A fine timing synchronization method on group communication system enablers for LTE

Recently, 3rd generation partnership project has adopted a new study item for device-to-device (D2D) communication service in long term evolution (LTE) system, called the group communication system enablers for LTE (GCSE_LTE). In GCSE_LTE, synchronization is an important issue; therefore, many synchronization methods of wireless sensor network and ad-hoc network can be considered. In these conventional methods, they only consider synchronizing the transmission time of signal. However, in case of ideal synchronization method, conventional methods cause a link delay spread (LDS) problem. LDS means a time difference between received signals which are caused by the different propagation delays among user equipments (UEs). The problem is that all UE need an extra length of cyclic prefix (CP) to receive multi-path delayed signals, and it can be a substantial resource waste. Therefore, in this paper, we propose a fine timing synchronization method by a master node which can reduce the maximum LDS in D2D group. We verify that the proposed method can reduce the average length of additionally required CP compared to conventional methods.