Consider a source broadcasting Ml pack-other hand, use of coding nmay allow to achieve higher inets to N receivers over independent erasure channels, fornmation rates, thus reducing the delay. Thus rate and where perfect feedback is available from the receivers delay are clearly intertwined quantities. to the source, and the source is allowed to use coding.We define a schenme to be rate-optimal if every suc-We investigate offline and online algorithms that op-cessfully received packet brings new infornmation to its timize delay, both through theoretical analysis as well receiver. We say that a scheme has zero delay, if it is as simulation results. rate optimal, and additionally, each receiver can instantaneously decode an inforination packet froin each received I. INTRODUCTION 978-1-4244-1689-9/08/$25.00 ©2008 IEEE