Repetition Protocols for Block Fading Channels that Combine Transmission Requests and State Information

In this paper, we study the throughput performance of incremental redundancy repetition protocols over block fading channels. We propose new protocols that use the available feedback bits not only to request a retransmission, but also to inform the transmitter about the channel quality. We give an explicit protocol construction for any number of retransmissions and any number of feedback bits. We show remarkable throughput improvements, especially at low and moderate SNR, where our protocols can perform power control thanks to the partial channel state obtained through feedback. For the case of a single retransmission and a single feedback bit, we show that the repetition is not needed at low SNR and that the throughput improvement is due to power control only. On the other hand, at high SNR the repetition is useful and the performance comes form a combination of power control and ability to resend.