Slotted Aloha has been proposed for medium access control layer in IoT applications. Consider the following multiple access scheme that combines TDMA and slotted ALOHA. There are 30 IoT devices, separated into two groups, one of 4 users and the other of 26 users. One third of slots are reserved for the 4-user group and remaining two thirds are reserved for the 26-user group. Contention within each group is resolved by the slotted ALOHA protocol (e.g., when a user in the 26-user group wants to send, it waits for an odd slot and then transmits with a probability p)