Sub Tiling - a flexible CSI Reference Signal Concept for 5G New Radio Systems

Abstract

Mobile cellular radio systems have to support a multitude of user end devices with varying channel characteristics, ranging from static sensors over nomadic users up to high speed UEs on roads or highways. The channel characteristics of these devices vary accordingly from highly frequency selective in non line of sight scenarios to highly time variant on motor highways. Covering all these use cases simultaneously by a single CSI reference signal pattern, conventionally, leads to a high overhead for reference signals as it requires a dense grid of pilot signals, fulfilling the sampling theorem in time and frequency. In 5G new radio (NR) standardization adaptive CSI RS patterns per frequency subband are being proposed and discussed. Here, we suggest as alternative solution a so called sub tiling concept, which provides inherent flexibility for an either dense in time or in frequency channel estimation. That way simultaneously nomadic users with frequency selective NLOS channels can be supported from the same CSI RS pattern as fast moving UEs with relatively flat radio channels.