近年來無線區域網路 (Wireless LAN) 的發展技術逐漸成熟,加上各種可攜式的行動裝置也越來越普遍,許多在有線網路上的多媒體應用在無線區域網路也逐漸被考量,
因此在 802.11e 無線區域網路中可給予不同優先 (Priority) 順序以考量多媒體傳輸不同的服務品質 (QoS) 需求,但以不同優先順序傳輸將造成低優先權產生飢餓問題,因此在此環境下如何同時考量公平 (Fairness) 及服務品質傳輸實為重要議題。
本碩士論文提出四個具服務品質考量之公平排程機制,分別是具後退程序之增強型分散式逆差循環資源配置機制 (Enhanced Distributed Deficit Round Robin with Backoff Interval, EDDRR--BI) 、具後退程序之增強型分散式彈性循環資源配置機制 (Enhanced Distributed Elastic Round Robin with Backoff Interval, EDERR--BI) 、
增強型分散式逆差循環資源配置機制 (Enhanced Distributed Deficit Round Robin, EDDRR) 、增強型分散式彈性循環資源配置機制 (Enhanced Distributed Elastic Round Robin, EDERR),在機制 EDDRR--BI 與 EDDRR 中,我們加入 DC 計數器進行排程,
而在機制 EDERR--BI 與 EDERR ,則加入動態允許值進行排程,
經由模擬得到具後退程序的排程機制與 802.11e 的增強型分散式通道分配機制 (Enhanced Distributed Channel Access, EDCA)
及較早提出的 Elastic Enhanced Distributed Coordination Function (EEDCF) 在流通量 、 碰撞率 、 延遲時間 、 服務品質及公平性上皆有所改善,
而在不具後退程序的排程機制中,我們與 802.11e EDCA 機制及較早提出的 Distributed Elastic Round Robin (DERR) 機制相比,亦獲得較佳的結果,相較於具後退程序方法,其效能改善更為顯著。

With the rapid development of wireless LAN technologies and the popularization of various kinds of mobile devices,
multimedia applications in wired networks are also expected in wireless networks.
In the IEEE 802.11e wireless LAN, different priorities are given to multimedia transmissions depending on the quality of service requirements.
Because prioritized transmission results in the starvation problem for low-priority services or flows,
how to simultaneously achieve fairness and quality of service in such an environment is an important issue.
Therefore, four fair scheduling schemes, i.e., enhanced distributed deficit round robin with backoff interval (EDDRR-BI),
enhanced distributed elastic round robin with backoff interval (EDERR-BI),
enhanced distributed deficit round robin (EDDRR),
and enhanced distributed elastic round robin (EDERR) are proposed and studied in this thesis.
EDDRR-BI and EDDRR use deficit counters for fair scheduling,
while dynamic values of allowance are utilized for EDERR-BI and EDERR to take care of fairness.
Through a simulation approach, EDDRR-BI and EDERR--BI are compared with enhanced distributed channel access (EDCA) of IEEE 802.11e and a previously proposed scheme called elastic enhanced distributed coordination function (EEDCF).
Based on simulation results, we show that EDDRR-BI and EDERR-BI can improve throughput, collision rate, delay, and fairness.
For schemes without backoff intervals, they are also compared with EDCA and a previously proposed scheme called distributed elastic round robin (DERR).
Again, we demonstrate that the two proposed schemes have better performance and fairness.
Our results also show that schemes without backoff intervals perform even better than schemes utilizing backoff intervals.

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