Physical downlink control channel for 5G new radio

Abstract

New radio technologies for the fifth generation of wireless system have been extensively studied globally. Specifically, air interface protocols for 5G radio access network will be standardized in coming years by 3GPP. All basic physical layer functions for the new radio system are currently under active development in 3GPP. Due to its crucial function in scheduled system, physical layer control channel is a core element to enable all physical layer data transmission. In particular, search space allocation and transmission schemes are fundamental problems of control channel design. Both aspects have ultimate impacts on achievable control channel coverage, capacity and spectrum efficiency. As such, search space design and promising transmission schemes for control channels are thoroughly studied in this paper. Both distributed and localized search spaces are proposed to accommodate different means of control channel transmission depending on availability of channel state information at the base station. Furthermore, two types of transmit diversity schemes with different diversity orders are developed and compared by Monte-Carlo simulations. It is demonstrated from simulation results that SFBC based transmit diversity outperforms per-RE precoder cycling scheme. Moreover, high order transmit diversity schemes are also proposed and simulation results thereof exhibit clear performance benefits.