RS-Coded M-QAM Schemes Using Error-and-Erasure Decoding over Wireless Fading Channels

In this paper, the optimal threshold for the erasure-marking technique suitable for RS-coded quadrature amplitude modulation (QAM) schemes using error-and-erasure decoding (EED) over i.i.d. fading channels is determined for the system. The performance and capacity of the RS-coded QAM system using EED with the obtained optimal erasure thresholds, and error-only decoding (ED) over i.i.d. Rayleigh and Nakagami-m fading channels are derived and compared. It is shown that EED outperforms ED, and this performance improvement increases significantly when the fading in the channel is more severe. Furthermore, the use of RS codes is investigated over correlated fading channels through a RS-coded QAM-OFDM system over multipath fading channels. The results indicate that, while the increase in number of resolvable taps introduces more frequency selectivity in fading, it reduces the fading correlation between sub-carriers. As a result, for the same RS-coded QAM-OFDM system, its performance is better with shorter interleaving (and hence shorter delay) in multipath fading channels with more resolvable taps.