request for RA at the beginning of each minislot without checking the status of channels, IoT devices may simultaneously transmit preambles. It may incur severe slice congestion that may lower the RA success probabilities of IoT devices and degrade the system performance. Access control has been considered as an efficient proposal of alleviating congestion, and many access control schemes have been proposed [@jiang2018analyzing; @Study163GPP]. In this paper, we aim at illustrating the performance difference between a network slicing system without access control and with access control. Therefore, we adopt the following two schemes [@jiang2018analyzing]:

-   **Unrestricted scheme:** each active IoT device requests the RACH at the beginning of minislot $t$ without access restriction. If mIoT slices are not crowded or in a light-crowded condition, then this scheme may quickly flush queues of IoT devices. However, if a heavy-crowded condition is encountered, then this scheme may result in a high packet queueing delay.

-   **Access class barring (ACB) scheme:** at the beginning of $t$, each active IoT device throws a random number $q \in [0, 1]$ and can request the RACH only if $q < P_{ACB}$, where $P_{ACB}$ is an ACB factor determined by RRHs based on the slice congestion condition. 