Advanced Grant-Free Transmission for Small Packets URLLC Services

The next generation new radio (NR) network, or the fifth generation (5G) system, will be able to enhance significantly the current Long Term Evolution (LTE), or the fourth generation (4G) network from many perspectives and initiations. One of such initiations is to support Ultra Reliable and Low Latency Communication (URLLC) services, especially to support the transmission of small but critical control related packets with periodic and aperiodic traffic patterns with very stringent latency (e.g, less than 1 ms)and reliability (up to 99.999% or 99.9999%). Grant-free transmission is one of the feasible and promising technology to meet such requirement especially for uplink transmissions. While some basic grant-free features have been proposed and standardized in NR Release 15, there are still space to improve. In this paper, three enhanced features for grant-free transmission are proposed and carefully evaluated via system level simulations. It can be demonstrated from the evaluation results that the proposed grant-free transmission schemes are able to work together and accomplish the latency and the reliability requirements for the URLLC services, showing significant gains over the basic grant-free transmission design.