D2D Physical‐Layer Design

Abstract

The device‐to‐device (D2D) communication technology is one of the most significant evolutionary development of the LTE system. It introduces the new defined physical‐layer sidelink channel for the direct transmission between terminal devices, apart from the traditional base station‐assisted data transmission. The service and business opportunities motivated by the D2D communication technique are rapidly growing. In Rel‐12 of LTE system, the development of D2D is initiated by supporting the public‐safety application and proximity‐based service for commercial use. In Rel‐14, LTE has the ambition of supporting vehicular communication through the sidelink channel. It becomes one of the essential services and applications of sidelink communication technology. The sidelink technology has also been rapidly evolved with the new radio (NR) framework of 5G defined in Rel‐15. Atop of 5G NR technology, the standard of NR vehicle‐to‐everything (V2X) is under the normative work of the Rel‐16 LTE standardization. In this article, we introduce the fundamental physical‐layer design of D2D communication standardized for the LTE system. Additionally, we provide our views on the challenges and opportunities of NR sidelink in the physical layer. The low‐altitude unmanned aircraft vehicle (UAV) is another potential application that will benefit from the sidelink communication technology. Along with the evolution of the next‐generation mobile technology, the sidelink will play a more vital role and introduce more business and research opportunities than before.