IEEE802.16是一種都會型無線通訊網路(Wireless Metropolitan Access Network; WMAN)，它提供高速網路存取以及較長的傳輸距離以及5種不同類型的服務品質(Quality of service; QoS)。但是IEEE 802.16標準中並未將頻寬分配方法詳加規定，因此，如何在有限的頻寬資源中既要確保即時性服務封包的吞吐量(Throughput)與平均延遲時間(Average Delay Time)，並且不使非即時性封包分配不到頻寬，導致產生飢餓問題(Starving problem)，達到最有效的資源分配，便成為一個非常熱門的研究題目。
IEEE802.16支援多種不同的服務像是VoIP, FTP, video conference等等，即時性封包具有時效性，一旦封包的延遲時間超過可容忍時間，則此封包就會被丟棄。也就是說，封包只要能在期限內送出即可滿足其QoS的要求，可以不必急著送出所有這類型的封包。本論文所使用之排程演算法是針對即時性服務，當封包從上層抵達至MAC層時，根據其剩餘的傳送時限，可以計算出封包在過期之前能再等幾個訊框的時間，將此封包排在適當的訊框來傳送，因為即時性的封包都等到時限快到前才傳送，可讓後來的即時性或非即時性的封包有更多的機會傳送，因此，此演算法能讓緊急的封包提前傳送，而且有更多剩餘的頻寬給非即時性封包使用，確保更多即時性封包能在期限時間內傳送的同時，也能降低非時即性封包飢餓問題的發生。

IEEE802.16 is a new technology for wireless metropolitan area network (WMAN). It provides high speed access, longer transmission distance and five service classes with different Quality of Service (QoS). However, IEEE802.16 does not define the scheduling algorithm. It becomes a main issue to ensure throughput and delay time for the real-time service while preventing starvation problem for the non-real-time service.
IEEE802.16 supports various kinds of services such as VoIP, FTP, video conference, .. etc. The real-time services have constraint on transmission time. If the packets of these services cannot be transmitted before the deadline, they will be dropped. Considering from another way, this type of packet can wait and be sent just before the deadline. In WiMAX, the time axis is divided into frames with fixed length. With the deadline, the maximum number of frames that packet can wait before sending can be decided. In this paper, the real-time packets are queued in a virtual frame queue according to the last frame it must be sent. Therefore, they can wait as longer as possible and be sent before their deadline. In this way, the earlier frames can be saved for packets arriving later and let them have a larger opportunity to be sent before deadline. Since the length of a virtual frame queue cannot exceed the length of a frame, a problem is arisen about those packets exceeding this limit. In this paper, we propose a scheduling algorithm to solve this problem and a good result is obtained according to the simulation result and discussion.

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