放大轉送中繼站網路中無偏通道估計的克拉馬-羅下限

Abstract

由於合作式通訊可以提供空間分集，有效降低在無線通道下傳輸資料所會面臨的衰落效應，並且不會提高硬體複雜度，使其在近年來越來越受到重視。合作式通訊的主要概念，乃是利用閒置的行動裝置，其也被稱為中繼節點，來幫助來源節點傳送資料。這種中繼站網路形成一個分散式的虛擬天線陣列。然而在文獻上，尚未有人對中繼站網路的通道估計效能做詳盡的探討。在這篇論文中，我們會用著名的估計下限，也就是克拉馬-羅下限，來分析在放大轉送中繼站網路下，通道估計的效能。首先，我們會介紹各種中繼協定和其對應的訊號模型。接著，我們將會分別推導在採用集中式無偏通道估計和分散式無偏通道估計的情況下，其所對應的克拉馬-羅下限。最後，我們將會就各種中繼網路的參數，對所導出的克拉馬-羅下限產生的影響，做深入的探討。

Cooperative communication has gained increasing popularity recently since spatial diversity can be provided so as to mitigate fading over wireless transmission without raising hardware complexity of mobile devices. The main concept of cooperative communication is that idle mobile devices, termed as relay nodes, can be utilized to send data for the source node. The relay networks form a virtual antenna array in a distributed manner. In the literature, however, the performance analysis of channel estimation for relay networks has not been well addressed yet. In this thesis, the performance of channel estimation for amplify-and-forward (AF) relay networks will be analyzed in terms of Cramér-Rao bound (CRB), which is the renowned lower bound for estimation. First, we will introduce the relaying protocols and corresponding signal models. Then we will derive the CRB of AF relay networks for unbiased centralized channel estimation, and for unbiased distributed channel estimation, respectively. Finally, the influence of relay parameters on the derived CRB will be discussed in detail.