eNB-Assisted Peer Discovery Mechanisms for D2D Communications in LTE-Advanced Networks

Device-to-Device (D2D) communication is one of the important applications in 4G and 5G technologies. Because it is necessary to let two nearby User Equipments (UEs) discover each other before exchanging data in order to support D2D communications in LTE networks. The discovery process is initiated by sending discovery beacon. The UEs located inside signaling coverage will receive and recognize the sending UE’s information. However, the interference, half-duplex behavior and in-band emission may cause the failure of beacon receiving and decoding which may result in discovery failure. This paper proposes a centralized D2D discovery mechanisms to reduce the discovery failure problem. Based on location information of each UE, the eNB can efficiently determine resources used by which UE to send its Discovery Beacon. The proposed approach will also try to minimize the signal collision and shorten the completion time for discovery process. Since eNB can retrieve the locations of all UEs, the centralized scheme should be able to find the optimal solution for the Discovery Beacon scheduling ideally. However, centralized schedule may suffer additional overhead. The distributed approach by which each UE decides the Discovery scheduling by itself can reduce the signaling overhead, but result in efficiency decreased. The performance criteria compares the proposed mechanisms with other conventional discovery methods. Simulation results show that the number of cycles for discovering all peers by using proposed mechanisms is smaller than other conventional mechanisms in case of highly UE density.