第三代夥伴計畫(3GPP)提出進階的多媒體廣播群播服務(eMBMS)以在進階長程演進技術(LTE-A)網路中提供更有效的多媒體群播服務，然而頻道的衰弱可能導致資料的遺失與損壞。現今利用單播檔案修復(UFR)機制來修復遺失的資料，消耗了大量的傳輸功率，而最近研究顯示利用裝置對裝置(D2D)的傳輸能有效的改善群播服務的效能，因此本研究提出D2D的檔案修復(DFR)機制以最小化eMBMS傳輸的修復成本，此成本為D2D傳輸成本。而最小化D2D傳輸成本的問題被視為NP-complete的資料源選擇問題。資料源選擇問題則是將有正確檔案的使用者當作是其D2D鄰居的潛在來源，並從中選出適合的資料源。模擬結果顯示DFR機制只消耗UFR機制使用功率的5%~30%。為了更進一步降低DFR機制的傳輸成本，本研究提出了利用鄰居檢查的多重資料源選擇(MSSNC)演算法來選擇資料源。本研究中模擬顯示，與DFR-greedy相比，DFR-MSSNC可降低約6%的D2D傳輸成本。

The 3rd Generation Partnership Project (3GPP) standardized enhanced Multimedia Broadcast Multicast Services (eMBMS) to provide an efficient multicast service for the distribution of multimedia content over LTE-Advanced (LTE-A) networks. However, data losses and corruption may occur as a result of channel fading. Recovering these losses using the Unicast File Repair (UFR) method consumes a significant transmission power. Recent studies showed that device-to-device (D2D) communications can be utilized to enhance the performance of multicast service. Accordingly, this study proposes a D2D File Repair (DFR) scheme for minimizing the repair cost of eMBMS transmissions. In formulating the proposed scheme, the problem of minimizing the D2D transmission cost is treated as an NP-complete source selection problem, in which users having the correct file block are regarded as potential sources for D2D neighbors who do not. The simulation results show that the DFR scheme consumes just 5%~30% of the power consumed by the UFR scheme. To further reduce the DFR transmission cost, a Multi-Source Selection with Neighbor Checking (MSSNC) algorithm is proposed for source selection. It is shown that the DFR-MSSNC scheme reduces the D2D transmission cost by 6% compared to that of the DFR-greedy scheme.

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