Frequency Domain Equalization For Single Carrier Block Transmission In Wireless Communication System

Single carrier block transmission (SCBT) is a transmission technology similar to orthogonal frequency division multiplexing (OFDM) transmission. On the one hand it has the features of block transmission and processing as OFDM, on the other hand it sends signals by single carrier whose peak to average power ratio(PAPR) is very low. At the same time, SCBT receiver eliminates frequency selective fading in wireless channel with low complexity frequency domain equalization. So SCBT is a highly competitive physical layer technology in broadband wireless communications. Frequency domain equalization, which is an important part of SCBT, is directly affects the performance of SCBT system.This thesis had an overview of the development of frequency domain equalization in SCBT. Simulation results showed how frequency selective fading affected the transited signals. The commonly used frequency domain equalization algorithms were firstly introduced, and then this thesis focused on the theoretical analysis of the time frequency hybrid decision feedback equalizer (H-DFE) and noise prediction based on decision feedback equalizers (DFE-NP), which were non-linear equalizers. The bit error ratio (BER) caparison between linear and non-linear frequency domain equalization in two multi-path channel models were given. Simulation results indicate that the performance of non-linear equalizers with a few feedback taps is significantly better than linear equalizers in frequency selective channels, especially in the channel with deep frequency fading.The block structure in SCBT system was generally similar to cyclic prefix (CP) extension in OFDM system. But a kind of extension namely unique word (UW) was more suited for SCBT system. Because special UW extension is more advantageous than CP in synchronization, channel estimation, etc. It was easy to separate UW and useful data after through the channel at receiver owing to the known nature of UW. Basing on this thinking, this thesis proposed a UW based time frequency hybrid equalizer (H-DFE-UW) that could yield a better performance. Both optimal and suboptimal designs were presented by a detailed derivation through the matrix operations, and the algorithm's computational complexity was analyzed. After that, this thesis showed BER simulation of the new equalizers. Simulation results indicate that the performance of the optimal design is highly improved and the suboptimal one with lower complexity is slightly better than H-DFE-CP.This thesis derived the equivalent SCBT model of single carrier frequency division multiple access (SC-FDMA), which is the uplink physical layer technology of 3GPP's Long Term Evolution (LTE), and then frequency domain equalization was used in SC-FDMA system. H-DFE could also be use in SC-FDMA system, but there was unreasonable design in the feedback part in practice. So an improved method, that the decision and feedback of H-DFE was iterative, was proposed. The simulation results show that the improved algorithm can improve the probability of correct bits which used to initialize the feedback of H-DFE in SC-FDMA system and inhibit possible error propagation and improved the overall BER performance.