Link Adaptation with Retransmissions for Partial Channel State Information

We consider the performance of adaptive coding and modulation (ACM) over a fading channel for the case that the transmitter has only partial channel state information (CSI). We evaluate the degradation due to the partial CSI in terms of additionally required SNR by simulations and an analytical approximation. Then, we propose an ACM scheme with fast link-level retransmissions based on cyclic incremental redundancy and compare its performance to an equivalent scheme based on Chase combining. For both HARQ (hybrid automatic repeat request) schemes, we develop an analytical approximation for the throughput and the delay.