Utilising objective perceptual image quality metrics for implicit link adaptation

An implicit link adaptation technique based on hybrid automatic repeat request (H-ARQ) using a soft-combining algorithm is considered for image transmission over wireless channels. Instead of the conventional link-level metrics such as bit error rate and frame error rate that do not correlate well with the quality as perceived by the end user, adaptation is carried out using metrics obtained from models that take the human perception into account. In this paper, a novel reduced-reference hybrid image quality metric (RR-HIQM) is proposed and used as a criterion to terminate the retransmission request in link adaptation. Numerical results show that the use of RR-HIQM in link adaptation provides robust link performance while meeting satisfactory quality constraints.