在LTE資料排程中考量通道環境及QoS限制以最小化耗電

Abstract

LTE已成為新一代的通訊技術，其擁有高傳輸率及廣涵蓋率，但也因此產生高耗電的問題。為此LTE制定了Discontinuous Reception (DRX)省電機制，原理為周期性的關閉射頻電路以達到省電效果，但在關閉期間無法接收封包，而影響服務品質。為了最小化耗電並滿足服務品質，需要找出一組在最佳的DRX參數設定，但在變動的通道環境下，此參數設定也會有所變動。因此本論文提出一稱為Dynamic Scheduling with Extensible Allocation and Dispersed Offsets (DXD)的方法，其分為兩個演算法：DRX參數決定演算法及DRX-aware排程演算法，DRX參數決定演算法會考量通道環境及服務品質限制以決定出最佳的DRX周期，並分散各使用者的開啟時間，使其在射頻電路開啟時，能完整利用LTE頻寬來快速傳輸資料，即有更多的時間關閉射頻電路以達到省電效果。而DRX-aware排程演算法判斷是否延長電路開啟時間使得服務品質不會受到DRX影響。實驗結果可發現DXD與未採用DRX省電機制時相比，最多可節省96.9%的耗電，在服務品質滿足率方面，亦可接近未採用DRX省電機制的效能。

LTE has become the next generation of communication technology. It has high data rate and broad network coverage, but it conversely introduces high power consumption. To resolve this problem, 3GPP has developed the Discontinuous Reception (DRX) power saving mechanism, which periodically turns off the radio interface to reduce power consumption. However, packets cannot be received during the turn-off time, as a result that the Quality of Services (QoS) may be violated. Therefore, optimal DRX parameters should be configured. In addition, channel condition may be unstable during the transmission, so the optimal DRX parameters should also be dynamically adjusted. In this thesis, we propose the Dynamic Scheduling with Extensible Allocation and Dispersed Offsets (DXD) scheme, which is composed of two algorithms, DRX parameter decision algorithm and DRX-aware scheduling algorithm. DRX parameter decision algorithm determines the DRX period by considering channel condition and QoS constraints, and then interlaces the turn-on time of each user. The scheduling algorithm determines whether to extend the turn-on time or not, so that QoS will not be affected by DRX. Simulation results demonstrate that our DXD approach can reduce power consumption up to 96.9% compared to No DRX scheme and guarantee QoS as good as no DRX scheme.