多輸入/輸出正交分頻多工與多輸入/輸出多載波分碼多重進接系統之電腦模擬與效能鑑定

Abstract

這篇論文使用電腦模擬來評估以正交分頻多工為基礎的蜂巢系統。模擬的系統應用空間多重傳輸來增加頻譜使用效率。對於多輸入/輸出正交分頻多工系統，我們模擬一個經過改良的V-BLAST偵測技術和迴旋編碼的通訊系統。至於多輸入/輸出多載波分碼多重進接系統，我們使用一種遞迴式多層級偵測技術。我們使用一種簡單的適應性最小平均平方誤差等化器和層級式天線干擾消除概念來減輕天線間的相互干擾並得到初始的資料偵測。接著藉由多路徑干擾消除技術達到空間分集及多重路徑分集的目的。我們也對這兩種系統的錯誤率效能以及複雜度做分析比較。模擬結果顯示在高訊號雜訊比時多輸入/輸出正交分頻多工系統有較好的表現，而在低訊號雜訊比時則是多輸入/輸出多載波分碼多重進接系統表現較佳。以行動台的所在位置來考量路徑損失和遮蔽衰減，模擬系統所處的蜂巢環境。運用電腦模擬來計算訊號干擾比的分佈。我們也驗證了用高斯訊號模擬干擾訊號的可靠性。

This paper addresses cellular systems based on orthogonal frequency division multiplexing (OFDM). The simulated systems apply spatial multiplexing to increase spectral efficiency. For MIMO-OFDM system, we simulate a communication system based on modified V-BLAST detections and convolutional encoding. For MIMO MC-CDMA systems, we use a multi-layered detection method. We use a simple adaptive MMSE equalizer followed by a layered antenna interference cancellation technique to suppress the inter-antenna interference and obtain initial decision results. Afterwards, a multipath interference cancellation is exploited to fully achieve both spatial diversity and multipath diversity. We also investigate and compare the error performances and complexity of these two systems. Simulation results show that MIMO-OFDM systems have better performance at high SNR while MIMO MC-CDMA systems perform better at low SNR. The systems are then situated in a cellular structure whereas the cellular environment model takes into account path loss and shadowing depending on the position of the mobile station. Computer simulations are used to calculate the distributions of signal-to-noise ratio. We also show that the Gaussian approximation for interference signals is an appropriate assumption.