Performance Analysis of HARQ in WiMAX Networks Considering Imperfect Channel Estimation

Hybrid Automatic Repeat Query (HARQ) is an error correction technique that has become an integral part of most current broadband wireless standards such as IEEE 802.16 and 3GPP-LTE (Long Term Evolution). Although extensive studies have been made on the performance of HARQ, they usually assume perfect channel state information at the receiver. This paper addresses the performance of incremental redundancy HARQ under the specifications of the physical layer of the WiMAX standard considering imperfect channel state information, such as the one obtained by channel estimation. Several combinations of modulation, channel code rates and information block size are considered, and a realistic physical channel model used for standardization is used throughout the simulations to evaluate the performance of HARQ. Results show that the link throughput can be severely degraded, specifically at low values of signal-to-noise ratio, and HARQ performance may be too optimistic if channel estimation is ignored.