個人通信服務系統之資源規劃

Abstract

個人通訊服務的技術讓行動使用者也可享受電信的服務。這項技術不僅能應用於公眾蜂巢式電話系統，也可應用在企業網路。現今的企業網路的一個趨勢，便是將行動通訊的技術與現存的通訊系統密切地整合在一起。許多公司的員工常會離開他們的座位與分配的有線電話，但仍然在辦公室內或是在公司的其他地方。在企業網路上提供行動通訊的一個可行方案，就是利用無線私用交換機系統，在辦公室的環境裡提供無線電話的服務。在一個無線私用交換機系統中，許多基地台連接到私用交換機，再透過私用交換機與公眾電話網路相連。既然只有少數的外線電話會同時處於忙線中，因此私用交換機與公眾電話網路之間的外線數目，通常會少於所有基地台可提供的無線電通道的總合。所以決定無線私用交換機的容量，以使系統達到最佳的狀態，是一個重要的課題。 此外，無線私用交換機也可採用使用於一般個人通訊服務網路的微細胞/巨細胞的架構，與公眾的蜂巢式電話系統相結合。在這樣的網路裡，公司的無線私用交換機基地台所涵蓋的小區域可視為微細胞，這些微細胞同時也被提供大範圍服務的公眾蜂巢式電話系統之基地台所覆蓋。當微細胞與巨細胞使用不同的頻道來通訊時，就會形成所謂的雙頻系統。雙頻系統網路的課題之一，是探討如何在不同的服務提供者網路之間的達成連結與互動。非重疊與重疊這兩種雙頻網路之連結互動的架構，我們將深入的介紹。 在此論文中，針對能提供使用者在通話中跨越不同基地台時線路交遞的無線私用交換機，我們提出了數學分析模型與電腦模擬模型，用以探討無線私用交換機的容量，使系統達到最佳的狀態。我們特別評估使用者在一個基地台範圍內停留時間與跨越基地台的線路交遞，對系統資源的影響。當我們知道一個無線私用交換機的話務量，我們的研究便可做為交換機與基地台資源規劃的指導方針。此外，我們也探討雙頻架構的系統效能。我們的研究將解釋無線電資源、跨系統間交遞之失敗機率、使用者在一個基地台範圍內停留時間、主動通話的比率與系統話務量是如何影響系統的效能。我們的研究指出以適當的重疊架構規劃雙頻網路系統，可大幅改善公眾蜂巢式電話系統的服務品質。

Personal communications services (PCS) technologies provide telecommunication services for mobile users. PCS technologies are not only for public cellular services but also for enterprise networks. One of the major trends in enterprise networking is to add mobility solutions to the existing corporate communications systems and integrate them as seamlessly as possible. Many company employees spend time away from their assigned wired phone but are still in their offices or other locations of the company. The emerging answer is wireless private branch exchange (WPBX) system, which offers wireless telephone access in an office environment. In a WPBX, several base stations are connected to the PBX, and the PBX is connected to the public switched telephone network (PSTN). Since only a small number of telephones are expected to be busy at the same time, the capacity (number of the external lines) between the PBX and the PSTN is typically smaller than the sum of the capacities (radio channels) of the individual base stations. It is important to determine the capacity of the WPBX to optimize the performance of the system. Additionally, WPBX may be integrated with cellular systems based on the microcell/macrocell architecture used in general PCS networks. In such a network, company areas may be covered by microcells that overlay macrocells supported by general cellular service providers. Microcells and macrocells utilize different frequency bands to form a dual-band system. One of the major dual-band network issues is the interconnection of two networks among various service providers. Two types of interconnection configurations, non-overlap and overlap, are introduced. In this dissertation, we propose both analytic and simulation models to determine the capacity of the WPBX with user mobility to optimize the performance of the system. Specifically, we study the effects of handoff and the variance of the cell residence times on resource planning. Based on the workload to the WPBX, our study provides the guidelines to determine the capacities of the PBX and the base stations. We also study the performance of dual-band architectures. Experimental results explain how the radio channel capacities, the inter-system handoff failure rate, the cell residence time distribution, the originating call traffic ratio and the offered loads affect the system performance. Our study indicates that with appropriate overlap configuration, the dual-band network can significantly improve the quality of cellular service.