使用者導向之異質行動網路管理

Abstract

隨著無線網路技術發展，例如WiMAX、HSDPA和Wi-Fi，無線網路的服務型態逐漸形成在異質網路上提供各種各樣的應用服務。對於網路服務提供者而言，要如何善用這些不同種網路的資源，才能提供給使用者適當的服務就成為一個重要的願景。本文首先提出了一個使用者導向的合作型異質網路的服務模式，透過這種模式網路服務提供者可以更好的管理各種網路的資源，並提供給使用者各種不同層級服務品質的服務，這些層級的資訊包括服務品質和費用，讓使用者可以依其個人偏好，選取他所要的服務等級。文中，我們以串流媒體作為應用服務的例子，來描述這種服務模式。實驗結果證明，我們的方法不但可以提高使用者的滿意度、系統使用率，還能提升所有網路服務提供者的收入，使得使用者和網路服務提供者能夠達到雙贏的效果。因此，在合作型異質網路上定義這樣一個使用者導向的服務模式是非常重要且有效的。為了能讓這個服務在使用者移動過程中也能順暢進行，我們以WiMAX和HSDPA為例，提出一個WiMAX與HSDPA的連結架構來幫助網路換手的進行。此架構中的關鍵網路元件為VHOM(Vertical Handoff Manager，垂直換手管理器)，可以協助管理並改善在WiMAX和HSDPA下的換手。實驗結果顯示，VHOM可以讓使用者在異質網路中進行無縫換手(亦即較低的換手延遲、避免換手過程中產生的封包遺失)，同時，還能保持其所使用的應用服務品質的延續性。

Employing multiple radio access technologies such as WiMAX, HSDPA and Wi-Fi in a mobile network to provide users with more cost-effective communication services has long been a vision of many service network providers. In this thesis, we propose a novel user-decided service model for a cooperative wireless network in which the radio resources of multiple wireless networks are collectively managed. Under the model, users are provided with multiple service options with different levels of service quality and charges. It is up to users to choose the most suitable service option (and access network) based on their personal preference and the amount of money they are willing to pay. We use a video streaming service in a WiMAX/HSDPA network as an example to illustrate the key concepts and resource management of our approach. The results of simulation show that, under the model, the service network can accommodate more users and provide higher user satisfaction than the traditional network-decided service model. It can also achieve higher resource utilization and revenues. This demonstrates the importance of defining the concept of user-decided service model in a cooperative heterogeneous networking environment. It is necessary to investigate the technical feasibility of performing vertical handoff between heterogeneous networks one of the important roaming scenarios under such a service model. Based on the user-decided service model, we design an operation model to enable effective and seamless switching from one network to another. We take the HSDPA and WiMAX as example in this work, and the simulation result show that the operation model lowers the handoff latency, avoid the packet loss, and the service level is guaranteed.