| The rapid development of wireless communication has facilitated the transfer and exchange of information. Following the unceasing increase in the application and market, wireless communication is going forward with high-capacity, high-speed and high-quality. And wireless communication technology also faces more demands and criteria. Multiple-input multiple-output (MIMO) which is one of key technologies in modern and future mobile communications has manifested enormous superiorities in advancement of channel capacity and spectrum utilization rate. MIMO system performances mainly rely on two aspects, one is wireless fading channel which has effects on signals propagation, and the other is transceiver array antenna which possesses spatial correlation and effect of mutual couple to influence signal transceiver especially when transceiver array antenna is compact architecture. This paper, which centers on analysis of geometrical-based wireless channel properties and research on MIMO array antenna system performance, analyze wireless channel modeling, spatial correlation and channel capacity in depth, and establish a solid theoretical foundation. The research of this paper as follows:Firstly, an improved hollow-disc model was proposed for indoor communication environments based on the hollow-disc model for outdoor communication environments. The joint and marginal probability density function of angle of arrive and time of arrive were derived in closed-form expressions. The spatial and temporal statistical properties of these two hollow-disc models were analyzed and compared. By varying the hollow-disc ratio and the distance between base station and mobile station, simulations illustrate the variation mechanism when hollow-disc models transited from the circle-disc to ring model, and channel information under different wireless communication environments.Secondly, with directional antenna applied in a two-dimensional geometrically based single bounce circular model, the spatial statistical properties of uplink and downlink are derived. And the effect of power azimuth spectrum on the spatial correlation of uniform circular array in base station is also studied. Subsequently, based on the modified Clarke classic model, the Doppler spectrum, the level crossing rate, average fading periods and time correlations are researched respectively with different channel parameters. The results demonstrate that the directional antenna mounted on mobile station effectively decrease the spatial correlation among antenna elements. However, mobile station utilizes omnidirectional antenna better than directional antenna to beam concentrators. Therefore, base station utilizes directional antenna to better restrain the Doppler spectrum from mobile station. Furthermore, even though the higher Doppler frequency effectively reduces time autocorrelation of multipath component, small-scale fast fading become worse.Thirdly, electromagnetic vector sensor is introduced to be the element of array antenna, base on which we combine electromagnetic vector sensor signal processing method with traditional MIMO signal processing method and set up three-dimensional channel model of multi-antenna array. This chapter adopts the algorithm of multiple signal classification to make spatial spectrum estimation for direction of arrival signal, derives analytical expressions of three-dimensional spatial channel base on electromagnetic vector sensor for MIMO receiver system and clarifies the relationship between electromagnetic vector sensor signal processing and MIMO multipath channel correlation. To compare with traditional MIMO antenna array, electromagnetic vector sensor array possesses abilities of obtaining multidimensional polarization information, processing spatial and polarization domain for arrival signal and degrading effects of spatial factors on MIMO channel capacity. Theoretical analysis and simulation results indicate that electromagnetic vector sensor array provide more advantages than traditional scalar sensor array on enhancing MIMO system performance.Lastly, based on the three-dimensional spatial channel model of MIMO system and equivalent circuit model of array antenna, this chapter explains physical significance of coupling coefficient and derives closed-form expressions of spatial fading correlation between elements, which are applied to analyze and evaluate the MIMO system capacity and error rate. Due to effect of mutual coupling, the direction and angle spread of incident signal have different influence on MIMO system capacity and error rate when the array antenna of receiver adopts various geometrical topologies. To sum up, the effect of mutual coupling improves MIMO system performance to a certain extent. |
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