Researches On Key Techniques Of Differential Detection In Multi-Carrier Wireless Communication Systems

Because of the time variation of channel, getting the exact channel estimation and good synchronization is difficult for the receiver, the differential detection enables the receiver to detect the data symbols without knowledge of the reference phase, so it can be applied into these environments. Multi-carrier wireless communications have been obtained extensive research in these years. This thesis will respectively research the performances of differential detection on the three multi-carrier wireless communications systems: Orthogonal frequency division multiplexing (OFDM) system, multi-carrier frequency domain spread spectrum (MC-FDSS) system and Two-Dimension Spread Spectrum (2D-SS) system.We firstly introduced the characteristics of multi-carrier wireless communications and the research background of differential detection, and summarized the questions needed to be further researched.Research on the performance of differential detection in OFDM system will be introduced in the second part of this thesis. For OFDM system, the differential detection can be carried out either in time domain or in frequency. There are more results of research on the performance of time domain differential detection (TDDD) OFDM system than that of frequency domain differential detection (FDDD) OFDM system, so the further research on the FDDD is a necessary part of differential detection OFDM system. In this thesis, the performance of FDDD in different fading channels was firstly analyzed, and then we compare the results with the performance of TDDD, further more, the effect of intersymbol interference on the performance of FDDD was analyzed, at last, we obtained the results of the research on the performance of multiple-symbol differential detection FDDD system.Chip-level differential detection (CLDD) was proposed in the direct sequence spread spectrum (DS-SS) system, in which the differential encoding/detection is implemented on chips rather than on data symbols, and it had been found to make the DS-SS system resistant to the time-selective fading. In the third part of this thesis, The CLDD was proposed in MC-FDSS system, and the bit error rate (BER) performance of CLDD in MC-FDSS was analyzed, and the results of research indicated that CLDD made the MC-FDSS system resistant to the frequency-selective fading. At last, we...