Impact of Imperfect Channel State Information on RS Coding Aided Hybrid-ARQ in Rayleigh Fading Channels

Hybrid Automatic-Repeat-reQuest (ARQ) schemes are capable of maintaining reliable communications for transmission over hostile wireless channels. In coherent detection aided schemes, the achievable performance substantially depends on the accuracy of channel state information (CSI). In this paper, the impact of imperfect CSI on Reed-Solomon (RS) coded HybridARQ systems is investigated for transmission over block-Rayleigh fading channels. The corresponding goodput equation is derived and used to evaluate the system´s performance. The effects of code rate and channel quality are also visualized. Furthermore, the results are utilized for the optimization of the pilot versus data symbols power allocation in order to maximize the system´s goodput. Quantitatively, the proposed scheme provides a 2.5 dB E_b/N₀ gain at a given goodput for the (255/223) RS code defined over the GF(256).