Performance Evaluation of Hybrid ARQ Schemes of 3GPP LTE OFDMA System

Expectations and requirements for future wireless communication systems continue to grow and evolve. Thus, recently, the third generation partnership project (3GPP) has considered the long term evolution (LTE) of 3G - also known as super 3G - to ensure its competitiveness in the future. It is generally assumed that the downlink of the new air interface would be OFDMA based and that some form of hybrid ARQ (HARQ) might be employed. This paper aims to evaluate the performance of various HARQ schemes over the OFDMA downlink of the currently proposed 3GPP LTE specification. Schemes are compared in terms of throughput and PER in the context their differing memory requirements for implementation. Simulation results show that type II incremental redundancy offers the best throughput performance but at the cost of higher memory requirement. However, when the schemes are enhanced with subcarrier and constellation rearrangement techniques, the performance gap between the different HARQ types is reduced significantly.