Coding In The Sc-fde System

Broadband wireless communication technology has been drawing great attention recent years. This thesis focuses on the coding schemes in SC-FDE system, which is based on investigating the system character of OFDM and SC-FDE, and conventional coding schemes in both systems.This thesis analyzes the character of wideband wireless channel in brief firstly, and points out that the wideband wireless channel has double selectivity, which are time selectivity and frequency selectivity. How to deal with the multipath fading of the channel becomes a difficult problem of wireless communication.After simple introduction of the basic principles of OFDM and SC-FDE, this thesis compares OFDM and SC-FDE in some aspects, analyzes some problems of OFDM and SC-FDE.Then, this thesis introduces the convolutional code, interleaving technique and conventional coded OFDM and coded SC-FDE. After simulations, this thesis analyzes the effect of channel coding and interleaving to both systems.Based on the investigations of OFDM and SC-FDE, this thesis founds that the error characteristic of SC-FDE is quite different from that of OFDM. In OFDM, the number of errors doesn't change greatly from one OFDM frame to another; while in SC-FDE, there are bursts of errors in some frames. We refer to it as the inherent bursty frame nature of SC-FDE. The channel condition is crucial to it. With no deep fadings, the error characteristic of SC-FDE is similar to that of OFDM; While with spectral deep depressions, the number of errors in some frame of SC-FDE is greatly larger than the others.This thesis points out the reason why OFDM and SC-FDE have different error characteristic, and proposes a new coding scheme in SC-FDE. This scheme could utilize the correspondence of the bits transmitted at different times. We store the block containing fixed number of frames at the transmitter and encode the information bits locating in the same time domain subchannel among frames. The receiver operates the opposite.This thesis simulates the new coding scheme in SC-FDE, and compares the new coded SC-FDE with conventional coded SC-FDE and conventional coded OFDM. In one hand, simulation results indicate that the new coded SC-FDE behaves better than conventional coded SC-FDE. In the other hand, at present, the classical conclusion is that, SC-FDE and OFDM performances become very similar at the channel decoder output, with small advantages for OFDM with low-rate code and for SC-FDE with high-rate code. While, the simulation results indicate that, when the new coding scheme is applied, the low coded SC-FDE behaves better than coded OFDM as the value of snr increases.