Effect of space-time transmit diversity on orthogonal multi-code DS-CDMA
نویسندگان
چکیده
あらまし 直交マルチコード DS-CDMA は,コード多重数を可変にすることで低速から高速までフレキシブルに 伝送レートを変化させることができるのが特徴である.しかし,周波数選択性の強いチャネルにおいては拡散符号 間の直交性の崩れによりビット誤り率(BER)特性が大きく劣化してしまう.周波数領域等化はこのような伝搬路の 周波数選択性を低減し,伝送特性を改善させることができる.送信ダイバーシチ技術はさらなる特性改善に有効で ある.本論文では最小平均二乗誤差合成(MMSEC)等化と開ループ型送信ダイバーシチを組み合わせることを考え, 遅延送信ダイバーシチ(DTD)と時空間符号化送信ダイバーシチ(STTD)を考えている.STTD については,周波数領 域で復号する時空間符号化を提案している.周波数選択性フェージング環境下での BER 特性を計算機シミュレーシ ョンにより求め,周波数領域 STTD はチャネルの周波数選択性の強弱にかかわらず BER 特性を大幅に改善できるこ とを示した.
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تاریخ انتشار 2004