延遲與調變感知的WiMAX基地台動態頻寬分配演算法

Abstract

基於802.16e-2005標準的WiMAX行動系統宣稱在高速行動無線網路下可支援高速率且長距離的傳輸。然而連線品質受到長距離及空氣干擾而不穩定，使得及時應用程式面臨嚴峻的考驗。因此，一個適當的頻寬分配演算法同時滿足及時應用程式延遲要求且充分利用可用的頻寬來提供差異式服務和公平性是需要的。在本論文中提出一個藉由考慮調適調變及編碼比率與需求急迫性的最高急迫優先演算法來克服上述的問題。在上下行頻寬的動態調節中，分別優先保留最急迫需求的頻寬，接著根據上下行個別不急迫的需求量比例地分配剩餘頻寬。在上下行獨自分配頻寬給行動裝置階段，則利用一新穎的係數來決定每個需求的急迫性，以最急迫優先的分配方式來反映出延遲保證與公平性。實驗模擬證實最高急迫優先演算法具備調變感知，同時保證即時串流的延遲而沒有超過其要求且維持跟其他演算法一樣的高流量表現。

The mobile WiMAX systems based on IEEE 802.16e-2005 provides high data rate for the mobile wireless network. However, the link quality is frequently unstable owing to the long-distance and air interference, leading to the crucible of real-time applications. Thus, a bandwidth allocation algorithm is required to satisfy (1) the latency requirement for real-time applications while supporting (2) service differentiation and (3) fairness. This work proposes the Highest Urgency First (HUF) algorithm to conquer the above challenges by taking into consideration the adaptive modulation and coding scheme (MCS) and the urgency of requests. This approach determines the downlink and uplink sub-frames by reserving the bandwidth for the most urgent requests and then proportionating the remaining bandwidth according to the non-urgent ones. Then, independently in the downlink and uplink, the HUF allocates bandwidth to every MS according to a pre-calculated U-factor which considers urgency, priority and fairness. The simulation results prove the HUF is modulation-aware and achieves the above three objectives, notably the zero violation rate within system capacity as well as the throughput paralleling to the best of the existing approaches.