WiMAX 系統的行動管理機制之改進

Abstract

隨著行動用戶的快速增加，行動寬頻服務已成為人們生活的一部分。 全球互通微波存取(WiMAX)系統為新一代的行動網路，能提供大服務範圍、高吞吐量與支援快速移動的無線寬頻服務。為了提供行動服務，WiMAX的行動管理(包含位置管理功能與交遞管理功能)當為最重要的議題之ㄧ。其中，位置管理功能負責追蹤用戶之移動以提供服務，而交遞管理功能負責在用戶的移動中維持服務正常運作。此二項功能對一些較耗資源的電信服務尤為重要，例如影像電話、隨按即說等。本研究即探討WiMAX 系統的行動管理相關議題。 在行動管理方面，首先我們提出數學模型來評估當位置區域(LA)部分 重疊時，對位置更新(LU)機制效能的影響。本研究結果提供了如何選取適當重疊範圍的準則。接著我們研究WiMAX 的LU 機制之效能。由於WiMAX會為每個行動用戶指定一主傳呼控制中心(APC)來管理與追蹤該用戶，並可在用戶更新位置時即時更換APC。此研究找出了能依照使用者移動模式，即時更換APC 的準則。在交遞管理方面，為了支援WiMAX 用戶的高速移動，本研究在考量不同的使用者移動速度後，提出了基於階層式WiMAX 網路架構的隨需重整(RoD)方法。本研究指出隨需重整方法較不受使用者移動速度影響，且其效能明顯優於其他通道配置方法。 本論文的研究成果提供了一些可供WiMAX業者參考使用的機制與準 則，以期提升WiMAX 系統的行動管理機制之效能。

As mobile subscriber population rapidly grows, mobile access for broadband services becomes an important part of human life. IEEE 802.16e mobile Worldwide Interoperability for Microwave Access (WiMAX) provides broadband wireless services with wide service coverage, high data throughput, and high mobility. In WiMAX, mobility management (i.e., location management and handoff management) is one of the most important issues to support mobile services. Location management function tracks the roaming Mobile Stations (MSs) for service delivery, and handoff management function maintains service continuity during MS mobility. Such functions are important for mobile telephony services, including conference/video call and Push to Talk over Cellular (PoC). In this dissertation, we investigate the mobility management issues for WiMAX networks. For location management, we first propose an analytic model to study the Location Update (LU) performance with overlapping Location Area (LA) configuration. Our study indicates how to determine the appropriate overlap among LAs. Then we investigate the performance for WiMAX LU procedure with Anchor Paging Controller (APC) relocation. In WiMAX, an APC is assigned to an MS to handle its location tracking and can be dynamically relocated during the LU procedure. By the analytic results, we provide guidelines to utilize the APC relocation for MSs with various moving behaviors. For handoff management, to support service continuity for high mobility MSs, we proposed the Repacking on Demand (RoD) for the Hierarchical WiMAX Network (HWN) by considering the MS moving speeds. Our study quantitatively indicates that RoD is less sensitive to MS speeds and outperforms the other previous proposed schemes significantly. The research results presented in this dissertation provide some useful mechanisms and guidelines for WiMAX operators to achieve high system performance in their networks.