發展混合式無線電空-時通道模型與探討巨細胞環境下之散射群集效應

Abstract

本論文建構一個新的混合式無線電空-時通道模型來探討巨細胞環境下的散射群集效應。該混合模型結合適應環境性傳播模型（site-specific model）以及幾何分佈式統計模型。適應環境性傳播模型能夠預估無線電波在巨細胞環境中的主要傳播機制；幾何分佈式統計模型則可描述巨細胞環境中的隨機散射體效應。 本論文採用先進的向量通道響應系統於台北市都會區巨細胞環境下，進行通道響應及特徵之實地量測，分析無線電波在空間與時間之分佈特性。在分析巨細胞的脈衝響應量測數據中，發現來自各主要反射點或繞射點之接收信號，大多以群集式脈衝響應顯示。於是論文中以“等效散射區”代表有效反射或繞射區域，並在該區以隨機散射體分佈模型，描述該區所產生之散射群集效應。 本論文針對實際環境並利用量測統計結果，擬定選取等效散射區與決定等效散射體數的方法，藉由等效散射區與等效散射體有效地量化巨細胞傳播環境中的散射群集效應，混和模型能夠正確地預估無線電波在空間與時間之分佈特徵。吾人將以抵達時間、抵達角度、角度擴展以及時間擴展之量測值驗證混和模型的預估效能。

This paper presents a new hybrid spatio-temporal radio channel model, which can characterize both the space-time property and the scatterer cluster effect well for macrocellular radio channel in urban environment. The hybrid model combines a site-specific model with a statistical model. The former model employs a deterministic approach to describe the direct wave, specular reflection wave and diffraction wave. The latter one employs a statistical approach to describe the scattered or diffused fields, which is due to the local scatterers around the mobile station, rough surface of dominant buildings, and multiple scattering effect of corners/edges of dominant buildings. It is found that the scattering or the diffused fields from each dominant building are arrived in groups in space-time domain, which can be modeled by applying the scatterer cluster. Here, a scatterer cluster is described by introducing randomly positioned scatterers in the associated “effective scattering zone”, which represents the effective diffused-reflection or -diffraction area of the buildings. The rules to determine the scattering zone size and the scatterer number are investigated by measurement-based method. By comparing the computed time of arrival, angle of arrival, r.m.s. angle spread and r.m.s. delay spread with the measured one, the hybrid model has been proved to be an effective and accurate spatio-temporal radio channel model.