Diversity Integration in Hybrid-ARQ With Chase Combining Under Partial CSI

We consider a receiver design for a Hybrid Automatic-Repeat-reQuest (HARQ) system protected by polar codes against transmission errors. This integrated detection-decoding receiver targets a packet link for which channel state information during HARQ retransmission is unavailable at the receiver. Under such channel uncertainties, we propose a second-order cone programming (SOCP) approach for diversity combining without resorting to decision-directed channel estimation prone to error propagation. We formulate an integrated SOCP receiver by jointly exploiting the constraints from diversity channel models, subspace separation, and forward error correction codes. Unlike traditional turbo receiver algorithms that require iterative exchange of soft information between detector and decoder, our proposed SOCP receiver solves as a single-integrated convex optimization problem. This formulation is also versatile and extendable to a plurality of practical scenarios. We further investigate the means for enhancing the receiver performance and the HARQ throughput. Numerical results demonstrate the substantial performance benefits of the proposed joint SOCP receiver.