| Summary: | 博士 === 國立清華大學 === 資訊工程學系 === 94 === Thanks to the advancement of wireless technology, the mobile service increasingly catches more attention in the post era of the booming voice service in cellular networks. In order to stay competitive, carriers are expected to provide superior mobile services - allowing access to mobile broadband services anywhere and anytime regardless of the wireless bearers (2.5, 2.75, 3G or Wi-Fi). In this thesis, I focus on the construction of mobile service platform over a dual-mode network in wireless communications.
In the first portion of this thesis, we try to conduct an emerging mobile service system - Blog Rendering and Accessing INstantly (BRAINS). A blog (shortened from ‘weblog’) is a trendy way to share personal journal with others in the cyber world. Traditionally rendering and accessing blogs are normally conducted at a stationary PC. However, such a scheme hinders blog users from writing and reading blogs timely. A short-lived idea came out and passed away suddenly. To facilitate the instant blog updating and retrieving, we combined cellular messaging (SMS/MMS messaging and MMS/WAP push) and open-source software (Blosxom and Apache) to develop such a novel system. BRAINS enables blog users to note down their whims and share interests anytime and anywhere. Blog journalists can utilize their mobile phones at hand to compose and deliver blogs to BRAINS by SMS and MMS messaging at their pleasure. Through pre-registering on BRAINS, readers also can get the up-to-date blogs content or the incoming blog notification immediately by MMS push or WAP push. With pervasive networks like the 2.5G, 3G, PWLAN or fixed DSL networks, BRAINS makes mobile blog rendering and accessing more evident.
In the second part of this thesis, we try to conduct a deep investigation on the construction of the dual-mode networks from a carrier viewpoint. To offer a more efficient wireless data access service than General Packet Radio Service (GPRS) or Universal Mobile Telecommunications System (UMTS) networks, PWLAN stands a predominant position to embrace the wireless broadband era. PWLAN and cellular networks forming an overlayed network can complement each other to provide a higher wireless accessibility to users. Furthermore, reusing the existing mechanisms for user authentication, access control, unified billing and roaming handling procedures in mobile territory to construct a complementary network - PWLAN draws the attention of cellular operators, like Vodafone, T-Mobile. Therefore, we give an insight into a practical end-to-end PWLAN architecture capable of using GPRS/UMTS SIM-based authentication for the existing mobile users and carrying out Web-based authentication for the occasional users without SIM modules simultaneously. Additionally, we give consideration to confederate various PWLAN service providers by Remote Access/Authentication Dial-In User Server (RADIUS) based roaming mechanism and leverage the existing resources in cellular operators. The proposed considerations and guidelines provide a baseline skeleton to build an extendable environment and to successfully construct a flexible Cellular/PWLAN hotspot.
Finally, since confederating sprinkled PWLAN operators under the PWLAN roaming agreements can intensify the PWLAN service coverage. There are lots of RADIUS-based AAA messages that traverse among pan-PWLAN operators including PWLAN operators, Cellular/PWLAN operators and WLAN roaming brokers. Hence, we try to improve the message forwarding lookup latency by a hashing-based scheme against the traditional one by a linear scheme. For the collision resolution in hashing, we use the customer bases of different partners as weights to construct a descending chained list to eliminate the overhead. Simulation results depict that the proposed scheme can effectively decrease the consumed time of deciding how to forward messages compared to the conventional approach.
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