IEEE802.16是一種無線通訊網路標準，此一標準具有高速網路傳輸、長距離通訊以及低成本的特性。可以支援多種不同類型的服務流QoS(Quality of Service)，在IEEE 802.16標準中並沒有對於頻寬分配的演算法詳細定義，而在有限的頻寬中，不但需要確保即時性資料的所需要頻寬，並且也不能使非即時性資料發生飢餓現象，所以如何設計能滿足各服務需求的頻寬演算法，是一個非常重要的議題。
在本論文中，提出了根據封包截止期限及大小的排序法(DAL)，藉由調整佇列封包的排序，使得系統能夠在不影響資料傳輸率及增加系統的複雜性的情況之下，達到降低封包遺失率的目的。每個即時性封包都有截止期限，超過此一期限未能得到排程傳送的封包,就會被排程器丟棄，以免浪費頻寬。 未能在此一訊框傳送，就會超過截止期限的封包，則被稱為緊急封包。首先，針對延伸性即時性 (Extended Real-Time Polling Service ;ertps)及即時輪詢服務(Real-Time Polling Service ;rtps) 封包，依照截止期限進行排序，接下來把所有的緊急封包，根據封包長度進行排序，短封包在前，長封包在後。再將剩餘的封包，也根據封包長度進行排序。 也就是說，緊急封包會優先得到排程，不管緊急封包或非緊急封包，短封包會優先得到排程。 排序後，再對於所有的佇列，以考慮佇列長度的頻寬分配法進行排程。由於多考慮到緊急封包，相對於根據封包大小的排程法[1]，對於即時性服務流的封包遺失率有著一定程度的改善。

IEEE 802.16 is a standard of wireless communication network. This standard is for networks of high-speed transmission, long-distance communication, and low cost. It provides different types of QOS for different service flows. However, IEEE 802.16 does not define the scheduling method for service flows. Because of limited bandwidth, both the throughput of the real-time traffic and starvation of non-real-time traffic must be solved. So, the main issue is to design a scheduling algorithm which can satisfy demands of all classes.
In this thesis, a scheduling algorithm according to deadline and length of packet(DAL) is proposed. By reordering the order of packets in the queues, the packet loss rate can be reduced without affecting the throughput. Each real time packet has its deadline. If a packet is not scheduled before its deadline, it will be discarded to avoid the wasting of bandwidth. If a packet is not scheduled in this frame and over its deadline before the following frame, it will be called emergency packet. First, for the packets of Extended Real-Time Polling Service (ertps) and Real-Time Polling Service (RTPS), all packets are sorted according to their deadlines. Then, all emergency packets are sorted according to packet length. Shorter packet is in front of longer packets. The remaining packets then are sorted according to the packets. In other word, the emergency packet will have higher priority in scheduling. Then, shorter packets have higher priority regardless of emergency or non-emergency. After sorting, BAQL algorithm is applied with weights which the scheduled bandwidth is proportion to queue length and weight. Since the emergency packet is considered, the packet loss rate of the real-time service flow is improved relative to the scheduling algorithm considering only the packet length.

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