JP3812705B2 - Receiver - Google Patents

Description

【００５１】
この場合、１段目の各レプリカ生成手段Ｐ１〜Ｐｎで生成されるレプリカ信号の総和ｒ’（ｔ）は式２で示される。ここで、式２中のＸｊは例えば雑音や干渉等により生じるユーザ信号＃ｊのレプリカ生成誤差に基づいて定められ、通常、このＸｊは１未満の値となる。
【００５２】
【数２】

【００５３】
また、減算器３から出力される第１残差信号｛ｒ（ｔ）−ｒ’（ｔ）｝は式３で示される。
【００５４】
【数３】

【００５５】
上記式３に示されるように、もしも１段目の各レプリカ生成手段Ｐ１〜Ｐｎにより各ユーザ信号のレプリカ信号が理想的に生成されるとすれば、各Ｘｊ＝１となるため、減算器３から出力される第１残差信号は｛ｒ（ｔ）−ｒ’（ｔ）｝＝Ｎ（ｔ）となって雑音等の成分のみとなる。しかしながら、通常は各レプリカ生成手段Ｐ１〜Ｐｎにより生成されるレプリカ信号には多少の誤差が含まれるため、本例では、２段目にも１段目と同様な処理を行うレプリカ生成手段Ｑ１〜Ｑｎを備えてマルチステージ化することにより、総じてレプリカ生成誤差を軽減する構成としてある。
【００５６】
上記したように２段目の各レプリカ生成手段Ｑ１〜Ｑｎ及び減算器５においても１段目とほぼ同様な処理が行われ、各加算器Ｍ１〜Ｍｎでは入力された第２残差信号と各ユーザ信号のレプリカ信号とを加算して出力することが行われる。ここで、例えばユーザ信号＃１に対応した加算器Ｍ１から出力される加算信号Ｂ１（ｔ）は式４で示される。なお、他の加算器Ｍ２〜Ｍｎから出力される加算信号についても、それぞれの加算器Ｍ１〜Ｍｎがそれぞれのユーザ信号＃１〜＃ｎに対応しているといった点を除いては、同様である。
【００５７】
【数４】

【００５８】
ここで、上記式４中のｒ’’（ｔ）は２段目の各レプリカ生成手段Ｑ１〜Ｑｎで生成されたレプリカ信号の総和を示しており、また、Ｙｊは１段目のレプリカ生成手段Ｐ１〜Ｐｎで生成された各ユーザ信号＃ｊのレプリカ信号と２段目のレプリカ生成手段Ｑ１〜Ｑｎで生成された各ユーザ信号＃ｊのレプリカ信号との加算結果にかかる係数を示している。
【００５９】
上記式４に示されるように、各加算器Ｍ１〜Ｍｎから出力される加算信号（拡散信号）中では、各加算器Ｍ１〜Ｍｎに対応したユーザ信号については受信信号中の当該ユーザ信号と同程度（理想的には受信時と同一）の大きな信号強度となる一方、他のユーザ信号（干渉信号）については除去されて上記した（１−Ｙｊ）の項の値に応じて小さくなっている。なお、通常、この（１−Ｙｊ）の項はかなり小さい値となるが０にまではならない。
【００６０】
以上のようにして各加算器Ｍ１〜Ｍｎから拡散信号として出力される各ユーザ信号は各パス検出部Ｄ１〜Ｄｎに入力され、各パス検出部Ｄ１〜Ｄｎでは入力された各ユーザ信号に基づいて当該信号のパスタイミングを検出する。
ここで、各パス検出部Ｄ１〜Ｄｎにより行われるパス検出処理の具体例を示す。
すなわち、各パス検出部Ｄ１〜Ｄｎでは、例えば各加算器Ｍ１〜Ｍｎから入力した拡散信号を逆拡散するに際して当該拡散信号に対して各ユーザ信号の拡散符号を乗算するタイミングをずらしながら両者の相関値を演算し、演算した相関値のピーク位置を各ユーザ信号の到来時間位置（パスタイミング）として検出する。
【００６１】
図２には、各パス検出部Ｄ１〜Ｄｎが入力信号を逆拡散したときに得られる逆拡散信号の一例を示してあり、横軸は時間を示し、縦軸は信号レベルを示している。同図に示した例では、例えば１シンボルの時間幅に３つのパス（“パス０”、“パス１”、“パス２”）による相関ピークが得られており、これら３つの相関ピークのパスタイミングがそれぞれ“τ１”、“τ２”、“τ３”として検出される。
【００６２】
このようなパス検出を行うに際して、本例では、上記のように受信信号から他のユーザ信号（干渉信号）が除去された後の信号がパス検出部Ｄ１〜Ｄｎに入力されて、パス検出部Ｄ１〜Ｄｎでは他のユーザ信号による干渉をほとんど受けていない信号に基づいて各ユーザ信号のパスタイミングを検出する構成であるため、例えば従来の場合と比べてパス誤検出の確率を大幅に減少させることができ、これにより、例えば干渉信号となる他のユーザ信号の数が多い場合であっても、安定したパス検出を行うことができ、パスタイミングの検出の精度を大幅に向上させることができる。
【００６３】
また、各パス検出部Ｄ１〜Ｄｎで検出された各ユーザ信号のパスタイミングの情報は各ユーザ信号に対応するレプリカ生成手段Ｐ１〜Ｐｎ、Ｑ１〜Ｑｎへフィードバックされ、各レプリカ生成手段Ｐ１〜Ｐｎ、Ｑ１〜Ｑｎにおける処理で参照されて用いられる。
具体例として、各レプリカ生成手段Ｐ１〜Ｐｎ、Ｑ１〜Ｑｎでは、各パス毎のユーザ信号を再拡散するに際して、フィードバックされたパスタイミング情報を参照することを行い、すなわち、このパスタイミング情報で示される時間位置に再拡散した各パス信号を割り当てることを行う。
【００６４】
このような割り当てにより、再拡散された各パス信号の時間位置と遅延手段２、４を介して減算器３、５へ出力される信号中の当該各パス信号の時間位置とが一致するように調整される。本例では、上記のように各パス検出部Ｄ１〜Ｄｎにおけるパスタイミングの検出精度が向上しているため、各レプリカ生成手段Ｐ１〜Ｐｎ、Ｑ１〜Ｑｎにおける再拡散の精度も向上し、これにより、干渉除去の精度を向上させることができ、例えば２段目の各レプリカ生成手段Ｑ１〜Ｑｎが入力信号から各ユーザ信号を逆拡散により抽出する処理の精度を向上させることができる。
【００６５】
また、他の具体例として、各レプリカ生成手段Ｐ１〜Ｐｎ、Ｑ１〜Ｑｎでは、フィードバックされたパスタイミング情報を逆拡散処理（相関処理）等において参照して用いることも可能である。すなわち、各レプリカ生成手段Ｐ１〜Ｐｎ、Ｑ１〜Ｑｎでは、例えば入力信号から各ユーザ信号を逆拡散（相関処理）により抽出するに際して、入力信号と乗算するための拡散符号を生成するタイミングをフィードバックされたパスタイミング情報で示される時間位置に合わせるといった処理を行うことにより、逆拡散による各ユーザ信号の抽出処理の精度を向上させることや、当該処理を効率化することができる。なお、拡散符号の生成は例えば各レプリカ生成手段Ｐ１〜Ｐｎ、Ｑ１〜Ｑｎに内蔵された拡散符号生成器により行われる。
【００６６】
また、本例の構成では、例えば干渉除去部に電源を投入した直後や、新規なユーザ信号が通信対象として加わった直後においては、パス検出部Ｄ１〜Ｄｎでは例えば干渉除去が行われていない受信信号に基づいて各ユーザ信号のパスタイミングを検出する場合もあるが、この場合においても、或る程度の精度で各ユーザ信号のパスタイミングを検出することが可能であり、本例では、当該パスタイミングの情報が得られた後に干渉除去部による干渉除去処理（レプリカ信号の生成処理等）が開始される。
【００６７】
そして、上記のように初めの内はパスタイミングの検出精度は或る程度実用上で有効な程度のものとはなるが、本例では、干渉除去部により当該パスタイミングの情報に基づいて受信信号から干渉信号（他のユーザ信号）を除去し、干渉信号を除去した信号に基づいて各ユーザ信号のパスタイミングを検出し、検出したパスタイミングの情報を各レプリカ生成手段Ｐ１〜Ｐｎ、Ｑ１〜Ｑｎへフィードバックするといった一連の処理を繰り返していくに従って、パスタイミングの検出精度や干渉除去の精度等を非常に高めることができる。
【００６８】
なお、本例の干渉除去部では、過去に受信した信号に基づいて検出したパスタイミングの情報をフィードバックすることにより後に受信した信号の処理に用いているが、一般に、各ユーザ信号の位置変動（すなわち、例えば各ユーザ信号を通信する移動局の位置の変動）はフィードバックに要する時間内ではほとんど発生せず、すなわち、各ユーザ信号のパスタイミングはフィードバックに要する程度の短時間ではほとんど変動するものではないため、フィードバックの効果を十分に得ることができる。
【００６９】
また、本例の各パス検出部Ｄ１〜Ｄｎから出力されるタイミング情報の伝送の仕方の具体例を示す。
本例では、各パス検出部Ｄ１〜Ｄｎから出力される各ユーザ信号のタイミング情報を時分割により共通のバスラインを介して各レプリカ生成手段Ｐ１〜Ｐｎ、Ｑ１〜Ｑｎ等へ配信することにより、タイミング情報を伝送するためのバスラインを大幅に削減し、これにより、装置の小型化やコストの削減を図る。
【００７０】
図３には、上記した共通のバスラインを伝送するパスタイミング情報の一例を示してある。この例では、説明の便宜上からユーザ信号の数が３であるとし、各ユーザ信号（ユーザ信号＃１（Ｕ１）、ユーザ信号＃２（Ｕ２）、ユーザ信号＃３（Ｕ３））には１シンボル時間幅に４つのパスの情報を伝送することが可能な時間（４つのスロット）を割り当てている。同図の例では、図示のように、ユーザ信号＃１については１シンボル時間幅に３つのパス（“τ１”、“τ２”、“τ３”）が検出され、ユーザ信号＃２については４つのパス（“α１”、“α２”、“α３”、“α４”）が検出され、ユーザ信号＃３については２つのパス（“β１”、“β２”）が検出されている。なお、１シンボル時間幅に検出したパスの数が４パス未満である場合には、同図に示したように、各ユーザ信号毎に準備された４パス分のスロットの内の一部は空き（例えば情報無し）となる。
【００７１】
本例では、上記のような共通のバスラインを用いてパスタイミング情報を例えばシンボルレートで伝送する構成とすることにより、例えば各ユーザ信号毎に異なるバスラインを用いてタイミング情報をチップレートで伝送する従来の場合と比べて、バスラインの数を大幅に減少させることができる。具体例として、例えば１シンボル（拡散符号）当たりのサンプル数が１０２４点であってシンボルレートが６４ｋＨｚである場合には、１つのパスのタイミング情報を伝送するのに１ユーザ信号当たり１０ビット必要となるが、本例では、この場合に、例えば１０ビットのバスラインを用いて２０．４８ＭＨｚの伝送を行うこととすれば、３２０パス分（２０．４８ＭＨｚ／６４ｋＨｚ＝３２０）のタイミング情報を共通のバスラインにより伝送することができる。
【００７２】
また、本例の２段目の各レプリカ生成手段Ｑ１〜Ｑｎから各信号処理部Ｓ１〜Ｓｎに対して出力される逆拡散信号（各ユーザ信号）の伝送の仕方の具体例を示す。
本例では、２段目の各レプリカ生成手段Ｑ１〜Ｑｎでは逆拡散により抽出した各ユーザ信号として例えばシンボルレートで生成される相関ピークの信号を出力しており、当該シンボルレートの各ユーザ信号を時分割により共通のバスラインを介して各信号処理部Ｓ１〜Ｓｎへ配信する。
【００７３】
本例では、上記のような共通のバスラインを用いて各ユーザ信号をシンボルレート（例えば６４ｋＨｚ）で伝送する構成とすることにより、例えば各ユーザ信号を拡散信号（拡散されている信号）としてサンプリングレート（例えば１６ＭＨｚ）で多数のバスラインを用いて伝送する従来の場合と比べて、各ユーザ信号のシンボル情報を伝送するためのバスラインの数を大幅に減少させることができ、これにより、例えば後述するように干渉除去部と変復調部とが着脱自在に構成された場合等においても、両者の接続のためのインタフェースを簡易化することができる。
【００７４】
具体例として、例えば１シンボル（拡散符号）当たりのビット数が１０ビット（但し、例えば相関演算により得られる複素信号ではＩ相とＱ相とが存在するため計２０ビット）であってシンボルレートが６４ｋＨｚである場合には、本例では、例えば２０ビットのバスラインを用いて２０．４８ＭＨｚの伝送を行うこととすれば、３２０ユーザ信号分のタイミング情報（２０．４８ＭＨｚ／６４ｋＨｚ＝３２０）を共通のバスラインにより伝送することができる。
【００７５】
なお、従来のように各ユーザ信号毎に異なるバスラインを用いて各ユーザ信号を例えば１６ＭＨｚのサンプリングレートで伝送する場合には、相関演算前の拡散信号を伝送することから各サンプリング点のデータが４ビットであるとすると、３２０のユーザ信号を伝送するためには１２８０ビット分（３２０×４＝１２８０）ものバスラインが必要となってしまう。また、一般に、４０ＭＨｚを超える伝送（転送）は困難であるため、この従来例において時分割しようとしても、６４０ビット分程度ものバスラインが必要となってしまう（すなわち、１６ＭＨｚの２倍程度の伝送速度しか実現することができない）。また、光ファイバを用いれば高速伝送も可能ではあるが、コストが非常に高くなってしまうといった問題がある。
【００７６】
以上のように、本例では、前記干渉除去手段（上記したように本例ではレプリカ生成手段Ｑ１〜Ｑｎ等）が受信信号から逆拡散により抽出した各ユーザ信号を受信処理手段（上記したように本例では信号処理部Ｓ１〜Ｓｎ等）へ出力し、当該受信処理手段が当該逆拡散信号を受信処理する構成とすることにより、上記のように各ユーザ信号をシンボルレートで伝送することから例えばバスラインを大幅に削減することが可能であり、これにより、装置の小型化やコストの削減を図ることができる。
【００７７】
次に、上記図１に示した変復調部の構成の仕方や当該変復調部により行われる処理について説明する。
以下では、変復調部の構成の態様例を幾つか示しつつ、各態様例における処理動作等を説明する。
上記図１に示した本例のＣＤＭＡ基地局では、干渉除去部と変復調部とが接続された構成を示してあるが、例えば従来では干渉除去部を備えていない既存のＣＤＭＡ基地局もあり、このようなＣＤＭＡ基地局では既存の変復調部に本発明に係る干渉除去部を追加的に接続することが可能な構成とすることにより、ハードウエアの変更を少なくし、コストの削減等を実現することができる。
【００７８】
なお、例えば上記図５に示したような従来において提案されている干渉キャンセラ（干渉除去部）の構成では、本例のように干渉除去部と変復調部とを着脱自在な構成とすることまでは検討等されていなかった。このため、従来において提案されている構成を既存のＣＤＭＡ基地局に適用する場合には、干渉キャンセラと変復調部とを一体として備えた新たな装置を準備して既存の変復調部と交換しなければならず、既存の変復調部が無駄になってしまうといった問題がある。本例では、干渉除去部を着脱自在な構成とすることも可能であるため、このような問題を解決することができる。
【００７９】
上記のような既存の変復調部では、ＣＤＭＡ方式により受信した複数のユーザ信号（拡散信号）を受信処理する構成であるため、例えば各信号処理部Ｓ１〜Ｓｎには受信信号から各ユーザ信号を逆拡散により抽出する相関器の機能が備えられており、また、各判定部Ｉ１〜Ｉｎには逆拡散により抽出された各ユーザ信号を同期検波し、ＲＡＫＥ受信し、判定等する機能が備えられている。また、このような既存の変復調部では、例えば各ユーザ信号のパスタイミングを検出するパス検出手段が備えられている。なお、上記図１では、説明の便宜上から干渉除去部の各パス検出部Ｄ１〜Ｄｎが変復調部にも含まれているように示してあるが、必ずしも干渉除去部と変復調部とで同一のパス検出部Ｄ１〜Ｄｎを共用しなければならないということではない。
【００８０】
一般に、ＣＤＭＡ基地局では、例えばＷ−ＣＤＭＡ初期導入時等において通信対象とするユーザ信号の数が少ない場合には必ずしも干渉除去部は必要ではなく、例えば既存の変復調部のみによっても受信信号を正確に復調することが可能である。しかしながら、ＣＤＭＡ基地局が通信対象とするユーザ信号の数が増加して、例えば当該ＣＤＭＡ基地局のキャパシティがほぼ満杯状態に陥ってしまった場合等には、各ユーザ信号による干渉のレベルが無視できないほどに大きくなるため、干渉除去部を変復調部と共に設ける必要が生じる。
【００８１】
例えば、既存のＣＤＭＡ基地局の変復調部に干渉除去部を接続せずに単体で動作させる場合には、変復調部に各ユーザ信号毎に備えられたパス検出部に受信信号（チップレート或いはサンプリングレート）を入力させるとともに、相関器の機能を有する各信号処理部Ｓ１〜Ｓｎへ受信信号を入力させる。これにより、変復調部では、受信信号から逆拡散により各ユーザ信号を抽出して、ＲＡＫＥ受信処理や判定処理等を行う。
【００８２】
また、上記した変復調部に干渉除去部を接続する場合には、例えば上記図１に示したように変復調部と干渉除去部とを接続し、干渉除去部の各加算器Ｍ１〜Ｍｎから各信号処理部Ｓ１〜Ｓｎへ各ユーザ信号を拡散信号として出力させる。これにより、変復調部では、各信号処理部Ｓ１〜Ｓｎへ入力された拡散信号から逆拡散により各ユーザ信号を抽出して、ＲＡＫＥ受信処理や判定処理や誤り訂正処理等を行う。なお、この場合、概念的には、上記図１に示した各スイッチＳＷ１〜ＳＷｎが上側に切替えられた状態となる。
【００８３】
また、この場合には、例えば干渉除去部の各パス検出部Ｄ１〜Ｄｎによりパス検出が行われるため、必ずしも変復調部に備えられたパス検出部を動作させる必要はなく、干渉除去部の各パス検出部Ｄ１〜Ｄｎにより検出された各ユーザ信号のパスタイミング情報を各信号処理部Ｓ１〜Ｓｎの相関器中の拡散符号生成器へ出力する構成とすることも可能である。また、例えば上記図３に示したのと同様に、各パス検出部Ｄ１〜Ｄｎと各レプリカ生成手段Ｐ１〜Ｐｎ、Ｑ１〜Ｑｎと各信号処理部Ｓ１〜Ｓｎとを共通のバスラインにより接続し、各パス検出部Ｄ１〜Ｄｎから各信号処理部Ｓ１〜Ｓｎへのパスタイミング情報の伝送を時分割により共通のバスラインを介して行うこともできる。
【００８４】
以上のように、本例の干渉除去部の構成では、例えば既存のＣＤＭＡ基地局の変復調部に干渉除去部を追加的に接続することが可能であるため、既存の変復調部を無駄にしてしまうといったことを防止することができる。また、以上では、既存の変復調部を例として干渉除去部との接続の仕方を示したが、既存のものでなくとも、同様に例えば各信号処理部Ｓ１〜Ｓｎに相関器の機能が備えられているような構成の変復調部についても、上記と同様に本例の干渉除去部を接続することが可能である。
【００８５】
また、変復調部の他の構成態様として、例えば各信号処理部Ｓ１〜Ｓｎには逆拡散信号として入力される各ユーザ信号を各判定部Ｉ１〜Ｉｎへそのまま出力する機能が備えられるとともに、各判定部Ｉ１〜Ｉｎには当該各ユーザ信号のデータを判定等する機能が備えられるといった態様で変復調部が構成されることも考えられる。この構成態様は、例えば主として干渉除去部と接続されて用いられることを考慮して採用されるものであり、変復調部には必ずしも相関処理や同期検波処理やＲＡＫＥ受信処理やパス検出処理を行う機能が備えられていないこともある。
【００８６】
この構成態様では、例えば上記図１に示したように変復調部と干渉除去部とを接続し、干渉除去部の２段目の各レプリカ生成手段Ｑ１〜Ｑｎから各信号処理部Ｓ１〜Ｓｎへ各ユーザ信号を逆拡散信号（例えば相関ピークの信号）として出力させる。これにより、変復調部では、各信号処理部Ｓ１〜Ｓｎへ入力された各ユーザ信号を各判定部Ｉ１〜Ｉｎへ伝送して各ユーザ信号のデータを判定し、誤り訂正処理等を行う。なお、この場合、概念的には、上記図１に示した各スイッチＳＷ１〜ＳＷｎが下側に切替えられた状態となる。
【００８７】
以上のように、本例では、例えば前記干渉除去手段（本例ではレプリカ生成手段Ｑ１〜Ｑｎ等）及びタイミング検出手段（本例ではパス検出部Ｄ１〜Ｄｎ）から成る干渉除去部を着脱自在な１つのユニットとして構成し、前記干渉除去手段が接続される受信処理手段（本例では信号処理部Ｓ１〜Ｓｎ等）により受信処理可能な信号が逆拡散信号であるか拡散信号であるかに応じて当該受信処理手段へ出力するユーザ信号をそれぞれの信号に切替える切替手段を備えた。
【００８８】
従って、本例では、例えばＣＤＭＡ基地局において種々な態様で構成される変復調部に対して干渉除去部の汎用性をもたせることができ、これにより、干渉除去部をＣＤＭＡ基地局に追加装備する場合等におけるコストの大幅な削減を実現することができる。なお、干渉除去部から出力するユーザ信号を拡散信号と逆拡散信号とに切替える切替手段の構成の仕方としては、特に限定はなく、例えば本例のように切替スイッチ等を用いることができる。
【００８９】
また、変復調部の他の構成態様として、本例では、干渉除去部が接続（装着）された場合と干渉除去部が接続されていない（離脱された）場合とで信号処理の仕方を切替えることが可能な態様で変復調部を構成する。なお、この構成態様の変復調部は、例えば干渉除去部から各ユーザ信号を逆拡散信号として出力するが拡散信号としては出力しない構成を用いる場合に特に有効である。
【００９０】
具体的には、本構成態様の変復調部では、例えば干渉除去部が離脱されている場合には、ＣＤＭＡ方式により受信した複数のユーザ信号（受信信号）を各信号処理部Ｓ１〜Ｓｎにより相関処理して各判定部Ｉ１〜Ｉｎにより同期検波処理やＲＡＫＥ受信処理や判定処理や誤り訂正処理等を行う受信処理に切替える。なお、この場合には、概念的には、上記図１に示した各スイッチＳＷ１〜ＳＷｎには受信部１からの受信信号が入力されて、当該受信信号が各信号処理部Ｓ１〜Ｓｎに入力される状態となる。また、この場合には、例えば変復調部に備えられたパス検出部が各ユーザ信号のパスタイミングを検出して、当該パスタイミングの情報を各信号処理部Ｓ１〜Ｓｎの相関器中の拡散符号生成器へ出力する。
【００９１】
また、本構成態様の変復調部では、例えば干渉除去部が装着されている場合には、当該干渉除去部の２段目の各レプリカ生成手段Ｑ１〜Ｑｎから逆拡散信号として入力される各ユーザ信号を各信号処理部Ｓ１〜Ｓｎにより各判定部Ｉ１〜Ｉｎへ伝送して各判定部Ｉ１〜Ｉｎにより当該各ユーザ信号のデータ判定処理や誤り訂正処理等を行う受信処理に切替える。なお、この場合、概念的には、上記図１に示した各スイッチＳＷ１〜ＳＷｎが下側へ切替えられた状態となる。また、例えば変復調部に備えられたパス検出部は動作しないように切替えられる。
【００９２】
以上のように、本構成態様では、例えば前記干渉除去手段（本例ではレプリカ生成手段Ｑ１〜Ｑｎ等）及びタイミング検出手段（本例ではパス検出部Ｄ１〜Ｄｎ）から成る干渉除去部が着脱自在な１つのユニットとして構成され、当該干渉除去手段が受信信号から逆拡散により抽出した各ユーザ信号を受信処理手段（本例では信号処理部Ｓ１〜Ｓｎ等）へ出力する構成が用いられる場合に、受信処理手段では干渉除去手段が装着されている場合には当該干渉除去手段から入力される逆拡散信号の受信処理に切替える一方、干渉除去手段が離脱されている場合にはＣＤＭＡ方式により受信した複数のユーザ信号の受信処理に切替える切替手段を備えた。
【００９３】
従って、例えばＣＤＭＡ基地局において干渉除去処理を行う場合と行わない場合とで変復調部の汎用性をもたせることができ、これにより、干渉除去部をＣＤＭＡ基地局に追加装備する場合等におけるコストの大幅な削減を実現することができる。
なお、変復調部により受信処理する信号を切替える切替手段の構成の仕方としては、特に限定はなく、例えばプログラムによる切替の仕方やスイッチによる切替の仕方を用いることができる。
【００９４】
具体的には、例えば、各信号処理部Ｓ１〜Ｓｎでの相関処理のように拡散信号（受信信号）として入力される各ユーザ信号を処理するための機能をプログラマブルなデバイス（例えばＦＰＧＡ：Field Programable G ate Array）から構成するとともに、ブートプログラムを２種類備えておき、変復調部を単体で用いる場合には相関処理等を行うプログラムをロードしてプロセッサに実行させる一方、変復調部と干渉除去部とを接続して用いる場合には逆拡散信号として入力される各ユーザ信号を受信処理するプログラムをロード等する切替の仕方を用いることができる。
【００９５】
また、他の態様として、例えば、各信号処理部Ｓ１〜Ｓｎに相関処理を行う相関器の機能を備えるとともに入力信号をそのまま判定部Ｉ１〜Ｉｎへ伝送（転送）するデータ転送機能を備えておき、干渉除去部を離脱する場合と装着する場合とで、それぞれスイッチにより相関器の機能とデータ転送機能とを切り替えるといった切替の仕方を用いることもできる。
【００９６】
図４（ａ）には、本構成態様の変復調部から干渉除去部を離脱した場合のＣＤＭＡ基地局の状態例を示す一方、図４（ｂ）には、本構成態様の変復調部に干渉除去部を装着した場合のＣＤＭＡ基地局の状態例を示してある。
同図（ａ）に示されるように干渉除去部が離脱された状態では、受信部（ＲＸ）１１により信号を受信して、変復調部１３ではパス検出や相関処理等を行う構成に切替える。なお、この状態では、干渉除去部を装着する部分１２は空き状態となる。一方、同図（ｂ）に示されるように干渉除去部１４が接続された状態では、受信部（ＲＸ）１１により信号を受信して、干渉除去部１４によりパス検出や相関処理等を行い、変復調部１５ではパス検出や相関処理等を行わずにデータの判定処理等を行う構成に切替える。
【００９７】
ここで、以上では、好ましい態様として、本発明に係る受信装置をＣＤＭＡ基地局に適用した場合の構成例を示したが、本発明に係る受信装置の構成としては、必ずしも上記実施例で示したものに限られることはなく、種々な構成が用いられてもよい。
例えば通信対象とするユーザ信号の数としては複数であれば特に限定はなく、また、干渉除去手段やタイミング検出手段や受信処理手段の構成としても種々なものが用いられてもよい。
【００９８】
具体的には、例えば干渉除去手段の構成として上記図５に示したような干渉除去処理を行う構成を用いることもでき、要は、干渉除去処理が施された信号に基づいてタイミング検出手段が各ユーザ信号のタイミングを検出し、当該タイミングの情報を干渉除去手段へフィードバックするような構成であれば、種々な構成が用いられてもよい。なお、上記実施例では干渉除去手段の段数（ステージ数、すなわち上記実施例では各ユーザ信号に対して備えられたレプリカ生成手段の段数）を２としたが、この段数としては特に限定はなく、例えば段数を多くするに従って干渉除去の精度を大きくする（すなわち、干渉除去の誤差を小さくする）ことができる。
【００９９】
また、本発明に係る受信装置により行われる干渉除去処理やタイミング検出処理や各ユーザ信号の受信処理としては、例えばプロセッサやメモリ等を備えたハードウエア資源においてプロセッサが制御プログラムを実行することにより当該処理を制御する構成とすることもでき、また、例えば当該処理を実行するための各機能手段を独立したハードウエア回路として構成することもできる。
また、本発明に係る受信装置の適用分野としては特に限定はなく、例えば上記したＣＤＭＡ基地局ばかりでなく、ＣＤＭＡ方式を用いて移動通信を行う移動局等といったものに本発明を適用することもできる。
【０１００】
【発明の効果】
以上説明したように、本発明に係る受信装置によると、ＣＤＭＡ方式により受信した複数のユーザ信号から各ユーザ信号を分離受信するに際して、干渉除去手段が受信信号から各ユーザ信号を逆拡散により抽出するとともに抽出した各ユーザ信号を再び拡散し、再拡散した他のユーザ信号を減算することにより前記受信信号中の各ユーザ信号を検出することをタイミング情報に基づいて行う場合に、このようにして検出した各ユーザ信号に基づいて当該信号のタイミングを検出するとともに当該タイミングの情報を干渉除去手段へフィードバックするようにしたため、当該タイミング情報の検出精度を向上させることができ、これにより、例えば干渉除去手段から出力されて受信処理される各ユーザ信号の品質を向上させることができる。
【０１０１】
また、本発明に係る受信装置では、上記した干渉除去手段が受信信号から逆拡散により抽出した各ユーザ信号を受信処理手段へ出力する構成としたため、当該信号伝送をシンボルレートで行うことにより、例えば上記実施例で示したように信号伝送の効率化を図ることができる。
【０１０２】
また、本発明に係る受信装置では、例えば当該受信装置をＣＤＭＡ基地局として構成する場合に、干渉除去手段等を着脱自在な構成とし、受信処理手段により受信処理可能な信号が逆拡散信号であるか拡散信号であるかに応じて干渉除去手段から当該受信処理手段へ出力するユーザ信号をそれぞれの信号に切替えることができるようにしたため、例えば既存のＣＤＭＡ基地局の受信処理部に干渉除去手段等を追加的に装着する場合等における干渉除去手段等の汎用性を優れたものとすることができる。
【０１０３】
また、本発明に係る受信装置では、例えば当該受信装置をＣＤＭＡ基地局として構成し、干渉除去手段等を着脱自在な構成とするとともに当該干渉除去手段が受信信号から逆拡散により抽出した各ユーザ信号を受信処理手段へ出力する構成とした場合に、受信処理手段では干渉除去手段が装着されている場合には当該干渉除去手段から入力される逆拡散信号の受信処理に切替える一方、干渉除去手段が離脱されている場合にはＣＤＭＡ方式により受信した複数のユーザ信号の受信処理に切替えることができるようにしたため、例えばＣＤＭＡ基地局の受信処理部に干渉除去手段等を着脱する場合における干渉除去手段等の汎用性を優れたものとすることができる。
【図面の簡単な説明】
【図１】本発明に係る受信装置をＣＤＭＡ基地局として構成した場合の一構成例を示す図である。
【図２】パスタイミングの検出処理の一例を説明するための図である。
【図３】パスタイミング情報の伝送の仕方の一例を説明するための図である。
【図４】干渉除去部を装着した場合と離脱した場合とにおけるＣＤＭＡ基地局の状態例を示す図である。
【図５】従来例に係る干渉キャンセラの構成を示す図である。
【図６】従来例に係るパスタイミング情報の伝送の仕方を説明するための図である。
【符号の説明】
１、１１・・受信部（ＲＸ）、 ２、４・・遅延手段、 ３、５・・減算器、
Ｐ１〜Ｐｎ、Ｑ１〜Ｑｎ・・レプリカ生成手段、 Ｍ１〜Ｍｎ・・加算器、
Ｄ１〜Ｄｎ・・パス検出部、 ＳＷ１〜ＳＷｎ・・スイッチ、
Ｓ１〜Ｓｎ・・信号処理部、 Ｉ１〜Ｉｎ・・判定部、
１３、１５・・変復調部（ＭＤＥ）、 １４・・干渉除去部、[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a receiving apparatus that separates and receives each user signal from a plurality of user signals received by the CDMA method, and in particular, when detecting each user signal by removing other user signals from the received plurality of user signals. The present invention relates to a receiving apparatus that improves the reception characteristics of each user signal by improving the detection accuracy of the timing of each user signal used for the detection.
[0002]
[Prior art]
For example, in a base station (CDMA base station) of a mobile communication system that performs radio communication using a DS-CDMA (Direct Sequence-Code Division Multiple Access) system, each user is received from a plurality of received user signals. It has been studied to provide an interference canceller that removes other user signals, which are interference components, from a received signal in which a plurality of user signals are mixed when receiving signals separately.
[0003]
As a specific example, “Sequential channel estimation type serial canceller using pilot symbols in DS-CDMA” (Sawahashi, Miki, Ando, Higuchi, IEICE Technical Report, RCS95-50 (1995-07)) and “Multistage "Examination of capacity increase effect by type DS-CDMA interference canceller" (Suzuki, Takeuchi, 1997 IEICE General Conference B-5-46) describes a configuration example of the interference canceller as described above.
[0004]
FIG. 5 shows a configuration example of an interference canceller described in the above-mentioned “Sequential channel estimation type serial canceller using pilot symbols in DS-CDMA” as an example of the interference canceller of such a CDMA base station.
In this interference canceller, first, each matched filter (MF) F1 to Fk acquires a correlation between a spread code in the received signal and a preset spread code for each user signal. Here, different spreading codes are assigned to each user signal, and matched filters F1 to Fk are provided in the same number (k) as the number of user signals to be communicated, for example.
[0005]
Next, the level detectors L1 to Lk connected to the matched filters F1 to Fk average the outputs from the matched filters F1 to Fk, detect paths (received incoming waves) existing in the transmission path, and Detect average power. Next, based on the power level (power level) detected by each of the level detectors L1 to Lk, the user ranking generation unit 21 performs interference cancellation units (ICU: VCUs) V1 to Vk that constitute a subsequent serial canceller. For example, the order of user signals for executing serial cancellation is determined in descending order of power level.
[0006]
Then, in the interference canceller, according to the order determined as described above, interference cancellation processing is executed by the subsequent serial canceller as follows.
That is, first, in the first stage of the serial canceller, for example, the user signal # 1 is estimated and detected from the received signal by the interference cancellation unit V1.
Here, the process performed by the interference removal unit V1 will be described in more detail. Note that substantially the same processing is performed in other interference removal units V2 to Vk and W1 to Wk described later.
[0007]
In the interference cancellation unit V1, first, the correlation detection unit 24 provided for each path existing in the transmission path despreads the user signal # 1 from the received signal, and the transmission path estimation unit 26 transmits the transmission path of the user signal # 1. The complex multiplier 25 compensates for the phase rotation of the despread user signal # 1 according to the information from the transmission path estimation unit 26. When the user signal # 1 is synchronously detected in this way, the RAKE receiving unit 27 then combines the signals of the respective paths obtained for the user signal # 1, and the determining unit 28 receives the RAKE-received user signal. It is determined whether the data of # 1 is, for example, a “1” value or a “0” value, and the inverse modulation unit 29 decomposes the determined data into path signals again by the weighting received by the RAKE.
[0008]
Next, in the re-spreading unit 30 provided for each path, the complex multiplier 31 corrects the phase signal, which is decomposed by the inverse modulation unit 29 according to the information from the transmission path estimation unit 26, corrected by the complex multiplier 25. The rotation is given again, and the respreading block 32 respreads (respreads) each path signal using the spreading code of the user signal # 1 and outputs it. This respreading is performed based on the timing information of each path, and this path timing is detected based on the received signal. Then, the adder 33 adds the respread signals of each path output from the respreading block 32 of each respreading unit 30, and outputs the added signal to a subtractor Y2 or the like to be described later.
[0009]
When the user signal # 1 is estimated and detected by the interference cancellation unit V1 as described above, in the first stage of the serial canceller, next, the subtractor Y2 subtracts the user signal # 1 estimated and detected from the received signal, The interference cancellation unit V2 estimates and detects, for example, the user signal # 2 from the subtraction signal. The delay means X2 provided in the previous stage of the subtractor Y2 is means for adjusting the signal processing timing by absorbing the delay time of the signal processing generated in other processing units (interference canceling unit V1 etc.). The same applies to the other delay means X2 to Xk, 22, 23 shown in FIG.
[0010]
Next, in the first stage of the serial canceller, as in the case of the estimation detection of the user signal # 2 described above, the subsequent estimation detection of the user signal #m (m = 3 to k) is already estimated from the received signal. The detected user signal # 1 to user signal # (m−1) are subtracted by the subtractor Ym, and the user signal #m is estimated and detected by the interference removal unit Vm based on the subtracted signal.
[0011]
Also in the second stage of the serial canceller, as in the case of the first stage described above, for example, a user other than the user signal # 1 whose subtractor Z1 has been estimated and detected in the first stage from the received signal, for example. Subsequent estimation detection of the user signal #m (m = 2 to k), for example, such that the signal is subtracted and the interference cancellation unit W1 estimates and detects the user signal # 1 from the subtraction signal, the received signal Is subtracted by the subtracter Zm, and the user signal #m is estimated and detected by the interference removal unit Wm based on the subtracted signal.
[0012]
As described above, the interference canceller of the CDMA base station shown in FIG. 5 can detect each user signal by removing another estimated user signal, that is, the interference signal, from the received signal. As a result, the SIR (signal power to interference power ratio) of the received signal can be improved and the reception characteristics can be improved. In addition, each of the interference cancellation units V1 to Vk and W1 to Wk of the interference canceller is configured to re-spread after each RAKE received user signal is determined by the determination unit 28. It has been reported that the accuracy of can be improved.
[0013]
Further, for example, in the interference canceller shown in FIG. 5 described above, it is considered to serially transmit path timing information detected for each user signal with a separate bit line for each user signal. Specifically, for example, in a CDMA base station where the number of user signals to be communicated is 300, 300 bus lines are provided, and the path timing information of each user signal is transmitted to each interference line V1 via each bus line. Transmit to ~ Vk etc. FIG. 6 shows an example of path timing information for transmitting one bus line. In this example, a time width corresponding to one symbol (spread code) (between “symbol timings” in the figure) is shown. Timing information (“τ1”, “τ2”, “τ3”) corresponding to the three paths is transmitted.
[0014]
Further, for example, in the interference canceller shown in FIG. 5 described above, signal output from each of the interference cancellation units V1 to Vk, W1 to W (k−1) to the subtractors Y2 to Yk and Z1 to Zk, In the signal transmission from the first-stage interference cancellation units V1 to Vk to the second-stage interference cancellation units W1 to Wk corresponding to the same user signal, for example, the respread signal may be transmitted at the sampling rate. It has been studied.
[0015]
[Problems to be solved by the invention]
However, in the interference canceller of the conventional CDMA base station as shown in FIG. 5, for example, the path timing of each user signal described above is detected based on a poor quality signal in which a plurality of user signals are mixed as described above. Because of this configuration, for example, errors (path misdetection) are likely to occur in the detection, and such a path misdetection may cause a malfunction of the interference canceller or deterioration of RAKE reception, which is a feature of CDMA reception. It was.
[0016]
Specifically, since a large number of user signals are generally received at an arbitrary phase and different reception levels in a CDMA base station, for example, in the first stage of an interference canceller, due to interference of user signals other than user signals that are subject to path detection. Although the noise level is large and the reception quality of the user signal subject to path detection is poor, the path detection based on such a poor quality signal has been conventionally performed. Path detection cannot be performed, and reception characteristics of each user signal are deteriorated.
[0017]
In addition, for the above-described interference canceller of the CDMA base station, for example, the construction of its algorithm has been studied with priority, but the configuration for realizing it by hardware or the like has not yet been studied so much. In particular, much consideration has not been given to the signal transmission rate and the like. Therefore, there has been a demand for an invention that can be more effective in actually constructing such an interference canceller.
[0018]
The present invention has been made to solve such a conventional problem, and improves the timing detection accuracy of each user signal when separately receiving each user signal from a plurality of user signals received by the CDMA system. Accordingly, an object of the present invention is to provide a receiving apparatus capable of improving the reception characteristics of each user signal.
It is another object of the present invention to provide a receiver that can improve the efficiency of signal transmission in terms of signal transmission rate.
It is another object of the present invention to provide a receiving apparatus capable of providing a practically useful effect when configuring a CDMA base station having the above-described interference cancellation function as the receiving apparatus.
[0019]
[Means for Solving the Problems]
In order to achieve the above object, in the receiving apparatus according to the present invention, when each user signal is separated and received from a plurality of user signals received by the CDMA system, the interference removing means extracts each user signal from the received signal by despreading. When the user signals in the received signal are detected based on the timing information by re-spreading the user signals extracted together and subtracting the other user signals that have been re-spread based on the timing information, the timing detection means Based on each user signal detected by the removing means, the timing of the signal is detected and information on the timing is fed back to the interference removing means, and the reception processing means receives each user signal output from the interference removing means.
[0020]
Therefore, since the timing detection means detects the timing of each user signal based on the signal from which other user signals (ie, interference signals) have been removed by the interference removal means, the quality is higher than in the conventional case. The timing can be detected based on a good signal, thereby improving the accuracy of the timing detection. In addition, since this timing information is fed back to the interference removing means, the interference removing means can improve the accuracy of interference removal (that is, detection of each user signal), for example, thereby improving the reception characteristics of each user signal. Can be improved.
[0021]
Note that the timing information fed back from the timing detection unit to the interference removal unit is used, for example, when the interference removal unit re-spreads each user signal once extracted from the received signal by despreading to the original signal position. In the present invention, since the accuracy of this re-diffusion can be improved, the accuracy of interference removal can be improved.
The timing information described above can also be used as the extraction timing of each user signal when the interference removing unit extracts each user signal from the received signal by despreading. In this case, the extraction of each user signal is performed. Can be performed accurately and the extraction can be performed efficiently.
[0022]
In the receiving apparatus according to the present invention, the interference canceling means outputs each user signal extracted from the received signal by despreading to the receiving processing means, and the receiving processing means receives and processes the despread signal.
In this way, by transmitting each user signal as a despread signal from the interference removal means to the reception processing means, the signal transmission can be performed at the symbol rate, thereby improving the efficiency of signal transmission. .
[0023]
Further, in the receiving apparatus according to the present invention, for example, the receiving apparatus is a CDMA base station, and the above-described interference removing means and timing detecting means are detachable, and the interference removing means is received by the above-described receiving processing means. According to whether the signal that can be processed is a despread signal or a spread signal, there is provided switching means for switching the user signal output to the reception processing means to each signal.
[0024]
As described above, the signal output from the interference removing unit can be switched between the despread signal and the spread signal in accordance with the reception processing function of the reception processing unit connected to the interference removing unit. The versatility of the interference removal means and the timing detection means can be expanded. Specifically, as shown in the embodiments of the present invention to be described later, the reception processing means has a function of receiving a despread signal and a function of receiving a spread signal. May be put into practical use, and the present invention corresponds to this.
[0025]
In the receiving apparatus according to the present invention, for example, the receiving apparatus is a CDMA base station, and the above-described interference canceling means and timing detecting means are detachable, and the interference canceling means is extracted from the received signal by despreading. Each user signal is output to the reception processing means described above, the reception processing means is switched to the reception processing of the despread signal input from the interference removal means when the interference removal means is mounted, When the above-described interference canceling unit is disconnected, the switching unit switches to reception processing of a plurality of user signals received by the CDMA system.
[0026]
Thus, when each user signal is output as a despread signal from the detachable interference canceling means, each user signal received by the reception processing means is despread (that is, a signal input from the interference canceling means). ) And spread signals (that is, a plurality of user signals received by the above-described CDMA system), the versatility of the reception processing means can be expanded. Specifically, as shown in an embodiment of the present invention to be described later, in the CDMA base station, when the number of user signals to be communicated is small, the interference removal unit is removed and the interference removal process is omitted. In some cases, this is more efficient, and the present invention addresses this.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment according to the present invention will be described with reference to the drawings.
FIG. 1 shows an example of a receiving apparatus according to the present invention. Here, in this example, the case where the receiving apparatus according to the present invention is configured as a CDMA base station is shown. In this CDMA base station, each user signal is separately received from a plurality of user signals received by the CDMA system. I do.
[0028]
The CDMA base station shown in FIG. 1 includes a receiving unit (RX) 1 for down-converting a received signal, two delay means 2 and 4 for delaying the signal, and a respread signal (replica signal) of each user signal. A plurality of replica generation units (RGU) P1 to Pn and Q1 to Qn, two subtractors 3 and 5 for subtracting signals, and a plurality of adders M1 to Mn for adding signals , A plurality of path detection units D1 to Dn for detecting the path timing of each user signal, a plurality of switches SW1 to SWn, a plurality of signal processing units S1 to Sn for processing each user signal, and data of each user signal Are provided with a plurality of determination units I1 to In.
[0029]
Here, the replica generation means P1 to Pn and Q1 to Qn described above are provided for each user signal to be communicated by the CDMA base station of this example. In this example, the user to be communicated is provided. Assuming that the number of signals is n, n replica generation means P1 to Pn are provided in the first stage corresponding to each user signal, and n replica generation means Q1 to Qn are provided for each user signal. Correspondingly, a second stage is provided.
Similarly, the adders M1 to Mn, the path detection units D1 to Dn, the signal processing units S1 to Sn, and the determination units I1 to In are also provided for each user signal.
[0030]
The CDMA base station of this example is roughly classified as shown in FIG. 1 above. The receiving unit 1, an interference removing unit that removes an interference signal from the received signal, and each user signal are determined. In this example, each of these processing units is shown as an integral configuration, and the interference removal unit is also detachable. It will be described later.
[0031]
For example, the receiving unit 1 has a function of down-converting a received radio frequency (RF) signal from a signal in the carrier frequency band to a baseband signal. Here, in general, in wireless communication using the CDMA system, a plurality of user signals are communicated while sharing a frequency band and time. Therefore, for example, a plurality of user signals are mixed in the received signal described above. A plurality of signals modulated using a code are included.
[0032]
The delay means 2 has a function of delaying and outputting the input signal in accordance with the operation time of the signal processing by the first-stage replica generation means P1 to Pn. It has a function of delaying and outputting an input signal in accordance with the operation time of signal processing by the eye replica generation means Q1 to Qn, and the timing of signal processing is adjusted by these delay means 2 and 4.
[0033]
As an example, each of the replica generation means P1 to Pn in the first stage has the same configuration and function as the interference cancellation unit V1 shown in FIG. 5 and a function of outputting each user signal as a despread signal. ing. Specifically, for example, as in the case of the interference cancellation unit V1, each replica generation means P1 to Pn in the first stage first inputs a received signal and sets each of the spread codes in the received signal as set. By acquiring the correlation with the spreading code for each user signal, each user signal is despread for each path existing in the transmission path, and the phase of each user signal is estimated by estimating the transmission path of each despread user signal. Synchronous detection is performed by compensating for. Next, each of the replica generation means P1 to Pn performs RAKE reception by synthesizing the signals of the paths compensated for phase rotation, and determines the data of each user signal received by RAKE.
[0034]
Then, each replica generation means P1 to Pn decomposes the determined data again into each path signal by the weighting received by the RAKE, gives the original phase rotation to each decomposed path signal, and uses the spreading code of each user signal. Each path signal is respread and a respread signal (replica signal) is output. Here, this re-spreading is performed based on timing information (path timing information) of each path, which will be described later, and this path timing information will be described later.
Moreover, each replica production | generation means P1-Pn of this example also outputs each user signal (de-spread signal) extracted from the received signal by de-spreading.
[0035]
Each of the second-stage replica generation means Q1 to Qn has, for example, substantially the same configuration and function as each of the first-stage replica generation means P1 to Pn, but each of the second-stage replica generation means Q1 to Qn. Then, a signal output from a subtracter 3 to be described later is input and processed, and a transmission path is estimated using each user signal extracted by despreading by each replica generation means P1 to Pn in the first stage. Etc. are different from the first stage. Details of these processes will be described later.
[0036]
The subtractor 3 inputs the reception signal output from the delay unit 2 and also receives the replica signal output from each replica generation unit P1 to Pn in the first stage, and subtracts each replica signal from the input reception signal. The function of outputting the subtraction result.
Similarly, the subtracter 5 has a function of subtracting the replica signal input from the replica generation means Q1 to Qn in the second stage from the signal input from the delay means 4 and outputting the subtraction result.
Each of the adders M1 to Mn has a function of adding a plurality of input signals and outputting the addition result to path detection units D1 to Dn and signal processing units S1 to Sn described later.
[0037]
In this example, each of the delay means 2 and 4 and the replica generation means P1 to Pn, Q1 to Qn, the subtractors 3 and 5 and the adders M1 to Mn perform the above processing in synchronization, so Based on the timing information, the user signal is extracted by despreading and each user signal extracted is re-spread and another user signal that has been re-spread is subtracted to detect each user signal in the received signal. Interference canceling means is configured.
[0038]
Each path detection unit D1 to Dn has a function of detecting a delay profile in the transmission path of each user signal based on the signal input from each adder M1 to Mn. The signal path timing is detected, and the detected path timing information is output to, for example, replica generation means P1 to Pn, Q1 to Qn corresponding to each user signal.
In this example, the above-described path detection units D1 to Dn detect the timing of the signal based on each user signal detected by the interference removal unit and feed back the timing information to the interference removal unit. Is configured.
[0039]
Each signal processing unit S1 to Sn has a function of processing each user signal output from the interference removal unit described above, for example, and in this example, as a configuration mode of each signal processing unit S1 to Sn, When a function such as a correlator for inputting a spread signal such as a received signal and extracting each user signal from the signal by a correlation operation, and for each user signal despread from the received signal The above diagram collectively shows a case where a data transfer function for inputting and transmitting the signal as it is to the determination units I1 to In, which will be described later, and a case where a function capable of switching both of these functions is provided. 1. Details of these will be described later.
[0040]
Each determination unit I1 to In has a function of determining data from each user signal (despread signal) input from each signal processing unit S1 to Sn, and the data of each determined user signal to, for example, a network Send output. As in this example, for example, the despread signals (each user signal) after the synchronous detection processing and the RAKE reception processing are already performed in each replica generation means Q1 to Qn in the second stage are sent to the respective determination units I1 to In. When the input configuration is used, each of the determination units I1 to In does not have to have a function of performing the synchronous detection process or the RAKE reception process. However, the despread signal before each synchronous detection process (each user signal) Is used for each determination unit I1 to In, each determination unit I1 to In has a function of performing a synchronous detection process and a RAKE reception process.
[0041]
In this example, the reception processing means for receiving and processing each user signal output from the interference removing means by the function of performing reception processing of each user signal using the signal processing sections S1 to Sn and the determination sections I1 to In described above. Is configured.
[0042]
Next, a specific example of the procedure of processing performed by the interference removing unit shown in FIG.
That is, first, the reception signal down-converted to the baseband by the receiving unit 1 is input to the delay unit 2 and the replica generation units P1 to Pn at the first stage. In each first-stage replica generation means P1 to Pn, each user signal is extracted from the input received signal by despreading, and each extracted user signal is extracted to the second-stage replica generation means Q1 corresponding to the user signal. .. To Qn, and the replica signal generated by re-spreading each extracted user signal is output to the subtractor 3 or the like.
[0043]
Next, the subtracter 3 subtracts the n replica signals input from the replica generation means P1 to Pn at the first stage from the reception signal input via the delay means 2, and the subtraction result is the first subtraction result. One residual signal is output to the delay means 4 and the replica generation means Q1 to Qn in the second stage.
[0044]
Next, each replica generation means Q1 to Qn in the second stage extracts each user signal from the input first residual signal by despreading, and extracts each extracted user signal to each signal processing unit S1 to Sn. The replica signal generated by re-spreading the extracted user signals is output to the subtracter 5 and the adders M1 to Mn. Here, as described above, the replica generation means Q1 to Qn at the second stage perform, for example, estimation of the transmission path using the despread signals input from the replica generation means P1 to Pn at the first stage.
[0045]
Specifically, for example, the first residual signal input to each replica generation means Q1 to Qn at the second stage is obtained by receiving each user signal (replica signal) estimated and detected at the first stage from the received signal as described above. Since the subtraction is performed, the components of other user signals (interference signals) are removed from the received signal, but the components of the user signals to be estimated and detected by the replica generation means Q1 to Qn are also removed. I'm stuck. For this reason, if each of the replica generation means Q1 to Qn in the second stage performs the synchronous detection process and the determination process using the input first residual signal as it is, a transmission path estimation error and a determination error are likely to occur. In many cases.
[0046]
Therefore, in each replica generation means Q1 to Qn in the second stage of this example, for example, after despreading the input first residual signal, the despread signal and the despread signal input from the first stage are used. Addition is performed, and subsequent transmission path estimation processing and determination processing are performed on the addition result. With such addition processing, each replica generation means Q1 to Qn in the second stage performs transmission path estimation processing by increasing only the component of the user signal to be estimated and detected while keeping the interference signal component low. It can be carried out.
[0047]
In each replica generation means Q1 to Qn in the second stage, the inverse spread signal obtained by increasing only the despread signal obtained by the addition as described above, that is, the component of the user signal corresponding to the replica generation means Q1 to Qn. The spread signal is output to each signal processing unit S1 to Sn. In each replica generation means Q1 to Qn at the second stage, for example, from the despread signals obtained by adding the despread signals input from the first stage before performing the respreading process as described above. By subtracting, the replica signal generated by re-spreading only the component of each user signal extracted from the first residual signal is output to the subtractor 5.
[0048]
Next, the subtracter 5 subtracts n replica signals input from the replica generation means Q1 to Qn in the second stage from the first residual signal input via the delay means 4, and uses the subtraction result as a result. A second residual signal is output to each adder M1 to Mn.
The adders M1 to Mn include, for example, the above-described second residual signal of the chip rate and replica signals of the user signals output from the first and second stage replica generation means P1 to Pn and Q1 to Qn. And the adders M1 to Mn add these input signals, and add the respective user signals (spread signals) as the addition results to the path detection units D1 to Dn and the signal processing units S1 to Sn. Output.
[0049]
Here, specific examples of signals obtained by the above-described processes will be shown using mathematical expressions.
For example, the received signal r (t) is expressed by Equation 1. Here, assuming that j = 1 to n, Aj (t) in Equation 1 indicates transmission path fluctuation of user signal #j, Dj (t) indicates transmission data of user signal #j, and Cj (t) is The spreading code of the user signal #j is shown, and N (t) shows a thermal noise component. Each signal is represented by a complex number, and * in Equation 1 indicates a complex multiplication parameter. Further, in this example, a case where a signal is received by a plurality of paths (multipath) is shown, and Σ in Equation 1 represents addition for all paths.
[0050]
[Expression 1]

[0051]
In this case, the sum r ′ (t) of replica signals generated by the replica generation means P1 to Pn at the first stage is expressed by Expression 2. Here, Xj in Equation 2 is determined based on, for example, a replica generation error of user signal #j caused by noise, interference, or the like. Normally, Xj is a value less than 1.
[0052]
[Expression 2]

[0053]
Further, the first residual signal {r (t) −r ′ (t)} output from the subtractor 3 is expressed by Equation 3.
[0054]
[Equation 3]

[0055]
As shown in the above equation 3, if each replica signal of each user signal is ideally generated by each replica generating means P1 to Pn in the first stage, each Xj = 1. The first residual signal output from is {r (t) −r ′ (t)} = N (t) and only the components such as noise are present. However, since the replica signal normally generated by each of the replica generation means P1 to Pn includes some errors, in this example, the replica generation means Q1 to Q1 that perform the same process as the first stage at the second stage. By providing Qn and making it multi-stage, it is configured to reduce the replica generation error as a whole.
[0056]
As described above, the replica generation means Q1 to Qn and the subtractor 5 in the second stage perform substantially the same processing as in the first stage, and the adders M1 to Mn each input the second residual signal and each The replica signal of the user signal is added and output. Here, for example, the addition signal B1 (t) output from the adder M1 corresponding to the user signal # 1 is expressed by Expression 4. The addition signals output from the other adders M2 to Mn are the same except that the respective adders M1 to Mn correspond to the respective user signals # 1 to #n. .
[0057]
[Expression 4]

[0058]
Here, r ″ (t) in the above equation 4 indicates the sum of replica signals generated by the replica generators Q1 to Qn at the second stage, and Yj is the replica generator at the first stage. The coefficient concerning the addition result of the replica signal of each user signal #j generated by P1 to Pn and the replica signal of each user signal #j generated by the second-stage replica generation means Q1 to Qn is shown.
[0059]
As shown in the above equation 4, in the addition signal (spread signal) output from each adder M1 to Mn, the user signal corresponding to each adder M1 to Mn is the same as the user signal in the received signal. While the signal strength is large (ideally the same as when receiving), other user signals (interference signals) are removed and become smaller according to the value of the term (1-Yj) described above. . Normally, this (1-Yj) term is a fairly small value, but does not reach zero.
[0060]
As described above, each user signal output as a spread signal from each adder M1 to Mn is input to each path detection unit D1 to Dn, and each path detection unit D1 to Dn is based on each input user signal. The path timing of the signal is detected.
Here, a specific example of the path detection process performed by each of the path detection units D1 to Dn is shown.
That is, in each path detection unit D1 to Dn, for example, when despreading the spread signal input from each adder M1 to Mn, the correlation between the two is shifted while shifting the timing of multiplying the spread signal by the spread code of each user signal. The value is calculated, and the peak position of the calculated correlation value is detected as the arrival time position (path timing) of each user signal.
[0061]
FIG. 2 shows an example of a despread signal obtained when each of the path detection units D1 to Dn despreads the input signal, the horizontal axis indicates time, and the vertical axis indicates the signal level. In the example shown in the figure, for example, correlation peaks by three paths (“path 0”, “path 1”, “path 2”) are obtained in a time width of one symbol, and the paths of these three correlation peaks are obtained. The timings are detected as “τ1”, “τ2”, and “τ3”, respectively.
[0062]
In performing this kind of path detection, in this example, the signal after other user signals (interference signals) are removed from the received signal as described above is input to the path detection units D1 to Dn, and the path detection unit Since D1 to Dn are configured to detect the path timing of each user signal based on a signal that is hardly affected by other user signals, for example, the probability of erroneous path detection is greatly reduced as compared with the conventional case. Thus, for example, even when the number of other user signals that become interference signals is large, stable path detection can be performed, and the accuracy of path timing detection can be greatly improved. .
[0063]
Further, information on the path timing of each user signal detected by each path detection unit D1 to Dn is fed back to the replica generation means P1 to Pn and Q1 to Qn corresponding to each user signal, and each replica generation means P1 to Pn, Referenced and used in the processing in Q1 to Qn.
As a specific example, each of the replica generation means P1 to Pn and Q1 to Qn refers to the fed back path timing information when re-spreading the user signal for each path, that is, indicated by this path timing information. Each re-spread path signal is assigned to a time position.
[0064]
By such assignment, the time position of each re-spread path signal and the time position of each path signal in the signal output to the subtracters 3 and 5 via the delay means 2 and 4 are matched. Adjusted. In this example, since the detection accuracy of the path timing in each of the path detection units D1 to Dn is improved as described above, the accuracy of re-diffusion in each of the replica generation units P1 to Pn and Q1 to Qn is also improved. Thus, the accuracy of interference removal can be improved, and for example, the accuracy of the process in which each replica generation means Q1 to Qn in the second stage extracts each user signal from the input signal by despreading can be improved.
[0065]
As another specific example, the replica generation means P1 to Pn and Q1 to Qn can also refer to and use the fed back path timing information in a despreading process (correlation process) or the like. That is, in each of the replica generation means P1 to Pn and Q1 to Qn, for example, when each user signal is extracted from the input signal by despreading (correlation processing), the timing for generating a spreading code for multiplication with the input signal is fed back. By performing processing such as matching the time position indicated by the path timing information, it is possible to improve the accuracy of the extraction processing of each user signal by despreading and to make the processing more efficient. Note that the generation of the spread code is performed by, for example, a spread code generator built in each of the replica generation means P1 to Pn and Q1 to Qn.
[0066]
Further, in the configuration of this example, for example, immediately after the power is supplied to the interference removal unit or immediately after a new user signal is added as a communication target, the path detection units D1 to Dn do not perform interference removal, for example. In some cases, the path timing of each user signal is detected based on the signal. In this case, the path timing of each user signal can be detected with a certain degree of accuracy. After the timing information is obtained, interference removal processing (replica signal generation processing or the like) by the interference removal unit is started.
[0067]
As described above, the detection accuracy of the path timing is somewhat effective in practice at first, but in this example, the received signal is received based on the information of the path timing by the interference removing unit. The interference signal (other user signals) is removed from the signal, the path timing of each user signal is detected based on the signal from which the interference signal has been removed, and the information of the detected path timing is used as each replica generation means P1 to Pn, Q1 to Qn As the series of processing such as feedback to the process is repeated, the accuracy of detecting the path timing and the accuracy of removing the interference can be greatly increased.
[0068]
In addition, in the interference removal part of this example, it uses for the process of the signal received later by feeding back the information of the path timing detected based on the signal received in the past. That is, for example, a change in the position of a mobile station that communicates each user signal) hardly occurs within the time required for feedback, that is, the path timing of each user signal does not substantially change in a short time required for feedback. Therefore, a sufficient feedback effect can be obtained.
[0069]
Also, a specific example of how to transmit timing information output from each of the path detection units D1 to Dn of this example will be shown.
In this example, by distributing the timing information of each user signal output from each path detection unit D1 to Dn to each replica generation means P1 to Pn, Q1 to Qn, etc. via a common bus line by time division, The bus lines for transmitting timing information will be greatly reduced, thereby reducing the size and cost of the device.
[0070]
FIG. 3 shows an example of path timing information for transmitting the above-described common bus line. In this example, for convenience of explanation, it is assumed that the number of user signals is 3, and each user signal (user signal # 1 (U1), user signal # 2 (U2), user signal # 3 (U3)) has one symbol. Time (4 slots) in which information of four paths can be transmitted is allocated to the time width. In the example of the figure, as shown in the figure, for user signal # 1, three paths (“τ1”, “τ2”, “τ3”) are detected in one symbol time width, and for user signal # 2, four paths are detected. Paths (“α1”, “α2”, “α3”, “α4”) are detected, and two paths (“β1”, “β2”) are detected for user signal # 3. When the number of paths detected in one symbol time width is less than 4 paths, as shown in the figure, a part of the slots for 4 paths prepared for each user signal is empty. (For example, no information).
[0071]
In this example, the path timing information is transmitted at, for example, a symbol rate using the common bus line as described above, so that the timing information is transmitted at a chip rate using a different bus line for each user signal, for example. Compared to the conventional case, the number of bus lines can be greatly reduced. As a specific example, for example, when the number of samples per symbol (spreading code) is 1024 points and the symbol rate is 64 kHz, 10 bits are required per user signal to transmit timing information of one path. In this example, in this case, for example, if transmission of 20.48 MHz is performed using a 10-bit bus line, the timing information for 320 paths (20.48 MHz / 64 kHz = 320) is shared. It can be transmitted by a bus line.
[0072]
Further, a specific example of how to transmit a despread signal (each user signal) output from each replica generation means Q1 to Qn in the second stage of this example to each signal processing unit S1 to Sn will be shown.
In this example, each replica generation means Q1 to Qn in the second stage outputs a correlation peak signal generated at, for example, a symbol rate as each user signal extracted by despreading. The signals are distributed to the signal processing units S1 to Sn via a common bus line by time division.
[0073]
In this example, each user signal is transmitted at a symbol rate (for example, 64 kHz) using the common bus line as described above, so that each user signal is sampled as a spread signal (spread signal), for example. Compared to the conventional case where transmission is performed using a large number of bus lines at a rate (for example, 16 MHz), the number of bus lines for transmitting symbol information of each user signal can be greatly reduced. As will be described later, even when the interference removal unit and the modulation / demodulation unit are configured to be detachable, the interface for connecting them can be simplified.
[0074]
As a specific example, for example, the number of bits per symbol (spreading code) is 10 bits (however, for example, a complex signal obtained by correlation calculation has a total of 20 bits because there are I and Q phases), and the symbol rate is In the case of 64 kHz, in this example, for example, if 20.48 MHz transmission is performed using a 20-bit bus line, timing information (20.48 MHz / 64 kHz = 320) for 320 user signals is shared. It can be transmitted by the bus line.
[0075]
In addition, when each user signal is transmitted at a sampling rate of 16 MHz, for example, using a different bus line for each user signal as in the prior art, the data at each sampling point is transmitted because a spread signal before correlation calculation is transmitted. If it is 4 bits, a bus line of 1280 bits (320 × 4 = 1280) is required to transmit 320 user signals. In general, since transmission (transfer) exceeding 40 MHz is difficult, even if time division is attempted in this conventional example, a bus line of about 640 bits is required (that is, transmission twice as high as 16 MHz). Only speed can be achieved). Moreover, although high-speed transmission is possible if an optical fiber is used, there is a problem that the cost becomes very high.
[0076]
As described above, in this example, each user signal extracted by despreading from the received signal by the interference removing unit (in this example, the replica generating units Q1 to Qn as described above) is received processing unit (as described above). In this example, it is output to the signal processing units S1 to Sn, etc., and the reception processing means receives the despread signal, thereby transmitting each user signal at the symbol rate as described above. It is possible to significantly reduce the bus line, thereby reducing the size and cost of the apparatus.
[0077]
Next, a configuration method of the modulation / demodulation unit shown in FIG. 1 and processing performed by the modulation / demodulation unit will be described.
Hereinafter, the processing operation and the like in each example will be described while showing some examples of the configuration of the modem unit.
In the CDMA base station of the present example shown in FIG. 1 above, a configuration in which an interference canceller and a modem are connected is shown. For example, there is an existing CDMA base station that does not include an interference canceler in the prior art, In such a CDMA base station, it is possible to reduce the hardware change, reduce the cost, etc. by adopting a configuration in which the interference canceling unit according to the present invention can be additionally connected to the existing modem unit. be able to.
[0078]
For example, in the configuration of the interference canceller (interference removal unit) proposed in the related art as shown in FIG. 5 above, until the interference removal unit and the modulation / demodulation unit are detachable as in this example. It was not examined. For this reason, when the configuration proposed in the past is applied to an existing CDMA base station, a new apparatus including an interference canceller and a modem unit must be prepared and replaced with the existing modem unit. In other words, there is a problem that the existing modulation / demodulation unit is wasted. In this example, the interference removal unit can be configured to be detachable, so that such a problem can be solved.
[0079]
Since the existing modulation / demodulation unit as described above is configured to receive and process a plurality of user signals (spread signals) received by the CDMA method, for example, each signal processing unit S1 to Sn receives each user signal from the received signal. A function of a correlator that extracts by spreading is provided, and each of the determination units I1 to In has a function of synchronously detecting each user signal extracted by despreading, receiving RAKE, and making a determination. Yes. Further, such an existing modulation / demodulation unit is provided with path detection means for detecting the path timing of each user signal, for example. In FIG. 1, for convenience of explanation, the path detection units D1 to Dn of the interference removal unit are shown to be included in the modulation / demodulation unit, but the same path is not necessarily used in the interference removal unit and the modulation / demodulation unit. This does not mean that the detection units D1 to Dn must be shared.
[0080]
In general, in a CDMA base station, for example, when the number of user signals to be communicated is small at the time of initial introduction of W-CDMA, for example, an interference canceller is not necessarily required. Can be demodulated. However, when the number of user signals to be communicated to by the CDMA base station increases, for example, when the capacity of the CDMA base station is almost full, the level of interference due to each user signal is ignored. Since it becomes so large as to be impossible, it is necessary to provide an interference removal unit together with the modem unit.
[0081]
For example, when the modem unit of a conventional CDMA base station is operated as a single unit without connecting an interference canceling unit, a received signal (chip rate or sampling rate) is supplied to the path detecting unit provided for each user signal in the modem unit. ) And a received signal is input to each of the signal processing units S1 to Sn having a correlator function. As a result, the modem unit extracts each user signal from the received signal by despreading, and performs RAKE reception processing, determination processing, and the like.
[0082]
Further, when the interference removal unit is connected to the above-described modulation / demodulation unit, for example, as shown in FIG. 1, the modulation / demodulation unit and the interference removal unit are connected, and each signal is sent from each adder M1 to Mn of the interference removal unit. Each processing unit S1 to Sn is caused to output each user signal as a spread signal. Accordingly, the modem unit extracts each user signal by despreading from the spread signal input to each signal processing unit S1 to Sn, and performs RAKE reception processing, determination processing, error correction processing, and the like. In this case, conceptually, the switches SW1 to SWn shown in FIG. 1 are switched to the upper side.
[0083]
In this case, for example, path detection is performed by each of the path detection units D1 to Dn of the interference removal unit. Therefore, it is not always necessary to operate the path detection unit provided in the modulation / demodulation unit. A configuration may be adopted in which path timing information of each user signal detected by the detection units D1 to Dn is output to a spread code generator in the correlator of each signal processing unit S1 to Sn. Further, for example, as shown in FIG. 3, the path detection units D1 to Dn, the replica generation units P1 to Pn, Q1 to Qn, and the signal processing units S1 to Sn are connected by a common bus line. In addition, transmission of path timing information from each of the path detection units D1 to Dn to each of the signal processing units S1 to Sn can be performed via a common bus line by time division.
[0084]
As described above, in the configuration of the interference removal unit of this example, the interference removal unit can be additionally connected to the modulation / demodulation unit of the existing CDMA base station, for example, so that the existing modulation / demodulation unit is wasted. Can be prevented. In the above description, the connection method with the interference removal unit has been described using the existing modulation / demodulation unit as an example. However, the signal processing units S1 to Sn are similarly provided with a function of a correlator, for example, even if not existing. The modulation / demodulation unit configured as described above can be connected to the interference removal unit of this example in the same manner as described above.
[0085]
As another configuration mode of the modulation / demodulation unit, for example, each signal processing unit S1 to Sn has a function of outputting each user signal input as a despread signal to each determination unit I1 to In as it is, and each determination It is also conceivable that the modulation / demodulation unit is configured in such a manner that the units I1 to In have a function of determining the data of each user signal. This configuration mode is adopted in consideration of, for example, being used mainly connected to an interference removal unit, and the modulation / demodulation unit does not necessarily have a function of performing correlation processing, synchronous detection processing, RAKE reception processing, and path detection processing. May not be provided.
[0086]
In this configuration mode, for example, as shown in FIG. 1, the modulation / demodulation unit and the interference removal unit are connected, and each replica generation means Q1 to Qn in the second stage of the interference removal unit transmits each of the signal processing units S1 to Sn. The user signal is output as a despread signal (for example, a correlation peak signal). Thus, the modem unit transmits each user signal input to each signal processing unit S1 to Sn to each determination unit I1 to In, determines data of each user signal, and performs error correction processing or the like. In this case, conceptually, the switches SW1 to SWn shown in FIG. 1 are switched to the lower side.
[0087]
As described above, in this example, for example, the interference removal unit including the interference removal unit (in this example, replica generation units Q1 to Qn) and the timing detection unit (in this example, path detection units D1 to Dn) is detachable. Depending on whether a signal that can be received and processed by a reception processing unit (in this example, signal processing units S1 to Sn, etc.) to which the interference cancellation unit is connected is a despread signal or a spread signal. Switching means for switching the user signal output to the reception processing means to each signal.
[0088]
Therefore, in this example, the versatility of the interference canceling unit can be given to the modulation / demodulation unit configured in various manners in the CDMA base station, for example, so that the interference canceling unit is additionally provided in the CDMA base station. The cost can be greatly reduced. Note that there is no particular limitation on the configuration of the switching unit that switches the user signal output from the interference removal unit between the spread signal and the despread signal. For example, a switch or the like can be used as in this example.
[0089]
Further, as another configuration mode of the modem unit, in this example, the signal processing method is switched between when the interference removing unit is connected (attached) and when the interference removing unit is not connected (detached). The modulation / demodulation unit is configured in such a manner as to be possible. Note that the modulation / demodulation unit of this configuration mode is particularly effective when, for example, a configuration in which each user signal is output as a despread signal but not as a spread signal from the interference removal unit is used.
[0090]
Specifically, in the modulation / demodulation unit of this configuration mode, for example, when the interference removal unit is disconnected, a plurality of user signals (reception signals) received by the CDMA system are correlated by the signal processing units S1 to Sn. Then, each determination unit I1 to In switches to reception processing for performing synchronous detection processing, RAKE reception processing, determination processing, error correction processing, and the like. In this case, conceptually, a reception signal from the reception unit 1 is input to each of the switches SW1 to SWn illustrated in FIG. 1 and the reception signal is input to each of the signal processing units S1 to Sn. It will be in a state to be. In this case, for example, the path detection unit provided in the modem unit detects the path timing of each user signal, and the information on the path timing is generated in the correlator of each of the signal processing units S1 to Sn. Output to the instrument.
[0091]
Further, in the modulation / demodulation unit of this configuration mode, for example, when an interference removal unit is mounted, each user signal input as a despread signal from each replica generation means Q1 to Qn in the second stage of the interference removal unit Is transmitted to each determination unit I1 to In by each signal processing unit S1 to Sn, and the determination unit I1 to In switches to reception processing for performing data determination processing, error correction processing, and the like of each user signal. In this case, conceptually, the switches SW1 to SWn shown in FIG. 1 are switched to the lower side. Further, for example, the path detection unit provided in the modem unit is switched so as not to operate.
[0092]
As described above, in this configuration aspect, for example, the interference removal unit including the interference removal unit (in this example, replica generation units Q1 to Qn) and the timing detection unit (in this example, path detection units D1 to Dn) is detachable. When a configuration is used in which each user signal extracted by despreading from the received signal by the interference canceling unit is output to the receiving processing unit (in this example, the signal processing units S1 to Sn, etc.), The reception processing means switches to reception processing of a despread signal input from the interference removal means when the interference removal means is attached, while a plurality of signals received by the CDMA method when the interference removal means is detached. Switching means for switching to the user signal reception process.
[0093]
Therefore, for example, the versatility of the modulation / demodulation unit can be provided depending on whether or not the interference cancellation processing is performed in the CDMA base station, thereby greatly increasing the cost when the interference cancellation unit is additionally provided in the CDMA base station. Reduction can be realized.
The configuration of the switching means for switching the signal to be received and processed by the modem unit is not particularly limited. For example, a switching method using a program or a switching method using a switch can be used.
[0094]
Specifically, for example, a function (such as FPGA: Field Programable) that processes each user signal input as a spread signal (received signal) as in correlation processing in each signal processing unit S1 to Sn. Gate Array) and two types of boot programs are provided, and when the modem unit is used alone, a program for performing correlation processing or the like is loaded and executed by the processor, while the modem unit and the interference removal unit are When connecting and using, a switching method of loading a program for receiving and processing each user signal input as a despread signal can be used.
[0095]
As another aspect, for example, each signal processing unit S1 to Sn has a function of a correlator for performing correlation processing and a data transfer function for transmitting (transferring) an input signal to the determination units I1 to In as it is. It is also possible to use a switching method in which the function of the correlator and the data transfer function are switched by a switch depending on whether the interference removing unit is detached or mounted.
[0096]
FIG. 4 (a) shows an example of the state of the CDMA base station when the interference removal unit is removed from the modulation / demodulation unit of this configuration mode, while FIG. 4 (b) shows interference cancellation in the modulation / demodulation unit of this configuration mode. An example of the state of the CDMA base station when the unit is mounted is shown.
In the state where the interference removing unit is detached as shown in FIG. 5A, the signal is received by the receiving unit (RX) 11, and the modulation / demodulating unit 13 is switched to a configuration for performing path detection, correlation processing, and the like. In this state, the portion 12 to which the interference removing unit is attached is in an empty state. On the other hand, in the state where the interference removing unit 14 is connected as shown in FIG. 5B, a signal is received by the receiving unit (RX) 11, and path detection and correlation processing are performed by the interference removing unit 14, The modem unit 15 switches to a configuration in which data determination processing or the like is performed without performing path detection or correlation processing.
[0097]
Here, in the above, as a preferred embodiment, a configuration example when the receiving apparatus according to the present invention is applied to a CDMA base station has been shown. However, the configuration of the receiving apparatus according to the present invention is not necessarily shown in the above embodiment. It is not restricted to a thing, A various structure may be used.
For example, the number of user signals to be communicated is not particularly limited as long as there are a plurality of user signals, and various configurations of interference removing means, timing detecting means, and reception processing means may be used.
[0098]
Specifically, for example, a configuration for performing the interference cancellation processing as shown in FIG. 5 can be used as the configuration of the interference cancellation means. In short, the timing detection means is based on the signal subjected to the interference cancellation processing. Various configurations may be used as long as the timing of each user signal is detected and the timing information is fed back to the interference removing unit. In the above embodiment, the number of stages of interference canceling means (the number of stages, that is, the number of replica generating means provided for each user signal in the above embodiment) is 2, but the number of stages is not particularly limited. For example, the accuracy of interference cancellation can be increased as the number of stages is increased (that is, the error of interference cancellation can be reduced).
[0099]
In addition, as interference cancellation processing, timing detection processing, and reception processing of each user signal performed by the receiving apparatus according to the present invention, the processor executes a control program in a hardware resource including a processor, a memory, and the like, for example. For example, each functional unit for executing the processing can be configured as an independent hardware circuit.
The field of application of the receiving apparatus according to the present invention is not particularly limited. For example, the present invention may be applied not only to the above-described CDMA base station but also to a mobile station that performs mobile communication using the CDMA scheme. it can.
[0100]
【The invention's effect】
As described above, according to the receiving apparatus of the present invention, when each user signal is separated and received from a plurality of user signals received by the CDMA method, the interference removing means extracts each user signal from the received signal by despreading. In this way, each user signal extracted together with the received user signal in the received signal by respreading and subtracting the other user signal that has been respread is detected based on the timing information. Since the timing of the signal is detected based on each user signal and the timing information is fed back to the interference removal means, the detection accuracy of the timing information can be improved. For example, the interference removal means It is possible to improve the quality of each user signal that is output from and processed for reception.
[0101]
Further, in the receiving apparatus according to the present invention, since the above-described interference canceling unit outputs each user signal extracted from the received signal by despreading to the receiving processing unit, by performing the signal transmission at the symbol rate, for example, As shown in the above embodiment, the efficiency of signal transmission can be improved.
[0102]
Further, in the receiving apparatus according to the present invention, for example, when the receiving apparatus is configured as a CDMA base station, the interference canceling means is detachable, and the signal that can be received by the receiving processing means is a despread signal. Since the user signal output from the interference canceling means to the reception processing means can be switched to each signal depending on whether the signal is a spread signal or not, the interference canceling means or the like is added to the reception processing unit of an existing CDMA base station, for example. The general versatility of the interference removing means in the case of additionally mounting the lens can be made excellent.
[0103]
Further, in the receiving apparatus according to the present invention, for example, the receiving apparatus is configured as a CDMA base station, and the interference removing means and the like are configured to be removable, and each user signal extracted by the interference removing means from the received signal by despreading. Is output to the reception processing means, and when the interference removal means is attached to the reception processing means, the reception processing means switches to reception processing of the despread signal input from the interference removal means, while the interference removal means Since it is possible to switch to reception processing of a plurality of user signals received by the CDMA method when it is detached, for example, interference removal means when attaching / detaching interference removal means to / from the reception processing unit of the CDMA base station, etc. The versatility can be made excellent.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration example when a receiving apparatus according to the present invention is configured as a CDMA base station.
FIG. 2 is a diagram for explaining an example of a path timing detection process;
FIG. 3 is a diagram for explaining an example of how to transmit path timing information;
FIG. 4 is a diagram illustrating a state example of a CDMA base station when an interference removing unit is attached and when the interference removing unit is detached.
FIG. 5 is a diagram illustrating a configuration of an interference canceller according to a conventional example.
FIG. 6 is a diagram for explaining how to transmit path timing information according to a conventional example.
[Explanation of symbols]
1, 11 ··· Receiver (RX), 2, 4 ··· Delay means, 3, 5 ··· Subtractor,
P1 to Pn, Q1 to Qn, replica generating means, M1 to Mn, an adder,
D1 to Dn ··· path detector, SW1 to SWn ··· switch,
S1-Sn ... signal processing unit, I1-In ... determination unit,
13, 15 .. Modulator / Demodulator (MDE), 14. Interference remover,

Claims (4)

In a receiving apparatus that separates and receives each user signal from a plurality of user signals received by the CDMA system,
Timing information that each user signal is extracted from the received signal by despreading, each extracted user signal is again spread, and another user signal that has been respread is subtracted to detect each user signal in the received signal Interference canceling means based on
Timing detecting means for detecting the timing of the signal based on each user signal detected by the interference removing means and feeding back the timing information to the interference removing means;
Reception processing means for receiving and processing each user signal output from the interference cancellation means;
A receiving apparatus comprising: The receiving device according to claim 1,
The interference canceling means outputs each user signal extracted from the received signal by despreading to the receiving processing means, and the receiving processing means receives and processes the despread signal. The receiving device according to claim 1,
A CDMA base station,
The interference removing means and the timing detecting means are detachable configurations,
The interference canceling means has switching means for switching a user signal output to the reception processing means to each signal depending on whether the signal that can be received by the reception processing means is a despread signal or a spread signal. A receiving device. The receiving device according to claim 1,
A CDMA base station,
The interference removing means and the timing detecting means are detachable configurations,
The interference cancellation means outputs each user signal extracted from the received signal by despreading to the reception processing means,
The reception processing means switches to reception processing of the despread signal input from the interference cancellation means when the interference cancellation means is attached, while the reception processing means switches to the reception processing by the CDMA method when the interference cancellation means is detached. A receiving device comprising switching means for switching to the reception processing of the user signal.

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