Experimental Research On Ultra-wideband Wireless Communications Based On Time Reversal

High speed information transmission will be one of the main research aspects in wireless communication. Compared with other systems, Ultra-Wide Band Communication (UWB) wireless communication system has received widely study in the research of next generation wireless communication for the advantages of high capacity, high multipath resolution, compatibility with existing communication frequency spectrum, high security and so on.Time reversal (TR) technology was first applied in acoustics field by M.Fink, and in recent years it was introduced into electromagnetic wave field. If TR is applied to ultra-wideband (UWB) wireless communication, it will tremendously increase the capacity of the channel, reduce the co-channel interference, reduce inter-symbol interference, and increase the information transmission rate. So TR has attracted a lot of wireless communication researchers. The thesis does some research of TR, and it is divided into following chapters.Chapter 1 introduces the development history of UWB wireless communications, problems to be solved, present solutions and the advantages of TR technique. Then we simply explain the temporal and spatial focusing of TR, and finally introduce the development status of TR-UWB.Chapter 2 introduces the techniques of TR-UWB wireless transmissions experiment, including pulse generator, limitation of power, Clean algorithm, and so on. Then we utilize advanced instruments to construct a TR-UWB wireless transmission experiment platform,and introduces the parameters of all the hardware.Chapter 3 introduces the TR combined with SIMO technique for multi-user UWB communications, and theoretically testifies the feasibility of MIMO-TR. We point out the technical difficulty of experiment and propose corresponding solutions. And then we apply the full time domain method to investigate the SIMO-TR-UWB wireless transmissions under the environments of a small office. The investigations include the recovering of the signal waveform, the multi-path effect suppression ability of TR, the energy focusing characteristic of TR, as well as the impacts of transmit diversity technique on system performance, and finally achieve two users wireless transimission with information rate of 500Mbps.Based on SIMO-TR, Chapter 4 applies the MIMO-TR technique to multi-uesr UWB transimission. Firstly, in the enviroment of 2×2 multi-user system, transmitter sends Gaussian pulse signal for sounding channel, and the properties of the four channels are obtained. Secondly, we investigate the focusing characteristic of TR using software Matlab and simulate the two users wireless transimission under the information rate are 250Mbps, 330Mbps as well as 500Mbps, respectively. The results shows that the focusing characteristic of TR deeply impoves the quality of MIMO communication, and the MIMO system also could reach 500Mbps wireless communications with low bit error ratio.Chapter 5 summarizes the thesis and points out the direction of future research.