具加強干擾消除能力之空-時多載波分碼多重進接接收器

Abstract

在未來的無線通訊系統中最重要的需求為高速傳輸。然而，通道的多路徑衰退現象會限制系統的傳輸速率。多載波 (multi-carrier) 傳輸為一種可有效對付頻率選擇性衰退之技術，可用來克服上述的問題。在本論文中，吾人考慮一種新的多重進接技術，此技術結合了多載波傳輸及分碼多重進接，成為所謂之多載波分碼多重進接 (MC CDMA) 系統。此種技術可分為兩種類型：第一種為在頻域上傳送展頻碼，另一種則是在時域上傳送展頻碼。吾人針對此兩種不同之多載波分碼多重進接系統提出陣列天線接收器 (antenna array receiver) 架構。陣列天線接收器可提供額外的空間多重進接，並可有效地降低其它使用者的干擾。此乃一種能有效解決近-遠問題 (near-far problem)，並提升整個系統容量的方法。吾人更進一步提出多階平行干擾消除演算法 (MPIC) 及傳送功率控制 (TPC) 兩種不同的方法來解決其他使用者所造成的多重進接干擾 (MAI)。由電腦模擬結果顯示，在強干擾的環境下，吾人所提之空-時多載波分碼多重進接接收器，其效能明顯優於傳統之時域接收器。

A major requirement in future advanced wireless communication systems is high transmission data rate. Unfortunately, multipath fading limits a system's transmission rate. To mitigate this problem, the multi-carrier (MC) transmission scheme is proposed which is robust to frequency selective fading. In this thesis, we consider a new multiple access technique based on a combination of code-division multiple access (CDMA) and MC transmission, called MC CDMA system. The proposed technique can be categorized into two types: one spreads across frequency domain, and the other spreads across time domain. We then propose an adaptive antenna array receiver for the two types of MC CDMA systems. The antenna array receiver provides an extra dimension for space division multiple access (SDMA), which can be used to reduce the interference from other users. This makes it an effective remedy for overcoming the near-far problem and potential solution for increasing the capacity. Furthermore, we propose a scheme of multistage parallel interference cancellation (MPIC) and transmission power control (TPC) methods to reduce the multiple access interference (MAI) from other users. From simulation results, we demonstrate that the proposed space-time receiver outperforms the conventional time-only MC CDMA receiver in the presence of strong MAI.