JP4153208B2 - Base station antenna directivity control apparatus in CDMA system and base station antenna directivity control apparatus in CDMA cellular system - Google Patents

Description

なお、図３（ｂ）に示すように、基地局１から送信電力T_iで送信したとき移動局が受信電力P_miで受けるときも同じ伝搬損失L_iである。
【００４５】
推定されたユーザiの移動局の信号到来方向と下り回線周波数およびアレー形状によって決まるアレー伝搬ベクトル（アレー方向ベクトル）をｖ_iと表す（アレー伝搬ベクトルについては、菊間,“アレーアンテナによる適応信号処理”，科学技術出版（1998）p.30―31参照）。
P_iを「i番目のユーザ電力として想定する値」、f_iを自セルのi番目のユーザの重み付け関数、Pnを熱雑音電力としたとき、ウエイト計算のための相関行列Ｒ_xxを、
【数２】

と定義する。
ここで、ユーザkの移動局を送信相手とするアンテナウエイトｗ_kを、
【数３】

と与える。Ｒ_xx ^-1は、Ｒ_xxの逆行列を表す。
【００４６】
上述した「i番目のユーザ電力として想定する値」P_iには、基地局１のユーザiの移動局に対する送信電力や伝搬損失等のパラメータに依存した値が用いられる。
すなわち、図３（ｂ）に示したP_mi（＝T_i/L_i）のように、基地局から自セル内のユーザiの移動局を送信相手とするときの推定希望受信電力を代入してもよいし、図３（ｂ）に示したT_iのように、基地局１から自セル内のユーザiの移動局を送信相手とした希望波送信電力の値を代入してもよい。したがって、上述した式(1)から得られるL_iは必ずしも必要とはされない。
一般的には、ｋ番目の移動局を希望波移動局とした場合、その他の移動局に対して、P_iの値を大きくすることで、i番目のユーザ方向（すなわちθ_i）に指向性のヌルを意図的に設けることができる。
【００４７】
一方、f_iは重み付け関数であり、詳細は後述するとして、ここでは、簡単な例を示す。従来技術の説明において引用した文献(2)を解釈すると、Ｒ_xxを全ユーザ1〜Kのアレー応答ベクトルと電力とを用いて計算する場合は、全てのユーザについて、f_i＝１とした場合に対応する。また、Ｒ_xxを下り回線で高速となるユーザのみのアレー応答ベクトルと電力とを用いて計算する場合は、高速ユーザに対してはf_i＝１、低速ユーザに対してはf_i＝０と設定した場合に対応する。
【００４８】
図４は、本発明の、第２の実施の形態を説明するためのブロック構成図である。
図中、図１２，図１と同様な部分には同じ符号を付して説明を省略する。
この実施の形態は、周辺セルのユーザの移動局に対する干渉も考慮して上で、送信ウエイトを決定するものである。
３１は周辺セルの移動局からの到来波推定部、３２は情報管理部である。周辺セルの移動局を自セルからどの程度離れた移動局までとするかは、任意に決定できる。セル単位で収集する移動局の範囲を決めたり、自セルの基地局から所定距離にある移動局までを周辺セルの範囲としたりすることもできる。
【００４９】
周辺セルの移動局からの到来波推定部３１においては、周辺セルに位置する移動局からの到来波に関し、その到来方向を推定しその受信電力を測定する。到来方向推定値を到来方向情報とし、受信電力から伝搬損失情報を得る。
周辺セルの各ユーザ通信装置から受信した到来波を推定する方法としては、例えば、自セルのアンテナ受信信号から、MUSIC，ESPRITなどの既知の到来方向推定手段を利用する方法がある。
【００５０】
図５は、図２に示した周辺セルの移動局からの到来波推定部３１において、推定された複数の到来方向の中から、周辺セルの移動局からの到来波を抽出する一例の説明図である。図中、横軸は到来波の到来角θ、縦軸は到来波の受信電力Ｐrである。
例えば、ビームフォーマ法によって、メインビームを走査することによって全ての到来方向θを推定し、その到来方向θの電力Ｐrを測定する。その中から、ユーザ1のＡＡＡ受信部１１₁〜ユーザKのＡＡＡ受信部１１_Kにおいて得られた各希望波の受信電力Ｐr₁，Ｐr₂，……，Ｐr_Kの成分（到来方向情報θ₁，θ₂，……，θ_K、図中、実線で示した矢印）以外の成分（図中、破線で示した矢印）について、周辺セルの移動局からの到来波を推定する。
【００５１】
あるいは、自セル内ユーザによる信号を打ち消した後に、MUSIC，ESPRITなどの既知の到来方向推定を用いることで、さらに、正確に到来波を推定することができる。すなわち、受信電力Ｐr₁，Ｐr₂，……，Ｐr_K（到来方向情報θ₁，θ₂，……，θ_K）の成分や、自セルのユーザの復元データ等に基づいて、各希望波（受信電力Ｐr₁，Ｐr₂，……，Ｐr_K、到来方向情報θ₁，θ₂，……，θ_K）が、ＲＦ受信部２１（図１では、ＲＦ受信部６ａ〜６ｄ）から出力されるときの受信信号のレプリカを生成する。次に、ＲＦ受信部６ａ〜６ｄの出力からレプリカを減算した信号について、MUSIC，ESPRITなどの既知の到来方向推定を行うようにしてもよい（例えば、北原 他「多ユーザ環境におけるDS-CDMAシステムの下り回線用アダプティブアレーアンテナ」RCS99-216（2000））
【００５２】
図５を参照して説明すると、図示の各希望波の受信電力Ｐr₁，Ｐr₂，……，Ｐr_Kの成分（到来方向情報θ₁，θ₂，……，θ_K、図中、実線で示した矢印）の電力が除去されたものについて、改めて到来波推定を行うことを意味する。
すなわち、自セルユーザの移動局の到来波が除去されたものについて到来波推定を行うことになるので、推定する必要のある到来波の総数が少なくなるので、アレーアンテナによる到来波情報推定精度が向上する。
【００５３】
周辺セルの移動局からの到来波推定部３１は、周辺セルの移動局（ユーザ１〜ユーザMまでの移動局とする。いずれの周辺セルの移動局であるかを区別する必要はない）からの到来波推定結果として、到来方向情報θ^Δ ₁,θ^Δ ₂,……,θ^Δ _M、受信電力情報Ｐr^Δ ₁，Ｐr^Δ ₂，……，Ｐr^Δ _Mを、情報管理部３２に出力する。その際、図示の例では、受信電力情報Ｐr^Δ ₁，Ｐr^Δ ₂，……，Ｐr^Δ _Mを伝搬損失情報Ｌ^Δ ₁,Ｌ^Δ ₂,……,Ｌ^Δ _Mに置き換えて管理している。
情報管理部３２は、また、周辺セルの移動局（ユーザ１〜ユーザM）に対する送信レート（送信チャネル数）情報を管理する。この送信レートは、この移動局が在圏するセルの基地局からの下り回線の送信レートである。
この送信レート（送信チャネル数）情報は、送信電力情報Ｔ^Δ ₁,Ｔ^Δ ₂,……,Ｔ^Δ _Mに変換して情報管理してもよいし、情報管理後に、送信電力情報に変換してもよい。
【００５４】
周辺セルの基地局がこの周辺セルの各ユーザ通信装置に送信する送信信号の送信電力情報については、自セルの基地局１で受信電力やセル半径等の情報から推定するか、あらかじめ定められている移動局の基準送信電力値を管理しておく。この送信電力情報が、基準送信電力値のように、どの周辺セルのどの移動局が送信したものであるかを特定しないものであるときには、周辺セルのユーザ通信装置に関して、その到来波情報とその送信電力情報との対応付けができないので、MUSIC，ESPRITなどの既知の到来方向推定を利用する際も、どの周辺セルのどの移動局からの到来波であるかを特定する必要はなく、ある到来方向からある受信電力の到来波があることがわかればよい。
【００５５】
また、基地局１に、周辺セルの基地局から、この周辺セルの各ユーザ通信装置に送信する送信信号の送信レート情報（チャネル数）あるいは送信電力情報、を収集できる機能を持たせた場合は、到来波の推定の際に、どの周辺セルのどの移動局からの到来波であるかを、何らかの方法で特定して、到来波情報と上述した送信信号の送信電力情報との対応付けを行うようにすればよい。
到来波推定の際に、どの周辺セルのどの移動局からの到来波であるかを特定するには、周辺セルの基地局から、例えば、周辺セルの各ユーザ通信装置が送信に使用している拡散符号を入手したり、周辺セルの各ユーザ通信装置の位置情報を入手したりすればよい。
【００５６】
アダプティブアレーアンテナを動作させる場合には、振幅情報よりも、位相情報（到来方向）が優勢であるので、少なくとも位相情報（到来方向）が正確に推定できればよい。
なお、情報管理部３２は、また、自セル内ユーザ1〜Kの移動局に対する重み付け関数f₁〜f_K、および、周辺セルユーザの移動局に対する重み付け関数f^Δ ₁〜f^Δ _Mを管理していてもよい。
【００５７】
次に、自セルおよび周辺セル移動局からの到来波推定によって、どのように、自セル内の各ユーザの移動局に対する送信ウエイト（下り回線）ウエイトを決定するかについて説明を加えておく。基本的には、従来技術において示した文献(2)の計算方法が用いられる。
上り回線の信号を用い、基地局１で各移動局からの電波到来方向θ_iと伝搬損失L_iを推定する。電波到来方向推定や伝搬損失推定にはどのような方法を用いてもよい。
【００５８】
図６は、本発明の、第２の実施の形態において使用する伝搬損失推定手段の一例に関する概念図である。図６（ａ）は基地局の送信電力と移動局での受信電力、および、伝搬損失との関係、図６（ｂ）は、移動局の送信電力と基地局での受信電力、および、伝搬損失との関係を示したものである。
図３を参照して説明した送信ウエイト計算の概念が周辺セルまで拡張されている。自セルのユーザには添字i（i＝1〜K）を使用し、周辺セルのユーザには添字j（j＝１〜M）を使用して区別する。
【００５９】
伝搬損失L_iの推定方法については、基地局１で自セルのユーザiの移動局の送信電力Ｔ_miを把握していれば、次式の関係式を用いて、受信電力P_riから容易に求めることができる。
【数４】

周辺セルのユーザj（jは周辺セルのユーザを表す）の移動局４２についても、同様な関係式を用いて、受信電力から容易に求めることができる。この場合は周辺セルからの干渉波として基地局１で受信される電力である。
【数５】

推定されたi番目およびj番目のユーザの信号到来方向と下り回線周波数およびアレー形状によって決まるアレー伝搬ベクトル（アレー方向ベクトル）をｖ_i，ｖ_jと表す。
【００６０】
P_iを自セルの「i番目のユーザ電力として想定する値」、f_iを自セルのi番目のユーザの重み付け関数、P_jを周辺セルの「j番目のユーザ電力として想定する値」、f_jを周辺セルのj番目のユーザの重み付け関数、Pnを熱雑音電力としたとき、ウエイト計算のための相関行列Ｒ_xxを、
【数６】

と定義する。
ここで、k番目のユーザ（kは自セル内のユーザ）のアンテナウエイトｗ_kを、
【数７】

と与える。Ｒ_xx ^-1は、Ｒ_xxの逆行列を表す。
【００６１】
上述した自セルの「i番目のユーザ電力として想定する値」P_iには、図６（ｂ）に示されている、P_mi（＝T_i/L_i）が代入される。
一方、周辺セルの「j番目のユーザ電力として想定する値」P_jには、図６（ｂ）に示されたP_mj（＝T_j/L_j）が代入される。ここで、L_jは基地局１と周辺セルのユーザjの移動局４２との間の伝搬損失であり、T_jは周辺セルの基地局４１が周辺セルのユーザjの移動局４２を送信相手として送信するときの送信電力の値である。
基地局１は実際に周辺セルのユーザjの移動局４２を送信相手として送信電力T_jで送信するわけではないが、仮想的にこのように考えたとしたときに周辺セルのユーザjの移動局４２が受信する受信電力の値を計算して用いる。
また、図６（ｂ）に示したT_iのように、基地局１から自セル内のユーザiの移動局を送信相手とした希望波送信電力の値を代入してもよい。したがって、上述した式(4)から得られるL_iは必ずしも必要とはされない。同様に、図６（ｂ）に示したT_jのように、周辺セルの基地局４１から周辺セル内のユーザjの移動局４２を送信相手とした希望波送信電力の値を代入してもよい。したがって、上述した式(5)から得られるL_jは必ずしも必要とはされない。
【００６２】
式(6)のP_i，P_jおよび式(7）のP_kはk番目のユーザの送信アンテナ指向性を決定するにあたり、それぞれ、i，j，k番目のユーザに関する影響度を表すものである。一般的には、自セルのユーザkの移動局を希望波移動局とした場合、P_i（i≠k），P_jの値を大きくすることで、自セルのユーザiの移動局，周辺セルのユーザjの移動局４２方向に、指向性のヌルを意図的に向けることができる。
一方、f_i，f_jは重み付け関数であり、例えばf_jに０でない正の値を入れることで、周辺セルに対する干渉を考慮することができる。特に、周辺セルへの干渉を大きく押さえたい場合には、f_jに大きな値を入れればよい。
【００６３】
次に、上述した重み付け関数f_i，f_jについて詳述する。
既に説明したように、短区間変動や瞬時変動は考慮していないが、基地局１と移動局との距離による伝搬損失は、伝搬損失情報として考慮していた。
すなわち、基地局１とユーザiの移動局間の距離をr_iとすると、受信電力変動E（r_i）は次式で決まる。
E（r_i）＝Ar^{- α} (8)
ここで、Aは送信電力等で決まる定数であり、αは伝搬定数である。伝搬定数αの市街地での標準的な値は、α＝3.5である。
したがって、上述した伝搬損失情報L_iは、基本的には次式のように表される。
Ｌ_i＝Br^α (9)
Bは定数である。
【００６４】
ところが、最後に説明するシミュレーションによれば、上述した伝搬損失情報Ｌ_iを考慮しただけでは、干渉が遠いところにある移動局に及ぼす影響が大きいことがわかった。そのため、基地局から距離r_iにあるユーザiの移動局に対して、重み付け関数f_iを次のように定義する。
f_i ＝r_i ^γ （γ＞0） (10)
なお、図４に示す情報管理部３２では周辺セルの移動局に対して、f_jの代わりにf_i ^Δの記号を用いているが同じ関数である。
式(10)の場合の重み付け関数f_iの値は、伝搬損失情報L_iと同じ距離r_iの関数であるから、伝搬路損失を推定する際に、伝搬損失情報L_iと同様に、受信電力情報Prから推定する。あるいは、伝搬損失情報L_iからr_iを得て計算することもできる。
【００６５】
図４では、重み付け付け関数f_i，f_jをどこのブロックで計算するかについては記載していない。設定する重み付け関数の内容に依存するが、ユーザ毎に一度計算しておいて情報管理部３２で保持しておく。あるいは、ウエイト計算をする直前の時点で求めることも可能である。
あるいは、図１で説明すれば、変換部１５の後に重み付け部を設けて重み付け関数f_i ，f_jを乗算し、ユーザ別処理部８₁〜８_Kの送信ウエイト計算部１８に出力するようにしてもよい。
ただし、式(10)のような距離の関数、あるいは到来方向の関数とした場合には、到来波を推定するブロックで距離を求めて重み付け関数を計算する方法が可能である。
【００６６】
この関数は、基地局から遠い移動局ほど受信電力が大きくなるように作用する。すなわち基地局から近い移動局よりも基地局から遠い移動局の干渉を抑圧するように作用する。
したがって、特に、周辺セルの移動局を考慮する場合に、この重み付け関数f_i ^Δを導入することは有効である。しかし、図１〜図３を参照して説明した第１の実施の形態にも適用可能である。
【００６７】
なお、上述した伝搬損失情報Ｌ_iと合わせて１式とすると、
f_i /Ｌ_i＝Br_i ^{γ - α} （γ＞0） (11)
となる。
したがって、式(12)を新たに伝搬損失情報とすることも可能である。
なお、上述した式(11)，(12)の重み付け関数f_i，f_i ^Δは、単なる一例であって、f_i，f_i ^Δ＝１であるときよりも良好な結果が得られる関数であれば、他の特性の関数であってもよい。
【００６８】
図７は、本発明の、第３の実施の形態を説明するためのブロック構成図である。図中、図１２，図１と同様な部分には同じ符号を付して説明を省略する。
この実施の形態は、図１ないし図３を参照して説明した実施の形態の構成に変更を加えたものであって、送信ウエイト計算に考慮する干渉ユーザ数を減らすことにより、干渉量低減効果を改善するものである。
５１は選択部であって、５１₁，５１₂，……，５１_Kは、ユーザ1,2，……Kの選択部である。各選択部は、各ユーザに対応する到来波（希望波）の情報を選択するのは当然として、それ以外に、干渉波抑圧のために他のユーザに対応する到来波の情報を選択する。
【００６９】
その際、到来波の情報の数を、希望波を含めてKs（Ks≦K）に絞り込む。したがって、送信時にアレーアンテナのビーム制御の自由度が増大する。その結果、干渉量低減効果が大きくなる。なお、Ks＝Kのときは絞り込みを行っていないが、状況によっては、絞り込みを行わずに、全ユーザの到来波（希望波＋干渉波）を選択する場合がありうるので、この実施の形態では、このような場合を想定してKs＝Kとしている。
例えば、選択する到来波の数Ksを、アレーアンテナの自由度未満に減らせば、干渉波を与えてしまう移動局に対してビームヌルを向けることができる。
【００７０】
ユーザ数Kは、通常、アレーアンテナの自由度よりもかなり多いので、干渉波抑圧のために選択する干渉波の情報を絞り込む基準が必要である。
干渉波の第１の絞り込み方法は、基地局送信電力の高いユーザ（高速レート受信ユーザ）の移動局情報を、上位から順に(Ks−1）個を選択するというものである。これらの情報を用いて、下り回線の低速レート受信ユーザにメインローブを向けて送信する時に、(Ks−1）個の高速レート受信ユーザに対して、ヌルを生成するビームパターンを生成すると、高速レート受信ユーザに対する干渉が低減する。
その結果、高速レート受信ユーザにメインローブを向けて送信する際の送信電力を低減することが可能となり、ひいては、高速レート受信ユーザにメインローブを向けて送信する時に、低速レート受信ユーザへの干渉が低減する。
【００７１】
干渉波の第２の絞り込み方法は、上述した第１の方法とは逆である。基地局送信電力の低い干渉ユーザ（低速レート受信ユーザ）の移動局情報を、下位から順に(Ks−1)個を選択するというものである。
これらの情報を用いて、下り回線の高速レート受信ユーザにメインローブを向けて送信する時に、(Ks−1）個の低速レート受信ユーザに対して、ヌルを生成するビームパターンを生成すると、低速レート受信ユーザへの干渉が直接的に低減される。
いずれの場合でも、考慮する干渉波数を絞り込むことにより、所望の方向にビームヌルを向けることができ、干渉波抑圧の効果が高まることになる。
【００７２】
干渉波の第３の絞り込み方法は、基地局で受信された多数の到来波の到来角について、計算に用いる到来波をまとめ上げるものである。
図８は、図７に示した第３の実施の形態において、計算に用いる干渉波を絞り込む第３の方法の原理的説明図である。10ユーザが同時に通信しているとし、そのうち、ユーザ10の選択部５１について例示的に説明する。
図８（ａ）は、情報管理部２２で管理された、到来波の到来角と受信電力を示す線図である。ユーザiからの到来波の到来角をθ'_i，受信電力をＰ'_iとする。i＝10がユーザ10に対する参照波に関するものであり、i＝1〜9がユーザ10に対しては干渉波として受信されたものである。
【００７３】
ここで、到来角θの全範囲をΔθで分割し、分割された小区間に複数の干渉波があった場合には、その小区間内の近接する到来波をまとめ上げて、１つの干渉波に置き換えたものを選択することによって、到来波の情報の数を減らした上で送信ウエイト計算に用いる。
まとめ上げの方法としては、例えば、図８（ｂ），図８（ｃ），図８（ｄ）の方法がある。以下、置き換えられて選択される１つの干渉波の到来角及び受信電力を、各小区間ごとに、（θ₁，P₁），（θ₂，P₂），（θ₃，P₃），（θ₄，P₄）……とする。
【００７４】
いずれの場合も、選択される受信電力P₁，P₂，P₃は、図示するように、各小区間内の受信電力の和とする。すなわち、
P₁＝P'₁＋P'₂＋P'₃
P₂＝P'₄
P₃＝P'₅＋P'₆＋P'₇
P₄＝P'₈＋P'₉
【００７５】
図８（ｂ）においては、選択される干渉波の到来角θを、各小区間における受信電力最大のパス（到来波）の到来角とする。すなわち、
θ₁＝θ'₂ ，θ₂＝θ'₄ ，θ₃＝θ'₇ ，θ₄＝θ'₉
図８（ｃ）においては、選択される干渉波の到来角θを、各小区間における受信電力を重みとして重み付け合成された到来角とする。すなわち、
θ₁＝（P'₁θ'₁＋P'₂θ'₂＋P'₃θ'₃）／（P'₁＋P'₂＋P'₃）
θ₂＝θ'₄
θ₃＝（P'₅θ'₅＋P'₆θ'₆＋P'₇θ'₇）／（P'₅＋P'₆＋P'₇）
θ₄＝（P'₈θ'₈＋P'₉θ'₉）／（P'₈＋P'₉）
図８（ｄ）においては、選択される干渉波の到来角θを、各小区間の中央値とする。すなわち、縦軸の位置する到来角を０とすると、
θ₁＝(1/2)Δθ，θ₂＝(3/2)Δθ，θ₃＝(5/2)Δθ，θ₄＝(7/2)Δθ
【００７６】
上述した干渉波の絞り込み方法において、干渉電力が、平均電力等に応じて決まる所定の閾値以上でなければ選択しないようにしてもよい。このようにした場合、あるユーザからの希望波の受信電力がこの閾値以下であるとき、絞り込み方法やそのときの受信電力の分布によっては、このユーザの干渉波選択数Ksの値が、他ユーザの干渉波選択数Ksの値と異なる場合がある。
【００７７】
図９は、本発明の、第４の実施の形態を説明するためのブロック構成図である。図中、図１２，図１，図４，図７と同様な部分には同じ符号を付して説明を省略する。
この実施の形態は、図４〜図６を参照して説明した実施の形態の構成に変更を加えたものであって、図７と同様に、送信ウエイト計算に考慮する干渉ユーザの情報数を減らすことにより、干渉量低減効果を上げるものである。
すなわち、周辺セルユーザからの到来波も含めた（K＋M）の中から送信ウエイト計算に考慮する到来波の情報を希望波も含めてKs個だけ選択するものである。
選択の基準は、図７の場合と同様である。また、第３の方法をとるときには、図８に例示したような到来波の到来角のまとめ上げを行うことができる。
【００７８】
図１０は、周辺セルの移動局を考慮することによる干渉波抑圧の効果を評価するシミュレーション結果を説明するため線図である。本発明を実施した結果を表すものではないが、本発明を適用することにより期待できる作用効果が推定できる。
セル構成はセル半径をR [km]とした正六角形セルとする。移動局はセル内に一様分布している。伝搬変動として距離変動だけを考慮し、伝搬定数α＝3.5とした。アレイアンテナ構成はリニアアレーアンテナとし、アンテナ素子は無指向性とする。
【００７９】
符号間干渉は、拡散符号が完全に直交していれば0となるが，直交関係が崩れれば1/PG（PG：拡散率）だけの干渉が生じる。一般に、同一基地局から送信した電波は，直交関係が保たれ干渉は0となる。しかし伝搬遅延波があれば拡散符号間の直交関係が崩れるため干渉を生じる。
簡単のため干渉率（以下、非直交係数という）をβとして定義して用いる。すなわち，干渉量はβ/PGとなる。一方，異なる基地局から送信された信号は、一般に直交関係が保てないので1/PGの干渉を生じる。
【００８０】
(1)各セル毎の移動局数を2つの伝送速度移動局群（高速伝送移動局群，低速伝送移動局群）に分類し，送信電力を決定する．続いて各セル毎に移動局の位置を一様乱数で決定する。
(2)基地局において、各移動局の到来方向と伝搬損失とは、基地局側で理想的に推定できるものと仮定する。推定した情報を基に、移動局毎に伝送速度に応じた下り送信電力の変換及び重み付け関数の追加を行い、アレーベクトルを作成して，アンテナパターンを求める。
(3)各移動局においては、下り回線のアンテナパターン，送信電力，伝搬損失に基づいて希望波電力と干渉波電力を求める。干渉波電力は，自セルの干渉波(セル内全ユーザ数−１）と他セルからの干渉波(セル内全ユーザ数×他セルの数)の総電力であり，自セルの干渉波に関しては、非直交成分β/PGを考慮し，他セルの干渉波に対しては1/PG(β=1)を考慮して計算する。
(1)〜(3)の試行を繰返し行い，希望波電力対干渉波電力比CIRの分布を求める．ただし、評価は干渉が最も厳しい中心セルの移動局に対してだけ行った。
【００８１】
シミュレーション条件は、次の通りである。日本における第３世代移動体通信の割り当て周波数に着目すれば、上り回線の搬送波周波数に対してアンテナ素子間隔dがλ/2となるように設定した場合、下り回線の搬送波周波数に対しては約0.55λとなる。また，アンテナ素子数は8、各セルの移動局数は20としている。ここでは例示していないが、特に伝送速度を考慮した場合には、高速伝送移動局数を5，低速伝送移動局数を15としている。また，高速伝送移動局群の送信電力は低速伝送移動局群に対して15dB高い送信電力を設定している。
【００８２】
評価は以下に示す方法と比較する。
(i)上り回線で計算したアンテナウエイトを下り回線のウエイトとして用いる方法(下りCOPY法)
(ii)各移動局の電波到来方向と伝搬損失は完全に推定できるものとして、下り回線の送信電力を補正し，最適アンテナウエイトを計算する方法(下り最適法)とする。すなわち、f_i＝1（γ＝0）の場合である。
(iii)参考までに、f_i＝1（γ＝0）で、かつ、送受信の搬送波周波数が等しい時分割多元接続TDDの場合(TDD法)も示した。
【００８３】
図１０(a)は重み付け関数の指数部γをパラメータとした場合の希望波電力対干渉波電力比CIR/PGの累積分布を示す。
ただし、移動局は全て低速伝送移動局群に属しているものとし、非直交係数βはβ=0.4としている。例えば、累積確率の20％値で比較すると、γ=3.5〜5において大きなCIR/PGの改善が得られている。例えばγ=3.5とすれば、提案法は、下りCOPY法や下り最適法（γ=0の場合と等価）に比べてCIR/PGを大幅に改善できることがわかる。
【００８４】
ところで、上述した結果は、全移動局の到来方向と伝搬損失とが既知である場合のシミュレーション結果であった。しかし、全移動局の到来方向と伝搬損失とが既知となる場合は、必ずしも現実的ではない。そこで、移動局の到来方向および伝搬損失の情報が得られる範囲を限定した評価も行った。
図１０（ｂ）は、移動局情報を得られる範囲Rthを、セル半径Rの1，1.2，1.5倍，及び∞とした場合の、CIR/PGの累積分布を示す。ただし、移動局は全て低速伝送移動局群に属しているものとし、重み付け関数の指数部をγ=3.5，非直交係数をβ=0.4としている。
【００８５】
この線図からわかるように、移動局情報を得られる範囲Rthを大きくする程、CIR/PGは改善される。例えば、累積確率の20%値で比較すると、提案法は、下りCOPY法に比べてRth＝Rで約3dB、Rth＝1.2Rで約5 dBの改善が得られている。また、TDD法に比べても、Rth＝1.2Rで約1 dBの改善効果が得られている。
図示を省略するが、高速伝送移動局と低速伝送移動局とが併存している場合も、提案法は、従来法に比べてCIR/PGを大幅に改善できている。
Rth＝Rのときは、ほぼ自セルの範囲になるが、自セルは１辺がRの正６角形セルであるので、周辺セルの移動局の影響も一部含まれることになる。
【００８６】
以上の説明では、基地局から下り回線方向の送信アレーアンテナウエイトの計算について説明した。しかし、到来波推定を行うことによってアレーアンテナのビームパターンを所望の特性になるように制御するものであればよい。
本発明は、アレーアンテナの形状、取り扱う偏波については特に制約がない。また、アレーアンテナエレメント数やエレメント間隔についても特に制約はない。また、FDD方式、TDD方式いずれにも適用することができる。
上述した説明は、複数のセルで構成されたCDMAセルラー方式における基地局アンテナ指向性制御装置について説明した。しかし、独立した１つのカバーエリア内に複数の移動局が存在するようなCDMA方式における基地局アンテナ指向性制御装置に用いることもできる。また、CDMAセルラー方式であっても、周辺セルの移動局の影響を考慮しない場合は、実質的に、上述したCDMA方式における基地局装置と同じである。
【００８７】
【発明の効果】
上述した説明から明らかなように、本発明によれば、干渉波の推定精度を向上させたり、周辺セルからの干渉波の影響を考慮したりすることにより、複数のアンテナ素子に対する最適な送信ウエイトを正確に計算できるという効果がある。
また、距離に対する干渉波の影響の程度を考慮することにより、複数のアンテナ素子に対する最適な送信ウエイトを正確に計算できるという効果がある。
複数のアンテナ素子を有するアンテナ装置に対する最適な送信ウエイトにより、干渉量抑圧の効果がこれまでよりも向上する結果、セルに収容可能なユーザ数を増やして周波数利用率が向上するという効果がある。
【図面の簡単な説明】
【図１】本発明のＣＤＭＡセルラー方式における基地局アンテナ指向性制御装置に関する第１の実施の形態を説明するためのブロック構成図である。
【図２】図１の全てのユーザ別処理部におけるアレーアンテナのウエイト計算を示す説明図である。
【図３】本発明の、第１の実施の形態において使用する伝搬損失推定の一例に関する概念図である。
【図４】本発明の、第２の実施の形態を説明するためのブロック構成図である。
【図５】図２に示した周辺セルの移動局からの到来波推定部において、推定された複数の到来方向の中から、周辺セルの移動局からの到来波を抽出する一例の説明図である。
【図６】本発明の、第２の実施の形態において使用する伝搬損失推定の一例に関する概念図である。
【図７】本発明の、第３の実施の形態を説明するためのブロック構成図である。
【図８】図７に示した第３の実施の形態において、計算に用いる干渉波を絞り込む第３の方法の原理的説明図である。
【図９】本発明の、第４の実施の形態を説明するためのブロック構成図である。
【図１０】周辺セルの移動局を考慮することによる干渉波抑圧の効果を評価するシミュレーション結果を示す線図である。
【図１１】アダプティブアレーアンテナを用いたCDMAセルラー移動通信システムの一例を示す説明図である。
【図１２】従来のＣＤＭＡセルラー方式における基地局アンテナ指向性制御装置の一例を説明するためのブロック構成図である。
【図１３】到来方向推定を利用した従来のアダプティブアレーアンテナのウエイト計算を模式的に説明するブロック図である。
【図１４】図１２の全てのユーザ別処理部における送信ウエイト計算の説明図である。
【符号の説明】
１…基地局、２…ユーザ１の移動局、３…ユーザ２の移動局、４ａ〜４ｄ…アレーアンテナエレメント、８₁〜８_K…ユーザ別処理部、１１…ＡＡＡ（アダプティブアレーアンテナ）受信部、１３…希望波推定部、１４，２２，３２…情報管理部、１５…変換部、１７…ＡＡＡ送信部、１８…送信ウエイト計算部、２１…ＲＦ受信部、４１…周辺セルの基地局、４２…周辺セルユーザ１の移動局、５１…選択部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a CDMA system used in a CDMA (Code Division Multiple Access) cellular mobile radio communication system to which an antenna apparatus having a plurality of antenna elements is applied, and a base station antenna directivity control apparatus in the CDMA cellular system.
In particular, it is suitable for a base station that needs to calculate a transmission weight in an FDD (Frequency Division Duplex) method or a method in which uplink and downlink transmission rates are different.
[0002]
[Prior art]
One of the third-generation mobile communication systems is W-CDMA, which is expected to provide high-speed and wide-band communication such as moving images as well as voice. Recently, the study of the 4th generation mobile communication system aiming at high-speed and broadband transmission about 10 times that of the 3rd generation system has begun. In order to provide a high-speed service with limited frequency resources, it is necessary to make further effective use of frequencies. As one of countermeasures, it is considered to apply an adaptive array antenna (AAA) to a base station. Yes.
In the DS-CDMA communication system, a large number of users can communicate simultaneously by using different spreading codes even in the same frequency band. However, intersymbol interference cannot be ignored as the number of simultaneous communication users increases. Therefore, by applying an adaptive array antenna, it is possible to perform communication with less interference signals by generating a beam pattern that selects only a desired wave spatially and does not select an interference wave.
[0003]
FIG. 11 is a block diagram for explaining an example of a base station antenna directivity control apparatus in a conventional CDMA cellular system.
In the figure, reference numeral 1 denotes a base station having a cover area (cell) 61. 2 is a mobile station of user 1, and 3 is a mobile station of user 2. Reference numerals 4a to 4d denote a plurality of array antenna elements of the base station 1, which constitute one array antenna as a whole, and control antenna weights (complex numbers) that are multiplied by output signals of the elements at the time of reception, The beam pattern can be freely controlled by controlling the antenna weight (complex number) multiplied by the input signal to the element.
[0004]
The direction of the beam pattern will be described in a simplified manner. In the uplink where the base station 1 receives the transmission wave from each mobile station, the mobile station 2 of the user 1 generates and receives a beam pattern as schematically shown as the user 1 directivity 62. . The mobile station 3 of the user 2 generates and receives a beam pattern schematically shown as the user 2 directivity 63.
The user 1 directivity 62 has a main lobe in the direction of the mobile station 2 of the user 1 and a beam null in the direction of the mobile station 3 of the user 2. Similarly, the user 2 directivity 63 has a main lobe in the direction of the mobile station 3 of the user 2 and a beam null in the direction of the mobile station 2 of the user 1.
[0005]
On the other hand, in the downlink for transmitting transmission information to each mobile station from the base station 1, it has a main lobe in the direction of the mobile station of the user as the transmission partner, and has a beam null in the direction of the mobile station of other users. The beam patterns of the user 1 directivity 62 and the user 2 directivity 63 described above are generated and used.
However, since the number of beam nulls that can be controlled by the adaptive array antenna is determined by the degree of freedom of (number of elements of array antenna-1), there is a restriction that the total number of mobile stations other than the transmission partner is within the degree of freedom. However, in a CDMA communication system, communication with users exceeding the degree of freedom of an array antenna is usually performed simultaneously.
[0006]
Therefore, even if a beam pattern is generated by an array antenna, the direction of other users does not match the direction of the beam null, interference waves cannot be sufficiently removed, and there is a limit to increasing the number of users that can be accommodated. There was a limit to improving efficiency.
In particular, in the downlink transmitted from the base station 1 to each mobile station, the transmission beam pattern is generated in a situation where the direction and magnitude of the incoming wave at the mobile station is unknown, so the accuracy of calculating the antenna weight is degraded. It's easy to do. Therefore, it is difficult to determine the antenna weight that optimizes the interference characteristics of each mobile station in the downlink.
[0007]
As a method of determining the optimum antenna weight in the downlink relatively easily, (1) a method of determining the antenna weight of the downlink using the antenna weight obtained in the uplink as it is or by performing calibration. is there.
In addition, (2) there is a method of estimating the incoming wave from each mobile station from the received signal obtained on the uplink and determining the antenna weight of the downlink based on the information (Kitahara et al., “W-CDMA downlink Adaptive Array Antenna for Lines "2001 IEICE Total, B-5-15, Kitahara et al.," Study on Path Selection for Adaptive Array Antenna for W-CDMA Downlink ", IEICE Technical Report, A / P2001-117 (2001) reference)
[0008]
In the method (1) described above, an error occurs in the optimum antenna weight as the carrier frequency difference between the uplink and the downlink increases. Also, when performing multi-rate service, when the transmission speed is asymmetric between the uplink and the downlink, there is no correlation between the transmission power of the uplink and the downlink, so the downlink base station reception characteristics and the uplink Symmetry with the mobile station reception characteristics is not established. As a result, since the optimum antenna weight obtained in the uplink is not the optimum antenna weight in the downlink, the application effect of the adaptive array antenna is reduced.
[0009]
On the other hand, the method (2) described above estimates the received power of each mobile station in the downlink using the propagation loss estimated using the uplink. However, the downlink transmission power differs depending on the downlink transmission rate of each mobile station. Next, the optimum weight is calculated using the received power of each mobile station on the downlink and the estimated arrival direction.
This method can obtain a relatively good optimum antenna weight even when the symmetry of the reception characteristics is not established such that the transmission speed differs between the uplink and the downlink.
[0010]
FIG. 12 is a block diagram showing an example of a base station in a conventional CDMA cellular system. The downlink antenna weight is determined from the information obtained by estimating the arrival direction and propagation loss of each mobile station from the received signal obtained on the uplink.
Parts corresponding to those in FIG. 11 are denoted by the same reference numerals.
Reference numerals 5a to 5d denote duplexers, and reference numerals 6a to 6d denote RF receivers. All are provided for each of the array antenna elements 4a to 4d, and the subscripts correspond to the subscripts of the array antenna elements 4a to 4d. The number of elements may be arbitrary as long as it is plural.
The duplexers 5a to 5d are inserted to share the antenna and transmit and receive the outputs of the array antenna elements 4a to 4d to the RF receivers 6a to 6d. The RF receivers 6a to 6d perform amplification, frequency conversion, digital demodulation, A / D conversion, and output.
[0011]
7 is a distributor, 8₁~ 8_KIs a user-specific processing unit. The same configuration is provided for each user, and the subscripts indicate user numbers 1 to K. The distributor 7 outputs the outputs of the RF receiving units 6a to 6d to the user-specific processing unit 8.₁~ 8_KDistribute to any of these.
Processing unit 8 for each user₁~ 8_KAll receive signals output from the RF receiving units 6a to 6d corresponding to the array antenna elements 4a to 4d, and the despreading process using the spreading codes of the users 1 to K in the AAA receiving unit 11 to be described later Then, the reception weight multiplication is performed, and the decoding unit 12 described later outputs the restored data of each user 1 to K.
[0012]
Further, transmission data of each user 1 to K is input, error correction coding is performed by an encoding unit 16 to be described later, transmission weight multiplication is performed on what is distributed to a plurality of systems by an AAA transmitting unit 17 to be described later, and each system Is subjected to spreading processing using a spreading code for the user, and a plurality of transmission signals corresponding to the array antenna elements 4 a to 4 d are generated and output to the combiner 9.
The synthesizer 9 includes a processing unit 8 for each user.₁~ 8_KAre added and synthesized for each system of the array antenna elements 4a to 4d, and output to the RF transmitters 10a to 10d. The RF transmitters 10a to 10d perform frequency conversion and amplification, and supply and transmit to the array antenna elements 4a to 4d via the duplexers 5a to 5d.
[0013]
For user-specific processing, user-specific processing unit 8₁Will be described.
The AAA (adaptive array antenna) receiving unit 11 performs despreading by multiplying the reception output of the array antenna elements 4a to 4d by the spreading code for the user 1, and then weights and combines them with antenna weights. If necessary, fading fluctuation estimation, RAKE synthesis, and de-interleaving are performed and output to the decoding unit 12. The decoding unit 12 performs decoding for error correction and restores the transmitted data. Further, the AAA receiving unit 11 performs direction-of-arrival estimation and outputs information on the result to the transmission weight calculation unit 18.
[0014]
On the other hand, the transmission data is subjected to error correction coding in the encoding unit 16 and distributed and output to a plurality of systems in the AAA transmission unit 17, where weighting of transmission weights for the array antenna elements 4a to 4d is performed. The transmission weight calculation unit 18 calculates a transmission weight based on the arrival direction estimation result information and outputs it to a multiplier (not shown) provided in each system, and each output of the multiplier is input to the spreading unit, Each spreading unit multiplies the spreading code of user 1 and outputs the transmission signal of user 1.
Note that the AAA receiving unit 11 may perform despreading after multiplication of the reception weight. The AAA transmitter 17 may perform transmission weight multiplication after spreading the error correction code.
[0015]
FIG. 13 is a block diagram schematically illustrating weight calculation of a conventional adaptive array antenna using arrival direction estimation.
User-specific processing unit 8 in FIG.₁An example of the weight calculation in FIG. The illustration of the despreading unit and the diffusing unit is omitted.
In the figure, reference numeral 81 denotes a reception weight calculation unit, which is provided in the AAA reception unit 11 of FIG. 82a to 82d are multipliers, and receive weights w are respectively received by the reception outputs of the array antenna elements 4a to 4d.₁~ W_FourAnd an adder 83 synthesizes the multiplication results and outputs them to the decoding unit 12 of FIG. 12 and also to the reception weight calculation unit 18.
[0016]
The reception weight calculation unit 81 calculates an antenna weight by a known minimum square error method (MMSE) or the like. The MMSE control gives an optimal solution for the reception weight. However, in consideration of the follow-up of the control in an actual environment, other control using a steering beam or the like that directs only the main beam direction to the desired wave direction has been proposed.
At the same time, estimation of incoming waves from all users i (i = 1 to K) using the well-known MUSIC (MUltiple SIgnal Classification), ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques), or beamformer method I do.
[0017]
As a result of the arrival wave estimation, the estimated arrival direction information of the reception wave from the mobile station i of the user i is expressed as θ ′._iAnd this direction of arrival θ ′_iThe received power of the received power information Pr ′_iAnd Based on this received power information, the base station 1 can estimate the propagation loss from the mobile station to the base station 1. As the simplest method, a transmission loss can be obtained by setting and storing the reference transmission power of the transmission power on the mobile station side in advance and dividing the received transmission power by this reference transmission power. In the following description, the propagation loss information L ′_iWill be described.
Therefore, for all received waves from mobile stations 1 to K of all users, all arrival direction information θ ′₁, Θ '₂,… Θ '_KAnd all propagation loss information L ′₁, L '₂, ..., L '_KIs estimated.
[0018]
The transmission weight calculation will be described in detail with reference to FIG. 2 and FIG.
The transmission weight calculation unit 18 generates an array propagation vector (array direction vector) determined by the estimated signal arrival direction of the mobile station of the i-th user, the downlink frequency, and the array shape. Also, the estimated user reception power is obtained based on the base station transmission power for the i-th user's mobile station and the above-described propagation loss information.
[0019]
According to the method of the paper shown in (2) above, a correlation matrix is generated using the above-described array direction vector and user reception power assumption value, and this correlation matrix and the array direction with respect to the user's mobile station as a transmission partner The transmit antenna weight is determined using the vector.
The transmission weight calculation unit 18 transmits the transmission weight w for the mobile station 2 of the user 1.₁ ⁽¹⁾~ W_Four ⁽¹⁾Is output to the multipliers 71a to 71d.
The multipliers 71a to 71d receive the respective transmission weights w from the output of the encoding unit 16 shown in FIG.₁ ⁽¹⁾~ W_Four ⁽¹⁾And the transmission signals are output to the corresponding array antennas 4a to 4d.
[0020]
In the above description, the user-specific processing unit 8₁Explained. In the base station 1, the same processing is performed for each of the users 1 to K. Therefore, the transmission weight calculation is as shown in FIG.
FIG. 14 shows all user-specific processing units 8 in FIG.₁~ 8_KIt is explanatory drawing of the transmission weight calculation in. In this figure, only transmission weights for the two mobile stations of user 1 and user 2 are shown.
Reference numeral 21 denotes the RF transmitters 6a to 6d shown in FIG. The distributor 7 is not shown in the figure, and distribution is shown by branching of the connection. The AAA receiving unit 11 and the transmission weight calculating unit 18 have subscripts indicating the users 1 and 2, respectively.
[0021]
Processing unit 8 for each user₁~ 8_KAs shown in FIG. 13, all the direction-of-arrival information and all the propagation loss information in FIG.₁, Θ '₂,… Θ '_K, L '₁, L '₂, ..., L '_KMet. The AAA receiving unit 11 of the user 2 performs the same calculation to thereby calculate the total arrival direction estimated value and the total propagation loss estimated value θ ".₁, Θ "₂, ……, θ "_K, L "₁, L "₂, ..., L "_KIs obtained.
User 1 transmission weight calculation unit 18₁And the transmission weight calculation part 18 of the user 2₂Is based on these estimated values, the antenna weight vector w for the mobile stations of users 1 and 2⁽¹⁾, W⁽²⁾Calculate
[0022]
However, the above-described calculation is for a single isolated cell. When an adaptive array antenna is introduced into an actual cellular system, the effect of applying the adaptive array antenna is reduced if the weight calculation of the array antenna is performed ignoring the influence of mobile stations in neighboring cells. It is necessary to evaluate the control method of the adaptive array antenna including the neighboring cells.
In addition, each user processing unit 8₁~ 8_KIn FIG. 5, the same arrival wave estimation is repeated. In addition, each user processing unit 8₁~ 8_KHowever, the estimation accuracy does not deteriorate because the desired wave is reliably received with higher power than the interference wave, but the interference wave estimation accuracy is deteriorated when processing to reduce the reception power of the interference wave is involved. .
[0023]
[Problems to be solved by the invention]
The present invention has been made to solve the above-described problems, and improves the arrival direction estimation accuracy of interference waves or considers the influence of interference waves from surrounding cells, thereby enabling a plurality of antenna elements. It is an object of the present invention to provide a base station antenna directivity control apparatus in a CDMA system and a base station antenna directivity control apparatus in a CDMA cellular system that can accurately calculate an optimum transmission weight for the CDMA system.
Further, by considering the degree of the influence of the interference wave on the distance, the base station antenna directivity control apparatus in the CDMA system and the base station antenna directivity in the CDMA cellular system that can accurately calculate the optimum transmission weight for the plurality of antenna elements. The object is to provide a control device.
[0024]
[Means for Solving the Problems]
[0029]
According to the present invention, in the first aspect of the present invention, communication from a base station to each user communication device is performed with a plurality of user communication devices in the own cell using an antenna device having a plurality of antenna elements. A base station antenna directivity control device in a CDMA system for performing communication using a different carrier frequency and the same antenna element in communication from each user communication device to a base station,
  To received signals of a plurality of systems received by the plurality of antenna elements of the own cellOn the other hand, despreading is performed with the spreading code of each user, and the received wave information of the desired wave of each user of the own cell is obtained using the received signals of the plurality of systems after despreading of each user obtained as a result.A desired wave estimating means for estimating and outputting arrival wave information relating to each user communication device of the own cell; and each of the neighboring cells based on a plurality of received signals received by a plurality of antenna elements of the own cell. A neighboring cell arrival wave estimating means for estimating an incoming wave received from a user communication device and outputting arrival wave information relating to each user communication device of the neighboring cell; arrival wave information relating to each user communication device of the own cell; and Transmission power information of a signal to be transmitted to each user communication device in the own cell, arrival wave information on each user communication device in the neighboring cell, and transmission to be transmitted to each user communication device in the neighboring cell by the base station in the neighboring cell Information management means for managing transmission power information of signals, information on each user communication device managed in the own cell, and information on each user managed in the managed neighboring cell Using the information on the device, the directivity gain to the user communication device of the own cell that is the transmission partner is large, and the directivity gain to the user communication device of the other cell and the neighboring cell is small. Antenna weight output means for calculating and outputting the antenna weight for each antenna element of the own cell for each user communication device of the own cell serving as the transmission partner so as to generate such a beam pattern. .
  Accordingly, the arrival wave information related to the other user communication device of the own cell that is not the transmission partner is output by estimating the desired wave received from the other user communication device, so that the estimation accuracy of the interference wave is improved. .
  Moreover, since the incoming wave information regarding the user communication device in the neighboring cell is managed, the transmission weight can be calculated in consideration of the influence on the neighboring cell. As a result, an interference reduction effect superior to the conventional method can be realized, and the frequency utilization rate can be improved. In particular, in an environment where there is an interference wave exceeding the degree of freedom of the array antenna, it is possible to perform antenna weight calculation that can most reduce the interference wave.
  In addition, as a method of estimating the incoming wave received from each user communication apparatus in the neighboring cell, for example, there is a method of estimating using a known arrival direction estimation unit from the antenna reception signal of the own cell.
  On the other hand, the transmission power information of the transmission signal transmitted by the base station of the neighboring cell to each user communication device of the neighboring cell is estimated from information such as the received power and the cell radius, or is transmitted to a predetermined mobile station. The reference transmission power is used. In some cases, the transmission power information described above can be collected from the base station of the neighboring cell including the positional information of each user communication device of the neighboring cell. Regarding the user communication device of the neighboring cell, when the arrival wave information and the transmission power information do not match, it is necessary to specify which mobile station of which neighboring cell is in the above-described arrival wave information. Absent. In this case, the reference transmission power to the mobile station determined in advance is used as the transmission power.
[0030]
Claim 2In the base station antenna directivity control apparatus in the CDMA cellular system according to claim 6, the desired wave estimation means estimates only the direction of arrival of the desired wave, and each of the user communication apparatuses As the arrival wave information, only the direction of arrival information is output, and the neighboring cell arrival wave estimation means estimates only the arrival direction of the arrival wave as arrival wave information about each user communication device of the neighboring cell. Only the direction of arrival information is output.is there.
  Therefore,Claim 1The same effect as the invention described in (1) is exhibited.
[0031]
Claim 3In the invention described inClaim 1 or 2In the base station antenna directivity control device in the CDMA cellular system described in the above, the information management means selects the arrival wave information and the transmission power information related to the user communication device of the own cell serving as the transmission partner, It has information selection means for narrowing down the incoming wave information and the transmission power information and outputting them to the antenna weight output means regarding other user communication devices of the own cell and user communication devices of the neighboring cells. .
  Therefore,Claim 1The same effect as the invention described in (1) is exhibited.
[0032]
Claim 4In the invention described inClaim 3In the base station antenna directivity control apparatus in the CDMA cellular system described in the above, the information selection means is configured to determine an arrival angle with respect to the arrival wave information from the other user communication apparatuses of the own cell and the user communication apparatuses of the neighboring cells. The number of the incoming wave information is reduced by combining adjacent ones, and the transmission power information is combined according to the combined incoming wave information, and the arrival related to the combined incoming wave information The direction information and the combined transmission power information are output as information about other user communication devices of the own cell and user communication devices of neighboring cells.
  Therefore, the number of interference waves to be considered when calculating the transmission weight can be easily reduced, and the effect of the reduction can be minimized.
  In addition, a predetermined number of information related to other user communication devices of the own cell and the user communication devices of the neighboring cells are selected in descending order of transmission power, and directivity to other user communication devices with a predetermined number of high transmission powers is selected. A beam pattern that reduces the gain is generated, or conversely, a predetermined number of pieces of information related to other user communication devices of the own cell and user communication devices of neighboring cells are selected in order from the lowest transmission power. It is also possible to generate a beam pattern such that the directivity gain with respect to another user communication apparatus having a low predetermined transmission power is small.
[0033]
Claim 5In the invention described inClaims 1 to 4The base station antenna directivity control apparatus in the CDMA cellular system according to any one of the preceding claims, wherein a user of the own cell serving as a reception partner based on a plurality of received signals received by the plurality of antenna elements of the own cell Receiving means for outputting reception information by calculating a reception weight for each antenna element for each communication device, wherein the desired wave estimation means uses each halfway calculation result in the receiving means to The desired wave received from the communication device is estimated.
  Therefore,Claim 1The same effect as the invention described in (1) is exhibited.
[0034]
In invention of Claim 6, between the some user communication apparatuses using the antenna apparatus which has several antenna elementsUsing different carrier frequencies and the same antenna elements for communication from the base station to each user communication device and communication from each user communication device to the base stationA base station antenna directivity control apparatus in a CDMA system that performs communication, wherein arrival direction information, propagation loss information, transmission power information, and distance from the base station for each user communication apparatus areThe farther awayTo reduce interference to each user communication deviceThe weight of each user communication device is increased as the distance from the base station increases.For each antenna element, a weighting function is used to generate a beam pattern that has a large directivity gain for the user communication device as a transmission partner and a small directivity gain for the other user transmission device. The antenna weight is calculated and output for each user communication device as the transmission partner.
  Therefore, by using the above-described weighting function, it is possible to generate an antenna directivity pattern considering the influence of distance. As a result, an interference reduction effect superior to the conventional method can be realized, and the frequency utilization rate can be improved.
  Note that any method may be used as a method of estimating an incoming wave received from each user communication device.
[0035]
Claim 7In the invention described inClaim 412. The base station antenna directivity control apparatus according to claim 11, wherein the transmission power for each user communication apparatus is multiplied by the weighting function in consideration of propagation loss in the base station antenna directivity control apparatus according to CDMA system according to claim 11. The received value is regarded as the estimated received power value of each user communication device, and a correlation matrix for the received signal of each user communication device is generated, and the antenna weight for each antenna element is determined for each user communication device that is the transmission partner. It is to calculate.
  Therefore, an antenna directivity pattern considering the influence of distance can be easily realized.
[0036]
In invention of Claim 8, between the several user communication apparatuses of the own cell using the antenna apparatus which has several antenna elements.Using different carrier frequencies and the same antenna elements for communication from the base station to each user communication device and communication from each user communication device to the base stationA base station antenna directivity control apparatus in a CDMA cellular system for performing communication, wherein the arrival direction information, propagation loss information, transmission power information regarding each user communication apparatus of the own cell, and the arrival direction regarding each user communication apparatus of the neighboring cell Information, propagation loss information, transmission power information related to transmission power transmitted from the neighboring cell base station to each user communication device of the neighboring cell, and distance from the base station of the own cell.The farther awayIn order to reduce interference given to each user communication device of the own cell and each user communication device of the neighboring cellThe weight of each user communication device is increased as the distance from the base station increases.Using the weighting function, the directivity gain to the user communication device of the own cell that is the transmission partner is large, and the directivity gain to the other user communication device of the self cell and the user communication device of the peripheral cell is small. In order to generate a simple beam pattern, the antenna weight for each antenna element is calculated and output for each user communication device of the own cell serving as the transmission partner.
  Therefore, the arrival wave information, propagation loss information, and transmission power information regarding the transmission power transmitted from the neighboring cell base station to each user communication device of the neighboring cell are obtained. The transmission weight can be calculated with the influence taken into account.
  Further, by using a weighting function, an antenna directivity pattern considering the influence of distance can be formed. In particular, interference given to user communication devices in neighboring cells is reduced. As a result, an interference reduction effect superior to the conventional method can be realized, and the frequency utilization rate can be improved.
  Note that the direction-of-arrival information related to each user communication device in the neighboring cell can be obtained by any method as described for the transmission power information transmitted to each user communication device in the neighboring cell, as described in the invention of claim 6. Also good.
[0037]
  Claim 9In the invention described inClaim 8In the base station antenna directivity control apparatus according to CDMA cellular system described above, the transmission power for each user communication apparatus of the own cell is multiplied by the weighting function, and a value taking propagation loss into consideration is assigned to each user communication apparatus of the own cell. The transmission power from the base station of the neighboring cell for each user communication device of the neighboring cell is multiplied by the weighting function, and a value considering the propagation loss is multiplied by each user of the neighboring cell. A correlation matrix related to the received signal of each user communication device is generated assuming that the received power of the communication device is assumed, and the antenna weight for each antenna element is calculated and output for each user communication device that is the transmission partner It is.
  Therefore, an antenna directivity pattern considering the influence of distance can be easily realized.
DETAILED DESCRIPTION OF THE INVENTION
  FIG. 1 is a block diagram for explaining a first embodiment of a base station antenna directivity control apparatus in a CDMA cellular system according to the present invention.
  In the figure, the same parts as those in the conventional FIG. Reference numeral 13 denotes a desired wave estimator, which clearly shows what is included in the AAA receiver 11 in FIG.
  However, in the conventional configuration, as shown in FIG. 13 and FIG.₁~ 8_K, The direction of arrival estimation of all users in the same cell is performed redundantly.
  In contrast, in this embodiment, the user-specific processing unit 8₁~ 8_KEach estimate only the desired wave from the signal received from each user's mobile station. For example, the user-specific processing unit 8₁In the direction of arrival information θ₁And propagation path loss information L₁Are only estimated for the transmission weight calculation.
[0038]
Incoming wave estimation may be partially performed in the same way as the reception weight calculation process, and in this case, the process can be shared. As a result, the arrival wave estimation unit 13 can simplify the configuration of the desired wave estimation itself.
Alternatively, as indicated by a broken line in the figure, the AAA receiving unit 11 is not passed, or the AAA receiving unit 11 is passed through, and the output of the distributor 7, that is, the array antenna elements 4a to 4d. The received output is output to the desired wave estimator 13, where all processing for direction of arrival estimation may be performed only for the desired wave transmitted from the target user's mobile station. .
[0039]
The information management unit 14 includes a processing unit 8 for each user.₁~ 8_KDirection-of-arrival information θ output by the direction-of-arrival estimation unit 13 of each user₁, Θ₂, ... θ_KAnd propagation loss information L₁, L₂, ……, L_KAt the same time, the transmission rate information Ps for the mobile stations of the users 1 to K is stored as information related to base station transmission, which is held by components not shown of the base station 1._iTo list them. As described above, the information management unit 14 centrally manages the arrival direction information and the propagation loss information related to the communication device of each user, so that it is possible to generate an optimum beam pattern by using these information. .
For example, in the case of DS-CDMA, it is necessary to increase the transmission power as the transmission rate is increased. For the same modulation method, transmission power proportional to the transmission rate is required.
[0040]
Reference numeral 15 denotes a conversion unit which transmits transmission rate information Ps._iTransmit power information T_iIt is converted into (relative transmission power) and output to the transmission weight calculation unit 18. Direction of arrival information θ_i, Propagation loss information L_iIs output as is.
In the information management unit 14, the transmission rate information Ps_iInstead of this, information on the number of transmission channels may be managed. There is usually a correspondence between the number of transmission channels and transmission rate information. Alternatively, transmission power information T_iIs managed, the conversion unit 15 becomes unnecessary.
The transmission weight calculator 18 calculates the transmission weight and outputs it to the AAA transmitter 17.
[0041]
FIG. 2 shows all user-specific processing units 8 in FIG.₁~ 8_KIt is explanatory drawing which shows the weight calculation of the array antenna in FIG.
In the figure, the AAA receiver 11 and the transmission weight calculator 18 are given subscripts indicating the user.
The AAA receiver 11 includes the desired wave estimator 13 of FIG. Further, there is a case where the desired wave estimation unit 13 obtains the received signal of the array antenna element directly from the distributor 11. Reference numeral 22 denotes an information management unit, which combines the information management unit 14 and the conversion unit 15 of FIG.
[0042]
Transmission weight calculation unit 18 for each user₁~ 18_KAt first glance, the arrival direction information and the propagation loss information input to FIG. 12 seem to be input as the conventional information shown in FIG. 12, but in the embodiment of the present invention, the arrival direction information θ_iAnd propagation loss information L_i, Each of which is estimated with the highest accuracy as a desired wave that is reliably received with higher power than the interference wave.₁~ 8_KHave gained from. As a result, the accuracy of transmission weight calculation is improved.
[0043]
Here, the transmission weight w for each user's mobile station⁽¹⁾~ W^(K)A description of the calculation method is added. Basically, the literature calculation method shown in the prior art is used.
Direction of radio wave arrival θ from each mobile station at the base station 1 using an uplink signal_iAnd propagation loss L_iIs estimated.
Any radio wave arrival direction estimation method may be used. For example, a known method such as MUSIC or ESPRIT may be used. Any propagation path loss estimation method may be used.
[0044]
FIG. 3 is a conceptual diagram relating to an example of propagation loss estimation used in the first embodiment of the present invention. FIG. 3A shows the relationship between the transmission power of the base station, the reception power at the mobile station, and the propagation loss. FIG. 3B shows the transmission power of the mobile station, the reception power at the base station, and the propagation. It shows the relationship with loss.
In FIG. 3A, the propagation loss L_iIs the transmission power T of mobile station of user i at base station 1_miCan be easily estimated from the received power using the following relational expression.
[Expression 1]

As shown in FIG. 3B, the transmission power T from the base station 1_iWhen the mobile station receives the received power P_miThe same propagation loss L_iIt is.
[0045]
An array propagation vector (array direction vector) determined by the estimated signal arrival direction of user i's mobile station, downlink frequency, and array shape is v_i(For the array propagation vector, see Kikuma, “Adaptive signal processing by array antenna”, Science and Technology Publication (1998) p.30-31).
P_iIs the value assumed as the i-th user power, f_iIs the weighting function of the i-th user of the own cell and Pn is the thermal noise power, the correlation matrix R for weight calculation_xxThe
[Expression 2]

It is defined as
Here, the antenna weight w with the mobile station of user k as the transmission partner is_kThe
[Equation 3]

And give. R_xx ^-1Is R_xxRepresents the inverse matrix of.
[0046]
“Value assumed as i-th user power” P described above_iFor this, a value depending on parameters such as transmission power and propagation loss for the user i's mobile station of the base station 1 is used.
That is, P shown in FIG._mi(= T_i/ L_iAs shown in FIG. 3B, the estimated desired received power when the mobile station of the user i in the own cell is the transmission partner may be substituted from the base station, or the T shown in FIG._iAs described above, the value of the desired wave transmission power may be substituted from the base station 1 with the mobile station of the user i in the own cell as the transmission partner. Therefore, L obtained from the above equation (1)_iIs not necessarily required.
In general, when the k-th mobile station is a desired wave mobile station, P_iBy increasing the i-th user direction (i.e., θ_i) Can be intentionally provided with a directivity null.
[0047]
Meanwhile, f_iIs a weighting function, and details will be described later. Here, a simple example is shown. Interpreting document (2) cited in the description of the prior art, R_xxFor all users 1 to K using the array response vector and power,_iThis corresponds to the case of = 1. R_xxIs calculated using the array response vector and power of only the users that are fast on the downlink,_i= 1, f for low speed users_iThis corresponds to the case where = 0 is set.
[0048]
FIG. 4 is a block configuration diagram for explaining a second embodiment of the present invention.
In the figure, parts similar to those in FIGS. 12 and 1 are denoted by the same reference numerals and description thereof is omitted.
In this embodiment, a transmission weight is determined in consideration of interference with a mobile station of a user in a neighboring cell.
Reference numeral 31 denotes an arrival wave estimation unit from a mobile station in a neighboring cell, and 32 denotes an information management unit. It can be arbitrarily determined how far away from the own cell the mobile station of the neighboring cell is. It is also possible to determine the range of mobile stations to be collected in cell units, or to set the range of neighboring cells from the base station of the own cell to a mobile station at a predetermined distance.
[0049]
The arrival wave estimation unit 31 from the mobile station in the neighboring cell estimates the arrival direction of the incoming wave from the mobile station located in the neighboring cell and measures the received power. Using the estimated arrival direction value as arrival direction information, propagation loss information is obtained from the received power.
As a method for estimating an incoming wave received from each user communication device in a neighboring cell, for example, there is a method using known arrival direction estimation means such as MUSIC or ESPRIT from the antenna reception signal of the own cell.
[0050]
FIG. 5 is an explanatory diagram of an example in which the arrival wave estimation unit 31 from the mobile station in the neighboring cell shown in FIG. 2 extracts the incoming wave from the mobile station in the neighboring cell from the estimated arrival directions. It is. In the figure, the horizontal axis represents the arrival angle θ of the incoming wave, and the vertical axis represents the received power Pr of the incoming wave.
For example, all the arrival directions θ are estimated by scanning the main beam by the beam former method, and the power Pr in the arrival direction θ is measured. Among them, the AAA receiving unit 11 of the user 1₁-AAA receiver 11 of user K_KReceived power Pr of each desired wave obtained in₁, Pr₂, ..., Pr_KComponent (direction-of-arrival information θ₁, Θ₂, ……, θ_KThe incoming waves from the mobile stations in the neighboring cells are estimated for components other than the arrows (indicated by solid lines in the figure) (indicated by broken lines in the figure).
[0051]
Or after canceling the signal by the user in the own cell, the arrival wave can be estimated more accurately by using known arrival direction estimation such as MUSIC and ESPRIT. That is, the received power Pr₁, Pr₂, ..., Pr_K(Direction of arrival information θ₁, Θ₂, ……, θ_K) And the desired data (received power Pr) based on the user's cell restoration data, etc.₁, Pr₂, ..., Pr_K, Direction of arrival information θ₁, Θ₂, ……, θ_K) Generates a replica of the received signal when output from the RF receiver 21 (in FIG. 1, RF receivers 6a to 6d). Next, known direction-of-arrival estimation such as MUSIC and ESPRIT may be performed on the signal obtained by subtracting the replica from the output of the RF receivers 6a to 6d (for example, Kitahara et al. “DS-CDMA system in a multi-user environment”). Adaptive Array Antenna for Downlink "RCS99-216 (2000))
[0052]
Referring to FIG. 5, the received power Pr of each desired wave shown in the figure.₁, Pr₂, ..., Pr_KComponent (direction-of-arrival information θ₁, Θ₂, ……, θ_KThis means that the arrival wave estimation is performed again for the power from which the power indicated by the solid line in FIG.
That is, since the arrival wave estimation is performed for the one from which the arrival wave of the mobile station of the own cell user is removed, the total number of arrival waves that need to be estimated is reduced, so the arrival wave information estimation accuracy by the array antenna is reduced. improves.
[0053]
The arrival wave estimation unit 31 from the mobile station in the neighboring cell is the mobile station in the neighboring cell (the mobile station is from user 1 to user M. It is not necessary to distinguish which mobile station is in the neighboring cell). Direction-of-arrival information θ^Δ ₁, θ^Δ ₂, ……, θ^Δ _M, Received power information Pr^Δ ₁, Pr^Δ ₂, ..., Pr^Δ _MIs output to the information management unit 32. At that time, in the illustrated example, the received power information Pr^Δ ₁, Pr^Δ ₂, ..., Pr^Δ _MPropagation loss information L^Δ ₁, L^Δ ₂, ……, L^Δ _MIt is managed by replacing with.
The information management unit 32 also manages transmission rate (number of transmission channels) information for mobile stations (users 1 to M) in neighboring cells. This transmission rate is the downlink transmission rate from the base station of the cell in which this mobile station is located.
This transmission rate (number of transmission channels) information is transmitted power information T^Δ ₁, T^Δ ₂, ……, T^Δ _MInformation management may be performed by converting the information into the transmission power information, or may be converted into transmission power information after the information management.
[0054]
The transmission power information of the transmission signal transmitted from the neighboring cell base station to each user communication device in this neighboring cell is estimated from information such as the received power and the cell radius at the base station 1 of the own cell, or determined in advance. The reference transmission power value of the mobile station is managed. When this transmission power information does not specify which mobile station of which neighboring cell has transmitted, such as the reference transmission power value, the incoming wave information and its Since it is not possible to correlate with transmission power information, it is not necessary to specify which mobile station of which neighboring cell is arriving when using a known direction of arrival estimation such as MUSIC or ESPRIT. It is only necessary to know that there is an incoming wave of a certain received power from the direction.
[0055]
Further, when the base station 1 has a function capable of collecting transmission rate information (number of channels) or transmission power information of transmission signals transmitted from the base station of the neighboring cell to each user communication device of the neighboring cell. In the estimation of the incoming wave, the mobile station from which mobile station of which neighboring cell is identified by some method, and the incoming wave information is associated with the transmission power information of the transmission signal described above. What should I do?
In order to identify which mobile station of which neighboring cell is the incoming wave when estimating the incoming wave, for example, each user communication device of the neighboring cell uses it for transmission from the base station of the neighboring cell. What is necessary is just to acquire a spreading code and to acquire the positional information of each user communication apparatus of a periphery cell.
[0056]
When an adaptive array antenna is operated, phase information (direction of arrival) is more dominant than amplitude information, and therefore it is sufficient that at least phase information (direction of arrival) can be accurately estimated.
The information management unit 32 also weights the mobile station of the users 1 to K in its own cell.₁~ F_K, And the weighting function f for the mobile station of neighboring cell users^Δ ₁~ F^Δ _MYou may manage.
[0057]
Next, how to determine the transmission weight (downlink) weight for each user's mobile station in the own cell by estimating the arrival waves from the own cell and neighboring cell mobile stations will be described. Basically, the calculation method of document (2) shown in the prior art is used.
Direction of radio wave arrival θ from each mobile station at the base station 1 using an uplink signal_iAnd propagation loss L_iIs estimated. Any method may be used for radio wave arrival direction estimation and propagation loss estimation.
[0058]
FIG. 6 is a conceptual diagram relating to an example of propagation loss estimation means used in the second embodiment of the present invention. 6A shows the relationship between the transmission power of the base station, the reception power at the mobile station, and the propagation loss. FIG. 6B shows the transmission power of the mobile station, the reception power at the base station, and the propagation. It shows the relationship with loss.
The concept of transmission weight calculation described with reference to FIG. 3 is extended to neighboring cells. The user i of the own cell uses the subscript i (i = 1 to K), and the user of the surrounding cell uses the subscript j (j = 1 to M) to distinguish.
[0059]
Propagation loss L_iAs for the estimation method, the transmission power T of the mobile station of the user i of the own cell in the base station 1_miCan be used to determine the received power P using the following relational expression:_riCan be easily obtained.
[Expression 4]

The mobile station 42 of the user j of the neighboring cell (j represents the user of the neighboring cell) can also be easily obtained from the received power using the same relational expression. In this case, it is the power received by the base station 1 as an interference wave from a neighboring cell.
[Equation 5]

An array propagation vector (array direction vector) determined by the estimated signal arrival directions of i-th and j-th users, downlink frequency, and array shape is v._i, V_jIt expresses.
[0060]
P_iIs the “assumed value for the i-th user power” of its own cell, f_iThe weighting function of the i-th user of the own cell, P_jIs the “assumed value for the j-th user power” of the neighboring cell, f_jIs the weighting function of the j-th user of the neighboring cell, and Pn is the thermal noise power, the correlation matrix R for weight calculation_xxThe
[Formula 6]

It is defined as
Here, the antenna weight w of the kth user (k is a user in the own cell)_kThe
[Expression 7]

And give. R_xx ^-1Is R_xxRepresents the inverse matrix of.
[0061]
“Value to be assumed as the i-th user power” P of the own cell mentioned above_iIn FIG. 6 (b), P_mi(= T_i/ L_i) Is substituted.
On the other hand, “value assumed as the j-th user power” P of the neighboring cell_jIncludes P shown in FIG._mj(= T_j/ L_j) Is substituted. Where L_jIs a propagation loss between the base station 1 and the mobile station 42 of the user j in the neighboring cell, and T_jIs a value of transmission power when the base station 41 of the neighboring cell transmits the mobile station 42 of the user j of the neighboring cell as the transmission partner.
The base station 1 actually uses the mobile station 42 of the user j in the neighboring cell as the transmission partner, and transmits the transmission power T_jIn this case, the received power value received by the mobile station 42 of the user j in the neighboring cell is calculated and used.
In addition, T shown in FIG._iAs described above, the value of the desired wave transmission power may be substituted from the base station 1 with the mobile station of the user i in the own cell as the transmission partner. Therefore, L obtained from the above equation (4)_iIs not necessarily required. Similarly, the T shown in FIG._jAs described above, the value of the desired wave transmission power may be substituted from the base station 41 of the neighboring cell to the mobile station 42 of the user j in the neighboring cell. Therefore, L obtained from the above equation (5)_jIs not necessarily required.
[0062]
P in equation (6)_i, P_jAnd P in equation (7)_kRepresents the degree of influence on the i, j, and kth users in determining the transmit antenna directivity of the kth user, respectively. In general, if the mobile station of user k in its own cell is the desired wave mobile station, P_i(I ≠ k), P_jCan be intentionally directed toward the mobile station 42 of the user i in the own cell and the mobile station 42 of the user j in the neighboring cell.
Meanwhile, f_i, F_jIs a weighting function, for example f_jBy putting a positive value other than 0 in, interference with neighboring cells can be taken into consideration. Especially when you want to greatly suppress interference to neighboring cells,_jA large value should be put into.
[0063]
Next, the weighting function f described above_i, F_jWill be described in detail.
As already described, short-term fluctuations and instantaneous fluctuations are not considered, but propagation loss due to the distance between the base station 1 and the mobile station is considered as propagation loss information.
That is, the distance between base station 1 and user i's mobile station is r_iThen, the received power fluctuation E (r_i) Is determined by the following equation.
E (r_i) = Ar^{- α}          (8)
Here, A is a constant determined by transmission power and the like, and α is a propagation constant. The standard value of the propagation constant α in an urban area is α = 3.5.
Therefore, the propagation loss information L described above_iIs basically expressed as:
L_i= Br^α              (9)
B is a constant.
[0064]
However, according to the simulation described at the end, the above-described propagation loss information L_iIt was found that the influence of interference on a mobile station far away is large only by considering the above. Therefore, the distance r from the base station_iFor the mobile station of user i at_iIs defined as follows.
f_i= R_i ^γ  (Γ> 0) (10)
Note that the information management unit 32 shown in FIG._jInstead of f_i ^ΔIs the same function.
Weighting function f for equation (10)_iIs the propagation loss information L_iSame distance r_iTherefore, when estimating the propagation path loss, the propagation loss information L_iIn the same manner as above, it is estimated from the received power information Pr. Or, propagation loss information L_iTo r_iCan also be calculated.
[0065]
In FIG. 4, the weighting function f_i, F_jIt is not described in which block to calculate. Although it depends on the content of the weighting function to be set, it is calculated once for each user and stored in the information management unit 32. Alternatively, it can be obtained immediately before the weight calculation.
Alternatively, as illustrated in FIG. 1, a weighting unit is provided after the conversion unit 15 to provide a weighting function f._i, F_jAnd the user-specific processing unit 8₁~ 8_KMay be output to the transmission weight calculator 18.
However, in the case of using a distance function or an arrival direction function as shown in Equation (10), a method of calculating a weighting function by obtaining a distance using a block for estimating an incoming wave is possible.
[0066]
This function works so that the received power increases as the mobile station is farther from the base station. That is, it acts to suppress interference of mobile stations farther from the base station than mobile stations closer to the base station.
Therefore, especially when considering mobile stations in neighboring cells, this weighting function f_i ^ΔIt is effective to introduce However, the present invention can also be applied to the first embodiment described with reference to FIGS.
[0067]
The above-mentioned propagation loss information L_iAnd set it as one set
f_i/ L_i= Br_i ^{γ - α}  (Γ> 0) (11)
It becomes.
Therefore, Equation (12) can be newly set as propagation loss information.
It should be noted that the weighting function f in the above equations (11) and (12)_i, F_i ^ΔIs just an example, and f_i, F_i ^ΔAny other characteristic function may be used as long as a better result can be obtained than when = 1.
[0068]
FIG. 7 is a block configuration diagram for explaining a third embodiment of the present invention. In the figure, parts similar to those in FIGS. 12 and 1 are denoted by the same reference numerals and description thereof is omitted.
This embodiment is a modification of the configuration of the embodiment described with reference to FIG. 1 to FIG. 3, and reduces the amount of interference by reducing the number of interfering users considered for transmission weight calculation. Is to improve.
Reference numeral 51 denotes a selection unit.₁, 51₂, ......, 51_KIs the selection part of users 1, 2, ... K. Each selection unit naturally selects information on an incoming wave (desired wave) corresponding to each user, and in addition, selects information on an incoming wave corresponding to another user for interference wave suppression.
[0069]
At that time, the number of incoming wave information is narrowed down to Ks (Ks ≦ K) including the desired wave. Therefore, the degree of freedom of array antenna beam control during transmission increases. As a result, the interference amount reducing effect is increased. Although narrowing is not performed when Ks = K, depending on the situation, it may be possible to select the arriving wave (desired wave + interference wave) of all users without performing narrowing. Then, assuming such a case, Ks = K.
For example, if the number of incoming waves Ks to be selected is reduced to less than the degree of freedom of the array antenna, a beam null can be directed to a mobile station that gives an interference wave.
[0070]
Since the number of users K is usually much greater than the degree of freedom of the array antenna, a criterion for narrowing down information on interference waves to be selected for interference wave suppression is necessary.
The first method for narrowing down interference waves is to select (Ks−1) pieces of mobile station information of users with high base station transmission power (high-speed rate receiving users) in order from the top. Using these pieces of information, when a beam pattern that generates nulls is generated for (Ks-1) high-rate receiving users when transmitting a main lobe toward a low-speed receiving user on the downlink, Interference for rate receiving users is reduced.
As a result, it is possible to reduce the transmission power when transmitting the main lobe toward the high-rate receiving user, and as a result, when transmitting the main lobe toward the high-rate receiving user, the interference to the low-rate receiving user. Is reduced.
[0071]
The second method for narrowing down interference waves is the reverse of the first method described above. In this example, (Ks−1) pieces of mobile station information of interference users (low-rate receiving users) having low base station transmission power are selected in order from the lower order.
When using these pieces of information to generate a beam pattern that generates nulls for (Ks-1) low-rate rate receiving users when transmitting a main lobe toward a downlink high-rate receiving user, Interference to rate receiving users is directly reduced.
In any case, by narrowing down the number of interference waves to be considered, the beam null can be directed in a desired direction, and the effect of interference wave suppression is enhanced.
[0072]
The third method of narrowing down interference waves is to collect the incoming waves used for calculation for the arrival angles of a large number of incoming waves received by the base station.
FIG. 8 is a principle explanatory view of a third method for narrowing down interference waves used for calculation in the third embodiment shown in FIG. Assuming that 10 users are communicating simultaneously, the selection unit 51 of the user 10 will be described as an example.
FIG. 8A is a diagram showing the arrival angle and received power of an incoming wave managed by the information management unit 22. Let θ ′ be the angle of arrival of the incoming wave from user i_i, Receive power P '_iAnd i = 10 relates to the reference wave for the user 10, and i = 1 to 9 are received as interference waves for the user 10.
[0073]
Here, when the entire range of the arrival angle θ is divided by Δθ and there are a plurality of interference waves in the divided small section, the adjacent arrival waves in the small section are gathered together to form one interference wave. By selecting the replacement, the number of incoming wave information is reduced and used for transmission weight calculation.
As a grouping method, for example, there are methods shown in FIGS. 8B, 8C, and 8D. Hereinafter, the arrival angle and received power of one interference wave selected by replacement are expressed as (θ₁, P₁), (Θ₂, P₂), (Θ_Three, P_Three), (Θ_Four, P_Four) ...
[0074]
In any case, the selected received power P₁, P₂, P_ThreeIs the sum of received power in each small section, as shown in the figure. That is,
P₁= P '₁+ P '₂+ P '_Three
P₂= P '_Four
P_Three= P '_Five+ P '₆+ P '₇
P_Four= P '₈+ P '₉
[0075]
In FIG. 8B, the arrival angle θ of the selected interference wave is the arrival angle of the path (arrival wave) with the maximum received power in each small section. That is,
θ₁= Θ '₂, Θ₂= Θ '_Four, Θ_Three= Θ '₇, Θ_Four= Θ '₉
In FIG. 8C, the arrival angle θ of the selected interference wave is set as an arrival angle that is weighted and synthesized using the received power in each small section as a weight. That is,
θ₁= (P '₁θ '₁+ P '₂θ '₂+ P '_Threeθ '_Three) / (P '₁+ P '₂+ P '_Three)
θ₂= Θ '_Four
θ_Three= (P '_Fiveθ '_Five+ P '₆θ '₆+ P '₇θ '₇) / (P '_Five+ P '₆+ P '₇)
θ_Four= (P '₈θ '₈+ P '₉θ '₉) / (P '₈+ P '₉)
In FIG. 8D, the arrival angle θ of the selected interference wave is the median value of each small section. That is, if the arrival angle on the vertical axis is 0,
θ₁= (1/2) Δθ, θ₂= (3/2) Δθ, θ_Three= (5/2) Δθ, θ_Four= (7/2) Δθ
[0076]
In the interference wave narrowing-down method described above, the interference power may not be selected unless the interference power is not less than a predetermined threshold determined according to the average power or the like. In this case, when the received power of a desired wave from a certain user is less than or equal to this threshold, depending on the narrowing down method and the distribution of received power at that time, the value of this user's interference wave selection number Ks may vary. May be different from the value of the number of selected interference waves Ks.
[0077]
FIG. 9 is a block configuration diagram for explaining a fourth embodiment of the present invention. In the figure, the same parts as those in FIGS. 12, 1, 4, and 7 are denoted by the same reference numerals, and description thereof is omitted.
This embodiment is a modification of the configuration of the embodiment described with reference to FIGS. 4 to 6, and similarly to FIG. 7, the number of information of interference users to be considered in the transmission weight calculation is set. By reducing this, the effect of reducing the amount of interference is increased.
That is, from the (K + M) including the incoming waves from the neighboring cell users, only Ks pieces of incoming wave information including the desired wave are selected for the transmission weight calculation.
Selection criteria are the same as in FIG. Further, when the third method is adopted, the arrival angles of the incoming waves as illustrated in FIG. 8 can be summed up.
[0078]
FIG. 10 is a diagram for explaining a simulation result for evaluating the effect of interference wave suppression by considering mobile stations in neighboring cells. Although it does not represent the result of carrying out the present invention, the expected effects can be estimated by applying the present invention.
The cell configuration is a regular hexagonal cell with a cell radius of R [km]. Mobile stations are uniformly distributed within the cell. Considering only the distance fluctuation as the propagation fluctuation, the propagation constant α is set to 3.5. The array antenna configuration is a linear array antenna, and the antenna element is omnidirectional.
[0079]
Intersymbol interference is 0 if the spreading codes are completely orthogonal, but if the orthogonal relationship is broken, interference of 1 / PG (PG: spreading factor) occurs. In general, radio waves transmitted from the same base station maintain an orthogonal relationship and have zero interference. However, if there is a propagation delay wave, the orthogonal relationship between the spreading codes is lost, causing interference.
For simplicity, the interference rate (hereinafter referred to as non-orthogonal coefficient) is defined as β and used. That is, the amount of interference is β / PG. On the other hand, signals transmitted from different base stations generally do not maintain an orthogonal relationship and thus cause 1 / PG interference.
[0080]
(1) Classify the number of mobile stations in each cell into two transmission rate mobile station groups (high-speed transmission mobile station group and low-speed transmission mobile station group), and determine the transmission power. Subsequently, the position of the mobile station is determined for each cell with a uniform random number.
(2) In the base station, it is assumed that the arrival direction and propagation loss of each mobile station can be ideally estimated on the base station side. Based on the estimated information, the downlink transmission power is converted and the weighting function is added according to the transmission rate for each mobile station, an array vector is created, and an antenna pattern is obtained.
(3) Each mobile station obtains desired signal power and interference signal power based on the downlink antenna pattern, transmission power, and propagation loss. The interference wave power is the total power of the interference wave of the own cell (total number of users in the cell −1) and the interference wave from other cells (total number of users in the cell × number of other cells). Is calculated taking into account the non-orthogonal component β / PG and 1 / PG (β = 1) for interference waves of other cells.
The trials (1) to (3) are repeated, and the distribution of the desired signal power to interference signal power ratio CIR is obtained. However, the evaluation was performed only for the mobile station of the central cell where the interference is most severe.
[0081]
The simulation conditions are as follows. Paying attention to the allocated frequency of the 3rd generation mobile communication in Japan, when the antenna element spacing d is set to λ / 2 with respect to the uplink carrier frequency, the downlink carrier frequency is about 0.55λ. The number of antenna elements is 8, and the number of mobile stations in each cell is 20. Although not illustrated here, the number of high-speed transmission mobile stations is set to 5 and the number of low-speed transmission mobile stations is set to 15 particularly when the transmission speed is taken into consideration. The transmission power of the high-speed transmission mobile station group is set to 15 dB higher than that of the low-speed transmission mobile station group.
[0082]
Evaluation is compared with the method shown below.
(i) Method using antenna weight calculated in uplink as downlink weight (downlink COPY method)
(ii) Assuming that the radio wave arrival direction and propagation loss of each mobile station can be completely estimated, a method of calculating the optimum antenna weight (downlink optimal method) by correcting the transmission power of the downlink. That is, f_i= 1 (γ = 0).
(iii) For reference, f_i= 1 (γ = 0) and the case of time division multiple access TDD (TDD method) with the same transmission / reception carrier frequency is also shown.
[0083]
FIG. 10 (a) shows the cumulative distribution of the desired wave power to interference wave power ratio CIR / PG when the exponent γ of the weighting function is used as a parameter.
However, all mobile stations belong to the group of low-speed transmission mobile stations, and the non-orthogonal coefficient β is β = 0.4. For example, when the 20% value of the cumulative probability is compared, a large CIR / PG improvement is obtained at γ = 3.5-5. For example, if γ = 3.5, it can be seen that the proposed method can greatly improve CIR / PG compared to the downlink COPY method and the downlink optimal method (equivalent to the case of γ = 0).
[0084]
By the way, the result mentioned above was a simulation result when the arrival direction and propagation loss of all the mobile stations are known. However, when the arrival directions and propagation losses of all mobile stations are known, it is not always realistic. In view of this, the evaluation was limited to the range in which the mobile station arrival direction and propagation loss information can be obtained.
FIG. 10B shows the cumulative distribution of CIR / PG when the range Rth in which mobile station information can be obtained is 1, 1.2, 1.5 times the cell radius R, and ∞. However, all mobile stations are assumed to belong to the group of low-speed transmission mobile stations, and the exponent part of the weighting function is γ = 3.5 and the non-orthogonal coefficient is β = 0.4.
[0085]
As can be seen from this diagram, the CIR / PG is improved as the range Rth in which the mobile station information can be obtained is increased. For example, when compared with the 20% value of the cumulative probability, the proposed method has an improvement of about 3 dB at Rth = R and about 5 dB at Rth = 1.2R compared to the downstream COPY method. Compared with the TDD method, an improvement effect of about 1 dB is obtained at Rth = 1.2R.
Although not shown, the proposed method can significantly improve CIR / PG compared to the conventional method even when a high-speed transmission mobile station and a low-speed transmission mobile station coexist.
When Rth = R, the range is almost the range of the own cell. However, since the own cell is a regular hexagonal cell with one side being R, a part of the influence of the mobile station in the peripheral cell is included.
[0086]
In the above description, calculation of the transmission array antenna weight in the downlink direction from the base station has been described. However, what is necessary is just to control the beam pattern of the array antenna to have a desired characteristic by performing the arrival wave estimation.
In the present invention, there are no particular restrictions on the shape of the array antenna and the polarization to be handled. There are no particular restrictions on the number of array antenna elements and the element spacing. Further, it can be applied to both the FDD method and the TDD method.
In the above description, the base station antenna directivity control apparatus in the CDMA cellular system configured with a plurality of cells has been described. However, the present invention can also be used for a base station antenna directivity control apparatus in a CDMA system in which a plurality of mobile stations exist in one independent cover area. Further, even in the CDMA cellular system, when the influence of the mobile station in the neighboring cell is not taken into consideration, it is substantially the same as the base station apparatus in the CDMA system described above.
[0087]
【The invention's effect】
As is clear from the above description, according to the present invention, the optimum transmission weight for a plurality of antenna elements is improved by improving the estimation accuracy of interference waves or considering the influence of interference waves from neighboring cells. There is an effect that can be accurately calculated.
Further, by considering the degree of influence of the interference wave on the distance, there is an effect that the optimum transmission weight for the plurality of antenna elements can be accurately calculated.
The optimum transmission weight for the antenna device having a plurality of antenna elements improves the effect of suppressing the amount of interference more than before. As a result, there is an effect that the number of users that can be accommodated in the cell is increased and the frequency utilization rate is improved.
[Brief description of the drawings]
FIG. 1 is a block configuration diagram for explaining a first embodiment of a base station antenna directivity control apparatus in a CDMA cellular system according to the present invention;
2 is an explanatory diagram showing array antenna weight calculation in all user-specific processing units in FIG. 1; FIG.
FIG. 3 is a conceptual diagram relating to an example of propagation loss estimation used in the first embodiment of the present invention.
FIG. 4 is a block configuration diagram for explaining a second embodiment of the present invention;
5 is an explanatory diagram of an example in which the arrival wave estimation unit from the mobile station in the neighboring cell shown in FIG. 2 extracts the incoming wave from the mobile station in the neighboring cell from a plurality of estimated arrival directions. is there.
FIG. 6 is a conceptual diagram related to an example of propagation loss estimation used in the second embodiment of the present invention.
FIG. 7 is a block configuration diagram for explaining a third embodiment of the present invention;
FIG. 8 is a principle explanatory view of a third method for narrowing down interference waves used for calculation in the third embodiment shown in FIG. 7;
FIG. 9 is a block configuration diagram for explaining a fourth embodiment of the present invention;
FIG. 10 is a diagram showing simulation results for evaluating the effect of interference wave suppression by considering mobile stations in neighboring cells.
FIG. 11 is an explanatory diagram showing an example of a CDMA cellular mobile communication system using an adaptive array antenna.
FIG. 12 is a block diagram for explaining an example of a base station antenna directivity control apparatus in a conventional CDMA cellular system.
FIG. 13 is a block diagram schematically illustrating weight calculation of a conventional adaptive array antenna using direction-of-arrival estimation.
14 is an explanatory diagram of transmission weight calculation in all the user-specific processing units in FIG. 12. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Base station, 2 ... Mobile station of user 1 3 ... Mobile station of user 2 4a-4d ... Array antenna element, 8₁~ 8_KProcessing unit for each user, 11: AAA (adaptive array antenna) receiving unit, 13: Desired wave estimation unit, 14, 22, 32 ... Information management unit, 15 ... Conversion unit, 17 ... AAA transmission unit, 18 ... Transmission weight calculation , 21 ... RF receiver, 41 ... base station of neighboring cell, 42 ... mobile station of neighboring cell user 1, 51 ... selecting unit

Claims (9)

By using an antenna device having a plurality of antenna elements, the communication from the base station to each user communication device and the communication from each user communication device to the base station are different between a plurality of user communication devices in the own cell. A base station antenna directivity control apparatus in a CDMA system for performing communication using the same antenna element at a frequency,
The against the received signal of the plurality of a plurality of systems received by the antenna element of the own cell, performs inverse spread by the spreading code of each user, a reception signal of a plurality of systems of despread for each user obtained result used, the estimate of the arrival wave information of a desired wave of each user in the own cell, and the desired wave estimation means for outputting an incoming wave information for each user communication device the free-cell, a plurality of antenna elements of the own cell Estimating the arrival wave received from each user communication device of the neighboring cell based on the received signals of the plurality of systems received in step, and neighboring cell arrival wave estimation for outputting the arrival wave information regarding each user communication device of the neighboring cell Means, arrival wave information regarding each user communication device of the own cell, transmission power information of a signal transmitted to each user communication device of the own cell, and arrival of each user communication device of the neighboring cell Information management means for managing wave information and transmission power information of a transmission signal transmitted from the base station of the neighboring cell to each user communication device of the neighboring cell, information on each user communication device of the managed own cell, and The directional gain to the user communication device of the own cell serving as a transmission partner is large using information on the managed user communication devices of the neighboring cell, and the other user communication device and the neighboring cell of the own cell. The antenna weight for each antenna element of the own cell is calculated and output for each user communication device of the own cell as the transmission partner so as to generate a beam pattern that reduces the directivity gain for the user communication device of A base station antenna directivity control apparatus in a CDMA system.   The desired wave estimation means estimates only the arrival direction of the desired wave and outputs only arrival direction information as arrival wave information related to each user communication device, and the neighboring cell arrival wave estimation means 2. The CDMA cellular system according to claim 1, wherein only the direction of arrival of an incoming wave is estimated and only the direction of arrival information is output as arrival wave information related to each user communication device of the neighboring cell. Base station antenna directivity control device.   The information management means uses the incoming wave information and the transmission power information regarding the user communication device of the own cell that is the transmission partner, and other user communication devices of the own cell and user communication devices of the neighboring cells. The base station in the CDMA cellular system according to claim 1, further comprising information selection means for narrowing down the incoming wave information and the transmission power information and outputting the information to the antenna weight output means Antenna directivity control device.   The information selection means determines the number of the arrival wave information by combining the arrival wave information from other user communication devices of the own cell and the user communication devices of the neighboring cells by combining the arrival wave information close to each other. The transmission power information is synthesized according to the synthesized arrival wave information, and the arrival direction information related to the synthesized arrival wave information and the synthesized transmission power information are 4. The base station antenna directivity control device in the CDMA cellular system according to claim 3, wherein the base station antenna directivity control device is output as information relating to another user communication device of a cell and a user communication device of a neighboring cell.   Reception that outputs reception information by calculating a reception weight for each antenna element for each user communication device of the own cell that is a reception partner based on a plurality of received signals received by a plurality of antenna elements of the own cell 5. The desired wave estimation means estimates the desired wave received from each of the user communication devices using a midway calculation result in the receiving means. The base station antenna directivity control apparatus in the CDMA cellular system according to any one of the above.   Using the antenna device having a plurality of antenna elements, the same carrier frequency between the plurality of user communication devices and the communication from the base station to each user communication device and the communication from each user communication device to the base station, the same A base station antenna directivity control apparatus in a CDMA system for performing communication using an antenna element, wherein arrival direction information, propagation loss information, transmission power information, and distance from the base station regarding each user communication apparatus are Using a weighting function that increases the weighting of each user communication device as the distance from the base station for reducing the interference to each user communication device increases as the distance increases, directs the user communication device to be a transmission partner. Each antenna is generated so as to generate a beam pattern that has a large directivity gain and a small directivity gain with respect to the other user transmitters. The antenna weight for Na element, the transmission calculates and outputs for each user communication device as a counterpart, that the base station antenna directivity control apparatus in a CDMA system characterized by.   Multiply the transmission power for each user communication device by the weighting function, and consider a value considering propagation loss as a reception power assumption value for each user communication device to generate a correlation matrix for the received signal of each user communication device 7. The base station antenna directivity control apparatus in the CDMA system according to claim 6, wherein an antenna weight for each antenna element is calculated for each user communication apparatus that is a transmission partner.   By using an antenna device having a plurality of antenna elements, the communication from the base station to each user communication device and the communication from each user communication device to the base station are different between a plurality of user communication devices in the own cell. A base station antenna directivity control apparatus in a CDMA cellular system for performing communication using the same antenna element at a frequency, wherein the direction-of-arrival information, propagation loss information, transmission power information, and neighboring cells for each user communication apparatus of the own cell Direction-of-arrival information, propagation loss information, transmission power information about transmission power transmitted from the neighboring cell base station to each user communication device of the neighboring cell, and distance from the base station of the own cell The distance from the base station for reducing the interference given to each user communication device of the own cell and each user communication device of the neighboring cell, Using a weighting function that increases the weight of each user communication device as the distance increases, the directivity gain to the user communication device of the own cell that is the transmission partner is large, and the other user communication devices of the own cell and the periphery The antenna weight for each antenna element is calculated and output for each user communication device of the own cell that is the transmission partner, so as to generate a beam pattern that reduces the directivity gain for the user communication device of the cell, A base station antenna directivity control apparatus in a CDMA cellular system. The transmission power for each user communication device of the own cell is multiplied by the weighting function, a value considering propagation loss is regarded as a reception power assumed value of each user communication device of the own cell, and each user of the neighboring cell The transmission power from the base station of the neighboring cell to the communication device is multiplied by the weighting function, and a value considering the propagation loss is regarded as a reception power expected value of each user communication device of the neighboring cell and received by each user communication device. 9. The base station in the CDMA cellular system according to claim 8, wherein a correlation matrix for a signal is generated, and an antenna weight for each antenna element is calculated and output for each user communication device as a transmission partner. Station antenna directivity control device.

Images