| With the success of the4th generation mobile communication system all over the world, the research on the Beyond IMT-Advanced system, also known as the5th generation (5G) mobile communication system, has been paid a lot of attention and discussed both in the academy and the industry.5G looks forward to a great prograss of its capability. On one hand, for the traditional technical requirements, it is expected that reaching tens of Gbps of peak data transmis-sion rate, reducing the end-to-end delay to milisecond level, and obtaining5to10times improvement of frequency efficency. On the other hand, the ener-gy efficiency are made great efforts to increase hundredfold. In order to meet those goals, large quantities of new scenarios and technologies are emerging. The channel meansurement and modeling, which is the prerequisite of the new technology study and evaluation as well as the system development and opti-mization, is a neccessary and beforehand work. The research in the thesis is performed for the Beyond IMT-Advanced system, focusing on the wideband wireless channel measurement and modeling in the high-speed railway (HSR) and device-to-device (D2D) scenarios, and using the antenna selection to in-crease the time synchronization performance in MIMO-OFDM system based on the MIMO channel fading characteristics. The main contribution are as fol-lows.·Study on the wideband wireless channel characteristics and modeling in HSR scenarios. HSR has become an important scenario for the future mobile communication. However, for the reason of the high speed and the difficulties of channel measurement, the present research is lack of the wideband channel measurement and modeling on HSR. In the the-sis, the wideband channel measurement campaigns are conducted on the Zhengzhou-Xian HSR Line at the center frequency of2.35GHz and50MHz bandwidth for typical HSR scenarios including viaduct and U-shape cutting, collecting tens of hundreds of channel samples. Based on the col-lected channel data, the large scale fading characteristics in the two typical scenarios are studied with establishing the path loss and shadow fading model; The statistical distribution of Ricean K factor is extracted, and the linear model is established to descript the variation of Ricean K factor with the distance between the transmitter and receiver (T-R distance). Es-pecially, the statistical characteristics of delay domain, which is important in wideband system, are analyzed. The F and Log-normal distributions are found to fit the path number and the delay spread well. Also, a linear model is established to model the tendence of the delay spread with T-R distance. In addtion, the doppler is analyzed, and the tendency of the max-imum doppler frequency shift variation is given. Finally, on the basis of all the results, the simulation method for HSR is proposed.· Study on the non-stationary characteristics of the HSR channel. Since the high mobility of the train and the scatters in HSR scenario, the time varia-tion of the channel is more severe than that in the cellular network, which results in the inapplicapability of the present low mobility and stationary hypothesis of channel. So it is deserving to study the non-stationary char-acteristics of HSR channel. In the thesis, refferring to the anslysis method of non-stationary signal, the non-stationary index of channel is defined. Furthermore, the calculation procedure of the non-stationary index from the measured channel impulse responses is proposed. Based on the chan-nel data in the U-shape cutting of HSR scenario, the non-stationary char-acteritics are analyzed in terms of the non-stationary.·Study on the wireless channel characteristics and modeling in D2D out- door scenarios. D2D scenarios is different from the traditional cellular network with the characters like the low antenna height, and there is no unified channel model based on the channel measurement for simulation. In the thesis, two typical outdoor D2D scenarios, outdoor open area and outdoor street, are difined, in which the channel measurement campaign-s are carried out. The channel characteristics such as path loss, shadow fading, Ricean K factor, and delay parameters are analyzed in different propagation conditions of line-of-sight(LoS), obstructed LoS (OLoS) and non-LoS(NLoS) based on the measurement data. With the founded path loss and shadow fading model, it is observed that the measured path loss is higher than the proposed D2D model in3GPP. In the LoS of street s-cenario, the average value of Ricean K factor is13dB, which is much bigger than that in the model of3GPP due to the "Wave Guide" effect. the distribution of the measured delay spread is well fitted by the Log-logistic distribution rather than the Log-normal distribution proposed in3GPP. Al-so, the statistical average value of delay spread is bigger than that in3GPP model. Finally, comparing with the3GPP reconmmended D2D channel model, the modification suggestions are proposed.·Study on the time synchronization schemes of MIMO-OFDM system. MI MO-OFDM system is sensitive to the synchronization error, which makes the timing synchronization is very impotant in the design of the receiver. In the thesis, by using the MIMO fading channel, we propose a scheme to perform the timing synchronization. The selection transmitting (ST) is utilized at the transmitter by choosing antenna with the best channel state whereas the maximum ratio combinining (MRC) is applied at the receiver to improve the precision of the synchronization. For the flat fad-ing channel, the colsed form expressions of the correct timing probabili-ty (CTP) and error timing probability (ETP) of different schemes including ST/MRC, ST, MRT and MRC are derived. Also, the application of the ST/MRC time sychornization scheme to the multi-path fading channel is analyzed. Comparing the CTP of different schemes in different antenna configurations by computer simulation, the advantage of ST/MRC timng synchronization scheme is demostrated.Above all, in the thesis, the wideband wireless channel measurement cam-paigns are conducted in HSR and D2D scenarios, and the large scale and s-mall scall fading characteristics are analyzed based on the measured data. The analyses and results can be used as the reference of the thechnology evaluation and system simulation for the future mobile communication systems. In ad-dtion, ST/MRC scheme is used in MIMO-OFDM system to improve the timing synchronization. In practical use, the proposed scheme would reduce the com-plexity of the system with usding less number of channel links in the timing synchronization procedure. |
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