在無接縫垂直交接情況下的網路成本最小化研究

Abstract

在下一代的行動電話系統當中，使用者會希望系統業者提供一種連線方式，讓其即時的傳輸服務可以總是保持在最佳的網路上，除此之外，使用者也預期在進行垂直交接的時候不會有延遲的情況發生。因此在此篇論文中，我們針對現有的3G UMTS 以及 WLAN 來提供使用者這樣的需求。我們提出一種新的方案叫做“Designated Crossover Point”(DCP) 來支援快速的垂直交接，接下來，我們讓DCP可以交接到使用者所在的路由器上，以增進路由的效率，最後，根據VHE user profiles 所提供的移動特性，我們可以利用馬可夫決定過程計算出最佳的交接方式，並且這些交接方式只需要網路最小的成本。在模擬結果當中，我們考慮了兩種情況：1)只考慮一個3G UMTS 以及一個WLAN的結合，2)考慮一個3G UMTS 以及兩個WLAN的結合，不管是在哪種情況之下，我們都可以為系統業者找出最佳的策略去執行DCP的交接，並且將網路的成本最小化，此外，我們也將討論不同參數對於交接策略的影響。

In the next generation of mobile system, it is expected to support the concept of Always Best Connected (ABC). Besides, from user’s perspective, the seamless vertical handover for real-time service is also very important. Therefore, in this thesis, we focus on the integration of 3G UMTS and WLAN through loosely-coupled interworking architecture, and propose a scheme called “Designated Crossover Point” (DCP) to execute vertical handover in a fast way. Next, we let the DCP to handover to increase routing efficiency, and finally, by the value iteration method of Markov Decision Process, we can find the optimal DCP handover policy when we can get the mobility characteristic form VHE user profiles in advance. According to the policy the network operator can decide when to perform a DCP handover, which can minimize the network cost. We consider two cases: 1) there are only one UMTS and one WLAN, 2) there are one UMTS and two WLANs. In both case we can always minimize the network cost by the best DCP handover policy. Furthermore, we discuss the effect of tuning the system parameters.