高空平台應用於第三代行動電話系統中上鏈容量之研究

Abstract

高空平台(high altitude platform stations，HAPS)系統的出現，提供了一個除了地面基地台(base station，BS)與衛星(satellite)以外通訊平台的新選擇，高空平台結合了地面通訊和衛星通訊兩者之優點，擁有良好的通道特性，例如：直視波(line-of-sight)存在、多重路徑的延遲變動較小。隨著此系統之發展，將深深地影響和改變目前通信網路結構的設計。 由於現今地面3G 行動電話系統已被廣泛建置，因此我們希望能整合現有通訊系統與高空平台系統，提供一個更理想之整合型系統。 因此，本論文首先是探討空中平台與地面基地台整合型分碼多重存取(code division multiple access，CDMA)系統之上鏈(uplink)傳輸效能，其中系統是採共用頻段組態。對於整合型系統傳輸效能，我們分別提出三種整合型之系統模型，以提升整體系統容量(capacity)或提供偏遠區域服務。接著，在本論文第二部份，有鑑於高空平台穩定度不如地面基地台，所以本論文將討論高空平台系統穩定性之問題，針對高空平台受風力而造成偏移對系統容量之影響，並提出雙平台系統以降低此影響。本論文採用數值分析軟體MATLAB並利用數學模型去分析整合型系統之容量，其分析結果可為未來規劃高空平台系統之重要依據。High altitude platform stations (HAPS) is a new means of providing Third Generation (3G) mobile services. It combines advantages of terrestrial and satellite systems such as line-of-sight, low multi-path fading and no shadowing for high elevation angles. It will change the design of communication network by the developing of the HAPS. Terrestrial mobile system has constructed throughout. We want to combine the existing terrestrial cellular systems and HAPS system to provide an ideal integrated system. First of all, we consider the uplink capacity for integrated HAPS-terrestrial code division multiple access (CDMA) system in which sharing band overlay. In this integrated system, we propose three integrated system models respectively to increase the system capacity and to serve remote area. Second, Previous studies have shown that platform instability caused by stratospheric winds may lead to system level performance degradation. We discuss instability of HAPS system, and we propose to combat this problem by using multiple HAPSs to provide diversity of signal reception.