在3GPP長期演進技術上之省電效能分析及基於流量之非連續接收週期調整機制

Abstract

3GPP長期演進技術(long term evolution, LTE)是為了增強行動服務而從前一代之第三代行動通訊系統發展而來。為了延長行動裝置的電池使用時間，在長期演進技術標準裡制定了非連續接收(discontinuous reception, DRX)機制去減少用戶裝置的功率消耗。然而，現有針對非連續接收操作的效能分析模型在一些情況下會導致精確度不足。因此，此篇論文針對非連續接收操作提出一個考慮更多參數的效能分析。對於此提出的模型，其正確性以及效能改進可以在模擬中分別被驗證及觀察。此外，根據非連續接收操作的效能分析結果，其機制的參數會顯著地影響省電效益及服務品質。因此，此篇論文提出一個基於流量之非連續接收週期調整(TDCA)機制去適應性的控制非連續接收操作。此提出的TDCA機制會根據流量的估測，去調整睡眠週期以平衡用戶裝置的睡眠比例及平均的封包延遲。此篇論文應用了部分可觀測之馬可夫決策過程，去推測現在的流量狀態以及提供一個決策方針。模擬結果顯示，在服務品質規約仍被滿足的情況下，TDCA機制可以在現有的非連續接收機制上增強省電效益。

The 3GPP long term evolution (LTE) system is developed to enhance mobile services from the former 3G systems. In order to prolong the battery life time of mobile device, a novel discontinuous reception (DRX) scheme is specified in LTE standards to reduce the power consumption of user equipment. Since the existing analytical models are not accurate enough in some situations. A performance analysis including more parameters is proposed for DRX operation in this thesis. For the proposed model, the correctness is validated and the improvement can be observed by performing simulations. Besides, according to performance evaluations of DRX operation, the DRX parameters may significantly influence the power saving efficiency and quality-of-service (QoS). Hence, a traffic-based DRX cycles adjustment (TDCA) scheme is proposed to adaptively control the DRX operation. The proposed TDCA scheme will adjust the sleep cycles to balance the sleep ratio and mean packet delay based on traffic estimation. A partially observable Markov decision process is applied in this thesis to conjecture the present traffic state and offer a decision policy. Simulation results show that the TDCA scheme can enhance the energy saving efficiency for the existing DRX operation while the QoS constraint is still satisfied.