LTE下行傳輸中具公平性之封包排程策略

LTE對排程相關的探討文獻不多，而針對LTE所設計的排程器，其最主要的目標都是爲了達到系統最高效能。但如果以達到系統最高效能為排程依據，容易在後續資源分配時候，造成優先權(Priority)較低的連線(Connection)出現延遲(Latency)或飢餓(Starvation)的情況，而這樣的排程設計反而有可能降低了系統整體效能。所以本論文針對LTE在下行排程中提出一個有效的排程方式及資源分配方法，盡可能提高系統效能，又可同時維持資源分配的基本公平性，有效的避免優先權較低的連線出現延遲或飢餓的情況。我們針對整體效能和五種不同頻寬需求狀態的延遲程度和飢餓問題進行實驗結果的探討。實驗以延遲程度(Latency)和飢餓程度(Starvation)代表排程器的整體效能狀況，因為這兩個考量因子最能反映QoS需求滿足的情形。由實驗結果我們得知，使用有效的排程演算法，可以有效解決連線延遲和飢餓問題並能同時盡可能的提高系統整體效能且兼顧資源分配的基本公平性。

關鍵字

長期演進技術；下行；排程；通道品質質量；公平性

並列摘要

Nowadays, the main purpose of the scheduler for Long Term Evolution (LTE) aims to provide the best system performance. However, it may decrease the system performance for the latency and starvation of lower priority connections in resource allocation phase. This paper proposed an efficient algorithm including scheduling strategy and resource allocation mechanism to avoid the latency or starvation of the lower priority connections and maintain the system performance in downlink of LTE. This algorithm discusses five levels of the bandwidth request situations to assign the priority and allocate the bandwidth for each connection. The simulations utilize the condition of the latency and starvation, which are the most important factors to identify the satisfaction of QoS, to express the performance of the scheduler. As shown in the results of simulations, the proposed algorithm could provide the proportional fairness and high system performance in downlink of LTE.

並列關鍵字

Long Term Evolution(LTE) ； Downlink ； Scheduling ； CQI ； Fairness

參考文獻

[1] ITU Telecommunications indicators update 2006, http://www.itu.int/ITU-D/ict/statistics/

[3] Hossam Fattah, and Cyril Leung, “An overview of scheduling algorithms in wireless multimedia networks,” IEEE Wireless Communications, vol. 9, no. 5, pp. 76–83, Oct. 2002.

[4] Yaxin CAC and Victor O. K. Li, “Scheduling Algorithms in Broad-Band Wireless Networks,” IEEE Proceedings of The IEEE, VOL. 89, NO. 1, pp. 76–87, Jan. 2001.

[6] A. M. Mourad, L. Brunel, A. Okazaki, and U. Salim, “Channel Quality Indicator Estimation for OFDMA Systems in the Downlink,” IEEE 65th Vehicular Technology Conference, pp. 1771-1775, April 2007.].

[7] E. Dahlman, S. Parkvall, J. Skold, and P. Beming, 3G Evolution: HSPA and LTE for Mobile Broadband, First ed.: Elsevier Ltd., 2007.

國際替代計量

LTE下行傳輸中具公平性之封包排程策略

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