Timing synchronization method for device-to-device communication system

In this paper, we propose a timing synchronization method for device-to-device (D2D) system. In the past several years, many synchronization protocols have been investigated for ad-hoc network system. However, it is difficult to apply them to D2D system directly because of some difficulties. In D2D system, these protocols have some structural limitations and might show inefficient performance, because cellular base station can be employed to D2D network to enhance performance and reduce resources. Also, D2D network should be able to support a variable number of devices. Therefore, in this paper, we propose a new timing synchronization method for D2D system. In the proposed method, synchronization can be achieved in different ways according to the existence of available cellular base station. In the proposed method, we first consider cellular-assisted (CA) method based on random access process in cellular uplink procedure. On the other hand, when cellular base station is not available, user equipment performs stand-alone (SA) method. In SA-D2D, three step synchronization process and a new reference clock decision rule are proposed. We verify that the proposed method can achieve high accuracy synchronization in a short period.