植基於雙網無線網路之行動服務平台

A Study on Mobile Service Platform over a Dual-mode Network in Wireless Communications

呂政修(Jenq-Shiou Leu)

指導教授 ： 石維寬

國立清華大學/電機資訊學院/資訊工程學系/博士(2006年)

https://doi.org/10.6843/NTHU.2006.00170

摘要

近年來，由於無線通訊技術的進展，在後語音服務時代，繼之而起的行動服務逐漸受到廣大的注意。電信業者為保有其原有之競爭力，被期許於異質網路上(2.5, 2.75, 3G or Wi-Fi) 建置可不受時空限制的行動寬頻服務。
在行動服務建置方面，由於”部落格”(Blog) 是當今流行的一種於網際網路上紀錄及分享記事之應用。傳統上存取”部落格”的方式，都是透過於固定的個人電腦前完成的，然而此種方式無法讓”部落格”使用者即時地攥寫及讀取”部落格”內容，我們嘗試結合行動網路的訊息平台(短訊系統及多媒體系統)及異質網路，建置一個行動”部落格”系統- Blog Rendering and Accessing INstantly (BRAINS) ,使得”部落格”的應用更具行動力。
此外，異質網路的建置亦是一個重要之課題，異質網路的互補逐漸受到多種無線網路之成熟而受到注目，更是未來4G的一個基礎。當前較成熟的兩個主要無線通訊網路是行動蜂巢網路(2.5, 3G)及無線區域網路 (WLAN) 。一些以行動蜂巢網路起家的電信業者，例如：Vodafone, T-Mobile，都紛紛建置公眾無線區域網路 (Public WLAN) 來提供給使用者使用，以彌補行動蜂巢網路所提供數據網路(GPRS,3G) 存取速度之不足，形成一個後3G時代 (B3G)，於是我們著力於研究探討在實務上建置以行動蜂巢網路認證為基礎的公眾無線區域網路時，所可能面臨的課題。
再者，由於WLAN的涵蓋範圍有限，為了提供一個更好的服務範圍，必須透過漫遊服務將泛公眾無線區域網路業者所提供之網路串聯起來，因而導致會有眾多認證或計費訊息傳遞於漫遊業者之間，於是我們研究一個較有效率之訊息終端位址查詢方式來降低於進行公眾無線區域網路漫遊時，訊息終端位址查詢的延遲負擔。

關鍵字

行動服務 ； 異質網路 ； 公眾無線區域網路 ； 無線區域網路漫遊

並列摘要

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.

並列關鍵字

Mobile Service ； Heterogeneous Networks ； Public WLAN ； WLAN Roaming

參考文獻

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