Performance of HARQ with AMC Schemes in LTE Downlink

The downlink of the Long Term Evolution (LTE) would be OFDMA based and combination of Hybrid ARQ at the data link layer with adaptive modulation and coding (AMC) at the physical layer might be employed. Constellation rearrangement (CR) technique is used in HARQ to enhance MQAM performance. An improved mapping method is used in full IR to enhance system performance. An improved SNR estimation algorithm which reduces computational time is applied to get CQI and corresponding modulation and coding scheme is chosen to maximize throughput performance. Simulation results show that the joint design of AMC and HARQ can achieve considerable spectral efficiency gain.