Sliding frame R-ALOHA (SFRA) protocol for microcellular systems

SFRA protocols for mobile radio communication via a base station in a microcellular system are evaluated. The proposed model can accommodate a general model for capture, in which the probability that one packet is received successfully depends on the threshold of power ratio of packets involved in the collision. Variations on the PRMA (packet reservation multiple access) protocol are considered and simulated. The probability that a user with a new message chooses the next free slot depends on the fraction of reserved slots in a sliding window. If collision occurs in a time slot, the colliding mobile stations choose at random a slot among the free ones in the next sliding frame for retransmission. Reservation is made by the successful transmission of the first packet of messages as in R-ALOHA. The near/far phenomenon and the shadowing effect introduce collision resolution and improve system performance. A signature technique is considered for reducing packet collision