Integrated 2–4 Step Random Access for Heterogeneous and Massive IoT Devices

Since massive number of User Equipment (UE)s will cause more collisions and increase delay, improved Random Access (RA) methods have been researched and proposed. With the introduction of the new two step RA procedure in 3rd Generation Partnership Project (3GPP) Release 16, the average RA delay of UE could be further reduced. To further enhance two step RA in association with four step RA, we propose a new RA method that integrates four step RA and two step RA for heterogeneous IoT devices, so that UEs can perform two types of RA methods in parallel. With the proposed method, we aim to minimize the UE conflicts with the available RA resources, increasing the efficiency of RA and decreasing the average RA delay. We optimize the probability of two step RA in the proposed method and present algorithm to provide the optimal resource configuration and parameter settings in the RA procedure according to the RA status of UEs. A Markov chain model is formulated to analyze and confirm the effectiveness of the proposed RA method. As a result of extensive simulations, we present that the proposed RA method can enhance the property of the RA procedure for massive and heterogeneous devices access scenarios in 5G and 6G communications.