DRaMa: Device-Specific Repetition-Aided Multiple Access for Ultra-Reliable and Low-Latency Communication

In Fifth-Generation (5G) New Radio (NR), satisfying a scenario called Ultra-Reliable and Low-Latency Communication (URLLC) is one of main goals. URLLC requires very high reliability with low latency, 1 ms user plane latency and 99.999% reliability. In Long Term Evolution-Advanced (LTE-A) system, however, latency requirement required by URLLC cannot be satisfied because resource allocation process increases latency. In this paper, we propose DRaMA, a grant-free uplink transmission scheme for low latency required in URLLC. With its own preamble and repetition pattern, a device repeatedly transmits the same packet using different frequency resources across consecutive mini- slots right after sending the preamble. We develop a mathematical model of collision probability to design repetition patterns, which determine the device- specific frequency resources. We demonstrate that DRaMA satisfied URLLC requirements in most cases by using system level simulation.