多天線隨意無線系統的統計通道模型之研究

Abstract

在智慧型運輸系統及隨意網路的應用下，移動通訊(mobile-to-mobile)是一個非常重要的元素。在此種系統下，傳送及接收兩端皆同時處在移動狀態之下，且同時受到散射(Scattering)與萊斯衰變(Rician fading)的影響。因此在本篇論文裡，我們將會提出一個具相關性的雙環散射模型(correlated double-ring)以及正弦函數累加的模擬方法(sum-of-sinusoids simulation method)來描述在傳收兩端間具有直視能量(line-of-sight)下的移動通訊系統之通道模型(mobile-to-mobile Rician fading channel model)。我們所提出的模型將可應用在隨意通訊系統的物理層模擬。 隨著現代通訊系統對通道容量(capacity)的需求增加，把多根天線(MIMO)的技術應用在移動通訊系統上的方法，已逐漸受到軍事及商業上的重視。就如同在傳統的蜂巢式通訊網路(cellular network)下，多天線技術可以提供媒體存取控制(MAC)協定設計時的空間(spatial)自由度一樣，在隨意網路下我們也可以藉由多天線的技術來提供足夠的多樣性與通道容量。 不過，在多天線隨意網路下如何能夠準確的模擬出空間及時間的通道相關性(spatial/temporal channel correlation)對移動通訊環境的影響，是一個重要且基本的問題。在此種多天線系統的通道中，傳收兩端間直視的能量以及不同的散射環境將會對通道容量與通道容量的平均衰變時間(average fade duration)有所影響。在此篇論文中，我們以所提出的相關性雙環散射模型為基礎，建立一個以正弦函數累加方法所構成的移動性多天線通道模型(mobile-to-mobile MIMO)，此模型將可以精確的描述出空間的相關性、時間的相關性與萊斯參數對通道衰變的影響。我們最後則觀察多天線系統的通道容量其衰變情形和萊斯參數之間的關係。

Mobile to mobile communication is one of important applications for the intelligent transport systems and mobile ad hoc networks. In such a system, both the transmitter and receiver are in motion, of which the signals experience Rician fading and different scattering effect. In this thesis, we present a correlated double-ring scattering model and a sum-of-sinusoids simulation method to characterize such a mobile-to-mobile Rician fading channel. The developed model can facilitate the physical layer simulation of a mobile ad hoc communication system. With the increasing of the demand on channel capacity in modern communications, multiple-input Multiple-output (MIMO) mobile ad hoc networks have been receiving increasingly attention in both commercial and military applications. Just as in cellular networks, MIMO technology can benefit ad-hoc networks by providing the diversity and capacity advantages as well as the spatial degree of freedom in designing the media access control (MAC) protocol. Hence, it is of importance to understand the MIMO channel. However, one fundamental issue to MIMO mobile ad-hoc networks is how to accurately model the impact of spatial/temporal channel correlation in mobile-to-mobile communication environment. In such a channel, a line-of-sight (LOS) component and different scattering environments will affect both ergodic capacity and average capacity fade duration of the MIMO system. In this thesis, based on the correlated double-ring scattering model we have also suggest a sum-of-sinusoids MIMO mobile-to-mobile channel simulation method, which can characterize the spatial/temporal channel correlation and Rician fading effect. We investigate how often the MIMO capacity experience the fades and relate this to the Rician factor.