Reseach On Multi-dimension Spread Based Wireless Transmission Technique

The wireless mobile communication channel has the characters of time domain selective fading and frequency domain selective fading, which can be reduced by the diversity gain obtained from signal spread. Multi-dimension spread can take advantages of multi dimensions’ diversity gains to make the system performance better. Besides, spread in multi dimension promots the system energy efficiency and the channel capacity. In this sense, multi-dimension spread becomes a research focus.This thesis studies the multi-dimension spread based wireless transmission technology. At first, three traditional spread techniques and the responding detection methods are introduced. Then the enhanced transimission schemes based on the modifying transmitter are studied. Finally a new multi-dimension spread sheme is studied, and existing technologies are utilized to promote the performance of the new spread sheme in different transmission environments. The details are shown as follow:Chapter 1 is the research background and the research actuality. The major work and structure are also described.Chapter 2 introduces several traditional signal spread technologies, the frequency domain spread based discrete Fourier transform(DFT) spread based orthogonal frequency division multiplexing(OFDM) technology(DFT-S-OFDM), the frequency domain spread based multi-carrier code division multiple access(MC-CDMA) technology, and the time and frequency domains spread based orthogonal frequency and code division multiplexing(OFCDM) technology. The basic principles and linear equalization methods are discussed, followed with the performances of different detection methods.Chapter 3 studies the enhanced DFT-S-OFDM technologies. Two near maximum likelihood detection methods are discussed firstly. Then a preprocessing based transmitter is introduced. Simulation results of the two technologies mentioned above are given. Index modulation based DFT-S-OFDM system is proposed in the next, the modulation principle is detailed discussed and the corresponding detection algorithms are studied. Sphere decoding method is mentioned to be applied in SIM DFT-S-OFDM system and then the simulation results.Chapter 4 investigates a new signal spread technology. At first, the application scenario is introduced and then the basic principle is showed with the simulation result. The application of the new spread shceme in MC-CDMA and OFCDM systems are in the next. The performance of the new spread shceme in different dimensions and different channels are studied in this way. Then focuse on the performance limitation, low density parity check(LDPC) code is applied. Finally, a new peak-to-average power ratio(PAPR) reduction method is proposed to deal with the MC-CDMA’s high PAPR. Simulation results show the performance comparison.Chapter 5 is the summary of this thesis. This chapter also looks forward the research directions based on this thesis.