異質性無線網路之快速認證與連結性管理機制

Abstract

無線寬頻網路（如：WiMAX、LTE）的發展逐漸走向整合不同的接取技術（如，WiFi、 Zigbee）形成一異質無線網路。為了符合不同使用者的需求，無線寬頻網路整合了WiFi無線區域網路，讓室內使用者透過無線區域網路享受高頻寬高品質的接取服務，而室外使用者則可利用無線寬頻網路享有行動接取服務。當使用者在不同的網路間切換（換手）時常遭遇到認證時間過長的問題，為了提供使用者好的接取服務品質，本論文提出了一快速認證的行動管理機制，並且利用一我們提出的數學模型來分析及驗證其效能。另，一無線網路的使用者會經驗不同的換手流程。為了了解無線網路的行動管理效能，我們在一通用使用者行動模型中，探討使用者所經驗之各式換手的比例，進而了解平均換手延遲時間、平均封包遺失量等效能指標。再者，為了提供更多樣化的應用，無線感測網路以作為使用者的形式，被整合至無線寬頻網路中。此整合概念的標準化正由無線寬頻網路的標準制定組織（WiMAX Forum、3GPP）制定中。當無線寬頻網路的使用者是一個感測網路時，如何管理其網路連結性是主要重點之一。為此，本論文也提出了三種網路連結性管理機制，包括：骨幹覺知的網路拓樸形成機制、非對稱式繞送與路徑重建機制以及一負載平衡機制。我們以NS-2的模擬探討了這些機制的效能。

A wireless broadband network such as WiMAX integrates various communication technologies to form a heterogeneous wireless network for multiple purposes. Integration of wireless access networks extends the access service to a wider range of users. To this end, wireless local area networks such as WiFi are integrated with a WiMAX network. A wireless local area network is considered complementary to a wireless broadband network, due to its cost-effectiveness on covering signal dead zones of WiMAX networks and its plentiful bandwidth for quality of service. However, vertical handovers in a heterogeneous wireless network suffers from the lengthy authentication problem. Therefore, we propose an fast authentication mechanism for mobility management in this network environment. In addition, a mobile user receiving a session call in a wireless network experiences various kinds of handovers. To evaluate the performance of mobility management of a wireless network, the ratio of one to another handovers is an important parameter, which can be used to compute average handover delay, average signaling cost, etc. Hence, we investigate the cluster-to-cell crossing ratio for session-based service in a general user mobility model, where cluster crossings and cell crossings trigger different types of handovers.

On the other hand, to provide a wider range of application services, a wireless sensor network is integrated into a wireless broadband network through which the sensor network reports sensing data back to a server on Internet. Standardization groups, such as WiMAX Forum and 3GPP, have been working on such an integration. A wireless sensor network always faces the connectivity management issue due to battery-powered sensor nodes. Therefore, we propose three connectivity management schemes: a backbone-aware topology formation scheme allowing power-rich nodes forming a backbone, an asynchronous routing and route recovery scheme for mobile sensor nodes, and a load balancing scheme. We conduct NS-2 simulations to evaluate performance of the schemes.