RS-coded M-QAM transmission techniques for Wireless Communications.

摘要

Reed-Solomon (RS) codes are one important class of maximum distance separable (MDS) codes, and have been widely used for error control in many wireless and wireline communication systems. It is known that RS codes can correct more erasures than errors, and, thus, Error-and-Erasure Decoding (EED) has a potential to outperform Error-Only Decoding (ED). In order to mark the low reliability symbols as erasures, an erasure marking technique should be established. Previous works show that a threshold can be employed to mark symbols as erasures, and the selection of the threshold is critical to the performance of RS codes with EED. However, methods to determine suitable and optimal thresholds have not been investigated in those works.;The use of RS codes is further investigated over correlated fading channels through a RS coded QAM orthogonal frequency division multiplexing (OFDM) system over multipath fading channels. The investigation focuses on the effects of number of resolvable taps, which represents the multipath fading channel, on the fading correlation between sub-carriers, the choice of interleaving depth and the performance of the RS coded QAM OFDM system. 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.;In this thesis, the use of RS codes in quadrature amplitude modulation (QAM) system over additive white Gaussian noise (AWGN), independent and identically distributed (i.i.d.) and correlated fading channels and their performance are investigated. At first, the focus of the investigation is on the derivation of the optimal thresholds for the erasure-marking technique in AWGN and i.i.d. fading channels. By employing the obtained optimal erasure thresholds, the performance and capacity of the system using EED and ED are derived and compared. It is shown that EED outperforms ED over both AWGN and i.i.d. fading channels. Specifically, the performance and capacity improvement provided by EED is significant over i.i.d. fading channels, and increases when the fading in the channel is more severe. Hence, EED is preferable to ED over i.i.d. fading channels, especially when the fading is severe.