A timing synchronization method for D2D communication in asynchronous cellular system

Device-to-device (D2D) communication has received considerable attention in recent years as one of the key technologies for future communication system. In 3GPP, Proximity Services (ProSe) includes scenarios for D2D user equipments (DUEs) which are served by evolved Node B (eNB). If D2D system assumes that user equipments (UEs), which include cellular user equipments (CUEs) and DUEs, operate as overlay communication and DUEs are located in a same cell, timing synchronization is accomplished. However, when DUEs is positioned in different cells, it is not guaranteed the interference from CUEs is low enough to communicate between D2D links. According to conventional methods, one of the problems is severe performance degradation due to the asynchronous interference and another problem is higher control complexity to acquire timing advance (TA) from neighbor eNB. Therefore, in this paper, we propose the timing synchronization method for DUEs in LTE system. We define the optimal transmission timing for minimizing interference and the process of timing synchronization by exchanging own their reference signals independently.