第三代行動通訊系統之通話控制與身份認證

Abstract

Universal Mobile Telecommunication System (UMTS) 為第三代行動通訊標準的主流之ㄧ，該系統整合了數據服務與多媒體服務，並且具有高服務容量、高速傳輸、服務品質保證、客製化服務等特性。UMTS網路可以分為四層，包括無線傳輸層、UMTS核心網路、多媒體子系統、與應用服務層。在本論文中，我們分別就各層討論設計的議題。在無線傳輸層中，無線網路與UMTS的整合將UMTS的服務擴及到無線網路的涵蓋範圍中，因此使用者可以透過無線網路存取服務，獲得較高的服務品質。在本論文，我們提出了ㄧ個整合的架構稱之為WLAN-based GPRS Support Node (WGSN)。WGSN符合3GPP標準文件TS 22.934中第三階段的整合特徵。WGSN為了省電，手機上的網路電話程式可能會被關閉，因而打到該手機的電話便無法接通。為了解決這樣的問題，我們提出了push mechanism以簡訊的方法開啟受話端手機上的程式，以接通電話。 在UMTS網路中，Authentication Vector (AV) usage mechanism 可以減低SGSN與HSS/AuC之間的訊號交換，然而該機制也會造成SGSN所需的記憶體增多。本論文利用數學分析以及電腦模擬的方法來研究AV usage mechanism的效能。我們的研究結果可以提供行動通訊業者用以設定AV usage mechanism的相關參數。 針對使用者的身分認證問題，3GPP制定了two-pass authentication程序，分別在General Packet Radio Service (GPRS)網路以及多媒體子系統認證使用者。我們發現在two-pass authentication中，有許多步驟是重複的，因此在論文中我們提出了one-pass authentication的方法。在此方法中，GPRS網路執行相同的認證程序，但是多媒體子系統以簡化的方法在使用者註冊的過程完成認證。我們證明，one-pass authentication可以正確的認證使用者，同時省下了50%的訊息交換。 UMTS的應用服務層可以Open Service Access (OSA)做為服務開發的平台。在這個平台之上，我們實作了Push to Talk over Cellular (PoC)服務。我們描述了使用者端程式的設計架構，也詳盡說明了服務運作的流程。 以上的研究成果提供讀者在研究UMTS通話控制以及身分認證的議題上，可供參考之基礎。

Universal Mobile Telecommunication System (UMTS) is an integrated solution for multimedia and data services with wide area coverage. UMTS is developed towards large system capacity, high data transmission, and customized services with quality of services. The UMTS all-IP architecture can be horizontally partitioned into four layers: radio network layer, UMTS core network, IP Multimedia Subsystem (IMS), application layer. In this dissertation, we discuss design issues of each layer. In the radio network layer, UMTS and WLAN interworking extends the UMTS services to the WLAN coverage, and the UMTS subscribers can acquire services with better quality through WLAN. We propose WLAN-based GPRS Support Node (WGSN), which is a loosely-coupled architecture satisfying Scenario 3 features in 3GPP TS 22.934. A push mechanism is implemented in WGSN to connect the MS-terminated call where the Voice over IP (VoIP) client in the callee is not activated. In the UMTS authentication, the Authentication Vector (AV) usage mechanism is used to reduce the signaling traffic between the SGSN and the HSS/AuC. However the AV usage mechanism also consumes extra storage at the SGSN. Therefore, we propose analytic and simulation models to investigate the performance of the AV usage mechanism. In UMTS two-pass authentication, many steps in the GPRS authentication and IMS authentication are duplicated. Therefore, we propose an one-pass authentication procedure, in which only the GPRS authentication procedure is performed. In the IMS network, the authentication is implicitly executed in the IMS registration. We formally prove that the IMS user is correctly authenticated, and the one-pass authentication saves up to 50% of the IMS registration/authentication traffic. In the application layer, we implement the Push to Talk over Cellular (PoC) on the Open Service Access (OSA) platform. We focus on the design and implementation of the PoC client. The detailed architecture and message flows are described. These research results presented in this dissertation can be viewed as a useful foundation for further study in UMTS call control and authentication.