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Week2&3: Study Multichannel Slotted ALOHA

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Multichannel Slotted ALOHA System Model

  • 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.
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