分碼多重進接蜂巢式系統中使用多用戶檢測器之乏晰

Abstract

近幾年來，多用戶檢測器（MUD）是一項相當熱門的主題。由於它對系統容量具有顯著提升的能力，使得越來越多新的無線分碼多重進接（CDMA）系統採用這種新的技術。目前已經發展出許多多用戶檢測器的方法，這些方法多半在設法提升檢測器的效能以及增加實作的可行性。然而在蜂巢式（cellular）系統中，系統仍然會受到其他細胞（cell）的多重進接干擾（MAI）使得容量受到限制，因此使用多用戶檢測器時仍然需要一套呼叫允諾控制（CAC）的機制來控制語音用戶數。在本篇論文中，我們首先針對主要的多用戶檢測器做綜合性的評估，並且對於所使用的基本概念、效能以及複雜度等加以比較。接下來我們考慮在上鏈路中，配合連續式干擾消除（SIC）之多用戶檢測器的使用提出一套乏晰（fuzzy）允諾控制器。此種多用戶檢測器具有較低的複雜度，並且較適合在衰褪效應（fading）頻道以及非最佳化功率控制（imperfect power control）的環境中使用。本乏晰允諾控制器同時考慮到分碼多重進接之蜂巢式系統中，蜂巢內（intra-cell）與蜂巢間（inter-cell）的多重進接干擾，藉此提供比傳統SIR型（SIR-based）的允諾控制更為精確的系統容量管理。

Multiuser detection (MUD) is a very popular topic in recent years. Its impressive increase in capacity has caused that more and more latest wireless code division multiple access (CDMA) systems adopt this new technology. A lot of methods to implement the MUD were proposed and most of them tried to upgrade their performances and make them more feasible. The capacity limit, however, still exists due to other cells' multiple access interference (MAI) in a cellular system. As a result, a call admission control (CAC) scheme is required to control the number of voice users when using MUD. In this thesis, we first make a survey of the major types of MUDs and make comparisons among them, such as the important concepts, the performances, and the complexities, etc. Then we propose a fuzzy CAC using uplink MUD of successive interference cancellation (SIC), which has lower complexity and more advantages under the fading channel and imperfect power control. The fuzzy CAC considers both intra-cell and inter-cell MAI and it provides more accurate management of capacity than conventional (SIR-based) CAC in the CDMA cellular system.