つの端末からの、１つのサブバンド内のデータ信号のソフト推定値を取得する。本発明のこの実施形態では、上記Ｅ［ｓ］は、いわゆるゼロ強制方式で、雑音エネルギーを考慮せずに、チャンネル歪みを最大限に消滅させるように計算される。この実施形態では、Ｅ［ｓ］は、数５のＵ個のセットの線形方程式に従う。
【００６３】
【数５】

【００６４】
本発明の一実施形態では、アップリンク通信に関するサブバンド毎の合成処理の方式は、例えば最尤シンボル推定（ＭＬＳＥ）といった非線形方式によって、コンポジットピア内の１つの端末からの、１つのサブバンド内の（複数の）データ信号のソフト推定値を取得する。
【００６５】
本発明では、ダウンリンク通信に関する合成処理の方式が提示され、これはダウンリンク合成処理方式と呼ばれる。上記ダウンリンク合成処理方式は、処理ピアから送信されたデータ信号の、コンポジットピアでの推定を容易にするために処理ピア内で実行される。上記ダウンリンク合成処理方式は、少なくとも２つのデータ信号に基づいて空間ダイバーシティサンプルを生成して、その結果、合成データ信号を得る。それから上記合成データ信号はＩＳＰが施されて後に空間ダイバーシティ手段によって送信され、結果的にスペクトルが少なくとも部分的にオーバーラップしている送信データ信号となる。次いでこの送信データ信号は、チャンネル上で送信される。上記合成処理は、上記データ信号の変換されたものである合成データ信号を上記送信端末で決定するステップとして説明できる。その後、上記合成データ信号の逆サブバンド処理が実行され、続いて上記逆サブバンド処理された合成データ信号を上記空間ダイバーシティ手段によって送信するが、この送信される逆サブバンド処理された合成データ信号のスペクトルは少なくとも部分的にオーバーラップしている。
【００６６】
本発明の一実施形態では、ダウンリンク通信に関する合成処理の方式は、少なくとも１つのサブバンド内でダウンリンク通信用のサブバンド毎の合成処理を適用する。この実施形態では、上記ダウンリンク合成処理方式は、１つのサブバンドのデータ信号に基づいてこの特定の１つのサブバンド内に合成データ信号を生成する。これは、上記送信端末において合成データ信号を１つのサブバンドずつ決定することとして説明できる。
【００６７】
本発明の一実施形態では、上記ダウンリンク合成処理方式は、Ｘ［ｓ］というデータ信号と前置補償行列Ｅ_PRE［ｓ］とを線形結合させることによって、Ｙ［ｓ］という上記合成データシンボルを計算する。この実施形態では、次式の数６が成立する。
【００６８】
【数６】

【００６９】
一実施形態では、Ｕ＝Ａであり、またＥ_PRE［ｓ］はチャンネル行列の逆行列Ｈ^T(-1)［ｓ］である。
【００７０】
他の実施形態では、Ｕ＜Ａであり、またＥ_PRE［ｓ］は次式の数７が成立するようなチャンネル行列の擬似逆行列である。
【００７１】
【数７】

【００７２】
本発明の一実施形態では、ダウンリンク通信に関する合成処理の上記方式は、（複数の）送信及び／又は受信端末における（複数の）アナログフロントエンドの非理想的特性を考慮に入れる。
【００７３】
本発明の一実施形態では、ダウンリンク通信に関する合成処理の上記方式は、（複数の）アナログフロントエンドの歪みの発生を防止する。
【００７４】
本発明の一実施形態では、上記前置補償行列は、１つ以上の特定のサブバンド上の１つ以上のデータ信号についてゼロを備える。この実施形態では、効率的で有効な電力使用が得られる。
【００７５】
本発明の一実施形態では、コンポジットピアの端末ばかりでなく処理ピアの端末も、空間ダイバーシティ手段とサブバンド処理手段と合成処理手段とを有しており、処理ピアとコンポジットピアの両者は、少なくとも部分的にオーバーラップするスペクトルを有する送信データ信号を少なくとも部分的に同時に送信する少なくとも２つの端末を具体化している。この実施形態では、アップリンク合成処理方式とダウンリンク合成処理方式の両者とも、２つのピアの間でいずれの伝送方向にも使用できる。
【００７６】
好適な実施形態では、処理ピアは星形構成ネットワークの基地局であって、これはケーブルネットワークのバックボーンに接続可能である。異なる端末は、同一の周波数帯域で同時に基地局と通信する。これらの端末は、単一のフロントエンドとプレーンＯＦＤＭモデム（すなわち、ＳＤＭＡ処理機能を持たない）とを必要とするだけである。この実施形態は、例えば無線ローカルエリアネットワークといった用途のためにマルチパスフェージング環境で動作できる。この実施形態は、５〜６ＧＨｚ帯域で動作でき、１５５Ｍｂｐｓ以上のネットワーク性能を達成できる。この実施形態では、多数の送信手段及び／又は受信手段を備えた空間ダイバーシティ手段は基地局に集中しており、こうして全体的なハードウエアの複雑さと構成のコストとを削減している。この実施形態では、空間ダイバーシティ手段は、半波長の間隔を空けて配列された多数のアンテナを備える。また、各ピアは、変調技術としてＯＦＤＭに基づいて通信を行う。ＩＳＰとＳＰはそれぞれ、ＩＤＦＴ（Inverse Discrete Fourier Transform：離散フーリエ逆変換）処理とＤＦＴ（Discrete Fourier Transform：離散フーリエ変換）処理とに基づいて実行され、またサブバンドはキャリアと呼ぶことができる。巡回プレフィックスを含むガードインターバルは、送信機側のＯＦＤＭシンボルの間に挿入される。次いで、ＳＤＭＡは周波数領域に適用される。ＯＦＤＭとＳＤＭＡの両者の利点を集めたものに加えて、このアプローチは、時間領域方式と比較して空間ダイバーシティのさらに簡単な利用をもたらす。ＯＦＤＭ／ＳＤＭＡシステムの推定アルゴリズムに関しては、既知の最小２乗（ＬＳ）又は最尤シンボル推定（ＭＬＳＥ）アルゴリズムが適用できる。また、改良された性能とさらに低い複雑さとを有する新しいクラスのアップリンクＯＦＤＭ／ＳＤＭＡ方式も適用可能である。これらの方式は、キャリア毎の連続的干渉除去（相殺）と状態挿入とコヒーレンスによるグループ分けとを実現する。
【００７７】
性能を例示するために、これらのアルゴリズムが、１００ＭｂｐｓのＯＦＤＭ／ＳＤＭＡのＷＬＡＮに適用される。このＷＬＡＮは、最大で４人同時に存在するユーザをＳＤＭＡによって分離する、４つのアンテナの基地局を持つ。これらのアンテナの各々は、ＱＰＳＫ変調によって２５Ｍｂｐｓのデータ速度で２５６個のＯＦＤＭシンボルを送信する。ガードインターバルは、チャンネルの畳み込みがガードインターバルを除去した後に巡回的になるように、マルチパス伝搬チャンネルで受信されるすべてのエコーを備えるように設計される。このようにして周波数領域では、これはチャンネルのフーリエ変換ｈ^U _a［ｓ］による乗算と等価になる。同一の帯域で同時に通信する異なるユーザを同期させる対策が取られる。これらの条件下で受信データＹ［ｓ］は、数８のように書くことができる。所定の状況下では、データシーケンスＸ^U［ｓ］の推定値
【外２】

を１つのキャリア（搬送波）ずつ計算することが可能である。このキャリア毎の推定は、ＳＤＭＡ処理を大幅に単純化し、この処理の大幅な並行処理化を可能にする。実際のＳＤＭＡ／ＯＦＤＭを実行する装置は、サブバンド処理された受信データ信号のサブバンドの一部に基づいて、好ましくは、各回路部毎に１つのサブバンドで、データ信号の推定値を決定するように適応された複数の回路を備える。キャリア毎の推定に引き続いて、送信アルファベットの何れの要素がこのキャリア毎の推定から得られた信号に最も近いかの決定が実行される。この決定の結果、ハード推定値
【外３】

が得られる。
【００７８】
【数８】

【００７９】
アップリンクにおけるキャリア毎のＳＤＭＡ処理は、線形な方法で実行することができる。この場合、端末によって送信されるデータ信号の推定値
【外４】

は、異なるアンテナで受信される単一の対応するキャリアの信号と等化器係数Ｅ［ｓ］とを数１に従って、線形結合させることによって計算される。
【００８０】
上記Ｅ［ｓ］は、数２によって与えられる期待値を最小にするように計算される。所定の雑音エネルギー（シグマの２乗）と数３によって与えられるｘについての条件とに関して、Ｅ［ｓ］は数４のＵ個のセットの線形方程式に従う。ここで上付き文字Ｈはエルミート転置行列を表す。
【００８１】
等化に続いてソフト推定値が、ある決定方式によって最も近い配列点を決定するスライサに供給される。この結果としてハード推定値
【外５】

が得られる。その代わりに、いわゆるゼロ強制方式で、雑音エネルギーを考慮せずにチャンネル歪みを最大限に消滅させるような等化器係数Ｅ［ｓ］が計算できる。Ｅ［ｓ］は数５によって与えられるように、Ｕ個のセットの線形方程式に従う。
【００８２】
このシステムの性能は、レイトレーシングから得られる現実的なチャンネルデータによるシミュレーションによって評価される。この結果得られる曲線は、ビット当たりの受信信号対雑音比（ＳＮＲ）の関数としてのビット誤り率（ＢＥＲ）を示す。
【００８３】
図３は、同時に存在する１人から４人のユーザに関するＬＳ−ＯＦＤＭ／ＳＤＭＡの性能を示す。参考として破線の曲線は、１人のユーザと１個のアンテナの１００ＭｂｐｓプレーンＯＦＤＭリンクの性能を示す。重要な観測結果は、４個のアンテナと４人のユーザのＬＳ−ＯＦＤＭ／ＳＤＭＡシステムが性能的にプレーンＯＦＤＭより優れていることである。これは、帯域幅再使用係数４が性能低下なしに達成可能であることを示している。
【００８４】
実施形態の複雑さを評価するために、我々はＬＳ−ＯＦＤＭ／ＳＤＭＡアルゴリズムを実行するために必要とされる演算の総回数を決定する。機能全体を初期設定と処理とに分けることができる。初期設定時には、等化器Ｅ_LS［ｓ］は、複数の右辺を用いるガウスの消去法によって数４から計算される。処理時には、それぞれが行列乗算と１組のコンパレータ（比較器）とに対応する等化とスライシングとを実行しなくてはならない。１回だけ計算される初期設定とは反対に、処理はシンボルレートで連続的に実行されることに留意されたい。図９は、１つのサブキャリア（副搬送波）当たり、これら両方の段階（フェーズ）の実行に必要とされる乗算と加算とデータ転送との近似的な回数を要約している。データ転送の回数は、メモリ／レジスタ転送の量を示す数である。このアーキテクチャはまだ決定されていないので、メモリ又はレジスタバンクへのデータ転送の割当ては未解決の問題である。しかしながら、データ転送がしばしば実用化の障害となることを強調することは重要である。例として４人のユーザと４個のアンテナのシステムは、初期設定時に７２ｋＦＬＯＰＳで２００ｋ個のデータ転送とを必要とし、処理時に４００ＭＦＬＯＰＳ／秒と１．２Ｇワード／秒のデータ転送帯域幅とを必要とする。
【００８５】
ＯＦＤＭ／ＳＤＭＡシステムでは、一定のサブキャリアに関して、１人以上のユーザがマルチユーザ干渉（ＭＵＩ）内に完全に埋め込まれるか、高度に相関的なチャンネルベクトルを持つことができる。明らかにこれらのユーザは、線形等化の後に残りのＭＵＩと雑音とから悪影響を受ける。この効果を軽減するために本発明では、連続的干渉除去（Successive Interference Cancellation：ＳＩＣ）が、好ましくはキャリア毎に（Per Carrier）使用される（ｐｃＳＩＣ）。ＬＳ−ＯＦＤＭ／ＳＤＭＡとは逆にこの技術は、すべてのユーザを同時に評価することはなく、連続的にこれを、好ましくはある１つのサブキャリアについて行う。そのようなものとして、既に検出されているユーザから発生するＭＵＩは、除去することができる（それによって元の単一のキャリアを修正する）。この技術は、中間ハード推定値のフィードバックに依存し、従って非線形である。ｐｃＳＩＣ−ＯＦＤＭ／ＳＤＭＡは、−キャリア毎を基準として働くことが好ましいので−ＯＦＤＭ／ＳＤＭＡ合成の相乗効果の他の例である周波数ダイバーシティを巧みに利用していることにも留意されたい。さらに、キャリア毎の連続干渉除去法（ｐｃＳＩＣ）が提示されるが、本発明はこれに限定されることはない。各サブキャリアｎについて、先ず検出順序が、好ましくは受信信号電力に従って決定される。ユーザ１からユーザＵが適当に順序づけられるものと仮定する。続いて各ユーザのソフト推定値が、数９に従って最小２乗線形結合によって計算される。
【００８６】
【数９】

【数１０】

【００８７】
この方程式では、各繰り返しｕに関してＨ［ｓ］が数１０によって数８からの初期値ｙ_a［ｓ］に等しいｙ¹ _a［ｓ］に置き換えられるということを除いて、Ｅ_LS［ｓ］は数４におけるものとして見いだされる。その後、（決定方式である）スライシングの後に、ユーザｕのハード中間推定値である
【外６】

を有する数１１におけるように、ユーザｕから発生したＭＵＩは、再構成され（一般に再合成と呼ばれる）、残りのＭＵＩから差し引かれる（それによって修正される）。普通のｐｃＳＩＣアルゴリズムには、（選択方式である）ハード推定値としてその後に選択される、各キャリア毎に各データ信号のただ１個の中間ハード推定値が存在する。
【００８８】
【数１１】

【００８９】
連続干渉除去（ＳＩＣ）は、アップリンク伝送方式として説明でき、ここでは、少なくとも１つの（ただし１つに限定されない）データ信号に関する上記受信端末における上記サブバンド処理された受信データ信号からの上記データ信号の上記推定値の上記決定は、次のステップを備える。すなわち、（第１のステップ）上記データ信号から１つの選択信号を選択するステップ。この選択ステップは例えば、受信信号電力に従って順序づけられているデータ信号から第１の信号を選択することであるが、これに限定されない。（第２のステップ）上記サブバンド処理された受信データ信号から上記選択されたデータ信号の推定値を決定するステップであって、例えば、スライシングを含む、サブバンド処理された受信データ信号の線形な合成法であるが、これに限定されない。（第３のステップ）上記選択された受信データ信号の上記推定値に基づいて上記サブバンド処理された受信データ信号を修正するステップであって、例えば、修正されたサブバンド処理済みの受信データ信号が得られるように、数１１に従って再合成して除算することであるが、これに限定されない。（第４のステップ）最後に上記修正されたサブバンド処理済みの受信データ信号からの上記残りのデータ信号の推定値が、恐らくこれらの同一のステップを逐次に適用することによって決定される。サブバンドは、キャリアとも表記できることに留意されたい。
【００９０】
連続干渉除去アップリンク伝送方式の一実施形態では、推定値の上記決定（すべてのステップ）は１つのサブバンドずつ実行される。
【００９１】
図４は、ｐｃＳＩＣ−ＯＦＤＭ／ＳＤＭＡの性能を示す。再び、ＳＮＲ曲線についてのＢＥＲは、１人から４人のユーザについて与えられている。参考として破線の曲線は１人のユーザと１個のアンテナの１００ＭｂｐｓプレーンＯＦＤＭの性能を示し、細い曲線は、ＬＳ−ＯＦＤＭ／ＳＤＭＡの性能を示す。これは、ｐｃＳＩＣ−ＯＦＤＭ／ＳＤＭＡがＬＳ−ＯＦＤＭ／ＳＤＭＡと比較して、ユーザ数の増加と共に増加する性能の改善をもたらすことを示している。詳しくは、ＢＥＲが０．００１で同時に４人のユーザが存在する場合に、我々は５ｄＢの利得を観測した。ＯＦＤＭ／ＳＤＭＡに関するｐｃＳＩＣアルゴリズムの複雑さの評価については、我々も初期設定と処理とを区別して見ている。初期設定時には除去順序が決定されて、等化器が計算される。チャンネル行列はユーザｕ毎に異なるので、後者はＵ回の異なるガウス消去を必要とする。しかしながら、各Ｈ_u［ｓ］間の構造的関係を利用することによって、我々は、Ｏ（Ａ² Ｕ²）による演算の必要回数をうまく削減した。処理時には等化とスライシングに加えて、再構成（再合成）と減算（修正）とを実行しなくてはならない。ｐｃＳＩＣ−ＯＦＤＭ／ＳＤＭＡアルゴリズムのこれら両段階についての演算の近似的な総回数は、図１０に与えられている。詳しくは、４人のユーザと４個のアンテナのシステムはそれぞれ、初期設定段階において１７０ｋＦＬＯＰＳで２５０ｋ個のデータ転送を必要とし、（処理の段階では）７００ＭＦＬＯＰＳ／秒と１．８Ｇワード／秒のデータ転送帯域幅とを必要とする。
【００９２】
（ｐｃ）ＳＩＣ−ＯＦＤＭ／ＳＤＭＡの潜在的弱点は、少なくとも二人のユーザが略等しい電力で受信されたときその性能が低下するということである。このような伝送条件下では誤った決定を行う確率が増加し、誤りが伝搬するという結果を招く。この潜在的欠点は図５に図示されており、この図は、各キャリアに関して−下の図で−第１の反復時の信号対干渉比（ＳＩＲ）を示し、−上の図で−発生した誤りの数を示す。しかしながら情報理論の観点からはすべてのユーザが同一の電力を持つことが最適であるということに留意されたい。誤り伝搬の問題を解決するために、我々は干渉依存状態挿入（ＳＩ）を使用する。本質的には、悪いＳＩＲから損害を受けているこれらのキャリアに関する追加の状態情報を挿入することによって、我々は妥当なコストで誤り伝搬の確率を著しく減少させることができる。状態挿入は、（ｐｃ）ＳＩＣ−ＯＦＤＭ／ＳＤＭＡ方式で適用されることが好ましい。この状態挿入方式はさらに、１つのサブキャリアずつのアプローチで提示されるが、これに限定されることはない。
【００９３】
先ず第１に、各サブキャリアｎのユーザ１のＳＩＲは、等化器Ｅ_LS［ｓ］の知見から計算される。次に、ＳＩＲから最も損害を受けているＭ個のサブキャリアｎ_mの各々に１つの追加の状態ｍが割り当てられる。これらＭ個の状態は、上述の中間ハード推定値と呼ばれる、ユーザ１についての代替推定値
【外７】

の経過を追跡している。これらは、
【外８】

のスライスされたものである
【外９】

を除いて
【外１０】

に最も近い配列点として定義される。これらの割当ての後に、ｕ＝２からＵに関して逐次に
【外１１】

を取得するために、Ｍ個の追加の状態が正常なサブキャリアとして処理される。明確には、ユーザｕ−１から発生したＭＵＩは、数１２に従って（チャンネル応答推定による再合成の後に）再構成されて、減算され（それによって元の信号を修正し）、そして数１３に従って最小２乗結合によってソフト推定値
【外１２】

が計算される。最後に、これらＭ個のサブバンドの各々に関してこのアルゴリズムは、数１３の２個のノルムの第１又は第２が最小であるとき、それぞれ
【外１３】

又は
【外１４】

の何れかをハード推定値として中間ハード推定値から選択する。
【００９４】
【数１２】

【数１３】

【００９５】
状態挿入アップリンク伝送方式は、上記受信端末における上記サブバンド処理された受信データ信号からの上記データ信号の上記推定値の上記決定が、少なくとも１つの（しかし、１つに限定されない）データ信号に関して下記のステップをさらに備える、という方式として説明できる。すなわち、これらのステップは、（第１のステップ）上記データ信号から１つの選択データ信号を選択するステップと、（第２のステップ）上記で中間ハード推定値と表記された推定値であって、上記サブバンド処理された受信データ信号から上記選択されたデータ信号の複数の上記推定値を決定するステップと、（第３のステップ）修正されたサブバンド処理済み受信データ信号の各々が上記選択されたデータ信号の上記（中間ハード）推定値の１つに基づいている、複数の上記修正されたサブバンド処理済み受信データ信号を決定するステップ（ここでは、再合成及び修正器方式が利用されている）と、（第４のステップ）例えば最小２乗線形結合法、しかしこれに限定されない方法によって、上記複数の修正されたサブバンド処理済み受信データ信号の各々から上記残りのデータ信号の少なくとも１つの信号の複数の推定値を決定するステップと、（最後のステップ）それから例えば上記修正されたサブバンド処理済み受信データ信号のノルムの評価法、しかしこれに限定されない方法によって、上記選択されたデータ信号の上記推定値の１つを選択するステップとを備える。
【００９６】
状態挿入アップリンク伝送方式の一実施形態では、推定値の上記決定（すべてのステップ）は、１つのサブバンドずつ実行される。
【００９７】
本発明の一実施形態では、上記状態挿入アップリンク伝送方式は、連続干渉除去方式と組み合わせて使用され、好ましくは１つのサブバンドずつ実行される。
【００９８】
図６は、例示的システムとしての干渉依存状態挿入を有するｐｃＳＩＣ−ＯＦＤＭ／ＳＤＭＡの性能を示す。追加の状態の数は、Ｍ＝６４に設定された。参考として破線の曲線は１人のユーザと１個のアンテナの１００ＭｂｐｓプレーンＯＦＤＭの性能を示し、細い曲線は、状態挿入のないｐｃＳＩＣ−ＯＦＤＭ／ＳＤＭＡの性能を示す。これは、ＳＩを持たないｐｃＳＩＣ−ＯＦＤＭ／ＳＤＭＡと比較して、６４個の追加の状態を有するｐｃＳＩＣ−ＯＦＤＭ／ＳＤＭＡは、ＢＥＲが０．００１で同時に４人のユーザが存在する場合に利得６ｄＢを達成していることを示している。他のシミュレーションもまた、３２個の状態と１６個の状態によるＳＩに関する性能改善は、それぞれ５ｄＢと４ｄＢであることを示している。
【００９９】
ＳＩを有するｐｃＳＩＣ−ＯＦＤＭ／ＳＤＭＡの複雑さの評価に関しては、機能を再び初期設定と処理部分とに分割することができる。初期設定時では等化後の各サブキャリアのＳＩＲを計算してその後にＭ個の最悪ＳＩＲサブキャリアのために状態挿入を行う必要がある。処理時ではＭ個の追加の状態を数１２及び数１３を使って追跡してその後に数１４の残りの２個のノルムに基づいて選択を行う必要がある。
【０１００】
【数１４】

【０１０１】
Ｎ個うちのＭ個のサブキャリアへの状態挿入のために必要とされる演算は、図１１に示されている。ＳＩを有するｐｃＳＩＣ−ＯＦＤＭ／ＳＤＭＡのための演算の総回数を取得するためには、図１０からの演算をこれに加えなくてはならない。４人のユーザと４個のアンテナのシステムに関しては、６４個の追加の状態を有するｐｃＳＩＣ−ＯＦＤＭ／ＳＤＭＡは、初期設定段階で２２０ｋＦＬＯＰＳで３１０ｋ個のデータ転送とを必要とし、処理段階で１．１ＧＦＬＯＰＳ／秒と２．６Ｇワード／秒のデータ転送帯域幅とを必要とする。
【０１０２】
ダウンリンク伝送では、コンポジットピアの端末は信号を受信しており、処理ピアは信号を送信している。この実施形態ではこれらの受信端末は、単一のアンテナとプレーンＯＦＤＭモデムとだけを持っている（すなわちＳＤＭＡ処理機能を持たない）。ユーザ端末は単一のアンテナを持つだけであり、我々は処理能力の大部分を基地局に集中したいので、これらのユーザ端末はダウンリンクにおけるマルチユーザ干渉を軽減できない。従って、基地局は、データシンボルベクトルＹ［ｓ］に前置補償行列Ｅ_PREを乗算してＹ_TR［ｓ］を得る。このＹ_TR［ｓ］は、Ａ個のアンテナから送信される。数６の入出力関係が得られる。
【０１０３】
非理想的なものをすべて無視すれば、このアプローチは結果的に各ユーザのデータシンボルの完全な分離と受信時の完全な等化とをもたらす。従って移動体では、チャンネル情報も等化器も必要としない。各キャリアｎにこれらの前置補償行列を与えることによって、入出力関係は、数１５のようになる。
【０１０４】
【数１５】

【０１０５】
このようにして各ユーザは、１つのキャリア（搬送波）毎の単一ユーザのＡＷＧＮチャンネルを見る。図７はユーザ数の異なる場合のダウンリンクにおける平均ＢＥＲを示す。干渉は存在しないので、同時ユーザの数は性能に影響しない（ユーザ数がアンテナ数を超えておらず、非理想的なものも発生しないとして）。
【０１０６】
再び、ダウンリンクにおける処理は、初期設定と処理の両者を備える。初期設定段階では、前置補償行列が計算される。処理時には、ユーザデータＹ［ｓ］に上記前置補償行列が乗算される。初期設定と処理の両者の複雑さは、アップリンクにおけるＬＳ−ＯＦＤＭ／ＳＤＭＡスキームの場合とほぼ同じである。
【０１０７】
アップリンク通信とダウンリンク通信の両者のために提案された提案ＯＦＤＭ／ＳＤＭＡに加えて、コヒーレンスによるグループ分けを適用することにより、両状況における初期設定の努力が単純化できる。この初期設定の努力は、数４、数５、又は数７が利用される等化器又は前置補償行列の決定として特徴付けられる。上記等化器行列によって、上記データ信号とサブバンド処理された受信データ信号との間の関係は数１、数９、又は数１３におけるのと同様に定義される。上記前置補償行列によって、上記データ信号の変換されたものである上記合成データ信号間の関係は数６又は数１５におけるのと同様に定義される。各サブバンド毎に上記行列を別々に決定する代わりに、上記サブバンドは、少なくとも１つのセットが少なくとも２つのサブバンドを備える複数のセットにグループ分けすることができ、次いで、上記行列又はさらに一般的には上記関係は、１セットずつ決定することができる。これらのグループは、このコヒーレンスによるグループ分けの方式の実施形態ではすべて等しいサイズＧである。図８は、Ｇの幾つかの値に関して、ＳＩを有するｐｃＳＩＣ−ＯＦＤＭ／ＳＤＭＡに適用されたキャリアグルーピングに関連する性能低下を示している。シミュレートされたチャンネルについての性能低下は、４以下のＧに関しては無視できることが観測されている。３２以上のＧに関しては、性能は１人のユーザと１個のアンテナのプレーンＯＦＤＭよりも劣化する。対象のシステムに関して初期設定の複雑さは、係数８だけ削減できると結論してもよい。４人の同時に存在する２５Ｍｂｐｓユーザを分離するためにＳＤＭＡを使う１００ＭｂｐｓのＯＦＤＭ／ＳＤＭＡ ＷＬＡＮの例として、性能利得と複雑さとに関する幾つかの数値的結果を得ることができる。もし６４個のＳＩとサイズが８のグループとを有するｐｃＳＩＣ−ＯＦＤＭ／ＳＤＭＡが実施されるならば、最小２乗法アプローチと比較して０．００１というＢＥＲで１１ｄＢという性能利得が得られる。必要とされる計算能力はそれぞれ、初期設定時には２７ｋＦＬＯＰＳで４０ｋ個のデータ転送とであり、処理時には１．１ＧＦＬＯＰＳ／秒と２．６Ｇワード／秒のデータ転送帯域幅とである。
【０１０８】
他の好適な実施形態では、処理ピアは接続ネットワークへのアクセスポイントを備えており（この接続ネットワークは例えば、ケーブルネットワークでも衛星ネットワークでもよい）、また、コンポジットピアはコストが主要な問題となる無線端末を備える。この実施形態では、アクセスポイントだけがＤＦＴ（離散フーリエ変換）手段とＩＤＦＴ（離散フーリエ逆変換）手段とを持つ。このことは、送信信号のピーク対平均電力比の上昇が防止されるので、コンポジットピア内の端末のデジタルベースバンドモデム部とシステム内のすべての端末のフロントエンドとの両方を安価に実現することを可能にする。非対称周波数領域ＳＤＭＡの典型的な応用例は、例えば２．４ＧＨｚ帯域の無線ホームネットワーキングのアプリケーションである。このような非対称構成は、サブバンド処理と逆サブバンド処理とが処理ピアに配置される、いわゆる集中化されたシナリオを実現するものである。この伝送方式では、上記受信端末における上記サブバンド処理された受信データ信号からの上記データ信号の推定値の決定は、下記のステップ、すなわち（第１のステップ）上記受信端末において上記サブバンド処理された受信データ信号から上記データ信号の中間推定値を決定するステップと、（第２のステップ）上記中間推定値を上記逆サブバンド処理することによって上記データ信号の上記推定値を取得するステップとを備える。この実施形態では本発明の方法は、同一の周波数帯域で同時に送信する異なる端末の信号を検出するためばかりでなく、例えばこの帯域に妨害信号を引き起こす電子レンジからの干渉を軽減するためにも使用することができる。例えば家庭環境といったマルチパスフェージング環境では、送信に先立ってデータ信号にガードインターバルを挿入することができる。もしこれらのガードインターバルが再びマルチパスチャンネルで受信されるすべてのエコーを備えるように設計されるならば、ガードインターバルの除去後にチャンネル畳み込みは巡回的になる。従って周波数領域ではこれは、チャンネルのフーリエ変換との乗算と等価になる。この実施形態は、処理ピアの端末を安価にすることを可能にし、連続干渉除去と、好ましくはサブバンド毎と状態挿入とを含んで、ＯＦＤＭ／ＳＤＭＡと同様の方法でアップリンクならびにダウンリンク合成処理の実現を可能にする。
【図面の簡単な説明】
【図１】 各々が少なくとも１つの送信手段（６０）を有する少なくとも２つの送信端末（２０）を備えるコンポジットピア（１０）と、空間ダイバーシティ受信手段（ここでは空間的に離れた２つの受信手段（８０）で表されているがそれに限定されない）を有する少なくとも１つの受信端末（４０）を備える処理ピア（３０）とを備えた（アップリンク）通信装置を示す。上記受信端末（４０）は少なくとも、サブバンド処理（９０）を実行する。図１の上段は、集中化されたシナリオを示し、この場合、上記受信端末はさらに、逆サブバンド処理（１１０）を実行する。図１の下段は、分割シナリオを示し、この場合、送信端末はさらに、逆サブバンド処理（１６０）を実行する。
【図２】 各々が少なくとも１つの受信手段（３２０）を有する少なくとも２つの受信端末（３３０）を備えるコンポジットピア（３４０）と、空間ダイバーシティ送信手段（ここでは空間的に離れた２つの送信手段（２２０）で表されているがそれに限定されない）を有する少なくとも１つの送信端末（２４０）を有する処理ピア（２３０）とを備えた（ダウンリンク）通信装置を示す。上記送信端末（２４０）は少なくとも、逆サブバンド処理（２６０）を実行する。図２の上段は、集中化されたシナリオを示し、この場合、上記送信端末（２４０）はさらに、サブバンド処理（２８０）を実行する。図２の下段は、分割シナリオを示し、この場合、受信端末は、サブバンド処理（３５０）を実行する。
【図３】 同時に存在する１人から４人のユーザの場合のアップリンク最小２乗法ＯＦＤＭ／ＳＤＭＡである本発明の一実施形態の性能を示す。ビット誤り率（ＢＥＲ）は、信号対雑音比（ＳＮＲ）の関数として表される。上記実施形態は、任意数のユーザについて利用可能である。上記実施形態においてＯＦＤＭは、高速フーリエ逆変換と高速フーリエ変換とを利用することによってサブバンド方式として利用される。上記実施形態ではサブバンド処理された受信データ信号からのデータ信号の推定値の上記決定は、最小２乗法に基づいている。
【図４】 同時に存在する１人から４人のユーザの場合のアップリンクＯＦＤＭ／ＳＤＭＡのｐｃＳＩＣ（キャリア毎の連続干渉除去）の性能を示す。ビット誤り率（ＢＥＲ）は、信号対雑音比（ＳＮＲ）の関数として表される。上記実施形態は、任意数のユーザについて利用可能である。上記実施形態ではサブバンド処理された受信データ信号からのデータ信号の推定値の上記決定は、最小２乗法という意味で、選択されたデータ信号の推定値を決定することと、それからサブバンド処理された受信データ信号を修正することと、最後に、上記選択されたデータ信号を除くすべてのデータ信号である残りのデータ信号の推定値を決定することとに基づいている。上記残りのデータ信号に関しては、ある選択されたデータ信号の推定値の上記決定が利用されることもある。データ信号の上記選択アプローチは結果的に、データ信号の推定値が決定される順序づけを導入することになる。
【図５】 アップリンクＳＩＣ（連続干渉除去）−ＯＦＤＭ／ＳＤＭＡによる誤り伝搬を示す。誤り数と信号対干渉比（ＳＩＲ）は周波数の関数として表される。誤り伝搬の上記観測は、状態挿入方式の使用に動機を与える。
【図６】 同時に存在する１人から４人のユーザの場合の状態挿入によるアップリンクＯＦＤＭ／ＳＤＭＡのｐｃＳＩＣの性能を示す。上記実施形態は、任意数のユーザについて利用可能である。ビット誤り率（ＢＥＲ）は、信号対雑音比（ＳＮＲ）の関数として示される。上記実施形態ではサブバンド処理された受信データ信号からのデータ信号の推定値の上記決定は、選択されたデータ信号の複数の推定値を決定することと、それから従って、上記サブバンド処理された受信データ信号を修正することと、それから上記選択されたデータ信号を除くすべてのデータ信号である残りのデータ信号の内の少なくとも１つのデータ信号の推定値を決定することと、最後に上記選択されたデータ信号の上記複数の推定値の中の１つを選択することとに基づいている。上記データ信号選択アプローチは結果的に、データ信号の推定値が決定される順序づけの導入をもたらす。データ信号毎に決定される推定値の量は、異なることがあり、又は幾つかのデータ信号について１つのこともある。
【図７】 同時に存在する１人から４人のユーザの場合のダウンリンクＯＦＤＭ／ＳＤＭＡの性能を示す。上記実施形態は、任意数のユーザについて利用可能である。ビット誤り率（ＢＥＲ）は、信号対雑音比（ＳＮＲ）の関数として示される。
【図８】 異なるコヒーレンスによるグループ分け係数についてのアップリンクＯＦＤＭ／ＳＤＭＡの性能を示す。ビット誤り率（ＢＥＲ）は、信号対雑音比（ＳＮＲ）の関数として示される。上記実施形態では、データ信号とサブバンド処理された受信データ信号との間の関係の決定である初期設定は、１セットずつ実行される。上記コヒーレンスによるグループ分け係数は、１セット内のサブバンドの量を表す。
【図９】 最小２乗法ＯＦＤＭ／ＳＤＭＡの演算回数（初期設定と処理）を表す。
【図１０】 ｐｃＳＩＣ（キャリア毎の連続干渉除去）−ＯＦＤＭ／ＳＤＭＡの演算回数（初期設定と処理）を表す。
【図１１】 状態挿入に関する追加の演算回数（初期設定と処理）を表す。
【符号の説明】
１０，３４０…コンポジットピア、
２０，２４０…送信端末、
３０，２３０…処理ピア、
４０，３３０…受信端末、
５０，２００…データ信号、
６０，２２０…送信手段、
７０…変換されたデータ信号、
８０，３２０…受信手段、
９０，２８０，３５０…サブバンド処理、
１００…受信端末におけるサブバンド処理された受信データ信号からのデータ信号の中間推定値の決定、
１１０，１６０，２６０…逆サブバンド処理、
１２０…データ信号の推定値、
１３０…データ信号の中間推定値、
１４０…サブバンド処理された受信データ信号、
１５０…受信端末におけるサブバンド処理された受信データ信号からのデータ信号の推定値の決定、
２５０…合成されたデータ信号の決定、
２７０…中間合成データ信号からの合成データ信号の決定、
２９０…中間合成データ信号、
３００…合成されたデータ信号、
３６０…受信端末におけるサブバンド処理後の信号。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus and method for high-speed multi-user wireless communication.
[0002]
[Prior art]
The idea of using a multi-carrier scheme as a modulation technique is known in the art “R. W. Chan,“ Band-Limited Orthogonal Signal Synthesis for Multi-Channel Data Transmission ”, Bell Systems Technical Journal, Volume 45. Pp. 1775-1796, December 1966 (Chang, RW “Synthesis of band-limited orthogonal signals for multichannel data transmission” Bell syst. Tech. J., vol. 45, pp. 1775-1796, Dec. 1966) ” , "B. Salzburg," Performance of an Efficient Parallel Data Transmission System ", American Institute of Electrical and Electronics Engineers, Transactions, Communication Technology, COM-15, December 1967 (Saltzberg, BR" Performance of an efficient parallel data transmission system "IEEE Trans. Comm. Technol., vol. COM-15, Dec. 1967)". Possible benefits from multi-carrier modulation are described in many papers such as “T. Müller, K. Bruninghaus, H. Rolling,“ Coherent OFDM-CDMA Performance for Broadband Mobile Communications ”, Wireless Personal Communications 2, Krewer Academic Publishers, 1996, pages 295-305 (Meuller, T. Brueninghaus, K. and Rohling H. “Performance of Coherent OFDM-CDMA for Broadband Mobile Communications”, Wireless Personal Communications 2 , Kluwer Academic Publishers, 1996, pp. 295-305), “S. Kaiser,“ OFDM-CDMA vs. DS-CDMA: Performance Evaluation on Fading Channels ”ICC '95, pages 1722-1726, (Kaiser, S.” OFDM-CDMA versus DS-CDMA: Performance Evaluation for Fading Channels ”, ICC '95, pp. 1722-1726)”. With regard to the above attractive modulation techniques, a number of theoretical publications have been written by "Kallet," Multitone Channel ", American Institute of Electrical and Electronics Engineers, Transaction, Vol. 37, No. 2, February 1989 ( Kalet, “The multitone Channel”, IEEE Trans. Commun., Vol. 37, no. 2, Feb. 1989) ”,“ Fazel, G. Fetweiss, “Multi-carrier spread spectrum”, Krewer Academic Publishers, 1997. (Fazel, G. Fettweis, “Multi-Carrier Spread-Spectrum”, Kluwer Academic Publ., 1997) ”. Multi-carrier modulation is a useful technique, especially in multi-path fading propagation situations, such as encountered in indoor environments. This technique in fact allows a very efficient way of dealing with ISI (intersymbol interference) by inserting guard intervals including cyclic prefixes. In addition, adaptive loading techniques allow for significantly increased throughput performance “L. van der Pell, S. Toen, P. Vandena Mer, B. Giselink, M. Engels,” Fast OFDM-based Adaptive loading strategy for WLAN ", November 1998, at Globecom'98 in Sydney, Australia (L. Van der Perre, S. Thoen, P. Vandenameele, B. Gyselinckx, M. Engels.) Adaptive loading strategy for A high speed OFDM-based WLAN “In Globecom'98. Sydney, Australia, November 1998)”. However, for a given carrier modulation, the bandwidth efficiency expressed in bits / second / hertz is fixed. Given the enormous growth of wireless communications and the importance of broadband services, the spectrum will become increasingly scarce. One way to increase the capacity or bandwidth efficiency of a wireless system is to apply cellularization (partitioning) to reuse the spectrum in different cells that do not interfere. While this technology has been successfully applied in mobile telephone networks, (from an economic point of view) it is unsuitable for small or medium-sized indoor networks as WLAN or home LAN. First of all, a high operating frequency (ie millimeter wave band) is required to achieve a reasonable reuse rate “M. Chiani, D. Dardari, A. Zanella, O. Andrisano,” Miri "Availability of broadband wireless network services for indoor multimedia in the waves", September 1998, ISSSE '98, Pisa, Italy, pages 29-33, (M. Chiani, D. Dardari, A. Zanella , O. Andrisano. “Service Availability of Broadband Wireless Networks for Indoor Multimedia at Millimeter Waves” In ISSSE '98. Pp. 29-33, Pisa, Italy, September 1998) ”,“ T. Itohara, T. Manabe, M. Fujita, T. Matsui and W. Sugimoto, “Research Activities on Millimeter-Wave Indoor Wireless Communications”, ICUPC'95 in Tokyo, Japan, November 1995 (T. Ithara, T. Manabe, M. Fujita, T. Matsui and Y. Sugimoto. “Research Activities on Millimeter-Wave Indoor Wireless Communications”, in ICUPC '95, Tokyo, Japan, November 1995). Second, cellularization (partitioning) introduces extra layers in the hierarchy and complicates the protocol stack. Thirdly, cellularization increases the burden on installation. Another method that allows spectrum reuse and does not have the disadvantages of cellularity is the application of Space Division Multiple Access (SDMA) technology, “A. Paulradi, C. Papadias,” wireless communication. "Space-Time Processing for Wireless Communications", American Electrical and Electronic Communication Society, Signal Processing Magazine, pp. 49-83, November 1997 (A. Paulraj, C. Papadias. "Space-Time Processing for Wireless Communications", IEEE Signal Processing Magazine , pp. 49-83, November 1997). Utilizing antenna arrays, SDMA can separate different users communicating simultaneously in the same frequency band by utilizing their individual spatial signatures. As such, this technique allows reuse of the cellized space within a single cell. SDMA has been proposed for single carrier systems, and its benefits are widely known “G. Thurs, M. Beach, Jay McZeehan,” 21st Century Wireless Personal Communications: Adaptation European technological advances in antennas, "American Institute of Electrical and Electronics Engineers, Communications Magazine, Vol. 35, No. 9, pp. 102-9, September 1997 (G.Tsoulos, M.Beach and J.MacGeehan," Wireless personal communications for the 21st Century: European technological advances in adaptive antennas ”, Communications Magazine, vol. 35, No. 9, pp. 102-9, Sept 1997),“ R. Roy, ”Smart antenna technology and its wireless communication system Overview of Applications to the American Institute of Electrical and Electronics Engineers, International Conference, Personal Radio Communications, pages 234-8, New York, NY, 1997, (R. Roy, An overview of smart antenna technology and its application to wireless communication sytems ”, IEEE International Conf. On Personal Wireless Communications, pp234-8, New York, NY, 1997)”, “S. V. Vogel, "An Experimental Study of Antenna Arrays for Indoor Wireless Communications," Asilomar Conference on Signals, Systems, and Computers, pp. 766-70, Los Alamitos, California, 1996 (S. Jeng, G.XU, H. Lin and W. Vogel, “Experimantal study of antenna arrays in indoor wireless applications”, Asilomar Conference on Signals, Systems and Computers, pp. 766-70 Los Alamitos, CA, 1996) ”. However, these single carrier SDMA systems for high speed (eg, 100 Mbps) wireless systems require a tremendous amount of processing (eg, on the order of GFLOPS) “P. Vandenamer, L. van der. Pell, B. Giselink, M. Engels and H. de Man, "SDMA Algorithm for High Speed Wireless LANs", Globecom 98, 189-194, Sydney, Australia, November 1998 (P. Vandenameele, L. Van der Perre, B. Gyselinckx, M. Engels and H. De Man, “An SDMA Algorithm for High-Speed Wireless LAN”, Globecom 98 Sydney, Australia, pp. 189-194, November 1998). In this technology, the combination of OFDM and antenna array as modulation techniques is known, “G. Laurie and J. Thioffy,“ Spatial and temporal coding for wireless communication ”, American Institute of Electrical and Electronics Engineers, Transactions Commun., 46, 3, 357-366, March 1998 (G. Raleigh and J. Cioffi, “Spatio-Temporal Coding for Wireless Communication”, IEEE Transaction on Communications, Vol. 46, No. 3 , pp. 357-366, March 1998). However, these algorithms are limited to a single user scenario and cannot use SDMA.
[0003]
“Spread spectrum multi-carrier multiple access system for mobile communications” in 1997, “Multi-carrier spread spectrum 49-56” published by Krewer Academic Publishers, Dordrecht, The Netherlands (“A spread-spectrum multi- "carrier multiple-access system for mobile communications", Kluwer Academic Publishers, Multi-Carrier Spread-Spectrum 49-56). Kaiser and K. Fazel (K. Fazel) describes a point-to-point method (fixed method) in which both transmitting and receiving peers have one antenna. Different users, each user having a separate set of carriers, are handled by FDMA. One user id's data is spread to a subset of carriers using spread spectrum techniques.
[0004]
In WO 97/416647, the separation of these users is based on the spread spectrum code together with the channel information. The operation of the ZF or MMSE combiner is performed simultaneously for all carriers.
[0005]
A. A. Kuzminskiy et al., November 1, 1998, 1998, on Signals, Systems and Computers, Volume 2, pages 1887-1891, “Multi-stage semi-conductor for multi-user SDMA systems with short bursts”. Blind space-time processing "(" Multistage semi-blind spatio-temporal processing for short burst multiuser SDMA systems "Conference on Signals, Systems & Computers, Vol 2, 1-4 November 1998, pages 1887-1891) In the context of a mixed / training detection approach, a continuous interference cancellation technique for SDMA is described. This does not depend on subband processing such as OFDM. Furthermore, it does not use a multi-carrier approach. From a frequency perspective, this technique uses an entire band. The choice of determining one user's signal affects this signal for the entire frequency band.
[0006]
[Problems to be solved by the invention]
The object of the present invention is essentially a multi-user, multi-carrier communication scheme that utilizes the principle of space division multiple access (a transmission scheme that transmits from at least one peer and receives at least one other peer). And a dedicated device to improve the performance / cost ratio of the high speed wireless network. The transmission scheme and the device enable high spectral efficiency communication under multipath fading conditions.
[0007]
[Means for Solving the Problems]
In a first aspect of the present invention (FIG. 1), a method for transmitting a data signal from at least two transmitting terminals each having at least one transmitting means to at least one receiving terminal having spatial diversity receiving means is disclosed. . The spatial diversity receiving means may be a plurality of at least two antennas that are spatially separated or have different polarizations. The transmitting terminals can be grouped into one composite peer. Receiving terminals can be grouped into one processing peer. The spatial diversity receiving means comprises at least two receiving means related to each other in such a way that said receiving means provides different spatial samples of the same data signal. In the first step of the transmission method, a data signal to be transmitted is transmitted from the transmission terminal. This transmission can occur substantially simultaneously. The spectrum of the transmitted data signal may at least partially overlap. These transmitted data signals are converted data signals. In the second step of the transmission scheme, the received data signal is received by the spatial diversity means. The received data signal is at least a function of at least two signals of the transmitted data signal. In a third step, at least two of the received data signals are subband processed at the receiving terminal. In the last step, an estimate of the data signal is determined from the subband processed received data signal at the receiving terminal.
[0008]
In principle, subband processing of a data signal having a certain data rate involves dividing the data signal into a plurality of data signals having a lower data rate, and modulating each of the plurality of data signals with another carrier. With. The carrier is preferably orthogonal. In one embodiment, the subband processing of a data signal can be achieved by using a serial / parallel converter and using a transform on a group of data samples of the data signal.
[0009]
Thus, this transmission scheme utilizes the multi-carrier approach simultaneously in a multi-user environment since there are at least two transmitting terminals. This transmission scheme separates different users or different transmitting terminals based on different spatial samples of the signals received by the spatial diversity means. As such, this transmission system can be understood as a space division multiple access technology, but at the same time, it can be understood that a multicarrier arrangement (arrangement) is used instead of a single carrier. However, this method is more than a simple combination (cascade connection) between the space division multiple access technology and the multicarrier method. In fact, such a combination results in time domain processing of the data signal, while the present invention results in less complex data signals in the frequency domain compared to ordinary SDMA, which is a time domain technique. The natural frequency parallel processing of the subband processing technology to be processed is used. This allows non-linear processing of data signals with low complexity and significantly improves performance. In fact, with such non-linear processing of data signals, the present invention takes advantage of the frequency diversity observed for different users. Since the data signal to be transmitted originates from different users, it can often be said that it is at least partially independent, but the transmission scheme does not depend on this.
[0010]
In one embodiment of this first aspect of the invention, processing for each subband is disclosed. The processing for each subband can also be called processing for each subband or processing for each carrier.
[0011]
In another embodiment of this first aspect of the invention, a method of continuous interference cancellation is disclosed. The continuous interference cancellation method can be realized by a processing approach for each subband, but is not limited thereto.
[0012]
In yet another embodiment of this first aspect of the invention, a method of interference dependent state insertion is disclosed.
[0013]
In yet a further embodiment of this first aspect of the invention, a method is disclosed that utilizes coherence grouping (subband grouping) during initialization.
[0014]
The above embodiments of the first aspect can be combined.
[0015]
In a second aspect of the present invention, a method for transmitting a data signal from at least one transmitting terminal having spatial diversity transmitting means to at least two receiving terminals having at least one receiving means is disclosed. These sending terminals can be grouped into one processing peer. These receiving terminals can be grouped into one composite peer. The spatial diversity transmission means comprises at least two transmission means that are related to each other in such a way that said transmission means provides different spatial samples of the same data signal. In the first step of the transmission scheme, a plurality of combined data signals are determined at the transmitting terminal. The synthesized data signal is a converted version of the data signal. In the second step of the transmission method of the present invention, the composite data signal is subjected to inverse subband processing. In the next step, the inverse subband processed composite data signal is transmitted by the spatial diversity means. The spectrum of the transmitted inverse subband processed composite data signal may be at least partially overlapping. In a further step, at least one of the receiving means of at least one receiving terminal receives a reception data signal subjected to inverse subband processing, and then receives the data signal from the reception data signal subjected to inverse subband processing. An estimate is determined. Since the data signals have different destinations, the data signals are often at least partially independent, but the transmission system of the present invention does not depend on this. The first and second aspects of the present invention can be combined.
[0016]
In a third aspect of the present invention, an apparatus for determining an estimate of a data signal from at least two data signals received at least substantially simultaneously is disclosed. The received data signal has at least partially overlapping spectra. The apparatus includes at least one spatial diversity receiving means, a circuit unit adapted to receive the received data signal by the spatial diversity receiving means, and subband processing at least two signals of the received data signal And a circuit unit adapted to determine an estimate of the data signal from the subband processed received data signal. The apparatus can be used in the uplink transmission scheme at the processing peer.
[0017]
In one embodiment of this third aspect of the invention, parallel processing is disclosed in the device configuration. This type of parallel processing is available for typical natural frequency parallel processing for the transmission scheme of the present invention. Indeed, the circuit unit is adapted to determine an estimate of the data signal from the subband processed received data signal and comprises a plurality of circuits, each circuit receiving the subband processed received data A portion of the estimate of the data signal is adapted to be determined based on a portion of the signal subband.
[0018]
In another embodiment of this third aspect of the present invention, further parallel processing is introduced into the device configuration in the circuit unit adapted to receive the received data signal.
[0019]
In a fourth aspect of the present invention, an apparatus for transmitting a composite data signal subjected to inverse subband processing, wherein the circuit is adapted to combine at least one spatial diversity transmission means and a plurality of data signals. And a circuit unit adapted to reverse-subband process the combined data signal, and a circuit unit adapted to transmit the combined sub-band processed combined data signal by the spatial diversity means Is disclosed. The apparatus can be used in a downlink transmission scheme at the processing peer.
[0020]
In one embodiment of the present invention, the parallel processing in the apparatus configuration is a circuit unit adapted to synthesize data, or (and) a circuit adapted to transmit a composite data signal subjected to inverse subband processing. Introduced into the department.
[0021]
A device having the functionality and architectural characteristics of both devices in the third and fourth aspects of the invention can be defined.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is not limited to the detailed description of the invention described below.
[0023]
The present invention relates to (wireless) communication between terminals (20), (40), (330), (240). We logically group these terminals on each side of the communication and call them peers (340), (230), (10), (30). Each peer can embody one or more terminals, whereby at least one peer embodies two or more terminals. Therefore, the focus of the present invention is multi-user. These peers can send and / or receive information. For example, these peers can communicate in a half-duplex mode that either transmits or receives at a time, or a full-duplex mode that transmits and receives substantially simultaneously.
[0024]
The present invention introduces Spatial Division Multiple Access (SDMA) technology for systems that utilize subband processing, thereby adapting to a multi-carrier approach. In the present invention, at least one of the communication peers (30), (230) has transmission and / or reception means (80), (220) capable of providing different spatial samples of the transmitted and / or received signals. Having terminals (40) and (240). We refer to these transmission and / or reception means as spatial diversity means. We call the peer (s) with the above spatial diversity means as processing peers (30), (230). The processing peer communicates with at least two terminals of opposing peers (10), (340), which can operate at least partly simultaneously, and the spectrum of the signals communicated is at least partly Can overlap. While frequency division multiple access technology relies on non-overlapping signal spectra, time division multiple access technology relies on communicating signals in different time slots, and therefore not simultaneously. Please note that. We call this opposing peer comprising at least two terminals (20), (330) simultaneously using the same frequency as a composite peer (10), (340). The invention relates to (wireless) communication between terminals in which at least processing peers (30), (230) have subband processing means.
[0025]
Communication between the composite peer and the processing peer can consist of uplink (FIG. 1) transmission and downlink (FIG. 2) transmission. Uplink transmission refers to a transmission in which a composite peer sends data signals and a processing peer receives data signals. Downlink transmission refers to a transmission in which a processing peer sends a data signal and a composite peer receives the data signal. Uplink and downlink transmissions can be simultaneous (full duplex) (eg using different frequency bands) or in time duplex mode (half duplex) (eg using the same frequency band) It may operate or have any other configuration.
[0026]
The (wireless) transmission of data or digital signals from the transmission circuit to the reception circuit requires digital / analog conversion at the transmission circuit and analog / digital conversion at the reception circuit. In the following description, the apparatus of the present communication mechanism has transmission / reception means also called a front end, and the transmission / reception means includes amplification or signal level gain control, and converts an RF (radio frequency) signal to a required baseband signal. It is assumed that these analog / digital and digital / analog conversion means for realizing conversion and inverse conversion are included. The front end includes an amplifier, a filter, and a mixer (down converter). In such text (herein) it is assumed that all signals are represented as a series of sample sequences (digital representation), whereby the above-described transformation is also performed. However, the above assumptions do not limit the scope of the present invention. In this way, communication of data signals or digital signals is symbolized as transmission and reception of (individual) sample sequences. Prior to transmission, the information contained in the data signal is mapped by mapping the data signal to symbols that eventually modulate the phase and / or amplitude of the carrier or pulse train (eg, using QAM modulation or QPSK modulation). One or more carriers or pulse trains can be provided. The symbols belong to a finite set called a transmission alphabet. A signal obtained as a result of performing a modulation operation and / or a front-end operation on the data signal is called a converted data signal to be further transmitted.
[0027]
After reception by the receiving means, information included in the received signal is restored and reproduced by a conversion process and an estimation process. These transformation and estimation processes may include demodulation, subband processing, decoding, and equalization, but may not. After the above estimation and conversion process, a received data signal is obtained comprising symbols belonging to a finite set called the received alphabet. The reception alphabet is preferably equal to the transmission alphabet.
[0028]
The invention can further utilize a method and means for measuring the channel impulse response between the individual terminal transmission and / or reception means of one composite peer and the spatial diversity means of the other processing peer. . This measurement of the channel impulse response can be obtained either based on uplink transmission and / or based on downlink transmission. The channel impulse response measured in this way can be used by processing peers and / or composite peers in uplink transmissions and / or downlink transmissions. The present invention can further utilize a method for determining the signal power of received data and a method for determining the interference ratio of data signals.
[0029]
Spatial diversity means ensure the reception or transmission of individual spatial samples of the same signal. This set of individual spatial samples of the same signal is called a spatial diversity sample. In one embodiment, the spatial diversity means embodies separate antennas. In this embodiment, multiple antennas belonging to one terminal can be spatially separated (as shown in FIGS. 1 and 2), or they can use different polarizations. A large number of antennas belonging to one terminal may be collectively referred to as an antenna array. The present invention is most efficient when the individual samples of the spatial diversity sample are sufficiently uncorrelated. In one embodiment, sufficiently uncorrelated samples are obtained by placing different antennas at a sufficiently large distance. For example, the distance between different antennas can be selected to be half the wavelength of the carrier frequency at which communication is performed. The spatial diversity samples are thus different from each other due to different spatial propagation paths from the transmitting means to the respective receiving means and vice versa. Apart from this, the spatial diversity samples are different from each other due to the different polarizations of the respective receiving or transmitting means.
[0030]
In the above method, at least the processing peer performs subband processing, hereinafter referred to as SP, in the uplink mode (FIG. 1) and reverse subband processing, hereinafter referred to as ISP, in the downlink mode (FIG. 2). Depends on running. Further, in the uplink mode, ISP is performed either at the composite peer (see lower part of FIG. 1) prior to transmission or at the processing peer (see upper part of FIG. 1) after SP. In downlink mode, the SP is executed either at the composite peer after reception (see lower part of FIG. 2) or at the processing peer (see upper part of FIG. 2) before ISP. A scenario where both ISP and SP are executed in either transmission direction at the processing peer is called a centralized scenario. The remaining scenario, i.e. the scenario where the ISP and SP are executed in either transmission direction at different peers, is called a split scenario.
[0031]
The uplink transmission scheme can be formulated as a first aspect of the present invention, which comprises spatial diversity receiving means (80) from at least two transmitting terminals (20) each having at least one transmitting means (60). A method of transmitting a data signal (50) to at least one receiving terminal (40) having the following steps: a converted data signal (70), which is a converted version of the data signal, is transmitted to the transmitting terminal ( 20) transmitting from the spatial diversity means (80) a received data signal that is at least a function of at least two signals in the (transmitted) converted data signal (70) (first step) And at least two of the received data signals at the receiving terminal (40). Performing a subband processing (90) of the signal (third step), and an estimated value (120) of the data signal from the received data signal (140) subjected to the subband processing (obtained above) at the receiving terminal A step (fourth step) for determining
[0032]
The transmission of the converted data signal can be performed substantially simultaneously. The spectrum of the converted data signal can at least partially overlap.
[0033]
In the uplink split scenario, the conversion of the data signal (50) to the converted data signal (70) comprises inverse subband processing (160). In the uplink centralized scenario, the determination (150) of the estimate of the data signal from the (subjected) subband processed received data signal at the receiving terminal comprises the following steps: A step (100) of determining an intermediate estimation value (130) of the data signal from the received data signal subjected to the subband processing in the terminal (first step), and inverse subband processing of the intermediate estimation value (110) Thereby obtaining the estimated value (120) of the data signal (second step).
[0034]
The downlink transmission scheme can be formulated as a second aspect of the present invention, which method comprises at least one receiving means (320) from at least one transmitting terminal (240) having spatial diversity transmitting means (220). A method for transmitting a data signal (200) to at least two receiving terminals (330), comprising: determining a combined data signal (300) that is a transformed version of the data signal in the following steps: (250) step (first step), inverse subband processing of the synthesized data signal (260) step (second step), and (obtained) inverse subband processed synthesized data signal Is transmitted by the spatial diversity means (220) (third step), and the inverse subband processing is performed Receiving a received data signal by at least one of the receiving means (320) of at least one receiving terminal (330) (fourth step), and receiving the data signal from the received data signal subjected to the inverse subband processing. And a step of determining an estimated value (fifth step).
[0035]
The transmissions can be made substantially simultaneously. The spectrum of the composite data signal that has been (transmitted) inverse subband processed may at least partially overlap.
[0036]
In the downlink split scenario, the determination of the estimate of the data signal at the receiving terminal comprises subband processing (350). In a downlink centralized scenario, the determination of the combined data signal at the transmitting terminal includes the following steps: determining the intermediate combined data signal (290) by subband processing the data signal (280) ( A first step) and a step (270) of determining the synthesized data signal from the intermediate synthesized data signal (270).
[0037]
The above transmission method is intended to transmit a data signal from one peer to another peer, but it is not said that only the estimated value of the above data signal may actually be obtained at the receiving peer depending on the transmission conditions. must not. The transmission scheme is naturally intended to make the estimated value of the data signal as close as possible to the data signal technically possible.
[0038]
It is a feature of the present invention that the transmission scheme is not a simple combination of a space division multiple access technique and a multicarrier modulation scheme. In fact, if it is a simple combination, different data signals modulated by such a multi-carrier scheme at the transmitting terminal, then transmitted by the space division multiple access apparatus, and received at the receiving terminal by the spatial diversity means are combined into one combined signal. And then the demodulated signal is demodulated. In the split scenario of the present invention, the converted signal (to be transmitted) is also modulated by the multicarrier scheme at the transmitting terminal and transmitted by the spatial division multiple access apparatus, but is first received by the spatial diversity means at the receiving terminal. Different signals are demodulated and then only these demodulated received signals are combined. In a centralized scenario, both modulation and demodulation are concentrated on the receiving peer on the uplink and on the transmitting peer on the downlink. Here, it should be noted that modulation and demodulation mean subband processing and inverse subband processing, not normal modulation.
[0039]
In the embodiments of the first and second aspects of the present invention, a multicarrier modulation technique is realized. One example of such a multi-carrier modulation technique uses IFFT as the ISP and FFT as the SP, and this modulation technique is called orthogonal frequency multiplexing (OFDM) modulation. In the uplink transmission scheme, it can be said that the subband processing is orthogonal frequency division multiplexing. In the uplink transmission scheme, it can be said that the inverse subband processing is orthogonal frequency division multiplexing. In the downlink transmission scheme, it can be said that the subband processing is orthogonal frequency division multiplexing. In the downlink transmission scheme, it can be said that the inverse subband processing is orthogonal frequency division multiplexing.
[0040]
In a centralized scenario, the processing performed at the processing peer on the samples between SP (90), (280) and ISP (110), (260) is subband domain processing (270), ( 100). In the split scenario, the processing executed before the ISPs (160) and (260) at the transmitting terminal and the processing executed after the SPs (90) and (350) at the receiving terminal are subband region processing (for example, (250 )) Called. Here, “before” means that it occurs earlier in time during transmission or reception, and “after” means that it occurs later in time during transmission or reception. means. In a centralized scenario, the signals (130), (140), (290), (300) between the SP and ISP are called signals in the subband domain representation. In the split scenario, the signals (50), (300), (200) before the ISP at the transmitting terminal and the signals (360), (140), (120) after the SP at the receiving terminal are subband regions. Called a signal in representation.
[0041]
In one embodiment, the subband process comprises a fast Fourier transform (FFT) process, and the inverse subband process comprises a fast Fourier inverse transform process. FFT processing means performing a fast Fourier transform of the signal. Inverse FFT processing means performing fast Fourier inverse transform of the signal.
[0042]
In the present invention, a data string to be transmitted is divided into a plurality of data subsequences prior to transmission. The data subsequence corresponds to a subsequence processed as one block by the subband processing means. In the case of a multipath condition, a guard interval including a cyclic prefix or a cyclic postfix is inserted between each pair of data subsequences in the transmission terminal (s). If, in wireless communication, a multipath propagation condition that results in receiving a non-negligible echo of the transmitted signal occurs, and the subband processing means is composed of FFT and / or IFFT operations, The introduction of this guard interval obtains equivalence between the convolution of the time domain data signal and the time domain channel response and the multiplication of the frequency domain data signal and the frequency domain channel response. The insertion of the guard interval can occur in both a centralized scenario and a split scenario. Thus, in one embodiment of the present invention, in a split scenario, the transmitting terminal (s) perform an ISP between a data subsequence and then send each pair of data subsequences before transmitting the data subsequence. It can be said that a guard interval including a cyclic prefix or a cyclic postfix is inserted into. In another embodiment of the present invention, in a centralized scenario, the guard interval is inserted into a transmitted sequence between each pair of data subsequences without performing ISP processing on the data subblock at the transmitting terminal. Is done. This can be formulated as described above by demonstrating that the conversion of the data signal to the transmission data signal further comprises the introduction of a guard interval in the uplink transmission scheme. The introduction of the guard interval is also applicable to the downlink transmission method. Other overlap and save techniques are also available.
[0043]
The terminal (s) with spatial diversity means (and therefore at the processing peer) have SP and / or ISP means that allow subband processing of individual samples of spatial diversity samples. It also has a means of synthesis processing. Synthetic processing means means means for processing data coming from subbands of individual samples in a spatial diversity sample. In the synthesizing processing means, different techniques can be applied to restore and reproduce or estimate data coming from different individual terminals, or to synthesize data to be transmitted to individual terminals. The present invention discloses a method for performing the above combining process for both uplink transmission and downlink transmission.
[0044]
The combining process in the uplink is different where peers with spatial diversity means, called processing peers, transmit (at least partially simultaneously) converted data signals (with at least partially overlapping spectra). The present invention relates to a communication situation in which a signal is received from a composite peer that embodies a terminal. In the uplink transmission scheme, the determination of the estimated value of the data signal (120) from the subband-processed received data signal (140) at the receiving terminal means the combining process.
[0045]
Combining processing in the downlink consists of a so-called reverse subband processed combined data signal (at least partly simultaneously), called a processing peer, which has a spatial diversity means and has a spectrum that has at least partly overlapping spectra. The present invention relates to a communication situation in which a signal is transmitted to a composite peer that embodies different terminals to transmit. In the downlink transmission scheme, the determination (250) of the combined data signal (300) at the transmitting terminal means the combining process.
[0046]
In the present invention, the following notation is further used. That is, x is used for transmitted data samples. The notation y is used for received data samples. The notation n is used for noise samples. The notation X is used for the transmitted data sample matrix. The notation Y is used for the received data sample matrix. The notation N is used for the noise sample matrix. The notation Greek symbol sigma (σ) is used as noise variance. The notation h (t) is used as a channel impulse response expressed in the time domain. The notation h [s] is used as a channel impulse response expressed in the frequency domain. The array index s (1 to S) refers to the particular subband to which the sample or channel impulse response corresponds. The notation S is used as the total number of subbands processed by the subband processing means. The superscript u (from 1 to U) refers to the individual terminal of the composite peer that has transmitted the data signal in the uplink mode or steered the data signal in the downlink mode thereto. The notation U is used as the number of simultaneous terminals of the same subband in the composite peer. The subscript a (from 1 to A) refers to a particular spatial sample of spatial diversity samples at the processing peer. The notation A is used as the number of individual samples within the spatial diversity sample at the processing peer. The notation e is used as an equalizer coefficient. The notation E is used as an equalizer coefficient matrix. The notation Greek letter epsilon (ε) is used as a stochastic expectation operator. The symbol “˜” above a symbol indicates a soft estimate of the symbol. A soft estimate means an estimate that is not necessarily included in the received alphabet. The bar above the symbol shows the hard estimate for that symbol. The hard estimated value means an estimated value equal to a symbol included in the received alphabet.
[0047]
In the present invention, a plurality of determination methods are used. The determination method obtains one or more intermediate hard estimates based on a single soft estimate. In one embodiment of the invention, the determination method obtains one intermediate hard estimate by determining from the received alphabet the signal having the smallest distance to the soft estimate. In another embodiment of the invention, the determination method obtains a number of intermediate hard estimates by determining from the received alphabet a signal having a minimum distance to the soft estimate.
[0048]
In the present invention, a plurality of selection methods are used. The selection method acquires a hard estimation value as the specific data symbol based on an intermediate hard estimation value of a specific data symbol. In one embodiment of the present invention, there is only one intermediate hard estimate for a particular data signal / symbol, and the hard estimate is equal to this intermediate hard estimate. In other embodiments, there are several intermediate hard estimates for at least one data signal. Of the multiple intermediate hard estimates, one intermediate hard estimate for one particular data signal is selected as a hard estimate based on some probability criterion.
[0049]
In the present invention, a plurality of recombiner schemes are used. The re-synthesizer scheme calculates the hard estimate or intermediate hard estimate by calculating the spatial diversity sample that would have been received if a data symbol corresponding to the hard estimate or intermediate estimate was transmitted. Based on this, a re-synthesized diversity sample is obtained.
[0050]
In the present invention, a plurality of modifier systems are used. The corrector scheme obtains a modified spatial diversity sample by applying the following steps: First, these schemes obtain recombined spatial diversity samples by applying a recombiner scheme based on previously acquired hard estimates or intermediate hard estimates. Second, these schemes obtain a modified spatial diversity sample by utilizing the recombined spatial diversity sample and the original spatial diversity sample.
[0051]
The corrector scheme is used in an uplink transmission scheme that means a continuous interference cancellation scheme, where the determination of the estimate of the data signal from the subband processed received data signal at the receiving terminal is , Further with respect to at least one data signal, the following steps: selecting one selected signal from the data signal (first step), and selecting the selected from the subband processed received data signal A step of determining an estimated value of the data signal (second step), and a step of correcting the subband-processed received data signal by a corrector method based on the estimated value of the selected data signal (third step) Step) and estimation of the remaining data signal from the modified subband processed received data signal It has from step (fourth step) of determining. Note that the selection of the data signal to be selected is simply to determine which signal the scheme is applied to. The selection should not be confused with the selection method described above.
[0052]
The corrector scheme is also used in an uplink transmission scheme, which means a state insertion scheme, where the determination of the estimate of the data signal from the subband processed received data signal at the receiving terminal is: The following steps with respect to at least one data signal: the step of selecting one selected signal from the data signal (first step); and the selected data signal from the subband processed received data signal Determining a plurality of estimated values of the second sub-band processed received data signal, wherein each of the modified subband processed received data signals is based on one of the estimated values of the selected data signal. Determining a modified subband processed received data signal by a modifier scheme (third step); Determining a plurality of estimates of at least one signal of the remaining data signal from a plurality of modified subband processed received data signals (fourth step); and Selecting (by a selection method) one of the estimated values (fifth step). Note that the selection of the data signal to be selected is simply to determine which signal the scheme is applied to. The selection should not be confused with the selection method described above.
[0053]
It can be said that the estimated value of the selected data signal in the continuous interference cancellation scheme can be regarded as a hard estimated value. The plurality of estimated values of the selected data signal in the state insertion scheme can be considered as intermediate hard estimated values. The plurality of estimates of the remaining data signals in both of the above equations can be either (intermediate) hard or soft estimates.
[0054]
In the present invention, a method of grouping by subband coherence is presented. The coherence grouping scheme reduces the initial setting effort and can be used for both uplink transmission and downlink transmission. The coherence grouping method is such that S subbands are assigned to each group i as G._IDivide into groups of adjacent subbands with subbands. In the grouping scheme by coherence, the initial setting calculation is performed only once for each subgroup, not separately for each subband. The grouping method by coherence does not affect the performance of the synthesis processing method as long as all subbands in one subgroup receive a sufficiently correlated channel impulse response. Thus, for the present invention to be maximally efficient, several G_IIs limited by the communication status. For the initial setting process, the coherence grouping method is the number of subbands G in a subgroup._IThe result is that the computational complexity is reduced by a factor G that is the average of. In one embodiment, the communication is based on OFDM transmission and the number G_IAre all selected equal to a fixed portion of the coherence bandwidth divided by the spacing between each carrier. The coherence bandwidth of a channel is the bandwidth with which the channel response is correlated. On a multipath propagation channel, the coherence bandwidth is inversely proportional to the relative delay of echoes on this channel. In other embodiments, the number G_IIs calculated based on the measured channel impulse response, and more specifically, the slope of this channel impulse response. Furthermore, in the formulation, it can be said that the determination of the estimated value of the data signal at the receiving terminal comprises two steps. The first step is an initial setting step in which the relationship between the data signal and the subband-processed received data signal is determined. In the second step, which is the actual combining process, the relationship between the data signal and the subband processed received data signal is utilized to determine the data signal. Then, this coherence grouping method includes that the subbands are grouped into a plurality of sets in which at least one set includes at least two subbands, and that the initial setting step is executed one by one. It is characterized by specifying.
[0055]
In the present invention, a method of combining processing related to uplink communication is presented. The above uplink communication combining processing method is based on subband-processed spatial diversity samples, which can also be referred to as subband-processed received data signals, by calculating an estimated value of a data signal transmitted from one or more terminals of a composite peer. Get at the receiving terminal.
[0056]
In the present invention, a method of combining processing for each subband related to uplink communication is presented. The above-mentioned combining processing method for each subband for uplink communication is a received data signal subjected to subband processing within one specific subband, and can be referred to as subband processed spatial diversity within the specific one subband. Based on the samples, an estimate of the data signal (s) in that particular subband transmitted from one or more terminals in the composite peer is obtained at the receiving terminal. The combination processing method for each subband can be formulated as a method in which the determination of the estimated value of the data signal at the receiving terminal is executed for each subband.
[0057]
In one embodiment of the present invention, the above method of combining processing per subband for uplink communication is performed in a particular subband from at least one terminal in the composite peer by applying the following steps: Obtain an estimate of the data signal (s). First, these methods apply a scalar synthesis scheme for each subband for uplink communication, thereby softening the data signal (s) in that particular subband from each of these terminals. Get an estimate. Secondly, these methods obtain an estimated value by applying a decision scheme to each of the soft estimated values.
[0058]
In the present invention, a method of scalar synthesis processing for each subband related to uplink communication is presented. The scalar combination processing scheme for each subband for uplink communication is based on the spatial diversity sample in one subband or the modified spatial diversity sample, and the one subband from one terminal in the composite peer. Obtain a soft estimate of the data signal (s) in the band. In one embodiment of the present invention, the above-described scheme of scalar synthesis processing for each subband related to uplink communication is performed by a linear scheme of data signal (s) in one subband from one terminal in the composite peer. Get a soft estimate. In this embodiment, an estimate of the data signal (s) transmitted by the terminal (s) of the composite peer
[Outside 1]

Is calculated by linearly combining a single corresponding carrier signal or subband received at different antennas and an equalizer coefficient E [s] according to Equation 1 below.
[0059]
[Expression 1]

[0060]
In one embodiment, this linear estimation is performed based on a least squares (LS) method. In this embodiment of the present invention, E [s] is calculated so as to minimize the expected value given by Equation 2. For a given noise energy (sigma squared) and the condition for x given by Equation 3, E [s] follows the U set of linear equations of Equation 4. Here, the superscript H represents a Hermitian transpose matrix.
[0061]
[Expression 2]

[Equation 3]

[Expression 4]

[0062]
In one embodiment of the present invention, the scheme of scalar synthesis processing per subband for uplink communication is a data signal in one subband from one terminal in the composite peer by a linear zero forcing (ZF) scheme. Get a soft estimate of. In this embodiment of the invention, the E [s] is calculated in a so-called zero-forcing manner so as to eliminate channel distortion to the maximum without considering noise energy. In this embodiment, E [s] follows the U set of linear equations of Equation 5.
[0063]
[Equation 5]

[0064]
In one embodiment of the present invention, the combination processing method for each subband related to uplink communication is performed in one subband from one terminal in the composite peer by a non-linear method such as maximum likelihood symbol estimation (MLSE). Obtain a soft estimate of the data signal (s).
[0065]
In the present invention, a method of combining processing related to downlink communication is presented, which is called a downlink combining processing method. The downlink combining processing scheme is executed in the processing peer to facilitate estimation at the composite peer of the data signal transmitted from the processing peer. The downlink combining processing method generates a spatial diversity sample based on at least two data signals, and as a result, obtains a combined data signal. The composite data signal is then subjected to ISP and then transmitted by spatial diversity means, resulting in a transmission data signal having at least partially overlapping spectra. This transmission data signal is then transmitted on the channel. The synthesizing process can be described as a step in which the transmitting terminal determines a synthesized data signal that is a converted version of the data signal. Thereafter, reverse subband processing of the composite data signal is performed, and then the composite data signal subjected to the reverse subband processing is transmitted by the spatial diversity means. The transmitted composite data signal subjected to the reverse subband processing is transmitted. The spectra of at least partially overlap.
[0066]
In one embodiment of the present invention, a combination processing method for downlink communication applies a combination processing for each subband for downlink communication within at least one subband. In this embodiment, the downlink combining processing method generates a combined data signal in this specific subband based on the data signal of one subband. This can be explained as determining the combined data signal for each subband at the transmitting terminal.
[0067]
In one embodiment of the present invention, the downlink combining processing method includes a data signal X [s] and a pre-compensation matrix E._PREThe combined data symbol Y [s] is calculated by linearly combining [s]. In this embodiment, the following equation (6) is established.
[0068]
[Formula 6]

[0069]
In one embodiment, U = A and E_PRE[S] is the inverse matrix H of the channel matrix^{T (-1)}[S].
[0070]
In other embodiments, U <A and E_PRE[S] is a pseudo inverse matrix of the channel matrix such that the following equation (7) holds.
[0071]
[Expression 7]

[0072]
In one embodiment of the invention, the above scheme of combining processing for downlink communication takes into account the non-ideal characteristics of the analog front end (s) at the transmitting (s) and / or receiving terminals.
[0073]
In one embodiment of the present invention, the above method of combining processing for downlink communication prevents the occurrence of distortion (s) in the analog front end.
[0074]
In one embodiment of the invention, the pre-compensation matrix comprises zeros for one or more data signals on one or more specific subbands. In this embodiment, efficient and effective power usage is obtained.
[0075]
In one embodiment of the present invention, not only the composite peer terminal but also the processing peer terminal has spatial diversity means, subband processing means and combining processing means, and both the processing peer and the composite peer are at least It embodies at least two terminals that transmit at least partially simultaneously transmitted data signals having partially overlapping spectra. In this embodiment, both the uplink combining processing method and the downlink combining processing method can be used in any transmission direction between two peers.
[0076]
In a preferred embodiment, the processing peer is a base station of a star configuration network, which can be connected to the backbone of the cable network. Different terminals communicate with the base station simultaneously in the same frequency band. These terminals only require a single front end and a plain OFDM modem (ie, no SDMA processing capability). This embodiment can operate in a multipath fading environment for applications such as wireless local area networks. This embodiment can operate in the 5-6 GHz band and can achieve network performance of 155 Mbps or higher. In this embodiment, the spatial diversity means comprising a large number of transmission means and / or reception means is concentrated in the base station, thus reducing the overall hardware complexity and configuration costs. In this embodiment, the spatial diversity means comprises a number of antennas arranged at half wavelength intervals. Each peer communicates based on OFDM as a modulation technique. ISP and SP are executed based on IDFT (Inverse Discrete Fourier Transform) processing and DFT (Discrete Fourier Transform) processing, respectively, and subbands can be called carriers. A guard interval including a cyclic prefix is inserted between OFDM symbols on the transmitter side. SDMA is then applied in the frequency domain. In addition to combining the advantages of both OFDM and SDMA, this approach provides a simpler use of space diversity compared to the time domain scheme. As for the estimation algorithm of the OFDM / SDMA system, a known least square (LS) or maximum likelihood symbol estimation (MLSE) algorithm can be applied. A new class of uplink OFDM / SDMA schemes with improved performance and lower complexity is also applicable. These methods realize continuous interference cancellation (cancellation) for each carrier, state insertion, and grouping by coherence.
[0077]
To illustrate the performance, these algorithms are applied to a 100 Mbps OFDM / SDMA WLAN. This WLAN has a base station with four antennas that separates up to four simultaneous users by SDMA. Each of these antennas transmits 256 OFDM symbols at a data rate of 25 Mbps with QPSK modulation. The guard interval is designed to have all echoes received on the multipath propagation channel so that the convolution of the channel is cyclic after removing the guard interval. Thus in the frequency domain this is the Fourier transform of the channel h^U _aEquivalent to multiplication by [s]. Measures are taken to synchronize different users communicating simultaneously in the same band. Under these conditions, the received data Y [s] can be written as Under certain circumstances, the data sequence X^UEstimated value of [s]
[Outside 2]

Can be calculated for each carrier. This carrier-by-carrier estimation greatly simplifies the SDMA process and allows this process to be processed in parallel. An apparatus that performs actual SDMA / OFDM determines an estimated value of a data signal based on a part of a subband of a received data signal subjected to subband processing, preferably in one subband for each circuit unit. A plurality of circuits adapted to do so. Subsequent to the carrier-by-carrier estimation, a determination is made as to which element of the transmission alphabet is closest to the signal obtained from this carrier-by-carrier estimation. As a result of this decision, hard estimates
[Outside 3]

Is obtained.
[0078]
[Equation 8]

[0079]
SDMA processing for each carrier in the uplink can be performed in a linear manner. In this case, an estimate of the data signal transmitted by the terminal
[Outside 4]

Is calculated by linearly combining the signal of a single corresponding carrier received by different antennas and the equalizer coefficient E [s] according to equation (1).
[0080]
The E [s] is calculated so as to minimize the expected value given by Equation 2. For a given noise energy (sigma squared) and the condition for x given by Equation 3, E [s] follows the U set of linear equations of Equation 4. Here, the superscript H represents a Hermitian transpose matrix.
[0081]
Following equalization, the soft estimate is supplied to a slicer that determines the closest array point by some decision scheme. This results in a hard estimate
[Outside 5]

Is obtained. Instead, an equalizer coefficient E [s] that can eliminate channel distortion to the maximum without considering noise energy can be calculated by a so-called zero forcing method. E [s] follows a set of U linear equations as given by Eq.
[0082]
The performance of this system is evaluated by simulation with realistic channel data obtained from ray tracing. The resulting curve shows the bit error rate (BER) as a function of the received signal-to-noise ratio (SNR) per bit.
[0083]
FIG. 3 shows the performance of LS-OFDM / SDMA for 1 to 4 users present at the same time. For reference, the dashed curve shows the performance of a 100 Mbps plain OFDM link with one user and one antenna. An important observation is that the LS-OFDM / SDMA system with 4 antennas and 4 users is superior to plain OFDM in performance. This indicates that a bandwidth reuse factor of 4 can be achieved without performance degradation.
[0084]
In order to evaluate the complexity of the embodiment, we determine the total number of operations required to implement the LS-OFDM / SDMA algorithm. The entire function can be divided into initial setting and processing. During initialization, equalizer E_LS[S] is calculated from Equation 4 by Gaussian elimination using a plurality of right sides. During processing, equalization and slicing must be performed, each corresponding to a matrix multiplication and a set of comparators. Note that the processing is performed continuously at the symbol rate, as opposed to the initial setting, which is calculated only once. FIG. 9 summarizes the approximate number of multiplications, additions, and data transfers required to perform both of these phases per subcarrier. The number of data transfers is a number indicating the amount of memory / register transfer. Since this architecture has not yet been determined, the assignment of data transfers to memory or register banks is an open issue. However, it is important to emphasize that data transfer is often an impediment to practical use. As an example, a system with 4 users and 4 antennas requires 200k data transfer at 72kFLOPS at initial setup and requires 400MFLOPS / s and 1.2G word / s data transfer bandwidth during processing. And
[0085]
In an OFDM / SDMA system, for a given subcarrier, one or more users can be fully embedded in multiuser interference (MUI) or have a highly correlated channel vector. Obviously, these users are adversely affected by the remaining MUI and noise after linear equalization. In order to reduce this effect, in the present invention, continuous interference cancellation (SIC) is preferably used for each carrier (Per Carrier) (pcSIC). Contrary to LS-OFDM / SDMA, this technique does not evaluate all users at the same time, but does this continuously, preferably for one subcarrier. As such, the MUI that originates from a user that has already been detected can be removed (thus modifying the original single carrier). This technique relies on intermediate hard estimate feedback and is therefore non-linear. It should also be noted that pcSIC-OFDM / SDMA exploits frequency diversity, which is another example of the synergistic effect of OFDM / SDMA synthesis, since it preferably works on a per carrier basis. Further, although a continuous interference cancellation method (pcSIC) for each carrier is presented, the present invention is not limited to this. For each subcarrier n, first the detection order is preferably determined according to the received signal power. Assume that user 1 to user U are ordered appropriately. Subsequently, each user's soft estimate is calculated by least squares linear combination according to Equation 9.
[0086]
[Equation 9]

[Expression 10]

[0087]
In this equation, for each iteration u, H [s] is an initial value y from Equation 8 by Equation 10._aY equal to [s]¹ _aE, except that it is replaced by [s]_LS[S] is found as in Equation 4. Then, after slicing (which is the decision method), it is the hard intermediate estimate for user u
[Outside 6]

The MUI generated from user u is reconstructed (generally referred to as recombining) and subtracted (and modified thereby) from the remaining MUI, as in Equation 11 with In a typical pcSIC algorithm, there is only one intermediate hard estimate for each data signal for each carrier, which is then selected as the hard estimate (which is the selection scheme).
[0088]
## EQU11 ##

[0089]
Continuous interference cancellation (SIC) can be described as an uplink transmission scheme, where the data from the subband processed received data signal at the receiving terminal for at least one (but not limited to) data signal. The determination of the estimated value of the signal comprises the following steps. That is, (first step) a step of selecting one selection signal from the data signal. This selection step is, for example, selecting the first signal from the data signals ordered according to the received signal power, but is not limited thereto. (Second Step) A step of determining an estimated value of the selected data signal from the received data signal subjected to the subband processing, and includes, for example, linear processing of the received data signal subjected to subband processing including slicing. Although it is a synthetic method, it is not limited to this. (Third step) A step of modifying the subband-processed received data signal based on the estimated value of the selected received data signal, for example, a modified subband-processed received data signal Is obtained by recombining and dividing according to Equation 11, but is not limited thereto. (Fourth Step) Finally, an estimate of the remaining data signal from the modified subband processed received data signal is determined, probably by applying these same steps sequentially. Note that subbands can also be described as carriers.
[0090]
In one embodiment of a continuous interference cancellation uplink transmission scheme, the above determination of estimates (all steps) is performed one subband at a time.
[0091]
FIG. 4 shows the performance of pcSIC-OFDM / SDMA. Again, the BER for the SNR curve is given for 1 to 4 users. As a reference, the dashed curve shows the performance of a 100 Mbps plane OFDM with one user and one antenna, and the thin curve shows the performance of LS-OFDM / SDMA. This indicates that pcSIC-OFDM / SDMA provides improved performance with increasing number of users compared to LS-OFDM / SDMA. Specifically, we observed a gain of 5 dB when the BER was 0.001 and there were 4 users at the same time. For the assessment of the complexity of the pcSIC algorithm for OFDM / SDMA, we also look at the distinction between initialization and processing. At initialization, the removal order is determined and the equalizer is calculated. Since the channel matrix is different for each user u, the latter requires U different Gaussian eliminations. However, each H_uBy exploiting the structural relationship between [s], we have O (A²  U²) Has been successfully reduced in the number of calculations required. During processing, in addition to equalization and slicing, reconstruction (resynthesis) and subtraction (correction) must be performed. The approximate total number of operations for both these stages of the pcSIC-OFDM / SDMA algorithm is given in FIG. Specifically, each system of 4 users and 4 antennas requires 250k data transfers at 170kFLOPS in the initial setup phase, and (in the processing stage) 700MFLOPS / sec and 1.8Gword / sec data. Transfer bandwidth.
[0092]
(Pc) A potential weakness of SIC-OFDM / SDMA is that its performance degrades when at least two users are received with approximately equal power. Under such transmission conditions, the probability of making an incorrect decision increases, resulting in the propagation of errors. This potential drawback is illustrated in FIG. 5, which for each carrier—in the bottom diagram—shows the signal-to-interference ratio (SIR) during the first iteration, and—in the top diagram—occurs. Indicates the number of errors. However, it should be noted that it is optimal from an information theory perspective that all users have the same power. To solve the error propagation problem, we use interference dependent state insertion (SI). In essence, we can significantly reduce the probability of error propagation at a reasonable cost by inserting additional state information about those carriers that have suffered from bad SIR. State insertion is preferably applied in the (pc) SIC-OFDM / SDMA scheme. This state insertion scheme is further presented with a single subcarrier approach, but is not limited thereto.
[0093]
First of all, the SIR of user 1 of each subcarrier n is equalized by the equalizer E_LSCalculated from knowledge of [s]. Next, M subcarriers n most damaged from SIR_mIs assigned one additional state m. These M states are alternative estimates for user 1, referred to as the intermediate hard estimate above.
[Outside 7]

Keep track of the progress. They are,
[Outside 8]

Is a slice of
[Outside 9]

except
[Outside 10]

Is defined as the closest alignment point to. After these assignments, u = 2 to U sequentially
[Outside 11]

To get M additional states are treated as normal subcarriers. Specifically, the MUI generated from user u-1 is reconstructed and subtracted (after recombining with channel response estimation) according to Equation 12 (and thereby modifying the original signal) and minimized according to Equation 13 Soft estimate by square combination
[Outside 12]

Is calculated. Finally, for each of these M subbands, the algorithm can be used when the first or second of the two norms of Equation 13 is minimum, respectively.
[Outside 13]

Or
[Outside 14]

Is selected as the hard estimated value from the intermediate hard estimated value.
[0094]
[Expression 12]

[Formula 13]

[0095]
A state insertion uplink transmission scheme is such that the determination of the estimate of the data signal from the subband processed received data signal at the receiving terminal is related to at least one (but not limited to) data signal. This can be explained as a method of further comprising the following steps. That is, these steps are (first step) selecting one selected data signal from the data signals, and (second step) estimated values expressed as intermediate hardware estimated values above, Determining a plurality of the estimated values of the selected data signal from the subband processed received data signal; and (third step) each of the modified subband processed received data signals is selected. Determining a plurality of the modified subband processed received data signals based on one of the (intermediate hard) estimates of the received data signal (where a recombining and modifying scheme is utilized) And (fourth step) the modified subbands described above, for example, by a least square linear combination method, but not limited thereto Determining a plurality of estimates of at least one of the remaining data signals from each of the received data signals; and (last step) and then a method for evaluating the norm of the modified subband processed received data signal, for example Selecting one of the estimated values of the selected data signal by a method that is not limited thereto.
[0096]
In one embodiment of the state insertion uplink transmission scheme, the above determination of estimates (all steps) is performed one subband at a time.
[0097]
In one embodiment of the present invention, the state insertion uplink transmission scheme is used in combination with a continuous interference cancellation scheme, and is preferably performed one subband at a time.
[0098]
FIG. 6 shows the performance of pcSIC-OFDM / SDMA with interference dependent state insertion as an exemplary system. The number of additional states was set to M = 64. For reference, the dashed curve shows the performance of a 100 Mbps plane OFDM with one user and one antenna, and the thin curve shows the performance of pcSIC-OFDM / SDMA without state insertion. This compares to pcSIC-OFDM / SDMA with 64 additional states compared to pcSIC-OFDM / SDMA without SI, with a gain of 6 dB when BER is 0.001 and there are 4 users at the same time. It shows that has been achieved. Other simulations also show that the performance improvement for SI with 32 states and 16 states is 5 dB and 4 dB, respectively.
[0099]
Regarding the assessment of the complexity of pcSIC-OFDM / SDMA with SI, the function can be divided again into the initial configuration and the processing part. At the time of initialization, it is necessary to calculate the SIR of each subcarrier after equalization and then perform state insertion for the M worst SIR subcarriers. At the time of processing, it is necessary to track M additional states using Equations 12 and 13, and then select based on the remaining two norms of Equation 14.
[0100]
[Expression 14]

[0101]
The operations required for state insertion into M out of N subcarriers are shown in FIG. To obtain the total number of operations for pcSIC-OFDM / SDMA with SI, the operation from FIG. 10 must be added to this. For a system of 4 users and 4 antennas, pcSIC-OFDM / SDMA with 64 additional states requires 310k data transfers at 220kFLOPS in the initialization phase and 1. Requires 1 GFLOPS / sec and a data transfer bandwidth of 2.6 Gwords / sec.
[0102]
In downlink transmission, the composite peer terminal is receiving the signal and the processing peer is transmitting the signal. In this embodiment, these receiving terminals have only a single antenna and a plain OFDM modem (ie, no SDMA processing capability). Since user terminals only have a single antenna and we want to concentrate most of the processing power on the base station, these user terminals cannot mitigate multi-user interference in the downlink. Therefore, the base station adds the pre-compensation matrix E to the data symbol vector Y [s]._PREMultiply by Y_TR[S] is obtained. This Y_TR[S] is transmitted from A antennas. The input / output relationship of Equation 6 is obtained.
[0103]
Ignoring all non-ideal ones, this approach results in complete separation of each user's data symbols and complete equalization upon reception. Thus, the mobile does not require channel information or an equalizer. By giving these pre-compensation matrices to each carrier n, the input / output relationship is as shown in Equation 15.
[0104]
[Expression 15]

[0105]
In this way, each user sees a single user's AWGN channel per carrier. FIG. 7 shows the average BER in the downlink when the number of users is different. Since there is no interference, the number of concurrent users does not affect performance (assuming that the number of users does not exceed the number of antennas and that there are no non-ideal ones).
[0106]
Again, processing in the downlink comprises both initialization and processing. In the initial setting stage, a pre-compensation matrix is calculated. At the time of processing, the user data Y [s] is multiplied by the pre-compensation matrix. The complexity of both initialization and processing is almost the same as in the LS-OFDM / SDMA scheme in the uplink.
[0107]
By applying coherence grouping in addition to the proposed OFDM / SDMA proposed for both uplink and downlink communications, the initialization effort in both situations can be simplified. This initialization effort is characterized as the determination of the equalizer or pre-compensation matrix where Equation 4, Equation 5, or Equation 7 is utilized. By means of the equalizer matrix, the relationship between the data signal and the subband processed received data signal is defined in the same way as in Equation 1, Equation 9, or Equation 13. The relationship between the synthesized data signals, which are converted data signals, is defined in the same manner as in Equation 6 or Equation 15 by the pre-compensation matrix. Instead of determining the matrix separately for each subband, the subbands can be grouped into multiple sets, at least one set comprising at least two subbands, and then the matrix or more generally Specifically, the above relationship can be determined one set at a time. These groups are all of equal size G in this coherence grouping scheme embodiment. FIG. 8 shows the performance degradation associated with carrier grouping applied to pcSIC-OFDM / SDMA with SI for several values of G. It has been observed that the performance degradation for the simulated channel is negligible for G below 4. For G over 32, the performance is worse than plain OFDM with one user and one antenna. It may be concluded that the initialization complexity for the subject system can be reduced by a factor of 8. As an example of a 100 Mbps OFDM / SDMA WLAN that uses SDMA to separate four concurrent 25 Mbps users, some numerical results on performance gain and complexity can be obtained. If a pcSIC-OFDM / SDMA with 64 SIs and a group of size 8 is implemented, a performance gain of 11 dB is obtained with a BER of 0.001 compared to the least squares approach. The required computing power is 40 k data transfer at 27 kFLOPS at the initial setting, and 1.1 GFLOPS / sec and 2.6 Gword / sec data transfer bandwidth at the time of processing.
[0108]
In another preferred embodiment, the processing peer comprises an access point to a connection network (this connection network may be, for example, a cable network or a satellite network), and the composite peer is a radio where cost is a major issue. A terminal is provided. In this embodiment, only the access point has DFT (Discrete Fourier Transform) means and IDFT (Inverse Discrete Fourier Transform) means. This prevents an increase in the peak-to-average power ratio of the transmitted signal, so that both the digital baseband modem part of the terminal in the composite peer and the front end of all terminals in the system can be realized inexpensively. Enable. A typical application of asymmetric frequency domain SDMA is, for example, a wireless home networking application in the 2.4 GHz band. Such an asymmetric configuration realizes a so-called centralized scenario in which subband processing and reverse subband processing are arranged at processing peers. In this transmission method, the determination of the estimated value of the data signal from the received data signal subjected to the subband processing at the receiving terminal is performed by the subband processing at the receiving terminal as follows: (first step) Determining an intermediate estimated value of the data signal from the received data signal; and (second step) obtaining the estimated value of the data signal by subjecting the intermediate estimated value to the inverse subband processing. Prepare. In this embodiment, the method of the invention is used not only to detect signals of different terminals transmitting simultaneously in the same frequency band, but also to reduce interference from microwave ovens that cause jamming signals in this band, for example. can do. For example, in a multipath fading environment such as a home environment, a guard interval can be inserted into a data signal prior to transmission. If these guard intervals are again designed to have all echoes received on the multipath channel, channel convolution becomes cyclic after removal of the guard intervals. Thus, in the frequency domain, this is equivalent to multiplication with the Fourier transform of the channel. This embodiment allows the processing peer's terminal to be inexpensive and includes uplink and downlink combining in a manner similar to OFDM / SDMA, including continuous interference cancellation, preferably per subband and state insertion. Enable processing.
[Brief description of the drawings]
FIG. 1 shows a composite peer (10) comprising at least two transmitting terminals (20) each having at least one transmitting means (60) and a spatial diversity receiving means (here two receiving means spatially separated ( 1 shows a (uplink) communication device with a processing peer (30) comprising at least one receiving terminal (40) with (but not limited to) 80). The receiving terminal (40) performs at least subband processing (90). The upper part of FIG. 1 shows a centralized scenario. In this case, the receiving terminal further performs reverse subband processing (110). The lower part of FIG. 1 shows a split scenario. In this case, the transmitting terminal further executes reverse subband processing (160).
FIG. 2 shows a composite peer (340) comprising at least two receiving terminals (330) each having at least one receiving means (320) and a spatial diversity transmitting means (here two spatially separated transmitting means ( 2 illustrates a (downlink) communication device with a processing peer (230) having at least one transmitting terminal (240) having (but not limited to) 220). The transmitting terminal (240) performs at least the inverse subband processing (260). The upper part of FIG. 2 shows a centralized scenario. In this case, the transmitting terminal (240) further executes subband processing (280). The lower part of FIG. 2 shows a split scenario. In this case, the receiving terminal executes subband processing (350).
FIG. 3 illustrates the performance of an embodiment of the present invention that is uplink least squares OFDM / SDMA for 1 to 4 users present at the same time. Bit error rate (BER) is expressed as a function of signal-to-noise ratio (SNR). The above embodiments can be used for any number of users. In the above embodiment, OFDM is used as a subband method by using fast Fourier inverse transform and fast Fourier transform. In the above embodiment, the determination of the estimated value of the data signal from the subband-processed received data signal is based on the least square method.
FIG. 4 shows the performance of uplink OFDM / SDMA pcSIC (Continuous Interference Cancellation per Carrier) for 1 to 4 users present simultaneously. Bit error rate (BER) is expressed as a function of signal-to-noise ratio (SNR). The above embodiments can be used for any number of users. In the above embodiment, the determination of the estimated value of the data signal from the received data signal subjected to the subband processing is to determine the estimated value of the selected data signal in the meaning of the least square method, and then the subband processing is performed. Based on modifying the received data signal and finally determining an estimate of the remaining data signals, which are all data signals except the selected data signal. For the remaining data signals, the above determination of an estimate of a selected data signal may be used. The above selection approach for data signals results in an ordering in which estimates of the data signal are determined.
FIG. 5 shows uplink SIC (Continuous Interference Cancellation) —Error propagation with OFDM / SDMA. The number of errors and the signal to interference ratio (SIR) are expressed as a function of frequency. The above observations of error propagation motivate the use of state insertion schemes.
FIG. 6 shows the performance of uplink OFDM / SDMA pcSIC with state insertion for 1 to 4 users present at the same time. The above embodiments can be used for any number of users. Bit error rate (BER) is shown as a function of signal-to-noise ratio (SNR). In the above embodiment, the determination of the estimated value of the data signal from the subband processed received data signal includes determining a plurality of estimated values of the selected data signal, and thus the subband processed reception. Modifying the data signal, then determining an estimate of at least one of the remaining data signals, all data signals except the selected data signal, and finally the selected Selecting one of the plurality of estimates of the data signal. The above data signal selection approach results in the introduction of an ordering in which estimates of the data signal are determined. The amount of estimate determined for each data signal may be different, or may be one for several data signals.
FIG. 7 shows downlink OFDM / SDMA performance for 1 to 4 users present at the same time. The above embodiments can be used for any number of users. Bit error rate (BER) is shown as a function of signal-to-noise ratio (SNR).
FIG. 8 shows uplink OFDM / SDMA performance for grouping factors with different coherence. Bit error rate (BER) is shown as a function of signal-to-noise ratio (SNR). In the above embodiment, the initial setting, which is the determination of the relationship between the data signal and the subband processed received data signal, is performed one set at a time. The coherence grouping factor represents the amount of subbands in a set.
FIG. 9 represents the number of operations (initial setting and processing) of least squares OFDM / SDMA.
FIG. 10 shows pcSIC (continuous interference cancellation for each carrier) -OFDM / SDMA operation count (initial setting and processing).
FIG. 11 shows the number of additional operations (initial setting and processing) related to state insertion.
[Explanation of symbols]
10,340 ... Composite peer,
20, 240 ... transmitting terminal,
30, 230 ... processing peer,
40, 330 ... receiving terminal,
50, 200 ... data signal,
60, 220 ... transmission means,
70 ... converted data signal,
80, 320 ... receiving means,
90, 280, 350 ... subband processing,
100 ... Determination of an intermediate estimate of the data signal from the subband processed received data signal at the receiving terminal,
110, 160, 260 ... reverse subband processing,
120 ... an estimate of the data signal,
130: Intermediate estimate of the data signal,
140... Received data signal subjected to subband processing,
150 ... Determination of an estimate of the data signal from the subband processed received data signal at the receiving terminal,
250 ... determination of the synthesized data signal,
270 ... determination of a composite data signal from the intermediate composite data signal,
290 ... Intermediate composite data signal,
300 ... the synthesized data signal,
360. Signal after subband processing at receiving terminal.

Claims (25)

From at least two transmitting end end each having one transmit hands stage even without low, a method of transmitting a plurality of data signals to at least one of the receiver end has a space diversity receiving hands stage,
The data signal after the plurality of conversion converted from the plurality of data signals transmitted from the transmitting end end, a plurality of the received data signal is at least a function of at least two signals among the data signals of the converted receiving by the spatial diversity hand stages,
A step you subband processing at least two of the received data signal in the receiving end late,
In the receiving terminal, from the received data signal that has been processed the plurality of sub-bands, and determining an estimate of said plurality of data signals,
The determining step is
Selecting one data signal from the plurality of data signals;
Determining an estimate of the selected data signal from the plurality of subband processed received data signals;
Modifying the plurality of subband processed received data signals based on the estimated values of the selected data signals;
Determining an estimate of the remaining data signal from the plurality of subband processed and modified received data signals,
The method of determining estimates of the plurality of data signals is based on individual spatial signatures of the plurality of received data signals .   The method of claim 1, wherein the transmissions are performed substantially simultaneously. The spectra of the plurality of the converted data signals are at least partially overlapping with the method of claim 1, wherein are. The method of claim 1, wherein each one subband is performed to determine the estimated values of the plurality of data signals in the receiving terminal. Step you select the one data signal The method of claim 1 wherein is performed based on the received power of the data signal. Step you select the one data signal The method of claim 1, wherein the executed based on the interference ratio of the data signal. A plurality of subbands related to the subband processing are grouped into a plurality of sets such that at least one set includes at least two subbands;
Determining the estimated values of the plurality of data signal Te the receiving terminal smell,
Between said plurality of data signals and said plurality of sub-bands processed received data signals and the step and the plurality of data signals and said plurality of sub-bands processed received data signals for determining relationship one set between the method of claim 1 further comprising determining an estimate of said plurality of data signals using the above relationship. The method according to claim 1, wherein the conversion from the data signal to the converted data signal includes inverse subband processing. In the receiving terminal, from the plurality of sub-bands processed received data signals, that determine the estimated values of the plurality of data signal step,
In the receiving terminal, from the plurality of sub-bands processed received data signals, the steps that determine the estimated value between among the plurality of data signals,
By the child inverse subband processing said plurality of intermediate estimates method of claim 1, including the step of obtaining an estimate of the plurality of data signals. The method of claim 1, wherein the conversion from the data signal to the converted data signal further comprises introducing a guard interval.   The method of claim 1, wherein the subband processing is orthogonal frequency division demultiplexing. The method according to claim 8 or 9 , wherein the inverse subband processing is orthogonal frequency division multiplexing. And at least one method for transmitting a plurality of data signals into at least two receiving end late, each having at least one receiving hand stage from the transmitting end end having one spatial diversity transmitting hand stage,
A step that determine a plurality of composite data signals converted from the plurality of data signals in the transmitting terminal,
A step you reverse sub-band processing the plurality of combined data signals,
And transmitting said plurality of inverse subband processed combined data signals with said spatial diversity hand stage,
The received data signal a plurality of inverse subband processing is at least a function of said plurality of inverse subband processed combined data signals, at least one of the receiving hands stage in at least one of the receiving end late One step of receiving,
Said plurality of inverse subband processed received data signals, and determining the estimated values of the plurality of data signals,
Determining the plurality of combined data signals at the transmitting terminal;
Determining a plurality of intermediate synthesized data signals by subband processing the plurality of data signals;
Determining the plurality of composite data signals from the plurality of intermediate composite data signals,
The method of determining the plurality of composite data signals is based on individual spatial signatures of the plurality of inverse subband processed composite data signals to be transmitted . The transmission of a plurality of inverse subband processed combined data signals The method of claim 13, wherein are performed substantially simultaneously. The method of claim 13 , wherein spectra of the plurality of inverse subband processed composite data signals overlap at least partially. The method of claim 13, wherein each one subband is performed to determine the plurality of composite data signal Te the transmitting terminal smell. The method of claim 13 further comprising a sub-band processing to determine the estimated values of the plurality of data signals in the receiving terminal. The method according to claim 13 or 17 , wherein the subband processing is orthogonal frequency division multiplexing. The method of claim 13 , wherein the inverse subband processing is orthogonal frequency division multiplexing. The plurality of subbands related to the inverse subband processing are grouped into a plurality of sets such that at least one set includes at least two subbands;
Step that determine a plurality of composite data signal in the transmitting end weekend,
Determining a set of relationships between the plurality of data signals and the plurality of combined data signals one by one;
The method of claim 13 further comprising the step of determining the plurality of combined data signal using the above relationship between the upper Symbol plurality of data signals and said plurality of composite data signal. The method of claim 13 , wherein a guard interval is introduced into the plurality of inverse subband processed composite data signals. An apparatus for determining an estimate of a data signal from at least two received data signals,
At least one spatial diversity reception hand stage,
A first circuit unit for receiving the plurality of received data signals by the spatial diversity receiving means;
A second circuit portion you subband processing at least two of the received data signal,
At least Bei example and a third circuit for determining the estimated values of the plurality of data signals from the plurality of sub-bands processed received data signals,
The apparatus for determining an estimate of the plurality of data signals is based on individual spatial signatures of the plurality of received data signals . The third circuit unit includes a plurality of circuits for determining each a portion of the estimated values of the plurality of data signals based on a portion of the plurality of subbands of the plurality of sub-bands processed received data signals the apparatus of claim 22, wherein the. The spatial diversity means comprises at least two receiving means;
23. The apparatus of claim 22 , wherein the first circuit section comprises a plurality of circuits that respectively receive the plurality of received data signals from one of the receiving means of the spatial diversity means. The plurality of determining the estimated values of the data signal, The apparatus of claim 22, wherein each one subband is performed.

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