Optimization of delivery time in broadcast with acknowledgement and partial retransmission

In this paper, we discuss a hybrid scheduling approach of content delivery for broadcast systems. TWo components are considered: the broadcast component and the unicast component. The broadcast component is used to deliver the content to part of the mobiles located in the cell. The remaining mobiles, that do not successfully receive the content because are in a deep fade or suffer from bad channel conditions, use retransmissions in order to improve the packet detection probability. We show that there is a compromise between the number of users that are allowed to use retransmissions and the data rate at which the broadcast content is transmitted. Unlike the pure broadcast approach where there is a race to the bottom in order to serve the weakest user in the cell, this approach frees up the scheduler from building on the worst channel quality in the cell by allowing a degree of retransmission for cell edge users.