考量群播服務品質之高效省電排程方法於LTE-A網路

Abstract

3GPP LTE-A (Long Term Evolution Ad-vanced，長期演進技術)是目前最受推崇的4G無 線通訊標準，其支援高達1Gbps的傳輸頻寬，及多樣且豐富的媒體串流服務，尤其 是IPTV、Voice/Video over IP等高頻寬的影音群播(multicast)服務。然而，隨著乘載的 媒體服務增加，行動用戶端的能源耗損情形也隨之加劇。因此， LTE-A標準中制訂 了Discontinuous Reception Mechanism (DRX)機制，讓行動用戶端在沒有資料傳收時能 關閉無線介面以進入睡眠狀態，來達成省電。然而，如何設置DRX仍是一個開放的問 題。有鑑於此，本篇論文主要是探討如何保證用戶端群播服務的品質及保證用戶端 收看媒體串流之品質，同時最小化行動用戶端的能源耗損。我們首先證明此問題是一 個NP-complete問題。接著，我們提出一個高效且低複雜度的方法。該方法包含兩個階 段：第一階段中，我們儘可能聚合用戶的群播需求以減少用戶額外的wake-up時間；在 第二階段中，我們最佳化DRX參數以最大化用戶的睡眠時間。模擬結果顯示，我們方 法具有優異的省電效益，其效能直逼最佳解。

The 3GPP LTE-A (Long Term Evolution-Advanced) is the most promising technology for the next-generation wireless communications. It provides high transmission rates up to 1 Gbps and supports various broadband multimedia services, such as IPTV and Voice/Video-over-IP services. To reduce the energy consumption of user equipments (UEs), the LTE-A standard defines the Discontinuous Reception Mechanism (DRX) to allow UEs to turn off their radio interfaces and go to sleep when no data needs to be received. However, how to optimally configure DRX for UEs is still left as an open issue. In this paper, we address the DRX optimization problem for multicast services. This problem asks how to guarantee the quality of service (QoS) of the multicast streams under the Evolved Node B (eNB) while minimizing the UEs’ wake-up time. We prove this problem to be NP-complete and propose an energy-efficient heuristic. This heuristic consists of two phases. The first phase tries to aggregate the required bandwidth of the multicast streams for UEs to reduce their wake-up periods. The second phase further minimizes UEs’ unnecessary wake-up periods by optimizing their DRX configurations. Extensive simulation results show that our scheduling is close to the optimum in most cases.