以服務品質為基礎的迅速換手分析模型於IEEE802.16jWiMAX網路

Analytical Model for QoS-based Fast Handoff in IEEE 802.16j WiMAX Networks

謝松儒(Sung-ju Hsieh)

指導教授 ： 張本杰

朝陽科技大學/資訊學院/資訊工程系/碩士(2009年)

摘要

IEEE 802.16依據基地台所剩餘頻寬在集中式資源分配機制中使用三種輪詢方式來輪詢使用者：單點輪詢、群播輪詢及廣播。在群播輪詢及廣播模式中，當網路流量接近飽合時，基地台於分散式行動節點在競爭解決程序中使用Truncated Binary Exponential Backoff(TBEB)演算法。雖然TBEB在IR及BR中支援了隨機競爭，但在高流量負載中它會遭受高碰撞機率的情況產生。因此TBEB明顯地降低了服務等級，尤其是考慮到在移動或多重跳躍轉傳WiMAX網路中有換手節點。無論如何，在WiMAX中的TBEB會有二個問題產生，如下列。首先，TBEB未考慮到節點優先權(也就是新節點或是換手節點)及服務流等級(也就是低或高服務等級)。其次，當一個連線贏得了競爭後將會被回到最小相同的倒數階級，並且在下次競爭中導致不必要的碰撞產生。因此，此研究首先提出了一有效的競爭決解演算法，它包含了三個主要的貢獻：1)提出了一適性調整最小-最大的倒數值演算法(AM2)來分割碰撞區域，2)對競爭成功連線支援一動態的等待-懲罰演算法，及3)有區別的減少競爭視窗演算法，當隨機地選取到相同CW時去動態地減少CWs。接著，我們將所提出的方法模型為一不連續時間的馬可夫鏈模組，並且使用數學分析重要的參數：碰撞機率，取存延遲、服務等級及效能。數據結果指出分析數據是非常接近模擬數據，它可以證明了分析模組的正確性，所提出的演算法在碰撞機率，延遲，服務等級及網路效能上勝過了IEEE 802.16及所有比較的方法。

關鍵字

無線都會型網路技術 ； 馬可夫鏈 ； 競爭解決程序 ； 進入區域 ； 頻寬要求 ； 倒數視窗

並列摘要

IEEE 802.16 adopts a centralized resource allocation mechanism that polls nodes with three modes: the unicast, multicast and broadcast polling modes, depending on the residual bandwidth of the base station. In the multicast and broadcast polling modes, the base station uses the Truncated Binary Exponential Backoff (TBEB) algorithm as the Contention Resolution Process among distributed mobile nodes while the network traffic load is nearly saturation. Although TBEB supports random contentions in Initial Ranging and Bandwidth Request, it suffers from high collision probability under a high traffic load. TBEB thus significantly degrades the grade of service especially while considering handoff in the mobile (IEEE 802.16e) or multi-hop relay WiMAX (IEEE 802.16j) networks. Moreover, two problems exhibit in WiMAX’s TBEB. First, TBEB neglects the node priority (i.e., new or handoff node) and the service flow class (i.e., low or high service class). Second, in TBEB the connections win the contention will go back to the same minimum backoff stage, and then lead to unnecessary collisions at the next contention. Thus, this work first proposes an efficient contention resolution algorithm that consists of three key contributions: 1) providing an adaptive minimum-maximum backoff values algorithm (AM2) to partition collision domains, 2) supporting a dynamic waiting-penalty algorithm (DWP) for successful contentions, and 3) differentiating the decrement of contention window algorithm (DDW) to dynamically decrease CWs while contentions randomly selecting the same CW. Second, we model the proposed approach as a discrete-time Markov chain model, and then mathematically analyze important metrics: collision probability, access delay, GoS, and throughput. Numerical
results indicate that the analytical results are very close to the simulation results, which justifies the accuracy of the analytical model. Additionally, the proposed algorithm outperforms IEEE 802.16 and all compared approaches in collision probability, delay, GoS and network throughput.

並列關鍵字

WiMAX ； backoff window ； Markov chain ； contention resolution procedure ； ranging region ； bandwidth request

參考文獻

[2] “IEEE Standard for Local and Metropolitan Area Networks Part 16: Air Interface for Fixed Broadband Wireless Access Systems,” IEEE 802.16e std., pp. 1-864, Feb. 2006.

[4] L. Lin, B. Han and W. Jia, “Modeling and Performance Analysis of Initial Connection in IEEE 802.16 PMP Networks,” IEEE 63rd International Conference on Multimedia and Expo, pp. 609 - 612, Jul. 2006.

[5] W. Jia, W. Lu and L. Lin, “Performance Analysis of IEEE 802.16 Multicast and Broadcast Polling based Bandwidth Request,” IEEE Wireless Communications and Networking Conference, pp. 1854-1859, Mar. 2007.

[6] L. Lin, W. Jia, B.o Han and L. Zhang, “Performance Improvement using Dynamic Contention Window Adjustment for Initial Ranging in IEEE 802.16 P2MP Networks,” IEEE Wireless Communications and Networking Conference, pp. 1877-1882, Mar. 2007.

[7] B.-J. Chang, Y.-L. Chen and C.-M. Chou, “Adaptive Hierarchical Polling and Cost-based Call Admission Control in IEEE 802.16 WiMAX Networks,” IEEE Wireless Communications and Networking Conference, pp. 1954-1958, Mar. 2007.