微微細胞與微細胞無線電通道多重路徑模型之建構

Abstract

本論文提出合併模型，研究微微細胞(室內)及微細胞(都會區)無線電波多重路徑衰落(multipath fading)的特性。它是由二維適應環境式模型(Site-Specific Model)和散射模型組合而成，適應環境式模型可包含傳播環境中邊界的反射、散涉及穿透效應，而散射模型則可用來描述傳播環境中隨機擺放的散射體或粗糙表面邊界，所造成的散射場。該模式能減少適應環境式模型中射線追跡的樹狀階層數，進而大量節省計算時間，同時可精確地預估平均場強值，並藉由相對散射參數 r 有效地量化傳播環境中之散射場分量(相對於平均值)的貢獻。不同地點的大量實驗數據（2.44-GHz 於微微細胞，900-MHz 於微細胞）顯示Nakagami分佈可有效地描述室內的衰落分佈（Fading distribution）。經實地量測，我們發現在微微細胞環境中:（1）如接收或發射天線處於雜亂散射嚴重(heavy cluttering)的環境中 r 設定 0.65~0.72 ；（2）如處於雜亂散射輕微的環境中(light clutter) r 設定 0.26~0.35。在微細胞模型，因發射及接收天線均處於輕微散射的環境中,當 r 設定 0.1~0.2 ，既可有效model不同環境之無線電波多重路徑衰落的統計特性。

In this thesis, we present the hybrid model to research the characteristic of multipath fading in picocell (indoor) and microcell (urban). It is composed of 2-dimension adaptive site-specific model and scattering model. Adaptive site-specific model comprises the reflection, scattering and transmission effect of boundary in the transmission environment. Scattering model can be used to describe the scattering field as a result of random distribution of scattering object and the rough surface boundary. It is found that this treatment can decrease the number ray-tree levels of the site-specific model and saves a lot of computational time. In addition to accurately predicting mean field strength, the hybrid model can effectively quantify the contribution of scattering field (relative to mean value) with the relative scattering factor r. A large amount of experiment data at many different sites (2.44GHz for picocell, 900MHz for microcell) shows that a Nakagami distribution describes the fading distribution well in picocellular and microcellular environment. After measuring live on the spot, we find that in the picocell: (1) r = 0.65~0.72 if the receiving or transmitting antenna is in a heavy cluttering environment; (2) r = 0.26~0.35 if the receiving or transmitting antenna is in a light cluttering environment. While in microcell model, r = 0.1~0.2 because both transmitting and receiving are in light cluttering environment, it can model the statistical characteristic of multipath fading in different environment effectively.