# Week2&3: Study Multichannel Slotted ALOHA >home : https://hackmd.io/@bariqsufif/mynotes ###### tag: `NTUST-RESEARCH` ## Multichannel Slotted ALOHA System Model ![](https://i.imgur.com/ku3Eepv.png) - All users are in the same communications environment and thus can transmit to or receive from any of M channels that have equal bandwidth in Hz - The system consists of a finite population of N users sharing M parallel channels with equal probability 1/M. Users can transmit to or receive from any of M channels according to the slotted ALOHA protocol. - If two or more packets are simultaneously transmitted over the same channel at the same slot, a collision of the packets occurs. - Each user is in either of the two states: the idle state if he does not have a packet in his own buffer to transmit; the backlogged state if he has a packet awaiting or undergoing transmission. - **In the IFT protocol**, an idle user generates a new packet only at the beginning of a slot with probability and upon a new packet arrival, the user transmits the packet with probability one. - **In the DFT protocol**, a packet is generated only at the end of a slot with probability and when a new packet arrives, the user joins the backlogged state at once, then transmits the packet after slots with mean of where is the retransmission probability.