分增益多重存取，低密度簽名碼分碼多重存取及高密度簽名碼分碼多重存取在衰落通道的研究

Abstract

分增益多重存取（Gain-Division Multiple Access）技術是一種近幾年來無線通信領域中提出的非正交多重存取（Non-Orthogonal Multiple Access）。主要的原理是在設計多個用戶透過各自不同的通道係數在相同的通道資源下進行傳送。 先前的論文中描述，基於低密度簽名碼分碼多重存取（Low-Density Signature Code Division Multiple Access，LDS-CDMA）可視為具多樣（diversity）的GDMA系統。在此我們進一步將低密度簽名碼分碼多重接取視為具相關性的多個分增益多重存取系統的組合，其中每個資源對應到一個GDMA系統。原始應用於LDS-CDMA解碼中的消息傳遞演算法 (Message Passing Algorithm, MPA)也可以理解為多個GDMA系統之間的消息傳遞。我們將其概念進一步擴展至高密度分碼多重存取 (High-Density Code Division Multiple Access, HDS-CDMA)。HDS-CDMA系統的優點可以是對資源數量有較少的需求，或是讓系統擁有更多diversity進而使系統可以容納更多用戶等。

The multiple access technique in wireless communication, Gain-Division Multiple Access (GDMA), is a non-orthogonal multiple access method proposed in recent years. The main principle of GDMA is that multiple users can transmit message under the same channel resource through their distinct channel coefficients associated with distinct users. In a previous thesis, based on the view of point that Low-Density Signature Code Division Multiple Access (LDS-CDMA) can be regarded as GDMA systems with diversity. Here, we further interpret the LDS-CDMA scheme as a combination of several dependent GDMA systems, where a GDMA system is applied to each resource. The original message passing for LDS-CDMA may also be interpreted as the message passing among various GDMA systems. We extend the interpretation to construct high-density (HDS) CDMA schemes. The advantage of HDS-CDMA schemes can be the requirement of smaller number of resources, or achieve more diversity that result in capability of accommodating more users in overall system, etc.