Optimal adaptive ARQ protocols for point-to-multipoint communication

A study is made of some data-link-layer error-control protocols suitable for point-to-multipoint communication over broadcast channels where data are delivered to the destinations in the order they are sent. The authors study a series of 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). The authors generalize their proposed protocols to the case where multiple copies of a message are sent (instead of just a single copy). The optimum number of copies is determined, which depends not only on the round-trip propagation delay of the channel and the error probability, but also on the number of receivers that have not yet received the message. A dynamic programming technique is used to solve this optimization problem. The 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.<>