Optimal adaptive multireceiver ARQ protocols

The authors study data link error control protocols suitable for point-to-multipoint communication where data are delivered to the destinations in the order they are sent. They study a series of adaptive protocols differing in the way that the sender uses the outcomes of the previous transmissions. The protocols are based on the go-back-N schemes discussed by I.S. Gopal and J.M. Jaffe (1984), whose protocols are generalized to the case where multiple copies of a message are sent (instead of just a single copy). The optimum number of copies is determined and is found to depend on how many receivers have not yet received the message. These adaptive protocols can be applied to all three basic ARQ (automatic repeat request) schemes, namely, stop-and-wait, go-back-N, and selective-repeat. A dynamic programming technique is used to solve this optimization problem. A throughput comparison shows that, by sending the optimum number of copies of a data frame instead of just a single copy, the performance will be significantly improved