長期演進技術中非連續接收機制之服務品質與省電效能分析

Abstract

隨著越來越快速的無線通訊及智慧型手機的普及，用戶端設備如何達 到省電功效是一項亟需研究的課題。為了提高用戶設備於資料傳輸中的省 電效能，進階長程演進計畫在標準中訂定一項非連續接收機制，透過此機 制可減少不必要的電力消耗，然而降低電力消耗與維持服務品質是一體兩 面，本研究將探討非連續接收機制電力消耗與封包遺失狀況的關係。過去 探討非連續接收機制省電效能的研究，都僅以平均封包延遲時間做為服務 品質的衡量標準。本次研究在給定非連續接收機制參數設定值的情況下， 推導出封包遺失機率及用戶省電效能的計算式。由於目前尚未有通用的非 連續機收機制參數設定方式，本次研究也提出一套設定參數的方法。設定 的概念為在不違反服務品質要求下，選擇能盡量增加省電效率的參數組合。 研究所提出的數學計算式與參數設定方式都分別與電腦模擬與最佳參數設 定做比較。比較結果顯示由數學式求得的封包遺失機率及省電效能與電腦 模擬結果相符，本次研究提出的參數設定在不違反服務品質要求下，所對 應的省電效率也與最佳參數設定的省電效能相差不多。

With demand for better user experience, performance of power saving on mobile phones has been a critical issue in recent years. In LTE-Advanced network, a Discontinuous Reception (DRX) mechanism is provided to support power saving functionality. It is clear that there is a trade-off between energy saving and quality of service (QoS). Unlike previous studies, which analyzed the average packet delay as QoS requirement, an analytical model for ratio of packet loss due to violation of delay bound requirement is proposed in this work and given DRX parameter values, equations for power consumption are also derived. Under the constraint that the packet loss ratio is no greater than a pre-defined threshold, an approach to maximizing average power saving is presented for selection of values for DRX parameters. The analytical model is verified with computer simulation and the result of analytical calculation matches that of simulation. Moreover, the power saving efficiency achieved by the proposed approach is close to that of optimum configuration. This work is expected to provide a fundamental analysis for packet loss probability and power saving efficiency under DRX mechanism.