Two-Step Random Access With Message Replication for Low-Earth Orbit Satellite Networks

Abstract

Low-earth orbit (LEO) satellite networks have attracted great attention, and it is utmost important to reduce signalings during the entire communications to support low-latency services with LEO satellite networks. To this end, this letter newly proposes an enhanced two-step random access (2sRA) with message replication (MR) technique to particularly improve the satellite access performance. Key feature is to allow each device to transmit multiple replicas of the original message during the 2sRA, which enables each device to significantly improve the probability that the 2sRA is successfully completed without converting to the time-consuming 4-step RA (4sRA). We mathematically analyze the performance of our proposed scheme in terms of the 2sRA success probability and the probability of falling back to the 4sRA, and formulate an optimization problem to find the optimal number of message replications which can minimize fallback probability. Through simulations, we validate the effectiveness of our proposed scheme to resolve the collision problem, and verify the occurrence of transitions to the 4sRA can be significantly reduced under the optimal parameter setting.