兩階段比例: 一個綜合802.16e-2005媒體存取層的上行和下行頻寬分配演算法

Abstract

IEEE 802.16e-2005宣稱可為無線都會型網路支援高頻寬傳輸。然而通道的品質非常容易受到長距離、不穩定的無線環境而降低，造成對及時應用程式的損害。因此，一個合適可行的頻寬分配演算法來充份利用可使用的頻寬並提供差別式服務是有所需要的。在本論文中提出了一個兩階段比例演算法來解決上述的問題。在第一階段中，根據用戶台所發出的頻寬要求去動態決定上下行的次訊框，同時考慮上下行不同的時槽大小。在第兩階段中，則是利用累加的最大可支援速率當作權重和一新穎的調整係數用來增加權重給頻寬要求較多的佇列，來進一步去差別各個服務等級。實驗模擬結果証實兩階段比例在頻寬利用上比靜態分配改善了20%的效率，並且仍能嚴格地保證差別式服務。此外，針對和其它方法的效能比較，顯示兩階段比例在頻寬利用率和差別式服務上來的較好。

The IEEE 802.16e-2005 claims to support high bandwidth for the wireless metropolitan area network. However, the link quality is very likely to degrade due to the long-distance and unstable wireless link, bringing ordeals to the real-time applications. Therefore, a feasible bandwidth allocation algorithm is required to utilize the precious bandwidth and to provide service differentiation. This work proposes a Two-Phase Proportionating (TPP) algorithm to tackle the above challenges. Considering different slot sizes for the uplink and downlink whose ratio is 3:2, the first phase dynamically determines the subframe sizes according to the bandwidth requests from subscriber stations. The second phase further differentiates a service class along with a weight which denotes the accumulated maximum sustained rates and with a novel adjustment factor practically reflecting the bandwidth demand of the service class. The simulation results demonstrate that the TPP improves the bandwidth utilization by 20% compared to the static allocation, and the service differentiation are strictly guaranteed. Besides, the performance comparison with other schemes shows TPP has the highest bandwidth utilization and most differentiated for every service class.