隨著行動通訊日漸普及，愈來愈多使用者希望能夠在任何時間、任何地點，不受限制地使用他們所需的服務。但是由於IEEE 802.11通訊協定的限制，導致使用者無法獲得適當的服務品質保障，特別是使用者在享受即時性的服務，例如：網路電話、視訊會議、線上即時影音等。雖然在2001年IEEE提出802.11e草案，提供具有服務品質的無線通訊協定，但是在服務品質的效能方面表現並非完美，特別是在隨時變化的真實網路中。我們提出一個隨時根據網路狀況動態調整系統參數且容易實作並相容於IEEE 802.11e網路下的新機制。根據實驗模擬結果中，我們可以看到我們所提出的方法提供比EDCA更好的服務品質，就語音方面的延遲而言，我們減少約80%，就視訊方面的延遲，我們改善約25%，而輸出量方面約增加45%的效能，並且提高系統約6% - 40%最大的容納數。而我們也導入了允入控管，根據事先模擬的結果及設定的系統參數門檻，達到允入控管的目地，確保系統所提供的服務品質能夠滿足使用者的需求。 / Wireless LANs (WLANs) based on the IEEE 802.11 family have recently become popular for allowing high data rates at relatively low cost. However, due to the limitation of 802.11 DCF, they are not suitable for real-time service and do not support service differentiation. To expand providing applications with quality of service (QoS) requirements in WLANs, the IEEE 802.11E Task Group was formed to enhance the current 802.11 medium access control (MAC) protocol. In real networks, the network condition is dynamic. The 802.11e cannot reach high performance of QoS. Besides, design of efficient MAC protocols with both high-throughput and low-jitter performance is the major focus in distributed contention-based MAC protocol research. In view of this, we propose a new and applicable approach, called Dynamic-EDCA (D-EDCA), adjusts the parameters of system based on the network condition. The result of simulation shows that in comparison with EDCA, our proposed algorithm improves total throughput more than 45%, and the maximum of connection more than 40%. It also reduces voice delay about 80%, and video delay about 25%. Thus, the proposed D-EDCA utilizes bandwidth more efficiently and improves performance for service differentiation.
| Identifer | oai:union.ndltd.org:CHENGCHI/G0927530181 |
| Creators | 洪立韋, Hung, Li-Wei |
| Publisher | 國立政治大學 |
| Source Sets | National Chengchi University Libraries |
| Language | 英文 |
| Detected Language | English |
| Type | text |
| Rights | Copyright © nccu library on behalf of the copyright holders |
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