Performance Evaluation of Two-Step Random Access for Low-Latency Communications in 6G

In this paper, we investigate a two-step random access (RA) scheme in cellular systems, which is considered as one of essential techniques for enabling low-latency communications in 6G. We provide detailed description on the overall procedure of the two-step RA. Thereafter, we mathematically analyze its performance especially in terms of the one-shot success probability, the probability of success after fallback to the conventional 4-step RA, and the probability of failure after fallback to the 4-step RA. Through extensive simulations, we verify the validity of our numerical analysis, and investigate the effect of the primary control parameter (i.e., mapping coefficient between physical RA channel and physical uplink shared channel) on the overall performance of the two-step RA procedure.