分碼多工多使用者偵測方法的改良

Abstract

直接序號的分碼多工是分碼多工這個領域最熱門的無線通訊技術，在直接序號的分碼多工通訊系統裡，每個使用者所使用的傳輸信號再同一個時間同一個頻率上重疊在一起，彼此照成了相互間的干擾。 為了克服彼此間相互的干擾，我們採用匹配濾波器的輸出和MMSE的理論，當使用者時常的變動的情形下，為了避免去計算大的反矩陣，我們回顧和使用分群概念，我們回顧GSIC的理念它一個群組一個群組去偵測並用SIC的方法順序去消除群組的干擾，我們同時發展出GPIC和GISIC。 在GPIC中，我們同時的偵測所有群組並使用PIC的架構去消除群組間的干擾。在GISIC，中我們改變兩級GSIC的第二級的偵測順序。除此之外，回顧之前的MMSE所做的群組偵測方法，我們把群組之間的干擾考慮進來，改良了MMSE的群組偵測方法。最後我們用電腦模擬的方法去比較我們所發展出來的方法。

Direct-Sequence Code-Division Multiple Access (DS-CDMA) is a most popular wireless technology in CDMA communication, and all of the users' signals overlap in time and frequency and cause mutual interferences. We use the MMSE detection to overcome the interferences, but when users change frequently, we review and use the group concept to avoid calculating large matrices inverses. We review the Group Successive Interference Cancellation (GSIC) group detection concept which detects each group one by one, and use the SIC scheme to cancel intergroup’s interferences, and we develop Group Parallel Interference Cancellation (GPIC) and Group Iterative Successive Interference Cancellation (GISIC) methods. In GPIC, we detect each group at once, and cancel intergroup’s interferences by using the PIC scheme. In GISIC, we modify two stages GSIC and make the second stage to have reverse detection direction. Besides that, we modify the MMSE group detection function by considering the intergroup’s interferences. Finally, we compare the performances of those detectors in computer simulation.