Aristides S. Galanopoulos and R. Lee Hamilton, Jr.

We develop a first-order recursive retransmission control policy for a two-station slotted-ALOHA network. Under this policy, terminals adjust their retransmission prob- ability at the end of each slot based on feedback from the current slot. The fundamental difference between a single- station and a two-station network is the interaction between the terminal groups. This interaction occurs because some terminals are in transmission range of both stations; when these terminals transmit to their station they also interfere with the other station. The retransmission control keeps the offered traffic levels near the maximum throughput point and divides the channel capacity fairly between the two ter- minal groups. The control is intuitively appealing: to ac- quire channel capacity in proportion to its arrival rate, each group balances efforts to increase its throughput with a cer- tain backoff that permits channel use by the other group. Keywords-packet radio network, slotted ALOHA, multista- tion, stochastic approximation, retransmission control pol- icy.